JP2018118260A - Method for production of molded article, and molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molded article production method capable of obtaining the molded article suppressing occurrence of rough surface and excellent in designability.SOLUTION: There is provided a method for production of a molded article comprising applying such fabrication that a biaxial tensile deformation is generated and at least a part of a metal plate becomes 10% or more but 30% or less in plate thickness decrement rate to the metal plate which has an fcc structure and satisfies the conditions of the following (a) or (b) on the surface of the metal plate: (a) the area fraction of a crystal grain having a crystal orientation within 15° from a (001) plane parallel to the surface of the metal plate is 0.20 or more but 0.35 or less; and (b) the area fraction of the crystal grain having the crystal orientation within 15° from the (001) plane parallel to the metal plate surface is 0.45 or less, and an average crystal grain size is 15 μm or less. A molded article satisfies the above (a) or (b).SELECTED DRAWING: None

Description

  The present invention relates to a method for manufacturing a molded article and a molded article.

  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. However, fine irregularities are likely to occur on the surface of the molded product as the amount of processing increases, resulting in rough skin. There is a problem that the aesthetic appearance is impaired.

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

: Patent No. 5683193

  However, Patent Document 1 only shows that ridging is suppressed in a metal plate forming process 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 stretch forming.

On the other hand, it is required to manufacture a molded product having a complicated shape in recent years also in the forming processing of a metal plate in which biaxial tensile deformation occurs, such as deep drawing forming and stretch forming. However, if a metal plate is molded with a large amount of processing (a processing amount at which the thickness reduction rate of the metal plate is 10% or more), unevenness develops on the surface of the molded product, which causes rough skin and impairs the appearance. The current situation is causing problems.
For the above reasons, for example, the products of conventional outer plates of automobiles are produced by limiting the amount of strain applied to the product surface to a processing amount that results in a metal plate thickness reduction rate of less than 10%. That is, there are restrictions on the processing conditions in order to avoid rough skin. However, more complex automotive outer plate product shapes are required, and there is a demand for a method that can achieve both a reduction in the thickness of the metal plate of 10% or more and the suppression of rough skin during forming.

Accordingly, in view of the above circumstances, the problem of the present invention is that biaxial tensile deformation occurs with respect to a metal plate having an fcc structure, and at least a part of the metal plate has a thickness reduction rate of 10% to 30%. An object of the present invention is to provide a method for producing a molded product in which the occurrence of rough skin is suppressed and a molded product having excellent design properties can be obtained even when molding is performed.
Another subject 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, wherein the maximum thickness of the molded product is D1, and the minimum thickness of the molded product is Where D2 is the formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30, or the maximum hardness of the molded product is H1, and the minimum hardness of the molded product is H2, the formula: 15 ≦ ( Even a molded product that satisfies the condition of (H1-H2) / H1 × 100 ≦ 40 is to provide a molded product that suppresses the occurrence of rough skin and is excellent in design.

  In order to manufacture a molded product having a complicated shape in recent years, the inventors have determined the surface properties when forming a metal plate with a large processing amount (processing amount that achieves a plate thickness reduction rate of 10% or more of the metal plate). investigated. As a result, the inventors obtained the following knowledge. 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 the bcc structure are preferentially deformed to develop irregularities. Therefore, the inventors focused on the area fraction and 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 a molded product having excellent design properties can be obtained by suppressing the development of irregularities and suppressing the occurrence of rough skin by the area fraction and average crystal grain size of these crystal grains.

  Furthermore, the inventors obtained the following knowledge. Under biaxial tensile deformation, crystal grains other than crystal grains having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate having the bcc structure are preferentially deformed and unevenness is developed. Therefore, the inventors focused on the area fraction of crystal grains other than crystal grains 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, by the area fraction of these crystal grains, it is possible to obtain a molded product that suppresses the development of unevenness, suppresses the occurrence of rough skin, and has an excellent design.

The inventors then assumed a slip system of a metal plate having an fcc structure, and investigated the influence of crystal orientation on the rough surface after processing of the metal plate by numerical analysis. As a result, the following knowledge was obtained. Similar to the metal plate having the bcc structure, the metal plate having the fcc structure is preferentially deformed by crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate under biaxial tensile deformation. And unevenness develops. Further, under biaxial tensile deformation, crystal grains other than crystal grains having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate are preferentially deformed, and irregularities develop.
Therefore, the inventors have also found that in the metal plate having the 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. Attention was paid to the area fraction of crystal grains other than crystal grains having a crystal orientation within 15 ° from the parallel {111} plane. As a result, the inventors have found that, by the area fraction of these crystal grains, it is possible to obtain a molded product that suppresses the development of unevenness and suppresses the occurrence of rough skin and has excellent design properties.

  The gist of the present invention is as follows.

<1>
Biaxial tensile deformation occurs with respect to a metal plate having an fcc structure and satisfying the following condition (a) or (b) on the surface of the metal plate, and at least a part of the metal plate has a thickness reduction rate of 10 The manufacturing method of the molded article which gives the shaping | molding process used as% or more and 30% or less, and manufactures a molded article.
(A) The area fraction 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) The crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate have an area fraction of 0.45 or less and an average crystal grain size of 15 μm or less.
<2>
Biaxial tensile deformation occurs with respect to a metal plate having an fcc structure and satisfying the following condition (A) or (B) on the surface of the metal plate, and at least a part of the metal plate has a thickness reduction rate of 10 The manufacturing method of the molded article which gives the shaping | molding process used as% or more and 30% or less, and manufactures a molded article.
(A) The area fraction of crystal grains other than crystal grains 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) The area fraction of crystal grains other than crystal grains having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate is 0.55 or less and the average crystal grain size is 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 thickness of the molded product is D1 and the minimum 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 condition (c) or (d) on the surface of the molded product.
(C) The area fraction of 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) The 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 thickness of the molded product is D1 and the minimum 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 condition (C) or (D) on the surface of the molded product.
(C) The area fraction of crystal grains other than 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.
(D) The area fraction of crystal grains other than crystal grains having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product is 0.55 or less and the average crystal grain size is 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 condition (c) or (d) on the surface of the molded product.
(C) The area fraction of 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) The 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 condition (C) or (D) on the surface of the molded product.
(C) The area fraction of crystal grains other than 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.
(D) The area fraction of crystal grains other than crystal grains having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product is 0.55 or less and the average crystal grain size is 15 μm or less. is there.

