KR20160079967A - Ferritic stainless steel having excellentridging resistance and excellent in surface quality - Google Patents

Abstract

The present invention relates to a ferritic stainless steel having improved anti-ridging properties by adjusting the content of components constituting a molten steel for producing stainless steel. The ferritic stainless steel according to one embodiment of the present invention has excellent ridging resistance and moldability The stainless steel according to any one of claims 1 to 3, wherein the stainless steel has a composition of 12.5 to 18.5% Cr, 0.001 to 0.025% of Cr, 0.01 to 0.05% of N, 0.05 to 0.4% of Ti, 0.01 to 0.2% of Al, 0.01 to 0.5% (1), which contains 0.01 to 0.5% of Mn, 0.01 to 0.5% of Cu, 0.001 to 0.5% of Mo, 0.01 to 0.5% of Nb, 0.01 to 0.5% of Ni, It is characterized by being satisfied.
TiN deposition amount (Vol%) > 1.1 x 10 < ^-3 > ^- (1)
In the above formula (1), the amount of TiN precipitates (Vol%) = 47N + 102Ti x N + 10C + 0.39, and N, Ti and C mean the content (wt%) of each component.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a ferritic stainless steel having excellent surface quality and anti-ridging property,

TECHNICAL FIELD The present invention relates to a ferritic stainless steel, and more particularly, to a ferritic stainless steel having improved surface quality and anti-ridging property by adjusting the content of components constituting molten steel for producing stainless steel, .

Stainless steels can be broadly classified into ferritic stainless steels and austenitic stainless steels.

Generally, ferritic stainless steels are preferentially priced lower than austenitic stainless steels and have good surface gloss, drawability and oxidation resistance, and are widely used in kitchen appliances, building exterior materials, home appliances, electronic parts and the like.

In the ferritic stainless steel, wrinkle-like surface defects are generated parallel to the rolling direction during the molding process for application to the above-mentioned parts, and this phenomenon is referred to as ridging.

Such ridging defects may deteriorate the appearance of the product, requiring additional polishing steps at the portion where the ridging occurs after the forming, which may cause the manufacturing cost of the final product to rise.

STS430 steel, which is one of ferritic stainless steels, is a steel containing about 16% by weight of chromium (Cr) and is a representative steel of ferritic stainless steel and widely used for tableware and household appliances.

STS430 steels have superior ridging resistance among other ferritic stainless steels, but they still have ridging defects, and therefore, there is a need for steady ridging reduction ferritic stainless steels in order to reduce the polishing cost or the mechanical defects caused by ridging.

The reason for this ridging is mainly due to the unbreakable coarse casting structure.

That is, when the cast structure remains in the coarse band structure without being broken in the rolling or annealing process, it is expressed as a ridging defect due to the width and thickness direction deformation behavior different from the surrounding recrystallized structure during the tensile processing.

1 is a view for explaining the refinement of a casting structure using TiN to improve the anti-ridging property.

As shown in Fig. 1, the columnar structure of the slab is subject to shear deformation during hot rolling, and thus the slab is easily broken in the subsequent process. However, the slab isotropic structure undergoes plane deformation during hot rolling, so that the band structure is not easily broken in the subsequent process.

In order to solve this problem, TiN precipitates are formed at the temperature range of casting by adding Ti and high N and TiN pinning effect can be used to finely stabilize the equiaxed texture to suppress the formation of coarse band structure.

Conventionally, a ferritic stainless steel sheet having improved ridging resistance by appropriately controlling the composition of steels, rolling conditions and annealing conditions so as to develop unique unique textures and a manufacturing method thereof has been disclosed in "Ferritic stainless steel sheet having small in- (Japanese Patent Application Laid-Open No. 10-1997-0015775) "

However, in the ferritic stainless steel having the austenite transformation period, it is necessary to subject the ferritic stainless steel to heat treatment for decomposing the austenite after hot rolling, but the cost is increased and the production cost is increased and the manufacturing time is increased. As the manufacturing time increases, the productivity is lowered.

It also fails to specify a critical range of specific components that can prevent scab defects and intergranular corrosion.

