NON-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR ITS MANUFACTURE

Abstract

A non-oriented electrical steel sheet is provided that has excellent adhesion to an insulating coating even if the thickness of the insulating coating is reduced. The non-oriented electrical steel sheet of this disclosure has an insulating coating on at least one surface of the steel sheet, wherein the insulating coating has a concentrated layer of P on both a surface side and an interface side with a steel substrate, and the concentration of P in the concentrated layer is greater than the concentration of P in the steel substrate.

Description

This disclosure relates to a non-oriented electrical steel sheet and a method for manufacturing the same. BACKGROUND OF THE INVENTION A non-oriented electrical steel sheet is a type of soft magnetic material widely used as an iron core material for motors and similar applications. In recent years, the practical use of electric and hybrid vehicles has increased, motor drive systems have been developed, and motor drive frequencies have been rising year after year. Today, drive frequencies of several hundred to several thousand Hz are common, and the iron loss properties of an iron core at high frequencies are becoming increasingly important. Therefore, efforts have been made to reduce iron loss at high frequencies, for example, by adding alloying elements such as silicon and aluminum, or by reducing the sheet thickness.In addition, technologies to improve iron loss properties in high-frequency ranges by controlling the Si concentration distribution in the thickness direction and similar methods have also been studied. Among these technologies, thickness reduction significantly improves iron loss at high frequencies, so the thickness of electrical steel laminations has been decreasing in recent years. Furthermore, thickness reduction decreases the stacking factor of electrical steel laminations in motor cores manufactured by rolling electrical steel laminations, causing problems such as reduced torque during motor manufacturing. This is because the relative proportion of electrical steel lamination, excluding insulating coatings, in an iron core decreases as lamination thickness decreases, even if the thickness of any insulating coating on the lamination surface remains the same.Therefore, it has been desirable to further reduce the thickness of the insulating coating formed on the surface of the electrical steel sheet to prevent a decrease in the stacking factor. Various technologies for reducing the thickness of the insulating coating have been studied. For example, JP3603385B (PTL 1) describes a technology for manufacturing an electrical steel sheet that achieves excellent adhesion of an insulating coating by containing 20 mg / m2o more and 160 mg / m2o less of C in the insulating coating. LIST OF APPOINTMENTS Patent Documents PTL 1:JP3603385B BRIEF DESCRIPTION OF THE INVENTION (Technical Problem) However, conventional technologies cannot sufficiently ensure adhesion between a steel sheet and an insulating coating when the thickness of the insulating coating is reduced, and the improvement is insufficient in the stacking factor of an electrical steel sheet with a reduced thickness. 7. ir Lnn / zznz / B / Yi It might be useful in this way to provide an electrical steel sheet that has excellent adhesion with an insulating coating even if the thickness of the insulating coating is reduced, as well as a method of manufacturing the same. (Solution to the Problem) We focused on the concentration of phosphorus (P) on the surface of an insulating coating and at the interface between an electrical steel sheet and the insulating coating to address the aforementioned problem, and we conducted in-depth studies. As a result, we recently discovered that excellent adhesion of the insulating coating can be achieved by concentrating P on both the surface and interface sides with a steel substrate, which forms an electrical steel sheet, of the insulating coating, thus completing this disclosure. We consider the mechanism to be as follows: The coating itself is hardened by the concentration of P on both the surface and interface sides with the steel substrate of the insulating coating, and the P concentrated on the interface side with the steel substrate acts as a binder between the steel substrate and the insulating coating.This effect allows for the production of an electrical steel sheet with a firm and highly adhesive insulating coating, even when the thickness of the coating itself is reduced. This effect can be achieved regardless of the type or structure of the insulating coating, whether it is organic, inorganic, or a mixture of both. Furthermore, P can be concentrated on the interface side with the steel substrate of the insulating coating by containing 0.005% to 0.20% by mass of P in steel threading components as specified by a block and subjecting the block to final annealing at 1100°C or higher, or by using a rolling oil containing a phosphoric ester-type emulsifier at a concentration of 1% or more as a rolling oil in the final cold rolling to adhere the P to the surface of the steel sheet. Additionally, a concentrated layer of P can be formed on the interface side with the steel substrate of the insulating coating by applying an aqueous solution containing 5 parts by mass or more of a phosphoric acid compound between the final annealing and final cold rolling and the drying of the aqueous