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测试了特厚(80 mm)TMCP海工钢板E500模拟焊接粗晶区(coarse grained heat affected zone,CGHAZ)连续冷却相变曲线;采用扫描电镜(SEM)、示波冲击试验、电子背散射衍射(EBSD)等技术,研究CGHAZ以及后续再加热峰值温度t2p对其组织性能的影响。结果表明,CGHAZ的显微硬度值(HV10)、冲击功及大角度晶界(大于15°)分数均随着焊接热输入量E的增大而减小;E≤50 k J/cm,组织以细密板条贝氏体(LB)为主,不同位向的板条束之间存在大角度晶界,对裂纹扩展的阻碍作用强;随着E增大,组织逐渐转变成粗大粒状贝氏体(GB),GB中的亚晶界取向差为3°~15°,对裂纹扩展的阻碍作用减弱。t2p为750℃时,各种热输入条件的临界加热粗晶区(IRCGHAZ)均呈现脆性断裂,显微组织出现网状MA组元。E≤50 k J/cm,t2p高于850℃时,再加热粗晶区大角度晶界分数增加,冲击韧性得到显著改善,呈现韧性断裂。
The phase transition curve of continuous cooling of coarse grained heat affected zone (CGHAZ) was measured with a TMCP (80 mm) TMCP marine engineering steel plate. The microstructure and mechanical properties were investigated by scanning electron microscopy (SEM), oscillometric test, electron backscatter diffraction EBSD) and other techniques to study CGHAZ and subsequent reheating peak temperature t2p its organizational performance. The results show that the microhardness values (HV10), impact energy and large angle grain boundaries (greater than 15 °) of CGHAZ decrease with the increase of welding heat input E; E≤50 kJ / cm, The fine lath bainite (LB) is the dominant one. The large angle grain boundaries exist between the lamellar strands in different directions, which hinders the crack propagation. With the increase of E, the tissues gradually transform into coarse granular Belle Body (GB), GB in sub-grain boundary orientation difference of 3 ° ~ 15 °, the inhibition of crack growth weakened. At t2p of 750 ℃, the critical heating coarse grains (IRCGHAZ) at various heat input conditions showed brittle fracture, and the mesh MA elements appeared in the microstructure. When E≤50 kJ / cm, when t2p is higher than 850 ℃, the fraction of high-angle grain boundaries in the reheated coarse grains increases and the impact toughness is significantly improved, showing ductile fracture.