15. - 17. 5. 2013, Brno, Czech Republic, EU UTILIZATION OF ECOLOGICAL FRIENDLY CORES FOR MAGNESIUM ALLOYS CASTINGS Jaroslav BEŇO a , Petr LICHÝ a , Eliška ADÁMKOVÁ a , Michal CAGALA a , Petr JELÍNEK a , Marek BŘUSKA a , Karel GÁL a , Marcin MORYS b a VSB – Technical University of Ostrava, Faculty of Metallurgy and Material Engineering, 17. Listopadu 15/2172, 708 33, Ostrava – Poruba, CZ, jaroslav.beno@vsb.cz b Silesian University of Technology, Faculty of Mechanical Engineering, Akademicka 2A, 44-100, Gliwice, PL Abstract The goal of this study is determination of utilization of cores based on inorganic materials without negative impacts on environment in gravity casting technology of Mg-alloys. The contribution includes analysis of preparation and treatment of these cores and their influence on quality, structure and properties of casting samples with regard to surface defects of castings. Experimental data obtained in this work can be also used in other casting technologies of Mg – alloys. Keywords: inorganic salt cores, magnesium alloys, surface quality, solubility 1. INTRODUCTION For pre-casting the holes and cavities the core mixtures based on organic resins (e.g. PUR COLD-BOX etc.) are used as a standard at present. Rapid and easy sand preparation with regard to large lot production of castings (automobile industry), good shootability, high primary strengths, good collapsibility, easy and unpretentious reclaimability are their characteristic features. As the questions are organic materials that under the influence of thermal destruction are split up to more simple organic compounds the use of them is connected with deterioration of hygienic and environmental conditions of foundry production. Therefore the modified inorganic binders are getting in the limelight. Their use isn’t connected with negative impacts on living and working environment while technological parameters of molding mixtures are comparable with organic binders. We are talking about so called “Renaissance” of inorganic binders [1]. One of progressive technologies for preparations of molding mixtures (cores) is the utilization of cores based on inorganic salts for pre-casting of cavities and holes in non-ferrous alloys (in particular Al – alloys). 1.1 Salt cores technology Foreshadowing of using the cores based on inorganic salts goes back to the 70th of last century. To be extended this idea waited 20 years when in the 90th the cores from crystalline salts began to be mass used in large lot production of Diesel engine pistons by gravity and low-pressure casting methods. They are made by a method of high-pressure compacting of crystalline salts, by casting or high-pressure injecting of salt melts in core boxes or by utilization of “classic” foundry technologies of cores preparation – by shooting the salt matrix with inorganic (organic) binder [2, 3, 4, 5]. After 2003 (International Foundry Fair GIFA, Düsseldorf) the manufacture of cores tended towards the utilization of salt solutions of sand cores or high - pressure compacting particularly of NaCl in a solid crystalline state. New technologies, as e.g. BEACH BOX, HYDROBOND [6, 7] are appearing. In particular the high primary strengths comparable with common core mixtures (PUR CB) [8], dimensional accuracy and smoothness of castings, a possibility of pre-casting the holes that are mechanically cleanable with difficulties are the common elements of individual technologies using inorganic salts for manufacture of cores. In addition to it the cores show a good benchlife without moistening. Cores can be produced in a closed ecological cycle; salt removed (elutriated) from the casting cavity is crystallized from the solution (brine) and it is usable for next manufacture of cores. An ecological