KR20010072126A - Method for Producing Steel Sheet for Shadow Mask Being Excellent in Accuracy of Thickness in Longitudinal Direction - Google Patents

Abstract

The present invention is less than 0.1 mass% of carbon (C), 0.05 mass% or less of silicon (Si), 0.1 to 0.5 mass% of manganese (Mn), 0.03 mass% or less of phosphorus (P), 0.001 to 0.05 mass% of Hot rolling a steel comprising sulfur (S), 0.002 to 0.15 mass% aluminum (Sol.Al), or less than 0.008 mass% nitrogen (N), the balance being substantially composed of iron (Fe), wherein The present invention relates to a method for producing a shadow mask steel sheet having an excellent plate thickness precision in a longitudinal direction, including the step of decarburizing annealing the hot rolled steel sheet and cold rolling the annealed steel sheet to a desired plate thickness.

Description

Method for Producing Steel Sheet for Shadow Mask Being Excellent in Accuracy of Thickness in Longitudinal Direction}

Shadow masks are used as color selection mechanisms such as CRTs and color displays of color TVs. Such shadow masks can be obtained by hot rolling and cold rolling of low carbon or ultra low carbon aluminum killed steels, decarbonization annealing in a box furnace, and secondary cold rolling (Japanese Patent Laid-Open No. 55-62123), or ultra low carbon aluminum killed steels. By hot rolling, primary cold rolling, continuous annealing, and secondary cold rolling (Japanese Patent Laid-Open No. 9-53122) to produce a steel sheet having a desired thickness as a shadow mask, and a plurality of apertures in the steel sheet by photoetching. The steel sheet is secondary annealed, subjected to leverer processing, press formed and blackened after forming a).

In recent years, with the higher precision of a shadow mask, the thickness of a shadow mask becomes gradually smaller and it is calculated | required that the plate | board thickness precision of the lateral direction and the longitudinal direction of a steel plate coil is further excellent.

In order to improve the plate | board thickness precision of the lateral direction and the longitudinal direction of the shadow mask steel plate coil, the thickness precision of the steel plate which carries out preliminary primary cold rolling and hot rolling needs to be improved.

As a hot rolling finishing process, a work-roll corssing method has been conventionally used. The improvement of the lateral plate thickness precision of the hot rolled steel sheet has been expected and various advantages have been obtained.

However, in order to obtain a primary cold rolled steel sheet having more preferable sheet thickness precision, it is necessary not only to improve the plate thickness precision in the lateral and longitudinal directions of the hot rolled steel sheet, but also in the longitudinal mechanical properties of the hot rolled steel sheet coil. Needs to be homogenized. In a typical hot rolled steel sheet, the finish temperature, coiling temperature and cooling rate are different from the middle part at the top and bottom of the coil. Therefore, the mechanical properties in the longitudinal direction of the coil are very inhomogeneous, so that it is difficult to control the rolling load in the primary cold rolling, and thus it is sometimes impossible to obtain a primary cold rolled steel sheet having good thickness precision with high yield. For this reason, in order to apply primary cold rolled steel sheets with poor plate thickness precision to high-precision shadow masks, the number of rolling processes in secondary cold rolling must be increased, and the cutting length at the top and bottom of the coil is increased. Since is larger, the manufacturing cost of the steel sheet is increased and the yield is lowered.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ultra low carbon aluminum killed steel sheets for shadow masks used in color selection mechanisms such as CRTs and color displays of color TVs.

1 is a graph showing the relationship between the plate thickness of the primary cold rolled material and the length of the off gauge part in the case where the steel sheet is subjected to decarbonization annealing according to the present invention (example) and not (comparative example). ;

2 is a graph showing the change in yield strength in the longitudinal direction before and after decarbonization annealing of hot rolled steel sheets according to Examples 3, 14, 22 and 29 of the present invention;

3 is a graph showing the sheet thickness precision (ie, the difference between the desired hammer and actual thickness) in the longitudinal direction of a hot rolled steel sheet according to Examples 5, 6, 15, and 16 of the present invention;

4 is a graph showing the effect of sheet thickness and initial carbon content of hot rolled steel sheet on decarbonization annealing time;

5 is a graph showing the effect of the total cold rolling rate of the primary and secondary cold rolling, the finishing temperature during hot rolling, and the amount of carbon after decarbonization annealing on the yield strength of the secondary annealing material.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a shadow mask steel sheet having an excellent plate thickness precision in the longitudinal direction.

