3. Translate at sight

1. Только некоторые заводы применяют штамповку с вытяж­кой, или горячее прессование, для производства стальных труб.

2. Процесс производства стальных труб необходимой длины за определенный период времени называется холодным прессова­нием полых изделий, или ударным истечением.

3. В этом процессе рабочий ход при прессовании труб дли­ной в 30 футов завершается менее, чем за 3 секунды.

4. Цельные или сверленые круги нагревают и опускают в цилиндрический контейнер.

5. При использовании цельных кругов имеет место опера­ция пробивки.

Unit 23

COLD FORMING OF METALS

It is possible to shape most of the commonly used metals and their alloys by cold working at ordinary temperature, and many operations of hot working processes may also be used in cold working. Cold working has been used many years for the shaping and hardening of metals. In alt likelihood the first process was insti­tuted by cold hammering, and forming operations such as cold rolling and cold drawing were later developed.

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Hot forming operations are conducted while the metals are in a plastic state, the grain structure of the metal being refined and im­proved thereby. Contrarily, cold forming distorts the grain structure of the metal treated and does little to reduce the grain size. Cold working of metals usually is done at low temperature, but for steel, the tempera­ture may ascend to a point within the critical range.

Cold working operations frequently follow preliminary hot working operations as a means of imparting a finished appearance to the parts produced, thus, making them suitable for commercial use. Good examples are hot-rolled plates, sheets and stripe, the surface of which are rough and irregular. Products made from raw materials, such as these, would lack dimensional accuracy and would be wanting in required physical properties, as well. Cold rolling can provide dimen­sional accuracy by slightly reducing the sizes originally obtained, and by producing a smooth surface and increasing the strength and hard­ness of the material. Cold rolling of shafting and cold drawing of wires are accomplished by cold forming processes. Frequently, a consider­able amount of cold working is necessary to achieve desired results, and one or several annealing treatments may be required between forming operations to avoid overwork and fracture of the metal.

Notes to the text

in all likelihood по всей вероятности

was instituted был введён

thereby вследствие этого

Exercises

1. Answer the following questions

1. What was the first cold working process used by man?

2. What is the principal difference in the effects produced by cold and hot working?

3. Which of these two operations is the preliminary one and which is the final one?

4. What effect does cold working operation have in industry?

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2. Find the English equivalents for the following Russian word combinations

операция холодной обработки

предварительная горячая обработка

придать окончательный внешний вид производимым деталям

сделать пригодным для промышленного использования

грубые и неправильные поверхности

беспечить точность размеров

остичь желаемых результатов

увеличение прочности и твердости

избежать перегрузку и излом металла

провести несколько операций отжига

незначительное уменьшение размеров

получить гладкую поверхность

находиться в пластическом состоянии

очистить и улучшить зернистую (кристаллическую) струк­туру металла

исказить зернистую (кристаллическую) структуру металла

в кристаллическом пределе

пластическая обработка (обработка давлением) и закалка металла

3. Translate at sight

1. Многие металлы можно обрабатывать при нормальной температуре.

2. Операции горячей обработки выполняются тогда, когда металл находится в пластическом состоянии.

3. Эти операции очищают и улучшают кристаллическую (зернистую) структуру обрабатываемого металла.

4.Холодная обработка искажает зернистую структуру обра­батываемого металла и практически не уменьшает размер зерна.

5. Операции холодной обработки часто следуют за горячей обработкой.

6. Холодная обработка обеспечивает точность размеров, гладкую поверхность, а также повышает прочность и твердость материала.

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Unit 24

COLD ROLLING

This process is used extensively to produce a bright and smooth surface finish on steel previously hot rolled. Cold foiling is applied for finishing various shapes of steel to the tolerances required for proper application of these materials in industry. Also, cer­tain physical properties, such as tensile strength and hardness, are ap­preciably improved as the result of cold rolling.

The equipment used for this work is similar to that needed in hot rolling i.e. two-high, three-high, or continuous mills.

The similar equipment is used for rolling plates of steel and other metals and also for rolling steel for shafting and stock need in screw machine operations. As a result of being cold rolled, the metal acquires a surface skin which increases the strength and wear resis­tance inherent in the metal. To obtain the smooth finish on the product, the roll surface is polished smooth and all the scratches are obliterated. The mirror-like surface of the rolls imparts a high finish to the steel, which is protected by a strip of paper that forms a shield as the steel is wound on the reels.

Excessive cold rolling causes the metal to become overhard and brittle.To obtain a product of the desired size, it may be necessary to resort to annealing after the metal has passed through the mill several times. A final pass through the rolls is made to obtain the correct size of the piece. The annealed metal must, of course, be cleaned by pick­ling before being passed through the finishing rolls, unless the anneal­ing ftirnace is of the open type, but of«a design, which leaves it possible to complete the annealing without the formation of the surface scale and discolouration of the metal.

уничтожаются

зеркальная поверхость

прибегнуть к...

изменение цвета; обесцвечивание

Notes to the text яге obliterated mirror-like surface to resort to decolouration

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Exercises