In the regular work, as soon ,as the ingot cast from the metal purified in the converters, is set, the mold is drawn from it by a hydraulic stripper and it is raised by an ove.iiiead electric crane and then lowered into the soaking pit, where it is brought to the proper temperature (white heat) for rolling. It is then taken to the blooming mill and passed through the blooms (rollers) seven times and reduced to a section varying in size according to the size of the de sired rail. The section of the ordinary rail used on the railroads is nine and one-fourth inches square, and the ingot when rolled to that section attains a length of about 15 feet.
It is then sheared into two or three lengths, as the case may be. These pieces called blooms after being heated in the bloom furnaces are carried to the rail mill, which consists of three sets of rollers — the roughing rolls, the inter mediate rolls and the finishing rolls, through which the bloom is passed successively, Through the first set it is passed five times and reduced approximately to the section of the desired rail. It is then, without being reheated, passed five times through the intermediate rolls and reduced more closely to the desired shape.. If the rail is of the lighter variety, weighing from 50 to 70 pounds per linear yard, it is then passed through the last set of rolls and finished on a single heat, with satisfactory results. But if the rail is of the heavier class, ranging In weight from 80 to 120 pounds per linear yard, its tendency to retain heat longer, and, there fore, be passed through the finishing rolls at a temperature too high to give good results, is overcome by allowing it to remain upon a cool ing table for an interval of time ranging from 45 to 90 seconds, and it is then passed through the finishing rolls at a lower temperature, thus giving a rail of a much better quality of metal, especially in the head of the rail. The rail is now sawed into the desired lengths, usually of 30 feet, and then passed through the cambering rolls, where it receives sufficient camber to prevent warping when it is being cooled. After being cooled off on the hot beds it is straight ened, chipped and filed and is then ready for shipment as a finished product. Improved ap paratus has in recent years greatly facilitated the operations in rolling rails. Electricity hai been a prime factor in their operations.
In the manufacture of shape: (a term which includes a great variety of angle, irons, T-irons, I-beams, Z-bars, eye-bars, chan nel-irons and built-up posts, beams and gird ers), used in the construction of modern buildings and bridges, the shapes are rolled from basic open-hearth steel of three grades— the rivet steel with an ultimate strength ranging from 48,000 to 58,000 pounds; the soft steel from 52,000 to 62,000 pounds; and the medium steel' from 60,0(X/ to 70,000 pounds. The elastic
limit generally required is not less than one half of the ultimate strength, and the test pieces are required to be capable of being bent over through an angle of 180 degrees, without frac ture. The raw materials, consisting of ore and pig-iron, are melted down in the cupolas and are then run into the open-hearth tilting fur nace, where an equal amount of cold scrap, in the form of steel junk, crop-ends, punchings, etc., from the construction shops, is added. The contents of this furnace, sometimes amounting to 75 tons, are poured into a hydraulic ladle crane, which is then swung over the casting pit., and the molten metal poured into the ingot molds in the usual way through the bottom of the ladle. The ingots when set are reheated in the soaking pit and then passed through the blooming mill and reduced to blooms and bil lets of any required size. They are then rolled ited to not more than 10,000 pounds below the test specimen of the grade of steel from which they are rolled. The eye-bar heads are formed by upsetting machines operated by hydraulic power, in which the heated end of the eye-bar is pressed to the desired circular form by the three-fold die of a hydraulic press, in a single operation. The head is then forged and punched at one heat, and then finished bored. Eye-bars are tested in a hydraulic testing machine capa ble of exerting a maximum pull of 700 When an order of eye-bars is completed, one of the bars is pulled asunder in the machine. In general, they are required to show not less than 10 per cent elongation in the body of the bar and they must break in the body_ and not in the ge. See BUILDING IN THE. UNITED STATES; ELECTROCHEMICAL INDUSTRIES; IRON ; IRON, to the desired shapes, sawed into the required lengths and then cooled on the hot beds. From the hot beds they are passed through the straightening rolls, and after being cut into ex act lengths, as required, they are ready for the construction shop.
In the production of finished bridge mem bers, the shapes are carefully laid out by wooden templates, in which the precise positions of rivets, angles, gussets, etc., are marked. The operation of building up requires great care and accuracy. The shapes are sawed or sheared to exact length and the sides and ends faced and planed down as required by the drawings. The small holes for bolts and rivets are punched by lighter forms of machinery driven by elec tric power; on the other hand, all pin-holes are first punched and then bored to exact diameter. In assembling, the rivet holes are properly reg istered, being reamed if necessary, and the sep arate parts bolted together and finally riveted up by hydraulic or pneumatic riveters. See