Warping metal

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I recently just purchased a millermatic 251 MIG and am trying to weld some 1/2" plate - steel. How do you weld stuff without warping the crap out of it? it is basically a 1/2" plate and im welding a 1/4" thickness x3"x6"tube to the top of it. the plate is roughly 12" long by 6" wide. i tack the tube into place so it is square and then i run a bead around it by the time i get that done the 1/2" plate is warped around 1/8"-3/16" in the center..... so when i do the next one would i just want to keep tacking it untill i have it completly welded? and if so dosent that weaken the weld to not have a continous bead around the whole thing??? It needs to be very strong because it is for a car rotesseire - i have welded many things before but never any thing really huge - i mainly do sheet metal work where you must cool often.... any comments would be appreciatedLast edited by turbotoys; 07-10-2007 at 09:23 PM.
Reply:Extreme heat + metal = warping ...even more with Stainless Steel. Take your time with it. Tack in a few spots, weld a 1/2 to 1 inch bead then let it cool. Either that or do the opposing side, then let it cool. After it is just warm to the touch or a bit more, hit the other two sides. Always weld opposing sides...like tightening the nuts on a wheel - tighten, move to bolt across from it, tighten, move to the other bolt across from that bolt, etc., etc.BTW - welcome to Weldingweb!John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:Originally Posted by turbotoysI recently just purchased a millermatic 251 MIG and am trying to weld some 1/2" plate - steel. How do you weld stuff without warping the crap out of it? it is basically a 1/2" plate and im welding a 1/4" thickness x3"x6"tube to the top of it. the plate is roughly 12" long by 6" wide. i tack the tube into place so it is square and then i run a bead around it by the time i get that done the 1/2" plate is warped around 1/8"-3/16" in the center..... so when i do the next one would i just want to keep tacking it untill i have it completly welded? and if so dosent that weaken the weld to not have a continous bead around the whole thing??? It needs to be very strong because it is for a car rotesseire - i have welded many things before but never any thing really huge - i mainly do sheet metal work where you must cool often.... any comments would be appreciated
Reply:Could you put a hole in the 1/2" and weld BOTH sides of the tube?DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:You can control that kind of warpage depending on the time you want to spend. Good method is to do about like ZAP says and clamp/clamp/clamp only maybe add a thin spacer under the plate in the area to be welded and then clamp the perimeter. You're putting counter directional forces in place. With the heat input abilities of a 251 you might even get some relaxing in the opposite direction of the expected warpage. If you still get some warpage in the expected direction then some heat on the backside just might bring it back. Some have been known to weld a mirror image of the bead on the backside to bring it back into alignment then grind that bead flat. I'd use some heat and influence.
Reply:Originally Posted by zapsterInstead of going back and fourth...For what your doing you need major clamping to a table..No way around it...You can't just blast away at it without it being pinned down.. You can skip from side to side once tacked on the ends for an inch or so each time...But counterclamping is in order to do it in one shot......zap!
Reply:i sometimes have problems with square tubing, especially long pieces. i put 200 clamps on the piece ,weld a little, skip from one end to the other.just when i think its perfect, i take the clamps off and then viola, a warped and twisted mess. nothing a little heat and my bfh cant fix, but its still a pita!
Reply:thanx for everyones input - i think im going to try the clamping process and the 1" beads at a time - see how it turns out....
Reply:As another suggestion, I remember seeing in a video that you can TIG braze steel parts with silicon bronze filler and you will get far less warpage.If a part is critical and brazing would be strong enough, that might be worth a try.Favorite right now is a Miller Syncro 200.Tons of tools and I blame at least one of them when things don't go right.