347 Stainless Steel Flange Supplier: 347, 347H
347 stainless steel flange (UNS S34700) is a chromium-nickel stainless steel alloy that incorporates niobium (and a small amount of tantalum) to prevent intergranular corrosion within the carbide precipitation range of 800°F to 1500°F (427°C to 816°C).
347H stainless steel flange (UNS S34709) is a high-carbon version of 347 stainless steel flanges.
347H stainless steel flange (UNS S34709) is a high-carbon version of 347 stainless steel flanges.
Since 2007, Kaysuns has been supplying custom stainless steel flanges to industries such as oil and gas,chemicals,offshore operations,and marine vessels.Contact us to get your personalized quote.
Chemical Composition of 347 Stainless Steel Flange (347/H)
According to the ASTM A182 standard (Standard Specification for Forged or Rolled Alloy Stainless Steel Pipe Fittings, Flanges,and Valves),the primary difference between 347 and 347H stainless steel lies in their carbon content ranges.
| Element | C | Mn | P | S | Si | Cr | Ni | Nb+Ta | Fe |
|---|---|---|---|---|---|---|---|---|---|
| 347 | ≤ 0.08 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | ≤ 1.00 | 17.0 – 19.0 | 9.0 – 13.0 | 10 × C Min / 1.10 Max | Balance |
| 347H | 0.04 – 0.10 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | ≤ 1.00 | 17.0 – 19.0 | 9.0 – 13.0 | 8 × C Min / 1.10 Max | Balance |
Analysis of Key Ingredients
Carbon:
The 347H grade specifies a lower minimum limit (0.04%),which ensures higher creep strength at high temperatures.
Niobium:
This is the core element of the 347 series.Niobium has a very strong affinity for carbon and preferentially forms niobium carbides,thereby preventing chromium from combining with carbon to form chromium carbides.This preserves the chromium content at the grain boundaries,preventing intergranular corrosion during welding or in high-temperature environments ranging from 427°C to 816°C.
Dual Certification (347/347H)
A 347/347H dual-certified flange refers to a single product that meets the requirements of both ASTM A182 F347 and ASTM A182 F347H standards.
On the Material Test Report (MTR), this flange is designated as “347/347H,” indicating that it possesses both the general corrosion resistance of 347 and the high-temperature mechanical properties of 347H.
On the Material Test Report (MTR), this flange is designated as “347/347H,” indicating that it possesses both the general corrosion resistance of 347 and the high-temperature mechanical properties of 347H.
Dual certification is performed to strike a balance between inventory management and application flexibility.To qualify for dual certification,the carbon content must be between 0.04% and 0.08%,the grain size must be No.7 or coarser,and the material must undergo solution treatment in accordance with the requirements of 347H.
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Mechanical Properties of 347 Stainless Steel Flange Series
According to the ASTM A182 standard,the basic mechanical properties of 347 and 347H stainless steel flanges at room temperature are very similar.However,because 347H has a higher carbon content and requires a coarser grain size,it performs far better than standard 347 at extremely high temperatures.
| Performance Metrics | 347 | 347H |
|---|---|---|
| Tensile Strength | ≥ 515 MPa (75 ksi) | ≥ 485 MPa (70 ksi) |
| Yield Strength 0.2% | ≥ 205 MPa (30 ksi) | ≥ 205 MPa (30 ksi) |
| Elongation in 50mm | ≥ 30% | ≥ 30% |
| Hardness | ≤ 187 HBW | ≤ 187 HBW |
Comparison of Maximum Allowable Stress (ASME BPVC Section II, Part D)
| Temperature | 347 Flange (ksi) | 347H Flange (ksi) | Performance Gap |
|---|---|---|---|
| 1000°F / 538°C | 13.5 | 14.2 | 347H is ~5% stronger |
| 1100°F / 593°C | 10.1 | 13.2 | 347H is ~30% stronger |
| 1200°F / 649°C | 6.4 | 10.5 | 347H is ~64% stronger |
| 1300°F / 704°C | 3.5 | 6.5 | 347H is ~85% stronger |
| 1400°F / 760°C | 1.8 | 3.8 | 347H is ~110% stronger |
| 1500°F / 816°C | 0.9 | 1.9 | 347H is ~111% stronger |
4 Manufacturing Methods for 347 Stainless Steel Flange
Forging
Forging is performed in accordance with the ASTM A182 standard.The forging process eliminates defects such as porosity that arise during smelting and optimizes the microstructure.It is the most commonly used method for manufacturing high-quality 347/347H flanges.
Plate Cutting & Machining
Steel plate cutting and machining are commonly used to manufacture slip-on flanges or blind flanges.Circular blanks are cut directly from hot-rolled and annealed 347/347H stainless steel plates using plasma,laser,or waterjet cutting,and then precision-machined on CNC lathes.
Centrifugal Casting
Centrifugal casting offers cost advantages in the production of large-diameter 347 series flanges.The castings have a dense microstructure and can be used to produce large-sized,annular components with uniform wall thickness.
Seamless Rolled Ring Forging
Ring rolling is an advanced forging process specifically designed for manufacturing circular flanges.Because the metal fibers are continuously distributed in the circumferential direction,flanges produced using this method exhibit excellent impact resistance and fatigue life.
Applications of 347 Stainless Steel Flange (347/H)
347 Stainless Steel Flange
- Aerospace Exhaust Systems
- Chemical Processing
- Nuclear Power Components
- Oil & Gas Refining (Sour Service)
- Pharmaceutical Equipment
347H Stainless Steel Flange
- Supercritical Power Boilers
- Petrochemical Hydrocracking
- Steam Reformers
- Heat Recovery Steam Generators
- Waste Incineration Plants
FAQs About 347 Stainless Steel Flange Grades
This is because it contains niobium (Nb). At high temperatures, niobium reacts with carbon first to form stable niobium carbides, thereby preventing chromium (Cr) from combining with carbon. This protects the material from intergranular corrosion caused by “chromium depletion,” which is why it is referred to as “stabilized” steel.
Applicable.The 347 series is an austenitic stainless steel that retains excellent toughness and strength even at cryogenic temperatures.However,in cryogenic environments,304L stainless steel flange or 316L stainless steel flange is typically the preferred choice,unless the system must also withstand subsequent high-temperature cycling.
Both are stabilized steels;the difference is that 321 contains titanium,while 347 contains niobium.A 347/347H stainless steel flange exhibits slightly better oxidation resistance and strength at high temperatures than a 321H stainless steel flange.In highly oxidative environments (such as nitric acid),347 performs better than 321.
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