Influence of Microstructure in the Heat-Affected-Zone on the Reheat Cracking Susceptibility

概要

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Influence of microstructure in the Heat-Affected-Zone on the reheat cracking susceptibility was studied. Reheat cracking tests on H.T. 80 steel were carried out by means of ring type specimens and three point bending method. Influence of microstructure of synthetic HAZ at high temperature on the reheat treatment process was investigated by high temperature hardness measurements, X-ray analysis, atomic absorption spectrometry and scanning electron microscopic observation. As a result, the critical stress of martensitic structure specimens (water quenched) which is responsible for the reheat cracking was found to be generally double that of bainitic and ferritic structure specimens (air cooled). Carbides of A.C. specimens precipitated were mainly M_3C type carbides during the cooling process of synthetic heat treatment. But, the carbides of W.Q. specimens were precipitates of M_3C type and M_2C type carbides. M_2C type carbides were precipitated in the final reheat process. The precipitation of M_2C type carbides in the matrix affected greatly the reheat cracking susceptibility. It seems that the precipitation of M_2C type carbides during reheat process on W.Q. specimens is responsible for decreasing of the alloying elements concentration in the matrix, and for a good deformability of the matrix.
社団法人溶接学会の論文
1987-10-01