5Cr9Si3钢的高温变形行为及流变应力异常变化机理

Hot deformation behavior and flow-stress anomaly of 5Cr9Si3 valve steel at elevated temperatures

通过不同热加工参数下的热压缩试验,研究了新型阀门钢5Cr9Si3的高温变形行为.5Cr9Si3钢在850-900℃和1000-1100℃温度区间内峰值应力分别随温度的升高而减小,而在900-1000℃温度区间内出现峰值应力随温度升高而增大的异常现象.进一步的微观组织及相结构演化分析表明：5Cr9Si3钢在900-1000℃温度区间内发生了由铁素体向奥氏体的转变,产生奥氏体相变强化;同时,随着变形温度的提高,碳化物的回溶造成碳元素和铬元素对5Cr9Si3基体固溶强化效果增强.相变强化和固溶强化是导致5Cr9Si3在900-1000℃温度区间内流变应力异常变化的主要原因.

The hot deformation behavior of 5Cr9Si3 valve steel was investigated by hot working simulation test at different hot working parameters. When the deformation temperature increases from 850 to 900 ℃ or from 1000 to 1100 ℃, the peak stress decreases ; but when the deformation temperature increases in the range of 900 to 1000 ℃, the peak stress rises. Further microstructural and phase transformation analyses show that a transformation from a-ferrite to austenite occurring within the deformation temperature range from 900 ℃ to 1000 ℃ causes austenite phase transformation strengthening, indueing the increasing of hot deformation resistance. Al- so, with the increasing of deformation temperature, the dissolution of carbides leads to solution strengthening for the matrix. Thus, phase transformation strengthening and solution strengthening at elevated temperatures are the main reason for the abnormal variation of flow stress for 5Cr9Si3 valve steel.