JPH0987741A - Production of iron-nickel base invar alloy thin sheet for shadow mask excellent in sheet shape and heat shrinkage resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an alloy thin sheet excellent in the sheet shape and anti-heat-shrinkability and suitable for a high precision shadow mask, at the tie of subjecting an Fe-Ni base invar alloy thin sheet for a shadow mask to stress relieving annealing, by applying specified tension to the alloy thin sheet. SOLUTION: The Fe-Ni base invar alloy thin sheet is subjected to stress relieving annealing in such a manner that tension of 5 to 45% of 0.2% proof stress thereof in the stress relieving annealing temp. is applied thereto. Since the steeping degree (%) of the parameter expressing the flattening degree of the thin sheet needed as the stock for a shadow mask = height (mm)/pitch (mm) × 100 is regulated to <=0.5%, the ratio of the tension/proof need to be regulated to >=0.05. Namely, there occurs the need that the annealing is executed in such a manner that tension of 5 to 45% of 0.2% proof stress of the above alloy thin sheet in the annealing temp. is applied thereto. Moreover, if the ratio of the tension/proof stress increases, its heat shrinkability increases. Since heat shrinkability needed as that of the stock for a shadow mask is <=0.08%, the ratio of the tension/proof stress need to be regulated to <=0.45. Namely, it is necessary that the annealing is executed in such a manner that tension of <=45% of 0.2% proof stress of the above alloy thin sheet in the annealing temp. is applied thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an Fe-Ni based amber alloy thin plate used for a shadow mask used in a television or a computer display.

[0002]

2. Description of the Related Art A shadow mask is arranged in a cathode ray tube of a television and a computer display and accurately irradiates an electron beam emitted from an electron gun to a predetermined point on a fluorescent surface supported by a glass body. Has pores for. At this time, about 20% of the emitted beam is applied to the phosphor, and about 80% of the remaining beam collides with the shadow mask. Therefore, the shadow mask is compared to the glass body that supports the phosphor screen. It gets hot.

When the shadow mask body is heated to a high temperature, in the case of a mild steel plate such as low carbon rimmed steel or low carbon aluminum killed steel which has been conventionally used as a material for a shadow mask,
Since the coefficient of thermal expansion is much larger than that of the glass body that supports the phosphor screen, it becomes impossible to precisely irradiate the electron beam to a predetermined point on the phosphor screen by causing a positional deviation between each other.
Images were often blurred.

In order to prevent the image from becoming unclear, attempts have been made to compensate for the mutual positional deviation by devising the structure of the support body that serves as a suspension system for the shadow mask, but this is not always sufficient. It was

Against this background, Fe-Ni containing about 36 wt% Ni as a shadow mask material is used.
System alloys, so-called amber alloys, have been studied and their use is currently expanding. Since this alloy has a small thermal expansion coefficient of about 1/10 as compared with the conventional low carbon steel, color shift due to thermal expansion hardly occurs even when heated by an electron beam, and it is suitable for a high brightness type screen.

The Fe-Ni type amber alloy thin plate for shadow mask is usually melted by a continuous casting method or an ingot making method, and then, in the case of the ingot making method, slabbing rolling, hot rolling, cold rolling and annealing. Is manufactured. Then, this alloy thin plate is subjected to photoetching processing to form electron beam passage holes, and then subjected to annealing, molding processing, blackening processing, etc. to form a shadow mask.

On the other hand, as television screens have become larger and their application to computer displays has expanded, demands for finer image quality and higher brightness for CRTs have further increased, and the problems of positional deviation and color misregistration have become apparent. For this reason, it has become necessary to carry out an etching process for making a hole for passing an electron beam finer and with higher precision. A material is used, and holes having a diameter of 120 μm are formed at a fine pitch of 270 μm pitch.

As described above, since the etching hole of the shadow mask requires high precision, the original plate before etching is required to have a good plate shape, that is, flat. In addition, since post-etching heat treatment and press molding are repeatedly performed, it is also necessary that the dimensional change (heat shrinkage) is small. If the heat shrinkage is large, the vertical to horizontal ratio of the etching hole diameter after press molding deviates from the vertical to horizontal ratio immediately after etching, which is one cause of poor resolution.

