The Development of High Hard and Tough Matrix Type High Speed Tool Steels 
By SHUN-SUKE NAKAHAMA*1, YUKINORI MATSUDA*2, KUNIO NAMIKI*3, KOZO OZAKI*4

Synopsis

The best way to attain high toughness in high carbon-high hard tool steels is to refine carbides. Besides powder metallurgy, carbides control by alloy designing and production process is the key technology.

This time we have developed three matrix type high speed tool steels, DRM steels, and have clarified their superiority to conventional type steels not only in fundamental study but also in practical use.

This series is composed of three steels DRM1 to 3 which are used with the maximum hardness 58, 62 and 66 HRC, respectively. These steels are produced by ESR and characterized by their more finely dispersed carbides free from coarse primary ones, higher toughness and fatigue strength than conventional steels.

The Charpy impact values, DRM1 for example, are two times as those of conventional grades. DRM1 is mainly used for hot and warm forging tools with hardness 56 to 58 HRC. DRM2 is applied to warm and cold forging tools with a higher hardness 58 to 62 HRC. DRM3, the highest hardness one, is the best grade for cold tooling.

These DRM steels have shown longer life and contributed to total cost reduction mainly in forging tools of automobile and machinery components. They are further expected to expand their application fields.

Keywords:

Matrix Type High Speed Tool Steels, Hot Forging, Warm Forging, Cold Forging, Charpy Impact Values, Low Cycle Fatigue, Fine Carbides, ESR

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