Stainless steel 304 and 316 are both common austenitic stainless steels, which differ in composition, performance and application. The following are the main differences between the two stainless steels:
1. Chemical composition difference
Main alloying elements: 18% chromium (Cr) and 8% nickel (Ni).
Contains a small amount of carbon (C) and manganese (Mn), and may also contain a small amount of silicon (Si) and nitrogen (N) and other elements.
304 stainless steel does not contain molybdenum (Mo).
316 stainless steel:
Main alloying elements: 16% chromium (Cr), 10% nickel (Ni), and contains 2-3% molybdenum (Mo).
The addition of molybdenum makes 316 stainless steel have better corrosion resistance, especially in chloride-containing environments.
2. Corrosion resistance
304 stainless steel has good corrosion resistance and can withstand corrosion in most household and industrial environments, such as atmospheric oxidation, food processing and other common environments. However, it may suffer from stress corrosion cracking (SCC) in chloride environments (such as seawater, salt spray, etc.).
316 stainless steel has better corrosion resistance than 304, especially in chloride-containing environments. The addition of molybdenum (Mo) makes it more resistant to chloride corrosion, so 316 stainless steel is often used in highly corrosive environments such as the ocean and chemical industry, and can effectively prevent pitting and crack corrosion.
3. High temperature resistance
304 stainless steel has good high temperature resistance and can be used for a long time in high temperature environments below 870°C, but at higher temperatures, problems such as intergranular corrosion may occur.
The high temperature resistance of 316 stainless steel is similar to that of 304, but due to the addition of molybdenum, it has better tolerance to certain chemical media at high temperatures and is suitable for more extreme high temperature and corrosive environments.
4. Mechanical properties
304 stainless steel has good mechanical properties and is suitable for most conventional applications, with good strength, toughness and machinability.
The mechanical properties of 316 stainless steel are similar to those of 304, but due to the addition of molybdenum, its corrosion resistance is enhanced, so in some occasions requiring higher corrosion resistance, it is more appropriate to choose 316 stainless steel.
5. Price
304 stainless steel is relatively cheap because it does not contain molybdenum, and is the most common industrial stainless steel material.
316 stainless steel is relatively expensive because the addition of molybdenum increases the cost. However, this material has stronger corrosion resistance, so it is more suitable for use in special environments.
6. Application areas
304 stainless steel is widely used in food processing, home appliances, kitchen equipment, architectural decoration, medical equipment and other fields, especially for various applications in ordinary environments.
316 stainless steel is often used in occasions requiring higher corrosion resistance, such as marine environments, chemical processing, pharmaceutical equipment, medical equipment, chemical reactors, seawater contact parts, etc.
Summary
Corrosion resistance: 316 > 304 (especially in chloride and seawater environments).
Cost: 304 < 316 (304 is relatively cheap).
High temperature performance: The two are similar, 316 is slightly better.
Common applications:
304 is suitable for general environments and applications that do not require special corrosion resistance.
316 is suitable for extreme corrosive environments and marine industries.
The choice of 304 or 316 stainless steel is mainly based on the corrosive requirements of the use environment and cost factors. If the use environment is more severe, especially when exposed to chlorides, seawater or chemicals, 316 stainless steel is more suitable.
