Description
Stainless Steel Boiler Tubes — Boiler & Super-heater Tube Specification
Material
Austenitic stainless steel boiler and super-heater tubes conforming to BS 3059-2:1990 “Steel boiler and superheater tubes – Specification for carbon, alloy and austenitic stainless steel tubes with specified elevated temperature properties.”
The designation “CFS304S59”, “CFS316S59”, “CFS321S59 (1010)”, “CFS321S59 (1105)”, “CFS347S59” refers to cold-finished seamless (CFS) austenitic stainless steel tube grades under BS 3059-2 (Category 2) for elevated-temperature service.
Specification
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BS 3059-2 covers tubes (outside diameter ≤ 127 mm and wall thickness ≤ 12.5 mm) for boiler and super-heater applications.
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Manufacturing method: seamless cold-finished (CFS) for all austenitic grades.
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Delivery condition: solution-annealed and straightened, suitable for long-term elevated-temperature service.
Major Characteristics
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Excellent corrosion resistance typical of austenitic stainless steels such as 304, 316, 321, 347.
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High elevated-temperature strength; BS 3059-2 defines required properties such as Rp1.0 at 250 °C, 300 °C, etc.
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Good fabricability: cold-finished seamless tubes ensure tight tolerances and uniform wall thickness.
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The “S59” suffix indicates compliance with BS 3059-2 Category 2 elevated-temperature testing.
Our Advantages
From a professional mill/manufacturer perspective, we address key concerns of boiler-tube buyers:
1. Straightness & Dimensional Control
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CFS manufacturing ensures superior control of ovality, wall thickness variation, and straightness compared to hot-finished or welded tubes.
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BS 3059-2 tolerance examples: OD ±0.5 % (min ±0.10 mm); wall thickness ≤3.25 mm ±10 %; >3.25 mm ±7.5 %.
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Each tube undergoes OD, wall, straightness, and internal-surface inspections to ensure compliance.
2. Material Chemistry & Traceability
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Chemical composition of each heat is verified and fully traceable.
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No unapproved alloy additions are permitted under BS 3059-2, ensuring consistent heat-resistant performance.
3. Elevated-Temperature Mechanical Reliability
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Proper solution annealing (e.g., 321S59 (1010): ~950-1070 °C; 321S59 (1105): ~1070-1140 °C) ensures compliance with elevated-temperature proof-stress requirements.
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Full testing: tensile strength, yield, elongation, elevated-temperature proof stress.
4. Surface Quality & NDT Assurance
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Seamless CFS structure eliminates weld-defect concerns and provides superior internal finish.
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100% NDT, hydrostatic testing, dimensional verification, and defect inspection ensure reliability.
5. Long Service Life & International Compliance
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Austenitic grades 304/316/321/347 are widely proven for boiler/super-heater service.
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Full documentation package: chemical report, mechanical test report, NDT results, dimensional checks.
Chemical Composition
| Grade | C (max) | Si (max) | Mn (max) | P (max) | S (max) | Cr (min) | Ni (min) | Mo (typical) |
|---|---|---|---|---|---|---|---|---|
| CFS 304S59 | ~0.10 | ~1.00 | ~2.00 | 0.04 | 0.03 | ~17 % | ~8-12 % | – |
| CFS 316S59 | ≤0.08 | ≤1.00 | ≤2.00 | 0.045 | 0.030 | ~16-18 % | ~10-14 % | ~2-3 % |
| CFS 321S59 (1010) | ≤0.10 | ≤1.00 | ≤2.00 | 0.04 | 0.03 | ~17-19 % | ~9-12 % | – |
| CFS 321S59 (1105) | ≤0.10 | ≤1.00 | ≤2.00 | 0.04 | 0.03 | ~17-19 % | ~9-12 % | – |
| CFS 347S59 | ≤0.10 | ≤1.00 | ≤2.00 | 0.04 | 0.03 | ~17-19 % | ~10-13 % | – |
Mechanical Properties
| Grade | Tensile Strength (Rm) | Yield / Proof Stress (Min) | Elongation (Min) | Elevated-Temp Proof Stress (Example at 250 °C) |
|---|---|---|---|---|
| CFS 304S59 | ~490-690 MPa | ≥235 MPa | ≥35 % | ~139 MPa |
| CFS 316S59 | ~510-710 MPa | ≥245 MPa | ≥35 % | ~150 MPa |
| CFS 321S59 (1010) | ~490-690 MPa | ≥235 MPa | ≥35 % | ~164 MPa |
| CFS 321S59 (1105) | ~490-690 MPa | ≥195 MPa | ≥35 % | ~125 MPa |
| CFS 347S59 | ~510-710 MPa | ≥245 MPa | ≥35 % | ~172 MPa |
Execution Standards
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Primary Standard: BS 3059-2:1990 (Category 2)
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Manufacturing Method: Seamless Cold-Finished (CFS)
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Testing: Tensile test, flattening test, drift-expansion test, elevated-temperature proof test
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Global Equivalence: Comparable to ASTM/EN/JIS austenitic boiler-tube grades (304/316/321/347 series)
Application Fields
General Applications
High-temperature steam boiler components, super-heaters, heat-exchangers, economizers, and thermal-process tubes.
Specific Use Cases
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Super-heater coils in industrial boilers
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Heat-recovery steam generator (HRSG) tube bundles
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Furnace and radiant-section tubes in chemical plants
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High-pressure steam lines exposed to thermal cycling and oxidation
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Heat-exchanger tubes in corrosive or elevated-temperature environments
