JP6776908B2 - Molded product manufacturing method and molded product - Google Patents

Description

The present invention relates to a method for producing a molded product and a molded product.

In recent years, in the fields of automobiles, aircraft, ships, building materials, home appliances, etc., design has been emphasized in order to meet the needs of users. Therefore, in particular, the shape of the exterior member tends to be complicated. However, in order to mold a molded product with a complicated shape from a metal plate, it is necessary to give a large strain to the metal plate, but as the amount of processing increases, fine irregularities are likely to occur on the surface of the molded product, resulting in rough skin. There is a problem that it spoils the appearance.

For example, Patent Document 1 discloses that an uneven striped pattern appears (rigging) in parallel with the rolling direction. Specifically, Patent Document 1 discloses the following. An aluminum alloy rolled plate for forming with excellent rigging resistance can be obtained by controlling the average Taylor factor when the forming process is regarded as a plane strain deformation with the rolling width direction as the main strain direction. The average Taylor factor calculated from all the crystal orientations present in the texture is greatly related to the rigging resistance. By controlling the texture so that the value of the average Taylor factor satisfies a specific condition, the rigging resistance can be reliably and stably improved.

: Patent No. 5683193

However, Patent Document 1 only shows that rigging is suppressed in the molding process of a metal plate in which uniaxial tensile deformation occurs with the rolling width direction as the main strain direction. Further, no consideration is given to the forming process of the metal plate in which biaxial tensile deformation occurs, such as deep drawing forming and overhang forming.

On the other hand, even in the molding process of a metal plate in which biaxial tensile deformation occurs such as deep drawing molding and overhang molding, it is required to manufacture a molded product having a complicated shape in recent years. However, when a metal plate is molded with a large amount of processing (a processing amount that reduces the thickness of the metal plate by 10% or more), unevenness develops on the surface of the molded product, resulting in rough skin and spoiling the appearance. The current situation is that problems are occurring.
For the above reasons, for example, conventional automobile outer panel products are produced by limiting the amount of strain applied to the product surface to a processing amount such that the plate thickness reduction rate of the metal plate is less than 10%. That is, there are restrictions on the processing conditions in order to avoid the occurrence of rough skin. However, a more complicated shape of the outer panel product of an automobile is required, and a method capable of achieving both a plate thickness reduction rate of 10% or more of a metal plate during molding and suppression of rough skin is desired.

Therefore, in view of the above circumstances, the subject of the present invention is that biaxial tensile deformation occurs in a metal plate having an fcc structure, and at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less. It is an object of the present invention to provide a method for producing a molded product, which suppresses the occurrence of rough skin and can obtain a molded product having excellent design even when the molding process is performed.
Another object of the present invention is a molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs, the maximum plate thickness of the molded product is D1, and the minimum plate thickness of the molded product. When D2, the condition of formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30, or when the maximum hardness of the molded product is H1 and the minimum hardness of the molded product is H2, the formula: 15 ≦ ( It is an object of the present invention to provide a molded product having excellent designability in which the occurrence of rough skin is suppressed even if the molded product satisfies the condition of H1-H2) / H1 × 100 ≦ 40.

The inventors have determined the surface texture when molding a metal plate with a large processing amount (a processing amount at which the plate thickness reduction rate of the metal plate is 10% or more) in order to manufacture a molded product having a complicated shape in recent years. investigated. As a result, the inventors obtained the following findings. Under biaxial tensile deformation, crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate having a bcc structure are preferentially deformed, and unevenness develops. Therefore, the inventors focused on the area division and the average crystal grain size of crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate. As a result, the inventors have found that the area fraction and the average crystal grain size of these crystal grains suppress the development of unevenness, suppress the occurrence of rough skin, and obtain a molded product having excellent design.

Furthermore, the inventors obtained the following findings. Under biaxial tensile deformation, crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate having a bcc structure are preferentially deformed, and unevenness develops. Therefore, the inventors focused on the area division of crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate. As a result, the inventors have found that the area fraction of these crystal grains suppresses the development of unevenness, suppresses the occurrence of rough skin, and provides a molded product having excellent design.

Then, the inventors assumed a slip system of a metal plate having an fcc structure, and investigated the influence of crystal orientation on the rough skin after processing of the metal plate by numerical analysis. As a result, the following findings were obtained. Similar to the metal plate having the bcc structure, in the metal plate having the fcc structure, the crystal grains having the crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate are preferentially deformed under biaxial tensile deformation. However, unevenness develops. Further, under biaxial tensile deformation, crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate are preferentially deformed, and unevenness develops.
Therefore, the inventors have found that even in a metal plate having an fcc structure, the area fraction of crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate and the surface of the metal plate We focused on the area division of crystal grains other than those having a crystal orientation within 15 ° from the parallel {111} plane. As a result, the inventors have found that the area fraction of these crystal grains suppresses the development of unevenness, suppresses the occurrence of rough skin, and can obtain a molded product having excellent design.

The gist of the present invention is as follows.

<1>
A metal plate having an fcc structure and satisfying the following conditions (a) or (b) on the surface of the metal plate undergoes biaxial tensile deformation, and at least a part of the metal plate has a plate thickness reduction rate of 10. A method for manufacturing a molded product, in which a molded product is manufactured by performing a molding process of% or more and 30% or less.
(A) The area division of crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate is 0.20 or more and 0.35 or less.
(B) Crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate have an area division of 0.45 or less and an average crystal grain size of 15 μm or less.
<2>
A metal plate having an fcc structure and satisfying the following conditions (A) or (B) on the surface of the metal plate undergoes biaxial tensile deformation, and at least a part of the metal plate has a plate thickness reduction rate of 10. A method for manufacturing a molded product, in which a molded product is manufactured by performing a molding process of% or more and 30% or less.
(A) The area division of crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate is 0.25 or more and 0.55 or less.
(B) Crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate have an area division of 0.55 or less and an average crystal grain size of 15 μm or less. is there.
<3>
A molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs.
When the maximum plate thickness of the molded product is D1 and the minimum plate thickness of the molded product is D2, the condition of the formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30 is satisfied.
A molded product that satisfies the following conditions (c) or (d) on the surface of the molded product.
(C) The area fraction of the crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product is 0.20 or more and 0.35 or less.
(D) Crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product have an area fraction of 0.45 or less and an average crystal grain size of 15 μm or less.
<4>
A molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs.
When the maximum plate thickness of the molded product is D1 and the minimum plate thickness of the molded product is D2, the condition of the formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30 is satisfied.
A molded product that satisfies the following conditions (C) or (D) on the surface of the molded product.
(C) The area fraction of crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product is 0.25 or more and 0.55 or less.
(D) Crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product have an area division of 0.55 or less and an average crystal grain size of 15 μm or less. is there.
<5>
A molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs.
When the maximum hardness of the molded product is H1 and the minimum hardness of the molded product is H2, the condition of the formula: 15 ≦ (H1-H2) / H1 × 100 ≦ 40 is satisfied.
A molded product that satisfies the following conditions (c) or (d) on the surface of the molded product.
(C) The area fraction of the crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product is 0.20 or more and 0.35 or less.
(D) Crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product have an area fraction of 0.45 or less and an average crystal grain size of 15 μm or less.
<6>
A molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs.
When the maximum hardness of the molded product is H1 and the minimum hardness of the molded product is H2, the condition of the formula: 15 ≦ (H1-H2) / H1 × 100 ≦ 40 is satisfied.
A molded product that satisfies the following conditions (C) or (D) on the surface of the molded product.
(C) The area fraction of crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product is 0.25 or more and 0.55 or less.
(D) Crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product have an area division of 0.55 or less and an average crystal grain size of 15 μm or less. is there.

According to the present invention, even when a metal plate having an fcc structure is subjected to a molding process in which biaxial tensile deformation occurs and at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less. It is possible to provide a method for producing a molded product, which suppresses the occurrence of rough skin and can obtain a molded product having excellent design.
Further, according to another invention, it is a molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs, the maximum plate thickness of the molded product is D1, and the minimum plate thickness of the molded product. When D2, the condition: 10 ≦ (D1-D2) / D1 × 100 ≦ 30, or when the maximum hardness of the molded product is H1 and the minimum hardness of the molded product is H2, the formula: 15 ≦ Even if the molded product satisfies the condition of (H1-H2) / H1 × 100 ≦ 30, it is possible to provide a molded product in which the occurrence of rough skin is suppressed and the design is excellent.

