please help improve my welding... 4130 thinwall tube

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Hi all,I've recently got my own TIG welder after losing access a few years ago to a friend's one and want to start building bicycles. So I've been trying to weld 0.9mm wall (0.035") 4130 tube. With my welder that seems to mean the minimum current setting (it says 1 amp but the knob has ~10 degrees travel at the same display value and the welding current seems to change). I have a scary array of knobs on the front of the welder and a manual, but I'm used to an Esab 180 that only had a current control so it's all a bit new.I'm hoping that some of you will be willing to look at some photos of my attempts and suggest ways I can improve the welds. I've mitred the tubes then welded then cut through the welds to see what's going on inside: http://moz.net.nz/photo/2008/01/23-welderplay/Please feel free to suggest anything, including that I a:learn to weld and b: learn to take photos. I'm happy to cut the practice pieces up more if you want to see different bits. And weld more.To me it looks as though I need to get the weld puddle off the main tube a little more and into the joint/butting tube. But when I try to do that I get holes, the butt tube just melts away from the weld. I'm using a 1.6mm electrode sharpened a little to perhaps a 1mm diameter tip. And probably 3-5A current (the welder display says 1A).thanksmoz
Reply:Sharpen your tungsten to a point. Sand your tubes down to shinny metal a few inches beyond the weld area. What size filler are you using?
Reply:It looks to me like you're either getting way too hot or very poor gas coverage.
Reply:use a ss wire brush and its helps to clean with acetonedoes look a little hot gives us more info: heat range,tung size, filler size,gas cfhlooks like you may have dipped tung into it?
Reply:With a little more information, we will be able to give you more help.   JohnSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:I'll take a guess, you're arc length is too long, you're electrode tip is 1/4" or more from the weld joint?You should be around 1/16", maybe 1/8" max.If you're arc length is too long, the heat from the arc is too diffuse and inefficient, causing excessive generalized heating of the base metal and not enough concentrated precise melting of the weld joint, also causing you to travel very slowly to build up enough heat to melt a spot.This will also cause excessive oxidation of the weld and heat affected zone since the shielding cannot cover the huge heated area and the whole weldment is still too hot after the shielding flow is turned off.Am I right?You say probably 3-5A current, that doesn't make sense, should be in the ball park of 35 amps dc electrode negative for your 0.035" thick tubing.You say you "have a scary array of knobs on the front of the welder", let's see what they are, what make & model welder is it?
Reply:pulser x 2  =)My Babies: HF Drill pressHF Pipe Bender3   4.5" Black and Decker angle grindersLincoln Electric PROMIG 175that´s it!
Reply:I think MOZ needs to post more information.   JohnSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:Thanks team, I'll try again with your suggestions. (and work out exactly what sort of welder I have).Pulser, I'm maintaining ~1/16th spacing, definitely not as far as 1/4" away. The arc is less than 1/8" wide. I will see if my "spare" digital camera can get a photo of it (I'm not willing to use my expensive DSLR)I'll try sharpening the electrode and cleaning the joint area more thoroughly tonight and post more photos.
Reply:Well, first guess was wrong.Second guess, I'll go along with the suggestion to clean and prep. the joint to shiny metal, and you could have a shielding problem.
Reply:Pulser nailed just about everything, but you can't even begin to assess that unless the material is shiny bright metal and wiped with acetone as mentioned.  Be sure to at least wipe the inside rim of the tubing as well.  Without doing so, accurately interpreting the problems associated with GTAW is like pissing in the wind.
