JP2001049395A - Iron-nickel-cobalt alloy excellent in etching characteristic and low thermal expansion characteristic, and shadow mask excellent in smoothness of inside peripheral shape of etch pit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alloy applicable to a shadow mask and combining etching characteristic with low thermal expansion characteristic at a low cost. SOLUTION: The alloy has a composition consisting of, by weight, >2.5 to 7% Co, 35.5 to 38% (Ni+Co), <0.1% Mn, 0.0005 to 0.004% B, and the balance essentially Fe and further has a composition consisting of, by weight, >2.5 to 7% Co, 35.5 to 38% (Ni+Co), <0.1% Mn, 0.0005 to 0.004%, in total, of (B+ Ca+Kg) (the total content of B as an essential element and either or both of Ca and Mg), and the balance essentially Fe. It is preferable to control S content to <=0.002% or C content to <0.005%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Fe--Ni--Co alloy for a shadow mask used in a color cathode ray tube, and more particularly to a material excellent in low thermal expansion characteristics.

[0002]

2. Description of the Related Art The technical trend of cathode ray tubes used in televisions and personal computers has recently been increasing in size, flattening, and increasing definition. Along with this, the characteristics required for the shadow mask material include the current ordinary Fe-N
There is a demand for a lower thermal expansion than the thermal expansion characteristics obtained with an i-based invar alloy (Fe-36% Ni).

The following two methods have been disclosed as methods for further reducing the thermal expansion of Fe--Ni-based invar alloys having a normal composition. One is that the main component is Fe-36% N
i is to suppress impurities, and the other is Co
To form a Fe—Ni—Co system. Known examples in which low thermal expansion is achieved by these effects are disclosed in JP-A-61-76651, JP-A-7-3401, and JP-A-8-801.
There is 311622. JP-A-8-209306, JP-A-8-33338, and JP-T-8-512363 are examples of those in which the amount of Co is suppressed to the minimum addition amount.

[0004]

The above means is effective as a method for obtaining excellent low thermal expansion characteristics. However, in the case of a material for a shadow mask, it is required that a high-definition electron beam passage hole can be etched and formed in an accurate shape. With the traditional method,
From this viewpoint, the study of the amount of Co and the study of trace elements cannot be said to be sufficient. As a result, for example, in order to obtain low thermal expansion characteristics,
Although a certain cost improvement is sacrificed by the inclusion of o, the etching properties are poor unless the trace elements are adjusted.

[0005]

In order to solve the above-mentioned problems and to put the invention into practical use, the present invention has conducted a detailed investigation on the amount of Co and the component range of trace elements from the viewpoint of low thermal expansion characteristics and etching properties. It has been found that a material having the following components is effective. That is, in terms of% by weight, Co: more than 2.5% and 7% or less, (Ni + Co): 35.5 to 38%, Mn:
Fe-Ni-Co-based alloy containing less than 0.1%, B: 0.0005 to 0.004%, and the balance substantially consisting of Fe.

Then, in terms of% by weight, Co: more than 2.5% and 7% or less, (Ni + Co): 35.5-38%, Mn:
Less than 0.1%, B is indispensable, and the total amount (B + Ca + Mg) with one or two of Ca or Mg is 0.1%.
It is an Fe-Ni-Co-based alloy containing 0005 to 0.004% with the balance being substantially Fe. Preferably, in the present invention, Fe-Ni-C in which S is suppressed to 0.002% or less or C is suppressed to less than 0.005%.
It is an o-based alloy.

The Fe—Ni—Co of the present invention
The shadow mask is made of a base alloy and has excellent low thermal expansion characteristics and excellent smoothness of the inner shape of the etching hole.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The most important feature of the present invention is to achieve an alloy having excellent etching properties and low thermal expansion properties.
As a result of taking into account in detail the effect of each of the Co content and the trace element range on the properties of the Invar alloy as well as the phenomenon occurring in the inner shape of the etching hole formed by etching, the alloy of the present invention It has been found. Hereinafter, the alloy components constituting the present invention and the reasons for the limitation will be described.

Co: It is known as an element for lowering the coefficient of thermal expansion in an Fe-Ni-based invar alloy. In the case of the present invention, in addition to the adjustment of the amount of Mn to be described later, by solving the problem of the etching property due to the low Mn, the excellent low thermal expansion characteristic based on the effect of the Co content of the present invention is achieved. We have found a means that can achieve this and also achieve excellent etching properties.

