Art
[1]The present invention relates to a method of making relates to a steel sheet used for the outer sheet material, such as cars, home appliances, and then coated steel sheet having excellent distinctness with them.
[2]
BACKGROUND
[3]
In general, cold-rolled steel sheet of the steel sheet produced in the process has been widely used as outer sheet material such as cars, home appliances, and workability is excellent, due to the relative, low price compared to other materials. These cold-rolled steel sheet through the most painting processes in order to secure corrosion resistance, and improved aesthetics have been used in the coating state. Therefore, there has been research on the technology for such coating solution, coating methods focused in order to secure the beautiful appearance after coating.
[4]
[5]
However, even as the coated steel sheet surface quality of the steel sheet is influenced by the surface quality of the steel sheet itself. According to Non-Patent Document 1, the more the surface roughness (Roughness average, Ra) of the steel plate is lower to lower medium frequency section roughness of the steel sheet (Waviness curve average, Wca), lower the Wca of the steel sheet becomes the good appearance after painting, in particular in the probabilistic (stochastic) roll processing methods, such as the EDT, shot blasting (short blast) and that this trend is occurring significantly. Non-patent Document 1, but the material and the surface roughness and the image clarity is referred to some of the relationship between performance in, there is a limit does not look to the relationship of the material tissues (grain) and image clarity performance.
[6]
[7]
(비특허문헌 1) Assessment of steel surface roughness and waviness in relation with paint appearance. (Int. J. Mach. Tools Manufact. Vol. 38. Nos 5-6, PP. 647-656. 199
[8]
Detailed Description of the Invention
SUMMARY
[9]
One aspect of the present invention is to control the microstructure of the steel plate, to provide a method for producing that can obtain an excellent distinctness of image after painting the steel sheet with them.
[10]
[11]
An object of the present invention is not limited to the aforementioned locations. Additional object of the present invention are described in the specification general information, Those having ordinary skill in the art will not have any difficulty in understanding a further object of the present invention from the contents described in the specification of the present invention.
[12]
Problem solving means
[13]
One aspect of the present invention in weight%, C: 0.001 ~ 0.03%, Si: 0.001 ~ 0.35%, Mn: 0.05 ~ 2.2%, P: 0.003 ~ 0.1%, S: 0.001 ~ 0.025%, Al: 0.01 ~ 0.1 %, N: 0.001 ~ 0.007%, the remainder includes Fe and unavoidable impurities,
[14]
Microstructure of steel this week an organization made up of ferrite phase,
[15]
The distinctness of image after painting 5% or less of {001} <110> texture (R-cube texture), the area fraction of the steel sheet surface layer portion relates to a steel sheet excellent.
[16]
[17]
Another aspect of the present invention in weight%, C: 0.001 ~ 0.03%, Si: 0.001 ~ 0.35%, Mn: 0.05 ~ 2.2%, P: 0.003 ~ 0.1%, S: 0.001 ~ 0.025%, Al: 0.01 ~ 0.1%, N: 0.001 ~ 0.007%, the remainder comprising: heating the steel slab, which contains Fe and inevitable impurities;
[18]
Preparing a hot rolled steel sheet by hot rolling the heated steel slab;
[19]
Step for winding the hot-rolled steel sheet; And
[20]
And a step for producing a cold-rolled steel sheet and cold rolling the hot-rolled steel sheet,
[21]
The distinctness of image after painting is performed by injecting the time of hot rolling, the rolling oil at a rate of 400 ~ 1000cc / minute includes a method of manufacturing the steel sheet excellent.
[22]
Effects of the Invention
[23]
Steel sheet of the present invention can be obtained even when performing the conventional coating or thin film coating is excellent in the steel sheet surface appearance is beautiful, and distinctness of image effects. In addition, it is possible to improve the workability due to the fine, uniform microstructure of the steel sheet, there is an effect that it is possible to reduce the cost of processing defective.
[24]
Brief Description of the Drawings
[25]
(A) and (b) of FIG. 1 is a photograph of a human eye compared to the coating on the distinctness of Comparative Example 1 and Inventive Example 1 of each embodiment of the present invention.
