AISI 304 Stainless Steel
AISI 304 stainless steel (UNS S30400) is the most commonly used material in stainless steels, and is usually purchased in an annealed or cold worked state. It contains 18% chromium and 8% nickel, making it a versatile stainless steel which is widely used in domestic and industrial applications. Its machinability, physical and mechanical properties, and resistance to corrosion make AISI 304 stainless steel an ideal choice for a wide range of uses.
Mechanical Properties
AISI 304 stainless steel has a very good yield strength, with values ranging from 0.2% to 1.5%. It is fairly ductile, providing good formability, and it offers good resistance against impact and abrasion. As a result, it is a good structural material for a wide range of applications. It also has a higher thermal conductivity than most other stainless steels, making it suitable for applications which involve heat transfer.
The tensile strength of AISI 304 stainless steel ranges from 58-80 ksi (400- 550 MPa). It has a Rockwell Hardness of 90 and a Brinell Hardness of 150. It has a melting point of 1454-1455°C (2650-2652°F).
Chemical Properties
AISI 304 stainless steel is composed of a minimum of 18% chromium and 8-10.5% nickel combined with sulfur, silicon, phosphorus and carbon. It contains 18-20% chromium and 8-10.5% nickel. Its chemical makeup makes it resistant to various forms of corrosion, particularly mild and sulfuric acid corrosion.
It also has excellent welding properties, due to the higher amount of iron alloyed with chromium and nickel. It is generally easier to weld than other stainless steels.
Corrosion Resistance
AISI 304 stainless steel is highly resistant to corrosion due to the high levels of chromium and nickel alloyed within its composition. The addition of molybdenum increases its corrosion resistance in more aggressive environments.
It is also immune to stress-corrosion cracking. It is even able to withstand high concentrations of chlorides such as the salt water of a swimming pool or the ocean. Due to its excellent resistance to corrosion, it is a popular choice for marine and other extreme environments.
Magnetic Properties
AISI 304 stainless steel is generally non-magnetic, due to the presence of chromium and nickel within its composition. However, it may become slightly magnetic when it is cold worked or welded. Cold working can cause some of the chromium to form small amounts of magnetic domains, resulting in a slight degree of magnetic moments.
Heat Treatment
AISI 304 stainless steel is usually annealed at temperatures ranging from 1010-1121°C (1850-2050°F) depending on its composition. It is often used in slightly tempered condition in the range of 815-871°C (1500-1600°F).
AISI 304 stainless steel can be hardened by cold working, by heat treating or by a combination of both. It is hardened by annealing at temperatures between 1010-1121°C (1850-2050°F).
Applications of AISI 304 Stainless Steel
AISI 304 stainless steel is widely used in many applications due to its excellent properties. It is well-known for its good corrosion resistance, excellent formability, and superior weldability. It is commonly used in food processing equipment, medical equipment, process piping, and architectural applications.
It is also used in cookware, sinks, utensils, and eye-wear frames. Its corrosion resistance makes it suitable for use in outdoor applications and extremes of temperature. Its good formability allows it to be deep drawn into components with complex shapes. It is also used in automotive applications such as tailpipes, mufflers, and exhaust systems.
Conclusion
AISI 304 stainless steel is a versatile material which has many excellent properties. It has very good mechanical and physical properties, as well as being highly corrosion resistant. It is a popular choice for many applications due to its cost effectiveness, formability and weldability. Its superior combination of properties makes it suitable for a wide range of uses, from food processing to architectural applications.
