JP2000096190A - Stock for shadow mask, free from striped irregularity at etching, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Fe-Ni alloy stock for shadow mask, causing no striped irregularity at the time of etching. SOLUTION: The stock is a <=0.3 mm-thick sheet of an Fe-Ni alloy having a composition consisting of, by weight, 30-50% Ni, 0.01-1.0% Cr, <=0.015% C, <=0.2% Si, <=0.5% Mn, <=0.02% Al, <=0.0040% B, and the balance Fe with inevitable impurities. Further, the range of fluctuation in the Ni concentration in a sheet-thickness direction in the cross section perpendicular to the rolling direction of the sheet is regulated to <=1.0 wt.%. This stock can be manufactured by carrying out continuous casting without performing electromagnetic stirring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for a shadow mask which does not cause stripes when a large number of electron beam passage holes are formed by etching.

[0002]

2. Description of the Related Art A picture tube such as a cathode ray tube for a color television or a display of an office automation apparatus incorporates a shadow mask having a large number of electron beam passage holes formed therein. The electron beam emitted from the electron gun passes through a specific beam passage hole, and projects a beam spot on each fluorescent part according to each color tone.

[0003] As a material for a shadow mask, it is required to have excellent etching properties so that an accurate electron beam passage hole is formed, and a low carbon Al-killed steel has been conventionally used. However, the shadow mask is heated by the collision of the electron beam and thermally expands. If the thermal expansion at this time is large, the position of the electron beam passage hole is displaced, and a doming phenomenon occurs in which the electron beam does not hit a predetermined phosphor screen.

[0004] The doming phenomenon has become a major problem as color televisions, displays and the like have become more accurate and brighter. Since the doming phenomenon is suppressed by the use of a material having low thermal expansion characteristics, it is more expensive and slightly inferior to etching than low carbon Al-killed steel, but an Fe-Ni alloy having a low thermal expansion coefficient is used for shadow masks. It is being used as a material.

[0005] However, the Fe-Ni-based alloy has a drawback that "streaks" occur in the shadow mask after etching. The stripe unevenness is etching unevenness that looks like a band or a streak in appearance, and is a serious problem as it degrades the quality of a cathode ray tube.

In order to eliminate this unevenness, Fe—Ni
Various measures for modifying a system alloy have been proposed. For example, in Japanese Unexamined Patent Publication No. 60-56053, the cause of the stripe irregularity is N
In the component segregation of i, by controlling the Ni component segregation rate on the premise that the unevenness occurs due to the etching property difference between the segregated portion and the base material portion, the occurrence of the unevenness is suppressed. It is introduced to do. That is, assuming that a segregated portion in which Ni is concentrated in a string shape is present in the material, the volume ratio and length of the string-like segregated material are regulated and segregation is reduced by 10%.
It is regulated as follows.

In Japanese Patent Application Laid-Open No. Sho 60-128253, 1
This paper introduces a method for eliminating Ni segregation, in which forging of the ingot with a cross-section reduction rate of 40% or more with heat or two or more heats is performed. JP-A-2-54743 discloses that C, Si, Mn, Cr
It is assumed that the segregation of impurity elements such as impurity elements and the columnar structure having a specific orientation that occurs during casting are the main causes of streaking unevenness. A method has been proposed to prevent streaking by holding the film for one hour or more.

Japanese Patent Application Laid-Open No. 1-252725 also discloses that a dominant cause of line unevenness is component segregation, and introduces a method of reducing line unevenness by homogenizing a slab or a hot-rolled coil under specific conditions. ing. Specifically, the rate of reduction of the Ni concentration range in the thin plate product with respect to the Ni concentration range in the slab is defined as the Ni segregation level. They say they will be suppressed.

[0009]

SUMMARY OF THE INVENTION As stated above,
Casting, hot working, and homogenizing heat treatment for eliminating component segregation are considered as causes of line unevenness due to component segregation of Ni or other elements. However, with the recent movement of color televisions to be larger and more multimedia, a shadow mask is required which has a high density of electron beam passage holes with a smaller diameter than the conventional one and a fine pitch between the holes. It is becoming. On the other hand, in the materials manufactured by the conventionally proposed method,
The current situation is that streaking has not been sufficiently eliminated. An object of the present invention is to provide an Fe-Ni alloy material for a shadow mask which does not cause line unevenness at the time of etching in accordance with such a situation.

