JPH0726330A - Production of steel sheet excellent in deep drawability - Google Patents

Abstract

PURPOSE:To produce a steel sheet excellent in deep drawability in high yield by specifying chemical components and manufacturing conditions, respectively. CONSTITUTION:A steel stock, which has a composition containing, by weight, <=0.01% C and 0.005-0.2% Ti and/or 0.001-0.2% Nb and satisfying relational inequality 1.2X[C]/12<=[Ti]/48+[NB]/93, is hot-roughed. In the course in which the resulting sheet bar is coiled temporarily and then decoiled and subjected to hot finish rolling at a temp. higher than the Ar, point, the head end of the sheet bar is joined to the tail end of a preceding sheet bar and then subjected to hot finish rolling at a temp. not lower than the Ar3. point. The resulting plate is successively cooled at (20 to 30) deg.C/s cooling rate down to a temp. not higher than the Ar3 point and subjected to lubricating rolling at a temp. between Ar3 and 500 deg.C at 50-85% total draft, followed by recrystallization treatment. By this method, the steel sheet excellent in deep drawability can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin steel sheet having excellent deep drawability, which is useful for use as a steel sheet for automobiles and the like, and proposes a method which can be particularly efficiently manufactured.

[Prior art]

Thin steel sheets used for automobile panels and the like are required to have excellent deep drawability as a characteristic.
In order to improve such deep drawability, it is necessary to provide a steel sheet with high r value (Rankford value) and high ductility (El.) As mechanical properties. As such a deep-drawing thin steel sheet, after performing hot rolling at an Ar ₃ transformation point or higher, a cold-rolled steel sheet manufactured by subjecting it to a thin sheet having a final thickness by cold rolling and then performing recrystallization annealing is used. It has been commonly used. However, in recent years, for the purpose of cost reduction, there is an increasing tendency to replace hot-rolled steel sheets with materials that used to be cold-rolled steel sheets. Has begun to proceed.

Here, in the conventional hot-rolled steel sheet for working, in order to secure sufficient workability, particularly ductility, rolling is terminated at an Ar ₃ transformation point or higher in order to avoid formation of an unrecrystallized ferrite structure. Met. Therefore, the deep drawability of the hot-rolled steel sheet is generally significantly inferior to that of the cold-rolled steel sheet because the texture is randomized during the γ-α transformation.

There are some disclosures regarding a manufacturing method for improving the deep drawability of a hot rolled steel sheet. For example, JP-A-59-226
No. 149 discloses that steel containing Ti and / or Nb is 500 ° C.
It is proposed to perform rolling with a total reduction amount of 50% or more while performing lubrication in a temperature range of Ar ₃ transformation point or lower, and then recrystallize. According to the example, C: 0.002 wt%, S
i: 0.02 wt%, Mn: 0.23 wt%, P: 0.009 wt%, S: 0.0
08 wt%, Al: 0.025 wt%, N: 0.0021 wt%, Ti: 0.10w
An average r value of 1.21 is obtained by rolling t% low carbon Al-killed steel at a temperature of 500 to 900 ° C and rolling it at a rolling reduction of 76% to obtain a steel strip with a thickness of 1.6 mm. It is said that. However, with this method, strong lubrication rolling must be performed during hot rolling, and thus there are operational difficulties such as defective biting of the steel sheet and slippage. Therefore, in actual operation, the above-mentioned strong lubrication cannot be performed at the front and rear ends of the hot-rolled steel sheet in order to avoid defective biting and slipping, so that a hot-rolled steel sheet that is non-uniform in the coil longitudinal direction is obtained. Will be done. Since the material of the front and rear ends of such a coil is deteriorated, there is a problem that the product yield is reduced.

[0005]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems and provides a thin steel sheet having a deep drawability superior to that of the prior art with a high production efficiency without lowering the yield. The purpose is to propose a method that can be manufactured in.

