THE ROLE OF MICROSTRUCTURES AND THE DIFFUSION OF HYDROGEN IN A PLAIN CARBON EUTECTOID STEEL FOR PRESSURE VESSELS

An electrochemical technique was used to measure the room temperature diffusivity and trapping of hydrogen in a 0.82%C steel for chemical pressure vessels in two micro structural conditions (a) the cold worked pearlitic state and (b) the hardened and tempered state. Trapping of hydrogen occurs in both structures but with more traps in the cold worked structure. Base on experimental results and observation, different hydrogen retention (trapping) behavior operates in the two structures. It was also found that patented and cold worked steels are much less susceptible to hydrogen induced embrittlement than similar steels in the hardened and tempered condition.