ASTM A213 TP347 Stainless Steel Seamless Boiler Tube

Why do austenitic stainless steel tubes in high-temperature boiler systems still suffer from intergranular corrosion, strength degradation, or even premature failure after long-term service? The key lies in whether the stabilization elements and high-temperature microstructural stability are properly controlled to meet demanding operating conditions.

 

As a leading manufacturer and supplier of TP347 stainless steel tubes, GNEE effectively addresses common issues in boiler applications, including weld sensitization corrosion, high-temperature creep deformation, and early failure. Our annual supply capacity reaches up to 25,000 tons. For stock materials, delivery can be completed within one week, while customized production orders are typically fulfilled within 15 to 60 days.

 

Our ASTM A213 TP347 Stainless Steel Seamless Boiler Tube is specifically designed for high-temperature and high-pressure boiler environments, fully complying with international standards such as ASTM A213, ASME SA213, AMS 5571, and EN 10216-5. TP347 is stabilized with niobium (Nb), typically at Nb ≥ 10×C, which preferentially combines with carbon to form stable NbC. This effectively prevents chromium carbide precipitation and eliminates the risk of intergranular corrosion, especially after welding or prolonged high-temperature exposure.

In terms of high-temperature performance, TP347 seamless boiler tubes offer excellent creep resistance and oxidation resistance, making them suitable for long-term service in the 600–800°C range. All tubes undergo strict solution annealing (typically above 1040°C followed by rapid cooling) to ensure uniform grain structure and full carbide dissolution. In addition, an extra stabilization annealing process at 850–900°C is applied to further enhance corrosion resistance, particularly in the temperature range of 427°C to 816°C.

 

Chemical Composition of ASTM A213 TP347 Stainless Steel Seamless Tube

UNS No	Grade	C	Si	Mn	P	S	Cr	Mo	Ni	N	Other
S34700	347	0.08	0.75	2.00	0.045	0.030	17.00/19.00	–	9.00/13.00	–	Cb:10xC1.00

 

Mechanical Properties of ASTM A213 TP347 Stainless Steel Seamless Tubes

UNS No	Grade	Proof Stress 0.2% (MPa)	Tensile Strength (MPa)	Elongation A5(%)	Hardness Max
					HB	HRB
S34700	347	205	515	40	201	92

 

ASTM A213 TP347 Stainless Steel Seamless Tubes Physical Properties

Properties	Metric	Imperial
Density	7.7 – 8.03 g/cm3	0.278 – 0.290 lb/in³

 

ASTM-A213 TP347H Seamless Boiler Superheater and Heat Exchanger Tubes

Allowable Outside Diameter Variation in mm			Allowable Wall Thickness Variation		Exact Length Tolerance in mm		Testing
Nominal Diameter	Over	Under	%Over	%Under	Over	Under
Under 25.4	.1016	.1016	+20	-0	3.175	0	Flattening Test
25.4-38.1 incl	.1524	.1524	+22	-0	3.175	0	Tension Test
38.1-50.8 excl	.2032	.2032	+22	-0	3.176	0	Flare Test
50.8-63.5 excl	.254	.254	+2	-0	4.46	0	Hardness Test
63.5-76.2 excl	.347H8	.347H8	+22	-0	4.76	0	100% Hydrostatic test
76.2-101.6 incl	.381	.381	+22	-0	4.76	0	Refer to ASTM A-450

 

ASTM A213 TP347 Stainless Steel Boiler Tube Applications

ASTM A213 TP347/TP347H stainless steel boiler tubes are high-temperature and corrosion-resistant, niobium-stabilized austenitic tubes, specifically designed for severe operating environments with maximum temperatures reaching up to 1500°F (816°C). They are primarily utilized in boilers, superheaters, reheaters, and heat exchangers within supercritical and subcritical power plants, as well as in chemical processing equipment.

 

We offer the following testing services:

Flattening Test and Flaring Test: Boiler tubes frequently undergo bending and expanding during installation; therefore, the material must possess excellent ductility and remain free of any cracks.
100% Hydrostatic Test: A mandatory pressure test.
Eddy Current Testing (ET) or Ultrasonic Testing (UT): Customers typically request 100% Eddy Current Testing to detect surface defects. For tubes with thicker walls, Ultrasonic Testing is mandatory.
Intergranular Corrosion (IGC) Test: Customers typically request testing in accordance with ASTM A262 Practice E to verify that the material will not develop intergranular corrosion following welding or exposure to high-temperature service conditions.

 

Note:

Mill test certificates will be issued according to EN10204-3.1 or 3.2

All tubes shall be supplied as per applicable ASME SA213/213M Specification.

 

Standard Packaging for Boiler Tubes (TP347)

Hexagonal Bundling: For smaller-diameter boiler tubes, hexagonal bundling is typically employed.
Tube Caps (Plastic Caps): Secure-fitting plastic caps must be installed on both ends of every tube.
Purpose: To maintain internal cleanliness (free from dust, moisture, and foreign objects) and to protect the beveled tube ends from impact damage.
Surface Wrapping: Each bundle of tubes is typically wrapped externally with one or two layers of woven bags or plastic sheeting to prevent corrosion caused by salt spray during sea transport.

FAQ

Q: What is the difference between TP347 and TP347H?
A: The "H" in TP347H stands for High Carbon. TP347 typically has Carbon ≤ 0.08%, while TP347H requires Carbon between 0.04% and 0.10%. The higher carbon content, combined with a coarser grain size, provides significantly higher creep strength at temperatures above 538°C (1000°F).

 

Q: Is Grain Size testing mandatory for TP347 boiler tubes?
A: Yes, for TP347H used in high-temperature service, ASTM A213 requires a grain size of No. 7 or coarser. This is critical to ensure the long-term structural integrity of the tubes under high pressure and heat. For standard TP347, grain size is usually reported but the "coarser than No. 7" rule is strictly enforced for the H-grade.

 

Q: Can TP347 be easily welded?
A: Yes, TP347 has good weldability. It is recommended to use TP347/347L filler metals (containing Niobium) to maintain the corrosion resistance of the weld seam. Because it is stabilized, post-weld heat treatment (PWHT) is usually not required to prevent intergranular corrosion.