|
Typical analysis
%
|
|
C
0.50
|
Si
0.3
|
Mn
0.8
|
Cr
3.3
|
Mo
1.4
|
|
|
Standard
specification
|
AISI S 7
|
|
Delivery
condition
|
Soft annealed to approx. 200
HB
|
|
Color code
|
Black
|
EDRO #7™ is a
chromium-molybdenum steel characterized by:
- High toughness
- Good wear
resistance
- High impact
resistance
- Good through hardening
properties
- Good machinability
- Good dimensional stability
during hardening
EDRO #7™ is suitable
for plastic molding including injection, compression and transfer molds.
EDRO #7™ has a
favorable combination of toughness and wear resistance for heavy duty blanking
and forming tools. It is ideally suited for shear blades and cropping tools,
both hot and cold. Other applications include rivet punches, chisels, cold
heading dies and forging tools.
|
Blanking and
shearing
|
Material
thickness
|
|
Tools for:
Blanking, punching,
cropping, shearing,
trimming
|
up to
1/8"
(3mm)
1/8-1/4"
(3-6mm)
1/4-13/32"
(6-10mm)
|
|
Material
hardness (HB)
|
<180
HRC
|
>180
HRC
|
|
56-58
56-58
54-56
|
56-58
54-56
52-54
|
|
|
Shear blades - cold
Shredding knives
Shear blades - hot
Circular shears
Trimming tools for forgings
|
56-58
56-58
50-54
54-58
56-58
|
|
Structural
applications
|
HRC
|
|
Machine parts, rolls,
grippers, mandrels, chisels, hammer tools, slides, clutch parts, stripper
plates
|
52-58
|
|
Turning with carbide tools
|
|
Turning
|
Rough Turning
|
Medium Turning
|
Finish Turning
|
|
Depth
of cut (t)
in
mm
|
min.
0.4
min. 10
|
0.08-0.4
2-10
|
max.
0.08
max. 2
|
|
Feed(s)
in/tooth
mm/tooth
|
min.
0.04
min. 1
|
0.12-0.04
0.3-1
|
max.
0.012
max. 0.3
|
|
ISO
machining group
|
P30-P40
|
P20-P30
|
P10
|
|
Cutting
speed (v)
f.p.m.
m/min.
|
165-285
50-90
|
230-360
70-110
|
325-525
100-160
|
|
Electrical-discharge machining |
(EDM, "spark
machining")If the spark-erosion is
performed in the hardened and tempered condition, the tool should be stress
relieved at 50° - 75°F (27° - 42°C) below the previous
tempering temperature after the EDM process is complete.
Correct grinding technique
will avoid grinding cracks and improve tool life. Tools that have been tempered
at low temperatures are especially sensitive during grinding. Only properly
dressed, soft, open-grained grinding wheels should be used. Restrict the
peripheral speed and use plenty of coolant. More detailed instructions
can be obtained from the grinding wheel manufacturer.
EDRO #7™ has good
polishability in the hardened and tempered condition. After grinding, polish
with aluminum oxide or diamond paste.
- Grind to .002 in. (0.05mm)
from finished size.
- Polish with diamond paste
grade 45, to obtain a dull, even surface.
- Polish with a diamond
paste grade 15.
- Polish with a diamond
paste grade 3 or grade 1 for particularly high demands on surface
finish.
Note: Each steel grade has
an optimum polishing time which largely depends on hardness and polishing
technique. Over-polishing can lead to a poor surface finish (e.g., an
"orange peel" effect).
Welding of tool steel
should generally be avoided, due to the risk of cracking. Where repair welding
is necessary, it is essential to pre-heat the part prior to welding.
Immediately after the welding operation:
- Stress-relieve material
that has been welded in soft annealed state.
- Temper material twice that
has been welded in the hardened and tempered condition.
Nitriding gives a hard
surface which is very resistant to wear and erosion. A nitrided surface also
increases the corrosion resistance. The surface hardness after nitriding at a
temperature of 980°F (525°C) in ammonia gas will be approx.
