REX M2®(S)
(AISI M2)
REX M2 is a tungsten-molybdenum high speed steel which gives outstanding performance in all operations where a general purpose high speed steel is required. REX M2 has a wide hardening range, excellent toughness, with good wear and red hardness characteristics. REX M2S is the sulfur-bearing counterpart of REX M2. The sulfur addition provides good grindability and an improvement in machinability of 25 to 35 per cent over a comparable nonsulfurized grade.
Typical Chemistry
Carbon 0.85%
Manganese 0.30%
Silicon 0.30%
Chromium 4.15%
Vanadium 1.95%
Tungsten 6.40%
Molybdenum 5.00%
Sulfur 0.03% max. (0.10%)
Typical Applications
Broaches Milling Cutters
Counterbores Punches
End Mills Taps
Form Tools Tool Bits
Annealed Hardness: 217/255 BHN

Machinability in the annealed condition is approximately 45% of W1 Tool Steel (1%C).

Thermal Treatments

Critical Temperature: 1530F(830C).

Forging: 2075F(1135C) Do not forge below 1700F(925C). Slow cool after forging.

Annealing: 1600F(870C), hold 2 hours, slow cool 25F(15C)/ hr max. to 1000F(535C), then air or furnace cool. Hardness BHN 217/255. Stress Relieving: 1100-1300F(595-740C), hold 2 hrs. and air or furnace cool.

Straightening: Best done warm 400-800F(205-425C.)

Hardening: (Salt Baths or Vacuum Furnace preferred.)

Preheat: 1500-1550F(815-845C), equalize.

High Heat: 2100-2225F(1150-1220C), soak 2 to 5 minutes. For vacuum hardening, use the high side of the high heat range and soak times.

Quench: Salt or oil to 1000-1100F(540-595C), equalize, then air cool to hand warm, 150F(65C). Temper immediately. The vacuum quench rate to below 1000F(540C) is critical to achieve comparable results.

Temper: Tempering at 1000F(540C) or higher 2 times for at least 2 hours at temperature is recommended. Air cool to room temperature between tempers.
Hardening Data
Oil quenched.
Tempering
Hardness HRC
Temperature
2100F
(1150C)
2150F
(1175C)
2250F
(1230C)
°F
°C
975
524
64
65
66
1000
540
64
65.2
66.8
OPTIMUM FOR MAXIMUM TOUGHNESS AND EFFECTIVE STRESS-RELIEVING.
1025
550
63.5
65.1
66.8
1050
565
62.6
64.8
66
1075
580
61.3
64
65
1100
595
60
62.5
64
1125
605
58.4
60.5
62.4
1150
620
57
58
60.9
1175
635
–
–
59
1200
650
–
–
57
Size Change During Hardening
Hardening
Temp.
Tempering
Temp.
HRC
Longitudinal
Size Change
%
°F
°C
°F
°C
2200
1204
1025
552
65
+.22
Surface Treatments
REX M2 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 ...................................................................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
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