Title of invention : Hot-rolled steel sheet for non-oriented electrical steel sheet
Technical field
[0001]
The present invention relates to hot-rolled steel sheets for non-oriented electrical steel sheets with excellent magnetic properties, which are mainly used as iron core materials for electrical equipment.
This application claims priority based on Japanese Patent Application No. 2020-027503 filed in Japan on February 20, 2020, the content of which is incorporated herein.
Background technology
[0002]
In recent years, electrical equipment, especially in the fields of rotating machines, small and medium-sized transformers, electrical equipment, etc., where non-oriented electrical steel sheets are used as core materials, are represented by global power and energy savings, CO2 reduction, etc. In the global environment conservation movement, the demand for high efficiency and miniaturization is increasing more and more. Under such a social environment, it is of course an urgent task to improve the performance of non-oriented electrical steel sheets.
[0003]
Iron loss and magnetic flux density are required for non-oriented electrical steel sheets to improve the characteristics of motors. In the conventional technology, the grain size before cold rolling is increased by high temperature coiling after hot rolling to control the texture of the product non-oriented electrical steel sheet and improve these properties. .
[0004]
In Patent Document 1, by controlling the columnar crystal ratio and average crystal grain size in casting or rapid solidification of molten steel, controlling the rolling reduction in cold rolling, and controlling the threading tension and cooling rate during final annealing, , to obtain a non-oriented electrical steel sheet capable of obtaining excellent magnetic properties in all directions within the sheet surface.
prior art documents
patent literature
[0005]
Patent Document 1: Japanese Patent Application Laid-Open No. 2019-157247
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0006]
As the demand for non-oriented electrical steel sheets (hereinafter also simply referred to as "electromagnetic steel sheets") increases, there is also a demand for cost reduction. As one of the methods for reducing the manufacturing cost, it is conceivable to omit the annealing after hot rolling by increasing the hot rolling temperature in the hot rolling process. However, in order to achieve low iron loss in electrical steel sheets, a large amount of Si is added compared to ordinary steel sheets, and this is due to the acidity after hot rolling accompanied by bending-unbending in a continuous line. During the washing process, cracks form at the edge of the steel sheet, causing breakage. If annealing after hot rolling is simply omitted, the toughness deteriorates and the risk of breaking the steel sheet increases.
[0007]
In view of the above circumstances, the present invention can suppress breakage due to bending and unbending in the subsequent pickling process even if annealing after hot rolling is omitted, and has excellent magnetic properties when used as an electromagnetic steel sheet. An object of the present invention is to provide a hot-rolled steel sheet for non-oriented electrical steel sheet with improved toughness.
Means to solve problems
[0008]
The present inventors have found that hot-rolled steel sheets for non-oriented electrical steel sheets omit annealing in the hot-rolling process and have sufficient hot-rolled sheet toughness to suppress the occurrence of breakage at the steel sheet edges during pickling. , and conducted intensive research on methods for achieving both magnetic properties in electrical steel sheets.
[0009]
As a result, by controlling the soaking temperature and time during self-annealing of the hot-rolled steel sheet by high-temperature coiling after hot rolling and the cooling rate of the subsequent cooling, grains at the ends of the hot-rolled steel sheet in the width direction can be improved. The segregation amount of C present in the boundary can be increased relative to the segregation amount of P that reduces toughness, and as a result, the toughness of the hot-rolled steel sheet can be improved and breakage due to bending-unbending can be prevented, and It has been found that excellent magnetic properties can be realized when made into a non-oriented electrical steel sheet.
[0010]
The present invention was made based on the above findings, and the gist thereof is as follows.
[0011]
(1) In mass %, C: 0.0010 to 0.0050%, Si: 1.90% to 3.50%, Al: 0.10% to 3.00%, Mn: 0.05 to 2.0%. 00%, P: 0.10% or less, S: 0.005% or less, N: 0.0040% or less, B: 0.0060% or less, Sn: 0-0.50%, Sb: 0-0. 50%, Cu: 0-0.50%, REM: 0-0.0400%, Ca: 0-0.0400%, and Mg: 0-0.0400%, the balance being Fe and impurities A hot-rolled steel sheet for non-oriented electrical steel sheet, wherein the C concentration [atomic %] at the grain boundary is 3 of the P concentration [atomic %] at the end in the width direction of the hot-rolled steel sheet for non-oriented electrical steel sheet 0 times or more, and the C concentration [atomic %] at the grain boundaries is 3.5 times or more the C concentration in the grains.