The first invention is less than 0.1 mass% of carbon (C), less than 0.05 mass% of silicon (Si), 0.1 to 0.5 mass% of manganese (Mn), less than 0.03 mass% of phosphorus (P), 0.001 to 0.05 mass Hot rolling a steel comprising% sulfur (S), 0.002 to 0.15 mass% aluminum (Sol.Al), 0.008 mass% or less nitrogen (N), and the balance being substantially composed of iron (Fe) ; Decarbonizing annealing the hot rolled steel sheet; And a cold rolling of the annealing steel sheet to a desired plate thickness.

The second invention is a method of manufacturing a shadow mask steel sheet according to the first invention, wherein the hot rolling step includes reheating and finishing rolling the steel after roughing.

In the third invention, in the hot rolling step, roughing is performed at a temperature of at least Ar ₃ point, and finish rolling is carried out by adjusting to a temperature lower than Ar ₃ point at least in the last rolling step. Or the manufacturing method of the steel plate for shadow masks which concerns on said 2nd invention.

The fourth invention is the manufacture of the shadow mask steel sheet according to any one of the first to the third invention, characterized in that the cold rolling comprises a first cold rolling step and a second cold rolling step. Way.

5th invention is a manufacturing method of the shadow mask steel plate which concerns on any one of said 1st invention-said 3rd invention characterized by performing said cold rolling once.

According to the present invention, by performing decarbonization annealing after hot rolling, it is possible to manufacture a steel sheet for shadow mask having excellent plate thickness precision in the longitudinal direction.

Hereinafter, the present invention will be described in more detail.

According to the object of the present invention, in order to manufacture a high quality steel sheet for shadow masks having improved sheet thickness precision in the longitudinal direction of the coil, it is necessary to improve the sheet thickness precision of the primary cold rolled material. As a result of examining the manufacturing method of the primary cold rolled material having improved plate thickness precision, the inventors found the following fact. In other words, if the mechanical properties of the upper and lower parts of the hot rolled steel sheet are significantly different from the middle part, the rolling load becomes uneven due to the plate thickness control function of the primary cold rolling, which is performed in tandem. Plate thickness changes easily along the direction.

According to the findings, the inventors have found that the decarbonization annealing using the open coil after the primary cold rolling is carried out before the primary cold rolling and after the hot rolling, while suppressing the increase in the manufacturing cost, the mechanical properties of the hot rolled steel sheet It was also found that primary cold rolled steel with excellent plate thickness precision can be obtained because it can be homogenized along the direction. In addition, according to the present inventors, it has also been found that it is possible to omit the secondary cold rolling, which has been known as an essential process, so that the manufacturing cost can be significantly reduced.

The present invention has been made on the basis of the finding of the above facts, and its object is to uniformize the longitudinal mechanical properties of the hot rolled coil by decarbonization annealing of the hot rolled coil to control the rolling load during the primary cold rolling. It is intended to obtain a cold rolled steel sheet having good sheet thickness precision by making it easy.

According to the present invention, the steel sheet for shadow mask having excellent sheet thickness precision can be obtained by reducing the number of processes in secondary cold rolling. Furthermore, it is also possible to omit the secondary cold rolling process itself.

Next, the chemical composition of the steel sheet for hot rolling and cold rolling after decarbonization annealing is demonstrated.

Carbon (C): The steel sheet for shadow mask obtained by the manufacturing method of the present invention is perforated by photoetching, secondary annealing (annealing before press forming), and press forming process. When spring-back or stretcher strain appears after press molding, the shape or aperture of the curved part changes, resulting in color drift or image distortion. Therefore, after the secondary annealing, a small yield strength and a small yield point extension are required as mechanical properties of the steel sheet for shadow mask. Recently, there is a tendency to lower the secondary annealing temperature for energy saving and rationalization, and it is necessary to suppress addition of carbide forming elements such as Ti, Nb, Zr, etc., which raises the recrystallization temperature of the steel sheet. In addition, since the secondary annealing temperature is low and decarburization of the steel sheet is difficult in the secondary annealing, the steel sheet for shadow mask needs an appropriate decarbonization treatment in the primary annealing. If the carbon content of the steel sheet increases before the decarbonization annealing, the decarbonization annealing time becomes long, resulting in an increase in the manufacturing cost. Therefore, the carbon content of the steel sheet for primary annealing treatment is 0.1 mass% or less.

