Research On The Microstructures And Properties Of HT350High Strength Gray Cast Iron

Gray cast iron could be more widespread application in high-strength structural parts ofautomobile owing to its better casting performance, low manufacturing cost, and thecharacteristics of the casting quality easy to control. But with the development of industrialtechnology, more and more high performance requirements are proposed to the performanceof cast iron in various fields, so we need through continuous research to preparing highperformance cast iron. Through inoculation treatment and adding alloying elements in castiron is one of the means for making high performance cast iron.In this article, we through changing the types of nucleating agent, inoculants additionamount and adding alloying elements Mo to influence the morphology of graphite, pearliteand primary austenitic microstructure, so as to improve the performance of the gray castiron.The effects of four different kinds of inoculants on the microscostructure,mechanicalproperties and the cutting processing performance of high strength gray cast iron afterinoculation treatment are studied. The results show that the graphite and the matrix ofpearlite microstructures of high strength gray cast iron after different inoculation treatmentsare different. The small, bended graphite and small lamellar-spaced matrix pearlite,thecomplex network frame structure primary austenite are obtained by ZrSiMn inoculation,therefore make the tensile strength, the matrix microhardness and the mechanicalperformance of the gray cast iron can be improved.In terms of the effects on raising themechanical properties of four different kinds inoculants from low to high as follows: ZrSiAl→75SiFe→ZrSi→ZrSiMn; According to comprehensive evaluation analysis about the areaof cutting force, tool wear, workpiece surface roughness after cutting and so on, we canconclude that in terms of the cutting processing performance, the effect of four differentkinds inoculants from low to high, in order: ZrSi→ZrSiMn→ZrSiAl→75SiFe.The modification changes the primary austenite transformation process of growth, notonly increase the amount of primary austenite, but also makes primary austenite in spacenetwork development.The network space of the primary austenite will limit the space of theeutectic transformation of gray cast iron, make the eutectic group size reduces, provide favorable conditions for obtain small bending of graphite.With the increasing of the modifieramount, the flake graphite of the experimental gray cast iron is finer and more bending, thelamellar spacing of the matrix pearlite is smaller, the framework of the primary austenite ismore complicated, so the higher mechanical properties of gray cast iron can be obtained.Thisthesis studies that when adding1.0wt.%JF-1inoculants for modification and adding0.25wt.%Mo alloy elements, the graphite of the gray cast iron is smaller and more bending, itsdistribution is more uniform, the pearlite spacing of the gray cast iron is the least, so themechanical performance of the gray cast iron is the best. After the modification process, thethermal fatigue resistance of gray cast iron can be improved, and the more modifier amount,the better the thermal fatigue resistance.