CHRO-MOW®
(AISI H12)
Chro-Mow is a general purpose hot work tool steel, combining good high-temperature strength with moderate toughness and heat check resistance. It is suited for applications where drastic coolants are used. It may be used up to tool temperatures of about 1000F, with brief exposures up to about 1100F.
Typical Chemistry
Carbon 0.35%
Manganese 0.35%
Silicon 1.00%
Chromium 5.00%
Molybdenum 1.30%
Tungsten 1.20%
Vanadium 0.35%
Typical Applications
Extrusion Tooling Forging Dies
Hot Upset Dies Hot Piercing Punches
Gripper/Header Dies
Hardening

Critical Temperature: 1535F.

Preheat: 1100/1200F, equalize, 1400/1500F, equalize.

High Heat: 1850/1900F, hold 15/40 minutes at temperature.

Quench: Air, positive pressure vacuum, salt, or interrupted oil to 125/150F.

Temper: 1000/1150F, hold one hour per inch of thickness (two hours minimum. Temper twice.
Typical Properties
Air cooled from 1850F, double tempered as shown.
Tempering
Temperature °F
 Hardness
HRC
 CVN
1000 51-53 8
1050 44-46 11
1100 40-42 13
1150 30-32 —
Effect of Temperature on Impact Properties
Air cooled from 1850F, double tempered to original hardness indicated, tested at elevated temperature as shown.
Original RT
HRC
 Charpy V-Notch at (°F)
RT
 300F
 500
 800
 1000
 1050
 1100
50 8 12 15 18 19 18 —
46 11 20 23 — 26 — 26
42 14 25 31 34 36 — 36
Surface Treatments
Because of its high tempering temperatures (>1000F), Chro-Mow may be treated by most surface treating processes, including conventional and ion nitriding, titanium nitriding, and other coatings or treatments. Nitrided surface hardness will be about 60/65 HRC.

Annealing
Heat to 1600F. Hold 2 hours at temperature. Cool slowly (50F per hour maximum) to 1200F, then air cool to room temperature.
or
Heat to 1600F. Hold 2 hours at temperature. Cool to 1400F. Hold 6 hours at temperature, then air cool to room temperature.

Typical annealed hardness: 192/235 BHN.

Stress Relieving
Annealed material: Heat uniformly to 1200/1250F, hold two hours at temperature, cool in still air to room temperature.

Hardened material: Heat uniformly to 25/50F below tempering temperature, hold two hours, cool in still air to room temperature.

Welding
Use H11 or other hot work tool steel filler material.

Annealed material: Preheat to 800/1000F. Maintain above 700F during welding. Reanneal, or temper 1400F 6 hours.

Hardened material: Preheat to 800/1000F. Maintain above 700F during welding. Allow to cool to hand warm (150F) after welding. Retemper at 25/50F below original tempering temperature (1000F minimum).

Physical Properties
Modulus of Elasticity ..............................................................30 psi x 106
Density ......................................................................................0.281 lbs/in3
Thermal Conductivity.....................200F............................14 BTU/hr/ft/°F
                                       .....................600F ............................15 BTU/hr/ft/°F
Thermal Expansion
        RT - 200F ...................................................................6.1 x 10-6 in/in/°F
        RT - 400F ...................................................................6.5 x 10-6 in/in/°F
        RT - 800F ...................................................................7.0 x 10-6 in/in/°F
        RT - 1200F .................................................................7.4 x 10-6 in/in/°F
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