Electrical steel and electrical steel processing

Abstract

Embodiments are directed to an electrical steel composition formed from one or more charges of iron units and prime scrap, wherein the electrical steel formed from the one or more charges has a B50 greater than or equal to 1.58 T and a core loss less than or equal to 13.5 W / kg when tested at 1.0T at 400 Hz.

Description

ELECTRICAL STEEL AND ELECTRICAL STEEL PROCESSINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to and benefit from U.S. Provisional Patent Application No. 63 / 665,509. filed June 28, 2024, U.S. Provisional Patent Application No. 63 / 665,347, filed June 28, 2024, U.S. Provisional Patent Application No. 63 / 665,332, filed June 28, 2024, and U.S. Provisional Patent Application No. 63 / 665,352, filed June 28, 2024. The foregoing patent applications are hereby incorporated by reference in their entirety.BACKGROUND

[0002] This invention relates generally to the field of electrical steel sheet manufacturing, and more particularly embodiments of the invention relate to achieving electrical steel sheet products with the desired final magnetic properties utilizing an electronic arc furnace (EAF) and continuous casting, such as in a mini-mill environment.BRIEF SUMMARY

[0003] The present invention relates to electrical steel sheet having improved magnetic properties formed using EAFs and continuous casting and methods of manufacturing the electrical steel sheets.

[0004] In various applications, such as in electrical motors, lighting ballasts, electrical generators, or the like, it may be desirable to use electrical steel (e.g., sheets, rotors and / or stators formed therefrom, and other components formed from the sheets) that have high saturation, high permeability, and low core loss properties. Moreover, for electrical motors that operate at high frequencies, such as for electrical motors in cars or aircraft, the electrical steel sheets often have thickness less than 0.38mm (e.g., between 0.18 to 0.38 mm, 0.20 to 0.30mm, 0.23mm to 0.27mm, 0. 18 to 0.25mm or the like). For electrical steels, there comes a point in production that improving one or more of the high saturation, high permeability, and low core loss properties becomes a detriment to one or more of these properties, or other properties. As such, the present invention provides an improved electrical steel with improved processing that results in improved properties (e.g., improved saturation, permeability, and / orcore loss). The improved properties of the electrical steel have previously not been achievable utilizing traditional EAF and continuous casting and downstream processing.

[0005] The saturation of the electrical steel is an indication of the highest induction that the steel can achieve. The permeability of the electrical steel is the measure of the ability of the steel to support the formation of a magnetic field within itself and is expressed as the ratio of the magnetic flux to the field of strength. Electrical steel with high permeability allow s for an increased induction for a given magnetic field, and thus, with respect to motor applications, reduces the need for copper windings, which results in lower copper costs. The core loss is the energy wasted in the electrical steel. Low' core loss in electrical steels results in a higher efficiency in the end products, such as motors, generators, ballasts, and the like. Therefore, it may be desirable in many products to use electrical steels with a high ability to support a magnetic field and a high efficiency (e.g., high permeability and low' core loss) if it is not detrimental to the cost of manufacturing or other desirable steel properties.

[0006] Electrical steel is processed with specific compositions, using specific systems, and using specific methods in order to achieve electrical steels with the desired properties, such as saturation, permeability, and core loss, as well as other properties. For example, processing the same composition using different methods will change the resulting properties of the electrical steel, likewise, using different compositions (e.g., even slight changes in the ranges of one or more of the components) but processing the steel in the same way will also change the resulting properties of the electrical steel. As such, in order to achieve the desired properties, it is important to control both the composition of the electrical steel as well as the methods of manufacturing such electrical steel, including the raw materials utilized in the EAF. Moreover, improving one property (e.g., through changes in the composition and / or the processing thereof) may come at the detriment of another property. For example, when increasing the permeability, a higher core loss may result (and vice versa). Consequently, electrical steels are processed with specific compositions using specific methods in order to optimize the desired magnetic properties.

[0007] Electrical steel sheets may be produced by melting one or more charges of material (e.g., scrap steel or iron) in an EAF. refining, tapping the EAF, ladle refining (e.g., ladle transfer, ladle metallurgy furnace (LMF), vacuum degassing (VTD), Vacuum Oxygen Decarburization (VOD), Ruhrstahl-Hausen (RH)), casting (e.g., tundish and caster), heating in a furnace, hot rolling, continuous or batch annealing (e.g., annealing, annealing-pickling, or the like, or pickling-annealing during batch annealing), cold rolling, and annealing (e.g., annealing,annealing and coating, or the like). Alternatively, electrical steel may also be processed from iron ore in a blast furnace, described as integrated production.

[0008] In either case (e.g., a blast furnace, or an EAF) the decarburizer (e.g., vacuum degasser, argon decarburizer, etc.) is used to create a vacuum, or change the pressure, in order to remove the carbon and / or nitrogen (e.g., which may or may not use oxygen lances) from the molten metal.

[0009] The hot rolling process reduces the thickness of the steel sheet and controls the grain structure of the electrical steel. After the hot rolling stage(s) the steel may be annealed and / or pickled in an anneal-pickling continuous annealing line and / or in a batch annealing process. It should be understood that annealing may be performed before or after pickling. During annealing, the steel is heated, and thereafter cooled, to coarsen the structure of the steel to achieve good magnetic properties. The pickling may occur in a bath (e.g., sulfuric, nitric, hydrochloric, other acids, or combinations of these, etc.) either before or after annealing (for continuous or batch annealing) in order to remove scale on the surface of the steel from oxidization. The electrical steel sheet is then cold rolled after annealing, which comprises rolling the electrical steel sheet below the recrystallization temperature. Cold rolling may begin at room temperatures; however, the temperature of the steel sheet may be elevated at the beginning of the cold rolling process, or otherwise rise during cold rolling due to the cold rolling process itself. The cold rolling process increases the strength of the steel, improves the surface finish, and rolls the steel sheet to the desired thickness. The finish and / or final annealing is performed by heating the steel to a specific temperature and letting it cool in order to achieve the desired magnetic properties of the electrical steel sheet. The annealing processes, both before, during, or after cold rolling, may be done via a continuous annealing process. In continuous annealing the sheets of steel are passed through a heating furnace and thereafter cooled in a continuous sheet. The steel may be coated during or after annealing. In some embodiments, such as during a double reduction process (e.g., formed from partial cold rolling steps) batch annealing may be utilized for annealing after cold rolling.

[0010] The processing steps described herein occur under various conditions to produce electrical steel sheets with the desired magnetic properties and physical properties (e.g., thickness, surface finish, etc.). Other steps may also be described herein or otherwise performed in order to achieve the desired magnetic properties.

[0011] In the present invention, scrap steel and / or iron is melted into molten steel in an EAF; the molten steel is tapped into ladles and sent for decarburization and for alloy additions;the steel is transferred into a tundish and continuously cast and heated in a furnace before hot- rolling; the cast steel is hot rolled, annealed and / or pickled (e.g., continuously annealed, batch annealed, or the like, where pickling may occur before annealing for batch annealing processes, or after annealing for continuous annealing processes); the hot-rolled and annealed sheet is cold rolled into sheets having the desired thickness; cold rolled steel sheets are annealed (e.g., continuously annealed, or the like); and the steel sheets are coated.

[0012] To the accomplishment of the foregoing and the related ends, the one or more embodiments comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth certain illustrative features of the one or more embodiments. These features are indicative, however, of but a few of the various ways in which the principles of various embodiments may be employed, and this description is intended to include all such embodiments and their equivalents.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0013] Having thus described embodiments of the invention in general terms, reference will now be made to the accompanying drawings, wherein:

[0014] FIG. 1 provides a process flow for producing electrical steel, in accordance with an embodiment of the invention;

[0015] FIG. 2 is a schematic diagram of an exemplary ladle vacuum degasser used in a method of manufacturing slabs for non-oriented electrical steel sheets in accordance with an embodiment of the invention;

[0016] FIG. 3 is a schematic diagram of an exemplary RH vacuum degasser used in a method of manufacturing slabs for non-oriented electrical steel sheets in accordance with an embodiment of this invention;

[0017] FIG. 4 is an example measurement of the Ti precipitates in a finished annealed sheet in the method for producing a non-oriented electrical steel sheet in accordance with an embodiment of the invention and shows an example of Ti precipitates having a particle size of 30-2000 nm;

[0018] FIG. 5 is an example of measuring the particle size of Ti precipitates in a finish- annealed sheet in the method for producing a non-oriented electrical steel sheet according to an embodiment of the invention and shows an example of Ti precipitates having a particle size of less than 30 nm; and

[0019] FIG. 6 is a graph showing the relationship between the iron loss W10 / 400 and AT (= hot rolling start temperature -TO) in accordance with an embodiment of the invention.DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0020] Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. Furthermore, the ranges discussed herein are inclusive ranges.Section A - Composition of the Electrical Steels

[0021] In embodiments of the present invention, the composition of the electrical steel is preferably C: 0.0050 mass% or less, or 0.0045 mass% or less, 0.004 mass% or less. 0.0035 mass% or less, 0.003 mass% or less, and / or greater than 0.001 mass% and below- any of these values. The composition of the steel may further comprise Si: 2.00-4.50 mass%, or between 2.0 mass% and 4.0 mass%, or between 3.00 and 4.50 mass%, between 3.5 and 4 mass%, between 3.6, 3.7, 3.8 and 4, 4.1, 4.2, 4.3, or 4.4 mass%, or the like. The composition of the steel may further comprise Mn: 2.00 mass% or less, 1.9, 1.8, 1.7, 1.6, 1.5 mass% or less, and / or below any of the foregoing values and above, 0.005, 0.1, 0.3, 0.5, 0.75, 1.0 mass%. The composition of the steel may further comprise Al: 2.50 mass% or less, 2.0, 1.5, 1.0 mass% or less, and / or below any of the foregoing and above 0.0. 0.2, 0.4, 0.5. 0.6, 0.75, 1.0, 1.25, 1.5 mass%. The composition of the steel may further comprise Ti: 0.0100 mass% or less, 0.009, 0.008, 0.007, 0.006, 0.005, 0.004, 0.003, 0.002 or the like mass% or less, and / or below- any of the forgoing and above 0.0, 0.001 mass%. The composition may further comprise P: 0.20 mass% or less, 0.15, 0.10, 0.05, 0.03, 0.02, 0.015, 0.014, 0.013, 0.012, 0.011. 0.010 mass% or less, and / or below any of these values and above 0.0, 0.002, 0.004, 0.006, 0.008, 0.009 mass%. The composition may further comprise N: 0.005 mass% or less, 0.004, 0.003, 0.002, mass% or less, and / or below any of the foregoing and above 0.0, 0.0005, 0.001 mass%. The composition may further comprise O: 0.0050 mass% or less, 0.0020. 0.0015, 0.001, 0.0005 mass%. and / or below any of the foregoing and above 0.0, 0.0001 mass%. The composition may furthercomprise S: less than 0.003 mass%, less than 0.002 mass%, less than 0.0015, 0.001, or 0.0005 mass%, and / or below any of the foregoing and above 0.0 or 0.0001 mass%. The composition may further comprise Sb and / or Sn: in the total amount of 0. 1 mass% or less, 0.05 mass% or less, and / or below any of the foregoing and above 0.0, 0.0005 or 0.01 mass%. As long as the necessary' characteristics are satisfied, the compositions may further comprise, chromium (Cr): less than 5 mass% or less than 1 mass%, copper (Cu): less than 5 mass% or less than 2 mass%, nickel (Ni): less than 5 mass% or less than 1 mass%, molybdenum (Mo): less than 0. 1 mass%, tungsten (W): less than 0.1 mass%, less than 0.05 mass%, or less than 0.02 mass%, cobalt (Co): less than 5 mass% or less than 1 mass%, arsenic (As): less than 0.05 mass%, less than 0.01 mass%, or less than 0.005 mass%, boron (B): less than 0.05 mass%. less than 0.003 mass%, or less than 0.001 mass%, calcium (Ca): less than 0.02 mass% or less than 0.01 mass%, magnesium (Mg): 0.005 mass% or less, 0.003 mass% or less, 0.002 mass% or less, cerium (Ce): less than 0.02 mass%, less than 0.01 mass%, or less than 0.005 mass%, lanthanum (La): less than 0.02 mass%, less than 0.01 mass%, or less than 0.0005 mass%, neodymium (Nd), less than 0.02 mass%, less than 0.01 mass%, or less than 0.005 mass%, bismuth (Bi), less than 0. 10 mass%, less than 0.01 mass%. less than 0.005 mass%, or less than 0.002 mass%. yttrium (Y): less than 0.10 mass%, less than 0.01 mass%, or less than 0.005 mass%, zirconium(Zr) : less than 0. 10 mass% or less than 0.010 mass%, niobium (Nb): less than 0.02 mass%, less than 0.01 mass%, less than 0.005 mass%, or less than 0.001 mass%, vanadium (V): less than 0.1 mass% less than 0.05 mass%, or less than 0.02 mass%, tantalum (Ta): less than 0.1 mass%, less than 0.05 mass%, or less than 0.02 mass%, germanium (Ge): less than 0.1 mass% or less than 0.05 mass%, gallium (Ga): less than 0.1 mass% or less than 0.05 mass%, lead (Pb): less than 0.01 mass%, less than 0.004 mass%, or less than 0.001 mass%, zinc (Zn): less than 0.1 mass% or less than 0.01 mass%.

