Ti+Nb处理超低碳BH钢奥氏体变形和铁素体变形动态再结晶规律研究

Study on Austenite Deformation and Ferrite Deformation Dynamic Recrystallizations of Ti+Nb Stabilized Ultra-low Carbon Bake Hardening Steel

在Gleeble-1500热模拟机上利用单道次压缩实验研究了Ti+Nb处理超低碳BH钢奥氏体变形和铁素体变形的流变行为和动态再结晶规律。结果表明,900℃变形时超低碳BH钢处于(γ+α)两相区,γ→α相变使得较软铁素体相越来越多,软化了变形金属,金属流动应力随之降低。700℃变形时,除了应变速率为0.1 s^(-1)时未发生动态再结晶,只发生了动态回复外,应变速率为1、10、40 s^(-1)时均发生了动态再结晶。变形温度从750℃升高到850℃,应变速率为0.1 s^(-1)和1 s^(-1)时基本上均未发生动态再结晶,只发生了动态回复,应变速率为10 s^(-1)和40 s^(-1)时均发生了动态再结晶的现象。Ti+Nb处理超低碳BH钢奥氏体变形时形变激活能为Q_(def)=131984 J·mol^(-1),奥氏体变形动态再结晶模型为Z=εexp(131984/(RT)),铁素体变形时形变激活能为Q_(def)=268995 J·mol^(-1),铁素体变形动态再结晶模型为Z=εexp(268995/(RT))。

The flow deformation behavior and dynamic recrystallizations of austenite deformation and ferrite deformation of Ti+Nb stabilized ultra-low carbon bake hardening steel were studied by single pass hot compression test using Gleeble-1500 thermal simulator.The results show that Ti+Nb stabilized ultra-low carbon bake hardening steel is in the dual phase region at deformation temperature of 900℃.The softening of deformation metal and decrease of flow stress are induced by more and more softer ferrite due to phase transformation of austenite to ferrite.The dynamic recrystallization occurs with the strain rates of 1 s^(-1),10 s^(-1)and 40 s^(-1)at deformation temperature of 700℃,while there is no dynamic recrystallization and only dynamic recovery occurs for the strain rate of 0.1 s^(-1).Only dynamic recovery occurs with the strain rates of 0.1 s^(-1)and 1 s^(-1)over a temperature range from 750℃to 850℃,while the dynamical recrystallization occurs with the strain rates of 10 s^(-1)and 40 s^(-1).The activation energy of austenite deformation of Ti+Nb stabilized ultra-low carbon bake hardening steel is Q_(def)=131984J·mol^(-1).The dynamic recrystallization model of austenite deformation is Z=εexp(131984/(RT)).The activation energy of ferrite deformation is Q_(def)=268995 J·mol^(-1).The dynamic recrystallization model of ferrite deformation is Z=εexp(268995/(RT))。