KR101630965B1 - Porcelain anamel steel sheet having excellent formability and fishscale resistance and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a steel sheet used as a base metal of an enamel product, and more particularly to a cold-rolled steel sheet for an enamel excellent in formability and fish scale resistance and a method for producing the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold rolled steel sheet for an enamel having excellent formability and fish scale resistance and a method for producing the cold rolled steel sheet for an enamel,

The present invention relates to a steel sheet used as a base metal of an enamel product, and more particularly to a cold-rolled steel sheet for an enamel excellent in formability and fish scale resistance and a method for producing the same.

The enamel steel sheet is a kind of surface treatment product which is coated with vitreous glaze on the cold-rolled steel sheet and then baked at high temperature to improve corrosion resistance, weather resistance and heat resistance. Such enamel steel sheet is mainly used for building exterior, home appliance and tableware do.

In order to provide a steel sheet for enamel which prevents fishscale defects, which are known to be the most lethal defects in the enameled product, or which has improved formability, fish scale resistance is ensured by passing through a decarburization annealing process or a sandwiching process. However, Resulting in an increase in the cost of the product.

Recently, a steel sheet (Patent Document 1) prepared by adding Ti and continuously annealing for the purpose of reducing manufacturing cost has been provided. However, due to the high content of Ti, Ti oxide There is a problem that the nozzle is clogged. In addition, when these inclusions are exposed on the surface of the steel sheet, there is a problem of bubble defects, and since the recrystallization temperature is high, the annealing must be performed at a high temperature, which not only lowers the productivity, but also has a disadvantage of high manufacturing cost.

As another method, there has been provided a high-oxygen steel (Patent Document 2) in which the content of oxygen is increased to secure the hydrogen absorbing ability by using oxides in steel. However, in this case, since excessive loss of refractories occurs due to high oxygen content, This has a very low disadvantage.

Japanese Patent Application Laid-Open No. 2000-001741 Japanese Laid-Open Patent Publication No. 2002-249850

One aspect of the present invention is to provide a cold rolled steel sheet for an enamel and a cold rolled steel sheet for an enamel having excellent formability as well as to ensure the fish scale of the steel sheet to be produced by controlling the production conditions thereof, And a method for producing the same.

One aspect of the present invention provides a method of manufacturing a semiconductor device comprising the steps of: (a) providing a semiconductor substrate having a composition of (C): less than 0.003% (excluding 0), silicon: 0.1 to 0.5%, manganese (Mn) (D) expressed by the following relational expression 1 and containing not more than 0.02 to 0.05% sulfur (S): 0.008 to 0.020%, titanium (Ti): 0.03 to 0.07%, and nitrogen (N) Is 2 to 8, the formability-related index (F) expressed by the following relational expression 2 is 3 or more, and the remaining Fe and other unavoidable impurities are excellent in formability and fish scale resistance, .

[Relation 1]

D = (Ti-N-C) / S

[Relation 2]

F = {Ti-N-C- (0.3 * P) - (0.8 * S)} / C

(Ti, N, C, S, P, etc. used in the calculation of the D value and the F value of the relational expression 1 are values obtained by dividing the weight% of the respective components by the atomic weight.)

According to another aspect of the present invention, there is provided a method of manufacturing a steel slab, comprising the steps of: reheating a steel slab satisfying the above-described composition and composition relationship to 1100 to 1200 占 폚; Hot-rolling the reheated steel slab at a hot finish temperature of 900 ° C or higher to produce a hot-rolled steel sheet; Winding the hot-rolled steel sheet at 550 DEG C or higher; Rolling the rolled hot-rolled steel sheet at a cold rolling reduction rate of 65% or more to produce a cold-rolled steel sheet; And a step of subjecting the cold-rolled steel sheet to annealing at a temperature of 800 ° C or more for one minute or more, and a method for producing the cold-rolled steel sheet for an enamel excellent in formability and fish scale resistance.

According to the present invention, it is possible to provide an enamel steel sheet which has no occurrence of surface defects such as fish scale after enamel treatment and has excellent moldability, by optimizing the composition and composition of steel components and the manufacturing conditions.

Further, the cold-rolled steel sheet of the present invention has an effect of being advantageously provided as a base metal of an enamel product.

One of the most fatal defects of the steel sheet for enamel is fishscale defects. Fishscale defects are caused by the release of hydrogen, which was dissolved in steel during the manufacturing process of enamel steel, to the surface of the steel in a cooled state.

