JPH11293339A - Manufacture of unidirectional magnetic steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and stably improve the magnetic characteristic at a low cost by controlling the hot-rolling of a slab of a specified composition consisting of C, Si, Mn, Al, N, S, Se and Fe the annealing of a hot-rolled sheet to realize a specified thickness and a specified grain size of W17/50, B8 (T). SOLUTION: A slab having the composition consisting of, by weight, 0.02-0.15% C, 2.5-4.0% Si, 0.02-0.20% Mn, 0.015-0.065 Sol. Al, 0.0030-0.0150% N, 0.005-0.040% one or more kinds of S and Se, and 0.003-0.3% one or more kinds of Sb, Sn, Cu, Mo and B as necessary, and the balance substantially Fe, is heated to 1320-1490 deg.C with the heating speed of 5 deg.C/second from 1200 deg.C, and hot-rolled. After the hot-rolled sheet is annealed at 900-1100 deg.C, the cold- rolling, decarburizing annealing, the final finish-annealing and the final finish- coating are executed. A unidirectional magnetic steel plate of 0.20-0.55 mm in product thickness, 1.5-5.5 mm in mean grain size, and to satisfy the inequalities of 0.5884l<1.9154> X<t> <=W17/50 (W/kg)<=0.7558e, 1.80<=B8(T)<=1.88 (where, (t) is the thickness mm) can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet used for an iron core such as a transformer.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used for core materials of transformers and generators. The grain-oriented electrical steel sheet uses {110} by secondary recrystallization in the finish annealing in the manufacturing process.
A low iron loss is obtained as a structure highly integrated in the <001> direction, the so-called Goss direction. In order to stably express secondary recrystallization, it is important to control the tissue, texture, and inhibitor. As for the inhibitor, it is necessary that a precipitate-dispersed phase of about 100 to 1000 angstroms is uniformly and finely present in the steel before the finish annealing is performed, and AlN, MnS, MnSe and the like are generally known. Since these are coarsely precipitated in continuous casting, the slab is heated to a high temperature of 1250 ° C. or more to sufficiently form a solution, and then MnS and MnSe are uniformly and finely precipitated by hot rolling, and AlN is formed by hot rolling sheet annealing. It is important to uniformly and finely precipitate Sb, Sn, Cu, Mo, B, and the like of grain boundary segregating elements at crystal grain boundaries from hot rolling to decarburizing annealing.

[0003] As a typical method for producing a grain-oriented electrical steel sheet, US Pat. No. 1,965,559 and US Pat.
No. 51 and U.S. Pat. No. 2,599,340, and the like, using MnS as an inhibitor,
It is characterized by performing a plurality of cold rollings including an intermediate annealing and a plurality of annealings. However, these methods involve many steps,
Rising production costs were inevitable.

[0004]

However, the above-mentioned prior art has not been satisfactory in terms of cost reduction and improvement in productivity. In addition, when the slab was heated to a high temperature, the slab grew abnormally, and the structure of the hot-rolled sheet became non-uniform, and the magnetic properties were likely to vary or deteriorate.

[0005] The present invention solves such a problem in the production of a grain-oriented electrical steel sheet by drastically combining combinations of components including Si content, sheet thickness, product average crystal grain size, and crystal orientation. The slab heating rate, the slab heating temperature, and fine control such as applying hot deformation to the slab to be subjected to high-temperature heating are performed, and the manufacturing process is simplified to reduce costs and increase productivity. An object of the present invention is to provide a method for producing a grain-oriented electrical steel sheet having a magnetic property equal to or higher than the conventional one and having little variation.

