JPH0453930B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a steel plate material for manufacturing a shadow mask to be attached to a color television cathode ray tube. [Prior Art] A low carbon aluminum killed steel plate is used as a material for the shadow mask of a color TV cathode ray tube. For example, in Japanese Patent Publication No. 58-30929, an ultra-thin material steel sheet for manufacturing shadow masks is produced by annealing an aluminium-killed cold-rolled steel sheet with a C content of 0.01% or less and then cold-rolling it again to a thickness of 0.2 mm or less. Disclose a method to do so. The invention described in this publication is Sol.Al
The occurrence of stretcher strain during press forming is suppressed by regulating the N content and N content to have a specific relationship, and by optimizing the annealing conditions after photoetching. By using a low-carbon aluminum-killed steel sheet, including the method described in this publication, it is generally possible to obtain a raw material steel sheet that has a good hole shape during photoetching and does not generate stretcher strain during press forming. In the case of a post-annealed material, a series of steps for manufacturing a shadow mask using such a steel plate material is generally as follows. Low carbon aluminum killed steel (C≦0.01%) hot rolled steel plate → pickling →
Cold rolling (primary cold rolling, plate thickness 0.6 mm or more) → decarburization annealing → cold rolling again (referred to as re-cold rolling in the above publication, which involves cooling to 0.2 mm or less with a reduction rate of about 40%) Processing) → cutting → photo etching perforation → annealing (post annealing) → leveler processing → press molding → blackening treatment → mounting on cathode ray tube. [Problems to be Solved by the Invention] The present invention attempts to solve the problem of magnetic properties when a low carbon aluminum killed cold rolled steel sheet is used as a material for manufacturing a shadow mask. Steel sheets used for manufacturing shadow masks have chemical properties that improve the pore shape when subjected to a chemical treatment called photoetching, as well as various mechanical properties (e.g., elimination of elongation at yield point, formability, strength, etc.). In addition, it is also necessary to have excellent magnetic properties. The most important magnetic property is coercive force. If the material is made of a material with a high coercive force, the shadow mask will be charged when it is affected by an external magnetic field during imaging, causing disturbances in the deflection of electron beams and color shift. The shadow mask is normally demagnetized, but if the coercive force is high, there is a risk that this demagnetization may be incomplete. Conventional shadow masks made of low-carbon aluminum-killed cold-rolled steel sheets have the above-mentioned chemical and mechanical properties that are satisfactory to some extent, but there is a problem in that their magnetic properties are not necessarily good. The present invention attempts to solve this problem by satisfying the above-mentioned chemical properties and mechanical properties. [Means for Solving the Problems] The present inventors have repeatedly conducted various tests and studies on the relationship between the above-mentioned magnetic properties of aluminium-killed cold-rolled steel sheets, component elements, and manufacturing conditions.
It is necessary to suppress the N content to 0.014% or less and the N content to 50ppm or less, and to reduce the rolling reduction rate during cold rolling again to 50%.
It has been found that setting the ratio to 70% is very useful in solving this problem. Therefore, the present invention provides a method for manufacturing an ultra-thin steel sheet for manufacturing a shadow mask by annealing an aluminum-killed cold-rolled steel sheet with a C content of 0.01% or less and then cold-rolling it again to a thickness of 0.2 mm or less. S content in material steel
0.014% or less, N content is suppressed to 50ppm or less, and the reduction rate during the above-mentioned cold rolling is 50 to 70.
% of a cold-rolled steel sheet for a shadow mask, which has a low coercive force. According to the present invention, the coercive force (Hc) is 1.4 (Oe)
The following shadow masks can be manufactured. One feature of the method of the present invention is that it uses a material in which the S content and N content of low carbon aluminum killed steel are suppressed to below a certain value.
In addition to N, ordinary Mn and Sol.
Contains Al. That is, the steel plate for a shadow mask of the present invention has, as its chemical components, in weight%,
C: 0.01% or less, N: 50ppm or less (0.0050% or less) S: 0.014% or less, and the amount of Mn contained in ordinary aluminum killed steel: 0.05 to 0.5%,
Contains Sol.Al; 0.020-0.12%. First, the content of each of these elements will be explained. C: When the C content exceeds 0.01%, the amount of cementite (Fe ₃ C) produced increases, and during the photo-etching drilling process, this cementite, which is difficult to etch, remains on the surface of the hole and worsens the hole shape. , and the coercive force increases as the amount of carbide increases. As the solid solution C increases, the yield point elongation increases. Therefore, C needs to be 0.01% or less. Regarding S: 0.014% or less, N: 50ppm or less. Figure 1 shows the relationship between coercive force and coercive force when the reduction rate of re-cold rolling and the S content are changed among the steel plate manufacturing conditions for low carbon aluminum killed steel with a C content of 0.002%. This is what is shown. In Figure 1, the circle mark indicates a rolling reduction of 65% and N of 50ppm.
Below, the □ marks are low carbon aluminum killed steel sheets with a rolling reduction of 75% and N content of 60 ppm, and the △ marks with a rolling reduction ratio of 80% and N content of 60 ppm. From FIG. 1, it can be seen that as the S content increases, the coercive force tends to increase. And especially N
After setting the S content to 50ppm or less (○ mark),