[26]
2 is compared with the invention example embodiment of this invention embodiment
[27]
Example the surface layer is a graph showing the relationship between the fraction of the grain size and R-cube texture.
[28]
Figure 3 is a graph illustrating a present invention embodiment of invention example and the comparative example Wa distribution.
[29]
(A) and (b) of Figure 4 shows the EBSD (Electron Back Scatter Diffraction) results for Comparative Example 1 and Inventive Example 1 of each embodiment of the present invention.
[30]
Best Mode for Carrying Out the Invention
[31]
It will be described in detail below, the steel sheet of the present invention.
[32]
[33]
First, a detailed description will be given to the steel sheet composition of the present invention. A steel sheet of the present invention (referred to below, "%") by weight%, C: 0.001 ~ 0.03%, Si: 0.001 ~ 0.35%, Mn: 0.05 ~ 2.2%, P: 0.003 ~ 0.1%, S: 0.001 ~ 0.025%, Al: preferably comprises 0.001 ~ 0.007%: 0.01 ~ 0.1%, N.
[34]
[35]
C: 0.001~0.03%
[36]
In the case of less than 0.001% content of carbon (C) is to lower the crystal grains of this Article strength to the hot-rolled steel sheet has in-plane anisotropy is increased, while the amount of solute C in steel becomes large when it exceeds 0.03% Nash Hyosung secured one difficulty and increase the strength by solid-solution strengthening significantly lower the ductility. Thus, the C preferably comprises 0.001 ~ 0.03%. To more preferably limited to 0.002 ~ 0.015% is advantageous.
[37]
[38]
And: 0.001 ~ 0.35%
[39]
The silicon (Si) is advantageous in securing strength as the steel solid solution strengthening element, the content thereof is less than 0.001% of the increased strength effects rarely, as well as the content of Si is more than 0.35% result in a surface scale defects during hot rolling, ferrite stabilizing station becomes wider to have a fine structure is hot-rolled, when rolling two sangyeok can result in non-uniformity. Therefore, it is preferable that the content of 0.001 to 0.35%. It is more preferred to preferably 0.01 to 0.3%.
[40]
[41]
Mn: 0.05 ~ 2.2%
[42]
Manganese (Mn) is an effective element to strengthen the steel employed as in the Si. In order to obtain such effect it is preferably contained by 0.05% or more. If it is less than 0.05% had a small effect of improving the strength decreases the hot ductility. On the other hand, the plating property is lowered by the amount of Mn exceeds 2.2%, the plastic anisotropy increases, and increase in the surface layer of the annealed oxide. Therefore, the content of Mn is preferably 0.05 to 2.2%. It is more preferred to preferably 0.1 to 0.8%.
[43]
[44]
S: 0.001~0.025%
[45]
The sulfur (S) is an impurity present in the steel, the content is, if it exceeds 0.025%, the form of non-metallic inclusions in combination with Mn, This is also disadvantageous gender likely to occur, fine cracks during processing lecture cutting molding . However, in order to produce the content to less than 0.001%, there is a problem that it takes is that the time during steel-making operation excessive decrease in productivity. Accordingly, the content of S is preferably limited to 0.001 to 0.025%.
[46]
[47]
Al: 0.01~0.1%
[48]
The aluminum (Al) is an element added as a deoxidizer, in the aging characteristics are improved by forming the AlN precipitates by combining with a steel nitrogen. For the content is less than 0.01% is not enough to obtain the above effect. On the other hand, if that the content is more than 0.1% is liable to generate defects in the slab during the continuous casting to the formation of the AlN precipitates. Therefore, it is preferred to limit its content to 0.01 to 0.1%.
[49]
[50]
N: 0.001~0.007%
[51]
The nitrogen (N) are combined as inevitably the additional element or a solid solution strengthening effect large Ti, Al which is of steel to form a precipitate of crude. When the content exceeds 0.007%, the inside and the aging characteristics deteriorated to increase the employment N, in order to produce less than 0.001%, there is a problem that the productivity during steel-making operation decreases. Therefore, it is desirable to limit 0.001 to 0.007% in the present invention.