[0012]
(2) % by mass, Sn: 0.01% or more and 0.50% or less, Sb: 0.01% or more and 0.50% or less, Cu: 0.01% or more and 0.50% or less, REM: 0.0005 % or more and 0.0400% or less, Ca: 0.0005% or more and 0.0400% or less, Mg: 0.0005% or more and 0.0400% or less. The hot-rolled steel sheet for non-oriented electrical steel sheet according to (1).
Effect of the invention
[0013]
According to the present invention, even when annealing is omitted in the hot rolling process, the hot-rolled sheet has sufficient toughness, and when it is made into a non-oriented electrical steel sheet, it achieves both low core loss and high magnetic flux density. A hot-rolled steel sheet for non-oriented electrical steel sheet can be provided.
MODE FOR CARRYING OUT THE INVENTION
[0014]
A preferred embodiment of the present invention will be described in detail below. However, the present invention is not limited to the configuration disclosed in this embodiment, and various modifications can be made without departing from the gist of the present invention. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present invention can be obtained. Also, each component of the following embodiments can be combined with each other. Moreover, the lower limit value and the upper limit value are included in the range of numerical limits described below. Any numerical value indicated as "greater than" or "less than" is not included in the numerical range.
[0015]
[Chemical composition of hot-rolled steel sheets for non-oriented electrical steel sheets]
First, the reason for limiting the steel composition of the present invention will be described. Hereinafter, "%" for the components of the steel sheet means "% by mass".
[0016]
C: 0.0010-0.0050%
C segregates at grain boundaries to strengthen toughness, so it is preferable to add 0.0010% or more. On the other hand, it is a harmful component that deteriorates iron loss and causes magnetic aging, so it is made 0.0050% or less, preferably 0.0040% or less.
[0017]
　Si: 1.90% to 3.50%
Si is a component that has the effect of reducing iron loss by increasing electrical resistance and reducing eddy current loss, and by increasing the yield ratio, it has the effect of improving the punching workability of the iron core. also have In order to exhibit these actions, it is necessary to contain 1.90% or more. On the other hand, if the content is increased, the magnetic flux density is lowered, and in the manufacturing process itself of the non-oriented electrical steel sheet, workability such as cold rolling is lowered and the cost is increased. It is preferably 3.00% or less.
[0018]
Al: 0.10% to 3.00%
Al is also a component that has the effect of reducing iron loss by increasing electrical resistance and reducing eddy current loss, like Si, but the increase in hardness is less than that of Si. Therefore, it is necessary to contain 0.10% or more. On the other hand, if the content increases, the saturation magnetic flux density will decrease, leading to a decrease in the magnetic flux density, and further to a decrease in the yield ratio, which will also deteriorate the punching accuracy. 2.50% or less.
[0019]
　Mn: 0.05 to 2.00%
Mn has the effect of increasing the electrical resistance and reducing the eddy current loss, as well as improving the primary recrystallization texture and developing the {110}<001> crystal orientation desirable for improving rolling direction magnetic properties. Furthermore, precipitation of fine sulfides such as MnS, which is harmful to grain growth, is suppressed. For these purposes, the content should be 0.05% or more, preferably 0.20% or more. However, if the content increases, the crystal grain growth itself during annealing deteriorates and iron loss increases.
[0020]
P: 0.10% or less
P has the effect of increasing the punching accuracy and may be added, but if the content increases, the steel sheet containing Si≧2% becomes very brittle, so 0.10% or less, preferably 0.05 % or less. Although the lower limit of the P content is not particularly limited, it is preferably 0.005% or more from the viewpoint of magnetic flux density deterioration due to P reduction.
[0021]
S: 0.005% or less
S is 0.005% or less, preferably 0.004% or less, because fine precipitation of sulfides such as MnS inhibits recrystallization and grain growth during final annealing. Although the lower limit of the S content is not particularly limited, it is preferably 0.0005% or more from the viewpoint of cost increase due to desulfurization.
