US20040177900A1

US20040177900A1 - Fe-Cr-Ni alloy for electron gun electrode

Info

Publication number: US20040177900A1
Application number: US10/740,471
Authority: US
Inventors: Seong-Hun Choo; Young-Hoon Lee; Yong-geol Kwon
Original assignee: Individual
Current assignee: Samsung SDI Co Ltd
Priority date: 2003-03-13
Filing date: 2003-12-22
Publication date: 2004-09-16
Also published as: KR20040080733A; CN1530999A

Abstract

An electron gun includes a cathode, a control electrode, a screen electrode arranged in front of the control electrode, at least one focusing electrode arranged in front of the screen electrode to form a pre-focusing lens unit, a final accelerating electrode arranged in front of the focusing electrode(s) to form a main lens unit, and a shield cup electrically connected to the final accelerating electrode. The iron-chromium-nickel alloy for the focusing electrode(s), the final accelerating electrode, and the shield cup contains 18-20% or less by weight of chromium, 8-10% by weight of nickel, 0.03% or less by weight of carbon, 1.00% by weight of silicon, 2.00% or less by weight of manganese, 0.04% or less by weight of phosphorous, 0.03% or less by weight of sulfur, a balance of iron, and a trace of impurities, and has an average granularity of 0.010-0.022 mm. The iron-chromium-nickel alloy for the electrode of an electron gun contains a smaller amount of expensive Ni so that the manufacturing cost of electron guns can be greatly reduced. In addition, an electron gun electrode made of the iron-chromium-nickel alloy steel has effective drawing properties and pressing formability. The iron-chromium-nickel alloy is nonmagnetic, and can prevent focusing and convergence drift properties from deteriorating. Accordingly, more reliable cathode ray tubes can be manufactured with the iron-chromium-nickel alloy.

Description

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for Fe—Cr—Ni ALLOY FOR ELECTRON GUN ELECTRODE earlier filed in the Korean Intellectual Property Office on 13 Mar. 2003 and thereby duly assigned Serial No. 2003-15690.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an electron gun and, more particularly, to an iron-chromium-nickel alloy for electron gun electrodes that has effective drawing and pressing properties and has improved non-magnetic properties so as not to deteriorate focusing and convergence drift properties.

2. Prior Art

In general, in cathode ray tubes, an electron beam is emitted from an electron gun fitted into a neck portion of a bulb when predetermined power is applied to the electron gun. The emitted electron beam is deflected by a deflection yoke on a corn portion of the bulb, and excites the phosphor of a fluorescent layer coated on the inner surface of a display screen panel to form images. Various connection methods have been applied to such cathode ray tubes in order to reduce aberration components at the display screen.

The electron gun includes a triode unit consisting of a cathode emitting electrons, a control electrode, and a screen electrode. A group of focusing electrodes is successively arranged in front of the screen electrode, and a final accelerating electrode forming a main lens unit is installed facing the last focusing electrode.

The electrodes forming the triode unit of an electron gun are mostly made of a nickel-based super alloy having a small thermal expansion coefficient. In addition, superior pressing properties are required, especially for the control and screen electrodes, which are processed to be flat.

Electrodes other than the control and screen electrodes, in particular electrodes forming the main lens unit, are formed into a cup shape. Accordingly, materials for these electrodes should be formable by deep-drawing. Such cup shaped electrodes should remain non-magnetic to prevent deterioration in focusing and convergence drift characteristics due to the distortion of deflection magnetic fields. Furthermore, such electrodes should have superior resistance to heat and corrosion and low gas emission so as not to affect the vacuum state of the cathode tube.

A common material for electrodes is stainless alloy steel. An available stainless alloy steel contains iron (Fe), 15-70% of chromium (Cr), 13.5-15.5% of nickel (Ni), and 0.05% or less of carbon (C) on a weight basis. However, such stainless alloy steel requires a large amount of expensive Ni, ranging from 13% to 16% by weight, so as to be formable by deep-drawing and to have nonmagnetic properties.

