Soft magnetic steel sheet and method for producing the same

Abstract

To enable suppression of performance degradation even in cases where a raw material contains impurities originating from steel scrap.SOLUTION: A soft magnetic steel sheet produced from a raw material containing steel scrap comprises Fe as a base material; 1.0-7.0 wt.% of Si; and, as components derived from the steel scrap, 0.10-1.0 wt.% of Cu, 0.01-0.5 wt.% of Cr, 0.01-0.5 wt.% of Ni, and 0.01-0.3 wt.% of Sn. A total amount of the components derived from the scrap is within a range of 0.1-1.2 wt.%, and an average value of crystal grain size is within a range of 150-550 μm.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a soft magnetic steel sheet and a method for manufacturing the same. [Background technology]

[0002] In recent years, efforts to significantly reduce waste through waste prevention, reduction, reuse, and recycling have become more active. To achieve this, research and development into the recycling of steel scrap is being conducted.

[0003] Conventionally, there has been a technology for recycling iron scrap to produce electrical steel sheets for use in iron cores, etc. For example, a non-oriented electrical steel sheet is known that contains 0.0050% by mass or less of C, 1.5 to 5.0% by mass of Si, 0.2 to 3.0% by mass of Mn, 0.0030% by mass or less of sol. Al, 0.2% by mass or less of P, 0.0050% by mass or less of S, 0.0040% by mass or less of N, 0.0010 to 0.0080% by mass of T. Ca, 0.0100% by mass or less of TO, and 0.0001 to 0.0050% by mass of REM, with the balance being Fe and unavoidable impurities (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6989000 Summary of the Invention [Problem to be solved by the invention]

[0005] In the prior art described in Patent Document 1, when manufacturing an electrical steel sheet, a slab cast as the raw material is hot-rolled to form a hot-rolled steel sheet, and the hot-rolled steel sheet is further cold-rolled to form a cold-rolled steel sheet. When adopting such a manufacturing method that performs hot rolling, in order to avoid problems in manufacturing (e.g., the occurrence of cracks in the steel sheet during rolling) while ensuring the required magnetic properties, it is necessary to limit the unavoidable impurities contained in the electrical steel sheet to a predetermined allowable value (e.g., Cu is 0.01 mass% or less).

[0006] On the other hand, unlike iron ore, which is a raw material for steelmaking, iron scrap contains relatively high concentrations of elements that become impurities in electrical steel sheets. Some of these impurities (e.g., Cu, etc.) are difficult to remove even by refining using an electric furnace, etc., so it may be difficult to achieve the allowable values ​​for unavoidable impurities in electrical steel sheets described in Patent Document 1. Among the unavoidable impurities contained in iron scrap, Cu and Sn cause precipitation embrittlement in high-temperature, oxidizing atmospheres, adversely affecting hot workability, and it is known that this is further exacerbated when Cu and Sn are present simultaneously. Furthermore, Ni and Cr harden steel materials, adversely affecting cold workability. Furthermore, inclusions formed in the crystalline structure due to these impurity elements not only adversely affect cold workability but also significantly degrade magnetic properties by pinning domain wall motion and generating magnetic domains.

[0007] Furthermore, since the crystal grain size of an electrical steel sheet containing such impurities is different from that of an electrical steel sheet containing no impurities (for example, the crystal grain size is smaller), there is concern that this may have an adverse effect on the performance (magnetic properties, etc.) of the electrical steel sheet. Therefore, as a result of extensive research, the inventors of the present application have found that the deterioration of the performance of the electrical steel sheet can be suppressed by subjecting the electrical steel sheet containing impurities to an appropriate heat treatment to control the crystal grain size.

