JP2002129293A - Fe-Cr-Ni BASED ALLOY FOR ELECTRON GUN ELECTRODE HAVING EXCELLENT CORROSION RESISTANCE AND STRIP THEREOF - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for an electron gun electrode having high corrosion resistance and to provide a material exhibiting good corrosion resistance even after heat treatment and free from the generation of rust both in the process of production and after production. SOLUTION: This Fe-Cr-Ni based alloy for an electron gun electrode having excellent corrosion resistance has a composition containing, by mass, 15 to 20% Cr, 9 to 15% Ni, 0.2 to 2.5% Mn and 0.001 to 0.04% C, and the balance Fe with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloy for an electron gun electrode which requires non-magnetism and its strip, and more particularly to an Fe-Cr-Ni-based alloy for an electron gun electrode with improved corrosion resistance and its strip. .

[0002]

2. Description of the Related Art An electrode of an electron gun used for a color cathode ray tube or the like uses a nonmagnetic stainless steel Fe-Cr-Ni alloy strip. The thickness of this strip is usually 0.1 to 0.7
mm. In the manufacture of an electron gun electrode, first, a strip is drawn into a predetermined shape by press working, and then burring is performed (a process in which a round hole is formed and the periphery of the hole is projected like a cylinder), and finally, annealing is performed. In this series of processes,
A step of joining a plurality of components by spot welding may be added.

[0003] Stainless steel exhibits excellent corrosion resistance due to the formation of a passivation film by Cr in the alloy, but heat treatment may significantly deteriorate the corrosion resistance. The form of corrosion in this case is usually intergranular corrosion. This phenomenon is called sensitization. During cooling after heating, carbon in the alloy diffuses to the grain boundaries and selectively combines with Cr to form chromium carbides. It is said that this is due to the decrease in concentration.

[0004] Sensitivity occurs during annealing or welding in the manufacturing process of the electron gun electrode, and the product may rust during the manufacturing process or during storage after manufacturing. Conventionally, in order to solve this problem, the appearance of the product is inspected, and products with rust are selected and removed. The cooling rate after annealing or after welding is made very fast so that chromium carbides do not precipitate at the grain boundaries during cooling. In order to prevent rust even if sensitization occurs, the humidity, dust amount, etc. in the environment, which are factors that promote corrosion, are kept low. And other measures have been taken, for which a great deal of labor and cost has been spent.

[0005] On the other hand, most studies on Fe-Cr-Ni alloys and their strips, which are materials for electron gun electrodes, relate to improvement of drawability (for example, Japanese Patent Application No. 2000-225437).
No studies have been performed to improve corrosion resistance.

[0006]

In recent years, the demand for focus characteristics of an electron gun has become stricter due to the progress of higher definition and higher brightness in a CRT for a computer. It has become more sophisticated. And shows good corrosion resistance even after heat treatment
Fe-Cr-Ni alloy materials have been desired.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an alloy for an electron gun electrode having excellent corrosion resistance and a strip thereof.

[0008]

Means for Solving the Problems As a means for preventing the sensitization of stainless steel, a method of reducing the concentration of C, which causes the formation of chromium carbides, has an element (Ti, Zr, Nb, Nb, V, Ta, Hf, etc.) are known to suppress the diffusion of C to the grain boundaries during cooling.

When these means are applied to Fe-Cr-Ni alloys for electron gun electrodes and their strips, taking into consideration other characteristics required for electron gun electrodes such as drawability, the C concentration and the addition of The concentration of the elements must be adjusted. For example, if the C concentration is too low, the O concentration increases when the alloy is smelted, and oxide-based inclusions frequently occur, and the drawability decreases. Also, if a large amount of elements having a strong affinity for C are added, these elements form coarse carbides and also cause the formation of oxide-based inclusions, which lowers the drawability.

