A bloom is a rolled steel workpiece with a square cross section of about 150 mm by 150 mm. The starting work unit for a bloom is an ingot heated in a soaking pit. A slab is rolled from an ingot or a bloom and has a rectangular cross section of about 250 mm by 40 mm. A billet is rolled from a bloom and has a square cross section of about 40 mm by 40 mm.
"A bloom usually has a square cross, at least (6 in) on side. Also blooms are processed further by shape rolling into structural shapes as I-beams and railroad rails. A slab usually is rectangular in cross section that is rolled into plates and sheets. (c) Billets Usually are square (with a cross-sectional areas smaller than blooms) and later are rolled into various shapes such as round rods and bars. (d) Wavy edges are the result of roll bending. The stipe is thinner along its edges than at its center; thus the edges elongate more than the center"