Molybdenum application. Many-sided molybdenum: where it is used, properties, biological role in the human body
Molybdenum lead wires in incandescent lamps appeared in the early days of the 20th century.
Molybdenum was chosen for this for its stability and strength at elevated temperatures.
Since this first application, scientists and engineers have discovered that other properties of molybdenum make it an indispensable material for many technical solutions. Molybdenum and its alloys are widely used in industry and electronics, especially in ferrous metallurgy for high-temperature alloys.
Many of them use molybdenum's strength and stability at high temperatures, much like the first conductive wire in an incandescent lamp. However, molybdenum has many other properties that make it attractive for industrial use and manufacturing, including as a traditional component of high temperature industrial alloys. You can buy a molybdenum crucible here at a very attractive price.
The main properties of molybdenum:
High thermal conductivity;
. High electrical conductivity;
. Low odds thermal expansion;
. Resistant to molten metal;
. Compatible with most glass compositions;
. Thermal resistance;
. High rigidity and strong adhesion to glass is used in lamps and electronic devices;
Since many of its properties are attractive to engineers and designers, molybdenum metal and its alloys are used in:
Lighting;
. Electrical and electronic appliances;
. Medical equipment;
. Material handling equipment;
. High-temperature furnaces and related equipment for thermal spraying of coatings;
. Aerospace and defense components;
Applications in all of these areas require unique combinations of several properties. Molybdenum and its alloys, as well as composite materials that use molybdenum metal, provide unique combinations of thermal and electrical conductivity, thermal expansion, high temperature strength and creep resistance, vapor pressure, environmental stability,
abrasion and wear resistance that make them ideal.
This article intends to help the reader understand why this unique material finds applications in such diverse fields. It also provides some information on the application and manufacture of machinery from molybdenum and its alloys.
How molybdenum metal products are made
Because pure molybdenum melts at a very high temperature, and because it oxidizes at relatively low temperatures, traditional smelting processes cannot extract the metal from the ore. Instead, the ore is processed through a series of grinding and separation steps to isolate the MoS (molybdenum disulphide) from other components. This isolated material, containing up to about 90% MoS, is "roasted" in air to produce MoO (Molybdenum Oxide) and (Sulphur Dioxide). Sulfur dioxide is converted to sulfuric acid and can be sold for chemical applications.
Technical oxide contains about 57% Mo and less than 0.1% S, but this is not a problem for the vast majority of production technologies that use oxide, including the production of molybdenum steel alloy.
However, the technical oxide must be chemically purified in order to be used in the production of molybdenum metal. The oxide is first dissolved in sodium or ammonium hydroxide, and then this
the solution is treated by precipitation and filtration, subjected to solvent extraction, or a combination of both methods together to remove impurities.
Properties and Applications of Molybdenum
There is an inextricable link between the properties of a material and its application.
In some cases, the application of a particular property (such as electrical conductivity) is
of paramount importance. In other countries, a combination of properties allows you to make the best choice.
Optimum is an important word in this context. This means that while other materials may
have an advantage in one or the other property, the combination of properties provides the best solution to engineering design problems.
Sometimes the best solution is not to use a single material, but to use a combination of materials, or a composite material, which allows the designer to tailor the properties of interest to a particular problem.
In all cases, cost-effective solutions are those that ultimately win the competition. This means that molybdenum metal materials, which are very costly as construction materials compared to conventional design office standards, should demonstrate a significant advantage over competitors. For example, molybdenum alloys provide greater strength than pure molybdenum and help maintain that strength at temperatures higher than pure molybdenum can tolerate.
Electrical and electronic appliances and manufacturing
In electronics, molybdenum alloys are widely used by manufacturers in vacuum vacuum tubes, using molybdenum for filament and grid poles due to its high temperature
strength and mechanical stability.
Solid-state device designers have discovered properties other than heat resistance that have made molybdenum compounds indispensable in the manufacture of electronic devices.
Molybdenum in its properties is close to silicon, has excellent thermal and electrical conductivity properties. These properties make it ideal as a substrate for fragile belt devices. Molybdenum provides a strong, rigid base that conducts electricity to and from the device and conducts heat efficiently. Its low CTE minimizes differential expansion stresses.
