Effect Of Alloying Elements On Microstructure And Wear Properties Of Low Temperature Bainite Steel

The excellent strength and toughness of low temperature bainitic steel make it have high research value and broad development prospects.The purpose of this paper is to discuss the effects of heat treatment process and alloying elements(carbon and vanadium)on the structure and properties of low temperature bainitic steel.The microstructures of the samples were observed and analyzed by OM,SEM,EBSD,XRD and EPMA.The experiment explored the influence of one-step bainite isothermal time on the phase transformation of experimental steel bainite,and compared the microstructure and mechanical properties of the experimental steel under the conditions of one-step bainite isothermal treatment,multi-step bainite isothermal treatment and deep cryogenic treatment.At the same time,the microstructure and impact abrasive wear properties of two sets of experimental steels with different carbon and vanadium contents were analyzed and compared under the same multi-step bainite isothermal conditions.The main results are as follows:1.Bainite transformation is incomplete transformation.With the increase of bainite isothermal time at 300 ?,the bainite content in the steel increases continuously.When the isothermal time reaches 5 hours,the bainite content does not increase significantly.2.After one-step bainite isothermal treatment and multi-step bainite isothermal treatment,the structure of the experimental steel is composed of blocky retained austenite,bainite ferrite and thin film retained austenite between bainite bundles.After multi-step bainite isothermal treatment,the sample has the best ductility and toughness.Its strength-elongation product reaches 19.66 GPa· % and U-shaped impact absorbed energy reaches 80 J.3.Compared with 0.4C experimental steel,the difference of carbon content between film retained austenite and blocky retained austenite is increased by0.177 wt.%.At the same time,the ductility and toughness of 0.3C experimental steelare improved,the strength-elongation product has increased by 30.6%,and the U-type impact absorbed energy has increased by 14 J.4.During the impact abrasive wear process,the TRIP effect occurred in both 0.3C experimental steel and 0.4C experimental steel.The surface hardness of 0.3C experimental steels increased by 127 HV1 on the basis of 5.7 % reduction of retained austenite content,while 0.4C experimental steels only increased by 63 HV1 with 6.5 %reduction of retained austenite content.This indicates that the retained austenite in the0.3C experimental steel is more stable,and the effect of surface hardening is more remarkable.