According to the present invention, even when a metal plate having an fcc structure is subjected to a forming process in which biaxial tensile deformation occurs and at least a part of the metal plate has a thickness reduction rate of 10% to 30%. In addition, it is possible to provide a method for producing a molded product in which the occurrence of rough skin is suppressed and a molded product having excellent design properties can be obtained.
According to another aspect of the present invention, a metal plate molded product having an fcc structure and having a biaxial tensile deformation, wherein the maximum thickness of the molded product is D1, and the minimum thickness of the molded product is D1. Where D2 is the formula: 10 ≦ (D1-D2) / D1 × 100 ≦ 30, or the maximum hardness of the molded product is H1, and the minimum hardness of the molded product is H2, the formula is 15 ≦ Even in the case of a molded product that satisfies the condition of (H1-H2) / H1 × 100 ≦ 30, it is possible to provide a molded product that is suppressed in occurrence of rough skin and has excellent design properties.

FIG. 1 is a view of the surface of a metal plate (metal plate having a bcc structure) after a bulge forming test is observed using an SEM. FIG. 2 is a view of the surface of a metal plate (metal plate having a bcc structure) that has been further electropolished after the bulge forming test was observed using an SEM. FIG. 3A is a schematic diagram when the surface of a metal plate (metal plate having a bcc structure) with less development of unevenness after a bulge forming test is analyzed by the EBSD method. FIG. 3B is a schematic diagram showing surface irregularities of the metal plate (metal plate having a bcc structure) in the A1-A2 cross section of FIG. 3A. FIG. 4A is a schematic diagram when the surface of a metal plate (a metal plate having a bcc structure) with many unevenness development after the bulge forming test is analyzed by the EBSD method. FIG. 4B is a schematic diagram showing surface irregularities of the metal plate (metal plate having a bcc structure) in the B1-B2 cross section of FIG. 4A. FIG. 5A is a schematic view when the surface of a metal plate (a metal plate having a bcc structure) with many unevenness development after a bulge forming test is analyzed by the EBSD method. FIG. 5B is a schematic diagram showing surface irregularities 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 "the crystal grain which has a crystal orientation within 15 degrees from the {001} plane parallel to the surface of a metal plate." FIG. 7A is a schematic diagram illustrating an example of an overhang forming process. FIG. 7B is a schematic view showing an example of a molded product obtained by the stretch forming process shown in FIG. 7A. FIG. 8A is a schematic diagram illustrating an example of drawing and forming. FIG. 8B is a schematic diagram showing an example of a molded product obtained by the drawing and forming 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 result by the EBSD method. FIG. 11 is a schematic diagram for explaining a molded product produced in the reference example. FIG. 12 is a schematic view of the steel plate observed from above. 13 shows a molded product No. corresponding to the reference example. It is a schematic diagram which shows 2 cross-sectional microstructures and surface irregularities. 14 shows a molded product No. corresponding to the reference example. It is a schematic diagram which shows the cross-sectional microstructure of 3 and surface asperity. 15 shows a molded product No. corresponding to the comparative reference example. It is a schematic diagram which shows 1 cross-sectional microstructure and surface unevenness | corrugation. 16 shows a molded product No. corresponding to the reference example. It is a schematic diagram which shows the cross-sectional microstructure and surface unevenness | corrugation of 102. 17 shows a molded product No. corresponding to the reference example. It is a schematic diagram which shows the cross-sectional microstructure of 103, and surface asperity. 18 shows a molded product No. corresponding to the comparative reference example. It is a schematic diagram which shows the cross-sectional microstructure of 101, and surface asperity. FIG. It is a figure which shows the relationship between the result of Pa evaluation about the virtual material after the shaping | molding simulation of A1-A10, and the average crystal grain size and crystal grain size of a {001} crystal grain.

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

(Method for manufacturing molded products)
The inventors conducted various studies on the structure of the metal plate to be formed.
First, the inventors conducted various studies on the structure of a metal plate having a bcc structure. As a result, the following knowledge was obtained.

  (1) In a metal plate having a bcc structure, the {001} plane is less susceptible to equal biaxial tensile deformation and unequal biaxial tensile deformation stress than the {111} plane. . In addition, the {101} plane is weaker than the {111} plane in terms of equal biaxial tensile deformation and unequal biaxial tensile deformation stress close to equal biaxial tensile deformation. Therefore, metal plate forming processing that causes biaxial tensile deformation, such as deep drawing and stretch forming, with a large processing amount (processing amount in which at least a part of the metal plate is 10% or more and 30% or less). As a result, strain concentrates on crystal grains having a crystal orientation of 15 ° from the {001} plane parallel to the surface of the metal plate.

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

  (3) When the developed irregularities are connected to the surface of the metal plate having the bcc structure, the surface properties are 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 the bcc structure, it is 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 15 ° to 30 ° with respect to the {001} plane). Therefore, unevenness on 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 the metal plate that was further electropolished after the bulge forming test. In both FIG. 1 and FIG. 2, the observation location is the apex portion of the metal plate raised in a mountain shape by the bulge forming test. With reference to FIG.1 and FIG.2, when the bulge forming test was performed with respect to the metal plate, the recessed part 1 and the recessed part 2 of about 10-20 micrometers were observed.

  That is, when an overhang forming process is performed on a metal plate, stress is concentrated on a certain point of the metal plate. In places where stress is concentrated, irregularities develop on the surface of the metal plate. Further, the developed irregularities are connected to further develop irregularities. 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 an EBSD (Electron Backscattering Diffraction) method. FIG. 3A shows that when the overhang height by bulge forming is 40 mm (corresponding to a forming 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 little unevenness. It is a schematic diagram of a metal plate. 4A and 5A show that when the overhang height by bulge forming is 40 mm (corresponding to forming processing in which at least a part of the metal plate has a plate thickness reduction rate of 25%), the surface of the metal plate is uneven. It is a schematic diagram of the metal plate with much development.

