Alloy Steel Grade 9 Explained
Alloy Steel Grade 9 is a low-alloy chromium-molybdenum steel developed for superior creep resistance and high-temperature strength under continuous service conditions. It performs exceptionally well in high-pressure and high-temperature environments such as power plant headers, refinery heaters, and steam piping systems. The alloying elements provide excellent resistance to oxidation and thermal fatigue, making it suitable for prolonged exposure to heat. With good toughness and reliable weldability using proper pre-heating and post-weld heat treatment, Alloy Steel Grade 9 sheets and plates are widely trusted in critical thermal applications.
GR 9 ALLOY STEEL SHEETS AND PLATES EQUIVALENT GRADES
| STANDARD | UNS |
|---|---|
| A387 / SA 387 | K90941 |
SPECIFICATION OF ALLOY STEEL GR 9 SHEETS AND PLATES
| Standard | ASTM A387 / ASME SA387 |
|---|---|
| Dimension Standard | JIS, AISI, ASTM, GB, DIN, EN, etc |
| Width | 1000mm, 1219mm, 1500mm, 1800mm, 2000mm, 2500mm, 3000mm, 3500mm, etc |
| Length | 2000mm, 2440mm, 3000mm, 5800mm, 6000mm, etc |
| Thickness | 0.3 mm to 120 mm |
| Form | Coils, Foils, Rolls, Plain Sheet, Shim Sheet, Perforated Sheet, Chequered Plate, Strip, Flats, Blank (Circle), Ring (Flange) etc. |
| Surface Finishing | Hot rolled plate (HR), Cold rolled sheet (CR), 2B, 2D, BA, NO.1, NO.4, NO.8, 8K, mirror, Chequered, embossed, hair line, sand blast, Brush, etching, SATIN (Met with Plastic Coated) etc. |
CHEMICAL COMPOSITION OF ALLOY STEEL GR 9 SHEETS AND PLATES
| C% | Mn% | P% | S% | Si% | Cr% | Mo% |
|---|---|---|---|---|---|---|
| 0.15 max | 0.25-0.66 | 0.030 max | 0.030 max | 1.05 max | 7.9-10.1 | 0.85-1.15 |
MECHANICAL PROPERTIES OF ALLOY STEEL GR 9 SHEETS AND PLATES
| Property | Class 1 | Class 2 |
|---|---|---|
| Tensile Strength (ksi) | 60-85 | 75-100 |
| Tensile Strength (MPa) | 415-585 | 515-690 |
| Yield Strength (ksi) | 30 | 45 |
| Yield Strength (MPa) | 205 | 310 |
| Elongation in 50mm (%) | 18 | 18 |
| Reduction of area (%) | 45 | 45 |
💡 Practical Difference in Use
Use Alloy Steel Grade 9 when: high-temperature strength, excellent creep resistance, and good toughness are required along with reliable weldability. → Example: high-pressure boilers, power plant piping, steam turbine components, and heat exchangers operating under severe conditions.
Applications of Alloy Steel Grade 9 Sheets and Plates
Alloy Steel Grade 9 is a chromium-molybdenum steel designed for elevated-temperature service, providing excellent strength, toughness, and resistance to oxidation and creep.
- Power Plant Equipment: High-temperature boilers, superheaters, and steam piping.
- Pressure Vessels: Reactors, high-pressure vessels, and storage tanks.
- Piping Systems: Oil refineries, chemical plants, and high-temperature pipelines.
When to Choose Alloy Steel Grade 9?
Alloy Steel Grade 9 is selected for applications where high creep strength, long-term reliability, and toughness under high temperatures are critical.
Choose Alloy Steel Grade 9 when:
- Service temperatures are up to 600–620°C
- High resistance to creep, oxidation, and fatigue is required
- Used in high-pressure boilers, turbines, and piping systems
- Fabrication, welding, and long-term operational safety are essential
- Corrosion resistance under steam and high-temperature fluids is important
Industries That Use Alloy Steel Grade 9 Sheets and Plates
Alloy Steel Grade 9 is widely used in industries requiring high-temperature reliability, toughness, and resistance to creep and fatigue.
Essential for boilers, turbines, and high-temperature piping.
Uses
Superheaters, steam lines, heat exchangers.
Why Alloy Steel Grade 9?
Superior creep resistance and toughness at elevated temperatures.
Used in high-pressure and high-temperature process equipment.
Uses
Refinery piping, reactor vessels, and high-temperature valves.
Why Alloy Steel Grade 9?
Excellent resistance to thermal fatigue and stress rupture.
Used where high-pressure and high-temperature resistance is required.
Uses
Pressure vessels, piping systems, and high-temperature reactors.
Why Alloy Steel Grade 9?
High strength and reliability in severe chemical and thermal conditions.
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