[0008] In order to solve the above-mentioned problems, the present invention aims to provide a soft magnetic steel sheet and a manufacturing method thereof that can suppress deterioration in performance related to magnetic properties, etc., even when impurities derived from iron scrap are contained in the raw materials, and ultimately contribute to a significant reduction in the generation of iron scrap as waste. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, one aspect of the present invention is a soft magnetic steel sheet manufactured from raw materials including iron scrap, which contains Fe as a base material, 1.0 to 7.0 wt% Si, and components derived from the iron scrap, wherein the components derived from the iron scrap include 0.10 to 1.0 wt% Cu, 0.01 to 0.5 wt% Cr, 0.01 to 0.5 wt% Ni, and 0.01 to 0.3 wt% Sn, and the sum of these components is in the range of 0.1 to 1.2 wt%, and the average crystal grain size is in the range of 150 to 550 μm.

[0010] According to this aspect, even if impurities derived from iron scrap are contained in the raw material, deterioration of performance such as magnetic properties can be suppressed.

[0011] In the above embodiment, the grain size of the Cu-Sn based precipitates is preferably 60 nm or less.

[0012] According to this aspect, even if impurities derived from iron scrap are contained in the raw material, deterioration of performance such as magnetic properties can be more reliably suppressed.

[0013] In the above aspect, the soft magnetic steel plate may have a thickness of 0.03 to 0.15 mm and an iron loss W10 / 400 of 8 W / kg or less.

[0014] According to this aspect, a high-quality soft magnetic steel sheet can be obtained.

[0015] In addition, in order to solve the above problem, one aspect of the present invention is a method for manufacturing the above soft magnetic steel sheet, which includes a strip-shaped thin plate formation process in which a strip-shaped thin plate is formed from the raw material by a single-roll liquid rapid solidification method, and a heat treatment process in which the strip-shaped thin plate is heat-treated in an inert atmosphere at 1100 to 1300°C for 10 minutes to 48 hours.

[0016] According to this embodiment, even when impurities derived from iron scrap are contained in the raw material, the strip is formed by the single-roll liquid quenching solidification method, so that it is possible to avoid the occurrence of cracks in the steel sheet, which occurs when hot rolling a slab cast. Furthermore, even when impurities derived from iron scrap are contained in the raw material, it is possible to suppress the deterioration of performance such as magnetic properties.

[0017] In the above embodiment, the temperature of the heat treatment is preferably 1150 to 1250°C.

[0018] According to this aspect, even if impurities derived from iron scrap are contained in the raw material, deterioration of performance such as magnetic properties can be more reliably suppressed.

[0019] In the above aspect, the treatment time for the heat treatment is preferably 2 to 24 hours.

[0020] According to this aspect, even if impurities derived from iron scrap are contained in the raw material, deterioration of performance such as magnetic properties can be more reliably suppressed. [Effects of the Invention]

[0021] According to the above-described embodiment, even if impurities derived from iron scrap are contained in the raw material, deterioration in performance such as magnetic properties of the soft magnetic steel sheet can be suppressed. [Brief explanation of the drawings]

[0022] [Figure 1] An explanatory diagram showing an outline of a manufacturing apparatus for soft magnetic steel sheets to which the single-roll method is applied. [Figure 2] Graph showing the relationship between impurity content and iron loss W10 / 400 [Figure 3] Graph showing the relationship between grain size and iron loss W10 / 400 [Figure 4] Graph showing the relationship between impurity content and crystal grain size [Figure 5] Graph showing the relationship between heat treatment temperature and crystal grain size [Figure 6] TEM image of soft magnetic steel sheet [Figure 7] Graph showing the relationship between the amount of impurities and the grain size of Cu-Sn precipitates [Figure 8] Graph showing the relationship between the amount of impurities and the grain size of Cu-Sn precipitates [Figure 9] Graph showing the relationship between the grain size of Cu-Sn precipitates and iron loss W10 / 400 [Figure 10] Graph showing the relationship between the grain size of Cu-Sn precipitates and iron loss W10 / 400 DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0024] As shown in Fig. 1, the soft magnetic steel sheet manufacturing apparatus 1 is an apparatus that applies the single roll method (single roll liquid rapid solidification method). The manufacturing apparatus 1 includes a rotatable cooling roll 2 and a nozzle 4 that sprays molten metal 3, which is the raw material for the soft magnetic steel sheet.

