KR100368255B1 - A method of manufacturing blackplate with lower planar anisotropy - Google Patents

Abstract

The present invention relates to a method of manufacturing a cold-rolled steel sheet for a tin-plated steel sheet having a low planar anisotropy, and its object is to provide a method for manufacturing a cold- And to provide a method for manufacturing cold-rolled steel sheets for T4 grade tin-plated steel sheet in which anisotropy is reduced and processing defects such as earing are suppressed during processing such as deep-drawing.

In order to accomplish the above object, the present invention provides a method of producing a cold rolled steel sheet for a tinplate steel sheet, comprising the steps of: 0.045-0.060% carbon, 0.2-0.5% manganese, 0.02-0.05% aluminum, 0.001% or less of nitrogen, 0.01% or less of sulfur, and an aluminum killed steel having an atomic ratio of manganese to sulfur of 15-30 and other unavoidable impurities is homogenized at 1200-1250 ° C , Hot finish rolling is performed at 880-900 占 폚, hot rolling is performed at 640-700 占 폚, cold rolling is performed at a cold rolling reduction rate of 85.5-87.0%, continuous annealing is performed at a temperature range of 650-700 占 폚 (111) / {I (110) + I (200)} is controlled so as to be 2.0-3.5. It is about the method.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cold rolled steel sheet for a tinplate steel sheet having a low planar anisotropy,

The present invention relates to a method of manufacturing a cold-rolled steel sheet (hereinafter, also referred to as a "seaweed disc") used for a tinplate steel sheet. More specifically, the present invention relates to a cold- And to a method for manufacturing a stone disc.

The cold-rolled steel sheet for the tin plate is used as a container for storing various beverages and foods because the surface is beautiful and has excellent corrosion resistance to the contents when tin-plated. The material of the tin plate and the tin plate coated with tin on the surface are evaluated by the quality of Rockhwell surface hardness (HR30T) and the quality is T1 (49 ± 3), T2 (53 ± 3) and T3 (57 ± 3), and hard stone discs of T4 (61 ± 3), T5 (65 ± 3) and T6 (70 ± 3). In addition, according to the method of producing the stone disk, the SR (Single Reduced) method in which a hot-rolled sheet is subjected to primary cold rolling in order to obtain a final thickness, annealing is carried out to obtain a target material, (Double Reduced) method in which the material subjected to cold rolling and annealing is subjected to secondary cold rolling to reduce the thickness and increase the strength of the material. Particularly, in the case of passing through the second cold rolling, the material saving effect and the high strength due to the reduction in thickness are also excellent as the container for food storage to prevent damage from external impacts.

The raw stone for plaster which is used as a material for a container requiring a high degree of processing has been mainly manufactured by the stitching method. However, since it requires a long annealing time, productivity is low and the material of the steel sheet is not uniform in width and length . Therefore, in recent years, the ratio of production by applying the continuous annealing method, which has a low production cost, uniform material, and excellent flatness and surface characteristics, is increasing.

On the other hand, in the case of container materials, it is used to store the contents after processing. Therefore, in order to secure the storage stability of the stored materials and the stability in the manufacturing process, .

As a method of processing the container, there is a method of processing without welding such as a two-piece can consisting of two parts of the container and the body, and a method of processing the can with the body, the upper lid and the lower lid And the like, which is generally manufactured by welding or the like, such as 3-Pscan which is composed of three parts. The method of welding without welding is a method of drawing a tinplate steel sheet or ironing it after ironing. In the case of a pipe-making method for welding, generally, the upper and lower lids are processed and attached, And then processed into a disk.

In the process of manufacturing a two-piece can, the height of the cup processed in the drawing process is not constant, and the height tends to appear differently from the shape of the ear. This is called an ear. It is known that ear generation in such a cup is a phenomenon related to planar anisotropy of a material, and it is possible to suppress occurrence of ear when planar anisotropy is small. Since the ear generated in the drawing process must be cut (or trimmed) at a predetermined height to finally fill the lid of the can, it is necessary to remove the ear, so that it is preferable to reduce the occurrence of ear. In addition, when the ear is severe, the can is caught by the tool and it is a factor to lower the workability.