[0022] Maintaining a level of Si above a threshold reduces high-frequency iron loss and increases specific resistance of the steel. However, higher values of Si make the steel easier to fracture in subsequent cold rolling steps. Thus, a Si content is preferred to be between 2.00 mass% and 4.50 mass% in some embodiments, or between 2.0 mass% and 4.0 mass%, or between 2.50 mass% and 4.50 mass%, or between 2.50 mass% and 4.00 mass%, or between 3.00 mass% and 4.00 mass%, or between 3.5 and 4.00 mass%. Maintaining a level of Mn below a threshold reduces high-frequency iron loss. Maintaining a level of Mn above a certain threshold generates Mn carbide and leads to more high-frequency iron loss, and while higher levels of Mn improve the eddy currents through the finished steel. Mn at higher concentrationsalso reduces the B50 (i. e. , the magnetic flux density in a 5000 A / m magnetic field). Thus, a Mn content is preferred to be 2.00 mass% or less in some embodiments. In other embodiments, the Mn content may be between 0.005 % mass and 1.5 % mass, between 0.005 % mass and 1.0 % mass, between 0.20 mass% and 2.00 mass%, between 0.25 mass% and 2.0 mass%, or between 0.5 mass% and 1.00 mass%. Maintaining higher levels of Al reduces frequency losses but also lowers B50. Furthermore, too much Al leads to embrittlement of the steel and strength issues during cold rolling. Thus, an Al content below 2.50 mass% or less in some embodiments is preferred, or below 2.20 mass%, 2.00 mass%, 1.50 mass%, or 1.00 mass% in other embodiments. Maintaining a level of Ti below a certain threshold avoids the creation of carbides, nitrides, and carbonitrides, and avoids high-frequency iron loss. Furthermore, it prevents the need to have a higher hot rolling temperature, which would otherwise be inefficient. However, Ti levels below a certain threshold become too costly to produce due to the extra refinement necessary. Thus, a Ti content is preferred to be 0.0100 mass% or less in some embodiments. In other embodiments, the Ti content may be between 0.0010 mass% and 0.0100 mass%. between 0.001 mass% and 0.005 mass%, or between 0.002 mass% and 0.004 mass%.

[0023] Maintaining a level of P above a certain threshold embrittles the steel and reduces rollability. However, P levels below a certain threshold become too costly to produce due to the extra refinement necessary. Thus, a P content is preferred to be 0.20% or less in some embodiments. In other embodiments, the P content may be below 0.15 mass%, below 0.100 mass%, between 0.005 mass% and 0.100 mass%, between 0.010 mass% and 0.100 mass%, or between 0.010 mass% and 0.050 mass%. Maintaining a level of N above a certain threshold forms nitride and degrades high-frequency iron loss. Furthermore, when Ti is present in the molten steel, carbonitride is formed with N, leading to further degradation of the iron loss. However, N levels below a certain threshold become too costly to produce due to the extra refinement necessary. Thus, a N content is preferred to be 0.005 mass% or less in some embodiments. In other embodiments, the N content may be below 0.0025 mass%, below 0.004 mass%, between 0.0005 mass% and 0.0040 mass%, between 0.0005 mass% and 0.0030 mass%, or between 0.001 mass% and 0.0025 mass%.

[0024] Maintaining a level of S above a certain threshold forms fine sulfide and degrades iron loss. Furthermore, it may lead to Mn precipitation and subsequent high frequency iron loss. However, S levels below a certain threshold become too costly to produce due to the extra refinement necessary. Thus, a S content is preferred to be 0.0030 mass% orless in some embodiments. In other embodiments, the S content may be below 0.0020 mass%, below 0.0010 mass%, between 0.0004 mass% and 0.002 mass%. between 0.0004 mass% and 0.001 mass%, or between 0.001 mass% and 0.002 mass%.

[0025] Other additives and / or impurities may exist in the slab or strip, such as Sn and / or Sb, which improve the texture and magnetic properties of the steel, one or more of which may be added up to 0. 100 mass%, between 0.001 mass% and 0. 100 mass%, between 0.005 mass% and 0. 100 mass%, or between 0.010 mass% and 0. 100 mass%.

[0026] Ca and Mg may be added because they are elements that fix S as sulfide and contribute to improvement of iron loss. In order to obtain the above effect, 0.0005 mass% or more of Ca and Mg, respectively, may be added. On the other hand, when Ca and Mg are added excessively, inclusions are formed and manufacturability is impaired. Therefore, the upper limit of Ca may be 0.020 mass% or 0.010 mass% and the upper limit of Mg may be 0.0030 mass% or 0.0050 mass%.

[0027] Ce, La, Nd, and Y are all elements that fix S as sulfide and contribute to the improvement of iron loss, and are therefore may be added. In order to obtain the above effect, Ce. La. Nd and Y may be added in an amount of 0.0002 mass% or more, respectively. On the other hand, if Ce, La, Nd, or Y is added excessively, inclusions are formed to impair the manufacturability'. Therefore, the upper limits of Ce, La, and Nd may be set to 0.020 mass%, respectively. The upper limit of Y may be set to 0.01 mass%. Alternatively, the upper limits of Ce, La, Nd and Y may be each 0.010 or 0.005 mass%.

[0028] Cu, Ni, and Cr each may have an effect of improving iron loss by increasing the specific resistance of the steel sheet. In order to obtain the above effects, Cu may be added at 0.02 mass% or more, 0.01 mass% or more of Ni, and 0.02 mass% or more of Cr. On the other hand, when Cu, Ni and Cr are added excessively, the surface properties are deteriorated and the iron loss is deteriorated. Therefore, the upper limit of Cu may be 5.0 mass% or 2.0 mass%, the upper limit of Ni may be 5.0 mass% or 1.0 mass%, and the upper limit of Cr may be 5.0 mass% or 1.0 mass%.

[0029] Mo may be added because it promotes the precipitation of Ti at high temperatures and has an effect of contributing to the coarsening of Ti precipitates. In order to obtain the above effect, it may be added at 0.0010 mass% or more. On the other hand, when Mo is added excessively, grain growth is suppressed and iron loss is deteriorated. Therefore, the upper limit of Mo may be 0. 10 mass%.

[0030] Nb, like Ti. may be a harmful element that forms precipitates and deterioratesiron loss, but if Nb is added (mixed) up to 0.020 mass%, the effect of the present invention is not inhibited. The upper limit of Nb may be 0.010 mass%, 0.005 mass%, or 0.001 mass%.

[0031] V, like Ti, is a harmful element that forms precipitates and deteriorates iron loss, but the addition of V up to 0.100 mass% may not inhibit the effect of the present invention. The upper limit of V may be 0.050 or 0.020 mass%.

[0032] Although W, like Ti, may be a harmful element that forms precipitates and deteriorates iron loss, the addition of W up to 0.10 mass% may not inhibit the effect of the present invention. The upper limit of W may be 0.05 or 0.02 mass%.

[0033] Like Ti, Ta may be a harmful element that forms precipitates and deteriorates iron loss, but the addition of Ta up to 0.10 mass% may not inhibit the effect of the present invention. The upper limit of Ta may be 0.05 or 0.02 mass%.

[0034] Since Co may have an effect of improving magnetic flux density, it may be added at 0.001 mass% or more of Co. On the other hand, when Co is added excessively, precipitates may be formed and iron loss is deteriorated. Therefore, the upper limit of Co may be 5.0 or 1.0 mass%.

[0035] B may be a harmful element that segregates to grain boundaries, inhibits grain growth, and deteriorates iron loss, but the effect of the present invention may not be inhibited even if it is added up to 0.050 mass%. The upper limit of B may be 0.010 mass%, 0.0030 mass%, or 0.0010 mass%.

[0036] Although Pb may be a harmful element that forms fine precipitates and deteriorates iron loss, the addition of Pb up to 0.0100 mass% may not inhibit the effect of the present invention. The upper limit of Pb may be 0.0040 mass% or 0.0010 mass%.

[0037] Zn is preferably added because it may have an effect of suppressing nitriding during the finish annealing. In order to obtain the above effect, Zn may be added in an amount of 0.002 mass% or more. On the other hand, when the amount of Zn added exceeds 0.10 mass%, sulfide is formed and iron loss may be deteriorated. Therefore, the upper limit of Zn may be 0.010 or 0.100 mass%.

[0038] Although As is an element which may be brittle due to grain boundary segregation and lowers the rollability, the addition of As up to 0.050 mass% may not inhibit the effect of the present invention. The upper limit of As may be 0.010 or 0.005 mass%.

[0039] Zr may be a harmful element that forms precipitates and deteriorates iron loss, but the addition of Zr up to 0.10 mass% may not inhibit the effect of the present invention. Therefore, the upper limit of Zr may be 0.01 mass%.

[0040] Although Bi may be a harmful element that forms fine precipitates and deteriorates iron loss, the addition of Bi up to 0.10 mass% may not inhibit the effect of the present invention. The upper limit of Bi may be 0.010 mass%, 0.005 mass%, or 0.002 mass%.

