Welding did not really replace brazing, brazing is just welding with brass rod rather than steel. What you probibly mean is when did electric welding replace torch welding. I don't know when electric welding was invented, but it was in wide use before WWII. Brass welding (with a torch)is still useful for welding cast iron or steel castings, where excessive heat might cause cracking and you don't have the skill or equipment to properly weld it electrically. Torch welding, with brass or steel rod, is still used for thin sheet metal when you don't have access to a wire feed welder.

Note that electric welds are not necessarily stronger than torch welds, but they are faster and easier to produce.