  On the other hand, FIG. 3B to FIG. 5B are schematic views showing surface irregularities of the metal plate in the cross sections of FIG. 3A to FIG. 5A. That is, FIG. 3B is a schematic cross-sectional view showing the surface unevenness of the metal plate with less development of unevenness on the surface of the metal plate. FIG. 4B and FIG. 5B are schematic views of a metal plate with a lot of unevenness on the surface of the metal plate.

Here, among the crystal grains in FIGS. 3A to 5A, the dark gray crystal grains 3 are crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate. Hereinafter, this crystal grain is also referred to as “{001} crystal grain”. In addition, 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, { 001} plane and a crystal grain having a crystal orientation in a range of more than 15 ° and not more than 20 °. Hereinafter, this crystal grain is also referred to as “{001} vicinity crystal grain”.
3B to FIG. 5B, 31 indicates the surface of the metal plate on which the {001} crystal grains 3 are present. Reference numeral 41 denotes the surface of the metal plate on which {001} neighboring crystal grains 4 exist.

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

  With reference to FIGS. 4A to 5A and FIGS. 4B to 5B, is the surface fraction of {001} crystal grains 3 smaller than 0.20 on the surface of the metal plate where the surface of the metal plate has a lot of unevenness? Or greater than 0.35.

  This is because strain is concentrated on the {001} crystal grains 3 during the stretch forming process. Then, the strain concentrated on the {001} crystal grains 3 develops irregularities on the surface of the metal plate. Further, when the area fraction of {001} crystal grains 3 is high, the probability that {001} crystal grains 3 are in contact with each other increases, and the generated irregularities are easily connected. On the other hand, if the area fraction of {001} crystal grains 3 is too low, local deformation is dispersed also in {001} neighboring crystal grains 4 and develops irregularities on the surface of the metal plate.

Specifically, when the area fraction of {001} crystal grains 3 is within an appropriate range, local deformation is not dispersed in {001} neighboring crystal grains 4 on the surface of the metal plate. As a result, local deformation occurs only at {001} crystal grains 3. Therefore, a deep recess is formed in the region where {001} crystal grains 3 are present, but a flat portion is secured in a region where other crystal grains (such as {001} neighboring crystal grains 4) exist (FIG. 3B). reference). This indicates that even if high unevenness is formed, a flat portion is secured if the recess is deep and fine.
On the other hand, when the area fraction of {001} crystal grains 3 is too low, local deformation is dispersed in {001} neighboring crystal grains 4 on the surface of the metal plate. As a result, local deformation occurs in the {001} crystal grains 4 as well as the {001} crystal grains 4. For this reason, the area | region where a shallow recessed part is formed becomes large, and a flat part becomes comparatively few (refer FIG. 4B).
In addition, when the area fraction of {001} crystal grains 3 is too high, {001} crystal grain 3 local deformation occurs on the surface of the metal plate, and a region where a shallow concave portion is formed is increased and a flat portion is decreased. (FIG. 5B).

  Therefore, even if the area fraction of {001} crystal grains 3 is too high or too low, irregularities on the surface of the metal plate develop, the resulting irregularities are easily connected, and the irregularities are further developed by the connection.

  Therefore, the inventors considered the following. When forming a metal plate having a bcc structure to cause biaxial tensile deformation, the ratio of the {001} crystal grains 3 can be controlled within a predetermined range, thereby suppressing the development of irregularities on the surface of the metal plate that occurs during processing. it can. That is, if the development of irregularities 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 ratio of {001} crystal grains 3 is low, if the size of {001} crystal grains 3 is sufficiently small, the irregularities developed on the surface of the metal plate even if the irregularities on the surface of the metal plate generated during processing develop. Is not conspicuous and is difficult to recognize as rough skin that impairs the appearance of the molded product.

  The inventors have paid attention to the slip system (slip surface and slip direction) of the crystal structure of the metal plate having the bcc structure and the metal plate having the 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 is parallel to the slip surface of the crystal structure of the metal plate having the fcc structure. The metal plate having the fcc structure was estimated to have 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 paying attention to the slip system of both crystal structures, in a metal plate having an fcc structure, the crystal orientation and forming of the crystal grains in a biaxial deformation field (equal biaxial deformation field and unequal biaxial tensile deformation field). The relationship between the surface roughness and the surface roughness of the product is analyzed by the finite element analysis method (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 {001} on the surface of the metal plate The area fraction of the crystal grains 3 was changed. The influence of the surface roughness of the metal plate due to the plastic strain was investigated by numerical analysis.

  As a result, the inventors, as well as the metal plate having the bcc structure, the metal plate having the fcc structure has the same biaxial tensile deformation field and the unequal biaxial tensile deformation field close to the equal biaxial tensile deformation field. It was found that strain concentrates on the 001} crystal grains 3 and preferentially deforms.

Therefore, the inventors considered the following. Even when the metal plate having the fcc structure is subjected to forming processing that causes biaxial tensile deformation, the ratio of the {001} crystal grains 3 is set within a predetermined range, thereby suppressing the development of unevenness on the surface of the metal plate that occurs during processing. Possible. That is, if the development of irregularities can be suppressed, rough skin that impairs the appearance of the molded product can be suppressed.
In addition, when the ratio of {001} crystal grains 3 is low, if the size of {001} crystal grains 3 is sufficiently small, the surface of the metal plate develops even when the surface irregularities of the metal plate develop during processing. Such irregularities are not conspicuous and are difficult to recognize as rough skin that impairs the appearance of the molded product.

The manufacturing method of the molded product of the first present invention completed based on the above knowledge has an fcc structure, and a metal plate that satisfies the following condition (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 so that the plate thickness reduction rate is 10% or more and 30% or less.
(A) The area fraction 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) The crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate have an area fraction of 0.45 or less and an average crystal grain size of 15 μm or less.

