JP2014196559A - Grain-oriented electrical steel sheet and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain a grain-oriented electrical steel sheet which is excellent in film adhesiveness of a substrate film and thus in magnetic characteristics by advantageously eliminating unstable formation of the substrate film which may occur in production by using a sulfur increasing method.SOLUTION: In the analysis of ingredient profiles of Mg and Mn from the surface to the center of the sheet thickness of a forsterite substrate film-provided grain-oriented electrical steel sheet, the concentration change of Mg shows a peak in the steel sheet surface layer part. For the concentration change of Mn, when the concentration of the steel sheet surface layer part shows a peak lower than that of the base iron in the central part of the sheet thickness or shows a peak higher than that of the base iron in the central part of the sheet thickness in the steel sheet surface layer part, the grain-oriented electrical steel sheet meets the relationship t(Mn)>t(Mg), where t(Mn) is the distance from the surface of the steel sheet to the concentration peak position of Mn, and t(Mg) is the distance from the surface of the steel sheet to the concentration peak position of Mg.

Description

  The present invention relates to a grain-oriented electrical steel sheet excellent in film adhesion and suitable for use in transformers and iron cores of other electrical equipment, and a method for producing the same.

  A grain-oriented electrical steel sheet is a soft magnetic material used as a core material for transformers and generators, and has a crystal structure in which the <001> orientation, which is the easy axis of iron, is highly aligned in the rolling direction of the steel sheet. . Such a texture preferentially grows crystal grains with a (110) [001] orientation, which is referred to as a so-called Goss orientation, during secondary recrystallization annealing during the production process of grain-oriented electrical steel sheets. It is formed through so-called secondary recrystallization.

  Conventionally, such a grain-oriented electrical steel sheet is heated to a high temperature of 1300 ° C. or higher by heating a slab containing 4.5% by mass or less of Si and an inhibitor component such as MnS, MnSe, and AlN to once dissolve the inhibitor component. After that, after hot rolling and performing hot-rolled sheet annealing as necessary, the final sheet thickness is obtained by cold rolling at least once with one or two intermediate sandwiches, followed by primary recrystallization in a wet hydrogen atmosphere. After annealing, primary recrystallization and decarburization, and after applying an annealing separator mainly composed of magnesia (MgO), the secondary recrystallization and inhibitor components are purified at 1200 ° C for about 5 hours. Have been manufactured by performing final finish annealing (for example, Patent Document 1, Patent Document 2, and Patent Document 3).

As described above, in manufacturing conventional grain-oriented electrical steel sheets, precipitates (inhibitor components) such as MnS, MnSe, and AlN are included in the slab stage, and these inhibitor components are added by heating at a high temperature of 1300 ° C or higher. A process of causing secondary recrystallization by once forming a solid solution and precipitating finely in a subsequent process has been adopted.
However, the high-temperature heating of the slab not only increases the equipment cost in realizing the heating, but also increases the amount of scale generated during hot rolling, lowers the yield, and further complicates the maintenance of the equipment. However, the problem remains in that it cannot meet the recent demand for manufacturing cost reduction.

In order to solve this problem, studies have been made on a technique for causing secondary recrystallization without containing an inhibitor component in the slab.
As a result, even when no inhibitor component is contained in the slab, a technique (inhibitorless method) capable of expressing secondary recrystallization has been developed and disclosed in Patent Document 4. This inhibitorless method is a technology that uses secondary steel with higher purity and develops secondary recrystallization by texture (control of texture).

On the other hand, when the inhibitorless method is used, there is a problem in forming a forsterite film (so-called undercoat film).
On the other hand, in Patent Document 5, the Sr compound is added to the annealing separator, and the temperature condition necessary for forming the forsterite film in the final finish annealing process is defined, thereby providing a highly adherent forsterite film. Successfully formed.

In addition, the inhibitorless method does not require high-temperature slab heating, and although it is possible to manufacture grain-oriented electrical steel sheets at low cost, it does not contain an inhibitor, and therefore, temperature fluctuations during the manufacturing process. In some cases, there is a problem that the magnetic characteristics of the product vary.
For this, as a technique for stably expressing secondary recrystallization, a technique for performing a so-called vulcanization process for increasing the amount of S in the steel after the primary recrystallization annealing and before the secondary recrystallization annealing. Was developed and disclosed in US Pat. According to this vulcanization method, the amount of sulfur segregated at the primary recrystallized grain boundary is increased by performing the vulcanization process from the primary recrystallization to the secondary recrystallization, so the most important assembly in the inhibitorless technology. It is considered that the difference in grain boundary character of the crystal due to the structure is strengthened, and the movement of the grain boundary surrounding the orientation grain other than the Goth orientation is moderately suppressed, and as a result, the secondary recrystallization is stabilized.

  However, when the vulcanization method is used to stabilize the secondary recrystallization, a new problem arises that the formation of the undercoat becomes unstable and the adhesion of the coat may deteriorate. From the viewpoint of efficient production, the improvement was demanded.

