JPH08269644A - Grain oriented silicon steel sheet excellent in magnetic property and film characteristic and its production - Google Patents

Abstract

PURPOSE: To improve magnetic properties by incorporating specific amounts of Si, Cu, Mn, and Fe and regulating the magnetic flux density B8 , secondary recrystallized grain size, and iron loss of a product to specific values, respectively. CONSTITUTION: This material has a composition consisting of, by weight, 2.5-5% Si, 0.05-0.5% Cu, 0.06-0.8% Mn, and the balance essentially Fe and further satisfying 0.005<=Cu×Mn<=0.15. Moreover, B8 (T) is regulated to >=1.88, and also the average value d(mm) of secondary recrystallized grain sizes is regulated so that it satisfies 1<=d<=23B8 -40. Further the relation of W MWP>=0 08 is satisfied when WP and WM mean the iron loss W13/50 (W/kg) of a product and that after film removal, respectively. By this method, iron loss characteristic as high as to satisfy W13/50 <=0.4 can be provided and also high magnetic flux density can be provided without requiring magnetic domain controlling technique.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, which is used as an iron core of a transformer or the like.

[0002]

2. Description of the Related Art Unidirectional electrical steel sheets are mainly used as iron core materials for transformers and other electrical equipment, and are required to have excellent magnetic characteristics such as excitation characteristics and iron loss characteristics. As a numerical value showing the excitation characteristic, the strength of a normal magnetic field is 8
A magnetic flux density B _{8 at} 00 A / m is used. Further, as a numerical value showing the iron loss characteristic, the iron loss W _17/50 per 1 kg when magnetized to 1.7 Tesler (T) at a frequency of 50 Hz is used.

The magnetic flux density is the most dominant factor of the iron loss characteristics. Generally speaking, the higher the magnetic flux density, the better the iron loss characteristics. Generally, when the magnetic flux density is increased, the secondary recrystallized grains become large, which may result in poor iron loss characteristics.
On the other hand, by controlling the magnetic domains, the iron loss characteristics can be improved regardless of the grain size of the secondary recrystallized grains.

This unidirectional electrical steel sheet is produced by causing secondary recrystallization in the final finishing annealing step to develop a so-called Goss structure having {110} axis on the steel sheet surface and <001> axis in the rolling direction. Has been done. In order to obtain good magnetic properties, it is necessary that <001>, which is the axis of easy magnetization, be highly aligned in the rolling direction. Typical techniques for producing such a high magnetic flux density unidirectional electrical steel sheet include Japanese Patent Publication No. 40-15644 and Japanese Patent Publication No. 51-1346.
There is a method described in Japanese Patent No. 9 publication.

In the former, M is the main inhibitor
nS and AlN are used, and the latter uses MnS, MnSe, Sb and the like. Therefore, in the current technology, it is essential to appropriately control the size, morphology and dispersion state of the precipitates that function as these inhibitors.

As for MnS, in the present process, after the MnS is completely solid-soluted at the time of heating the slab before hot rolling,
The method of precipitation during hot rolling is adopted. A temperature of about 1400 ° C. is necessary to completely form a solid solution of the required amount of MnS for secondary recrystallization. This is higher than the slab heating temperature of ordinary steel by 200 ° C. or more, and this high-temperature slab heating treatment has the following disadvantages. 1) A high-temperature slab heating furnace dedicated to directional magnetic steel is required. 2) The energy intensity of the heating furnace is high. 3) The amount of molten scale increases, and the adverse effect on operation is large, as seen in so-called shaving.

In order to avoid such problems, the slab heating temperature may be lowered to the same level as that of ordinary steel, but at the same time, the amount of MnS effective as an inhibitor is reduced or not used at all. This means that the destabilization of the secondary recrystallization is inevitably brought about. Therefore, in order to realize low-temperature slab heating, some form of MnS
It is necessary to strengthen the inhibitor with precipitates other than those mentioned above to sufficiently suppress normal grain growth during finish annealing.

As such inhibitors, in addition to sulfides, nitrides, oxides, grain boundary precipitation elements, etc. are considered.
Examples of known techniques include the following.
In Japanese Examined Patent Publication No. 54-24685, As, Bi, Sn,
A method of controlling the slab heating temperature in the range of 1050 to 1350 ° C. by containing grain boundary segregation elements such as Sb in steel is disclosed.

In JP-A-52-24116, the slab heating temperature is 1100 to 1260 ° C. by containing a nitride forming element such as Zr, Ti, B, Nb, Ta, V, Cr and Mo in addition to Al. Is disclosed. Further, in JP-A-57-158322, low-temperature slab heating is performed by lowering the Mn content and setting the Mn / S ratio to 2.5 or less, and further adding Cu to stabilize secondary recrystallization. The technology to do is disclosed.

Techniques have also been disclosed in which improvements are made from the metallographic side in combination with the reinforcement of these inhibitors. That is, in JP-A-57-89433, S, in addition to Mn,
Elements such as Se, Sb, Bi, Pb, Sn, and B are added, and the columnar crystal ratio of the slab and the secondary cold rolling reduction are combined to realize low-temperature slab heating at 1100 to 1250 ° C. Further, in Japanese Patent Laid-Open No. 59-1990324, in addition to S or Se, an inhibitor is mainly composed of Al and B and nitrogen, which is subjected to pulse annealing during primary recrystallization annealing after cold rolling to carry out secondary recrystallization. The technology to stabilize is released.

As described above, in order to realize low temperature slab heating in the production of grain-oriented electrical steel sheets, great efforts have been made so far. Furthermore, JP-A-59-5652
Japanese Patent Publication No. 2 discloses a technique that enables low temperature slab heating by setting Mn to 0.08 to 0.45% and S to 0.007% or less. By this method, the problem of defective linear secondary recrystallization of the product due to coarsening of the slab crystal grains during heating of the high temperature slab was solved.