  And in the manufacturing method of the molded product of 1st this invention, with respect to the metal plate which has an fcc structure, biaxial tensile deformation arises, and at least one part of a metal plate is plate thickness reduction rate 10% or more and 30% or less Even when the forming process is performed, the occurrence of rough skin is suppressed, and a molded product excellent in design is obtained.

  Here, “a crystal grain having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate” means that one of the metal plates with respect to the {001} plane 3A as shown in FIG. Means a crystal grain having a crystal orientation in a range from a crystal orientation 3B inclined at an acute angle of 15 ° to the other surface side to a crystal orientation 3C inclined at an acute angle of 15 ° to 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 studied the structure of the metal plate having the bcc structure based on the above findings. As a result, the inventors have found the following. In a biaxial tensile deformation field (especially an unequal biaxial tensile deformation field close to a plane strain deformation field), not only {001} crystal grains 3 but crystals within 15 ° from a {111} plane parallel to the surface of the metal plate. It has been found that strain concentrates on crystal grains other than crystal grains having an orientation (hereinafter also referred to as “{111} crystal grains”) and preferentially deforms.

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

  The inventors also considered the following. When the ratio of crystal grains other than {111} crystal grains is low, the metal plate can be developed even if the surface irregularities of the metal plate developed during processing develop if the size of the crystal grains other than {111} crystal grains is sufficiently small. The unevenness developed on the surface of the film is not conspicuous and is difficult to recognize as rough skin that impairs the appearance of the molded product.

  Similarly to the above, the inventors paying attention to the slip system of the crystal structure of the metal plate having the bcc structure and the metal plate having the fcc structure, the metal plate having the fcc structure has a biaxial deformation field (equal biaxial). 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 crystal plastic finite element analysis.

  As a result, the inventors, like the metal plate having the bcc structure, in the biaxial tensile deformation field (particularly the unequal biaxial tensile deformation field close to the plane strain deformation field), {111 } It was discovered that strain concentrates on crystal grains other than crystal grains and preferentially deforms.

Therefore, the inventors considered the following. Even when the metal plate having the fcc structure is subjected to forming processing in which biaxial tensile deformation occurs, by setting the ratio of crystal grains other than {111} crystal grains within a predetermined range, unevenness on the surface of the metal plate generated during processing can be achieved. Development can be suppressed. That is, if the development of irregularities can be suppressed, rough skin that impairs the appearance of the molded product can be suppressed.
In addition, when the proportion of crystal grains other than {111} crystal grains is low, if the size of crystal grains other than {111} crystal grains is sufficiently small, even if the surface irregularities of the metal plate developed during processing develop, The unevenness developed on the surface of the metal plate is not conspicuous and is difficult to recognize as rough skin that impairs the appearance of the molded product.

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

  And in the manufacturing method of the molded article of the second aspect of the present invention, biaxial tensile deformation occurs with respect to 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 forming process is performed, the occurrence of rough skin is suppressed, and a molded product excellent in design is obtained.

  Here, “a crystal grain having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate” means an acute angle of 15 ° on one surface 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 tilted crystal orientation to the crystal orientation tilted at an acute angle of 15 ° to 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 these two crystal orientations.

(Molding)
The metal plate is subjected to a forming process that causes biaxial tensile deformation. As this forming process, there are deep drawing forming, stretch forming, drawing extending forming, and bending forming. Specifically, as the forming process, for example, a method of stretching and forming the metal plate 10 as shown in FIG. 7A can be mentioned. In this forming 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 bitten into the surface of the edge of the metal plate 10 and the metal plate 10 is fixed. In this state, the punch 13 having a flat top surface is pressed against the metal plate 10, and the metal plate 10 is stretched and formed. Here, FIG. 7B shows an example of a molded product obtained by the overhang forming process shown in FIG. 7A.
In the overhang forming process shown in FIG. 7A, for example, the metal plate 10 (the top surface of the molded product) positioned on the top surface of the punch 10 is unequal biaxially deformed or is relatively close to equal biaxial deformation. Tensile deformation occurs.

Moreover, as a shaping | molding process, the method of drawing and forming the metal plate 10 as shown to FIG. 8A is mentioned, for example. In this forming 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 bitten into the surface of the edge of the metal plate 10 and the metal plate 10 is fixed. 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 and formed. Here, FIG. 8B shows an example of a molded product obtained by the drawing and drawing process shown in FIG. 8A.
8A, for example, the metal plate 10 (the 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. Biaxial tensile deformation is deformation that extends in the ε1 direction and also in the ε2 direction. Specifically, the plane strain tensile deformation is a deformation in which the strain ratio β (= ε2 / ε1) becomes β = 0 when the strains in the biaxial directions are respectively the maximum main strain ε1 and the minimum main strain ε2. Biaxial tensile deformation is deformation in which the strain ratio β (= ε2 / ε1) is 0 <β ≦ 1. Note that the deformation where the strain ratio β (= ε2 / ε1) is 0 <β <1 is unequal biaxial deformation, and the deformation where the strain ratio β (= ε2 / ε1) is β = 1 is equal biaxial deformation. It is. Incidentally, the uniaxial tensile deformation is a deformation that extends in the ε1 direction and contracts in the ε2 direction and has a strain ratio β (= ε2 / ε1) of −0.5 ≦ β <0.

However, the range of the strain ratio β is a theoretical value, for example, calculated from the maximum principal strain and the minimum principal strain measured from the shape change before and after forming the steel sheet (before and after 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 forming process, at least a part of the metal plate is processed with a processing amount such that the plate thickness reduction rate is 10% or more and 30% or less. If the processing amount is less than 10%, the strain concentration on crystal grains other than {111} crystal grains (especially {001} crystal grains) is small, and unevenness tends to hardly develop during forming. Therefore, even if the metal plate does not satisfy the above conditions (a) and (b) or the above conditions (A) and (B), the rough surface of the molded product itself hardly occurs. On the other hand, if the plate thickness reduction rate exceeds 30%, the tendency of the metal plate (molded product) to break due to the forming process increases. Therefore, the processing amount of the forming process is set to the above range.