U.S. Patent No. 1965559 Japanese Patent Publication No. 40-15644 Japanese Patent Publication No.51-13469 JP 2000-129356 JP Japanese Patent No. 4258185 Japanese Patent No. 4321120

  The present invention advantageously solves the above problems, and proposes a grain-oriented electrical steel sheet that effectively improves the adhesion of the undercoat in the production technique using the vulcanization method, together with its advantageous production method. For the purpose.

Now, in order to solve the above problems, the inventors have repeatedly studied the relationship between the formation state of the base film and the film adhesion.
As a result, it has been found that the distribution of Mn and Mg from the surface undercoat to the steel sheet has a great influence on the film adhesion, and the optimum control improves the adhesion of the undercoat stably. I got the knowledge.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
(1) A grain-oriented electrical steel sheet with a forsterite undercoat comprising a composition containing, by mass%, Si: 4.5% or less and Mn: 0.5% or less,
In the component profile analysis of Mg and Mn from the surface of the grain-oriented electrical steel sheet with the undercoat to the thickness center direction,
Mg concentration change shows a peak in the steel sheet surface layer,
On the other hand, if the concentration of Mn is low in the steel plate surface layer compared to the steel plate at the center of the plate thickness, or if the steel plate surface layer has a high concentration peak compared to the steel plate at the center of the plate thickness. The directionality characterized by satisfying the relationship of t (Mn)> t (Mg) where t (Mn) and t (Mg) are the distances from the steel sheet surface to the Mn and Mg concentration peak positions, respectively. Electrical steel sheet.

(2) The steel sheet is further mass%,
Cu: 0.005-0.20%,
Ti: 0.0005-0.0050%,
Ca: 0.0001 to 0.0050%,
Mg: 0.0001-0.0050% and
Na: 0.0001 to 0.0050%
The grain-oriented electrical steel sheet according to (1) above, which contains at least one selected from the above.

(3) The steel sheet is further mass%,
Ni: 0.02-0.50%,
Sn: 0.01 to 0.50%,
Sb: 0.005-0.20%,
Cr: 0.005-1.5% and P: 0.005-0.20%
The grain-oriented electrical steel sheet according to (1) or (2) above, which contains at least one selected from among the above.

(4) By mass%, C: 0.08% or less, Si: 4.5% or less and Mn: 0.5% or less, sol.Al less than 100ppm, N less than 60ppm, and S, Se and O less than 50ppm respectively Suppress, and after the steel slab consisting of the composition of Fe and inevitable impurities is hot-rolled and then subjected to hot-rolled sheet annealing as necessary, it is cold-rolled twice or more with one or intermediate annealing in between , Electrical pickling, followed by primary recrystallization annealing that also serves as decarburization, and after applying an annealing separator mainly composed of MgO, a grain-oriented electrical steel sheet comprising a series of processes for final finishing annealing In the manufacturing method of
The Mn concentration on the surface is adjusted by pickling so that the Mn concentration on the outermost surface of the steel plate before the primary recrystallization annealing is 0.85 times or less the Mn concentration at the center of the plate thickness, and sulfide in the annealing separator. A method for producing a grain-oriented electrical steel sheet characterized by containing sulfate in the range of 0.2 to 15% by mass and further setting the maximum temperature reached in final finish annealing to 1250 ° C. or lower.

(5) The steel sheet is further mass%,
Cu: 0.005-0.20%,
Ti: 0.0005-0.0050%,
Ca: 0.0001 to 0.0050%,
Mg: 0.0001-0.0050% and
Na: 0.0001 to 0.0050%
The method for producing a grain-oriented electrical steel sheet according to (4) above, comprising at least one selected from the above.

(6) The steel slab is further mass%,
Ni: 0.02-0.50%,
Sn: 0.01 to 0.50%,
Sb: 0.005-0.20%,
Cr: 0.005-1.5% and P: 0.005-0.20%
The method for producing a grain-oriented electrical steel sheet according to the above (4) or (5), comprising at least one selected from the above.

  According to the present invention, the unstable formation of the undercoat can be advantageously eliminated, and the grain-oriented electrical steel sheet excellent in the adhesion of the undercoat and thus in the magnetic properties can be stably obtained, and its industrial value is extremely high. high.

It is a graph which shows the change of Mn density | concentration from the surface of the cold rolled sheet before the primary recrystallization annealing measured toward the inside of a steel plate by GDS. It is a graph which shows the change of Mg and Mn density | concentration from the surface of the base film which peeled the insulation coating of the product board to the steel plate inside measured by GDS. It is a graph which shows the other example of the change of Mg and Mn density | concentration measured from GDS to the steel plate inside from the base film surface which peeled the insulating coating of the product board.

