SS 304 stainless steel is the most common stainless steel. The steel contains both chromium (between 18% and 20%) and nickel (between 8% and 10.5%) metals as the main non-iron constituents. It is an austenitic stainless steel. It is less electrically and thermally conductive than carbon steel. It is magnetic, but less magnetic than steel. It has a higher corrosion resistance than regular steel and is widely used because of the ease in which it is formed into various shapes.
| Type 304 Stainless Steel Chemical Composition, % | ||||||||
|---|---|---|---|---|---|---|---|---|
|
Standard |
AISI (UNS) |
C, ≤ |
Si, ≤ |
Mn, ≤ |
P, ≤ |
S, ≤ |
Cr |
Ni |
|
ASTM A276/A276M |
304 (S30400) |
0.08 |
1.00 |
2.00 |
0.045 |
0.030 |
18.0-20.0 |
8.0-11.0 |
Corrosion resistance
304 stainless steel has excellent resistance to a wide range of atmospheric environments and many corrosive media. It is subject to pitting and crevice corrosion in warm chloride environments and to stress corrosion cracking above about 60 °C. It is considered resistant to pitting corrosion in water with up to about 400 mg/L chlorides at ambient temperatures, reducing to about 150 mg/L at 60 °C.
For more severe corrosion conditions, when 304 stainless steel is too sensitive to pitting or crevice corrosion by chlorides or general corrosion in acidic applications, it is commonly replaced by 316 stainless steel.
Applications
Gastro norm containers in a salad bar.
304 stainless steel is used for a variety of household and industrial applications such as food handling and processing equipment, screws, machinery parts, utensils, and exhaust manifolds. 304 stainless steel is also used in the architectural field for exterior accents such as water and fire features. It is also a common coil material for vaporizers.
Early SpaceX Starships used SS 301 Stainless Steel in their construction.
Carbon content
304, 304H and 304L all possess the same nominal chromium and nickel content and thus possess the same corrosion resistance, ease of fabrication and weld ability. The difference between 304, 304H and 304L is the carbon content which is >0.03, >0.05 and <0.03 respectively.
The carbon content of 304 (UNS 30400) is restricted to a maximum of 0.08%. Thus 304 is not useful for corrosive applications where welding is required such as tanks and pipes where corrosive solutions are involved, thus, 304L is preferred. And its lack of minimum carbon content is not ideal for high temperature applications where optimal strength is required, thus, 304H is preferred. Thus 304 is typically restricted to bars that will be machined into components where welding is not required or thin sheets that are formed in articles such as kitchen sinks or cookware that are also not welded.
Use of Stainless Steel
Stainless steel is a type of steel that contains a minimum of 10.5% chromium, which gives it its unique properties such as corrosion resistance, high strength, and durability. Stainless steel is widely used in various industries and applications, including:
Construction: Stainless steel is used in construction for structural components, cladding, and roofing. It is also used for interior and exterior decorative elements like handrails, door handles, and fittings.
Food and Beverage Industry: Stainless steel is used extensively in the food and beverage industry because of its corrosion resistance and ease of cleaning. It is used for equipment such as tanks, pipes, and fittings.
Medical Industry: Stainless steel is used in the medical industry for surgical instruments, orthopedic implants, and medical equipment because it is corrosion-resistant, strong, and hygienic.
Automotive Industry: Stainless steel is used in the automotive industry for exhaust systems, trim, and other components that require corrosion resistance and durability.
Aerospace Industry: Stainless steel is used in the aerospace industry for aircraft parts, such as engine components, structural parts, and fasteners, because of its high strength-to-weight ratio and resistance to extreme temperatures.
Household Appliances: Stainless steel is used for household appliances such as refrigerators, ovens, and dishwashers because it is easy to clean, durable, and has a modern, sleek appearance.
Overall, stainless steel’s unique properties make it a versatile and highly valued material in many different industries and applications.