DEVELOPMENT OF A STRIP DRAW TEST TO BENCH TEST THE FRICTIONAL BEHAVIOUR OF ZINC COATED STEELS IN PRESS FORMING

摘要

A strip draw test was developed to examine the frictional properties of the various zinc coated automotive steels. During press forming operations the temperature in the press is known to exceed 100℃. The design of the test included heating elements to allow tests to be performed at up to 200℃. The sheet materials examined were various Galvanneal samples with delta and zeta alloy phases on the surface, and hot-dip galvanised steel. Initial tests were performed at various speeds, loads and temperatures. Then a more definitive experimental set was carried out at a fixed speed under a range of loads and various lubrication conditions to examine the frictional values of the various zinc morphologies. The coefficient of friction was found to increase in the following order: GI, zeta phase, and delta phase, with some variation with the introduction of lubricant. Powdering performance of the zinc coated test samples was measured and found to deteriorate with increasing load and temperature. Surface roughness was also measured at several points along each test sample after testing, where the maximum value of surface roughness was found to decrease with increasing load.