JPH0665641A - Production of thin steel sheet excellent in deep drawability - Google Patents

Abstract

PURPOSE:To produce a hot rolled thin steel sheet having high strength and excellent in deep drawability by subjecting a sheet bar having a specified compsn. constituted of C, Si, Mn, P, S, Al, N, Ti, Nb and iron to specified cooling and rolling and thereafter executing recrystallization treatment. CONSTITUTION:A steel sheet bar contg., by weight, <=0.01% C, <=2.0% Si, <=3.0% Mn, <=0.20% P, <=0.05% S, 0.01 to 0.20% Al and <=0.01% N as well as 0.005 to 0.2% Ti and/or 0.001 to 0.2% Nb, furthermore contg., at need, 0.0001 to 0.0050% B and moreover contg. one or more kinds among 0.1 to 1.5% Ni, 0.01 to 1.5% Mo and 0.1 to 1.5% Cu is used as stock, and finish hot rolling is started at the Ar3 point or above. In the process of the rolling, it is cooled by >=30 deg.C at >=20 deg.C/S cooling rate to regulate its temp. into the Ar, point or below. Successively, it is subjected to lubrication rolling at the Ar3 point to 500 deg.C at 50 to 95% total draft to regulate its sheet thickness into a final one. After that, it is coiled into a hot rolled sheet, or recrystallization treatment is executed in an annealing stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention proposes a method for producing a hot-rolled thin steel sheet which is useful as a steel sheet for automobiles and is excellent in deep drawability.

The deep drawing thin steel sheet used for automobile panels and the like is required to have excellent deep drawing properties. In order to improve the deep drawability, it is important to impart a steel sheet with a high Rankford value (average r value) and high ductility (El) as mechanical properties. Such a deep-drawing steel sheet is generally a cold-rolled steel sheet produced by hot rolling at an Ar ₃ transformation point or higher, then cold rolling to obtain a thin sheet having a final thickness, and then performing recrystallization annealing. Is being used for.
However, in recent years, for the purpose of cost reduction, there has been an increasing demand for replacing a member that has conventionally used a cold-rolled steel sheet with a hot-rolled steel sheet.

In recent years, the tensile strength is 35 to 60 for the purpose of reducing the weight of automobile bodies and improving safety.
The momentum to use high strength steel such as Kgf / mm ² has been rapidly increasing. Needless to say, even such a high-strength steel sheet is required to exhibit excellent deep drawability during press forming, and is required to have high tensile strength and excellent deep drawability. .

[0004]

However, in the conventional hot-rolled steel sheet for working, in order to secure workability, particularly ductility, rolling was completed at the Ar ₃ transformation point or higher, avoiding the formation of an unrecrystallized ferrite structure. Therefore, the deep drawing property of the hot-rolled steel sheet is significantly inferior to that of the cold-rolled steel sheet because the texture is generally randomized during the γ → α transformation.

Up to now, there have been some disclosures of hot-rolled steel sheets excellent in deep drawability and manufacturing methods. For example,
The hot-rolled steel sheet having excellent formability and the manufacturing method thereof disclosed in JP-A-59-226149 include C: 0.002%, Si: 0.02%, Mn:
0.23%, P: 0.009%, S: 0.008%, Al: 0.025
%, N: 0.0021%, Ti: 0.10% containing low carbon Al killed steel, while applying lubricating oil in the temperature range of 500 to 900 ° C from the beginning of finish rolling, hot rolling with a rolling reduction of 76% or 93%. An example of manufacturing a thin steel sheet having a characteristic of an average r value of 1.21 or 1.48 by recrystallization annealing a steel strip having a thickness of 1.6 mm by rolling is shown. Further, in the method for producing a high r-value hot rolled steel sheet disclosed in JP-A-62-192539, C: 0.008%, Si: 0.04%,
Mn: 1.53%, P: 0.015%, S: 0.004%, Ti: 0.068
%, Nb: 0.024% of low carbon Al killed steel, Ar _{3 to} Ar ₃
An example of manufacturing a thin steel sheet having characteristics of an average r value of about 1.41 by rolling in a temperature range of + 150 ° C. and performing recrystallization annealing is shown. However, the average r value obtained by these means is at most about 1.5, and it cannot be said that the deep drawability is sufficiently satisfied.

