H13 is a premium chromium-molybdenum hot work tool steel manufactured via electro-slag remelting (ESR) for exceptional purity, offering high toughness, excellent high-temperature strength, superior thermal fatigue resistance (heat checking resistance), and good wear resistance—making it the most widely used global standard for aluminum and magnesium die casting molds, hot forging dies, extrusion tools, and high-toughness plastic molds where extreme thermal cycling and mechanical stresses are present.