The Research On Nano-modified CO₂-hardening High-modulus Waterglass Sand For Foundry Moulding And Coremaking

Waterglass which serve as a binder for foundry was introduced into foundry practies in the fifties of the 20th century. Because of a number of technical advantages, such as no pollution, low cost, rapid hardened rate, higher productivity, abundant resources, the waterglass binder have the widest application all over the world. At present this process is employed in the manufacture of more than 80% of steel castings, partial iron castings and nonferrous alloy castings, the annual consumption of waterglass in our country has reached more than 10 thousand ton. At that time low modulus waterglass sand(M=2.1-2.3) gassed by 100% CO₂ gas are mainly used. The protruberant disadvantages of this process are higher Na₂O content in the low modulus waterglass, thus causing lower bonding strength, higher consumption of binder, low moisture resistance and poor collapsibility, the used sands can not be reused beneficially and have to be discarded as waste, which causes undesirable soil and water pollution problems. Much effort has since been expended by our foundry specialists to overcome the poor collapsibility of CO₂-low modulus waterglass sand process by admixing organic- or inorganic break-down agents, which fails to produce the good results.In recent years owing to deeply understanding of the basic constituent and "aging" phenomena of waterglass, in the nineties of the 20th century, ester selfsetting low modulus waterglass sand process was developed, because the addition levels of waterglass binder in moulding mixture can be reduced to 2.0%-2.5%, it plays an important role in solving poor collapsibility of low modulus waterglass sand and reclamation of its used sand. But the ester-low modulus waterglass sand also has several essential disadvantages, such as the high cost of modified waterglass and organic ester, high brittleness of molding sand, lower productivity, much investment in equipment for used sand reclamation.In order to overcome existential problems of CO₂-low modulus waterglass sand...