On the other hand, in order to cope with the weight reduction and safety improvement of automobiles as described above, research and development of a steel sheet having higher strength and a deep drawability equal to or higher than that of the conventional steel is advanced. However, regarding research on hot rolled steel sheets with higher strength and excellent deep drawability,
The current situation is that almost nothing is done.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems in an advantageous manner. By controlling the chemical composition and manufacturing conditions of steel, the strength is higher and the steel is significantly superior to the conventional steel. It is an object of the present invention to propose a method for manufacturing a hot-rolled thin steel sheet having deep drawability.

[0008]

DISCLOSURE OF THE INVENTION As a result of intensive studies to improve deep drawability, the present invention has found that a thin steel sheet having excellent deep drawability can be produced without cold rolling. is there.

That is, the gist of the present invention is: C: 0.01 wt% or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less, P: 0.20 wt% or less, S: 0.05 wt% or less, Al: 0.01 wt% % Or more and 0.20 wt% or less and N: 0.01 wt% or less, and Ti: 0.005 wt% or more, 0.2 wt% or less and Nb: 0.001 wt% or more, 0.2 wt% or less, one or two types Of which the balance is iron and unavoidable impurities, and the rest hot rolling is started at a temperature not lower than the Ar ₃ transformation point and rolled at 20 ° C without rolling during the rolling. / S or more cooling rate
After cooling to 30 ° C or higher to a temperature not higher than the Ar ₃ transformation point, while continuously lubricating at temperatures lower than the Ar ₃ transformation point and not lower than 500 ° C, the total rolling reduction below the Ar ₃ transformation point is 50% or more, 95
% Of the final thickness by rolling, and then a recrystallization treatment in a winding or annealing step is a method for producing a thin steel sheet having excellent deep drawability (first invention),

A method for producing a thin steel sheet excellent in deep drawability (second invention), which comprises B: 0.0001 wt% or more and 0.0050 wt% or less, substituting a part of iron of the first invention, Substituting a part of iron of the first or second invention, Ni: 0.1 wt% or more, 1.5 wt% or less, Mo: 0.01 wt% or more, 1.5 wt% or less and Cu: 0.1 wt% or more, 1.5 wt% A method for producing a thin steel sheet excellent in deep drawability (third invention, fourth invention), each of which contains one or more of the following,

Further, the method for producing a thin steel sheet having excellent deep drawability, which is characterized in that the recrystallization treatment of the first, second, third or fourth invention is carried out in a continuous hot dip galvanizing process (fifth invention). Is.

[0012]

The present invention will be described in more detail below. First,
The experimental results which are the basis of the present invention will be described.

C: 0.002 wt%, Si: 0.01 wt%, Mn:
0.15wt%, P: 0.01wt%, S: 0.005wt%, Al: 0.05w
t%, N: 0.002 wt%, Ti: 0.045 wt% and Nb: 0.015
The steel slab containing wt% was heated soaking after rough rolling to a temperature of 1150 ° C., finish rolling start temperature: 920 ° C., finishing rolling temperature: 700 ° C. and Ar ₃ transformation point of the reduction ratio: between 70% heat Rolled to a plate thickness of 1.6 mm.

At this time, cooling in a temperature range sandwiching the Ar ₃ transformation point (870 ° C.) between the finish rolling passes is performed at a cooling rate of 50 ° C. /
The temperature difference between the cooling start temperature and the cooling end temperature (hereinafter simply referred to as the cooling temperature difference) was changed while keeping the temperature constant at s. The rolling in the temperature range below the Ar ₃ transformation point after cooling was lubrication rolling, and the rolling finishing temperature was adjusted to 700 ° C. by this lubrication rolling. Subsequent to the hot rolling, recrystallization annealing was performed at 750 ° C. for 5 hours, and the average r value of the obtained hot rolled steel sheet was investigated.

The results of these investigations are summarized in FIG.
FIG. 1 is a graph showing the relationship between the cooling temperature difference and the average r value. As is clear from this figure, the average r value strongly depends on the cooling temperature difference, and is higher when the cooling temperature difference is 30 ° C. or more. An average r value is obtained.