[0006]

The present invention provides C: 0.01 wt.
% Or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less, Al: 0.
01 to 0.20 wt%, P: 0.20 wt% or less, S: 0.05 wt% or less and N: 0.01 wt% or less, and Ti: 0.005 to 0.2 wt%
And Nb: 1 type or 2 types selected from 0.001 to 0.2 wt%, C content [C], Ti content [Ti] and Nb content [N
b), the following formula 1.2 x [C] / 12 ≤ [Ti] / 48 + [Nb] / 93 (wt%) is satisfied, and the balance is steel material consisting of iron and unavoidable impurities. The sheet bar obtained by subjecting the sheet bar to the rough rolling is temporarily wound, then unwound and subjected to hot finish rolling at a temperature higher than the Ar ₃ transformation point, and the tip of the sheet bar is rolled in advance. Join to the rear end of the bar,
After that, hot finish rolling is performed at an Ar ₃ transformation point or higher, followed by cooling at a cooling rate of 20 ° C / s or higher to 30 ° C or higher, and then to Ar.
Lubrication rolling with a total reduction of 50 to 95% in the temperature range of Ar ₃ transformation point to 500 ℃ after making ₃ transformation points or less, and then recrystallization treatment. Is.

Further, in the present invention, B: 0.0001 to 0.0080 wt% may be further contained as a component of the above steel material.

When a cold-rolled steel sheet excellent in deep drawability is manufactured using the hot-rolled steel sheet or hot-rolled steel strip obtained by the present invention, the hot-rolled steel sheet or hot-rolled steel strip is cold-rolled. Then, it is preferable to perform recrystallization annealing.

The experimental results which are the basis of the present invention will be described below. Experiment 1 C: 0.002 wt%, Si: 0.01 wt%, Mn: 0.10 wt%, P: 0.
01 wt%, S: 0.007 wt%, Al: 0.05 wt%, N: 0.002 wt%
%, Ti: 0.055 wt% and Nb: 0.015 wt%, and the balance was a slab (thickness 30 mm) consisting essentially of iron composition. The slab was heated and soaked at a temperature of 1150 ° C, and then hot-rolled. During this hot rolling, the hot rolling start temperature was set to 930 ° C and the hot rolling finishing temperature was set to 700 ° C.
Set to 1 and lubricated, and the Ar ₃ transformation point (approximately 87
The cooling rate is 50 ℃ between rolling passes in the temperature range between
The cooling was started at / s, and the cooling start temperature and the cooling end temperature were variously changed. The plate thickness immediately before cooling was 10 mm, and the finished plate thickness was 3.5 mm by rolling after cooling. Then
Recrystallization annealing was performed at 750 ° C. for 5 hours.

The r value of the steel sheet thus obtained was investigated, and the effect of the temperature difference between the cooling start temperature and the cooling end temperature on the average r value is shown in a graph in FIG. As is apparent from FIG. 1, the average r-value after annealing strongly depends on the temperature difference between the cooling start temperature and the cooling end temperature in the vicinity of Ar ₃ , that is, the cooling temperature range, and when this is 30 ° C. or higher. In addition, a high average r value was obtained.

Experiment 2 C: 0.002 wt%, Si: 0.01 wt%, Mn: 0.13 wt%, P: 0.
01 wt%, S: 0.005 wt%, Al: 0.05 wt%, N: 0.002 wt%
%, Ti: 0.055 wt% and Nb: 0.013 wt%, with the balance being a slab (thickness 30 mm) consisting essentially of iron at 1150 ° C.
After heating and soaking at the temperature of 1, hot rolling was performed. During this hot rolling, the hot rolling start temperature was set to 930 ° C and the hot rolling finishing temperature was set to 700
The temperature is set to ℃ and lubricated, and the Ar ₃ transformation point (almost
(870 ℃) between the rolling passes, the cooling start temperature is 900 ℃ and the cooling end temperature is 85 ℃.
The cooling zone of 50 ° C which was brought to 0 ° C was cooled at various cooling rates. The plate thickness immediately before cooling was 10 mm, and the finished plate thickness was 3.5 mm by rolling after cooling. Then, recrystallization annealing was performed at 750 ° C. for 5 hours.

The r value of the steel sheet thus obtained was investigated, and the effect of the cooling rate near the Ar ₃ transformation point on the average r value is shown in the graph of FIG. As is clear from FIG. 2, the average r value after annealing strongly depends on the cooling rate, and a high average r value was obtained when the cooling rate was 20 ° C./s or more.

