Originally Posted by
92dlxman
weldingfordummies may be a decent read, but I think I could make it much shorter.
basically, in arc welding, you are using high amp, low volt (relatively) current to arc from an electrode (big word for something that conducts electricity) to what you are welding. jumping electricity through air creates a LOT of heat, and this heat will melt your base metal, or what you want to weld. now we have problem: you sent electricity through the air, got the air hot, and melted metal. ever take any basic science or chemistry classes? this melted, heated metal has been exposed to oxygen, and since just about everything will react with oxygen, the carbon in the steel has turned into co2, and the iron has turned into iron-oxide. . . .neither one is strong soooooo
we need to protect the weld with something.. . . A NON REACTIVE GAS! you may remember your periodic table, and the "noble gasses" (argon, helium, etc). but, there are other gases that are quite stable too, like nitrogen and co2. different ones work in different quantities to produce welds for different materials and processes. lets just use argon, so, with a non-consumable electrode, (tungsten has a high melting point, I bet that would work), we can send our current through our makeshift little argon atmosphere, and melt some metal! no reaction, metals have fused together and made a strong weld.
new problem though: the weld holding two pieces has taken material from each to make the weld, rendering them thinner and weaker than we want them soooooo. . . . .we need to add material to the weld. pick an alloy that is compatible, but stronger than the base metal would be really cool right? it is often so with common filler metals. they also contain various elements that may sacrifice themselves to bond with impurities/ oxides to make the weld cleaner than the base metal. you could hold a wire or rod of this material in the hand not holding the electrode, and manually feed into the weldment. this is basic tig (tungsten inert gas) welding or GTAW (gas tungsten arc welding) as they would teach you in school. they got away from using the inert gas lingo because some shielding gasses are not inert (not a noble gas) but are still considered "non-reactive"
other processes try to outsmart tig welding, but are more or less similar. maybe, in our non-reactive atmosphere, we could make the filler metal into the electrode, and mechanically feed it into the weldment at a constant speed. . . . . .so, lets take a spool of compatible wire, let an electrode contact it, (wire is energized) and let it feed itself at a rate decided by a dial on the machine. . . .this is basic mig (metal inert gas) or gmaw (gas metal arc welding). various shielding Gasses, and various Metal filler/ electrodes could be used.
now, where it all started, but to me is the most complex, is stick-welding. take the consumable electrode/ filler idea from mig, and the manual filler feed from tig, and combine the result to get stick. like mig, the filler is energized to become the electrode at the same time. like tig, this filler must be manually fed into the weldment. so, take a rod of compatible material, put it into something you can hold onto that will energize it, and feed it into the weld. the rod gets shorter and shorter as you push it in to make the weld, and is replaced when used up.
but heres the problem with stick welding or SMAW (shielded metal arc welding), we talked about filling the weld, but with our varying distance from the non-consumable rod-holding thing we hold in our hand (electrode holder, but its a filler holder at the same time) to the actual weld, how do we provide a shielding, non-reactive gas? you cant, not from a bottle anyway. so, some smart chemists found some chemicals they could coat the rod with, that would sacrifice themselves to the oxygenated, natural atmosphere, and create a shielding gas!!!! that's why stick welding rods have a coating on them, the coating is sacrificial, and "burns" to create an atmosphere around the weld to protect it from oxygen. some components in the coating liquefy, and cover the weld to further protect from the harms of oxygen. they harden outside the weld and are easy chipped off to expose the weld.
you can take the principal of this coating, and add it to the mig process. fill the wire with the same chemical makeup, and it creates its own shielding gas. now, we don't have to haul a bottle around to wherever we work!
these are the basics and there is still a lot to cover as far as polarities, voltages vs amperages, and the unique characteristics of each shielding gas, but in school what I just told you would have taken a huge amount of time and money. this to me, is as much education as is required to start welding for a living
