Overview
These ferroalloys are commonly used in steelmaking and electric arc furnace (EAF) production for deoxidation and alloying, covering stainless steels, high-manganese steels, tool steels, bearing steels, and more.
Ferromanganese and silicomanganese: characteristics and uses
Definitions and classification
- Ferromanganese is an alloy of manganese and iron that also contains carbon, silicon, and other elements. By carbon content it can be classified into medium-carbon and low-carbon grades.
- An alloy containing sufficient manganese and silicon is called silicomanganese; it consists of silicon, manganese, and small amounts of impurities.
Functions and applications
- Approximately 80% of manganese is used as a deoxidizer in steelmaking; it refines grain size and improves steel hardenability.
- As an alloying element, manganese increases atmospheric corrosion resistance and improves forgeability and rollability.
- Wear-resistant high-manganese steel is widely used for parts in excavators and crushers.
- In some stainless steels, manganese can partially replace scarce nickel.
- Silicomanganese serves as a composite deoxidizer and alloying additive in steelmaking; its deoxidation products have low melting points and float up easily.
Low-carbon ferromanganese (composition and use)
- Definition: carbon content <0.7% and manganese content >80%.
- Use: an important raw material for the steel industry and welding electrode production, especially critical for smelting special steels such as high-manganese steels and stainless acid-resistant steels.
Common compositions for EAF steelmaking
- Silicomanganese: about 17% Si and about 65% Mn.
- High-silicon silicomanganese: about 28% Si and about 60% Mn.
Ferrochrome and silicon-chromium alloy: characteristics and uses
Definitions and classification
- Ferrochrome is an alloy of chromium and iron that also contains carbon, silicon, and other elements. By carbon content it is classified as high-, medium-, low-, and micro-carbon ferrochrome.
- An alloy with sufficient chromium and silicon is called silicon-chromium alloy.
Functions and applications
- Chromium added to steel improves toughness, wear resistance, and corrosion resistance.
- Chromium strongly passivates; with increasing chromium content, oxidation resistance improves.
- The main use of ferrochrome is the production of stainless steel; it is also used in tool steels and bearing steels.
Ferrovanadium: characteristics and uses
- Ferrovanadium is used for smelting quality steels and special steels.
- Vanadium acts both as an alloying element and a deoxidizer; it increases toughness, elasticity, and strength, and provides high wear and impact resistance.
Ferrosilicon: uses and the powdering of FeSi with about 75% Si
Uses
- In steelmaking, ferrosilicon is used as a deoxidizer and alloying agent; adding appropriate silicon significantly improves strength, hardness, and elasticity, so it is used in structural, tool, and spring steels.
- In cast iron, ferrosilicon is an important inoculant and a component in spheroidizing practice.
- In ferroalloy production, ferrosilicon is often used as a reducing agent.
Powdering phenomenon of ferrosilicon containing about 75% Si (FeSi75)
- Under normal conditions, products stored for several months show no obvious powdering.
- Powdering is more likely with excessively thick castings (>100 mm), low silicon content (Si <72%), and high impurity levels (e.g., elevated Al, P, Ca).
- When raw materials are seriously impure and one or more impurities exceed limits, the product may appear normal at first, then develop surface cracks after about one week and progressively powder; moisture or rain accelerates powdering.
- If sulfur in ferrosilicon exceeds 0.01% and there is certain calcium, stored ferrosilicon tends to crack and release gases due to reactions of sulfides and carbides with atmospheric moisture.
- In humid air, phosphorus in ferrosilicon can react with water vapor to form phosphine (PH3), causing powdering and posing poisoning risks.
