What is the difference between low pressure casting and differential pressure casting?
First, low pressure casting 1, principle low-pressure casting is to make liquid metal under the action of pressure to complete the filling cavity and solidification process two to obtain a casting method. Because of lower pressure (20~60kPa), it is called low pressure casting. The process is: in the sealed crucible (or sealed tank), pass into the dry compressed air, liquid metal under the action of gas pressure, along the riser tube into the sprue 3 rises through the ingate 2 smoothly into the cavity 1, and keep the gas pressure on the surface of the crucible until the casting solidification totally. The gas pressure on the liquid surface is then lifted, and the uncured metal liquid in the riser flows back into the crucible, and then the mold is removed and cast out. The basic characteristics of low pressure casting process: filling speed and pressure can be adjusted properly. The mould used in low pressure casting has two types, metal and nonmetal.
Metal type used for mass production, non-ferrous metal castings, non-metallic mold used for small batch production, such as sand, graphite, ceramic and molten shell model can be used for low pressure casting, and production in the sand or to use more. However, the permeability and strength of the molding material for low pressure casting shall be higher than that of gravity casting, and the gas in the cavity will be exhausted through the exhaust passage and sand pores. In order to make full use of low pressure casting liquid metal under pressure from top to bottom feeding casting, in process design, should consider the casting away from the site of the first gate to gate the end of solidification, solidification, casting during solidification process to get through the gate feeding, realize sequential solidification. 2, the low pressure casting unique advantages: 1). The liquid metal filling smoothly; 2). Casting is good, is conducive to the formation of clear, smooth surface castings, for forming large thin-walled castings is more favorable; 3). Casting microstructure, mechanical properties (high pressure forming) 4;). To improve the technology of liquid metal yield, generally do not need to riser, so that the liquid metal yield is greatly improved, the yield can reach 90%. In addition, the labor condition is good, the equipment is simple, easy to realize mechanization and automation, and it is also the outstanding advantage of low pressure casting.
