What is the difference between 321 and 304 materials?

1. Composition difference
304 stainless steel: The main components include iron, chromium and nickel, of which the chromium content is more than 18% and the nickel content is more than 8%. This alloy composition makes 304 stainless steel have good corrosion resistance and formability.
321 stainless steel: It also contains iron, chromium and nickel as the main components, but titanium or niobium elements are added to its alloy composition. Specifically, the chromium content in 321 stainless steel is about 17%, the nickel content is about 9%, and it contains about 0.3% titanium. The addition of these elements makes 321 stainless steel have better strength and creep properties in high temperature environments.

2. Mechanical property difference
304 stainless steel: It shows good strength, ductility and toughness at room temperature and is a representative of general stainless steel.
321 stainless steel: Due to the presence of titanium or niobium elements, its strength and creep properties at high temperatures are better than 304 stainless steel. In high temperature environments, 321 stainless steel can maintain better mechanical properties and is suitable for high temperature applications.
3. Corrosion resistance difference
304 stainless steel: It shows good corrosion resistance under general environmental conditions and is widely used in many industries. However, its corrosion resistance may be affected to a certain extent in highly corrosive media or high temperature environments.
321 stainless steel: In addition to having corrosion resistance comparable to that of 304 stainless steel, it exhibits superior corrosion resistance in high temperature and highly corrosive media environments. This is because the addition of titanium or niobium elements helps to reduce intergranular corrosion and improve the overall corrosion resistance of the material.
4. Differences in application areas
304 stainless steel: Due to its good corrosion resistance and formability, it is widely used in the industrial and furniture decoration industries as well as the food and medical industries. These fields have high requirements for the corrosion resistance and processing properties of the material.
321 stainless steel: Due to its excellent high temperature stress rupture performance and high temperature creep resistance, it is more suitable for manufacturing welded components used at high temperatures. For example, applications in high temperature environments such as petroleum exhaust gas combustion pipelines, engine exhaust pipes, and boiler shells.