微合金化热轧TRIP钢的相变行为研究

Study on transformation behavior of hot-rolled microalloyed TRIP steel

借助MMS-300热模拟实验机研究了变形方式、变形温度、变形速率、冷却速度以及缓冷结束温度对微合金化热轧TRIP钢相变行为的影响。结果表明,实验钢经单道次或双道次变形后,连续冷却转变曲线中的铁素体相变区域扩大,珠光体相变区域出现,马氏体相变区域消失。随着变形温度升高或冷却速度增大,铁素体相变开始温度Ar3、贝氏体相变开始温度Bs、贝氏体相变结束温度Bf均降低,扩散型相变受到抑制,中温相变得到加强。变形温度为850℃时,随着变形速率增大,Ar3、Bs、Bf均升高,组织中的铁素体含量增加,贝氏体含量减少。随着缓冷结束温度的降低,组织中的铁素体含量增加,铁素体晶粒长大,残余奥氏体含量先增加后减少。

Effects of deformation mode, deformation temperature, deformation rate, cooling rate and slow-cooling stop temperature on the transformation behavior of hot-rolled microalloyed TRIP steel were studied by means of MMS-300 thermomechanical simulator. The results show that for the samples subjected to the single or double pass deformation, ferrite transformation area is expanded, pearlite transformation area appears, and martensite transformation area disappears in the continuous cooling transformation diagrams. Transformation temperatures of Ar3, Bs and Bf decrease, diffusional transformation is prevented and intermediate temperature transformation is promoted with the increase of deformation temperature or cooling rate. When deformation temperature is 850 ℃, transformation temperatures of Ar3, Bs and Bf increase, the amount of ferrite also increases, and the amount of bainite decreases in the microstructure with the increase of deformation rate. With the decrease of slow-cooling stop temperature, ferrite amount increases, ferrite grains grow and retained austenite amount first increases and then decreases.