• May 18th 2023

Stainless steels 304 and 420 are two commonly used alloy types, with each grade offering different properties and applications. Understanding the key differences between these stainless steel alloys can help determine which is best suited for a particular purpose.

Chemical Composition

304 stainless contains 18% chromium and 8% nickel which provide excellent corrosion resistance. The nickel also improves strength and durability. How to Buy 304 Stainless Steel Coil?

420 stainless contains 12-14% chromium but no nickel. It achieves strength through a higher carbon content of 0.15-0.25%. The increased carbon also reduces corrosion resistance compared to grade 304.

Properties

Strength: 420 stainless steel has higher yield and tensile strength thanks to its higher carbon content. It is often used for applications that require strength over corrosion resistance.

•Grade 420 yield strength - 90-135 ksi
•Grade 304 yield strength - 30-35 ksi

Corrosion Resistance: 304 stainless has better corrosion resistance due to the nickel content. It is designed to withstand chemicals, acids and marine exposure.

• Suitable for moderate corrosive environments
• Resists corrosion caused by chlorides and acids

420 stainless has lower corrosion resistance and is not suitable for prolonged exposure to corrosive environments.

Workability: The lower alloy content of grade 420 makes it easier to form, bend and weld. 304 stainless requires more complex welding techniques due to higher nickel and chromium.

Structural Differences

Microstructure: 420 stainless forms a martensitic structure due to the carbon content, while 304 forms an austenitic structure. This impacts their mechanical properties.

Grain Size: The martensitic structure of 420 steel results in a larger grain size compared to 304 steel, impacting strength and corrosion resistance.

Applications

Grade 304 is used for architectural and design applications, food processing equipment, and chemical handling equipment due to its high corrosion resistance.

Grade 420 is used for applications requiring wear resistance and higher strength over corrosion resistance like cutting tools, nails, screws, and gear components.

In summary

The key differences between 304 and 420 stainless steel result from their chemical composition and carbon content. While grade 304 has higher corrosion resistance due to nickel, grade 420 has better strength and wear resistance due to more carbon - making it ideal for applications that emphasize mechanical properties over chemical resistance. By considering the properties required for their intended uses,you can determine which stainless steel grade is best suited to meet your needs.