The ears that occur during the processing of the tinplate steel sheet are caused by the difference in workability in the rolling direction due to the change of the manufacturing process of the material, and the height of the ears is increased in the direction of good workability. In the direction of relatively low workability, The difference in the height of the ears is increased as the difference in the workability by the direction increases. In order to minimize the occurrence of ear, it is desirable to minimize the difference in workability in each direction. In general, the workability is greatly influenced by the texture structure developed in the material. Thus, the occurrence of the ear is greatly influenced by controlling the aggregate tissue by a proper manufacturing process, which means that the occurrence of the ear can be reduced by controlling the aggregate tissue by an appropriate manufacturing process. The texture of the ear to the ear is different depending on the manufacturing process of the material, and it is influenced by the chemical composition and cold rolling.

Thus, the ear formation at the time of drawing processing is influenced by the texture, and the degree of earing can be evaluated as planar anisotropy (Δr). _{Where, Δr = (r 0 + r} 90 -2r 45) / represents a two, which workability in 45 ° direction with respect to the workability (r ₉₀₎ in the working property in the rolling direction (r ₀₎ and 90 ° direction (r ₄₅ ). That is, the planar anisotropy indicates the difference in workability in each direction, and the greater the absolute value of the value of r (|? R |), the greater the difference in workability between directions. Also, when Δr is 0, it indicates that there is no difference in machinability between directions. The planar anisotropy is influenced by the texture of the material, and when there is a specific texture, the value of Δr is the smallest and the occurrence of the ear is minimized.

The planar anisotropy is influenced by the texture, and the texture is influenced by the manufacturing conditions of the material. Therefore, by changing the texture by adjusting the manufacturing conditions, it is possible to manufacture a cold rolled steel sheet having few ear holes. On the other hand, the texture that develops on the cold-rolled steel sheet is very diverse such as (110), (200), (211), (554), (222) The correlation between the ratio of the tissue to the ear and the occurrence of ear is very important.

(222), (110), and (200), which affect the planar anisotropy and affect the ear formation in the drawing process. Therefore, control of these texture components is required.

The present inventors have repeatedly conducted research and experiments in order to meet the above demand, and have made the present invention based on the results. The present invention has been made to solve the above- By appropriately controlling the structure, it is possible to manufacture a cold-rolled steel sheet for a rough grade T4 grade tin-plated steel sheet in which planar anisotropy is reduced and processing defects such as ear formation are suppressed during processing such as deep drawing Which has the purpose.

In order to accomplish the above object, the present invention provides a method of producing a cold rolled steel sheet for a tinplate steel sheet, comprising the steps of: 0.045-0.060% carbon, 0.2-0.5% manganese, 0.02-0.05% aluminum, 0.001% or less of nitrogen, 0.01% or less of sulfur, and an aluminum killed steel having an atomic ratio of manganese to sulfur of 15-30 and other unavoidable impurities is homogenized at 1200-1250 ° C , Hot finish rolling is performed at 880-900 占 폚, hot rolling is performed at 640-700 占 폚, cold rolling is performed at a cold rolling reduction rate of 85.5-87.0%, continuous annealing is performed at a temperature range of 650-700 占 폚 (111) / {I (110) + I (200)} is controlled so as to be 2.0-3.5. ≪ / RTI >

Hereinafter, the present invention will be described in detail.

The present invention relates to an improved method for manufacturing a cold rolled steel sheet for a tinplate steel sheet capable of suppressing occurrence of ear when a continuous annealing method is applied using low carbon aluminum killed steel, Will be described.

If the content of the carbon (C) is less than 0.045%, it is difficult to secure the desired quality of the T4 grade material. If the content of the carbon (C) exceeds 0.060%, the hardness increases but the corrosion resistance of the machined can decreases, , It is preferable to limit it to 0.045-0.060%.

If the content of manganese (Mn) is less than 0.2%, it is difficult to prevent the embrittlement of embrittlement caused by sulfur and make the steel weak, and it is difficult to secure the target quality of the quality of T4 material. If it exceeds 0.5% There is a problem that the segregation band on the band is formed to deteriorate the workability of the final product and also to lower the rolling property. Therefore, it is preferable to limit the ratio to 0.2-0.5%.

The aluminum (Al) is added for deoxidation, and nitrogen in the steel is precipitated in the form of aluminum nitride (AlN) to inhibit strain aging by solid nitrogen. If it is less than 0.02%, the addition effect is insignificant. If it exceeds 0.05%, the production cost increases. Therefore, it is preferable that the addition amount is limited to 0.02-0.05%.