Semiconductor manufacturing
Semiconductor manufacturing equipment has long used molybdenum components, requiring temperature strength and compatibility with aggressive process environments. The ion implantation process is used to dope silicon wafers with atoms to create semiconductor devices.
Use in metallurgy
High temperature processing
Hot working, heat resistance and deformation resistance are important properties
for hot working equipment. Molybdenum alloy allows the formation temperature regime higher
1100°C. Molybdenum alloys are ideal for brass extrusion, metal casting, liquid metal processing and even plastic injection molding.
Three scientists were involved in the discovery of molybdenum: first, the Swede Karl Scheele obtained MoO 3 oxide from molybdic acid (1778), then the Frenchman P. Guelm reduced it with coal and obtained a metal with impurities (1782), and after J. Berzelius obtained pure molybdenum as a result of the combination of oxide and hydrogen.
Molybdenum is mined all over the planet, since it is relatively evenly distributed both over the earth's crust and in the waters of the oceans. This element is found both in coal and in oil, but its greatest amount is in feldspars.
Molybdenum: physical properties
Externally, molybdenum is a metal of traditional light gray color. It belongs to the category of refractory, but the purer it becomes softer. The main characteristics of molybdenum:
- density (n.a.) - 10.22 g / cm³
- melting point - 2620°C (2890 K)
- boiling point - 4639°C (4885 K)
- thermal conductivity at 300 K – 138 W/(m K)
Molybdenum: chemical properties
The Mo element is stable up to 400°C, after which it oxidizes. To date, several molybdenum oxides have been obtained, including MoO 3 trioxide, molybdenum (IV) oxide MoO 2, etc. There are also carbides - Mo 2 C and MoC, which are crystalline high-melting substances. 
Molybdenum is present in more than 20 types of minerals. The most common can be considered:
- >molybdenite - MoS 2
- molybdite - Fe(MoO 4) 3 nH 2 O
- wulfenite - PbMoO 4
- powellite - SaMoO 4
Molybdenum: where it is applied
The widespread production of molybdenum in the world is primarily due to the needs of the world's metallurgy. This metal acts as an alloying component for most corrosion-resistant and heat-resistant steels. In addition, it is indispensable for giving the metal increased strength characteristics and increasing viscosity. Do not do without molybdenum and manufacturers of light bulbs and high-temperature furnaces. The chemical industry uses Mo and its compounds as catalysts chemical reactions, pigments for dyes, etc. 
Another area of application of molybdenum is medicine: pure Mo helps doctors diagnose oncological diseases. The same element can be found in the composition of the material for mirrors of high-power gas-dynamic lasers.
Biological role
Molybdenum cannot be called a common element, but it is present in every human body. Moreover, the lack of Mo in the human body can disrupt the most important biological processes, thereby causing serious diseases. It is known that the highest concentration of molybdenum is present in following products: in milk, liver, cereals, legumes, leafy vegetables.
Due to its properties, the use of molybdenum in industry is widespread in Russia and the world. Metallurgy, aviation industry, mechanical engineering, agriculture - this is not the whole list where this strategic metal is used. It is so in demand that the price of molybdenum is steadily increasing year by year.
Material characteristic
Physical Properties. Molybdenum is a rare earth metal gray color, externally similar to lead. Melting point 2619 ºС. 
Differs in the increased plasticity. Young's modulus is 336 GPa, which is 1.5 times greater than that of steel. The density is 10.2 g/cm3. Tungsten is considered the most heat-resistant metal. But with regards to specific heat resistance at temperatures up to 1400 ºС, molybdenum has no competitors. Molybdenum has a low linear expansion coefficient. When the temperature changes by 1000 ºС, its size will increase by only 0.0049 mm.
The thermal conductivity is 300 W / m K. The electrical resistance is 5.6 μOhm cm. After preliminary mechanical and thermal treatments, the strength of the metal can be 20-23 kg / mm2. It has paramagnetic properties.
Among the shortcomings, we note low plasticity at temperatures below -30 ºС.
Chemical properties. Molybdenum is completely resistant to environmental influences under normal atmospheric conditions. The oxidation process begins at 420 ºС, forming a compound of low hardness molybdenum oxide.
