Preparation method of electrical steel and electrical steel

Abstract

The invention provides a preparation method of electrical steel and the electrical steel. The method comprises the following steps: smelting molten iron in a converter to obtain converter molten steel, transferring the converter molten steel to a converter steel ladle, and adding a steel ladle modifying agent into the molten steel in the converter steel ladle to change the components of steel ladle top slag; molten steel in a converter steel ladle is subjected to RH vacuum smelting, RH refined molten steel is obtained, in the RH vacuum smelting process, a silicon agent is added firstly, then an aluminum agent is added, and the RH refined molten steel comprises, by mass, not larger than 0.0035% of C, not smaller than 0.30% and not larger than 0.60% of Si, not smaller than 0.25% and not larger than 0.40% of Mn, not smaller than 0.15% and not larger than 0.35% of Al, not smaller than 0.03% and not larger than 0.05% of P, not larger than 0.005% of S, not larger than 0.0030% of N, not larger than 0.0030% of Ti and the balance iron and inevitable impurity elements; the RH refined molten steel is subjected to continuous casting through a crystallizer at the pulling speed of 3.6-5.7 m / min, a casting blank is obtained, and the electromagnetic braking current of the crystallizer ranges from 150 A to 210 A; and the casting blank is subjected to aftertreatment, and the electrical steel is obtained. The surface inclusions, slag inclusions and broken edges of the electrical steel are reduced, and the yield of the electrical steel is increased.

Description

Technical Field

[0001] The present application relates to the field of electrical steel, and in particular to a method for preparing electrical steel and electrical steel. Background Art

[0002] As the core material for rotating machinery, electrical steel boasts excellent low iron loss and high magnetic induction properties. However, with the intensifying competition in the electrical steel market, improving product yield and reducing product costs while maintaining excellent magnetic properties and surface quality have become the key research and development directions for electrical steel. Summary of the Invention

[0003] In view of the above problems, the present application provides a preparation method of electrical steel and electrical steel, aiming to solve the problems of electrical steel inclusions, slag inclusions and edge rot while ensuring good magnetic properties and surface quality, reduce quality loss, improve the yield rate of electrical steel, and reduce product costs.

[0004] In a first aspect, the present invention also provides a method for preparing electrical steel, the method comprising:

[0005] smelting the molten iron in a converter to obtain molten steel and transferring the molten steel to a converter ladle, wherein a ladle modifier is added to the molten steel in the converter ladle to change the composition of the ladle top slag;

[0006] RH vacuum smelting is performed on the molten steel in the converter ladle to obtain RH refined molten steel, wherein, in the RH vacuum smelting, a silicon agent is first added and then an aluminum agent is added, and the RH refined molten steel comprises the following components by mass percentage: C≤0.0035%, 0.30%≤Si≤0.60%, 0.25%≤Mn≤0.40%, 0.15%≤Al≤0.35%, 0.03%≤P≤0.05%, S≤0.005%, N≤0.0030%, Ti≤0.0030%, and the remainder is iron and unavoidable impurity elements;

[0007] RH refined molten steel is continuously cast using a crystallizer at a casting speed of 3.6-5.7 m / min to obtain a cast billet, wherein the electromagnetic braking current of the crystallizer is 150A to 210A;

[0008] The ingot is post-processed to obtain electrical steel.

[0009] In some optional embodiments, the ladle reforming agent includes the following components in mass percentage: Al element: 40%-45%; Al2O3: 15%-20%; SiO2: 5%-10%; CaO: 25%-30%; and the rest is unavoidable impurity content.

[0010] In some optional embodiments, the addition amount of the ladle reformer is 1.60-1.82 kg / t molten steel.

[0011] In some optional embodiments, the amount of silicon agent added is 4.2-8.2 kg / t molten steel, calculated as the amount of silicon element added; and the amount of aluminum agent added is 2.55-5.95 kg / t molten steel, calculated as the amount of aluminum element added.

[0012] In some optional embodiments, the TO content of the molten steel in the converter ladle is 15-20 ppm.

[0013] In some optional embodiments, the cross-sectional width W of the crystallizer satisfies 900 mm < W ≤ 1120 mm, and the electromagnetic braking current is 150 to 170 A; the cross-sectional width W of the crystallizer satisfies 1120 mm < W ≤ 1320 mm, and the electromagnetic braking current is 170 to 190 A. The cross-sectional width W of the crystallizer satisfies 1320 mm < W ≤ 1520 mm, and the electromagnetic braking current is 190 to 210 A.

