High speed tool steels are divided into molybdenum high-speed steels and tungsten high-speed steels. Group M steels or molybdenum high speed steels have less initial cost. Tungsten is found in types M1 to M10, except type M6, and cobalt is not present in these types of molybdenum high speed steels.
M3 Class 2 molybdenum high speed tool steel, also known as tungsten moly high speed tool steel, provides excellent wear resistance in severe cutting operations.
The chemical composition of M3 Class 2 molybdenum high speed tool steel is outlined in the following table:
The following table shows the physical properties of M3 Class 2 molybdenum high speed tool steel.
The mechanical properties of M3 Class 2 tool steel are displayed in the following table.
|Hardness, Rockwell C (tempered at 1150�F)||57.0 - 59.0||57.0 - 59.0|
|Hardness, Rockwell C (as quenched)||65.0 - 66.0||65.0 - 66.0|
|Izod impact unnotched||32.5 - 42.0 J||24.0 - 31.0 ft-lb|
|Elastic modulus||190-210 GPa||27557-30458 ksi|
Equivalent materials to M3 Class 2 molybdenum high speed tool steel are:
ASTM A600 (M-3, Cl.2)
SAE J437 (M3)
SAE J438 (m3)
Fabrication and Heat Treatment
M3 Class 2 molybdenum high speed tool steel is hardened when preheated to 871°C (1599°F) and it is then soaked thoroughly, furnace cooled through 593°C (1099°F) and finally air cooled.
In the annealed condition, M3 Class 2 tool steel is referred to as medium machinability tool steel. It has a machinability rating of 50% when compared to Group W steels. It has very poor grinding capability even though it can be shaped by a grinding process.
Triple tempering is recommended for M3 Class 2 steel. Specified tempering temperatures enable obtaining many different hardness values and this steel is usually tempered at 566°C (1051°F).
M3 Class 2 molybdenum high speed tool steels are used in the production of taps, broaches, end mills, milling cutters and reamers.
Source - www.azom.com