JP3275291B2 - Method of manufacturing magnetic shield material having high magnetic permeability and high ductility - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube (Cathode-RayTub) which is usually called a cathode ray tube.
The present invention relates to a method for producing a magnetic shield material having high magnetic permeability and high ductility to be mounted inside e).

[0002]

2. Description of the Related Art In general, a funnel-shaped magnetic shield member is provided inside a color cathode-ray tube in order to prevent geomagnetic or other externally disturbing magnetic fields from affecting an electron beam. A ferromagnetic steel plate (steel strip) used as a material of the magnetic shield member has a geomagnetism (about 0.35O).
e: high magnetic permeability in a low magnetic field such as Oersted), good molding workability, high heat emissivity to effectively radiate the heat generated during use of the color cathode ray tube to the outside, and It is required that the gas emission is small.

[0003] In recent color cathode ray tubes, applications for still images are increasing in addition to uses as displays for moving images. Since the picture tube for a still image is more affected by an external magnetic field such as terrestrial magnetism than that for a moving image, the magnetic shield member mounted inside the picture tube has a higher relative permeability (below 0.35 Oe). ) Is being demanded.

Conventionally, a magnetic shield material for a picture tube has been manufactured by, for example, the following method in order to obtain a material having a high magnetic permeability. That is, a continuous cast slab of low carbon aluminum killed steel is hot-rolled, pickled and then cold-rolled, and decarbonized by open coil annealing (OCA decarburized annealing) to obtain an extremely low carbon of 0.001% or less. And then the reduction rate is 1
A magnetic shield material was manufactured by a method of performing a coarse graining treatment (grain number: about 1) by batch annealing after secondary cold rolling under light pressure of about 0%, and then performing final cold rolling. .

[0005] Next, the above-mentioned magnetic shield material is formed into a shape of a predetermined magnetic shield material for a picture tube, and then the magnetic shield material is heated at 650 to 800 ° C in a reducing atmosphere at 30 to 6 ° C.
Magnetic annealing is performed to recover and improve the magnetic properties by heating for 0 minutes. Thereafter, the surface of the magnetic shield material is subjected to a blackening treatment to prevent rust and improve the thermal emissivity. The blackening process is
For example, by heating the magnetic shield material at 560 to 600 ° C. for 5 to 20 minutes in a humid atmosphere such as steam-added air and / or an oxidizing gas atmosphere such as carbon dioxide, about 1 to 6 μm of magnetite (Fe
A blackening film mainly composed of ₃ O ₄ ) is formed.

It is generally known that the formation of a blackened film on the surface of a magnetic shield material is largely affected by the composition of steel. In particular, when oxide-forming elements such as Si and Al are present in steel, hematite (Fe ₂ O ₃ ) is easily generated in addition to magnetite, and the structure of the blackened film is coarse.
It tends to lack denseness, and the blackened film may be peeled off in the picture tube. For this reason, in a conventional method for manufacturing a magnetic shield material, for example, Japanese Patent Application Laid-Open No. 59-173219
JP-A-59-172431, Japanese Patent Publication No.
As disclosed in Japanese Patent Publication No. 13730, many devices using rimmed steel have been proposed.

On the other hand, in recent years, the steelmaking method has shifted from the steel ingot method to the continuous casting method, which is easy in cost, due to the development of steelmaking technology and the rationalization of the ingot making method. Limited. For this reason, the manufacture of a magnetic shield material using rimmed steel is becoming increasingly difficult. Moreover, there is a problem that a magnetic shield material using rimmed steel does not have sufficient performance as a magnetic shield material for a picture tube. Further, in the case of manufacturing a magnetic shield material using rimmed steel, it is necessary to perform a decarburization treatment by a so-called open coil annealing method in an intermediate step, so that an increase in cost is inevitable.

