ASTM A312 TP309 / TP309H Welded Stainless Steel Pipe: Manufacturing Capabilities & Product Specifications

Why Partner with Womic Steel for TP309/309H Welded Pipe?

Complete Size Range: ERW 1/4″ – 24″, EFW/LSAW 8″ – 60″.

Full solution annealing after welding (1040-1120°C, water quench).

TP309H available for creep service above 650°C.

Competitive lead times: 25-35 days for ERW, 35-50 days for EFW/LSAW.

Global Certification: ISO 9001, PED (CE), EN 10204 Type 3.2.

Frequently Asked Questions (FAQ) – ASTM A312 TP309/309H Welded Pipe

Q: What is the difference between TP309, TP309S, and TP309H?
A: TP309S has low carbon (≤ 0.08%) for better weldability and resistance to intergranular corrosion in as-welded condition. TP309 (often means same as 309S) is general purpose. TP309H has higher carbon (0.04-0.10%) for enhanced creep strength at elevated temperatures (above 650°C). For continuous high-temperature service under stress (e.g., radiant tubes, creep-critical), choose TP309H. For cyclic service or where post-weld heat treatment is not possible, choose TP309S.

Q: What is the maximum service temperature for TP309?
A: TP309 is suitable for continuous service in air up to 1000°C (1830°F) with good oxidation resistance. For intermittent service, it can withstand up to 1035°C. Above 1000°C, scaling increases; TP310 (25Cr-20Ni) is recommended for 1100°C service.

Q: How does TP309 compare to TP304 for high-temperature service?
A: TP309 has higher chromium (23% vs 18%) and nickel (13% vs 8%), providing significantly better oxidation resistance (up to 1000°C vs 850°C for 304). TP309 also has better carburization and sulfidation resistance. For service above 850°C, TP309 is preferred.

Q: Is TP309H necessary for radiant tubes in heat treating furnaces?
A: For radiant tubes operating above 650°C under stress (creep conditions), TP309H is recommended because its higher carbon content provides higher creep rupture strength. For lower stress applications (e.g., heat baskets, fixtures), TP309S is acceptable.

Q: Does TP309 require solution annealing after welding?
A: ASTM A312 requires solution annealing for welded pipe. For TP309S, post-weld solution annealing is required to meet mechanical properties and corrosion resistance. For field welding of TP309S, no PWHT is typically required for oxidation-limited service, but for full corrosion resistance, solution annealing is beneficial. Womic performs solution annealing on all TP309 welded pipes.

Q: What welding filler metal is recommended for TP309?
A: For welding TP309, AWS A5.9 ER309L (or ER309) filler is recommended. ER309L (low carbon) is preferred to maintain corrosion resistance. For TP309H, ER309 (regular carbon) matches better. For joining TP309 to other stainless steels, ER309L is commonly used as an overlay.

Q: What is the typical lead time for TP309 welded stainless steel pipe?
A: 25-35 days for ERW (small to medium diameters), 35-50 days for EFW/LSAW (large diameters). TP309H may have slightly longer lead times due to specialty plate sourcing.

Q: Can TP309 be used for sulfuric or hydrochloric acid service?
A: No. TP309 is not designed for acid service; it is a high-temperature alloy. For acid service at room temperature, use 304L, 316L, or duplex. TP309 is for oxidation resistance at high temperatures, not for chemical corrosion resistance at low temperatures.

Project Reference – Cement Plant Riser Duct & Cooler Tube Replacement

Country: Vietnam (Ha Nam province)
Standard & Grade: ASTM A312 TP309H (welded)
Dimensions & Quantity:

OD 508mm (20″) × Schedule 40S (15.09mm WT) – 200 meters (approx. 33 tons) – EFW process

OD 406mm (16″) × Schedule 40S (12.70mm WT) – 300 meters (approx. 33 tons) – EFW process

OD 168.3mm (6″) × Schedule 40S (7.11mm WT) – 500 meters (approx. 13 tons) – ERW process
Total: 1,000 meters, approx. 79 tons

Specifications: ASTM A312 TP309H solution annealed and pickled, beveled ends. Hydrostatic testing. 100% UT for EFW pipes, eddy current for ERW. PMI on every pipe. Mandatory elevated temperature tensile test at 800°C (spec minimum 100 MPa, achieved 135-160 MPa). Intergranular corrosion test per ASTM A262 Practice E (pass). Third-party inspection by TÜV Vietnam.

Application: Replacement of riser duct and grate cooler tubes in a cement plant (clinker production). The riser duct carries hot kiln exhaust gases (850-950°C) containing dust (cement clinker particles) and combustion gases (CO₂, SOx, NOx). The cooler tubes are part of the clinker cooling system, handling hot clinker at 500-800°C with abrasive conditions. Previous 304H piping failed after 3 years due to oxidation scaling, carburization, and creep deformation.

Technical Challenges & Solutions:

Oxidation and carburization at 850-950°C – TP304H (18% Cr) scales rapidly above 850°C. TP309H with 23% Cr forms a more stable Cr₂O₃ scale, resisting oxidation and carburization. Womic performed oxidation test (air at 950°C for 500h): weight gain 0.8 mg/cm² (vs 304H typical 4.5 mg/cm²). Client accepted.

Creep strength at high temperature – Riser duct is under self-weight and thermal expansion stress. TP309H with carbon 0.07-0.09% provided higher creep strength. Elevated temperature tensile at 800°C: yield 145 MPa, tensile 210 MPa. Creep test (1,000h at 800°C, 40 MPa) – no rupture.

Thermal fatigue resistance – Cement kiln stops/starts cause thermal cycling. TP309H with solution annealed microstructure (fine grain ASTM 6-7) provided good thermal fatigue resistance. No cracking observed after 500 thermal cycles in lab test.

Abrasion resistance to cement dust – The riser duct sees erosive cement dust. TP309H hardness 85 HRB provides moderate abrasion resistance. For severe abrasion, refractory lining is still used; TP309H serves as structural support.

Welding procedure for field repair – Cement plant turnaround schedule limited welding time. Womic provided WPS using ER309L filler, GTAW + SMAW, with interpass ≤ 150°C. 15 weld coupons passed RT, PT, and elevated temperature tensile.

Logistics to Ha Nam – Pipes shipped from Shanghai to Haiphong port, then trucked 100km to site. All 79 tons delivered in 2 shipments over 6 weeks. TÜV inspection passed with zero non-conformances.

Result: New TP309H riser duct and cooler tubes installed during 2023 turnaround. After 18 months of operation, inspection showed minimal oxidation (scale thickness < 0.1mm) and no creep deformation or cracking. Client estimates service life 8-10 years (vs 3 years for 304H). Womic Steel is now a preferred supplier for this cement plant'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 TP309/TP309H welded stainless steel pipes for high-temperature furnace, cement, thermal oxidizer, and heat treatment applications worldwide.