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The bearing industry has long recognized that reducing the total number and size of large aluminum oxide inclusions proportionately increases contact fatigue life. Improved geometric accuracy and surface finish on heavy duty off-highway carburized gearing has increased the significance of oxide inclusions in nucleating contact and bending fatigue fractures. While modern steel making technology can regularly provide high quality steel with controlled cleanliness, the absence of an industry standard specification makes procurement difficult. Key quality and steel cleanliness requirements have been written into CNH's alloy gear steel specification. A detailed questionnaire has been developed and is utilized to help identify steel mills that have the modern equipment and processes needed to produce high quality gear steel.

Modern steelmaking practices enable closer control of chemical composition and hardenability, and some manufacturers are already specifying narrow hardenability limits. This paper reviews a recent activity of SAE Division 8, Carbon and Alloy Steel Hardenability, that developed restricted hardenability bands for a series of steels. The paper summarizes the need for restricted hardenability limits and the methods used to develop the new bands for the proposed SAE Standard J1868.