Higher Macro-Cleanliness of Bearing Steels Needs More Accurate Measuring- Methods

摘要

Increasing requirements of trendsetter-industry (automotive and railway) on the performance of bearings demand also an improvement of the applied materials. That means principally to reduce macroscopic, non-metallic inclusions. Therefore, steel works need new targets to optimize metallurgical and casting techniques. For this reason, ultrasonic examination methods are more and more applied to test bigger volumes instead of plains. Especially the immersion ultrasonic testing allows to detect smailer inhomogenities. To get optimal testing conditions, SAARSTAHL AG and FhG-IZfP made pretests. Then, the german steel industry in the VDEh made a circle examination to optimize and standardize the test conditions. The reproducible limit size of detectable defects seems to be an equivalent flat bottom hole of 300 to 400 μm for the chosen conditions. All results of the circle examination were used to prepare detailed prescriptions for a test in form of a german standard (SEP 1927), presented in this paper.