Hereinafter, the present invention will be specifically described.
First, the experimental results that led to the present invention will be described. Unless otherwise specified, “%” in relation to ingredients means mass%.
Experiment 1
Contains C: 0.03%, Si: 3.4%, Mn: 0.05%, sol.Al: 45ppm, N: 35ppm, S: 20ppm, Se: 20ppm and O: 10ppm, the balance from the composition of Fe and inevitable impurities The resulting continuous cast slab was heated to 1200 ° C., and hot rolled into a hot rolled sheet having a thickness of 2.5 mm, and then subjected to hot rolled sheet annealing at 1050 ° C. for 30 seconds. At this time, the surface of the steel sheet after hot-rolled sheet annealing was shot blasted and then pickled using a 5% hydrochloric acid aqueous solution at 80 ° C. for 60 seconds or 150 seconds to remove the surface scale. Next, after cold rolling to a plate thickness of 0.30 mm, primary recrystallization annealing that also serves as a decarburization soaking at 840 ° C for 120 seconds was carried out. Hydrogen partial pressure: 50%, nitrogen partial pressure: 50%, dew point ( DP): Performed at 45 ° C.

Thereafter, an annealing separator containing MgO as a main component and containing 10% MgSO ₄ was applied to the surface of the primary recrystallization plate at 12.5 g / m ² , dried, and then the rate of temperature increase: 15 ° C./h, atmosphere gas: Secondary recrystallization annealing was performed under conditions of N ₂ gas up to 900 ° C., H ₂ gas above 900 ° C., soaking treatment: 1160 ° C., 5 hours. The maximum temperature reached (plate temperature) was 1190 ° C.
Next, after removing the remaining annealing separator, an insulating coating treatment liquid was applied, and annealing was performed at 850 ° C. for 30 seconds, which was combined with baking and heat flattening treatment, to obtain a final product.

After removing the product insulation film thus obtained, a test piece having a length of 300 mm in the rolling direction and 30 mm in the direction perpendicular to the rolling was collected, and the film adhesion of the undercoat was investigated. The film adhesion was evaluated by bending the test piece against a round bar having various diameters by bending 180 ° and by the minimum diameter at which the bent portion does not peel off.
As a result, it was found that the minimum diameter was as good as 20 mm when the pickling time was as short as 60 seconds, whereas the minimum diameter was greatly deteriorated to 55 mm when the pickling time was as long as 150 seconds.

Therefore, in order to clarify the mechanism by which these phenomena occur, the inventors have used various methods to obtain the surface layer of the cold-rolled sheet and the steel sheet with the base coating before the primary recrystallization annealing obtained in the above experiment. We investigated in.
As a result, it was found that the Mn distribution on the surface of the cold-rolled sheet was different depending on the pickling conditions, and that the distribution state of Mn and Mg was significantly different on the surface of the product sheet. And it was investigated that the quality of adhesion of the formed undercoat had a strong correlation with the concentration distribution of Mn and Mg in the surface layer of this product plate.

FIG. 1 shows the result of GDS (Glow Discharge Spectrometer) measurement of the change in Mn concentration from the surface of the cold rolled sheet before the primary recrystallization annealing to the inside of the steel sheet. FIG. 1A shows the case where the pickling time is 60 seconds, and FIG. 1B shows the case where the pickling time is 150 seconds.
As shown in FIG. 1, the distribution of Mn concentration is affected by the pickling time, and although Mn tends to decrease in concentration at the outermost surface, the decrease in concentration decreases with increasing pickling time. Was recognized.

Next, FIG. 2 shows the results of GDS measurement of changes in Mg and Mn concentrations from the surface of the base coating from which the insulating coating on the product plate was peeled to the inside of the steel plate.
Under any pickling conditions, a peak was observed in the Mg and Mn concentration distribution from the undercoat to the steel sheet. However, when the pickling time was as short as 60 seconds, there was a Mg peak near the surface layer. Whereas the Mn peak was present at the inner side of the steel plate, the Mn peak was further on the surface side than the Mg peak near the surface layer when the pickling time was 150 seconds. Was found to exist.

  The peak positions of Mn intensity and Mg intensity were measured by examining the intensity distribution in the plate thickness direction using GDS, but the measurement method is not limited to this GDS alone, and peak positions of Mn intensity and Mg intensity are measured. As long as it is a measurement method that can evaluate the above, physical analysis such as SIMS (Secondary Ion Mass Spectroscopy) or other chemical analysis may be used.

From the above results, it can be seen that the difference in Mg and Mn concentration distribution on the product plate affects the adhesion of the undercoat, and this change is due to the Mn concentration profile of the cold-rolled plate before primary recrystallization. It was thought to be affected.
Therefore, next, an experiment was conducted to confirm this.

Experiment 2
Contains C: 0.03%, Si: 3.4%, Mn: 0.05%, sol.Al: 45ppm, N: 35ppm, S: 20ppm, Se: 20ppm and O: 10ppm, the balance from the composition of Fe and inevitable impurities The resulting continuous cast slab was heated to 1200 ° C., and then hot rolled into a hot rolled sheet having a thickness of 2.2 mm, and then subjected to hot rolled sheet annealing at 1050 ° C. for 30 seconds. At this time, shot blasting was performed on the surface of the steel sheet after the hot-rolled sheet annealing, and then steel sheets having different surface scale removal states were produced under the seven conditions shown in Table 1 (conditions A to G). Next, after cold rolling to a plate thickness of 0.30 mm, decarburization and primary recrystallization annealing, soaking at 840 ° C for 120 seconds, hydrogen partial pressure: 50%, nitrogen partial pressure: 50%, dew point: 45 ° C Performed under conditions.

