JPH0768580B2 - High magnetic flux density grain-oriented electrical steel sheet with excellent iron loss - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high magnetic flux density unidirectional electrical steel sheet in which magnetic domain control is performed on the surface of the steel sheet and which is remarkably excellent in iron loss.

(Prior Art) A method is known in which iron loss is reduced by artificially performing magnetic domain control on the surface of a high magnetic flux density unidirectional electrical steel sheet in a direction substantially perpendicular to the rolling direction. That is, JP-A-55-
18566 and JP-A-58-73724, a method of irradiating a laser beam at intervals, JP-A-61-9603
In JP-A-6, a method of forming an intruder at intervals, in JP-A-61-117218, a method of forming grooves at an interval, in JP-A-61-117284,
Japanese Patent Laid-Open No. 62-151511 discloses a method of irradiating a plasma flame at intervals with a method of removing a part of the base iron at intervals and applying a phosphoric acid tension coating.

(Problems to be Solved by the Invention) By applying the artificial magnetic domain control technique described above, it has become possible to considerably improve the iron loss of the high magnetic flux density unidirectional electrical steel sheet.

However, there is an ever-increasing demand for a material having more excellent iron loss and a small variation in iron loss, and it is necessary to further improve the performance of the material.

(Means for Solving the Problem) A high magnetic flux density unidirectional electrical steel sheet having a tension coating and subjected to magnetic domain control treatment in a direction substantially perpendicular to the rolling direction after secondary recrystallization is The present inventors have found that remarkably excellent iron loss can be obtained by limiting the average particle size to a certain range, and completed the present invention.

The background of the invention will be described below.

[Experiment I]

Containing Si3.2%, as an inhibitor, in addition to AlN, Mn
Utilizing one or more of S, MnSe, CuxS, Sn, Sb,
Final cold-rolled sheet thickness is 0.17 mm, decarburization annealing is applied, annealing separator is applied, steel sheet is kept flat and high temperature finish annealing is performed, and annealing separator is removed to obtain various unidirectional properties. We obtain electromagnetic steel sheets, apply tension coating to these steel sheets so that the tension per unit cross-sectional area of the steel sheets is 1.0 kg / mm ^2, and apply energy density of 2.0 J / c to the surface of the steel sheets in the direction perpendicular to the rolling direction.
A magnetic flux density B ₈ (magnetic flux density at a magnetizing force of 800 A / m) and iron loss W15 / 50 were measured by irradiating a pulsed laser at m ² , irradiation width of 0.25 mm, and irradiation interval of 5 m / m. The surface coating is removed, and the grain size in the rolling plane of the secondary recrystallized grains
The average grain size was determined by measuring the direction of the rolling direction and the rolling direction and the direction of 90 ° by the line segment method (the average grain size according to the present invention is based on this method). Average particle size and magnetic flux density B ₈ and iron loss
The relationship of W15 / 50 is shown in Fig. 1.

In Fig. 1, the horizontal axis is the average particle size and the vertical axis is the magnetic flux density.
It is a B _8. The symbol (indicated by ◎ ○ △ ×) indicates iron loss W15 / 50.

As is clear from FIG. 1, it was found that particularly good iron loss was obtained when the average particle size was 11 mm or more and B ₈ was 1.88 T or more.

[Experiment II]

Until the application of the annealing separator, the same method as in Experiment I was applied, and a jig was used to perform high-temperature finishing annealing in a state where the steel sheet was bent to a radius of curvature of 400 mm to remove the annealing separator and remove the steel sheet. After flattening annealing, tension coating and laser irradiation were performed in the same manner as in Experiment I, and the magnetic flux density B ₈ and the average grain size of secondary recrystallized grains were measured. The relationship between the average particle size and B ₈ is shown in FIG. In FIG. 2, the horizontal axis is the average particle size and the vertical axis is B ₈ .

As is clear from FIG. 2, when the high temperature finish annealing is performed with the steel sheet bent, if the average grain size becomes too large, B ₈
Is observed to deteriorate, and when the average particle size exceeds 50 mm
It was found that B ₈ deteriorated significantly. It is estimated from Fig. 1 that when the average grain size exceeds 50 mm, B ₈ deteriorates, and thus iron loss deteriorates.

Since high-temperature finish annealing requires high temperature and a long time, it is usually annealed in a coiled state with the end faces in the vertical direction. In this case, the radius of curvature of the inner circumference of the coil is roughly
It is 400 mm or less. If the radius of curvature of the coil is increased,
The equipment scale becomes large, which is disadvantageous in terms of manufacturing cost.

From the results of Experiment I and Experiment II, high-temperature finish annealing was performed by a usual method of annealing in a coiled state, a tension coating was provided, and after secondary recrystallization, magnetic domain control treatment was performed in a direction substantially perpendicular to the rolling direction. It was clarified that in the high magnetic flux density unidirectional electrical steel sheet subjected to the heat treatment, by limiting the average grain size of the secondary recrystallized grains to 11 to 50 mm, remarkably excellent iron loss can be obtained.