[52]
[53]
P: 0.003~0.1%
[54]
Steel, phosphorus (P) and causes the typical solid solution strengthening element which is added for strength increase, causing brittleness due to grain boundary segregation inferior impact resistance. Increases significantly brittle instruction, with a sharp decrease in elongation when shall contain at least 0.003%, but the content is more than 0.1% in order to obtain the strengthening effect. But is required to manufacturing cost is excessive it is economically disadvantageous to control its content to less than 0.003%. Therefore, it is desirable to limit the content of 0.003 ~ 0.1%
[55]
[56]
Additionally, in addition to the above compositions, niobium (Nb): it may include at least one member selected from the group consisting of 0.005 ~ 0.10% 0.005 to 0.03%, and titanium (Ti).
[57]
The Nb serves to prevent aging by precipitation of carbon due to the employment of carbon. It is difficult to prevent the back Nb amount is less than 0.005%, the aging, the amount of the employed carbon many phenomena, if Nb amount exceeds 0.03%, is increased in strength, and to the hot-workability of the ferritic steel sheet inferior, increasing the strength of the final product and it is disadvantageous in molding. Therefore, the Nb content is preferably comprises 0.005 ~ 0.03%.
[58]
Wherein Ti is in addition for the purpose of bicyclic Hyosung secured and improved moldability Ti is added to steel as a strong nitride and carbide generation element to deposit TiN and TiC precipitate by precipitating the nitrogen and carbon in solid solution state ensures a bicyclic Hyosung. If the addition amount of Ti is less than 0.005%, it is difficult to obtain the effect of the amount of precipitation of TiC precipitates too small, the action of the TiN formed, TiC precipitates size increases disadvantage becomes plating property Chengdu molding in case of Ti exceeds 0.10% this can greatly be reduced. Accordingly, it is the content of Ti is preferably 0.005 ~ 0.10%, more preferably 0.005 ~ 0.06%.
[59]
[60]
In addition to the above components and the remainder including Fe and inevitable impurities. However, within the scope and spirit of the present invention, it does not exclude the addition of other alloying elements.
[61]
[62]
Steel sheet of the present invention is preferably a ferrite phase as a primary tissue. That is, the steel sheet of the present invention is a ferrite phase comprises at least 95% in area fraction, preferably a ferrite single-phase tissue.
[63]
[64]
Average crystal grain size of the surface layer of the present invention, the steel sheet is preferably not more than 30㎛. The surface layer of the steel sheet is preferably to mean up to 1/16 of the sheet thickness from the steel sheet surface. And more preferably it is preferably up to 1/32 of the thickness. When the average crystal grain size in the surface layer portion of the steel sheet by more than one trillion 30㎛, be molded is increased, the non-uniformity of the tissue during processing decreases, and gender, and the long wavelength roughness (Wca or Wa) increasing the spiritual line after coating becomes inferior can. On the other hand, the and crystal grain average size is smaller the addition of excess alloying element or significantly be subjected to rolling reduction in order to reduce one crystal grain average size glass gender image clarity, it may be the strength and ductility vary substantially depending on the crystal grain average size, the crystal grain it is of more than pyeonggyunneun 1㎛ preferred.
[65]
[66]
In the surface layer portion of the steel sheet, the grain size more than 30㎛ area fraction grain size 10㎛ or less the ratio of the area fraction of crystal grains on the crystal grains (grain size less than the area of ​​the grain fraction 10㎛ / grain size 30㎛ area fraction of crystal grains or more) of 0.5 preferably at least. For a grain size less than 10㎛ area fraction of the grain size not less than 30㎛ area fraction in the steel sheet surface layer portion it is less than the ratio of 0.5, due to tissue non-uniformity becomes inferior in formability, the spiritual line due to non-uniformity of the tissue may become inferior.
