Brazing Aluminium and Copper

Brazing aluminium to copper is common in the refrigeration industry where copper tubes are brazed to aluminium roll-bond panels or tubes. To join aluminium and copper using brazing technology and standard NOCOLOK® Flux, flame brazing would be applicable (as well as using a low-melting flux with a low-melting filler metal). It is very similar to brazing aluminium to aluminium, but some precautions are necessary.

However, when copper is brazed to aluminium and the heating process takes too long, the copper will diffuse into the aluminium at the joints. A low melting Al-Cu alloy (Al-Cu33 eutectic temperature 548°C) is thus formatted, and this could lead to erosion by perforation.

Therefore, during the brazing process, the flame should never be directly applied to the joint, because the heat should be transferred by conduction through the parts to be brazed. As soon as the filler metal begins to melt, the flame must be quickly removed.

A second issue with brazing copper to aluminium is that the aluminium has a much lower melting point than copper (Al: app. 650°C; and Cu: above 1000°C). Therefore, the flame is usually directed on the copper. Nevertheless, once the heat transferred from the copper to the aluminium reaches the melting range of aluminium, it will start to burn down very fast, while the copper is still taking the heat. The formation of the above mentioned low melting Al-Cu alloy accelerates the destruction of the aluminium components.

Consequently, flame Brazing of aluminium to copper is a delicate process and requires some experience. But it is used by many companies for large scale production. But it is next to impossible in furnace brazing. There are no conventional furnace designs which will cool quickly enough to halt the continual formation of the aluminium-copper eutectic. For this reason, brazing copper to aluminium in a furnace is not practiced.

There are three different ways to provide (or generate) filler metal in flame brazing of aluminium to copper.

  • Use of Al-Si filler alloy (Al-Si 12 – AA4047). Standard procedure like in flame brazing of aluminium to aluminium – just a little bit faster to avoid burn-through.
  • Rely on the formation of Al-Cu alloy during the brazing cycle. If this method is used, a support provided by a thin Stainless Steel tube along the interior joint area can provide additional structural integrity.
  • A pre-heated copper tube is inserted very fast into an aluminium tube. The mechanical energy released will generate additional heat. Abrasion of surface oxide by the inserted tube promotes the formation of Al-Cu filler alloy. This process works with and without flux (however, results are better with flux).
26 Kommentare
  1. Sudhir sharma
    Sudhir sharma sagte:


    we want to make joint between two Al tubes of dia 6.35 mm OD ant 0.5 thickness and second tube 2 mm od

    Pls suggest suitable brazing rod for thesame.

  2. Derek Davies
    Derek Davies sagte:

    The first you need to do is form a capillary joint between the two tubes by crimping down the 6.35 tube to the 2mm tube. Parts should be clean and heated uniformly. Most common Brazing rod would 4047 and flux would be non-corrosive applied as a flux paste or combined with alloy in the form of fluxed cored rod. Brazed paste (alloy and flux) may also be used but joint design may not be suitable.
    Zn/Al alloys are also availble used with a different type of non-corrosive flux and again can be used with flux paste or flux cored options.
    Final selction depends on specific application details

  3. Ganesh Naik
    Ganesh Naik sagte:

    We want to make joints ( Lap & Butt) between Al to copper , Al to brass strips of thicness 3.5 mm & width 12mm. Pl.suggest the filler metal, brazing rods for the same.& availability of the material in India.

  4. Derek Davies
    Derek Davies sagte:

    Zn/Al 78/22 alloy and cesium flux is the combination used to braze Al to Cu and Al to brass. Al to Cu is most common but Al to brass can be done but tensile strength not very high, but maybe enough depending on application. Difference of mass is important make sure joint is brought to temp evenly before applying wire.
    Chemical composition of brass can impact on results, lead and sulfur are both coming to surface during heating and will effect action of the flux so wettability is not so good.
    I would recomend you first have a go with some seperate pieces of material simulating joint dimensions and masses and check the joint quality.

  5. Saurabh Bhandari
    Saurabh Bhandari sagte:

    We want to make pipe joints between Al to copper through brazing with tube dia
    Al Tube Dia 9.5 with Cu tube Dia 9.5
    Al Tube Dia 12.5 with Cu tube Dia 12.5.
    plz.suggest the filler metal, brazing rods for the same.& availability of the material in India

  6. Derek Davies
    Derek Davies sagte:

    Flame brazing with Zn/Al filler metals and Cesium flux is currently the most popular method to join Copper and Aluminium. There are several different alloy flux combinations available and selection isdependant on application details such as joint design, heating method etc.

    If you forward your full contact details via my web site or e-mail on then I can forward details of suppliers in India.

  7. Jamie
    Jamie sagte:

    Thanks for posting this. I have been trying to read up on information about aluminum brazing, aluminum bonding and soldering so this was very useful. I am looking to join copper and aluminum so any help is always appreciated.

