JP2011089167A - Composite panel having excellent stretch rigidity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite panel in which two steel sheets are stuck, and which has excellent stretch rigidity. <P>SOLUTION: The composite panel is obtained by sticking a first steel sheet whose Young's modulus in the width direction is high with a second steel sheet in which the Young's modulus in a 55&deg; direction to a rolling direction is high in such a manner that the rolling direction is controlled to 90&deg;. The first steel sheet comprises one or more selected from Ti, Nb, V and B, and in which the X-ray random intensity ratio in the ä211}&lt;011&gt; orientation at the 1/2 sheet thickness part is &ge;5, and the Young's modulus in the width direction is 225 to 290 GPa. The second steel sheet comprises &gt;1.50 to 10.00% Al, and further comprises one or more selected from Bi, Pb, Sb and Sn, and in which the X-ray random intensity ratio in the ä110}&lt;001&gt; orientation in the 1/2 sheet thickness part is &ge;6, and the Young's modulus in a 55&deg; direction to the rolling direction is 225 to 290 GPa. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a composite panel in which two steel plates are bonded, and has excellent tension rigidity, which is suitable for a panel member having a large area such as an automobile roof or a door panel and having a gently curved surface. Related to composite panels.

  In recent years, for the purpose of reducing the environmental load, the development of a vehicle body structure that can reduce the weight of automobiles has become an urgent issue. As an effective means for reducing the weight, there is a method of increasing the material strength to reduce the thickness, and the application of a high-tensile steel plate called “HITEN” is being promoted. On the other hand, the thinning of the steel sheet due to high tensile strength is limited because the rigidity of the member does not depend on the strength but depends on the thickness and Young's modulus.

  In particular, in the case of panel members, the decrease in tension rigidity becomes a bottleneck, and it is difficult to further reduce the thickness. Until now, in order to increase the rigidity of the panel member, improvement of the forming method (for example, Patent Document 1), and a method of bonding a resin between a steel plate and a steel plate or between structures (for example, Patent Documents 2 to 4). ) Has been proposed.

  However, these do not increase the rigidity of the steel plate itself. The rigidity of the steel sheet has a correlation with the Young's modulus, and many techniques have been proposed including the proposal by the present inventors to improve the Young's modulus in a specific direction by controlling the crystal orientation of the steel sheet (for example, patents). Literature 5-7).

JP-A-4-357261 JP 58-177745 A Japanese Patent Laid-Open No. 2-182448 JP-A-6-171001 JP-A-9-53118 JP-A-4-147717 JP 2005-273001 A

  However, with the conventional technology, it has been difficult to improve the Young's modulus in all directions in the same manner. Therefore, it is extremely difficult to improve the tension rigidity of a panel having a three-dimensional shape using a single steel plate. This invention is made | formed in view of such a situation, and provides the composite panel excellent in tension rigidity which stuck two steel plates.

Compared to the case where two steel plates of the same type are bonded, the present inventors have two types of steel plates with different directions of the elastic main axis, that is, the first steel plate having a high Young's modulus in the width direction and the rolling direction. It was found that when the second steel plate having a high Young's modulus in the 55 ° direction is bonded so that the angle between the rolling directions is 90 °, the tension rigidity is further improved. In the present invention, the elastic main axis means an axis that maximizes the Young's modulus in the plane of the steel sheet.
This invention is made | formed based on such knowledge, The summary is as follows.

(1) It is a composite panel in which two steel plates are bonded, and the component of the first steel plate is mass%,
C: 0.0005% or more, 0.150% or less,
Mn: 0.05% or more and 2.50% or less,
Containing
P: 0.200% or less,
S: 0.0200% or less,
N: 0.0100% or less,
Si: 2.00% or less,
Al: 0.15% or less,
In addition to
Ti: 0.005 to 0.150%,
Nb: 0.001 to 0.100%,
V: 0.005-0.100%,
B: 0.0001 to 0.0100%
And the balance consists of inevitable impurities, and the X-ray random intensity ratio of the {211} <011> orientation in the 1/2 sheet thickness part of the first steel sheet is 5 or more Yes, the Young's modulus in the width direction of the first steel plate is maximum and 225 to 290 GPa, and the component of the second steel plate is mass%,
C: 0.0003 to 0.250%,
Mn: 0.20% to 4.00%,
Al: more than 1.50% to 10.00%
Containing
Si: 2.20% or less,
P: 0.200% or less,
S: 0.0500% or less,
N: limited to 0.0150% or less,
Bi: 0.001 to 0.300%,
Pb: 0.001 to 0.300%,
Sb: 0.001 to 0.300%,
Sn: 0.0005 to 0.300%
And the balance is Fe and inevitable impurities, and the X-ray random intensity ratio of {110} <001> orientation in the ½ plate thickness part of the second steel plate is 6 or more. The Young's modulus in the direction of 55 ° is the maximum with respect to the rolling direction of the second steel plate and is 225 to 290 GPa, and the rolling direction of the first steel plate and the rolling direction of the second steel plate are A composite panel with excellent tension rigidity, characterized by a right angle.

(2) The component of the first steel plate is further mass%,
Cr: 3.00% or less,
Cu: 0.35% or less,
Ni: 1.00% or less,
Mo: One or two or more of 1.00% or less is contained, and the composite panel having excellent tensile rigidity as described in (1) above.
(3) The component of the second steel plate is further mass%,
Ti: 0.150% or less,
Nb: 0.150% or less,
V: 0.150% or less,
Cr: 3.00% or less,
Ni: 3.00% or less,
Mo: 3.00% or less,
Cu: 3.00% or less,
B: A composite panel having excellent tension rigidity according to the above (1) or (2), which contains one or two of 0.0060% or less.
(4) The plate thickness a [mm] of the first steel plate to be adhered and the plate thickness b [mm] of the second steel plate are
0 ≦ | a−b | / (a + b) ≦ 0.6,
0.5mm ≦ a + b ≦ 2.0mm
The composite panel having excellent tension rigidity according to any one of (1) to (3) above, wherein:
(5) The composite panel having excellent tensile rigidity according to any one of (1) to (4), wherein the first steel plate and the second steel plate are cold-rolled steel plates.
(6) One or both of the first steel plate and the second steel plate is a hot-dip galvanized cold-rolled steel plate, and has excellent tensile rigidity according to any one of (1) to (5) above Composite panel.

