JP2978007B2 - High tensile strength steel sheet for deep drawing excellent in surface treatment property and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has high tensile strength of at least 40 kgf / mm ² and good formability, suitable for use as inner and outer panels for automobiles, and has particularly excellent surface treatment properties. The present invention proposes a cold-rolled steel sheet for deep drawing composed of a ferrite single phase structure and a method for producing the same.

2. Description of the Related Art High-strength steel sheets have been widely used as cold rolled steel sheets for use in automobile body components, exterior panels and the like in order to reduce the body. The characteristics of such high-strength steel sheets for automobiles include, at the same time, good formability represented by press working, as well as having sufficient strength required for ensuring the safety of automobiles, after forming. It is important that the secondary work brittle resistance is good. Furthermore, recently, rust prevention of steel sheets has been emphasized, and therefore, surface treatment properties of the steel sheets themselves have become important. In addition, in recent years, under the situation where the regulation on the total amount of exhaust gas from automobiles has been increasing remarkably, it is expected that the weight of the vehicle body will be promoted in order to further reduce the fuel cost in the future. There is an urgent need to further increase the strength.

[0003]

2. Description of the Related Art For high-tensile steel sheets having excellent workability,
For example, Japanese Unexamined Patent Publication No. 57-181361 discloses a cold-rolled steel sheet having excellent tensile rigidity (high Young's modulus) for large-size forming and a method for producing the same. A method for producing a cold-rolled steel sheet for deep drawing with small anisotropy is disclosed.
These are based on ultra-low C steel, and add a small amount of Nb, Ti, etc., and further control the continuous annealing conditions.
In order to increase the tensile strength, P with little material deterioration is used as a reinforcing component. However, according to the inventors' detailed experiments using several kinds of high P component systems similar to those in the above publications, it was found that the average r value was degraded after cold rolling and annealing, and further, that after coating, It was confirmed that the performance was adversely affected. In addition, this high P-added extremely low C steel, especially C
Tensile strength of content 0.002 wt% less than ultra-low C steel, a limit at most 40 kgf / mm ² approximately, with respect to high strength requirements of the steel sheet due to the body weight of automobiles, and its corresponding difficulty Obviously.

Further, Japanese Patent Publication No. 63-9579 discloses a high-strength cold-rolled steel sheet having good surface properties and capable of obtaining a tensile strength of 40 kgf / mm ² or more using Cu as well as P as a reinforcing component. ing. However, this steel sheet is still insufficient in its surface treatment properties.

[0005]

SUMMARY OF THE INVENTION The present invention provides a steel sheet having a tensile strength of at least 40 kgf / mm ² which is suitable for use as an inner and outer panel for automobiles in which the composition of steel is optimized to achieve both mechanical properties and surface treatment properties. An object of the present invention is to propose a cold-rolled steel sheet for high-strength deep drawing and a method for producing the same.

[0006]

As a result of repeated experiments and studies by the inventors, the present invention has revealed that Si,
The relationship between Mn and P contents was optimized, and Mo, T
By adding appropriate amounts of i and Nb, a tensile strength of 40 kgf / mm, which is suitable for use in automobile inner and outer panels and has excellent surface treatment properties.
^This is because it has been found that ^two or more high-strength cold-rolled steel sheets for deep drawing can be manufactured.

That is, the gist of the present invention is as follows: C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, B : 0.0005 wt% or more, 0.01 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% or less, and N: 0.006 wt% or less, and further Ti: 0.3 wt% % Or less and Nb: 0.001 wt% or more and 0.2 wt% or less selected from the group consisting of the above Si, Mn and P by containing one or two kinds selected from the following formulas (1) and (2). It is a high-strength steel sheet for deep drawing having excellent surface treatment properties (first invention), characterized in that the content satisfies the relationship of the following formula (3), and the balance is composed of iron and inevitable impurities. ^* wt% = Ti wt%-(48/32) S wt%-(48/14) N wt% --- (1) Ti ^* wt% + (48/93) Nb wt% ≥ (48/12) Cwt% --- (2) However, Ti wt%-(48/32) S wt%-(48/14) N wt% <
In the case of 0, it is assumed that Ti ^* = 0. 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3)

[0008] The high tensile strength steel sheet for deep drawing, which has excellent surface treatment properties and is further substituted with a part of iron as the remaining component of the first invention to further contain Ni: 0.05 wt% to 2.0 wt% (second invention). And a high tensile strength steel sheet for deep drawing having excellent surface treatment properties, in which Cu is replaced by a part of iron as the remaining component of the second invention to further contain Cu: 0.05 wt% or more and 2.0 wt% or less (third invention) And

C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, Ti: 0.3 wt% or less, and B: 0.0005 wt% or more, 0.01 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% less and N: 0.006 contains wt% or less the Si, satisfy the content of Mn and P is a relationship represented by the following formula (3), the balance as material a steel slab having a composition of iron and inevitable impurities, Ar ₃ Hot rolling at a finish rolling temperature higher than the transformation point, coiling in a temperature range of 300 ° C or higher and 615 ° C or lower, cold rolling at a rolling reduction of 65% or higher, and then at a recrystallization temperature higher than Ac ₃ A method for producing a high-strength steel sheet for deep drawing having excellent surface treatment properties, characterized by performing recrystallization annealing in a temperature range below the transformation point (No. Invention), Tiwt% ≧ (48/12) Cwt% + (48/32) S wt% + (48/14) N wt% --- (1 ′) 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3)

A method for producing a high-strength steel sheet for deep drawing with excellent surface treatment properties, wherein Ni is replaced by a part of iron as the remaining component of the fourth invention and further contains Ni in an amount of 0.05 wt% or more and 2.0 wt% or less (No. Production of high tensile strength steel sheet for deep drawing excellent in surface treatment properties, which further contains Cu: 0.05 wt% or more and 2.0 wt% or less by substituting a part of iron as the remaining component of the fifth invention. A method (sixth invention).

C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, Nb: 0.001 wt% or more, 0.2 wt% % Or less and the following formula
(2 ') in a range that satisfies the following requirements: B: 0.0005 wt% or more, 0.01 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% or less, N: not more than 0.006 wt%, the contents of the above Si, Mn and P satisfy the relationship of the following formula (3), and the remainder is a steel slab composed of iron and unavoidable impurities, and the Ar ₃ transformation point. After hot rolling at the above finishing rolling temperature, winding into a coil in a temperature range of 500 ° C or more and 700 ° C or less, cold rolling at a rolling reduction of 65% or more, and then at a recrystallization temperature or more and an Ac ₃ transformation point A method for producing a high-strength steel sheet for deep drawing having excellent surface treatment properties, characterized by performing recrystallization annealing in a temperature range of less than (the seventh invention), wherein Nb wt% ≧ (93/12) Cwt% − -(2 ') 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3)

A method for producing a high-strength steel sheet for deep drawing having excellent surface treatment properties, in which Ni is further substituted by a part of iron as the remaining component according to the seventh aspect, and Ni is contained in an amount of 0.05 wt% or more and 2.0 wt% or less (No. 8) The production of a high-strength steel sheet for deep drawing having excellent surface treatment properties in which Cu is replaced by part of iron as the remaining component of the eighth invention and further contains Cu: 0.05 wt% or more and 2.0 wt% or less. A method (ninth invention).

C: 0.001 wt% or more and 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Mo: 0.05 wt% or more and 1.0 wt% or less, and Ti: 0.3 wt%. The following and Nb: 0.001 wt% or more and 0.2 wt% or less are contained under the relationship of the following formulas (1) and (2). B: 0.0005 wt% or more and 0.01 wt% or less, Al: 0.01 wt% %, 0.10 wt% or less, P: 0.15 wt% or less, S: 0.010 wt% or less, and N: 0.006 wt% or less, the content of the above Si, Mn and P satisfy the relationship of the following formula (3), The remainder is hot-rolled at a finish rolling temperature of the Ar ₃ transformation point or higher using a steel slab composed of iron and unavoidable impurities, and wound into a coil at a temperature range of 500 ° C. or more and 700 ° C. or less. Cold-rolling at a rolling reduction of 65% or more, and then performing recrystallization annealing in a temperature range from the recrystallization temperature to the Ac ₃ transformation point. This is a method for producing a high-strength steel sheet for deep drawing with excellent heat resistance (the tenth invention), where Ti ^* wt% = Ti wt% − (48/32) S wt% − (48/14) N wt% --- (1) Ti ^* wt% + (48/93) Nb wt% ≥ (48/12) Cwt% --- (2) However, Ti wt%-(48/32) S wt%-(48/14) N wt% <
In the case of 0, it is assumed that Ti ^* = 0. 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3)
A method for producing a high-strength steel sheet for deep drawing having excellent surface treatment properties, wherein Ni is replaced by a part of iron as the remaining component of the tenth invention and further contains Ni: 0.05 wt% or more and 2.0 wt% or less (eleventh invention). And a method for producing a high-strength steel sheet for deep drawing having excellent surface treatment properties in which Cu is replaced by a part of iron as the remaining component of the eleventh invention to further contain Cu: 0.05 wt% or more and 2.0 wt% or less (No. 12 inventions).

[0014]

First, the experimental results on which the present invention is based will be described. Experiment 1 A total of four types of steel slabs, each having a chemical composition shown in Table 1 and having different C contents and a Mo-added steel, were hot-rolled at a finish rolling temperature of 890 ° C and wound at a temperature of 600 ° C. Later, 75
%, And continuously annealed at a temperature of 800 ° C. to obtain a steel sheet having a thickness of 0.7 mm.

[0015]

[Table 1]

The tensile properties of the four types of steel sheets thus obtained were examined. Based on these findings, the average r
The effect of the C content and the addition of Mo on the relationship between the tensile strength and the tensile strength is shown in FIG. As is apparent from FIG. 1, when the C content is increased based on the 45C steel to increase the strength, the average r value decreases with the increase in TS, but the average r value decreases with the addition of Mo.
CM steel showed a slight decrease in average r-value and TS was 7
It is higher than 0C steel. Thus, Mo
It is not clear at this time that the addition of Mo suppresses the decrease in the average r value despite an increase in TS, but the change in texture due to the addition of Mo is very small. Conceivable. From the above, it can be seen that the addition of Mo is effective in increasing TS while maintaining a good average r value.

Experiment 2 A steel containing a large amount of each of Si, Mn and P having the chemical composition shown in Table 2 and a steel slab containing a total of four steel slabs containing these components in a balanced manner were subjected to 900 ° C.
Hot rolling at a finishing rolling temperature of 580 ° C., and then cold rolling at a rolling reduction in the range of 70 to 75% to 830 to 86
Continuous annealing was performed in a temperature range of 0 ° C to obtain a 0.7 mm thick steel sheet. Some of these steel sheets were subjected to phosphate treatment, hot-dip galvanizing, and electro-Zn-Ni plating.

[0018]

[Table 2]

Here, the phosphate treatment was performed by a full dip method using Palbond L3020 treatment liquid manufactured by Nippon Parkerizing Co., Ltd. as the treatment liquid. Processing conditions are 42 ° C and 120
It was immersed for seconds. For hot-dip galvanizing, bath temperature: 475 ° C: penetration plate temperature: 475 ° C, immersion time: 3 seconds, alloying temperature: 485 ° C
The weight was 45 g / m ² . Electric Zn-Ni plating is
The test was carried out at a basis weight of 30 g / m ² . Each of the steel sheets obtained as described above was examined for tensile properties, phosphatability, and plating properties. Table 3 shows the results of these investigations.

[0020]

[Table 3]

Here, the phosphatability is determined by the film weight, P
The overall evaluation was made from the ratio, the size and distribution of crystal grains, and the plating properties were evaluated for the electro-Zn-Ni plating and hot-dip galvanizing from the plating adhesion and appearance. These are all shown in Table 3 as ○, Δ, and × as three-step evaluations in the order of goodness.

