ZHY gear senior engineer team proposed a new heat treatment process for obtaining Austempered bainite ductile iron, namely room temperature oil staged isothermal quenching process. It has been successfully applied in the processing of large gear of 8.826kw small four-wheel tractor. It improves the comprehensive mechanical and technological properties of the gear, reduces the cost, obtains good technical and economic benefits, and provides an important new heat treatment process for gear production. The research and development work and production application results show that:
1. Step isothermal quenching with room temperature oil is a new process to produce Austenite Bainite Ductile Iron and high strength toughened ductile iron without salt bath and corrosion.
By selecting reasonable process parameters, Austempered bainite ductile iron with good comprehensive mechanical properties can be obtained. The process also reduces the sensitivity to isothermal temperature and time.
2. On the premise of ensuring hardenability, for workpieces with large equivalent wall thickness and large structural size, the step quenching time shall be extended accordingly.
Compared with salt bath isothermal quenching, room temperature oil staged isothermal quenching process can improve the depth of hardening layer and reduce the amount of alloy elements.
3. In the Austenite Bainite structure obtained by step isothermal quenching in room temperature oil, the bainite is significantly refined, the strength and hardness are improved without reducing the plasticity and toughness. In addition, the presence of a small amount of lower bainite is conducive to the improvement of wear resistance. Therefore, this kind of Austenite Bainite Ductile iron has high strength, toughness and high wear resistance. It is a new technology and material for the production of gears.
4. The transmission big gear of 8.826kw small four-wheel tractor is treated by step isothermal quenching with room temperature oil. The heat treatment deformation is within the allowable range, the performance meets the technical requirements of the tractor, and the economic benefit is remarkable.