This thesis focuses on the tribological performance of tool surfaces in two steel working operations, namely wire drawing and hot rolling. In all forming operations dimensions and surface finish of the products are of utmost importance. Forming basically includes three parts – forming conditions excluded – that may be changed; work material, tool and (possibly) lubricant. In the interface between work material and tool, the conditions are very aggressive with – generally or locally – high temperatures and pressures. The surfaces will be worn in various ways and this will change the conditions in the process. Consequently, the surface finish as well as the dimensions of the formed product may change and in the end, the product will not fulfil the requirements of the customer. Therefore, research and development in regard to wear, and consequently tribology, of the forming tools is of great interest. The investigations of wire drawing dies focus on coating adhesion/cohesion, surface characteristics and material transfer onto the coated steel both in laboratory scale as well as in the wire drawing process. Results show that it in wire drawing is possible to enhance the tribological performance of drawing dies by using a lubricant together with a steel substrate coated by a polished, dual-layer coating containing both hard and friction-lowering layers. The investigations of hot rolling work rolls focus on microstructure and hardness as well as cracking- and surface characteristics in both laboratory scale and in the hot strip mill. Results show that an ideal hot work roll material should be made up of a matrix with high hardness and a large amount of complex, hard carbides evenly distributed in the microstructure. The surface failure mechanisms of work rolls are very complex involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. This knowledge may be used to develop new tools with higher wear resistance giving better performance, lower costs and lower environmental impact.

Outokumpu Stainless AB operates in the production and development of stainless steels. In their hot rolling mill in Avesta there is a need to introduce an equipment to shift bearing housings on the steckel mill work rolls. Today this is accomplished manually with an overhead crane, jack, sledgehammer and pry-bar. It causes strain on the operators and the equipment may be damaged in the process.On behalf of Outokumpu Stainless AB, Bilfinger started this project as a thesis with the objective to develop a design proposal for a machine that meets the requirements for an easier and better handling of the bearing housing changes. In this thesis the author presents some concepts on how the machine could work, analysis of forces which occur when the roll assembly is placed on the table, a simple model to estimate the needed force to remove the bearing housing from the work roll as well as force and FEM analysis of the machine. The result was a machine consisting of a table to place the roll upon and two pullers, one for each bearing housing, which brings the bearing housing with it when actuated by a hydraulic cylinder. The machine meets all of the set requirements except for the production cost and the power of the hydraulic cylinder while retracting (30% lower). A rough estimation of the production and installation cost is estimated at just over 1 MSEK. / Outokumpu Stainless AB är verksamma inom tillverkning och utveckling av rotsfria stål. I deras varmvalsverk i Avesta finns ett behov att införa en utrustning för att enkelt byta lagerhusen på steckel valsverkets arbetsvalsar. Idag förs detta manuellt med travers, domkraft, slägga och spett. Det ger slitage på operatörer och även utrustningen kan skadas i denna process. På uppdrag av Outokumpu Stainless AB har Bilfinger startat detta projekt som ett examensarbete med målsättning att ta fram ett konstruktionsförslag för en maskin som uppfyller kraven på en smidigare och bättre hantering av lagerhusbytena. I detta arbete presenteras några koncept på hur maskinen skulle kunna fungera, några analyser av krafter som uppstår när vals och lagerhus placeras i sitt stativ, en enklare modell för att uppskatta den kraft som krävs för att ta av lagerhusen från valsen samt kraft och FEM analyser av maskinen. Resultatet blev en maskin som består av ett stativ att placera valsen med lagerhusen på samt två avtagare, en för varje lagerhus som drar med lagerhuset då den påverkas av en hydraulisk cylinder. Maskinen uppfyller alla satta krav förutom produktions pris och kraften i hydraulikcylindern då den dras in (30% lägre). En grov uppskattning av produktions och installations kostnad beräknas till lite över 1 MSEK.

This thesis focuses on the tribological performance of tool surfaces in two steel working operations, namely wire drawing and hot rolling. In all forming operations dimensions and surface finish of the products are of utmost importance. Forming basically includes three parts – forming conditions excluded – that may be changed; work material, tool and (possibly) lubricant. In the interface between work material and tool, the conditions are very aggressive with – generally or locally – high temperatures and pressures. The surfaces will be worn in various ways and this will change the conditions in the process. Consequently, the surface finish as well as the dimensions of the formed product may change and in the end, the product will not fulfil the requirements of the customer. Therefore, research and development in regard to wear, and consequently tribology, of the forming tools is of great interest. The investigations of wire drawing dies focus on coating adhesion/cohesion, surface characteristics and material transfer onto the coated steel both in laboratory scale as well as in the wire drawing process. Results show that it in wire drawing is possible to enhance the tribological performance of drawing dies by using a lubricant together with a steel substrate coated by a polished, dual-layer coating containing both hard and friction-lowering layers. The investigations of hot rolling work rolls focus on microstructure and hardness as well as cracking- and surface characteristics in both laboratory scale and in the hot strip mill. Results show that an ideal hot work roll material should be made up of a matrix with high hardness and a large amount of complex, hard carbides evenly distributed in the microstructure. The surface failure mechanisms of work rolls are very complex involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. This knowledge may be used to develop new tools with higher wear resistance giving better performance, lower costs and lower environmental impact.