JP2755414B2 - Manufacturing method of thin high magnetic flux density unidirectional electrical steel sheet by single-stage cold rolling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for stably producing a thin high magnetic flux density unidirectional magnetic steel sheet having excellent product magnetic properties by a single-stage cold rolling method.

[Conventional technology]

A grain-oriented magnetic steel sheet is mainly used as a soft magnetic material as a magnetic core material of transformers and other electric devices, and must have good magnetic characteristics such as excitation characteristics and iron loss characteristics.

In order to obtain a magnetic steel sheet having excellent magnetic properties, it is necessary that the <001> axis, which is the axis of easy magnetization, be highly aligned in the rolling direction. In addition, the thickness, crystal grain size, specific resistance, surface coating, and the like greatly affect the magnetic properties.

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

On the other hand, in recent years, reflecting the soaring energy prices, transformer manufacturers
The focus on low iron loss magnetic materials has been further strengthened.

As low iron loss magnetic materials, amorphous alloys and 6.5% Si
The development of high Si materials such as alloys is also underway, but there are drawbacks in transformer materials such as price and workability.

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

The present inventors previously described in Japanese Patent Application Laid-Open No. 58-217630, a silicon steel slab containing acid-soluble Al, N, and Sn as a starting material, and a one-stage cold rolling method under high pressure accompanied by hot-rolled sheet annealing. And a method of manufacturing a thin high magnetic flux density unidirectional magnetic steel sheet. By this method, thin high magnetic flux density unidirectional magnetic steel sheets with excellent iron loss, especially thin materials with a thickness of up to 0.225 m / m, can be industrially produced at low cost. Through iron loss, we were able to contribute to energy conservation, a challenge for the times.

However, after that, the demands of the times for energy saving were
With further strengthening, it has become necessary to further improve the performance of the grain-oriented electrical steel sheet, which is a material for transformers. That is, the thickness
It has become an urgent issue to establish a low-cost and stable manufacturing method of a thin high-flux-density unidirectional magnetic steel sheet having a sheet thickness of 0.175 m / m or less, which has a lower core loss than 0.225 m / m material.

[Problems to be solved by the invention]

0.175 m by the method disclosed in JP-A-58-217630.
/ m, 0.150m / m material can be manufactured, but the sheet thickness is 0.175m / m
m or less, as shown in Tables 8 and 11 of the above publication, secondary recrystallization is not complete, and in the case of industrial production, the process yield is low, and the level and stability of product magnetic characteristics are low. It turned out to be a problem.

The present invention uses a silicon steel slab containing acid-soluble Al, N, and Sn as a starting material, and a product that is cold-rolled to a sheet thickness of 0.12 to 0.17 m / m by a single-stage cold rolling method under high pressure accompanied by hot-rolled sheet annealing. The purpose of the present invention is to provide a method for stably producing a thin high magnetic flux density unidirectional magnetic steel sheet having excellent magnetic properties.

[Means for solving the problem]

The feature of the present invention is that a silicon steel slab containing acid-soluble Al, N, Sn is used as a starting material, and the sheet thickness is reduced to 0.12 to 0.17 m / m by a one-stage cold rolling method under high pressure accompanied by hot rolling sheet annealing. In the method for producing a cold-rolled thin unidirectional magnetic steel sheet, the N and the acid-soluble Al contained in the slab, N: 0.0050-0.
0100%, 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 85-92%, and the content of NasAlN in the hot-rolled sheet Is controlled to 0.0005 to 0.0020%, thereby making it possible to stably produce a thin high magnetic flux density unidirectional magnetic steel sheet with perfect secondary recrystallization and excellent product magnetic properties.

(Operation)

Hereinafter, the circumstances that led to the present invention will be described based on experimental results.