[0010]

The object of the present invention is to provide Ni: 30
To 50% by weight, Cr: 0.01 to 1.0% by weight, C:
0.015% by weight or less, Si: 0.2% by weight or less, M
n: not more than 0.5% by weight, Al: not more than 0.02% by weight and B: not more than 0.0040% by weight, and 0.3 mm or less in thickness of Fe-Ni-based alloy composed of other unavoidable impurities and the balance of Fe Wherein the fluctuation range of the Ni concentration in the thickness direction in the cross section perpendicular to the rolling direction of the plate material is 1.
This is achieved by using a shadow mask material that is not more than 0% by weight and does not cause line unevenness during etching.

[0011] In addition, the present invention provides a method of continuously casting without performing electromagnetic stirring in producing the above-mentioned material.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors examined the relationship between the form of occurrence of stripe unevenness in a Fe-Ni-based alloy material and the segregation of components in examining measures for eliminating the stripe unevenness. As a result of closely observing the shadow mask in which the stripes were generated, it was confirmed that the etched surface of the perforated portion had more irregularities than in the case where the stripes were not generated. Then, as a result of analyzing the distribution state of Ni in the cross section of the plate perpendicular to the rolling direction using an X-ray microanalyzer, it was found that a Ni-deficient region was distributed in a layer at a position corresponding to the concave portion of the perforated portion. FIG. 1 schematically shows this state. Since a difference occurs in the etching rate in response to such a change in the Ni concentration in the thickness direction, minute irregularities are generated on the surface of the formed hole. As a result, the hole shape and the hole diameter become non-uniform, which causes stripe unevenness.

[0013] The segregation of Ni is micro segregation occurring between dendrite trees during casting, and remains without being eliminated even after rolling and heat treatment in the subsequent steps. Furthermore, in continuous casting, “macroscopic” component segregation generally called a white band occurs by performing electromagnetic stirring. Generally, in continuous casting, electromagnetic stirring is performed for the purpose of preventing center segregation, or for the purpose of making the cast structure equiaxed. Fe-N of about 36% by weight of Ni used for a shadow mask material
In the solidification of an i-based alloy, the crystal at the start of crystallization has a low Ni concentration, while the Ni component is concentrated in the molten steel. However, when electromagnetic stirring is performed during continuous casting, the Ni-enriched molten steel between the dendrite crystals of the solidified shell grown from the water-cooled mold wall is washed out by the molten steel flow, so that the area affected by the electromagnetic stirring is more Ni than the other parts. Macroscopic segregation with a low concentration, generally called a white band. Although the degree of segregation varies depending on the electromagnetic stirring conditions, steel type, and the like, for example, the electromagnetic stirring current of a Fe-36% Ni alloy becomes about 0.5% negatively segregated with Ni at about 1200 A as shown in FIG. This is a concentration fluctuation larger than the above-mentioned micro-segregation, and is not easily eliminated by rolling and annealing during the subsequent steps and remains in the final product. The generation area of the white band varies depending on the position of the electromagnetic stirrer and the cooling condition of the slab, but is generally several tens mm inward from the slab surface.
Appears with a width of m. The inventors have found that depending on the extent to which the white band remains in the product, unevenness occurs on the etched surface of the shadow mask perforated portion, and as a result, the quality of the level of the unevenness greatly differs.

The inventors of the present invention have studied various methods for eliminating component segregation occurring during casting in the subsequent steps, and have examined the degree of residual component segregation of the raw material obtained by each method and the streak unevenness after etching. The relationship with degree was investigated. As a result, when a cross section perpendicular to the rolling direction of the material was analyzed by an X-ray microanalyzer,
When the fluctuation width of the Ni concentration in the thickness direction is 1.0% or less,
It was found that there was almost no line unevenness. Here, the fluctuation range of the Ni concentration is defined as the difference between the maximum value and the minimum value of the Ni concentration as shown in FIG. In addition, when the material is manufactured by continuous casting, if the generation of white bands is suppressed by not performing electromagnetic stirring, the N
It has been found that the fluctuation range of the concentration of i is 1.0% by weight, and the occurrence of stripe unevenness can be prevented.