FIG. 3 schematically shows a method of installing the shadow mask material in the press die. The left view of the figure shows a shadow mask material with positioning holes. The right side of the figure is a view showing a position where the shadow mask material is set in the press die by aligning the positioning hole of the shadow mask material with the positioning guide provided in the press die.

When the heat shrinkage of the shadow mask material is large,
The position of the positioning hole of the material is displaced from the positioning guide of the press die, causing rattling, which causes a problem of impairing productivity.

Up to now, the shape correction for improving the flatness of the shadow mask original plate is intended for aluminum killed steel, but it is disclosed in Japanese Patent Laid-Open No. 175820/1990. According to this, the rolling reduction during cold rolling was 70 to 85%, and the annealing temperature for strain relief annealing was 45.
By defining 0 to 500 ° C, the plate shape after cold rolling is improved.

Regarding reduction of heat shrinkage and improvement of plate shape,
Although it is intended for a lead frame material, it is disclosed in JP-A-6-271936. According to it, carbon, nitrogen, chromium, boron, etc. are added in trace amounts,
Further, niobium, zirconium, copper, titanium and the like are added individually or in combination to increase the hardness, and the hardness is increased to 720 to 950.
Recrystallization annealing at ℃, cold rolling at a reduction rate of 20% or more,
650 to 80 under tension of 0.3 to 8.0 kgf / mm ^2.
By performing the tension annealing for 10 seconds or more at the annealing temperature of 0 ° C., the plate shape and the heat shrinkage resistance are improved.

Similarly, although it is intended for a lead frame material, in JP-A-6-216304, the final annealing is performed at a temperature of 530 to 700 ° C., preferably 6
By performing tension annealing under the conditions of 30 to 670 ° C. and a tension of 3 kgf / mm ² or less, preferably 1 kgf / mm ² or less, the strain and the spring limit value are improved, and the heat shrinkage during annealing performed in the middle of the two-stage press is performed. Techniques for suppressing are disclosed.

[0014]

However, even if the technique described in the above-mentioned patent application is applied to a Fe—Ni-based amber alloy thin plate for a shadow mask in which highly precise fine etching holes are formed, the plate shape and heat Improving contractility is
It was insufficient for the following reasons.

In the method described in Japanese Patent Application Laid-Open No. 2-175820, the plate shape is improved by defining the strain relief annealing conditions, but the heat shrinkability is not improved.

Japanese Unexamined Patent Publication No. Hei 6-271936 and Japanese Unexamined Patent Publication No.
The techniques described in Japanese Patent Laid-Open No. 216304 all attempt to improve the heat shrinkage of the lead frame after the heat treatment for non-recrystallization. That is, residual strain generated during cold rolling is removed by applying tension, and at the same time, thermal shrinkage is suppressed by reducing residual compressive stress in the rolling direction. This means that the thermal shrinkage can be suppressed as the tension of tension annealing is increased, considering that the thermal shrinkage cannot be prevented because the residual compressive stress cannot be relaxed if the tension is less than a certain limit. .

However, in applications such as shadow masks where recrystallization annealing is performed to soften the material so that it can be easily pressed, heat shrinkage after recrystallization annealing increases as the tension in tension annealing increases. This is because recrystallization releases microscopic residual stress caused by dislocations introduced into crystal grains and their grain boundaries during tension annealing. The heat shrinkage due to such micro residual stress increases as the tension increases. Therefore, the heat treatment at the unrecrystallized temperature or lower in the lead frame cannot be directly applied to the shadow mask.

Further, these techniques have a product size of 100.
Since it is applied to a lead frame material having a length of about mm, it is not necessary to consider the plate shape as long as tension annealing can be performed at a certain tension or less to prevent thermal contraction at a non-recrystallization temperature. However, since the shadow mask material is used for a large CRT, it is necessary to strictly control the plate shape with a dimension of 600 to 800 mm or more. If these techniques are diverted and the tension is reduced to suppress heat shrinkage, the plate can be reduced. There was also a problem that the shape deteriorates.

Further, the method described in Japanese Patent Laid-Open No. 6-271936 has the following problems. That is, trace elements such as niobium and zirconium are added alone or in combination, but these elements impair the blackening processability of the shadow mask. If these elements are not added, Hv17
It has a low hardness of 0 or less and is not suitable for a shadow mask.

