Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Patent
1998-02-06
2000-01-18
Sheehan, John
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
148120, 148306, 148332, 148651, H01J 2980
Patent
active
060160292
DESCRIPTION:
BRIEF SUMMARY
FIELD OF ART
The present invention relates to magnetic shield materials used in color picture tubes, a method for producing the materials and color picture tubes incorporating the materials, and more particularly, magnetic shield materials employed in color picture tubes, a method for producing the materials and color picture tubes incorporating the materials which show an improved strength in handling.
BACKGROUND
A color picture tube such as a picture tube employed in a color television set substantially comprises an electron gun and a fluorescent surface which converts electron beams into an image. The inside of the picture tube is covered with magnetic shield materials for preventing electron beams from being deflected by a terrestrial magnetism.
As such magnetic shield materials, thin steel sheets on which a black treatment or a nickel plating is provided are used, wherein the thin steel sheets are formed in a desired shape by bending and sealed to a Braun tube at a temperature around 600.degree. C. The steel sheets used as the magnetic shield materials are required to meet favorable mechanical characteristics such as a favorable formability including bending and a handling strength capable of preventing the deformation of workpieces at the time of conveying the magnetic shield materials before or after forming operation as well as at the time of piling the workpieces, in addition to excellent magnetic shield properties such as high permeability and low coercive force.
To decrease the coercive force while increasing the permeability, the presence of precipitation such as carbon, nitrogen, carbide or nitride in the steels which impedes the movement of ferromagnetic domain wall must be minimized and the grain growth must be promoted while decreasing grain boundary. Decreasing of carbon and nitrogen in the steels while increasing the grain growth of the steels provides an improvement of formability such as bending since the strength of the steels is lowered. However, at the time of conveying the steel sheets or workpieces which are produced by bending, they tend to suffer from irregularities even when a slight impact is applied to them or the workpieces tend to be deformed due to the weight of the workpieces piled. Although the handling strength of the steel sheets can be enhanced by grain refining or by an addition of a certain amount of carbon and nitrogen into the steels so as to precipitate carbide and nitride in the steels, such a method causes deterioration of magnetic characteristics. In this manner, the steel sheets used as the magnetic shield materials must simultaneously meet the excellent magnetic characteristics and the favorable handling strength which conflict with each other.
Accordingly, it is an object of the present invention to provide magnetic shield materials used in color picture tubes which has excellent inner magnetic shield characteristics and an excellent handling strength and color picture tubes incorporating such magnetic shield materials.
DISCLOSURE OF INVENTION
The magnetic shield materials used in color picture tubes according to the present invention are produced by subjecting hot rolled low carbon steel strips essentially consisting of equal to or less than 0.006 weight % of C, equal to or less than 0.002 weight % of N, equal to or less than 0.5 weight % of Mn, 0.1-1.5% weight of Cu, Fe as a balance and unavoidable impurities to a cold rolling and annealing the cold rolled steel strips at a temperature of 550-850.degree. C.
According to the present invention, by adding Cu to hyper-low carbon steels, carbon is held in a solid solution or finely precipitated so that the tensile strength of the hyper-low carbon steels can be held equal to or more than 40 kg/mm.sup.2 while the coercive force is held equal to or less than 1.2 oersted whereby the magnetic shield materials used in color picture tubes having excellent magnetic characteristics and an excellent handling strength at the same time can be obtained.
BEST MODE FOR CARRYING OUT INVENTION
The present invention is
REFERENCES:
patent: 3620856 (1971-11-01), Hiraoka et al.
patent: 4961793 (1990-10-01), Kishida et al.AL.
patent: 5803988 (1998-09-01), Bae et al.
Rickett and Leslie, "Recrystallization, Structure, and Hardness of Low Carbon Steels Containing Up to 1 % Copper," Fortieth Annual Convention of the American Society for Metals, Cleveland, Ohio, Oct. 27, 1958 to Dec. 31, 1958, pp. 1-24.
Ikeda Akira
Okayama Hironao
Oltmans Andrew L.
Sheehan John
Toyo Kohan Co. Ltd.
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