Experiment 3 C: 0.002 wt%, Si: 0.01 wt%, Mn: 0.10 wt%, P: 0.
01 wt%, S: 0.006 wt%, Al: 0.05 wt%, N: 0.002 wt%
%, Ti: 0.058 wt% and Nb: 0.012 wt%, and the balance is a slab (thickness 30 mm) consisting essentially of iron composition at 1150 ° C.
After heating and soaking at the above temperature, the hot rolling finish temperature is variously changed in the range of 930 to 600 ° C and hot rolling is applied to finish the sheet thickness 3.5m.
m. When finishing at a temperature lower than the Ar ₃ transformation point during this hot rolling, cooling is performed between the rolling passes in the temperature range sandwiching the Ar ₃ transformation point (approximately 870 ° C). The thickness is 10 mm, the cooling start temperature is 900 ° C, the cooling end temperature is 850 ° C, and the cooling range of 50 ° C is 50%.
Cooled at ° C / s. Moreover, the rolling after the cooling was performed by the lubrication rolling and the non-lubrication rolling, respectively. Then 750 ℃, 5
Recrystallization annealing of h was performed.

The r value of the steel sheet thus obtained was investigated, and the effects of hot rolling finish temperature and lubrication rolling on the average r value are shown in the graph of FIG. As is clear from FIG. 3, the average r value after annealing strongly depends on the hot rolling finishing temperature and the lubrication rolling, and the hot rolling finishing temperature is set to the Ar ₃ transformation point or lower, and
When the rolling below this Ar ₃ transformation point is lubrication rolling,
A high average r value was obtained.

[0015]

Based on the above experimental results, the requirements for the component composition range and manufacturing conditions of the present invention, which have been achieved through further research, will be described below. (1) Ingredient composition In this invention, the ingredient composition of steel is important and is a sufficient condition for obtaining excellent deep drawability. The reasons for limitation of each component will be described below.

(A) C: 0.01 wt% or less C is preferable because the smaller the content, the better the deep drawability. However, if the C content is 0.01 wt% or less, it does not exert a bad influence. Of 0.01 wt%. (b) Si: 2.0 wt% or less Si has an action of strengthening steel and is contained in a necessary amount according to the desired strength. However, when Si content exceeds 2.0 wt%, deep drawability and As it adversely affects the surface quality,
The upper limit was limited to 2.0 wt%. The lower limit for obtaining the strengthening effect is about 0.01 wt%. (c) 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, the Mn content is 3.0
If it exceeds wt%, the deep drawability is adversely affected, so the upper limit of its content is 3.0 wt%. The lower limit for obtaining the strengthening effect is about 0.05 wt%.

(D) Al: 0.01 to 0.20 wt% Al is a component used for deoxidizing, and an appropriate amount is added to improve the retention of carbonitride forming components. Content is less than 0.01 wt%, on the other hand, if more than 0.20 wt% is contained, no further effect can be obtained, and conversely it leads to deterioration of ductility, so 0.01-0.2 wt% did.

(E) P: 0.20 wt% or less P has the action of strengthening the steel, and the necessary amount is contained according to the desired strength, but if the P content exceeds 0.20 wt%, deep drawability is improved. The upper limit was 0.20 wt% to have an adverse effect. The lower limit for obtaining the strengthening effect is about 0.005 wt%.

(F) S: 0.05 wt% or less S is preferable because the smaller the content, the better the deep drawability. However, if the S content is 0.05 wt% or less, there is no significant adverse effect, so the upper limit is 0.05 wt. %. (g) N: 0.01 wt% or less N is preferable because the smaller the content, the better the deep drawability. However, when the N content is 0.01 wt% or less, it does not exert a bad influence so much. Therefore, 0.01 wt% is set as the upper limit. .

(H) Ti: 0.005 to 0.2 wt%, Nb: 0.001 to
1 type or 2 type Ti selected from 0.2 wt% is an important component in the present invention, and solid solution C and solid solution N in steel are precipitated and fixed as carbonitrides to be reduced,
This has the effect of preferentially forming crystal grains in the {111} orientation, which is advantageous for deep drawability. If the Ti content is less than 0.005 wt%, the effect will not be obtained. On the other hand, if the Ti content exceeds 0.2 wt%, no further effect will be obtained, and on the contrary, it will lead to deterioration of ductility. It was limited to the range of 0.2 wt%.

Nb has the effect of precipitating and fixing the solid solution C in the steel as carbides and reducing it, and preferentially forming {111} oriented crystal grains advantageous for deep drawability. It also has the effect of refining the microstructure before finish rolling and preferentially forming {111} oriented crystal grains advantageous for deep drawability in the steel sheet after hot-rolled sheet annealing. If the Nb content is less than 0.001 wt%, it has no effect.On the other hand, if the Nb content exceeds 0.2 wt%, no further effect is obtained, and conversely it leads to deterioration of ductility.
It was limited to the range of 0.2 wt%.

