Hello MDG
The main process is actually GMAW spray transfer using an 0.035" hard wire ER70S-6 with a 95/5 argon co2 shield gas.
The weld is a v-groove. It is a round solid mild steel bar being welded to another mild steel bar the same. The O.D. of both bars is 1 3/8" . One bar has a machined dowel on it that is 3/8" in diameter with the bevel coming up to the OD to form that half of the v-prep. The mating part has a 3/8" diameter hole in it that the dowel is inserted into with the other half of the v-prep. The v-prep works out to a 60 degree angle. I leave a 1/8" root opening to allow pentration into the dowel. I use the GTAW process to tack weld to hold position, the tacks are small as to not disturb the GMAW root pass, the tacks are completely consumed not causing any LOF. I have it all set up on a rotator and perform a root pass, filler pass then split the cap into two passes (half overlap). This works very well and has been passing x-ray without any problems.
The need for the tig with helium comes in to play to remove any defects. The surface of the welds are polished flush to the OD. Should there be any porosity or undercutting I need to fill these in, the material is cold by this point and I will blow the fuses in my shop if I push the little square wave too hard for too long. I prefer to do the re-work with the tig as it allows for a minimal build up for polishing. The GMAW doesn't push the limits of the fuses as the weld is only on for a short period of time, while the tig may be going for awhile on a severe case. I'm also currently reworking all the pieces from a previous vendor that are filled with porosity, so lots of grinding and tig welding.
If the fuses were in my shop I would be fine, but they are located in a locked room for the units I rent from. if I blow the fuses in the mioddle of the night I'm SOL until the next day......I can't afford to take this risk so I would like to make up for my shops short comings by the use of the helium gas.
Thanks for all the help.
Regards
JD369
P.s. Maybe once this job this job is in full production I'll get a bigger shop.
Hay JD, I totally understand the small shop shortcomings. We started (and still are) small. I had a square wave 175 for our first shop tig welder. Even had a SP-135 as the main mig welder for the first few months. Just do good work, and the cards will fall right!
Some years back I had a discussion with a guy who had a local fab shop about the capacity of His [at that time fairly new on the market] Miller Econo-TIG. He was forced to use it on a job that He normally did with a Hobart 300 that was down with a blown board. The job was a pharmacutical drum, stainless steel. He was able to do it with the small machine only because He had some Hellium/Argon mix on hand. The point being that on a job where the machine is marginal, it can make a difference.
I used the argon/ helium mix on the mild steel over the weekend and it worked fine. Doesn't seem to generate as much noticeable heat on the steel as it seems to on the aluminum by comparison but it definitley helped with the job. I noticed a bit more soot using this gas, the argon doesn't give any and it did tend to want to erode the very tip of the tungsten a bit but everything worked fine.
Thanks for all the help
Regards
JD369
You were definetly misinformed. TIG or Heliarc got it's name from using straight helium gas back in the day to weld just about whatever you wanted. We've since developed more cost effective ways to weld things.
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