18Cr-3Mn-1Ni-0.22N节镍型双相不锈钢热压缩再结晶行为研究

Study on the Hot Compression Recrystallization Behavior of 18Cr-3Mn-1Ni-0.22N Low Nickel Type Duplex Stainless Steel

采用物理模拟方法研究了18Cr-3Mn-1Ni-0.22N节镍型双相不锈钢在1123~1423 K/0.01~10 s^(-1)、变形量为70%条件下的热压缩变形行为。不锈钢的流变曲线在1223~1423 K/0.01~1 s^(-1)条件下发生了流变软化和二次硬化现象,且二次硬化随应变速率增至10 s^(-1)而减缓。动态再结晶组织演变主要受温度和变形量的影响,在1123 K/0.01~10 s^(-1)变形时主要发生在铁素体相,而在1323 K/0.01~10 s^(-1)变形时主要发生在奥氏体相。不同应变速率条件下,1123 K变形时不锈钢发生动态软化的程度最大,并随温度升至1223 K时应力降幅较快。不同温度下1 s^(-1)变形时不锈钢的软化程度最差,0.1 s^(-1)且高于1223 K变形时不锈钢的软化程度最好。当应变速率一定时,再结晶临界应变随温度升高呈先增加后下降趋势。建立了0.2~1.2真应变条件下功率耗散系数η与失稳因子ξ的3D热加工图。随应变的增大,η>0.3的区域逐渐从1300~1400 K/0.01 s^(-1)向1300~1400 K/10 s^(-1)扩大,ξ>0的安全区域集中在高温区。预测热加工的最佳参数范围为T=1280~1423 K,ε=0.033~0.326 s^(-1),功率耗散系数η=0.39~0.44。

Aphysical simulation method was used to study the hot compression behavior of 18Cr-3Mn-1Ni-0.22N low nickel type duplex stainless steel(DSS)in the deformation conditions of 1123-1423 K/0.01-10 s^(-1)with deformation amount of 70%.The flow curves of stainless steel exhibited the occurrence of deformation softening and secondary hardening in the deformation conditions of 1223-1423 K/0.01-1 s^(-1),and the extent of secondary hardening slowed down with strain rate increases to 10 s^(-1).The deformation microstructure evolution of dynamic recrystallization(DRX)was mainly affected by deformation temperature and strain ratio,which mainly occurred on ferrite phase deformed at 1123 K/0.01-10 s^(-1),while on austenite phase deformed at 1323 K/0.01-10 s^(-1).The maximum effect of dynamic softening was achieved deformed at 1123 K,and then the stress decreased rapidly with increasing temperature to 1223 K under strain rates of 0.01-10 s^(-1).The worst softening degree for the specimens deformed at 1 s^(-1)was obtained under different deformation temperatures,and the best softening degree was achieved when the deformation conditions were at 0.1 s^(-1)and greater than 1223 K.The critical strains of DRX tend to increase first and then decrease with increasing temperature as the strain rate is constant.The 3D hot processing diagrams of power dissipation coefficient(η)and instability factor(ξ)with true strain of 0.2-1.2 were established.With the increase of strain,the zones withη>0.3 gradually expand from 1300-1400 K/0.01 s^(-1)to 1300-1400 K/10 s^(-1),and the safe hot working areas withξ>0 is concentrated in the high temperature ranges.The optimum parameters of hot working are in the deformation conditions of T=1280-1423 K andε·=0.033-0.326 s^(-1),and the corresponding values ofη=0.39-0.44.