The present invention rolls two types of steel plates having different elastic principal axis directions, that is, a first steel plate having a high Young's modulus in the width direction and a second steel plate having a high Young's modulus in the 55 ° direction with respect to the rolling direction. It is a composite panel that is bonded with the direction at right angles.
According to the present invention, a high Young's modulus can be obtained in any direction within the plate surface, and a panel having high tension rigidity can be obtained more easily. In particular, when compared to a composite panel in which the elastic principal axes of two steel plates of the same kind are tilted and bonded, the total stiffness of the two steel plates is the same, and the tension stiffness is improved. Can reduce the plate thickness. Moreover, since it is not necessary to incline the cutting direction of a steel plate with respect to the rolling direction, productivity is improved and yield is also improved.

  Therefore, according to the present invention, it is possible to increase the rigidity of a panel member of an automobile or the like, or it is possible to reduce the thickness of the panel member, contributing to the reduction of the weight of the automobile and the improvement of fuel consumption. .

It is a graph for demonstrating the in-plane anisotropy of the Young's modulus of a 1st steel plate. It is a graph for demonstrating the in-plane anisotropy of the Young's modulus of a 2nd steel plate. It is the graph which showed the influence which the angle between elastic principal axes exerts on bending rigidity. It is the graph which showed the relationship between the load of a composite panel, and the amount of pushing. It is a display of a crystal orientation distribution function (ODF). It is the graph which showed the relationship between the sum total of board thickness and tension rigidity.

As shown in the following formula (Formula 1), it is known that the panel stiffness has a correlation with the plate thickness and Young's modulus.
S∝E. t ^m (Formula 1)
Here, S is the tension rigidity, E is the Young's modulus, t is the plate thickness, and m is a constant depending on the panel shape and has a value of 1 to 3.
At this time, E is uniform in the plane and in the thickness direction, and in the case of steel, a value of about 205 GPa is generally given as a fixed value. However, in an actual steel plate, the Young's modulus of the steel plate changes depending on the crystal orientation, and thus usually has in-plane elastic anisotropy. Below, the axis | shaft in which Young's modulus becomes the maximum within a steel plate surface is called an elastic main axis | shaft.

  FIG. 1 shows the relationship between the rotation angle (referred to as the orientation angle) and the Young's modulus with the rolling direction of the Nb, Ti-added cold rolled steel sheet (steel sheet A) corresponding to the first steel sheet as the base point (0 °). As shown in FIG. 1, in the steel sheet A, the axis having the maximum Young's modulus, that is, the elastic main axis exists in the direction (width direction) perpendicular to the rolling direction. In the steel sheet A, the Young's modulus is lower than 205 GPa in the direction rotated by 45 ° from the rolling direction.

Next, FIG. 2 shows the anisotropy of the Young's modulus of a cold-rolled steel sheet (steel sheet B) corresponding to the second steel sheet, having a high Al content and added with an inhibitor such as Sn. As shown in FIG. 2, the anisotropy of the Young's modulus of the steel plate B is different from the anisotropy of the steel plate A shown in FIG. In the steel plate B, the Young's modulus in the direction rotated 55 ° from the rolling direction is the highest and exceeds 250 GPa. On the other hand, in the steel plate B, the Young's modulus in the rolling direction is about 180 GPa.
Therefore, in the steel plate A and the steel plate B, the direction in which the Young's modulus is high differs from the direction in which the Young's modulus is significantly reduced. When such steel plates A and B are bonded so that the rolling direction is at right angles, the direction with the lowest Young's modulus of one steel plate and the direction with the highest Young's modulus of the other substantially overlap. As a result, the Young's modulus anisotropy is most efficiently eliminated, and an average high Young's modulus can be obtained.

Next, the present inventors bonded two steel sheets having different directions of the elastic principal axis so that the rolling directions are parallel (shift angle 0 °) and perpendicular (shift angle 90 °). The bending stiffness of the panel was studied.
Based on the rolling direction of the steel sheet A, the bending rigidity EI in each direction was determined from the following relationship at intervals of 5 °.

In the above (Formula 2),
E ₁ : Young's modulus (GPa) of a reference plate
E ₂ : Young's modulus (GPa) of the plate to be attached
t ₁ : thickness of the reference plate (mm)
t ₂ : board thickness (mm) of the board to be adhered
y _n : height of the neutral shaft (mm)
It is.

The height y _n of the neutral axis in Equation (2) is determined from the balance of the formula in the axial direction of the cross section shown in (Equation 3) stress. In addition, the left side of this formula shows the stress on the compression side, and the right side shows the stress on the tension side.

In the above (Formula 3),
σ ₁ : Stress applied at the position of the outermost layer of the reference plate (N / mm ² )
σ ₂ : Stress applied at the position of the outermost layer of the plate to be attached (N / mm ² )
It is.

  FIG. 3 is a plot of the ratio of the bending stiffness of the composite panel to the bending stiffness of a general material having a Young's modulus of 205 GPa (referred to as the bending stiffness ratio) against the angle from the rolling direction of the steel sheet A. As shown in FIG. 3, when two types of steel plates are bonded so that the rolling direction is a right angle (shift angle 90 °), a high bending rigidity is obtained on average in any direction compared to the comparative material. I understand that On the other hand, when two types of steel plates are bonded so that the rolling direction is parallel (shift angle 0 °), the bending rigidity in the rolling direction is maximized and the bending rigidity in the width direction is reduced.

  In addition, the normal Young's modulus in a steel plate is generally set to 205 GPa as shown in non-patent literature (Japan Architectural Institute, Steel Structure Design Standard -Allowable Stress Design Method-, 2005). In the present invention, this value of 205 GPa is treated as the “reference value” for the Young's modulus of the steel sheet. This reference value is determined on the basis of a stable state when the orientation of anisotropic iron crystal grains is aligned without deviation, but in actuality, about ± 5% of this value. There will be a bias. Therefore, it is generally considered that the Young's modulus of a normal steel sheet is in the range of 195 GPa to 215 GPa. That is, it can be said that the Young's modulus of a normal steel material does not exceed 215 GPa even if it exceeds the reference value of 205 GPa.

Next, a composite panel simulating an actual roof panel was manufactured, and the stiffness was evaluated as shown in FIG. A steel plate X (first steel plate) having a plate thickness of 0.5 mm and having the same elastic anisotropy as in FIG. 1 and a steel plate Y (second steel plate) having the same elastic anisotropy as in FIG. Prepared. These steel plates were pasted with a resin so that the rolling direction was a right angle to obtain a composite panel of the present invention.
The composite panel of the present invention was press-molded into a shape simulating a roof panel having a maximum curvature of 8000 R, 700 mm square, and a molding height of 30 mm. A test was performed in which the center of the composite panel after molding was pushed at a speed of 10 mm / min with an indenter having a diameter of 100 mm and a radius of curvature of 300 mm, and the load and the amount of indentation (indenter displacement) were measured.
For comparison, two steel plates Z (plate thickness 0.5 mm) with almost random textures are prepared, and are bonded so that the rolling direction becomes a right angle in the same manner as the composite panel of the present invention. A panel (comparative panel) was subjected to press molding in the same manner as the composite panel of the present invention, and the load and indentation amount were measured and evaluated.

