WO2010047414A1 - Method for manufacturing grain-oriented electrical steel sheet - Google Patents

Abstract

Provided is a method for manufacturing a grain-oriented electrical steel sheet with highly stable magnetic characteristics using a component system containing no inhibitor. In the manufacture of the grain-oriented electrical steel sheet using a slab made of the component system containing no inhibitor, the slab contains a total of 10-150 ppm of at least one kind of microelement selected from B, Nb, and V, the mass ratio of Al and N included as impurities is Al/N = 1.4; and preferably, the average temperature increase rate between 600°C and 800°C during recrystallization annealing is 15°C/s or higher.

Description

Method for producing grain-oriented electrical steel sheet

The present invention relates to a method for producing a grain oriented electrical steel sheet suitable for use in transformer core materials and the like.

For grain-oriented electrical steel sheets, pre-precipitates called inhibitors are used to preferentially recrystallize grains having Goss orientation during final annealing. (Secondary recrystallization) is known as a general technique. For example, Patent Document 1 discloses a method of containing specified amounts of Al and S, that is, a method of using AlN and MnS as inhibitors. Patent Document 2 discloses a method of containing a specified amount of at least one of S and Se, that is, a method of using MnS or MnSe as an inhibitor. These methods are industrially put into practical use.

Further, for the purpose of enhancing the action of these inhibitors, Patent Document 3 discloses a method using Pb, Sb, Nb, Te, and Patent Document 4 discloses Zr, Ti, B, Nb, Ta. , V, Cr, and Mo are disclosed.

Although the method using these inhibitors is an effective method for developing secondary recrystallized grains stably, it is necessary to finely disperse the inhibitors in steel. It was necessary to re-dissolve the inhibitor component (inhibitor-forming element) once by slab heating at a high temperature of 1300 ° C. or higher. Further, since the inhibitor component causes deterioration of magnetic properties after secondary recrystallization, a purification annealing step for removing the inhibitor is required, and the step is performed at 1100 ° C. or higher. It was necessary to control the atmosphere at a high temperature.

On the other hand, Patent Document 5 proposes a technique for developing Goss oriented crystal grains by secondary recrystallization in a material that does not contain an inhibitor component. This method reveals the grain boundary misorientation dependence of the grain boundary energy of the grain boundary during primary recrystallization by eliminating impurities such as inhibitor components as much as possible. This is a technique for performing secondary recrystallization of grains having Goth orientation without using an inhibitor. This effect is called a texture inhibition effect. Since the method of Patent Document 5 does not require a step of purifying the inhibitor, the final finish annealing does not need to be performed at a high temperature, and since the inhibitor does not need to be finely dispersed in the steel, high-temperature slab heating is also possible. Since this method is not necessary, it is a method having great merit in terms of manufacturing cost and equipment maintenance.

Japanese Patent Publication No. 40-15644 Japanese Patent Publication No. 51-13469 Japanese Patent Publication No. 38-8214 JP-A-52-24116 JP 2000-129356 A

However, the component system that does not contain an inhibitor has few precipitates that suppress grain growth, so that the grain size tends to increase due to grain growth during annealing, that is, the annealing temperature dependency is strong. For this reason, the grain size after hot band annealing and after recrystallization annealing also fluctuates due to slight variations in process conditions, specifically variations in each annealing temperature. The magnetic characteristics at the full length and the full width fluctuate, and the problem that good magnetic characteristics cannot be obtained as a whole coil has become apparent.

The present invention advantageously solves the above-described problems, and an object of the present invention is to propose an advantageous method for producing a grain-oriented electrical steel sheet that can achieve high-level stabilization of product magnetic properties.

Now, as a result of intensive studies focusing on elements that seem to have an influence on particle size control in order to solve the above problems, the inventors have regulated the ratio of Al and N within a predetermined range. The inventors have found that good and stable magnetic characteristics can be obtained by adding a small amount of a specific element. Hereinafter, experiments that have made the present invention successful will be described.
In the following description, “%” means “% by mass” unless otherwise specified. The ppm display is also a value by mass.

(Experiment 1a)
C: 0.012 to 0.073%, Si: 3.15 to 3.33%, Mn: 0.06 to 0.09%, Cr: 0.02 to 0.06%, Sb: 0.018 to A steel slab having 0.045%, Al: 35 to 100 ppm, N: 14 to 70 ppm, S: 11 to 25 ppm and Nb: 20 to 50 ppm and having a composition of the balance Fe and unavoidable impurities is continuously cast. A slab was heated at 1250 ° C. and then hot rolled to form a hot rolled sheet sheet having a thickness of 2.3 mm. Next, hot-rolled sheet annealing was performed at 1050 ° C. for 15 seconds, and then finished to a sheet thickness of 0.23 mm by cold rolling. Furthermore, after applying recrystallization annealing at 850 ° C. for 60 seconds, after applying an annealing separator mainly composed of MgO, finish annealing was performed by holding at 1200 ° C. for 10 hours. Finally, flattening annealing was performed at 900 ° C. for 15 seconds, which also served as the formation of tension coating mainly composed of magnesium phosphate and boric acid, to produce a grain-oriented electrical steel sheet.

Magnetic flux density B ₈ (magnetizing force 800 A / m) of the obtained sample was measured according to the method of JIS C2550. Although the obtained magnetic flux density seemed to fluctuate at first glance, a very good correlation was obtained when arranged by the ratio of Al and N of steel slab components.

The result is shown in FIG.
As shown in the figure, when Al / N (horizontal axis: mass ratio) is small, the magnetic flux density B ₈ (vertical axis: unit T) tends to decrease. Can be seen to be larger.