The fluctuation range of the Ni concentration is measured by an X-ray microanalyzer according to the following method. In a cross section perpendicular to the rolling direction of the material, a quantitative mapping analysis of Ni is performed at a probe diameter of 1 μm and a measurement interval of 1 μm in a square area having a plate thickness of one side. The obtained quantitative analysis value (% by weight) at each measurement point is converted into a density fluctuation line in the thickness direction by setting the average value in the width direction as a representative value. The difference between the maximum value and the minimum value in this line is defined as the fluctuation range of the Ni concentration.

Hereinafter, the alloy components in the raw material provided by the present invention will be described. Ni: 30 to 50% by weight Ni is an important alloy element for maintaining a low coefficient of thermal expansion of the Fe-Ni alloy.
It is necessary to regulate the Ni content to not less than 50% by weight and not more than 50% by weight.

Cr: 0.01 to 1.0% by weight Cr is an effective alloying element for increasing the etching rate of an Fe-Ni alloy. When the content is 0.01% by weight or more, the effect of adding Cr is remarkable. become. However, when a large amount of Cr exceeding 1.0% by weight is contained, the thermal expansion coefficient of the Fe—Ni-based alloy increases.

C: 0.015% by weight or less C is a harmful element which forms carbides in the material and impairs the etching property. Therefore, in the present invention, the upper limit of the C content is set to 0.0
It was regulated to 15% by weight.

Si: 0.2% by weight or less Si is an element added as a deoxidizing agent, but tends to increase the thermal expansion coefficient and deteriorate the etching property and the blackening film property. Therefore, in the present invention, the upper limit of the Si content is set to 0.1.
It was regulated to 2% by weight.

Mn: 0.5% by weight or less Mn is an element effective as a deoxidizing agent, but has an effect of increasing the coefficient of thermal expansion. Therefore, the Mn content has an upper limit of 0.1.
Regulated to 5% by weight.

Al: 0.02% by weight or less Although it is an element effective as a deoxidizing agent, the upper limit of the Al content is restricted to 0.02% by weight in order to deteriorate the surface quality due to generation of surface flaws and the like.

B: 0.004% by weight or less B is an effective component for increasing the etching rate. However, when the content exceeds 0.0040% by weight, unevenness in annealing tends to occur after softening annealing, which promotes unevenness in formation of a blackened film. Therefore, the upper limit of the B content is 0.0040.
It was restricted to wt%.

In the Fe—Ni alloy to which the present invention is applied, there are S, P, O, N, and the like as other inevitable components. The amount of each of these unavoidable components contained in the alloy is not more than 0.010% by weight, and such an amount does not adversely affect the performance as a material for a shadow mask.

If the fluctuation width of the Ni concentration in the cross section perpendicular to the rolling direction of a material having a thickness of 0.3 mm in the thickness direction exceeds 1.0% by weight or less, stripes occur after etching. For this reason, it is regulated to 1.0% by weight or less.

[0025]

EXAMPLE Four slabs (10 tons) of Fe--Ni alloys having the compositions shown in Table 1 were produced by melting, and each charge was provided with and without electromagnetic stirring during continuous casting.

[0026]

[Table 1]