Therefore, there is a need to develop a new material for electron gun electrodes that contains less Ni for cost reduction and has superior drawing properties and formability by pressing.

SUMMARY OF THE INVENTION

The present invention provides an iron-chromium-nickel alloy for electron gun electrodes, the composition of which is appropriately adjusted to provide required drawing and pressing properties and to remain non-magnetic after thermal treatment for improved focusing and convergence drift properties.

In accordance with one aspect of the present invention, there is provided an iron-chromium-nickel alloy for an electrode of an electron gun which includes a cathode, a control electrode, a screen electrode arranged in front of the control electrode, at least one focusing electrode arranged in front of the screen electrode to form a pre-focusing lens unit, a final accelerating electrode arranged in front of the focusing electrode to form a main lens unit, and a shield cup electrically connected to the final accelerating electrode. The iron-chromium-nickel alloy for the focusing electrode(s), the final accelerating electrode, and the shield cup comprises 18-20% by weight of chromium, 8-10% by weight of nickel, 0.03% or less by weight of carbon, 1.00% or less by weight of silicon, 2.00% or less by weight of manganese, 0.04% or less by weight of phosphorous, 0.03% or less by weight of sulfur, a balance of iron, and a trace of impurities, and has an average granularity of 0.010-0.022 mm.

The present invention also provides an iron-chromium-nickel alloy for an electrode of an electron gun which includes a cathode, a control electrode, a screen electrode arranged in front of the control electrode, at least one focusing electrode arranged in front of the screen electrode to form a pre-focusing lens unit, a final accelerating electrode arranged in front of the focusing electrode to form a main lens unit, and a shield cup electrically connected to the final accelerating electrode, wherein the iron-chromium-nickel alloy comprises 18-20% by weight of chromium, 8-10% by weight of nickel, 0.03% or less by weight of carbon, 1.00% or less by weight of silicon, 2.00% or less by weight of manganese, 0.04% or less by weight of phosphorous, 0.03% or less by weight of sulfur, a balance of iron, and a trace of impurities. The iron-chromium-nickel alloy is subjected to annealing at a temperature of 1,000° C. or greater to restore a ferromagnetic martensitic structure formed as a result of cold working into an original non-magnetic ostenitic structure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: [0014]
FIG. 1 is a vertical sectional view of a general cathode ray tube (CRT); [0015]
FIG. 2 is an exploded perspective view of an electron gun of FIG. 1; [0016]
FIG. 3 is a sectional view of a main lens unit of FIG. 2; [0017]
FIG. 4 is a graph of magnetic permeability versus cold working rate for electrode materials containing different amounts of nickel; [0018]
FIG. 5 is a graph of tensile strength versus average granularity for electrode materials according to the present invention; [0019]
FIG. 6 is a graph of yield strength versus average granularity for the electrode materials according to the present invention; [0020]
FIG. 7 is a graph of elongation versus average granularity for the electrode materials according to the present invention; and [0021]
FIG. 8 is a graph of plastic strain ratio versus average granularity for the electrode materials according to the present invention.[0022]