solution, thereby achieving the effect described herein. Furthermore, the concentrated P layer on the surface side of the insulating coating can form as follows. When a coating solution containing one or more parts by mass of a phosphoric acid compound or similar is used during the formation of the insulating coating, the P rises to the surface of the insulating coating as the solution dries, thereby forming a concentrated layer. Concentrated P-type layers form on both the surface and interface sides of the insulating coating with the steel substrate when the above processes are combined. As a result, an electrical steel sheet with excellent coating adhesion can be obtained even if the thickness of the insulating coating is reduced. We provide the following in this way. (1) A non-oriented electrical steel sheet, which is an electrical steel sheet having an insulating coating over at least one surface of the steel sheet, wherein the insulating coating has a concentrated layer of P on both a surface side and an interface side with a steel substrate, and a concentration of P of the concentrated P layer is greater than a concentration of P in the steel substrate. (2) The non-oriented electrical steel sheet in accordance with (1), wherein the sheet of 7. ir Lnn / zznz / B / Yi steel comprises (consists of) a chemical composition containing, in % by mass, C: less than 0.010%, Yes: 1.5% or more and 10.0% or less, To: 0.001% or more and 2.0% or less, and Mn: 0.005% or more and 1.0% or less, with the remainder being Fe and unavoidable impurities. (3) The non-oriented electrical steel sheet according to (2), wherein the steel sheet additionally contains, in % by mass, P: 0.005% or more and 0.20% or less. (4) Non-oriented electrical steel sheet in accordance with (2) or (3), wherein the chemical composition further contains, in % by mass, at least one selected from the group consisting of Sn: 0.002% or more and 0.10% or less, Mo: 0.005% or more and 0.10% or less, Sb: 0.005% or more and 0.30% or less, Cu: 0.01% or more and 0.50% or less, Cr: 0.01% or more and 0.50% or less, and Ni: 0.010% or more and 1.0% or less. (5) The non-oriented electrical steel sheet in accordance with any of (1) to (4), wherein the insulating coating has a concentrated layer of Fe on the interface side with the steel substrate. (6) Non-oriented electrical steel sheet in accordance with any of (1) to (5), wherein the steel sheet has a thickness of 0.20 mm or less. (7) The non-oriented electrical steel sheet in accordance with any of (1) to (6), wherein the steel sheet has a concentration gradient in which a concentration of Si decreases from a surface side of the steel sheet towards a central side of the steel sheet, and a difference in the concentration of Si between a surface layer of the steel sheet and a central layer of the steel sheet in the concentration gradient is from 1.0% by mass to 5.0% by mass. (8) A method for manufacturing a non-oriented electrical steel sheet, which is a method for manufacturing the electrical steel sheet in accordance with any of (1) to (7), comprising subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein the cold rolling is carried out using a rolling oil containing 1% or more of a phosphoric ester-type emulsifier, and the insulating coating is formed by applying a solution containing one or more mass parts of a phosphoric acid compound. (9) A method for manufacturing a non-oriented electrical steel sheet, which is a method for manufacturing the electrical steel sheet in accordance with any of (1) to (7), comprising subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein after cold rolling and before final annealing, an aqueous solution is applied that 7. ir Lnn / zznz / E / Yi contains 5 parts by mass or more of a phosphoric acid compound on a surface of the steel sheet that has been subjected to cold rolling, and the aqueous solution dries, and the insulating coating is formed by applying a solution containing one part by mass or more of a phosphoric acid compound. (10) A method for manufacturing a non-oriented electrical steel sheet, which is a method for manufacturing the electrical steel sheet in accordance with any of (1) to (7), comprising subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein the cold rolling is carried out using a rolling oil containing 1% or more of a phosphoric ester-type emulsifier, after cold rolling and before final annealing, an aqueous solution containing 5 parts by mass or more of a phosphoric acid compound is applied to a surface of the steel sheet that has been subjected to cold rolling, and the aqueous solution is dried,and the insulating coating is formed by applying a solution containing one or more parts by mass of a phosphoric acid compound. (11) A method for manufacturing a non-oriented electrical steel sheet, which is a method for manufacturing the electrical steel sheet in accordance with any of (1) to (7), comprising subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein the block contains 0.005% by mass to 0.20% by mass of P, and an annealing temperature in the final annealing is set at 1100°C or higher, and the insulating coating is formed by applying a solution containing one or more mass parts of a phosphoric acid compound. (12) A method for manufacturing a non-oriented electrical steel sheet, wherein in the method for manufacturing an electrical steel sheet according to (11), cold rolling is carried out using a rolling oil containing 