Difference between TIG and Mig welding?...

[Nickathome]

I'm sitting here watching American Chopper(its on all day today), and they just Mig Welded a sissy bar. Then Paul Sr. tells Rick to finish "TIGging it up". What is the difference between the MIG and TIG welding? I plan to buy a wire feed Mig welder soon to use on my M37, etc, and am wondering what the purpose of the TIG welder is, and should I consider buying one of those as well.

[JimmieD]

Hi Nick,

The two processes are entirely different. A MIG welder is in general a glorified arc-stick welder. With MIG the stick welding rod is replaced with a continuous spool of wire and in some instances an inert gas is used as well. The inert gas forms a cloud around the area of weldment and excludes oxygen and other impurities, thus preventing contamination of weld puddle and also hydrogen embrittlement as weld cools. This same thing is done by the flux coat on a stick welding rod, but MIG does it better, and more cleanly on lighter gauge metals.

With MIG you can also run a flux-cored wire, which has the chemical cleaning agents trapped within it. It serves the same purposes of cleaning and exclusion of contaminants in the weld puddle, but the weld spatter is much worse and the welds do not come out as pleasing to the eye.

In the use of inert gases there are different combinations of gas which may be used. 25%argon/75% CO2 is common, as is pure CO2. This allows the process to be used on a variety of metals including steel, cast iron, stainless and aluminum as well as more exotic alloys. Of course one must use a compatible welding wire suitable to the parent metals and to desired strength and elasticity of finished weld.

The MIG was originally called Heli-Arc. which was a patented Linde process as I recall.

In TIG welding we find a cross between oxy/acetylene or gas welding and arc-stick welding, and again with an inert gas shield. Here a tungsten electrode generates the electrical arc, and the tungsten is relatively non-consumable compared to a normal arc-stick rod. However the tungsten is consumed nonetheless, though far more slowly.

Note that this electrode is often containing other metals which are inherently hazardous to one's health. I'll leave study of that aspect up to you and from a more expert source than my own.

The arc is 'struck' and this in an inert gas envelope, and then usually a thin rod of welding rod is fed into the pool, very similar to oxy/acetlyene process. The rod depends on the parent metals of course, and the choice of inert gases is specific to the job at hand as well. This process may be used with all known metals.

The work of an accomplished expert in Tig ranges somewhere between art, poetry and song and it is near breathtaking to behold. Next time you drop by your friendly local nuclear power plant ask them if you can eyeball the reactor vessel: beauty, sheer beauty.

But Tig is quite difficult to learn and more difficult to master. I was TIG welding within 5 minutes of seeing it done, and the results looked like it. It's all about technique, and that deft and precise, as you carefully heat and carefully feed your filler rod, after you figured out which gas, which rod, and super-cleaned the parent metals. No wind is allowed, as that blows away the inert gas envelope; so its a strictly indoors process unless you build suitable windbreaks.

For general use around your shop a MIG is very hard to beat. It can give beautiful and strong welds, in any thickness of metal. It is relatively cheap, fairly easy to learn, and extremely portable, as suitable to outdoors or on top of a scaffold or whatever. For the same use TIG is not all that suitable, quite a bit more expensive, and much harder to learn.

TIG is arguably better for thin stock sheetmetal and bodywork. But you have to ask yourself if it's really worth the hassle when MIG or acetylene can both do a highly satisfactory job, and on the learning and dollars curve, much sooner!

My next major purchase will be a Miller 175 Mig, if not a 210. Hobart [a division of Miller] and Lincoln both make comparable units, though Lincoln doesn't sem to meet Miller's amperage and duty cycles in some instances. Miller may offer stronger product support in your area. Those are the only three brands I will personally consider for purchase, as all three are excellent quality and highly reliable, but many more brands are out there.
JimmieD

[Nickathome]

Thanks for the info

Very informative indeed. Form what I've read, I think an inexpensive MIG unit will probably more than support my needs. I have a Hobart unit in mind that I saw at the local Tractor Supply store. I will probably in the beginning just go with the flux cored wire to keep things simple.

Again, thanks for the very informative info.

[Gordon Maney]

Heliarc is actually TIG, not MIG. A very thorough commentary, however. MIG stands for metal inert gas, TIG stands for tungsten inert gas.

MIG uses a consumable electrode, TIG uses a non-consumable electrode. Both historically have used a gas shield. The flux core for MIG was developed for outdoor use where wind would blow the shield gas away. And it is true that it does not look as good as a gas shielded MIG weld, but better than many people's stick welds.