FIG. 1 is a view of observing the surface of a metal plate (a metal plate having a bcc structure) after performing a bulge forming test using an SEM. FIG. 2 is a diagram in which the surface of a metal plate (metal plate having a bcc structure) that has been electropolished after performing a bulge forming test is observed using an SEM. FIG. 3A is a schematic view when the surface of a metal plate (metal plate having a bcc structure) with less unevenness development after the bulge forming test is analyzed by the EBSD method. FIG. 3B is a schematic view showing the surface unevenness of the metal plate (metal plate having a bcc structure) in the A1-A2 cross section of FIG. 3A. FIG. 4A is a schematic view when the surface of a metal plate (a metal plate having a bcc structure) having many irregularities developed after the bulge forming test is analyzed by the EBSD method. FIG. 4B is a schematic view showing the surface unevenness of the metal plate (metal plate having a bcc structure) in the cross section of B1-B2 of FIG. 4A. FIG. 5A is a schematic view when the surface of a metal plate (a metal plate having a bcc structure) having many irregularities developed after the bulge forming test is analyzed by the EBSD method. FIG. 5B is a schematic view showing the surface unevenness of the metal plate (metal plate having a bcc structure) in the C1-C2 cross section of FIG. 5A. It is a schematic diagram for demonstrating the definition of "a crystal grain having a crystal orientation within 15 ° from a {001} plane parallel to the surface of a metal plate". FIG. 7A is a schematic view showing an example of overhang molding processing. FIG. 7B is a schematic view showing an example of a molded product obtained by the overhang molding process shown in FIG. 7A. FIG. 8A is a schematic view showing an example of draw-out molding processing. FIG. 8B is a schematic view showing an example of a molded product obtained by the draw-out molding process shown in FIG. 8A. FIG. 9 is a schematic diagram for explaining plane strain tensile deformation, biaxial tensile deformation, and uniaxial tensile deformation. FIG. 10 is a schematic diagram illustrating a method of obtaining the average crystal grain size of {001} crystal grains from the analysis results by the EBSD method. FIG. 11 is a schematic view for explaining the molded product produced in the reference example. FIG. 12 is a schematic view of the steel plate observed from above. FIG. 13 shows the molded product No. corresponding to the reference example. It is a schematic diagram which shows the cross-sectional microstructure and the surface unevenness of 2. FIG. 14 shows the molded product No. corresponding to the reference example. It is a schematic diagram which shows the cross-sectional microstructure and the surface unevenness of 3. FIG. 15 shows the molded product No. corresponding to the comparative reference example. It is a schematic diagram which shows the cross-sectional microstructure and surface unevenness of 1. FIG. 16 shows the molded product No. corresponding to the reference example. It is a schematic diagram which shows the cross-sectional microstructure and surface unevenness of 102. FIG. 17 shows the molded product No. corresponding to the reference example. It is a schematic diagram which shows the cross-sectional microstructure and the surface unevenness of 103. FIG. 18 shows the molded product No. corresponding to the comparative reference example. It is a schematic diagram which shows the cross-sectional microstructure and the surface unevenness of 101. FIG. 19 shows No. It is a figure which shows the relationship between the result of Pa evaluation, the average crystal grain size and the crystal grain size of {001} crystal grain about the virtual material after the molding simulation of A1 to A10.

Hereinafter, the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.

(Manufacturing method of molded products)
The inventors have conducted various studies on the structure of the metal plate to be molded.
First, the inventors conducted various studies on the structure of a metal plate having a bcc structure. As a result, the following findings were obtained.

(1) In a metal plate having a bcc structure, the {001} plane is more vulnerable to the stress of equal biaxial tensile deformation and unequal biaxial tensile deformation close to equal biaxial tensile deformation than the {111} plane. .. Further, the {101} plane is more vulnerable to the stress of isobiaxial tensile deformation and unequal biaxial tensile deformation close to equibiaxial tensile deformation than the {111} plane. Therefore, with a large processing amount (a processing amount in which at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less), a metal plate forming process in which biaxial tensile deformation occurs, such as deep drawing forming and overhang forming, is performed. When this is done, the strain is concentrated on the crystal grains having a crystal orientation of 15 ° from the {001} plane parallel to the surface of the metal plate.

(2) Strain concentrated on crystal grains having a crystal orientation of 15 ° from the {001} plane parallel to the surface of the metal plate having a bcc structure develops the surface of the metal plate and deteriorates the surface texture (that is, rough skin). Causes).

(3) When the unevenness developed on the surface of the metal plate having the bcc structure is connected, the surface texture is further deteriorated (that is, rough skin is remarkably generated).

(4) Even if there are too few crystal grains having a crystal orientation of 15 ° from the {001} plane parallel to the surface of the metal plate having a bcc structure, 15 ° to the {001} plane parallel to the surface of the metal plate. Local deformation is also dispersed in crystal grains having a crystal orientation close to (for example, crystal grains having a crystal orientation in the range of more than 15 ° and 30 ° or less with respect to the {001} plane). Therefore, the unevenness of the surface of the metal plate develops.

FIG. 1 is a scanning electron microscope (SEM) image of the surface of a metal plate after performing a bulge forming test. FIG. 2 is an SEM image of the surface of a metal plate that has been electropolished after performing a bulge forming test. In both FIGS. 1 and 2, the observation point is the apex of the metal plate raised in a mountain shape by the bulge forming test. When a bulge forming test was performed on a metal plate with reference to FIGS. 1 and 2, recesses 1 and recesses 2 having a size of about 10 to 20 μm were observed.

That is, when the metal plate is overhanged and molded, the stress is concentrated at a certain point on the metal plate. In the place where stress is concentrated, unevenness develops on the surface of the metal plate. In addition, the developed unevenness is connected to further develop the unevenness. These cause rough skin.

3A to 5A are schematic views when the surface of the metal plate after the bulge forming test is analyzed by the EBSD (Electron Backscattering Diffraction) method. FIG. 3A shows that when the overhang height by bulge forming is 40 mm (corresponding to the molding process in which at least a part of the metal plate has a plate thickness reduction rate of 25%), the surface of the metal plate has less unevenness. It is a schematic diagram of a metal plate. In FIGS. 4A and 5A, when the overhang height by bulge forming is 40 mm (corresponding to the molding process in which at least a part of the metal plate has a plate thickness reduction rate of 25%), the surface of the metal plate has irregularities. It is a schematic diagram of a metal plate that was often developed.

On the other hand, FIGS. 3B to 5B are schematic views showing the surface irregularities of the metal plate in the cross sections of FIGS. 3A to 5A. That is, FIG. 3B is a schematic cross-sectional view showing the surface irregularities of the metal plate in which the development of irregularities on the surface of the metal plate is small. 4B and 5B are schematic views of a metal plate having many irregularities on the surface of the metal plate.

Here, among the crystal grains in FIGS. 3A to 5A, the dark gray crystal grain 3 is a crystal grain having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate. Hereinafter, these crystal grains are also referred to as "{001} crystal grains". Further, among the crystal grains in FIGS. 3A to 5A, the light gray crystal grains 4 are crystal grains having a crystal orientation close to 15 ° with respect to the {001} plane parallel to the surface of the metal plate (for example, {{ A crystal grain having a crystal orientation in the range of more than 15 ° and 20 ° or less with respect to the 001} plane). Hereinafter, these crystal grains are also referred to as "{001} near crystal grains".
In FIGS. 3B to 5B, 31 indicates the surface of the metal plate in which the {001} crystal grains 3 are present. Further, 41 indicates the surface of the metal plate in which the crystal grains 4 in the vicinity of {001} are present.

With reference to FIGS. 3A and 3B, the area fraction of the {001} crystal grains 3 was 0.20 or more and 0.35 or less on the surface of the metal plate in which the development of unevenness was small on the surface of the metal plate.

With reference to FIGS. 4A to 5A and FIGS. 4B to 5B, is the area fraction of {001} crystal grains 3 smaller than 0.20 on the surface of the metal plate in which the surface of the metal plate has many irregularities? , Or was greater than 0.35.