[67]
[68]
In the surface layer portion of the steel sheet, the standard deviation of the grain size is preferably 8 or less. When the standard deviation is greater than 8, due to non-uniformity of the tissue, it may be in formability and distinctness of disadvantage.
[69]
[70]
In the surface layer portion of the steel sheet, it is preferable that the aspect ratio (Aspect Ratio, the minor axis / major axis) is 0.3 or less area fraction occupied by the crystal grains is 15% or less. When the above aspect ratio is 0.3 or less crystal grains exceeds 15%, there may be a distinctness of disadvantage due to the non-uniform microstructure of the surface layer.
[71]
[72]
The steel sheet surface layer portion is a {001} <110> texture (Rotated-Cube texture) is preferably in the area fraction is less than 5.0%. As an example of a method of analyzing the area fraction of the texture, it can be analyzed using electron backscatter diffraction (. Electron Back Scattered Diffraction EBSD).
[73]
The {001} <110> texture (Rotated-Cube texture, R-cube texture) is the most stable texture which is mainly formed of cold-rolled, plastic anisotropy factor (r) values ​​represent the lowest value of the texture , is energetically stable and has a characteristic that does not occur in the recrystallization during annealing.
[74]
To form a set of steel sheet structure <111> texture (γ-fiber texture, γ- fiber organization and rolled grain or vertical direction is the <111> plane and the parallel direction) to increase the firing index anisotropy value of drawing-forming Good one, image clarity castle it is important that the presence of R-cube set in a steel sheet surface layer tissue. Accordingly, the present invention When the R-cube texture in the surface layer exceeds 5.0% in area fraction, displayed the cluster (cluster) of the steel sheet surface by rolling, tongpan, tension R-cube and the surface texture (texture) of flexure is visually recognized, the distinctness of image becomes inferior.
[75]
[76]
The average grain size of the {001} <110> texture in the surface layer in the present invention is preferably smaller than the average grain size of the entire steel sheet. And more preferably less than 20㎛. When the {001} <110> is larger than the average grain size of texture average grain size of the entire plate, the distinctness of image by the curved surface generation may become inferior.
[77]
[78]
Steel sheet of the present invention is preferably not more than 0.5㎛ the long wavelength roughness (Wa). More preferably not more than 0.45㎛.
[79]
[80]
On the other hand, the steel sheet of the present invention may be a coated steel sheet comprising a plated layer. Type of the plated steel sheet is not limited to, Al-based plated steel sheet, Zn-based plating (GI, GA) steel sheet, Zn-Al-Mg-based may be alloy-plated steel sheet, and how the side the EG plating, melt plating or the like can be applied in have.
[81]
[82]
Will be described in detail below, an example relates to a process for producing the steel sheet of the present invention. In order to manufacture the steel sheet of the present invention, heating the steel slab in which the alloy composition satisfies the river and can be produced by hot-rolling the heated steel slab. It can be cold rolled to Additionally, the hot rolled steel sheet. It will be described in detail in the respective steps.
[83]
[84]
Preparing the above-described Steel alloy composition to meet steel slab, and heating it. Wherein the steel slab heating is by way is usually performed in the art. In a preferred example, the heating is preferably performed at 100 ~ 300 minutes in an atmosphere of 1100 ~ 1300 ℃ for steel slab homogenized tissue. And if the heating temperature is less than 1100 ℃ mothayeo a sufficient tissue uniform and coarse carbides and nitrides, etc. it is not re-employed for forming disadvantage gender River, exceeding 1300 ℃ is formed with a non-uniform microstructure due to grain growth. If the heating time is less than 100 minutes, the slab simcheungbu mothamyeo to be heated to a uniform temperature, and if it exceeds 300 minutes and can result in excessive grain growth, which is not economically preferred.
[85]
[86]
And hot rolling the heated steel slab.
