What is mold powder?

Mold powder (or flux) is a synthetic slag added to the mold during the continuous casting of steel. The mold flux is made up of many raw materials. The primary make up of the flux is calcium silicate, with varying amounts of Na2O, MgO, Al2O3, Li2O, F, and free carbon. The specific chemistry of the mold flux is determined by the casting conditions and the grade of steel being produced.


Unmelted Layer

1. Provides Insulation

2. Prevents Heat Loss by Radiation

Melted Layer

1. Provides Lubrication between the water cooled mold and the solidified shell surface of the steel. Proper lubrication helps reduce mold wear and decreases sticking type breakouts.

2. Prevents Reoxidation of the molten steel by shielding it from the air.

3. Dissolves and Removes non-metallic inclusions such as alumina, silica, and zirconia along with gas bubbles that float to the surface of the molten steel. This “cleaning process” helps reduce inclusions.

4. Influences Mold Heat Removal - a steady heat flow from the solidifying steel slab will result in consistent internal structure, and greatly reduce the cracking incidence.