Ex. 25 Read the text. Translate the main
part of the text. Think up the title
Metals are materials most widely used in industry
because of their properties. The study of the production and properties of
metals is known as metallurgy.
The separation between the atoms in metals is small,
so most metals are dense. The atoms are arranged regularly and can slide over
each other. That is why metals are malleable (can be deformed and bent without
fracture) and ductile (can be drawn into wire). Metals vary greatly in their
properties. For example, lead is soft and can be bent by hand, while iron can
only be worked by hammering at red heat.
The regular arrangement of atoms in metals gives them
a crystalline structure. Irregular crystals are called grains. The properties
of the metals depend on the size, shape, orientation, and composition of these
grains. In general, a metal with small grains will be harder and stronger than
one with coarse grains.
Heat treatment such as quenching, tempering, or annealing
controls the nature of the grains and their size in the metal. Small amounts of
other metals (less than 1 per cent) are often added to a pure metal. This is
called alloying (легирование) and it changes the grain structure and properties
of metals.
All metals can be formed by drawing, rolling,
hammering and extrusion, but some require hot-working. Metals are subject to
metal fatigue and to creep (the slow increase in length under stress) causing
deformation and failure. Both effects are taken into account by engineers when
designing, for example, airplanes, gas-turbines, and pressure vessels for
high-temperature chemical processes. Metals can be worked using machine-tools
such as lathe, milling machine, shaper and grinder.
The ways of working a metal depend on its properties.
Many metals can be melted and cast in moulds, but special conditions are
required for metals that react with air.
Ex. 25.1 Correct the mistakes
1. Metals
are materials least widely used in industry because of their properties.
2. Metals
can be formed and can’t be bent without fracture.
3. The
rare arrangement of atoms in metals gives them a crystalline structure.
4. Metals
can be worked using scissors.
5. The
ways of working a metal don’t depend on its properties.
Ex. 25.2 Complete the sentences
1. The
study of the production and properties of metals is known as
2. Lead
is soft and can be
3. Heat
treatment such as quenching, tempering, or annealing
4. All
metals can
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