The present invention has been made to solve such problems, and provides a method for producing a Fe-Ni-based amber alloy thin plate which is suitable for a high-definition shadow mask and has excellent heat shrinkage resistance. The purpose is to

[0021]

Means for Solving the Problems The above-mentioned problems are solved in the above-mentioned Fe-Ni at the strain-relief annealing temperature in the strain-relief annealing of Fe-Ni-based amber alloy thin plates for shadow masks.
Of Fe-Ni type amber alloy thin plate for shadow mask excellent in plate shape and heat shrinkage characterized by applying strain of 5 to 45% of 0.2% proof stress of amber type amber alloy thin plate and annealing Be solved by the method.

FIG. 1 shows the steepness of a Fe—Ni-based amber alloy sheet after strain relief annealing, and 0.2% of the Fe—Ni-based amber alloy sheet at the tension and annealing temperature applied during annealing.
The relationship with the yield strength ratio (hereinafter referred to as the tension / bearing strength ratio) is shown.

Here, the steepness is defined by the following equation, which is obtained by measuring the height and pitch of the ear wave or medium elongation of the thin plate after the strain relief annealing.

Steepness (%) = Height (mm) / Pitch (mm) × 100 A parameter that represents the flatness of a thin plate. The lower the steepness, the better the flatness.

Annealing temperatures are 570 ° C., 610 ° C. and 650 ° C.
In either case, the steepness decreases as the tension / proof strength ratio increases.

The steepness required as a material for the shadow mask was 0.5% or less when examined separately.
The tension / proof stress ratio must be 0.05 or more. That is, it is necessary to give a tension of 5% or more of the 0.2% proof stress of the Fe—Ni-based amber alloy thin plate at the annealing temperature to perform strain relief annealing.

The reason why the steepness decreases with an increase in the tension / proof stress ratio is that strain such as medium elongation existing in the sheet width direction after cold rolling causes local yield elongation by applying tension during annealing. It is thought that this is because it is stretched uniformly.
It is understood that the relationship between the steepness and the tension / proof strength ratio is not affected by the annealing temperature.

FIG. 2 shows the relationship between the heat shrinkage ratio and the tension / proof stress ratio of the Fe-Ni amber alloy sheet after strain relief annealing.

Here, the heat shrinkage is 300 mm (l) × 100 mm (w) × thickness (t) in the longitudinal direction of the thin plate from the portion 100 mm from the center and the end of the sheet width after the strain relief annealing. ), The heat treatment at 850 to 900 ° C. for 30 minutes simulating the annealing step before shadow mask formation is performed, and the difference in the length of the test piece before and after the heat treatment and the length of the test piece before the heat treatment are performed. Is a value obtained by averaging the two values obtained for the central portion and the end portion of the plate width.

Annealing temperatures are 570 ° C., 610 ° C. and 650 ° C.
In either case, the thermal contraction rate increases as the tension / proof stress ratio increases. Further, as in the case of steepness, the thermal shrinkage is not affected by the annealing temperature.

The heat shrinkage ratio required as the material for the shadow mask was 0.08% or less when examined separately, so that the tension / proof stress ratio needs to be 0.45 or less. That is, it is necessary to give a tension of 45% or less of the 0.2% proof stress of the Fe-Ni-based amber alloy thin plate at the annealing temperature to perform strain relief annealing.

Although the detailed mechanism of the occurrence of heat shrinkage is unknown, a minute strain such as dislocation is accumulated in the crystal grain boundaries and crystal grains by applying tension, and recrystallization annealing in the shadow mask manufacturing process is performed. At, it is considered that this micro residual stress is released and causes thermal contraction. In addition,
Sources of micro residual stress are as follows: 1) due to anisotropy of crystal grains, (coefficient of thermal expansion of crystal,
Anisotropy such as elastic constant and misorientation between crystal grains), 2) plastic deformation inside and outside the crystal grains, 3) appearance of impurities, precipitates, or different phases due to transformation,
(Quotation: Shigeru Yoneya: Occurrence and Countermeasures for Residual Stress, P13 [Yokendo]).

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION As the Fe-Ni-based amber alloy in the present invention, any component-based alloy can be applied as long as it is an Fe-Ni-based alloy exhibiting an amber characteristic.