[0014] In some optional embodiments, the ladle top slag includes the following components in mass percentage: CaO: 26%-32%; SiO2: 12%-18%; Al2O3: 25%-30%; MgO: 5%-8%; FeO: 3%-6%; MnO: 1%-4%, and inevitable impurities.

[0015] In some optional embodiments, RH refined molten steel is continuously cast using a crystallizer at a pulling speed of 3.6-5.7 m / min to obtain ingots, and the continuous casting includes continuously pouring a tundish at a temperature of 1550-1570°C, and using an alkaline covering agent and electrical steel protective slag in the tundish.

[0016] In some optional embodiments, the cast billet is post-processed to obtain electrical steel, including: heating, hot rolling and coiling the cast billet to obtain electrical steel.

[0017] In a second aspect, an embodiment of the present application provides an electrical steel produced by the method of the first aspect.

[0018] In the electrical steel of the embodiment of the present application, a ladle reforming agent is added to the molten steel in the converter ladle to change the composition of the ladle top slag and improve the purity of the molten steel so that inclusions mainly composed of SiO2 can be formed in the molten steel later. Silicon agent is first added and then aluminum agent is added to form inclusions mainly composed of SiO2 in the molten steel, which facilitates the floating of such inclusions and improves the inclusion and slag of the electrical steel. The electromagnetic braking current of the crystallizer is 170A to 190A, which can promote the spreading of protective slag on the edge of the meniscus, reduce the direct friction between the shell and the copper plate, reduce the risk of transverse cracks, solve the problem of edge rot of electrical steel, improve the yield rate of electrical steel, and reduce the cost of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solution of the implementation regulations of this application, the following is a brief introduction to the drawings required for use in the embodiments of this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 A cross-sectional view of a crystallizer according to an embodiment of the present application is shown;

[0021] Figure 2 Shows the appearance of slag inclusion defects on the surface of electrical steel in the comparative example of this application;

[0022] Figure 3 The figure shows the appearance of the edge rot defect of the electrical steel hot coil in the comparative example of the present application. DETAILED DESCRIPTION

[0023] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first" and "second" in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0025] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0026] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0027] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of this application, as well as the overall thickness, length, width, and other dimensions of the integrated device shown in the drawings are merely illustrative and should not constitute any limitation on this application.

[0028] The term "plurality" used in this application refers to two or more (including two).

[0029] As the core material for rotating machinery, electrical steel boasts superior magnetic properties, resulting in higher efficiency. Therefore, low iron loss and high magnetic induction are key development priorities for electrical steel. Reducing product costs to enhance market competitiveness is also a key development direction for electrical steel.

[0030] Based on this, the inventors conducted a lot of research, aiming to improve the problems of slag inclusions and edge rot in electrical steel, reduce quality loss, increase the yield rate of electrical steel, and reduce product costs while ensuring good magnetic properties and surface quality.

[0031] The embodiment of the present application further provides a method for preparing electrical steel, which includes steps 100 to 400.

[0032] Step 100: subjecting molten iron to converter smelting to obtain converter molten steel and transferring the converter molten steel to a converter ladle, wherein a ladle modifier is added to the molten steel in the converter ladle to change the composition of the ladle top slag.

[0033] In step 200, the molten steel in the converter ladle is subjected to RH vacuum smelting to obtain RH refined molten steel, wherein, in the RH vacuum smelting, a silicon agent is added first and then an aluminum agent is added. The RH refined molten steel includes the following components by mass percentage: C≤0.0035%, 0.30%≤Si≤0.60%, 0.25%≤Mn≤0.40%, 0.15%≤Al≤0.35%, 0.03%≤P≤0.05%, S≤0.005%, N≤0.0030%, Ti≤0.0030%, and the rest are iron and unavoidable impurity elements.

[0034] In this step, the silicon agent may be ferrosilicon alloy, and the aluminum agent may be aluminum block.

[0035] In the prior art, aluminum is added first, followed by silicon, resulting in inclusions primarily consisting of high-melting-point Al2O3. This method, however, adds silicon first and then aluminum, shifting the inclusion type from Al2O3 to SiO2. This changes the primary inclusion type, allowing silicon-deoxidized inclusions to float and be removed from the molten steel, thereby reducing the total number of inclusions. This reduction in inclusions improves the steel's plasticity, improving its plasticity and reducing its crack sensitivity, making it less susceptible to cracking under the same tensile and compressive forces.

[0036] Step 300: Continuously cast the RH refined molten steel using a crystallizer at a casting speed of 3.6-5.7 m / min to obtain a cast billet, wherein the electromagnetic braking current of the crystallizer is 150A to 210A.

