Q&P工艺对1 800 MPa新型热成形钢微观组织和力学性能的影响

Influence of Quenching and Partitioning Process on Microstructure and Mechanical Properties of a Novel 1 800 MPa Hot Stamping Steel

现阶段热冲压成形钢一直存在塑性差、冲击韧性低、弯曲吸能有限等潜在问题,需要采用一些新兴的技术来提高其塑韧性,使其更好地服役于车身轻量化。采用盐浴的方式对1800MPa新型热冲压成形钢进行一步Q&P热处理,研究淬火温度、配分时间和配分温度对热冲压成形钢微观组织和力学性能的影响,并通过XRD,EBSD研究残余奥氏体的含量与分布以及残余奥氏体的含碳量,得到最佳热处理工艺参数。研究结果表明:当配分温度一定时,随着配分时间的延长,试样的抗拉强度和屈服强度呈现下降趋势,而伸长率呈现增加的趋势。在230℃配分30s时,试验钢的综合力学性能达到最佳,其抗拉强度、伸长率和强塑积分别达到2 034 MPa、10.2%和20 747 MPa·%;相比直接淬火分别提高9.5%、73.5%和90.0%。在保持超高强度的同时,塑韧性得到显著提高,满足汽车用钢要求,能够更好地服役于汽车轻量化制造。

At present,hot stamping forming steel has some potential problems,such as poor plasticity,low impact toughness,limited bending energy absorption,which need to be sloved by some new technologies to make it serve the automobile lightweigh better.So microstructure and mechanical properties of a novel 1 800 MPa hot stamping steel carried out one step method quenching and partitioning process are investigated.Quenching temperature,partitioning temperature and partitioning time are controlled by salt bath.What's more,the content and distribution of retained austenite are observed via XRD and EBSD and carbon content in retained austenite is calculated.It is found that when the partitioning temperature is constant,the tensile strength and yield strength of the specimens decrease with the increase of the partitioning time,while the elongation increases,and when the partitioning temperature and the partitioning time are 230℃and 30 s respectively,the comprehensive mechanical properties of the experimental steel are best,the tensile strength is up to 2 034 MPa,while the elongation is up to 10.2%,and the production of tensile strength and plasticity is 20 747 MPa·%.Compared to the direct quenching,the tensile strength,elongation and production of them are increased by 9.5%,73.5%,and 90%,respectively.This is that the plasticity and toughness have been significantly improved to meet the requirements of automotive steel,while maintaining ultrahigh strength,and this steel can better serve in automotive lightweight manufacturing.