This is because strain is concentrated on the {001} crystal grains 3 during the overhang molding process. Then, the strain concentrated on the {001} crystal grains 3 develops irregularities on the surface of the metal plate. Further, when the surface integral of the {001} crystal grains 3 is high, the probability that the {001} crystal grains 3 are in contact with each other is high, and the generated irregularities are easily connected. On the other hand, if the area division of the {001} crystal grains 3 is too low, the local deformation is dispersed in the crystal grains 4 in the vicinity of {001}, and the unevenness of the surface of the metal plate is developed.

Specifically, when the area division of the {001} crystal grains 3 is within an appropriate range, the local deformation is not dispersed in the crystal grains 4 near {001} on the surface of the metal plate. As a result, local deformation occurs only in the {001} crystal grains 3. Therefore, a deep recess is formed in the region where the {001} crystal grain 3 exists, but a flat portion is secured in the region where other crystal grains (such as the crystal grain 4 near {001}) exist (FIG. 3B). reference). This indicates that even if high unevenness is formed, a flat portion is secured if the concave portion is deep and fine.
On the other hand, when the area division of the {001} crystal grains 3 is too low, the local deformation is dispersed in the crystal grains 4 in the vicinity of {001} on the surface of the metal plate. As a result, local deformation occurs not only in the {001} crystal grains 3 but also in the {001} neighboring crystal grains 4. Therefore, the region where the shallow recess is formed becomes large, and the flat portion becomes relatively small (see FIG. 4B).
Further, when the area fraction of the {001} crystal grain 3 is too high, the {001} crystal grain 3 is locally deformed on the surface of the metal plate, the region where the shallow recess is formed becomes large, and the flat portion becomes small. (Fig. 5B).

Therefore, if the surface integral of the {001} crystal grain 3 is too high or too low, the unevenness on the surface of the metal plate develops, and the generated unevenness is easily connected, and the unevenness is further developed by the connection.

Therefore, the inventors considered the following. When a metal plate having a bcc structure is subjected to a molding process that causes biaxial tensile deformation, the development of irregularities on the surface of the metal plate that occurs during processing can be suppressed by setting the ratio of {001} crystal grains 3 within a predetermined range. it can. That is, if the development of unevenness can be suppressed, rough skin that impairs the appearance of the molded product can be suppressed.

On the other hand, the inventors considered the following. When the proportion of {001} crystal grains 3 is low and the size of {001} crystal grains 3 is sufficiently small, even if the unevenness of the surface of the metal plate generated during processing develops, the unevenness developed on the surface of the metal plate Is inconspicuous and is less likely to be recognized as rough skin that spoils the appearance of the molded product.

Then, the inventors paid attention to the slip system (slip surface and slip direction) of the crystal structure of the metal plate having a bcc structure and the metal plate having an fcc structure. In other words, the inventors focused on the following. The slip surface of the crystal structure of the metal plate having the bcc structure and the slip direction of the crystal structure of the metal plate having the fcc structure are in a parallel relationship. The slip direction of the crystal structure of the metal plate having the bcc structure and the slip surface of the crystal structure of the metal plate having the fcc structure are in a parallel relationship. Then, it was estimated that the metal plate having the fcc structure has the same strength distribution for each crystal orientation in the biaxial tensile deformation as the metal plate having the bcc structure. (See Table 1 below).

The inventors focusing on the slip system of both crystal structures have found that the crystal orientation and molding of crystal grains in a biaxial deformation field (equal biaxial deformation field and unequal biaxial tensile deformation field) in a metal plate having an fcc structure. R.BECKER, "Effects of strain localization on surface roughening during sheet forming", Acta Mater. Vol. 46.No. 4.pp. 1385-1401, 1998 ).
Specifically, the slip system of the crystal orientation of the cross section of the metal plate having the bcc structure (for example, FIGS. 13 to 18) is changed to the slip system of the metal plate having the fcc structure, and the surface of the metal plate is {001}. The area fraction of the crystal grains 3 was changed. The effect of surface roughness of the metal plate due to plastic strain at that time was investigated by numerical analysis.

As a result, the inventors have found that, like the metal plate having the bcc structure, the metal plate having the fcc structure also has the equal biaxial tensile deformation field and the unequal biaxial tensile deformation field close to the equal biaxial tensile deformation field. 001} It was found that strain is concentrated on the crystal grain 3 and preferential deformation occurs.

Therefore, the inventors considered the following. Even when a metal plate having an fcc structure is subjected to a molding process that causes biaxial tensile deformation, the development of unevenness on the surface of the metal plate that occurs during processing is suppressed by setting the ratio of {001} crystal grains 3 within a predetermined range. It is possible. That is, if the development of unevenness can be suppressed, rough skin that impairs the appearance of the molded product can be suppressed.
Further, when the ratio of the {001} crystal grains 3 is low and the size of the {001} crystal grains 3 is sufficiently small, even if the unevenness of the surface of the metal plate generated during processing develops, it develops on the surface of the metal plate. The unevenness is not noticeable, and it is difficult to recognize it as rough skin that spoils the appearance of the molded product.

The first method for producing a molded product of the present invention completed based on the above findings is based on a metal plate having an fcc structure and satisfying the following conditions (a) or (b) on the surface of the metal plate. This is a method for manufacturing a molded product in which biaxial tensile deformation occurs and at least a part of the metal plate is subjected to a molding process in which the plate thickness reduction rate is 10% or more and 30% or less.
(A) The area division of crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate is 0.20 or more and 0.35 or less.
(B) Crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate have an area division of 0.45 or less and an average crystal grain size of 15 μm or less.

In the first method for producing a molded product of the present invention, biaxial tensile deformation occurs in a metal plate having an fcc structure, and at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less. Even when the molding process is performed, the occurrence of rough skin is suppressed and a molded product having excellent design can be obtained.

Here, "crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate" means one of the metal plates with respect to the {001} plane 3A, as shown in FIG. It means a crystal grain having a crystal orientation in the range from the crystal orientation 3B inclined at a sharp angle of 15 ° to the surface side of the metal plate to the crystal orientation 3C inclined at a sharp angle of 15 ° toward the other surface side of the metal plate. That is, it means a crystal grain having a crystal orientation in the range of the angle θ formed by the crystal orientation 3B and the crystal orientation 3C.

On the other hand, the inventors further investigated the structure of the metal plate having a bcc structure based on the above findings. As a result, the inventors have found the following. In a biaxial tensile deformation field (particularly an unequal biaxial tensile deformation field close to a plane strain deformation field), not only {001} grain 3 but also crystals within 15 ° from the {111} plane parallel to the surface of the metal plate. It was found that strain is concentrated on crystal grains other than the crystal grains having an orientation (hereinafter, also referred to as "{111} crystal grains"), and preferential deformation occurs.

In other words, the inventors considered the following. When a metal plate having a bcc structure is subjected to a molding process that causes biaxial tensile deformation, if the ratio of crystal grains other than {111} crystal grains is within a predetermined range, the development of irregularities on the surface of the metal plate that occurs during processing can be prevented. It can be suppressed. That is, if the development of unevenness can be suppressed, rough skin that impairs the appearance of the molded product can be suppressed.

In addition, the inventors considered the following. If the proportion of crystal grains other than {111} crystal grains is low, and if the size of the crystal grains other than {111} crystal grains is sufficiently small, even if the surface irregularities of the metal plate that occur during processing develop, the metal plate The unevenness developed on the surface of the product is inconspicuous, and it is difficult to recognize it as rough skin that spoils the appearance of the molded product.

Similarly, the inventors focusing on the slip system of the crystal structure of the metal plate having the bcc structure and the metal plate having the fcc structure have found that the biaxial deformation field (equal biaxial) in the metal plate having the fcc structure The relationship between the crystal orientation of the crystal grains and the rough surface of the molded product in the deformation field and the unequal biaxial tensile deformation field was investigated by the crystal plasticity finite element analysis method.

As a result, the inventors have found that, like the metal plate having the bcc structure, the metal plate having the fcc structure is also {111 in the biaxial tensile deformation field (particularly the unequal biaxial tensile deformation field close to the plane strain deformation field). } It was found that strain is concentrated on crystal grains other than crystal grains and preferential deformation occurs.

