Oct 25 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesThermal Properties
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 tools made of this kind of steels through physical vapor deposition process to improve the performance and life span of the tool.
Chemical Composition
The following table shows the chemical composition of M35 molybdenum high speed tool steels.
| Element |
Content (%) |
| C |
0.93 |
| Cr |
4.2 |
| Co |
4.9 |
| Fe |
76.52 |
| Mo |
5 |
| Si |
0.3 |
| W |
6.25 |
| V |
1.9 |
Physical Properties
The physical properties of M35 molybdenum high speed tool steels are given in the following table.
| Physical properties |
Metric |
Imperial |
| Density |
8.14 g/cm3 |
0.294 lb/in3 |
Mechanical Properties
The mechanical properties of M35 molybdenum high speed tool steels are tabulated below.
| Mechanical properties |
Metric |
Imperial |
| Hardness, Rockwell C (oil quenched from 1232°C, 5 mins) |
64.8 |
64.8 |
| Hardness, Rockwell C (oil quenched from 1177°C, 5 mins) |
65.2 |
65.2 |
| Hardness, Rockwell C (oil quenched from 1204°C, 5 mins) |
65.2 |
65.2 |
| Modulus of elasticity |
207 GPa |
30000 ksi |
| Machinability (1% carbon steel) |
45.0 - 50.0% |
45.0 - 50.0% |
Thermal Properties
The following table shows the thermal properties of M35 molybdenum high speed tool steels.
| Thermal properties |
Metric |
Imperial |
| CTE, linear (@21 - 399°C / 69.8 - 750°F) |
11.4 μm/m°C |
6.33 μin/in°F |
| CTE, linear (@21 - 593°C /69.8 - 1100°F) |
11.5 μm/m°C |
6.39 μin/in°F |