TIG Welding Thin Aluminum lap joints

this video gives a few tips for tig welding thin aluminum lap joints.

The main tip is to make sure to tack weld it up without any gaps.

another tip is to try to make the tack welds as small as possible so that they are not obvious when you weld over them.

things go bad quickly on thin aluminum lap joints with gaps.

So, however many clamps it takes or  tack welds it takes to not have gaps, thats how many you should use.

I try to make my tack welds as small as possible...or at least smaller than the final weld but since aluminum tack welds tend to crack, sometimes you just have to live with bigger tack welds than you would prefer.

Ideally, a 1/16" electrode might be used for this lap joint but I dont like switching out electrodes often unless I really need to...so I just used a 3/32 2% lanthanated electrode with a tapered point.

( in fact, I use a 3/32" 2% lanthanated electrode for about 99% of my tig welding)

the tapered point allows for a crisp start without a lot of arc wandering and works good on thin metal with low amp starts.

If I need to weld up around 200 amps on thicker aluminum, I will simple round the tip of the tungsten using the AC balance knob set to max cleaning.

I didnt mention AC frequency settings but I did use a higher than normal setting of around 200hz for this thin aluminum lap joint.

Using a higher ac frequency focusses the arc a bit and helps to keep the bead from getting too wide.

I used a #6 gas lens cup for this but I have also used a standard #5 collet body cup with good results.

tig welding thin aluminum lap joint

Settings for TIG Welding Thin Aluminum Lap joints

I used the CK worldwide mt200 for this video and I mention that because all tig welders are a bit different so my setting for AC balance might be different than other machines.

But just in case it helps, here are my settings:

  • AC balance was set to between 6 and 7
  • AC frequency was set to around 200hz because higher ac frequency settings help to constrict and focus the arc
  • Amperage was set to around 100 on the machine but I used a foot pedal and probably did no go over 80 amps
  • argon flow was 14-16 cfh with a #6 stubby gas lens cup on a ck 17 air cooled torch.
  • I used 1/16" 4043 filler metal and base metal is .063" 6061 t6
  • 5356 filler might have looked better and is commonly used on 6061 but both rods are actually commonly used on 6061 depending on anodizing requirements as well as service temperature of the piece welded.

One last thought on tig welding thin aluminum lap joints

Inverter tig welders with ac frequency settings set at 200hz seem to help a little bit.

But if you look at old aluminum lap joints on aircraft and other products some of the welds look amazing and are very small.

These welds were done back when there were no fancy settings.

Skill is the main thing...and those old timers deserve some real credit

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