JPH0372027A - Production of grain-oriented silicon steel sheet having high magnetic flux density and excellent in iron loss - Google Patents

Abstract

PURPOSE:To produce the silicon steel sheet excellent in iron loss by controlling the average grain size of secondary recrystallized grains to a value in a specific range in a steel sheet of a specific composition to which tension coating is applied and also specific magnetic domain control treatment is applied after secondary recrystallization. CONSTITUTION:A strop of 0.2-10mm thickness having a composition consisting of, by weight, <=0.12% C, 2.5-4.5% Si, 0.030-0.200% Mn, 0.01-0.06%, in total, of S and/or Se, 0.010-0.050% acid-soluble Al, 0.0030-0.0100% N, and the balance Fe with inevitable impurities is cast by a rapid solidification process. Subsequently, after cold rolling, decarburizing annealing, and high-temp. finish annealing are successively performed to form secondary recrystallization grains of 11-50mm average grain size, the resulting steel sheet is subjected to tension coating by 0.7kg/mm<2> coating weight per unit cross-sectional area of the steel sheet, to flattening annealing, and further to artificial magnetic domain control treatment in a direction practically perpendicular to the rolling direction. By this method, the grain-oriented silicon steel sheet having high magnetic flux density and excellent in iron loss can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a high magnetic flux density unidirectional electrical steel sheet with significantly superior iron loss, in which magnetic domain control is applied to the surface of the steel sheet.

(Prior Art) A method is known in which iron loss is reduced by artificially controlling magnetic domains 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
- A method of irradiating a laser beam at intervals, as disclosed in Japanese Patent Application Laid-open No. 18566 and Japanese Patent Application Laid-Open No. 58-73724,
A method of forming intruders at intervals in JP-A-61-96036, a method of forming grooves at intervals in JP-A-61-117218, and a method of forming grooves at intervals in JP-A-61-117284.
A method of removing a part of the steel base and applying a phosphoric acid-based tension-adding coating, and a method of irradiating plasma flame at intervals in Japanese Patent Application Laid-open No. 151511/1983 are disclosed.

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

However, there is an increasing demand for materials with even better iron loss and less variation in iron loss, and there is a need for materials with even higher performance.

(Means for solving the problem) Regarding a high magnetic flux density unidirectional electrical steel sheet that has a tension coating and is subjected to magnetic domain control treatment in a direction approximately perpendicular to the rolling direction after secondary recrystallization, the secondary recrystallized grains are It has been discovered that significantly superior core loss can be obtained by controlling the average particle size within a certain range, leading to the present invention.

The circumstances leading to the present invention will be explained below.

[Experiment■]

Contains 3.2% Si, and in addition to AZN as inhibitors, MnS, MnSe, CuxS, Sn,
Utilizing one or more types of Sb, the final cold-rolled plate thickness is 0.17 mm, decarburization annealing is performed, an annealing separator is applied, and the steel plate is kept in a flat state for high-temperature finish annealing. The annealing separator is removed to obtain various unidirectional electrical steel sheets, and these steel sheets have a tension of 1 per unit cross-sectional area of the steel sheet.
．． 0) Apply a tension coating with cg/mm2, and apply an energy density of 2 to the surface of the steel plate in the direction perpendicular to the rolling direction.
．． OJ/ci, irradiation width 0.25mm, irradiation interval 5I
Irradiated with a pulsed laser at 111!1, magnetic flux density B8 (
iffing force 800 (magnetic flux density in Arm) and iron loss W
IS15° was measured.The surface coating was removed and the grain size of the secondary recrystallized grains in the rolling plane was measured in the rolling direction and in the rolling direction.
The average grain size was determined by measuring the 5° direction, the rolling direction, and the 90' direction using the line segment method (all average grain sizes related to the present invention are determined by this method).The average grain size, magnetic flux density B, and iron loss The relationship between WIS/S is shown in FIG.

In FIG. 1, the horizontal axis is the average particle diameter, and the vertical axis is the magnetic flux density B8. The sign (indicated by ◎○△×) is iron loss W 151
50 is shown.

As is clear from FIG. 1, it has been found that particularly good iron loss can be obtained when the average grain size is 11 mm or more and B is 1.887 or more.

