Method for bending metal plate

Abstract

To solve such a problem occurring in a conventional metal plate bending, that efficient bending of the metal plate by laser irradiation is difficult when the metal plate is material having a low laser absorption rate.SOLUTION: A method for bending a metal plate 1 comprises: forming a groove 2 functioning a bending portion on one main surface of the metal plate 1; forming fine corrugation 3 on an inner surface of the groove 2; and then repeating heating and cooling the groove 2 thereby bending the metal plate 1 toward a heated side while melting an inside of the groove 2 to integrate a groove opening portion. Thereby the method can achieve efficient bending by laser irradiation even when the metal plate 1 is material having a low laser absorption rate such as aluminum.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for bending a metal plate used, for example, when bending a metal plate for a vehicle body. [Background technology]

[0002] Conventionally, there is a method for bending a metal plate, for example, as described in Patent Document 1. Patent Document 1 describes a method for bending a metal plate, which includes a thermal bending process in which heat is input to a groove formed in the metal plate to bend the metal plate toward the heat input side, and in which heat is input so as to melt the metal on the surface of the groove and integrate the groove opening while bending the metal plate in the thermal bending process. In this method for bending a metal plate, laser irradiation can be used as a means for inputting heat, and deterioration of the mechanical properties of the bent part due to the groove can be suppressed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-154377 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional metal plate bending method as described above, if the metal plate is made of a material with low laser absorption, such as aluminum, there is a risk that efficient bending by laser irradiation may be difficult.

[0005] The present invention has been made in consideration of the above-mentioned conventional situation, and aims to provide a method for bending a metal plate, which can realize efficient bending by laser irradiation even if the metal plate is made of a material with low laser absorption rate, such as aluminum. [Means for solving the problem]

[0006] The method for bending a metal plate according to the present invention is characterized in that a groove is formed on one main surface of the metal plate to be a bending portion, and fine irregularities are formed on the inner surface of the groove. Thereafter, the method for bending a metal plate is characterized in that the metal plate is bent toward the heat input side by repeatedly inputting heat into the groove and cooling it, and the inside of the groove is melted to integrate the groove opening. Effect of the Invention

[0007] Since the metal plate bending method according to the present invention employs the above-mentioned configuration, the fine irregularities enlarge the surface area of ​​the inner surface of the groove, increasing the laser absorption rate. As a result, the metal plate bending method according to the present invention can achieve efficient bending by laser irradiation even if the metal plate is made of a material with low laser absorption rate, such as aluminum. [Brief description of the drawings]

[0008] [Figure 1] 1A to 1F are explanatory views showing a process sequence of one embodiment of a bending method for a metal sheet according to the present invention. [Diagram 2] FIG. 4 is a cross-sectional view of a main part showing a heat input state in a metal plate. [Diagram 3] FIG. 10 is an explanatory diagram showing an example of laser irradiation on a metal plate. [Figure 4] 1 is an explanatory diagram showing a heat input direction to a metal plate and a process of bending the metal plate. FIG. [Diagram 5] 1 is an explanatory diagram showing the relationship between the shape of a groove in a metal plate and laser irradiation. FIG. [Figure 6] FIG. 4 is a cross-sectional view showing an example of fine projections and recesses formed in a groove. [Figure 7] FIG. 4 is an explanatory diagram showing the metal plate after bending. [Figure 8] 1 is a graph showing the relationship between the mechanical properties and grain size of metals and temperature. [Figure 9] 1 is a graph showing the relationship between abrasive grain size and laser absorption rate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] First embodiment The metal plate bending method according to the present invention is outlined as follows: grooves 2 to bend are formed on one main surface of a metal plate 1 shown in Fig. 1(A) as shown in Fig. 1(B) and (C), and fine irregularities 3 are formed on the inner surface of the groove 2 as shown in Fig. 1(D). Thereafter, the bending method bends the metal plate 1 toward the heat input side by repeatedly inputting heat into the groove 2 and cooling it, and melts the inside of the groove 2 to integrate the groove opening, as shown in Fig. 1(E) and (F).

[0010] In the bending method described above, the metal plate 1 is made of a precipitation hardening material, for example, aluminum (including alloys), and is used, for example, for automobile body panels. It is well known that such metal plates 1 have a low absorption rate of laser.

[0011] The groove 2 in the metal plate 1 is formed linearly along the bent portion of the metal plate 2, and can be formed by either plastic working by pressing with a tool or cutting, and in this embodiment, as shown in Fig. 1(B), it is formed by plastic working by pressing with a tool 4. In a more preferred embodiment, the groove 2 has a curved cross-sectional shape.

[0012] The fine irregularities 3 in the groove 2 are formed over the entire inner surface of the groove 2 and can be formed by at least one of cutting, rolling, polishing, and laser processing, and in this embodiment, as shown in Fig. 1(D), are formed using a laser irradiator 5 that oscillates a pulsed laser L. In a more preferred embodiment, the fine irregularities 3 have a shape in which triangular irregularities are continuous in the cross section of the groove 2 shown in Fig. 1(D). In other words, the fine irregularities 3 have triangular cross-sectional irregularities over the length direction of the groove 2.

