Chromium, molybdenum and tungsten. Their preparation, properties and applications (1972)

Periodic table of elements of Mendeleev.

A map of the world with the percentage of chromium, molybdenum and tungsten in the Earth's crust.

Map of the USSR with deposits of these metals.

Chromium, molybdenum and tungsten are naturally found in the form of various compounds.

Of the most common chromium compounds, crocaid, chromic garnet, and chromspineide are known.

Samples of minerals.

The formula of a mineral of industrial importance, chromide.

Of molybdenum minerals, there are often povelite, molebdite, wolfinite.

Samples of minerals.

The most important is molybdenum.

Of the tungsten minerals, such as scheelite, stalzite, wolframite are known, which have received the main industrial application.

Samples of minerals.

The formula of wolframite.

Molybdenum and tungsten ores are transported along the conveyor.

They contain little pure metal, and therefore they are enriched, i.e. they are freed from waste rock in various ways.

Ore enrichment by flotation.

After crushing and grinding in ball mills, the ore concentrate enters the spiral classifier, from which it goes to the flotation department for further processing in the form of pulp.

For better surfacing of particles, flotation reagents are added to the pulp.

During mixing, the floated material floats to the surface and accumulates in the foam.

The mineral-rich foam is converted into a suspension, which is subjected to filtration, dehydration and drying.

After flotation, ore concentrates can serve as a starting material for the production of metallic chromium, molybdenum and tungsten.

A cartoon explaining the production of tungsten.

Getting afloat.

The composition of the float.

Continuation of the cartoon about the production of tungsten.

The formula of sodium tungstate.

The isolation of tungsten from sodium tungstate occurs under the influence of a solution of calcium chloride.

As a result, the resulting sodium chloride remains in solution, and calcium tungstate falls out as a crystalline white precipitate.

Then the calcium tungstate precipitate is decomposed by hot hydrochloric acid.

As a result of the reaction, the resulting calcium chloride remains in solution, and tungstic acid is released as a yellow precipitate.

The sediment is washed with water several times and dried.

Tungstic acid is the final product of hydrometallurgical processing of tungsten concentrates.

The metallurgical cycle of producing metallic tungsten consists of many sequential operations.

A cartoon explaining the production of metallic tungsten.

Powdered molybdenum is produced in a similar way.

Ingots of tungsten.

Sintering and welding of ingots.

As a result, the loose powder is turned into parts of different profiles.

Samples of parts.

Electric arc furnaces.

Ferromolybdenum or ferrovolfram obtained in electric arc furnaces are used as alloying additives in the production of high-grade steel.

Obtaining chromium from chromite ores.

The pre-crushed ore is dried in drum dryers.

Then fine grinding is carried out in ball mills.

A cartoon explaining the receipt of chromium.

Firing of the charge with soda at a temperature of about 1200 degrees.

The formula of sodium chromate.

Continuation of the cartoon explaining the receipt of chrome.

Commercial sodium dichromate.

If a concentrated solution of sodium dichromate is decomposed with hydrochloric acid, chromium anhydrite is obtained.

Chromium anhydrite is subjected to thermal decomposition, calcination to obtain chromium oxide.

Chromium oxide is reduced to metallic chromium by aluminothermic method.

The resulting chromium is well separated from the slag.

Frozen chromium is crushed and used for alloying carbon steels.

Chromium, molybdenum and tungsten have similar physical and mechanical properties.

With an increase in the atomic weight of the elements, their melting point increases.

The value for each element.

High boiling point.

These data allow us to classify these metals as refractory.

The density of the elements.

Cartoon explaining the structure of refractory metals.

Chromium, molybdenum and tungsten of industrial purity are not plastic.

Various pressing methods contribute to the transition of molybdenum and tungsten from a brittle state to a plastic one.

The hardness of refractory metals depends on the method of their manufacture and significantly exceeds other metals.

Comparative table of hardness of metals.

Chromium, molybdenum and tungsten are in the sixth group of the periodic table of elements.

This determines the similarity of their properties and forms.

The chemical properties of elements depend on the structure of the electron shells of their atoms.

Chromium, molybdenum and tungsten have a great similarity in the structure of the structural shells.

The ionization potential is the most important characteristic of a metal.

It depends on the size of the nucleus and the radius of the atom.

Cartoon explaining the ionization potential of chromium, molybdenum and tungsten, their electroactivity.

Formation of an oxide film on metals.

Laboratory.

Experiments on the production of various chromium compounds.

Experiments on the production of molybdenum compounds.

Experiments on the production of tungsten compounds.

Samples of paints based on compounds

Samples of paints based on chromium, molybdenum and tungsten compounds.

Such paints are used in the dyeing of fabrics and are used in paint and varnish products.

Chromium oxide is used when staining dishes and glass in green.

Product samples.

Sodium dichromates are used in fur and leather industries, when tanning leather.

Product samples.

Chromium compounds and salts are used in film and photographic production.

Chrome plating of parts to increase their wear resistance.

Samples of processed products.

Alloys and mixtures of tungsten carbide and cobalt metal obtained by powder metallurgy are almost as hard as diamond.

They serve as surfacing of cutting edges of tools, drills, cutters, milling cutters.

Samples.

Due to the high melting point, molybdenum and tungsten are used in radio and electric vacuum installations.

Cathodes are made of tungsten, and anodes and grids are made of molybdenum.

The thread holders in incandescent lamps are made of molybdenum, and the threads and spirals are made of tungsten.

In metallurgy, chromium, molybdenum and tungsten are added to steel in the form of alloying additives to obtain acid-resistant, heat-resistant stainless types.

The additive process.

Rolled sheet steel.

Cars are driving down the street.

The propeller of the aircraft.

The ship is at the wall.

A warship.

Rockets on Red Square.

Tanks.