JPH0613730B2 - Method for manufacturing internal magnetic shield for color picture tube - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an internal magnetic shield for a color picture tube, and more particularly to a method for manufacturing an internal magnetic shield for a color picture tube while achieving a high shielding effect while omitting steps.

Generally, in order to avoid the influence of the earth's magnetism and other external dominant magnetic fields on the electron beam, a funnel-shaped magnetic shield has been provided inside or outside the color picture tube.

In particular, a magnetic shield enclosed in a color picture tube is generally used. In this case, the steel sheet (steel strip) that is a ferromagnetic material used as a material has high magnetic permeability and good formability. In addition to high mechanical strength, high thermal emissivity and low gas emission are particularly required.

Heretofore, these magnetic shields for color picture tubes have been manufactured as follows.

That is, rimmed steel (capped steel) or aluminum-killed steel hot-rolled steel strip is subjected to primary cold rolling at a rolling reduction of 50% or more to finish to an intermediate plate thickness, and then subjected to so-called open coil annealing after passing through an electric cleaning device. After decarburization, secondary cold rolling with a reduction rate of 40 to 90% is performed, electrolytic cleaning is performed, and then tight coil-shaped box annealing is performed.

After that, it is temper-rolled (reduction of 0.3 to 3%) and then slittered to form a coiled shield material (steel strip).
Then, blanking is cut out from this shielding material, blanks are cut, and the blanks are drawn or the polymerized parts are spot welded after bending to form a shield structure, and then in a reducing atmosphere. Shield structure (65
(0 to 800 ° C.) × (30 to 60 minutes) Heating, so-called magnetic annealing for recovering and improving magnetic characteristics is performed. After that, the shield structure is further blackened to prevent rust and improve the thermal emissivity. The blackening treatment is performed, for example, in a wet atmosphere such as steam-added air and / or a gas atmosphere such as CO ₂ (550 to 550).
This is a step of heating (600 ° C.) × (10 to 30 minutes).

The above is the conventional magnetic shield manufacturing method, but this has the following several problems.

(1) Open coil annealing, box-type annealing, magnetic annealing, and blackening treatment are required, so the process is complicated and energetically uneconomical, and the crystal grain coarsening is also possible in nature. As a result, mechanical strength is lowered and deformation during handling is likely to occur.

(2) The temper rolling process is indispensable.

(3) As described above, the blackened film formed on the surface of the shield structure in which the crystal grains are coarsened has a rough texture and tends to lack compactness, and therefore the blackened film is apt to fall off.

(4) The magnetic properties (permeability) cannot always be said to be sufficient.

(5) It is disadvantageous in terms of cost.

Therefore, considering that the forming method of the magnetic shield structure has been changed from drawing by pressing to bending, spot welding, etc., the present inventors have found that the material for shielding does not necessarily have a high degree of press formability. Therefore, the present invention has been achieved as a result of various considerations and experiments focusing on the fact that the box-type annealing, temper rolling and magnetic annealing in the conventional method can be omitted.

An object of the present invention is to provide a manufacturing method for obtaining an internal magnetic shield for a color picture tube having excellent magnetic properties while saving energy and reducing costs by omitting manufacturing steps.

Another object of the present invention is to provide a method of manufacturing a magnetic shield having a high mechanical strength, that is, a high synthetic strength during a process as a shield structure and as a product.

Still another object of the present invention is that the product grain size is fine,
Therefore, it is an object of the present invention to provide a method of manufacturing a magnetic shield having a dense blackened film.

According to the present invention, C: 0.12% or less (same as below by weight%), Mn: 0.1
0 to 0.50%, Si: 0.02% or less, P: 0.03
% Or less, S: 0.03% or less, Sol. Al: 0.01
% Or less, N: 0.0001 to 0.01%, balance Fe and unavoidable impurities in a hot rolled steel strip of rimmed steel (cabbed steel) containing at least the C component of the steel strip after primary cold rolling and annealing. Open coil decarburization annealing of 01% or less, and a shield material manufacturing process of performing secondary cold rolling with a reduction rate of 40 to 90%, blanking from the shield material, cutting a blank, and bending the blank. There is provided a method of manufacturing an internal magnetic shield for a color picture tube, comprising: a molding process mainly including a process, a blackening process, and a shield manufacturing process in which a magnetic annealing process is omitted.

Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 is a sectional view of a color picture tube having a magnetic shield incorporated therein.

FIG. 1 shows a state in which an internal magnetic shield is mounted from the panel portion 1A of the glass bulb 1 to the inside of the funnel portion 1B. The three electron beams 4 are emitted from the electron gun 3, driven by the horizontal and vertical deflection coils 5 to scan over the shadow mask 6, and strike the fluorescent film 7 on the inner wall of the panel to emit light. It is the magnetic shield 2 that functions so that the electron beam stroke during this period does not cause mislanding due to the external disturbing magnetic field.

FIG. 2 and FIG. 3 are perspective views of a conventional magnetic shield formed by drawing and a magnetic shield formed by bending and spot welding according to the present invention. As a processing method for the magnetic shield, bending processing within the elastic limit or a joining method other than spot welding may be used.

Since the conventional drawing process (Fig. 2) has a high forming workability, it must be soft (low hardness, low yield point) and have good workability (high rank Ford r value, n value, low yield point elongation). However, in the bending process (Fig. 3), there is only one squeeze overhang process to the extent that a reinforcing bead is attached, and since it is only a bending process, the workability as in the drawing process (Fig. 2) is high. Does not need much.

Also, regarding the magnetic properties, even with the most common geomagnetism (1 Gauss or less) as an external disturbing magnetic field, for example, in the case of a 20-inch color picture tube without a magnetic shield, the electron beam projecting point on the fluorescent surface 100μ
A shift of m or more occurs. The structure of the internal magnetic shield is important to improve the shielding effect of the internal magnetic shield, but it is more important to increase the magnetic permeability of the material used, and the relative magnetic permeability (0.35 oersted) of a practical steel strip is more important. ) Is necessary 650 or more from experience.

In order to increase the magnetic permeability, it is necessary to minimize the amount of carbon C and nitrogen N that inhibit the domain wall motion and their precipitates, reduce the number of crystal grain boundaries, and increase the crystal grain size. The present invention aims to obtain high magnetic permeability by reducing C and N and keeping the crystal grain size relatively small.

Therefore, the material steel type used in the present invention should not be aluminum-killed steel with a large amount of precipitates such as AlN, and must be ingot material rimmed steel (including capped steel). In addition,
Capped steel is a kind of rimmed steel, which is a rimmed steel in which the rimming action and inclusions are dispersed by adjusting the capping time. Incidentally, in order to reduce the C and N components, it is possible to adopt an external refining method such as a DH method or an RH method in the steelmaking stage, and simplify or omit the subsequent open coil annealing step.

The steel components to be used in the present invention will be described below.

C is required to be 0.01% or less finally in order to improve press formability and magnetic permeability and reduce gas emission. Shielding materials with a C content of 0.01% or less have a C content of 0.12%.
The following low carbon steel hot-rolled steel strips are obtained by first cold rolling to obtain steel strips having an intermediate thickness of 0.4 to 1.0 mm and performing decarburization treatment using the open coil annealing method after electrical cleaning.

If Mn is less than 0.10%, hot brittleness occurs, making hot rolling difficult, and if it exceeds 0.50%, the steel strip hardens and press formability deteriorates. Therefore, Mn is set to the range of 0.10 to 0.50%.

Si is a major constituent factor of the non-metallic inclusions, and the presence of these inclusions deteriorates the magnetic properties and the adhesion of the blackening film as described above, so the amount of Si is preferably small. However, it is unavoidable to mix from refractory materials, so 0.02%
Below.

If the content of P increases, it impairs press formability due to hardening of steel, so the content of P was made 0.03% or less.

S is 0.03% because sulfide inclusions tend to deteriorate magnetic properties like Si and also deteriorate hot workability.
Below.

If the content of Sol and Al is large, it inhibits crystal grain growth during the blackening treatment, adversely affects the magnetic properties, and deteriorates the adhesion of the blackened film, so the content was made 0.01% or less.

Since N deteriorates the press formability and magnetic properties, it is desirable that it is as small as possible, but the lower limit of denitrification is practically 0.
Since it is 0001% or more, the range is set to 0.0001 to 0.01%.

Next, the manufacturing process will be described.

FIG. 4 is a process diagram showing the present invention in comparison with the conventional manufacturing process.

As can be seen from FIG. 4, in the present invention, box-type annealing after secondary cold rolling, temper rolling, and magnetic annealing after forming can be omitted.

The technical contents will be described in detail below.

The feature of the present invention is that after the secondary cold rolling, the shield structure is formed by bending and spot welding in a sufficiently work-hardened state (full hard), and blackening treatment (for example, 575 ° C x In the step (heating for 15 minutes), the strain due to recrystallization and crystal grain growth is removed simultaneously with blackening, and the magnetic characteristics are improved. That is, the work hardening strain in the secondary cold rolling is used as a driving force for recrystallization.

Therefore, in the present invention, the secondary cold rolling reduction is set to 40 to 90%. If the rolling reduction is less than 40%, the effect of the present invention is difficult to occur, and 90
This is because it is difficult to guarantee the shape of the steel strip at a rolling reduction of more than%, which is also disadvantageous in terms of energy.

In the embodiment of the present invention, the rimmed steel (capped steel) hot-rolled steel strip having the above-mentioned compositional range is manufactured in accordance with the process of the present invention shown in FIG.
I made a 15mm shield material. In this case, the secondary cold rolling rate (reduction rate) is 75%. Since this steel strip has no elongation at yield, stretcher strain does not occur, and C
Since the amount of N and N is small, the inner magnetic shield structure can be bent and formed as it is in the secondary cold rolling, and box annealing and temper rolling are unnecessary. Then, the magnetic shield structure is placed in a wet atmosphere and / or a gas atmosphere at 575 ° C.
The surface is blackened by heating at the temperature of 15 minutes. As a result, an internal magnetic shield having a crystal grain size of ASTM No. 7 to 9 and a relative magnetic permeability (0.35 oersted) of 750 could be obtained.

Table 1 shows the chemical compositions of the examples of the present invention and the comparative examples. The upper column of the carbon column shows the Ladle analysis value, and the lower column shows the composition after decarburization treatment. Steel having various chemical compositions as described above is hot-rolled to 2.0 mm and further primary cold-rolled to 0.6 mm. Then about 710 by open coil annealing
Decarburizing atmosphere (H ₂ + N ₂ mixed gas, dew point +2)
(0 ° C.) soaking, then dried in dry gas (dew point −40 ° C.) for about 710 ° C. × 7 hours, and decarburized to C: 0.001% or less.

Then, secondary cold rolling (75% reduction) was carried out to produce a shield material of the present invention having a plate thickness of 0.15 mm.

As a comparative example, a sample was further subjected to bright box annealing at 630 ° C. for 14 hours after secondary cold rolling and dry temper rolling at a reduction rate of about 1%.

In Table 1, sample A of the example of the present invention is a strong decarburized rimmed steel (capped steel), sample B is a strong decarburized sample, and sample C is a strong decarburized sample. And strongly denitrified. Open coil annealing conditions of Sample B is slightly _{H 2} partial pressure high _H 2 + _{N 2} mixed gas atmosphere (e.g., _{H 2 10% + N 2 90} %, the dew point + 45 ° C.) to about 710 ° C. × 14 hours soaked in, followed About 710 ℃ × 10
It is to dry in the same dry gas (dew point −40 ° C.) for the same time. Similarly, sample C is soaked in a mixed gas atmosphere (dew point + 30 ° C) of the same type as sample B for about 750 ° C x 14 hours, and then dried in a similar dry gas (dew point -40 ° C) for about 750 ° C x 10 hours. did. Sample D of the comparative example is an aluminum-killed continuous cast material that has been normally decarburized, and sample E
Is usually decarburized rimmed steel (capped steel).

Table 2 shows the effects of the examples of the present invention on the relative magnetic permeability, the amount of released gas, and the mechanical properties for each blackening treatment condition, in comparison with the comparative examples. However, the data of the mechanical properties are the measured values at the stage of the material for shielding as the secondary cold rolling for the samples A, B and C which are the examples of the present invention, and the data for the samples D and E which are the comparative examples are all included. Is also a measured value at the stage of the shield material after bright box annealing and temper rolling.

In Table 2, in the case of Samples A, B, and C, which are the examples of the present invention, the relative magnetic permeability at a magnetic field of 0.35 oersted (Oe) was all 70 under normal blackening treatment conditions (575 ° C. × 15 minutes).
0 or more, and in particular, since the sample C is subjected to the strong decarburization and the strong denitrification, the relative magnetic permeability is further improved as compared with the samples A and B.

This is probably because when strong decarburization and strong denitrification are performed, recrystallization at a relatively low temperature becomes easy and the crystal grain size becomes larger than the others.

Incidentally, the blackening treatment of the examples and comparative examples (575 ° C. × 15
Table 3 shows the crystal grain size, the adhesion of the blackened film, and the magnetic properties after the (minute).

As shown in Table 3, the crystal grain sizes of Examples A, B and C of the present invention are within the range of ASTM No. 7 to 9 and moderate grain growth is recognized, but Comparative Example D has fine crystal grains and is magnetic. Poor characteristics. In Comparative Example E, the crystal grains are coarsened, which hinders the formation of a dense blackened film, resulting in poor blackened film adhesion.

Regarding the amount of gas released, the amount of gas released (cm ³ × Torr.at 24 ° C.) when heated in a vacuum of 10 ⁻⁴ to 10 ⁻⁴ Torr. For 450 ° × 60 minutes for each sample (about 100 g) It was measured. Since Comparative Example D was an aluminum-killed continuous cast material, the amount of gas released was originally small and was 4.92 (cm ³ × Torr.), And Comparative Example E was slightly larger than that, 5.30 (cm ³ × Torr.). On the other hand, in Examples A, B, and C of the present invention, 5.25 to 5.30 (cm ³ × T
orr.), and the amount of gas released was the same as or smaller than that of the comparative example.

As for the mechanical properties, as shown in Table 2, the tensile strength T. S is more than twice as large as that of Comparative Examples D and E, and the elongation El is only 1/20 to 1/40.
However, it has been confirmed that even with such mechanical properties, as long as the magnetic shield structure is practically made by bending, spot welding, etc., the forming process can be sufficiently endured.

Moreover, on the other hand, there is an effect that the rigidity (mechanical strength) is high and the yield is good even after the shield manufacturing process and the product are completed.

Fig. 5 shows the heating temperature and 0.
It is a graph which shows the relationship of product relative magnetic permeability in 35 Oe direct-current magnetic field. As shown in FIG. 5, in contrast to the conventional comparative example (broken line) accompanied by magnetic annealing, the inventive example (solid line) crosses only at the blackening treatment at a heating temperature of about 400 ° C., and at a heating temperature higher than that. However, it can be seen that the relative magnetic permeability is surpassed. In the case of the comparative example, the relative magnetic permeability hardly changed even if blackening treatment was performed at about 575 ° C. after the magnetic annealing, so comparison was performed after the magnetic annealing.

Therefore, very common working conditions of 550 ° C to 6
Only by the heat treatment (blackening treatment) at 50 ° C., excellent relative magnetic permeability can be obtained, though the process is omitted as compared with the comparative example (conventional product).

If the blackening temperature is lower than 550 ° C, recrystallization may not occur, so the lower limit is 550 ° C and the upper limit is 6
If the temperature exceeds 50 ° C, it becomes difficult to form a dense blackened film, so the temperature is set to 650 ° C.

Further, when the magnetic shield according to the present invention is used in a 22 ″ -110 ° color tube, the relative magnetic permeability of the example of the present invention is 700 or more, whereas that of the comparative example is around 640.
Accordingly, the deviation of the electron beam is 10 in the embodiment of the present invention.
~ 20% reduction.

By carrying out the present invention described in detail above, all of the above objects can be achieved. That is, in order to save energy and reduce costs by omitting a total of three steps of box-type annealing and temper rolling in the shield material manufacturing process and magnetic annealing in the shield manufacturing process, a dense blackening film is provided and a shielding effect is obtained. An excellent internal magnetic shield for a color picture tube can be manufactured with high yield.

[Brief description of drawings]

FIG. 1 is a sectional view of a color picture tube having a magnetic shield incorporated therein, FIGS. 2 and 3 are perspective views of magnetic shield structures according to manufacturing methods of the conventional and the present invention, respectively, and FIG. 4 is a process diagram of the conventional and the present invention. FIG. 5 is a graph showing the relationship between heating temperature and relative permeability. 1 ... Glass bulb, 2 ... Internal magnetic shield.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // C22C 38/00 301 Z 38/06 (72) Inventor Yutaka Tanaka 2 Nijigaoka, Hikari City, Yamaguchi Prefecture No. 18 No. 30

Claims (2)

[Claims] 1. C: 0.12% or less (same as for weight% or less),
Mn: 0.10 to 0.50%, Si: 0.02% or less,
P: 0.03% or less, S: 0.03% or less, Sol. A
1: 0.01% or less, N: 0.0001 to 0.01%,
Open coil decarburization annealing with a C component of 0.01% or less in at least primary cold rolling and annealing of a hot rolled steel strip of rimmed steel (cabbed steel) consisting of the balance Fe and unavoidable impurities, and a rolling reduction of 40 ˜90% secondary cold rolling of the shield material manufacturing process, blanking of the shield material by blanking, cutting the blank, bending mainly, and then blackening treatment. A method for manufacturing an internal magnetic shield for a color picture tube, comprising: a shield manufacturing step in which the magnetic annealing step is omitted. 2. The production method according to claim 1, wherein the blackening treatment is a heating treatment of heating at (550 to 650 ° C.) × (10 to 30 minutes) in a humid atmosphere or a gas atmosphere.