JP2014028998A - Cold rolled steel sheet, electrogalvanized cold rolled steel sheet, hot-dip galvanized cold rolled steel sheet and galvannealed cold rolled steel sheet having excellent deep drawability, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cold rolled steel sheet, an electrogalvanized cold rolled steel sheet, a hot-dip galvanized cold rolled steel sheet and a galvannealed cold rolled steel sheet having excellent deep drawability, and a method for manufacturing them.SOLUTION: A cold rolled steel sheet contains, in mass%, C:0.0005-0.0045%, Si:1.0% or less, Mn:0.10-1.6%, P:0.01-0.15%, S:0.010% or less, Al:0.10% or less, N:0.006% or less, Ti:0.002-0.150% and B:0.0002-0.0010% so as to satisfy the formula: {0.2<(Mn(mass%)-Mn*(mass%))/(B(ppm)-B*(ppm))≤0.5}. In a 1/4 thick position in the cold rolled steel sheet, a random intensity ratio (A) of a {332}<110> orientation is greater than 3.0, both a random intensity ratio (B) of a {557}<9 16 5> orientation and a random intensity ratio (C) of a {111}<112> orientation are 7 or more, and they satisfy the formula: {2.0≤(B)/(A)<5.0}.

Description

  The present invention relates to a cold-rolled steel sheet excellent in deep drawability, an electrogalvanized cold-rolled steel sheet, a hot-dip galvanized cold-rolled steel sheet, an alloyed hot-dip galvanized cold-rolled steel sheet, and a method for producing them.

  In the automobile field, there is an increasing need for weight reduction from the viewpoint of improving fuel efficiency, and various high-strength steel sheets are applied to automobile members from the viewpoint of ensuring collision safety. In recent years, high-strength steel plates are being provided for inner panels and outer panels for panels such as doors, hoods, and fenders. Such outer plates, panel parts, and the like are required to have high workability, particularly deep drawability. Conventionally, many techniques have been disclosed regarding high-strength steel sheets having good workability. Many of these technologies related to high-strength steel sheets for panels, etc. are 340 to 440 MPa class IF high strength obtained by solid solution strengthening of ultra-low carbon steel added with Nb and Ti with Mn and P, but they are deeper than IF mild steel. The r value that is an index of the drawability is low, and the anisotropy of the r value is particularly large. Therefore, many techniques for reducing Δr which is an index of anisotropy are also disclosed.

  For example, Patent Document 1 secures secondary workability by performing low temperature hot rolling at a finishing temperature of 800 to 900 ° C., performing low temperature winding at 650 ° C. or lower, and performing high temperature annealing at 830 ° C. or higher. However, the present invention relates to a technique for reducing Δr of a steel sheet. However, as in the technique described in Patent Document 1, always ensuring a high annealing temperature of 830 ° C. or more has a problem of significantly reducing productivity.

  Patent Document 2 suppresses the deterioration of the r value of the steel sheet due to the addition of Mn by adding 0.05% of any one or more of Cr, Mo, and W. Further, Patent Document 2 mentions the influence of the interaction due to the combined addition of Mn and B on the transformation behavior. However, in the technique described in Patent Document 2, it is necessary to perform cold rolling within the range of the cold rolling rate determined from the amount of B and the coiling temperature, and there are large manufacturing restrictions.

  Patent Document 3 is a technique for providing a steel sheet having a high average r value and a low Δr by performing low temperature hot rolling and high temperature winding. However, as in the technique described in Patent Document 3, performing hot rolling at a low temperature of 860 ° C. or lower and then winding at 700 to 800 ° C. has a very high load on the current equipment.

  Moreover, patent document 4 is related with the technique which raises r value of a steel plate by giving a ferrite region hot rolling. However, in Patent Document 4, only the average r value is evaluated, and there is no description regarding anisotropy.

  Patent Document 5 is a technique for reducing the in-plane anisotropy of the r value of a steel sheet by defining the size and density of a Ti—Mg—O-based oxide. This technology increases the r value and inhibits Δr by inhibiting the nucleation and growth of {110} <001> and {100} <110>, which increase the anisotropy of the r value, with an oxide. It is. However, in Patent Document 5, there is no description regarding the control of the other direction for increasing the r value, and there is no disclosure of the r value in each direction.

  As described above, many conventional techniques use Δr as an index for controlling anisotropy. However, since Δr is the difference between the average value of r values in the rolling direction and the perpendicular direction of rolling and the r value in the 45 ° direction, the r value in the perpendicular direction of rolling can be increased even if the r value in the rolling direction is low. In some cases, Δr does not increase. Considering actual press forming, if there is even one direction with a low r value, cracks and wrinkles will occur from that direction, so that not only Δr but also the absolute value of the r value in each direction can be increased. is important.

JP-A-5-247540 JP-A-10-270768 JP 2005-15882 A JP-A-6-2069 JP-A-11-323476

  The present invention has been made in view of the above problems, and the r values in the rolling direction, the direction perpendicular to the rolling direction, and the 45 ° direction are all 1.4 or more, the average r value is 1.6 or more, Δr Is 0.2 or less, the in-plane anisotropy of the r value is small, and cold drawn steel sheet, electrogalvanized cold-rolled steel sheet, hot-dip galvanized cold-rolled steel sheet, alloyed hot-dip galvanized cold steel excellent in deep drawability An object of the present invention is to provide a rolled steel sheet and a manufacturing method thereof.

In order to solve the above problems, the present inventors have conducted intensive research. As a result, the amount of addition of C is reduced, and further, Nb and Ti are added to the steel in which the amount of dissolved C is reduced as much as possible. Further, Mn, P, and B are added within an appropriate range, It has been found that in-plane anisotropy can be reduced by optimizing rolling conditions. That is, by adopting the above conditions, {111} <112>, which is one of the γ fiber orientations, is developed during the subsequent cold rolling and annealing, and the r value in the 45 ° and perpendicular direction of rolling is high. Has a low in-plane anisotropy by balancing the {557} <9 16 5> orientation with a low r value in the rolling direction and the {332} <110> orientation with a very high r value in the rolling direction. It was found that can be manufactured.
As described above, the present invention reduces the in-plane anisotropy and is excellent in deep drawability, such as cold-rolled steel sheet, electrogalvanized cold-rolled steel sheet, hot-dip galvanized cold-rolled steel sheet, alloyed hot-dip galvanized cold steel. It is a rolled steel sheet and manufacturing methods thereof, and the gist thereof is as follows.

[1] By mass%, C: 0.0005 to 0.0045%, Si: 1.0% or less, Mn: 0.10 to 1.6%, P: 0.01 to 0.15%, S: 0.010% or less, Al: 0.10% or less, N: 0.006% or less, Ti: 0.002-0.150%, B: 0.0002-0.0010%, the following formula (1) And the balance is a steel composition consisting of iron and inevitable impurities, and the {332} <110> orientation random strength ratio (A) at a thickness of ¼ thickness is 3.0. The random intensity ratio (B) of {557} <9 16 5> orientation and the random intensity ratio (C) of {111} <112> orientation are both 7 or more and the following expression {2.0 ≦ ( B) / (A) A cold-rolled steel sheet excellent in deep drawability characterized by satisfying <5.0}.
0.2 <(Mn (mass%) − Mn * (mass%)) / (B (ppm) −B * (ppm)) ≦ 0.5 (1)
However, in the above equation (1),
Mn * (mass%) = 55S (mass%) / 32
B * (ppm) = 10 (N (mass%)-14Ti (mass%) / 48) / 14 × 10000
When Mn * <0 and B * <0, B * is set to 0.

