Types and Uses of Stainless Steel
Stainless steel material is an alloy metal material that appeared in the early 20th century. The biggest feature of stainless steel material is corrosion resistance and not easy to wear. Since it was invented and entered the market, it has become the new darling of people. At present, all kinds of products made of stainless steel have become the most common type of daily utensils.
What is stainless steel material?
Stainless steel material, as the name implies, is a steel material that is not easy to rust. It belongs to a kind of metal material. It is an alloy metal material with both corrosion resistance and stainless properties. The main alloying element in stainless steel is chromium. The content of chromium is usually between 10% and 20%. Stainless steel is popular for its high corrosion resistance. The corrosion resistance of stainless steel is 200 times that of mild steel.
Types and Uses of Stainless Steel Material
After years of research and development, stainless steel has many classifications. Among them, according to the different matrix structure of stainless steel materials, it is mainly divided into: ferritic stainless steel, austenitic stainless steel and austenitic-ferritic (duplex) stainless steel, martensitic stainless steel and precipitation hardening stainless steel. Now, I will bring you relevant information on the types and uses of stainless steel materials.
1. Ferritic stainless steel
Ferritic stainless steel is the most common type of stainless steel material, and it is a kind of stainless steel mainly composed of ferrite in use. Ferritic steels contain trace amounts of nickel, 12-17% chromium, less than 0.1% carbon, and other alloying elements such as molybdenum, aluminum or titanium. The American Iron and Steel Institute designates 430 and 446.
Use: In addition to good corrosion resistance, ferritic stainless steel is characterized by good oxidation resistance and excellent stress resistance, and it also has good ductility, formability, thermal conductivity and minimal expansion. coefficient. However, ferritic stainless steel has poor plasticity, so it is mostly used to manufacture parts that are resistant to corrosion by the atmosphere, water vapor, water and oxidative acids. In addition, its price is relatively low and stable, and it is often used in construction and automobile decoration.
Certain ferritic stainless steels are priced lower than others, such as 409 and 405. These metals are magnetic but cannot be heat treated and can be strengthened by cold working.
2. Austenitic stainless steel
Austenitic stainless steel is a kind of stainless steel material with stable austenite structure inside. In addition to containing 18% chromium and about 8% nickel, it also contains a small amount of molybdenum, titanium, nitrogen and other elements. This kind of stainless steel material belongs to the product with good comprehensive performance, which can resist the corrosion of various media. Moreover, the toughness and plasticity of austenitic stainless steel are relatively good, and at the same time, its free cutting performance is also very good. The American Iron and Steel Institute is designated by numbers in the 200 and 300 series, such as 304.
Use: Currently, austenitic stainless steels account for the largest share of the global stainless steel market. Austenitic stainless steel materials are widely used in various industries. Its functional uses are mostly food processing equipment, kitchen utensils and medical equipment. Austenitic stainless steels are weldable stainless steels. It can be roughly divided into three categories: ordinary chromium nickel (300 series), manganese chromium nickel nickel nitrogen (200 series) and special alloys. These metals are non-magnetic and not heat treatable. It is commonly used in chemical industry, marine engineering, food, biomedicine, petrochemical aircraft industry, etc. Among them, 304 stainless steel is the most common austenitic stainless steel. It is also called 18/8 stainless steel in the industry. Its metal products have high temperature resistance and good processing performance, so it is widely used in industry, furniture decoration industry and food and medical industry.
3. Martensitic stainless steel
Martensitic stainless steels are hardenable stainless steels. According to the chemical composition, it can be divided into two categories: martensitic chromium steel and martensitic chromium-nickel steel. The American Iron and Steel Institute is designated by the numbers 410, 420 and 440.
Martensitic steels contain 11-17% chromium, less than 0.4% nickel and up to 1.2% carbon. The carbon content of this hardenable steel affects forming and welding. To obtain practical properties and prevent cracking, preheating and post-weld heat treatment are required. Martensitic stainless steels are magnetic and heat treatable, such as types 403, 410, 410NiMo and 420.
Use: At present, this kind of stainless steel material is mainly used in the production of cutting tools, wrenches and turbines, cutting tools, steam turbine blades, dental and surgical instruments and other products. Martensitic chromium steels are often used in parts, components, tools, knives, etc. that require high hardness but less corrosion resistance; typical steel grades are 2Crl3, 4Crl3, 9Crl8, etc. The strength of martensitic chromium-nickel steel is relatively high, generally reaching 1200-1400MPa, and it is often used to make structural parts that do not require high corrosion resistance but require high strength, such as aircraft skins.
4 austenitic - ferritic duplex stainless steel
Austenitic-ferritic duplex stainless steel is a stainless steel product with a half internal austenite and half ferrite structure. Duplex stainless steels typically contain about 22-25% chromium, 5% nickel, and molybdenum and nitrogen. 329 is a typical duplex stainless steel.
Use: It has the characteristics of austenitic stainless steel and ferritic stainless steel, and compared with ferritic stainless steel, it has better plasticity and higher toughness, and compared with austenitic stainless steel, its thermal conductivity is better, expansion coefficient is smaller. This is mainly used in chemical plants and pipeline applications.
5. Precipitation hardening stainless steel
Precipitation hardening stainless steel is a chromium-nickel stainless steel that contains other alloying components such as aluminum, copper or titanium. The American Iron and Steel Institute is marked with a 600 series number, such as 630, which is 17-4PH.
These alloys allow stainless steel to be hardened by solution and aging heat treatments. In the aged state, they can be austenitic steels or martensitic steels.
In addition, stainless steel can be divided into: chromium stainless steel, chromium-nickel stainless steel and chromium-manganese-nitrogen stainless steel according to the composition. According to its corrosion resistance: stainless steel (can resist corrosion in the air) and stainless acid-resistant steel (can resist corrosion in some chemical media).
Use: Precipitation hardening stainless steel has comprehensive properties such as high strength, high toughness, high corrosion resistance, high oxidation resistance and excellent formability and weldability, and is widely used in cutting-edge industries such as nuclear industry, aviation and aerospace industry and civil industry.