PROPOSAL OF A CLASSIFICATION OF DEFECTS OF HIGH-PRESSURE DIECAST PRODUCTS

Abstract

The paper gives an introduction to the one of the current actions of the WG “Quality of High Pressure DieCast (HPDC) products” within the TC “High pressure diecasting” of the Italian Association of Metallurgy, The preparation and dissemination of common tools to allow foundries to define a proper, comparable, quality standard is in fact one of the current targets of this WG. The basic tool, to which this paper refers, is a common terminology and classification of defects of HPDC products. An initial survey of literature and industrially adopted classifications of defect in components cast in metallic dies, revealed that the geometry and origin-based approaches are often mixed giving rise to a wide range of hybrid classifications. The proposed classification of defects of HPDC products, discussed within the WG with the contribution of several foundries, is a multi-level, hybrid-type classification. In the first level defects are grouped on the basis of their position (surface/internal and geometry defects) according to the typical control operations during which they can be detected and to the effects of defects on the functionality of the parts. The second level of the classification groups defect in classes according to their general metallurgical origin. The proposed classification doss not specify defect/cause correlations, but gives starting points to the identification of their specific causes. In order to better specify these features the analogies between the origin of internal/surface defects are highlighted by corresponding names for Level II classes: gas-related, shrinkagerelated, filling-related, thermal contraction defects and undesired phases. In addition the class of metal/die interaction defects is proposed for surface defects. The specific defects identified are those included in the third level of the classification. In the present paper an introduction to the general classes of defects defined in Level II is proposed. The action of the WG concerning defect classification of HPDC parts will be completed with the compilation of the official document including the proposed classification and multi-language terminology equivalences.