[Experiment III]

C: 0.065%, Si: 3.0%, Mn: 0.075%, S: 0.025%, Acid-soluble Al: 0.0260%, N: 0.0085%, Residual: Silicon steel slab containing elements inevitably mixed at 1350 ° C Heated for 120 minutes, hot rolled to a sheet thickness of 1.1 to 5.0 mm, annealed at 1120 ° C for 2 minutes, cooled to 300 ° C at 30 ° C / sec, cold rolled to a sheet thickness of 0.285 mm, 75 3% at 850 ° C in a humid atmosphere of% H ₂ and 25% N _2.
A decarburization annealing was performed for a minute, an annealing separating agent mainly composed of magnesia was applied, the steel sheet was kept flat, and a high temperature finish annealing was performed. In high temperature finish annealing, the atmosphere during heating is 75%
With H ₂ and 25% N ₂ , the temperature was raised to 1200 ° C. at a heating rate of 15 ° C./hour and annealed at 1200 ° C. for 20 hours in a hydrogen atmosphere. The magnetic flux density B _{8 of the} product and the average grain size of the secondary recrystallized grains were measured, and the relationship between the cold rolling reduction and B ₈ and the average grain size is shown in FIG.

In FIG. 3, the horizontal axis is the cold rolling reduction rate and the vertical axis is B ₈
And the average particle size.

As is clear from FIG. 3, a high magnetic flux density unidirectional electrical steel sheet having an average grain size of 11 to 50 mm and a magnetic flux density B ₈ of 1.88 T or more is obtained in the range of cold rolling reduction of 83 to 92%.

Next, material components and other conditions will be described.

C: 0.12% or less is desirable. If it exceeds 0.12%, decarburization during decarburization annealing becomes difficult. Si: 2.5-4.5% is desirable.
If it is less than 2.5%, good iron loss cannot be obtained, and if it exceeds 4.5%, workability deteriorates.

Mn: 0.030 to 0.200% is desirable. If it is less than 0.030%, the workability deteriorates, and if it exceeds 0.200%, good iron loss cannot be obtained.

The total of one or two kinds of S or Se: 0.01 to 0.06% is desirable. If it is less than 0.01% or exceeds 0.06%, good iron loss cannot be obtained.

Acid-soluble Al: 0.010 to 0.050% is desirable. If it is less than 0.010%, good magnetic flux density cannot be obtained, and if it exceeds 0.050%,
Secondary recrystallization becomes poor.

N: 0.0030 to 0.0100% is desirable. If it is less than 0.0030%, secondary recrystallization will be poor, and if it exceeds 0.0100%, blister defects will occur.

After the hot rolling is completed, at least once before the final cold rolling, from 1050
Good magnetic properties of the product cannot be obtained without annealing and quenching in the temperature range of 1200 ° C.

The tension due to the surface coating (including forsterite) per unit cross-sectional area of the steel sheet shall be 0.7 kg / mm ² or more. If it is less than 0.7 kg / mm ² , good iron loss cannot be obtained. Good core loss characteristics can be obtained with a magnetic flux density of 1.88 T or more at a magnetizing force of 800 A / m. 1.8
If it is less than 8T, good iron loss cannot be obtained.

(Function) The secondary recrystallization has an average grain size of 11 to 50 mm, has a surface coating with a tension per unit cross-sectional area of the steel sheet of 0.7 kg / mm ² or more, and has a magnetic flux density of 1.88 T at a magnetizing force of 800 A / m. As described above, a remarkably excellent iron loss can be obtained with a high magnetic flux density unidirectional electrical steel sheet in which magnetic domain control is artificially performed on the steel sheet surface in a direction substantially perpendicular to the rolling direction.

In the case of the magnetic domain control material according to the present invention, it is considered that the cause of the iron loss deterioration when the average grain size is less than 11 mm is that fine grain boundaries are harmful to the magnetic domain formation pattern that minimizes the iron loss. When high-temperature finish annealing is performed in the bent state of steel sheet (based on industrial products), B ₈ decreases when the average grain size exceeds 50 mm, because the deviation of the Goss orientation from the rolling surface due to flattening annealing after high-temperature annealing, etc. It is considered to be involved.

In the production of the grain-oriented electrical steel sheet utilizing AlN as the main inhibitor, after hot rolling, annealing is performed at least once in the temperature range of 1050 to 1200 ° C. before the final cold rolling, and after this annealing,
By quenching and performing final cold rolling at a reduction rate of 83 to 92%,
When the magnetic flux density B ₈ is 1.88T or more, the average grain size of secondary recrystallized grains is 1
High magnetic flux density unidirectional electrical steel sheet with 1 to 50 mm can be obtained.

(Example) Example 1 C: 0.080%, Si: 3.2%, Mn: 0.075%, acid-soluble Al: 0.0250
%, N: 0.0085%, S: 0.025% or 0.015%, S
e: 0.020%, Sn: 0.12%, Cu: 0.07%, Sb: 0.020%, a silicon steel slab containing at least one selected from the group is heated at 1350 ° C. for 120 minutes and hot rolled, A hot-rolled sheet having a thickness of 0.9 to 4.4 mm was used.

