What is 1.4948 Stainless Steel?

1.4948 stainless steel, commonly known as 304H or UNS S30409, is the high-carbon variant of the standard 304 austenitic stainless steel. The "H" designation indicates its suitability for high-temperature service, where increased carbon content provides improved creep strength and stress rupture resistance. It is widely used in pressure vessels, boilers, superheaters, and other components operating at elevated temperatures in power generation and petrochemical industries.

 

This high-temperature austenitic grade is standardized under key international systems.

Standard	Equivalent Grade
EN (Europe)	1.4948
ASTM/AISI (USA)	304H, UNS S30409
JIS (Japan)	SUS304H
KS (Korea)	STS304H

Its carbon content is controlled within a higher range to enhance high-temperature strength while maintaining good corrosion resistance.

Element	C	Si	Mn	P	S	Cr	Ni
Content (%)	0.04 - 0.10	≤ 0.75	≤ 2.0	≤ 0.045	≤ 0.03	18.0 - 20.0	8.0 - 10.5

It maintains good mechanical properties at both room and elevated temperatures, with enhanced performance above 500°C.

Property	Yield Strength (Rp0.2)	Tensile Strength (Rm)	Elongation (A)	Hardness (HB)
Typical Value	≥ 205 MPa	500 - 750 MPa	≥ 40%	≤ 215

 

Key Characteristics and Applications of 1.4948 / 304H

Enhanced High-Temperature Strength: The controlled higher carbon content provides improved creep and stress rupture strength at temperatures above 500°C compared to standard 304 or 304L.

Good Oxidation Resistance: Maintains resistance to scaling and oxidation in continuous service up to about 900°C, suitable for many high-temperature industrial applications.

Code-Approved for Pressure Service: Recognized in ASME Boiler and Pressure Vessel Code for high-temperature applications where creep strength is essential.

Excellent Formability: Retains the good forming characteristics of the 304 family, though higher carbon may slightly reduce ductility compared to 304L.

 

Primary Applications:

Power Generation: Superheater and reheater tubing, boiler components, and high-temperature headers.

Petrochemical: Catalytic converter shells, reformer tubes, and high-temperature process piping.

Heat Exchangers: Tubing and plates in services involving elevated temperatures.

Pressure Vessels: Components designed under ASME codes for high-temperature service.

Refinery Equipment: High-temperature process equipment and piping systems.

 

What is the key difference between 304H (1.4948) and 304L (1.4307)?
The primary difference is carbon content and intended service. 304H has a controlled carbon range of 0.04–0.10% to ensure high-temperature strength, while 304L has a maximum carbon content of 0.03% to prevent sensitization and ensure excellent weldability and intergranular corrosion resistance. 304H is specifically designed for high-temperature structural applications where creep resistance is critical, whereas 304L is preferred for welded fabrications operating at lower temperatures or in corrosive environments where weld integrity is paramount.

 

Why is 304H specified in high-temperature pressure vessel codes?
Codes such as ASME Section I and Section VIII include 304H for high-temperature service because its guaranteed minimum carbon content ensures predictable creep strength and stress rupture values at elevated temperatures. These mechanical properties are essential for the safe design of pressure-containing components operating under high temperature and pressure over extended periods. Standard 304 or 304L do not have guaranteed minimum carbon levels and therefore cannot provide the same long-term strength assurance required by code calculations for high-temperature service life.

 

Looking for a Reliable Supplier of 1.4948 / 304H Stainless Steel?
GNEE Steel supplies high-temperature grade 304H (1.4948) 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 including ASME and EN 10204 3.1. If you have any requirements, please feel free to contact us.