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a [0023] cathode ray tube 10 includes a panel 11 with a fluorescent layer (not shown) on its inner surface, a funnel 12 fitted to the panel 11 to form a bulb, a shadow mask 13 having numerous electron beam apertures and spaced a predetermined distance from the inner surface of the panel 11, and a shadow mask frame 14 to which the shadow mask 13 is fixed.
The position of the [0024] shadow mask frame 14 inside the panel 11 is fixed by a stud pin 15 and a hook spring 16 elastically supported against the stud pin 15.
An [0025] electron gun 20, which scans red, green, and blue electron beams over the fluorescent layer on the inner surface of the panel 11, is fitted into a neck portion 12 a of the funnel 12. A shield cup 17 is installed in front of the electron gun 20. A deflection yoke 18 for deflecting 18 electron beams is installed on a cone portion 12 b of the funnel 12.
As shown in FIG. 2, the [0026] electron gun 20 includes a plurality of cathodes 21 as thermion emitters, a control electrode 22 arranged in front of the cathodes 21, a screen electrode 23 arranged in front of the control electrode 22, a group of focusing electrodes 24 thru 27 installed in front of the screen electrode 23, and a final accelerating electrode 28 installed facing the last focusing electrode 27.
The three [0027] cathodes 21 for emitting red, green, and red thermions are arranged in a line. The control electrode 22 controls the emission of electrons from the cathodes 21 using an external signal and has separate small electron beam apertures. The screen electrode 23 also has separate small electron beam apertures so as to constitute a pre-focusing lens unit along with the first focusing electrode 24 facing the screen electrode 23.
The focusing [0028] electrodes 24 thru 27, which are successively arranged in front of the screen electrode 23, constitute an electron lens unit along with the screen electrode 23 so as to focus and accelerate electron beams.
The number of focusing [0029] electrodes 24 thru 27 is not limited to the above. The number of focusing electrodes 24 thru 27 may be increased to form a multi-step focusing electron lens. Each of the focusing electrodes 24 thru 27 has three in-line electron beam apertures, which allow electron beams to pass to excite red, green, and blue phosphors coated on the inner surface of the panel 11. The shape of the electron beam apertures may be varied depending on the size of the electron lens formed by the electrodes 24 thru 27. Alternatively, a single large electron beam aperture may be formed in each of the electrodes 24 thru 27.
In the [0030] electron gun 20 with the above structure, a predetermined voltage is applied to each of the electrodes 22 thru 28 so as to focus and accelerate electrons emitted from the cathodes 21, which acts as a thermion emitter, the electrons passing the electron beam apertures. The emission of thermions from the cathodes 21 is controlled by a potential difference between the cathodes 21 and the control electrode 22. The electron beams are accelerated while passing the screen electrode 23, and are focused onto the fluorescent layer by the focusing electrodes 24 thru 27 and the final accelerating electrode 28 so as to form images.
The [0031] control electrode 22 and the screen electrode 23 have a flat shape, and the other electrodes 24 thru 28 have a cup shape. Among these electrodes, the focusing electrode 27 and the final accelerating electrode 28, which form a main lens unit, are formed or drawn into a cup shape bypressing, as illustrated in FIG. 3. Electron beam apertures 27 a and 28 a are formed therein using a puncher, and burrs 27 b and 28 b are formed on the electron beam entry and exit surfaces of the focusing electrode 27 and the final accelerating electrode 28, respectively.
According to a feature of the present invention, the [0032] electrodes 24 thru 28, excluding the control electrode 22 and the screen electrode 23, and the shield cup 17 (see FIG. 1), which is installed in front of the electron gun 20, contain less nickel compared to conventional electron guns and are made of ostenitic iron-chromium-nickel (Fe—Cr—Ni) stainless steel having a particular average granularity and surface roughness.
In particular, an ostenitic Fe—Cr—Ni alloy is used for the electron gun electrodes in the present invention. The ostenitic Fe—Cr—Ni alloy contains 18-20% by weight of Cr, 8-10% by weight of Ni, 0.03% or less by weight of carbon (C), 1.00% or less by weight of silicon (Si), 2.00% or less by weight of manganese (Mn), 0.04% or less by weight of phosphorous (P), 0.03% or less by weight of sulfur (S), a balance of Fe, and a trace of impurities. [0033]
A source alloy having the above composition is processed into a material for electron gun electrodes as follows. The source alloy is processed through primary cold rolling, annealing, acid washing, secondary skin pass rolling, and degreasing. Then, the resulting source alloy is subjected to bright annealing, tension leveling, and slitting for wrapping. [0034]
