中炭素3Cr-2Mo-V型高硬度強靱工具鋼の熱処理特性,組織,機械的性質について

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The hardenability, hardness, microstructure, and mechanical properties of medium carbon 3Cr-2Mo-V type cold-work tool steel have been investigated. The hardenability of this steel is as high as that of air hardening tool steel SKD11. When quenched in air from 975°C, this steel has hardness of HRC 64, and consists of martensite, retained austenite of about 15 per cent, and fine M6C and M7C3 type carbide. The hardness of HRC 60-55 can be maintained in the range of tempering temperature 200-600°C. From the results of the static torsion test, static bending test, and Charpy impact test, it is shown that the high toughness is obtained in high strength levels by tempering of the temperature range 200-400°C. With fine carbide, the matrix containing lower carbon contributes to the high toughness of this steel. When tempered in the range 200-400°C, the retained austenite is stabilized. Although the presence of stabilized retained austenite decreases yield strength, it contributes to improving toughness. For tool applications in which toughness is considered to be more important, this steel is expected widely to be used.
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