JPH02305941A - Blank for low thermal expansion shadow mask and production thereof - Google Patents

Abstract

PURPOSE:To produce a blank for a low thermal expansion shadow mask having superior press formability by successively subjecting an Fe-Ni alloy strip contg. specified percentages of Ni and Cr to cold rolling, continuous annealing and mask annealing under specified conditions. CONSTITUTION:An Fe-Ni alloy strip consisting of 30-45wt.% Ni, 0-1-2-5wt.% Cr and the balance Fe with inevitable impurities is cold rolled at a cold rolling rate (R%) satisfying an inequality 12Cr<2>55Cr+71<=R<=96. The cold rolled strip is continuously annealed by soaking at 650-900 deg.C for 10-120sec, holes are pierced by etching and mask annealing is carried out by soaking at 650-1, 250 deg.C for 30-100min. A blank for a low thermal expansion shadow mask having superior press formability and 18-22kgf/mm<2> yield strength sigma0.2 is obtd. when the average grain size of the blank is expressed by (d), d<-1/2> is 0.5-2.5mm<-1/2>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a material for a shadow mask, and more particularly to a method for producing a material for a shadow mask with good press formability using a low coefficient of thermal expansion alloy.

[Prior art and problems] Conventionally, low carbon steel sheets have been generally used for the shadow masks of cathode ray tubes for color televisions, but color CR sheets used for various computers, word processors, and instruments
As high-quality images have become required, especially in televisions, and also in home color television receivers,
Invar has begun to be used in shadow masks as a measure to prevent color shift caused by thermal expansion caused by electron bombardment of shadow masks.

However, amber has poor press formability compared to low carbon steel, and has the disadvantage that processing does not go well in the mask doming process after etching and perforation.

Therefore, the present inventors conducted extensive experiments and studies to improve press formability by combining various cold rolling rates and heat treatment conditions for amber-based materials, and as a result, they completed the present invention.

[Object of the Invention] An object of the present invention is to provide a low thermal expansion shadow mask material with good press moldability and a method for producing the same.

Another object of the invention is σ. An object of the present invention is to provide an amber-based low thermal expansion type shadow mask material having a low Eio (proof stress when 2% is applied) and a method for manufacturing the same.

[Structure and operation of the invention] According to the present invention, an Fe-Ni alloy thin plate containing Ni: 30 to 45%, Cr: 0.1 to 2.5%, and the balance being Fe and unavoidable impurities, When the crystal grain size is d, d-1/2
is 0.5 to 2.5-1/2, and the yield strength σ. 2 is 18
Low thermal expansion shadow mask material (invention 1) characterized by ~22 kgf 7 mm2 and containing ~45% Ni: 3Q, 0.1 ~ 2.5% Cr, the balance being Fe and unavoidable impurities. The Fe-NL alloy strip was cold rolled at a cold rolling rate (R%) satisfying the formula 12Cr' -550r+71≦R≦96, and then (650 to 900
℃)×(10-120SeC9), and after etching and perforation, further annealing of (650-1250℃)×(30
~100min. ) A method for producing a low thermal expansion shadow mask material (invention 2)
) is provided.

The present invention will be explained in detail below.

Conventionally, so-called invar material, that is, Fe-Ni with a low coefficient of thermal expansion, was used.
As mentioned above, shadow mask materials made from alloys lack formability during the press processing performed after etching, and therefore, after being incorporated into a cathode ray tube as a shadow mask, they deform toward the electron gun side due to springback, resulting in color distortion. There was a tendency for misalignment to occur.

As a countermeasure to this problem, it became urgent to improve the press formability of the amber material after etching.

Therefore, as a result of intensive experiments and research, the present inventors found that when the average crystal grain size is d, d-1/2 is 0.5 to 2°5 and 1
72 and yield strength σ. .

The reason why the Ni content is set to 30 to 45% in common to Inventions 1 and 2 is that if the Ni content is less than 30% or more than 45%, the coefficient of thermal expansion will increase in either case. This is because it is not suitable for the use of the present invention.

In addition, in the present invention 1, d-1/2 is 0. 5-2.5m
The reason why it is set to m''2 is that when the crystal grain size d satisfies this range, the yield strength σ0.2 falls within a desirable range.

