Welding with oxygen and acetylene gas (the fuel) has been around for many years—at least since 1903, when two French engineers, Edmond Fouche and Charles Picard, put their name on it. By using pure oxygen rather than air the flame burns at a high temperature (about 3,500 F) and easily melts common metals such as steel and aluminum. Welding is typically done by causing the two pieces of metal to melt and feeding the resulting “puddle” with a “filler rod”.
Before oxy-acetylene welding, metal was welded by heating in a forge and then pounding the two pieces together. But oxy-acetylene provided a much more convenient and controllable way to weld metal. Of course, any temperature hot enough to melt steel can be used to braze and solder, and by increasing the oxygen pressure (it is usually about twice the acetylene pressure) steel can be easily cut.
I like to weld, and was taught to weld both with oxy-acetylene, and with an arc, or stick welder. In this form of welding, a consumable electrode of metal is used to strike an arc with the metal to be welded. The material from the melting electrode combines with the molten area on the material to form the weld. Stick welding is used in situations where larger amounts of material are to be involved and electricity of the proper voltage is available.
Now there are more sophisticated approaches to welding. Tungsten intert gas, or TIG, uses a non-consumable tungsten electrode to draw an arc and melt the metal and a filler rod, and an inert gas atmosphere is used locally to prevent oxidation of the metal. TIG units have a foot pedal to vary the voltage of the current, making for much closer control. And there is MIG (metal inert gas) in which the consumable electrode in wire form is automatically fed into the weld at a chosen speed and voltage. This can be done in an inert gas or with a flux included in the wire.
And there are many more. I must admit I usually use TIG and MIG equipment rather than oxy-acetlyene, but my trusty oxy-acetylene tank set, consisting of the two tanks of gas with pressure regulators, a double hose to conduct them to the torch, and miscellaneous tips, lighters, goggles, etc. (see photo) still gets a great deal of use. For one thing, I love it, because it is the first kind of welding I ever did, and is extremely flexible. But also it can be used for endless purposes other than welding, brazing, and soldering— from heating rusty nuts and bolts so that they will unscrew, to re-warming coffee, to removing stubborn paint, to partially burning new wood to make it match older wood, to melting a large number of materials other than metal, to showing off for my grandchildren and repairing things for my wife.
I also like it because to me, fire is endlessly fascinating. Why should combining two gases, one of which we need for life (oxygen), and one which comes from dropping calcium oxide into water (acetylene) and lighting the mixture cause such a hot flame? And unlike electric welding (and heating), such things as extension cords and generators are not required. It is just you and the fire performing miracles. The oxy-acetyline welding set is an old, but still high quality product.