The properties of ferritic stainless steel

Ferritic stainless steel is a chromium-based stainless steel without nickel. It possesses the forming properties, economic advantages, corrosion resistance, and oxidation resistance that nickel-containing stainless steel has. Its characteristics are low cost and excellent stress corrosion resistance. It is also known as economical stainless steel. 

Ferritic stainless steel has a body-centered cubic crystal structure. Except for a few grades, it generally does not contain the scarce alloy element nickel. Compared with the chromium-nickel body-stainless steel that can be used as a substitute, it has obvious cost advantages. 

Chromium-nickel stainless steel is highly sensitive to stress corrosion. In some ineffective accidents involving stainless steel equipment and components, stress corrosion failure accounts for a significant proportion. In contrast, ferritic stainless steel has excellent resistance to stress corrosion. 

The ferritic stainless steel has a higher ferromagnetic property and thermal conductivity. It is approximately 130% to 150% of that of chromium-nickel stainless steel. It is highly suitable for applications involving heat exchange. Its coefficient of linear expansion is only 60% to 70% of that of chromium-nickel stainless steel, making it particularly suitable for applications involving thermal expansion, contraction, and cyclic heat exposure. 

The magnetic properties of ferritic stainless steel are utilized in various applications such as in refrigerators, knives, and other metal items for closing purposes. However, the drawback of ferritic stainless steel is its poor weldability and relatively high brittleness, which limits its usage scope. Ferritic stainless steel can be classified into ordinary ferritic stainless steel, ultra-low carbon ferritic stainless steel, high-purity ferritic stainless steel, and ultra-pure ferritic stainless steel based on the content of carbon and nitrogen. 

Among them, the ultra-pure iron matrix reduces the content of carbon and nitrogen in ferritic stainless steel, ensuring that the content of carbon and nitrogen is less than or equal to 0.01%. Additionally, a small amount of alloy elements such as titanium, niobium, copper, aluminum, and vanadium are also added. This has significantly improved the corrosion resistance, mechanical properties, and welding performance of this type of stainless steel, achieving superior performance compared to ordinary ferritic stainless steel. This is also a development trend of ferritic stainless steel. 

The application of ferritic stainless steel 

Currently, in line with the requirements of sustainable development, ultra-pure ferritic stainless steel that does not contain the metal element nickel (which can cause allergies in humans) is a relatively high-quality resource-saving and environmentally friendly stainless steel material. Especially in recent years, the niobium-containing ferritic stainless steel that has been rapidly developed has demonstrated excellent corrosion resistance, formability, and stress corrosion resistance, with lower costs, and is commonly used in the automotive and construction industries, etc.