That is, d-1/2 is 2. If d is larger than 5mm-''', d becomes small and the crystal grains become fine, the yield strength increases and undesirable springback occurs, and if d-1/2 is smaller than 0.5, the crystal grains become fine. The grains become coarse and the skin becomes rough.
1), which is not only undesirable in terms of press molding, but also causes the etched holes to become irregularly shaped, making them unsuitable for high-definition cathode ray tubes.

And proof stress σ. The reason why 2 is set to 18 to 22 kgf/hole 2 is that if the above crystal grain range is selected, the yield strength will almost inevitably fall within this range.

Approximately 10 kg f/1r due to handling during mask process
A yield strength of trn2 or higher is required, but as long as it is higher than this, the lower the yield strength is, the better, so 18 kg f / am2
The lower limit is 18 kgf/mm' according to the crystal grain size limitation, and even if it is larger than this, if it is below the upper limit of 22 kgf/mm2, there will be no problems during press forming in practice. Does not occur. 22)cgf
If it exceeds 22 kg f'/am 2, problems with pressability will occur as with conventional amber, so it was set to 22 kg f'/am 2 or less.

Present invention 2 is one of the methods for manufacturing present invention 1.

In view of the above-mentioned problems, the present inventors searched for a manufacturing method, and as a result, they were able to increase the final cold rolling rate, which was conventionally about 10 to 20%, to an extremely high 65.6 to 96%. It was discovered that the present invention 1 can be easily and stably obtained by combining appropriate heat treatments, and the present invention 2 was completed.

Conventionally, when the cold rolling rate was increased, the microscopic structure became a so-called fibrous structure, and if etched as it was, irregularly shaped perforations could occur.Therefore, the cold rolling rate was 20% at most, but it was intentionally increased to 65.6% or more. The present invention is characterized in that it provides a high cold rolling rate. However, continuous annealing (short-time strain relief annealing) is performed as a measure to prevent the above-mentioned irregularly shaped holes. This continuous annealing removes the work hardening strain caused by high cold rolling reduction and eliminates the fibrous structure, so it is an extremely effective means to prevent irregular holes during etching, and on the other hand, it is more effective than normal coil annealing. Since the soaking time is short, there is an advantage that grain growth after recrystallization is suppressed. Therefore, sufficient grain growth occurs for the first time during mask annealing after etching and perforation, resulting in a reduction in yield strength, that is, an improvement in press formability.

The reason for limiting the cold rolling rate in the present invention 2 is as follows. That is, if the cold rolling rate is lower than 65.6%, the effect of the present invention will not be achieved, and if it exceeds 96%, grain coarsening will eventually occur after mask annealing, resulting in warpage and deterioration of pressability. Preferably, a cold rolling ratio of 75 to 95% is employed.

The reasons for limiting the conditions for continuous annealing are as follows.

If the soaking temperature is less than 650℃, there will be many parts that do not reach the recrystallization temperature, and the fibrous structure will not disappear sufficiently, and if it exceeds 900℃, the furnace walls of the continuous annealing furnace, hearth rolls, etc. The upper limit was set at 900° C. since the life would be shortened and it would also be uneconomical from the standpoint of energy conservation.

In particular, a temperature range of 800 to 850°C is preferably employed.

In this case, the atmosphere used is HNX, NX gas, etc., but various other endothermic or exothermic gases can also be used. Vacuum etc. can also be applied.

If the soaking time is less than 10 seconds, the recrystallization will be incomplete, and if it exceeds 120 seconds, the line speed must be extremely slow or the furnace body must be made long, which is uneconomical. , closed.

Note that skin pass rolling may be performed after continuous annealing.

Next, mask annealing will be described.

The shadow mask material is usually etched and perforated in the form of a strip, and then sheared or blanked to form a flat mask.

Mask annealing is a heat treatment carried out in the state of this flat mask, and is a process carried out to remove etching distortion and ensure subsequent press formability.

The annealing atmosphere is similar to the above-mentioned continuous annealing, but currently it is often set to a vacuum of about 10-' to 10-6 Torr. This is because the surface of the mask after etching is clean and easily oxidized, so the gas adsorbed on the surface is sufficiently degassed during mask annealing to prevent oxidation.

The flat masks are stacked in a furnace and batch annealed at a soaking temperature of 650-1250℃.
, especially preferably 1100 to 1170°C. The reason for this is that if the temperature is lower than 650°C, some parts will not be recrystallized, whereas if the temperature exceeds 1250°C, not only no further grain growth effect can be expected, but also undesirable from the standpoint of energy saving.

If the soaking time does not reach 30 min, the grain growth will be insufficient, and even if the soaking time exceeds 100 min, the grain growth will already be saturated, which is uneconomical.
0~LOOmin, closed.

Then, the flat mask is given a spherical protrusion by pressing, either as annealed or after leveling if necessary, and then blackened to form a shadow mask.

That is, the shadow mask material in the first and second inventions refers to a flat mask before leveler processing or press processing.

Next, the second invention will be explained in more detail.

The second invention, together with the first invention, contains Cr in addition to Ni as an active ingredient.

FIG. 1 is a graph showing the relationship between cold rolling ratio R and Cr.

Note that this graph was obtained through experiment.

In Fig. 1, the horizontal axis represents the amount of Cr, and the amount of Cr is 0.1
~2.5% is the range of the present invention. If the amount of Cr is less than 0.1%, no effect will be recognized, and if it exceeds 2.5%, the coefficient of thermal expansion of the material will increase, making it impossible to achieve the original purpose. Therefore, it was set at 0.1 to 2.5%.

The vertical axis represents the cold rolling rate R, and the curve R-12Cr2-55C
The range of the second invention is a combination of Cr content and cold rolling rate R that is above r+71 and belongs to the hatched region of R≦96.

When R is below the curve shown by this formula, it becomes a high yield strength region and press formability is poor.

In addition, when R exceeds 96%, processing distortion accumulates. [Example] Component composition as shown in Table 1 (Cr: 0.041-2
．． 01%) was used as the test material, and the second
As shown in the table, after cold rolling at a final cold rolling ratio of 10 to 95%, continuous annealing and mask annealing after etching and perforation were performed.

That is, Table 1 is a table showing the chemical components of the test materials, and Table 2 is a table showing processing conditions.

Table 3 is a table showing the characteristics of the mask material thus obtained. The larger the grain size after mask annealing, the higher the yield strength σ. , 2 becomes lower, and the yield strength σ.

2 exceeds 24 kgf/mm2, press formability becomes poor due to springback of the material.

As in the present invention, in the Cr range of 0.1% or more, according to the formula R≧12Cr'-55Cr+71, 18 to
Proof strength σ of 22kgf/en2. 2 is obtained, and a low thermal expansion type shadow mask element material with excellent press formability can be obtained with a relatively low cold rolling rate when the material has a large amount of Cr.

All of the examples of the present invention listed in Table 3 exhibited superior press formability than the comparative examples.

[Effects of the Invention] By implementing the present invention, all of the above objects are achieved.

In other words, a low thermal expansion shadow mask material with excellent press moldability is provided. Further, in the present invention, since an appropriate amount of Cr is added, there is an effect that press formability can be ensured without increasing the cold rolling rate too much.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the Cr content and the cold rolling rate R in the second invention.

Claims (2)

[Claims] (1) Ni: 30-45% (weight%, same below), Cr
: Fe-Ni alloy thin plate containing 0.1 to 2.5%, the balance being Fe and unavoidable impurities, where d^-^1^/^2 is 0 when the average grain size is d. .5~2.5m
m^-^1^/^2, and proof stress σ_0_. _2 is 18
A low thermal expansion shadow mask material characterized by ~22 kgf/mm^2. (2) Fe-Ni alloy strip containing Ni: 30 to 45%, Cr: 0.1 to 2.5%, and the balance being Fe and inevitable impurities, with the formula 12Cr^2-55Cr+71≦R≦96 cold rolling at a cold rolling rate (R%) that satisfies (650-900
℃) × (10 to 120 sec.), and after etching and perforation, further annealing (650 to 1250 °C) × (30
~100min. ) A method for producing a material for a low thermal expansion shadow mask, characterized by subjecting it to mask annealing.