CPM® REX® 45(HS)
CPM REX 45 is an 8% cobalt super high speed steel which has excellent hot hardness along with good wear resistance and toughness, making it suitable for difficult machining applications. Made by the Crucible Particle Metallurgy process, CPM REX 45 has good machinability and grindability characteristics.
Typical Chemistry
Carbon 1.30%
Manganese 0.30% (0.70%)*
Silicon 0.50%
Chromium 4.05%
Vanadium 3.05%
Tungsten 6.25%
Molybdenum 5.00%
Cobalt 8.00%
Sulfur 0.06% (0.22%)
Typical Applications
Broaches Milling Cutters
End Mills Extrusion Punches
Form Tools Shaper Cutters
Gear Hobs Taps
* 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.
Annealed Hardness: BHN 255/285.

Machinability in the annealed condition is approximately 30% of W1 Tool Steel (1%C).

Thermal Treatments

Critical Temperature: 1500F(816C)

Forging: 2000-2100F(1095-1150C). Do not forge below 1700F(925C). Slow cool after forging.

Annealing: 1600F(870C), hold 2 hours, slow cool 30F(15C)/ hr max. to 1000F(540C), then air or furnace cool. Hardness BHN 255/285.

Stress Relieving (After machining): 1100-1300F(595-740C), hold 2 hrs. and air or furnace cool.

Straightening: Best done warm 400-800F(200-4300C).

Hardening: (Salt, Vacuum or Atmosphere).

Preheat: 1500-1550F(820-845C), equalize. A second preheat at 1800-1900(C1010-1040C) is suggested for vacuum or atmosphere hardening.

High heat: 2100-2190F(1150-1200C). Standard recommendation to achieve HRC 66/68 is to use 2175F(1190C).
Quench: Salt, Oil or Atmosphere quench to 1000-1100F(540-595C), equalize, then air cool to below 125F(50C) or hand warm. Vacuum or atmosphere quench rate through 1850-1300F(1010-705C) range critical to achieve optimum heat treat response.

Temper: 1000F(540C) minimum recommended. Triple tempering is required.

Stress-relieving (Hardened parts): Temper 25F(15C) below original tempering temperature or 1000F(540C) minimum.
Hardening Data
Tempering
HEAT TREAT RESPONSE ±1 HRC (NOTE A)
Temperature
2100F
2125F
2150F
2175F
2190F
°C
°F
(1150C)
(1165C)
(1175C)
(1190C)
(1200C)
As Quenced
66
67
67
66
65.5
540
1000
65
66
67
67.5
68
OPTIMUM FOR MAXIMUM TOUGHNESS AND EFFECTIVE STRESS-RELIEVING.
550
1025
64.5
65.5
66.5
67
67.5
565
1050
63.5
64.5
65.5
66.5
67
595
1100
61
62
63.5
65
66
620
1150
57
59
61
63
64
650
1200
52
54
56
58
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)
10
10
5
5
3
MINIMUM NUMBER
OF TEMPERS (2 HRS)
3
3
3
3
3
Size Change During Hardening
Hardening
Temp.
Tempering
Temp.
HRC
Longitudinal
Size Change
%
°F
°C
°F
°C
2175
1190
1025
550
67
+.2
Surface Treatments
CPM REX 45 can be nitrided, steam tempered, or titanium-nitride coated if desired. If the CVD TiN treatment is used, care is required in vacuum hardening.

Physical Properties
Modulus of Elasticity ...................................................................31 psi x 106 (214 GPa)
Specific gravity ............................................................................................................8.05
Density .......................................................................................0.291 lb/in3 (8050 kg/m3)
Coefficient of Thermal Expansion
Temperature
Range
Coefficient of Thermal
Expansion
°F
°C
in/in/°Fx10-6
mm/mm/°Cx10-6
70-750
20-400
6.3
11.4
70-1000
20-595
6.4
11.5
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