Molybdenum is inert to hydrogen at temperatures up to 2620 ºС. It is neutral to such elements as carbon, fluorine, silicon, nitrogen, sulfur. Molybdenum does not enter into chemical reactions with the main types of acids: hydrochloric, sulfuric, nitric, fluoric.
Technological properties. At room temperature, a molybdenum circle with a radius of 5 mm can be tied into a knot without the use of special equipment or rolled out to a thickness of 0.1 mm. Such malleability of the metal contributes to obtaining different types profile rental.
Molybdenum is well processed by cutting, provided that a cutting fluid based on sulfur is used.
Molybdenum is not distinguished by quality welds. Refers to group 3 weldability. The welding process is carried out by the arc method. To give welded joints greater plasticity, the contact zone must be in a shielding gas environment. Preference here is given to helium or argon.
Biological properties. Molybdenum is contained in the human body in the range of 8-10 mg. First of all, it affects the course of anabolic processes. Enhances the effects of vitamin C, thereby strengthening the immune system. Molybdenum is a regulator of copper, preventing its accumulation in the blood.
Molybdenum alloys have salient feature chemical composition- low percentage of alloying elements. Only two-component solid solutions have a significant percentage of tungsten in their composition (up to 50%).
The main domestic brands of molybdenum alloy are:
- Molybdenum alloy TsM-2A. Alloying additives are titanium (0.07-03%) and zirconium (0.07-0.15%). In addition to these elements, it may include carbide phases (up to 0.004%). The tensile strength is 30 kg\mm2. It drops significantly after passing the temperature threshold of 1200 C. The main advantages of the alloy are manufacturability and ductility, which make it possible to obtain industrial semi-finished products from it.
- Molybdenum alloy VM-1 does not differ significantly from the alloy described above. It has similar indicators of both chemical and mechanical properties.
- Molybdenum VM-2 contains a larger percentage of zirconium, making it more heat resistant. This allows it to withstand temperatures in the 1300-1400 C environment. It has a tensile strength of 48 kg / mm2, 1.6 times higher than that of TsM-2A.
- Additional doping of the VM-3 molybdenum alloy with titanium (1.3%), zirconium (0.6%), niobium (1.8%) leads to a further increase in heat resistance. Withstands loads up to 27 kg \ mm2 at temperatures up to 1360 C. However, VM-3 has a reduced level of plasticity. This makes it less technologically advanced and limits its use in production.
Applications for molybdenum
As a heat- and corrosion-resistant material, it is used in the production of the most loaded parts of mechanisms and structures different kind industry. Among its main purposes it should be noted:
- Application in the aviation industry in the manufacture of various components of turboprop jet engines: air intakes, turbine blades, etc.
- The rocket and space industry uses molybdenum in the production of individual parts aircraft units: nose cones, heat reflectors, rudders, honeycomb panels, skin, etc. This happens due to the ratio of heat resistance and density. Although molybdenum is inferior in absolute heat resistance to tungsten, it is ahead of it in specific. Therefore, at temperatures below 1350, it is more profitable to use molybdenum, because. significantly reduces the weight of the structure.
- Application in metallurgy as an alloying additive. Molybdenum breaks down the grain structure of the steel, thereby strengthening it. In addition, there is an increase in corrosion resistance, hardenability and hardness. Adding 0.3% molybdenum to steel increases its strength by 3 times.
- In electrical engineering, they are used in the manufacture of holders for tungsten filaments in incandescent lamps. This use is associated with the possession of molybdenum properties of maintaining linear dimensions at elevated temperatures.
- In mechanical engineering, molybdenum is used as a material for cages of plain bearings and balls of rolling bearings. Tips of the cutting tool: countersinks, drills, turning tools, cutters.
- Molybdenum electrodes are used in electric furnaces for melting glass, due to the fact that the metal does not enter into chemical reactions with silicon oxide.
- Molybdenum sulfides serve as high-temperature lubricants in critical friction units.
- In heat engineering, it is used as a material for heaters and thermal insulation of vacuum furnaces.
