Cold working drastically changes the mechanical properties of metals, the most important being increase in strength and hardness with a simultaneous reduction of ductility. The metal becomes harder and stronger. Cold working is "permanent deformation of metal at a temperature and rate such that strain hardening is produced". Cold deformation requires more force than hot defomation, and it has greater effect on the mechanical and metallurgical properties of the metal. In general, cold-working processes are used to provide finished products and are used in preference to hot working because of the improved surface finish, increased mechanical properties, and better control of finished size and shape. Cold rolling is the most
widely used cold working method. Rolling is done by passing the stock through a rolling mill, compressing and elongating the metal. Cold rolling uses techniques that are relatively the same as hot rolling. Cold rolling is used in the production of sheets, strip steel, bar stock and flat wire. Cold rolling, like hot rolling, may be done on a two-high or a four-high rolling mill, or in a continuous rolling mill.
X. Найдите в тексте предложения, в которых говорится о том, что:
· также применяется ковка молотом или кузнечным прессом;
· во время горячей обработки используется минимальная энергия;
· горячая обработка производится по двум причинам;
· происходит механическое упрочнение;
· холодная деформация требует больших усилий.
XI. Выберите утверждения, соответствующие содержанию текста.
l. Cold working drastically changes …
a) the rate of production;
b) the mechanical properties of metals;
c) the metal temperature.
2. Cold-working processes are used ...
a) to prevent hardening;
b) to plastically deform metal;
c) to provide finished products.
3. Each method has . . .
a) its special properties;
b) its advantages and disadvantages;
c) its own techniques.
XII.Укажите, какие из данных предложений соответствуют содержанию текста.
1. Quantity production is best made through the continuous type of rolling mill.
2. Softening of cold-worked metal is principally due to recrystallization.
3. During hot working annealing occurs, and recrystallization takes place — following plastic deformation.
4. It is usually done hot in order to reduce the required force and increase the metal's plasticity.
5. Cold rolling is the most widely used cold working method.
XIII. Вставьте нужные по смыслу слова.
1. The . . . action prevents . . . and loss of ...
a) annealing, hardening, ductility;
b) forging, strengthening, cracking;
c) rolling, heating, brittleness.
2. Cold . . . has . . . effect on the mechanical and . . . properties of the metal.
a) annealing, little, chemical;
b) deformation, greater, metallurgical;
c) rolling, no, physical.
3. Hot... is done to ... the properties of ...
a) forging, increase, alloys;
b) alloying, prevent, products;
c) working, improve, metal.
4. Cold rolling . . . hot. . . may be done in a ... rolling mill.
a) unlike, quenching, two-high;
b) like, rolling, continuous;
c) with, deformation, reversing.
5. There are many hot working . . . , but only ... are widely ...
a) processes, most of all, improved;
b) features, several, increased;
c) methods, a few, used.
IX. Выберите из текста предложения, в которых говорится о преимуществах холодной обработки перед горячей обработкой.
X. Составьте план к тексту на русском языке.
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