JPH09157800A - Shadow mask material having excellent press formability and production of shadow mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shadow mask material having excellent press formability and a process for producing a shadow mask by the material. SOLUTION: This shadow mask material having the excellent press formability contains, by weight%, 31 to 39% Ni and 0.0005 to 0.0040% B and the balance Fe and inevitable impurities and is regulated to <=0.050% Mn and <=0.0030% N as impurities. Such material is subjected to formation of electron beam pass holes by etching, annealing at <=950 deg.C and press forming at 80 to 150 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a method for manufacturing a shadow mask made of an Fe--Ni alloy used in a color cathode ray tube and a material for manufacturing a shadow mask, and more particularly to a press mask having improved press formability. Is.

[0002]

2. Description of the Related Art In recent years, Fe-36% Ni alloy has been used as a material capable of coping with the problem of color shift due to thermal expansion in response to the demand for high-quality imaging of color CRTs such as color televisions. This material has a higher yield strength and a lower Young's modulus than the conventionally used aluminum-killed iron material (hereinafter referred to as AK material), so the amount of springback when press-molding into a mask shape is large and it is faithful to the mold. There is a problem that it is difficult to form the shape (the press formability is poor). Therefore, this press forming is performed at a heating temperature of about 200 ° C. after softening and annealing the material after the etching and perforation. However, in this warm press forming, a great deal of attention must be paid to temperature control, and in particular, as the press temperature is raised, stricter acceleration is required. That is, as the temperature rises, a difference in thermal expansion occurs between the press molds, and the quality of the molded product is likely to be seriously affected. On the other hand, regarding the improvement method from the material side,
Known examples are known.

That is, in Japanese Patent Laid-Open No. 6-93385, by controlling the amount of impurities and reducing the amount of precipitates composed of nitrides and carbides, Japanese Laid-Open Patent Publication No. 6-264140.
JP-A No. 2003-242242 discloses that press formability is improved by improving the (111) crystal plane aggregation of the material after annealing. Further, JP-A-7-166278 discloses that alloying elements such as Cr, Mn, Ti, Mo and V are added to improve formability. On the other hand, Mn
As a publicly known example of restricting 0.05% or less,
JP-A-1-124940, JP-A-7-3401,
There is JP-A-7-207415.

[0004]

The above-mentioned known materials include Mn in an amount of 0.2 to 0.3%. In softening annealing performed before press forming into a mask shape, N is usually N.
_{In the} atmosphere of ₂ gases or Brown gas, the dew point is processed at a high condition such as 5 ° C. or more due to the demand from the subsequent blackening process, but according to the experiment of the present inventor, the material surface is oxidized during the annealing. When the Mn content is high, Mn is preferentially oxidized to form an oxide at the grain boundary, which hinders the growth of crystal grains in the surface layer of the material and does not provide sufficiently satisfactory formability. I understand.

Further, according to the experiments conducted by the present inventor, in the case of annealing before press forming, if the N content is not sufficiently reduced, the crystal grain growth inside the material is insufficient and the good formability is obtained. I found that I could not get. Further, the above-mentioned known examples and are to reduce the amount of Mn in order to improve the etching property and to reduce the thermal expansion, respectively, and the relationship between the Mn amount or N amount and the press formability will be specifically described. Has not been done. The present invention, by appropriately controlling the components, manufacturability, without directly deteriorating hot workability, a shadow mask material excellent in press formability, particularly at a press forming temperature of about 80 to 170 ° C. An object of the present invention is to provide a shadow mask material that can be lowered in temperature and a shadow mask manufacturing method using the same.

[0006]

Means for Solving the Problems As a result of various experiments conducted by the present inventor to improve the formability (decrease in springback amount) in press forming into a mask shape, the surface layer portion during annealing before press forming And promoting the growth of crystal grains inside, and for this purpose, it is effective to suppress the formation of non-metallic inclusions. Specifically, (i) Mn content is 0.050%.
To reduce Mn-based inclusions by controlling the following:
(ii) The reduction of nitride-based inclusions is more effective than the reduction of carbide-based, oxide-based, and sulfide-based inclusions, mainly for promoting internal grain growth. It has been found that it is effective to set the content to not more than%, desirably (iii) O content to 0.0050% or less, and the Al / O ratio to 2.5 or less.

[0007] Further, the present inventor, by satisfying the above two points (i) and (ii) or (i) to (iii) three points of component requirements at the same time, synergistically acts on both the surface layer and the inside. It has been found that sufficient grain growth can be obtained synergistically, resulting in better press formability. However, when the Mn content is 0.050% or less, it is related to the S content, but the hot workability is apt to deteriorate, and in order to improve this, it is effective to add B in an amount of 0.0005% or more and 0.0040% or less. Etc. The present inventor has also found that Be, Ti, Z as impurities.
It has been found that r is particularly detrimental to the press formability when the annealing temperature before press forming is low, or when the cooling after the annealing is slow cooling.