[0025] In the manufacturing apparatus 1, molten metal 3 is discharged from an injection hole 4a of a nozzle 4 toward a chill roll 2 rotating at a predetermined speed (for example, 500 to 2000 rpm). The discharged molten metal 3 is quenched on the surface of the chill roll 2, thereby forming a strip-shaped thin plate 5 along the surface of the chill roll 2 (an example of a strip-shaped thin plate forming process). After peeling off from the surface of the chill roll 2, the strip-shaped thin plate 5 is continuously wound up by a winding device (not shown). In this way, a coil of the strip-shaped thin plate 5 is formed.

[0026] Chill roll 2 has a diameter of 200 mm and an outer circumferential surface made of a Cu-Cr alloy or carbon steel. A heater 7 is attached to the periphery of nozzle 4, which maintains the temperature of molten metal 3 inside nozzle 4 at an appropriate level. The molten metal 3 is ejected from injection hole 4a by the pressure of gas (e.g., nitrogen gas) supplied into nozzle 4.

[0027] The coil of strip 5 formed by manufacturing apparatus 1 is heat treated (annealed) in an inert atmosphere in a heating furnace (not shown) (an example of a heat treatment process). This results in a soft magnetic steel sheet with predetermined magnetic properties. The inert atmosphere can be achieved by filling the furnace with an inert gas such as argon gas or helium gas. However, the furnace may also be filled with nitrogen gas or hydrogen gas. Furthermore, the heat treatment in the heating furnace removes internal stress from the strip 5 and improves its structure.

[0028] The heat treatment temperature is preferably set in the range of 1100 to 1300°C, for example, and more preferably in the range of 1150 to 1250°C. The heat treatment time is preferably set in the range of 10 minutes to 48 hours, for example, and more preferably in the range of 2 to 24 hours. This allows the crystal grain size (average value) of the strip 5 to be within an appropriate range (here, 150 to 550 μm) even when the raw material contains impurities derived from iron scrap, as described below. Furthermore, the grain size of Cu-Sn-based precipitates in the strip 5, which are caused by impurities derived from iron scrap, can be kept within an appropriate range (here, 60 nm or less). As a result, the deterioration of the performance (here, iron loss) of the strip 5 can be suppressed compared to when the raw material does not contain impurities derived from iron scrap.

[0029] Furthermore, in the production of soft magnetic steel sheets, after forming the strip-shaped thin sheet 5, at least one of warm rolling and cold rolling may be performed on the strip-shaped thin sheet 5 before heat treatment. Warm rolling is performed, for example, on the strip-shaped thin sheet 5 in a temperature range of 600 to 900°C using a known warm rolling mill. Cold rolling is performed on the strip-shaped thin sheet 5 at room temperature using a known cold rolling mill. By performing warm rolling or cold rolling, the surface of the strip-shaped thin sheet 5 can be smoothed, and the thickness, width, and properties of the finally obtained strip-shaped thin sheet 5 (i.e., soft magnetic steel sheet) can be appropriately adjusted.

[0030] The raw materials used in the production of soft magnetic steel sheets mainly include iron scrap. As the iron scrap, commercially available scrap that is generally available in the market can be used. For example, iron scrap discharged from automobile manufacturing plants or iron scrap recovered from scrapped automobiles may be used as the raw material.

[0031] The raw material, iron scrap, may contain not only Fe (iron), which is the base material of soft magnetic steel sheets, but also Cu (copper), Cr (chromium), Ni (nickel), Sn (tin), and the like, which are impurities (i.e., unnecessary components) for soft magnetic steel sheets. In other words, Cu, Cr, Ni, and Sn in soft magnetic steel sheets are components derived from iron scrap.

[0032] From the viewpoint of stably producing the soft magnetic steel sheet and ensuring good magnetic properties, the content of impurities (that is, Cu, Cr, Ni, and Sn) is preferably set within a predetermined range.

