JPH0717954B2 - Manufacturing method of thin high magnetic flux density unidirectional electrical steel sheet with excellent magnetic properties by one-step cold rolling method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a stable production method of a thin high magnetic flux density unidirectional electrical steel sheet having excellent product magnetic characteristics by a one-step cold rolling method.

[Conventional technology]

The unidirectional electrical steel sheet is mainly used as a soft magnetic material as a magnetic core material for transformers and other electric devices, and it must have good magnetic excitation characteristics and iron loss characteristics.

In order to obtain a steel sheet with excellent magnetic properties, the easy axis of magnetization <00
The 1> axis must be highly aligned in the rolling direction. In addition, the plate thickness, grain size, specific resistance, surface coating, etc. have a great influence on the magnetic properties.

The directionality of electrical steel sheets has been greatly improved by the high-pressure single-stage cold rolling process that causes AlN and MnS to function as inhibitors, and at present, magnetic flux densities up to about 96% of the theoretical value are being manufactured. .

On the other hand, in recent years, the transformer manufacturers have been increasingly oriented to low iron loss magnetic materials as materials for energy-saving transformers, reflecting the sharp rise in energy prices.

High Si materials such as amorphous alloys and 6.5% Si alloys are under development as low iron loss magnetic materials, but there are drawbacks in terms of price and workability as materials for transformers.

On the other hand, it is known that the iron loss of the electromagnetic steel sheet is greatly affected by the sheet thickness in addition to the Si content, and the iron loss decreases when the sheet thickness of the product is reduced by chemical polishing or the like.

The present inventors previously disclosed in JP-A-58-217630 that a silicon steel slab containing acid-soluble Al, N, Sn was used as a starting material, and a thin sheet was formed by a high-pressure single-stage cold rolling method involving hot-rolled sheet annealing. A method of manufacturing magnetic flux density unidirectional electrical steel sheet was proposed. With this method, thin high magnetic flux density unidirectional electrical steel sheets with excellent iron loss, and in particular, thin materials up to a sheet thickness of 0.225 mm, can be industrially manufactured at low cost. We were able to contribute to energy saving, which is an issue of the times.

However, the demands of the times for energy saving have further increased since then, and it has become necessary to further improve the performance of the unidirectional electrical steel sheet, which is a material for transformers. That is, the plate thickness
It has become an urgent task to establish a cheap and stable manufacturing method for thin high magnetic flux density unidirectional electrical steel sheets having a thickness of 0.175 mm or less, which has a lower iron loss than 0.225 mm material.

[Problems to be Solved by the Invention]

By the method disclosed in JP-A-58-217630, 0.175 mm,
Although it is possible to manufacture 0.150 mm material, if the plate thickness is 0.175 mm or less, as shown in Tables 8 and 11 of the above publication, the secondary recrystallization is not complete, and in the case of industrial production, the process steps are It was found that the retention was low and there were problems in the level and stability of the magnetic properties of the product.

The present invention uses a silicon steel slab containing acid-soluble Al, N, Sn as a starting material, and has excellent magnetic properties of a product cold-rolled to a sheet thickness of 0.12 to 0.17 mm by a high-pressure single-stage cold rolling method involving hot-rolled sheet annealing. The aim is to stably manufacture thin, high magnetic flux density unidirectional electrical steel sheets.

[Means for Solving the Problems]

Where the gist of the present invention is, acid-soluble Al, N, using a silicon steel slab containing Sn, as a starting material, cold rolled to a sheet thickness of 0.12 to 0.17 mm by a high pressure single-stage cold rolling method involving hot rolled sheet annealing. In the method for producing a thin unidirectional electrical steel sheet, N: 0.0050 to 0.0100 with respect to N and acid-soluble Al contained in the slab
%, Acid-soluble Al: {(27/14) × N (%) + 0.0035} 〜
{(27/14) × N (%) + 0.0100}%, and the thickness of the hot-rolled sheet with a cold rolling reduction of 85 to 92%, and containing N as AlN in the hot-rolled sheet By performing hot rolling in which the amount is controlled to 0.0005 to 0.0020% and controlling the average hardness in the thickness direction of the steel sheet cross section after annealing after cooling the hot rolled sheet to Hv (1 kg) 200 or more and less than 230, the secondary This is to enable stable production of thin high magnetic flux density grain-oriented electrical steel sheets that are completely recrystallized and have excellent product magnetic properties.