In order to prevent such a fish scale defect, it is necessary to form a large number of sites inside the steel in which hydrogen adsorbed in the steel can be adsorbed. As a hydrogen storage site, nonmetal inclusions such as MnO and CrO, precipitates such as BN, TiN, TiS, and TiN, and micropores generated after decarburization annealing Micro-void) have been used.

On the other hand, in the present invention, mainly (Ti, Fe) P and (Ti, Mn) S precipitates are used as hydrogen occlusion sites by controlling the steel components of the steel sheet for enamel, And controlling the components affecting the formability, thereby providing a steel sheet having excellent fish scale resistance and moldability.

Hereinafter, embodiments of the cold rolled steel sheet for an enamel and a method of manufacturing the same according to the present invention will be described in detail, but the present invention is not limited to the following embodiments. Accordingly, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Hereinafter, the present invention will be described in detail.

The cold rolled steel sheet for an enamel excellent in the fish scale and moldability according to one aspect of the present invention is characterized by containing, by weight%, less than 0.003% (excluding 0) of carbon (C), 0.1 to 0.5% (Ti) and 0.03 to 0.07% of nitrogen (S), 0.003 to 0.03% of nitrogen (N), 0.2 to 0.5% of phosphorus (P), 0.02 to 0.05% of phosphorus .

Hereinafter, the reason for restricting the components as described above in the cold rolled steel sheet for enamel of the present invention will be described in detail. At this time, the content of the elemental elements means the weight% unless otherwise specified.

C: Less than 0.003% (excluding 0)

In the present invention, when 0.003% or more of carbon (C) is added, the amount of the solid carbon in the steel increases, which hinders the development of the aggregate structure during annealing, thereby deteriorating the formability. In addition, since the aging phenomenon occurs and machining is performed after a long period of time after production, there is a high possibility that surface defects (stressor strain defects) will occur, so that the upper limit is preferably limited to less than 0.003%.

Si: 0.1 to 0.5%

Silicon (Si) is an element that improves enamel adhesion by covalent bonding with enamel glaze and oxygen on the surface during enamel treatment. In order to effectively improve the enamel adhesion of the steel sheet, it is preferable to add Si at 0.1% or more. However, if the content exceeds 0.5%, the steel becomes too strong and may cause surface defects during the steel making process. Can not do it.

Therefore, the content of Si in the present invention is preferably limited to 0.1 to 0.5%.

Mn: 0.2 to 0.5%

Manganese (Mn) is an element to be added for the purpose of preventing the embrittlement caused by FeS, but in the present invention, not only the prevention of the red brittleness but also the prevention of the fish scale defect due to the precipitation of the (Ti, Mn) For the purpose of.

In order to obtain the above-mentioned effect, it is necessary to add Mn to not less than 0.2%. If the content of Mn is less than 0.2%, it is difficult to effectively prevent fish scale defects because the size of the (Ti, Mn) S precipitates is of course too small. On the other hand, if the content exceeds 0.5%, the size of the formed (Ti, Mn) S precipitate becomes too large, and a sufficient amount of precipitate can not be secured.

Therefore, the content of Mn in the present invention is preferably limited to 0.2 to 0.5%.

P: 0.02 to 0.05%

Generally, phosphorus (P) is inevitably included in the present invention. In order to minimize the content of P in the present invention, the present invention uses the (Ti, Fe) P precipitate to secure the fish scale of the steel sheet .

If the content of P is less than 0.02%, the (Ti, Fe) P precipitate is not sufficiently formed or its size is too small to sufficiently improve the fish scale property. On the other hand, when the content of P exceeds 0.05% The strength of the steel sheet becomes too high, and the formation of aggregate structure during annealing is impaired, resulting in a problem of deterioration of moldability.

Therefore, in the present invention, the content of P is preferably limited to 0.02 to 0.05%.

S: 0.008 to 0.020%

Sulfur (S) is generally known as an element which hinders the physical properties of steel. In the present invention, however, (S, Mn) S precipitates are formed to absorb and store hydrogen generated during the enamel treatment process to prevent occurrence of fish scale defects Do not add.

