Molybdenum wire MCH 8 micron - 500 micron
Relevance
Molybdenum wire has a high elastic modulus, low coefficient of thermal expansion, viscosity, hardness, resistance to aggressive environments. These advantages allow to apply it in various fields of modern industry. It has excellent mechanical strength and corrosion resistance. Compared with tungsten — it is half the size, and therefore has a large specific strength (at t° to 1370°C).
| Physical quality | |
|---|---|
| The temperature at which the obtained data the features of t°C | 20°C |
| The linear thermal expansion coefficient α [1/°C] | Of 4.9x10-6 |
| Density [g/cm3] | 10,2 |
| The melting temperature t°C | 2620°C |
| Specific heat at 20 °C [kJ/(kg·deg)] | 0,256 |
| The thermal conductivity K [W/(m·K)] | 142 |
| Electrical resistivity R, Mhmm2/m | 0,054 |
Chemical properties
Mo is stable in cold alkali, but hot slowly destroyed. It dissolves hydrochloric, sulfuric acids at 80 °C. Nitric acid, Aqua Regia dissolve it only at 100 °C. the Impurities of carbon, oxygen, silicon, aluminum, nitrogen, iron, sulphur, calcium, phosphorus significantly change its properties. The bulk of these impurities increases the fragility. Most harmful of all impurities is considered to be oxygen. If it is contained in a volume 0,0008−0,004%, the low-melting oxides can lead to a sharp increase in brittleness of the material, hindering plastic deformation, especially in the simultaneous presence of carbon with nitrogen. With increasing percentage of oxygen than 0.015%, the processing pressure because of the fragility becomes impossible.
Disadvantages
Molybdenum refers to rare earth elements, in its purest form is quite difficult to identify, it is refractory and hard to work — all this affects the high cost of the final products.
The production of wire made of molybdenum
| True annealing temperature, ° C | The diameter of molybdenum wire |
|---|---|
| 1500−1550 | 200 — 800 µm |
| 1450−1500 | 801 — 1000 µm |
| 1400−1450 | 1001 — 1250 µm |
| 1300−1350 | 1251 — 2500 µm |
MOLYBDENUM WIRE FOR FILAMENT LAMPS GOST 27266−87.
| Mark Mo | Application | Group | Type | Precision production | Wire diameter |
|---|---|---|---|---|---|
| MRN | The inputs of the core with the helix of molybdenum and its alloys, traverse | And | - | Normal | 600−2500 |
| MK | The core for the manufacture of molybdenum monosperma, hooks, supports, etc. parts of lamps | A B | To | Increased, normal | 30−2500 15−400 |
| MCH | The inputs, support, cathodes of gas discharge devices, traverses powerful, special incandescent lamps | And | - | Normal | 200−2500 |
| Auxiliary spiral | And | Sun | Increased | 45−120 | |
| Kern spirality for the production of bispira molybdenum | And | KS | Increased | 45−300 |
Quality requirements
Wire, ∅ 0.4 mm is available in black or dark gray, and the wire of larger diameter, usually light gray. In accordance with the technical specifications, not on its surface may be traces of oxidation, grease or other contaminants. The surface must be free of cracks, smooth, and without burrs. Requirements molybdenum wire ∅ 0.5 mm more not so hard, here are allowed burrs, beyond the minimum. In the special tables set forth the rules and tear stretching. Quality wire can withstand spiralization.
| The grade of molybdenum | Ultimate strength, kgf/mm2 | Wire diameter, µm | Group | Conditional tensile strength of the HS/mg/200mm |
|---|---|---|---|---|
| MCH-K | 173 163 142 | 15 — 70 71 — 90 91 — 200 | A, B | 85 80 70 |
| MK | 121 | 200 — 500 | And | 60 |
| MCH-KS | 152 142 121 | 45 — 70 71 — 90 91 — 200 | And | 75 70 60 |
Application
Molybdenum wire has outstanding mechanical strength, refractoriness, corrosion resistance. It is resistant to most aggressive environments, and also in solutions of concentrated alkalis and acids — sulphuric, hydrofluoric and hydrochloric. The lifetime of molybdenum wire is significantly higher than the similar products of other metals. She is very reliable, durable, popular in the most difficult conditions of modern production, is widely used in the nuclear power industry, mechanical engineering, industrial chemistry. It is hardly replaceable in the manufacture of resistance elements for heating furnaces, lighting devices that require high heat resistance. Molybdenum piercing mandrels are used for punching stainless steel seamless pipes and for drilling steel. The most popular brand of wire is grade MCH.
| The grade of molybdenum | Group | The condition of the wire | Wire diameter | Accuracy class production | The purpose of the wire |
|---|---|---|---|---|---|
| MCH | And | Black | 20 — 2500 µm | 1,2 | support, hooks, beams, Plushenko core with the helix |
| B | Purified | 20 — 1000 µm | at the core of helix, hooks of tubes | ||
| In | Annealed | details vacuum devices | |||
| G | Purified, annealed | at the core of helix, traverse | |||
| D | Annealed | 1 | at the core of helix | ||
| MRN | And | Black | 600 — 2500 µm | 1 | |
| In | Annealed | 600 — 1000 µm | |||
| G | Purified, annealed | ||||
| D | Annealed | 1,2 | traverse | ||
| MK | And | Black | 200 — 2500 µm | 1,2 | the inputs to junction with metallic ceramics and refractory glass and other high-temperature parts |
| B | Purified | 200 — 1000 µm | |||
| In | Annealed | ||||
| G | Purified, annealed |
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