(Experiment 1b)
C: 0.035 to 0.043%, Si: 3.23 to 3.30%, Mn: 0.06 to 0.09%, Sb: 0.027 to 0.045%, Cr: 0.02 to Contains 0.06%, P: 0.012 to 0.015%, Al: 28 to 100 ppm, N: 17 to 50 ppm, S: 15 to 26 ppm and Nb: 25 to 47 ppm, the balance being Fe and inevitable impurities A steel slab made of the above is manufactured by continuous casting, heated at 1250 ° C., then hot rolled to a 2.3 mm thick hot rolled sheet, and then annealed at 1050 ° C. for 15 seconds and then cold rolled. A final thickness of 0.23 mm was obtained by rolling. Then, after recrystallization annealing in a soaking condition of 50% N ₂ -50% H ₂ at 850 ° C. for 60 seconds, an annealing separator mainly composed of MgO is applied, and then 1200 Finish annealing was performed at 10 ° C. for 10 hours. Thereafter, planarization annealing was performed at 900 ° C. for 15 seconds under the condition of forming a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

After flattening annealing, measure the iron loss of the entire length of the coil with an in-line iron loss meter in advance, and sample 5 locations in total: 3 locations where the iron loss was bad in the overall length measurement and 2 ends of the coil: 2 locations. Collected. The magnetic properties (magnetic flux density B ₈ ) of the obtained sample were measured by the method described in JIS C 2550, and the value having the worst magnetic properties among the five locations was taken as the representative value of the coil. In this method, when the variation in the magnetic characteristics is large, the representative value is deteriorated. Therefore, it can be considered that the variation in the coil can be quantified.

Although the obtained magnetic characteristics seemed to vary at first glance, a good correlation was obtained by arranging the ratio of Al to N in the steel slab component Al / N. The result is shown in FIG.
As can be seen from FIG. 2, the magnetic properties (vertical axis: magnetic flux density B ₈ (T)) deteriorate as Al / N (horizontal axis: mass ratio) decreases, and the variation increases especially when the ratio is below 1.4.
In both FIG. 1 and FIG. 2, when Al / N ≧ 2.0, the magnetic flux density tends to be somewhat higher.

Therefore, further experiments were conducted to investigate the reason why Al / N has a correlation with the magnetic flux density. That is, in the above experiments 1a and 1b, a change in the magnetic flux density was observed even when Al / N was around 2.0, so that Al and N present as impurities formed AlN (Al / N is a mass ratio) 27 / 14≈1.93), and it was speculated that the behavior of this compound might be involved. In order to further pursue this assumption, an experiment was conducted in which various nitride forming elements were added.

(Experiment 2a)
C: 0.045 to 0.062%, Si: 3.20 to 3.31%, Mn: 0.04 to 0.16%, Cr: 0.03 to 0.11%, Sb: 0.015 to 0.037%, Mo: 0.03-0.05%, Al: 55-97 ppm, N: 20-49 ppm (however, Al / N: 1.98-3.10) and S: 17-27 ppm, Further, a steel slab selected from one of Zr, Ti, B, Nb and V and containing about 50 ppm each, and a steel slab containing none of these trace elements (Zr, Ti, B, Nb and V), Each was manufactured by continuous casting. The balance of the composition of each steel slab was Fe and inevitable impurities. These steel slabs were slab heated at 1250 ° C. and then hot rolled into hot rolled sheets having a thickness of 2.2 mm. Subsequently, hot-rolled sheet annealing was performed at 1100 ° C. for 60 seconds, and then finished to a sheet thickness of 0.23 mm by cold rolling. Further, after recrystallization annealing at 840 ° C. for 80 seconds, an annealing separator mainly composed of MgO was applied, and then finish annealing was performed at 1200 ° C. for 10 hours. Finally, planarization annealing was performed at 900 ° C. for 15 seconds to form a tension-imparting coating mainly composed of magnesium phosphate and boric acid, to produce a grain-oriented electrical steel sheet.

The magnetic flux density _{B 8} of the resulting samples was measured according to the method of JIS C2550. The result is shown in FIG.
As shown in the figure, it can be seen that the magnetic flux density B ₈ (vertical axis: unit T) obtained varies greatly depending on the types of added Zr, Ti, B, Nb and V. That is, the sample to which Zr (left end) and Ti (second from the left) were added had a low magnetic flux density and did not develop secondary recrystallization. On the other hand, when Nb (third from the same), B (third from the right), and V (second from the right) are added, the magnetic flux density is higher than when not added (right end). It became clear.

(Experiment 2b)
C: 0.045 to 0.062%, Si: 3.20 to 3.31%, Mn: 0.04 to 0.16%, Sb: 0.015 to 0.037%, Cr: 0.03 to 0.11%, Mo: 0.03-0.05%, Al: 55-97ppm, N: 20-49ppm (however, Al / N: 1.98-3.10) and S: 17-27ppm Further, a steel slab in which one of Zr, Ti, Nb, B, and V is selected and about 50 ppm is added, and a steel slab that does not contain any of these trace elements (Zr, Ti, Nb, B, and V), Each was manufactured by continuous casting. The balance of all steel slabs was Fe and inevitable impurities. After each steel slab was slab heated at 1250 ° C., it was hot-rolled to a hot-rolled sheet having a thickness of 2.8 mm, then annealed at 1100 ° C. for 60 seconds and then cold-rolled to a final thickness of 0.30 mm. Finished. Then, after recrystallization annealing in a soaking condition of 50% N ₂ -50% H ₂ at 840 ° C. for 80 seconds, after applying an annealing separator mainly composed of MgO, 1200 Finish annealing was performed at 10 ° C. for 10 hours. Thereafter, planarization annealing was performed at 900 ° C. for 15 seconds under the condition of forming a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

After flattening annealing, the iron loss of the entire length of the coil is measured in advance with an in-line iron loss meter, a total of five samples are taken from the inside of the coil by the same method as in Experiment 1b, and the magnetic properties of the obtained sample are JIS C 2550 As a representative value of the coil, the value having the worst magnetic characteristics among the five locations was measured.