For the above-mentioned effect, it is preferable to add S to 0.008% or more. If the content of S is less than 0.008%, the amount of generated (Ti, Mn) S precipitate is small and the hydrogen absorption capacity is lowered, There is a high possibility. On the other hand, if the content exceeds 0.020%, the ductility is greatly lowered and there is a problem that the brittleness due to S is likely to occur. Therefore, it is preferable to limit the content to 0.008 to 0.020%.

Ti: 0.03 to 0.07%

Titanium (Ti) is an additive element important for forming (Ti, Fe) P precipitate and (Ti, Mn) S precipitate for preventing fish scale formation in the present invention.

If the content of Ti is less than 0.03%, the possibility of occurrence of fish scale defects is high because the amount of precipitates to be produced is too small. On the other hand, if the content exceeds 0.07%, Ti-oxide is excessively produced during steel making, There is a problem that the steelmaking workability is significantly lowered by adhering to the nozzle wall.

Therefore, in the present invention, it is preferable to limit the Ti content to 0.03 to 0.07%.

N: not more than 0.003%

As the content of nitrogen (N) added in the steel is increased, the formability is lowered and bubble defects are more likely to occur. Therefore, it is preferable to limit the upper limit to 0.003%.

It is preferable that the present invention is to form (Ti, Fe) P precipitate and (Ti, Mn) S precipitate by adding Ti, P, Mn and S or the like and the related components are closely related to surface defects or moldability of steel .

That is, the S added in large amounts for the formation of the (Ti, Fe) P precipitate and the (Ti, Mn) S precipitate in the steel has a high possibility of generating a surface flaw by generating a heat brittleness. In addition, the amount of Ti precipitates is closely correlated with the content of Ti. When the content of Ti is too high, there is a problem that Ti oxide adheres to the nozzle wall during steel making process to cause surface defects. If the Ti content is too low, There is a problem that the amount of the precipitate to be formed is insufficient and the effect of suppressing the fish scale defects is small and the formability is lowered or the probability of generating surface defects due to the heat and brittleness is increased.

Accordingly, in the present invention, the components affecting the surface defects and the formability of the steel, particularly, the component contents of Ti and S are defined by the surface defect related index (D) expressed by the following relational expression 1 and the moldability related index (F), and to control the correlation with other components affecting surface defects and formability of steel.

[Relation 1]

D = (Ti-N-C) / S

[Relation 2]

F = {Ti-N-C- (0.3 * P) - (0.8 * S)} / C

(Ti, N, C, S, P, etc. used in the calculation of the D value and the F value of the relational expression 1 are values obtained by dividing the weight% of the respective components by the atomic weight.)

More specifically, in the present invention, it is preferable to add Ti, P and S so that the surface defect related index D satisfies 2 to 8 and the formability index (F) satisfies 3 or more.

At this time, if the surface defect related index (D) expressed by the correlation between the contents of Ti, N, C and S is less than 2, there is a problem that the probability of surface defect occurrence becomes very high. On the other hand, There is a problem that adhesion is significantly lowered.

In addition, if the formability index (F) expressed by the correlation between the contents of Ti, N, C, P and S is less than 3, the formability becomes too low, and there is a problem that the probability of occurrence of defects increases during processing.

It includes a S precipitates (Ti, Fe) P precipitate, and (Ti, Mn) in the steel, by properly controlling the composition components as described above, in which the precipitates are 4 × 10 ⁷ per observation field of view per square cm (cm ²⁾ Or more, it is possible to secure a steel sheet free from surface defects such as fish scale defects.

The (Ti, Fe) P precipitate and the (Ti, Mn) S precipitate formed in the above-described distribution cause the precipitates to be broken at the time of hot rolling and cold rolling, and at the same time cause internal cracks, the formation of micro-voids can be greatly improved. The formed micropores can be utilized as a storage site capable of absorbing and storing hydrogen.

In the present invention, it is preferable that the size of the precipitate including the precipitate itself or the surrounding fine pores is 0.1 to 0.7 mu m. If the average size of the precipitates is less than 0.1 탆, the size of the micropores produced by crushing during hot rolling and cold rolling is too small to sufficiently obtain the adsorption effect of hydrogenated hydrogen. On the other hand, when the average size of the precipitates is larger than 0.7 탆, And it may be difficult to secure the fish scale property.

Hereinafter, a method of manufacturing the cold rolled steel sheet for enamel according to the present invention will be described in detail.

The following production method is a preferred example of producing the cold rolled steel sheet for enamel of the present invention, but is not limited thereto.