[0033] The Cu content in the soft magnetic steel sheet is preferably 0.10 to 1.0 wt% (weight %). The Cr content in the soft magnetic steel sheet is preferably 0.01 to 0.5 wt%. The Ni content in the soft magnetic steel sheet is preferably 0.01 to 0.5 wt%. The Sn content in the soft magnetic steel sheet is preferably 0.01 to 0.3 wt%. Furthermore, the total of Cu, Cr, Ni, and Sn in the soft magnetic steel sheet is preferably within the range of 0.1 to 1.2 wt%, more preferably 1.0 wt% or less. Note that although the lower limit of the content of each impurity is indicated here, these are not essential components for the soft magnetic steel sheet. Therefore, the content of some of these impurities may be zero.

[0034] If the content of impurities is outside the above range (upper limit), it is possible to adjust it to be below the allowable value by, for example, selecting the type of iron scrap used as the raw material.

[0035] Furthermore, silicon (Si) is added to the raw material as an element that is insufficient in iron scrap in order to reduce iron loss. The Si content in the manufactured soft magnetic steel sheet is preferably 1.0 to 7.0 wt%.

[0036] The thickness of the soft magnetic steel sheet obtained finally is preferably 0.03 to 0.15 mm. Furthermore, in terms of performance, the soft magnetic steel sheet should have at least an iron loss W10 / 400 of 8 W / kg or less. "Iron loss W10 / 400" indicates the iron loss at a frequency of 400 Hz and a magnetic flux density of 1.0 T. [Example]

[0037] As Examples 1 to 40, soft magnetic steel sheets were manufactured using raw materials in which the content of Cu, Cr, Ni, and Sn as impurities relative to Fe as the base material (i.e., the main component excluding other components such as impurities) was varied, and their magnetic properties, etc. were evaluated. However, Examples 1 to 40 also include examples in which the content of impurities and heat treatment conditions were the same.

[0038] In the manufacture of the soft magnetic steel sheets according to Examples 1 to 40, first, raw materials containing predetermined impurity contents were prepared. More specifically, pure iron and ferrosilicon were mixed and melted, and the raw materials were prepared so that the impurity contents, when the total content of Fe, Si, and impurities (here, Cu, Cr, Ni, and Sn) was taken as 100 wt%, were each predetermined chemical composition (see Table 1). The Si content was adjusted to 1.0 to 7.0 wt%.

[0039] Thereafter, as described above, a strip-shaped thin plate 5 was formed using the manufacturing apparatus 1 (see FIG. 1) employing the single-roll method. More specifically, the molten metal 3 was discharged from the injection hole 4a of the nozzle 4 onto the outer peripheral surface of the chill roll 2, and then rapidly cooled and solidified to form a strip-shaped thin plate 5 having a predetermined thickness range (0.03 to 0.15 mm) and a width of 20 mm. The temperature of the molten metal 3 was adjusted to 1400 to 1700°C, the peripheral speed of the chill roll 2 to 5 to 20 m / s, the discharge pressure of the molten metal 3 to 10 kPa to 40 kPa, and the gap between the tip of the nozzle 4 and the chill roll 2 to 0.2 mm to 0.4 mm.

[0040] Furthermore, the obtained strip-shaped thin plate 5 was subjected to heat treatment in an inert atmosphere (here, Ar gas) in a heating furnace under a plurality of conditions (see Table 1), as described above.

[0041] Furthermore, as Comparative Examples 1 to 25, soft magnetic steel sheets were produced in the same manner as in Examples 1 to 40 using raw materials that did not substantially contain Cu, Cr, Ni, and Sn as impurities, and their magnetic properties, etc. were evaluated. However, Comparative Examples 1 to 25 also include Examples in which the heat treatment conditions were identical to one another.

[0042] In addition, soft magnetic steel sheets were manufactured using a conventional hot rolling technique (hereinafter referred to as "Prior Art 1"), and their magnetic properties were evaluated. In Prior Art 1, an ingot whose chemical composition was adjusted using a vacuum melting furnace was hot rolled to a thickness of 2 mm at a temperature of 1100°C, and then cold rolled to form a steel sheet with a thickness of 0.1 mm. The obtained steel sheet was subjected to heat treatment in the same manner as in Examples 1 to 40.

