A couple years ago tried this technique of using a butane torch to fuse fine silver metal rings without using solder to create a chain bracelet. It was a lot of fun but a bit frustrating at first. The class was using thinner gauge wire then in this video, so it was easy to over heat the metal and melt the connection point. If I do this technique again, I would use a thicker gauge wire like in the video such as 16, 18, or 20 gauge.
Also, the instructor points out that that the connection point where the two pieces of metal meet is important. She is not kidding! Take that information to heart and make that your number one priority when lining up the ring halves.
Lastly, if you are going to make a chain of fused metal links, make a bunch separately and create a stack of them. Then go back and interconnect the links with an unclosed ring and fuse that one. You will need to create some kind of ditch in your block to place the fused rings into. This keeps them from heating up and losing their joins.
I photographed a similar process of linking rings during soldering, which you could use for this fusing method too. You can check out that blog post by clicking here.