JPH07268469A - Sheet material for grain oriented silicon steel sheet with high magnetic flux density - Google Patents

Abstract

PURPOSE:To stably produce a grain oriented silicon steel sheet extremely excellent in magnetic properties by controlling the average diameter (d) of primary recrystallized grains, the fluctuation coefficient (sigma) of diameter, and the texture in a grain oriented silicon steel sheet for transformer, in the steel sheet condition after decarburizing annealing and before finish annealing. CONSTITUTION:In the steel sheet condition after decarburizing annealing and before finish annealing, this steel sheet has a texture which is a crystalline structure having >=15mum average diameter (d) of primary recrystallized grains and <=0.6 fluctuation coefficient (sigma) of diameter and in which the value of [111]/[110], as the ratio between [111] pole density and [110] pole density, is regulated to <=50. By providing these values, the grain oriented silicon steel sheet having high magnetic flux density and extremely excellent in magnetic properties can be stably produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate material produced for a high magnetic flux density unidirectional electrical steel sheet having a highly developed {110} <001> orientation integration degree used as an iron core of a transformer or the like.

[0002]

2. Description of the Related Art Unidirectional electrical steel sheets are mainly used as iron core materials for transformers and other electric equipment, and are required to have excellent magnetic characteristics such as excitation characteristics and iron loss characteristics. Normally, 800A / m is used as the numerical value for the excitation characteristics.
The magnetic flux density B in the magnetic field of B (which is shown below as B ₈ ) is used. Moreover, as a typical numerical value showing the iron loss characteristic,
W _17/50 (iron loss per unit kg when magnetized to 1.7 _{T at a} frequency of 50 Hz) is used. The magnetic flux density is an important controlling factor of the iron loss characteristics, and generally speaking, the higher the magnetic flux density, the better the iron loss. However, if the magnetic flux density becomes too high, the abnormal eddy current loss may increase due to the increase in the size of the secondary recrystallized grains, which may deteriorate the iron loss. On the other hand, iron loss can be improved by controlling the magnetic domains regardless of the secondary recrystallized grains.

The product thickness is also an important controlling factor of iron loss characteristics. By reducing the plate thickness while maintaining the magnetic flux density, the eddy current loss is reduced and the iron loss characteristics can be improved. A unidirectional electrical steel sheet undergoes secondary recrystallization during finish annealing in the manufacturing process to cause {110},
It is obtained by developing a so-called Goss structure having <001> in the rolling direction. Among them, B ₈ ≧ 1.
Those having excellent excitation characteristics of 88T are called high magnetic flux density grain-oriented electrical steel sheets.

Typical methods for producing high magnetic flux density unidirectional electrical steel sheets include Japanese Patent Publication No. 40-15644 and Japanese Patent Publication No. 51-13469 by Taguchi et al. In the former, MnS and AlN were used as the main inhibitors that caused the secondary recrystallization of the Goss structure.
In the latter, MnS, MnSe, Sb, etc. are used. Products based on the above patents are currently produced on a global scale. According to Japanese Examined Patent Publication No. 40-15644, the manufacturing method is characterized by performing hot-rolled sheet annealing and then performing cold rolling once at a cold rolling rate of 80 to 95%.

By the way, in the production of high magnetic flux density unidirectional electrical steel sheet, various factors in each process affect the magnetic properties, so that extremely strict standards are set for each condition in each process. Therefore, a great deal of labor and cost are spent on process control. Nevertheless, it is not uncommon for secondary recrystallization defects whose cause is unclear or defective magnetic properties with low magnetic flux density to occur even after secondary recrystallization. If the above problems of the product can be predicted in the middle of the manufacturing process, that is, in the intermediate product, it is possible to take measures at that time, and it is possible to solve the secondary recrystallization defect or the magnetic characteristic defect. Is.

