JPS6339646B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a shadow mask for a color television cathode ray tube, and more particularly to a method of manufacturing a shadow mask that improves the annealing step performed after the cold finish rolling step and before the photoetching step. Conventionally, shadow masks for color television cathode ray tubes have been manufactured through the following steps.
Material rolling manufacturers are increasing the rolling reduction rate of low carbon steel.
Cold finish rolling is performed at 40% or more to obtain the desired thickness of 0.2 mm or less. The coil is then shipped to an etching perforation manufacturer. At etching perforation manufacturers, the coiled shadow mask material is unwound and subjected to pretreatment such as degreasing, then a photosensitive liquid (resist) is applied to both sides, and after drying, a predetermined dot shape or slot shape is formed. A reference pattern is brought into close contact with both sides, exposed, and developed. After that, in order to harden the resist film, approximately
Burning treatment is performed at a temperature of around 200℃, predetermined holes are made by etching with a spray of ferric chloride liquid, etc., and the remaining resist film is removed, after which each mask is shipped to a cathode ray tube manufacturer as a flat mask. be done. Next, the cathode ray tube manufacturer applies deformability to enable press molding by annealing the etched and perforated flat mask. This annealing is typically performed from 750 to
It is carried out at a high temperature of 900℃. In this as-annealed state, the yield point elongation is large, and stretch strain occurs during press forming, which can be a fatal defect in the shadow mask. In order to correct the loss of its properties, it is run through a roller leveler several times before press molding, and then press molded into a predetermined spherical shape. Thereafter, an oxide film is formed on the surface of the shadow mask through blackening and anti-corrosion treatment, resulting in a finished product. In the conventional manufacturing process (hereinafter referred to as post-annealing method) described above, several problems have emerged, particularly in the annealing process performed by cathode ray tube manufacturers. In other words, in this annealing process, not only is the annealing efficiency extremely poor and the annealing cost is high because the flat masks are stacked or suspended as described above, but also the flat masks are annealed at a high temperature of 750 to 900°C. Frequent adhesion of
This causes a significant decrease in yield. Furthermore, even in flat masks that do not cause adhesion seizure, they lose their smoothness due to this high-temperature annealing, and the roller leveler that is performed later causes the holes to become misaligned, and if the flatness is extremely poor, wrinkles are caused by the leveler. It has built-in factors that cause a high number of defective products. In addition, when low carbon steel, which is the material of the shadow mask, is annealed at high temperatures, the carbon in the steel diffuses and aggregates near the surface of the steel plate, but this agglomeration is uneven, making it difficult to give uniform elongation during press forming. Therefore, defective products discovered after press molding are also recognized. Among these problems, adhesion seizure, thermal deformation, product unevenness, etc. are all phenomena that spread due to high-temperature annealing, and it is easy to think that lowering the annealing temperature will have a large effect on solving these problems. . Cathode ray tube manufacturers have also attempted to lower the annealing temperature based on this idea. However, if the temperature is lowered to the extent that it is possible to prevent adhesion seizure and thermal deformation, the grain size becomes finer, and as a result, the yield point elongation increases, and a leveler is required to eliminate the yield point elongation. The number of repetitions had to be increased to an extent that was impossible in terms of work efficiency. Therefore, low-carbon steel is cold-rolled at a reduction rate of 10-35% in cold finish rolling to obtain a product with a thickness of 0.2 mm or less, and the cold-rolled steel strip is heated to 520-600℃ as a tight coil.
A method for producing a shadow mask for a color television cathode ray tube (this is called the pre-annealing method) has been proposed, which involves annealing at a temperature of , followed by temper rolling, followed by an etching perforation process, a leveler threading process, and a press forming process. . By following this pre-annealing method, cathode ray tube manufacturers can omit annealing, which is essential in post-annealing methods, and material manufacturers can obtain stable press formability through high-efficiency, low-cost annealing. However, this previously proposed pre-annealing method also has the following problems. In other words, even if the yield point elongation is suppressed by temper rolling after annealing at the material manufacturer, approximately 200
