Method for preparing low-cost clean steel

A method for preparing low-cost clean steel, comprising steps of:

• a) preliminarily desulfurizing iron melt:
• preliminarily desulfurizing in an iron melt channel during blast furnace tapping by adding a desulfurizing ball into the iron melt during the blast furnace tapping, in such a manner that after preliminarily desulfurizing, S≦0.01% by weight in the iron melt before being sent into a converter;
• b) finely desulfurizing the iron melt:
• after the step a) finely desulfurizing the iron melt by filtering out desulfurized slags by a slag filter, in such a manner that S≦0.0015% by weight in the iron melt after finely desulfurizing;
• c) dephosphorizing and controlling sulfur:
• after the step b) dephosphorizing and controlling sulfur during converter steelmaking, in such a manner that P≦0.014% and S≦0.004% during converter tapping;
• d) rapidly dephosphorizing by slag-forming:
• after the step c) rapidly dephosphorizing by slag-forming during the converter tapping;
• at a converter end point, controlling a C content in iron at 0.02˜0.10%, controlling an oxygen activity value αO in the iron at 600˜1000 ppm, adding a dephosphorizing ball through an alloy chute during the converter tapping, blowing argon and stirring at the same time;
• e) purifying steel melt during RH refining:
• after the step d), RH refining the iron obtained in the step d), and adding a purifying ball at a late stage of the RH refining when a vacuum degree is at 66.7˜500 Pa;
• and
• f) after the step e), continuously casting the iron obtained in the step e) with whole-process protection;
• wherein the desulfurizing balls comprises:
• white slags cool-collected by a ladle furnace from 20˜55% by weight, CaO from 20˜50% by weight, CaF2 from 5˜15% by weight, and CaCO3 from 5˜15% by weight, wherein particle sizes of the CaO, CaF2, CaCO3 and the white slags cool-collected by the ladle furnace are less than 100 μm;
• wherein the dephosphorizing ball comprises:
• white slags cool-collected by a ladle furnace from 10˜65% by weight, CaO from 10˜65% by weight, CaF2 from 1˜15% by weight, and CaCO3 from 5˜30% by weight, particle sizes of the CaO, CaF2, CaCO3 and the white slags cool-collected by the ladle furnace are less than 100 μm;
• and
• wherein the purifying ball comprises:
• white slags cool-collected by a ladle furnace from 10˜60% by weight, CaO from 15˜65% by weight, CaF2 from 1˜15% by weight, CaCO3 from 5˜30% by weight, and Ca powder from 1˜15% by weight, particle sizes of the CaO, CaF2, CaCO3 and the white slags cool-collected by the ladle furnace are less than 100 μm.