Usually, during hot rolling, the bloom is a semi-finished nearly square solid metal form between the ingot and the billet. The cross-section of the slab bloom is usually greater than 225 square centimeters and about 8 to 12 meters long. In the rolling mill, it is broken down into finished products such as bars, beams and sheet piles. In earlier mills, ingots were made from cast ingots (called "nodular iron"), but in modern mills they are made by continuous casting.
The ingots, still hot sometimes, reach the tram plate mill and billet mill and are placed upright in a soaking pit under the floor by a special crane. Steel bloom are rectangular gas chambers about 5 meters deep, in which four to eight ingots are simultaneously heated to about 1,250°C (2,300°F). The soaking pit is highly computerized and can be used for scheduling, firing rate, heating time (lasting 8 to 18 hours) and rolling programs.
After heating, the conveyor carries the hot ingot to a two-high reversing mill, which passes, again and again, turning the roll and roll table over each time the ingot passes. Since each pass reduces the bloom by only about 50mm, 21 passes may be required, including several edges pass, and the bloom stands upright on its edge to obtain a slab bloom billet of 150mm*150mm.