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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
4. Special
features of DRM steels
(continued)
4.3 Properties
of DRM3
The heat treatment conditions are
almost same as those of conventional MHS steel as shown in
Fig.24.
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Fig. 24 Heat treatment of DRM3
steel.
Figure 25 (below)
shows tempering hardness curve of DRM3 which is almost
equivalent to that of AISI M2. DRM3 is characterized by its
superior hardenability to that of M2. The relation between
quenching cooling rate and maximum tempered hardness is shown in
Fig.26 (below). In this figure it can be estimated the quenching
cooling rate of the center of the given diameter bar when
quenched by 6bar nitrogen gas in vacuum furnace. Compared to M2,
DRM3 shows higher hardness even cooled with slower quenching
rate.
Charpy impact values
and S-N curves are shown in Fig. 27 and 28 (below),
respectively. Toughness and fatigue strength are both improved
by the finely and uniformly distributed primary carbides.
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