Reply:Without knowing awhat kind of machine you are using it does not help.SCARY - knobs???? Type of torch ,tungsten sizeetc.,etc.,etc.,.Like preflow and post flow and arc length????ANYWAY I will give you the WHOLE story.What the others (PULSER)  have said so far is right. TOO hot and oily metal???FIRST the metal MUST BE CLEAN and no oil. Inside or outside.For this job you will need to go down to 1/16 size tungsten..o35 is thin ! A 3/32 tungsten would even be diffacult for the BEST welder with a Miller or Lincoln syncrowave..Set your machine controls at about 70 amps. You should be using a foot control. You could use a hand control, but the foot control will make it easier.So you will only be using a small fraction of the 70 amps.Other wise you will have to experiment with AIR COOLED untill you get just the right setting.Very diffacult. That is why foot controls are used so that at the strart of the weld you can have a little more power and then let up on the heat as you progress .Preflow about 5 seconds and post flow about 10 seconds.The filler wire size will be very important too. For this job even .045 ER70S2 may be a bit large.See if you can get some .035 filler wire.I will tell you a little secret.....HOT,CLOSE FAST.Learn to count (in your head) as you are welding and your welds will be consistant. Like 1.2,3.4  1234 etc.,.The torch should have a gas lens and be water cooled IF POSSIBLE.The air cooled torches are generally larger and clumsier. Use a gas lens if possible and a # 9 cup or smaller.The tungsten should be 2% thoriated or (your choice) don't want to get into that debate now.The tungsten should be sharpened to a point that is simular to a pencil point, about 70º. The tungsten should stick out of the cup about 1/8 inch.Gas pressure at the regulator should be about 10-15lbs. Argon gas.With chromoly it is alway wise to pass a torch flame (neutral) over the joint before welding to remove any moisture. It may look dry but if you just pass a flame over the joint you will actually see moisture accumulate for a second then dissappear.Of coarse the joint should be tacked together with small tacks befor welding.This helps draw the two pieces together very tightly also making it easier to weld.For small work like this you may want to use a magnifying lens (1.50,1.75) with your other lens which is really helpfull. Fon't think about it having anything to do about being old. Forget the macho stuff and your weld will be very good because you can SEE the details.DO NOT cool the weld with water !!Let it cool down by itself.Last edited by Donald Branscom; 01-25-2008 at 05:38 PM.
Reply:OK, I had a play yesterday after work and just did one quick joint before I had to go out again. I'm going to dig out my clamp meter and see what it says about current, because the welder says 1A for about 20-30 degrees of knob movement and the arc heat does seem to change in that range. I cleaned the tubing up wityh a file then a wire brush in my Dremel tool because I don't have acetone handy. I will find some kind of solvent and see if that helps later this weekend. Also buy a gas lens, I'm not sure I can stretch to a water cooled torch right now.I'm welding quite slowly, which is where the low current helps. Also in multiple short chunks as I rotate the tubing to get access all round. I suspect that with short bits of tube like this I could weld in one continuous pass but once I start making bikes that won't be an option so I'm inclined to keep doing it this way. These two (click for bigger image) are the inside and outside of one section that I tacked twice and welded in three sections: I made a hole at one stage, and left it so you can suggest things that I was doing wrong just in case that helps:My girlfriend has been practicing on the simpler stuff, welding 5mm offcuts together. Aside from not having enough filler going in there does this look ok (she did this while I was out so I couldn't correct this while she was working)http://moz.net.nz/photo/2008/01/26-welderplay/
Reply:Either your base metal is contaminated, or you've got gas shielding problems for certain.
Reply:Agreed..Do you hear anything like sssssssssssss coming out of the torch when you hit the pedal??...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Moz, you are using PURE argon, not a mix right?
Reply:Looks to me as if you may be going too slow, too hot. Remember to keep moving to avoid the base metal from getting too hot. Just keep practicing with a good clean shap tungsten.
Reply:My welder is a UniTig 200 with "jasic" on the front panel. It's a cheap Chinese one, cost me about $2000 Australian. Compared to $7000 for the ESAB 180 a few years ago that I went three was on with friends. The extra socket on the front was added by the shop I bought from to take the cheap generic foot pedal. But I can't find anything about it on the web, the closest google comes is one of those dodgy companies that put hundreds of keywords on their front page to attract search results.Photos: Currently I'm running it in non-pulsed mode in the hope that if I keep it simple it'll be easier to understand.
Reply:Your girlfriend's weld isn't bad for a first-timer! Get her to help you. You're getting good advice here, just keep reading and practicing.As said above, you should be pushing 30-35 amps with that material. If you use less current and try to make up for it by welding slower you will actually end up putting more heat in the metal. Some of the above pics look like this may be the case, IMO. With thin material like that you need a perfect, tight fitup, and you need to weld fast.It wouldn't be a bad idea to grab some ~1/8" plate to practice on. Once you get the grasp of that the .035" isn't so tough.Miller EconotigCutmaster 38Yes ma'am, that IS a screwdriver in my pocket!
Reply:In the first series of photos you showed a 90* flange weld.   I think you were concentrating too much on the flange and not running your bead up onto the foot of the tube.  You could have continued the burn up the foot of the tube.  Good welds.  Need more puddle control.
Reply:what are you using for filler wire? a clothes hanger?
Reply:Originally Posted by mfurickwhat are you using for filler wire? a clothes hanger?
