1. Material Specification
Base Tube Standard: ASTM A179 specifies seamless cold-drawn low-carbon steel tubes, designed for heat exchangers and condensers in medium-low temperature and high-pressure environments.
Chemical Composition (precise ranges and functions):
| Grade | C | M | P | S |
| A179 | 0.06–0.18 | 0.27–0.63 | Max0.035 | Max0.035 |
2. Mechanical Properties:
- Tensile Strength: ≥325 MPa
- Ensures resistance to fracture under high pressure.
- Yield Strength: ≥180 MPa
- Reflects load-bearing capacity before plastic deformation.
- Elongation: ≥35% (50mm gauge length)
- High elongation indicates ductility, suitable for cold-working processes (e.g., fin extrusion).
3. Manufacturing Process:
- Cold Drawing: Refines grain structure, improves surface finish, and ensures dimensional accuracy.
- Heat Treatment: Annealing may be applied to relieve stress, but ASTM A179 tubes are typically delivered in the "as-drawn" condition.
4. Extruded Fin Manufacturing Process
- Tube Pre-Treatment: Surface cleaning (pickling or sandblasting) to remove oxides and contaminants, ensuring fin formation quality.
- Die Design: Die Material: Tungsten carbide (high wear resistance). Die Structure: Spiral groove design to control fin height (H), pitch, and thickness.
- Extrusion: Mechanical Extrusion: The base tube is forced through rotating dies, integrally forming helical fins without welding or bonding. Cold Work Hardening: Fin regions undergo lattice distortion, increasing hardness (HV +20–30%) and fatigue resistance.
- Post-Processing: Dimensional calibration (fin height/pitch tolerance: ±0.1mm). Surface treatments: Optional galvanizing, aluminizing, or anti-corrosion coatings (e.g., epoxy).
5. Process Advantages
- Seamless Integration: Fins and base tube are monolithic, eliminating interfacial corrosion risks.
- High Thermal Conductivity: No contact thermal resistance (superior to welded or wrapped fins).
- Adjustable Fin Density: 5–11 FPI (fins per inch) balances heat transfer and pressure drop.
6. Applications
- Power Generation: Boiler economizers, air preheaters (APH), condensers.
- Petrochemical & Refining: Hydrocracker feed/effluent exchangers, crude oil preheaters.
- HVAC & Refrigeration: Industrial chiller condensers, heat pump evaporators/condensers.
- Renewable Energy: Biomass boiler flue gas heat recovery, geothermal heat exchangers.
