No abstract

Elaborated shapes of many car components are the reason for which the use of casting techniques to fabricate them is a solution wellfounded from the economical point of view. Currently applicable regulatory requirements concerning emissions of exhaust fumes force the carmakers to reduce the overall weight of their products, as this is a basic precondition for reducing fuel consumption. As a result, newly launched car models contain a continuously increasing share of thin-walled castings made of materials which ensure a satisfactory level of service properties. At the same time, developing new technological processes allowing to extend the service life of individual components by means of surface improving becomes more and more important.

Surface fusions were performed by the gas tungsten arc welding (GTAW) surfacing process on plate castings of spheroidal graphite cast iron with a travel speed from 200 to 800 mm/min. Their geometry and hardness were measured. Calorimetric measurments of the net heat input for the GTAW process have been conducted. A stepwise regression method was used to develop the relationship between GTAW process parameters and those of fusion geometry, microhardness, arc efficiency, and melting efficiency for the obtained data set.

The cooling rate is one of the main tools available to the process engineer by means of which it is possible to influence the crystallisation process. Imposing a desired microstructure on a casting as early as in the casting solidification phase widens significantly the scope of technological options at disposal in the process of aluminium-silicon alloy parts design and application. By changing the cooling rate it is possible to influence the course of the crystallisation process and thus also the material properties of individual microstructure components. In the study reported in this paper it has been found that the increase of cooling rate within the range of solidification temperatures of a complex aluminium-silicon alloy resulted in a decrease of values of the instrumented indentation hardness (H IT ) and the instrumented indentation elastic modulus (E IT ) characterising the intermetallic phase occurring in the form of polygons, rich in aluminium, iron, silicon, manganese, and chromium, containing also copper, nickel, and vanadium. Increased cooling rate resulted in supersaturation of the matrix with alloying elements.

The paper presents results of metallographic examination of faults occurring in the course of founding thin-walled cast-iron castings in furan resin sand molds. A non-conformance of the scab type was Observed on surface of the casting as well as sand buckles and cold shots. Studied the chemical composition by means of a scanning electron microscope in a region of casting defects: microanalysis point and microanalysis surface. Around the observed defects discloses high concentration of oxides of iron, manganese and silicon. A computer simulation of the casting process has been carried out with the objective to establish the cause of occurrence of cold shots on casting surface. The simulation was carried out with the use of NovaFlow & Solid program. We analyzed the flowing metal in the mold cavity. The main reason for the occurrence of casting defects on the surface of the casting was gating system, which caused turbulent flow of metal with a distinctive splash stream of liquid alloy.