What a perfect TIG bead is supposed to look like?

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High schooler here, so please excuse any immaturity or ignorance I'm learning to TIG weld at a vocational school and have been working on lap-welding (what I estimate to be about 1/8") plates of cold-rolled mild steel with filler rod on DCEN at about 80 amps. My teacher doesn't like us getting ahead of schedule, but I still want to know what my ultimate goal is with these beads. I understand it's meant to be convex, but all convex welds I've made ended up being YPW*. I'll attach some photos of a plate I ran today - the beads are labeled on both sides so that in both photos "2" will be the same actual weld, etc - what is that weird rainbow thing in the center of the plate? I know it's got something to do with the cleaning action of the inert gas but am I supposed to be avoiding it? And those shiny parts where the outer layer of steel flaked away - what's up with that? Sorry if I'm being a douche and asking basic questions, but sometimes I feel like there's just so much stuff I don't know that there's nowhere to start  Attached Images
Reply:Originally Posted by Stack O'Dimes what is that weird rainbow thing in the center of the plate? I know it's got something to do with the cleaning action of the inert gas but am I supposed to be avoiding it? And those shiny parts where the outer layer of steel flaked away - what's up with that?
Reply:wow there is undercut all over. Cool it with the amps =] Practice makes perfect! So go at it since you paid for the class already.I wouldn't worry too much about the stack of dimes, try to focus on the proper fusion. The stack of dimes is just an added bonus.
Reply:welcome seems to me the backside is excessively melted through. theres too much heat. from the very close spacing of your dimes id say that might be the problem, idont know what amps you are using but for that 80 shouldbe plenty. but if you are too long inone spot it wil get too hot. try moving a little further when you finish feeding one puddle, maybe  50 % overlap insteaad of the maybe 20% you are getting..but it looks consistent and that meansz steady hands..
Reply:I can't really say there is such a thing as a 'perfect' bead in terms of aesthetics.  The way a bead looks has a lot to do with the 'style' of a welder, what this means is a welder can choose to make the beads look.  Frankly, it's far more important that the joint you do is well done.  I suggest asking yourself, not what a perfect weld looks like on the outside, but what a perfect weld looks like on the inside.The term you are looking for is penetration.  The best way to determine your penetration, at least in this situation, is to grab a jig saw and cut through your weld.  You will be able to see how deeply the weld is fused by doing this.  I don't mean to cut along the weld, I mean to cut across it.  The function of welding is to join two pieces of metal, when you are very proficient in accomplishing that, I believe that naturally you will be able to determine what aesthetics to give the bead.As you mentioned, some joints call for convex beads, I feel like that means nothing more than a bead with a bit more filler.  In my mind though, that seems fairly irrelevant at this moment, your stuff looks like you need to run a lot of 'fake beads' before trying to create any joints.  What this means is, you need to grab yourself a small piece of material, and just run an arc over the surface with filler in your other hand, you may want to start without filler to get yourself a bit more comfortable with the torch in your hand.  It takes a while to get 'there', but it'll come.  A website that has a lot of links and information about this sort of stuff is weldingtipsandtricks.com .As mentioned by DSW, the rainbow you see is the area where the heat has affected.  The technical acronym is HAZ, or heat affected zone.Miller 330 a/bp water cooledI believe in gun control, I hold my gun with two hands.  If you want to know why, click here.Buy American or bye America.
Reply:A lap or fillet weld only requires that the deposited weld metal is fused to the surface of each plate, and the root of the joint at the corner is consumed.  As noted above, this can be confirmed by cross sectioning the weld, sanding the surface smooth, and etching the weld area with acid.Fully penetrating the plate, or totally overpenetrating X 3, as you have demonstrated is not needed, it is detrimental to the strength of the joint since it has been severely overheated creating an excessive heat affected zone (HAZ) .So, basically the weld is way too hot.  Current is too high and/or travel speed is too slow and most likely the arc length was excessive.I suggest trying some lap joints without adding filler wire to start with.  Hold the tip of the tungsten as close as possible pointed directly at the root of the joint, angled to apply more heat to the base piece, use enough current to form a small puddle that consumes the root, move forward at a constant speed (about 6 inches/minute), no weaving or pausing, just traveling straight as steady as possible, holding a consistent tight arc length.  When you're comfortable with this, then begin working with adding filler wire in a consistent manner.Take a look at some TIG videos on http://www.weldingtipsandtricks.com/ to see what the puddle should look like.Sorry, just noticed Pinjas already mentioned tips and tricks site.
Reply:It just don't exist. I have been trying for 30+ years to make just 1 inch of perfect GTAW weld, I aint seen it yet.
Reply:Thanks for the help guys I wasn't really sure what I was supposed to be aiming for in terms of technique, or how to tell if I was making a crappy weld or not. Practice makes perfect, but I think incorrect practice makes horrible... I'll get some photos tomorrow when I make more welds.
Reply:Vince Lombardi said, "Perfect practice makes perfect."...If you really want to learn how to Tig well, try this...Start with the torch only, no filler. Put some outside corner joints together and just fuse the corners together. The result should be a convex bead with uniform width and thickness. Depending on material thickness, you may have to tack weld multpile spots along the joint to prevent keyholing. Also, a backstepping technique can minimize heat input allowing more continuos practice without overheating.I recommend this first so a real beginner can focus on torch/puddle control without the added dynamic of adding filler metal.Good luck, post some pics.Weldtek
Reply:Weldtek,good recommendation, an autogeneous corner joint is a great, easy starter for TIG.  No need to add wire, just hold a tight arc, and carry the puddle at a constant speed.  This and the standing edge joint are the easiest of all welds.This is a good video on how NOT to TIG weld a corner joint.  http://www.weldingtipsandtricks.com/...o-steel-2.htmlThis fellow is way too out of control and the this weld "ends up looking like Fido's ***".  I'll be generous and assume he is not willing to admit that he really cannot see the puddle, and needs reading glasses or a cheater lens.Good anaysis of the video by the host of Welding Tips and Tricks, be sure to read this below the video window.  "Happiness is a tight arc", words of wisdom to live by.Last edited by pulser; 10-19-2010 at 11:46 PM.
Reply:Thanks Pulser.When my students say I can't see, it can take a while to figger out what they mean. Sometimes I can't see means,  What the H@#$ am I supposed to be looking at?Stack O' Dimes,Try this. Take a piece of 11ga carbon steel. Stand it on edge and try to fuse the edge. In other words, just make a puddle so small that the toes of the bead stop at the edges without rolling over the corners. With 3/32 tungsten and about 30 amps + or -. Good luck.Weldtek
Reply:keep up the good work!!!