  FIG. 4 shows the relationship between the pushing amount and the load of the composite panel and the comparative panel of the present invention. It can be seen that the indentation amount under the same load is significantly smaller in the composite panel of the present invention than in the comparative panel, and the tension rigidity is improved.

  In order to increase the tension stiffness in the circumferential direction of the composite panel, it is necessary to set the maximum Young's modulus of the first steel plate and the second steel plate to 225 GPa or more. In order to increase the tension rigidity of the composite panel, a higher Young's modulus is preferable. However, the maximum Young's modulus of pure iron is about 285 GPa. The Young's modulus of the first steel plate and the second steel plate of the present invention does not exceed 290 GPa, although there are some changes due to the effects of additive elements and the like, and measurement errors. Therefore, in the present invention, the Young's modulus in the elastic principal axis direction of the first steel plate and the second steel plate is set to 225 to 290 MPa.

  The Young's modulus has a very strong correlation with the crystal orientation. If the <111> direction of iron is aligned in the direction in which the Young's modulus is desired to be increased, a high Young's modulus exceeding 280 GPa is ideally obtained. On the other hand, the <100> direction has a very low Young's modulus of 130 GPa. In addition, the <110> direction is about 220 GPa, and the <113> direction is about 205 GPa. When ordinary polycrystalline iron does not have an orientation in a specific orientation, that is, a steel sheet without a texture, a Young's modulus of about 205 GPa is shown as an average value of Young's modulus in all orientations.

  Therefore, in order to increase the Young's modulus, it is necessary to align the orientation of each crystal grain with a specific orientation. When the number of crystal grains with the plate surface orientation {211} and the rolling direction orientation <011> increases as in the first steel plate, the rolling direction vertical orientation (width direction) becomes <111>. When the X-ray random intensity ratio in the {211} <011> orientation at the ½ plate thickness portion of the first steel plate is 5 or more, the width direction becomes the elastic principal axis and a Young's modulus of 225 GPa or more is obtained. If all crystal orientations are aligned to {211} <011>, a Young's modulus of about 290 GPa is ideally obtained.

  However, in practice, it is extremely difficult to align all crystal orientations to {211} <011>. Therefore, the Young's modulus in the width direction of the first steel plate is preferably 230 to 250 GPa. In the first steel plate, the Young's modulus has a relatively small in-plane anisotropy, and the Young's modulus in the 45 ° direction at which the Young's modulus is minimized does not fall below 190 GPa.

  On the other hand, when the number of crystal grains with the plate surface orientation {110} and the rolling direction orientation {001} increases as in the second steel plate, the 55 ° direction with respect to the rolling direction becomes <111>. When the X-ray random intensity ratio of {110} <001> orientation in the ½ plate thickness part of the second steel plate is 6 or more, the 55 ° direction with respect to the rolling direction becomes the elastic principal axis, and the Young's modulus is 225 GPa or more. Since the {110} <001> orientation can increase the degree of integration relatively easily, the upper limit of the Young's modulus in the 55 ° direction with respect to the rolling direction of the second steel plate is 290 GPa. On the other hand, since the {110} <001> orientation has a large in-plane anisotropy, there is a possibility that the Young's modulus in the rolling direction at which the Young's modulus is minimized decreases to about 130 GPa.

Next, a plate material having in-plane elastic anisotropy for realizing the above effects will be described below.
First, the reason for limiting the steel composition of the first steel sheet in the present invention will be described.
C is an element that increases the strength and needs to be added in an amount of 0.0005% or more. In order to ensure strength, 0.005% or more of C is preferably added. Further, from the viewpoint of Young's modulus, it is more preferable that the lower limit of the C content is 0.01% or more. This is because when the C content is reduced to less than 0.01%, the Ar ₃ transformation temperature rises, it becomes difficult to hot-roll at low temperatures, and the Young's modulus may decrease. Furthermore, in order to suppress the deterioration of the fatigue characteristics of the welded portion, it is preferably 0.020% or more. On the other hand, if the amount of C exceeds 0.150%, the formability deteriorates and the weldability may also deteriorate, so the upper limit is made 0.150% or less. A more preferable upper limit of the amount of C is 0.10% or less.

  Si is a deoxidizing element, and the lower limit is not particularly specified, but if it is less than 0.001%, the production cost becomes high. Si is an element that increases the strength by solid solution strengthening, and is also effective for obtaining a structure containing martensite, bainite, and retained austenite. Therefore, it may be positively added according to the target strength level. However, if the addition amount exceeds 2.00%, the press formability deteriorates and the chemical conversion processability is lowered. The upper limit is 00% or less. Moreover, since chemical conversion processability will fall when there is much Si amount, it is preferable to set it as 1.20% or less. Furthermore, when hot dip galvanizing is performed, problems such as a decrease in plating adhesion and a decrease in productivity due to a delay in the alloying reaction may occur. From this point, the upper limit of Si content is 1.00% or less. It is preferable that From the viewpoint of Young's modulus, the upper limit of the Si addition amount is more preferably 0.60% or less. From this viewpoint, the content is more preferably 0.30% or less.

Mn lowers the Ar ₃ transformation point, which is the temperature at which the γ phase is transformed into the ferrite phase during hot rolling. By adding Mn, the γ phase becomes stable to a low temperature, and the temperature of finish rolling can be lowered. When the finish rolling temperature is lowered, crystal orientations that increase the Young's modulus in the width direction of the steel sheet accumulate, so Mn is an important element for improving the Young's modulus. In order to obtain this effect, it is necessary to add 0.05% or more of Mn, and it is more desirable to add 1.0% or more. Further, Mn is an effective solid solution strengthening element, and from this point of view, it is desirable to add it positively according to the desired strength level. On the other hand, even if the amount of Mn added exceeds 2.50%, a significant Young's modulus improvement effect cannot be obtained, so the upper limit is made 2.5% or less. Further, if Mn is added excessively, the strength becomes too high and the ductility may decrease or the adhesion of the plating may decrease, so the upper limit is preferably made 2.0% or less.