The obtained results are shown in FIG.
FIG. 4 shows that the magnetic flux density B ₈ (vertical axis: unit T) varies greatly depending on the trace element added by about 50 ppm. Here, secondary recrystallization did not appear in the Zr additive (left end) and the Ti additive (second from the left) having a low magnetic flux density. Further, when Nb (third from the left), B (third from the right), and V (second from the same) are added, the magnetic flux density is higher than when nothing is added (right end). It became clear.

As described above, the reason why the magnetic characteristics change due to the addition of a trace element or the reason why the magnetic characteristics improve by adding at least one of B, Nb, and V is not necessarily clearly elucidated. The inventors consider as follows.
The thermodynamic stability of nitrides in additives (especially trace additives) and impurities has been investigated in detail, and it has been found that the stability varies depending on the elements bound to nitrogen. In the elements added in the experiments 2a and 2b, the stability of the nitride is Zr, Ti, Al, B, Nb and V from the stable side.
According to the results of FIG. 3 and FIG. 4, the elements having poor magnetic characteristics are Zr and Ti whose nitride is more stable than Al, and the elements having good magnetic characteristics are B and B whose nitride is unstable than Al. Nb and V. From this, when Zr and Ti are present, it is presumed that N in the steel is combined with these elements and the formation of ZrN and TiN deteriorates the magnetic properties. On the other hand, even if B, Nb, or V exists, N in the steel is considered to form a stable nitride with Al, and a nitride with B, Nb, or V is not formed.

Further, in Experiments 1a and 1b, when Al / N was low, the magnetic properties were low even in the presence of Nb. The reason for this is thought to be that N is excessively stoichiometrically compared to Al and Nb is combined with excess N to form a nitride.
In extreme terms, it is considered that the presence of nitrides of Zr, Ti, B, Nb or V deteriorates the magnetic properties. Presumably, the increase in the number of microprecipitates such as nitrides of these trace elements reduces the texture inhibition effect with the grain boundary energy difference between the crystal grains of the steel sheet as the driving force. The

On the other hand, as described above, when a small amount of B, Nb, or V was added under the condition where no nitride was formed, the magnetic characteristics were improved as compared with the case where it was not added. The reason for this is not clear, but it has been found by further investigations by the inventors that the crystal grain size after recrystallization annealing becomes fine and uniform when at least one of B, Nb and V is added. This eliminates the influence of the size effect on the particle size (a phenomenon in which grains that are approximately twice the average value of the particle size are prone to abnormal grain growth) and maximizes the texture inhibition effect. It is speculated that this has led to improved magnetic properties. The effect of uniforming the particle size contributes to the improvement of the variation in magnetic properties within the same sample, which was a problem of the component system not containing an inhibitor.

In response to the above results and considerations, the inventors conducted further experiments to investigate the effect of uniformizing the particle size. As a result, a specific element is added in a small amount as described above, and the ratio of the impurities Al and N is specified, and further, the intended purpose is further controlled by controlling the rate of temperature increase during recrystallization annealing. The knowledge that it was achieved advantageously was obtained.

(Experiment 3)
C: 0.034%, Si: 3.30%, Mn: 0.07%, Sb: 0.030%, Sn: 0.059%, Cr: 0.05%, Al: 56 ppm, N: 29 ppm ( A steel slab containing Al / N: 1.93), S: 15 ppm and Nb: 35 ppm with the balance being Fe and inevitable impurities was produced by continuous casting. This steel slab was slab heated at 1150 ° C., then hot rolled to a 3.0 mm thick hot rolled sheet, then annealed at 950 ° C. for 30 seconds, and then cold rolled for the first time to 1.8 mm. An intermediate thickness was obtained, and after an intermediate annealing at 1000 ° C. for 40 seconds, the final thickness was 0.23 mm by the second cold rolling. Thereafter, recrystallization annealing was performed in a soaking condition of 50% N ₂ -50% H ₂ at 850 ° C. for 60 seconds. At this time, the average rate of temperature increase between 600 and 800 ° C. was variously changed.

The recrystallized particle size of the obtained sample was measured, and the average particle size and its standard deviation were determined from the particle size distribution. The recrystallized grain size is measured by cutting a section perpendicular to the rolling direction of the sample, etching with a nital liquid (nitral) and observing it with an optical microscope, and using an image processing device to check the grains in the field of view by an elliptical approximation method (fitting an approximate to an ellipse, and the average of the major axis and minor axis dimensions was taken as the grain size of the grains. The above samples were collected from both ends and the center in the width direction of the produced recrystallized plate, and the observation location was set to the full thickness. Samples were collected so that the number of observed grains was at least 2000 in total in both ends and the center.

In FIG. 5, the standard deviation (vertical axis) when the average grain size is normalized to 1.0 is the temperature increase rate of recrystallization annealing (horizontal axis (average temperature increase rate between 600 to 800 ° C.): unit ° C. / S).
As shown in the figure, it can be seen that the faster the average heating rate between 600 and 800 ° C., the smaller the standard deviation, that is, the smaller the variation in particle size.

