Carbide Behavior in STD11 Tool Steel during Heat Treatment

Carbide precipitation and dissolution behavior at various temperatures during heat treatment has been studied in STD11 cold working die steel through confocal scanning laser microscopy; dilatometry; and X-ray diffraction analysis. The equilibrium phase diagram and phase fractions with temperature were calculated using a FactSage program. Confocal laser microscopic observation revealed that to transformation temperature is near ; M7C3 carbides melt at ; and the melting temperature of STD11 is near . XRD results indicated that the M23C6 carbides dissolve in the matrix if austenitized at over ; while the M7C3 carbides remain up to although their amount decreases. The calculated equilibrium phase diagram showed good agreement with experimental results on carbide dissolution and phase transformation temperatures.