JPH105810A - Production of thin steel sheet for work with excellent forming property using continuous hot rolling process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniform the quality of hot rolling steel sheet over the total length and to improve the productivity by roughly rolling a steel slab of a specific carbon content into a steel sheet, joining its top end to the rear end of an advancing rough-rolled steel sheet and continuously executing hot finish rolling. SOLUTION: A steel slab which contains <=0.1% C and is heated to <=1150 deg.C in a heating furnace 1 is hot-rolled by a roughing mill 2, and this is coiled and made a rough rolled coil 3. Its rear end is cut with a welding cutter 4, and a rear end groove suitable for welding is formed. The rear end of the preceding rough-rolled steel sheet and the top end of a succeeding rough-rolled steel sheet are welded with a welding equipment 5. The rough-rolled steel sheet welded in a long size is subjected continuously to a finish rolling by a finishing mill 6, next, it is wound as a coil with a coiler 9 after it is cooled with water by a cooling device 7 installed on run-out table. Therefore, the product yield, affected by the defective quality of the top end of the hot rolled steel sheet, can be improved and the cost merit is improved also.

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 hot-rolled steel sheet by a continuous hot-rolling method and a method for producing a cold-rolled steel sheet using the same as a material, and particularly to a formability used for automobiles and industrial machines. The present invention relates to a method for producing a thin steel sheet for processing excellent in quality.

[0002]

2. Description of the Related Art Conventionally, in the technical field of steel sheets for processing of automobiles and the like, cold-rolled steel sheets having good workability have been used. Hot rolled steel sheets for processing have been used.

On the other hand, in the field where surface quality and thickness accuracy are required, there is a demand for a cold rolled steel sheet which is less expensive than the conventional one without deteriorating the quality.

The present invention relates to a method for producing a hot-rolled steel sheet by a continuous hot-rolling method and a method for producing a cold-rolled steel sheet using the same as a material, and particularly to a process excellent in formability used for automobiles and industrial machines. The present invention relates to a method for producing a thin steel sheet for use.

[0005] A method for producing a hot-rolled steel sheet as a material for a hot-rolled steel sheet for processing and a cold-rolled steel sheet for processing used in automobiles, industrial machines, and the like (hereinafter, these are collectively simply referred to as a hot-rolled steel sheet) is described below. Continuously cast steel slab is heated to about 120
It is common to heat to 0 ° C., then rough-roll with a hot rolling mill, finish-roll, cool with cooling water and wind it up into a coil. In such a conventional method for manufacturing a hot-rolled steel sheet,
Hot rolling is performed for each steel slab, and the finished steel sheet is subjected to laminar cooling with cooling water in a cooling device provided on a run-out table, and the hot rolled steel sheet at the winding temperature is wound into a coil. However, when cooling the hot-finished steel sheet, even if it is attempted to cool from the tip of the steel sheet, the tip of the steel sheet collides with the water column of the cooling water, and the steel plate deforms and stalls due to the influence of the water column, causing trouble on the passing plate. The cooling process could not be performed because of the occurrence of. This phenomenon becomes more remarkable as the plate thickness becomes thinner.

Therefore, conventionally, when cooling a hot-rolled steel sheet to the winding temperature, the front end of the hot-rolled steel sheet is pinched without cooling the front end of the hot-rolled steel sheet in order to avoid troubles in passing the steel sheet. They were bitten by rolls and then cooled. In such a conventional method for cooling a hot-rolled steel sheet, since the leading end of the steel sheet is not subjected to a cooling treatment, that part becomes defective in material, and when the steel sheet is shipped as a product or used as a material for a cold-rolled steel sheet, the steel sheet is cooled. Since the tip portion that has not been cooled is cut off, there is a problem that the product yield is poor.

[0007] Next, considering heat treatment in a heating furnace, in order to perform hot rolling without deteriorating workability, it is necessary to set the temperature of the steel sheet to be rolled to at least the Ar ₃ transformation point or higher. is there. FIG. 1 is a diagram showing a finishing temperature distribution of a hot-rolled steel sheet. As shown in FIG. 1, the finishing temperature of the front end portion of the steel sheet to be hot-rolled is the lowest, and the finishing temperature becomes higher toward the rear end portion. It is considered that the reason why the finishing temperature at the rear end is increased is due to the heat generated during processing.

