Weld Penetration

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I'm not new to welding but new to thicker than 1/8" welding. With that said I've boughtboth 2 1/2 and 2" square pipe 3/16" to make an auto rotisserie. I'm have trouble withpenetration of the weld with my miller 175. Started with .035 and started with settingsshown in door but welds were pretty much on top with little penetration. Changed to.030 and its better but ran the heat all the way up and speed up the speed. Much betterbut I don't get why I have to do this.  Is the .030 wire where I want to stay or play morewith the .035. How much penetration should I expect for the 3/16" pipe? Only doing teststrips now and with the .030 getting about 1/2 of the 3/16"Also did check the voltage and took the welder over to have checked out and its in greatshape. But they were busy and couldn't get much info from the guy there.Sorry for the long post.Chuck
Reply:Can you post pics?Are you cleaning the metal? there isn't a thick coat of mill scale or anything is there?I almost wonder if you are moving too fast. Try slowing down a little bit. Let the puddle build and go a little slower. Also pulling the gun gets you better penetration than pushing. Keep the filler in the puddle but near the leading edge. Pics would be helpful though.Lincoln precision TIG 275Millermatic 140 MIG
Reply:Thanks for the helpYes I'm wire wheeling the pipe, I even flap disc a couple of pieces.Yes I'm at the front of the puddle and it seems like its a fair size bead asI'm zig zag across for more weld area and to help build heat. This is acorner bead.And yes I'm pulling.I'll get a couple of picts when I'm at the shop tomorrow and post them.Thanks Chuck
Reply:If it's a corner joint are you doing it open like this?If so penetration shouldn't be hard.Lincoln precision TIG 275Millermatic 140 MIG
Reply:No, maybe I said that wrong.I cut off about 8" of 2" tube then cut off 2+" again of 2" and the long piece is horiz.with the small piece running vertical. Maybe a butt weld but it forms a 90.Thanks Chuck
Reply:Crap, Its an inside corner. Couldn't think of it for the life of me jeezChuck
Reply:Ah gotcha.How are you determining your depth? Did you cut it or try to break it?Lincoln precision TIG 275Millermatic 140 MIG
Reply:Well you're not going to get great direct penetration off the MM175 and things like 3/16ths if you want to do it with arc power alone and no joint prep. The .030 is the better wire tho. The MM175  just doesn't have the whatever to get the full benefit of .035..You will be able to get real decent fusion, just not great depth of penetration without some joint prep. For penetration you'll need to make a quick run around the edges to be butted and grind those down to about one half of the 3/16th or or more. That 3/16ths will be easy to do at about a 30º angle. Quicker than you'd think even with a flap disc. Get the rest of the strength with the fillet.
Reply:3/16" ?Do the Plans call for this ? Seems like 1/8" would do.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Originally Posted by CCT Only doing teststrips now and with the .030 getting about 1/2 of the 3/16"
Reply:Thanks a lot guys!yoshimitsuspeed, Pried up the scrap piece as only did one side.Sandy, Grinding the edge sounds like a good idea.Broccoli1, 3/16" is what the plans call for. Most of the good rotisseries arethis to help it from sagging. Good to hear that's enough penetration. Witha car shell hanging there I want to make sure it stays I don't wantto be one of these Thanks all for the helpChuck
Reply:If you want full penetration, prep your joint like this.  The rounded corner of the side tube allows full penetration on the groove weld.  The bevel on the end of the other tube allows full penetration on the fillet (inside corner) weld.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Originally Posted by Broccoli13/16" ?Do the Plans call for this ? Seems like 1/8" would do.
Reply:DesertRider33, Thanks for the info and pictures. Good infoAs far as the rotisserie goes 2 1/2" is the largest tube size. Of course manyparts to it but many have built it. It has 10" tires, jacks and it has redundantsafety backups to it. And yes its a one hand turning unit.Chuck Attached Images
Reply:That's pretty elaborate. It should be a fun build.
