The History of Low Pressure Casting Method  In the early 20th century, foreign countries began to research and apply low-pressure casting technology. E.H. Lake in the UK has registered its first low-pressure casting patent, mainly used for the casting of babbitt alloys. The French developed plans for aluminum and copper alloys, which were first promoted and used in aluminum alloy casting production. After the outbreak of World War II, with the development of the aviation industry, the UK widely used low-pressure casting technology to produce light aluminum alloy castings such as cylinders for aircraft engines with high technical requirements, and used metal mold low-pressure casting. Low pressure casting technology was widely used in China in the 1950s and 1960s, and the earliest liquid level pressurization device and a simple metal mold low-pressure casting machine were developed. In the 1990s, with the introduction of advanced equipment from abroad, low-pressure casting equipment and processes in China have also been rapidly developed and applied, and a single-chip computer controlled liquid level pressurization device has been developed, greatly improving the level of low-pressure casting technology. Nowadays, low-pressure casting machines have been widely used in fields such as automobiles, electricity, and aviation, and have become a mature casting process equipment. The Principle of Low Pressure Casting  Apply a dry compressed air pressure of 0.01~0.1Mpa or inert gas pressure on the surface of the metal liquid in a closed metal liquid insulation furnace, causing the metal liquid to rise through a rising pipe immersed in the metal liquid and be pressed into the upper mold connected to the insulation furnace. Then the metal liquid slowly starts filling from the lower part of the casting cavity until it fills the entire cavity, which is called filling. After filling the mold cavity, the pressure increases to the holding pressure, causing the casting to begin solidification at a higher pressure. Solidification starts from the upper part of the casting and transfers towards the direction of the gate. The moment when the gate solidifies is the end of the pressurization process. After the gate solidifies, the insulation furnace exhausts and depressurizes, and the non solidified metal liquid in the riser flows back into the insulation furnace. After the casting cools to a certain strength, open the mold, take out the casting, and a complete low-pressure pouring process is completed.  The molds used for low-pressure casting can be metal, sand, shell, ceramic, gypsum, graphite, etc. The method of further improving the low-pressure casting process to make liquid metal fill under differential pressure and solidify under pressure is called differential pressure casting, which is a special form of low-pressure casting.  A low-pressure casting machine is a device that completes the production process of low-pressure casting. According to the different casting types, it can be divided into metal mold low-pressure casting machines, sand mold low-pressure casting machines, etc. Among them, the insulation furnace and liquid level pressure device are essential parts of low-pressure casting equipment. The animation demonstration of the low-pressure casting process is as follows: Advantages and disadvantages of low-pressure casting: (1) The pressure and rate of pressure during pouring can be adjusted, making it suitable for various casting molds (such as metal molds, sand molds, etc.), casting various alloys and castings of various sizes;(2) Adopting bottom injection filling method, the filling speed is controllable, the metal liquid filling is stable, without turbulence or splashing, which can avoid gas entrapment and erosion of the mold wall and core. At the same time, the gas in the mold cavity can be fully discharged, thus improving the qualification rate of the casting;(3) Castings crystallize under pressure, with dense microstructure, clear contour, smooth surface, and high mechanical properties, making them particularly advantageous for the casting of large and thin-walled parts; (4) Due to the fact that casting solidification is carried out from top to bottom under pressure, the gate is always in a liquid state, and the metal liquid in the riser acts as a riser. Therefore, eliminating the process feeding riser increases the metal utilization rate to 90-98%;  & nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp; Comparison of material utilization rates among different casting methods Process methods& nbsp;& nbsp;& nbsp;& nbsp; Gravity Mold Casting& nbsp; High pressure casting& nbsp;& nbsp;& nbsp;& nbsp;& nbsp; Low pressure casting; Material utilization rate (%) 45~55& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp; 50~60 & nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp;& nbsp; 85~95 (5) Sand cores can be used to produce complex castings, such as engine cylinder heads;(6) Low labor intensity, good working conditions, simple equipment, easy to achieve mechanization and automation. Multiple operations and multiple processes are possible& nbsp; Disadvantages: (1) The gate scheme has low degrees of freedom, which limits the product. (Restrictions on gate position and quantity, changes in internal wall thickness of the product, etc.) (2) Long casting cycle and poor productivity. In order to maintain directional solidification and melt fluidity, the mold temperature is higher and the solidification speed is slower; (3) The structure near the gate is relatively coarse, and the mechanical properties of the lower surface are not high& nbsp; (4) Need comprehensive and rigorous management (temperature, pressure, etc.).   & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; The complete production process of low-pressure casting includes: (1) metal melting, slag removal, and degassing, while preheating the insulation furnace to the pouring temperature;(2) Preheat the mold, apply paint, install the mold, and ensure the sealing connection between the mold and the night tube; (3) Add qualified metal liquid to the insulation furnace, seal the insulation furnace door, and bring the insulation furnace to the pouring temperature; (4) Install the slag filter mesh at the gate; (5) Lower sand core; (6) Blowing and cleaning; (7) Mold closing and core insertion in place; (8) Start the liquid level pressurization system to pressurize and complete the process of liquid lifting, mold filling, and shell pressurization; (9) Pressure holding solidification; (10) When the holding time is up, start core pulling and mold opening; (11) Remove the product.