ANALYSIS OF METHOD FOR POROSITY ASSESSMENT OF THE RECYCLED ALUMINUM CASTINGS

Abstract

In the context of the recycling of waste from wrought aluminum alloys, especially food packaging, these were re-melted and cast into bars. The alloy thus obtained contains up to 2.0% Si, 0.8% Cu, 2.0% Fe, 2.5% Mn and other elements in tenths of %. The problem in its further processing is the porosity. Several methods were used to quantify it, of which the most accurate method was weighing. The disadvantage of this method is the requirements of the competence of the personnel as well as technical equipment. Other methods based on metallography, stereometric analysis, defectoscopy, comparison with standards and measurement of macro-hardness were compared with this method in terms of accuracy and complexity. Each of the analysed methods has advantages and disadvantages. The best results were obtained in metallographic analysis using the ImageJ software. The paper presents regression equations, which allow to compare results of the porosity obtained by used methods. None of the tested methods can fully replace the labor-intensive and equipment-intensive weighting method for determining porosity. Closest to the standard is stereological method which is done after the penetration test and hardness test. Unfortunately, in addition to experienced operators, they also require relatively special equipment. For a small manufacturer, the most reasonable way is to make a cut using only grinding and compare the area thus obtained with the standard according to ISO 10 049.