Papers by Author: Wei Jun Hui

Abstract: Microalloyed medium carbon steels have been applied for auto forging products at the aim of lower cost since 1980’s in China. Without quenching and tempering processes, the cost of heat treatment was greatly decreased, so they are widely applied in car forgings such as crankshaft, connecting rod. Recently, with the aim of improving performance and reducing production cost, new technologies, such as: reductions of microalloyed elements, tailored components, and mechanical properties forecast, have been developed in China auto industry. The designation, processing, properties prediction and microstructure of auto components have been controlled comprehensively. With the development of new technologies, microalloyed medium carbon steel gradually began to be applied to product important parts, and replace Quenching and Tempering steels. Both steel makers and end product users are expressed their desire to share benefits of technological innovation. The technologies will have a huge developing space and very bright developing prospects in motor parts industry in future.

Abstract: The yield strength and impact energy properties for martensitic steel fabricated by vacuum induction melting, is investigated. It is found that the addition of Ti can improve the yield strength property of the martensitic steel after reheat quenching process, which can be attributed to increase in precipitation hardening from formation of TiC precipitates in the martensitic matrix and a superfine sized (~8μm) grains in the martensitic structure. Moreover, the yield strength can be further enhanced by Mo addition, which can be ascribed to a large amount of freshly nano-sized (1-10nm) precipitates in the final martensitic structure. The experimental and theoretical results on the contribution of TiC precipitates to hardening of the martensitic steel are in excellent agreement. In addition, the impact toughness also has been improved along with yield strength followed by the heat treatment, which can be attributed to the grain refinement and high ratio of high-angle grain boundaries after Mo addition.