SYMPOSIA PAPER Published: 08 September 2020

VIM-VAR Steelmaking for Bearing Steel Grades


Vacuum induction melting (VIM) of the feedstock ingot for vacuum arc refining (VAR) was introduced in the 1970s to improve the reliability of steels for aerospace rolling bearings. VIM-VAR bearing steel manufacturers must meet the constraints imposed by Aerospace Materials Specifications (AMS) and customer specifications with respect to nonmetallic inclusions and segregation, particularly of carbide-forming elements in the highly alloyed secondary hardening grades. Product analytical consistency and the absence of deleterious gasses and residual elements must also be achieved. With reference to its application at Liberty Speciality Steels (LSS), the paper will review the intrinsic benefits of the VIM process and the measures required to address its inherent risks and limitations. For example, normal slag-based desulfurization is not possible in the VIM process. The improvements in product performance and consistency attributable to the VAR process will be described, along with the key parameters that must be controlled to avoid its pitfalls, such as “freckle” (channel segregation within the solidifying pool in the VAR process) and other segregation features. VIM and VAR furnace and refractory design features that contribute to product quality will be described along with the crucial importance of nondestructive testing in ensuring the quality of the delivered product. LSS is a long-established producer of bearing steels and of remelted aerospace steels but a relatively new entrant to the VIM-VAR bearings steel supply chain. Initial product data will be presented for bearing steels and steels for other highly stressed applications.

Author Information

Carey, Stephen
Liberty Speciality Steels, Sheffield, GB
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Pages: 499–514
DOI: 10.1520/STP162320190108
ISBN-EB: 978-0-8031-7693-5
ISBN-13: 978-0-8031-7692-8