[0041] Ge and Ga are preferably added in an amount of 0.0005 mass% or more because they have an effect of improving the texture and the magnetic characteristics. On the other hand, if Ge or Ga is added excessively, not only the effect is saturated but also the cost may be increased. Therefore, the upper limit of Ge and Ga may be 0. 10 mass% or 0.05 mass%.Section B - Processing of the Electrical Steels

[0042] Returning to the process in Figurel, block 102 illustrates that prime scrap steel and / or virgin iron units may be melted into molten steel in an EAF (e.g., through the use of one or more charges of scrap and / or iron). In other embodiments of the invention other types of furnaces may also be used to produce molten steel from prime scrap steel. The one or more charges used in the EAFs may include in a predetermined ratio of raw materials selected from one or more of prime scrap steel (e.g.. in bundles, home scrap, or other like scrap) and virgin iron units (e.g., iron ore, pig iron, direct reduced iron (DRI), or the like). In particular embodiments, the charges may comprise of a combination of prime scrap and virgin iron units.

[0043] As used herein, “prime scrap steel'’ may refer to scrap steel which may include bundles made of industrial scrap, consisting of clean and / or sorted steel materials generated from manufacturing processes. Prime scrap may also include home scrap, which is steel scrap generated within steel mills during the production process, and may include steel trimmings, offcuts, and other internally generated steel waste.

[0044] In some embodiments, the range of total mass percentage of the virgin iron units (e.g., iron ore, pig iron, DRI, or the like) in the one or more charges may vary between 0 to 70 %, or between 30 to 70%, or between 35 to 65 %, or between 40 and 60 %, or between 45 and 55 %, or otherwise may range between 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, or the like. In some embodiments, the range of total mass percentage of the prime scrap steel (which may include home scrap) in the one or more charges may vary between 30 to 100%, or between 30 to 70%, or between 35 to 65 %, or between 40 and 60 %, or between 45 and 55 %, or otherwise may range between 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, or the like. For example, in one particular embodiment, the one or more charges may include 100% of prime scrap. In another particular embodiment, the one or more charges may include 30% by mass virgin ironunits, and 70% by mass of prime scrap steel. In another particular embodiment, the one or more charges may include 70% by mass virgin iron units, and 30% by mass of prime scrap steel. In another particular embodiment, the one or more charges may include 35% by mass virgin iron units, and 65% by mass of prime scrap steel. In another particular embodiment, the one or more charges may include 65% by mass iron charges, and 35% by mass of prime scrap. In another particular embodiment, the one or more charges may include 60% by mass virgin iron units, and 40% by mass of prime scrap steel. In another particular embodiment, the one or more charges may include 45% by mass virgin iron units, and 55% by mass of prime scrap steel. In another particular embodiment, the one or more charges may include 55% by mass virgin iron units, and 45% by mass of prime scrap steel. In another particular embodiment, the one or more charges may include 50% by mass virgin iron units, and 50% by mass of prime scrap steel. In other embodiments of the invention, molten steel may alternatively be produced from iron ore in a blast furnace.

[0045] The materials utilized in the EAF may be important in controlling the composition of the electrical steels. Traditionally, scrap steel may have various impurities that are detrimental to the resulting properties of the electrical steel. Consequently, the composition of the charges of materials to the EAF may result in improved control of the composition of the electrical steel, and thus, the ultimate properties of the electrical steel. As will be described in detail herein, the reduction of carbon, nitrogen, sulfur, and titanium contents in the molten steel allow for low concentrations thereof in the end product (e.g., the cast non-oriented electrical steel, and thus or the non-oriented electrical steel sheets formed therefrom). The one or more charges in the EAFs may include scrap steel that is not prime scrap steel, but the ratio of the scrap steel that is not prime scrap steel in one or more charges is small to avoid increase of impurities and deterioration of properties of electrical steels.

[0046] As illustrated in block 104 of Figure 1, the molten steel is transferred from the EAF after melting to one or more ladles for further refining (e.g., addition of components, decarburization, deoxidation, denitrification, or the like). The steel from the EAF is transferred through tapping the EAF and transferring the molten steel into a ladle for further processing in an LMF and degassing and / or decarburization in a vacuum degasser. In some embodiments, to reduce carbon, nitrogen, titanium, and / or sulfur contents in the molten steel, the molten steel may be tapped from the electric arc furnace (EAF) without deoxidization. The Ti content (including its oxides) of materials contacting with the molten steel shall be controlled as low as possible. The total input of Ti may be 0.05kg / t-steel or less. The tapping temperature occursin a range of 2700 to 3200°F, or between 2700 and 3000°F, preferably at 2950°F. The oxygen concentration in the molten steel at the tapping ranges from 600ppm to lOOOppm.

[0047] In order to further improve the control of components the composition of the molten steel in the ladle, the slag-contact area of the ladle may be lined with magnesia-based materials or ALCh-basc refractory ty pe materials. A AhCh-base refractory7may be used in the barrel. As used herein, ‘‘refractory materials'’ may refer to refractory bricks, such as “barrel bricks” and / or “slag-line bricks”, or any other material or object used to line a ladle and make contact with the molten steel and / or slag.

[0048] For example, the refractory' materials at the slag line (for example, “slag line bricks”) may contain high purity7MgO, with zero carbon, or may be a Magnesia-Chromite. Additionally, or alternatively, in order to further control the Ti concentration of the steel, which is to be maintained at 0.0100% or less, materials are selected based on a specific composition with a low Ti level as an impurity to the materials. As such, the refractory' materials may contain high purity alumina (fused alumina), with zero carbon content. Consequently, in some embodiments the refractory materials may be a pure alumina and non-spinel refractory material. In some embodiments, the refractory materials may be monolithic (e.g., one piece refractory', such as a cast brick).

[0049] To keep the Ti levels in the steel at the desired concentration of 0.0100% or less, it may be beneficial to reduce the mixing of Ti in the molten steel. In particular, it may be beneficial that the combined Ti levels in (i) the slag before deoxidation (e.g., by an Al- containing substance), (ii) the component-adjusting additive added after deoxidation, and (iii) the temperature-adjusting coolant, be equal to or less than 0.05 kg per ton of molten steel. Since the present steel may have high Al concentrations, much of the Ti oxide that may be present in the slag may be reduced, and Ti is mixed into the steel. Thus, the amount of Ti in the slag may need to be controlled within a suitable range.

[0050] As illustrated in block 106 in Figure 1, in some embodiments, the ladle may be conveyed to a ladle metallurgy7furnace (“LMF”). At the LMF, the molten steel is treated to obtain proper chemical compositions and temperature for the next vacuum treatment. At the LMF, the O2 content of the molten steel may be controlled to 300, 350. 400, 450. 500, 550, 600, 650, 700, or the like ppm, for example by introducing aluminum wire or cone, or other suitable control measures, if necessary7for the O2 content of the molten steel to be at the desired concentrations. Mn may also be added to the molten steel at the tap as an ironmanganese alloy (Fe-Mn) until the desired range of Mn for the grade of steel and itscorresponding magnetic properties is achieved. The temperature of the molten steel is controlled to obtain the target temperature at the end of the next RH, VTD, or VOD,

[0051] As illustrated by block 108 in Figure 108, the molten steel may be moved from the LMF to a degasser for decarburization, deoxidation, and / or denitrification. The decarburization is performed first to remove substantially all of the carbon from the molten steel (e.g., to below 0.005% carbon), and thereafter, alloys may be added to produce the desired composition of the electrical steel. Al and Si are added in the amounts necessary to facilitate the “kill’’ (i.e., deoxidation) removal of oxygen and ensure the desired steel composition is achieved. The decarburized process step may be performed in a vacuum degasser, argon decarburizer, or other like system (e.g., with or without oxygen lances blowing oxygen into the degasser), while the alloying additions may be made after breaking the vacuum.

[0052] During the decarburizing process, the molten steel may be stirred in a reduced atmospheric pressure (e.g., in a vacuum via a vacuum degasser such as a RH vacuum degasser or a ladle vacuum degasser, i.e., a “VTD” or a “VOD”). To stir, an inert gas is blown into the molten steel within the vacuum, such as argon gas or the like. Preferably, the inert gas contains no nitrogen.

[0053] An exemplary ladle vacuum degasser 200 is illustrated in FIG. 2. In embodiments where a ladle vacuum degasser, i.e., a “VTD” or a “VOD” is implemented, the inert gas is typically blown through plugs installed at the bottom of the ladle. Additional O2 may be blown via a top lance to aid in decarburization. As a result, carbon monoxide (CO) gas may be generated in the molten steel, which is subsequently trapped by the slag. This may result in “slag foaming”, which is an undesirable phenomenon that results in wasted material via overflow from the ladle. To counteract this, CaO and or AI2O3 may be added to the ladle during the decarburization process, preferably any time between the beginning up to about 2 / 5ths of the duration of the decarburization process. The CaO and / or AI2O3 may be added to the top of the ladle, creating one or more holes in the slag, which release CO to reduce the foaming and / or prevent further foaming. As show n in FIG. 2, the ladle vacuum degasser may include a ladle pot 2 with alumina-based refractory materials 21 for receiving the molten steel 1 and slag 5 forming thereon, the ladle pot in fluid communication with a nozzle 4 (e.g., a bottom blowing gas blowing pipe), all of which is surrounded by a vacuum tank 3.

[0054] In some embodiments, the CaO and / or AI2O3 is added to the ladle at a constant rate during the decarburization process. In other embodiments, the CaO and / or AI2O3 may be added to the ladle all-at-once. In yet additional embodiments, the CaO and / or AI2O3 may beadded to the ladle split and added at separate times. In some embodiments, the molten steel may be decarburized first with CaO, then subsequently with the addition of AI2O3 or other aluminum after the vacuum is removed.

[0055] An exemplary RH vacuum degasser 300 is illustrated in FIG. 3. In embodiments w here a RH vacuum degasser is implemented, a vacuum chamber may be in fluid communication with one or more snorkels, lancets, or nozzles. The one or more snorkels, lancets, or nozzles may be in fluid communication with gas blowing tubes for supplying the inert gas. With a vacuum applied, the inert gas in is blown from the gas blowing tubes to the one or more snorkels, lancets, or nozzles and into the molten steel. In some embodiments, the inert gas may be blow n at least partially during stirring of the molten steel within the vacuum, with the inert gas being provided at a rate of, for example, between 20 and 50 standard cubic feet per minute ('‘scfm”). In other embodiments, the inert gas may be provided at a rate of between 10 and 60 scfm, betw een 25 and 45 scfm, or between 30 and 40 scfm. How ever, it is to be understood that a suitable vacuum gas flow' rate may depend on the size and shape of the ladle, vacuum chamber, etc. In some embodiments, oxygen gas may be provided through a top blowing lance or otherwise injected to increase the rate at which decarburization occurs. As shown in FIG. 3, the RH vacuum degasser may include a ladle pot 2 with alumina-based refractory materials 21 for receiving the molten steel 1 and slag 5 forming thereon, the molten steel 1 in fluid communication with one or more snorkels 7 of a vacuum chamber 6, and in fluid communication with a circulation gas blowing pipe 8.

[0056] Decarburization may last approximately 5 to 30 minutes, and in particular may last 10, 12, 14, 16, 18, 20, 22, 24, or 28 minutes of time (or fall within a range of any of these values, overlap these values, fall between these values, or fall outside of these values). In some embodiments, chill bars may be used, which are used to absorb heat to provide a controlled temperature for casting as excess heat is generated from the aluminum addition.