[87]
The hot rolling is preferably performed at a temperature range of 850 ~ 1150 ℃. If the rolling temperature is started to hot rolling at a temperature above 1150 ℃ is the temperature of the hot-rolled steel sheet increases the grain size of the surface quality of the hot rolled steel sheet becomes coarse disadvantage. On the other hand, if the end of the hot rolling at a temperature lower than 850 ℃ deteriorates anisotropy deep being moldability of the crystal grains is developed stretched by excessive recrystallization delay and microstructures a surface layer is the second sangyeok (ferrite + austenite) rolling unevenness this is development.
[88]
When the hot rolling, the rolling oil is sprayed on the steel surface by 400 ~ 1000cc / min it is preferable to carry out the hydraulic open. By forming an oil film on the calender roll surface to the hydraulic open embodiment improves the surface of the steel sheet due to a decreased rolling load, the friction coefficient decreased quality, and it is advantageous to form a uniform microstructure on the surface layer to reduce the shear deformation of the surface layer to simcheungbu. When the rolling oil injection amount to the hydraulic open 400cc / min becomes less than for when it is difficult to expect the effect, it exceeds 1000cc / minute defects in the surface caused by the slip phenomenon of the rolling and the heat tongpan sex is economically disadvantageous.
[89]
Typically it reduces the hot rolling temperature the more will have a microstructure which is fine and uniform crystal grains. However, if the temperature is reduced further increase the friction of the rolling rolls and the hot rolled sheet to increase the shear strain in the surface layer to not have a uniform structure in the thickness direction. Further, when the rolling temperature is reduced to a phase transformation temperature is below the second sangyeok rolled microstructure of the surface layer portion becomes even more non-uniform. Accordingly, when subjected to an appropriate hydraulic open and also alleviate the shear deformation of the surface layer to reduce the rolling temperature is also reduced phase transformation temperature of the surface layer. As a result, when subjected to the hydraulic open as described above it is that the temperature range in which the shear deformation narrows the tissue at an appropriate rolling temperature is so fine to form into a uniform state.
[90]
Next, a cooling said rolled steel plate. The cooling is preferably cooled at an average cooling rate of 10 ~ 100 ℃ / sec for the hot-rolled steel sheet to a temperature of 500 ~ 750 ℃. Performs a take-up after cooling to the 500 ~ 750 ℃. Preferably it is cooled to a temperature of 600 ~ 700 ℃ and take-up. When winding by cooling the cooling to less than 500 ℃ is formed in the required low-temperature steel the ferrite phase is the rolling load during cold rolling increases the strength of the hot rolled steel sheet increases, and this disadvantage tongpan sex. On the other hand, if the take-up is cooled in excess of 750 ℃ ​​the ferrite crystal grains are formed is not preferable because given a non-uniform microstructure. The average speed during the cooling is less than 10 ℃ / sec of base tissue grain coarsening become the microstructure is non-uniform it becomes, if the average cooling rate exceeds 100 ℃ / sec the shape of the easy-rolled sheet is cold ferrite phase formed disadvantage do.
[91]
The rolled steel sheet is cooled in a conventional way is carried out in the art to room temperature. As an example, the through air-cooling or water-cooling cooling at a cooling rate of 0.001 ~ 100 ℃ / sec. The cooling rate may occur due to the slow cooling rate is less than 0.001 ℃ / sec and crystal grain growth to lower the productivity in manufacturing. On the other hand there is a uniform cooling of the entire coil can be a non-uniform microstructure by a coil forming position difficult if it exceeds 100 ℃ / sec.
[92]
[93]
The hot rolled steel sheet may be cold-rolled. The cold rolling is preferably hot-rolled steel sheet after pickling process the removal of the scale is deposited on the surface, performing a rolling reduction of 60 to 90%. If the rolling reduction is less than 60% to obtain a sufficient strain energy to become a recrystallization annealing of the formed not to have a non-uniform microstructure and moldability is inferior. The upper limit of the cold rolling reduction is, but needs to be limited, if it exceeds 90%, it is preferable because it is rolling the plate-like quality, inferior in cold rolling to less than 90%.
[94]
At a temperature of 700 ~ 900 ℃ after the cold rolling can be carried out an annealing heat treatment.
