Tacking 0.040 plates on outside corners.

By Lawrence (*****)

Date 07-09-2003 20:52

A couple of things will help

On an outside corner joint and GTA

a good inside heatsink, copper is best but even a tightly clamped piece of angle iron inside will help

a perfect *touching* fitup is important.

50 amps sounds kinda high. go down to 30, Further, this is where learning to use the foot pedal is important

a pointed tungsten

Increase your argon flow to 20 cfh. (this is probably why your filler looks like chewed gum) 12 may be barely sufficient on an inside corner but not outside

If your plate is 6061 don't get too caught up in an effort to produce super-small tacks.. this alloy requires some filler metal or those small tacks will crack. You can always blend off the excess buildup as you go until you have mastered your process.

By welder_guy2001 (***)

Date 07-10-2003 02:28

something else you could try that might work better for a corner is bend a tab on one of the sheets. just measure 1/4" - 1/2" and bend it to a 90 degree angle, then put the other sheet on the inside of the bent corner you just made. then you don't have to mess around with a corner joint and all you have to weld is a much easier lap joint. and clamp the whole joint to a piece of copper or 1/4" aluminum, or a steel angle iron so you don't burn through.

By ssbn727 (*****)

Date 07-12-2003 08:36

This is a neat trick if you are'nt following a blueprint,code or WPS, and the customer or the company you're working for does'nt mind.
However, you might want to check with either the customer or your place of employment before simply using this kind of technique because, if you have to follow a drawing detail that does'nt specify this technique then, you may be causing more harm than good.
The base metal properties change when bending the tabs, such as grains being "stretched" in the area of the metal that's bent.
This could cause a different result in the area adjacent to the weld enough to actually weaken the base material. This is just one example so, the best suggestion would be to check with the person responsible for quality assurance or welding engineer if you work for a company before you try this technique.
The same goes if you are self-employed, and are producing these joints for a customer because, if the customer does'nt approve of this method of tacking the joints together, You will have a PROBLEM...

Lawrence seems to have good suggestions so, I'll only add that it is very important to make sure that the base metal surface, filler metal, and tungsten be clean!!!
If your arc is "wandering" , and changing it's color then either the base metal, filler metal, or the tungsten may be contaminated. Also, you want to check the gas cup and your tungsten stickout because, if you have the incorrect size cup then, you're creating more turbulence or insufficient gas shielding even if the flow rate is correct.
The tungsten stickout is crucial too because, if you have too much, then more of your tungsten is exposed to the atmosphere, therefore increasing the chance of contamination. If your tungsten is'nt "extended" enough from the gas cup then, your arc has a tendency to "wander" or not enough current is being transferred to the base material causing the "lumps of gum" result.
You might want to make sure that you're using the correct tungsten diameter and grade of Wolfram!
Finally, if you are using filler metal then, feeding the filler into the joint before you've established a puddle might be the cause of the "lumps",and if you're feeding the filler into the middle of the puddle then, changing the position of the filler to the "leading" edge of the puddle will help you produce a uniform bead. Most important is not to overfeed filler into the puddle!!! If you still have this problem after considering all of these suggestions then, check the power source for the appropriate settings such as AC, DCSP, polarity, High Frequency continuous, etc., and if you're still getting the same results then, check your lenses on your welding helmet to see if there is anything that may be causing an obstruction or distortion in your vision when viewing the arc.
In other words, check everything!!!
I hope this helps!

Respectfully,

SSBN727 Run Silent - Run Deep!!!

By bmaas1

Date 07-12-2003 15:19

If all parameters are set fine why not just fuse the material together for tacks.

Brian Maas

By Lawrence (*****)

Date 07-14-2003 13:41

Brian,

The most commonly welded aluminum sheet metal is alloy 6061. One of the properties of 6061 is its resistance to fusion tacking, namely it requires the additional alloying provided by the filler metal to make a sound tack. Rather than an in-depth breakdown of why this is true, sufice it to say experience will quickly prove it to be true.

As a matter of fact in situations such as the one mentioned above (Alum 0.040 thickness) 6061 can be prone to cracking in butt/groove joints at the ends, if the puddle is starved (insufficient filler added) at either the beginning or end of the weld.

The Canadians have something to say about this here and even provide a very good picture to illustrate
http://www.cwa-acs.org/journal/Spring2003/James.html

By jwright650 (*****)

Date 07-14-2003 14:15

Lawrence,
Great picture shown.
John Wright