(Experiment I) C: 0.080%, Si: 3.25%, Mn: 0.075%, S: 0.025%, Sn:
0.13%, N: 0.0040-0.0120%, acid-soluble Al: 0.0100-0.0
500%, balance: 1370 multiple slabs consisting essentially of Fe
It heated at 60 degreeC for 60 minutes, extracted from the heating furnace, and hot rolled to the board thickness of 1.4 m / m. The hot rolling end temperature was 1,040 to 1,050 ° C. After the completion of hot rolling, the sample was cooled to 550 ° C. at a rate of about 70 ° C./sec, and then allowed to cool in the air. 0.0010-0.0012% of NasAlN contained in hot rolled sheet
Met. Anneal the hot rolled sheet at 1100 ° C for 30 seconds, then 35 ° C
/ Second at room temperature. Pickling the annealed plate to a thickness of 0.
Cold rolled to 15m / m. Next, decarburization annealing was performed at 850 ° C. for 150 seconds in an atmosphere of 75% H ₂ , 25% N ₂ and a dew point of 65 ° C. Next, an annealing separator containing magnesium powder as a main component is applied and heated to 1200 ° C. at a rate of 25 ° C./hour in an atmosphere of 85% H ₂ and 15% N ₂ , and then in an H ₂ atmosphere. At 1200 ° C
After soaking for 20 hours, the product was cooled, the annealing separating agent was removed, and the product was obtained by performing tension coating. The magnetic flux density B8 and iron loss W15 / 50 of the product were measured. The coating and the glass coating were then removed and the macrostructure was observed. N and acid soluble Al content of slab and secondary recrystallization situation, B8, W15 / 50
Are shown in FIGS. 1, 2 and 3, respectively.

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

Linear ab: acid-soluble Al (%) = (27/14) × N (%) + 0.0100 (%) That is, N: 0.0050 to 0.0120%, and acid-soluble Al: 0.010
When 0 to {(27/14) × N (%) + 0.0100}%, the secondary recrystallization was found to be complete.

In FIG. 2, the horizontal axis represents the N content, and the vertical axis represents the acid-soluble Al content. In the region shown in the figure, good B8 was obtained in the region surrounded by the straight lines ab, bc, cd, and da.

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

Linear ab: Acid-soluble Al (%) = (27/14) x N (%) + 0.0100 (%) Linear cd: Acid-soluble Al (%) = (27/14) x N (%) + 0.0035 ( %) That is, N: 0.0050 to 0.0100%, and acid-soluble Al: ｛(2
7/14) × N (%) + 0.0035｝ ～ ｛(27/14) × N (%)
At + 0.0100%, it was found that good B8 was obtained.

In FIG. 3, the horizontal axis represents the N content, and the vertical axis represents the acid-soluble Al content. The value of W15 / 50 is indicated by the symbols ○, △, ×. In the figure, in the region surrounded by the straight lines ab, bc, cd, and da, good W15 / 50 was obtained.

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

Linear ab: Acid-soluble Al (%) = (27/14) x N (%) + 0.0100 (%) Linear cd: Acid-soluble Al (%) = (27/14) x N (%) + 0.0035 ( %) That is, N: 0.0050 to 0.0100%, and acid-soluble Al: ｛(2
7/14) × N (%) + 0.0035｝ ～ ｛(27/14) × N (%)
It became clear that good W15 / 50 was obtained at + 0.0100%.

From the results of FIGS. 1, 2 and 3, N: 0.0050 to 0.01
At 00%, acid soluble Al: {(27/14) × N (%) + 0.0035}
When ｛(27/14) × N (%) + 0.0100｝%, secondary recrystallization is complete, and it is clear that good products can be obtained for both B8 and W15 / 50. .

Although the secondary recrystallization is complete, B8 is low in the region where W15 / 50 is defective. That is, low Al,
On the high N side, the secondary recrystallization is stable, but the directionality is poor, and it is 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. AlN
In the present method, which utilizes as a main inhibitor, the secondary recrystallization phenomenon that affects the magnetic flux density and iron loss
4) It is understood that it is strongly influenced by the acid-soluble Al content based on xN (%).

(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: A large number of slabs consisting essentially of Fe are heated at 1370 ° C for 60 minutes, extracted from the heating furnace, and various types of 0.75-3.0m / m It was hot rolled to the thickness. In this case, before the rolling, during the rolling and after the rolling, various cooling conditions were changed, and the amount of NasAlN in the hot-rolled sheet was 0.0001 to 0.0036.
%. Here, AlN is an analysis value of the total thickness of the plate, and the analysis method was a bromine methanol method (all analysis of AlN according to the present invention was by a 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 B8 and the iron loss W15 / 50 of the product were measured.
The coating and the glass coating were then removed and the macrostructure was observed. Fig. 4 and Fig. 5 show the relationship between NasAlN of hot-rolled sheet, cold rolling reduction and secondary recrystallization, and B8 and W15 / 50, respectively.
FIG. 6 and FIG.

