Low-pressure casting is to inject the molten metal into the sealed electric resistance furnace. The mold (usually of the metal type) is placed on the sealing cap, and the vertical riser allows the molten metal to communicate with the gate that faces downward. The mold is horizontally divided, and the metal type must be preheated before spraying and sprayed with paint.
List of content for this article：
1.The basic principle of low-pressure casting valve.
2.The characteristics and scope of application of low-pressure casting valves.
3.Low-pressure casting has different characteristics.
First, the basic principle of low-pressure casting valve
In die casting, the upper half is first locked, and the compression chamber is slowly introduced into the chamber so that the molten metal is pressed into the mold through the riser. After the mold is filled, the air is compressed to raise the air pressure to the specified working pressure and maintained for a suitable period of time to crystallize the alloy under pressure. Then, the pressure on the liquid surface is removed, so that the metal liquid that has not solidified in the riser pipe and the gate flows back under the action of gravity. Finally, the mold is opened and the casting is taken out. Since the gate also serves as a supplementary function for low-pressure casting, in order to achieve top-down directional solidification of the casting, the gate should be opened at the thick wall of the casting, and the cross-sectional area of the gate must be sufficiently large.
Second, the characteristics and scope of application of low-pressure casting valves
Third, low-pressure casting has the following characteristics:
(1) The filling pressure and filling speed are easy to control, so it can be adapted to various casting types, such as metal type, sand type, molten model shell, and tree type shell. Since the filling is stable, the flushing force is small, and the directions of the liquid flow and the airflow are uniform, defects such as pores and slag inclusions are reduced.
(2) The structure of the casting is denser than that of the sand casting, and the prevention effect of the pinhole defects of the aluminum alloy casting is particularly obvious.
(3) The utilization rate of metal is increased to 90%~98% due to the elimination of the feeding riser.
(4) Due to the improved filling ability, it is advantageous to form casting with a clear outline and a smooth surface.
In addition, the equipment is simpler than die casting and has less investment. Low-pressure casting is a new technology developed in the 1960s. Although its history is not long, it has been widely recognized at home and abroad and has achieved rapid development. Low-pressure casting is currently mainly used to produce high-quality aluminum and magnesium alloy castings, such as cylinders, cylinder heads, crankcases, high-speed internal combustion engine pistons, textile machine parts, etc., and has successfully produced copper propellers and ductile irons weighing up to 30 tons.