SS 347 and 347H Welded Tubes Manufacturer
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Midland Alloys Inc. is a trusted supplier and manufacturer of SS 347 and 347H welded tubes, offering precision-engineered plumbing solutions for harsh environments. Our experience with stainless steel manufacture ensures that each stainless steel 347 welded tube we deliver meets the stringent criteria of high-temperature and extremely corrosive environments. These niobium-stabilised austenitic grades are specifically engineered to remain stable during the welding process, effectively preventing damaging carbide precipitation, which often compromises structural integrity. While both grades are extremely durable, the SS 347H welded tube has a larger carbon content, which increases its strength when operating at high temperatures. As a leading provider of SS 347 welded tubes, we consistently adhere to international standards such as ASTM A312, ASTM A358, and ASME SA312. Our manufacturing facility produces high-quality stainless steel coils and plates into reliable tubes with various wall thicknesses and surface treatments. Midland Alloys Inc., an ISO-certified exporter, maintains a ready stock to service global projects with timely dispatch and complete traceability.
What is SS 347 and 347H Welded Tubes?
SS 347 and 347H welded tubes are high-performance tubular products manufactured by roll-forming stainless steel strips or plates and joining them with a continuous longitudinal weld. These tubes are identified by their specific UNS designations: SS 347 is known as UNS S34700, while the high-carbon version, SS 347H, carries the UNS S34709 label. We use advanced welding techniques like TIG (Tungsten Inert Gas), laser welding, or automated plasma arc methods to ensure the joints are as strong as the parent metal itself. This process creates a remarkably uniform weld seam that can withstand significant mechanical stress. The defining characteristic of a stainless steel 347 welded tube is the addition of niobium, which “stabilises” the alloy against intergranular corrosion during the heat of welding. The SS 347H welded tube is the preferred option for applications involving elevated temperatures due to its chemical composition, which is designed to improve creep resistance. Every SS 347 welded tube we produce undergoes stringent testing to ensure that it can withstand oxidation and heat cycling without failing.
Benefits of Welded 347 and 347H SS Tubing
Welded 347 and 347H tubing delivers dependable performance in heat-exposed systems where weld integrity cannot fail. These grades maintain a balance between corrosion resistance and thermal strength, making them ideal for fabrication-heavy tasks. Even as temperatures fluctuate, performance stays consistent.
Excellent resistance to intergranular corrosion after welding
- Niobium stabilisation prevents carbide precipitatio
- Suitable for continuous high-temperature service
- 347H provides improved creep strength at elevated temperatures
- Good oxidation resistance in heated environments
- Reliable mechanical strength under thermal cycling
- A smooth internal surface supports efficient fluid flow
- Consistent dimensional accuracy in welded tube production
- Good weldability and fabrication properties
Specification of SS 347 and 347H Welded Tubes
The following specifications table defines manufacturing standards, dimensional tolerances, and testing requirements for SS 347 and 347H welded tubes supplied by Midland Alloys Inc.
Tube OD : 1/8″NB TO 30″NB
ASTM /ASME SA269/A269
Welded
Round, Square, Rectangular, Hydraulic Etc
Single Random, Double Random, Standard & Cut length
Plain Ends (PE), Threaded Ends (TE), Bevelled Ends (BW), Grooved Mechanical Joints or Grooved Ends, TBE (Treaded Both Ends)
SCH 5, SCH10, SCH 40, SCH 80, SCH 80S, SCH 160, SCH XXS, SCH XS
2B, No.4, No.1, No.8 Mirror Finish for Stainless Steel Tubes, Finish as per customer Requirements
Types of SS 347 and 347H Welded Tubing
SS 347 and 347H welded tubes are produced using controlled longitudinal welding processes that ensure structural stability and consistent wall thickness. These tubes handle high-temperature exposure with steady mechanical performance. Fabricators prefer them for both process and structural applications. Options vary by shape and finish to suit industrial layouts.
Pipe Forms
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Round TubeUsed for process piping and fluid transport.
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Square TubeUsed in structural and fabrication applications.
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Rectangular TubeUsed in construction and support structures.
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Polished TubeUsed in architectural and visible installations.
