Feeding Cored-wire And Heat Treatment Technology Research On ADI Camshaft Of Mini Car

In order to better meet the requirement of producing austempered ductileiron and form a set of technique in ductile iron camshaft manufacturing, firstly,the author detect the chemical composition of ductile iron camshaft:3.8~3.9Cwt.%,2.5~2.7Si wt.%,0.4~0.5Mn wt.%,1.1~1.26Cu wt.%,0.02Smaxwt.%,0.054Mgmaxwt.%,0.08Pmaxwt.%. Secondly, the author produce high qualityductile iron camshaft in wire injection process and pour-over process respectively.Comparison of results shows that wire injection process was superior inspheroidizing, spherical degree, size and quantity of nodular graphite to pour-over process. And the results are stable, the castings have a better mechanicalproperties.In this paper, The author introduces the theoretical basis for us to choose thetemperature and time in austempering. The author use the orthogonal test L9(34)to get a better process in producing ductile iron camshaft(as-cast microstructure:95%pearlite+free cementite and ferrite is less than5%and the level for two ofthe spheroidization) with the methods of injection process. In this experiment,temperature is the most important effect on the mechanical properties of ADIcamshaft. The author find that the best process of austenitizing temperature is850℃, and isothermal quenching is290℃for1hour.The microstructure of ADIcamshaft is lower bainite, retained austenite and graphite after the austempering.In the test, the tensile strength, elongation, and hardness rise with theincrease of austenitizing temperature (830℃-850℃). In the range of theexperimental temperature（290℃-350℃）, the hardness and the tensile strengthof ADI camshaft reduce with the increasing temperature, but the elongation ratiois contrary. In the study of holding time (within1h to2h) of austempering, withthe prolonging of the holding time, the tensile strength and hardness of ADIcamshaft slightly reduce, but the elongation ratio does not change significantly.With the same isothermal quenching process and equipment, the ductile iron will obtain better mechanical properties in the wire injection process than thepour-over process. Average wear rate of camshaft Produced by feeding cored-wire technology and pour-over technology is18.12mg/h,24.76mg/h.