[0012]

In order to improve the quality of the grain-oriented electrical steel sheet, a measure to improve the magnetic flux density is usually tried. The same applies to the process of performing low temperature slab heating. However, if the magnetic flux density is improved, the secondary recrystallized grain size of the product tends to increase, and it becomes difficult to improve the iron loss characteristics. Therefore, the magnetic domain control technique has been used to improve the iron loss characteristics as the magnetic flux density is higher regardless of the secondary recrystallized grain size.

However, since the addition of the magnetic domain control technique naturally raises the cost, there has been a demand for a technique for improving the iron loss characteristics without applying the magnetic domain control technique. . An object of the present invention is to provide a product and a manufacturing method thereof that simultaneously achieve high magnetic flux density and low iron loss.

[0014]

The gist of the present invention is as follows. (1) In weight%, Si: 2.5 to 5.0%, Cu: 0.
05 to 0.50%, Mn: 0.06 to 0.8%, the balance being Fe and unavoidable impurities in the grain-oriented electrical steel sheet,
0.005 ≦ Cu (%) × Mn (%) ≦ 0.15 is satisfied, B ₈ (T) ≧ 1.88, and the average value d ( mm) satisfies 1.0 ≦ d ≦ 23 × B ₈ -40, and the iron loss W _13/50 (w / k) after product and film removal
g) is W _P and W _M , respectively, W _M −W _P ≧ 0.08. A unidirectional electrical steel sheet having excellent magnetic properties and coating properties.

(2) In weight%, Cu: 0.20 to 0.4
A unidirectional electrical steel sheet containing 0% and having excellent magnetic properties and coating properties according to (1). (3) The grain-oriented electrical steel sheet having excellent magnetic properties and coating properties according to (1) or (2), which contains Sn: 0.01 to 0.15% by weight.

(4) C: 0.025 to 0.0% by weight
75%, Si: 2.5 to 5.0%, acid-soluble Al: 0.
010 to 0.060%, N: 0.0010 to 0.013
0%, S + 0.405Se: 0.005-0.020
%, Mn: 0.06 to 0.8%, Cu: 0.01 to 0.
A slab consisting of 50% and the balance of Fe and unavoidable impurities is heated at a temperature of less than 1280 ° C., hot-rolled, followed by hot-rolled sheet annealing if necessary, and then final cold-rolling with a rolling reduction of 80% or more. In the method of producing a unidirectional electrical steel sheet by performing cold rolling one or more times with intermediate annealing if necessary, followed by decarburization annealing and final finishing annealing, the content of Cu and Mn in the slab ( (% By weight) is controlled within the range of the following formula (1), the average particle diameter (D (μm)) of the primary recrystallized grains after completion of decarburization annealing until the start of final finishing annealing is set to 18 to 35 μm, and the Cu content of the slab is set. And D are controlled within the range of the following formula (2), and the total SiO in the surface oxide film of the steel sheet after decarburizing and annealing is controlled.
₂ amount (SIO2 (g / m ² )) and Cu amount of slab (Cu
(%)) Is controlled within the range of the following formula (3), and the steel sheet is subjected to a nitriding treatment of 0.0010% or more with a nitrogen increase amount before the secondary recrystallization of the final finish annealing after hot rolling. ,
(1) A method for producing a grain-oriented electrical steel sheet having good magnetic properties and coating properties as described above. 0.005 ≤ Cu (%) x Mn (%) ≤ 0.15 ………… (1) 16 x Cu (%) + 14 ≤ D ≤ 16 x Cu (%) + 27 ………… (2) 0.8- 0.6 × Cu (%) ≦ SIO2 ≦ 1.8 −0.6 × Cu (%) (3)

(5) A method for producing a grain-oriented electrical steel sheet excellent in magnetic properties and coating properties according to (4), characterized in that a slab containing Cu: 0.20 to 0.40 wt% is used. (6) A method for producing a grain-oriented electrical steel sheet excellent in magnetic properties and coating properties according to (4) or (5), characterized in that a slab containing Sn: 0.01 to 0.15 wt% is used. .

[0018]

The unidirectional electrical steel sheet targeted by the present invention is
Molten steel obtained by the conventional steelmaking method is cast by a continuous casting method or an ingot casting method, and if necessary, a slab is formed by interposing the agglomeration process, and subsequently hot rolled into a hot rolled sheet. Annealing the hot-rolled sheet according to the above, and then including final cold rolling with a rolling reduction of 80% or more, if necessary, performing one or more cold rollings with intermediate annealing, followed by decarburizing annealing and final finishing. It is manufactured by sequentially performing annealing.

The inventors of the present invention have made detailed studies on measures for improving magnetic properties when a low-temperature slab heating material is manufactured and the conditions for equipping a product that simultaneously achieves high magnetic flux density and low iron loss.

As a measure for this, Cu, Mn are contained, the product of the Cu amount and the Mn amount is controlled, and the relationship between the average value of the secondary recrystallized grain size of the product and the magnetic flux density B ₈ is controlled to a predetermined condition. Then, the iron loss difference before and after the film removal is set to a predetermined range, and the Cu content is precisely controlled to a predetermined range.
Was found to be effective. It was also possible to clarify the necessary conditions for manufacturing this characteristic product.

The present invention will be described in detail below based on the experimental results. % By weight, C = 0.052%, Si = 3.50
%, Acid-soluble Al = 0.020 to 0.041%, N =
0.0076%, S = 0.010%, Mn = 0.06-
0.57%, Cu = 0 to 0.63%, balance Fe
A slab having a thickness of 250 mm composed of unavoidable impurities was prepared. Then, after soaking at 1120 ° C. for 60 minutes, rough hot rolling for 5 passes and finish hot rolling for 6 passes were performed to obtain a hot rolled sheet having a thickness of 2.3 mm. At this time, the finish hot rolling temperature was 837 to 1040 ° C.