[0043] Table 1 shows the chemical composition and heat treatment conditions (temperature, time) for Examples 1 to 40, and Table 2 shows the evaluation items (Cu-Sn precipitate grain size, crystal grain size, and magnetic properties) for each. The Cu-Sn precipitates correspond to the areas where Cu and Sn are concentrated at the grain boundaries, etc. (Cu-Sn concentrated alloy).

[0044] The crystal grain size of the soft magnetic steel sheet was calculated as follows. A portion (1 cm square) of the soft magnetic steel sheet sample was cut out and embedded in resin. The observation surface was then mechanically polished to a mirror finish and etched using a nital solution (nitric acid concentration 5%). The observation sample prepared in this manner was observed under a stereomicroscope at 5 to 50x magnification. The average crystal grain size (average value of crystal grain size) was calculated from the observed microstructure photographs using a cutting method using a circular test line. The calculation of the average crystal grain size was performed in accordance with JIS G0551, and analysis was performed using images magnified so that the circular test line captured 50 or more crystal grains.

[0045] The grain size of Cu-Sn-based precipitates in the soft magnetic steel sheets was calculated as follows. The surface of the soft magnetic steel sheet samples was polished and punched out to a diameter of 3 mm. Observation specimens were then prepared using electrolytic polishing. The observation specimens were observed at magnifications of 10,000 to 500,000 times using a transmission electron microscope (Talos F200X, Thermo Scientific). Elemental analysis by energy dispersive X-ray spectroscopy (EDX) and TEM diffraction patterns were used to identify the Cu-Sn-based precipitates. The minimum and maximum grain sizes of the Cu-Sn-based precipitates were calculated as the equivalent circle diameter from the area of ​​the Cu-Sn-based precipitates within the observation region.

[0046] [Table 1]

[0047] In Table 2, "W10 / 400" indicates iron loss at a frequency of 400 Hz and a magnetic flux density of 1.0 T. Also, "B10," "B50," and "B100" indicate magnetic flux densities at magnetic field strengths of 1000 A / m, 5000 A / m, and 10000 A / m, respectively.

[0048] [Table 2]

[0049] As with Examples 1 to 40 described above, Table 3 shows the chemical compositions and heat treatment conditions for Comparative Examples 1 to 25 and Prior Art 1, and Table 4 shows the evaluation items for each.

[0050] [Table 3]

[0051] [Table 4]

[0052] Next, the evaluation results of the magnetic properties and the like of the soft magnetic steel sheets of Examples 1 to 40 and Comparative Examples 1 to 25 will be described with reference to Tables 1 to 4 and Figures 2 to 10. The graphs in Figures 2 to 5 and Figures 7 to 10 are based on the data shown in Tables 1 to 4.

[0053] Figure 2 shows the relationship between the impurity content [wt%] and iron loss W10 / 400 [W / kg] for Examples 1 to 17, Comparative Examples 1 to 7, and Prior Art 1. Here, the iron loss W10 / 400 of the soft magnetic steel sheet is preferably 8 W / kg or less to reduce energy consumption. The bold frame in Figure 2 indicates the region where the iron loss W10 / 400 is 8 W / kg or less and the impurity content [wt%] is 1.2 wt% or less.

[0054] As shown in Fig. 2 (also see Tables 1 to 4), in Examples 1 to 12 (see the plots within the bold frames in Fig. 2) in which the total content of Cu, Cr, Ni, and Sn is 1.2 wt% or less, the iron loss W10 / 400 is 8 W / kg or less. Similarly, in Comparative Examples 1 to 7 in which the content of Cu, Cr, Ni, and Sn is zero, the iron loss W10 / 400 is 8 W / kg or less.

[0055] On the other hand, in Examples 13 to 17 (see the plots outside the bold frame in FIG. 2) in which the total content of Cu, Cr, Ni, and Sn exceeds 1.2 wt%, the iron loss W10 / 400 exceeds 8 W / kg.

