JP2001192775A - Fe-Ni ALLOY THIN SHEET FOR SHADOW MASK OF EXTENSION SYSTEM - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Fe-Ni alloy thin sheet for a shadow mask of an extension system small in the reduction rate of tensile strength even by heating treatment such as blackening treatment. SOLUTION: This Fe-Ni alloy thin sheet has a composition consisting of, by mass, 34 to 37% Ni, and the balance substantial Fe, in which the average thermal expansion coefficient in the temperature region of 30 to 100 deg.C is controlled to the range of 2.0×10-6/ deg.C or less, and Vickers hardness is controlled to the range of 170 to 240. Since the reduction of tensile strength before and after heating treatment is small, deformation such as wrinkles is suppressed, and a cathode ray tube of high quality free from the generation of color slurring, the unsharpening of an image or the like can be assembled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch-type Fe--Ni alloy thin plate for a shadow mask which is excellent in high-temperature creep resistance during baking in a cathode ray tube assembling process.

[0002]

2. Description of the Related Art A shadow mask type cathode ray tube has a structure in which a shadow mask is partially fixed to a frame. In recent years, as the cathode ray tube becomes larger and higher definition, an Fe--Ni based material having a small thermal expansion coefficient is used. Alloys are beginning to be used. By forming a large number of holes by photo-etching in a thin plate of an Fe-Ni-based alloy to form an electron beam passage hole, sufficiently softening by heating annealing at a recrystallization temperature or higher, and then press-forming to a predetermined curved surface. It is used as a shadow mask. In a shadow mask manufactured by a press method, there is no particular hardness regulation for the material because the material is softened and annealed before pressing. By the way, recently, a flat-panel CRT with a smaller screen curvature has begun to be adopted.
There is also adopted a stretching method in which a shadow mask made of a Ni alloy is stretched and fixed directly to a frame while maintaining the tension (see Japanese Patent Application Laid-Open No. 7-296736).

[0003]

The shadow mask has a temperature of 400 to 700 ° C. as seen in a blackening process, a baking process for removing distortion, a frit process for sealing glass, and the like in the manufacturing process of a cathode ray tube. Heat treatment in the area several times. Therefore, the shadow mask stretched over the frame is heated to 400 to 700 ° C., so that creep deformation is likely to occur, and the tension applied when the temperature returns to room temperature decreases. The drop in tension causes deformation such as wrinkles in the shadow mask being handled, and causes a shape collapse even by vibration.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been devised to solve such a problem, and it is an object of the present invention to improve cathode ray tube manufacturing by improving an Fe-Ni alloy used as a material for a shadow mask. An object of the present invention is to provide a high-quality Fe—Ni alloy thin plate for a shadow mask, which suppresses deformation during a heat treatment in a process and is fixed to a frame by a stretching method. In order to achieve the object, the Fe—Ni alloy thin plate of the present invention has a composition of 34 to 37% by mass of Ni and substantially the balance of Fe, and has an average thermal expansion coefficient of 2 in a temperature range of 30 to 100 ° C. 0.0 × 10 ⁻⁶ / ° C. or less, and Vickers hardness is adjusted in the range of 170 to 240.

[0005]

The shadow mask is disposed immediately before the fluorescent screen of the color picture tube, generates heat by the collision of the electron beam emitted from the electron gun, and expands thermally. If the shape or size of the electron beam passage hole changes due to a rise in the temperature of the shadow mask, a predetermined electron beam does not hit a predetermined phosphor screen, causing color shift and blurring of an image.
In this regard, especially for high-definition and large CRTs,
Fe—Ni-based alloys having a small coefficient of thermal expansion have been widely used as materials for shadow masks. Fe-
The conventional shadow mask made of 36% Ni alloy is
It is fixed to the frame without being stretched. Therefore, it is not necessary to consider creep deformation in the heat treatment stage in the assembly process of the cathode ray tube, and in order to secure workability at the time of press forming, the Vickers hardness is adjusted to 150 or less by heat annealing at a recrystallization temperature or higher. .

On the other hand, in the case of a shadow mask fixed to a frame by the stretching method, the tension decreases due to the creep deformation in the heat treatment step, so that it is necessary to suppress the creep deformation. Then, the present inventors investigated and studied an Fe—Ni alloy having a small coefficient of thermal expansion. As a result, the coefficient of thermal expansion was reduced to 2.0 × 10 ⁻⁶ / ° C. or less by regulating the Ni content, and the Vickers alloy was reduced. When the hardness is adjusted to 170 to 240, the drop in the tension of the shadow mask is suppressed to 20% or less, and the deformation of the shadow mask during the conventional cathode ray tube manufacturing and the quality deterioration due to the vibration in the cathode ray tube do not occur. I found it. The Fe-Ni-based alloy used in the present invention has a thickness of 34 to 30 to ensure the required low thermal expansion characteristics.
It contains 37% by mass of Ni. Ni content is 34 to 3
Outside the range of 7% by mass, the coefficient of thermal expansion increases.
Furthermore, in order to prevent color misregistration, the present inventors
Research has shown that the average thermal expansion coefficient in the temperature range of 30 to 100 ° C. needs to be 2.0 × 10 ⁻⁶ / ° C. or less.

[0007] The material for the shadow mask used in the present invention is an Fe-Ni alloy whose Ni content is regulated.
As long as a coefficient of thermal expansion of 2.0 × 10 ⁻⁶ / ° C. or less is maintained, M having an effect of improving productivity such as hot workability is exhibited.
Alloy components such as n and B can be contained, and there is no particular quantitative restriction on C, Si, P, S and the like inevitably mixed in from the manufacturing process. However, in order to provide the characteristics required as a shadow mask in consideration of manufacturability and to secure an average coefficient of thermal expansion of 2.0 × 10 ⁻⁶ / ° C. or less, the Ni content should be in the range of 34 to 37% by mass. And the elements to be mixed as raw material impurities and deoxidizing agents are C ≦ 0.
01% by mass, N ≦ 0.004% by mass, Si ≦ 0.2% by mass, Mn ≦ 0.5% by mass, Al ≦ 0.05% by mass, S ≦
0.005% by mass, B: preferably 0.0005 to 0.005% by mass.