[0006]

The gist of the present invention is as follows. (1) By weight%, C: 0.02 to 0.15%, Si: 2.
5 to 4.0%, Mn: 0.02 to 0.20%, Sol. A
l: 0.015 to 0.065%, N: 0.0030 to
0.0150%, one or two of S and Se in total: 0.005 to 0.040%, and the remainder is hot-rolled after heating a slab substantially having a Fe composition. In a method of manufacturing a grain-oriented electrical steel sheet by the steps of annealing a rolled sheet, cold rolling, decarburizing annealing, final finishing annealing, and final coating, a slab is heated at a high temperature of 1200 ° C. or more. At a heating rate of 5 ° C./min or more.
Heat to 320 to 1490 ° C and perform hot rolled sheet annealing at 900 to 1
It is carried out at 100 ° C., the product thickness is 0.20 to 0.55 mm, the average crystal grain size is 1.5 to 5.5 mm, and W17 / 50 is represented by the following formula: 1.80 ≦ B8 (T) ≦ 1.
88. A method for producing a grain-oriented electrical steel sheet. 0.5884e ^{1.9154 × t} ≦ W17 / 50 (W / kg) ≦ 0.7558e
^{1.7378 × t} , where t: plate thickness (mm) (2) In weight%, C: 0.02 to 0.15%, Si: 1.
5 to less than 2.5%, Mn: 0.02 to 0.20%, Sol.
Al: 0.015 to 0.065%, N: 0.0030 to
A slab containing 0.0150%, one or two of S and Se: 0.005 to 0.040%, and the balance substantially consisting of Fe is hot-rolled after slab heating;
Hot rolled sheet annealing, cold rolling, decarburizing annealing, final finish annealing,
Then, in the method of manufacturing a grain-oriented electrical steel sheet by a step of applying a final coating, the slab is heated at a temperature of 1200 ° C. or higher in a high temperature range at a rate of 5 ° C./min or higher to reach 1320 to 1490 ° C. Heat and perform hot rolled sheet annealing 90
0 to 1100 ° C, product thickness is 0.20 to 0.55
mm, the average crystal grain size is 1.5 to 5.5 mm, and W17 / 50 is represented by the following formula: 1.88 ≦ B8 (T) ≦
1. A method for producing a unidirectional magnetic steel sheet. 0.5884e ^{1.9154 × t} ≦ W17 / 50 (W / kg) ≦ 0.7558e
^{1.7378 × t} where t: plate thickness (mm) (3) The slab to be heated to a temperature range of 1320 ° C. to 1490 ° C. is a slab subjected to hot deformation at a rolling reduction of 50% or less. The method for producing a grain-oriented electrical steel sheet according to the above (1) or (2). (4) One or more elements selected from Sb, Sn, Cu, Mo and B are further added to the slab in an amount of 0.005% for each element.
The method for producing a grain-oriented electrical steel sheet according to any one of the above (1) to (3), wherein the content is 3 to 0.3% by weight.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. The present inventors have conducted various studies on the conditions to be provided for the iron loss characteristics and the manufacturing process of such a grain-oriented electrical steel sheet. As a result, the Si content and other components, the sheet thickness,
In addition to drastically reviewing the combination of product average crystal grain size and crystal orientation, slab heating rate, slab heating temperature, fine control such as applying hot deformation to slab to be subjected to high temperature heating, By simplifying the manufacturing process, we succeeded in manufacturing a unidirectional magnetic steel sheet that is inexpensive, has high productivity, and has magnetic characteristics equal to or higher than the conventional one and little variation.

First, the reasons for limiting the component composition of the present invention will be described. If the lower limit of C is less than 0.02%, the secondary recrystallization becomes unstable, and the upper limit of 0.15% is because if more C, the decarburization time becomes longer, which is economically disadvantageous. Limited.

[0009] If the lower limit of Si is less than 1.5%, eddy current loss increases and good iron loss cannot be obtained, and if the upper limit exceeds 4.0%, the cold-rolling property deteriorates remarkably.

[0010] Mn is a main inhibitor constituent element that affects secondary recrystallization for obtaining magnetic properties as a grain-oriented electrical steel sheet. When the lower limit is less than 0.02%, the absolute amount of MnS necessary for causing secondary recrystallization is insufficient, and when the upper limit is more than 0.20%, solid solution of MnS during slab heating becomes difficult. In addition, the precipitation size during hot rolling tends to be coarsened, and the appropriate size distribution as an inhibitor is impaired, deteriorating the magnetic properties.

S and Se are elements necessary for forming MnS and MnSe. If the total of one or two of them is less than the lower limit of 0.005%, the absolute amounts of MnS and MnSe are insufficient and the upper limit is 0. If it exceeds 0.040%, hot cracking occurs,
In addition, purification by final finish annealing becomes difficult.