[Action]

The background of the present invention will be described below based on experimental results.

(Experiment I) C: 0.080%, Si: 3.25%, Mn: 0.075%, S: 0.025%, Sn: 0.13
%, N: 0.0040 to 0.0120%, Acid-soluble Al: 0.0100 to 0.0500
%, Balance: a large number of silicon steel slabs consisting essentially of Fe 13
It was heated at 70 ° C. for 60 minutes, extracted from the heating furnace, and hot-rolled to a plate thickness of 1.4 mm. The hot rolling finish temperature was 1040 to 1050 ° C.
After the hot rolling was completed, it was cooled to 550 ° C. at about 70 ° C./sec and then left to cool in the atmosphere. N as AlN contained in the hot rolled sheet is 0.0010 to 0.00
It was 12%. Anneal the hot-rolled sheet at 1100 ° C for 30 seconds, then
It was immersed in 100 ° C. water and cooled. The average hardness in the plate thickness direction of the steel plate cross section after cooling was Hv (1 kg) 210 to 215. The annealed plate was pickled and cold rolled to a plate thickness of 0.15 mm. Then 75%
Decarburization annealing was performed at 850 ° C for 150 seconds in an atmosphere of H ₂ , 25% N ₂ , dew point of 65 ° C. Then, an annealing separator containing magnesia powder as a main component was applied, and heated to 1200 ° C at a temperature rising rate of 25 ° C / hour in an atmosphere of 85% H ₂ and 15% N ₂ and then
The product was obtained by soaking in H ₂ atmosphere at 1200 ° C. for 20 hours and then cooling, removing the annealing separator, and performing tension coating. The magnetic flux density B ₈ and iron loss W _15/50 of the product were measured. The coating and glass coating were then removed and the macrostructure was observed. The relationship between the N and acid soluble Al contents of the slab and the state of secondary recrystallization, B ₈ and W _15/50 is shown in Fig. 1 and Fig. 2 respectively.
Shown in Fig. And Fig. 3.

In FIG. 1, the horizontal axis represents the N content, and the vertical axis represents the acid-soluble Al content. The secondary recrystallization state is indicated by the symbols of ○, △, ×. The secondary recrystallization was complete in the region surrounded by the straight lines ab, bc, cd, and da in the figure. The straight line ab is expressed by the following equation.

Straight line ab: Acid soluble Al (%) = (27/14) x N (%) + 0.01
00 (%) That is, N: 0.0050 to 0.0120%, acid-soluble Al: 0.0100
It was revealed that the secondary recrystallization was complete when ~ ((27/14) x N (%) + 0.0100}%.

In FIG. 2, the horizontal axis represents the N content, and the vertical axis represents the acid-soluble Al content. The value of B ₈ is indicated by the symbols of ○, △, ×.
Good B ₈ was obtained in the region surrounded by the straight lines ab, bc, cd, and da in the figure.

The straight lines ab and cd are represented by the following equations, respectively.

Straight line ab: Acid soluble Al (%) = (27/14) x N (%) + 0.01
00 (%) Linear cd: Acid soluble Al (%) = (27/14) x N (%) + 0.00
35 (%) That is, N: 0.0050 to 0.0100%, acid-soluble Al: {(27 /
14) x N (%) + 0.0035} ~ {(27/14) x N (%) +
It was revealed that good B ₈ can be obtained at 0.0100}%.

