Continuous casting mold covering slag for die steel and manufacturing method thereof

The invention discloses a continuous casting mold covering slag for die steel, which is prepared through crushing, mixing, pulping and pelleting pre-melt, fly ash, bentonite, industrial sodium carbonate, lithium carbonate and charcoal; the covering slag contains the following components in percentage by weight: 32.3-37.8% of SiO2, 31.0-40.0% of CaO, 3.0-6.0% of Al2O3, 5.5-7.5% of Li2O, 10.5-18.5% of Na2O, 4.5-6.5% of TC, larger than 0.4% and not more than 2.2% of Fe2O3, the balances of K2O, MnO and other trace components, wherein the K2O is not more than 2%, and MnO is not more than 1%; the binary basicity of CaO/SiO2 in the covering slag is controlled between 1.07 and 1.15, and the parameters of the physical and chemical properties of the covering slag are as follows: the hemispherical point melting temperature is 1094-1250 DEG C, and the viscosity at the temperature of 1250 DEG C is 0.18-0.28 Pa.s. The covering slag is uniformly melted inside a crystallizer, the lubrication for a casting blank is good, and