Topics Covered
Introduction
Mechanical Properties
Other Designations
Fabrication and Heat Treatment
Hardening
Forging
Tempering
Annealing
Machinability
Applications
Introduction
High speed tool steels are of two types that include molybdenum high speed steels and tungsten high speed steels. Molybdenum high speed steels or group M steels range from M1 to M10. Group M steels cover more than 95% of all high speed tool steels manufactured in the U.S. In comparison with the tungsten high speed steels, the group M steels have lower initial cost. Tungsten is present in types M1 to M10, except type M6, and cobalt is absent in these types of molybdenum high speed steels.
Intermediate high speed steels which comprise M50 and M52 form a sub-group of group M steels. M52 intermediate high speed tool steels are molybdenum – chromium – vanadium type intermediate high speed tool steels.
Mechanical Properties
The mechanical properties of M52 tool steels are displayed in the following table.
|
Properties |
Metric |
Imperial |
|---|---|---|
|
Hardness, Rockwell C (oil quenched from 1175°C; 622°C temper temperature) |
54.5 |
54.5 |
|
Hardness, Rockwell C (oil quenched from 1175°C; 482°C temper temperature) |
62.5 |
62.5 |
|
Hardness, Rockwell C (oil quenched from 1175°C; 520°C temper temperature) |
63.5 |
63.5 |
|
Izod impact unnotched (oil quenched at 1175°C; 482°C temper temperature) |
38.0 J |
28.0 ft-lb |
|
Izod impact unnotched (oil quenched at 1175°C; 594°C temper temperature) |
59.7 J |
44.0 ft-lb |
|
Izod impact unnotched (oil quenched at 1175°C; 622°C temper temperature) |
63.7 J |
47.0 ft-lb |
Other Designations
Equivalent materials to M52 tool steels are:
Fabrication and Heat Treatment
Hardening
M52 tool steels are preheated to 871°C (1600°F) and then soaked in order to obtain stability and optimum performance. They are then superheated to 1177°C (2150°F) to reach furnace temperature and they are immediately quenched in oil.
Forging
M52 tool steels are preheated to 1500°F (816°C) and soaked. The temperature is then increased to 1093°C (2000°F) prior to working. Forging of the M52 tool steels should not be carried out below 982°C (1800°F).
Tempering
M52 tool steels are tempered immediately after being quenched and double tempering at 552°C (1025°F) is recommended to obtain optimum performance.
Annealing
M52 tool steels are heated to 843°C (1550°F) and then cooled very slowly. These steels are susceptible to decarburization during heat treatment.
Machinability
M52 tool steels are machined in the annealed condition and their machinability is 65% of a 1% carbon steel, or 50% of a B1112 steel.
Applications
M52 tool steels are mostly used in tooling applications in which abrasion resistance is not very important. These tooling applications include commercial twist drills and woodworking tools.