[95]
[96]
On the other hand, subjected to plating after the cold rolling, it is possible to manufacture a coated steel sheet. The type of the plating is not intended to particularly limited, and is applicable to the coating that may be used in the art. Or Al-based plated, such as molten zinc (GI), alloyed hot-dip galvanized, and the Zn-based plating and Zn-Al-Mg-based alloy plating, such as (GA) can be applied, the method typically are electroplating, hot dipping and vacuum evaporation It can be applied. In a preferred example, it may be applied to the galvanized steel sheet using a melt coating. This steel sheet subjected to annealing is cooled to 5 ~ 50 ℃ / sec, after having passed by immersing the Zn plating bath. Since it is possible to achieve the roughness, improve the shape correction, the yield point elongation through the skin-pass rolling.
[97]
Mode for the Invention
[98]
It will be described in detail below, embodiments of the present invention. The following examples are to be noted in that not intended to limit the may make the scope of the invention for the understanding of the present invention. The scope of the present invention is because it is determined by what is a reasonable inference from this information and set forth in the claims.
[99]
[100]
(Example)
[101]
For the manufacture of a steel slab having a composition shown in Table 1, and was prepared in the cold-rolled steel sheet to process the conditions shown in Table 2. With respect to the thus prepared cold-rolled steel sheet, and the results are shown in Table 3 was analyzed. The units of the composition of Table 1 is% by weight, and the remainder includes Fe and unavoidable impurities. To the size of the hot-rolled steel sheet produced by the process of Table 2 is the thickness 3.2㎜, length, width 1200㎜, rolling speed, is prepared be constant under the conditions of 700 ~ 800mpm.
[102]
[103]
TABLE 1
division C And Mn P S Al N Nb Ti
Grades one 0.002 0.010 0.08 0.009 0.003 0.03 0.003 0.009 0.029
Grades 2 0.003 0.002 0.07 0.009 0.004 0.03 0.003 0.001 0.046
Grades 3 0.002 0.028 0.14 0.018 0.01 0.03 0.003 0.003 0.001

[104]
In Table 1, Nb and Ti in steel grade 2 grades 3 and Nb, not to a particular administration, illustrating inevitably contained a very small amount.
[105]
[106]
TABLE 2
division Grades Slab heating temperature (℃) Slab heating time (minutes) Hot-rolling temperature (℃) Rolling oil injection amount (cc / min) The coiling temperature (℃) Cold-rolling reduction (%)
Examples 1 Grades one 1176 171 920 600 720 78
Comparative Example 1 Grades one 1180 150 890 - 720 78
To honor two Grades one 1192 177 923 800 720 78
Comparative Example 2 Grades one 1178 145 880 1200 720 78
To honor 3 Grades one 1182 184 920 650 720 78
Comparative Example 3 Grades one 1185 158 885 - 720 78
To honor four Grades 2 1177 179 920 850 700 79
Comparative Example 4 Grades 2 1178 149 890 - 700 79
To honor five Grades 2 1184 173 923 600 700 79
Comparative Example 5 Grades 2 1182 149 880 250 700 79
To honor 6 Grades 2 1182 169 920 750 700 79
Comparative Example 6 Grades 2 1178 157 885 300 700 79
To honor 7 Grades 3 1180 166 920 650 620 80
Comparative Example 7 Grades 3 1177 148 890 300 620 80
To honor eight Grades 3 1178 178 923 700 620 80
Comparative Example 8 Grades 3 1181 148 880 350 620 80
To honor nine Grades 3 1171 172 920 850 620 80
Comparative Example 9 Grades 3 1175 156 885 - 620 80

[107]
[108]
With respect to the Inventive Example and Comparative Example as prepared above in Table 2, a back-scattered electron diffraction (Electron Back Scattered Diffraction, EBSD) for the texture, particularly R-cube texture in the surface layer part of each of the specimens, the {001} the area fraction of <110> texture (Rotated-Cube texture, R-cube texture) was calculated.
