JP3323676B2 - Manufacturing method of cold rolled steel sheet with excellent perforated corrosion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cold-rolled steel sheet having excellent perforation-corrosion resistance which can be suitably used in the fields of automobiles, construction, shipbuilding and the like.

[0002]

2. Description of the Related Art Since iron is corroded even in the atmosphere, conventionally, in the field of industrial use of steel sheets, in order to prevent the corrosion or to secure sufficient characteristics even if corrosion occurs. , A great deal of cost is incurred. For example, a large amount of steel plates are used in automobiles.
Extremely severe corrosive environment, such as large temperature changes, high-speed flying stones, and snow melting agents in cold regions.

[0003] On the other hand, in recent years, in order to improve the fuel efficiency of automobiles, the steel sheets used have been increasingly thinned. In particular, in the case of members such as automobile outer panels and floor materials, it is required that the steel sheet not be perforated due to corrosion. Therefore, when thinning the members, it is necessary to improve the rust prevention ability. is there. In addition, from the viewpoint of higher quality and higher quality feel, there is a demand for the use of a steel sheet which generates less rust and has excellent perforated corrosion resistance.

In particular, in areas such as North America and Northern Europe where sodium chloride, potassium chloride, magnesium chloride, etc. are sprayed as road deicing agents in winter, or gravel is sprayed on roads to prevent slippage, only gravel that destroys the coating film is used. Rather, the wet and dry conditions are repeated in the presence of chloride ions that promote the corrosion of the steel sheet, so that particularly excellent rustproofing performance is required. In addition, scrap generated from steel sheets for automobiles is melted by automobile manufacturers and recycled as a raw material for castings such as engines, so if the steel sheet contains a large amount of elements that deteriorate the properties of castings, especially toughness, However, there is a problem that recycling is limited.

Conventionally, in order to improve the perforation-corrosion resistance of steel sheets, for example, as described in JP-A-2-22416, P or Cu is added alone or in combination. It is known that the method is effective, and this method forms a dense rust layer of P or Cu to improve the corrosion resistance against perforation. However, steel sheets to which P and Cu are added in large amounts deteriorate the toughness of the castings when the scraps are used for castings, so that it is necessary to remove them when the scraps are melted. It is impossible, and an expensive melting facility such as a cupola furnace is required to remove P.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems in a conventional steel plate having perforated corrosion resistance, and it is intended to prevent the presence of chlorine ions which promote the corrosion of iron. An object of the present invention is to provide a method for producing a cold-rolled steel sheet which has excellent corrosion resistance to perforation even in a severe corrosive environment where dry and wet conditions are repeated under a low temperature and can be easily recycled as scrap.

[0007]

According to the present invention, there is provided a method for producing a cold-rolled steel sheet having excellent resistance to pitting corrosion.
(a) C 0.001 to 0.015%, Si 0.005 to 0.005%
5%, Mn 0.02 to 0.70%, P less than 0.03%,
S 0.01% or less, Al 0.01-0.05%, all Ti
A steel containing 0.02 to 0.30% and N of 0.008% or less, with the balance being iron and unavoidable impurities, was heated to a temperature of 120%.
Heating to 0 ° C. or more, and cooling the temperature range from immediately after finish rolling to 600 ° C. at an average cooling rate of 20 to 200 ° C./sec.
Winding at a temperature in the range of 600 to 250 ° C. to produce a hot-rolled steel sheet, followed by pickling, removing the scale of the surface, performing cold rolling, and then performing 600 °
After annealing at a temperature in the range of 750 ° C. to 750 ° C., the temperature range up to 600 ° C. is cooled at an average cooling rate of 5 ° C./sec or more to contain solid solution Ti in a range of 0.02 to 0.25%. It is characterized by the following.

First, the elements added to steel in the present invention will be described. C needs to be added at least 0.001%, which is necessary for obtaining the required strength in steel plates used industrially, but 0.015%.
%, The strength of the steel is too high,
Deteriorate workability. Also, from the viewpoint of corrosion, a large amount of carbide such as cementite, which becomes a cathode at the time of corrosion, is generated, and corrosion is promoted by a potential difference between the carbide and the ground iron. As a result, perforated corrosion resistance is reduced. To 0.00
The range is 1 to 0.015%.

