Threaded fasteners are used to connect a pair of internal and external threads to connect the fastening of some parts, they have a similar characteristic is the thread of the tooth type, which is used to determine the geometry of the thread, and only the core When the elements are the same, the internal and external threads can be rotated together. What are the elements of the threaded fasteners? Mainly have the following six core elements.
1, the working height: two-phase matching thread teeth on each other in the direction perpendicular to the direction of the thread axis and so on. Nominal diameter of the thread In addition to the pipe diameter to the diameter of the pipe diameter, the rest are the diameter of the nominal diameter. Threads are standardized, with metric (metric) and imperial. International standards are metric, and China uses metric.
2, lead: adjacent two teeth in the diameter of the corresponding two-point axial distance known as the pitch. On the same helix, the adjacent two teeth in the diameter of the corresponding two-point axial distance called lead. The relationship between the number of lines n, the pitch P and the lead S is: S = n · P.
3, the rotation: the direction of the axis, the clockwise rotation of the thread to become the right-hand thread, counter-clockwise rotation of the thread called the left-hand thread.
4, large diameter, diameter and diameter: large diameter and the external thread of the crest, the internal thread of the tooth bottom coincidence of the imaginary cylinder or cone diameter, external diameter of the large diameter with d, the internal thread Large diameter with D said. Trail refers to the diameter of the imaginary cylinder or conical surface of the tooth bottom of the external thread, the diameter of the external thread is denoted by d1, and the diameter of the internal thread is indicated by D1. For example, a car screw, between the large diameter and the small diameter, is assumed to have a cylinder (or cone), in its axis profile, the width and groove width on the line, the imaginary cylinder diameter is called Medium diameter, with d2 (or D2) said.
5, tooth type: through the thread through the axis of the profile, the contour shape of the thread called the tooth type. The angle between adjacent teeth is called the tooth angle. Commonly used common thread of the tooth type for the triangle, tooth angle of 60 °.
6, the number of lines: the number of threads forming the thread is called the number of lines. There are single and multi-thread threads, multi-thread in the vertical axis of the profile is evenly distributed.
Phosphating fastener process: the total acidity is too high will make the film is too thin, the total acidity is too low will make the film loose rough. The acid ratio refers to the relationship between the free acidity (Tb) and the total acidity (Ta). Free acidity is too high, and the role of iron and steel parts will be a lot of hydrogen, so that the interface layer of phosphate is not easy to saturate, resulting in the formation of difficult nuclei, thick crystalline layer, loose holes, corrosion resistance, and phosphating time Prolonged; free acidity is too low, phosphating film is thin, even without phosphating film generation.
Solution main component low: add the main liquid. Acid ratio is not correct: free acidity is too high, can add manganese carbonate and other regulation: the total acid is too low, can add the main agent regulation, total acid control at 85 points or more. Poor solution composition: improved phosphating solution formula, the use of PL-VM phosphating solution.
The use of PL-VM phosphating solution, the solution parameters of simple adjustment, less sediment, the workpiece hanging ash, the film crystal fine honey, the resistance to neutral salt spray time can be improved, the workpiece by the neutral salt spray test after a small degree of corrosion.
Self-phosphating solution composition control is not good, the solution is difficult to adjust, precipitation, the workpiece hanging ash, in the phosphating process parts easily lead to corrosion.
Causes and Countermeasures of Poor Corrosion Resistance of Phosphating Fasteners
1, the solution composition ratio is poor: to improve the phosphating liquid formula, the use of PL-VM phosphating solution.
2, acid ratio is not correct: free acidity is too high, can add manganese carbonate and other regulation: the total acid is too low, can add the main agent regulation, total acid control at 85 points or more.
3, the main components of the solution is low: add the main liquid.
4, the main components of the solution is not correct: solution Shenqing, the tank temperature control at 95 ℃ or so.
5, phosphating time is too short: phosphating time control in 10 ~ 15min.
6, the solution of high Fe2 + content: plus hydrogen peroxide and other oxidants to adjust the Fe2 + content, or replace the bath.
7, there are oxides in the solution: replace the bath, or to strengthen the workpiece before the pickling cleaning.
8, the former treatment is not clean: the use of sandblasting or fasteners to maintain a good surface before the phosphating conditions.
9, loading too much: the use of hanging or reduce the load, so that the fasteners to maintain a certain gap, so that it can fully respond.
1. The contaminants generated when rinsing are quenched and cleaned with a silicate cleaning agent, then rinsed and appear on the surface of the XX solid material. This material is analyzed by an infrared spectrometer, which is confirmed to be inorganic silicates and iron oxides. This is due to rinsing is not completely on the surface of the fastener residue due to silicate.
2. Fasteners stacked unreasonable fasteners after the signs of discoloration, soaked with ether, so that ether volatile and found that the remaining oily residue, such substances are high levels of lipids. Indicating that the fastener in the rinse period by the cleaning agent and quenching oil pollution, melting at the heat treatment temperature, leaving chemical burning scars, such substances confirmed that the fastener surface is not clean. It is analyzed by infrared spectrometer and is a mixture of base oil and ether in quenched oil. The ether may come from the addition of the quenching oil. The results of the quenching oil analysis in the mesh belt furnace show that the fasteners are slightly oxidized in the quenching oil due to the unreasonable stacking of the fasteners, but are almost negligible. This phenomenon is related to the cleaning process, not the quenching oil The problem.
3. Surface residue High-strength screws on the white residue, with infrared spectrometer for analysis, confirmed that the phosphide. There is no acid cleaning agent cleaning, and rinse tank inspection found that the bath has a higher carbon solubility, the tank should be drained on a regular basis, often detect the concentration of lye tank lye concentration.
4. Alkaline burns High strength screws Quenching waste heat blacks with uniform, flat oil black outer surface. But in the outer circle there are orange XX visible area. In addition, there are visible slightly blue or light red area. Raw bar and wire rod coated with phosphating film to facilitate cold heading and tapping, without rinsing Direct heat treatment, in the quenching oil cooling, alkaline cleaning agent cleaning, dry (not rinse), 550 ℃ tempering, heat State from the back to the furnace to remove the dip oil, the results found in the screw thread red spots. The red area on the tested screw is caused by alkali burns. Alkaline cleaning agents contain chlorinated substances. Calcium-containing compounds burn the steel fasteners during heat treatment and leave marks on the surface of the fastener. Iron and steel fasteners in the quenching oil can not remove the surface of alkaline objects, which in the high temperature austenitic state to burn the surface, and in the next step tempering increased damage. It is advisable to thoroughly clean and rinse the fasteners before heat treatment to completely remove the alkaline residue that causes the burner to burn.
5. Rinse improperly on the large size of the fasteners are often used in polymer water quenching, quenching with alkaline cleaning agent cleaning and rinsing, quenching after the fasteners have rusted in the inside. Analysis of the infrared spectrometer, confirmed in addition to iron oxide, there are sodium, potassium and sulfur, indicating that the inside of the fastener with alkaline cleaning agent, is likely to be potassium hydroxide, sodium carbonate or similar substances, to promote its rust. Check for fastener rinsing for excessive contamination. It is also advisable to exchange rinse water frequently. In addition, adding rust inhibitor to water is also a good way.
6. Excessive rust High-strength fasteners often see some black stripes, also found in the test, had used inorganic and organic cleaning agent rinse the heat before the fasteners, after quenching or found still black stripes or even before heat treatment Aberdeen carefully cleaned, will also be left after the heat treatment stripes. Analysis of surface residual contaminants by infrared spectroscopy revealed a higher concentration of sulfur and calcium. With a small amount of acetic acid isopropyl alcohol, a small piece of test paper in the dark spot at the force of folding, the black spots on the filter paper. The analysis of filter paper by infrared spectroscopy confirmed that calcium, sulfur, iron, manganese and chromium were the main elements. There are calcium and sulfur in the rust that this material is dried and quenched oil, but also in the process of quenching the evolution of gas phase. Because the quenching oil is over-aged, it is recommended to pour out the old oil, add new oil, carry out the process supervision and quenching oil maintenance in the whole process cycle.
When tightening the anchor bolts, it is possible to pull the bolts, and the bolts should be adjusted to the original position, and the foundation around the bolts will be shoveled enough positions, then the two U-shaped bars will be welded and bolted on the bolts. The pit clean and grout, until the concrete solidification to the design strength and then tighten the live foot bolt deviation treatment of live foot bolt deviation of the treatment method, roughly the same with the method of dead feet bolts, but can pull out the anchor bolts to deal with. If the bolt is too long, you can cut a thread on the machine tool; if the bolt is too short, can be hot forging method elongation; if the location does not match, with bending method correction.
Mainly carbon steel, stainless steel, copper three kinds of materials.
A carbon steel. We distinguish between low carbon steel, medium carbon steel and high carbon steel and alloy steel in the carbon content of carbon steel.
1 low carbon steel C% ≤ 0.25% domestic is often referred to as A3 steel. Foreign basic known as 1008,1015,1018,1022 and so on. Mainly used for 4.8 grade bolts and 4 nuts, small screws and other products without hardness requirements. (Note: drilling tail nails mainly with 1022 material.)
2 Medium carbon steel 0.25%
3 high carbon steel C%> 0.45%. Currently on the market basically did not use
4 alloy steel: in the carbon steel by adding alloying elements, to increase the steel of some special properties: such as 35,40 chromium molybdenum, SCM435, 10B38. The main components are C, Si, Mn, P, S, Cr, Mo. The main components are SCM435 chrome molybdenum alloy steel.