- In medicine, molybdenum is a raw material in the production of technetium, which serves as a means of diagnosing malignant tumors.
- IN agriculture molybdenum is added to fertilizers. Molybdenum has been proven to increase plant growth.
It is even added to machine oil due to its anti-corrosion properties.
Properties of molybdenum
Molybdenum, like tungsten, in the periodic system of elements of D. I. Mendeleev is located in group VI, but in the 5th period. The hexavalent state is most characteristic of it, although compounds are known in which molybdenum has other valences. Its serial number is 42; atomic mass 95.95; density at room temperature 10200 kg/m3. Molybdenum is a refractory metal and is a transition element. It melts at 2620±10°C and boils at about 4800°C.
Molybdenum and its alloys are also distinguished by a high modulus of elasticity, a low thermal expansion coefficient, good thermal stability, and a small thermal neutron capture cross section. The electrical conductivity of molybdenum is lower than that of copper, but higher than that of iron. In terms of mechanical strength, it is somewhat inferior to tungsten, but is easier to process by pressure.
Physical and mechanical properties molybdenum
| Property | Molybdenum |
| atomic number | 42 |
| Atomic mass | 95,94 |
| Unit cell parameter, nm | 0,3147 |
| Atomic diameter, nm | 0,272 |
| Density at 20°С, g/cm3 | 10,2 |
| Melting point, °С | 2610 |
| Boiling point, °C | 5687 |
| Melting heat, kJ/mol: | 28 |
| Heat of vaporization, kJ/mol: | 590 |
| Molar volume, cm³/mol: | 9,4 |
| Specific heat capacity, J/(g.K) | 0,256 |
| Thermal conductivity, W/(m K) | 142 |
| Linear expansion coefficient, 10-6 K-1 | 4,9 |
| Electrical resistance, µOhm cm | 5,7 |
| Young's modulus, GPa | 336,3 |
| Shear modulus, GPa | 122 |
| Poisson's ratio | 0,3 |
| Hardness, HB | 125 |
| spark color | Short yellow intermittent beam of sparks |
| Metal group | refractory metal |
Chemical properties of molybdenum
Advantages / disadvantages of molybdenum
Advantages:
has a high melting point, and therefore - heat resistance;
because the density of molybdenum (10200 kg/m3) is almost two times less than the density of tungsten (19300 kg/m3), then molybdenum-based alloys have a much higher specific strength (at temperatures below 1370 °C);
molybdenum has a high modulus of elasticity;
low temperature coefficient of expansion;
has good heat resistance;
low thermal neutron capture cross section;
molybdenum is characterized by high corrosion resistance. This metal stable in most alkaline solutions, as well as in sulfuric, hydrochloric and hydrofluoric acids at different temperatures and concentrations.
Flaws:
molybdenum has a small amount of scale;
high brittleness of welds;
low plasticity at low temperatures;
hardening of molybdenum by work hardening can be used only up to 700-800 °C; at higher temperatures, softening occurs due to recovery.
Application of molybdenum
Molybdenum is used as an alloying addition to various alloys, including high-quality steels. Molybdenum and molybdenum alloys are used in parts operating for a long time in vacuum up to 1800°C (in rocket nozzles and in electric vacuum devices), as a structural material in power nuclear reactors, for the manufacture of equipment operating in aggressive environments. Molybdenum wire and molybdenum tape are used for the manufacture of high-temperature furnaces, electric current inputs in light bulbs.
Molybdenum and its alloys are refractory materials. For the manufacture of shells for the head parts of rockets and aircraft, refractory metals and alloys based on them are used in two versions. In one version, these metals serve only as thermal shields, which are separated from the main structural material by thermal insulation. In the second case, refractory metals and their alloys serve as the main structural material. Molybdenum ranks second after tungsten and its alloys in strength properties. However, in terms of specific strength at temperatures below 1350-1450°C, molybdenum and its alloys take first place. Thus, molybdenum and niobium and their alloys, which have a higher specific strength up to 1370 ° C compared to tantalum, tungsten and alloys based on them, are most widely used for the manufacture of skin and frame elements of rockets and supersonic aircraft.
