CPM® REX® 54(HS)
(AISI M4 Modified with Cobalt)
CPM REX 54 is a new cobalt bearing high speed steel designed to combine the wear properties of the popular high vanadium M4 grade with the red hardness of the cobalt-bearing M35/Rex 45 grades. CPM Rex 54 may be used as an upgrade for improved red hardness over M3 or M4 (added cobalt for higher cutting speeds) without giving up the abrasion resistance from the high vanadium, or as an upgrade for improved wear resistance over M35 or Rex 45 (higher vanadium for abrasive work materials) with similar red hardness.
    Because of the extremely fine and uniform CPM microstructure, sulfur may be added if desired, to improve the machinability. The higher sulfur content benefits the toolmaker by allowing ease of manufacture, and the tool user by allowing easier resharpening. The CPM process ensures that the additional sulfur will not detrimentally affect the tool’s toughness.
Typical Chemistry
Carbon 1.48%
Manganese 0.30% (0.70%)*
Chromium 4.00%
Vanadium 3.75%
Tungsten 5.50%
Molybdenum 5.00%
Cobalt 5.00%
Sulfur 0.06% (0.22%)
Typical Applications
Hobs Broaches
End Mills Milling Cutters
Form Tools Counterbores
Taps Tool Bits
Punches/Dies
* The addition of .20/.25 S in larger diameter rounds (e.g. 2-9/16" and over) provides a uniform dispersion of small sulfides throughout the structure, resulting in machinability and grindability benefits with no deleterious effect on toughness.
Thermal Treatments

Annealing: Heat to 1600F (870C), hold two hours, slow cool no faster than 25F (15C) per hour to 1000F (540C), then air or furnace cool.

Annealed hardness: about BHN 225/255.

Stress Relieving:
Annealed material – Heat to 1100-1300F (595-705C), hold two hours and air or furnace cool.
Hardened material – Heat to 25-50F (15-30C) below original tempering temperature, hold two hours and air or furnace cool.

Hardening: (Salt or high pressure vacuum preferred)

Preheat: Heat to 1500-1550F (815-845C), hold long enough to equalize. For vacuum heat treating, an additional preheat at 1850-1950F (1010-1065C) is recommended, to minimize hold time needed at austenitizing temperature.

High heat: 2100-2200F (1150-1205C).

Quench: Quench repidly to below 1100F (595C), equalize, then air cool to hand warm, 150F (65C). Salt or interrupted oil quenching usually gives best heat treat response for high speed steels. Vacuum hardening may result in 1-1.5 points HRC lower hardness for larger tools. A fast quench rate from hardening temperature to below 1100F (595C) is critical to achieve optimum results.
Temper: Tempering three times at 1000F (540C) or higher for at least two hours at temperature is recommended. Air cool completely to room temperature between tempers.

Straightening: Best done warm 400-900F (205-485C). Straightening after salt quenching, before tempering, is preferred if possible.

Comparative Properties
Wear resistance similar to CPM Rex M4HCHS.
Toughness similar to CPM M35HCHS, slightly better than CPM Rex 45 HS.
Red Hardness between CPM M35HCHS and CPM Rex 45.
Hardening Data
Tempering
HEAT TREAT RESPONSE (HRC) -
Oil or Salt Quench (NOTE A)
Temperature
2100F
2125F
2150F
2175F
2190F
°F
°C
(1150C)
(1165C)
(1175C)
(1190C)
(1200C)
As Quenced
65.5
65.5
65
65
64.5
1000
540
65
66
66
66.5
67
OPTIMUM FOR MAXIMUM TOUGHNESS AND EFFECTIVE STRESS-RELIEVING.
1025
550
64.5
65
65.5
66
66.5
1050
565
63.5
64
64.5
65
66
1100
595
61
62
62.5
63
64
1150
620
57
58
58.5
59
60
NOTE A:
RESULTS MAY VARY WITH HARDENING METHOD AND SECTION SIZE. SALT OR OIL QUENCHING WILL GIVE MAXIMUM RESPONSE. VACUUM OR ATMOSPHERE COOLING MAY RESULT IN UP TO 1-2 HRC POINTS LOWER.
MINIMUM TIME AT
AUST TEMP (MINS)
15
10
10
5
5
MINIMUM NUMBER
OF TEMPERS (2 HRS)
3
3
3
3
3
Physical Properties
Modulus of Elasticity ...................................................................30 psi x 106 (207 GPa)
Specific gravity ............................................................................................................8.14
Density .......................................................................................0.294 lb/in3 (8144 kg/m3)
Coefficient of Thermal Expansion
Temperature
Range
Coefficient of Thermal
Expansion
°F
°C
in/in/°Fx10-6
mm/mm/°Cx10-6
70-500
21-260
6.40
11.5
70-800
21-425
6.58
11.8
70-1000
21-540
6.72
12.1
CPM Rex 54 is designed as an upgrade to M35 type grades, for improved wear resistance. CPM Rex 54 offers the same base chemistry as CPM M35HC, but with increased vanadium and carbon, for greater wear resistance. The fine carbide size and sulfur additions typical of the CPM grades ensure excellent machining and grinding characteristics, even with the elevated vanadium content. CPM Rex 54 also provides higher attainable hardness and heat resistance compared to CPM M4HCHS.
    CPM Rex 54 may be substituted for M35 in nearly any application, for better performance. It may be substituted for Rex 45 in most applications, where higher wear resistance is desired. CPM Rex 54 offers the same cobalt level as M35, T15, and other cobalt-bearing high speed steels. Where the increased red hardness of a higher cobalt level is required, due to high cutting speeds, for instance, CPM Rex 76 may offer a better combination of properties. Refer to the HIGH SPEED STEEL COMPARAGRAPH in the General Section for more details.
Return to top of page