[0057] In some embodiments, deoxidation occurs after decarburization and before or during the denitrification and / or desulfurization process. Such deoxidation occurs by adding aluminum-containing components to the ladle, including, for example, aluminum-containing wire, aluminum-containing cones, a combination of both aluminum-containing wire and aluminum-containing cones, or the like. This deoxidation may additionally occur at various other points in the process. Typically, although not required, deoxidation occurs in the ladle through the use of the vacuum degasser. Indeed, in some embodiments, the method of manufacturing the electrical steel sheet may include steel-taking, decarburizing, deoxidizing,denitrifying desulfurizing, and casting, which, in some embodiments, are performed in this order. In other embodiments, other sequences are contemplated.

[0058] In some embodiments, deoxidizing may occur by setting the MgO concentration in the slag prior to deoxidation to 5 mass% or less, 4 mass% or less, 3 mass% or less, or the like, such as to lower the MgO reduction and thereby maintain the Mg concentration in the steel sheet. Should the MgO concentration in the slag exceed 5 mass%, a substance containing CaO and / or A12O3 may be added to the ladle prior to the completion of the decarburization process to reduce MgO to 5 mass% or less, or 4 mass% of less, or 3 mass% or less, or 2 mass% or less, or the like.

[0059] Pressure of the vacuum is generally preferred to be between 0 and 10 Torr, between 2 and 8 Torr, between 4 and 6 Torr, between 5 and 7 Ton, between 6 and 8 Torr, or the like. The temperature may be varied, but is held between approximately 2600 F and 3100 F, 2700 F and 3000 F, 2800 F and 2900 F, or the like. During the denitrification and desulfurization reaction, the molten steel is continuously stirred by blowing an inert gas into the molten steel. The slag, having been formed using CaO and AI2O3 may have additional AI2O3 added (via materials containing AI2O3, such as calcium aluminate pre-melt, white fused or calcined alumina) prior to deoxidation. Such additional AI2O3 should be added as early as possible, such as during the tapping of the electric furnace.

[0060] The controlling of the thickness of the slag may occur as a result of the amount of CaO and / or AI2O3 materials added, and should be greater than or equal to 80, 90, 100, 110, 120mm, or the like mm prior to denitrification and desulfurization.

[0061] In some embodiments, the C / A ratio (the ratio of calcium oxide to alumina) in the formation of slag may be controlled. While a C / A ratio within a specified range is generally favorable for melting slag, the effectiveness of melting slag is influenced not only by this ratio but also by the proximity of C / A to its upper or lower limits. Even if C / A is within the recommended range, optimal slag melting may not occur if it is too close to these limits. Thus, the aforementioned denitrification and desulfurization process C / A (-) between about 0.8 and about 1.4, between about 0.7 and about 1.7, between about 0.9 and about 1.3, or between about 1.0 and about 1.2, such that the slag thickness remains 100mm or more prior to the denitrification and desulfurization process.

[0062] Additionally, or alternatively, it may be desirable to control and / or minimize TiO2 concentrations of the slag by of adjusting C / A (-). Because the refractory materials come into contact with the slag and erode, changes to the C / A (-) of the slag may result in the controlof the level of TiO2 therein. However, even refractory materials that are not otherwise intended to come into contact with the slag may erode into the slag. Thus, minimizing the TiO2 composition of the refractor}’ materials themselves (e.g., as an impurity or otherwise) may also prevent unwanted TiO2 in the slag.

[0063] Erosion of the refractor}’ materials may be reduced if the C / A of the slag is held between 1.0 and 1.4 (as previously described). However, the erosion of the refractory materials may not be completely eliminated. Therefore, a material containing MgO may be added to the ladle prior to denitrification (i.e., after the adding of the Al-containing substance), and the MgO concentration in the slag may be set to 6 mass% or higher, 7 mass% or higher, 8 mass% or higher, 9 mass% or higher, or the like, which may reduce the elution of MgO from the refractor}’ materials.

[0064] Such control may occur by adding CaO and / or AhO? to the ladle from the beginning of decarburization through approximately 40% or 50% through the decarburization. It was found that in the range of C / A (-) between 0.4 and 1.8, or between 0.8 and 1.4, 0.7 and 1.7, or between 1.0 and 1.4, a higher C / A (-) leads to less erosion of magnesia-base refractory materials. Indeed, with C / A outside of the discovered ranges, if the refractory materials include C and / or Ti oxides, the Ti oxide may be reduced by the Al in the steel, and part of the C becomes an unwanted impurity. It was also found that the lower limit of C / A (-) should be set to 0.7 or 1.0 in order to suppress MgO in the slag to the degree that the C / A (-) does not adversely affect the denitrification process, even if MgO is dissolved in the slag. Furthermore, when C / A (-) is high, such as that which is above 1.2 or 1.4, the melting slag ratio decreases with lower temperatures and or dissolving MgO into the slag. A target of between 8 and 10% MgO, or in some embodiments between 6 and 8% MgO, conditions the slag and improves the lifespan of the materials by reducing the chemical interaction between the slag and the materials, although some tests have shown as low as 0% or up to between 9% and 13% MgO with carbonless materials. As such, the target range may occur between 0, 0.5, 1.0, 1.5, 2.0,2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0,12.5, 13.0, 13.5, 14.0, or the like percent MgO.

[0065] The desired properties of the electrical steel sheet may be impaired if the concentration therein of Mg is too high. If metallic Al is added to the slag while the slag contains MgO, the MgO is reduced to Mg or Mg vapor (when it passes into the gas phase), and the steel sheet thus may have an increased concentration of Mg. However, if MgO concentrations of the slag are too low, the refractor}’ materials may erode as a result. Onetechnique for reducing the MgO concentration in the slag to prevent the generation of Mg vapor is to maintain the C / A (-) of the slag to between 0.5 and 0.7. In doing so, Mg vapor generation during Al addition may be suppressed. Thus, in some embodiments, the method for manufacturing the electric steel sheet may include low-cost magnesia refractor}' materials, which denitrification desulfurization is promoted, while the erosion of the refractory' materials and the increase in Mg concentration in the electrical steel is reduced.

[0066] In some embodiments, a magnesium removal treatment may be performed to reduce the Mg concentration in the steel. For example, after the metal Al-containing material is added (e.g., after the dentitrification and / or desulfurization), an agitation treatment may be performed at 5000 Pa or lower, or 4000 Pa or low er, 3000 pa or lower, or the like, for a duration of 5 minutes or higher, 6 minutes or higher. 7 minutes or higher, 10 minutes or higher, or the like.

[0067] In some embodiments, depressurization treatment may be performed by the ladle vacuum degasser having an exhaust system that implements a bag filter. When Mg vapor evaporates from the steel, the Mg vapor may become metallic (i. e. , solid) and adhere to the bag filter during exhaust. Decompression gas that is released after the depressurization treatment may come into contact w ith this Mg in the bag filter and pose a threat of combustion. Thus, it may be beneficial to route the exhaust gas through an exhaust line that circumvents the bag filter (e.g., by switching valve or the like). Additionally, or alternatively, the exhaust gas may be cooled such that the bag filter remains below the ignition temperature of Mg (Air: 420 C, Nitrogen: 490 C) in the decompression gas.

[0068] The temperature of the molten steel at this point may be between 1580°C and 1620°C. For example, in some embodiments the temperature may be 1580°C, 1590°C, 1600°C, 1610°C, or 1620°C (or range between, overlap, or fall outside of these values). The temperature of the molten steel is primarily determined by maximizing the temperature to the point at which the amount of molten slag can be reactive and also avoid the contamination caused by erosion of materials in the ladle, while still allowing for the decrease to a castable temperature in an acceptable time period.

[0069] Indeed, the manufacturing of slabs for non-oriented electrical steel sheets having a high Si concentration, the cost to lower the temperature of the molten steel to a suitable temperature to supply to the caster is high due to the increase in cooling times and the requirement of a large volume of coolant.

[0070] In some embodiments, the liquidous temperature (TLL) of the steel is calculatedby a formula:TLL= 1538-(55(%C)+80(%C)2+ 13(%Si)+4.8(%Mn)+4.3(%Ni)+l .5(%Cr)).The molten steel may be stirred in the ladle to maintain contact with the slag, such as to denitrify and desulfurize the molten steel. The total concentration of S1O2. MnO, and T. Fe in slag may be controlled to not exceed 3.0% mass in the denitrification and desulfurization processing step. The stirring for denitrification may require up to 90 minutes of stirring. However, the stirring may be 15, 20, 30, 40, 50, 60, 70, 80, 100, 120, or the like minutes (or may range between, fall within, or overlap any of these values).

[0071] It shall be appreciated that if the SiCh, MnO, and T.Fe components are at too high of a mass% within the slag, the subsequent introduction of Aluminum-containing materials to reduce such components may prolong the denitrification and desulfurization processes. To avoid such prolonging, in some embodiments, the reduction of SiO2, MnO, and Ti Fe of the slag may occur during the first half of the time required for the denitrification and desulfurization.

[0072] In some embodiments, the stirring energy density is desired to be 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300. 310, 320, 330, 340, 350 W / t or more (or may range between, fall within, or overlap any of these values — for example, between 100 and 270 W / t), and is controlled by the gas flow rate during denitrification and desulfurization.

[0073] The stirring energy' density' E (W / t) of the molten steel can be calculated, for example, by the following formula:E =370.4xGxT / Wx(l-297 / T+ln(l+pxgxH / P))G: blow-in gas flow rate (Nm3 / s)T : molten steel temperature (K)W: weight of molten steel (ton) p : molten steel density (kg / m3) g: gravity (m / s2)H: gas blowing depth (m)P: atmospheric pressure (Pa)

[0074] In order to further control the Ti concentration of the steel, which is to be maintained at 0.0100% or less, three additional variables may be controlled. The sum, byweight, of the amount of Ti in (1) the slag prior to deoxidation, (2) any component adjusting additives, and (3) temperature adjusting coolant, shall be no more than 0.05 kilograms per ton of molten steel.

[0075] As described above, according to the method for manufacturing slabs for nonoriented electrical steel sheets according to this invention, carbon, nitrogen and sulfur in molten steel can be removed to low concentrations while suppressing the erosion of the refractory lined in the ladle in the electric furnace process.

[0076] As illustrated in block 1 10 of Figure 1 , after the LMF and / or degassing, the molten steel in the ladle 204 is transferred to a tundish 206 for casting in a castor 208 (e.g., into slabs, strips, or the like), as illustrated in Figure 2. The tundish 206 may be superheated above the liquidus temperature by 20. 30. 40, 50, 60, 70, 80, or the like °F, and the use of ULC tundish Flux may be required. Such tundish fluxes may include a combination of one or more of CaO, AI2O3, SiCh, and MgO. Such temperatures at the tundish may range between 2700 and 2800°F, between 2600 and 2900°F, or between 2725 and 2775°F. Tundish powder may be used, including acidic covering compounds (e.g., rice ash and / or fly ash) or basic covering compounds (e.g.. MgO-based and active slags).

