Heat Resistant Steel
Heat resistant steel is a special type of steel alloy that is engineered to resist high temperatures. Heat resistant steels are commonly used in industrial applications such as boilers, furnaces, and heat exchangers, where extreme temperatures and pressures are common. Heat resistant steel is typically made with high-alloy elements such as molybdenum or chrome-nickel which provide enhanced corrosion resistance and accelerated oxidation of the steel when exposed to high temperatures.
Unlike standard steels, heat-resistant steels are designed to be able to withstand high temperatures without losing their strength and/or other mechanical properties. In general, as the temperature of a material increases, the strength and stiffness decrease. For heat-resistant steels, this decrease is minimized due to the alloying elements that are added to the steel.
Heat-resistant steels are often classified into three major groups – ferritic, austenitic, and martensitic. These groups differ based on the microstructural characteristics of the steel and the alloying elements used.
Ferritic steels are composed of a ferrite matrix and a small amount of additional alloying elements. They maintain ferrite up to temperatures of around 900°C, making them good at resisting corrosion. They are often used in applications including petrochemical, refinery, and power plant equipment.
Austenitic steels consist of an austenite matrix, making them highly ductile, formable, and weldable. They exhibit excellent corrosion and oxidation resistance, even at higher temperatures, making them the most popular type of heat-resistant steels. Austenitic steels are often used in equipment such as boilers and pressure vessels.
The third major group of heat-resistant steels is the martensitic group. Martensitic steels are known for their ability to resist tough mechanical circumstances. They are characterized by their high ultimate tensile strength, making them an excellent option for power plant equipment.
Heat- resistant steels can also be divided into categories based on their high temperature strength. Grade A or B steels are commonly used as high-temperature strength steels. These steels contain molybdenum, chromium, and silicon in their composition, offering excellent strength and oxidation resistance at elevated temperatures. Grade C stainless steel contains a higher concentration of molybdenum and chromium, providing superior oxidation, corrosion, creep and ductility strength.
Heat-resistant steels come in a variety of forms, including plate, bar, and sheet. Plate is used for applications such as heat exchanger tubing and large pressure vessels, while bar and sheet are used for smaller equipment such as exhaust manifolds, furnace linings, and heat exchangers.
Heat-resistant steels are an essential material in a variety of industries, offering excellent strength and corrosion resistance at elevated temperatures. Through their special alloying elements and distinct microstructural characteristics, heat-resistant steels are able to withstand extremely high temperatures while still retaining their mechanical properties.
