M2 High speed steel | 1.3343 steel | HS-6-5-2C | SKH51

M2 High speed steel | 1.3343 steel |

HS-6-5-2C| SKH51

M2 molybdenum high speed tool steel, which has high carbon content and better wear resistance than M1 molybdenum high speed tool steel.

M2 high-speed steel is a tungsten-molybdenum tool steel. M2 is characterised by well-balanced toughness, wear resistance and red hardness properties.

AISI M2 high-speed steel has largely replaced T1 in most applications due to its superior properties and advantageous pricing. M2 is medium-alloyed and is a good all-round performer with good machinability, in this respect it is superior to the high alloyed cold work steels.

Designation by Standards

Chemical Composition (%)

Physical Properties

The physical properties of M2 molybdenum high speed tool steel are given in the following table.

Mechanical Properties

The mechanical properties of M2 molybdenum high speed tool steel are tabulated below.

Thermal Properties

The following table shows the thermal properties of M2 molybdenum high speed tool steels.

Fabrication and Heat Treatment

Machinability

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.

Heat Treatment

M2 tool steels are pre-heated prior to hardening at 815.5°C (1500°F) followed by rapid heating from 815.5°C (1500°F) to 843.3°C (1550°F). These steels are then cooled for 3 to 5 min and quenched in air, salt bath, or oil.

Annealing

ASTM M2 tool steels are annealed at approx 885°C (1625°F) and cooled at 72°C (162°F) per hour or even less. Heat the M2 high-speed steel to 850 - 900°C. Hold at temperature for at least two hours or one hour per 25 mm of thickness. Furnace cool slowly. The maximum hardness should be 248 Brinell.

Tempering

ASTM M2 steels are tempered at 565.5°C (1050°F) to obtain Rockwell C hardness from 60 to 65.

Hardening

Finally, M2 steels are hardened by heat treatment and quenching. Heat the M2 high-speed steel to 850 - 900°C. Hold at temperature for at least two hours or one hour per 25 mm of thickness. Furnace cool slowly. The maximum hardness should be 248 Brinell.

Applications

ASTM M2 tool steels are suitable for making cutting tools. 

The well balance properties of M2 means it is used in a wide range of cutting tools where demands for hot hardness are moderate, such as twist drills, reamers, broaching tools, milling tools, taps and metal saws.

M2 is also suitable for cold work applications such as tools for punching, forming and pressing.