JPH10259453A - Base stock for shadow mask free from generation of unevenness in stripe at the time of etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base stock for a shadow mask having an etching face free from the generation of unevenness in stripes at the time of piercing many electron beam passing pores by etching. SOLUTION: This base stock for a shadow mask is composed of a sheet material using an Fe-Ni series alloy contg. 30 to 50% Ni, 0.01 to 1.0% Cr, <=0.015% C, <=0.2% Si, <=0.5% Mn, <=0.02% Al and <=0.0040% B, and in which the standard deviation σ Ni of the concn. of Ni in the cross-section vertical to the rolling direction of the stock is regulated to be <=1.076. By the standard deviation σ Ni of the concn. of Ni in the cross-section vertical to the rolling direction of the stock, the generation of the unevenness in stripes can be grasped with high precision, so that the obtd stock for shadow mask can be a high grade.

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 uneven 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. As a material for a shadow mask, it is required that the material has excellent etching properties so that an accurate electron beam passage hole is formed, and a low-carbon Al-killed steel is 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 electron beam passage hole is displaced, and a doming phenomenon occurs in which the electron beam does not hit a predetermined phosphor screen.

[0003] The doming phenomenon has become a serious problem as color televisions, displays and the like have become more precise and have higher luminance. Since the doming phenomenon is suppressed by using a material having a low thermal expansion characteristic, Fe having a low coefficient of thermal expansion is used.
-Ni-based alloys have been used as materials for shadow masks. However, Fe-Ni-based alloys
Since it contains a large amount of Ni, the material price is higher than that of the low-carbon Al-killed steel, and of course, it has greater strength than the low-carbon Al-killed steel and is inferior in press formability. In addition, there are also problems that the Young's modulus is low and the rigidity of the shadow mask is inferior, and the etching rate is low and the etching piercing property is inferior.

[0004] Various attempts have been made to modify Fe-Ni-based alloys so as to satisfy the characteristics required as a material for shadow masks. Above all, streak unevenness appearing in the shadow mask after the etching perforation lowers the quality of the CRT. In Japanese Patent Application Laid-Open No. 60-56053, the unevenness of the stripes is caused by the segregation of the Ni component, and the unevenness of the Ni is presumed to be caused by the difference in the etching property between the segregated portion and the base material. The introduction of suppressing the occurrence of streak unevenness by regulating the component segregation rate is introduced. That is, assuming that a segregated portion in which Ni is concentrated in a string shape exists in the material, the volume ratio and the length of the string-like segregated material are regulated, and the segregation ratio is regulated to 10% or less.

[0005] In Japanese Patent Application Laid-Open No. Sho 60-128253, 1
It introduces a method for eliminating Ni segregation in which ingot is subjected to forging with a cross section reduction rate of 40% or more with heat or two or more heats. In Japanese Patent Application Laid-Open No. 2-54743, the segregation of impurity elements such as C, Si, Mn, and Cr and the retention of a columnar structure having a specific orientation which occur during casting are the main causes of streak unevenness. Controlled continuous cast slab at 950 ° C or 1100
A method for preventing streak unevenness by maintaining the temperature at not less than 1 ° C. for at least one hour has been proposed. JP-A-1-25272
No. 5 also discloses a method of reducing streak unevenness by homogenizing a slab or a hot-rolled coil under specific conditions, assuming that the dominant cause of streak unevenness is component segregation. Specifically, the ratio of the Ni concentration range in the thin plate product to the Ni concentration range in the slab is defined as the Ni segregation level, and when this value is 0.7 or less, the line unevenness is suppressed to a practically acceptable level. It is going to be.

[0006]

SUMMARY OF THE INVENTION As stated above,
Conventionally, the segregation of components of Ni or other impurity elements causes uneven stripes, and a casting method, a hot working method, a homogenizing heat treatment, and the like for eliminating the segregation of components have been studied.
However, recent demands for color televisions, large-sized displays, and high-luminance images are severe. In response to this demand, there has been a demand for a shadow mask in which electron beam passing holes having a smaller hole diameter than before are formed at a high density, and the pitch between the holes is reduced. Therefore, in a material manufactured by a conventionally proposed method, unevenness of stripes is not sufficiently eliminated in a shadow mask requiring high quality.