1% or more of a phosphoric ester-type emulsifier. (13) A method for manufacturing a non-oriented electrical steel sheet, wherein in the method for manufacturing an electrical steel sheet according to (11) or (12), after cold rolling and before final annealing, an aqueous solution containing 5 parts by mass or more of a phosphoric acid compound is applied to a surface of the steel sheet that has been subjected to cold rolling, and the aqueous solution is dried. (14) A method for manufacturing a non-oriented electrical steel sheet in accordance with any of (8) to (13), comprising subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein a siliconization treatment is carried out after the final annealing, or the final annealing is a final annealing that also serves as a siliconization treatment. (Advantageous Effect) 7. ir Lnn / zznz / B / Yi The non-oriented electrical steel sheet conforming to this disclosure has an insulating coating whose adhesion does not deteriorate even if the thickness is reduced, regardless of the type of insulating coating. Therefore, it is possible to improve the stacking factor reduction, which has been a problem with electrical steel sheets of reduced thickness. BRIEF DESCRIPTION OF THE FIGURES In the attached figures: FIG. 1 illustrates the GDS measurement profile of an example from this disclosure. DETAILED DESCRIPTION OF THE INVENTION In the non-oriented electrical steel sheet with an insulating coating of this disclosure, the insulating coating has a structure as described below. An electrical steel sheet serving as a base sheet for the insulating coating is not particularly restricted and may follow general practice for electrical steel. [The insulating coating has a concentrated layer of P on both a surface side and an interface side with a steel substrate, where the concentrated layer of P has a higher concentration of P than that of the steel substrate] By concentrating phosphorus (P) on both the surface and interface sides of the insulating coating with a steel substrate, the coating hardens. The P concentrated on the interface side with the steel substrate acts as a binder between the insulating coating and the steel substrate. This effect allows for the production of an electrical steel sheet with a strong and highly adhesive insulating coating, even with a reduction in the coating thickness. The concentration of phosphorus (P) in the insulating coating can be evaluated using light discharge spectroscopy (GDS). GDS evaluation in this mode was performed under conditions of an argon gas pressure of 600 Pa and a high-frequency output of 35 W using a GDS-Profiler 2 manufactured by HORIBA, Ltd. However, any equipment capable of performing the same evaluation can be used. The presence or absence of a concentrated P layer can be determined as follows. Figure 1 illustrates an example of the GDS measurement profile result for P and Fe in a steel sheet with an insulating coating that meets the requirements of this disclosure. First, the interface side with the steel substrate of the insulating coating is a region where the Fe intensity decreases rapidly toward the surface side of the insulating coating (in other words, the left of the depth of analysis in the graph of Figure 1). As used herein, the broad detection intensity of P in the steel substrate region is denoted as Ia, the maximum value of the detection intensity of P on the interface side with the steel substrate in the insulating coating is denoted as Ib, and the maximum value of the detection intensity of P on the surface side of the insulating coating is denoted as Ie.The concentrated layer of P on the interface side with the steel substrate of the insulating coating satisfies the following equation (1), and the concentrated layer of P on the surface side of the insulating coating satisfies the following equation (2). Note that the “concentration of P on the steel substrate” is the one described above. Therefore, the concentration of P is defined as that which satisfies both the following equation (1) and the following equation (2). Ib > la (1) le > la (2) 7. ir Lnn / zznz / B / Yi [Thickness and composition of the insulating coating] The thickness of the insulating coating is preferably 2.0 pm or less. The stacking factor increases as the coating thickness decreases, and therefore a thickness of 1.0 pm or less is more preferable. There is no preferred lower limit for the coating thickness, and the thickness can be as small as necessary to ensure insulation between layers, depending on the type of insulating coating to be formed. The insulating coating can be composed of only organic components, only inorganic components, or organic / inorganic composite materials. Specific examples of organic components include acrylic-based resins, silica-acrylic-based resins, polyester-based resins, epoxy-based resins, and fluorine-based resins. Examples of inorganic components include chromate-based, dichromate-based, borate-based, and silicate-based resins.Examples of organic / inorganic (semi-organic) composite material include a mixture of the organic component and the inorganic component mentioned above. The chemical composition of the non-oriented electrical steel sheet of the present disclosure may follow the general practice of an electrical steel sheet, and a suitable chemical composition is described below. C: less than 0.010% by mass Carbon causes magnetic aging and deteriorates magnetic properties. Therefore, the carbon