JP2001140043A - Fe-Ni SERIES ALLOY HOT ROLLED SHEET FOR SHADOW MASK AND METHOD FOR PRODUCING Fe-Ni SERIES ALLOY SHEET FOR SHADOW MASK - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an Fe-Ni series alloy sheet high in the grade of unevenness in stripes and suitable as a shadow mask for a high precision picture tube. SOLUTION: This Fe-Ni series alloy hot rolled sheet contains 30 to 50% Ni, <=0.015% C, <=0.20% Si, <=0.5% Mn, <=0.02% Al and <=0.0040% B, and the pitch of the variation of the Ni concentration along the sheet thickness direction is controlled to <=16 μm. The Fe-Ni series alloy sheet for a shadow mask is produced by casting an Fe-Ni series alloy into an ingot having a thickness T (mm), and, at the time of subjecting the same to hot rolling, annealing and cold rolling, by executing the hot rolling and cold rolling at drafts in which the total draft radio R=T/t by the hot rolling and cold rolling is controlled to >=7,000 when the sheet thickness after the final cold rolling is defined as t (mm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolled Fe--Ni alloy sheet and a method for producing an Fe--Ni alloy sheet suitable as a material for a shadow mask incorporated in a display of OA equipment, a cathode ray tube of a color television, and the like. .

[0002]

2. Description of the Related Art A cathode ray tube having a large number of electron beam passage holes is incorporated in a picture tube such as a display of OA equipment and a cathode ray tube of a color television. The electron beam emitted from the electron gun passes through a specific electron beam passage hole, and projects a beam spot on each fluorescent portion according to each color tone. As a material for shadow masks,
Since excellent etching properties are required to form accurate electron beam passage holes, 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. Low carbon A
In a shadow mask made of l-killed steel, the thermal expansion at this time is large, the electron beam passage hole is displaced, and a doming phenomenon in which the electron beam does not hit a predetermined phosphor screen easily occurs.

The doming phenomenon has become a serious problem as the definition and brightness of color televisions and displays have increased. Since the doming phenomenon is caused by the thermal expansion characteristic of the material, it can be suppressed by using a material having a low thermal expansion characteristic. Therefore, Fe-Ni-based alloys having a small coefficient of thermal expansion have begun to be used as materials for shadow masks in picture tubes requiring high definition and high brightness. However, since the Fe-Ni-based alloy contains a large amount of Ni, the material cost is higher than that of the low-carbon Al-killed steel. In addition, it is inferior in press formability due to higher strength than low carbon Al-killed steel, and inferior in rigidity due to low Young's modulus. Concerning the etching properties, it is also disadvantageous that the etching rate is lower than that of the low carbon Al killed steel and the etching piercing property is inferior. Above all, stripes appearing in a shadow mask after etching are a serious problem that degrades the quality of the shadow mask.

It is considered that the occurrence of stripe unevenness is caused by the concentration segregation of Ni or other components having different etching properties between the segregated portion and the base material portion. Therefore, various methods for modifying the Fe-Ni-based alloy by a casting method, a hot working method, a homogeneous heat treatment or the like so as to eliminate the segregation of Ni or the like have been conventionally proposed. For example, Japanese Patent Application Laid-Open No. 60-5605
In Japanese Patent Publication No. 3 (KOKAI), the volume ratio and length of the segregated product of Ni concentrated in a string shape are regulated, and the segregation ratio is suppressed to 10% or less. A method of forging a Fe-Ni alloy ingot heated to a temperature range of 850 ° C. to the melting point with a cross-sectional reduction rate of 40% or more (Japanese Patent Application Laid-Open No. 60-128253). A method of heating to a temperature of 1100 ° C. or more for 1 hour or more (Japanese Patent Laid-Open No. 2-54343);
A method of homogenizing a slab or a hot-rolled coil of a Ni-based alloy under specific conditions (JP-A-1-252725) is also known.