As described above, since the finishing temperature of the steel sheet is not uniform over the entire length of the steel sheet, the material of the steel sheet is different between the front end portion and the intermediate portion, and thus there is a problem.

The heating temperature in the heating furnace must be selected so that the minimum finishing temperature of the steel sheet to be hot-worked, that is, the finishing temperature at the tip of the steel sheet is equal to or higher than the Ar ₃ transformation point. I had to.

[0010] Therefore, the heating in the conventional heating furnace is performed by Ar
Heating to a temperature of about 1200 ° C., considerably higher than the _three transformation points, has been performed. When this heating is viewed from a cost balance in terms of energy saving, excessive heating is performed at portions other than the front end portion of the steel sheet, and there is a problem that the cost balance is poor.

A method for producing a hot-rolled steel sheet for processing which aims to reduce the unit consumption of a heating furnace by extremely reducing heat consumption is disclosed in Japanese Patent Publication No. Sho.
No. 4-11695. In this method, the temperature of the hot slab obtained by continuous casting is reduced to 5 to 30% at a temperature of Ar _{3 to} 1200 ° C. without lowering the temperature to the Ar ₃ transformation point or lower.
And then hot rolling is performed after charging and heating in a heating furnace maintained at 950 to 1150 ° C.
In this method, even though the hot rolling conditions for the temperature of the intermediate portion of the hot rolled steel sheet are appropriate, consideration has been given to solving the above-described problem of the temperature drop at the tip of the hot rolled steel sheet. It is technically difficult to obtain a homogeneous steel sheet by performing hot finish rolling without deteriorating the workability over the entire steel sheet, even if the heating furnace basic unit is reduced. .

[0012]

SUMMARY OF THE INVENTION Accordingly, the present invention is to provide a hot rolled steel sheet having a uniform material over its entire length, to improve the yield due to a defective material at the tip, and to provide a cost merit by saving energy in a heating furnace. It is an object of the present invention to provide a thin steel sheet for processing having improved formability and improved productivity and excellent in formability.

[0013]

[Means for Solving the Problems]

(1) A steel slab having a carbon content of 0.1% or less is heated in a heating furnace, rough-rolled by a hot rough rolling mill to form a steel sheet, and then finish-rolled by a hot finishing rolling mill, and then cooled to form a coil. In the method for producing a hot-rolled steel sheet for processing excellent in formability characterized by being wound up, the leading end of the rough-rolled steel sheet is joined to the rear end of the preceding steel sheet with the rough-rolled rolling line preceding it. A method for producing a hot-rolled steel sheet for processing excellent in formability, characterized by continuously performing hot finish rolling.

(2) A steel slab having a carbon content of 0.1% or less is heated in a heating furnace, rough-rolled by a hot rough rolling mill to form a steel sheet, and then finish-rolled by a hot finishing mill and then cooled. And forming a hot-rolled steel sheet for processing excellent in formability, wherein the heating in the heating furnace is performed for 1 hour.
Low-temperature heating of 150 ° C. or less, and the hot-rolling is continuously performed by joining the front end of the rough-rolled steel sheet to the front end of the rough-rolled rolling line before the rear end of the preceding steel sheet. Of hot rolled steel sheets for processing with excellent formability.

(3) A steel slab having a carbon content of 0.1% or less is heated in a heating furnace, rough-rolled by a hot rough rolling mill to form a steel sheet, and then finish-rolled by a hot finishing rolling mill and then cooled. And forming a hot-rolled steel sheet for processing excellent in formability, wherein the heating in the heating furnace is performed for 1 hour.
1. Low-temperature heating of 150 ° C. or less, and the front end of the rough-rolled steel sheet is joined to the rear end of the preceding steel sheet by rough-rolling before the rolling line to continuously perform hot finish rolling.
A method for producing a hot-rolled steel sheet for processing excellent in formability, wherein the hot-rolled steel sheet has a thickness of 0 mm or less.

