SS question in Knife Making Posted August 8, 2017 5640 is 303, which can be forged, but it must be forged very hot, otherwise I think it crumbles. As far as heat treatment, I believe it will work harden, but heating/quenching won't harden it. When I was looking for a good alloy to use to make medical type instruments, I researched the 300 series and wound up going with 304. Quenching 304 optimizes it's corrosion resistance but like 303, it won't harden I honestly know nothing about 5673 without looking it up. By the way, I just looked in my stainless section of my Forge log and the site I have written down for info is steelforge.com. Tons of info on alloys there.