content is desirable to be as low as possible. However, excessively reducing the carbon content leads to increased manufacturing costs. Therefore, the carbon content is preferably less than 0.010% by mass, at which point magnetic aging does not cause any practical problems. More preferably, the carbon content is less than 0.0050% by mass. Yes: 1.5% by mass or more and 10.0% by mass or lessSilicon (Si) is an element that increases the specific strength of steel and improves iron loss properties. In this disclosure, a Si content of 1.5% by mass or more is preferred to achieve the desired iron loss property improvement. However, when the Si content exceeds 10.0% by mass, the saturation magnetic flux density is significantly reduced, resulting in a substantial drop in torque during motor manufacturing. Therefore, in this disclosure, the Si content is preferably 1.5% by mass or more, and more preferably 2.0% by mass or more, and the Si content is preferably 10.0% by mass or less, and more preferably 7.0% by mass or less. The Si content is most preferably in the range of 1.5% to 10.0% by mass, and even more preferably in the range of 2.0% to 7.0% by mass.As used herein, the Si content is an average value of the Si content for the thickness direction. Al: 0.001% by mass or more and 2.0% by mass or less Aluminum, like silicon, increases the specific strength of steel and is therefore an effective element in reducing iron loss. On the other hand, excessive addition of aluminum not only decreases the saturation magnetic flux density but also causes alanine precipitation because the aluminum combines with nitrogen in the steel or with nitrogen caused by nitriding of the steel sheet during stress-relief annealing. Therefore, the aluminum content is preferably 2.0% by mass or less, and more preferably 0.50% by mass or less. To achieve an increase in specific strength that is effective in reducing iron loss, the aluminum content is preferably 0.001% by mass or more and more preferably 0.002% by mass or more. The Al content is even more preferably from 0.002% by mass to 0.50% by mass. Mn: 0.005% by mass or more and 1.0% by mass or less To improve workability during hot rolling, the Mn content is preferably 0.005% by mass or more, 1.0% by mass or less, and most preferably between 0.005% and 1.0% by mass. The reason is that when the Mn content is less than 0.005% by mass, the aforementioned improvement in workability is small; moreover, when the Mn content is greater than 1.0% by mass, the saturation magnetic flux density decreases. The Mn content is most preferably 0.01% by mass or more. The Mn content is most preferably 0.30% by mass or less. The Mn content is even more preferably between 0.010% and 0.30% by mass. P: 0.005% by mass or more and 0.20% by mass or less As will be described later, adding phosphorus (P) to a block and performing heat treatment is one way to form a concentrated P layer on the interface side with the steel substrate in the insulating coating. Besides its effect on the coating, P also effectively improves texture and enhances magnetic properties by increasing specific strength. Therefore, the P content is preferably 0.005% by mass or more. The P content is preferably 0.030% by mass or more. On the other hand, when the P content exceeds 0.20% by mass, rapid embrittlement occurs, impairing manufacturability and workability. Therefore, the P content is preferably 0.20% by mass or less. The P content is preferably 0.10% by mass or less. The P content is more preferably between 0.030% and 0.10% by mass. Examples of methods for forming a concentrated layer of phosphorus (P) on the interface side with the steel substrate in insulating coatings include using a rolling oil containing a phosphoric ester emulsifier, or applying an aqueous solution containing a phosphoric acid compound to the surface of the steel sheet and allowing the aqueous solution to dry. In this case, P is not always required in the block. However, even then, adding P at a concentration of 0.001% by mass or more is preferable, adding P at a concentration of 0.10% by mass or less is preferable, and adding P at a concentration of 0.001% to 0.10% by mass is most preferable in order to improve texture. The following components can be added as needed in addition to the appropriate basic components mentioned above. Sn: 0.002% by mass or more and 0.10% by mass or less; Mo: 0.005% by mass or more and 0.10% by mass or less; Sb: 0.005% by mass or more and 0.30% by mass or less; Cu: 0.01% by mass or more and 0.50% by mass or less; Cr: 0.01% by mass or more and 0.50% by mass or less; and Ni: 0.010% by mass or more and 1.0% by mass or less All of the above components are effective elements that are added to improve magnetic properties, so it is more desirable to add at least one of the above elements in an amount equal to or greater than the lower limit of each element. However, excessive addition leads to a deterioration of magnetic properties and a decline in manufacturability, so it is desirable to add the element within a range up to the upper limit. 