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Pig iron production, steel making and rolled stock production are three main components of a complete ore-to-finished product cycle at a metallurgical plant. The rolling process is the plastic shaping of the metal. Passing between two rolls revolving in opposite directions, the metal assumes the required dimensions. The rolls are installed in a roll stand which may be of 2-high, 3-high and 4-high roll stands as a rule. The rolling mill may consist of one roll stand as the cogging mills or of a number of stands. There are two types of cogging mills: blooming mills and slabbing mills. The sequence of operations in conventional rolling is as follows: the metal is rolled in a blooming mill, then in a billet mill, then in section mills, which are in case of producing wire, rails, bars, sections, or the metal is rolled in a slabbing mill and then in a plate mill if it is required to produce the plate or the metal, after passing a slabbing mill, is rolled in a continuous hot strip mill and then in a continuous cold strip mill if it is required to produce the sheet.
The difference between hot rolling and cold rolling lies in the temperature of the metal under operation. The hot working temperature is around 1200 degrees centigrade and bears some relation to the melting point. The metal when being hot worked is soft and plastic, and therefore less power is required and a greater reduction is possible. Against these advantages must be placed the facts that hot working is not an accurate process due to contraction on cooling, and oxidation, which gives a poor surface finish. Besides, temperature control must be accurate or the metal will become overheated or even burnt.
Индивидуальное задание к модулю 1
Научно-технический перевод. Общая характеристика.
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A crude is any mixture of minerals in the form in which it occurs as a part of the earth’s crust. An ore is a solid crude containing a valuable constituent in such amounts as to constitute a promise of possible profit in extraction, treatment and sale.
The valuable constituent of an ore is ordinary called valuable mineral or often just mineral: the associate worthless material is called gangue. In some ores the mineral is the chemical state in which it is desired by primary consumer, e. g. graphite, sulphur, asbestos, talc, garnet; in fact this is true of the majority of non-metallic minerals. In metallic ores, however, the valuable mineral is rarely the product desired by the consumer, and chemical treatment of such minerals is a necessary step in the process of beneficiation. In such cases the sale product is usually the result of concentration by the method of ore-dressing followed by further concentration by the chemical methods of metallurgy. The valuable product of ore-dressing is called concentrate, the discarded waste material is tailing.
Concentrate is, in most cases, the feed to the metallurgical plant. If the metallurgical processes is one in which separation is effected in melt, the process is called smelting; if the separation is effected by differential or selective solution, the process is leaching or lixiviation.
Metals occur in ores either in the native state (e.g. Au, Ag, Pt, Cu) or as salts or oxides (CuS, Fe2O3, PbCO3), etc. But no matter what chemical form, the metal or mineral is invariably associated with more or less – usually more – barren rock. The form, in which the metal is required by the primary customers, is a relatively pure substance. Hence a more or less extended process of purification, usually involving, in order, ore-dressing, metallurgical extraction, and chemical refining, intervenes between delivery of ore at the mine exit and delivery of the metal to the customer.
One way in which the nonferrous metals differ from iron is the manner of its occurrence. Iron oxides occur in large and comparatively pure deposits; the other metals and compounds from which metals are delivered are scattered through large volumes of rock, such as limestone or quartz. Since it would be difficult and costly to smelt these large amounts of barren rock, metallurgists have recourse to concentration or ore-dressing by which the metals or metallic compounds are partially separated from the gangue or worthless material, before smelting.
Flotation is a method of concentrating solid minerals in a relatively finely divided state. It is essentially a method of gravity concentration in water in which the effective specific gravity of certain of the ore minerals is substantially decreased by causing air bubbles to attach more or less tenaciously to particles of that particular mineral, whereupon they float on the separating medium while unaffected minerals sink. When the selected mineral is separated in the form of a froth the operation is called froth flotation.
Steps of Froth-Flotation Method
In essential outline the ordinary simple froth-flotation operation comprises the following steps: 1) Grinding the ore in water to a maximum size of 35 or 48-m. 2) Dilution to a pulp consistency of 15 to 35 per cent solids; 3) Addition to the pulp a small quantities of one or more various inorganic conditioning agents, which have a number of functions; 4) Addition of a collector reagent which has the function of coating the mineral to be floated with a water-repellent film; 5) Addition of frothing agent which imparts persistence to bubbles when they reach the surface; 6) Aeration either by agitation, or by air injection as through the porous bottom of the containing tank, or through pipes, during which the coated mineral particles become more or less firmly attached to gas bubbles; 7) Separation of mineral-bearing froth from a liquid pulp containing residual particles which did not take on collector coating.
Соедините термины- эквиваленты.
c) commercial product
3. Выберете правильную дефиницию терминов:
а) добавление ценного элемента в руду;
б) увлечение доли ценного составляющего руды путем удаления пустой породы, песка, глины.
а) Мягкая, сочная или мучнистая масса, составляющая мякоть плодов.
б) Смесь какого-либо сыпучего, измельченного вещества с жидкостью.
в) Рыхлая, мягкая соединительная ткань, составляющая основную массу селезенки, а также заполняющая полость зуба.
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