Through the experiments and considerations as described above, the inventors regulate the ratio of Al and N present as impurities in the component-oriented grain-oriented electrical steel sheet not containing an inhibitor, and in addition, B, Nb and It was concluded that good magnetic properties can be obtained by adding a trace amount of at least one of V.

Further, through further experiments and discussions, the inventors define the ratio of Al and N, and control the rate of temperature rise during recrystallization annealing in a system in which at least one of B, Nb and V is added in a trace amount. This led to the conclusion that a grain-oriented electrical steel sheet having even better magnetic properties (including uniformity of magnetic properties) can be obtained.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
(1) By mass%, C: 0.10% or less, Si: 2.0 to 8.0% and Mn: 0.005 to 1.0%, Al 100 ppm or less, N, S and A grain-oriented electrical steel sheet comprising a series of steps in which Se is set to 50 ppm or less, and the balance is finished by rolling a slab composed of Fe and inevitable impurities to finish the final plate thickness, and then performing recrystallization annealing and then finishing annealing. In the manufacturing method,
The ratio of the amount of Al and the amount of N contained in the slab is set to 1.4 or more in terms of mass ratio, and one or more selected from B, Nb and V are further added to the slab. A method for producing a grain-oriented electrical steel sheet, characterized by containing 10 to 150 ppm in total.

(2) After the slab is rolled and finished to the final plate thickness, the slab is hot-rolled and subjected to hot-rolled sheet annealing as necessary, and then cold once or two times with intermediate annealing interposed therebetween. The method for producing a grain-oriented electrical steel sheet according to (1), which is a step of rolling.

(3) In the slab, Ni: 0.010 to 1.50%, Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.005 to 0 .50%, Sn: 0.005 to 0.50%, Sb: 0.005 to 0.50%, Bi: 0.005 to 0.50% and Mo: 0.005 to 0.10% The method for producing a grain-oriented electrical steel sheet according to the above (1) or (2), comprising at least one selected.

(4) By mass%, C: 0.10% or less, Si: 2.0 to 8.0% and Mn: 0.005 to 1.0%, Al 100 ppm or less, N, S And Se are each reduced to 50 ppm or less, and the balance is composed of a series of steps in which a final slab is rolled by rolling a slab composed of Fe and inevitable impurities, and then subjected to recrystallization annealing and then finish annealing. In the manufacturing method of electrical steel sheet,
The slab further contains one or more selected from B, Nb and V in a total range of 10 to 150 ppm, and the ratio of Al to N contained as impurities is expressed as Al by mass ratio. /N≧1.4, and the average heating rate between 600 and 800 ° C. in recrystallization annealing is set to 15 ° C./s or more.

(5) After the slab is rolled and finished to the final sheet thickness, the slab is hot-rolled and subjected to hot-rolled sheet annealing as necessary, and then cold once or two times sandwiching the intermediate annealing. The method for producing a grain-oriented electrical steel sheet according to (4), which is a step of rolling.

(6) In the slab, Ni: 0.010 to 1.50%, Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.0. 005 to 0.50%, Sn: 0.005 to 0.50%, Sb: 0.005 to 0.50%, Bi: 0.005 to 0.50%, and Mo: 0.005 to 0.100% 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.

(7) The above-mentioned (4), wherein the grain size distribution of the recrystallized grains of the steel sheet after the recrystallization annealing satisfies a standard deviation of 0.3 or less when the average grain size is normalized to 1.0. A method for producing a grain-oriented electrical steel sheet according to any one of (6).

According to the present invention, in a component system that does not substantially contain an inhibitor, it is possible to reduce variations in magnetic characteristics in the longitudinal direction and width direction of the coil, and as a result, excellent magnetic characteristics (that is, high-level stability) as a whole product coil. Can be obtained.

FIG. 1 is a graph showing the relationship between the Al / N ratio Al / N (horizontal axis: mass ratio) in steel and the magnetic flux density B ₈ (vertical axis: unit T). FIG. 2 is a graph showing the relationship between the ratio Al / N (horizontal axis: mass ratio) between impurities Al and N in steel and the magnetic flux density B ₈ (vertical axis: unit T). FIG. 3 is a diagram showing a comparison of the relationship between the type of trace elements added to steel (horizontal axis) and the magnetic flux density B ₈ (vertical axis: unit T). FIG. 4 is a diagram showing the relationship between the type of trace elements added to the steel (horizontal axis) and the magnetic flux density B ₈ (vertical axis: unit T). FIG. 5 is a diagram showing the standard deviation (vertical axis) when the average grain size is normalized to 1.0 in relation to the rate of temperature increase of recrystallization annealing (horizontal axis: ° C./s).

The present invention will be specifically described below.
First, the reason why the component composition of the slab is limited to the above range in the present invention will be described.
In principle, the reason for limitation will be described for each element, but this does not mean that each element affects each other independently, and it is effective on the assumption that other elements are within the scope of the present specification. . In other words, the range limitation of each element achieves the target effect or a more preferable effect by the range limitation of other elements or the combination effect with manufacturing conditions.
As described above,% and ppm in the composition are based on mass unless otherwise specified.

C: 0.10% or less When the amount of C exceeds 0.10%, it is difficult to reduce to 50 ppm or less where magnetic aging does not occur even when decarburization treatment is performed. Therefore, the C content is limited to 0.10% or less. A particularly preferable range is 0.04% or less. A smaller amount of C is desirable, but industrially, it is generally contained at 30 ppm or more.