Takahashi et al., In Japanese Patent Laid-Open No. 182866/1990, paying attention to the average grain size of primary recrystallized grains and the coefficient of variation of diameter in the state after decarburization annealing and before finish annealing, product quality prediction at an intermediate stage. It is said that it is possible to stably produce a grain-oriented electrical steel sheet having excellent magnetic properties by controlling the content within a certain range. However, in the state after decarburization annealing and before finish annealing, even if it has an average particle diameter and a diameter variation coefficient of a certain primary recrystallized particle diameter,
The current situation is that secondary recrystallization defects or magnetic property defects have not been completely resolved.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to avoid such problems and provide a plate material for unidirectional electromagnetic steel having excellent magnetic properties.

[0008]

The features of the present invention are as follows. 1) In the steel sheet state after decarburization annealing and before finish annealing, the average diameter d of the primary recrystallized grains is 15 μm.
A texture having a crystalline structure with a coefficient of variation σ of diameter of 0.6 or less at m or more, and {111} / {110} which is a ratio of {111} polar density to {110} polar density of 50 or less. A plate material for a high magnetic flux density unidirectional electrical steel sheet, which comprises:

The details of the present invention will be described below. The present inventor has improved the final product quality prediction accuracy in the middle manufacturing process of so-called high magnetic flux density unidirectional electrical steel sheet, and as a result of various studies to establish a stable manufacturing technology,
In the steel sheet state after decarburization annealing and before finish annealing, by controlling the average diameter d of primary recrystallized grains and the coefficient of variation σ of the recrystallized grain, and the recrystallized texture within a certain range, the unidirectionality with excellent magnetic properties can be obtained. Succeeded in stable production of electrical steel sheets.

A detailed description will be given below based on experimental results. 1, FIG. 2 and FIG. 3 are obtained from X-ray diffraction and the average diameter d obtained by image analysis from the L-thickness full-thickness structure of the decarburized annealed plate observed with an optical microscope, and the variation coefficient σ of the diameter. Ratio of {111} pole density to {110} pole density {11
It shows the effect of 1} / {110} on the magnetic flux density B _{8 of the} product. Here, in% by weight, C: 0.02
0.06%, Si: 3.2 to 3.3%, acid-soluble Al:
0.01-0.045%, N: 0.003-0.010
%, The balance Fe and unavoidable impurities in the slab 1
After heating to 100 ~ 1300 ℃ and hot rolling to 2.3mm thickness, 9
Hot-rolled sheet is annealed at a temperature of 00 to 1200 ° C, about 88%
The final strong cold rolling was performed to obtain a cold rolled sheet having a final sheet thickness of 0.220 mm. After that, decarburization annealing was performed at a temperature of 800 to 1000 ° C., and subsequently, a primary film forming agent that also serves as an annealing separating agent containing MgO as a main component was applied to perform final finish annealing.

As is apparent from FIGS. 1, 2 and 3, a crystal structure having an average diameter d of 15 μn or more and a diameter variation coefficient σ of 0.6 or less, and having a {111} polar density and a {110} pole density. } The pole density ratio {111} / {11
B ₈ ≧ within a range having a texture in which 0} is 50 or less
A high magnetic flux density of 1.88T is obtained. In addition,
2 and 3 properly control the average grain size d of the decarburized annealed sheet, the variation coefficient σ of the diameter, and {111} / {110} which is the ratio of the {111} polar density to the {110} polar density. It has been shown that it is possible to improve secondary recrystallization and magnetic properties by doing so.

The reason why the above-described relationship is established between the average diameter d of the decarburized annealed sheet, the variation coefficient σ of the diameter, and {111} / {110} and the secondary recrystallization defect of the product and the magnetic flux density B _8. Although it is not always clear about this, the present inventors presume as follows. Factors that influence the secondary recrystallization behavior, including the orientation of secondary recrystallization, include the crystal structure (average diameter, particle size distribution) of primary recrystallization, texture, inhibitor strength, and the like.

After the completion of primary recrystallization, the crystal grain size distribution changes with the growth of crystal grains, so that the average diameter is considered to indirectly represent the crystal grain size distribution. The average diameter is an amount that is inversely proportional to the crystal grain boundary area, and these crystal grain boundary energies serve as the driving force for secondary recrystallized grain growth. Therefore, the average diameter can be considered as a parameter that simultaneously represents the grain size distribution and the grain boundary area, which are considered to influence the secondary recrystallization phenomenon.