C: 0.002 wt%, Si: 0.01 wt%, Mn:
0.17wt%, P: 0.01wt%, S: 0.005wt%, Al: 0.05w
t%, N: 0.002 wt%, Ti: 0.048 wt% and Nb: 0.017
A steel slab containing wt% is heated to a temperature of 1150 ° C, soaked, and then rough-rolled. Finish rolling starting temperature: 920 ° C, rolling finishing temperature: 700 ° C, and a rolling reduction of 70% or less below the Ar ₃ transformation point: hot rolling. Rolled to a plate thickness of 1.6 mm.

At this time, the cooling in the temperature range sandwiching the Ar ₃ transformation point (870 ° C.) between the finish rolling passes is a cooling temperature difference: 50 ° C.
Was kept constant and the cooling rate was changed. The rolling in the temperature range below the Ar ₃ transformation point after cooling was lubrication rolling, and the rolling finishing temperature was adjusted to 700 ° C. by this lubrication rolling. Following the hot rolling, recrystallization annealing was performed at 750 ° C. for 5 hours, and the average r value of the obtained hot rolled steel sheet was investigated.

The results of these investigations are summarized in FIG.
Fig. 2 is a graph showing the influence of the cooling rate on the average r value. As is clear from this figure, the average r value also strongly depends on the cooling rate, and is higher when the cooling rate is 20 ° C / s or more. An average r value is obtained.

C: 0.002 wt%, Si: 0.01 wt%, Mn:
0.11wt%, P: 0.01wt%, S: 0.006wt%, Al: 0.05w
t%, N: 0.002 wt%, Ti: 0.052 wt% and Nb: 0.015
A steel slab containing wt% is heated to a temperature of 1150 ° C, soaked, and then rough-rolled, finishing rolling is started at a temperature of the Ar ₃ transformation point or higher, and the rolling finishing temperature is changed in the temperature range of 600 to 930 ° C. It was hot-rolled to a plate thickness of 1.6 mm.

At this time, the cooling between the finishing rolling passes was performed at a cooling rate of 30 ° C./s and a cooling temperature difference of 50 ° C., and the rolling after cooling was in a temperature range below the Ar ₃ transformation point (870 ° C.). For, the rolling reduction in the temperature range below the Ar ₃ transformation point is 70%,
The rolling was performed in two ways: lubrication rolling and non-lubrication rolling. Subsequent to the hot rolling, recrystallization annealing was performed at 750 ° C. for 5 hours, and the average r value of the obtained hot rolled steel sheet was investigated.

The results of these investigations are summarized in FIG.
FIG. 3 is a graph showing the influence of the presence or absence of lubrication in rolling in the temperature range below the Ar ₃ transformation point on the rolling finish temperature and the average r value. As is clear from this figure, the average r value is the rolling finish temperature and rolling. Depending on the presence or absence of lubrication at that time, a high average r value can be obtained by setting the rolling finishing temperature to the Ar ₃ transformation point or lower and rolling at the Ar ₃ transformation point or lower to the lubrication rolling.

As a result of further research based on the above experimental results, the scope of the present invention was limited as follows.

(1) Compositional Composition of Steel In the present invention, the compositional composition of steel is important, and C: 0.
01 wt% or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less,
P: 0.20 wt% or less, S: 0.05 wt% or less, Al: 0.01-0.
Contains 20wt% and N: 0.01wt% or less, and Ti: 0.005〜
It is necessary to contain one or two of 0.2 wt% and Nb: 0.001 to 0.2 wt%. If necessary,
B: 0.0001 to 0.0050 wt% and / or Ni: 0.1 to 1.5 wt
%, Mo: 0.01 to 1.5 wt%, Cu: 0.1 to 1.5 wt%, and one or more of them may be contained, and if the composition of the steel does not satisfy these conditions, excellent deep drawability is obtained. Can't get

The reasons for limiting each component will be described below. C: 0.01 wt% or less C is preferable because the smaller the content is, the deeper drawability is improved. However, since the content does not have a bad influence up to 0.01 wt%, the upper limit of the content is 0.01 wt%. To do.