The above Ti and Nb are represented by the following formula 1.2 × [C] / 12 ≦ [Ti] / 48 + [Nb] in relation to the C content [C], the Ti content [Ti] and the Nb content [Nb]. ] / 93 (wt%) is required to be contained. Ti and Nb are
As already mentioned, solid solution C in steel is precipitated and fixed to reduce it, and {111} oriented crystal grains advantageous for deep drawability are preferentially formed. 1 type or 2 types are contained. When the content is 1.2 x [C] / 12> [Ti] / 48 + [Nb] / 93 (wt%), a large amount of solute C remains in the steel and the deep drawability deteriorates. Therefore, it was decided to satisfy the following formula 1.2 × [C] / 12 ≦ [Ti] / 48 + [Nb] / 93 (wt%).

(I) B: 0.0001 to 0.0080 wt% B is contained as necessary for improving the secondary processing brittleness resistance. If the B content is less than 0.0001 wt%, the effect is not exerted. On the other hand, if the B content is more than 0.0080 wt%, the deep drawability deteriorates, so the range is limited to 0.0001 to 0.0080 wt%.

(2) Hot rolling step The hot rolling step is the most important in the present invention, and the steel materials having the above-described composition are made into steel according to a conventional method and continuously cast or ingot-agglomerated. Higher than Ar ₃ transformation point by reheating the slab, or immediately after continuous casting or after heat retention treatment and hot rough rolling to form a sheet bar, then winding the sheet bar once and then rewinding. On the way to hot finish rolling at a temperature, the leading end of the sheet bar is joined to the trailing end of the sheet bar to be rolled in advance,
After that, hot finish rolling is performed at an Ar ₃ transformation point or higher, followed by cooling at a cooling rate of 20 ° C / s or higher to 30 ° C or higher, and then to Ar.
After reducing the temperature to ₃ transformation points or less, it is necessary to perform lubrication rolling at a total reduction rate of 50 to 95% in a temperature range of Ar ₃ transformation point to 500 ° C.

After the hot rough rolling, the sheet bar is wound in a coil box, for example, to make the temperature in the longitudinal direction of the coil uniform and promote the precipitation of (Ti, Nb) C and the like to form a solid solution in the steel. It has an effect of reducing (C, N).

Next, when hot finish rolling is performed, the leading end of the sheet bar rewound from the coil is joined to the trailing end of the sheet bar to be rolled in advance at the entrance side of the hot finishing rolling facility. A plurality of sheet bars are continuously hot-rolled so as to be subjected to rolling subsequent to the preceding sheet bar. Thus, even after the strong lubrication rolling performed thereafter, problems such as defective biting and slippage do not occur, and uniform strong lubrication rolling can be performed over the entire length from the coil front end to the rear end. Examples of the joining method include a method of heating by energization heating or induction heating, or heating the tip end / rear end portion to be joined by a burner or the like to a target temperature, and then pressing.

If the starting temperature of hot finish rolling is lower than the Ar ₃ transformation point, it is impossible to refine the γ grains in this finish rolling, and as a result, the {111} texture is not formed in the hot rolled sheet, Therefore, only a low r value can be obtained, so the Ar ₃ transformation point or higher is set.

Subsequent to the hot rolling finish rolling with the Ar ₃ transformation point or higher, the cooling rate is 20 ° C. without rolling.
It is cooled to 30 ° C or higher at / s or higher to bring it to the Ar ₃ transformation point or lower. This is a process for improving the deep drawability of the steel sheet after recrystallization annealing, and when the cooling rate is less than 20 ° C / s, the cooling zone is less than 30 ° C, or the cooling stop temperature is Ar ₃ When the temperature is higher than the transformation point, the γ grains refined by the above-mentioned Ar ₃ transformation point or higher rolling again become coarse, so that the {111} texture is not formed in the hot rolled sheet, Therefore, only a low r value can be obtained. Note that this cooling is preferably performed between finish rolling stands, and can be performed, for example, between one stand or between two and three stands sandwiching the stand where rolling is stopped.

