Pulse MIG or AC TIG for Alu welding ?

[SV1BDO]

Hi to all, I have bought a Riland 175GD multi mode (3-in-1) machine & have less than a year of occasional experience in welding, mainly on gavalized square hollow sections, using flux wire E71T-11 with good results.

I tried to weld also aluminum square tubes (6063T6 alloy, 2mm thickness) using 0,8mm 5356 wire & Argon gas, but the results did not satisfied me. Despite of the thin wire that I used (they told me that I should use 1,0mm wire), the major problem was that I had some swelling points at the back of the welding points, that I don't want at all, as they obstruct the functionality of the square tubing. I have asked an experienced TIG welder to make a sample for me and the results were superb.

As I am going to make these Alu weldings more often (always welding square box sections), I am thinking either to upgrade the exisiting MIG machine to a PULSE MIG, or to buy an AC TIG for the Alu jobs. The maximum Alu thickness that I will weld will be 4mm. My site has only 1 phase.

Bellow is a short list of PROS & CONS on both options, please feel free to add yours.

PROS of TIG = Superior results, I believe also that I will have not the swelling points on the back of welded surfaces.
CONS of TIG = Needs extra time practice for learning. Maybe more time expensive.

PROS of PULSE MIG = No need for extra learning. Welding progress will be shorter (compared to TIG)
CONS of PULSE MIG = Maybe the welds will not have the same nice feeling (compared to TIG) I am not shure if the swelling points will disapeared using pulse welding.

 

[Hood]

Pulse Mig can work well on thin materials but Tig will always be neater and tidier.

With a standard Mig the thinnest that I would consider welding is 3mm and in reality I tend not to go below 4mm unless I really need to. The reason for this is Mig welding Alu really requires spray transfer and thin material just can not stand the heat input required for spray.
With a pulse Mig you can still get spray but due to the pulsing the heat input can be lessened by an enormous amount and that will let you weld thinner Aluminium.
I have an EWM Phoenix which has pulse and super pulse (double pulse) and have now been able to Mig thinner Alu than I would previously have done with the Tig, however if wanting the best looking weld possible then I will still use Tig.

Post here showing my very first attempt at 1m Alu with the EWM.
http://www.mig-welding.co.uk/forum/threads/mig-like-tig-or-almost-anyway.74184/


To summarise though, for the thicknesses you are wanting to weld, the look you are after and the mains power supply you have available, then I would say a 200Amp Tig would be your best choice.

 

[Brad93]

Get a AC/DC tig.

The swelling you mentioned is just penetration. This is required in a butt joint generally.

You need to assess whether not penetrating right through the material, with reinforcement behind will be strong enough for the parts intended application.

 

[SV1BDO]

Many thanks to all for the replies. Unfortunatelly I cannot add any reinforcement inside the square tubes, as I use the internal path for another smaller square tube.
As the projects will be mainly with 2mm square tubing, I am searching now for TIG AC/DC machines, I will come back later with the short list.

 

[Brad93]

What is the project/what are the tubes supporting/holding. You need to look seriously at the intended application.
Aluminium butt welds need to be well fused with reinforcement in thin sections to reach any satisfactory tensile results.
Particularly in thinner sections.

 

[SV1BDO]

The project is Telescopic mast for HF antennas. There is not so much load on the top, max. weight 20-30 Kg plus weight of the square hollows. A civil engineer that has studied the project said that there will be no problem with propper welding.