The electron gun electrode material has an average granularity of 0.01-0.02 mm to provide effective drawing properties, dimensional accuracy, and good product appearance. [0035]
The electron gun electrode material according to the present invention has a paramagnetic ostenitic structure to ensure non-magnetic properties in order to prevent deterioration in focusing and convergence characteristics of the electron gun. Such a microstructure can be achieved with the above ostenitic Fe—Cr—Ni alloy, which contains 18-20% by weight of Cr, 8-10% by weight of Ni, 0.03% or less by weight of C, 1.00% or less by weight of Si, 2.00% or less by weight of Mn, 0.04% or less by weight of P, 0.03% or less by weight of S, a balance of Fe, and a trace of impurities. [0036]
When manufacturing an electrode using the above electrode material, annealing is performed at a temperature of 1,000° C. or greater to restore a ferromagnetic martensitic structure formed as a result of cold working into the original non-magnetic ostenitic structure. [0037]
The electrode material according to the present invention may have magnetic properties when the rolling ratio or cold working percentage is increased. However, the magnetic properties of the electrode material disappear after annealing at a temperature of 1,050° C., and the original non-magnetic properties before the cold rolling are restored. [0038]
The electrode material according to the present invention originally has a non-magnetic ostenitic microstructure. This non-magnetic ostenitic microstructure is changed during cold working into a ferromagnetic martensitic microstructure by a modified martensitic transformation mechanism. However, the original non-magnetic ostenitic microstructure can be recovered through thermal treatment. [0039]
It is preferable that the electrode material contain 8-10% by weight of Ni. If the amount of Ni is less than 8% by weight, the ferromagnetic structure cannot be fully changed into the non-magnetic structure after thermal treatment. Using more than 10% by weight of Ni is costly and uneconomical. [0040]
The surface roughness of the electrode material affects the coefficient of friction with a molding puncher and a die and drawing properties. In addition, the surface roughness is related to the surface gas emission property and the appearance of the final product. An appropriate degree of surface roughness is required for desired appearance of the final product and formability. To this end, the surface of the electrode material is brush finished so as to have a particular roughness. [0041]
In the present invention, the surface of the electrode material is made rough by using an uneven roller, instead of using an abrasive as in general methods, so that the uneven surface pattern of the roller is transferred to the surface of the electrode material. A discontinuous dot pattern, rather than a continuous linear pattern parallel to the rolling direction, is preferred as an uneven surface pattern to reduce the anisotropy of the electrode material. [0042]
The electrode material according to the present invention has an arithmetic mean roughness (Ra) of 0.05-0.2 μm and a maximum roughness (Rmax) of 1.5-2.0 μm. The arithmetic mean roughness (Ra) is calculated in micrometers using the following equation from a roughness curve defined as y=f(x), wherein the X-axis of the roughness curve denotes the direction in which an extracted average line having a reference length extends, and the Y-axis denotes a direction perpendicular to the direction in which the extracted average line extends: [0043] $Ra = \frac{1}{L} \int_{0}^{L} \langle y (x) \rangle \partial x$
If the surface roughness of the electrode material exceeds the above ranges, the lubricating effect is insufficient, and serious abrasion occurs. As described above, a discontinuous dot pattern is preferred over a continuous line pattern to reduce the anisotropy of the electrode material. [0044]
For the dimensional accuracy and hardness of electron gun electrodes and improved drawing properties, when the focusing [0045] electrode 27 or the final accelerating electrode 28 has a single large electron beam aperture and a height of 7 mm or greater, and the shield cup 17 has a height of 7 mm or greater, it is preferable that the electrode material for the focusing electrode 27, the final accelerating electrode 28, and the shield cup 17 have a micro Vickers hardness of 165-180 Hv. However, when the focusing electrode 17 or the final accelerating electrode 28 has independent small electron beam apertures and a height of 7 mm or less, an electrode material for the focusing electrode 17 and the final accelerating electrode 28 should have a micro Vickers hardness of 160 or 175 Hv. When the focusing electrode 17 or the final accelerating electrode 28 includes an inner electrode and has a height of 7 mm or less, and the shield cup has a height of 7 mm or less, an electrode material for the focusing electrode 17, the final accelerating electrode 28, and the shield chip should have a micro Veckers hardness of 160 or 175 Hv.
Hereinafter, the properties of electrode materials according to the present invention will be described in detail with reference to the following experimental examples. [0046]