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

In FIG. 5, the horizontal axis represents NasAlN content, and the vertical axis represents cold rolling reduction. The value of B8 is indicated by the symbols ○, Δ, ×.
In the area surrounded by ab, bc, cd, and da in FIG.
8 was obtained. That is, it became clear that good B8 was obtained when NasAlN: 0.0005 to 0.0020% and the rolling reduction was 85 to 92%.

In FIG. 6, the horizontal axis is the NasAlN content, and the vertical axis is the cold rolling reduction. The value of W15 / 50 is indicated by the symbols ○, △, ×. Good W15 / 50 was obtained in the area surrounded by ab, bc, cd, and da in FIG. That is, NasAlN: 0.0005-0.0
It was found that good W15 / 50 was obtained when the rolling reduction was 020% and the rolling reduction was 85 to 92%.

From the results of FIGS. 4, 5 and 6, NasAlN: 0.0005
When the rolling reduction was 85-92% and the rolling reduction was 85-92%, it was clarified that the secondary recrystallization was complete and that both B8 and W15 / 50 gave good products.

In the region where W15 / 50 is bad, B8 is low even though the secondary recrystallization is complete.

From the results of Experiment I and Experiment II, using a silicon steel slab containing acid-soluble Al, N, and Sn as a starting material, the sheet thickness was reduced to 0.12 to 0.17 m / m by a one-stage cold rolling method under high pressure accompanied by hot-rolled sheet annealing. In the method of manufacturing a cold-rolled thin unidirectional magnetic steel sheet, N: 0.0050 to 0.0100 for 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 the content of NasAlN in the hot-rolled sheet By conducting hot rolling at 0.0005 to 0.0020%, it became clear that secondary recrystallization is complete and stable production of thin high magnetic flux density unidirectional electrical steel sheets with excellent product magnetic properties is possible. .

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

When manufacturing a thin high magnetic flux density unidirectional magnetic steel sheet with a cold-rolled sheet thickness of 0.17 m / m or less by a single-stage cold rolling method, compared with a case of manufacturing a thick product or a case of manufacturing by a multi-stage cold rolling method, The condition of the microstructure and precipitates after annealing of hot-rolled sheet
It may have a stronger effect. On the other hand, the NasAlN content in the hot-rolled sheet is considered to have a delicate effect on the structural change of the steel sheet and the behavior of precipitates during hot-rolled sheet annealing, and the NasAlN content in the hot-rolled sheet is 0.0005 to 0.0020. %, The most advantageous properties of the steel sheet after hot-rolled sheet annealing will be obtained with respect to the product properties.

The method for controlling the NasAlN content in the hot-rolled sheet to 0.0005 to 0.0020% includes slab heating conditions, rough rolling conditions,
There are finish rolling conditions, cooling conditions after finish rolling, and the like, and any of them may be used.

When either or both of Cu and Sb were added to the material components shown in Experiments I and II, experiments similar to Experiments I and II were performed, and similar results were obtained.

(Experiment III) 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 added and 0.01 to 0.20%, balance: For many slabs substantially consisting of Fe, the steps after hot rolling were performed in the same manner as in Experiment I. Processed and obtained the product. FIG. 7 shows the relationship between the Cu content and iron loss. As is clear from FIG. 7, improvement in iron loss characteristics was observed in the range of Cu: 0.03 to 0.08%.

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 additive and 0.001 to 0.050%, balance: For many slabs substantially composed of Fe, the steps after hot rolling were performed in the same manner as in Experiment I. Processed and obtained the product. FIG. 8 shows the relationship between the Sb content and iron loss. As is clear from FIG. 8, Sb: 0.005 to 0.035%
In the range, the iron loss characteristics were improved.

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

C is preferably 0.060 to 0.120%. If it is less than 0.060% or exceeds 0.120%, the secondary recrystallization becomes unstable.

Si is preferably 2.9 to 4.5%. If it is less than 2.9, good (low) iron loss cannot be obtained, and if it exceeds 4.5%, workability (easiness of cold rolling) is deteriorated.

