焊接热循环对09MnNiDR钢热影响区低温韧性的影响

利用Gleeble-3800研究了焊接热循环对09MnNiDR钢焊接热影响区粗晶区（CGHAZ）和中间临界再热粗晶区(IRCGHAZ)低温韧性的影响. 结果表明，热输入为15 kJ/cm、层间温度为150 ℃时，CGHAZ组织形态为板条状马氏体+下贝氏体，下贝氏体的存在限制了马氏体的生长，提高了低温韧性，而IRCGHAZ继续保持了CGHAZ的组织. ?70 ℃冲击试验中，IRCGHAZ相比于CGHAZ具有较好的低温冲击韧性，热输入为15 kJ/cm、层间温度为150 ℃时，冲击吸收能量最高为65 J. 根据热模拟结果，采用焊接热输入15 ~ 22 J/cm、层间温度为150 ℃的工艺参数对09MnNiDR钢进行焊接，?70 ℃冲击试验中热影响区冲击吸收能量值为101 J，冲击断口存在大量的等轴韧窝，具有较好的低温韧性；?70 ℃拉伸试验屈服强度为477 MPa、抗拉强度607 MPa、断后伸长率为28.5%，表现出较好的强度和塑性；硬度试验结果表明母材、焊缝和热影响区硬度依次增大，且没有软化现象.

Effect of weld thermal cycle on low temperature toughness of 09MnNiDR steel heat affected zone

The effect of welding heat cycle on low temperature toughness of the coarse-grained heat affected zone (CGHAZ) and inter-critically reheated coarse-grained heat affected zone (IRCGHAZ) of 09MnNiDR steel was studied by Gleeble-3800. The results show that when the heat input is 15 kJ/cm and the interpass temperature is 150 ℃, the microstructure of CGHAZ is lath martensite and lower bainite. The lower bainite restricts the growth of martensite and improves the low temperature toughness. While IRCGHAZ is continue to maintain the microstructure of CGHAZ. In the impact test at ?70 ℃, IRCGHAZ has the better low-temperature impact toughness than CGHAZ. When the heat input is 15 kJ/cm and the interpass temperature is 150 ℃, the impact energy is the highest of 65 . According to the thermal simulation results, the 09MnNiDR steel was welded with the welding heat input of 15 ~22 J/cm and interpass temperature of 150 ℃, the impact energy of heat-affected zone is 101 J at ?70 ℃, and the fracture morphology has a large number of isometric dimples, which has good low-temperature toughness. In the tensile test at ?70 ℃, the yield strength is 477 MPa, the tensile strength is 607 MPa, and the elongation is 28.5%, showing the better strength and plasticity. Hardness test results show that the hardness of base metal, weld and heat affected zone increase successively, and there is no softening phenomenon.