Wear and fatigue failure of slitting discs used in fine friction cutting of metals

Abstract

Metals may be slit by pressing them against toothless, spinning, mild steel discs. In this paper is reported a study of the wear and failure of such discs used to slit mild and stainless steels and a nickel-chromium-iron alloy. The wear volume varied from 10% of the volume removed from the slit metal when slitting mild steel, to 1% when slitting stainless steel. Disc wear did not prevent the use of the process. Cracks were generated in the disc rims. Most of the cracks were radial, transgranular, and heavily oxidized, and became dormant at lengths of less than 1mm. However, a few became intergranular and greu: along the rolling direction of the disc sheet metal, eventually causing the disc to fail by ‘crumpling’. This growth occurred at abnormally low nominal levels of stress concentration (∆K ≤ 2 MN m⁻³²). Whether the cold-worked disc material was abnormally prone to cracking, or whether sources of stress not considered here were responsible for failure, remains to be studied. The use of the process to make fine slits in hard and abrasive metals has already been proved. Better understanding and control of the cracking is needed before it is accepted as a general production process.