[Experiment■]

The process was carried out in the same manner as in Experiment I until the application of the annealing separator, and a jig was used to perform high-temperature finish annealing with the steel plate bent to a radius of curvature of 400 mm in the rolling direction, and the annealing separator was removed.
The steel plate was flattened and annealed, then subjected to tension coating and laser irradiation in the same manner as in Experiment ①, and the magnetic flux density B and the average grain size of secondary recrystallized grains were measured. The relationship between the average particle diameter and B is shown in FIG.

In FIG. 2, the horizontal axis is the average particle diameter, and the vertical axis is B@.

As is clear from Figure 2, when the steel plate is subjected to high temperature finish annealing in a bent state, if the average grain size becomes too large, B
It was found that Bll deteriorated significantly when the average particle size exceeded 50 mm. When the average grain size exceeds 50 mm, it is estimated from FIG. 2 that B deteriorates and therefore the iron loss deteriorates.

Note that SI/, I finish annealing requires high temperatures and a long time, so it is usually annealed in a coiled state with the end faces between the top and bottom. In this case, the radius of curvature of the inner peripheral portion of the coil is approximately 400 mm or less. Increasing the radius of curvature of the coil increases the scale of the equipment, which is disadvantageous in terms of manufacturing costs.

From the results of Experiments ■ and Experiment ■, high-temperature finishing annealing was performed using the usual method of annealing the coiled state, the tension coating was applied, and after secondary recrystallization, magnetic domain control treatment was performed in a direction approximately perpendicular to the rolling direction. The average grain size of secondary recrystallized grains is 11 to 50
It has become clear that significantly superior iron loss can be obtained by controlling the iron loss to Im.

[Experiment■]

C: 0.065%, Si: 3.0%, Mn: 0.07
5%, S: 0.025%, acid soluble y: 0.0
1 to 5 by rapid solidification of molten steel consisting of 260%, N: 0.0085%, balance diFe and inevitable impurities.
．． A thin slab with a thickness of 0 mm was annealed at 1120°C for 2 minutes,
Cooled to 300°C at 30°C/sec, plate thickness 0.285
The plate was cold-rolled to a thickness of 1.5 mm, decarburized annealed at 850°C for 3 minutes in a humid atmosphere of 75% Hz and 25% N2, and an annealing separator mainly composed of magnesia was applied to flatten the A-plate. Then, high-temperature finish annealing was performed. In high-temperature finish annealing, the atmosphere during heating was 75%N2.25%N2, the temperature was raised to 1200°C at a heating rate of 15°C/hour, and annealing was performed at 1200°C for 20 hours in a hydrogen atmosphere. The magnetic flux density B8 of the product and the average grain size of the secondary recrystallized grains were measured, and the relationship between the cold rolling reduction ratio, B, and the average grain size is shown in FIG.

In Fig. 3, the horizontal axis is the cold rolling reduction ratio, and the vertical axis is the B
II and the average particle size.

As is clear from Figure 3, the cold rolling reduction ratio is 83 to 92%.
Within the range of , the average particle size is 11 to 50 mm, and the magnetic flux density B8 is 1.
．． A unidirectional electrical steel sheet with a high magnetic flux density of 88 T or more can be obtained.

Next, the reasons for limiting the material components and other conditions will be described.

C shall be 0.12% or less. If it exceeds 0.12%, decarburization during decarburization annealing becomes difficult. Si is 2°5~4.5
%. If it is less than 2.5%, good iron loss cannot be obtained;
．． If it exceeds 5%, workability deteriorates. Mn is 0,030
~0.200%. If it is less than 0.030%, workability deteriorates, and if it exceeds 0.200%, good iron loss cannot be obtained. Total of one or two types of S or Se: 0.01-0.
06%. If it is less than 0.01% or more than 0.06%, good iron loss cannot be obtained. Acid soluble M is 0.010~
It shall be 0.050%. 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 is 0.0030% to 0.0100%. If it is less than 0.0030%, secondary recrystallization will be poor, and if it exceeds 0.0100%, blister flaws will occur.

The thickness of the thin slab is 0.2 to 10 mm. 0.2 m
If it is less than 10 mm or more than 10 mm, good magnetic properties cannot be obtained.