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

  The plate thickness reduction rate is expressed by the formula: plate thickness reduction rate = (Ti−), where Ti is the thickness of the metal plate before forming and Ta is the thickness of the metal plate (molded product) after forming. 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 the fcc structure include 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 formability.

[{001} crystal grains]
When a forming process causing biaxial tensile deformation is performed, a crystal grain ({001} crystal grain having a crystal orientation within 15 ° from a {001} plane parallel to the surface of the metal plate on the surface of the metal plate having the fcc structure. ) Satisfies the following (a) or (b).
(A) The area fraction of {001} crystal grains is 0.20 or more and 0.35 or less.
(B) The {001} crystal grains have an area fraction of 0.45 or less and an average crystal grain size of 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 stress of unequal biaxial tensile deformation that is close to equal biaxial tensile deformation and equal biaxial tensile deformation. Therefore, with a large amount of processing (a processing amount at which at least a part of the metal plate has a thickness reduction rate of 10% or more and 30% or less), the forming processing of the metal plate in which biaxial tensile deformation occurs, such as deep drawing and stretch forming. If implemented, the strain tends to concentrate on the {001} crystal grains, and the unevenness tends to develop on the {001} crystal grains. And when there are many ratios of {001} crystal grain, distortion tends to concentrate and an unevenness | corrugation tends to develop. On the other hand, when the ratio of {001} crystal grains is small, the number of locations where strain concentrates is small, and local deformation is dispersed also in crystal grains near {001}. However, even when the ratio of {001} crystal grains is small, if the size of {001} crystal grains is sufficiently small, the region that locally deforms in {001} neighboring crystal grains also becomes small, and even if unevenness develops, it is fine. 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 concentration of strain by the forming process is realized. Therefore, the development of unevenness is suppressed, and the occurrence of rough skin on the molded product is suppressed. On the other hand, if the metal plate having the fcc structure satisfies the above (b), moderate strain concentration by forming is realized when the area fraction of {001} crystal grains is 0.20 or more and 0.45 or less. Is done. When the area fraction of the {001} crystal grains is less than 0.20, even if the unevenness develops, it becomes difficult to be recognized as rough skin of the molded product. Therefore, the occurrence of rough skin of the molded product is suppressed.

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

  The average crystal grain size of {001} crystal grains is measured by the following method. Using the SEM, the surface of the metal plate is observed and the measurement area is arbitrarily selected. Using the EBSD method, {001} crystal grains are selected in each measurement region. Two test lines are drawn for each selected {001} grain. By calculating the arithmetic average of the two test lines, the average crystal grain size of {001} crystal grains is determined. Specifically, it is as follows. FIG. 10 is a schematic diagram illustrating a method of obtaining the average crystal grain size from the analysis result by the EBSD method. Referring to FIG. 10, 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 average of the lengths of the two test lines 5 and 6 is defined as the crystal grain size of the crystal grains. The arithmetic average 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 area fraction of {001} crystal grains is measured by the following method. Using SEM, observe the cross section (cut surface along the plate thickness direction) of the metal plate, and include any region (linear region) corresponding to the surface of the metal plate (surface facing the plate thickness direction) Select the measurement area. {001} crystal grain 3 is selected using the EBSD method. In each field of view, the area fraction of {001} crystal grains 3 is obtained by calculating the area fraction of {001} crystal grains 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 fraction of {001} crystal grains 3 in an arbitrary measurement region is defined as the area fraction of {001} crystal grains.
Here, in the case where a plating layer or the like is formed on the surface of the metal plate, the area of the {001} crystal grains 3 with respect to a 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} grains]
When a forming process causing biaxial tensile deformation is performed, crystal grains ({111} crystal grains having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate on the surface of the metal plate having the fcc structure. ) (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 area fraction of crystal grains other than {111} crystal grains is 0.25 or more and 0.55 or less.
(B) The area fraction of crystal grains other than {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 weak against stress of biaxial tensile deformation (particularly unequal biaxial tensile deformation close to a plane strain deformation field) (that is, {111). } The grain is the strongest). Therefore, with a large amount of processing (a processing amount at which at least a part of the metal plate has a thickness reduction rate of 10% or more and 30% or less), the forming processing of the metal plate in which biaxial tensile deformation occurs, such as deep drawing and stretch forming. If implemented, the strain tends to concentrate on crystal grains other than {111} crystal grains, and irregularities tend to develop in crystal grains other than {111} crystal grains. And when there are many ratios of crystal grains other than {111} crystal grains, distortion tends to concentrate and an unevenness | corrugation tends to develop. On the other hand, when the proportion of crystal grains other than {111} crystal grains is small, the number of locations where strain concentrates is small, and local deformation is dispersed also in {111} crystal grains. . 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 {111} crystal grains is also reduced, resulting in unevenness. Even if it develops, it becomes fine and is 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 concentration of strain by the forming process is realized. Therefore, the development of unevenness is suppressed, and the occurrence of rough skin on the molded product is suppressed. On the other hand, if the metal plate having the fcc structure satisfies the above (B), an appropriate strain due to the forming process is obtained when the area fraction of crystal grains other than {111} crystal grains is in the range of 0.25 to 0.55. Concentration is realized. When the area fraction of crystal grains other than {111} crystal grains is less than 0.25, even if unevenness develops, it becomes difficult to be recognized as rough skin of the molded product. Therefore, the occurrence of rough skin of the molded product is suppressed.

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

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

(Molding)
The molded product of the first aspect 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 molded product of the first aspect of the present invention has a formula: 10 ≦ (D1−D2) / D1 × 100 ≦ 30, where D1 is the maximum thickness of the molded product and D2 is the minimum thickness of the molded product. 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 the surface of the molded product is The following condition (c) or (d) is satisfied.
(C) The area fraction 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) The 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 fraction of 0.45 or less and an average crystal grain size of 15 μm. It is as follows.

