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topic 10649

How to test for hydrogen embrittlement in hardened high tensile fastener


 

I had a posted an inquiry earlier [letter 9912] about hydrogen embrittlemnt, we are manufacturing high tensile hardened fastener zn plated gradr10.9. CAN ANYBODY TELL ME HOW TO CONDUCT TEST FOR HYDROGEN EMBRITTLEMENT after final process?

Vikas Kaushal
Magnus Steels P Ltd - MOHALI(chandigarh), INDIA


 

Pull the fastner apart in a tensile test rig. If it snaps at a lower force than an unplated one it is embrittled.

Martin Trigg-Hogarth
Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England


 

The answer given is incorrect. The proper way to test is to mount your samples in a threaded plate with either washers or another plate with a clearence hole in order to put the fastener under load. You should follow the recommended torque spec for the size and grade fastener you are testing and take it to at least 80% of the suggest max. We are trying to reach the beginning point of yeild strength of the fastener. Because hydrogen embrittlement can be a delay failure it is recommended that you keep the fasteners in the test fixture for 72 hours. You must revisit the test samples after each 24 hours and retorque them to the original value that they are torqued at the beginning. Beware, when a failure does occur under load it is not uncommon that the head of the fastener will become a projectile with potential for damage or injury. My background is 15 years in the fastener industry that includes 5 years working for Ford Motor in their fastener lab.

Jim Baker
Mid-States Bolt and Screw - Burton, Michigan


June 30, 2009

What is the most suitable hydrogen embrittlement test method for shear bolts made of EN 24 (ESR route) steel? It's tensile strength is 1250Mpa class but it is used for shear load transfer.( 60% of UTS)

P.N GOPAKUMAR
Quality control Engineer - Trivandrum, Kerala, INDIA



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