SPLAVY of metals

From Big Medical Encyclopedia

ALLOYS of metals (synonym metal alloys) — macroscopically homogeneous firm or liquid systems consisting of two or more metals, and also metals and nonmetals.

Higher technical qualities of S. in comparison with pure metals, an opportunity to receive S. with predetermined properties are a basis of their broad use in various fields of science and technology, including in medicine and the medical equipment. More than 5 thousand various S. use at production of medical devices, surgical instruments (see. Surgical tools ), dentures (see), etc.

Properties C. of metals depend on their structure, interior and processing (mechanical, thermal, etc.).

Pages usually have boly low melting temperature in comparison with tekhmperatury melting of the components forming them. Temperature of melting of S. of metals depends on a quantitative ratio of these metals in the Village. Microcrystallic mix of the metals taken in certain ratios, low melting temperature having most in comparison with temperatures of melting of mixes of the same metals, but in other ratios, is called the eutectic mixture or just an eutectic (the Greek eutektos which is easily melting), and temperature, at a cut the eutectic melts or crystallizes — the eutectic temperature. The eutectic representing mechanical mix of microcrystals of different metals like individual chemical connection has a certain structure and constant temperature of melting.

Pages can consist only of metals, napr, brass (copper alloy with zinc), bronze (alloy of tin with copper), duralyumin (alloy of aluminum — St. 90%, magnesium — 0,4 — 2,4%, copper — 3 — 5% and manganese — 0,3 — 1%); may contain metals with the small content of nonmetals, napr, cast iron (the iron alloy containing usually more than 2% of carbon), steel (the iron alloy containing less than 2% of carbon); special steel several various elements, and stainless steel, not corrodible, used in medicine for production of dentures and surgical tools contain in the structure, contains not less than 12% of chrome.

Occupational health

Alloys of metals receive, applying alloyage of elementary substances, smelting directly from ores, electrolysis of fusions and solutions, diffusion, methods of powder metallurgy, etc. For this purpose use the same equipment, as in black and color metallurgy (see) and mechanical engineering (see. Mechanical engineering industry ). Production of alloys of metals is accompanied by an expenditure of a large amount of fuel and the electric power therefore on production Wednesday the considerable excess of convection and radiant heat causing a specific microclimate arrives hot workshops (see). Many types of the equipment and technological operations by S.'s production are sources intensive noise (see) and vibrations (see). Fuel burning, chemical and mechanical, chemical and thermal and other ways of processing of alloys of metals are followed by allocation on air Wednesday of various gaseous harmful substances, aerosols of alloys or the metals which are their part (see. Aerosols ). During the crushing, use of powder materials, abrasive cleaning of products aerosols of disintegration are formed of alloys and other processes with use or receiving products of stress rupture of S. At steam condensation of the metals which are emitted during melting at fire cleaning and other high-temperature impacts on S. of metals, so-called aerosols of condensation are formed. At implementation of health control of the environment in production rooms it is necessary to consider that the content in air of aerosols of condensation of nek-ry metals can be considerable though metals in alloys are in small amounts. It is caused by various evaporation rate of separate metals from fusion. Temperature of melting of oxides of many metals is much lower than temperature of melting of the metal owing to what at oxidation of alloys of metals there is an intensive allocation on air Wednesday of an aerosol of condensation of the metal oxides entering alloy. In this regard for hygienic reasons it is more preferable those processes and the equipment, to-rye most prevent oxidation of alloys and their components (e.g., S.'s receiving in the atmosphere of inert gases, protective mixes, etc.). At hygienic assessment of technological processes it is also necessary to consider reduction in the rate of evaporation of metals at build-up of pressure and its increase in vacuum (e.g., evaporation rate of beryllium in vacuum increases by 43 times). In alloy many metals to a lesser extent show the toxic properties. Thanks to it aerosols of disintegration possess more hypotoxicity, than aerosols of condensation of the same alloys. Extremely high dispersion of aerosols of condensation even more aggravates their toxic impact on an organism due to the increased solubility and deeper penetration of particles into a respiratory organs. Therefore instead of high-temperature processing of S. promoting formation of aerosols of condensation machining is preferable. More high toxicity of aerosols of condensation of metals in comparison with aerosols of disintegration is considered during the rationing of their content in air of production rooms. The increased concentration of aerosols of alloys of the metals, in an individual state which do not have the expressed toxic properties can make an adverse effect on a respiratory organs and cause hron. diseases of a mucous membrane of upper respiratory tracts, dust bronchitis (see), pneumoconiosis (see). It is necessary to consider also that salts of metals are more toxic, than their oxides. It is characteristic for moderately toxic (titanium, zinc, etc.) and is less characteristic of more toxic (vanadium, mercury, lead, etc.) metals. Therefore the special attention is required by those operations and stages of technological process of receiving S., at to-rykh perhaps formation of salts of metals, e.g., at interaction of alloys of metals with gumboils in the melting unit, etc.

Measures of prevention are directed to improvement of working conditions during the receiving and S.'s processing metals, and also to prevention of their adverse influence on an organism. It is reached by automation of works, implementation of complex mechanization and distance steering, the equipment of the pressurized shelters and use of effective local positive-pressure ventilation (see), and also use of individual protection equipment. Workers are subject to obligatory periodic medical examinations (see. Medical examination ).

See also Metallurgy, occupational health .

Bibliography: Topical issues of occupational health in ferrous metallurgy, under the editorship of A. A. Kasparov and Yu. G. Shirokov, M., 1981; 3 l about and N with to and y B. M., And about f-f e V. G. and 3 l about and N with to and y V. B. Vosplamenyaemost and toxicity of metals and alloys, M., 1972; Lev and N and E. N. General toxicology of metals, L., 1972; M and c and to V. G. and X about c I am a N about in L. K. Hygienic value of evaporation rate and steam pressure of the toxicants applied in production, M., 1959; Poling of L. The general chemistry, the lane with English, M., 1974; Roshchin A. V. Toxicology of metals and prevention of professional poisonings, Zhurn. Vsesoyuz. chemical about-va of Mendeleyev, t. 19, No. 2, page 186, 1974.

R. A. Kucherskoy; V. P. Mishin.