Si: 2.0 to 8.0%
Si is an element necessary for increasing the specific resistance of steel and improving iron loss, but its effect is poor at less than 2.0%. On the other hand, if it exceeds 8.0%, workability deteriorates and rolling becomes difficult. Therefore, the Si content is limited to the range of 2.0 to 8.0%. A particularly preferred lower limit is 2.8%. A particularly preferred upper limit is 3.5%.

Mn: 0.005 to 1.0%
Mn is an element necessary for improving the hot workability, but its effect is poor when it is less than 0.005%. On the other hand, if it exceeds 1.0%, the magnetic flux density of the product plate decreases. For this reason, the amount of Mn was limited to the range of 0.005 to 1.0%. A particularly preferred lower limit is 0.02%. A particularly preferred upper limit is 0.20%.

Al: 100 ppm or less, and N, S, Se: 50 ppm or less In the present invention, the amount of Al is 100 ppm or less, and the amount of N, S, and Se is 50 ppm or less. Indispensable for recrystallization. Although it is desirable to reduce these components as much as possible from the viewpoint of magnetic characteristics, since the reduction of these components increases the cost, there is no problem even if they are left within the above range.

Of these, Al and Se are elements that are difficult to remove (purify) from the steel by finish annealing or the like, and therefore, it is more preferable that Al is 80 ppm and Se is 20 ppm or less. In general, it is generally contained 20 ppm or more and 6 ppm or more, respectively.

Also, N and S, which are light elements, are difficult to remove completely at the time of adjusting the components before making the steel slab, and if no special treatment is performed, about 20 ppm each remains in the steel plate. It is common.

Among these impurities, the mass ratio of Al to N (Al / N) is required to be 1.4 or more for the reasons described above, and in particular, when Al / N is set to 2.0 or more, the magnetic properties are improved. More desirable. Further, as described above, since it is difficult to completely remove N, addition of a trace amount of Al in the range of 100 ppm or less to satisfy Al / N ≧ 1.4 is not prevented.
The upper limit of Al / N is not necessary from the viewpoint of the effect, but generally does not exceed 5 from the lower limit of 20 ppm of the industrial N amount.

One or more selected from B, Nb and V: 10 to 150 ppm in total
Furthermore, in order to sufficiently obtain the effect of improving the magnetic characteristics in the present invention, it is necessary to add 10 ppm or more of one or more of B, Nb and V. The reason is as described above. If the total addition amount is less than 10 ppm, the addition effect is small. Preferably, when each addition amount is 10 ppm or more, the effect of the present invention can be obtained more reliably. More preferably, each is 20 ppm or more. However, since these trace additive elements remain in the base iron even in the final product and cause deterioration of iron loss, the total amount is limited to 150 ppm or less. From the viewpoint of suppressing iron loss deterioration, the total amount is preferably 100 ppm or less, and more preferably 50 ppm or less.
The most preferable element is Nb, which is superior to others in the effect of making the crystal grain size uniform after recrystallization annealing.

As described above, the essential element and the suppressing element have been described. In the present invention, at least one selected from Ni, Cr, Cu, P, Sn, Sb, Bi, and Mo as other magnetic property improving elements is described below. It can contain suitably in the range.

Ni: 0.01-1.50%
Ni is an element useful for improving the magnetic properties by improving the hot-rolled sheet structure, but if the addition amount is less than 0.01%, the addition effect is poor. On the other hand, if it exceeds 1.50%, the secondary recrystallization becomes unstable and the magnetic properties deteriorate. Preferably it is 0.010% or more.

Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.005 to 0.50%
All of these elements are useful elements for improving the iron loss, but their addition effect is poor unless the lower limit is reached. On the other hand, when the upper limit is exceeded, the development of secondary recrystallized grains is suppressed, and rather the magnetic properties are deteriorated.

Sn: 0.005 to 0.50%, Sb: 0.005 to 0.50%, Bi: 0.005 to 0.50%, Mo: 0.005 to 0.10%
These elements are also elements useful for improving the magnetic properties, but their addition effect is poor unless the lower limit is reached. On the other hand, when the upper limit is exceeded, the development of secondary recrystallized grains is suppressed, and rather the magnetic properties are deteriorated. The upper limit of Mo is preferably 0.100% or less.

Next, the manufacturing process of the present invention will be described.
The molten steel adjusted to the above preferred component composition is made into a slab by a normal ingot-making method or a continuous casting method. Further, a thin cast piece having a thickness of 100 mm or less may be manufactured by a direct casting method. In the case of a slab, it is heated and rolled by a normal method, but may be immediately subjected to hot rolling without heating after casting. In the case of a thin slab, hot rolling may be performed, or the hot rolling may be omitted and the process may proceed as it is.

Since the slab heating temperature before hot rolling is a component system that does not contain an inhibitor component with reduced Al, N, S, and Se, high temperature annealing is required to dissolve the inhibitor, which has been essential in the past. do not do. Therefore, a low temperature of 1250 ° C. or lower is desirable in terms of cost.

Next, hot-rolled sheet annealing is performed as necessary. The hot-rolled sheet annealing temperature for obtaining good magnetic properties is preferably about 800 to 1150 ° C. If the hot-rolled sheet annealing temperature is less than 800 ° C., a band texture in hot rolling remains, making it difficult to achieve a sized primary recrystallized structure and inhibiting the development of secondary recrystallization. (When a band structure that requires hot-rolled sheet annealing is present in advance). On the other hand, if the hot-rolled sheet annealing temperature exceeds 1150 ° C., the grain size after the hot-rolled sheet annealing is excessively coarsened, which is extremely disadvantageous in realizing a sized primary recrystallized structure.

