Composition of rail structure for supporting shadow mask in color CRT

Abstract

Composition of a rail structure that can cut down cost of alloy composition, and enhance strength of the rail structure to minimize defects occurred in a fabrication process of the CRT, consisting of Fe as a main constituent, 22.about.27 wt % of Cr, C.ltoreq.0.02 wt %, Si.ltoreq.0.40 wt %, Mn.ltoreq.0.40 wt %, and P.ltoreq.0.02 wt %, with addition of Mn as required.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a rail structure for supporting a shadow mask in a color cathode ray tube(CRT), and more particularly, to alloy composition of a rail structure that can cut down cost of alloy composition, and enhance strength of the rail structure to minimize defects occurred in a fabrication process of the CRT.

[0003] 2. Background of the Related Art

[0004] Referring to FIG. 1, a related art flat color CRT is provided with a panel 3 of explosion proof glass 2, a funnel 4 sealed to the panel, an electron gun 7 sealed in the funnel 4 for emitting red, green, and blue electron beams 6 toward the panel 3, and a fluorescent film 1 of red, green, and blue color fluorescent materials coated on an inside surface of the panel 3 for emitting lights of respective colors in response to the electron beams 6. The panel 3 is provided with a rail structure 9 for maintaining a fixed gap between the inside surface of the panel 3 and a shadow mask 8 having countless slots formed therein. As shown in FIG. 2, the rail structure 9 is welded on the panel 3 with the frit 11 for enduring a tension from the shadow mask 8. The related art flat color CRT is further provided with a magnetic shield 10 for protecting the electron beams traveling toward the fluorescent film from an external magnetic field.

[0005] When a power is applied to the CRT, the electron beams 6 are emitted from the electron gun 7 sealed in a neck part of the funnel 4, accelerated and converged as the electron beams 6 pass a plurality of electrodes in succession, selected of colors as the electron beams 6 pass through the slots in the shadow mask 8, and hit the fluorescent film 1 coated on the inside surface of the panel 3, to reproduce a picture.

[0006] Referring to FIG. 3, the rail structure 9 has two long side rails 9a, two short side rails 9b, and four end caps 9c, welded together to form a rectangular structure. As shown in FIG. 2, Frit glass, a mixture of Frit powder and vehicle, is filled in an empty space of the rectangular rail structure, and melted in a furnace to fuse with the panel 3. Top surface of the rail structure 9 is ground for providing the fixed gap between the panel 3 and the shadow mask 8. After the fluorescent material is coated on the panel with the rail structure fused thereon, the shadow mask is subjected to a tension, and welded on the rail structure on an accurate position of the rail structure. Then, the panel 3 and the funnel 4 joined, and the electron gun 7 is inserted, and the completed CRT is evacuated.

[0007] In general, the rail structure 9 has compositions of 28.about.29 wt % of Cr. and balance of Fe. As Cr costs approx. 7.about.8 times higher than Fe, Cr is a cost raising element and is a cause of poor grinding due to the toughness of the Cr. Moreover, as Cr forms Cr oxide during refining process in a Cr steel production, high Cr steel has difficulty in fabrication process, poor in acid cleaning after rolling, and liable to deformation during fabrication of the CRT owing to a low hardness.

SUMMARY OF THE INVENTION

[0008] Accordingly, the present invention is directed to composition of a rail structure that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

[0009] An object of the present invention is to provide composition of a rail structure, which can cut down a production cost, prevent production of unnecessary oxide to improve mechanical properties, for preventing deformation of rail during fabrication coming from a low hardness.

[0010] Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the composition of a rail structure consisting of Fe as a main constituent, 22.about.27 wt % of Cr, and inevitable impurities.

[0011] 1.about.3 wt % of Mo is added thereto.

[0012] The inevitable impurities include C.ltoreq.0.02 wt %, Si.ltoreq.0.40 wt %, Mn.ltoreq.0.40 wt %, and P.ltoreq.0.02 wt %.