The present inventors have optimized the above-mentioned method used to prevent sensitization of stainless steel for Fe-Cr-Ni alloys for electron gun electrodes and their strips. This is for electron gun electrode
This is the first attempt in the field of Fe-Cr-Ni alloys and their strips. Then, measures to further improve the corrosion resistance were examined. (1) Cr: 15 to 20 mass%, Ni: 9 to 15 mass%, Mn: 0.2 to
2.5 mass%, C: 0.001 to 0.04 mass%, the balance being Fe
Fe-Cr-Ni alloys for electron gun electrodes with excellent corrosion resistance, characterized by being composed of unavoidable impurities.

(2) Cr: 15 to 20 mass%, Ni: 9 to 15 mass
%, Mn: 0.2 to 2.5 mass%, C: 0.001 to 0.04 mass%, and further, Ti, Zr, Nb, V, Ta and Hf, [% C] / 12 ≤ ([% Ti] / 48 + [% Zr] / 91 + [% Nb] / 93 + [% V] / 51
+ [% Ta] / 181 + [% Hf] / 178) ≦ 0.01 ([% i] is the mass% concentration of element i), with the balance being Fe and unavoidable impurities , Fe-Cr-Ni alloy for electron gun electrodes with excellent corrosion resistance.

(3) Mo and Cu in total of 0.05 to 5 mass%
The Fe-Cr-Ni alloy for an electron gun electrode having excellent corrosion resistance according to claim 1 or 2, characterized by being contained. (4) In the case where X-ray diffraction was performed using a Co tube on the rolled surface, the X-ray diffraction integrated intensity I
_(hkl) is such that I ₍₂₀₀₎ / (I ₍₂₂₀₎ + I ₍₁₁₁₎ + I ₍₂₀₀₎ + I ₍₃₁₁₎ ) ≦ 0.5. Excellent Fe-Cr-Ni alloy for electron gun electrodes.

(5) When the roughness is measured in a direction perpendicular to the rolling direction using a contact roughness meter, Ry is 3 μm or less, wherein the corrosion resistance is excellent. Fe-Cr-Ni alloy for electron gun electrodes. (6) The Fe-Cr-Ni for an electron gun electrode according to any one of claims 1 to 5, wherein the average number of inclusions having a diameter exceeding 20 µm is 3 / mm ² or less on the rolled surface after mirror polishing. System alloy.

(7) An Fe-Cr-Ni alloy strip for an electron gun electrode, wherein the alloy according to (1) to (6) is used. Showed excellent corrosion resistance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The Fe-Cr-Ni-based alloy for an electron gun electrode of the present invention, the reasons for limiting the alloy components in the strip, and the reasons for limiting the inclusions will be described below.

1. The Cr electron gun electrode is required to be non-magnetic. Usually, in order to be non-magnetic, the magnetic permeability needs to be 1.005 or less. To satisfy this, the Cr content was set to 15 to 20 mass%. Note that a more preferable range is 15 to 17 mass%.

2. Ni If the content of Ni is less than 9 mass%, the magnetism becomes too high, and 15 mass%
If more, the cost will increase. Therefore Ni content 9 ~ 15mass%
And 3.Mn Mn is the purpose of deoxidation and MnS to improve press punching
However, if it is less than 0.2 mass%, there is no effect, and if it exceeds 2.5 mass%, the material hardness increases and the drawability deteriorates. Therefore, the Mn content was set to 0.2 to 2.5 mass%.

4. CC is an element which causes sensitization which causes deterioration of corrosion resistance of stainless steel. Sensitization is reduced when the concentration is 0.04 mass% or less, and no sensitization occurs when the concentration is 0.02 mass% or less. On the other hand, when the C concentration is lower than 0.001 mass%, the O concentration increases when the alloy is melted, and oxide inclusions are frequently generated, and the drawability decreases. The generation of coarse inclusions also causes a decrease in corrosion resistance for the reason described in 9. Therefore, the C concentration is specified to be 0.001 to 0.04 mass%, but a more preferable concentration is 0.005 to 0.02 mass%.

5. Ti, Zr, Nb, V, Ta, Hf Since these elements have a strong affinity for C, when added to the alloy, the diffusion of C to the grain boundaries is suppressed, and the chromium carbide Precipitation (sensitization) is reduced. That is, the same effect as when the C concentration is reduced can be obtained. The addition of these elements is particularly effective when the C concentration is relatively high (C = 0.04 to 0.02 mass
%). The optimal addition amount is T = [% Ti] / 48
+ [% Zr] / 91 + [% Nb] / 93 + [% V] / 51 + [% Ta] / 181 + [% H
f] / 178, and the range is [% C] /12≦T≦0.01. Here, [% i] is the mass% concentration of element i, 12, 48, 91, 93, 51, 1
81 and 178 are the atomic weights of C, Ti, Zr, Nb, V, Ta, and Hf, respectively.

That is, the effect of preventing sensitization is caused by Ti,
Occurs when the total molar concentration of Zr, Nb, V, Ta and Hf exceeds the molar concentration of C. On the other hand, when T exceeds 0.01 mass%, the drawability is reduced due to the generation of coarse carbides and the formation of oxide-based inclusions, and the corrosion resistance is rather deteriorated for the reason described in Section 9 below.

6. Mo, Cu Mo and Cu have an effect of improving corrosion resistance. This effect appears when the total concentration of Mo and Cu is 0.05 mass% or more. On the other hand, if it exceeds 5 mass%, the material hardness increases and the drawability deteriorates. Therefore, the total content of Mo and Cu is adjusted to 0.05 to 5 mass%.
And

7. Crystal Orientation There is a correlation between the degree of development of the (200) orientation on the rolled surface and the corrosion resistance. As the (200) orientation develops, the corrosion resistance decreases. The mechanism is unknown, but phenomenally, in the range of I ₍₂₀₀₎ / (I ₍₂₂₀₎ + I ₍₁₁₁₎ + I ₍₂₀₀₎ + I ₍₃₁₁₎ ) ≦ 0.5, the (200) orientation No adverse effect on corrosion resistance was observed. Therefore, the crystal orientation is defined in this range. Here, I _(hkl) is the X-ray diffraction integrated intensity of the (hkl) plane, and is a value measured using a Co tube.

8. Surface Roughness In order to generate rust, the presence of an electrolyte solution is indispensable. If there are minute irregularities on the surface, water in the atmosphere will adhere to the concave portion, or the cleaning liquid will remain in the concave portion during cleaning, and corrosion will start from this portion. Therefore, it is desirable to reduce asperities on the material surface as much as possible. Asperity related to corrosion resistance is reflected in the roughness parameter Ry. In the case of rolled material, Ry measured in a direction perpendicular to the rolling direction is larger than Ry measured in a direction parallel to the rolling direction. Ry value is important. When Ry value is 3μm or less, adverse effect of surface irregularities on corrosion resistance (correlation between Ry value and corrosion resistance)
Was not found. Therefore, the Ry value was set to 3 μm or less.

9. Surface Inclusions If water in the air adheres to the gap between the coarse inclusions on the surface and the mother ground or the cleaning liquid during cleaning remains, corrosion starts from this portion. Such a corrosion promoting effect is observed in inclusions having a diameter exceeding 20 μm, and when the average number of the inclusions exceeds 3 / mm ² , deterioration of corrosion resistance cannot be ignored. Therefore, the average number of inclusions with a diameter of more than 20 μm is 3
/ mm ² or less. The diameter of the inclusion was defined as the average value of the short axis and the long axis when the shape of the inclusion was elliptical, rod-like, linear, or the like (see FIG. 1).

10. Impurities The Fe-Cr-Ni-based alloy of the present invention contains some impurities which are impurities of raw materials, refractories, slag and additional elements during refining, and the like. Although not a requirement of the present invention, examples of impurities are described below. (A) Si (0.005 to 1.0 mass%): added for the purpose of deoxidation during scouring. At less than 0.005 mass%, there is no deoxidizing effect and 1.
If the content exceeds 0 mass%, the workability will deteriorate.

