铸钢机车车钩精密铸造工艺及其凝固组织研究

Process and Solidification Microstructure of Investment Casting Steel Locomotive Couplers

为获得致密组织和良好性能、防止产生裂纹,设计了精密铸造车钩的正交试验,确定了最优参数,即浇注温度为1570℃、型壳预热温度为425℃、浇注时间为29 s。通过铸造仿真分析了最优参数下铸件温度场、应力场对于缩孔缩松及裂纹形成的影响,同时通过KGT模型对铸件关键部位进行组织模拟。最后对试制车钩进行X射线探伤,未发现内部存在裂纹及孔隙,各部位金相组织与组织仿真结果基本一致,车钩经热处理后其平均抗拉强度可达1020 MPa。结果表明,正交优化后获得了合理的车钩铸造工艺参数,晶粒较细,性能高于标准要求。

In order to prevent cracks from forming in investment casting couplers and obtain dense microstructure and desirable performance,the optimum parameters for simulation orthogonal test of investment casting were determined as follows:pouring temperature of 1570℃,preheating temperature of 425℃and pouring time of 29 s.The influence of casting temperature field and stress field on formation of shrinkage porosity and crack under optimal parameters was analyzed through casting simulation.Meanwhile,key parts of castings were simulated by KGT model.Absence of internal cracks and pores is observed by X-ray detection,and the microstructure of corresponding parts is basically consistent with simulated ones.The average tensile strength of coupler after heat treatment can reach 1020 MPa.The results indicate that the casting parameters are reasonable after orthogonal optimization,and the grain is fine,of which the performance exceeds the railway standard requirements.