After hot-rolled sheet annealing, it is subjected to recrystallization annealing after cold rolling at least once with intermediate or intermediate annealing. When performing cold rolling, the temperature is raised to 100 to 300 ° C., and the aging treatment at 100 to 300 ° C. is performed once or a plurality of times in the course of cold rolling in order to improve the magnetic properties. It is advantageous.

Recrystallization annealing is performed in a wet atmosphere when decarburization is required, but may be performed in a dry atmosphere when decarburization is not required. The soaking temperature in this recrystallization annealing is not particularly limited as long as it is equal to or higher than the recrystallization temperature, but there is a concern that annealing at an excessively high temperature results in a coarse crystal grain size and unstable secondary recrystallization. Therefore, the upper limit of the annealing temperature is preferably about 1050 ° C. In addition, after recrystallization annealing, a technique for increasing the amount of Si by a siliconization method may be used in combination.

In the present invention, in the above-described recrystallization annealing step, it is extremely preferable that the average temperature increase rate from 600 ° C. to 800 ° C. is 15 ° C./s or more. This is because when the average value of the heating rate is 15 ° C./s or more, as shown in FIG. 5, the standard deviation when the average particle size is normalized to 1.0 is extremely small. This is because the variation in the particle size becomes very small, which is further advantageous in obtaining excellent magnetic characteristics stably. The upper limit value of the average temperature increase rate is not particularly limited and is preferably as large as possible. However, from the viewpoint of temperature control, it is preferable to adjust the temperature increase rate within a range of 300 ° C./s or less. The average rate of temperature rise may be determined by measuring the surface temperature of the plate with a radiation thermometer and dividing the temperature rise (200 ° C.) by the time from 600 ° C. to 800 ° C.

Thereafter, when forming a forsterite film with an emphasis on iron loss, a secondary recrystallized structure is developed by applying a final annealing after applying an annealing separator mainly composed of MgO. It is possible to form a forsterite film.
On the other hand, if the forsterite film is not formed with emphasis on the punching processability, the main component is silica or alumina that inhibits the formation of the forsterite film even if it is used or not used. Use things. When these annealing separators are applied, it is effective to perform electrostatic coating that does not carry moisture, and a heat-resistant inorganic material sheet (silica, alumina, mica) may be used.

The finish annealing is desirably performed at 800 ° C. or higher for secondary recrystallization. In order to complete the secondary recrystallization, it is desirable to hold at a temperature of 800 ° C. or higher for 20 hours or longer. If the forsterite film is not formed with emphasis on punchability, secondary recrystallization should be completed, so the holding temperature is preferably about 850 to 950 ° C., and the finish annealing is finished at the holding stage. It is also possible. When emphasizing iron loss or forming a forsterite film to reduce transformer noise, it is desirable to raise the temperature to about 1200 ° C.
In the present invention, it is not necessary to remove the inhibitor in the finish annealing, and therefore the degree of freedom of the finish annealing temperature is high, but it is still preferable to remove (purify) impurities by finish annealing even if it is other than the inhibitor. . Therefore, in the present invention, finish annealing also has the meaning of purification annealing.

After finishing annealing, water washing, brushing, pickling, etc. are performed to remove the unreacted annealing separator adhering. After that, it is effective to reduce the iron loss by performing flattening annealing to correct the shape.

In addition, when laminating and using steel plates, it is effective to apply an insulating coating to the steel plate surface before or after flattening annealing for the purpose of improving iron loss. This insulating coating is desirably a coating that can apply tension to the steel sheet in order to reduce iron loss. In other words, if a coating method that deposits inorganic material on the steel sheet surface by a tension coating application method through a binder, physical vapor deposition method, or chemical vapor deposition method, a coating film with excellent adhesion can be obtained, and iron loss reduction effect Will also improve.

Example 1
C: 0.018 to 0.023%, Si: 3.20 to 3.40%, Mn: 0.10 to 0.15%, Cr: 0.03 to 0.05%, Al: 30 to 140 ppm and A steel slab containing N: 29 to 50 ppm, having an Al / N ratio shown in Table 1, further containing the Nb amount shown in Table 1, and the balance being Fe and inevitable impurities was produced by continuous casting. . Subsequently, the slab was heated at 1200 ° C., and a hot rolled sheet having a thickness of 2.2 mm was formed by hot rolling. Next, hot-rolled sheet annealing was performed at 1060 ° C. for 40 seconds, and finished to a thickness of 0.23 mm by one cold rolling. Furthermore, after applying recrystallization annealing at 850 ° C. for 100 seconds, after applying an annealing separator mainly composed of MgO, it was held at 900 ° C. for 50 hours for secondary recrystallization, The forsterite film was formed by holding at 1200 ° C. for 10 hours. Finally, flattening annealing was performed at 1200 ° C. for 60 seconds, and then TiN was vapor-deposited on the steel sheet surface by chemical vapor deposition to form a coating.

Here, the collection of the magnetic property measurement sample and the measurement of the magnetic property in this example were performed according to the following procedure.
First, the iron loss is measured over the entire length of the coil by an in-line iron loss meter installed on the exit side of the annealing furnace of the flattening annealing line, and the iron loss profile in the coil longitudinal direction is acquired. Next, after TiN coating, samples were taken from a total of 5 locations, from the location where the iron loss in the iron loss profile was high, to 3 locations in the plate width direction and 2 locations in the coil longitudinal direction (center in the width direction) The magnetic properties were collected and measured according to the method of JIS C2550.
Of the above five locations, the magnetic flux density B8 and W17 / 50 in the sample having the worst magnetic characteristics is used as a representative value of the coil. Was evaluated.
The above measurement evaluation results are also shown in Table 1.