Conversationally, it is suggested that if you can oxyacetylene weld, you can TIG weld, and if you can stick weld, you can MIG weld. All of that is the rationale given for teaching gas and stick first. There is still a lot of stick being run.

TIG offers the advantage of very precise, localized control of heat. And Jimmie is right, an accomplished TIG operator can do work that appears as fine as jewelry. I have long admired TIG operators who do food grade welding on stainless steel.

Two alternative forms of TIG welders are the scratch start and the high frequency machines that will start an arc while the pointed electrode is separated from the surface of the metal. The high freq units are more desirable, and more expensive.

For MIG and TIG your metals need to be clean. Stick, on the other hand, with the right rod, is a process that can be run on metal that is less clean. Often times in a repair welding situation that is an important factor.

[Bruce]

Check This Site Out

www.weldingweb.com/

[W_A_Watson_II]

Great Info. I bought the MillerMatic 175.

[HWooldridge]

I learned to weld with an O/A torch and am a fair hand at it but TIG was harder for me to learn because the electrode cannot be touched to the work so I often slipped and contaminated the weld. However, TIG gives excellent results on any weldable metal. With that said, I have stick, MIG, O/A and TIG in the shop and use the MIG more than anything else. It is very easy to turn on the gas and pull the trigger. I don't know anyone who likes flux-core wire so would stick with hard wire and inert gas if starting someone from scratch. I think you will like the Millermatic 175 unit.

[Ron in Indiana]

I would go with a Mig and gas as opposed to flux core especially for working sheet metal. It will produce a cleaner looking weld and save much time in grinding the welds. I looked a TSC but found a better deal at my welding supply house plus the added support they offer as opposed to a general sales person on the floor at TSC. I have been happy with my Hobart 135 Handler but a larger machine would have been better yet, the contributing factor in my selection was budget. I am not a pro by any means, my younger brother is a welder by trade and he guided me in my choice also. Don't be afraid to ask questions at the welding supply house that's what they are there for.

[JimmieD]

I stand corrected Gordon, Heli-Arc is a TIG process!

One other piece of advice hinted at by others: buy all the machine you can possibly afford! Why? Because it's addictive, and for a couple of hundred dollars difference you can go from a 135 that is good, to a 175-180 amp that has much greater capabilities, and a longer duty cycle.

The duty cycle represents how long you can weld at a certain amperage for a given amount of time. Embarrased to say I can't remember what the standard time frame is, 10 minutes? A 20% duty cycle means you can weld for 2 minutes out of 10, and then the machine has to cool down, and 50% duty cycle is 5 minutes out of 10. Big difference, but also see that a machine rated at 175 amps and rated at 60% duty cycle at 150 amps can actually run at nearly 100% duty cycle at a lower amperage of say 90-100 amps!

In addition the larger machine, say 175 amp, can easily weld much thicker metal in a single pass, without tedious back filling while still able to do anything that the smaller machine can do.

I also suggest that if you go for a package deal lean more towards getting the gas parts, especially the tank, rather than the welding cart, which you can easily build yourself with your new welder! You'll want the gas soon enough, and sometimes the shops wil toss you a killer deal at original purchase, knowing you'll be back later for tank refills.

Last suggestion is to buy local if at all possible, even if it costs a few bucks more. The local support can make a huge difference when you need service or parts.
JimmieD

[Frank Irons]

Re: Difference between TIG and Mig welding?...

Originally posted by Nickathome
I'm sitting here watching American Chopper(its on all day today), and they just Mig Welded a sissy bar. Then Paul Sr. tells Rick to finish "TIGging it up". What is the difference between the MIG and TIG welding? I plan to buy a wire feed Mig welder soon to use on my M37, etc, and am wondering what the purpose of the TIG welder is, and should I consider buying one of those as well.

The nice thing about MIG is that you only need one hand to weld, whereas with the TIG welder you need both hands and and a foot . If you are offhand welding inside your truck cab the TIG welder is very awkward to use. I speak from experience, I did the floorboard repair in my C3PW with a TIG welder. That experience is what prompted me to get a Miller 135 to do body work. With the MIG you just point and click, so to speak. The guys on American Chopper are using the MIG to tack their fabrications together and then using the TIG welder to finish and make the welds look pretty. The TIG process gives the operator the most control and beautiful welds can be produced using it. I use a Miller 135 MIG for sheet metal and a Miller Syncrowave 300 TIG for heavier welding and more control on light gauge material. The TIG welder can also be used for stick welding but I don't do much of that anymore. I find that I use the MIG the most because of it's ease of use and the fact that I can wheel the machine around and just plug it into a 110 outlet.


Frank