The Rolling of Sheets
Most plates are rolled from slabs which are about 36 inches wide, but “sheets,” which are plates less than ³⁄₁₆″ thick are rolled from much smaller-sized slabs known as “sheet bars.” After “pulling out” into sheets these may be folded once or even more times, so that from two to eight thinner sheets are rolled at once. That they may not weld or stick together under the heavy pressure, they must be rolled colder than are single plates. They are later trimmed and pulled apart. Some mills start sheet bars of smaller size, for each sheet a separate piece, which, after drawing out somewhat are piled, two, three, four or five high. With coal or charcoal dust—either dry or mixed with water—between them, they are heated and rolled, the charcoal and coal dust keeping them from sticking together. After annealing, pickling, etc., they may be cold finished in polished rolls or otherwise treated according to the purpose for which they are intended. After straightening some are galvanized, others are tinned, blued or painted. Most of them are sold “black,” i.e., with no coating at all. Terneplate has a coating of 75% of lead and 25% of tin.
The Rolling of Rails and Structural Shapes
It will be readily understood after reading the above, that, instead of using plain rolls, mills for rolling steel rails, I beams, channels, angles, Z bars, rods, etc., must have grooved rolls. For these products the first pass will be through a groove slightly smaller than the bloom or billet. Successive passes will be through other grooves in the same set of rolls which will gradually make smaller and bring more nearly to the finished shape the piece being rolled.
Rail in the Finishing Rolls
Before our eyes the white-hot bloom enters the three-high mill, goes backward and forward through the rolls and very shortly assumes the general shape desired. Each pass thereafter brings it nearer to the finished shape. Rails, for instance, are rolled out from the blooms into one long rail perhaps 140 feet in length which glides along like a huge snake to the swiftly revolving “hot” saws which are so spaced that four 33–foot rails are sawed from it at the same time. As the rails pass from the saws to the cooling bed they are marked by a revolving stamp. When cool they go to the straightening yard, are straightened, drilled, inspected and later loaded into cars for shipment.
The production of all kinds of finished rolled iron and steel products in the United States during the past twenty-eight years is given in the following table which shows how extensive are our rolling mill industries and the rapidity of their development.
| Year | Iron and Steel Rails | Plates and Sheets | Nail Plate | Wire Rods | Structural Shapes | All Other Finished Rolled Prod. | Total Gross Tons |
|---|---|---|---|---|---|---|---|
| 1887 | 2,139,640 | 603,355 | 308,432 | 2,184,279 | 5,235,706 | ||
| 1890 | 1,885,307 | 809,981 | 251,828 | 457,099 | 2,618,660 | 6,022,875 | |
| 1895 | 1,306,135 | 991,459 | 95,085 | 791,130 | 517,920 | 2,487,845 | 6,189,574 |
| 1899 | 2,272,700 | 1,903,505 | 85,015 | 1,036,398 | 850,376 | 4,146,425 | 10,294,419 |
| 1901 | 2,874,639 | 2,254,425 | 68,850 | 1,365,934 | 1,013,150 | 4,772,329 | 12,349,327 |
| 1903 | 2,992,477 | 2,599,665 | 64,102 | 1,503,455 | 1,095,813 | 4,952,185 | 13,207,697 |
| 1905 | 3,375,929 | 3,532,230 | 64,542 | 1,808,688 | 1,660,519 | 6,398,107 | 16,840,015 |
| 1907 | 3,633,654 | 4,248,832 | 52,027 | 2,017,583 | 1,940,352 | 7,972,374 | 19,864,822 |
| 1909 | 3,023,845 | 4,234,346 | 63,746 | 2,335,685 | 2,275,562 | 7,711,506 | 19,644,690 |
| 1911 | 2,822,790 | 4,488,049 | 48,522 | 2,450,453 | 1,912,367 | 7,316,990 | 19,039,171 |
| 1913 | 3,502,780 | 5,751,037 | 37,503 | 2,464,807 | 3,004,972 | 10,030,144 | 24,791,243 |
| 1915 | 2,204,203 | 6,077,694 | 31,929 | 3,095,907 | 2,437,003 | 10,546,188 | 24,392,924 |