As shown in the table, according to the present invention, it was possible to obtain a grain-oriented electrical steel sheet having good magnetic properties over the entire coil length in a component system that does not contain an inhibitor.
(Example 2)

C: 0.018 to 0.023%, Si: 3.20 to 3.40%, Mn: 0.10 to 0.15%, Cr: 0.03 to 0.05%, Al: 30 to 140 ppm and N: 29 to 50 ppm, the Al / N ratio is the value shown in Table 2, and further contains the amount of Nb shown in Table 2, with the balance being a steel slab composed of Fe and inevitable impurities. Manufactured, and slab heated at 1200 ° C., then hot-rolled to a 2.2 mm thick hot-rolled sheet, then annealed at 1060 ° C. for 40 seconds and then cold-rolled to a final thickness of 0.23 mm Finished. Thereafter, recrystallization annealing was performed at 820 ° C. for 90 seconds in a humid atmosphere of 25% N ₂ -75% H ₂ . At this time, the average heating rate between 600 and 800 ° C. was 36 ° C./s. The standard deviation of the recrystallized grain size distribution was about 0.21. Next, after applying an annealing separator mainly composed of MgO, purification annealing was performed at 1200 ° C. for 10 hours. Thereafter, planarization annealing was performed at 1200 ° C. for 60 seconds. At that time, TiN was vapor-deposited on the steel sheet surface layer by chemical vapor deposition to form a coating.

After the flattening annealing, the iron loss of the entire length of the coil was measured in advance with an in-line iron loss meter, and a total of 5 samples were collected: 3 places where the iron loss was bad in the full length measurement and 2 ends of the coil: 2 places.
The magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ) of the obtained sample were measured by the method described in JIS C 2550, and the value with the worst magnetic properties among the five locations was taken as the representative value of the coil. did. In this method, when the variation in the magnetic characteristics is large, the representative value is deteriorated. Therefore, it can be considered that the variation in the coil can be quantified.
The obtained results are also shown in Table 2.

As is apparent from the table, it is understood that good magnetic properties can be obtained by adding an appropriate amount of Nb as a trace element and adjusting the Al / N ratio to an appropriate range.

(Example 3)
A steel slab containing the components shown in Table 3 with the balance being Fe and inevitable impurities was produced by continuous casting. Subsequently, the slab was heated at 1250 ° C., and a hot-rolled sheet having a thickness of 2.3 mm was formed by hot rolling. Next, hot-rolled sheet annealing was performed at 1000 ° C. for 35 seconds, and a steel sheet having a thickness of 0.82 mm was formed by the first cold rolling. Subsequently, after performing an intermediate annealing at 1000 ° C. for 40 seconds, a final thickness of 0.23 mm was obtained by the second cold rolling. Subsequently, recrystallization annealing was performed at 850 ° C. for 60 seconds, an annealing separator mainly composed of MgO was applied, and final annealing was performed at 1250 ° C. for 10 hours. In this case, the Ar atmosphere was set for the latter half 5 hours out of the 10-hour holding, and the hydrogen atmosphere was set for the rest. Finally, planarization annealing was performed at 900 ° C. for 15 seconds, which also served to form a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

The magnetic properties of the obtained samples were measured and evaluated for the steel plates after annealing according to the same procedure as in Example 1.
The results are also shown in Table 3.

As shown in the table, according to the present invention, it was possible to obtain a grain-oriented electrical steel sheet having good magnetic properties over the entire coil length in a component system that does not contain an inhibitor.
Example 4

Steel slabs having the composition shown in Table 4 were manufactured by continuous casting, and after heating the slabs at 1200 ° C., hot-rolled sheets having a thickness of 2.8 mm were formed by hot rolling. Then, the intermediate sheet thickness was 2.0 mm by the first cold rolling, and after the intermediate annealing at 1000 ° C. for 40 seconds, the final sheet thickness was 0.23 mm by the second cold rolling. Thereafter, recrystallization annealing was performed at 830 ° C. for 60 seconds in a wet atmosphere of 40% N ₂ -60% H ₂ . At this time, the average temperature rising rate between 600 and 800 ° C. was 70 ° C./s. The standard deviation of the recrystallized grain size distribution was about 0.19 in all cases. Then, after applying an annealing separator mainly composed of MgO, purification annealing was performed at 1250 ° C. for 10 hours. At that time, out of the 10-hour retention, the latter half 5 hours was set to Ar atmosphere, and the rest was set to hydrogen atmosphere. Thereafter, flattening annealing was performed at 900 ° C. for 15 seconds under the condition of forming a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

After the flattening annealing, the iron loss of the entire length of the coil was measured in advance with an in-line iron loss meter, and a total of 5 samples were collected: 3 places where the iron loss was bad in the full length measurement and 2 ends of the coil: 2 places.
The magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ) of the obtained sample were measured by the method described in JIS C 2550, and the value with the worst magnetic properties among the five locations was taken as the representative value of the coil. did. In this method, when the variation in the magnetic characteristics is large, the representative value is deteriorated. Therefore, it can be considered that the variation in the coil can be quantified.
The obtained results are also shown in Table 4.