(4) A steel slab having a carbon content of 0.1% or less is heated in a heating furnace, rough-rolled by a hot rough rolling mill to form a steel sheet, and then finish-rolled by a hot finishing mill and then cooled. In the method of manufacturing a cold-rolled steel sheet for processing, comprising a hot-rolling step of winding and winding the coil, and then a cold-rolling step of further performing cold rolling and recrystallization annealing, the leading end of the rough-rolled steel sheet, before the A cold-rolled steel sheet for processing excellent in formability characterized by having a hot-rolling step of continuously performing finish rolling and cooling after rolling by joining a rough rolling and a rolling line to a rear end of a preceding steel sheet. Manufacturing method.

(5) A steel slab having a carbon content of 0.1% or less is heated in a heating furnace, rough-rolled by a hot rough rolling mill to form a steel sheet, and then finish-rolled by a hot finishing rolling mill and then cooled. In a hot-rolling steel sheet for processing, comprising: a hot-rolling step of rolling and coiling, and a cold-rolling step of further performing cold rolling and recrystallization annealing. The hot rolling process of continuously performing finish rolling and cooling after rolling by heating, and joining the leading end of the rough-rolled steel sheet to the rear end of the preceding steel sheet that is rough-rolled before the rolling line. A method for producing a cold-rolled steel sheet for processing excellent in formability, comprising:

(6) In the method for producing a cold-rolled steel sheet for processing according to the above (5), the thickness after hot finish rolling is 2.0 m.
m or less, and a method for producing a cold-rolled steel sheet for processing excellent in formability.

Hereinafter, the present invention will be described in detail.

In the present invention, in order to enable the cooling treatment of the front end portion of the hot-rolled steel sheet and to improve the yield by eliminating material defects, the front end of the rough-rolled hot-rolled steel sheet and the rear end of the preceding hot-rolled steel sheet And are joined by welding. Since the joined steel sheets are united, hot finish rolling can be performed continuously.If the first end of the hot rolled finished steel sheet is bitten by the pinch roll of the winding machine, then it will be continuous. Then, cooling by cooling water is enabled by the cooling device, and the hot-rolled finished steel sheet cooled to the winding temperature is wound up by the winder.
The hot-rolled finished steel sheet is cut at a predetermined length by a cutter and wound up by a winder, and the cut portion is preferably a joint.

In the conventional hot-rolling method, when the hot-rolled finished steel sheet is subjected to laminar cooling by a cooling device, even if an attempt is made to cool from the front end of the steel sheet, the front end of the steel plate collides with the water column of the cooling water, and the influence of the water column is exerted. As a result, the steel plate was deformed and stalled, causing troubles in the passing of the steel plate and preventing cooling. This phenomenon was particularly remarkable for a thin plate (a plate thickness of 2 mm or less).

However, according to the present invention, although the tip of the first hot-rolled steel sheet is not cooled as in the prior art, the material becomes defective, but the steel sheet continuously hot-rolled thereafter is
Since the front end of the steel sheet does not exist, it is possible to cool the entirety, and there is no defective portion of the material, so that the product yield due to the defective material can be improved.

The thin steel sheet for processing produced by the present invention, which has excellent formability, can be used in automobiles, industrial machines and the like.
It is intended for soft steel sheets of the class of 0 MPa, and specific examples of the components and component ranges of these steel plates are as follows.

Example 1 Low carbon steel sheet C: 0.1% or less, Mn: 0.1-1.0%, Si:
0.1% or less, P: 0.025% or less, S: 0.025
% Or less, with the balance substantially consisting of Fe and excellent in formability.

Example 2 Ultra-low carbon steel sheet C: 0.0050% or less, Mn: 0.05-0.6%,
Si: 0.05% or less, P: 0.015% or less, S:
0.015% or less, and B: 0.0002 to 0.004
0%, Ti: 0.015 to 0.06%, Nb: 0.01
A thin steel sheet for processing which contains at least one selected from 0 to 0.040% and is substantially composed of Fe, and has excellent formability.

C contained in a thin steel sheet for processing excellent in formability is a hardening element, and if the C content is large, it becomes hard and the formability is deteriorated. Less is preferred. In low carbon steel sheets, C can be contained up to 0.1% at maximum, and in ultra low carbon steel sheets, C can be contained up to 0.0050% at maximum.

Mn is an element necessary for imparting toughness, but when it is increased, workability is deteriorated. Si is added as a deoxidizing agent, but hardens as it increases. P and S are
Although it is inevitably contained, an increase in the content adversely affects workability. B, Ti and Nb form fine carbonitrides,
If it increases, workability deteriorates.

