The Study Of Multi-element Low Alloy Wear Resistant Cast Steel

In the subject, we study the effect of the alloys on the microstructure and mechanical property of low alloy wear-resistant cast steel systematically and synthetically, by means of the orthogonal test. The result shows that, if the alloys C, Si, Mn, Mo are arranged rationally, the steel's microstructure can be bainite mostly in the condition of air continuous cooling and a wide range of component.On the other hand, the more C, Mn in steel, the hardness higher, impact toughness lower, and Mn is more effective than C. The effect of Si and Mo on the steel's mechanical property is less; the steel gets the best mechanical property when they are in middle content in the study. The alloys C, Si Mn should be in their middle level, Mo in its low level if we want to develop steel with high strength and impact toughness, good anti-wear property, in consideration of the steel's cost at the same time.The experiment of heat treatment process shows that with the austenitizing temperature increasing, the hardness increases firstly and begins to decrease in some temperature. Though the temperature in which the steel get the highest hardness is deferent, all get it in the temperature between 850℃ to 910℃, and the difference of the same sample's hardness is small in the range.After austenizing and air-cooling, the microstructure of the sample is smaller and more homogeneous; the crystal boundary disappears comparing with samples ascast. The microstructure is coarser and gets more lamella-like structure and retained austenite when the austenitizing temperature is too high. There is some ferrite and carbide in the microstructure when the austenitizing temperature is too low, and so the hardness and impact toughness lowers intensively.The steel should be tempered in lower temperature, and the temperature must be lower than 250 "C.Test of some samples shows that the kind of steel has good harden ability. In consideration of the big space between the austenitizing temperatures, the steel can be stable to apply practically, and adapt to make wear-resistant parts with big size.The study of toughness mechanism shows that the hardness and impact toughness is both higher when the steel's matrix is the compound of lower bainite and martensite, or lower bainite and austenite.Flat plane scanning the alloys Si, Mn, Mo, Cr with spectrometer shows that Mo enriches on the boundary of original austenite and the edge of bainite beam with different vector, Cr on the interface of bainite and retained austenite, Si in retained austenite, Mn mostly on the interface of bainite and retained austenite, and some in retained austenite. They affect bainitic structure and transformation kinetics by influencing the diffusion of carbon in their own manner. The optimistic component is that the content of Si must be defined strictly; the rational arrangement of Mn and Cr can replace Mo as to their effect in steel in order to lower the steel's cost.With impact load of 1 Okg/cm2,15kg/cm2 and abrasive particle, the abrasive test of some samples and high-Cr white cast iron indicates that, the anti-wear property of sample y-2 we studied is near to high-Cr white cast iron when impact load is 1 Okg/cm2, the anti-wear property increases when impact load is 15kg/cm , and is better than high-Cr white cast iron.According to the achievement of the subject, adjusting the chemical constitution and heat treatment process rationally, the low alloy wear-resistant cast steel we studied can completely replace the classical wear-resistant materials which have broad application in industry at the present time, when the impact load is in the middle level.