【摘要】 使用Gleeble-3500热模拟机对Q690D低合金高强钢进行了焊接热模拟，得到了一次和二次焊接热循环时不同峰值温度和冷却时间下的热影响区组织，并进行了显微组织观察、硬度测试、冲击性能测试及断口形貌分析。结果表明，一次焊接热循环时，随着焊接热循环峰值温度的增加，试样显微组织逐渐粗化，并由粒状贝氏体组织向上贝氏体和板条马氏体组织转变，硬度增加，冲击性能恶化。热循环峰值温度为900℃时，冲击吸收能量最大为78.95 J;峰值温度为1350℃时，冲击吸收能量最小值仅为17 J。冲击断口由延性断裂向解理断裂转变。在同一峰值温度下，随着冷却时间t_8/5的增加，试样硬度降低，而冲击吸收能量也随之降低。二次焊接热循环时，试样显微组织晶粒粗大，主要为板条马氏体，且硬度更高，冲击性能继续恶化，冲击吸收能量最低值仅为24.99 J,冲击断口主要为解理断离和准解理断裂，说明二次焊接热循环导致试样性能变差。更多还原

【Abstract】 Gleeble-3500 thermal simulator was used to simulate the welding heat of Q690D low alloy high strength steel, and the microstructure of the heat-affected zone under different peak temperatures and cooling times during the first and second welding thermal cycles was obtained. The microstructure observation, hardness test, impact property test and fracture morphology analysis were carried out. The result showed that in the first welding thermal cycle, with the increase of the peak temperature of the welding thermal cycle, microstructure of samples became gradually coarsened, the granular bainite transformed to upper bainite and lath martensite, the hardness increased and the impact performance deteriorated. When the thermal cycle peak temperature was 900 ℃, the maximum impact energy absorption was 78.95 J. When the peak temperature was 1 350 ℃, the minimum impact energy absorption was only 17 J. The impact fracture changed from ductile fracture to dissociative fracture. At the same peak temperature, as the cooling time t_8/5 increased, the hardness of the sample decreased and the impact performance deteriorated. In the second welding thermal cycle, microstructure of samples was coarse grain, mainly lath martensite, the hardness was higher and the impact performance continued to deteriorate. The lowest value of impact energy absorption was only 24.99 J, and the impact fracture was mainly cleavage fracture and quasi cleavage fracture, which indicated that the performance of samples deteriorated due to the second welding thermal cycle.更多还原