ASTM A312 TP316H Seamless Stainless Steel Pipe

Why Partner with Womic Steel for TP316H Seamless Pipe?

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

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

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

Molybdenum content (2.0-3.0%) – verified by PMI.

Elevated temperature tensile and creep testing available.

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

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

Frequently Asked Questions (FAQ) – ASTM A312 TP316H Seamless Stainless Steel Pipe

Q: What is the difference between TP316H and TP316L?
A: TP316H has higher carbon (0.04-0.10% vs ≤ 0.03% for 316L), which provides significantly higher creep rupture strength at temperatures above 550°C. 316L is more resistant to intergranular corrosion after welding. For applications with sustained high temperatures (above 550°C) and stresses, use TP316H. For welded equipment without post-weld heat treatment at lower temperatures, 316L is preferred. TP316H also contains the same molybdenum (2-3%) for pitting resistance.

Q: When should I choose TP316H over TP304H?
A: If the high-temperature environment contains chlorides (e.g., steam with trace chlorides, cooling tower carryover, crude with chloride salts), choose TP316H for its molybdenum-enhanced pitting resistance. If chlorides are not present, TP304H is more economical. Both have similar creep strength at temperatures up to 650°C.

Q: What is the maximum service temperature for TP316H?
A: TP316H has allowable stress values in ASME Section II, Part D up to 815°C (1500°F). However, for long-term creep service, it is typically used up to 700°C. Above 700°C, grades with higher chromium (309, 310) or nickel alloys may be required for oxidation resistance. In chloride-containing environments, maximum service temperature may be limited by pitting resistance rather than creep.

Q: Can TP316H be used in the as-welded condition?
A: For pressure-containing applications, ASTM A312 requires solution annealing after pipe manufacturing (not after field welding). For field welding of TP316H, post-weld heat treatment (solution annealing) is generally not practical, so many fabricators use 316L filler metal to avoid sensitization in the HAZ. However, for high-temperature service where creep is critical, 316H filler may be required. Womic supplies TP316H pipes in the solution annealed condition; field welding should use appropriate filler and low heat input.

Q: Does TP316H require grain size control for creep service?
A: For elevated temperature service where creep is a design consideration, ASME Section I and VIII require grain size control. TP316H typically has ASTM grain size 5-7. Womic can provide grain size measurement reports upon request.

Q: What welding filler metal is recommended for TP316H?
A: AWS A5.9 ER316H (matching higher carbon) or ER316L (low carbon) can be used. For matching creep strength in the weld, ER316H is recommended. However, for field welding where post-weld heat treatment is not possible, ER316L is often used to avoid sensitization. The designer should specify based on service temperature and stress requirements.

Q: What is the typical lead time for TP316H seamless pipe?
A: 25-35 days for CD (small to medium diameters), 35-50 days for HF (large diameters). TP316H lead times are similar to 316L. Third-party inspection adds 7-14 days. Creep testing adds 14-21 days.

Project Reference – Middle East Combined Cycle Power Plant Superheater Replacement (UAE)

Country: United Arab Emirates (Abu Dhabi – Arabian Gulf coast)
Standard & Grade: ASTM A312 TP316H (seamless) – with supplementary creep and pitting resistance testing
Dimensions & Quantity:

OD 60.3mm (2″) × Schedule 80S (5.54mm WT) – 2,000 meters (approx. 14 tons) – Cold Drawn

OD 88.9mm (3″) × Schedule 80S (7.62mm WT) – 1,500 meters (approx. 18 tons) – Cold Drawn

OD 114.3mm (4″) × Schedule 80S (8.56mm WT) – 800 meters (approx. 14 tons) – Cold Drawn

OD 168.3mm (6″) × Schedule 80S (10.97mm WT) – 400 meters (approx. 12 tons) – Hot Finished
Total: 4,700 meters, approx. 58 tons