On the other hand, the molded product of the second aspect 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 molded product of the second aspect of the present invention has the formula: 10 ≦ (D1−D2) / D1 × 100 ≦ 30, where D1 is the maximum thickness of the molded product and D2 is the minimum thickness of the molded product. 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 the surface of the molded product is The following condition (C) or (D) is satisfied.
(C) The area fraction of crystal grains other than 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) The area fraction of crystal grains other than crystal grains ({111} crystal grains) having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product, and an average crystal The particle size is 15 μm or less.

Here, the metal plate which has an fcc structure is synonymous with the metal plate used with the manufacturing method of the molded product of the 1st and 2nd this invention. The molded product of the metal plate is subjected to a forming 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 computer inverse analysis. Then, a ratio (the β) between the maximum principal strain and the minimum principal strain in each mesh is calculated. By this calculation, it can be confirmed that a forming process causing 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, mesh shape data of the molded product is obtained. Next, by using the obtained mesh shape data, numerical analysis of the one-step method (work hardening calculation tool “HYCRASH (JSOL)”, etc.), based on the shape of the molded product, once to a flat plate expand. The thickness change of the molded product, the residual strain, etc. are calculated from the shape information such as the elongation and bending state of the molded product at that time. Also by this calculation, it can be confirmed that a forming process causing biaxial tensile deformation is performed.

Further, satisfying the condition of the formula: 10 ≦ (D1−D2) / D1 × 100 ≦ 30 means that the molded product is molded by a molding process in which at least a part of the metal plate has a thickness reduction rate of 10% to 30%. Can be considered.
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) having the largest thickness reduction rate after the molding process. Product).

On the other hand, if the condition of the formula: 15 ≦ (H1−H2) / H1 × 100 ≦ 40 is satisfied, the molded product is formed by a forming process in which at least a part of the metal plate has a plate thickness reduction rate of 10% to 30%. Can be considered. This is because work hardening (that is, work hardness: Vickers hardness) increases as the processing amount (thickness reduction) of the forming 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) at the portion where the plate thickness reduction rate is the largest after the molding process, and the minimum hardness H2 of the molded product is It can be regarded as the hardness of the metal plate.

  The hardness is measured according to the Vickers hardness measurement 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 employed.

In addition, in the conditions indicated by (c) or (d) and the conditions indicated by (C) or (D) above, the area fraction and the average crystal grain size of {001} crystal grains on the surface of the molded product, and The area fraction and the average crystal grain size of crystal grains other than {111} crystal grains on the surface of the molded product are measured at a site where the maximum plate thickness D1 or the minimum hardness H2 of the molded product is obtained.
And the conditions shown by said (c) or (d) are the conditions shown by said (a) or (b) demonstrated by the manufacturing method of the molded article of 1st this invention, and the metal plate before a shaping | molding process. Instead of this, they are synonymous except that the area fraction of {001} crystal grains and the average crystal grain size on the surface of the molded product are used as conditions.
Similarly, the conditions indicated by the above (C) or (D) are the same as the conditions indicated by the above (A) or (B) described in the method for producing a molded product of the second invention, and the metal before the forming process. It is synonymous except that instead of the plate, the area fraction of crystal grains other than {111} crystal grains and the average crystal grain size on the surface of the molded product are used as conditions.

  As described above, the molded product of the first and second inventions can be regarded as a molded product formed by the manufacturing method of the molded product of the first and second inventions by satisfying the above requirements. Can do. The molded product of the first and second inventions is a molded product of a metal plate having an fcc structure and a shape in which biaxial tensile deformation has occurred, and the formula: 10 ≦ (D1-D2) / D1 Even if the molded product satisfies the condition of x100 ≦ 30 or the formula: 10 ≦ (H1−H2) / H1 × 100 ≦ 30, the occurrence of rough skin is suppressed and the molded product is excellent in design. Become.

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

[Evaluation method]
The following measurement test and visual evaluation were performed on each obtained steel sheet and each molded product. The results are shown in Tables 2 and 3.

[Measurement test of average grain size]
A measurement test of the average crystal grain size of {001} crystal grains was performed 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. Referring to FIG. 12, three measurement areas 4 each having a 1 mm square were selected arbitrarily in the center portion from ¼ in the width direction of the steel plate. In each measurement region 4, a crystal grain ({001} crystal grain 3) having a crystal orientation within 15 ° from a {001} plane parallel to the steel sheet surface on the surface of the steel sheet was selected.

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

[Area fraction measurement test]
A measurement test of the area fraction of {001} crystal grains was performed on the steel sheet. As described above, the measurement region 4 was selected from the steel sheet, and {001} crystal grains 3 were selected using the EBSD method. In each field of view, the area fraction of {001} crystal grains 3 was calculated, and the average value was obtained. Note that the area fraction of {001} crystal grains 3 of the formed product is the same value as the area fraction of {001} crystal grains 3 of the steel plate.

[Thickness measurement test]
A thickness thickness measurement test was performed on the molded product. Specifically, a molding simulation by a computer of a molded product was performed, and a portion where the plate thickness was maximum and minimum was specified. Thereafter, the thickness of the molded product was measured by using a thickness gauge at each of the portions where the thickness was maximum and minimum. Thus, the maximum plate thickness D1 and the minimum plate thickness D2 were obtained. However, the maximum plate thickness D1 determined the maximum plate thickness of the molded product (the entire molded product), and the minimum plate thickness D2 calculated the minimum plate thickness of the evaluation part of the molded product.

[Measurement test of hardness]
A hardness measurement test was performed on the molded product. Specifically, a molding simulation by a computer of the molded product was performed, and a portion where the equivalent plastic strain was maximum and minimum was specified. Thereafter, the hardness of the molded product was measured in accordance with the JIS standard (JIS Z 2244) at each of the portions where the plate thickness was maximum and minimum. Thereby, the maximum hardness H1 and the minimum hardness H2 were obtained. However, the maximum hardness H1 calculated | required the maximum hardness of the molded article (the whole molded article), and minimum hardness H2 calculated | required the minimum hardness of the evaluation part of a molded article.

[Unevenness measurement test]
A measurement test of the uneven height 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 unevenness in the longitudinal direction was measured with a contact-type roughness meter. In order to confirm the crystal orientation, the portion with the most prominent irregularities was cut using a cross section polisher, and the relationship between the crystal orientation of the surface layer and the irregularities was analyzed.