Thereafter, an annealing separator containing MgO as a main component and containing 10% MgSO ₄ was applied to the surface of the primary recrystallization plate at 12.5 g / m ² , dried, and then the rate of temperature increase: 15 ° C./h, atmosphere gas: Secondary recrystallization annealing was performed under conditions of N ₂ gas up to 900 ° C., H ₂ gas above 900 ° C., soaking treatment: 1160 ° C., 5 hours. The maximum temperature reached (plate temperature) was 1190 ° C.
Next, after removing the remaining annealing separator, an insulating coating treatment solution was applied, and annealing was performed at 850 ° C. for 30 seconds, which was combined with baking and heat flattening treatment, to obtain a final product, which was subjected to an evaluation test.

As in Experiment 1, the adhesion of the undercoat was taken from a test piece having a length of 300 mm in the rolling direction and 30 mm in the direction perpendicular to the rolling direction, and bent 180 ° while pressing the test piece against a round bar having various diameters. The evaluation was performed with the minimum diameter at which the bent portion did not peel off. In addition, the smaller the minimum peel peel diameter is, the better the adhesion of the undercoat is, and 50 mm or less is required for normal use.
Moreover, the Mn concentration profile of the cold rolled sheet surface layer before the primary recrystallization annealing and the Mn and Mg concentration profiles of the product sheet surface layer were measured by GDS. In addition, the measurement of the product board surface layer was performed after peeling an insulating film.

FIG. 3 shows the results of GDS measurement of changes in Mg and Mn concentrations from the surface of the base coating from which the insulating coating on the product plate was peeled to the inside of the steel plate.
As shown in FIG. 3, the Mn concentration profile is lower than that of the ground iron, although a clear peak is not recognized near the surface layer in addition to the result having a peak near the surface layer as obtained in FIG. The results are also obtained.
And if a clear peak is not recognized near the surface layer, but a state where the Mn concentration is lower than that of the ground iron is realized, the pickling time is 60 seconds, and the surface layer is processed. It has been found that there is a Mg peak in the vicinity, and that sufficient adhesion can be obtained as in the case where the Mn peak is present somewhere inside the steel plate.

Table 2 summarizes the results obtained.
In the table, the Mn concentration in the outermost surface of the cold rolled sheet and the inside of the iron core before the primary recrystallization annealing is the Mn intensity at the outermost surface when the surface is analyzed in the depth direction by GDS and the Mn with a sputtering time of 120 to 150 seconds. It was defined by the average value of intensity, and the concentration ratio was evaluated from the intensity ratio. Table 2 also shows the results of examining the coating appearance of the steel sheet with the base coating.

As shown in Table 2, when the Mn concentration on the outermost surface of the steel sheet exceeds 0.85 times the Mn concentration inside the steel, the film adhesion is poor, but the Mn concentration on the outermost surface is 0.85 of the Mn concentration inside the steel. In the case of less than twice, it can be seen that the film adhesion is greatly improved. Moreover, it can be seen that with the stabilization of the film adhesion, the magnetic properties have reached a good level. Further, it can be seen that the appearance of the film is also improved.
And in the material with poor film adhesion of the undercoat, a peak of Mn concentration was present on the surface side of the Mg concentration peak position. On the other hand, in the material with good film adhesion, the Mn concentration change is lower in the steel plate surface layer than the steel plate in the center of the plate thickness, or the steel plate in the plate thickness center in the surface layer. In the case of having a higher concentration peak than Mn, the Mn peak position was present on the inner side of the steel plate than the Mg peak position.

That is, when the concentration change of Mn is lower than that of the steel plate surface layer, or when the surface layer has a higher Mn concentration peak than that of the plate thickness center, When the distance from the surface to the peak position of the Mn intensity and the peak position of the Mg intensity is t (Mn) and t (Mg), respectively, when these satisfy the relationship of t (Mn)> t (Mg), It has been found that good film adhesion can be obtained.
In the present invention, the surface layer portion of the steel sheet refers to a region from the outermost surface of the steel sheet with an undercoat to a depth position of 0.5 μm to 8 μm, and roughly corresponds to the thickness of the undercoat.