The diameter variation coefficient σ represents the nonuniformity of the crystal grain size. If this value becomes high, it is presumed that nucleation of secondary recrystallization and grain growth become difficult and secondary recrystallization failure occurs. It The texture represents the quantitative ratio of crystal orientation,
In the grain-oriented electrical steel sheet, there are mainly oriented grains that undergo secondary recrystallization ({110} <001> grains, etc.) and oriented grains that facilitate secondary recrystallization grains ({111} <112> grains, etc.). is important. For {110} and {111} grains including these orientations, controlling the amount and the quantitative balance enhances the {110} <001> orientation integration degree of the product, that is, the magnetic flux density to improve the magnetic characteristics. It is very important for that. Thus, the average grain size d and the coefficient of variation σ are closely related to the occurrence of defects in secondary recrystallization, and the texture {111} /
The {110} intensity ratio is closely related to the magnetic flux density when the secondary recrystallization is good.

The slab component conditions of the present invention will be described. If C is less than 0.03%, crystal grains may grow abnormally during slab heating prior to hot rolling, which may cause secondary recrystallization defects called linear fine grains in the product, which is not preferable. On the other hand, if the content exceeds 0.15%, decarburization annealing after cold rolling requires a long time for decarburization, which is not economical, and the decarburization tends to be incomplete, resulting in a magnetic aging called magnetic aging in the product. It is not preferable because it causes defects.

Si is an extremely effective element for increasing the electrical resistance of steel and reducing the eddy current loss that constitutes a part of iron loss, but if it is less than 2.5%, the eddy current loss of the product cannot be suppressed. . Further, if it exceeds 4.0%, the workability is remarkably deteriorated and cold rolling at room temperature becomes difficult, which is not preferable.
As an inhibitor constituent element, if necessary, Al, N,
Mn, S, Se, Sb, B, Cu, Bi, Nb, Cr,
Sn and Ti can be added.

Next, the manufacturing method of the present invention will be described. The heating temperature of the slab with the ingredients adjusted as above is:
Although not particularly limited, the cost is 130
It is desirable that the temperature is 0 ° C. or lower. Then, it is rolled into a hot rolled coil by ordinary hot rolling. The hot rolled coil is annealed and pickled if necessary. Then, the final product sheet thickness is obtained by cold rolling once or two or more times with intermediate annealing sandwiched. The final cold rolling rate at this time is not particularly limited, but it is preferably 80% or more in order to increase the magnetic flux density B ₈ . By setting the rolling rate within the above range,
In decarburized and annealed sheet, sharp {110} <001> grains and corresponding oriented grains ({111} <112> that are easily eroded by silkworms)
Granules) can be obtained in an appropriate amount.

After cold rolling, continuous decarburization annealing / primary film forming agent coating, finish annealing, continuous strain relief annealing / secondary film coating and baking are performed. Continuous decarburization annealing before this finish annealing
The average diameter d of the primary recrystallized grains is 15 μm or more, the variation coefficient σ of the diameter is 0.6 or less, and the {111} / {110} strength ratio is 50 or less in the state where the primary film forming agent is applied. The method for controlling the crystal structure and texture in such a state is not particularly limited. For example, a method of adjusting the number of primary recrystallization nuclei and texture by cold rolling rate or grain size before cold rolling, component range of inhibitor constituent elements, slab heating temperature, hot rolling coiling temperature, hot rolled sheet annealing temperature For example, a method of adjusting the inhibitor strength during decarburization annealing to suppress crystal grain growth during decarburization annealing can be adopted. Further, the hot-rolled sheet annealing temperature, the decarburizing annealing temperature, and the temperature rising rate are methods for suppressing the texture.

A primary film-forming agent which also serves the purpose of annealing separation,
There are no particular restrictions on finish annealing, continuous strain relief annealing, secondary coating application, baking, etc., but the proper crystal structure of the decarburized annealed sheet is It is advantageous for stable production to carry out a treatment (for example, nitrification, sulfurization, etc.) such that the inhibitor strength is increased during the final annealing temperature rise so that the growth does not become unsuitable.

Further, in order to obtain a desired crystal structure by decarburization annealing at a relatively low temperature (up to 800 ° C.), the inhibitor strength during decarburization annealing must be lowered, but this inhibitor strength causes secondary recrystallization. When it is insufficient to stably carry out the heat treatment, the above-mentioned inhibitor strengthening treatment in finish annealing is required. As an example of the inhibitor strengthening method, A
A method is known in which the nitrogen partial pressure of the finish annealing atmosphere gas is set high in the steel containing 1 l. Since the cold-rolled sheet subjected to a relatively high cold-rolling rate (90%) lacks {110} grains, in order to obtain the desired texture by decarburizing annealing,
It is necessary to supplement this during decarburization annealing. As an example of such a method, a method is known in which the temperature rising rate during decarburization annealing is set to a high value.

[0021]

【Example】

(Example 1) C: 0.054%, Si: 3.25%, M
n: 0.15%, S: 0.005%, acid-soluble Al:
A slab containing 0.027% and N: 0.0078% was heated at 1150 ° C. and immediately hot rolled to give a hot rolled coil having a thickness of 2.3 mm. The hot rolled coil was annealed at 1150 ° C. to have a cold rolling ratio of about 90% and a thickness of 0.220 mm.

Continuing, 810, 830, 850, 870
Decarburization annealing at 60 ℃ for 60,600sec.
After applying the primary coating / annealing separation agent containing
Finish annealing was performed at 0 ° C. After washing with water, 60mm width x 300
It was sheared to a length of mm, subjected to strain relief annealing at 850 ° C., and then subjected to magnetic measurement. After the decarburization annealing, the average diameter d of the decarburized annealed sheet (total cross-section thickness) and the variation coefficient σ of the diameter were measured using an image analyzer. Moreover, {111} polar density and {110} polar density were measured using an X-ray diffractometer. Table 1 shows the image analysis result, the X-ray diffraction result, the secondary recrystallization rate, and the magnetic flux density.

[0023]

[Table 1]

(Example 2) C: 0.055%, Si:
A slab containing 3.25%, Mn: 0.15%, S: 0.007%, acid-soluble Al: 0.027%, N: 0.0078% was heated at 1150 ° C. and immediately hot-rolled to 1 .8
A hot rolled coil having a thickness of mm was used. The hot rolled coil was annealed at 1100 ° C. to have a cold rolling rate of about 91% and a thickness of 0.170 mm. Then, decarburization annealing at 830,870 ° C. for 70 seconds is performed at a temperature rising rate of 100,30,15.5 ° C./sec, and then a primary coating / annealing separating agent containing MgO as a main component is applied and then 1200 ° C. Finish annealing was performed. 60 mm after washing with water
It was sheared to a width of 300 mm and subjected to strain relief annealing at 850 ° C., and then subjected to magnetic measurement.

After decarburization annealing, the average diameter d of the decarburized annealed plate (total cross-section thickness) and the variation coefficient σ of the diameter were measured using an image analyzer. Moreover, {111} polar density and {110} polar density were measured using an X-ray diffractometer. Table 2 shows the image analysis result, the X-ray diffraction result, the secondary recrystallization rate, and the magnetic flux density.

[0026]

[Table 2]

(Example 3) C: 0.054%, Si:
3.22%, Mn: 0.12%, S: 0.005%, acid-soluble Al: 0.027%, N: 0.0078%, S
n: 11 slabs containing 0.002% and 0.05%
Immediately after heating at 50 ° C., hot rolling was performed to obtain a hot rolled coil having a thickness of 1.4 mm. The hot rolled coil was annealed at 1100 ° C. to have a cold rolling rate of about 90% and a thickness of 0.145 mm. Subsequently, decarburization annealing was performed at 810 ° C. for 70 seconds, then a primary coating / annealing separating agent containing MgO as a main component was applied, and finish annealing was performed at 1200 ° C. After washing with water, it was sheared to a width of 60 mm and a length of 300 mm, subjected to strain relief annealing at 850 ° C., and then subjected to magnetic measurement.