[Visual evaluation]
Originally, electrodeposition coating is performed after chemical conversion treatment, but as a simple evaluation method, the surface of the molded product is uniformly coated with lacquer spray, then visually observed, and according to the following criteria, the degree of occurrence of rough skin and the evaluation surface The sharpness was examined.
Furthermore, as another parameter indicating the superiority or inferiority of the surface property, the value of arithmetic mean waviness Wa was measured with a laser microscope manufactured by Keyence. The measurement conditions were an evaluation length of 1.25 mm and a cutoff wavelength 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 ((double-circle)): A pattern is not visually confirmed on the evaluation part surface of the top plate part of a molded article, and the surface is glossy (Wa <= 0.5micrometer). It is more desirable as an automobile outer plate part, and it can be used as an outer plate part of a luxury car.
B (◯): A pattern is not visually confirmed on the surface of the evaluation part of the top plate part 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 ((triangle | delta)): Although a pattern is visually confirmed on the evaluation part surface of the top-plate part of a molded article, the surface is glossy (1.0 micrometer <Wa <= 1.5micrometer). It cannot be used as a car outer plate part.
D (x): A pattern is visually confirmed on the evaluation portion surface of the top plate portion of the molded product, and the surface is not glossy (1.5 μm <Wa). It cannot be used as a car part.

From the above results, the molded article No. corresponding to the comparative reference example, in which a steel sheet having a bcc structure was formed. Compared to 1, 6 and 9, the molded product corresponding to the reference example No. 2-5, 7, 8, and 10 show that rough skin is suppressed and the design is excellent.
Here, the molded product No. 2, 3 and molded article No. corresponding to the comparative reference example. Schematic diagrams showing the cross-sectional microstructure of 1 and surface irregularities are shown in FIGS. 13 to 15 are schematic diagrams obtained by analyzing the cross section of the molded product by the EBSD method. 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 product No. corresponding to the comparative reference example is obtained. Compared with No. 1, the molded product corresponding to the reference example No. Nos. 2 and 3 show that the unevenness of the surface of the molded product is low, the rough skin is suppressed, and the design is excellent. However, from comparison between FIG. 13 and FIG. 2 compared with the molded product No. 3 shows that although the unevenness of the surface of the molded product is high, the rough surface is suppressed and the design is excellent. This is because even if the unevenness of the surface 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.)
Molded product no. No. 7 and Comparative Article No. From comparison with 9, even if the area fraction of {001} crystal grains is as low as less than 0.20, if the average crystal grain size of {001} crystal grains is less than 15 μm, rough skin is suppressed and the design is excellent. I understand that.
Molded product no. 10, it can be seen that even if the area fraction of {001} crystal grains is as high as 0.45, if the average crystal grain size of {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, the steel sheet having the characteristics shown in Table 4 (steel having a bcc structure) was subjected to an overhanging process. Accordingly, 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. Shaped molded product No. 101-105 and 108 were molded. In addition, except for the height H of the molded product 20 being 15 mm, the molded product No. In the same manner as in 101-105, 108, the molded product No. 106-107, 109, 125 were molded.
In this molding, the thickness reduction rate of the steel plate to be the top plate portion 20A (the thickness reduction rate of the evaluation portion A of the top plate portion 20A (center portion of the top plate portion 20A) in FIG. 11) is shown in Table 4. It was carried out with a processing amount that gave the plate thickness reduction rate shown.

  Furthermore, in FIG. 11, the plate thickness reduction rate of the evaluation part B (the center part between the center and the edge of the top plate part 20 </ b> A) of the top plate part plate 20 </ b> A of the molded product 20 is the molded product No. Except for adjusting the height H of the molded product 20 to be the same as the plate thickness reduction rate of 101 to 109, 125 (in FIG. 11, the plate thickness reduction rate of the evaluation portion A of the top plate portion plate 20A), Molded product No. In the same manner as in 101 to 109 and 125, the molded product No. 110-118 and 126 were molded.

  In addition, in FIG. 11, the plate thickness reduction rate of the evaluation portion C (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 for adjusting the height H of the molded product 20 to be the same as the plate thickness reduction rate of 101 to 109, 125 (in FIG. 11, the plate thickness reduction rate of the evaluation portion A of the top plate portion plate 20A), Molded product No. In the same manner as in 101 to 109 and 125, the molded product No. 119 to 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, Maximum principal strain and minimum principal strain were measured. From these values, the deformation ratio β in the evaluation part of the molded product was calculated.

[Evaluation method]
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) thickness test, 3) hardness measurement Test, 4) Concavity and convexity height measurement test, 5) Visual evaluation was performed according to the first reference example. The results are shown in Tables 4 and 5.

From the above results, the molded product No. 101, 106, 109 to 110, 115, 118 to 119, 124, molded article 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, and 125 to 127 are suppressed in rough skin and excellent in design.
Here, the molded product No. 102, 103, the molded product No. corresponding to the comparative reference example. Schematic diagrams showing 101 cross-sectional microstructure and surface irregularities are shown in FIGS. 16 to 18 are schematic diagrams obtained by analyzing the cross section of the molded product by the EBSD method. 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 product No. corresponding to the comparative reference example. Compared to 101, the molded product corresponding to the reference example No. It can be seen that Nos. 102 and 103 have low unevenness on the surface of the molded product, and the rough surface is suppressed and the design is excellent. However, from comparison between FIG. 16 and FIG. Compared to 102, the molded product No. No. 103 has a high unevenness on the surface of the molded product, but it can be seen that rough skin is suppressed and the design is excellent. This is because even if the unevenness of the surface 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.)
From the above results, it can be seen that in the molded product corresponding to the reference example, in which the steel sheet having the bcc structure is molded, the rough surface of the molded product is suppressed in the biaxial deformation field.