Sol. Al is an element necessary for forming AlN. When the lower limit is less than 0.015%, the absolute amount of AlN is insufficient, and when the upper limit is more than 0.065%, an appropriate dispersion state of AlN is obtained. I can't.

N is an element necessary for forming AlN. If the lower limit is less than 0.0030%, the absolute amount of AlN is insufficient, and if the upper limit is more than 0.0150%, an appropriate dispersion state of AlN cannot be obtained. .

Sb, Sn, Cu, Mo and B segregate at the grain boundaries to stabilize the secondary recrystallization, but if the amount of each element is less than the lower limit of 0.003%, the amount of segregation will be insufficient and the upper limit will be 0. The reason for the decrease of 0.3% was due to economic reasons and the deterioration of decarburization. One type of element may be added, or two or more types may be added.

Next, a method of manufacturing the grain-oriented electrical steel sheet according to the present invention will be described. The molten steel whose components are adjusted as described above is cast into a slab, hot-rolled, and finished into a coil.
At that time, slab heating in the high temperature range of 1200 ° C or more is 5 ° C.
Perform at a heating rate of / min or more.

FIG. 1 shows the results of experiments conducted by the present inventors.
C: 0.065%, Si: 3.00%, Mn: 0.08
%, S: 0.026%, Sol. Al: 0.030%, N:
A slab containing 0.0089% was continuously cast and heated to 1350 ° C. at various heating rates in an induction heating furnace, and then a hot-rolled sheet having a thickness of 2.30 mm was produced. And 10
The relationship of W17 / 50 is shown for a product which has been hot-rolled at 80 ° C., cold-rolled to 0.300 mm, decarburized, finished, flattened and coated with a secondary coating.

FIG. 2 shows that C: 0.037%, Si:
00%, Mn: 0.08%, S: 0.028%, Sol.
A slab containing l: 0.032% and N: 0.0077% was continuously cast and 135 at various heating rates in an induction heating furnace.
After heating the slab to 0 ° C., a hot-rolled sheet having a thickness of 2.30 mm was prepared. Then, hot rolled sheet annealing at 1080 ° C.
The relationship of W17 / 50 of the product cold rolled to 300 mm and subjected to decarburizing annealing, finish annealing, flattening and secondary film coating baking annealing is shown.

In the experiments shown in FIGS. 1 and 2, when the slab heating at 1200 ° C. or more was performed at a rate of less than 5 ° C./min, there were some defective secondary recrystallization portions. At 5 ° C./min or more, the average crystal grain size is 2.
2 to 2.6 mm. It can be seen that if slab heating at 1200 ° C. or more is performed at a rate of less than 5 ° C./min, the variation in iron loss is large, and there may be cases where poor iron loss occurs. 5 ℃ /
Above min, the desired iron loss (the following formula) can be obtained stably. 0.5884e ^{1.9154 × t} ≦ W17 / 50 (W / kg) ≦ 0.7558e
^{1.7378 × t} , where t: plate thickness (mm)

The cause is considered as follows. That is,
When the slab is heated at a high temperature, abnormal grain growth of the slab occurs, the structure of the hot-rolled sheet becomes non-uniform, and the magnetic properties tend to vary. Therefore, heating at a high temperature range of 1200 ° C or higher
With the above rate of temperature increase, abnormal grain growth of crystal grains during slab heating is suppressed, the structure of the hot-rolled sheet is made uniform, and variations in magnetic properties are suppressed.

The slab heating temperature is from 1320 ° C. to 1490
° C, but below 1320 ° C, the inhibitor Al
The solution of N, MnS, and MnSe is insufficient, secondary recrystallization is not stabilized, and the desired iron loss cannot be obtained. If it exceeds 1490 ° C., the slab melts. A slab heated to a temperature range of 1320 ° C. to 1490 ° C. breaks columnar crystals of the slab when subjected to hot deformation at a rolling reduction of 50% or less, is effective in homogenizing the structure of a hot-rolled sheet, and has further improved magnetic properties. Stabilize. Upper limit of 50
% Is because the effect is saturated even if the rolling reduction is further increased.