[0077] The casting step may be classified as a continuous casting step in which the molten steel in continuously cast to produce a slab or strip. Ideally, the slab is 40, 50, 60, 70, 80, 90, 100, 110, 120. 130, 140, 150, 160, or 170mm in thickness (or may range between, overlap, or fall outside of these values). In some embodiments the thickness may range between 40 and 70 mm thick, betw een 45 and 70 mm thick, or 50 to 60 mm thick, with at least one embodiment having 56mm slab thickness. While slab thicknesses below 40mm are contemplated, one limiting factor for slab thicknesses less than 40mm is the resulting inclusion of unwanted oxides due to the fast cooling rate of the thinner slab. Moreover, the nozzle entry size required for processing may result in a flow rate too high to obtain slab thicknesses lower than 40mm. Slab thicknesses are maintained to be less than 170mm to maintain the efficiency and speed of the slab casting process, although slabs at thicknesses larger than 170mm are also contemplated (e.g.. 180, 190, 200, 220 or the like mm).

[0078] In some embodiments, the speed of the caster may be between 120 and 210 inches / minute, between 140 and 190 inches / minute, between 140 and 250 inches / minute, between 150 and 180 inches / minute, between 155 and 175 inches / minute, between 160 and 170 inches / minute, or the like. In other embodiments, the speed of the caster may be between 60 and 120 inches per minute, between 70 and 110 inches per minute, between 80 and 100inches per minute, or the like. Thus, a suitable range of the speed of the caster may be between 60 and 190 inches per minute, between 90 and 180 inches per minute, between 90 and 200 inches per minute, between 90 and 150 inches per minute, or the like. The temperature of the slab is targeted to be between 1800 and 2200°F, between 1900 and 2100°F, between 1925 and 2075°F, between 2000 and 2200°F, between 1950 and 2050°F, between 1975°F and 2025°F, or the like, such temperature being raised or lowered in conditions to accommodate for bowing of the slab and / or desired slab characteristics. To accomplish such, the cooling rate of the slab may be approximately 1 degrees F / sec, approximately 1.5 degrees F / sec, approximately 2.0 degrees F / sec, approximately 2.5 degrees F / sec, approximately 3 degrees F / sec, approximately 4 degrees F / sec, approximately 5 degrees F / sec, approximately 6 degrees F / sec, approximately 7 degrees F / sec, or approximately 8 degrees F / sec.

[0079] During the continuous casting process, mold powders selected to be compatible with the high Al content of the present steel may be continuously fed to molten material to influence the heat transfer from the caster and increase the surface quality of the cast slabs.

[0080] After being cast, the slabs or strips may be heated before hot rolling. The heating apparatus may heat the slabs for hot rolling using an electnc furnace, a gas furnace, an induction furnace, or any combination thereof. For example, the slabs or strips may be heated in a tunnel furnace to maintain the desired temperature of the slab, as illustrated by block 112 of Figure 10. The tunnel furnace may maintain a slab temperature of between 2000 and 2200°F, between 1800 and 2200°F, between 1850 and 2150°F. between 1900 and 2100°F, between 1950 and 2050°F, or the like, for a time of between 8 and 15 minutes, between 5 and 15 minutes, between 10 and 15 minutes, between 12 and 15 minutes, between 8 and 20 minutes, between 8 and 30 minutes, or the like. Upon exiting the tunnel furnace, the slabs or strips may be sent directly to the rolling mill for hot rolling.

[0081] The heating temperature of the slab is generally preferred to remain between 2000°F and 2200°F. Heating temperatures below 2000°F may lead to iron loss increases, while heating temperatures above 2200°F often lead to an increase in scale generation and surface abnormalities.

[0082] As illustrated in block 114 of Figure 1, the steel may be hot rolled in one or more hot rolling steps. The ideal temperature of the slab at the beginning of the hot rolling (e.g., the hot rolling start temperature) was found to be the equilibrium precipitation temperature minus 158F (70°C) or more. When the hot rolling start temperature lower than T0-70 degrees in Celsius (see FIG. 6), magnetic properties are deteriorated because of poorrecrystallization and grain growth during subsequent annealing and grain growth. Furthermore, the equilibrium precipitation temperature (in degrees C) was found to relate to the mass percentage of Aluminum, Titanium, and Carbon in the slab according to the equation:TO = 1898+ 36.5 x ln(Mass% of C)-178.4 x In (Mass% of Al) + 123.3 x ln(Mass% of Ti)Here, In represents the natural logarithm.

[0083] The mechanism of obtaining non-oriented electrical steel sheet with good high frequency iron loss under this hot rolling condition is unknown in detail. However, starting hot rolling at a temperature range where the degree of undercooling of precipitation of Ti carbonitride is small and introducing dislocations into the steel sheet, fine precipitation of Ti carbonitride is suppressed, and as a result, recry stallization and grain grow th are sufficiently generated to improve iron loss.

[0084] The ideal end temperature of the hot rolling is 1400°F or higher, or in some embodiments, 1450°F or higher, or in other embodiments, 1500°F or higher to avoid the iron loss. However, if the end temperature is above 1800°F, the scale is too thick. In embodiments where coiling occurs after hot rolling, the coiling temperature was found to be ideal between 800°F and 1300°F. to improve iron loss but also to prevent excel scale thickness.

[0085] Descaling of the slabs or strips may occur to remove scale from the steel before or during hot rolling. The descaling may occur between 2500 and 3200 psi, between 2600 and 3100 psi, between 2700 and 3000psi, between 2800 and 2900psi. between 2825 and 2875psi, or the like.

[0086] During hot rolling the steel may be rolled to a thickness of the between 1.2mm and 2.7mm, 1.3mm and 2.6mm, 1.4mm to 2.5mm, 1.5mm to 2.4mm, 1.6mm to 2.3mm, 1.7mm to 2.2mm, 1.8mm to 2.1mm, 1.9mm to 2.0mm, or the like. Moreover, the coiling temperature of the steel sheet after hot rolling may range from 900°F to 1300°F, 950°F to 1250°F, 1000°F to 1200°F, 1050°F to 1150°F, 1075°F to 1125°F, or the like.

[0087] As illustrated in block 116 of Figure 1, after hot rolling, the formed sheet may be annealed and / or pickled in an anneal pickle line individually and / or together. In some embodiments, the hot rolled sheet may be subjected to a continuous annealing step to form an annealed hot rolled sheet. The continuous annealing temperature is kept between 700°C and1200°C (1292°F and 2192°F) to promote recry stallization and grain growth, while also preventing the fracture in cold rolling due to excessive temperatures during annealing. In some embodiments where the annealing time is greater than 10 seconds, in order to coarsen precipitates, it may be preferable to keep the annealing temperature betw een 800°C and 1100°C (1472°F and 2012°F), between 900°C and 1000°C (1652°F and 1832°F), between 925°C and 975°C (1697°F and 1787°F), or the like. Annealing time is preferred to be no longer than 60 seconds to avoid Ti carbonitride precipitates and increased iron loss. Alternatively, batch annealing may be performed at block 11 . It should be understood that regardless of the type of annealing, picking may be performed before or after the annealing. For example, in batch annealing embodiments, pickling may be performed prior to the annealing of block 116. In other examples, in continuous annealing embodiments, pickling may be performed after the annealing of block 116.

[0088] The pickling will remove scale (e.g., iron oxide) from the steel sheet. The pickling may occur in a bath (e.g., sulfuric, nitric, hydrochloric, other acids, or combinations of these, etc.) in order to remove scale on the surface of the steel from oxidization. In some embodiments, prior to entry into the pickling bath, the steel sheet may be pre-heated to avoid temperature shock and subsequent breakage. Accordingly, in some embodiments, the temperature of the steel sheet may be raised, prior to entry7, to above 100°F but below7the boiling point of the bath. In some embodiments, pickling occurs in a bath held at a temperature between 150°F and 190°F, or between 160°F and 180°F, or between 165 °F and 175 °F, or between 168°F and 172°F. The amount of time that the steel sheet is held in the bath (i.e., “residence time”) will dictate the level of scale removal. In some embodiments, the residence time is between lOseconds and 200seconds.

[0089] As illustrated in block 118 of Figure 1, after the annealing and / or pickling, a cold rolling step may be performed to result in thinner sheets in one or more cold rolling passes through one or more sets of cold rolls 214. One or more edge heaters may be used to heat the edges during cold rolling. The cold rolling may result in a final sheet thickness produced between 0.0. 18 to 0.38 mm, 0.20 to 0.35 mm, 0.22 to 0.32 mm, 0.24 to 0.26 mm, 0.26 to 0.28 mm, 0.29 to 0.31 mm, or the like.

[0090] Finally, as illustrated by block 120 in Figure 1, after cold rolling the annealed hot-rolled sheet, a continuous finish annealing may be performed on the cold-rolled sheet (e.g., after cleaning, or the like). Various parameters of the finishing annealing process may be adjusted to result in the desired magnetic properties. Accordingly, the annealing temperatureis targeted to be above 800°C, 825°C, 850°C, 875°C, 900°C, 925°C, 950°C, or in some embodiments above 970°C, to reduce iron loss, and below 1000°C, 1025°C, 1050°C. 1100°C, 1150°C, or 1250°C to avoid coarse grain sizes. The annealing time is kept between 2 seconds and 120 seconds for similar reasons.

[0091] It may be beneficial to suppress the fine precipitation of Ti. By suppressing the fine precipitation of Ti, recry stallization and grain growth are promoted in the hot-rolled sheet annealing and finishing annealing process, and good iron loss can be obtained. Therefore, the particle diameter of the Ti precipitate present in the steel sheet after finish-annealing may be 30 nm or more. On the other hand, if the Ti precipitate becomes too coarse, it may cause surface defects or rupture in cold rolling. Therefore, the particle diameter of the Ti precipitate is preferably 2000 nm or less.

[0092] The particle diameter of the Ti precipitates can be determined by measuring the square root of the major axis diameter and the minor axis diameter of the precipitates confirmed to contain Ti by, for example, TEM analysis or SEM analysis having a component analysis function, for example, forlO or more than 10 precipitates, and using the average value thereof (as shown in FIG. 4). For example, FIG. 4 shows an example of measuring the particle size of Ti precipitates in a finish-annealed sheet and shows an example of Ti precipitates having a particle size of 30-2000 nm. FIG. 5 is a measurement example of the particle size of Ti precipitates in the finish-annealed sheet and shows an example of Ti precipitates having a particle size of less than 30 nm.

[0093] In some embodiments, and as illustrated in block 122 of Figure 1, a coating may be added to the electrical steel sheet. The coating may be added by running the sheet through a bath or rolling a coating onto the sheet when passing the sheet through a set of coating rolls 218, as illustrated in Figure 2. The coating may be applied to the sheet because finished sheets or parts formed therefrom may stick together such that they may not be separated if the sheet does not have a coating. Different types of coatings may be applied to the electrical steel sheets depending on the needs of the customer.

[0094] The desired properties (e.g., saturation, permeability, and core loss) produced by the composition and processing conditions of the manufacturing process of the electrical steel produce the desired grain sizes and / or crystalline structure. The compositions and process conditions, and the resulting grain sizes and / or crystalline structure of the electrical steels produced using the present invention described herein, for achieving the desired magnetic properties, are described below in more detail in contrast to the traditional processes used forcreating electrical steels and the associated magnetic properties obtained from the traditional processing methods.

