PM M4This high-speed tool steel epitomizes versatility, boasting an extraordinary blend of high wear-resistance, superior impact toughness, and remarkable bend strength. These attributes stem from its fine grain size, minuscule carbides, and exceptional cleanliness. PM M4delivers superior cutting tool longevity when compared to traditionally-wrought M1,M2,M7,and other lower-alloyed high-speed steels. PM M4 outperforms high-carbon, high-chromium die steels like D2 and D3 in cold work tooling applications.
Other Known Names:CPM REX M4 steel®, ASP 2004, S690
Common Usage
Ideal for Broaches, End Mills, Punches, Hobs, Fine Blanking, and Forming Dies.
Physical Properties
Density:
0.286 lb/in3(7806 kg/m3)
Specific Gravity:
7.92
Modulus Of Elasticity:
31 x 106psi (214 GPa)
Machinability:
40-45% of 1% carbon steel
PM M4 High Speed Steel Chemical Composition
| MAXIMUM | TYPICAL | ||||||
|---|---|---|---|---|---|---|---|
| Carbon | Chromium | Tungsten | Molybdenum | Vanadium | Cobalt | Annealed | Tempered |
| C | Cr | W | Mo | V | Co | Hb | HrC |
| 1.4 | 4 | 5.65 | 5.2 | 4 | - | 255 | 65 |
PM M4 High Speed Steel Heat Treating
| ANNEALING | PREHEAT | AUSTENITIZING | QUENCH | TEMPERING |
|---|---|---|---|---|
| Temp | Temp | Temp | Medium | Temp |
| °F | °F | °F | °F | |
| 1550/1600 | 1500/1550 | 2175/2220 | Salt/Oil/Atm | 1025/1050 |
PM M4 High Speed Steel Thermal Treatments
Preheating:Gradually heat at a maximum rate of 400°F per hour (222°C per hour) to 1500-1600°F (816-871°C), then equalize.
Austenizing (High Heat):
Heat rapidly from the preheat stage.
For Cutting Tools:
- Soak for 5 to 15 minutes.
- Furnace: 2150-2175°F (1177-1191°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)
To maximize toughness, opt for the lowest temperature. For optimal hot hardness, select the highest temperature.
Quenching:
Utilize pressurized gas, warm oil, or salt.
For pressurized gas, the furnace should maintain a minimum quench pressure of 4 bars. Achieve a quench rate of roughly 400°F (222°C) per minute down to below 1000°F (538°C) to secure the desired properties.
For oil quenching, quench until black (about 900°F or 482°C), then let cool in still air to 150-125°F (66-51°C).
To maintain optimal salt conditions, hold the temperature steady at 1000-1100°F (538-593°C). Let the material equalize in the salt bath, then allow it to cool in still air until it reaches 150-125°F (66-51°C).
Tempering:
Begin tempering immediately after quenching to preserve the material's properties.
The recommended tempering temperature range is 1000-1100°F (538-593°C). Ensure not to temper below 1000°F (538°C). Maintain the material at the tempering temperature for 2 hours, followed by air cooling to ambient temperature. Double tempering is essential, and triple tempering is mandatory when austenitized at 2100°F (1149°C) or higher.
Annealing:
Annealing should be performed post hot-working and prior to re-hardening to ensure material stability.
Heat the material at a controlled rate not exceeding 400°F per hour (222°C per hour) until reaching 1550-1600°F (843-871°C). Maintain this temperature for a minimum of 2 hours, or 1 hour per inch (25.4 mm) of thickness. Gradually cool with the furnace at a rate not exceeding 50°F per hour (15°C per hour) until it reaches 1000°F (538°C). Continue cooling to ambient temperature, either in the furnace or in open air.
