It may be possible to braze the two parts back together, for moderate use.
I grew up with a vice that had suffered in exactly the same way, that my father had had brazed, and we used it (more carefully )for years, certainly until I left home.
Welding would need the parts to be preheated and cooled slowly. Not impossible, but more difficult
I was lucky, just before retiring found a new Record that had been left boutside and was rusty, at work.
Got it for a song, but the rust cleaned up, and it has served well, despite my abuse, for many years. Checked, and it was a top of the range, so glad that I didn't buy it new!
Howard