JP3414929B2 - Method of manufacturing material for shadow mask - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a material for a shadow mask used for a color selection electrode disposed in a cathode ray tube of a color television. 2. Description of the Related Art A shadow mask for a color television or a color display is subjected to primary cold pressure → annealing → secondary cold pressure at a material maker, and then etched → annealed → leveler applied → press-formed → blackened. It is manufactured through each process of processing. As materials for shadow masks, low carbon A
1 Killed steel decarburized material is widely used. This steel is required to have not only press formability and blackening properties but also etching properties for perforating a shadow mask. [0004] With respect to the perforation by this etching, the etching rate has been increased due to the rationalization of the etching manufacturer. Accordingly, even in a steel material which has not caused any problem in the past, when light is transmitted after etching, streaky unevenness of gloss may be observed. Since the streaks cause color unevenness of the television, a steel sheet free of streaks is desired. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method of manufacturing a material for a shadow mask which does not cause streaks even at a high etching rate. And According to the present invention, in order to solve the above problems, C: 0.01 to 0.03% by weight%;
Si: 0.03% or less, Mn: 0.05 to 0.5%,
P: 0.05% or less, S: 0.03% or less, sol. A
l: Steel containing 0.1% or less and Cr: 0.01 to 0.1% is melted , hot-rolled , and rolled at 650 ° C or less.
For a shadow mask which does not generate stripe unevenness after etching, characterized in that after cold rolling to a thickness of 1 mm or less, decarburizing annealing is performed until C becomes 0.002% or less, and further cold rolling is performed to a product thickness. Provide a method of manufacturing the material. Hereinafter, the present invention will be specifically described. The following are known as causes of streaks generated after etching. (1) Inclusions such as MnS, Al ₂ O _3, etc. (2) Segregation of P etc. (3) Abnormal structure of several μm in the center of plate thickness due to slab center segregation It has become apparent with the recent increase in etching rate. The streak portion was inspected in a direction perpendicular to the cross section of the rolled sheet and corroded for a long time with picric acid. As shown in FIG. 1, a streak was also observed in the central portion of the sheet thickness corresponding to the streak in appearance. . This streak is also observed in the decarburized annealed plate after the primary cold pressure, and when that portion is observed with a scanning electron microscope (SEM), it is found that the crystal grains are locally etched as shown in FIG. confirmed. No inclusions such as MnS and segregation of P were found in such streaks, and no abnormal structure was found. The cross section of this streak is analyzed by secondary ion mass spectrometry (SIM
S) As a result of examination by line analysis, as shown in FIG. 3, carbon concentration was recognized at the center of the sheet thickness. The shadow mask material is usually made of low carbon Al.
After the primary rolling of killed steel, open coil annealing (OC
Since the decarburization annealing is performed to extremely low carbon in A), the amount of carbon in the steel is extremely small. However, since decarburization is performed from the surface of the steel sheet, carbon in the central part of the sheet thickness is difficult to escape, and carbon tends to remain in the central part of the sheet thickness. As a result, carbon is concentrated in the central part of the sheet thickness. Since the concentration of carbon in the central portion of the plate thickness is relatively small, no streak is generated under the conventional etching conditions. However, when the etching rate is increased, the carbon enriched portion is likely to be selectively corroded. This is because the roughness of the hole side wall portion becomes large when etching is performed at a high speed, and this causes streaks to become apparent. In order to prevent the occurrence of streaks, it is conceivable to increase the amount of decarburization in the primary annealing. However, if an attempt is made to increase the decarburization amount by increasing the decarburization time, the decarburization rate will decrease as the decarburization progresses. Time consuming and inefficient. On the other hand, in the method of increasing the decarburization amount by raising the decarburization temperature,
Steel may be oxidized, and OCA causes bending of the coil and sticking of the steel sheets, and continuous annealing (CAL)
In this case, a shape defect due to a decrease in the sheet width is likely to occur. Therefore, in the present invention, the C content is set to a relatively low value of 0.01 to 0.03% in the smelting stage, and after the primary cooling pressure, the C content is decarburized to 0.002% or less. The method was adopted. Conventionally, as disclosed in JP-A-56-108822 and the like, the C content is set to 0.04 at the melting stage.
