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I am making an aluminum part with a sort of a built in pipeline where water runs to cool the system. To close and seal the "pipe" I would need a lot (at least 144!)screws and two very long (maybe 2m) oring seals. That feels like a recipe for disaster. So instead I would like to weld the cover. Is it doable? What should I think about?

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    $\begingroup$ A drawing would help a lot. $\endgroup$
    – Eric S
    Nov 1, 2021 at 1:00
  • $\begingroup$ How long is the pipeline and how much the temperature differential it is subjected to? $\endgroup$
    – r13
    Nov 1, 2021 at 1:14
  • $\begingroup$ Is this a one off part or something you want to mass manufacture? Its very possible you could employ friction stir welding. SpaceX uses this with their Booster tanks for high pressure and structural applications. As Eric said, a drawing would help a lot. $\endgroup$ Nov 1, 2021 at 2:04
  • $\begingroup$ @r13 about 1m length, bent as a maze. Sorry, can't show the picture yet. The temperature should be in range of 10-20 degrees. $\endgroup$
    – TQQQ
    Nov 1, 2021 at 2:40
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    $\begingroup$ No, i can barely hold a screwdriver :) but I only design the thing $\endgroup$
    – TQQQ
    Nov 1, 2021 at 5:26

1 Answer 1

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An option available to you along with welding is a product known as aluminum brazing rod.

When aluminum is heated to melting point, an oxide forms which prevents bonding. In a welding environment, a flux or enclosing gas is used to prevent the oxide. The aluminum brazing rod works in a different manner, by reacting with the aluminum and forming a different compound which does not oxidize in the same manner.

I've used this product to braze two 25 mm square tubes mitered at a corner. It is fairly easy to use and surprisingly strong. The rod also flows well into the joint. One must necessarily clean thoroughly the area to be bonded, but that's good practice with all joining technology.

I suspect that you would use a large number of these rods as they are consumed quickly. I used four rods to complete the above noted joint, which had an effective perimeter of 100 mm. Perhaps some of the flowing metal entered the tubing and dripped away, but what remained sealed nicely the angle.

An internet search shows many retailers provide the product, as well as the usual online sources. Prices vary from two rods for five dollars (US) to seven for US$18 (not much better).

aluminum brazing rods

Photo from Northern Tool web listing.

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  • $\begingroup$ Wow, this is a great advice. After watching a few videos, I think this is what I should do. Although, I think i need a more controlled environment, not a propane torch, rather a thermostat - controlled electric heater and perhaps a simple x-y machine to move and appl the rod $\endgroup$
    – TQQQ
    Nov 1, 2021 at 14:45
  • $\begingroup$ That sounds rather complex a process for a product designed to be used in hand. Of course, if you can get the surface to melt and the machine is able to scratch the surface to start the alloying process, you'll have quite an impressive device. $\endgroup$
    – fred_dot_u
    Nov 1, 2021 at 17:14
  • $\begingroup$ @TQQQ Keep in mind for the 'Heat Affected Zone' which will anneal your aluminum. This applies to all forms of welding, but its something you should keep in mind if your structure is load bearing. $\endgroup$ Nov 1, 2021 at 17:39
  • $\begingroup$ It is aluminum /zinc brazing metal (nothing to do with copper/bronze). Not welding, but it will stick the aluminum together. You may be able to do it with an electric soldering iron. I suggest seriously considering epoxy . $\endgroup$ Nov 1, 2021 at 18:48
  • $\begingroup$ @blacksmith37 I am a bit skeptical about epoxy- for it to stay in place I would need a mold or something, which seems too complicated with the shape I have. The melted metal should simply fill the gap, i see this effect a lot when soldering electronics. So it will stay in place due to surface tension and capillary effect, then cool down. Shouldn't take much time either. $\endgroup$
    – TQQQ
    Nov 1, 2021 at 23:05

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