Stainless steel 304 is one of the most widely used grades of stainless steel, known for its excellent corrosion resistance, good mechanical properties, and ease of fabrication. It belongs to the austenitic family of stainless steels, which are non-magnetic and characterized by high toughness and good weldability. Due to these attributes, 304 stainless steel is used across various industries, including food processing, chemical processing, construction, and household appliances. This article will delve into the key characteristics of 304 stainless steel, including its chemical composition, physical properties, mechanical properties, and corrosion resistance.
1. Chemical Composition
Stainless steel 304 consists primarily of iron, with a significant percentage of chromium and nickel. The typical chemical composition of 304 stainless steel is as follows:
• Chromium (Cr): 18–20%
• Nickel (Ni): 8–10.5%
• Manganese (Mn): 2%
• Silicon (Si): 1%
• Carbon (C): 0.08% max
• Phosphorus (P): 0.045% max
• Sulfur (S): 0.03% max
• Iron (Fe): balance
The high chromium content provides the stainless steel with its resistance to corrosion, while nickel enhances its formability and weldability. The balance of iron forms the base material, providing the necessary strength and structure to the alloy.
2. Physical Properties
The physical properties of 304 stainless steel make it suitable for a wide range of applications. Some of its key physical characteristics include:
• Density: 7.93 g/cm³
• Melting Point: 1400°C (2552°F)
• Thermal Conductivity: 16 W/m·K at 100°C
• Electrical Resistivity: 0.72 µΩ·cm at 20°C
• Magnetic Properties: 304 stainless steel is non-magnetic in the annealed condition, which is a key feature for applications where magnetic properties must be minimized, such as in certain medical and electronic devices.
Due to its relatively low density, 304 stainless steel is lightweight compared to many other metals, which is advantageous for applications in sectors like aerospace and automotive industries.
3. Mechanical Properties
304 stainless steel exhibits excellent mechanical properties, particularly in terms of strength and ductility. The alloy maintains its mechanical strength at both high and low temperatures, which makes it suitable for use in a variety of environments. The following are key mechanical properties:
• Tensile Strength: 520–750 MPa
• Yield Strength: 215 MPa (min)
• Elongation: 40% (in 50 mm gauge length)
• Hardness: Brinell hardness ~170 HB, Rockwell B ~90 HRB
• Modulus of Elasticity: 193 GPa
304 stainless steel maintains its strength even at high temperatures, up to around 870°C (1600°F) in intermittent service, and up to 925°C (1700°F) in continuous service. This makes it suitable for applications that involve high heat, such as heat exchangers, boilers, and pressure vessels.
