Induction Furnaces. Induction furnaces are of two types – the coreless high-frequency type and the cored units which operate at low frequency. Principles of operation of both units are similar, although the design details are quite different.
A high-frequency induction melting unit consists of a refractory crucible surrounded by a water-cooled copper coil through which high-frequency current is passed. An electric current is induced within the metal charge causing very rapid heating; it also insures a thorough mixing of the molten metal. By this method high melting temperatures are obtained, as well as exact and controllable melting conditions. High-frequency induction furnaces are especially useful for melting small amounts of special steels and high-quality steels, and are also very useful for general steel melting. It is more economical than the electric-arc type of furnace. In some cases it may replace the open-hearth furnace, particularly when the volume requirements are relatively low. When large amounts of metal are needed, other methods are usually more economical.
A Puddling Furnace. Wrought iron is produced in a puddling furnace. This is a furnace somewhat similar to the open-hearth, with combustion taking place at one end only. The furnace is lined with iron oxide in the form of mill scale or ore. Cold pig iron is charged into the furnace and as this melts, its carbon is eliminated by the iron oxide lining. When practically all of the carbon and other impurities have been eliminated, the metal has a higher melting point and begins to form into a pasty mass. This pasty mass of metal and slag is well stirred and formed into a ball, which is then removed from the furnace. The bulk of the slag is then squeezed from this mass by means of a mechanical squeezer and the iron is then rolled into bars. The material is now a mixture of high purity iron and some slag (about 2 or 3%). A process for manufacturing synthetic wrought iron has been developed by professor Aston. In this process, pig iron is melted in a cupola and blown to soft steel in a Bessemer. The steel is then poured into liquid slag; the excess slag is then poured off and squeezed out. After this squeezing, the resulting material is rolled into bars for fabrication into pipe and other products.
IX. Установите, какие из приведенных утверждений соответствуют содержанию текста.
1. Электрический ток индуцируется в металлической засыпке, вызывая очень быстрый нагрев.
2. Сварочное железо – черный металл, который достаточно ковкий и производится из вязкого состояния.
3. Печь облицована оксидом железа в форме прокатной окалины или руды.
4. Регенеративные камеры изготавливаются из свободно расположенного кирпича в форме шахматной кладки так, чтобы газ и воздух могли свободно циркулировать.
5. Этим методом достигаются высокие температуры плавления, а также точные и контролируемые условия выплавки.
X. Вставьте подходящие по смыслу слова.
1. When large ... of ... are needed, other methods are usually more
a) shapes, alloy, important;
b) sizes, charge, effective;
c) amounts, metal, economical.
2. An electric current is ... within the metal . . . causing very rapid ..
a) forced, alloy, refining;
b) induced, charge, heating;
c) used, tube, melting.
3. This . . . mass of metal and ... is well stirred and formed into a ...
a) liquid, non-metal, shape;
b) solid, semimetal, bar;
c) pasty, slag, ball.
XI. Укажите, какие из данных предложений не имеют отношения к тексту.
1. A process for manufacturing synthetic wrought iron has been developed by professor Aston.
2. Because of its toughness and ductility, wrought iron is usually broken slowly.
3. The term "charge" refers to the materials fed at the top and includes the fuel, the ore and the flux.
4. Principles of operation of both units are similar, although the design details are quite different.
5. Fuel, metal and flux enter the cupola through the charging door.
XII. Закончите следующие предложения в соответствии с содержанием текста.
1. A high-frequency induction melting unit consists of ... .
a) a large cylinder;
b) a refractory crucible;
c) a bath or hearth.
2. Wrought iron is produced in ... .
a) a Bessemer converter;
b) a low-frequency induction furnace;
c) a puddling furnace.
3. The furnace is lined with iron oxide in the form of... .
a) mill scale or ore;
b) pasty mass of metal and slag;
c) small amounts of special steels.
XIII. Выберите из текста предложения, в которых рассказывается о производстве сварочного железа в конвертере Бессемера.
XIV. Составьте план к тексту на русском языке.