[0009] Si is an element added for the deoxidation of steel, and it is necessary to add at least 0.005% in order to effectively obtain the effect of deoxidation. If it is added excessively in excess of 5%, the strength of the steel is made too high, thereby deteriorating the workability. At the same time, Si concentrates on the steel sheet surface during hot rolling, lowers the pickling properties of the steel sheet, and causes Since the surface flaws occur after the elongation, the amount of addition is set in the range of 0.005 to 0.5%.

Mn is added in an amount of at least 0.02% in order to prevent hot cracking due to S. However, 0.70
%, The steel is excessively high in strength and deteriorates workability. When P is added in excess of 0.3%, the strength of the steel is increased, the workability is deteriorated, and the steel becomes brittle after working. Further, the cold-rolled steel sheet according to the present invention is used for scrap casting. When used, the toughness of the casting deteriorates, so the upper limit is 0.3%.

S combines with metal elements and the like in steel,
Exists as sulfide inclusions. This sulfide-based inclusion causes a potential difference between the sulfide-based inclusion and the metal and becomes a starting point of corrosion. Therefore, the lower the S content, the better. In particular, when S exceeds 0.01%, the amount of sulfide-based inclusions increases and the corrosion resistance to pitting is extremely deteriorated, so the upper limit is made 0.01%. A
l needs to be added at 0.01% or more for deoxidation of steel. However, even if it is added in excess of 0.05%, the deoxidizing effect is saturated.

[0012] Ti is an element effective in improving the workability of steel. In the present invention, Ti is present as solid solution Ti and has an effect of improving the pitting corrosion resistance of steel. Element. The reason why the presence of solute Ti improves the pitting corrosion resistance of steel will be described. Iron rust is the leaching of iron as Fe ²⁺ (or Fe ³⁺ ) ions, which are then converted to hydroxides or oxides. Iron is Fe
^When eluted as ²⁺ (or Fe ³⁺ ) ions, the solid solution element elutes at the same time as iron. According to the present invention, as shown in FIG. 1, when solid solution Ti is present, the pitting corrosion resistance is improved. In the figure, the steel sheet according to the present invention is indicated by ○, and the comparative example is indicated by △. The addition of Ti significantly enhances the passivation ability, improves the structure and form of iron oxyhydroxide by Ti ions, specifically stabilizes the generated rust, and forms a dense rust layer such as TiO _2. It will contribute to the improvement of the corrosion resistance against perforation.

According to the present invention, at least 0.02% of solid-solution Ti is required in order to effectively obtain the effect of improving the pitting corrosion resistance by such solid-solution Ti. However, when the amount of solid solution Ti exceeds 0.25% by weight, the size of the Ti-based inclusions increases, and workability deteriorates. Therefore, in the present invention, the lower limit of the amount of solid solution Ti is 0.02%, preferably 0.03%, most preferably 0.05%, and the upper limit is 0.2.
5%. However, according to the present technology, it is difficult to directly measure the amount of solid solution Ti, and therefore, in the present invention, TiC, TiS and Ti
It is an amount excluding the amount of Ti present as N.

Regarding the added amount of Ti (total Ti),
When excessive amounts of Ti are added, the amount of precipitated Ti increases, so that the total T
The lower limit of the i content is 0.02%, preferably 0.03%, most preferably 0.05%, and the upper limit is 0.30%. N in steel
When the amount increases, aging occurs, and a part of N combines with Ti to form TiN, thereby reducing the amount of solid-dissolved Ti and deteriorating perforated corrosion resistance. The upper limit is 0.
008%.

Further, according to the present invention, in addition to the above elements, (b) Cu 0.05 to 0.50%, Ni 0.05
~ 0.50%, Nb 0.005 ~ 0.05%, Ca 0.00
04-0.0100%, and REM 0.0004-0.01
At least one element selected from the group consisting of 00%;
Or (c) V 0.005 to 0.05%, Zr 0.005 to
0.05%, Mo 0.01-0.05%, W 0.01-0.05%
And at least one element selected from the group consisting of B. 0.05% and B 0.0003 to 0.0060%.

It is also possible to add at least one element selected from the group (b) and at least one element selected from the group (c). Cu densifies the generated rust and improves the pitting corrosion resistance of the obtained cold-rolled steel sheet. To achieve this effect effectively, at least 0.
It is necessary to add 0.05%, but 0.50
%, The effect of perforating corrosion resistance of the obtained steel sheet is not only saturated, but also the workability is reduced.

