The invention discloses high-strength medium-heat-resistance
alloy cast iron smelted through an electric furnace and a
smelting method of the high-strength medium-heat-resistance
alloy cast iron in the technical field of
cast iron production. The
alloy cast iron is prepared from, by
mass, 3.2%-3.4% of carbon, 1.9%-2.2% of
silicon, 0.01%-0.06% of
phosphorus, 0.06%-0.12% of
sulfur, 0.6%-0.9% of
manganese, 0.2%-0.35% of
chromium, 0.6%-0.9% of
copper, 0.005%-0.03% of
titanium and the balance iron and inevitable impurities. Different from traditional gray cast iron raw materials,
pig iron is not added in the scheme of the invention, but a proportioning process of
scrap steel,
foundry returns and a carburant is used, and meanwhile, a precious
molybdenum alloy is replaced by adopting alloy matching of
copper and
chromium, so that the manufacturing cost is greatly reduced, in addition, a treatment mode of
silicon iron pretreatment of a part of the carburant and tapping composite
inoculation is adopted, and the production efficiency is greatly improved. By means of the method, more than 90% of A-type
graphite is obtained in a metallographic phase of a
casting body, the
lanthanum-containing inoculant can promote isometric
crystal growth and inhibit dendritic
crystal growth in the cast iron solidification process, a feeding channel in molten iron is effectively prolonged, the
shrinkage porosity tendency of the
casting is reduced, and it is guaranteed that leakage does not exist in an installation pressure test.