[0022]
N: 0.0040% or less
N reduces the coverage of the internal oxide layer on the surface of the hot-rolled sheet by fine precipitation of nitrides such as AlN generated during hot-rolled sheet annealing and finish annealing, and further reduces recrystallization and grain growth during finish annealing. 0.0040% or less, preferably 0.0030% or less. Although the lower limit of the N content is not particularly limited, it is preferably 0.0005% or more from the viewpoint of cost increase for reducing N.
[0023]
B: 0.0060% or less
B is 0.0060% or less, preferably 0.0040% or less, because fine precipitation of nitrides such as BN inhibits recrystallization and grain growth during final annealing. Although the lower limit of the B content is not particularly limited, it is preferably 0.0001% or more from the viewpoint of cost increase for reducing B.
[0024]
Sn: 0-0.50%
Sb: 0-0.50%
Although Sn and Sb are not essential elements, they improve the primary recrystallization texture of the steel sheet to develop a {110}<001> texture desirable for improving rolling direction magnetic properties, and are not desirable for magnetic properties. Since it has the effect of suppressing the {111}<112> texture, etc., it may be added as necessary. For these purposes, Sn and Sb are preferably contained in an amount of 0.01% or more. On the other hand, even if the content of Sn is increased, the effect is saturated, and rather the toughness of the hot-rolled sheet may be lowered. .
[0025]
Cu: 0-0.50%
Although Cu is not an essential element, it precipitates in steel and exhibits the effect of improving strength, so it may be added as necessary. In order to obtain this action, it is preferably contained in an amount of 0.01% or more. On the other hand, if the Cu content exceeds 0.50%, cracks and flaws may occur during rolling. Therefore, the Cu content is preferably 0.01 to 0.50%. Even if Sn, Sb, or Cu is contained as an impurity, the effects of the basic elements are not impaired.
[0026]
　REM: 0 to 0.0400% or less
　Ca: 0 to 0.0400% or less
　Mg: 0 to 0.0400% or less
Although REM, Ca, and Mg are not essential elements, they are elements that promote grain growth and may be added as necessary. In order to obtain this effect, the content of each is preferably 0.0005% or more. Any element is preferably 0.0010% or more, more preferably 0.0050% or more. On the other hand, if REM, Ca, and Mg exceed 0.0400%, the magnetic properties deteriorate, so the content should be 0.0040% or less. Preferably, any element is 0.0300% or less, more preferably 0.0200% or less. Note that REM is an abbreviation for Rare Earth Metal, and refers to elements belonging to the Sc, Y, and lanthanide series. In the case of lanthanides, they are industrially added in the form of misch metals.
[0027]
The components other than those mentioned above are Fe and impurity elements.
[0028]
By using the components as described above, it is possible to obtain a non-oriented electrical steel sheet having excellent magnetic properties when made into an electrical steel sheet.
[0029]
The above steel components can be measured by a general steel analysis method. For example, the steel composition is ICP-AES (Inductively Coupled Plasma-Atomic Emission spectrometry). Incidentally, C and S may be measured using the combustion-infrared absorption method, and N may be measured using the inert gas fusion-thermal conductivity method.
[0030]
[Concentration of grain boundary elements in hot-rolled steel sheets for non-oriented electrical steel sheets]
Next, the concentration of elements at grain boundaries of hot-rolled steel sheets for non-oriented electrical steel sheets will be described.
[0031]
　
Next, in the hot-rolled steel sheet for non-oriented electrical steel sheet of the present embodiment, the ratio TR=C/P of the C concentration (C) and the P concentration (P) [atomic %] contained in the grain boundary is 3.0 or more. It is characterized by one thing. P is a typical element that lowers cohesive force between atoms, and lowers toughness by segregating at grain boundaries. Therefore, the amount of P that segregates at grain boundaries is preferably as small as possible, but since P is usually inevitably contained in steel sheets as an impurity element, it is difficult to avoid a decrease in toughness due to grain boundary segregation of P. In other words, the ratio TR=C/P of the C concentration (C) and the P concentration (P) [atomic %] contained in the grain boundaries of the hot-rolled steel sheet for non-oriented electrical steel sheet is 3.0 or more. , means that the C concentration [atomic %] at the grain boundary is 3.0 times or more the P concentration [atomic %].