As is clear from Table 3, high Si steel and high P
For steel, satisfactory values were obtained for tensile properties, but there was a problem with surface treatment properties. Conversely, high Mn steels had good surface treatment properties, but tensile properties, especially elongation
The deterioration at the average r value is remarkable. On the other hand, Si-Mn-
P balance steel has good tensile properties and surface treatment properties. The tensile properties are not affected by the presence or absence of plating on the surface at the TS level targeted in the present invention.

Experiment 3 Further, based on the above results, regarding the balance of the contents of Si, Mn and P, Si and P whose large addition affects the surface treatment property, and that large addition adds ductility and depth. The present inventors have conducted intensive experiments and studies on Mn which significantly deteriorates the drawability, and have obtained new findings.

Hereinafter, the results of the experiment will be described. Si: 0.01 to 1.00 wt%, Mn: 0.30 to 2.50 wt% and
P: contained in the range of 0.01 to 0.15 wt%, C: 0.008 wt%
%, Mo: 0.25 wt%, Ti: 0.055 wt%, Nb: 0.030
wt%, B: 0.001 wt%, Al: 0.045 wt%, S: 0.002
wt% and various steel slabs adjusted to the composition of N: 0.002 wt% were hot-rolled at a finish rolling temperature of 890 ° C.
After winding at a temperature of 560 ° C, it was cold-rolled at a rolling reduction of 70 to 75% and continuously annealed at a temperature of 800 to 830 ° C to obtain a steel sheet having a thickness of 0.8 mm. For some of these steel sheets, phosphate treatment, hot-dip galvanizing, and electric Zn-N
i Plated. Here, phosphate treatment, hot-dip galvanizing, electro-Zn-Ni plating, etc. were performed in the same manner as in Experiment 2.

With respect to each of the steel sheets thus obtained, the tensile properties and the surface treatment properties, such as phosphating properties, powdering properties of hot-dip galvanizing, and adhesion of electric Zn-Ni plating were examined.

Here, the phosphatability was evaluated in the same manner as in Experiment 2 and evaluated on a 5-point scale, and both the powdering property and the adhesion were evaluated on a 5-point scale in a bending test.

From these survey results, (Siwt% + 10 ·
FIG. 2 shows the relationship between (Pwt%) / Mnwt%, tensile strength, elongation, average r value, and various surface treatment properties. As is clear from FIG. 2, when (Siwt% + 10 · Pwt%) / Mnwt% is 0.2 or less, the El, the average r value and the various surface treatment properties are good, but the TS reaches the target of 40 kgf / mm ² . Do not reach. On the other hand, when (Si wt% + 10 · P wt%) / Mn wt% is 3.3 or more, the El, the average r value, and various surface treatment properties are significantly deteriorated. Therefore, the range in which both the tensile properties and various surface treatment properties are good is 0.2 <(Siwt% + 10 · Pwt%) / Mnwt.
It can be seen that% <3.3.

Further, it has been found from other experiments that various characteristics similar to those described above can be maintained even when Ni or Ni and Cu are contained within an appropriate range.

Experiment 4 A total of eight types of steel slabs, each having a chemical composition shown in Table 4 and different in Mn content and a steel containing Mo and Nb were hot-rolled at a finish rolling temperature of 890 ° C. After winding on a coil at the indicated temperature, cold rolling was performed at a rolling reduction of 75% to achieve a thickness of 0.
After forming a 7 mm cold-rolled sheet, continuous annealing was performed at a temperature of 800 ° C. The winding temperature was 400 for steel symbol F.
The temperature was varied in the temperature range of ~ 700 ° C, and the other steels were at 600 ° C.

[0030]

[Table 4]

The tensile properties of the eight types of steel sheets thus obtained were examined. Based on the results of these investigations, the relationship between the tensile strength and the average r value is shown in FIG.

As is clear from FIG. 3, when the Mn content is increased in the order of B, C, G, and H steels based on the A steel to increase the strength, the average r value decreases with an increase in TS. But M
The D, E, and F steels to which o and / or Nb are added have a small decrease in the average r value, and the TS is higher than that of the C steel having substantially the same Mn content.

Further, among the samples having a coil winding temperature (CT) of 600 ° C., F steel to which both Mo and Nb are added has the best strength-average r value balance and a high TS. The effect of CT on F steel is shown in FIG.
It can be seen that the strength-average r value balance is excellent in the temperature range of 0 ° C.

From these results, it was found that Mo and Nb were added, and that the Mo and Nb added steels
It can be seen that coiling in a temperature range of up to 700 ° C. is effective for increasing TS while maintaining the deep drawability.

Although the above reason is not clear at present,
It is considered as follows. Mo has a relatively high strengthening ability,
Further, it is considered to be a component that hardly changes the texture, and as a result, it is considered that high strength can be achieved without deterioration of deep drawability. Nb, although not as strong as Mo, has a remarkable effect of improving the texture, and when used together with Mo, it is possible to make the balance between deep drawability and strength extremely excellent. The effect of improving the texture of Nb largely depends on the crystal grain size of the hot-rolled sheet and the grain size of the precipitate (mainly Nb carbide). That is,
If the coil winding temperature is high, the crystal grain size becomes too large, and the formation of a recrystallization texture advantageous for deep drawability is hindered.If the coil winding temperature is low, the precipitates become too fine and during recrystallization, The growth of crystals having an advantageous texture tends to be inhibited. Therefore, it is considered that the optimum range of the coil winding temperature clarified by the experiment is determined by the above circumstances.

Next, the reasons for limiting the composition range of the chemical components in the present invention will be described.

C: 0.001 to 0.05 wt% If the content of C is small, the target tensile strength is 40 kgf / C.
In order to obtain mm ² or more, it is disadvantageous that many other strengthening components must be added, but the lower limit of the content is 0.001 wt%
Up to acceptable. On the other hand, if the content exceeds 0.05 wt%, desired ductility cannot be obtained, and the cost increases because Ti and Nb added for fixing C must be increased. Therefore, its content is 0.
The content is 001 wt% or more and 0.05 wt% or less, but 0.002 wt% or more is preferable in order to obtain higher strength.