[0010] In particular, when the alloy of the present invention is applied to a shadow mask, for example, the effect of improving the color shift of a cathode ray tube is 30% less than the thermal expansion coefficient of an ordinary Invar alloy.
%, The significant difference can be obtained. Specifically, excellent low thermal expansion characteristics are achieved with a Co content exceeding 2.5%. In addition, Co has a very high raw material cost and a content exceeding 7% saturates the effect of improving the low thermal expansion characteristic. Therefore, in the present invention, the content of Co exceeds 2.5% to 7%. It was as follows.

Mn: an element that improves hot workability, but has an effect of increasing the thermal expansion coefficient of an Fe—Ni-based invar alloy or an Fe—Ni—Co-based invar alloy. In the present invention, the content is set to less than 0.1% in order to sufficiently achieve the mutual effect of the above.

[0012] B, Mg, Ca: Mn amount is 0.25
By limiting the% level to less than 0.1%, a new problem (FIG. 2) arises in that the inner contour of the etching hole is jagged, and in this case, a shadow mask ( Especially shadow masks for personal computers)
May cause problems in application to Then, when various trace elements were investigated, it was found that by incorporating these elements in appropriate amounts, this problem could be solved and a normal etching hole could be formed.

That is, the phenomenon that the inner hole contour of the etching hole is jagged is caused by the fact that S in the matrix is not fixed by reducing the amount of Mn, and the amount of S existing in the grain boundary increases. It is thought to be the result of increased susceptibility. In order to solve this problem, it is effective to contain a proper amount of trace elements B, Ca and Mg. In the case of the present invention, B is particularly effective for obtaining the effect.
Is set to 0.0005% or more. As for Ca and Mg which can be expected to have the same effect on B, the content of B is essential and the total amount of one or two of them (B + Ca + M
g) is 0.0005% or more.

However, if their total amount exceeds 0.004%, problems arise in terms of etching rate and pits. In other words, in the case of B, the phenomenon that the corrosion resistance of the grain boundaries increases and the etching rate is greatly reduced, and in the case of Ca and Mg, a phenomenon occurs in which inclusions that are easily corroded are formed and large etching pits are generated. . Therefore, the appropriate content range in the present invention is B: 0.0005% to 0.005%.
In the case where the effect of Ca and Mg is expected, the content of B is indispensable and the total amount of one or two of them (B + Ca + Mg): 0.0005% to 0.004
%. Further, the content of (Ca + Mg) is 0.002
% Is preferably added. in addition,
It is preferable that S is suppressed to 0.002% or less.

C: In the Fe—Ni—Co-based alloy of the present invention, which aims to reduce the Mn in order to achieve excellent low thermal expansion characteristics, the adjustment of the C content compensates for the hindrance to etching due to the low Mn. It is effective for In the alloy of the present invention, adjustment of the amounts of Co and Mn is indispensable to achieve the excellent low thermal expansion properties, and as a result, the Mn content is lower than the conventional 0.25% level of less than 0.1%. It is. That is, in the present invention, the above-mentioned deterioration of the etching property newly caused by the conventional improvement of Mn reduction is
It is necessary to consider a means sufficient to compensate for this, and various studies were made. As a result, it has been found that the deterioration of the etching property which occurs in the Fe-Ni-Co alloy having Mn of less than 0.1% can be compensated for by adjusting the C content. Specifically, it is effective to adjust the C content to less than 0.005%, and to adjust the S content to 0.002% or less.

In the present invention, it is important to optimally adjust the (Ni + Co) amount in addition to the Co content in order to achieve excellent low thermal expansion characteristics. Specifically, (Ni +
By adjusting the Co) amount to 35.5 to 38%, it is possible to maintain low thermal expansion characteristics sufficient for application to a shadow mask. Preferably, 30% more than Fe-36% Ni material
As a composition range effective for achieving the above low thermal expansion coefficient, the case of Co: 3.3% (Ni + Co) is 36.0 to 36.0.
When 37.2% and Co: 5%, (Ni + Co) is 3
5.7-37.7%.

In the case of the Fe—Ni—Co alloy of the present invention, for example, Si used as a deoxidizing agent in the melting process is used.
Is also possible, and specifically, may contain 0.1% or less, preferably 0.05% or less of Si.

If the above-described Fe—Ni—Co alloy of the present invention is applied to, for example, a shadow mask,
In addition to its excellent low thermal expansion characteristics, an electron beam passage hole having an accurate hole shape is also formed, so that it is most suitable as a shadow mask material.

[0019]

EXAMPLES (Example 1) An Fe-Ni-Co alloy was melted and cast in a vacuum induction melting furnace to produce an ingot having the components shown in Table 1. Forging this ingot,
A plate material having a thickness of 10 mm was used. For the measurement of the coefficient of thermal expansion, a test piece of 5 mmφ × 20 mmL was prepared from the forged plate material, and then annealed at 800 ° C. for 30 minutes in a N ₂ atmosphere condition. The measurement temperature range of the coefficient of thermal expansion was 30 to 100 ° C. The results are summarized in Table 1.