[0013] Heat input to the groove 2 of the metal plate 1 is performed using a laser irradiator 5 that oscillates a laser L, as shown in Figures 1(E) and (F). In this bending method, as shown in Figure 2, the thickness T from the other main surface of the metal plate 1 to the bottom surface of the groove 2 is adjusted so that the temperature at which the transformation ability of a certain region is improved (for example, 200°C or higher) is reached. The temperature gradient at the time of heat input is shown by a dotted line in Figure 2, and the metal plate 1 is heated up to the back side of the groove 2.

[0014] As described above, when the metal plate 1 is made of a precipitation hardening material, the heat input to the groove 2 is set to a solution temperature (for example, 500°C or higher) at which the transformation ability of a certain region is improved. Furthermore, as shown in Fig. 3, it is more preferable that the heat input to the groove 2 is performed by repeatedly irradiating the same location with laser light L, which scans along the groove 2.

[0015] In other words, in the above bending method, the depth of the groove 2 is set according to the material and thickness of the metal plate 1, and various conditions such as the focus diameter of the laser L, the heating temperature, and the number of scans are set so that the temperature at which the transformation ability of the certain region is improved becomes equal to the solution temperature when the metal plate 1 is made of a precipitation hardening material.

[0016] Furthermore, it is desirable to input heat to the groove 2 in an oblique direction from the inner corner side of the final bending angle of the metal plate 1. For example, as shown in Fig. 4, when one side (left side) of the groove 2 of the flat metal plate 1 is raised by 90 degrees, as shown in the left diagram of Fig. 4, a laser irradiator 5 is placed on the other side (right side) that is the inner corner side of the final bending angle (90 degrees) based on a perpendicular line S to the flat metal plate 1 as shown in the left diagram of Fig. 4, and a laser L is irradiated to the groove 2 from an oblique direction as shown in the center diagram and the right diagram of Fig. 4. At this time, in the bending method, it is also effective to fix the other side (right side) of the groove 2 of the metal plate 1 with a jig or the like.

[0017] By repeating the above-mentioned heat input and cooling into the grooves 2, the metal sheet 1 melts and bends at the grooves 2, gradually increasing the bending angle, and finally forming the metal sheet 1 into the desired bending angle. During this process, the volume of the grooves 2 of the metal sheet 1 gradually decreases as the bending angle increases, and finally the molten metal is integrated to fill the groove openings, forming a shape as if the metal sheet 1 of a certain thickness had been bent.

[0018] The bending method for a metal plate described in the above embodiment makes the metal plate 1 easier to bend by forming grooves 2 in advance, forms fine irregularities 3 on the inner surface of the grooves 2 to increase the surface area, and imparts distortion to increase resistance and improve the laser absorption rate.

[0019] In this way, the metal plate bending method can suppress the effect of the reduction in plate thickness due to the groove 2 provided as pre-processing, and can achieve efficient bending by laser irradiation even if the metal plate is made of a material with low laser absorption rate, such as aluminum.

[0020] In addition, in the above-mentioned method of bending a metal plate, as shown in FIG. 2, by adjusting the thickness from the other main surface of the metal plate 1 to the bottom surface of the groove 2 so that the temperature is such that the transformation ability of a certain region is improved, the plastic fluidity of the material is improved by heat, or dislocations are reduced by recrystallization, etc., thereby improving the plastic workability during bending.

[0021] Furthermore, in the above-mentioned method of bending a metal plate, when the metal plate 1 is made of a precipitation-hardening material, by setting the temperature at which the transformation ability of the certain region is improved as the solution temperature, the precipitates are dissolved in the metal parent phase, thereby improving the plastic workability during bending.

[0022] Furthermore, in the above-mentioned method for bending a metal plate, heat is input into the groove 2 by laser irradiation, so that it is possible to bend a metal material that is difficult to plastically process due to age hardening.

[0023] Furthermore, in the above-mentioned metal plate bending method, as shown in FIG. 3, laser irradiation is performed repeatedly at the same location by scanning the laser light L along the groove 2, so that the heat required for bending is not applied all at once but is applied in multiple steps, thereby making it possible to increase the bending angle.

[0024] Furthermore, in the above-mentioned metal plate bending method, as shown in FIG. 4, heat is input obliquely from the inner corner side of the final bending angle of the metal plate 1, so that interference between the metal plate 1 that is raised by the heat input and the laser L is prevented, and laser irradiation to parts that do not require heat input is prevented, thereby enabling an increase in the bending angle.

[0025] Furthermore, in the above-mentioned metal plate bending method, as shown in FIG. 5, by making the cross-sectional shape of the groove 2 a curved shape, i.e., a two-dimensional shape or a three-dimensional shape, it is possible to prevent the laser beam L from being reflected outside the groove 2, thereby allowing the laser beam L to be efficiently absorbed and promoting the bending deformation.