On the other hand, in the production of the above-mentioned conventional magnetic shield material for a picture tube using aluminum-killed steel by open coil annealing, decarburization treatment by open coil annealing, cold rolling under light pressure, grain coarsening annealing, cold Since the rolling process involves a series of complicated processes, such as a rolling process, there is a problem that a normal cold-rolled steel strip manufacturing process may be significantly hindered, and the cost may be increased. In addition, since the crystal grains of the picture tube magnetic shield material are coarse, they cannot withstand strong processing, and as a result, there is a problem that the processing method of the inner shield material is also limited. There was a problem that the structure was coarse and the denseness was poor.

In recent steelmaking methods, advances in vacuum degassing technology and optimization of the amount of Al used for steelmaking deoxidation have led to
It has become possible to obtain a very low carbon killed steel (hereinafter, referred to as “non-deoxidized killed steel”) containing little Al by a continuous casting method. This non-deoxidized killed steel does not need to be decarburized by the open coil annealing method, and the billet as a raw material can be manufactured by continuous casting with high production efficiency. In addition, the magnetic shield material can be manufactured at low cost.

[0010]

The undeoxidized killed steel does not require the decarburization treatment by the open coil annealing method, whereas the rimmed steel does not require the decarburization treatment by the open coil annealing method. The carbon content is larger than that of rimed steel that has been decarburized by the annealing method. For this reason, in the case of non-deoxidized killed steel, in the same manufacturing process as that of rimed steel subjected to decarburization treatment by open coil annealing, crystal grains are refined and the relative magnetic permeability is reduced by open coil annealing. It is inferior to that produced from charcoal-treated rimmed steel.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a magnetic shield material suitable for a magnetic shield for a picture tube without using aluminum-killed steel which hinders the adhesion of a blackening film, and Relative permeability equal to or higher than that of rimed steel decarburized by open coil annealing can be obtained without decarburization by open coil annealing which leads to cost increase like rimed steel, and excellent workability It is an object of the present invention to provide a method of manufacturing a magnetic shield material having high magnetic permeability and high ductility, which can manufacture a magnetic shield material at a low cost.

[0012]

In order to achieve the above object, the present inventor has used non-deoxidized killed steel and has both high magnetic permeability and high workability suitable for an inner shield material such as a picture tube. Magnetic shield material, specifically, relative permeability at 0.35 Oe (hereinafter referred to as “relative permeability (0.35 Oe)”)
Using a No. 13B test piece of a metal material tensile test specimen having a JIS of 1000 or more and specified in JIS Z 2201
Various tests were conducted to produce a magnetic shielding material having a tensile elongation of 35% or more as measured by a metal material tensile test method specified in Z 2241. As a result, the following findings were obtained. (1) Since the magnetic permeability is significantly reduced by temper rolling performed to improve flatness and finish after annealing of a cold-rolled steel strip, for example, the relative magnetic permeability (0 .35 Oe) In order to obtain 750 or more, the relative magnetic permeability (0.35 Oe) immediately after annealing must be 1000 or more. (2) Relative permeability immediately after annealing (0.35 Oe) 100
As shown in FIG. 2, a high magnetic permeability of 0 or more must be obtained on the coarse grain side having a recrystallized grain size of 7.5 or less specified in the method for testing ferrite grain size of steel according to JIS G 0552. (3) High elongation with a tensile elongation of 35% or more as measured by a metal material tensile test method specified in JIS Z 2241 using a metal material tensile test specimen No. 13B specified in JIS Z 2201 is shown in FIG. As shown, the recrystallized grain size must be obtained on the fine grain side having a grain size number of 6.5 or more specified in the ferrite grain size test method for steel of JIS G 0552. (4) Such an ideal recrystallized grain size is determined by the rolling reduction in the intermediate cold rolling before the final cold rolling and the rolling reduction in the final cold rolling, and is not necessarily decarburization treatment by the open coil annealing method. And can be adjusted by the cold rolling schedule.

[0013] Based on the above findings, the present applicant has developed C:
0.005% or less, Si: 0.03% or less, Mn: 0.
15-0.5%, Al: 0.003% or less, S: 0.0
An undeoxidized killed steel containing 1% or less, with the balance being Fe and unavoidable impurities, is converted into a slab by continuous casting.
After subjecting this slab to normal hot rolling, 720 ° C.
When hot-rolled sheet annealing is performed in the range of 850 ° C. and then cold rolling is performed twice or more with intermediate annealing interposed, the crystal grain size after intermediate annealing before final cold rolling is determined by the grain size number (JIS G0552).
Particle size number when measured by the comparison method specified in Section 4.0)
After adjusting to 6.0, final rolling reduction 40% to 75%
It has been found that a magnetic shield material having excellent relative magnetic permeability can be manufactured by cold rolling at a ratio of 0.1%.
Patent application No. 67440.

According to the method disclosed in Japanese Patent Application No. 7-67440, in order to perform hot-rolled sheet annealing, if a relative magnetic permeability μ ≧ 1000 at 0.35 Oe is to be obtained, ultra-coarse graining is required. Therefore, it is difficult to ensure ductility because the product is mixed. Further, in the method disclosed in Japanese Patent Application No. 7-67440, the adjustment of the crystal grain size can be finally performed only by the rolling reduction in the cold rolling, so that a variation occurs.

As a result of further study, the inventor of the present invention has found that, after hot rolling a continuous cast slab of undeoxidized killed steel, two or more times of intermediate annealing are performed without performing hot-rolled sheet annealing. When performing cold rolling, the rolling reduction is 2 before the final cold rolling.
After intermediate cold rolling at 0 to 50% and intermediate annealing, final cold rolling at a reduction ratio of 40 to 75% and then finish annealing can be performed to control the grain size number to 6.5 or more and 7.5 or less,
It has been confirmed that a high elongation of 35% or more in tensile elongation can be ensured and a high magnetic permeability of not less than 1,000 (0.35 Oe) immediately after annealing can be obtained.

The method for producing a magnetic shield material of the present invention comprises:
C: 0.005% or less, Si: 0.03% or less, Mn:
0.15 to 0.5%, Al: 0.003% or less, S:
An undeoxidized killed steel containing 0.01% or less, with the balance being Fe and unavoidable impurities, is made into a slab by continuous casting, and this slab is subjected to ordinary hot rolling, and then subjected to intermediate annealing twice. In performing the above cold rolling, before the final cold rolling, intermediate cold rolling is performed at a reduction rate of 20 to 50% and intermediate annealing is performed, and then final cold rolling is performed at a reduction rate of 40 to 75%, and then finish annealing is performed. And Thus, C: 0.0
05% or less, Si: 0.03% or less, Mn: 0.15 to
An undeoxidized killed steel containing 0.5%, Al: 0.003% or less, S: 0.01% or less, and the balance being Fe and unavoidable impurities is formed into a slab by continuous casting. After hot rolling, and intermediate annealing
When performing cold rolling more than once, before the final cold rolling, intermediate cold rolling is performed at a reduction rate of 20 to 50% and intermediate annealing is performed, and then final cold rolling is performed at a reduction rate of 40 to 75%, and then finish annealing is performed. This makes it possible to reduce the recrystallized grain size after finish annealing to JIS G0.
552 can be controlled to a grain size number of 6.5 or more and 7.5 or less specified in the ferrite crystal grain size test method, and the tensile elongation is 35
% Or more, and a high magnetic permeability of not less than 1000 (0.35 Oe) relative permeability immediately after annealing can be obtained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a method of manufacturing a magnetic shield material according to the present invention is shown in FIG.
005% or less, Si: 0.03% or less, Mn: 0.15
0.5%, Al: 0.003% or less, S: 0.01%
An ultra-low carbon steel slab containing the following, with the remainder being continuously cast undeoxidized killed steel consisting of Fe and unavoidable impurities,
After performing normal hot rolling to form a hot-rolled steel strip, cold rolling is performed two or more times (three times in FIG. 1) with intermediate annealing therebetween.
At that time, before the final cold rolling, intermediate cold rolling is performed at a reduction ratio of 20 to 50% and intermediate annealing is performed. After final cold rolling is performed at a reduction ratio of 40 to 75%, finish annealing is performed to obtain a material having a predetermined thickness. As a result, a material having a predetermined thickness excellent in magnetic properties and ductility from which internal strain has been removed can be obtained. The cold rolling step may be performed three times or more with the intermediate annealing interposed therebetween, or may be subjected to temper rolling for improving flatness and finish between both the final annealing step and the forming step.

The material thus obtained is then formed into a predetermined magnetic shielding material such as an inner shield for a picture tube, as shown in FIG. 1, and further processed in an oxidizing atmosphere such as water vapor or CO _2. By performing the blackening process, a blackened film is formed on the surface of the magnetic shield material and the internal strain is removed. In this case, in the present invention, by adjusting the rolling reduction in the intermediate cold rolling before the final cold rolling and the final cold rolling as described above, the recrystallized grains having an appropriate grain size in the subsequent intermediate annealing and final annealing. And the relative magnetic permeability (0.35 Oe) 1 after the blackening treatment
000 or more can be secured. The magnetic shield material manufactured in this manner is not subjected to decarburization by the open coil annealing method, but is not subjected to the subsequent blackening treatment, but to the killed steel decarburized by the open coil annealing method or to the open coil annealing method. A magnetic shield material for a picture tube that surpasses the magnetic properties of a magnetic shield material manufactured from decarburized rimmed steel and at the same time has a high degree of workability can be obtained.

Further, in the present invention, the use of undeoxidized killed steel in which Si, Mn, Al and the like having a strong affinity for oxygen are limited to a predetermined value or less, as a raw material,
Since no oxide such as hematite is formed during the blackening treatment, blackening unevenness and a blackened film with poor adhesion are not formed below or around the magnetic shield material.

In the present invention, the reason why the steel component is limited to the above range is as follows. If the content of C is large, it inhibits the growth of recrystallized grains and lowers the magnetic permeability.
It must be: Si is a major component of non-metallic inclusions, and the presence of the non-metallic inclusions degrades magnetic properties and the adhesion of the blackened film. From 0.03% or less, since it is unavoidable to mix them in from water. If Mn is less than 0.15%, hot brittleness occurs, making it difficult to perform hot rolling.
The steel strip is hardened exceeds, the press formability is deteriorated, hematite (Fe ₂ O ₃₎ is generated blackened film, as it reduces the adhesion was from 0.15 to 0.5%. If the content of Al is large, it inhibits the growth of crystal grains during the blackening treatment, adversely affects the magnetic properties, and deteriorates the adhesion of the blackened film. S is sulfide-based inclusion
As in the case of i, the magnetic properties tend to deteriorate, and the hot workability also deteriorates.
% Or less.

Further, in the present invention, the rolling reduction in the intermediate cold rolling before the final cold rolling is set to 20 to 50%,
If it is less than 20%, ultra-coarse grains are generated by intermediate annealing, and the recrystallized grains have a large mixed grain size of coarse grains and fine grains, and it is difficult to secure ductility even if the rolling reduction in the final cold rolling is adjusted no matter how much. Also, if it exceeds 50%, the recrystallized grains will be fine and it will be difficult to secure the magnetic permeability, regardless of how the rolling reduction in the final cold rolling is adjusted. The rolling reduction in the intermediate cold rolling before the final cold rolling is desirably 30 to 40%.

Further, in the present invention, the reduction ratio in the final cold rolling is set to 40 to 75%. If the reduction ratio is less than 40%, the intermediate annealing is performed by adjusting the reduction ratio in the intermediate cold rolling before the final cold rolling. Even if the recrystallized grains are appropriately uniform, the recrystallized grains in the final annealing become coarse grains, making it difficult to ensure ductility. If it exceeds 75%, conversely, the recrystallization in the final annealing This is because the grains become fine and it becomes difficult to secure magnetic permeability.