Si: 1.0 wt% or less Si is a component excellent in solid solution strengthening ability, and is added to improve strength. However, when the content exceeds 1.0% by weight, not only the phosphatability, the melting and the electroplating properties are deteriorated, but also the descalability during hot rolling is deteriorated. Therefore, its content should be 1.0 wt% or less.

Mn: 2.5 wt% or less Mn is a component excellent in solid solution strengthening ability like Si, and is added to improve strength. In addition, steel that does not contain Ti also has the effect of fixing S. However, 2.5wt%
If it is contained in excess of, the ductility and deep drawability are significantly deteriorated. Therefore, its content should be 2.5 wt% or less.

Mo: 0.05 to 1.0 wt% Mo is a component that, when contained in an appropriate range, decreases the ductility and the deep drawability with respect to an increase in strength.
The effect is manifested when the content is 0.05 wt% or more.
If it exceeds t%, on the contrary, not only the ductility and the deep drawability deteriorate significantly, but also the cost increases. Therefore, the content is set to 0.05 wt% or more and 1.0 wt% or less, and desirably 0.5 wt% or less.

B: 0.0005 to 0.01 wt% B has the effect of improving the resistance to secondary working brittleness, phosphatability and spot weldability. These effects are exhibited when the content is 0.0005 wt% or more, but when the content exceeds 0.01 wt%, not only slab cracking is caused but also the deep drawability is deteriorated. Therefore, the content is set to 0.0005 wt% or more and 0.01 wt% or less.

Al: 0.01 to 0.10 wt% Al is an effective component for fixing O in the steel and avoiding a decrease in the amount of effective Ti due to bonding with O, and a steel containing no Ti. Then, there is also an effect of fixing N. 0.
If the content is less than 01 wt%, the effect is poor. If the content exceeds 0.10 wt%, not only the effect is saturated, but also nonmetallic inclusions increase rapidly and cause deterioration of surface properties. Therefore, the content is set to 0.01 wt% or more and 0.10 wt% or less.

P: not more than 0.15 wt% P is a component excellent in solid solution strengthening ability like Si and Mn, and is added to improve the strength. Not only deteriorates phosphatability, melting and electroplating properties, but also adversely affects the quality of the steel sheet surface itself. In addition, coarse FeTiP is likely to be generated in the hot rolling step, which causes the average r value to deteriorate after cold rolling and annealing. Therefore, the content is 0.15 wt% or less.

S: not more than 0.010 wt% S causes not only the occurrence of cracks during hot rolling, but also the amount of Ti added for fixing S increases with the increase of S. It also increases costs due to the increase. Therefore, the content is preferably as small as possible, but the upper limit is set to 0.010% by weight.

N: 0.006 wt% or less N, when contained in a large amount, causes deterioration of the average r value and ductility,
Further, the cost increases due to an increase in the amount of Ti added to fix N. Therefore, its content is made 0.006 wt% as an allowable upper limit.

Ti: 0.3 wt% or less, Nb: 0.001 to 0.2
wt% each alone or in combination, and Ti ^* wt% + (48/9
3) Nb wt% ≧ (48/12) Cwt% (However, Ti ^* wt% = Tiwt% −
(48/32) Swt%-(48/14) Nwt% and Ti wt%-(48/32) S wt
% ^* (48/14) N wt% <0, Ti ^* = 0. ) Ti has the effect of fixing C, S and N, and Nb
Is also a component that fixes C. C and N are components that adversely affect workability in a solid solution state, and S is a component that causes hot working cracks in a solid solution state. Therefore, it is important to fix C, S and N by Ti and / or Nb. Further, Nb also has the effect of improving the strength-deep drawability balance as described above. Note that Nb
It should be noted that the optimum coil winding temperature in the manufacturing process differs depending on the presence or absence of the coil.

Whether or not the most important effect of depositing and fixing C, which is important for improving workability, is determined as follows.
Since Ti has a stronger tendency to bond with S and N than C, Ti
The effective Ti amount capable of forming C, that is, Ti ^* is Tiwt% − (48 /
32) Swt%-(48/14) Nwt%. On the other hand, Nb is mainly C
Binds only to form NbC, the effective amount of Nb is Nb
It is almost equal to the content. Therefore, the lower limit of the amount of Ti and Nb necessary for fixing C is Ti ^* wt% + (48/93) Nb wt%.
= (48/12) Cwt%.

In order for Nb to contribute to the improvement of the balance between strength and deep drawability, it is necessary to contain Nb in an amount of 0.001 wt% or more. On the other hand, the content is 0.3 wt% in Ti,
If b exceeds 0.2 wt%, not only deterioration of the material due to excessive solid solution Ti and Nb is caused, but also a bad influence on the surface quality of the steel sheet. Therefore, their content is T
i: 0.3 wt% or less, Nb: 0.001 wt% or more, 0.2 wt% or less, and Ti ^* wt% + (48/93) Nb wt% ≧ (48/12) Cwt%
(However, Ti ^* wt% = Tiwt%-(48/32) Swt%-(48/14) Nwt
If Ti wt% − (48/32) S wt% − (48/14) N wt% <0, Ti ^* = 0. In addition, in order to set the upper limit of the Nb content to 0.2 wt% in the above description, in the case of adding Nb alone, it is preferable to set the upper limit to 0.025 wt% as the C content corresponding to the equivalent.

It should be noted that Ti is Tiwt% ≧ (48/12) Cwt% + (48 /
32) In the case where it is contained under the condition satisfying Swt% + (48/14) Nwt%, the total amount of solute C should be fixed only by Ti in the equilibrium state. However, according to the experiments performed by the inventors, even in this case, the dependence of the recrystallized grain size and the texture of the Nb-added material on the coil winding temperature is observed, and a considerable amount of NbC is present under the hot rolling conditions in the normal process. It is thought to be.

