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

Abstract

Disclosed are a non-oriented silicon steel and a production method therefor. The non-oriented silicon steel is prepared using molten iron desulfurization, converter smelting, RH refining, continuous casting, hot rolling, acid continuous rolling, annealing, coating and finishing. The chemical components of the non-oriented silicon steel, in mass percent, are: C≤0.003%; S≤0.008%; Si: 0.35%+Δ1; Mn: 0.15-0.25%; P: 0.04-0.06%; Sn: 0.015%+Δ2; Nb≤0.004%; V≤0.004%; Ti≤0.005%; Mo≤0.004%; Cr≤0.03%; Ni≤0.03%; Cu≤0.03%; N≤ 0.003%; the remainder being Fe and inevitable impurities. When the thickness of the non-oriented silicon steel is 0.5 mm, P₁.₅ / ₅₀ ≤5.5 W / kg and B₅₀₀₀≥1.75, and the RH refining requires no desulfurization treatment.

Description

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

[0001] This application claims priority to Chinese patent application filed on September 27, 2020, with application number 202011031589.3, and invention name “Production method of non-oriented silicon steel and non-oriented silicon steel”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the technical field of steel material preparation, relates to a production method of non-oriented silicon steel, and also relates to non-oriented silicon steel prepared by adopting the production method. Background Art

[0003] Non-oriented silicon steel is the core material for rotors in electric motors and generators operating in a rotating magnetic field, requiring excellent magnetic properties. To ensure the magnetic properties of non-oriented silicon steel, strict control of its chemical composition is typically required. During the production of non-oriented silicon steel, the element S dissolves and precipitates in the steel as MnS, hindering grain growth during annealing and, in turn, affecting the magnetic properties of the finished product. This is manifested in reduced magnetic induction intensity and increased iron loss. Therefore, in the prior art, the pursuit of ultra-low S control is generally the goal of chemical composition design and production processes for non-oriented silicon steel.

[0004] Furthermore, the ultra-low S chemical composition design of non-oriented silicon steel requires strict control in the steps of molten iron desulfurization, converter smelting, RH refining, etc. during the production process, resulting in high production costs and even affecting the smooth operation of the operation.

[0005] For example, during the RH refining step, a desulfurizer is required to desulfurize the molten steel. As the molten steel circulates, the desulfurizer comes into contact with the RH refining furnace's dip tube. The CaF2 in the desulfurizer reacts with the CaO and Al2O3 in the immersion tube's lining castable to form a low-melting-point substance, 11CaO·7Al2O3·CaF2. This product, eroded by the molten steel, flakes off and enters the molten steel. Consequently, the desulfurization treatment during the RH refining process can cause severe corrosion of the RH refining furnace's dip tube, increasing production costs and significantly impacting smooth operation.

[0006] Therefore, developing a chemical composition design scheme for non-oriented silicon steel that can relax the requirements on S content while meeting the magnetic properties of low-grade products is very valuable in the industrial production of non-oriented silicon steel.

[0007] Summary of the Invention

[0008] To solve the technical problem in the prior art that the ultra-low S chemical composition design scheme of non-oriented silicon steel leads to high production costs, the purpose of the present invention is to provide a production method of non-oriented silicon steel, and also relates to a non-oriented silicon steel prepared by using this production method.

[0009] To achieve the above invention purpose, an embodiment of the present invention provides a production method of non-oriented silicon steel, which is prepared by the processes of hot metal desulfurization, converter smelting, RH refining, continuous casting, hot rolling, acid continuous rolling, annealing, coating and finishing to obtain a non-oriented silicon steel finished product that meets the following chemical composition design scheme;

[0010] The chemical composition design scheme is in mass percentage:

[0011] C ≤ 0.003%, S ≤ 0.008%, Si: 0.35% + Δ1, Mn: 0.15 - 0.25%, P: 0.04 - 0.06%, Sn: 0.015% + Δ2, 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 others are Fe and inevitable inclusions;

[0012] Wherein, when the molten steel reaches RH refining and S ≤ 0.0030%, then Δ1 = Δ2 = 0;

[0013] When the molten steel reaches RH refining and 0.0030% < S ≤ 0.0045%, then Δ1 = 0.05% and Δ2 = 0.005%;

[0014] When the molten steel reaches RH refining and 0.0045% < S ≤ 0.060%, then Δ1 = 0.15% and Δ2 = 0.010%;

[0015] When the molten steel reaches RH refining and 0.0060% < S ≤ 0.0075%, then Δ1 = 0.25% and Δ2 = 0.020%.

[0016] Preferably, the thickness of the non-oriented silicon steel finished product is 0.500 ± 0.005 mm, and its iron loss P 1.5 / 50 ≤ 5.5 W / kg, and the magnetic induction intensity B 5000 ≥ 1.75.

[0017] Preferably, during the hot metal desulfurization process:

[0018] The temperature of the molten iron before desulfurization is controlled to be ≥1350°C and the chemical composition thereof is controlled to meet the following conditions: 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% by mass; and the molten iron before desulfurization is desulfurized to control the temperature of the molten iron after desulfurization to be ≥1320°C and the S content thereof to be ≤0.0015% by mass.

[0019] During the converter smelting process:

[0020] The desulfurized molten iron is mixed with scrap steel and smelted in a converter. During the tapping process, a sufficient amount of tin ingot is added to the tapped steel according to the basic chemical composition scheme of Δ1=Δ2=0 in the chemical composition design scheme; after the tapping is completed, a slag surface deoxidizer is added to the steel liquid;

[0021] In the RH refining process:

[0022] The mass percentage of S contained in the molten steel when it reaches RH refining is detected, and the values ​​of Δ1 and Δ2 in the chemical composition design scheme are determined to obtain a final chemical composition scheme. The molten steel is decarburized in a pre-vacuumed RH refining furnace, and then ultra-low titanium ferrosilicon, tin ingots, low titanium ferrophosphorus and metallic manganese are added to the molten steel according to the final chemical composition scheme. The steel is tapped after a net circulation of more than 7 minutes; no desulfurizer is added in the RH refining process.

[0023] Preferably, during the molten iron desulfurization process, the slagging rate of the molten iron after desulfurization is controlled to be ≥98%;

[0024] Preferably, during the converter smelting process, the amount of scrap steel added accounts for 20-25% of the total amount of scrap steel and molten iron, and lime is added first and then tin ingots during the tapping process.

[0025] Preferably, during the hot rolling process: the continuous casting billet is sequentially subjected to continuous casting billet heating, intermediate billet rolling, finish rolling, and coiling to prepare a hot coil, wherein the heating temperature of the continuous casting billet is 1130-1160°C and the holding time is ≥180min, the intermediate billet thickness is 35-40mm, the final rolling temperature is 865±15°C, the coiling temperature is 680°C±20°C, and the hot coil thickness is 2.70±0.1mm.

