Heat treatment is one of the indispensable steps in the forming process of many workpieces. Forging grinding steel balls are no exception. The so-called forging grinding steel balls heat treatment is to heat the billets to a certain temperature and maintain a certain temperature in a certain environment. After a time, then a process program that cools at different speeds.
The heat treatment process of forged grinding media balls generally includes three processes of heating, heat preservation and cooling, and sometimes only heating and cooling processes. These processes are connected with one another and cannot be interrupted. Heating is one of the most important processes. When the forged grinding medium steel ball is heated, the workpiece is exposed to the air, and oxidation and decarburization often occur, which has an adverse effect on the surface properties of the heat-treated parts. Therefore, the steel ball should usually be heated in a controlled atmosphere or protective atmosphere, in molten salt and in vacuum, and can also be protected and heated by coating or packaging methods.
The heating temperature is one of the important process parameters of the forging grinding medium steel ball heat treatment process. Selecting and controlling the heating temperature is the main problem to ensure the quality of the heat treatment. The heating temperature differs depending on the purpose of the steel ball material being processed and the heat treatment, but generally it is heated above the phase transition temperature to obtain a high temperature structure.
In addition, the transformation requires a certain time, so when the surface of forged grinding media ball reaches the required heating temperature, it must be maintained at this temperature for a certain time, so that the temperature inside and outside the same, so that the complete transformation of the microstructure, this time is called holding time . With high energy density heating and surface heat treatment, the heating rate is extremely fast, generally there is no heat preservation time, and the heat treatment time of chemical heat treatment is often longer.
Cooling is also an indispensable step in the heat treatment process of the forged grinding medium steel ball. The cooling method differs depending on the process, and mainly controls the cooling rate. In general, the cooling rate of the annealing is the slowest, the normalized cooling rate is faster, and the quenching cooling rate is faster.
Forging grinding medium steel ball heat treatment process can be divided into three categories: overall heat treatment, surface heat treatment and chemical heat treatment. According to the different heating medium, heating temperature and cooling method, each major category can be divided into several different heat treatment processes. The same kind of forged grinding media balls use different heat treatment processes to obtain different structures and thus have different properties.