Hell of a time welding on thick aluminum.....

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Hello fellas and possible ladies present,I worked on a project today for a client that involved cutting and welding a pair of end plates with holes drilled in them onto a pair of I-beams.  This was heavy aluminum plate.I have rarely worked with aluminum over 1/4" and this stuff was 1/2" plate and the I-beam had 1/2" flanges.  I have never tried to weld aluminum that thickness before and I will say I had a hell of a time with it.  I was able to tack the plates in place and weld half of the plate and burned up the water cooled power lead.  I was welding away and my customer (who was helping out) noticed smoke pouring from my welding machine.  Luckily it was the tig torch power cable and not something worse.I replaced it and increased the pressure coming from the water cooler's pump as I attributed the burn out to lack of coolant circulating quick enough to keep the cable cool at the temperature I was working in.  It stayed cool after that.  I am going to invest in one of those fuse link type connection that goes between the power lug and the power cable.  I have read that they will prevent such a burn out from happening.  I have to date burned 4 of my cables.  Three of them for forgetting to plug my water cooler in ( I couldn't stand the noise of it and would unplug it for stick welding and forgot to plug it back in.).  I now live with the noise and even find it reassuring.  No more burn ups due to that cause.In the normal course of my work I will probably never be called on to weld aluminum that thick again.  As it is this is the first time in seven years that I have been free lancing that I have had to do so.  I had to stop the job and bow out of it because I was not satisfied with how it was turning out.  I billed only for cutting and fitting the plates onto the beams (drilling the holes, etc.).  My client was a good about it and I cleaned up the welds where I goobered it so the next welder would have a clean surface to work with.Here's what happened:1) I preheated the aluminum prior to welding as I had often read about when welding heavy sections.  I used a 200 degree temp stick.  When I tried to start my puddle I noticed that instead of getting nice and shiny, it was acting as if it was contaminated and got an oxide film right right away.  I couldn't get the puddle started.After swirling the torch around one spot it finally began to give me the beginnings of a puddle but when I tried to dip my rod into it, the arc force blew it away almost immediately.  Thus in order to feed the puddle I had to stab the rod quickly into it and withdraw it in the blink of an eye.  Once I got my fillet weld started, then the puddle seemed to run easier and I could feed it and progress normally.  This was because once the puddle started I could touch the rod to the edge of the puddle and it would be sucked right in and continue the puddle.The trouble I had I attributed this to the fact that the heat was probably being drawn away too quickly and that the aluminum was not ready to weld.2) As I approached the corner, where the web meets the flange, I found I needed more stick out in order to see what I was doing and to get the cup out of the way so I could feed my rod into the puddle and turn the corner.  I found that as soon as I increased the stick out, it was like I was welding with out an argon shield or like when you are running out of argon. The puddle just fizzles and looks all ****ty and black.  Wow!  I was using a gas lens and a 1/8" tungsten.  I was using 1/8" rod.I found that the only way I could get a decent puddle going and running was to keep my stick out to no more than 1/4".   I had a hell of a time turning the corner to weld the flange to the plate.3) I had my client hold a torch to the beam while I was welding and that helped considerably but the arc still behaved erratically and I was not satisfied with the bead being laid down.  I stopped and suggested to my client to take it to a shop that had a beefier welder than I .  I use an old Hobart TR-250 HF.  It has served me well for several years without a hitch on all types of repair and fab jobs with lighter metal.  I was somewhat embarrassed and humbled by this experience.I am hoping that others can jump in and tell me what I was doing wrong.  I noticed that at higher amperage (at least with my machine) the arc would wander a lot and would tend to dig in rather than create a nice puddle from which I could start the bead.Could it be that I needed a bigger torch (and tungsten) to do this job?  I'm somewhat at a loss and so far am still summing it up.  Is it true that the tungsten stick out must be minimal and that further stick out is not recommended at higher amperages?  As soon as I put the tungsten back to 1/4", the puddle smoothed out and behaved better without the lack of gas coverage symptom.Anyone have some thoughts on this?Thanks,Tony
Reply:Huh? I don't get it?Last edited by 7A749; 01-09-2013 at 07:31 AM.ESAB Migmaster 250Ltec ST23 spoolgunMiller Passport
Reply:Originally Posted by SLAGINSHOEHuh? I don't get it?
Reply:Originally Posted by Drf255Spam.
Reply:I welded some pretty thick aluminum pipe in a fab shop a long time back, the inspector had us run straight acetylene flame on it with the rosebud till it was black as hell with soot, then turn on the oxygen and heat the hell out of it till the black went away, then it was ready to weld. I don't know how hot it was, but I'm guessing it was a lot higher than 200 degrees.
Reply:Might be time to talk to BC about DC TIG with helium.http://weldingweb.com/vbb/showthread.php?t=205071Jump down to post 13.Dynasty 300DXSmith He/Ar gas mixerMM350PHobart Handler 120Smith LW7, MW5, AW1A
Reply:You need a 330A/BP set to Kill as Zap would say or maybe time to buy a Dynasty 700 heh! And a torch that can handle the current.  Props for doing right by your customer though...Tiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:So could this have been done with aluminum MIG?  What kind of amperage would that take for something this thick?
Reply:Welded  a 1/2" thick aluminum bridgerail H-post to a 3/4" base plate last year. Used my Miller 211 and Spoolmate 100 loaded with .035 and preheated fairly hot with acetylene. For a fairly light duty rig, it did a reasonable job with a couple of passes. Can't vouch for the penetration, though. Just a one-off emergency repair. Thing is still standing tall.