热轧低碳无碳化物贝氏体钢的组织性能  

On structure-property relationship in hot-rolled low-carbon carbide-free bainitic steel

作　　者：梁佳伟 杨达朋 周骏龙 易红亮[1,2] 王国栋 LIANG Jiawei;YANG Dapeng;ZHOU Junlong;YI Hongliang;WANG Guodong(State Key Laboratory of Rolling and Automation,Northeastern University,Shenyang 110819,Liaoning,China;Easyforming Materials Technology Co.,Ltd.,Suzhou 215123,Jiangsu,China)

机构地区：[1]东北大学轧制技术及连轧自动化国家重点实验室,辽宁沈阳110819 [2]育材堂(苏州)材料科技有限公司,江苏苏州215123

出　　处：《钢铁》2024年第4期127-135,共9页Iron and Steel

基　　金：国家自然科学基金资助项目(52101128);中国博士后科学基金资助项目(2022M710021)。

摘　　要：无碳化物贝氏体钢(carbide-free bainitic steel,CFB steel)由于存在精细的贝氏体微观结构和残余奥氏体结合,因此展现出良好的强塑性平衡。然而,这种优异的力学性能通常是添加高碳含量并结合额外的贝氏体等温处理来实现,这不仅恶化焊接性能,而且也不利于经济成本和生产效率。为了克服这种缺点,通过热轧后的卷曲冷却过程代替了传统的贝氏体等温处理,设计了2种热轧低碳CFB钢,其微观结构分别为铁素体+贝氏体(命名为FB钢)和完全的贝氏体(命名为B钢)。研究了这2种钢的微观结构和力学性能之间的关系。F-B钢的屈服强度、抗拉强度、伸长率和断裂应变分别为(575±8) MPa、(853±12) MPa、19.0%±0.1%和0.63±0.03。相对比F-B钢,B钢展现出稍低的伸长率,为14.7%±0.2%,而屈服强度、抗拉强度和断裂应变明显提高,分别为(772±11) MPa、(1 160±10) MPa和0.78±0.02。其中B钢展现出更高的屈服强度和抗拉强度主要归结于其完全的贝氏体结构,其可以实现类似于位错强化、细晶强化和第二相强化的作用。此外,进一步详细地研究了它们的变形与损伤行为。结果表明,F-B钢中由于存在铁素体和含量多且更稳定的残余奥氏体,其促进了更持久的加工硬化能力,这是其具有更高伸长率的关键。而B钢由于具有更均匀的微观结构和更低的碳含量,因此变形过程中有助于微观应变的分布均匀,这有利于抑制变形损伤的形成,从而促进断裂应变的提升。Carbide-free bainitic steel(CFB steel)exhibits a good balance of strength and ductility due to the presence of a fine bainite microstructure combined with residual austenite.However,these superior mechanical properties are usually achieved by adding a high carbon content in combination with additional bainitic isothermal treatment,which not only deteriorates the weldability,but also discourages economic costs and productivity.To overcome this drawback,instead of the conventional bainitic isothermal treatment,two hot rolled low carbon CFB steels with ferrite+bainite microstructures(refer as F-B steels)and complete bainite(refer as B steels)were designed by the curling process after hot rolling.The relationship between the microstructure and mechanical properties of these two steels was investigated.The yield strength,ultimate tensile strength,total elongation,and fracture strain of F-B steel are(575±8)MPa,(853±12)MPa,19.0%±0.1%and 0.63±0.03,respectively.Compared to F-B steel,B steel exhibits a lower total elongation of 14.7%±0.2%,while its yield strength,ultimate tensile strength,and fracture strain are significantly improved to(772±11)MPa,(1160±10)MPa,and 0.78±0.02,respectively.The higher yield strength and ultimate tensile strength exhibited by B steel are mainly attributed to the complete bainite structure,which can achieve effects similar to dislocation strengthening,fine grain strengthening and second-phase strengthening.Moreover,their deformation and damage behavior were further revealed and the related results showed that the presence of ferrite and more stable residual austenite in F-B steel contributes to the more durable work-hardening ability of F-B,which is the key to its higher total elongation.For B steel,a more homogeneous microstructure and lower carbon content result in better-coordinated deformation,which significantly inhibits the deformation damage formation and thus contributes to higher fracture strain.

关 键 词：无碳化物贝氏体钢 残余奥氏体 微观结构 力学性能 变形损伤 

分 类 号：TG142.1[一般工业技术—材料科学与工程] TG335.11[金属学及工艺—金属材料]