Research On The Passivation Reclamation Technology Of Sodium Silicate Used Sand

In the current foundry industry,resin sand,clay sand and sodium silicate sand are the three most widely used sand types.Among them,sodium silicate sand has been used more and more in casting steel production since the 21st century due to its good technological performance.At present,for every ton of steel castings produced,almost equivalent sodium silicate used sand is produced.China's current annual output of steel castings can reach tens of millions of tons.If the used sand produced is not recycled,it will cause harm to the environment.Green clean production is the development trend of the foundry industry in the 21st century.Sodium silicate sand is the foundry sand most likely to achieve green clean production.Therefore,it is of great significance to further develop the sodium silicate used sand recycling technology.This subject takes ester hardening sodium silicate sand and CO₂hardening sodium silicate sand as the research object.For wet reclamation,when the technological parameters were 1200r/min of the SXW sand washer and the sand-water ratio was 1.5:2,the reclamation method of 3min scrub+3min rinse was adopted.For dry reclamation,the suitable process and process parameters were determined as regeneration 15min each time,recycling reclamation three times,and the rotation speed of reclamation grinding wheel was 1000r/min.The study found that the tensile strength of sodium silicate sand hardened by reclamation sand mixed with ester is lower than that of sodium silicate sand hardened by new sand mixed with ester whether reclamation by wet or dry method.In the four working cycles,the tensile strength of the wet reclamation sand mixed with CO₂hardening sodium silicate sand reached the level of the new sand mixed with CO₂hardening sodium silicate sand,and then decreased with the increase of working cycles.The tensile strength of CO₂hardened sodium silicate sand produced by dry process of CO₂hardened sodium silicate sand is much lower than that of CO₂hardened sodium silicate sand produced by new sand.The suitable process and technological parameters for passivation reclamation of sodium silicate sand are the passivation reclamation temperature of 850?and heating for15min.Within three working cycles,the tensile strength of the reclamation sand is close to or higher than that of the original sand.After three working cycles,the tensile strength of the reclamation sand decreases.The tensile strength of the CO₂hardened sodium silicate sand produced by the passivated reclamation sand was close to that of the CO₂hardened sodium silicate sand produced by the new sand within three working cycles.After three working cycles,the tensile strength of the CO₂hardened sodium silicate sand produced by the passivated reclamation sand decreased.