CPM Rex M4 HC Powder Metal High Speed Steel

CPM Rex M4 HC high-speed steel is an extremely versatile high speed steel that provides a unique combination of high wear resistance with high impact toughness and transverse bend strength. A large volume of vanadium carbides provides the high wear resistance. The high impact toughness and high transverse bend strength are results of the fine grain size, small carbides, and superior cleanliness of the pwder metallurgy (PM) microstructure. CPM Rex M4 HC offers improved cutting tool life compared to conventionally-wrought M1, M2, M7 and other lower-alloyed high speed steels. CPM Rex M4 HC also excels in cold work tooling applications, where it provides better toughness and wear resistance than high-carbon, high-chromium die steels such as D2 and D3.

Composition

Relative Properties

Physical Properties

• Density: 0.286 lb/in³ (7916 kg/m³)
• Specific Gravity: 7.92
• Modulus of Elasticity: 31 x 10⁶ psi (214 GPa)
• Machinability: 40-45% of a 1% carbon steel

Heat Treating Instructions

Critical Temperature: Ac1: 1545°F (840°C)

Hardening

Preheating: 1500-1550°F (816-845°C), equalize. A second preheat at 1850-1900°F (1010-1040°C) is recommended for vacuum hardening.

Austenitizing (High Heat): Heat rapidly from the preheat.

For Cutting Tools:
Soak for 5 to 15 minutes.
Furnace: 2150-2200°F (1177-1204°C)
Salt Bath: 2125-2175°F (1163-1191°C)

For Cold Work Tooling:
Soak for 20 to 45 minutes.
Furnace: 1875-2125°F (1023-1163°C)
Salt Bath: 1850-2100°F (1010-1149°C)

Quenching: Pressurized gas, warm oil, or salt. For pressurized gas, the furnace should have a minimum quench pressure of 4 bars. A quench rate of approximately 400°F (222°C) per minute to below 1000°F (538°C) is critical to obtain the desired properties.

For oil, quench until black, about 900°F (482°C), then cool in still air to 150-125°F (66-51°C).
For salt maintained at 1000-1100°F (538-593°C), equalize in the salt, then cool in still air to 150-125°F (66-51°C).

Tempering: Temper immediately after quenching. Typical temperature range is 1000-1100°F (538- 593°C). Do not temper below 1000°F (538°C). Hold at temperature for 2 hours then air cool to ambient temperature. Double tempering is required. Triple tempering is required when austenitized at 2100°F (1149°C) or higher.

Annealing

Annealing must be performed after hot working and before rehardening.

Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1575-1600°F (857-871°C), and hold at temperature for 1 hour per inch of maximum thickness; 2 hours minimum.

Then cool slowly with the furnace at a rate not exceeding 50°F per hour (28°C per hour) to 1000°F (538°C).

Continue cooling to ambient temperature in the furnace or in air. The resultant hardness should be a maximum of 255 HBW.

*CPM, 1V, 3V, 9V, 10V, 15V, S30V, S90V, Rex M4, Rex T15, and Rex 76 are trademarks of Crucible Industries LLC