One for the techies

[KemppiFrog]

I have an ally tank to weld up out of 3mm sheet. While waiting for the pure argon, I tried a few short runs with argon/co2 mix. The results were quite good for a first go. So...what is the actual reason for using pure argon with a MIG? Obviously for TIG it is the tungsten, but what effect on the ally would some co2 have?
The gas is from Linde and in the Mison range. There are different nos for the mixes. Mine is 8, but I am not sure exactly what % of co2 it has. Their site is not helpful, except that some of the Mison types are OK for light alloys (but don't specify the no.)

Any ideas? Are you there, backpurge...
KF

 

[backpurge]

KF, is there an EN number on the cylinder label, will have a word with one of my mates at Linde in Munich for you to see what it is. Mison is a product from what was AGA gas

 

[KemppiFrog]

Thanks for that BP, I will have a look at the cyinder in the morning and post up the info.
Rgs
KF

Edit, nipped out in the cold & wet...EN 439. Hope that helps

 

[hotrodder]

Any CO2 should have an oxidising effect as it's dissociated in the arc, I would've thought 8% CO2 would result in a right mess on ally

http://www.aga.com/international/web/lg/aga/like35agacom.nsf/docbyalias/mison_gases does things by material vs process and lists the ingredients of the different flavours.

 

[KemppiFrog]

Any CO2 should have an oxidising effect as it's dissociated in the arc, I would've thought 8% CO2 would result in a right mess on ally

http://www.aga.com/international/web/lg/aga/like35agacom.nsf/docbyalias/mison_gases does things by material vs process and lists the ingredients of the different flavours.

Thank you HR, that is the sort of info that Linde france wasn't putting on their site, or at least not easy to access. So it is 8% co2. I will put up a pic of the weld in an hour or so. There was a lot of spatter with hot globs onthe floor, but, to my untutored eye, the weld didn't look too bad for a first attempt.
Cheers
KF

 

[normspanners]

Possible the gas has not been mixed correctly or the co2 has not been put in because you can mig steel with straight argon. I have a feeling this happens more than we realise, I have seen this before where I was really struggling with some heavy steel bubbling and contamination, I checked every thing on the welder no difference, I changed the cylinder and bingo sorted.

 

[KemppiFrog]

Here goes. The surface is a bit grainy and I wire brushed it to get the soot off. The left hand one is too cool and in a couple of goes. But the right is not too bad?
KF

 

[backpurge]

KP
Sorry for the delay in replying, I have been having to earn a crust, HR has covered it all above, as you will have seen Mison 8 is a 3 component mix (Ar + 8%CO2 + 0.03%NO), your weld will have a high oxide content, porosity and will suffer from poor fusion and penetration due to the active comonent in the shielding gas. That we have found that trace additions, around 0.03%, of O2 to inert mixtures do have a beneficial effect when MIG and TIG welding aluminium alloys

 

[KemppiFrog]

Thanks for the reply, crust earning comes first.., so the weld will be weaker because of the co2. Back to waiting for the Mison AR then. I was just curious as to why it was not a good idea.
KF