<Example>
[Molding molding simulation]
Using the cross section of the metal plate having the bcc structure used in the reference example (for example, FIGS. 13 to 18), the crystal grains of the cross section of the metal plate having the fcc structure were modeled. And while changing the grain size of the crystal grain of the cross section of the metal plate which has fcc structure, the average area fraction of crystal grains other than {001} crystal grain or {111} crystal grain is changed, and Table 6-Table A virtual material having the characteristics shown in FIG.
Next, a molding simulation corresponding to the molding of the molded product 20 shown in FIG. 11 was performed on the modeled virtual material. That is, the thickness of the virtual material that becomes the top plate portion 20A of the molded product with respect to the modeled virtual material (the plate of the evaluation portion A of the top plate portion 20A (the center portion of the top plate portion 20A) in FIG. 11). A forming simulation was performed to give "equivalent plastic strain" corresponding to (thickness reduction rate).
Specifically, first, in order to give the virtual material a displacement corresponding to “equivalent plastic strain” shown in Tables 6 to 7, a model-shaped press molding simulation shown in FIG. 8B (hereinafter referred to as a press molding simulation) is finite. The element analysis method was used. Thereby, in the virtual material after the press molding simulation, “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)”, maximum Hardness H1 (corresponding to the maximum hardness H1 of the molded product) and “minimum hardness H2 (corresponding to the minimum hardness H2 of the molded product)” were calculated.
Then, as a virtual material forming simulation corresponding to the press forming simulation, a displacement corresponding to “equivalent plastic strain” shown in Tables 6 to 7 is given to the left, right, near side, and depth direction of the cross section of the virtual material. A forming simulation (hereinafter referred to as forming simulation) for axial tensile deformation was performed by a crystal plasticity finite element analysis method.

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

In addition, the “maximum hardness H1 (corresponding to the maximum hardness H1 of the molded product)” and “minimum hardness H2 (corresponding to the minimum hardness H2 of the molded product)” in the virtual material after the press molding simulation was performed are as follows. .
For the maximum hardness H1, the hardness before molding was calculated from the average yield strength YP ₁ (MPa) of the virtual material according to the following formula.
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 according to the following formula.
Formula: Maximum hardness H2 = YP ₂ (MPa) / 3

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

  And the following evaluation was implemented about the virtual material after implementation of the said shaping | molding simulation. The results are shown in Tables 6 and 7.

(Uneven height)
About the virtual material after the said forming simulation implementation, the uneven | corrugated height of the surface was computed with the following method. The surface profile of the virtual material after the forming simulation was taken 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 the cross section curve)
For the surface properties of the virtual material after the molding simulation, the arithmetic average height Pa of the cross-sectional curve was calculated after obtaining the cross-sectional curve of the virtual material. And it evaluated by the following evaluation criteria.
The arithmetic average height Pa of the cross-sectional curve is the arithmetic average height defined in JIS B0601 (2001). The measurement conditions are as follows.
・ Evaluation length: 1 mm
・ Standard length: 1mm

The evaluation criteria for the surface properties of the virtual material are as follows.
A (◎): Pa ≦ 0.5 μm (more desirable as an automobile outer plate part, which can also be used as an outer plate part of a luxury car)
B (◯): 0.5 μm <Pa ≦ 1.0 μm (can be used as automobile parts)
C ((triangle | delta)): 1.0 micrometer <Pa <= 1.5micrometer (it cannot utilize as an outer plate | board component of a motor vehicle)
D (x): 1.5 μm <Pa (cannot be used as an automobile part)

From the above results, it can be seen from the above results that the No. Compared with A1, A6, A9, A101, A106, A109, No. corresponding to the embodiment. It can be seen that A2 to A5, A7, A8, A10, A102 to A105, A107, A108, and A110 are suppressed in rough skin and excellent in design.
Here, in FIG. About virtual material after forming simulation of A1 to A10 (indicated by numbers 1 to 10 with circles in FIG. 19), results of Pa evaluation, and average crystal grain size and crystal grain size of {001} crystal grains The relationship is shown.
As described above, a virtual material having an fcc structure was subjected to a forming simulation in which biaxial deformation occurred, and as a result, a metal plate having an fcc structure had a grain size of {001} grains as well as a steel sheet having a bcc structure. It can be seen that, by controlling the area fraction, or the grain size and area fraction of the {111} crystal grains, the rough surface of the molded product is suppressed even when a molding process causing biaxial deformation is performed.

3 {001} grain 4 Near {001} grain

Claims (6)

Biaxial tensile deformation occurs with respect to a metal plate having an fcc structure and satisfying the following condition (a) or (b) on the surface of the metal plate, and at least a part of the metal plate has a thickness reduction rate of 10 The manufacturing method of the molded article which gives the shaping | molding process used as% or more and 30% or less, and manufactures a molded article.
(A) The area fraction 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) The crystal grains having a crystal orientation within 15 ° from the {001} plane parallel to the surface of the metal plate have an area fraction of 0.45 or less and an average crystal grain size of 15 μm or less. Biaxial tensile deformation occurs with respect to a metal plate having an fcc structure and satisfying the following condition (A) or (B) on the surface of the metal plate, and at least a part of the metal plate has a thickness reduction rate of 10 The manufacturing method of the molded article which gives the shaping | molding process used as% or more and 30% or less, and manufactures a molded article.
(A) The area fraction of crystal grains other than crystal grains 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) The area fraction of crystal grains other than crystal grains having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the metal plate is 0.55 or less and the average crystal grain size is 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 thickness of the molded product is D1 and the minimum 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 condition (c) or (d) on the surface of the molded product.
(C) The area fraction of 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) The 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 thickness of the molded product is D1 and the minimum 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 condition (C) or (D) on the surface of the molded product.
(C) The area fraction of crystal grains other than 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.
(D) The area fraction of crystal grains other than crystal grains having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product is 0.55 or less and the average crystal grain size is 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 condition (c) or (d) on the surface of the molded product.
(C) The area fraction of 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) The 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 condition (C) or (D) on the surface of the molded product.
(C) The area fraction of crystal grains other than 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.
(D) The area fraction of crystal grains other than crystal grains having a crystal orientation within 15 ° from the {111} plane parallel to the surface of the molded product is 0.55 or less and the average crystal grain size is 15 μm or less. is there.