gas or flux on thicker metal

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I have this welder...[ame]http://www.youtube.com/watch?v=G9wN5gZVc6Q[/ame]The lincoln powermig 180c When doing bigger jobs, like 1/4 or even 3/16in steel am I better off going to flux core or pre heating the metal with a torch then welding with gas? Most of the thicker stuff like 3/16 and 1/4 are brackets on a frame for suspension. TIA, ChrisLast edited by New2Fab; 01-31-2013 at 12:05 PM.
Reply:Fluxcore will get you better penetration without preheat.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:I built an automobile rotisserie with a Lincoln HD 180 (home depot, tapped version).  I welded and cut up about 40' worth of 2"x2"x3/16" before I would trust my welds.  Even at max power, I could not get sufficient penetration with the 180hd with single-pass using hard wire and gas,  it had to be flux core.  That said, I'm sure there are many with more skill that could do it, or I could have done multiple passes.MillerMatic 252, HTP 221 w/cooler, Hypertherm PM45, Lincoln IdealArc 250 AC/DC"I'd like to believe as many true things and as few false things as possible"
Reply:Only pipeliners weld 100% penetration passes.  Everybody else welds one side, grinds our gouges out the other side, then builds passes until they have a nice bead.  Ceramic tape welding would be the only exception.
Reply:Honestly if you have to ask this question, you probably aren't ready to weld up any suspension components. I'll also comment that I hope these brackets are bolt on vs welded on, since welding brackets to frames is usually a bad idea for quite a few reasons I'll get to later.Given a choice, I'd opt for solid wire and gas vs flux core for a different reason. I see way too many people who are new bury slag when welding with stick and FC wire. That's not an issue with solid wire/ gas. The down side to solid wire is that it's easier to make cold welds that look pretty to the untrained eye, but lack penetration.That machine should be more than capable to do 3/16" with solid wire and gas as long as you stay within the duty cycle limits on that machine, use the right size wire and do good prep. 1/4" is pushing the machine to it's max, and for something critical like a suspension component, I'd really want more output than that machine has to be safe.As far as welding to vehicle frames. Many newer vehicles have high tensile alloy or heat treated frames, and most manufacturers do not recommend welding to them as they require very special fillers and weld procedures. Also on average I've found very few "hobby" welders who can make good code quality welds in vertical and overhead positions that are almost a requirement any time you need to weld on a frame. Most times these people can't control the puddle, so they end up with huge amounts of undercutting, many times severly weakening the frame next to the weld rather than increasing it's strength. Also many times, to compensate for the undercutting they have made, they keep welding on top, increasing the heat input which is very bad for HT and treated steels. Also there is a tendency to compensate for lack of skill in vertical by welding vertical down vs vertical up. Vert down gives you very little penetration even if it gives you a "pretty " bead. That's really the wrong thing for structural components. Note that most components attached to a frame are usually put on with rivets or bolted connections, rather than welded from the factory. There are quite a few reasons why engineers choose to assemble the components this way..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan