JP2002180212A - Magnetic shield material, steel sheet for magnetic shield material and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a technique for economically producing a magnetic shield material of high quality in which the content of P is suppressed as much as possible, and magnetic permeability and coercive force are secured. SOLUTION: The steel sheet has a chemical composition containing, by mass, <=0.005% C, <=0.03% Si, 0.10 to 0.50% Mn, <=0.020% P, <=0.010% S, <=0.002% sol.Al, <=0.0030% N and <=0.030% O, and in which the contents of C, Mn, S, sol.Al and N also satisfy the following formula (1) and inequality (2): NSR= N-14/27×sol.Al...(1), and 5.0<=-(Mn-55/32×S)/(55/12×C+55/14×NSR)<=50...(2). A continuously cast slab is heated to a heating temperature T( deg.C) satisfying the following inequality (3), is hot-rolled under the conditions where finishing temperature is >=750 deg.C, and coiling temperature is >=550 deg.C, is pickled, and is thereafter cold-rolled at a draft of 60 to 90% into a cold rolled steel sheet having a sheet thickness of 0.3 to 0.6 mm, and next, annealing is performed thereto, so that the crystal grain size measured in accordance with JIS G0552 is allowed to satisfy 5.0 to 8.5: T( deg.C)-<=(9020)/(2.929-log[Mn.S])-200...(3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic shield material mounted inside a cathode ray tube such as a color television, a steel plate therefor, and a method of manufacturing the same. Hereinafter, an inner shield incorporating a cathode ray tube as a magnetic shield material will be described as an example.

[0002]

2. Description of the Related Art The basic structure of a cathode ray tube of a color television comprises an electron gun and a phosphor screen for converting an electron beam into an image. An inner surface of the cathode ray tube is provided inside the cathode ray tube in order to avoid the influence of geomagnetism and other external magnetism on the electron beam. A magnetic shield material called a shield is incorporated.

As important characteristics required of this kind of magnetic shield material, the following are mainly required. High permeability in low magnetic fields such as geomagnetism (about 0.35 Oe: Oersted).

[0004] To reduce the coercive force in order to improve the demagnetizing characteristics (synonymous with the reduction of the number of turns and current of the degaussing coil). Excellent heat radiation that can efficiently release the heat inside the CRT during use to the outside.

[0005] Excellent workability that can be adapted to various shapes of the inner shield. Ultra-thin steel sheets having a thickness of 0.1 to 0.25 mm are generally used as the magnetic shield material steel sheets used for the inner shield, and are usually formed into a predetermined inner shield shape and then formed. Blackening treatment on the surface of thin steel sheet
(Blackening annealing). In this case, the blackening treatment is performed on a thin steel sheet in an oxidizing atmosphere such as steam or carbon dioxide.
By heating at 0 to 600 ° C. for 5 to 20 minutes, a blackened film mainly composed of magnetite (Fe ₃ O ₄ ) having a thickness of about 1 to 6 μm is formed on the surface. After the blackening process, the inner shield is required to have desired magnetic properties.

In recent years, there has been an increasing demand for improving the image quality of color televisions, and the DC relative permeability of a DC magnetic field of 0.3 Oe (μ _0.3 ) has been increased to 75 _%.
An invention in which the coercive force Hc at a maximum magnetization force of 10 Oe is 1.2 Oe or less is disclosed in Japanese Patent Application Laid-Open No. 2-61029.

The purpose of reducing the coercive force is to change the orientation of the television.
In order to demagnetize the magnetized magnetism on the shield material,
It is necessary to keep it low. This coercive force Hc
Is μ _0.35Is known to have a strong correlation with
_0.35Is considered to be synonymous with the low Hc.

In order to increase the magnetic permeability and elongation and suppress the coercive force, it is necessary to increase the grain size and suppress carbon in steel as much as possible, as disclosed in JP-A-58-81926 and JP-A-62-280329. As disclosed in each of the publications, a hot-rolled steel sheet made of a low-carbon aluminum-killed steel is pickled, cold-rolled, and
After decarburizing annealing (decarburizing annealing using an open coil), the carbon in steel is reduced to 10 ppm or less by steam decarburization, and then cold rolling under light pressure and box annealing are performed to coarsen the ferrite. Has been used.

Further, as a method that can achieve both high magnetic permeability and stable formation of a blackened film without using OCA decarburizing annealing and without using rimmed steel, vacuum degassing technology developed in recent years has been developed. For example, Japanese Patent Application Laid-Open No. 8-260051 discloses a technique using an extremely low carbon steel with extremely low Al (hereinafter referred to as “non-deoxidized killed steel”) in which Al usage is optimized by steelmaking deoxidation. I have.

[0010] In the technique disclosed herein, undeoxidized killed steel with reduced Al and Si is used, hot-rolled steel sheet is pickled, then annealed, and then cold-rolled and box-annealed twice or more. Introduces a method that uses a cold-rolled steel strip with a coarsened ferrite grain as the raw material, further increases the permeability by performing cold rolling and continuous annealing, suppresses the coercive force, and stabilizes the blackened film. Have been.

This method has a smaller ferrite grain size and is slightly inferior in magnetic properties such as magnetic permeability as compared with a process using OCA decarburizing annealing, but it is an effective method in consideration of production economics. It is considered to be. In addition, in terms of the stability of the blackened film, there is an expectation that the same characteristics as rimed steel can be obtained by using a low-Si, Al undeoxidized killed steel.

However, according to this method, a hot-rolled sheet is annealed for the purpose of coarsening the ferrite grain size, and then cold rolling and box annealing at a light reduction rate in an intermediate step in order to reduce the size of the hot-rolled sheet. Need to be repeated two or more times. Therefore, cold rolling and annealing are required in the process, and many manufacturing steps are required, which is not an economical manufacturing method.

In Japanese Patent Application Laid-Open No. Sho 62-280328, sol.
Al: A method for manufacturing an inner shield from a slab containing a considerably large amount of 0.005 to 0.06% is disclosed.
In this case, it may be difficult to grow ferrite grains or to form a blackened film uniformly.

In Japanese Patent Application Laid-Open No. 9-806285, Cu:
Although there is disclosed an example in which the addition amount of Cu is as extremely high as 0.1 to 1.5%, it is uneconomical and no consideration is given to improving the magnetic permeability.

In addition, Japanese Patent Application Laid-Open No. H10-46249 discloses a manufacturing method in which cold rolling and annealing are repeated three times in order to improve magnetic properties, which may reduce economic efficiency. is there.

Further, Japanese Patent Application Laid-Open No. 2000-169945 discloses Mg
Is contained as an essential component, and the composition has a relatively high Si content of 0.5% or less, but in this case, the stability of the blackened film is deteriorated.

Further, heat radiation from the inside of the cathode ray tube includes
A blackening film is formed on the shield surface to improve the efficiency. In the formation of the blackened film, the composition of steel generally has a great influence. In particular, if oxide-forming elements such as Si and Al are present in the steel component, a large amount of hematite (Fe ₂ O ₃ ) is likely to be generated in addition to magnetite, which may cause the blackening film to peel off in the cathode ray tube .

Hematite is easily produced when steel contains Al and Si. For this reason, rimmed steel in which Al and Si are suppressed is often used.
It is disclosed in publications such as 173219.

[0019]

As means for improving the economical efficiency of such a manufacturing process, Japanese Patent Application Laid-Open No. 2-61029 is based on the premise that an inner shield for a television cathode-ray tube which is the same as the object of the present invention is provided. Discloses a method for producing a steel sheet for a magnetic shield material having a certain degree of magnetic permeability and coercive force by defining an alloy element ratio and a ferrite grain size in an ultra-low carbon steel. However, in this method, in order to improve flatness and the like in the final continuous annealing process, P is added in an amount of 0.1% or more in order to increase strength in advance. This leads to deterioration of workability and the like.

Therefore, if the present inventors suppress the addition of P, the workability as the inner shield can be secured even if the annealing after the final cold rolling is omitted, and an extremely economical manufacturing method can be obtained. It is noted that is established.

An object of the present invention is to develop a technology for ensuring magnetic permeability and coercive force while minimizing P, which degrades workability, and for economically producing a high-quality magnetic shield material. It is to be.

[0022]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted various studies on undeoxidized killed steel in order to improve the magnetic permeability and reduce the coercive force by making the crystal grains coarse. The following findings were obtained.

(1) The grain size before final rolling is determined according to JIS G0552.
Particle size number 5.0 to 8.5 when measured by the comparison method specified in
If cold rolling is performed with the final rolling reduction set in the range of 50 to 80%, blackening treatment (steam or CO ₂ gas) is performed by two cold rollings via intermediate annealing. 560 in
(600 ° C x 5-20 minutes), DC magnetic field 0.35 Oe, relative permeability 750, coercive force 1.25 Oe or less (maximum magnetizing force 10 Oe)
Magnetic properties of

(2) In order to ensure this magnetic property, Mn, Al, S, N are suppressed to a specific value or less on the premise of an ultra-low carbon steel, and Mn, Al, S, N added with C is added. A specific correlation between the alloy components of the steel and the oxides in the steel, Si
O ₂ , MnO and Al ₂ O ₃ have a specific relationship.

