Axilleas, That is a great article on Soldering that is linked above.
Here are the basic differances between soldering, brazing, & welding.

-Soldering requires lowest temperature, and produces the weakest joint of the 3 processes. Its like glueing a joint with molten metal.
Usually a led/tin aloy. Silver-solder is stronger but not much.
-Brazing requires much higher temperatures, and produces a very strong joint, but is still just glueing the joint. This is done with a brass rod and torch usually. It requires oxy/acet to reach thease temperatures. A Map-Gas torch may get hot enough but I have not tried one.
* Both soldering & brazing will join most disimilar metals like copper,brass,steel, etc, but don't melt the metals togeather.*
-Welding is the strongest of all by far! Welding actually melts and mechanically joins the pieces togeather. Almost any aloy can be welded using differant processes, but not many disimillar metals can be welded as they have to mix togeather in molten form to make the joint. The filler metal (rod) also has to be simillar to the weldment. (2 base metals)This is why aluminum can not be welded,brazed, or soldered to steel, brass, copper, etc, but steel brass, & copper can be soldered or brazed togeather. They typically can not be welded togeather though. (steel to brass for example)

In my professional opinion, forget about "welding". It requires at least an oxy/acet torch set (only good on some metals) that costs a few hundred dollars, or an electric arc-welder that costs much more. Even though I have over $16,000 invested in my welding equipment, I could NOT "weld" thease tiny parts that thease guys use on thease landing gears and pipes! For all practical purposes, SOLDERING in some form or other is about all a modeler can really do without some very expensive equipment, and high level of skill.

Hope this helps you understand the differances better! Q.