[2] The cold-rolled steel sheet having excellent deep drawability according to the above [1], further comprising Nb: 0.005 to 0.040% by mass.
[3] Furthermore, by mass%, Mo: 0.005 to 0.500%, Cr: 0.005 to 3.000%, W: 0.005 to 3.000%, Cu: 0.005 to 3. The cold-rolled steel sheet having excellent deep drawability according to the above [1] or [2], comprising 000%, Ni: one or more of 0.005 to 3.000% .
[4] Containing one or more of Ca: 0.0005 to 0.1000%, Rem: 0.0005 to 0.1000%, and V: 0.001 to 0.100% by mass% The cold-rolled steel sheet excellent in deep drawability according to any one of [1] to [3] above.
[5] The r value in the rolling direction, the direction perpendicular to the rolling direction, and the 45 ° direction are all 1.4 or more, the average r value is 1.6 or more, and Δr is 0.2 or less. The cold-rolled steel sheet excellent in deep drawability according to any one of [1] to [4] above.
here,
Average r value = (rL + 2 × rD + rC) / 4
Δr = | (rL + rC) −2 × rD) / 2 |
And
rL: r value in the rolling direction rD: r value in the 45 ° direction rC: r value in the direction perpendicular to the rolling.
[6] A depth characterized in that the surface of the cold-rolled steel sheet excellent in deep drawability according to any one of [1] to [5] is further subjected to electrozinc plating. Electro-galvanized cold-rolled steel sheet with excellent drawability.
[7] Deep drawing, wherein the surface of the cold-rolled steel sheet excellent in deep drawing property according to any one of [1] to [5] is further hot-dip galvanized. Hot-dip galvanized cold-rolled steel sheet with excellent properties.
[8] The surface of the cold-rolled steel sheet excellent in deep drawability according to any one of [1] to [5] is further subjected to alloying galvanizing. Alloyed hot-dip galvanized cold-rolled steel sheet with excellent deep drawability.

[9] The steel slab having the chemical component according to any one of [1] to [4] above is heated to 1150 ° C. or higher, and then the finish rolling start temperature is 1000 to 1100 ° C. ) expressions determined _{(a 3} transformation temperature -40) ° C. or higher, at a temperature range of 960 ° C. or less, the rolling following (3) shape ratio determined by the formula (X) is from 3.0 to 4.2 Then, after performing at least one pass and then cooling to 700 ° C. at a cooling rate of 40 ° C./s or less, winding in a temperature range of 550 to 700 ° C., and then pickling, the rolling reduction is 50 to It is characterized in that it is subjected to 90% cold rolling, and is further heated at 700 ° C. to 900 ° C. at an average heating rate of 2 to 20 ° C./s from room temperature to 650 ° C. and held for 1 second or longer. The manufacturing method of the cold-rolled steel plate excellent in deep drawability to do.
A ₃ (° C.) = 937.2-476.5C + 56Si-19.7Mn-16.3Cu-26.6Ni-4.9Cr + 38.1Mo + 136.3Ti-19.1Nb + 124.8V + 198.4Al + 3315.0B (2 )
X (shape ratio) = ld / hm (3)
However, in the above equation (2), C, Si, Mn, P, Cu, Ni, Cr, Mo, Ti. Nb, V, Al, and B are the content [% by mass] of each element.
In the above equation (3),
ld (contact arc length of hot-rolled roll and steel plate): √ (L × (hin-hout) / 2),
hm: (hin + hout) / 2,
And also
L: roll diameter,
Hin: Thickness on the rolling roll entry side,
hout: thickness of the roll exit side,
It is.

[10] A method for producing an electrogalvanized cold-rolled steel sheet having excellent deep drawability according to [6] above, wherein the surface of the steel sheet produced by the method according to [9] is electrozinc-plated The manufacturing method of the electrogalvanized cold-rolled steel plate excellent in deep drawability characterized by performing this.
[11] A method for producing a hot-dip galvanized cold-rolled steel sheet having excellent deep drawability as described in [7] above, wherein the surface of the steel sheet produced by the method as described in [9] is hot-dip galvanized. A method for producing a hot-dip galvanized cold-rolled steel sheet excellent in deep drawability.
[12] A method for producing an alloyed hot-dip galvanized cold-rolled steel sheet having excellent deep drawability according to [8] above, wherein the surface of the steel sheet produced by the method according to [9] is 11], followed by hot dip galvanizing by the method described in [11], followed by heat treatment for 10 s or more in a temperature range from 450 to 600 ° C. A method of manufacturing a steel sheet.

  According to the cold-rolled steel sheet excellent in deep drawability of the present invention, electrogalvanized cold-rolled steel sheet, hot-dip galvanized cold-rolled steel sheet, alloyed hot-dip galvanized cold-rolled steel sheet, and production methods thereof, the above configuration The r value in the rolling direction, the direction perpendicular to the rolling direction, and the 45 ° direction are all 1.4 or more, the average r value is 1.6 or more, Δr is 0.2 or less, and the r value is in the plane. A cold-rolled steel sheet, electrogalvanized cold-rolled steel sheet, hot-dip galvanized cold-rolled steel sheet or alloyed hot-dip galvanized cold-rolled steel sheet having small anisotropy and excellent deep drawability can be obtained. Therefore, for example, by applying the present invention to automobile members such as inner panels for panels such as doors, hoods, and fenders, and outer panels, it is possible to fully enjoy the benefits of improving fuel efficiency and reducing vehicle weight in addition to improving workability. The social contribution is immeasurable.

DESCRIPTION OF EMBODIMENTS Embodiments of the present invention describe a cold-rolled steel sheet excellent in deep drawability, an electrogalvanized cold-rolled steel sheet, a hot-dip galvanized cold-rolled steel sheet, an alloyed hot-dip galvanized cold-rolled steel sheet, and a production method thereof. FIG. 4 is a diagram showing the position of each crystal orientation on ODF (Crystallite Orientation Distribution Function; φ2 = 45 ° cross section).

  Hereinafter, a cold-rolled steel sheet excellent in deep drawability, an electrogalvanized cold-rolled steel sheet, a hot-dip galvanized cold-rolled steel sheet, an alloyed hot-dip galvanized cold-rolled steel sheet, and a production method thereof, which are embodiments of the present invention Will be described. In addition, since this embodiment is described in detail for better understanding of the gist of the present invention, the present invention is not limited unless otherwise specified.

  The present inventors have known γ fibers ({111} <112> to {111} <110> orientation groups)), which are well known as orientations that increase the r value of a steel sheet, and the difference in r values of orientations close thereto. Investigating the directionality, the orientation of {557} <9 16 5> slightly deviated from the γ-fiber is a low r value in the rolling direction and a high r value in the 45 ° azimuth direction and the perpendicular direction of the rolling, Since the {332} <110> orientation is an orientation in which the r value in the rolling direction is extremely high, increasing the gamma fiber orientation and developing these two orientations in a balanced manner reduces the anisotropy of the r value. And it was found to be the best way to increase the average r value. In order to develop these two orientations in a well-balanced manner, an appropriate shear deformation is given at the time of hot rolling to give an initial orientation which is the basis of {557} <9 16 5>, and the hot-rolled plate grain size is increased. Then, it was found important to promote the development of {332} <110> during cold rolling. In addition, when annealing such a cold-rolled steel sheet, the above two orientations can be easily recrystallized by utilizing the weak interaction between Mn and B to moderately suppress recovery. It is what I found.

[Cold rolled steel sheet]
The cold-rolled steel sheet excellent in deep drawability of the present invention is mass%, C: 0.0005 to 0.0045%, Si: 1.0% or less, Mn: 0.10 to 1.6%, P : 0.01 to 0.15%, S: 0.010% or less, Al: 0.10% or less, N: 0.006% or less, Ti: 0.002 to 0.150%, B: 0.0002 ˜0.0010% is contained so as to satisfy the following formula (1), and the balance has a steel composition composed of iron and inevitable impurities, and {332} <110> at a thickness of ¼ thickness. Random intensity ratio (A) of orientation exceeds 3.0, random intensity ratio (B) of {557} <9 16 5> orientation and random intensity ratio (C) of {111} <112> orientation are both 7 or more And the following expression {2.0 ≦ (B) / (A) <5.0} is satisfied.
0.2 <(Mn (mass%) − Mn * (mass%)) / (B (ppm) −B * (ppm)) ≦ 0.5 (1)
However, in the above equation (1),
Mn * (mass%) = 55S (mass%) / 32
B * (ppm) = 10 (N (mass%)-14Ti (mass%) / 48) / 14 × 10000
When Mn * <0 and B * <0, B * is set to 0.