Patent Document 10-1997-0015775 (Apr. 28, 1997)

SUMMARY OF THE INVENTION The present invention has been devised to solve the problems as described above, and it is an object of the present invention to provide a method for manufacturing a steel sheet, which is capable of optimizing the content of an alloy component affecting improvement in ridging resistance, The present invention provides a ferritic stainless steel excellent in surface quality and anti-ridging properties.

According to an embodiment of the present invention, a ferritic stainless steel having excellent surface quality and anti-ridging property comprises 12.5 to 18.5% of Cr, 0.001 to 0.025% of C, 0.01 to 0.05% of N, 0.05 to 0.05% of Ti, 0.01 to 0.5% of Al, 0.01 to 0.5% of Al, 0.01 to 0.5% of Si, 0.01 to 0.5% of Mn, 0.01 to 0.5% of Cu, 0.001 to 0.5% of Mo, 0.01 to 0.5% of Nb, 0.01 to 0.5% of Ni, %, Remaining Fe and impurities, and satisfies the following formula (1).

TiN deposition amount (Vol%) > 1.1 x 10 < ^-3 > ^- (1)

In the above formula (1), the amount of TiN precipitates (Vol%) = 47N + 102Ti x N + 10C + 0.39, and N, Ti and C mean the content (wt%) of each component.

The stainless steel may be characterized by satisfying the following formula (2).

TiN crystallization temperature (占 폚)? 1520 ------------------------------ (2)

TiN and Cr are the content (wt%) of each component, and the content of each component (wt%) in the formula (2) ).

It is preferable that the stainless steel has an N / C ratio of 1.5 or more and 6 or less in a mass ratio.

The stainless steel may be characterized by satisfying the following formula (3).

Ti / (C + N) > 5.0 ---------------------------------- (3)

In the formula (3), Ti, C and N mean the content (wt%) of each component.

The stainless steel may be characterized in that, in the cast state, the crystal grain diameter of the equiaxed crystal structure is 2 mm or less.

The stainless steel may have a ridging height (Wt) of less than 11 mu m in the cold rolled steel sheet.

According to the embodiment of the present invention, it is possible to improve the anti-ridging property and minimize the generation of intergranular corrosion defects by adjusting the amount of Ti, C and N to adjust the TiN precipitation amount.

Further, by optimizing the contents of N, Ti and Cr and controlling the TiN crystallization temperature to be less than 1520 占 폚, the occurrence of scab defects can be minimized and the surface quality can be improved.

1 is a view for explaining refinement of a cast structure using TiN in order to improve anti-ridging property,
FIG. 2A is a graph showing a correlation between a threshold value of TiN precipitation amount and equiaxed fineness (2 mm or less) according to an embodiment of the present invention,
FIG. 2B is a graph showing a range of amounts of Ti and N in which equiaxed refinement is implemented from the threshold of the minimum TiN derived in FIG.
FIG. 3A is a graph showing a correlation between a threshold of a TiN crystallization temperature and occurrence of a Scab defect according to an embodiment of the present invention,
FIG. 3B is a graph showing the range of Ti and N amounts at which scab defects do not occur from the threshold value of the TiN crystallization temperature derived in FIG. 3A,
FIG. 4A is a graph showing a correlation between a threshold value of Ti / (C + N) according to an embodiment of the present invention and intergranular corrosion defects during HAPL pickling,
FIG. 4B is a graph showing a range of Ti and N amounts at which intergranular corrosion does not occur from the threshold value of Ti / (C + N) derived from FIG. 4A,
5 is a graph showing the relationship between Scab, grain boundary erosion and equilibrium fineness according to the content of Ti and N. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know.

According to an embodiment of the present invention, a ferritic stainless steel having excellent surface quality and anti-ridging property comprises 12.5 to 18.5% of Cr, 0.001 to 0.025% of C, 0.01 to 0.05% of N, 0.05 to 0.05% of Ti, 0.01 to 0.5% of Al, 0.01 to 0.5% of Al, 0.01 to 0.5% of Si, 0.01 to 0.5% of Mn, 0.01 to 0.5% of Cu, 0.001 to 0.5% of Mo, 0.01 to 0.5% of Nb, 0.01 to 0.5% of Ni, %, The balance of Fe and impurities.

