Page images

have proven that the lower grades of basic slag. In the acid process, where the crucible steel can readily be manufact- phosphorus and sulphur are but little afured by the open hearth method without fected by the chemical reaction, a sand any visible difference except for the very lining is usually employed. much decreased expense. The furnaces in which open hearth

All Done by Machinery steel is made, vary in size from five to

During the past few years the open fifty tons' capacity, the modern ones be

hearth plants have been entirely revoluing of the latter tonnage. In design

tionized. Under the present methods, wonderful mechanical devices enter into the operation at every turn. Accordingly, whereas, in former days, the pig iron was charged in a cold state, to-day it is almost universally poured into the furnace in its maiden liquid condition, thus economizing in heat, labor, and time in melting.

By the present methods, the large ladles of iron are carried directly from the blast furnace to the mixer. Here they are lifted bodily over the opening

on top of the mixer. They are next inA CAR OF Ingot Moulds.

verted, and their teeming contents gradually poured in. Receiving as it does the

products of the various casts of the blast they consist of an oblong brick structure furnaces, the mixer acts as an immense alike at both ends. As in the case of the storage room, at the same time thoroughblast furnace, every particle of heat is lymixing the several casts together, caught and utilized. The air and gas, forming a uniform, homogeneous mass. entering one end of the furnace and be When the iron is required in the open ing thrown down upon the charge or hearth or Bessemer departments, the “bath" by the curvature of the roof, dart large furnace is swung down upon its across the furnace or hearth, making axis, permitting the molten metal to flow their escape through the ports on the op- through the mouth into the ladles standposite side, into the reheating chambers ing upon the floor below. below. Thoroughly heating these, they T he open hearth furnaces, being the finally pass up the stack. At regular in- scavengers of the mill, are charged with tervals the air is allowed to circulate all manner of scrap, old castings, rails, through the previously heated chambers etc. As required, the desired quantity of prior to its entrance into the furnace, the each ingredient is placed in large castescaping gases entering and heating the iron charging boxes similar in shape to opposite or cool set.

a bath-tub, having a capacity of about The bottom or hearth, which converges 5,000 pounds each. These in turn are to one point in the center of the furnace, picked up and placed sidewise upon thus facilitating the tapping, is usually small, flat, narrow-gauge cars. When a lined or covered with a special material, sufficient amount to make a charge has dependent upon the nature of the chemi- thus been collected, the cars are drawn cal reaction desired. If a basic reaction into the building, close to the front of the -one in which some of the foreign sub- furnace. The furnace being ready for stances are eliminated or reduced—is de- charging, the immense electric charging sired, a basic lining is placed upon the machine is brought into action. By means bottom. This usually consists of dolo- of this powerful device, one man, who mite, although magnesite, chromite, and manipulates the electric levers, can lime have been used in a few cases. These charge a furnace in less than twenty minmaterials are able to withstand the strong utes, whereas, a few years ago, this was

[merged small][merged small][graphic]


the charge are not removed, but the steel continues to hold almost every atom of these ingredients as they were present in the iron, scrap, and ore. So the composition of the raw stock, as regards these two elements, must be positively ascertained ; and if a low phosphorus and sulphur steel is desired, the charge must be regulated accordingly. On the other hand, the carbon, manganese, and silicon contained in the raw stock are oxidized.

In this process the iron is usually charged first (though many plants charge

to melt first and trickle over the hot iron, the latter being thus protected by the carbon and silicon, for which oxygen has a greater affinity than for iron.

After the metal becomes molten, a covering of slag forms upon the bath, due to the sand from the pig iron if the iron has been charged in the form of sandcast pigs, and to the silica produced by oxidation. If the pig iron is free from sand and low in silicon, the slag will be very thin and of a basic nature, which would ruin the bottom. As a result, an

addition of silica would have to be made. verter. By this means the vessel can be If the opposite, iron is usually added, rotated almost seven-eighths of a revoluwhich forms an iron oxide.

tion, thus permitting it to be placed hori

zontally on one side to be filled, then perTests Made by the Eye

pendicularly or vertically to be blown, When the entire bath has been melted, horizontally on the opposite side to be iron ore is added at intervals, thus oxi- emptied, and upside down to permit the dizing the carbon, manganese, and sili- slag to run out. con, and forming silica and oxide of manganese, which pass into the slag,

Converters Spout Flames . while the carbon forms carbonic oxide The charge of five to twenty tons of which unites with the flames. The car molten iron, taken either from the mixer bon thus causes the entire bath to bubble, or from a cupola, being introduced, a which exposes the metal to the flames and strong blast of air of fifteen to twenty keeps it hot. The metallic iron which is pounds' pressure per square inch is perset free by the union of oxygen with the mitted to rush through one of the trun- . silicon and carbon, is dissolved by the nions into the small chamber in the botbath.

tom of the vessel. From here it makes At intervals a small cup is placed in its exit into the interior of the vessel the bath, and à test of the steel poured through the numerous small holes in the into small test ingots about one inch false bottom. At the same instant, the square in cross-section. After chilling in vessel revolves on its mighty arms and water, these ingots are broken, and the points its infernal mouth skyward, as percentage of carbon is determined by the though hurling the hottest defiance in the eye. If too high in carbon, the molten very teeth of the sleeping night. Here mass is oxidized still more; if too low, it remains for several minutes, the first iron is added.