Therefore, the inventors considered the following. Even when a metal plate having an fcc structure is subjected to a molding process that causes biaxial tensile deformation, by setting the ratio of crystal grains other than {111} crystal grains within a predetermined range, the unevenness of the surface of the metal plate that occurs during processing is set. Development can be suppressed. That is, if the development of unevenness can be suppressed, rough skin that impairs the appearance of the molded product can be suppressed.
Further, when the ratio of the crystal grains other than the {111} crystal grains is low and the size of the crystal grains other than the {111} crystal grains is sufficiently small, even if the unevenness of the surface of the metal plate generated during processing develops, The unevenness developed on the surface of the metal plate is inconspicuous, and it is difficult to recognize it as rough skin that spoils the appearance of the molded product.

The second method for producing a molded product of the present invention completed based on the above findings is for a metal plate having an fcc structure and satisfying the following conditions (A) or (B) on the surface of the metal plate. A method for producing a molded product, wherein biaxial tensile deformation occurs and at least a part of the metal plate is subjected to a molding process in which the plate thickness reduction rate is 10% or more and 30% or less.
(A) The area division of crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate is 0.25 or more and 0.55 or less.
(B) Crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate have an area division of 0.55 or less and an average crystal grain size of 15 μm or less. is there.

Then, in the second method for producing a molded product of the present invention, biaxial tensile deformation occurs in the metal plate having the fcc structure, and at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less. Even when the molding process is performed, the occurrence of rough skin is suppressed and a molded product having excellent design can be obtained.

Here, "a crystal grain having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate" means a sharp angle of 15 ° to one side of the metal plate with respect to the {111} plane. It means a crystal grain having a crystal orientation in the range from the inclined crystal orientation to the crystal orientation inclined at a sharp angle of 15 ° toward the other surface side of the metal plate. That is, it means a crystal grain having a crystal orientation within the range of the angle θ formed by these two crystal orientations.

(Molding)
The metal plate is subjected to a molding process that causes biaxial tensile deformation. This molding process includes deep drawing, overhanging, drawing overhanging, and bending. Specifically, as the molding process, for example, a method of overhanging the metal plate 10 as shown in FIG. 7A can be mentioned. In this molding process, the edge of the metal plate 10 is sandwiched between the die 11 and the holder 12 on which the draw beads 12A are arranged. As a result, the draw bead 12A is made to bite into the surface of the edge of the metal plate 10 to fix the metal plate 10. Then, in this state, the punch 13 having a flat top surface is pressed against the metal plate 10, and the metal plate 10 is overhanged and molded. Here, an example of a molded product obtained by the overhang molding process shown in FIG. 7A is shown in FIG. 7B.
In the overhang molding process shown in FIG. 7A, for example, the metal plate 10 (top surface of the molded product) located on the top surface of the punch 10 has an equal biaxial deformation or an unequal biaxial deformation relatively close to the equal biaxial deformation. Tensile deformation occurs.

Further, as the molding process, for example, a method of drawing and overhanging the metal plate 10 as shown in FIG. 8A can be mentioned. In this molding process, the edge of the metal plate 10 is sandwiched between the die 11 and the holder 12 on which the draw beads 12A are arranged. As a result, the draw bead 12A is made to bite into the surface of the edge of the metal plate 10 to fix the metal plate 10. Then, in this state, the punch 13 whose top surface protrudes in a substantially V shape is pressed against the metal plate 10, and the metal plate 10 is drawn out and formed. Here, an example of a molded product obtained by the draw-out molding process shown in FIG. 8A is shown in FIG. 8B.
In the draw-out molding process shown in FIG. 8A, for example, the metal plate 10 (top surface of the molded product) located on the top surface of the punch 10 undergoes unequal biaxial tensile deformation that is relatively close to plane strain deformation.

Here, as shown in FIG. 9, the plane strain tensile deformation is a deformation that extends in the ε1 direction and does not cause deformation in the ε2 direction. The biaxial tensile deformation is a deformation that extends in the ε1 direction and also extends in the ε2 direction. Specifically, the planar strain tensile deformation is a deformation in which the strain ratio β (= ε2 / ε1) becomes β = 0 when the strains in the biaxial direction are the maximum principal strain ε1 and the minimum principal strain ε2, respectively. The biaxial tensile deformation is a deformation in which the strain ratio β (= ε2 / ε1) is 0 <β ≦ 1. The deformation in which the strain ratio β (= ε2 / ε1) is 0 <β <1 is the unequal biaxial deformation, and the deformation in which the strain ratio β (= ε2 / ε1) is β = 1 is the equibiaxial deformation. Is. Incidentally, the uniaxial tensile deformation is a deformation in which the deformation occurs in the ε1 direction and the contraction occurs in the ε2 direction, and the strain ratio β (= ε2 / ε1) is −0.5 ≦ β <0.

However, the range of the strain ratio β is a theoretical value, and is calculated from, for example, the maximum principal strain and the minimum principal strain measured from the shape change before and after forming the steel sheet (before and after the deformation of the steel sheet) in the scribed circle transferred to the surface of the steel sheet. The range of the strain ratio β of each deformation is as follows.
-Uniaxial tensile deformation: -0.5 <β ≤ -0.1
・ Plane strain Tensile deformation: −0.1 <β ≤ 0.1
・ Unequal biaxial deformation: 0.1 <β ≤ 0.8
・ Equal biaxial deformation: 0.8 <β ≤ 1.0

On the other hand, in the molding process, at least a part of the metal plate is processed at a processing amount such that the plate thickness reduction rate is 10% or more and 30% or less. When the processing amount has a plate thickness reduction rate of less than 10%, strain concentration on crystal grains other than {111} crystal grains (particularly {001} crystal grains) is small, and unevenness tends to be less likely to develop during molding. Therefore, even if the metal plate does not satisfy the above conditions (a) and (b) or the above conditions (A) and (B), the rough skin of the molded product itself is unlikely to occur. On the other hand, when the plate thickness reduction rate exceeds 30%, the tendency of the metal plate (molded product) to break due to the molding process increases. Therefore, the processing amount of the molding process is within the above range.

The molding process is performed at a processing amount such that at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less. However, the molding process may be performed with a processing amount such that the entire metal plate excluding the edge portion (the portion sandwiched between the die and the holder) has a plate thickness reduction rate of 10% or more and 30% or less. Although it depends on the shape of the molded product to be molded, in particular, in the molding process, the part of the metal plate located on the top surface of the punch (the part where the metal plate is biaxially tensilely deformed) has a plate thickness reduction rate of 10% or more and 30% or less. It is preferable to carry out with the processing amount that becomes. The portion of the metal plate located on the top surface of the punch is often the portion most exposed to the line of sight when the molded product is applied as an exterior member. Therefore, when the portion of the metal plate is molded with a large processing amount of 10% or more and 30% or less in thickness reduction rate, if the development of unevenness is suppressed, the effect of suppressing rough skin becomes remarkable.

The plate thickness reduction rate is calculated when the plate thickness of the metal plate before the molding process is Ti and the plate thickness of the metal plate (molded product) after the molding process is Ta. The formula: plate thickness reduction rate = (Ti−). It is indicated by Ta) / Ti.

(Metal plate)
[type]
The metal plate is a metal plate having an fcc structure (body-centered cubic lattice structure). Examples of the metal plate having an fcc structure include metal plates such as γ-Fe (austenitic stainless steel), Al, Cu, Au, Pt, and Pb.

The thickness of the metal plate is not particularly limited, but is preferably 3 mm or less from the viewpoint of moldability.

[{001} Crystal grain]
When performing molding processing that causes biaxial tensile deformation, crystal grains ({001} crystal grains) having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate on the surface of the metal plate having an fcc structure. ) Satisfies the following (a) or (b).
(A) The surface integral of the {001} crystal grains is 0.20 or more and 0.35 or less.
(B) The area fraction of the {001} crystal grains is 0.45 or less, and the average crystal grain size is 15 μm or less.

As described above, in the case of a metal plate having an fcc structure, {001} crystal grains are most vulnerable to the stress of isobiaxial tensile deformation and unequal biaxial tensile deformation close to equibiaxial tensile deformation. Therefore, with a large processing amount (a processing amount in which at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less), a metal plate forming process in which biaxial tensile deformation occurs, such as deep drawing and overhanging, is performed. If carried out, strain is likely to be concentrated on the {001} crystal grains, and unevenness is likely to develop on the {001} crystal grains. When the proportion of {001} crystal grains is large, strain is likely to be concentrated and unevenness is likely to develop. On the other hand, when the proportion of {001} crystal grains is small, the number of places where strain is concentrated is reduced, and local deformation is dispersed in the crystal grains in the vicinity of {001}, so that unevenness is likely to develop. However, even when the proportion of {001} crystal grains is small, if the size of the {001} crystal grains is sufficiently small, the region that is locally deformed by the crystal grains in the vicinity of {001} is also small, and even if unevenness develops, it is fine. Therefore, it becomes difficult to be recognized as rough skin of the molded product.

Therefore, if the metal plate having the fcc structure satisfies the above (a), an appropriate strain concentration due to the molding process is realized. Therefore, the development of unevenness is suppressed, and the occurrence of rough skin of the molded product is suppressed. On the other hand, if the metal plate having the fcc structure satisfies the above (b), appropriate strain concentration due to molding is realized in the range where the area fraction of the {001} crystal grains is 0.20 or more and 0.45 or less. Will be done. In the range where the surface integral of {001} crystal grains is less than 0.20, even if unevenness develops, it is difficult to be recognized as rough skin of the molded product. Therefore, the occurrence of rough skin of the molded product is suppressed.

Further, under the condition (b), the average crystal grain size of the {001} crystal grains is 15 μm or less, but it is preferably 10 μm or less from the viewpoint of suppressing rough skin. The smaller the average crystal grain size of the {001} crystal grains, the more preferable it is from the viewpoint of suppressing rough skin, but it is preferably 1 μm or more. This is because the orientation is controlled by recrystallization, so it is difficult to achieve both ultrafine grain size and orientation control.

The average crystal grain size of {001} crystal grains is measured by the following method. Observe the surface of the metal plate using SEM and select the measurement area arbitrarily. Using the EBSD method, {001} grains are selected in each measurement region. Two test lines are drawn on each of the selected {001} grains. By obtaining the arithmetic mean of the two test lines, the average crystal grain size of the {001} crystal grains can be obtained. Specifically, it is as follows. FIG. 10 is a schematic diagram illustrating a method of obtaining an average crystal grain size from the analysis results by the EBSD method. With reference to FIG. 10, a test line 5 passing through the center of gravity of each {001} crystal grain 3 is drawn so that all {001} crystal grains 3 have the same orientation. Further, a test line 6 passing through the center of gravity of each {001} crystal grain 3 is drawn so as to be orthogonal to the test line 5. The arithmetic mean of the lengths of the two test lines 5 and 6 is taken as the crystal grain size of the crystal grains. The arithmetic mean of the crystal grain sizes of all {001} crystal grains 3 in an arbitrary measurement region is defined as the average crystal grain size.

The surface integral of the {001} crystal grains is measured by the following method. Using SEM, observe the cross section of the metal plate (cut surface along the plate thickness direction), and any region including the region (linear region) corresponding to the surface of the metal plate (surface facing the plate thickness direction). Select the measurement area. The {001} grain 3 is selected using the EBSD method. In each field of view, the area fraction of the {001} crystal grain 3 is obtained by calculating the area fraction of the {001} crystal grain 3 in the region corresponding to the surface of the metal plate (the surface facing the plate thickness direction). .. Then, the average of the area divisions of the {001} crystal grains 3 in the arbitrary measurement region is defined as the area division of the {001} crystal grains.
Here, when a plating layer or the like is formed on the surface of the metal plate, the area of the {001} crystal grains 3 in the region (linear region) corresponding to the surface of the metal plate in contact with the plating layer or the like. Measure the fraction.

[Crystal grains other than {111} crystal grains]
When performing a molding process that causes biaxial tensile deformation, on the surface of a metal plate having an fcc structure, crystal grains ({111} crystal grains) having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate. ) (That is, crystal grains having a crystal orientation exceeding 15 ° from the {111} plane parallel to the surface of the metal plate) satisfy the following (A) or (B).
(A) The surface integral of the crystal grains other than the {111} crystal grains is 0.25 or more and 0.55 or less.
(B) The area division of the crystal grains other than the {111} crystal grains is 0.55 or less, and the average crystal grain size is 15 μm or less.

As described above, in the case of a metal plate having an fcc structure, crystal grains other than {111} crystal grains are vulnerable to the stress of biaxial tensile deformation (particularly unequal biaxial tensile deformation close to a plane strain deformation field) (that is, {111). } Crystal grains are the strongest). Therefore, with a large processing amount (a processing amount in which at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less), a metal plate forming process in which biaxial tensile deformation occurs, such as deep drawing and overhanging, is performed. If carried out, strain is likely to be concentrated on the crystal grains other than the {111} crystal grains, and unevenness is likely to develop in the crystal grains other than the {111} crystal grains. When the proportion of crystal grains other than {111} crystal grains is large, strain is likely to be concentrated and unevenness is likely to develop. On the other hand, when the proportion of crystal grains other than {111} crystal grains is small, there are few places where strain is concentrated, and local deformation is dispersed in {111} crystal grains, so that unevenness is likely to develop. .. However, even when the proportion of crystal grains other than {111} crystal grains is small, if the size of the crystal grains other than {111} crystal grains is sufficiently small, the region that is locally deformed by the {111} crystal grains becomes small and uneven. Even if it develops, it becomes fine and it becomes difficult to recognize it as rough skin of the molded product.

Therefore, if the metal plate having the fcc structure satisfies the above (A), an appropriate strain concentration due to the molding process is realized. Therefore, the development of unevenness is suppressed, and the occurrence of rough skin of the molded product is suppressed. On the other hand, if the metal plate having the fcc structure satisfies the above (B), the area fraction of the crystal grains other than the {111} crystal grains is in the range of 0.25 or more and 0.55 or less, and the strain is appropriate due to the molding process. Concentration is realized. In the range where the surface integral of the crystal grains other than the {111} crystal grains is less than 0.25, even if the unevenness develops, it is difficult to be recognized as rough skin of the molded product. Therefore, the occurrence of rough skin of the molded product is suppressed.

Further, under the condition (B), the average crystal grain size of the crystal grains other than the {111} crystal grains is 15 μm or less, but it is preferably 10 μm or less from the viewpoint of suppressing rough skin. The smaller the average crystal grain size of the crystal grains other than the {111} crystal grains, the more preferable it is from the viewpoint of suppressing rough skin, but it is preferably 1 μm or more. This is because the orientation is controlled by recrystallization, so it is difficult to achieve both ultrafine grain size and orientation control.

The average crystal grain size of the crystal grains other than the {111} crystal grain is measured by the same method as the average crystal grain size of the {001} crystal grain except that the crystal grain to be measured is different.
On the other hand, the area division of the crystal grains other than the {111} crystal grains is measured by the same method as the {001} crystal grains except that the crystal grains to be measured are different.

(Molding)
The first molded product of the present invention is a molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs. Then, in the first molded product of the present invention, when the maximum plate thickness of the molded product is D1 and the minimum plate thickness of the molded product is D2, the formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30. When the condition or the maximum hardness of the molded product is H1 and the minimum hardness of the molded product is H2, the condition of the formula: 15 ≦ (H1-H2) / H1 × 100 ≦ 40 is satisfied, and on the surface of the molded product. The condition of the following (c) or (d) is satisfied.
(C) The area division of crystal grains ({001} crystal grains) having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product is 0.20 or more and 0.35 or less.
(D) Crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product ({001} crystal grains) have an area division of 0.45 or less and an average crystal grain size of 15 μm. It is as follows.

On the other hand, the second molded product of the present invention is a molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs. Then, in the second molded product of the present invention, when the maximum plate thickness of the molded product is D1 and the minimum plate thickness of the molded product is D2, the formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30. When the condition or the maximum hardness of the molded product is H1 and the minimum hardness of the molded product is H2, the condition of the formula: 15 ≦ (H1-H2) / H1 × 100 ≦ 40 is satisfied, and on the surface of the molded product. The following conditions (C) or (D) are satisfied.
(C) When the area fraction of the crystal grains other than the crystal grains ({111} crystal grains) having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product is 0.25 or more and 0.55 or less. is there.
(D) Crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product ({111} crystal grains), the area division is 0.55 or less, and the average crystal The particle size is 15 μm or less.

Here, the metal plate having the fcc structure is synonymous with the metal plate used in the first and second methods for producing the molded product of the present invention. Then, the molded product of this metal plate is subjected to a molding process that causes biaxial tensile deformation.
The method for confirming that the molded product is subjected to a molding process that causes biaxial tensile deformation is as follows.
The three-dimensional shape of the molded product is measured, a mesh for numerical analysis is produced, and the process from the plate material to the three-dimensional shape is derived by inverse analysis by a computer. Then, the ratio of the maximum principal strain to the minimum principal strain (β) in each mesh is calculated. From this calculation, it can be confirmed that the molding process that causes biaxial tensile deformation is performed.
For example, the three-dimensional shape of the molded product is measured by a three-dimensional measuring machine such as Comet L3D (Tokyo Trading Techno System Co., Ltd.). Based on the obtained measurement data, the mesh shape data of the molded product is obtained. Next, using the obtained mesh shape data, numerical analysis of the one-step method (work hardening calculation tool "HYCRASH (JSOL Co., Ltd.)", etc.) is performed to make a flat plate once based on the shape of the molded product. expand. From the shape information such as the elongation and bending state of the molded product at that time, the plate thickness change and residual strain of the molded product are calculated. By this calculation, it can be confirmed that the molding process that causes biaxial tensile deformation is performed.

Further, satisfying the condition of the formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30, the molded product is molded by the molding process in which at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less. Can be considered to be.
That is, the maximum plate thickness D1 of the molded product can be regarded as the plate thickness of the metal plate before the molding process, and the minimum plate thickness D2 of the molded product is the metal plate (molding) at the portion where the plate thickness reduction rate is the largest after the molding process. It can be regarded as the plate thickness of the product).

On the other hand, the condition of the formula: 15 ≦ (H1-H2) / H1 × 100 ≦ 40 is also satisfied, and the molded product is molded by the molding process in which at least a part of the metal plate has a plate thickness reduction rate of 10% or more and 30% or less. Can be considered to be. This is due to the fact that work hardening (that is, Vickers hardness) increases as the processing amount (thickness reduction) of the molding process increases.
That is, the portion having the maximum hardness H1 of the molded product can be regarded as the hardness of the metal plate (molded product) of the portion having the largest plate thickness reduction rate after the molding process, and the minimum hardness H2 of the molded product is the hardness before the molding process. It can be regarded as the hardness of the metal plate.

The hardness is measured according to the Vickers hardness measuring method described in the JIS standard (JIS Z 2244). However, the measurement of hardness is not limited to this method, and a method of measuring hardness by another method and converting it to Vickers hardness using a hardness conversion table may be adopted.

Further, under the conditions indicated by (c) or (d) above and the conditions indicated by (C) or (D) above, the area fraction and average crystal grain size of {001} crystal grains on the surface of the molded product, and the average crystal grain size, and The area fraction and the average crystal grain size of the crystal grains other than the {111} crystal grains on the surface of the molded product are measured at the portion where the maximum plate thickness D1 or the minimum hardness H2 of the molded product is obtained.
The conditions shown in (c) or (d) above are the conditions shown in (a) or (b) above described in the first method for producing a molded product of the present invention, and the metal plate before molding. Instead, they have the same meaning except that the area fraction of {001} crystal grains on the surface of the molded product and the average crystal grain size are the conditions.
Similarly, the conditions indicated by the above (C) or (D) are the conditions indicated by the above (A) or (B) described in the second method for producing a molded product of the present invention, and the metal before molding. It is synonymous except that the area fraction and the average crystal grain size of the crystal grains other than the {111} crystal grains on the surface of the molded product are used instead of the plate.

As described above, the first and second molded articles of the present invention shall be regarded as molded articles formed by the first and second methods for producing the molded articles of the present invention by satisfying the above requirements. Can be done. The first and second molded products of the present invention are molded products of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs, and the formula: 10 ≦ (D1-D2) / D1. Even if the molded product satisfies the condition of × 100 ≦ 30 or the condition of the formula: 10 ≦ (H1-H2) / H1 × 100 ≦ 30, the occurrence of rough skin is suppressed and the molded product has excellent design. Become.

<First reference example>
[Molding of molded products]
Next, the steel plate having the characteristics shown in Table 2 (steel plate having a bcc structure) is then overhanged, and as shown in FIG. 11, the diameter R = 150 mm of the top plate portion 20A of the molded product 20. A dish-shaped molded product No. having a height H of the molded product 20 of 18 mm and an angle θ of the vertical wall portion 20B of the molded product 20 of 90 ° C. 1 to 5, 8 and 10 were molded. In addition, except that the height H of the molded product 20 was H = 15 mm, the molded product No. In the same manner as 1 to 5, 8 and 10, molded product No. 6 to 7 and 9 were molded.
In this molding, the plate thickness reduction rate of the steel plate to be the top plate portion 20A (in FIG. 11, the plate thickness reduction rate of the evaluation portion A (center portion of the top plate portion 20A) of the top plate portion 20A) is shown in Table 2. It was carried out with the amount of processing that was the rate of decrease in plate thickness shown.

[Evaluation methods]
The following measurement tests and visual evaluations were carried out on each of the obtained steel sheets and each molded product. The results are shown in Tables 2 and 3.

[Measurement test of average crystal grain size]
A measurement test of the average crystal grain size of {001} crystal grains was carried out on the steel sheet. The EBSD method was used for the measurement test. FIG. 12 is a schematic view of the steel plate observed from above. With reference to FIG. 12, three measurement regions 4 of 1 mm square were arbitrarily selected from the edge to the center in the width direction of the steel sheet. In each measurement region 4, crystal grains ({001} crystal grains 3) having a crystal orientation within 15 ° from the {001} plane parallel to the steel sheet surface on the surface of the steel sheet were selected.

As described above, the average crystal grain size of the {001} crystal grains 3 was calculated. The measurement was performed on all {001} crystal grains 3 in the three measurement regions 4. The arithmetic mean of the crystal grain sizes of the obtained {001} crystal grains 3 was taken as the average crystal grain size. The average crystal grain size of the {001} crystal grains 3 on the surface of the molded product is also the same as the average crystal grain size of the {001} crystal grains 3 of the steel sheet.

[Surface integral measurement test]
A measurement test of the surface integral of {001} crystal grains was carried out on the steel sheet. As described above, the measurement region 4 was selected from the steel sheet, and the {001} crystal grains 3 were selected using the EBSD method. In each field of view, the surface integral of the {001} crystal grain 3 was calculated, and the average value was calculated. The area fraction of the {001} crystal grains 3 of the molded product is also the same as the area fraction of the {001} crystal grains 3 of the steel sheet.

[Measurement test of plate thickness]
A plate thickness measurement test was performed on the molded product. Specifically, a computer-based molding simulation of the molded product was carried out to identify the portion where the plate thickness was the maximum and the minimum. After that, the plate thickness of the molded product was measured using a plate thickness gauge at each of the parts where the plate thickness was the maximum and the minimum. As a result, the maximum plate thickness D1 and the minimum plate thickness D2 were obtained. However, the maximum plate thickness D1 is the maximum plate thickness of the molded product (the entire molded product), and the minimum plate thickness D2 is the minimum plate thickness of the evaluation part of the molded product.

[Hardness measurement test]
A hardness measurement test was performed on the molded product. Specifically, a computer-based molding simulation of the molded product was carried out to identify the sites where the equivalent plastic strain was maximum and minimum. Then, the hardness of the molded product was measured according to the JIS standard (JIS Z 2244) at each of the parts where the plate thickness was the maximum and the minimum. As a result, the maximum hardness H1 and the minimum hardness H2 were obtained. However, the maximum hardness H1 was the maximum hardness of the molded product (the entire molded product), and the minimum hardness H2 was the minimum hardness of the evaluation part of the molded product.

[Concavo-convex height measurement test]
A measurement test of the height of unevenness on the surface of the molded product was performed on the molded product. Specifically, the evaluation part of the molded product was cut out, and the unevenness in the longitudinal direction was measured with a contact-type roughness meter. In order to confirm the crystal orientation, the portion where the unevenness was most prominent was cut by using a cross section polisher process, and the relationship between the crystal orientation of the surface layer and the unevenness was analyzed.

