The Finned Steel Tube (also known as a finned tube, fin pipe, or extended surface tube) is a high-performance heat transfer component manufactured by attaching continuous metal fins—either solid or serrated—to the outer surface of a seamless or welded base tube. The fins dramatically increase the tube's external surface area, typically by 4 to 10 times compared to a bare (plain) tube, thereby significantly enhancing heat exchange efficiency between the tube wall and the surrounding fluid—most commonly air or flue gas. Among the various manufacturing methods available, high-frequency resistance welding (HFW) has emerged as the industry standard for producing finned tubes that combine strong metallurgical bonds with excellent thermal performance.
High-Frequency Welded (HFW) Manufacturing Process
High-frequency welded fin tubes are produced by helically wrapping a continuous fin strip (carbon steel, stainless steel, or alloy steel) around the base tube while applying a high-frequency electric current (typically 200–450 kHz) to the interface. The electrical resistance at the contact point generates intense localized heat, instantly bringing the metal to a molten state (1200–1400°C) without melting the filler material, while a forging pressure of 0.8–1.5 MPa is applied to achieve a continuous metallurgical bond.
The result is a fin-to-tube attachment with tensile strength approaching that of the base materials themselves, offering superior durability under thermal cycling and vibration.
Fin Profiles & Performance
HFW fin tubes are available in two primary fin types:
Solid (Flat) Fins: For general-purpose applications.
Serrated (Toothed) Fins: Create turbulence, breaking the boundary layer for an additional 35–45% increase in the heat transfer coefficient compared to standard solid fins.
The effective heat transfer area can be expanded to 4–10 times that of a plain tube, with thermal conductivity of approximately 15.1 W/(m·K) for stainless steel grades.
Material Grade & Chemical Composition Table
Base Tube Standard | Base Tube Grade | Fin Material Options | Fin Material Grade | Key Characteristics |
ASTM A179 | Seamless low-carbon steel | Carbon steel / Aluminum | Q235B / AL1060 | Most economical; suitable for general heat exchanger service up to 400°C |
ASTM A192 | Seamless carbon steel (high pressure) | Carbon steel / Stainless steel | Q235B / SS304 | High-pressure boiler applications |
ASTM A106 | Gr.B seamless carbon steel | Carbon steel / Stainless steel | Q235B / SS304/316 | High-temperature service; API 5L equivalent |
ASTM A213 | T11, T22, T91 (alloy Cr-Mo) | Alloy steel / Stainless steel | Matching grade / SS304/316 | Creep-resistant for 550-650°C service |
ASTM A213 | TP304, TP304L (stainless steel) | Stainless steel | SS304 / SS304L | Corrosion-resistant; food/pharma grade |
ASTM A213 | TP316, TP316L (stainless steel) | Stainless steel | SS316 / SS316L | Superior chloride resistance; marine/chemical applications |
EN 10216-2 | P235GH, P265GH, 16Mo3 | Carbon steel / Stainless steel | As required | European standard; CE-marked for PED |
GB 5310 | 20G, 15CrMoG, 12Cr1MoVG | Carbon steel / Alloy steel | As required | Chinese national standard for high-pressure boilers |
Mechanical & Thermal Performance Table
Parameter | Carbon Steel (A179) | Alloy Steel (T11/T22) | Stainless Steel (TP304/316L) |
Base Tube Tensile Strength (min) | 325 MPa | 415 – 585 MPa | 485 – 515 MPa |
Base Tube Yield Strength (min) | 180 MPa | 205 – 415 MPa | 170 – 205 MPa |
Base Tube Elongation (min) | 35% | 20 – 30% | 35 – 40% |
Max Continuous Operating Temperature | ~400°C | ~565°C (T22); ~650°C (T91) | ~750°C |
Thermal Conductivity | ~45 W/(m·K) | ~35 – 40 W/(m·K) | ~15 – 16 W/(m·K) |
Heat Transfer Coefficient (HFW solid fin) | 250 – 350 W/m²·K | 250 – 350 W/m²·K | 250 – 350 W/m²·K |
Heat Transfer Coefficient (HFW serrated fin) | 380 – 500 W/m²·K | 380 – 500 W/m²·K | 380 – 500 W/m²·K |
Thermal Efficiency Improvement | 25 – 45% over solid fin | 25 – 45% over solid fin | 25 – 45% over solid fin |
Types of Finned Tubes
Core Products:
HFW Spiral Finned Tube — Continuous fin strip helically welded to the base tube. The most widely used type for boilers, economizers, and air preheaters.
Serrated Finned Tube — Serrated fin edges create turbulence and break the boundary layer, delivering a 35–45% higher heat transfer coefficient than solid fins.
Longitudinal Finned Tube — Fins run parallel to the tube axis. Low fluid resistance, suitable for air coolers and low-pressure-drop applications.
Extruded Finned Tube — Fins cold-extruded directly from the base tube wall. Zero contact resistance, maximum reliability for condensers and coolers.
U-Bend Finned Tube Bundle — Finned tubes bent into U-shapes and assembled into bundles for easy installation and maintenance in shell-and-tube exchangers.
Additional Capabilities (Available Upon Request):
Embedded (G-Fin) Finned Tube — for high-temperature air coolers where tube wall thinning from welding is not acceptable.
L / LL / KL Wound Finned Tube — cost-effective option for stable-temperature air coolers and dry cooling towers.
Studded Tube — for highly fouling or abrasive flue gas environments.
Inner Finned Tube — for enhancing internal fluid heat transfer in compact exchangers.
Custom fin profiles and alternative manufacturing methods are available. Please contact us with your technical drawings.
Applications
Our finned steel tubes are widely utilized in demanding thermal engineering environments, including:
1) Power Generation: Boiler Economizer, Air Preheater
2) Petrochemical: Heat Exchanger, Fired Heater
3) HVAC: Condenser, Air Cooler
4) Energy Recovery: Waste Heat Recovery, HRSG