Specifications: ASTM A312 TP316H seamless, solution annealed and pickled, beveled ends. Hydrostatic testing. Eddy current (CD) and UT (HF). PMI on every pipe with Mo verification (2.2-2.6% Mo). Mandatory grain size measurement (ASTM 5-7, achieved 5.5-6.5). Charpy impact at -20°C (spec 27J, achieved 80-140J). Elevated temperature tensile test at 600°C (spec: yield ≥ 100 MPa, achieved 120-150 MPa; tensile ≥ 200 MPa, achieved 260-310 MPa). Creep rupture test at 600°C, 50 MPa for 1,000h – no rupture. Pitting corrosion test per ASTM G48 Method A (6% FeCl₃, 24h at 22°C) – no pitting. Intergranular corrosion test per ASTM A262 Practice E (pass – no sensitization). Third-party inspection by TÜV UAE.

Application: Replacement of superheater outlet tubes and headers in a combined cycle power plant (gas turbine + HRSG) located on the Arabian Gulf coast. The superheater produces steam at 580°C, 12.5 MPa. The plant uses seawater cooling for the condenser, and the HRSG feedwater contains trace chlorides (2-5 ppm Cl⁻ from cooling water leakage). The previous TP304H superheater tubes suffered from pitting corrosion after 8 years of operation due to chloride-induced pitting in the high-temperature zone. TP316H was selected for its molybdenum content (2-3%) providing pitting resistance, combined with higher carbon (0.06-0.08%) for creep strength at 580°C.

Technical Challenges & Solutions:

Pitting corrosion at 580°C from trace chlorides – TP304H (0% Mo) pitted in service when chlorides (2-5 ppm) concentrated in deposits. TP316H with Mo 2.3-2.5% provided PREN 25-26. Womic performed G48 pitting test at 22°C, 40°C, and 50°C (simulating deposit conditions). No pitting at 22°C and 40°C; slight pitting at 50°C after 72h (acceptable as service temperature is 580°C but no liquid water, only deposits). Client accepted.

Creep strength at 580°C – TP316H with carbon 0.06-0.08% and grain size ASTM 6 provided creep rupture strength of 55 MPa at 600°C for 100,000 hr (predicted). Womic performed 1,000h creep test at 600°C, 50 MPa – no rupture, total elongation 11%. Client accepted.

Grain size control for ASME Section I compliance – Superheater tubing requires ASTM grain size 5-7. Womic controlled grain size through solution annealing temperature (1070-1100°C) and cooling rate. Results: ASTM 5.5-6.5 on base metal, ASTM 6-7 on weld (for field joint qualification). Acceptable.

Field welding procedure qualification – The plant maintenance team needed qualified WPS for tube replacement. Womic provided 25 weld coupons (2″ and 4″ Schedule 80S) with WPS using GTAW with ER316L filler (to avoid sensitization), preheat 10-20°C, interpass ≤ 150°C, heat input ≤ 1.5 kJ/mm. Coupons passed RT, PT, tensile, Charpy at -20°C, and G48 pitting test at 40°C. Client qualified the procedure.

Oxidation resistance at 580°C with trace chlorides – TP316H forms a protective Cr₂O₃ scale, but chlorides can disrupt the scale. Womic performed cyclic oxidation test (500 cycles, 580°C → ambient, with 50 ppm Cl⁻ spray every 10 cycles). Weight gain 0.15 mg/cm² – acceptable.

Logistics to Abu Dhabi power plant – Pipes shipped from Shanghai to Abu Dhabi, then trucked to the plant. TÜV inspected pipes at port. All 58 tons delivered in 2 shipments over 8 weeks. No non-conformances.

Result: New TP316H superheater piping installed during Q2 2024 outage. After 10 months of operation, inspection using borescope showed no pitting, no creep deformation, and no oxidation scaling. The plant expects 20+ year service life (vs 8 years for 304H). The operator has standardized on TP316H for all superheater and reheater sections in their coastal power plants where trace chlorides are present.

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 TP316H seamless stainless steel pipes for superheater service, refinery heater tubes, high-temperature chloride environments, and power generation applications worldwide.