What are the characteristics of low pressure casting
Low pressure casting means that the casting mold is generally placed above a sealed crucible, and compressed air is introduced into the crucible to cause a low pressure (0.06-0.15MPa) on the surface of the molten metal
Low pressure casting means that the casting mold is generally placed above a sealed crucible, and compressed air is introduced into the crucible to cause a low pressure (0.06-0.15MPa) on the surface of the molten metal, so that the molten metal rises from the riser pipe to fill the mold and control Solidified casting method. This casting method has good feeding and compact structure of the casting, and it is easy to cast large and thin-walled and complex castings without a riser, and the metal yield is 95%. No pollution, easy to realize automation. But the equipment cost is high and the production efficiency is low. Generally used for casting non-ferrous alloys.
Low pressure casting can use sand mold, metal mold, graphite mold, etc. The filling process is not only different from gravity casting such as metal mold casting and sand casting, but also different from pressure casting with high pressure and high speed filling, and has the following advantages:
1) Filling with pure metal liquid improves the purity of castings. Since the molten slag generally floats on the surface of the molten metal, the low-pressure casting is filled by the molten metal in the lower part of the crucible through the liquid riser, which completely avoids the possibility of the molten slag entering the mold cavity.
2) The metal liquid filling is stable, which reduces or avoids the churning, impact and splashing of the metal liquid during filling, thereby reducing the formation of oxide slag.
3) The casting has good formability, and the molten metal is filled under the action of pressure, which can improve the fluidity of the molten metal, which is conducive to the formation of castings with clear contours and smooth surfaces, which is more beneficial for the forming of large thin-walled castings.
4) The casting crystallizes and solidifies under the action of pressure, which can be fully fed and the structure of the casting is dense.
5) The yield of molten metal is improved. Generally, no riser is required, and the uncondensed metal in the liquid riser can be returned to the crucible for repeated use, which greatly improves the yield of molten metal. Generally up to 90%.
6) The production and operation are convenient, the labor conditions are good, the production efficiency is high, it is easy to realize mechanization and automation, and low-pressure casting also has some shortcomings, and the investment in equipment and molds is large; when producing aluminum alloy castings, the crucible and the riser are in contact with the molten metal for a long time. , It is easily eroded and scrapped, and it will also increase the iron and deteriorate the performance of the molten metal.