模具分区控温热冲压工艺及零部件组织性能研究
发布时间：2018-11-16 07:57
【摘要】：随着高强钢热冲压技术在汽车行业的广泛应用,对热冲压件提出了更高的要求,例如B柱、车门防撞梁及保险杠等对碰撞安全性能要求比较高的零件来说,仅具有较高的强度,并不能显著提高碰撞过程的安全性能。为了进一步提高碰撞安全性能,需要一种具有性能梯度分布的冲压件,通过高强度区域在碰撞过程中材料的高强度,来保障乘员的安全,并依靠局部的强度相对比较低、塑形比较好的区域的塑性变形达到吸收碰撞能的目的。高能耗一直是制约热冲压成形技术广泛应用的一个主要因素,目前广泛采用的辊底炉坯料加热方式,存在加热设备相对体积和能耗相对较大,加热效率不高等缺点。自阻加热作为一种新型的板材加热方式,具有设备体积小、控制方便、加热速度快且效率高等优点,是板材热成形技术的理想热源。本文以高强度22MnB5钢板为实验材料,设计开发了分区控温模具及自阻加热装置,实现了具有性能梯度U形件的热冲压成形,对自阻电加热方式进行了探索,并对冲压件的梯度性能进行深入研究。首先,采用平板模试验方法分析了模具温度对22MnB5钢板组织性能的影响规律。22MnB5钢板的屈服强度和抗拉强度均随着模具温度的逐渐升高而下降,而延伸率逐渐升高的趋势。模具温度低于250℃时组织以板条状马氏体为主,抗拉强度大于1200MPa,延伸率大于5%,满足对梯度性能冲压件的高强区性能要求。模具温度高于450℃时组织以铁素体+珠光体+碳化物为主,抗拉强度大于600MPa,延伸率大于15%,满足对梯度性能冲压件的低强度区力学性能要求。其次,应用分区控温的U形件试验模具装置,采用数值模拟与实验相结合的研究方法,分析了热模温度对过渡区组织与性能的影响规律。随着热模温度的升高,高强区与低强区的硬度差值逐渐增大,高强区平均硬度约为500HV,低强度区的硬度随模具温度的上升呈逐渐下降的趋势,热模温度在200℃~500℃之间,硬度在450HV~250HV范围以内,过渡区的宽度约为60mm,位于空气间隙处且偏向冷模一侧,高强度侧微观组织以马氏体为主,向低强度区过渡过程中逐渐出现贝氏体组织,而低强度区域主要以铁素体和碳化物为主。自阻电加热延伸率高于炉加热,而抗拉强度略有下降,高强区的组织中马氏体板条中间存在铁素体相,而低强度区域存在更多的碳化物析出相。最后,分析了具有梯度性能管形件轴向压溃的变形规律及能量吸收性能。随着热模温度的升高,轴向压溃所需载荷逐渐降低,压溃吸收的总能量呈下降趋势。原始母材及整体冷模淬火件压溃变形开始于试样的中部,而具有梯度性能的成形件变形集中在低强度区。压溃的主要失效方式为焊点的开裂,强度较高的管形件出现撕裂的现象。
[Abstract]:With the wide application of hot stamping technology of high-strength steel in automobile industry, higher requirements are put forward for hot stamping parts, such as B-column, door anti-collision beam, bumper and other parts with high impact safety performance, which only have higher strength. It can not significantly improve the safety performance of collision process. In order to further improve the safety of collision, a kind of stamping parts with gradient distribution of performance is needed to ensure the safety of the occupants by the high strength of the materials in the high strength area during the impact process, and the relative low strength depends on the local strength. The plastic deformation of the better shape region can absorb the collision energy. High energy consumption has been one of the main factors restricting the wide application of hot stamping forming technology. At present, the widely used heating method of roll furnace billet has some shortcomings, such as the relative volume and energy consumption of heating equipment is relatively large, and the heating efficiency is not high. As a new type of plate heating, autoresistive heating has the advantages of small volume, convenient control, high heating speed and high efficiency. It is an ideal heat source for sheet metal hot forming technology. In this paper, using high strength 22MnB5 steel plate as experimental material, a zonal temperature-control die and a self-resistive heating device are designed and developed. The hot stamping forming of U-shaped parts with performance gradient is realized, and the self-resistive electric heating method is explored. The gradient performance of stamping parts is studied. Firstly, the influence of die temperature on the microstructure and properties of 22MnB5 steel plate was analyzed by plate die test. The yield strength and tensile strength of 22MnB5 steel plate decreased with the increasing of die temperature, but the elongation increased gradually. When the temperature of die is lower than 250 鈩，
本文编号：2334922
[Abstract]:With the wide application of hot stamping technology of high-strength steel in automobile industry, higher requirements are put forward for hot stamping parts, such as B-column, door anti-collision beam, bumper and other parts with high impact safety performance, which only have higher strength. It can not significantly improve the safety performance of collision process. In order to further improve the safety of collision, a kind of stamping parts with gradient distribution of performance is needed to ensure the safety of the occupants by the high strength of the materials in the high strength area during the impact process, and the relative low strength depends on the local strength. The plastic deformation of the better shape region can absorb the collision energy. High energy consumption has been one of the main factors restricting the wide application of hot stamping forming technology. At present, the widely used heating method of roll furnace billet has some shortcomings, such as the relative volume and energy consumption of heating equipment is relatively large, and the heating efficiency is not high. As a new type of plate heating, autoresistive heating has the advantages of small volume, convenient control, high heating speed and high efficiency. It is an ideal heat source for sheet metal hot forming technology. In this paper, using high strength 22MnB5 steel plate as experimental material, a zonal temperature-control die and a self-resistive heating device are designed and developed. The hot stamping forming of U-shaped parts with performance gradient is realized, and the self-resistive electric heating method is explored. The gradient performance of stamping parts is studied. Firstly, the influence of die temperature on the microstructure and properties of 22MnB5 steel plate was analyzed by plate die test. The yield strength and tensile strength of 22MnB5 steel plate decreased with the increasing of die temperature, but the elongation increased gradually. When the temperature of die is lower than 250 鈩，
本文编号：2334922
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