1000HV.
|
Nitriding
temperature
|
Nitriding
time hours
|
Depth of
case
approx.
|
|
|
20
30
60
|
|
0.010
0.012
0.014
|
0.25
0.30
0.35
|
|
Tufftriding at 1068°F
(570°C) will give a surface hardness of approx. 850 HV. After 2 hours'
treatment, the hard layer will be approx. 0.0004 in (0.01mm).
After
hard-chromium-plating, the tool should be tempered for approx. 4 hours at
350°F (180°C) in order to avoid hydrogen embrittlement. |
Physical data: Hardened and tempered to
hardness HRC 57. Data at room temperature and elevated temperatures.
|
Temperature
|
68°F
(20°C)
|
390°F
(200°C)
|
750°F
(400°C)
|
|
Density
kg/m3
lbs/in3
|
7800
.282
|
7750
.280
|
7700
.278
|
|
Modulus
of elasticity
N/mm2
psi
|
197000
29X10-6
|
192000
29X10-6
|
177000
26X10-6
|
|
Coefficient of thermal expansion
/°C from 20°C
/°F from 68°F
|
-
-
|
12.2X10-6
6.7X10-6
|
12.5X10-6
6.9X10-6
|
|
Thermal
conductivity
W/m °C
Btu in/(ft2h°F)
|
28.9
202
|
30.0
207
|
31.0
215
|
|
Specific heat
J/kg °C
Btu/lb °F
|
460
0.11
|
-
-
|
-
-
|
Compressive
strength The figures are to be
considered as approximate.
|
Compressive strength
|
|
Hardness
HRC
|
psi 1000
X
|
N/mm2
|
psi 1000
X
|
N/mm2
|
|
58
55
50
45
|
385
355
295
250
|
1700
1550
1250
1100
|
300
295
240
200
|
1300
1250
1100
900
|
|
Heat Treatment - EDRO #7™ |
Soft
annealing Protect the steel and heat
through to 1530°F (830°C). Then cool in the furnace at 20°F
(10°C) per hour to 1000°F (540°C), then freely in air.
Stress-relieving After rough machining the
tool should be heated through to 1200°F (650°C), holding time 2
hours. Cool slowly to 930°F (500°C), then freely in air.
Hardening Preheating temperature:
1110-1560°F (600-850°C).Austenitizing temperature:
1690-1780°F (920-970°C) but usually 1725°F (940°C).
| Temperature
|
Soaking*
time minutes |
Hardness
before tempering (HRC) |
|
|
40
2
2 |
52±2
56±2
57±2 |
*Soaking time = time at
hardening temperature after the tool is fully heated through.
Protection against
decarburization Protect the tool against
decarburization and oxidation during the hardening process.
| Typical analysis %
|
C
0.50
|
Si
0.3
|
Mn
0.8
|
Cr
3.3
|
Mo
1.4
|
| Standard spec.
|
AISI S-7
|
| Delivery condition |
Soft annealed to approx 200 HB
|
| Color code |
Black
|
Quenching
media
- Forced air or gas
- Martempering bath at
360-480°F (180-250°C), then cool in air.
- Circulating air or
atmosphere
- Oil (large cross
sections)
Temper the tool as soon as
its temperature reaches 120-160°F (50-70°C)
Choose the tempering
temperature according to the hardness required by reference to the tempering
graph. Temper twice with intermediate cooling to room temperature. Lowest
tempering temperature 360°F (180°C). Holding time at temperature
minimum 2 hours.
During hardening
Sample plate, 100 x 100 x
25mm, 4" x 4" x 1"
|
Hardening from 1020°C (1870°F)
|
Width %
|
Length %
|
Thickness %
|
|
Oil
hardened
min.
max.
|
+0.02
-0.05
|
+0.02
+0.03
|
+0.04
|
MarTempered
min.
max.
|
+0.02
-0.03
|
+-0
+0.03
|
-0.04
|
Air
hardened
min.
max. |
-0.02
+0.02
|
+-0
+0.03
|
+-0
|
|
Vacuum Hardened
min.
max.
|
+0.01
-0.02
|
+-0
+0.01
|
-0.04
|
|
