TIG questions

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I'm trying to learn how to tig weld and I've watched some videos and read the Miller tig handbook as well but still have some questions.1) I've read that when tig welding increasing the arc length put's more heat into the base metal.Why is that? TIG is a constant current process so wouldn't the same amount of current flow regardless of the arc length?2) Also when using lift tig without remote power control is it possible to avoid a crater when finishing?3) When welding on clean mild steel should the bead look shiny or dull?4) I'm sharpening my ceriated tungsten (1/16") on my 4 1/2" angle grinder with a diamond grinder wheel, 60 grit (see below). Will that cause any problems? To my untrained eye the arc looks fine.Thanks for any help with my questions. Unfortunately I don' have anyone who can teach me tig welding. Attached Images
Reply:Originally Posted by Pete.S.I'm trying to learn how to tig weld and I've watched some videos and read the Miller tig handbook as well but still have some questions.1) I've read that when tig welding increasing the arc length put's more heat into the base metal.Why is that? TIG is a constant current process so wouldn't the same amount of current flow regardless of the arc length?2) Also when using lift tig without remote power control is it possible to avoid a crater when finishing?3) When welding on clean mild steel should the bead look shiny or dull?4) I'm sharpening my ceriated tungsten (1/16") on my 4 1/2" angle grinder with a diamond grinder wheel, 60 grit (see below). Will that cause any problems? To my untrained eye the arc looks fine.Thanks for any help with my questions. Unfortunately I don' have anyone who can teach me tig welding.
Reply:Originally Posted by Pete.S.I'm trying to learn how to tig weld and I've watched some videos and read the Miller tig handbook as well but still have some questions.1) I've read that when tig welding increasing the arc length put's more heat into the base metal.Why is that? TIG is a constant current process so wouldn't the same amount of current flow regardless of the arc length?.
Reply:I'll put another view on it. Stick and tig are constant current/variable voltage processes. When you increase your arc length, the current (amperage) stays constant but your arc voltage increases which creates more heat. Shorten your arc length and your arc voltage decreases while current stays constant. Mig on the other hand is opposite. Constant voltage/variable current.JasonLincoln Idealarc 250 stick/tigThermal Dynamics Cutmaster 52Miller Bobcat 250Torchmate CNC tableThermal Arc Hefty 2Ironworkers Local 720
Reply:Originally Posted by Pete.S.1) I've read that when tig welding increasing the arc length put's more heat into the base metal.Why is that? TIG is a constant current process so wouldn't the same amount of current flow regardless of the arc length?
Reply:Nah, you are thinking too hard. What you need is hours, and hours, and hours to self inflicted tig time. Your arc length will become second nature to you. What I tell newbies is to determine your tungsten diameter by the thickness metal and amps you are welding with. Then keep your arc length as close to the tungsten diameter as possible. That way you will try to avoid wandering away from the metal and loosing gas coverage. I grind my tungstens to a pencil profile. Needle sharp for DC, and not needle sharp for AC. That way I keep the same geometry for both AC and DC.  Personally I think cross contamination on tungstens is folly. Who cares how you got it sharp as long as the profile is correct and the blobs of filler are gone IMO. I use a simple belt sander that I use for multiple purposes. Good luck and get tigging.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Originally Posted by Pete.S.I'm trying to learn how to tig weld and I've watched some videos and read the Miller tig handbook as well but still have some questions.1) I've read that when tig welding increasing the arc length put's more heat into the base metal.Why is that? TIG is a constant current process so wouldn't the same amount of current flow regardless of the arc length?
