Teeming the Finished Steel into the Ingot Molds
When the molds have been filled and a strong crust develops on the steel the cars are pulled to the “stripper” where the molds are removed, leaving the white-hot ingots standing on the cars.
The ingots mentioned in the chapter on Cementation and Crucible Steel were usually small enough that one pot of 100 pounds of metal filled the mold. A four pot furnace therefore produced 400 pounds. Now for the first time, we are talking in tonnage figures. Instead of a batch of steel making four 3″ × 3″ × 36″ ingots of 100 pounds each, the ordinary “heat” of Bessemer steel from the 15–ton converter gives six or seven ingots about 18″ × 20″ × 60″ in size. Each of these weighs about two tons. The total is 30,000 pounds.
From the stripper the ingots go to the gas-fired soaking pits where the molten interiors of the ingots gradually solidify by cooling while the outer crusts are reheated. After equalizing the temperatures of exteriors and interiors in this way, the ingots are white-hot again and ready for rolling.
Molds Being Stripped from Ingots
The purpose for which the steel is intended, of course, determines the shapes and sizes into which the ingots are rolled. For rails they are rolled down directly, each ingot making about six rails, of thirty-three-foot length. For most other purposes the ingots are rolled in the slabbing mill into billets or slabs which are of intermediate shapes and sizes which are reheated and further rolled down into axles, bars, shapes, wire or other products.
Meanwhile the converter which we saw emptied has not been idle. The American steel engineer has genius for mechanical efficiency and all parts of a great steel plant are so co-ordinated that enormous quantities of material can be handled with not a moment lost between trips. Almost before the ladle of steel had swung away from the converter’s mouth, any remaining slag was dumped from the converter by further tipping, the vessel returned to receiving position and the ladle car, back again from the mixer, poured in the next charge.
Thus blow after blow is made without loss of time.