Study on Critical CTOD Property in Heat Affected Zone of C-Mn Microalloyed Steel

概要

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The critical Crack Tip Opening Displacement (CTOD) property in the Heat-Affected Zone (HAZ) was examined on 490^N/mm^2 class C-Mn microalloyed steel plate. As a result, the critical CTOD property of low Al content steel was found the most excellent. The temperature. at which the minimum critical CTOD value was 0.25 mm, was -84℃, whereas it was -26℃for the conventional Al content steel with carbon content of 0.09 mass%, and - 10 to 0℃ for other carbon content steels. The reason .for this is that the microstructure of HAZ in low Al content steel consisted of fine ferrite without Martensite-Austenite (M-A) constituent. In addition the deteriortaion of the critical CTOD property was observed when hard M-A constituent with high carbon content of over 1 mass% was present in HAZ. From these results, it seems that Al content affects the transformation behaviour during welding heat cycle, namely, reduction in Al content in the base metal promotes the diffusion of carbon atoms and the precipitation of carbide, resulting in fine ferrite microstructure without M-A constituent.
社団法人溶接学会の論文
1992-10-01