have proven that the lower grades of crucible steel can readily be manufactured by the open hearth method without any visible difference except for the very much decreased expense.

The furnaces in which open hearth steel is made, vary in size from five to fifty tons' capacity, the modern ones being of the latter tonnage. In design

A CAR OF INGOT MOULDS.

they consist of an oblong brick structure alike at both ends. As in the case of the blast furnace, every particle of heat is caught and utilized. The air and gas, entering one end of the furnace and being thrown down upon the charge or "bath" by the curvature of the roof, dart across the furnace or hearth, making their escape through the ports on the opposite side, into the reheating chambers below. Thoroughly heating these, they finally pass up the stack. At regular intervals the air is allowed to circulate through the previously heated chambers prior to its entrance into the furnace, the escaping gases entering and heating the opposite or cool set.

The bottom or hearth, which converges to one point in the center of the furnace, thus facilitating the tapping, is usually lined or covered with a special material, dependent upon the nature of the chemical reaction desired. If a basic reaction -one in which some of the foreign substances are eliminated or reduced-is desired, a basic lining is placed upon the bottom. This usually consists of dolomite, although magnesite, chromite, and lime have been used in a few cases. These materials are able to withstand the strong

basic slag. In the acid process, where the phosphorus and sulphur are but little affected by the chemical reaction, a sand lining is usually employed.

All Done by Machinery

During the past few years the open hearth plants have been entirely revolutionized. 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 inverted, and their teeming contents gradually poured in. Receiving as it does the products of the various casts of the blast furnaces, the mixer acts as an immense storage room, at the same time thoroughly mixing the several casts together, forming a uniform, homogeneous mass.

When the iron is required in the open hearth or Bessemer departments, the large furnace is swung down upon its axis, permitting the molten metal to flow through the mouth into the ladles standing upon the floor below.

The open hearth furnaces, being the scavengers of the mill, are charged with all manner of scrap, old castings, rails, etc. As required, the desired quantity of each ingredient is placed in large castiron charging boxes similar in shape to a bath-tub, having a capacity of about 5,000 pounds each. These in turn are picked up and placed sidewise upon small, flat, narrow-gauge cars. When a sufficient amount to make a charge has thus been collected, the cars are drawn into the building, close to the front of the furnace. The furnace being ready for charging, the immense electric charging machine is brought into action. By means of this powerful device, one man, who manipulates the electric levers, can charge a furnace in less than twenty minutes, whereas, a few years ago, this was

The "acid" process is practically no more nor less than a case of oxidation, in which the phosphorus and sulphur of

to insure its equal distribution over the bottom and on the banks or sides, the scrap being placed as evenly as possible over the iron, thus permitting the scrap

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. If the opposite, iron is usually added, which forms an iron oxide.

Tests Made by the Eye

When the entire bath has been melted, iron ore is added at intervals, thus oxidizing the carbon, manganese, and silicon, and forming silica and oxide of manganese, which pass into the slag, while the carbon forms carbonic oxide which unites with the flames. The carbon thus causes the entire bath to bubble, which exposes the metal to the flames and keeps it hot. The metallic iron which is set free by the union of oxygen with the silicon and carbon, is dissolved by the bath.

At intervals a small cup is placed in the bath, and a test of the steel poured into small test ingots about one inch square in cross-section. After chilling in water, these ingots are broken, and the percentage of carbon is determined by the eye. If too high in carbon, the molten mass is oxidized still more; if too low, iron is added.

When the desired point is reached, ferro-manganese or some other recarbonizer is thrown into the bath, the furnace being tapped instantly and the steel permitted to run into the ladle. If this is not performed at once, the manganese will become oxidized through the intense heat of the flames and the slag.

The Bessemer Process

Although there are two kinds of Bessemer steel, the "acid" and the "basic," the acid process is the one almost altogether employed, the conditions in this country proving adverse to the basic. In a nutshell, the Bessemer process consists in forcing a strong blast through molten pig iron, thus oxidizing the carbon and leaving the iron free from the same. In order to recarbonize it to the required percentage, ferro-manganese, coal, or Spiegel is added, while the molten iron is being poured into the ladle.

The furnace itself consists of an ironcovered, brick-lined, pear-shaped vessel suspended upon standards by means of two trunnion arms attached to the con

verter. By this means the vessel can be rotated almost seven-eighths of a revolution, thus permitting it to be placed horizontally on one side to be filled, then perpendicularly or vertically to be blown, horizontally on the opposite side to be emptied, and upside down to permit the slag to run out.

Converters Spout Flames

The charge of five to twenty tons of molten iron, taken either from the mixer or from a cupola, being introduced, at strong blast of air of fifteen to twenty pounds' pressure per square inch is permitted to rush through one of the trun- . nions into the small chamber in the bottom of the vessel. From here it makes its exit into the interior of the vessel through the numerous small holes in the false bottom. At the same instant, the vessel revolves on its mighty arms and points its infernal mouth skyward, as though hurling the hottest defiance in the very teeth of the sleeping night. Here it remains for several minutes, the first four or five minutes witnessing a flame of light yellowish-red color and a shower of glittering sparks. During this stage the uncombined or graphitic carbon passes into combined form, the silicon being oxidized to form silica, which unites with ferrous and manganous oxides to form slags. This change is accompanied by a rapid rise of temperature, the flames becoming brilliant, large, and of a very dense yellow color. The metal now boils, the agitation being due to the formation of carbonic oxide from the oxidation of the iron by the oxygen of the blast. During this stage the pressure of the blast is reduced.

The next stage in the process is signaled by the pale rosy hue of the flame, which becomes more transparent and less brilliant, together with the small number of sparks now issuing from the vessel.

Ready for Last Steps

These are signs that the carbon is nearly eliminated and the contents of the vessel almost ready for the last steps. When the flame drops, the vessel is at once turned down, and the blast shut off. Its contents are then poured into a ladle;

molten steel being lifted by the strong iron arms of the hydraulic crane over a set of moulds, into which the newly born steel is poured. As soon as filled, a brisk little engine takes hold of the long row of cars upon which the freshly cast steel ingots and their moulds are resting. With a warning toot, it goes puffing away amid the sparks, flames, and din, to the open yard beyond.

Handling of Bessemer Steels After the moulds have been filled with the molten steel, they are taken to the "stripper," which is usually next to the open hearth or Bessemer buildings. Here the cars containing the moulds are run

When of the proper heat, they are lifted out of the large furnaces by means of an electric crane and are carried to the table.

The latest method of transferring the ingots from the soaking pits to the rolls is by lifting them one at a time from the furnaces, as above stated; but, instead of carrying them to the rolls by the crane, they are placed on end on a specially constructed cast-iron car operated by electricity. The car is then run to the end of the table, where a lever attached to the rail throws the body of the car towards the rolls, the ingot falling upon the table. The car then returns for another load.