The Difference Between 304 and 316 Stainless Steel
Austenitic stainless steels are typically used when selecting a stainless steel that must endure corrosive environments. Possessing excellent mechanical properties, the high amounts of nickel and chromium in austenitic stainless steels also provide outstanding corrosion resistance. Additionally, many austenitic stainless steels are weldable and formable. Two of the more commonly used grades of austenitic stainless steel are grades 304 and 316. To help you determine which grade is right for your project, this blog will examine the difference between 304 stainless steel and 316 stainless steel.
304 Stainless Steel
Grade 304 stainless steel is generally regarded as the most common austenitic stainless steel. It contains a high nickel content, typically between 8 and 10.5 percent by weight, and a high amount of chromium, approximately 18 to 20 percent by weight. Other major alloying elements include manganese, silicon, and carbon. The remainder of the chemical composition is primarily iron.
The high amounts of chromium and nickel give 304 stainless steel excellent corrosion resistance. Common applications of 304 stainless steel include:
- Appliances such as refrigerators and dishwashers
- Commercial food processing equipment
- Fasteners
- Piping
- Heat exchangers
- Structures in environments that would corrode standard carbon steel
316 Stainless Steel
Like 304 stainless steel, Grade 316 stainless steel has high amounts of chromium and nickel. 316 also contains silicon, manganese, and carbon, with much of the composition being iron. A major difference between 304 stainless steel and 316 stainless steel is the chemical composition, with 316 stainless steel containing a significant amount of molybdenum, typically 2 to 3 percent by weight, compared to only trace amounts found in 304 stainless steel. The higher molybdenum content results in grade 316 stainless steel possessing increased corrosion resistance.
316 stainless steel is often considered one of the most suitable choices when selecting an austenitic stainless steel for marine applications. Other common applications of 316 stainless steel include:
- Chemical processing and storage equipment
- Refinery equipment
- Medical devices
- Marine environments, especially those with chlorides present
Which Should You Use: Grade 304 or Grade 316?
Here are some situations where 304 stainless steel may be the better choice:
- The application requires excellent formability. The higher molybdenum content in Grade 316 stainless steel can have adverse effects on formability.
- The application has cost concerns. Grade 304 stainless steel is typically more affordable than Grade 316 stainless steel.
Here are some situations where 316 stainless steel may be the better choice:
- The environment includes a high amount of corrosive elements
- The material will be placed underwater or be exposed to water consistently
- In applications where greater strength and hardness are required
What is 304 Stainless Steel?
304 stainless steel is a common grade of austenitic stainless steel and one of the most versatile and widely used varieties. It’s known for its excellent corrosion resistance, durability, and weldability. Here are some key characteristics and uses of 304 stainless steel:
Stainless steel 304 typically contains 18% chromium and 8% nickel, often called 18/8 stainless steel. The chromium content provides corrosion resistance and lustre, while nickel enhances the formability and ductility of the steel. The alloy may also contain small amounts of carbon, manganese, silicon, phosphorus, sulphur, and possibly molybdenum to enhance specific properties.
There are several variants of ss 304 grade, including 304L, which has a lower carbon content for better weldability and lower risk of corrosion after welding, and 304H, with a higher carbon content, suitable for use at high temperatures.
What is 316 Stainless Steel?
316 stainless steel is a grade of austenitic stainless steel like 304 but with the addition of molybdenum, which significantly increases its corrosion resistance, especially to chlorides and other industrial solvents. Adding molybdenum is crucial as it enhances corrosion resistance, particularly against chlorides and other industrial solvents. It makes 316 stainless steel suitable for applications in harsh chemical environments or marine conditions where higher chloride concentrations can cause pitting and corrosion in less resistant alloys.
The typical composition of 316 stainless steel includes approximately:
- 16% to 18% chromium
- 10% to 14% nickel
- 2% to 3% molybdenum
- Smaller amounts of manganese, silicon, and carbon
There are several variants of 316 stainless steel, including 316L, which has a lower carbon content to improve weldability and decrease the risk of corrosion after welding. Another variant is 316Ti, which includes titanium for stabilization against chromium carbide formation.