Ni: 0.05-2.0 wt% Ni is effective for improving strength by its solid solution strengthening ability and
Has an effect of suppressing surface defects generated at the time of hot rolling. These effects are exhibited when the content is 0.05 wt% or more, but when the content exceeds 2.0 wt%, ductility and deep drawability are deteriorated. Therefore, its content is
0.05 wt% or more and 2.0 wt% or less, preferably 0.7 wt% or less.
It is good to be below wt%.

Cu: 0.05 to 2.0 wt% Cu is contained in order to improve the strength by using its solid solution strengthening ability, like Ni, and its effect is exhibited when the content is 0.05 wt% or more. I do. However, when the content exceeds 2.0 wt%, in addition to ductility and deep drawability, the surface quality of the steel sheet is significantly deteriorated. Therefore, its content is more than 0.05wt%,
The content is 2.0 wt% or less, preferably 0.7 wt% or less. When the content is 0.2 wt% or less, the strengthening ability is slightly reduced, but the adverse effect is hardly a problem. Note that Cu
Is liable to cause surface defects during hot rolling when added alone, so it needs to be added in combination with Ni to suppress the surface defects.

Further, in the present invention, in addition to the above-mentioned chemical composition range limitation, the contents of Si, Mn and P are reduced.
It is necessary to satisfy the relationship of 0.2 <(Si wt% + 10 · Pwt%) / Mnwt% <3.3. This is, as described above, (Si wt%
If the value of (+ 10 · Pwt%) / Mn wt% is less than 0.2, the desired tensile properties cannot be obtained, while if the value is more than 3.3, the surface treatment property, ductility and deep drawability are remarkably deteriorated.

Next, the reasons for limiting the manufacturing conditions will be described. Hot Rolling Conditions If the finish rolling temperature in the hot rolling is lower than the Ar ₃ transformation point, the average r value after cold rolling and annealing decreases and the in-plane anisotropy increases. Therefore, its temperature is A
r ₃ transformation point or higher. The upper limit is not particularly limited, but is preferably set to be equal to or lower than the Ar ₃ transformation point + 50 ° C. The hot rolling conditions of the present invention include, in addition to cooling the continuous casting slab once and then reheating it to perform rough rolling, from the viewpoint of energy saving,
Rough rolling may be performed immediately or after performing a heat retaining treatment without lowering the temperature to the r ₃ transformation point or lower.

If the coil winding temperature exceeds 615 ° C. in steel containing no Nb, FeTiP is likely to be formed, resulting in a decrease in the average r value after cold rolling and annealing.
If the temperature is lower than 0 ° C., the rolling load at the time of cold rolling becomes excessive, so that a large load is applied to the rolling mill, and the operation disadvantage is great. As described above, in steel containing Nb, 500
The effect of the present invention can be most enhanced in the temperature range of -700 ° C. Therefore, the coiling temperature should be 300 ° C. or more and 615 ° C. or less for steel not containing Nb, and 500 ° C. or more and 700 ° C. or less for steel containing Nb.

Cold Rolling-Annealing If the rolling reduction in cold rolling is less than 65% even if other process conditions are optimized, sufficient workability cannot be obtained.
Therefore, the rolling reduction is 65% or more. The annealing temperature after cold rolling is usually higher than the recrystallization temperature. However, when the temperature exceeds the Ac ₃ transformation point, the average r value after cooling significantly decreases. Therefore, its temperature is above the recrystallization temperature,
Ac ₃ transformation point or less. In addition, as an annealing method, continuous annealing or box annealing may be used.

Further, the steel sheet may be subjected to a temper rolling for the purpose of correcting the shape of the sheet, etc., in a range of ordinary common sense, that is, a rolling reduction (%) equal to the sheet thickness (mm).

[0057]

【Example】

Example 1 Using steel slabs of 10 types of compatible steels of the present invention and 8 types of comparative steels having a chemical composition shown in Table 5 and a total of 18 types of steels, each was finished to a steel plate of 0.7 mm in thickness. Surface treatments such as phosphate treatment, hot-dip galvanizing, and electro-Zn-Ni plating were performed, and the tensile properties and surface treatment properties of these steel sheets were investigated.

[0058]

[Table 5]

Table 6 summarizes the results of the above hot rolling, cold rolling, annealing conditions, tensile properties, and surface treatment properties.

[0060]

[Table 6]

Here, phosphate treatment, hot-dip galvanizing,
Electro-Zn-Ni plating was performed under the following conditions. Phosphate treatment Treatment solution: Palbond L3020 manufactured by Nippon Parkerizing Co., Ltd. Treatment method: Full dip Treatment condition: Immersion at 42 ° C for 120 seconds Hot-dip galvanizing Bath temperature: 475 ° C Alloying temperature: 485 ° C Penetration plate temperature: 475 ° C Weight per unit area: 45 g / m ² immersion time: 3 seconds Electric Zn-Ni plating Weight per unit area: 30 g / m ²

Further, each of these investigations was performed by the following method. Tensile properties: JIS No. 5 test pieces were used for tensile tests, and tensile strength, yield stress, and elongation were examined in the rolling direction. The average r value was determined by the following formula from each r value in the rolling direction (r ₀ ), 45 ° direction (r ₄₅ ) and 90 ° direction (r ₉₀ ) with respect to the rolling direction. Average r value = (r ₀ + 2r ₄₅ + r ₉₀ ) / 4 Each r value is obtained by measuring the width at three points at the center of the specimen in the length direction at 15% strain and 12.5 mm on both sides from the center thereof. I asked. Phosphate treatment: Comprehensive evaluation based on coating weight, P ratio, crystal grain size and distribution. Hot-dip galvanizing property: Evaluated from patterning property. Electric Zn-Ni Plating property: Evaluated from adhesion. The above phosphating properties, hot-dip galvanizing properties,
The Zn-Ni plating property was evaluated on a three-point scale, and was indicated by ○, Δ, and × in Table 6 in ascending order.

As is clear from Table 6, in all of the conforming examples, a tensile strength of 40 kgf / mm ² or more was obtained, and good ductility and deep drawability were obtained. Comparative Examples in which the component composition or the production conditions are out of the limited range of the present invention are inferior in tensile properties or surface treatment properties. In addition, the metal structures of the conforming examples were all ferrite single-phase structures.

