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Thread: Thin Aluminum Lap Joint

  1. #1
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    Thin Aluminum Lap Joint

    I am welding a lap joint between two aluminum sheets, 2mm (top) and 1.5mm (bottom) and always end up with some degree of penetration through the 1.5mm sheet. I have read somewhere that for lap joints penetration is not necessary. I ask: If penetration occurs, is it wrong? Is it better? It's worse?

    Current 60-70A, 120Hz

    Thanks all.


    Outside:

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    Last edited by Dalzani Lima; 03-07-2018 at 02:31 PM.

  2. #2
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    Re: Thin Aluminum Lap Joint

    Additional detail would be helpful, pictures if possible. Full penetration is not always required, depends on many variables.
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    Re: Thin Aluminum Lap Joint

    Additional detail would be helpful, pictures if possible. Full penetration is not always required, depends on many variables.
    I edited my post and added images.

    Electrode (Blue) 1.6mm, filler rod 4043 also 1.6mm.
    Aluminum sheets 5052-H32.

    Thanks.
    Last edited by Dalzani Lima; 03-07-2018 at 02:42 PM.

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    Re: Thin Aluminum Lap Joint

    Nothing wrong with some melt thru provided there is no suck back. You are right that penetration is not needed. Best case would be none, as the extra heat can distort the weldment, and soften the temper more in the sheet surrounding.

    5356 is a more stable filler for your welding. Whether it is the proper filler for the finish is another question. In your case I would choose 5356 every time for ease of weld. Also I would up your freq to constrict the arc more to prevent the top piece from melting back as much, and personally I like bigger tungsten and point it sharp.
    Last edited by shovelon; 03-07-2018 at 04:43 PM.
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    Re: Thin Aluminum Lap Joint

    Quote Originally Posted by shovelon View Post
    Nothing wrong with some melt thru provided there is no suck back. You are right that penetration is not needed. Best case would be none, as the extra heat can distort the weldment, and soften the temper more in the sheet surrounding.

    5356 is a more stable filler for your welding. Whether it is the proper filler for the finish is another question. In your case I would choose 5356 every time for ease of weld. Also I would up your freq to constrict the arc more to prevent the top piece from melting back as much, and personally I like bigger tungsten and point it sharp.
    Before they were two 1.5mm plates and 50A were enough and there was no melt thru. Now with the top plate of 2mm if using 50A the puddle does not seem to be fluid enough then added 10A, but always results in a slight melt thru.

    If there is no structural problem, weakening the weld or material I am satisfied.

    Thank you!

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    Re: Thin Aluminum Lap Joint

    If you are on 120 Hz and not quite happy with what it's doing, Try 180 hz. It can make a pretty big difference in how deep the heat goes.

    I use 240 Hz on 16 gauge butt welds, seems to penetrate but not build melt through boogers like my normal 100-120 Hz setup for thicker material does.

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    Re: Thin Aluminum Lap Joint

    Quote Originally Posted by Chad86tsi View Post
    If you are on 120 Hz and not quite happy with what it's doing, Try 180 hz. It can make a pretty big difference in how deep the heat goes.

    I use 240 Hz on 16 gauge butt welds, seems to penetrate but not build melt through boogers like my normal 100-120 Hz setup for thicker material does.
    The reason I use 120Hz is that it seems less unpleasant to the ears and improves the stability of the arc (very welcome in certain cases). But ok I'll try with 180Hz and see how it goes.

    Thanks.

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    Re: Thin Aluminum Lap Joint

    Quote Originally Posted by Dalzani Lima View Post
    The reason I use 120Hz is that it seems less unpleasant to the ears and improves the stability of the arc (very welcome in certain cases). But ok I'll try with 180Hz and see how it goes.

    Thanks.
    Agree with the noise irritation, but the arc will be more focused and a bit chilled to hold the puddle in place. Can you change your waveform? Once you find the magic formula, write it down for future reference.

    Otherwise your degree of penetration should not compromise the structural properties too much. And personally I would use 3/32" filler to also chill the puddle as when you cram sucks out heat. Have you tried 4943?
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: Thin Aluminum Lap Joint

    Quote Originally Posted by shovelon View Post
    Agree with the noise irritation, but the arc will be more focused and a bit chilled to hold the puddle in place. Can you change your waveform? Once you find the magic formula, write it down for future reference.

    Otherwise your degree of penetration should not compromise the structural properties too much. And personally I would use 3/32" filler to also chill the puddle as when you cram sucks out heat. Have you tried 4943?
    I tried with 180Hz. I realized that there is apparently a loss of energy and so I slowed down to compensate. Unfortunately the final result was not very different or even the same. I'm using the 4043 1.6mm. Anyway, my concern is only relative to integrity of the solder / material. If they do not get weaker, I do not care because the side (inside the box) that occurs penetration is subsequently covered not impacting on the visual aspect.

    One thing I realize is that in but-joint I can "push" the puddle using the torch before adding more material resulting in a nice finish. In the lap-joint however, the torch has small pushing effect leaving behind a significant part of the deposited material. At this point I add more material or I will melt the edge of the top sheet. With less amperage this effect becomes even more pronounced.