First, a steel slab satisfying the above-described composition and composition relationship is manufactured, and then the steel slab is reheated.

In the present invention, the temperature during the reheating treatment is one of the important factors, and has an important influence on the determination of the size and distribution amount of the precipitate according to the present invention. The temperature at this time depends on the kind and content of the element added to the steel. Redissolution / precipitation temperature changes. If the reheating temperature exceeds 1200 ° C, the size of the precipitate becomes too small to cause a fish scale defect.

Therefore, the reheating temperature is preferably controlled to 1200 ° C or less, more preferably 1100 to 1200 ° C.

It is preferable that the reheated steel slab is hot-rolled at a hot-rolling temperature of 900 ° C or higher to produce a hot-rolled steel sheet.

If the hot rolling temperature is lower than 900 캜, the {111} texture is severely degraded after the subsequent annealing process due to the formation of the drawn ferrite. When the {111} texture is deteriorated, the r value is significantly lowered, and the processability of the shrubs is deteriorated.

Therefore, the hot finish rolling temperature is preferably controlled to 900 ° C or higher, more preferably 900 to 1000 ° C.

It is preferable to wind the hot rolled steel sheet at 550 DEG C or higher.

If the temperature is less than 550 캜 at the time of winding, the size of the precipitate becomes too small, and the hot-rolled grain size becomes too small, which lowers the formability.

Therefore, the coiling temperature is preferably controlled to 550 DEG C or higher, and more preferably 550 DEG C to 650 DEG C.

Thereafter, the rolled hot-rolled steel sheet is preferably cold-rolled to produce a cold-rolled steel sheet.

If the cold rolling reduction rate in the cold rolling is less than 65%, the amount of micropores between the precipitate and the matrix is small, causing fish scale defects, and the recrystallization texture is low, resulting in poor moldability.

Therefore, it is preferable to control the cold reduction rate to 65% or more, and more preferably 65 to 90%.

Thereafter, the cold-rolled steel sheet is preferably subjected to continuous annealing at 800 DEG C or higher for one minute or longer.

In the present invention, continuous annealing is a step for imparting ductility and formability to a cold-rolled steel sheet. When the annealing temperature is less than 800 ° C, recrystallization is not completed and it is difficult to secure ductility and formability. , The recrystallization is not completed and it is difficult to secure ductility and moldability.

Therefore, the continuous annealing is preferably performed at 800 DEG C or more for 1 minute or more, more preferably 800 to 900 DEG C for 1 to 5 minutes.

Hereinafter, the present invention will be described more specifically by way of examples. It should be noted, however, that the following examples are intended to illustrate the invention in more detail and not to limit the scope of the invention. The scope of the present invention is determined by the matters set forth in the claims and the matters reasonably inferred therefrom.

( Example )

Steel slabs having the composition shown in Table 1 below were prepared, and then the steel slabs were held in a heating furnace at 1150 DEG C for 1 hour and then subjected to hot rolling. During the hot rolling, the finish temperature was 920 占 폚, and then the hot-rolled steel sheet was rolled at 650 占 폚 to produce a hot-rolled steel sheet having a thickness of 3.2 mm. The hot-rolled steel sheet was subjected to pickling treatment to remove the oxide film on the surface, and then cold-rolled at a cold rolling reduction rate of 75% to prepare a cold-rolled steel sheet having a final thickness of 0.8 mm.

Then, the cold-rolled steel sheet was processed into enamel treated specimens for inspection of enamel characteristics and tensile specimens for investigating mechanical properties, and then subjected to continuous annealing. At this time, the enamel-treated specimen was cut into a size of 70 mm × 150 mm, and the tensile specimen was processed into a standard specimen according to the ASTM standard (ASRM E-8 standard).

The thus processed specimen was continuously annealed at 830 캜 for 3 minutes. After the annealing, the enamel-treated specimens were thoroughly degreased, coated with a low-temperature glaze, dried at 200 ° C for 10 minutes to remove moisture completely, and then baked at 830 ° C for 7 minutes and then cooled to room temperature. After that, the specimens after the low-enamel treatment were applied again with the oil-based glaze, and then dried at 200 ° C for 10 minutes to completely remove moisture. The dried specimens were baked at 800 ° C for 7 minutes and then subjected to air-cooling enamel treatment. At this time, the atmospheric conditions of the firing furnace were set at a dew point temperature of 30 占 폚 to apply harsh conditions in which fish scale defects were most likely to occur. Then, the enamel-treated specimens were maintained at 200 ° C in a holding furnace for 20 hours to accelerate the fish scale. Thereafter, the number of fish scale defects occurred was visually inspected. At this time, the adhesion index was measured using an adhesion test apparatus (test apparatus according to ASTM C313-78).