(B) P (0.03 mass% or less): If it exceeds 0.03 mass%, the drawability is significantly deteriorated. (C) S (0.0003-0.01mass%): Mn and MnS when contained in appropriate amounts
Is formed, and the press punching property is improved. But 0.01 m
If the content exceeds ass%, coarse MnS is generated, and the drawability deteriorates. (D) Al (0.001 to 0.2 mass%): added as a deoxidizer. At less than 0.001 mass%, the deoxidizing effect is not sufficient,
If the content exceeds mass%, the workability deteriorates.

(E) O (0.005 mass% or less): When the O content is large, the amount of oxide-based inclusions increases and the drawability deteriorates. (F) N (0.1 mass% or less): If it exceeds 0.1 mass%, the workability is deteriorated. (G) Ca (0.05 mass% or less): If it exceeds 0.05 mass%, sulfides and oxides are formed and the drawability deteriorates.

(H) Mg (0.02 mass% or less): If it exceeds 0.02 mass%, sulfides and oxides are formed and the drawability deteriorates.

[0028]

Next, the present invention will be described with reference to examples. Table 1
The following Fe-Cr-Ni was melted and continuously cast. Then 1180 ~
After heating to 1230 ° C, bulk rolling, peeling, heating to the same temperature, hot rolling, descaling, cold rolling and annealing were repeated to produce a 0.30 mm thick annealed material. . In the last rolling, the surface roughness of the material was changed by changing the surface roughness of the rolling roll. This material was evaluated as follows.

[0029]

[Table 1]

(A) Surface roughness: Ry (maximum height) in a direction perpendicular to the rolling direction was determined according to JISB0601 (1994). Crystal orientation: Using a Co tube, the integrated values of the diffraction intensities of the (111), (200), (220) and (311) planes were obtained under the conditions of a tube voltage of 30 kV and a tube current of 20 mA. (B) Surface inclusions: After polishing the surface to a mirror surface by mechanical polishing, the number of inclusions having a diameter exceeding 20 μm was measured using an optical microscope. The observation area was 400 mm ² .

(C) Corrosion resistance: The sample was heated at 700 ° C. in a hydrogen stream.
For 5 minutes. Fe-Cr-Ni for conventional electron gun electrodes
The alloy is sensitized by this heat treatment. The samples were then exposed to the seaside industrial zone air (70-90% relative humidity, 25-35 ° C). This atmosphere has an SO ₂ concentration of about 1 ppm, and is an environment where Cl ions are constantly supplied due to the arrival of sea salt particles. Therefore, the test environment is an environment in which corrosion is remarkably promoted as compared with the environment of the electron gun electrode assembly process. Every 12 hours after the exposure, the surface of the sample was observed under a microscope at a magnification of 50 times to observe the presence or absence of rust. Observation was continued for up to 10 days.

Table 1 shows the ratio of the Ry and (200) directions (I ₍₂₀₀₎ /
(I ₍₂₂₀₎ + I ₍₁₁₁₎ + I ₍₂₀₀₎ + I ₍₃₁₁₎ )), the number of surface inclusions exceeding 20 μm in diameter, and the exposure time when rust was observed. No. 16 is a conventional Fe-Cr-Ni alloy for an electron gun electrode in which C exceeds 0.04 mass%. The material was rusted after 0.5 days (first observation).

Nos. 1-3 have a C concentration of 0.02 mass% or less, [% Mo] + [% Cu]> 0.05 mass%, Ry <3 μm, and inclusions exceeding 20 μm <3 / mm ² . is there. In these, [% Ti] / 48 + [%
No rust occurred in 10 days regardless of Zr] / 91 + [% Nb] / 93 + [% V] / 51 + [% Ta] / 181 + [% Hf] / 178 (hereinafter T) .

