高强钢热成形不同冷却速率力学性能研究

发布时间：2018-07-30 07:54

【摘要】：近些年,制造业技术不断进步,汽车行业的需求也不断提高,对零件的力学性能有了更高的要求,并且为了节约能源减少排放量开始越来越多地使用高强钢。但是由于超高强度钢冷冲压成形后强度可以达到1000MPa,这就导致超高强度钢冷冲压成形具有回弹大,零件精度低等问题。然而传统的冷冲压工艺在高强钢的成形过程中存在很多工艺问题,为了解决这些问题人们开始关注高强钢热成形。人们逐渐认识到通过不同的热成形工艺可以得到不同的组织,不同性能的零件,这样根据零件的不同要求设计不同的热成形工艺非常必要。本文从热成形的基本原理入手,通过改变模具的温度及成形工艺,探究模具温度及各种成形工艺对零件的力学性能的影响。本文以USibor1500(22MnB5)作为研究对象,针对模具温度,保压时间,冷却工艺设计了不同的实验方案。前期通过数值分析的方法做了初步的分析,后期进行了平模实验,并且观察了组织结构,研究了不同工艺不同拉伸速率下零件的力学性能。结果表明:逐渐升高模具的温度,板料冷却速率下降,零件微观组织中贝氏体含量增加,零件的抗拉强度降低,硬度降低,延展率增加。零件虽然牺牲了强度,但是获得了更好的变形和碰撞的能力。本文还根据采集温度的曲线,与温度模拟进行了对比,找到了较为准确的模拟方法,并且跟实际温度曲线做了对比。
[Abstract]:In recent years, with the development of manufacturing technology and the increasing demand of automobile industry, the mechanical properties of parts have higher requirements, and in order to save energy and reduce emissions, more and more high-strength steel has been used. However, the strength of ultra-high strength steel can reach 1000MPa after cold stamping, which leads to the problems of large springback and low precision of parts. However, the traditional cold stamping process has many problems in the forming process of high strength steel. In order to solve these problems, people begin to pay attention to the hot forming of high strength steel. People have come to realize that different parts with different structures and properties can be obtained by different hot forming processes, so it is necessary to design different hot forming processes according to different requirements of parts. Based on the basic principle of hot forming, the influence of die temperature and various forming processes on the mechanical properties of parts is investigated by changing the temperature and forming process of the die. In this paper, USibor1500 (22MnB5) is taken as the research object. Different experimental schemes are designed for mold temperature, pressure holding time and cooling process. The preliminary analysis was done by numerical analysis in the early stage, and the flat die experiment was carried out in the later stage, and the microstructure was observed, and the mechanical properties of the parts with different drawing rates were studied. The results show that the cooling rate of sheet metal decreases, the bainite content in the microstructure increases, the tensile strength decreases, the hardness decreases and the extension rate increases with increasing the die temperature. The parts sacrifice strength, but gain better ability to deform and collide. According to the curve of collecting temperature, this paper compares it with temperature simulation, finds a more accurate simulation method, and makes a comparison with the actual temperature curve.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG142.1

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