To a high level of about 0.06%;
As disclosed in Japanese Patent No. 68149 or the like, there is known a method in which the C content is reduced to 0.005%. But,
If the C content is large as in the former case, it is necessary to increase the decarburization amount in the decarburization annealing, and the above-described problem occurs. Also,
As in the latter case, it is difficult to decarburize to a low level in the casting stage, and it is necessary to increase the amount of oxygen blown during decarburization, so the amount of oxides in the steel increases and is caused by oxides Streaks are likely to occur. According to the present invention, in addition to adjusting the amount of carbon before and after decarburization annealing, (1) reducing the amount of Mn, S, P, Al, and Si, etching defects due to inclusions and P segregation are reduced. The essence is to avoid and (2) fix a part of C by adding Cr to reduce the amount of C in the central part of the plate thickness. Next, the reason why the amounts of the respective components in the melting stage are specified as in the present invention will be described. C: C: 0.01 to 0.03% C at the center of the sheet thickness is difficult to be removed even by decarburizing annealing.
Such residual C tends to remain after annealing, but such residual C changes the etching rate and exposes the sidewall of the hole, resulting in streaks after etching. Therefore, it is necessary to reduce the amount of C to the extent that no streaks occur after annealing,
It is conceivable to reduce the amount of C to a desired value in the smelting stage. However, excessive decarburization at the smelting stage inevitably increases the oxygen content in the steel, and tends to cause streaks due to oxides. Therefore, in the present invention, the amount of C is defined in a range of 0.01 to 0.03% which does not cause such inconvenience and can easily decarburize to a necessary level during decarburization annealing. The preferred range is 0.01-0.2%. Si: 0.03% or less sol. Al: 0.1% or less Si and Al are added as necessary to deoxidize steel. However, if added in large amounts, the oxides in the steel will increase, and the oxides that could not be floated by casting will become inclusions. The inclusions remain undissolved by the etching and disturb the shape of the hole side wall. Further, since the inclusions are extended in the rolling direction in the rolling step, fine streaks are easily generated after etching.
Therefore, it is better that Si and Al are small, and Si: 0.0
3% or less, sol. Al: Regulated to 0.1% or less. A
The preferable range of 1 is 0.05% or less. Mn: 0.05-0.5% S: 0.03% or less S is an element inevitably contained in steel and causes hot embrittlement. Therefore, Mn is added to fix S as MnS. However, if the amount of Mn is too large, such effects are not only saturated, but also only harden the steel. Therefore, Mn is set to 0.05 to 0.5.
% Range. On the other hand, MnS remains undissolved in the etching and disturbs the shape of the hole side wall. In addition, since MnS is extended in the rolling direction in rolling, streaks tend to occur after etching. Therefore, the smaller the value of S, the better. Preferably 0.02
% Or less. P: 0.05% or less If P is contained in a large amount, segregation is likely to occur. Since the P segregation part locally increases the etching rate, the roughness of the hole side wall part increases, which causes streaks after etching. Therefore, P is restricted to 0.05% or less. Cr: 0.01-0.1% Since Cr combines with C, it reduces solid solution C in steel,
This has the effect of reducing the amount of C remaining in the central part of the sheet thickness after decarburizing annealing. 0.01% to achieve this effect
The above addition is necessary. However, adding more than 0.1% saturates the effect and only raises the cost. Therefore, the Cr content is set in the range of 0.01 to 0.1%. Preferably it is 0.03-0.1%. In addition, Ti, Nb, B, Ta, W, Mo
Since carbonitride-forming elements such as these raise the recrystallization temperature during annealing, if they are contained, an unrecrystallized structure remains after final annealing, causing non-uniform deformation when mounted on a cathode ray tube as a shadow mask In addition, the arrangement of the holes is easily disturbed.
