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.
Casting process simulation and visualization: A JOM-e perspective
With the increasing power of computer hardware and software, computational simulation and visualization are becoming increasingly important tools to understand and improve industrial processes, such as metal casting. Computer-aided visualization is increasing the power of all of the tools available to the solidification process engineer, including previous literature, mathematical modeling, laboratory experimentation, and online measurement of the casting processes. This article exemplifies all four of these. This article is possible only through the format of on-line publication. The article features six separate contributions, published by TMS in the electronic portion of this journal: JOM-e, at www.tms.org/pubs/journals/JOM/ articles.html. Each contribution provides several state-of-the-art computer animations and explains how these visualizations are being used to increase understanding and to improve a wide range of different casting processes. This relatively new format of archival publication allows anyone with an Internet browser to search and read the articles and watch the animations, all at no cost. Video publication was pioneered in 1996 with the Wiley journal, Visualization of Engineering Research, edited by V. Voller. Online publication in JOM-e and elsewhere now provides researchers a powerful medium to showcase their results through animation, and to thereby communicate their knowledge faster and better than ever before. The first four articles feature advanced computational simulations of transient solidification phenomena. As solidification is inherently a transient process, it should not be surprising that our understanding of the modeling results is greatly aided by animations. A diverse range of casting process phenomena are simulated in these articles, starting with fluid flow during the filling of foundry castings in “The Mold Filling and Solidification of a Complex Foundry Casting,” by S.G.R. Brown et al. Also reviewed is transient flow during the continuous casting of aluminum, in “The Multiphysics Modeling of Solidification
Solidification and foundry studies of Zn/Al alloys
Abstract It is well known that the commercial Zn/Al alloys, particularly the Zn-11%Al and Zn-27%Al alloys, segregate markedly during founding and also that an “inverted pipe” is commonly present. A detailed study of the solidification of 8, 11 and 27% aluminum alloys has been carried-out to investigate the manner of an extent to which segregation arises in order to develop better foundry procedures to exploit the considerable potential of these alloys. This work has involved the uni-directional solidification of many samples under a wide variety of conditions selected to exploit naturally-induced and forced fluid flow in the melt. The results of this work are being applied to develop various foundry procedures aimed at the production of sound homogeneous castings. Since it is possible to eliminate the major foundry problem with these alloys, namely, underside shrinkage, in the case of the Zn-8%Al and Zn-11%Al by adjusting such casting variables as pouring temperature, mold type and riser volume and placement, discussion of the results will be confined to the Zn-27%Al alloys. This alloy type displays the greatest mechanical strength and is most prone to underside shrinkage in “chunky” castings.