H13 is called “hot work steel” not because it needs to be heated during production, but because it is used as a mold material in hot working processes such as die casting, hot forging, and hot extrusion.
Furthermore, H13 is called a “hot work steel” primarily because it possesses two core capabilities:
- Red hardness: It maintains sufficient hardness and strength at high temperatures without softening or deforming.
- Resistance to thermal fatigue: It resists cracking caused by repeated heating-cooling cycles.
In summary, H13 is a hot work (mold) steel specifically designed for processing high-temperature metals.