When phosphorus (P) is contained in steel, it is advantageous to easily obtain hardening effect of material as a strong reinforcing element. However, in the case of a can material, when phosphorus is added in a large amount, corrosion resistance of the container is lowered, It is segregated at the grain boundaries to cause secondary process brittleness, which deteriorates the processability of the final product. Therefore, in the present invention, the content thereof is preferably limited to 0.015% or less for securing the properties.

Although nitrogen (N) has a large effect of increasing the hardness by solid solution strengthening, it causes deformation aging due to solid nitrogen when it is added in excess, deteriorating workability. Therefore, in order to secure a stable material, .

Since the sulfur (S) partially binds to manganese and precipitates as a sulfide-based precipitate, there is a fear of excessive hot brittleness if the amount of sulfur is not strictly controlled. Therefore, in the present invention, the content is limited to 0.01% or less .

On the other hand, since the atomic ratio of manganese and sulfur can not only determine the size and distribution of manganese sulfide precipitates but also act as a cause of cracking in the performance stage, its control is important from the standpoint of ensuring the material stability. In the steel of the present invention, when the atomic ratio of manganese and sulfur is low (less than 15), it acts as a cause of the embrittlement brittleness. When the elemental ratio exceeds 30, the molten manganese content increases to secure the desired quality and workability It is preferable to limit the atomic ratio of manganese and sulfur to 15-30.

In the following, a method of manufacturing a cold-rolled steel sheet using the aluminum killed steel as described above will be described in detail

In the present invention, the aluminum killed steel as described above is homogenized at 1200-1250 ° C.

When the reheating temperature of the slab is less than 1200 ° C, the material does not become a uniform austenite grain state and blistering occurs. When the temperature exceeds 1250 ° C, the scale layer is excessively formed on the surface, The treatment is preferably carried out at 1200 to 1250 占 폚.

Further, in the present invention, the finish hot rolling is performed at 880 - 900 占 폚.

When the temperature of the finish hot rolling is lower than 880 캜, which is lower than the austenite single phase reverse temperature, the ferrite structure is promoted to be blistered and the rolling load is increased during hot rolling to deteriorate the productivity, The tail portion and the like fall into the two-phase region of the ferrite and the austenite, which causes deterioration of workability. On the other hand, if the temperature exceeds 900 ° C, the workability of steel is deteriorated by coarsening of ferrite grains. Therefore, in the present invention, it is preferable to limit the working range of the finish hot rolling to 880 - 900 占 폚, which is a direct transformation temperature of Ar ₃ .

In the present invention, hot rolling is performed at 640-700 占 폚.

If the coiling temperature is lower than 640 占 폚, the workability may deteriorate. On the other hand, at the coiling temperature exceeding 700 占 폚, not only the corrosion resistance of the final product is deteriorated due to the coarsening of carbide, It is preferable to limit the hot rolled coiling temperature to 640-700 占 폚 in the present invention because it induces defects such as orange peel in which defects having the same shape as the orange surface occur.

In the present invention, cold rolling is performed after hot rolling under the above-described conditions, and cold rolling is performed at a cold rolling reduction rate in the range of 85.5-87.0%.

When the cold rolling reduction rate is less than 85.5%, as the ratio of the texture decreases, the planar anisotropy is increased, and ear production in the direction of 0 deg. On the other hand, when the cold rolling reduction rate exceeds 87.0%, it is difficult to secure the target tempering degree due to the hardening effect of the material due to work hardening, and as the plastic deformation ratio (r value) in the rolling direction increases, The absolute value of? R, which is a measure of the anisotropy, increases, thereby causing a deterioration of the drawing processability. Therefore, in the present invention, it is preferable that cold rolling is carried out at a reduction rate of 85.5-87.0%.

In the present invention, continuous annealing is performed in a temperature range of 650-700 캜.

When the annealing is carried out at a temperature of less than 650 ° C, recrystallization of the ferrite crystal grains is not completed and some deformed grains remain. However, the hardness is high, while the workability is remarkably low . On the other hand, if the work is performed at a temperature exceeding 700 ° C, the hardness can be lowered by the growth of the ferrite crystal grains, but since the thickness of the cold rolled steel sheet for a tinplate steel sheet produced usually is thin to about 0.30 mm, Which is not only difficult to control but also acts as a factor to cause defects such as heat buckles during the annealing operation, thereby remarkably reducing annealing workability. Therefore, in the present invention, continuous annealing is performed in a temperature range of 650-700 占 폚, which is a temperature range in which productivity can be ensured while attaining desired physical properties.