The slab heating may be performed by a normal gas heating furnace, but may be performed by an induction heating furnace or an electric heating furnace. The low temperature range may be combined with a gas heating furnace, and the high temperature range may be combined with an induction heating furnace or an electric heating furnace. That is, 1) gas heating furnace (low temperature range)-hot deformation (0% to 50%)-
Gas heating furnace (high temperature range) 2) Gas heating furnace (low temperature range)-Hot deformation (0% to 50%)-
Induction heating furnace or electric heating furnace (high temperature area) 3) Induction heating furnace or electric heating furnace (low temperature area)-hot deformation (0% to 50%)-gas heating furnace (high temperature area) 4) Induction heating furnace or electric current Heating furnace (low temperature range)-Hot deformation (0% to 50%)-Induction heating furnace or electric heating furnace (high temperature range) may be used. Here, 0% hot deformation means, for example,
Taking 2) as an example, it means that the low temperature region is heated by a gas heating furnace, and then heated by an induction heating furnace or an electric heating furnace without hot working.

5 ° C./m in a high temperature range of 1200 ° C. or more of the slab
If the heating at a heating rate of at least in is performed in an induction heating furnace or an electric heating furnace, the slab heating can be performed in a non-oxidizing atmosphere (for example, nitrogen) in the induction heating furnace or the electric heating furnace. No oxide melt) is generated, the surface defects of the steel sheet are reduced, and the work of removing the slag accumulated on the hearth of the heating furnace becomes unnecessary. If the slab is heated in a gas heating furnace before applying hot deformation, the slab can be heated at a lower cost and with higher productivity than an induction heating furnace or an electric heating furnace.

The hot-rolled coil continuously performs hot-rolled sheet annealing,
Inhibitor precipitation control is performed. 900 for hot rolled sheet annealing
It is characterized by annealing at １1100 ° C. for 30 seconds to 30 minutes. If the temperature is lower than 900 ° C., secondary recrystallization is not stabilized due to insufficient precipitation of the inhibitor. If the temperature is higher than 1100 ° C., secondary recrystallization failure due to the coarsening of the inhibitor tends to occur.

The cold-rolling of a grain-oriented electrical steel sheet is usually carried out by two or more cold-rolling steps with intermediate annealing, but the present invention is characterized in that it is produced by a single cold-rolling step. Cost and productivity can be improved. The conditions for the decarburization annealing are not particularly limited, but are preferably performed in a temperature range of 700 to 900 ° C. for 30 seconds to 30 minutes in wet hydrogen or a mixed atmosphere of wet hydrogen and nitrogen.

The surface of the steel sheet after the decarburizing annealing is coated with an annealing separating agent by a usual method to prevent seizure in finish annealing and to form an insulating film. Finish annealing is 1000 ° C
The above is performed for 5 hours or more in an atmosphere of hydrogen, nitrogen, or a mixture thereof. After that, remove excess annealing separating agent, perform flattening annealing to correct coil set,
At the same time, a secondary film is applied and baked.

If the product thickness is smaller than 0.20 mm, the hysteresis loss increases and the productivity decreases, which is not preferable. On the other hand, if it exceeds 0.55 mm, it is not preferable because eddy current loss increases and productivity decreases due to a long decarburization time. The average grain size of the product is
If it is smaller than 1.5 mm, the hysteresis loss increases, and if it exceeds 5.5 mm, the eddy current loss increases. In addition, US Patent No. 2,533,351,
And the product according to U.S. Pat. No. 2,599,340 has an average grain size of from 1.0 to 1.4 mm.

FIG. 3 shows that C: 0.065%, Si: 3.0
0%, Mn: 0.08%, S: 0.026%, Sol. A
l: A slab containing 0.030% and N: 0.0089% is heated at 1200 ° C or higher at 10 ° C / min in an induction heating furnace, heated at 1380 ° C, hot rolled, and then hot rolled at 1080 ° C. The relationship between the sheet thickness and W17 / 50 of the product which has been subjected to sheet annealing, finished to 0.20 to 0.55 mm by one cold rolling, decarburized annealing, finished annealing, flattening and secondary film coating baking annealing Show.
Ingredients including Si content, plate thickness, product average crystal grain size,
Furthermore, by drastically revising the combination of crystal orientations and simplifying the manufacturing process as never before, the following equation was obtained ^: 0.5884e ^{1.9154 × t} ≤ W17 / 50 (W / kg) ≤ 0.7558e
^{1.7378 × t} Here, t: a unidirectional magnetic steel sheet which is inexpensive, has high productivity and has magnetic properties equal to or higher than the conventional steel sheet, represented by t: sheet thickness (mm).

