Advances in Billet Cast Carbon Steel Quality for High-Performance Rolling Bearings

摘要

In today's steelmaking business, the importance of clean steels has grown significantly due to increasing market demands. The need for lightweight design and parts with increased performance is more important than ever. Bearing steels are a clear example of this and the same has extended to other applications such as gears, pinions, and shafts. Each one may have its own unique production process and product testing requirements. However, a significant contribution to the improved performance relies on the quality of the steel used. Compared to just 20 years ago, improvements in steel manufacturing processes and advancements in the science of microstructural analysis have substantially improved steel quality. These advancements have resulted in critical chemistry control, as well as enhanced refining techniques to raise the purity of steel. As a result, clean steels are capable of outperforming other materials and excel in high applied stress conditions. Reducing the frequency of larger inclusions has a direct impact on the potential failure of a part, but also the frequency of smaller inclusions can have an impact on premature failure, fatigue life, and mechanical properties overall. Gerdau Special Steel has tailored its Monroe plant process to produce high-quality clean steels in a billet continuous casting process, enabling the use of a single conversion step to final rolled products. New production practices have been developed to reduce the size and frequency of nonmetallic inclusions. Improvements have been validated using several cleanliness assessment techniques, including scanning electron microscopy automated analysis and immersion ultrasonic testing at low and high frequencies.