Si: 2.0 wt% or less Si has a function of strengthening steel and is contained in a necessary amount according to desired strength. However, if the content exceeds 2.0 wt%, deep drawability and surface properties are improved. Adversely affect the. Therefore, the upper limit of the content is 2.0 wt%.

Mn: 3.0 wt% or less Mn has a function of strengthening steel, and is contained in a required amount according to desired strength. However, if the content exceeds 3.0 wt%, the deep drawability is adversely affected, so the upper limit is 3.0 wt%.

P: 0.2 wt% or less P has an action of strengthening steel and is contained in a necessary amount according to the desired strength. However, if the content exceeds 0.20 wt%, the deep drawability is adversely affected. Therefore, its content is 0.2
The upper limit is 0 wt%.

S: 0.05 wt% or less S is preferable because the smaller the content is, the deeper drawability is improved, but since the content does not have a bad influence up to 0.05 wt%, the upper limit of the content is 0.05. wt%

Al: 0.01 to 0.20 wt% Al is deoxidized and added as necessary to improve the yield of carbonitride forming components, but the content is 0.01 wt%.
If it is less than 0.2 wt%, the effect is not obtained, and if it is contained in excess of 0.2 wt%, no further effect is obtained and, conversely, it leads to deterioration of ductility. Therefore, its content is 0.01 wt% or more, 0.2
wt% or less.

N: 0.01 wt% or less N is preferable because the smaller the content, the better the deep drawability, but since the content does not have a bad influence up to 0.01 wt%, the content is 0.01 wt%. Is the upper limit.

Ti: 0.005-0.2 wt% Ti has the effect of precipitating and fixing the solid solution C and the solid solution N in the steel as carbonitrides and preferentially forming the {111} orientation, which is advantageous for deep drawability. is there. If the content is less than 0.005 wt%, the effect will not be obtained, while if it is contained over 0.2 wt%, no further effect will be obtained, which will lead to deterioration of ductility.
Therefore, its content should be 0.005 wt% or more and 0.2 wt% or less. In addition, it is preferable in terms of material to contain Ti / 48 ≧ (C / 12 + N / 14) in a relational expression.

Nb: 0.001 to 0.2 wt% Nb is used to precipitate and fix solid solution C in steel as a carbide.
Since the microstructure before finish rolling is refined, the {111} orientation advantageous for deep drawability is preferentially formed. If the content is less than 0.001wt%, the effect will be
If it is contained in excess of wt%, no further effect will be obtained, and conversely the ductility will be deteriorated. Therefore, its content is
0.001 wt% or more and 0.2 wt% or less. Nb / 93 ≧
It is preferable in terms of material that the C / 12 relational expression is satisfied and contained.

B: 0.0001 to 0.005 wt% B is contained for improving the secondary work embrittlement resistance. If the content is less than 0.0001 wt%, the effect is not obtained, while 0.00
If the content exceeds 5 wt%, the deep drawability deteriorates. Therefore, its content should be 0.0001 wt% or more and 0.005 wt% or less.

Ni: 0.1-1.5 wt% Ni has the effect of strengthening the steel and is effective in improving the surface properties of the steel sheet when Cu is added. The effect is that the content is
It appears at 0.1 wt% or more, but if it exceeds 1.5 wt%, it adversely affects the deep drawability. Therefore, its content should be 0.1 wt% or more and 1.5 wt% or less.

Mo: 0.01 to 1.5 wt% Mo has the effect of strengthening the steel, and is contained in a required amount according to the desired strength. The effect appears when the content is 0.01 wt% or more, but if it exceeds 1.5 wt%, the deep drawability is adversely affected. Therefore, its content is 0.01 wt% or more,
It should be 1.5 wt% or less.

Cu: 0.1 to 1.5 wt% Cu has the effect of strengthening the steel, and is contained in a required amount according to the desired strength. The effect is exhibited when the content is 0.1 wt% or more, but if the content exceeds 1.5 wt%, the deep drawability and surface properties are adversely affected. Therefore, its content is
0.1 wt% or more and 1.5 wt% or less.