Mn is preferably 0.050 to 0.090%. If it is less than 0.050% or exceeds 0.090%, the secondary recrystallization becomes unstable.

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

Sn is preferably 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 slab heating, high-temperature heating is required to sufficiently dissolve sulfides and nitrides, and heating at 1300 ° C. or more is desirable.

It is preferable to anneal the hot-rolled sheet at 1030 to 1200 ° C. within 10 minutes. If it is lower than 1030 ° C, good product magnetic properties cannot be obtained, and if it exceeds 1200 ° C, secondary recrystallization becomes unstable. Ten
No improvement in product properties can be expected even after annealing for more than a minute.
Economically disadvantaged. 10 ° C / sec to 60 ° C up to 200 ° C after annealing
/ Sec. At less than 10 ° C./sec, good product magnetic properties cannot be obtained, and at more than 60 ° C./sec, secondary recrystallization becomes unstable. The one-stage cold rolling method is preferable because the production cost is significantly easier than the two-stage cold rolling method. The sheet thickness after cold rolling is
0.12 to 0.17 m / m is preferred. If it is less than 0.12 m / m, the secondary recrystallization becomes unstable and inexpensive, and if it exceeds 0.17 m / m, the expected iron loss value cannot be obtained. During cold rolling, 200-300
Holding at 1 ° C. for 1 to 5 minutes is effective for improving product magnetic properties. During the high-temperature finish annealing, up to at least 1000 ° C
It is preferable to use an atmosphere containing nitrogen. Without nitrogen, secondary recrystallization becomes unstable.

〔Example〕

C: 0.080%, Si: 3.25%, Mn: 0.076%, S: not added, 0.01
5,0.025%, Se: not added, 0.015,0.025%, Sn: 0.13%, N:
0.0045,0.0085,0.0110%, acid soluble Al: 0.0150,0.0170,
0.0230, 0.0260, 0.0300%, Cu: no added, 0.07%, Sb added, 0.020%, balance: A large number of slabs substantially consisting of Fe were heated at 1360 ° C. for 60 minutes, extracted from the heating furnace, 1.0
It was hot rolled to a thickness of 0, 1.31, 2.43 m / m. In this case, the cooling conditions before, during, and after the rolling were variously changed. The NasAlN content of the hot rolled sheet was 0.0002 to 0.0035%.

The hot rolled sheet was annealed at 1120 ° C. for 60 seconds, and then cooled to room temperature at about 35 ° C./second. Pickling of the annealed plate and plate thickness 0.12m / m and 0.1
Cold rolled to 7m / m. Next, decarburization annealing was performed at 850 ° C. for 150 seconds in an atmosphere of 75% H ₂ , 25% N ₂ and a dew point of 65 ° C. Next, an annealing separator containing magnesium powder as a main component is applied and heated to 1200 ° C. at a rate of 25 ° C./hour in an atmosphere of 85% H ₂ and 15% N ₂ , and then in an H ₂ atmosphere. At 1200 ° C
After soaking for 20 hours, the product was cooled, the annealing separating agent was removed, and the product was obtained by performing tension coating. The magnetic flux density B8 and iron loss W15 / 50 of the product were measured. The coating and the glass coating were then removed and the macrostructure was observed. Table 1 shows the results. As is evident from Table 1, only when the N of the slab, the acid-soluble Al content, the NasAlN content of the hot-rolled sheet and the cold-rolling reduction were the conditions of the present invention, the secondary recrystallization was complete and B8 Excellent product was obtained for both W15 / 50.

Further, when the content of Cu and Sb was in the range of the present invention, more excellent product characteristics were obtained.

