Surface treatment of steel tool, especially cold pilger rolling mandrel

摘要

A surface treatment process for steel tools, especially cold pilger rolling mandrels, involves: (i) providing the functional surface of the tool with a roughness according to DIN 4761-8.3 with a round crested roughness profile without curling of the profile tips; (ii) coating the surface with CrN by PVD; and (iii) eliminating the resulting growth spikes from the tool surface. Preferably, the process involves: (a) production of the tool by turning and grinding the surface with a grinding medium of /-400 grain; (b) fine grinding with a grinding medium of 900-1200 grain; (c) electrolytic polishing of the tool surface; (d) coating of the tool with CrN by plasma-activated PVD; and (e) fine grinding of the coated tool surface with diamond paste of D1 to D3 grain (ISO R6109-80). In step (a), finish grinding is preferably carried out using silicon carbide or boron nitride grinding belts, and in step (b), nonwoven fibre fabric or belts are used.