1. The main control point of the forged steel ball is the temperature of the steel ball.
In the production process of steel balls, temperature is always an important quality control point. Temperature control plays a very important role in forging heating, isothermal waiting for heat treatment, tempering and storage after tempering, and even affects the metallographic structure of steel balls.
2. Analysis under heating conditions.
1. Problems caused by high temperature: Oxidation and overburning will cause the internal structure of the steel ball to be coarse and unstable, the hardness is asymmetric and uneven, and the physical toughness impact value is low, even reaching about 3J/cm2. Take the heating of round steel as an example.
The oxidation rate of round steel is slower before heating to 550-600 degrees, and it rises rapidly when it reaches 700 degrees. Assume that the oxidation rate before 900°C is 1, 1000C is 2 and 1100°C is 3,1300%.
Best forging temperature: 980-1080°C;
The best temperature for rolling: 950-1050 degrees;
Scale-ferric oxide, ferric oxide, etc.
Note: No. 45 steel is carbon structural steel, and the above B2 steel is composite steel (alloy structural steel).
(1). Oxide scale is not only produced during the heating process, but also produced during the forging process;
(2) The longer the heating time, the more scale. Solution: rapid heating, reduce heating time.
2. Problems caused by too low temperature:-Generally speaking, quenching is impenetrable. Regardless of the surface hardness or core hardness, HRC cannot reach the required range value, which causes the steel ball to fail after the actual operation in the ball mill. Wear (eccentric wear), or even break.
3. The heating furnace affects the heat energy conversion differently. The medium frequency induction heating is fast, but it can not burn through, commonly known as "hard fire". For example, the heating of bonded steel seems to be 1000 degrees, but the actual forging will have great elasticity, which is not conducive to forging; but the same material,
It is easy to burn after being heated by coal stove, natural gas stove and oil stove, commonly known as "soft fire". The heating process of "soft fire" includes a slow process such as preheating and high temperature.