Nos. 4 to 8 have a C concentration of 0.02 to 0.04 mass% or less, [% Mo] + [% Cu]> 0.05 mass%, Ry <3 μm, inclusions exceeding 20 μm <3 / mm ² It is. T ≧ [% C] / 12 of these
In the case of (Nos. 6 to 8), no rust occurred in 10 days.
On the other hand, for Nos. 4 and 5 with T <[% C] / 12, 6.5 days or
Rust occurred in 8.5 days, but the corrosion resistance was significantly improved compared to the conventional material (No. 16).

Nos. 9 to 12 have a C concentration of 0.04 mass% or less, while No. 9 has [% Mo] + [% Cu] of less than 0.05 mass% and No. 10
Ry exceeds 3 μm, No. 11 has more than 3 inclusions / mm ² with a diameter of more than 20 μm, and No. 12 has a (200) plane composition ratio of 0.5
Is over. In these, rust occurred within 10 days, but the time until rust occurred was 0.5% of that of the conventional material (No. 16).
Days, significantly improving the corrosion resistance of conventional materials.

No. 13 is an example in which Ti, Zr, and V were added in a relatively large amount to a material having a C concentration of more than 0.04 mass%, but rather coarse carbides increased, and the corrosion resistance was not so improved. In addition to this, drawing cracks also occurred. No. 14 is a material having a C concentration of less than 0.001 mass%. During the scouring, the O concentration increased and coarse oxide inclusions were generated, which caused squeezing cracks and reduced corrosion resistance.

In No. 15, cracks occurred in the drawing because the total concentration of Mo and Cu exceeded 5 mass%.

[0038]

According to the present invention, the following effects can be obtained. (1) A highly corrosion-resistant material for an electron gun electrode can be obtained. (2) A material exhibiting good corrosion resistance can be obtained even after heat treatment, and a material that does not rust can be obtained during and after production.

[Brief description of the drawings]

FIG. 1 defines a method for measuring a diameter based on the shape of an inclusion.

Claims (7)

[Claims] [Claim 1] Cr: 15 to 20 mass%, Ni: 9 to 15 mass%, Mn:
Fe-Cr-Ni alloy for electron gun electrodes with excellent corrosion resistance, characterized by containing 0.2 to 2.5 mass% and C: 0.001 to 0.04 mass%, with the balance being Fe and unavoidable impurities. 2. Cr: 15 to 20 mass%, Ni: 9 to 15 mass%, M
n: 0.2 to 2.5 mass%, C: 0.001 to 0.04 mass%,
Furthermore, Ti, Zr, Nb, V, Ta, and Hf were converted to [% C] / 12 ≤ ([% Ti] / 48 + [% Zr] / 91 + [% Nb] / 93 + [% V] / 51
+ [% Ta] / 181 + [% Hf] / 178) ≦ 0.01 ([% i] is the mass% concentration of element i), with the balance being Fe and unavoidable impurities , Fe-Cr-Ni alloy for electron gun electrodes with excellent corrosion resistance. 3. The Fe—Cr—Ni alloy according to claim 1, wherein Mo and Cu are contained in a total amount of 0.05 to 5 mass%. 4. When the X-ray diffraction is performed on a rolled surface using a Co tube, the X-ray diffraction integrated intensity I of the (hkl) plane is obtained.
_(hkl) is such that I ₍₂₀₀₎ / (I ₍₂₂₀₎ + I ₍₁₁₁₎ + I ₍₂₀₀₎ + I ₍₃₁₁₎ ) ≦ 0.5. Excellent Fe-Cr-Ni alloy for electron gun electrodes. 5. The electronic device according to claim 1, wherein Ry is 3 μm or less when the roughness is measured in a direction perpendicular to the rolling direction using a contact roughness meter. Fe-Cr-Ni alloy for gun electrodes. 6. The rolled surface after mirror polishing has a diameter of 20 μm.
average number is 3 / mm ² or less electron gun for Fe-Cr-Ni based alloy of claim 1 to 5, characterized in that the inclusions exceeding m. 7. An Fe-Cr-Ni alloy strip for an electron gun electrode, wherein the alloy according to claim 1 is used.