Cracking Causes of Austenitic Stainless Steel Head in an Ethylene Glycol Unit and Preventive Measures

The cracking causes of austenitic stainless steel heads in an ethylene glycol unit were tested by nondestructive testing, metallography, hardness and ferrite content inspection, and the countermeasures were put forward. The results show that the cracking from of the stainless steel heads was transgranular stress corrosion cracking. After cold forming, the heads contained a large amount of deformation induced martensite, and the hardness was greatly increased. Under the joint action of welding residual stress and cold forming residual stress, the chloride stress corrosion cracking was caused in the heads. The weak acidic environment containing acetic acid and formic acid promoted the cracking significantly. It was suggested that the head after forming should be treated by solid solution treatment to eliminate the effect of work hardening.