ASTM A268 TP405 / UNS S40500 Ferritic Stainless Steel Tube Boiler and Heat Exchanger Tube
ASTM A268 TP405 / UNS S40500 Stainless Steel Seamless Tube Heat Exchanger Tube
ASTM A268 TP405 is a low‑cost, SCC‑resistant ferritic tube ideal for moderate‑temperature heat exchangers and boilers where austenitic grades fail due to chloride cracking. Its key limitation is embrittlement at 475°C and poor low‑temperature toughness. For welded tube, post‑weld annealing is mandatory to achieve acceptable ductility.
Advantages of Grade 405 ferritic stainless steel
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Excellent chloride stress corrosion cracking (SCC) resistance
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Lower cost
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Lower thermal expansion
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Higher thermal conductivity
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Magnetic
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Good oxidation resistance
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Resists polythionic acid SCC
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No sensitization
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Good weldability (with PWHT)
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Good resistance to hydrogen attack
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Lower allowable stress at moderate temperatures
Chemical Composition % of STM A268 TP405 Ferritic Stainless Steel Seamless Tube
| Grade | C | Mn | Si | P | S | Cr | Ni | Mo | Cu | N |
|
TP405 |
0.08 max | 1.00 max | 1.00 max | 0.045 max | 0.030 max | 11.0-13.0 | 0.50 max | 0.60 max | 0.25 max | 0.10 max |
Mechanical Properties of ASTM A268 TP405 Ferritic Stainless Steel Seamless Tube
| Grade | Tensile Strength | Yield Strength | Elongation | Hardness |
| TP405 |
480 - 620 MPa (70 - 90 ksi) |
205 MPa (30 ksi) |
20-25%(acc. thickness) |
160-190 HB |
When to Specify TP405 vs. Austenitic (TP304/316)
| Condition | Recommendation |
|---|---|
| Chloride SCC risk (e.g., seawater, brine, caustic) | TP405 (or other ferritic) |
| High temperature > 600°C (1112°F) | Austenitic (e.g., TP304H) |
| Cryogenic or sub‑zero service | Austenitic (TP304) – ferritic becomes brittle |
| High pressure steam (> 500 psi, > 400°C) | Austenitic (creep strength) |
| Cost‑sensitive, moderate corrosion, no SCC risk | TP405 |
| Welding without PWHT possible | Austenitic (ferritic requires PWHT) |
Application
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Heat exchanger bundles in hydrotreaters, catalytic reformers, and amine service (where chloride SCC is a concern).
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Boiler feedwater heaters (low temperature end).
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Condensers using brackish or chlorinated cooling water.
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Refinery overhead condensers (wet H₂S / chloride environment).
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Automotive exhaust heat exchangers (EGR coolers).
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