The sensitivity of hydrogen embrittlement increa […]
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.