ASTM A213 T9 High-Frequency Welded Finned Tubes for Economizers
ASTM A213 T9 is a chromium-molybdenum alloy steel tube grade used for seamless boiler, superheater, and heat-exchanger service. In this product form, the T9 base tube is fitted with high-frequency welded fins to increase external surface area and improve gas-side heat transfer, making it a strong fit for economizer duty in high-temperature heat-recovery systems. ASTM A213 also defines typical tube supply sizes, chemical limits, mechanical requirements, and test expectations for this material family.
This product is commonly selected for boiler economizers, industrial boiler rear-end heat-recovery sections, waste heat recovery equipment, HRSG-related heat-transfer modules, and other high-temperature exchanger service where durable heat transfer and reliable tube strength are required. Because T9 is a Cr-Mo alloy grade with elevated high-temperature capability, it is especially suitable where flue-gas-side heat recovery and long service life are both priorities.
- High-temperature alloy base tube for demanding thermal service.
- High-frequency welded fins for efficient and stable fin attachment.
- Increased heat-transfer surface area for improved economizer performance.
- Suitable for continuous service in boiler and heat-recovery environments.
- Custom fin height, fin pitch, fin thickness, and bare-length design can be made to project requirements.
ASTM A213 requires each tube to be subjected to either a hydrostatic test or a nondestructive electric test, unless otherwise specified in the purchase order. The specification also includes tension testing, hardness testing, flattening tests, and flaring tests as part of tube qualification.
| Item | Typical ASTM A213 Supply Range |
|---|---|
| Base tube outside diameter | 1/8 in to 5 in (3.2 mm to 127 mm) |
| Minimum wall thickness | 0.015 in to 0.500 in (0.4 mm to 12.7 mm) |
| Length | Specific or random, by order |
| Other diameters | Can be furnished if they meet the other requirements of the specification |
Note: The size range above refers to the ASTM A213 base tube supply range; the finned-tube geometry is typically customized for each project.
| Element | Composition (%) |
|---|---|
| Carbon (C) | ≤ 0.15 |
| Manganese (Mn) | 0.30–0.60 |
| Phosphorus (P) | ≤ 0.025 |
| Sulfur (S) | ≤ 0.025 |
| Silicon (Si) | 0.25–1.00 |
| Chromium (Cr) | 8.00–10.00 |
| Molybdenum (Mo) | 0.90–1.10 |
UNS designation: K90941.
| Property | Requirement |
|---|---|
| Tensile strength, min. | 415 MPa (60 ksi) |
| Yield strength, min. | 205 MPa (30 ksi) |
| Elongation, min. | 30% |
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