Effect of PWHT on microstructure and mechanical properties of Sanicro25/G115 hetero-steel welded joint

doi:10.13251/j.issn.0254-6051.2024.11.027

Abstract

Abstract: Sanicro25/G115 hetero-steel welded joint was prepared by using gas tungsten arc welding (GTAW), then the microstructure and mechanical properties of the joints as-welded, tempered at 760 ℃ and tempered at 780 ℃ were investigated, respectively, by means of optical microscope, scanning electron microscope and tensile testing machine. The results show that the microstructure of base metal and heat-affected zone (HAZ) at the Sanicro25 steel side is austenite with precipitated phase. The welding seam has a cellular dendritic morphology, and the HAZ and base metal at the G115 steel side are tempered martensite. After post-weld heat treatment (PWHT), the number of precipitated phases in CGHAZ, FGHAZ and base metal of the G115 steel side increases, and M₂₃C₆ and MX precipitated phases are distributed in the prior austenite grain boundary and martensitic lath boundary. Under tensile test at room temperature, quasi-cleavage brittle fracture occurs in the joint as-welded, and ductile fracture occurs in the joints tempered at 760 ℃ and 780 ℃. The rupture position is transferred from the welding seam to the FGHAZ at the G115 steel side. Under 650 ℃ tensile test, the joints under different states all show ductile fracture, and the rupture position is transferred from G115 steel side base metal to G115 steel side FGHAZ. It is recommended that the PWHT temperature should be controlled at 780 ℃.

Key words: Sanicro25 steel, G115 steel, hetero-steel welded joint, post-weld heat treatment (PWHT), microstructure, tensile properties

CLC Number:

Li Linping, Liu Yanrong, Yang Maohong, Du Jinfeng, Zhang Zheng. Effect of PWHT on microstructure and mechanical properties of Sanicro25/G115 hetero-steel welded joint[J]. Heat Treatment of Metals, 2024, 49(11): 178-184.

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