Reply:That's a ton of load on each of those t-joints on each end of the car, the part that holds the pieces that  attatch to the car.  I'm not an engineer, but I'd use at least 1/4" thick tube in a larger size, 3x3 or bigger, and add tube braces on each side at 45* angles as far up and out as possible, similar to how the bases are braced.If you know how to stick weld and have access to a dc stick machine, you can run a root pass with 6010 or 6011 to ensure you get deep penetration and then run a cover pass with 7018.   Otherwise, with mig, I'd use a bigger machine capable of spray transfer, which is much hotter and gives better fusion and penetration on thicker metal than short circuit transfer.  If you look at trailer hitches on trucks, they're not done with short circuit mig.  Super hot spray mig is what the hitch manufacturers use.The joint prep I posted pics of above works good for getting full joint penetration with mig, if using a machine with enough heat.  I used the Millermatic 350P on that with spray and pulsed spray.  The tubes were 3/16 2x2.  I cut a joint apart after I welded it to test the procedure, since this project  was an excersize gym that could kill someone if it were to break and fall down on somebody.   When I measured the cut apart welds, the fillets were 1/2" thick and the grooves were 5/16" thick. Plenty of weld there to hold it together for the life of the structure.Last edited by DesertRider33; 12-06-2009 at 02:48 AM.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Originally Posted by DesertRider33That's a ton of load on each of those t-joints on each end of the car
Reply:I'm afraid you've reached the point that a lot of guys eventually reach.  You've outgrown the small wire welder.I harp on this more than everybody wants to hearStart with a good Lincoln/Miller/Hobart stick machine, then buy the wire machine later.  Unless you go out and spend 4 figures, you won't get a wire machine capable of anything more than relatively thin material.With stick, a lousy looking weld can be very strong(well, there are limits) because of the heat capabilities of the machine With wire, a beautiful weld can be weak if the paramaters aren't correct.115v machines are also sensitive to extension cord length and guage.  Longer cords cause voltage drop, and can be a weld ruiner.I don't fault the guys that go out and buy these machines as their main welder.  I fault the manufacturers for pie-in-sky ratings they give the machines.  People believe what they see on the box, or side of the machine.  Under perfect conditions, perfect prep, and with an experienced dude at the trigger, the machines will do the job........just do it.Even though the machine may not kick off when overheated, the duty cycle at high volts/amps is limited and the current drops off to some degree before the breaker trips.If you have concerns about penetration you're smart enough to be worried.  2-400 dollars invested in a good used stick machine is cheap insurance.  It's gonna be your skinny azz under that car.  (besides, once you start burning rod, you'll never go back the smell, the slag, the general filth and the smoke)If this were a static load my concern would not be as great as it is.  But you're dealing with a moving load which really increases stress on joints and materials.  And the fact that the load is over your head increases the safety factor requirements 4 fold."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Thanks for the concern guys.The rotisserie is rated at 3 tons and like I said many have been built. The bodyshells which are stripped are only 7-800lbs but some have left on the frame andare over 1,000. That t bar is 2" with 1 1/2" x 3/16" angle on the sides and 2"x 3/16" strap on the flat side. The sch. 40 round pipes are welded in and 2 more layers of 1/4" flatis added. Most of these things bow in the middle some, this one has very littlebow to it.There are rotisseries sold that are only 1/8" and they work....but I wouldn'tbuy one. Here is an example http://www.gregsmithequipment.com/Pr...Show=TechSpecsChuck
Reply:farmersamm,We most be posting at the same timeBought this miller 175 for my ac business and all I need it for is 1/8" angle, buthave since used it for 20 ga.  up to 16 ga on my cars. Its fine for that but your right is loaded for this. I can borrow my buddies Lincoln 250 which I'm sure itwill do this thing but wanted to work mine if possible. Btw this one is 220 not115.I'm also building this thing so my butt is not under it  but standing beside it. I'm6'2 and if the car is rotated on its side it will be about 1-2' taller. Thanks for thegood info I'm taking it all in.Chuck
Reply:What no one has pointed out is that there is a difference in penetration, depending upon the type of gas that you are using.  Pure CO2 will give the most penetration, though some will argue about the quality of weld produced,  it is the gas of choice across the world. It won't be smooth or clean, but it will put the wire in there much deeper than an Argon blend.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:Originally Posted by lugweldWhat no one has pointed out is that there is a difference in penetration, depending upon the type of gas that you are using.  Pure CO2 will give the most penetration, though some will argue about the quality of weld produced,  it is the gas of choice across the world. It won't be smooth or clean, but it will put the wire in there much deeper than an Argon blend.
Reply:Originally Posted by DesertRider33Agreed.T-11 fluxcore wire would also be a good choice for increased penetration.  Cleaning between passes is required.
Reply:My 2 cents...which may be worth more or less depending on the exchange rate for the day...You should have a bit bigger machine..250Amp.You can preheat the parts, which will help with penetration.Using a 75%Ar/25CO2 mix will help with penetration if you stay with the 175Amp machine.You should push the wire, and not pull. Age old saying, if it has a slag, drag...Which brings up the next point, a flux cored wire will help you out a bit.If I was going to be working under this, I'd do a mock up joint, weld it up and then do some destructive testing on it to make sure the welds will perform.  (sounds like you are doing this already!)As far as sizing of tubing ect, hopefully you are working off of some sort of engineered plan.
Reply:Pulling the gun yields deeper penetration and a narrower bead than pushing.  Pushing yields shallower penetration and a wider, flatter bead.You need good heat to get good fusion and wet in the toes, as well as penetration.   Joint prep can help with penetration, but only heat will get you the fusion with the base metal.  Poor fusion = weak bond = failure of weld.  Fluxcore wire burns hotter, so is able to weld thicker sections with the same machine than solid wire and gas.  If the machine is a little small, using fluxcore and good joint prep can save the day.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith opDesert RiderI will only agree with your push vs pull on 2 conditions.  You have an experienced GMAW welder and he/she keeps the wire at the leading edge of the weld pool, and you are more concerned with the depth of penetration, and not the total penetration/bead profile.  Having a narrow, ropier bead with a deep but narrow penetration profile can get you into depth to width ratio issues and in certain joint types with high stress cyclic loading, lead to weld failures.  Agree totally with you on the "heat" (that's why sometimes with a bit of preheat, you can cheat with a 115V unit), and your flux cored comments.