[0032]
C is a representative element that improves cohesive force between atoms, and segregates at grain boundaries to improve toughness. Therefore, in the hot-rolled steel sheet for non-oriented electrical steel sheet of the present invention, the concentration of C segregating at the grain boundary is set to be 3.0 times or more the concentration of P segregating at the grain boundary. This can improve the toughness of the hot-rolled steel sheet and prevent the edge of the steel sheet from breaking due to bending and unbending in the pickling process.
[0033]
When the steel sheet breaks due to bending and unbending, cracks occur at the edges and break, so the concentration of C and P contained in the grain boundaries at the edges of the steel sheet should be in the above relationship. Specifically, the C concentration and P concentration contained in the grain boundary are measured by placing the Charpy test piece at a position 10 mm from the width direction end face of the steel plate (hereinafter referred to as the width direction end). A notch is added to the side surface of the steel sheet, a Charpy test is performed in an atmosphere of -50°C or less, and the grain boundary fracture surface is measured by analyzing it with Auger Electron Spectroscopy (AES). The C concentration and P concentration are calculated from the ratio of the spectral intensity of the grain boundary fracture surface analyzed by AES and the spectral intensity of the existing element amount. Here, the L section means a section parallel to the thickness direction and the rolling direction (or the longitudinal direction of the steel sheet) of the steel sheet.
[0034]
B also has the same effect as C, but B is also an element that deteriorates the magnetic properties, so it is difficult to achieve both magnetic properties and toughness. In the present invention, C is segregated at grain boundaries because it inhibits recrystallization and grain growth during finish annealing and the like.
[0035]
　
In addition to the ratio of C concentration and P concentration in the grain boundaries described above, the C concentration (C GB) [atomic %] present in the grain boundaries of the hot-rolled steel sheet for non-oriented electrical steel sheets and the C concentration present in the grains By setting the (C IG) [atomic %] ratio CR=C GB/C IG to 3.5 or more, the toughness can be further improved. The grain boundary C concentration and the intragranular C concentration can be measured in the same manner as the above-described C concentration and P concentration. The ratio of the C concentration (C GB) [atomic %] existing in the grain boundaries of the hot-rolled steel sheet for non-oriented electrical steel sheets to the C concentration (C IG) [atomic %] present in the grains CR=C GB/C IG is 3.5 or more, in other words, the C concentration [atomic %] at the grain boundary of the hot-rolled steel sheet for non-oriented electrical steel sheet is 3.5 times or more the C concentration in the grain. It means that there is
[0036]
[Production method]
Next, the method for manufacturing the hot-rolled steel sheet for non-oriented electrical steel sheet of the present invention will be described.
[0037]
The hot-rolled steel sheet for non-oriented electrical steel sheet of the present invention is obtained by continuously casting molten steel having the above-described components into a slab, further hot-rolling it into a hot-rolled sheet (hot-rolling process), and winding it after hot-rolling. It is manufactured by self-annealing with the heat of the coil and then cooling. A conventional method may be used to manufacture the slab.
[0038]

The slab is then preferably heated to 1080-1200°C and subjected to hot rolling. The reason why the heating temperature is preferably set to 1080° C. or higher is that the finishing temperature is set to 850° C. or higher to omit annealing by reheating after winding, as will be described later. The reason why the finishing temperature is preferably 1200° C. or less is to prevent solid solution and fine precipitation of impurities such as sulfides and to prevent an increase in iron loss.
[0039]
The finishing temperature is preferably 850-1000°C. This is because annealing by reheating is omitted by self-annealing with the heat of the coil at a coiling temperature of 700 to 800° C., as will be described later. Also, if the finishing temperature is low, the hot workability may deteriorate, and the thickness accuracy in the width direction of the steel sheet may deteriorate. On the other hand, the finishing temperature is preferably 1000° C. or less in order to prevent deterioration of toughness due to coarsening of the ferrite grain size.