After decarburization annealing, the average diameter d and the variation coefficient σ of the diameter of the decarburized annealed plate (total cross-section thickness) were measured using an image analyzer. Moreover, {111} polar density and {110} polar density were measured using an X-ray diffractometer. Table 3 shows the image analysis result, the X-ray diffraction result, the secondary recrystallization rate, and the magnetic flux density.

[0029]

[Table 3]

(Example 4) C: 0.054%, Si:
3.24%, Mn: 0.10%, S: 0.007%, acid-soluble Al: 0.027%, N: 0.0078%, S
n: 11 slabs containing 0.002% and 0.05%
Immediately after heating at 50 ° C., hot rolling was performed to obtain a hot rolled coil having a thickness of 1.8 mm. Before annealing the hot rolled coil at 1100 ° C 1.
It was cold rolled to 4 mm, and the cold rolling rate was about 90% to a thickness of 0.145 mm. Subsequently, decarburization annealing was carried out at 850 ° C. for 70 seconds, after which a primary coating / annealing separating agent containing MgO as a main component was applied, and finish annealing was carried out at 1200 ° C. After washing with water
It was sheared to a width of 60 mm and a length of 300 mm, subjected to strain relief annealing at 850 ° C., and then subjected to magnetic measurement. After the decarburization annealing, the average diameter d of the decarburized annealed sheet (total cross-section thickness) and the variation coefficient σ of the diameter were measured using an image analyzer. Using an X-ray diffractometer,
The {111} pole density and the {110} pole density were measured. Table 4
Is the image analysis result and X-ray diffraction result and the secondary recrystallization rate,
The magnetic flux density is shown.

[0031]

[Table 4]

(Example 5) C: 0.055%, Si:
3.25%, Mn: 0.10%, S: 0.007%, acid-soluble Al: 0.028%, N: 0.0078%, S
The slab containing n: 0.05% was heated at 1150 ° C. and immediately hot rolled to obtain a hot rolled coil having a thickness of 2.3 mm. The hot-rolled coil was annealed at 1100 ° C., and the cold rolling rate was about 90%.
It was 220 mm thick. Continue to 60 at 830 and 850 ° C
Decarburization annealing is carried out for 0 sec, and then a primary coating / annealing separating agent containing MgO as a main component is applied. N ₂ : 25% +
Finish annealing was performed at 1200 ° C. in an atmosphere gas of H ₂ : 75%, N ₂ : 75% + H ₂ : 25%. After washing with water, 60
mm width × 300 mm length was sheared, strain relief annealing was performed at 850 ° C., and then subjected to magnetic measurement.

After decarburization annealing, the average diameter d of the decarburized annealed plate (total cross-section thickness) and the variation coefficient σ of the diameter were measured using an image analyzer. Moreover, {111} polar density and {110} polar density were measured using an X-ray diffractometer. Table 5 shows the image analysis result, the X-ray diffraction result, the secondary recrystallization rate, and the magnetic flux density.

[0034]

[Table 5]

[0035]

According to the present invention, in the steel sheet state after decarburization annealing and before finish annealing, the average grain diameter d of the primary recrystallized grains is 15 μm or more and the variation coefficient σ of the diameter is 0.6 or less. And having a texture with {111} / {110}, which is the ratio of {111} pole density to {110} pole density, of 50 or less, high magnetic flux density unidirectionality with extremely excellent magnetic characteristics It is possible to stably manufacture an electromagnetic steel sheet.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the average diameter and the magnetic flux density of a decarburized annealed plate.

FIG. 2 is a graph showing the relationship between the diameter variation coefficient and the magnetic flux density of a decarburized annealed plate.

FIG. 3 is a diagram showing the relationship between {111} / {110} and magnetic flux density of a decarburized annealed plate.

Claims (1)

[Claims] 1. In a steel sheet state after decarburization annealing and before finish annealing, the primary recrystallized grains have a crystal structure having an average diameter d of 15 μm or more and a variation coefficient σ of diameter of 0.6 or less, and {111 {11} which is the ratio of the pole density to the {110} pole density
A plate material for high magnetic flux density unidirectional electrical steel sheet, having a texture of 1} / {110} of 50 or less.