Study On Phosphate Inorganic Coated Sand

Phosphate inorganic binder has good disintegration and low pollution,and is a potential casting material.For the current application of inorganic binders,there is the problem of poor fluidity of molding sand.The inorganic phosphate binder is prefabricated into dry coated sand.Developed a dry coated sand with good fluidity.It replaces the organic coated sand,and has the inorganic phosphate coated sand with low gas generation and no pollution during casting.Optimize the process parameters of the pretreatment process of coated sand for freezing and drying.Determine the appropriate amount of liquid nitrogen added to the cold.coated coated sand,the drying method of liquid nitrogen and the equipment that is designed to ensure that the cold.coated coated sand can be heated and solidified under industrial conditions.Determine the drying time and drying temperature of the thermal coated sand to ensure that the thermal coated sand can have a longer use time and has strength comparable to that of the organic coated sand after curing.The auxiliary materials added during the formation of the thermal coated sand are to ensure the rapid and complete molding of the coated sand,and have a longer storage time in a low humidity environment.Finally,through the analysis and identification of the fracture morphology of the phosphate coated sand and the components of the bonding bridge,a certain analysis and summary of the coating and hardening process mechanism are made.Experiments show that the coupling agent will promote the dehydration reaction of the phosphate binder and make the coated sand sample form more bonding bridges,but the coupling agent is alkaline,and the acid and alkali of the coated sand system will be changed after the addition.In addition,excessive addition will cause the phosphate binder to lose its curing ability.Coupling agent will also affect the preservation of the sample after curing,to a certain extent,slow the moisture absorption of the coated sand,so that the coated sand sample can be stored in a low humidity environment for a longer period of time.Passing compressed air can assist dehydration to quickly solidify the coated sand and accelerate the curing speed of the coated sand sample.Passing compressed air to assist curing can obtain higher instant strength samples.The low temperature storage of the sample will reduce the gas evolution of the inorganic phosphate coated sand to some extent.When experimenting with different coated sand processes,the cold coated sand has the disadvantage of high forming strength,but it is not easy to control the prefabrication and sand shooting process.The prefabrication process of thermal coated sand is simple,and the process of introducing high pressure water vapor into the molding process is not easy to control.The inorganic phosphate coated sand wets the coated sand by water decomposed by hydrates,and is further heated to solidify the coated sand.After adjusting through the electron microscope observation process,each component is evenly coated on the surface of the sand.Through the distribution of elements after curing,the effect achieved by the additives in the prefabrication process can be seen.