[109]
Further, the average crystal grain size in the surface layer and the grain size not less than 30㎛ area fraction grain size 10㎛ or less the ratio of the area fraction of crystal grains on the crystal grains (grain size less than the area of ​​the grain fraction 10㎛ / grain size not less than the area of ​​the grain 30㎛ fraction) were also calculated in a further, aspect ratio of crystal grains (area the aspect Ratio, short diameter / long diameter) is occupied by crystal grains not more than 0.30 fraction of the surface layer portion of the steel sheet were also the calculation.
[110]
In addition, and also on the surface Wa values ​​after processing (two-axis processing tension of about 5%) for each of the specimens subjected to the measurement and deliver results.
[111]
It showed the derived results are shown in Table 3.
[112]
[113]
TABLE 3
division Surface layer R-cube texture area fraction (%) The surface layer grain average size (㎛) The area ratio of the surface layer (10㎛ or more grains / 30㎛ than grain) Grain aspect ratio greater than 0.3 in the surface layer area fraction (%) Wa (㎛)
Examples 1 4.5 20.3 0.70 11.0 0.30
To honor two 4.6 19.4 0.60 10.2 0.27
To honor 3 4.7 20.6 0.63 13.8 0.36
To honor four 4.6 20.2 0.93 12.7 0.27
To honor five 4.5 25.3 0.96 15.0 0.41
To honor 6 4.9 23.5 0.61 13.6 0.26
To honor 7 4.7 17.8 0.54 9.7 0.41
To honor eight 4.5 17.5 0.78 9.8 0.24
To honor nine 4.2 18.0 0.84 11.5 0.23
Comparative Example 1 6.1 33.2 0.25 17.1 0.56
Comparative Example 2 5.9 35.0 0.53 17.7 0.49
Comparative Example 3 4.7 32.0 0.28 17.4 0.63
Comparative Example 4 6.3 30.4 0.39 14.9 0.61
Comparative Example 5 6.5 36.1 0.41 14.4 0.54
Comparative Example 6 5.9 31.4 0.18 16.0 0.55
Comparative Example 7 6.5 23.9 0.33 17.3 0.60
Comparative Example 8 7.5 22.6 0.14 15.4 0.50
Comparative Example 9 6.2 22.4 0.24 17.5 0.59

[114]
[115]
On the other hand, (a) and (b) of Figure 1, respectively, the grid for Comparative Example 1 and after the cold-rolled steel sheets of Examples 1 processing tension before application of about 5% biaxial subjected to coating and then visually compare the surface and the result of comparison used to clarity the light source. From the results of Figure 1, Examples 1 it can be seen that the apparent sharpness as compared to Comparative Example 1. 2 is a graph showing the percentage relationship of an invention example and comparative example, the surface layer grain size and R-cube texture present invention, invention example are all by securing a homogeneous crystals in the surface layer portion, R-cube texture is also present it can be seen that to meet the scope of the invention.
[116]
Figure 3 shows the average value Wa and the deviation for example cold-rolled steel sheet compared with the invention example. Wherein Wa is measured after about 5% processed into biaxially stretched state, it was measured using a medium frequency field intensity meter of the surface. Also for example, as shown in Comparative 3, the present example can be seen that excellent spiritual Wa is low value lines.
[117]
On the other hand, (a) and (b) of Figure 4, respectively, through the EBSD analysis of Comparative Example 1 and Examples 1, calculating the area fraction of the R-cube texture of the surface layer. In the case of Comparative Example 1, whereas 6.1 percent to honor one can see that it comprises 4.5%.
[118]
[119]
When the results seen from the results of Table 3 above and the drawings, meet the conditions of the present invention could secure a superior distinctness.

Claims

[Claim 1]By weight%, C: 0.001 ~ 0.03%, Si: 0.001 ~ 0.35%, Mn: 0.05 ~ 2.2%, P: 0.003 ~ 0.1%, S: 0.001 ~ 0.025%, Al: 0.01 ~ 0.1%, N: 0.001 ~ 0.007%, the rest is a {001} <110> texture (R-cube texture) the area fraction of the Fe and inevitable contain impurities, and becomes the microstructure of the steel sheet this week tissue composed of ferrite phase, the steel sheet surface layer portion 5 % or less after coating distinctness of the steel sheet excellent.
