热成形工艺参数对硼钢B1500HS微观组织及性能的影响

发布时间：2018-04-30 09:31

  本文选题：热冲压 + B1500HS硼钢　； 参考：《山东科技大学》2017年硕士论文

【摘要】：人民物质生活水平的上升以及日益严重的能源危机和环境问题,对汽车行业提出了新的更高要求。因此,安全、环保、节能、舒适现已成为汽车行业的热点研究课题和方向。汽车车身轻量化是实现汽车节能减排的最有效措施之一。研究汽车的轻量化设计现已成为现代汽车设计制造的一项重要课题。热冲压成形工艺由于结合了冲压变形和淬火的优势,即材料高温时的良好成形性及冷却时材料的相变强化,能够生产出形貌完整、尺寸精确、强度高的热冲压件,而受到广泛关注。热冲压工艺参数对板料的成形性能起着至关重要的影响。本文以B1500HS为研究材料,以U型冲压件为研究对象进行了相关研究,具体研究内容为:1.利用自制模温控制设备,研究了加热和模具温度对U型冲压件不同部位组织性能的影响,结果表明:对于U型件不同部位,力学性能及一致性表现为:底部法兰部位直壁部位;870℃保温5min后冷却,试样发生不完全淬火,热冲压件的性能不满足设计要求;加热温度达到900℃并逐渐升高,热冲压件的力学性能下降;随着模具温度的升高,热冲压件的力学性能呈梯度下降。当模具温度超过300℃及以上时,试样的微观组织开始出现大量的贝氏体组织。2.通过控制冲压设备的冲压压力,研究了压力及保压时间对于板料组织性能的影响,结果表明:在热力耦合作用下,随着压力逐渐增加至40MPa,板料力学性能近似呈线性关系增加。压力继续增加,板料力学性能变化趋于稳定。保压时间较短时试样的微观组织颗粒粗大,力学性能较差。试样的强、硬度随着保压时间的延长而增强,在保压时间为7.5s,试样的组织形态变为均匀的马氏体,此时试样的强、硬度较高,力学性能良好。3.通过DIL805A高温相变仪,绘制了 B1500HS的热膨胀曲线。并结合金相观察和硬度测试,分析了加热和冷却速度对于板料组织性能的影响。结果表明:800℃并未达到试样的奥氏体化开始温度,由于珠光体转变需要孕育期,冷速越快,珠光体在奥氏体晶界处的先共析相(此时为铁素体)上形核越困难,导致珠光体转变量减少。亚温快速淬火,保温时间的延长会使Ms点相应升高。对于完全马氏体转变,连续冷却时过快的冷却速度会导致较大的过冷度,过冷度的增加会增大马氏体转变体积分数,导致Ms点降低。50℃/s快速加热至900℃并未使试样完全奥氏体化。同时对于奥氏体这种扩散型相变,快速加热会使碳原子的扩散不均匀性加重,从而使组织的不均匀化程度加深,冷却后扔保持明显的带状组织特点。保温时间的延长可以缓解这种不均匀化。
[Abstract]:The rise of people's material living standards and the increasingly serious energy crisis and environmental problems put forward new and higher requirements for the automobile industry. Therefore, safety, environmental protection, energy-saving, comfort has become a hot topic and direction of automotive industry. Lightweight automobile body is one of the most effective measures to achieve energy saving and emission reduction. Research on lightweight design of automobile has become an important subject in modern automobile design and manufacture. Because the hot stamping process combines the advantages of stamping deformation and quenching, that is, the good formability of the material at high temperature and the strengthening of the phase change of the material during cooling, it can produce hot stamping parts with complete morphology, precise size and high strength. And received widespread attention. Hot stamping process parameters play an important role in sheet metal formability. In this paper, B1500HS is used as the research material and U type stamping parts as the research object. The specific research contents are: 1. 1. The effects of heating and die temperature on the microstructure and properties of different parts of U type stamping parts were studied by using the self-made mould temperature control equipment. The results showed that: for different parts of U type stamping parts, The mechanical properties and consistency are as follows: after cooling at 870 鈩，

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