In general, barge flaws tend to occur on the surface of steel having a large amount of Cu. However, the addition of Ni to steel having a large amount of Cu can prevent the generation of the bare flaws. Therefore, in the present invention, Ni is added to improve the surface properties of the product. Ni also contributes to improving the puncture corrosion resistance of the obtained cold-rolled steel sheet.
In order to effectively obtain this effect, 0.05% or more must be added. On the other hand, even if it is added excessively, the effect of improving the surface properties and the perforated corrosion resistance is saturated. Moreover, Ni is an expensive element. Therefore, in the present invention, the upper limit is 0.50%. In particular, in the present invention, from the viewpoint of surface properties, when the added amount of Cu exceeds 0.20%,
It is desirable that Ni be added in an amount equal to or more than half the amount of Cu added.

Nb is very effective for improving the workability of steel, and is useful for increasing the amount of solid-dissolved Ti by adding Nb, and thus improving the pitting corrosion resistance. To obtain this effect effectively, it is necessary to add at least 0.005%, however,
When added in excess of 0.05%, the steel becomes brittle and makes the steel expensive.

V is useful for improving the workability of steel, and it is necessary to add at least 0.005% to effectively obtain this effect. However, the addition of more than 0.05% saturates the above effect, makes the steel brittle, and makes the steel expensive. Zr is also useful for improving the workability of steel, and in order to obtain this effect effectively, at least 0.000 is required.
5% addition is required. However, even if it is added in excess of 0.05%, the above effect is saturated, the steel becomes brittle, and the steel becomes expensive.

Mo is also useful for improving the workability of steel,
To obtain this effect effectively, it is necessary to add at least 0.01%. However, even if it is added in excess of 0.05%, the above effect is saturated, the steel becomes brittle, and the steel becomes expensive. W is also useful for improving the workability of steel, and in order to obtain this effect effectively, at least 0.0
1% addition is required. However, even if it is added in excess of 0.05%, the above effects are saturated, the steel becomes brittle, and the steel becomes expensive.

B is added to improve the embrittlement of steel after working. In order to effectively obtain this effect, it is necessary to add at least 0.0003%. However, 0.006
If it is added in excess of 0%, the steel is rather embrittled.

Ca is added to prevent pitting corrosion in the steel sheet. When the corrosion of iron is progressing, the inside of the pit is acidified by the reaction of Fe → Fe ²⁺ + e ⁻ Fe ²⁺ + 2H ₂ O → Fe (OH) ₂ + 2H ⁺ , and the iron further increases. Corrosion is promoted. However, if Ca exists here,
Ca dissolves simultaneously with iron, and since Ca is an alkali metal, it basifies the inside of the pit and suppresses the progress of the pit.

In order to obtain such an effect effectively, Ca
Is required to be added in an amount of at least 0.0004%. However, if it is added in excess of 0.01%, not only the above effect is saturated, but also the steel becomes brittle.
Similar to Ca, REM (rare earth element) is also added to basify the inside of the pit and suppress the progress of the pit. To obtain this effect effectively, at least 0.0004%
On the other hand, if the addition exceeds 0.01%, not only the effect is saturated, but also the steel becomes brittle.

Next, a method of manufacturing a cold-rolled steel sheet according to the present invention will be described. The cold-rolled steel sheet according to the present invention is produced by melting a steel having the above-mentioned chemical components by a conventional method, and casting the steel.
This can be obtained by hot rolling and annealing under the following conditions according to the present invention.

In the method of the present invention, the heating temperature of the steel is 1
200 ° C or higher. Some of the Ti added to the steel precipitates during the casting, but according to the present invention, in order to ensure the perforated corrosion resistance of the obtained cold-rolled steel sheet, the above-mentioned Ti precipitated during the casting is removed from the steel. It is necessary to secure solid solution Ti by re-dissolving at the time of heating. When the heating temperature is lower than 1200 ° C., the precipitated Ti cannot be solid-dissolved again, and as shown in FIG. 2, the resulting cold-rolled steel sheet deteriorates in perforated corrosion. Here, in the figure, the steel sheet according to the present invention is indicated by ○, and the comparative example is indicated by △. The heating temperature of the steel is usually 1350 ° C or lower. Heating temperature is 1350
When the temperature exceeds ℃, it is not preferable because a large amount of scale is generated.