[Visual evaluation]
Originally, electrodeposition coating is performed after chemical conversion treatment, but as a simple evaluation method, after uniformly coating the surface of the molded product with lacquer spray, visually observe it, and according to the following criteria, the degree of occurrence of rough skin and the evaluation surface I investigated the sharpness.
Furthermore, as another parameter indicating the superiority or inferiority of the surface texture, the value of the arithmetic mean swell Wa was measured with a laser microscope manufactured by Keyence Corporation. The measurement conditions were an evaluation length of 1.25 mm and a cutoff wavelength of λc of 0.25 mm. Then, the profile on the longer wavelength side than the cutoff wavelength λc was evaluated.
The evaluation criteria are as follows.
A (◎): A pattern is not visually confirmed on the surface of the evaluation part of the top plate of the molded product, and the surface is glossy (Wa ≤ 0.5 μm). It is more desirable as an automobile outer panel part, and can also be used as an automobile outer panel component.
B (○): A pattern is not visually confirmed on the surface of the evaluation part of the top plate of the molded product, but the surface is not glossy (0.5 μm <Wa ≦ 1.0 μm). It can be used as an automobile part.
C (Δ): A pattern is visually confirmed on the surface of the evaluation part of the top plate of the molded product, but the surface is glossy (1.0 μm <Wa ≦ 1.5 μm). It cannot be used as an outer panel part of an automobile.
D (x): A pattern is visually confirmed on the surface of the evaluation part of the top plate of the molded product, and the surface is not glossy (1.5 μm <Wa). It cannot be used as an automobile part.

From the above results, a molded product No. corresponding to the comparative reference example obtained by molding a steel plate having a bcc structure. Compared with 1, 6 and 9, the molded product No. corresponding to the reference example. It can be seen that 2 to 5, 7, 8 and 10 are excellent in design because rough skin is suppressed.
Here, the molded product No. corresponding to the reference example. 2, 3, Molded product No. corresponding to the comparative reference example. Schematic diagrams showing the cross-sectional microstructure and surface unevenness of No. 1 are shown in FIGS. 13 to 15. 13 to 15 are schematic views obtained by analyzing a cross section of a molded product by the EBSD method. In FIGS. 13 to 15, ND indicates the plate thickness direction and TD indicates the plate width direction.
From the comparison of FIGS. 13 to 15, the molded article No. corresponding to the comparative reference example. Compared to No. 1, the molded product No. corresponding to the reference example. It can be seen that in Nos. 2 and 3, the height of unevenness on the surface of the molded product is low, rough skin is suppressed, and the design is excellent. However, from the comparison between FIGS. 13 and 14, the molded product No. Compared to No. 2, molded product No. In No. 3, the uneven height of the surface of the molded product is high, but it can be seen that rough skin is suppressed and the design is excellent. This is because even if the surface unevenness of the molded product is high or equivalent, if the concave portion is deep and fine, it may be difficult to be recognized as rough skin (molded product No. 6 and molded product No. 7). See also comparison with).
Molded product No. corresponding to the reference example. No. 7 and the molded product No. corresponding to the reference example. From the comparison with 9, even if the area fraction of the {001} crystal grains is as low as less than 0.20, if the average crystal grain size of the {001} crystal grains is less than 15 μm, rough skin is suppressed and the design is excellent. You can see that.
Molded product No. corresponding to the reference example. From No. 10, it can be seen that even if the area fraction of the {001} crystal grains is as high as 0.45, if the average crystal grain size of the {001} crystal grains is less than 15 μm, rough skin is suppressed and the design is excellent.

<Second reference example>
[Molding of molded products]
Next, a steel sheet having the characteristics shown in Table 4 (a steel sheet having a bcc structure) was overhanged. As a result, as shown in FIG. 11, a dish having a diameter R = 150 mm of the top plate portion 20A of the molded product 20, a height H = 18 mm of the molded product 20, and an angle θ = 90 ° C. of the vertical wall portion 20B of the molded product 20. Molded product No. 101-105 and 108 were molded. In addition, except that the height H of the molded product 20 was H = 15 mm, the molded product No. In the same manner as in 101-105 and 108, the molded product No. 106-107, 109, 125 were molded.
In this molding, the plate thickness reduction rate of the steel plate to be the top plate portion 20A (in FIG. 11, the plate thickness reduction rate of the evaluation portion A (center portion of the top plate portion 20A) of the top plate portion 20A) is shown in Table 4. It was carried out with the amount of processing that was the rate of decrease in plate thickness shown.

Further, in FIG. 11, the plate thickness reduction rate of the evaluation portion B (the central portion between the center and the edge of the top plate portion 20A) of the top plate portion plate 20A of the molded product 20 is the molded product No. Except that the height H of the molded product 20 was adjusted so as to be the same as the plate thickness reduction rate of 101 to 109 and 125 (the plate thickness reduction rate of the evaluation portion A of the top plate 20A in FIG. 11). Molded product No. In the same manner as in 101-109 and 125, the molded product No. 110-118 and 126 were molded.

Further, in FIG. 11, the plate thickness reduction rate of the evaluation portion C (edge portion of the top plate portion 20A) of the top plate portion plate 20A of the molded product 20 is the molded product No. Except that the height H of the molded product 20 was adjusted so as to be the same as the plate thickness reduction rate of 101 to 109 and 125 (the plate thickness reduction rate of the evaluation portion A of the top plate 20A in FIG. 11). Molded product No. In the same manner as in 101-109 and 125, the molded product No. 119-124, 127 were molded.

Here, in the molding of the molded product, the scribed circle is transferred to the surface of the steel plate corresponding to the evaluation part of the molded product, and the shape change of the scribed circle before and after molding (before and after deformation) is measured. The maximum principal strain and the minimum principal strain were measured. From these values, the deformation ratio β in the evaluation section of the molded product was calculated.

[Evaluation methods]
For each steel plate used and each molded product obtained, 1) average crystal grain size and area fraction of crystal grains other than {111} crystal grains, 2) measurement test of plate thickness, 3) measurement of hardness The test, 4) unevenness height measurement test, and 5) visual evaluation were performed according to the first reference example. The results are shown in Tables 4 and 5.

From the above results, the molded product No. corresponding to the comparative reference example. Compared with 101, 106, 109-110, 115, 118-119, 124, the molded product No. corresponding to the reference example. It can be seen that 102 to 105, 107 to 108, 111 to 114, 116 to 117, 120 to 123, 125 to 127 are excellent in design while suppressing rough skin.
Here, the molded product No. corresponding to the reference example. 102, 103, molded product No. corresponding to the comparative reference example. Schematic diagrams showing the cross-sectional microstructure and surface unevenness of 101 are shown in FIGS. 16 to 18. 16 to 18 are schematic views of a cross section of a molded product analyzed by the EBSD method. In FIGS. 16 to 18, ND indicates the plate thickness direction and TD indicates the plate width direction.
From the comparison of FIGS. 16 to 18, the molded article No. corresponding to the comparative reference example. Compared to 101, the molded product No. corresponding to the reference example. It can be seen that 102 and 103 have a low uneven height on the surface of the molded product, suppress rough skin, and are excellent in design. However, from the comparison between FIGS. 16 and 17, the molded product No. Compared to 102, molded product No. It can be seen that No. 103 has a high unevenness on the surface of the molded product, but is excellent in designability by suppressing rough skin. This is because even if the surface unevenness of the molded product is high or equivalent, if the concave portion is deep and fine, it may be difficult to be recognized as rough skin (molded product No. 106 and molded product No. 107). See also comparison with).
From the above results, it can be seen that in the molded product corresponding to the reference example obtained by molding the steel plate having the bcc structure, the rough skin of the molded product is suppressed in the biaxial deformation field.