For such a reason, the components as shown in the above example,
It has been adjusted to the component range. However, the thin steel sheet for processing in the present invention is not limited to the above specific examples.

Next, the heating temperature of the heating furnace will be described.

FIG. 2 is a diagram schematically showing a relationship between a heating furnace temperature and a finishing temperature of a hot-rolled steel sheet. As shown in FIG.
In the conventional hot rolling method, usually, about 1200 ° C in a heating furnace.
Hot-rolled steel slab in a heated state, the temperature of the middle part of the hot-rolled finished steel sheet is about 900 ° C., and the tip of the hot-rolled finished steel sheet has dropped to a temperature near the Ar ₃ transformation point, respectively. Was. As described above, the temperature at the tip of the hot-rolled finished steel sheet was significantly reduced.

However, in the present invention, since the leading end of the rough-rolled hot-rolled steel sheet is joined to the rear end of the preceding hot-rolled steel sheet by the rough-rolled hot-rolling line, the hot-rolled steel sheet is continuously hot-rolled. Rolling becomes possible, and the hot rolling can be performed at a constant speed, so that the rolling conditions are the same over the entire length of the steel sheet, and the conventional batch type hot rolling accelerated rolling is Differently, there is no variation in the temperature drop of the hot-rolled finished steel sheet. That is, according to the continuous hot rolling method of the present invention, since the leading end of the steel sheet does not exist, the hot rolling condition becomes rolling equivalent to the intermediate portion of the conventional hot rolled finished steel sheet. The temperature drop is constant, and the temperature drop is small as shown by the mark ● in FIG. In particular, when a thin steel plate having a thickness of 2.0 mm or less is to be manufactured only by hot rolling, heat is quickly released and it is difficult to secure a finishing temperature. Even a thin steel plate of 0 mm or less can be manufactured effectively.

For this reason, in the present invention, the temperature in the heating furnace can be set lower than the conventional temperature, and according to experiments, it is necessary to set the temperature of the hot-rolled finished steel sheet to the Ar ₃ transformation point or higher. It has been found that heating at a low temperature of 1150 ° C. or lower and 950 ° C. or higher is sufficient. Also, as in the past, 12
At a heating temperature of 00 ° C., precipitation of MnS or AlN does not occur in the steel, and the crystal grains become coarse. Therefore, the crystal grains are not sufficiently refined by recrystallization after rolling, thereby deteriorating the workability of the steel sheet. However, if heating at a low temperature of 1150 ° C. or less, Mn is contained in steel.
It has been found that the precipitation of S and AlN is promoted and grain refinement occurs, an effect of improving workability, particularly elongation, of the steel sheet occurs, and the material is improved over the entire length of the steel sheet.

That is, if the heating temperature exceeds 1150 ° C., excessive heating results in no energy saving cost merit, and MnS and AlN do not precipitate in steel, and the material is not improved. At a low temperature of 1150 ° C. or less. On the other hand, if the temperature is 950 ° C. or lower, the hot finishing temperature is lower than the Ar ₃ transformation point, which deteriorates the workability, which is not preferable.

In the present invention, a cold-rolled steel sheet for processing excellent in formability can be manufactured by using the hot-rolled steel sheet obtained in the hot-rolling step as a raw material and further using a cold-rolling step.

Next, the conditions of the cold rolling step will be described.

In the cold rolling step, the hot rolled steel sheet obtained through the hot rolling step described above is subjected to cold rolling and recrystallization annealing. In this step, the rolling reduction of the cold rolling is desirably 50% or more and 90% or less, and the recrystallization annealing after the cold rolling is performed at 650 ° C. or more and 950 ° C. or more in order to obtain a good recrystallized structure.
It is desirable that the temperature be less than or equal to ° C. The method of annealing is box annealing,
Any of the continuous annealing methods may be used. Further, this annealing can be performed in a continuous hot-dip galvanizing step. Still further, the steel plate subjected to the recrystallization annealing may be subjected to temper rolling at a rolling ratio of 10% or less to adjust the surface properties and correct the plate shape.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings.

FIG. 3 is a diagram showing an outline of a method of manufacturing a hot-rolled steel sheet in the hot-rolling continuous method.

