MIG pulse vs Tig for Ally

[F.J.]

I have a Cebora 2035m pulse mig set which I soley use for welding aluminium. It welds great on new ally but for some reason the welds arent so great on old ally no matter how much I clean it. Ive been on a job today welding splits on an aluminium tankers flitch plates and have had to come away with only getting one weld down due to cleaning back and re-welding the same crack!! I take off cuts of new ally with me on jobs so I can set the welder before tackling any job but im getting increasingly frustrated with the appearance of my welds. My question is, does Tig welding produce better results on old ally? I have always wanted a Tig set but have never really had the call for it until now. This particular customer today said if I do a good job then he will put all his welding work my way as he only services the tankers. I have only slight experience with Tig welding but im sure with practice I will pick it up quite quickly. I would consider selling the Cebora once I am good enough with a tig but could I buy a decent brand new acdc tig for say £1000. If I can stretch to it then possibly £2000, but then id like to come a way with a pulse or even double pulse for that price. (Obviously second hand im guessing?).

thanks for any replies

Dean

 

[hotrodder]

If anything TIG is less tolerant of old/contaminated/manky material... weldpool spits crud out, contaminates tungsten resulting in arc wander etc so as well as cutting the mess out of the workpiece you have to reprep the tungsten too

On the other hand as the filler wire is a seperate deal with TIG you're not commited to laying down metal as soon as you strike an arc... if the weld pool is misbehaving you can 'boil' some of the crud out, stop and tickle it with a burr and repeat until it puddles cleanly. Downside of this control for the sort of work you're talking about is speed, total job time is a very different thing to welding speed but when it comes to laying down metal MIG is much faster

With TIG pulse is more about thin, heat sensitive materials. Personally i don't find it useful on ally (if anything it slows me down) and AFAIK there's no such thing as double pulse with TIG as the wire is a seperate deal, with MIG pulse/double pulse etc effects the way wire is added to the weld/melted

Solidification cracking with ally... http://www.mig-welding.co.uk/forum/threads/cracks-when-tacking-aluminium.40267/#post-445812 A tanker is obviously a big lump of metal and so a smallish offcut to dial the machine in isn't representitive of the heat input needed for the job. Advantage TIG as you can wait before adding wire although many MIG sets (especially posh synergic ones) have a hot start thing to help counter the thermal conductivity issues with ally. Preheat, especially at this time of year can make a big difference both from cold starts/cracking POV and with regards to hydrogen porosity- hydrogen is very soluble in liquid ally but not when it's solid. ANY source of hydrogen (moisture, hydrocarbons etc) can leave the weld looking like an aero bar inside