[0026] Preferably, during the acid continuous rolling process, the hot rolled coil is pickled with HCl, rinsed and dried, and then cold rolled to obtain a hard rolled coil; wherein the cold rolling reduction is 80-83%, and the hard rolled thickness is 0.501±0.005 mm.

[0027] Preferably, HCl is used for three-stage pickling, wherein the concentration of the first-stage acid solution is 50-80 g / L and the Fe 2+Concentration ≤ 130g / L, the concentration of the second-stage acid solution is 90-120g / L and the Fe content in the acid solution is 2+ Concentration ≤90g / L, the concentration of the third-level acid solution is 140-160g / L and the Fe content in the acid solution is 2+ Concentration ≤50g / L;

[0028] During each stage of pickling, the acid solution temperature is 75-85°C, and a silicon steel pickling accelerator is added to the acid solution, with the weight percentage of the silicon steel pickling accelerator in the acid solution being 0.05-0.10%;

[0029] The rinsing water temperature is 45-55°C, and the pickling and rinsing speeds are controlled at 100-180 mpm.

[0030] Preferably, during the annealing process, the chilled steel strip is annealed in a continuous annealing furnace in a mixed atmosphere of H2 and N2 at a temperature of 850±5°C for a time of 60±5 seconds, and the annealed steel strip is cooled using a three-stage cooling method, wherein:

[0031] The first cooling stage is a slow cooling at a high temperature, where the steel strip is cooled from the annealing temperature to 800°C at a cooling rate of ≤5°C / s;

[0032] The second stage of cooling is controlled by circulating gas injection, and the steel strip continues to cool to below 300℃ at a cooling rate of ≤15℃ / s;

[0033] The third stage of cooling is circulating water jet cooling, and the steel strip continues to cool to below 100℃.

[0034] Preferably, during the coating and finishing process, the steel strip cooled to below 100° C. during annealing is subjected to coating and finishing to obtain a non-oriented silicon steel product with a thickness of 0.500±0.005 mm.

[0035] One embodiment further provides a non-oriented silicon steel, which is prepared by the processes of molten iron desulfurization, converter smelting, RH refining, continuous casting, hot rolling, acid continuous rolling, annealing, coating and finishing, wherein the chemical composition of the non-oriented silicon steel is as follows in terms of mass percentage:

[0036] C≤0.003%, S≤0.008%, Si:0.35%+Δ1, Mn:0.15~0.25%, P:0.04~0.06%, Sn:0.015%+Δ2, Nb≤0.004%, V≤0.004%, Ti≤0.005%, Mo≤0.004%, Cr≤0.03%, Ni≤0.03%, Cu≤0.03%, N≤0.003%, others are Fe and unavoidable inclusions;

[0037] Among them, when the molten steel reaches RH refining, S≤0.0030%, then Δ1=Δ2=0;

[0038] When the molten steel reaches RH refining and 0.0030% < S ≤ 0.0045%, then Δ1 = 0.05% and Δ2 = 0.005%;

[0039] When the molten steel reaches RH refining and 0.0045% < S ≤ 0.060%, then Δ1 = 0.15% and Δ2 = 0.010%;

[0040] When the molten steel reaches RH refining and 0.0060% < S ≤ 0.0075%, then Δ1 = 0.25% and Δ2 = 0.020%.

[0041] To achieve the above invention purpose, an embodiment of the present invention provides a non-oriented electrical steel and a production method of the non-oriented electrical steel. The production method is prepared by the processes of hot metal desulfurization, converter smelting, RH refining, continuous casting, hot rolling, pickling continuous rolling, annealing, coating and finishing to obtain a non-oriented electrical steel product with a thickness of 0.5 ± 0.005 mm. The iron loss P 1.5 / 50 ≤ 5.5 W / kg, and the magnetic induction intensity B 5000 ≥ 1.75; wherein,

[0042] In the hot metal desulfurization process:

[0043] Control the temperature of the hot metal before desulfurization ≥ 1350 °C and the chemical composition in mass percentage satisfies 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%. Desulfurize the hot metal before desulfurization to control the temperature of the hot metal after desulfurization ≥ 1320 °C and the S content in mass percentage ≤ 0.0015%;

[0044] In the converter smelting process:

[0045] Mix the hot metal after desulfurization with scrap steel and smelt it in a converter. During the steelmaking process, add sufficient tin ingots to the molten steel during steel tapping according to the basic chemical composition plan; after the steel tapping is completed, add a slag surface deoxidizer to the molten steel; wherein, the basic chemical composition plan in mass percentage is: 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 rest is Fe and inevitable inclusions;

[0046] In the RH refining process:

[0047] In a pre-evacuated RH refining furnace, decarburization treatment is carried out on the molten steel;

[0048] After that, alloying treatment is carried out according to the mass percentage of S contained in the molten steel when it reaches RH refining. Among them: if S ≤ 0.0030% when the molten steel reaches RH refining, then ultra-low titanium ferrosilicon, low titanium ferrophosphorus and metallic manganese are added to the molten steel according to the basic chemical composition plan; if 0.0030% < S ≤ 0.0045% when the molten steel reaches RH refining, then Si and Sn in the basic chemical composition plan are adjusted to Si: 0.40% and Sn: 0.020% respectively. If 0.0045% < S ≤ 0.060% when the molten steel reaches RH refining, then Si and Sn in the basic chemical composition plan are adjusted to Si: 0.50% and Sn: 0.025% respectively. If 0.0060% < S ≤ 0.0075% when the molten steel reaches RH refining, then Si and Sn in the basic chemical composition plan are adjusted to Si: 0.60% and Sn: 0.035% respectively, and ultra-low titanium ferrosilicon, tin ingots, low titanium ferrophosphorus and metallic manganese are added to the molten steel according to the adjusted chemical composition plan;

[0049] Then, after pure circulation for more than 7 minutes, the molten steel is tapped; no desulfurizer is added in the RH refining process.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] (1) The non-oriented silicon steel finished product with a thickness of 0.500 ± 0.005 mm prepared by the said production method has an iron loss P 1.5 / 50 ≤ 5.5 W / kg and a magnetic induction intensity B 5000 ≥ 1.75, with excellent magnetic properties, which can meet the requirements of medium and small motors for low-grade non-oriented silicon steel, and has low production cost, promoting smooth operation of the working conditions;

[0052] (2) By controlling the contents of elements such as C, Nb, V, Ti, Mo, Cr, Ni, Cu, N, etc., at the same time, by optimizing the corresponding relationship between the contents of Si, Sn and S, the upper limit of the content of S can be relaxed to 0.0080%, that is, it is only necessary to control to meet S ≤ 0.008%. On the basis of S ≤ 0.008%, it is also allowed that S > 0.0050% or even ≥ 0.0060%, ensuring the stability of the magnetic properties of the non-oriented silicon steel and not causing instability of the magnetic properties due to the increase in the content of S, realizing the stability of the yield;

