Plaster casting method for large-sized complex thin-walled magnesium alloy part

Abstract

The invention relates to a plaster casting method for a large-sized complex thin-walled magnesium alloy part. The method comprises the following steps of coating the surface of an assembled form with a coating in situ, and arranging shapeless cold iron on a hot spot part, wherein a mixture for manufacturing the shapeless cold iron comprises the following components in percentage by mass: 1.25 percent of phenolic resin, 0.4 percent of toluenesulfonic acid, 1 to 1.5 percent of boric acid, 2 percent of bentonite and the balance of 70 to 140-mesh chromite sand; pouring a casting in an adjustable pressure casting device, arranging a plaster mold poured by the form at the casting position of the adjustable pressure casting device, filling a tank with dry air or a CO2 atmosphere with SF6 content of 0.1 to 1.0 percent, and performing vacuum casting and pressurized solidification, wherein the casting temperature is 710 to 750 DEG C, vacuum degree for primary mold filling is minus 0.6Mpa to minus 0.8Mpa, and the solidification pressure is 0.020 to 0.025Mpa. According to the method, oxidization can be prevented, the mold filling capability can be improved, shrinkage cavities and shrinkage porosities in the casting are reduced, and the obtained magnesium alloy casting is higher in density.

Description

technical field [0001] The invention relates to a casting method, in particular to a gypsum mold casting method for a large complex thin-walled magnesium alloy piece. Background technique [0002] Sand casting is mostly used for large magnesium alloy castings, but the precision of the castings is low, and it is very difficult to produce large-sized, thin-walled and complex castings. Therefore, in recent years, many research and development workers have carried out a series of research on the application of gypsum molds in magnesium alloy casting. When casting high-magnesium-containing aluminum alloys and magnesium alloys in gypsum molds, there are many oxidized inclusions, high liquid surface tension, poor mold filling effect, and a high tendency to produce defects such as pores, inclusions, and shrinkage porosity. The main reason is that the chemical activity of magnesium is high, and its liquid temperature will have a violent exothermic reaction with gypsum. Therefore, gy...

AI Technical Summary

Problems solved by technology

Magnesium alloy has less solidification latent heat, and the thin wall may not be poured enough, especially the large flat part with thin wall is difficult to fill; the gas permeability of the gypsum mold is very poor, and it is difficult to hold the breath during the pouring process and stay in the mold; the gypsum cast magnesium alloy solidifies slowly, Prone to coarse grains, resulting in reduced mechanical properties

Images