JP4280197B2 - Non-oriented electrical steel sheet and manufacturing method thereof - Google Patents

Description

  The present invention reduces the iron loss of non-oriented electrical steel sheets used for motor iron cores, etc., reduces energy loss, increases the efficiency of electrical equipment, and contributes to energy saving. It aims at providing the non-oriented electrical steel sheet excellent in the iron loss after annealing.

  Non-oriented electrical steel sheets are known to have a minimum iron loss when the crystal grain size is about 150 μm. For this reason, from the viewpoint of product characteristics, or from the viewpoint of simplification of production and high productivity, a steel sheet having better crystal grain growth in finish annealing is desired.

  On the other hand, when an iron core is punched by a customer, the punching accuracy in punching is better as the crystal grains are finer, and the crystal grain size is preferably, for example, 40 μm or less. As described above, there is a case where the iron loss with respect to the crystal grain size and the requirement of the punching accuracy are contradictory.

  In particular, when satisfying these conflicting requirements, the product plate is shipped with the crystal grain size being fine, and after punching by the customer, for example, 750 ° C. × 2 hours of strain relief annealing is performed to obtain the crystal grains. Measures to grow are selected.

  In recent years, demand for low iron loss materials has been stronger than customers, and shortening of strain relief annealing has been aimed at by improving productivity of customers, and better grain growth in strain relief annealing. The need for product plates has increased.

  One of the main factors that hinders grain growth is inclusions that are finely dispersed in the steel. It is known that the larger the number of inclusions contained in the product and the smaller the size, the more the grain growth is inhibited.

  In other words, as suggested by Zener, the smaller the r / f value represented by the sphere equivalent radius r of inclusions and the volume occupancy f of inclusions in the steel, the more the grain growth becomes. Getting worse. Therefore, in order to improve the crystal grain growth, it is important not only to reduce the number of inclusions but also to increase the size of the inclusions.

Regarding a preferable range of the diameter and the number of inclusions in the non-oriented electrical steel sheet, for example, in Patent Document 1, inclusions having an inclusion diameter of 0.1 [μm] to 1 [μm] and more than 1 [μm] are used. In addition, it is disclosed that the unit cross-sectional area is within the range of 5000 to 10 ⁵ [piece / mm ² ] and 500 or less [piece / mm ² ], respectively.

In order to make the actual situation easier to understand, when this number is converted into the number of inclusions present in a unit volume of steel, that is, the number density of inclusions, 5 × 10 ⁶ to 1 × 10 ⁹ [pieces / piece], respectively. mm ³ ] and 5 × 10 ⁵ or less [pieces / mm ³ ].

  Known inclusions that inhibit the grain growth of non-oriented electrical steel sheets include oxides such as silica and alumina, sulfides such as manganese sulfide, and nitrides such as aluminum nitride and titanium nitride.

  In order to remove these inclusions, it is obvious that high purity can be achieved at the molten steel stage. However, as an alternative method, there are several methods for detoxifying inclusions by adding various elements to steel. Is known.

  Regarding oxides, it is possible to remove the oxides at the molten steel stage and make them harmless by adding a sufficient amount of Al, which is a strong deoxidizing element, and taking sufficient time to lift and remove the oxides. It has become.

  Regarding sulfides, in addition to purifying at the molten steel stage, as disclosed in, for example, Patent Document 2, Patent Document 3, and Patent Document 4, a method of fixing S by adding a desulfurization element REM or the like is known. ing. As for nitrides, as disclosed in Patent Document 5 or Patent Document 6 or the like, a method of fixing N as coarse inclusions by adding B is known.

JP 2001-271147 A JP 51-62115 A JP 56-102550 A Japanese Patent No. 3037878 Japanese Patent No. 11678896 Japanese Patent No. 1245901

  However, high purity in the molten steel stage is not preferable because it is inevitable that steelmaking costs are unavoidable, and the methods using the above-mentioned additive elements are also capable of further shortening the temperature at a lower temperature, such as finish annealing of the product plate or strain relief annealing after punching. The improvement of the crystal grain growth and the reduction of the iron loss accompanying the above were insufficient.

  It should be noted in particular that even if the number density of inclusions is adjusted within the recommended range disclosed in the above-mentioned Patent Document 1, if the strain relief annealing is performed at a lower temperature for a shorter time, crystal grain growth may still not be improved. It was.

  The reason for this is that the inclusion diameter and number density adjusted based on conventional knowledge are different from the composition, diameter and number density of inclusions that actually inhibit crystal grain growth, as will be described later. there were.

  The present invention makes it possible to reduce the iron loss by sufficiently growing the crystal grains sufficiently, and in particular, sufficiently growing the crystal grains even if the annealing after punching is performed at a lower temperature and for a shorter time. An object of the present invention is to provide a non-oriented electrical steel sheet that can be reduced in iron loss.

  The gist of the present invention is as follows.