Hereinafter, the reason for limiting the numerical value of the component content in the examples according to the present invention will be described. Unless otherwise stated, the unit is wt%.

Cr: 12.5 to 18.5%

The amount of chromium (Cr) is preferably 12.5 wt% to 16.5 wt%.

If chromium (Cr) is contained in an amount of less than 12.5 wt% as an alloy element added to improve the corrosion resistance of steel, the corrosion resistance of the ferritic stainless steel is deteriorated and the corrosion resistance of the ferritic stainless steel is more than 18.5 wt% This would unnecessarily increase the manufacturing cost.

Therefore, it is preferable that chromium (Cr) is limited to 12.5 to 18.5% by weight in the embodiment according to the present invention.

C: 0.001 to 0.025%

The amount of carbon (C) is preferably 0.001 wt% to 0.025 wt%.

Because carbon (C) is an austenite stabilizing element of steel, it is necessary to limit it because it acts to maximize the austenite fraction. When carbon (C) exceeds 0.025 wt% as solid solution strengthening element, And reduces the corrosion resistance, and if it is less than 0.001% by weight, it causes an additional refining cost.

Herein, the elongation is a widely used term as one of the quality characteristics that indicates the workability of a cold-rolled product of a ferritic stainless steel. When the cold rolled product of the ferritic stainless steel is uniaxially stretched, Calculate from divided by length.

N: 0.01 to 0.05%

The amount of nitrogen (N) is preferably 0.01 wt% to 0.05 wt%.

This is because nitrogen (N) is added as an important element having an effect of refining the microstructure of the slab by forming titanium nitride (TiN) in combination with titanium (Ti) during casting and solidification in an amount of 0.01 wt% N) is added in an amount exceeding 0.05% by weight, this not only deteriorates the workability, but also causes a stretcher strain of cold rolled products.

The more specific range of nitrogen (N) is affected by the amount of titanium (Ti) and will be described later in detail.

Ti: 0.05 to 0.40%

The amount of titanium (Ti) is preferably 0.05% by weight to 0.30% by weight.

Titanium (Ti) is an element which plays an important role in miniaturizing the equiaxed crystal grain size of the cast steel, and it is added in an amount of 0.05 wt% or more since it functions to fix the carbon (C) and nitrogen (N) .

However, when titanium (Ti) is added in an amount exceeding 0.40 wt%, the production cost of stainless steel increases and scab defects are generated on the surface of the cast steel and hot rolled product, which also causes sliver defects in cold rolled products.

More specifically, the range of titanium (Ti) is influenced by the content of nitrogen (N) and is specifically described later.

Al: 0.01 to 0.2%

The amount of aluminum (Al) is preferably 0.01 wt% to 0.2 wt%.

If aluminum (Al) is added in an amount exceeding 0.3% by weight, the aluminum (Al) is present as a nonmetallic inclusion, and the cold-rolled strip Which is a cause of the sleeve defect of the welded portion and deteriorates the weldability.

Si: 0.01 to 0.5%

The amount of silicon (Si) is preferably 0.01 wt% to 0.5 wt%.

Because silicon (Si) is an element to be added as a deoxidizer in steelmaking, it is preferably contained in an amount of 0.01 wt% or more because it is a ferrite stabilizing element.

On the other hand, if it is contained in an amount exceeding 0.5% by weight, it may cause curing of the material, resulting in deterioration of ductility. Therefore, the content is preferably limited to 0.5% by weight or less.

Mn: 0.01 to 0.5%

The amount of manganese (Mn) is preferably 0.01 wt% to 0.5 wt%.

This is because manganese (Mn) is an impurity inevitably included in the steel, but when it is contained in a large amount, manganese fume is generated at the time of welding, which causes precipitation of the MnS phase and lowers the elongation.

Cu: 0.01 to 0.5%

The amount of copper (Cu) is preferably 0.01 wt% to 0.5 wt%.

This is because copper (Cu) is an impurity inevitably contained in steel, and has an effect of improving the corrosion resistance by adding 0.01% or more, but when it is added in excess of 0.5%, the workability is deteriorated.

