ASTM A336 / A336M Standard Specification for Alloy Steel Forgings for Pressure and High-Temperature Parts
This specification covers heavy-duty alloy steel forgings intended for pressure vessel components, valves, flanges, fittings, and other high-stress parts in elevated temperature service. These forgings are crucial in industries like power generation, petrochemical, and oil & gas for critical equipment.
Key Characteristics
| Feature | Description |
|---|---|
| Product Form | Forgings – shaped by hammering or pressing. |
| Material | Alloy Steel (Chromium-Molybdenum types). |
| Key Property | High strength, toughness, and creep resistance at elevated temperatures. |
| Primary Use | Critical components in pressure vessels, reactors, and high-temperature piping systems. |
Common Grades
ASTM A336 grades are designated with an "F" (for Forging). Common grades and their equivalent pipe/tube grades:
| Forging Grade (A336) | Similar Pipe Grade (A335) | Key Alloy | Typical Application |
|---|---|---|---|
| F11 | P11 | 1¼Cr-½Mo | Valve bodies, fittings for moderate temp service. |
| F22 | P22 | 2¼Cr-1Mo | Pressure vessel shells, heavy-duty flanges, reactor parts. |
| F5 | P5 | 5Cr-½Mo | High-temperature components with better oxidation resistance. |
| F9 | P9 | 9Cr-1Mo | High-strength, high-temperature parts. |
| F91 | P91 | 9Cr-1Mo-V-Nb | Critical components in modern high-pressure/temperature plants. |
Chemical Requirements (Example: Grade F22)
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.05 – 0.15 |
| Manganese (Mn) | 0.30 – 0.60 |
| Phosphorus (P), max | 0.025 |
| Sulfur (S), max | 0.025 |
| Silicon (Si) | 0.50 max |
| Chromium (Cr) | 1.90 – 2.60 |
| Molybdenum (Mo) | 0.87 – 1.13 |
Mechanical Requirements (Example: Grade F22, Normalized & Tempered)
| Property | Requirement |
|---|---|
| Tensile Strength | ≥ 415 MPa (60,000 psi) |
| Yield Strength | ≥ 205 MPa (30,000 psi) |
| Elongation (in 50mm) | ≥ 22% |
| Reduction of Area | ≥ 45% |
| Charpy V-Notch Impact | Typically required (e.g., min. 20 J at room temp). |
Manufacturing & Testing
Melting Process: Electric furnace, often with secondary refining (e.g., AOD, VOD).
Forging: Heated ingot is mechanically worked to refine grain structure.
Heat Treatment: Mandatory – usually normalized and tempered or quenched and tempered.
Testing: Extensive testing including:
Chemical analysis
Tensile test
Impact test
Hardness survey
Non-destructive examination (NDE) like ultrasonic testing (UT) for critical applications.
Typical Applications
Pressure Vessels: Shells, heads, nozzle necks, manway flanges.
Valves: Gate valve bodies, globe valves, check valves for high-temperature service.
Piping Components: Large-diameter, high-pressure flanges (WNRTJ), reducers, tees.
Turbine & Power: Steam chests, turbine casings, valve chests.
Reactors: Hydroprocessing reactor sections and internals.
Important Notes
Heat Treatment is Critical: Properties are achieved through controlled heat treatment, not just chemistry.
NDE Requirements: Extent of ultrasonic examination (UT) is often specified by the purchaser per ASME Section VIII or other codes.
Welding & PWHT: These forgings are weldable but require proper procedures and mandatory Post-Weld Heat Treatment (PWHT).
Not a Pipe Standard: This is a forging standard for discrete, heavy components. For continuous piping runs, use ASTM A335 seamless pipe.
In summary, ASTM A336 defines high-integrity alloy steel forgings that form the backbone of critical high-temperature, high-pressure industrial equipment, where reliability and strength under extreme conditions are paramount.
