How to Braze Aluminum to Copper

How to Braze Aluminum to Copper


Hello! Lucas-Milhaupt brings you more
than 70 years of experience brazing metals. Today, we are seeing manufacturers in the
HVAC and Refrigeration industries using more all-aluminum components. With
this comes the need to join aluminum components to copper. The difference in these base materials
properties, such as melt temperatures, can make joining more difficult. Today, we will discuss alloy options, and
the proper procedures for joining copper to aluminum. Lucas-Milhaupt offers three alloy options
for joining aluminum to copper. All these are part of our Handy One, flux-cored
brazing line. Handy One consists of a filler metal in strip form that is rolled around
a powdered flux. Al 802 has a low melting temperature
and is free flowing. This alloy is preferred for joining single copper-to-aluminum
transition joints. Al 822 has a moderate melting
temperature and is commonly used for repair. It can be used for joining copper-
to-aluminum joints with larger gaps. Al 718 has a higher melting temperature,
with the best joint quality and good leak tightness. It may be used when high
production quantities and tighter process control can be achieved. The advantages of using Handy One are: First, no separate flux is required. Second, you achieve consistent alloy-
and-flux application, and Third, our non-corrosive fluxes require no
clean up. An example of an all-aluminum component
often requiring a transition joint would be an evaporator coil. Other copper to
aluminum joints may include line sets and other transition joints. Lets walk through the steps of producing a
transition joint. Please note that a joint gap of three-
thousandths to six-thousandths (.003- .006) of an inch, or .0762 to .1524
millimeters, is preferred. First, clean both copper and aluminum
materials to remove any dirt, oil, or other potential contamination. Then, mechanically roughen the outer
and inner diameter surfaces. Next, heat the joint area. We are using a methane/ oxygen flame.
However, air/acetylene, with a proper tip, or any fuel gas that can uniformly heat the
assembly, would also be suitable. A reducing flame is recommended. The flame should be soft enough and
large enough to envelop the joint. Heat should be applied starting at the
joint line and working up, down, and around both base materials. Your joint orientation having copper on
inside or outside may change depending upon the components, and this may affect
heating. Please note that a color change will be
seen in copper, but not aluminum. Take care not to overheat or melt the
aluminum. Depending on the grade of the aluminum base metal, this can happen
between 1100 and 1200 degrees Fahrenheit. Step three is to apply the Handy One
alloy to the joint surface to test temperature. If the alloy and flux begins
to melt and flow, the assembly is at proper brazing temperature. Next, focus heat to the outside tube to
draw the alloy into the interface of the joint. Minimize time and temperature.
Overheating can cause erosion and melting of the assembly. Allow the alloy to solidify and cool prior
to moving the assembly. Finally, inspect your joint for any gaps or
voids. No post-joining clean-up is required. To summarize, when joining aluminum to
copper, choose your alloy based on temperature and production
requirements. Ensure that the joint gaps are maintained
properly as mentioned beforehand. To braze, clean your materials and
prepare the surfaces. Then, heat the joint area starting at the
joint line. Apply the Handy One alloy and Continue heating to draw the alloy. Finally, cool, and inspect the finished
joint. For more information, please visit our
website, or contact your Lucas-Milhaupt representative. Thank you!

14 Comments

  1. So what would happen do the joint over time if this copper/aluminum joint was used in an electrical application?

  2. Hello. This is Hai from HYIMEX.,JSC. We would like to buy Al802? How can we buy it? Pls tell me. Thank in advance

  3. Hello

    I cannot find the product on the given link in the bio. Please send me another link for the purchase of the Al 802 welding rods

  4. Pl don't make aluminum Evaporator coil it's really hard to fix in field .
    In the Lab very easy but real situation wind, water, so fast heat transfer etc …
    Inside coil pin hole How do you fix it .

  5. Split AC के outdoor unit के aluminium condenser pipe और coper paip के जोड़ के लीकेज को ,बिना गैस निकाले और बिना bilding के, किस प्रकार जोड़े की , वहाँ पर का गैस लीकेज हमेशा के लिये बन्द हो जाये ।

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