1. Have a clean surface

2. Heat the joint evenly to brazing Temperature

3. Choose the right brazing alloy for the job

4. Select the appropriate means of removing the oxide skin from the faying surfaces of the joint

5. Use a capillary gap of the appropriate size

6. Apply the brazing alloy to the last part of the joint to reach brazing temperature.

15 replies
  1. Hans Swidersky
    Hans Swidersky says:

    Very good rules – however, I would suggest to prioritize as follows:
    0. Choose the right alloys suitable for your joining process
    1. Use a capillary gap of the appropriate size
    2. Select the appropriate means of removing the oxide skin from the faying surfaces of the joint
    3. Have a clean surface
    4. Choose the right brazing alloy (and flux – if applicable) for the job
    5. Apply an adequate quantity of brazing alloy to the last part of the joint to reach brazing temperature
    6. Heat the joint evenly to brazing Temperature

    Reply
  2. Ahsan Riaz
    Ahsan Riaz says:

    But in case of Nocolok Brazing, the seventh rule should be the right atmosphere (Oxygen and Moisture contents) and i think this rule would be among top 3.

    Reply
  3. Hans Swidersky
    Hans Swidersky says:

    Dear Mr. Riaz; You are correct for furnace brazing (controlled atmosphere brazing) with NOCOLOK®. Low oxygen (i.e. below 100ppm – better below 50ppm) and low humidity/moisture level (below minus 40°C) are essential.
    More or less, the above rules 1 to 6 apply for brazing in general – and specifically for flame brazing and induction brazing.

    Reply
  4. Ahsan Riaz
    Ahsan Riaz says:

    Can you plz tell me what is the maximum possible clearance, that can be flled with the help of CLAD during CAB with NOCOLOK.

    I am a learner, so please dont mind if i ask some silly questions 🙂

    Reply
  5. Hans Swidersky
    Hans Swidersky says:

    Gap Clearances:
    Requirements
    Joints to be metallurgically bonded must have intimate contact at some point along the joint. Adequate filler metal, but not an excessive amount, must be available to fill the joint. A common phrase to emphasize this point is that “filler metal can run, but it cannot jump”. This means that is necessary to have intimate contact between the two components to be joined and the filler metal at some point along the joint. This contact point is what initiates the capillary flow of the filler metal.
    A gap between the two components to be joined is necessary to 1) allow the molten flux to be drawn into and clean and dissolve the oxides and 2) allow the filler metal to be drawn in freely and evenly. The size of the gap determines the strength of the capillary pull. For NOCOLOK® Flux aluminium brazing, gap clearances of 0.10 mm to 0.15 mm are recommended for non-clad components (when the filler metal is fed externally – via filler metal wire). For clad components such as in a tube to header joint where the tube is clad, the clearance is provided by the thickness of the cladding layer and so intimate contact is recommended.
    Larger gap clearances reduce capillary action while smaller gaps may restrict filler metal flow causing discontinuities in the joint. Friction fits must be avoided with non-clad components.

    Reply
  6. Shyam Gopal
    Shyam Gopal says:

    Dear Mr.Hans,
    Greetings.
    Your inputs are very useful and we brazers hope to use this blog to share industry issues. I would like your comments on the percentage of clad on tube
    requirements. The standard is 10% but it seems many are scaling down to
    5%. Will this have any effect on the brazing joint and stability.
    With prices the major factor in cooling industry gauges are coming down and so are specs.
    best wishes
    shyam

    Reply
  7. Leszek Orman
    Leszek Orman says:

    To be accurate amount of filler alloy should be in fact expressed by clad thickness in microns not in percentages of the tube material thickness (for thinner material thinner clad layer is present for the same percentage). Also the optimal amount of clad will depend on the type of tube to header joint (pierced or cut), amount of clad on the header and finally on the base material both of the tubes and the header.
    Generaly I agrree that in many cases it is possible to cut down the amount of the filler alloy on the tube to 7,5 or even 5% but it can not be looked at as a rule and each individual case should be considered seperatly.

    Reply
  8. Amy
    Amy says:

    Dear Mr.Hans,
    Greetings.
    Your inputs are very useful and we brazers hope to use this blog to share industry issues. I would like your comments on the percentage of clad on tube
    requirements. The standard is 10% but it seems many are scaling down to
    5%. Will this have any effect on the brazing joint and stability.
    With prices the major factor in cooling industry gauges are coming down and so are specs.
    best wishes
    shyam

    Reply
  9. Amy
    Amy says:

    But in case of Nocolok Brazing, the seventh rule should be the right atmosphere (Oxygen and Moisture contents) and i think this rule would be among top 3.

    Reply
  10. Ahsan Riaz
    Ahsan Riaz says:

    A few months back we faced a problem related to Clad material.
    In one of our product we use 7% and 15% Cladded Aluminium sheet to produce Cap Headers, except these caps all other parts were getting brazed normally where as the caps were not getting brazed at all.

    We doubted that the supplier has sent us non-cladded material and ask him to send the Material Certificate, the certificate then sent to us showed the specifications as OK.

    Is there any method available for Checking Clad materials quantities by ourselves.

    Reply
  11. Hans Swidersky
    Hans Swidersky says:

    Atmosphere

    Yes – for controlled atmosphere brazing (furnace brazing) the atmosphere conditions are very important. The recommendations for aluminium brazing with non-corrosive fluxes is: oxygen level below 100 ppm (most CAB furnaces run at O2 levels below 50 ppm) – and moisture level (expressed as dew point) below -40°C. Other contaminants must also be avoided (e.g. oil/lubricant fumes, dust, metal fines, rust particles).

    “The six fundamental rules for successful brazing” refer to basic requirements – without specifying the brazing method – may it be flame, induction, or furnace brazing.

    Reply
  12. Leszek Orman
    Leszek Orman says:

    Clad material

    Thank you for inquiry.
    There are two basic methods you can check presence of filler alloy on the braze sheet.

    Pure qualitative method is to heat the sheet or end cup in this case with a gas flame burner. You should direct the flame on the surface on which you expect presence of clad. After relatively short time (30 sec to one minute) of heating with open flame you should see a flow of the clad on the surface without the basic material being molten.

    The second method which provides some quantitative data is to make a cross section of the braze sheet, prepare a metallographic sample and observe it under light microscope (magnification about 100 to 200 times). Filler alloy is clearly distinguishable and you can measure its thickness as well.

    I hope this will help you with answering your question

    Reply
  13. Ahsan Riaz
    Ahsan Riaz says:

    Dear Leszek Orman,
    Thank you very much for this help. We will also perform the quantitative inspection for measuring clad as taught by you very soon after acquiring lens upto 200 times(200x) magnification. Currently we have magnification capability upto 80x
    Very best regards,

    Ahsan Riaz

    Reply

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