Mig Tacks And Cool Water ?

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Hey Guys.I'm practicing on 18 gauage sheet metal with a gap of about 1/32 in. I'm using my MillerMatic135 welder.My first practice was coming along fine till towards the end of sealing it ~ I BLEW SOME BIG HOLES IN IT Anyway, I have some more practice plates lined up.My second practice plate I tried something different. After spacing my first row of tacks roughly 1/2in. apart. I poured cool water over the tacks. I continued doing that each time my tacks got closer and closer to each other.Tacks some, water plate. NO WARPAGE Still watch-out for HEAT WARPAGE, I finished all the tacks and seal the plate.It can out nice.QUESTIONS:1. Do you think that the cool water will have any effect on the weld ?2. Do you guys have another suggestions other than what I've done ?Thanks GuysGOD BLESSSCHOONER
Reply:Can I ask some questions?What size wire are you using? What gas?How big are the plates?When you say warpage, do you mean the weld is shrinking, pulling the plates up of the table? Have you tried clamping them?Even with 18 ga. you should be able to run a bead without blowin holes and quenching it. Quenching CAN make it more brittle. Try running the bead continuously, but do it vertical down (downhill) and fast.I am not familiar with you machine or its setting but I can try to help Last edited by Burnit; 08-01-2008 at 08:41 PM.Yup
Reply:Be very careful with water and welding. There is an electrocution hazard.It would be best to use a damp cloth.Putting water on a weld immediately after welding can affect the temper.Putting water or damp towel next to the weld is a different story.The end result of all welding is shrinkage. The metal WILL swell up at first but as it cools it actually shrinks.  That is why it should be tacked FIRST.If a sheet of steel is welded around the outsides the outside edges shrink and you can have warpage. For instance welding the cabin roof on a steel boat.Afterwards you can take a torch and heat spots in a grid and immediately apply a damp towel to the spot you heated, the metal in the center of the roof will also shrink and will have the proper fit up. so this is a technique that CAN be used. Just do not apply water to a just completed weld.AWS certified welding inspectorAWS certified welder
Reply:Are you making a "weld bead" strictly out of tack welds?Miller Syncrowave 180SDMillermatic 175
Reply:With mild steel and wire, I don't think you will hurt the welds on thin plate with water.  It will be just as strong.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Mild steel is not heat treatable so dunk it or spray it or whatever. I usually let the red go out before quenching but I don't think its necessary since it won't harden. I've done it for a lot of years and never had a problem.
Reply:Originally Posted by OldtimerMild steel is not heat treatable so dunk it or spray it or whatever. I usually let the red go out before quenching but I don't think its necessary since it won't harden. I've done it for a lot of years and never had a problem.
Reply:Like I said , I've never had a problem doing it and that's for over 40 years. If you arent comfortable with it, don't do it. I'm just telling you what has worked for me.Last edited by Oldtimer; 08-03-2008 at 05:05 PM.
Reply:Originally Posted by BurnitCan I ask some questions?What size wire are you using? What gas?How big are the plates?When you say warpage, do you mean the weld is shrinking, pulling the plates up of the table? Have you tried clamping them?Even with 18 ga. you should be able to run a bead without blowin holes and quenching it. Quenching CAN make it more brittle. Try running the bead continuously, but do it vertical down (downhill) and fast.I am not familiar with you machine or its setting but I can try to help
Reply:If you are blowing holes in the thin stuff you heat is to high or you are going to slow. Try .030 wire. I use a spool gun with .030 on the thin stuff.
Reply:All to AVOID WARPAGE. Meaning the twisting out of shape of my practice plate due to over heating with my welding and grinding. I took a basic mig auto-body class, we used .023 wire. I don't remember what gauge we used but the coupons were about 2 x 3". All warped some. Our beads were 1 1/4 to 1 1/2" long.You'll need to make a LOT of tack welds, no beads. 1/2" is too long. I saw a thread somewhere showing tacks at 2" spacing, splitting that to 1" then 1/2", etc. The poster had no warping. Sorry, I don't remember where it was. He used butts not flanging.One other thing to find out about is 'planishing'. Tack then hammer & dolly immediately. One tack at a time, over and over......... That's all I know about it though. 9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:Originally Posted by SCHOONERHi I'm using .035 mig wire with 15bls. gas mix: 25% oxgen 75% argon.GOD BLESS
Reply:Originally Posted by KubsBut couldn't you crack the weld even if its not glowing red due to rapid thermal contraction?
Reply:Welds are hot. Metal expands when heated and contracts when cooled. Welds shrink. Quenching it will restrict the area that shrinks but it's still gonna shrinkPreventing the area from getting as hot will reduce shrinkage and thus distortion- as said one method for bodywork with MIG is to keep tacking until the entire seam is welded. A wet rag will keep the heat from building up to allow you work fasterPlanish: to make smooth by hammering. Hammering 'on dolly' will squash the highs down and stretch the metal where it contacts both the dolly and hammer headMIG welds are relatively big, several times the metals thickness in this case and too thick to planish out. Assuming the back of the panel can be accessed i would knock down the weld (flap wheel etc) before planishing- you need to be somewhere close to gauge how much planishing is required to stretch the shrunk area AND only the shrunk area. Overstretch it and the problem gets bigger