7. go Lnn / zznz / B / Yi of each element. [Having a concentrated layer of Fe on the interface side with the steel substrate of the insulating coating] As illustrated in the example in FIG. 1, by concentrating both Fe and P on the interface side with the steel substrate of the insulating coating, a compound of Fe and P acts as a binder between the steel substrate and the insulating coating, resulting in a more firmly formed insulating coating on the electrical steel sheet. The presence or absence of Fe concentration can be assessed using GDS. When the difference between the depth of analysis at which the maximum Fe intensity is obtained and the depth of analysis at which the maximum P intensity (i.e., Ib) is obtained is 0.5 pm or less, a concentrated Fe layer is considered to be present on the interface side with the steel substrate of the insulating coating. [Thickness of the electrical steel sheet] The stacking factor decreases as the sheet thickness decreases, which causes problems. Therefore, the effect of this disclosure is easily achieved when the sheet thickness is 0.25 mm or less. This disclosure is most effective when the sheet thickness is 0.20 mm or less. From an effect standpoint, it is not necessary to establish a lower limit on the sheet thickness. However, when the sheet thickness is 0.05 mm or less, the cutting and similar costs involved in core manufacturing increase significantly. Therefore, a thickness greater than 0.05 mm is desirable. As used herein, the “electrical steel sheet thickness” or simply the “sheet thickness” includes the thickness of the insulating coating. [Having a concentration gradient in which the concentration of Si decreases from the surface side of the steel sheet towards the central side of the steel sheet, where the difference in concentration of Si between the surface layer of the steel sheet and the central layer of the steel sheet in the concentration gradient is from 1.0% by mass to 5.0% by mass] Having a silicon concentration gradient along the thickness of the steel sheet can improve iron loss at high frequencies. This concentration gradient can be achieved, for example, by siliconizing the steel in an atmosphere containing SiCk, or by a manufacturing method that uses a coating in which materials with different silicon concentrations are stacked. The lower limit of the silicon concentration difference is preferably 1.0% by mass, and more preferably 1.5% by mass, to sufficiently improve eddy current loss reduction. The upper limit of the silicon concentration difference is preferably 5.0% by mass, and more preferably 3.5% by mass, to suppress the hysteresis loss degradation. Even more preferably, the silicon concentration difference ranges from 1.5% to 3.5%. The “surface layer of the steel sheet” and the “core layer of the steel sheet” are specifically defined as follows. The “surface layer of the steel sheet” is a region 1 / 3 the thickness of the sheet on each of the two surfaces of the steel sheet (excluding the insulating coating), and the “core layer of the steel sheet” is a region of the remaining 1 / 3 thickness of the sheet. The concentration of Si in the core layer of the steel sheet is the average concentration in the corresponding region, and the concentration of Si in the surface layer of the steel sheet is the average of the average concentrations in the corresponding regions of the two surfaces (in other words, 7. ir Lnn / zznz / E / Yi the average concentration of the two surface layers). The above average concentration can be evaluated from the concentration profile by measuring the concentration of Si in the thickness direction using ERMA. [Manufacturing method] The electrical steel sheet of the present disclosure can be manufactured by subjecting an electrical steel sheet block to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet according to a conventional method. [Method for forming a concentrated layer of P on the interface side with the steel substrate in the insulating coating] Any of the following treatments are required in the above manufacturing process to form a concentrated layer of P on the interface side with the steel substrate in the insulating coating. - Use a rolling oil containing 1% or more of a phosphoric ester-type emulsifier during cold rolling - After cold rolling and before final annealing (or siliconizing treatment), apply an aqueous solution containing 5 parts by mass or more of a phosphoric acid compound to the surface of the cold-rolled steel sheet, and dry the aqueous solution - Contain 0.005% by mass or more and 0.20% by mass or less of P in the block, and set the annealing temperature at final annealing to 1100°C or higher [Method for forming a concentrated layer of P on the surface side of the insulating coating] Furthermore, the following treatment is necessary in order to form a concentrated layer of P on the surface side of the insulating coating. - During the formation of the insulating coating, apply a solution containing one part by mass or more of a phosphoric acid compound [Silicinization treatment] To achieve the desired silicon concentration difference, the steel sheet can undergo additional siliconization treatment after final annealing. Alternatively, for cost reduction, the final annealing can be combined with the siliconization treatment. A mixture of silicon tetrachloride and nitrogen can be used as the atmospheric gas for siliconization. When performing siliconization, the heat treatment temperature is ideally between 1100°C and 1300°C, and the annealing time is ideally between 30 and 120 seconds, depending on the required silicon immersion time. [Method for forming a concentrated layer of Fe] The siliconization treatment temperature or final annealing temperature is preferably 1000°C or higher to form a concentrated Fe layer on the insulating coating. It is preferably 1300°C or