[0023]

【Example】

Example 1 Undeoxidized killed steel having the chemical composition shown in Table 1 subjected to vacuum degassing in the steelmaking stage was continuously cast into a slab, the heating temperature in hot rolling was as low as possible, and the finishing temperature was the transformation point. Thereafter, it was hot-rolled at about 800 ° C. and wound up at about 600 ° C. to obtain a hot-rolled steel strip having a thickness of 2.30 mm. As shown in Table 2, this hot-rolled steel strip was subjected to a primary cold rolling, a primary continuous annealing, an intermediate cold rolling, an intermediate box annealing, a final cold rolling, and an intermediate cold rolling in a cold rolling process including a final continuous annealing. The rolling reduction is 10
Cold rolling was performed while changing the rolling rate to 60% to obtain a very low carbon cold rolled steel strip having a thickness of 0.15 mm. From each of these extremely low carbon cold rolled steel strips,
A specified ring test piece (outer diameter: 45 mm, inner diameter: 33 mm) was punched out from an iron-nickel magnetic alloy plate and a strip of IS C 2531, and CO ₂ : 12%, the remaining nitrogen,
After subjecting to a blackening treatment at 590 ° C. for 10 minutes in an atmosphere composed of hydrogen and CO, the relative magnetic permeability (0.
35Oe), a thermal emissivity measurement at a temperature of 90 ° C., and a test for the peeling resistance of the blackened film were performed. In addition, a specified No. 13B test piece was cut out from each ultra-low carbon cold rolled steel strip into a tensile test piece of a metal material of JIS Z 2201, and the test piece was subjected to JIS.
The tensile elongation was measured by a metal material tensile test method specified in Z2241. Table 3 shows the results. The thermal emissivity indicates the ratio of the luminance (or divergence) of the heat radiation of the test piece to the luminance (or divergence) of the heat radiation of the black body at the same temperature. Regarding the blackening film adhesion peeling limit ρ (mm) indicating the peeling resistance of the blackening film, the test piece was bent 180 ° with a gauge plate of a predetermined thickness interposed therebetween, and the surface of the test piece was bent at the bent portion. The bending radius was easily obtained from the value of the thickness of the gauge plate when the blackening film was peeled off.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

As shown in Tables 2 and 3, the rolling reduction in the intermediate cold rolling before the final cold rolling was within the range of the present invention.
５０50%, and the rolling reduction in the final cold rolling was 60% within the range of the present invention. In the case of a few examples of the present invention,
A magnetic shield material having a high magnetic permeability and high ductility, having a relative magnetic permeability of 1150 or more and a tensile elongation of 36 or more at 0.35 Oe, and having excellent thermal emissivity and blackening film adhesion peeling limit. Turned out to be. On the other hand, the rolling reduction in the intermediate cold rolling before the final cold rolling is 10 out of the range of the present invention.
% Test No. In the case of Comparative Example No. 1, the relative magnetic permeability at 0.35 Oe indicates a high magnetic permeability of 1100, but the tensile elongation indicates a low value of 25%. The rolling reduction in the intermediate cold rolling before the final cold rolling is 60% out of the range of the present invention.
Test No. In the case of No. 4, the tensile elongation is 43% and has high ductility, but the relative magnetic permeability at 0.35 Oe shows a low value of 750.

