What is 1.4878 Stainless Steel?

1.4878 stainless steel, commonly known as 321H or UNS S32109, is the higher carbon variant of the titanium-stabilized 321 austenitic stainless steel. The increased carbon content provides improved high-temperature strength and creep resistance, making it the material of choice for high-temperature structural applications such as superheaters, heat exchangers, and pressure vessels in power generation and petrochemical industries.

 

This high-temperature grade is standardized under key international designations.

	1.4878
	321H, UNS S32109
	SUS321H
	STS321H

Its composition balances carbon for strength and titanium for stabilization.

	C			P	S
	0.04 - 0.10	<= 1.0	<= 2.0	<= 0.045	<= 0.03	17.0 - 19.0	9.0 - 12.0	>= 4xC%

It offers enhanced high-temperature mechanical properties compared to standard 321.

	Yield Strength (Rp0.2)
	>= 205 MPa	500 - 750 MPa	>= 40%	<= 215

 

Key Characteristics and Applications of 1.4878 / 321H

Enhanced High-Temperature Strength: The higher carbon content provides improved creep and stress rupture strength at temperatures above 500℃ compared to standard 321, making it suitable for load-bearing applications at elevated temperatures.

Like standard 321, the titanium addition binds with carbon to prevent chromium carbide formation, ensuring resistance to intergranular corrosion in the sensitization temperature range (450-850℃).

Maintains good resistance to scaling and oxidation in continuous service up to about 900℃ and intermittent service up to 925℃.

 

Superheater and reheater tubing, boiler components, and high-temperature headers in fossil fuel and nuclear plants.

Catalytic converter housings, reforming furnace tubing, and pyrolysis coils.

High-temperature engine components and exhaust systems.

Heat exchanger tubing and radiant tubes in industrial furnaces.

 

What is the main difference between 321 (1.4541) and 321H (1.4878)?
The key difference lies in the carbon content specification. Standard 321 has a maximum carbon content of 0.08%, while 321H has a controlled carbon range of 0.04-0.10%. This intentional higher minimum carbon content in 321H is designed to provide higher tensile and creep strength at elevated temperatures. Both grades contain titanium for stabilization, but 321H is engineered specifically for applications where high-temperature mechanical performance is more critical than maximum intergranular corrosion resistance in the as-welded condition.

 

Why is 321H preferred for high-temperature pressure vessel codes?
Pressure vessel codes such as ASME Section I and Section VIII recognize 321H for high-temperature service because its guaranteed minimum carbon content ensures predictable and reliable creep strength at elevated temperatures. The material meets specific minimum stress values at high temperatures that are not guaranteed by the standard 321 grade, making it a code-approved choice for critical high-temperature, high-pressure components.

 

Looking for a Reliable Supplier of 1.4878 / 321H Stainless Steel?
GNEE Steel supplies high-temperature grade 321H (1.4878) stainless steel in tubular, plate, and bar forms, suitable for demanding power and process industry applications. We provide full material traceability and certification to relevant standards. If you have any requirements, please feel free to contact us.