ASTM A815 CR446
ASTM A815 CR446 Ferritic Stainless Steel Pipe Fittings
ASTM A815 CR446 pipe fittings are manufactured from high-chromium ferritic stainless steel Grade 446 (commonly aligned with UNS S44600 or similar high-Cr alloys) under the CR class, meaning they are cold-worked welded stainless steel fittings manufactured to the MSS SP-43 standard. These fittings are designed for excellent resistance to high-temperature oxidation, sulfidation, and severe corrosion in industrial environments.
With chromium content up to ~27%, CR446 fittings offer superior performance in elevated temperature and aggressive chemical service, making them ideal for furnace systems, heat-exchanger plants, flue gas handling, and petrochemical processing units. Their high structural stability and thermal strength ensure reliable operation in heat-intensive and corrosive service conditions.
Key Features
High-chromium ferritic stainless steel
Manufactured to CR Class (MSS SP-43)
Exceptional high-temperature oxidation and scaling resistance
Superior sulfidation resistance in combustion & gas environments
Excellent chloride stress corrosion cracking resistance
Stable microstructure in elevated temperature applications
Reliable mechanical performance in aggressive chemical service
Specifications
| Specification | Details |
|---|---|
| Standard | ASTM A815 / A815M |
| Grade / Class | CR446 |
| UNS Designation | S44600 / (or equivalent high-Cr ferritic grade) |
| Manufacturing Class | CR – Cold-worked welded fittings per MSS SP-43 |
| Material Type | Ferritic stainless steel |
| Form | Butt-weld pipe fittings |
| Standards | MSS SP-43 / ASME B16.9 / B16.28 (as applicable) |
Equivalent Grades
| Standard | Grade |
|---|---|
| UNS | S44600 (commonly used) |
| AISI | 446 |
| EN | 1.4762 / 1.4763 (approx.) |
| JIS | SUS 446 |
Available Sizes
NPS: ½” to 24”
Schedules: SCH 10S to SCH 80
Availability: Welded cold-worked fittings
Chemical Composition
| Element | % |
|---|---|
| Chromium (Cr) | 23.0 – 27.0 |
| Carbon (C) | ≤ 0.20 |
| Manganese (Mn) | ≤ 1.50 |
| Silicon (Si) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.040 |
| Sulfur (S) | ≤ 0.030 |
| Iron (Fe) | Balance |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | ≥ 485 MPa |
| Yield Strength | ≥ 275 MPa |
| Elongation | ≥ 20% |
Physical Properties
| Property | Value |
|---|---|
| Density | ~7.70 g/cm³ |
| Melting Point | Approx. 1500°C |
| Modulus of Elasticity | ~200 GPa |
| Thermal Conductivity | Higher than austenitic stainless steels |
Types of ASTM A815 CR446 Fittings
ASTM A815 CR446 Elbow
ASTM A815 CR446 Tee
ASTM A815 CR446 Reducers
ASTM A815 CR446 Caps
ASTM A815 CR446 Cross Fittings
ASTM A815 CR446 Nipples
ASTM A815 CR446 Couplings
ASTM A815 CR446 Stub Ends
Corrosion Resistance
Excellent resistance to:
High-temperature oxidation & scaling
Sulfur-containing gases and combustion atmospheres
Industrial chemical exposure
Chlorides (stress corrosion cracking resistance)
Performance remains stable under thermal cycling & corrosive gas streams.
Heat Resistance
Reliable service in temperatures up to ~1100°C
Outstanding resistance to:
Thermal shock
Carburization & sulfidation
High-temperature oxidation
Heat Treatment
| Process | Description |
|---|---|
| Annealing | 800°C – 900°C, air cool |
| Hardening | Not hardenable by heat treatment |
| Stress Relief | Recommended after heavy cold-work |
Welding
Weldability: Moderate
Suggested welding processes: TIG / MIG / SMAW
Preheat & post-weld heat treatment advisable
Ferritic stainless steel filler recommended
Proper heat control is essential to avoid grain growth.
Fabrication
Good machinability with correct tooling
Suitable for forming & moderate cold-work
Avoid excessive hot-working without controlled heat treatment
Applications
Furnace & thermal processing equipment
Heat exchangers & superheaters
Petrochemical & refinery components
Flue gas & exhaust systems
Industrial kilns & burners
Power plant boiler systems
Metallurgical and combustion environments