2 stainless steel. Performance level: 45,50,60,70,80
1 main austenite (18% Cr, 8% Ni) good heat resistance, good corrosion resistance, good weldability. A1, A2, A4
2 martensite, 13% Cr corrosion resistance is poor, high strength, good wear resistance. C1, C2, C4 ferritic stainless steel. 18% Cr upsetting is better, corrosion resistance is stronger than martensite. Imported materials on the market are mainly Japanese products. According to the level of the main points SUS302, SUS304, SUS316.
3 bronze. Common materials for the brass ... Zinc and copper alloy. The market mainly with H62, H65, H68 copper standard parts.
1. Check the temperature control is intact, heating appliances in good condition, the temperature is below the target range.
2. Check the operation of the motor check current, speed, temperature rise, accuracy, noise and mechanical transmission are in line with the standards. Check gearbox oil level and mechanical lubrication.
3. Check the traction speed, film width, thickness control is accurate.
4. Observe the uniform thickness of the film, folding diameter is in line with the standards.
5. Film plasticization observed the situation and found that the crystallization point, stiff, water and timely treatment.
6. Check the control of raw material ratio, the mixing situation is in line with standards.
7. Regularly adjust the mold, traction, roller center, horizontal, parallelism.
Stainless steel screws and other fastener products are widely used, but its application is different, so the product requirements are different. As a result, stainless steel screws and other connecting fasteners are divided into A, B, C three levels to suit different applications.
The difference between the three levels is that A and B levels are higher-precision levels and are suitable for demanding occasions. C-level is more general and is generally used for less demanding situations. Roughly the highest level A, B level, C level the lowest. (The difference between the accuracy such as tolerance, surface, etc., specific reference to the specific fastener standards).
Screw fasteners your best use of things, just right, not the best A-class, should buy A-class, C-class worst, is inferior goods. Should follow their own product assembly requirements, select the corresponding screw fasteners.
The so-called yield is the premise of ensuring the plasticization of the quality of the nose by a given amount of production or extrusion. As mentioned earlier, the output is usually expressed in kg / h or kg / rev. A good screw, should have a high plasticizing ability. (Consumption ability)
(B) plastics quality (screw)
A screw must first be able to consume products that meet the quality requirements. The so-called quality requirements meet the requirements of the products produced should meet the following requirements:
1, with a variety of performance requirements. With the provisions of the physical, chemical, mechanical, electrical properties;
2, with the desired apparent quality. If users can achieve the bubble, crystal point, dyeing dispersion uniformity requirements.
3, with the plasticization of the screw quality requirements:
1) Whether the temperature of the melt extruded by the screw is even, axial fluctuation, radial temperature difference.
2) Is there any minimum melt temperature that can be molded?
3) Extruded melt pressure fluctuations.
(C) unit consumption
The so-called unit consumption, refers to the energy consumed per one kilogram of plastic (rubber), generally expressed in N. Where N is the power (kW), Q is the output (kg / h).
The larger this value, the more energy is required to plasticize the same weight of plastic (rubber), meaning that the more heating power is consumed, the more mechanical work done by the motor goes in the form of shear and frictional heat many. vice versa. A good screw, plasticizing the premise of ensuring the quality, consumption should be as low as possible.
The so-called screw adaptability refers to the screw on the processing of different plastics, matching different head and adaptability of different products. In general, the more adaptable, often accompanied by plasticizing efficiency.
Therefore, we always hope that a good screw, its adaptability and high plasticizing efficiency should be both.
(E) the difficulty of manufacturing
A good screw must also be easy to manufacture, low cost.
Bolts are also fasteners, fasteners generally have a permanent connection, semi-permanent, removable. Like a permanent connection, as its name implies, the parts to be joined are not separated, such as riveted and welded; semi-permanent, parts joined with such fasteners can be disassembled.
However, they usually cause damage to fasteners used, such as cotter pins; stainless steel chemical anchor fasteners are detachable and parts that are fastened using this type of fastener are easily disassembled. For example, ordinary non-standard stainless steel bolt and nut connections. Three types of connections have their own use of the place, it can not be used because of its reasons can not disassemble the connection method. T-type screws, also known as T-bolts, the European standard for the hammer bolts, materials for the SUS304 stainless steel and carbon steel, carbon steel T-screw surface can be galvanized or nickel plated and Dacromet, carbon steel T The material of the bolt is 1045 medium carbon steel, which is produced by the process of red satin. The grade after the heat treatment is 8.8, generally the mold plate bolts, the T-shaped screws can be directly put into the grooves, the positioning can be automatically locked during the installation, the T- Bolts are generally used with flange nuts. They are standard connecting fasteners for mounting angle fittings. T-bolts are selected according to the groove width of the profile. T-screw commonly used specifications are generally above M8.
Screw is the use of objects, bevel circular rotation and friction of the physical and mathematical principles, step by step fasteners objects mechanical tools. Screws are the general term for fasteners. Screws are indispensable industrial necessities in daily life: the smallest screws such as cameras, eyeglasses, clocks and watches, and electronics; general screws for television, electrical products, musical instruments, furniture, etc. For engineering, construction, bridges, Screws, nuts; traffic equipment, aircraft, trams, cars, etc. for the size of screws and use. Screws have an important industrial mission. As long as there is industry on earth, the function of screws is always important. Screws are the common invention of people's life and production for thousands of years
Screw, it was also called "screw" (screw), "screw" (screw rod). In fact, the screw is known, while the screws, screw rod are different from each other. Screws are generally called wood screws; is the kind of pointed tip, larger pitch, generally used for fastening wooden parts, plastic parts. Screw rod is machine screws (machine screws), is the kind of front-end flat, small pitch, uniform, generally used for fastening metal, machine parts.
Wood screws, machine screws; but according to different purposes can also be divided into many categories; machine screws can be divided into longitudinal fastening screws and horizontal expansion screws; according to the thread can be divided into:
A: Triangular thread (60 degrees): bonding / locking / expansion
B: Threaded tube (55 degrees): binding / locking 3)
C: Trapezoidal thread (30 or 29 degrees): power transmission
D: square thread (90 degrees): power transmission
Comparison of physical properties data of stainless steel and carbon steel, the density of carbon steel slightly higher than the ferritic and martensitic stainless steel, while slightly lower than the austenitic stainless steel; resistivity by carbon steel, ferrite, martensitic And austenitic stainless steel in increasing order of magnitude; the coefficient of linear expansion is similar in rankings, with the highest in austenitic stainless steel and the smallest in carbon steel; carbon steel, ferritic and martensitic stainless steels are magnetic and austenitic stainless steels are nonmagnetic , But the cold work-hardened into a martensitic transformation will produce magnetic, heat treatment can be used to eliminate this martensitic tissue to restore its non-magnetic. Austenitic stainless steel and carbon steel compared with the following characteristics:
1) High electrowetting rate, about 5 times of carbon steel.
2) Large linear expansion coefficient, 40% larger than that of carbon steel, and as the temperature rises, the linear expansion coefficient of stainless steel screws also increases accordingly.
3) Low thermal conductivity, about 1/3 of carbon steel.
Screw is the use of objects, bevel circular rotation and friction of the physical and mathematical principles, step by step fasteners objects mechanical tools. Screw is a common saying of fasteners, everyday spoken language. Screws are indispensable industrial necessities in daily life: the smallest screws such as cameras, eyeglasses, clocks and watches, and electronics; general screws for television, electrical products, musical instruments, furniture, etc. For engineering, construction, bridges, Screws, nuts; traffic equipment, aircraft, trams, cars, etc. for the size of screws and use. Screws have an important industrial mission. As long as there is industry on earth, the function of screws is always important. Screws are the common hair of people's production and life for thousands of years
Screw, it was also called "screw" (screw), "screw" (screw rod). In fact, the screw is known, while the screws, screw rod are different from each other. Screws are generally called wood screws; is the kind of pointed tip, larger pitch, generally used for fastening wooden parts, plastic parts. Screw rod is machine screws (machine screws), is the kind of front-end flat, small pitch, uniform, generally used for fastening metal, machine parts.
Wood screws, machine screws; but according to different purposes can also be divided into many categories; machine screws can be divided into longitudinal fastening screws and horizontal expansion screws; according to the thread can be divided into:
A: Triangular thread (60 degrees): bonding / locking / expansion
B: Threaded tube (55 degrees): binding / locking 3)
C: Trapezoidal thread (30 or 29 degrees): power transmission
D: square thread (90 degrees): power transmission
It can be easily screwed into the drywall when assembled, self-drilling a hole in the steel strip, and mating with a female thread.The concave head of the horn can be screwed in without damaging the wallpaper or gypsum surface. Most self-tapping screws are for commercial use, for example, when self-tapping screws are provided with a combination screw (SEMS), tighter service can be provided, while screws, such as those with thick and thin threads, are designed to be loosened after assembly.
Thread forming ─ ─ directly from the metal screws from the use of thread forming self-tapping screws used to be pre-drilling, and then screw into the hole, the strong extrusion with the female thread, while the original position in the female thread material will be Squeezed between the male thread, the so-called thread forming self-tapping screws. It can only be applied to the thin and plastic material, and thus developed; thread cutting tapping screw ─ ─ tail at the end of the thread cut one or more Cut-out, enabling the use of screw tails and teeth in the pre-drilling pre-drilling, with a screw-like way to cut out the mating female thread.It can be used in the thick plate, the more hard or fragile material is not easy to shape.
