With increasing tendency of die castings production, also the possibility to produce castings with maximum usage of molten metal grows. Residual of non-used molten metal, e.g. sprues, feeders, splashes and saw-dusts are used in next production as returning material. With returning material a lot of non-suitable elements is brought into the melting process, but with decreasing of input costs it creates inseparable part of production process. Usage of returning material in melt production has negative influence on final quality of produced castings, because of bringing of inheritable properties into produced melt. Important factor in melt production with the amount of returning material is to know to set its optimal amount and the way of melt treatment to achieve the same results in casting quality in comparison to the casting production from clean materials.

Recently, the castings made from aluminum-silicon alloys by pressure die casting are increasingly used in the automotive industry. In practice, on these castings are high demands, mainly demands on quality of their structure, operating life and safety ensuring of their utilization. The AlSi5Cu3 alloy castings are widely used for production of car components. After the prescribed tests, the cracks and low mechanical properties have been identified for several castings of this alloy, which were produced by low pressure casting into a metal mould and subsequent they were heat treated. Therefore, analyses of the castings were realized to determine the causes of these defects. Evaluation of structure of the AlSi5Cu3 alloy and causes of failure were the subjects of investigation presented in this article.Keywords: AlSi5Cu3 alloy, microstructure, cracks, hardnessZastosowanie odlewów ciśnieniowych ze stopów Al-Si ustawicznie wzrasta w przemyśle samochodowym, gdzie stopy te muszą spełniać wysokie wymagania odnośnie do jakości ich struktury, żywotności i bezpiecznego użytkowania. Odlewy ze stopu AlSi5Cu3 są szeroko stosowane w produkcji części samochodów. Wg pracy wady pęknięć wewnętrznych i niskie właściwości mechaniczne posiada część odlewów obrabianych cieplnie, odlanych do form metalowych pod niskim ciśnieniem. Praca poświęcona jest ocenie struktury i przyczynom pękania odlewów ze stopu AlSi5Cu3.

The demand for castings of high quality and sound work is nowadays very high. The production of sound castings without foundry errors is the big issue in modern foundries. Foundry simulation software can do a lot to help improve the disposition of castings, gating system and feeder system, and assure good filling and solidification conditions, and also produce sound casting without the need of the old method of "try and error". One can easily change a lot of parameters for filling and solidification, and create the best proposal for production. Connor inlets have two functions. One is that it serves as an ingate, through which molten metal passes and comes into the mould cavity. The second function is that it serves as a feeder and substitutes the metal contracted during solidification and cooling of the castings. It can also save quite a lot of metal in comparison to classic feeders.