The invention provides a low-cost method for preparing high-strength building steel from a
niobium-
phosphorus alloy, and belongs to the technical field of steel preparation. The method comprises the steps that waste steel is smelted in an electric furnace, the P content of
molten steel at the end point of the electric furnace is controlled to be smaller than or equal to 0.012%, the C content of the
molten steel is controlled to be 0.06%-0.1%,
vanadium slag and
silicon-
manganese alloy are added along with steel flow in the tapping process, and then
argon blowing stirring is conducted;
molten steel is conveyed to an LF refining furnace, a first batch of
ferrosilicon alloy, carbon
powder and
lime are added, the molten steel is electrified and heated to 1520-1540 DEG C, the P content in the molten steel is controlled to be smaller than or equal to 0.012%, the C content is controlled to be 0.14-0.16%, the
silicon content is controlled to be 0.13-0.15%, and the
phosphorus content is controlled to be smaller than or equal to 0.012%, the molten steel continues to be electrified and heated to make white
slag, the
lime and the remaining
ferrosilicon alloy are supplemented, and when the molten steel meets the refining requirement,
niobium-
phosphorus alloy is added into the LF refining furnace; and controlling the temperature of the molten steel at the end of refining to obtain the high-strength building steel. According to the method, the absolute limitation on the phosphorus content of the raw materials in the
steelmaking process is broken through, and the high-phosphorus alloy can be safely applied in the
steelmaking process through the phosphorus content balance control strategy that the phosphorus content is low in the front and high in the rear.