The effects of post-weld aging and cryogenic treatment on self-fusion welded austenitic stainless steel

The effects of post-weld aging and cryogenic treatment on self-fusion welded austenitic stainless steel thick plates were investigated in the present work. The results showed that fusion zone microstructure consisted of austenite matrix and vermicular ferrite. Aging treatment promoted the decomposition of d-ferrite into s-ferrites as well as the precipi-tation of carbides. Isothermal martensitic transformation in the Tungsten Inert Gas Welding (TIG) specimen was induced by cryogenic treatment, and stacking faults were increased. The fusion zone microstructure of Electron Beam Welding (EBW) and Laser Welding (LW) was finer than that of TIG, with acicular ferrite distributed in the austenite matrix. A large number of twins were generated in the austenite matrix after LW. Cryo-genic treatment produced a large number of sub-grains in LW specimens, which was due to the entanglement and accumulation of dislocations in the vicinity of ferrite. Post-weld aging and cryogenic treatment have no influence on the strength of weldments with different welding methods while cryogenic treatment could improve the impact toughness of EBW and LW weldments by the extent of 7.4% and 8.8%, respectively. The aging treat-ment reduced the impact toughness by 49%, 33% and 15.5%, as well as the uniform elon-gation by 44%, 39% and 17% for TIG, EBW and LW, respectively. Aging treatment reduced the surface residual stress of TIG weldment by 58.8% in Y direction and 61.2% in X direc-tion. Cryogenic treatment at could also release the surface residual stress of TIG weldment by 36.8% in X direction and 16.3% in Y direction.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This study investigated the effects of post-weld aging and cryogenic treatment on self-fusion welded austenitic stainless steel thick plates. The results showed that different welding methods resulted in variations in the fusion zone microstructure, and both aging treatment and cryogenic treatment had an influence on the impact toughness and residual stress of the material.