[0005]

However, with the recent trend that displays used in color televisions and OA equipment have been rapidly increasing in size and multimedia, an electron beam passage hole having a smaller diameter than in the past. Perforated with high density,
In addition, there is an increasing demand for making the pitch adjacent to the electron beam passage holes fine. However, in the case of a conventional Fe—Ni alloy modified by casting, hot working, heat treatment, etc., the required characteristics as a material for a shadow mask in which many electron beam passage holes are densely formed at a fine pitch. Do not have enough.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been devised to solve such a problem, and regulates Ni segregation in a hot-rolled sheet stage, and also converts an ingot into a final cold-rolled sheet. It is an object of the present invention to provide a shadow mask material suitable for high definition and high brightness by suppressing the total reduction ratio up to the point, thereby suppressing streak unevenness which is likely to occur at the time of etching.

The hot rolled Fe-Ni alloy sheet for a shadow mask according to the present invention has a Ni: 30 to 5 to achieve the object.
0 mass%, C: 0.015 mass% or less, Si: 0.20
Mass% or less, Mn: 0.5 mass% or less, Al: 0.02
Mass% or less, B: 0.0040 mass% or less, the balance substantially has a composition of Fe, and the variation pitch of the Ni concentration along the thickness direction is 16 μm or less. When the Fe-Ni-based alloy sheet for a shadow mask is cast from an Fe-Ni-based alloy into an ingot having a thickness of T (mm), and then cold-rolled through hot rolling and annealing, the thickness of the sheet after final cold rolling is reduced. When t (mm), the total reduction ratio R = T / by hot rolling and cold rolling
It is manufactured by performing hot rolling and cold rolling at a rolling reduction at which t becomes 7000 or more.

[0008]

The present inventors have studied the relationship between the form of occurrence of stripe unevenness in the Fe-Ni-based alloy material and the segregation of components when examining measures for suppressing stripe unevenness. As a result of detailed observation of the shadow mask in which the stripes were generated, it was confirmed that the etched surface of the perforated portion had more irregularities than the shadow mask in which the stripes were not generated. Then, when the distribution state of Ni in the cross section of the plate perpendicular to the rolling direction was analyzed with an X-ray microanalyzer, a layered distribution in a Ni-deficient region was observed. That is, when a cross section 1 perpendicular to the rolling direction D is observed as schematically shown in FIG. 1, the Ni-deficient regions 2 overlap in a layered manner. The Ni concentration fluctuates in the thickness direction due to the layered distribution of the Ni deficiency region 2. The fluctuation of the Ni concentration causes a difference in the etching rate, and fine irregularities occur on the surface of the perforated portion 3 formed by etching. As a result, the hole shape and the hole diameter of the perforated portion 3 become non-uniform, and are observed as stripes.

Ni segregation is macro-segregation caused by micro-segregation between dendrite dendrites during casting and the flow of residual molten steel in the solidification process, etc. Also easily remain without being eliminated. Above all, macro segregation is hardly eliminated even in the final product stage because the Ni concentration varies greatly.
As a method for eliminating segregation that occurs during solidification, that is, concentration fluctuation, there is rolling or the like that homogenizes an Fe—Ni-based alloy material by mechanical deformation. In this method, the inherent density fluctuation is elongated in the longitudinal direction by rolling and is compressed in the thickness direction. As a result, the interval between the density fluctuations is reduced, and mechanical homogenization occurs. On the other hand, in the method by annealing, the diffusion is promoted by heating the Fe-Ni-based alloy, and homogenization is achieved by reducing the fluctuation range of the concentration.

In the homogenization process by diffusion, generally, the diffusion progresses at a lower temperature and in a shorter time as the interval between the density fluctuations is smaller. For this reason, the homogenizing effect by annealing increases as the material in which the interval between the concentration fluctuations is reduced by rolling. That is, when component segregation occurring during casting is eliminated in the subsequent steps, Ni segregation is affected by the total reduction ratio R from the ingot to the final plate thickness, and the homogenization effect increases as the total reduction ratio R increases. It is presumed that it becomes. The total reduction ratio R is T (mm) for the thickness of the ingot and t for the thickness after cold rolling.
(Mm), it is represented by R = T / t.