( 1 ) By mass%, C: 0.01% or less, Si: 0.1% or more and 7.0% or less, Al: 0.1% or more and 3.0% or less, Mn: 0.1% or more. 0% or less, REM: 0.0003% to 0.05%, Ti: more than 0.0015%, 0.02% or less, S: 0.005% or less, N: 0.005% or less, the balance Is composed of iron and inevitable impurities, and the mass% of Al shown by [Al], the mass% of N shown by [N], and the mass% of Ti shown by [Ti] meets the following equation (1), non-oriented electrical steel sheet you wherein a number density of inclusions of less than equivalent spherical diameter 100nm contained within the steel sheet is 1 × 10 10 ^[pieces / mm ^3] or less .
log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.84> 0 (1)
(2) By mass%, C: 0.01% or less, Si: 0.1% or more and 7.0% or less, Al: 0.1% or more and 3.0% or less, Mn: 0.1% or more. 0% or less, REM: 0.0003% to 0.05%, Ti: more than 0.0015%, 0.02% or less, S: 0.005% or less, N: 0.005% or less, the balance Is composed of iron and inevitable impurities, and the mass% of Al shown by [Al], the mass% of N shown by [N], and the mass% of Ti shown by [Ti] The non-oriented electrical steel sheet satisfying the following formula (1) and having a number density of inclusions having a sphere equivalent diameter of less than 50 nm contained in the steel sheet is 2.5 × 10 ⁹ [pieces / mm ³ ] or less. .
log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.84> 0 (1)

(3) the steel sheet further contains, by mass%, P: 0.1% or less, Cu: according to the which is characterized by containing one or more under 0.5% or less (1) or (2) Non- oriented electrical steel sheet.

( 4 ) By mass%, C: 0.01% or less, Si: 0.1% to 7.0%, Al: 0.1% to 3.0%, Mn: 0.1% to 2. 0% or less, REM: 0.0003% to 0.05%, Ti: more than 0.0015%, 0.02% or less, S: 0.005% or less, N: 0.005% or less, the balance Is composed of iron and inevitable impurities, and the mass% of Al shown by [Al], the mass% of N shown by [N], and the mass% of Ti shown by [Ti] the steel satisfies the following formula (1), the manufacturing method of the non-oriented electrical steel sheet you characterized thereby over one minute to a temperature range of 1200 ° C. or higher 1300 ° C. or less.
log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.84> 0 (1)

(5) the steel further contains, by mass%, P: 0.1% or less, Cu: non-oriented according to the characterized in that it contains one or more kinds of under 0.5% or less (4) A method for producing electrical steel sheets.

  According to the present invention, the size and number density of fine inclusions contained in a non-oriented electrical steel sheet can be within an appropriate range, and magnetic characteristics sufficiently good even with simple finish annealing and strain relief annealing compared to conventional ones. Can contribute to energy saving while meeting the needs of consumers.

  The present invention will be specifically described below.

  The present inventor noted that the fine magnetic inclusions included in the steel sheet have an influence on the magnetic characteristics of the non-oriented electrical steel sheet, and the size of the inclusions for showing good magnetic characteristics and punchability. And the appropriate range of number density was found.

  The influence of the size and number density of inclusions on the magnetic properties will be described using the steel shown below. However, this steel is an example, and the present invention is not limited to this.

  Containing C, Si, Al, Mn, REM, Ti, S, N, the steel of the component consisting of iron and inevitable impurities in the remainder, continuously hot-rolled, hot-rolled sheet annealed, Cold-rolled to a thickness of 0.5 mm, subjected to final annealing at 850 ° C. for 30 seconds, and further subjected to strain relief annealing at 750 ° C. for 1.5 hours on the product plate coated with an insulating film. .

  The inclusions, crystal grain size, and iron loss in the product plate after strain relief annealing were investigated. The results are shown in Table 1 and FIGS.

As is clear from Table 1 and FIG. 1, the crystal grain size and iron loss after annealing are the equivalent sphere diameter of inclusions (hereinafter, the inclusion equivalent diameter is referred to as inclusion diameter or diameter for inclusions of the present invention). There was a correlation with the inclusion number density of less than 100 nm, the inclusion number density was 1 × 10 ¹⁰ [pieces / mm ³ ] or less, and the crystal grain growth and the iron loss were good.

In addition, as shown in FIG. 2, when the inclusion number density with an inclusion diameter of less than 50 nm is 2.5 × 10 ⁹ [pieces / mm ³ ] or less, the characteristics are markedly good.

On the other hand, even if the number density of inclusions with an inclusion diameter of 100 nm or more is 1 × 10 ⁹ [pieces / mm ³ ] or less, the number density of inclusions with an inclusion diameter of less than 100 nm is 1 × 10 ¹⁰ [pieces / mm ^3]. ] If it was over, it was a characteristic defect.

It should be noted that there are many inclusions of less than 100 nm in a sample in which the number density of inclusions having an inclusion diameter of 0.1 μm (= 100 nm) or more was 1 × 10 ⁹ [pieces / mm ³ ] or less. Specified that inclusions with an inclusion diameter of less than 100 nm, in particular fine inclusions with an inclusion diameter of less than 50 nm, are the main impeding factors for crystal grain growth, and in turn cause deterioration of iron loss. did it.

  In addition, the above result is a case where the strain relief annealing is performed at 750 ° C. × 1.5 hours, and is a result obtained by performing the strain relief annealing at 750 ° C. × 2 hours in a short time, When conventional strain relief annealing is performed, the difference in crystal grain growth due to the pinning action of fine inclusions becomes more prominent. Needless to say.