In FIG. 3, the horizontal axis represents the N content, and the vertical axis represents the acid-soluble Al content. The value of W _15/50 is shown by the symbols of ○, △, ×. In the region surrounded by the straight lines ab, bc, cd, da in the figure, good W _15/50 was obtained.

The straight lines ab and cd are represented by the following equations, respectively.

Straight line ab: Acid soluble Al (%) = (27/14) x N (%) + 0.01
00 (%) Linear cd: Acid soluble Al (%) = (27/14) x N (%) + 0.00
35 (%) That is, N: 0.0050 to 0.0100%, acid-soluble Al: {(27 /
14) x N (%) + 0.0035} ~ {(27/14) x N (%) +
It was revealed that when W is 0.0100}%, good W _15/50 is obtained.

From the results of Fig. 1, Fig. 2 and Fig. 3, N: 0.0050 to 0.0100
%, Acid-soluble Al: {(27/14) × N (%) + 0.0035} 〜
When {(27/14) × N (%) + 0.0100}%, secondary recrystallization was complete, and it was revealed that good products of B ₈ and W _15/50 were obtained.

Despite complete secondary recrystallization, B ₈ is low in the region where W _15/50 is defective. That is, the secondary recrystallization is stable on the low Al and high N sides, but the directionality is poor and it tends to be difficult to obtain a good iron loss value.

Here, (27/14) × N (%) corresponds to the Al content necessary when all the N contained in the steel is AlN. In this method that uses AlN as the main inhibitor, the secondary recrystallization phenomenon that affects the magnetic flux density and iron loss value of the product is (27/1
4) It is understood that it is strongly influenced by the acid-soluble Al content based on (N)%.

(Experiment II) C: 0.082%, Si: 3.25%, Mn: 0.070%, S: 0.025%, Sn: 0.14
%, N: 0.0085%, acid-soluble Al: 0.0240%, balance: substantially
A large number of silicon steel slabs made of Fe were heated at 1370 ° C. for 60 minutes, extracted from a heating furnace, and hot-rolled to various plate thicknesses of 0.75 to 3.0 mm. In this case, the cooling conditions before rolling, during rolling, and after rolling were variously changed, and the amount of N as AlN in the hot rolled sheet was 0.0001 to 0.0036.
Changed to%. Here, AlN is an analysis value of the total plate thickness, and the bromine-methanol method was used as the analysis method (all analyzes of AlN relating to the present invention were made by the bromine-methanol method). These hot-rolled sheets were treated in the same manner as in Experiment I to obtain products.

Next, the magnetic flux density B ₈ and the iron loss W _15/50 of the product were measured. The coating and glass coating were then removed and the macrostructure was observed. The relationship between N as AlN, cold rolling reduction and secondary recrystallization condition, B ₈ and W _15/50 of hot rolled sheet is shown in Fig. 4 and 5 respectively.
Figure and Figure 6 show.

In FIG. 4, the horizontal axis represents N as AlN content, and the vertical axis represents cold rolling reduction. The secondary recrystallization state is indicated by the symbols of ○, △, ×. The secondary recrystallization was complete in the region surrounded by the straight lines ab, bc, cd, and da in the figure. That is, N as AlN:
It was revealed that the secondary recrystallization was complete when the cold rolling reduction was 0.0001 to 0.0020% and the cold rolling reduction was 80 to 92%.

In FIG. 5, the horizontal axis represents N as AlN content, and the vertical axis represents cold rolling reduction. The value of B ₈ is indicated by the symbols of ○, △, ×.
In the area surrounded by ab, bc, cd, and da in the figure, good B ₈
was gotten. That is, N as AlN: 0.0005 to 0.0020%,
It was revealed that good B ₈ was obtained when the cold rolling reduction rate was 85 to 92%.

In FIG. 6, the horizontal axis is the N as AlN content, and the vertical axis is the cold rolling reduction. The value of W _15/50 is shown by the symbols of ○, △, ×. Good W _15/50 was obtained in the region surrounded by ab, bc, cd, and da in the figure. That is, N as AlN: 0.0005 to 0.0
It was clarified that good W _15/50 was obtained at 020% and cold rolling reduction of 85 to 92%.