Further, it has not been clarified yet what level of segregation remains at what position in a product and the amount of segregation remains, and various methods for eliminating segregation have been set as targets. Lack of clarity about the degree of elimination of segregation. The present invention has been devised in order to solve such a problem, and has found that the segregation distribution of Ni in a cross section perpendicular to the rolling direction of the shadow mask material is closely related to the occurrence of streak unevenness. It is another object of the present invention to provide a high-quality shadow mask material free from uneven stripes by strictly controlling the Ni segregation concentration in a vertical cross section.

[0008]

According to the present invention, there is provided a material for a shadow mask, wherein Ni: 30 to 50 is used.
% By weight, Cr: 0.01 to 1.0% by weight, C: 0.01
5% by weight or less, Si: 0.2% by weight or less, Mn: 0.5
Wt% or less, Al: 0.02 wt% or less and B: 0.0
A plate material made of an Fe-Ni-based alloy containing 040% by weight or less, and Ni in a cross section perpendicular to the rolling direction of the material.
The standard deviation of the concentration σNi is 1.076 or less.

[0009]

The stripe unevenness after etching perforation is observed as a linear or band-like difference in brightness, and some of them reach a length of 300 mm. The present inventors have investigated and studied the relationship between uneven stripes generated in a shadow mask and the distribution form of component segregation existing inside the material. As a result, as shown schematically in FIG. 1, when the cross section 1 perpendicular to the rolling direction 2 was observed in the material in which the stripe unevenness occurred, the Ni-deficient region 4 having a certain thickness in the plate thickness direction was rolled. It was found to extend in a streak shape in parallel with the direction 2, and it was found that many Ni-deficient regions 4 were distributed inside the material. Then, the present inventors quantitatively analyzed the degree of Ni segregation in the cross section 1 perpendicular to the rolling direction 2 using an X-ray microanalyzer, and statistically analyzed the analysis results. That is, when the Ni concentration value at each measurement point by the mapping quantitative analysis is plotted with the distribution frequency as the vertical axis, the distribution curve in FIG. 2 is obtained. In addition,
In FIG. 2, the smaller the standard deviation σNi is,
In other words, it means that the degree of segregation is small.

The present inventors have studied various manufacturing conditions such as ingot rolling and soaking conditions in order to reduce the standard deviation σNi under such a premise, and examined the rolling direction of the obtained product material. The relationship between the standard deviation σNi in the cross section perpendicular to the graph and the uneven stripe level was investigated. As a result, the standard deviation σ
It has been found that there is a strong correlation between Ni and the line streak unevenness level, and it has been clarified that when the standard deviation σNi is 1.076 or less, the line streak unevenness is reduced to such an extent that it is hardly observed with the naked eye. The present inventors have already proposed, in Japanese Patent Application No. 8-271490, to use the standard deviation σNi on the half-etched surface with respect to suppressing the occurrence of streak unevenness using the standard deviation σNi as an index. . However, in the method proposed here, since the standard deviation σNi of the half-etched surface is used as an index, an inspection step of sampling the material and performing half-etching is required. On the other hand, in the present invention, since the standard deviation σNi is obtained by observing a cross section perpendicular to the rolling direction, an index useful for preventing the occurrence of uneven stripes can be easily obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The components, contents and the like of the Fe-Ni alloy used in 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.
More than weight percent is required. However, if the Ni content exceeds 50% by weight, press formability is reduced due to an increase in proof stress. Cr: 0.01 to 1.0% by weight Cr is an effective alloying element for increasing the etching rate of the Fe-Ni-based alloy. When the content is 0.01% by weight or more, the effect of adding Cr becomes remarkable. 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 raw material and impairs the etching property. In the present invention, in order to prevent the adverse effects caused by C,
The upper limit of the C content was regulated to 0.015% by weight. Si: 0.2% by weight or less This component is 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 This component is 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: not more than 0.02% by weight Hard inclusions are formed and the surface quality is adversely affected by the occurrence of surface flaws. Therefore, the upper limit of the Al content is restricted to 0.02% by weight. B: 0.0040% 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. In the Fe—Ni-based alloy targeted by the present invention, S, P, O, N
And so on. The amount of each of these unavoidable components contained in the Fe-Ni-based alloy is 0.010% by weight or less, and such a content does not adversely affect the performance as a material for a shadow mask.