Molybdenum is used to make honeycomb panels for spacecraft, heat exchangers, shells for rockets and capsules returning to earth, heat shields, wing edge trim, and stabilizers in supersonic aircraft. Some parts of ramjet and turbojet engines operate under very difficult conditions (turbine blades, tail skirts, nozzle shutters, rocket engine nozzles, control surfaces in missiles with solid fuel). In this case, not only high resistance to oxidation and gas erosion, but also high long-term strength and impact resistance are required from the material. At temperatures below 1370°C, molybdenum and its alloys are used for the manufacture of these parts.
Molybdenum is a promising material for equipment operating in sulfuric, hydrochloric and phosphoric acids. Due to the high resistance of molybdenum in molten glass, it is widely used in the glass industry, in particular for the manufacture of electrodes for glass melting. At present, molds and cores of machines for die-casting aluminum, zinc and copper alloys are made from molybdepium alloys. The high strength and hardness of molybdenum alloys at elevated temperatures led to their use as a tool for hot working of steels and alloys by pressure (drilling mill mandrels, dies, press dies).
Molybdenum significantly improves the properties of steels. The addition of molybdenum significantly increases their hardenability. Small additions of Mo (0.15-0.8%) to structural steels increase their strength, toughness and corrosion resistance to such an extent that they are used in the manufacture of the most critical parts and products. To increase the hardness, molybdenum is introduced into cobalt and chromium alloys (stellites), which are used for surfacing the edges of ordinary steel parts that are subject to wear (abrasion). It is also part of a number of heat-resistant and acid-resistant alloys based on nickel, cobalt and chromium.
IN pure form molybdenum is used in the form of a tape or wire as heating elements in electric furnaces operating in a hydrogen atmosphere at temperatures up to 1600°C. Molybdenum wire and tin are widely used in the radio-electronic industry and X-ray engineering for the manufacture of various parts of electronic lamps, X-ray tubes and other vacuum devices.
Molybdenum compounds - sulfide, oxides, molybdates - are catalysts for chemical reactions, dye pigments, glaze components. Also, molybdenum as a microadditive is part of fertilizers. Molybdenum hexafluoride is used when applying metallic molybdenum to various materials. MoSi2 is used as a solid high temperature lubricant. Pure single-crystal molybdenum is used to produce mirrors for high-power gas-dynamic lasers. Molybdenum telluride is a very good thermoelectric material for the production of thermoelectric generators (thermo-emf with 780 μV/K). Molybdenum trioxide (molybdenum anhydride) is widely used as a positive electrode in lithium current sources.
Chemical compounds of molybdenum are also used. MoS2 disulfide and MoSe2 diselenide of molybdenum are used as lubricants for friction parts operating at temperatures from -45 to +400°C. In the paint and varnish and light industry for the manufacture of paints and varnishes and for the dyeing of fabrics and furs, a number of chemical compounds of Mo are used as pigments.
| Grades of molybdenum and alloysStandard | brand | The basis % | DR. % | Avg. impurity content. and landings % no more |
| WIRE: OST11 021.004-76, | ||||
| TU48-19-203-76, TU11-77 Yae0.021.122TU, | ||||
| TU11-77 Yae0.021.123TU | MCH | Mo osn. | Al+Fe-0.018. Fe-0.009. Ca+Mg-0.005. Ni-0.005. Si-0.014. C-0.005. | |
| ROD: TU11-77YaeO.O21.O57TU. | ||||