As shown in FIG.
A steel slab having a carbon content of 0.1% or less, which has been heated below, is hot-rolled by a rough rolling mill 2 and wound up to form a rough-rolled coil 3. The tip of the rough-rolled coil 3 is cut by the welding cutting machine 4 to form a tip groove suitable for welding. The preceding rough-rolled steel sheet is conveyed to a finish rolling mill and finish-rolled. The trailing end is similarly cut by the welding cutting machine 4 to form a trailing edge suitable for welding. The rear end of the preceding rough rolled steel sheet and the front end of the subsequent rough rolled steel sheet are welded and joined by the welding device 5.

The welding device 5 is composed of a moving carriage, and is controlled so as to be able to move in synchronization with the moving speed of the rear end of the rough-rolled steel sheet. Is welded to the leading end of the subsequent rough-rolled steel plate. As a welding method, a laser beam welding method is suitable, but other known welding methods can also be applied.

The long rolled steel sheet integrally joined and lengthened by the welding device 5 is finish-rolled continuously by the finishing mill 6 and then cooled to a winding temperature by a cooling device 7 installed on a run-out table. After being cooled, it is wound up by the winder 9 as a coil. When the finished steel sheet is wound by a predetermined length, the finished steel sheet is cut by a cutting machine 8 to be used as another coil.
Wound up. In addition, it is preferable to cut the part joined by the welding device 5 in the cutting part by the cutting machine 8.

In the present invention, the front end of the rough rolled steel sheet is joined to the rear end of the preceding rough rolled steel sheet to form a long steel sheet, so that hot finish rolling can be continuously performed.
Therefore, the hot-rolled steel sheet does not have a tip other than the initial tip, and the steel sheet is always supported by the pinch roll of the winding machine. Even so, the hot finished steel sheet can be continuously cooled with water by a cooling device. Therefore, the tip portion of the steel sheet, which is not cooled and becomes defective in the material as in the conventional batch-type hot rolling method, is eliminated except at the beginning.

Further, in the present invention, since the hot finish rolling is continuously performed as described above, there is no variation in the temperature drop throughout the steel sheet during the hot finish rolling, and the steel slab is heated. The heating temperature is the same as the heating temperature of the conventional hot rolling method.
The heating temperature can be set to a low temperature of 1150 ° C. or lower, which is lower than 0 ° C. In addition, a hot-rolled steel sheet excellent in material, particularly elongation, can be obtained by low-temperature heating. Furthermore, it goes without saying that the steel sheet obtained through such a hot rolling step is also excellent as a material for a cold rolled steel sheet.

[0044]

EXAMPLES Examples of the present invention and comparative examples will be described below.

Example 1 A hot-rolled steel sheet for processing was manufactured using steel materials having the components shown in Table 1 at heating temperatures and rolling conditions shown in Table 2.

As shown in Table 2, In each of Examples 1 to 5 of the present invention, the materials of the front portion and the middle portion each have better tensile strength (TS) and elongation (El) than the comparative example. It was satisfactory.

[0047]

[Table 1]

[0048]

[Table 2] As shown in the examples of the present invention, the heating temperature is 11
No. performed at a temperature of 50 ° C. or less. The material of 2-5 is 12
No. heated at 00 ° C. It was superior in material quality to 1.

(Example 2) Using a steel material having the components shown in Table 1, a hot-rolled steel sheet was formed by hot rolling at the heating temperature and rolling conditions shown in Table 3, and then cold-rolled under the same conditions shown in Table 3. Then, recrystallization annealing was performed to produce a cold-rolled steel sheet for processing. Table 3 also shows the results of the investigation on these steel sheets.

[0050]

[Table 3] As shown in Table 3, In Examples 1 to 5 of the present invention,
In each case, the material of the front portion and the middle portion was superior in tensile strength (TS) and elongation (El) to the comparative material, and was satisfactory as a material evaluation.

Incidentally, as shown in the examples of the present invention, the heating was performed at a heating temperature of 1150 ° C. or less. No. Two
Material No. 5 heated at 1200 ° C. It was superior in material quality to 1.