[0011] Based on such a premise, the present inventors,
A plurality of ingots cast so as to have different total reduction ratios R were lumped and hot-rolled, and the fluctuation pitch p of the Ni concentration was measured in the hot-rolled sheet stage along the thickness direction. When measuring the fluctuation pitch p, the cross section of the hot-rolled sheet perpendicular to the rolling direction D is measured with an X-ray microanalyzer, and a square area of 300 μm on a side is probed with a diameter of 0.8 μm and measured at an interval of 0.8 μm.
i was subjected to quantitative mapping analysis. The obtained quantitative analysis values (% by mass) at each measurement point were averaged in the plate width direction, and the average value was converted to a concentration fluctuation line in the plate thickness direction as a representative value (FIG. 2). Then, the interval between the minimum values adjacent to each other in the density variation line was read as the interval along the thickness direction of the low Ni concentration region. The same reading was performed for the density fluctuation lines in a plurality of visual fields, and the average value was used as the fluctuation pitch p of the Ni concentration.

Next, a material obtained by cold rolling the same hot-rolled sheet to the final sheet thickness was etched, and the degree of occurrence of stripe unevenness was examined. As a result, it was found that the fluctuation pitch p of the Ni concentration became smaller as the total draft ratio R increased, and that the stripe unevenness generated after etching became smaller. As a result of a more detailed investigation, as shown in FIGS. 3 and 4, by setting the fluctuation pitch p of the Ni concentration to 16 μm or less, and by setting the total reduction ratio R to 7000 or more, a high-definition shadow mask is obtained. It has been found that the level of A and B required to satisfy the requirements can be achieved.

Next, the alloy components, contents, and manufacturing conditions of the Fe—Ni-based alloy targeted by the present invention will be described. [Alloy component] Ni: 30 to 50% by mass Ni is an important alloy component in lowering the thermal expansion coefficient of the Fe-Ni-based alloy, and has a Ni content of 30 to 50% in order to maintain low thermal expansion required for the shadow mask. It is regulated within the range of 50% by mass. C: 0.015% by mass or less C is a harmful element that is dispersed as a carbide in the matrix and impairs the etching property. Therefore, the C content is preferably as low as possible. In the present invention, considering the production cost, the upper limit of the C content is set to 0.015% by mass so as not to cause an adverse effect due to carbides. Si: 0.20% by mass or less This component is added as a deoxidizing agent in the steelmaking stage, but has a large thermal expansion coefficient and adversely affects etching properties and blackening properties. Therefore, in the present invention, the upper limit of the Si content is set to 0.20% by mass.

Mn: 0.5% by mass or less Mn is a component added as a deoxidizing agent in the steelmaking stage. However, since the thermal expansion coefficient is increased, the upper limit of the Mn content is 0.5%.
It was defined as% by mass. Al: 0.02% by mass or less This component is added as a deoxidizing agent in the steelmaking stage. However, an excessive amount of Al induces defects such as surface flaws and causes deterioration of the surface quality. 0.02% by mass. B: 0.0040% by mass or less Although it is an effective alloy component for improving the etching rate, if an excessive amount of B exceeding 0.0040% by mass is contained, annealing unevenness is likely to occur after softening annealing, and black This also promotes unevenness in the formation of the oxide film. The Fe—Ni-based alloy targeted by the present invention further contains unavoidable impurities such as S, P, O, and N. These unavoidable impurities do not adversely affect the required characteristics as a shadow mask material when their contents are regulated to 0.010% by mass or less.