lower because it is necessary to avoid particle size oiling to reduce eddy current losses at high frequencies. EXAMPLES 7. go Lnn / zznz / E / Yi (Example 1) Blocks having the components indicated in Table 1 were heated to 1200°C and hot-rolled to obtain 1.8 mm hot-rolled sheets. The hot-rolled sheets were then annealed at 1050°C and subsequently cold-rolled so that each sheet was rolled to the sheet thicknesses (product sheet thickness) indicated in Table 1. In some cases, a rolling oil containing 1% ADEKA COL PS807 as a phosphoric ester-type emulsifier (defined as “rolling oil A”) was used during cold rolling, and in other cases, a general-purpose cold-rolling oil for steel (defined as “rolling oil B”), which did not contain a phosphoric ester-type emulsifier, was used.In some cases, an additional pretreatment was carried out where Al phosphate, which was used as an aqueous solution containing 5 parts by mass or more of a phosphoric acid compound, was applied and dried after cold rolling and before final annealing, and whether the pretreatment was carried out or not was indicated as “Yes” or “No” in the “Annealing Pretreatment” column of Table 1. Next, final annealing was carried out at 1000°C for 10 seconds in a dry atmosphere of 20% H2-80% N2. In Table 1, Nos. 21, 23, and 24 were subjected to final annealing under conditions of 1100°C x 10 seconds, and No. 25 was subjected to final annealing under conditions of 950°C x 10 seconds. To form an insulating coating, an organic / inorganic composite coating solution containing chromic acid and acrylic resin was added with one part by mass of magnesium phosphate, and the solution was applied to each sheet. The sheets were then oven-baked at 300°C to obtain electrical steel sheet products. Note that, for comparison, only No. 22 in Table 1 did not have magnesium phosphate added to the coating solution. The stacking factor, insulating coating adhesion (coating peel), and W10 / 1000 iron loss of the electrical steel sheet products obtained in this manner were evaluated. The stacking factor was evaluated using the method in accordance with JIS C 2550-5, and the magnetic properties were evaluated using the method in accordance with JIS C 2550-1.The adhesion of the insulating coating was evaluated according to JIS K 56005-6 (cross-section method). Six cut lines were made at 1 mm intervals on the surface of the steel sheet using a cutting blade. Cellophane tape was applied over these cut lines, and the coating's peelability was assessed by removing the tape. Adhesion was considered good when the ratio of the peeled area to the cross-sectional area was less than 10%. Adhesion was considered poor when the ratio was 10% or greater. Additionally, the coating structure on the steel sheet surface was evaluated using GDS to determine whether it met both equations 1 and 2. Coatings that met both equations were rated as "good," while those that did not meet either were rated as "poor."In addition, they were considered to have a concentrated layer of Fe (Fe peak: yes) when there was a maximum intensity of Fe and the difference in depth between the maximum intensity of Fe and the maximum intensity of P, i.e., Ib, was 0.5 pm or less. 7. ir Lnn / zznz / B / Yi w ω μ tn ο σι μ Or I Heard OI > achhcco Ñ Table 1 Sample No. Steel ID Component (% by mass) Rolling Oil Product Sheet Thickness (mm) Annealing Pretreatment Annealing Temperature (°C) C Si Al Mn P Other 1 A 0.0025 3.4 0.50 0.20 0.008 A 0.20 No 1000 2 A 0.0025 3.4 0.50 0.20 0.008 A 0.20 No 1000 3 A 0.0025 3.4 0.50 0.20 0.008 A 0.20 No 1000 4 A 0.0025 3.4 0.50 0.20 0.008 B 0.20 No 1000 5 A 0.0025 3.4 0.50 0.20 0.008 A 0.20 Yes 1000 6 B 0.0030 2.8 0.30 0.10 0.10 Sn:0.040 B 0.20 No 1000 7 B 0.0030 2.8 0.30 0.10 0.10 Sn:0.040 A 0.20 No 1000 8 C 0.0010 3.8 0.020 0.050 0.050 Cr:0.01, Sb:0.020 B 0.20 No 1000 9 C 0.0010 3.8 0.020 0.050 0.050 Cr:0.01, Sb:0.020 A 0.20 Yes 1000 10A 0.0025 3.4 0.50 0.20 0.008 - A 0.10 No 1000 11 A 0.0025 3.4 0.50 0.20 0.008 - A 0.10 No 1000 12 A 0.0025 3.4 0.50 0.20 0.008 - B 0.10 No 1000 13 D 0.0035 5.8 0.003 0.020 0.005 A 0.10 No 1000 14 E 0.0300 1.8 0.60 0.40 0.010 Cu:0.10, Mo:0.010 A 0.10 No 1000 15 F 0.0010 3.0 0.10 0.010 0.070 N¡:0.020 A 0.10 No 1000 16 F 0.0010 3.0 0.10 0.010 0.070 Ni:0.020 B 0.10 No 1000 17 G 0.0020 4.6 0.60 0.20 0.10 Sn:0.010,Sb:0.020 A 0.10 Yes 1000 18 H 0.0010 1.4 0.60 0.40 0.050 - A 0.20 No 1000 19 I 0.0020 3.1 0.80 0.20 0.004 Sn:0.050 B 0.20 No 1000 20 I 0.0020 3.1 0.80 0.20 0.004 Sn:0.050 B 0.20 Yes 1000 21 C 0.0010 3.8 0.020 0.050 0.050 Cr:0.01, Sb:0.020 B 0.20 No 1100 22 G 0.0020 4.6 0.60 0.20 0.10 Sn:0.010, Sb:0.020 A 0.10 Yes 1000 23 A 0.0025 3.4 0.50 0.20 0.008 A 0.10 No 1100 24 D 0.0035 5.8 0.003 0.020 0.005 - A 0.10 Yes 1100 25 D 0.0035 5.8 0.003 0.020 0.005 A 0.10 Yes 950. The underlined portion is outside the scope of this disclosure. £ ω ω Μ ο ϋι ο ϋι Κ) ο ϋι en Continued from Table 1 > α rchhcco Ñ No. Addition of Mg phosphate to insulating coating Insulating coating thickness (pm) GDS evaluation result Material test Observations Coating structure Fe peak Stacking factor (%) Coating detachment Iron loss W10 / 1000 (W / kg) 1 Yes 1.5 0.032 0.034 0.096 Good Yes 97.2 Good 43.5 Example 2 Yes 1.0 0.018 0.024 0.032 Good Yes 97.6 Good 43.2 Example 3 Yes 0.5 0.032 0.078 0.092 Good Yes 98.0 Good 43.1 Example 4 Yes 0.5 0.022 0.020 0.042 Bad Yes 97.9 Bad 43.3 Comparative Example 5 Yes 0.5 0.072 0.099 0.171 Good Yes 98.1 Good 43.2 Example 6 Yes 0.5 0.398 0.355 0.856 Bad Yes 