Hello,
I would like to know if there are any advantages to TIG welding over MIG welding in terms of strength and reliability?
Thanks , Ben

I'm not a welder, but my understanding is that TIG offers much better results for welding thin walled chromoly tubing than MIG. The usual advice is that MIG is much more difficult to do clean work and avoid burning through thin walled tubing.

MIG welding chromoly tubing | BikeForums

When I put together my cargo bike. I thought I'd mig it due to speed...

I found that I was blowing far too many holes in the thin metal (ok, so I am good at blowing holes in stuff). And my welds were quite ragged.

The second half of my welds were tigging, and they turned out much nicer with fewer problems.

Anyway, the bicycle tubing is mighty thin, and tig welding just seems to work better. Do the factories use some kind of automated tig welders?

no usually they just train a lot of people to do the work, thats why so many bikes come out of Asia, low labor cost.

Tig welding generally gets much better penetration/ much stronger welds than mig welding.

The actual answer is:

1) When you are trying to do critical welds you want to eliminate cold start problems. This is when you start welding if the method is such that you can't separate heat input and filler addition, then you get bad welds. With Tig you can heat the weld pool to the point where you add filler independent of the rate at which you add filler. You can adjust heat and filler rates independent of each other and on the fly.

There are a lot of starts and stops in bike welding as you work around the tube, or make tacks to hold parts and reduce distortion. Later you have to burn through the tacks.

2) for the same reasons as above you can control heat and filler as you progress around the tube. You may run into structures like plate drops where you need to pump in a little more heat, or as you progress around the tube, the overall heat in the part goes up, and you need to lower the heat. Constant independent control is a must.

3) There are more filler rods available to work with odd alloys in tubes for TIG.

4) Torch is more configurable, and can be made smaller as it does only one thing, pour on the arc.

5) Shielding is more accurate and adjustable, with more control features, and more structural formats. Custom gas lenses as an example.

All that said some of these limits can be overcome through MIG configuration, though that is not a home shop thing as much as TIG. You are basically forced to come up with custom TIG configs just to get going, while in MIG it is more something on bikes that might be done as part of a robotics set-up.

I want to thank all for taking the time to answer my questions...I have the answers I was looking for....thanks again.
Regards, Ben

I have one cannondale R300 aluminium frame. I not see any welding is so well put toogether. How i found what type of welding have this bike

TIG welded 6061 T6

Thank you for the very helpfull answer. Kinnesis 6061 aluminum is same as my cannondale R300?. I see that aluminum frames type in bikes direct. My bike is 1998 you think is worth i upgrade that bike and i not look to buy newer bike? My bike have 126 mm dropouts. When i buy the bike used is had wheels with 7 speeds cassete. But i put wheels 130mm. Is fit but i have to pull the dropouts for make the wheel seat correct in the dropouts. that is go give problem in long run? I have stop ride the bike for now because need new bottom bracket. And now have downtube shifters but i want put brifters on this bike. Is worth i do that in old bike or is better i found new bike. I ride 56cm bike buy my cannondale is 58cm. that is sounds much difference ? Now when i ride the bike i feel okay

6061 is the aluminum alloy and T6 is the heat treatment, so the alloy chemistry is the same but depending on the diameters, wall thicknesses, and butting profiles of the tubing used, two bikes using 6061 aluminum alloy may ride very differently. I can't advise you on whether or not you should get a new bike, but if you want to use rear wheels with 130mm OLD hubs and the rear dropout spacing on your frame is 126mm, spreading an aluminum rear triangle does stress it which isn't good. I would suggest getting fit by a professional to ensure you get the correct size frame. Having a well fitting bike makes a huge difference in comfort.

Thank you for the answer and i am sorry for my late reply. I buy the bike with the wheels 130mm. But i do feel is stretch the dropouts. Do you know anythink about bikes direct and one road bike i see is the wellington winsdor 2.0?

You would probably get better advice about the pros and cons of specific production bikes over on the Road Cycling forum.

TIG welding gives you a lot of fine control. You can use the arc, without filler rod as needed to blend, fill etc. I only tried MIG a few times, and it seemed a lot cruder because the wire generates the arc, giving you fewer options. Quite likely there are better MIG systems and skills than my very limited experience.

Can you use MIG on aluminum ?? I only TIG welded AL.