M2 is one of the most commonly used high-speed tool steels

1. Overview of M2 High-Speed ​​Tool Steel

 

Type: M2 is one of the most commonly used high-speed tool steels, suitable for cold-forming tools such as cold extrusion heads. Its high wear resistance makes it suitable for plastic molds and some hot working applications. The addition of tungsten and molybdenum imparts this high-speed tool steel with excellent toughness, wear resistance, hot hardness, and good edge retention, making it suitable for a wide range of applications.
Stainless Steel: M2 has a chromium content of 3.8-4.5%, making it not stainless steel. Stainless steel contains at least 10.5% chromium.

Corrosion Resistance: While M2 has some corrosion resistance, it readily oxidizes in humid and corrosive environments. This resistance can be enhanced by coating materials, limiting exposure, and using good maintenance and storage practices to help prevent corrosion.

Magnetism: As a ferromagnetic material, high-speed tool steel M2 can be magnetized, making it suitable for magnetic clamping.

Wear Resistance: On a scale of 1 to 6, M2 has a wear resistance of 6.

 

 

2. Physical Properties

 

Hardness: M2 has a working hardness of 658-711 BHN (62-65 HRC).

Density: The density of high-speed tool steel M2 is typically 0.293 lb/in³ (8.12 g/cm³).

Tensile Strength: M2 has a tensile strength of approximately 133.4 ksi.

Thermal Conductivity: The thermal conductivity of M2 is 32.8 W/(m*K).

Coefficient of Thermal Expansion: The coefficient of expansion or contraction of M2 with temperature changes.

Resistivity: The resistivity value of M2.

Modulus of Elasticity (Young's Modulus): The modulus of elasticity of M2 is 32.488 ksi.

 

3. Heat Treatment

 

Annealing: Heat M2 uniformly to 1600°F (871°C) for 1 hour per inch (25.4 mm) of thickness, but for a minimum of 2 hours. Cool in the furnace at a rate of 25°F (10°C) per hour to 1000°F (538°C) and continue to cool in the furnace or in air to ambient temperature.

Stress Relief: After heavy machining of M2, stress relief is recommended before hardening to minimize distortion. Heat the material to 1166-1202°F (630-650°C), hold for approximately 2 hours, and then cool in air to room temperature.

Quenching: Preheat M2 to 752°F (400°C), then uniformly heat to 1562°F (850°C). In the final preheating stage, increase the temperature from 1562°F (850°C) to 1922°F (1050°C). Then, rapidly increase the temperature to 2174-2246°F (1190-1230°C) and soak for 5-15 minutes.

Tempering: Heat the material to 986-1040°F (530-560°C) and hold for at least 2 hours. Double tempering is recommended for this material.

 

4. Surface Treatment

 

Nitriding: This process introduces nitrogen to the material surface, improving surface hardness, wear resistance, and fatigue life without affecting the steel's stated properties.

Coating: Various coatings, such as TiN (titanium nitride), TiAlN (titanium aluminum nitride), AlTiN (aluminum titanium nitride), or diamond coatings, can enhance surface hardness, wear resistance, extend tool life, and reduce friction.

Chromium Plating: Chrome plating adds a thin layer of chromium to the surface, typically for aesthetic reasons but also to enhance wear resistance, strength, and corrosion resistance.

 

5. Machinability

 

Machinability: In the annealed condition, M2 is considered a "medium" machinability steel with poor grindability.

Electrical Discharge Machining (EDM): EDM is used for parts made from a single piece of material, for cutting molds or creating complex shapes. As a non-contact, heat-based machining process, it can be used for hard materials like M2.

 

6. Applications

 

M2 high-speed tool steel is commonly used in drills, taps, turning tools, and milling cutters. It cuts 3-4 times faster than conventional cold-work tool steels and maintains its hardness at temperatures up to 1112°F (600°C).

 

7. Conclusion

 

M2 high-speed tool steel is well-suited for high-speed and high-wear applications. It offers excellent wear resistance, high impact toughness, and good compressive strength. However, care should be taken when performing EDM or welding, as these processes can cause brittle areas, potentially creating rust and weak spots where the material may crack. A good surface treatment can create a harder surface and reduce friction, which is essential for working with the material to create taps or drills, for example. With proper care and use, this material can be used in a variety of applications.