摘要
汽车轻量化与高安全性需求推动了高强韧双相钢的应用,但提高双相钢强度往往伴随着韧性的下降。为此,开发了1款1000 MPa级含Ti双相钢,旨在通过细化晶粒和缩小两相强度差异来提升其强韧性。研究结果表明,添加Ti元素后,设计钢成功引入了大量平均直径为8 nm的TiC粒子,使得铁素体晶粒尺寸从初始双相钢的3.2μm细化至1.7μm,同时马氏体形态也由初始双相钢的大尺寸块状转变为均匀细小的岛状。这得益于TiC的析出强化和细晶强化效果,该设计钢的屈服强度和抗拉强度相比初始双相钢有显著提升,分别由606 MPa和926 MPa提升至771 MPa和1028 MPa。此外,TiC粒子的引入不仅实现了晶粒细化,还有效降低了铁素体与马氏体之间的强度差异,提高了铁素体与马氏体之间的协调变形能力。尽管这在一定程度上降低了设计钢的均匀伸长率,但其更细致的微观结构和优异的两相协调变形能力促进了拉伸变形中应变的均匀分布,有效缓解了应力集中,显著抑制了裂纹的形成与扩展,从而提高了后均匀伸长率。因此,设计钢的总伸长率仍保持在16.2%,与初始双相钢相当。另外,设计钢细致的微观组织和优异的两相协调变形能力也有利于抑制弯曲变形过程中裂纹的形成和扩展,进而提升了弯曲韧性,使得弯曲角度极限从初始双相钢的75°提升至86°。该研究有助于对设计高强韧性双相钢提供一定的理论依据。
The demand for lightweight and high safety in automotive drives the requirement for dual-phase steels with high strength and toughness.However,increasing the strength of dual-phase steels is usually accompanied by the challenge of toughness reduction.A 1000 MPa grade Ti-bearing dual-phase steel was designed with the aim of improving toughness by grain refinement and reducing the strength difference between the ferrite and martensite.The results demonstrate that,after adding Ti,the designed steel successfully introduces numerous TiC particles with an average diameter of 8 nm,which fine the ferrite grain size from 3.2μm in the initial dual-phase steel to 1.7μm,and transform the martensitic morphology from large-size massive in the initial dual-phase steel to uniform and fine island-like.Owing to the precipitation strengthening and fine grain strengthening of TiC,the yield strength and ultimate tensile strength of the designed steel are significantly increased from 606 MPa and 926 MPa to 771 MPa and 1028 MPa,respectively,compared with the initial dual-phase steel.In addition,introducing TiC particles not only achieves grain refinement,but also effectively reduces the strength difference between ferrite and martensite,which improves the coordinated deformation ability between both phases.Although this reduces the uniform elongation of the design steel to a certain extent,its fine microstructure and excellent two-phase coordinated deformation ability promote the uniform strain distribution during tensile deformation,which effectively alleviates the stress concentration and significantly suppresses the crack formation and extension,thus increasing the post-uniform elongation.As a result,the total elongation of the designed steel remains at 16.2%,which is comparable to that of the initial dual-phase steel.In addition,the fine microstructure and excellent two-phase coordinated deformation of the design steel also contribute to the suppression of crack formation and propagation during bending deformation,which improves the bending toughness and increases the bending angle limit to 86°from 75°in the initial dual-phase steel.The result contributes to providing a certain theoretical basis for the design of high-strength and toughness dual-phase steels.
作者
王锦旭
钱玲
陶长虎
WANG Jinxu;QIAN Ling;TAO Changhu(Dongtai Branch,Jiangsu Union Technical Institute,Yancheng 224000,Jiangsu,China;Jiangsu Sheyang Secondary Specialized School,Yancheng 224000,Jiangsu,China)
出处
《钢铁》
北大核心
2025年第5期129-137,共9页
Iron and Steel
基金
江苏省教育科学规划重点课题资助项目(B/2023/02/89)。
关键词
双相钢
TiC粒子
细化晶粒
微观组织
力学性能
协调变形
韧性
裂纹
dual-phase steel
TiC particle
grain refinement
microstructure
mechanical property
coordinated deformation
toughness
crack