"Steel composition"
Hereinafter, the reason for limiting the steel composition in the present invention will be described in more detail. In the following description, “%” represents mass% unless otherwise specified.

(C: carbon) 0.0005 to 0.0045%
When C remains in the hot-rolled steel sheet as a solid solution state or coarse cementite, it forms a shear band in the grain during cold rolling, inhibits recovery / recrystallization during annealing, and increases the anisotropy of the r value. In order to increase the {110} <001> orientation and make the texture random, the content is set to 0.0045% or less. From this point of view, the C content is preferably limited to 0.004% or less, and more preferably 0.0035% or less. On the other hand, in order to make the amount of C less than 0.0005%, the vacuum degassing process cost becomes too high, so the lower limit of C is made 0.0005%.

(Si: silicon) 1.0% or less Although the lower limit of Si is not specified, it is desirable that Si is contained in an amount of 0.01% or more because it is a deoxidizing element. Moreover, since Si is an element that increases the strength by solid solution strengthening, 1.0% is added to the upper limit depending on the application. Since addition of Si exceeding 1.0% causes deterioration of workability, this value is set as the upper limit. Further, addition of Si causes a scale flaw during hot rolling called Si scale, and lowers the adhesion of plating, so that it is more preferably 0.8% or less. From this point of view, the Si content is more preferably 0.6% or less.

(Mn: Manganese) 0.10 to 1.6%
Mn is an important element in the present invention. Mn suppresses recovery during annealing after cold rolling by being combined with B. As described above, {557} <9 16 5> is easily recrystallized from the processed grains of the γ fiber orientation in which recovery is suppressed, and the r value in the 45 ° direction and the direction perpendicular to the rolling direction is improved. Therefore, in this invention, Mn is added 0.10% or more. From this point of view, it is desirable to add 0.3% or more of Mn.

  On the other hand, when Mn is added in excess of 1.6%, the hardenability is improved, the hot-rolled sheet structure becomes bainetic ferrite, and the {332} <110> orientation after cold rolling annealing is weakened. Further, since the effect of suppressing the recovery during annealing due to the interaction with B is too strong, the {557} <9 16 5> orientation becomes too strong. Therefore, in the present invention, the upper limit of Mn is set to 1.6%. From this viewpoint, Mn is more preferably 1.3% or less, and further preferably less than 1.0%.

(P: phosphorus) 0.01-0.15%
The lower limit of P is not limited, but it is desirable to add more than 0.01% because it is an element that can improve the strength at low cost. From this viewpoint, it is more desirable to add 0.03% or more of P. On the other hand, adding 0.15% or more of P causes secondary work cracking, so 0.15% is made the upper limit. From this point of view, the P content is more preferably 0.1% or less, and further preferably 0.07% or less.

(S: Sulfur) 0.010% or less S forms MnS, causes deterioration of workability, and reduces the amount of solid solution Mn, so 0.010% is made the upper limit. From this point of view, the S amount is more preferably 0.008% or less.

(Al: aluminum) 0.10% or less Al is a deoxidation preparation agent, and the lower limit is not particularly limited, but is preferably 0.010% or more from the viewpoint of deoxidation action. On the other hand, Al is an element that remarkably raises the transformation point. If over 0.10% is added, γ region rolling becomes difficult, so the upper limit is made 0.10%.

(N: Nitrogen) 0.006% or less N is an impurity contained in the steel, and the lower limit is not particularly set. However, if it is less than 0.0005%, the steelmaking cost increases, so it is 0.0005% or more. It is preferable to do. On the other hand, N forms Ti and TiN at a high temperature and suppresses recrystallization in the γ phase. However, if the amount of TiN increases too much, the workability deteriorates, so the upper limit is made 0.006%. From this point of view, the N content is 0.0040%, more preferably 0.0020% or less. If N equal to or greater than the Ti equivalent of TiN (48Ti / 14) is added, the remaining N forms BN, and the amount of solid solution B is reduced, so that the quenching effect and the recovery suppressing effect are reduced. More preferably, the amount is 48 Ti / 14 or less.

(Ti: titanium) 0.002 to 0.150%
Ti is an important element that contributes to the improvement of the r value. Ti forms nitrides in the γ phase high temperature region and suppresses recrystallization during hot rolling. Moreover, it precipitates as TiC during winding, reduces the amount of solute C, promotes the development of γ fiber orientation, and improves the r value. Furthermore, since Ti forms TiN at a high temperature, the precipitation of BN is suppressed, so that solid solution B is secured, and the interaction with Mn promotes the development of a texture that is favorable for improving the r value. . In order to obtain this effect, 0.002% or more of Ti needs to be added. On the other hand, if 0.150% or more of Ti is added, the workability deteriorates remarkably, so this value is made the upper limit. From this point of view, the Ti content is preferably 0.100% or less, and more preferably 0.060% or less.

(B: Boron) 0.0002 to 0.0010%
B, like Ti, is an important element in the present invention. B is added together with Mn to moderately delay the recovery during annealing after cold rolling and contribute to the formation of an optimal texture. In this respect, B is added by 0.0002% or more, more preferably 0.0003% or more. On the other hand, addition of B exceeding 0.001% improves the hardenability, and the hot-rolled sheet structure becomes bainetic ferrite, and the {332} <113> orientation after cold-rolling annealing is weakened. Further, the effect of delaying recovery due to the interaction with Mn is too great, and the {557} <9 16 5> orientation develops too much. For this reason, the amount of B makes 0.001% an upper limit. From this point of view, the B content is preferably 0.0008% or less, and more preferably 0.0006% or less.

(Relation between Mn content and B content)
Next, the following formula (1), which is a relational expression between the amount of Mn and the amount of B, will be described in detail.
In the present invention, Mn and B are added within a range satisfying the relationship represented by the following formula (1).
0.2 <(Mn (mass%) − Mn * (mass%)) / (B (ppm) −B * (ppm)) ≦ 0.5 (1)
However, in the above equation (1),
Mn * (mass%) = 55S (mass%) / 32
B * (ppm) = 10 (N (mass%)-14Ti (mass%) / 48) / 14 × 10000
When Mn * <0 and B * <0, B * is set to 0.

  The above formula (1) shows the ratio of the solid solution Mn amount to the solid solution B amount. When this value is 0.2 or less, the delay in recovery due to the interaction between Mn and B becomes insufficient, and {557} <9 16 5> Since this causes a decrease in orientation, this value is set as the lower limit. From this point of view, it is more desirable that the value represented by the above formula (1) has a lower limit of 0.25. On the other hand, even if the value represented by the above formula (1) exceeds 0.5, not only a special effect is not obtained, but also the {557} <9 16 5> orientation becomes too strong. Is the upper limit. Further, from this viewpoint, the value represented by the above formula (1) is more preferably 0.45 or less, and further preferably 0.35 or less.

(Nb: niobium) 0.005-0.040%
In the present invention, it is more desirable to add Nb in a predetermined range in addition to the above essential elements. Here, Nb remarkably suppresses recrystallization when the γ phase is processed in hot rolling, and significantly promotes the formation of a processed texture in the γ phase. Moreover, Nb contributes to the improvement of deep drawability by forming NbC during winding and reducing the solid solution C. In this respect, Nb is preferably added in an amount of 0.005% or more, and more preferably 0.015% or more. However, if the amount of Nb added exceeds 0.04%, recrystallization during annealing is suppressed and deep drawability deteriorates. For this reason, the upper limit of Nb addition amount is 0.04%. From this point of view, the amount of Nb added is more preferably 0.03% or less, and further preferably 0.025% or less.