[0056] In Prior Art 1 using hot rolling, although the total content of Cu, Cr, Ni, and Sn is 1.2 wt% or less, the iron loss W10 / 400 is significantly greater than 8 W / kg.

[0057] According to FIG. 2, when the soft magnetic steel sheet contains 0.10 to 1.0 wt% Cu, 0.01 to 0.5 wt% Cr, 0.01 to 0.5 wt% Ni, and 0.01 to 0.3 wt% Sn as impurities, and the total content of these impurities is 1.2 wt% or less, it can be seen that the iron loss W10 / 400 of the soft magnetic steel sheet can be kept to a good value (8 W / kg or less).

[0058] Fig. 3 shows the relationship between the grain size (average value) [µm] and the iron loss W10 / 400 [W / kg] for Examples 26 to 36 and Comparative Examples 12 to 25. The bold frame in Fig. 3 indicates the region where the iron loss W10 / 400 is 8 W / kg or less and the grain size is 150 to 550 µm.

[0059] As shown in Figure 3 (also see Tables 1 to 4), in Examples 26 to 33 and 35 to 36 (see the plots within the bold frames in Figure 3) where the crystal grain size is in the range of 150 to 550 µm, the iron loss W10 / 400 is all 8 W / kg or less. Similarly, in Comparative Examples 18 and 21 to 25 where the crystal grain size is in the range of 150 to 550 µm, the iron loss W10 / 400 is all 8 W / kg or less.

[0060] On the other hand, in Example 34, where the crystal grain size is less than 150 μm (47 μm), the iron loss W10 / 400 exceeds 8 W / kg. Also, in Comparative Examples 12 to 17 and 19 to 20, where the crystal grain size is less than 150 μm, the iron loss W10 / 400 exceeds 8 W / kg.

[0061] It can be seen from FIG. 3 that in order to make the iron loss W10 / 400 of the soft magnetic steel sheet 8 W / kg or less, the crystal grain size must be within the range of 150 to 550 μm.

[0062] Fig. 4 shows the relationship between the amount of impurities [wt%] and the average crystal grain size [µm] for Examples 18 to 22 and Comparative Example 8. In Examples 18 to 22 and Comparative Example 8, the heat treatment was performed under the same conditions (1150°C in an Ar atmosphere for 24 hours). The bold frame in Fig. 4 indicates the region where the amount of impurities [wt%] is 1.2 wt% or less and the crystal grain size is 150 to 550 µm.

[0063] According to FIG. 4, if the impurity amount [wt %] of the soft magnetic steel sheet is 1.2 wt % or less, the crystal grain size falls within the range of 150 to 550 μm.

[0064] Fig. 5 shows the relationship between the heat treatment temperature [°C] and the crystal grain size (average value) [µm] for Examples 23 to 25, 30, and 35 and Comparative Examples 9 to 11. The bold frame in Fig. 5 indicates the region where the crystal grain size is 150 to 500 µm (i.e., 550 µm or less) and the heat treatment temperature is 1100 to 1300°C.

[0065] According to FIG. 5, if the heat treatment temperature of the soft magnetic steel sheet is within the range of 1100 to 1300° C., the crystal grain size is within the range of 150 to 500 μm (that is, 550 μm or less).

[0066] As shown in Tables 1 and 2, for other examples not shown in FIGS. 4 and 5, if the impurity amount [wt%] is 1.2 wt% or less and the heat treatment temperature is within the range of 1100 to 1300°C, the crystal grain size is within the range of 150 to 550 μm or less.

[0067] Figure 6 shows transmission electron microscope (TEM) images for (A) Example 37, (B) Example 38, (C) Example 39, and (D) Example 40. The TEM images for each example include images of the interior of crystal grains and the grain boundaries. The grain size d of the Cu-Sn-based precipitates shown in Figure 6 was calculated using the method described above.