6 Thread Rolling - Triangular Self-Tapping Screw, also known as Type TT (Type Tai is still patented) is based on the principle of forming screw tapping. Thread rolling self tapping screws have specially designed thread and tail end Screws can be self-rolling under intermittent pressure into the mating female thread.At the same time in the hole around the material can be more easily filled self-tapping screw thread and tooth space, due to its friction than the thread forming self-tapping screws is small, So it can be used on thicker materials, the torque required for rotation is better controlled and the combined strength is higher Thread Rolling into Self Tapping Screws The engineering standards define the material, heat treatment, strength, The definition is higher and clearer, making thread rolling into self-tapping screws to become a true "construction" fastener.
The main purpose is to make industrial products form a fixed integration. In use, teeth and teeth can not be tightly closed, too hard to lock, screw heads are broken, or the teeth are not locked tightly. Screw is a "quantity product", not a hand-made artwork. In mass production, it aims to achieve high-accuracy, stable quality and popular price for consumers. The accuracy of the screw is usually 6G (grade 2, American specification "IFI" for 2A teeth), construction works for the rough snails for the 8g class (3, "IFI" 1A teeth).
The value of screws is very important. In the world, there is an example that the automobile factory is bankrupt due to the bad quality of screws, and there are also examples of aircraft falling and vehicle subversion due to the bad screw quantity.
Types of common screws
A: Machine Screw
B: Tapping Screw (used in metal and two kinds of plastics)
B-1: Sheet Metal Tapping Screw. (the self tapping screw of the iron plate)
B-2: Plastic Tapping Screw.
C: Wooden Screw
D: Drywall Screw
E: Self Drilling Screws
F: expansion screw, four expansion screws are also named: four pieces of house lizard.
The grades of expansion bolts are divided into 45, 50, 60, 70, 80,
Expansion screw material: Main austenite A1, A2, A4,
1 stainless steel plate, metal plate, galvanized steel plate, engineering installation.
2 metal curtain wall and light compartment indoor installation.
3 the general angle steel, channel steel, iron plate and other metal materials are installed in combination.
4, assembly projects such as car box, container box, shipbuilding industry, freezing equipment and so on.
Standard parts on the market mainly carbon steel, stainless steel, copper three kinds of materials.
ONE. Carbon steel. We distinguish between low carbon steel, medium carbon steel and high carbon steel and alloy steel by the carbon content of carbon steel.
1. Low carbon steel C% ≤ 0.25% Domestic commonly known as A3 steel. Abroad, basically called 1008,1015,1018,1022 and so on. Mainly used for 4.8 bolts and 4 nuts, small screws and other products without hardness requirements. (Note: Drill tail nail is mainly made of 1022 material.)
2. Medium carbon steel 0.25%
3. High carbon steel C%> 0.45%. Currently not used on the market
4. Alloy steel: carbon steel alloy elements added to increase the steel's special properties: such as 35,40 Cr-Mo, SCM435,10B38. Aromatic screws mainly use SCM435 chromium molybdenum alloy steel, the main ingredients are C, Si, Mn, P, S, Cr, Mo.
TWO. Stainless steel. Performance level: 45,50,60,70,80
1. The main sub austenite (18% Cr, 8% Ni) good heat resistance, corrosion resistance, good solderability. A1, A2, A4
2. Martensite, 13% Cr Corrosion resistance is poor, high strength, good wear resistance. C1, C2, C4 ferritic stainless steel. 18% Cr upsetability is better, corrosion resistance stronger than martensite. Imported materials on the market are mainly Japanese products. Mainly by grade SUS302, SUS304, SUS316.
THREE. Copper. Commonly used materials for brass ... zinc-copper alloy. The main market with H62, H65, H68 copper standard parts.
Common Materials a.Low Carbon Steel: carbon steel carbon steel sub-low carbon steel, medium carbon steel, high carbon steel and alloy steel.
b. SS-304: Stainless Steel 304, 316 are all stainless steel and the like
c. SS-302: Stainless Steel 302: better structural toughness
d. Aluminum 5052: Aluminum Alloy 5052
d. Brass: Brass
e. Bronze: Bronze
f. UNS C11000 Copper: antimony copper
Self-tapping screw is generally pointed, coarse teeth, hard wood screws, but also for aluminum, plastic. A special self-tapping screw used to thread metal holes is called a wire tapping.
Standard Self-Tapping Screws Identify characters, including symbols that represent the shape of the thread and tail Tailoring screws have one or two characters representing the thread used to represent a mechanical thread or a wide thread (SPACED), with the identifying character "B" Wide-brimmed screws. "B" stands for machine threads. Trailing-end stands for characterization of self-tapping screws for thread forming, cutting, rolling or self-drilling.
The same as the Anglo-American uniform thread with a thread angle of 60 degrees and coarse, fine thread the same pitch, if the screw is missing or need to be removed after the demolition, you can use the standard thread fastener instead.
The wide thread has a 60 degree thread angle but its pitch is wider, and because of its wide pitch, the thread is steeper and therefore has a larger thread lead than the machine thread. Another type of thread, The thread angle of 48 degrees, commonly known as PT dental screws.
Thread forming tapping screws A, AB, B, BP, C and other types have been gradually replaced by self-tapping screw thread screwing, it is not recommended in the new design. AB, B, BP only in the tail shape, AB There is a tapered end of the thread, B has a blunt end, BP has a tapered end without a thread, and the center of the tip enters the pre-drilled hole and begins to form the thread. Thread cutting Self-tapping screws BF, BP, D, F, G and T and other forms, BF, BP for the wide thread, the rest for the mechanical thread.
The distinguishing characters differ in their cutting tails. Each cutting tail has a shape that collects the waste material being cut. If the self-tapping screw is screwed into a blind hole (a hole that does not pass through), the debris will remain and seal to the bottom of the hole However, when penetrated into the through hole, the waste will fall on the other side of the workpiece, so in the selection of this type of self tapping screw must take into account and waste may cause pollution, fall into the running parts or electronic substrate can not Operation.
All thread rolling into self-tapping screws are machine threads, same as Anglo-American uniform thread coarse teeth, see SAE J81 Metric threads See SAE J1237 and DIN7500 regulations.
There are two types of self-tapping screws: wide thread BSD and machine thread CSD, special thread types, including high and low double threads, and various tapping drills are also applicable.Because drilling taillights and thread properties, Not suitable for blind hole operation. When assembling self-drilling screws, drilling and tail threading must be completed before the workpiece can be cut or formed, so there will usually be some debris. If thread-cutting thread is used, Therefore, it is necessary to consider this problem practically.For BSD and CSD drilling screws, please refer to SAE J78 and DIN7504 (Wide Thread).
1. From the types of standard parts
National standard, petrochemical standard, chemical standard, automobile standard, nuclear industry standard, etc.
2, From the state category
GB, American Standard, British standard, German standard, standard, Japanese standard, ISO standard etc..
3. Distinguish from the shape
Bolt: six angle bolts, six angle flange bolts, inner six angle cylinder head bolts, eye bolts, expansion bolts, countersunk head bolt head inner six angle, inner six angle screw, carriage bolt, stud bolt, butterfly screw, eyelet bolt, anchor bolts, U bolts, four angle bolt
4, Screw nuts: riveting nut, nut, nut six rings, six angle thick nuts, thin nuts, nylon six angle self-locking nuts, self-locking nuts, full metal Fulaigong Hot Springs Resort, a butterfly nut, cap nut, round nut, square nut, square nut, welding nut, slotted angle welding six six nut, nut fittings and so on
5, Washers: flat gaskets, wave washers, saddle washers, spring washers, opening retaining rings, shaft retaining rings, Kong Yong retaining rings, internal and external teeth locking washers, internal and external sawtooth locking washers, square washers, etc.
6, Precision: pan head tapping screws, countersunk head tapping screw, truss head screws, pan head machine screws, countersunk head machine screw, truss head machine screws, drilling screws, six angle wood screws, self tapping screws, various combinations of triangular teeth screw
7, Other categories: welding nail, rivet, threaded rods, chemical anchor bolt, steel screw and imported hose clamps, cotter pins, self-locking screws, elastic cylindrical pin, cylindrical pin, taper pin, flat round head rivets, rivet, flat countersunk head rivets, round head rivets, inner six angle flat end screw, in the six corners of the tip fastening screw, inner six angle concave end locking screws, turnbuckle and various customized non-standard fasteners etc.
Hexagon screw head screw head is round the outside, the middle is recessed into the hexagonal, hexagonal screw head is the common side of the hexagonal kind. Hexagon screwdriver looks like "7", with hexagonal steel strips at both ends of the cut and then turned into a 90-degree angle into a hexagon socket screwdriver, and the hardware tool shop to sell.
Hexagon socket screws in many industries are widely used, with some of the characteristics of the screw is inseparable, let's take a good look about the characteristics of the socket head screws.
Often used for the hexagonal screw is the Q235 wire, of course, is the use of iron wire screws, wire for these screws can determine some of the characteristics of the hexagon screws.
First of all, the first one is the use of stainless steel screws hardness is relatively high, but if the hardness of iron is obviously a lot worse, this iron itself with the wire is a certain relationship. The texture of iron itself is a relatively soft category, simply no way with stainless steel wire.
However, in order to make the iron screw can achieve the hardness, the iron screws are generally hardened with heat treatment, heat treatment in the process to ensure uniform heating of the screw, or not only to make the screw hardness less than demand , Will also allow the screw to bend easily, so that the production cost of the extra-high hexagon screw will be greatly reduced. After the heat treatment can be iron hexagonal screw up to the hardness, but because of the wire problem, there is still no way in the quality and the ratio of stainless steel wire.
There is a need to pay attention to the hexagon socket screws in the process of using as much as possible do not let the screw head skidding, otherwise it will lead to hard to remove the screw later. Above is some of the features on the hexagon screws, hoping to help our customers.
