The selection of gear shaft material is determined according to the working conditions, requirements and performance of the gear shaft. It is mainly determined by the size of the load at work, the level of speed and the accuracy of the gear. The size of the load mainly refers to the size of the torque transmitted by the gear, which is usually measured by the unit compressive stress on the tooth surface. Generally divided into: light load, medium load, heavy load and overweight load.

According to the requirements, the performance of 42CrMo steel is very good. After normalizing, quenching and tempering, induction heating quenching and low temperature tempering, the surface hardness can reach the high hardness of HRC50, the surface wear resistance is good, and the core hardness can reach HRC35~45 .42CrMo steel belongs to ultra-high-strength steel, with high strength and toughness, good hardenability, high fatigue limit and resistance to multiple impacts after quenching and tempering. Small deformation during quenching, high creep strength and lasting strength at high temperature, and no obvious temper brittleness.

The alloying elements Cr and Mo contained in 42CrMo steel. Among them, chromium can increase the hardenability of steel and has a secondary hardening effect. It can improve the hardness and wear resistance of high carbon steel without making the steel brittle; when the content exceeds 12%. Make the steel have good high temperature oxidation resistance and corrosion resistance of oxidizing media. It also increases the thermal strength of steel. Chromium is the main alloying element of stainless, acid-resistant steel and heat-resistant steel. The main role of chromium in quenched and tempered structural steel is to improve hardenability. After quenching and tempering, the steel has better comprehensive mechanical properties, and chromium-containing carbides can also be formed in the carburized steel, thereby improving the wear resistance of the material surface. Molybdenum can improve hardenability and thermal strength in steel. Prevent temper brittleness, increase remanence, coercivity, and corrosion resistance in certain media. In quenched and tempered steel, molybdenum can harden and harden parts with larger sections and improve the tempering resistance of steel Or tempering stability, so that parts can be tempered at a higher temperature, so as to more effectively eliminate (or reduce) residual stress and improve plasticity. Therefore, 42CrMo is often used as the material of the rolling mill gear shaft in production. Its comprehensive mechanical properties are excellent and meet the quality requirements.