For high productivity of stainless steel strips cold rolling: DLC roll coating potential analysis
摘要
Production rolling consists in reducing repeatedly the thickness of metal strips using counter-rotating rolls. Its productivity is determined by the thickness reduction per pass and the rotation speed of the rolls. For certain alloys, among which stainless steels, the rolling load generating the reduction and the speed are limited by the appearance of massive adhesive wear. The nature of the roll surface plays an important role in this phenomenon. In this work, using laboratory tribological tests, we analyze the potential of a hydrogenated DLC (diamond-like carbon) coating (20% at. of hydrogen) for rolling of stainless steel strips and compare it with, on the one hand, the same steel used for the rolls in the stainless steel strips rolling industry and, on the other hand, with well-known PVD (physical vapor deposition) coatings (TiN, TiBN, and CrN). The tribological performances were evaluated for these different materials in terms of conditions of occurrence of massive adhesive wear, of resistance to fatigue, of the level of adhesive transfer, and of level and stability of friction, thanks to a plate-on-ring test and a twin-disk Amsler test. The results show that DLC allows an increase of at least 50% in the load applied to the stainless steel strips (suggesting a possible increase of the reduction per pass in rolling), that it has very good fatigue resistance, and that adhesive transfer is almost negligible compared to other coatings and to uncoated roll steel.