UNS S34709|1.4912|TP347H Seamless Stainless Steel Pipe

Seamless Stainless Steel TP347H Pipes (UNS S34709 / W.Nr. 1.4912) are premium high-alloy austenitic solutions specifically engineered for superior creep-rupture strength and oxidation resistance in extreme thermal environments. As a leading manufacturer based in Wenzhou, China, XinZhe produces high-integrity seamless piping that strictly adheres to ASTM A213, ASTM A312, and ASME SA213 international standards.

Distinguished by the strategic addition of Niobium (Nb) and an optimized carbon content, our TP347H tubing ensures exceptional stability and resistance to intergranular corrosion at service temperatures up to 815°C (1500°F). These pipes are indispensable for mission-critical applications in superheater tubes, reheater coils, and high-pressure steam systems. Through advanced cold-drawing and precise solution annealing, XinZhe guarantees a uniform grain structure and maximum durability under intense thermal stress.

“Our precision control over the Niobium-to-Carbon ratio ensures that carbides are fully stabilized, preventing sensitization and maintaining superior structural integrity during prolonged high-temperature service.”

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What Is Seamless TP347H Pipe?

Seamless Stainless Steel TP347H Pipe (UNS S34709 / 1.4912) – High-Temperature Creep-Resistant Solution

1. Overview of Seamless TP347H Pipe

Product Overview

Seamless stainless steel TP347H pipe (UNS S34709 / W.Nr. 1.4912) is a high-carbon, niobium-stabilized austenitic stainless steel specifically designed for long-term service in elevated temperature environments.

Manufactured from solid billets through hot piercing and cold finishing processes, seamless TP347H pipes feature a uniform, weld-free structure, ensuring superior pressure resistance and structural integrity in critical applications.

The “H” grade designation indicates a higher carbon content (0.04%–0.10%), which significantly enhances creep rupture strength at high temperatures. The addition of Niobium (Nb) stabilizes the alloy, preventing chromium carbide precipitation and ensuring excellent resistance to intergranular corrosion (IGC) during welding and high-temperature exposure.

2. Key Technical Advantages

Enhanced Creep Rupture Strength Higher carbon content improves resistance to deformation under sustained stress at temperatures up to 815°C.
Niobium Stabilization (Anti-Sensitization) Prevents carbide precipitation at grain boundaries, ensuring long-term corrosion resistance.
Excellent Oxidation Resistance Comparable to TP321 and TP304, with improved mechanical stability under thermal cycling conditions.
High Pressure & Temperature Capability Manufactured according to ASTM A312 / ASME SA312 standards, suitable for high-pressure and high-temperature piping systems.
Good Fabrication & Weldability Maintains good ductility, allowing for bending, flaring, and welding using standard industrial processes.

Additional Information

To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for 347H stainless steel.

The enhanced strength of TP347H is a direct result of its high carbon content, while retaining the essential niobium, chromium, and nickel levels for heat and corrosion resistance.

Grade 347H is specifically designed to maintain its strength and shape in high-stress, high-temperature applications.

These physical properties highlight the material's ability to perform reliably under extreme thermal conditions.

Table 4: The Standard of Stainless Steel Seamless Pipe Size Tolerance Size Chart :

4 ,Applicable Standards

ASTM A312 / ASME SA312
ASTM A213 (for tubing applications)
EN 10216-5 (equivalent grade: 1.4912)

5. Typical Applications

Seamless TP347H pipes are widely used in high-temperature and high-pressure industries:

Power Generation Superheater and reheater tubes in coal-fired, biomass, and waste-to-energy plants
Oil & Gas Refineries Fluid Catalytic Cracking (FCC) units, hydrocrackers, and high-temperature process piping
Aerospace Industry Exhaust systems, collector rings, and high-temperature structural components
Chemical Processing Radiant coils and heat exchangers operating within the sensitization temperature range (427°C – 815°C)

6 ,Manufacturing Process & Quality Control

Each seamless TP347H pipe is produced under strict quality control procedures:

Billet Heating Controlled heating to optimize grain structure before piercing
Hot Piercing & Cold Finishing Seamless forming followed by cold drawing or rolling to achieve precise dimensions
Solution Annealing Heat treatment at ≥1095°C followed by rapid quenching to ensure full stabilization
Comprehensive Testing
Non-Destructive Testing (NDT) Ultrasonic Testing (UT), Eddy Current Testing (ET), Hydrostatic Testing (HT)
Chemical Analysis PMI (Positive Material Identification), carbon and sulfur analysis
Mechanical Testing Flattening, flaring, and grain size measurement (ASTM E112)

6. Quality Assurance & Certification

Material Certification EN 10204 3.1 / 3.2 Mill Test Certificate (MTC)
Inspection Capabilities Full traceability from raw material to finished product
Third-Party Inspection Available ABS, DNV, BV, TÜV, Lloyd’s Register, SGS