[0037] It is understandable that RH refining, performed directly after converter smelting, rather than LF refining, avoids the risk of new inclusions introduced during LF refining, which can occur due to electrode heating and slag addition. Skipping LF can reduce this risk, especially for high-grade electrical steels (which require low inclusions), by lowering iron losses and improving magnetic permeability. Reducing inclusions reduces the magnetic domain pinning they cause and improves domain motion. Skipping LF refining shortens the process, reduces costs, and avoids LF overheating. RH treatment results in a uniform temperature for the molten steel, facilitating thin slab continuous casting (a common process for electrical steel), reducing cracking risks, and providing more stable temperature control.

[0038] In this step, the RH refined molten steel can be continuously cast using a crystallizer at a pulling speed within a range of any value selected from 3.6m / min, 3.7m / min, 3.8m / min, 3.9m / min, 4.0m / min, 4.5m / min, 5.0m / min, 5.1m / min, 5.2m / min, 5.3m / min, 5.4m / min, 5.5m / min, 5.6m / min, and 5.7m / min.

[0039] The electromagnetic braking current of the crystallizer can be any value among 150A, 155A, 160A, 165A, 170A, 175A, 180A, 185A, 190A, 195A, 200A, 205A, and 210A.

[0040] Step 400: post-process the ingot to obtain electrical steel.

[0041] In the relevant technology, in RH refined molten steel, C≤0.0035%, which leads to lower viscosity of molten steel, higher fluidity, and faster flow rate of molten steel in the crystallizer. Under the working conditions of high continuous casting speed, the high-speed steel flow can easily break through the protective slag layer and be drawn into the liquid protective slag to form slag inclusions; during continuous casting, the billet shell is easily deformed by stress, and microcracks are formed in the meniscus area; high silicon (0.3%~0.6%) and aluminum (0.15%~0.35%) are easy to react with FeO and MnO in the protective slag to form SiO2 / Al2O3 inclusions, causing the inclusions to accumulate on the meniscus, deteriorating lubrication, and exacerbating slag inclusions and cracks. High pulling speed shortens the solidification time in the crystallizer, and the shell is thinner when it comes out of the crystallizer. The weak edges are prone to cracking and the rotten edges spread. High pulling speed requires stronger electromagnetic braking force, but high silicon steel has poor conductivity and high resistivity, which weakens the braking effect, resulting in poor control of the molten steel flow rate and increased risk of slag rolling, which further aggravates the cracking of weak edges.

[0042] According to the embodiments of the present application, appropriately reducing the electromagnetic braking (EMBr) current can improve the problems of slag inclusion and edge rot on the surface of the hot coil. At high pulling speeds, such as 5.5 to 5.7 m / min, excessive electromagnetic braking current (such as 200 A) will excessively suppress the flow rate of the molten steel, resulting in insufficient fluidity of the molten steel on the meniscus (especially the edge), inability of the protective slag to penetrate evenly, deterioration of lubrication, and causing edge rot. Reducing the current, such as to less than 170 A, can reduce the braking force, and the molten steel can flush the corner areas of the crystallizer at a higher flow rate. The current in the appropriate range can promote the spreading of the protective slag on the edge of the meniscus, reduce the direct friction between the shell and the copper plate, and reduce the risk of transverse cracks (edge ​​rot). Under the appropriate current, the surface flow rate of the molten steel is too slow, and the protective slag layer is easily "captured" by the solidified shell to form slag inclusions. The surface flow rate of the molten steel should be appropriately increased (but turbulence should still be avoided) to dynamically update the protective slag and reduce the involvement of solid slag droplets. The current needs to be reduced to a level that can avoid slag entanglement and the flow rate is not too high, while ensuring lubrication and flow rate.

[0043] In addition, after the current is reduced, the viscosity (e.g., 0.15 Pa·s) and melting point (≈1100°C) of the protective slag are simultaneously optimized to adapt to the RH refined steel liquid with this carbon content and a higher steel liquid flow rate.

[0044] In some optional embodiments, in step 100, the ladle slag is modified to include the following components, by mass percentage: elemental Al: 40%-45%; Al₂O₃: 15%-20%; SiO₂: 5%-10%; CaO: 25%-30%; the remainder being unavoidable impurities. This further reduces the TO content in the ladle slag. The TO content in steel is a measure of molten steel cleanliness. A high TO content indicates a high level of non-metallic inclusions and poor cleanliness, while a low TO content indicates a low level of inclusions and good cleanliness. Originally, the TO content in steel was 25-30 ppm; after optimization, the TO content is reduced to 15-20 ppm. This improves the purity of the molten steel and reduces surface inclusions and slag on electrical steel.