A comparative example of the sample No. 28 is a sample No. 9
(Si wt% + 10 · Pwt%) /
The value of Mn wt% is different and the value is 0.14 of 0.2 or less, which is out of the limited range of the present invention. However, although the surface treatment property is equivalent to that of sample No. 9, the elongation and the average r value are inferior. . On the other hand, the comparative example of the sample No. 29 is (Siwt% + 10 · Pwt%) / Mnwt compared with the conforming example of the sample No.16.
%, Which differs from 5.16 of 3.3 or more, which is out of the range of limitation of the present invention.
Although it is equivalent to, the surface treatment property is inferior.

Further, the comparative example of the sample No. 30 is the same as the sample No. 30.
This is an example in which the C content was increased in order to obtain the same level of TS as the Mo-added material of the 9 compatible examples, but the elongation and the average r value were inferior.

Example 2 Twelve steel slabs having a chemical composition shown in Tables 7 and 8 of the present invention and a total of 21 steels of a comparative steel type and a comparative steel type of 9 were used as materials, and each was finished to a steel plate having a thickness of 1.2 mm. Some of them were subjected to surface treatments such as phosphate treatment, hot-dip galvanizing, and electro-Zn-Ni plating, and the tensile properties and surface treatment properties of these steel sheets were investigated.

[0067]

[Table 7]

[0068]

[Table 8]

The results of the above hot rolling, cold rolling, annealing conditions, tensile properties, and surface treatment properties are summarized in Table 9 below.
It is shown in Table 10. The slab heating temperature was 1150 to 1250 ° C., the annealing was performed in a continuous annealing cycle (soaking for 5 seconds), and after the annealing, a 0.8% temper rolling was performed. Each surface treatment was performed in the same manner as in Example 1, and the tensile properties and surface treatment properties were investigated in the same manner as in Example 1.

[0070]

[Table 9]

[0071]

[Table 10]

As is clear from Tables 9 and 10, all of the conforming examples have excellent surface treatment properties and a tensile strength of 40 kgf / mm ² or more.
And, while good ductility, deep drawability, that is, excellent strength-deep drawability balance has been obtained, the comparative examples in which the chemical component composition is out of the limited range of the present invention are inferior in tensile properties or surface treatment properties. I have. In addition, the comparative examples of sample symbols 1B, 1C, 1D, and 3B whose component compositions conform to the present invention, but whose production conditions are out of the limited range of the present invention, are 1A and 1A whose component compositions and production conditions conform to the present invention, respectively. Material properties are inferior to 3A conforming examples. The metal structures of these conforming examples were all ferrite single-phase structures.

Further, the comparative example of sample code 13 is (Si wt% +
(10 · Pwt%) / Mn wt% is 0.18 of 0.2 or less, which is out of the limited range of the present invention, but the surface treatment property is equivalent to that of the applicable example, but the tensile strength has reached 40 kgf / mm ^2. Absent. On the other hand, the comparative example of the sample symbol 14 in which the above value is 3.3 or more and 4.40, which is outside the limited range of the present invention, is inferior in surface treatment properties.

[0074]

According to the present invention, in addition to the addition of Mo and B, Ti and / or Nb, Si, which has a large solid solution strengthening ability,
By taking Mn and P into consideration in consideration of their respective actions, and containing them in a well-balanced manner, a deep-drawing steel sheet excellent in various surface treatment properties and excellent in strength-deep-drawing property balance can be obtained, and particularly subjected to rust prevention treatment. It can be advantageously used for inner and outer plates for automobiles and the like. Further, the steel sheet according to the present invention does not require any pretreatment equipment before and after annealing required for surface treatment of a steel sheet having inferior surface treatment obtained by adding a large amount of Si, or at the entrance of a continuous hot-dip plating line. And the merits in this respect are also great.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the C content and the addition of Mo on the relationship between the average r value and the tensile strength.

Fig. 2 (Si wt% + 10 · Pwt%) / Mnwt% and tensile strength
It is a graph which shows the relationship between elongation, an average r value, and various surface treatment properties.

FIG. 3 is a graph showing the relationship between tensile strength and average r value.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Sakata 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (72) Inventor Masahiko Morita 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki (72) Inventor Toshiyuki Kato 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Corporation Technology Research Headquarters (56) References JP-A-4-325656 (JP, A) JP JP-A-3-274231 (JP, A) JP-A-3-17233 (JP, A) JP-A-62-50438 (JP, A) JP-A-59-140333 (JP, A) JP-A-55-141526 (JP, A) JP-A-51-72918 (JP, A) JP-A-50-51724 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00 301 C21D 8/04 C21D 9/48 C22C 38/14

Claims (12)