[0040]

Next, the hot-rolled steel sheet after finish rolling is wound up at 700-850°C. By winding at 700 to 850° C., self-annealing can be performed by the heat accumulated in the wound coil. It becomes possible to suppress the growth of crystal grains. In order to improve the magnetic properties, especially the magnetic flux density, it is preferable to make the grain size of the hot-rolled steel sheet coarser before cold rolling. is not obtained, the winding temperature is preferably 850° C. or lower.
[0041]
The process of self-annealing the coil after winding is also called a heat retention process. The heat retention step means the process from the time the hot-rolled steel sheet is wound into a coil to the time the temperature of the coil begins to drop. The time point at which the coil is formed is the time point at which one turn of the coil is finished from the hot-rolled steel sheet in one zone. The point at which the temperature of the coil begins to fall is the point at which the cooling rate of the coil changes, in other words, the point of inflection on the cooling rate curve. Depending on the heat retention temperature, the temperature change in the coil may be extremely small for a predetermined period of time after winding the coil, and after the predetermined period of time, the temperature of the coil begins to drop rapidly.
[0042]
In addition, in order to increase the crystal grain size of the hot-rolled steel sheet before cold rolling, the coil after winding may be covered with a heat insulating cover to retain heat. When the heat insulating cover is used to carry out the heat insulating process, the holding time is the time from when the heat insulating cover is put on the coil until it is removed. From the viewpoint of recrystallization of the hot-rolled sheet, the heat retention time is preferably 1 minute or longer. On the other hand, excessive grain growth tends to cause breakage in the pickling process and cold rolling process, so the holding time is preferably 2 hours or less.
[0043]
The process of covering the coil with a heat insulating cover to retain heat, or the process of performing self-annealing by the heat accumulated in the wound coil is also referred to as the heat retaining process. The temperature of the heat retention step is preferably 720°C to 830°C. By setting the temperature of the heat retention step to 720° C. or higher, the grain size before cold rolling is sufficiently grown, and a high magnetic flux density can be obtained. In addition, by setting the temperature of the heat retention step to 830° C. or less, an effect of suppressing the formation of an internal oxide layer on the surface of the steel sheet can be obtained.
[0044]

In the present invention, it is important to control the cooling rate so that the C concentration and P concentration at the grain boundary have the relationship described above.
[0045]
Specifically, by increasing the cooling rate in the temperature range from the coiling temperature to 600 ° C., which is the temperature at which P tends to segregate at the grain boundary, the segregation of P is suppressed, and the temperature at which C tends to segregate at the grain boundary. By reducing the cooling rate in the temperature range of 400 to 600° C., the segregation of C is promoted. This makes it possible to suppress toughness deterioration due to grain boundary segregation of P and prevent breakage of the steel sheet in the next step. The step of controlling the cooling rate in the temperature range from the winding temperature to 400°C is also called the cooling step.
[0046]
The average cooling rate from the winding temperature to 600°C is preferably 10-100°C/min. The average cooling rate from the winding temperature to 600° C. is more preferably over 10° C./min, more preferably 20° C./min, 30° C./min, or 40° C./min.
[0047]
The average cooling rate at 400 to 600°C is preferably small in order to promote the segregation of C to grain boundaries, but if it is too small, the self-annealing time will be long, the grain size will become too coarse, and the toughness will deteriorate. , 30° C./hr or more. If the cooling rate is too high, C will not segregate sufficiently, so the cooling rate is preferably 120° C./hr or less.
[0048]
As described above, cracks occur at the ends of the steel plate, leading to breakage of the steel plate, so the above cooling rates are for the ends of the steel plate (side surfaces of the coil). The cooling rate can be controlled by blowing air through the coils with a blower and adjusting the amount or temperature of the air. As for the temperature of the edge of the steel plate, the temperature of the steel plate cross section (desired location) is measured with a radiation thermometer. The time during which air is blown to the coil by the blower is defined as the cooling time. There is no particular specification for the cooling time.
