ASTM A312 TP347/347H Seamless Stainless Steel Pipe

Why Partner with Womic Steel for TP347/347H Seamless Pipe?

Complete Size Range: Cold Drawn 1/2″ – 8″, Hot Finished 4″ – 24″.

Full solution annealing (1050-1120°C, water quench) – critical for niobium stabilization.

Intergranular corrosion testing per ASTM A262 Practice E available (mandatory for TP347).

TP347H for elevated temperature creep strength (higher than TP321H).

Grain size control (ASTM 5-7) for optimal creep properties.

Lead times: 25-35 days for CD, 35-50 days for HF.

Frequently Asked Questions (FAQ) – ASTM A312 TP347/347H Seamless Stainless Steel Pipe

Q: What is the difference between TP347 and TP321 for high-temperature service?
A: TP347 uses niobium (columbium) stabilization while TP321 uses titanium. TP347 has better creep strength at elevated temperatures (above 550°C) and is the standard for catalytic reformer heater tubes. TP321 is more common for lower stress applications. For temperatures above 650°C, TP347H is preferred.

Q: What is TP347H and when should it be used?
A: TP347H has higher carbon content (0.04-0.10% vs ≤ 0.08% for TP347) and is specifically intended for elevated temperature service where creep strength is important. Use TP347H for thick wall sections, superheater tubes, and fired heater radiant coils operating above 550°C.

Q: Is solution annealing required for TP347 seamless pipe?
A: Yes, ASTM A312 requires solution annealing for TP347. The heat treatment dissolves niobium carbides formed during processing and ensures niobium is available to combine with carbon during service. Womic performs full solution annealing on all TP347 seamless pipes.

Q: Can TP347 be welded without post-weld heat treatment?
A: Yes. TP347 is designed to be used in the as-welded condition without post-weld heat treatment. The niobium stabilization prevents sensitization in the weld heat-affected zone (HAZ). This makes TP347 attractive for refinery turnarounds and field fabrication.

Q: What is the maximum service temperature for TP347?
A: TP347 has good oxidation resistance up to 900°C in air (intermittent service). For continuous service, 870°C is typical. For pressure-containing applications, allowable stress values per ASME B31.3 go up to 815°C (1500°F). For temperatures above 650°C with high stress, TP347H is recommended.

Q: What is the typical lead time for TP347 seamless pipe?
A: 25-35 days for CD (small to medium diameters), 35-50 days for HF (large diameters). IGC testing adds 7-10 days. Third-party inspection adds 7-14 days. TP347H may have longer lead times due to specialty billet sourcing.

Q: What documentation is provided?
A: MTC (EN 10204 3.1 or 3.2), hydrotest report, eddy current/UT reports, PMI report (with Nb verification), IGC test report, flattening/flaring reports, dimensional report, packing list, COO.

Project Reference – Midwestern USA Catalytic Reformer Heater Tube Replacement

Country: United States (Indiana, Midwest refinery)
Standard & Grade: ASTM A312 TP347H (seamless) – with supplementary creep testing
Dimensions & Quantity:

OD 88.9mm (3″) × Schedule 80 (8.89mm WT) – 800 meters (approx. 12 tons) – Cold Drawn

OD 114.3mm (4″) × Schedule 80 (11.13mm WT) – 500 meters (approx. 11 tons) – Cold Drawn

OD 168.3mm (6″) × Schedule 80 (15.09mm WT) – 200 meters (approx. 11 tons) – Hot Finished
Total: 1,500 meters, approx. 34 tons

Specifications: ASTM A312 TP347H seamless, solution annealed and pickled, beveled ends. Hydrostatic testing. Eddy current (CD) and UT (HF). PMI on every pipe with Nb verification (achieved 0.6-0.8% Nb). Mandatory intergranular corrosion test per ASTM A262 Practice E (no attack). Elevated temperature tensile test at 650°C (spec: yield ≥ 110 MPa, achieved 140-170 MPa). Creep rupture test at 650°C, 50 MPa, 1,000h – no rupture. Grain size ASTM 6-7. Third-party inspection by TÜV USA.

Application: Replacement of catalytic reformer (Platforming unit) heater tubes. The unit operates at 650-700°C with hydrogen-rich atmosphere (70% H₂, 20% hydrocarbons, 10% other gases). Operating pressure 3.5 MPa. The previous TP321 tubes failed after 12 years due to creep deformation and carburization. TP347H was selected for its superior creep strength and carburization resistance.

Technical Challenges & Solutions:

Creep strength at 650-700°C – TP347H with carbon 0.06-0.08% and grain size ASTM 6 provided creep rupture strength > 50 MPa at 650°C. Womic performed creep test at 650°C, 50 MPa, 1,000h – no rupture. Elevated temperature tensile at 650°C: yield 145-165 MPa. Client accepted.

Carburization resistance in hydrogen atmosphere – Niobium stabilization prevents carbide precipitation along grain boundaries. Womic performed carburization test (exposure to 5% CH₄/95% H₂ at 650°C for 500h): weight gain 0.15 mg/cm², carburized depth < 0.1mm. Client approved.

Intergranular corrosion resistance – ASTM A262 Practice E test (120h in copper sulfate-sulfuric acid) showed no intergranular attack. Passed.

Field welding qualification – Refinery maintenance team needed qualified WPS for tube replacement. Womic provided weld coupons with WPS using GTAW with ER347 filler, preheat 10-20°C, interpass ≤ 150°C, heat input ≤ 1.5 kJ/mm. Coupons passed RT, PT, and elevated temperature tensile.

Logistics to Indiana refinery – Pipes shipped from Shanghai to Chicago, then trucked to refinery. All 34 tons delivered during 4-week turnaround. TÜV inspected at port of entry. Documentation package accepted without queries.

Result: Catalytic reformer successfully restarted after turnaround. After 18 months of operation, inspection showed no creep deformation, no carburization, and no cracking. Client expects 20+ year service life. Womic Steel is now a preferred supplier for this refinery's high-temperature alloy needs.

Contact:
Website: www.womicsteel.com
E-mail: sales@womicsteel.com

Tel / WhatsApp / WeChat:
Victor: +86 15575100681
Jack: +86 18390957568

Womic Steel – Your reliable partner for ASTM A312 TP347/347H seamless stainless steel pipes for catalytic reformer service, high-temperature refinery, petrochemical, and power generation applications worldwide.