Why does steelmaking need deoxidation

In order to ensure smooth casting and rolling into qualified steel, a certain amount of deoxidizer is added to the molten steel for deoxidation at the end of smelting or during tapping, and an appropriate amount of alloy is added to adjust the chemical composition according to the requirements of the steel specification.

Generally, there are silicon-manganese alloys, ferrosilicon, ferromanganese, ferro-aluminum, silicon-aluminum-barium-calcium, etc.

The harmfulness of oxygen in steel is mainly manifested in the following three aspects.

1. produce inclusions. When molten steel solidifies, the excess oxygen combines with other elements in the steel to form non-metallic inclusions, which destroys the continuity of the steel matrix and reduces the strength limit, impact toughness, elongation and other mechanical properties and magnetic permeability of the steel. energy, welding performance, etc.

2. Bubbles form. If the oxygen content in the molten steel is too high, it will react with the carbon in the steel again during the casting process to generate CO gas, which will cause defects such as pores, looseness, and even rise in the steel ingot (bill), and in severe cases will cause the steel ingot (bill) scrapped.

3. Exacerbate the hazards of sulfur. Oxygen can reduce the solubility of sulfur in steel, aggravate the harmful effect of sulfur, and make the hot embrittlement tendency of steel more serious.