The hot-rolled sheet was annealed at 1100 ° C. for 30 seconds, then at 900 ° C. for 30 seconds, and then rapidly cooled. Then, strong reduction rolling was performed at a reduction rate of about 90% to obtain a cold rolled sheet having a final sheet thickness of 0.22 mm. The cold-rolled sheet decarburization annealing for 90 seconds held at eight hundred and ten to eight hundred and sixty ° C. The (N _2: 2
5%, H ₂ : 75%, D.I. P. = 40 to 71 ° C.), and then, at the time of annealing for holding at 750 ° C. for 30 seconds, NH ₃ gas was mixed into the annealing atmosphere to cause the steel sheet to absorb nitrogen. The amount of N after this nitriding treatment is 0.0161 to 0.02.
It was 37% by weight. The average primary recrystallization grain size of these nitride plates was 19 to 27 μm.

An annealing separator containing MgO as a main component was applied to the steel sheet after the nitriding treatment, and final finishing annealing was performed. In this final finish annealing, the temperature was raised to 1200 ° C. at 15 ° C./hour in an atmosphere of N ₂ : 50% and H ₂ : 50%, and then,
H ₂ : Performed in a 100% annealing atmosphere for 20 hours. After that, annealing was performed to combine tension coating and shape correction. Fig. 1 shows the relationship between product preparation conditions and iron loss.
Shown in

As is clear from FIG. 1, 0.005 ≦ C
u (%) × Mn (%) ≦ 0.15 and W _M −W _P ≧
The condition of 0.08 (w / kg) is iron loss of the product W _13/50 (w / k
It has been found that this is a necessary condition for obtaining good characteristics of g) ≦ 0.40. The result of examining this finding in more detail is shown in FIG.

FIG. 2 shows that in FIG. 1, W _13/50 (w / kg)
This is a necessary condition for obtaining ≦ 0.40. 0.005 ≦ Cu
(%) × Mn (%) ≦ 0.15 and W _M −W _P ≧ 0.
About 08 (w / kg) as a sample case made, in relation to the average value of the secondary recrystallized grain size of the product d as (mm) and the magnetic flux density _{B 8 (T), W 13/50} ≦ 0.40w / This is the result of examining sufficient conditions for realizing kg. In this case, the grains that penetrated the plate thickness of the product were determined as secondary recrystallized grains, and the grain size was measured as the equivalent circle diameter for the two-dimensional grains on the plate surface.

As is apparent from FIG. 2, B ₈ ≧ 1.88
When T and 1.0 ≦ d ≦ 23 × B ₈ −40 are satisfied, W
_13/50 ≦ 0.40 W / kg good magnetic properties comprising were obtained.
Although the mechanism of the phenomenon shown in FIGS. 1 and 2 is not always clear, the present inventors presume as follows.

The present invention is premised on containing Cu and Mn. Cu is an element that concentrates on the surface,
Suppresses oxidation during decarburization annealing and final finish annealing. On the other hand, Mn tends to oxidize and tends to accelerate oxidation. On the other hand, in the case of the product of the present invention, in the slab, S, Se
Will be included to some extent.

S and Se combine with Cu and Mn to form Cu
-S, Cu-Se, MnS, MnSe are formed. Cu
Compared with -S and Cu-Se, MnS and MnSe are more stable compounds, and when the temperature is raised for a long time in the final finish annealing (BOX annealing), Cu-S → MnS, Cu-Se. → Substitution of MnSe occurs. Therefore, the temperature of the final finish annealing temperature increase process of 80
It is considered that due to the increase in the amount of Cu solid solution generated in the temperature range of 0 to 1000 ° C., Cu partially diffuses to the surface portion in the temperature range.

On the other hand, SiO ₂ in the surface oxide layer and the internal oxide layer formed during decarburization annealing and MgO which is the main component of the annealing separating agent are contained in the final finish annealing (800 to 110).
(0 ° C.) to form Mg ₂ SiO ₄ . This Mg
_{2 The} SiO ₄ formation reaction, the substitution phenomenon of Cu—S → MnS and Cu—Se → MnSe, the diffusion of Cu surface and the suppression of oxidation occur almost in parallel. Therefore, the amounts of Mn and Cu are Mg ₂ SiO
_{4 It} is thought to affect the formation reaction.

Although the details of the process are not always clear, it was observed that the surface condition after the final finish annealing was changed due to the influence on the Mg ₂ SiO ₄ forming reaction. The surface condition of a steel sheet affects magnetic properties, especially iron loss properties.

In the case of the material of the present invention, the eddy current loss was drastically reduced, and the magnetic domains were also subdivided. Therefore, it is considered that a film having a magnetic domain subdivision effect was formed. As an example,
Sample comrade thickness 9mil of B ₈ = 1.935T, in the present invention, W _13/50 = of 0.38 W / kg, eddy current loss 0.21 W / kg, hysteresis loss 0.17 W / In contrast to W 13/50 = 0.47 w / kg, the eddy current loss is 0.3 when the condition of the present invention is not satisfied (comparative material) _.
It was 2 w / kg and the hysteresis loss was 0.15 w / kg.

In the case of the material of the present invention, the eddy current loss is 3 compared with the comparative material.
It is about 5% lower and the hysteresis loss is about 10% higher. This result suggests that in the case of the material of the present invention, a coating having a magnetic domain subdivision (eddy current loss reduction) effect is formed.

In the case of the present invention, the hysteresis loss tends to be slightly deteriorated in relation to the film properties. In addition, the iron loss advantage of the present invention disappears when the coating is removed. FIG. 1 is considered to be a phenomenon caused by the characteristics of the coating film of the present invention material. On the other hand, FIG. 2 shows that there is a necessary condition range in the relationship between the magnetic flux density and the secondary recrystallized grain size.

It is well known that the magnetic flux density is increased as a means for improving the iron loss characteristics, but normally, when the magnetic flux density is increased, the secondary recrystallized grain size becomes large and the eddy current loss deteriorates. Therefore, it is difficult to obtain good iron loss characteristics.