97.9 Bad 50.1 Comparative Example 7 Yes 0.5 0.351 0.492 0.712 Good Yes 97.9 Good 49.8 Example 8 Yes 1.0 0.218 0.209 0.465 Bad Yes 97.6 Bad 44.5 Comparative Example 9 Yes 0.3 0.135 0.165 0.311 Good Yes 98.3 Good 43.2 Example 10 Yes 1.5 0.096 0.117 0.215 Good Yes 95.0 Good 31.5 Example 11 Yes 0.5 0.053 0.087 0.090 Good Yes 96.6 Good 31.2 Example 12 Yes 2.0 0.053 0.050 0.104 Bad Yes 95.0 Bad 32.6 Comparative Example 13 Yes 1.5 0.036 0.041 0.051 Good Yes 95.4 Good 23.4 Example 14 Yes 1.0 0.064 0.094 0.168 Good Yes 96.2 Good 37.8 Example 15 Yes 0.3 0.283 0.430 0.574 Good Yes 97.1 Good 36.4 Example 16 Yes 0.3 0.269 0.025 0.576 Bad Yes 96.7 Bad 38.4 Comparative Example 17 Yes 0.3 0.328 0.443 0.705 Good Yes 97.3 Good 26.8 Example 18 Yes 0.5 0.152 0.206 0.332 Good Yes 97.4 Good 58.3 Example 19 Yes 0.4 0.086 0.083 0.172 Bad Yes 97.1 Bad 44.5 Comparative Example 20 Yes 0.4 0.086 0.105 0.168 Good Yes 97.1 Good 43.5 Example 21 Yes 1.0 0.225 0.302 0.475 Good Yes 97.7 Good 42.5 Example 22 No 0.3 0.327 0.444 0.165 Bad Yes 97.3 Bad 28.7 Comparative Example 23 Yes 2.0 0.055 0.056 0.104 Good Yes 95.1 Good 32.1 Example 24 Yes 1.5 0.039 0.044 0.051 Good Yes 95.6 Good 23.1 Example 25 Yes 1.5 0.038 0.044 0.054 Good No 95.1 Good 23.5 Example. 'The underlined portion is outside the scope of this disclosure, -TO M Table 1 shows the results. When a pretreatment was carried out in which, in addition to the application of an organic / inorganic composite coating solution containing one part by mass of Mg phosphate, a rolling oil containing 1% of ADEKA COL PS807 as a phosphoric ester-type emulsifier was used, and Al phosphate as an aqueous solution containing 5 parts by mass or more of a phosphoric acid compound was applied and dried after cold rolling and before final annealing, or when a block containing 0.005% by mass or more and 0.20% by mass or less of P was used and final annealing was carried out at 1100°C or higher, a coating structure was obtained that satisfied both equations 1 and 2, resulting in good test results in terms of coating peelability. (Example 2) Blocks containing the components listed in Table 2 were heated to 1200°C and hot-rolled to obtain 1.7 mm thick hot-rolled sheets. These sheets were then annealed at 1050°C and subsequently cold-rolled to the thicknesses (product sheet thickness) specified in Table 2. A rolling oil containing 1% ADEKA COL PS807 as a phosphoric ester emulsifier (rolling oil A) was used during cold rolling. The cold-rolled sheets were then heat-treated at 1200°C for 60 seconds in silicon tetrachloride + N2 gas for final annealing, which also served as a siliconization treatment.In the siliconization treatment, the Si concentration in the surface layer of the steel sheet (surface layer Si concentration) was controlled by regulating the flow rate of silicon tetrachloride gas in the furnace. The Si concentration gradient along the thickness direction was confirmed using ERMA. Steel sheets were obtained with a Si concentration gradient where the Si concentration was the same as that of the base material components in the core layer of the steel sheet, located on the central side of the sheet, and the Si concentration decreased from the surface side of the steel sheet towards the core along the thickness direction. In addition, an inorganic composite coating solution consisting mainly of aluminum phosphate with one mass part of magnesium phosphate was added, and the solution was applied to each steel sheet. The steel sheets were then oven-baked at 320°C to obtain electrical steel sheet products. The electrical steel sheet products obtained in this manner were evaluated in the same way as in Example 1, and the results of the evaluation are summarized in Table 2. 7. ir Lnn / zznz / E / Yi ω ω μ ο σι ο σι Table 2 > α chhcco h No. Component (% by mass) Product sheet thickness [mm] Surface coating Si concentration (% by mass) Difference in Si concentration (% by mass) Insulating coating thickness (pm) GDS evaluation result Material test Observations C Si Al Mn P Other Coating structure Sharpening factor (1%) Coating detachment Iron loss (W / kg) 1 0.0025 3.4 0.50 0.20 0.008 0.20 6.5 3.1 1.0 0.092 0.122 0.239 Good 97.5 Good 40.3 Example 2 0.0700 2.7 0.10 0.10 0.050 Sn:0.020, Sb:0.050 0.20 6.5 3.8 0.5 0.208 0.315 0.424 Good 97.8 Good 38.4 Example 3 0.0700 2.7 0.10 0.10 0.050 Sn:0.020, Sb:0.050 0.20 6.5 3.8 1.0 0.195 0.291 0.440 Good 97.4 Good 38.6 Example 4 0.0700 2.7 0.10 0.10 0.050 Sn:0.020, Sb:0.050 0.20 2.7 0.0 1.0 0.206 0.275 0.422 Good 97.7 Good 50.3 Example 5 0.0230 2.5 0.005 0.10 0.10 Cu:0.02 0.25 4.2 1.7 0.5 0.414 0.539 0.849 Good 98.7 Good 40.6 Example 6 0.0230 2.5 0.005 0.10 0.10 Cu:0.02 0.25 2.5 0.0 0.5 0.337 0.438 0.684 Good 98.6 Good 53.7 Example 7 0.0025 3.4 0.50 0.20 0.008 0.10 6.5 3.1 1.0 0.091 0.176 0.170 Good 97.5 Good 25.4 Example 8 0.0025 3.4 0.50 0.20 0.008 0.10 6.5 3.1 0.2 0.114 0.099 0.241 Good 98.1 Good 25.1 Example 9 0.0010 2.4 1.0 0.20 0.030 N¡:0.080 0.10 4.0 1.6 0.5 0.091 0.107 0.223 Good 98.1 Good 25.7 Example 10 0.0010 2.4 1.0 0.20 0.030 N¡:0.080 0.10 4.5 2.1 0.5 0.175 0.254 0.378 Good 98.1 Good 24.9 Example. Table 2 shows the results. As in Example 1, good test results were obtained in terms of coating detachment on the non-oriented electrical steel sheets with a coating structure that satisfied both equations 1 and 2. In addition, iron loss was improved by achieving a difference in Si concentration from 1.0% by mass to 5.0% by mass through the siliconization treatment.

Claims

1. A non-oriented electrical steel sheet, which is an electrical steel sheet having an insulating coating over at least one surface of the steel sheet, characterized in that the insulating coating has a concentrated layer of P on both a surface side and an interface side with a steel substrate, and a concentration of P of the concentrated P layer is greater than a concentration of P in the steel substrate.

2. The non-oriented electrical steel sheet according to claim 1, further characterized in that the steel sheet comprises a chemical composition containing, in % by mass, C: less than 0.010%, Si: 1.5% or more and 10.0% or less, Al: 0.001% or more and 2.0% or less, and Mn: 0.005% or more and 1.0% or less, the remainder being Fe and unavoidable impurities.

3. The non-oriented electrical steel sheet according to claim 2, further characterized in that the steel sheet additionally contains, in % by mass, P: 0.005% or more and 0.20% or less.

4. The non-oriented electrical steel sheet according to claim 2 or 3, further characterized in that the chemical composition additionally contains, in % by mass, at least one selected from the group consisting of Sn: 0.002% or more and 0.10% or less, Mo: 0.005% or more and 0.10% or less, Sb: 0.005% or more and 0.30% or less, Cu: 0.01% or more and 0.50% or less, Cr: 0.01% or more and 0.50% or less, and Ni: 0.010% or more and 1.0% or less.

5. The non-oriented electrical steel sheet according to any of claims 1 to 4, further characterized in that the insulating coating has a concentrated layer of Fe on the interface side with the steel substrate.

6. The non-oriented electrical steel sheet according to any of claims 1 to 5, further characterized in that the steel sheet has a thickness of 0.20 mm or less.

7. The non-oriented electrical steel sheet according to any of claims 1 to 6, further characterized in that the steel sheet has a concentration gradient in which a concentration of Si decreases from a surface side of the steel sheet towards a central side of the steel sheet, and a difference in the concentration of Si between a surface layer of the steel sheet and a central layer of the steel sheet in the concentration gradient is from 1.0% by mass to 5.0% by mass.

8. A method for manufacturing a non-oriented electrical steel sheet, which is a method for manufacturing the electrical steel sheet according to any of claims 1 to 7, characterized in that it comprises subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein the cold rolling is carried out using a rolling oil containing 1% or more of a phosphoric ester-type emulsifier, and the insulating coating is formed by applying a solution containing one or more mass parts of a phosphoric acid compound.

9. The method for manufacturing a non-oriented electrical steel sheet, which is a method for manufacturing the electrical steel sheet according to any of claims 1 to 7, further characterized in that it comprises subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein after cold rolling and before final annealing, an aqueous solution containing 5 parts by mass or more of a phosphoric acid compound is applied to a surface of the steel sheet that has been subjected to cold rolling, and the aqueous solution is dried, and the insulating coating is formed by applying a solution containing one part by mass or more of a phosphoric acid compound.

10. The method for manufacturing a non-oriented electrical steel sheet, which is a method for manufacturing the electrical steel sheet according to any of claims 1 to 7, characterized in that it comprises subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein the cold rolling is carried out using a rolling oil containing 1% or more of a phosphoric ester-type emulsifier, after cold rolling and before final annealing, an aqueous solution containing 5 parts by mass or more of a phosphoric acid compound is applied to a surface of the steel sheet that has been subjected to cold rolling, and the aqueous solution is dried,and the insulating coating is formed by applying a solution containing one or more parts by mass of a phosphoric acid compound.

11. The method for manufacturing a non-oriented electrical steel sheet, which is a method for manufacturing the electrical steel sheet according to any one of claims 1 to 7, further characterized in that it comprises subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein the block contains 0.005% by mass to 0.20% by mass of P, and an annealing temperature in the final annealing is set at 1100°C or higher, and the insulating coating is formed by applying a solution containing one or more parts by mass of a phosphoric acid compound.

12. A method for manufacturing a non-oriented electrical steel sheet, characterized in that 7. ir Lnn / zznz / E / Yi in the method for manufacturing an electrical steel sheet according to claim 11, the cold rolling is carried out using a rolling oil containing 1% or more of a phosphoric ester-type emulsifier.

13. A method for manufacturing a non-oriented electrical steel sheet, characterized in that in the method for manufacturing an electrical steel sheet according to claim 11 or 12, after cold rolling and before final annealing, an aqueous solution containing 5 parts by mass or more of a phosphoric acid compound is applied to a surface of the steel sheet that has been subjected to cold rolling, and the aqueous solution is dried.

14. A method for manufacturing a non-oriented electrical steel sheet according to any of claims 8 to 13, characterized in that it comprises subjecting a block for the electrical steel sheet to hot rolling, cold rolling, and then final annealing to obtain a final annealed sheet, and forming an insulating coating on a surface of the final annealed sheet, wherein a siliconization treatment is carried out after the final annealing, or the final annealing is a final annealing that also serves as a siliconization treatment.