JP4185000B2 - Manufacturing method of steel plate for magnetic shield inside TV CRT - Google Patents

Description

  The present invention relates to a material for a magnetic shield component disposed inside a color TV cathode ray tube so as to cover from the outer periphery of an electron beam passage, that is, a method for manufacturing a steel plate for an internal magnetic shield of a TV cathode ray tube.

  The basic configuration of a color TV CRT consists of an electron gun and a fluorescent surface that converts an electron beam into an image. Further, a magnetic shield component that prevents the electron beam from being deflected by geomagnetism covers the side. This magnetic shield component is also referred to as an inner shield component or an inner magnetic shield component. In the present invention, these parts are called TV CRT internal magnetic shields.

  The thickness of the steel plate for the magnetic shield inside a TV CRT is usually 0.1-0.4mm, and this thin steel plate coil is press-formed by an electric or processing manufacturer and then blackened before being incorporated into the CRT. A cathode ray tube sealing by frit glass melting at about 400-500 ° C., called a sealing process, is performed. In order to shield the geomagnetism, a so-called demagnetization coil wound around the outside of the color cathode ray tube is subjected to a demagnetization process by applying an alternating current to reduce the geomagnetism inside the magnetic shield.

  As for the press working, when the blackening process described later is omitted, it is possible to avoid introducing strain into the steel sheet by bending rather than drawing. However, when the blackening process that is the subject of the present invention is a prerequisite, the drawing process is often performed. The present invention presupposes this drawing process and blackening process. Conventionally, ordinary low-carbon steel plates or ultra-low carbon plates that do not contain Ti, B, etc. are used, and wrinkles and tears due to squeeze deformation (particularly corners that form an angle of 45 ° with the rolling direction of the magnetic shield) In addition, there were many problems in the adhesion of the blackened film in the blackening treatment.

The blackening treatment is an oxidation treatment on the surface of the steel sheet (formation of an Fe ₃ O ₄ film that prevents electron beam reflection). The temperature is such that Fe ₃ O ₄ is easily formed, for example, around 580 ° C., for example, about 580 ° C., and 3-30 minutes soaking is a normal heat treatment condition. As the atmosphere, a mixture of non-oxidizing gas such as N ₂ , H ₂ , Ar, CO and the like with oxidizing gas such as H ₂ O, O ₂ , CO ₂ is used. The heat of this blackening treatment also recovers the distortion of the steel sheet at the same time as the oxidation, and releases the magnetic deterioration due to the press working.

  In recent years, with the increase in the size and widening of consumer TVs, the traveling distance and scanning distance of electron beams have become longer, and the amount of movement of electron beams shaken by geomagnetism has increased, causing color unevenness. Also, although personal computers are growing rapidly, high-precision electron beam landing characteristics are required because they are still images and the screen can be viewed at a short distance. For these reasons, there is a need for a steel sheet for internal magnetic shielding that reduces the drift of electron beam landing. As the shielding performance, the smaller the coercive force, the better. For example, 3.0 Oe (Oersted) or less is desirable.

Patent Document 1 is known as a conventional technique. This method is decarburized by open coil annealing, and it is noted that the conventional drawing process has been changed to a bending process, but the manufacturing process is too complicated, such as the need for two cold rolling processes, and the cost is low. There was a high problem. Patent Document 2 proposes a steel plate for internal magnetic shielding containing B, Ti, Nb and the like. However, this method employs a process not premised on the blackening treatment, has no knowledge and technique about blackening film formation, and has a difficulty in drawing workability.
JP 59-173219 A JP 2001-49401 A

  The present invention provides a method for producing a steel sheet for an internal magnetic shield with a reduced coercive force in order to improve the above-described problems, that is, workability and blackened film, and further reduce drift of electron beam landing.

(1) A method for producing a steel plate for an internal magnetic shield of a color TV Braun tube, which is produced by press forming and then blackened on the surface, wherein C ≦ 0.005% by mass and Si ≦ 0. 0.05%, Mn ≦ 0.5%, P ≦ 0.03%, S ≦ 0.02%, Al: 0.02-0.10%, N ≦ 0.004%, Nb: 0.005-0 A hot rolled sheet containing 0.03%, Ti: 0.01-0.04%, B: 0.0001-0.0010%, Cu: 0.03-0.3%, the balance Fe and inevitable components. After pickling, it is cold rolled to 0.1-0.4 mm, then recrystallized annealing, temper rolling is performed at a reduction rate of 2% or less, and the surface roughness Ra is set to 0.4 μm or more. A method of manufacturing a steel plate for magnetic shielding inside a TV cathode ray tube.
(2) The method for manufacturing a steel plate for a TV Braun tube internal magnetic shield as described in the above item (1), wherein Ni plating of 2.5 g / m ² or less is performed between cold rolling and annealing.

  The present invention provides a method for producing a steel sheet for an internal magnetic shield material having a reduced coercive force in order to improve workability and blackening film, and also to reduce drift of electron beam landing.

The present invention is composed of the following three findings. One is to control the steel sheet surface roughness at the same time as using B element to improve the drawability. Second, the elements Ti, Nb, and Cu should be used at the same time to stabilize the blackened film. Furthermore, use a diffusion Ni-Fe layer. The third point is to limit the rolling reduction of temper rolling by using extremely low carbon in order to improve the coercive force. By combining these, the problems of drawing, blackening film, and magnetic properties can be solved at once.
Hereinafter, the reasons for limitation of the present invention will be described.

The amount of C is limited to 0.005% or less. As the amount of C increases, the crystal grain size after recrystallization decreases and the coercive force deteriorates. This limit is 0.005%.
The amount of Si is 0.05% or less. Si easily forms a part of the internal oxide layer, and the formation of the blackened film becomes unstable. This limit is 0.05%.
The amount of Mn is 0.5% or less. Mn also increases the hardness of the steel sheet and is effective in preventing creases during handling of the steel sheet, but if it is too much, there is a problem of the addition cost, so it is 0.5% or less.
The amount of P is 0.03% or less. P is also effective in increasing the hardness of the steel sheet, but if it exceeds 0.03%, it must be avoided because it may be cracked by drawing deformation during press working (particularly at low temperatures such as in winter).
The amount of Al is 0.02-0.10%. Al is effective for fixing N and preventing aging, and its effective range is 0.02% or more and 0.10% or less.
The amount of S is limited to 0.02% or less. The smaller the S, the better the coercive force, and 0.02% or less is necessary.
N amount is limited to 0.004% or less. The smaller N, the better the coercive force, and 0.004% or less is necessary.

The Nb content is 0.005-0.03%. Nb precipitates carbonitride, suppresses the formation of cementite (Fe ₃ C), and improves the adhesion of the blackened film. This effect appears at 0.005% or more, but if it exceeds 0.03%, the effect is saturated and the addition cost increases, so the content is made 0.03% or less. In addition, precipitation of cementite is effective for the adhesion of the blackened film. The adhesion of the oxide film enriched with hematite (Fe ₂ O ₃ ) oxidized with cementite as a nucleus deteriorates, and conversely, the magnetite (Fe ₃ It was found that the oxide layer mainly composed of O ₄ ) has excellent adhesion. This evaluation of adhesion is evaluated by counting the blackened film powder that has fallen on the white paper by vibrating the steel plate. However, for simplicity, the tape peeling test is often used instead.
The amount of Ti is 0.01-0.04%. Ti also precipitates carbonitride, suppresses the formation of cementite (Fe ₃ C), and improves the adhesion of the blackened film. This effect appears at 0.01% or more. However, if it exceeds 0.04%, the effect is saturated and the addition cost increases, so the content is made 0.04% or less.
The B content is 0.0001-0.0010%. B strengthens the grain boundaries and prevents cracking in the press. If the amount of B is less than 0.0001%, there is no effect, and if it exceeds 0.0010%, the effect is saturated, so 0.0001-0.0010% is made the range.
The amount of Cu is 0.03-0.3%. Cu also improves the adhesion of the blackened film. If the amount of Cu is less than 0.03%, the adhesion is insufficient, so 0.03% or more is necessary. Moreover, since there exists a problem of addition cost when there is too much, it is 0.3% or less.
As other impurities, there is no problem as long as the total amount of Sn, Ni, Cr, etc. is 0.2% or less.

Steelmaking, hot rolling, and the like in the production process are performed by methods that are usually performed. As a processing step after hot rolling, cold rolling is performed after pickling. Next, recrystallization annealing is performed. The annealing temperature is 680 ° C. or higher for recrystallization. The annealing can be performed by box annealing or continuous annealing. The annealing atmosphere is normal N ₂ and there is no need for decarburization. The subsequent temper rolling is performed for the purpose of shape correction and adjustment of the steel sheet surface roughness. If the steel plate shape is flat and the roughness is adjusted at the cold rolling stage before recrystallization annealing, temper rolling can be omitted. The surface roughness of the steel sheet is 0.4 μm or more in terms of centerline average roughness Ra. If it is less than 0.4 μm, scratches or the like are likely to occur during press molding, and drawing breakage occurs. The rolling reduction of temper rolling is 2% or less. When the rolling reduction of temper rolling increases, the coercive force deteriorates. The limit is 2%.

Although it is before recrystallization annealing, Ni plating (both sides) can be performed. The amount of Ni plating is 2.5 g / m ² (per one side) or less. Ni plating conditions may be normal plating conditions, but electroplating is more productive than electroless plating. Since this Ni plating is performed before annealing, there is no Ni single layer after recrystallization annealing, and all the layers are Fe-Ni diffusion layers. Improves adhesion of blackened film during processing. Even if Ni plating is not performed, predetermined black film adhesion can be obtained, but this Ni plating is effective when there is instability of atmospheric gas in the blackening furnace. If the Ni plating amount exceeds 2.5 g / m ² (per one side), the Ni single layer remains on the outermost surface layer of the steel sheet after annealing, and the iron oxide film becomes thin even in the blackening treatment.
Examples will be described below.

Ingots of various components shown in Table 1 were vacuum melted and cast, heated at 1200 ° C., and hot rolled into 2.1 mm thick hot rolled sheets. This was pickled and cold-rolled. This cold-rolled sheet having a thickness of 0.15 mm was degreased and then heat-treated at 760 ° C. for 30 seconds by continuous annealing in an atmosphere of 97% N ₂ + 3% H ₂ . Next, the rolling reduction of temper rolling is 0.5%, the steel sheet surface roughness Ra is 0.8 μm, and the coercive force is 20 Oe (Oersted) maximum in the rolling direction of the sample 55 mm square using a DC magnet single plate measuring device. Measured with magnetization. Next, a blackening treatment was performed in a nitrogen atmosphere containing 5% H ₂ at a dew point of 20 ° C. after annealing at 580 ° C. for 15 minutes. The adhesion of the blackened film was examined by a tape peeling test. A case where the blackened film was almost peeled off was evaluated as x, a case where the blackened film was partially peeled was evaluated as Δ, and a case where the blackened film was not peeled off was evaluated as ◯.
As shown in Table 1, a C amount, S amount and N amount within the range of the present invention and a coercive force of 3.0 Oe or less are obtained, and a Si amount, Nb amount, Ti amount and Cu amount within the range of the present invention are obtained. Thus, an excellent black film adhesion was obtained.

Continuous containing 0.0010% C, 0.04% Si, 0.20% Mn, 0.01% P, 0.011% S, 0.05% Al, 0.002% N, 0.07% Cu The cast component slab was cast, heated at 1100 ° C., and hot rolled into a 2.8 mm thick hot rolled coil. This was pickled and cold rolled to a thickness of 0.12 mm. After degreasing the cold-rolled sheet, double-sided Ni plating was applied to 1.0 g / m ² (per one side), and then heat treatment was performed for 1 minute at a soaking temperature of 740 ° C. by continuous annealing in a nitrogen gas atmosphere. went. Next, temper rolling was performed at the rolling reduction shown in Table 2. The coercive force of this steel plate was measured in the same manner as in Example 1.
As is clear from Table 2, a coercive force with a temper rolling reduction ratio within the range of the present invention was obtained.

0.0041% C, 0.01% Si, 0.20% Mn, 0.02% P, 0.005% S, 0.03% Al, 0.004% N, 0.04% Cu,. A continuous casting component slab containing 05% Sn and 0.05% Ni was cast, heated at 1200 ° C., and hot rolled into a 1.8 mm thick hot rolled coil. This was pickled and cold-rolled to a thickness of 0.30 mm. After degreasing the cold-rolled sheet, as shown in Table 3, the double-sided Ni plating was changed to an adhesion amount of 0-5.0 g / m ² (per one side), and then continuously annealed in a nitrogen gas atmosphere at 740 ° C. Heat treatment was performed for 1 minute at a soaking temperature. Next, temper rolling was performed at a rolling reduction of 0.3%. Next, a blackening treatment was performed by annealing at 620 ° C. for 15 minutes in a CO + CO ₂ atmosphere with a partial pressure ratio PCO ₂ /PCO=2.4. The adhesion of the blackened film was examined by the same tape peeling test and vibration test as in Example 1. In the vibration test, 10 mm square specimens were vibrated at a stroke of 50 mm / second and 0.5 mm for 5 hours, and the number of powders falling on white paper was counted. Moreover, the blackened film thickness was observed by the SEM structure of the steel plate cross section.

As shown in Table 3, when the Ni plating amount exceeds 2.5 g / m ² , the blackened film thickness becomes as thin as 2.5 μm or less, resulting in a film thickness that is considered to have a problem in preventing the reflection of electron beams. Met. In addition, when Ni plating was performed compared with the case without Ni plating, no significant difference was observed in the tape peeling, but the effect was recognized by a vibration test capable of discriminating adhesion in more detail.

Claims (2)

A method for manufacturing a steel plate for an internal magnetic shield of a color TV Braun tube manufactured by performing blackening treatment on the surface after being formed by pressing, wherein C ≦ 0.005% by mass and Si ≦ 0.05% , Mn ≦ 0.5%, P ≦ 0.03%, S ≦ 0.02%, Al: 0.02-0.10%, N ≦ 0.004%, Nb: 0.005-0.03% , Ti: 0.01-0.04%, B: 0.0001-0.0010%, Cu: 0.03-0.3%, after pickling hot rolled sheet containing the balance Fe and inevitable components The steel sheet is cold-rolled to 0.1 to 0.4 mm, then recrystallized and annealed, temper rolling is performed at a rolling reduction of 2% or less, and the surface roughness Ra is set to 0.4 μm or more. A method of manufacturing a steel plate for a TV Braun tube internal magnetic shield. The method for producing a steel plate for a TV Braun tube internal magnetic shield according to claim 1, wherein Ni plating of 2.5 g / m ² or less is performed between cold rolling and annealing.