Alloy Steel Grade 91 Explained
Alloy Steel Grade 91 is a high-strength 9% chromium–1% molybdenum alloy steel with added vanadium and nitrogen for exceptional creep resistance and superior high-temperature performance. It is specifically designed for ultra-supercritical power plants and advanced thermal systems operating under extreme pressure and temperature conditions. Grade 91 provides outstanding resistance to thermal fatigue, oxidation, and long-term deformation. Widely used in boiler headers, steam lines, and critical pressure parts, Alloy Steel Grade 91 sheets and plates deliver unmatched strength, reliability, and service life in modern power generation and high-energy industrial applications.
GR 91 ALLOY STEEL SHEETS AND PLATES EQUIVALENT GRADES
| STANDARD | UNS |
|---|---|
| Gr91 | K90901 |
SPECIFICATION OF ALLOY STEEL GR 91 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 91 SHEETS AND PLATES
| Grade | C% | Mn% | Si% | P% | S% | Cr% | Mo% |
|---|---|---|---|---|---|---|---|
| Alloy Steel F91 | 0.05-0.20 | 0.3-0.6 | 0.50 max | 0.045 max | 0.03 max | 0.8-1.25 | 0.044-0.65 |
MECHANICAL PROPERTIES OF ALLOY STEEL GR 91 SHEETS AND PLATES
| Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|
| 415 | 205 | 20 |
💡 Practical Difference in Use
Use Alloy Steel Grade 91 when: exceptional high-temperature strength, creep resistance, and oxidation resistance are required, along with excellent toughness and weldability. → Example: ultra-supercritical boilers, steam turbines, high-pressure piping, and heat exchangers in power generation and petrochemical industries.
Applications of Alloy Steel Grade 91 Sheets and Plates
Alloy Steel Grade 91 is a high-chromium, molybdenum steel designed for high-temperature service, offering excellent creep strength, durability, and toughness in critical industrial equipment.
- Power Generation: Ultra-supercritical boilers, steam turbines, heat exchangers, and piping systems.
- Chemical & Petrochemical: High-pressure vessels, reactor systems, and process piping.
- Oil & Gas: High-temperature and high-pressure pipelines, refinery vessels, and offshore equipment.
When to Choose Alloy Steel Grade 91?
Alloy Steel Grade 91 is chosen for applications requiring long-term high-temperature reliability, high creep resistance, and superior mechanical performance under severe conditions.
Choose Alloy Steel Grade 91 when:
- Operating temperatures reach 600–650°C or higher
- High creep, fatigue, and oxidation resistance are essential
- Used in ultra-supercritical boilers, turbines, and high-pressure piping
- Long-term safety, weldability, and toughness are critical
- Reliable performance under high-pressure and high-temperature conditions is required
Industries That Use Alloy Steel Grade 91 Sheets and Plates
Alloy Steel Grade 91 is extensively used in industries where extreme temperature, pressure, and long-term reliability are critical for operational safety.
Essential for ultra-supercritical boilers, turbines, and heat exchangers.
Uses
Steam lines, high-temperature piping, and superheater tubes.
Why Alloy Steel Grade 91?
Superior creep resistance, high-temperature strength, and durability.
Used in high-temperature and high-pressure process equipment.
Uses
Refinery pipelines, reactor vessels, and offshore high-pressure equipment.
Why Alloy Steel Grade 91?
High strength and toughness under severe thermal and pressure conditions.
Applied in high-temperature and high-pressure chemical processes.
Uses
Pressure vessels, piping systems, and high-temperature reactors.
Why Alloy Steel Grade 91?
Exceptional creep resistance, oxidation resistance, and long-term reliability.
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