40X13 is a Russian stainless steel, the international equivalent of which is the popular 420 steel. It contains up to 0.45% carbon and a significant amount of chromium, up to 14%. With a high-quality heat treatment, it can achieve a hardness of up to 58 HRC, but for mass-produced items, it's advisable to assume a knife made from this steel will have a hardness of 55-56 HRC. The steel is used in the production of surgical instruments and mid-range knives. It should be noted that 40X13 loses its temper easily when rapidly heated, so it is not recommended to use such a knife to poke around in a campfire.