On the other hand, when the ratio of the texture shown as the face strength of I (111) / {I (110) + I (200)} is less than 2.0, ear generation at 0 ° and 90 ° orientations to the rolling direction occurs severely, And if it is more than 3.5, the occurrence of ear becomes severe in the direction of 45 ° with respect to the rolling direction. Thus, it is possible to control the aggregate texture ratio to 2.0 to 3.5 by producing the cold-rolled steel sheet by the stretching property and the manufacturing method as in the present invention.

Hereinafter, the present invention will be described in more detail by way of examples.

Example

The steel and the conventional low carbon steel satisfying the conditions of the present invention were prepared. The composition of the steel and the Mn / S atomic ratio were as shown in Table 1 below.

Component composition (% by weight) Mn / S atomic ratio C Mn P S s.Al N Ti Inventive steel 0.049 0.35 0.011 0.008 0.036 0.0024 - 25.5 Invention river b 0.046 0.31 0.012 0.009 0.041 0.0019 - 20.1 Inventive Steel c 0.054 0.27 0.009 0.009 0.035 0.0026 - 17.5 Comparative steel a 0.0046 0.25 0.013 0.008 0.031 0.0018 0.034 18.2 Comparative river b 0.039 0.21 0.014 0.009 0.043 0.0029 - 13.6 Comparative Steel c 0.046 0.24 0.014 0.010 0.029 0.0019 0.024 14.0 Comparative River d 0.069 0.43 0.012 0.006 0.038 0.0027 - 41.7

The prepared steels were each subjected to hot rolling, cold rolling and annealing under the conditions shown in Table 2 below to obtain cold-rolled steel sheets. The hardness (HR30T) of the obtained cold-rolled steel sheet, the texture ratio, the degree of earing at the time of canning, and the processability were measured and the results are shown in Table 2 below. In this case, the texture ratio is expressed as a ratio of the strengths of I (111) / {I (110) + I (200)}, and the earing rate is represented by the difference between the maximum height Hmax and the minimum height Hmin And expressed as a percentage divided by the minimum height of the molding cup. That is, the ear generation rate (%) was calculated as {(Hmax-Hmin) / Hmin} × 100. In addition, the processability was evaluated as good when workability was good and poor when it was poor.

Steel grade Coiling temperature (캜) Cold Percentage (%) Annealing temperature (캜) Hardness (HR30T) Set organization fee Ear rate (%) Processability Comparative Example 1 Inventive steel 660 84.5 660 58.49 1.46 3.65 × Inventory 1 Inventive steel 660 86.0 680 59.02 2.21 1.58 ○ Comparative Example 2 Inventive steel 660 88.5 680 61.35 4.69 4.12 × Inventory 2 Invention river b 680 86.0 680 58.57 2.68 1.38 ○ Inventory 3 Invention river b 680 87.0 700 59.06 3.04 1.19 ○ Comparative Example 3 Invention river b 680 89.0 700 61.45 4.95 5.12 × Comparative Example 4 Inventive Steel c 700 86.0 630 66.98 0.51 9.45 × Honorable 4 Inventive Steel c 700 86.0 660 60.14 3.44 1.24 ○ Inventory 5 Inventive Steel c 700 86.0 700 59.35 2.75 0.95 ○ Comparative Example 5 Comparative steel a 680 86.0 660 70.94 0.32 11.42 × Comparative Example 6 Comparative steel a 680 87.0 740 51.46 3.46 1.82 ○ Comparative Example 7 Comparative river b 640 87.0 660 56.45 1.69 4.35 × Comparative Example 8 Comparative Steel c 600 85.5 640 71.10 0.92 8.34 × Comparative Example 9 Comparative Steel c 600 85.5 680 66.45 1.28 5.62 × Comparative Example 10 Comparative Steel c 600 85.5 720 62.54 1.59 3.09 × Comparative Example 11 Comparative River d 600 87.0 700 61.42 1.35 3.85 × Comparative Example 12 Comparative River d 700 87.0 700 60.39 1.87 3.27 ×

Table 2 was analyzed and the following conclusions were obtained.