1050-1200 at least once before final cold rolling
Good magnetic properties of the product cannot be obtained unless annealing and rapid cooling are performed in the temperature range of °C.

The tension due to the surface coating (including forsterite) per unit cross-sectional area of the steel plate is 7 kg/mm2 or more. 0
．． If it is less than 7 kg/m4, good iron loss cannot be obtained.

Good iron loss characteristics can be obtained when the magnetic flux density at a magnetizing force of 800 Nm is 1.88 T or more. If it is less than 1.88 T, good iron loss cannot be obtained.

(Function) The average grain size of secondary recrystallization is 11 to 50 mm, the surface coating has a tension per unit cross-sectional area of the steel sheet of 0.7 kg/mm2 or more, and the magnetic flux density is 1.8 at a magnetizing force of 800 Nm.
8 T or more, a high magnetic flux density unidirectional electrical steel sheet in which magnetic domains are artificially controlled in a direction substantially perpendicular to the rolling direction on the surface of the steel sheet can provide significantly superior iron loss.

The reason why the core loss deteriorates when the average grain size is less than 11 mm is considered to be that, in the case of the magnetic domain control material according to the present invention, fine grain boundaries are harmful to the magnetic domain formation pattern that minimizes the core loss. When a steel plate is subjected to high-temperature finish annealing in a bent state (industrial product basis), the reason why B decreases when the average grain size exceeds 50++n++ is due to deviation of the Goss orientation from the rolled surface due to flattening annealing after high-temperature annealing. It is thought that they are involved.

In the production of unidirectional '1ilt magnetic steel sheets using rapidly solidified thin cast slabs and using AZN as the main inhibitor, it is rolled at least once to
By annealing in a temperature range of 1200 ° C., rapid cooling after this annealing, and final cold rolling at a reduction rate of 83 to 92%,
When the magnetic flux density B is 1.88 T or more, a magnetic steel sheet with high magnetic flux density unidirectionality in which the average grain size of secondary recrystallized grains is 11 to 50 flll111 can be obtained.

(Example) Example 1 C: 0.080%, Si: 3.2%, Mn: 0.075
%, acid soluble A7: 0.0250%, N: 0.
0085%, and S: 0,025% or 0.015%
, Se: 0.020%, Sn: 0.12%, Cu:
1 selected from 0.07%, sb:o, o2o%
Thin slabs with a thickness of 0.9 to 4.4 mm were produced by a rapid solidification method from molten steel consisting of a seed or two or more, the balance being Fe and unavoidable impurities.

This thin slab was heated at various temperatures from 1000 to 1220℃ for 10
Annealed for 0 seconds and cooled to 300°C at 35°C/second. Thereafter, the following manufacturing process (■■) was performed until the final cold rolling. In the case of manufacturing process I, final cold rolling was performed immediately after annealing.

In the case of manufacturing process (■), after annealing, perform intermediate cold rolling to a specified thickness, annealing at 1000°C for 100 seconds, and then rolling at 300°C.
The sample was cooled at a rate of 25° C./sec until final cold rolling.

After the final cold rolling, decarburization annealing was performed at 850°C for 3 minutes in a humid atmosphere of 75% N2. It was rolled into a shape and subjected to high temperature finish annealing. In high-temperature finish annealing, the atmosphere during heating was 75% Hz and 25% N2, and the temperature was raised to 1200°C at a heating rate of 15"C/hour.
It was annealed at 1200° C. for 20 hours in a hydrogen atmosphere. after that,
The annealing separator was removed, and magnetic domain control treatment, tension coating, annealing, etc. were performed using the following four methods A, B, C, and D.

In method A, the tension per unit cross-sectional area of the steel plate is 1.0
Tension coating is applied so that it is kg/mm2,
In addition to baking the coating, flattening annealing was performed at 850°C for 30 seconds, and the surface of the steel plate was given an energy density of 2. OJ/ctA, irradiation width 0.
Pulse laser irradiation was performed at a distance of 25 mm and an irradiation interval of 5M.

In method B, after processing in method A, sb metal powder was applied and annealed at 800°C for 2 hours.

