A new generation of blooming breakdown mill for high-quality rod and bar

摘要

WITH the rapid introduction of continuous casting in China the need for blooming mills to roll ingot receded from the 1970s. Across the world, by the 1980s, continuous casting of billet was so common that most blooming/breakdown mills were phased out of steel plants. In China, breakdown mills remained only in a few special steel plants such as Fushun, Benxi and Changcheng Special Steel. China's steel industry has progressed to increasingly make high added-value quality alloy steels downstream of the now largely adopted continuous caster. To produce quality alloy steels such as special quality bar (SQB) requires a large reduction ratio during rolling. This demands the casting of larger cross-section blooms rather than billet. Besides enabling a greater rolling reduction casting larger-section blooms can provide remarkably better product quality as a result of fewer inclusions in the product and improved internal grain morphology. But the need to give heavy reductions of larger booms requires a revival of the breakdown (or blooming) mill.