Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
2002-04-15
2003-11-04
Yee, Deborah (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
C148S624000
Reexamination Certificate
active
06641682
ABSTRACT:
TECHNICAL FIELD
This invention concerns an aperture grill material for a color picture tube, a manufacturing method thereof, an aperture grill and a color picture tube incorporating the same. More specifically, it relates to an aperture grill material for a color picture tube having excellent tensile strength and high temperature creep strength, as well as having excellent magnetic characteristics, a manufacturing method thereof, an aperture grill and a color picture tube incorporating the same.
BACKGROUND ART
Since an aperture grill for use in a color picture tube is welded to a frame in a state undergoing a large tension upon manufacture, it is necessary for the aperture grill material for use in the color picture tube to have a tensile strength of at least 60 kgf/mm
2
. Accordingly, as the aperture grill material for use in the color picture tube used at present, low carbon steel sheets strengthened by applying working have been used.
Further, while a heat treatment is applied for blackening after welding to the frame, the heat treatment is conducted at 455° C. which is lower than the recrystallization temperature of steels in a short period of time for about 15 min in order to maintain each of the tapes constituting the aperture grill after blackening is kept in the state under tension without slackening. However, restoration is inevitable in the blackening heat treatment and restoration results in elongation of them, which causes twisting or disconnection of tapes. Accordingly, the aperture grill material for use in the color picture tube is required to have a tensile strength of 60 kgf/mm
2
or more, and result in no elongation under the blackening heat treatment at 455° C.×15 min, that is, have such a creeping strength that the elongation upon loading 30 kgf/mm
2
of tensile stress is 0.3% or less.
A color picture tube comprises electron guns and a fluorescent screen for converting electron beams into video images and the inside of the picture tube is covered with a magnetic shielding material for preventing the electron beams from being deflected by the geomagnetism. The aperture grill is also required to have a function as the magnetic shielding material and it has been demanded for a material having a large residual magnetic flux density (Br) and a small coercive force (Hc), that is, having a large ratio of the residual magnetic flux density to the coercive force (Br/Hc) as the magnetic characteristics. However, in the low carbon steel sheet which is applied with intense working for obtaining high yielding strength and the blackening heat treatment is conducted at a temperature lower than the recrystallization temperature, the residual magnetic flux density is as small as less than 8 kilo gauss (kG) and the coercive force is as large as 5 oersted (Oe) and, accordingly, Br (kG)/Hc (Oe) is as small as about 1.6, which is poor in the magnetic shield material.
Heretofore, the method of improving the tensile yield strength of the low carbon steel sheet includes, a solid-solution strengthening method with C or N but as the amount of C and N in the steel increases, carbides or nitrides increase to hinder the movement of magnetic walls to deteriorate the magnetic characteristics. Further, the method of improving the creep strength includes a method of precipitating carbide or the like in the steel but most of precipitates have a large grain size at the micron order and interfere the movement of magnetic walls to greatly deteriorate the magnetic characteristics, so that such methods have not been applied as the method of manufacturing current aperture grill materials for use in color picture tubes.
This invention has a subject of providing an aperture grill material for use in a color picture tube having excellent tensile strength and high temperature creep characteristics, as well as having more excellent magnetic characteristics than those of the existent materials, a manufacturing method thereof, an aperture grill and a color picture tube.
In order to solve the technical subjects, the present inventors have already proposed a low carbon alloy steel sheet with addition of Cu and P (Japanese Patent Application No. 36929/1997). The technical content is an aperture grill material provided with high strength and high creep strength by precipitating a fine Cu phase (&egr;-phase) of nanometer (nm) order and by the combined use of solid-solution strengthening of P by the addition of P. Since precipitated Cu grains are extremely fine, they scarcely inhibit movement of the magnetic walls and the extent of deteriorating the magnetic characteristics is extremely small. Since P is solid-solubilized in Fe, it less inhibits the magnetic characteristics to obtain an aperture grill material having both high strength and magnetic characteristics. This invention has intended to further improve the creep strength on the basis of the prior art described above.
Disclosure of the Invention
The aperture grill material for a color picture tube according to this invention contains 0.05 to 2.5% by weight of Cu, 0.001 to 0.4% by weight of P, and further containing 0.01 to 0.5% by weight of at least one of Cr and Mo.
The aperture grill material for a color picture tube according to this invention contains 0.05 to 2.5% by weight of Cu, 0.001 to 0.4% by weight of P, 0.01 to 1.75% by weight of Ni, and further containing 0.01 to 0.5% by weight of at least one of Cr and Mo.
The aperture grill for use in a color picture tube according to this invention comprises a low carbon alloy steel sheet containing 0.05 to 2.5% by weight of Cu, 0.001 to 0.4% by weight of P, and further containing 0.01 to 0.5% by weight of at least one of Cr and Mo.
The aperture grill for use in a color picture tube according to this invention comprises a low carbon alloy steel sheet containing 0.05 to 2.5% by weight of Cu, 0.001 to 0.4% by weight of P, 0.01 to 1.75% by weight of Ni, and further contains 0.01 to 0.5% by weight of at least one of Cr and Mo.
A color picture tube according to this invention is incorporated with an aperture grill comprising a low carbon alloy steel sheet containing 0.05 to 2.5% by weight of Cu, 0.001 to 0.4% by weight of P, and further containing 0.01 to 0.5% by weight of at least one of Cr and Mo.
A color picture tube according to this invention is incorporated with an aperture grill comprising a low carbon alloy steel sheet containing 0.05 to 2.5% by weight of Cu, 0.001 to 0.4% by weight of P, 0.01 to 1.75% by weight of Ni, and further containing 0.01 to 0.5% by weight of at least one of Cr and Mo.
An aperture grill material for use in a color picture tube according to this invention has 0.3% or less of elongation when kept at 455° C.×15 min under loading a stress of 30 kgf/mm
2
.
The aperture grill according to this invention, after being incorporated in a color picture tube, has an elongation of 0.6% or less when kept at 455° C.×15 min under loading a stress of 30 kgf/mm
2
.
A color aperture grill material for use in a color picture tube according to this invention has a value for the ratio of the residual magnetic flux density (Br) and the coercive force (Hc): Br/Hc=1.8 or more as the magnetic characteristics.
The aperture grill according to this invention has a ratio of the residual magnetic flux density (Br) and the coercive force (Hc): Br/Hc=2.0 or more, as the magnetic characteristics after being assembled into the color picture tube.
A method of manufacturing an aperture grill material for use in a color picture tube according to this invention comprises cold rolling a low carbon alloy steel hot rolled strip containing 0.05 to 2.5% by weight of Cu, 0.001 to 0.4% by weight of P, and further containing 0.01 to 0.5% by weight of at least one of Cr and Mo and then applying a precipitation treatment within a temperature range from 300 to 800° C.
A method of manufacturing an aperture grill material for use in a color picture tube according to this invention comprising cold rolling a low carbon alloy steel hot rolled strip containing 0.05 to 2.5% by weight of Cu, 0.001 to
Ide Tsuneyuki
Miyazaki Takahiko
Shigemasa Susumu
Tahara Yasuo
Browdy and Neimark , P.L.L.C.
Toyo Kohan Co. Ltd.
Yee Deborah
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