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讨论了焊后热处理制度对Q690CFD粗晶区冲击韧性的影响,发现焊后热处理温度在500℃附近存在脆韧转变点。金相、SEM、能谱试验结果表明碳化物在原奥氏体晶界析出是导致脆韧转变的原因,并利用Thermo-calc计算了碳化物的析出规律,与试验结果符合很好。最终根据试验结果优化了首钢Q690CFD焊后热处理工艺。
The effect of postweld heat treatment regime on the impact toughness of Q690CFD coarse grain region was discussed. It was found that there was brittle-to-ductile transition near the post-weld heat treatment temperature of 500 ℃. The results of metallography, SEM and EDS show that the precipitation of carbides in the former austenite grain boundary is the cause of brittle-to-ductile transformation. The precipitation regularity of carbide is calculated by Thermo-calc, which is in good agreement with the experimental results. Finally, according to the test results optimized Shougang Q690CFD post-weld heat treatment process.