热冲压成形钢板BR1500HS淬火热—力—相变耦合规律数值模拟研究及应力影响参数优化

发布时间：2018-07-08 13:59

本文选题：BR1500HS钢板 + 淬火　；参考：《重庆理工大学》2017年硕士论文

【摘要】：在汽车制造业领域中,制件轻量化、高碰撞性能和安全性保障理念正不断推进,一种可淬火硼钢板热冲压成形新工艺已脱颖而出,该工艺实现了汽车轻量化,突破了超高强钢板传统冷冲压成形难的问题。在热冲压成形过程中,制件的高强度、高硬度性能主要取决于成形制件的最终马氏体含量。而热成形过程中制件发生相变主要集中于板料高温冲压成形后的淬火热处理工艺。在高强度钢板热成形生产中,温度场不仅影响淬火后制件的最终马氏体相变,同时由于温差与组织转变还会使应力场发生变化,制件最终性能是其热-力-相三场综合效果的反映。所以,对易变形、易产生冲压缺陷的壁薄结构复杂的大多汽车制件热冲压成形而言,研究超高强度刚淬火过程热-力-相变耦合规律具有实际意义!本文以热冲压成形钢板BR1500HS为研究对象,在热成形理论以及有限元求解方法分析基础上,建立了淬火热-力-相耦合数学模型和有限元求解模型;结合研究目的,专门针对BR1500HS热冲压成形的淬火过程进行了平板模具结构设计。对BR1500HS热成形钢板室温组织成分及相关性能进行物理试验探究与分析,同时对其进行不同加热温度下、不同冷却时间内的直接水淬实验。对水淬后的板料金相分析,研究加热温度与冷却速度对板料组织的影响规律。同时利用Deform对该板料在相同实验参数下的直接水淬热处理进行数值模拟探究,将马氏体相变模拟结果与水淬实验结果对比分析,论证了Deform对BR1500HS直接水淬相变模拟方法的正确性。其次,利用Deform对超高强度钢板热冲压成形过程中的淬火热-力-相耦合变化规律及淬火应力影响参数优化展开数值模拟研究与实验验证。先从直接水淬中相对简单的热-力-相变出发,对BR1500HS钢板直接水淬模拟进行不同加热温度下直接水淬过程模拟分析,找出温度场对相变场、相变场对应力场影响规律。再建立板料在平板模具中淬火的简化有限元模型,进行不同板料初始温度、不同模具初始温度以及不同冷却通道与模具之间传热系数下的数值模拟。得到了三种影响参数下的板料在模具中淬火的热-力-相变耦合规律。最后对模具中的淬火应力影响参数进行了优化分析,找出了既能保证成形制件最终高强度性能同时又具有低应力的最佳淬火工艺参数。最后通过平板模具淬火的实验验证了模拟得到的研究结果。
[Abstract]:In the field of automobile manufacturing, the concept of lightweight parts, high impact performance and safety guarantee is being promoted, and a new hot stamping process for quenched boron steel sheet has emerged, which has realized the lightweight of automobile. It breaks through the problem of traditional cold stamping forming of ultra high strength steel plate. In the process of hot stamping, the high strength and high hardness of the parts mainly depend on the final martensite content of the forming parts. In hot forming process, phase transformation mainly focuses on the quenching heat treatment process after high temperature stamping of sheet metal. In the hot forming production of high strength steel plate, temperature field not only affects the final martensite transformation of quenched parts, but also changes the stress field due to temperature difference and microstructure transformation. The final performance of the workpiece is the reflection of its hot-force-phase three-field comprehensive effect. Therefore, it is of practical significance to study the thermo-force-phase transformation coupling law of ultra-high strength rigid quenching process for the hot stamping forming of most automobile parts with complex wall and thin structure which is easy to deform and produce stamping defects. In this paper, based on the hot forming theory and finite element method analysis, a heat force-phase coupled mathematical model and a finite element solution model for hot stamping steel BR1500HS are established. The structure design of plate die is carried out specially for the quenching process of BR1500HS hot stamping forming. The microstructure and properties of BR1500HS hot-formed steel sheet at room temperature were investigated and analyzed by physical experiments. At the same time, the direct water quenching experiments were carried out at different heating temperature and different cooling time. The effect of heating temperature and cooling rate on the microstructure of sheet metal was studied by means of metallographic analysis. At the same time, the deform is used to simulate the direct water quenching heat treatment of the plate under the same experimental parameters. The results of martensite transformation simulation and water quenching experiment are compared and analyzed, and the correctness of the deform method for direct water quenching phase transformation simulation of BR1500HS is demonstrated. Secondly, the numerical simulation and experimental verification are carried out on the variation law of quenching heat-force-phase coupling and the optimization of quenching stress effect parameters during hot stamping process of ultra high strength steel plate by deform. Starting from the relatively simple thermo-force-phase transformation in direct water quenching, the direct water quenching process of BR1500HS steel plate was simulated and analyzed at different heating temperatures, and the effect of temperature field on phase transition field and the corresponding force field was found out. Then a simplified finite element model of sheet metal quenching in flat die was established. The numerical simulation was carried out under different initial temperature of sheet metal, initial temperature of die and heat transfer coefficient between different cooling channel and die. The thermo-force-phase transformation coupling law of three kinds of sheet metal quenched in die under three kinds of influence parameters has been obtained. Finally, the influence parameters of quenching stress in die are optimized, and the best quenching process parameters which can guarantee the final high strength and low stress of the forming parts are found out. Finally, the simulation results are verified by the plate die quenching experiment.
【学位授予单位】：重庆理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG306

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