SS 347/347h
SS 347/347H: Specifications | Grades & Standards | Product Types | Equivalent | Chemical | Mechanical | BW Fittings | Forged Fittings | Flanges | FAQ
Manufacturers & Suppliers of SS 347 / 347H Pipe Fittings & Flanges – ASTM A403 / A182 Approved, available in Elbow, Tee, Reducer, Stub End, and Cross. Exported as UNS S34700 / S34709 Buttweld & Forged Fittings with WNRF, SORF, and Blind Flanges, engineered for high-temperature, creep-resistant, and corrosion-prone environments worldwide.
Best Export Prices: sales@midlandforgefittings.com
Midland Forge and Fittings Pvt. Ltd. is a reputed and professionally managed manufacturing company specializing in high-quality pipe fittings, flanges, and forged components for industrial piping solutions.
With years of engineering expertise and modern production facilities, we established ourselves as a reliable name known for precision, durability, and innovation. Our products are manufactured in compliance with international standards such as ASME, ASTM, DIN, EN, and BS, ensuring consistent quality and superior performance in every application.
We take pride in combining advanced manufacturing technology with deep industry experience to deliver products that meet the toughest challenges in the oil & gas, petrochemical, power, marine, and process industries. A commitment to excellence, rigorous quality control, and a customer-centric approach define our success. With a growing presence across India, the Middle East, Europe, and the USA, we continue to be a trusted partner for high-performance piping components known for reliability and long service life.
Stainless Steel 347 (UNS S34700) is a niobium-stabilized austenitic stainless steel that provides outstanding resistance to intergranular corrosion in the temperature range of 427–816°C. The addition of niobium prevents carbide precipitation during welding and prolonged heating, ensuring structural stability under high-temperature conditions.
SS 347 Buttweld Fittings, Forged Fittings, and Flanges exhibit excellent oxidation and creep resistance up to 870°C, along with superior tensile and yield strength. These properties make them ideal for demanding applications such as heat exchangers, exhaust manifolds, and pressure vessels, where both corrosion resistance and mechanical strength are critical.
Stainless Steel 347H (UNS S34709) is a high-carbon modification of SS 347, engineered to deliver enhanced creep strength and thermal stability. The increased carbon content (0.04–0.10%) provides improved resistance to high-temperature deformation, making it suitable for continuous service under severe thermal stress.
SS 347H Buttweld Fittings, Forged Fittings, and Flanges perform exceptionally well in environments up to 870°C, offering strong resistance to oxidation, scaling, and intergranular corrosion. Typical applications include boiler tubes, superheaters, furnace components, and chemical processing systems. All fittings and flanges conform to ASTM A403 (fittings) and ASTM A182 (flanges) standards, ensuring dimensional precision and mechanical integrity for critical high-temperature piping operations.
SS 347 Pipe Fittings – ASTM A403 Specifications
Stainless Steel 347H Forged Fittings – Material Grades
| Grade | Buttweld Fittings Standards | Forged Fittings Standards | Flanges Standards |
|---|---|---|---|
| 347 | ASTM A403 / ASME B16.9 / MSS-SP-43 | ASTM A182 / ASME B16.11 | ASTM A182 / ASME B16.5 / B16.47 |
| 347H | ASTM A403 / ASME B16.9 / MSS-SP-43 | ASTM A182 / ASME B16.11 | ASTM A182 / ASME B16.5 / B16.47 |
SS 347/347H Piping Products – Industrial Flanges & Fittings
ASTM A182 SS 347 Flange - Equivalent Grades
| Grade | UNS | ASTM | EN (DIN) | JIS | GOST | BS | AFNOR |
|---|---|---|---|---|---|---|---|