Standard deviation of Ni concentration in a cross section perpendicular to the rolling direction: σNi ≦ 1.076 The larger the fluctuation of Ni concentration, the larger the standard deviation σNi becomes, and uneven stripes are clearly observed after etching.
A small standard deviation σNi means that the Ni concentration fluctuation is small or the segregation region itself does not exist. According to the research and research by the present inventors, the standard deviation σN
When i was 1.076 or less, it was found that line unevenness was hardly observed with the naked eye, and a material usable for a high-quality shadow mask was obtained. The standard deviation σNi is
For example, it is measured in the following procedure by quantitative mapping analysis using an X-ray microanalyzer. A test piece is embedded in a resin or the like by exposing a cross section perpendicular to the rolling direction of the material, and the cross section perpendicular to the rolling direction is polished with alumina particles, diamond particles, or the like. An X-ray microanalyzer was used to measure Ni in a range of a square having one side of the thickness of the obtained polished surface.
For quantitative mapping analysis. At this time, the analysis range per point was about 0.4 μm in diameter, and as a result, about 250 analysis points were taken per side of the analysis surface, and the total number of analysis points was about 6250.
Score 0. The analysis value at each point was ± 4
The range of% is organized into a histogram obtained by dividing the range into 16 with a class width of 0.5%. At this time, the area ratio of each concentration class in the entire analysis area in the mapping data is defined as a frequency. The standard deviation is calculated from the obtained histogram to obtain the standard deviation σNi of the Ni concentration.

[0015]

EXAMPLE An Fe-Ni alloy having the composition shown in Table 1 was melted, and a 9-ton ingot was cast using a mold.
M material. In addition, a slab of 10 tons was manufactured by continuous casting to obtain a CC material.

[0016]

Each ingot was divided and soaked under the production conditions shown in Table 2. That is, the IM material was subjected to bulk rolling or further soaking, and the CC material was subjected to soaking as it was. Next, the surface of each slab was cared for, and the plate thickness was 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 0.12 mm. A pattern was printed on a test piece cut out from each cold-rolled steel strip with a photoresist, and then spray-etched with a ferric chloride solution having a specific gravity of 51 Baume and a temperature of 60 ° C. to produce a shadow mask. Observation of the occurrence of streak unevenness in the obtained shadow mask. If no streak unevenness was observed, the highest level was A, and no streak unevenness was observed. If it was more than this, it could be used as a material for high quality shadow mask. The level of occurrence of streak unevenness was evaluated in four stages: level B, a level C where a relatively large number of streaks were observed, and a minimum level D where a large number of streaks were observed.

Further, a section perpendicular to the rolling direction of the material is mirror-finished by polishing, and N-ray is analyzed by an X-ray microanalyzer.
i was subjected to quantitative mapping analysis. Table 2 also shows the standard deviation σNi of the Ni concentration and the line unevenness level in each test piece. FIG. 3 shows the relationship between the standard deviation σNi and the line unevenness level. FIG. 3 shows that there is a strong correlation between the standard deviation σNi and the line unevenness level. That is, in the example of the present invention in which the standard deviation σNi of the Ni concentration is 1.076 or less, the level of the line unevenness after the etching is B
As described above, it is used as an optimum material for a shadow mask requiring high quality. On the other hand, when the standard deviation σNi is 1.
If it exceeds 076, the line unevenness level becomes C or D,
It was unsuitable as a material for a high-quality shadow mask.