The ratio σ / E between the 0.2% proof stress σ and the Young's modulus E is proportional to the springback amount, which is convenient for quantifying the press formability. The material of the present application has a small value of 7.4 × 10 −4 or less even at a low temperature of 150 ° C., and is excellent in press formability. Further, as described above, the material in which the reduction of Mn and the reduction of N are performed in parallel has a protective gas atmosphere in the annealing before press molding due to the removal of the crystal grain growth inhibiting factor as described above. It is possible to set the dew point to a high temperature of 5 ° C or higher, and there is little need to raise the annealing temperature above 950 ° C.
It was found that the temperature can be lowered to 0 ° C, preferably about 100 to 150 ° C.

That is, the first aspect of the present invention is, by weight,
Ni 31-39% and B 0.0005-0.0040%, balance Fe
And unavoidable impurities, and Mn 0.0
It is a shadow mask material having excellent press formability, which is characterized by being regulated to 50% or less and N 0.0030% or less. In the first invention, the impurities Be, Ti, and Zr are 0.01% or less singly or in combination, O is 0.0050% or less, and A
Ratio of 1 and O Al / O is set to 2.5 or less, and C
One or two or more of r, V, Mo, W in total is 0.
It is preferable that the content of each of them be 5 to 2.5% by weight.
A second invention of the present application is the method for manufacturing a shadow mask according to the first invention (any one of claims 1 to 5).
Using the above shadow mask material, punching of electron beam passage holes by etching, annealing in a gas atmosphere with a dew point of 5 ° C or more and below 950 ° C, and press forming into a shadow mask shape at 80 to 170 ° C, respectively. And a shadow mask manufacturing method.

Next, the action of each element in the first invention and the reason for limiting the numerical values will be described. Ni is a basic component of the present alloy and reduces the coefficient of thermal expansion within the range of 31 to 39%. Outside this range, the Invar effect becomes small, so the coefficient of thermal expansion becomes large, and color misregistration easily occurs and the performance as a shadow mask deteriorates. Therefore, the content of Ni is set to 31 to 39%. From the viewpoint of lowering the 0.2% proof stress and improving the Young's modulus, it is preferably 33 to less than 36%, and more preferably 33 to 35%. B is an element that suppresses the segregation of S to the grain boundaries and prevents the deterioration of hot workability, and is particularly effective when low Mn is used as in the present invention. Addition amount
This effect is obtained at 0.0005% or more, but if it exceeds 0.0040%, the formation of an oxide film is hindered during the blackening treatment in the shadow mask manufacturing process, so B is added at 0.0005 to 0.0040%. Moreover, since B also has the effect of positively promoting grain growth when added in an amount of 0.0010% or more, it is preferably 0.0010 to 0.0030.
It is in the range of%.

Mn is an element that is easily oxidized. Mainly in the surface layer portion, annealing before pressing diffuses to the surface through defects such as crystal grain boundaries and is preferentially oxidized to form an oxide. Inhibits grain growth. When the Mn content is 0.050% or less, this effect is reduced and crystal grain growth in the surface layer is likely to occur. On the other hand, it has been found that Mn mainly produces Mn-based inclusions inside and inhibits the growth of crystal grains.

That is, by suppressing the amount of Mn to 0.05% or less, the amount of Mn-based inclusions (including MnS, Mn-SO, Mn-Si-SO, etc.) precipitated in the matrix is reduced. In addition to the above, it was also found that the effect of incidentally affecting the precipitation amount of AlN and simultaneously reducing the effect of promoting AlN generation can be obtained. Therefore, Mn
By reducing the amount, precipitation of these Mn-based inclusions and AlN, which hinder grain growth during annealing before pressing, is suppressed, so that crystal grain growth easily progresses and becomes coarse. It has the effect of lowering and improves press formability. If the Mn content exceeds 0.05%, the above effect is not observed, and it is necessary to suppress it to 0.05% or less. M
The effect of n-type inclusions on the precipitation of AlN is Mn.
Since the interface between the system inclusions and AlN is aligned with the crystal plane, M
When n-type inclusions are present, the amount of AlN is much lower than the amount of AlN that precipitates in austenite due to equilibrium theory. It is considered that a large amount was deposited.