[0020]

[Table 1]

The results in Table 1 are summarized in FIG. 3 as the effect of the (Ni + Co) amount on the thermal expansion coefficient corresponding to each Co amount. From FIG. 3, even if the alloy satisfies the Mn content of the present invention, the Co content of the present invention is more than 2.5% to 7% and ( Ni + C
o) An alloy whose amount is adjusted to 35.5 to 38% has a smaller coefficient of thermal expansion, and can also achieve low thermal expansion characteristics effective for improving color misregistration when used as a shadow mask. The composition range in which the thermal expansion coefficient is 30% or more lower than that of the Fe-36% Ni material is as follows: Co: 3.3% (Ni + Co): 36.0 to 37.2%; Co: 5% , (Ni + C
o) is 35.7 to 37.7%.

(Example 2) An ingot having the components shown in Table 2 was produced by the same manufacturing method as in Example 1 described above, and a plate material having a thickness of 3 mm was formed by forging and hot working.
Then, cold rolling and annealing are repeated to obtain a thickness of 0.12 mm.
And a thin plate test material for etching property evaluation.
The etching property is determined by using a FeCl ₃ solution at a concentration of 47B.
After forming an etching hole in the shape of a shadow mask under the conditions of e degree, temperature: 50 ° C., and spray pressure: 2 kg / cm ² , judgment was made based on the contour shape of the inside of the etching hole, the speed, and the state of pit generation. .

In the judgment, the outline shape in the hole was ○ for a smooth one, a little jagged deformation was recognized, but it was acceptable for use as a shadow mask, and a jagged deformation was recognized for a shadow mask. Those that could hinder use were marked as x. Regarding the state of pit generation, ○ indicates that no occurrence was observed, も の indicates that some occurrence was recognized but did not interfere with use as a shadow mask, △ indicates occurrence of pits, which may hinder use as a shadow mask Those were marked as x. Regarding the etching rate, the one that is not inferior to the etching rate in the normal shadow mask manufacturing process is evaluated as ○, the one that is slightly inferior to the normal etching speed but has no problem in manufacturing is Δ, and the etching speed is slow and may interfere with the manufacturing process. Those were marked as x. The results are shown in Table 2.

[0024]

[Table 2]

From now on, if B is contained by 0.0005% or more, or if B is essential, B, Ca, Mg
Is contained in a total amount of 0.0005% or more, the shape of the inner surface of the etching hole is improved. However, if the content exceeds 0.004%, a problem occurs in the etching rate or the pit. FIG. 1 is the etching hole of FIG. 2 times the etching hole 300 times, 100
Observed with a 0 × electron microscope. The inner shape of the etching hole shown in FIG. 1 that satisfies the present invention has a smooth circular shape, and is found to be improved as compared with FIG.

[0026]

According to the present invention, a material having a lower thermal expansion can be obtained than a conventional Fe-Ni-based invar alloy, and the cost and cost can be reduced.
As for the etching property, a material that satisfies the required cost and performance of the shadow mask can be obtained, so that it can be put to practical use and the image quality of the CRT can be improved.

[Brief description of the drawings]

FIG. 1 is an electron micrograph showing an example of the effect of the present invention.

FIG. 2 is an electron micrograph showing a comparative example.

FIG. 3 is a diagram showing an example of the effect of the present invention.

Claims (5)

[Claims] (1) In terms of weight%, Co: more than 2.5% and 7% or less, (Ni + Co): 35.5-38%, Mn: 0.1
%, B: 0.0005 to 0.004%, the balance being substantially Fe, Fe-Ni-Co-based alloy excellent in etching properties and low thermal expansion properties. 2. Co% by weight, more than 2.5% and 7% or less, (Ni + Co): 35.5-38%, Mn: 0.1
%, B is essential and one of Ca and Mg
0.000 for the total amount (B + Ca + Mg) of the species or two species
An Fe-Ni-Co-based alloy excellent in etching properties and low thermal expansion characteristics, characterized in that it contains 5 to 0.004% and the balance substantially consists of Fe. 3. The Fe—Ni—Co alloy according to claim 1 or 2, wherein S is suppressed to 0.002% or less. 4. The Fe—Ni—Co-based alloy according to claim 1, wherein C is suppressed to less than 0.005%. 5. The F according to claim 1, wherein
A shadow mask excellent in smoothness of an inner shape of an etching hole, which is made of an e-Ni-Co alloy.