  Furthermore, in the present invention, it is more desirable to add one or more of Mo, Cr, W, Cu, and Ni as elements for improving the steel characteristics. Specifically, depending on the application, Mo is 0.005 to 0.500%, Cr, W, Cu, and Ni are 0.005 to 3.000%, respectively, or one or more of them in a range of 0.005 to 3.000%. It is desirable to add.

(Mo: Molybdenum) 0.005-0.500%
Mo is an element that has the effect of improving hardenability and forming carbides to increase strength. Therefore, when adding Mo, adding 0.005% or more is desirable. On the other hand, addition of Mo in excess of 0.5% reduces ductility and weldability. From the above viewpoint, it is desirable to add Mo as needed in the range of 0.005% to 0.500%.

(Cr: chrome) 0.005% to 3.000%
Cr is also an element that has the effect of improving hardenability and forming carbides to increase strength. Therefore, when adding Cr, it is desirable to add 0.005% or more. On the other hand, addition of Cr in excess of 3.000% reduces ductility and weldability. From the above viewpoint, Cr is desirably added as necessary in the range of 0.005% to 3.000%.

(W: Tungsten) 0.005% to 3.000%
W is an element that has the effect of improving hardenability and forming carbides to increase strength. Therefore, when adding W, it is desirable to add 0.005% or more. On the other hand, addition of more than 3.000% of W decreases ductility and weldability. From the above viewpoint, W is preferably added as necessary in the range of 0.005% to 3.000%.

(Cu: Copper) 0.005% to 3.000%
Cu is an element that increases the strength of the steel sheet and improves the corrosion resistance and the peelability of the scale. Therefore, when adding Cu, adding 0.005% or more is desirable. On the other hand, addition of Cu in excess of 3.000% causes surface defects. Therefore, it is desirable to add Cu within a range of 0.005% to 3.000% as necessary.

(Ni: nickel) 0.005% to 3.000%
Ni is an element that increases the steel sheet strength and improves toughness. Therefore, when adding Ni, it is desirable to add 0.005% or more. On the other hand, since addition of Ni exceeding 3.000% causes ductile deterioration, it is desirable to add as necessary within a range of 0.005% to 3.000%.

  Further, in the present invention, Ca, REM (rare earth element), or one or more of V are added as an element for obtaining an effect of increasing the strength or improving the material of the steel sheet. It is preferable.

 When the addition amount of Ca and REM is less than 0.0005% and the addition amount of V is less than 0.001%, the above-described sufficient effect may not be obtained. On the other hand, if Ca and REM are added so that the addition amount of Ca and REM exceeds 0.1000% and the addition amount of V exceeds 0.100%, ductility may be impaired. Therefore, when adding Ca, REM, and V, the ranges of Ca: 0.0005 to 0.1000%, REM: 0.0005 to 0.1000%, and V: 0.001 to 0.100%, respectively. It is preferable to add at.

  In addition to the above elements, the steel of the present invention may further contain an element for improving the steel characteristics, and the balance contains iron and inevitable Sn, As and the like. It may also contain elements (inevitable impurities) mixed in.

"Crystal orientation"
Next, the reason for limiting the crystal orientation in the cold-rolled steel sheet of the present invention will be described.
The cold-rolled steel sheet of the present invention has a {332} <110> orientation random strength ratio (A) of more than 3.0 and {557} <9 16 5> orientation random strength ratio at the 1/4 thickness position. Both (B) and {111} <112> orientation random intensity ratio (C) is 7 or more and satisfies the following formula {2.0 ≦ (B) / (A) <5.0} It is prescribed as

  FIG. 1 shows an ODF (Crystallite Orientation Distribution Function) having a φ2 = 45 ° cross section in which the crystal orientation of the cold rolled steel sheet of the present invention is displayed. Here, as for the crystal orientation, the orientation perpendicular to the plate surface is usually represented by [hkl] or {hkl}, and the orientation parallel to the rolling direction is represented by (uvw) or <uvw>. {Hkl} and <uvw> are generic names of equivalent planes, and [hkl] and (uvw) indicate individual crystal planes. That is, in the present invention, b. c. c. Since the structure is targeted, for example, (111), (-111), (1-11), (11-1), (-1-11), (-11-1), (1-1-1) ), (-1-1-1) planes are equivalent and cannot be distinguished. In such a case, these orientations are collectively referred to as {111}.

  Note that ODF is also used to display the orientation of a crystal structure with low symmetry, and is generally expressed as φ1 = 0 to 360 °, Φ = 0 to 180 °, and φ2 = 0 to 360 °. Is displayed in [hkl] (uvw). However, since the present invention is intended for highly symmetrical body-centered cubic crystals, Φ and φ2 are expressed in the range of 0 to 90 °. Further, the range of φ1 varies depending on whether or not symmetry due to deformation is taken into account when performing calculation, but in the present invention, φ1 = 0 to 90 ° in consideration of symmetry, that is, In the present invention, a method of selecting an average value in the same orientation at φ1 = 0 to 360 ° on an ODF of 0 to 90 ° is selected. In this case, [hkl] (uvw) and {hkl} <uvw> are synonymous. Therefore, for example, the random intensity ratio of (110) [1-11] of the ODF in the φ2 = 45 ° section shown in FIG. 1 is the random intensity ratio of the {110} <111> orientation.

  Here, the {332} <110> orientation, {557} <9 16 5> orientation, and {111} <112> orientation random intensity ratios are measured by X-ray diffraction {110}, {100}, What is necessary is just to obtain | require from the orientation distribution function (ODF: Orientation Distribution Function) showing the three-dimensional texture calculated by the series expansion method based on several pole figure among {211}, {310} pole figures. The random intensity ratio refers to the X-ray intensity of a standard sample that does not have accumulation in a specific orientation and the test material measured under the same conditions by the X-ray diffraction method or the like. It is a numerical value obtained by dividing the intensity by the X-ray intensity of the standard sample.

  As shown in FIG. 1, {332} <110>, which is one of the crystal orientations of the cold-rolled steel sheet of the present invention, is represented on the ODF as φ1 = 0 °, φ = 65 °, φ2 = 45 °. Is done. However, since measurement errors due to specimen processing and sample setting may occur, the values of the random intensity ratio (A) in the {332} <110> orientation are φ1 = 0 to 2 °, φ = 63 to The maximum random intensity ratio within a range of 67 ° is set, and the lower limit is set to more than 3.0. When this value is 3.0 or less, particularly the r value in the rolling direction is lowered, so this value is the upper limit. From this viewpoint, the random intensity ratio (A) is more preferably 3.5 or more. The upper limit of the value of the random intensity ratio (A) is not particularly limited as long as the relationship with the random intensity ratio of the {557} <9 16 5> orientation described later is satisfied.

  Further, the {557} <9 16 5> orientation is represented by φ1 = 20 °, Φ = 45 °, and φ2 = 45 ° on the ODF. As described above, in the present invention, the measurement error due to the processing of the specimen is taken into consideration, and the value of the random intensity ratio (B) in the {557} <9 16 5> orientation is indicated by the hatched portion in FIG. The maximum random intensity ratio is within the range of φ1 = 18-22 ° and Φ = 43-47 °, and the lower limit of the value is 7. If this value is less than 7, the lower limit of the r value cannot be satisfied. From this viewpoint, the value of the random intensity ratio (B) is more preferably 9 or more. The upper limit of the random strength ratio (B) is not provided, but a random strength ratio of 30 or more indicates that all crystal grain orientations in the steel sheet are aligned, that is, a single crystal. Since the relationship with the random intensity ratio (A) cannot be satisfied, it is preferably less than 30.

