6缸柴油机高强度球墨铸铁曲轴的研制

Development of High Strength Ductile Cast Iron Crankshaft for a Six-Cylinder Diesel Engine

通过成分设计、凝固模拟、铁模覆砂铸造和等温正火复合新工艺应用,研制了一种高强度6缸柴油机球墨铸铁曲轴,分析了其内部质量、显微组织和力学性能.中试结果表明:采用复合新工艺研制的6缸球墨铸铁曲轴,其组织致密,没有内部铸造缺陷;与树脂砂铸造工艺相比,球墨铸铁曲轴的基体组织更均匀,共晶团数增多,晶粒显著细化,基体组织中索氏体比例大于90%,自由渗碳体比例小于1%.6缸球墨铸铁曲轴沿轴向不同位置的平均拉伸强度R_(m)、平均伸长率和基体平均硬度分别为946 MPa、5.6%和287 HB.负荷为2900N·m下,其弯曲疲劳试验加载次数达到10×10^(7)次而未出现裂纹和开裂现象,各项性能指标均超过L6R040301Q曲轴的技术要求,可代替现用的45锻钢和42CrMo锻钢曲轴,成本分别降低44.0%和66.2%.

A high strength six-cylinder ductile cast iron crankshaft was developed by the composition design,solidification simulation,application of new compound technique of sand coated iron mould and isothermal normalizing treatment.The microstructure,properties and internal soundness were analyzed.Pilot-scale test results show that internal quality of the ductile iron crankshaft casted by the new compound technique is better,and free from casting defects such as shrinkages porosity,slag inclusion,etc.Compared with the resin sand casting,the ductile cast iron crankshaft has a more uniform matrix microstructure,more eutectic cell numbers,finer grain size.The percentage of Sorbite is more than 90%with proeutectoid cementite less than 1%in the matrix microstructure of the ductile cast iron crankshaft.The average tensile strength R_(m),average elongation ratio and average hardness of the ductile cast iron crankshaft at different locations along axis reach 946MPa,5.6%and 287 HB,respectively.The numbers of loading cycles under 2900N·m bending fatigue load are up 10×10^(7)without occurring fatigue crack and cracking in the crankshaft bending fatigue test.All properties indexes of the ductile cast iron crankshaft exceeds the technology requirements of the L6R040301Q crankshaft,which can replace the current 45 steel and 42CrMo steel forging crankshaft with a cost reduction of 44.0%and 66.2%,respectively.