Silicon (Si): Since Si forms a non-metallic material and deteriorates etching characteristics, the content thereof should be 0.05mass% or less.

Manganese (Mn): In order to prevent hot brittleness caused by the presence of sulfur (S), the content of Mn needs to be maintained at 0.1 mass% or more. However, if the content exceeds 0.5 mass%, the steel sheet is excessively hardened and the press molding characteristics deteriorate, so that an appropriate content of Mn is appropriately 0.1 to 0.5 mass%.

Phosphorus (P): P is a hardening element of steel, and it is recommended to maintain P content of 0.03mass% or less in the steel sheet for shadow mask because it causes surface unevenness during etching due to segregation.

Sulfur (S): S is an unavoidable element in the river. Too much S causes hot brittleness and surface irregularities during etching due to segregation of S. On the contrary, when the content of S is less than 0.001 mass%, the steel is easily nitrided during annealing and causes shape defects during press working. Therefore, the content of S is preferably suppressed as much as possible in a range that does not cause nitriding, and the appropriate range is 0.001 to 0.05 mass%.

Aluminum (Sol.Al): Al is an element necessary to fix solute N with AlN, to lower yield point elongation, and to suppress aging. However, if the content is increased more than necessary, the manufacturing cost is increased, so the proper content is 0.002 to 0.15 mass%.

Nitrogen (N): N is to increase the yield point, and as a result of aging causes the shape defect of the aperture during the pressing process, it is good to suppress as little as possible. The proper content is less than 0.008 mass%.

Next, the manufacturing method of this invention is demonstrated.

(Hot rolled)

The steel having the chemical composition is hot rolled. Hot rolling is carried out in a conventional general process. However, if finish rolling is carried out after reheating for temperature control and temperature homogenization in the lateral and longitudinal directions during finishing rolling of roughed steel, the plate thickness precision of the hot rolled steel sheet is further increased. Can be improved.

The reheating method is not particularly limited, but induction heating, direct heating, a method of winding the steel in the form of a coil and heating it in a box furnace may be applied.

When finish rolling is performed while the temperature of the roughed steel is cooled below Ar ₃ point, or finish rolling is performed while temperature is controlled to cool below Ar ₃ point during finish rolling, The crystals become too large. Then, the characteristic obtained after secondary annealing (anneal before press molding) softens more. As the thickness of the hot rolled steel sheet increases, the time required for decarbonization annealing becomes longer, and a larger rolling rate is required in cold rolling. If the rolling rate during cold rolling increases, the steel after the secondary annealing will have finer grains, thereby promoting hardening of the steel. Therefore, the thickness of the hot rolled steel sheet should be as thin as possible. The thickness of the hot rolled steel sheet is not particularly limited, but the steel having a carbon content of 0.01 mass% or less is preferably 2.8 mm or less, and the steel having a carbon content of more than 0.01 mass% and 0.1 mass% or less is preferably 2.3 mm or less. In this case, if the finish rolling is continuously performed by welding the roughly rolled steel to some extent, the rolling work of the thin hot rolled steel is stable and the plate thickness precision of the hot rolled steel sheet can be improved.

If the conventional work-roll crossing method and the rolling method of the steel sheet are used together with the hot rolling together, the sheet thickness precision in the lateral direction of the hot rolled steel sheet can be further improved, thereby obtaining a steel sheet for shadow mask having a higher sheet thickness precision.

(Decarbonization Annealing)

When the carbon content in the steel sheet is excessively high, cementite precipitates, the etching characteristics deteriorate, the yield strength increases, and the spring back after pressing increases. Decarbonization annealing is carried out for the purpose of suppressing this carbon content as much as possible. In addition, in the present invention, when the decarbonization annealing after hot rolling, the mechanical properties in the longitudinal direction of the hot rolled steel sheet are homogenized. Decarbonization annealing conditions are similar to those in conventional methods. For example, annealing atmosphere is a mixed gas atmosphere of hydrogen and nitrogen, annealing temperature is 650-800 degreeC, and dew point temperature is the range of 10-30 degreeC. The annealing time can be appropriately selected in consideration of the degree of decarbonization, the weight of the coil, the thickness of the steel sheet, and the like. If decarburization of the steel sheet is hardly performed during secondary annealing (annealing before press forming), it is preferable to decarbonize the steel sheet so that the carbon content is 0.0015 mass% or less from the viewpoint of pressing. When decarbonation annealing the hot rolled steel sheet, the steel sheet is pickled and rewinded into an open coil. In some cases, the steel sheet may be softened after the decarbonization annealing treatment because the distortion is imparted to the steel sheet by skin pass rolling, which may cause grain growth at the time of decarbonization annealing and before and after pickling.