Next, according to the present invention, immediately after the hot finish rolling, the temperature range up to 600 ° C. is cooled at an average cooling rate in the range of 20 to 200 ° C., and the temperature range is 600 to 250 ° C. Winding to obtain a hot-rolled steel sheet. As mentioned above,
According to the present invention, it is necessary to secure a predetermined amount of solid-solution Ti in order to secure the puncture corrosion resistance in the obtained cold-rolled steel sheet. Since certain TiC mainly precipitates in a temperature range of 600 ° C. or higher, it is necessary to rapidly cool this temperature range.

Therefore, after the finish rolling, the cooling rate and the maximum porosity were determined in order to prevent the precipitation of Ti, secure solid solution Ti, and determine the conditions for securing the pitting corrosion resistance in the obtained cold rolled steel sheet. As a result of examining the relationship with the depth, according to the present invention, as shown in FIG. 3, after finish rolling, it is necessary to rapidly cool the temperature range up to 600 ° C. at a cooling rate of 20 ° C./sec or more. is there. This cooling rate is usually in the range of 200 ° C./second or less, based on the current capacity of the hot rolling equipment. In FIG. 3, the steel sheet according to the present invention is indicated by ○, and the comparative example is indicated by △.

Generally, the cooling rate after winding is 10 ° C./hour or less. As described above, TiC, which is a main component of the Ti precipitate, mainly precipitates in a temperature range of 600 ° C. or higher. Therefore, it is necessary to rapidly cool this temperature range and then wind up. On the other hand, as shown in FIG. 4, when the winding temperature exceeds 600 ° C., the perforated corrosiveness deteriorates.
Therefore, in the present invention, the upper limit of the winding temperature is 600 ° C.
And However, when winding at a temperature lower than the Ms (martensite) point, workability deteriorates. Therefore, the lower limit of the winding temperature is set to 250 ° C. In the figure, the steel sheet according to the present invention is indicated by ○, and the comparative example is indicated by △.

According to the present invention, a hot-rolled steel sheet is manufactured in this manner, and then the surface of the hot-rolled steel sheet is subjected to pickling, grinding, and shot blasting to remove scale from the surface and cold-rolled. After that, when the obtained cold-rolled steel sheet is subjected to continuous annealing, it is heated and maintained at a temperature in the range of 600 to 750 ° C, and then cooled in a temperature range up to 600 ° C at an average cooling rate of 5 ° C / sec or more. In this way, solid solution Ti
The amount can be contained in the range of 0.02 to 0.25%.

According to the present invention, in order to obtain solid solution Ti in the steel and obtain excellent pitting corrosion resistance, annealing at a low temperature that does not precipitate much TiC, which is the main component of Ti-based precipitates, is performed. is necessary. Here, TiC is mainly
Precipitates in the temperature range above 600 ° C,
And C bond stoichiometrically, so that the amount of solute Ti decreases. That is, the annealing temperature needs to be 750 ° C. or less. However, when the annealing temperature is lower than 600 ° C,
No recovery or recrystallization occurs. Therefore, cold rolled steel sheets
It is necessary to heat to a temperature of 0 ° C. or higher and perform annealing. Thus, when the annealing temperature is 750 ° C. or higher, a sufficient amount of solid solution Ti cannot be obtained, and as shown in FIG. 5, the corrosion resistance deteriorates. Based on these, according to the present invention, the annealing temperature is in the range of 600 to 750 ° C,
It is preferably at most 720 ° C, most preferably at most 700 ° C. In the figure, the steel sheet according to the present invention is indicated by ○, and the comparative example is indicated by △.

After annealing, it is necessary to secure solid solution Ti in order to secure pitting corrosion resistance. However, as described above, TiC, which is a main component of Ti precipitates, is mainly heated to 600 ° C. or more. Since precipitation occurs in a temperature range, by cooling the temperature range up to 600 ° C. at an average cooling rate of 5 ° C./sec, precipitation of Ti can be suppressed and solid solution Ti can be secured. As described above, according to the present invention, as shown in FIG. 6, in order to improve the perforated corrosion resistance, the temperature range up to 600 ° C. can be cooled at an average cooling rate of 5 ° C./sec or more. It is necessary, and it is preferably at least 10 ° C./sec. In the figure, the steel sheet according to the present invention is indicated by ○, and the comparative example is indicated by △.

