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采用膨胀法并结合金相-硬度法,在Gleeble-1500D热模拟机上测定了Cr4钢的临界转变点Ac1,Ac3以及Ms点;测定了不同冷却速度下连续冷却时的膨胀曲线,得到了该材料的连续冷却转变曲线(CCT曲线);结合金相组织观察方法,研究了连续冷却过程中奥氏体转变过程及转变产物的组织形貌;测定了不同冷却速度下相转变后的硬度值。结果表明,随着冷却速度的增加,材料的硬度也越来越大。为大型支承辊热加工工艺过程微观组织模拟提供了重要的基础参数,同时也为大型支承辊的锻造及热加工工艺路线的制定提供了理论依据。
The critical transformation points Ac1, Ac3 and Ms of Cr4 steel were measured on the Gleeble-1500D thermal simulator by the dilatometry method and the metallography-hardness method. The expansion curves of the Cr4 steel at different cooling rates were measured and the results were obtained. The continuous cooling transformation curve (CCT curve) was obtained. The austenite transformation process and the morphology of the transformation product were investigated by metallographic observation. The hardness values after phase transformation were measured at different cooling rates. The results show that with the increase of cooling rate, the hardness of the material is also increasing. It provides an important basic parameter for the microstructure simulation of the hot rolling process of the large back-up roll, and also provides the theoretical basis for the forging of the large back-up roll and the formulation of the hot working process route.