It can be seen that if it is 0.014% or less, the coercive force will be 1.4 (Oe) or less, which is the target characteristic of the shadow mask. That is, while it is important for the purpose of the present invention to suppress the S content to 0.014%, it is also important to suppress the N content to 50 ppm or less. Note that this relationship will also be shown in Examples below. Further, since N causes an increase in elongation at yield point, from this point of view as well, it is better to reduce the amount of N as much as possible. Mn has a useful effect on the hot workability of steel, but as Mn increases, S-based inclusions increase, which has a negative effect on the magnetic properties and the hole shape of the shadow mask. Therefore, Mn is 0.15-0.50
The content is preferably in the range of %. Sol.Al is used as a deoxidizing agent during steel melting. It fixes N in steel as Al and reduces solid solute N, which causes elongation at yield point. It works effectively. 0.02% to get such an effect
Requires more than Sol.Al. However, if it exceeds 0.12%, nonmetallic inclusions will increase and cause surface defects, so Sol.Al should be 0.02 to 0.12%, preferably 0.02%.
It is best to set it to ~0.080%. One feature of the method of the present invention is that steel having such a composition, especially aluminum killed steel with C≦0.01%, is used as a material steel with an S content of 0.014% or less and a N content of 50ppm or less. However, it is also characterized by the fact that the rolling reduction ratio in re-cold rolling is set at 50 to 70% in the manufacturing process to produce ultra-thin cold-rolled steel sheets before photo-etching. In other words, in the case of post-annealed materials, the manufacturing process for the shadow mask until it is attached to a color TV cathode ray tube is, as mentioned above, a hot-rolled steel plate of low carbon aluminum killed steel (C≦0.01%) → pickling → cold rolling. Rolling (primary cold rolling, plate thickness 0.6 mm or more) → Decarburization annealing → Cold rolling again (re-cold rolling, plate thickness 0.2 mm or less) → Cutting → Photo etching perforation → (This perforated plate is usually (called flat mask) → annealing (post-annealing; when annealing is done in the state of the steel strip before cutting, it is called pre-annealing) → leveler → processing → press forming → blackening treatment → attachment to the cathode ray tube. However, in the method of the present invention, the steps other than re-cold rolling remain the same as in the conventional method, and the rolling reduction ratio of this re-cold rolling is set to 50 to 70%. When this rolling reduction exceeds 70%, the coercive force increases as shown in the examples below. Furthermore, if the rolling reduction ratio is less than 50%, uneven elongation will occur when press-molding the flat mask. [Example] A hot rolled steel strip with the chemical composition values shown in Table 1 was rolled at a rolling reduction rate of 70%.
The above is first cold rolled, then decarbonized annealed in an open coil annealing furnace under the treatment conditions of 740℃ x 1.5Hr/T, and re-cold rolled to a plate thickness of 0.2mm or less with the rolling reduction as shown. did. Each of the ultra-thin cold-rolled steel sheets obtained in this way was photoetched, and the dew point was 20℃.
At 750℃ in a gas atmosphere of 90% N ₂ + 10% H ₂
The coercive force of the sample annealed for 10 minutes was measured, and the annealed flat mask was formed into a spherical shape using a press, and the elongation unevenness was evaluated. The coercive force was measured according to the method of JIS C 2531. Moreover, the measurement of elongation unevenness was evaluated as follows. A 360mm x 360mm flat mask with holes evenly drilled through photoetching (hole diameter =
(100 μm, pitch = 250 μm) was formed into a spherical surface by applying stretching processing with its center aligned with the center of the die. The diameter of the spherical surface is 200 mm, and the radius of curvature of the curved surface is 460.
mm. After molding, four measurement areas located at the same radial position from the center of the spherical surface were selected at 90° intervals, the same amount of light was applied to each measurement area, and the transmittance was measured using a light transmittance meter. Each measurement area corresponds to the area of a circle with a radius of 25 mm, and the four measurement areas are located at symmetrical positions on all sides. The average value () of the transmittance of these four measurement areas is determined, and the maximum transmittance is calculated using the following formula from the transmittance (Xmax) of the area with the largest difference from this average value and this average value (). The rate difference (%) was calculated. Maximum transmittance difference (%) = | (same x mark). These measurement results are also listed in Table 1. From the results in Table 1, it was found that an aluminum killed steel sheet with an S content of 0.014% or less and a N content of 50 ppm was used, and the rolling reduction rate of re-cold rolling was 50~50 ppm.
It can be seen that when the three requirements of 70% are satisfied at the same time, the coercive force is 1.4 (Oe) or less and no uneven elongation occurs after pressing. In the case of Comparative Examples Nos. 8 to 11 in which any of these three requirements is not met, the object of the present invention cannot be achieved because the coercive force is high or elongation is uneven.

【table】

【table】 [Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the coercive force and the rolling reduction in re-cold rolling for low carbon aluminum killed steel with a C content of 0.002%. is less than 50ppm, □ indicates rolling reduction rate of 75
%, N is 60ppm, △ mark is 80% reduction rate, N is 60ppm
It is a low carbon aluminum killed steel plate.

Claims (1)

[Claims] 1 In a method of manufacturing an ultra-thin material steel sheet for manufacturing a shadow mask by annealing an aluminium-killed cold-rolled steel sheet with a C content of 0.01% or less and then cold-rolling it again to a thickness of 0.2 mm or less, S in the material steel is content
0.014% or less, N content is suppressed to 50ppm or less, and the reduction rate during the above-mentioned cold rolling is 50 to 70.
% of a cold-rolled steel sheet for shadow masks having a low coercive force.