典型热成形零件的显微组织及力学性能

Microstructure and mechanical properties of typical hot formed parts

基于某白车身典型热成形零件,系统研究了不同热成形零件本体的显微组织和力学性能。结果表明,典型热成形零件显微组织主要为板条状马氏体,个别零件局部区域存在少量残留奥氏体组织,模内软区显微组织主要由铁素体、马氏体以及少量的贝氏体构成,马氏体无明显的板条状特征,且马氏体的比例相对较低。左前/后车门防撞梁脱碳层厚度分布在38.55~45.57μm,左前门防撞梁三点弯曲平均力值达6962 N,最大力值达9709 N;左后车门防撞梁平均力值达8740 N,最大力值达11392 N,三点弯曲后零件表面状态良好,且无裂纹产生,防撞梁性能满足整车安全碰撞测试要求。热成形零件本体平均维氏硬度分布在456~507 HV10;拉伸性能方面,屈服强度>1000 MPa,抗拉强度>1400 MPa,伸长率≥5.5%;软区测点维氏硬度分布在225~243 HV10,拉伸性能方面,屈服强度>470 MPa,抗拉强度>650 MPa,伸长率≥17%,零件性能均满足标准要求。

Microstructure and mechanical properties of different hot formed parts based on a body⁃in⁃white were systematically studied.The results show that the microstructure of the typical hot formed parts is mainly lath martensite,and some parts have residual austenite structure in local areas.The microstructure of the soft zone in the mold is mainly composed of ferrite,martensite and a small amount of bainite,where the martensite has no obvious lath characteristics and relatively low proportion.The decarburization layer thickness of the left front/rear door collision beam is distributed between 38.55⁃45.57μm.The average force value of the three⁃point bending of the left front door anti⁃collision beam is 6962 N,and the maximum force value is 9709 N;while the average force value of the left rear door anti⁃collision beam is 8740 N,and the maximum force value is 11392 N.The surface of the parts is in good condition and there are no cracks generate after three⁃point bending.The performance of the anti⁃collision beams meets the requirements of vehicle safety collision testing.For the typical hot formed parts,the average hardness distribution is 456⁃507 HV10,the yield strength is greater than 1000 MPa,the tensile strength is greater than 1400 MPa,and the elongation is≥5.5%.While in the soft zone,the hardness distribution is between 225⁃243 HV10,the yield strength is greater than 470 MPa,the tensile strength is greater than 650 MPa,and the elongation is≥17%.The performance of the parts meets the standard requirements.