<Example>
[Molding simulation of molded products]
Using the cross section of the metal plate having the bcc structure (for example, FIGS. 13 to 18) used in the reference example, the crystal grains of the cross section of the metal plate having the fcc structure were modeled. Then, the particle size of the crystal grains in the cross section of the metal plate having the fcc structure is changed, and the average area fraction of the crystal grains other than the {001} crystal grains or the {111} crystal grains is changed, and Tables 6 to 6 are shown. A virtual material having the characteristics shown in 7 was modeled.
Next, a molding simulation corresponding to the molding of the molded product 20 shown in FIG. 11 was carried out on the modeled virtual material by overhanging. That is, with respect to the modeled virtual material, the plate thickness reduction rate of the virtual material that becomes the top plate portion 20A of the molded product (in FIG. 11, the plate of the evaluation portion A of the top plate portion 20A (the central portion of the top plate portion 20A)). A molding simulation was carried out in which "equivalent plastic strain" corresponding to (thickness reduction rate) was applied.
Specifically, first, in order to impart a displacement of "equivalent plastic strain" shown in Tables 6 to 7 to the virtual material, a finite press forming simulation (hereinafter referred to as a press forming simulation) of the model shape shown in FIG. 8B is performed. It was carried out by the element analysis method. As a result, "maximum plate thickness D1 (corresponding to the maximum plate thickness D1 of the molded product)", "minimum plate thickness D2 (corresponding to the minimum plate thickness D2 of the molded product)", and maximum in the virtual material after the press molding simulation are performed. The hardness H1 (corresponding to the maximum hardness H1 of the molded product) and the "minimum hardness H2 (corresponding to the minimum hardness H2 of the molded product)" were calculated.
Then, as a molding simulation of the virtual material corresponding to this press molding simulation, a displacement of "equivalent plastic strain" shown in Tables 6 to 7 is applied to the left and right, front, and depth directions of the cross section of the virtual material. A molding simulation for axial tensile deformation (hereinafter referred to as a molding simulation) was carried out by a crystal-plastic finite element analysis method.

Here, the "maximum plate thickness D1 (corresponding to the maximum plate thickness D1 of the molded product)" and the "minimum plate thickness D2 (corresponding to the minimum plate thickness D2 of the molded product)" in the virtual material after the press molding simulation are performed are It was as follows.
The maximum plate thickness D1 is the plate thickness at the place where the plate thickness is maximum in the plate surface of the press-formed product.
The minimum plate thickness D2 is the plate thickness at the place where the plate thickness is the minimum in the plate surface of the press-formed product.

Further, the "maximum hardness H1 (corresponding to the maximum hardness H1 of the molded product)" and the "minimum hardness H2 (corresponding to the minimum hardness H2 of the molded product)" in the virtual material after the press molding simulation are performed are as follows. ..
The maximum hardness H1 was calculated by the following formula from the average yield strength YP ₁ (MPa) of the virtual material before molding.
-Formula: Maximum hardness H1 = YP ₁ (MPa) / 3
For the minimum hardness H2, the hardness after molding (after work hardening) was calculated from the average yield strength YP ₂ (MPa) of the virtual material by the following formula.
-Formula: Maximum hardness H2 = YP ₂ (MPa) / 3

However, the hardness before molding was calculated as the average yield strength YP ₁ (MPa) of the virtual material based on the yield strength of the 6000 series aluminum alloy plate and its crystal orientation dependence as the virtual material.
Also, the hardness after shaping (after work hardening) average yield strength of the virtual material YP 2 _(MPa) is in a plate surface of the press molded product by the press forming simulation input the mechanical properties of 6000 series aluminum alloy plate It was calculated using the equivalent stress value at the place where the plate thickness is the minimum.

Then, the following evaluation was carried out for the virtual material after the molding simulation was carried out. The results are shown in Tables 6 and 7.

(Uneven height)
The height of unevenness on the surface of the virtual material after the molding simulation was performed was calculated by the following method. The surface profile of the virtual material after the molding simulation was performed was used as the cross-sectional curve of the virtual material, and was calculated from the maximum and minimum values of the cross-sectional curve.

(Arithmetic mean height Pa of cross-section curve)
With respect to the surface texture of the virtual material after the molding simulation was performed, the arithmetic average height Pa of the cross-sectional curve was calculated after obtaining the cross-sectional curve of the virtual material. Then, it was evaluated according to the following evaluation criteria.
The arithmetic mean height Pa of the cross-sectional curve is the arithmetic mean height specified in JIS B0601 (2001). The measurement conditions are as follows.
・ Evaluation length: 1 mm
・ Standard length: 1 mm

The evaluation criteria for the surface texture of the virtual material are as follows.
A (◎): Pa ≤ 0.5 μm (more desirable as an automobile outer panel part, and can also be used as an outer panel part of a luxury car.)
B (○): 0.5 μm <Pa ≦ 1.0 μm (can be used as an automobile part)
C (Δ): 1.0 μm <Pa ≦ 1.5 μm (cannot be used as an outer panel part of an automobile.)
D (x): 1.5 μm <Pa (cannot be used as an automobile part)

From the above results, from the above results, No. Compared with A1, A6, A9, A101, A106, and A109, No. It can be seen that A2 to A5, A7, A8, A10, A102 to A105, A107, A108, and A110 are excellent in design by suppressing rough skin.
Here, in FIG. 19, No. For the virtual materials after molding simulation of A1 to A10 (indicated by the numbers 1 to 10 circled in FIG. 19), the result of Pa evaluation and the average crystal grain size and crystal grain size of {001} crystal grains. The relationship is shown.
As a result of performing a molding simulation in which biaxial deformation occurs in a virtual material having a fcc structure as described above, a metal plate having a fcc structure has a particle size of {001} crystal grains as well as a steel plate having a bcc structure. It can be seen that by controlling the area fraction, or the particle size and area fraction of the {111} crystal grains, the rough skin of the molded product is suppressed even if the molding process that causes biaxial deformation is performed.

3 {001} crystal grains 4 {001} neighboring crystal grains

Claims (6)

A metal plate having an fcc structure and satisfying the following conditions (a) or (b) on the surface of the metal plate undergoes biaxial tensile deformation, and at least a part of the metal plate has a plate thickness reduction rate of 10. A method for manufacturing a molded product, in which a molded product is manufactured by performing a molding process of% or more and 30% or less.
(A) The area division of crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate is 0.20 or more and 0.35 or less.
(B) Crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate have an area division of 0.45 or less and an average crystal grain size of 15 μm or less. A metal plate having an fcc structure and satisfying the following conditions (A) or (B) on the surface of the metal plate undergoes biaxial tensile deformation, and at least a part of the metal plate has a plate thickness reduction rate of 10. A method for manufacturing a molded product, in which a molded product is manufactured by performing a molding process of% or more and 30% or less.
(A) The area division of crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate is 0.25 or more and 0.55 or less.
(B) Crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate have an area division of 0.55 or less and an average crystal grain size of 15 μm or less. is there. A molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs.
When the maximum plate thickness of the molded product is D1 and the minimum plate thickness of the molded product is D2, the condition of the formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30 is satisfied.
A molded product that satisfies the following conditions (c) or (d) on the surface of the molded product.
(C) The area fraction of the crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product is 0.20 or more and 0.35 or less.
(D) Crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product have an area fraction of 0.45 or less and an average crystal grain size of 15 μm or less. A molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs.
When the maximum plate thickness of the molded product is D1 and the minimum plate thickness of the molded product is D2, the condition of the formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30 is satisfied.
A molded product that satisfies the following conditions (C) or (D) on the surface of the molded product.
(C) The area fraction of crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product is 0.25 or more and 0.55 or less.
(D) Crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product have an area division of 0.55 or less and an average crystal grain size of 15 μm or less. is there. A molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs.
When the maximum hardness of the molded product is H1 and the minimum hardness of the molded product is H2, the condition of the formula: 15 ≦ (H1-H2) / H1 × 100 ≦ 40 is satisfied.
A molded product that satisfies the following conditions (c) or (d) on the surface of the molded product.
(C) The area fraction of the crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product is 0.20 or more and 0.35 or less.
(D) Crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the molded product have an area fraction of 0.45 or less and an average crystal grain size of 15 μm or less. A molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation occurs.
When the maximum hardness of the molded product is H1 and the minimum hardness of the molded product is H2, the condition of the formula: 15 ≦ (H1-H2) / H1 × 100 ≦ 40 is satisfied.
A molded product that satisfies the following conditions (C) or (D) on the surface of the molded product.
(C) The area fraction of crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product is 0.25 or more and 0.55 or less.
(D) Crystal grains other than those having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product have an area division of 0.55 or less and an average crystal grain size of 15 μm or less. is there.