This evening I tried some more Fusion welding using the Tig.. To review my previous attempt:
When using the Tig torch on that pass, I had set the amperage, mashed the pedal, and used the speed of the pass to control the heat. The slight undercut in the center is likely due to the fact that I made a straight run from one end to the other. I wanted to try this again, giving the torch a circular motion to see if it helped. Here's our sample pieces..Some practice at fusion welding using the Tig, here's the front showing some slight undercutting..
The rear side shows some good weld penetration in some areas and needs more practice in others..
Just to show that slight undercutting on fusion welding was not an issue in the joint's strength, the seam was clamped in the apron brake and bent to 135 degrees, with no detriment to the weld..
For tacking purposes, I set the electrode depth so it was just sticking out past the cup. The electrode is fairly easy to position using this method, drag it side to side and it will find the exact joint between the two pieces. Then rotate the torch backwards just enough for the cup to pick up the electrode off the metal, and give the pedal a quick push. These "tacks" were about 1/2 second in duration, amps set at 82. This shows the front:
And the rear side weld penetration:
For the weld pass, the sample is raised above the "table" to simulate welding the panels on a car in free air...
In order to maintain consistency for the test, the cup is modified so as to use it as a "glide" (think plasma cutter guide) and the electrode is now moved just inside the low point on the cup. This should hold our electrode height exactly the same, to limit one of the walking, talking, chewing gum factors.
This was welded using a circular motion with the torch while making the pass:
Rear shows some undercutting
Planishing to bring the weld proud down flush with the front surface
Front:
Rear:
Now to test the weld to see how structurally sound it is with the undercut....
Here's the front side with the weld pass...
This is the rear side with the undercut..
This was bent approx. 150 to 160 degrees and the weld held..
I definitely need more practice to build up my "comfort level" with using this process, but sure beats all that grinding with using the Mig!