Mo: 0.001 to 0.5%

The amount of molybdenum (Mo) is preferably 0.001 wt% to 0.5 wt%.

This is because molybdenum (Mo) is added in an amount of 0.010% or more to improve the corrosion resistance, particularly the pitting resistance. However, when the amount of molybdenum is more than 0.5% by adding an expensive element, the manufacturing cost is increased and the workability is lowered It is because.

Nb: 0.001 to 0.5%

The amount of niobium (Nb) is preferably 0.001 wt% to 0.5 wt%.

Nb is an expensive element and 0.001% or more is added to precipitate solid carbon (C) and nitrogen (N) as carbonitride to improve corrosion resistance and formability, while 0.5% And if it is added in an excessively large amount, the appearance defects and toughness due to the inclusions are lowered and the manufacturing cost is increased.

Ni: 0.01 to 0.5%

The amount of nickel (Ni) is preferably 0.01 wt% to 0.5 wt%.

This is because nickel (Ni) is an impurity inevitably contained in steel, and has an effect of improving the corrosion resistance by adding 0.01% or more. On the other hand, when added in a large amount, the austenite stabilization degree is increased and the production cost Because it has the problem of rising.

The remaining elements except for the above-mentioned elements are made of iron (Fe) and other unavoidable impurities.

Generally, as a cause of ridging in ferritic stainless steels, coarse grains formed at the time of casting are rolled without being removed during hot rolling. According to one embodiment of the present invention, at the time of casting By forming fine equiaxed crystals by the TiN compound to be formed, a ferritic stainless steel slab having a fine structure can be produced and ferritic stainless steel excellent in anti-ridging property can be manufactured.

Therefore, ferritic stainless steels excellent in surface quality and anti-ridging property according to one embodiment of the present invention are more limited in terms of limiting the deposition amount of TiN, which affects the miniaturization of equiaxed crystals, .

For example, it is preferable to cast by a component system satisfying the following equations (1) and (2).

TiN deposition amount (Vol%) > 1.1 x 10 < -3 > - (1)

In this case, the TiN precipitation amount (Vol%) in the formula (1) is 47 N + 102 Ti x N + 10 C + 0.39, and N, Ti and C mean the content (wt%) of each component.

TiN crystallization temperature (占 폚)> 1520 ------------------------------ (2)

In this case, the TiN crystallization temperature (° C) in the formula (2) = [-19755 / {logN- (7.78 + 0.07 Ti-logTi + 0.045 Cr)}] - 275. N, Ti and Cr are the content wt%).

On the other hand, in the present invention, it is preferable to control the N / C ratio to 1.5 or more and 6 or less.

The reason for this is that it is necessary to have a relatively large content of N in order to form TiN which can make the structure finer during casting. Even if N is added in a certain amount, it is difficult to form TiN compound in all N, Ti ratio should be applied according to the Ti / N ratio.

Further, the ferritic stainless steel according to the embodiment of the present invention is characterized in that it does not contain the austenite phase transformation until reaching the normal temperature after casting.

This is because, when the austenite phase transformation is included, especially when the austenite phase transformation is included in the hot rolling section such as the ordinary STS 430 steel, after the hot rolling, the austenite phase decomposition and the incomplete heat treatment for removing the Cr depletion layer are indispensable, And the production time is increased.

Therefore, according to the present invention, the heat treatment process is not performed with the complete waste light component system, and the continuous annealing process is performed. The production cost can be reduced, the production time can be shortened, and the productivity can be improved.

As described above, the STS 430 steel, which is a representative steel of ferritic stainless steels, is superior in the anti-ridging property to other ferritic stainless steels by including austenite phase transformation in the hot rolling section to partially remove the coarse structure formed during casting On the other hand, in the present invention, even though it is a component system which does not contain an austenite phase transformation, excellent ridging property can be obtained by forming a fine cast structure by the above-mentioned component system.

At this time, the formation of the austenite phase can be determined by observing the microstructure by heating the material at a temperature in the range of 900 ° C. to 1100 ° C., and it can be discriminated based on the standard in material engineering.

Hereinafter, examples and comparative examples according to the present invention will be described.

However, the following examples are only a preferred embodiment of the present invention, and the scope of the present invention is not limited by the following examples.

