A NEW TECHNOLOGICAL PROCESS OF RHEOCASTING ALUMINUM ALLOY АК7ч USING A SECTIONAL COOLING SLOPE
DOI:
https://doi.org/10.15407/plit2026.03.025Keywords:
new technological process of rheocasting, sectional cooling slope, aluminum alloy, mechanical stirring, metal suspension, casting, non-dendritic globular structure, primary phaseAbstract
This article describes a new technological process of rheocasting АК7ч aluminum alloy using a sectional cooling slope. It is noted that the sectional cooling slope consists of two sections. The first section, with a U-shaped cross-section, is designed for the mass nucleation of a large num- ber of crystallization centers and is inclined at an angle of 60 ° to the horizontal. This section of the cooling slope was made of thin metal and coated with non-stick paint. The second section of the cooling slope an warmed «pocket» was a thin-walled steel «cup» warmed with thin asbestos sheets pre-baked in a resistance furnace to remove moisture. The specified section of the cooling slope was designed to slow the cooling rate of solid phase crystals that formed in the first section of the cooling slope and to create favorable conditions for their globularization. It is noted that the new rheocasting process involves pouring low-superheated (Tpour = 620 °C and Tpour = 630 °C) alloy onto the inclined first section of the cooling slope, followed by the metal slurry entering the second section of the cooling slope an warmed «pocket». It is also noted that a turbine mixer was then inserted into the «pocket» of the sectional cooling slope, and the metal slurry was mechanically stirred for 2 to 12 seconds, depending on the process conditions. To monitor the alloy temperature in the sectional cooling slope, thermocouples were pre-installed and secured at the melt stream’s inlet and outlet on the inclined first section of the cooling slope, before the metal slurry entered the warmed «pocket» of the cooling slope. The article notes that the newly developed rheocasting process enables the production of castings with a non-dendritic globular primary phase structure from АК7ч aluminum alloy with an average globular crystal size of 38–88 µm. The resulting castings are noted to have increased ductility in the as-cast condition without additional strengthening heat treatment. The relative elongation of the studied alloy is reported to increase from 2 to 9 %, with a relative reduction of 10–12 %. It was also noted that the new rheocasting process increases the durability of steel molds for melt casting by 13–14 % by reducing the alloy pouring temperature by 90–100 °C compared to traditional mold casting. It is also noted that the newly developed rheocasting process does not require additional complex technological equipment for its implementation and does not require significant financial costs for implementation in modern foundries at enterprises.
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