TIG welding

C

chevy_power427

I have never used a tig, I have seen the welds, and they are beautiful. I only use mig for my welds. I have always wanted to learn. Is there any advantages over mig when tig welding sheet metal, patches and intricate work? What amperage rating would be sufficient for our kind of work, thick stuff I will mig weld.
 
I am learning TIG, just started doing it on sheetmetal. It is so much easier to grind and planish than MIG, especially the backside. For a starting point, I used .040" tungsten, and 40 amps. (.001" per metal thickness). Then fine-tune from there with the pedal. Here is a good video on how-to TIG sheetmetal:

I am hooked on TIG welding now. For more, go to weldingtipsandtricks.com
 
Tig has been a pretty quick learn. It has helped when we moved to 3/16 tungsten since you grind it to a point anyway. Most of the automotive stuff has been less than 50 amps. I think the tacks are definitely stronger with the extra heat than a mig gives you as far as an advantage.
 
How does sheet metal warp compared to mig? I guess we don't need machines over 200 amps for our line of work, am I correct?
 
I usually have mine set on 45 amps and throttle the pedal to adjust. I've had both for almost 10 years now and rarely do I use the mig. Maybe to tack something because tacking with tig usually requires 3 hands.

To me they both warp but the tig is easier to planish back as the weld isn't rock hard which allows the metal to hammer and dolly back easier and better.

Huge thing to look for is low start up amps. Some of the cheaper tig machines don't start very low. The pedal allows a soft start and then you ramp it up on the good ones. Some of them kick off at 20 + amps as soon as you hit the pedal. I haven't experimented but you might get some burn throughs with sheet metal with the higher start current. You might want to research that info. It would be a deal breaker for me as I use the welder to repair delicate auto trim and stuff. Your probably not gonna be able to repair cracked stainless trim pieces with a cheaper one. My lincoln 225 has been an outstanding tig welder.
 
How does sheet metal warp compared to mig? I guess we don't need machines over 200 amps for our line of work, am I correct?

I have a 200 amp inverter machine and have run to 200 for welding 4 link brackets to the rear end and endlessly trying to fix the shrinker dye. If you want to weld aluminum you need ac/dc.

I think its more important to spread the heat around more with the tig because it is has alot more heat.
 
How does sheet metal warp compared to mig?
Tig welding is light years ahead of mig for welding sheet metal, but like anything else it has a learning curve, and that curve is much more involved than mig.

I have tried the speed welding described in this link and it works great!
http://allmetalshaping.com/showthread.php?t=1116&highlight=buick+door

Here is the Buick door he welded in the link, which was without filler rod, without stopping and without planishing.
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Interesting. And what about high frequency start, is it a must or can we still do without it. AC and DC is a must for me, aluminum is starting to show on cars, worked on a new F-150 last week, wasn't anything major, but must be prepared. Plus I don't like the idea of investing into something that I know I will have to upgrade in the future.
 
Your welding process begins with panel fitup. If you have difficulty in getting tight fitting joints, your attempts at TIG welding will suffer. That doesn't mean you can't do it, just that your results will not be as nice.

For a preface, some examples of MIG:

Note tight gaps, good weld penetration...

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Used the crowned hammer to planish the welds.


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After planishing, 1/16" wide cutoff wheel used perpendicular to the weld for grinding the welds with minimal contact patch and less heat buildup. Ground welds just proud of the metal surface, front and back, to make room for planishing the next set of weld dots. Then rather than weld the next dots in the middle, I overlapped each of the previous welds to help eliminate missed spots and pinholes. Weld, planish, grind, repeat.


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Here are the results after dressing out all the welds...


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Back side....


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The down side to using the MIG is the weld, planish, grind, repeat process. Because the MIG weld is slightly harder, planishing efforts are more of a chore, all the grinding makes a mess of the shop, and the time spent from start to finish is considerable given sheet metal is not user friendly to full pass welds.
 
