MIG welding

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Ok. I have been MIG welding. I believe I have been doing decent lately. I have been laying decent welds from what I think..I notice everybody saying 3G and 4G and what not.. Well let me in on the secret.I guess I have been doing alright by doing the circles and laying a nice bead.
Reply:3G and 4G refer to weld joint positions, ie: flat, horizontal, vertical, overhead, etc.  I forget what position each number refers to.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:OH ok.. I have only been doing flat. Is it harder to weld with a MIG overhead?I am going to have to weld over hear when I weld my subframe connectors.What am I trying to accomplish when I lay a bead? All I am doing now is just trying to get the circle marks in the finished weld. Is that a good way of looking at it?
Reply:Flat is the easiest position.  T-fillets and butt joints are probly the easiest flat position joints to learn.   All the other positions are more difficult than flat.  Overhead is not that much harder, except for the hot metal falling down on you that you dont get when welding in the other positions.  Verticle is the hardest, for me anyways.It is most important that your weld penetrate all the way through to the inside of the joint and that you fill the joint completely and dont have undercut at the sides or cold lap at the sides, or porosity.  The look of the surface of the weld is less important.  It's more for aesthetics than strength.   A nice weld can look like a stack of dimes like a tig weld, but a weld can be just as good and have smooth appearance on top too.  Concentrate primarily on welding a strong joint, then worry about what the surface looks like after you have the basics down.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Originally Posted by pyroracing85OH ok.. I have only been doing flat. Is it harder to weld with a MIG overhead?I am going to have to weld over hear when I weld my subframe connectors.What am I trying to accomplish when I lay a bead? All I am doing now is just trying to get the circle marks in the finished weld. Is that a good way of looking at it?
Reply:Originally Posted by DesertRider33Flat is the easiest position.  T-fillets and butt joints are probly the easiest flat position joints to learn.   All the other positions are more difficult than flat.  Overhead is not that much harder, except for the hot metal falling down on you that you dont get when welding in the other positions.  Verticle is the hardest, for me anyways.It is most important that your weld penetrate all the way through to the inside of the joint and that you fill the joint completely and dont have undercut at the sides or cold lap at the sides, or porosity.  The look of the surface of the weld is less important.  It's more for aesthetics than strength.   A nice weld can look like a stack of dimes like a tig weld, but a weld can be just as good and have smooth appearance on top too.  Concentrate primarily on welding a strong joint, then worry about what the surface looks like after you have the basics down.
Reply:You will accomplish penetration through- joint prep, heat/wire settings, and torch movement.  Depending on the joint, you may need to grind a bevel on the edge of each piece so your weld can get down fully into the joint.  This is useful on butt joints.  You wont need to grind on a t-fillet joint.  You also wont need to grind a bevel if you're welding thin material. You can also help get penetration by leaving a small gap, say 1/8", between the pieces and tacking them into place before you weld to help allow the weld to get down in between the plates.You need to set the voltage so you have enough heat to melt the wire and both pieces of metal fully into the weld joint.  Then you need to set a wire feed speed fast enough to fill the weld with filler metal but not so fast that the weld goes cold.  Use the settings chart that comes on your machine to help you decide what voltage and wire speed to set, then experiment to see if you need a little more or less of either for the type of joint and how you're moving the torch.As you're welding, you will need to decide what speed to move the torch to keep a puddle of the right size going to penetrate and fill the joint.  You will also need to decide if you need to move the torch side to side or go straight to fill the sides of the joint and get both pieces of metal melted into the joint equally.  On a t-fillet joint, this usually means going back and forth from one plate to the other untill you build up the weld size to match the plate thickness.  On a butt joint you may need to do this too if you had to grind a bevel and the joint is too wide to fill just by moving the torch straight.  You'll also need to concentrate on holding the torch at a constant distance from the metal, as well as at a constant angle to the metal as you move along the joint so that, together with moving forward at a smooth, constant speed,  you weld will have that uniform width and height that David was describing earlier.Just keep practicing and you will get it all after a while.  Pay attention to your puddle.Last edited by DesertRider33; 01-21-2008 at 04:41 PM.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Thanks a lot guys. I will try to keep the width of my metal consistent. I still don't know how you would check for depth and compare depth to width.
Reply:Originally Posted by pyroracing85Thanks a lot guys. I will try to keep the width of my metal consistent. I still don't know how you would check for depth and compare depth to width.
Reply:Ya don't need no stinkin dimes!David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Watch the puddle as you go, you want to be melting both pieces of metal and flowing them into the consistent bead mentioned above.If you don't want to stand behind our Troops, feel free to stand in front of them.
Reply:Dimes, schimes...  LOL... 1G flat,2G horizontal,3G vertical,4G overhead...And sometimes you can be in those positions but weld in different directions and that will completely change how you weld...  I.e. left to right, or right to left...  bottom to top, top to bottom... etc.. etc...
Reply:Originally Posted by David RYa don't need no stinkin dimes!David
Reply:Dimes are for the kids! My first production welding job was at a place calle Hutchens ind. We made trailer truck suspentions 90% world wide. This is the best known in the world. All of our welds were smooth as glass. When the parts were welded by hand like when I started I was 16. If you weld was not smooth it was you butt and you would be on the road. I personally welded 100,000 plus parts by hand and all were smooth what we looked at penetration you had one part cut everyday and iodine rubed on the cut. If it was bad the line stoped and they pulled parts from the day and tested them. To my knowlege there has never been a main component failer. My dad retired after 46 years and he was the plant maneger so he would have known. Steel Thunder Welding LLC. St. Thomas VI USAMM350PBOBCAT 3MAXSTAR 150 STH375 EXTREME PLASMA6.5 HP COMPRESORDEWALT 18, 24, AND 36 VOLTO/A TORCH SETAND SO MUCH MORE I DONT REMEMBERALL IN MY 2005 2500HD EXTENDED CAB L/B
Reply:Perhaps this will help.http://www.millerwelds.com/interests...rs/pdf/MIG.pdfDavid Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by David RPerhaps this will help.http://www.millerwelds.com/interests...rs/pdf/MIG.pdfDavid
Reply:OK, I welded some 1/8" plate in a butt weld.  1/16" gap between plates with SP100 on J8 (the highest setting)  C/25 gas, .023 wire.  I went back and forth from each piece.  I can tell I got full penetration because there is a bead on the back side.DavidReal world weldin.  When I grow up I want to be a tig weldor.