Example 2 Undeoxidized killed steel having the chemical composition shown in Table 1 of Example 1 subjected to vacuum degassing in the steelmaking stage was continuously cast into a slab, and the heating temperature in hot rolling was as low as possible. Low temperature,
The finishing temperature is about 800 ° C below the transformation point and hot-rolled to 60 ° C.
It was wound at around 0 ° C. to form a hot-rolled steel strip having a thickness of 2.30 mm. As shown in Table 4, this hot rolled steel strip was subjected to primary cold rolling,
In the cold rolling process consisting of primary box annealing, intermediate cold rolling, intermediate box annealing, final cold rolling and final continuous annealing, the rolling reduction in the intermediate cold rolling is constant at 30%, and the rolling reduction in the final cold rolling is 35.
Cold-rolled while varying in the range of ~ 85%,
mm low-carbon cold rolled steel strip was obtained. From each of the extremely low carbon cold rolled steel strips, a ring test piece (outer diameter: 45 mm, inner diameter: 33 mm) specified in JIS C 2531 iron-nickel magnetic alloy plate and strip
mm) was punched out, and each ring test piece was subjected to ₁ % at 590 ° C. in an atmosphere consisting of 12% of CO ₂ and the balance nitrogen, hydrogen and CO
After performing the blackening treatment for 0 minutes, the relative magnetic permeability (0.35 Oe) by DC magnetization was measured in the same manner as in Example 1, and the measurement of the thermal emissivity at a temperature of 90 ° C. A peel resistance test was performed. In addition, from each ultra-low carbon cold rolled steel strip,
13B specified for metal material tensile test specimen of SZ2201
No. test piece was cut out, and the tensile elongation was measured by a metal material tensile test method specified in JIS Z 2241. Table 5 shows the results.

[0029]

[Table 4]

[0030]

[Table 5]

As shown in Tables 4 and 5, Test No. 6 ~
8, the relative magnetic permeability at 0.35 Oe is 1180 or more, the tensile elongation is 38% or more, and has high magnetic permeability and high ductility. It has been found that a magnetic shield material having excellent adhesion peeling limit can be obtained. On the other hand, in the test No. of 35% in which the rolling reduction in the final cold rolling was lower than the range of 40 to 85% of the present invention. In Comparative Example No. 5, the relative magnetic permeability at 0.35 Oe is as high as 1055, but the tensile elongation is as low as 21%. Test No. in which the rolling reduction in the final cold rolling was higher than the range of 40 to 85% of the present invention. In Comparative Example No. 9, the tensile elongation is 40% and has high ductility, but 0.35 O
The relative magnetic permeability at e is significantly lower at 805.

[0032]

The method for manufacturing a magnetic shield material according to the present invention comprises:
An undeoxidized killed steel of a predetermined component is continuously cast to form a slab, which is hot-rolled, and then subjected to cold rolling two or more times with intermediate annealing therebetween.
Intermediate cold rolling at ５０50% and intermediate annealing, then reduction ratio 4
After the final cold rolling at 0 to 75%, and then the finish annealing is performed, the recrystallized grain size after the finish annealing is determined according to JIS G 055.
2 can be controlled to a grain size number of 6.5 or more and 7.5 or less specified in the ferrite crystal grain size test method, a high elongation with a tensile elongation of 35% or more can be secured, and the relative magnetic permeability (0.35 Oe) A high magnetic permeability of 1000 or more can be obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram illustrating a manufacturing process of a magnetic shield material of the present invention.

FIG. 2 is a graph showing the relationship between the recrystallized grain size after annealing and the relative magnetic permeability when an undeoxidized killed steel is used.

FIG. 3 is a graph showing a relationship between a grain size after annealing and a tensile elongation when an undeoxidized killed steel is used.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 8/12 C22C 38/00 303 C22C 38/06

Claims (1)

(57) [Claims] 1. C: 0.005% or less, Si: 0.03
%, Mn: 0.15 to 0.5%, Al: 0.003
% Or less, S: 0.01% or less, and the rest is made of an undeoxidized killed steel consisting of Fe and inevitable impurities into a slab by continuous casting. In performing cold rolling twice or more with annealing, before the final cold rolling, intermediate cold rolling is performed at a reduction rate of 20 to 50% and intermediate annealing is performed, and then final cold rolling is performed at a reduction rate of 40 to 75%. High magnetic permeability characterized by finish annealing afterwards
A method of manufacturing a magnetic shield material having high ductility.