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Steel Shapes 18

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STEEL SHAPES 18. Manufacture of Steel Shapes. When the ingot is taken from the soaking pit and "cropped," it is placed on the table of the rolls, or blooming table. This table consists of a num ber of cylinders placed close together and made tc revolve either forward or backward as de sired. The table moves the ingot to the rolls, where it is rolled through an opening but slightly smaller than the ingot itself. The ingot comes out on the other side longer than it was before, and of uniform section throughout its entire length. Here it is automatically moved to one side, and, the cylinders of the rolling table being put in motion, the steel goes to another set of rolls and is again reduced in sectional dimen sions. The first few passes generally reduce the ingot to a rectangular or square section. The steel is then moved sidewise to the different roll openings in turn. Each of these shapes the steel into something approaching its final shape; and at the last pass, what was an ingot only 63 inches long becomes a rail, a plate, or some structural shape 20 to 120 feet or more in length. In cases where the number of passes is great, instead of two rolls, three or more are used. The "bloom ing table" is so arranged in this case that it may be raised or lowered, thus carrying the steel to the upper set after it has passed through the lower one. Plate 5 (upper figure) illustrates the rolls in a 16-inch "three-high" mill; and in Plate 4 is seen a blooming table.

The completed shape is now still at a weld ing heat. It is run to the cold saws, and cut to the required length. This length must be con siderably greater than the length required when the piece is cold. As a usual thing, for each ten feet in length of the cold piece, the piece must be cut four inches longer when hot. This of course depends upon the temperature of the steel as it comes from the rolls. The piece is then put on the cooling table and allowed to cool, and is afterwards straightened.

19. Production of Steel Shapes. In 1905 there were 5,253,816 tons of structural shapes rolled in the United States. This includes plates

and bars and rods, and constitutes about 26 per cent of all the Bessemer and open-hearth steel made in that year. Of this amount, by far the greater part was open-hearth steel.

20. Steel-Makers' Handbooks. In order to work in structural steel or to study structural engineering, it is necessary to have a handbook of at least one of the steel companies. Structural steel workers and students can usually obtain these handbooks from the head offices of the com panies for 50 cents a copy; to others, the price is $2.00. The handbooks of the Carnegie Steel Company, the Cambria Steel Company, the Bethlehem Steel Company, and others, are equally good. Throughout this text the Car negie handbook (edition of 1903) will be re (erred to. The number of the page or pages, for example, will be signified thus: (C 45), (C 183-187), or (C 189 and 200), which means that the matter referred to will be found on page 45, or pages 183 to 187, or on page 189 and page 200.

No student of steel construction should be without one or more of these handbooks.

21. Classes of Shapes. Shapes for struc tural work are classified by names characteristic of their form. In Table IV the shapes com monly used in structural work are listed, with a sectional view of each.

Rounds.

The circular form of the rounds is obtained by turning them half-way around each time that they are passed through the rolls. They are made from inch to inches in diameter (C 27). They are used in tension— that is, to withstand a pull. The connection at the ends is made by means of a washer and nut. In case the area of the cross-section is required, or the circumference (distance around the out side), it can be found (C 261-266). The large bars listed in (C 263-266) are not, as a general thing, used for anything except to cut in short lengths, turn on a lathe, and use as pins to connect members or as rollers for different purposes.

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