A question about TIG

[danny dorito]

Ive Never TIG welded so I just have a quick question. Can TIG penetrate thicker steel than MIG at the same amps? i.e can you hold the arc on the same spot for longer to put more heat in or will it just open up and run away from you?

Cheers

 

[hotrodder]

Generalising, sorta but not really and you're not comparing apples to apples anyway as they're very different processes... different amounts of CO2 are used with MIG MAG on steels for various reasons. One of which is that CO2 adds energy to the weld. No use with TIG as the CO2 is dissociated in the arc (adding energy) and immediatly oxidises the tungsten. Amperage with MIG/MAG is kinda a red herring as it's a variable related to wire speed, wire dia and the voltage selected

With TIG the arc and the filler wire are totally seperate deals so can pause without throwing at filler wire at the same spot but regardless of process penetration is, or should be, taken care of by prepping/bevelling the parts and with root gaps. For fillet welds turning the juice up lets you burn in/penetrate more but the goal with a fillet is usually to just penetrate far enough to ensure complete fusion of the weld. Thicker parts obviously need more heat input to achieve this but depositing a larger weld (with multiple passes) is more common than burning in deeper as throwing more and more heat at it has metallurgical side effects. It's also easier to measure fillet size than ensuring a weld has penetrated far enough. When penetration is important things like a T-butt weld or compound weld can be done

TIG is usually at the bottom of the list of processes when it comes to thick stuff as it's a slower, low deposition process. When it used on thick stuff it's usually for it's precision... using TIG for the root (first pass) run on pipe before swapping to stick or MIG/MAG to fill the joint up more quickly for example

 

[super noob]

Simple, use the TIG as the root pass then blast it with a few 7018 rods as the TIG welder will no doubt run stick too!

 

[NickyEng]

Great explanation from Hotrodder. Clearly some extremely knowledgeable guys on here

 

[Adeel]

@hotrodder nice explanation with amazing use of analogies. It was really good to learn this issue with T-joint. Regards