[0013] The composition consists of Fe as a main constituent, 25.ltoreq.27 wt % of Cr, 1.about.3 wt % of Mo, Ni.ltoreq.0.5 wt %, Ti.ltoreq.0.2 wt %, and the inevitable impurities including C.ltoreq.0.02 wt %, Si.ltoreq.0.40 wt %, Mn.ltoreq.0.40 wt %, and P.ltoreq.0.02 wt %.

[0014] The composition consists of Fe as a main constituent, 22.about.24 wt % of Cr, 1.about.3 wt % of Mo, Ni.ltoreq.0.25 wt %, Ti.ltoreq.0.3 wt %, and the inevitable impurities including C.ltoreq.0.02 wt %, Si.ltoreq.0.40 wt %, Mn.ltoreq.0.40 wt %, and P.ltoreq.0.02 wt %.

[0015] Thus, though the related art composition of a rail structure costs high owing to use of more than 28 wt % of expensive Cr, but with inadequate tensile strength and hardness despite of a high content of Cr, the present invention provides a composition of a rail structure consisting of a reduced content of Cr less than 27 wt %, and appropriate amount of elements, such as Mo and the like, thereby cutting down a production cost, preventing production of unnecessary oxides acting as foreign matter caused by oxidation of the rail structure during heat treatment of the CRT, and preventing deformation of the rail structure by improving mechanical properties thereof.

[0016] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention:

[0018] In the drawings:

[0019] FIG. 1 illustrates a section of a color CRT;

[0020] FIG. 2 illustrates a process for fixing a rail to a panel, schematically; and, FIG. 3 illustrates a perspective view of a rail fixed to a panel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. After rail is formed of an alloy with chemical composition as shown in the following table 1, the alloy is heated up, kept at an elevated temperature ranging 580.about.1,150.degree. C. for 1.about.30 min., cooled down, and mechanical properties thereof are tested.

1TABLE 1 unit: weight % C Si Mn P Ni Ti Mo Cr Fe *1 1 0.02 0.40 0.55 0.011 0.35 0.50 19-21 Balance 2 0.06 0.39 0.36 0.016 0.23 0.23 0.30 19-21 Balance 3 0.02 0.39 0.36 0.016 0.23 0.30 0.30 19-21 Balance 2* 1 .ltoreq.0.02 .ltoreq.0.40 .ltoreq.0.40 .ltoreq.0.02 .ltoreq.0.25 .ltoreq.0.20 1.5-2.5 22-24 Balance 2 .ltoreq.0.02 .ltoreq.0.40 .ltoreq.0.40 .ltoreq.0.04 .ltoreq.0.50 .ltoreq.0.20 1.0-3.0 25-27 Balance *1: Comparative inventions, *2: the present invention

[0022]

2 TABLE 2 Comparative The present inventions invention Tube size (1,2,3) 1 2 15".about.17" 0 0 0 19" 50 0 0 21" and over 50 7 0

[0023]

3 TABLE 3 Y.S (kg/mm.sup.2) Hardness (HrB) 20% Cr steel 33.46 83.2 Comparative inventions 26% Cr steel 41.18 89.5 The present invention 28% Cr steel 37.70 85.8 The related art

Comparative Invention 1

[0024] Hardness of the alloy of the comparative invention 1 is measured to obtain HrB 110-15, which drops at a heat treatment temperature higher than 950.degree. C., to cause deformation of the rail structure during fabrication of the CRT. Since a heat expansion coefficient of the alloy is in a range of 11.5E-6, approx. 9.5% higher than glass with a heat expansion coefficient of 10.5E-6 at 30-400.degree. C., that allows application to a 17" size CRT, application of the alloy to a CRT with a size greater than 17" has difficulty owing to frequent occurrence of cracks during fabrication.