Since the burning process is carried out at 100°C, aging occurs and yield point elongation occurs again. This has caused problems such as an increase in the number of levelers and press breakage. The present invention has been made primarily to solve these problems in manufacturing conventional shadow masks. For this purpose, the invention provides that as a material
By using ultra-low carbon cold-rolled aluminum-killed steel sheets that have been decarburized by OCA (open coil annealing), we can avoid the problem of poor hole shape, and by appropriately adjusting the annealing atmosphere, we can improve the photo-etching process. Even when subjected to burning treatment, the yield point elongation due to aging was almost completely suppressed, and stable press formability was successfully obtained. That is, the present invention provides a method for manufacturing a shadow mask according to the pre-annealing method, in which the material is 0.2 mm.
Cold rolled to the following plate thickness, C; 0.004%
Below, sol.Al; 0.01~0.08%, Mn; 0.15~0.40%,
N: 100 ppm or less, the balance is iron and unavoidable manufacturing impurities using an aluminum killed cold-rolled steel sheet, which is kept as a tight coil at a temperature of 520 to 650°C, and CO + CO ₂ : 15 ppm or less (capacity standard) , H ₂ ; 0.5% (capacity basis) or more, the remainder being substantially
It is characterized by annealing in an atmosphere consisting of N ₂ and H ₂ O. In general, aluminum-killed steel has better cleanliness than rimmed steel or capped steel, can avoid poor hole shape due to non-metallic inclusions, and can fix the solid N in the steel as AlN. As a result, the elongation at yield point can be reduced. If decarburization is performed in the OCA step in the production process of cold rolled steel sheets, the elongation at yield point can be further reduced. This is known to some extent. However, no matter what measures are taken to suppress elongation at yield point during the steel manufacturing process, elongation at yield point may significantly increase depending on the final annealing conditions performed by the material manufacturer. The inventors of the present invention have conducted intensive research to find conditions that are advantageous for preventing yield point elongation during final annealing (annealing after cold finish rolling and before photo etching) performed at material manufacturers.
If annealing is performed in an atmosphere consisting of CO ₂ ; 15 ppm or less (by volume), H ₂ ; 0.5% (by volume) or more, and the balance substantially consisting of N ₂ and H ₂ O, the yield point elongation will also be reduced by this annealing. It was found that stable press formability was obtained, with no occurrence of yield point elongation due to aging during the burning process during the photoetching process. Moreover, the annealing temperature in this case may be as low as 520 to 650°C.
Moreover, it has become clear that even at this low temperature, there is a region where sufficient annealing can be performed without yield point elongation occurring. Therefore, if the annealing conditions according to the present invention are followed, high-temperature annealing at the cathode ray tube manufacturer is no longer necessary, and by performing high-efficiency, low-cost annealing at the material manufacturer, not only is it possible to save energy and reduce costs, The effect of extremely stable moldability during molding of a flat mask can be obtained. This effect is not affected by temper rolling at a reduction rate of 0.3 to 1.2% after this annealing. This is advantageous in terms of surface quality and flatness. The present invention will be specifically explained below based on representative test results. Figure 1 shows that when steel containing 0.003% C and 0.04% sol.Al is annealed at an annealing temperature of 600°C, the hydrogen concentration (volume %) and dew point of the steel during the burning process (200°C x This figure shows the results of an investigation into how it affects the elongation at yield point after 3 minutes). The test was conducted under the condition that CO + CO ₂ in the atmosphere was 6 ppm (capacity basis), and it is clear from these results that there is a region where no elongation at yield point occurs. Figure 2 shows steel containing 0.003% C, 0.04% sol.Al, annealed at 600°C, dew point 0°C, and hydrogen concentration 10°C.
