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AISI P 20 MODIFIED
MOLD QUALITY STEEL
AISI P 20 is mold quality alloy steel supplied in the prehardened condition. Special
melting and refining practices are utilized to produce a uniform product with exceptional
cleanliness. These characteristics allow AISI P 20 to be polished to an extremely
high finish required for plastic molding. The material is tested to rigorous tool
steel standards to ensure uniformity of structure and freedom from defects. AISI
P 20 is supplied prehardened to 262/321 BHN. The balanced alloy composition of AISI
P 20 ensures a uniform cross-sectional hardness.
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ANALYSIS
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Carbon
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.36/.40
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Manganese
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.90/1.30
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Sulfur
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.002 Max
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Silicon
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.35/.45
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Molybdenum
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.15/.35
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Phosphorus
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.010 Max
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Chromium
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1.00/1.20
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Nickel
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.25/.50
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Copper
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.250 Max
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SIZE AVAILABILITY
Flats - Rounds - Squares - Hollowbar
Standard Sizes - Non-Standard Sizes - Metric Sizes
STRESS RELIEF
Heat slowly and uniformly to a 800/900°F and soak one hour per inch of section
thickness. Air cool or furnace cool to room temperature.
ANNEALING
It is recommended that AISI P 20 be annealed prior to rehardening. Heat slowly and
uniformly to 1500/1600°F for four hours. Cool slowly (50°F per hour max)
to 1200°F and air cool.
HEAT TREATING
AISI P 20 may be heat treated to higher hardness levels for higher strength or for
lens mold applications. Preheat to 1250°F and hold one hour. Heat to 1550/1600°F
and soak one half hour when material is up to temperature. Oil quench or air cool
to hand warm (approximately 150°F) and temper immediately.
NITRIDING
AISI P 20 may be nitrided to a surface hardness in excess of RC 60 for improved
wear resistance.
TEMPERING
Temper one hour per inch of section thickness to desired hardness. Representative
hardness levels after tempering are tabulated below:
Oil Quenched from 1600°F -Tempered 4 hours
(Section Size -4"x4")
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Tempering
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Tempering
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Temperature (°F)
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Hardness
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Temperature (°F)
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Hardness
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400
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42
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900
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36
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500
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41
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1000
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34
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600
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40
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1100
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29
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700
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39
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1200
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25
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Note: Variations in section size, heating rate, soak time, quench and tempering
will cause deviations from the above values. Diehl Steel should be consulted for
specific applications.
EDM
Electro-discharge machining is widely used in the production of plastic molds and
other tooling. However, this operation produces recast, rehardened and retempered
layers on the die surface. It is recommended that AISI P 20 be stress relieved after
electro-discharge machining to temper the rehardened layer produced by EDM.
MACHINING DATA
Normalized and Tempered Brinell 262/321
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High Speed Tooling
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CarbideTooling
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Operation
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Depth ofCut
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Speed
(fpm)
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Feed
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Speed
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Feed
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(In)
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(in/rev)
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(fpm)
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(in/rev)
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Drilling
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1/8
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45
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.002
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1/4
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45
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.004
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1/2
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45
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.006
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1
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45
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.009
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2
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45
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.015
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Gun Drilling
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1/4
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165
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.0005
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1/2
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165
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.0008
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1
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165
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.0015
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2
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165
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.002
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Single Point
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.O4O
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90
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.007
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440
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.007
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Turning
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.150
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70
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.015
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340
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.015
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.300
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55
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.020
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270
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.020
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Cut Off
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.062
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55
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.0013
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.125
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55
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.0016
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.250
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55
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.002
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Face Milling
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.O4O
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105
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.006*
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485
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.006*
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.150
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85
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.009*
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375
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.008*
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.300
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65
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.012*
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290
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.010*
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*Feed in inches per tooth.
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