In the case of the present invention, since a film having a magnetic domain refining effect is formed, good iron loss characteristics are easily obtained even if the magnetic flux density is high, but if the secondary recrystallized grain size is too large. It becomes difficult to secure iron loss characteristics.

The upper limit of the secondary recrystallized grain size in FIG. 2 is considered to be due to the above reason. The reason for the lower limit of the secondary recrystallized grain size for obtaining good iron loss is presumed as follows. When the average grain size of the secondary recrystallized grains is less than 1.0 mm, the destabilization phenomenon of the secondary recrystallization occurs, and the crystal structure becomes a mixture of many grains of 1.0 mm or less. ing. In this case, it is difficult to maintain the magnetic flux density at a high level, and it is difficult to exert the magnetic domain subdivision effect as in the present invention.

The present inventors have 1, result different and samples of process conditions showing in FIG. 2, as a result of extensive research the characteristics of the intermediate product, W _13/50 ≦ 0.40w / kg become better The following were confirmed as conditions for obtaining good magnetic properties. Regarding the Cu content (Cu (%)) and Mn content (Mn (%)) of the slab, the relationship 0.005 ≤ Cu (%) x Mn (%) ≤ 0.15 (A) holds, and The total amount of SiO ₂ in the surface oxide film of the steel sheet after completion of decarburization annealing and nitriding treatment (SIO2 (g /
m ² )) and the above Cu content, the relationship of 0.8-0.6 × Cu (%) ≤ SIO2 ≤ 1.8-0.6 × Cu (%) (B) is established, and after the decarburization annealing and the nitriding treatment are completed, 16 × Cu (%) + 14 ≦ D ≦ 16 × Cu (%) + 27 ……………… (C) between the average grain size (D (μm)) of the primary recrystallized steel sheet and the above Cu content He found that the following relationship was established.

(A), (B) and (C) are W _13/50 ≦ 0.
Although the reason for the requirement of being 40 w / kg is not always clear, the present inventors presume as follows.

Regarding the condition (A), if this is satisfied,
A necessary condition as a product for obtaining a W _13/50 ≦ 0.40w / kg in Fig. 1 Cu (%) and includes conditions related to Mn (%) is considered to be because the easily satisfied.

Regarding the existence of the lower limit value of SiO ₂ in the condition (B), Mg ₂ SiO ₄ at the time of the temperature of the final annealing is raised.
The following mechanism can be considered in relation to the formation reaction. The product of the invention is characterized by the coating of the product. Conditions of the lower limit of (B), the more Cu amount is large, it indicates that the lower limit of the SiO ₂ amount of steel required for the Mg ₂ SiO ₄ formation is low, the amount and the Cu content of Mg ₂ SiO ₄ is It is considered that they are in a mutually complementary relationship.

This mechanism is based on Cu against eddy current loss.
It can be understood from the influence of the amount and the amount of Mg ₂ SiO ₄ . That is,
When the amount of Mg ₂ SiO _{4 in} the product is small, the film tension tends to decrease and the eddy current loss tends to increase. On the other hand, when the amount of Cu was increased, it was observed that the eddy current loss tended to decrease even if the amount of Mg ₂ SiO _{4 in the} coating was the same.

That is, the condition of the lower limit value of (B) is considered to be a necessary condition for reducing the eddy current loss. Therefore,
It is considered that the condition of the lower limit value of (B) is a necessary condition for realizing the condition W _M −W _P ≧ 0.08 (w / kg) that the product shown in FIG. 1 has.

On the other hand, the existence of the upper limit value of (B) is considered as follows from the relationship with the oxidation behavior of Al at the time of final finish annealing temperature rise. The main inhibitor for secondary recrystallization in the present invention is AlN, and the larger the amount of SiO _{2 in} the surface oxide film, the easier the decomposition of AlN due to the oxidation of Al near the surface.

In other words, the greater the amount of SiO ₂ , the more Al
Decomposition of N is likely to occur. On the other hand, the higher the amount of Cu, the more A
Since the size of 1N becomes smaller and it becomes easier to disassemble,
The existence of the upper limit value of the condition (B) is a regulation to prevent excessive decomposition of AlN. Therefore, by complying with the upper limit of the condition (B), it is possible to realize the proper range of B ₈ and d which is the condition of the product shown in FIG.

Regarding the condition (C), the following mechanism can be considered from the relationship with the appropriate value of the secondary recrystallization temperature. When the amount of Cu in the slab is increased, the sulfide composition becomes Cu.
It was observed that the size tended to decrease with increasing amount. Since AlN, (Al, Si) N precipitates with this Cu-rich sulfide as a nucleus at the time of final finish annealing temperature rise, the larger the amount of Cu, the smaller the size of the precipitate at the time of final finish annealing temperature rise. It was

It was observed that the smaller the size, the more easily the precipitate decomposes, so that the larger the amount of Cu, the lower the secondary recrystallization starting temperature tends to be.

Originally, secondary recrystallization is considered to be a phenomenon resulting from the grain boundary character dependence of grain boundary movement, and {110} <00
1) In the case of secondary recrystallization of oriented grains, the degree of integration of {110} <001> orientation occurs when secondary recrystallization occurs in a temperature range where the difference in grain boundary migration speed between general grain boundaries and Σ9 grain boundaries is large. Is considered to be high.

When the amount of Cu is increased, the temperature at which the secondary recrystallization occurs decreases, so it is necessary to take measures to keep the secondary recrystallization temperature within an appropriate range.

As shown in (C), increasing the primary recrystallized grain size according to the amount of Cu and lowering the driving force for the grain growth of the secondary recrystallized grain can increase the secondary recrystallized temperature appropriately. It is effective to keep the range, and as a result, when the condition (C) is satisfied, it becomes possible to satisfy the condition B ₈ ≧ 1.88T of the product in FIG.

Further, if the condition (C) is satisfied, the secondary recrystallization temperature and the advancing speed can be controlled, so that the condition for the secondary recrystallization grain size of the product in FIG. 2 can be satisfied. .