| PLUSHENKA: TU11 Yae0.021.016.-75 | MCH | Mo osn. | ||
| Ni-0.0030. Si-0.003. W-0.2000. C-0.300. | ||||
| O-0.1000. N-0.0030. H-0.0005. | ||||
| MCH BLANKS: TU48-19-88-78, TU48-19-250-77. STRIPS: TU11-77 YaeO.021.055, TU48-19-315-80, TU48-19-272-77, | ||||
| GOST 5.1820-73. FOIL: TU48-19-245-76. PIPES: TU48-19-251-77. | ||||
| WIRE FOR LIGHT SOURCES GOST 27266-87 | MCH | Mo 99.96 | The sum of impurities is 0.04. | |
| ROD: TU11-77 Yae0.021.057TU, | ||||
| TU48-19-203-76, TU48-19-247-77 | ||||
| PLUSHENKA: TU11 YaeO.02 1.016-75. | MCHVP | Mo osn. | According to the statistical data K-0.0100. Ca+Mg-0.0030. Al+Fe-0.014. | |
| Ni-0.0030. Si-0.003. W-0.2000. | ||||
| C-0.300. O-0.1000. N-0.0030. H-0.0005. | ||||
| MCHVP BLANKS: TU48-19-88-78, TU48-19-250-77. STRIPS: TU11-77 YaeO.021.055, TU48-19-315-80, GOST 5.1820-73. | ||||
| FOIL: TU48-19-245-76. PIPES: TU48-19-251-77. | ||||
| STRIPS: TU48-19-272-77 | MCHVP | Mo osn. | Ti-0.007 | |
| B 0.005-0.025 | Fe+A1-0.018 Ca+Mg-0.005. Ni-0.005. Si-0.014. C-0.003. N-0.005. O-0.005. H-0.0008. | |||
| Formula | Connection name | Molecular weight | % |
| MoCl5 | Molybdenum pentachloride | 273,24 | 35,12 |
| MoO2 | molybdenum dioxide | 127,95 | 74,99 |
| Mo03 | Molybdic anhydride | 143,95 | 66,66 |
| MoS2 | Molybdenum disulphide | 160,08 | 59,94 |
| MoSi2 | Molybdenum disilicyl | 152,12 | 63,07 |
| MoCl | molybdenum chloride | 131,39 | 73,02 |
| MoF6 | molybdenum fluoride | 209,94 | 45,7 |
Refractory metal standards
GOSTs and TUs for molybdenum
| Mo | GOST 17434-72 | SHEETS. RODS. FORGINGS FROM POWDER M-MP | |
| Mo | GOST 18905-73 | Molybdenum wire. Assortment | |
| Mo | GOST 25442-82 | Molybdenum strips annealed for deep drawing. | |
| Mo | GOST 27266-87 | Molybdenum wire for light sources MCH, MK, MRN. | |
| Mo | GOST 4759-91 | Ferromolybdenum. Technical requirements and delivery conditions (ISO 5452-80) | |
| Mo | GOST 5.1820-73 | Molybdenum strips | |
| Mo | OST1 90022-71 | Molybdenum wrought alloys | |
| Mo | OST11 021.004-76 | WIRE MOLYBDENUM DDYA IET. OTU MCH, MRN, MK, MS | |
| Mo | SuO,021,001TU TU11-80 | STABIKOV MOLYBDENUM MCH, MRN, MK, MS | |
| Mo | SuO,021,118TU | WIRE MOLYBDENUM CARBIDED FROM WIRE. TU48-9-47-66 AND ANNEALED IN HYDROGEN | |
| Mo | SuO,021,141TU TU11-77 | BLANKS FROM MOLYBDENUM UNGROUND MCH, MK, MRN | |
Molybdenum owes its name to the metal resemblance molybdenum disulfide with lead ore - galena (the Greek name for lead is molybdos).
Element Discovery History
In the Middle Ages in Europe, three minerals of different composition, but almost similar in color and structure, were called molybdenum - galena (Pbs), molybdenite (MoS 2) and graphite (C). By the way, the mineral "molybdenum luster" (another name for molybdenite) was used as a lead for pencils, which left a greenish-gray mark on the sheet.
Sweden is rightfully considered the birthplace of metallic molybdenum, 42 periodic elements. In 1758, the chemist and mineralogist from this country, the discoverer of nickel, Axel Cronstedt, suggested that the above minerals have a completely different nature. Two decades later, his countryman, a pharmaceutical chemist from Köping, Karl Scheele, obtained molybdic acid in the form of a white precipitate ("white earth") by boiling molybdenite in concentrated nitric acid. The scientist intuitively understood that if molybdic acid is calcined with coal, then the metal can be isolated. Not having a suitable furnace, he sent samples to Peter Gjelm, who in 1782 isolated a new metal with big amount carbide impurities. Colleagues named the element "molybdenum" (the formula in the periodic table is Mo).
