[sz.barti]

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

[Colt45GTO]

sounds like a DC weld. i'm no expert but i had tried to weld ally with my rig, seems like a similar problem.

[TamJeff]

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.

[WerkSpace]

Here are a few links that may help solve your problem.
https://www.youtube.com/watch?v=9KWdXUt3Bv8
http://www.lincolnelectric.com/en-ca/su ... etail.aspx
http://www.lincolnelectric.com/en-ca/su ... etail.aspx
http://www.esabna.com/us/en/education/k ... Alloys.cfm

[sz.barti]

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

[WerkSpace]

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

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]

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

[noddybrian]

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 !

[Otto Nobedder]

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

[TamJeff]

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.

[Otto Nobedder]

I realized, while reading Jeff's reply, I left out an important point...

If you don't solve (or prevent) cracks in the tacks, and fix every one, those cracks will grow into your finish weld.

While there are many causes for a weld to fail in any material, if you have a crack in your tack weld, and don't fix it, you WILL be haunted by it later.

Steve S

[TamJeff]

I realized, while reading Jeff's reply, I left out an important point...

If you don't solve (or prevent) cracks in the tacks, and fix every one, those cracks will grow into your finish weld.

While there are many causes for a weld to fail in any material, if you have a crack in your tack weld, and don't fix it, you WILL be haunted by it later.

Steve S

They are sneaky sometimes too, only showing a faint telegraph of a crack in the weld. You may look once and think you see it, then look again and think something else. I had it happen to me recently with a weld I had reached too far around a pipe away from me and it didn't show until a day or two later and only when the lighting was right. Even then it wasn't entirely visible until I hit it with an arc. I ended up grooving it all the way to the root with an air saw and re-welding it.

[sz.barti]

Cracking tack problem is solve thank you all welders!!! But there is another thing I want to ask you. Dont really weld ally ticker than 3mm as Im working for sheet metal shop but this time I have got 6 mm ally checker plate to weld together. Its a butt joint 1500mm (5ft)long each section is 1200mm (4ft) width I have weld one with your advices and came out good no crack at all but one problem occured I mine it pull like fu** is not usuable. I need to make it again 7 all together so round 3 tomorrow. I have stager the welds 5 inch each 5 inch space plus it was clamped right on the joint so I had 2 inch gap where my torch fit and I tack one side fully tack (aprox 10-15 mm long) around every 5-6 inches and I turn it over. When I welded both side and I took clamps off looks like a brige ( bent all over) why it happens? Im not an ally expert but as far as I know ally cant be cooled it has to cool it self am I right or I should cool it down with air or water?

And please dont laugh

[TamJeff]

No laughing here. It is incredibly difficult to weld that big of aluminum sections with TIG without distortion. Nothing short of sandwiching between heavy steel plates. That operation is better suited for MIG. Even then there is going to be distortion. Look at the many commercial aluminum boat hulls built in heavy plate and there is significant distortion even with MIG. I am not an expert for that type of fit up so take what I say lightly. Personally, I would have to either subdue the joints as mentioned or employ a press after the fact if TIG was the only option.

[weldin mike 27]

Hey,

I realise this is not always posible but 1way to avoid and or limit distortion is to preset your parts. That means to bend or restrain them in the opposite way of the way the are bending so that during welding, when they distort , the end up closer to the right spot because they have had to move farther from the starting point. Simply put, Before welding, curve them the other way to which they are ending up. I DONT KNOW IF THIS IS AN OPTION WITH YOUR JOB. IT MAY NOT SUIT..


Mick.

[weldin mike 27]

Hey,

Ps it is quite normal to straighten things on a press after welding. We had a whole department at my factory for it.

Mick

[Otto Nobedder]

It's unlikely diamondplate will look right straightened in a press.

I think MIG is the better option, and friction-stir the best, but friction-stir is a specialized process.

Perhaps a MIG weld, followed by a thorough planishing in a hammer mill?

Not sure what facilities you may have access to.

Steve S

[TamJeff]

The whole joint would have to be pressed like on a press brake with an adapter or using the cross brake die backed with a piece of flat bar or angle iron. Pre-distorting it does work somewhat.

I have had to weld large sections of 3/16" for sump well covers and I sandwiched each section between two heavy pieces of 1/2"x 12" x 4' steel plate and clamped those where I could with big C's and leaving just enough room for TIG work. It worked well but was a beating to set up each time.

[sz.barti]

Hi mates!!!

I tryied to sandwich those two plates when I was welding it with Tig and really help but still pull a bit, was acceptable any way. Unfortunatley was very slow so at the end I welded it with Mig. Still sandwiched two plates and welded fully both side, and looks very good was quite straight.

It was very good lesson for me I learned a lot. Thank you all welders that you here when I need you.

Thanks

Bart

[weldin mike 27]

Hey, Glad it helped you out. Hope you stay around.

Mick

[sz.barti]

I definetley will stay on the forum, I see you are from oz where are you?

[weldin mike 27]

Hey,

Im in Bendigo, Victoria.

Where are you?

Mick