Hybrid HPDC&HSC technology

W artykule przedstawiono rys historyczny oraz stan obecny technologii odlewania z wykorzystaniem ciśnienia zewnętrznego na przykładzie odlewania pod wysokim ciśnieniem (High Pressure Die Casting – HPDC) oraz prasowania w stanie ciekłym (Squeeze Casting – SC). Wykazano podobieństwa i różnice obu technologii oraz obszary wspólne, które zostały wykorzystane do budowy współczesnych, hybrydowych maszyn łączących cechy HPDC i SC. Ostatnie lata przyniosły rozwój konstrukcji maszyn ciśnieniowych, które umożliwiły hybrydyzację technologii z wysoką elastycznością procesu, polegającą na wyborze takiego sposobu przyłożenia ciśnienia zewnętrznego, w którym można pełniej wykorzystać jego wpływ jako czynnika termodynamicznego. Zaprezentowano doświadczenia w zakresie prasowania w stanie ciekłym i stało-ciekłym, uzyskane w badaniach prowadzonych w Instytucie Odlewnictwa w Krakowie.The article presents the history and current state of the technology of external pressure casting in the case of High Pressure Die Casting (HPDC) and Squeeze Casting (SC). The similarities and differences between the two technologies and the common areas that were used in the construction of modern hybrid machines combining the features of HPDC and SC were shown. Recent years have seen the development of pressure machine designs that have enabled the hybridisation of technologies with high flexibility of the process, consisting in the choice of such a method of applying external pressure in which its influence can be more effectively used as a thermodynamic factor. The following experiments were presented in the field of liquid and solid-liquid casting, obtained from research conducted at the Foundry Research Institute in Kraków

Non-Wetting and Non-Reactive Behavior of Liquid Pure Magnesium on Pure Tungsten Substrates

The wetting behavior of liquid magnesium drop on pure tungsten substrates was investigated, for the first time, with the sessile drop method combined with non-contact heating and capillary purification of a Mg drop from a native oxide film. A specially designed apparatus dedicated to the investigation of the high-temperature interaction of dissimilar materials was used. The comparative experiments were performed under isothermal conditions at temperatures of 700 °C and 740 °C using two atmospheres: Ar + 5 wt.% H2 and pure Ar, respectively. During high-temperature tests for 180 s, the images of the Mg/W couples were recorded with CCD cameras (57 fps) from two directions of observation. The solidified drop/substrate couples were subjected to structural characterization using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). Under the applied measurement conditions, liquid Mg revealed non-wetting behavior on W substrates (a contact angle θ > 90°). The average value of the contact angle under the flowing Ar atmosphere at 740 °C was θav = 115°, whereas it was higher under the flowing Ar + 5 wt.%. H2 atmosphere at a lower temperature of 700 °C, showing θav = 122°. Independently on employed atmosphere and temperature, SEM + EDS analysis of solidified sessile drop couples did not display any new phases and mass transfer between the Mg drop and the W substrate, whereas the presence of discontinuities at the Mg/W interface of cross-sectioned couples were well-distinguished. Non-wetting and a lack of permanent bonding between the Mg drop and W substrates have a good agreement with the Mg–W phase diagram calculated with the help of FactSage software and FTlite database, i.e., the non-reactive nature of the Mg/W couple because W does not dissolve in liquid Mg and it does not form any compounds with Mg. These findings allow for the recommendation of tungsten as a suitable refractory material for long-time contact with liquid Mg in different container-assisted methods of materials characterization as well as in liquid-assisted processing of Mg components