回火工艺对1200 MPa级贝氏体钢轨组织性能的影响

对贝氏体钢轨钢不同工艺回火后的组织和性能进行研究.结果表明,350℃回火4h及以上,贝氏体钢轨屈服强度大于1000 MPa,抗拉强度大于1200 MPa,伸长率和断面收缩率分别大于15％和45％,室温冲击功大于150 J；在450～550℃回火时,出现明显的回火脆性.金相显微镜和透射电子显微镜观察表明,贝氏体轨钢以粒状贝氏体组织为主,残留奥氏体在板条间以M-A岛状形式分布.不同回火温度及3％拉伸变形后试验贝氏体轨钢残留奥氏体的测定结果表明,350℃回火时的残留奥氏体机械稳定性最好.贝氏体钢轨的强韧性随回火温度的变化与残留奥氏体的机械稳定性密切相关.

Influence of temper technology on mechanical properties and microstructure of 1200 MPa bainitic rail steel

The influence of difference temper technologies on microstructure and mechanical behaviors of the bainitic steel was studied.The results show that the yield strength,ultimate tensile strength,elongation,reduction of area of the alloy are above 1000 MPa,1200 MPa,15% and 45%,respectively,when the bainitic steel is tempered at 350 ℃ for 4 h or longer.However,the steel appears obviously temper brittleness when the temper temperature is 450-550 ℃.TEM and optical observations show that the microstructure of the bainitic steel is composed of mainly granular bainite,and that the retained austenite is distributed as M-A island structure in lathes.The retained austenite in bainitic steel tempered at different temperatures and deformed by 3% stretching strain was tested.The results show that the mechanical stability of the retained austenite is the best when the steel is tempered at 350 ℃.The strength and toughness of the bainitic steel tempered with different technologies have a close relation to mechanical stability of the retained austenite.