ASTM A312 TP304H stainless steel seamless pipe is an austenitic stainless steel pipe designed for high-temperature and general corrosive service. TP304H is the higher-carbon version of TP304, with a controlled carbon content of 0.04–0.10%, providing improved creep and stress-rupture strength at elevated temperatures.

The material is designated UNS S30409 and is commonly associated with EN 1.4948 / X6CrNi18-10 in European material specifications.

We supply ASTM A312 / ASME SA312 TP304H seamless stainless steel pipes for petroleum, petrochemical, chemical processing, power generation, boiler, heat exchanger and high-temperature process piping applications.

Material Identification

Item	Specification
Material	Austenitic Stainless Steel
ASTM Grade	TP304H
UNS Number	S30409
EN Material No.	1.4948
EN Designation	X6CrNi18-10
Pipe Standard	ASTM A312 / ASME SA312
Manufacturing	Seamless
Primary Feature	Improved high-temperature strength
Typical Service	High-temperature and general corrosive piping

What Is ASTM A312 TP304H Stainless Steel Pipe?

TP304H is a high-carbon modification of conventional TP304 austenitic stainless steel. Unlike stabilized stainless steels such as TP321H, TP304H does not rely on titanium stabilization. Its high-temperature performance is mainly achieved through controlled carbon content and appropriate heat treatment.

ASTM A312 specifically identifies TP304H as a modification of TP304 intended for applications where creep strength and stress-rupture properties are important.

TP304H retains many of the characteristics associated with the 18Cr-8Ni family of austenitic stainless steels, including:

• Good general corrosion resistance
• Good oxidation resistance at elevated temperatures
• Good fabrication characteristics
• Good weldability
• Good forming and bending properties
• Improved elevated-temperature strength compared with standard TP304
• Good structural stability in high-temperature service

For projects involving elevated operating temperatures, TP304H is often considered where standard TP304 or low-carbon TP304L does not provide sufficient long-term creep strength.

ASTM A312 TP304H Pipe Specifications

Specification	Details
Standard	ASTM A312 / ASME SA312
Grade	TP304H
UNS	S30409
EN Reference	1.4948 / X6CrNi18-10
Product Form	Seamless Stainless Steel Pipe
Dimension Standard	ASME B36.19M or specified dimensions
Wall Thickness	SCH 5S, 10S, 40S, 80S and project-specific thicknesses
Ends	Plain End, Beveled End, Threaded End when specified
Heat Treatment	Solution heat treated in accordance with ASTM A312
Surface	Pickled, Passivated, Bright Annealed or as specified
Inspection Certificate	EN 10204 3.1; additional certification subject to project requirements
Testing	Mechanical, Hydrostatic or NDE, PMI and additional testing when specified

Non-standard outside diameters, wall thicknesses and fixed lengths can be supplied subject to mill capability and technical review.

ASTM A312 TP304H Chemical Composition

The controlled carbon range is one of the most important differences between TP304H and TP304/TP304L.

Element	ASTM A312 TP304H / UNS S30409
Carbon, C	0.04–0.10%
Manganese, Mn	≤ 2.00%
Phosphorus, P	≤ 0.045%
Sulfur, S	≤ 0.030%
Silicon, Si	≤ 1.00%
Chromium, Cr	18.00–20.00%
Nickel, Ni	8.00–11.00%

The 0.04–0.10% carbon range distinguishes TP304H from conventional TP304 and low-carbon TP304L. The controlled higher carbon content contributes to improved strength and creep resistance during prolonged exposure to elevated temperatures.

ASTM A312 TP304H Mechanical Properties

Typical minimum room-temperature mechanical requirements for ASTM A312 TP304H include:

Property	Requirement
Tensile Strength	≥ 515 MPa / 75 ksi
Yield Strength	≥ 205 MPa / 30 ksi
Elongation	According to ASTM A312 specimen and wall-thickness requirements
Condition	Solution Heat Treated

Actual mechanical properties shall be verified against the applicable edition of ASTM A312 / ASME SA312, the pipe dimensions and the purchase specification.

