Hand Tools Archive
Mujingfang makes most of their chisels and plane blades out of a high speed steel similar to the T series steels.
It's chinese made HSS and probably much easier to harden and temper reliably (as in without warping or cracking) than a plain carbon steel would be.
It's quite good. You can't really rely on their descriptions, though, because when someone like JWW describes mujingfang stuff, they often use meaningless descriptions.
For some time (and maybe still), they called the bench plane irons A2 steel, but they are instead some type of HSS. I'm supposing they are T series steel because I believe I read that somewhere and they take quite a good edge for HSS and even on a natural japanese stone (though such a stone doesn't remove much of their metal).
For what it's worth, a T series HSS would be far superior for hand tools compared to M2. The chisels that muji makes are wonderful. It's too bad nobody sells them over here. They're tapered along their length which is really nice for some things.