This hot-rolled sheet was annealed at various temperatures of 1000 to 1220 ° C for 100 seconds and cooled to 300 ° C at 35 ° C / second. Then, it was processed by the following manufacturing processes I and II until the final cold rolling.
In the case of manufacturing process I, final cold rolling was performed immediately after hot-rolled sheet annealing.

In the case of manufacturing process II, after hot-rolled sheet annealing, intermediate cold rolling is performed to a specified thickness, annealing is performed at 1000 ° C for 100 seconds, and 300 ° C at 25 ° C /
After cooling in seconds, final cold rolling was performed.

After final cold rolling, 850 ℃ in a humid atmosphere of 75% H ₂ and 25% N _2.
Decarburization anneal for 3 minutes, apply an annealing separator mainly composed of magnesia, and wrap it in a coil with a radius of curvature of about 400 mm,
High temperature finish annealing was performed. In the high-temperature finish annealing, the atmosphere during heating was 75% H ₂ and 25% N ₂ , the temperature was raised to 1200 ° C. at a heating rate of 15 ° C./hour, and annealing was performed in a hydrogen atmosphere at 1200 ° C. for 20 hours. After that, the annealing separator was removed, and the following A, B, C, D
Magnetic domain control treatment by four methods, tension coating,
Annealing etc. were performed.

In method A, the tension per unit cross-sectional area of steel sheet is 1.0 kg /
Tension coating was performed to obtain a surface area of ² mm2, flattening annealing was performed for 30 seconds at 850 ° C also as a coating baking, and the energy density was 2.0 J / cm _{2 on} the surface of the steel sheet in the direction perpendicular to the rolling direction. The pulse laser was irradiated with an irradiation width of 0.25 mm and an irradiation interval of 5 mm.

In method B, after processing in method A, Sb metal powder is applied,
Annealed at 800 ° C for 2 hours.

In the C method, the energy density was 3.0 J / cm ₂ , the irradiation width was 0.2 mm, and the irradiation interval was 5 on the surface of the steel sheet in the direction perpendicular to the rolling direction.
The forsterite layer is partially removed by irradiating it with a pulsed laser at mm, and it is immersed in a 61% nitric acid solution for 20 seconds, and a tension coating is applied so that the tension per unit cross-sectional area of the steel plate is 1.0 kg / mm ^2. 850, which also serves as a coating baking
Flattening annealing was performed at 30 ° C. for 30 seconds.

In method D, gear pitch 8 m / m, gear tip curvature radius 10
Tension coating is performed by introducing strain with a load of 180 kg / mm ² by a gear type roll with 0 μm and blade inclination of 75 ° to the rolling direction, so that the tension per unit cross-sectional area of the steel plate is 1.0 kg / mm ^2. 850, which doubles as the coating baking.
Flattening annealing was performed at 30 ° C. for 30 seconds.

Magnetic flux density after processing by method A, method B, method C or method D
B ₈ and iron loss were measured, and then the surface coating was removed, followed by pickling, and the average grain size in the rolling plane of the secondary recrystallized grains was measured.

Material composition, hot rolled sheet thickness, manufacturing process (I or I
I), soaking temperature of hot-rolled sheet annealing, sheet thickness after intermediate cold rolling, sheet thickness after final cold rolling, final cold rolling reduction, average grain size of secondary recrystallized grains, magnetic domain control method (A , B, C or D), magnetic flux density B ₈ and iron loss are shown in Table 1.

As is clear from Table 1, in the case of the example of the present invention, a high magnetic flux density unidirectional electrical steel sheet having a remarkably excellent iron loss can be obtained.

(Effects of the Invention) According to the present invention, it is possible to supply a material such as an iron core of a transformer having a remarkably low iron loss, and it is possible to significantly reduce energy loss of electric equipment such as a transformer.

[Brief description of drawings]

Fig. 1 shows the average of magnetic flux density B ₈ and secondary recrystallized grains after the magnetic domain control was performed on the surface of the unidirectional electrical steel sheet with tension coating which was subjected to high temperature finish annealing in a flat state. It is a figure which shows the particle size and iron loss W15 / 50 relationship. Fig. 2 shows the secondary magnetic flux density B ₈ of the unidirectional electrical steel sheet in which the steel sheet is bent and subjected to high-temperature finishing annealing, then flattening annealing, tension coating, and the surface of which is subjected to domain control by laser irradiation. It is the figure shown in relation with the average particle diameter of a recrystallized grain. FIG. 3 is a diagram showing the relationship between the final cold rolling reduction and the magnetic flux density B ₈ and the average grain size of secondary recrystallized grains after high-temperature finish annealing of a steel sheet in a flat state.

Claims (1)

[Claims] 1. A method produced by a method known per se using AlN and at least one of MnS and MnSe as an inhibitor,
In a unidirectional electrical steel sheet that has a tension coating that imparts a tension per unit cross-sectional area of 0.7 kg / mm ² or more to the steel sheet, and is subjected to an artificial magnetic domain control treatment, in the rolling plane of the secondary recrystallized grains. A high magnetic flux density unidirectional electrical steel sheet with an average particle size of 11 to 50 mm and a magnetic flux density of 800 A / m or more at 1.88 T or more and excellent iron loss.