退火工艺对Nb-V微合金化双相钢组织性能的影响

Effect of annealing process on microstructure and properties of Nb-V microalloyed dual phase steel

为了进一步提升双相钢性能、探究Nb-V元素复合添加对双相钢组织性能的影响,在实验室研发了Nb-V微合金化的冷轧双相钢。利用连退模拟试验机、扫描电镜等设备,系统地研究了退火温度和过时效温度对双相钢组织性能的影响。结果表明,抗拉强度和伸长率随着退火温度的升高变化不大,屈服强度在组织中铁素体含量明显减少后有显著提升;Nb、V元素的添加细化了组织,可以提高综合性能。随着过时效温度的升高,试验钢主要组织由起初低温时的淬火马氏体+回火马氏体变为高温时的粒状贝氏体,残余奥氏体比例也逐渐增大。高温过时效时,试验钢强度的降低主要由回火马氏体的软化造成;低温过时效时,V析出量的增加也对试验钢的强化起到了重要作用。

In order to further improve the properties of dual phase steel and explore the effect of Nb-V elements compound addition on the microstructure and properties of dual phase steel, a cold-rolled dual phase steel with Nb-V microalloying was developed in the laboratory. The effects of annealing temperature and over-aging temperature on the microstructure and properties of dual phase steel were systematically studied using equipment such as continuous annealing simulation tester and scanning electron microscope. The results show that tensile strength and elongation do not change much with the increase of annealing temperature, while the yield strength increases significantly after the ferrite content in microstructure significantly reducing. The addition of Nb and V elements refines the microstructure and can improve the overall performance. With the increase of over-aging temperature, the main microstructure of test steel changes from quenched martensite and tempered martensite at low temperature to granular bainite at high temperature, and the proportion of retained austenite also increases gradually. When over-aging at high temperature, the decrease of test steel strength is mainly caused by softening of tempered martensite, and when over-aging at low temperature, the increase of V precipitation also plays an important role in the strengthening of test steel.