(Cold rolled)

Cold rolling is carried out under the same conditions as the thickness of the cold rolled steel sheet. In general, secondary cold rolling is not necessary as long as the desired plate thickness precision can be obtained in the primary cold rolling. However, secondary cold rolling is carried out when it is necessary to adjust the surface roughness of the steel sheet or when more stringent sheet thickness precision is required. However, also in this case, the rolling process should only be performed once or twice. This is because the cold rolled steel of the present invention has excellent plate thickness precision in the longitudinal direction, so that the desired plate thickness precision can be easily obtained.

In the present invention, there is no particular limitation on the plate thickness of the primary cold rolled steel and the steel sheet for shadow mask. Recently, for the high resolution, the sheet thickness of the steel sheet having a range of 0.0020 to 0.20 mm is used for the shadow mask.

An embodiment of the present invention will be described.

The steels having the compositions A, B, C and D shown in Table 1 were hot rolled to obtain No. 1 ~ No. 72 hot rolled steel sheet was obtained. No. 1 ~ No. The hot rolled steel sheet of 37 was subjected to decarbonization annealing treatment. The decarbonization annealing treatment was carried out in an open coil type hot rolled steel sheet in a box furnace of H ₂ and N ₂ mixed gas atmospheres, with a dew point temperature of 30 ° C and a process temperature of 700 ° C. Decarbonization annealing was stopped when the atmosphere in the furnace reached a CO concentration of 0.05% or less (ie, the carbon content in the steel sheet was calculated to be 0.0015 mass% or less). The tested hot rolled steel sheet became a relatively good coil having a variation in plate thickness in the lateral and longitudinal directions of ± 30 µm or less.

Next, primary cold rolling was performed on the decarbonized annealing coils (No. 1 to No. 37) and the coils not subjected to decarbonization annealing (No. 38 to No. 72). The plate thickness of the primary cold rolled steel sheet is four types, that is, 0.15 mm (No. 1 to No. 33 and No. 38 to No. 68) in consideration of omission of the secondary cold rolling, and in consideration of the execution of the secondary cold rolling. 0.25 mm (No. 34, 35, 69 and 70), 0.40 mm (No. 36 and 71), and 0.65 mm (No. 37 and 72) were set. For each thickness type, the allowable plate thickness precision of the primary cold rolled steel was set in consideration of the plate thickness precision required for the high resolution steel sheet for shadow mask and the plate thickness precision that can be easily corrected in the secondary cold rolling. The length of the part exceeding the allowable range was measured by the length of the off gauge part.

For the primary cold rolled steel sheets (No. 1 to No. 37) subjected to decarbonization annealing in the hot rolling step, those having a plate thickness of 0.15 mm were left as they were, and those having a plate thickness of 0.25 mm or more were subjected to secondary cold rolling. It was. After the thickness of all the rolled materials became uniform to 0.15 mm, the yield strength was measured when a small sample was taken and subjected to secondary annealing in a 100% Ar atmosphere.

The process conditions of hot rolling, the carbon content of the decarbonized annealing steel sheet, the sheet thickness of the primary cold rolled steel sheet and the acceptable sheet thickness precision of the primary cold rolled steel sheet are shown in Tables 2 and 3. The relationship between the plate thickness of the primary cold rolled steel sheet and the length of the off gauge portion is shown in FIG. 1. The change in yield strength in the longitudinal direction of the hot rolled steel sheets (No. 3, 14, 22, and 29) before and after the decarbonization annealing treatment is shown in FIG. 2. From Table 2, the carbon content of almost all hot rolled steel sheets was less than 0.0015 mass% before and after the decarbonization annealing treatment, but in the same annealing time, the carbon content of some steel sheets slightly decreased to 0.0015 mass%. Exceeded.

