含铜时效钢焊接粗晶区组织与韧性分析

Coarse-grained heat affected zone microstructure and toughness of copper-bearing age-hardening steels

摘要: 研究了含铜时效钢焊接粗晶区的组织与韧性,并测定了含铜时效钢焊接粗晶区连续冷却转变曲线(SHCCT曲线)。结果表明,冷却速度对含铜时效钢焊接粗晶区的组织和韧性有显著影响。随着冷却速度的增加,粗晶区的组织由粗大的粒状贝氏体转变为细小的板条贝氏体;当t_8/5≤40s时,焊接粗晶区无塑性转变温度低于-50℃,可获得良好的低温韧性。当t_8/5>40s时,焊接粗晶区冲击韧度显著降低,大尺寸M-A组元的增多是导致含铜时效钢韧性恶化的重要原因。

Abstract: Microstructure and toughness of copper-bearing age hardening steel was studied and SHCCT curve was also measured.The result showed that cooling rate have a great effect on microstructure of coarse-grained zone and the tougness.Microstructure of coarse-grained was changed from thick granular-bainite to thin lath bainite with the increase of cooling rate.It can obtain good NDT results under -50℃ when the cooling time from 800℃ to 500℃ is lower than 40s.On the contrary,the toughness of coarse-grain zone was decrease greatly because of the increase mount of M-A island which was considered to be the important reason leading to deteriorate of coarse-grain toughness.