[0019]

Further, the following can be read from the relationship between the manufacturing conditions shown in Table 2, the standard deviation σNi of the Ni concentration, and the line unevenness level. In the IM material, the line unevenness level of Comparative Example 7 in which reheating was not performed during slab rolling was D, whereas 1
In Examples 1 and 2 of the present invention in which reheating was performed more than once, the standard deviation σ
Ni is reduced, and the stripe unevenness level is improved to B.
This is a result of promoting Ni diffusion by reheating. However, even if reheating is performed once, if the soaking time is short as in Comparative Example 8, a sufficient improvement effect does not appear, and streak unevenness occurs because the degree of reduction of the standard deviation σNi is small.

From these results and other manufacturing experiments, it was found that re-heating at 1250 to 1350 ° C. twice or twice at 1250 to 1350 ° C. for 24 hours or more at the time of slab rolling. , Standard deviation σNi is 1.076
As described below, it was found that a shadow mask material with almost no uneven stripes can be manufactured. The higher the reheating temperature, the lower the segregation due to the promotion of Ni diffusion. However, the upper limit temperature was set to 1350 ° C. from the viewpoints of oxidation loss of the material, life of the furnace material, and the like. Standard deviation of Ni concentration σNi
Are 1250 to 1350, as seen in Example 3 of the present invention.
The temperature is further reduced by performing reheating twice at 24 ° C. for 24 hours or more. In addition, the slab after the slab rolling is 1250-135.
As can be seen from Comparative Example 4 in which soaking was performed at 0 ° C. for 24 hours, diffusion of Ni was sufficiently advanced by soaking, and the standard deviation σNi showed the lowest value of 1.021 in the inventive examples and comparative examples. . In each of Examples 3 and 4 of the present invention having a low standard deviation σNi, the level A was such that no line unevenness was observed.

Regarding the CC material, it can be generally said that Ni segregation is eliminated by slab soaking. However, in Comparative Example 10 in which soaking was performed at 1150 ° C. for 24 hours, the standard deviation σNi exceeded 1.076,
The level was at a level C at which the occurrence of uneven stripes was observed. On the other hand,
In Examples 5 and 6 of the present invention in which the soaking temperature was set to 1250 to 1350 ° C., the standard deviation σNi was 1.076 or less, and a shadow mask material free from streak unevenness could be manufactured. As described above, in both the slab-rolled material and the continuous cast material, by appropriately setting the sizing condition, the soaking condition, and the like, the component segregation of Ni is effectively eliminated, and the standard deviation σNi is 1.076. The following materials for shadow masks were produced. The thus obtained shadow mask materials of Examples 1 to 6 of the present invention have a Ni concentration standard deviation σNi of 1.076 or less, as shown in FIG.
It can be said that it is a material suitable for a shadow mask that requires a high quality when the level of the uneven stripe after etching is B or more.

[0023]

As described above, the shadow mask material of the present invention has a Ni cross section perpendicular to the rolling direction.
Since the standard deviation σNi of the concentration is regulated to 1.076 or less, an etched surface free from uneven stripes when a large number of electron beam passage holes are formed by etching can be obtained. Therefore, color televisions that require high-definition image quality,
Used as a material for shadow masks for cathode ray tubes for displays and the like.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the distribution of a Ni deficiency region inside a material.

FIG. 2 is a graph showing a frequency distribution of Ni concentration in a cross section perpendicular to a rolling direction.

FIG. 3 is a graph showing the relationship between the standard deviation σNi of the Ni concentration and the level of streak unevenness.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiko Takemoto 4976 Nomura Minamicho, Shinnanyo-shi, Yamaguchi Pref.

Claims (1)

[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:
A plate made of a Fe—Ni alloy containing 0.02% by weight or less and B: 0.0040% by weight or less, and a standard deviation σN of Ni concentration in a cross section perpendicular to the rolling direction of the material.
A material for a shadow mask which does not cause stripe unevenness during etching, wherein i is 1.076 or less.