Evaluation of Stamping Lubricants in Forming Galvannealed Steels for Industrial Application

Abstract

Lubrication is one of the process variables that affect the quality of stamping sheet materials. Using a good lubricant can significantly reduce scrap rate and/or improve the quality of stamping. In this study, different types of lubricants were evaluated using strip draw test (SDT) and deep draw test (DDT) for stamping of galvannealed steel sheets. Finite element (FE) simulations were carried out to determine the coefficient of friction at tool-work piece interface during deep drawing under different lubrication conditions and blank holder forces. Flow stress data of materials under biaxial load which are used in FE simulations are obtained by viscous pressure bulge tests. SDT was used as a preliminary test to evaluate the relative performance of the lubricants. Lubricants that showed good performance in this test were tested using DDT. Dimensions of the formed strips and cups and the maximum applicable blank holder force to draw parts without fracturing were the criteria used for evaluation of lubricants in both tests. In general, it was possible to form cups with higher blank holder force when synthetic/water-based lubricants were applied to the sheet. In conclusion, evaluated synthetic/water-based lubricants had better lubricity than petroleum-based lubricants.