I stuck a GoPro on the end of the die of a Coal Iron forging press.
This is not my billet, but it’s a fair illustration of what setting a stacked weld looks like. You get the steel around 2300F and flux it up nicely, wait till the flux starts boiling, and smush it gently. By the time the first smush is done, the metal is a single piece.
When you are dealing with forged welds, you need to get out of your mind the idea that there are two pieces of metal (or whatever) anymore. After the weld takes, it’s a single piece and it’s not going to come apart. If it comes apart, it was not welded, Q.E.D.
The die is only about 6″ long, so the camera was about 5″ from the metal. That’s a nice thing about GoPros: they are not quite disposable but with the wifi/app control you can put them in places where you really don’t want to have your hand.