FIG. 4 shows that C: 0.039%, Si: 2.0
0%, Mn: 0.08%, S: 0.026%, Sol. A
l: A slab containing 0.030% and N: 0.0078% is heated in an induction heating furnace at 1200 ° C or higher at 10 ° C / min, heated at 1380 ° C, hot-rolled, and then hot-rolled at 1080 ° C. The relationship between the sheet thickness and W17 / 50 of the product which has been subjected to sheet annealing, finished to 0.20 to 0.55 mm by one cold rolling, decarburized annealing, finished annealing, flattening and secondary film coating baking annealing Show.
Ingredients including Si content, plate thickness, product average crystal grain size,
Furthermore, by drastically reviewing combinations of crystal orientations and simplifying the manufacturing process as never before,
The following formula 0.5884e ^{1.9154 × t} ≦ W17 / 50 (W / kg) ≦ 0.7558e
^{1.7378 × t} Here, t: a unidirectional magnetic steel sheet which is inexpensive, has high productivity and has magnetic properties equal to or higher than the conventional steel sheet, represented by t: sheet thickness (mm).

[0029]

EXAMPLES [Example 1] As component system A, C: 0.05
0%, Si: 2.92%, Mn: 0.08%, S: 0.
022%, Sol. Al: 0.023%, N: 0.0088
% In a temperature range of 1200 ° C. or higher at various heating rates in an induction heating furnace, and the slab was heated to 1350 ° C. Thereafter, the product was hot-rolled to 2.0 mm, annealed at 1060 ° C., and cold-rolled to 0.300 mm by one cold rolling to obtain a product sheet thickness. After that, decarburization annealing, finish annealing, flattening
The coating was baked and annealed to obtain a product.

On the other hand, when the conventional method is used as the component system B, C: 0.
038%, Si: 3.05%, Mn: 0.06%, S:
0.026%, Sol. Al: 0.001%, N: 0.00
The slab containing 37% was heated in an induction heating furnace at a temperature range of 1200 ° C. or higher to 1350 ° C. at a rate of 10 ° C./min and hot-rolled to form a 2.0 mm thick hot coil. Then, 0.30 in two cold rollings with an intermediate annealing at 840 ° C.
The product was cold rolled to 0 mm to obtain a product thickness. Thereafter, decarburized annealing, finish annealing, flattening and secondary film coating baking annealing were performed to obtain a product. As shown in Table 1, it can be seen that in the example of the present invention, good magnetic properties were obtained by the single cold rolling method.

[0031]

[Table 1]

Example 2 As the component system A, C: 0.0
31%, Si: 2.10%, Mn: 0.08%, S:
0.026%, Sol. Al: 0.026%, N: 0.00
The slab containing 90% was heated in an induction heating furnace in a temperature range of 1200 ° C. or more at various heating rates, and was heated to 1350 ° C. After that, it was hot-rolled to 2.3 mm and 1040
The hot-rolled sheet was annealed at ℃, and was cold-rolled to 0.350 mm by one cold rolling to obtain a product sheet thickness. Thereafter, decarburized annealing, finish annealing, flattening and secondary film coating baking annealing were performed to obtain a product.

On the other hand, when the conventional method is used as a component system B, C: 0.
039%, Si: 3.08%, Mn: 0.06%, S:
0.022%, Sol. Al: 0.001%, [N] 0.0
The slab containing 037% was heated in an induction heating furnace at a temperature range of 1200 ° C. or higher at 10 ° C./min and heated to 1350 ° C. After the slab was heated, hot rolling was performed to obtain a hot coil having a thickness of 2.3 mm. Then, the product was cold-rolled to 0.350 mm by two cold-rollings sandwiching an intermediate annealing at 840 ° C. to obtain a product sheet thickness. Thereafter, decarburized annealing, finish annealing, flattening and secondary film coating baking annealing were performed to obtain a product. As shown in Table 2, the present invention example
It can be seen that good magnetic properties were obtained by the single cold rolling method.

