• 열처리공학회지
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• 제30권4호
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• pp.156-163
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• 2017

In the present study, we investigated the optimal austenitizing temperature of high-alloyed tool steels from an industrial point of view. Austenitizing temperatures for manufacturing 25 commercial tool steels were surveyed with their alloy compositions. The relationship between the austenitizing temperatures and the critical equilibrium temperatures by thermodynamic-based calculation was analyzed and a correlation was found. Based on the austenitizing temperatures of 25 commercial tool steels and the thermodynamic calculation results, we proposed a simple equation to predict an optimal austenitizing temperature to achieve superior mechanical properties of high-alloyed tool steels. The applicability of the proposed equation was experimentally validated with a new developed tool steel.

• 한국주조공학회지
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• 제15권3호
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• pp.242-251
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• 1995

Highly alloyed high speed tool steels(ASP steels) were rapidly solidified by melt spinning process, and the microstructures of melt spun tool steel ribbons were examined by optical microscopy and transmission electron microscopy with energy dispersive x-ray spectroscope. The microstructure of melt spun tool steel ribbon was found to be consisted of ${\delta}-ferrite$ cells surrounded by austenite and V-rich MC carbides. The size of ${\delta}-ferrite$ cells and intercellular MC carbides were about $0.4{\mu}m$ or less and 30nm or less, respectively. From the melt spun tool steel ribbons, only the MC type carbide phase was observed, instead of $M_2C$, $M_{23}C_6$ and $M_6C$ carbides which were generally observed in other rapidly solidified high speed steels. Such a change in type of carbide phase formed could be attributed to the increase in alloying content of vanadium and carbon. However, changes in microsturcture of melt spun tool steels with alloying content of cobalt, vanadium and carbon were not observed.

• Tribology and Lubricants
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• 제35권2호
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• pp.139-147
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• 2019

This study investigates the effects of corrosion resistance characteristics of opponent materials in relative motion on the sliding wear behavior of mild carbon steel. Pin specimens made of mild carbon steel are tested at several sliding speeds against mating discs made of two types of alloyed steels, such as type D2 tool steel (STD11) and type 420 stainless steel (STS420J2), with different corrosion resistance characteristics in a pin-on-disc type sliding wear test machine. The results clearly show that the sliding wear behavior of mild carbon steel is influenced by the corrosion resistance characteristics of the mating disc materials at low sliding speeds. However, the sliding wear behavior at high sliding speeds is irrelevant to the characteristics because of the rising temperature. During the steady state wear period, the sliding wear rate of mild carbon steel against the type 420 stainless steel at a sliding speed of 0.5 m/s increases considerably unlike against the type D2 tool steel. This may be because the better corrosion resistance characteristics achieve a worse tribochemical reactivity. However, during the running-in wear period at low sliding speeds, the wear behavior of mild carbon steel is influenced by the microstructure after heat treatment of the mating disc materials rather than by their corrosion resistance characteristics.