A relatively pure metal was obtained only in 1817 by the president of the Swedish Academy of Sciences, Jens Berzelius.
Characteristics of a simple substance
The method of obtaining has a great influence on physical properties molybdenum and its appearance. Powdered metal, blanks and rods before sintering - dark gray. The palette of processed rolled products is much richer - from almost black to light silver. The density of molybdenum is 10.28 t/m 3 . The metal melts at a temperature of 2623˚С, and at 4639˚С it boils. Completely pure molybdenum has excellent malleability and ductility, which guarantees easy rolling and stamping. A workpiece with a diameter of up to 12 mm, even at room temperature, can be freely tied with a double knot or rolled out to a thin foil. The metal has good electrical conductivity. The presence of impurities increases the hardness and brittleness and largely determines the mechanical properties of molybdenum.
The most important connections
As part of complex substances the element exhibits a different degree of oxidation from +2 to the highest (the latter compounds are the most stable), which determines the chemical properties of molybdenum. This metal is characterized by compounds with oxygen and halogens (MoO 3 , MoCl5) and molybdates (salts of molybdic acid). Oxidation reactions are possible only at high temperatures (from 600˚С). Further increase will cause molybdenum to interact with carbon, phosphorus, and sulfur. It dissolves well in nitric or heated sulfuric acid.
Phosphoric, arsenic, boric and silicic acids form complex compounds with molybdenum. The most famous and common salt is ammonium phosphomolybdate. Substances containing molybdenum are distinguished by a wide color palette and a variety of shades.
Technology of enrichment of molybdenum ores
Industrial production of absolutely pure molybdenum was mastered only in XX century. The chemical processing of molybdenum ore is preceded by its beneficiation: after grinding in crushers and ball mills, the main method is five- or six-fold flotation. As a result, a high concentration (up to 95%) of molybdenum disulfide is achieved in the raw material.
The next and most important step is firing. Here undesirable impurities of water, sulfur, residues of flotation reagents are removed and molybdenum disulfide is oxidized to trioxide. Further cleaning is possible in several ways, but the following are the most popular:
- ammonia method, in which molybdenum compounds are completely dissolved, and impurities are removed;
- sublimation at a temperature of 900 to 1100 WITH. The result - the concentration of MoO 3 rises to 90-95%.
Industrial production of metallic molybdenum
By passing hydrogen through purified molybdenum trioxide (in laboratories, carbon or carbon-containing gases, aluminum, silicon are often used for reduction), powdered metal is obtained. The process takes place in special tube furnaces with a gradual increase in temperature from 500 to 1000 ˚С.
The process chain for the production of compact metallic molybdenum includes:
- Pressing. The process takes place under pressure up to 300 MPa. The binding component is an alcohol solution of glycerin. The maximum cross section of blanks (rods) does not exceed 16 cm 2, and the length is 600 cm. For larger ones, rubber or polymer forms are used. Pressing takes place in the working chambers, where under high pressure liquid is injected.
- Sintering. It happens in two stages. The first - low-temperature, lasting 30-180 minutes (depending on the size of the workpiece), is carried out in muffle furnaces in a hydrogen atmosphere at a temperature of 1200 ˚С. At the second stage (welding), the workpiece is heated to a temperature close to the melting point (2400-2500 ˚С). As a result, the porosity decreases and the density of molybdenum increases.
Large workpieces weighing up to 3 tons are sintered in induction, electron beam or arc furnaces. The process ends with mechanical processing of sintered products.
The richest deposits
Molybdenum is a fairly rare element in the earth's crust and in the universe as a whole. Of the two dozen minerals that exist in nature, so far only molybdenite (MoS 2) has significant industrial significance. Its resources are not endless, and technologies for extracting metal from powellites and molybdates have already been developed. Depending on the mineral composition and shape of the ore bodies, the deposits are divided into vein, vein-disseminated and skarn.
The world's proven reserves of the element are 19 million tons, with almost half in China. Since 1924, the largest molybdenum deposit has been the Climax mine (USA, Colorado) with an average content of up to 0.4%. Often, the extraction of molybdenum ores is carried out along with the extraction of copper and tungsten.