From the results of FIGS. 4, 5, and 6, N as AlN: 0.0005 ~
At 0.0020% and cold rolling reduction of 85-92%, it was clarified that secondary recrystallization was complete and good products of B ₈ and W _15/50 were obtained.

Despite the complete secondary recrystallization, B ₈ is low in the region where W _15/50 is defective.

From the results of Experiment I and Experiment II, a silicon steel slab containing acid-soluble Al, N, and Sn was used as the starting material, and cold-rolled to a sheet thickness of 0.12 to 0.17 mm by the high-pressure single-stage cold rolling method involving hot-rolled sheet annealing. In the method for producing the thin unidirectional electrical steel sheet described above, N: 0.0050 to 0.0100% with respect to N and acid-soluble Al contained in the slab,
Acid-soluble Al: {(27/14) × N (%) + 0.0035} to {(27
/ 14) × N (%) + 0.0100}% and the thickness of the hot rolled sheet with a cold rolling reduction of 85 to 92%, and
By performing hot rolling with the N as AlN content controlled to 0.0005 to 0.0020%, it is possible to stably manufacture thin high magnetic flux density unidirectional electrical steel sheets with perfect secondary magnetic recrystallization and excellent product magnetic properties. It became clear.

By performing hot rolling to control the N as AlN content in the hot rolled sheet to 0.0005 to 0.0020%, good secondary recrystallization, and,
It is not always clear why a product with excellent magnetic properties can be obtained.

When a thin high magnetic flux density unidirectional electrical steel sheet with a cold-rolled sheet thickness of 0.17 mm or less is produced by the single-stage cold rolling method, compared with the case of producing thick products or the multi-stage cold rolling method, hot-rolled sheet annealing It is conceivable that the subsequent structure and the state of precipitates have a stronger influence on the product properties.

On the other hand, the N as AlN content in the hot rolled sheet is considered to have a subtle influence on the microstructural change of the steel sheet during hot rolled sheet annealing and the behavior of precipitates, and the N as AlN content in the hot rolled sheet is 0.0005
In the case of up to 0.0020%, the properties of the steel sheet after hot-rolled sheet annealing that are most advantageous for the product properties will be obtained.

In addition, as a method for controlling the N as AlN content in the hot-rolled sheet to 0.0005 to 0.0020%, slab heating conditions, rough rolling conditions,
Although there are finish rolling conditions, cooling conditions after finish rolling, and the like, any of them may be used.

(Experiment III) C: 0.075%, Si: 3.25%, Mn: 0.070%, S: 0.025%, acid soluble
Al: 0.0255%, N: 0.0085%, Sn: 0.15%, balance: Fe
A silicon steel slab consisting of the above was treated in the same manner as in Experiment I except for the quenching condition after annealing the hot rolled sheet to obtain a product. With respect to the quenching conditions, various conditions were changed, and the average hardness Hv (1 kg) in the plate thickness direction of the steel plate cross section after cooling was set to 185 to 290.

The iron loss value and magnetic flux density of the product were measured.

FIG. 7 shows the relationship among the average hardness, iron loss value and magnetic flux density.
In FIG. 7, the horizontal axis represents average hardness, and the vertical axis represents iron loss value and magnetic flux density.

As is clear from FIG. 7, good iron loss values and magnetic flux densities were obtained in the range of average hardness Hv (1 kg) of 200 or more and less than 230.

In the case of adding one or both of Cu and Sb to the material components shown in Experiment I, Experiment II, and Experiment III, Experiment I, Experiment I
Experiments similar to I and Experiment III were performed and similar results were obtained.

