Casting mold, counter-pressure casting method and low-pressure casting method

Abstract

The application relates to the technical field of casting and provides a casting mold, a counter-pressure casting method and a low-pressure casting method. The casting mold includes an upper mold insert arranged on an upper mold, a riser cavity is formed in a lower part of the upper mold insert, the riser cavity communicates with a mold cavity, an air pipe is arranged on the upper mold insert, one end of the air pipe is located at a top of the riser cavity, and compressed air can be introduced. The compressed air is introduced into the air pipe in the casting process, an upper part of the riser cavity forms a pressure with the same order of magnitude in a heat-insulating furnace, and the pressure of the riser is transmitted to a far-end defect position through local extrusion.

What is claimed is: 
     
         1 . A casting mold, comprising an upper mold and a lower mold, wherein a mold cavity is formed by enclosing of the upper mold and the lower mold, an upper mold insert is arranged on the upper mold, a riser cavity is formed in a lower part of the upper mold insert, and the riser cavity communicates with the mold cavity; and
 an air pipe communicating with the riser cavity is arranged on the upper mold insert, one end of the air pipe is located at a top of the riser cavity, and compressed air can be introduced.   
     
     
         2 . The casting mold according to  claim 1 , wherein a venting plug is arranged between the riser cavity and the air pipe. 
     
     
         3 . The casting mold according to  claim 1 , wherein a check valve is arranged on the air pipe. 
     
     
         4 . The casting mold according to  claim 1 , wherein a cross section of the riser cavity is in a shape of cone with a narrow upper part and a wide lower part. 
     
     
         5 . A counter-pressure casting method of the casting mold according to  claim 1 , comprising the following steps:
 after the mold is closed, introducing dry compressed air into a heat-insulating furnace and the mold cavity, increasing pressure to 0.2-0.6 MPa, then stopping pressurizing the mold cavity and maintaining the pressure, continuing to perform pressurization in the heat-insulating furnace at a speed of 4 mbar/s-20 mbar/s according to a set pressure curve, and slowly filling the mold cavity with molten aluminum in the heat-insulating furnace; and   introducing compressed air into the air pipe, forming a pressure with the same order of magnitude as a mold-filling pressure in the heat-insulating furnace on an upper part of the riser cavity, and continuously forming an extrusion effect on a riser in the solidification process of a casting.   
     
     
         6 . A low-pressure casting method of the casting mold according to  claim 1 , comprising the following steps:
 after the mold is closed, performing pressurization in the heat-insulating furnace at a speed of 4 mbar/s-30 mbar/s according to a set pressure curve, and slowly filling the mold cavity with molten aluminum in the heat-insulating furnace; and   introducing compressed air into the air pipe, forming a pressure with the same order of magnitude as a mold-filling pressure in the heat-insulating furnace on an upper part of the riser cavity, and continuously forming an extrusion effect on a riser in the solidification process of a casting.