[0095] The electrical steel sheets typically have a grain size in the range of 70 to 150 microns. The grain size of electrical steel impacts its magnetic properties, in particular the B50 parameter. Finer grain sizes lead to improved permeability, which in turn reduces core losses at higher frequencies. A smaller grain size in the present invention helps to create high permeability in the electrical steel because it is easier to magnetize smaller domain structures. Magnetic domain structures are regions within the grains that have the same magnetic orientation. The boundary' (e.g., walls) of the domains move when an applied magnetic field changes size or direction.

[0096] As it pertains to core loss, overly large grain sizes result in higher losses at higher frequencies (because of long paths for domain travel), while too fine of a grain size causes hysteresis. Put differently, there is an optimal grain size larger than that which causes hysteresis, but smaller than that which results in higher losses as higher frequencies. The smaller the grain size, the smaller the magnetic domain structure and preferred crystallographic texture, and thus, the easier it is to support the magnetic field. Therefore, the permeability of the magnetic structure is increased. Alternatively, a smaller grain size may have a negative effect on the core loss, that is, the smaller the grain size the greater the hysteresis portion of core loss realized in the electrical steel. At the lower levels of grain size, the increased core loss may not be ideal for some electrical steels depending on the products in which they are used. It shall be appreciated that the correlation between B50 and grain size is not a straightforward cause-and-effect relationship; increased annealing temperature and duration leading to larger grain size can disrupt the favorable grain texture (cry stallographic orientation), especially considering the anisotropic nature of BCC iron with orientations more conducive to B50

[0097] As will be described in further detail herein, the core loss W10 / 400 of the electrical steel produced by the process described herein, when tested on a steel sheet having a final thickness (i.e., after cold-rolling) of 0.30mm or less, or 0.25mm or less, is below 13.5 W / kg, below 13.0 W / kg, or below 12.5 W / kg. It shall be appreciated that W10 / 400 is the core loss at 400Hz, lT(=10kG) when the magnetic flux sine wave is excited. In some embodiments, the magnetic flux density is a B50 of at least 1.58 T. In other embodiments, the magnetic flux density is a B50 of at least 1.60 T.Section C - Examples of the Steel with Respect to the Ladle

[0098] A description will now be given of Embodiment 1 regarding a method for manufacturing slabs for non-oriented electrical steel sheets according to this invention. In this embodiment, an example of a decarburization process using a ladle vacuum degasser will be described. In this embodiment, about 150 tons of molten steel having a C concentration of 0.02-0.06 mass% was first tapped from an electric furnace into a ladle in a non-deoxidized state. Additives (fluxes) of CaO (CaO: 98 mass%), AI2O3 (Al 2 0 3: 99 mass%), and CaO • AI2O3 (CaO: 55 mass%. AI2O3: 45 mass%) were charged into the ladle. The ladle was lined with MgO-C^Ch bricks (MgO: 60 mass%, C^Os: 25 mass%, TiO2: 0.1 mass%) so that the inner diameter was 2.9 m. After tapping from the electric furnace, vacuum decarburization was carried out for 8-25 minutes in a ladle vacuum degasser. CaO and / or AI2O3 were added 4 minutes after the start of vacuum decarburization. The amount of CaO added was calculated for C / A (-) to be in the range of 1.0-1.4 by estimating the amount of AI2O3 to be generated by deoxidizing molten steel and slag with Al. As a comparison, decarburization without adding CaO and / or AI2O3 was also carried out. After the decarburization process, the amount of metallic Al to meet the deoxidation and component adjustment was added, and the stirring process was carried out by blowing an inert gas into the molten steel. After that, the ladle was carried to the tundish for continuous casting, and molten steel was teemed to be cast. Then, at a stage when about half of the molten steel in the ladle was teemed into the tundish, a molten steel sample in the tundish was collected and analyzed. Table 1 shows the process conditions and results. Tables 1A-1C, illustrate these examples of the target compositions that include in range and out of range C / A ratios, slag thicknesses, and / or stirring energy.Table 1ATable IBTable 1C

[0099] As shown in Tables 1 A-1C, Examples 1-10 achieved all the target values of C: 0.0050% or less, S: 0.0030% or less, and N: 0.0050% or less. In Comparative Examples 1-3, where the slag C / A (-) at the start of the denitrification and desulfurization process is out of the range of 1.0 to 1.4, and Comparative Example 4, where the slag thickness at the start of the denitrification and desulfurization process is less than 100 mm, N did not reach the target value. In Comparative Example 4, in which the stirring energy density was small (less than 100 W per ton of molten steel) and the degree of slag oxidation during the denitrification and desulfurization process was high, S also exceeded the target value.

[0100] Further, in Comparative Examples 5 and 6 in which CaO was not added during vacuum decarburization, because slag foaming occurred during decarburization, it was necessary’ to temporarily reduce the degree of vacuum, and as a result the processing time became longer and the molten steel temperature was lowered to such an extent that the molten steel could not be cast. Therefore, in Comparative Examples 5 and 6, the target components of both C and N w ere achieved after the denitrification and desulfurization process, but C and N exceeded the target upper limit because the molten steel was heated up at the LF apparatus in order to raise the temperature to the castable one.

[0101] A description will now be given of Embodiment 2 of a method for manufacturing slabs for non-oriented electrical steel sheets according to this invention. In this embodiment, an example of the decarburization process using the RH vacuum degasser will be described.

[0102] In this embodiment, about 150 tons of molten steel having a C concentration of 0.02-0.05 mass% was first tapped from an electric furnace into a ladle in a non-deoxidized state. Additives (fluxes) of CaO (CaO: 98 mass%), AI2O3 (AI2O3: 99 mass%), and CaO • AI2O3 (CaO: 55 mass%, AI2O3: 45 mass%) were charged into the ladle. The ladle was lined with MgO-Cr2C>3 bricks (MgO: 60 mass%, C^Os: 25 mass%, TiO2: 0.1 mass%) sothat the inner diameter was 2.9 m.

[0103] After the steel was tapped into the ladle, a vacuum decarburization process was carried out for 10-24 minutes at a RH vacuum degasser. After the decarburization process, the ladle was conveyed to a ladle refining apparatus, the amount of metallic Al corresponding to deoxidation and component adjustment was added, and an inert gas for stirring was blown into the molten steel. After that, the ladle was carried to the tundish for continuous casting, and molten steel was teemed into the mold. Then, at a stage when about half of the molten steel in the ladle was teemed into the tundish, a molten steel sample in the tundish w as collected and analyzed. Tables 2A-2C show the process conditions and results.Table 2ATable 2BTable 2C

[0104] As shown in Tables 2A-2C, Examples 11-18 achieved all the target values of C: 0.0050% or less, S: 0.0030% or less, and N: 0.0050% or less. In Comparative Examples 7-9. where the slag C / A (-) at the start of the denitrification and desulfurization process was out of the range of 1 .0 to 1 .4, N did not reach the target value, and in Comparative Examples 10 and 11, where the slag thickness at the start of the denitrification and desulfurization process was less than 100mm, neither N nor S reached the target values.

[0105] A description will now be given of Embodiment 3 regarding a methodfor manufacturing slabs for non-oriented electrical steel sheets according to this invention. In this embodiment, a ladle lined with magnesia carbon brick (MgO: 89 mass%, C: 5 mass%, TiC>2:0.2 mass%) was used and arranged to have an inner diameter of 2.9 m. Denitrification was performed in a ladle refining apparatus.

[0106] Hereinafter, the experimental method will be described. Approximately 130 tons of molten steel was transferred from the electric furnace to the ladle. Additives (flux) of CaO (CaO: 98 mass%). AI2O3 (AhO3:99 mass%) and CaO • AhChCCaO: 55 mass%, AI2O3A5 mass%) were charged into the ladle during the steel tapping. After taking out the steel, the ladle was transported to the ladle refining unit. Vacuum decarburization was carried out for 10-22 minutes in a ladle refining unit. CaO and / or AI2O3 were added 4 min after the start of vacuum decarburization. At that time, CaO and / or AI2O3 were added so that C / A (-) was in the range of 1 .0-1 .4 in consideration of the amount of AI2O3 generated when the molten steel and slag were deoxidized with Al, as will be described. The slag on the ladle molten steel was sampled and analyzed. Metallic Al was added in an amount suitable for deoxidation and composition adjustment. MgO (MgO: 70 mass%, CaO: 8 mass%, SiO2:6 mass%) was added to the slag. The slag on the ladle molten steel was sampled and analyzed. Stirring treatment was performed for 20 minutes by blowing inert gas for stirring into the molten steel. The ladle was conveyed to the tundish for continuous casting, and molten steel was injected to perform casting. When about half of the molten steel in the ladle was poured into the tundish, a sample of the molten steel in the tundish was collected for analysis.

[0107] In some ladles, the same treatment was repeated five times, and the amount of erosion (erosion thickness) of the refractory at the slag contact part was measured. Tables 3A-3B show the processing conditions and results.Table 3ATable 3B

[0108] In Tables 3A-3B, Examples 19-23 and Comparative Examples 12-15 illustrate examples in which the MgO concentration in the slag before the deoxidation treatment is 5% or less and MgO is added after the deoxidation treatment.

[0109] In Examples 19-23. since the MgO concentration in the slag before the deoxidation treatment was 5% or less, the Mg concentration in the steel was 0.0025% (25ppm) or less. In contrast, the MgO concentration in the slag before the deoxidation treatment in Comparative Examples 12 and 13 exceeded 5%, resulting in the Mg concentration in the steel exceeding 0.0030% (30ppm).

[0110] Further, in Examples 19-23, since the MgO concentration in the slag before the deoxidation treatment was 5% or less and MgO was added after the deoxidation treatment, the amount of erosion of the refractory was 20 mm or less. In contrast, in Comparative Examples 14 and 15, although the MgO concentration in the slag before the deoxidation treatment was 5% or less, since MgO was not added after the deoxidationtreatment, the melting loss of the refractory exceeded 40 mm.

[0111] In Examples 19-23 and Comparative Examples 12-15, target concentrations of C, N, S, and Ti achieved the target composition levels, with 0.0050% or less C, 0.0050% or less N, 0.0030% or less S, and 0.0100% or less Ti.