According to the present invention, after the continuous annealing is performed in this way, the amount of solute Ti is contained in the range of 0.02 to 0.25% to obtain a cold-rolled steel sheet. Excellent perforated corrosion resistance can be provided.

[0033]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples. Tables 1 to 4 show the chemical components of various steels used, their hot rolling conditions, annealing conditions, and the maximum piercing depth of the obtained cold-rolled steel sheets.

In both of the present invention example and the comparative example, the steels having the chemical components shown in Tables 1 and 3 were obtained by performing smelting at the actual machine level, and the steels were subjected to a predetermined temperature as shown in Tables 2 and 4. To 700 ° C. after hot rolling and finish rolling.
To 600 ° C. at an average cooling rate shown in Tables 2 and 4, was wound at a temperature shown in Tables 2 and 4, and was subjected to actual hot rolling.

Next, the obtained hot-rolled steel sheet was pickled, and after removing scale, cold rolling was performed on an actual machine, and then heated to the temperatures shown in Tables 2 and 4 to raise the temperature range up to 600 ° C. It cooled at the average cooling rate shown in Table 2 and Table 4, and performed continuous annealing. The cold rolled steel sheet thus obtained was evaluated for perforated corrosion resistance.

The resistance to pitting corrosion was determined by subjecting each of the cold-rolled steel sheets obtained as described above to a phosphate treatment (SD5000, manufactured by Nippon Paint Co., Ltd.), and applying a cationic electrodeposition coating (Nihon Baint). PT-U-80, 15μ
m application), and a cross cut reaching the substrate was performed. Salt water is sprayed on the steel sheet treated in this way, kept at 50 ° C. for 16 hours, dried at 70 ° C. for 4 hours, and heated to 50 ° C.
100 cycles of a corrosion promotion test in which one cycle of holding at 4 ° C. in an environment of 85 ° C. and a humidity of 85% was performed, and the maximum erosion depth (maximum hole depth) of the cross cut portion was obtained and evaluated. Tables 2 and 4 show the above results.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

[0041]

According to the present invention, even in a severe corrosive environment where dryness and wetness are repeated in the presence of chlorine ions which promote the corrosion of iron, the steel has excellent corrosion resistance to perforation and is easily recycled as scrap. Can be easily manufactured.

Such a cold-rolled steel sheet according to the present invention can be suitably used not only for automobiles but also in industrial fields where corrosion of steel is a problem, such as construction and shipbuilding. In addition, the cold-rolled steel sheet according to the present invention exhibits excellent performance when used naked or painted, but exhibits more excellent effects when combined with surface treatment such as plating and application of an organic film. .

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of solute Ti and the maximum perforated depth, that is, the perforated corrosion resistance of the test steel used in the examples.

FIG. 2 is a graph showing the relationship between the heating temperature of the test steel used in the examples and the maximum perforated depth, that is, the perforated corrosion resistance.

FIG. 3 shows the average cooling rate up to 600 ° C. and the maximum hole depth after finish rolling of the test steel used in the examples.
That is, it is a graph showing the relationship between the pitting resistance and the corrosion resistance.

FIG. 4 is a graph showing the relationship between the winding temperature of the test steel used in the examples and the maximum perforated depth, that is, the perforated corrosion resistance.

FIG. 5 is a graph showing the relationship between the annealing temperature and the maximum perforated depth, ie, the perforated corrosion resistance, of the test steel used in the examples.

FIG. 6 is a graph showing the relationship between the average cooling rate and the maximum perforated depth, that is, the perforated corrosion resistance in a temperature range of 600 ° C. or higher after annealing the test steel used in the examples. is there.

Continuation of front page (56) References JP-A-4-246128 (JP, A) JP-A-5-140654 (JP, A) JP-A-5-195078 (JP, A) JP-A-8-104945 (JP, A) , A) (58) Surveyed fields (Int. Cl. ⁷ , DB name) C21D 9/46-9/48 C21D 8/00-8/04 C22C 38/00-38/60

Claims (4)