Next, the reasons for limiting the constituent features of the present invention will be described. First, the reasons for limiting the components of the slab will be described. C is 0.025% by weight (hereinafter simply referred to as%)
If it is less than the above value, the secondary recrystallization becomes unstable, and even if the secondary recrystallization is performed, it is difficult to obtain B ₈ > 1.80 (T), so the content is limited to 0.025% or more. On the other hand, if the amount of C is too large, the decarburization annealing time becomes long and it is not economical, so 0.07
It was defined as 5% or less.

If Si exceeds 5.0%, cracking during cold rolling becomes significant, so the content was made 5.0% or less. On the other hand, if it is less than 2.5%, the specific resistance of the material is too low, and a low iron loss required as a transformer core material cannot be obtained. It is preferably 3.2% or more.

Al is AlN necessary for stabilizing the secondary recrystallization.
Alternatively, to secure (Al, Si) N, acid-soluble A
It is necessary to set l to 0.010% or more. If the acid-soluble Al exceeds 0.060%, the AlN of the hot-rolled sheet becomes unsuitable and the secondary recrystallization becomes unstable, so it is necessary to set it to 0.060% or less.

N is preferably 0.0010 to 0.0130%. Within this range, it becomes possible to achieve both the control of primary recrystallized grain size, which will be described later, and the securing of a free Al amount during nitriding. In addition, N is 0.013
If it exceeds 0%, blisters called blister are generated on the steel sheet, which is not preferable.

The range of S + 0.405Se is 0.005.
It was defined as ~ 0.020%. If it is less than 0.005%, Cu-S (or Cu-Se), which is the essence of the present invention, is changed to Mn.
The substitution phenomenon of S (or MnSe) in the final finishing annealing temperature rising process hardly occurs, which is not preferable. On the other hand, if it exceeds 0.020%, a secondary recrystallization failure phenomenon occurs in rows in the rolling direction, which is not preferable.

The range of Mn content and Cu content is 0.06 to
It is necessary to set it to 0.8% and 0.01 to 0.50%. Higher magnetic flux density can be achieved by setting these ranges. The Cu content of 0.20 to 0.40% is more preferable for increasing the magnetic flux density.

The range of Sn is more preferably 0.01 to 0.15%. Sn has the effect of increasing the {110} <001> oriented grains in the primary recrystallization texture and, as a result, reducing the secondary recrystallized grain size and the effect of making the precipitation of sulfide uniform. is there. Therefore, the effect of controlling sulfide precipitation as in the present invention is further enhanced. If the amount of Sn is less than 0.01%, the above effect is insufficient, and if it exceeds 0.15%, nitriding of the steel sheet becomes difficult, which causes secondary recrystallization failure, which is not preferable.
Sb, which is also known as an inhibitor constituent element,
There is no problem in containing a minute amount of Cr, Ni, B, Ti, Nb or the like.

The slab heating temperature was limited to less than 1280 ° C. for the purpose of cost reduction in the same manner as ordinary steel. It is preferably 1200 ° C or lower. The heated slab is subsequently hot rolled to form a hot rolled plate.

This hot rolling consists of rough rolling which is carried out at a low speed in reverse or tandem, and high speed finish hot rolling which is carried out in a tandem. Although not particularly limited, it is preferable that the temperature of the hot rolling for finishing is 700 to 1100 ° C.
This is because by performing finish hot rolling within this temperature range, precipitation of Cu—S with dislocations introduced by hot rolling as nuclei is likely to occur, and a fine precipitation dispersed phase of Cu—S is easily obtained.

The hot-rolled sheet is then cold-rolled once or twice or more with intermediate annealing. At this time, the final cold rolling reduction is 80% or more. Final cold rolling reduction of 80%
The reason for the above is that by setting the reduction ratio in the above range, sharp {110} <001> oriented grains in the decarburized plate and corresponding oriented grains ({111} <1
12> oriented grains) can be obtained in an appropriate amount, which is preferable for increasing the magnetic flux density.

Although not particularly limited, it is more preferable to perform hot-rolled sheet annealing at 800 to 1200 ° C. after the hot rolling, if necessary, in order to stabilize the magnetic properties at a high level. The heat treatment in this temperature range is effective for AlN, MnS,
It is effective in reducing the spatial non-uniformity of the hot rolled sheet such as Cu-S.

The steel sheet after the final cold rolling is subjected to decarburizing annealing, applying an annealing separating agent, and finally finishing annealing to obtain a final product. Here, it is necessary to control the average grain size (D) of the primary recrystallized grains to 18 to 35 μm after the completion of decarburization annealing and before the start of final finish annealing.

The reason is that a good magnetic flux density is easily obtained within the range of the average particle diameter, and the change of the magnetic flux density due to the particle diameter variation is small. Furthermore, it is necessary to satisfy the relationship of 16 × Cu (%) + 14 ≦ D ≦ 16 × Cu (%) + 27 between the D (μm) and the Cu content of the slab.

The reason for this is that by satisfying the above relationship, in the product, the formation of secondary recrystallized textures highly integrated in the {110} <001> orientation and the generation of a large number of secondary recrystallized grains are achieved at the same time. it can. Thus in order to obtain a W _13/50 ≦ 0.40w / kg good magnetic properties comprising, it Mitsurusu the relationship is essential.

The means for controlling the primary recrystallized grain size is not particularly limited. It is effective to control the slab heating temperature, heat history of hot rolling, hot rolled sheet annealing conditions, and decarburization annealing conditions. Cu
When the amount is increased and the process treatment is performed under the same conditions, the primary recrystallized grain size tends to be small. Therefore, in order to increase the primary recrystallized grain size according to the Cu amount, it is necessary to change the process condition. There is.

The relationship between the total amount of SiO ₂ (SIO ₂ (g / m ² )) in the surface oxide film of the steel sheet after decarburization annealing and the amount of Cu (Cu (%)) in the slab is 0.8-0. 6 × Cu (%) ≦ SIO2 ≦ 1.8-0.
It is necessary to set 6 × Cu (%). The provisions of the lower limit of the SIO2 is the condition that Mitsurusu, provided the conditions of the product in Fig. 1 W _M -W
_This is because it is necessary to satisfy _P ≧ 0.08.

