ANALYSIS OF SELECTED PROPERTIES OF STEEL USED FOR TOOLS FORMING A BAND ASSIGNED FOR THE PRODUCTION OF CERAMIC ROOFING TILES IN THE ASPECT OF METHODS OF PROLONGING THE PERFORMCANCE LIFE

The article presents results of a complex wear analysis of forming tools in the process of band extrusion for ceramic roofing tiles. The materials for such tools must be especially resistant to abrasive wear, which occurs because of contact with the extruded ceramic mass band, which consists mostly of clay (70 %), quartz sand (10 %) and flour from ceramics recycling (20 %). Investigated material was tool steel NC11LV characterized in different hardness levels, collected directly from the forming tools. Tests included an analysis of the abrasion resistance conducted with the use of a dry abradant, tests of the microstructure and topography of the worn surface, as well as nanohardness and Young modulus measurements using a nano indenter. The whole can be confronted with the results of performance tests carried out so far, during which the tools working on the production lines were subjected to 3D scanning. The obtained results confirm better abrasive wear resistance parameters, with respect to forming tools, is demonstrated by steel NC11LV with a higher hardness, which is illustrated by the relative wear resistance index Kb obtained during the dry abradant tests, which, for NC11LV with a lower hardness, equals 1,548, and for the hardened steel with a higher hardness, it is 1,810. NC11LV owes good properties mostly to the hard carbide precipitates. Higher niobium content results in niobium carbides in the microstructure and in this way to a higher hardness of material. Other possibilities of prolonging the life of forming tools represents e.g. the nitriding.