[Claim 2]
The method according to claim 1, wherein the steel sheet is Nb: 0.005 ~ 0.03%, and Ti: including at least one selected from the group consisting of 0.005 ~ 0.10% distinctness of image after painting the steel sheet excellent in that.
[Claim 3]
The method according to claim 1, average crystal grain size of the surface layer portion of the steel sheet after paint 30㎛ less distinctness of the steel sheet excellent.
[Claim 4]
The method according to claim 1, the standard deviation of the crystal grains of the surface layer portion of the steel sheet 8 or less distinctness of image after painting the steel sheet excellent.
[Claim 5]
The method according to claim 1, in the surface layer portion of the steel sheet, the grain size more than 30㎛ area fraction grain size 10㎛ or less the ratio of the area fraction of crystal grains on the crystal grains (grain size of the area fraction 10㎛ / 30㎛ grain size than the crystal grains of less than the grain area fraction) of 0.5 or more after coating distinctness of the steel sheet excellent.
[Claim 6]
The method according to claim 1, wherein the aspect ratio of the steel surface layer portion (Aspect Ratio) of 0.3 or less crystal grains occupying an area fraction of 15% or less after coating the steel sheet having excellent distinctness.
[Claim 7]
The method according to claim 1, wherein the steel sheet after the coating to more than 95% in area fraction containing the ferrite phase distinctness of the steel sheet excellent.
[Claim 8]
The method according to claim 1, wherein the steel sheet further comprises a coating layer on the surface, and the plated layer is Al-based plating layer, Zn-based plating layer, Zn-Al-Mg-based alloy one after the coated steel sheet of excellent distinctness of the plating layer.
[Claim 9]
By weight%, C: 0.001 ~ 0.03%, Si: 0.001 ~ 0.35%, Mn: 0.05 ~ 2.2%, P: 0.003 ~ 0.1%, S: 0.001 ~ 0.025%, Al: 0.01 ~ 0.1%, N: 0.001 ~ 0.007%, the remainder comprising: heating the steel slab, which contains Fe and inevitable impurities; Preparing a hot rolled steel sheet by hot rolling the heated steel slab; Step for winding the hot-rolled steel sheet; And a method for producing the hot rolled steel sheet to cold rolling, including a step of manufacturing a cold-rolled steel sheet, and the coating after the hot rolling upon distinctness performed by spraying the rolling oil at a rate of 400 ~ 1000cc / min steel sheet excellent.
[Claim 10]
In the steel slab is Nb to claim 9, 0.005 to 0.03%, and Ti: 0.005 ~ 0.10% of the production method excellent distinctness of image after painting, which comprises at least one selected from the group consisting of steel sheet.
[Claim 11]
The method according to claim 9, wherein the heating process for producing a superior distinctness of image after painting is performed at 100 ~ 300 minutes in the temperature range of 1100 ~ 1300 ℃ steel.
[Claim 12]
The method according to claim 9, the method for producing the hot-rolled after 10 ~ 100 ℃ / sec excellent distinctness of image after painting the steel sheet to cool at a cooling rate.
[Claim 13]
The method of manufacturing the hot excellent distinctness of image after painting the steel sheet wound in a range of 500 ~ 750 ℃ ​​after rolling to claim 9.
[Claim 14]
The method according to claim 9, the method for producing the cold rolling is superior distinctness of image after painting is performed by a reduction ratio of 60 to 90% steel.
[Claim 15]
The method according to claim 9, of the cold further comprising the step of forming the coating layer after rolling, and the plate layer is Al-based plating layer, Zn-based plating layer, Zn-Al-Mg-based alloy any one of superior distinctness of image after painting the steel sheet during the plating layer method.
[Claim 16]
The method according to claim 9, wherein forming the coating layer The method of electroplating, hot dipping and excellent distinctness of image after painting the steel sheet is performed by the method of any one of vacuum evaporation.