For TIG, especially if you can get your gaps "PERFECT", you can tack the panel together using zero filler and then come back and do a more continuous weld. Most of the distortion you see in welding is from starting and stopping, which causes inconsistency in the HAZ and thus differing amounts of shrink in those areas. So the more you can hone your skills in trimming and fitup (yes, this is very much part of the welding process) the less the amount of time you'll see needed in planishing, removing distortion, and finishing the panel.

Here's an ideal situation for tacking two panels together, a sheared edge for a zero gap. Not that we always get perfect results like these in trimming, but look at what you can then do for tacking. A quick zap of the pedal and the panels are tacked with minimal if any HAZ noticed.


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These "tacks" were about 1/2 second in duration, amps set at 82. This shows the front:


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And the rear side weld penetration:


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Again, we don't normally have a sheared edge in our fitment, but this goes to show how that extra time spent getting BETTER fitment will yield better results.

Now for real-world application using the TIG over that of a sheared panel....

The patch is securely clamped. Note that using HF or Eastwood butt welding clamps does not give you a tight fit or a good representation of the gap from one end to another. To see the true results of your trimming efforts, the panels need to be touching each other..... intimately.


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Tacked in with the TIG


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Then the TIG passes were done in about 3" increments. The longer you can make your pass here, the less of those start and stop areas that add distortion. I will add, however, that TIG induces much less distortion in these areas than the shrinking effects of the MIG. So the start and stops with the TIG are much more forgiving in panel distortion.


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Then the planishing was performed, and the welds will be dressed afterward. Comparatively, the MIG is more of a point and shoot, the TIG does require a bit more finesse. but from start to finish, fitup to finishing the welds, the fender at the top using the MIG welding is likely about a 4 hour evolution. The fender at the bottom using the TIG is about 1-1/2 hours max. Less time, less distortion, easier planishing and panel finishing, less mess in the shop. IF you can get good fit-up, and that includes having your panels matching. I have plenty of scraps through the years that would show how imperfect fitting panels will add to distortion, planishing, and cleanup of the welds. Some bothered me enough that I replaced them.
 
I think even gaps are more important than tight gaps. Tight gap to start, yes, but as you continue to weld, the panel closes back up. The best results we have had is to run that thin cutoff saw back in the opening when you are doing an entire square patch in the center of a fender or door because what started as a nice gap is now two panels touching together that start to buckle since you cannot clamp them . Tack the 4 corners and reopen the gaps to accept the weld, otherwise you are just grinding it all away.
 
Anyone by chance got to try the new 3 in 1 inverter machines? I know they don't do AC.
 
I have tried the speed welding described in this link and it works great!
http://allmetalshaping.com/showthread.php?t=1116&highlight=buick+door

Here is the Buick door he welded in the link, which was without filler rod, without stopping and without planishing.
As a beginner, I'm not too good with filler wire. I like no-filler for this reason. However, there is a slight undercut. Next one, I will try using .035" filler. Here is a no-filler weld, you can see the little bit of undercut after dressing it out. I wasn't brave enough to run the entire bead without stopping. I ran it in 4" sections. Next time, I will try continuous bead.



Interesting. And what about high frequency start, is it a must or can we still do without it. AC and DC is a must for me, aluminum is starting to show on cars, worked on a new F-150 last week, wasn't anything major, but must be prepared. Plus I don't like the idea of investing into something that I know I will have to upgrade in the future.
The AC machines I looked at have HF start. The more you spend, the more features you get. AC balance, slope, post flow, pulse, etc.

Anyone by chance got to try the new 3 in 1 inverter machines? I know they don't do AC.
Yes, I have the new Miller 215. Nice machine, though I have not set it up for TIG yet. No HF start, but I don't think that will be a problem. So far, reviews have said it is great for TIG. I was going to buy the 211, but for only $300 more to have TIG capability, why not. I have access to a nice AC TIG machine if I ever need it. But for 95% of what I do, this machine is more than I need. I wouldn't bother with any of the other 3/1 inverter machines. They don't have TIG gas solenoid. I will post an update when I start using it for TIG.
 