[0034]

[Table 2]

Example 3 C: 0.034%, Si:
2.01%, Mn: 0.08%, S: 0.026%, So
l. A slab containing 0.023% of Al and 0.0092% of N was heated to a temperature range of 1200 ° C. or more at 10 ° C. in an electric heating furnace.
1. Heat to 1360 ° C. at a heating rate of / min and hot roll.
A 6 mm thick hot coil was used. Then, the hot-rolled sheet was annealed at 1050 ° C. and cold-rolled to 0.500 mm to obtain a product sheet thickness. Thereafter, decarburized annealing, finish annealing, flattening and secondary film coating baking annealing were performed to obtain a product.

On the other hand, when the conventional method is used as the component system B, C: 0.
040%, Si: 3.07%, Mn: 0.07%, S:
0.023%, Sol. Al: 0.001%, N: 0.00
The slab containing 39% was heated in an induction heating furnace at a temperature range of 1200 ° C. or higher to 1360 ° C. at a rate of 10 ° C./min, and hot-rolled to form a 2.6 mm thick hot coil. Then, 0.500 in two cold rollings with an intermediate annealing at 840 ° C.
It was cold rolled to mm to obtain the product thickness. Thereafter, decarburization annealing, finish annealing, flattening and secondary film coating baking annealing were performed to obtain a product. As shown in Table 3, it can be seen that the examples of the present invention can obtain good magnetic properties by the single cold rolling method.

[0037]

[Table 3]

Example 4 C: 0.048%, Si:
3.00%, Mn: 0.08%, S: 0.012%, S
e: 0.012%, Sol. Al: 0.020%, N: 0.
0088% in addition to Sb, Sn, Cu, Mo
And slabs containing various amounts of B in an induction furnace.
The slab was heated to 1370 ° C. in a temperature range of 0 ° C. or higher at a rate of 5 ° C./min, and then hot-rolled to 2.1 mm. And 10
The hot rolled sheet was annealed at 80 ° C., and was cold rolled to 0.300 mm in one cold rolling to obtain a product sheet thickness. After that, decarburizing annealing, finish annealing,
Flattened, secondary film coated, baked and annealed product. Table 4
As shown in the graph, it can be seen that in the example of the present invention, good magnetic properties were obtained by the single cold rolling method.

[0039]

[Table 4]

Example 5 C: 0.050%, Si:
2.92%, Mn: 0.08%, S: 0.022%, So
l. A slab containing Al: 0.023% and N: 0.0088% is heated to 1120 ° C in a gas heating furnace, then inserted into an induction heating furnace, and the temperature range of 1200 ° C or higher is raised at 10 ° C / min. And slab heated to various temperatures. Thereafter, hot rolling was performed, and a hot-rolled sheet was annealed at 1070 ° C., and 0.3% in one cold rolling.
It was cold rolled to 00 mm to obtain a product plate thickness. Thereafter, decarburized annealing, finish annealing, flattening and secondary film coating baking annealing were performed to obtain a product. As shown in Table 5, it can be seen that in the example of the present invention, good magnetic properties were obtained by the single cold rolling method.

[0041]

[Table 5]

Example 6 C: 0.050%, Si:
2.92%, Mn: 0.08%, S: 0.022%, So
l. A slab containing 0.023% Al and 0.0088% N was heated to 1150 ° C in a gas heating furnace. Thereafter, some slabs are hot-deformed at various rolling reduction rates, and then heated in a gas heating furnace and an induction heating furnace (atmosphere: nitrogen) at a temperature range of 1200 ° C. or more at various slab heating rates, and 1375 ° C. The slab was heated. Then, hot-rolled to 2.0 mm, 104
The hot-rolled sheet was annealed at 0 ° C., and was cold-rolled to 0.300 mm in one cold rolling to obtain a product sheet thickness. Thereafter, decarburized annealing, finish annealing, flattening and secondary film coating baking annealing were performed to obtain a product. As shown in Table 6, it can be seen that the examples of the present invention can obtain good magnetic properties by the single cold rolling method.

