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이영선(Y. S. Lee),권용남(Y. N. Kwon),김상우(S. W. Kim),유재무(J. M. Yoo) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5
Reducing friction between tool and workpiece is very important to enhance the forming limit on both sheet and bulk forming. Various kinds of lubricant and coating are used to reduce the friction coefficient on metal forming. Friction has to be reduced because sheet forming of Mg alloy sheet is usually performed on warm temperature. Various lubricants are almost used on metal forming process. However, it is difficult to use the lubricant on multi-stage sheet forming process, especially, on warm temperature. Therefore, tool coating is better than lubricant on Mg ally sheet warm forming. The importance of friction effect has been studied through real formed part of AZ31 sheet according to the different lubricant. Two different non-metallic coating layers are compared with no-coating tool by pin-on-disc friction testing. Friction coefficients for different coating layers are measured. The materials of pin and disc are SKD61 and AZ31, respectively. The coefficients are measured at room temperature, 170 and 250℃. Until now, tool coating for Mg warm forming is not effective and coulomb friction coefficient is 0.4 in ambient.