ASTM A213 / SA213 - Seamless Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes
ASTM A213 (SA213) is the comprehensive specification covering seamless ferritic and austenitic alloy-steel tubes for high-temperature and corrosive service in boilers, superheaters, heat exchangers, and condensers.
Key Characteristics
| Feature | Description |
|---|---|
| Material | Alloy Steel (Ferritic & Austenitic grades) |
| Manufacturing | Seamless (SMLS) only - Hot-finished or cold-drawn |
| Temperature Range | Up to 700°C (1300°F) depending on grade |
| Primary Use | High-temperature/corrosive service where carbon steel is inadequate |
Common Grades & Applications
Ferritic Grades (Chromium-Molybdenum):
| Grade | Alloy Type | Key Elements | Max Temp* | Primary Application |
|---|---|---|---|---|
| T2 | ½Cr-½Mo | 0.5% Cr, 0.5% Mo | 500°C | Low-alloy superheater |
| T5 | 5Cr-½Mo | 5% Cr, 0.5% Mo | 600°C | High-temp oxidation resistance |
| T11 | 1¼Cr-½Mo | 1.25% Cr, 0.5% Mo | 525°C | General superheater tubes |
| T12 | 1Cr-½Mo | 1% Cr, 0.5% Mo | 510°C | Similar to T11 |
| T22 | 2¼Cr-1Mo | 2.25% Cr, 1% Mo | 575°C | Industry standard superheater |
| T91 | 9Cr-1Mo-V | 9% Cr, 1% Mo, V, Nb | 650°C | Advanced high-temperature |
Austenitic Grades (Stainless Steels):
| Grade | AISI Equivalent | Key Elements | Max Temp* | Primary Application |
|---|---|---|---|---|
| TP304 | 304 | 18Cr-8Ni | 700°C | General corrosion resistance |
| TP304H | 304H | 18Cr-8Ni (high carbon) | 700°C | High-temp strength |
| TP316 | 316 | 16Cr-10Ni-2Mo | 700°C | Chloride corrosion resistance |
| TP321 | 321 | 18Cr-10Ni-Ti | 700°C | Intergranular corrosion protection |
| TP347 | 347 | 18Cr-10Ni-Nb | 700°C | High-temp strength, steam oxidation |
*Approximate maximum metal temperature for long-term service
Chemical Requirements (Examples)
Ferritic Grade T22:
| 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), max | 0.50 |
| Chromium (Cr) | 1.90 - 2.60 |
| Molybdenum (Mo) | 0.87 - 1.13 |
Austenitic Grade TP304H:
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.04 - 0.10 |
| Manganese (Mn), max | 2.00 |
| Phosphorus (P), max | 0.045 |
| Sulfur (S), max | 0.030 |
| Silicon (Si), max | 1.00 |
| Chromium (Cr) | 18.0 - 20.0 |
| Nickel (Ni) | 8.0 - 11.0 |
Mechanical Properties
Ferritic Grades (Example - T22):
| Property | Requirement |
|---|---|
| Tensile Strength, min | 415 MPa (60,000 psi) |
| Yield Strength, min | 205 MPa (30,000 psi) |
| Elongation (in 50mm), min | 30% |
Austenitic Grades (Example - TP304H):
| Property | Requirement |
|---|---|
| Tensile Strength, min | 515 MPa (75,000 psi) |
| Yield Strength, min | 205 MPa (30,000 psi) |
| Elongation (in 50mm), min | 35% |
Manufacturing & Heat Treatment
Production Methods:
Hot-finished - For standard applications
Cold-drawn - For closer tolerances (must be heat treated)
Heat Treatment Requirements:
| Grade Type | Required Heat Treatment |
|---|---|
| Ferritic Grades | Normalized & Tempered or Annealed |
| Austenitic Grades | Solution Annealed (≥1040°C) & Quenched |
| T91/T92 | Normalized (1040-1080°C) & Tempered (730-800°C) |
Dimensional Tolerances:
Tighter than pressure pipe standards
Critical for tube-to-tubesheet fit
Special tolerances available for U-bend tubes
Testing & Inspection
| Test | Requirement |
|---|---|
| Hydrostatic Test | Mandatory (or nondestructive test) |
| Flattening Test | Required (tests ductility) |
| Flaring Test | Required (tests expandability) |
| Hardness Test | Optional/for certain grades |
| Grain Size | Required for austenitic grades |
| Intergranular Corrosion | Optional for austenitic grades (ASTM A262) |
| Nondestructive Test | Optional (eddy current/ultrasonic) |
Hydrostatic Test Pressure:
text
P = 2St/D (minimum 70 bar/1000 psi) Where S = 60% of specified minimum yield strength
Primary Applications
1. Power Generation:
Superheater/Reheater tubes (T22, T91, TP304H, TP347)
Water wall tubes in corrosive fuel service (T11, T22)
Heat recovery steam generator (HRSG) tubes
Condenser tubes (austenitic grades for brackish/seawater)
2. Petrochemical & Refining:
Fired heater tubes (T5, T9, T11, T22)
Heat exchanger tubes for corrosive process streams
Catalytic reformer tubes
Ethylene cracker tubes
3. Industrial Boilers:
Waste heat boiler tubes
