A MOLDING SAND FOR MANUFACTURING ONE-TIME GREEN MOLDS TO OBTAIN CASTINGS OF IRON AND STEEL CASTING ALLOYS

摘要

A molding sand for manufacturing one-time green molds to obtain castings of iron and steel casting alloys relates to compositions of molding sands used when manufacturing molds of sand clay (bentonite) molding mixes. The essence of the invention is characterized in that the sand containing silica sand, bentonite and water, further contains schungite at the following ratio of the components, (mass per cent): bentonite 5-10, schungite 2-5 of the bentonite concentration, silica sand is the rest up to 100%, water 2.5-3.5 in excess of 100%. When manufacturing molds for iron castings the sand in addition contains antiburning-on carbon-bearing additive at a rate of 2-4 (mass per cent). Use of offered composition of the sand at the same time ensures simultaneously high values of fluidity of a mold and green bond; facilitating increase of durability of the packed mold toward additional strains; increase of accuracy, as well as improving state of a obtaining casting surface. Totality of these properties allows to obtaining high-quality castings by patterns of various complexity, including the castings with deep "pockets".