[Manufacturing conditions] The ingot of an Fe-Ni alloy is
The hot rolled sheet having a thickness of 3 to 8 mm is preferably formed by hot rolling after the bulk rolling. In a hot-rolled sheet having a sheet thickness of more than 8 mm, the load of the subsequent cold-rolling step is increased and productivity is lowered, and Ni segregation generated during casting is not sufficiently crushed and divided. Conversely, if the thickness is less than 3 mm, the load in the step of grinding and removing the oxide scale formed on the surface of the hot-rolled sheet increases, and the yield decreases. After pickling and annealing, the hot-rolled sheet is rolled to a final sheet thickness t by cold rolling and annealing repeated one or more times. The final plate thickness t is preferably selected in the range of 0.1 to 0.15 mm from the necessity of perforating the fine etching perforated portion 3 at high density as a shadow mask for a high definition picture tube. In the cold rolling step, it is preferable to perform intermediate annealing twice or more in order to achieve homogenization by diffusion. In the intermediate annealing, it is preferable to set the annealing temperature in the range of 900 to 1200 ° C. in order to enhance the diffusion effect.
When the Fe—Ni-based alloy sheet for a shadow mask is manufactured through hot rolling, cold rolling and annealing in this way, the pitch p of the Ni concentration along the sheet thickness direction at the hot rolling step is set to 16 μm or less. Setting the reduction ratio R (= T / t) to 7000 or more is effective in preventing the occurrence of stripes.

Variation pitch of Ni concentration along the thickness direction in the hot-rolled sheet stage: p ≦ 16 μm Ni segregation is reduced to such an extent that uniform heat treatment or cold rolling after hot-rolling or cold rolling does not adversely affect unevenness. In order to achieve this, it is important to suppress the fluctuation pitch p of the Ni concentration along the thickness direction in the hot rolling step to 16 μm or less. If the fluctuation pitch p exceeds 16 μm, mechanical homogenization and homogenization due to diffusion do not sufficiently proceed in the cold rolling and annealing steps, and line unevenness tends to occur after etching. The variable pitch p is affected by the rolling reduction from the ingot to the hot rolled sheet, and the variable pitch p of 16 μm or less can be achieved by a large rolling reduction. Specifically, under the condition where the total draft ratio R is 7000 or more, the draft from the ingot to the hot-rolled sheet is also set large, so that the fluctuation pitch p becomes 16 μm or less.

Total reduction ratio: R ≧ 7000 Ni segregation generated in the ingot resulted in the ingot having a thickness T of 1/7000.
By performing lumping, hot rolling and cold rolling to the following final plate thickness t, the size can be reduced until the streak quality required for a shadow mask of a high definition picture tube is obtained. At a total reduction ratio R of less than 7000, the total reduction ratio R with respect to the segregation interval during casting is small, so that slab rolling, hot rolling and subsequent cold rolling,
Homogenization does not sufficiently proceed in the annealing step, and stripe unevenness due to Ni segregation tends to occur after etching.

[0018]

EXAMPLE A molten Fe-Ni alloy melted in an electric furnace was roughly decarburized in a converter, charged into a vacuum degassing apparatus, and adjusted to the composition shown in Table 1. This Fe—Ni alloy was cast into ingots of various thicknesses, heated to a high temperature of 1200 ° C. or higher, and then slab-rolled into slabs having a thickness of 180 mm.

[0019]

After the surface of the obtained slab was prepared, it was hot-rolled to a thickness of 4 mm. A sample was cut out from the center in the width direction of the hot-rolled sheet, and a cross section orthogonal to the rolling direction was analyzed with an X-ray microanalyzer to measure the fluctuation pitch p of the Ni concentration along the sheet thickness direction. Next, after the hot-rolled sheet is subjected to annealing and pickling, cold rolling and annealing are repeated, and finally the sheet thickness t = 0.12.
mm was obtained. In the cold rolling step, intermediate annealing at 1000 ° C. was performed twice.

