Hello,
I need your support to find the heat treatment for C70 carbon steel, hardening and tempering with relative curve to get to get different hardness.
Thanks in advance
knife

I don't have any experience with "unalloyed" steels, but it looks like it would be alright to work with.
Probably a brine quench.
Then play with tempering temps until it no longer chips.
They must call it C70 as the "C" content is .70%.

Chemical Composition (in weight %)

C    Si    Mn    Cr    Mo    Ni    
0.70    0.20    0.25    -    -    -    

V    W    Others
-    -    -

Description
Unalloyed carbon steel.

Applications
Quenched and tempered steel for heavy duty parts in machines, vechicles.

Physical properties (avarage values) at ambient temperature
Modulus of elasticity [103 x N/mm2]: 210
Density [g/cm3]: 7.85

Soft Annealing
Heat to 680-710oC, cool slowly. This will produce a maximum Brinell hardness of 183.

Hardening
Harden from a temperature of 790-820oC followed by water. Hardness after quenching is 63-64 HRC.

Tempering
Tempering temperature: 180-300oC.

Forging
Hot forming temperature: 1100-850oC.

maybe im just very opinionated and stuck on simple steels but to me it seems like there would be no advantage to using a crazy unknown steel with lots of important variables.   but i know nothing compared to most i just would not wanna mess with anything like that.