Density	Melting Point	Thermal Expansion	Thermal Conductivity	Modulus of Elasticity	Electrical Resistivity
8.0 g/cm³	1398 - 1454 °C	16.6 µm/m·°C (20-100°C)	16.3 W/m·K (20°C)	193 GPa	0.72 x 10⁻⁶ Ω·m (20°C)

Chemical Composition

Grade	C	Cr	Ni	Mn	P	S	Si	Others
347	≤0.08	17.00-19.00	9.00-13.00	≤2.00	≤0.045	≤0.030	≤1.00	Nb ≥ 10×C, ≤ 1.00
347H	0.04-0.10	17.00-19.00	9.00-13.00	≤2.00	≤0.045	≤0.030	≤1.00	Nb ≥ 8×C, ≤ 1.10

Mechanical Properties

Grade	Yield strength ksi(MPa)	Tensile Strength ksi(MPa)	Elongation %	Hardness Brinell/Vickers	Hardness Rockwell
347	≥30(205)	≥75(515)	≥35	≤ 192 HBW/200HV	≤ 90HRB
347H	≥30(205)	≥75(515)	≥35	≤ 192 HBW/200HV	≤ 90HRB

Size Tolerance Chart

Standard	OD(D)	Tolerance （MM)		Thickness(S)	Tolerance(MM)	Length	Tolerance
	MM	Common	High	MM			MM
ASTM A312	D ≤48.3	+0.4/-0.8		10.3 ≤73	+20%-12.5%		+6.0/0
	48.3 ≤114.30	±0.8		88.9 ≤457.2,t/D ≤5%	+22.5%/-12.5%
	114.3 ≤219.1	+1.6/-0.8		88.9 ≤457.2,t/D >5%	+15%/-12.5%
	219.1 ≤457.2	+2.4/-0.8		D ≥508, t/D≤5%,SMLS	+22.5%/-12.5%
	457.2 ≤660.4	+3.2/-0.8		D ≥508, t/D>5%,SMLS	+15%/-12.5%
	660.4 ≤863.6	+4.0/-0.8		D ≥508, WELD	+17.5%/-12.5%
	863.6 ≤1219.2	+4.8/-0.8
JIS 3459 Hot-Finished Smls Pipe	D ＜50	±0.51		S ＜4	±0.5
	D ≥50	±1.0%		S ≥4	±12.5%
JIS 3459 Cold-Finished	D ＜30	±0.3		S ＜2	±0.2
	D ≥30	±1.0%		S ≥2	±10.0%
JIS G3463 Hot-Finished Smls Pipe	100	+0.4/-0.8		D ＜100， S	/	D	+7/0
				D ＜100， 2≤S	+40%/0	D	+10/0
				D ＜100， 2.4≤S	+35%/0
				D ＜100， 3.8≤S	+33%/0
				D ＜100， 4.6≤S	+28%/0	D	+13/0
	100 ≤D	+0.4/-1.2		D>100, S ＜2	/
	120 ≤D			D>100 ， 2≤S	/	D	+15/0
	160 ≤D	+0.4/-1.8		D>100 ， 2.4≤S	+35%/0
	200 ≤D	+0.4/-2.4		D>100 ， 3.8≤S	+33%/0	D>50,7	+10/0
				D>100 ， 4.6≤S	+28%/0
JIS G3463 Cold-finished		+0.4/-0.8		D	+0.4/0
	60 ≤D	±0.3		D ≥2.0	+20%/0	D>50,7	+13/0
	80 ≤D	±0.4		D ≥40	+22%/0
	100 ≤D	+0.4/-0.6
	120 ≤D	+0.4/-0.8				D>50,10M	+15/0
	160 ≤D	+0.4/-1.2
	200 ≤D	+0.4/-1.6
GB/T 14975 冷拔(扎)钢管	D	±0.3	±0.1	所有壁厚，普通级PA	+12.5%/-10%
	12.7		±0.15
	38.1	±0.4	±0.3
	88.9	±0.9%	±0.4
	139.7		±0.8	所有壁厚，高级PC	±10%
	203.2		±1.1
	219.1		±1.6
	D ≥323.9		±0.5%
GB/T 14976 冷拔(轧)钢管	6	±0.2	±0.15	S ≤3	±12%(10% /0 高级PC)
	10 ≤D	±0.2	±0.2
	30 ≤D	±0.2	±0.3	S>3	+12.5%/-10%(10%/0 高级PC)
	50 ≤D	0.85%	0.75%
	D>219	0.9%	0.8%	Smin, all	+22%/0(+20%/0 高级PC)

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Send your Seamless TP347H Pipe enquiry with grade, applicable ASTM/ASME standard and edition, OD × wall thickness, length, quantity, end finish, delivery destination and inspection documents — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.

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