Non-metallic inclusions in special steels - nitrides, rare earth inclusions

Nonmetallic inclusion in special steels

Non-metallic inclusions in special steels are an important indicator of the quality of special steels. Non-metallic inclusions are tiny particles that are not part of the basic structure of the metal, but are incorporated while the steel is still in a molten form. These inclusions can vary in type, size and quantity and affect the mechanical properties of the steel or its surface finish during the working process.

The most common type of nonmetallic inclusions found in special steels is nitride inclusions. Nitrides are compounds formed when nitrogen reacts with the surface of the metal, usually at elevated temperatures. Nitride inclusions have a greater potential to cause brittleness and cracking in special steels, especially when the steel is subjected to prolonged heating.

Rare earth inclusions are also common in special steels. These inclusions are usually composed of rare earth oxides, and are formed from the atmosphere of the steel-making process. The higher the concentration of rare earth elements found in the steel, the higher the strength of the steel will be. When rare earth inclusions are excessive, they tend to weaken the steel leading to cracks and deformation during working.

Inclusion of other nonmetals such as carbon, phosphorus and sulfur are also common in special steels. These elements can both improve the machinability of the metal and its corrosion resistance. The presence of carbon and phosphorus in the metal can also aid in the quenching process, allowing the steel to be tempered to its maximum strength. Too much phosphorus, however, can reduce the toughness of the steel and lead to cracking.

Sulfur, on the other hand, can lead to the formation of very brittle non-metallic inclusions known as sulfide inclusions. These inclusions can cause cracking during the working process, leading to premature failure of the part or component. Too much sulfur in the steel will reduce the ductility, or ability of the steel to be rolled or forged, as well as reduce its fatigue strength.

The presence of non-metallic inclusions in special steel can have a significant effect on the performance of the steel. In order to ensure the best possible quality of the metal, it is important to properly identify and remove any non-metallic inclusions present. The steel manufacturer must have detailed knowledge of the type, size and quantity of non-metallic inclusions in order to determine the best way to remove them. Special steels with properly controlled inclusions can produce stronger, more durable components, while poorly controlled inclusions can lead to cracking, brittleness and crack propagation.

Nonmetallic Inclusions in Special Steels

Non-metallic inclusions in special steels include nitrogen-bearing compounds and rare earth compounds. These non-metallic inclusions are foreign inclusions in steel, and they will not form part of the desired products. The presence of these non-metallic inclusions in the steel affects the properties of the steel and the properties of the mechanical parts made with this steel.

Nitrogen-bearing compounds are compounds that contain nitrogen, such as nitrogen oxides, nitrides, and carbides. Nitrogen oxides are the most commonly encountered and are believed to be formed in the steel-making process. Nitrogen-bearing compounds can improve the strength and toughness of the steel, but they can also make the steel susceptible to corrosion and embrittlement.

Rare earth compounds are compounds that contain rare earth elements, such as scandium, yttrium, and lanthanum. Rare earth compounds are believed to form when steel is cast or welded. They can also be present in steel products due to the use of rare earth-based alloys. Rare earth compounds are beneficial because they can improve the mechanical properties of steel.

Non-metallic inclusions can have adverse effects on the properties and performance of a product if they are not addressed. It is important for steel manufacturers and users to control the levels of nitrogen-bearing compounds and rare earth compounds in special steel products. Controlling the levels of these compounds can help ensure the desired properties, performance, and quality of the steel.