Casting powder and its function

Casting powder also called mould powder is an important raw and auxiliary material in the continuous casting process, which is called the "industrial MSG" in the continuous casting process by some metallurgical experts. It is one of the three key technologies in continuous casting process.

The three key technologies of continuous casting are crystallizer, casting powder and submerged nozzle. After the application of self-casting powder in the continuous casting process, the process of continuous casting has been greatly improved, and the surface quality of continuous casting billet has been qualitatively improved.

The casting powder plays two main roles in the continuous casting process: ensuring the continuous casting process and improving the surface quality of the billet;

The two major functions of the casting powder in the continuous casting process are realized by the five functions of the casting powder.

1. Heat insulation and insulation

Adding casting powder to the surface of high temperature steel can effectively prevent the radiation temperature drop of molten steel, effectively increase the temperature of mold meniscus, and obviously reduce the formation or excessive growth of slag ring. Especially in the casting of high carbon steel, it is beneficial to improve the lubrication of the casting billet by improving the thermal insulation performance of the casting powder.

The insulation property of the casting powder is mainly achieved by the specific gravity control of the casting powder and the matching of carbon. Generally, the insulation property of the casting powder with small specific gravity and high carbon content is better.

2. Prevent secondary oxidation of molten steel;

After the casting powder is added to the mold and melted, the molten steel is isolated from the outside world, thus avoiding the direct contact between the high-temperature molten steel and the air, and effectively preventing the secondary oxidation of the molten steel, which has great benefits for improving the quality of the molten steel and preventing the oxidation of trace alloying elements in the molten steel.

3. Lubricate the billet to ensure the continuous casting process;

After melting and being consumed, the casting powder enters the gap between the solidified billet shells and is liquid on the contact side of the casting billet. It plays a lubricating role in the process of casting billet pulling down, effectively reduces the pulling resistance of billet and prevents the occurrence of bonding accidents.

4. Adsorption of inclusions floating in molten steel to purify the quality of molten steel;

In order to prevent the inclusions floating in the liquid steel from being sucked into the initial solidified billet shell, resulting in surface or subskin defects of the billet, the liquid slag layer formed by melting of the casting powder should have the ability to absorb and assimilate the non-metallic inclusions floating in the liquid steel, and at the same time make the physical properties of the casting powder change little.

5. Improve the heat transfer structure

When using rapeseed oil as lubricant, in the lower part of the crystallizer, due to the shrinkage of the billet shell, the air gap is generated, resulting in increased thermal resistance, reduced heat transfer is very uneven.

The liquid slag formed by melting of the casting powder can improve the uniformity of heat transfer and improve the quality of the casting billet. The main technology used to control the heat transfer of the slag film is to improve the basicity of the casting powder, increase the solidification temperature, crystallization temperature and crystallization rate of the casting powder, and reduce the effective thermal conductivity of the slag film. This is also one of the reasons why medium carbon steel basically uses high alkalinity casting powder.

The five basic functions of the casting powder are closely related to the quality of the billet and the forward casting process. Due to the improvement of the casting speed and the expansion of the casting steel, these five basic functions have been given a new connotation, so that these five basic functions are closely linked together, and the change of each function will cause the change of other functions.