  The {111} <112> orientation is represented on the ODF as φ1 = 90 °, Φ = 55 °, and φ2 = 45 °. In the present invention, considering the measurement error due to the processing of the specimen as described above, the value of the random intensity ratio (C) in the {111} <112> orientation is φ1 = 88 indicated by the hatched portion in the figure. The maximum random intensity ratio within the range of -90 ° and Φ = 53-57 ° is set, and the lower limit of the value is 7. If this value is less than 7, the lower limit of the r value cannot be satisfied.

  Further, the random intensity ratio (A) of {332} <110> orientation and the random intensity ratio (B) of {557} <9 16 5> orientation are given by the following formula {2.0 ≦ (B) / (A) < 5.0}. If this value is less than 2.0, the r value in the 45 ° direction decreases, so this is the lower limit. Further, from this viewpoint, the value represented by the above formula is more preferably 3.0 or more. On the other hand, if this value exceeds 5.0. Since the r value in the rolling direction is lowered, it is desirable to set it to 4.0 or less from this viewpoint.

The X-ray diffraction sample is produced as follows.
First, the steel plate is polished to a predetermined position in the plate thickness direction by mechanical polishing or chemical polishing, and finished to a mirror surface by buff polishing, and then the distortion is removed by electrolytic polishing or chemical polishing, and at the same time, the 1/4 plate thickness part is Adjust to the measurement surface. Here, since it is difficult to accurately set the measurement surface to the predetermined plate thickness position, the sample is prepared so that the measurement surface is within a range of 3% of the plate thickness with the target position as the center. do it. When measurement by X-ray diffraction is difficult, a statistically sufficient number of measurements may be performed by an EBSP (Electron Back Scattering Pattern) method or an ECP (Electron Channeling Pattern) method.

"Production method"
Next, the reasons for limiting the production conditions of the cold-rolled steel sheet excellent in deep drawability of the present invention will be described in detail.
The method for producing a cold-rolled steel sheet of the present invention is a method for producing the above-described cold-rolled steel sheet having excellent deep drawability. First, the steel slab having the above chemical components is heated to 1150 ° C. or higher, and then finish rolling. the starting temperature of 1000 to 1100 ° C., the following equation (2) in determined _{(a 3} transformation temperature -40) ° C. or higher, at a temperature range of 960 ° C. or less, the shape ratio determined by the following equation (3) (X ) At least one pass or more is rolled. Next, after cooling to 700 ° C. at a cooling rate of 40 ° C./s or less, winding in a temperature range of 550 to 700 ° C., and then pickling, followed by cold rolling with a rolling reduction of 50 to 90% Apply. And it is the method of performing the annealing which heats to 700 degreeC or more and 900 degrees C or less with the average heating rate of 2-20 degrees C / s from room temperature to 650 degreeC, and hold | maintains for 1 second or more.
A ₃ (° C.) = 937.2-476.5C + 56Si-19.7Mn-16.3Cu-26.6Ni-4.9Cr + 38.1Mo + 136.3Ti-19.1Nb + 124.8V + 198.4Al + 3315.0B (2 )
X (shape ratio) = ld / hm (3)
However, in the above equation (2), C, Si, Mn, P, Cu, Ni, Cr, Mo, Ti. Nb, V, Al, and B are the content [% by mass] of each element.
In the above equation (3),
ld (contact arc length of hot-rolled roll and steel plate): √ (L × (hin-hout) / 2),
hm: (hin + hout) / 2,
And also
L: roll diameter,
Hin: Thickness on the rolling roll entry side,
hout: thickness of the roll exit side,
It is.
In the above formula (2), for the steel sheet to which Cu, Ni, Cr, Mo, Nb, and V are not intentionally added, the above formula (2) may be used with the content rate being 0%.

  In the production method of the present invention, first, steel is melted and cast by a conventional method to obtain a steel piece to be subjected to hot rolling. Although this steel slab may be a forged or rolled steel ingot, it is preferable to manufacture the steel slab by continuous casting from the viewpoint of productivity. Moreover, you may manufacture using a thin slab caster etc.

  Usually, the steel slab is cooled again after casting, and then heated again for hot rolling. In this case, the heating temperature of the steel slab when hot rolling is set to 1150 ° C. or higher. This is because when the heating temperature of the steel slab is less than 1150 ° C., Nb and Ti are not sufficiently dissolved, and formation of a texture suitable for the r value is hindered during hot rolling. Also, from the viewpoint of heating the steel slab efficiently and uniformly, the heating temperature is set to 1150 ° C. or higher. The upper limit of the heating temperature is not specified, but when heated to over 1300 ° C., the crystal grain size of the steel sheet becomes coarse and the workability may be impaired. A process such as continuous casting-direct rolling (CC-DR) in which hot rolling is performed immediately after casting the molten steel may be employed.

In the present invention, the start temperature of finish rolling is important, and the temperature range is 1000 to 1100 ° C. If the start temperature of finish rolling exceeds 1100 ° C., distortion during rolling in the preceding stage of finish rolling is not sufficiently accumulated, and the working texture does not develop during hot rolling. From this point of view, it is more desirable that the finish rolling is started at 1050 ° C. or less. On the other hand, when rolling is started at less than 1000 ° C., it becomes difficult to finish hot rolling at (A ₃ transformation temperature −40) ° C. or higher determined by the above formula (2), and there is an orientation that degrades the r value. Since it develops, the lower limit is 1000 ° C. From this point of view, it is more desirable that the finish rolling start temperature is 1020 ° C. or higher.

Further, in the method for manufacturing a cold-rolled steel sheet of the present invention, with _{(A 3} transformation temperature -40) ° C. or higher 960 ° C. or less of the temperature range, the shape ratio determined in the above (3) (X) is 3.0 The rolling to be -4.2 is performed at least one pass.

When the rolling is performed in less than (A ₃ transformation temperature -40) ° C., since the orientation lowering the r value develops and the temperature and the lower limit. On the other hand, if moderate shear deformation is not applied in a temperature range where recrystallization at 960 ° C. or lower is suppressed, an initial structure that forms nucleation sites in the {557} <9 16 5> orientation is formed during cold rolling recrystallization annealing. Since this is not done, this temperature is the upper limit. From this viewpoint, the rolling temperature is preferably 930 ° C. or lower.

  If the shape ratio determined by the above equation (3) is less than 3.0, sufficient shear deformation will not be applied, so this value is taken as the lower limit. On the other hand, when rolling is performed at a shape ratio of 4.2 or more, an orientation that lowers the r value after cold rolling / annealing develops in the outermost surface layer of the hot rolled sheet, so this value is made the upper limit. In addition, the diameter L of a rolling roll is measured at room temperature, and it is not necessary to consider the flatness during hot rolling. Moreover, the thickness hin on the entry side and the thickness hout on the exit side of each rolling roll may be measured on the spot using radiation or the like, or calculated by considering deformation resistance and the like from the rolling load. You may ask for it.

  Next, after the hot rolling is finished, the steel sheet is cooled to 700 ° C. at a cooling rate of 40 ° C./s or less. When the temperature reached during cooling is over 700 ° C. and the cooling rate is over 40 ° C./s, the hardenability is too high, the hot-rolled sheet structure becomes bainetic ferrite, and the grain size becomes fine. Development of {332} <113> after rolling and annealing becomes insufficient, and the anisotropy of the r value increases. On the other hand, controlling the cooling rate of the hot-rolled sheet to less than 2 ° C. has a high load on production and decreases productivity, but a remarkable effect cannot be obtained, so this value is set as the lower limit.

  After cooling under the above conditions, winding is performed in a temperature range of 550 to 700 ° C. When the coiling temperature is less than 550 ° C., TiC or NbC does not precipitate, solute C remains, the r value decreases, and the hot-rolled sheet structure becomes bainetic ferrite, resulting in a smaller particle size. , {332} <113> orientation decreases. Therefore, the above range is set as the lower limit of the coiling temperature. On the other hand, when the coiling temperature is higher than 700 ° C., the manufacturing load is increased and a special effect is not obtained.