[0053] (3) While ensuring the magnetic properties, the contents of elements such as Mn and P are also correspondingly designed to take into account the strength and welding properties of the non-oriented silicon steel;

[0054] (4) In the production method, the difficulty of the requirement for S content is reduced, and accordingly the difficulty of S control in processes such as molten iron desulfurization, converter smelting, and RH refining is reduced. The requirement for scrap steel in converter smelting is reduced and the cost is reduced. The RH refining process does not require desulfurization treatment, which solves the problem of desulfurizer erosion on the RH refining furnace immersion tube in the prior art, improves the service life of the RH refining furnace immersion tube, reduces production costs, and avoids affecting the working sequence due to equipment damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG1 is a metallographic microstructure photograph of a finished sample of non-oriented silicon steel in Example 1 of the present invention;

[0056] FIG2 is a metallographic microstructure photograph of a finished sample of non-oriented silicon steel in Example 2 of the present invention;

[0057] FIG3 is a metallographic microstructure photograph of a finished sample of non-oriented silicon steel in Example 3 of the present invention;

[0058] FIG4 is a metallographic microstructure photograph of a finished sample of non-oriented silicon steel in Example 4 of the present invention;

[0059] FIG5 is a metallographic microstructure photograph of the finished product sample of the non-oriented silicon steel in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0060] In one embodiment of the present invention, a method for producing non-oriented silicon steel is provided, comprising sequentially performing the following steps: hot metal desulfurization, converter smelting, RH refining, continuous casting, hot rolling, acid continuous rolling, annealing, coating, and finishing. This embodiment also provides non-oriented silicon steel produced using the production method, namely, the non-oriented silicon steel is produced using the steps of hot metal desulfurization, converter smelting, RH refining, continuous casting, hot rolling, acid continuous rolling, annealing, coating, and finishing.

[0061] The chemical composition design scheme of the non-oriented silicon steel is as follows, calculated in mass percentage: C≤0.003%, S≤0.008%, Si:0.35%+Δ1, Mn:0.15-0.25%, P:0.04-0.06%, Sn:0.015%+Δ2, 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 rest is Fe and unavoidable inclusions;

[0062] Among them, when the molten steel reaches RH refining and S ≤ 0.0030%, then Δ1 = Δ2 = 0; when the molten steel reaches RH refining and 0.0030% < S ≤ 0.0045%, then Δ1 = 0.05% and Δ2 = 0.005%; when the molten steel reaches RH refining and 0.0045% < S ≤ 0.0060%, then Δ1 = 0.15% and Δ2 = 0.010%; when the molten steel reaches RH refining and 0.0060% < S ≤ 0.0075%, then Δ1 = 0.25% and Δ2 = 0.020%.

[0063] That is to say, in the production method of the present invention, during the entire steelmaking process from the start of the hot metal desulfurization process, through the converter smelting process and the RH refining process, until before the continuous casting process, the content of each element is controlled according to the above chemical composition design scheme, and then a continuous casting billet and non-oriented silicon steel that meet the above chemical composition design scheme are prepared.

[0064] Among them, according to the mass percentage of S contained in the molten steel when it reaches RH refining (that is, when it arrives at the RH refining station, that is, at the beginning when the molten steel enters the RH refining furnace and before the RH refining process has started), according to the corresponding relationship between Δ1, Δ2 and the S content in the molten steel, the mass percentages of Si and Sn in the chemical composition design scheme are adjusted, and then the content of each element is accurately controlled.

[0065] Using the said production method, a non-oriented silicon steel finished product with a thickness of 0.500 ± 0.005 mm is prepared. After testing, the iron loss P 1.5 / 50 ≤ 5.5 W / kg, and the magnetic induction intensity B 5000 ≥ 1.75. It has excellent magnetic properties, can meet the requirements of medium and small motors for low-grade non-oriented silicon steel, and has low production cost, which promotes smooth operation of the working conditions.

[0066] The descriptions of each element in the chemical composition design scheme are as follows.

[0067] C, Nb, V, Ti, Mo, Cr, Ni, Cu, N: The more these elements are, the more unfavorable it is for the growth of grains during annealing, and then it will deteriorate the magnetic properties of non-oriented silicon steel, resulting in an increase in iron loss and a decrease in magnetic induction intensity. Therefore, the lower the content within the controllable range, the better. For example, C ≤ 0.003%, Nb ≤ 0.004%, V ≤ 0.004%, Ti ≤ 0.005%, Mo ≤ 0.004%, Cr ≤ 0.03%, Ni ≤ 0.03%, Cu ≤ 0.03%, N ≤ 0.003%.

[0068] S: As mentioned in the background art, S forms a solid solution and precipitates in the form of MnS in steel, hindering grain growth during annealing and thus affecting the magnetic properties of the finished product. The prior art generally targets ultra-low S content, for example, below 0.0050%. However, by optimizing the corresponding relationship between the Si and Sn contents and S, the present invention relaxes the upper limit of S content to 0.0080%, that is, controlling S to ≤ 0.008%. Furthermore, as shown in Examples 3 and 4 below, S content greater than 0.0050% or even ≥ 0.0060% is also permitted.

[0069] Si: controlled at 0.35-0.60%. Increasing its content can increase resistivity and effectively reduce iron loss.

[0070] Sn: controlled at 0.015-0.035%, which is a grain boundary segregation element. Increasing Sn in the non-oriented silicon steel of the present invention can significantly reduce the proportion of the unfavorable {111} texture and improve the magnetic induction intensity of the finished product;

[0071] Mn: controlled at 0.15-0.25%, while ensuring magnetic properties, suppressing hot brittleness caused by S;

[0072] P: Controlled at 0.04-0.06%, can effectively improve the strength of non-oriented silicon steel, enhance punching performance, and at the same time ensure better welding performance. Especially for the medium and low grade non-oriented silicon steel of the present invention, the Si content is relatively low, and the strengthening effect of P ensures sufficient strength.

[0073] In general, the present invention controls the contents of elements such as C, Nb, V, Ti, Mo, Cr, Ni, Cu, and N in the chemical composition design scheme. At the same time, by designing the contents of elements such as Si, Sn, Mn and P, it breaks the traditional technology and relaxes the upper limit requirement of S content to 0.0080%. This not only ensures the magnetic properties, strength and welding performance of non-oriented silicon steel, but also solves the problems of high production cost and poor working condition caused by the strict control of ultra-low S in the existing practice, reduces production cost and promotes smooth working condition.

[0074] Specifically, each process of the production method according to one embodiment is described in detail below.

