Aluminium MIG, porosity problem with pics

[Keith_]

Hi All,

Wonder if I could borrow on the experience here. Bought the cheap ali MIG gun from Ebay.. you know the one (if anyone wants details of my experience PM me).. now it seems to work okay, welds look okay, bit cold but okay. However when I came to a destructive test the body of the weld looked like an Aero!

Set up:

Material - 1/8 equal angle to 1/8 channel freshly cleaned (prob 6082)
Gas - pure Argon at 30l/min (high I know.. it's the same at 7l/m and 15l/m)
Plant - Clarke 255 with Ebay gun
Wire - 0.9mm 4043 (came with the gun)
Transfer - short circuit
Gun angle - about 15 degs leading

The problem is pretty clear from the pics. Any ideas anyone?

 

[gordon stephenson]

Watching with interest!! for the answers. i bought one in Blackburn from LTS, got him down to £50-00, must admit it has not been out of the box yet.

 

[doubleboost]

Did you clean the metal with a grinder
Could be contamination from that
Weld looks a bit "dry"

 

[pedrobedro]

Are you pushing the gun in the travel direction ? If you trail it you will not get gas cover and have black soot and aero welds.

 

[Keith_]

Gordon: - same as.. probably worth getting it out of the box in case you need to use it in a hurry.. I had to slightly modify mine so it could be wired into the PWM output in the welder.

Doubleboost: Did use a grinder as I suspected people would comment on dirty material.. it was exactly the same on cleanish, but not ground, material.

Pedro: I am pushing in the direction of travel yes.. maybe not enough. Do you know why aluminium is so much more sensitive than steel to this?

I'm working on something else at the mo but will report back when I can muster the patience to try again.

Thanks for your answers so far.

 

[matt1978]

Mig welding Aluminium is always going to present problems with Porosity. Even high integrity work has porosity, but it's measured against what's deemed to be acceptable levels.

Porosity is already in the material and in the filler wire itself on a macroscopic level. This is caused by Hydrogen, In order to minimise it during welding you need to agitate the weld pool, imagine the surface of a drum vibrating. It's the vibration of the weld pool which helps to increase the degassing time. On some modern pulse migs this can be achieved via the arc characteristic from the machine but for normal units on spray arc you can try by doing a slight back weave

 

[julieanncharters]

you have no fusion as the weld bead is sat on top and is high and a lot of "smut" the tech name for the black soot.
High weld no fusion usually not enough amps.
looking at the end of you weld its just getting enough to get going.
you used a grinder to clean before welding what disc did you have in it not one for steel i hope.
smut could be poor gas coverage due to not enough flow or poor torch angle more common in 50-- series filler wire.
i would up the amps start your weld at the finish light up and immediately drag it to the start then weld as normal to the end,this will put some preheat into the material and prevent that big coldstart lump.
and use a flap disc to clean the ali and keep it just for that job

 

[TechnicAl]

First 3 rules for welding aluminium
1 clean it
2 clean it again
3 clean it again

As Matt said theres always porosity its just the quantity that varies

Aluminium in its molten states can dissolve loads of hydrogen but virtually none in its solid state. Aluminium readily forms an oxide layer, which contains hydrogen, this is dissolved in the molten metal. Therefore you need to remove the oxide layer and weld it before another one forms.....which is impossible, but you can get there before its too thick.

 

[david1991]

I always just use scotchbrite to clean ally never ever ever a grinder. Also aluminium passivates which is why it doesn't rust, this hydrogen layer just doesn't get on with mig. I have a synergic mig for ally and that works great.

 

[BrokenBiker]

I have had the same problems with dc tig on ali, the only way I have reduced the issue (not gotten rid of) is by cleaning with a dedicated stainless wire brush, then a scotchbirte pad and then acetone, then immediately weld it and hope for the best. ac tig is better as it 'cleans' the puddle

 

[david1991]

A.C tig is always the best way to go with ally better than synergic and loads better than mig. You can get a cheap tig inverter d.c and a.c for maybe £100. On eBay

 

[BrokenBiker]

ac/dc inverter tig for £100? got any links?

 

[pedrobedro]

A.C tig is always the best way to go with ally better than synergic and loads better than mig. You can get a cheap tig inverter d.c and a.c for maybe £100. On eBay

I'll have 10 please I never heard of anyone having any success with DC tig in the DIY context because of the oxide layer which melts at about 4 times the temperature of the aluminium beneath it.

 

[Robotstar5]

A.C tig is always the best way to go with ally better than synergic and loads better than mig. You can get a cheap tig inverter d.c and a.c for maybe £100. On eBay

Can you post an Ebay link please.

 

[skotl]

Group buy! I'm in, too

 

[KemppiFrog]

If enough of us get in, should be a decent discount on that £100.

I had similar probs with a 150amp MIG on 3mm ally. Not enough amps, but no big probs with porosity. I started with a propane torch to pre heat the work, then started the arc off the joint. Moved to the joint, by which time it was hot enough to get a pool. But I still had probs with the oxide separating layers and causing pin holes. It was a boat diesel tank, so had to fix them. Lotta grinding with a fresh flap disk, then going over again. Def not try it again. AC Tig is the way.

 

[Jan]

Whether this is a POS or a good welder I know not, but the price seems more than fair.

Obviously at that price there's no TIG torch and it's scratch start only.

 

[Rig Pig]

Whether this is a POS or a good welder I know not, but the price seems more than fair.

Obviously at that price there's no TIG torch and it's scratch start only.

Wow look at the duty cycle! It's even worse than a Wolf!! I also love the little disclaimer that removes the warranty if you use it for anything but DIY!

 

[skotl]

So..... it's a 50A arc welder for £100? Or am I missing something?
I don't know much about TIG but it reads to me as "Everything you need to do TIG*! (*except all the bits you need to do TIG)"...

Oh... and I'm out of the £100 ebay tig group buy, by the way

 

[Jan]

It's almost impossible to see the controls in that small pic, but the output(s) appear to be DC which is what you need for TIG. Torches can be picked up for reasonable prices from new and even cheaper as used. Unfortunately the shielding gas has to be supplied directly to the torch, so a manual valve becomes necessary at that end. Obviously the cheaper the main unit then the lower the duty cycle will be at full chat.