The effect of TiN precipitated particles on the austenite grain and hardenability of 20CrMnTi gear steel

Abstract

To study the effect of TiN precipitated particles on two end-quenching specimens of 20CrMnTi steel with different hardenability characteristics, the peripheral hardness of the samples is tested. The microstructures, austenite grain structures, characteristics of TiN particles are analyzed. The larger the grain size, the higher the martensite fraction and the higher the hardness. More uniform and more refined grains reduce the maximum peripheral hardness difference of end-quenched samples from 9.1HRC to 3.3HRC. The precipitation of as much fine TiN as possible in the solid phase plays an important role in obtaining more refined and more uniform austenite grains. TiN precipitates less during solidification and more in the solid phase in the sample with better hardenability, promoting grain refinement and more uniform peripheral hardness. In production, with a specific mass fraction of Ti, effectively inhibiting the precipitation of coarse TiN during solidification is the key to control narrow hardenability bandwidth for 20CrMnTi gear steel.

Research on 20CrMnTi gear steel continuous cooling transformation behavior

“…20CrMnTi steel is a low carbon carburized gear steel with good carburization, hardenability, and high fatigue resistance, and is the main material for domestic gear steels, accounting for about 60% or more of all gear steel usage [3] . At present, research on 20CrMnTi gear steel is mainly focused on hardenability control [4] and inclusions control, while less research work has been conducted on its continuous cooling transformation behavior. During the heat treatment process, the cooling rate of 20CrMnTi gear steel has a crucial effect on the gear steel's microstructure, as well as on the mechanical properties.…”

Study on the technology of controlling nitrogen content in molten steel

“…With the speedy development of industrial science and technology, customers have increasingly higher requirements for the performance and stability of gear steel, especially for the nitrogen content of the steel. Take the high-standard 20CrMnTiH gear steel as an example, the nitrogen content is usually below 70 ppm [8][9][10]. Based on the practical production process, the paper explores the nitrogen control technology in the steel production process, conducts targeted nitrogen control and nitrogen reduction in stages, reduces the nitrogen content in the casting billet, and expects to obtain the rolling material with nitrogen content in line with the standard.…”