tig welding alum.. serious questions
 

my work has me welding lift eyes into $7000 heat exchangers and ive never welded aluminum before. So i practiced on some scrap 1/4" plate welding a bunch the 1" round lift eyes on. After about 4 of them i got the hang of it, but today i set everything up to weld on the heat exchanger and i cant get it to melt. The lift eye will puddle, but not the h/e. Do i have to preheat it because of its size? its 5'x4', .250" wall on the endtanks. Im guessing the huge difference in extra metal is pulling the heat out of my weld. The tungsten was also eroding, i could see it spray transfer into the weld, too many amps for 3/32? Heres settings on the welder and all

h/e was SS wire wheeled (for alum only)
Best weld hydrochloric acid alum cleaner used after that
Old school industrial style miller tig. 460v 3ph set on high and 55-65%, which should be about 250-300amps
weldcraft water cooled torch
#6 cup
green tungsten ground to a point and then i weld on a scrap piece to ball the end

for my first time welding alum, my scrap pieces looked real good. But i already ground down one of these heat exchangers and tacked on the lift eye, im pretty locked into finishing now and im kinda stuck. Someone help me out by monday please! My tungsten is tuning oil stain rainbow color and the ceramic cup glows for a few seconds when im done welding. The tungsten will also burn back the 3/32 it was sticking out of the cup in about 30 seconds of welding. Am i not using enough heat? And staying in the same spot to try and get a puddle going is getting it too hot? alum is wack yo.. ill try and get some pics of the good practice welds

Re: tig welding alum.. serious questions
 

are you sure the welder is set on AC and not dcep, also does your machine have waveform controls?
what i think is happening is someone screwed with the machine and turned the clean action (electrode positive) too high and its causing your tungsten to melt, becuase all the heat is going into the tungsten and not the workpiece at that time. you meed to just turn the balance more to negative or 'penetration' as it may be called. also it is useless to grind to a point as it is just going to ball up in notime, i just stick it in there without grinding or anything.

Re: tig welding alum.. serious questions
 

def turn up the frequency anf you are gonna need at least 300amps .def need bigger tungsten, 1/8 should get you through the job but will start to fail at 350+ amps so you may wanna get a stick of 5/32 tung and go with that to begin with.

Re: tig welding alum.. serious questions
 

The welder is definetly on AC, its kinda hard to mistake that sound when your welding. i fucked with what i thought was the waveform adj under the door on the front of the welder. It has 2 high freq adjustments. Start (which is on the front panel) going from 0-100%. Im assuming this is how hot the HF start arc is but i dont really know. The other one is under the front panel of the welder and it just says high frequency on it, also going from 0-100. I assumed this was the waveform adj, but should it be labeled + from 0-50% and - on the other side from like 50%-0? Either way, it was set at 30 and i turned it up to 45 and it definetly started to weld better. I did do some reading on the EP and EN cycles of the AC current and how it affects the weld. Still kinda hard to say if the knob i fucked with was this or not.

No one has any thoughts on the preheating? Like i said, my practice pieces came out really nice looking for my first time doing alum. No settings were changed on the machine, just went from a 4"x2" piece of .250" plate and 3 of the lift eyes welded to it, to the 5'x4' or so heat exchanger. Could it be diff alum alloy? Maybe i need different rod? I dont even know what ---- im using to tell you the truth, we have 2 blue containers for alum- the thicker ---- worked better.

Re: tig welding alum.. serious questions
 

frequency is measured in Hz and balance is in %.

frequency is how many times a second the polarity changes, more Hz and more heat gets put into the aluminum per second. it also has arc shaping abilities as well. more Hz more focused arc, better penetration

balance is the percentage of + and - in one change in polarity. less balance = more cleaning, broader arc. a good starting point is 55-60%, you want the least amount of cleaning as possible as it will start to affect penetration.



grab some scrap and start playing, using scrap from the same material you will be final welding is best so you can figure out your settings before going to a final product



i dont know the adjustment ranges on your machine but i would start 325amps, 65-70% balance, and 225hz (prob gonna need more though, unless you like waiting ten minutes for a puddle to form)

Re: tig welding alum.. serious questions
 

no hz adj on my machine. Just arc start and the knob inside that only says "high frequency" 0-100 scale.

Re: tig welding alum.. serious questions
 

i have no idea about welding but like the advice your getting on the question. makes me feel good when somebody has enough confidence in HMT to come here for advice for welding at work ;D. my other question is, if your boss knows you cant weld it why woul dhe ask you to without teaching you or showing you the proper settings?

but like guy above said, would be best to practice on same materials you will be doing final work on. sounds like your almost there.

Re: tig welding alum.. serious questions
 

I tig welded a few stainless parts last week that looked pretty good. Having a foot pedal instead of bullshit lift arc makes a huge difference. So the other day my boss asked me if i ever tigged alum before.. i told him i could probably figure it out pretty quick if he wanted. No one else in the shop can tig alum so he had me practice for a whole day. yeah i got paid for that ;D My test pieces were on 1/4" plate with the same lift eyes on it, but the plate was only a foot long or so, not nearly the amount of alum in the heat exchanger.

Doesnt really matter anymore, i had to go out on the road today and they had a guy that lives next to the shop mig them on with a spool gun, he did a shitty job

If anyone else does have any advice to what may have been going on *engloid* Id still like to know

Re: tig welding alum.. serious questions
 

its nice to work at a place that lets you play. thats all i did once a week for the first few weeks at my current job

Re: tig welding alum.. serious questions
 

your balance was leaning too much towards cleaning