321 Stainless Steel: A Solid Choice | Intamet

10 May 2024

At Intamet, we pride ourselves on providing top-quality stainless steel solutions to meet the diverse needs of our clients across the UK. Our range includes the robust 321 stainless steel, known for its exceptional resistance to corrosion and impressive performance at high temperatures. This makes it a versatile choice for various demanding applications.

Understanding 321

321 stainless steel is a titanium-stabilised austenitic stainless steel. It is renowned for its excellent resistance to intergranular corrosion following exposure to temperatures in the chromium carbide precipitation range of 800–1500°F (427–816°C). This alloy maintains its strength and resistance in high-temperature environments, making it ideal for applications that involve continuous or intermittent service at these temperatures.

Composition and Properties:

Chemical Composition: It contains a minimum of 17% chromium, 9% nickel, and is stabilised with titanium. This unique composition enhances its resistance to oxidation and corrosion.
Mechanical Properties: It boasts a tensile strength of 620 MPa and a yield strength of 310 MPa. The elongation of 321 stainless steel is approximately 40%, providing excellent flexibility.

Types of 321

321H Stainless Steel

Attributes: This variant has a higher carbon content, enhancing its strength and making it suitable for high-temperature applications. It offers improved creep resistance and can withstand long-term exposure to elevated temperatures.
Uses: Commonly used in high-temperature chemical processing, petroleum refining, and heat exchanger components.

321F Stainless Steel

Attributes: Stabilised with titanium to prevent carbide precipitation, 321F stainless steel is designed for applications where high temperatures are a concern.
Uses: Ideal for exhaust manifolds, high-temperature furnace parts, and thermal oxidisers.

321L Stainless Steel

Attributes: This variant has a lower carbon content than standard 321, which enhances its resistance to intergranular corrosion, particularly in welding applications.
Uses: Suitable for welding applications and environments that require strong corrosion resistance.

321Ti Stainless Steel

Attributes: Similar to 321F, but uses titanium as a stabilising element, enhancing its strength and resistance to high-temperature oxidation.
Uses: Commonly used in heat exchangers, furnace parts, and chemical processing equipment.

321LN Stainless Steel

Attributes: A low-carbon, nitrogen-strengthened version of 321. It offers improved toughness and resistance to intergranular corrosion.
Uses: Ideal for cryogenic applications and environments that demand high impact strength.

Physical & Mechanical Properties of 321/321H

Physical Properties:

Density: 0.28 lb/in³ (7.99 g/cm³)
Melting Point: 2550-2650°F (1399-1454°C)

Mechanical Properties:

Tensile Strength: 90 ksi (620 MPa)
Yield Strength: 45 ksi (310 MPa)
Elongation: 40%
Hardness: Rb 95
Impact Strength: 20 ft-lb (27 J)

321/321H stainless steel’s combination of physical and mechanical properties makes it ideal for high-temperature applications such as furnace parts, heat exchangers, and boilers.

Variants of 321

321 stainless steel is versatile and has several variants, each tailored to specific needs:

321F: Stabilised with titanium, designed for high-temperature stability.
321L: Lower carbon content, enhancing resistance to intergranular corrosion.
321H: Higher carbon content for improved strength at high temperatures.
321Ti: Uses titanium for stabilisation, enhancing high-temperature strength.
321LN: Low-carbon, nitrogen-strengthened, offering improved toughness and corrosion resistance.

Each variant offers unique properties and benefits, making them suitable for a wide range of applications. It is crucial to choose the right variant based on specific requirements to ensure optimal performance.

FAQs

Q: What is the difference between 321 and 321H stainless steel?

A: 321H has a higher carbon content, which improves its strength and high-temperature performance compared to standard 321.

Q: Can 321 stainless steel be welded?

A: Yes, 321 stainless steel can be welded using standard welding methods. 321L is preferred for welding due to its lower carbon content, reducing the risk of intergranular corrosion.

Q: What industries commonly use 321 stainless steel?

A: Industries such as aerospace, petrochemical, and chemical processing frequently use 321 stainless steel for its high-temperature and corrosion-resistant properties.

Q: How does titanium stabilisation benefit 321 stainless steel?

A: Titanium stabilisation prevents carbide precipitation during welding, enhancing the alloy’s resistance to intergranular corrosion.