Molybdenum reserves in Russia amount to 360 thousand tons. Of the 10 explored deposits, only 7 have been commercially developed:
- Sorskoe and Agaskyrskoe (Khakassia);
- Bugdainskoe and Zhirekenskoe (Eastern Transbaikalia);
- Orekitkanskoe (Buryatia);
- Labash (Karelia);
- Tyrnyauz (Northern Caucasus).
Mining is carried out both by open and closed methods.
The Secret of the Samurai Swords
For several centuries, European gunsmiths and scientists have struggled with the mystery of the sharpness and strength of ancient Japanese swords from the beginning of the second millennium, unsuccessfully trying to make the same high-quality edged weapons. Only at the end In the 19th century, having discovered molybdenum impurities in Japanese steel, it was possible to solve this riddle.
For the first time, the industrial use of molybdenum as an alloying additive to improve the quality of steel (giving it hardness and toughness) was mastered in 1891 by the company Schneider & Co from France. 
A significant stimulus for the development of molybdenum metallurgy was the First World War. It is significant that the thickness of the frontal armor, easily pierced by German shells of the same caliber, was reduced from 75 mm to 25 mm by adding 1.5-2% molybdenum to the steel of the armor plates. This significantly increased the strength of the machine.
Application of molybdenum
More than 80% of all molybdenum used in industry falls on ferrous metallurgy. Without it, the production of heat-resistant cast iron, structural and tool steels is unthinkable. One weight part of the element improves the quality of steel is equivalent to two weight parts of tungsten. Since the density of molybdenum is two times less, its alloys are significantly superior in quality to tungsten alloys at operating temperatures below 1370 ˚С. Molybdenum steels lend themselves better to carburizing.
Molybdenum is in demand in the radio-electronic, chemical and paint industries. In mechanical engineering, it is used as a heat-resistant material. In agriculture, weak solutions of element compounds significantly improve the absorption of nutrients by plants. It should be borne in mind that in large doses, molybdenum has a toxic effect on living and plant organisms, and negatively affects the environment.
biological significance
In the diet of humans and animals, molybdenum is one of the most important trace elements. In the form of an active biological form - molybdenum coenzyme - (Moco) it is necessary for the implementation of catabolic processes in living tissues.
Research in the field of anticancer activity of molybdenum looks very promising. A high percentage of the incidence of cancer of the digestive tract among the population of the town of Lin Xian (Honan Province, China) was significantly reduced after the introduction of mineral fertilizers containing molybdenum into the soil.
In rare cases of deficiency of an element in the human body, the development of disorientation in space, brain defects, mental abnormalities and other severe nervous diseases is possible. The daily dose of molybdenum for an adult is from 100 to 300 mcg. When it is increased to 5-15 mg, toxic poisoning is inevitable, up to 50 mg - death. The most rich in molybdenum are leafy vegetables, cereals, legumes and berries (blackcurrant, gooseberry) crops, dairy products, eggs, liver and kidneys of animals.
Environmental aspects
The biological characteristics of molybdenum impose increased requirements for the disposal of waste from the processing of ore material, strict adherence to technological process in enterprises to prevent negative impact on the health of workers and the environment.
All measures should be taken to prevent the ingress of processed products into groundwater. It should be borne in mind that plants have the ability to absorb and accumulate molybdenum, so its content in shoots and leaves may exceed the permissible concentrations. This green mass can be dangerous for animals. To prevent winds from spreading the used rock, the dumps are covered with a layer of earth.
Molybdenum Global Market Trends
With the onset of the global financial crisis, global consumption of molybdenum decreased by 9%. The exception was China, where there is an increase of up to 5%. The response to the sharp decline in consumer demand in 2009 was a decrease in production volumes. It was possible to approach the previous level of output only after four years, and in 2014 a new maximum of 245 thousand tons was set. China remains the main consumer and producer of molybdenum and its products.
Molybdenum's density and amazing properties have made it indispensable for steel and alloy applications where a combination of light weight, high strength and corrosion resistance materials. Projected growth in the number of nuclear power plants, other energy and industrial facilities, development of new oil and gas fields in harsh conditions Far North and the Arctic will inevitably lead to an increase in demand for molybdenum and its derivatives.
