Study On Forming Technology And Microstructure And Properties Of Three Kinds Of Low Alloy Ultra-high Strengh Wear Resistant Steel

In this paper,three kinds of low alloy ultra high strength steel,which have been invented by independent design,named 1# steel,2# steel and 3# steel.Reasonable rolling forming technology and heat treatment process will be used.OM and SEM were used to observe the microcosmic of the three new steels structure.The mechanical properties of the three steels were tested by universal testing machine and hardness tester.The characteristic parameters of three high strength low alloy steel will be simulated by simulation software.At the same time,the wear resistance of the sample was characterized by the hardness and plasticity after heat treatment.The main results are as follows:Based on the characteristic parameters simulation of the three kinds of super high strength low alloy steel,the temperature of phase transformation point of various steel grades respectively,1# steel Ac1?770?,Bs?400?,Ms?110?;2# steel Ac1?810?,Bs?440?,Ms?87?;3# Steel Ac1?750?,Bs?430?,Ms?141?.Through an isothermal spheroidizing,two isothermal spheroidizing and normalizing plus isothermal spheroidizing of 1# steel by study the effect on the band structure in hot rolling process,found an isothermal spheroidizing and two isothermal spheroidizing can not completely eliminate the banded structure,and after the normalization process can to eliminate the banded structure,at the same time the spheroidizing annealing can obtain good microstructurs before quenching.Compared with the quenching and isothermal quenching process of 1# steel,it was found that after quenching at 820?,the microstructure of the sample was basically martensite,and the yield strength was 1200 MPa,the tensile strength was 1780 MPa.After 300? isothermal quenching,the microstructure of the sample was mixed by lower bainite and martensite,and the yield strength was 1220 MPa,the tensile strength was 1660 MPa.Compared with the mechanical properties of 1# steel after quenching and isothermal quenching,it was found that the strength of the sample after isothermal quenching is reduced,but the plasticity is improved,in the same temperature.Compared with 2# and 3# steel found that after isothermal quenching the tensile strength of 2# and 3# steel were respectively 1280 MPa and 1530 MPa,and the yield strength were 1052 MPa and 1227 MPa.At the same time,the microstructure of the 2# steel after isothermal quenching treatment was lower bainite,martensite,carbide and retained austenite,but the microstructure of 3# steel was mainly bainite and residual austenite.Through the analysis of the microstructure and properties of the three kinds of high strength steel,it was found that the comprehensive mechanical properties of 1# steel and 3# steel have reached the goal of experiment.The tensile strength is more than 1500 MPa and the yield strength is more than 1200 MPa.However,the mechanical properties of 1# steel was better than 3# steel and better meet the grinding machine steel ball,crusher jaw plate requirements.