  From the above, it has been found that desirable product characteristics cannot always be obtained simply by specifying the number density of inclusions having an inclusion diameter of 100 nm or more with reference to conventional knowledge. Furthermore, by specifying the inclusion number density with a diameter of less than 100 nm, it is possible to obtain preferable product characteristics, and by specifying the inclusion number density with a diameter of less than 50 nm, it is possible to obtain even better product characteristics. It became clear.

  In the present invention, if the size and number density of inclusions in the steel sheet satisfy the scope of the present invention, good product characteristics are exhibited, so the components constituting the steel are particularly limited. It is not a thing.

  Here, an example of the inclusion investigation method will be described. The product plate as a sample was polished from the surface to an appropriate thickness to give a mirror surface, and after performing etching described later, the replica was collected, and the inclusions transferred to the replica were observed with a field emission type transmission electron microscope. In this case, instead of replicas, a thin film may be created and observed.

  The diameter and number density of inclusions were evaluated by measuring all inclusions in a fixed observation area, and the composition of inclusions was determined by an energy dispersive X-ray analyzer and a diffraction pattern analysis.

  Regarding the minimum size of inclusions, since the lattice constant of inclusions is about several angstroms, it is clear that no smaller size can exist, but the lower limit of the diameter of inclusion nuclei that exist stably Is about 5 nm, and a method (for example, magnification) that allows observation up to that level may be selected.

  Etching is performed by, for example, electrolytic corrosion of a sample in a non-aqueous solvent solution by the method of Kurosawa et al. (Fumio Kurosawa, Isamu Taguchi, Ryutaro Matsumoto: Journal of the Japan Institute of Metals, 43 (1979), p. 1068). Only the steel was dissolved with the remaining, and inclusions were extracted.

  As a result of investigating the composition of fine inclusions in the product of the steel containing Ti as described above by such a method, the main inclusions (the number is 50% or less) among the inclusions having a diameter of less than 100 nm. , TiN, TiS, or Ti compounds such as TiC.

  This will be described below. In the electromagnetic steel, it is clear from separate examination that the generation start temperatures of TiN, TiS, and TiC are in the ranges of 1200 to 1300 ° C, 1000 to 1100 ° C, and 700 to 800 ° C, respectively.

  That is, TiN is generated in a cooling process after casting such as a slab, and TiS and TiC are generated in a cooling process after casting such as a slab, and then melted in an ordinary annealing process and then regenerated by subsequent cooling. .

  At this time, the Ti diffusion rate in the steel is about a fraction of that of other metal elements in each production start temperature region, so the Ti compound is in comparison with other inclusions. The Ti compound cannot be increased to an inclusion diameter of 100 nm or more, and becomes fine with an inclusion diameter of less than 100 nm or, in some cases, an inclusion diameter of less than 50 nm.

  As the inclusion diameter is finer, the number density of inclusions inevitably increases, and as described above, it is obvious that the crystal grain growth is more strongly inhibited.

  However, the main inclusion that particularly strongly inhibits the grain growth in the electromagnetic steel is a fine inclusion having an inclusion diameter of less than 100 nm. By limiting the number density of these inclusions, the grain growth and thus the iron loss is reduced. It is a finding for the first time disclosed by the present invention that it is remarkably improved and that many inclusions having an inclusion diameter of less than 100 nm are Ti compounds such as TiN, TiS, or TiC.

  Note that it is usually difficult to prevent a small amount of Ti from being mixed in the manufacturing process. In other words, in the normal steelmaking process, steel types containing a considerable amount of Ti are produced in addition to electromagnetic steel, so that Ti may be inevitably mixed into electromagnetic steel from steel adhering to refractories and adhering slag. is there.

  Alternatively, even in the production of only electromagnetic steel, for example, contamination from a ferrosilicon alloy used for Si component adjustment, or slag and molten steel react to reduce titanium oxide in the slag, so that metal Ti is contained in the steel. When Ti is covered, Ti may be mixed in the steel.

  Conventionally, it was known that Ti inevitably contained in a small amount inhibits crystal grain growth, but according to the investigation by the present inventor, Ti inevitably mixed in is allowed, and further, a preferable Ti range is obtained. It was found that a non-oriented electrical steel sheet with better crystal grain growth can be obtained by controlling the amount of Ti by vigorously adding it.

  Below, the content examined in detail about the influence of the steel component to inclusions is explained.

  A technique using REM for detoxifying TiS among Ti compounds, that is, a technique for fixing S by adding REM to reduce sulfide inclusions has been conventionally known.

  Here, REM is a generic name for a total of 17 elements including 15 elements from lanthanum having an atomic number of 57 to lutesium having an atomic number of 57 plus scandium having an atomic number of 21 and yttrium having an atomic number of 39.

  As a result of detailed study of the phenomenon caused by the addition of REM, the present inventor not only can suppress the formation of fine TiS by fixing S as oxysulfide or sulfide, but also on REM oxysulfide or REM sulfide. As a result, TiN was combined and precipitated, and an appropriate component range capable of detoxifying Ti was found.

  That is, in the electromagnetic steel, TiN and AlN production start temperatures are close, but since Al is predominant in quantity, if the AlN production start temperature is slightly higher than the TiN production start temperature, N is preferentially bonded to Al and consumed for the generation of AlN, and the chance of bonding Ti and N which is slightly smaller than that of Al is remarkably reduced.

