Novel tool steel for application in hot stamping

Abstract

Hot stamping is a commonly used procedure to manufacture components from high strength steels, which are used for parts of car bodies. Against the background of production efficiency and costs, there is a number of factors which determine the performance of tools used in hot stamping, e.g. cycle time in production and lifetime of the tools. Main requirement is a high wear resistance, while additional properties such as high thermal conductivity can be considered being beneficial. Many steel grades, which are currently applied in hot stamping tools (e.g. hot work tool steel 1.2367) contain high amounts of alloying elements which gives them good mechanical properties, particularly at high temperatures. However, these steels in turn suffer from a rather low thermal conductivity and only moderate wear resistance. Optimization of the balance of mechanical properties, wear resistance, and thermal conductivity can lead to a better general performance of hot working tool steels used in hot stamping applications. In this study, a novel tool steel is characterized with special focus on properties relevant for hot stamping tools. Results are compared to those of reference hot work tool steels. Wear tests that were conducted in the framework of this paper include laboratory setups like ASTM G65 / G75 and high-temperature strip-drawing test setups to simulate the conditions of the process closer to reality. Results show that the novel tool steel is characterized by an increased wear resistance in combination with a higher thermal conductivity compared with common hot work tool steels. Furthermore it is approved that a wide range of desired properties can be adjusted in this alloy via heat treatment. The favourable combination of properties makes the novel tool steel suitable for application in hot stamping tools.