[0045] In some optional embodiments, in step 100, the amount of the ladle reformer added is 1.60-1.82 kg / t molten steel.

[0046] Optionally, the addition amount of the ladle reformer can be any value in 1.60kg / t, 1.61kg / t, 1.62kg / t, 1.63kg / t, 1.64kg / t, 1.65kg / t, 1.66kg / t, 1.67kg / t, 1.68kg / t, 1.69kg / t, 1.70kg / t, 1.71kg / t, 1.72kg / t, 1.73kg / t, 1.74kg / t, 1.75kg / t, 1.76kg / t, 1.77kg / t, 1.78kg / t, 1.79kg / t, 1.80kg / t, 1.81kg / t, or 1.82kg / t of molten steel, or a range of their compositions.

[0047] Compared with before the improvement, the addition amount of ladle top slag modifier increased from 1.09-1.45 kg / t to 1.60-1.82 kg / t molten steel, further reducing the TO content in the ladle slag, improving the purity of the molten steel, and reducing slag inclusions on the surface of electrical steel.

[0048] It can be understood that the ladle modifier is added to the ladle after the steel is produced from the converter and is weighed through the slag silo behind the converter. Due to its low density, it floats on the ladle slag surface and plays the role of mixing and reacting with the ladle slag.

[0049] In some optional embodiments, in step 100, the total oxygen (TO) content of the molten steel in the converter ladle is 15-20 ppm. Alternatively, the TO content of the molten steel in the converter ladle can be any value selected from 15.0 ppm, 15.5 ppm, 16.0 ppm, 16.5 ppm, 17.0 ppm, 17.5 ppm, 18.0 ppm, 18.5 ppm, 19.0 ppm, 19.5 ppm, and 20.0 ppm, or a range thereof.

[0050] In some optional embodiments, the ladle top slag comprises the following components, by mass percentage: CaO: 25%-30%; SiO2: 10%-15%; Al2O3: 20%-25%; MgO: 6%-10%; FeO: 5%-10%; MnO: 3%-6%, as well as unavoidable impurities. By adding a ladle modifier in an appropriate amount and composition, the ladle top slag can be enriched with the above-mentioned components, thereby improving the cleanliness of the molten steel.

[0051] The aforementioned CaO content is the core alkaline component of ladle top slag. The alkalinity (1.5-3.0) determines the slag's desulfurization capacity and inclusion adsorption efficiency. High-alkalinity slag effectively adsorbs inclusions such as [Al2O3] and [SiO2] in steel and promotes desulfurization. The aforementioned SiO2 content works synergistically with CaO to control alkalinity: excessive SiO2 reduces alkalinity and weakens desulfurization capacity. However, an appropriate amount of SiO2 improves slag fluidity, for example, by forming a silicate network, participating in deoxidation reactions and reducing the total oxygen content in molten steel. It reacts with CaO to form liquid calcium aluminates (e.g., CaO·Al2O3), which promote the aggregation and floating removal of Al2O3 inclusions, facilitating inclusion modification and adsorption.

[0052] In some optional embodiments, in step 200, the amount of silicon agent added is 4.2-8.2 kg / t molten steel, based on the amount of silicon element added. In some optional embodiments, in step 200, the amount of aluminum agent added is 2.55-5.95 kg / t molten steel, based on the amount of aluminum element added.

[0053] Aluminum deoxidation process with aluminum additives: Steel produced by aluminum deoxidation contains non-metallic inclusions. The deoxidation reaction products are primarily clustered and massive Al2O3 inclusions. While aluminum deoxidation is highly efficient, it produces high-melting-point alumina. Both clustered and massive Al2O3 inclusions have a high melting point (2050°C), are solid, and appear in clusters, sharp corners, or chains. They are large and cluster-like.

[0054] Silicon deoxidation process of silicon agent: the deoxidation product is CaO-MnO-SiO2-Al2O3. Silicon deoxidation often generates composite oxides, such as manganese silicate MnO·SiO2 or MnO-SiO2-Al2O3 inclusions, which have a low melting point, such as 1200-1400℃; the inclusions are liquid or partially liquid, spherical or elliptical, and the density of the inclusions is 3.5-4.0g / cm 3 , are smaller in size, such as 1-10 μm, and are highly dispersible. The silicon deoxidation process of the silicon agent may contain other oxides (such as CaO and Al2O3), forming complex silicates. These liquid inclusions have good fluidity and are easily floated and removed.

