Pressure-Assisted Lubrication of DC01 Steel Sheets to Reduce Friction in Sheet-Metal-Forming Processes

Abstract

Friction in sheet-metal-forming processes not only affects the values of the force parameters of the process but also determines the quality of the surface of the drawpieces. This paper presents an approach to reducing the coefficient of friction by directly applying pressurized oil to the contact zone. For this purpose, a special test stand was built to carry out the strip draw test, commonly used to model the phenomenon of friction in the deep-drawing process. This test consisted of pulling a strip between flat countersamples made of 145Cr6 cold-work tool steel covered with an abrasion-resistant Mtec (AlTiN) coating. During the pilot tests, various contact pressures, lubricants with different viscosities, and different lubricant pressures were used. The influence of friction conditions on the surface roughness of the samples and the relationship between the friction conditions and the value of the coefficient of friction were determined. The supply of the lubricant under pressure into the contact zone has a beneficial effect on reducing friction. The coefficient of friction decreases with increasing lubricant pressure for contact pressures of 2–6 MPa. For a contact pressure of 8 MPa, the lubricant pressure is the least favorable for reducing the coefficient of friction. At higher lubricant pressures (12 and 18 bar), the lubrication efficiency depends on the viscosity of the lubricant and decreases with increasing contact pressure.