基于焊接热模拟的工程机械用高强钢热影响区组织和力学性能研究

Study on Microstructure and Mechanical Properties of HAZ of High Strength Steel for Engineering Machinery Based on Welding Thermal Simulation

以工程机械用高强钢Q890为研究对象,采用Gleeble-3800焊接热模拟试验机分别进行了不同t_(8/5)和峰值温度条件下的热模拟试验,并对热模拟试样的显微组织进行了观察,对冲击性能、硬度等力学性能进行了检测。结果表明,随着t_(8/5)的延长,热影响区粗晶区组织逐渐由板条马氏体转变为板条贝氏体、粒状贝氏体,原始奥氏体晶粒逐渐长大;冲击功先升高后降低,t_(8/5)为10 s时冲击性能最差,t_(8/5)为30 s时冲击性能最佳;硬度值逐渐降低,但降低幅度减小。模拟的热影响区粗晶区组织为粗大的板条马氏体,细晶区为细小贝氏体+板条马氏体混合组织,临界区为细小贝氏体组织和回火贝氏体的不均匀组织。随着峰值温度提高,冲击功和硬度值均是先升高后略有降低,峰值温度为950℃时冲击性能最佳,硬度最高。

Taking Q890 high strength steel for engineering machinery as research object, the welding thermal simulation tests with different t8/5 and peak temperatures were carried out based on Glecble-3800 machine. The microstructure of the thermal simulatad samples was observed, and the mechanical properties such as impact toughness and hardness were measured. The results show that with the prolongation of t8/5, the microstructure of CGHAZ gradually transforms from lath martensite into lath bainite and granular bainite, and the original anstenite grains also gradually grow. With the increase of t8/5, the impact energy increases firstly and then decreases, when t8/5 is 10 s, the impact performance is the worst, and when t8/5 is 30 s, the impact performance is the best. The hardness gradually decreases, and the decreasing speed slows down. The microstructure of the simulated HAZ is coarse lath martensite for CGHAZ, fine grain bainite and lath martensite for FGHAZ, and nonuniform microstructure of bainite and tempered bainite for ICHAZ. With the increase of peak temperature, the impact energy and the hardness both increase firstly and then decrease slightly. When the peak temperature is 950 ℃, the impact toughness is the best and the hardness is the highest.