Using the manufactured cold rolled sheet, a shadow mask for a high definition picture tube was manufactured by photoetching.
In the photoetching, a ferric chloride solution having a liquid temperature of 50 ° C. and a specific gravity of 46 Baume was used. The shadow mask after the etching was visually observed, and the occurrence of stripe unevenness was examined. The streak quality was determined to be the highest level A when no streaks were observed, the level B when there was almost no streaks and usable for high-definition shadow masks, and the level A when relatively many streaks were observed. A level C, and a clear and many streaks appeared, were evaluated as a lowest level D, and evaluated on a four-point scale.

The evaluation results are shown in Table 2 in relation to the total reduction ratio R and the fluctuation pitch p of the Ni concentration. As is clear from Table 2, Test Nos. 1 to 3 in which the total reduction ratio R was 7000 or more
In each case, the streak quality was B or higher, indicating that it had sufficient quality to be used as a shadow mask for a high-definition picture tube. In addition, Ni along the thickness direction at this time is
Each of the density fluctuation pitches p was 16 μm or less.
On the other hand, test numbers 4 to 7 in which the total reduction ratio R does not reach 7000
In (Comparative Example), the quality of streaks was C or less, and the material was not suitable for a shadow mask for a high-definition picture tube. Further, the fluctuation pitch p of the Ni concentration along the thickness direction is also 16
μm was exceeded.

[0023]

[0024]

As described above, as described above, the Fe-
The Ni-based alloy hot-rolled sheet regulates the fluctuation pitch of the Ni concentration along the sheet thickness direction to 16 μm or less, thereby promoting homogenization by diffusion in the subsequent cold rolling and annealing steps, and causing streaks caused by Ni segregation. Manufactured into a uniform shadow mask material. Ni segregation, which has an adverse effect on line streaks, is caused by reducing the ingot thickness until the final ingot thickness becomes 1/7000 or less.
The problem can also be solved by hot rolling and cold rolling a Ni-based alloy. In this way, the occurrence of stripe unevenness is suppressed.
-A Ni-based alloy plate is a material suitable as a shadow mask for a high definition picture tube.

[Brief description of the drawings]

FIG. 1 shows Ni in an Fe—Ni-based alloy alloy plate.
Diagram showing concentration fluctuation

FIG. 2 is a graph showing a change in Ni concentration along a thickness direction in a cross section orthogonal to a rolling direction of a hot-rolled Fe—Ni alloy sheet.

FIG. 3 is a graph showing the influence of the fluctuation pitch of the Ni concentration at the hot-rolled sheet stage on the streak quality.

FIG. 4 is a graph showing the effect of the total draft ratio from the ingot to the production of a cold rolled sheet on the streak quality.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Takashi Yamauchi 4976 Nomura Minamicho, Shinnanyo-shi, Yamaguchi Prefecture F-term in Nisshin Steel R & D Co., Ltd. (Reference) 4K037 EA01 EA02 EA04 EA15 EA21 EA27 EB02 EB03 FB06 FB07

Claims (2)

[Claims] 1. Ni: 30 to 50% by mass, C: 0.01
5% by mass or less, Si: 0.20% by mass or less, Mn: 0.
5 mass% or less, Al: 0.02 mass% or less, B: 0.0
040% by mass or less, and the balance substantially has a composition of Fe;
A hot-rolled Fe—Ni alloy sheet for a shadow mask, wherein a fluctuation pitch of the Ni concentration along the thickness direction is 16 μm or less. 2. Ni: 30 to 50% by mass, C: 0.01
5% by mass or less, Si: 0.20% by mass or less, Mn: 0.
5 mass% or less, Al: 0.02 mass% or less, B: 0.0
040% by mass or less, with the balance being substantially Fe
When an e-Ni-based alloy is cast into an ingot having a thickness T (mm), and hot-rolled and then cold-rolled through annealing, when the thickness after final cold-rolling is t (mm), hot rolling is performed. And a hot-rolling and a cold-rolling at a rolling reduction of a total reduction ratio R = T / t of 7000 or more by cold rolling.