  However, TiN is produced under the conditions that TiN is produced. However, since the amount of N is insufficient, it cannot grow sufficiently, and the opportunity to grow on REM oxysulfide or REM sulfide is deprived. As a result, TiN is finely produced alone.

  Thus, a requirement that governs the production of fine TiN is that the TiN production temperature exceeds the AlN production temperature, which is determined by the solubility product.

  That is, when [Ti] represents the mass% of Ti, [N] represents the mass% of N, and [Al] represents the mass% of Al, the generation temperatures of TiN and AlN are respectively [Ti] × [N]. , [Al] × [N].

  As a result of intensive studies, the present inventor, when the amount of REM is in the range of 0.0003 to 0.05 mass% and the component value satisfies the following formula (1), the REM oxysulfide or REM sulfide is used. The present inventors have found that Ti is fixed as TiN and the production of fine TiN is suppressed.

log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.84> 0 (1)
However, [Ti] represents mass% of Ti, [N] represents mass% of N, and [Al] represents mass% of Al.

Accordingly, the number density of inclusions having a sphere equivalent diameter of less than 100 nm contained in the steel sheet is 1 × 10 ¹⁰ [pieces / mm ³ ] or less, or the number density of inclusions having a sphere equivalent diameter of less than 50 nm contained in the steel sheet. Can be made 2.5 × 10 ⁹ [pieces / mm ³ ] or less, and therefore, the grain growth is better even under the same annealing conditions, and therefore a non-oriented electrical steel sheet capable of shortening the annealing time is provided. It became possible.

  In particular, in the strain relief annealing, a good iron loss can be obtained in a short time at a low temperature. Moreover, the further low iron loss came to be obtained by 750 degreeC x 2 hour annealing which is the conventional general distortion removal annealing conditions.

  Specific description will be given below with reference to Table 2.

  No. 11 is mass%, C: 0.0024%, Si: 2.1%, Al: 0.32%, Mn: 0.2%, S: 0.0025%, Ti: 0.0016%, N : 0.0019%, REM: Steel containing 0.0045%.

No. 1 3, No. 1 15 to No. 20 is mass% and contains C: 0.0024%, Si: 2.1%, Mn: 0.2%, S: 0.0025%, P: 0.02%, Cu: 0.01% In addition, the steel has various contents of Al, Ti, N and REM as shown in Table 2.

  These steels are continuously cast, hot-rolled, hot-rolled sheet annealed, cold-rolled to a thickness of 0.50 mm, finish-annealed at 850 ° C x 30 seconds, coated with an insulating film, Created. The crystal grain size of the product plate at this time was in the range of 30 to 33 μm.

Next, these product plates were subjected to strain relief annealing at 750 ° C. for 1.5 hours, which is shorter than conventionally performed. Thereafter, the crystal grain size and magnetic properties were investigated. Results Table 2, and, 3 to 5.

No. 11 and no . As shown in 1 3, an appropriate product component value, if the intervening amount is within the scope of the present invention, the crystal grain size after subjected to stress relief annealing is 67~71μm and grain growth, also The magnetic properties (iron loss: W15 / 50) were as good as 2.7 [W / kg] or less.

As a result of investigating the diameter, number density and composition of inclusions in the product plate by the above-mentioned method, No. 11 contains 0.6 × 10 ¹⁰ [pieces / mm ³ ] of MnS having a diameter of less than 100 nm. The 1 3, Cu ₂ S is less than the diameter 100nm is 0.3 × 10 ¹⁰ [pieces / mm ^3] exists, both were below 1.0 × 10 ¹⁰ [pieces / mm ^3]. In the product, REM oxysulfide and REM sulfide having a diameter of 0.2 [μm] to 2.0 [μm] were observed.

  FIG. 3 shows an example of REM oxysulfide. As shown in FIG. 3, it was observed that TiN was compositely precipitated and coarsened around the REM inclusions.

  In this way, REM in steel forms oxysulfide or REM sulfide and fixes S, thereby preventing or suppressing the formation of fine sulfide, and further, on the REM oxysulfide or REM sulfide, the diameter is several tens of nm. It became clear that the formation of fine Ti-containing inclusions was prevented by superprecipitation of TiN and the fixation of Ti.

No. No. 15 has a REM amount in the range of 0.0003 to 0.05% by mass, but the Ti amount exceeds 0.02% by mass. In this product plate, TiS having a diameter of less than 100 nm is 2. 5 × 10 ¹⁰ [pieces / mm ³ ] was observed, whereby the crystal grain growth was hindered, the crystal grain size after strain relief annealing remained at 35 μm, and the W15 / 50 value was 3.06. [W / kg] and poor.

  In this case, as inclusions having a diameter of more than 100 nm, REM oxysulfide and REM sulfide accompanied by TiN were observed. As described above, although the detoxifying effect of Ti was generated, Therefore, it could not be fixed to REM oxysulfide or REM sulfide, and Ti remained in the steel. Ti in this steel produced a considerable amount of TiC in the temperature history after the hot rolling step. Therefore, the upper limit of the Ti amount is preferably 0.02% by mass.

