瞬时淬火工艺下低碳钢的组织演变规律

为了探究瞬时淬火工艺下低碳钢组织的演变规律,在热模拟机上对Q195和CR340试样进行了瞬时淬火处理.结果表明,瞬时淬火工艺初期得到马氏体+贝氏体+铁素体+未溶渗碳体的复杂混合组织;保温足够时间后,未溶渗碳体逐渐溶解使奥氏体平均碳浓度升高,奥氏体晶粒内碳浓度梯度减小,从而增加组织中马氏体相对量,最终得到全部板条马氏体组织.瞬时淬火工艺与传统淬火工艺相比可明显细化试验钢晶粒尺寸,提高升温速率对试验钢晶粒细化作用更明显.

Mechanism of Microstructure Evolution in Low Carbon Steels by Flash Processing

The mechanism of microstructure evolution of low carbon steels Q195 and CR340 during flash processing was studied by utilizing hot simulation device. The results indicated that complex microstructure consisting of martensite， bainite， ferrite and undissolved cementite was observed in the early stage of flash processing. The average concentration of carbon increases owing to the gradual dissolution of undissolved cementite， leading to the decrease of carbon concentration in austenite grain. Finally， the relative amount of martensite increases， and the microstructure is wholly comprised of lath martensite. Comparing with the traditional quenching process， flash processing can significantly refine grain size of experimental steels. Simultaneously， the role of grain refinement will become more obvious by increasing heating rate.