[0008] C is a component for improving the strength.
When a large amount of C exceeding 01% by mass is contained, not only the coefficient of thermal expansion is increased, but also the etching processability is deteriorated. N is also an effective component for improving strength, but 0.004.
When a large amount of N exceeding mass% is contained, residual bubbles are generated in the alloy, resulting in defects. Although Si is a component added as a deoxidizing agent, if a large amount of Si exceeding 0.2% by mass is contained, the Si concentration of the surface layer increases after bright annealing, and a blackened film formed on the shadow mask surface The degree of blackening decreases.
Mn is a component that fixes S to be segregated at grain boundaries and improves hot workability. However, when a large amount of Mn exceeding 0.5% by mass is included, the coefficient of thermal expansion increases. Al is a component acting as a strong deoxidizing agent, but 0.05% by mass
If a large amount of Al is added, hard Al ₂ O ₃ -based inclusions that cause flaws on the product surface increase, and the surface quality deteriorates. Since S is a component that significantly reduces hot workability, it is necessary to remove S as much as possible in the refining stage,
In order to prevent significant cracking during hot working such as hot rolling,
0.005% by mass or less, preferably 0.003% by mass
It is regulated as follows. B is a component effective for improving hot workability, and when B is 0.0005% by mass or more,
The surface crack of the slab becomes small during hot working. But,
When an excessive amount of B exceeding 0.005% by mass is added, not only the coefficient of thermal expansion becomes large, but also B concentrated on the surface.
As a result, a non-uniform blackened film is formed.

The Vickers hardness of the material affects the creep strain during the heat treatment performed in the cathode ray tube assembling process. According to investigations and studies by the present inventors, it has been found that the relationship shown in FIG. 1 is established between Vickers hardness and creep strain under a temperature condition of 700 ° C. or less assuming heat treatment. That is, as the Vickers hardness increases, the creep strain decreases. Above all, when the Vickers hardness is 170 or more, the decrease in tension is suppressed to 20% or less even by heat treatment in the cathode ray tube manufacturing process, and a high quality shadow mask is obtained. However, when the Vickers hardness exceeds 240, recrystallization starts in a part of the material during the blackening treatment in a temperature range of 400 to 700 ° C., and when the material is stretched and baked, the creep strain increases. As a result, the decrease in tension becomes 20% or more. Vickers hardness is adjusted by the final draft in the cold rolling step. Specifically, the final draft is 15 to 8
By setting it to 0%, a material having the required Vickers hardness can be obtained.

[0010]

EXAMPLE An Fe-Ni alloy having the components shown in Table 1 was melted and an ingot was cast by an ingot casting method.

[0011]

After soaking the ingot at 1250 ° C., it was slab-rolled into slabs. The slab was heated to 1200 ° C and hot rolled to produce a hot rolled sheet. 1000 hot rolled sheets
° C, cold-rolled and annealed to a thickness of 0.1
mm was prepared. In the cold rolling step, the final draft was changed in the range of 5 to 85%, and the Vickers hardness was adjusted to different values as shown in Table 2. Each of the obtained cold-rolled sheets was perforated by photoetching, soaked at 500 ° C. for 30 minutes to perform a blackening treatment, thereby obtaining a shadow mask.

The blackened shadow mask is
In a state of being stretched so as to apply a tension of N / mm ² , it was welded to a frame made of Fe-36% Ni having the same composition as the shadow mask. 30 minutes at 500 ° C
After the heat treatment for one minute, the reduction ratio of the tension after the heat treatment to the tension before the heat treatment was measured. As can be seen from the measurement results in Table 2, in Examples 1 to 5 of the present invention having a coefficient of thermal expansion of 2 × 10 ⁻⁶ / ° C. or less and a Vickers hardness of 170 to 240, the rate of decrease in tension before and after the heat treatment Was 20% or less. On the other hand, in Comparative Examples 9 and 10, in which the Vickers hardness is 170 or more but the Ni content and the thermal expansion coefficient are out of the ranges specified in the present invention, the thermal expansion coefficient exceeds 2 × 10 ⁻⁶ / ° C. Was. In Comparative Examples 6 to 8 in which the Vickers hardness did not reach 170 or exceeded 240, 20%
The tension drop exceeding.

[0014]

[0015]

As described above, when the Fe-Ni alloy thin plate for a stretchable shadow mask of the present invention is used, the decrease in the shadow mask tension before and after the heat treatment in the cathode ray tube assembling process is small. In addition, a low thermal expansion coefficient can be combined with a high quality cathode ray tube without deformation during handling.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of Vickers hardness on the rate of decrease in tension that is reduced by heat treatment.

Continued on the front page (72) Inventor Takashi Yamauchi 4976 Nomura Minamicho, Shinnanyo-shi, Yamaguchi F-term in the stainless steel division of Nisshin Steel Corporation (reference) 5C027 HH02 5C031 EE05

Claims (1)

[Claims] 1. Ni: 34 to 37% by mass, the balance substantially consisting of Fe, an average coefficient of thermal expansion in a temperature range of 30 to 100 ° C. of 2.0 × 10 ⁻⁶ / ° C. or less, Vickers hardness An Fe-Ni alloy thin plate for a shadow mask of a stretching method having a thickness in the range of 170 to 240.