(2) Hot Rolling The hot rolling step is the most important in the present invention, and in performing the final hot rolling to the final predetermined plate thickness, the finishing rolling should be started at a temperature not lower than the Ar ₃ transformation point. And, cooling rate: 20 ℃ / without rolling during the rolling
s or more, cooling temperature difference across the Ar ₃ transformation point: After cooling at 30 ° C or more, total reduction below the Ar ₃ transformation point while lubricating at temperatures below the Ar ₃ transformation point and 500 ° C or more Rate 50
It is necessary to carry out rolling processing of between 95% and 95%.

The finish rolling start temperature is set to the Ar ₃ transformation point or higher, but if it is lower than this temperature, the γ grains cannot be refined in the finish rolling, and as a result, the {111} texture of the hot rolled steel sheet is obtained. Are not formed, so that only low average r values are obtained. Further, after finishing rolling is started at the Ar ₃ transformation point or higher, the cooling rate is not applied during the rolling, and the cooling rate is:
It is necessary to cool at a temperature of 20 ° C / s or more and a cooling temperature difference of 30 ° C or more to a temperature below the Ar ₃ transformation point, but if such cooling is not performed, fine rolling is performed at a temperature above the Ar ₃ transformation point. Since the converted γ-grains become coarse again, no {111} texture is formed in the hot-rolled sheet, and only a low average r value can be obtained as is clear from the above experimental results. The cooling across the Ar ₃ transformation point can be performed between intermediate stands or between 1 and 3 stands of the finishing rolling mill group.

The rolling temperature after cooling across the Ar ₃ transformation point is A
In the temperature range above the r ₃ transformation point, the texture becomes random due to γ → α transformation no matter how much rolling is performed, so that the {111} texture is not formed in the hot-rolled steel sheet and only a low average r value is obtained. On the other hand, even if the rolling temperature is lowered to below 500 ° C,
Further improvement of the average r value cannot be expected, and only the rolling load increases. Therefore, the rolling temperature after cooling is set to the Ar ₃ transformation point or lower and 500 ° C. or higher.

If the total rolling reduction below the Ar ₃ transformation point in finish rolling is less than 50%, the {111} texture will not be formed in the hot-rolled steel sheet, while if it exceeds 95%, the hot-rolled steel sheet will be averaged. r
Since the disadvantage of forming an unfavorable texture occurs in the value, the total rolling reduction below the Ar ₃ transformation point is 50% or more, 95% or less.
% Or less.

Further, if the rolling below the Ar ₃ transformation point is made non-lubricated, the {110} orientation, which is unfavorable for deep drawability, is caused by the shear deformation due to the frictional force between the roll and the steel sheet. Since it is preferentially formed in No. 1 and the improvement of the average r value cannot be expected as is clear from the above experimental results, it is necessary to perform lubrication rolling in order to secure deep drawability.

As the rolled material, a sheet bar is used which is prepared by reheating a slab that is steel-made or continuously cast in accordance with a conventional method, or is subjected to rough rolling immediately after continuous casting or after heat treatment and rough rolling. Further, the roll diameter, the structure of the roll and the rolling mill, the type of lubricating oil, etc. may be arbitrary.

(3) Recrystallization Treatment In this invention, since the rolling temperature after cooling in the course of finish rolling is below the Ar ₃ transformation point, the as-rolled hot-rolled steel sheet has a worked structure. Therefore, the as-rolled hot-rolled steel sheet needs to be recrystallized to form a {111} texture. Without this recrystallization treatment, a high average r value cannot be obtained because no {111} texture is formed.

This recrystallization treatment can be carried out in a winding step after hot rolling or a recrystallization annealing step. When performing the recrystallization treatment in the winding process, it is important that the winding temperature is 650 ° C or higher. This is because when the coiling temperature is lower than 650 ° C., recrystallization does not occur, so that the {111} orientation is not formed and the improvement of the average r value cannot be expected. On the other hand, when the recrystallization annealing step is performed, both the batch annealing method and the continuous annealing method are suitable, and the annealing temperature is preferably 650 to 950 ° C. Also, it may be annealed in the continuous hot dip galvanizing process,
This anneal can be followed by galvanization.