| 347 | S34700 | A182 / A403 / A240 / A276 | 1.4550 (X6CrNbN18-10) | SUS347 | 08Х18Н12Б (08X18H12B) | 347S31 | Z6CN18-10Nb |
| 347H | S34709 | A182 / A403 / A240 / A276 | 1.4961 (X6CrNbN18-10) | SUS347H | 08Х18Н12Б (08X18H12B) | 347S51 | Z6CN18-10Nb |
347h SS Buttweld Fittings - Chemical Composition
| Element | SS 347 (S34700) % | SS 347H (S34709) % |
|---|---|---|
| Carbon (C) | 0.08 max | 0.04 – 0.10 |
| Manganese (Mn) | 2.0 max | 2.0 max |
| Phosphorus (P) | 0.045 max | 0.045 max |
| Sulfur (S) | 0.03 max | 0.03 max |
| Silicon (Si) | 1.0 max | 1.0 max |
| Chromium (Cr) | 17.0 – 19.0 | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 13.0 | 9.0 – 13.0 |
| Molybdenum (Mo) | 0 – 1.0 | 0 – 1.0 |
| Niobium (Nb + Ta) | 10 × C min | 10 × C min |
| Nitrogen (N) | 0.10 max | 0.10 max |
| Iron (Fe) | Balance | Balance |
WNR 1.4550 Pipe Fittings & Flanges - Mechanical Properties
| Property | SS 347 (S34700) | SS 347H (S34709) |
|---|---|---|
| Tensile Strength (MPa) | 515 – 750 | 515 – 750 |
| Yield Strength (0.2% Offset) (MPa) | 205 min | 205 min |
| Elongation (%) | 40 min | 40 min |
| Hardness (HB) | ≤ 201 | ≤ 201 |
| Hardness (HRB) | ≤ 92 | ≤ 92 |
| Hardness (HRC) | ≤ 25 | ≤ 25 |
| Modulus of Elasticity (GPa) | 193 – 200 | 193 – 200 |
| Poisson’s Ratio | 0.27 – 0.30 | 0.27 – 0.30 |
| Melting Point (°C) | 1420 – 1450 | 1420 – 1450 |
| Service Temperature (Max °C) | 870 | 870 |
WP347 / WP347h Buttweld Pipe Fittings – Seamless & Welded
A182 F347/ F347h SS Flanges – Types and Industrial Applications
ASME SA182 Stainless Steel 347 / 347h Forged Fittings – Complete Range
What are the key differences between SS 347 and SS 347H, and how do these differences affect their application in piping systems?
Carbon Content:
SS 347: Max 0.08% carbon
SS 347H: Higher carbon range 0.04–0.10%
High-Temperature Strength:
347H has superior creep strength and stress-rupture resistance at elevated temperatures, making it more suitable for boilers, superheaters, and furnace components.
Corrosion Resistance:
Both grades are stabilized with niobium (columbium), which prevents intergranular corrosion. However, the higher carbon content in 347H improves mechanical stability under sustained high-temperature stress.
Typical Applications:
SS 347: Heat exchangers, exhaust manifolds, chemical piping at moderately elevated temperatures
SS 347H: Boilers, superheaters, chemical processing equipment, and any high-temperature service where long-term stress is expected
How are SS 347 / 347H fittings inspected and tested for quality assurance?
Dimensional Inspection: Using calipers, gauges, and templates to verify compliance with ASME/ASTM dimensions
Mechanical Testing: Tensile, yield, elongation, and hardness testing to verify strength and ductility
Chemical Composition Verification: Optical emission spectroscopy (OES) or PMI testing to ensure correct alloy content, including chromium, nickel, niobium, and carbon
Non-Destructive Testing (NDT):
Radiographic testing (RT) for weld quality
Ultrasonic testing (UT) for internal defects
Dye penetrant or magnetic particle testing (where applicable) for surface defects
Hydrostatic Testing: Pressure testing of fittings and flanges for leak-proof certification
What are the differences in service life and performance between buttweld and forged fittings for SS 347 / 347H?
Buttweld Fittings:
Seamless or welded construction, ideal for high-pressure, high-temperature applications
Provides smooth internal flow, minimal turbulence, and no crevices
Forged Fittings:
Produced by forging, offering higher mechanical strength and impact resistance
Suitable for thicker-wall, high-stress piping systems
Performance Implications:
Buttweld: Best for pipelines where welding is part of installation
Forged: Best for extreme pressure, structural support, or mechanical load-bearing piping