The reason why the coating adhesion is good when the concentration profile of Mn and Mg in the steel sheet surface layer satisfies the above requirements has not yet been clearly clarified, but the inventors speculate as follows. ing.
When forming a forsterite film (Mg ₂ SiO ₄ ), the forsterite film can be formed more quickly by passing through a solid solution such as (Mg, Mn) ₂ SiO ₄ or (Mg, Fe) ₂ SiO _4. It is known to progress to. In an oxidizing atmosphere, Mn near the extreme surface layer of the steel sheet diffuses to the surface layer side to form stable MnO, and then effectively forms a film by forming a solid solution as described above.
In general, the state that the Mn content of the steel sheet surface layer is high (t (Mn) <t (Mg)) at the time of forming the forsterite film means that it is easy to form such a solid solution and that the film formation is promoted. Conceivable. However, when vulcanization is carried out by the vulcanization treatment, the affinity between Mn and S is high, so a part of S that wants to enter the steel sheet is bonded to Mn, fixed as MnS, and grows near the surface layer. There is a possibility that coarse MnS is formed. Moreover, although the final finish annealing is performed at a high temperature exceeding 1100 ° C., there is a concern that defects may occur in the forsterite film due to partial solid solution of coarsely grown MnS. This is consistent with the fact that coating failure tends to occur only when the vulcanization method is applied. Mn is contained in the slab in a considerable amount in order to ensure the rollability at the time of hot rolling, so that the formed MnS tends to grow coarsely and is expected to be a problem.

The present invention suppresses the precipitation and growth of MnS during the formation of forsterite film by leaving an Mn-deficient layer originally useful for film formation in the vicinity of the surface layer. By suppressing defects in the forsterite film, the adhesion of the film is improved.
The forsterite film obtained in this way is inhibited from incorporating Mn into the forsterite film. As a result, the distances from the steel sheet surface to the Mn and Mg concentration peak positions are t (Mn) and t (Mg), respectively. ), A forsterite film having a relationship of t (Mn)> t (Mg) is provided.

Although the above hypothesis is not proved, elements having stronger affinity with S than Mn, such as Cu (Cu ₂ S), Ti (TiS), Ca (CaS), Mg (MgS), Na (NaS) It was newly found that the adhesion of the forsterite film is improved when it is contained in a small amount in steel. These are expected to be combined with elements with stronger affinity when S diffuses into the steel, but by making the target elements extremely small, the precipitates are finely precipitated, and eventually This is probably because defects generated in the stellite film could be reduced.

Next, the reason why the composition of the steel slab, which is the steel plate and material of the present invention, is limited to the above range will be described.
First, the component composition of the steel sheet of the present invention will be described as follows.

Si: 4.5% or less
Si increases the electrical resistance of steel and contributes effectively to reducing iron loss. However, if the content exceeds 4.5%, the workability deteriorates significantly and cold rolling becomes difficult, so the Si content is 4.5%. Limited to: A desirable addition amount from the viewpoint of iron loss is in the range of 2.0 to 4.0%. Depending on the required iron loss level, Si may not be added.

Mn: 0.5% or less
Mn is a useful element for improving hot workability. However, if the content exceeds 0.5%, the primary recrystallization texture deteriorates and the magnetic properties deteriorate, so the Mn content is 0.5% or less. Limited to.

In the present invention, in addition to the above-described components, it is useful to contain the following elements as a film adhesion improving component.
Cu: 0.005 to 0.20%, Ti: 0.0005 to 0.0050%, Ca: 0.0001 to 0.0050%, Mg: 0.0001 to 0.0050%, and Na: 0.0001 to 0.0050% It is an element that can form a sulfide that is thermodynamically more stable than MnS in the sulfurating temperature range when performing the treatment. By adding an appropriate amount of these elements, it is possible to form a forsterite-coated steel sheet. Adhesion can be improved. On the other hand, in inhibitorless steels, these elements form precipitates with trace amounts of S present in the steel, and may behave like inhibitors and deteriorate their properties. It is necessary to Further, when excessively added, as in the case where Mn forms MnS, it leads to the formation of coarse sulfides in the forsterite film, and ultimately promotes defects in the forsterite film. Therefore, each is limited to the above range.
Among these element groups, Cu, in particular, was able to obtain the same effect even when added in a larger amount than other elements, and an effect of improving magnetic properties was also observed. Although the detailed mechanism is not clear, the precipitation form is different from other elements like Cu ₂ S, and the role of Cu, which is a substitutional element and does not have a high diffusion rate, is strongly influenced, and it is difficult to coarsely precipitate I guess.

Furthermore, in the present invention, in addition to the above-described components, the following elements can be appropriately contained as magnetic property improving components.
Ni: 0.02-0.50%, Sn: 0.01-0.50%, Sb: 0.005-0.20%, Cr: 0.005-1.5% and P: 0.005-0.20%
Ni is a useful element that improves the magnetic properties by improving the hot-rolled sheet structure. However, if the content is less than 0.02%, the effect of improving the magnetic properties is small. On the other hand, if it exceeds 0.50%, secondary recrystallization becomes unstable and the magnetic properties deteriorate, so the Ni content is set to 0.02 to 0.50%.
Sn, Sb, Cr, and P are elements useful for improving the iron loss. However, if any of the elements does not satisfy the lower limit of the above range, the effect of improving the iron loss is small. Since the development of the next recrystallized grains is hindered, Sn: 0.01 to 0.50%, Sb: 0.005 to 0.20%, Cr: 0.005 to 1.5%, and P: 0.005 to 0.20%, respectively.

Next, the component composition of the steel slab will be described as follows.
In addition, Si content and Mn content are the same as the component composition range prescribed | regulated about this invention steel plate.
The above-mentioned optional components are also the same as in the case of the steel sheet of the present invention.