  8. Hans Swidersky
    Hans Swidersky sagte:

    For joining copper with aluminum, Al/Si filler alloy /AA4047) and NOCOLOK® Flux is suitable. However, most companies use Zn/Al filler alloys (there are several alloy combinations commercially available – from 2 to 25% Al content). When Zn/Al filler alloy is used, the flux must be a low melting flux (i.e. Cs-Al-F flux as non-corrosive flux: CsAlF Complex). A low melting Zn/Al filler alloy with a low melting flux is often preferred, because the brazing window (i.e. the temperature between filler metal melting and melting of the base alloys is broader when compared to Al/Si filler alloy.
    In flame brazing applications, pastes are the most popular choice. There are also filler alloy rings available which are coated or filled with flux (i.e. flux coated – resp. flux cored rings and wires).
    Several companies are offering such products.

  9. vijay
    vijay sagte:


  10. Derek Davies
    Derek Davies sagte:

    As mentioned on the previous replies, the most common alloy choice for flame brazing copper to aluminium is the Zn/Al range 98/02, 85/15 and 78/22.
    Zn78/Al22 is increasingly becoming more popular due its melting range being simliar to the Cesium Complex flux.
    These materials are available in separate solid wire and flux pastes and also flux cored wire.
    As in all flame brazing applications it is important to heat the joint uniformly. This becomes more challenging as the diameter increases. For 25mm dia joint multiple gas/air flames would provide better heating and control than use of a single torch flame.
    Specific application details such as, joint design, joint length, accessibility for heating equipment etc also need to be considered when developing the process.
    Derek Davies

  11. Jimmy Zhou
    Jimmy Zhou sagte:

    Hello, I’m Jimmy.
    well, if you want to join Copper with Aluminium, i’d like to recommend AA4047 to brazing it. it’s a very stable product for joining Copper with Aluminium.
    for some special apply on joining Copper with Aluminium, our product AA4015 can do some special things on it, as it has the lower melting point and narrow melting temperature, easy to control brazing.

  12. P G Vinay
    P G Vinay sagte:

    I want to braze Aluminium to Aluminium, can you please suggest me the chemical composition of Alumiweld / Durafix / HTS-2000 rods so that my job will be done very easily,.

  13. kamal
    kamal sagte:

    we want to make joint between Al sheets to copper tubes

    Plz suggest suitable brazing rod or any solution for the same.

  14. Ms.Osmond
    Ms.Osmond sagte:

    Dear Mr Davies,
    I want to braze AA6061 alloy bar of (10 mm X 10 mm square bar with 80 mm length) and brass (with the same dimension as AA6061) .

    Please suggest suitable brazing rod and/or flux for these brazing process.

  15. Narayan
    Narayan sagte:

    Dear sir,

    Please let me know can we braze aluminium with mild steel or SS. We want to braze mild steel tube with al strip. Please let us know the procedure and supplier in india


  16. Ricardo Santiago
    Ricardo Santiago sagte:

    I’m working in a heat exchangers production line and we need to braze copper connectors at the end of an aluminium tube and i have some questions about this process:
    the tube were we will braze the connectors is not cladded, what kind of flux and filler is suitable to braze this pices?
    we are going to braze the heat exchangers in a CAB furnace, can we braze the copper in this process?
    if not, what kind of machine do you recommend for the brazing of the copper connectors?
    we are expecting a large production volume, 200 pieces per hour, so we need a easy and quick method to braze this pices.
    if you could help us with this i will appreciate your help a lot.

  17. Paul Knight
    Paul Knight sagte:

    Another option is to use a bimetal clad coupler. The aluminum and copper (or whatever two materials) are metullurgically bonded and then you can just braze the like materials.. which is easy. Through electron sharing, the roll bond is stronger than the aluminum. Not a solution for everything, but just letting people know of options. Most people don’t know dissimilar metal bonding exists.

  18. kirti
    kirti sagte:

    It’s never either or – both processes have their place, and indeed there is some narrow overlap. In general thought, I find this class of bickering a bit sterile.

  19. rakesh Kumar
    rakesh Kumar sagte:

    plz tell me how to reduce aluminium brazing defects like leakage after brazing less flow of material, or overheat parts due to temp

  20. Dharmik Patel
    Dharmik Patel sagte:

    Joining copper plate to aluminium plate using brazing or soldering without defects. Can you suggest solutions for these

  21. Md. Atik
    Md. Atik sagte:

    We found a lot of corrosion on Aluminum tube in Al-Copper brazing joint.
    What is the main root cause of these type of problem.
    My Whats app number : +8801558924896

    Can we develop these types of failure problem.


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  1. […] To join aluminium and copper using brazing technology and standard NOCOLOK® Flux, flame brazing would be applicable (as well as using a low-melting flux with a low-melting filler metal). It is very similar to brazing aluminium to aluminium, but some precautions are necessary. via […]

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