HALGRAPH®
(AISI O6)
Halgraph is an oil-hardening graphitic tool steel with excellent non-deforming properties. Free graphite in its structure affords exceptional free-machining properties. The combination of graphite and hard carbides give Halgraph tools excellent resistance to adhesive wear (galling) in applications such as ring gauges, plug gauges, and bushings.
Typical Chemistry
Carbon 1.50%
Manganese 0.75%
Silicon 1.00%
Molybdenum 0.30%
Typical Applications
Gauges Bushings
Blanking Dies Perforating Dies
Draw Dies Punches
Hardening

Note: Full hardness will only be attained in sections less than about 2 inches thick.

Critical Temperature: 1385F(750C).

Preheat: 1250/1350F(675/730C)

High Heat: 1450/1500F(790/815C), hold 10/30 minutes at temperature. The higher temperatures encourage better through-hardening in larger sections.

Quench: Quench in oil to hand warm, 150F(65C).

Temper: 300/700F(150/370C); hold one hour per inch of thickness, two hours minimum, four hours preferred.

Cryogenic treatments: Refrigeration treatments may improve long-term dimensional stability by transforming retained austenite. Refrigeration treatments should be performed after at least one temper, to minimize risk of cracking, and should always be followed by a temper.
Typical Properties
Hardness and Impact Toughness Data
Oil quenched from 1475F(800C).
Tempering
Temperature
Hardness
HRC
Toughness,
Charpy C-Notch
°F
°C
ft-lbs
Joules
As Quenched 64-66 – –
300 150 62-64 20 27
350 175 61-63 – –
400 205 60-62 27 36
450 230 59-61 – –
500 260 58-60 20 27
550 290 57-59 – –
600 315 57-59 27 36
650 345 55-57 – –
700 370 53-55 35 47
800 425 49-51 42 57
900 480 45-47 53 72
Size Change During Hardening
Tempered:
Oil quenched from:
°F
°C
1450F(790C)
1500F(815C)
400
205
+ 0.06%
+ 0.06%
500
260
+ 0.13%
+ 0.17%
600
315
+ 0.13%
+ 0.17%
Surface Treatments
Halgraph can be given standard surface treatments such as hard chrome plating if desired. Nitriding is not generally practical due to a substantial loss of core hardness.

Annealing
A. Heat to 1425/1450F(775/790C), hold two hours, cool slowly, 50F (30C) per hour maximum, to below 1100F(595C), then air cool.
OR
B. Heat to 1425/1450F(775/790C), hold 2 hours, cool to 1200F(650 C) 2 hours, then air cool.

Typical annealed hardness: 187/221 BHN

Stress Relieving
Annealed Material: 1100/1300F(595/740C), hold 2 hours, cool in still air.

Hardened Material: 50F(30C) below last tempering temperature, hold two hour, cool in still air.

Welding
Use oil-hardening (O1) tool steel filler material.

Annealed material: Preheat to 400/600F(205/315C). Maintain over 400F(205C) during welding. Allow to cool to hand warm (150F(65C) after welding. Reanneal, or temper 1100/1200F(595/650C) for 2 hours.

Hardened material: Preheat to 50F(30C) below tempering temperature (300F(150C) minimum). Maintain over 300F(150C) during welding. Allow to cool to hand warm (150F(65C)) after welding. Retemper at 25/50F (15/30C) below original tempering temperature.

Physical Properties
Modulus of Elasticity ...................................................................30 psi x 106 (207 GPa)
Density .......................................................................................0.278 lb/in3 (7700 kg/m3)
Specific gravity ..............................................................................................................7.70
Thermal Conductivity ........................................................200F.............. 20 BTU/hr/ft/°F
                                                                                     .............95C ...................34.5 W/m°K
Thermal Expansion
Temperature
Range
        Coefficient of Thermal
Expansion
°F
°C
in/in/°Fx10-6
mm/mm/°Cx10-6
RT/400
RT/205
6.2
11.2
RT/600
RT/315
6.7
12.1
RT/800
RT/425
7.1
12.6
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