N reacts with Al, which is an impurity in the alloy, to form minute inclusions of 1 μm or less, which are more internal to the material than carbide-based, oxide-based, and sulfide-based inclusions. Strongly suppresses the crystal grain growth of. In order to reduce this effect and obtain good press formability, the N content needs to be 0.0030% or less, preferably 0.0020% or less or even 0.0010% or less. Although O is less harmful than nitride-based inclusions, it forms oxide-based inclusions with Mn, Al, Si, etc., and these inclusions inhibit the growth of crystal grains.
It is desirable that the O content be as low as possible. For this reason,
In the present invention, O is set to 0.0050% or less (desirably 0.0030% or less).

As described above, Al easily forms AlN and tends to hinder crystal grain growth. Therefore, it is important to reduce the amount of AlN that hinders grain growth during mask annealing as much as possible.
It is effective to combine with O as ₂ O ₃ . Therefore, by limiting Al / O to 2.5 or less as the amount of Al, most of Al can be in the form of Al ₂ O ₃ and the precipitation of AlN can be prevented.

In the first material invention of the present invention, the Mn content is restricted to 0.050% or less as described above, and
Even if B is added in an amount of 0.0005 to 0.0040%, if the S content is high, the hot workability is greatly reduced. Since S deteriorates the hot workability of the material as described above, the content should be reduced as much as possible, but excessive reduction leads to an increase in cost, so Mn is usually added to compensate. But,
In the present invention, Mn is 0.050% or less, which is lower than usual, so this compensation effect is supplemented by the addition of B. But,
The compensating effect of B is insufficient, and in order to reduce the adverse effects at the time of the blackening treatment due to the addition of a large amount of B,
The S content decreases as much as possible. It is preferably 0.0015% or less, and more preferably 0.0010% or less.

The three elements Be, Ti and Zr are Fe-Ni.
When contained in the alloy, the mask annealing is at low temperature 700-800 ℃
In the case of being treated with, or when the cooling rate after press pre-annealing is low, during cooling, a compound with Ni is formed to form a precipitation strengthening phenomenon even if the content thereof is a trace amount, and 0.2%
It was found that the yield strength was increased and the press formability was hindered. By setting the total amount of the three elements Be, Ti, and Zr to 0.01% or less, the above-mentioned problems can be solved.

The effect of adding Cr, V, Mo, and W is to increase the Young's modulus to reduce springback during press forming and improve press formability. This effect is strongest in Cr, and in order to obtain this effect, one or more of these elements are added in a total amount of 0.
It is necessary to add 5% or more, but if it exceeds 2.5%, the coefficient of thermal expansion becomes large, causing a color shift, so the appropriate range is 0.5 to 2.5%. It is preferably 0.8 to 2.5%, particularly preferably 1.5 to 2.5% of Cr. This Cr
The most desirable composition example when Ni, etc. is contained is Ni 33% to 36
%, Cr 1.5 to 2.5%, balance Fe.
The desirable composition combination as the first invention of the present application described above is Ni 33 to 35%, B 0.0005 to 0.0025%, and N 0.0030%.
Hereafter, O 0.0030% or less, S 0.0015% or less, and the balance Fe and other impurities.

The ratio σ / E between the 0.2% proof stress σ and the Young's modulus E is proportional to the springback, and it is desirable that this value is 7.4 × 10 −4 or less for ordinary televisions. Since the material of the first invention of the present application has a low Mn content and a low N content, the factor inhibiting grain growth is removed.
Not only for pre-press annealing at high temperature of about ℃ or higher, but also for low temperature of about 700-800 ℃,
The value of σ / E at ℃ can satisfy the range of 7.4 × 10 -4 or less. In particular, by adding appropriate amounts of Cr, V, Mo, and W, it is possible to make this value at 150 ° C. 7.0 × 10 −4 or less, or 6.0 × 10 −4 or less. It can have moldability.

Next, a method of manufacturing the shadow mask according to the second invention of the present application will be described. Generally, the higher the annealing temperature before press forming, the more the crystal grain growth is promoted and the press formability is improved. In the material of the first invention, since the crystal grain growth inhibiting factor is removed as described above, the crystal grain growth is sufficient even when the annealing atmosphere has a high gas dew point of 5 ° C., 10 ° C. or even 15 ° C. Moreover, it is not necessary to set the annealing temperature to a temperature higher than 950 ° C. Therefore, if the processing temperature is lowered to 700 to 800 ° C., it is possible to receive benefits such as reduction of processing time and reduction of energy cost.
Further, the material of the present invention can be annealed at 950 ° C. or lower or 700 to 800 ° C., and then low springback molded at a low temperature of 80 to 170 ° C. By lowering the press molding temperature, the need for strict control of molding temperature is reduced, and the uneven thermal expansion in the press die and the difference in thermal expansion between a pair of press dies are reduced. It is possible to perform press molding with a mold, and thus to press into a shape faithful to the shape of the mold.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Various elements were added to a Fe-36% Ni alloy and melted in a vacuum induction melting furnace to prepare an ingot having the components shown in Table 1. This ingot was subjected to hot forging and hot rolling to obtain a plate material having a thickness of 4 mm, and then cold rolling and annealing were repeated to obtain a thin plate having a thickness of 0.22 mm. This thin plate was annealed before press at 750 ° C for 20 minutes, N ₂
A heat treatment was performed in a gas (dew point + 10 ° C) to obtain a press-moldability evaluation (springback) test piece. The press formability test method uses a test piece with a width of 10 mm and a length of 50 mm at 150 ° C.
As shown in FIG. 1, one end was fixed in the constant temperature bath of No. 2 and the return angle θ (spring back amount) was evaluated after bending the swing-off part by 60 ° as shown in the figure.