That is, in the case of using the comparative steel a in which the content of carbon is low and titanium (Ti) is added and the manufacturing method of the present invention is applied (Comparative Example 5), the recrystallization is not completed, As this material remained on the annealed sheet, the deviation of the material was severely caused and the workability of the material was considerably lowered. In addition, since the (111) plane strength value was low, the aggregate structure ratio was lowered and the processability of the steel pipe could not be secured.

In addition, when comparative steel a is annealed at a high temperature (Comparative Example 6), the machining characteristics can be ensured, but the hardness that can be secured is as low as 51.5, which makes it impossible to secure the stability of the can, There is a problem that the risk of occurrence of defects increases.

When the comparative steel c, which satisfies the stress range of the present invention but has a low Mn / S ratio and is partially doped with titanium, is used, the recrystallization temperature rises due to the formation of fine titanium precipitates, Examples 8 and 9) It was difficult to secure the desired hardness and to secure the processability to obtain the low aggregate texture ratio and high earing rate because the development of the aggregate structure useful for suppressing the planar anisotropy was insufficient. On the other hand, in the case of annealing at an annealing temperature of the present invention or higher (Comparative Example 10), it is possible to secure a quality of T4 grade but it is difficult to solve the problem of a high earing rate.

When the carbon content and the Mn / S ratio are compared with the conditions of the present invention, the comparative steel b and the comparative steel d are applied, and when the method of the present invention is used (Comparative Examples 7, 11 and 12) In Comparative Example 7, it was difficult to secure a target material. Comparative Examples 11 and 12, which had a high carbon content, also contributed to a considerable deterioration in workability due to a low aggregate structure ratio and a high earing rate even in steel materials capable of securing materials.

On the other hand, Inventive Steel (ac) satisfying the steel composition of the present invention is applied, and Inventive Example (1-5) satisfying the conditions of the present invention also can be managed at a level of 2.0-3.5 , And a cold-rolled steel sheet for a quartz plaster disk having a low planar anisotropy of T4 grade and excellent processability in pipe making was obtained. That is, by applying the emphasis property and the manufacturing method of the present invention, it becomes possible to establish a correlation between the texture of the texture and the texture of the texture, which is a problem at the time of drawing, I could prevent it.

However, even when a steel satisfying the steel component composition of the present invention was applied, the following problems occurred when the rolling condition of the present invention was out of the rolling condition (Comparative Example 1-3) and when the annealing condition was out (Comparative Example 4). That is, in the case where the annealing temperature was low (Comparative Example 4), since the recrystallization was not completed, the target quality of the quality of the T4 material could not be ensured as well as the deviation of the material became large and the workability in the steel making process was remarkably deteriorated. (Comparative Example 1), there was a phenomenon that the occurrence of ear at 0 ° and 90 ° azimuth increases and the value of Δr, which is a measure of planar anisotropy, has a high value of (+), When the ratio was high (Comparative Examples 2 and 3), the occurrence of earing at 45 degrees relative to the rolling direction was increased, and the drawability was degraded as the value of? R, which is a measure of planar anisotropy, was high (-).

INDUSTRIAL APPLICABILITY As described above, according to the present invention, by using aluminum killed steel in which components are appropriately controlled, and by controlling the hot rolling, cold rolling and annealing conditions appropriately during production of cold rolled steel sheet, It is possible to obtain a tin-plated base plate for T4 grade that can be managed. The tin-plated base plate has excellent characteristics when it is used for continuous operation while being subjected to severe processing such as drawing processing as well as 2- In addition, it is possible to effectively suppress the problem of deterioration in the workability of the steel pipe due to the occurrence of ear, which has been a problem in these processes, and thus shows a characteristic that the flat anisotropy due to continuous annealing and ear generation are small.

Claims (1)

A method for manufacturing a cold rolled steel sheet for a tinplate steel sheet to which deep drawing processing is applied, The content of manganese and the content of manganese in a content of 0.045-0.060%, manganese: 0.2-0.5%, aluminum: 0.02-0.05%, phosphorus: 0.015% or less, nitrogen: 0.003% The aluminum killed steel having an atomic ratio of sulfur of 15-30 and other unavoidable impurities is homogenized at 1200-1250 占 폚 and then subjected to finish hot rolling at 880-900 占 폚 and hot rolling at 640-700 占 폚 (111) / {I (110) + I (200)} in the temperature range of 650-700 ° C, and then cold rolling is carried out with the cold reduction ratio in the range of 85.5-87.0% Wherein the ratio of the texture to the texture displayed as the surface strength is controlled to 2.0 to 3.5.