  P is an impurity, but may be positively added when the strength needs to be increased. P also has the effect of making the hot-rolled structure fine and improving workability. However, if the added amount exceeds 0.200%, the fatigue strength after spot welding deteriorates, so the upper limit is made 0.200% or less. Moreover, when P is contained excessively, the yield strength becomes too high, and surface shape defects may be caused during pressing, and the upper limit of the amount of P is preferably 0.05% or less. Furthermore, if the amount of P is too large, the alloying reaction at the time of continuous hot dip galvanization becomes slow, the productivity is lowered, and the secondary workability may be deteriorated, so the upper limit value is 0.02% or less. It is preferable that

S is an impurity, and if it contains more than 0.0200%, it causes hot cracking, so the upper limit is limited to 0.0200% or less. Moreover, since processability may be impaired when S is contained excessively, it is preferable to make an upper limit 0.01% or less.
Al is a deoxidation preparation agent, and the lower limit is preferably 0.01% or more from the viewpoint of deacidification. On the other hand, Al significantly increases the transformation point, so if adding over 0.15%, γ-region rolling at low temperatures becomes difficult, so the upper limit is made 0.15% or less.

  N is an impurity, and the lower limit is not particularly set, but the cost is increased to make it lower than 0.0005%. Therefore, the N content is preferably 0.0005% or more. Further, N may form Ti and nitride to suppress recrystallization of the γ phase, so it may be positively added. However, N reduces the recrystallization suppressing effect of B to 0.0100% or less. suppress. From this viewpoint, the content is preferably 0.0050% or less.

  Ti, Nb, V, and B are important elements in the present invention, and one or more of them are selectively added. Ti, Nb, V and B are all elements that remarkably suppress recrystallization, and have an effect of suppressing destruction of the texture formed during hot rolling or cold rolling during recrystallization. It is necessary to add one or more of Ti 0.005% or more, Nb 0.001% or more, V 0.005% or more, and B 0.0001% or more. On the other hand, addition of Ti exceeding 0.150%, Nb and V exceeding 0.100%, and B exceeding 0.0100% not only does not provide a further improvement in Young's modulus, but also significantly reduces workability. Therefore, these values are the upper limit. From this viewpoint, more preferable upper limit values are 0.05% or less for Ti, Nb, and V, respectively, and 0.005% or less for B.

  Cr, Cu, Ni, and Mo are 0.01% to 3.00%, 0.01% to 0.35%, 0.01% to 1.00%, and 0.01% to 1.00% by mass, respectively. It is preferable to add two or more of one type. These elements have the effect of accelerating the development of the processed texture in the γ phase by being added together with Mn. However, even if it is added above the upper limit value, a special effect cannot be obtained from the viewpoint of texture development, and the workability deteriorates, so an upper limit value is set for each.

Next, the reason for limiting the steel composition of the second steel plate will be described.
Al is an extremely important element for increasing the X-ray random intensity ratio in the {110} <001> orientation in the present invention. In order to increase the Young's modulus in the direction of 35 to 75 ° with respect to the rolling direction of the steel sheet, it is necessary to add more than 1.50% Al. Al is an effective element for reducing the specific gravity of the steel material, and it is preferable to add 2.00% or more. On the other hand, when the Al content exceeds 10.00%, precipitation of intermetallic compounds becomes remarkable, and hot workability and cold workability deteriorate, so the upper limit is made 10.00% or less. In order to suppress the decrease in ductility, the Al content is preferably 6.00% or less. A more preferable range of the Al addition amount is 2.50 to 4.50%. When the Al amount is less than 2.50%, Si is simultaneously added so as to satisfy (Al + Si) ≧ 2.50% in order to increase the X-ray random intensity ratio in the {110} <001> orientation. It is preferable to add.

  By adding Bi, Pb, Sb, and Sn simultaneously with Al, the effect of increasing the X-ray random intensity ratio in the {110} <001> orientation becomes remarkable, and is important in the present invention. In order to increase the Young's modulus in the direction of 35 to 75 ° with respect to the rolling direction of the steel sheet, Bi, Pb, and Sb each need to be added by 0.001% or more, and Sn by 0.0005% or more. In either case, the effect is saturated even if 0.300% is added. Therefore, in the present invention, Bi: 0.001 to 0.300%, Pb: 0.001 to 0.300%, Sb: 0.001 to 0.300%, Sn: 0.0005 to 0.300% It is necessary to add one or two or more. The preferable ranges of the addition amount of Bi, Pb, Sb and Sn are Bi: 0.010 to 0.150%, Pb: 0.010 to 0.150%, Sb: 0.020 to 0.150%, Sn: 0.050 to 0.150%.

  C is an effective element for improving the strength, but if the content is less than 0.0003%, the effect is small, so 0.0003% or more is the lower limit. On the other hand, addition of C exceeding 0.250% deteriorates workability, so 0.250% or less is made the upper limit of the C amount. From the viewpoint of cold rollability and formability of the steel sheet, it is better that the amount of C is smaller, and it is preferably 0.100% or less. It is more preferable if it is 0.050% or less, and it is still more preferable if it is 0.020% or less.

  Si is a deoxidizing element, but excessive addition exceeding 2.20% lowers hot workability and remarkably deteriorates the peelability and chemical conversion treatment of scale caused by hot rolling. On the other hand, Si is an element useful for increasing the strength of the steel sheet by solid solution strengthening, and 0.003% or more is preferably added. Further, when it is contained at the same time as Al, the effect of increasing the X-ray random intensity ratio in the {110} <001> orientation is manifested. Therefore, particularly when the amount of Al is small, the total amount of Al and Si is 2.50%. It is preferable to add so that it may become above. A preferable range of the Si content is 0.005 to 2.00%, and 0.005% to 0.80% is a more preferable range.

  Since Mn forms MnS and suppresses grain boundary embrittlement due to solute S, 0.20% or more is added. Further, Mn is an element effective for increasing the strength of the steel sheet, and addition of 0.50% or more is preferable. On the other hand, when Mn exceeding 4.00% is added, the X-ray random intensity ratio in the {110} <001> orientation decreases. In order to increase the Young's modulus in the direction of 35 to 75 ° with respect to the rolling direction of the steel sheet, the amount of Mn added is preferably 3.00% or less. A more preferable range of the amount of Mn added is 0.55 to 2.60%.

  P is an impurity and segregates at the crystal grain boundary to lower the grain boundary strength, so the upper limit is made 0.200% or less. However, if P is reduced to less than 0.001%, the manufacturing cost increases. Further, since P is an element effective for strengthening, it is preferable to contain 0.005% or more of P in order to increase the strength. In order to suppress secondary work brittleness resistance and toughness deterioration due to P segregation, the upper limit is preferably made 0.080% or less. Furthermore, in order to suppress the deterioration of workability, it is preferable to make it 0.040% or less.

  S is an impurity element that degrades hot workability, and the upper limit is 0.0500% or less. However, if S is reduced to less than 0,0005%, the manufacturing cost increases. Further, in order to suppress a decrease in toughness and improve cold workability, the S content is preferably made 0.0150% or less.

