JP6614944B2 - Quality inspection method for metal products - Google Patents

Description

  The present invention relates to a quality inspection method for metal products.

  Conventionally, a PoDFA (porous disk filtration apparatus) method or a K-mold method similar to this has been used to inspect the quality of metal products such as aluminum products or aluminum alloy products (Patent Documents 1 and 2).

  These methods basically involve melting the metal product, filtering a part of the molten metal with a filter, solidifying the remaining part of the molten metal on the filter to prepare the specimen, and intervening existing in the cross section of the specimen. This counts the number of objects and specific impurities having a certain size or more.

  However, these methods cannot perform an appropriate evaluation on the mechanical properties of the metal product.

Japanese Patent No. 5750219 JP 2008-224220 A

  The objective of this invention is providing the quality inspection method of a metal product which can evaluate the mechanical characteristic of a metal product appropriately.

  In the metal product quality inspection method according to one aspect of the present invention, the metal product is melted and a part of the molten metal is filtered through a filter, and the remaining part of the molten metal is solidified on the filter to prepare a specimen. In the cross section of the subject, the area of inclusions, gas holes, and nests present in a region separated by 1 mm or more from the interface with the filter in the thickness direction of the subject is obtained by image analysis.

  According to the metal product quality inspection method of the present invention, the mechanical properties of the metal product can be appropriately evaluated.

No. in Table 1 3 is a photograph showing the state of inclusions, gas holes, and burrows in the cross section of 3 specimens. No. in Table 1 5 is a photograph showing the state of inclusions, gas holes, and burrows in the cross section of 5 specimen. No. in Table 1 The photograph which shows the state of the inclusion, the gas hole, and the burrow in the cross section of 10 specimens. No. in Table 1 The photograph which shows the state of the inclusion in the cross section of 11 test objects, a gas hole, and a burrow. No. in Table 1 The photograph which shows the state of the inclusion, the gas hole, and the burrow in the cross section of 13 specimens. The figure which shows the plot which shows the relationship between the elongation and inclusion area in Table 1, and the calibration curve obtained by fitting. The figure which shows the calibration curve obtained by the plot which shows the relationship between the tensile strength and inclusion area in Table 1, and fitting.

  The metal product quality inspection method according to the present invention is a metal product quality inspection based on a PoDFA (porous disk filtration apparatus) method in which a molten metal product is filtered through a filter and a cross-section of a specimen solidified on the filter is inspected. This method is characterized in that the area of inclusions, gas holes, and nests existing in a region 1 mm or more away from the interface with the filter in the thickness direction of the subject in the cross section of the subject is obtained by image analysis. And

  Here, the “inclusions, gas holes, and area of the nest” are individual inclusions that exist in a region 1 mm or more away from the interface with the filter along the thickness direction of the subject in the cross section of the subject. , The total area of the gas holes and the nesting area.

  Examples of the metal product to be subjected to the method of the present invention include aluminum products and aluminum alloy products, but are not particularly limited.

In the present invention, inclusions are not original alloy components such as oxides (for example, Al ₃ O ₃ , MgO), carbides (for example, Al ₄ C ₃ ), and boride (for example, AlB ₂ ) of constituent elements of metal products. A foreign object.

  In the present invention, the gas hole and the hollow are the portions that are hollow in the process of solidifying the metal. Such cavities are considered to be generated by the following mechanism. In the molten metal, oxides as inclusions float with gas. As the molten metal solidifies, crystals grow around the oxide that accompanies the gas. When the solid solubility limit in the crystal is reached, the oxide accompanying the gas is released to the grain boundary, the oxide aggregates and a cavity is formed by the gas.

  When a cross-section of the subject is photographed with an imaging device such as a CCD camera and subjected to color shading processing at the time of image analysis, it is possible to discriminate the metal from inclusions, gas holes, and burrows. At this time, it is not necessary to distinguish between inclusions, gas holes, and burrows, as long as inclusions, gas holes, and burrows are displayed with the same level of shading. This is because inclusions, gas holes, and shrinkage are considered to have the same effect on the mechanical properties of the metal product. By using appropriate image analysis software for the color-shaded image, the total area of the individual inclusions, gas holes, and burrows in the cross section can be obtained.

  Conventionally, in the region from the filter interface to 1 mm along the direction of the thickness of the subject, the area of inclusions, gas holes, and nests has been obtained. However, the area from the filter interface to 1 mm along the thickness direction of the specimen corresponds to the surface layer portion of the metal product formed by solidification at the initial stage when the molten metal is solidified, and often disappears by cutting. For this reason, it has been found that even if the area of inclusions, gas holes, and burrows is obtained in this region, the mechanical properties inside the metal product are not reflected.

  On the other hand, a region 1 mm or more away from the interface of the filter along the thickness direction of the specimen is considered to correspond to the inside of the metal product formed by gradually solidifying when the molten metal is solidified. Gas holes and burrows may be observed. Furthermore, there is a correlation between the area of inclusions, gas holes, and nests present in a region 1 mm or more away from the filter interface along the thickness direction of the specimen and the mechanical properties of the metal product. all right.

  In the present invention, the mechanical properties of the metal product include, for example, elongation and tensile strength, but are not particularly limited.

  In the present invention, if a calibration curve showing the relationship between the inclusions and gas holes, the area of the shrinkage and the mechanical properties (elongation, tensile strength, etc.) of the metal product is prepared in advance, the inclusions and gas holes Based on the area of the nest, it can be determined whether or not the metal product satisfies the required mechanical properties.

