Steel ball surface treatment knowledge

- Sep 27, 2020-

A large number of studies and observations have pointed out that no matter which mode of fatigue failure, fatigue cracks in most cases originate on the surface or subsurface of the material, and most of the external forces on the parts are concentrated on the surface or decrease from the surface to the inside. After a period of expansion, the parts fatigue. Therefore, in order to extend the life of fatigue crack initiation of steel balls or increase the load level of fatigue crack initiation, it is important to improve the quality and performance of the surface of steel balls on the basis of improving the quality of the bearing materials for steel balls. One of the most effective methods is to change the surface integrity of the material (part) (mainly including the surface microstructure and phase structure, residual stress state, etc.). At present, the main methods to improve the surface properties of steel parts are:


a. Functional plating on the surface of metal materials: including chemical plating, electroplating, composite plating, brush plating and amorphization treatment, etc.


b. High-energy beam treatment on the surface of metal materials: including laser surface treatment, electron beam surface modification treatment and example injection technology.


c. Vapor deposition technology on the surface of metal materials: including physical and chemical vapor deposition methods.


d. Thermal diffusion and infiltration process on the surface of metal materials: including carburizing. Chemical heat treatment such as nitriding and carbonitriding.


e. Surface quenching: such as high frequency surface quenching, flame surface quenching, etc.


f. Cold work hardening treatment: such as shot peening, rolling, cold pressing and cold rails.


The above methods all improve the fatigue performance by changing the surface integrity of the material. Over the past few decades, the research and development of surface strengthening and surface modification technology has sprung up, becoming a very prominent application field in materials science and friction science. Among the many surface treatment processes that have been used in engineering in various countries in the world to improve the fatigue properties of materials, the surface shot peening process is the most used, the most adaptable, and the cheapest.


Among the technological measures to improve the contact fatigue strength and surface quality of steel balls, the application of surface modification technology is the surface strengthening treatment of steel balls. The method is to put the steel balls into a special drum machine after the steel balls are heat treated. Due to the rotation of the drum, the lifting bucket in the drum lifts the steel balls to the top height and falls, and the falling steel balls and the steel balls in the drum Collide with each other. Each time the steel ball collides, there is only a small circle area. As the drum rotation time increases, the number of collisions of the steel ball increases, and the entire collision surface of the steel ball becomes larger and larger. Through this method of repeatedly colliding with each other, the collision surface of the steel balls becomes larger and larger. This surface strengthening process of steel balls is equivalent to a low-speed shot peening process. Through this processing method, the steel balls produce elasto-plastic deformation on the surface of the steel balls when they collide with each other, resulting in great changes in the microstructure and stress state of the steel balls, and achieving the purpose of improving the surface strength of the steel balls. This method is an economical and effective technological means to increase the life of steel balls. Its advantages are:


a. Simple and easy. As long as there is roller strengthening equipment, no other complicated auxiliary equipment is needed.


b. High production efficiency. As long as the enhanced process parameters are selected, mechanized production can be realized.


c. The economic benefit is high, and the service life of the steel ball can be greatly improved after the surface of the steel ball is strengthened. Improve the efficiency of surface grinding of steel balls, and reduce surface bumps and scratches caused by steel balls during transportation.