[0055] Therefore, adding the aforementioned silicon additive to the molten steel, followed by the aforementioned aluminum additive, can promote the formation of complex oxides such as CaO-MnO-SiO2-Al2O3 in the molten steel, thereby promoting the floating of inclusions. The addition of these silicon and aluminum additives can, on the one hand, mitigate inclusion defects caused by flocculent flow and alluvial accumulation at the continuous casting nozzle, and, on the other hand, reduce stopper rise during continuous casting, mold level fluctuation, and mold slag entrainment.

[0056] Figure 1 The cross-sectional view of the crystallizer of the embodiment of the present application is shown. Figure 1 The cross section of the molten steel punching the crystallizer can be observed in the figure. By observing the cross section of the crystallizer, the cross section width W can be observed.

[0057] In some optional embodiments, the cross-sectional width W of the crystallizer satisfies 900mm<W≤1120mm, and the electromagnetic braking current is 150 to 170A; the cross-sectional width W of the crystallizer satisfies 1120mm<W≤1320mm, and the electromagnetic braking current is 170 to 190A. The cross-sectional width W of the crystallizer satisfies 1320mm<W≤1520mm, and the electromagnetic braking current is 190 to 210A. The electromagnetic braking current is closely related to the cross-sectional width of the crystallizer. For example, if the current is too high, the liquid surface velocity in the crystallizer is too low, the melting effect of the mold slag is poor, and there is insufficient liquid slag layer thickness to ensure lubrication of the continuous casting billet, resulting in excessive friction in the crystallizer, causing transverse cracks at the corners, and forming edge rot defects after hot rolling. If the current is too low, the liquid steel surface velocity is too high, which in turn makes slag roll-off more likely. Therefore, appropriate electromagnetic braking currents are set for different cross-sectional widths of the crystallizer to avoid excessive friction in the crystallizer, which can cause transverse cracks at the corners, and reduce the formation of edge rot defects after hot rolling.

[0058] Therefore, the electromagnetic braking current can increase the flow rate of molten steel on the basis of the existing technology, promote the melting of the mold protection slag, increase the thickness of the liquid slag layer, and meet the high-speed lubrication requirements of the cast billet in the crystallizer.

[0059] Furthermore, the relationship between the cross-sectional width W of the crystallizer, the electromagnetic braking current and the continuous casting speed is shown in Table 1. Therefore, under the appropriate current, the liquid surface flow rate of the crystallizer can be appropriate, the protective slag melting effect can be stabilized, and the thickness of the liquid slag layer can be ensured to ensure the lubrication of the continuous casting billet, avoid excessive friction in the crystallizer causing transverse cracks in the corners, and reduce the formation of edge defects after hot rolling.

[0060] Table 1

[0061]

[0062]

[0063] In some optional embodiments, step 300 involves continuously casting the RH refined molten steel using a crystallizer at a casting speed of 3.6-5.7 m / min to obtain a cast ingot. Specifically, the process includes: after the molten steel enters the RH, temperature sampling is performed, with the appropriate temperature range being 1600-1610°C. A vacuum operation is then performed to remove the carbon content from the molten steel, reducing the carbon content from 0.02%-0.05% to ≤0.0025%. Ferrosilicon alloy is then added, with an estimated addition amount of 4.2-8.2 kg / t. One minute later, aluminum blocks and ferromanganese are added, with an estimated addition amount of 2.55-5.95 kg / t. The molten steel is recirculated for 5-8 minutes before exiting the station. Before exiting the station, the TO content in the molten steel is measured to be 15-20 ppm. Casting is then performed on the continuous casting platform, resulting in electrical steel.

[0064] In some optional embodiments, RH refined molten steel is continuously cast using a crystallizer at a pulling speed of 3.6-5.7 m / min to obtain ingots, and the continuous casting includes continuously pouring a tundish at a temperature of 1550-1570°C, and using an alkaline covering agent and electrical steel protective slag in the tundish.

[0065] Generally speaking, the production of electrical steel follows a sequence of blast furnace molten iron smelting, desulfurization station treatment, converter smelting, RH refining treatment, and continuous casting. Continuous casting is the process of pouring molten steel into slabs, which requires certain process equipment and other conditions.

[0066] The sulfur content at the desulfurization station is ≤0.0015%, and the outlet temperature is 1250-1350°C. The carbon content at the converter tapping is controlled at 0.030%-0.050%, and the carbon content at the argon station is controlled at 0.025%-0.050%, with the temperature at the argon station being 1610-1630°C. The RH inlet temperature is 1610-1620°C, and the outlet temperature is 1590-1600°C.

[0067] In some optional embodiments, the cast billet is post-processed to obtain electrical steel, including: heating, hot rolling and coiling the cast billet to obtain electrical steel.