(57) [Claims] C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, B: 0.0005 wt% or more, 0.01% by weight or less, Al: 0.01% by weight or more, 0.10% by weight or less P: 0.15% by weight or less, S: 0.010% by weight or less and N: 0.006% by weight or less, further Ti: 0.3% by weight or less and Nb: 0.001% One or two selected from the range of wt% or more and 0.2 wt% or less are contained under the relationship of the following formulas (1) and (2), and the contents of Si, Mn and P are expressed by the following formula ( A high-strength steel sheet for deep drawing with excellent surface treatment properties, which satisfies the relationship of 3) and the balance is composed of iron and unavoidable impurities. Note Ti ^* wt% = Ti wt%-(48/32) S wt%-(48/14) N wt% --- (1) Ti ^* wt% + (48/93) Nb wt% ≥ (48 / 12) Cwt% --- (2) However, Ti wt%-(48/32) S wt%-(48/14) N wt% <
In the case of 0, it is assumed that Ti ^* = 0. 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3) 2. C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Ni: 0.05 wt% or more, 2.0 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, B: 0.0005 wt% or more, 0.01 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% or less, and N: 0.006 wt% or less And one or two kinds selected from Ti: 0.3 wt% or less and Nb: 0.001 wt% or more and 0.2 wt% or less under the relationship of the following formulas (1) and (2). A high-strength steel sheet for deep drawing having excellent surface treatment properties, characterized in that the contents of Si, Mn and P satisfy the relationship of the following formula (3), and the balance is composed of iron and unavoidable impurities. Note Ti ^* wt% = Ti wt%-(48/32) S wt%-(48/14) N wt% --- (1) Ti ^* wt% + (48/93) Nb wt% ≥ (48 / 12) Cwt% --- (2) However, Ti wt%-(48/32) S wt%-(48/14) N wt% <
In the case of 0, it is assumed that Ti ^* = 0. 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3) 3. C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Ni: 0.05 wt% or more, 2.0 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, B: 0.0005 wt% or more, 0.01 wt% or less, Cu: 0.05 wt% or more, 2.0 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% or less and N: 0.006 wt% or less, and one or two selected from Ti: 0.3 wt% or less and Nb: 0.001 wt% or more and 0.2 wt% or less are represented by the following formulas (1) and ( The surface treatment properties characterized in that the content of Si, Mn and P satisfies the relationship of the following formula (3) contained under the relationship of 2), and the balance consists of the composition of iron and unavoidable impurities. High tensile strength steel sheet for deep drawing. Note Ti ^* wt% = Ti wt%-(48/32) S wt%-(48/14) N wt% --- (1) Ti ^* wt% + (48/93) Nb wt% ≥ (48 / 12) Cwt% --- (2) However, Ti wt%-(48/32) S wt%-(48/14) N wt% <
In the case of 0, it is assumed that Ti ^* = 0. 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3) 4. C: 0.001 wt% or more and 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, Ti: 0.3 wt% or less. And B in the range satisfying the following formula (1 '). B: 0.0005 wt% or more, 0.01 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% or less and N: 0.006 wt% or less, the contents of the above Si, Mn and P satisfy the relationship of the following formula (3), and the balance is made of a steel slab composed of iron and unavoidable impurities. Hot rolling at a finish rolling temperature of Ar ₃ transformation point or higher, winding on a coil in a temperature range of 300 ° C or higher and 615 ° C or lower, cold rolling at a rolling reduction of 65% or higher, and then recrystallization temperature or higher A method for producing a high-strength steel sheet for deep drawing having excellent surface treatment properties, wherein recrystallization annealing is performed in a temperature range lower than the Ac ₃ transformation point. Notation Tiwt% ≧ (48/12) Cwt% + (48/32) S wt% + (48/14) N wt% --- (1 ′) 0.2 <(Si wt% + 10 · P wt%) / Mnwt % <3.3 --- (3) 5. C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Ni: 0.05 wt% or more, 2.0 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, Ti: 0.3 wt% or less, and contained in a range satisfying the following formula (1 '). B: 0.0005 wt% or more, 0.01 wt% or less, Al: 0.01 wt% or more, 0.10 wt% % Or less P: 0.15 wt% or less, S: 0.010 wt% or less and N: 0.006 wt% or less, the content of the above Si, Mn and P satisfy the relationship of the following formula (3), and the balance is iron and unavoidable Steel slab composed of chemical impurities, hot-rolled at a finish rolling temperature of the Ar ₃ transformation point or higher, wound around a coil in a temperature range of 300 ° C or higher and 615 ° C or lower, and a reduction of 65% or more in cold-rolled, followed recrystallization temperature or higher, the depth excellent surface treatability, characterized in that performing recrystallization annealing Ac ₃ transformation point of less than the temperature range Method of manufacturing a high-tensile steel sheet for Ri. Notation Tiwt% ≧ (48/12) Cwt% + (48/32) S wt% + (48/14) N wt% --- (1 ′) 0.2 <(Si wt% + 10 · P wt%) / Mnwt % <3.3 --- (3) 6. C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Ni: 0.05 wt% or more, 2.0 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, Ti: 0.3 wt% or less, and contained in a range satisfying the following formula (1 ′). B: 0.0005 wt% or more, 0.01 wt% or less, Cu: 0.05 wt% or more, 2.0 wt% %, Al: 0.01 wt% or more, 0.10 wt% or less, P: 0.15 wt% or less, S: 0.010 wt% or less, and N: 0.006 wt% or less. The relationship of 3) is satisfied, and the remainder is hot-rolled at a finish rolling temperature of the Ar ₃ transformation point or higher using a steel slab composed of iron and unavoidable impurities at a temperature range of 300 ° C or higher and 615 ° C or lower. After being wound on a coil, cold rolling is performed at a rolling reduction of 65% or more, and then recrystallization annealing is performed at a temperature range of the recrystallization temperature or higher and lower than the Ac ₃ transformation point. A method for producing high-strength steel sheets for deep drawing with excellent surface treatment properties. Notation Tiwt% ≧ (48/12) Cwt% + (48/32) S wt% + (48/14) N wt% --- (1 ′) 0.2 <(Si wt% + 10 · P wt%) / Mnwt % <3.3 --- (3) 7. C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, Nb: 0.001 wt% or more, 0.2 wt% or less and the following formula