  N is an impurity element, and if it exceeds 0.0150%, toughness deteriorates. In particular, the second steel plate has a high Al content, and Al-based nitrides are likely to be coarsened. Therefore, the preferable upper limit is 0.0040% or less. On the other hand, in order to increase the X-ray random intensity ratio in the {110} <001> orientation, fine Al-based nitride is effective, and it is preferable to contain 0.0005% or more of N. In order to increase the Young's modulus in the direction of 35 to 75 ° with respect to the rolling direction of the steel sheet, when using Al-based nitride, the particularly preferable range of the N amount is 0.0010 to 0.0030%.

  Furthermore, in order to increase strength, ductility, toughness and manufacturability, one or two of Ti, Nb, Cr, Ni, Mo, Cu, B, V, Ca, Mg, Zr, and REM depending on the required characteristics The above may be added.

  Ti, Nb, and V are elements that generate precipitates and contribute to strengthening, and it is preferable to add one or two or more of each in an amount of 0.003% or more. Moreover, since it also has the effect of improving castability, the preferable lower limit of the addition amount is 0.012% or more, respectively. On the other hand, when 0.150% or more is added, crystal grains become finer and workability may be reduced. In order to prevent a decrease in Young's modulus in the direction of 35 to 75 ° with respect to the rolling direction of the steel sheet, the upper limit of each is more preferably 0.050% or less.

  Cr, Ni, Mo, and Cu are effective elements for improving ductility and toughness, and it is preferable to add one or more elements each in an amount of 0.01% or more. On the other hand, if adding more than 3.00% of Cr, Ni, Mo and Cu, respectively, ductility and toughness may deteriorate, so the upper limit of the content of each element is preferably 3.00% or less. . A more preferable range is 0.10% to 1.40%.

  B is an element that segregates at the grain boundary and improves the grain boundary bonding force. B is also effective in suppressing the grain boundary segregation of P and S. In order to increase the grain boundary strength by utilizing the segregation of B, addition of 0.0001% or more of B is preferable. Furthermore, in order to improve ductility, toughness, and hot workability, 0.0003% or more of B is preferably added. On the other hand, since the effect is saturated even if B is added excessively, the upper limit of the amount of B is preferably 0.0060% or less. Moreover, since coarse precipitates may be generated at the grain boundaries and the hot workability may deteriorate, the upper limit of the B content is preferably 0.0025% or less.

  Ca, Mg, Zr, and REM are all elements that control the form of sulfide and are effective in suppressing deterioration of hot workability and toughness, and it is preferable to add one or more of them. In order to obtain this effect, it is preferable to add 0.001% or more of Ca, 0.0005% or more of Mg, 0.001% or more of Zr, and 0.001% or more of REM. On the other hand, if Ca is added in excess of 0.010%, Mg is 0.050%, Zr is 0.200%, and REM exceeds 0.050%, toughness may deteriorate.

Next, the X-ray random strength ratio and Young's modulus of the steel sheet used in the present invention will be described.
For the first steel plate, the X-ray random intensity ratio in the {211} <011> orientation in the ½ plate thickness portion is 5 or more. The {211} <011> orientation is a crystal orientation that increases the Young's modulus in the direction perpendicular to the rolling direction of the cold-rolled steel sheet. If the X-ray random strength ratio is 5 or more, the maximum Young's modulus of the steel sheet may be 225 GPa or more. it can. In order to further increase the Young's modulus, the X-ray random intensity ratio in the {211} <011> orientation is preferably 8 or more. More preferably, it is 10 or more. In order to increase the Young's modulus, the higher the degree of integration of the {211} <011> orientation, the better. The upper limit of the {211} <011> orientation X-ray random intensity ratio is not provided, but in order to exceed 20, the crystal grain size must be increased. Therefore, in order to prevent deterioration of mechanical properties such as strength and workability, the upper limit of the X-ray random intensity ratio in the {211} <011> orientation is preferably 20 or less.

  For the second steel plate, the X-ray random intensity ratio of {110} <001> orientation in the ½ plate thickness part is set to 6 or more. The {110} <001> orientation is a crystal orientation that increases the Young's modulus in the direction of 55 ° with respect to the rolling direction of the cold-rolled steel sheet. In order to increase the maximum Young's modulus of the steel sheet to 225 GPa or more, it is necessary to set the X-ray random intensity ratio in the {110} <001> orientation to 6 or more. In order to further increase the Young's modulus in the 55 ° direction, the X-ray random intensity ratio in the {110} <001> orientation is preferably 8 or more. More preferably, it is 10 or more. In order to increase the Young's modulus, the higher the degree of integration in the {110} <001> orientation, the better. The upper limit of the X-ray random intensity ratio in the {110} <001> orientation is not provided, but in order to exceed 20, the crystal grain size needs to be coarsened. Therefore, in order to prevent deterioration of mechanical properties such as strength and workability, the upper limit of the X-ray random intensity ratio in the {110} <001> orientation is preferably 20 or less.

The X-ray random intensity ratio of the {211} <011> orientation and the {110} <001> orientation is a plurality of the {110}, {100}, {211}, {310} pole figures measured by X-ray diffraction. What is necessary is just to obtain | require from the crystal orientation distribution function (Orientation Distribution Function, ODF) showing the three-dimensional texture calculated by the series expansion method based on the pole figure of.
Note that the X-ray random intensity ratio means that the X-ray intensity of a standard sample that does not accumulate in a specific orientation and the test material is measured under the same conditions by the X-ray diffraction method or the like. It is a numerical value obtained by dividing the line intensity by the X-ray intensity of the standard sample.

  FIG. 5 shows an ODF of a φ2 = 45 ° cross section where the crystal orientation of the present invention is displayed. FIG. 5 is a Bunge display showing a three-dimensional texture by a crystal orientation distribution function, where Euler angle φ2 is 45 °, and a specific crystal orientation (hkl) [uvw] is Euler angle of the crystal orientation distribution function. These are indicated by φ1 and φ. As indicated by the point on the axis of φ1 = 0 ° in FIG. 5, the {211} <011> orientation strictly indicates φ1 = 0 ° and φ = 35.26. However, since measurement errors due to specimen processing and sample setting may occur, the maximum value in the range of φ1 = 0 to 5 ° and Φ = 30 to 40 ° is set to the intensity of the {211} <011> orientation. Represent as a ratio. Similarly, although the {110} <001> orientation strictly inserts φ1 = 90 ° and Φ = 90 °, the maximum value in the range of 80 to 90 ° for both φ1 and Φ is {110} <001. > Represented as intensity ratio of orientation.

