Billet Mill

a rolling mill designed for the rolling of blooms or ingots into billets of square or round cross section. The billets are later processed in specialized rolling mills (section and tube rolling mills).

Continuous and tandem billet mills, as well as mills with sequential arrangement of roll stands, are distinguished. Continuous mills are the most common type (see Figure 1). In such mills the metal being rolled is roughed alternately in stands with vertical and horizontal rolls, without edging, thus reducing the danger of crack and scratch formation on the surface of the metal. Individual drives for the mill rolls ensure regulation of the rolling speed and simplify the set-up of the mill and the roll-pass design. Continuous billet mills of very high capacity are in operation in the USSR; their output can be as high as 5 million tons of billets per year (1970).

Figure 1. Diagram of a 730/530 continuous billet mill with alternation of stands with horizontal and vertical rolls: (1)-(6) roll stands with rolls 730 mm in diameter, (7)-(12) roll stands with rolls 530 mm in diameter, (13) approach table, (14) intermediate table, (15) repeating table, (16)-(18) shears, (19) run-out table, (20) cooling bed for billets, (21) and (22) bridge cranes

In a modern continuous billet mill all technological operations are mechanized and automated; in some mills operations are controlled by electronic computers. In the USSR, continuous billet mills installed immediately following blooming mills roll blooms with cross sections of 300 x 300 to 400 x 400 mm into square billets with cross sections of 50 x 50 to 150 x 150 mm and, in some cases, into round billets with diameters up to 300 mm. Some billet mills are used to roll slabs (sheet bars) 180–600 mm wide and 50–100 mm thick. Tandem billet mills are used mainly to roll billets made from high-grade steel in small quantities. Billet mills with sequential arrangement of stands are used in rolling of skelp.