Table 1 shows the composition of a conventional electrode material (Comparative Example) and the composition ofelectrode materials according to the present invention (Examples 1 thru 6) and their average granularity.

TABLE 1


									Average
Example	C	Si	Mn	P	S	Ni	Cr	Fe	granularity, mm

Comparative	0.04	0.68	1.61	0.021	0.002	14.12	16.13	Bal.	0.019
Example
Example 1	0.02	0.62	1.21	0.025	0.003	9.48	18.55	Bal.	0.030
Example 2	0.02	0.62	1.21	0.025	0.003	9.48	18.55	Bal.	0.025
Example 3	0.02	0.62	1.21	0.025	0.003	9.48	18.55	Bal.	0.019
Example 4	0.02	0.62	1.21	0.025	0.003	9.48	18.55	Bal.	0.013
Example 5	0.02	0.62	1.21	0.025	0.003	9.48	18.55	Bal.	0.008
Example 6	0.02	0.62	1.21	0.025	0.003	9.48	18.55	Bal.	0.002

In Table 1 above, the composition of the electrode materials is based on % by weight. The conventional electrode material was a Fe-16% Cr-14% Ni stainless alloy steel, and the electrode materials of Examples 1 thru 6 according to the present invention, were ostenitic stainless alloy steels, the compositions of which were varied within a predetermined range. [0048]
Referring to Table 1, the electrode materials according to the present invention contain only 9.48% by weight of Ni compared to the conventional electrode material, which contains 14.12% by weight of Ni. In addition, the electrode materials according to the present invention contain only 0.02% or less by weight of C, compared to the conventional electrode material containing 0.04% by weight of C, so as to suppress the separation of carbon at grain boundaries and improve the anti-corrosion and brittleness of the electrode materials. [0049]
The term average granularity refers to the average size of ostenitic grains split along each grain boundary in the microstructure of stainless alloy steel. [0050]
The properties of the electrode materials with different compositions according to the present invention were measured. The results are as follows. [0051]
FIG. 4 is a graph of magnetic permeability versus cold working rate for electrode materials containing different amounts of Ni. [0052]
As shown in FIG. 4, as the cold working rate increases, the magnetic permeability increases more linearly for the electrode material containing 8.0% by weight of Ni (curve C) than for the electrode material containing 12% by weight of Ni (curve A) and the electrode material containing 9.5% by weight of Ni (curve B). [0053]
In particular, for the electrode material containing 8% by weight of Ni, the magnetic permeability sharply increases with greater cold working rate. The magnetic permeability indicates how easily magnetic field lines can pass through the electrode material. Ferromagnetic materials do not allow magnetic field lines to pass through them unless magnetic saturation occurs therein. Meanwhile, non-magnetic materials allow magnetic field lines to easily pass through them. The magnetic permeability is equal to 1 in a vacuum. It is preferable that the magnetic permeability approximate 1 so as not to affect deflected magnetic fields and not to deteriorate the focusing properties of electron guns. [0054]
FIGS. [0055] 5 thru 7 are regression curves of tensile strength, yield strength, and elongation versus average granularity for electrode materials according to the present invention. As shown in FIGS. 5 thru 7, the tensile strength and yield strength of the electrode material decrease linearly, but the elongation increases, with greater average granularity.
The formability of electrode materials according to the present invention was evaluated using a plastic strain ratio, the R-value suggested by Lankford, as expressed in the following equation: [0056] $R = \frac{ɛ_{w}}{ɛ_{t}} = \frac{\ln (W_{f} / W_{0})}{\ln (t_{f} / t_{0})} = \frac{\ln (W_{f} / W_{0})}{\ln (W_{0} l_{0} / W_{f} l_{f})}$
where ε[0057] _wand ε_tdenote the strain in the width and thickness directions, respectively, W_fand W₀denote the width of the electrode material before and after strain, respectively, t_fand t₀denote the thickness of the electrode material before and after strain, respectively, W₀l₀denotes the distance in the width and depth directions before tensile test, and W_fl_fdenotes the distance in the width and depth directions after 18% elongation.
The plastic strain ratio, the R-value, is a factor determining the initiation of necking as a result of unstable plastic behavior of an electrode material during processing, i.e., the local thinning of the electrode material. A greater R-value means that strain occurs more easily in the width and rolling directions due to small resistance to strain, but necking is more likely to occur in the thickness direction due to great resistance to strain. Accordingly, the greater the R-value, the better the drawing properties. [0058]
The electrode material according to the present invention has an ostenitic structure. The R value of alloy steel having a face centered cubic structure (FCC), like an ostenitic structure, can be calculated using the following multiple regression equation: [0059]
R=1.165−6.86×10⁻³(TS/YS)−1.111n+5.928×10⁻³ EL
where TS denotes tensile strength in Mpa, YS denotes yield strength in Mpa, n denotes a strain hardening exponent, and EL denotes elongation percentage. [0060]

