The Test And Analysis Of Powder Lubrication And Heat Transfer Characteristics Of Warm Forming

Warm forming is a metal processing method between cold forming and hot forming. In the warm forming process, because of the need to reach a certain temperature and pressure, the traditional lubricating oil cannot meet the requirements. The characteristics of particle flow lubrication which adapt to extreme conditions make it widely used in the warm forming. The friction properties of granular flow lubrication in a certain environment temperature is studied based on the particle flow lubrication usually used in extreme condition. And using the steady state method to measure the interface contact heat transfer coefficient with the middle tier, which provide the reference to heat transfer problems between the friction pairs in the process of granular flow lubrication of warm forming.First of all, the multi-function environment controllable friction and wear testing machine is used to study the characteristics of granular flow lubrication. The structure of upper sample was improved, which can make the powder be sustained into the friction pair. According to the changes of friction coefficient in the process of test and the surface condition and Raman spectra of lubrication film after the test, to make the analysis and evaluation of grain flow lubrication conditions. The experimental results are as follows:The grain flow lubrication can work normally under low load condition, and the sample does not wear seriously. The friction coefficient decreases with proper load increasing. However, the sample will accentuate surface wear. Proper increasing of speed can have a good anti-friction effect. Under the condition of equal load, improve speed accelerates wear. With the increase of temperature, the quality of lubrication film is better, reducing the friction coefficient. By the temperature field of the sample, the sample has certain temperature difference from top to bottom. The lubrication film has the thermal insulation effect, which requires for subsequent contact heat transfer coefficient measurement.Secondly, mainly using the steady state method to study the influence of temperature, load, the middle layer thickness with graphite and oxidation aluminium powder to contact heat transfer coefficient between the H62copper alloy and45steel. The measurement results are shown as follows:When the stress and the middle layer thickness is invariant, with the increase of temperature, the interface contact heat transfer coefficient with graphite layer increases first, then decreases; however, the interface contact heat transfer coefficient with oxidation aluminium powder middle layer always increases. When the temperature, and the middle layer thickness do not change, with the increase of load, the interface contact heat transfer coefficient with graphite layer or oxidation aluminium layer is slowly increase first, then a sharp increase in supposedly, will eventually flatten out. When the load and temperature do not change, the interface contact heat transfer coefficient with oxidation aluminium middle layer decreases with increasing of the thickness of the middle layer; The contact heat transfer coefficient with graphite layer increases with the increase of the thickness of the middle layer. The curve of oxidation aluminium thermal conductivity coefficient change with temperature was derived according to the principle of steady-state method. With the increase of temperature, the thermal conductivity of oxidation aluminium powder slightly increases, the temperature has little effect on the coefficient of thermal conductivity.