AIRKOOL®
(AISI A2)
AIRKOOL is an air hardening tool steel with high wear resistance and good toughness. Its combination of properties makes it well suited to a wide variety of tooling applications, particularly molding and processing of abrasive plastics.
Typical Chemistry
Carbon 1.00%
Manganese 0.85%
Silicon 0.35%
Chromium 5.25%
Molybdenum 1.10%
Vanadium 0.25%
Typical Applications
Blanking Dies Thread Roll Dies
Forming Tools Trim Dies
Punches Shear Blades
Gauges Wear Inserts

Hardening

Preheat: 1100/1250F (595/675C), equalize, 1350/1450F (775/790C), equalize.

High Heat: 1750/1800F (995/895C), 30/45 minutes at temperature.

Quench: Air, positive pressure vacuum to 150F (65C).

Temper: 400/1000F (205/540C), hold 2 hours at temperature, air cool. Temper twice.

Cryogenic Treating: Refrigeration treatments may improve long term dimensional stability by transforming retained austenite. Refrigeration treatments should generally be performed after the first temper, and must be followed by a temper.

Hardness and Impact Toughness Data
Air cooled from 1775F(970C)

Tempering
Temp.
Hardness
Toughness,
Charpy C-notch
°F
°C
HRC
ft-lbs
Joules

As quenched 64 -
300 150 62 -
400 205 61 31 42
500 260 60 41 56
600 315 59 37 50
700 379 58 33 45
800 425 58 31 42
900 480 58 29 39
1000 540 57 41 56
1100 595 51 -

Size Change During Hardening

Hardening
Temp.
Tempering
Temp.
HRC
Longitudinal
Size Change
%
°F
°C
°F
°C

1775
970
400
205
62.5
+.07
1775
970
500
260
59
+.10
1775
970
600
315
58
+.09

Surface Treatments
Airkool can be given standard surface treatments such as nitriding, titanium nitride coating, or hard chrome plating if desired. When gas nitriding, harden from the high side of the temperature range and single temper at 1000F (540C); then use standard nitriding procedures.

Annealing
A. Heat to 1600F (870C), hold 2 hours, slow cool 50F (30C)/hour maximum) to 1200F (650C), air cool.
OR
B. Heat to 1600F (870C), hold 2 hours, cool to 1400F (760C), hold 6 hours, air cool.
Typical annealed hardness: 197/241 BHN.

Stress Relieving
Annealed Material: Heat to 1200/1250F(650/675C), hold two hours, cool in still air.
Hardened Material: Heat to 25F(15C) below original tempering temperature, hold two hours, cool in still air.

Welding
Use air hardening tool steel filler material.

Annealed Material: Preheat to 400/600F(205/315C). Maintain above 400F(205C) during welding. Reanneal or temper 1400F(760C) 6 hours.

Hardened Material: Preheat to 25F(15C) below original tempering temperature (300F(150C) minimum). Maintain above 300F(150C) during welding. Cool to 150F(65C) after welding. Temper 25F(15C) below original tempering temperature.

Physical Properties
Modulus of Elasticity ..............................30 psi x 106 ..................(207 GPa)
Density ......................................................0.284 lb/in3 ...............(7861 kg/M3)
Thermal Conductivity ..........................15 BTU/hr./ft./F ............(26 W/m/ °K)
Thermal Expansion
Temperature Range
Coefficient of Thermal Expansion
°F
°C
x10-6 in./in./°F
x10-6 mm/mm/°C
100-500
38-260
5.9
10.6
100-800
38-427
7.2
13.0
100-1000
38-540
7.7
13.9
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