The self tapping screws are of high hardness, wide thread spacing, deep thread, and smooth surface. Wood screws are the opposite. The other difference is more obvious. There is no thread on the rear part of wood screws. The screw thread is thin, sharp and soft. The self tapping screw thread is coarser, sharp and hard.
The self tapping screws are composed of three parts of the head, the rod and the end of the rod from the beginning to the end. Each self - tapping screw consists of four main elements: the head shape, the wrench, the type of thread, the end type.
The shape of the head - the head of the head is all kinds of shapes. A round (half round), flat round head, round flange (with PAD), flat round head flange (with PAD), pan, pan head (with flange pad), countersunk head, countersunk head, cylinder head, cylinder head, spherical horn head, six head, six head, six flange angle (angle flange with pad and so on).
Wrench the way - wrench a variety of ways. External wrench: six corners, six corners, six corners of the flange flange, six flower shaped; inner wrench: slotted type H (Phillips), cross slot type Z (Pozidriv), cross slot type F (Frearson), four (Scrulox), composite groove groove and the inner spline. In six (plum flower shaped groove), triangle, inner six angle, inner 12 angle, the clutch groove, six blade groove, high torque posidriv etc..
Type of thread - a wide variety of threads. There are self tapping thread (wide tooth thread), machine thread, dry wall screw thread, fiberboard screw thread, and some other special threads. The other threads can be divided into single guide (Dan Tou), double lead (double head), multi lead (multiple head) and high and low teeth and double head threads.
The end type and terminal type are mainly saw end and flat end. But the cutting function can be processed according to the use function, such as the groove, the groove, the cut or the shape of the bit similar to the bit. In some standards, it is also the saw end or the flat end, and there are different forms.
From the above introduction, we can see that there are various changes in the shape of the head, the way of twisting, the type of thread and the type of the end of the rod. They can be combined with each other to release a lot of different products that belong to the category of self tapping screws.
The sensitivity of hydrogen embrittlement increases with the strength of the fastener. For the 10.9 and above the external thread fasteners or surface hardened self-tapping screws and combination hardened steel washers and other screws should be carried out after the hydrogen treatment.
In addition to hydrogen treatment is generally in an oven or tempering furnace, incubated at 190 ~ 230 ℃ 4h or more, the hydrogen diffusion.
Threaded fasteners available tightening approach, in the special fixture, screwed to screw the screw to withstand considerable tension under the pressure, to maintain 48h, release the threaded fasteners do not produce fracture. This method is used as a check of hydrogen embrittlement.
Square head bolt, six angle bolts, carriage bolts, eye bolts, stud bolt, single head bolts, inner six angle bolts, tower bolts, U bolts, flange bolts, T bolts, steel bolt, bolt connection pair, high strength bolt, lock bolt, bolt, ball head bolt, flat head bolts, B7 bolts, guardrail bolts, nibbed bolt hub bolt, stud bolt hole, hook bolt, bolt, countersunk bolts, special slotted bolts, necking bolts, plastic bolts, nylon bolts, stainless steel bolts, bolts, bolts, short thin buckle fastening bolt, bolt, welding the adjusting bolt countersunk head bolts, hinged bolts, six angle recess bolts, whole fastening bolts, fish bolts, wall bolt and the screw sleeve bolt, screw bolts and other high iron.
(1) The preprocessing is incomplete. The surface of the workpiece has an oxide film, which affects the normal accumulation of zinc.
(2) Poor electrical conductivity. The current is consumed on the wire, and the current distribution to the surface of the workpiece is too small.
(3) The carbon content of the workpiece is high. The separation potential of hydrogen is reduced by high carbon steel and cast iron. The surface of the workpiece is accelerated and the current efficiency decreases.
(4) The work of the workpiece is too dense. During galvanizing, the part of the workpiece is shielded and the coating is too thin.
(5) The temperature of the plating bath is low. When the temperature of the plating bath is low, the current density of the distribution will decrease, and the deposition rate of the coating will also decrease.
(6) The content of sodium hydroxide in the bath is high. The current efficiency decreases when the sodium hydroxide content is high.
(7) The content of additives in the plating bath is low. The low content of the additive will affect the laxity, and the part of the coating appears to be too thin.
(8) The area of the plating area is short, and the current density of the distribution is too small when the plating is applied.
(9) The suspension method of the workpiece is improper, and the distance between the zinc anode and the zinc anode is too large, and the azimuth should be adjusted.
(10) Corrosion of the workpiece. The separation potential of hydrogen is reduced, and the surface hydrogen evolution of the workpiece decreases the current efficiency, and then affects the deposition rate of zinc. A proper amount of corrosion inhibitor should be added to the acid pickling solution, and part of the overthickness of the oxide skin should be removed by mechanical method first and more in the process of acid washing.
(11) Anodic passivation. Useful area reduction, affecting the normal distribution of current.
(12) The content of sodium hydroxide is low. If the sodium hydroxide content is low, the current density is not high and the anode is passivated.
According to major categories
1. Bolts: Bolts are fasteners composed of various shapes of heads and threaded shanks and must be used in conjunction with nuts.
2. Stud: also known as stud bolt, is a full threaded rod or the middle of the non-threaded rod. Mostly used for connecting parts is very thick, but also need to frequently disassemble
3. Screws: Also known as machine screws or screws, the main feature is the head made of slotted or cross slot, for a part is very thick, without having to
Often disassembled, or unidirectionally tightened.
4. Nut: It is a type of fastener with screw holes for connecting with bolts (or screws, studs).
5.Self-tapping screws: Mainly used for fastening of thin metal plates with non-metallic materials, but also for connection between non-metal plates
6. Washers: Fasteners used with bolts, screws, and nuts. According to the use can be divided into three types: gasket, anti-loose and sealed.
7. Retainer ring: The main purpose is to position the part in the hole in the shaft and lock it to stop it.
8. Wood screw: The head of the wood screw is basically the same as the bolt and screw. The shank is a special wood screw thread, used for general metal parts and wood.
Fastening connection between quality equipment.
9. Rivets: Mainly used in connection fastening that is not dismantled. Can be divided into solid, hollow and semi-hollow three types.
10. Pin: A light rod locator. It is mainly used for positioning connection and anti-looseness, it can also be used as an overload shearing device to protect the main
The role of machine parts safety.
11. Assembly: It is a combination of bolts or screws, spring washers and flat washers, which will not fall off and loosen before fastening.
The assembly is characterized by its ease of automated assembly and improved assembly efficiency and assembly quality.
12. Welded nails and other parts: Welded nails are a type of arc welding method that welds one end to the structure of various civil engineering projects.
Firmware used as a shear, embedment or anchor. Other parts include fasteners that have not yet been incorporated into national standards, industry standards, or corporate standards, and that are worth promoting.
Expansion bolts, special parts, special parts, wire screw sleeves and other fasteners.
Fasteners are a type of mechanical part that is used for fastening connections and is widely used. Various kinds of fasteners can be seen on various machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, meters and supplies. It is characterized by a wide variety of specifications, different performance and usage, and a high degree of standardization, serialization, and generalization. Therefore, it is also known as a standard type of fasteners that are already in the national standard, or simply referred to as standard parts. Fasteners are the most widely used mechanical basic parts. With China's accession to the WTO in 2001 and entering the ranks of major countries in international trade. Fast fastener products that are exported to fasteners in many countries in the world and countries in the world are also constantly flowing into the Chinese market. Fasteners, as one of the products with a large volume of imports and exports in China, are in line with international standards. They have important practical significance for promoting the global participation of fastener companies in the world and promoting the full participation of fastener enterprises in international cooperation and competition. Strategic significance. Due to the specific requirements of each specific fastener product's specifications, dimensions, tolerances, weight, performance, surface conditions, marking methods, and acceptance inspections, markings, and packaging.
Common detection equipment
The most important link in the development and design of fasteners is quality control. There are several major junctures from feeding to finished products. There are different inspection methods for these major junctures. The first thing related to feed is appearance, size, element, performance, detection of harmful substances, etc.; the process is more about appearance, size, knocking test, forging line; heat treatment is more about appearance, hardness, torque, pull , metallographic, etc.; surface treatment is more of a hydrogen embrittlement test, plating, salt spray, etc., including shipping a hazardous material test. In terms of size and appearance detection, secondary elements, contour measuring instruments, coordinate measuring machines, and image sorting machines (this is a full sorting machine) are common; and hardness and hardness testing machines (Luo and Vickers) are used for mechanical and chemical testing. ), Rally machine, metallurgical microscope; material testing, there is a spectrum analyzer, salt spray testing machine.
The surface of the hardware screw product shall not be allowed to have local non-plating, scorch, rough, gray, peeling, crusting, and obvious streaks. It is not allowed to have pinhole pits, black plating slag, loose passivation film, cracking, shedding and Severe passivation traces.
02. Hydrogen embrittlement
Metal Screws Fasteners During processing and processing, especially during the pickling and caustic washing before plating, and subsequent plating, the surface absorbs hydrogen atoms and the deposited metal coating traps hydrogen. When the fasteners are tightened, hydrogen is transferred toward the most concentrated part of the stress, causing the pressure to increase beyond the strength of the base metal and create a subtle surface crack. Hydrogen is particularly active and penetrates quickly into newly formed fractures.
03. Coating distribution
With different deposition methods, the coating is also concentrated on the surface of the fastener. Metal Screws Fasteners Plating metals are not uniformly deposited on the peripheral edges during plating, and thicker coatings are obtained at the corners. In the threaded part of the fastener, the thickest coating is located on the crest of the thread, gradually thinning along the flanks of the thread, depositing the thinnest at the bottom of the tooth, and hot dip galvanizing is the opposite, with thicker deposits deposited on the inner corners and At the bottom of the thread, the mechanically deposited plating metal tends to deposit the same as the hot dip, but it is smoother and the thickness is much more uniform over the entire surface.
