Steel Quality Improvements with Vertical Continuous Casting at Faircrest Steel Plant

摘要

The life of a steel bearing component can be strongly influenced by the quality of the bulk material. The shape, surface, and internal structure of the component can be affected by the upstream steelmaking processes. The steel material must positively affect these characteristics through resistance to distortion and superior surface quality and internal cleanness. The TimkenSteel Faircrest jumbo bloom vertical continuous caster was designed to meet these high standards for the production of high-quality bearing steels. Improved segregation symmetry through the implementation of dynamic mechanical soft reduction and controlled cooling has resulted in customer testing to similar levels of finished product distortion as the bottom poured ingot product. The vertical nature of the machine avoids any bending or unbending strains and stresses that are placed on the surface of the curved cast product, and uniform heat extraction is more easily achieved. The straight shape of the strand also provides a greater potential for inclusion removal by flotation without producing any localized inclusion distribution such as an increased inner radius concentration often found in a curved machine cast product. Significant resources were dedicated to developing a unique and robust tundish design through physical and computational modeling efforts. The tundish produces consistent quality characteristics across all three strands and manages steady-state and transitional operational practices while incorporating a sealed inert tundish atmosphere to minimize reoxidation for increased levels of cleanness. The customized features of the machine have led to rapid qualifications from demanding bearing and gear customers using various testing methods, and quality levels have met or exceeded the TimkenSteel quality expectations.