[0068] After the continuous casting machine produces the ingot, it is heated to 1100-1150℃ in a heating furnace for hot rolling and rolled to a specification of 2.5-3.0mm. The finishing temperature (FDT) is 800±20℃, and the coiling temperature (CT) is 600±20℃, completing the entire production process of electrical steel from molten iron to hot-rolled coils.

[0069] In a second aspect, an embodiment of the present application provides an electrical steel produced by the method of the first aspect.

[0070] The surface inclusions, slag inclusions and edge rot defects of the hot coil of the electrical steel are improved, and the electrical steel has good mechanical properties.

[0071] Example

[0072] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0073] Example 1

[0074] This embodiment provides an electrical steel including the following components, in percentage by mass: C ≤ 0.0035%, 0.30% ≤ Si ≤ 0.60%, 0.25% ≤ Mn ≤ 0.40%, 0.15% ≤ Al ≤ 0.35%, 0.03% ≤ P ≤ 0.05%, S ≤ 0.005%, N ≤ 0.0030%, Ti ≤ 0.0030%, and the remainder being iron and unavoidable impurity elements.

[0075] This embodiment provides a method for preparing electrical steel, comprising:

[0076] During converter smelting, molten iron is smelted in a converter to produce molten steel, which is then transferred to a converter ladle. A ladle modifier is added to the molten steel in the converter ladle to alter the composition of the ladle top slag. The ladle modifier comprises the following components by mass: Al: 45%; Al₂O₃: 20%; SiO₂: 10%; CaO: 25%; the remainder being unavoidable impurities. The amount of ladle modifier added is 1.7 kg / t of molten steel.

[0077] RH vacuum smelting involves subjecting molten steel from the converter ladle to RH vacuum smelting to produce RH refined molten steel. During the RH vacuum smelting process, silicon additives are added first, followed by aluminum additives. The RH refined molten steel comprises the following components, by mass percentage: C ≤ 0.0035%, 0.30% ≤ Si ≤ 0.60%, 0.25% ≤ Mn ≤ 0.40%, 0.15% ≤ Al ≤ 0.35%, 0.03% ≤ P ≤ 0.05%, S ≤ 0.005%, N ≤ 0.0030%, and Ti ≤ 0.0030%. The remainder is iron and unavoidable impurities. The silicon additive is ferrosilicon, and the aluminum additive is aluminum. The silicon additive dosage is 6 kg / t of molten steel, and the aluminum additive dosage is 4 kg / t of molten steel.

[0078] Continuous casting: RH refined molten steel is continuously cast using a crystallizer at a pulling speed of 5.6 m / min to obtain a cast billet, wherein the cross-section W of the crystallizer is 1150 mm and the electromagnetic braking current parameter is 190 A.

[0079] The cast slabs were post-processed to obtain electrical steel. The post-processing included hot rolling and coiling the slabs to obtain electrical steel. Table 2 shows the chemical composition of the electrical steels of Examples 1-1 to 1-3.

[0080] Table 2

[0081]

[0082] Example 2

[0083] The difference between this embodiment and embodiment 1-1 is that the cross-section of the crystallizer, the pulling speed during continuous casting and the current are slightly different. In embodiment 2-1, the continuous casting pulling speed is 5.2 m / min; in embodiment 2-2, the continuous casting pulling speed is 5.7 m / min. In embodiment 2-3, the cross-section of the crystallizer is 1100 mm, the continuous casting pulling speed is 5.0 m / min, and the electromagnetic braking current parameter is 150 A. In embodiment 2-4, the cross-section of the crystallizer is 1100 mm, the continuous casting pulling speed is 5.4 m / min, and the electromagnetic braking current parameter is 170 A. In embodiment 2-5, the cross-section of the crystallizer is 1480 mm, the continuous casting pulling speed is 4.8 m / min, and the electromagnetic braking current parameter is 170 A. In embodiment 2-6, the cross-section of the crystallizer is 1480 mm, the continuous casting pulling speed is 5.5 m / min, and the electromagnetic braking current parameter is 210 A.

[0084] Example 3

[0085] This embodiment differs from embodiment 1-1 in that the amount of the ladle top slag modifier added to the electrical steel is different: the amount added in embodiment 3-1 is 1.60 kg / t of molten steel, while the amount added in embodiment 3-2 is 1.82 kg / t of molten steel.