(Experiment IV) C: 0.083%, Si: 3.25%, Mn: 0.076%, S: 0.025%, Sn: 0.14
%, N: 0.0085%, acid-soluble Al: 0.0235%, Cu: no additive and
0.01 to 0.20%, balance: A large number of silicon steel slabs substantially made of Fe were processed in the same manner as in Experiment I in the steps after hot rolling to obtain products. Fig. 8 shows the relationship between the Cu content and the iron loss value. As is clear from FIG. 8, the improvement of the iron loss characteristics was recognized in the range of Cu: 0.03 to 0.08%.

(Experiment V) C: 0.080%, Si: 3.23%, Mn: 0.075%, S: 0.025%, Sn: 0.13
%, N: 0.0085%, acid-soluble Al: 0.0230%, Sb: no addition and
0.001 to 0.050%, balance: A large number of silicon steel slabs substantially made of Fe were processed in the same manner as in Experiment I in the steps after hot rolling to obtain products. The relationship between Sb content and iron loss is shown in FIG. As is clear from Fig. 9, Sb: 0.005 to 0.035%
It was confirmed that the iron loss characteristics were improved in the range.

Next, the reasons for limiting the components of the silicon steel slab and the processing conditions of the manufacturing process in the present invention will be described.

C is 0.060 to 0.120%. Less than 0.060% or 0.1
If it exceeds 20%, the secondary recrystallization becomes unstable.

Si is 2.9 to 4.5%. Less than 2.9% is good (low)
If the iron loss value cannot be obtained and exceeds 4.5%, the workability (ease of cold rolling) deteriorates.

Mn is 0.050 to 0.090%. Less than 0.050% or 0.0
If it exceeds 90%, the secondary recrystallization becomes unstable.

Either or both of S and Se are 0.020 to 0.060%. If less than 0.020%, the secondary recrystallization becomes unstable, and 0.060%
If it exceeds%, the iron loss value becomes poor.

Also, when S and Se are added in combination, particularly excellent product magnetic characteristics are obtained.

Sn is 0.05 to 0.25%. If it is less than 0.05%, the secondary recrystallization becomes unstable, and if it exceeds 0.25%, the workability deteriorates.

In the slab heating, high temperature heating is required to sufficiently dissolve sulfides and nitrides, and heating at 1300 ° C or higher is desirable.

The reason for annealing a hot-rolled sheet at 1030 to 1200 ° C within 10 minutes is 10
This is because if the temperature is lower than 30 ° C, good magnetic properties of the product cannot be obtained, and if it exceeds 1200 ° C, the secondary recrystallization becomes unstable, and improvement of the magnetic properties of the product can be expected even if annealing is performed for more than 10 minutes. Because it is economically disadvantageous.

Quench after annealing. Good magnetic properties cannot be obtained without rapid cooling.

The one-step cold rolling method is preferable because the manufacturing cost is significantly lower than that of the two-step cold rolling method.

The plate thickness after cold rolling is 0.12 to 0.17 mm. If it is less than 0.12 mm, secondary recrystallization tends to be unstable, and if it exceeds 0.17 mm, the expected iron loss value cannot be obtained.

In addition, holding during the cold rolling at 200 to 300 ° C. for 1 to 5 minutes is effective in improving the magnetic properties of the product.

At the time of high temperature finish annealing, at least 1000 ° C during heating,
An atmosphere containing nitrogen is used. If nitrogen is not contained, the secondary recrystallization becomes unstable.

〔Example〕

Example 1 C: 0.080%, Si: 3.25%, Mn: 0.076%, S: no additive, 0.015%, 0.
025%, Se: no additive, 0.015%, 0.025%, Sn: 0.13%, N: 0.0
045%, 0.0085%, 0.0110%, acid soluble Al: 0.0150%, 0.017
0%, 0.0230%, 0.0260%, 0.0300%, Cu: No additive, 0.07%, S
b: Additive-free, 0.020%, balance: A large number of silicon steel slabs consisting essentially of Fe are heated at 1360 ° C for 60 minutes, extracted from a heating furnace, and 0.92mm, 1.00mm, 1.31mm, 2.43mm plates Hot rolled. In this case, the cooling conditions before rolling, during rolling, and after rolling were changed variously. N as AlN content of hot rolled sheet is 0.0002 to 0.00
It was 35%.