four or five minutes witnessing a flame When the desired point is reached, fer- of light yellowish-red color and a shower ro-manganese or some other recarbonizer of glittering sparks. During this stage is thrown into the bath, the furnace be- the uncombined or graphitic carbon ing tapped instantly and the steel per- passes into combined form, the silicon mitted to run into the ladle. If this is being oxidized to form silica, which not performed at once, the manganese unites with ferrous and manganous oxwill become oxidized through the intense ides to form slags. This change is acheat of the flames and the slag.

companied by a rapid rise of temperature,

the flames becoming brilliant, large, and The Bessemer Process

of a very dense yellow color. The metal Although there are two kinds of Bes- now boils, the agitation being due to the semer steel, the “acid” and the forination of carbonic oxide from the ox"basic," the acid process is the one al- idation of the iron by the oxygen of the most altogether employed, the conditions blast. During this stage the pressure of in this country proving adverse to the the blast is reduced. basic. In a nutshell, the Bessemer pro- The next stage in the process is sigcess consists in forcing a strong blast naled by the pale rosy hue of the flame, through molten pig iron, thus oxidizing which becomes more transparent and less the carbon and leaving the iron free from brilliant, together with the small numthe same. In order to recarbonize it ber of sparks now issuing from the vesto the required percentage, ferro-man- sel. ganese, coal, or Spiegel is added, while

Ready for Last Steps the molten iron is being poured into the These are signs that the carbon is ladle.

nearly eliminated and the contents of The furnace itself consists of an iron- the vessel almost ready for the last steps. covered, brick-lined, pear-shaped vessel When the flame drops, the vessel is at suspended upon. standards by means of once turned down, and the blast shut off. two trunnion arms attached to the con- Its contents are then poured into a ladle ;

and at the same time, a certain percent under a large electric crane, which is so age of Spiegel or ferro-manganese is constructed that two arms fit over a proadded, in either cold or liquid state, to jection on each side of the mould. As the recarbonize the metal to the required mould is lifted, a central ram presses amount. The phosphorus and sulphur upon the top of the ingot, leaving the in the steel are practically the same as ingot upon the car, while the mould is in the iron before blowing, the silicon, picked up and placed upon a car located carbon, and manganese having been re- upon the next track. duced.

From here the red-hot ingots are taken Quick as a flash the vessel is turned to the heating furnaces of a plate or over, filled, and the operation repeated; "blooming” mill, where they are heated the brimming, fiery ladle containing the to a higher temperature for rolling.

[graphic][subsumed][ocr errors][ocr errors][merged small]

molten steel being lifted by the strong · When of the proper heat, they are lifted iron arms of the hydraulic crane over a out of the large furnaces by means of an set of moulds, into which the newly born electric crane and are carried to the table. steel is poured. As soon as filled, a brisk The latest method of transferring the little engine takes hold of the long row ingots from the soaking pits to the rolls of cars upon which the freshly cast steel is by lifting them one at a time from the ingots and their moulds are resting. With furnaces, as above stated; but, instead a warning toot, it goes puffing away amid of carrying them to the rolls by the crane, the sparks, flames, and din, to the open they are placed on end on a specially conyard beyond.

structed cast-iron car operated by elecHandling of Bessemer Steels tricity. The car is then run to the end After the moulds have been filled with of the table, where a lever attached to the molten steel, they are taken to the the rail throws the body of the car to“stripper,” which is usually next to the wards the rolls, the ingot falling upon open hearth or Bessemer buildings. Here the table. The car then returns for anthe cars containing the moulds are run other load.


After the steel is sheared, it passes up an incline and into the bins, where the billets are cooled and, when ready, are permitted to fall into the cars.

Rolling the Steel Ingots

The rolls rotating, the ingot is advanced towards the large rolls through which it is to pass. Here the race begins. Faster and faster revolve the small rolls, carrying the heavy solid block of steel at a terrific pace towards the yawning mouths of the large rolls. Through these it goes with a terrible protest, throwing its scale in every direction. The ingot having reached the other side in a somewhat flattened condition, the mighty engines stop and reverse at a breakneck speed, the table again carrying the ingot between the rolls. Backward and forward it is hurled, each pass reducing its shape and thickness until of the proper dimensions, when it is carried between the sharp and powerful teeth of the shears which cut it to the desired lengths.

If billets are being made, they are conveyed as rapidly as sheared, by means of an endless chain, up an incline, to the top of the bins. Here is a long, narrow platform over which the chain travels. Along the side of the platform are the steel bins, with gates at both ends. The bottoms of the bins slant at an angle of sixty-five degrees from the chain to the ground. The billets, being carried up the incline and along the narrow platform, come in contact with the switch or upper door of the bin, which opens and allows them to enter. One after another they go tumbling down; and when the bin is filled, that gate is closed and the door of the next bin opened. When the billets have cooled, the lower gates are opened, and the billets fall into the cars beneath. Thus the steel is made, taken from

« PreviousContinue »