Under the conditions shown in Table 2, the soaking temperature before hot rolling was 1
After applying at 150 ° C., the thickness was reduced to 6 mm by hot rolling. Further, annealing at 1000 ° C. and cold rolling were repeated several times to finally obtain a cold-rolled steel strip having a thickness of 0.25 mm. After printing a pattern on each cold-rolled steel strip with a photoresist, a shadow mask was prepared by spray etching with a ferric chloride solution having a specific gravity of 51 Baume and a temperature of 60 ° C., and the occurrence of streaks was observed. At this time, those having no streaking observed were at the highest level A, and those having almost no streaks were observed. The level of occurrence of line unevenness was evaluated in four stages, where the level where unevenness was observed was level C and the level where a large number of clear unevenness appeared was the lowest level D. In addition, the cross section perpendicular to the rolling direction of the test piece cut from the cold-rolled steel strip was polished to a mirror finish, and quantitative mapping analysis was performed with an X-ray microanalyzer to measure the fluctuation range of the Ni concentration in the thickness direction. did. The values are shown in Table 2 together with the line unevenness level.
In contrast to the material subjected to electromagnetic stirring (Comparative Examples 5 to 8), the difference in Ni concentration was reduced to 1.0% or less in the materials (1 to 4) not subjected to electromagnetic stirring, and the line unevenness level was reduced to B. It has improved to a level or higher.

[0028]

[Table 2]

FIG. 3 shows the relationship between the fluctuation range of the Ni concentration and the level of the stripe unevenness. FIG. 3 shows that there is a strong correlation between the fluctuation range of the Ni concentration and the line unevenness level. That is, Example 1 of the present invention in which the fluctuation range of the Ni concentration is 1.0% or less.
In Nos. To 4, the level of the stripe unevenness after etching is B or more, and is used as an optimal material for a shadow mask requiring high quality. On the other hand, when the concentration difference of Ni exceeds 1.0% as in Comparative Examples 5 to 8, the level of streaking becomes C or D, which is unsuitable as a high-quality shadow mask.

For reference, FIGS. 4 and 5 show examples of the measurement of the Ni concentration distribution in the thickness direction in the cross section of the slab depending on the presence or absence of electric stirring during continuous casting. 4 shows an example of Test No. 6 in Table 2 (Comparative Example), and FIG. 5 shows an example of Test No. 2 (Inventive Example).

[0031]

As described above, since the shadow mask material of the present invention regulates the fluctuation range of the Ni concentration in the cross section perpendicular to the rolling direction to 1.0% by weight or less, a large number of electron beams are formed. An etched surface free from streaking when a through hole is formed by photoetching can be obtained. Therefore, it is used as a material for a shadow mask for a cathode ray tube of a color television, which requires high definition image quality.

[Brief description of the drawings]

FIG. 1 is a partial perspective view schematically showing a distribution of a Ni deficient region in a cross section of a shadow mask after material etching.

FIG. 2 is a view showing a concept of a fluctuation width of a Ni concentration in a sheet thickness direction in a cross section perpendicular to a rolling direction of a material.

FIG. 3 is a graph showing the relationship between the fluctuation range of the Ni concentration and the level of the stripe unevenness.

FIG. 4 is a graph showing an example of a Ni concentration distribution in a slab thickness direction when electromagnetic stirring is performed in continuous casting.

FIG. 5 is a graph showing an example of a Ni concentration distribution in a slab thickness direction when electromagnetic stirring is not performed in continuous casting.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Section perpendicular to rolling direction 2 Rolling direction 3 Etching perforated part 4 Ni deficiency area 5 Section perpendicular to rolling direction of material 6 Surface of material 7 Quantitative mapping analysis range 8 Ni concentration fluctuation in thickness direction 9 Maximum value of Ni concentration 10 Minimum value of Ni concentration 11 Fluctuation width of Ni concentration

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Morikawa 4976 Nomura Minami-cho, Shinnanyo-shi, Yamaguchi Prefecture F-term in Nissin Steel Engineering Laboratory (reference)

Claims (2)

[Claims] 1. Ni: 30 to 50% by weight, Cr: 0.0
1 to 1.0% by weight, C: 0.015% by weight or less, Si:
0.2% by weight or less, Mn: 0.5% by weight or less, Al:
0.02% by weight or less and B: 0.0040% by weight or less, and other unavoidable impurities and the balance of Fe
An e-Ni-based alloy having a plate thickness of 0.3 mm or less,
N in the sheet thickness direction in a cross section perpendicular to the rolling direction of the sheet material
A material for a shadow mask in which the fluctuation range of the i-concentration is 1.0% by weight or less and no streaking occurs during etching. 2. The method for producing a material for a shadow mask according to claim 1, wherein the material is continuously cast without performing electromagnetic stirring.