custom wastegate linkage (stainless steel TIG welding) jakeru's #13

[jakeru]

I fabricated a custom waste linkage for a hybrid turbocharger (large compressor wheel, small turbine wheel) in stainless steel.

I probably had more time in cutting and grinding of the pieces to fit just right (maybe 20 minutes) than I did in the actual welding (10-15 minutes.) I used 304 stainless rod, plus the cut apart pieces of the original wastegate linkage, (which may have been nickel plated steel of some sort, as it was magnetic.)

I tack welded the linkage with it installed on the turbo (using the welder's finger / third hand for grounding) and actually held the piece with my left hand, as I zapped the first tack autogenously right TIG torch (and plenty of current) in my right hand. It worked like a charm!


Then after getting the second tack weld on there, I removed the linkage and welded it up on the benchtop.

I was going for some rainbow coloration in the weld beads, for a fun and kind of a neat "custom welded" look. And I think it turned out that way pretty much. I used a #6 gas lens with about 12 cfh argon. To get the look, I would purposely pull the torch away during the later stages of post-flow. If you held the post flow on there too long, you would have a silver spot where the weld ended. If the heat was just right when you pulled away the torch during post-flow, the area turns a pretty color. (Actually, I've noticed the "oxidation film colors" are actually inverted rainbow colors; the same colors one sees when looking at a thin oil film/slick floating on water.)

Here is the completed product after being installed back on the turbo:


I used 1/16" 309LSi for the filler rod. 1/16" tungsten with fairly sharp tip (small flat in the end). Low frequency pulsing about 1.5 pulses per second, 60% pulse duty, and 60% background. Footpedal for current control. (Turned way up quite a bit for the first tack welds, then turned down to about 2/3rds of tack weld setting for the full welding.)

Before I welded this, I was welding some mild steel on another project and was having problems on arc starting (arc would try to start back up near the collet body, before moving down to tungsten tip.) For this project I had all of the shielding gas flow related parameters the same, the only adjustment I made was a slight increase in pre-flow. And it was only a very small change in the pre-flow setting... like increased from .5 second to .6 second. It however made all the difference in helping the arc start smoothly.