  No. 16, no. 17, no. No. 18 has a REM amount in the range of 0.0003 to 0.05% by mass and a Ti amount of 0.02% by mass or less, but the component value is defined by the above-described evaluation formula (1). In this product plate, AlN was observed as inclusions having a diameter of more than 100 nm.

Further, 1.6 to 1.8 × 10 ¹⁰ [pieces / mm ³ ] TiN having a diameter of less than 100 nm was observed. Thereby, the crystal grain size after performing strain relief annealing was 38 to 41 [μm], and W15 / 50 was poor at 2.76 to 2.83 [W / kg].

  Next, FIG. 4 shows the relationship between the value of the left side of the equation (1) and the presence or absence of fine TiN having an inclusion diameter of less than 100 nm. As is apparent from the figure, it is understood that fine TiN is suppressed when the expression (1) is satisfied.

  FIG. 5 shows the relationship between the value on the left side of the equation (1), the crystal grain size after annealing, and the iron loss value. As can be seen from the figure, when the formula (1) is satisfied, the crystal grain growth is good and the iron loss value is good.

  Here, it should be noted that no. 17 and no. As shown in FIG. 18, when the amount of Ti is small, fine TiN may be generated. This is because the generation of AlN is given higher priority when the amount of Ti is too small, as suggested from the equation (1).

  According to conventional knowledge, it is preferable that the amount of Ti is as small as possible. Therefore, even if a great deal of effort has been taken, it has been necessary to prevent Ti from being mixed into the steel. However, according to the present invention, a great deal of effort is required to reduce Ti. In some cases, Ti is actively added, and an action is taken to increase the amount of Ti in the steel rather than the amount of Ti inevitably mixed.

  Thereby, since TiN is complex-formed on REM oxysulfide or REM sulfide and Ti is fixed, TiN is re-dissolved in the heat history after hot rolling and does not reprecipitate finely alone. For this reason, it is possible to obtain good product characteristics while increasing the degree of freedom in setting the hot rolling schedule.

  That is, in order to obtain an electrical steel sheet with good grain growth and excellent iron loss, control is performed by aggressive addition of Ti so as to be within the preferable range of Ti amount described above, or Ti contamination is suppressed. In this case, the technique of the present invention is decisively different from the conventional technique in that the restriction of the Ti content can be relaxed.

  Furthermore, if the TiN production start temperature is more reliably higher than the AlN production start temperature, the production of fine TiN can be more stably suppressed. The difference between the TiN and AlN generation start temperatures is about 10 ° C. or more.

  The inventor has also found that the conditions for achieving this are as follows: each mass% value of Ti, N, and Al should satisfy the following formula (2).

log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.70> 0 (2)
However, [Ti] represents mass% of Ti, [N] represents mass% of N, and [Al] represents mass% of Al.

  Alternatively, if the difference between the TiN and AlN production start temperatures is about 15 ° C. or more, the TiN production start temperature more reliably exceeds the AlN production start temperature, and the production of fine TiN is more stable. Since it becomes possible to suppress, it is more preferable.

  The inventors of the present invention have also found that, as conditions for achieving this, each mass% value of Ti, N, and Al should satisfy the following formula (3).

log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.58> 0 (3)
However, [Ti] represents mass% of Ti, [N] represents mass% of N, and [Al] represents mass% of Al.

  Alternatively, if the difference between the TiN and AlN production start temperatures is about 20 ° C. or more, the TiN production start temperature more reliably exceeds the AlN production start temperature, and the production of fine TiN is more stable. Since it becomes possible to suppress, it is more preferable.

  The inventors of the present invention have also found that, as conditions for achieving this, each mass% value of Ti, N, and Al should satisfy the following formula (4).

log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.49> 0 (4)
However, [Ti] represents mass% of Ti, [N] represents mass% of N, and [Al] represents mass% of Al.

  More preferably, the present inventors have also found that each mass% value of Ti, N, and Al should satisfy the following formula (5).

log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.35> 0 (5)
However, [Ti] represents mass% of Ti, [N] represents mass% of N, and [Al] represents mass% of Al.

By the way, no. No. 19 does not contain any REM, and no. No. 20 had a REM amount of 0.0002% by mass, and all of them were less than 0.0003% by mass. As a result of investigating the inclusions in the product plate by the above-mentioned method, fine TiS was found to be 2.3 to 2.9 × 10 ¹⁰ [pieces / mm ³ ]. Therefore, in this case, it can be seen that the fixation of S by REM was insufficient.

  The crystal grain size after annealing remained at 33 to 36 [μm] and no grain growth occurred, and the W15 / 50 value was poor at around 3.0 [W / kg].

  By the way, the above results are the results of performing the strain relief annealing in a shorter time than conventionally performed, but when the conventional level of strain relief annealing is performed, the pinning action of the fine inclusions Of course, the difference in crystal grain growth due to the above becomes more prominent, and it is needless to say that the above-described crystal grain growth property and the suitability of iron loss are further clarified.

Next, a description will be given reasons for limiting the free organic amount of component composition of the present invention.

  [C]: C is not only harmful to magnetic properties, but also magnetic aging due to precipitation of C becomes remarkable, so the upper limit was made 0.01 mass%. The lower limit includes 0% by mass.

  [Si]: Si is an element that reduces iron loss. When Si is less than the lower limit of 0.1% by mass, the iron loss is deteriorated. From the viewpoint of further reducing the iron loss, the preferable lower limit is 0.3% by mass, more preferably 0.7% by mass, and still more preferably 1.0% by mass.