% (capacity basis) atmosphere, the relationship between CO + CO ₂ concentration and elongation at yield point after burning treatment (200°C x 3 minutes) was investigated. As is clear from FIG. 2, when CO+CO ₂ is below 15 ppm (capacity basis), elongation at yield point does not substantially occur. However, when it exceeds 15 ppm (capacity standard), the yield point elongation increases rapidly. From these test results, in order to prevent the occurrence of stretcher strain caused by yield point elongation when press forming flat masks, the annealing atmosphere at the material manufacturer should be adjusted to 15ppm of CO + CO ₂ .
(capacity standard) or less, and the hydrogen concentration is 0.5%
(capacity standard) or more is clearly desirable. If the hydrogen concentration is less than 0.5% (volume standard),
As shown in FIG. 1, the region where no yield point elongation occurs rapidly becomes narrower, making actual operation difficult. Further, an annealing temperature of 520 to 650°C is sufficient. 520
At an annealing temperature lower than °C, recrystallization does not occur and pressing becomes impossible. Furthermore, at an annealing temperature exceeding 650°C, a problem of adhesion seizure due to tight annealing occurs. In addition, regarding the component values of the ultra-low carbon aluminum killed steel sheet to which the present invention is applied, C: 0.004% or less, sol.
Al; 0.01-0.08%, Mn; 0.15-0.40%, N;
It is best to use one with a content of 100ppm or less. C is
If it exceeds 0.004%, stretcher strain tends to occur during press molding. Since N causes an increase in elongation at yield point, it is better to have as little as possible, and if it is included in a large amount, the amount of AlN increases and suppresses the growth of crystal grains, which prevents the annealing temperature from lowering. Because of this, N
It is best to keep it below 100ppm. Al is a deoxidizing agent in steelmaking, and the amount is necessary to reduce nonmetallic inclusions in steel, and it also eliminates solid solution N, which causes elongation at yield point.
It is sufficient to add the amount necessary to fix it as AlN. This includes 0.01-0.08% as sol.Al in steel
A range of is appropriate. Further, Mn is preferably contained in an amount that satisfies Mn/S>15 in order to prevent hot embrittlement due to S, and in consideration of crystal grain growth, it is preferably contained in an amount of 0.15% or more. but,
The upper limit may be around 0.40%, which is the same level as rimmed steel. Example The test material was low carbon aluminum killed steel (C: 0.07%, Mn: 0.25%,
P; 0.0014%, S; 0.008%, Si; 0.014%, sol.
Continuous casting → hot rolling (plate thickness 2.5 mm, coiling temperature 570°C) → pickling → cold rolling (0.42 mm) → open coil annealing (C: 0.003%). This is an ultra-low carbon aluminum killed cold-rolled steel sheet manufactured using the process of charcoal) → finish rolling (0.17 mm) → tight annealing (above the recrystallization temperature) → skin pass 1.0%.
This sample material had C; 0.003%, Si; 0.014%, Mn;
It has a composition of 0.25%, sol.Al; 0.04%, N; 45ppm. Various dew points, hydrogen concentrations, CO
The specimens were annealed in an atmosphere with a +CO ₂ concentration, and the characteristic values and press formability after burning treatment in the photoetching process were investigated. The results are shown in Table 1. From the results in Table 1, it can be seen that in the annealing atmosphere within the range according to the present invention, yield point elongation does not occur, and even if it occurs, it is extremely small compared to the comparative example. Therefore, according to the present invention, stable press moldability of the flat mask can be obtained, and great effects can be obtained in terms of energy saving and cost.

【table】

【table】 [Brief explanation of drawings]

Figure 1 shows annealing temperature 600℃, CO + CO ₂ ; 6ppm
Figure 2 shows the relationship between dew point, hydrogen concentration and yield point elongation under the conditions of (capacity basis), annealing temperature of 600℃,
It is a relationship diagram between CO + CO ₂ concentration and yield point elongation when steel containing 0.003% C and 0.04% sol.Al is annealed in an atmosphere with a dew point of 0°C and a hydrogen concentration of 10% (by volume). .

Claims (1)

[Claims] 1 C; 0.004% or less, sol.Al; 0.01-0.08%,
A cold-rolled steel strip with a thickness of 0.2 mm or less is produced, consisting of Mn: 0.15 to 0.40%, N: 100 ppm or less, and the balance is iron and unavoidable impurities. This cold-rolled steel strip is kept as a tight coil at 520 to 650℃. At a temperature of , CO + CO ₂ ; 15ppm
(capacity standard) or less, H ₂ ; 0.5% (capacity standard) or more,
A method for producing a shadow mask for a color television cathode ray tube, which comprises annealing in an atmosphere in which the remainder is substantially composed of N ₂ and H ₂ O, followed by temper rolling, followed by an etching perforation process and a press molding process.