SS 347 & 347H Seamless Pipes Manufacturer
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Midland Alloys Inc. is a dependable manufacturer and supplier of Stainless Steel 347 and 347H seamless pipes for high-temperature industrial service. SS 347 and 347H are niobium-stabilized austenitic stainless steel grades developed to resist intergranular corrosion during prolonged heat exposure. The seamless pipe construction ensures uniform wall thickness, excellent pressure resistance, and consistent mechanical performance. Grade 347H contains controlled higher carbon content to enhance creep strength at elevated temperatures. These seamless pipes are manufactured in accordance with ASTM, ASME, and EN piping standards. We supply SS 347 seamless pipes in multiple sizes, schedules, and surface finishes with global export support.
What Is Stainless Steel 347 & 347H Seamless Pipe?
Stainless Steel 347 and 347H seamless pipes are niobium-stabilized austenitic stainless steel piping products designed for high-temperature and stress-intensive environments. Seamless manufacturing eliminates longitudinal welds, improving structural reliability under pressure. Niobium stabilizes carbon, preventing carbide precipitation during thermal exposure. SS 347H is specifically formulated with higher carbon to provide increased strength at elevated service temperatures. These seamless pipes are commonly produced as per ASTM A312 for industrial piping systems.
Benefits of SS 347 & 347H Seamless Pipes
- Intergranular Corrosion Resistance – Niobium stabilization protects the pipe from sensitization during high-temperature service.
- High-Temperature Strength Retention – SS 347H seamless pipes maintain mechanical strength at elevated operating temperatures.
- Creep Resistance Capability – Designed to withstand long-term stress without deformation under heat.
- Seamless Structural Consistency – Joint-free construction ensures uniform strength across the pipe length.
- Thermal Fatigue Stability – Performs reliably under repeated heating and cooling cycles.
- Oxidation Resistance at Elevated Temperatures – Resists surface degradation in oxidizing high-heat environments.
- Weld-Zone Integrity Stability – Maintains corrosion resistance and strength after welding operations.
Difference Between Stainless Steel 347/347H Seamless Pipes and Stainless Steel 316 Seamless Pipes
Stainless Steel 347/347H Pipes differ from Stainless Steel 316 Pipes primarily in stabilization and thermal performance. While 316 pipes contain molybdenum for improved corrosion resistance in chloride-rich environments, 347/347H pipes are stabilized using niobium to prevent intergranular corrosion caused by carbide precipitation during high-temperature exposure. This makes 347/347H superior for continuous service in the 425–875°C range. 347H’s higher carbon content improves mechanical integrity and creep strength in thermal circuits and pressure vessels something that 316 might not be able to support as consistently under extended high-temperature service.
Specifications of SS 347 / 347H Seamless Pipes
Include nominal size, outside diameter, schedule, wall thickness, length, and surface finish as per ASTM A312.
Seamless Pipe OD : 1/8 -12" NPS
ASTM A312 / ASME SA312
Seamless
Round, Square, Rectangular, Hydraulic Etc
Single Random, Double Random & Cut Length.
Plain End, Beveled End, Treaded
SCH5, SCH10, SCH20, SCH30, SCH40, STD, SCH80, SCH 80S, SCH60, SCH80, SCH120, SCH140, SCH160, SCH XXS, SCH XS
No. 2B - Mill finish/ Matte finish, No.8 - Mirror finish, No. 4 - Brushed finish, Bright, Annealing, Polished, Mirror
Types of 347H & 347 Seamless Pipes
Stainless Steel 347 and 347H seamless pipes are available in various forms to support high-temperature piping systems. Each type is designed for thermal stability and mechanical reliability.
Pipe Forms
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Round Seamless PipeUsed for high-temperature fluid and gas transfer
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Schedule PipesManufactured to meet specific pressure ratings
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Heavy Wall PipesSuitable for creep and stress-intensive environments
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Precision PipesUsed where dimensional accuracy is critical
- Process Pipes
Designed for continuous high-heat industrial flow
Contact us today to discuss how Stainless Steel 347/347H Seamless Pipes can benefit your application. Whether you need guidance in selecting the right pipes or have specific requirements, our team of experts is here to help you find the optimal solution.
Technical Details & Delivery Condition
Include chromium, nickel, niobium, carbon, manganese, silicon, phosphorus, and sulfur values.
| Grade | Ni | Mn | Si | S | C | Cr | P | Mo | N | |
| TP347 | min. | 9.0 | – | – | – | – | 17.0 | – | 2.00 | – |
| max. | 13.0 | 2.0 | 1.00 | 0.030 | 0.08 | 20.0 | 0.045 | 3.00 | – | |
| TP347H | min. | 9.0 | – | – | – | 0.04 | 17.0 | – | 3.00 | – |
| max. | 13.0 | 2.0 | 1.00 | 0.030 | 0.10 | 19.0 | 0.045 | 4.00 | – | |
| Grade | Tensile Strength minimum (MPa) | Yield Strength 0.2% Proof minimum (MPa) | Elongation minimum (% in 50mm) | Hardness | |
| Rockwell B (HR B) maximum | Brinell (HB) maximum | ||||
| 347 | 515 | 205 | 40 | 95 | 201 |
| 347H | 515 | 205 | 40 | 92 | 201 |
Stainless Steel Seamless Pipe Grades We Also Offer
How SS 347 Seamless Pipes Are Manufactured
Round Bar
Analytic
Cut to Length
Centering
Heating
Perforation
Inspection of Size
Pickling
Inspection of Surface
Lubricating
Cold Drawing (Cold Rolling)
Degreasing
Annealing
Straightening
Cut
Pickling / Passivating
Inspection
Analytic
Marking
Packing & Shipping
Industrial Applications of SS 347 & 347H Seamless Pipes
SS 347 and 347H seamless pipes are widely used in industries requiring high-temperature strength and corrosion resistance. Typical applications include boilers and superheater piping systems. These pipes are suitable for heat exchangers and condensers operating under thermal stress. Power generation plants rely on them for elevated-temperature flow lines. Additional usage includes furnace equipment, petrochemical high-temperature units, and stress-critical industrial components.
Why Choose SS 347 / 347H Seamless Pipes from Midland Alloys Inc.
Midland Alloys Inc. supplies SS 347 and 347H seamless pipes manufactured with strict metallurgical control for high-temperature performance. Our pipes are engineered to deliver excellent creep resistance, oxidation stability, and pressure integrity. Seamless construction ensures defect-free reliability in stress-critical piping systems. We adhere to international quality standards and conduct comprehensive inspections. Our export-ready documentation and packaging support global industrial projects.
FAQs
Niobium prevents carbide precipitation during prolonged heat exposure.
347H is preferred when higher creep strength at elevated temperatures is required.
