Molybdenum - what is it?

2024 Author: Howard Calhoun | [email protected]. Last modified: 2024-01-17 18:37

Not many people know that molybdenum is a chemical element of the sixth group of the periodic table, related to transition metals. In the classification structure, it is next to chromium and tungsten. It is distinguished by a rich gray color and a specific metallic sheen. This refractory element has found wide application in the metallurgical industry.

Brief history of discovery

Not much information has survived to this day about the discovery of molybdenum. This is because the element is not very common. However, the first mention of it was made in 1778, when analytical chemistry had not yet reached its maturity. First, the substance was isolated in the form of an oxide.

Despite the discovery of the chemical element in 1778, the name currently used is much earlier. It was often mentioned for lead-colored minerals as early as the Middle Ages.

Presence in the environment

Although molybdenum is not a very common element, it is relatively evenly distributed in the earth's crust. It does not occur in free form. The smallest amount of this metal includes carbonate andultrabasic rocks. A certain proportion of the substance is contained in river and sea water. There is much less metal in the upper layers than at depth.

There are two forms of occurrence:

• sulfide;
• molybdate.

They appear as microscopic secretions. Crystallization of molybdenite occurs with increased acidity and the presence of a reducing environment. Oxygen compounds are usually formed on the surface. As for primary ores, molybdenite can be found in them together with minerals of copper, bismuthine, and wolframite. The metal is found in large quantities in sediments.

Large deposits in Russia

In the Russian Federation, the use of molybdenum is carried out in many areas of activity. The country has one of the largest mineral resource base in the world for the extraction of this metal. The main share of enterprises is concentrated in the southern part of Siberia.

In terms of reserves, Russia is second only to three countries - the United States, China and Chile. The main part of the mineral resource base is represented by stockwork deposits containing more than 87% of explored resources. However, Russian deposits are characterized by not very high quality ores.

The table shows the largest deposits.

Name	Region
Zhirekenskoe	Chita Region
Orekitkanskoe	Buryatia
Sorskoe	Khakassia
Tyrnyauzskoe	Kabardino-Balkaria

Practical application

In its pure form, the use of molybdenum is carried out in the production of wires or tapes designed to withstand high temperatures. Such products can act as heating elements for electric ovens, electronic lamps or X-ray tubes.

Introduced metal significantly improves the performance of steels. After its introduction into the composition, their strength qualities and resistance to corrosion increase, which is necessary in the manufacture of important parts. Heat-resistant alloys are often produced with the addition of molybdenum, which are also acid-resistant.

Compounds with this metal are actively used in the manufacture of the front skin of aircraft and missiles. On the basis of alloys, honeycomb panels of aircraft and thermal screens are produced. Resistance to high temperatures allows the use of products with the introduction of molybdenum for the processing of steels. Many compounds act as catalysts for chemical reactions.

Physical and chemical properties

Molybdenum is a light gray metal with a volume centered cubic lattice. Its mechanical properties are determined by the purity of the material itself, as well as pre-treatment and heat treatment. Physical properties are discussed in more detail in the table below.below.

Parameter	Meaning
Melting point	2610 degrees
Thermal conductivity index	142W/(mK)
Heat of evaporation	590 kJ/mol
Shear modulus	122 GPa
Metal hardness	125 HB
Molar volume	9, 4 cu. cm/mol

Under normal conditions, a component of the periodic table is resistant to many substances. The oxidation process begins to proceed at temperatures above 400 degrees. Alkaline solutions have a slow effect on molybdenum. Moisture resistance without aeration is quite high.

Compounds with other metals

The quality of the resulting molybdenum alloys largely depends on the proportion, as well as the ability of the impurities used and the base component to interact with the substance. Doping technology plays an important role. However, certain types of connections raise doubts among experts in terms of suitability for further use.

Molybdenum does not mix well with tungsten. With its introduction, the heat resistance of the material significantly increases, but at the same time, the resistance to deformation worsens. Similar problems arise in combinations with other metals, so suchdoping types are no longer implemented.

Despite the existing difficulties, it was still possible to find some compounds that can increase the thermal threshold for the use of molybdenum. At the same time, plasticity, resistance to deformation and other characteristics are at the same level.

