DIAGNOSTIC METHODS OF TECHNOLOGICAL PROPERTIES AND CASTING CORES QUALITY

摘要

The presentation of the developed diagnostic methods of technological properties and qualities of casting cores produced by shooting method is the aim of the hereby paper. Special attention was directed towards parameters decisive for the obtained apparent density of casting core sand, its porosity and permeability in cores made of various kinds of core sands. Those factors, of a significant influence for the effectiveness and quality of produced castings, force laboratories to apply simple, fast and simultaneously reliable quality assessment methods, allowing to determine optimal operation conditions of a blowing machine for the given core sand. To determine quality of a core compaction performed by blowing and shooting method, Boenisch and Knauf proposed a complex analysis of several factors. The technological tests, together with the special method for assessing the core box filling ratio FG as well as the equipment suitable for the realisation of this method, were developed. The physical meaning of coefficient denoted as filling ratio FG is useful at assessing of an apparent compactability of various sands in the same core box. Proposed own method of assessment of a core compaction quality is based on the analysis of the filling ability factor of sands, determined by the value of coefficient K_(zr) which is simplier and better exhibits the influence of a complicated shape of the core box cavity on a sand core compaction. Experiments presented in the article encompass an operational pressure range p_r=0.4÷0.7 MPa and diameters of shooting nozzles d_1=15÷25 mm. The examination results obtained by the approximation, of various measurements data from the examined range of variables, done by means of the arbitrarily selected analytical curve of an extended structure similar to the one applied in Aksionov's works, take into account, for the given shooting machine and kind of core sand, an initial apparent density of loosely poured sands phi_(us), a shooting pressure p_r, and also a diameter of a shooting head outlet d_1. The analysis of ultrasound examinations of classic sands and sands with chemical binding agents confirmed the possibility of utilising the ultrasound technique for the development of non-destructive investigation methods of cores assessing the compaction distribution uniformity, strength and permeability. In this aspect the examination results performed for a broad range of working parameters constitute the reference basis allowing for a practical application of an ultrasound technique as a modern alternative diagnostic method assessing the quality and correctness of the employed core production technology.