[0075] (1) Molten iron desulfurization process

[0076] The molten iron is desulfurized by KR desulfurization technology.

[0077] Among them, the temperature of the molten iron before desulfurization is controlled to be ≥1350℃, and the chemical composition of the molten iron before desulfurization satisfies the following in terms of mass percentage: 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%.

[0078] The temperature of the molten iron after desulfurization is controlled to be ≥1320°C and the sulfur content in the molten iron is controlled to be ≤0.0015% by mass. That is, after the molten iron desulfurization process, the sulfur content in the molten iron is controlled to be ≤0.0015% by mass.

[0079] Preferably, the slagging rate of the molten iron after desulfurization is controlled to be ≥98%.

[0080] (2) Converter smelting process

[0081] The steel tapped from the hot metal desulfurization process (i.e., the desulfurized hot metal) is transferred to a converter and mixed with scrap steel in the converter. The desulfurized hot metal and scrap steel are then smelted together in the converter to form molten steel. Preferably, the scrap steel can be clean scrap steel, with the added scrap steel accounting for 20-25% of the total scrap steel and hot metal.

[0082] During the tapping process, a sufficient amount of tin ingots is added to the tapping molten steel according to the basic chemical composition scheme where Δ1=Δ2=0 in the chemical composition design scheme. Specifically, the chemical composition when Δ1=Δ2=0 in the chemical composition design scheme can be regarded as a basic chemical composition scheme, which specifically, in terms of mass percentage, is as follows: 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 remainder is Fe and unavoidable inclusions. According to this basic chemical composition scheme, the weight of the tin ingots required is temporarily calculated based on the Sn content of 0.015% in the final non-oriented silicon steel product, and a sufficient amount of the tin ingots is added to the molten steel.

[0083] Here, the method of determining the weight of the tin ingot is illustrated. Assuming that the total amount of molten steel in the converter smelting process is M1, the weight of the tin ingot to be added in the converter smelting process is set as M2. According to the basic design scheme of Δ1=Δ2=0, the weights of ultra-low titanium ferrosilicon, low titanium ferrophosphorus and metallic manganese to be added in the subsequent RH refining process are set as M3, M4 and M5. Then, the weight of the tin ingot M2 is calculated by taking (M1+M2+M3+M4+M5) as the total amount of molten steel, the mass percentage of Sn in the total amount of molten steel as 0.015%, and the mass percentage of Si in the total amount of molten steel as The weight M3 of ultra-low titanium ferrosilicon is calculated based on the ratio of 0.35%, the weight M4 of low titanium ferrophosphorus is calculated based on P: 0.04-0.06% in the total amount of molten steel, and the weight M5 of ultra-low titanium ferrosilicon is calculated based on Mn: 0.15-0.25% in the total amount of molten steel. It can be understood that in the calculation process, M3, M4 and M5 are also roughly calculated according to the basic design scheme. They are only temporary data for assisting in determining M2, and under certain conditions (such as when S>0.0030% in the subsequent RH refining station), they are not the actual addition amounts in the subsequent RH refining process.

[0084] Preferably, lime is added first during the steel tapping process, and then sufficient tin ingots are added, that is, lime is added before the tin ingots are added.

[0085] After tapping is completed, slag surface deoxidizer is added to the molten steel.

[0086] (3) RH refining process

[0087] This step is carried out in the RH refining furnace, using a decarburization treatment mode, and is carried out in the order of pre-vacuuming, decarburization, alloying, clean circulation, and vacuum breaking.

[0088] The mass percentage of S in the molten steel when it reaches RH refining is detected, and the values ​​of Δ1 and Δ2 in the chemical composition design scheme are determined to obtain the final chemical composition scheme, so as to facilitate the control of the corresponding alloy addition amount during alloying.

[0089] Specifically, when the molten steel reaches RH refining, S≤0.0075%, and, as mentioned above, when the molten steel reaches RH refining, S≤0.0030%, then Δ1=Δ2=0, which corresponds to the chemical composition basic scheme, that is, the continuous casting billet finally cast from the molten steel and the final non-oriented silicon steel product meet the chemical composition basic scheme;

[0090] When the molten steel reaches RH refining and 0.0030% < S ≤ 0.0045%, then Δ1 = 0.05% and Δ2 = 0.005%. At this time, it corresponds to the first adjusted design plan: Si: 0.40%, Sn: 0.020%; when the molten steel reaches RH refining and 0.0045% < S ≤ 0.060%, then Δ1 = 0.15% and Δ2 = 0.010%. At this time, it corresponds to the second adjusted design plan: Si: 0.50%, Sn: 0.025%; when the molten steel reaches RH refining and 0.0060% < S ≤ 0.0075%, then Δ1 = 0.25% and Δ2 = 0.020%. At this time, it corresponds to the third adjusted design plan: Si: 0.60%, Sn: 0.035%. The first design plan, the second design plan and the third design plan here are all the final chemical composition plans obtained after adjusting Si and Sn in the basic chemical composition plan. That is, the continuous casting billets finally cast from the molten steel and the final non-oriented silicon steel products meet the final chemical composition plan.

[0091] In a pre-evacuated RH refining furnace, decarburization treatment is carried out on the molten steel to control the mass percentage of C contained.

[0092] After that, according to the mass percentage of S contained in the molten steel when it reaches RH refining, alloying of the molten steel is carried out according to the final chemical composition plan. Specifically: if S ≤ 0.0030% when the molten steel reaches RH refining, then ultra-low titanium ferrosilicon, low titanium ferrophosphorus and metallic manganese are added to the molten steel according to the basic chemical composition plan, that is, M3, M4 and M5 calculated in the previous converter smelting step; if 0.0030% < S ≤ 0.0045% when the molten steel reaches RH refining, then according to the first adjusted design plan, ultra-low titanium ferrosilicon, tin ingots, low titanium ferrophosphorus and metallic manganese are added to the molten steel; if 0.0045% < S ≤ 0.060% when the molten steel reaches RH refining, then according to the second adjusted design plan, ultra-low titanium ferrosilicon, tin ingots, low titanium ferrophosphorus and metallic manganese are added to the molten steel; if 0.0060% < S ≤ 0.0075% when the molten steel reaches RH refining, then according to the third adjusted design plan, ultra-low titanium ferrosilicon, tin ingots, low titanium ferrophosphorus and metallic manganese are added to the molten steel.

[0093] The aforementioned first design plan, second design plan and third design plan all further increase the addition amount of ultra-low titanium ferrosilicon and supplement tin ingots under the condition of the basic chemical composition plan. Regarding the determination method of the addition amounts of ultra-low titanium ferrosilicon, tin ingots, low titanium ferrophosphorus and metallic manganese under these three design plans, the first design plan is taken as an example to illustrate as follows.