  Next, the hot-rolled steel sheet produced by the above method is pickled and then cold-rolled at a rolling reduction in the range of 50 to 90%. When the rolling reduction in cold rolling is less than 50%, a sufficient cold-rolling texture does not develop and the r value decreases, so this value is the lower limit. From this point of view, the rolling reduction in cold rolling is more preferably 60% or more, and even more preferably 65% or more. On the other hand, when the rolling reduction exceeds 90%, the load on the cold rolling machine increases, and the {110} <001> orientation, which is the orientation that increases the anisotropy of the r value, and the absolute value of the r value are lowered. Since the integration degree of {100} <012> orientation increases, this value is set as the upper limit. From this point of view, the rolling reduction in cold rolling is more preferably 85% or less, and still more preferably 80% or less.

  Next, in the method for producing a cold-rolled steel sheet according to the present invention, annealing is performed. At this time, the average heating rate from room temperature to 650 ° C. is 2 to 20 ° C./s. If this heating rate is less than 2 ° C./s, recrystallization occurs at a low temperature and the {557} <9 16 5> orientation becomes weak, so this value is set as the lower limit. From this point of view, the heating rate is more preferably 4 ° C./s or more. On the other hand, when the heating rate exceeds 20 ° C./s, recrystallization does not start during heating, and the {112} <110> orientation develops, leading to a decrease in the r value in the 45 ° direction. From this viewpoint, it is more desirable to set the heating rate to 15 ° C./s or less.

  In the method for producing a cold-rolled steel sheet according to the present invention, after heating to 650 ° C. at the heating rate, the heating is further performed to 700 ° C. or higher and 900 ° C. or lower for 1 second or longer. When the annealing temperature is 700 ° C. or lower, the work structure at the time of cold rolling remains as it is, so that the formability is remarkably lowered. Therefore, this temperature is set as the lower limit of annealing. On the other hand, when the annealing temperature exceeds 900 ° C., the texture is destroyed and the shape freezing property is deteriorated.

  In the method for producing a cold-rolled steel sheet of the present invention, after annealing under the above conditions, temper rolling with a rolling reduction of 10% or less may be performed inline or offline.

[Electrogalvanized cold-rolled steel sheet, hot-dip galvanized cold-rolled steel sheet, alloyed hot-dip galvanized cold-rolled steel sheet]
The electrogalvanized cold-rolled steel sheet excellent in deep drawability of the present invention is obtained by further electrogalvanizing the surface of the cold-rolled steel sheet of the present invention. Moreover, the hot-dip galvanized cold-rolled steel sheet excellent in deep drawability of the present invention is obtained by further hot-dip galvanizing on the surface of the cold-rolled steel sheet excellent in deep drawability of the present invention. . Moreover, the alloyed hot-dip galvanized cold-rolled steel sheet excellent in deep drawability of the present invention is obtained by further subjecting the surface of the cold-rolled steel sheet of the present invention to alloying hot-dip galvanizing. Thus, in the present invention, the surface of the cold rolled steel sheet may be subjected to electrogalvanizing, hot dip galvanizing, or alloyed hot dip galvanizing depending on the application.

In the method for producing an electrogalvanized cold-rolled steel sheet according to the present invention, the surface of the cold-rolled steel sheet produced under the above conditions and procedures is subjected to electrozinc plating by a conventionally known method. Moreover, the manufacturing method of the hot-dip galvanized cold-rolled steel sheet (alloyed hot-dip galvanized cold-rolled steel sheet) of the present invention applies hot-dip galvanizing to the surface of the cold-rolled steel sheet manufactured under the above conditions and procedures by a conventionally known method. .
At this time, the composition of the galvanizing is not particularly limited, and in addition to zinc, Fe, Al, Mn, Cr, Mg, Pb, Sn, Ni, or the like may be added as necessary.
By such a method, the electrogalvanized cold-rolled steel sheet and hot-dip galvanized cold-rolled steel sheet of the present invention are obtained.

  And when manufacturing the galvannealed cold-rolled steel sheet of this invention, it is 10 s in the temperature range to 450-600 degreeC with respect to the hot-dip galvanized cold-rolled steel sheet of this invention obtained by the said method. It can be set as the method of performing an alloying process by performing the above heat processing.

  The alloying treatment (heat treatment) needs to be performed within a range of 450 to 600 ° C. If this temperature is less than 450 ° C., there is a problem that alloying does not proceed sufficiently, and if it is 600 ° C. or more, alloying proceeds excessively and the plating layer becomes brittle. Trigger problems such as

  Also, the alloying treatment time is 10 s or longer. When the alloying treatment time is less than 10 s, alloying does not proceed sufficiently. In addition, although the upper limit of the time of alloying treatment is not specified in particular, since it is usually performed by a heat treatment facility installed in a continuous line, if it exceeds 3000 s, productivity is impaired, or capital investment is required. Since manufacturing cost becomes high, it is preferable to make this into an upper limit.

In the present invention, prior to the alloying treatment, annealing at an Ac ₃ transformation temperature or lower may be performed in advance according to the configuration of the manufacturing equipment. If the temperature of the annealing performed before the alloying treatment is a temperature lower than the above temperature range, the texture is hardly changed, so that a decrease in the r value can be suppressed.
In the present invention, the temper rolling described above may be performed after galvanizing and alloying treatment.

As described above, the cold-rolled steel sheet excellent in deep drawability of the present invention, electrogalvanized cold-rolled steel sheet, hot-dip galvanized cold-rolled steel sheet, alloyed hot-dip galvanized cold-rolled steel sheet, and production methods thereof According to the above configuration, the r value in the rolling direction, the direction perpendicular to the rolling direction, and the 45 ° direction are all 1.4 or more, the average r value is 1.6 or more, and Δr is 0.2 or less. A cold-rolled steel sheet, an electrogalvanized cold-rolled steel sheet, a hot-dip galvanized cold-rolled steel sheet or an alloyed hot-dip galvanized cold-rolled steel sheet having a small in-plane anisotropy of r value and excellent deep drawability can be obtained. .
Therefore, for example, by applying the present invention to automobile members such as inner panels for panels such as doors, hoods, and fenders, and outer panels, it is possible to fully enjoy the benefits of improving fuel efficiency and reducing vehicle weight in addition to improving workability. The social contribution is immeasurable.

  Examples of cold-rolled steel sheet, electrogalvanized cold-rolled steel sheet, hot-dip galvanized cold-rolled steel sheet, alloyed hot-dip galvanized cold-rolled steel sheet, and production methods thereof according to the present invention with excellent deep drawability The present invention will be described in more detail, but the present invention is not limited to the following examples, and may be implemented with appropriate modifications within a range that can meet the purpose described above and below. These are all included in the technical scope of the present invention.

In this example, first, steel having the composition shown in Table 1 below was melted to produce a steel slab, and this steel slab was heated and subjected to hot rough rolling, followed by the following. Finish rolling was performed under the conditions shown in Table 2. This finish rolling stand consists of seven stages, and the roll diameter is 650 to 830 mm. The finished plate thickness after the final pass was set to 2.3 mm to 4.5 mm. Furthermore, in Table 2 below, SRT [° C.] is the heating temperature of the steel slab, F ₀ T [° C.] is the entrance temperature of the first pass of finish rolling, and FT [° C.] is after the final pass of finish rolling, that is, finish The outlet side temperature and cooling rate are the average cooling rate from the end of finish rolling to 700 ° C., and CT [° C.] indicates the coiling temperature. The shape ratio column shows the shape ratio of the seventh pass. The cold rolling rate is a value obtained by dividing the difference between the thickness of the hot-rolled plate and the thickness after completion of cold rolling by the thickness of the hot-rolled plate, and is expressed as a percentage. The heating rate represents an average heating rate from room temperature to 650 ° C.

