Properties of Thixocast Spring Steel Ratchets

Abstract

Forging is state of the art for the production of hand tools in industrial scales. Due to high demands on stiffness and fracture toughness high-strength forged steels are used to provide components with high mechanical load capacity. In spite of all advantages forging is restricted by some means like the freedom of scope. However, because of the extreme thermal load and the hardly avoidable casting defects, hand tools are nowadays not cast. By thixocasting steel technical difficulties can be reduced and new options are provided, which allow manufacturing of components with much higher complexity than forging. During this work ratchets were thixocast successfully using spring steel type 61SiCr7. Based on the STC-concept, a new method to prevent the shot sleeve from damage was tested. Dies made of hot forming tool steel X38CrMoV5 were optimized by simulation and coated by plasma chemical deposition of crystalline Al2O3 protective coatings. The cast parts were heat treated successfully to enhance the toughness, which was measured by tensile and Charpy impact tests.