JPH0366369B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a material for magnetic shielding,
More specifically, the present invention relates to a method for manufacturing a magnetic shielding material suitable for manufacturing an internal magnetic shield for a color picture tube, which can achieve a high degree of shielding effect while omitting steps. Conventionally, in order to prevent the earth's magnetism and other external disturbing magnetic fields from affecting the electron beam, a funnel-shaped magnetic shield has been provided inside or outside the color picture tube. In particular, a magnetic shield enclosed inside a color picture tube is common, and in this case, the ferromagnetic steel plate (steel strip) used as the material has high magnetic permeability, good formability, In addition to high mechanical strength, high thermal emissivity and low gas emissions are particularly required. Conventionally, these magnetic shields for color picture tubes have been manufactured in the following manner. In other words, rimmed steel (capped steel) or aluminium-killed hot-rolled steel strip is subjected to primary cold rolling at a reduction rate of 50% or more to finish it to an intermediate thickness, and then passed through an electric cleaning device and then subjected to so-called open coil annealing to remove it. It is subjected to charcoal treatment, then subjected to secondary cold rolling at a reduction rate of 40 to 90%, and after electrical cleaning, box-shaped annealing is applied to form a tight coil. Thereafter, it is subjected to skin pass rolling (reduction ratio of 0.3 to 3%) and then passed through a slitter to produce a coiled shielding material (steel strip). Next, blanks are cut out from this shielding material, the blanks are drawn, or the overlapping parts are spot welded after bending to form a shield structure, and then the shield structure is assembled in a reducing atmosphere. (650~800℃)
x (30 to 60 minutes) Perform so-called magnetic annealing to recover and improve magnetic properties. Thereafter, the shield structure is blackened to prevent rust and improve heat radiation. The blackening treatment is a process of heating (550 to 600° C.) x (10 to 30 minutes) in a humid atmosphere such as steam-added air and/or a gas atmosphere such as _CO2 . The above is a conventional magnetic shield manufacturing method, but this method has several problems as described below. (1) Since it requires four heating steps: open coil annealing, box annealing, magnetic annealing, and blackening treatment, the process is complex, energy-efficient, and tends to coarsen grains. This results in a decrease in mechanical strength and a tendency to deform during handling. (2) Skin pass rolling process is essential. (3) The blackened film formed on the surface of the shield structure with coarse crystal grains as described above tends to have a coarse structure and lack density, and therefore is likely to fall off. (4) Magnetic properties (magnetic permeability) are not necessarily sufficient. (5) It is disadvantageous in terms of cost. Therefore, the present inventors believe that shielding materials do not necessarily have a high degree of press formability, especially considering that the forming method for magnetic shield structures has shifted from drawing using presses to bending, spot welding, etc. Therefore, various considerations were made, focusing on the fact that box annealing and temper rolling can be omitted in the conventional manufacturing method for magnetic shield materials, and that magnetic annealing in the shield processing method can also be omitted. As a result of repeated experiments, we have arrived at the present invention. An object of the present invention is to provide a method for manufacturing a magnetic shielding material suitable for obtaining an internal magnetic shield for a color picture tube with excellent magnetic properties while saving energy and reducing costs by omitting manufacturing steps. Another object of the present invention is to provide a method for manufacturing a magnetic shield material suitable for obtaining a magnetic shield having high mechanical strength, that is, rigidity, during the process of forming a shield structure and as a product. Still another object of the present invention is to provide a method for producing a magnetic shield material suitable for obtaining a magnetic shield having a fine crystal grain size and a dense blackened film. According to the present invention, after the blank is bent and subjected to blackening treatment,
In the manufacturing method of the material for the internal magnetic shield of color picture tubes, which has a crystal grain size of ASTM No. 7 to 9 and a relative magnetic permeability (0.350e) of 700 or more, low carbon rimmed steel (capped steel) hot-rolled steel strip is used. , at least primary cold rolling, open coil decarburization annealing with a C content of 0.01% or less after treatment, and a rolling reduction of 40 to 90%.
Provided is a method for producing a material for a magnetic shield inside a color picture tube, which is characterized by performing secondary cold rolling and omitting the subsequent box annealing and temper rolling. The present invention will be explained in detail below with reference to examples. FIG. 1 is a sectional view of a color picture tube equipped with a magnetic shield. In FIG. 1, the panel portion 1A of the glass bulb 1
A state in which an internal magnetic shield 2 is attached from the inside of the funnel portion 1B is shown.
Three electron beams 4 are emitted from an electron gun 3, are driven by horizontal and vertical deflection coils 5, scan a shadow mask 6, impinge on a fluorescent film 7 on the inner wall of the panel, and emit light. The magnetic shield 2 functions to prevent the electron beam path from being mislanded by an external disturbing magnetic field during this time. FIGS. 2 and 3 are perspective views of a magnetic shield formed by a conventional drawing process and a magnetic shield formed by a bending and spot welding process according to the present invention, respectively. Note that as a processing method for the magnetic shield structure, there are cases where bending within the elastic limit is performed, and there are cases where a joining method other than spot welding is used. Conventional drawing processing (Figure 2) requires a large degree of forming, so it is necessary to be soft (low hardness, low yield point) and have good workability (high rank Ford r value, n value, low yield point elongation). However, the bending process (third
In the case of drawing (Fig. 2), the drawing process only involves the addition of reinforcing beads, and only bending is required, so it does not require much workability as in the case of drawing (Fig. 2). Regarding magnetic properties, even with the most common external disturbance magnetic field, terrestrial magnetism (1 Gauss or less), for example, in the case of a 20-inch color picture tube without a magnetic shield, the electron beam impinges on the fluorescent surface. A deviation of 100 μm or more occurs at the point. In order to improve the shielding effect of the internal magnetic shield, the structure of the internal magnetic shield is important, but it is even more important to increase the magnetic permeability of the material used. Based on my experience, 650 or more is required for Elsted. In order to increase the magnetic permeability, it is necessary to minimize the amount of carbon C, nitrogen N, and their precipitates that inhibit domain wall motion, as well as to reduce the number of grain boundaries and increase the 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 used in the present invention must not be aluminum killed steel with many precipitates such as AlN, but must be ingot-rimmed steel (including capped steel). Note that capped steel is rimmed steel in which the rimming action and inclusions are dispersed by adjusting the capping time, and is a type of rimmed steel.
In addition, in order to reduce C and N components, DH is applied at the steel manufacturing stage.
It is also possible to simplify or omit the subsequent open coil annealing process by adopting an outside-furnace refining method such as the RH method or the RH method. The steel components to be used in the present invention will be described below. C ultimately needs to be 0.01% or less in order to improve press formability and magnetic permeability and to reduce gas release. The material for shielding with a C content of 0.01% or less is produced by first cold rolling a low carbon steel hot-rolled steel strip with a C content of 0.12% or less into a steel strip with an intermediate thickness of 0.4 to 1.0 mm, which is then electrically cleaned and then subjected to open coil annealing. It can be obtained by decarburizing using. If Mn is less than 0.10%, hot brittleness occurs and hot rolling becomes difficult, and if it exceeds 0.50%, the steel strip will harden and the press forming method will deteriorate. Therefore, Mn is
The range was 0.10% to 0.50%. Si is a major component of nonmetallic inclusions, and the presence of these inclusions deteriorates the magnetic properties and the adhesion of the blackened film as described above, so it is desirable to have a small amount. However, since contamination from refractories is unavoidable, the content was set at 0.02% or less. P content was set to 0.03% or less because as the content increases, it hardens the steel and inhibits press formability. S is set to 0.03% or less because sulfide-based inclusions, like Si, tend to deteriorate magnetic properties and also impair hot workability. Sol and Al are set at 0.01% or less because if the content is too high, it inhibits crystal grain growth during the blackening process, adversely affects the magnetic properties, and deteriorates the adhesion of the blackened film. N deteriorates press formability and magnetic properties, so it is desirable to reduce it as much as possible, but the lower limit of possible denitrification is practically 0.0001% or more, so the range should be limited.
It was set at 0.0001 to 0.01%. Next, we will discuss the manufacturing process. FIG. 4 is a process chart showing a comparison between the present invention and a conventional manufacturing process. As can be seen from FIG. 4, in the present invention, box annealing and temper rolling after secondary cold rolling can be omitted, and color picture tube manufacturers can also omit magnetic annealing after forming. . The technical content will be explained in detail below. The feature of the present invention is that after the secondary cold rolling, the shield structure is formed into a shield structure by bending, spot welding, etc. in a sufficiently work-hardened state (fully hardened), and the blackening treatment (for example, 575°C In the 15-minute heating process, the blackening process simultaneously removes distortion due to recrystallization and crystal grain growth and improves magnetic properties. In other words, the work hardening strain in the secondary cold rolling is used as a driving force for recrystallization. Therefore, the present invention should be understood by comparing it with the conventional method shown in FIG. 4, but its application is not the old shield processing method but the new shield processing method. That is, the present invention exhibits the expected effects only in combination with the new shield processing method. In an example of the present invention, a shielding material having a thickness of 0.15 mm was produced at a steel plate manufacturer using hot-rolled rimmed steel (capped steel) steel strips having the above-mentioned composition range according to the process of the present invention shown in FIG. In this case, the secondary cold rolling ratio (reduction ratio) is 75%. This steel strip has no elongation at the drop point, so no stretch strain occurs, and since it contains little C and N, it can be bent and formed into an internal magnetic shield structure without being secondary cold rolled. Yes, box annealing and temper rolling are not required. Next, at a color picture tube manufacturer, the magnetic shield structure is heated in a humid atmosphere and/or gas atmosphere at a temperature of 575° C. for 15 minutes to perform a surface blackening treatment. It was possible to obtain an internal magnetic shield with a crystal grain size of ASTM No. 7 to 9 and a relative magnetic permeability (0.35 oersted) of about 750. Table 1 shows the chemical compositions of Examples and Comparative Examples of the present invention. The upper row of the carbon column shows the ladle analysis value, and the lower row shows the composition after decarburization. Steels having various chemical compositions are hot rolled to a thickness of 2.0 mm, and then primary cold rolled to a thickness of 0.6 mm. Next, it was soaked in a decarburizing atmosphere (H ₂ + N ₂ mixed gas, dew point +20°C) for about 710°C x 10 hours using the open coil annealing method, and then soaked in a dry gas (dew point -40°C) for about 710°C x 7 hours. It was dried and decarburized to C: 0.001% or less. Then, it is subjected to secondary cold rolling (reduction ratio 75%) to a plate thickness of 0.15mm.
A material for shielding according to the present invention was prepared. As a comparative example, a sample was prepared which was subjected to bright box type annealing at 630° C. for 14 hours after secondary cold rolling, and dry skin pass rolling at a rolling reduction of about 1%. In Table 1, sample A of the present invention is a rimmed steel (capped steel) that has been strongly decarburized, sample B is a rimmed steel that has been strongly denitrified, and sample C is a rimmed steel that has been strongly denitrified. It is. Sample D of the comparative example is a continuously cast aluminium-killed steel material that is normally decarburized, and Sample E is a rimmed steel (capped steel) that is normally decarburized. Table 2 compares the effects of the embodiments of the present invention in terms of relative magnetic permeability, gas release amount, and mechanical properties depending on the blackening treatment conditions.

[Table] Upper row: Before decarburization Lower row: After decarburization

[Table] Shown in comparison with comparative examples. However, the mechanical property data is for samples A, B, and C, which are examples of the present invention.
is the measured value at the stage of the shielding material as it is in the secondary cold rolling, and is a comparative example of sample D,
E is a measured value at the shielding material stage after bright box annealing and temper rolling. In Table 2, sample A, which is an example of the present invention,
In the case of B and C, the normal blackening treatment conditions (575℃ x 15
The relative magnetic permeability at a magnetic field of 0.35 oersted (Oe) is 700 or higher in all cases.Specimen C in particular has a higher relative permeability than Samples A and B because strong decarburization and strong denitrification have been carried out. is getting better. This is probably because when strong decarburization and strong denitrification are carried out, recrystallization at relatively low temperatures becomes easier and the crystal grain size becomes larger than in other cases. Regarding the amount of gas released, each sample (approximately 100g)
The amount of gas released (cm ³ ×Torr.at 24°C) when heated at 450° for 60 minutes in a vacuum of 10 ^-4 to 10 ^-5 Torr was measured for each sample. Since Comparative Example D is a continuously cast aluminium-killed steel material, the amount of gas released is originally small at 4.92 (cm ³ × Torr.), while Comparative Example E has a slightly higher gas emission amount of 5.30 (cm ³ × Torr.).