As is clear from the table, good magnetic properties were obtained in any of the invention examples in which the component composition satisfied the proper range of the present invention.
(Example 5)

C: 0.082%, Si: 3.30%, Mn: 0.07%, Cr: 0.05%, P: 0.012%, Sn: 0.054%, Sb: 0.035%, Al : 70 ppm, N: 32 ppm (Al / N = 2.19) and V: 40 ppm, and the balance is produced by continuous casting of a steel slab composed of Fe and inevitable impurities, and after heating at 1200 ° C., A hot-rolled sheet having a thickness of 2.7 mm was obtained by hot rolling. Then, after hot-rolled sheet annealing at 950 ° C. for 30 seconds, a final sheet thickness of 0.30 mm was finished by warm rolling at 150 ° C. Thereafter, recrystallization annealing was performed at 835 ° C. for 90 seconds in a wet atmosphere of 60% N ₂ -40% H ₂ . At this time, the average temperature increase rate between 600 and 800 ° C. was variously changed as shown in Table 5. Then, after applying an annealing separator mainly composed of MgO, purification annealing was performed at 1200 ° C. for 25 hours. Thereafter, flattening annealing was performed at 900 ° C. for 15 seconds under the condition of forming a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

After the flattening annealing, the iron loss of the entire length of the coil was measured in advance with an in-line iron loss meter, and a total of 5 samples were collected: 3 places where the iron loss was bad in the full length measurement and 2 ends of the coil: 2 places.
The magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ) of the obtained sample were measured by the method described in JIS C 2550, and the value with the worst magnetic properties among the five locations was taken as the representative value of the coil. did. In this method, when the variation in the magnetic characteristics is large, the representative value is deteriorated. Therefore, it can be considered that the variation in the coil can be quantified.
The obtained results are also shown in Table 5.

As is clear from the table, it can be seen that by setting the average temperature increase rate between 600 to 800 ° C. in the recrystallization annealing step to 15 ° C./s or more, even better magnetic properties can be obtained. In addition, when the average temperature rising rate is less than 15 ° C./s, the magnetic properties deteriorate due to variations. In this case, the magnetic properties can be improved by making Al / N 1.4 or more and containing a predetermined amount of trace elements. Can do.

According to the present invention, in a component system that does not contain an inhibitor, variation in magnetic characteristics in the longitudinal direction and width direction of the coil can be reduced, and as a result, good magnetic characteristics can be obtained as a whole product coil. That is, it is possible to obtain a grain-oriented electrical steel sheet having excellent magnetic characteristics over the entire length and width of the coil, and this grain-oriented electrical steel sheet is extremely effective for applications such as a coil core that requires a strong magnetic flux density.

Claims (8)

1. In mass%, C: 0.10% or less, Si: 2.0-8.0% and Mn: 0.005-1.0%, Al is 100 ppm or less, and N, S and Se are each In the manufacturing method of grain-oriented electrical steel sheet comprising a series of steps of rolling a slab composed of Fe and inevitable impurities to the final sheet thickness and then performing recrystallization annealing and then finishing annealing. ,
   The ratio of the amount of Al and the amount of N contained in the slab is set to 1.4 or more in terms of mass ratio, and one or more selected from B, Nb and V are further added to the slab. A method for producing a grain-oriented electrical steel sheet, characterized by containing 10 to 150 ppm in total.
2. The step of rolling the slab to finish to the final plate thickness is performed by hot rolling the slab and, if necessary, performing hot-rolled sheet annealing, and then performing cold rolling at least once with one or intermediate annealing in between. The manufacturing method of the grain-oriented electrical steel sheet according to claim 1, which is a process.
3. In the slab, Ni: 0.01 to 1.50%, Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.005 to 0% by mass%. .50%, Sn: 0.005 to 0.50%, Sb: 0.005 to 0.50%, Bi: 0.005 to 0.50% and Mo: 0.005 to 0.10% The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, comprising at least one selected.
4. In mass%, C: 0.10% or less, Si: 2.0 to 8.0% and Mn: 0.005 to 1.0%, Al is 100 ppm or less, and N, S, and Se are contained. Each is reduced to 50 ppm or less, and the balance is made of a grain-oriented electrical steel sheet consisting of a series of steps of rolling a slab composed of Fe and inevitable impurities to finish the final plate thickness, then performing recrystallization annealing, and then finishing annealing. In the manufacturing method,
   The slab further contains one or more selected from B, Nb and V in a total range of 10 to 150 ppm, and the ratio of Al to N is expressed as Al / N ≧ 1 by mass ratio. And a mean temperature increase rate between 600 and 800 ° C. in recrystallization annealing is set to 15 ° C./s or more.
5. The above-mentioned process of rolling the slab to finish to the final plate thickness is performed by hot rolling the slab and performing hot-rolled sheet annealing as necessary, followed by one or more cold rollings with intermediate annealing interposed therebetween. The manufacturing method of the grain-oriented electrical steel sheet according to claim 4, which is a process.
6. In the slab, Ni: 0.010 to 1.50%, Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.005 to 0% by mass%. .50%, Sn: 0.005 to 0.50%, Sb: 0.005 to 0.50%, Bi: 0.005 to 0.50% and Mo: 0.005 to 0.100% The method for producing a grain-oriented electrical steel sheet according to claim 4 or 5, comprising at least one selected.
7. 6. The grain size distribution of recrystallized grains of a steel sheet after recrystallization annealing satisfies a standard deviation of 0.3 or less when the average grain size is normalized to 1.0. Method for producing a grain-oriented electrical steel sheet.
8. The direction according to claim 6, wherein the grain size distribution of the recrystallized grains of the steel sheet after recrystallization annealing satisfies a standard deviation of 0.3 or less when the average grain size is normalized to 1.0. Method for producing an electrical steel sheet.

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