[0086] Example 4

[0087] This example differs from Example 1-1 in the amounts of silicon and aluminum added. Specifically, in Example 4-1, the silicon addition amount, calculated as silicon, was 4.2 kg / t of molten steel; and the aluminum addition amount, calculated as aluminum, was 2.55 kg / t of molten steel. In Example 4-2, the silicon addition amount, calculated as silicon, was 8.2 kg / t of molten steel; and the aluminum addition amount, calculated as aluminum, was 5.95 kg / t of molten steel.

[0088] Example 5

[0089] The difference between this embodiment and embodiment 1-1 is that the cross-section W of the crystallizer is 1120 mm and the electromagnetic braking current parameter is 170 A.

[0090] Example 6

[0091] The difference between this embodiment and embodiment 1-1 is that the electromagnetic braking current parameters are different. In embodiment 6-1, the cross-section W of the crystallizer is 1120 mm, the pulling speed of continuous casting is 5.0 m / min, and the electromagnetic braking current parameter is 170 A. In embodiment 6-2, the cross-section W of the crystallizer is 1120 mm, the pulling speed of continuous casting is 5.6 m / min, and the electromagnetic braking current parameter is 190 A; in embodiment 6-3, the cross-section W of the crystallizer is 1150 mm, and the electromagnetic braking current parameter is 200 A. In embodiment 6-4, the cross-section W of the crystallizer is 1480 mm, the pulling speed of continuous casting is 5.0 m / min, and the electromagnetic braking current parameter is 205 A. In embodiment 6-5, the cross-section W of the crystallizer is 1480 mm, the pulling speed of continuous casting is 5.6 m / min, and the electromagnetic braking current parameter is 220 A.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1-1 is that the chemical composition of the electrical steel is different, as shown in Table 3.

[0094] Table 3

[0095]

[0096]

[0097] Comparative Example 2

[0098] The difference between this comparative example and Example 1-1 is that the pulling speed of comparative example 2-1 is 6.2 m / min, and the pulling speed of comparative example 2-2 is 5.0 m / min.

[0099] Comparative Example 3

[0100] This comparative example differs from Example 1-1 in that the amount of ladle top slag modifier added to the electrical steel is different. The amount of ladle top slag modifier added in Comparative Example 3-1 is 12 kg / t of molten steel. The amount of ladle top slag modifier added in Comparative Example 3-2 is 19 kg / t of molten steel.

[0101] Comparative Example 4

[0102] The difference between this comparative example and Example 1-1 is that in comparative example 4, during RH vacuum smelting, the aluminum agent is added first and then the silicon agent.

[0103] Test section

[0104] The magnetic properties, inclusions, and edge rot of 50 batches of electrical steel produced in the examples and comparative examples were tested. The test results are shown in Table 3. The tests are as follows:

[0105] (1) Magnetic performance test method:

[0106] The electrical steel samples of the embodiment and the comparative example were processed into 0.5 mm × 500 mm × 500 mm templates, and the transverse and longitudinal magnetic properties of the templates were measured using a magnetic property tester. The average value of the transverse and longitudinal iron losses was taken as the iron loss detection value, and the average value of the transverse and longitudinal magnetic induction was taken as the magnetic induction detection value.

[0107] (2) Detection method of grade reduction rate caused by inclusions: total weight of the hot coil surface removed and repaired due to inclusions and slag / total weight of production.

[0108] (3) Edge rot rate: the weight of the hot coil with edge rot divided by the total weight of production.

[0109] The test results are shown in Table 4 and Figure 2-3 .

[0110] Table 4 is the test results of the embodiments and comparative examples.

[0111]

[0112]

[0113] Here, the iron loss is the average iron loss when a magnetic flux density of 1.5 T is excited at a frequency of 50 Hz, and the magnetic induction intensity is the average magnetic induction intensity induced in a magnetic field of 5000 A / m.

[0114] As can be seen from Table 4, by adopting the solution of the embodiment of the present application, electrical steel with good magnetic induction performance and low iron loss can be obtained. In addition, compared with the comparative example, the hot-rolled electrical steel of the embodiment has a lower tumbling rate and a lower edge rot rate, thereby improving the yield rate of the electrical steel and improving the economic benefits.

[0115] Figure 2 The appearance of the slag inclusion defect on the surface of the electrical steel of comparative example 1 of the present application is shown; Figure 2 It can be seen that the surface of the electrical steel hot coil has inclusions and slag defects. The reasons for this are: the quality of the molten steel is poor, the purity of the molten steel is not high, which easily leads to the enrichment of fine inclusions on the inner wall of the continuous casting immersion nozzle, blocking the nozzle, causing the nozzle side holes to be of different sizes, different flow rates, and asymmetric steel flow. The area with faster flow rate is prone to slag, resulting in slag inclusion defects on the surface of the electrical steel hot coil; the continuous casting stopper rod rises and falls, and the accumulated inclusions continue to fall off and gather. The large-particle enriched and fallen inclusions are extremely easy to be captured by the primary solidified shell, resulting in inclusion defects on the surface of the electrical steel hot coil; the electrical steel in this comparative ratio has seriously deteriorated its surface quality, resulting in a certain quality loss, affecting the fulfillment of product orders.