[0094] As mentioned above, assuming that the total amount of molten steel in the converter smelting step is M1, and the weight of tin ingot M2 has been added in the converter smelting process, then, in the RH refining process, according to the first design scheme, it is necessary to add ultra-low titanium ferrosilicon, tin ingot, low titanium ferrophosphorus and metallic manganese, the weights of which are set as M3', M2', M4' and M5' respectively. Then, the weight of the tin ingot M2' that needs to be added at this time is calculated by taking (M1+M2+M3'+M2'+M4'+M5') as the total amount of molten steel, the mass percentage of Sn in the total amount of molten steel as 0.020% (that is, Sn in the non-oriented silicon steel product: 0.020%), and the weight of the tin ingot M3' that needs to be added at this time is calculated by taking the mass percentage of Sn in the total amount of molten steel as 0.020%. The weight M3' of ultra-low titanium ferrosilicon is calculated based on the mass percentage of Si in the total amount of molten steel being 0.40% (i.e., Si in the non-oriented silicon steel product: 0.40%), the weight M4' of low titanium ferrophosphorus is calculated based on the mass percentage of P in the total amount of molten steel being 0.04-0.06% (i.e., P in the non-oriented silicon steel product: 0.04-0.06%), and the weight M5' of ultra-low titanium ferrosilicon is calculated based on the mass percentage of Mn in the total amount of molten steel being 0.15-0.25% (i.e., Mn in the non-oriented silicon steel product: 0.15-0.25%). Subsequently, sufficient amounts of ultra-low titanium ferrosilicon, tin ingots, low titanium ferrophosphorus and metallic manganese are respectively added to the molten steel according to the calculated results.

[0095] After alloying, the net circulation is more than 7 minutes, and then the steel is tapped.

[0096] In the present invention, no desulfurizing agent is added in the RH refining process, that is, the desulfurization treatment in the RH refining process in the prior art is eliminated. It can be seen that the present invention, through the design of chemical composition and the improvement of the production method, breaks with the traditional technology and relaxes the upper limit requirement of S content to 0.0080%, which not only ensures the magnetic properties, strength and welding performance of non-oriented silicon steel, but also reduces the difficulty of S control in processes such as molten iron desulfurization, converter smelting, and RH refining. In particular, the RH refining process does not require desulfurization treatment, which solves the problem of desulfurizer erosion on the RH refining furnace immersion tube in the prior art, improves the service life of the RH refining furnace immersion tube, reduces production costs, and avoids the impact of equipment damage on the working sequence.

[0097] (4) Continuous casting process

[0098] The steel tapping from the RH refining process (i.e. the final molten steel obtained after steelmaking) is prepared into continuous casting billets using continuous casting equipment. The specific operations of this continuous casting process can be achieved using existing feasible continuous casting technologies and will not be described in detail.

[0099] (5) Hot rolling process

[0100] The continuous casting billet is sequentially subjected to the steps of continuous casting billet heating, intermediate billet rolling, finish rolling and coiling to obtain a hot coil.

[0101] The heating temperature of the continuous casting billet is 1130-1160°C and the holding time is ≥180min, and the thickness of the intermediate billet is 35-40mm. In this way, while avoiding the extension of heating time, increase of rolling force, increase of production difficulty, reduction of production efficiency and increase of production cost caused by low-temperature rolling, low-temperature rolling can prevent the solid solution of precipitates such as MnS in the steel during the heating process, thereby further ensuring the magnetic properties of the non-oriented silicon steel product.

[0102] The finishing temperature is 865±15°C. When the Si content is less than 1.7%, an austenite-ferrite phase transition occurs during the hot rolling process. Generally, when the Si content is 0.35%, the phase transition temperature is 880-910°C, and as the Si content increases, the phase transition temperature increases. Due to heat loss during the rolling process, the finishing temperature is generally controlled between 800-920°C. Moreover, for high silicon steel, due to the high phase transition temperature, finishing rolling between 800-920°C is all rolling in the ferrite region. Therefore, in order to obtain coarse grains, the finishing temperature is usually as high as possible. However, for the non-oriented silicon steel of the present invention, controlling the finishing temperature at 865±15°C can avoid the finishing pass being in the austenite region, thereby avoiding the deterioration of magnetic properties due to the phase transition to fine grains after rolling, and can ensure that the finishing pass is rolled in the two-phase region or the ferrite region to ensure the formation of coarse grains and optimize the magnetic properties.

[0103] The coiling temperature is 680℃±20℃, which is conducive to the growth of grains during the coiling process, improves the magnetic properties, and avoids the formation of iron oxide scale that is difficult to pickle.

[0104] The thickness of the hot rolled coil is 2.70±0.1mm. The hot rolled thickness affects the cold rolled deformation. The thinner the hot rolled thickness, the smaller the cold rolled deformation and the larger the grains obtained.

[0105] (6) Acid rolling process

[0106] The hot rolled coil is pickled with HCl, rinsed and dried, and then cold rolled to obtain a hard rolled coil; wherein the cold rolling reduction is 80-83% and the hard rolled thickness is 0.501±0.005 mm.

[0107] Preferably, HCl is used for three-stage pickling, wherein the concentration of the first-stage acid solution is 50-80 g / L and the Fe 2+ Concentration ≤ 130g / L, the concentration of the second-stage acid solution is 90-120g / L and the Fe content in the acid solution is 2+ Concentration ≤90g / L, the concentration of the third-level acid solution is 140-160g / L and the Fe content in the acid solution is 2+ Concentration ≤50g / L;

[0108] During each stage of pickling, the acid solution temperature is 75-85°C, and a silicon steel pickling accelerator is added to the acid solution, with the weight percentage of the silicon steel pickling accelerator in the acid solution being 0.05-0.10%;

[0109] The rinsing water temperature is 45-55°C, and the pickling and rinsing speeds are controlled at 100-180 mpm.

[0110] (7) Annealing process

[0111] The chilled steel strip is annealed in a mixed atmosphere of H2 and N2 in a continuous annealing furnace at an annealing temperature of 850±5°C and an annealing time of 60±5 seconds. The annealed steel strip is cooled by a three-stage cooling method, wherein: the first stage of cooling is slow cooling at a high temperature, cooling the steel strip from the annealing temperature to 800°C at a cooling rate of ≤5°C / s; the second stage of cooling is circulating gas jet controlled cooling, cooling the steel strip after the first stage of cooling further to below 300°C at a cooling rate of ≤15°C / s; the third stage of cooling is circulating water jet cooling, cooling the steel strip after the second stage of cooling further to below 100°C.

[0112] The slower the cooling speed of the steel strip, the more conducive it is to reducing the cooling internal stress of the steel plate. However, if the cooling section is too long, the production cost will be greatly increased. By controlling the three-stage cooling method described above, the residual stress of the steel plate can be effectively controlled to ≤50MPa at low cost, which is beneficial to the control of the plate shape.

