CPM® REX® 76®(HS)*
(AISI M48)
CPM REX 76 is a super high speed steel made by the Crucible Particle Metallurgy Process. It has high carbon, vanadium and cobalt for abrasion resistance comparable to T15 and superior red hardness. CPM REX 76 is heat treatable to 68/70 HRC. Its high hardness, fine grain size and uniform carbide distribution make it outstanding for special purpose cutting tools beyond the capabilities of the AISI Type M40 series high speed steels. The best applications are where high red hardness, high abrasion resistance, and good toughness can be used to advantage.
Typical Chemistry
Carbon 1.50%
Manganese 0.30% (0.70%)*
Silicon 0.30%
Chromium 3.75%
Vanadium 3.10%
Tungsten 9.75%
Molybdenum 5.25%
Cobalt 8.50%
Sulfur 0.06% (0.22%)*
Typical Applications
End Mills Shaper Cutters
Form Tools Broaching Tools
Gear Hobs Tool Bits
Milling Cutters Special Taps, etc.
*HS The addition of .20/25S 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 285/311.

Machinability in the annealed condition is approximately 15% of W1 Tool Steel (1%C).

Thermal Treatments

Critical Temperature: 1535F(835C)

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

Annealing: 1600F (870C), hold 2 hours, slow cool maximum 30F (15C)/hr. to 1000F (540C), then air or furnace cool. Hardness BHN 285/311.

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

Straightening: Best done warm 400-800F(200-430C).

Hardening: (Salt, Vacuum or Atmosphere)

Preheat: 1500-1550F (820-845C), equalize. Second preheat at 1850-1900F (1010-1040C).

High heat: 2100-2190F(1150-1200C). Standard recommendation to achieve HRC 67/69 is 2150-2175(1175-1190C).
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. Temper or quadruple tempering required. (See Table).

Stress-relieving (Hardened Parts): Temper 25F(15C) below original tempering 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
68
68
67
66.5
65.5
540
1000
67
67.5
68
68.5
69
OPTIMUM FOR MAXIMUM TOUGHNESS AND EFFECTIVE STRESS-RELIEVING.
550
1025
66.5
67
67.5
68
68.5
565
1050
65.5
66.5
67
67.5
68
595
1100
63
64
65
66
66.5
620
1150
59
60
61.5
63
64
650
1200
53
55
57
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)
10
10
5
5
3
MINIMUM NUMBER
OF TEMPERS (2 HRS)
3
3
3
4
4
Size Change During Hardening
Hardening
Temp.
Tempering
Temp.
HRC
Longitudinal
Size Change
%
°F
°C
°F
°C
2175
1190
1025
550
68.5
+.22
Surface Treatments
CPM REX 76 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 ............................................................................................................8.26
Density .......................................................................................0.298 lb/in3 (8255 kg/m3)
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