[0068] 6, it can be seen that the particle size d of the Cu-Sn based precipitates increases with an increase in the amount of Cu and Sn (i.e., the content of Cu and Sn). Furthermore, as will be described later with reference to FIGS. 9 and 10, it can be seen that in order to make the iron loss W10 / 400 of the soft magnetic steel sheet 8 W / kg or less (corresponding to Examples 37 to 39), it is necessary to make the particle size d of the Cu-Sn based precipitates approximately 60 nm or less (here, 56 nm or less).

[0069] Fig. 7 shows the relationship between the amount of impurities [wt%] and the particle size [µm] of Cu-Sn-based precipitates for Examples 37-40 and Conventional Technique 1. Fig. 8 shows the results for Examples 37-40 with the scale of the vertical axis shown in Fig. 7 changed.

[0070] 7 and 8 show that when the amount of impurities (i.e., the total content of impurities) is 1.2 wt% or less (corresponding to Examples 37 to 39), the grain size of Cu—Sn-based precipitates is 60 nm or less.

[0071] Fig. 9 shows the relationship between the particle size [μm] of Cu-Sn-based precipitates and the iron loss W10 / 400 [W / kg] for Examples 37-40 and Conventional Technique 1. Also, Fig. 10 changes the scale of the vertical axis shown in Fig. 9 to focus on Examples 37-40.

[0072] 9 and 10, it can be seen that in order to make the iron loss W10 / 400 of the soft magnetic steel sheet 8 W / kg or less (corresponding to Examples 37 to 39), it is necessary to make the grain size of the Cu—Sn-based precipitates 60 nm or less.

[0073] Thus, according to the soft magnetic steel sheet and its manufacturing method of the present invention, by appropriately determining the content and average grain size of components derived from iron scrap, it is possible to suppress degradation of performance, such as magnetic properties, even when impurities derived from iron scrap are contained in the raw materials. Furthermore, by setting the grain size of Cu-Sn-based precipitates to 60 nm or less, it is possible to more reliably suppress degradation of performance, such as magnetic properties, of the soft magnetic steel sheet. The range of grain size of the soft magnetic steel sheet can be controlled by appropriately setting the heat treatment conditions (temperature and time).

[0074] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and its modifications, and can be modified in a wide range of ways. [Explanation of symbols]

[0075] 1: Manufacturing equipment 2: Cooling roll 3: Molten metal 4: Nozzle 4a: Injection hole 5: Thin strip 7: Heater

Claims

1. A soft magnetic steel plate manufactured from raw materials including iron scrap, Fe as a base material, 1.0 to 7.0 wt% Si; a component derived from the iron scrap; Including, The components derived from the iron scrap include 0.10 to 1.0 wt% Cu, 0.01 to 0.5 wt% Cr, 0.01 to 0.5 wt% Ni, and 0.01 to 0.3 wt% Sn, and the sum of these components is within a range of 0.1 to 1.2 wt%; A soft magnetic steel sheet having an average crystal grain size in the range of 150 to 550 μm.

2. 2. The soft magnetic steel sheet according to claim 1, wherein the grain size of the Cu-Sn based precipitates is 60 nm or less.

3. The soft magnetic steel plate according to claim 1, wherein the soft magnetic steel plate has a thickness of 0.03 to 0.15 mm and an iron loss W10 / 400 of 8 W / kg or less.

4. A method for manufacturing a soft magnetic steel sheet according to any one of claims 1 to 3, a strip-shaped thin plate forming step of forming a strip-shaped thin plate from the raw material by a single-roll liquid quenching solidification method; a heat treatment step of heat treating the strip-shaped thin plate in an inert atmosphere at 1100 to 1300°C for 10 minutes to 48 hours; A method for manufacturing a soft magnetic steel sheet, comprising:

5. The method for producing a soft magnetic steel sheet according to claim 4, wherein the heat treatment temperature is 1150 to 1250°C.

6. The method for producing a soft magnetic steel sheet according to claim 5, wherein the heat treatment is carried out for 2 to 24 hours.

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