TP304H vs TP304 vs TP304L

Although TP304, TP304L and TP304H have similar chromium-nickel base compositions, they are intended for different service conditions.

Grade	UNS	Carbon Control	Main Characteristic	Typical Selection
TP304L	S30403	Low carbon	Reduced sensitization risk after welding	Welded fabrication and corrosive service
TP304	S30400	Standard carbon	General-purpose 18Cr-8Ni stainless steel	General process piping
TP304H	S30409	0.04–0.10%	Improved creep and stress-rupture strength	High-temperature process piping

Why Choose TP304H Instead of TP304?

The principal reason for specifying TP304H is elevated-temperature performance.

At high operating temperatures and during prolonged service, pressure-containing materials must resist gradual deformation caused by creep. TP304H’s controlled carbon content helps provide better high-temperature strength than standard TP304.

TP304H is therefore commonly selected when the design temperature reaches a range where creep and stress-rupture properties become significant design considerations.

TP304H vs TP304L

TP304L is optimized for low carbon content, particularly where welding and resistance to sensitization are priorities.

TP304H follows the opposite approach by maintaining a specified minimum carbon content to improve high-temperature mechanical properties.

For this reason:

• TP304L is generally favored for welded equipment where post-weld corrosion behavior is important.
• TP304H is generally favored for elevated-temperature service where creep strength is important.

The final material selection should always be based on the applicable piping design code, operating temperature, pressure, corrosion environment and project specification.

ASTM A312 TP304H Heat Treatment

ASTM A312 stainless steel pipe is supplied in the heat-treated condition required by the specification.

For TP304H, proper solution heat treatment is essential to obtain the required austenitic microstructure and mechanical properties.

After heat treatment, pipes are cooled in accordance with the applicable material specification and manufacturing procedure.

Heat-treatment records can be included in the material documentation where required by the purchase order or inspection plan.

Surface Condition

ASTM A312 TP304H seamless pipes can be supplied with different surface finishes depending on manufacturing route and project requirements.

Common conditions include:

• Pickled surface
• Pickled and passivated
• Bright annealed surface, where manufacturing route permits
• Mechanically cleaned surface
• Polished surface when specifically required

For most industrial pressure-piping applications, a pickled or pickled-and-passivated surface is commonly specified.

ASTM A312 TP304H Pipe Manufacturing

TP304H seamless pipe is normally produced through hot or cold forming processes followed by the required heat treatment and finishing operations.

A typical manufacturing sequence may include:

1. Raw material inspection
2. Billet preparation
3. Hot piercing or extrusion
4. Hot or cold drawing / rolling
5. Intermediate heat treatment when required
6. Final solution heat treatment
7. Straightening
8. Pickling and surface treatment
9. Dimensional inspection
10. Mechanical and chemical testing
11. Hydrostatic or nondestructive examination
12. Final marking and packing

Manufacturing routes may vary according to pipe diameter, wall thickness, quantity and project specifications.

Inspection and Testing of ASTM A312 TP304H Pipe

Inspection requirements should be separated into standard specification tests and additional project tests.

Standard Inspection

Testing and examination required by the applicable ASTM A312 specification may include:

• Chemical composition verification
• Tensile test
• Flattening test where applicable
• Dimensional inspection
• Visual examination
• Heat-treatment verification
• Hydrostatic test or nondestructive electric examination
• Material identification and marking

Additional Tests Available on Request

Depending on the project specification, purchaser’s inspection and ITP requirements, additional testing can include:

• 100% Positive Material Identification (PMI)
• Ultrasonic Testing (UT)
• Eddy Current Testing (ET)
• Intergranular Corrosion Test (IGC)
• Grain Size Determination
• Surface Roughness Test
• Ferrite measurement where technically applicable
• Additional hardness testing
• Additional chemical analysis
• Third-party laboratory testing
• Third-party witness inspection

Additional tests should be specified in the purchase order before production.

Positive Material Identification — PMI

For critical process piping, 100% PMI can be performed to confirm the alloy identity before shipment.

PMI is particularly useful when several grades of stainless steel or alloy steel are handled within the same project and material traceability is critical.