  Further, when Si exceeds the upper limit of 7.0% by mass, the workability becomes extremely poor, so the upper limit was set to 7.0% by mass. A more preferable value as the upper limit is 4.0% by mass with better cold-rollability, a further preferable value is 3.0% by mass, and a more preferable value is 2.5% by mass.

  [Al]: Al is an element that reduces the iron loss similarly to Si. When Al is less than the lower limit of 0.1% by mass, the iron loss is deteriorated, and when it exceeds 3.0% by mass of the upper limit, the cost is remarkably increased. The lower limit of Al is preferably 0.2% by mass, more preferably 0.3% by mass, and still more preferably 0.6% by mass from the viewpoint of iron loss.

  [Mn]: Mn is added in an amount of 0.1% by mass or more in order to increase the hardness of the steel sheet and improve the punchability. The upper limit of 2.0% by mass is due to economic reasons.

  [S]: S becomes a sulfide such as MnS or TiS, which deteriorates grain growth and iron loss. Although it is fixed as a REM inclusion according to the present invention, its practical upper limit is 0.005% by mass, more preferably 0.003% by mass. The lower limit includes 0% by mass.

  [N]: N becomes a nitride such as AlN or TiN and deteriorates the iron loss. According to the present invention, although TiN is fixed to the REM inclusion, the practical upper limit is set to 0.005% by mass. For the above reason, the upper limit is preferably 0.003% by mass, more preferably 0.0025% by mass, and still more preferably 0.002% by mass.

  For the above reasons, it is preferable that N is as small as possible. However, in order to make it as close as possible to 0% by mass, there are many industrial restrictions, so the lower limit is made more than 0% by mass. As a practical lower limit, 0.001% by mass is taken as a guide, and if it is reduced to 0.0005% by mass, nitride is suppressed, more preferably, and if it is reduced to 0.0001% by mass, it is more preferable.

  [Ti]: Ti produces fine inclusions such as TiN and TiS, and deteriorates grain growth and iron loss. According to the present invention, although TiN is fixed to the REM inclusion, the practical upper limit is 0.02% by mass. For the above reason, the upper limit is preferably 0.01% by mass, more preferably 0.005% by mass.

However , when the amount of Ti is too small, the fixing effect to the REM inclusion is not exhibited.

If the amount of Ti exceeds 0.0015% by mass , the effect of fixing to the REM inclusion is preferably enhanced, more preferably 0.002% by mass or more, and further preferably 0.0025% by mass or more. Even more preferred.

  [REM]: REM forms oxysulfide or sulfide to fix S and prevents or suppresses the formation of fine sulfide. Moreover, it becomes a TiN composite production site and exerts a Ti fixing effect.

  When the lower limit is less than 0.0003% by mass, the above effect is not sufficient, and when the upper limit of 0.05% by mass is exceeded, crystal grain growth is inhibited by the REM-containing inclusions. 0003 mass% or more and 0.05 mass% or less was made into the suitable range.

  Moreover, even if it uses only 1 type if it is an element of REM, or it uses combining 2 or more types of elements, the said effect will be exhibited if it is in the range of this invention.

  Since the effect of fixing S increases in proportion to the amount of REM, the lower limit of REM is preferably 0.001% by mass, more preferably 0.002% by mass, and further preferably 0.0025% by mass. 0.003 mass% is more preferable.

  In addition, as described above, Ti is fixed by forming and growing on REM oxysulfide or REM sulfide. Therefore, as the amount of REM relative to the amount of Ti increases, REM oxysulfide as a TiN generation site, or It is obvious that the above effect is promoted because REM sulfide is increased.

  Practically, if the ratio of the REM amount to the Ti amount, that is, the [REM] / [Ti] value exceeds 0.25, it is sufficient, but if the [REM] / [Ti] value exceeds 0.5, it is sufficient. The above effect is preferably promoted, more preferably [REM] / [Ti] value exceeding 1.0, and further preferably [REM] / [Ti] value exceeding 1.25. .

  As long as it is an element other than the components described above and does not greatly interfere with the effect of the steel of the present invention, it may be contained and is included in the scope of the present invention.

  Below, a selective element is demonstrated. In addition, since the lower limit of these content should just be contained even if it is trace amount, it is all over 0 mass%.

  [P]: P increases the strength of the material and improves workability. However, if excessive, the cold rolling property is impaired, so 0.1% by mass or less is preferable.

  [Cu]: Cu improves corrosion resistance and increases specific resistance to improve iron loss. However, if the amount is excessive, scabs or the like are generated on the surface of the product plate and the surface quality is impaired, so 0.5 mass% or less is preferable.

  [Ca] and [Mg]: Ca and Mg are desulfurization elements, react with S in steel to form sulfide, and fix S. However, unlike REM, the effect of compounding and depositing TiN is small. If the addition amount is increased, the desulfurization effect is enhanced, but if the upper limit of 0.05% by mass is exceeded, grain growth is hindered by excess Ca and Mg sulfide. Therefore, 0.05 mass% or less is preferable.

  [Cr]: Cr improves the corrosion resistance and increases the specific resistance to improve the iron loss. However, excessive addition increases the cost, so 20 mass% was made the upper limit.