  Here, the orientation of the crystal is usually expressed as [hkl] or {hkl} in the direction perpendicular to the plate surface, and (uvw) or <uvw> in the direction parallel to the rolling direction. {Hkl} and <uvw> are generic terms for equivalent planes, and [hkl] and (uvw) indicate individual crystal planes. That is, in the present invention, a body-centered cubic structure (referred to as a body-centered cubic, bcc structure) is targeted, and for example, (111), (−111), (1-11), (11 -1), (-1-11), (-11-1), (1-1-1), and (-1-1-1) planes are equivalent and indistinguishable. In such a case, these orientations are collectively referred to as {111}.

  The 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 °, φ2 = 0 to 360 °, The direction is displayed in [hkl] (uvw). However, in the present invention, b. c. c. Since the structure is targeted, Φ and φ2 are expressed in the range of 0 to 90 °. In addition, the range of φ1 varies depending on whether or not symmetry due to deformation is taken into account when performing the calculation. In the present invention, φ1 = 0 to 90 ° in consideration of symmetry, that is, φ1. = Select a method for expressing an average value in the same orientation at 0 to 360 ° on an ODF of 0 to 90 °. In this case, [hkl] (uvw) and {hkl} <uvw> are synonymous. Therefore, for example, the X-ray random intensity ratio of (112) [1-10] of the ODF in the φ2 = 45 ° section shown in FIG. 5 is the X-ray random intensity ratio in the {211} <011> orientation.

  The sample for X-ray diffraction is produced as follows. The steel plate is polished to a specified position in the thickness direction by mechanical polishing or chemical polishing, and finished to a mirror surface by buffing, and then the distortion is removed by electrolytic polishing or chemical polishing. Adjust so that Since it is difficult to accurately set the measurement surface to ½ plate thickness, the sample should be prepared so that the measurement surface is within 3% of the plate thickness with the target position as the center. That's fine. When abnormalities such as segregation are observed at the center of the plate thickness, the sample may be prepared within the range of 7/16 to 9/16 of the plate thickness while avoiding the segregated portion. If 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.

Measurement of the Young's modulus of these steel sheets may be performed based on a transverse resonance method at room temperature or a static tensile test method in accordance with JIS Z 2280.
In the lateral resonance method, vibration is applied without fixing the sample, the primary resonance frequency is measured by gradually changing the frequency of the oscillator, and the Young's modulus is calculated from the following equation.
E _D = 0.946 × (l / h) ³ × m / w × f ²
Here, E _D : dynamic Young's modulus (N / m ² ), l: length of test piece (m), h: thickness of test piece (m), m: mass (kg), w: test piece (M), f: primary resonance frequency (s ⁻¹ ) of the transverse resonance method.

  In the static tensile Young's modulus test method, a stress-strain was measured by applying a tensile force repeatedly 5 times to a tensile stress level corresponding to 1/2 of the material yield strength using a tensile test piece in accordance with JIS Z 2201. Calculate based on the slope of the diagram. In order to eliminate variation in measurement, the value calculated as the average value of three measurement values excluding the maximum value and the minimum value among the five measurement results is generally used as the Young's modulus of the steel sheet.

Next, the plate thickness of each steel plate will be described. The plate thickness a (mm) of the first steel plate and the plate thickness b (mm) of the second steel plate are 0 ≦ | a−b | / (a + b) ≦ 0.6,
0.5mm ≦ a + b ≦ 2.0mm
Will be satisfied.

  The first expression | a−b | / (a + b) relates to the thickness ratio of the two steel plates, and if it exceeds 0.6, the difference in thickness between the two steel plates becomes large. As a result, the properties on the side of the thick steel plate become dominant, and the effect as a multilayer plate cannot be obtained. From this viewpoint, it is more desirable to set the upper limit of | a−b | / (a + b) to 0.5 or less. On the other hand, the lower limit of | a−b | / (a + b) is the case where the thicknesses of the two sheets are the same and, by definition, does not become a negative value, so the lower limit is 0.

  (A + b) in the following formula is the total thickness of the two steel plates. In order to make (a + b) less than 0.5, it is necessary to constantly produce a steel sheet of less than 0.1 to 0.4 mm. However, it is difficult and costly to produce such an ultrathin steel sheet with a wide width in a normal cold rolling-annealing process. Therefore, the lower limit of (a + b) is set to 0.5 mm or more. The upper limit of (a + b) is 2 mm or less from the viewpoint of weight reduction. From the viewpoint of weight reduction, the upper limit of (a + b) is preferably 1.6 mm or less. In order to further reduce the weight, it is preferable to set the upper limit of (a + b) to 1.2 mm or less.

  Further, when the thickness of the steel plate is increased, not only the weight is increased, but also the rigidity of the composite panel is increased, so that the effect of improving the Young's modulus is reduced depending on the shape. FIG. 6 shows the tension rigidity of the composite panel when the plate thickness (a + b) is changed. In the example of the present invention shown in FIG. 6, the thickness of the steel plate X (first steel plate) and the steel plate Y (second steel plate) described above is changed, and these steel plates are made of resin so that the rolling direction becomes a right angle. This is a bonded composite panel. The comparative example is a panel manufactured by using a steel sheet Z having a substantially random texture and changing the plate thickness.

  The stiffness of the composite panel simulating a roof panel with a maximum curvature of 8000R, 700mm square and molding height of 30mm was pushed in at a speed of 10mm / min with an indenter with a diameter of 100mm and a curvature radius of 300mm at a load of 20N. The amount of indentation (displacement of the indenter) was evaluated. When the total thickness exceeds 2 mm, the difference in tension rigidity between the present invention and the comparative example becomes small.

The characteristics of the cold-rolled steel sheet used in the present invention are realized by manufacturing under the following conditions, for example.
First, steel is melted and cast by a conventional method to obtain a slab for hot rolling. The slab may be a forged or rolled steel ingot, but it is preferable to manufacture the slab by continuous casting from the viewpoint of productivity. Moreover, you may manufacture with a thin slab caster. In general, the slab is cooled after casting, and then heated again for hot rolling.

About a 1st steel plate, the heating temperature of the slab at the time of performing hot rolling shall be 1100 degreeC or more. This is a temperature necessary for setting the finishing temperature of hot rolling to the Ar ₃ transformation point or higher. The finishing temperature of the hot rolling is not less than the Ar ₃ transformation point. This is because when rolling is performed below the Ar ₃ transformation point, a texture unfavorable for the Young's modulus in the width direction develops. On the other hand, if the finishing temperature of hot rolling exceeds 950 ° C., recrystallization proceeds during hot rolling, the formation of texture becomes insufficient, and the X-ray random intensity ratio in the {211} <011> orientation decreases. It is necessary to wind up at 700 degrees C or less after completion | finish of hot rolling. This is because if the winding is performed at over 700 ° C., the texture is broken during the winding, and the Young's modulus in the width direction may be lowered.