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Process TubeUsed in high-temperature chemical and utility systems.
Contact us today to discuss how Stainless Steel 347/347H Welded Tubes can benefit your application. Whether you need guidance in selecting the right Tubes or have specific requirements, our team of experts is here to help you find the optimal solution.
Technical Details & Delivery Condition
The chemical composition ensures stability at high temperatures while maintaining corrosion resistance. Values comply with ASTM requirements:
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | N | |
| 347 | min. | – | – | – | – | – | 17.0 | 2.00 | 9.0 | – |
| max. | 0.08 | 2.0 | 1.00 | 0.045 | 0.030 | 20.0 | 3.00 | 13.0 | – | |
| 347H | min. | 0.04 | – | – | – | – | 17.0 | 3.00 | 9.0 | – |
| max. | 0.10 | 2.0 | 1.00 | 0.045 | 0.030 | 19.0 | 4.00 | 13.0 | – | |
Mechanical values confirm suitability for pressure and temperature service. Typical minimum properties under ASTM A312:
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | N | |
| 347 | min. | – | – | – | – | – | 17.0 | 2.00 | 9.0 | – |
| max. | 0.08 | 2.0 | 1.00 | 0.045 | 0.030 | 20.0 | 3.00 | 13.0 | – | |
| 347H | min. | 0.04 | – | – | – | – | 17.0 | 3.00 | 9.0 | – |
| max. | 0.10 | 2.0 | 1.00 | 0.045 | 0.030 | 19.0 | 4.00 | 13.0 | – | |
Stainless Steel Seamless Tubes Grades We Offer
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 for SS 347 and 347H Welded Tubes
These tubes are the core components of the heavy industrial industry, especially where heat and chemicals interact. Our tubes are used in the manufacturing process of heat exchangers and high-pressure boilers, as they do not become brittle with continuous thermal cycling, in oil and gas refineries, petrochemical plants, and power generation industries where thermal stability is critical. The alloy’s oxidation resistance in process pipework and exhaust systems ensures that the interior remains clear, and effective for a long time. The SS 347H welded tube is especially useful in thermal equipment due to its superior creep strength at high temperatures. These tubes not only convey fluid but also provide essential structural support in corrosive situations. Welded construction is a low-cost option that also meets the durability requirements of tough industrial applications.
Why Choose SS 347 and 347H Welded Tubes
Engineers prefer these grades because they solve the problem of “weld decay” in high-temperature environments where other stainless steels might fail. As a prominent stainless steel 347 welded tube supplier, we provide materials that excel in welding-intensive applications due to their niobium-stabilised chemistry. This prevents intergranular corrosion, ensuring the tubes remain tough and leakproof even after being joined into complex systems. The 347H variant stands out for its thermal stability, which makes it ideal for power plants and refineries. We prioritise export quality manufacturing, which means that each tube goes through rigorous ISO-certified inspections before leaving our manufacturing plant. One can get a product that combines long service life with incredible reliability under heat. It is a smart, durable investment for any high-stress project.
FAQs
The primary difference is in carbon concentration and high-temperature strength. SS 347 welded tubes (UNS S34700) contain regulated carbon up to 0.08% and are highly resistant to intergranular corrosion due to niobium stabilisation. SS 347H welded tubes (UNS S34709) contain higher carbon, typically 0.04–0.10%, which improves creep strength and load-bearing capacity at elevated temperatures.
No. In most industrial applications, SS 347H welded tubes do not require post-weld heat treatment. Niobium stabilisation controls carbide precipitation during welding, which reduces the risk of intergranular corrosion.
Industries use SS 347 welded tubes in oil and gas processing, petrochemical plants, power generation units, and chemical facilities. These tubes serve in process piping, exhaust systems, heat exchangers, and boiler components where elevated temperature and welded construction are common. Their oxidation resistance and structural stability make them suitable for thermal equipment and high-pressure lines.
SS 347 includes carbon up to 0.08%, but SS 347H has a higher and more regulated range of 0.04-0.10%. The higher carbon content in 347H improves creep strength at high temperatures, making it more suitable for long-term high-heat service conditions.
