ASTM A403 WP321H
ASTM A403 WP321H Stainless Steel Pipe Fittings
ASTM A403 WP321H is a high-temperature grade of austenitic stainless steel butt-weld fittings, stabilized with titanium for exceptional resistance to carbide precipitation and intergranular corrosion. The “H” grade contains higher carbon content, enhancing high-temperature strength, creep resistance, and mechanical performance in elevated temperature services.
WP321H stainless steel fittings are widely used in refineries, petrochemical units, boilers, superheaters, power plants, heat exchangers, and high-temperature steam piping, offering long-term stability and superior corrosion protection in oxidizing environments.
Key Features
Titanium-stabilized grade for excellent intergranular corrosion resistance
Superior creep strength and elevated temperature durability
Designed for high-temperature applications
Good resistance to oxidation and thermal fatigue
High strength retention in 650°C and above environments
Suitable for welded constructions
Great durability in steam & thermal processing environments
Technical Specification
| Specification | Details |
|---|---|
| Standard | ASTM A403 / ASME SA403 |
| Grade | WP321H |
| UNS | S32109 |
| Material | Titanium-stabilized Austenitic Stainless Steel |
| Size Range | ½” to 48” |
| Thickness | SCH 10S – SCH XXS |
| Form | Seamless / Welded / Fabricated |
| Fittings Standard | ASME B16.9 / B16.28 / MSS-SP-43 |
| End Types | Beveled / Plain End |
Equivalent Grades
| Standard | Grade |
|---|---|
| ASTM / ASME | A403 / SA403 WP321H |
| UNS | S32109 |
| EN | 1.4878 |
| DIN | X8CrNiTi18-10 |
Available Sizes
Sizes: ½” – 48”
Thickness: SCH 10S, SCH 40S, SCH 80S, SCH 160, XXS
Types: Seamless / Welded / Fabricated
Chemical Composition
| Element | % |
|---|---|
| Carbon (C) | 0.04 – 0.10 |
| Chromium (Cr) | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 12.0 |
| Titanium (Ti) | ≥ 5 × C to 0.70 max |
| Manganese (Mn) | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 |
| Nitrogen (N) | ≤ 0.10 |
| Iron (Fe) | Balance |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | ≥ 515 MPa |
| Yield Strength | ≥ 205 MPa |
| Elongation | ≥ 40% |
| Hardness | ≤ 217 HB |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.9 g/cm³ |
| Melting Point | 1400 – 1425°C |
| Thermal Conductivity | 16 W/m-K |
| Specific Heat | 500 J/kg-K |
| Modulus of Elasticity | ~193 GPa |
Types of WP321H Pipe Fittings
ASTM A403 WP321H Elbow
ASTM A403 WP321H Tee
ASTM A403 WP321H Reducers
ASTM A403 WP321H Caps
ASTM A403 WP321H Cross Fittings
ASTM A403 WP321H Nipples
ASTM A403 WP321H Couplings
ASTM A403 WP321H Stub Ends
Corrosion Resistance
Excellent resistance to intergranular corrosion after welding
Highly resistant to oxidizing and acidic environments
Better performance than 304H in high-temperature service
Suitable for chloride & mild chemical media
Heat Resistance
Can withstand continuous service up to 870°C
Excellent resistance to carbide precipitation
High creep & rupture strength in elevated temperatures
Suitable for thermal cycling & steam service
Heat Treatment
| Process | Requirement |
|---|---|
| Solution Annealing | 925°C – 1120°C |
| Cooling | Rapid air or water quench |
Welding
Excellent weldability by all common methods
No post-weld heat treatment usually required
Titanium stabilization minimizes carbide precipitation
Recommended filler metals: ER321 / E321
Fabrication
Good formability & machinability
Harder than 304/316 grades—use carbide tools
Pre-heating not required
Suitable for hot & cold forming
Applications
Petrochemical & Refinery Plants
Heat Exchangers & Boilers
Power Plants & Superheater Systems
Furnace & Thermal Processing Lines
High-Temperature Steam Lines
Oil & Gas Industry
Chemical Processing Equipment
Aerospace & Exhaust Systems