The open hearth furnace

The name open hearth is given to it because the hearth of the furnace is exposed to the sweep of the flames which melt the steel.

The open-hearth process is one of the most important me­thods of making steel. It is much slower than the Bessemer but it is easier to control, and for that reason it is more fre­quently used.

The furnace is lined with firebrick to withstand the very high temperatures used. The charge consists of molten pig iron, scrap iron and steel and some hematite. Lime is added to the charge to take out the phosphorus and sulphur as slag. Man­ganese, carbon, nickel, vanadium, or other materials are added to make the kind of steel desired.

The fuel is blown into furnace through one of the two large openings, or ports, located on each end of the furnace. To fa­cilitate combustion, previously heated air is blown through the port along with the fuel. Combustion occurs above the hearth, and the smoke and other products of combustion escape through the ports at the other end of the furnace.

Beneath the furnace are two large chambers through which air or gas flows freely.

There are three stages in the operation of this furnace. The first is known as the process of charging; the second — as the melting down process; the third — the period of refining. The period of refining is especially important and requires the con­stant supervision of the operator. The refining consists first in removing objectionable impurities and then controlling the elements other than iron which the final product must contain. Alloying elements are added to the steel before it is tapped or when it is in the ladle.

NOTES AND COMMENTARY

open-hearth furnace – мартеновская печь for that reason - по этой причине the hearth is exposed to the sweep of the flames – дно печи подвергается воздействию факела пламени the charge consists of molten pig iron, scrap iron and steel and some hematite – загрузка состоит из расплавленного чугуна, лома и стали и небольшого количества красного железняка to take out – чтобы перевести to make the kind of steel desired – чтобы получить нужный сорт стали

to facilitate combustion previously heated air is blown – чтобы ускорить горение, вдувается заранее нагретый воздух сombustion occurs above the hearth – горение происходит над подиной (ванной) melting down process – процесс плавления the period of refining – период рафинирования the constant supervision of the operator – постоянное наблюдение оператора the elements other than iron which the final product must contain – элементы кроме чугуна, которые должны содержаться в окончательном продукте

The electric furnace

The finest grades of steel are produced by the electric fur­nace method. Stainless and heat resistant steels are made al­most exclusively by that process.

Electricity is used only for the production of heat and does not of itself impart any superior quality of steel. Nevertheless, the electric furnace method gives certain advantages impossible in other steel melting processes. The electric furnace generates extremely high temperatures. The temperature is at all times under precise control and is easily regulated.

The production of heat by electricity is unique, oxygen is not necessary to support combustion and the atmosphere within an electric furnace may be regulated at will.

The electric furnace is a circular steel shell resembling a huge tea-kettle in general appearance. It is mounted on rockers so that the furnace can be tilted to pour off molten metal and slag. The bottom of the furnace consists of a layer of heat re­sistant materials below which it is lined with refractory bricks. The side walls which are also lined with refractory bricks con­tain three or more openings.

The roof of the furnace is lined with 250 mm or more of refractory bricks and is shaped like a flat dome. Through this dome great columns of carbon reach into the furnace. These are the electrodes which carry the current to the steel charge.

NOTES AND COMMENTARY

finest grades of steel – лучшие марки стали does not of itself impart any su­perior quality of steel – само по себе не придает стали какого-либо высшего качества is at all times under precise control and easily regulated – все время находится под точным контролем и легко регулируется at will – по желанию

Is mounted on rockers so that the furnace can be tilted to pour off molten metal – установлена на поворотных опорах так, что печь может наклоняться для слива расплавленного металла is lined with - облицована is shaped like flat dome – имеет форму, похожую на плоский колпак