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347 stainless steel Sheet & Plate

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347 Stainless Steel Sheet & Plate (UNS S34700, 1.4550)

347 stainless steel, classified under UNS S34700, is an austenitic stainless steel alloy that is stabilized with niobium (also known as columbium). The addition of niobium helps prevent the formation of chromium carbides during welding, making 347 particularly resistant to intergranular corrosion in high-temperature environments. This alloy is often chosen for applications where the material is exposed to elevated temperatures or where welding is required, and it offers superior resistance to sensitization, a common issue in other stainless steel grades.

 

Key Features

  • High-Temperature Resistance: 347 stainless steel is highly resistant to oxidation and corrosion at temperatures up to 900°C (1650°F) in continuous service and can withstand intermittent temperatures up to 925°C. This makes it ideal for applications in high-temperature environments.
  • Corrosion Resistance: The niobium addition stabilizes the stainless steel, reducing the risk of chromium carbide precipitation during welding. This makes 347 stainless steel resistant to intergranular corrosion, particularly in high-temperature, welded components.
  • Weldability: 347 stainless steel is easy to weld, with reduced risk of carbide precipitation due to niobium’s stabilizing effect. It can be welded using conventional methods such as TIG, MIG, and spot welding.
  • Mechanical Properties: With good tensile strength (~520 MPa) and ductility, 347 stainless steel exhibits high mechanical properties even under extreme thermal and mechanical stress.
  • Good Formability: 347 stainless steel is highly formable and can be used in a wide variety of applications requiring complex shapes and configurations.

 

Technical Specifications:

  • UNS Number: S34700
  • DIN/EN Designation: 1.4550

Available Thickness

3/16″1/4″5/16″3/8″1/2″5/8″3/4″7/8″1″1 1/8″
4.8mm6.3mm7.9mm9.5mm12.7mm15.9mm19mm22.2mm25.4mm28.6mm
1 1/4″1 1/2″1 3/4″2″2 1/4″2 1/2″2 3/4″3″3 1/2″4″
31.8mm38.1mm44.5mm50.8mm57.2mm63.5mm69.9mm76.2mm88.9mm101.6mm
347-stainless-steel-sheet-plate

Application

  • Automotive
  • Chemical and Pharmaceutical
  • Fertilizer
  • Food Processing and Handling
  • Manufacturing
  • Mining
  • Oil & Gas
  • Phosphate Mining

Standard

  • ASTM A240 / A240M
  • ASTM A276 / A276M
  • ASTM A312 / A312M
  • ISO 15510
  • EN 10088-2
  • IN 10204
  • HE G4304
  • HE G4305
  • ASME SA240 / SA240M
  • ASME SA312 / SA312M

Corrosion Resistance

  • High-Temperature Oxidation Resistance: Alloy 347 performs well at elevated temperatures, with excellent resistance to oxidation and scaling up to about 1600°F (870°C). Its resistance is due to the presence of niobium, which helps prevent the formation of chromium carbides that can lead to intergranular corrosion.
  • Resistance to Intergranular Corrosion: The addition of niobium (or tantalum) stabilizes the steel against carbide precipitation, which makes it less susceptible to intergranular corrosion compared to other stainless steels like 304 or 316 when exposed to high temperatures.
  • Resistance to Sulfuric Acid: While Alloy 347 has good general corrosion resistance, it’s not as resistant to sulfuric acid as other alloys like Alloy 316L. For environments involving sulfuric acid, specific grades with higher resistance may be required.
  • Resistance to Chloride Stress Corrosion Cracking: Although Alloy 347 offers better resistance to chloride stress corrosion cracking than some other alloys, it’s not as resistant as Alloy 316L. In highly chloride environments, a more resistant grade might be necessary.
  • Resistance to Carburization: Alloy 347 provides good resistance to carburization, which is beneficial in environments where there’s a risk of carbon infiltration at high temperatures.
  • General Corrosion Resistance: It has excellent resistance to general corrosion in many environments, including a range of acids, bases, and salts. It’s used in applications where resistance to chemical attack is required.

347 Chemical Composition

Element Range (%)
Carbon (C) 0.04 – 0.10
Chromium (Cr) 17.0 – 19.0
Nickel (Ni) 9.0 – 12.0
Niobium (Nb) 0.4 – 1.0
Manganese (Mn) 2.0 max
Silicon (Si) 1.0 max
Phosphorus (P) 0.045 max
Sulfur (S) 0.03 max
Iron (Fe) Balance

347 Physical Properties

Property Value
Density 8.03 g/cm³
Melting Point 1450 – 1510°C
Modulus of Elasticity 193 – 200 GPa
Thermal Conductivity 15.1 W/m·K
Specific Heat Capacity 500 J/kg·K
Electrical Resistivity 0.72 µΩ·m
Thermal Expansion 16.0 × 10⁻⁶/K

347 Mechanical Properties

Property Value
Yield Strength 240 MPa (35 ksi)
Tensile Strength 550 MPa (80 ksi)
Elongation in 50 mm 40%
Hardness ~190 HB (Brinell)
Modulus of Elasticity 193 – 200 GPa
Fatigue Strength Varies with conditions

Fabrication Data

1. Welding

  • Welding Process: Common methods include TIG (Tungsten Inert Gas), MIG (Metal Inert Gas), and Stick welding.
  • Filler Material: Use stainless steel electrodes or filler rods matching the 347 grade (e.g., ER347).
  • Preheat Temperature: Generally, preheating is not necessary but can help in reducing thermal stresses for thicker sections.
  • Post-Weld Heat Treatment: Stress relieving at 675-750°C (1250-1380°F) can be done to relieve internal stresses and improve toughness.
  • Avoid Contamination: Ensure cleanliness to avoid contamination of the weld area which could lead to weld defects.

2. Machining

  • Cutting: Plasma, laser, or water jet cutting are commonly used.
  • Drilling and Tapping: Stainless steel can be challenging to machine; use sharp tools and appropriate speeds/feeds.
  • Tooling: Use high-speed steel (HSS) or carbide tools; cutting fluids can help in reducing heat and improving tool life.

3. Forming

  • Bending: Stainless steel 347 can be bent cold; however, for sharp bends or heavy gauges, heat may be required.
  • Rolling: Hot or cold rolling is used depending on the thickness and the desired finish.

4. Heat Treatment

  • Solution Annealing: Heat to 1040-1150°C (1900-2100°F) and quench rapidly to dissolve carbides and restore corrosion resistance.
  • Aging: Not typically required but can be done at lower temperatures to enhance mechanical properties if needed.

5. Corrosion Resistance

  • Oxidation Resistance: Excellent resistance to oxidation and general corrosion due to the high chromium content.
  • Intergranular Corrosion: 347 is less susceptible to intergranular corrosion due to the presence of columbium, which stabilizes the grain boundaries.
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