模具间隙对热冲压钢板BR1500HS性能影响研究

菜单

摘要在汽车上使用高强度硼锰钢板从而减少不必要的补强件，这样能有效地避免增加车身重量并且强度得到保证。但钢板抗拉和屈服强度提高，材料的变形抗力和回弹几率随之增加，不仅对加工设备提出了更高的要求，所以冷冲压工艺的成形难度较高。采用热成形方式能够有效的改善降低变形抗力和避免回弹。热冲压成形是集落料、加热、冲压、淬火冷却等一体的新型成形技术。热冲压成形整个过程中，板料预热至900℃再放入模具后，部分热量被冷模具带走，板料温度会降低，因此会低于加热后的温度，所以实际生产过程中是一个不断变化温度的非等温成形过程。然而现在的热冲压成形研究都是设定等温的成型过程与实际存在较大差异。特别是模具与板料之间的间隙会严重影响热冲压工件的成型质量，因为此有必要研究热冲压在非等温状态下的组织性能，特别是模具间隙的影响。模具间隙过大过小都不合理。间隙过大，板料与模具的凹凸模贴合较差，使得冷却速度不够，不能形成大量马氏体影响成形件强度。相反间隙过小，虽然材料与模具贴合变好，但是会导致之间摩擦力变大，不利于成形以及传热过快会使得形成的马氏体晶粒粗大，影响综合性能。43671

本文以高强钢BR1500HS为实验对象，首先开展高强钢板的等温和非等温变形的实验研究，对比分析了不同温度场和不同间隙下对该材料微观组织的影响，然后研究模具间隙的实验是以三种不同厚度的板料在相同的模具间隙下达到变化间隙的效果，分析了不同间隙对硼钢板的组织性能的影响。

研究结果得出以下结论BR1500HS在等温和非等温变形实验中的微观组织有所不同。冷却速度都在10-20℃/s 范围内，等温变形的微观组织为马氏体和贝氏体的混合组织；然而非等温变形的微观组织只出现较少马氏体，变形在高温结束时组织为铁素体和珠光体的混合组织。

此外模具间隙对BR1500HS组织性能影响的实验，进行了零件局部微观组织观察，通过对比研究1.0mm、1.4mm和1.6mm分析得出在1.8mm的模具间隙下1.6mm厚的硼钢板冲压成型出的盒型的表面质量和零件局部马氏体含量都是比较理想的。

毕业论文关键词：高强度钢板；热冲压；微观组织；

Abstract

Using high-strength boron manganese steel plate in the car to reduce unnecessary reinforcement, this can effectively avoid increasing body weight and strength. But steel tensile and yield strength increase, material deformation resistance and springback increase risk, not only puts forward higher requirements on processing equipment, so the cold stamping process of the forming difficulty is higher. Adopts the hot forming method can effectively improve lower deformation resistance and avoid the springback. Hot stamping is colony material, heating, punching, quenching and so on the integration of new forming technology. The whole process of hot stamping, sheet metal preheat to 900 ℃ and then into the mold, the part of the heat taken away by cold mold, sheet metal temperature decreases, so will be lower than the temperature of the heated, so the actual production process is a non-isothermal forming process of temperature changing. But now the hot stamping of research are set isothermal forming process and the actual there is a big difference. Especially the gap between mold and sheet metal will seriously affect the forming quality of hot stamping workpiece, because this is necessary to study hot stamping in the organization performance under non-isothermal condition, especially the influence of die clearance. Die clearance than small are unreasonable. Clearance is too large, sheet metal and die is concave and convex mold joint is bad, not enough cooling speed, not to form martensite influence forming a strength. Opposite clearance is too small, although material and mold fit better, but will cause friction between, is not conducive to forming and heat transfer too fast will make the formation of the martensite coarse grains, affect the comprehensive performance.