24 July 2021 High Speed Steel Bar
M2 High Speed Steel Bar
M2 is a molybdenum-type high-speed steel with well-balanced toughness, wear-resistance and red hardness properties. It is easy to overheat, so the quenching heating temperature should be strictly controlled, and the heat treatment protection requirements are strict. Because of its good hardness and wear resistance, it is mostly used Manufacturing tools for cutting materials that are difficult to cut.
M2 high-speed steel has a greater tendency to carbides, so it has strict requirements for heat treatment protection and is suitable for molds that can withstand vibration and impact loads. Factory hardness: ≤255HB, can be used to make cold forging dies, Precision punching dies, powder pressing dies, etc., shearing machine dies, plastic dies with glass fiber addition, etc. Suitable for molds that bear vibration and impact loads: deep drawing molds, punching molds. Metal cutting saw blades, cold heading and extrusion tools, etc. This grade is commonly used in cold work punches and dies and cutting applications involving high-speed and light cuts. M2 high-speed steel is by far the most popular high-speed steel to replace T1 in most applications because of its superior properties such as its bending strength, toughness and thermo-plasticity.
Chemical Composition:
| C(％) | Si(％) | Mn(％) | P(％) | S(％) | Cr(％) | Ni(％) | Cu(％) | V(％) | Mo(%) | W(%) |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.80～0.90 | 0.20 ~ 0.45 | 0.15 ~ 0.40 | ≤0.030 | ≤0.030 | 3.80～4.40 | ≤0.30 | ≤0.25 | 1.75 ~ 2.20 | 4.50 ~ 5.50 | 5.50 ~ 6.75 |
Mechanical Propoerties:
| Yield Strength Rp0.2(MPa) | Tensile Strength Rm(MPa) | Impact Energy KV(J) | Elongation at Fracture A(%) | Impact toughness value αkv (J/cm2) | Hardness |
|---|---|---|---|---|---|
| ≥ 1960(100) | ≥ 2080(110) | ≥ 98 | ≥ 9 | ≥ 90 | ≥ 63 HRC |
Physical Properties:
- Density: 0.294 lb/in3 (8138 kg/m3)
- Specific Gravity: 8.14
- Modulus of Elasticity: 30 x 106 psi (207GPa)
- Machinability: 50-60% of a 1% carbon steel
Coefficient of Thermal Expansion (65-66 HRC):
| Temperature °F | in/in °Fx10-6 | Temperature °c | mm/mm °Cx10-6 |
|---|---|---|---|
| 70-200 | 5.69 | 21-93 | 10.23 |
| 70-400 | 6.09 | 21-204 | 10.95 |
| 70-600 | 6.42 | 21-316 | 11.55 |
| 70-800 | 6.67 | 21-427 | 12 |
| 70-1000 | 6.97 | 21-358 | 12.54 |
Heat treatment response of M2 high speed steel:
Imapct Toughness of M2 high speed steel:
Heat treatment and after process advice:
Hardening:
Critical Temperature:
Ac1: 1530°F (832°C) Ac3: 1610°F (877°C)
Ar1: 1430°F (777°C) Ar3: 1380°F (749°C)
Preheating:
To minimize distortion and stresses in large or complex tools use a double preheat. Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1100°F (593°C) equalize, then heat to 1450-1550°F (788-843°C). For normal tools, use only the second temperature range as a single preheating treatment.
Austenitizing (High Heat):
Heat rapidly from the preheat.
For Cutting Tools:
Furnace: 2200-2250°F (1204-1232°C)
Salt: 2175-2225°F (1191-1218°C)
To maximize toughness, use the lowest temperature.
To maximize hot hardness, use the highest temperature.
For punches, dies, and tools that require maximum
toughness without hot hardness:
Furnace: 2075-2175°F (1175-1191°C)
Salt: 2050-2150°F (1121-1177°C)
Quenching:
Pressurized gas, warm oil, or salt. For pressurized gas, a rapid quench rate 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, then cool in still air to 150 -125°F (66-51°C).
Tempering:
Temper immediately after quenching. Typical tempering range is 1025-1050°F (552-566°C). Hold at temperature for 2 hours, then air cool to ambient temperature. Double tempering is required. For large cross sections, and especially for blanks from which tools will be cut by wire EDM, triple tempering is strongly recommended.
Annealing:
Annealing must be performed after hot working and before re-hardening.
Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1525-1550°F (829-843°C), and hold at temperature for 1 hour per inch (25.4 mm) of 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 248 HBW or lower.