Tig Heat Management

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Hello, this is my first post. I just started to learn TIG for a project I am working on and I have a few questions that I have not been able to find answers to.I am practicing a butt weld of two 0.065" wall tubes (mild steel). I am using 1/16" electrode and 1/16" filler (70S-2 type) for all of the welds. I am using a gas lens with a #5 cup. So far I have learned that 65 amps seems to work well. I say this because 55 amps has a little bit more heat input (because the travel speed slows down) and I get little bit larger HAZ and more stickout penetration on the backside of the weld. Going with 75 or 85 amps and the HAZ is about the same as using 65 amps but travel speed is much faster and the weld puddle gets more concave.My question is about the grey area surrounding the weld. Is that grey band an indication that the weld is too hot? On most professional welds that I have seen there is no grey band, rather there is just the HAZ rainbow that is up against the weld.The tubes are being welded for a structural application, so I want to make sure I am on the right track.Thanks for any help Attached Images
Reply:the two on the left are too hot. The 65 amps looks like just on the verge of too hot. Split the difference and try 60. You should try walking the cup on that, and personally, I wouldn't worry about a little penetration on a structural weld. Excessive penetration is an issue on fluid containing pipes because it disrupts the flow and causes turbulence. It won't matter on structural pipe.
Reply:Try the same thing just with some smaller filler rod like .045 . Take it for what its worth because I don't tig much, but having the filler rod thinner the what your welding will make it easier by melting into the weld puddle with out cooling it down so much.
Reply:Looks like 65 amps works well for you, but that you may be moving a little too slow. Try moving a little faster. What CFH are you using with the #5 cup? The steel looks clean but doesn't look like you hit it with a grinder, if you clean it with a flap disk to shiny metal you will get more color and a cleaner weld. Also the roots look very dirty, was the tube coated? Try cleaning the inside with a die grinder with a round flap disk.Airco Ac/Dc 300 HeliwelderMillerMatic 200 (stolen)Miller Maxstar 150STLMiller AEAD200LE (welding and generating power) Hobart MIG
Reply:yeah the inside looks like it is dirty?  The yellow color looks like what you get when you try to weld galvanize?  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Originally Posted by Jay OTry the same thing just with some smaller filler rod like .045 . Take it for what its worth because I don't tig much, but having the filler rod thinner the what your welding will make it easier by melting into the weld puddle with out cooling it down so much.
Reply:I agree with squirmypug about the cleaning.  Make sure you get it down to shiny bare metal, and not just "polished" millscale.  I used practically the same tubing in my longtube headers.  1.625" mild steel, 0.065 wall.  I ended up setting the footpedal to around 45A, but I think perhaps the scale of the sticker by the knob was a bit off and I really think it was closer to 55A after playing around with the knob on the machine.  Anything higher than that, and I'd have to add a lot of filler rod and move alot quicker to prevent blowing a hole through the pipe.Anyways, I liked 0.045" filler rod, but I also used 1/16" at times.
Reply:Thanks for the quick responces.but that you may be moving a little too slow. Try moving a little faster.
Reply:For me 11 CFH is on the low side for #5 cup, try around 15CFH to see if that keeps the weld from getting grey. A wire wheel won't get it clean enough, you need to grind it. Cold rolled can be welded without grinding but you will get better welds if you do. Even though you are only practicing you still need to clean both the inside and outside of the tube.     Walking the cup isn't really needed on something like this but some guys do it. Most of your welds are looking good, keep practicing to see what works best for you Airco Ac/Dc 300 HeliwelderMillerMatic 200 (stolen)Miller Maxstar 150STLMiller AEAD200LE (welding and generating power) Hobart MIG
Reply:Originally Posted by maccos So back to the question, you guys dont see a major concern with the grey area surrounding the weld? It seems to me like the joint is plenty strong, I was just concerned that the colorless band around the weld was a bad thing...