(3) For stable generation of a blackened film, Si,
Al, Mn, etc. have a strong affinity for oxygen, so they form oxides during blackening and form blackening unevenness or a blackened film with poor adhesion under or around the oxides. Restrict.

The present invention has been completed based on the above findings.
Here, the present invention is based on the following.
3% or less, Mn: 0.10 to 0.50%, P: 0.020% or less, S: 0.0
10% or less, sol.Al: 0.002% or less, N: 0.0030% or less,
O: contains 0.030% or less, and contains C, Mn, S, sol.
N is a steel sheet for a magnetic shielding material satisfying the following expression.

N _SR = N−14 / 27 × sol.Al... 5.0 ≦ (Mn−55 / 32 × S) / (55/12 × C + 55/14 × N _SR ) ≦ 50. is there.

Further, at this time, the oxides in the steel have a mass ratio of SiO ₂ ≦ 25% and MnO ≧ 70%, with the balance being mainly composed of Al ₂ O _3. , N
A steel sheet for a magnetic shielding material having excellent magnetic properties, characterized in that the total amount of b, W, V and Zr is less than 0.01% by mass ratio.

Further, by adding Sn and / or Sb as needed in a total amount of 0.0002% or more, the grain growth is further promoted, and a steel sheet for a magnetic shield material having excellent magnetic properties can be applied. A preferable range is 0.0050% or less in consideration of brittleness.

According to another aspect of the present invention, a slab is produced by continuously casting molten steel into a slab, and a slab heating temperature is defined as T (° C.), and T (° C.) satisfies the following equation. 750
Hot rolling at a temperature of 550 ° C or higher and a winding temperature of 550 ° C or higher.
After pickling, cold rolling is performed at a rolling reduction of 60 to 90% to a thickness of 0.3
~ 0.6mm cold-rolled steel sheet and then annealed to make JI
A method for producing a steel sheet for a magnetic shielding material having the above-mentioned chemical composition, characterized in that the crystal grain size measured according to SG0552 satisfies 5.0 to 8.5.

[0031] The steel sheet for magnetic shield material manufactured in this way can be press-formed in the state of full hard (unannealed) after cold rolling,
After molding, in an oxidizing atmosphere, such as steam or CO ₂ 560 to 60
The blackening annealing is performed at 0 ° C. for 5 to 20 minutes. At this time, the crystal grain size measured according to JIS G0552 satisfies 6.0 to 9.0.

As a result, the formation of the blackening film, the removal of the internal distortion, and the primary recrystallization are simultaneously performed, and a magnetic shield material having predetermined characteristics such as an inner shield for a color television is manufactured.

According to the present invention, as a material particularly suitable for an inner shield material for a color television, a magnetic shield material having both high magnetic permeability and high workability using the above-described non-deoxidized killed steel, Specifically, a magnetic shield material having a relative magnetic permeability at 0.35 Oe (hereinafter, referred to as a relative magnetic permeability of 0.35 Oe) of 750 or more and a coercive force of 1.25 Oe or less (maximum magnetizing force of 20 Oe) can be obtained. Manufacturing has become possible.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for defining the chemical composition of steel and the like in the present invention as described above are as follows. In this specification, “%” for defining the chemical composition is “% by mass” unless otherwise specified.

Chemical composition of steel: C: As a means for promoting ferrite grain growth for increasing magnetic permeability, C must be suppressed as much as possible. Therefore, in the present invention, the upper limit of the content is set to 0.005%. Desirably, better properties are obtained at 0.002% or less.

Si: It is desirable to suppress Si as much as possible for the stable formation of the blackened film of the inner shield. Therefore, the upper limit of the content is set to 0.03%. Desirably, better properties are obtained at 0.01% or less.

Mn: Mn finely precipitates MnS (Mn-based sulfide) and significantly inhibits ferrite grain growth. In order to promote the growth of ferrite grains, it is necessary to suppress the amount of MnS precipitates and to increase the size of the precipitates.
Is added in an amount of 0.10 to 0.50% in consideration of the content of S that forms Desirably, better properties are obtained at 0.10 to 0.20%.

P: P is inevitably contained in the steelmaking stage. However, if the content is increased, processing cracks may occur when the inner shield, which is the magnetic shield material targeted by the present invention, is processed. is there. Therefore, it is necessary to suppress the content as much as possible. In the present invention, the upper limit is set to 0.020%. Desirably, better properties are obtained at 0.015% or less.