C: 0.08% or less C contributes effectively to the improvement of the primary recrystallized structure, but if the content exceeds 0.08%, it is difficult to reduce it to 0.0050% (50ppm) or less where magnetic aging does not occur in the product plate. Therefore, the C content is limited to 0.08% or less. If the amount of C is less than 0.02%, the magnetic properties may be deteriorated due to the deterioration of the primary recrystallization structure. Therefore, C is preferably contained in an amount of 0.02% or more.

sol.Al: less than 100ppm
If Al is present in excess, secondary recrystallization becomes difficult. In particular, when the amount of sol.Al is 100 ppm or more, secondary recrystallization becomes difficult under low-temperature slab heating conditions, and magnetic properties deteriorate. Therefore, Al is suppressed to less than 100 ppm in terms of the amount of sol.Al.

N: Less than 60 ppm N, like Al, makes secondary recrystallization difficult if it is present in excess. In particular, when the N content is 60 ppm or more, secondary recrystallization hardly occurs and the magnetic properties are deteriorated. Therefore, N is suppressed to less than 60 ppm.

S, Se, and O: each less than 50 ppm When the amounts of S, Se, and O are each 50 ppm or more, secondary recrystallization becomes difficult. The reason for this is that coarse oxides and MnS and MnSe coarsened by slab heating make the primary recrystallized structure non-uniform. Accordingly, S, Se, and O are all suppressed to less than 50 ppm. Preferably, both are 40 ppm or less.

  In addition, Nb, B, Ta, V, and the like, which are nitride forming elements, are each effectively reduced to 60 ppm or less in order to prevent deterioration of iron loss and ensure good workability.

Next, the manufacturing method of this invention is demonstrated.
The molten steel adjusted to the above preferred component composition is refined by a known method using a converter, an electric furnace, etc., and subjected to vacuum treatment as necessary, and then using a normal ingot forming method or a continuous casting method. Manufacture slabs. Further, a thin cast piece having a thickness of 100 mm or less may be directly produced using a direct casting method. The slab is hot-rolled by heating by a normal method, but may be immediately subjected to hot-rolling without being heated after casting. In the case of a thin slab, hot rolling may be performed, or the hot rolling may be omitted and the subsequent process may be performed as it is.

  In the present invention, since an inhibitor component is not contained in the slab, it is particularly effective to reduce the scale amount generated during hot rolling to suppress the slab heating temperature before hot rolling to 1250 ° C. or less. Also, it is desirable to lower the slab heating temperature in order to realize a uniform sized primary recrystallized structure by making the crystal structure finer and harming the unavoidable effects of inhibitor components.

  Next, hot-rolled sheet annealing is performed as necessary. The hot-rolled sheet annealing temperature is preferably in the range of 800 to 1100 ° C. in order to develop a goth structure at a high level in the product sheet. This is because when the annealing temperature of the hot-rolled sheet is less than 800 ° C, the band structure in the hot-rolling remains and it becomes difficult to realize the primary recrystallized structure of the sized particles. On the other hand, when the hot-rolled sheet annealing temperature exceeds 1100 ° C, the unavoidably mixed inhibitor components are solid-solved and re-deposited non-uniformly during cooling, making it difficult to achieve a sized primary recrystallized structure. This is because the development of secondary recrystallization is inhibited. Further, when the hot-rolled sheet annealing temperature exceeds 1100 ° C., the grain size after the hot-rolled sheet annealing is too coarse, which is disadvantageous for realizing a primary recrystallized structure of sized particles.

Then, it cold-rolls twice or more across 1 time or intermediate annealing, and is set as a final cold rolled sheet.
In the cold rolling described above, the rolling temperature is raised to 100 to 250 ° C., or the aging treatment in the range of 100 to 250 ° C. is performed once or a plurality of times during the cold rolling, It is effective in developing Gothic tissue.

Next, pickling is performed. In the present invention, this pickling step is important.
That is, by this pickling, the Mn concentration on the surface is adjusted so that the Mn concentration on the outermost surface of the cold rolled sheet before the primary recrystallization annealing is 0.85 times or less of the Mn concentration at the center of the plate thickness.
If the above-mentioned regulations are satisfied, the treatment liquid and the treatment time are not particularly defined, but suitable treatment liquids, their concentrations, and pickling times are as follows.
(1) Treatment liquid
HCl, H ₂ SO ₄ , HNO ₃
(2) Treatment solution concentration 3-18% aqueous solution
(3) Pickling time 2 to 120 seconds

After the above pickling, decarburization and primary recrystallization annealing are performed to reduce C to 50 ppm or less, preferably 30 ppm or less, at which magnetic aging does not occur.
This decarburization and primary recrystallization annealing is preferably performed at a temperature of 700 to 1000 ° C. using a humid atmosphere. In addition, you may use together the technique which increases Si amount by a siliconization method after decarburization and primary recrystallization annealing.