Reply:Thanks for your replies guys! It's really helpful. I asked about the arc length because I was in my mind trying to figure out if I could slightly change the arc length to control the heat when welding, similar to O/A welding. Anyway after reading your posts I understand better what is happening. I guess the effect with tig is similar to long arcing when stick welding? I also did a test after reading your posts where I started the arc on a piece of thin sheet metal and held it stationery for 10 seconds, first with a 1/16" arc length and then with a 1/4" arc length. Comparing the heat affected zone it's was about 20% larger with the 1/4" arc length. The puddle was perhaps 40% larger with the longer arc length. It was no scientific test so conclusions might be hard to draw but I actually thought that the arc length would make an even bigger difference.A question about the argon flow: I run 1/16" tungsten with a #5 cup and have the argon set to 15 cfm (ball flow meter). It seems like it takes a 3/4" to 1" arc length before I get air sucked into the argon flow. Is this a normal amount or should I run a lower gas flow? Are there any drawbacks to runner a higher than needed amount of argon flow (except cost of course)? Also thanks for the tips on ending without a creater. I tried to end the bead slightly early, put some filler in, go back a little, whip out the arc and then go back to the end of the bead with the argon post flow. It worked great when I got it right! Regarding grinding the tungsten I will stick to my current method for now. I put the grinder on the table, set the variable speed on the grinder to the lowest and then rest the tungsten on the guard in the same place and rotate. The angle looks consistant from tungsten to tungsten.Thanks again! PS. Regarding the arc length I understand that consistency is the key to getting a uniform bead. But would it be okay to run a slightly longer arc length to get a bigger puddle if I wanted to do that? Assuming that I have gas coverage of course. Or does the slightly longer arc length have some other drawbacks?Last edited by Pete.S.; 04-18-2013 at 06:41 PM.
Reply:Seems most is well covered. Just want to add I use my bench grinder that I use for EVERYTHING for sharpening my tungsten.I have found that the tungsten cleans the aluminum boogers off the wheel well.
Reply:In theory, too much argon flow and you run the risk of turbulence which could draw in oxygen.  But the range of 'acceptable' is wide.   The 'perfect' flow rate depends on the size cup you use.   On steel, 15cfh is plenty with a #5 cup.  You could probably get away with 11-12.  At some point you might want to read up on 'gas lens' for your torch.  No rush.As for using arc length to fine tune - perfectly acceptable.   Arc length + travel speed + torch angle all play a roll.   Even filler size.  Dip a big enough rod and you will cool the puddle down to the point of it freezing....  So if it's too hot, move faster, dip faster.  The limit on arc length is typically arc control.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:I certainly may be wrong, but I'm pretty sure the increased heat into the workpiece with increased arc length has to do with the wider arc you are creating by doing so.  Yes, a CC machine is gonna vary the voltage to keep the amp the same, so the power stays the same.So if you're holding a tight arc, the heat is focused, you get a smaller bead that forms faster and you piece is welded over time with alot less heat input.  A long arc gives you a really large HAZ, so a larger bead that you spend more time producing.  If you search you tube under videos from Lincoln welding, there's a very good one that's NOT from Mr. tig.  The Weldor shows the difference that a long vs short arc creates in a welded piece.  The long arced one had a ton more heat retained in it than the short arced one.I try to hold te tightest arc that I can without dipping.  Long arcing just seems wrong to my eyes when I'm doing it.Last edited by Drf255; 04-19-2013 at 05:01 AM.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:Drf, as noted above, power = voltage x current. If one variable is constant (current in this case) and the other increases (longer arc length in this case), power must increase.
Reply:Awesome guys, I'm learning lots! I checked out the videos from Lincoln on youtube. There's some good info there, thanks!I was wondering about electrode stickout. As I understand the amount of stickout doesn't really matter one bit as long as you have sufficient gas coverage. We might as well call it cup position. Is that correct?  Also, it would be better to have more stickout and higher gas flow and keep a shorter arc length because you can see what you're doing? Compared to having a very short stickout that you really can't see causing you to run a longer arc.
Reply:Originally Posted by Pete.S.Awesome guys, I'm learning lots! Also, it would be better to have more stickout and higher gas flow and keep a shorter arc length because you can see what you're doing? Compared to having a very short stickout that you really can't see causing you to run a longer arc.
Reply:60 grit seems a little heavy to clean a tungsten, but shouldn't cause any trouble, I also think cross contamination is a myth, but I don't weld on spaceships. I have gotten shiny welds on clean steel with a bit of post flow, but If you want to play with the colour try some stainless. I like a fair bit of stickout, maybe 1.25 x the diameter of the cup, but you can use more with a gas lens. Just for visibility in inside corners. I'll use less stickout on outside corners. 1/2" of arc length is ridiculous, I'd use that to pre heat some copper maybe?SqWave 200Millermatic 190Airco 200 ACHypertherm PM45Boice-Crane Band SawVictor O/A