Today, we systematically summarize the temperature of forged and rolled steel balls in the production process and the importance of steel balls.

1、 The main control point of forging and rolling steel ball is the temperature of steel ball

In the production process of steel ball, temperature is always the most important quality control point. Temperature control plays a very important role in forging and rolling heating, isothermal waiting for temperature, heat treatment, tempering and warehousing after tempering, and even affects the metallographic structure of steel balls.

2、 Analysis under heating condition

1. Problems caused by too high temperature: oxidation overburning, resulting in coarse internal structure of steel ball, unstable, asymmetric and uneven hardness, and low impact value of physical toughness, even up to about 3j / cm2.

Taking the heating of round steel as an example, the following explanations are made: after heating, the oxidation rate of round steel is slow before 550-600 degrees, and the oxidation rate rises rapidly only when it reaches more than 700 degrees; It is assumed that the oxidation rate before 900 degrees is 1, 1000 degrees is 2, 1100 degrees is 3 and 1300 degrees is 7

The best forging temperature: 980 ℃ - 1080 ℃;

The best rolling temperature: 950 ℃ - 1050 ℃;

Oxide scale - ferric oxide, ferric oxide, etc.

Note: 45 steel is carbon structural steel, and above B2 is bonded steel (alloy structural steel).

(1) oxide scale is produced not only in the heating process, but also in the forging process;

(2) the longer the heating time, the more oxide scale;

(3) solution: heat quickly and reduce heating time.

1. The problem caused by too low temperature: Generally speaking, it is that the quenching is not transparent. Regardless of the surface hardness or core hardness, HRC cannot reach the required range value, resulting in the non wear resistance (eccentric wear) and even crushing of the steel ball after the actual operation in the ball mill.

2. Influence of heating furnace: the heat energy conversion is different. The medium frequency induction heating speed is fast, but it can not burn through. It is commonly known as "hard fire". For example, the heating of bonded steel seems to be 1000 degrees, but it will be very elastic during actual forging, which is not conducive to forging; The same material is easy after heating in coal furnace, natural gas furnace and oil furnace. This is commonly known as "soft fire". The heating process of "soft fire" includes slow processes such as preheating and high temperature.

3、 Relationship between Grinding Mill Temperature and ball

1. The mill operation is divided into dry grinding and wet grinding, which is also a remarkable feature to distinguish cast steel ball from forged steel ball.

 

2. When the mill is operated, overhauled or the lining plate is replaced, all the steel balls in the mill need to be poured out, so it is necessary to pay attention to the change of steel ball temperature, especially the bonded steel ball. If the cooling of the steel ball after operation is obvious (or a large amount of water injection is adopted), the surface peeling, peeling and even direct crushing will occur.

4、 Why should forged steel balls be tempered

1. In terms of the performance of the steel ball, if the temperature of the steel ball after forging and rolling is lower than 30 degrees after quenching (it can be held directly by hand), it has generated internal stress, resulting in many problems in the use of the steel ball, such as crushing, surface peeling, etc. Only by relying on the residual temperature of the steel ball after quenching, quickly reheat it to reach the tempering temperature range and eliminate the internal stress, can we ensure the smooth completion of the whole production process and reduce the crushing rate at the same time;

2. Measures for rapid tempering: tempering temperature control range 180-200 degrees (plus or minus 20 degrees), special treatment of steel balls with special specifications and materials;

3. Factors causing stress: iron basket, iron bucket, ground, humid air, etc., but the most important two points are: first, if residual temperature tempering method is adopted, the temperature during tempering after steel ball quenching should not be too low, not less than 40 degrees; Second, when the tempered steel ball is put into the warehouse, the temperature into the warehouse should not be too high, not higher than 120-140 degrees. This high and low are the two most important nodes. Tempering shall be carried out when the temperature is low, and the time in the furnace shall be extended to ensure the penetration of the steel ball (such as 4 hours in normal condition and 6 hours in low temperature); When the temperature is high, the warehousing will produce stress again, resulting in the crushing phenomenon described above