KR100262487B1 - Method of manufacturing cold rolling steel sheet with using shadowmask - Google Patents

Abstract

PURPOSE: Provided is a method for manufacturing cold rolled steel sheets for shadow mask which has superior etching property and shape uniformity even without decarburization process. CONSTITUTION: The cold rolled steel sheet having superior etching property and shape uniformity is manufactured by heat treating a super low carbon Al-killed steel slab comprising C 0.005wt.% or less, Mn 0.1-0.4wt.% or less, P 0.03wt.% or less, S 0.015wt.% or less, sol-Al 0.06wt.% or less, N 0.004wt.% or less, Cr 0.02-0.04wt.% or less, Ti 0.03-0.05wt.% or less, a balance of Fe, and other inevitable impurities in the temperature range of 1200 to 1250deg.C; finish rolling at over Ar3 transformation point; coiling it in the temperature range of 640 to 680deg.C; cold rolling the steel sheet to final thickness at a reduction rate of 85% or higher; continuous annealing within the temperature range of 640 to 680deg.C; and then carrying out conventional skin-pass.

Description

Manufacturing method of cold rolled steel sheet for shadow mask

1 is a graph showing the relationship between secondary annealing invention material and comparative material.

The present invention relates to a method for manufacturing a cold rolled steel sheet for a shadow mask in a color TV brown tube and a monitor brown tube, and more particularly, to manufacturing a cold rolled steel sheet for shadow mask having excellent etching property, formability and shape uniformity. It is about a method.

The shadow mask is made up of hundreds of thousands of fine holes, and serves as color screening by reaching the fluorescent surface with electron beams from the electron gun. Cold rolled steel sheets used in such shadow masks are usually hot rolled, pickled, cold rolled and decarbonized using Cr-added low carbon Al-kilted steel. Recently, Cr-added ultra-low carbon Al-kilted steel is hot rolled, pickled, cold rolled, and annealed. It is becoming. The cold-rolled product thus manufactured is made through a photo-etching process to make fine holes, and then secondly annealed by a CRT manufacturer, and then formed into a curved surface and mounted on the CRT through a black film treatment.

In general, the shadow mask should have excellent etching characteristics and surface characteristics. In order to have excellent etching characteristics, the plate thickness of the cold rolled steel sheet, which is a material, should be uniform, and the shape should be excellent. Shape uniformity should be excellent without the resulting stretcher-strain.

On the other hand, low carbon Al-killed steel, which is commonly known as decarbonized annealing and cold rolling twice, has been added with Cr in order to improve black film adhesion, which has been a problem in Al-killed steel. In addition, a separate facility investment such as a secondary cold rolling mill to obtain an excellent shape is required, and a complicated manufacturing process causes a significant increase in manufacturing cost.

In order to remedy these disadvantages, the recently developed ultra low carbon based Cr-added low carbon Al-killed steel has a stretcher due to the presence of solid elements in the molding after secondary annealing of the etched material in the manufacture of shadow masks. In order to prevent the occurrence of strain-strain, a small amount of Nb is added. Nb fixes only the [C] of the employment elements, thereby completely preventing the strainer-strain caused by the other employment elements [N] and [S]. Nothing appears to be a disadvantage.

Therefore, the present invention has been proposed to solve the above-mentioned conventional problems, and the present invention provides Ti and blackening, which can fix solid elements [C], [N], and [S] of carbonaceous materials, sulfides, and sulfides. The ultra-low carbon Al-kilted steel containing a small amount of Cr, an element that improves the film adhesion, is rolled under normal hot rolling conditions including a low hot rolling temperature, and cold rolled to a final thickness by one cold rolling, without undergoing decarbonization. An object of the present invention is to provide a method for manufacturing a cold rolled steel sheet for a shadow mask having excellent etching uniformity when yielding fine holes as well as excellent uniformity of yield point at 0%.

Hereinafter, the present invention will be described.

The present invention is a method for producing a cold rolled steel sheet for shadow mask, in weight%, C: 0.005% or less, Mn: 0.1-0.4%, P: 0.03% or less, S: 0.015% or less, Sol-Al: 0.06% or less , N: 0.004% or less, Cr: 0.02-0.04%, Ti: 0.03-0.05%, and the remainder homogenize ultra low carbon Al-kilted steel composed of Fe and inevitable impurities in the temperature range of 1200-1250 ° C. After treatment, finish rolling directly above the Ar ₃ transformation point, wound at a temperature in the range of 450-550 ° C., cold rolled to the final thickness with a reduction ratio of 85% or more, then continuously annealed in the range of 640-680 ° C. The present invention relates to a method for producing a cold rolled steel sheet for shadow mask, which is rolled.

Hereinafter, the present invention will be described in detail.

When the carbon content is more than 0.005%, the amount of carbide is increased to deteriorate the etching characteristics in the photo-etching process, and the increase of the solid solution carbon causes the yield point to be stretched after the final annealing, thereby degrading the press formability and shape uniformity. It is preferable to limit it to 0.005% or less, and the lower the carbon content, the better.