The yield strength (YS), tensile strength (TS), elongation (El) and plastic anisotropy index ( _rm value) of the tensile specimens annealed were measured using a tensile tester (INSTRON Corporation, Model 6025). The plastic anisotropy index ( _rm value) indicating the formability was obtained by taking tensile specimens in the rolling direction, in the direction perpendicular to the rolling direction and in the direction of the rolling direction of 45 ° and calculating the shrinkage ratio in the width direction and the thickness direction at the time of 15% _{(w f -w 0) / ln} (t f / t 0) to a value calculated by measuring for each r _0, r ₄₅ and r _90, and r _m are as _{r m = (r 0 + 2r} 45 + r 90) / 4.

The mechanical properties, enamel characteristics, etc. of each of the above samples are shown in Table 2 below.

At this time, the number of fish scale defects and bubble defects finally occurred were visually observed and judged to be 'good' and 'occurred' according to occurrence. The number of titanium precipitates per 1 square cm (cm ² ) in the manufactured cold rolled steel sheets for enamel was measured by a point counting method using an electron microscope at an image of 5000 to 40 fields by a number of 0.1 to 0.7 μm And then converted into 1 square cm (cm ² ) by using an image analyzer (imaze analyzer).

division Component composition (% by weight) Formability
Index (F) Surface defect
Index (D) C Si Mn P S Ti N Inventive Steel 1 0.0013 0.15 0.24 0.033 0.009 0.062 0.0022 4.45 3.65 Invention river 2 0.0015 0.18 0.35 0.041 0.011 0.068 0.0012 4.27 3.51 Invention steel 3 0.0011 0.26 0.47 0.044 0.009 0.055 0.0014 3.31 3.39 Inventive Steel 4 0.0009 0.25 0.38 0.038 0.008 0.054 0.0014 5.10 3.80 Comparative River 1 0.0025 0.28 0.85 0.005 0.009 0.034 0.0012 0.68 1.47 Comparative River 2 0.0012 0.15 0.05 0.014 0.008 0.062 0.0007 8.06 4.57 Comparative Steel 3 0.0028 0.13 0.12 0.045 0.055 0.054 0.0021 -4.58 0.43 Comparative Steel 4 0.0011 0.18 0.21 0.012 0.008 0.150 0.0072 24.03 10.08 Comparative Steel 5 0.0012 0.88 0.42 0.033 0.008 0.058 0.0014 4.89 4.03

division YS
(MPa) TS
(MPa) Hand
(%) r _m Material
flaw bubble
flaw Fish Scale
Occurrences Enamel adhesion
Indices(%) Precipitate
Size (㎛) Number of precipitates
(Pieces / cm ² ) Inventive Steel 1 168 305 47 2.22 Good Good 0 98 0.32 6.2 × 10 ⁷ Invention river 2 175 312 48 2.17 Good Good 0 99 0.38 5.6 x 10 ⁷ Invention steel 3 186 327 46 2.09 Good Good 0 100 0.42 5.1 x 10 ⁷ Inventive Steel 4 188 321 47 2.12 Good Good 0 100 0.44 5.3 × 10 ⁷ Comparative River 1 208 309 48 1.39 Occur Good 129 100 1.23 1.3 × 10 ⁶ Comparative River 2 169 297 48 1.97 Good Good 38 95 0.08 5.9 x 10 ⁷ Comparative Steel 3 224 322 45 1.45 Good Good 0 85 0.36 5.8 x 10 ⁷ Comparative Steel 4 162 288 47 2.24 Occur Occur 22 75 0.53 8.2 × 10 ⁵ Comparative Steel 5 194 321 45 2.02 Occur Good 0 65 0.42 5.1 x 10 ⁷

(In Table 2, the number of precipitates indicates the total number of (Ti, Fe) P precipitates and (Ti, Mn) S precipitates, and the precipitate size indicates the average size of the precipitates.)

