REX® M7N
(AISI M7)
REX M7 is molybdenum type high speed steel designed with higher carbon and vanadium to provide higher hardness after heat treatment and improved wear resistance compared to M1 steel.
Typical Chemistry
Carbon 1.00%
Manganese 0.30%
Silicon 0.40%
Chromium 3.75%
Vanadium 2.00%
Tungsten 1.75%
Molybdenum 8.75%
Typical Applications
Chasers End Mills
Counterbores Form Tools
Countersinks Reamers
Drills Taps
Annealed Hardness: BHN 229/248.

Machinability in the annealed condition is approximately 40% of W1 Tool Steel (1%C).

Thermal Treatments

Critical Temperature: 1530F(830C).

Forging: 2000F(1095C) 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 229/248

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: 2150-2200F(1175-1205C), 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
2150F
(1170C)
2200F
(1205C)
°F
°C
1000
540
65.1
66
OPTIMUM FOR MAXIMUM TOUGHNESS AND EFFECTIVE STRESS-RELIEVING.
1025
550
64.9
66
1050
565
64
65.2
1075
580
61.2
64
1100
595
57.7
62
1125
605
–
60
1150
620
–
57
Size Change During Hardening
Hardening
Temp.
Tempering
Temp.
HRC
Longitudinal
Size Change
%
°F
°C
°F
°C
2200
1175
1025
550
66
+.22
Surface Treatments
REX M7 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 ............................................................................................................7.95
Density .......................................................................................0.287 lb/in3 (7950 kg/m3)
Coefficient of Thermal Expansion
Temperature
Range
Coefficient of Thermal
Expansion
°F
°C
in/in/°Fx10-6
mm/mm/°Cx10-6
100-500
21-260
5.34
9.61
100-800
21-427
6.35
11.40
100-1000
21-538
6.81
12.30
Return to top of page