Problems in Evaluting Non-Metallic Inclusions in Materials for Spring Use

Abstract

Adequate control of non-metallic inclusions (nmi) is one of the key techniques for modern spring materials to ensure their advanced quality and thus elevated fatigue performances. The paper describes the results of an inquiry study on the methods to evaluate nmi in steels actually employed in different field of industries, such as steel manufacturers, wire manufacturers, spring manufacturers, and spring users, in Japan.
Analysis of data reveals that the majority of the evaluating methods are the microscopic ones: the most popular is the microscopic testing method in the Japanese Industrial Standards (JIS), followed by the methods by the American Society for Testing and Materials, and other non-authorized methods practiced especially by the wire and spring manufacturers. It is pointed out that the focus of different ploblems related to nmi is on the fatigue properties of valve and/or suspension springs. The microscopic method in JIS currently used can be effective at the steel manufacturing stage from quality control point of view, though it may not be enough valid to quantify the effect of nmi acting as eventual fatigue origin.