[0113] (8) Coating and finishing process

[0114] After cooling to below 100°C during annealing, the steel strip is coated and finished. The specific operations can be accomplished using existing coating and finishing technologies, which will not be described in detail. The resulting non-oriented silicon steel product has a thickness of 0.500±0.005mm. Precise control of the hot coil thickness, hardened thickness (i.e., thickness after acid continuous rolling), and finished product thickness enhances magnetic stability.

[0115] Compared with the prior art, the present invention has the following beneficial effects:

[0116] (1) The non-oriented silicon steel product with a thickness of 0.500±0.005mm prepared by the production method has an iron loss P 1.5 / 50 ≤5.5W / kg, magnetic induction intensity B 5000 ≥1.75, excellent magnetic properties, can meet the needs of small and medium-sized motors for low-grade non-oriented silicon steel, and the production cost is low, which promotes smooth operation;

[0117] (2) By controlling the contents of elements such as C, Nb, V, Ti, Mo, Cr, Ni, Cu, and N, and by optimizing the corresponding relationship between the contents of Si, Sn, and S, the upper limit of the S content can be relaxed to 0.0080%, that is, S≤0.008% is sufficient. On the basis of S≤0.008%, as shown in Examples 3 and 4 below, S>0.0050% or even ≥0.0060% can be allowed, thereby ensuring the stability of the magnetic properties of the non-oriented silicon steel, preventing the magnetic properties from becoming unstable due to the increase in S content, and achieving a stable yield;

[0118] (3) While ensuring the magnetic properties, the strength and welding performance of non-oriented silicon steel are taken into account by correspondingly designing the content of elements such as Mn and P;

[0119] (4) In the production method, the difficulty of the requirement for S content is reduced, and accordingly the difficulty of S control in processes such as molten iron desulfurization, converter smelting, and RH refining is reduced. The requirement for scrap steel in converter smelting is reduced and the cost is reduced. The RH refining process does not require desulfurization treatment, which solves the problem of desulfurizer erosion on the RH refining furnace immersion tube in the prior art, improves the service life of the RH refining furnace immersion tube, reduces production costs, and avoids affecting the working sequence due to equipment damage.

[0120] The detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

[0121] Four examples according to this embodiment and one comparative example not according to this embodiment are selected below to further illustrate the remarkable progress of this embodiment. Of course, these four examples are only a part of the many variations of this embodiment, not all of them.

[0122] Specifically, four embodiments and one comparative example each provide a non-oriented silicon steel, and the production method thereof includes the following steps in sequence: molten iron desulfurization, converter smelting, RH refining, continuous casting, hot rolling, acid continuous rolling, annealing, coating and finishing.

[0123] The chemical compositions of the non-oriented silicon steels in the four embodiments and one comparative example (i.e., the chemical composition of the molten steel after RH refining / the chemical composition of the continuously cast ingot) are measured in percentage by mass and are shown in Table 1. In addition, the mass percentage of S contained in the molten steel when it reaches RH refining during the production processes of the four embodiments and one comparative example is also shown in Table 1.

[0124] [Table 1]

[0125]

[0126] Furthermore, in Examples 1-4 and Comparative Example 1, the finished product thickness, iron loss, and magnetic induction intensity of the non-oriented silicon steels prepared are shown in Table 2, respectively. Also, the metallographic microstructure photographs of the non-oriented silicon steels are shown in Figures 1 to 5, respectively.

[0127] [Table 2]

[0128]

[0129]

[0130] Comparing Examples 1 to 4 with Comparative Example 1, it can be seen that in one embodiment of the present invention, the chemical composition is designed according to the S content of the molten steel when it reaches RH refining, and ultra-low titanium ferrosilicon and tin ingots are added during the alloying of RH refining. The metallographic structure of the obtained non-oriented silicon steel has relatively coarse grains, and the iron loss P is also low when the thickness is 0.5 mm. 1.5 / 50 ≤5.5W / kg, magnetic induction intensity B 5000 ≥1.75, which is better than the magnetic properties of comparative document 1.

[0131] Specifically, the production processes of Examples 1 to 4 and Comparative Example 1 are as follows:

[0132] (1) Molten iron desulfurization process

[0133] In Examples 1-4 and Comparative Example 1, the molten iron desulfurization steps are all as follows: controlling the temperature of the molten iron before desulfurization to be ≥1350°C, and the chemical composition of the molten iron before desulfurization to satisfy, in terms of mass percentage, 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%; controlling the temperature of the molten iron after desulfurization to be ≥1320°C and containing S≤0.0015% by mass, and the slag skimming rate to be ≥98%.

[0134] (2) Converter smelting process

[0135] In Examples 1-4 and Comparative Example 1, the converter smelting steps are all as follows: the steel tapped in the aforementioned molten iron desulfurization step (i.e., the desulfurized molten iron) is transferred into a converter, and clean scrap steel is mixed in the converter, with the added amount of scrap steel accounting for 20-25% of the total of the scrap steel and the molten iron, and the desulfurized molten iron and the scrap steel are smelted into molten steel together in the converter; during the tapping process, lime is first added, and then a sufficient amount of tin ingots is added to the tapped steel liquid according to the Sn content of the final non-oriented silicon steel product: 0.015%; after the tapping is completed, a slag surface deoxidizer is added to the steel liquid.

[0136] (3) RH refining process

[0137] Examples 1-4 and Comparative Example 1, the RH refining process is as follows: The decarburization treatment mode is adopted, and the treatment is carried out in the order of preliminary vacuum pumping, decarburization, alloying, net circulation, and breaking vacuum. After alloying, the net circulation is carried out for more than 7 minutes, and then the steel is tapped; moreover, no desulfurizing agent is added in this RH refining process, that is, desulfurization treatment is not carried out.