In the examples of the present invention, the strain hardening exponent, n, of the electrode materials is about 0.5. The R-value with respect average granularity variation was calculated using the above multiple regression equation. The results are shown in FIG. 8, and the results of FIGS. 5 thru 8 are presented in Table 2.

TABLE 2


	Tensile	Yield
Average	strength	strength	Elongation		Dimensional	Shape of
granularity, mm	(TS), MPa	(YS), Mpa	(EL), %	R-value	accuracy	burr

0.033	593.7	238.0	64.3	0.97	Δ	X
0.030	594.9	237.2	62.5	0.96	Δ	X
0.028	598.7	239.0	60.7	0.95	Δ	Δ
0.025	605.2	243.5	59.1	0.94	Δ	Δ
0.022	614.4	250.8	57.5	0.93	◯	◯
0.019	626.2	260.7	56.0	0.93	◯	◯
0.016	640.8	273.3	54.6	0.92	◯	◯
0.013	658.0	288.6	53.3	0.91	◯	◯
0.010	677.9	306.6	52.1	0.90	◯	◯
0.008	700.4	327.3	50.9	0.90	Δ	◯
0.005	725.7	350.7	49.9	0.89	Δ	◯
0.002	753.6	376.8	48.9	0.89	Δ	◯

Referring to FIG. 8 and Table 2, the plastic strain ratio, R-value, increases with greater average granularity. However, it is preferable that the average granularity be in a range of 0.010-0.022 mm in terms of dimensional accuracy and the shape of burr after electrode formation. [0062]
As described above, the Fe—Cr—Ni alloy steel for electron gun electrodes according to the present invention, the composition of which is adjusted within a predetermined range for a particular average granularity and surface roughness, provides the following effects. [0063]
The Fe—Cr—Ni alloy steel for electron gun electrodes contains a smaller amount of expensive Ni, compared to conventional ones, so that the manufacturing cost of electron guns can be greatly reduced. In addition, an electron gun electrode made of the Fe—Cr—Ni alloy steel has effective drawing properties and pressing formability. The Fe—Cr—Ni alloy steel is non-magnetic and can prevent focusing and convergence drift properties from deteriorating. Accordingly, more reliable cathode ray tubes can be manufactured with the Fe—Cr—Ni alloy steel. [0064]
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. [0065]

Claims

What is claimed is:

1. An iron-chromium-nickel alloy for an electrode of an electron gun which includes a cathode, a control electrode, a screen electrode arranged in front of said control electrode, at least one focusing electrode arranged in front of said screen electrode to form a pre-focusing lens unit, a final accelerating electrode arranged in front of said at least focusing electrode to form a main lens unit, and a shield cup electrically connected to said final accelerating electrode, said iron-chromium-nickel alloy for said at least one focusing electrode, said final accelerating electrode, and said shield cup comprising chromium in a range of 18-20% by weight, nickel in a range of 8-10% by weight, no greater than 0.03% by weight of carbon, no greater than 1.00% by weight of silicon, no greater than 2.00% by weight of manganese, no greater than 0.04% by weight of phosphorous, no greater than 0.03% by weight of sulfur, a balance of iron, and a trace of impurities.

2. The iron-chromium-nickel alloy of claim 1, having a surface roughness Ra in a range of 0.05-0.2 μm and a maximum roughness Rmax in a range of 1.5-2.0 μm.

