交变不对称温度场的热冲压模面激光熔覆及磨损控制研究

Hot stamping is an advanced forming technology of lightweight automotive body in recent years. Its unique heat transfer between high-temperature sheet and water-cooling die causes sheet metal and dieface to be in an alternating asymmetrical temperature field. That leads to conventional strengthening dieface easy to wear failure and a difficult problem to be solved in the research field of hot stamping. A pin-type cooling pipe structure is innovatively proposed in this project. Based on restriction condition of dieface temperature field fulfilling the quality of hot stamping part, a mathematical function of the honeycomb dot-matrix temperature field, concerning the quenching process and pipeline parameters, is constructed. A new method for precise control of dieface temperature field in hot stamping is established. A new laser cladding technology is proposed that takes not only thermal conductivity and cladding layer wear resistance but also adaption to large-sized and complex-shaped dieface into account. A mathematical model with geometric characteristic of the multi-track-joined laser cladding layer is established to control the composite performance of the layer. A friction and wear experimental device is innovatively developed that can simulate the actual conditions of hot stamping. The wear mechanism of the laser cladding layer under various and alternating friction conditions is studied. Particularly, the evaluation index of composite performance of the cladding layer and quenching process parameters are introduced to construct the wear rate calculation model of hot stamping dieface, by which the wear life of dieface can be predicted..In summary, the "Temperature field model - Laser cladding strengthening - Dieface wear control" technical prototype will be established, which has important scientific significance and application value.

热冲压是近年来出现的一种实现车身轻量化的先进成形技术，其独特的高温板料和水冷模具间的热传递，使得板料和模面间处于交变不对称温度场下，导致常规强化模面容易磨损而至失效，成为热冲压研究领域亟待解决的难题。本项目创新性地提出销式冷却管道结构，以满足热冲压制件质量的模面温度场指标作为约束，构建蜂窝点阵式温度场关于淬火工艺和管道参数的数学描述，建立热冲压模面温度场精确控制新方法。提出兼顾熔覆层热导率和耐磨性、适应大尺寸复杂形状模面的激光熔覆新工艺，建立多道搭接的熔覆层几何特征数学模型，实现激光熔覆层复合性能控制。自主研发可模拟热冲压真实工况的摩擦磨损实验装置，研究激光熔覆层在多样、交变摩擦工况下的磨损机理，特别引入熔覆层复合性能评价指标和淬火工艺参数以构建热冲压模面磨损率计算模型，实现模面磨损寿命预测。.综上，可建立“温度场模型-激光熔覆强化-模面磨损控制”技术原型，具有重要科学意义和应用价值。

热冲压是近年来出现的一种实现车身轻量化的先进成形技术，其独特的高温板料和水冷模具间的热传递，使得板料和模面间处于交变不对称温度场下，导致常规强化模面容易磨损而至失效，成为热冲压研究领域亟待解决的难题。.在热冲压模面温度场精确控制研究方面：运用传热学理论分析热冲压制件特定的淬火质量要求，建立淬火过程中制件平均温度变化路径的函数表达，提出基于管道参数域的热冲压件淬火质量控制方法；研究直通式和销式冷却管道结构和布局参数对模面温度场分布的影响，提出“直通式+销式”组合冷却管道设计方案，在保证热冲压件淬火速率同时改善制件淬火均匀性，最终建立热冲压模面温度场精确控制新方法。.在模面激光熔覆层复合性能控制研究方面：建立多道搭接的熔覆层几何特征数学模型，以预测和控制激光熔覆层的几何形状及相应性能；研究不同粉末配比熔覆层的硬度、耐磨性及微观组织演变规律，优化激光熔覆层的物相组成、微观组织、显微硬度和磨损性能等；以熔覆层稀释率、宽高比、高径比、平均硬度为指标，研究激光功率、扫描速度、送粉量、光斑直径对熔覆质量的影响，以获得最佳熔覆工艺参数。.在交变不对称温度下的模面磨损机理及磨损率计算模型研究方面：自主研发可模拟热冲压真实工况的摩擦磨损实验装置，建立热冲压工艺参数对模面微观形貌和组织成分的影响规律，研究交变不对称温度下的热冲压模面磨损机理；研究镀层超高强钢板与激光熔覆层模面间的高温摩擦磨损行为，建立激光熔覆层与镀层钢板高温销盘实验磨损率模型，实现模面寿命预测。.总之，本项目研制1副U形件热冲压模具样机，完成带圆角方形件、U形件、真实拉延模的曲面激光熔覆，研制出差温摩擦磨损试验装置，已建立“温度场模型-激光熔覆强化-模面磨损控制”技术原型，具有重要科学意义和应用价值。