The upper limit value of SIO2 must satisfy this condition if the condition B ₈ ≧ 1.88 of the product in FIG. 2 is satisfied.
This is because it is necessary to satisfy T. The means for satisfying the above conditions is not particularly limited. Temperature during decarburization annealing,
The above relationship can be satisfied by controlling the dew point.

Oxidation behavior is affected by the elements added to the steel and their amounts. Therefore, in order to satisfy the above relationship, it is necessary to set the conditions according to the material. Since Sn and Cu are elements that suppress oxidation, special attention is required.

The dew point, atmosphere gas and heat cycle during decarburization annealing are not particularly limited. The dew point is 30 to 8
At 0 ° C., a mixed gas of N ₂ and H ₂ is usually used as the atmosphere gas. About heat cycle, 800 ~ 900 ℃
Until the steel plate is heated. It is preferable to control the dew point, the atmospheric gas, and the heat cycle according to Mn, Cu, etc. in order to realize the effects of the present invention as shown in FIGS.

When low-temperature slab heating below 1280 ° C. is performed, the inhibitor strength required for secondary recrystallization tends to be insufficient, so it is necessary to perform nitriding treatment after hot rolling and before the start of secondary recrystallization in final annealing. There is. Further, the nitriding method is not particularly limited, and a method of nitriding by mixing NH ₃ gas in an annealing atmosphere after decarburization annealing, a method of using plasma, a nitride is added to an annealing separator and a final finishing annealing is performed. Any method such as a method of absorbing nitrogen generated by decomposition of nitride during temperature rise into a steel sheet, a method of increasing the N ₂ partial pressure in the atmosphere of final annealing and nitriding the steel sheet may be used.

The amount of nitriding is 0.0010 as the amount of nitrogen increase.
It must be at least%. If it is less than 0.0010%, Si or M in the final finishing annealing temperature rising process which is the essence of the present invention is used.
AlN or (Al, Si) from n-rich nitrides
It is not preferable because the phenomenon of substitution with N does not occur sufficiently. The upper limit of the amount of nitrogen increase is not particularly specified, but in order to suppress the defects of the forsterite coating to be small, it is 0.1000.
% Or less is preferable.

Further, although not particularly limited, the temperature between 800 and 1000 ° C. during the final finish annealing temperature increase is 100 ° C.
It is preferable to heat at a heating rate of not more than / hour. This is because, in the temperature range of 800 to 1000 ° C., the substitution of Cu—S with MnS and the nitride containing a large amount of Si or Mn give A.
This is because substitution with 1N or (Al, Si) N occurs, and it is preferable to secure a time for these phenomena to sufficiently occur.

The atmosphere for the final finish annealing is not particularly limited, but from the viewpoint of securing the oxidation potential, it is preferable to perform the annealing in an atmosphere containing N ₂ gas.

After the final finish annealing, annealing is performed for both shape correction and tension coating. This annealing was performed on the steel plate at 80
The heating is performed at 0 to 900 ° C., and a coating containing phosphoric acid or the like is also applied.

The reasons for limiting the conditions for equipping the product, which is a feature of the present invention, will be described. Si needs to be contained in 2.5 to 5.0%. If it exceeds 5.0%, cracking may occur during product processing, which is not preferable. If it is less than 2.5%, the specific resistance is too low and a low iron loss cannot be obtained. Desirably, it is 3.2% or more.

Cu was set to 0.05 to 0.50%. C
By setting the amount of u in this range, the effect of the present invention shown in FIG. 1 can be easily obtained. Further, the Cu content is 0.20 to 0.
The content of 40% is more preferable because the magnetic flux density is improved. About Mn, it was 0.06-0.8%. With respect to the amount of Mn as well, the effect of the present invention shown in FIG. 1 can be easily obtained by setting it in this range.

Cu (%) × Mn (%) amount and W _M −W _P
As shown in FIG. 1, the values of 0.005 to 0.005
It should be 0.15, 0.08 or more. Good iron loss characteristics can be obtained by controlling within this range of values.

The magnetic flux density B ₈ (T) and the average value d (mm) of the secondary recrystallized grain size of the product are respectively B as shown in FIG.
₈ (T) ≧ 1.88, 1.0 ≦ d ≦ 23 × B ₈ -40. Good iron loss characteristics can be obtained by controlling within this range of values. Regarding the Sn amount,
It is more preferable to set it to 0.01 to 0.15%. By setting the range of this value, it is easy to obtain high magnetic flux density and low iron loss.

[0079]

【Example】

[Example 1] C: 0.056% (% is weight%, the same applies hereinafter), Si: 3.40%, Mn: 0.11%, S: 0.
010%, acid-soluble Al: 0.030%, N: 0.00
85% as a basic component, Cu content <0.001%,
Three kinds of slabs having a thickness of 250 mm were added at three levels of 0.15% and 0.35%. At this time, Cu
The value of (%) × Mn (%) is <0.0001, respectively.
It was 1, 0.0165 and 0.0385.

After soaking the slab at 1150 ° C. for 60 minutes, hot rolling was immediately started, and after 5 passes of rough hot rolling to 40 mm thickness, 6 passes of finish hot rolling to 2.3 mm thick hot rolling. It was a plate.

The hot-rolled sheet was annealed at 1050 ° C. for 3 minutes, then 0.285 at a rolling reduction of about 88%.
A cold-rolled sheet having a thickness of mm was subjected to decarburization annealing at 845 ° C. for 150 seconds.