[0049]
Furthermore, by setting the cooling rate at 400 to 600 ° C. to 50 to 80 ° C./hr, the C concentration C GB [atomic %] existing at the grain boundary of the hot rolled steel sheet for non-oriented electrical steel sheet and The ratio CR=C GB/C IG of the C concentration C IG [atomic %] can be set to 3.5 or more.
[0050]
Specifically, the cooling rate is controlled by blowing air, for example, with a blower to the coil that has undergone self-annealing (heat retention process) to cool the coil.
[0051]
It should be noted that it is more preferable to start cooling immediately after removing the cover described above. Alternatively, cooling is more preferably initiated by the time the temperature of the coil begins to drop.
[0052]

When Sn and Sb are added to the steel sheet, these elements contribute to low iron loss and high magnetic flux density, so the heat retention temperature can be lowered, and as a result, toughness can be improved. can be done. At this time, by setting the heat retention temperature to 850° C. or lower, preferably 800° C. or lower, and more preferably 750° C. or lower, it is possible to highly achieve both appropriate toughness, low iron loss, and high magnetic flux density. can.
[0053]
The mechanism by which the addition of Sn and Sb contributes to low core loss and high magnetic flux density is thought to be that these elements suppress the growth of {111} oriented grains that adversely affect magnetic properties.
[0054]
The hot-rolled steel sheet for a non-oriented electrical steel sheet of the present invention obtained as described above is subjected to pickling, cold rolling, and finish annealing by a conventional method to obtain a non-oriented electromagnetic steel sheet having excellent magnetic properties. You can get steel plates. At this time, as described above, since the hot-rolled steel sheet for non-oriented electrical steel sheet of the present invention is excellent in toughness, even if it is pickled by a normal method, cracks do not occur due to bending and unbending. As described above, the hot-rolled steel sheet for non-oriented electrical steel sheet according to the present invention undergoes a hot rolling process, a heat retention process, and a cooling process. The cooling step may be performed, for example, during the transportation of the coil to a pickling apparatus used in the pickling step prior to cold rolling the steel sheet in the method for manufacturing a non-oriented electrical steel sheet.
[0055]
In the present invention, the toughness of a hot-rolled sheet means the toughness of a steel sheet for non-oriented electrical steel sheets that has undergone a cooling process after the self-annealing described above and before the pickling process.
Example
[0056]
Next, examples of the present invention will be described, but the conditions in the examples are examples of one condition adopted to confirm the feasibility and effect of the present invention, and the present invention is based on this example. It is not limited. Various conditions can be adopted in the present invention as long as the objects of the present invention are achieved without departing from the gist of the present invention.
[0057]

Steel was cast with the ingredients shown in Table 1 and hot rolled to produce a hot rolled sheet with a thickness of 2.0 mm. After that, it was wound into a coil under the conditions shown in Table 2, heat-retained, and then cooled to obtain a hot-rolled steel sheet for non-oriented electrical steel sheet.
[0058]
Cooling was done by blowing air on the edge. The cooling rate is The cooling rate at the edge position was measured using a radiation thermometer.
[0059]
It should be noted that production code B0 is a reference example in which the hot-rolled sheet was annealed in a 100% nitrogen atmosphere after coiling and cooling. Table 3 shows the measurement results of the transition temperature in the Charpy test conducted to evaluate the C and P concentrations at the grain boundaries and the toughness of the produced hot-rolled steel sheets for non-oriented electrical steel sheets.
[0060]
For the grain boundary C and P concentrations, a Charpy test piece is cut from the end of the steel sheet in the width direction, a notch is attached to the side surface of the steel sheet, a Charpy test is performed in an atmosphere of -50 ° C or less, and the grain boundary fracture surface is measured. It was measured by analyzing with Auger Electron Spectroscopy (AES).
[0061]
The fracture surface transition temperature was measured by performing a Charpy test in accordance with JIS Z 2242. In this example, when the fracture surface transition temperature was less than 0°C, it was determined that the toughness was good.
[0062]
Next, the prepared hot-rolled steel sheet for non-oriented electrical steel sheet is immersed in hydrochloric acid (7.5 mass%) at 85° C. for 30 seconds for pickling, and then cold-rolled to a thickness of 0.5 mm at a rolling reduction of 75%. Finish annealing was performed at 1050° C. for 30 seconds to obtain a non-oriented electrical steel sheet.
