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对工程机械用Q550D钢进行不同热输入的焊接热模拟试验,研究其金相组织、硬度、冲击性能和冲击断口形貌。结果表明,模拟的粗晶区主要组织为板条贝氏体,当线能量超过20 kJ/cm时组织中还出现了少量粒状贝氏体。随着热输入的提高,原始奥氏体晶粒和贝氏体板条逐渐粗化;粗晶区的平均硬度值逐渐降低,当线能量为15 kJ/cm时粗晶区明显硬化,而当线能量达到30 kJ/cm时软化;冲击功逐渐降低,特别是当线能量超过20 J/cm时模拟的粗晶区冲击韧性严重恶化。
Welding heat simulation test of different heat input of Q550D steel for construction machinery was carried out to study its microstructure, hardness, impact performance and impact fracture appearance. The results show that the main structure of the simulated coarse grain zone is lath bainite. When the energy of the line exceeds 20 kJ / cm, a small amount of granular bainite appears in the microstructure. With the increase of heat input, the original austenite grains and bainite slab gradually roughened; the average hardness value of the coarse grain region gradually decreased, while the coarse grain region was significantly hardened when the line energy was 15 kJ / cm, The softening of the linear energy reaches 30 kJ / cm; the impact energy decreases gradually, especially when the energy of the wire exceeds 20 J / cm.