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

3. The concept of the development

3.1 Fundamental concept

The concept to improve toughness and fatigue strength is shown in Fig.5 (below). To obtain these two properties at the same time there are two measures one is to decrease carbon contents and the other is refining carbides in high carbon steels. The drawbacks of medium carbon steel are a little lower strength and poorer wear resistance than high carbon grades. Then the measure to refine carbides with maintaining high carbon contents is to apply matrix type high speed steels and powder metallurgy high speed steels. But the latter is expensive due to its production process. Therefore, we decided to develop matrix type high speed steels by applying the new alloy designing, Electro Slag Remeltig and improved hot working processing. Hereinafter, the word "matrix type high speed tool steel" is abbreviated as MHS steel.

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