Chemical recovery boiler tubes
High-temperature process heaters
Selection Guidelines
Temperature-Based Selection:
| Temperature Range | Recommended Grades |
|---|---|
| < 425°C (800°F) | A192, A210 (carbon steels) |
| 425-525°C (800-975°F) | T11, T12, T22 |
| 525-600°C (975-1110°F) | T5, T9, T22, TP304H |
| 600-650°C (1110-1200°F) | T91, T92, TP304H, TP347 |
| > 650°C (1200°F) | TP304H, TP347, TP310, advanced alloys |
Corrosion-Based Selection:
| Corrosion Type | Recommended Grades |
|---|---|
| Oxidation (fireside) | T5 (5% Cr), T9 (9% Cr), T22 (2¼% Cr) |
| Sulfidation | T5, T9 (higher chromium) |
| Chloride Stress Corrosion | TP321, TP347 (stabilized grades) |
| General Corrosion | TP304, TP316 |
| Steamside Oxidation | TP347 (best), TP304H |
Fabrication Considerations
Welding Requirements:
| Grade Type | Key Welding Considerations |
|---|---|
| Ferritic Cr-Mo | Preheat mandatory, PWHT required, low-hydrogen electrodes |
| T91/T92 | Strict preheat (200°C), controlled interpass temp, specific PWHT |
| Austenitic | No preheat, but heat input control, avoid sensitization |
Tube Expanding:
Ferritic grades expand easily into tubesheets
Austenitic grades require care (work harden)
T91/T92 require special procedures
U-Bend Requirements:
Minimum bend radius specified
Heat treatment after bending often required
Special testing for bent sections
Comparison with Related Standards
| Standard | Material | Key Difference from A213 |
|---|---|---|
| ASTM A335 | Alloy Steel | Pipe for external piping (companion to A213 tubes) |
| ASTM A210 | Carbon Steel | Lower temperature capability |
| ASTM A269 | Stainless Steel | General service tubes, not specifically for boilers |
| ASTM A789/A790 | Duplex Stainless | For corrosive service, not high-temperature |
Failure Modes & Prevention
1. Creep Rupture:
Cause: Overheating beyond design limits
Prevention: Temperature monitoring, proper grade selection
Critical for: T11, T22 at upper temperature limits
2. Fireside Corrosion:
Cause: Sulfur, vanadium, alkali metals in fuel
Prevention: Higher chromium grades, fuel additives
Solutions: T5 for moderate, T9/T91 for severe
3. Steamside Oxidation:
Cause: High steam temperature/pressure
Prevention: TP347 for best resistance, oxide-dispersed coatings
Problematic for: TP304H in ultra-supercritical boilers
4. Stress Corrosion Cracking:
Cause: Chlorides + stress + temperature
Prevention: TP321/TP347 for stabilized grades, chloride control
Critical in: Coastal plants, certain process conditions
Economic Considerations
Cost Comparison (Relative to T22):
| Grade | Approximate Cost Factor |
|---|---|
| T11/T12 | 0.9-1.0x |
| T22 | 1.0x (Baseline) |
| T5 | 1.2-1.4x |
| T91 | 2.0-2.5x |
| TP304H | 3.0-4.0x |
| TP347 | 4.0-5.0x |
Life Cycle Cost Factors:
Initial material cost
Fabrication/welding costs
Replacement frequency
Plant efficiency (higher temps = better efficiency)
Outage costs for repairs
Ordering Information
Essential Specifications:
Standard: ASTM A213/SA213
Grade: Specific alloy designation (e.g., T22, TP304H)
Dimensions: OD × Wall Thickness × Length
Heat Treatment: Specify if other than standard
Grain Size: For austenitic grades (typically 7 or coarser)
Testing: Additional requirements (IGC, hydro, etc.)
End Preparation: Plain, beveled, special for U-bends
Sample Purchase Specification:
text
ASTM A213 T22 Tubes, 38.1 mm OD × 5.0 mm wall × 15,000 mm length, Normalized & tempered, plain ends, with hydrostatic, flattening, and flaring tests, Full MTC with heat number traceability, ultrasonic tested.
International Equivalents
| Grade | Europe (EN) | Japan (JIS) | China (GB) |
|---|---|---|---|
| T11 | 13CrMo4-5 | STBA 24 | 15CrMoG |
| T22 | 10CrMo9-10 | STBA 24 | 12Cr2MoG |
| T91 | X10CrMoVNb9-1 | STBA 29 | 10Cr9Mo1VNb |
| TP304H | X7CrNi18-9 | SUS 304H TB | 07Cr19Ni10 |
| TP347 | X7CrNiNb18-10 | SUS 347 TB | 07Cr18Ni11Nb |
Bottom Line: ASTM A213 is the definitive specification for alloy steel heat transfer tubes in demanding high-temperature and corrosive environments. Its comprehensive range of ferritic and austenitic grades provides tailored solutions for virtually any boiler, superheater, or heat exchanger application, balancing performance requirements with economic considerations.
