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.
