ASTM A234 WP91
A234 WP91: Specifications | Grades & Standards | Equivalent Grades | Chemical Composition | Mechanical Properties | BW Fittings
ASTM A234 WP91 Cr-Mo Fittings – Our range includes WP91 buttweld elbows, tees, reducers, caps, crosses, stub ends, and pipe bends, built for high-pressure, high-temperature piping systems, widely used in refineries, power plants, and chemical plants.
Best Export Prices: sales@midlandforgefittings.com
Midland Forge and Fittings Pvt. Ltd. is a leading manufacturer and global supplier of high-quality WP91 alloy steel buttweld fittings. The company operates with a well-structured production setup, combining advanced forging facilities, precision machining, and stringent quality control processes to ensure each product meets international standards.
Our emphasis on time delivery through efficient logistics and inventory management, catering to clients across power plants, refineries, petrochemical, and industrial piping projects. Every fitting is carefully inspected, tested, and packed using industry-standard protective packaging to maintain product integrity during transportation. With a strong focus on customer satisfaction, we ensure reliable performance, consistent quality, and professional service across all stages—from production to final delivery.
ASTM A234 WP91 is a high-strength chromium-molybdenum (Cr-Mo) alloy steel grade used for the fabrication of buttweld fittings such as elbows, tees, reducers, caps, crosses, stub ends, and bends. It is designed for high-temperature and high-pressure applications, offering excellent creep resistance, tensile strength, and toughness.
WP91 conforms to ASTM A234 specifications, ensuring controlled chemical composition and mechanical properties, which include tensile strength of 415–550 MPa, yield strength ≥205 MPa, elongation ≥20%, and Charpy impact ≥27 J at -29°C. The material exhibits superior weldability with standard processes like SMAW, GMAW, and GTAW, and is suitable for service in power plants, refineries, petrochemical plants, and industrial boilers. Its high Cr and Mo content provides enhanced oxidation resistance and dimensional stability at elevated temperatures, making it ideal for critical piping systems.
Alloy Steel A234 WP91 Pipe Fittings Specifications
Cr-Mo A234 WP91 Tee, Cross, Reducer Fittings– Grades & Standards
| Grade | ASTM Standard | Material Type | Application / Notes |
|---|---|---|---|
| WP91 | ASTM A234 | Cr-Mo Alloy Steel Buttweld Fitting | High-temperature and high-pressure service, superheaters, boilers, power plant piping, petrochemical and refinery lines |
Alloy Steel WP91 Seamless & Welded Fittings - Equivalent Grades
| Standard / Code | Equivalent Grade |
|---|---|
| ASTM / ASME | WP91 |
| EN / DIN | 13CrMo44 / 13CrMo4-5 |
| JIS | SCM4 |
| GOST / Russian | 15KhM |
| UNS | K11591 |
| BS | BS 8112-91 |
WP91 Buttweld Fittings - Chemical Composition
| Element | WP91 |
|---|---|
| Carbon (C) | 0.05 – 0.15 |
| Manganese (Mn) | 0.30 – 0.60 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.035 |
| Silicon (Si) | 0.10 – 0.35 |
| Chromium (Cr) | 1.90 – 2.30 |
| Molybdenum (Mo) | 0.90 – 1.05 |
| Nickel (Ni) | ≤ 0.30 |
| Copper (Cu) | ≤ 0.30 |
Alloy Steel WP91 Stub End - Mechanical Properties
| Property | WP91 |
|---|---|
| Tensile Strength (MPa / N/mm²) | 415 – 550 |
| Yield Strength (MPa / N/mm²) | ≥ 205 |
| Elongation (%) | ≥ 20 |
| Impact Test (Charpy V-Notch, -29°C) | ≥ 27 J |
| Hardness (Brinell, HB) | 137 – 187 |
| Maximum Operating Temperature | ~560°C |
Cr-Mo A234 WP91 Buttweld Fittings – Available in Seamless and Welded
How does WP91 differ from WP11 and WP22?
Chromium & Molybdenum Content: WP91 has higher Cr and Mo, providing superior creep strength and oxidation resistance.
Temperature Resistance: WP91 can operate at higher sustained temperatures (~560°C) compared to WP11 (~540°C) and WP22 (~560°C but slightly lower creep resistance than WP91 in long-term service).
Application Scope: WP11 for moderate high-temperature, WP22 for high-temperature and high-pressure, and WP91 for extreme temperature, long-duration service like superheaters and high-pressure steam lines.
Is WP91 weldable?
Yes, WP91 exhibits excellent weldability due to controlled carbon and alloying content.
Recommended Welding Processes: SMAW (Shielded Metal Arc Welding), GMAW (Gas Metal Arc Welding), GTAW (Gas Tungsten Arc Welding).
Preheating: Required for thicker sections to avoid thermal cracking.
Post-Weld Heat Treatment (PWHT): Essential to relieve residual stress and improve creep resistance for high-temperature service.
Why is WP91 preferred for high-pressure and high-temperature applications?
High-Temperature Strength: Maintains mechanical integrity at extreme temperatures.
Creep Resistance: Suitable for long-term service under sustained load.
Oxidation Resistance: High Cr and Mo content prevent scaling and oxidation.
Durability: Ensures long-term reliability in critical power plants, refineries, and petrochemical pipelines.
Weldability and Fabrication: Supports standard welding processes without compromising material performance.