[0043]

[Table 6]

[0044]

As described above, according to the present invention, it is possible to stably produce a grain-oriented electrical steel sheet which is inexpensive, has high productivity, and has magnetic properties equal to or higher than conventional ones, and its industrial effect is very large.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a slab heating rate and iron loss when Si is 3.00%.

FIG. 2 is a relationship diagram between a slab heating rate and iron loss when Si is 2.00%.

FIG. 3 is a graph showing the relationship between sheet thickness and iron loss when Si: 3.00%, B8: 1.87T, and average particle size: 2.4 mm.

FIG. 4 is a diagram showing the relationship between sheet thickness and iron loss when Si: 2.00%, B8: 1.94T, and average particle size: 3.8 mm.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuo Tachibana 1-Fuji-cho, Hirohata-ku, Himeji-shi Nippon Steel Corporation Hirohata Works (72) Inventor Chikuma ▲ Akira ▼ Taro 1 Fujimachi, Hirohata-ku, Himeji-shi Address Nippon Steel Corporation Hirohata Works

Claims (4)

[Claims] 1. C .: 0.02 to 0.15% by weight, Si: 2.5 to 4.0% by weight.
%, Mn: 0.02 to 0.20%, Sol. Al: 0.015
０．０0.065%, N: 0.0030 to 0.0150%, one or two of S and Se in total: 0.005 to
The slab containing 0.040%, the remainder being substantially Fe-composed, is heated, hot-rolled, hot-rolled sheet annealed, cold-rolled, decarburized and annealed, finally finished and annealed. -In a method of producing a grain-oriented electrical steel sheet by a step of applying
The slab is heated at a temperature of 1200 ° C. or higher in a high temperature range at a rate of 5 ° C./min or higher, heated to 1320 to 1490 ° C., and hot-rolled sheet is annealed at 900 to 1100 ° C. .20 to 0.55 mm, and the average grain size is 1.5 to
A method for producing a grain-oriented electrical steel sheet of 1.80 ≦ B8 (T) ≦ 1.88, wherein 5.5 mm and W17 / 50 are represented by the following formula: 0.5884e ^{1.9154 × t} ≦ W17 / 50 (W / kg) ≦ 0.7558e
^{1.7378 × t} , where t: plate thickness (mm) 2.% by weight: C: 0.02 to 0.15%, Si: 1.5 to 2.5%
%, Mn: 0.02 to 0.20%, Sol. Al: 0.015
０．０0.065%, N: 0.0030 to 0.0150%, one or two of S and Se in total: 0.005 to
The slab containing 0.040%, the remainder being substantially Fe-composed, is heated, hot-rolled, hot-rolled sheet annealed, cold-rolled, decarburized and annealed, finally finished and annealed. -In a method of producing a grain-oriented electrical steel sheet by a step of applying
The slab is heated at a temperature of 1200 ° C. or higher in a high temperature range at a rate of 5 ° C./min or higher, heated to 1320 to 1490 ° C., and hot-rolled sheet is annealed at 900 to 1100 ° C. .20 to 0.55 mm, and the average grain size is 1.5 to
5.5. A method for producing a grain-oriented electrical steel sheet in which 1.88≤B8 (T) ≤1.95 wherein W17 / 50 is represented by the following formula. 0.5884e ^{1.9154 × t} ≦ W17 / 50 (W / kg) ≦ 0.7558e
^{1.7378 × t} , where t: plate thickness (mm) 3. The one-way slab according to claim 1, wherein the slab to be heated to a temperature range of 1320 ° C. to 1490 ° C. is a slab subjected to hot deformation at a rolling reduction of 50% or less. Manufacturing method of conductive electrical steel sheet. 4. The slab further comprises Sb, Sn, Cu, M
The one-way direction according to any one of claims 1 to 3, wherein one or two or more kinds selected from o and B are contained in an amount of 0.003 to 0.3% by weight in each element amount. Manufacturing method of electrical steel sheet.