Moreover, about the 1st steel plate, cold rolling is performed by the reduction rate of 40 to 85%. If the rolling reduction is less than 40%, it is difficult to obtain a sufficiently developed texture, and the X-ray random intensity ratio in the {211} <011> orientation decreases. On the other hand, if the rolling reduction exceeds 85%, not only the load on the rolling mill increases, but also the Young's modulus in the width direction tends to decrease, so cold rolling is performed at 85% or less.
Furthermore, about the 1st steel plate, since the heating rate of annealing suppresses recrystallization, 1-100 degrees C / s is preferable. On the other hand, if the annealing temperature is less than 700 ° C., unrecrystallized grains remain after annealing, and workability deteriorates. On the other hand, if the annealing temperature is higher than 900 ° C., the γ grains become coarse, causing deterioration of the texture. Therefore, the heating temperature for annealing is set to 700 to 900 ° C.

Then, about the 2nd steel plate, since the heating temperature of hot rolling is less than 1000 degreeC, a rolling load will become excessive and productivity may be impaired, and it shall be 1000 degreeC or more. The finishing temperature in hot rolling is set to 800 ° C. or higher so that excessive strain is not introduced, and the total reduction amount at 890 ° C. or lower is set to less than 50%.
Moreover, about the 2nd steel plate, cold rolling is performed by the reduction rate of 20 to 80%. When the rolling reduction is less than 20%, the introduction of strain is insufficient, and after annealing, the X-ray random intensity ratio in the {110} <001> orientation decreases. On the other hand, if the rolling reduction of cold rolling exceeds 80%, the introduction of strain becomes excessive, recrystallization is promoted, and the X-ray random intensity ratio in the {110} <001> orientation decreases after final annealing. .

Furthermore, about the 2nd steel plate, final annealing is performed at the temperature of 850 degreeC or more following cold rolling. This annealing is for promoting grain growth and developing the {110} <001> orientation, but is preferably 1100 ° C. or less from the viewpoint of productivity. In the middle of cold rolling, intermediate annealing may be performed once or a plurality of times.
Moreover, about the 2nd steel plate, you may perform annealing before cold rolling which makes a maximum temperature 700-1200 degrees C or less before cold rolling. In addition to the effect of reducing the cold rolling load and avoiding troubles such as cracks during cold rolling, the development of the {110} <001> orientation can be promoted. The preferable range of the maximum temperature of annealing before cold rolling is 800-1000 degreeC. When intermediate annealing and annealing before cold rolling are performed, the rolling reduction of the cold rolling immediately before the final annealing is set in the above range, that is, 20 to 80%, preferably 30 to 70%.

The first steel plate and the second steel plate may be subjected to an overaging heat treatment at 150 ° C. or higher depending on purposes such as structure control and reduction of the amount of dissolved C. Moreover, you may give hot dip galvanization or alloying hot dip galvanization.
When alloying hot dip galvanization is performed, the alloying treatment is performed within a range of 450 to 600 ° C. When the temperature is lower than 450 ° C., alloying does not proceed sufficiently, and when the temperature is higher than 600 ° C., alloying proceeds excessively, and the plating layer becomes brittle, which causes problems such as peeling of the plating due to processing such as pressing. . The alloying treatment time is 10 s or longer. If it is less than 10 s, alloying does not proceed sufficiently.

  Further, temper rolling may be performed from the viewpoint of shape correction. Temper rolling does not affect the Young's modulus if the rolling reduction is 10% or less.

In the present invention, the method for attaching the two steel plates is not particularly limited. What is necessary is just an adhesive material which has the intensity | strength which does not peel before and after press molding. For example, an epoxy or urethane resin may be applied between the steel plates. In order to further improve the tension rigidity, a foam curable resin may be used. However, in any of the methods, if the entire steel sheet is bonded at a temperature exceeding the Ac ₁ transformation point, the texture is destroyed, the Young's modulus is lowered, and the desired tension rigidity may not be obtained.

Next, the present invention will be described with reference to examples.
First, the effect of maximum Young's modulus on tension stiffness is shown. Table 1 shows the chemical composition of the first steel sheet, and Table 2 shows the texture and Young's modulus. Similarly, Table 3 shows the chemical composition of the second steel sheet, and Table 4 shows the texture and Young's modulus. “◯” in the column of “Plating” in Tables 2 and 4 means a hot dip galvanized steel sheet.
The steel plate having the composition shown in Table 1 (the balance is Fe and inevitable impurities) is the first steel plate, and the steel having the composition shown in Table 3 (the balance is Fe and inevitable impurities) is the second steel plate. It is a steel plate. The 1st steel plate and the 2nd steel plate were made into a cold rolled steel plate by giving hot rolling, cold rolling, and annealing the steel piece obtained by melting and casting by a conventional method. Some steel plates were hot dip galvanized.

The first steel sheet was reheated to 1150 ° C., subjected to hot rolling at a finishing temperature of 800 to 890 ° C., and wound at 500 to 580 ° C. The obtained hot-rolled steel sheet had a thickness of 3 mm and was cold-rolled with a reduction rate of 80% to obtain a cold-rolled steel sheet with a thickness of 0.6 mm and annealed at 780 to 820 ° C.
The second steel plate was reheated to 1200 ° C., subjected to hot rolling at a finishing temperature of 880 to 930 ° C., and wound at 680 to 700 ° C. The obtained hot-rolled sheet had a thickness of 3 mm. After the primary cold rolling, intermediate annealing was performed at 800 ° C., and secondary cold rolling was performed to obtain a cold-rolled steel sheet having a thickness of 0.6 mm. The total rolling reduction of the cold rolling immediately before the final annealing was 80%, and the final annealing after the cold rolling was performed at 890 ° C.

  Measure the texture of these steel plates at 1/2 thickness (for the first steel plate, X-ray random strength ratio of {211} <011> orientation in the 1/2 plate thickness part, for the second steel plate Shows the result of {110} <001> orientation X-ray random intensity ratio in 1/2 plate thickness part and the Young's modulus in the rolling direction, 45 ° direction, 55 ° direction, and vertical direction of rolling (width direction). The results measured by the method are shown in Tables 2 and 4. The texture was measured by an X-ray diffraction method.