The blank in Table 1 means that the analysis value was less than the detection limit. Moreover, the formula (1) shown in Table 1 is the value of the middle side of the following formula (1) calculated by the content (mass%) of Mn, S, Ti, N, and B. The expression (2) shown below is calculated by the content (mass%) of each element of C, Si, Mn, Cu, Ni, Cr, Mo, Ti, Nb, Al, and B. The following expression {A ₃ transformation temperature ( It is a value of −40} ° C. according to the following formula (2).
0.2 <(Mn (mass%) − Mn * (mass%)) / (B (ppm) −B * (ppm)) ≦ 0.5 (1)
However, in the above equation (1),
Mn * (mass%) = 55S (mass%) / 32
B * (ppm) = 10 (N (mass%)-14Ti (mass%) / 48) / 14 × 10000
A ₃ (° C.) = 937.2-476.5C + 56Si-19.7Mn-16.3Cu-26.6Ni-4.9Cr + 38.1Mo + 136.3Ti-19.1Nb + 124.8V + 198.4Al + 3315.0B (2 )

  Here, when the contents of Mo, Ni, Cu, and Cr are about impurities, for example, when Mo, Ni, Cu, and Cr in Table 1 are blank, these elements are set to “0” and the above ( 2) The formula was calculated.

Moreover, the tensile test piece based on JISZ2201 was extract | collected from the obtained steel plate by making the perpendicular direction of rolling into a longitudinal direction, the tensile test was done based on JISZ2241, and the tensile strength was measured.
In addition, the r value was measured by taking a tensile test piece according to JIS Z 2201 in the same manner as the tensile test, with the rolling direction, 45 ° direction, and the direction perpendicular to the rolling as the longitudinal direction, and measuring the value with a strain amount of 15%.

Further, the random strength ratios of {332} <110>, {557} <9 16 7>, and {111} <112> orientations at the position of the steel sheet thickness ¼ were measured as follows. First, after mechanically polishing and buffing the steel plate, the strain was further removed by electrolytic polishing, and X-ray diffraction was performed using a sample adjusted so that the ¼ plate thickness portion became the measurement surface. Note that X-ray diffraction of a standard sample having no accumulation in a specific orientation was performed under the same conditions.
Next, ODF was obtained by the series expansion method based on {110}, {100}, {211}, {310} pole figures obtained by X-ray diffraction. And the random intensity ratio of said direction was determined from this ODF.

Of these steel sheets, when electrogalvanized plating is applied after cold rolling annealing, “electricity” is indicated in Table 2, and when hot dip galvanizing is applied, “melting” is indicated in Table 2. When the alloying treatment was carried out by holding at 520 ° C. for 15 seconds after the hot dip galvanizing and the hot galvanizing was applied, it was expressed as “alloy”.
In addition, as an electrogalvanizing process in a present Example, Zn-Ni plating (Ni = 11 mass%) was performed.
The basis weight was 20 g / m ^{2 in} all cases.

  The results in this example are shown in Table 3 below. In Table 3, L in the r value column means the rolling direction, D means the 45 ° direction relative to the rolling direction, and C means the direction perpendicular to the rolling direction.

  As is apparent from the results shown in Table 3, in the case of the present invention example (the present invention example in the remarks column of Tables 1 to 3) in which the steel having the chemical component of the present invention was produced under appropriate conditions, the rolling direction, 45 The r value in any direction of the ° direction and the direction perpendicular to the rolling is 1.4 or more, the average r value is 1.6 or more, and Δr is 0.2 or less, and the in-plane anisotropy of the r value is small. Can be confirmed. Moreover, in these examples of the present invention, it is clear that the overall El is high and the deep drawability is excellent.

  On the other hand, production No. Nos. 38 to 44 are steel Nos. Whose chemical components are outside the scope of the present invention. It is a comparative example using PV. Production No. 38 and no. No. 41 is a case where the value of the formula (2) exceeds 960 ° C. because the addition amount of Si is high or the addition amount of Al is high. Production No. In the case of 38, since the FT is lower than the value of the expression (2), it becomes α region hot rolling, and the {100} <012> orientation is developed to reduce the r value, and the random intensity ratio (A), Since the value of (C) is also low, the r value in the rolling direction is lowered and Δr cannot be satisfied. On the other hand, production No. No. 41 finished hot rolling at a temperature higher than the value of equation (2), but no shear deformation was applied at 960 ° C. or lower, so the development of the {557} <9 16 5> orientation was not good. Therefore, the r value in the 45 ° direction is lowered.

Production No. 39 shows an example in which the amount of B added is too large. In this case, since the hardenability and recovery delay effect by Mn and B are too high, the {557} <9 16 5> orientation becomes too strong and the {332} <110> orientation becomes weak, so The r value decreases.
Production No. 40 is the case where the amount of C added is too high. In this case, since solid solution C remains in the hot rolling, the development of any orientation of the random intensity ratios (A), (B), and (C) is suppressed.
Production No. 42 is an example when Mn is too high and Ti is not added. In this case, since the solid solution C remains, the aggregate coarse structure is weakened as a whole, the Mn is too high, the hardenability becomes too high, and the (332) <110> orientation is reduced, so the r value Neither the absolute value nor Δr is satisfactory.
Production No. 43 is a case where the amount of B is small. In this case, since recovery is not suppressed, the {557} <9 16 5> orientation is weak, the r value in the 45 ° direction is lowered, and Δr is not satisfactory.
Production No. 44 is a case where the amount of Ti is too large. In this case, since recovery and recrystallization are remarkably suppressed, unrecrystallized grains partially remain even after annealing, so that workability is degraded. In addition, since the {112} <110> orientation that degrades the r value remains and {332} <110> does not develop, the r value in the rolling direction deteriorates, and neither the average r value nor the Δr value can be satisfied.

Steel No. C, which is a comparative example of C. 7, when the shape ratio of the final pass of hot rolling is too low, sufficient shear deformation is not introduced and the B / A cannot be satisfied because the {557} <9 165> orientation is weak, so the rolling direction The r value of is decreased.
Steel No. E, which is a comparative example of E. 12, when the heating temperature is low and sufficient F ₀ T or FT cannot be secured, the {557} <9 165> orientation becomes strong due to α-region hot rolling, but {332} <110>, Since the {111} <112> orientation is weakened, the r value in the rolling direction is lowered and the anisotropy is increased.

Steel No. F, which is a comparative example of F. As shown in FIG. 15, when the annealing temperature is too high, the γ region annealing is performed, so that the texture is weakened and the r value is lowered.
Steel No. Production No. 4 which is a comparative example of G. When F ₀ T is too high as in 18, the {332} <110> orientation is too strong compared to the {557} <9 16 5> orientation, so the r value in the 45 ° direction decreases, Δr is increased.

Steel No. Production No. 1 which is a comparative example of H. When the cooling rate after hot rolling is high and the cold rolling rate is low as in 20, the {332} <110> orientation becomes weak and the {557} <9 16 5>, {111} <112> orientation Since it becomes weak, the r value decreases as a whole, but the r value in the rolling direction is particularly low.
Steel No. Production No. 1 which is a comparative example of I. 23, when the coiling temperature is too low, since the solid solution C remains in the hot-rolled sheet, the {557} <9 16 5> and {111} <112> orientations are not sufficiently developed. The value is decreasing.
Steel No. Production No. which is a comparative example of K. 27, when the cold rolling rate becomes too high, the ({557} <9 16 5>) orientation becomes strong, but the {332} <110>, {111} <112> orientation becomes weak, The r value could not be secured.