(2 ') in a range that satisfies the following requirements: B: 0.0005 wt% or more, 0.01 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% or less, N: not more than 0.006 wt%, the contents of the above Si, Mn and P satisfy the relationship of the following formula (3), and the remainder is a steel slab composed of iron and unavoidable impurities, and the Ar ₃ transformation point. After hot rolling at the above finishing rolling temperature, winding into a coil in a temperature range of 500 ° C or more and 700 ° C or less, cold rolling at a rolling reduction of 65% or more, and then at a recrystallization temperature or more and an Ac ₃ transformation point A method for producing a high-strength steel sheet for deep drawing having excellent surface treatment properties, wherein recrystallization annealing is performed in a temperature range of less than. Note Nb wt% ≧ (93/12) Cwt% --- (2 ') 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3) 8. C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Ni: 0.05 wt% or more, 2.0 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, Nb: 0.001 wt% or more, 0.2 wt% or less, and the following formula
(2 ') in a range that satisfies the following requirements: B: 0.0005 wt% or more, 0.01 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% or less, N: not more than 0.006 wt%, the contents of the above Si, Mn and P satisfy the relationship of the following formula (3), and the remainder is a steel slab composed of iron and unavoidable impurities, and the Ar ₃ transformation point. After hot rolling at the above finishing rolling temperature, winding into a coil in a temperature range of 500 ° C or more and 700 ° C or less, cold rolling at a rolling reduction of 65% or more, and then at a recrystallization temperature or more and an Ac ₃ transformation point A method for producing a high-strength steel sheet for deep drawing having excellent surface treatment properties, wherein recrystallization annealing is performed in a temperature range of less than. Note Nb wt% ≧ (93/12) Cwt% --- (2 ') 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3) 9. C: 0.001 wt% or more, 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Ni: 0.05 wt% or more, 2.0 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, Nb: 0.001 wt% or more, 0.2 wt% or less, and the following formula
(2 ') in a range that satisfies the following requirements: B: 0.0005% to 0.01% by weight; Cu: 0.05% to 2.0% by weight; Al: 0.01% to 0.1% by weight P: The content of Si, Mn and P satisfies the following formula (3), including 0.15 wt% or less, S: 0.010 wt% or less, and N: 0.006 wt% or less, and the balance is the composition of iron and unavoidable impurities. Hot rolled at a finish rolling temperature of the Ar ₃ transformation point or higher, wound up in a coil at a temperature range of 500 ° C or higher and 700 ° C or lower, and then cold rolled at a rolling reduction of 65% or higher A method for producing a high-strength steel sheet for deep drawing having excellent surface treatment properties, wherein recrystallization annealing is performed in a temperature range not lower than the recrystallization temperature and lower than the Ac ₃ transformation point. Note Nb wt% ≧ (93/12) Cwt% --- (2 ') 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3) 10. C: 0.001 wt% or more and 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Mo: 0.05 wt% or more and 1.0 wt% or less, and Ti: 0.3 wt% or less and Nb: 0.001 wt% or more and 0.2 wt% or less under the relationship of the following formulas (1) and (2). B: 0.0005 wt% or more and 0.01 wt% or less, Al: Not less than 0.01 wt%, not more than 0.10 wt%, P: not more than 0.15 wt%, S: not more than 0.010 wt% and N: not more than 0.006 wt%. Filled, the remainder was hot-rolled at a finish rolling temperature of the Ar ₃ transformation point or higher using a steel slab composed of iron and unavoidable impurities, and wound around a coil at a temperature range of 500 ° C. or more and 700 ° C. or less. After that, cold rolling is performed at a rolling reduction of 65% or more, and then recrystallization annealing is performed in a temperature range not lower than the recrystallization temperature and lower than the Ac ₃ transformation point. A method for manufacturing high-strength steel sheets for deep drawing with excellent reason. Note Ti ^* wt% = Ti wt%-(48/32) S wt%-(48/14) N wt% --- (1) Ti ^* wt% + (48/93) Nb wt% ≥ (48 / 12) Cwt% --- (2) However, Ti wt%-(48/32) S wt%-(48/14) N wt% <
In the case of 0, it is assumed that Ti ^* = 0. 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3) 11. C: 0.001 wt% or more and 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Ni: 0.05 wt% or more, 2.0 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, and Ti: 0.3 wt% or less and Nb: 0.001 wt% or more and 0.2 wt% or less under the relationship of the following formulas (1) and (2). 0.0005 wt% or more, 0.01 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% or less, and N: 0.006 wt% or less. The content of satisfies the relationship of the following formula (3), the remainder is hot-rolled at a finishing rolling temperature of Ar ₃ transformation point or higher using a steel slab having a composition of iron and unavoidable impurities, 500 ° C. or higher, After wound into a coil at a temperature less than 700 ℃, cold rolling at a reduction of 65% or more, then the recrystallization temperature or more, the recrystallization in a temperature range of Ac less than ₃ transformation point Method for manufacturing a deep drawing for high-tensile steel plate with excellent surface treatability, characterized in that performing blunt. Note Ti ^* wt% = Ti wt%-(48/32) S wt%-(48/14) N wt% --- (1) Ti ^* wt% + (48/93) Nb wt% ≥ (48 / 12) Cwt% --- (2) However, Ti wt%-(48/32) S wt%-(48/14) N wt% <
In the case of 0, it is assumed that Ti ^* = 0. 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3) 12. C: 0.001 wt% or more and 0.05 wt% or less, Si: 1.0 wt% or less, Mn: 2.5 wt% or less, Ni: 0.05 wt% or more, 2.0 wt% or less, Mo: 0.05 wt% or more, 1.0 wt% or less, and Ti: 0.3 wt% or less and Nb: 0.001 wt% or more and 0.2 wt% or less under the relationship of the following formulas (1) and (2). 0.0005 wt% or more, 0.01 wt% or less, Cu: 0.05 wt% or more, 2.0 wt% or less, Al: 0.01 wt% or more, 0.10 wt% or less P: 0.15 wt% or less, S: 0.010 wt% or less, and N: 0.006 the content of the Si, Mn and P satisfy a relationship represented by the following formula (3) include the following wt%, the balance as material a steel slab having a composition of iron and inevitable impurities, finishing above Ar ₃ transformation point After hot rolling at a rolling temperature, winding the coil in a temperature range of 500 ° C. or more and 700 ° C. or less, cold rolling at a rolling reduction of 65% or more, and then at a recrystallization temperature or higher, A method for producing a high-tensile steel plate for deep drawing having excellent surface treatability, characterized in that performing recrystallization annealing at c temperature range of less than ₃ transformation point. Note Ti ^* wt% = Ti wt%-(48/32) S wt%-(48/14) N wt% --- (1) Ti ^* wt% + (48/93) Nb wt% ≥ (48 / 12) Cwt% --- (2) However, Ti wt%-(48/32) S wt%-(48/14) N wt% <
In the case of 0, it is assumed that Ti ^* = 0. 0.2 <(Si wt% + 10 · P wt%) / Mnwt% <3.3 --- (3)