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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