  [Ni]: Ni develops a texture favorable to magnetic properties and improves iron loss. However, excessive addition increases the cost, so 1.0 mass% was made the upper limit.

  [Sn] and [Sb]: Sn or Sb is a segregating element, which inhibits the texture of the (111) plane that deteriorates the magnetic properties and improves the magnetic properties. Even if these are used singly or in combination of the two, the above-described effects are exhibited. However, if it exceeds 0.3% by mass, the cold rollability deteriorates, so 0.3% by mass was made the upper limit.

  [Zr]: Zr inhibits crystal grain growth even in a small amount, and worsens iron loss after strain relief annealing. Therefore, it is preferable to reduce it as much as possible to 0.01% by mass or less.

  [V]: V forms nitrides or carbides and inhibits domain wall movement and crystal grain growth. For this reason, it is preferable to set it as 0.01 mass% or less.

  [O]: When O is contained in an amount of more than 0.005% by mass, a large number of oxides are generated, and domain wall movement and crystal grain growth are inhibited by the oxides. Therefore, it is preferable to set it as 0.005 mass% or less.

  [B]: B is a grain boundary segregation element and forms a nitride. Grain boundary movement is hindered by this nitride, and iron loss deteriorates. Therefore, it is preferable to reduce as much as possible to 0.005 mass% or less.

  In addition to the above, a known element can be added. For example, Bi, Ge, or the like can be used as an element for improving magnetic characteristics, and these can be appropriately selected according to the required magnetic characteristics. Just choose.

  Next, preferable manufacturing conditions and the reason for the definition in the present invention will be described.

  First, at the steelmaking stage, when refining by a conventional method such as a converter or secondary refining furnace, the oxidation degree of slag, that is, the mass ratio of FeO + MnO in the slag is set within a range of 1.0 to 3.0%. It is preferable.

  The reason for this is that if the degree of oxidation of the slag is less than 1.0%, within the Si range of the electromagnetic steel, the activity of Ti rises due to the influence of Si, so it is difficult to effectively prevent the covered Ti from the slag, If the amount of Ti in steel rises unnecessarily and the degree of oxidation of slag exceeds 3.0%, the REM in the molten steel is oxidized unnecessarily by the supply of oxygen from the slag to become a sulfide. This is because the fixing of S in steel becomes insufficient.

  It is also important to examine the furnace material refractories and to eliminate foreign oxidation sources as much as possible. Furthermore, it is preferable that the time from the addition of REM to casting is set to 10 minutes or more in order to ensure a sufficient time for the REM oxide to be inevitably generated when REM is added. By the measures described above, it becomes possible to produce steel within the intended composition range.

  After the molten steel within the desired composition range is melted by the method as described above, a slab or other slab is cast by continuous casting or ingot casting.

  At this time, TiN is complex-formed in REM oxysulfide or REM sulfide in steel, but it is important from the viewpoint of securing sufficient time for growth of TiN to be complexly formed not to accelerate the cooling of the slab unnecessarily. In other words, it is essential to obtain the number density of inclusions having a size defined in the present invention.

  That is, it is important to appropriately adjust the time existing in the temperature range of 1200 ° C. to 1300 ° C., which is the TiN production start temperature.

  What should be added here is that, when the steel in the desired composition range reaches the TiN production start temperature for the first time from a high temperature state, TiN is produced for the first time. When passing through the range quickly, TiN generated accompanying the REM inclusions cannot be sufficiently grown, and fixing becomes insufficient.

  And once it fails to fix, Ti becomes inclusions generated at a lower temperature than TiN, such as TiS and TiC, and is re-dissolved and re-precipitated by subsequent heat treatment to become fine inclusions. Therefore, temperature control when passing the temperature range for the first time is important.

  The optimum temperature pattern varies depending on the components to be produced, but in the range of 1200 ° C. to 1300 ° C., which is the TiN production start temperature, at least 1 minute, preferably 5 minutes or more, more preferably 20 It is important to spend more than a minute. As a method for measuring the temperature of steel, measurement using a radiation thermometer or the like and calculation analysis by heat transfer calculation can be applied.

In Table 2 above, no. No. 11 is a temperature range of 1200 ° C. or higher and 1300 ° C. or lower in 1 minute or more and less than 20 minutes. No. 13 is obtained by adjusting the temperature pattern as much as possible for slow cooling over several times, and it can be seen that the crystal grain size and the iron loss value after strain relief annealing are further improved.

At this time, as a result of separately investigating inclusions smaller than 50 nm in diameter and less than 50 nm in diameter, No. The number density of inclusions of size less than 50nm included in the product of 13, respectively, a 2.1 × 10 ⁹ [pieces ^{/ mm 3], 2.5 × 10} 9 [ pieces / mm ^3] or less there were.

  That is, when the time existing in the temperature range of 1200 ° C. or more and 1300 ° C. or less is made longer, the Ti fixing effect becomes more prominent, and the number density of fine inclusions less than 50 nm is further reduced. It was clear that the product characteristics were further improved.

  In addition, the time which exists in said temperature range of 1200 to 1300 degreeC is an example, and is not limited to this.

  There are various methods for adjusting the time existing in the range of 1200 ° C. or more and 1300 ° C. or less, depending on the casting equipment. It can also be achieved by adjusting the density, or adjusting the casting size and casting speed.

