Vacuum casting can be roughly divided into vacuum suction casting, vacuum low-pressure casting and vacuum differential pressure casting:
Vacuum suction casting: the mold is placed in a closed container, and the air in the mold is extracted to create a certain negative pressure in the mold, causing the liquid metal to be sucked into the mold cavity. When the inner sprue of the casting solidifies, the negative pressure shall be removed to make the non solidified metal liquid in the vertical sprue flow back to the molten pool. The advantages are that the filling capacity of the alloy liquid is improved, the minimum wall thickness of the suction casting casting can reach o.2mm, the casting area is 300mm2, and the defects such as air holes and slag inclusions are reduced. It is suitable for producing thin and fine small precision castings, especially steel castings (including stainless steel). Its advantages are:
When it comes to vacuum casting, the technique of vacuum suction casting offers numerous advantages such as improved filling capacity, reduced defects like air holes and slag inclusions, and the ability to produce thin and precise small castings. To leverage the benefits of vacuum suction casting, it is crucial to work with a reliable vacuum casting supplier specializing in vacuum-assisted casting techniques for the successful production of high-quality castings. Its advantages are:
(1) Vacuum suction casting is helpful to eliminate the gas in the mold, restrain the generation of turbulent flow and entrainment, overcome the disadvantages of low-pressure casting and differential pressure casting, and significantly improve the filling capacity of molten metal.
(2) Due to the improvement of mold filling capacity during vacuum suction casting, the casting temperature of molten metal can be 20~30 ℃ lower than that during gravity casting.
(3) Castings with large wall thickness difference, thin wall and high quality requirements can be cast.
(4) A Stable Filling Effect Can Be Obtained By Selecting An Appropriate Rate Of Vacuum Change And Controlling The Speed Of Molten Metal Entering The Mold Cavity.
Vacuum low-pressure casting method is to vacuum the mold in the process of pressure filling. After filling, the pressure is maintained to make the casting crystallize and solidify under constant pressure, and the casting is fully fed. Therefore, the structure of the casting is dense and the mechanical properties are improved. This method is mostly used for precision casting of Al and Mg alloy castings. Its advantages are as follows:
The vacuum low-pressure casting method involves pressurized filling of the mold while maintaining a vacuum, resulting in dense castings and improved mechanical properties. This technique is commonly employed for precision casting of aluminum and magnesium alloy castings. To leverage the benefits of vacuum low-pressure casting, it is crucial to collaborate with a reliable vacuum casting supplier who specializes in this method to ensure the production of high-quality castings. Its advantages are as follows:
(1) The existence of vacuum negative pressure can compact the mold sand and increase the strength of the mold.
(2) The vacuum degree is moderately increased to shorten the filling time, so that the filling speed is accelerated and stable.
(3) Vacuum low-pressure casting can accelerate the fluidity of aluminum alloy at low temperature, avoid the gettering phenomenon of aluminum alloy caused by high-temperature casting, and increase the pinhole defects of castings.
(4) The casting has good formability, which is conducive to the formation of castings with clear outline and smooth surface and large thin-wall castings.
(5) The casting has compact structure and high mechanical properties.
(6) Generally, no riser is required, which greatly improves the yield of molten metal, usually up to 90%.
(7) The working environment is good and the equipment is simple, which is conducive to mechanization and automation.
Vacuum differential pressure casting is mainly to seal the resistance holding furnace and the mold, and fill the sealing cover with compressed air with high pressure, such as 500kPa. At this time, because the pressure inside the mold and the crucible is equal, the liquid metal will not rise, and then add 50kPa pressure on the metal liquid level, and the liquid metal will rise and fill the mold cavity. It is especially suitable for the production of complex thin-wall castings, but the equipment is large and the operation is troublesome. It can only be used when special requirements are met. Its advantages are as follows:
The vacuum differential pressure casting technique involves sealing the resistance holding furnace and the mold and using compressed air with high pressure to fill the sealing cover. This method, while suitable for producing complex thin-wall castings, requires specialized equipment and meticulous operation, limiting its use to specific requirements. To leverage the advantages of vacuum differential pressure casting, it is crucial to collaborate with a reliable vacuum casting supplier who possesses the necessary expertise and equipment for successful implementation. Its advantages are as follows:
(1) Compared with the traditional gravity casting and vacuum suction casting, the vacuum differential pressure casting shows a good filling ability on the 1mm thick sheet sample.
(2) The casting has dense crystalline structure and mechanical properties. The strength of the casting is about 20%~25% higher than that of vacuum suction casting and gravity casting, and the elongation is about 50%.
(3) Vacuum die casting can effectively reduce the porosity of die castings and increase the density of castings by more than 1%.