Then, after applying the annealing separation agent which has MgO as a main component, a secondary recrystallization structure is developed and a base film is formed by performing final finishing annealing.
At this time, it is important to contain 0.2 to 15% of sulfide and / or sulfate in the annealing separator in order to increase the amount of S in the base iron by the vulcanization treatment and improve the magnetic properties. .
In addition, as said sulfide and sulfate, Ag, Al, Ba, Ca, Co, Cr, Cu, Fe, In, K, Li, Mg, Mn, Na, Ni, Sn, Sb, Sr, Zn and Zr sulfides and sulfates are advantageously suitable. These may be added alone or in combination.

It is also important that the maximum temperature reached in the final finish annealing is 1100 ° C or higher and 1250 ° C or lower.
This is because if the maximum temperature is out of the above range, the Mn and Mg concentration profiles in the steel sheet surface layer portion do not satisfy the appropriate range of the invention, and as a result, good film adhesion and consequently good magnetic properties can be obtained. Because there is no.
The above final finish annealing needs to be performed at a temperature of 800 ° C. or higher for the purpose of secondary recrystallization. However, the heating rate up to 800 ° C. does not greatly affect the magnetic properties, and may be under any conditions.

  The phenomenon that the magnetic properties are improved by the above vulcanization effect is a phenomenon peculiar to the case of steel that does not contain an inhibitor component in the slab. In other words, when there are no inhibitor components (precipitates) such as AlN or MnS in the steel, the grain boundaries surrounding the goth-oriented grains in the primary recrystallized structure are more mobile than the grain boundaries surrounding the grains of other orientations. As a result, the Goss orientation preferentially grows (secondary recrystallization).

Thereafter, flattening annealing is performed to correct the shape of the steel sheet.
Then, after the above-described flattening annealing, for the purpose of improving the iron loss, it is advantageous to provide an insulating coating that imparts tension to the steel sheet surface.
Furthermore, it goes without saying that known magnetic domain refinement techniques can be applied.

Example 1
Continuously cast slabs with various composition shown in Table 3 are heated to 1230 ° C and hot rolled to a hot rolled sheet with a thickness of 2.2mm, and then subjected to hot rolled sheet annealing at 1050 ° C for 30 seconds. did. At this time, the surface of the steel sheet after hot-rolled sheet annealing was shot blasted and then pickled for 80 seconds using a 5% hydrochloric acid aqueous solution at 80 ° C. to remove the surface scale. Next, after cold rolling to a sheet thickness of 0.23 mm, decarburization and primary recrystallization annealing were performed at 850 ° C. for 180 s. _{Then, MgO: 87%, MgSO 4} : 10%, TiO 2: an annealing separating agent consisting of 3% of the composition, and 12.5 g / m ² coated on the surface of the primary recrystallization plate, after drying, heating rate: Secondary recrystallization annealing was performed under conditions of 10 ° C / h, atmospheric gas: Ar gas up to 950 ° C, H ₂ gas above 950 ° C, soaking treatment: 1100 ° C, 10h. In this case, the maximum temperature reached 1150 ° C.
Thereafter, a tension coating treatment liquid mainly composed of phosphate and colloidal silica was applied and baked at 800 ° C. to form a tension coating, followed by flattening annealing.

The magnetic properties and the undercoat adhesion of the product plates thus obtained were examined. Further, the Mn concentration profile of the surface layer of the cold rolled sheet was obtained, and the Mn concentration ratio (outermost surface / inner) between the outermost surface and the inner surface was examined. Furthermore, the Mn and Mg concentration profiles on the surface of the product plate were also investigated.
The obtained results are also shown in Table 3.

The magnetic characteristics were evaluated by the magnetic flux density B ₈ when excited at 800 A / m and the iron loss W _17/50 when excited up to 1.7 T at 50 Hz after performing stress relief annealing at 800 ° C. for 3 hours. did.
In addition, as in Experiment 1, the adhesion of the undercoat was taken from a test piece having a length of 300 mm in the rolling direction and 30 mm in the direction perpendicular to the rolling direction, and bent 180 ° while pressing the test piece against a round bar having various diameters. The evaluation was performed with the minimum diameter at which the bent portion did not peel off. In addition, the smaller the minimum peel peel diameter is, the better the adhesion of the undercoat is, and 50 mm or less is required for normal use. Preferably it is 30 mm or less.
Furthermore, the Mn concentration profile of the cold rolled sheet surface layer and the Mn and Mg concentration profiles of the product sheet surface layer were measured by GDS. The GDS measurement on the surface of the product plate was performed after the insulating coating was peeled off.

  As is apparent from the table, all the grain-oriented electrical steel sheets obtained according to the present invention not only have excellent film adhesion of the undercoat, but also have excellent magnetic properties.

