Crack analysis of T23/12Cr1MoV dissimilar steel welded joints during PWHT in the water-wall of USC boiler

doi:10.13251/j.issn.0254-6051.2021.07.042

Abstract

Abstract: Macro and micro morphologies of cracks occurring in T23/12Cr1MoV dissimilar steel welded joint (DSWJ) during PWHT were analyzed, the microstructure and fracture morphology of the DSWJ were observed, and the hardness distribution across the DSWJ was tested. Based on the experimental results, the types and causes of cracks were discussed, and the measures to prevent cracks were proposed. The results show that the crack initiates at the weld toe of T23 steel side, then propagates along the grain boundaries of its coarse grain heat-affected zone (CGHAZ), which exhibit the characteristics of reheat crack. After PWHT, the hardness of HAZs on both sides of the WM in DSWJ obviously decreases. The formation of reheat crack is related to the precipitation of carbides at grain boundary which promotes the formation of pores in the CGHAZ of T23 steel side during tempering. Before PWHT an intermediate heat treatment performed at 550 ℃ for 1 h is beneficial to suppress reheat crack.

Key words: dissimilar steel welded joint, PWHT, cracks

CLC Number:

TG162.84

Yang Qingxu, Wang Xue, Ma Junpeng, Yang Chao. Crack analysis of T23/12Cr1MoV dissimilar steel welded joints during PWHT in the water-wall of USC boiler[J]. Heat Treatment of Metals, 2021, 46(7): 218-222.

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