There are many times that you want to weld two metals together but you don't have an electric welder. Buying one for so rare use is not recommended, as it is very expensive, especially those electronic ones (with the inverter). That is exactly what Thanos had in mind when he started designing his welding machine. He spent about 2 months in tests and research to come up with a nice and simple circuit that works, and that its parts can be easily found. The welder is quite powerful, able to weld at 180 amperes. For more info visit this page.
The schematic is in this link.