The invention discloses a preparation method of a low-
silicon high-
calcium macrocrystalline fused
magnesite. The preparation method comprises the following steps: putting
magnesite with the MgO content of over 45% into a light
roasting furnace for continuous calcinations for 4 h, uniformly adding an Na2CO3 solution during calcinations, and smashing a product after calcinations to obtain a high-activity MgO
powder; adding the high-purity
graphite powder into the high-activity MgO
powder, putting the mixture into a full-automatic electric
smelting electric-arc furnace for
smelting for 5 to 8 h,and carrying out classification crushing after the
smelting is ended so as to obtain the low-
silicon high-
calcium macrocrystalline fused
magnesite. According to the preparation method, a
sodium carbonate solution is added, so that the
melting point is effectively reduced, the
calcination temperature is reduced, and the energy is saved; moreover,
sodium silicate and
carbon dioxide can be generatedthrough the reaction of
sodium carbonate and
impurity silicon dioxide, and the
silicon dioxide impurity inside the magnesite can be effectively removed, so that the content of
magnesium oxide is improved; the content of MgO inside the product reaches 99.90% or more than 99.90%, the
calcium-
silicate ratio reaches 2.30 or more, the fused magnesite has high high-temperature
fire resistance and high-temperature scouring resistance, and the fused magnesite can be applied to the industries such as
spaceflight, electrons, steel,
metallurgy and the like as a high-quality advanced
refractory material.