Heating and quenching is very unlikely to help a cheap tool like the one in your photos. Quenching works best with high-alloy steels since they have substitutional atoms (chromium, molybdenum, nickel, etc.) in the places where BCC iron would reside. Heating above the austentizing temperature and doing a quench to form martensite (the hard form of steel) usually only works as a surface treatment. The thicker the part, the less hardened steel you're going to get towards the center. With a wrench, that's not a bad thing, since hardened (martensitic) steel is also brittle, and you want a ductile core to your part to keep it from breaking.

That said, this part from China just looks like whatever cheap junky steel somebody's brother-in-law was selling that morning. You're not going to fix it with a BCC->FCC->BCC transition from a heat-and-quench.