The phenomenal success of the Bessemer process attracted many other inventors to the study of new and improved methods of steelmaking. The only process which was destined to become a rival of the Bessemer process was developed through the invention of the regenerative principle by Siemens.
Briefly the method of Siemens was as follows: a covered hearth was used to contain the charge of pig iron or pig iron and scrap. Most of the heat required to promote the chemical reactions necessary for purification of the charge was provided by passing burning fuel gas over the top of materials. The fuel gas, with a quantity of air more than sufficient to burn it, was introduced through ports at each end of the furnace, alternately at one end and then the other. The products of combustion passed out of the port which was not used for entrance of gas and air, and entered the chambers partly filled with brick checkerwork. During their passage through the checkers, the gases gave up a large part of their heat to the brickwork. After a short time, the air and gas were shut off at one end and introduced into the furnace through the preheated checkers, absorbing some of the heat stored in these checkers. The gas and air were thus preheated to a somewhat elevated temperature, and consequently developed a higher temperature in combustion than could be obtained without preheating. In about twenty minutes, the flow of the gas and air was again reversed so that they entered the furnace through the checkers and port used first. A series of such reversals, occurring every 15 or 20 minutes, was continued until the heat was finished.
The open-hearth furnace is both reverberatory and regenerative. It is reverberatory in that charge is melted on a refractory hearth, which is shallow, by passing a flame over the charge. The charge and the relatively low roof (above the hearth) built of refractory brick, are heated by the flame with a part of the heating effect on the charge being due to the radiation from the heated roof.
An open-hearth furnace consists of the furnace proper containing the covered hearth on which the charge is placed; ports for admitting the fuel and air for combustion to produce a flame which flows over the charge from the incoming port to the outgoing ports; regenerative chambers containing brick known as "the checkerwork (checkers)" which store up heat transferred to them from the products of combustion; flues and uptakes connecting the checker chambers with the furnace proper; slag pockets which are located at the base of the uptakes; flues leading from the air supply to the regenerative chambers, with connections to the stack; valves (dampers) for regulating flow of air, fuel gas and waste gases; and the stack itself.
Open-hearth furnaces are usually referred to as "acid" or "basic". If the furnace is made of dolomite or magnesia, it is called "a basic hearth", and so lime, which is chemically a basic material, can be added to the slag without causing damage to the hearth. Sulphur and phosphorus can be removed. If the hearth is made of silica sand, very little lime can be added, because it would attack the silica hearth. Hence, sulphur and phosphorus cannot be removed. Such a hearth is known as "an acid hearth". The steel made on it, which is called "acid steel", is generally of high quality.
Scrap is placed on the hearth by means of a charging machine. Limestone is next placed on top of the scrap and then more scrap is added. When this is partially melted, and some of the metal has combined with oxygen to give FeO, a quantity of hot metal is added by means of a ladle. The carbon in the iron reacts with the ferrous oxide :
C+FeO=Fe+CO,
giving off large volumes of carbon monoxide.
When the desirable carbon content has been reached and the amounts of other elements are satisfactory, the metal is tapped.
The fuel may be blast furnace gas, coke oven gas, tar, oil, natural gas.
Most of the open hearth furnaces that have been built during the last few years, have capacities between 200 and 800 tons per heat.
Дополнительные слова и словосочетания:
1) coke-oven gas – коксовый газ
2) reverberatory furnace – отражательная печь
3) regenerative principle – регенеративный принцип
VII. Определите, соответствуют ли содержанию текста данные утверждения.
1. The open-hearth furnace is both reverberatory and regenerative.
2. Traditionally, steelmaking has played a leading role in the economy.
3. The fuel may be blast furnace gas, coke oven gas, tar, oil, natural gas.
4. Molten steel is poured into large molds and solidified.
5. The carbon in the iron reacts with the ferrous oxide giving off large volumes of carbon monoxide.
VIII. Пользуясь текстом, переведите данные предложения на английский язык.
1. Лом поступает в горн при помощи загрузочной машины.
2. Холодные газ и воздух проходят через нагретые насадки регенераторов и сгорают в печи.
3. Продукты горения выходят через отверстия, которые не используются для впуска газа и воздуха.
4. Перекидка осуществляется каждые 15 – 20 минут.
5. Применение нагретого воздуха и газа дает возможность получить более высокие температуры в печи и значительно сократить расход тепла.
IX. Вставьте нужные по смыслу слова, в соответствии с содержанием текста.
1. Scrap is placed … by means of a charging machine.
a) into large molds;
b) on the hearth;
c) acid open-hearth.
2. After a short time, … were shut off at one end and introduced into the furnace through the preheated checkers.
a) loosely laid brick;
b) natural gas;
c) the air and gas.
3. The only process which was destined to become a rival of the Bessemer process was developed … of the regenerative principle by Siemens.
a) through elimination of impurities;
b) through the invention;
c) through recarburising agents.
4. The products of combustion passed out of the port which was not used for entrance of gas and air, and … partly filled with brick checkerwork.
a) broken slowly;
b) entered the chambers;
c) produced in pasty condition.
5. The gas and air were thus preheated to a somewhat elevated temperature, and consequently developed … a in combustion than could be obtained without preheating.
a) toughness and ductility;
b) higher temperature;
c) crystalline in character.
X. Задайте все возможные типы вопросов к данным предложениям.
1. An open-hearth furnace consists of the covered hearth, ports, regenerative chambers containing brick known as "the checkerwork (checkers)"
2. Open-hearth furnaces are usually referred to as "acid" or "basic.
3. Most of the heat was provided by passing burning fuel gas over the top of materials.
XI. Используя рис.2 (см. приложение), опишите мартеновскую печь.
XII. Переведите дополнительный текст без словаря.
About 1850 several revolutions in steelmaking took place. Until then steel had been made in small quantities in clay pots. A few years later it was being made in small quantities of several tons at a time. This led to the modern furnace the capacity of which may exceed 500 tons. The inventions of Frederick and William Siemens, who patented their first furnace in 1865, have had a great effect on the steel industry. The key idea behind the Siemens process is the preheating of the air and gas used to melt the charge. This preheating takes place before the air and gas enter the furnace by passing them through chambers filled with hot bricks. The bricks are heated by the waste gases when the furnace is working in the opposite direction, the flow of air and gas through the furnace being periodically reversed.