Reply:Question; I did not see a gas flow listed. Maybe up the gas just say 2 cfh?? Other thought was a very small interior purge might cure it. All said, the welds look good, the color is not far off, so it's just a small tweak somewhere.EDIT; just saw the gas at 11. Need to bump that to about 14 and see how it flies. I bet that does it.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Most of your welds are looking good, keep practicing to see what works best for you
Reply:I see you have "walking the cup, no filler" listed on the one pict. You still need filler on steel. With no filler, that sort of explains why you had some issues. Walking the cup will give you a nice consistent bead profile. Like anything it's a tool with right and wrong places for it's use, and you need to practice until you get it down. I wouldn't simply abandon the technique because it didn't work like you wanted at 1st. I think your biggest issue is the low amps causing you to have poor penetration, not the fact you walked the cup.I also you show "good" on the back of the other side. That's not what I'll call good or acceptable penetration personally. I see what mostly looks like a series of "spot" welds rather than the nice even reinforcing I'd expect to see. The "best area i see is just at the edge on the right side. The top looks a bit low, but the root face looks closer to what I'd want to see. It's hard to tell in the pict because the area is very short. and the pict doesn't give much detail in that area.I think the biggest reason this side didn't "fail" is because you have a lot of reinforcement on the face of the weld. This extra material forced the bend to occur away from the weld joint as it's plainly visible in the pict. The other weld failed here both because of the poor penetration, but also because with no filler the weld seam was thinner than the base material. Usually of you do a bend test, you grind the face and root smooth so the coupon is even in thickness across both the material and the weld faces. This way the reinforcement doesn't change the bend characteristics of the material..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:DSW, thanks for the tips. I played around with the gas flow and that did not seem to affect anything.I am just going to continue practicing with filler to get even penetration and a consistent looking bead. I think I just need more practice controlling the puddle.Speaking of gas flow. I purchased a new tank of Argon about 5 days ago and it is just about gone already. It is a fairly large tank (about 3 ft tall),sales receipt says size 80 (its was a little less than $50). Started at 2000 psi and is now down to about 200. With this tank I used up 1 package of filler rod which contained about 30 3ft rods, plus some practicing without filler. I've done a lot of practicing, but I was surprised to find out that I need a new tank already. I don't think there are any leaks in the system, but I haven't checked. I turn the gas off whenever I'm not welding. Does this seem like a normal amount of gas consumption? I've attached a picture to show the size of the tank. Attached Images
Reply:Gas usage is fairly easy to calculate. Take the size of your cylinder ( 80 cf) and divide it by your flow rate, say 11 CFH ( cubic feet per hour). Roughly you'd get about 7 hours of weld time using those numbers. If you upped your flow to say 20 CFH, you'd get a bit less than 4 hrs of weld time..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:so long as you got more than 14.7psi the tank will outpower the atmosphere, although that is cutting it real close, lol.
Reply:Thanks for the calculation, 7 hours seems about right. Thanks for the help!
Reply:How far is your tungsten sticking out? Pull it in as far as you can while still being usable, get the tungsten closer to the metal, and hold the torch as bit closer to 90 degrees to the work piece. I have a peddle so I am not good on amps so I won't comment there.
Reply:VPT, I have my tungsten sticking out at least 1/4" inch probably a bit more. I figure I can get away with more stickout because of the gas lens and because I am not in a tight joint (just a butt weld). I did a little playing around with the tungsten about 1/8th stickout, there was really no difference in my opinion, just much harder to keep an eye on the puddle.Yes I am keeping the torch pretty perpendicular to the weld and I dont have a problem keeping the tungsten close to the weld either. (Luckily I was born with a steady hand, just need more practice)I guess I didnt mention that I am using a pedal. As I have been practicing more and laying down beads about 3/4" spaced apart, all of the heat buildup in the metal changes things a bit. Rather than just stabbing it at 65 amps and going, I had to start out at 60 amps and throttle back a bit on each weld after about 1 inch of travel.
Reply:With a gas lens you can turn your regulator down some because of the design directing the gas flow more to the Tungsten tip......You just need to cover the weld...Unless your fighting a draft in your weld area and need to turn it up but that's something you shouldn't deal with for long.....Try to find a weld area NOT affected by drafts......  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock