It is currently Fri Dec 19, 2014 11:45 pm Advanced search

Aluminum weld cracking!!!!

Tig welding tips, questions, equipment, applications, instructions, techniques, tig welding machines, troubleshooting tig welding process

Aluminum weld cracking!!!!

Postby sz.barti » Sun Mar 03, 2013 11:59 pm

Hello welders!

I was welding checker ally plate 6 mm tick and during tackink the tack had cracked every one. When I start welding it weld cracked to question is why?

Facts: I was useing 2.4 ally filler with 5% silicone welder was setup around 200 amps plate was v grooved on both sides half way, I did not preheated whole plate only preheated around 2 inches whit a tig torch in the place where I started welding going forward and backward and when puddle was hot enough I pushed the filler in and still cracked.

So mates what could be a reason? join was clean free of grease or anything els.

thanks
sz.barti
New Member
 
Posts: 6
Joined: Sun Mar 03, 2013 11:45 pm

Re: Aluminum weld cracking!!!!

Postby Colt45GTO » Mon Mar 04, 2013 1:59 am

sounds like a DC weld. i'm no expert but i had tried to weld ally with my rig, seems like a similar problem.
Colt45GTO
Active Member
 
Posts: 43
Joined: Sat Feb 23, 2013 5:42 pm

Re: Aluminum weld cracking!!!!

Postby TamJeff » Mon Mar 04, 2013 2:44 am

sz.barti wrote:Hello welders!

I was welding checker ally plate 6 mm tick and during tackink the tack had cracked every one. When I start welding it weld cracked to question is why?

Facts: I was useing 2.4 ally filler with 5% silicone welder was setup around 200 amps plate was v grooved on both sides half way, I did not preheated whole plate only preheated around 2 inches whit a tig torch in the place where I started welding going forward and backward and when puddle was hot enough I pushed the filler in and still cracked.

So mates what could be a reason? join was clean free of grease or anything els.

thanks

I don't know what 2.4 filler (size?) is, but depending on the construction of whatever you're welding, provided it's the right filler, it has to be hot enough and enough filler metal with aluminum. Tacks have to be robust and more so as the metal gets thicker. I tack 6mm with no less than 200 amps AC and make sure the joint is completely wet out to the root. I use roughly 9mm long tacks on 6mm and they are notably convex. If I was using 200 amps on cold fit ups, I would expect to have to wait a spell to get full penetration on 6mm only half beveled. I use 250 amps on 6mm for tacking cold parts. I rarely bevel aluminum. I gap it slightly larger than the diameter tungsten I am using. Try spacing two sections of it slightly larger than your tungsten size without anything in the way of the open root. You will get much more substantial tacks all the way to the back side.
Miller ABP 330, Syncrowave 250, Dynasty 300 DX.
Honorary member of the Fraternity of Faded Tee Shirts.
TamJeff
Weldmonger
 
Posts: 755
Joined: Tue Dec 04, 2012 4:46 am


Re: Aluminum weld cracking!!!!

Postby sz.barti » Mon Mar 04, 2013 5:20 am

Many thanx guys for quick respond.

TamJeff I have follow your advices and its ok many thanks, 2.4 filler is 2.4 mm (3/32) ally filler 4043 5% silicone. I have more plates to weld tomorrow so will try tacking up with gap instead of beveled it. Im using 3.2 mm (white tip) tungsten and when I turn the welder up to 250 amps tungsten get melted during the tacking why? I had AC balance set up around 80 % thats ok ? Or what could be the problem, I kept tungsten stick out around 3 mm over the gas dyfusor gas was setup around 20 l/min
sz.barti
New Member
 
Posts: 6
Joined: Sun Mar 03, 2013 11:45 pm

Re: Aluminum weld cracking!!!!

Postby WerkSpace » Mon Mar 04, 2013 8:21 am

Perhaps you should set your AC balance in the middle and then adjust it either direction to verify the effect.
Too much DCEP (Direct Current Electrode Positive) will cause your tungsten to ball up and melt.
https://www.youtube.com/watch?v=u-daLs9Q7ac

sz.barti wrote:Many thanx guys for quick respond.

TamJeff I have follow your advices and its ok many thanks, 2.4 filler is 2.4 mm (3/32) ally filler 4043 5% silicone. I have more plates to weld tomorrow so will try tacking up with gap instead of beveled it. Im using 3.2 mm (white tip) tungsten and when I turn the welder up to 250 amps tungsten get melted during the tacking why? I had AC balance set up around 80 % thats ok ? Or what could be the problem, I kept tungsten stick out around 3 mm over the gas dyfusor gas was setup around 20 l/min
User avatar
WerkSpace
Weldmonger
 
Posts: 580
Joined: Tue Jun 26, 2012 8:05 pm

Re: Aluminum weld cracking!!!!

Postby sz.barti » Mon Mar 04, 2013 8:50 am

Thanks WerkSpace I watched the video and it make a sense I had to set up AC balance a bit higher. Good video explain clearly AC balance

Thanks
sz.barti
New Member
 
Posts: 6
Joined: Sun Mar 03, 2013 11:45 pm

Re: Aluminum weld cracking!!!!

Postby noddybrian » Mon Mar 04, 2013 4:53 pm

Hi - I've limited Tig experience on ally as I did'nt have regular access to a suitable machine though I have gas welded , arc welded & mig'd it - but for what it's worth heres my take on the your problem

Is the Material type known - there are a few different alloys that tread plate comes in - not just 3003 etc - your filler rod should work fine if it is 3003 or similar but i think a larger size will help - I would struggle to keep up feeding 3/32" on that thickness & the disparity between rod size & material thickness I've found makes it more difficult - if you can't beat the cracking problem any other way it could be worth trying something like 4046 with more silicon - but you should'nt need it.

When tacking you say stated a current - if that was without a footpedal to taper off that would encourage cracking - if you can't taper off then at least use 4T setting & set machine to a lower end amps to reduce heat once tack is made.

The tungsten seems the right size so excessive heat / burning I would think is AC balance - if you can trust the machine to give acccurately what is set then 80% is too high - 65 > 70 is more like it - though every machine is a little bit different - the white tip at least in the UK is zirconiated & in a video where Jody tried a variety it did'nt hold up that well - it seems to be the most common they try & sell you over here for AC but I tracked down some 2% lanthanated ( dark blue tip ) which came out best in test & I've got on much better since buying some - also the finer the stone stone you sharpen on the better - I had very bad arc wander & even tungsten splitting from too coarse a grinding wheel.

If you can design the job to have open corner welds this will make it easier as well - that way you don't need as much heat input as the arc can get right to the root of the joint - if you have adjustable frequency then setting this up a bit higher helps - I've made some truck tool boxes out of treadplate - only 3mm but kept all the corners as open joints - the same as I would if using mig - some people are going to hate on me for this - but I found tacking easier with the mig - so I tacked up with that - then tig'd the seams - simply flowed over where the tacks were & the thing came out looking OK.

Gas flow seems higher than needed - you said 20lt/min thats like 40ish cfh - I would think 25 maybe 30 was more like it.

Ultimatley I think you have a combination of only getting a partial thickness tack due to material thickness & edge prep - so it's just the nature of ally to crack in these circumstances - however you achieve it the weld needs to be full thickness - & this may well be compounded by the small filler rod & trying to leave the tacks low so as not to spoil the appearance of the final welds - by adding a small amount of a small filler the effect is almost a fusion weld which ally does'nt like.

Hope some of this helps. good luck with round 2 !
noddybrian
Weldmonger
 
Posts: 730
Joined: Thu Jan 24, 2013 12:13 pm

Re: Aluminum weld cracking!!!!

Postby Otto Nobedder » Mon Mar 04, 2013 8:19 pm

I learned some hard lessons in tacking alumimum, which have been touched on here.

The two biggest things to bite me were: tacks too small... Should cover at least 5% of the distance between tacks, preferably 10% if it's appropriate. BUTTON OFF the crater at the end of the tack THOROUGHLY... That's the end the crack always starts from!

When tacking, the "button-off" is easy to ignore... after all, you're just holding stuff in place... BUT, aluminum shrinks so much (and shows strong cohesion draw, meaning your puddle wants to move to the thicker material on the sides) that the end of a "quick" tack is so thin it will tear from the cooling stress and start the crack. The only solution if you do this is to stop-drill and grind.

Button off that tack, so the finish is as thick as the start, and if your tack is big enough for the weld, you've solved the problem.

Steve S
User avatar
Otto Nobedder
Weldmonger
 
Posts: 4932
Joined: Thu Jan 06, 2011 11:40 pm
Location: Near New Orleans

Re: Aluminum weld cracking!!!!

Postby TamJeff » Mon Mar 04, 2013 9:55 pm

Otto Nobedder wrote:I learned some hard lessons in tacking alumimum, which have been touched on here.

The two biggest things to bite me were: tacks too small...
Steve S


You said it better than I but you're right, The let off ends up flush or even concave. I essentially cap the ends of my tacks, which also changes the draw rate and even the direction of the shrinkage.

I have seen so many times that aluminum welders will go directly from a print to finish sizes on their cut list, allow for prep even, weld an open root to extend materials and end up with a smaller than needed piece. I leave it wild, weld it first and then cut it to size, thus chasing the shrinkage to where it is minimal, such as an open corner.

Your description of the tack crater cracking appears on stitch welds too. I see spider cracks on a lot of stitches that have been let pass like that.
Miller ABP 330, Syncrowave 250, Dynasty 300 DX.
Honorary member of the Fraternity of Faded Tee Shirts.
TamJeff
Weldmonger
 
Posts: 755
Joined: Tue Dec 04, 2012 4:46 am

Next

Return to Tig Welding - Tig Welding Aluminum - Tig Welding Techniques - Aluminum Tig Welding