Understanding the Types of Stainless Steel

Different types of stainless steel have different characteristics and strengths. The three major types of stainless steel are: 

• Austenitic: High chromium content plus nickel and/or molybdenum; extremely resistant to corrosion. The most common type of stainless steel.
• Ferritic: High chromium content with little or no nickel content; possess magnetic properties and are easier to cut and form. Second most common type of stainless steel. 
• Martensitic: High chromium content with relatively high carbon content; extremely hard and durable. Least common type of stainless steel. 

304 and 316 are two different types of stainless steel, but both fall into the austenitic stainless steel category. Austenitic stainless steels have internal crystal structures called austenites which give them their incredible strength and corrosion resistance. Now that we know a little more about stainless steel, in the next two sections, we’ll get more specific about the properties of both the 304 and 316 grades. 

Basics of 304 Stainless Steel

• Basic Attributes:
  • Strong resistance to corrosion
  • High durability and hardness
  • Excellent heat and cold resistance
  • More weldable and workable than other types of stainless steel
  • Most easily available and least expensive austenitic steel
• By the Numbers:
  • Melting Point: 1400-1450°C
  • Tensile Strength: 515-620 MPa
  • Yield Strength: 205-310 MPa
  • Max Service Temperature in Air: 870°C (intermittent), 925°C (continuous)
  • Density: 7.93 g/cm3
• Typical Composition:
  • 18 percent chromium
  • 8 percent nickel
• Frequently Used for:
  • Food service and kitchen hardware
  • Commercial and industrial fasteners
  • Piping and fittings for plumbing
  • Architectural elements
  • Heat exchange devices
  • Outdoor electrical enclosures

304 stainless steel is by far the most common type of stainless steel available on the market today. In fact, 304 stainless steel makes up over half of the world’s stainless steel supply. That’s because 304 stainless strikes an excellent balance between price and performance. Its substantial anti-corrosion properties and extreme durability combine to make it the standard choice for many applications, and it’s relatively easy to work into a variety of forms, including durable electrical enclosures to protect sensitive equipment. 

Thus, 304 is also the stainless steel you’ll find used in the widest range of everyday applications. From kitchen sinks to industrial control boxes, 304 stainless steel is the industry standard choice in many different sectors. 

Basics of 316 Stainless Steel

• Basic Attributes:
  • Extreme resistance to corrosion
  • High durability and hardness
  • Excellent heat and cold resistance
  • Molybdenum content can interfere with workability
  • A slightly more expensive and specialized austenitic steel
• By the Numbers:
  • Melting Point: 1378-1390°C
  • Tensile Strength: 515-620 MPa
  • Yield Strength: 240-415 MPa
  • Max Service Temperature in Air: 870°C (intermittent), 925°C (continuous) 
  • Density: 8.03 g/cm3
• Typical Composition:
  • 16 percent chromium
  • 10 percent nickel
  • 2 percent molybdenum
• Frequently Used for:
  • Marine equipment
  • Chemical storage and manufacturing equipment
  • Oil and gas extraction equipment
  • Medical equipment

316 stainless steel is another type of stainless steel popular in applications requiring hardness, durability and corrosion resistance, but it tends to have more specialized and limited uses than 304 stainless steel. The most notable property of 316 stainless steel is its extreme resistance to corrosion, particularly corrosion from chloride sources, such as seawater and many industrial chemicals. 

The anti-corrosion properties that set 316 steel apart come from the inclusion of molybdenum in its composition. These properties make 316 the preferred choice for a few specific applications requiring extreme resistance to corrosion. Such applications include heavy duty marine projects and industrial applications where the steel will frequently come in contact with harsh, corrosive substances.