Analysis of welding of the rear bridge semi-housing assembly of a firefighter truck by the semi-automatic procedure in gas protection

The problem considered in this paper is the welding technology of the steel assembly of a firefighter truck rear bridge semi-housing. Since in this procedure the welding is done of the two dissimilar steels, it is necessary to analyze effects of welding on mechanical properties and microstructure of individual joint's zones. The weldability of the base metal was considered first (semi-housing tube and flange), then the welding method and the filler metal were selected and, finally, the technological parameters of welding were calculated. The computational and experimental methods were used for the base metal weldability estimate, based on the hardness measurements in the joint's critical zones and analysis of their structures. Experimental investigations performed were aimed for verification and/or eventual correction of the proposed welding technology

Analysis of welding of the rear bridge semi-housing assembly of a firefighter truck by the semi-automatic procedure in gas protection

The problem considered in this paper is the welding technology of the steel assembly of a firefighter truck rear bridge semi-housing. Since in this procedure the welding is done of the two dissimilar steels, it is necessary to analyze effects of welding on mechanical properties and microstructure of individual joint's zones. The weldability of the base metal was considered first (semi-housing tube and flange), then the welding method and the filler metal were selected and, finally, the technological parameters of welding were calculated. The computational and experimental methods were used for the base metal weldability estimate, based on the hardness measurements in the joint's critical zones and analysis of their structures. Experimental investigations performed were aimed for verification and/or eventual correction of the proposed welding technology

Substantially Higher Corrosion Resistance in AE42 Magnesium Alloy through Corrosion Layer Stabilization by ECAP Treatment

The corrosion properties of magnesium alloy AE42, just extruded and with posterior eight passes through equal channel angular pressing after extrusion, were investigated in 0.1 M NaCl by electrochemical impedance spectroscopy. The obtained samples were compared using scanning electron microscopy micrographs of the corrosion layers created on the surface of the specimens. The background of the substantial higher corrosion resistance of the samples after equal channel angular pressing treatment was found to be the much thicker and stable corrosion layer and smaller separating fragments in comparison with the just extruded samples. The lowering of the grain size by severe plastic deformation, especially by the equal channel angular pressing treatment was found to be also responsible for the enhancement of the corrosion resistance in AE42 class of magnesium alloys

Substantially Higher Corrosion Resistance in AE42 Magnesium Alloy through Corrosion Layer Stabilization by ECAP Treatment

The corrosion properties of magnesium alloy AE42, just extruded and with posterior eight passes through equal channel angular pressing after extrusion, were investigated in 0.1 M NaCl by electrochemical impedance spectroscopy. The obtained samples were compared using scanning electron microscopy micrographs of the corrosion layers created on the surface of the specimens. The background of the substantial higher corrosion resistance of the samples after equal channel angular pressing treatment was found to be the much thicker and stable corrosion layer and smaller separating fragments in comparison with the just extruded samples. The lowering of the grain size by severe plastic deformation, especially by the equal channel angular pressing treatment was found to be also responsible for the enhancement of the corrosion resistance in AE42 class of magnesium alloys

Microstructure and corrosion properties of ultrafine- grained interstitial free steel

The microstructure and the corrosion behaviour of ultrafine-grained interstitial free (IF) ferritic steel processed by equal channel angular pressing (ECAP) at room temperature following route C were investigated. Already after the first pass of ECAP, the microstructure was refined by a factor of approximately 200. On further passes, ECAP was found to lead to continuous grain refinement, while elongated grain structure produced in the first pass was retained throughout all processing cycles. After 8 passes, the microstructure comprised bands of elongated grains of average length of 500-1000 nm and average width of 200-300 nm. Corrosion characteristics of a non-deformed coarse grained specimen and an ultrafine-grained specimen that had undergone 8 passes of ECAP were investigated using electrochemical potentiodynamic tests. ECAP induced grain refinement does not appear to influence the electrochemical characteristics in neutral NaCl solutions. This encouraging finding demonstrates that ECAP, while enhancing mechanical characteristics, does not compromise corrosion resistance of IF steel. A protective oxidic layer is formed in alkaline NaCl solution, which reduces the corrosion rate significantly. (C) 2006 Elsevier B.V. All rights reserved.X1173sciescopu

Revitalization of the damaged machine parts by hard facing as a way of saving funds

The objective of the research, presented in this paper, was to demonstrate the superiority of the hard facing as the revitalization technology of various damaged machine parts. The analysis of the two different revitalization methods of the damaged machine parts is presented – the replacement of the damaged part by the new – spare part and reparation by hard facing. The comparison is done on the example of hard facing and replacing of damaged loader's teeth. The paper presents a method for calculating costs of the two revitalization technologies based on their profitability and their comparison. That method could be applied for similar calculations for any machine part, with smallest or no adjustments. The paper presents a verification of advantage of applying the hard facing as the machine parts reparatory technology with respect to the other revitalization technology. The savings realized by application of hard facing reparation of the loader's teeth reach 73.5 % for one set of teeth and 82.40per annum of the costs for purchasing the new spare parts. The analysis was conducted under an assumption that organization of the maintenance function is at the exceptionally high level so that the purchasing of the new part/repairing of the damaged one is always done in time. This idealized approach was adopted since in that way one obtains the least economic effects of the reparatory technology application with respect to replacing the part with the spare one. In any other case the economic effects would be significantly higher, namely even more positive in favor of the hard facing revitalization technology