Comparative Inventions 2, and 3

[0025] Hardness of the alloys of the comparative inventions 1, and 2 are measured to obtain HrB 110-40. Since a heat expansion coefficients of the alloys are in a range of 11.3E-6 at 30-300.degree. C., approx. 7.6% higher than glass with a heat expansion coefficient of 10.5E-6 at 30-400.degree. C., that allows application to a color CRT, because application of the alloys to a CRT with a size 21" and over causes cracks in a range of 50% under fabrication conditions identical to the related art shown in table 2, while application of the alloys to a CRT with a size in a range of 15"-17" causes no cracks under fabrication conditions identical to the related art as shown in table 2, the alloys can be applicable to a limited products with a size of 15"-17".

Embodiment 1

[0026] Hardness of the alloy of the embodiment 1 is measured to obtain HrB 88-102, which is a value applicable to fabrication of the CRT without problem. Since a heat expansion coefficient of the alloy is in a range of 11.2E -6 at 30-300.degree. C., approx. 6.7% higher than glass with a heat expansion coefficient of 10.5E-6 at 30-400.degree. C., that allows application to a color CRT, because application of the alloys to a CRT with a size 21" and over causes cracks in a range of 7% under fabrication conditions identical to the related art shown in table 2, while application of the alloys to a CRT with a size in a range of 15"-19" causes no cracks under fabrication conditions identical to the related art as shown in table 2, the alloys can be applicable to a limited products with a size of 15"-19".

Embodiment 2

[0027] Hardness of the alloy of the embodiment 2 is measured to obtain HrB 88-105, which is a value applicable to fabrication of the CRT without problem. Since a heat expansion coefficient of the alloy is in a range of 11.0E -6 at 30-300.degree. C., approx. 4.8% higher than glass with a heat expansion coefficient of 10.5E-6 at 30-400.degree. C., so as not to cause cracks for entire models of color CRTs as shown in table 2, the alloys can be applicable to all sizes of products.

[0028] Thus, the comparative inventions and the embodiments of the present invention are applicable, as the application is limited by sizes of the CRTs, an alloy of the second embodiment of the present invention with Cr 25.about.27%, and Mo 2% is preferably the most applicable.

[0029] As has been explained, the present invention saves a production cost by forming a rail structure for supporting a shadow mask, of an alloy with low cost elements, enhances yield by dropping a chrome content, and minimizes defects occurred in a fabrication of CRT by enhancing mechanical properties of the shadow mask supporting structure.

[0030] It will be apparent to those skilled in the art that various modifications and variations can be made in the alloy composition of a rail structure of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A composition of a rail structure consisting of Fe as a main constituent, 22.about.27 wt % of Cr, and inevitable impurities.

2. A composition as claimed in claim 1, wherein the composition consists of Fe as a main constituent, 22.about.27 wt % of Cr, 1.about.3 wt % of Mo, and inevitable impurities.

3. A composition as claimed in claim 1 or 2, wherein the inevitable impurities include C.ltoreq.0.02 wt %, Si.ltoreq.0.40 wt %, Mn.ltoreq.0.40 wt %, and P.ltoreq.0.02 wt %.

4. A composition as claimed in claim 1, wherein the composition consists of Fe as a main constituent, 25.about.27 wt % of Cr, 1.about.3 wt % of Mo, Ni.ltoreq.0.5 wt %, Ti.ltoreq.0.2 wt %, and the inevitable impurities including C.ltoreq.0.02 wt %, Si.ltoreq.0.40 wt %, Mn.ltoreq.0.40 wt %, and P.ltoreq.0.02 wt %.

5. A composition as claimed in claim 1, wherein the composition consists of Fe as a main constituent, 22.about.24 wt % of Cr, 1.about.3 wt % of Mo, Ni.ltoreq.0.25 wt %, Ti.ltoreq.0.3 wt %, and the inevitable impurities including C.ltoreq.0.02 wt %, Si.ltoreq.0.40 wt %, Mn.ltoreq.0.40 wt %, and P.ltoreq.0.02 wt %.