There is a strong correlation between the degree of press formability in the case of actually press forming into the shape of the shadow mask and the return angle value in the above test. The degree of press formability this time is satisfactory if the return angle value is less than 6.0 °.
Less than 1 was judged to be good in moldability. Table 1 also shows the results and the presence or absence of cracking during hot forging.

[0022]

[Table 1]

Further, Table 1 shows typical materials of 150
The measurement results of the ratio of 0.2% proof stress σ at ℃ and Young's modulus E at the same temperature are shown. In Table 1, no. 1 to 6 are Mn amount,
No. 7 to 12 are N amounts, and No. 13 to 19 are alloy element amounts such as Cr, and No. No. 30 is the result of investigating the effect of adding no B. From this, it can be seen that when the Mn content is 0.050% or less and the N content is 0.0030% or less, the return angle value is less than 6.0 °, and good press formability can be obtained (however, No. 31 to 33 will be described later). Also, at this time, it is found that σ / E is 7.4 × 10 minus 4 or less.

Regarding the alloying elements, it is understood that the effect of adding Cr is the greatest, and that the effect of adding Cr 0.5% appears, and the formability is improved. Sample N
o. 6 and no. From the comparison with 30, it can be seen that the hot workability is improved by adding 0.0005% or more of B. In addition, No. 21 and 22 have an Al content of 0.003 to 0.005%
Was almost N except that Al / O was 1.3 to 2.1.
o. 34 and 35, but No. It shows that the return angle is much smaller and the springback is smaller than those of Nos. 21 and 22. No. 34, 35 and No. 31-
33 shows the effects of Be, Ti, and Zr. The former is similar to the latter except that the elements other than these elements are almost the same, but Be + Ti + Zr contains 0.01% or more, and the return angle, In other words, the springback is large.

[0025]

The shadow mask material of the present invention has a Mn content of 0.
050% or less, N 0.0030% or less, and B 0.000
By adding 5 to 0.0040%, the growth of crystal grains in the annealing before pressing can be sufficiently performed without lowering the hot workability,
This is a significant improvement in press formability of Invar alloy, which was previously insufficient, and enables press formability at around 100 to 150 ° C, and has the advantage that the temperature of pre-press annealing can be lowered. Therefore, the production cost can be reduced. Further, the method for manufacturing a shadow mask of the present invention has the advantages of the above-mentioned low temperature annealing, and in particular, enables to reduce the strictness of temperature control by low temperature press molding and enable precision molding by an accurate press die.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method of measuring a springback amount (θ) used in an experiment, where ˜ represents a chronological order, and P represents a load.

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Claims (6)

[Claims] 1. By weight percent, Ni 31-39% and B 0.0005-
A shadow mask material excellent in press formability, which contains 0.0040%, the balance Fe and unavoidable impurities, and regulates Mn as 0.050% or less and N as 0.0030% or less as impurities. 2. The shadow mask material excellent in press formability according to claim 1, wherein the content of one or more of Be, Ti and Zr as impurities is 0.01% or less. 3. A shadow mask material excellent in press formability according to claim 1, wherein the contained O is 0.0050% or less, and the Al / O ratio Al / O is 2.5 or less. 4. The press formability according to claim 1, wherein a part of Fe is replaced with an equivalent amount of 0.5 to 2.5% by weight in total of one or more of Cr, V, Mo and W. Excellent shadow mask material. 5. A shadow mask material excellent in press formability according to claim 1, wherein a ratio σ / E of 0.2% proof stress σ and Young's modulus E at 150 ° C. is 7.4 × 10 −4 or less. . 6. A shadow mask manufacturing method, wherein the shadow mask material according to claim 1 is used,
Drilling of electron beam passage hole by etching, dew point 5
A method for producing a shadow mask, which comprises performing an annealing treatment at 950 ° C. or lower in a gas atmosphere at a temperature of ℃ or higher and a press molding process to a shadow mask shape at 80 to 170 ° C., respectively.