The influence of micro coolers on the physical-mechanical characteristics of the steels used in making railway monoblock wheels
Original scientific paper The paper introduces the possibilities of improving mechanical characteristics of the steels used in making railway monoblock wheels, by using micro coolers on steel casting. The laboratory experiments are aimed at studying the control of round cross-section steel ingot solidification by adding crystallization germs in their central area, in order to influence the internal structure and the mechanical characteristics of the steel. The stimulation of heterogeneous germination on the surfaces generated by the particles introduced in the center of the ingot, while it was in a liquid state, leads to the formation of a second solidification front and heat absorption in this area. The data we obtained during the research have been processed in Excel, in order to obtain the correlation equations that express the variation of the steel mechanical characteristics as a function of the chemical structure both for the experimental samples and for the reference ones.
RESPECTS REGARDING THE USAGE MICRO-COOLERS TO CASTING STEEL
Basic problem, which must solve to casting steel, consists in the smooth ingots procurance insurance from chemical point of view, structural and of mechanical ownerships. For the defects mitigation to solidification classic, it is the needed adjustment to an efficient methods exhaust of warmth from the steel under solidification through the administration of micro-cooler under form of grains to casting. Micro-coolers you utilize with the view of process directing of solidification must achieve conditions series: to have a heaved purity respecting the content of oxide inclusions; the wet micro-coolers uttermost 0, 25%; to not have surface oxidant; to have a certain granulometric composition. The work clears the aspects related interaction micro-coolers you deal to casting steel over solidification to this. As parameters, which influence the process of solidification they were taken in the dimensions, study micro-coolers, the specific enlargement of micro-cooler, steel temperature in the enlargement moment while as the influenced parameter steel volume in which they acted microcoolers. Through analysis of regression by the agency of program Excel and Matlab they obtained dependence between meal micro-cooler you utilize to casting ingots from temperature and steel of casting, correlations which they allow the optimal areas establishment variation for temperature of casting, the quantity of micro-cooler dealt respective affected volume percent of cooling to the administration micro-coolers.
Rapidly solidified AlCu alloys—I. experimental determination of the microstructure selection map
Abstract Laser rapid solidification experiments have been performed on AlCu alloys of hypereutectic composition 36, 40 and 44 wt% Cu. By taking thin foils from the surface of the laser traces it has been possible to study the resulting growth morphologies using TEM; the microstructural orientation allowing the morphologies to be correlated with their local growth velocities. Microstructural orientation allowing velocity range 0.01–2.0 ms−1 have been studied, and eutectic (both with and without oscillatory) instabilities), dendritic, cellular, banded and planar front growth have all been observed. By combining these results with earlier observations made on alloys with lower Cu concentrations, it has been possible to produce a microstructure selection map for AlCu alloys. The map correlates microstructure to growth velocity and composition in the ranges 0.01–2.0 ms−1 and 0–44 wt% Cu, i.e. the major part of the binary AlAl2Cu eutectic (0–54 wt% Cu). As well as providing an interesting overview of solidification structures, several features of this map can be used to gain information on the AlCu phase diagram.