Wear criteria of cold forging tools

In the cold forging industry, the tooling makes an important contribution t o the cost price of the forged pieces. Predicting the degradation of the to ols would constitute a significant advantage. A possible definition of tool life is when the roughness parameters of the formed pieces exceed fixed cr iteria, at which point the tool must be replaced or polished. In order to q uantify the surface integrity of the tool, a new methodology of analysis ha s been developed by measuring the roughness of the formed piece. The upsett ing sliding test is used to reproduce the contact conditions of the studied process in the laboratory. It allows quantification of the scatter in the friction coefficients caused by wear, and observations of the formed pieces and the wear of the tool surface. An industrial application using the AISI M2 tool steel is studied. It is shown that the tool wear can be predicted by measuring the roughness parameters of the workpiece. The application of the methodology allows the lifetime of the tool to be predicted before form ing any workpiece.