Oct 25 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Fabrication and Heat Treatment
Hardening
Machinability
Tempering
Applications
Introduction
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.
Chemical Composition
The chemical composition of M3 Class 2 molybdenum high speed tool
steel is outlined in the following table:
| Element |
Content
(%) |
Fe
|
Balance
|
| C |
1.15-1.25 |
| Mn |
0.15-0.40 |
| Si |
0.20-0.45 |
| Cr |
3.75-4.50 |
| Ni |
0.3 |
| Mo |
4.75-6.50 |
| W |
5.00-6.75 |
| V |
2.75-3.75 |
| Cu |
0.25 |
| P |
0.03 |
| S |
0.03 |
Physical Properties
The following table shows the physical properties of M3 Class 2
molybdenum high speed tool steel.
| Physical
properties |
Metric |
Imperial |
| Density |
8.16g/cm3 |
0.294 lb/in3 |
Mechanical Properties
The mechanical properties of M3 Class 2 tool steel are displayed in
the following table.
| Mechanical
properties |
Metric |
Imperial |
| 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 |
| Poisson's ratio |
0.27-0.30 |
0.27-0.30 |
| Elastic modulus |
190-210 GPa |
27557-30458 ksi |
Other Designations
Equivalent materials to M3 Class 2 molybdenum high speed tool steel
are:
- ASTM A600 (M-3, Cl.2)
- DIN 1.3342
- DIN 1.3344
- SAE J437 (M3)
- SAE J438 (m3)
- UNS T11323
Fabrication and Heat Treatment
Hardening
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.
Machinability
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.
Tempering
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).
Applications
M3 Class 2 molybdenum high speed tool steels are used in the
production of taps, broaches, end mills, milling cutters and reamers.