Reply:OK, I've put my clamp meter on the welding cable while she runs the welder and it's a bit random. Seems to me that I'm getting about 25A for "1A" on the display, 35A for "10A" and 50A for "50A". So my "1A" welds above were actually done at 25A or so. I think I will take the welder back and get them to calibrate it properly. According to the meter there's no AC component, just DC, so the DC reading should be fairly accurate.I also used mineral turpentine to clean the metal after wire brushing it, 35A and less electrode poking out from the shield.  The dirt around second weld there is from the other day, the actual joint area is clean. Hopefully this week I'll also get a pile of offcuts from my tubing supplier so I'll feel a little more able to practice. Right not I'm making small, intricate things with lots of close-together welds because at $50/m or so I'm not that keen, you know. I'm also using mild steel filler rod - will that make a dramatic difference? The rod is fairly thick, sorry I forgot to actually measure it, but with a puddle about 1/8" it definitely cools right off when I dip. With 35A instead of 25A it's better but I have to keep moving right along or I get holes. And at 35A I can't fill the holes, I have to stop, wait for it to cool, then fill the hole.Also, my pedal right now is independent of the main current control - with that plugged in the pedal will run right up to 200A regardless of the knob on the machine. On the Esab the pedal cut the current from what we set on the machine, so the pedal was great for fine control. I suspect they wired it wrong, so I'm going to ring them and hassle them about it, and if they won't change it over I'll have a go myself (the Elec Eng degree does have *some* use  )Thanks so much for the help so far guys, it's making a real difference. I think I'm actually starting to get the hang of things a little, largely thanks to your comments.
Reply:Originally Posted by William McCormick JrYou need a lot of gas coverage, a gas lens for sure. And probably about 15-20 cubic feet an hour.
Reply:Product page for my welder: http://www.unimig.com.au/200acdc.html (I asked on a local forum and someone found it in minutes... after I spent ages in Google)DON'T USE mineral turpintine  (has an oil base) use ACETONE/ or lacquer thinner, drys fast leaves no residue. and don't set it on the welding tableLast edited by prop-doctor; 01-28-2008 at 10:25 AM.
Reply:When I said I might even risk using 0.030 MIG wire, I meant as TIG filler wire. Because we only get 1/16" 70S2 wire around here. I would not MIG it. I mentioned the 0.040" tungsten because if you are going to do this many many times. You will find the 0.040" very easy to sharpen. Just one turn and you are done. As far as letting it fusion together, with no filler wire, it is a proof of heat. If you can do that, you have the part hot enough to start welding. Anything short and it is a guess. You can always come back around and go over a bit. But it is just not the same. You may never get the root right there. You should try to put the heat into the flat uncut surface, and not into the piece that has a cut end exposed. This is also a form of making sure you have the right heat in both parts to start welding.        Sincerely,             William McCormick
Reply:When I said I might even risk using 0.030 MIG wire, I meant as TIG filler wire. Because we only get 1/16" 70S2 wire around here. I would not MIG it. I mentioned the 0.040" tungsten because if you are going to do this many many times. You will find the 0.040" very easy to sharpen. Just one turn and you are done. As far as letting it fusion together, with no filler wire, it is a proof of heat. If you can do that, you have the part hot enough to start welding. Anything short and it is a guess. You can always come back around and go over a bit. But it is just not the same. You may never get the root right there. You should try to put the heat into the flat uncut surface, and not into the piece that has a cut end exposed. This is also a form of making sure you have the right heat in both parts to start welding.        Sincerely,             William McCormick
Reply:I know that this is an old thread, but I use a similar Chinese machine, and I think I know what your problem in terms of amperage control.  I have had a similar problem on at least one occasion.  The "Arc Force" knob, which I imagine is similar in function to the dig knob on machines from more traditional manufacturers needs to set to 0 when in TIG mode, or the amperage dial seems only to add current beyond the "Arc Force".  I may post something similar elsewhere as a tip so that newcomers find it more easily.
Reply:You should start a new thread and post this. You can always put a link to the old one if you want as a reference."Common sense is not very common"http://www.tahoekeyshome.com
Reply:i wanted to help you so bad that i registered here. i have built a couple of bike frames and although i had been welding for several years before i did #1 i know what you are going thru. it looks like your shots are of a BB/down tube joint and since that it the thickest point on the frame the rest of it will only get harder. on the frames that i have built i did with 3/32 tungsten and .035 70s-2 not because it's what i had lying around either. i HATE welding with tiny tungsten. even doing aviation work i rarely used anything smaller than 3/32. at the end of the day you just need more practice. you have gotten lots of good advice here just spend more time doing it.