347 Stainless Steel Pipe Description
Main Characteristics:
- Contains tantalum and niobium for improved resistance to intergranular corrosion.
- Maintains high strength while preserving ductility, allowing for reduced material thickness.
- Used extensively in welding applications for high-temperature components.
Heat Treatment:
- Solid solution treatment (C) at 980-1150°C followed by rapid cooling.
Mechanical Properties (Solution Treated):
- Yield Strength: ≥ 205 MPa
- Tensile Strength: ≥ 520 MPa
- Elongation: ≥ 35%
- Hardness (HBS): ≤ 187
- Hardness (HRB): ≤ 90
- Hardness (HV): ≤ 200
Summary
347 stainless steel, known for its high chromium and nickel content, is enhanced with tantalum and niobium to resist intergranular corrosion. It maintains structural integrity under high temperatures and is particularly suitable for welding applications. After solid solution treatment, it exhibits excellent mechanical properties, making it a preferred choice in industries requiring strength and corrosion resistance.
347/347H Stainless Steel Product Introduction
347 and 347H stainless steels are stabilized austenitic stainless steels known for their excellent resistance to intergranular corrosion. This article provides a comprehensive overview of 347/347H stainless steel, covering its chemical composition, mechanical properties, performance characteristics at different temperatures, industry applications, shapes and sizes, production standards, welding and processing capabilities, advantages and disadvantages, and a comparison with similar alloys.
Chemical Composition
347 and 347H stainless steels have similar chemical compositions, with the main difference being the carbon content in 347H for improved high-temperature strength.
| Element | Composition (%) for 347 | Composition (%) for 347H |
|---|---|---|
| Chromium (Cr) | 17.0 – 19.0 | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 13.0 | 9.0 – 13.0 |
| Manganese (Mn) | 2.0 max | 2.0 max |
| Silicon (Si) | 0.75 max | 0.75 max |
| Carbon (C) | 0.08 max | 0.04 – 0.10 |
| Phosphorus (P) | 0.045 max | 0.045 max |
| Sulfur (S) | 0.030 max | 0.030 max |
| Niobium (Nb) | 10xC – 1.10 | 8xC – 1.10 |
Mechanical Properties
347/347H stainless steels exhibit excellent mechanical properties suitable for various applications:
| Property | Value |
|---|---|
| Tensile Strength, ksi (MPa) | 75 (515) min |
| Yield Strength (0.2% offset), ksi (MPa) | 30 (205) min |
| Elongation (% in 2 inches) | 40 min |
| Hardness, Rockwell B (HRB) | 90 max |
Performance Characteristics
347/347H stainless steels offer several performance advantages:
High Temperature Resistance: Excellent resistance to oxidation and creep at elevated temperatures up to 1000°C.
Intergranular Corrosion Resistance: Contains niobium which stabilizes the alloy against sensitization and intergranular corrosion.
Weldability: Good weldability with standard welding techniques, with care needed to avoid hot cracking.
Industry Applications
347/347H stainless steels find applications across various industries requiring corrosion resistance and high-temperature performance:
| Industry Sector | Applications |
|---|---|
| Chemical Processing | Reactor vessels, heat exchangers, and piping systems handling corrosive chemicals. |
| Aerospace | Exhaust systems, jet engine parts, and aircraft components. |
| Oil and Gas | Offshore platforms, oil refinery equipment, and pipelines. |
| Power Generation | Boiler components, superheater tubes, and turbine blades. |
Shapes and Sizes
347/347H stainless steels are available in various forms and sizes:
Forms: Sheets, plates, bars, pipes, tubes, and forgings.
Sizes: Thickness ranging from 0.1 mm to 100 mm for plates, and diameter ranging from 1 mm to 500 mm for round bars.
Production Standards
347/347H stainless steels conform to international production standards ensuring quality and reliability:
| Product Form | Shapes Available | Sizes Available | Production Standards |
|---|---|---|---|
| Plates/Sheets | Sheets, Plates | Thickness: 0.1 mm – 100 mm | ASTM A240, ASME SA-240 |
| Bars/Rods | Round bars, Square bars | Diameter: 1 mm – 500 mm | ASTM A276, ASME SA-276 |
| Pipes/Tubes | Seamless, Welded | OD: 6 mm – 2500 mm | ASTM A312, ASME SA-312 |
Welding and Processing
347/347H stainless steels offer good weldability and processing characteristics:
Welding: Can be welded using standard welding techniques such as GTAW (TIG) and GMAW (MIG), with preheating and post-weld heat treatment sometimes required for thick sections.
Machinability: Can be machined using conventional methods, with low cutting speeds and adequate coolant recommended.
Advantages and Disadvantages
| Aspect | Details |
|---|---|
| Advantages | Excellent high-temperature strength and corrosion resistance, good weldability, and intergranular corrosion resistance due to niobium stabilization. |
| Disadvantages | Higher cost compared to non-stabilized austenitic stainless steels, reduced mechanical properties at cryogenic temperatures. |
Comparison with Similar Alloys
347/347H stainless steels are often compared with other stabilized austenitic stainless steels like 321 and 317L. Here’s a brief comparison:
| Alloy Type/Property | 347/347H Alloy | 321 Alloy | 317L Alloy |
|---|---|---|---|
| Chemical Composition | Contains niobium for stabilization against intergranular corrosion. | Contains titanium for stabilization against sensitization. | Contains molybdenum for improved corrosion resistance in acidic environments. |
| Mechanical Properties | Higher strength and creep resistance compared to 321. | Similar strength, but lower creep resistance compared to 347. | Lower strength but better corrosion resistance compared to 347. |
| Applications | High-temperature applications requiring intergranular corrosion resistance. | Heat exchangers, chemical processing equipment. | Chemical and petrochemical industries requiring corrosion resistance. |
This detailed article introduces 347/347H stainless steel, highlighting its chemical composition, mechanical properties, performance characteristics, industry applications, available forms and sizes, production standards, welding and processing capabilities, as well as advantages, disadvantages, and a comparison with similar alloys. Engineers and professionals seeking a stainless steel alloy with excellent high-temperature performance and corrosion resistance will find 347/347H alloy suitable for a wide range of applications in challenging environments.
