What Is Killed Steel?
Killed steel refers to a type of steel characterized by specific manufacturing processes and properties. It is defined by certain conditions necessary for its categorization as killed steel.
During the steel manufacturing process, iron ore is melted to produce pig iron. Since pig iron contains many impurities, steel is produced through a series of processes, including pig iron making, refining, and steel-making.
In the refining stage, oxygen is removed from the molten steel (deoxidization), particularly towards the end of the process. This deoxidization prevents the generation of gases during cooling and solidification, resulting in higher-quality steel.
Based on the level of deoxidation, three types of raw materials (ingots) are produced. The most deoxidized form is known as killed steel, whereas other types include semi-killed and rimmed steel.
Killed steel typically contains about 50 to 100 parts per million (PPM) of oxygen, compared to 100 to 200 PPM in other steel types.
Uses of Killed Steel
Killed steel is distinguished by its manufacturing process, which involves extensive deoxidation and compositional adjustments. This results in a special steel material with exceptional hardness.
Due to the addition of alloying elements during manufacturing, it is possible to produce steel with desired properties, such as hardness, tenacity, wear resistance, heat resistance, and corrosion resistance.
This makes killed steel suitable for structural steel applications in vehicles, machinery, construction, and shipbuilding, where robustness is essential.
Additionally, tool steel, a variant of killed steel with high hardness, is utilized for cutting tools, molds, bits, drills, and similar applications.
Characteristics of Killed Steel
Killed steel is classified based on the deoxidizing agent used. If silicon (ferrosilicon) is employed, it is termed silicon-killed steel; if aluminum is used, it is known as aluminum-killed steel.
Killed steel serves as a raw material for carbon steel, alloy steel, SS material, etc. Its use varies widely based on its composition.
For example, structural steel, often required for its strength, is utilized in civil engineering, construction, and machinery. Stainless steel, another form of special steel, is commonly used in household items.
Tool steels, necessary for their extreme hardness, are employed in cutting and processing tools, as well as in molds for plastic molding. Superalloys, capable of maintaining high hardness at extreme temperatures, are used in aircraft, gas turbines, and similar high-performance applications.
Other steel types include spring steel for various springs and vehicle plate springs, bearing steel for bearings and rollers requiring wear resistance, and free-cutting steel, which is specialized for ease of machining rather than hardness, ideal for high-precision parts and products.