The annealing atmosphere during this decarburization annealing is (a)
N ₂ : 25%, H ₂ : 75%, dew point 62 ° C, (b)
N ₂ : 25%, H ₂ : 75%, dew point 40 ° C, (c)
Three conditions of N ₂ : 10%, H ₂ : 90%, and dew point 30 ° C. were set. After that, annealing is performed at 750 ° C. for 30 seconds,
NH ₃ gas was mixed into the annealing atmosphere to allow the steel sheet to absorb nitrogen. The N content of this steel sheet after nitriding is 0.0193-
It was 0.0231%.

Next, this steel sheet was mainly composed of MgO,
An annealing separator containing 0.3% and 5% of Na ₂ B ₄ O ₇ and TiO ₂ was applied, and N ₂ : 25%, H ₂ : 75%
In an atmosphere gas of 10 ° C./hour to 1200 ° C., and then H ₂ : 100% in an atmosphere gas of 1200.
Final finishing annealing was carried out at 20 ° C. for 20 hours. After that, annealing was carried out for both tension coating and shape correction. Table 1 shows the results of the experimental conditions, product characteristic amounts, and magnetic characteristics.

[0084]

[Table 1]

Example 2 C: 0.049%, Si:
3.39%, S: 0.008%, Cu: 0.27%,
N: 0.0020% and acid-soluble Al: 0.0029% are the basic components, Mn is added at two levels of 0.14% and 0.65%, and the balance is Fe and inevitable impurities. A variety of 250 mm thick slabs were created. At this time, the value of Cu (%) × Mn (%) is 0.037 each.
It was 8, 0.1755. 1120 this slab
After soaking at 60 ° C for 60 minutes, hot rolling is immediately started, and after 5 passes of rough hot rolling to a thickness of 40 mm, 6 passes of finishing hot rolling to 2.3.
A hot-rolled sheet having a thickness of mm was used.

The hot rolled sheet was kept at 1100 ° C. for 30 seconds,
Successively, hot-rolled sheet annealing was carried out by holding the material at 900 ° C. for 30 seconds and then rapidly cooling it. Next, a 0.220 mm cold-rolled sheet with a reduction rate of about 90% was subjected to decarburization annealing at 840 ° C. for 90 seconds. The annealing atmosphere during this decarburization annealing is (a) N ₂ : 25
%, H ₂ : 75%, dew point 60 ° C., (b) N ₂ : 75%,
H ₂ : 25% and dew point 75 ° C. under two conditions.

After that, annealing was carried out at 770 ° C. for 30 seconds, and NH ₃ gas was mixed during the annealing to make the steel sheet absorb nitrogen. The N content of this steel sheet after nitriding is 0.0195.
It was -0.0228%.

Next, this steel sheet was mainly composed of MgO,
An annealing separator containing 3% of TiO ₂ was applied and N ₂ : 5 was added.
Final finishing annealing was carried out by raising the temperature to 1200 ° C. at a rate of 25 ° C./hour in an atmosphere gas of 0% and H ₂ : 50%, and then maintaining the temperature in the atmosphere gas of H ₂ : 100% at 1200 ° C. for 20 hours. . After that, annealing was carried out for both tension coating and shape correction. Table 2 shows the relationship among the experimental conditions, the product characteristic amount, and the magnetic characteristics.

[0089]

[Table 2]

[Example 3] C: 0.040%, Si:
3.10%, Mn: 0.10%, S: 0.010%, C
u: 0.11%, acid-soluble Al: 0.032%, N:
0.0058% was added to form a 250 mm thick slab consisting of the balance Fe and unavoidable impurities. At this time, Cu
The value of (%) × Mn (%) was 0.011. After soaking the slab at 1100 ° C. for 60 minutes, hot rolling was immediately started, and after 5 passes of rough hot rolling to 40 mm thickness, 6 passes of finish hot rolling to 2.3 mm thick hot rolled sheet .

Then, the hot-rolled sheet was pickled to form a cold-rolled sheet of 0.335 mm with a reduction rate of about 85% and subjected to decarburization annealing at 840 ° C. for 150 seconds. The annealing atmosphere during this decarburization annealing is N ₂ : 50%, H ₂ : 50%, dew point 50 ° C., N
_{2: 50%, H 2:} 50%, has a two conditions that dew point 70 ° C.. After that, annealing is performed at 750 ° C. for 30 seconds,
NH ₃ gas was mixed into the annealing atmosphere to cause the steel sheet to absorb nitrogen. The N content of this steel sheet after nitriding is 0.0226%
Met. The average grain size of this steel sheet is 21 μm.
Met.

Then, an annealing separator containing MgO as a main component was applied to this steel sheet, and (a) N ₂ : 50%, H ₂ : 50.
%, (B) N ₂ : 10%, H ₂ : 90% in two levels of atmospheric gas, the temperature is raised to 1200 ° C. at a rate of 15 ° C./hour, and then H ₂ : 100% in atmospheric gas at 1200 ° C.
Final annealing was carried out for 20 hours. After a while
Annealing was performed for both tension coating and shape correction. Table 3 shows the relationship among the experimental conditions, the product characteristic amount, and the magnetic characteristics.

[0093]

[Table 3]

[0094]

According to the present invention, in the state of the product, S
i, Cu, Mn contents are controlled, the product of Cu amount and Mn amount is controlled, the magnetic flux density and the average value of the secondary recrystallized grain size of the product are controlled, and further, the product and the iron after film removal By controlling the loss difference, more preferably, the amount of Cu is violently controlled, and by containing a predetermined amount of Sn, it is possible to provide a grain-oriented electrical steel sheet having good magnetic properties. Therefore, its industrial significance is extremely high. Is large.

Further, in the method for producing this characteristic product, Cu is added to control the product of the amount of Cu and the amount of Mn, and depending on the amount of Cu in the slab, after completion of decarburization annealing until the start of final finishing annealing. Controlling the average grain size of the primary recrystallized grains, S of the steel sheet after decarburization annealing depending on the Cu content of the slab
Controlling the amount of iO ₂ , performing a predetermined amount of nitriding treatment on the steel sheet after the hot rolling and before the start of secondary recrystallization in the final finish annealing, and more preferably, by controlling the amount of Cu in the slab vigorously to a predetermined amount. Good magnetic characteristics can be stably obtained by adding the Sn amount, so that the industrial effect thereof is extremely large.