The steel sheet after the hot rolling and the recrystallization treatment has a reduction ratio in order to correct the shape and adjust the surface roughness.
Temper rolling of 10% or less may be added, and the hot-rolled thin steel sheet obtained by the present invention can also be applied as a raw material for a surface-treated steel sheet for working and a raw material for a cold-rolled steel sheet. Examples of the surface treatment include zinc plating (including alloy system), tin plating and enamel.

[0046]

[Examples] After roughly rolling a steel slab adjusted to the composition shown in Table 1, finish rolling was performed on a 7-stand hot rolling machine under the conditions shown in Table 2, and then recrystallization treatment shown in Table 2 was also performed. I went.

[0047]

[Table 1]

[0048]

[Table 2]

[0049] Incidentally, the sample No.1~3,9 and 11 F3 stand in Table 2, No. 7 is not performed each rolling in the F3 and F4 stands, the cooling sandwiching the Ar ₃ transformation point in this section went. Samples Nos. 5 and 6 were subjected to recrystallization annealing and plating treatment in a continuous hot dip galvanizing facility.
The tensile properties of the steel sheet thus obtained were investigated. The results of this investigation are also shown in Table 2 above.

Here, the tensile properties were measured using a JIS No. 5 tensile test piece, and the average r value was measured by the 3-point method after applying a 15% tensile prestrain to the L direction (rolling direction). As an average value in the D direction (45 ° to the rolling direction) and the C direction (90 ° to the rolling direction)

## EQU1 ## The average r value = (r _L + 2r _D + r _c ) / 4.

As is clear from Table 2, the hot-rolled steel sheet suitable for the present invention and the galvanized steel sheet having the same have excellent deep drawability as compared with the comparative examples.

[0052]

EFFECT OF THE INVENTION The present invention limits the composition of the composition of ultra-low carbon steel, and when performing finish hot rolling to the final plate thickness, Ar ₃
Finishing rolling is started at the point or higher, cooling is performed at 30 ° C or higher at a cooling rate of 20 ° C / s or higher to cool it to the Ar ₃ point or lower, and then lubrication rolling is performed in the temperature range of the Ar ₃ point to 500 ° C. And then recrystallizing it to obtain a hot-rolled thin steel sheet having excellent deep drawability, which can greatly contribute to expanding the applications of the hot-rolled steel sheet having excellent economical efficiency.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of a cooling temperature difference on the average r value.

FIG. 2 is a graph showing the effect of cooling rate on the average r value.

FIG. 3 is a graph showing the influence of the presence or absence of lubrication in rolling in the rolling finishing temperature and the temperature range below the Ar ₃ transformation point on the average r value.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 1, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 5

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction content]

The rolling temperature after cooling across the Ar ₃ transformation point is A
In the temperature range above the r ₃ transformation point, the texture becomes random due to γ → α transformation no matter how much rolling is performed, so that the {111} texture is not formed in the hot-rolled steel sheet and only a low average r value is obtained. On the other hand, even if the rolling temperature is lowered to below 500 ° C,
Further improvement of the average r value cannot be expected, and only the rolling load increases. Therefore, the rolling temperature after cooling is set to the Ar ₃ transformation point or lower and 500 ° C. or higher.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction content]

This recrystallization treatment can be carried out in a winding step after hot rolling or a recrystallization annealing step. When performing recrystallization treatment in the winding process, it is important to set the winding temperature to 650 ° C or higher. This is because when the coiling temperature is lower than 650 ° C., recrystallization does not occur, so that the {111} orientation is not formed and the improvement of the average r value cannot be expected. On the other hand, when the recrystallization annealing step is performed, both the batch annealing method and the continuous annealing method are suitable, and the annealing temperature is preferably 650 to 950 ° C. Also, it may be annealed in the continuous hot dip galvanizing process,
This anneal can be followed by galvanization.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

[0048]

[Table 2]

Claims (5)

