What advances in metalworking did early river civilizations make?
And it’s necessary not only to discuss these civilizations separately but also it’s important to determine a time segment. In general, the question is too large to answer it in short properly. New ways of processing, of purifying. And it’s still progressing. Nowadays mild steel laser cutting is a common thing, although, a couple of decades ago it was extremely expensive to buy laser cutting machines and even to outsource this work. Metalworking came through lots of stages which led it to very high productivity.
I think extraction, smelting, purifying and refining. Believe it or not though, the Japanese were not the first people to discover the steel purification process; steel purification, was actually invented in India, it was in China however, that the notion of folding steel to make it stronger began, and in Japan itself it was taken a step further. In other words the technology began in India traveled eastward, and it progressively got better and better culminating into the legend that is now the Japanese Katana. It was not just rudimentary things like that; they also perfecting the process of shaping metals, even hammering into thin leafs. The most famous examples of these, naturally are Egyptian sarcophagi, specifically, King Tut’s tomb. Hammering metal into sheets wasn’t a way to show off; layers of leaf were sometimes used in armor so that soldiers would have protection, but at the same time economize on what little metal reserves there were. See, surface metal is not native to plane