Development and application of high strength complex phase steel HR680/800CP for automobile chassis
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摘要: 顺应汽车轻量化发展需求，综合考虑汽车底盘结构件成型工艺特点，采用低C-Si-Mn-Nb-Ti-Mo复合成分体系设计实现良好焊接性能、第二相析出强化效果及促进中温贝氏体相变。通过理论计算制定热轧控轧控冷工艺，按照精轧终轧温度890 ℃、卷取温度570 ℃及前段3/4层流冷却模式，实现奥氏体区轧制稳定性、主要发生贝氏体相变，成功开发了铁素体/贝氏体为主、屈服强度769 MPa、抗拉强度840 MPa、延伸率17.92%、扩孔率高达110%、具有良好凸缘翻边和扩孔性能的高强度复相钢HR680/800CP，并成功应用于某车型底盘控制臂和新能源电池包支架。Abstract: Considering lightweight requirement and forming process characteristics of chassis structural parts, a complex alloying system of C-Si-Mn-Nb-Ti-Mo elements had been designed in order to achieve a better performance of weldability, second phase precipitation and bainite transformation at intermediate temperature. Based on theoretically calculation, a TMCP process where FET and CT are set at 890 ℃ and 570 ℃ and uses laminar cooling mode front 3/4, had been developed. During the TMCP process stable rolling steps were within austenite phase zone, and ferrite and bainite transformation occurred upon cooling period during and after laminar process. As a result HR680/800CP was produced which is featured with well flanging and hole expansion property. Microstructure mainly consists of Ferrite/Bainite, and mechanical properties reaches yield strength 769 MPa, tensile strength 840 MPa, elongation 17.92%, hole expansion ratio up to 110%. This product has been successfully used for structure parts of chassis control arm and battery pack bracket in new energy automobile.
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图 1 铸坯挡风墙集中堆垛缓冷
Figure 1. Concentrated stacking and slow cooling of slab in windshield wall
图 5 HR680/800CP试验钢Z/Y/Z方向的IPF图
(a) IPF-Z; (b) IPF-Y; (c) IPF-X
Figure 5. IPF diagram of developed HR680/800CP in Z/Y/Z direction
图 7 HR680/800CP应用零件
Figure 7. Application parts of HR680/800CP (a) Control arm, (b) battery pack bracket
表 1 HR680/800CP典型化学成分
Table 1. Typical chemical composition of HR680/800CP
% C Si Mn P S Als Al Nb Ti Mo N 0.07 0.13 1.68 0.011 0.001 0.029 0.030 0.049 0.11 0.11 0.0030 
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表 2 热轧工艺典型关键参数
Table 2. Key parameters of hot rolling process
加热温
度/ ℃在炉时
间/min粗轧道次
R1+R2中间坯
厚度/mmR2出口
温度/ ℃精轧入口
温度/ ℃终轧温度
均值/ ℃卷取温度
均值/ ℃层流冷却
方式凸度平均
值/μm1260 209 3+5 44 1080 1042 888 574 前段3/4
冷却40
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表 3 HR680/800CP力学性能
Table 3. Mechanical properties of developed HR680/800CP
项目 屈服强度Rp0.2/MPa 抗拉强度Rm/MPa 断后伸长率A/% 扩孔率λ/% 标准要求 680～830 800～980 ≥11 未要求 实测 769 840 17.92 110 注：轧向 L0=80 mm，b0=20 mm标样。
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