04. Coating thickness
The working life of a hardware screw fastener in a corrosive atmosphere is directly proportional to the thickness of its coating. The general recommended economic plating thickness is 0.00015 to 0.0005 in (4 to 12 um). Hot-dip galvanizing: The standard average thickness is 54 um (claim diameter ≤ 3/8 is 43 um), and the minimum thickness is 43 um (call diameter ≤ 3 /8 is 37um).
Fastener products include bolts, screws, studs or nuts, washers, etc. Some of them have a blackening process, which not only meets the appearance and rust prevention requirements of fasteners, but also has low cost and high production efficiency; It can also reduce the quenching stress, so that the fastener is not easy to break under stress conditions.
Blackening principle: The fasteners to be blackened are placed in a solution bath (145±5°C) of sodium hydroxide (NaOH) and sodium nitrite (NaNO2) oxidants for heating and oxidation to make the surface of the metal fasteners A layer of magnetic Fe3O4 film with a thickness of 0.6-0.8 μm in black or blue black is formed.
The purpose of blackening
1 Antirust effect on the surface of fasteners;
2 increase the appearance and gloss of the fastener surface;
3 Reduce the stress of the quenching process.
Mounting → boiling alkaline solution to oil → water cleaning → hydrochloric acid solution to rust → water cleaning → boiling water heating → oxidation → water cleaning → saponification → water cleaning → dry → dip hot oil → oil control → inspection → storage.
Blackening process operating points:
In order to ensure uniform surface quality of fasteners to be black, fasteners should be in point or line contact.
2, boiling water solution to oil
Add water to the alkali solution tank first, then add 15 g/L water-soluble sodium hydroxide (NaOH) to the boiling point, place the fasteners in the tank, wash for 5-10 minutes, and increase the time on the non-smooth surface.
3, water cleaning
Rinse with boiling water and rinse with cold water to remove residual lye from the surface of the fastener.
4, hydrochloric acid solution to rust
After adding clear water to the acid tank, slowly pour the hydrochloric acid into clean water with a concentration of 14%-18% (tested with a Baume concentration meter), temperature ≤ 30°C, and place the acid-washing fastener in the tank, pickling time For 3-5 minutes, the non-processed surface increases cleaning time as appropriate.
5, water cleaning
Rinse with cold water and rinse the fastener surface with residual acid.
6, boiling water heating
Place the rinsed fastener in boiling water, heat it to 90°C or more, and place it in an oxidation bath.
1 Into the oxidation tank into the distribution ratio: Each liter of water plus sodium hydroxide (NaOH) 600g, sodium nitrite (NaNO2) 60g, containing crystal water of trisodium phosphate (Na3PO4) 20-40g.
2 Preparation methods: first put 2/8 volume of water in the oxidation tank, and then add sodium hydroxide (NaOH) slowly, until the solution reaches 100 °C, then add trisodium phosphate (Na3PO4), made Oxidation solution.
3 Oxidation temperature time: Put the fastener heated by boiling water into the oxidizing temperature (145±5°C) oxidation solution (tested with a 0-200°C glass thermometer, calibrated with boiling water), oxidation time 30-50min.
8, water cleaning
Rinse the residual oxide on the surface of the fastener with clean water until it is saponified.
1 Saponify the rinsed fasteners into a saponification bath to produce a thin film of iron stearate on the fastener surface. Use 10 pieces of civilian soap, melt into 100L of water, adjust the concentration and capacity in proportion to make saponification solution.
2 heating temperature and saponification time: saponification solution temperature 80-90 °C (measured with a glass thermometer), saponification time 2-3min. Add soap to the saponification solution daily according to the size of the saponification fastener and add the appropriate amount of water to maintain the solution concentration.
10, water cleaning
Soak the fastener surface soap with water and heat it with boiling water.
11, since dry
Use your own heat to leave the water dry.
12, hot oil
The self-drying fasteners without water droplets were immersed in L-AN15 full-loss system oil at 80° C. (measured with a glass thermometer) for 1-3 minutes.
13, oil control
After the oil-soaked fasteners leave the oil sump, the surface of the fasteners and the surrounding oil droplets are controlled.
1 Appearance inspection: Place the fastener under the fluorescent light source, 300mm away from the naked eye, observe the surface, if the color is uniform, there is no obvious spotting and rust stains, then it is good, the color is black or blue black.
2 Oxide film looseness measurement: After the oiled fasteners were dropped on a few drops of 3% copper sulfate solution, the copper color was not qualified within 30 seconds.
According to the quality inspection requirements, after passing inspection, it will be stored in the warehouse, otherwise it will be reworked according to the original process procedure.
First, the program obtains the position of the hole by the user performing two interactive operations. One is to select the reference point or the position of the reference axis, and the other is to select the two ends of the fastener group.
Then, set the size and precision of the hole (usually including coarse, medium, and fine) control hole size through the interface, as shown in the figure. "Open hole data" hole data hole point axis selection hole diameter bolt side nut side automatic hole Selection of cylinder and piston rod diameter of high vacuum pneumatic flapper valve Huang Boxi determination method is provided for the selection of high vacuum flapper valve cylinder and piston rod diameter.
A vacuum valve is a component of a vacuum system that regulates air flow, shuts off, or connects a line. The high vacuum flapper valve is powered by compressed air. The direction of the gas path is changed by the electromagnetic directional valve, and the cylinder drive flapper valve is opened and closed. It is suitable for opening or blocking air flow in a vacuum system of 1.3x14Pa~1.0x105Pa. The baffle valve has the advantages of simple structure, short opening and closing time, safety, reliability, sturdiness and durability, and can be automatically controlled. It is widely used in electronics, chemical industry, metallurgy, aviation, aerospace, materials, biomedicine, atomic energy, cosmic exploration, etc. Technology. The design of the cylinder diameter and piston rod diameter of the high vacuum pneumatic flapper valve is very important. If the flapper valve is opened or closed, if the diameter of the cylinder and piston rod is not designed properly, the valve will fail to open and the opening and closing time will be long. This article describes how to estimate the diameter of cylinders and piston rods at a given pressure, to solve this problem.
Check the flapper valve bonnet seal face to calculate the pressure ratio. This article uses an atmospheric pressure, nominal diameter DN160 high vacuum pneumatic flapper valve as an example to calculate, see Table 1. Mechanical industry standardization and quality In addition, the fastener group will automatically Record hole feature information that matches with it. When the fastener group position moves, it can update the program to automatically modify the feature size of the hole.
Reasonable choice of secondary development tools and languages is the key to program portability. The Pro/TOOLKIT provided by PTC for Pro/E is a powerful secondary development tool for Pro/E. It encapsulates a number of library functions and header files for Pro/E bottom-level resource calls, which can take advantage of third-party compilation environments (C Language, VC++ language, etc.) for debugging. Pro/TOOLKIT provides seamless integration with Pro/E for user programs, software, and third-party programs.
The number enables external applications to access Pro/E databases and applications securely and efficiently. Through C language programming and the seamless integration of applications with Pro/E, users and third parties can add the required functionality to the Pro/E system. Therefore, the fastener tool software is developed in combination with VC++ and Pro/TOOLKIT.
According to the idea of group assembly and other concepts, using Microsoft Visual C++ for programming, a fastener tool that meets the assembly habits has been developed on the 3D CAD software Pro/E platform, enabling fast selection of fasteners, group assembly and intelligent punching. Other functions, and can be applied in the design of fasteners. Practice has proved that this tool is effective for improving the design efficiency of fasteners and facilitates the accumulation and transfer of commonly used fastener knowledge.
First, the fastener causes lock phenomenon
1. The probability of thread locking increases when bolts and nuts produced from the same heat material are assembled.
2, the impact of the accuracy of the thread, external thread grade 6H and 6H will increase the friction with the internal thread, (overfit) external thread produced by our company using 6g, (clearance fit) thread diameter size in the tolerance range within the lower limit.
3. The higher the content of Cu in the material composition, the higher the probability of thread locking and the corresponding increase, but some fasteners have to use materials with higher copper content because of the cold deformation. The materials used by our company will cause the thread locking deadlock probability from big to small: 320HQ≥304HC≥304≥316≥316L
Second, prevent stainless steel fasteners locked in use during the method
1, the correct choice of products.
a. Reasonably select the length and specifications of the screw, so as to tighten the nut 1-3 after screwing;
b. Before use, confirm whether the mechanical properties of the product can meet the requirements for use.
2, reduce the friction coefficient.
a. Thread surface cleaning (such as no sand, debris);
b. It is recommended to apply wax or add lubricant (such as butter, 40# oil) to the surface.
3, the correct method of operation.
a. must be screwed perpendicular to the axis of the thread, do not tilt;
b. During the tightening process, the rotation must be uniform and the tightening torque must not exceed the safety torque;
c. Use torque wrenches or socket wrenches as much as possible to avoid the use of adjustable wrenches;
d. Avoid high temperatures.
1,45 - high-quality carbon structural steel, is the most commonly used carbon quenched and tempered steel.
Main features: The most commonly used medium-carbon quenched and tempered steel, good comprehensive mechanical properties, low hardenability, easy to crack when water quenched. Small pieces should be tempered, and large pieces should be normalized.
Application example: It is mainly used for manufacturing high-strength moving parts such as turbine impeller and compressor piston. Shafts, gears, racks, worms, etc. The welding part pays attention to preheating before welding, and eliminates stress annealing after welding.