Next, rolling with a total reduction of 50 to 95% is carried out in a temperature range of Ar ₃ transformation point to 500 ° C. while lubricating. Ar
_In the temperature range of ₃ transformation points or higher, no matter how much rolling is performed, the texture is randomized by the subsequent γ-α transformation,
No {111} texture is formed on the hot-rolled sheet, so only a low r-value is obtained. On the other hand, even if the rolling temperature is lowered to a temperature lower than 500 ° C, the rolling load is only increased without further improvement of the r value, and therefore the rolling temperature is Ar.
₃ Transformation point to 500 ℃. If the rolling reduction is less than 50%, the {111} texture is not formed in the hot rolled sheet,
On the other hand, if it exceeds 95%, a disadvantage occurs that an unfavorable texture is formed in the hot rolled sheet, so the range is limited to 50 to 95%. Furthermore, when such rolling is performed as non-lubricating rolling, {110} orientation texture, which is unfavorable to deep drawability, is preferentially formed in the steel sheet surface layer portion due to shear deformation due to frictional force between the roll and the steel sheet, Since it cannot be expected to improve the r-value, it is necessary to carry out lubrication rolling in order to secure deep drawability, and it is desirable to use strong lubrication rolling with a friction coefficient of 0.2 or less.

The roll diameter of the hot rolling described above, the structure of the roll and the rolling mill, and the type of lubricating oil may be arbitrary.

(3) Hot-rolled sheet recrystallization treatment step In the present invention, since the rolling end temperature is not higher than the Ar ₃ transformation point, the hot-rolled sheet after rolling has a worked structure. Therefore, it is necessary to recrystallize this hot rolled sheet to form a {111} oriented texture. If this recrystallization treatment is not performed, a {111} orientation texture is not formed, and a high r value cannot be obtained.

This recrystallization treatment is carried out in a winding step after hot rolling or a recrystallization annealing step. When performing recrystallization treatment in the winding step, it is desirable that the winding temperature be 650 ° C or higher. If the coiling temperature is less than 650 ° C, recrystallization does not occur, so that the {111} orientation texture is not formed and it is difficult to expect the improvement of the r value. Also, when performing in the recrystallization annealing step,
Both the box annealing method and the continuous annealing method are suitable, and the annealing temperature is
650-950 ° C is preferred. If the annealing temperature is less than 650 ° C, recrystallization does not occur, so that it is difficult to expect the improvement of r value without forming the {111} orientation texture.
α-transformation occurs and the texture is randomized, so that the r value deteriorates. This recrystallization annealing step can also be performed in the annealing equipment of a continuous hot-dip galvanizing line.

The hot-rolled steel strip after the recrystallization treatment has a shape-correcting,
In order to adjust the surface roughness and the like, temper rolling of 10% or less may be added. The hot-rolled steel sheet obtained by the present invention can be applied as a raw material for a surface-treated steel sheet for working and a raw material for a cold-rolled steel sheet. The surface treatment includes zinc plating (including alloy system), tin plating, enamel and the like.

Next, cold rolling conditions and annealing conditions in the case of producing a cold rolled steel sheet using the hot rolled steel sheet obtained by the present invention as a raw material will be described. (4) Cold rolling step This step is essential to obtain a high r value, and the reduction rate is 50 to 95%. If the rolling reduction is less than 50%,
If it exceeds 95%, excellent deep drawability cannot be obtained.

(5) Recrystallization Annealing Step The cold rolled steel sheet that has undergone cold rolling needs to be subjected to recrystallization annealing. The annealing method may be either a box annealing method or a continuous annealing method, and the annealing temperature is 700 to 950 ° C. The recrystallization annealed steel sheet may be subjected to temper rolling with a reduction rate of 10% or less in order to correct the shape and adjust the surface roughness. Also,
The obtained cold rolled steel sheet can also be used as an original plate of a surface-treated steel sheet for processing. The surface treatment includes zinc plating (including alloy system), tin plating, enamel and the like.

[0036]

Example: A steel having the composition shown in Table 1 has a thickness of 260 mm.
Continuous casting into a slab, heating to 1150 ° C and hot rough rolling to obtain a sheet bar with a plate thickness of 30 mm, then temporarily winding it in a coil box, then rewinding it and rolling it in a finishing rolling line. The tip and the trailing edge of the preceding sheet bar were heated by the induction heating method and then pressed and joined together, and then rolled at the Ar ₃ transformation point or higher under the conditions shown in Table 2 in a hot stand rolling machine with 7 stands, and continuously. After cooling and then rolling at Ar ₃ transformation point to 500 ° C. to obtain a plate thickness of 3.5 mm, recrystallization treatment was performed under the conditions shown in Table 2. The coils of Nos. 3 and 6 in Table 2 are those cooled in the third stand without any reduction.

