Production method for non-oriented silicon steel and non-oriented silicon steel

A production method for the non-oriented silicon steel, wherein a product of the non-oriented silicon steel having the thickness of 0.5±0.005 mm is prepared by using the processes of molten iron desulfurization, converter smelting, RH refining, continuous casting, hot rolling, acid tandem rolling, annealing, coating and finishing, and the product of the non-oriented silicon steel has the iron loss P1.5/50≤5.5 W/kg and the magnetic induction intensity B5000≥1.75, wherein

• in the molten iron desulfurization process:
• the temperature of molten iron before desulfurization is controlled to be greater than or equal to 1350° C., the chemical composition is as follows in mass percent:
• Si:
• 0.20-0.70%, S≤0.05%, Nb≤0.005%, V≤0.04%, Ti≤0.06%, Mo≤0.001%, Cr≤0.03%, Ni≤0.03% and Cu≤0.03%, the molten iron before desulfurization is desulfurized so as to control the temperature of the molten iron after desulfurization to be greater than or equal to 1320° C., and the S content in mass percent is less than or equal to 0.0015%;
• in the converter smelting process:
• the molten iron after desulfurization is mixed with scrap steel to be smelted in a converter;
• in a steel tapping process, sufficient tin ingots are added to steel tapping liquid according to the chemical composition base solution;
• after steel tapping is finished, a slag surface deoxidizer is added to the molten steel;
• and the chemical composition base solution is as follows in mass percent:
• C≤0.003%, S≤0.008%, Si:
• 0.35%, Mn:
• 0.15-0.25%, P:
• 0.04-0.06%, Sn:
• 0.015%, Nb≤0.004%, V≤0.004%, Ti≤0.005%, Mo≤0.004%, Cr≤0.03%, Ni≤0.03%, Cu≤0.03%, N≤0.003% and the balance of Fe and inevitable inclusions;
• in the RH refining process:
• in the RH refining furnace to be vacuumized, decarburization is performed on the molten steel;
• then, alloying is performed according to the mass percent of S in the molten steel reaching RH refining, wherein if the mass percent of sulfur in the molten steel that reaches RH refining process is less than or equal to 0.0030%, ultra-low-titanium ferrosilicon, low-titanium ferrophosphorus and manganese metal are added to the molten steel according to the chemical composition base solution;
• if the mass percent of sulfur in the molten steel that reaches RH refining process is more than 0.0030% and less than or equal to 0.0045%0.0045%, Si and Sn in the chemical composition base solution are adjusted to 0.40% and 0.020% respectively;
• if the mass percent of sulfur in the molten steel that reaches RH refining process is more than 0.0045% and less than or equal to 0.0060%, Si and Sn in the chemical composition base solution are adjusted to 0.50% and 0.025% respectively;
• if the mass percent of sulfur in the molten steel that reaches RH refining process is more than 0.0060% and less than or equal to 0.0075%, Si and Sn in the chemical composition base solution are adjusted to 0.60% and 0.035% respectively, and ultra-low-titanium ferrosilicon, tin ingots, low-titanium ferrophosphorus and manganese metal are added to the molten steel according to the adjusted chemical composition solution;
• then, steel tapping is performed after net circulation for seven minutes;
• and the desulfurizer is not added in the RH refining process.