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Classification

Classification – is the distribution of objects, phenomena, concepts into classes, divisions, discharges and other structural levels by taking into account its common features.

Classification and systematization are important steps orderly label and describe a set of objects, the generators a certain area of knowledge or technology. The necessity to classification of objects occurs in all areas of the complex. There are : in science, engineering, manufacturing, agriculture, medicine, construction, and of course, in metallurgy.

Now The classification is widely used in the most various spheres of human activity. First of all, it exists as a kind of cognitive activity. Its purpose and result in this case is an open natural classification system (klassemy).

In some cases, as a subsidiary of the cognitive tools used artificial classification system. Such a system was once a classification system of plants Carl Linnaeus. Linnaeus himself was well aware of the artificiality of his system, but he believed that "the artificial systems are needed, if not natural." Linnaeus worked all his life to find natural classes instead of the artificial "artificial system serves only until there is a natural. Per-hand only teaches us to recognize the plant, - he said - the second will teach us the nature of the plant." Natural system should be based on the" Naturally method "- that was the scientific concept of Linnaeus. Objectives nerds, he thought, to find natural classes, the natural order, then there are groups of plants that nature itself.

Classification exists as a kind of practice. It’s result of the creation of a classification system that served the purpose-oriented in diversity. Such a system is either entirely artificial, or mixed - artificial-natural. The example of a practical classification system is a classifier of industrial and agricultural products. On the basis of the general idea of classification are formed by a variety of private-government: taxonomy, typology, zoning, periodization, sorting etc.

GENERAL DESCRIPTION OF METALS AND ALLOYS

Metals and alloys are commonly used for making constructs machinery, equipment, tools, etc. In spite of the wide range of man-made materials (ceramics, adhesives), metals are the main structural material and in the foreseeable future will continue to dominate.

Metals occur in nature in pure form and in ores, oxides and salts. In pure form, are chemically stable elements (Pt, Au, Ag, Cu). The Weight of the largest nugget of copper is 420 tons, of silver is 13.5 tones, of gold - is112 kg. Of the 111 open items presented in the periodic table of Mendeleev, 76 are metals, Si, Ge, As, Se, Te are intermediate between the metals and non-metals, sometimes referred to as semi-metals. All the elements to the left of the imaginary line drawn from boron to astatine (from number 5 to number 85) refer to metals and to the right - mostly to non-metals. This border is not clearly marked, as well as among the elements close to the border, and are semi-metals.

Metallic materials are usually divided into two groups: well-LEZO and iron alloys (steel and iron) are called ferrous metals, and The remaining metals and their alloys - colored. Furthermore,\ all non-ferrous metals used in the art, in turn, divided into the following groups:

  1. Light metals Mg, Be, Al, Ti with a density of up to 5 g/cm3;
  2. Heavy metals Pb, Mo, Ag, Au, Pt, W, Ta, Ir, Os with density exceeds 10 g/cm3;
  3. Fusible metals Sn, Pb, Zn, melting point 232, 327, 410 ° C, respectively;
  4. Melting metals W, Mo, Ta, Nb having a melting point higher than that of iron (> 1536 ° C);
  5. Precious metals Au, Ag, Pt with a high resistance against corrosion;
  6. Or actinide metals uranium used in nuclear engineering;
  7. The rare earth metals (REM) - lanthanides for a modification steel;
  8. -Alkali and alkaline earth metals, Na, K, Li, Ca in free state are used as the liquid metal in atomic reactors, and sodium is used as a catalyst in the production of synthetic rubber, and lithium - for alloying light and strong aluminum alloys used in aircraft.

Properties of the metals varied. Mercury freezing temperature by minus 38,8 ° C, tungsten withstand operating temperatures up to 2000 ° C (m.p. = 3420 ° C), lithium, sodium, potassium, lighter than water, and osmium and iridium - 42 times heavier than lithium-cha. Conductivity Silver 130 times higher than that of manganese. However, metals have a characteristic common properties. They are:

  1. High plasticity;
  2. High thermal and electrical conductivity;
  3. - Positive temperature factor of electrical resistance, meaning the electrical resistance meaning the resistance increases with increasing temperature with increasing temperature and superconductivity by many metals (30) at temperatures close to absolute zero;
  4. Good reflectivity (metals are opaque and have a distinctive metallic gloss);
  5. Thermionic emission, ie, the ability to emit electrons when heated;
  6. A crystalline structure in the solid state.

    7. GENERAL DESCRIPTION OF METALS AND ALLOYS

    Classification industry at the moment is not unique and requires improvements in this area. What we have worked in the master's work . At the time of this writing, many of the research are still in progress.

    References

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