In method C, an energy density of 3. OJ/ctll, irradiation width 0.2
The steel plate was irradiated with a pulsed laser at an irradiation interval of 5 to partially remove the forsterite layer, and immersed in a 61% nitric acid solution for 20 seconds, so that the tension per unit cross-sectional area of the steel plate was 1.0 kg/
Tension coating was performed so that the thickness was 2 mm2, and flattening annealing was performed at 850° C. for 30 seconds to also bake the coating.

In the D method, gear pitch is 8M, gear tip curvature radius is 1
Strain was introduced with a load of 180 kg/mj using a gear-shaped roll with a blade angle of 75° to the rolling direction, and the tension per unit cross-sectional area of the steel plate was 1.0 kg/mj.
Tension coating was performed so that the thickness was 2 mm2, and flattening annealing was performed at 850° C. for 30 seconds to also bake the coating.

After processing by method A, method B, method C, or method D, the magnetic flux density B and iron loss are measured, and then the surface coating is removed,
After pickling, the average grain size of the secondary recrystallized grains in the rolling plane was measured.

Material composition, thin slab thickness, manufacturing process (■ or ■), soaking temperature for thin slab annealing, plate thickness after intermediate cold rolling.

Sheet thickness after final cold rolling, rolling reduction ratio of final cold rolling, average grain size of secondary recrystallized grains, magnetic domain control method (A, B, C or D>).

The magnetic flux density BS+Si is shown in Table 1.

As is clear from Table 1, in the case of the examples of the present invention, high magnetic flux density unidirectional electrical steel sheets with significantly excellent core loss can be obtained.

(Effects of the Invention) According to the present invention, it is possible to supply materials such as iron cores of transformers with extremely low iron loss, and energy loss of electrical equipment such as transformers can be significantly reduced.

[Brief explanation of drawings]

Figure 1 shows the average magnetic flux density B and secondary recrystallized grains after controlling the magnetic domain by laser irradiation on the surface of a unidirectional electrical steel sheet with a tension coating that has been annealed at high temperature in a flat state. Particle size and iron loss WIS/S. FIG. Figure 2 shows the magnetic flux density B of a unidirectional electrical steel sheet, which has been bent and subjected to high-temperature finish annealing, flattened annealed, tension coated, and magnetic domain controlled by laser irradiation on the surface. FIG. 3 is a diagram showing the relationship with the average grain size of secondary recrystallized grains. Figure 3 shows the final cold rolling reduction and the magnetic flux density B after high temperature finish annealing of the steel plate in a flat state. FIG. 2 is a diagram showing the relationship between the average grain size of secondary recrystallized grains and secondary recrystallized grains. Figure 1, 30 40 50 Average grain size (ynyn)

Claims (1)

[Claims] By weight, C: 0.12% or less, Si: 2.5-4.5%
, Mn: 0.030-0.200%, Total of one or two of S or Se: 0.01-0.06%, Acid-soluble N:
0.010-0.050%, N: 0.0030-0.0
Molten steel consisting of 100%, balance: Fe and unavoidable impurities is made into thin slabs of 0.2 to 10 mm (
An annealing step of annealing and quenching at a temperature range of 1050 to 1200°C at least once before final cold rolling, and final cold rolling with a rolling reduction of 83 to 92%. The rolled surface of the steel plate of secondary recrystallized grains is removed by a process consisting of a decarburization annealing process on the final cold-rolled sheet, a decarburization annealing process in which an annealing separator is applied and coiled to form a strip coil, and a high-temperature finishing annealing process. The average particle size within 11
~ 50 mm, then remove the annealing separator, apply tension coating to 0.7 kg/mm^2 or more per unit cross-sectional area of the steel plate, and flatten annealing, and further, after the high-temperature finish annealing step or after the annealing. A process in which artificial magnetic domain control treatment is applied to the surface of the steel plate during, before, or after the process of removing the separating agent, applying tension coating to 0.7 kg/mm^2 or more per unit cross-sectional area of the steel plate, and flattening annealing. Magnetizing force of 800A characterized by adding
A method for producing a high magnetic flux density unidirectional electrical steel sheet having a magnetic flux density of 1.88 T or more at /m and excellent iron loss.