Tooling Technology
Matrix HighSpeed Steels
Economical Alternative to Powders
If fracturing, chipping and microchipping
plague your tooling, consider using
a new breed of tool steel.
BY TOM SCHADE
Applications for Matrix High-Speed Steels
Applications
Punch
owder metallurgy offers significant
advantages over traditionally melted cold-work and high-speed steels.
The ability to produce highly alloyed
steels free of segregation, with uniform
grain structure and carbide distribution, allows powdered-steel producers to
make claims about their steels’ high
performance. If your problems revolve
around pure abrasive wear, many of
these claims prove true.
P
Looking Beyond Abrasive Wear
In the Japanese tooling industry, it
has long been accepted that abrasive
wear is not always the cause of premature tool failure. Often, fracturing, chipping and microchipping—popping of
individual or groups of carbides from a
cutting surface—are the culprits. Japanese end-users sought a lower-cost material that could address all toughness
Tom Schade is vice president of International Mold Steel, Florence, KY; tel.
800/625-6653; www.imsteel.com.
48
METALFORMING / MAY 2004
MDS1
MDS3
MDS7
MDS9
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Trimming die
Bending/drawing die
Shear blades
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Blanking die
Slitter knife
Roll
Woodwork knife
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Heading die
Rolling die
Warm-forming die
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and fatigue problems, so the Japanese
specialty-steel industry searched for a
class of wrought alloys to do just that.
The research efforts of NachiFujikoshi Corp, Daido Steel Ltd and
others resulted in a new series of matrix
high-speed steels. As is common in
Japan, these steels are not classified by
AISI or JIS standards. Each producer
markets its variation under a trade
name. Nachi has the MDS series, MDS1,
MDS3, MDS7 (matrix high-speed) and
MDS9 (high-toughness cold-work).
Daido has MH85, MH88 (matrix highwww.metalformingmagazine.com
Charpy Impact Value of MDS Series, M2 and D2
150
Deflective Strength of MDS Series, M2 and D2
6
Specimen: 5 x 10 x 5mm (no-notch)
MDS3
MDS1
Bending strength (kN/mm2)
Charpy impact value (J/cm2)
MDS1
100
MDS3
50
MDS7
MDS7
5
MDS9
M2
4
3
MDS9
D2
M2
D2
0
2
55
60
65
55
60
Hardness (HRC)
Hardness (HRC)
Fig. 1
Fig. 2
Table 1—Heattreatment Characteristics of MDS Series
speed) and DC53 (high-toughness coldwork die steel).
Austenitizing
Tempering
Standard
hardness
(HRC)
MDS1
1100-1150
560-640
56-58
MDS3
1080-1160
540-600
60-64
MDS7
1100-1180
540-600
62-66
MDS9
DC53
1020-1050
180-200
500-560
58-62
60-64
Heattreatment temp. (C)
Grade
Carbide Size and Quantity
Limit Effectiveness
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Transverse rupture strength
(KN/mm2)
Transverse Rupture Strength
6
5
4
3
2
1
0
MDS1
60HRC
MDS3
62HRC
MDS7
64HRC
PM HSS
62HRC
Fig. 3
Charpy Impact Value
Charpy impact value (J/cm2)
Consider D2, a low-cost high-hardenability cold-work die steel. Large carbide particles and lack of toughness
can limit the life of tools made from D2
in certain applications, and the large
carbide particles also compromise
machinability and grindability. In the
1980s, Japanese researchers realized that
by lowering alloying elements and
increased hot-working grain refinement, they could produce super-tough
fine-grained cold-work die steels with
advantages over D2. Thirty-percent
improvement in machinability and
grindability, improvements in impact
and fatigue strength, and higher hardenability at high draw temperatures
caused the Japanese tool industry to
gravitate to these steels throughout the
1990s.
The Japanese specialty-steel industry
then shifted its focus to overcoming
the inherent low-fracture resistance of
high-speed and powdered steels. The
premise behind development of matrix
high-speed steels: Carbides were the
problem, not the solution. Developers
already had shown with the high-toughness cold-work materials that reducing the size and quantity of carbides had
65
100
80
60
40
20
0
MDS1
59HRC
MDS3
62HRC
MDS7
64HRC
PM HSS
60HRC
Fig. 4
METALFORMING / MAY 2004
49
Tooling Technology
Toughness—Matrix high-speed tool steel exhibits
high toughness and fracture resistance due to the special characteristics of its microstructure. Fig. 1 shows
the Charpy impact value of the MDS series and
Fig. 2 shows its deflective strength. When the Charpy
impact value is compared at the same hardness, the
value is higher for matrix high-speed steel than for
M2 or D2. The same can be said for deflective
strength. Figs. 3 and 4 show similar results when the
matrix formula is compared to high-vanadium (10)
powdered high-speed steel. This underscores the
retention of the matrix steel’s wear resistance and
improved fracture resistance.
Machinability—Benefits due to fine grain structure and reduced carbides in matrix high-speed
steels include improved machinability and grinding
after heattreatment. Fig. 5 compares the grinding
ratio (test-piece weight reduction divided by grinding-wheel weight reduction) as the indicator of
grindability—a higher ratio indicates improved
grindability. Reduced machining and grinding costs
significantly reduce tool costs.
Heattreatment—Matrix high-speed steels are
less sensitive than other high-speed steels to the
slower cooling rate of vacuum heattreat furnaces. For
example, the center hardness of an M2 100-mm bar
loses three points of HRC as a result of slower vacuum-furnace cooling. Matrix high-speed steels do
not lose HRC points. Table 1 shows austenitizing and
temper temperature ranges as well as expected hardness ranges for MDS steels
Wear Resistance—Cold-work die steels offer a
wide hardness range, extending from HRC 58 to
HRC 65. Matrix high-speed formulations contain
steels with differing wear-resistance levels. For example, the hardness for one is HRC 58, and HRC 62-64
for another. These levels are controlled by the quantity of the matrix. The results of this control can be
seen in Fig. 6, where a lower wear ratio indicates
superior wear resistance. Fig. 7 compares abrasive
wear resistance to high-vanadium (10) powderedMF
metal high-speed steel..
50
METALFORMING / MAY 2004
3
Cutting depth: 0.05 mm
Peripheral speed: 2000 rpm
2
1
0
MDS1
58
MDS3
63
MDS7
MDS9
65
62
Hardness (HRC)
M2
65
D2
62
Fig. 5
Wear Resistance
10-3
Friction speed (m/sec)
2.86
0.46
Wear ratio (mm3/(m * kg))
Characteristics Defined
10-4
10-5
MDS1 MDS3 MDS7 MDS9
58
63
65
62
Hardness (HCR)
M2
65
D2
62
Fig. 6
Wear Resistance Compared to Powdered-Metal
High-Speed Steel (PM HSS)
3
Abrasiveness (mm3/(m * kg))
benefits. With matrix high-speed steels, alloy elements are resubjected to a solid-solution treatment
with a base (matrix), reducing the quantity of carbides. The end result offers high toughness and fracture resistance. Additional benefits include improved
machinability and grindability. The trade off is
reduced abrasive wear when compared to M2 or
powdered steels.
Grindability
(weight loss of specimen/weight loss of grinding wheel)
Grindability
2
1
0
MDS1
58HRC
MDS3
63HRC
MDS7
65HRC
PM HSS
62HRC
Fig. 7
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