2, Q235A (A3 steel) - the most commonly used carbon structural steel.
Main features: High plasticity, toughness and welding performance, cold stamping performance, and a certain strength, good cold bending performance.
Application examples: Widely used for general requirements of parts and welded structures. Such as levers, connecting rods, pins, shafts, screws, nuts, ferrules, brackets, frames, building structures, bridges, etc.
3, 40Cr - one of the most widely used steel, is a structural steel alloy.
Main features: After quenched and tempered, it has good comprehensive mechanical properties, low temperature impact toughness, low notch sensitivity, good hardenability, high fatigue strength when oil is cooled, and complex parts in water cooling Cracks, cold-bending plasticity, tempering, or quenching and tempering after the cutting process is good, but the weldability is not good, easy to produce cracks, welding should be preheated to 100 ~ 150 °C, generally used in the state of conditioning, you can also Carbonitriding and high-frequency surface hardening.
Application example: after quenching and tempering, it is used to manufacture medium-speed and medium-load parts, such as machine tool gears, shafts, worms, spline shafts, thimble sleeves, etc.; Grinding parts, such as gears, shafts, spindles, crankshafts, mandrels, sleeves, pins, connecting rods, screws, nuts, intake valves, etc.; used for heavy-duty, medium-speed impact after quenching and tempering Parts, such as oil pump rotors, sliders, gears, spindles, collars, etc.; used after quenching and low temperature tempering for the manufacture of heavy load, low impact, wear-resistant parts, such as worm, spindle, shaft, collar, etc.; At the carbonitriding site, the drive components with larger dimensions and higher impact strength at low temperature, such as shafts and gears, are manufactured.
Reasons why fasteners lock up
Locking of fasteners Generally, it occurs on some traditional metal fasteners. Sometimes, fasteners on some stainless steel products can lock up. This seems to be different from what we think. Why does stainless steel appear rusty?
Because the stainless steel products can be rusted because the surface is once damaged, the oxide layer will provide protection. However, due to the special working environment of the fasteners, once locked, the force it receives will damage the oxide layer. Stainless steel loses its rust-free effect. This in turn blocks the gap and causes the fastener to lock.
Fasteners to avoid locking
1,Before the fastener is used, it should be cleaned and ensure that there is no dirt on the front of the fastener, so as to avoid the use effect of the fastener because of the emergence of the dirt. It also increases the probability of fasteners locking up.
2. When fasteners are used in important locations, the fasteners should be lubricated first, which can reduce the pressure on the fasteners during use, and reduce the chance of lock-up due to the use of fasteners.
3, When we purchase fasteners, regular large fastener manufacturers often use fastener washers. Using washers reasonably can greatly reduce the probability of fasteners locking. And extend the life of the fasteners. Improve safety performance.
4, choose a better quality, longer life of other materials, fasteners, the emergence of new materials to the problem of locking fasteners draw a full stop, many new materials are corrosion-resistant, not afraid of the characteristics of extrusion. The use of new materials made fasteners can well reduce or even completely avoid the problem of locking the fasteners.
1. Resistance - Aluminum forms a protective oxide that does resist standard environmental exposures.
2. The ratio of weight to strength - Among all the metals, aluminum has the best strength to weight ratio, which makes it an ideal material for fasteners. The weight of aluminum fasteners is about 1/3 of the standard metal, and the strength is comparable to low carbon steel.
3, conductivity - when the joint must be conductive, because its conductivity is 38-43%, aluminum is an attractive choice.
Non-magnetic - Aluminum alloy fasteners are non-magnetic and non-sparking.
5. Reduce galvanic corrosion - Use aluminum fasteners in the assembly to reduce the risk of galvanic corrosion.
6, appearance - appearance can be changed color, a variety of colors to choose from!
There are many anti-corrosion technologies for U-bolts. Electroplating and oxidation are commonly used for processing. Today we share with you the U-bolt oxidation anti-corrosion treatment technology, as well as the benefits of this technology.
The bolt is oxidized by immersing the steel part in an alkaline solution containing an oxidizing agent such as potassium nitrate or sodium nitrate in a sodium hydroxide solution and maintaining the boiling point at about 140°C, or immersing the steel part in sodium nitrate and nitric acid. In the molten salt of potassium, after being taken out and quenched in water, a pleasing layer of black oxide, ie, iron oxide film, is obtained on the surface thereof. The composition of the molten salt is a mixture of ferrous oxide and iron oxide, which is an improvement of corrosion resistance of ferrous metals. A simple and economical method. The thickness of the chemical oxide film is extremely thin, generally 0.5 to 1.6 μm, and the corrosion resistance is limited. The film with a thickness of 2 μm has a dull appearance and is black or dark gray. The film has good adsorption properties, such as dipping. After anti-rust oil or paint, its resistance to salt spray corrosion can increase several times to tens of times.
The bolts are generally of steel material, and the material is easily corroded. Therefore, it is necessary to remove the oil and pickle before the oxidation treatment to remove the surface rust. One oxidation treatment is performed in one bath, and two oxidation treatments are performed in two baths with different solution components. The oxidized parts must be thoroughly washed, then boiled in soapy water, dried and oiled.
Fasteners are generally subjected to anti-corrosion treatment because they are made of metal materials, and metal materials are easily oxidized and corroded in certain environments. Therefore, appropriate methods must be used for anti-corrosion treatment.
1. Bolt type
Drywall screws, high-strength screws, self-tapping screws, countersunk screws, wood screws, semicircular head screws, round head screws, fiberboard nail screws, drill screws, wallboard nails, combination screws, set screws, and screws Slot Screws, Eyebolts, Microscrews, Thumbscrews, Thumbscrews Pan Head Screws, Nylon Screws, Nails, Nails, Stainless Steel Screws, Other Screws
Hex nut, thin nut, thick nut, slotted nut, square nut, cap nut, anti-theft nut, flange surface nut, wing nut, ring nut, round nut, weld nut, T nut, four-claw nut, K-cap self-locking nuts, locknuts, cone nuts, stainless steel nuts, internal and external teeth nuts, nylon nuts, disk nuts, spring nuts, fine-tooth nuts, anti-tooth nuts, wheel nuts, high-strength nuts, cassette nuts, Reed nuts, tube nuts, embedded nuts, torque nuts, other nuts, lock nuts, pull rivet nuts, copper nut nuts, plastic nuts, inch nuts, cell phone nuts, embedded nuts.
Hollow rivets, semi-tubular rivets, headless rivets, blind rivets, quick rivets, rivets, rivets, rivets, rivet nuts, rivet nuts, riveting screws, panel fasteners, rivets, tubular rivets, ring groove rivets , Special Rivets, Riveting Nuts, Semicircular Head Rivets, Decorative Rivets, Studded Studs, Eyelets, Solid Rivets, Step Rivets, Other Rivets
Cotter pin, closed pin, cylindrical pin, tapered pin, elastic pin with hole pin, pin, T-pin, U-pin, step pin, positioning pin, combination pin other pin
Flat keys, hook head keys, semicircle keys, other keys
Flat Washer, Spring Washer, Taper Washer, Toothed Washer, Lockwasher, Stopper Washer, Spherical Washer, Split Washer, Square Oblique Washer, Design Washer, Bowl Washer, Nylon Washer, Other Washer Rings
Hole retainer, shaft retainer, open retainer, clamp retainer, other retainer
Expansion Bolt, Inner Expansion Nut, Internal Forced Gecko, External Forced Gecko, Chemical Anchor Bolt, Elevator Gecko, Car Gecko, Power Gecko, Plastic Plug, Nylon Plug, Casing Gecko, Fish Eye/Fish Gecko, Hammer Nails Gecko, window gecko, fork gecko, drive-in gecko, built-in expansion bolt, implosion, pull explosion, pull head, expansion hook, nylon gecko, anchor bolt, other expansion anchor
10 Construction Accessories
Fasteners, hooks, step-by-step, mountain-shaped pieces, jacking, tile hooks, scaffolding, U-shaped cards, building anchor bolts, T-wire, other construction accessories, industrial and mining railways
Shaped bolts, special-shaped screws, special-shaped nuts, turned parts/stamped parts, profiled washers, and other special-shaped pieces
Expansion screws, self-tapping screws, stainless steel screws, anti-theft screws, anchor screws, flower basket screws, eccentric screws, wall screws, furniture screws, license plate screws, double head screws, yoke screws, ring screws, automotive screws, hardware screws, Precision screws, rivets, butterfly screws, special screws, and mechanical screws.
Use of expansion bolts
When using, first use the impact drill (hammer) drilled holes in the corresponding size of the fixed body, and then bolts, expansion tube into the hole, tighten the nut can make the bolt, expansion tube, mounting parts and fixed body Between the tight expansion into one.
After being tightened, it will expand. There is a big head at the tail of the bolt. A round pipe with a diameter slightly larger than the bolt is put on the outside of the bolt. There are several openings in the tail part. When the bolt is tightened, the tail of the big head is brought into the open pipe. The purpose of the rooting is to fix the bolts on the ground or the wall by smashing the tube and expanding it.
Bolts: A type of fastener consisting of a head and a screw. It is required to cooperate with a nut to fasten two parts with through holes. This type of connection is called a bolted connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a detachable connection.
The screw is mainly used for a part with a tight threaded hole, and a fastening connection with a part with a through hole, does not require a nut to fit (this type of connection is called a screw connection and is also a detachable connection; it can also be Nut fittings for tight connection between two parts with through holes.) Set screws are mainly used to fix the relative position between two parts. Special-purpose screws such as eyebolts are used for lifting parts.
