Research on Forming method of digital Patternless Freezing Casting

Abstract:

In this paper, a digital Patternless freezing casting method is proposed. It is a new technology that pure water is used as the binder for sand mold casting, sand particles premixed with a proper amount of moisture are frozen at low temperature to form a frozen sand blank, and then the frozen sand mold cutting is carried out based on the principle of material reduction manufacturing and forming. In this paper, the evolution law of micro-morphology of the water film coating sand particles is revealed, which freezes into ice crystal bonding bridge after low-temperature phase transformation. It is found that the strength of frozen sand mold is produced by the interfacial bonding between ice crystal particles and sand particles, and the tensile strength of sand mold increases significantly with the decrease of freezing temperature. In addition, the rapid solidification forming mechanism of A356 aluminum alloy in the frozen sand mold was systematically studied, including the as-cast microstructure, composition distribution and mechanical behavior of the frozen sand mold Casting. The results show that with the increase of solidification rate, the secondary dendrite arm spacing (SDAS) of primary α-Al phase in the microstructure is significantly reduced, the grain size is significantly refined, and the solubility of Si element in the matrix is increased. Tensile strength, plastic value and microhardness value of the test piece are significantly increased, and the dimensional accuracy of the metal component can reach CT8 grade.

Key words:Patternless forming; Freezing casting; Microstructure; Mechanical properties