ASTM A789 S32750 Super Duplex Seamless Tube - High-Strength Heat Exchanger Tubing for Severe Corrosive Service
Ladle Analysis per ASTM A789
| Element | Content (%) | Element | Content (%) |
|---|---|---|---|
| Carbon (C) | ≤ 0.030 | Nickel (Ni) | 6.0 - 8.0 |
| Manganese (Mn) | ≤ 1.20 | Chromium (Cr) | 24.0 - 26.0 |
| Phosphorus (P) | ≤ 0.035 | Molybdenum (Mo) | 3.0 - 5.0 |
| Sulfur (S) | ≤ 0.020 | Nitrogen (N) | 0.24 - 0.32 |
| Silicon (Si) | ≤ 0.80 | Copper (Cu) | ≤ 0.50 |
Balance: Iron (Fe)
Source: ASTM A789 / ASME SA789 specification
The elevated chromium, molybdenum, and nitrogen content drives the material's resistance to chloride-induced localized corrosion - a critical factor in heat exchanger tube bundle longevity.
| Property | Requirement (ASTM A789) |
|---|---|
| Tensile Strength, min | 800 MPa (116 ksi) |
| Yield Strength (0.2% offset), min | 550 MPa (80 ksi) |
| Elongation (in 2 in. or 50 mm), min | 15% |
| Hardness, max | 32 HRC / 300 HBW |
| Heat Treatment Temperature | 1025 - 1125°C (rapid cooling) |
| Size Range | OD Tolerance | Wall Thickness Tolerance |
|---|---|---|
| ≤ 12.7 mm OD | ± 0.13 mm | ± 15% (avg wall) |
| 12.7 < OD ≤ 38.1 mm | ± 0.13 mm | ± 10% (avg wall) |
| 38.1 < OD ≤ 88.9 mm | ± 0.25 mm | ± 10% (avg wall) |
| 88.9 < OD ≤ 139.7 mm | ± 0.38 mm | ± 10% (avg wall) |
Tolerances per ASTM A1016/A1016M
ASTM A789 specifies seamless or welded manufacturing with no filler metal added. For seamless S32750 tubing, the cold drawing process is standard, followed by solution annealing at 1025-1125°C with rapid water or air quenching to maintain the balanced dual-phase microstructure.
- Surface finish: Bright annealed (BA) condition is typical for heat exchanger service, ensuring clean, scale-free inner and outer surfaces
- Straightness: 0.030 in. per 3 ft. per ASTM A789 requirements
- 100% NDT: Each tube must be subjected to either a hydrostatic test or nondestructive electric (eddy current) testing
- Flattening test (for ductility assessment)
- Flange test (for tube end soundness)
- Hydrostatic or eddy current test (100%)
- PMI (Positive Material Identification) for alloy verification
Beyond bare tube supply, Yuhong Group provides fully integrated heat exchanger components:
| Component | Common Materials | Service |
|---|---|---|
| Tube Sheets | SA105, SA182 F51, F53 | Forged or rolled, drilled to tube pattern |
| Baffles | SA516 Gr.70, duplex grades | Segmental or disc-doughnut design |
| Channel Covers / Heads | SA105, SA350 LF2 | Forged carbon or low-temp service |
| U-Tubes | Same as straight tubes | Custom bend radii per TEMA requirements |
ASTM A789 S32750 seamless tubes are specified for heat transfer equipment in severe service environments:
- Shell-and-tube heat exchangers - seawater cooling, brine service, chemical plant reboilers
- Condensers and coolers - offshore platforms, desalination plants
- High-pressure feedwater heaters - combined-cycle power generation
- Air-cooled heat exchangers (ACHEs) - where tube-side corrosion is the limiting factor
- Subsea and topside oil & gas equipment - instrument tubing, hydraulic lines, chemical injection
Q1: Can ASTM A789 S32750 tubes be bent into U-tubes?
Yes, but the bend radius should be sized to maintain wall thickness ≥ the minimum specified wall, and stress relief after bending is generally not recommended for super duplex grades. Post-bend solution annealing is required if significant deformation occurs.
Q2: What is the maximum service temperature for S32750?
Prolonged exposure above 600°F (316°C) can lead to embrittlement from sigma phase precipitation. For heat exchanger service, design should keep metal temperatures below this threshold.
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