How the bolt strength grade is divided is based on the mechanical properties. According to the relevant standards, the bolt performance grade is divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, and 12.9. Among them, grade 8.8 bolts or more are made of low carbon alloy steel or medium carbon steel and heat treated (quenching, tempering), commonly known as high-strength bolts, the rest known as ordinary bolts.
How to classify the bolt strength grade → Bolt performance grade designation has two parts, which respectively represent the nominal tensile strength value and yield ratio of the bolt material. For example: a bolt with a performance rating of 4.6 means:
1. Bolt material nominal tensile strength up to 400MPa;
2. The yield ratio of bolt material is 0.6;
3, the nominal yield strength of bolt material up to 400 × 0.6 = 240MPa level
Performance grade 10.9 high-strength bolts are heat treated to achieve:
1. The bolt material has a nominal tensile strength of 1000MPa;
2. The yield ratio of bolt material is 0.9;
3, the nominal yield strength of bolt material reaches 1000×0.9=900MPa grade
Bolts: Mechanical parts, cylindrical threaded fasteners with nuts. A type of fastener consisting of two parts, the head and the screw (cylindrical with an external thread), which is required to cooperate with the nut and is used to fasten two parts with through holes.
1, drilling depth: the depth of the concrete construction is better than the depth of the expansion tube is about 5 mm deep. As long as it is greater than or equal to the length of the expansion tube, the length of the inner expansion bolt left in the ground is equal to or less than the length of the expansion tube.
2. The requirement of the inner expansion bolts on the ground is of course the harder the better. This also depends on the condition you need to fix the object. The strength of the concrete installed in the concrete (C13-15) is five times that of the brick.
3. After an M6/8/10/12 inner expansion bolt is properly installed in the concrete, the ideal maximum static force is 120/170/320/510 kg.
The installation method of the inner expansion bolt is not very difficult, the specific operation is as follows; first select an alloy drill bit of the same diameter as the expansion screw bulging ring (tube), and then install it on the electric drill to drill holes in the wall. The depth of the hole is preferably the same The length of the bolt is the same, and then put the expansion screw kit together into the hole, remember; do not screw off the screw to prevent the hole drill when the deeper when the bolt fell into the hole and not take it out. Then tighten the screw and tighten 2-3 buckles, and feel that the inner expansion bolt is tight and not loosen before screwing off.
Screws have a wide range of uses in people's production and life. How to purchase the standard screw that meets the requirements is very important, otherwise it will cause various problems such as quality problems and high budgetary costs. The difference between the hex screw and the hex socket screw is for everyone to share.
The screws of the hexagon socket head cap screws and the hexagon socket head screws are divided into inner and hexagon socket screws according to the shape of the screw head, and it is irrelevant to the material of the screw and the bearing capacity of the screw.
The screw head of the hexagon socket screw is round, and the hexagon is recessed in the middle, and the hexagonal screw is the hexagonal screw with a hexagonal shape on the side of the screw head. Main differences: Hexagon socket screws are often used on machinery, and have the advantages of being easy to tighten, disassemble, and not easy to slip.
The Allen key is usually a 90° curved curved shape. The bent end is long and short. When using a short side to screw, the long side of the hand can save a lot of force and better tighten the screw. The long end is divided into a round head (hexagonal cylinder like a sphere) and a flat head. The round head can be easily removed and removed, and some parts of the wrench are inconvenient to be installed.
The manufacturing cost of the hexagonal screw is much lower than that of the inner hexagon. Its advantage is that the screw head (the position of the wrench is thinner than the inner hexagon), and some places are not replaced by the inner hexagon. In addition, the cost of the machine is low, the power is small, and the precision of the machine requires less hexagon socket screws than the outer hexagon.
Wood screws: also similar to machine screws, but the threads on the screw are special wood screws with ribs that can be screwed directly into the wood component (or part) for a metal (or non-metal) part with a through hole. A wooden component is fastened together. This connection is also a detachable connection.
The self-tapping screws have high hardness, wide thread pitch, deep thread, and the surface is not smooth. The wood screws are reversed, and the other difference is more obvious. The rear section of the wood screws has no thread. Wood screws are fine, blunt and soft. Self-tapping screws are thick, sharp and hard.
Advantages Wood screws have the advantage that the consolidation ability is stronger than the nail connection, and can be removed and exchanged, and it is convenient to not damage the wood surface.
First, the wood screw type is commonly made of iron and copper. The type has a round head type, a flat head type, and an elliptical head type depending on the nail head. The nail head is divided into a slotted screw and a Phillips screw. The head screws are made of soft steel in blue, and the flat head screws are polished. The elliptical head screws are usually plated with cadmium and chrome. They are often used to install loose-leaf, hooks and other hardware accessories. The specifications are determined by the diameter of the stem, the length and the type of the nail head. The unit is purchased at the time of purchase.
Second, the installation of wood screw tool screwdriver for its loading and unloading tool, the shape of the wood screw head groove shape and a word and cross shape; in addition, there is a special screwdriver installed on the bow drill, suitable for loading and unloading large wood screws, use It is more convenient and labor-saving.
The countersunk head screw, also known as the flat machine screw, has a 90-degree cone on the head. Similar to a common wood screw, the head has a tool-tightening groove, a shape, a cross, an inner hexagon, and the like.
Countersunk screws are mostly used in places where the surface of the parts cannot be raised after installation. The parts to be fastened are thick and thin. The so-called thick, that is, the thickness of the parts to be fastened is larger than the head of the countersunk head screw. Thickness, after the screw is tightened, there is still a part of the screw thread that does not enter the threaded hole. In this case, the countersunk screws can certainly be tightened. There is usually also a case where the thickness of the fastened part is less than the height of the head of the countersunk head screw, which is common in mechanical equipment in sheet metal parts, such as the hinge of the case and the connection of the door and the case; the sheet metal of the device The connection of the cover to the device, etc.
Due to the small thickness of the part, the fastened sheet metal part, the screw through hole completely becomes a tapered hole. In this case, when the countersunk screw is tightened, the screw head is not a tapered surface pressed sheet metal part. Instead, the bottom of the screw head is crushed to the top of the threaded hole. Although the screw is felt to be tightened, the sheet metal piece is jammed instead of being pressed. In this case, although the screw is felt to be tightened, The gold pieces are indeed not tightened. This is a very common situation.
Let me talk about the reason for the processing: the head of the countersunk screw has a 90° cone angle. Usually, the top angle of the newly purchased drill bit is 118°-120°. Some workers who lack training do not know the angle difference. It is often directly reamed with a 120° drill bit, which causes the countersunk head screw to be not a force on the conical surface of the head, but rather a line at the bottom of the screw head, which is one of the reasons why the so-called countersunk screw cannot be tightened.
During the use of fasteners, sometimes the temperature is very high. Under the operation of high-temperature fasteners, it is easy to damage the performance of the fasteners, and even some faults. For example, bolts are important connecting parts widely used in high-power boilers, steam turbines and steam pipeline valves. For the recommendations of high temperature fasteners in these areas, the following measures should be taken when using:
1. Temperature stress: When the unit is started and running, due to the temperature difference between the flange and the bolt (the temperature of the flange is higher than the bolt), and the coefficient of linear expansion of the two materials, the free thermal expansion of the flange is larger than that of the bolt. The bolt is subjected to an additional tensile force, and the stress caused by the additional tensile force in the bolt is called temperature stress.
2. Sealing stress: ensuring the sealing of the connecting parts is a basic requirement for bolting. In the case of the geometry of the flange, the processing quality of the joint surface, the pressure of the steam and the temperature, the sealing stress is determined by the tightening force of the bolt.
3. Hot tightening of bolts: Bolts that are subjected to pre-tightening force during installation. When the pilot is running, under the action of steam pressure, the bolts are forced to increase more than the initial pre-tightening force. For general horizontal flanges. The bolt tension is increased by 5%-15%, so that the initial stress of the bolt can be lower than when it is cold. In order to meet this initial stress requirement, it is sometimes impossible to manually tighten the bolt to the required degree in the cold state, and therefore, a heat tight method is usually required.
Changzhou Huyue Standard Parts Factory recommends that the bolts be tightened to a certain extent (cold tight) by hand, and then the bolts are heated by the special electric heater through the center hole of the bolts. After the bolts are heated and extended, the nuts are tightened. This method is called heat tight. Controlling the heat tightness makes it easier to control the preload.
1. When the fastener is quenched, the silicate cleaning agent should be used to clean the impurities, and then the rinsing should be carefully carried out to avoid the residual impurities on the fastener, which affects its normal application.
2. After the fastener is tempered, its color may change. After the fastener is soaked in the ether for a period of time, oily substance will be produced. When this happens, the fastener is indicated. Not clean enough. After the analysis, it will be found that the stacking is not very reasonable when heating the fasteners, and the fasteners may have some small oxidation in the quenching oil.
3. If there is a white substance on the fastener, it is likely to be some phosphide. The reason for this phenomenon is that there is no cleaning with an acid cleaner, and it is not careful enough to check the rinsing tank.
If these problems are not handled in time, it will directly affect the performance of the fasteners, and may also lead to shortened service life of the fasteners, resulting in early damage of the fasteners. I hope that the above three major issues can help you make better use of fasteners.
1. If you have the intention to remove it, the anti-theft screw is like a dummy, it is useless. Because no matter what the screw is, it can be removed, and there are ways to remove the welding, not to mention the anti-theft screw.
2. Anti-theft screws are still useful for ordinary people. After all, most people don't know much about screws. The most common ones are Phillips screws, hex screws, slotted screws, and Phillips screws. Fasteners for special shaped anti-theft screws. Most people have never seen it, and they don't know how to disassemble it. When an unfamiliar person sees the anti-theft screw and has no tools, most of them will give up the disassembly. Then the anti-theft screw will have a certain anti-theft effect.