Material traceability can normally be maintained from:

Heat Number → Pipe Marking → Test Report → Material Test Certificate

Hydrostatic and Nondestructive Examination

ASTM A312 requires each pipe to undergo the applicable hydrostatic test or nondestructive electric test in accordance with the specification.

Where required by the purchaser, additional UT or ET examination can be incorporated into the Inspection and Test Plan.

For critical refinery, petrochemical or power-generation projects, project specifications may impose testing requirements beyond the basic ASTM A312 requirements.

ASTM A312 TP304H Pipe Applications

Because of its combination of corrosion resistance and improved elevated-temperature strength, 304H seamless pipe is used in a wide range of industrial installations.

Typical applications include:

• Petroleum refineries
• Petrochemical plants
• Chemical processing plants
• High-temperature process piping
• Power-generation facilities
• Boiler systems
• Superheater and reheater systems
• Heat exchangers
• Furnace piping
• High-temperature steam lines
• Pressure equipment
• Process heaters
• Industrial thermal processing systems

TP304H is particularly relevant when piping remains under load for prolonged periods at elevated temperature.

TP304H for High-Temperature Service

The key advantage of UNS S30409 / TP304H is not simply higher room-temperature strength.

Its principal engineering value is improved resistance to creep deformation and stress rupture under sustained high-temperature loading.

This makes TP304H suitable for components exposed simultaneously to:

• Elevated temperature
• Internal pressure
• Long operating cycles
• Thermal cycling
• General industrial corrosion

Material producers also classify 304H / 1.4948 as an austenitic stainless steel with improved high-temperature or creep strength.

The actual allowable stress at the project design temperature must be determined from the applicable design code, such as the relevant ASME pressure piping or pressure vessel code.

UNS S30409 and EN 1.4948

UNS S30409 is the UNS designation for ASTM Type 304H.

The commonly associated European designation is:

• EN material number: 1.4948
• Steel name: X6CrNi18-10

The designation 304H / S30409 / 1.4948 is widely used when discussing comparable high-temperature austenitic stainless steel materials.

However, ASTM A312 and European product standards are not automatically interchangeable. Chemical composition, mechanical requirements, dimensional tolerances, testing, certification and acceptance criteria must always be checked against the project specification.

 

Dimensions and Wall Thickness

ASTM A312 TP304H seamless pipes can be supplied according to standard stainless-steel pipe dimensions such as ASME B36.19M, as well as other dimensions when permitted by the material specification and agreed between purchaser and manufacturer.

Common schedule designations include:

• SCH 5S
• SCH 10S
• SCH 40S
• SCH 80S
• Heavy-wall dimensions
• Custom OD × WT dimensions

For an accurate quotation, the inquiry should state outside diameter or NPS, wall thickness or schedule, length, quantity and required testing.

Material Certification

ASTM A312 TP304H seamless pipe can be supplied with traceable material certification.

Typical documentation includes:

• EN 10204 Type 3.1 Material Test Certificate
• Chemical composition report
• Mechanical test results
• Heat-treatment information
• Hydrostatic / NDE records where applicable
• PMI report when specified
• Additional laboratory test reports when specified
• Packing list and traceability records

Third-party inspection can also be arranged according to the purchase specification.

Marking and Traceability

Each pipe can be marked in accordance with the applicable material standard and purchase-order requirements.

Typical marking information may include:

Manufacturer / ASTM A312 / TP304H / S30409 / Size / Heat Number / Manufacturing Method

Additional project-specific marking can be provided where required.

Heat-number traceability is maintained through production, inspection and final certification.

Packing

Packing methods are selected according to pipe dimensions, transportation method and customer requirements.

Typical export packing includes:

• Bundled pipes with steel straps
• Protective end caps where required
• Waterproof wrapping
• Wooden cases for smaller sizes where appropriate
• Heat-number identification
• Shipping marks according to purchase order

Special seaworthy export packing can be arranged for long-distance ocean transportation.