MX442, nice job on the fusion welds. If you are seeing lows, typically the metal is displaced to the other side. Planishing by striking the high side with the hammer should easily move things back into place, where practically ZERO grinding is needed to finish the welds.


I think even gaps are more important than tight gaps. Tight gap to start, yes, but as you continue to weld, the panel closes back up. The best results we have had is to run that thin cutoff saw back in the opening when you are doing an entire square patch in the center of a fender or door because what started as a nice gap is now two panels touching together that start to buckle since you cannot clamp them . Tack the 4 corners and reopen the gaps to accept the weld, otherwise you are just grinding it all away.

This is a result from the weld shrinking as it cools. Here you should planish the last weld that is pulling anything together too tightly. If your tight gap is closing up, that indicates it is pulling/gathering metal from the surrounding area, likely causing a loose oil can or low area in the process. By now opening up the gap even more with a cutoff tool, this allows even more movement/pull from those areas. By keeping your trims to a consistent, tight fitting butted joint, the surrounding panel is not pulled into the weld area as much as if there were a gap. Tack approx. 1 to 1-1/2 inches apart, as shown in the examples above, and once everything is tacked then weld. Relying on 4 corners only allows too much movement of your patch. If things start to move while tacking, planish to correct.

I'd suggest for everyone to read the AMS link posted by Chevman above for a fusion weld using no filler. RodDoc (the author) states that he uses the smallest tungsten possible for the amperage needed, as the tungsten is more efficient in the higher amperage of it's range. For your typical 18 or 19 ga sheet metal, I don't think I'd go above a 1/16 diameter tungsten. That should still carry plenty of amperage for a full penetration weld in sheet metal. Leaving a gap and filling it in suggests that your heat setting is too low. Also, for anyone that made my mistake of making a sharp point on their tungsten, like you'd see on a pencil from a pencil sharpener, this actually spreads the heat pattern for more HAZ. Less sharp of a point should give you a more focused arc, for less amperage needed to fuse the metal, less HAZ.
 
Anyone by chance got to try the new 3 in 1 inverter machines? I know they don't do AC.

I have the Alpha Tig inverter, AC and DC machines. Mr Tig sells a kit to change the parts he does not like, but honestly, I have gotten a #17 torch off amazon from welding city for 12 bucks to replace what he replaced. Just got a deal on a machine for around 600 so I jumped on it. Never once gone off on duty cycle, even welding up a rear end housing, even just running on a 30 amp breaker.

https://weld.com/index.php/shop-wel....-tig-alphatig-200x-2015-accessory-kit-detail
 
MX442, nice job on the fusion welds. If you are seeing lows, typically the metal is displaced to the other side. Planishing by striking the high side with the hammer should easily move things back into place, where practically ZERO grinding is needed to finish the welds.
Thanks, Robert. In the first picture I posted, the right side is hammered out. Most of the undercut leveled out, but still there in places. Left side of the photo is untouched after fusion weldeing. Second photo is planished and D/A. Still some lows and udercut, but close enough for filler.
 
If you look at UK coach built cars from early 50's and back, you can pick out the seams inside where the panels were gas welded. Some low/undercut areas did not seem to affect those panels, I'd say what you're showing is perfectly fine. This is a 1951 Triumph Saloon I had in the shop, still had wooden framework inside the body in that era..

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Congrats on taking the bull by the horns..
 
Finally, I went ahead and purchased a TIG 185 ac dc inverter machine. Tried it the first time and was impressed, it's almost like using the old torches, but with a loss less heat. I have to experiment with the different tungsten sizes and cups. The salesman pushed me to purchase 3/32 E3 tungstens even after I told him I was going to work sheet metal. It still does the trick when they are very sharp, but I will try the thinner ones anyhow. Also tried it on a scrap piece of aluminum, nothing compared to a spool gun. Very happy to finally have tried it, it's been a long time I wanted to do this.

What tungstens are you using for sheet metal?
 
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