Dimensions
Width and height tolerances are usually tighter than general ASTM B221 / EN 755 tables and are agreed on the drawing, often within a few hundredths of a millimetre on height. Flatness and twist are checked on every coil.
Automotive heat-exchanger tube
1100 and 1200 H112 Automotive Flat Aluminium Tube
1100 and 1200 flat tube is a thin, multi-port extruded aluminium tube (often called microchannel or MPE tube) made from commercially pure aluminium in the as-extruded H112 temper. It is the heat-transfer element of brazed automotive condensers, radiators, oil coolers and battery cooling plates. Metline supplies coiled or cut-length flat tube, bare, zinc-sprayed or pre-fluxed, to heat-exchanger makers worldwide.
- Alloys
- 1100, 1200 (also 3102, 3003)
- Temper
- H112 (as extruded)
- Section
- Width 6 – 40 mm, height 0.8 – 8 mm
- Coatings
- Bare, zinc arc spray, flux roll coat
What is automotive flat aluminium tube?
A flat (microchannel) tube is a wide, thin extrusion divided internally by webs into a row of small parallel channels, typically between 2 and 35 ports. Refrigerant or coolant flows through the ports while air passes over brazed fins on the flat faces. The many small channels give a very large internal wetted surface in a small envelope, which is why flat tube has replaced round copper tube in almost every modern vehicle condenser.
Commercially pure alloys 1100 and 1200 are the classic choice for flat tube because they extrude through the very complex port dies at high speed, have thermal conductivity above 210 W/m·K and braze reliably in controlled-atmosphere (CAB) furnaces at about 600 °C. Their strength is low, but the small port sizes mean the walls carry refrigerant pressure through geometry rather than material strength.
Tube is extruded continuously, sized, optionally coated with zinc or brazing flux in line, and wound into coils. The heat-exchanger maker straightens and cuts the coil to length, assembles the tubes with louvred fins and headers, and brazes the whole core in one furnace pass.
1100 and 1200 chemical composition (wt %)
Both alloys are registered with the Aluminum Association and appear in EN 573-3 as EN AW-1100 (Al99,0Cu) and EN AW-1200 (Al99,0). The difference is copper: 1100 contains a deliberate copper addition, while 1200 limits copper to a trace. The certificate for each coil reports the actual analysis.
| Element | 1100 | 1200 | Comment |
|---|---|---|---|
| Si + Fe | 0.95 max | 1.00 max | Main impurities; lower levels help extrusion and corrosion |
| Copper (Cu) | 0.05 – 0.20 | 0.05 max | Cu raises the tube's corrosion potential slightly (more noble) |
| Manganese (Mn) | 0.05 max | 0.05 max | |
| Zinc (Zn) | 0.10 max | 0.10 max | Zinc from surface spraying diffuses in during brazing |
| Titanium (Ti) | — | 0.05 max | |
| Others, each / total | 0.05 / 0.15 | 0.05 / 0.15 | |
| Aluminium (Al) | 99.00 min | 99.00 min |
Because copper makes 1100 slightly more noble than 1200, some designers prefer 1100 tube with zinc-coated surfaces or zinc-bearing fins, so the fins and surface layer corrode sacrificially and protect the tube core.
Mechanical and physical properties
Flat tube is used in the H112 temper: as extruded, with no deliberate cold work or annealing. After brazing, the tube is effectively annealed, so heat-exchanger design should use O-temper properties for the finished core.
| Condition | Tensile strength | Yield strength (0.2 %) | Elongation |
|---|---|---|---|
| 1100 / 1200-H112, specified minimum (extruded) | 75 MPa / 11 ksi | 20 MPa / 3 ksi | — |
| 1100-O, typical (post-braze reference) | 90 MPa / 13 ksi | 34 MPa / 5 ksi | 35 – 45 % |
Physical properties (1100 / 1200)
- Density
- 2.71 g/cm³
- Melting range
- about 643 – 657 °C, well above CAB brazing temperature
- Thermal conductivity
- about 220 – 230 W/m·K
- Electrical conductivity
- about 57 – 59 % IACS
- Coefficient of thermal expansion
- 23.6 µm/m·°C (20 – 100 °C)
Flat tube dimensions and surface coatings
Typical supply range
- Width
- About 6 – 40 mm; common condenser widths 12 – 32 mm
- Height (thickness)
- About 0.8 – 8 mm; condenser tube usually 1.3 – 2 mm
- Wall and web thickness
- From about 0.12 mm webs; outer wall set by pressure rating
- Number of ports
- 2 – 35, round, rectangular or star-shaped
- Form
- Coils for in-line cutting, or straight cut lengths
- Alloys
- 1100, 1200; 3102 and 3003 for higher strength or corrosion life
Every port design is drawing-specific. Send the cross-section drawing with port geometry and tolerances.
Coatings are chosen to match the brazing process and the corrosion life the vehicle maker expects:
| Surface option | What it does | Typical specification |
|---|---|---|
| Bare (mill finish) | Lowest cost; fins or clad headers supply the filler metal and flux is sprayed on the core before brazing | Clean, oil-free surface |
| Zinc arc spray | Thin zinc layer applied in line; during brazing it diffuses into the surface and creates a sacrificial zinc-rich layer that protects against pitting perforation | Zinc load commonly specified in the range of about 6 – 12 g/m² per face, with an agreed tolerance |
| Flux roll coating | Pre-applied brazing flux (sometimes with silicon or zinc powder) bonded with a binder, so the core needs little or no flux spraying | Coating load agreed with the brazer, typically a few g/m² up to about 14 g/m² |
Tolerances, cleanliness and test requirements
Heat-exchanger tube is judged on dimensional consistency, internal cleanliness and leak tightness rather than on strength alone. A tube that is 0.02 mm too thick will not fit the header slot; one with a blocked port will cut cooling capacity and may fail leak test.
