Effect Of Quenching-Tempering Process And Alloying Elements On Structure And Mechanical Properties Of High Carbon Steel

Currently,there are many studies concerning the performance of high carbon steel in low temperature tempering at home and abroad,but fewer studies on its microstructure and properties in high temperature tempering.In order to meet product performance requirements,the new high carbon steel needs to obtain a good combination of strength,plasticity and toughness by high temperature tempering.On the basis of current 1.05%C high carbon steel,firstly,the quenching and tempering process of base steel was discussed,and then this article takes steels whose carbon content and alloying elements(Mn?Mo and V)have been adjusted as experimental materials,and makes observations on the changes of micro structure and mechanical properties during the quenching and tempering process.The quenching temperature range was determined to be from 800? to 920?,and tempering temperature range was from 400? to 650?.The effect of carbon and alloying elements content on microstructure and mechanical properties of test steels were analyzed and discussed.The main conclusions of the research in this thesis are as follows:With increasing quenching temperature,the residual carbides of base steel gradually decreased and totally disappeared after quenched at 920?;the tensile strength gradually increased,while the yield strength,plasticity and toughness decreased.The change of strength and toughness mainly related to the breakdown of the martensite,the precipitation of carbon atoms which weakened the solid solution strengthening effect and the recrystallization of matrix when the steel tempered in the temperature range of 400??650?.The Acm of test steels dropped with the decreased carbon content.As the quenching temperature rises,the tensile strength of 08C?10C steel gradually increased,and yield strength decreased,the strength of 07C steel,however,was almost invariant.At the same quenching temperature,the strength of test steel was elevated with the increase of carbon content.In tempering experiments,the tensile strength and yield strength increased,the percentage reduction of area decreased with the increase of carbon content when the tempering temperatures are the same.The strength has a strong connection with carbon content due to the solution strengthening of carbon atoms.The addition of alloying elements has the obvious function of improving the strength of test steels.Mn caused more uneven carbides distribution than base steel.In the same heat treatment condition,the tensile strength increased,the ductility and compact toughness decreased with increasing of Mn content.The carbides of steel with Mo addition are smaller than base steel and dispersively distributed.At the same quenching temperature,the addition of Mo leads to the increase of tensile strength and yield strength,but declining the plasticity and compact toughness.In tempering temperature range of 400??650?,Mo steel obtained higher tensile strength than base steel,but lower plasticity.The tensile strength and yield strength of V steel monotonically increased with increasing quenching temperature.At the same quenching temperature,the steel with V addition has higher strength,lower plasticity and toughness than base steel.Compare to base steel,the V steel has a slight increase in strength,but plasticity and compact toughness dropped significantly in tempering experiments.