JP2019166587A - Manufacturing method of automotive outer panel - Google Patents

Abstract

To provide a manufacturing method of an automotive outer panel capable of removing a surface defect, while reducing strain generation on the surface by a simple method.SOLUTION: In a polishing process for polishing a metal plate surface after press working of the metal plate, only a buffing abrasive is used, whose particle size is in the range of #320(34.2 μm-94 μm) to #600(18 μm-72 μm), or otherwise, a buff 3 is used, whose abrasive grain density exposed to a polished surface is, for example, 20/mmor more, preferably 35/mmor more, more preferably 50/mmor more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing an automobile skin.

  When pressing the outer plate of the automobile, surface defects such as biting of foreign matter and scratches may occur. Such surface defects can be eliminated by removing scratches or the like by a method such as polishing, etc., and smoothing with high accuracy and high quality by performing buffing (see, for example, Patent Document 1). A glossy finish can be performed.

JP-A-9-262552

  In recent years, automobile outer plates have been made thinner, and residual stress, which has not been a problem with conventional thick outer plates, has become manifest as distortion due to the thinner plates. Therefore, residual stress is generated in the outermost polishing layer, and the polished surface is distorted to be convex, and surface defects such as scratches can be removed, but the surface quality is newly deteriorated due to the distortion. Problem has occurred.

  SUMMARY OF THE INVENTION The present invention solves the above-described problems, and an object of the present invention is to provide a method for manufacturing an automobile outer plate that can remove surface defects while reducing the occurrence of surface distortion by a simple method.

In order to achieve the above object, a method for manufacturing an automobile outer plate of the present invention includes:
In the polishing step for buffing the surface of the metal plate after press working of the metal plate, the buffing grains having a particle size only in the range of # 320 (34.2 μm to 94 μm) to # 600 (18 μm to 72 μm) It is characterized by using.

In addition, another method for manufacturing an automobile outer plate of the present invention includes:
In the polishing step of buffing the surface of the metal plate after pressing the metal plate, the abrasive grain size is # 100 (125 to 212 μm), and the abrasive density exposed on the polishing surface is 20 / mm A buff that is ² or more is used.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the motor vehicle outer plate which can remove a surface defect can be provided, reducing the generation | occurrence | production of surface distortion with a simple method.

FIG. 1 is a diagram for explaining the occurrence of distortion in the method for manufacturing an automobile outer plate of the present invention. FIG. 2 is a graph showing the effect of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited or limited to the following examples. The drawings referred to below are schematically described, and the ratio of the dimensions of objects drawn in the drawings may be different from the ratio of dimensions of actual objects. The dimensional ratio of the object may be different between the drawings.

  FIG. 1 is a diagram for explaining the occurrence of distortion in the method for manufacturing an automobile outer plate of the present invention. FIG. 1A is a diagram schematically showing a state where rotary buffing is performed using a buff 3 on an automobile outer plate 1. FIG. 1B is an automotive outer plate 1 after buffing, and FIG. 1C is a cross-sectional view taken along the line AA in FIG. Show. As shown in FIG. 1, the automobile outer plate 1 after buffing may generate a distortion 7 with a polished surface. This is because residual stress is generated in the outermost polishing layer. Since the residual stress is such that it does not affect the shape of a conventional thick automobile outer plate (for example, a thickness of about 0.7 mm), this phenomenon has not been a problem. As a result of analyzing the surface distortion generation mechanism, it was found that the residual stress generated on the outer surface of the automobile by the buffing process is a driving force. The generation of the residual stress is accompanied by plastic deformation when the buffing abrasive scrapes the surface of the automobile outer plate. In this invention, in order to reduce the residual stress which generate | occur | produces by a grinding | polishing process, the subject of reducing the distortion of the motor vehicle outer plate | board 1 by two approaches which paid its attention to the buffing abrasive grain was solved.

  The first approach has a polishing step of buffing the surface of the metal plate after press working, and in the polishing step, the particle size is # 320 (34.2 μm to 94 μm) to # 600 (18 μm to 72 μm). It is characterized by using buffing abrasive grains only in the range. The particle size of the buff abrasive grains is preferably adjusted in the above range according to the size and height of the convex portions generated by the residual stress after the polishing process.