1, the primary cold rolled steel sheet according to the plate thickness is shown. As a result, compared with the Example (No. 38-No. 72) which did not carry out the decarbonization annealing treatment, the off-gauge was performed in the Example (No. 1-No. 37) of the hot rolled sheet steel which performed the decarbonization annealing treatment. A cold rolled steel sheet with a small branch length and a smaller change in plate thickness in the longitudinal direction of the coil could be obtained.

Referring to Fig. 2, the steel sheet was softened and the change in the yield strength in the longitudinal direction was very small in the examples after the decarbonization annealing treatment (Nos. 3, 14, 22 and 29) compared with the example before the decarbonization annealing treatment. . From this fact, it was found that the homogenization in the longitudinal direction of the hot rolled steel sheet coil material improves the plate thickness precision of the primary cold rolled steel sheet.

3 shows an example (Nos. 5 and 15) of a hot rolled steel sheet in which finish rolling was performed without reheating during hot rolling, and an example (No. 6 and 16) of a steel sheet subjected to finish rolling after reheating. It compares and shows the plate thickness precision (difference between desired plate thickness and actual plate thickness). The sheet thickness precision in the Examples (Nos. 6 and 16) of the steel sheet subjected to finish rolling after reheating is better than that of the Examples (Nos. 5 and 15) without reheating. From this fact, it can be seen that, as shown in Table 2, the length of the off gauge portion after the primary cold rolling is significantly reduced.

4 shows the effect of the initial carbon content of the steel sheet and the plate thickness of the hot rolled steel sheet on the decarbonization annealing time (ie, the time required for the concentration of CO to be 0.05% or less in the furnace). The smaller the carbon content before the decarbonization annealing treatment and the smaller the plate thickness of the hot rolled steel sheet, the shorter the decarbonization time. Considering the manufacturing cost, the decarbonization annealing time is suitable within 20 hours. Therefore, the thickness of the hot rolled steel sheet is preferably 2.8 mm or less for steels having a carbon content of 0.01 mass% or less, and 2.3 mm or less for steels having a carbon content of more than 0.01 mass% and 0.1 mass% or less. Do.

FIG. 5 shows the influence of the total cold rolling rate of primary and secondary cold rolling, the finishing temperature at the time of hot rolling, and the carbon content after decarbonization annealing on the yield strength of the secondary annealing steel. As the total cold rolling rate decreases, the secondary annealed steel softens. In addition, even if the total cold rolling rate is the same, finish rolling is performed after the steel temperature becomes lower than Ar ₃ point during hot rolling, or when lowering to lower temperature than Ar ₃ point during finish rolling, finishing at a temperature of ₃ or more Ar points. In comparison with the case of rolling, the secondary annealed steel can be softened. Moreover, the rolled material having a carbon content of more than 0.0015 mass% after the primary annealing showed a relatively high yield strength after the secondary annealing.

C Si Mn P S Sol.Al N A 0.002 0.01 0.20 0.012 0.016 0.053 0.0027 B 0.004 0.01 0.18 0.008 0.005 0.060 0.0032 C 0.03 0.03 0.20 0.004 0.016 0.047 0.0064 D 0.06 0.01 0.15 0.012 0.008 0.050 0.0062

Item No. River Hot rolled Temperature before finishing rolling (℃) Finishing temperature (℃) Desired thickness (mm) Example One A 1020 890 3.0 2 2.8 3 2.3 4 2.0 5 1.8 6 1080 (Reheat after roughing) 7 960 830 (lower than ₃ Ar) 8 1.2 9 0.8 10 870 (lower than ₃ Ar) 0.8 11 B 1000 870 2.8 12 2.6 13 2.3 14 1.8 15 1.2 16 1050 (Reheat after roughing) 17 930 830 (lower than ₃ Ar) 18 0.8 19 C 980 850 2.6 20 2.3 21 2.0 22 1.8 23 1.2 24 1.0 25 890 750 (lower than ₃ Ar) 26 0.8 27 D 980 870 2.3 28 2.0 29 1.8 30 1.2 31 1.0 32 870 730 (lower than ₃ Ar points) 33 0.8 34 A 1020 890 2.3 35 C 980 870 1.8 36 37

