The use of a new type of large vacuum batch furnace for the heat treatment of moulds and dies

The primary focus in vacuum heat treating of dies for the die casting industry is to reduce distortion, while obtaining a smooth surface finish with no post cleaning needed and easy process control. A slower gas quenching reduces distortion, but special larger dies show grain boundary precipitation with the consequence of a shorter die life. — With the increased use of high-pressure gas quenching and faster quench rates for moulds and dies, the quality of heat treatment has improved significantly over the last ten years. With quicker quench rates, distortion and post machining increased which, however, was accepted in return for the improvement in lifetime despite an increased risk of quench cracking. This paper discusses the vacuum heat treating of moulds and dies (over 5 metric tons) in the newly developed Super Turbo^TM vacuum furnace with 15·10⁵ Pa nitrogen gas quench combined with directional cooling.