Usually, Fe containing 32 to 38 wt% of Ni
-Ni alloys and Fe-Ni alloys with Co added thereto are often used. When Co is added, the amount of (Ni + Co) is 30 to 3 in order to secure the amber characteristic.
It is desirable that the amount of Co be 7 wt% or less so that the amount of Co is 8 wt% and the etching property is not impaired.

Si is necessary as a deoxidizing agent, but since the oxide of Si formed on the surface during annealing may cause galling during pressing, it is preferably 0.07 wt% or less.

Mn should be contained in an amount of 0.1 wt% or more in order to prevent deterioration of hot workability due to the impurity element S, and 0.5 wt% in order not to reduce the blackness of the blackened film of the shadow mask. The following is desirable.

In the melting of such an Fe-Ni alloy, it is desirable to perform a treatment such as electromagnetic stirring in order to prevent the occurrence of component segregation and abnormal structure.

The slab may be manufactured by slab-rolling an ingot or directly by continuous casting. Further, even a thin slab has no problem for the present invention. In the case of slab rolling, the ingot is heated at 1150 to 1250 ° C. for 20 hours or more to reduce component segregation,
It is desirable to have a slab thickness of 0 to 250 mm.

Such a slab has a temperature of 1050-1250 ° C.
It is preferable to heat for 30 minutes or more and hot-roll to a plate thickness of 2 to 3 mm.

Then, cold rolling, recrystallization annealing, and strain relief annealing are repeated at least once to obtain a sheet thickness of 0.1.
Use a 0.3 mm shadow mask master plate.

When starting from an ingot, it is desirable that the cumulative rolling rate from the ingot to the final original plate be 99.9% or more.

[0042]

EXAMPLES Three kinds of Fe having major components shown in Table 1
-Ni-based amber alloy No. A to C were melted, the ingot was heated at 1150 to 1250 ° C. for 20 to 50 hours, and slab-rolled to manufacture a slab. This slab is 11
After heating at 00 ° C for 1 to 5 hours, hot rolling was performed to a plate thickness of 2.0 mm. Then, cold rolling, recrystallization annealing at 750 ° C. or higher, and strain relief annealing under the conditions shown in Table 2 were performed to obtain a sheet thickness of 0.10.
32 kinds of samples having a size of 0.22 mm were prepared. In Table 2, N
o. Nos. 1 to 22 are examples of the present invention, and No. 23 to 32 are comparative examples.

The plate shape and the heat shrinkage ratio after the strain relief annealing were measured by the above-mentioned methods. Table 2 shows the results. Sample No. 1 which was given a tension within the range of the present invention at the time of strain relief annealing. 1
In the range of up to 22, a steepness of 0.5% or less and a good plate shape and 0.08% or less of low heat shrinkage are exhibited.

If the tension is less than 5% of the 0.2% proof stress of the sample at the plate temperature shown in Table 2, the plate shape becomes defective and 45
When it exceeds%, the heat shrinkage rate becomes high and exceeds 0.08%.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, it is possible to provide a method for producing a Fe—Ni-based amber alloy thin plate which is suitable for a high-definition shadow mask and has excellent heat shrinkage resistance.

[Brief description of drawings]

FIG. 1 shows the relationship between the steepness of a Fe—Ni based amber alloy sheet after strain relief annealing and the ratio of the tension applied during annealing to the 0.2% proof stress of the Fe—Ni based amber alloy sheet at the annealing temperature. It is a figure.

FIG. 2 shows the relationship between the heat shrinkage ratio of the Fe—Ni-based amber alloy sheet after strain relief annealing and the ratio of the tension applied during the annealing and the 0.2% proof stress of the Fe—Ni-based amber alloy sheet at the annealing temperature. FIG.

FIG. 3 is a diagram schematically showing a method of installing a shadow mask material in a press die.

Claims (1)

[Claims] 1. In the strain relief annealing of a Fe—Ni based amber alloy sheet for a shadow mask, 0.2 of the Fe—Ni based amber alloy sheet at the strain relief annealing temperature.
A method for producing a Fe—Ni-based amber alloy thin plate for a shadow mask, which is excellent in plate shape and heat shrinkage, characterized by applying a strain of 5 to 45% of% proof stress and annealing for strain relief.