Study On Microstructures And Properties Of Medium Chromium Alloy Cast Steel Roller

Based on medium chromium alloy cast steel for roller,the effect of heat treatment process on microstructures and properties of alloy cast steel was studied by the way of SEM,EDS,XRD and so on.In this paper,consider the different functions of alloy elements in steel, four kinds of alloy cast steel were designed and poured.Through work out the rational heat treatment process,improve and optimize the microstructures and properties of alloy cast steel and provide the support of theory and data for designing composition and heat treatment process.Results show that:(1) The process of argon blowing was effectual in cleaning steel throught facilitate growing and upward flowing of inclusion in liquid steel.(2)The four kinds of equilibrium phase diagram calculated by FactSage show that medium carbon steel had turn into the range of hypereutectoid steel.(3)Throught tested the properties of samples quenched at different austenitizing temperatures and holding times,Obtained the optimal austenitizing temperatures and holding times.(4)Tested and analysed microstructures and properties of samples tempered at different temperatures,knew that alloy element increased the tempering resistance of steel.The hardness showed a downward trend followed the increase of tempering temperature. Impact toughness increased significantly when tempered at high temperature.Tensile strength showed a downward trend followed the increase of tempering temperature.(5)Analysed 2# used XRD,obtained that retained austenite of quenched sample gradually increase followed the increase of austenitizing temperature,but carbon content had a little change.Followed the increase of tempering temperature, retained austenite of sample showed a downward trend as well as carbon content.With the same carbon content, the thermal fatigue properties of the material contained 5%-chromium is better, the thermal fatigue properties descend when the chromium content rise to 8%; chromium content in the same, the thermal fatigue properties of the material contained 0.5%-carbon is better, the thermal fatigue properties descend when the carbon content rise to 8%.Considering all the effects of chemical composition and heat treatment process on microstructures and propertiers of alloy cast steel, the optimum chemical compositions were: carbon 0.50%, silicon 0.68%, manganese 0.68%, chromium 5.00%, molybdenum 0.50%, nickel 0.40%, vanadium1.10%. The optimum heat treatment process should be: austenitizing temperature 960℃for holding time 50 minuter and oil quenching, tempering temperature 520℃for holding time 75 minuter and air cooling. The properties of materials after heat treatment are the hardness HRC 51.5,the impact toughness 11.9J/cm2, , the tensile strength 1564 MPa.