Steel Quality Requirements for Heavy Duty Off-Highway Gearing

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.