[0026] Furthermore, in the above-mentioned bending method of the metal plate, the groove 2 is formed by either plastic processing by pressing with a tool or cutting processing, which imparts distortion to the inner surface of the groove 2 and increases the electrical resistance, thereby improving the laser absorption rate.

[0027] Furthermore, in the above-mentioned bending method for a metal plate, by forming the fine irregularities 3 of the grooves 2 in a cross section thereof into a continuous triangular irregularity, as shown in FIG. 6, the laser K can be diffused and the absorption rate can be improved, thereby achieving further improvement in bending processability by laser irradiation.

[0028] Furthermore, in the bending method of the above-mentioned metal plate, by forming fine irregularities 3 of the grooves 2 by at least one of cutting, rolling, polishing, and laser processing, the laser can be diffusely reflected to improve the absorption rate, thereby achieving further improvement in bending processability by laser irradiation.

[0029] Furthermore, when the metal plate 1 is made of aluminum, the above-mentioned metal plate bending method can produce an aluminum part P shown in Fig. 7. This aluminum part P has an area PA on the outer corner side of the bent portion that has been solution-treated, and can be produced without causing cracks in the overaged metal plate 1.

[0030] Here, Fig. 8 is a graph showing the relationship between the temperature and the mechanical properties and crystal grain size of metals. When recrystallization occurs in a metal, the hardness decreases and workability improves. Recrystallization occurs when a certain temperature is reached, which is 200°C to 300°C in the case of aluminum. To bend the metal sheet 1 without causing cracks, it is desirable for the side opposite to the laser irradiated surface to reach the recrystallization temperature.

[0031] Therefore, in the above-mentioned method for bending a metal plate, the thickness is adjusted so that the temperature in a certain region of the thickness from the other main surface of the metal plate 1 to the bottom surface of the groove 2 is at a temperature at which the transformation ability is improved, and in particular, when the metal plate 1 is made of a precipitation hardening material, the temperature at which the transformation ability is improved is set to the solution temperature.

[0032] As described above, the metal plate bending method can form the fine irregularities 3 of the grooves 2 by polishing, and more preferably, the abrasive grain size during polishing is between 14 μm and 177 μm. FIG. 9 shows the relationship between the abrasive grain size and the laser absorptivity. As is clear from the figure, when the abrasive grain size is 14.5 μm or more, the laser absorptivity improves, and up to an abrasive grain size of 177 μm, the laser absorptivity improves. Thus, in the metal plate bending method, by setting the abrasive grain size during polishing to between 14 μm and 177 μm as described above, the metal plate 1 can be efficiently bent.

[0033] The configuration of the metal sheet bending method according to the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the gist of the present invention. [Explanation of symbols]

[0034] 1 metal plate 2 grooves 3 Fine irregularities 4 Tools L Laser P Aluminum Parts

Claims

1. A method for bending a metal plate, comprising the steps of: A groove is formed on one main surface of the metal plate to be a bending portion, After forming fine irregularities on the inner surface of the groove, A method for bending a metal plate, comprising repeatedly applying heat to and cooling the groove to bend the metal plate toward the heat input side, and melting the inside of the groove to integrate an opening of the groove.

2. The method for bending a metal plate according to claim 1, characterized in that the thickness from the other main surface of the metal plate to the bottom surface of the groove is adjusted so that the temperature of a certain region of the thickness from the other main surface of the metal plate to the bottom surface of the groove is improved.

3. The metal plate is made of a precipitation hardening material; 3. The method for bending a metal plate according to claim 2, wherein the temperature at which the transformation ability of the certain region is improved is a solution temperature.

4. 4. The method for bending a metal plate according to claim 1, wherein heat is input into the groove by laser irradiation.

5. 5. The method for bending a metal plate according to claim 4, wherein the laser irradiation for scanning the laser light along the groove is performed repeatedly at the same location.

6. 5. The method for bending a metal plate according to claim 4, wherein heat is input in an oblique direction from an inner corner side with respect to a final bending angle of the metal plate.

7. 5. The method for bending a metal plate according to claim 4, wherein the cross-sectional shape of the groove is a curved shape.

8. 2. The method for bending a metal plate according to claim 1, wherein the groove is formed by either plastic working by pressing with a tool or cutting.

9. 5. The method for bending a metal plate according to claim 4, wherein the minute irregularities of the groove have a shape of continuous triangular irregularities in a cross section of the groove.

10. 2. The method for bending a metal plate according to claim 1, wherein the minute projections and recesses of the groove are formed by at least one of cutting, rolling, polishing, and laser processing.

11. 2. The method for bending a metal plate according to claim 1, wherein the minute projections and recesses of the groove are formed by polishing, and the abrasive grain size is 14 μm or more and 177 μm or less.

12. An aluminum part obtained by the method for bending a metal plate according to any one of claims 1 to 11, characterized in that an area on an outer corner side of a bent portion is solution-treated.

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