    I added two photos of the test with 180Hz. My machine has only square wave.

    Thanks.

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  10. #10
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    Thin Aluminum Lap Joint

    I run a foot pedal max amperage for that thickness of about 140 myself. 1/8 blue tungsten with 3/32+ filler 4043.

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    Re: Thin Aluminum Lap Joint

    Quote Originally Posted by Dalzani Lima View Post
    I tried with 180Hz. I realized that there is apparently a loss of energy and so I slowed down to compensate. Unfortunately the final result was not very different or even the same. I'm using the 4043 1.6mm. Anyway, my concern is only relative to integrity of the solder / material. If they do not get weaker, I do not care because the side (inside the box) that occurs penetration is subsequently covered not impacting on the visual aspect.

    One thing I realize is that in but-joint I can "push" the puddle using the torch before adding more material resulting in a nice finish. In the lap-joint however, the torch has small pushing effect leaving behind a significant part of the deposited material. At this point I add more material or I will melt the edge of the top sheet. With less amperage this effect becomes even more pronounced.

    I added two photos of the test with 180Hz. My machine has only square wave.

    Thanks.

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    You weakness will probably come from the filler metal. 4043 is dependent on base metal dilution for strength that will match the base. Not so with 4943 or 5356 which is the best for 5052. Otherwise your work looks good to me. Again 5356 is easier to weld with as it does not flow and wander on you. A little research will find that 5052 marine fuel tanks most likely fail at the weld when using 4043 due to the concussive loads and vibration. The high strength of the 5356 overcomes that provided the weldor knows what he or she is doing.
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: Thin Aluminum Lap Joint

    Quote Originally Posted by shovelon View Post
    You weakness will probably come from the filler metal. 4043 is dependent on base metal dilution for strength that will match the base. Not so with 4943 or 5356 which is the best for 5052. Otherwise your work looks good to me. Again 5356 is easier to weld with as it does not flow and wander on you. A little research will find that 5052 marine fuel tanks most likely fail at the weld when using 4043 due to the concussive loads and vibration. The high strength of the 5356 overcomes that provided the weldor knows what he or she is doing.
    Interesting your comment on the 4043. The filler rod 5356 is not easily found in my region unlike the 4043 which is quite popular. I'll try to find a supplier and buy a box of these to test. Thank you very much.

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    Re: Thin Aluminum Lap Joint

    Quote Originally Posted by Dalzani Lima View Post
    Interesting your comment on the 4043. The filler rod 5356 is not easily found in my region unlike the 4043 which is quite popular. I'll try to find a supplier and buy a box of these to test. Thank you very much.
    I prefer 5356 in all cases with 4943 being the second. I only bring in 4043 if the customer specifies it. Then it is a pain to get rid of. I actually prefer 5356 when welding soda cans, as it stays put and contains the arc in the puddle letting me decide how to push the puddle.
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: Thin Aluminum Lap Joint

    shovelon, you da man!
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    Re: Thin Aluminum Lap Joint

    Yeah,

    When Shovelon/Terry is giving TIG welding pointers, that's when I'm paying attention too!

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    Re: Thin Aluminum Lap Joint

    I prefer 5356 in all cases with 4943 being the second. I only bring in 4043 if the customer specifies it. Then it is a pain to get rid of. I actually prefer 5356 when welding soda cans, as it stays put and contains the arc in the puddle letting me decide how to push the puddle.
    Filler rods 5356 arrived. I welded one of the boxes to see what the overlap would look like.

    I noticed:

    In order to have the same control of the puddle, I increased the amperage a little (compared to the 4043), it resulted that the penetration increased slightly. I also noticed that the weld bead is not as bright as with 4043.

    I also welded some butt-joints and, in this case, except for the brightness, I did not notice any significant difference.

    As I'm not worried about the aesthetics of welding (more or less bright), but with a good execution, I ask if what I said above would be what was expected, since I'm a beginner with 8 or 9 months of experience.

    Thanks.

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    Re: Thin Aluminum Lap Joint

    Wow! Not bad work for such little experience.

    The 5356 filler is not only stronger but wets out less, therefore for me I have a more controllable weld. That is one reason I use 5356 on soda cans. But if you like the other by all means keep using it. For me I put in a lot of heat and the 5356 looks better.

    4043 and 4047 were both formulated as brazing fillers, so they wet out, but pushing it forward is tough for me. I like to cram the rod in for better definition and throat.
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: Thin Aluminum Lap Joint

    Quote Originally Posted by C. Livingstone View Post
    Yeah,

    When Shovelon/Terry is giving TIG welding pointers, that's when I'm paying attention too!
    Yeah, I'll Vouch for this, Terry is a TIG God and hella nice guy on top of that too.
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    Re: Thin Aluminum Lap Joint

    Quote Originally Posted by soutthpaw View Post
    Yeah, I'll Vouch for this, Terry is a TIG God and hella nice guy on top of that too.
    Hey thanks DJ!
    Weld like a "WELDOR", not a wel-"DERR"
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