Molybdenum is the 42nd element of the periodic table of chemical elements D. AND. Mendeleev. It has a silver-white color and looks like lead. It is precisely because of this similarity that it got its name: in Greek, mólyvdos means “lead”.
Molybdenum has high electrical conductivity and low TCLR (temperature coefficient of linear expansion). Mo melts at t = 2,620°C, boils at t = 4,630°C. Under normal conditions, it does not react with air, but when heated above 400°C, it begins to oxidize rapidly, and at 700°C it loses its strength, which limits the use of Mo in its pure form at high temperatures.
To increase the strength characteristics of molybdenum, it is added to it tungsten (W). Such alloys usually contain from 49 to 51% Mo and at least 48% W, and may also include a number of different impurities. The resulting metal has high mechanical strength and resistance to corrosion at high temperatures, which makes it possible to use it in instrument making, including in the manufacture of heating elements for industrial electric furnaces.
The history of the discovery of molybdenum is associated simultaneously with several Swedish chemists:
Molybdenum was only used in industry at the beginning of the 20th century, after it was discovered that the addition of Mo made gun and armor steels more durable.
Molybdenum is present in the earth's crust in an amount of 0.003%. The main deposits are in China, Russia, the USA and Chile. Mo is extracted from ores containing up to 50% of the required metal, 30% sulfur, 10% silicon and some other elements.
After mining, the ore is roasted in special furnaces at a temperature of 550... 600°C, as a result of which molybdenum oxide contaminated with various impurities is obtained. Clean it using one of the following methods:
After purification, molybdenum oxide is heated in furnaces with working chambers protected from the surrounding atmosphere. At the first stage, the temperature in the furnace is set at 600... 700°C, at the second stage — 900... 1,000°C. As a result of such sequential heating, a powder is obtained, which is then converted into metal by heat treatment. Finished molybdenum products may take the form of a sheet, tape, rod, wire or rod.
In industry, molybdenum is mainly used as additives in smelting steels: the amount of Mo they add determines the type of product produced:
In addition, pure Mo is used to produce ferromolybdenum, an alloy containing 55 to 75% of molybdenum, which can later be used as an additive when alloying steels.
Only a third of the molybdenum extracted is used in the form of pure metal or alloys, in which Mo is the main component. Such materials are used in the manufacture of supersonic aircraft and space rockets to create skin elements, heat shields, and jet engine parts. Molybdenum alloys are also used to create nuclear reactors, various vacuum devices, electrodes for melting glass, parts of equipment operating in acidic media, including phosphoric, hydrochloric and sulfuric media.
