Die Failures in Copper Hot Extrusion

Low life service of steel dies used in copper extrusion brought us to inspect several discarded copper hot extrusion dies in order to identify failures and failure mechanisms. The investigations performed are mainly hardness tests and microscopic investigations. The profiles extruded are circular, rectangular and hexagonal. It was observed that die design is not at fault; rather the die material is to blame for low life service of the tool. Discarded extrusion dies after copper hot extrusions were investigated. The failure of the dies was first observed by naked eye and the observations recorded. From the dies the ones with most plastic deformations and obvious signs of failure were selected. An improvement in die design could expand the service life, but our main concern is the material: a balance between toughness and hot strength is critical, yet this balance is hard to achieve. Other thermal processing of the die is still in question and investigations are currently being performed. At least an increase of tool service life could be achieved by thermal processing of the material to a state prior nanometric carbide precipitation between martensitic plates.