When the Mn content is more than 0.4%, the material is hardened or the molding is deteriorated due to Mn solid solution strengthening. When the Mn content is less than 0.10%, the hot brittle element S cannot be sufficiently fixed. The content is preferably limited to 0.10-0.40%.

The P is a substitution alloy element having the largest solid solution effect, and when added in an amount of 0.03% or more, the material hardening and moldability deteriorate. Therefore, the content of P is preferably limited to 0.03% or less.

S is a fragile element with hot brittleness, and the lower the component range, the better. Further, the lower limit is 0.015% in order to lower Mn because it precipitates as Mn-based sulfide.

Al is a component added for deoxidation of steel, and if the amount is 0.06% or more, it causes material hardening. Therefore, the Al content is preferably limited to 0.06% or less.

As N is an invasive element, it inhibits {111} texture and impairs processability, impedes grain growth, and lowers elongation. Therefore, N is better for processability, and the upper limit thereof is limited to 0.004% to minimize aging. desirable.

The Cr is an element that improves black film adhesion. When the black film adhesion is deteriorated, small pieces of black film dropped in the CRT degrade the color of the TV screen and degrade the withstand voltage characteristics. Therefore, a small amount of Cr may improve the adhesion. However, when the Cr content is less than 0.02%, the effect is weak, and when the Cr content is more than 0.04%, the blackening film adhesion improvement is not only saturated, but also increases the manufacturing cost and material hardening effect.

On the other hand, the Ti precipitates the solid solution element (carbon, nitrogen, sulfur) by TiC, TiN, TiS lowers the yield strength after the second annealing and serves to suppress the generation of stretcher strain by removing the yield point stretch. In general, the yield strength after the second annealing and the stretcher strain generated during molding are increased in proportion to the amount of solid solution present in the steel. Ti addition in the present invention does not require a decarbonization furnace, which is a conventional process, and also has a function of completely depositing solid solution elements compared to Nb addition to lower yield strength and remove stretcher strain. However, if the amount of Ti is 0.03% or less, the solid solution cannot be effectively precipitated. If the amount of Ti is more than 0.05%, it is preferable to limit the amount of Ti to 0.03-0.05% because the formation of a large amount of precipitate may inhibit the etching characteristics.

The continuously cast slab manufactured to have the composition as described above is heated at 1200-1250 ° C. where the austenitic structure before hot rolling can be sufficiently homogenized, and then finish hot rolling is performed directly above the Ar ₃ temperature. If the hot finishing rolling temperature is less than the Ar ₃ transformation point, it is rolled in the ferrite + pearlite two-phase structure, so abnormal coarse grains are generated, which causes defects in processing the product. Therefore, the hot finish rolling temperature is preferably limited to around 910 ℃ which is more than the Ar ₃ transformation point.

The hot rolled steel sheet is preferably wound at a temperature in the range of 450-550 ° C. The reason is that when the winding temperature is higher than 550 ° C, the precipitates of Ti added for the purpose of preventing the strain strain are coarsened. This results in deterioration of the etching characteristics in the etching process. In addition, it is preferable to limit the temperature to 450-550 ° C. when the low temperature of less than 450 ° C. causes a large temperature deviation inside and outside the coils, causing variations in the material in the coil.

In the conventional process, the hot rolled steel sheet pickled by the conventional method is first cold rolled at a cold reduction rate of about 70%, and then subjected to recrystallization annealing from the decarbonization furnace to the ultra low carbon level, followed by secondary cold rolling to the final thickness. However, in the present invention, it is possible to omit the decarbonization furnace and the secondary cold rolling process.

To this end, in the present invention, the hot rolled plate subjected to pickling in a conventional method is cold rolled to a final thickness at a reduction ratio of 85% or more by one cold rolling, and then tempered rolling is performed by recovery annealing and a conventional method.

In this case, the cold rolling rate varies depending on the required thickness of the shadow mask. Therefore, cold rolling is carried out in consideration of shape and thickness precision control. When cold rolling is performed with the cold rolling rate being 85% or less, a cold rolled sheet having the same thickness is obtained. Since it means that the thickness of the hot rolled sheet required for the thinning is applied to the hot rolling process, the problem of deterioration of the shape of the hot rolled sheet occurs, so it is preferable to carry out the rolling reduction ratio in the cold rolling range of 85% or more.

On the other hand, since it is very difficult to give the surface roughness required for the shadow mask during cold rolling, a temper rolling process for surface roughness is required. However, the cold rolled steel sheet is difficult to temper rolling because the material is hardened, so it is necessary to continuously anneal at 640-680 ° C, which is a temperature at which the tissue can be recovered. At this time, when the annealing temperature is 680 ° C or more, the ferrite structure may be completely recrystallized, and thus the etching characteristics may be changed in the etching process.

Hereinafter, the present invention will be described in detail through examples.

Example 1

To prepare a steel slab by dissolving the ultra-low carbon Al-killed steel in the converter to have a composition as shown in Table 1 after the out-refining treatment and continuous casting. At this time, both the invention steel (1-3) and the comparative steel (4-6) shown in Table 1 are the final steel components after the external refining, the comparative steel (7) is decarbonized annealing steel with a carbon content of 0.02% before decarbonization The final steel component produced by application is shown.

