Hi there,
i am complete new to this topic - welding.
A friend if mine was welding aluminum and around the arc, the workpiece was cleaned.
He told me "spots on the surface" cleand it, I tried to google for spots but did not find anything
only resistance welding.
Hope someone knew anything about it, or has a hint were I get some information about that.
Thanks !
Cheers
Artie F. Emm
- Artie F. Emm
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Welcome, Katzenklo!
I wonder if your friend is referring to gas ionization. This is a clip from the Miller TIG Handbook:
The oxide can be removed by the welding arc during the
welding process when direct current electrode positive is
used. The positively charged gas ions which were flowing
from the workpiece to the tungsten when welding with DCEN
are now flowing from the tungsten to the negative workpiece
with DCEP. They strike the workpiece with sufficient force to
break up and chip away the brittle aluminum oxide, and
provide what is called a cleaning action.
I wonder if your friend is referring to gas ionization. This is a clip from the Miller TIG Handbook:
The oxide can be removed by the welding arc during the
welding process when direct current electrode positive is
used. The positively charged gas ions which were flowing
from the workpiece to the tungsten when welding with DCEN
are now flowing from the tungsten to the negative workpiece
with DCEP. They strike the workpiece with sufficient force to
break up and chip away the brittle aluminum oxide, and
provide what is called a cleaning action.
Dave
aka "RTFM"
aka "RTFM"
Sounds like the surface wasn't cleaned good enough. A picture would help. Crap on thee surfaace of aliminum will burn up and it's residue will float to the surface swirl around the puddle a bit and ultimately be left on the surface of the finished weld leaving black spots. On poor aluminum castings this is a big problem even if the surface is properly cleaned. Crap in the casting will float out and do the same thing, leaving black spots on the surface.
John
John
Learn 6010 and you will learn to weld
Follow the progress of my students on Twitter @PentaWelding
Follow the progress of my students on Twitter @PentaWelding
Bill Beauregard
- Bill Beauregard
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Location:Green Mountains of Vermont
It is during the Electrode positive half of the cycle the cleaning action takes place. The workpiece becomes a cathode throwing off electrons, along with those electrons or ions also the oxide molecules. This is called cathodic cleaning. When we adjust our ac TIG welders for less Electrode negative, or more EP we get more cleaning action. As heat is concentrated in the positive side of the arc, too much EP can overheat the tungsten. Too little EP it doesn't clean. AC balance influences penetration. Some manufacturers scale the balance knob as percentage of EP. Miller uses percentage of EN. In a Miller 75% EN is a compromise, some cleaning action, good penetration, reasonable tungsten life. 60% is better for cast aluminum where cleaning is needed, a larger tungsten may be needed.
Welders using older sine wave pattern often have ac balance fixed at 50 %. While you might expect too much cleaning action, the sine wave power allows the arc to stop twice a cycle. The oxide layer resists the re establishment of the arc, with it cleaning action is reduced.
Welders using older sine wave pattern often have ac balance fixed at 50 %. While you might expect too much cleaning action, the sine wave power allows the arc to stop twice a cycle. The oxide layer resists the re establishment of the arc, with it cleaning action is reduced.
- Otto Nobedder
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Location:Near New Orleans
The word you're looking for is "pepper"...katzenklo wrote: ...He told me "spots on the surface" cleand it, I tried to google for spots but did not find anything
only resistance welding...
Google "Pepper on aluminum welds", and you'll have more information than you can handle.
Steve S