[0112] A description will now be given of Embodiment 4 regarding a method for manufacturing slabs for non-oriented electrical steel sheets according to this invention. A ladle was used, having been lined with magnesia carbon brick (MgO: 89 mass%. C: 5 mass%, TiO2:0.2 mass%), in an arrangement resulting in an inner diameter of 2.9 m. Denitrification was performed in a ladle vacuum degassing apparatus equipped with an exhaust system that does not pass through a bag filter. About 130 tons of molten steel was transferred from the electric furnace to the ladle. Additives (flux) of CaO (CaO: 98 mass%), AI2O3 (A12O3:99 mass%), CaO • AI2O3 (CaO: 55 mass%, AI2O A5 mass%) and MgO(MgO: 70 mass%, CaO: 8 mass%, SiO2:6 mass%) were charged into the ladle during the steel tapping. After taking out the steel, the ladle was transferred to the ladle vacuum degassing unit. Vacuum decarburization was carried out for 9-20 minutes in a ladle vacuum degasser. CaO and / or AI2O3 were added 4 min after the start of vacuum decarburization. At that time, CaO and / or AI2O3 were added such that C / A (-) was in the range of 1.0-1 .4 in consideration of the amount of AI2O3 generated when the molten steel and slag were deoxidized with Al. Metallic Al was added in an amount suitable for deoxidation and composition adjustment. The slag on the ladle molten steel was sampled and analyzed. Stirring treatment was carried out for 20 minutes by blowing inert gas for stirring into the molten steel. The vacuum tank of the ladle vacuum degassing unit was depressurized, and agitation treatment was carried out by blowing inert gas for agitation into molten steel. The ladle was conveyed to the tundish for continuous casting, and molten steel was injected to perform casting. Once approximately half of the molten steel in the ladle was poured into the tundish, a sample of the molten steel in the tundish was collected for analysis. Tables 4A-4B show the processing conditions and results:Table 4 ATable 4B

[0113] As show n by Examples 24-27 of Tables 4A-4B, since the atmospheric pressure after denitrification desulfurization was 5000 Pa or less and the treatment time was 5 minutes or more, the Mg concentration in the steel was 0.0020% (20ppm) or less. In contrast, in Comparative Examples 16-18, the Mg concentration in the steel exceeded 0.0040% (40ppm) because the atmospheric pressure after denitrification and desulfurization exceeded 5000 Pa. In Comparative Examples 19 and 20, although the atmospheric pressure after denitrification desulfurization was 5000 Pa or less, the Mg concentration in the steel exceeded 0.0030% (30ppm) because the treatment time was less than 5 minutes.

[0114] In Examples 24-27 and Comparative Examples 16-20, C, N, S, and Ti achieved the target levels, with 0.0050% or less C, 0.0050% or less N, 0.0030% or less S, and 0.0100% or less Ti.

[0115] As described above, according to the method of manufacturing a slab for a non-oriented electrical steel plate according to the present invention, denitrification desulfurization can be promoted and an increase in the Mg concentration in the steel can be suppressed while the erosion of the refractory is suppressed in the electric furnace process.

[0116] A description will now be given of Embodiment 5 regarding a method for manufacturing slabs for non-oriented electrical steel sheets according to this invention. In this embodiment, an example of a decarburization process using a ladle vacuum degasser will be described. In this embodiment, about 150 tons of molten steel having a C concentration of0.02-0.04 mass% was first tapped from an electric furnace into a ladle in a non-deoxidized state. Additives (fluxes) of CaO (CaO: 98 mass%). AI2O3 (AI2O3: 99 mass%), and CaO • AI2O3 (CaO: 55 mass%, AI2O3: 45 mass%) were charged into the ladle. The ladle was lined with alumina-based bricks (AI2O3: 90 mass%, SiCh: 9 mass%, T1O2: 0.02 mass%) so that the inner diameter was 2.9 m. After tapping from the electric furnace, vacuum decarburization was carried out for 12-18 minutes in a ladle vacuum degasser. CaO and / or AI2O3 were added within 4 minutes after the start of vacuum decarburization. The amount of CaO added was calculated for C / A (-) to be in the range of 0.7-1.0 by estimating the amount of AI2O3 to be generated by deoxidizing molten steel and slag with Al. As a comparison, decarburization without adding CaO and / or AI2O3 was also carried out. After the decarburization process, the amount of metallic Al to meet the deoxidation and component adjustment was added, and the stirring process was carried out by blowing an inert gas into the molten steel. After that, the ladle was carried to the tundish for continuous casting, and molten steel was teemed to be cast. Then, at a stage when about half of the molten steel in the ladle was teemed into the tundish, a molten steel sample in the tundish was collected and analyzed. Table 5 shows the process conditions and results. Tables 5A-5C, illustrate these examples of the target compositions that include in range and out of range C / A ratios, slag thicknesses, and / or stirring energy .Table 5ATable 5BTable 5C[001 17] As shown in Tables 5A-5C, Examples 1 -10 achieved all the target values of C: 0.0050% or less, S: 0.0030% or less, and N: 0.0050% or less. In Comparative Example 1, where the slag C / A (-) at the start of the denitrification and desulfurization process is out of the range of 0.7 to 1.0, and Comparative Examples 2 and 3, where the slag thickness at the start of the denitrification and desulfurization process is less than 100 mm, N did not reach the target value. In Comparative Example 2, in which the stirring energy density was small (less than 100 W per ton of molten steel) and the degree of slag oxidation during the denitrification and desulfurization process was high, S also exceeded the target value.

[0118] Further, in Comparative Examples 4 and 5 in which CaO was not added during vacuum decarburization, because slag foaming occurred during decarburization, it was necessary' to temporarily reduce the degree of vacuum, and as a result the processing time became longer and the molten steel temperature was lowered to such an extent that the molten steel could not be cast. Therefore, in Comparative Examples 4 and 5, the target components of both C and N were achieved after the denitrification and desulfurization process, but C and N exceeded the target upper limit because the molten steel was heated up at the LF apparatus in order to raise the temperature to the castable one. In addition, when the C / A (-) exceeded the upper limit, since a red hot spot area was observed in the steel shell of the ladle, the operation was stopped.

[0119] A description will now be given of Embodiment 6 of a method for manufacturing slabs for non-oriented electrical steel sheets according to this invention. In this embodiment, an example of the decarburization process using the RH vacuum degasser will be described.

[0120] In this embodiment, about 150 tons of molten steel having a C concentration of 0.02-0.05 mass% was first tapped from an electric furnace into a ladle in a non-deoxidized state. Additives (fluxes) of CaO (CaO: 98 mass%), AI2O3 (AI2O3: 99 mass%), and CaO • AI2O3 (CaO: 55 mass%, AI2O3: 45 mass%) were charged into the ladle. The ladle was lined with alumina-based bricks (AI2O3: 90 mass%, SiO2: 9 mass%, TiO2: Trace) so that the inner diameter was 2.9 m.

[0121] After the steel was tapped into the ladle, a vacuum decarburization process was carried out inside a vacuum tank. Although an RH vacuum degasser may bereferred to herein, it shall be appreciated that various types of vacuum decarburization may be used. After the decarburization process, the ladle was conveyed to a ladle refining apparatus, the amount of metallic Al corresponding to deoxidation and component adjustment was added, and an inert gas for stirring was blown into the molten steel. After that, the ladle was carried to the tundish for continuous casting, and molten steel was teemed into the mold. Then, at a stage when about half of the molten steel in the ladle was teemed into the tundish, a molten steel sample in the tundish was collected and analyzed. Table 6 shows the process conditions and results.Table 6 ATable 6BTable 6C

[0122] As shown in Table 6, Examples 11 -19 achieved all the target values of C: 0.0050% or less, S: 0.0030% or less, and N: 0.0050% or less. In Comparative Example 6 and 7, where the slag C / A (-) at the start of the denitrification and desulfurization process was out of the range of 0.7 to 1.0, N did not reach the target value, and in Comparative Examples 8 and 9, where the slag thickness at the start of the denitrification and desulfurization process was less than 100mm, neither N nor S reached the target values.Section D - Examples of the Electrical Steels and the Resulting Properties

[0123] As described herein, the magnetic properties of the electrical steels can be controlled, by the composition and the processing of the electrical steels. The compositions of the electrical steels used in the present invention (e.g., as previously described herein) may have the ranges disclosed in Table 7. The ranges disclosed in Table 7 illustrate examples of the percent mass of Silicon, Aluminum, Manganese, Carbon. Titanium, Phosphorous, Nitrogen, Oxygen, and Sulfur that provide the desired electrical steel sheets with high permeability and low core loss using the process of the present invention:

[0124] The amount of silicon used in the electrical steel controls many aspects of the magnetic properties of the electrical steel. Silicon may be added to electrical steels to raise the resistivity of the material and concurrently reduce the eddy current loss component of the core loss. Alternatively, the lower the silicon level the higher the permeability and the higher the saturation. Thus, there is also a benefit to reducing the silicon in order to increase the permeability and allow the electrical steel to more easily support a magnetic field (e.g., at high magnitude inductions). Furthermore, the purer the electrical steel the higher the saturation level, and thus, the more magnetic induction can occur. Moreover, higher levels of Si (e.g., above 4.0%) are more difficult to roll because the higher levels of Si typically result in embrittlement of the steel which can lead to mechanical failure during rolling. Thus, the level of Si is targeted to be 4.0% or lower.

[0125] As discussed, the processing of the electrical steel also has an impact on the magnetic properties of the electrical steel. The ranges of conditions for processing the electrical steel in the present invention may vary based on the composition of the steelsand / or magnetic properties desired. Examples of the ranges of processing temperatures are provided in Table 8.

[0126] The following examples illustrate the improved magnetic properties that may be achieved using the present invention. Molten steel was generated in an electric furnace using raw materials such as prime scrap steel and / or virgin iron units (e.g., pig iron, DRI, or the like). The raw materials used in the following examples include approximately 50% by mass of virgin iron units and approximately 50% by mass of prime scrap steel, although variousother relative proportions of virgin iron units and prime scrap steel are considered, as has been described previously herein. The resulting molten steel was then discharged from the electric furnace into a ladle. Subsequently, a flux comprising 98% CaO (calcium oxide), 99% AI2O3 (aluminum oxide), and CaO AI2O3 (55% CaO, 45% AI2O3) was introduced into the ladle.

[0127] The ladle, featuring a lining composed of magnesian chrome brick (60% MgO, 25% C^Os,) with an inner diameter of 2.9 m, received the molten steel from the electric furnace. Following the transfer, a vacuum decarburization process occurred in a ladle vacuum degasser for a duration of about 9 to 23 minutes. Four minutes into the decarburization, CaO was added, with the quantity' estimated to be 1.2 times the amount of AI2O3 generated during the deoxidation of the molten steel and slag with aluminum.

[0128] Post-decarburization, metallic aluminum and other raw materials were introduced for deoxidation and composition adjustment, accompanied by a stirring process. Following these steps, the ladle was transported to the tundish for continuous casting. Molten steel was then poured into the tundish, and when approximately half of the molten steel in the ladle had been transferred to the tundish, a sample of the molten steel in the tundish was collected for analysis. The cast slab was sent directly to the tunnel furnace, heated, hot-rolled, annealed, cold-rolled, and finish-annealed to produce a product sheet. The pickling was performed after the hot-rolled sheet annealing when the annealing time of the hot-rolled sheet annealing was 60 seconds or less, and before the hot-rolled sheet annealing when the annealing time was over 60 seconds. From the product sheet, specimens of 30 mm width x 300 mm length were taken. The half of specimens were taken along the rolling direction and the half of specimen were taken along the rolling orthogonal direction, and the iron loss W10 / 400 was measured in accordance with "JIS C2550 -1."

[0129] As first through fourth examples, electrical steel slabs of the composition illustrated in Table 9 was processed in 4 test runs, each test run using the processing parameters illustrated in Tables 10A-10D, respectively, although there may be other process steps in addition to the steps illustrated in Tables 10A-10D.

[0130] As fifth through eighth examples, electrical steel slabs of the composition illustrated in Table 11 was processed in 4 test runs, each test run using the processing parameters illustrated in Tables 12A-12D, respectively, although there may be other process steps in addition to the steps illustrated in Tables 12A-12D.

[0131] As ninth and tenth examples, electrical steel slabs of the composition illustrated in Table 13 was processed in 2 test runs, each test run using the processing parameters illustrated in Tables 14A-14B, respectively, although there may be other process steps in addition to the steps illustrated in Tables 14A-14B.

