Contents
ASTM A234 WP91 Steel Pipe Fittings | Buttweld Fittings
- John
WP91 steel is a high-performance alloy built for extreme heat and pressure. SteelPro Group offers ASTM A234 WP91 pipe fittings, built to meet different global standards. This article explores WP91 steel’s properties, practical uses, and products details in high-performance piping systems.
What Is WP91 Steel?
WP91 steel is a high-strength chromium-molybdenum alloy used in high-temperature and high-pressure environments. It meets the ASTM A234/ASME SA234 standard for wrought alloy steel pipe fittings. With strong tensile and yield strength, it resists creep, oxidation, and thermal fatigue. It is applied in the petrochemical, energy, oil and gas, and nuclear sectors. WP91 maintains strength under extreme conditions and offers good weldability.
SteelPro Group WP91 steel is commonly used for buttweld fittings like elbows, tees, and reducers in critical piping systems.
WP91 Pipe Fittings & Buttweld Fittings Specifications
SteelPro Group WP91 pipe fittings conform to ASTM A234/ASME SA234 standards, which ensures their suitability for high pressure applications. The fittings are available in various sizes.
| Specification | Details |
| Dimensions Standards | ANSI/ASME B16.9, BS1560, MSS-SP-43, BS4504, BS10 |
| Thickness of Fittings | SCH 10 to SCH XXS, available with NACE MR 01-75 |
| Seamless ButtWeld Fittings | Range from 0.5 in (DN6) to 10 in (DN250) |
| Welded ButtWeld Fittings | Range from 0.5 in (DN6) to 48 in (DN1200) |
| Products Types | Elbows, tees, and reducers |
WP91 Pipe Fittings & Buttweld Fittings Standards
- ANSI/ASME B16.9: Governs dimensions, tolerances, and materials for buttwelding fittings.
- BS1560: Specifies dimensions and tolerances for pipes, flanges, and fittings.
- MSS-SP-43: Covers stainless steel butt-welded fittings, applicable to WP91 for its alloy composition.
- BS4504: Addresses circular flanges for pipes, valves, and fittings, focusing on pressure handling.
- BS10: Details dimensions for ferrous flanges in the UK, categorizing flanges by pressure capacity.
These standards ensure WP91 fittings are robust and suitable for high-pressure, high-temperature environments in industries like petrochemical, nuclear, and oil and gas.
WP91 Steel Chemical Composition
| Element | Content (%) | Function |
| Carbon (C) | 0.05 – 0.2 | Enhances strength and hardness |
| Manganese (Mn) | 0.3 – 0.8 | Aids in toughness and wear resistance |
| Silicon (Si) | 0.5 – 1.0 | Improves oxidation resistance and strength |
| Sulfur (S) | ≤ 0.030 | Helps machinability but in excess can cause brittleness |
| Chromium (Cr) | 8.0 – 9.5 | Provides corrosion and oxidation resistance, increases hardenability |
| Phosphorus (P) | ≤ 0.030 | Improves strength but may reduce toughness at high levels |
| Molybdenum (Mo) | 0.85 – 1.05 | Enhances high-temperature strength and creep resistance |
WP91 Steel Mechanical Properties
| Property | Value (Imperial) | Value (Metric) |
| Density | 0.284 lb/in³ | 7.85 g/cm³ |
| Yield Strength | ≥ 30,000 psi | ≥ 205 MPa |
| Tensile Strength | 60,200 – 84,800 psi | 415 – 585 MPa |
| Elongation | ≥ 20% | ≥ 20% |
WP91 Steel Applications
WP91 steel is widely used in industries requiring high-temperature and high-pressure resistance.
- Petrochemical Industry: Applied in piping systems, thermal exchangers, and high-pressure containers for handling corrosive substances and hydrocarbon processing.
- Oil and Gas Industry: Applied in oil extraction, offshore drilling, and natural gas processing for high-pressure pipelines and fittings.
- Power Generation & Nuclear Industry: Found in steam pipelines, superheater tubes, and boiler components in nuclear and fossil fuel power plants.
- Pulp and Paper Industry: Used in steam handling and chemical processing equipment in corrosive environments.
- Defense & Aerospace: Applied in military-grade piping, hydraulic systems, and heat-resistant components.
WP91 Steel Pipe & Buttweld Fittings Heat Treatment
Normalizing Process
This is the first step in heat treatment to refine the microstructure. It eliminates internal stresses, improves grain structure, and gets the steel ready for next processing.
- Normalizing Temperature: 1800°F – 1900°F (982°C – 1038°C)
- Holding Time: Sufficient to ensure uniform heat distribution
- Cooling Method: Air cooling (but not rapid cooling to avoid microcracking)
Tempering Process
This method minimizes fragility and improves durability while preserving superior strength. It is essential for long-term reliability.
- Temperature Range: 1350°F – 1450°F (732°C – 788°C)
- Holding Time: Minimum 1 hour per inch (25.4 mm) of thickness
- Cooling Method: Air cooling
Post-Weld Heat Treatment (PWHT) and Stress Relieving
After welding or high-temperature forming, WP91 steel must be stress relieved. This maintains its integrity and prevents cracking or premature failure.
Heat Treatment Precautions
- Avoid Rapid Cooling – Sudden cooling can cause microcracking and hardness variations.
- Ensure Uniform Heating – The entire component must be evenly heated to prevent stress concentrations.
- Use a Controlled Furnace Atmosphere – Protect against decarburization and oxidation by using a neutral or controlled gas environment.
If you are looking for WP91 steel pipe fittings that have undergone precise heat treatment, we offer high-quality, heat-treated WP91 components that meet ASTM A234 / ASME SA234 standards.
Reliable WP91 Steel Fittings for Your Next Project
For high-temperature, high-pressure applications, quality matters. SteelPro Group provides ASTM A234 WP91 fittings with various custom options.
We offer a full range of buttweld fittings—elbows, tees, and reducers—built to industry standards. Get the right fit for your project with expert support and reliable supply.
Browse our selection today and equip your system with the best.
