Enhanced Resistance to Delayed Cracking in Deep-drawn Lean Duplex Stainless Steel: the Role of Residual Stress

Abstract

The delayed cracking behavior of deep-drawn lean duplex stainless steel (LDSS) was investigated, and compared with that of conventional metastable austenitic stainless steels (MASS). Hydrogen charging was performed by electrochemical method, and the hydrogen-charged specimens were subjected to the slow-strain-rate test. Fractures occurred along the phase boundaries in the LDSS, whereas the MASS specimens showed typical intergranular fractures after the hydrogen charging. In particular, the LDSS exhibited a superior limiting drawing ratio in spite of the large amount of internal hydrogen as well as high sensitivity to hydrogen embrittlement. The high resistance to delayed cracking originated from the relatively lower residual stress generated during the deep drawing process. This is a consequence of the suppression of martensitic transformation in the LDSS, due to Mn partitioning.