  In the polishing step, buffing grains having a count of about # 100 are conventionally used. In the present invention, polishing is performed using a count used as an intermediate / finish buff, for example, # 600.

  Note that it is preferable that the buffing method is reciprocating buffing because residual stress is less likely to occur than in the case of rotary buffing. In rotating buff polishing, polishing tends to be biased in one direction. However, if a reciprocating buff is used, the polishing direction can be controlled and the generation of residual stress can be reduced.

The second approach has a polishing step of buffing the surface of the metal plate after press working. In the polishing step, the abrasive grain size is # 100 (125 to 212 μm), and the abrasive is exposed on the polishing surface. A buff having a particle density of 20 particles / mm ² or more is used. The abrasive density is preferably 35 pieces / mm ² or more, and more preferably 50 pieces / mm ² or more. The abrasive density is preferably adjusted in the above range according to the size and height of the convex portions generated by the residual stress after the polishing step.

  According to the above method for setting the abrasive density within the above range, it is possible to reduce the additional surface pressure during buffing per abrasive grain as compared with the conventional method, and the plasticity that one abrasive grain gives to the metal plate. Deformation can be suppressed and the occurrence of residual stress can be reduced.

Example 1
Rotating buffing with a buff of # 600 was performed on an automobile outer plate (thin plate outer panel) made of a galvanized 0.55 mm thin metal plate. After rotating buffing, the strain strength of the buffing part was measured. The strain strength is obtained by analyzing the curvature based on the measured three-dimensional shape data of an automobile outer plate (thin plate outer panel) and digitizing the magnitude of the strain in the panel.

(Comparative Example 1)
An automobile outer plate was manufactured in the same manner as in Example 1 except that the rotating buffing was performed using a # 100 buff used for conventional rotating buffing. After rotating buffing, the strain strength of the buffing part was measured in the same manner as in Example 1.

  The measurement results of the strain strength of Example 1 and Comparative Example 1 are shown in FIG. The strain strength in Example 1 was 21, and the strain strength in Comparative Example 1 was 4. By using # 600 buff, the strain value was reduced to about 1/5 of the conventional one.

(Example 2)
CAE analysis by a dynamic explicit method was performed on the amount of strain generated in the thin outer panel. Specifically, in a model in which a ball-shaped rigid body that looks like abrasive grains is rubbed against the steel sheet surface, the generated residual stress is calculated by a dynamic explicit method. In the analysis, the shared load per abrasive grain derived from the abrasive density (pieces / mm ² ) was used as a parameter. FIG. 2 (b) shows the result of analyzing a buff in which abrasive grains are densified five times with respect to the # 100 buff used in conventional rotary buff polishing. In the figure, the horizontal axis is taken with a conventional abrasive density of 1. When the load per abrasive grain is 1/5, it can be seen that the strain amount (displacement in the Z direction (mm)) is halved from 0.06 to 0.03. This result corresponds to the case where the abrasive density is 5 times.

  As described above, according to the present invention, according to the present invention, the residual stress generated in the polishing process is performed by using a buff abrasive grain having a small particle size or a polishing process using a buff having a high abrasive density. By doing so, it is possible to suppress appearance defects such as distortion.

DESCRIPTION OF SYMBOLS 1 ... Automotive outer plate 3 ... Buff 5 ... Buffing part 7 ... Convex part

Claims (2)

In the polishing step of buffing the surface of the metal plate after the metal plate is pressed,
A method for producing an automobile outer plate, characterized by using buffing abrasive grains having a particle size in a range of # 320 (34.2 μm to 94 μm) to # 600 (18 μm to 72 μm). In the polishing step for buffing the surface of the metal plate after the metal plate is pressed, the abrasive grain size is # 100 (125 to 212 μm), and the abrasive grain density exposed on the polishing surface is 20 / mm ^2. The manufacturing method of the outer plate | board of the motor vehicle characterized by using the buff which is the above.

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