[0037]

[Table 1]

[0038]

[Table 2]

The tensile strength and r value of the hot rolled steel sheet thus obtained were investigated. The results are also shown in Table 2. The tensile properties were measured using JIS No. 5 tensile test pieces.
In addition, the r value was measured by the 3-point method after 15% tensile prestrain, and was measured in the L direction (rolling direction), the D direction (45 ° direction with respect to the rolling direction) and the C direction (with respect to the rolling direction). (90 ° direction)
It was calculated from the average r value = (r _L + 2r _D + r _c ) / 4.

From Table 2, it can be seen that the conforming example according to the present invention has a better deep drawability than the comparative example.

Next, using the hot-rolled steel strips produced under the conditions shown in Table 2, cold rolling with a reduction rate of 75% was performed to obtain a sheet thickness of 0.7 mm.
After the cold-rolled steel strip of No. 1 was subjected to continuous annealing at 890 ° C for 20 seconds. Table 3 shows the results of an examination of the material properties of the cold-rolled steel sheet thus obtained.

[0042]

[Table 3]

From Table 3, it can be seen that the conforming example according to the present invention has a better deep drawability than the comparative example.

[0044]

EFFECTS OF THE INVENTION According to the present invention, the deep drawability superior to the conventional one was obtained due to the limitation of the component composition and the manufacturing conditions.
Further, the sheet bar is wound around the coil after the hot rough rolling, and the unwound sheet bar is joined prior to the hot finish rolling so as to be continuously subjected to rolling, which is effective in improving the deep drawability. Lubricating and rolling in the temperature range of Ar ₃ points to 500 ° C can be performed without causing biting failure or slipping, and the characteristic defective parts of the coil front and rear ends, which were inevitable in the past, are reduced. Yields have improved, and production efficiency has also improved.

[Brief description of drawings]

FIG. 1 is a graph showing an influence of a cooling temperature difference on an average r value.

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

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

Claims (3)

[Claims] 1. C: 0.01 wt% or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less, Al: 0.01 to 0.20 wt%, P: 0.20 wt% or less, S: 0.05 wt% or less and N: C content [C], Ti content [Ti] and Nb content containing 1 or 2 selected from Ti: 0.005 to 0.2 wt% and Nb: 0.001 to 0.2 wt% including 0.01 wt% or less. In relation to [Nb], the following formula 1.2 × [C] / 12 ≦ [Ti] / 48 + [Nb] / 93 (wt%) is satisfied and contained, and the balance is steel material consisting of iron and unavoidable impurities. Winding the sheet bar obtained by hot rough rolling,
Then, while being rewound and subjected to hot finish rolling at a temperature higher than the Ar ₃ transformation point, the leading end portion of the sheet bar is joined to the trailing end portion of the sheet bar to be rolled first, and then the Ar ₃ transformation point or higher. Hot finish rolling at a cooling rate of 20
After cooling to 30 ° C or higher at 30 ° C / s or more to bring it to the Ar ₃ transformation point or lower, the total reduction ratio of 50 at the Ar ₃ transformation point to 500 ° C temperature range.
Lubrication rolling of ~ 95%, followed by recrystallization treatment. 2. Steel material C: 0.01 wt% or less, Si: 2.0 wt% or less, Mn: 3.0 wt% or less, Al: 0.01 to 0.20 wt%, P: 0.20 wt% or less, S: 0.05 wt% or less And N: 0.01 wt% or less, and one or two selected from Ti: 0.005 to 0.2 wt% and Nb: 0.001 to 0.2 wt% as C content [C], Ti content [Ti] and In relation to the Nb content [Nb], the following formula 1.2 x [C] / 12 ≤ [Ti] / 48 + [Nb] / 93 (wt%) is contained, and further B: 0.0001 to 0.0080 wt% is contained. The method for producing a thin steel sheet excellent in deep drawability according to claim 1, wherein the balance comprises iron and inevitable impurities. 3. The method for producing a thin steel sheet excellent in deep drawability according to claim 1 or 2, wherein cold rolling and then recrystallization annealing are performed after the recrystallization treatment.