How to Order ASTM A312 TP304H Seamless Pipe

For a faster and more accurate quotation, please provide the following information:

1. Material: ASTM A312 TP304H / UNS S30409
2. Manufacturing: Seamless
3. Size: NPS or OD
4. Wall Thickness: Schedule or actual WT
5. Length: Random or fixed length
6. Quantity: Pieces, meters or weight
7. Ends: PE / BE / other
8. Certificate: EN 10204 3.1 or other requirement
9. Additional Testing: PMI / UT / ET / IGC / third-party inspection
10. Applicable Project Specification: if any

Example:

ASTM A312 TP304H SMLS Pipe, NPS 6, SCH 40S, BE, 6,000 mm Length, EN 10204 3.1, 100% PMI

Frequently Asked Questions

What is ASTM A312 TP304H?

ASTM A312 TP304H is an austenitic stainless steel pipe grade with UNS designation S30409. It is a higher-carbon modification of TP304 developed for service at elevated temperatures where creep and stress-rupture properties are important.

Is TP304H the same as 304?

No. TP304H belongs to the same 18Cr-8Ni stainless steel family as TP304, but it has a controlled carbon content of 0.04–0.10% to provide improved elevated-temperature strength.

What is the UNS number for 304H?

The UNS designation for 304H stainless steel is S30409.

What is EN 1.4948?

EN 1.4948 / X6CrNi18-10 is a European material designation commonly associated with 304H / UNS S30409 high-temperature austenitic stainless steel.

The relevant product standards should still be checked before treating ASTM and EN materials as directly interchangeable.

Is 304H titanium stabilized?

No. 304H is not a titanium-stabilized stainless steel.

Titanium-stabilized grades include materials such as 321/321H. TP304H achieves its high-temperature characteristics primarily through controlled carbon content and appropriate metallurgical processing.

What is the carbon content of TP304H?

ASTM A312 TP304H specifies a carbon range of 0.04–0.10%.

This controlled carbon level is a key difference between TP304H and conventional TP304 or low-carbon TP304L.

What is TP304H pipe used for?

TP304H pipe is commonly used for high-temperature process piping, refineries, petrochemical plants, power-generation equipment, boilers, heat exchangers, superheater and reheater systems, and other pressure piping exposed to elevated temperatures.

Is ASTM A312 TP304H available as seamless pipe?

Yes. ASTM A312 covers seamless and welded austenitic stainless steel pipe, and TP304H can be manufactured as seamless pipe.

What certificate can be supplied with TP304H seamless pipe?

A typical supply can include an EN 10204 Type 3.1 Material Test Certificate, together with chemical composition, mechanical properties and applicable inspection results.

Additional certification and third-party inspection can be supplied when specified in the purchase order.

Can 100% PMI be performed?

Yes. 100% PMI can be specified for ASTM A312 TP304H pipe to verify material identity and maintain traceability, particularly for refinery, petrochemical and power-generation projects.

Can TP304H replace TP304L?

Not automatically.

TP304H and TP304L are designed around different engineering priorities. TP304H is optimized for elevated-temperature strength, while TP304L uses lower carbon to improve performance in certain welded and corrosion-sensitive applications.

Substitution should only be made after review of the operating temperature, corrosion environment, design code and project material specification.

ASTM A312 TP304H Seamless Pipe Supplier in China

We supply ASTM A312 / ASME SA312 TP304H stainless steel seamless pipe for high-temperature process piping and industrial projects worldwide.

Our supply can be arranged with:

• UNS S30409 / 304H material
• Standard and project-specific dimensions
• EN 10204 3.1 certification
• Full heat-number traceability
• 100% PMI when specified
• UT / ET and additional NDE
• IGC and additional laboratory testing
• Third-party inspection
• Fixed-length cutting
• Export seaworthy packing

For project inquiries, please provide the pipe size, wall thickness, length, quantity, applicable standard, required certificate and additional inspection requirements.

Technical References

Technical material selection and acceptance should be based on the latest applicable edition of the project specifications and standards, including:

• ASTM A312/A312M — Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes
• ASME SA312 — Austenitic Stainless Steel Pipe
• ASME B36.19M — Stainless Steel Pipe Dimensions
• UNS S30409 — 304H Material Designation
• EN 1.4948 / X6CrNi18-10 — Related European Material Designation
• Applicable ASME design code and customer project specification