Silicon in Die Steels

Die steels are conventionally used in forging, stamping, casting and injection and so on. Metallurgical elements in die steels like silicon, maganese, carbon and others radically decide the comprehensive properties. This paper has reviewed the current state of the art of silicon effect in die steels in terms of cementite growth, size and distribution of alloy carbides, thermal stability of retained austenite, tempering kinetics, and mechanical properties. Results exposed in different works indicated that silicon tends to segregate at the cementite-ferrite grain boundaries in high-silicon die steels, and the presence of this silicon-rich region effectively delays the formation of cementite. On the other hand, a lower silicon content distributes the carbides between the martensitic laths more uniformly and reduces the particle size to avoid the brittle intergranular fracture. Thus a reduction in the silicon content can significantly improve the toughness and tempering resistance, as well as effectively inhibit the retention of austenite to achieve better dimensional stability of dies. Finally, the obstructive effect of silicon on carbon atoms was verified using an isothermal carbon diffusion model.

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