In addition, the comparative steel 4 is a steel without Ti, and in the case of the comparative steel 5, it is a can steel without adding Cr. In the comparative steel 6, Nb was added without adding Ti. Indicates a steel grade.

TABLE 1

The steel slab having the composition as shown in Table 1 was homogenized at a temperature of 1250 ° C., followed by finishing hot rolling to a thickness of 2.0 mm near 910 ° C., which is directly above Ar ₃ , and then wound at the hot rolling temperature indicated in Table 3. Pickling was performed and pickling was carried out in a usual manner. The pickled hot rolled steel sheet was applied to a manufacturing process as shown in Table 2 below to obtain a cold rolled steel sheet having a thickness of 0.25 mm. At this time, the cold reduction rate, the annealing temperature was carried out under the conditions shown in Table 3.

TABLE 2

TABLE 3

As shown in Tables 2 and 3 above, the invention materials added with Ti to fix the solid solution elements ([C], [N], [S]) to prevent the aging recovery recovery annealing to improve the etching characteristics during the etching process Hot rolled low temperature winding was performed.

As shown in Table 3, in the case of the invention material (1-3), it was confirmed that the porosity excellent in workability and characteristics during the etching operation, excellent in blackening film adhesion, and also excellent in shape uniformity. On the other hand, the comparative material (1A) in which the inventive steel (1) was annealed at a recrystallization temperature of 720 ° C., compared to the hard material, deteriorated workability and etching characteristics. Moreover, in the comparative material 2A which wound the invention steel 2 at 650 degreeC of high temperature, Ti-type precipitate coexisted and the etching characteristic worsened. In addition, in the case of the comparative material 4, the shape uniformity due to aging was poor without adding Ti, and in the case of the comparative material 5, Cr was not added, so that the adhesion of the blackening film was deteriorated. In addition, in the case of the comparative material 6, Nb was added instead of Ti. Since Nb could not fix all of the solid solution elements that cause aging, the shape uniformity due to aging was poor, and the excessive coercivity was poor due to the grain refinement by Nb. woke up. In the case of the comparative material (7), the characteristic evaluation is excellent, but unlike the present invention, decarburization annealing after primary cold rolling is completely recrystallized, and then secondary cold rolling is applied again. There are disadvantages.

Example 2

In order to evaluate the formability after secondary annealing, which is one of the important characteristics required for the steel sheet for shadow mask, secondary annealing was performed on the inventive steel and the comparative steel under actual conditions.

At this time, the second annealing was heat-treated at 20% H ₂ + 80% N ₂ atmosphere at 750 ° C. for 10 minutes, and the result was a room temperature tensile test with a crosshead speed (CROSS-HEAD SPEED) of 10 mm / min. Shown in In addition, the curve of the stress-strain for the invention material (1) and the comparative material (4) is shown in FIG.

In general, the secondary annealing shadow mask steel sheet has a yield point elongation of 0 in order to suppress the occurrence of stretcher strain during molding so that shape uniformity is good, and to ensure shape freezing of the molded shadow. The yield strength is required to be 13 kg / mm 2 or less. As shown in Table 4 and FIG. 1, the present invention material (1-3) satisfies the above two conditions well, but the comparative material (4, 6) In the case of high yield strength and yield point elongation, mold failure is expected. On the other hand, the comparative material (7) exhibits the same mechanical properties as the invention material, but unlike the present invention, the manufacturing process using this steel uses decarbonization annealing and two cold rolling processes, which require additional decarbonization annealing. There are disadvantages.

TABLE 4

As described above, according to the present invention, by adding a small amount of Ti to the ultra low carbon Al-kilted steel, precipitated solid elements ([C], [N], [S]) in the steel as carbon, quality, sulfide, hot rolled and cold Etchability and formability with the elongation of '0' at the yield point of the secondary annealing plate after the cold rolling by controlling the rolling conditions, followed by recovery annealing in a continuous annealing furnace used for ordinary cold rolled steel annealing. The steel sheet for shadow mask excellent in shape freezing can be manufactured.

Claims (1)

In the manufacturing method of the cold rolled steel sheet for shadow mask, in weight%, C: 0.005% or less, Mn: 0.1-0.4%, P: 0.03% or less, S: 0.015% or less, Sol-Al: 0.06% or less, N: 0.004% or less, Cr: 0.02-0.04%, Ti: 0.03-0.05%, and the remainder after homogenization of ultra-low carbon Al-killed steel slab composed of Fe and inevitable impurities in the temperature range of 1200-1250 ℃ , Finish rolled directly above the Ar ₃ transformation point, wound at a temperature in the range of 450-550 ° C., cold rolled to the final thickness with a reduction ratio of 85% or more, continued annealing in the range of 640-680 ° C., and the usual temper rolling. A method for producing a cold rolled steel sheet for a shadow mask, characterized in that the work.