500 MPa级V-N 微合金化热冲压桥壳用钢的开发

采用OM、SEM和TEM对500 MPa级V-N微合金化热冲压桥壳用钢的组织与性能进行了研究。结果表明,其屈服强度、抗拉强度分别达到了373和544 MPa,断后伸长率达到25.5%,低温冲击性能优异,在-60 ℃时的冲击功达到了145 J。其显微组织主要为铁素体和少量珠光体的混合组织,其中,铁素体基体上存在大量球形析出物,该析出物在规格上分为尺寸为30～50 nm且能谱分析显示主要为VCN的大颗粒第二相和尺寸在20 nm以下且能谱分析显示主要为VC的小颗粒第二相。热冲压后,500 MPa级V-N微合金化热冲压桥壳用钢的屈服强度和抗拉强度分别达到305和450 MPa,屈服强度和抗拉强度的下降率分别控制在18.2%和17.3%。

Development of 500 MPa grade V-N microalloyed hot stamping axle housing steel

Microstructures and properties of 500 MPa grade V-N microalloyed hot stamped axle housing steel were analyzed by OM, SEM and TEM. The results showed that the yield strength, tensile strength, and elongation of the tested steel reached 373 MPa, 544 MPa, and 25.5%, respectively. The low-temperature impact energy at -60 ℃ reached 145 J. The microstructure of the tested steel was mainly a mixed structure of ferrite and a small amount of pearlite. There were a large number of precipitates on the ferrite matrix which were mainly spherical, there were two types of precipitates, and one was large particles with a size of 30-50 nm, the spectral analysis showed that it was VCN, and the other was small particles with a size below 20 nm, and the spectral analysis showed that it was VC. After hot stamping, the yield strength and tensile strength of the tested steel could reach 305 and 450 MPa, respectively, and decline rates of yield strength and tensile strength were controlled at 18.2% and 17.3%, respectively.