JPH0712759A - Quality judgement method for cast component - Google Patents

Abstract

PURPOSE:To make efficient and precise judgement by reproducing the tomography of a cast component by an X-ray CT and then confirming a cast defect such as a shrinkage cavity, segregation and a machined condition. CONSTITUTION:An X-ray CT scanner system emits to a cast component an X-ray collimated to the thickness of the cross section thereof from each direction to detect a cast condition via a multi-channel sensor, and the data collecting section of the system collects projection data. The collected data undergoes a data correction and image processing in a high-speed arithmetic device, thereby being reconstituted. The beam absorption factor of each picture element constituting the cross section changes in proportion to the density of a substance and, therefore, the factor is converted to a CT value proportional to density. The CT value so obtained is shown on a CRT after brilliance modulation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quality judging method capable of efficiently confirming the casting quality of a cast part that is cast while partially pressurizing to prevent casting defects.

[0002]

2. Description of the Related Art Conventionally, in order to prevent a casting defect such as a shrinkage cavity of a cast product, the molten metal in the cavity is sometimes partially pressurized by a pressure pin. In such a case, whether the casting defect such as shrinkage cavity has not occurred in the cast product, or the effect of partial pressurization by the pressurizing pin is effective to the entire area, or if casting of molten alloy is specified In order to confirm the casting quality such as whether the components are partially biased and solidified, conventionally, a fracture inspection is performed as necessary to make a determination. That is, casting defects such as shrinkage cavities are X
It can be confirmed by non-destructive inspection by line transmission, but since the pressurized state and segregation cannot be confirmed by non-destructive inspection,
For example, the inspection object is cut into dice, weighed, and the density per volume is measured to check the pressure state, or the cut surface is polished to inspect the structure to confirm segregation, etc. The inspection is adopted.

[0003]

However, it may be difficult to find internal defects such as shrinkage cavities due to X-ray transmission as described above, depending on the relationship between the defect shape and the X-ray irradiation direction. There was a problem. In addition to the problem that destructive inspection such as cutting the inspection object into dice takes time and labor, it is not efficient, and there are many restrictions on the cutting accuracy and shape when cutting, which makes it more efficient. There has been a demand for an effective determination means.

[0004]

In order to solve such a problem, the present invention reproduces a tomographic image of a cast part by X-ray CT (Computed Tomography), and only non-destructive inspection shows only casting defects such as shrinkage cavities. Instead, the segregation and the pressurized state were also checked.

[0005]

If the CT value obtained by the CT scan is image-processed and reproduced, the state such as shrinkage cavity, the pressure state, and the segregation state can be determined from the tomographic image. Therefore, all can be efficiently judged without relying on the destructive inspection as in the prior art, and internal defects such as shrinkage cavities are not affected by the shape of the defect as compared with the conventional X-ray transmission. Moreover, it is possible to accurately determine even a cast product having a complicated shape.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a quality judgment method for cast parts according to the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a schematic diagram of a test result of a tomographic image according to a change in a pressurization state.
Is an explanatory diagram of an experimental procedure of the test.

[0007] Generally, casting has a large shape-imparting property and has a wide range of applicable metals and alloys, and mass production is possible, but on the other hand, shrinkage cavities, cracks, etc. due to the volume change of the metal In addition to casting defects, there are problems such as blowholes and gas holes due to absorption of gas in the molten metal, and segregation in which the solidification structure of the molten alloy becomes partially nonuniform.

Therefore, in order to prevent casting defects such as shrinkage cavities and blow holes, a molten metal is conventionally poured into the cavity, and then a pressure pin is press-fitted into a portion where casting defects are likely to occur. A method of applying secondary pressure is widely adopted, and such a pressure pin is often provided, for example, in a non-product shape portion close to the product shape portion.

Therefore, the quality of the cast product cast by such partial pressurization has to rely on the destructive inspection as described above in the past for checking the range of the pressurizing effect and for the segregation state. Although it was not translated, this proposal is X-ray CT
This makes it possible to make extremely efficient determinations.

Such an X-ray CT scanner system is a general system, and, for example, X-rays collimated to the thickness (slice width) of the cross section are radiated from each direction of the cast product and detected by a multi-channel sensor. The projection data is collected by the data collection unit. Then, this projection data is reconstructed by data correction and image processing by a high-speed arithmetic device.

At this time, the linear absorption coefficient μ of each pixel forming the cross section is obtained. This linear absorption coefficient μ is proportional to the density ρ (g / cm ³ ) of the substance, and μ = μ ₀ · ρ (Μ ₀ is a mass absorption coefficient), and this linear absorption coefficient μ is converted into a CT value proportional to the density ρ.
Display on RT.

Therefore, a specific example of the CT value distribution displayed on the CRT will be described.

As shown in FIG. 2 (A), considering the case where the pressure pin 2 is pressed into the molten metal 1 such as aluminum alloy poured into the cavity to pressurize the molten metal 1, the pressure pin 2 The pressure in the molten metal 1 increases as the pressurization stroke s increases.

The pressure stroke s is shown in FIG.
As shown in (B), the CT value (density) distribution chart shown in FIG. 1 is the result of testing each of four types. That is,
The pressure stroke s of A is 0.1 mm, the pressure stroke s of B is 3.5 mm, the pressure stroke s of C is 6.7 mm, and the pressure stroke s of D is 10.4 mm.

In the state of FIG. 1A, the pressing stroke s is small, and the CT value (density) distribution shows a wide range of cavities regions represented by levels 4 and 5. The level 5 shows that the CT value (× 4) is 286 or less, the density ρ is decreased by -25% or more from the reference density 2.81, and the level 4 shows that the CT value (× 4) is 324 to In the range of 286, the density ρ is decreased by -15% to -25% from the standard. Also, the CT value (x4) of level 3 is 362 to 362.
In the range of 324, the density ρ is −5% to −15 with respect to the standard.
%, CT value (× 4)
In the range of 400 to 362, the density ρ is +5 with respect to the reference.
% To −5%. And level 1
Indicates that the CT value (× 4) is in the range of 438 to 400, and the density ρ is in the range of + 15% to + 5% with respect to the reference.

Next, when the pressurization stroke s increases in the state of B, it is understood that the porosity regions of levels 4 and 5 decrease and the range of the applied pressure expands instead.

When the pressure stroke s is further increased as in the states C and D, the area of level 2 is further expanded and the porosity area is further decreased. In the level 1 portion represented by the state of D, for example, the density ρ is 10% of the reference density.
The segregation state exceeding the above is included, and the segregation state can be detected by this CT value.

By displaying the CT value (density) as described above, casting defects such as shrinkage cavities, pressurization state, and segregation can be immediately judged, and it is not necessary to carry out a destructive inspection as in the prior art.

[0019]

As described above, according to the method for determining the quality of a cast part of the present invention, when confirming internal defects such as shrinkage cavities of a cast product, a pressurizing state, and segregation, the object to be inspected is destroyed by X-ray CT. Since the inspection can be performed without any need, it has become possible to make an extremely efficient and precise determination.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a test result of a tomographic image according to a pressurized state.

[Fig. 2] Illustration of the experimental procedure of the test

[Explanation of symbols]

 1 molten metal 2 pressure pin

Claims (1)

[Claims] 1. A method for determining the quality of a cast part, which comprises reconstructing a tomographic image of the cast part by X-ray CT to check for casting defects such as shrinkage cavities, segregation, and pressure.