(Effect of the Invention) Since the present invention is configured as described above, a silicon steel slab containing acid-soluble Al, N, Sn is used as a starting material, and a one-stage cold-rolling method under high pressure accompanied by hot-rolled sheet annealing is used. Board thickness 0.12-0.
In the method of manufacturing thin unidirectional electrical steel sheet cold-rolled to 17m / m, secondary recrystallization is complete and thin high magnetic flux density unidirectional electrical steel sheet with excellent product magnetic properties can be manufactured stably. Became.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the N content (horizontal axis) and the acid-soluble Al content (vertical axis) of a slab and the state of secondary recrystallization (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 B8 (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 W15 / 50 (indicated by ，, ×, etc.) of the product. FIG. 4 is a diagram showing the relationship between the NasAlN content (horizontal axis) and the cold rolling reduction (vertical axis) of the hot-rolled sheet in the state of secondary recrystallization (indicated by ，, ×, etc.). FIG. 5 is a diagram showing the relationship between the content of NasAlN (horizontal axis) and the rolling reduction of the cold rolling (vertical axis) of the hot-rolled sheet and the magnetic flux density B8 (indicated by ○, ×, etc.) of the product. FIG. 6 is a diagram showing the relationship between NasAlN (horizontal axis) and cold rolling reduction (vertical axis) of a hot-rolled sheet and iron loss W15 / 50 (indicated by ，, ×, etc.) of a product. FIG. 7 is a diagram showing the relationship between the Cu content of the slab (horizontal axis) and the amount of change in the iron loss W15 / 50 of the product due to the addition of Cu (vertical axis). FIG. 8 is a diagram showing the relationship between the Sb content of the slab (horizontal axis) and the amount of change in the iron loss W15 / 50 of the product due to the addition of Sb (vertical axis).

Claims (2)

(57) [Claims] (1) C: 0.060 to 0.120% by weight, Si: 2.9 to 4.5% by weight
%, Mn: 0.050-0.090%, S or Se, or both: 0.020-0.060%, Sn: 0.05-0.25%, balance: acid-soluble slab consisting of Al, N, Fe and unavoidable impurities Heated, hot rolled, and annealed the hot rolled sheet within a temperature range of 1030 to 1200 ° C within 10 minutes, and after annealing up to 200 ° C at 10 ° C / sec to 60 ° C
/ Cold rolling at a cooling rate of / second, then cold rolling, the thickness after cold rolling to 0.12 ~ 0.17m / m, decarburizing annealing in a humid atmosphere containing hydrogen, mainly magnesium powder In the method of producing a thin unidirectional electrical steel sheet, performing a high-temperature finish annealing using an atmosphere containing nitrogen, applying an annealing separator to be applied, and raising the temperature to at least 1000 ° C.
N and acid-soluble Al contained in the slab, N: 0.0050 ~
0.0100%, acid soluble Al: ｛(27/14) × N (%) + 0.003
5｝-｛(27/14) × N (%) + 0.0100｝%, and
The thickness of the hot-rolled sheet with a cold rolling reduction of 85 to 92%, and
A method for producing a thin high magnetic flux density unidirectional magnetic steel sheet having excellent product magnetic properties by a single-stage cold rolling method, wherein hot rolling is performed to control the NasAlN content in a hot rolled sheet to 0.0005 to 0.0020%. 2. C: 0.060 to 0.120% by weight, Si: 2.9 to 4.5% by weight
%, Mn: 0.050 to 0.090%, either or both of S and Se: 0.020 to 0.060%, Sn: 0.05 to 0.25%, Cu: 0.03 to 0.0
Either 8% or Sb: 0.005 to 0.035% or both, and the balance: A slab composed of acid-soluble Al, N, Fe and unavoidable impurities is heated at a high temperature, hot-rolled, and the hot-rolled sheet is heated to 1030 to 1200 ° C.
Anneal within 10 minutes within the temperature range of
At a cooling rate of 60 ° C./sec to 60 ° C./sec, and then cold-rolled to a thickness of 0.12 to 0.17 m / m after cold rolling, decarburizing annealing in a humid atmosphere containing hydrogen, Apply an annealing separating agent mainly composed of shear powder.
Perform high-temperature finish annealing using an atmosphere containing nitrogen up to ℃
In the method for producing a thin unidirectional magnetic steel sheet subjected to tension coating, in the slab containing N and acid-soluble Al, N: 0.0050 to 0.0100%, acid-soluble Al: ｛(27/14) × N
(%) + 0.0035｝-{(27/14) × N (%) + 0.0100｝
%, And the thickness of the hot-rolled sheet having a cold-rolling reduction ratio of 85 to 92%, and the NasAlN content in the hot-rolled sheet is 0.0005 to 0.00%.
A method for producing a thin, high magnetic flux density, unidirectional magnetic steel sheet having excellent product magnetic properties by a single-stage cold rolling method, characterized by performing hot rolling at a control of 20%.