[0063]
In addition, the magnetic properties of the obtained non-oriented electrical steel sheets were measured according to JIS C 2556.
[0064]
For iron loss, a 55 mm square sample was taken from the non-oriented electrical steel sheet, and W15/50 (iron loss when the steel sheet was magnetized at 50 Hz to a magnetic flux density of 1.5 T) was measured using a Single Sheet Tester (SST). evaluated. The magnetic flux density was evaluated using B50, which is the magnetic flux density at a magnetic field strength of 5000 A/m. The measurement results are also shown in Table 3.
[0065]
[table 1]

[0066]
[Table 2]

[0067]
[Table 3]

[0068]

Using the steel shown in Table 1 and the manufacturing method shown in Table 2, hot-rolled steel sheets for non-oriented electrical steel sheets were similarly produced, and then non-oriented electrical steel sheets were obtained.
[0069]
For the obtained hot-rolled steel sheets for non-oriented electrical steel sheets, in addition to the measurement results of Example 1, the ratio of the C concentration at grain boundaries to the C concentration inside grains was measured. Magnetic properties of the non-oriented electrical steel sheets were measured in the same manner as in Example 1. Table 4 shows the results.
[0070]
[Table 4]

[0071]
By setting the ratio CR=C GB/C IG of the C concentration C GB [atomic %] present in the grain boundary to the C concentration C IG [atomic %] present in the grains to 3.5 or more, even better characteristics It was confirmed that Although not explicitly shown in Table 3, C1, C2, C3, C5, C9, C11, and C12 had a CR of 3.5 or more.
[0072]
By using the hot-rolled steel sheet for non-oriented electrical steel sheet of the present invention, the steel sheet does not break in pickling, and the non-oriented hot-rolled steel sheet for non-oriented electrical steel sheet subjected to conventional hot-rolled sheet annealing is used. It was confirmed that a non-oriented electrical steel sheet having excellent properties similar to the grain-oriented electrical steel sheet can be obtained.
Industrial applicability
[0073]
According to the present invention, even when annealing is omitted in the hot rolling process, the hot-rolled sheet has sufficient toughness, and when it is made into a non-oriented electrical steel sheet, it achieves both low core loss and high magnetic flux density. A hot-rolled steel sheet for non-oriented electrical steel sheet can be provided. As a result, non-oriented electrical steel sheets with low iron loss and high magnetic flux density can be produced stably without breakage. It can fully respond to production, and its industrial value is extremely high.
The scope of the claims
[Claim 1]
in % by mass,
　　C: 0.0010 to 0.0050%,
　　Si: 1.90% to 3.50%,
Al: 0.10% to 3.00%,
　Mn: 0.05 to 2.00%,
　　P: 0.10% or less,
　　S: 0.005% or less,
　　N: 0.0040% or less,
B: 0.0060% or less,
Sn: 0-0.50%,
Sb: 0 to 0.50%,
　　Cu: 0 to 0.50%,
REM: 0 to 0.0400%,
　　Ca: 0 to 0.0400%, and
　Mg: 0 to 0.0400%
A hot-rolled steel sheet for a non-oriented electrical steel sheet containing the balance Fe and impurities,
At the end of the hot-rolled steel sheet for non-oriented electrical steel sheet in the width direction, the C concentration [atomic %] at the grain boundary is 3.0 times or more the P concentration [atomic %],
The C concentration [atomic %] at the grain boundary of the hot-rolled steel sheet for non-oriented electrical steel sheet is 3.5 times or more the C concentration in the grain
A hot-rolled steel sheet for non-oriented electrical steel sheet characterized by:
[Claim 2]
% by mass, Sn: 0.01% or more and 0.50% or less, Sb: 0.01% or more and 0.50% or less, Cu: 0.01% or more and 0.50% or less, REM: 0.0005% or more, 0.0400% or less, Ca: 0.0005% or more and 0.0400% or less, Mg: 0.0005% or more and 0.0400% or less, one or more of the following: 2. The hot-rolled steel sheet for non-oriented electrical steel sheet according to 1.