Development of High Strength Ductile Cast Iron Crankshaft for a Six-Cylinder Diesel Engine
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 nor-malizing 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 Rm,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 2 900 N·m bending fatigue load are up 10 × 107 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.
diesel enginehigh strength ductile cast iron crankshaftsand coated iron mould
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