[0052]

According to the method for producing a thin steel sheet for processing excellent in formability by the hot rolling continuous method of the present invention, it is possible to improve the product yield due to defective material at the tip of the hot rolled steel sheet. By carrying out the heating of the steel slab at a low temperature, the cost merit due to the energy saving of the heating furnace can be improved, and the material of the hot-rolled steel sheet and the cold-rolled steel sheet made of the same can be improved by the low-temperature heating. And high productivity can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a finishing temperature distribution of a hot-rolled steel sheet.

FIG. 2 is a diagram schematically showing a relationship between a heating temperature and a finishing temperature of a hot-rolled steel sheet.

FIG. 3 is a diagram showing an outline of a method for producing a hot-rolled steel sheet by the hot-rolling continuous method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Rough rolling machine 3 Rough rolling coil 4 Cutting machine for welding 5 Welding equipment 6 Finishing rolling machine 7 Cooling device 8 Cutting machine 9 Winding machine

Claims (6)

[Claims] 1. A steel slab having a carbon content of 0.1% or less is heated in a heating furnace, rough-rolled by a hot rough rolling mill to form a steel sheet,
Then, in the method for producing a hot-rolled steel sheet for processing excellent in formability, which is characterized in that it is cooled and then wound into a coil after finish rolling in a hot finish rolling mill, the tip of the roughly rolled steel sheet is
A method for producing a hot-rolled steel sheet for processing excellent in formability, characterized in that a rough rolling is performed before that and a rolling line is joined to a rear end of a preceding steel sheet and hot finish rolling is continuously performed. 2. A steel slab having a carbon content of 0.1% or less is heated in a heating furnace and rough-rolled by a hot rough rolling mill to form a steel sheet.
Next, in the method for producing a hot-rolled steel sheet for processing excellent in formability, which is finished by a hot finish rolling mill, then cooled and wound up into a coil, the heating in the heating furnace is performed in a heating furnace.
Low-temperature heating of 0 ° C or less, and the front end of the rough-rolled steel sheet is joined to the rear end of the preceding steel sheet by rough-rolling before the rolling line to continuously perform hot finish rolling. Of hot rolled steel sheets for processing with excellent formability. 3. A steel slab having a carbon content of 0.1% or less is heated in a heating furnace and rough-rolled by a hot rough rolling mill to form a steel sheet.
Next, in the method for producing a hot-rolled steel sheet for processing excellent in formability, which is finished by a hot finish rolling mill, then cooled and wound up into a coil, the heating in the heating furnace is performed in a heating furnace.
It was heated to a low temperature of 0 ° C. or lower, and the front end of the rough-rolled steel sheet was joined to the rear end of the preceding steel sheet by rough-rolling before the rolling line, and continuously hot-finished and rolled to 2.0 m
A method for producing a hot-rolled steel sheet for processing excellent in formability, wherein the hot-rolled steel sheet has a thickness of not more than m. 4. A steel slab having a carbon content of 0.1% or less is heated in a heating furnace and rough-rolled by a hot rough rolling mill to form a steel sheet.
Next, in a method for producing a cold-rolled steel sheet for processing, comprising a hot-rolling step of cooling and winding into a coil after finish rolling in a hot finish rolling mill, and a cold-rolling step of further performing cold rolling and recrystallization annealing. It is characterized by having a hot rolling step of continuously performing finish rolling and cooling after rolling by joining the leading end of the rough-rolled steel sheet to the rear end of the preceding steel sheet that is rough-rolled before the rolling line. Method of manufacturing cold rolled steel sheet for processing with excellent formability. 5. A steel slab having a carbon content of 0.1% or less is heated in a heating furnace and rough-rolled by a hot rough rolling mill to form a steel sheet.
Next, in a method for producing a cold-rolled steel sheet for processing, comprising a hot-rolling step of cooling and winding into a coil after finish rolling in a hot finish rolling mill, and a cold-rolling step of further performing cold rolling and recrystallization annealing. The heating in the heating furnace is performed at a low temperature of 1150 ° C. or less, and the leading end of the rough-rolled steel sheet is joined to the rear end of the preceding steel sheet by rough-rolling the rolling line before finishing rolling and rolling. A method for producing a cold-rolled steel sheet for processing excellent in formability, comprising a hot-rolling step of continuously performing subsequent cooling. 6. The cold-rollable steel sheet according to claim 5, wherein the sheet thickness after hot finish rolling is 2.0 mm or less. Steel plate manufacturing method.