Thoughts/advice about welding

[Burnerman]

Everything you say here is essentially correct.......all welding is the fusing of similar materials to make them as one.
Naturally enough, this has to ensure that no oxidisation of the weld has taken place. With electric arc (stick welding) the rod is coated with flux that coats the join as it is fused. The technique here is to move the rod in like a mobile U movement towards you. This prevents the slag trapping oxide in the join......easier said than done, of course! with a good weld, the slag just taps off with little adhesion.
With MIG, the work is shrouded in an inert gas such as CO2 or argon, often mixed. Too little gas gets blown away, too much gas can cool the weld too quickly. MIG wire is thin, often 0.6 or 0.8 mm in diameter. Too high a wire speed gives a large gap between torch and the work piece, too low a speed or excess current causes the wire to fuse inside the shroud which encloses the wire nozzle. Gasless MIG wire has a flux within it that prevents oxidisation and the techniques mentioned above are much the same.
With MIG it's a juggling act between wire speed and current applied - this comes with practice. The beauty about this is that excess current 'blow holes' are easy to fill in, as oxidisation shouldn't be trapped.
With TIG welding, the arc produced is shielded with argon, and a filler rod of the same material as the weld is usually added - very similar to brazing, if you like. This is the way to go with non ferrous metals, and very thin stuff as the heat produced is strictly localised.
For starting out, I'd personally go for a MIG set with a larger gas cylinder than the throw away cylinders can provide, with 0.8mm wire. The set needs maybe three current choices and a variable wire speed.
John

 

[JohnW2]

Stick welding is where you you have a rod of welding material covered in a flux that shields the weld whilst you weld the material. ... MIG is where the welding material is a wire on a roll that has a flux core. The wire is fed out on a roller system contained in the welding machine.

Thanks. That all seems to correspond with what I wrote.

So, as I asked, what is the practical relevance of the difference between having a flux coating ('stick') and a flux core ('gasless MIG'), since that's really the only difference of which I am aware?

TIG welding uses a seperate welding rod, pretty much like soldering, and an electric arc to melt the materials.

As I said, my understanding is that 'pure TIG' does not use a rod (hence not really like soldering, more a question of 'fusing parts together') but that many people do also use a ('consumable') rod, thereby seemingly making it effectively similar to MIG?

I haven't tried TIG but I have tried MIG and stick and wasn't very good at either.

Whichever route I decide to go down, I don't realistically expect to become 'very good' at it, but have some hope of becoming able to create welds which don't immediatelt fall apart

 

[Burnerman]

With TIG welding - or any type of heat treatment really - the edges of the metals will retract a little to give a gap - this is where the filler rod comes in.
When you start welding, you practice 'laying down' the weld material. An example would be to place some 1/8" steel bar or plate on a bench, and clamp the earth lead to it.
With a stick weld, hold the electrode at 45 degrees, and move it down towards you in a slow 'U' movement, oscillating as you do so, keeping the rod maybe 4mm or so from the work as it burns away. The idea is to allow the welding rod to burn into the plate, with the arc continuous.
The laid down weld will be covered with a continuous layer of black slag which should chip away readily.
Try say 90 amps with a 1/8" diameter rod to kick off with.
With MIG, try say 3 psi gas pressure (listen for the hiss) with maybe 70% wire speed and 2/3rd available current, keeping the torch at 45 degrees but there's no need for the U movement. Lay the weld down until it's continuous with no breaks. Observe the molten wire closely until you get a continuous pool, again pulling the torch slowly towards you.
All electric welding emits very bright light, so use gauntlets to avoid serious sunburn, and you must have a suitable helmet.
John

 

[stevie888]

OK, so the start to my questions.

There’s clearly a lot I need to learn, and probably the first thing is probably to find out whether my ‘understanding’ of the various types of welding is correct. I am ignoring ‘gas (e.g. oxy-acetylene) welding, which is probably not worth considering for occasional DIY use. What I think is the situation is this:

1…What I would regard as ‘traditional arc welding’ is variously described as “stick welding”, “MMA”, “MMAW”, “SMAW” and various other things, all different names for the same thing. It involves an electrode/rod coated with flux which, when heated, gives off a vapour/gas which shields the weld from oxidation etc.

2…Then there came MIG welding. Initially, as the name implies, it involved the use of an inert gas from a bottle/cannister to shield the weld. However, we now hear a lot about ‘gasless’ MIG welding, and that seems to involve use of an electrode/rod which has flux in its core.

3…It therefore seems that the only difference between “stick” and ‘gasless MIG’ welding is that the flux exists as a coating in the former and as a core in the latter. Is that correct and, if so, what is the practical significance of this difference?

4…All of the above involve the use of a ‘consumable’ electrode/rod which melts and becomes the weld that becomes incorporated into the metals being welded – so seemingly in many senses analogous to soldering/brazing. TIG seems totally different, with a non-consumable electrode/rod -so I presume it works simply by melting the materials being welded – sort-of ‘fusing them together’, with no added matetrial (although I gather that material from a rod is often also added).

Is the above all roughly correct? If not, please put me right!

Thanks to all of you for your time (and patience!).
John

Your analysis is generally very good but a few small clarifications:

1. The flux coating melts to form a protective slag which protects the weld metal for the first vital seconds. One of the signs of a poor weld is the guy chipping away with a slagging hammer for ages trying to remove it. A slight tap should be enough and I've use so called production rods where the slag just curled up as it cooled. [There is a factory process called immersed arc which uses continuous bare wire like MIG but deposits a band of granulated flux around the weld pool. Some if this melts to form the slag layer , the surplus is hoovered up and recycled.]

2. MIG uses continuous wire (from about 0.6mm dia for diy sets rather larger for industrial) and the real advantage is that you can reduce the start stops which are always potential weaknesss in high stressed welds and the clean up time. The process is easily automated with moveable fixtures and torches

3. I doubt gasless MIG is much used in industry but rather something slanted at diy

4. Stick and MIG are adding material directly via the arc. TIG is akin to Oxy Acetylene in that heat is produced to melt the metal and filler rod is added as necessary to form the required weld profile. With TIG inert gas protects the molten metal while the Acetylene produces a "reducing" atmosphere (the opposite of oxidising.}

There is a fundamental difference between welding (where the parent metal is melted and unifies with or without the addition of filler) and soldering or brazing where the components are actually glued together by selecting a filler with a low melting point.

 

[Harry Bloomfield]

So, as I asked, what is the practical relevance of the difference between having a flux coating ('stick') and a flux core ('gasless MIG'), since that's really the only difference of which I am aware?

Gasless MIG, is good for the DIY'er occasional use - As it is always 'ready to go', no running out of gas. Just a roll of wire, but the result is not as clean/good, as MIG with a gas - Argon, or CO2. Mine setup was MIG with gas, but rare use, meant every time I needed it, the gas had leaked out.