[0138] Among them, the differences in the converter smelting process of Examples 1-4 and Comparative Example 1 are only as follows:

[0139] In Example 1, as shown in Table 1, when the molten steel reaches RH refining, S≤0.0030%, and ultra-low titanium ferrosilicon, low titanium ferrophosphorus and metallic manganese are added to the molten steel according to Si: 0.35%, P: 0.04-0.06%, Mn: 0.15-0.25% in the final non-oriented silicon steel finished product. The mass percentages of the actual chemical components of the steel tapped from the RH refining are shown in Table 1;

[0140] In Example 2, as shown in Table 1, when the molten steel reaches RH refining, 0.0030%<S≤0.0045%, and ultra-low titanium ferrosilicon, tin ingot, low titanium ferrophosphorus and metallic manganese are added to the molten steel according to Si: 0.40%, Sn: 0.020%, P: 0.04-0.06%, Mn: 0.15-0.25% in the final non-oriented silicon steel finished product. The mass percentages of the actual chemical components of the steel tapped from the RH refining are shown in Table 1;

[0141] In Example 3, as shown in Table 1, when the molten steel reaches RH refining, 0.0045%<S≤0.060%, and ultra-low titanium ferrosilicon, tin ingot, low titanium ferrophosphorus and metallic manganese are added to the molten steel according to Si: 0.50%, Sn: 0.025%, P: 0.04-0.06%, Mn: 0.15-0.25% in the final non-oriented silicon steel finished product. The mass percentages of the actual chemical components of the steel tapped from the RH refining are shown in Table 1;

[0142] In Example 4, when the molten steel reaches RH refining, 0.0060%<S≤0.0075%, and ultra-low titanium ferrosilicon, tin ingot, low titanium ferrophosphorus and metallic manganese are added to the molten steel according to Si: 0.60%, Sn: 0.035%, P: 0.04-0.06%, Mn: 0.15-0.25% in the final non-oriented silicon steel finished product. The mass percentages of the actual chemical components of the steel tapped from the RH refining are shown in Table 1;

[0143] In Comparative Example 1, although 0.0060%<S≤0.0075% when the molten steel reaches RH refining, ultra-low titanium ferrosilicon, low titanium ferrophosphorus and metallic manganese are still added to the molten steel according to Si: 0.35%, P: 0.04-0.06%, Mn: 0.15-0.25% in the final non-oriented silicon steel finished product. The mass percentages of the actual chemical components of the steel tapped from the RH refining are shown in Table 1.

[0144] (4) Continuous casting process

[0145] In Examples 1-4 and Comparative Example 1, the continuous casting process is: the steel produced in the RH refining process is prepared into a continuous casting billet using a continuous casting device.

[0146] (5) Hot rolling process

[0147] In Examples 1-4 and Comparative Example 1, the hot rolling process is as follows: heating the continuous casting billet, rolling the intermediate billet, finish rolling, and coiling to prepare a hot coil.

[0148] The specific values ​​of the heating temperature, holding time, intermediate billet thickness, final rolling temperature, coiling temperature, hot coil thickness, etc. of each continuous casting billet of Examples 1-4 and Comparative Example 1 are shown in Table 3.

[0149] (6) Acid rolling process

[0150] In Examples 1-4 and Comparative Example 1, the acid continuous rolling process is:

[0151] The hot rolled coils were pickled in three stages using HCl, wherein the concentration of the first stage acid solution was 50-80 g / L and the Fe 2+ Concentration ≤ 130g / L, the concentration of the second-stage acid solution is 90-120g / L and the Fe content in the acid solution is 2+ Concentration ≤90g / L, the concentration of the third-level acid solution is 140-160g / L and the Fe content in the acid solution is 2+ Concentration ≤ 50g / L; During each stage of pickling, the acid solution temperature is 75-85℃, and a silicon steel pickling accelerator is added to the acid solution, with the weight percentage of the silicon steel pickling accelerator in the acid solution being 0.05-0.10%;

[0152] After rinsing and drying, cold rolling is performed to obtain hard rolled coils; wherein, the rinsing water temperature is 45-55°C, and the pickling and rinsing speeds are controlled at 100-180 mpm. The cold rolling reduction ratios and hard rolled thicknesses of Examples 1-4 and Comparative Example 1 are shown in Table 3, respectively.

[0153] (7) Annealing process

[0154] In Examples 1-4 and Comparative Example 1, the annealing process is as follows: the chilled steel strip is annealed in a mixed atmosphere of H2 and N2 in a continuous annealing furnace. The annealing temperature and annealing time are shown in Table 3, respectively. The annealed steel strip is cooled by three-stage cooling, wherein: the first stage of cooling is slow cooling in a high-temperature stage, in which the steel strip is cooled from the annealing temperature to 800°C at a cooling rate of ≤5°C / s; the second stage of cooling is circulating gas jet-controlled cooling, in which the steel strip after the first stage of cooling is further cooled to below 300°C at a cooling rate of ≤15°C / s; and the third stage of cooling is circulating water jet cooling, in which the steel strip after the second stage of cooling is further cooled to below 100°C.

[0155] [Table 3]

[0156]

[0157] (8) Coating and finishing process

[0158] In Examples 1-4 and Comparative Example 1, the coating and finishing steps are as follows: the steel strip cooled to below 100° C. during annealing is subjected to coating and finishing, and the thickness of the final non-oriented silicon steel product is shown in Table 2.

[0159] In summary, it can be seen from the comparison between Examples 1-4 and Comparative Example 1 that the non-oriented silicon steel product with a thickness of 0.500±0.005mm prepared by the production method of this embodiment has an iron loss P 1.5 / 50 ≤5.5W / kg, magnetic induction intensity B 5000 ≥1.75, excellent magnetic properties; the RH refining process does not require desulfurization treatment, which solves the erosion of the desulfurizer on the RH refining furnace immersion tube in the existing technology, prolongs the service life of the RH refining furnace immersion tube, reduces production costs, and avoids affecting the working sequence due to equipment damage.

[0160] It should be noted that Experimental Example 1-4 is only an example in this embodiment, and this embodiment is not limited to being implemented in accordance with Experimental Examples 1-4. Without departing from the technical purpose of this embodiment, other implementations different from the Experimental Examples should be included in the scope of protection of the present invention.

Claims

1. A production method of non-oriented electrical steel, characterized in that, it is prepared by the processes of hot metal desulfurization, converter smelting, RH refining, continuous casting, hot rolling, pickling and tandem cold rolling, annealing, coating and finishing to obtain a non-oriented electrical steel finished product that meets the following chemical composition design scheme; the said chemical composition design scheme is by mass percentage: C ≤ 0.003%, S ≤ 0.008%, Si: 0.35% + Δ1, Mn: 0.15 - 0.25%, P: 0.04 - 0.06%, Sn: 0.015% + Δ2, 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 rest is Fe and inevitable inclusions; wherein, when the molten steel reaches RH refining and S ≤ 0.0030%, then Δ1 = Δ2 = 0; when the molten steel reaches RH refining and 0.0030% < S ≤ 0.0045%, then Δ1 = 0.05% and Δ2 = 0.005%; when the molten steel reaches RH refining and 0.0045% < S ≤ 0.060%, then Δ1 = 0.15% and Δ2 = 0.010%; when the molten steel reaches RH refining and 0.0060% < S ≤ 0.0075%, then Δ1 = 0.25% and Δ2 = 0.020%.

2. The production method of non-oriented electrical steel according to claim 1, characterized in that, The thickness of the non-oriented silicon steel product is 0.500±0.005mm, and its iron loss P 1.5 / 50 ≤5.5W / kg, magnetic induction intensity B 5000 ≥1.

75.