S: S is MnS (Mn-based sulfide) as described above.
Is finely precipitated, and remarkably inhibits the ferrite grain growth.
From this, for the purpose of promoting grain growth of ferrite,
In order to suppress the amount of precipitation of MnS, the content of S is to be suppressed as much as possible. Therefore, the upper limit of the content is set to 0.010%. Desirably, better properties are obtained at 0.003% or less.

Sol.Al: It is desirable that the content of sol.Al is minimized in order to stably form a blackened film of the inner shield. At the same time, AlN precipitated during the annealing process after hot rolling to cold rolling significantly inhibits ferrite grain growth, so it is desirable to suppress precipitation of AlN as much as possible and to make it coarse. For this reason, sol. Al needs to be suppressed as much as possible, and the upper limit is specified to 0.002% in the present invention. Desirably, better properties are obtained at 0.0015% or less.

N: N is sol.Al and Al in steel as described above.
It is necessary to reduce as much as possible because N forms N and hinders ferrite grain growth. Therefore, in the present invention, the upper limit of the addition amount is defined as 0.0030%. Desirably, better properties are obtained at 0.0020% or less.

O (oxygen): Since the target steel of the present invention is an undeoxidized killed steel, O is inevitably contained in the steel. This O inhibits ferrite grain growth, and further adversely affects the forming process of the inner shield product, which is the object of the present invention. For this reason, even if it is inevitably contained, the upper limit is specified as 0.030%. Desirably, better properties are obtained at 0.020% or less, but 0.01% or less.
If it is reduced to 0% or less, Si and sol.Al may be increased, making it difficult to stabilize the formation of a blackened film. Also,
If oxygen is reduced without increasing Si and sol.Al, steelmaking costs will increase. Thus, considering the balance between quality and economy, it is desirable to adjust the oxygen content to 0.010 to 0.020%.

Reason for stipulating the formula: In the steel sheet for a magnetic shielding material, which is an object of the present invention, it is necessary to make ferrite as coarse as possible.

On the other hand, the present inventors not only control the precipitation of MnS, AlN, etc. by adjusting the chemical composition of the steel as described above, but also control C, N, which is assumed to be dissolved in the steel. It has been found that ferrite grows efficiently when there is a specific correlation between the Mn content and the Mn content. As a condition, N _SR defined by the following equation is defined as N in the steel which is in solid solution during annealing, and the following equation is established between C in the steel and Mn in the steel that does not form MnS. In this case, it has been found as an empirical rule that the ferrite grain size tends to become coarse. Therefore, C in steel,
Mn, S, sol. Al, and N were specified to be adjusted to satisfy the following formula.

[0045]Oxide composition: SiO of total oxides present in steel_Two, MnO
 Is in a specific composition ratio, Mn_TwoSiO
_FourTo form a fine oxide of
The present inventors have found that the grain growth is significantly suppressed.
Was. This oxide is 3MnO_TwoO _Three・ 3SiO_TwoSpessortit
e) at a relatively low temperature during continuous casting.
It is thought that it is formed finely.

Therefore, in a preferred embodiment of the present invention, in terms of the balance of oxides in steel, SiO ₂ ≦ 25% and MnO ≧ 70%
Thus, the balance was mainly made of Al ₂ O ₃ . Here, “mainly composed of Al ₂ O ₃ ” means that a substantial part is Al ₂ O 3.
₃ means SiO ₂ --MnO--Al ₂ O
₃ as long as SiO ₂ ≤ 25% and MnO ≥ 70%
There is no particular limitation. However, at this time, Ti and Mg-based oxides also impair the magnetic properties, so that it is desirable to minimize their inclusion in steel.

Further, in order to suppress the formation of nitrides and carbides, it is preferable to limit the total of Ti, Nb, W, V and Zr in the steel to less than 0.01% by weight. In addition, the addition of a small amount of Sn and / or Sb promotes ferrite grain growth and enhances magnetic properties while suppressing oxidation of the surface layer during annealing. Therefore, the total amount of Sn and / or Sb is 0.0002%.
As described above, the addition of preferably 0.0050% or less is effective for the purpose of the present invention.

Specification of crystal grain size: The cold-rolled steel sheet having a thickness of 0.3 to 0.6 mm after box annealing obtained under the conditions according to the present invention has a crystal grain size (a value measured according to JIS G0552) of 5.0 to 8.
It is better to satisfy 5. Fine ferrite grains exceeding 8.5 have a small ferrite grain size after processing into an inner shield and forming a blackened film by appropriate heating, and high magnetic permeability cannot be obtained. On the other hand, for coarse ferrite grains less than 5.0, the economical efficiency is reduced by increasing the box annealing time, or the surface defects are increased by increasing the box annealing temperature. Was defined as above.

Definition of heating conditions: In the hot rolling step, it is necessary to apply appropriate temperature conditions for the purpose of minimizing the precipitation of MnS and AlN that inhibit ferrite grain growth and increasing the size of the ferrite grains. There is. The present inventors have specified that hot rolling should be performed under various temperature conditions, satisfying the following expression, and then hot rolling should be performed at a finishing temperature ≧ 750 ° C. and a winding temperature ≧ 550 ° C.

If the heating temperature exceeds the condition specified by the formula or the finish or winding temperature falls below any one of the specified conditions, the ferrite grain size after cold rolling and annealing, And processed into inner shield,
The ferrite particle size after forming the blackened film by appropriate heating is small, and high magnetic permeability cannot be obtained.

At this time, the condition of the equation for defining the slab heating temperature based on the knowledge of Mn and S and the knowledge of oxide as described above is necessary for the formation of a metal structure and the securing of magnetic properties in the present invention. I found something. However, in order to secure the finishing temperature and the winding temperature required for the present invention, it is desirable to secure 1050 ° C. or more.

[0052] Cold rolling: The obtained hot-rolled steel sheet is pickled and then reduced at a rolling reduction of 60 to 90.
% Cold rolling is performed. The rolling reduction at this time is to obtain a target crystal grain size after annealing described below, and
To ensure a thickness of 0.6mm, it is specified within the above range.

Annealing: Annealing is performed after cold rolling so that the grain size is 5.0 to 8.5 as measured according to JIS G0552. In other words, as long as such a grain size is obtained, Specific annealing conditions and the like are not limited, but generally box annealing may be performed.

Temper rolling: Since the steel sheet that has been subjected to the steps of hot rolling, pickling, cold rolling and annealing under these conditions is thin and soft, the surfaces of the steel sheets in the coil during annealing are thin. May cause a "burn-in" phenomenon in which they adhere to each other, and may cause surface defects. For this reason, it is possible to perform temper rolling before the final cold rolling, and to impart appropriate surface roughness to the steel sheet surface,
This is effective for preventing surface defects in a later step.

That is, the surface roughness of the steel sheet in the rolling direction was RaL
Is 0.4 μm or more, and when the surface roughness in the direction of 90 ° with respect to the rolling direction is defined as RaT, RaL / RaT indicating anisotropy of the surface roughness is 0.8 <RaL / RaT <1.2. As described above, it has been found that the temper rolling can provide a roughness condition suitable for this purpose. At this time, the elongation given by the temper rolling is desirably 0.4 to 1.0% for the purpose of homogenizing the surface roughness and preventing the material from being hardened.

In the case of the present invention, the characteristics as a magnetic shield material are as follows. Assuming that the characteristics of a cathode ray tube of a color television are improved, the relative permeability is 750 or more and the coercive force is 1.25 Oe or less under a DC magnetic field 0.35 Oe after blackening annealing. (Maximum magnetizing force of 20 Oe)
It is assumed that the ferrite satisfies a crystal grain size (a value measured according to JIS G0552) of 6.0 to 9.0.

Further, in order to ensure the quality of the final cold-rolled magnetic shield material such as flatness and surface properties, the surface hardness of the rolling roll in the final cold rolling is Hv.
It is desirable to be 800 or more.

[0058]

Next, the operation and effect of the present invention will be described more specifically with reference to examples. [Example 1] As a test production by converter melting, molten steel having the composition shown in Table 1 was smelted, and a slab of non-deoxidized killed steel degassed under vacuum was subjected to hot rolling. A hot-rolled steel sheet having the thickness shown in FIG.

Next, the hot-rolled steel sheet is pickled, cold-rolled to a sheet thickness of 0.35 mm by variously adjusting the draft according to the thickness of the hot-rolled steel sheet, and then heated at a heating temperature of 670 ° C. Box annealing, elongation 0.
Temper rolling was performed at 5%. At this time, the grain size number of the ferrite structure was measured according to JIS G0552.

Then, after further cold rolling to a thickness of 0.15 mm, each was processed directly into the shape of an inner shield product without annealing, and a stamped ring specified in JIS C2531 was used for each. % CO ₂ gas atmosphere
Blackening annealing was performed at 570 ° C. × 10 minutes.

Regarding the inner shield, the workability was determined based on whether or not the bent portion on each side of the box could secure the curvature 0.5 mmR specified by the design, and evaluated with “O” and “X”. In addition, the uniformity of the coloring state of the blackened film was visually determined, and “good” was evaluated with “○”, and “improper” was evaluated with “x”.

With respect to the ring test piece, the grain size of the ferrite structure after annealing, the magnetic permeability, and the coercive force were measured. At this time, the ferrite grain size after primary annealing is 5.0 to 8.5 measured according to JIS G0552, the ferrite grain size after blackening annealing is also 6.0 to 9.0, and the relative permeability μ at a DC magnetic field of 0.35 Oe.
_0.35 is 750 or more, and the coercive force Hc at the maximum magnetizing force of 20 Oe is 1.
A value of less than 25 Oe was determined as a satisfaction criterion for the purpose of the present invention.

[0063]

[Table 1]

As a result of comparison between the 24 steel types, steel No. 3
C content exceeds the range of the present invention, steel No. 4 Si, steel No. 5,
In No. 6, predetermined magnetic properties cannot be obtained because Mn is out of the range of the present invention. In steel No. 7, N
In o.8, S was steel, in steel No.10 was sol.Al, and in steel no.
In No. 12, predetermined magnetic properties cannot be obtained because O is out of the range of the present invention. Further, in steel Nos. 9 and 14, P exceeds the range of the present invention.
A predetermined shape cannot be obtained at the curvature of the corner. In addition, steel
In No. 11, the chemical composition satisfies the range of the present invention, but the desired magnetic properties cannot be obtained because the value of the formula is out of the specified range of the present invention.

The cold-rolled steel sheets made of other steels and the inner shield satisfied all the conditions targeted by the present invention. [Example 2] Based on the knowledge obtained in Example 1, various degassing conditions in the steelmaking stage were changed for molten steel satisfying the chemical composition of the present invention shown in Table 2.

These steels were prepared by setting the thickness of a hot-rolled steel sheet to 1.6 mm,
The cold-rolled steel sheet was box-annealed at 690 ° C. with a thickness of 0.4 mm, and then temper-rolled at an elongation of 0.5%. At this time, the grain size No. of the ferrite structure was measured according to JIS G0552.

Further, after the thickness of the final cold-rolled steel sheet was set to 0.15 mm, the sheet was processed into a punched ring, blackened and annealed in the same manner as in Example 1, and the grain size No. of the ferrite structure and the magnetic properties were examined. At this time, the cleanliness of inclusions in the steel was measured from the cold-rolled steel sheet after the first cold rolling in accordance with JIS G0555, and the composition ratio of oxides contained as inclusions in the cold-rolled steel sheet was determined. ,
The weight ratio was determined from the residuals extracted with iodomethanol and alkali-treated. The iodomethanol extraction method,
Based on the Iron and Steel Institute of Japan, Steel Analysis Subcommittee, "Extraction, Separation and Quantification of Oxide-Based Inclusions in Steel", January 1987, edited by the Subcommittee for the Analysis of Nonmetallic Inclusions in Steel.

Table 2 shows the correlation between this value and the ferrite structure and magnetic properties. The criteria for determining the ferrite structure and magnetic properties in this example were the same as those in Example 1. In the oxide evaluation, SiO ₂ ≦ 25% and MnO ₂ ≧ 70% were accepted.

[0069]

[Table 2]

In steels Nos. 30, 31, 34 and 36, it was found that SiO ₂ and MnO were out of the range specified in the present invention, and at this time, the ferrite grain size and magnetic properties were out of the range of the present invention. . Therefore, it was confirmed that it is necessary to satisfy the oxide mass ratio defined in the present invention in order to obtain the magnetic properties that are the object of the present invention.

[Example 3] Ti, Nb, V, W, Zr were added to the molten steel which satisfies the chemical composition of the present invention shown in Table 3 which was produced by converter melting.
In addition to analyzing the trace elements that form charcoal and nitrides, these steels were subjected to the same process from hot rolling to final cold rolling as in Example 2, and a punched ring was formed from the treated material. After processing, the same blackening annealing as in Example 2 was performed, and the grain size and magnetic properties of the ferrite structure were examined. At this time, the oxide analysis was performed in accordance with the conditions of Example 2.

Table 3 shows the correlation between this value and the ferrite structure and magnetic properties. At this time, the criteria for determining the ferrite structure and the magnetic characteristics were the same as those in Example 1.

[0073]

[Table 3]

As a result of this investigation, in steels Nos. 39 and 40 in which the sum of Ti, Nb, V, W and Zr exceeded the range of the present invention, the ferrite grain size No after annealing exceeded the range of the present invention. , Magnetic permeability and magnetic properties did not satisfy the target values.

[Example 4] The molten steel satisfying the chemical composition of the present invention shown in Table 4 was prepared by adding Ti, Nb, V, W, Zr
In addition to analyzing the trace elements that form the charcoal of Sn and Sb and nitrides, these steels were subjected to the same process as in Example 2 from hot rolling to final cold rolling. The blanking ring was processed from the material, and the same blackening annealing as in Example 2 was performed, and the grain size and magnetic properties of the ferrite structure were investigated.

The oxide analysis was performed under the same conditions as in Example 2. Table 4 shows the correlation between this value and the ferrite structure and magnetic properties. At this time, the criteria for determining the ferrite structure and the magnetic characteristics were the same as those in Example 1.

[0077]

[Table 4]

In a preferred embodiment of the present invention, the total amount of Sn and Sb is set to 0.1.
0002% or more, but according to the present example, as a result of investigation on the case where Sn and Sb are contained above and below this lower limit, respectively, steel Nos. 42, 43 and 46 are compared with steel Nos. The ferrite grains are slightly coarsened and the magnetic properties are improved.

Example 5 Based on the findings of Example 1, Table 5
For steel Nos. 50 and 51, the relations with the magnetic properties were arranged by changing the hot rolling conditions and the cold rolling conditions.

As an evaluation method, after pickling a hot-rolled steel sheet,
Cold-rolled to the thickness of the cold-rolled steel sheet shown in Table 6,
After cold-rolled steel sheet is box-annealed at 670 ° C, it is cold-pressed to 0.15mm thickness.
The punched ring employed in Example 1 was processed. this
12% CO for ring specimen _Two570 ℃ in gas atmosphere
10 minutes blackening annealing, ferrite structure after blackening annealing
The particle size, magnetic permeability, and coercive force were measured. At this time, the first embodiment
Similarly, relative permeability μ _0.3Is 750 or more and the coercive force Hc is 1.
A value of less than 25 Oe is a criterion for satisfying the purpose of the present invention.
Was.

[0081]

[Table 5]

[0082]

[Table 6]

As a result of the investigation, under the conditions A, E and F, the hot rolling finish temperature or the winding temperature was below the range of the present invention, and under the condition D, the slab heating temperature during hot rolling was reduced according to the present invention. And the grain size of the ferrite structure is too small to satisfy the magnetic properties after blackening annealing. Further, under the condition I, since the hot rolling conditions are out of the range of the present invention, the grain size of the ferrite structure is also fine and the magnetic properties after blackening annealing are not satisfied. Furthermore, under the condition J, the heating temperature exceeds the range of the present invention, and under the condition K, the desired reduction in magnetic properties cannot be obtained because the rolling reduction of the first cold rolling is out of the range of the present invention.

Example 6 Further, in order to prevent abrasion of coil products, the effect of temper rolling after the first annealing was investigated.

As the material, the steel No. 50 used in Example 5 was used.
Using the material cold-rolled and annealed under the conditions shown in Table 7, the temper rolling conditions were changed under the seven process conditions L to R shown in Table 8, and after the final cold rolling, a length of 5 mm or more on the front and back surfaces of the entire coil length was obtained. The case where a scratch was generated was designated as Δ. As a result,
Similarly, as shown in Table 8, the surface roughness anisotropy index RaL / RaT
However, under the conditions L, M, Q and R outside the range of the present invention, flaws corresponding to the judgment were found.

[0086]

[Table 7]

[0087]

[Table 8]

Example 7 Process B used in Example 5
For the cold rolled coils manufactured in accordance with Tables 9 for the steel Nos. 50 and 51 in Table 5 according to C, G and H, the rolling reduction in the final cold rolling as shown in Table 10 was determined by the process S, T, U, V,
The conditions were divided into W and X, and the influence of the reduction on the magnetic properties was investigated.

The annealing conditions, final blackening annealing conditions, and magnetic measurement method in this example are the same as in Example 2. If the rolling reduction of the final cold rolling exceeds the range of the present invention, the ferrite structure after blackening annealing is fine, and predetermined magnetic properties cannot be obtained. Further, the rolling reduction is at the lower limit of the range of the present invention,
The coercive force is increased, and when manufactured at a rolling reduction less than this, predetermined magnetic properties cannot be obtained.

[0090]

[Table 9]

[0091]

[Table 10]

Example 8 In a cold-rolled steel sheet manufactured by an optional process specified in the present invention, the degree of deterioration of flatness after final cold rolling with the increase in elongation and the roll The correlation of hardness was investigated.

The evaluation was made on the flatness at a pressure elongation of 10,000 m. As a result of comparing three types of rolls having different hardnesses, when the surface hardness exceeded Hv800 (converted value from Shore hardness), this value was determined. It was confirmed that the flatness did not deteriorate even when the pressure was extended.

[0094]

[Table 11]

[0095]

Industrial Applicability According to the present invention, economics can be achieved without the use of conventional rimmed steel, the use of OCA decarburizing annealing, the annealing of hot-rolled steel sheets after pickling, and the use of two or more cold rollings. It is now possible to manufacture magnetic shielding materials and steel sheets for magnetic shielding materials that can exhibit excellent magnetic properties.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kei Tsutsumi 1850 Minato, Wakayama City, Wakayama Prefecture Sumitomo Metal Works, Ltd. Inside Wakayama Works (72) Inventor Tsutomu Yoshida 1850 Minato, Wakayama City, Wakayama Prefecture Sumitomo Metal Industries, Ltd.Wakayama Works, Ltd. 72) Inventor Keiichi Yamanaka, 2nd Dejima Nishimachi, Sakai City, Osaka Sumitomo Metal Construction Materials Co., Ltd. Reference) 5E041 AA11 AA19 CA06 HB05 HB07 HB11 NN01 NN06 NN12 NN14 NN17 NN18

Claims (10)

[Claims] (1) In mass%, C: 0.005% or less, Si: 0.03%
Mn: 0.10 to 0.50%, P: 0.020% or less, S: 0.010%
Below, sol.Al:0.002% or less, N: 0.0030% or less, O: 0.0
A steel sheet for a magnetic shielding material containing not more than 30% and having C, Mn, S, sol. Al, and N satisfying the following formula. N _SR = N−14 / 27 × sol.Al ····· 5.0 ≦ (Mn−55 / 32 × S) / (55/12 × C + 55/14 × N _SR ) ≦ 50 ・ ・ ・ 2. The total oxides present in the steel, in mass%,
SiO ₂ : 25% or less, MnO: 70% or more, the balance being mainly Al ₂ O
_{3. The} steel sheet for a magnetic shield material according to claim 1, wherein the steel sheet comprises: 3. The steel sheet for a magnetic shielding material according to claim 1, wherein the total amount of Ti, Nb, W, V, and Zr in the steel is less than 0.01% by mass%. 4. Further, Sn and / or Sb are added in a mass%
The steel sheet for a magnetic shielding material according to any one of claims 1 to 3, wherein the steel sheet contains a total of 0.0002% or more. 5. A slab obtained by continuously casting the molten steel,
T (° C) satisfies the following formula, where slab heating temperature is T (° C), finishing temperature: 750 ° C or more, winding temperature: 550 ° C.
Perform hot rolling under the above conditions, and after pickling, the rolling reduction is 60 to 90.
% By cold rolling to obtain a cold-rolled steel sheet having a thickness of 0.3 to 0.6 mm, and then annealing, whereby the grain size measured in accordance with JIS G0552 satisfies 5.0 to 8.5. A method for producing a steel sheet for a magnetic shield material according to claim 1. 6. The steel sheet surface roughness in the rolling direction after the annealing.
When RaL is 0.4 μm or more and surface roughness in the 90 ° direction relative to the rolling direction is defined as RaT, RaL / Ra indicating anisotropy of surface roughness
The method for producing a steel sheet for a magnetic shield material according to claim 5, wherein temper rolling is performed so that T is 0.8 <RaL / RaT <1.2. 7. The steel sheet according to claim 1, having a sheet thickness of 0.1 to 0.3 mm, and JIS G05 after blackening annealing.
The crystal grain size measured according to 52 satisfies 6.0 to 9.0,
DC magnetic field 0.35 Oe, relative permeability is 750 or more, coercive force is 1.
A magnetic shield material with magnetic properties of 25 Oe or less (maximum magnetizing force 20 Oe). 8. The steel sheet obtained in claim 5 or 6 is further cold-rolled to a sheet thickness of 0.1 to 0.3 mm at a reduction of 50 to 80%, and then directly processed into a target product shape. It satisfies a crystal grain size of 6.0 to 9.0 measured according to JIS G0552 after blackening annealing, and has a DC magnetic field of 0.35.
Oe, relative permeability is 750 or more and coercive force is 1.25 Oe or less
A method for producing a magnetic shield material having magnetic properties of (maximum magnetizing force: 20 Oe). 9. The steel sheet obtained in claim 5 or 6 is further cold rolled to a sheet thickness of 0.1 to 0.3 mm at a reduction of 50 to 80% using a roll having a surface hardness of Hv 800 or more. After the blackening annealing, it satisfies the crystal grain size of 6.0 to 9.0 measured according to JIS G0552, and has a relative magnetic permeability of 750 or more at a DC magnetic field of 0.35 Oe. , Coercive force is 1.25 Oe or less (maximum magnetizing force 20
Oe) A method for producing a magnetic shield material having magnetic properties of: 10. The method according to claim 8, wherein the target product is an inner shield for a CRT of a television.