Problem of Tightness of Casting Alloys and Castings Made from them – New Research Methods

The article concerns the work on tightness as a functional property of casting alloys (primarily, cast iron). The authors’ methodology for tightness testing is presented. In the methods that have used thus far, tightness tests have been carried out on samples that are shaped like small disks; through these, a medium/penetrator in the form of a low-viscosity liquid is forced through. The measure of the tightness is the value of the pressure that the sample is able to transfer without penetration. The authors developed a modification of the test method using disks and proposed a new method in which the sample takes the shape of a sleeve. The modification includes the application of the penetration method to reveal the moment of the beginning of the penetration through the sample wall during the tightness test. Using the new research methodology, the tightness of grey cast iron samples was assessed as a function of the shape index of the graphite precipitates (fK), and research was carried out on the effect of the solidification rate of cast iron on its tightness. The tests covered grey cast iron and modified grey cast iron. The effect of the cooling rate on the tightness of the tested alloys was indirectly determined. At the stage that is described in the paper, the presented research was of an initial nature and was focused on refining the research methodology. The combination of the traditional method of testing the tightness of castings by using liquids with the visualisation of the penetrant method was also used to assess industrial castings.