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The procedure for experimental determination of the longitudinal and lateral residual stresses in the multi-layer hard-faced plates, made of the hot work tool steel used for forging dies manufacturing, is presented in this paper. The objective of this research was to establish the influence of the multi-layer hard-facing on residual stresses in the thin and thick plates, which could later, in exploitation, cause the appearance of cracks and fracture. The influence of tempering on decreasing the residual stresses was monitored, as well. The plates were hard-faced in three layers, while the stresses were measured by the magnetic method. The obtained results have shown, among others, that the residual stresses are higher in the thick plates, as well as that the proper regime of the heat treatment can significantly reduce the level of residual stresses. [ABSTRACT FROM AUTHOR]

The ironing process in the cold conditions is frequently accompanied by the high contact pressures and local loading of tools, especially in the multi-phase processes. In such conditions, lubrication has a decisive influence on the successful forming. Absence of lubricant would lead to direct contact of the thin sheet and the tool (die) what would consequently cause the disturbance of the forming process stability; frequently the process would be hindered. Lubrication, as a measure for decreasing the harmful influence of friction at the contact surfaces, enables increase of the deformation and drawing degree. In that sense, experimental investigations were conducted of influence of various types of lubricants on the single-phase and multi-phase ironing processes. The corresponding tribological model was adopted, which is based on sliding of the thin sheet strip between the two side contact elements, which are ironing it. The tribological model was realized according to original experimental device. The variation of the drawing (tensile) force, contact pressures and the friction coefficient were monitored for each type of lubricants, in the single-phase and the three-phase ironing conditions, at the constant sliding speed. In that way, the estimates of each individual lubricant was done. The objective of this research was to compare the tested lubricants from the aspect of their quality and applicability in the ironing processes. [ABSTRACT FROM AUTHOR]

The problems of a material selection for making the boiler pipes in a responsible steam plant and the technology for their welding are considered in this paper. The boiler is screened, complex, radiating energetic plant, with the natural water circulation in the hanging steel structure. Based on the legal regulations, the mandatory periodic reparation of the most important components is performed. This is why the check of mechanical properties, for the used and new materials for eventual replacement and building-in was done, as well as the check of the prescribed reparation procedures. The components that were in exploitation were checked, since their properties change with time. Checking consisted of testing the tensile material properties at room and elevated temperatures, measurements of hardness and analysis of materials’ microstructures. Besides the experimental tests, the numerical modeling and analysis of the workload of the fluid transporting pipes was conducted. In that way it was established which material is optimal for manufacturing the boiler pipes. [ABSTRACT FROM AUTHOR]

In the friction welding of dissimilar base metals occurs an uneven heating in the outside and inside zones of materials what causes appearance of various structures in the joint zone. Considering that the objective is achieving of the homogeneous welded joint, an imperative is to analyze the microstructure of the realized welded joint. By the microstructure analysis, one can establish the relationship between the friction welding parameters and the structure that appears in each of the joint's characteristic zones. In addition, it is possible to analyze the potential appearance of flaws during the welding process and to discover the causes for their appearance in order to prevent those in the future. This paper presents a review and analysis of microstructures of the characteristic joint zones in the friction plane of the two different steels, the high-speed steel and carbon steel for tempering. The experiment consisted of varying the friction welding parameters (friction pressure and friction time) and monitoring of micro structure in the joint zone and its immediate vicinity, both from the side of the tempering steel and the HS steel, as well as defining the present phases and compounds. The emphasis was set on analysis of the melting and the mixing zones and carbides created during the welding. [ABSTRACT FROM AUTHOR]

An experimental procedure for determination of the lateral and longitudinal deformations of the multi-layer hard faced samples made of steel for operating at elevated temperatures is presented in this paper. Two plates, which were hard faced in three passes, were used to determine the level of residual stresses. The cored electrodes UTOP 38 and UTOP 55 were used. Deformations were measured in two phases: before and after the hard facing. The objective of deformations measurements was to establish the correlation between deformations, namely the applied technology (the input energy/heat) and the level of residual stresses, for different plate thicknesses. [ABSTRACT FROM AUTHOR]

Results of experimental and numerical investigations of the three types of lubricants influence on the ironing process are presented in this paper. The tribological model was based on the strip sliding between the two lateral contact elements. The strip was made of the low carbon steel. Variations of the friction coefficient and the contact pressure in the single-stage ironing were recorded at the constant sliding speed for each of the tested lubricants. The effective normal stress distribution within the material was simulated by the finite element method (FEM). The objective was to compare the applied lubricants from the aspect of their applicability in the ironing process. [ABSTRACT FROM AUTHOR]

Res**ults of determination of the longitudinal, lateral and angular deformations in hard faced samples are presented in this paper, as well as the influence of the additional heat treatment on the level of residual deformations. Investigation assumed multi-layer hard facing of the two plates (thicknesses 7.4 and 29 mm) made of steel 55CrMo8. Deformations were measured before the hard facing – after the plates’ preparation by grinding, immediately after hard facing and after tempering. The objective was to determine if and how much the additional heat treatment (tempering) influences the level of residual deformations in the hard faced joints. [ABSTRACT FROM AUTHOR]