(Example 2)
Continuously cast slabs with various composition shown in Table 4 are heated to 1150 ° C, hot rolled into a hot rolled sheet with a thickness of 2.0mm, and then subjected to hot rolled sheet annealing at 1000 ° C for 60 seconds. did. At this time, using a 5% hydrochloric acid aqueous solution at 80 ° C. so that the same Mn concentration ratio (outermost surface / inside) as in Example 1 can be obtained after shot blasting the surface of the steel sheet after hot-rolled sheet annealing. The surface scale was removed by pickling for 2 seconds, and it was confirmed that the Mn concentration ratio (outermost surface / inner) was in the range of 0.6 to 0.7.
Next, after cold rolling to a sheet thickness of 0.27 mm, decarburization and primary recrystallization annealing at 830 ° C. for 120 s were performed. A test piece of 100 mm × 400 mm was cut out from the obtained actual coil, and in the laboratory, in addition to the composition of MgO: 87% and TiO ₂ : 3%, MgS was added as an additive for sulfur increase 9%, 12%, 15% 12.5 g / m ^{2 was} applied to the surface of the primary recrystallized plate and dried. Thereafter, secondary recrystallization annealing was performed under conditions of N ₂ gas up to 950 ° C., N ₂ gas up to 950 ° C., H ₂ gas up to 950 ° C. and above, soaking heat treatment: 1100 ° C. and 10 h. In this case, the maximum temperature reached 1150 ° C.
Thereafter, a tension coating treatment liquid mainly composed of phosphate and colloidal silica was applied and baked at 800 ° C. to form a tension coating, followed by flattening annealing.

A 30 mm × 300 mm sample was cut out from the center of the test piece thus obtained, and the undercoat adhesion was examined. The undercoat adhesion was evaluated by the same method as in Example 1. In addition, after performing strain relief annealing at 800 ° C. for 3 hours, the magnetic flux density B ₈ when excited at 800 A / m was investigated.
The obtained results are also shown in Table 4.

As is clear from the table, all the grain-oriented electrical steel sheets obtained according to the present invention have obtained an undercoat excellent in film adhesion of 40 mmφ or less, particularly by adding an appropriate amount of additive elements, It was confirmed that excellent film adhesion could be secured even under conditions with a large amount of vulcanization.

Claims (6)

A grain-oriented electrical steel sheet with a forsterite undercoating comprising a composition containing, by mass%, Si: 4.5% or less and Mn: 0.5% or less,
In the component profile analysis of Mg and Mn from the surface of the grain-oriented electrical steel sheet with the undercoat to the thickness center direction,
Mg concentration change shows a peak in the steel sheet surface layer,
On the other hand, if the concentration of Mn is low in the steel plate surface layer compared to the steel plate at the center of the plate thickness, or if the steel plate surface layer has a high concentration peak compared to the steel plate at the center of the plate thickness. The directionality characterized by satisfying the relationship of t (Mn)> t (Mg) where t (Mn) and t (Mg) are the distances from the steel sheet surface to the Mn and Mg concentration peak positions, respectively. Electrical steel sheet. The steel sheet is further mass%,
Cu: 0.005-0.20%,
Ti: 0.0005-0.0050%,
Ca: 0.0001 to 0.0050%,
Mg: 0.0001-0.0050% and
Na: 0.0001 to 0.0050%
The grain-oriented electrical steel sheet according to claim 1, comprising at least one selected from the group consisting of The steel sheet is further mass%,
Ni: 0.02-0.50%,
Sn: 0.01 to 0.50%,
Sb: 0.005-0.20%,
Cr: 0.005-1.5% and P: 0.005-0.20%
The grain-oriented electrical steel sheet according to claim 1 or 2, comprising at least one selected from the group consisting of Containing, by mass%, C: 0.08% or less, Si: 4.5% or less, and Mn: 0.5% or less, and suppressing sol.Al to less than 100 ppm and N to less than 60 ppm and S, Se and O to less than 50 ppm, The remainder is a steel slab composed of Fe and unavoidable impurities, and after hot rolling, after subjecting to hot rolling as necessary, it is subjected to one or more cold rolling sandwiching intermediate annealing, Next, after pickling, after performing primary recrystallization annealing that also serves as decarburization, after applying an annealing separator mainly composed of MgO, a method for producing a grain-oriented electrical steel sheet comprising a series of steps of final finishing annealing In
The Mn concentration on the surface is adjusted by pickling so that the Mn concentration on the outermost surface of the steel plate before the primary recrystallization annealing is 0.85 times or less the Mn concentration at the center of the plate thickness, and sulfide in the annealing separator. A method for producing a grain-oriented electrical steel sheet characterized by containing sulfate in the range of 0.2 to 15% by mass and further setting the maximum temperature reached in final finish annealing to 1250 ° C. or lower. The steel sheet is further mass%,
Cu: 0.005-0.20%,
Ti: 0.0005-0.0050%,
Ca: 0.0001 to 0.0050%,
Mg: 0.0001-0.0050% and
Na: 0.0001 to 0.0050%
The method for producing a grain-oriented electrical steel sheet according to claim 4, comprising at least one selected from the group consisting of: The steel slab is further mass%,
Ni: 0.02-0.50%,
Sn: 0.01 to 0.50%,
Sb: 0.005-0.20%,
Cr: 0.005-1.5% and P: 0.005-0.20%
The method for producing a grain-oriented electrical steel sheet according to claim 4 or 5, comprising at least one selected from the group consisting of:

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