[0132] As an eleventh example, an electrical steel slab of the composition illustrated in Table 15 was processed using the processing parameters illustrated in Table 16, although there may be other process steps in addition to the steps illustrated in Table 16.

[0133] As a twelfth example, an electrical steel slab of the composition illustrated in Table 17 was processed using the processing parameters illustrated in Table 18, although there may be other process steps in addition to the steps illustrated in Table 18.

[0134] As a thirteenth example, an electrical steel slab of the composition illustrated in Table 19 was processed using the processing parameters illustrated in Table 20, although there may be other process steps in addition to the steps illustrated in Table 20.

[0135] As a fourteenth example, an electrical steel slab of the composition illustrated in Table 21 was processed using the processing parameters illustrated in Table 22, although there may be other process steps in addition to the steps illustrated in Table 22.

[0136] Indeed, as a result of the foregoing tests, a non-oriented electrical steel sheet having good high-frequency iron loss can be produced by using an electric furnace and continuous casting, and the other processing described herein with low CO2 emissions versus traditional electrical steel processing that occurs using blast furnaces. In addition, the nonoriented electrical steel sheet according to the present invention can improve the high frequency iron loss.

[0137] Tables 23 and 24 below illustrate fifteenth through sixty-first examples. Nonoriented electrical steel sheets were manufactured under predetermined conditions. First, molten steel in the deoxidized state was taken out from the electric furnace to the ladle using scrap iron and / or directly reduced iron as the iron source. During the steel tapping out, a flux consisting of CaO (CaO: 98 mass%), A12O3 (A12O3:99 mass%) and CaO • A12O3(CaO: 55mass%, A12O3:45 mass%) was charged into the ladle. A ladle lined with magnesia chrome brick (MgO: 60 mass%, Cr2O3:25 mass%, TiO2:0.1 mass%) with an inner diameter of 2.9 m was used.

[0138] After tapping molten steel from the electric furnace to the ladle, vacuum decarburization treatment was carried out in a vacuum decarburization device that stores a ladle inside a vacuum tank. CaO was added 4 minutes after the start of the vacuum decarburization treatment. The amount of CaO added was estimated to be 1.2 times that of A12O3 generated during deoxidation of molten steel and slag with Al.

[0139] After the decarburization treatment, metal Al in an amount suitable for deoxidation and component adjustment and alloy raw materials for various component adjustment were added, and agitation treatment was performed. Then, the ladle was conveyed to the tundish for continuous casting, molten steel was poured, and casting was performed. When about half of the molten steel in the ladle was poured into the tundish, a sample of the molten steel in the tundish was collected and subjected to component analysis.

[0140] Table 23 shows the composition of the slabs. The remainder is Fe and inevitable impurities. The cast slab was directly sent to the tunnel furnace, heated, hot-rolled, hot-rolled, annealed, cold-rolled, and finish-annealed to produce a product sheet. The pickling was performed after the hot-rolled sheet annealing when the annealing time of the hot-rolled sheet annealing was 60 seconds or less, and before the hot-rolled sheet annealing when the annealing time was over 60 seconds.

[0141] From the product plate thus obtained, a test piece having a width of 30 mm and a length of 280 mm was taken from the rolling direction and the perpendicular rolling direction, and the iron loss W10 / 400 was measured. Table 24 shows the manufacturing conditions after the hot rolling process and the iron loss values measured from each test piece.TABLE 23TABLE 24

[0142] As shown in Table 24. in Example 13-48 of the invention in which the component composition and manufacturing conditions of the slab conform to the present invention, the iron loss W10 / 400 is a good value of “13.0 W / kg” or less. On the other hand, in Comparative Examples 3, 4, 6, 8, and 10-12, in which the component composition and manufacturing conditions of the slabs do not conform to the present invention, it is seen that the iron loss W10 / 400 exceeds “13.0 W / kg”. The steel plates No. 20, No. 25, and No. 30 were not subjected to finish annealing because they were fractured in the cold rolling process, and the iron loss W10 / 400 was not measured, so they were selected as Comparative Examples 5, 7, and 9.

[0143] The electrical steels of the present invention described herein may be utilized for various electric motor applications. For example, the electrical steels from the present invention may be utilized for applications in which higher strength electrical steels are needed, applications in which higher frequencies are required, or the like.

[0144] In some applications electric motors have a stationary stator that has windings or permanent magnets that surround a core comprising layers of electrical steel sheets. Therotor is located within the stator and has conductors that carry currents that interact with the magnetic field of the stator for driving a shaft attached to the rotor. In other applications electric motors may have rotors that are coupled to the permanent magnets instead of the stator, while the stator includes the conductors. The electrical steels of the present invention can be used in both applications, but in one embodiment of the invention the electrical steels may be particularly useful in electric motors in which the rotor has the permanent magnets and the stator has the conductors. In order to improve the efficiency of the motor for rotating at higher levels of rotations per minute (RPM) and higher levels of torque, the rotor strength has to be improved. As such, high strength steel can be used for the rotor to result in higher levels of RPM and torque for the electric motor.

[0145] While certain exemplary embodiments have been described herein, and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other changes, combinations, omissions, modifications and substitutions, in addition to those set forth in the above paragraphs, are possible. Those skilled in the art will appreciate that various adaptations and modifications of the just described embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.

Claims

WHAT IS CLAIMED IS:

1. An electrical steel at least partially formed from scrap steel, comprising: an electrical steel composition comprising: silicon (Si) in a range of 2.0-4.5% mass; aluminum (Al) of less than 2.5% mass; manganese (Mn) in a range of 0.005-2.0 % mass; carbon (C) in a range of 0.001-0.005% mass; nitrogen (N) of less than 0.005% mass: phosphorus (P) of less than 0.20 % mass; sulfur (S) of less than 0.003% mass; titanium (Ti) of less than 0.010% mass; one or more of antimony (Sb) and tin (Sn), present in a total amount of less than 0. 1% mass; and wherein a remainder comprises unavoidable impurities and iron; wherein the electrical steel is formed from one or more charges comprising: virgin iron units; prime scrap steel; wherein the electrical steel formed from the one or more charges having the electrical steel composition has a B50 greater than or equal to 1.58 T, and wherein the electrical steel has a core loss less than or equal to 13.5 W / kg when tested at LOT at 400 Hz and when the electrical steel has a final thickness of 0.30mm or less.

2. An electrical steel electrical steel at least partially formed from scrap steel, comprising: an electrical steel composition comprising: silicon (Si) in a range of 2.0-4.5% mass; aluminum (Al) of less than 2.5% mass; manganese (Mn) in a range of 0.005-2.0 % mass; carbon (C) in a range of 0.001-0.005% mass; nitrogen (N) of less than 0.005% mass: phosphorus (P) of less than 0.20 % mass; sulfur (S) of less than 0.003% mass;titanium (Ti) of less than 0.010% mass; antimony (Sb) or Tin (Sn) of less than 0.1% mass; chromium (Cr): less than 5 % mass; copper (Cu): less than 5 % mass; nickel (Ni): less than 5 % mass; molybdenum (Mo): less than 0.1% mass; tungsten (W): less than 0.1% mass; cobalt (Co): less than 5% mass; arsenic (As): less than 0.05% mass; boron (B): less than 0.05% mass; calcium (Ca): less than 0.02% mass; magnesium (Mg): less than 0.005% mass; cerium (Ce): less than 0.02% mass; lanthanum (La): less than 0.02% mass; neodymium (Nd): less than 0.02%; bismuth (Bi): less than 0.10%; yttrium (Y): less than 0. 10%; zirconium (Zr): less than 0.10%; niobium (Nb): less than 0.02% mass; vanadium (V): less than 0.1% mass; tantalum (Ta): less than 0.1% mass; germanium (Ge): less than 0.1% mass; gallium (Ga): less than 0.1% mass; lead (Pb): less than 0.01% mass; zinc (Zn): less than 0. 1% mass; oxygen (O): less than 0.005% mass; wherein a remainder comprises unavoidable impurities and iron; wherein the electrical steel is formed from one or more charges comprising: virgin iron units; prime scrap steel; wherein the electrical steel formed from the one or more charges having the electrical steel composition has a B50 greater than or equal to 1.58 T, and wherein the electricalsteel has a core loss less than or equal to 13.5 W / kg when tested at 1.0T at 400 Hz and when the electrical steel has a final thickness of 0.30mm or less.

3. The electrical steel of claim 1 or 2, wherein the one or more charges comprise: a range of 0 to 70 % mass of the virgin iron units; and a range of 30 to 100 % mass of prime scrap steel.

4. The electrical steel of claim 1 or 2, wherein the electrical steel is formed from the following processing in order to achieve the permeability and the core loss: melting the one or more charges into molten steel in an electric arc furnace (EAF); tapping the EAF and transferring the molten steel to a ladle; decarburizing, deoxidizing, and denitrifying the molten steel in the ladle in a vacuum degasser; transferring the molten steel from the ladle to a tundish; casting the molten steel from the tundish into a slab in a thin-strip caster, wherein the slab has a thickness of 45 to 170 mm; heating the slab in a furnace; hot rolling the slab into a sheet; anneal-pickling after hot rolling; cold rolling after the anneal-picking; and final annealing after cold rolling.

5. The electrical steel of claim 3, wherein the tapping temperature occurs in a range of 2700 to 3200°F.

6. The electrical steel of claim 3, wherein the tapping occurs through a taphole having taphole sand comprising fused alumina.

7. The electrical steel of claim 3, wherein oxygen in the molten steel at the tapping ranges from 600ppm to 1 OOOppm.

8. The electrical steel of claim 3, wherein the oxygen of the molten steel within the ladle before decarburization is controlled to 300 to 700ppm.

9. The electrical steel of claim 3, wherein the ladle utilizes AbCfi-base refractory in the barrel and magnesia or AbOs-base refractory materials in the slag line.

10. The electrical steel of claim 3, wherein molten steel in the ladle is transferred to the tundish at a temperature ranging between 2700 and 2800°F.

11. The electrical steel of claim 3, wherein the molten steel in the vacuum degasser is stirred for 20 to 90 mins at a stirring energy of between 100 and 270 W / t.

12. The electrical steel of claim 3, wherein the decarburizing, the deoxidizing, and the denitrifying in the vacuum degasser occurs at a temperature that ranges from 2600 to 3100°F.

13. The electrical steel of claim 3, wherein the casting comprises: casting at a speed of 90 to 200 inches per minute; cooling the thin strip steel at a rate of between 1.5 to 7 degrees F / sec such that the slab exit temperature ranges from 1800 to 2200°F.

14. The electrical steel of claim 3, wherein the heating after casting occurs at a temperature that ranges from 2000 to 2200°F for a time that ranges from 5 to 30 minutes.

15. The electrical steel of claim 3, wherein during the hot rolling descaling occurs at 2500 to 3200 psi.

16. The electrical steel of claim 3, wherein the slab is rolled into the sheet having a thickness of 1.4 to 2.5mm after hot rolling.

17. The electrical steel of claim 3, wherein the sheet is finished rolled during the hot rolling at a temperature ranges from 1400 to 1800°F.

18. The electrical steel of claim 3, wherein the sheet is coiled after the hot rolling at a temperature that ranges from 900 to 1300°F.

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