The history of welding dates back bronze age, much to the amusement of today’s generation. Around 3000 BC, Sumerians inUr(present dayIraq) made swords joined by hard soldering. Further, ‘pressure welding’ as practiced by Egyptians was recorded for the first time around this time. This ‘solid-phase’ welding was done by heating iron ore in a charcoal fire, thereby reducing it to sponge iron. The particles were then welded together by hammering.
A chronological development of welding can be found here.
History of Welding in India