Remarks alloy Alloy component (wt%) Cr Si Al Mn Ni Cu P S C N Ti Compare A #One 16.34 0.174 0.024 0.123 0.08 0.018 0.021 0.001 0.0068 0.0083 0.17 #2 16.24 0.182 0.043 0.156 0.05 0.015 0.023 0.0009 0.0069 0.0043 0.17 # 3 16.41 0.181 0.033 0.142 0.06 0.014 0.0223 0.0008 0.0072 0.0084 0.2 #4 16.52 0.176 0.051 0.136 0.07 0.021 0.021 0.0009 0.0072 0.0073 0.19 # 5 16.9 0.177 0.03 0.149 0.07 0.011 0.0234 0.001 0.0073 0.0058 0.245 Comparison B # 6 16.03 0.172 0.089 0.257 0.16 0.071 0.0239 0.0008 0.0083 0.0162 0.237 # 7 16.22 0.189 0.031 0.101 0.07 0.023 0.0185 0.0013 0.0043 0.0196 0.174 #8 16.12 0.191 0.077 0.115 0.07 0.021 0.0202 0.0008 0.0042 0.0172 0.239 # 9 16.2 0.19 0.057 0.098 0.06 0.031 0.0213 0.0008 0.0077 0.0197 0.213 # 10 16.1 0.174 0.037 0.092 0.07 0.025 0.0217 0.0008 0.0074 0.0187 0.193 # 11 16.26 0.087 0.048 0.181 0.19 0.092 0.0248 0.0008 0.0096 0.0217 0.169 # 12 16.36 0.081 0.107 0.222 0.17 0.078 0.0244 0.0013 0.0072 0.0172 0.222 # 13 16.14 0.106 0.049 0.205 0.18 0.085 0.0257 0.0014 0.0068 0.0208 0.198 # 14 16.31 0.247 0.02 0.207 0.13 0.069 0.0212 0.0009 0.0065 0.0203 0.182 # 15 16.02 0.166 0.063 0.177 0.15 0.073 0.0194 0.0008 0.0046 0.0207 0.202 Comparison C # 16 16.03 0.166 0.044 0.081 0.11 0.027 0.0195 0.001 0.0068 0.0213 0.118 # 17 16.2 0.2 0.033 0.115 0.11 0.026 0.0163 0.0008 0.0061 0.0194 0.117 # 18 16.03 0.183 0.038 0.136 0.1 0.028 0.015 0.0006 0.0063 0.0218 0.123 invent # 19 16.27 0.256 0.027 0.183 0.11 0.024 0.0224 0.0009 0.0067 0.018 0.179 # 20 16.33 0.24 0.03 0.188 0.12 0.02 0.0206 0.001 0.007 0.0218 0.149 # 21 16.25 0.297 0.036 0.181 0.12 0.021 0.0186 0.0009 0.0069 0.0196 0.176 # 22 16.1 0.181 0.048 0.131 0.08 0.013 0.0235 0.0009 0.007 0.0169 0.175 # 23 16.23 0.171 0.1 0.135 0.08 0.009 0.0231 0.0011 0.0061 0.0191 0.191 # 24 16.18 0.157 0.033 0.125 0.08 0.007 0.0217 0.001 0.0065 0.0171 0.172 # 25 16.4 0.176 0.036 0.159 0.09 0.023 0.0182 0.0005 0.0074 0.0146 0.143 # 26 16.28 0.189 0.041 0.171 0.09 0.021 0.0192 0.0005 0.0071 0.015 0.16 # 27 16.26 0.176 0.048 0.17 0.09 0.019 0.023 0.0005 0.0073 0.0149 0.182 # 28 16.2 0.206 0.03 0.167 0.09 0.02 0.0256 0.0005 0.0068 0.0138 0.182 # 29 16.27 0.179 0.039 0.107 0.07 0.028 0.018 0.0012 0.0055 0.0129 0.172 # 30 16.08 0.17 0.052 0.107 0.07 0.025 0.0159 0.0012 0.0044 0.0121 0.175 # 31 16.17 0.172 0.07 0.101 0.07 0.021 0.0165 0.0011 0.0053 0.014 0.171 # 32 16.47 0.134 0.04 0.127 0.07 0.015 0.0259 0.0011 0.0063 0.0126 0.181 # 33 16.22 0.178 0.074 0.135 0.16 0.019 0.0241 0.001 0.0062 0.0103 0.18 # 34 16.32 0.2 0.035 0.155 0.07 0.012 0.0265 0.0011 0.0054 0.0115 0.161

Table 1 is a table showing alloy compositions of various embodiments and comparative examples of ferritic stainless steels excellent in surface quality and anti-ridging property, which were produced according to one embodiment of the present invention.

