M2
M2 Grade Introduction:
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 of 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 steel through a physical vapor deposition process to improve the performance and life span of the tool.
M2 Grade Application:
- The main use of high-speed steel continues to be in the manufacture of various cutting tools.
- Twist drills
- Reamers
- Broaching tools
- Taps
- Milling tools
- Metal saws
- Cutting tools
M2 Equivalent Grades:
| Country |
USA |
German |
Japan |
| Standard |
ASTM A600 |
DIN EN ISO 4957 |
JIS G4403 |
| Grades |
M2 |
1.3343 |
SKH51 |
M2 Chemical Composition:
| Element |
C |
Si |
Mn |
P |
S |
Cr |
Mo |
Ni |
V |
Cu |
W |
| Content (%) |
0.78-1.05 |
0.20-0.45 |
0.15-0.40 |
0.03 |
0.03 |
0.20-0.45 |
4.5-5.5 |
0.3 |
1.75-2.2 |
0.25 |
5.50-6.75 |
Mechanical Properties:
| Property |
Metric |
Imperial |
| Hardness, Rockwell C (tempered at 1150°F, quenched at 2200°F) |
62 |
62 |
| Hardness, Rockwell C (as hardened, quenched at 2200°F) |
65 |
65 |
| Compressive yield strength (when tempered at 300°F) |
3250 MPa |
471000 psi |
| Izod impact unnotched (when tempered at 300°F) |
67 J |
49.4 ft-lb |
| Abrasion (loss in mm³, as-hardened; ASTM G65) |
25.8 |
25.8 |
| Abrasion (loss in mm³, tempered at 1275°F; ASTM G65) |
77.7 |
77.7 |
| Poisson’s ratio |
0.27-0.30 |
0.27-0.30 |
| Elastic modulus |
190-210 GPa |
27557-30458 ksi |
Physical Properties:
| Physical Properties |
Metric |
Imperial |
| Density |
8.16 g/cm3 |
0.294 lb/in3 |
| Melting point |
4680°C |
2600°F |
Thermal Properties:
| Thermal Properties |
Metric |
Imperial |
| 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 |
Forging Properties:
Pre heat M2 HSS steel slowly and uniformly to 850-900°C. The heat should then be increased more quickly to the forging temperature of 1050-1150°C. If during the forging the temperature of the M2 high-speed tool steel material drops below 880-900°C, re-heating will be necessary. Cool the M2 steel component very slowly after forging.
Stress Relieving:
Stress-relieving M2 is recommended after machining or grinding and before hardening to minimize the chance of distortion. Heat the component to 600 – 700°C and soak well (for approximately two hours), then cool in air.