Burst and leak
Tube is burst-tested to the pressure set by the customer for the refrigerant. CO2 (R744) systems run far higher pressures than R134a or R1234yf and need heavier walls or stronger 3xxx alloys.
Corrosion
Corrosion life is commonly proven by acidified salt spray tests such as SWAAT (ASTM G85 Annex A3) or neutral salt spray (ASTM B117), with the hours required set by the vehicle maker.
Coating checks
Zinc and flux loads are measured by weight per unit area; flux adhesion is checked by tape test.
Cleanliness
Ports must be free of extrusion debris and the surface free of oil that would stop flux wetting.
Traceability
Each coil is identified by alloy, lot and date and covered by a 3.1 certificate.
Where flat aluminium tube is used in vehicles
- Air-conditioning condensers: the largest use; parallel-flow condensers in front of the radiator
- Evaporators and gas coolers: including CO2 heat-pump systems in electric vehicles, with heavier wall designs
- Engine radiators and charge-air coolers: where flat tube or folded tube is brazed to fins and plastic or aluminium tanks
- Oil and transmission coolers: compact cores for engine oil, gearbox and power-steering fluid
- EV battery and power-electronics cooling: flat tubes or harp-style plates carrying coolant beneath cells and inverters
- Off-highway and HVAC: the same tube is used in truck, bus and residential heat exchangers
Older literature sometimes lists flat tube for brake lines. In practice brake pipes are round steel or copper-nickel tube; flat multi-port tube is a heat-transfer product.
1100 and 1200 compared with 3102 and 3003 flat tube
| Property | 1200 | 1100 | 3102 | 3003 |
|---|---|---|---|---|
| Alloy type | 99.0 % Al | 99.0 % Al + Cu | Al + low Mn | Al + 1.0 – 1.5 % Mn |
| Extrudability (thin webs) | Excellent | Excellent | Very good | Good |
| Strength after brazing | Lowest | Low | Moderate | Higher |
| Thermal conductivity | Highest | High | High | Lower (~160 – 190 W/m·K) |
| Typical use | Low-pressure coolers | Condensers with Zn spray | Mainstream condenser tube | Higher-pressure and thicker tube |
Many condenser programmes now specify 3102 or other low-manganese "long-life" alloys for better post-braze strength and corrosion behaviour. 1100 and 1200 remain the economical choice where pressures are modest and extrusion of very fine ports matters most.
How to order flat tube from Metline
- SpecifyAlloy (1100, 1200 or 3xxx), cross-section drawing with port geometry, coating type and load, coil weight or cut length, and annual volume.
- Confirm the standardYour drawing and test specification, with ASTM B221 or EN 755 as the general reference and the burst, leak and corrosion requirements of your programme.
- QuoteWe confirm availability, tolerances, certification and delivery terms (EXW, FOB, CIF or DAP) for your plant or port.
- Process and inspectCoils are dimensionally checked, coating loads measured and ends sealed to keep ports clean during transit.
- Document and shipEach lot ships with an EN 10204 3.1 mill test certificate, heat or lot traceability and a packing list, in seaworthy export packing. Third-party inspection can be arranged on request.
References and standards
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- EN 573-3 – Aluminium and aluminium alloys: chemical composition and form of wrought products
- ASTM G85 – Standard Practice for Modified Salt Spray (Fog) Testing (Annex A3, SWAAT)
- ASTM B117 – Standard Practice for Operating Salt Spray (Fog) Apparatus
- IATF 16949 – Quality management system requirements for automotive production and relevant service parts organisations
Automotive flat aluminium (aluminum) tube: frequently asked questions
What is the difference between 1100 and 1200 flat tube?
Both are 99.0 % aluminium. 1100 carries 0.05 – 0.20 % copper, which raises strength slightly and makes the tube a little more noble electrochemically; 1200 is essentially copper-free. Many designers pair 1100 tube with zinc spraying or zinc-bearing fins so that the outer layer corrodes sacrificially.
Why is flat tube zinc-sprayed?
During brazing the zinc diffuses into the tube surface and forms a zinc-rich layer that is anodic to the core. Corrosion then spreads sideways through that layer instead of pitting straight through the wall, which greatly delays leaks.
What temper is microchannel tube supplied in?
H112, the as-extruded condition. Brazing at about 600 °C anneals the tube anyway, so finished-core calculations use O-temper properties.
Can 1100 flat tube be used in CO2 (R744) systems?
Only with walls designed for the much higher pressures involved. Most CO2 gas coolers use 3xxx-series tube with heavier walls; the burst pressure on your drawing decides the choice.
How is flat tube supplied?
Usually in coils for in-line straightening and cutting, or as straight cut lengths. Port ends are sealed and coils are packed in moisture-protected cases.
Do you ship flat tube internationally?
Yes. Metline supplies flat tube worldwide from Mumbai with mill certificates, export packing and EXW, FOB, CIF or DAP terms.
Need flat tube for a condenser or cooler?
Send the cross-section drawing, alloy, coating and volume. Our team will reply with feasibility, certification and delivered pricing.
