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.