3. The production method of non-oriented electrical steel according to claim 1, characterized in that, During the hot metal desulfurization process: Control the temperature of the hot metal before desulfurization ≥ 1350°C and the chemical composition meets, by mass percentage, 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%. Desulfurize the hot metal before desulfurization to control the temperature of the hot metal after desulfurization ≥ 1320°C and the S content ≤ 0.0015% by mass percentage; During the converter smelting process: Mix the desulfurized hot metal with scrap steel and smelt it in the converter. During the tapping process, add sufficient tin ingots to the tapped molten steel according to the basic chemical composition scheme with Δ1 = Δ2 = 0 in the said chemical composition design scheme; after tapping, add a slag surface deoxidizer to the molten steel; During the RH refining process: Detect the mass percentage of S contained in the molten steel when it reaches RH refining, and determine the values of Δ1 and Δ2 in the said chemical composition design scheme to obtain the final chemical composition scheme. In the RH refining furnace with pre-evacuation, carry out decarburization treatment on the molten steel, and then add ultra-low titanium ferrosilicon, tin ingots, low-titanium ferrophosphorus and metallic manganese to the molten steel according to the said final chemical composition scheme. Tap the steel after a net circulation of more than 7 minutes; no desulfurizing agent is added during the RH refining process.

4. The production method of non-oriented electrical steel according to claim 3, characterized in that, During the hot metal desulfurization process, the slag removal rate of the hot metal after desulfurization is controlled to be ≥ 98%; 5. The production method of non-oriented electrical steel according to claim 3, characterized in that, During the converter smelting process, the amount of scrap steel added accounts for 20-25% of the total of scrap steel and molten iron. During the steel-making process, lime is added first and then tin ingots.

6. The method for producing non-oriented silicon steel according to claim 1, It is characterized in that During the hot rolling process: the continuous casting billet is sequentially subjected to continuous casting billet heating, intermediate billet rolling, finish rolling, and coiling to prepare a hot coil, wherein the heating temperature of the continuous casting billet is 1130-1160°C and the holding time is ≥180min, the intermediate billet thickness is 35-40mm, the final rolling temperature is 865±15°C, the coiling temperature is 680°C±20°C, and the hot coil thickness is 2.70±0.1mm.

7. The method for producing non-oriented silicon steel according to claim 1, It is characterized in that During the acid continuous rolling process: the hot coil obtained by hot rolling is pickled with HCl, rinsed and dried, and then cold rolled to obtain a hard rolled coil; wherein the cold rolling reduction rate is 80-83%, and the hard rolled thickness is 0.501±0.005mm.

8. The method for producing non-oriented silicon steel according to claim 7, It is characterized in that HCl is used for three-stage pickling, wherein the concentration of the first-stage acid solution is 50-80 g / L and the Fe 2+ Concentration ≤130g / L, the concentration of the second-stage acid solution is 90-120g / L and the Fe 2+ Concentration ≤90g / L, the concentration of the third-level acid solution is 140-160g / L and the Fe 2+ Concentration ≤50g / L; During each stage of pickling, the acid solution temperature is 75-85°C, and a silicon steel pickling accelerator is added to the acid solution, and the weight percentage of the silicon steel pickling accelerator in the acid solution is 0.05-0.10%; The rinsing water temperature is 45-55°C, and the pickling and rinsing speeds are controlled at 100-180 mpm.

9. The method for producing non-oriented silicon steel according to claim 1, It is characterized in that During the annealing process: the cold-hardened steel strip is placed in the H 2 and N 2 Annealing is carried out in a mixed atmosphere at a temperature of 850±5°C and an annealing time of 60±5 seconds. The annealed steel strip is cooled by three-stage cooling, wherein: The first stage of cooling is a slow cooling at a high temperature, where the steel strip is cooled from the annealing temperature to 800°C at a cooling rate of ≤5°C / s; The second stage of cooling is controlled by circulating gas injection, and the steel strip continues to cool to below 300℃ at a cooling rate of ≤15℃ / s; The third stage of cooling is circulating water jet cooling, and the steel strip continues to cool to below 100°C.

10. The method for producing non-oriented silicon steel according to claim 1, It is characterized in that During the coating and finishing process, the steel strip cooled to below 100° C. during annealing is coated and finished to obtain a non-oriented silicon steel product with a thickness of 0.500±0.005 mm.

11. A non-oriented silicon steel, It is characterized in that It is prepared by the production method described in claim 1.

12. A method for producing non-oriented silicon steel, It is characterized in that The non-oriented silicon steel product with a thickness of 0.5±0.005 mm is prepared by hot metal desulfurization, converter smelting, RH refining, continuous casting, hot rolling, acid continuous rolling, annealing, coating and finishing. The iron loss P of the non-oriented silicon steel product is 1.5 / 50 ≤5.5W / kg, magnetic induction intensity B 5000 ≥1.75; among them, In the hot metal desulfurization process: The temperature of the molten iron before desulfurization is controlled to be ≥1350°C and the chemical composition is controlled to meet the following conditions by mass percentage: 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 to control the temperature of the molten iron after desulfurization to be ≥1320°C and the S content by mass percentage to be ≤0.0015%; In the converter smelting process: Mix the hot metal after desulfurization with scrap steel and smelt it in a converter. During the tapping process, add sufficient tin ingots to the tapped molten steel according to the basic chemical composition plan. After the tapping is completed, add a slag surface deoxidizer to the molten steel. Among them, the basic chemical composition plan is by mass percentage: 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 rest are Fe and inevitable inclusions; In the RH refining process: In the RH refining furnace with preliminary vacuum pumping, carry out decarburization treatment on the molten steel; After that, according to the mass percentage of S contained in the molten steel when it reaches RH refining, carry out alloying treatment. Among them: if S≤0.0030% when the molten steel reaches RH refining, then add ultra-low titanium ferrosilicon, low titanium ferrophosphorus and metallic manganese to the molten steel according to the basic chemical composition plan; if 0.0030% < S≤0.0045% when the molten steel reaches RH refining, then adjust Si and Sn in the basic chemical composition plan to Si: 0.40% and Sn: 0.020% respectively; if 0.0045% < S≤0.060% when the molten steel reaches RH refining, then adjust Si and Sn in the basic chemical composition plan to Si: 0.50% and Sn: 0.025% respectively; if 0.0060% < S≤0.0075% when the molten steel reaches RH refining, then adjust Si and Sn in the basic chemical composition plan to Si: 0.60% and Sn: 0.035% respectively, and add ultra-low titanium ferrosilicon, tin ingots, low titanium ferrophosphorus and metallic manganese to the molten steel according to the adjusted chemical composition plan; Then, tap the steel after a net circulation of more than 7 minutes. No desulfurizer is added during the RH refining process.

13. An non-oriented electrical steel, characterized in that, it is prepared by using the production method described in claim 12.