Is 304 or 321 stainless steel better?

If your company uses metal for its products, you’ve probably heard of the terms “321 Stainless Steel” and “304 Stainless Steel.” But what do these two materials mean? This blog post will discuss the differences between 304 vs 321 stainless steel to help you understand which type of material is best for your project.

Definition of 304 vs 321 Stainless Steel

304 Stainless Steel

304 stainless steel is a widely used grade of austenitic stainless steel known for its excellent corrosion resistance. It contains 18% chromium and 8% nickel, providing good durability and formability. This stainless steel is commonly used in various applications such as kitchen equipment, food processing, architectural components, and industrial equipment.

321 Stainless Steel

321 stainless steel is an austenitic stainless steel alloy that contains titanium as an alloying element. This addition of titanium enhances its resistance to intergranular corrosion, particularly during welding and high-temperature operations. Due to its improved corrosion resistance at elevated temperatures, 321 stainless steel is often employed in applications such as exhaust systems, jet engine components, and high-temperature chemical processing.

In summary, 304 stainless steel offers general corrosion resistance and versatility, while 321 stainless steel provides enhanced resistance to intergranular corrosion and is well-suited for high-temperature environments.

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304 vs 321 Stainless Steel – What’s the Difference

Chemical Composition of 304, 321, 321H

GradesCSiMnCrNiSPNTi3040.081.02.018.0～20.08.0～10.50.030.045//3210.081.02.017.0-19.09.0-12.00.030.0450.15C-0.70321H0.04-0.11.02.017.0-19.09.0-12.00.030.0450.10.16-0.7

Physical Properties of 304 vs 321 Stainless Steel:

Property304 Stainless Steel321 Stainless SteelCrystal StructureFCCFCCTensile StrengthHighHighYield StrengthHighHighDensity~8 g/cm³~8 g/cm³Melting Point1400-1450°C1400-1450°CThermal Conductivity16.2 W/m·K16.3 W/m·K

Chemical Properties of 304 vs 321 Stainless Steel:

Property304 Stainless Steel321 Stainless SteelCorrosion ResistanceGoodGoodIntergranular CorrosionLimited (After Welding)Superior (Due to Titanium)Oxidation ResistanceGoodExcellentMaximum Service Temperature~870°C~900°C

Advantages of 304 Stainless Steel:

• Good general corrosion resistance, suitable for many environments.
• Good weldability and processability, suitable for a variety of manufacturing processes.
• Suitable for general industrial applications, such as food processing, construction, kitchen equipment, etc.

Disadvantages of 304 Stainless Steel:

• Limited high-temperature resistance, prone to intergranular corrosion above 800°C.
• Intergranular corrosion may occur after welding, especially at high temperatures.

Advantages of 321 Stainless Steel:

• Excellent high-temperature resistance, suitable for high-temperature environments and high-temperature chemical treatment.
• Excellent weldability, reducing the risk of intergranular corrosion after welding.
• Due to the titanium content, it has excellent resistance to intergranular corrosion.

Disadvantages of 321 Stainless Steel:

• Compared with 304 stainless steel, it may be more expensive.
• The corrosion performance in some general environments may be relatively weak.

Application of 304 vs 321 Stainless Steel

Here’s a comparison of the applications for 304 vs 321 stainless steel:

304 Stainless Steel Applications:

• Food Processing Equipment: 304 stainless steel is commonly used in the food industry for equipment such as sinks, countertops, utensils, and storage tanks due to its good corrosion resistance and hygienic properties.
• Architectural Components: It’s used for decorative elements like handrails, facades, and fixtures due to its aesthetic appeal and durability.
• Kitchen Appliances: Many household kitchen appliances are made from 304 stainless steel because of its corrosion resistance and easy-to-clean surface.
• Industrial Equipment: It’s used in various industrial applications like storage tanks, pressure vessels, and valves where resistance to corrosion and wide compatibility with different substances are important.
• Automotive Parts: Certain automotive components like exhaust systems and trim elements utilize 304 stainless steel for its corrosion resistance and appearance.
• Medical Equipment: 304 stainless steel is suitable for medical instruments and equipment that require corrosion resistance and ease of sterilization.

321 Stainless Steel Applications:

• High-Temperature Environments: 321 stainless steel excels in high-temperature applications where it is exposed to elevated temperatures, such as exhaust systems, headers, and manifolds in automobiles and aircraft.
• Jet Engine Components: Due to its excellent high-temperature strength and resistance to oxidation, 321 stainless steel is used in components like exhaust nozzles and flanges within jet engines.
• Chemical Processing: 321 stainless steel is chosen for equipment used in high-temperature chemical processing, where its corrosion resistance and ability to withstand aggressive chemical environments are important.
• Heat Exchangers: It’s suitable for heat exchangers that operate in corrosive and high-temperature environments.
• Oil and Gas Industry: 321 stainless steel can be used in components and equipment for oil refining, particularly in sections exposed to high temperatures.
• Welded Tubing and Piping: The improved intergranular corrosion resistance of 321 stainless steel makes it a good choice for welded tubing and piping used in high-temperature and corrosive environments.

In conclusion, the choice of 304 vs 321 stainless steel depends on your specific needs and applications. If high-temperature resistance and intergranular corrosion resistance are required, 321 stainless steel is a better choice. If general corrosion resistance and versatility are primary requirements, 304 stainless steel is a widely adopted option.

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304 Stainless and 321 Stainless are two common types of stainless steel alloys that differ in their chemical composition and mechanical properties. While both alloys are widely used in various industries, including the automotive industry, they have distinct differences that make them suitable for different applications.

CHEMICAL COMPOSITION

304 Stainless is a low-carbon austenitic stainless steel alloy that contains chromium (18%) and nickel (8%) as its main alloying elements. It is the most commonly used stainless steel alloy due to its good corrosion resistance, ease of fabrication, and low cost.

321 Stainless is a stabilized austenitic stainless steel alloy that contains chromium (17%-19%), nickel (9%-12%), and titanium (5x[C]+0.7%) as its main alloying elements. Titanium is added to the alloy to stabilize it at high temperatures, making it more resistant to intergranular corrosion and sensitization.

MECHANICAL PROPERTIES

304 Stainless has excellent corrosion resistance, good formability, and high strength. It has a maximum operating temperature of around 1472°F and a maximum strength of around 90 ksi.

321 Stainless has similar corrosion resistance, formability, and strength as 304 Stainless, but it is more resistant to high-temperature oxidation and creep. It has a maximum operating temperature of around 1580°F and a maximum strength of around 95 ksi.

AUTOMOTIVE APPLICATIONS

304 Stainless is commonly used in exhaust systems, catalytic converters, and mufflers due to its good corrosion resistance and low cost. 304 Stainless is suitable for most automotive applications, including turbo manifolds, where operating temperatures do not exceed 1,472°F. 

321 Stainless, due to its high-temperature resistance and resistance to sensitization, is commonly used in extremely high-temperature automotive applications where operating temperatures exceed 1,472°F but remain below 1,580°F. It is also used in welding applications where the alloy needs to be stabilized to avoid sensitization and intergranular corrosion.

In conclusion, both 304 Stainless and 321 Stainless are commonly used in automotive applications due to their excellent corrosion resistance, formability, and strength. However, they differ in their chemical composition and mechanical properties, which make them suitable for different applications. While 304 Stainless is commonly used applications where operating temperatures do not exceed 1,472°F, 321 Stainless is more suitable for extremely high-temperature applications due to its resistance to oxidation and creep.