[Brief description of drawings]

[Fig. 1] Cu (%) × Mn (%) of the product, and the iron loss W _13/50 (W _M ) of the product after removing the film and the product iron loss W _13/50
It is a graph showing the relationship between the difference with (W _P ) and the iron loss characteristics of the product.

FIG. 2 is a graph showing the relationship between the magnetic flux density (B ₈ ) of the product, the average grain size (d) of the secondary recrystallized grains of the product, and the iron loss characteristics of the product.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nao Mogi 1-1 No. 1 Tobata-cho, Tobata-ku, Kitakyushu City Inside Nippon Steel Yawata Works (72) Inventor Osamu Tanaka 46-59 Nakahara, Tobata-ku, Kitakyushu City Nittetsu Plant Design Co., Ltd. (72) Inventor Katsuro Kuroki 46-59 Nakahara, Tobata-ku, Kitakyushu City Nittetsu Plant Design Co., Ltd.

Claims (7)

[Claims] 1. By weight%, Si: 2.5-5.0%, C
u: 0.05 to 0.50%, Mn: 0.06 to 0.8
%, The balance is Fe and unavoidable impurities in the grain-oriented electrical steel sheet, which satisfies 0.005 ≦ Cu (%) × Mn (%) ≦ 0.15 and B ₈ (T) ≧ 1.88. And the average value d (mm) of the secondary recrystallized grain size of the product satisfies 1.0 ≦ d ≦ 23 × B ₈ −40, and the iron loss W _{13 / 50} (w / k
g) is W _P and W _M , respectively, W _M −W _P ≧ 0.08. A unidirectional electrical steel sheet having excellent magnetic properties and coating properties. 2. Cu: 0.20 to 0.40% by weight
The grain-oriented electrical steel sheet according to claim 1, which is excellent in magnetic properties and coating properties. 3. Sn: 0.01 to 0.15% by weight
A grain-oriented electrical steel sheet according to claim 1 or 2, which is excellent in magnetic properties and coating properties. 4. C: 0.025 to 0.07 in% by weight.
5%, Si: 2.5 to 5.0%, acid-soluble Al: 0.0
10 to 0.060%, N: 0.0010 to 0.013
0%, S + 0.405Se: 0.005-0.020
%, Mn: 0.06 to 0.8%, Cu: 0.01 to 0.
A slab consisting of 50%, the balance being Fe and unavoidable impurities, is heated at a temperature of less than 1280 ° C., hot-rolled, subsequently hot-rolled sheet annealed, and then finally cold-rolled with a rolling reduction of 80% or more, and an intermediate annealing. In the method for producing a grain-oriented electrical steel sheet by performing cold rolling one or more times after sandwiching, followed by decarburizing annealing and final finishing annealing, the Cu and Mn contents (% by weight) of the slab are set as follows (1). The average grain size of the primary recrystallized grains (D
(Μm)) is set to 18 to 35 μm, and the Cu content of the slab and D
In the range of the following formula (2), and the total amount of SiO ₂ in the surface oxide film of the steel sheet after decarburization annealing (SIO2 (g /
m ² )) and the Cu content (Cu (%)) of the slab are given in (3) below.
It is controlled within the range of the formula, and the steel sheet is subjected to a nitriding treatment of 0.0010% or more with a nitrogen increase amount before the secondary recrystallization of the final finish annealing after the hot rolling. An excellent method for producing grain-oriented electrical steel sheets. 0.005 ≤ Cu (%) x Mn (%) ≤ 0.15 ………… (1) 16 x Cu (%) + 14 ≤ D ≤ 16 x Cu (%) +27 ………… (2) 0.8 -0.6 × Cu (%) ≦ SIO2 ≦ 1.8 −0.6 × Cu (%) (3) 5. C: 0.025 to 0.07 in% by weight.
5%, Si: 2.5 to 5.0%, acid-soluble Al: 0.0
10 to 0.060%, N: 0.0010 to 0.013
0%, S + 0.405Se: 0.005-0.020
%, Mn: 0.06 to 0.8%, Cu: 0.01 to 0.
Slab consisting of 50% and the balance Fe and unavoidable impurities 128
Heating at a temperature of less than 0 ° C., hot rolling, followed by no hot-rolled sheet annealing, and then final cold rolling with a rolling reduction of 80% or more,
In the method of producing a grain-oriented electrical steel sheet by performing cold rolling one or more times with intermediate annealing, followed by decarburizing annealing and final finishing annealing, the content of Cu and Mn in the slab (% by weight)
Is controlled within the range of the following formula (1), and the average grain size of primary recrystallized grains (D (μ
m)) is 18 to 35 μm, the Cu amount and D of the slab are controlled within the range of the following formula (2), and the total amount of SiO ₂ (SIO2 (g / g) in the surface oxide film of the steel sheet after decarburization annealing is controlled. m ² ))
The Cu content (Cu (%)) of the slab and the slab is controlled within the range of the following formula (3), and the amount of nitrogen added to the steel sheet is 0.0010% or more after hot rolling and before the start of secondary recrystallization in final annealing. A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties and coating properties, which is characterized by performing nitriding treatment of. 0.005 ≤ Cu (%) x Mn (%) ≤ 0.15 ………… (1) 16 x Cu (%) + 14 ≤ D ≤ 16 x Cu (%) + 27 ………… (2) 0.8- 0.6 × Cu (%) ≦ SIO2 ≦ 1.8 −0.6 × Cu (%) (3) 6. A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties and coating properties according to claim 4, wherein a slab containing Cu: 0.20 to 0.40 wt% is used. . 7. A unidirectional electrical steel sheet having excellent magnetic properties and coating properties according to claim 4, 5 or 6, wherein a slab containing Sn: 0.01 to 0.15 wt% is used. Manufacturing method.