  In addition, the region for obtaining the area of inclusions, gas holes, and nests by image analysis may be a region that is 1 mm or more away from the interface with the filter along the thickness direction of the subject. It is not necessary to determine the area of inclusions, gas holes, and nests. This is the ability of a computer to be used (for example, memory capacity) when determining the area of inclusions, gas holes, and burrows over the entire thickness of the subject that is 1 mm or more away from the interface with the filter in the thickness direction of the subject. This is because there is a possibility that processing may not be possible due to restrictions. According to the research of the present inventor, if the area of inclusions, gas holes, and nests is determined in a region 1 mm or more and 5 mm or less away from the interface with the filter along the thickness direction of the specimen, the inclusions and gas holes It has been found that there is a sufficient correlation between the area of the nest and the mechanical properties of the metal product. Of course, within the range not limited by the ability of the computer, inclusions and gas holes in the region from the position separated by 1 mm or more along the thickness direction of the subject from the interface with the filter to the position separated by more than 5 mm, Although the area of the burrow may be obtained, the accuracy of the correlation between the inclusions, the gas holes, the area of the burrow and the mechanical properties of the metal product is not significantly improved. It is sufficient to determine the area of inclusions, gas holes, and nests in a region separated by 1 mm or more and 5 mm or less along the thickness direction of the specimen.

  Examples of the present invention will be described below.

  Based on the PoDFA (porous disk filtration apparatus) method, for various aluminum ingots manufactured under various conditions, the area of inclusions, gas holes, and nests in the cross section of the subject were determined as follows.

  A sample cut out from an aluminum ingot is placed in a crucible having a filter (14 mm in diameter) attached to the bottom, and charged into an electric furnace. The sample weighs about 3000g. A container for receiving molten aluminum and a weigh scale are installed below the filter at the bottom of the crucible.

  The electric furnace is energized to melt the sample in the crucible, and the inside of the electric furnace is pressurized with air to filter the molten metal. When the amount of filtration reaches 2000 g, pressurization is stopped and air cooling is performed to solidify the molten metal on the filter.

Take out the disk-like coagulum with the filter and cut along the diameter. When the cut surface is photographed with a CCD camera and subjected to color shading, inclusions, gas holes, and burrows are displayed in blue, for example, and are clearly distinguished from bullion. Image analysis of the cut surface is performed to determine the area of inclusions, gas holes, and burrows present in a region separated from the interface with the filter by 1 mm or more and 5 mm or less along the thickness direction of the subject. In the following, it is indicated as the inclusions, gas holes, and the area of the nest (mm ² ) per kg of the sample. At this time, for example, Media Cybernetics Image Pro series or Mitani Corporation WinROOF is used as image analysis software.

  For example, automotive aluminum foil is required to exhibit a certain degree of elongation and tensile strength. If the elongation is small and the tensile strength is weak, it may break. Therefore, the elongation and tensile strength of each aluminum product and the inclusions, gas holes, and nesting of the inclusions present in the region 1 mm or more and 5 mm or less along the thickness direction of the specimen from the interface with the filter of each specimen. The relationship with the area was examined.

  Table 1 shows the relationship among the area of inclusions, gas holes, and nests, elongation, and tensile strength. 1 to 5 show the subject numbers of Table 1. Photographs of cross sections 3, 5, 10, 11, and 13 are shown. FIG. 1 shows a position separated by 1 mm and a position separated by 5 mm along the thickness direction of the subject from the interface with the filter. Although these positions are not displayed in FIGS. 2 to 5, since FIGS. 1 to 5 are photographs taken at the same magnification, FIGS. 2 to 5 also show the thickness direction of the subject from the interface with the filter. The positions 1 mm apart and 5 mm apart are the same as in FIG.

  Further, FIG. 6 plots the relationship between the elongation in Table 1 and the area of inclusions, gas holes, and nests, and shows a calibration curve obtained by fitting. Similarly, FIG. 7 plots the relationship between the tensile strength in Table 1 and the area of inclusions, gas holes, and nests, and shows a calibration curve obtained by fitting. In FIGS. 6 and 7, the inclusions, the area of the gas holes, and the nests are collectively referred to as the inclusion area.

  After obtaining the area of inclusions, gas holes, and nests in the cross section of the subject, the elongation and / or the required aluminum ingot of the subject is required by referring to the calibration curves shown in FIGS. Alternatively, it can be determined whether the tensile strength is satisfied.

  As described above, according to the quality inspection method of the present invention, the mechanical characteristics of a metal product such as an aluminum product can be appropriately evaluated.

Claims (3)

A metal product is melted and a part of the molten metal is filtered through a filter, and the remaining part of the molten metal is solidified on the filter to prepare a specimen.
In the cross section of the subject, the area of inclusions, gas holes, and nests present in a region separated by 1 mm or more from the interface with the filter in the thickness direction of the subject is obtained by image analysis. Quality inspection method for metal products.   2. The quality inspection method for a metal product according to claim 1, wherein a calibration curve indicating a relationship between an area of the inclusion, the gas hole, and the nest and a mechanical property of the metal product is created in advance.   The quality inspection method for a metal product according to claim 1 or 2, wherein the metal product is an aluminum product or an aluminum alloy product.