Brands in the industry

The production process involves the use of the material not only in its pure form, but also with the addition of impurities. Below are the grades of molybdenum that are common in the industry.

Designation	Description
MCHVP	It is a pure metal produced by vacuum melting technology.
CM	The composition of the material contains specialized additives. Usually titanium or zirconium.
MCH	Molybdenum content is 99.96 percent. The rest comes from additives.
MK	The base metal contains silica additives to improve acid resistance.
MPH	A kind of pure molybdenum, but with a high content of impurities. Their composition is no more than 0.08 percent.

Receive process

For the production of molybdenum, ore is prepared, including up to 50 percent of the main substance, a significant amount of sulfur, a small concentrationsilicon and other components. It is fired at a temperature of 570 to 600 degrees in special furnaces. After thermal exposure, a concentrate is formed containing molybdenum oxide with impurities.

There are two ways to obtain a mass without foreign matter:

1. The method of successive effects of a chemical nature. When using ammonia water, the resulting cinder turns into a liquid state. Foreign impurities are removed from the resulting solution. After processing, their number should not exceed 0.05 percent.
2. By sublimation, which is the process of converting a solid compound into a gaseous state. With this option, the liquid phase is bypassed.

Molybdenum oxide purified from impurities is processed in tube furnaces by means of hydrogen. As a result, a powder is obtained, which, by melting and introducing special substances, is converted directly into metal. The shape of the blanks will depend on the production technology used.

Manufactured Molybdenum Items

The most common type of products are rods. They can not only be used independently, but also serve as the basis for the production of wire. Molybdenum rods with a square section of not more than 40 mm act as a raw material for the manufacture of products.

In the process of obtaining bars, rotational forging is carried out, which takes place in several stages. At each stage, bars with a specific cross section are produced. The forging conditions vary according to the diameter of the incoming billet. The disadvantages of the technology include the complexity of the production process.

Molybdenum is also used to make special wire. Manufacturers form it from properly prepared rods, the diameter of which does not exceed 3 mm. With this section, the products are easily wound on a coil for further production of wire.

During the manufacturing process, the broach method is used, which includes four main stages. The wire eventually gets the final diameter, which was set in advance. The temperature regime during the production process can vary from 300 to 700 degrees.

After drawing, the wire is cleaned by annealing in a hydrogen environment. In this case, the temperature reaches 1300-1400 degrees. Sometimes cleaning is done by electrolytic pickling using nitrogen.

Molybdenum can be made into solid sheets and strips. They can be obtained by forging and rolling. In production, pneumatic hammers and two-roll mills are used. The thickness of the resulting strip after hot rolling depends on the cross section of the original plate.

After manufacturing, molybdenum strips undergo chemical cleaning. They are placed in a special environment of active substances. Next, cold rolling is carried out at normal temperature. At the final stage, the tapes are again cleaned and, if necessary, polished.

There are production standards for metal products frommolybdenum. GOST 18905-73 establishes requirements for the manufacture of wire. It reflects the tolerances for mass and diameter.

Molybdenum producers in Russia

Skarn, stockwork and vein deposits are mainly developed on the territory of the Russian Federation. In terms of quality, the mined ore is not much inferior to foreign raw materials, but it still has certain features associated with the structure.

In Russia, the largest producers of molybdenum are two companies:

• Sorsky GOK LLC.
• JSC Zhirekensky GOK.

The listed enterprises provide up to 95 percent of domestic metal production.

In conclusion about the role of the element for the human body

Molybdenum acts as an important substance necessary for the normal functioning of people. It is found in many organs and bones. The daily requirement for a chemical element is on average 70-300 mcg. With its deficiency, these indicators increase.

Molybdenum takes part in metabolism, as well as in the process of cleansing the body of aldehydes, acids and other compounds. It promotes the utilization of iron, allowing you to quickly eliminate the consequences of various types of poisoning. The trace element effectively cleanses the body of toxic substances.

Studies have shown that molybdenum relieves pain in arthritis and other diseases, has a positive effect in the presence of asthma, reduces the risk of cancer inintestines and stomach. Most of the substance is found in leafy vegetables, buckwheat, barley, liver, eggs, milk, gooseberries and black currants.