Steel No. Production No. which is a comparative example of M. If the heating rate at the time of annealing is too high as in 31, the {112} <110> orientation becomes strong and the {557} <9 16 5> orientation becomes weak, so the r value in the rolling direction and the direction perpendicular to the rolling direction is It is falling.
Steel No. N, which is a comparative example of N. As in 34, when the annealing temperature is too low, recrystallization does not proceed sufficiently and unrecrystallized remains, so that ductility is lowered and r values in the rolling direction and the direction perpendicular to the rolling are deteriorated.
Steel No. Production No. which is a comparative example of O. 37, when the shape ratio is too high, the {332} <110> orientation is weakened and the {557} <9 16 5> orientation is strengthened after cold rolling annealing, so that the r value in the rolling direction is reduced. Yes.

  From the results of the examples described above, according to the present invention, it is possible to realize a cold-rolled steel sheet, an electrogalvanized cold-rolled steel sheet, a hot-dip galvanized cold-rolled steel sheet, and an alloyed hot-dip galvanized cold-rolled steel sheet excellent in deep drawability. It is clear that

  The cold-rolled steel sheet excellent in deep drawability of the present invention is used in, for example, automobiles, home appliances, buildings and the like. In addition, the cold-rolled steel sheet excellent in deep drawability of the present invention is a cold-rolled steel sheet in a narrow sense without surface treatment, and surface treatment such as hot dip Zn plating, alloyed hot dip Zn plating, electrogalvanizing plating for rust prevention. Including cold-rolled steel sheets in a broad sense. This surface treatment includes aluminum plating, formation of an organic film on the surface of various plated steel sheets, formation of an inorganic film, painting, and a combination thereof. And since the cold-rolled steel sheet of the present invention has less in-plane anisotropy and a high r value, it is possible to press in a more complicated shape than conventional steel sheets, and to increase the functionality of automobiles. At the same time, by applying to parts that could only be applied to mild steel so far, it is possible to reduce the plate thickness, that is, to reduce the weight, and to contribute to the conservation of the global environment, so its social contribution is immeasurable.

JP-A-5-247540 Japanese Unexamined Patent Publication No. 2000-96183 (Japanese Patent Application No. 10-270768) JP 2005-15882 A JP-A-6-2069 JP-A-11-323476

Claims (12)

% By mass
C: 0.0005 to 0.0045%,
Si: 1.0% or less,
Mn: 0.10 to 1.6%
P: 0.01 to 0.15%,
S: 0.010% or less,
Al: 0.10% or less,
N: 0.006% or less,
Ti: 0.002 to 0.150%,
B: 0.0002 to 0.0010%
In order to satisfy the following formula (1), and the balance has a steel composition consisting of iron and inevitable impurities,
Random intensity ratio (A) of {332} <110> orientation at a thickness of 1/4 thickness position is greater than 3.0, random intensity ratio (B) of {557} <9 16 5> orientation and {111} <112> Orientation random intensity ratio (C) is 7 or more, and satisfies the following formula {2.0 ≦ (B) / (A) <5.0}. Cold rolled steel sheet.
0.2 <(Mn (mass%) − Mn * (mass%)) / (B (ppm) −B * (ppm)) ≦ 0.5 (1)
However, in the above equation (1),
Mn * (mass%) = 55S (mass%) / 32
B * (ppm) = 10 (N (mass%)-14Ti (mass%) / 48) / 14 × 10000
When Mn * <0 and B * <0, B * is set to 0. Furthermore, in mass%,
Nb: 0.005 to 0.040%
The cold-rolled steel sheet having excellent deep drawability according to claim 1. Furthermore, in mass%,
Mo: 0.005 to 0.500%,
Cr: 0.005 to 3.000%
W: 0.005 to 3.000%,
Cu: 0.005 to 3.000%,
Ni: 0.005 to 3.000%
The cold-rolled steel sheet excellent in deep drawability according to claim 1 or 2, characterized by containing one or more of the above. % By mass
Ca: 0.0005 to 0.1000%,
Rem: 0.0005 to 0.1000%,
V: 0.001 to 0.100%
The cold-rolled steel sheet excellent in deep drawability according to any one of claims 1 to 3, comprising one or more of the above. The r value in the rolling direction, the direction perpendicular to the rolling direction, and the 45 ° direction are all 1.4 or more, the average r value is 1.6 or more, and Δr is 0.2 or less. The cold-rolled steel sheet excellent in deep drawability according to any one of claims 1 to 4.
here,
Average r value = (rL + 2 × rD + rC) / 4
Δr = | (rL + rC) −2 × rD) / 2 |
And
rL: r value in the rolling direction rD: r value in the 45 ° direction rC: r value in the direction perpendicular to the rolling.   The surface of the cold-rolled steel sheet excellent in deep drawability according to any one of claims 1 to 5 is further excellent in deep drawability characterized in that electrogalvanizing is further applied. Electro-galvanized cold-rolled steel sheet.   The surface of the cold-rolled steel sheet excellent in deep drawability according to any one of claims 1 to 5 is further excellent in deep drawability characterized by being further hot-dip galvanized. Hot-dip galvanized cold-rolled steel sheet.   The surface of the cold-rolled steel sheet excellent in deep drawability according to any one of claims 1 to 5 is further subjected to alloying hot dip galvanizing, and the deep drawability is characterized. Excellent galvannealed cold-rolled steel sheet. A steel slab having the chemical component according to any one of claims 1 to 4 is heated to 1150 ° C or higher,
Next, the finish rolling start temperature is set to 1000 to 1100 ° C., and is determined by the following equation (3) in a temperature range of (A ₃ transformation temperature −40) ° C. to 960 ° C. determined by the following equation (2). Rolling at a shape ratio (X) of 3.0 to 4.2 is performed at least one pass,
Next, after cooling to 700 ° C. at a cooling rate of 40 ° C./s or less, winding in a temperature range of 550 to 700 ° C.,
Next, after pickling, cold rolling with a rolling reduction of 50 to 90% is performed,
Furthermore, cold rolling excellent in deep drawability characterized by performing annealing at 700 to 900 ° C. at an average heating rate of 2 to 20 ° C./s from room temperature to 650 ° C. and holding for 1 second or more. A method of manufacturing a steel sheet.
A ₃ (° C.) = 937.2-476.5C + 56Si-19.7Mn-16.3Cu-26.6Ni-4.9Cr + 38.1Mo + 136.3Ti-19.1Nb + 124.8V + 198.4Al + 3315.0B (2 )
X (shape ratio) = ld / hm (3)
However, in the above equation (2), C, Si, Mn, P, Cu, Ni, Cr, Mo, Ti. Nb, V, Al, and B are the content [% by mass] of each element.
In the above equation (3),
ld (contact arc length of hot-rolled roll and steel plate): √ (L × (hin-hout) / 2),
hm: (hin + hout) / 2,
And also
L: roll diameter,
Hin: Thickness on the rolling roll entry side,
hout: thickness of the roll exit side,
It is. A method for producing an electrogalvanized cold-rolled steel sheet excellent in deep drawability according to claim 6,
The manufacturing method of the electrogalvanized cold-rolled steel plate excellent in the deep drawability characterized by performing electrogalvanizing on the surface of the steel plate manufactured by the method of Claim 9. A method for producing a hot-dip galvanized cold-rolled steel sheet excellent in deep drawability according to claim 7,
A method for producing a hot-dip galvanized cold-rolled steel sheet excellent in deep drawability, wherein hot-dip galvanizing is performed on the surface of the steel sheet produced by the method according to claim 9. A method for producing an alloyed hot-dip galvanized cold-rolled steel sheet excellent in deep drawability according to claim 8,
After performing hot dip galvanizing on the surface of the steel sheet manufactured by the method according to claim 9 by the method according to claim 11, heat treatment for 10 s or more is further performed in a temperature range of 450 to 600 ° C. A method for producing an alloyed hot-dip galvanized cold-rolled steel sheet with excellent deep drawability.

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