Production method of ultrahard high-chromium cast grinding ball

The invention relates to a production method of an ultrahard high-chromium cast grinding ball. The ultrahard high-chromium cast grinding ball comprises the following chemical components: 1.8-3.2 percent of carbon (C), 0.3-1.0 percent of silicon (Si), 0.2-0.9 percent of manganese (Mn), 10.0-10.5 percent of chromium (Cr), 0.02-0.1 percent of phosphorus (P), 0.02-0.1 percent of sulphur (S), 0.02-0.1 percent of copper (Cu), 0.02-0.1 percent of molybdenum (Mo), 0.02-0.1 percent of nickel (Ni), 0.02-0.1 percent of wolfram (W), 0.1-0.2 percent of rare-earth yttrium (Y-Re) and 80.1-83.7 percent of iron (Fe). In the invention, the rare-earth yttrium is adopted to carry out modification treatment so as to change the shapes and the distribution of carbides, thereby breaking nets; meanwhile, crystal particles are refined, tissues are thickened, and the toughness is improved. An oil-medium quenching and tempering heat treatment process is adopted to obtain a eutectic carbide of a martensite and a broken net, the hardness of the high-chromium grinding ball achieves HRc64 to 66, and the toughness and the abrasive resistance of the high-chromium grinding ball are obviously improved. The grinding ball is tried in ball grinders of various factories in cement industry, the abrasion is reduced by 20-32 percent on year-on-year basis, and the running cost of the ball grinder is obviously reduced.