The hot-rolled sheet was annealed at 1120 ° C for 60 seconds and then cooled by air cooling and immersion in 100 ° C water.

The average hardness of the cross section of the steel plate after cooling is Hv (1kg) 210 ~
It was 215. The annealed plate is pickled and the plate thickness is 0.12mm and 0.17mm
Cold rolled.

_{Then, 75% H 2, 25%} N 2, in an atmosphere of a dew point of 65 ° C., 850 ° C.
Decarburization annealing was performed for 150 seconds. Then, an annealing separator containing magnesia as a main component is applied, and heated in an atmosphere of 85% H ₂ , 15% N ₂ at a heating rate of 25 ° C./hour to 1200 ° C., and then in an H ₂ atmosphere, After soaking at 1200 ℃ for 20 hours, cool and
The annealing separator was removed, and tension coating was performed to obtain a product. The magnetic flux density B ₈ and iron loss W _15/50 of the product were measured. The coating and glass coating were then removed and the macrostructure was observed. The results are shown in Table 1. As is clear from Table 1, the secondary recrystallization is completed only when the N content of the slab, the acid-soluble Al content, the N as AlN content of the hot-rolled sheet and the cold rolling reduction are the conditions of the present invention. Thus, excellent products were obtained for both B ₈ and W _15/50 .

Further, when the Cu and Sb contents were within the range of the present invention, more excellent product magnetic characteristics were obtained.

Example 2 A silicon steel slab having A, B, C and D4 components shown in Table 2 was treated in the same manner as in Example 1 except for the cooling conditions for hot rolled sheet annealing, to obtain a product. Regarding the cooling conditions for hot rolled sheet annealing, the average hardness Hv (1 kg) in the sheet thickness direction of the steel sheet cross section after cooling is 190,215,240.
I adjusted it to be.

The _iron loss value (W _15/50 ) and magnetic flux density (B ₈ ) of the product were measured.
The results are shown in Table 3. As is clear from Table 3,
Excellent (low) only when the average hardness is within the range of the present invention
The iron loss value and the (high) magnetic flux density are shown.

EFFECTS OF THE INVENTION The present invention is configured as described above, and therefore acid-soluble A
Using a silicon steel slab containing l, N, Sn as a starting material, and by a high-pressure single-stage cold rolling method involving hot-rolled sheet annealing, a sheet thickness of 0.12 to 0.17 mm
In the method of manufacturing thin unidirectional electrical steel sheet cold-rolled into, it became possible to stably produce thin high magnetic flux density unidirectional electrical steel sheet with perfect secondary magnetic recrystallization and excellent product magnetic properties. .

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the N content (horizontal axis) and the acid-soluble Al content (vertical axis) of the slab and the secondary recrystallization state (indicated by ◯, ×, etc.). FIG. 2 is a diagram showing the relationship between the N content (horizontal axis) and the acid-soluble Al content (vertical axis) of the slab and the magnetic flux density B ₈ (indicated by ◯, ×, etc.) of the product. FIG. 3 is a diagram showing the relationship between the N content (horizontal axis) and the acid-soluble Al content (vertical axis) of the slab and the iron loss W _15/50 (indicated by ○, ×, etc.) of the product. FIG. 4 is a diagram showing the relationship between the N as AlN content (horizontal axis) and the cold rolling reduction rate (vertical axis) of the hot-rolled sheet and the secondary recrystallization state (indicated by ◯, ×, etc.). FIG. 5 is a diagram showing the relationship between the N as AlN content (horizontal axis) and the cold rolling reduction rate (vertical axis) of the hot-rolled sheet and the magnetic flux density B ₈ (indicated by ◯, ×, etc.) of the product. FIG. 6 is a diagram showing the relationship between N as AlN (horizontal axis) and cold rolling reduction rate (vertical axis) of hot-rolled sheet and iron loss W _15/50 (indicated by ○, ×, etc.) of the product. FIG. 7 is a diagram showing the relationship between the average hardness in the thickness direction (horizontal axis) of the cross section of the hot rolled annealed sheet, the iron loss value of the product, and the magnetic flux density (vertical axis). FIG. 8 is a diagram showing the relationship between the Cu content of the slab (horizontal axis) and the amount of change in iron loss W _15/50 of the product due to the addition of Cu (vertical axis). FIG. 9 is a graph showing the relationship between the Sb content of the slab (horizontal axis) and the amount of change in iron loss W _15/50 of the product due to Sb addition (vertical axis).