[0116] Figure 3 The following figure shows the appearance of the edge rot defect of the electrical steel hot coil in comparative example 1 of the present application. Figure 3It can be seen that the hot-rolled electrical steel has edge rot defects. The reasons for this are: the electromagnetic braking current is too large, the molten steel level flow rate is too low, the heat transfer between the molten steel and the protective slag is low, the protective slag melting efficiency is low, and sufficient liquid protective slag cannot be quickly and effectively provided to fill the gap between the copper plate and the solidified shell. This leads to excessive stress in the continuous casting shell under high-speed operation, forming surface transverse cracks or transverse cracks in the corners, and transverse cracks or edge rot defects after hot rolling. The electromagnetic braking current is too small to control the molten steel flow rate, increasing the risk of protective slag shearing and slag coiling in the crystallizer. Therefore, the appropriate current size can control edge rot without affecting the surface slag coiling defect of the hot-rolled coil.

[0117] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

Claims

1. A method for preparing electrical steel, characterized in that: The method comprises: smelting the molten iron in a converter to obtain molten steel and transferring the molten steel to a converter ladle, wherein a ladle modification agent is added to the molten steel in the converter ladle to change the composition of the ladle top slag; RH vacuum smelting is performed on the molten steel in the converter ladle to obtain RH refined molten steel, wherein, in the RH vacuum smelting, a silicon agent is added first and then an aluminum agent is added, and the RH refined molten steel comprises the following components by mass percentage: C≤0.0035%, 0.30%≤Si≤0.60%, 0.25%≤Mn≤0.40%, 0.15%≤Al≤0.35%, 0.03%≤P≤0.05%, S≤0.005%, N≤0.0030%, Ti≤0.0030%, and the remainder is iron and unavoidable impurity elements; The RH refined molten steel is continuously cast using a crystallizer at a casting speed of 3.6-5.7 m / min to obtain a cast billet, wherein the electromagnetic braking current of the crystallizer is 150 A to 210 A; The cast slab is post-processed to obtain the electrical steel.

2. The method according to claim 1, characterized in that The ladle reforming agent comprises the following components in mass percentage: Al element: 40%-45%; Al2O3: 15%-20%; SiO2: 5%-10%; CaO: 25%-30%; and the rest is unavoidable impurities.

3. The method according to claim 2, characterized in that The addition amount of the ladle reforming agent is 1.60-1.82 kg / t molten steel.

4. The method according to claim 1, wherein Calculated by the amount of silicon element added, the amount of the silicon agent added is 4.2-8.2 kg / t molten steel; calculated by the amount of aluminum element added, the amount of the aluminum agent added is 2.55-5.95 kg / t molten steel.

5. The method according to claim 1, wherein The total oxygen content of the molten steel in the converter ladle is 15-20 ppm.

6. The method according to claim 1, characterized in that The cross-sectional width W of the crystallizer satisfies 900mm<W≤1120mm, and the electromagnetic braking current is 150 to 170A; the cross-sectional width W of the crystallizer satisfies 1120mm<W≤1320mm, and the electromagnetic braking current is 170 to 190A; the cross-sectional width W of the crystallizer satisfies 1320mm<W≤1520mm; the electromagnetic braking current is 190 to 210A.

7. The method according to claim 1, characterized in that The ladle top slag comprises the following components by mass percentage: CaO: 26%-32%; SiO2: 12%-18%; Al2O3: 25%-30%; MgO: 5%-8%; FeO: 3%-6%; MnO: 1%-4%, and inevitable impurities.

8. The method according to claim 1, characterized in that The RH refined steel liquid is continuously cast using a crystallizer at a pulling speed of 3.6-5.7 m / min to obtain a cast ingot. The continuous casting includes continuously pouring a tundish at a temperature of 1550-1570° C., and using an alkaline covering agent and electrical steel protective slag in the tundish.

9. The method according to claim 1, characterized in that The post-processing of the cast billet to obtain the electrical steel comprises: heating, hot rolling and coiling the cast billet to obtain the electrical steel.

10. An electrical steel, characterized in that: It is prepared by the method according to claims 1 to 9.

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