Torr.). On the other hand, in Examples A, B, and C of the present invention, it is 5.25 to 5.30 (cm ³ × Torr.),
The amount of gas released was equal to or less than that of the comparative example. Regarding mechanical properties, as shown in Table 2, the tensile strength TS of Examples A, B, and C of the present invention is that of Comparative Example DE.
It is more than twice as large as that of , and the elongation El is 1/20 ~
It's only 1/40th. However, it has been confirmed that even with this level of mechanical properties, as long as a magnetic shielding structure is practically fabricated by bending, spot welding, etc., it can sufficiently withstand the forming process. Moreover, on the other hand, it has the effect of having high rigidity (mechanical strength) and good yield during the shield processing process and after becoming a product. FIG. 5 is a graph showing the relationship between the heating temperature during blackening treatment or magnetic annealing and the relative magnetic permeability of the product in a 0.35 Oe DC magnetic field. As shown in FIG. 5, in contrast to the comparative example (broken line) involving conventional magnetic annealing, the example of the present invention (solid line) uses only blackening treatment and intersects at a heating temperature of about 400°C.
It can be seen that at heating temperatures higher than that, the relative magnetic permeability is actually superior. In the case of the comparative example, the relative magnetic permeability hardly changes even if blackening treatment at about 575° C. is performed after magnetic annealing, so the comparison was made after magnetic annealing. Therefore, 550℃, which is a very common working condition.
By only heat treatment (blackening treatment) at temperatures between 650℃ and 650℃,
Even though the process is omitted compared to the comparative example (conventional product), superior relative magnetic permeability can be obtained. In addition, if the blackening treatment temperature is lower than 550℃, recrystallization may not occur, so the lower limit is set to 550℃.
The upper limit is 650°C, since it becomes difficult to form a dense blackened film if the temperature exceeds 650°C. In addition, the material for magnetic shielding, which is a product of the present invention,
When applied to a 22"-110° collar tube, the relative magnetic permeability of the embodiment of the present invention is over 700, while that of the comparative example is around 640. Accordingly, the shift of the electron beam in the embodiment of the present invention is By carrying out the present invention detailed above, all of the above objectives are achieved. That is, the two steps of box annealing and skin pass rolling are omitted in the shielding material manufacturing process. Not only can we do this, but we have also omitted the three steps of magnetic annealing in the shield processing process, saving energy and reducing costs.We have also made it possible to produce internal magnetic shields for color picture tubes that have a dense black coating and have excellent shielding effects. It can be manufactured well.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. After bending a blank and subjecting it to blackening treatment, the interior of a color picture tube is made to have a crystal grain size of ASTM No. 7 to 9 and a relative magnetic permeability (0.350e) of 700 or more. In the manufacturing method of magnetic shielding materials, low carbon rimmed steel (capped steel) hot-rolled steel strip is subjected to at least primary cold rolling and an open coil removal process in which the C content after treatment is 0.01% or less (weight %, the same shall apply hereinafter). Charcoal annealing and secondary cold rolling with a rolling reduction of 40 to 90%,
A method for producing a material for a magnetic shield inside a color picture tube, characterized in that the subsequent box-shaped annealing and temper rolling are omitted. 2 Low carbon rimmed steel (capped steel) hot rolled steel strip has C: 0.12% or less, Mn: 0.10 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
The manufacturing method according to claim 1, which is a rimmed steel (capped steel) hot-rolled steel strip comprising unavoidable impurities. 3. The manufacturing method according to claim 1 or 2, wherein the blackening treatment is a heat treatment of heating (550 to 650°C) x (10 to 30 minutes) in a humid atmosphere or gas atmosphere.