In Table 1, the various embodiments of the present invention are controlled in terms of the content of Ti, N, and C, and the components and the components thereof are confirmed by vacuum melting the above-described examples and comparative examples.

In the present invention, the cast steel is produced by continuous casting of Examples and Comparative Examples according to the composition ranges shown in Table 1, and the produced cast steel is subjected to rough rolling and continuous finishing using a rolling machine to produce a ferritic stainless steel hot rolled steel sheet Followed by continuous annealing and pickling, followed by cold rolling and cold rolling annealing to obtain a final ferrite stainless steel with a cold-rolled steel sheet.

Remarks alloy TiN precipitation amount
(Vol% x 10 ^-3 ) TiN
Crystallization temperature (캜) Ti / (C + N)
Whether the equilibrium is fine Scab not generated?
Whether intergranular corrosion has not occurred Rising Grade Compare A #One 0.99 1463 11.3 X O O 2 #2 0.69 1421 15.2 X O O 2 # 3 0.98 1474 12.8 X O O 2 #4 0.95 1461 13.1 X O O 2 # 5 0.86 1459 18.7 X O O 2 Comparison B # 6 1.58 1534 9.7 O X O One # 7 1.74 1525 7.3 O X O One #8 1.65 1538 11.2 O X O One # 9 1.79 1539 7.8 O X O One # 10 1.71 1529 7.4 O X O One # 11 1.85 1530 5.4 O X O One # 12 1.64 1531 9.1 O X O One # 13 1.84 1538 7.2 O X O One # 14 1.8 1530 6.8 O X O One # 15 1.84 1540 8 O X O One Comparison C # 16 1.66 1505 4.2 O O X One # 17 1.56 1497 4.6 O O X One # 18 1.74 1510 4.4 O O X One invent # 19 1.64 1510 7.2 O O O One # 20 1.81 1511 5.2 O O O One # 21 1.74 1516 6.6 O O O One # 22 1.57 1515 7.3 O O O One # 23 1.73 1519 7.6 O O O One # 24 1.58 1515 7.3 O O O One # 25 1.37 1490 6.5 O O O One # 26 1.43 1500 7.2 O O O One # 27 1.45 1508 8.2 O O O One # 28 1.38 1503 8.8 O O O One # 29 1.31 1494 9.3 O O O One # 30 1.26 1492 10.6 O O O One # 31 1.38 1500 8.9 O O O One # 32 1.3 1495 9.6 O O O One # 33 1.15 1482 10.9 O O O One # 34 1.2 1482 9.5 O O O One

Table 2 is a table showing the ratio of Ti / N and N / C of the various examples and comparative examples having the composition of Table 1 and the results of checking the ridging grade for each final ferritic stainless steel.

In this case, the ridging grade representing the ridging resistance is a ridging height grade (Wt standard) measured after 15% tensile test of cold-rolled steel sheet, the first grade is less than 11 탆, the second grade is 11 탆 to 14 탆, Mu m, and the fourth grade indicates 18 mu m or more, and the first grade corresponds to the target range in the present invention.

FIG. 2A is a graph showing a correlation between a threshold value of TiN precipitation amount according to an embodiment of the present invention and equilibrium fineness (2 mm or less), and FIG. 2B is a graph showing the relationship between the threshold value of minimum TiN, Is a graph showing the range of amounts of Ti and N to be realized.

As shown in Tables 1 and 2 and FIG. 2, it can be seen that the comparative A group composed of Comparative Examples 1 to 5 does not satisfy the Ti / N ratio of 5 to 20 and does not satisfy the N / C ratio of 1.5 to 6 .

