Q960E焊接粗晶区组织的再热脆化与软化分析

Analysis of reheat embrittlement and softening of coarsegrained zone of Q960E welding joint

为了精确获得不同温度梯度条件下焊接热影响区的组织和性能,采用焊接热模拟的方式对一种低碳当量Q960E及其对比钢进行了两次模拟热循环试验,并获得了一次热模拟后的CGHAZ,以及二次热模拟后的未变粗晶热影响区(UA CGHAZ)、过临界粗晶热影响区(SCR CGHAZ)、临界粗晶热影响区(ICR CGHAZ)和亚临界粗晶热影响区(SR CGHAZ)的显微组织,开展了组织分析、冲击韧性测试和硬度表征.结果表明,低碳当量Q960E和高碳当量对比钢的ICR CGHAZ和SR CGHAZ均有再热脆化敏感性,在-40℃下对比钢的SR CGHAZ的冲击韧性低至9 J,其晶界点状和条状碳化物分布是再热脆化的主要原因;低碳当量Q960E的SR CGHAZ软化最为严重,其原因是细晶强化、位错强化和析出强化联合丧失造成的.

In order to accurately obtain the microstructure and properties of the welding heat affected zone under different temperature gradient conditions, two simulated thermal cycle tests were carried out on a low carbon equivalent Q960E and its comparative steel by using the welding thermal simulation method. And the microstructures of CGHAZ after the first thermal simulation, and UA CGHAZ, SCR CGHAZ, ICR CGHAZ and SR CGHAZ after the second thermal simulation were obtained. Microstructures were analyzed, impact toughness test and hardness characterization were carried out in this paper. Results showed that both ICR CGHAZ and SR CGHAZ of Q960E and comparative steel had reheat embrittlement sensitivity. The impact toughness of SR CGHAZ of comparative steel was as low as 9 J at-40 ℃. And the distribution of pointtype and strip-type carbides formed at the grain boundary was the main reason for reheating embrittlement. The softening of SR CGHAZ with low carbon equivalent Q960E is the most serious, which is caused by the combined loss of fine-grain strengthening, dislocation strengthening and precipitation strengthening.