Item No. River Decarbonation Annealing Decarbonation Annealing Time (hr) Carbon content after decarbonization annealing (%) Primary cold rolling Desired thickness (mm) Length of off gauge part (m) Permissible Plate Thickness Accuracy (㎛) Example One A Execution 21.0 0.0011 0.15 40 ± 2 2 13.5 0.0013 35 3 5.5 0.0008 62 4 3.5 0.0003 56 5 3.0 0.0012 45 6 3.0 0.0011 30 7 3.1 0.0009 51 8 2.0 0.0010 68 9 1.5 0.0008 77 10 1.6 0.0005 72 11 B 20.0 0.0018 44 12 15.0 0.0016 42 13 10.0 0.0012 52 14 5.0 0.0008 43 15 3.0 0.0004 72 16 3.0 0.0003 33 17 3.3 0.0005 65 18 2.0 0.0004 76 19 C 23.0 0.0017 0.15 51 ± 2 20 17.5 0.0016 41 21 13.0 0.0010 45 22 9.0 0.0012 53 23 5.0 0.0008 61 24 4.2 0.0007 55 25 4.0 0.0009 63 26 3.0 0.0005 45 27 D 20.0 0.0017 30 28 16.0 0.0018 36 29 11.0 0.0016 32 30 5.5 0.0009 63 31 4.7 0.0007 58 32 4.5 0.0010 62 33 3.5 0.0010 58 34 A 5.5 0.0012 0.25 47 ± 3 35 C 9.0 0.0008 44 36 9.0 0.0007 0.4 36 ± 5 37 9.0 0.0010 0.65 28 ± 6

Item No. River Hot rolled Temperature (℃) before finish rolling Finishing temperature (℃) Desired thickness (mm) Comparative example 38 A 1020 850 3.0 39 2.8 40 2.3 41 2.0 42 1.8 43 960 830 (lower than ₃ Ar) 1.8 44 1.2 45 0.8 46 870 (lower than ₃ Ar) 0.8 47 B 1000 870 2.8 48 2.6 49 2.3 50 1.8 51 1.2 52 930 800 (lower than ₃ Ar points) 1.2 53 0.8 54 C 980 850 2.6 55 2.3 56 2.0 57 1.8 58 1.2 59 1.0 60 890 750 (lower than ₃ Ar) 1.2 61 1.0 62 D 980 870 2.3 63 2.0 64 1.8 65 1.2 66 1.0 67 870 730 (lower than ₃ Ar points) 1.0 68 0.8 69 A 1020 890 2.3 70 C 980 870 1.8 71 72

Item No. River Decarbonation Annealing Primary cold rolling Desired thickness (mm) Length of off gauge part (m) Permissible Plate Thickness Accuracy (㎛) Comparative example 38 A Do not run 0.15 95 ± 2 39 102 40 87 41 115 42 86 43 92 44 98 45 126 46 115 47 B 105 48 121 49 85 50 96 51 111 52 93 53 102 54 C 0.15 104 ± 2 55 96 56 110 57 98 58 104 59 124 60 112 61 121 62 D 87 63 92 64 96 65 89 66 86 67 91 68 88 69 A 0.25 65 ± 3 70 C 74 71 0.4 51 ± 5 72 0.65 43 ± 6

Claims (5)

0.1 mass% or less carbon (C), 0.05 mass% or less silicon (Si), 0.1-0.5 mass% manganese (Mn), 0.03 mass% or less phosphorus (P), 0.001-0.05 mass% sulfur (S ), Hot rolling a steel comprising 0.002 to 0.15 mass% of aluminum (Sol.Al) and 0.008 mass% or less of nitrogen (N), the balance being substantially composed of iron (Fe); Decarbonizing annealing the hot rolled steel sheet; And A method for producing a steel sheet for shadow mask having excellent precision in the longitudinal thickness of the sheet including the step of cold rolling the annealed steel sheet to a desired sheet thickness. The method of claim 1, wherein the hot rolling step comprises reheating the steel after roughing to finish rolling the steel sheet for the shadow mask. The method according to claim 1 or 2, wherein in the hot rolling step, roughing is carried out at a temperature of at least ₃ Ar points, and finish rolling is carried out by adjusting to a temperature lower than Ar ₃ at least in the last rolling step. A method for producing a steel sheet for shadow mask having excellent sheet thickness precision in the longitudinal direction. 4. The method of claim 1, wherein the cold rolling comprises a first cold rolling step and a second cold rolling step. . The said cold rolling is performed once, The manufacturing method of the shadow mask steel plate excellent in the longitudinal-plate thickness precision of any one of Claims 1-3 characterized by the above-mentioned.