3. The iron-chromium-nickel alloy of claim 2, wherein the surface roughness originates from a surface pattern of said iron-chromium-nickel alloy formed using an uneven roller.

4. The iron-chromium-nickel alloy of claim 3, wherein the surface pattern is a discontinuous dot pattern parallel to a rolling direction for smaller anisotropy of the iron-chromium-nickel alloy.

5. The iron-chromium-nickel alloy of claim 1, wherein one of said at least one focusing electrode and said final accelerating electrode has a single large electron beam aperture and a height of at least 7 mm.

6. The iron-chromium-nickel alloy of claim 5, having a micro Vickers hardness in a range of 165-180 Hv when used for said at least one focusing electrode and said final accelerating electrode having a single large electron beam aperture.

7. The iron-chromium-nickel alloy of claim 1, wherein said shield cup has a height of at least 7 mm.

8. The iron-chromium-nickel alloy of claim 7, having a micro Vickers hardness in a range of 165-180 Hv when used for said shield cup.

9. The iron-chromium-nickel alloy of claim 1, wherein one of said at least one focusing electrode and said final accelerating electrode has independent small electron beam apertures and a height no greater than 7 mm.

10. The iron-chromium-nickel alloy of claim 9, having a micro Vickers hardness in a range of 160-175 Hv when used for said at least one focusing electrode and said final accelerating electrode having independent small electron beam apertures.

11. The iron-chromium-nickel alloy of claim 1, wherein one of said at least one focusing electrode and said final accelerating electrode includes an inner electrode and has a height no greater than 7 mm.

12. The iron-chromium-nickel alloy of claim 11, having a micro Vickers hardness in a range of 160-175 Hv when used for said at least one focusing electrode and said final accelerating electrode.

13. The iron-chromium-nickel alloy of claim 1, having an average granularity in a range of 0.010-0.022 mm.

14. The iron-chromium-nickel alloy of claim 1, wherein said alloy is processed into a material for said electrode of said electron gun by at least one of primary cold rolling, annealing, acid washing, secondary skin pass rolling and degreasing.

15. The iron-chromium-nickel alloy of claim 1, wherein said alloy is subject to at least one of bright annealing, tension leveling and slitting for wrapping.

16. An iron-chromium-nickel alloy for an electrode of an electron gun which includes a cathode, a control electrode, a screen electrode arranged in front of said control electrode, at least one focusing electrode arranged in front of said screen electrode to form a pre-focusing lens unit, a final accelerating electrode arranged in front of said at least one focusing electrode to form a main lens unit, and a shield cup electrically connected to said final accelerating electrode, said iron-chromium-nickel alloy for said at least one focusing electrode, said final accelerating electrode, and said shield cup comprising chromium in a range of 18-20% by weight, nickel in a range of 8-10% by weight, no greater than 0.03% by weight of carbon, no greater than 1.00% by weight of silicon, no greater than 2.00% by weight of manganese, no greater than 0.04% by weight of phosphorous, no greater than 0.03% by weight of sulfur, a balance of iron, and a trace of impurities, wherein said iron-chromium-nickel alloy is subjected to annealing at a temperature of no less than 1,000° C. to restore a ferromagnetic martensitic structure formed as a result of cold working into an original non-magnetic ostenitic structure.

17. The iron-chromium-nickel alloy of claim 16, having an average granularity in a range of 0.010-0.022 mm when used for said at least one focusing electrode, said final accelerating electrode, and said shield cup.

18. The iron-chromium-nickel alloy of claim 16, having a surface roughness Ra in a range of 0.05-0.2 μm and a maximum roughness Rmax in a range of 1.5-2.0 μm.

19. The iron-chromium-nickel alloy of claim 16, wherein said alloy is processed into a material for said electrode of said electron gun by at least one of primary cold rolling, annealing, acid washing, secondary skin pass rolling and degreasing.

20. The iron-chromium-nickel alloy of claim 16, wherein said alloy is subject to at least one of bright annealing, tension leveling and slitting for wrapping.