Tool Steel
TYPICAL
ANALYSIS:
|
C.
|
Si.
|
Mn.
|
Cr.
|
Mo.
|
|
0.35%
|
0.40%
|
0.80%
|
1.20%
|
0.35%
|
P20
is a pre
hardened high tensile nitriding tool steel which offers ready
machineability in the hardened and tempered condition.
Forging:
Heat slowly
and uniformly to 1050°C. Do not forge below 930°C . After forging
cool slowly.
Annealing:
P20 should always be annealed after forging and before rehardening.
Heat uniformly to 770/790°C. Soak well and cool slowly in the
furnace.
Hardening:
Heat uniformly to 820/840°C until heated through. Quench in
oil.
Tempering:
Heat uniformly and thoroughly at the
selected tempering temperatures and hold for at least one hour
per inch of total thickness. For your guidance refer to our
colour charts for forging, hardening
and tempering.
|
Tempering °C
|
100
|
200
|
300
|
400
|
500
|
600
|
700
|
|
HRC
|
51
|
50
|
48
|
46
|
42
|
36
|
28
|
Nitriding:
Moulds
machined from pre hardened P20 may be nitrided to give 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 525° C in ammonia
gas will be approximately 650HV.
|
Temperature
|
Time
|
Approximate
Depth of Case
|
|
525°
C
525° C
525° C
|
20
hours
30 hours
60 hours
|
0.30mm
0.35mm
0.50mm
|
Tufftriding:
Tufftriding
at 570° C will give a surface hardness of approximately 700HV.
After hours treatment the hard layer will be approximately 0.01mm.
Flame
& Induction Hardening: P20
can be flame or induction hardened to a hardness of 50 to 55
HRC. Cooling in air is preferable. Smaller pieces may however
require forced cooling. Hardening should be immediately followed
by tempering.
Case
Hardening: In order to maintain maximum surface hardness P20
may be case hardened. Before case hardening is carried out,
the steel should be annealed. To carburise, pack with carburising
powder into a cast iron or heat resisting steel box and see
that the articles are separated from the sides by at least two
inches of carburising powder. Lute the lid with fireclay. Heat
to the carburising temperature of 880° C and soak for sufficient
time to give the required depth of case. Cool to 800/820° C
and quench in oil. Tempering will then be necessary. Reheat
to 200/300° C and allow to cool in the air to give a final surface
hardness of Rockwell C55/59.
Hard
Chromium Plating: After
hard chromium plating, the steel should be tempered for approximately
4 hours at 180°C, in order to avoid hydrogen embrittlement.
Welding:
Firstly
heat to approximately 400 to 500° C. Weld at approximately 400
to 500° C and stress relieve. Use Chromium-Nickel-Molybdenum-alloyed
basic electrodes for welding of structural steels. Welding may
also be carried out using an austenitic stainless steel electrode.
In this case the stipulated increased working temperature may
be modified, but the weld metal has a lower strength than the
parent material.
Physical
Properties:
|
|
Temperature
|
|
|
20°
C
|
200°
C
|
400°
C
|
|
Density
kg/m3
|
7800
|
7750
|
7700
|
|
Coefficient
of thermal expansion
per ° C
from 20°
|
-
|
12.7 x 10-6
|
13.6 x 10-6
|
|
Thermal
conductivity
J/m.s. ° C
|
29.0
|
29.5
|
31.0
|
|
Modulus
of elasticity
Kp/mm2
N/mm2
|
20 900
205 000
|
20 400
200 000
|
18 900
185 000
|
|
Specific
heat
J/kg° C
|
460
|
-
|
-
|
Machining:
|
Turning
Carbide Tools
|
Rough
Turning
|
Medium
Turning
|
Finish
Turning
|
|
Depth
of cut (t) mm
|
min.
10
|
2-10
|
max.
2
|
|
Feed
(s) mm.p.r.
|
mm
1.0
|
0.3-1.0
|
max.
0.3
|
|
ISO
Machining
Group
|
P30-P40
|
P20-P30
|
P10
|
|
Cutting
Speed (v)
m/min
|
40-60
|
60-100
|
90-160
|
|
Milling
Carbide Tools &
High Speed Steel Tools
|
Rough
Milling
|
Finish
Milling
|
|
Depth
of cut (t)
|
min.
2
|
max.
2
|
|
Feed
(s) mm/tooth
|
min.
0.2
|
max.
0.2
|
|
ISO
Machining Group
Cutting Speed
(v) m/min. (Carbide Tools)
|
P30-P40
55-85
|
P10-P20
75-95
|
|
Cutting
Speed
(v) m/min. (High Speed Steel Tools)
|
10-20
|
15-30
|
All information
is supplied as a guidance only
For price and availability
contact our friendly and helpful staff.
|