Therefore, it is preferable to eliminate these elements as much as possible. On the other hand, V, Sn, and As are 0.01% or less,
Even if Cu, Ni, and Co are contained in a range of 0.08% or less, the effect of the present invention is not impaired, and it is permissible to contain Cu, Ni, and Co in this range. Next, the manufacturing method will be described. In the present invention, a steel satisfying the above composition is melted and cast, and then subjected to a hot rolling step and a cold rolling step, followed by decarburizing annealing until C becomes 0.002% or less. Further cold rolling is performed to obtain a shadow mask material. When casting is performed by the ingot-making method, inclusions are easily formed at the boundary between the rim layer and the core portion, and segregation is liable to occur. Therefore, the casting is preferably performed by the continuous casting method. With respect to the subsequent hot rolling, the heating temperature and the finishing temperature are set in a range usually performed. On the other hand, if the winding temperature is too high, the carbides become coarse and it is difficult to decarburize to the central part of the sheet thickness during decarburization annealing. The conditions for the subsequent cold rolling may be set as appropriate,
If the thickness of the steel sheet after the cold rolling is too large, carbon in the central part of the sheet thickness is difficult to escape during decarburization annealing, so that the steel sheet is preferably rolled to a thickness of 1 mm or less. Regarding decarburization annealing, it is preferable to employ open coil annealing since carbon in the central portion of the sheet thickness is difficult to escape because continuous decarburization time is short if continuous annealing is employed. The annealing conditions in the open coil annealing are preferably maintained at 650 ° C. or more for 3 hours or more in order to decarburize to the center of the sheet thickness. The cold rolling after decarburization annealing may be appropriately set. In the present invention, hot rolling can be performed directly without cooling the slab after casting, and there is no problem if the thin slab is finish-rolled without rough rolling. Embodiments of the present invention will be described below. The slabs of the inventive steel and the comparative steel having the compositions shown in Table 1 were hot-rolled to a thickness of 2.8 mm,
The film was wound at a winding temperature of 620 ° C., cold-rolled to 0.65 mm after pickling. Thereafter, annealing was performed by the method shown in Table 2. Atmosphere decarburization _{annealing, H 2: 25%, N} 2: the remainder, dew point: was 25 ° C.. The atmosphere of the continuous annealing is H
₂ : 15%, N ₂ : balance, dew point: −50 ° C., under conditions not substantially decarburized. Next, cold rolling was performed again to obtain a shadow mask material with a plate thickness of 0.22 mm. Thereafter, high-speed etching was performed with ferric chloride to produce a shadow mask sample. Ten samples were prepared for each steel sheet, light was transmitted through the holes formed in these samples, and streaks were observed in any one of the ten samples. In the column, "X" was written, and when no streak was observed, "O" was written. [Table 1] [Table 2] Further, Si: 0.01%, Mn: 0.15 to 0.25
%, S: 0.01-0.02%, Cr: 0.05-0.
Hot rolling, cold rolling,
From a steel plate which has been decarburized and annealed to a plate thickness of 0.65 mm, a 695 mm speculum is taken in the direction perpendicular to the rolling direction, and a saturated aqueous solution of picric acid is boiled and corroded for 15 minutes. Was measured. The result is shown in FIG. From Table 2, it can be seen that the steel sheet 16 having a large C content in the hot-rolled sheet,
17, 18, 19, steel sheet 15, which has a large C content after decarburizing annealing,
17. The steel sheet 23 in which the C content was reduced to an extremely low carbon level in the steel making stage, the steel sheet 20 in which the P content is too large, the steel plate 21 in which the S content is too large, and the steel plate 22 in which the Cr content is small, all have streaks after etching. It was confirmed that. On the other hand, in the steel sheets 1 to 14 manufactured according to the present invention, no streaks occurred after etching. Further, as shown in FIG. 1, those in the range of the present invention also had a short streak length at the central portion of the sheet thickness after decarburizing annealing. In particular, when the C content after decarburizing annealing was 0.001% or less, the streak reduction was remarkable. As described above, according to the present invention,
A shadow mask material that does not generate streaks after etching even under severe etching conditions can be manufactured at low cost, and the industrial value of the present invention is extremely high.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a photomicrograph showing a streak present at the center of a strip thickness of a streak portion of an etched plate. FIG. 2 is a scanning electron micrograph of a streak in a central portion of a decarburized annealed plate in a thickness direction. FIG. 3 is a diagram showing C enrichment in a streak by secondary ion mass spectrometry normal analysis. FIG. 4 is a view showing the length of a streak at a central portion of a sheet thickness after decarburization annealing when the C amount of a hot-rolled sheet and the C amount after annealing are changed.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01J 31/20 H01J 31/20 A (72) Inventor Yasunobu Nagataki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Yoshihiro Hosoya 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Junji Okamoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) Reference Document JP-A-63-62821 (JP, A) JP-A-2-254139 (JP, A) JP-A-58-81926 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21D 9/46 C22C 38/00 301 C22C 38/18

Claims (1)

(57) [Claims 1] C: 0.01 to 0.03% by weight,
Si: 0.03% or less, Mn: 0.05 to 0.5%,
P: 0.05% or less, S: 0.03% or less, sol. A
l: Steel containing 0.1% or less and Cr: 0.01 to 0.1% is melted , hot-rolled , and rolled at 650 ° C or less.
For a shadow mask which does not generate streak defects after etching, characterized by cold rolling to a thickness of 1 mm or less, decarburizing annealing until C becomes 0.002% or less, and further cold rolling to a product thickness. The method of manufacturing the material.