▎ 摘　　要

NOVELTY - A medium-large foundry sand comprises sodium metasilicate, boric acid, magnesium silicate, graphene oxide, silica sand, tall oil, sawdust, sand, alumina abrasive, bentonite, modified coal powder, sodium carbonate and water. The modified coal powder comprises lignite powder, sorbitol, blue carbon, methanol, potassium chlorate, potassium carbonate, ferric chloride, limestone, calcium acetate, antimony sulfide, Tween 80 (RTM: polysorbate) and water. USE - Medium-large foundry sand is used in preparation of casting. ADVANTAGE - The medium-large foundry sand has uniform particle size, and excellent air-permeability, and less ash content, and is prepared with high yield. DETAILED DESCRIPTION - A medium-large foundry sand comprises 0.3-0.5 pt. wt. sodium metasilicate, 0.3-0.6 pt. wt. boric acid, 4-5 pts. wt. magnesium silicate, 0.5-1.1 pts. wt. graphene oxide, 45-50 pts. wt. silica sand, 0.1-0.2 pt. wt. tall oil, 1-1.6 pts. wt. sawdust, 35-40 pts. wt. sand, 3-5 pts. wt. alumina abrasive, 4-4.5 pts. wt. bentonite, 5-6 pts. wt. modified coal powder, 0.1-0.2 pt. wt. sodium carbonate and 4-5 pts. wt. water. The modified coal powder comprises 3-4 pts. wt. lignite powder, 0.05-0.08 pt. wt. sorbitol, 0.5-0.8 pt. wt. blue carbon, 0.3-0.5 pt. wt. methanol, 0.1-0.2 pt. wt. potassium chlorate, 0.2-0.3 pt. wt. potassium carbonate, 0.01-0.02 pt. wt. ferric chloride, 0.02-0.03 pt. wt. limestone, 0.1-0.2 pt. wt. calcium acetate, 0.2-0.3 pt. wt. antimony sulfide, 0.04-0.08 pt. wt. Tween 80 (RTM: polysorbate) and 2-2.5 pts. wt. water. The modified coal powder is prepared by mixing lignite powder and blue carbon, pulverizing to particle size of less than 100 mu m, obtaining powder, adding Tween 80 (RTM: polysorbate) and sorbitol to water, stirring, adding potassium chlorate, potassium carbonate, ferric chloride and calcium acetate to the resultant product, adding obtained powder, stirring, grinding to particle size of less than 40 mu m, spray-drying, stirring with methanol, milling for 10-15 minutes, uniformly mixing with remaining components, and sealing. An INDEPENDENT CLAIM is included for preparation of medium-large foundry sand.