Ex.1 Read the text. Translate it. Title
it.
The most important metal in industry is iron and its
alloy — steel. Steel is an alloy of iron and carbon. It is strong and stiff,
but corrodes easily through rusting, although stainless and other special steels
resist corrosion. The amount of carbon in a steel influences its properties
considerably. Steels of low carbon content (mild steels) are quite ductile and
are used in the manufacture of sheet iron, wire, and pipes. Medium-carbon
steels containing from 0.2 to 0.4 per cent carbon are tougher and stronger and
are used as structural steels. Both mild and medium-carbon steels are suitable
for forging and welding. High-carbon steels contain from 0.4 to 1.5 per cent
carbon, are hard and brittle and are used in cutting tools, surgical
instruments, razor blades and springs. Tool steel, also called silver steel,
contains about 1 per cent carbon and is strengthened and toughened by quenching
and tempering.
The inclusion of other elements affects the properties
of the steel. Manganese gives extra strength and toughness. Steel containing 4
per cent silicon is used for transformer cores or electromagnets because it has
large grains acting like small magnets. The addition of chromium gives extra
strength and corrosion resistance, so we can get rust-proof steels. Heating in
the presence of carbon or nitrogen-rich materials is used to form a hard
surface on steel (case-hardening). High-speed steels, which are extremely
important in machine-tools, contain chromium and tungsten plus smaller amounts
of vanadium, molybdenum and other metals.
Ex.2 Revise the text. Correct the mistakes
where necessary
1. The
least important metal in industry is iron and its alloy — steel.
2. Manganese
gives extra strength and toughness.
3. Steels
of high carbon content (mild steels) are quite ductile and are used in the
manufacture of sheet iron, wire, and pipes.
4. Tool
steel, also called silver steel, contains about 0.1 % carbon and is
strengthened and toughened by quenching and tempering.
5. Cooling
in the presence of carbon or nitrogen-rich materials is used to form a hard
surface on steel (case-hardening).
6. High-speed
steels, which are extremely important in machine-tools.
Ex.3 Revise the text. Answer the questions.
1. What
is a steel?
2. What
gives to the steel strength and toughness?
3. Where
steel can be used?
4. What
gives us the addition of chromium to steel?
Оставьте свой комментарий
Авторизуйтесь, чтобы задавать вопросы.