三体介质温成形界面接触换热特性的试验研究

温成形摩擦界面模具与工件之间的传热特性对工件质量和模具寿命有重要影响,固体粉末介质导入该摩擦副可实现高温润滑,但其传热特性与传统加工方式的有很大不同.采用稳态法自行设计了三体界面的传热特性试验,研究和分析了界面温度、接触载荷、层厚对带有石墨粉和氧化铝粉润滑层的H62铜合金和45钢之间的三体界面接触换热系数的影响.结果表明:带有石墨粉润滑层的三体界面接触换热系数随温度的增加先升高后降低,随载荷和层厚的增加先缓慢增加后迅速增加;带有氧化铝粉润滑层的三体界面接触换热系数随温度的变化缓慢升高,与载荷基本成线性关系,随层厚的增加而降低.温度改变了固体润滑剂的材料热阻和上下试样表面硬度及氧化层厚度,载荷改变了三体界面实际接触面积和接触属性,层厚决定能否完全隔开上下试样,不同物性固体润滑剂决定了其材料热阻在三体界面接触热阻中的主次关系.

Experimental Research on Contact Heat Transfer Characteristics of Three-body Interface during Warm Forming

Heat transfer characteristics of frictional interface between die and workpiece during worm forming has an important effect on the workpiece quality and die life. It can achieve high temperature lubrication by importing solid powder medium into the friction pair, and the heat transfer characteristic by powder lubrication is different from that by the traditional processing. An experiment of heat transfer characteristics about three-body interface was developed by using the steady-state method independently to investigate the impact of interface temperature, interface load, and layer thickness on the contact heat transfer coefficient of three-body interface. The intermediate layer, graphite or alumina oxide, was mounted between H62 copper alloy and 45 steel. The results show that contact heat transfer coefficient of the three-body interface increased firstly and then decreased as temperature rose while it increased softly first and then increased sharply as load and thickness increased. The coefficient with alumina oxide powder lubrication layer rose slowly with increasing temperature and decreased with the increasing layer thickness. And it had a linear relationship with the load approximately. Material resistances of the solid lubricants and superficial hardness as well as oxide thickness of samples varied over temperature. Load altered the real contact area and contact property of three-body interface. The separation of lower and upper sample was determined by the layer thickness. And the contribution to material thermal resistance in three-body interface contact thermal resistance was determined by physical properties of solid lubricant powder.