Ferroalloy is mainly used as deoxidizer and alloying agent in steelmaking to eliminate excessive oxygen and sulfur in molten steel and improve the quality and performance of steel.
When steelmaking, oxygen blowing is used to decarburize molten iron and remove harmful impurities such as phosphorus and sulfur. This process will increase the oxygen content in molten steel, and too high oxygen content will reduce the mechanical properties of steel. Adding some elements which have stronger binding force with oxygen than iron, and whose oxides are easily discharged from molten steel in the form of slag, and removing oxygen from molten steel, this process is called deoxidation. Silicon, manganese and chromium alloys are all used for this purpose.
Different alloy elements have different characteristics and uses.
Silicon can significantly improve the elasticity and magnetic conductivity of steel, so when smelting structural steel, tool steel, spring steel and transformer silicon steel, silicon-based alloys should be used. Generally, steel contains 0.15%-0.35% silicon, structural steel contains 0.40%-1.75% silicon, tool steel contains 0.30%-1.80% silicon, spring steel contains 0.40%-2.80% silicon, stainless acid-resistant steel contains 3.40%-4.00% silicon and heat-resistant steel contains 1.00% silicon.
Manganese can reduce the brittleness of steel, improve the hot workability, strength, hardness and wear resistance of steel. Manganese consumed by steel industry accounts for more than 90% of its output. Manganese is an indispensable functional basic raw material for the production of high-quality steel. In the steelmaking process, it can remove impurities such as oxygen and improve the strength and hardness.
One of the measures to improve the properties of cast iron and cast steel is to change the solidification conditions of castings. In order to change the solidification conditions, some ferroalloys are usually added as crystal nuclei before pouring to form grain centers, so that the formed graphite becomes fine and dispersed, and the grains are refined, thus improving the properties of castings.
Silicon is used as reducing agent in the production of ferromolybdenum, ferrovanadium and other ferroalloys. Cr-Si alloy and Mn-Si alloy are respectively used as reducing agents in the production of medium and low carbon ferromanganese.