(57) [Claims] 1. 0.001% to 0.015% of C, 0.005% to 0.5% of Si, 0.02% to 0.70% of Mn, less than 0.03% of P, and 0.01% of S by weight%. Hereinafter, a steel containing 0.01 to 0.05% of Al, 0.02 to 0.30% of total Ti, and 0.0008% of N, and consisting of iron and unavoidable impurities is heated to a temperature of 1200 ° C or more. 600 ° C immediately after finish rolling
Cooled at an average cooling rate of 20 to 200 ° C./sec and wound at a temperature in the range of 600 to 250 ° C. to produce a hot-rolled steel sheet, and then pickled to remove scale on the surface. After performing cold rolling and then continuous annealing, after annealing at a temperature in the range of 600 to 750 ° C.,
The temperature range up to 0 ° C. is cooled at an average cooling rate of 5 ° C./sec or more to contain solid solution Ti in the range of 0.02 to 0.25%. Manufacturing method of cold rolled steel sheet. (A) 0.001 to 0.015% of C, 0.005 to 0.5% of Si, 0.02 to 0.70% of Mn, P less than 0.03%, and S0. 0.01% or less, Al 0.01 to 0.05%, total Ti 0.02 to 0.30%, and N 0.008% or less, and (b) Cu 0.05 to 0.50 % Ni 0.05-0.50%, Nb 0.005-0.05%, Ca 0.0004-0.01%, and REM 0.0004%
A steel containing at least one element selected from the group consisting of 〜0.01% and consisting of iron and unavoidable impurities is heated to a temperature of 1200 ° C. or more, and immediately after finish rolling, 600
Cooling the temperature range up to 20 ° C at an average cooling rate of 20 to 200 ° C / sec, winding at a temperature in the range of 600 to 250 ° C to produce a hot-rolled steel sheet, and then pickling and scaling the surface. After performing cold rolling and then continuous annealing, after annealing at a temperature in the range of 600 to 750 ° C.,
The temperature range up to 0 ° C. is cooled at an average cooling rate of 5 ° C./sec or more to contain solid solution Ti in the range of 0.02 to 0.25%. Manufacturing method of cold rolled steel sheet. 3. In weight%: (a) 0.001 to 0.015% C, 0.005 to 0.5% Si, 0.02 to 0.70% Mn, P less than 0.03%, S 0 0.01% or less, Al 0.01 to 0.05%, total Ti 0.02 to 0.30%, and N 0.0008% or less, and (b) V 0.005 to 0.05 %, Zr 0.005 to 0.05%, Mo 0.01 to 0.05%, W 0.01 to 0.05%, and B 0.0003 to 0.0%.
06%, a steel containing at least one element selected from the group consisting of iron, and the balance consisting of iron and unavoidable impurities, heated to a temperature of 1200 ° C. or more, and 600 ° C. immediately after finish rolling.
Cooled at an average cooling rate of 20 to 200 ° C./sec and wound at a temperature in the range of 600 to 250 ° C. to produce a hot-rolled steel sheet, and then pickled to remove scale on the surface. After performing cold rolling and then continuous annealing, after annealing at a temperature in the range of 600 to 750 ° C.,
The temperature range up to 0 ° C. is cooled at an average cooling rate of 5 ° C./sec or more to contain solid solution Ti in the range of 0.02 to 0.25%. Manufacturing method of cold rolled steel sheet. 4. In weight%: (a) 0.001 to 0.015% C, 0.005 to 0.5% Si, 0.02 to 0.70% Mn, P less than 0.03%, S 0 0.01% or less, Al 0.01 to 0.05%, total Ti 0.02 to 0.30%, and N 0.008% or less, and (b) Cu 0.05 to 0.50 %, Ni 0.05-0.50 %, Nb 0.005-0.05%, Ca 0.0004-0.01%, and REM 0.0004-0.01% , at least one selected from the group consisting of: And (c) V 0.005 to 0.05%, Zr 0.005 to 0.05%, Mo 0.01 to 0.05%, W 0.01 to 0.05%, and B 0.000003 to 0.0060%, a steel containing at least one element selected from the group consisting of iron and unavoidable impurities at a temperature of 120%.
Heating to 0 ° C. or more, and cooling the temperature range from immediately after finish rolling to 600 ° C. at an average cooling rate of 20 to 200 ° C./sec.
Winding at a temperature in the range of 600 to 250 ° C. to produce a hot-rolled steel sheet, followed by pickling, removing the scale of the surface, performing cold rolling, and then performing 600 °
After annealing at a temperature in the range of 750 ° C. to 750 ° C., the temperature range up to 600 ° C. is cooled at an average cooling rate of 5 ° C./sec or more to contain solid solution Ti in a range of 0.02 to 0.25%. A method for producing a cold-rolled steel sheet having excellent perforated corrosion resistance.