Accordingly, since the precipitation amount of TiN is less than 1.1 x ^10-3 (vol%) and the above equation (1) can not be satisfied, the equiaxed crystal grain size exceeds 2 mm, It can be seen that the target value of the present invention is not satisfied.

FIG. 3A is a graph showing a correlation between the threshold of the TiN crystallization temperature and the occurrence of Scab defects according to the embodiment of the present invention. FIG. 3B is a graph showing the relationship between the TiN crystallization temperature , And the amount of N. FIG.

As shown in Tables 1 and 2 and FIG. 3, the comparative B group composed of Comparative Examples 6 to 15 satisfies the ratio of Ti / N and N / C according to the embodiment of the present invention, Is not more than 1520 DEG C, the above formula (2) is not satisfied.

Thus, it can be confirmed that a scab defect occurs and the surface quality is lowered.

4A is a graph showing a correlation between a threshold value of Ti / (C + N) according to an embodiment of the present invention and intergranular corrosion defects during HAPL pickling. FIG. 4B is a graph showing the relationship between Ti / (C + Of Ti and N without intergranular corrosion.

As shown in Tables 1 and 2 and FIG. 3, the Comparative C group composed of Comparative Examples 16 to 18 has not only the ratio of Ti / N and N / C according to the embodiment of the present invention, (C + N) value is less than 5.0, it can be understood that the above formula (3) is not satisfied.

As a result, it can be seen that the grain boundary equation is generated and the quality is deteriorated.

5 is a graph showing the relationship between Scab, grain boundary erosion and equilibrium fineness according to the content of Ti and N. FIG.

As shown in Tables 1 and 2 and FIG. 5, when satisfying the above formulas (1) to (3) while satisfying the composition range according to the embodiment of the present invention, Mm. In the cold-rolled steel sheet, the ridging height Wt is less than 11 占 퐉 and the ridging grade is excellent. It is confirmed that the surface quality is improved by preventing scabs and intergranular corrosion from occurring.

Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto but is limited by the following claims. Accordingly, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit of the following claims.

Claims (6)

The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains, by weight, 12.5 to 18.5% of Cr, 0.001 to 0.025% of C, 0.01 to 0.05% of N, 0.05 to 0.4% of Ti, 0.01 to 0.2% of Al, 0.01 to 0.5% And the balance Fe and the impurities are contained in an amount of 0.01 to 0.5%, 0.01 to 0.5% of Cu, 0.001 to 0.5% of Mo, 0.01 to 0.5% of Nb, 0.01 to 0.5% of Ni,
A ferritic stainless steel excellent in surface quality and anti-ridging property satisfying the following formula (1).
TiN deposition amount (Vol%) > 1.1 x 10 < ^-3 > ^- (1)
In the above formula (1), the amount of TiN precipitates (Vol%) = 47N + 102Ti x N + 10C + 0.39, and N, Ti and C mean the content (wt%) of each component.
The method according to claim 1,
In the stainless steel,
A ferritic stainless steel excellent in surface quality and anti-ridging property, which satisfies the following formula (2).
TiN crystallization temperature (占 폚)? 1520 ------------------------------ (2)
TiN and Cr are the content (wt%) of each component, and the content of each component (wt%) in the formula (2) ).
The method of claim 2,
In the stainless steel,
Wherein the N / C ratio is 1.5 or more and 6 or less in terms of mass ratio, and is excellent in surface quality and anti-ridging property.
The method according to claim 1,
In the stainless steel,
A ferritic stainless steel excellent in surface quality and anti-ridging property, characterized by satisfying the following formula (3).
Ti / (C + N) > 5.0 ------------------------------------ (3)
In the formula (3), Ti, C and N mean the content (wt%) of each component.
The method according to claim 1,
In the stainless steel,
A ferritic stainless steel excellent in surface quality and anti-ridging property, characterized in that the crystal grain diameter of the equiaxed crystal structure in the cast state is 2 mm or less.
The method according to claim 1,
The stainless steel
A ferritic stainless steel excellent in surface quality and anti-ridging property, wherein the ridging height (Wt) is less than 11 占 퐉 in the cold rolled steel sheet.

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