Hot Work Tool Steel M 2
M2 Molybdenum High Speed Tool Steel
M2 is a general purpose molybdenum high speed steel. This grade is characterized by balanced Combination of abrasion resistance, toughness and good red hardness. Due to its comparatively low Carbon content, M2 has an excellent combination of toughness properties and abrasion resistance When properly hardened and tempered. M2 is used in a wide used for all kinds of cutting tool, knife and punch and die applications.
Molybdenum high speed steels are designated as Group M steels according to the AISI classification system. Over 95% of high-speed steels manufactured in the US are group M steels. Tungsten is present in all types from M1 to M10, except M6, and cobalt is not present in any these steels. Molybdenum high speed steels have similar performance when compared to tungsten high-speed steels. However, the initial cost of molybdenum tool steels is lower. Titanium nitride, titanium carbide and several other coatings can be used in the tools made of this kind of steels through physical vapor deposition process to improve the performance and life span of the tool.
|Density (@20°C/68°F)||Density||0.294 lb/in3|
|Hardness, Rockwell C (air cooled from 899°C, 30 mins)||54.5||54.5|
|Hardness, Rockwell C (air cooled from 927°C, 30 mins)||56||56|
|Hardness, Rockwell C (air cooled from 982°C, 30 mins)||56.5||56.5|
|Modulus of elasticity||207 GPa||30000 ksi|
|Charpy impact (V-notch; oil quenched from 954°C; 149°C temper temperature)||10.8 J||8.00 ft-lb|
|Charpy impact (V-notch; oil quenched from 954°C; 625°C temper temperature)||29.8 J||22.0 ft-lb|
|Machinability (1% carbon steel)||70.0 - 75.0%||70.0 - 75.0%|
|CTE, linear (@20.0 - 100°C/ 68.0 - 212°F)||10 μm/m°C||5.56 μin/in°F|
|CTE, linear (@20.0 - 500°C/68.0 - 932°F)||12.2 μm/m°C||6.78 μin/in°F|
|CTE, linear (@20.0 - 850°C/68.0 - 1560°F)||12.6 μm/m°C||7 μin/in°F|
Shaping of M2 tool steels can be carried out using grinding methods. However, they have poor grinding capability and hence they are regarded as “medium” machinability tool steel under annealed conditions. The machinability of these steels is only 50% of that of the easily machinable W group or water hardening tool steels.
M2 tool steels are pre-heated prior to hardening at 2610°C (4730°F) followed by rapid heating from 2610°C (4730°F) to 3960°C (7160°F). These steels are then cooled for 3 to 5 min and quenched in air, salt bath or oil.
M2 tool steels are annealed at 2925°C (5297°F) and cooled at 72°C (162°F) per hour or even less.
M2 steels are tempered at 1890°C (3434°F) to obtain Rockwell C hardness from 60 to 65.
Typical applications for M2 high speed steel are twist drills, reamers, broaching tools, taps, milling tools, metal saws. M2 is suitable for cold forming tools such as extrusion rams and dies, also cutting tools, plastic moulds with elevated wear resistance and screws
If tools produced from M2 high speed steel are heavily machined or ground it is recommended to stress relieve after machining and prior to hardening to minimise the possibility of distortion. To stress relieve heat the component to 675-725°C and soak well (for approximately two hours), then cool in air. The tools can be finish machined before heat treatment.
Pre heat the steel in two steps; 450-500°C then 850-900°C. Then continue heating to the final hardening temperature of 1200-1250°C and ensure that the component is heated through. Care must be taken not to allow the component to remain too long at the hardening temperature. Quench in warm oil or brine. If quenching in brine allow the tools to equalize, then complete the quench in air. If quenching in oil remove the component from the oil at about 500°C and then air cool. M2 high speed steel is also suitable for vacuum hardening.