[Claims] 1. C: 0.01 wt% or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less, P: 0.20 wt% or less, S: 0.05 wt% or less, Al: 0.01 wt% or more, 0.20 wt% The following and N: 0.01 wt% or less, and Ti: 0.005 wt% or more, 0.2 wt% or less and Nb: 0.001 wt% or more, 0.2 wt% or less, and the balance is Finishing hot rolling is started at a temperature of Ar ₃ transformation point or higher using a sheet bar having a composition of iron and unavoidable impurities, and a cooling rate of 20 ° C / s or higher without rolling during the rolling. so
After cooling to 30 ° C or higher to a temperature not higher than the Ar ₃ transformation point, while continuously lubricating at temperatures lower than the Ar ₃ transformation point and not lower than 500 ° C, the total rolling reduction below the Ar ₃ transformation point is 50% or more, 95
% Of less than or equal to the final thickness, and then recrystallization treatment is performed in the winding or annealing process. 2. C: 0.01 wt% or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less, B: 0.0001 wt% or more, 0.0050 wt% or less, P: 0.20 wt% or less, S: 0.05 wt% Below, including Al: 0.01 wt% or more, 0.20 wt% or less and N: 0.01 wt% or less, and Ti: 0.005 wt% or more, 0.2 wt% or less and Nb: 0.001 wt% or more, 0.2 wt% or less 1) or 2), with the balance being iron and unavoidable impurities in the composition, and starting hot rolling at a temperature above the Ar ₃ transformation point, and rolling during the rolling. At a cooling rate of 20 ° C / s or more without applying
After cooling to 30 ° C or higher to a temperature not higher than the Ar ₃ transformation point, while continuously lubricating at temperatures lower than the Ar ₃ transformation point and not lower than 500 ° C, the total rolling reduction below the Ar ₃ transformation point is 50% or more, 95
% Of less than or equal to the final thickness, and then recrystallization treatment is performed in the winding or annealing process. 3. C: 0.01 wt% or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less, P: 0.20 wt% or less, S: 0.05 wt% or less, Al: 0.01 wt% or more, 0.20 wt% Or less and N: 0.01 wt% or less, and Ti: 0.005 wt% or more, 0.2 wt% or less and Nb: 0.001 wt% or more, 0.2 wt% or less, and Ni: 0.1 wt% or more, 1.5 wt% or less, Mo: 0.01 wt% or more, 1.5 wt% or less Cu: 0.1 wt% or more, 1.5 wt% or less One or more types are contained, and the balance is iron and unavoidable. Finishing hot rolling is started at a temperature above the Ar ₃ transformation point using a sheet bar that has an impurity composition, and 30 ° C or more at a cooling rate of 20 ° C / s or more without rolling during the rolling. a temperature below Ar ₃ transformation point performs cooling, subsequently Ar ₃ or less transformation point, the total reduction of less than Ar ₃ transformation point while performing lubrication in a temperature range of not lower than 500 ° C. There more than 50%, after a final thickness by rolling of 95% or less, thin steel sheet manufacturing method which is excellent in deep drawability, characterized in that performing recrystallization by coiling or annealing process. 4. C: 0.01 wt% or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less, B: 0.0001 wt% or more, 0.0050 wt% or less, P: 0.20 wt% or less, S: 0.05 wt% Below, including Al: 0.01 wt% or more, 0.20 wt% or less and N: 0.01 wt% or less, and Ti: 0.005 wt% or more, 0.2 wt% or less and Nb: 0.001 wt% or more, 0.2 wt% or less 1 or 2 kinds, and further, Ni: 0.1 wt% or more, 1.5 wt% or less, Mo: 0.01 wt% or more, 1.5 wt% or less, Cu: 0.1 wt% or more, 1.5 wt% or less, one of Alternatively, using a sheet bar containing two or more kinds and the balance being iron and unavoidable impurities, finishing hot rolling is started at a temperature of Ar ₃ transformation point or higher, and rolling is performed during the rolling. and 20 ° C. / s or more cooling rate at 30 ° C. or more temperatures below Ar ₃ transformation point to cool without subsequently Ar ₃ or less transformation point, lubrication at 500 ° C. or higher temperature range The deep drawing is characterized by performing recrystallization treatment in the winding or annealing process after the final plate thickness is obtained by rolling with a total reduction of 50% or more and 95% or less below the Ar ₃ transformation point while performing A method for manufacturing a thin steel sheet having excellent properties. 5. A method of manufacturing a thin steel sheet having excellent deep drawability, which comprises performing the recrystallization treatment according to any one of claims 1, 2, 3 and 4 in a continuous hot-dip galvanizing process.