Fe-Ni based material for shadow mask

Details Fe-Ni based material for shadow mask Fe-Ni based material for shadow mask

2001-12-04

2003-04-15

Yee, Deborah (Department: 1742)

Metal treatment

Stock

Ferrous

C420S094000, C420S095000

Reexamination Certificate

active

06547893

ABSTRACT:

TECHNICAL FIELD
This invention relates to a Fe—Ni based material for shadow mask composed of Fe—Ni alloy or Fe—Ni—Co alloy used as a material for a cathode-ray tube of a color television and proposes a Fe—Ni based shadow mask material having such a low thermal expansion that streak or mottling (hereinafter referred to as streaks) is not caused in the photoetching with an etching solution consisting essentially of ferric chloride solution or the like.
BACKGROUND ART
Heretofore, low carbon aluminum-killed steel plates have been used as a material for shadow mask. These steel sheets are manufactured by subjecting a steel sheet after a middle cold rolling to an adequate strain-relief middle annealing in a continuous annealing furnace or a batch annealing furnace, and subjecting to an injury removal, if necessary, and thereafter subjecting to a finish cold rolling and a temper rolling (inclusive of dull rolling).
On the contrary, low thermal expansion type Fe—Ni alloy plates are recently noticed as a material for a cathode tube or a display of a high quality color television. This Fe—Ni alloy plate is developed instead of the low carbon aluminum-killed steel plate previously used as a material for a shadow mask. Such a Fe—Ni alloy is noticed in a point that the prevention of color drift is excellent as compared with the above low carbon aluminum-killed steel plate and is particularly one of inevitable materials in the applications of the display, large-size television and the like.
However, the Fe—Ni alloy has a problem in the photoetching property. That is, it is pointed out that the Fe—Ni alloy is poor in the pierced hole shape during the photoetching and is apt to easily cause the defect called as a streak. Particularly, it is known that the defect called as the streak generates strip-like contrast streak in a white portion of an image in a color television cathode tube to considerably lower the grade as a display. As the cause on the generation of the streak, there are considered the presence of non-metal inclusion and the influence of the Ni segregation. For this end, it is effective to remove these causes in order to mitigate these causes. However, even when these causes are removed completely, unsolvable streak still remains, so that the inventors thought another factor other than the above causes and studied thereto.
It is a main object of the invention to pinpoint a true cause of a streak or mottling (whole streak) produced by poor etching and provide a Fe—Ni based material for shadow mask not generating such streaks.
It is another object of the invention to provide a Fe—Ni based material for shadow mask made of Fe—Ni alloy or Fe—Ni—Co alloy having a good piercing property in the etching and a good hole shape in the piercing.
It is the other object of the invention to cheaply and surely provide a material for a color television cathode tube or a display developing a beautiful image.
DISCLOSURE OF THE INVENTION
The inventors have made various studies on the problems of the aforementioned streaks and the like, which have not been solved in the conventional technique, and obtained the following knowledge. That is, it has been confirmed that the streak or the like generated in the shadow mask material is based on the disorder of the orientation of individual crystal grains in the etched surface. And also, it has been confirmed that the disorder of the orientation results from segregation of Ni, Mn or the like, the residue of mixed grain structure of non-metal inclusion and coarse grains produced in the course of the annealing, the presence of specified texture and the like or is generated by interengaging these factors. Furthermore, the orientation of such crystal grains is dependent upon the crystal orientation inherent to the individual crystal grains, so that it is concluded that it is required to unavoidably control the texture for preventing the occurrence of the above streak or the like.
And also, the inventors have recognized that the control of section cleanness of the product or surface roughness and control of inclusion are further inevitable for improving the piercing property in the etching and the hole shape after the piercing and concluded that the controls of the section cleanness, surface roughness and inclusion are required in addition to the control of segregation of various components and texture.
Furthermore, it has been found that the streak can stably be mitigated by controlling the segregation distribution of Ni, Mn and the like in a thickness direction, and as a result the invention has been accomplished.
The invention is a material having the following construction developed under the above knowledge.
{circle around (1)} The invention is a Fe—Ni based material for shadow mask of an iron-nickel alloy containing Ni: 34-38 wt %, characterized in that the material has a texture that an X-ray intensity ratio Ir of cubic orientation (100)<001> to twinning orientation (221)<212> thereof in a (111) pole figure is a range of 0.5-5:1 and a section cleanness defined according to JIS G0555 is not more than 0.05%.
{circle around (2)} The invention is a Fe—Ni based material for shadow mask of an iron-nickel alloy having a composition of C: not more than 0.1 wt %, Si: not more than 0.5 wt %, Mn: not more than 1.0 wt %, Ni: 34-38 wt % and the remainder being substantially Fe, characterized in that the material has a texture that an X-ray intensity ratio Ir of cubic orientation (100)<001> to twinning orientation (221)<212> thereof in a (111) pole figure is a range of 0.5-5:1 and a section cleanness defined according to JIS G0555 is not more than 0.05%.
{circle around (3)} The invention is a Fe—Ni—Co based material for shadow mask of an iron-nickel-cobalt alloy having a composition of Ni: 23-38 wt %, Co: not more than 10 wt % and the remainder being substantially Fe, characterized in that the material has a texture that an X-ray intensity ratio Ir of cubic orientation (100)<001> to twinning orientation (221)<212> thereof in a (111) pole figure is a range of 0.5-5:1 and a section cleanness defined according to JIS G0555 is not more than 0.05%.
In the materials according to the invention, the X-ray intensity ratio (X-ray count number ratio) is basically 0.5-5:1 as mentioned above, but is recommended that the ratio is preferably restricted to ranges of 0.5-4.5:1, 1-4.5:1, 1-4.0:1 and 1.5-4.0:1 and more preferably adjusted to a range of 2-3.5:1.
The above materials {circle around (1)}, {circle around (2)} and {circle around (
3
)} can be produced, for example, by treating an alloy comprising Ni: 34-38 wt % and the remainder being substantially Fe according to a usual manner to obtain a cold rolled material and subjecting to such an annealing that it is subjected to a middle annealing at an annealing temperature of 900-1150° C. for a soaking time of 5-60 seconds and then to a finish annealing at an annealing temperature of 700-900° C. for a soaking time of 60-600 seconds prior to a finish rolling.
Moreover, in the above production method, it is preferable to conduct each of the annealing conditions within a range enclosed in a, b, c, and d of FIG.
1
.
And also, in the materials {circle around (1)}, {circle around (2)} and {circle around (
3
)}, it is effective to satisfy the followings:
a. surface roughness is 0.2 &mgr;m≦Ra≦0.9 &mgr;m;
b. surface roughness is 20 &mgr;m≦Sm≦250 &mgr;m;
c. surface roughness is −0.5≦Rsk≦1.3.
Further, in the materials {circle around (1)}, {circle around (2)} and {circle around (
3
)}, it is recommended to satisfy the followings:
d. surface roughness is 0.2 &mgr;m≦Ra≦0.9 &mgr;m and −0.5Rsk≦1.3;
e. surface roughness is 0.2 &mgr;≦Ra≦0.9 &mgr;m, −0.5≦Rsk≦1.3 and 20 &mgr;m≦Sm≦250 &mgr;m.
Moreover, in the materials {circle around (1)}, {circle around (2)} and {circle around (3)}, it is favorable to satisfy the followings:
f. number of inclusions having a grain size of not less than 10 &mgr;m as measured on a section of the plate is not more than 80 grai

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