A1 to A7 in Tables 1 and 2 correspond to the first steel plate of the present invention, but all have {211} <011> orientation and the Young's modulus in the width direction exceeds 225 GPa. Yes. On the other hand, C1 and C2 to which Nb, Ti, V, and B are not added or a small amount of addition are not suppressed in recrystallization during hot rolling, so the {211} <011> orientation does not develop, and a high Young The rate is not obtained.
B1 to B7 in Tables 3 and 4 correspond to the second steel plate of the present invention, both of which {110} <001> orientation develops and the Young's modulus in the 55 ° direction from the rolling direction is 225 GPa. Over. However, in C4 in which C3, Bi, Pb, Sb, and Sn are not added, the {110} <001> orientation does not develop and a high Young's modulus cannot be obtained.

  The steel plates shown in Tables 1 to 4 were bonded with an epoxy resin so that the rolling direction was a right angle, and a composite panel was manufactured. The obtained composite panel was molded to a maximum curvature of 6500R, 700 mm square, and a molding height of 30 mm, and the center of the panel was pushed in at a speed of 10 mm / min with an indenter having a diameter of 100 mm and a curvature radius of 300 mm to evaluate the tension rigidity. The tension stiffness was evaluated by the amount of indentation when the load was 20N. Table 5 shows the evaluation results of the combination of the steel plates and the tension rigidity.

  In the case of the present invention example in which two steel plates having different anisotropies are pasted, it can be seen that the amount of indentation at a load of 20 N is smaller than that of the comparative example, and high tensile rigidity is obtained.

Next, the effect of the plate thickness ratio will be shown. Steel plates having various thicknesses were prepared using A1 and B2 and A2 and B7 in Tables 1 to 4. The hot-rolling reheating temperature, finishing temperature, and winding temperature were the same as in Example 1, but the thickness of the hot-rolled steel sheet was 1.5 to 4 mm. The cold rolling rate was changed in the range of 60 to 80% depending on the plate thickness. The conditions for annealing the cold-rolled steel sheet were the same as in Example 1.
In the same manner as in Example 1, a composite panel was manufactured by using an epoxy resin so that the rolling directions were perpendicular to each other. The molded composite panel has a maximum curvature of 7500R, 900 mm square, and a molding height of 40 mm. The tension rigidity of these composite panels was evaluated in the same manner as in Example 1. The results are shown in Table 6.

  From Table 6, the panel No. in which the plate thickness a (mm) of the steel plate A and the plate thickness b (mm) of the steel plate B satisfy 0 ≦ | a−b | / (a + b) ≦ 0.6. 16 to 19 and 22 to 25 are panel numbers of | a−b | / (a + b)> 0.6. Compared with 14, 15, 20, and 21, high tension rigidity is obtained.

Next, the effect of plate thickness is shown. Using A3 and B5 in Tables 1 to 4 and C2 and C4, steel plates with various plate thicknesses are produced, and two steel plates having the same plate thickness are epoxy resin so that the rolling directions are perpendicular to each other. Were bonded together to produce a composite panel. The manufacturing conditions of the steel plate are the same as in Example 2.
These composite panels were molded to a maximum curvature of 7800R, 900 mm square, and a molding height of 30 mm, and the center of the panel was pushed in at a speed of 10 mm / min with an indenter having a diameter of 100 mm and a curvature radius of 300 mm, and the stiffness was evaluated. The results are shown in Table 7.

  As shown in Table 7, the examples of the present invention are superior in tension rigidity as compared with the comparative example having the same total thickness (a + b), but when the total thickness exceeds 2 mm, the superiority is small. Become.

  The steel plate panel of the present invention is mainly used for automobile panel members, but is also used for home appliances, buildings and the like. Since the steel plate panel of the present invention has a high tensile rigidity, it is possible to reduce the thickness of the steel plate panel as compared with the conventional steel plate panel, that is, to reduce the weight, thereby contributing to the global environmental conservation.

Claims (6)

It is a composite panel in which two steel plates are bonded, and the component of the first steel plate is mass%,
C: 0.0005% or more, 0.150% or less,
Mn: 0.05% or more and 2.50% or less,
Containing
P: 0.200% or less,
S: 0.0200% or less,
N: 0.0100% or less,
Si: 2.00% or less,
Al: 0.15% or less,
In addition to
Ti: 0.005 to 0.150%,
Nb: 0.001 to 0.100%,
V: 0.005-0.100%,
B: 0.0001 to 0.0100%
And the balance consists of inevitable impurities, and the X-ray random intensity ratio of the {211} <011> orientation in the 1/2 sheet thickness part of the first steel sheet is 5 or more Yes, the Young's modulus in the width direction of the first steel plate is maximum and 225 to 290 GPa, and the component of the second steel plate is mass%,
C: 0.0003 to 0.250%,
Mn: 0.20% to 4.00%,
Al: more than 1.50% to 10.00%
Containing
Si: 2.20% or less,
P: 0.200% or less,
S: 0.0500% or less,
N: limited to 0.0150% or less,
Bi: 0.001 to 0.300%,
Pb: 0.001 to 0.300%,
Sb: 0.001 to 0.300%,
Sn: 0.0005 to 0.300%
And the balance is Fe and inevitable impurities, and the X-ray random intensity ratio of {110} <001> orientation in the ½ plate thickness part of the second steel plate is 6 or more. The Young's modulus in the direction of 55 ° is the maximum with respect to the rolling direction of the second steel plate and is 225 to 290 GPa, and the rolling direction of the first steel plate and the rolling direction of the second steel plate are A composite panel with excellent tension rigidity, characterized by a right angle. The component of the first steel plate is further mass%,
Cr: 3.00% or less,
Cu: 0.35% or less,
Ni: 1.00% or less,
Mo: 1.00% or less of 1 type or 2 types or more are contained, The composite panel excellent in tension rigidity of Claim 1 characterized by the above-mentioned. The component of the second steel plate is further mass%,
Ti: 0.150% or less,
Nb: 0.150% or less,
V: 0.150% or less,
Cr: 3.00% or less,
Ni: 3.00% or less,
Mo: 3.00% or less,
Cu: 3.00% or less,
B: 1 type or 2 types containing 0.0060% or less, The composite panel excellent in the tension rigidity of Claim 1 or 2 characterized by the above-mentioned. The thickness a [mm] of the first steel plate to be adhered and the thickness b [mm] of the second steel plate are:
0 ≦ | a−b | / (a + b) ≦ 0.6,
0.5mm ≦ a + b ≦ 2.0mm
The composite panel according to any one of claims 1 to 3, wherein the composite panel is excellent in tension rigidity.   The composite panel excellent in tensile rigidity according to any one of claims 1 to 4, wherein the first steel plate and the second steel plate are cold-rolled steel plates.   One or both of a 1st steel plate and a 2nd steel plate are hot-dip galvanized cold-rolled steel plates, The composite panel excellent in tension rigidity of any one of Claims 1-5 characterized by the above-mentioned.

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