Claims (2)

[Claims] 1. C: 0.060-0.120% by weight%, Si: 2.9-4.5
%, Mn: 0.050 to 0.090%, either or both of S and Se:
0.020 ~ 0.060%, Sn: 0.02 ~ 0.25% and acid-soluble Al, N, the balance: Fe and unavoidable impurities silicon steel slab heated at high temperature, hot rolled, hot rolled plate 1030 ~ 1200 ℃
Annealing within 10 minutes in the temperature range, quenching after annealing, then cold rolling, the thickness after cold rolling is 0.12 to 0.17 mm, decarburization annealing is performed in a humid atmosphere containing hydrogen, and magnesia is removed. Applying the main annealing separator, at least 1000 ° C during heating
In a method for manufacturing a thin unidirectional electrical steel sheet, in which high temperature finish annealing is performed using an atmosphere containing nitrogen and tension coating is performed, N and acid-soluble Al contained in the silicon steel slab are used.
N: 0.0050-0.0100%, acid-soluble Al: {(27/1
4) x N (%) + 0.0035} to {(27/14) x N (%) + 0.
0100}% and the thickness of the hot-rolled sheet with a cold rolling reduction of 85 to 92%, and the N as AlN content in the hot-rolled sheet is 0.00
Performs hot rolling controlled to 05 to 0.0020%, and the average hardness in the thickness direction of the steel sheet cross section after cooling after annealing the hot rolled sheet is Hv (1 kg) 200
A method for producing a thin high magnetic flux density grain-oriented electrical steel sheet excellent in product magnetic characteristics by the one-step cold rolling method, which is characterized by controlling to less than 230. 2. C: 0.060 to 0.120% by weight, Si: 2.9 to 4.5
%, Mn: 0.050 to 0.090%, either or both of S and Se:
0.020-0.060%, Sn: 0.02-0.25%, Cu: 0.03-0.08% or
Sb: 0.005 to 0.035% any one or both and acid-soluble Al, containing N, the balance: Fe and unavoidable impurities silicon steel slab heated at high temperature, hot-rolled, hot-rolled sheet 1030
〜1200 ℃, annealing within 10 minutes, annealing, quenching, cold rolling, cold rolling.
mm, decarburization annealing is performed in a moist atmosphere containing hydrogen, an annealing separating agent mainly containing magnesia is applied, and high temperature finishing annealing is performed at a temperature of at least 1000 ° C. while using a nitrogen-containing atmosphere to increase the tension. In the method for producing a thin unidirectional electrical steel sheet for coating, N: 0.0050 to 0.0100%, acid-soluble A with respect to N and acid-soluble Al contained in the silicon steel slab.
l: {(27/14) × N (%) + 0.0035} to {(27/14) × N
(%) + 0.0100}% and cold rolling reduction is 85-92%
And the thickness of the hot rolled sheet to be, and, and hot rolling to control the N as AlN content in the hot rolled sheet to 0.0005 to 0.0020%, and
Hv is the average hardness in the thickness direction of the steel sheet cross section after cooling after annealing the hot rolled sheet.
(1 kg) A method for producing a thin high magnetic flux density unidirectional electrical steel sheet with excellent product magnetic properties by a one-step cold rolling method, which is controlled to 200 or more and less than 230.