3. For people who don't understand very well, ordinary anti-theft screws are of no use, because many anti-theft screws now have certain specifications and standards, such as plum belt anti-theft screws, hexagonal column anti-theft screws. These commonly used anti-theft screws are sold on the market with disassembly tools. So I know that some will go to the hardware market to purchase tools for disassembly. So for this situation, how should the anti-theft screw be burglarproof? ?
Since ordinary anti-theft screws can be purchased on the market to get disassembled tools, then we only need to design new anti-theft screws, there is no corresponding disassembly tool on the market, then the anti-theft screws will have a certain anti-theft effect. Because the removal tool cannot be purchased, the cost of customization is high. Most people will give up disassembly after seeing it, and it will play an anti-disassembly effect.
So from the above analysis we can see. Anti-theft screws are not omnipotent, but they can also prevent some people from disassembling. So is there any use of anti-theft screws? Still benevolent see benevolence, wise see wisdom. When customizing anti-theft screws, understand the customer base and understand the market industry to decide whether to use anti-theft screws.
Expansion screws are generally referred to as metal expansion screws. The expansion screws are fixed by the wedge-shaped inclination to promote the expansion of the frictional grip force to achieve a fixed effect. The screw has a thread at one end and a taper at the end. The outer bread is a tin (some steel pipes), the iron cylinder (steel pipe) has a few cuts in half, and they are stuffed together into the hole in the wall, then the nut is locked, the nut is pulled outward, and the taper is pulled into the iron cylinder. The iron cylinder is opened, so it is tightly fixed on the wall, and is generally used for fastening the fence, awning, air conditioner and the like on cement, brick and the like. However, its fixing is not very reliable. If the load has a large vibration, looseness may occur, so it is not recommended to install a ceiling fan.
Bolted composite cable bracket
The expansion screw is composed of a screw and an expansion tube, and the tail of the screw is conical, and the inner diameter of the cone is larger than the inner diameter of the expansion tube. When the nut is tightened, the screw moves outward, and the conical portion is moved by the axial movement of the thread, thereby forming a large positive pressure on the outer peripheral surface of the expansion tube, and the angle of the cone is small, thereby making the wall and the expansion tube Friction self-locking is formed between the cones and the fixing effect is achieved. For example, the Sanfeng composite cable bracket is through the wall.
Due to the small drilling hole and large pulling force, the expansion screw is flat after use. If it is not used, it can be removed at will, and the advantages of maintaining the wall surface are remarkable. It is widely used in various decoration occasions.
☆ Fasten air conditioners, water heaters, range hoods, etc.
☆ Fixed frameless balcony windows, security doors and windows, kitchen, bathroom components, etc.
☆ Ceiling screw fixing (combined with casing and cone cap)
☆ Other occasions that need to be fixed
Most carbon steel screws require a heat treatment process. After the heat treatment process, in addition to general quality inspection and control, there are some special quality inspections and controls. To build high-quality products, you need to master these points.
First, decarburization and carburizing
In the mass production process of heat treatment, whether it is the metallographic method or the microhardness method, it can only be a timed sampling test, because if all the measurements are taken, the time required is too long and the cost is high. Therefore, in order to judge the carbon control of the furnace, the heat treatment manufacturer can use spark detection and Rockwell hardness test as the preliminary judgment for decarburization and carburization. The spark detection is to quench the over-fired parts. On the grinder, gently grind from the surface and the inside to determine whether the surface and the core are the same. This requires the operation technician to have skilled experience and spark identification capabilities.
The carbon steel screw also has a Rockwell hardness test on one side of the hexagonal bolt. Generally, a hexagonal plane of the quenched part is first lightly polished with a sandpaper to measure the first Rockwell hardness, and then Then grind this surface on the grinder to about 0.5MM. Rockwell hardness is measured again. If the hardness values of the two are almost the same, it means that the screw fasteners are neither decarburized nor carburized. When the previous carbonity is lower than the subsequent carbon degree, the surface is off. Carbon, when the previous hardness is higher than the latter time, it indicates carburization, but in general, when the hardness difference is less than 5HRC, the decarburization or carburization of the parts is basically qualified when examined by metallographic method or microhardness method. Within the scope.
The sensitivity of hydrogen embrittlement increases as the strength of the fastener increases. For the externally threaded fasteners of 10.9 and above or the surface hardened self-tapping screws and the combination screws with hardened steel washers, the hydrogen removal treatment shall be carried out.
The hydrogen removal treatment is generally carried out in an oven or a tempering furnace at 190 to 230 ° C for 4 hours or more to diffuse hydrogen.
Threaded fasteners can be tightened by tightening on a special clamp to maintain the screw under a relatively constant stress, for 48 hours. After the loosening, the threaded fasteners will not break. This method is used as a method of checking for hydrogen embrittlement.
Hexagon socket screws are often used on machinery. They are mainly used for easy fastening, disassembly, and easy slipping. The Allen key is usually a 90° turn. The bent end is long and short. When using a short side to screw, Holding the long side can save a lot of force and can better tighten the screw. The long end has a round head (hexagonal cylinder like a sphere) and a flat head. The round head can be easily removed and removed. Some installation is inconvenient. The part of the lower wrench. The manufacturing cost of the outer hexagon is much lower than that of the inner hexagon. Its advantage is that the screw head (the position of the wrench is thinner than the inner hexagon), and some places are not replaced by the inner hexagon. In addition, the cost is low, and the power is low. Machines with low strength and low precision require less hexagon socket screws than external hexagons.
Hexagon socket screws are used in a wide range of small, small hardware, small electronic products, and electrical products. Mechanical equipment products, large to cars, ships, aircraft cannons. In short, Hexagon socket screws are mainly used in electronics, electrical appliances, electrical, electric power, chemical, water conservancy, mechanical equipment, furniture and other fields.
Hexagon socket head screw plating is generally referred to as iron hexagon socket screw plating, and stainless steel hexagon socket screws are rarely plated. Iron hexagonal screw plating is environmentally friendly and environmentally friendly. Hexagon screw environmental protection plating has environmentally friendly blue zinc, environmentally friendly color zinc, environmentally friendly nickel, environmentally friendly black zinc, environmentally friendly white zinc, environmentally friendly black nickel and so on. Hexagon socket screws are not environmentally friendly, such as white zinc, color zinc, black zinc, black nickel, white nickel, black, blue and white zinc.
Of course, there are some special electroplatings, which are more like Jun Green, Dacromet. If the stainless steel hexagon socket screw needs to be plated, it is also possible. However, in order to increase the salt spray time of the stainless steel hexagon socket screw, it is generally used to pass the plating passivation treatment. Stainless steel hexagon socket screws are sometimes required by customers. In order to make the product and the stainless steel hexagon socket screw the same color. The stainless steel screws are plated.
In the detection of threaded fasteners, it is not possible to simply refer to the manual for the hardness value and fold it into the strength value. There is a hardenability factor in between. Because the national standard GB3098.1 and the national standard GB3098.3 specify the arbitration hardness is measured at 1/2 radius of the cross section of the part. The tensile test specimen is also taken from the 1/2 radius. Because it is not excluded that the central portion of the part has a low hardness and a low strength portion.
In general, the hardenability of the material is good, and the hardness of the cross section of the screw can be evenly distributed. As long as the hardness is acceptable, the strength and guaranteed stress can also meet the requirements. However, when the hardenability of the material is poor, although the hardness is acceptable according to the inspection of the specified portion, the strength and the guaranteed stress often fail to meet the requirements. Especially when the surface hardness tends to the lower limit.
In order to control the strength and the guaranteed stress within the acceptable range, the lower limit of the hardness is often increased. For example, the hardness control range of 8.8 grades is 26~31HRC for M16 and below, 28~34HRC for M16 and above, and 36~39HRC for 10.9. Level 10.9 or above is another matter.
Third, tempering test
Bolts, screws and studs of class 8.8~12.9 shall be tempered according to the minimum tempering temperature in actual production and kept at 10 °C for 30 min. On the same sample, the difference between the average values of the three points before and after the test shall not exceed 20 HV.
The tempering test can check the incorrect operation due to insufficient quenching hardness and too low temperature tempering to barely reach the specified hardness range, and ensure the comprehensive mechanical properties of the parts. In particular, threaded fasteners made of low-carbon martensitic steel use low-temperature tempering. Although other mechanical properties can be achieved, the residual elongation fluctuates greatly when measured to ensure stress, much larger than 12.5 um. And sudden breakage can occur under certain conditions of use. In some automotive and construction bolts, sudden breakage has occurred. This can be reduced by tempering with a minimum tempering temperature. However, special caution should be taken when manufacturing 10.9 bolts from low carbon martensitic steel.
Square head bolts, hexagon bolts, carriage bolts, joint bolts, stud bolts, single head bolts, anchor bolts, hexagon socket bolts, iron tower bolts, U-bolts, flange bolts, T-bolts, steel bolts, Connecting sub-grid bolts, high-strength bolts, anti-theft bolts, ball studs, ball studs, flat head bolts, B7 bolts, guardrail bolts, bolt bolts with bolts, bolts with holes, hook bolts, special bolts, countersunk bolts , slotted bolts, neck bolts, plastic bolts, nylon bolts, stainless steel bolts, ultra-short bolts, thin bolts, reverse bolts, welded bolts, adjusting bolts, countersunk bolts, reamed bolts, hexagonal recess bolts, Full-bolt bolts, fishtail bolts, wall bolts, threaded high-iron bolts, and other bolts.