Dec 20 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesOther DesignationsThermal PropertiesFabrication and Heat Treatment Machinability Forming Welding AnnealingApplications
Introduction
Molybdenum, a refractory metal is widely used as an alloying element. Due to its good thermal and electrical conductivity, high melting point and excellent strength at elevated temperatures, molybdenum can be used for various applications in its pure form. In addition, molybdenum has low thermal expansion coefficient. It has to be protected by a suitable coating to withstand temperatures above 500°C under an oxidizing environment.
The following section will explain in detail about molybdenum.
Chemical Composition
The following table shows the chemical composition of molybdenum.
| Element |
Content (%) |
| Molybdenum, Mo |
100 |
Physical Properties
The physical properties of molybdenum are outlined in the following table.
| Properties |
Metric |
Imperial |
| Density |
10.3 g/cm³ |
0.369 lb/in³ |
| Melting point |
2625°C |
4760°F |
Mechanical Properties
The mechanical properties of molybdenum are outlined in the following table.
| Properties |
Metric |
Imperial |
| Tensile strength (annealed) |
324 MPa |
47000 psi |
| Shear strength (torsional strain rate 0.25/s) |
500 MPa |
72500 psi |
| Compressive yield strength (0.01% yield) |
400 MPa |
58000 psi |
| Modulus of elasticity |
330 GPa |
47900 ksi |
| Modulus of elasticity at elevated temperature (@2000°C/3630°F) |
160 GPa |
23200 ksi |
| Poissons ratio (calculated) |
0.38 |
0.38 |
| Hardness, Brinell (converted from Vickers for 3000 kg load/10 mm ball Brinell test. annealed) |
225 |
225 |
| Hardness, Rockwell A (converted from Vickers. annealed) |
60 |
60 |
| Hardness, Rockwell B (converted from Vickers. annealed) |
98 |
98 |
| Hardness, Rockwell C (converted from Vickers. annealed) |
19 |
19 |
| Hardness, Vickers (annealed) |
230 |
230 |
Other Designations
Other designations that are equivalent to molybdenum include the following:
Thermal Properties
The thermal properties of molybdenum are outlined in the following table.
| Properties |
Metric |
Imperial |
| Thermal expansion coefficient (@20°C/68°F) |
5.35 µm/m°C |
2.97 µin/in°F |
| Thermal conductivity |
138 W/mK |
958 BTU in/hr.ft².°F |
Fabrication and Heat Treatment
Machinability
Machining molybdenum is similar to that of cast iron. Molybdenum tends to tear if positive feeds are not employed.
Forming
Molybdenum can be efficiently formed while bending in a transverse direction or against rolling or grain direction. The workpiece can be heated before forming to avoid cracking.
Welding
Molybdenum can be welded using electron beam methods and other resistance methods in helium or argon atmosphere.
Annealing
Annealing of molybdenum can be performed at 1149°C (2100°F).
Applications
The following are the major applications of molybdenum:
- Heating elements in furnaces
- Filament supports in electric lamps
- Heat shields
- Hearth trays, plates and racks
- Missile and aircraft parts
- Boring bars
- Thermocouples
- Nuclear energy applications