As shown in Tables 1 and 2, inventive steels 1 to 4 satisfying all the composition, composition and manufacturing conditions of the present invention had a plastic anisotropy index (r _m value) of not less than 2.00, and both strength and ductility It could be secured at the same time. In addition, since the size and number of precipitates satisfy the range controlled by the present invention, fish scale defects do not occur even in severe conditions, so that excellent fish scale resistance can be confirmed. In addition, .

On the other hand, the comparative steel 1 has a very low index (F) of 0.68 for the molding of the material and a low plastic anisotropy index of 1.39. Also, when the molding is complicated or the molding process is required, It is confirmed that the possibility of occurrence is high. In addition, the index (D) indicating the possibility of occurrence of surface defects of the material was as low as 1.47, causing defects on the surface of the material. The size of the precipitate was too large and the amount of the precipitate was insufficient.

In the comparative steel 2, the formability index (F) was 8.06 and the plastic anisotropy index ( _rm ) was 1.97, while the Mn content was out of the range of the present invention and the size of the precipitate was small.

In the case of the comparative steel 3, the plasticity index (F) was low at -4.58 and the plastic anisotropy index ( _rm ) was low at 1.45 and the surface defect index (D) was also low at 0.43, .

The comparative steel 4 showed good results in terms of moldability, but the content of P was too low in the composition of the components and the content of Ti was too large, so that the precipitates could not be sufficiently formed to an adequate level, causing fish scale defects. In addition, since N content was high, bubble defects occurred after enamel treatment, and the surface defect related index (D) was too high, resulting in poor enamel adhesion.

In the case of comparative steel 5, both the D value and the F value satisfied the range suggested by the present invention, but the Si content deviated from the range of the present invention, causing surface defects, and the enamel adhesion was extremely poor.

Claims (5)

(C): less than 0.003% (excluding 0), silicon (Si): 0.1 to 0.5%, manganese (Mn): 0.2 to 0.5%, phosphorus (P): 0.02 to 0.05% (D) expressed by the following relational expression 1 satisfies 2 to 8 (inclusive): 0.008 to 0.020% of titanium (Ti), 0.03 to 0.07% of titanium (Ti, Fe) P precipitate and (Ti, Mn) S precipitate are contained in the steel, which is composed of Fe and other unavoidable impurities and satisfies 3 or more, And the precipitates are excellent in formability and fish scale resistance of 4 x 10 ⁷ or more per 1 square cm (cm ² ) of observation field.
[Relation 1]
D = (Ti-NC) / S
[Relation 2]
F = {Ti-NC- (0.3 * P) - (0.8 * S)} / C
(Ti, N, C, S, P, etc. used in the calculation of the D value and the F value of the relational expression 1 are values obtained by dividing the weight% of the respective components by the atomic weight.)
delete The method according to claim 1,
Wherein the precipitate contains micro voids around the precipitate, and the precipitate has excellent formability and fish scale resistance.
The method according to claim 1,
Wherein the precipitate has an average size of 0.1 to 0.7 占 퐉, and is excellent in formability and fish scale resistance.
(C): less than 0.003% (excluding 0), silicon (Si): 0.1 to 0.5%, manganese (Mn): 0.2 to 0.5%, phosphorus (P): 0.02 to 0.05% (D) expressed by the following relational expression 1 satisfies 2 to 8 (inclusive): 0.008 to 0.020% of titanium (Ti), 0.03 to 0.07% of titanium , Reheating a steel slab satisfying a formability index (F) of 3 or more expressed by the following formula 2 and composed of the remainder Fe and other unavoidable impurities to 1100 to 1200 캜;
Hot-rolling the reheated steel slab at a hot finish temperature of 900 ° C or higher to produce a hot-rolled steel sheet;
Winding the hot-rolled steel sheet at 550 DEG C or higher;
Rolling the rolled hot-rolled steel sheet at a cold rolling reduction rate of 65% or more to produce a cold-rolled steel sheet; And
Annealing the cold-rolled steel sheet at 800 DEG C or more for one minute or more;
And a method of producing a cold rolled steel sheet for an enamel excellent in formability and fish scale resistance.
[Relation 1]
D = (Ti-NC) / S
[Relation 2]
F = {Ti-NC- (0.3 * P) - (0.8 * S)} / C
(Ti, N, C, S, P, etc. used in the calculation of the D value and the F value of the relational expression 1 are values obtained by dividing the weight% of the respective components by the atomic weight.)