  After this, it is further hot-rolled, hot-rolled sheet annealed as necessary, finished to product thickness by one or more cold rollings sandwiching intermediate annealing, then finish-annealed and coated with insulating film To do. By the method described above, the inclusions in the product plate can be controlled within the scope of the present invention.

  Steel containing, by mass%, C: 0.0024%, Si: 2.1%, Mn: 0.2%, S: 0.0025% and containing the components shown in Table 2, and , P: 0.02%, Cu: 0.01% steel was melted and refined, and the slab was continuously cast. At that time, the time for the slab temperature to drop from 1300 ° C to 1200 ° C was 3 minutes. After that, a cold-rolled sheet having a thickness of 0.5 mm was manufactured through hot rolling, hot-rolled sheet annealing, and cold rolling.

  Next, finish annealing at 850 ° C. × 30 seconds is performed, an insulating film is applied to produce a product plate, and further, after 750 ° C. × 1.5 hours of strain relief annealing, inclusions in the product plate are investigated. Then, the crystal grain size was investigated and the magnetic properties were investigated by 25 cm Epstein method.

  The inclusion investigation was performed as described above, and the crystal grain size was measured by mirror-polishing the plate thickness cross section, performing nital etching to reveal crystal grains, and measuring the average crystal grain size.

  As is apparent from Table 2 above, the product plate according to the present invention obtained good results with respect to crystal grain growth and iron loss values. On the other hand, the product plate outside the scope of the present invention was inferior in crystal grain growth and iron loss value.

  As described above, according to the present invention, sufficiently good magnetic properties can be obtained even by simple annealing by setting the size and number density of fine inclusions included in the non-oriented electrical steel sheet within an appropriate range. In particular, it is possible to obtain sufficiently good magnetic characteristics even with simple strain relief annealing, which can contribute to energy saving while satisfying the needs of consumers. Therefore, the present invention has great industrial applicability.

It is a figure which shows the relationship between the crystal grain diameter after annealing, and the iron loss value with respect to the density of inclusions having a diameter of less than 100 nm in steel. It is a figure which shows the relationship between the crystal grain diameter after annealing, and the iron loss value with respect to the density of inclusions having a diameter of less than 50 nm in steel. It is a figure which shows the inclusion which the TiN compounded around the REM oxysulfide. It is a figure which shows the relationship between the component value, the parameter | index calculated by said Formula (1), and presence of fine TiN in a product. It is a figure which shows the relationship between the component value, the parameter | index calculated by said Formula (1), the crystal grain diameter after annealing, and an iron loss value.

Claims (5)

In mass%, C: 0.01% or less, Si: 0.1% to 7.0%, Al: 0.1% to 3.0%, Mn: 0.1% to 2.0% REM: 0.0003% or more and 0.05% or less, Ti: more than 0.0015% and 0.02% or less, S: 0.005% or less, N: 0.005% or less, with the balance being iron and It consists of inevitable impurities, and the mass% of Al indicated by [Al], the mass% of N indicated by [N], and the mass% of Ti indicated by [Ti] are expressed by the following (1 ) meets equation non-oriented electrical steel sheet you wherein a number density of inclusions of less than equivalent spherical diameter 100nm contained within the steel sheet is 1 × 10 10 ^[pieces / mm ^3] or less.
log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.84> 0 (1) In mass%, C: 0.01% or less, Si: 0.1% to 7.0%, Al: 0.1% to 3.0%, Mn: 0.1% to 2.0% REM: 0.0003% or more and 0.05% or less, Ti: more than 0.0015% and 0.02% or less, S: 0.005% or less, N: 0.005% or less, with the balance being iron and It consists of inevitable impurities, and the mass% of Al indicated by [Al], the mass% of N indicated by [N], and the mass% of Ti indicated by [Ti] are expressed by the following (1 ) meets equation non-oriented electrical steel sheet you wherein a number density of inclusions of less than equivalent spherical diameter 50nm included in the steel sheet 2.5 × 10 9 ^[pieces / mm ^3] or less.
log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.84> 0 (1) Said steel sheet further contains, by mass%, P: 0.1% or less, Cu: non-oriented electrical steel sheet according to claim 1 or 2, characterized in that it contains one or more under 0.5% or less . In mass%, C: 0.01% or less, Si: 0.1% to 7.0%, Al: 0.1% to 3.0%, Mn: 0.1% to 2.0% REM: 0.0003% or more and 0.05% or less, Ti: more than 0.0015% and 0.02% or less, S: 0.005% or less, N: 0.005% or less, with the balance being iron and It consists of inevitable impurities, and the mass% of Al indicated by [Al], the mass% of N indicated by [N], and the mass% of Ti indicated by [Ti] are expressed by the following (1 ) steel satisfying expression method for producing a non-oriented electrical steel sheet you characterized thereby over one minute to a temperature range of 1200 ° C. or higher 1300 ° C. or less.
log ([Ti] × [N]) − 1.19 × log ([Al] × [N])
+1.84> 0 (1) Said steel further contains, by mass%, P: 0.1% or less, Cu: Production of non-oriented electrical steel sheet according to claim 4, characterized in that it contains one or more kinds of under 0.5% or less Method.