JP2006162331A - Core crease test method for casting molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a core crease testing method for casting mold capable of exactly detecting core crease. <P>SOLUTION: The core crease testing method for casting mold has a step preparing an engine cylinder head 10 (casting mold) provided with a casting body 11 and a water jacket 12 (hollow part) formed in the casting body by using a core 30 including a thin part 31 whose thickness is thinner than the other portion, a step for transmitting ultrasonic from a probe 21 toward a test surface 14 to be a test object among the boundary surfaces 13 between the casting body and the water jacket, a step for receiving ultrasonic reflected from the test surface with the probe and a step for detecting core creases based on the received ultrasonic. In the step preparing the engine cylinder head, a core provided with a flat part 32 having flat cross sectional shape at the end of the thin part is used so that the test surface is formed in a flat shape with the flat part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a core breakage inspection method for detecting a core breakage of a cast product.

  For example, a cylinder head, a gear carrier, or the like, which is a cast product for automobiles, includes a cast body part and a hollow part formed in the cast body part. In forming the hollow portion, a core formed by a shell mold method or a cold box method is generally used. The core may be broken or cracked during conveyance or casting. When casting is performed using a core that has been bent or the like, there arises a problem that a flow path to be formed by the core is not formed into a predetermined shape.

Before the cast molded product is shipped as a product, it is inspected whether the flow path is molded into a predetermined shape. In addition to visual inspection and sensory inspection using a fiberscope, there are techniques for inspecting a flow path using an ultrasonic sensor as disclosed in Patent Document 1. In the inspection method of Patent Document 1, an ultrasonic wave is transmitted from one opening that communicates with the flow path, and the transmitted ultrasonic wave is received by another opening that communicates with the flow path, thereby checking the degree of blockage of the flow path.
JP 2000-338090 A

  Some cores for forming the hollow portion include a thin portion that is thinner than other portions in accordance with the required shape of the hollow portion. Since this type of core tends to break or chip the thin-walled portion, it is necessary to inspect whether the core is broken or not before shipping a cast product as a product.

  In the inspection method of Patent Document 1 for inspecting the degree of blockage of the flow path, it is difficult to inspect the core breakage of the cast product.

  An object of the present invention is to provide a method for inspecting a core breakage of a cast product that can accurately detect the breakage of the core.

  The above object is achieved by the following means.

Preparing a cast molded article comprising a casting main body part and a hollow part formed in the casting main body part using a core including a thin part whose wall thickness is thinner than other parts;
Transmitting ultrasonic waves from the transmission probe toward the inspection surface to be inspected among the boundary surfaces between the casting main body portion and the hollow portion;
Receiving ultrasonic waves reflected on the inspection surface by a receiving probe;
Detecting breakage of the core based on the received ultrasonic wave, and
In the step of preparing the cast molded product, a cast molded product obtained by using a core provided with a flat portion having a cross-sectional planar shape at the tip of the thin portion, and molding the inspection surface into a planar shape by the flat portion. This is a core breakage inspection method.

  According to the present invention, by setting the shape of the reflection source to a planar shape, it is possible to reduce the dispersion and attenuation of the ultrasonic waves reflected on the inspection surface and increase the reflection efficiency. Therefore, a stable and clear echo signal can be obtained from the reflection source, the amplitude of the echo signal can be increased, and the detection performance (S / N) can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an inspection device 20 that embodies a core breakage inspection method for a cast product 10 according to the present invention, and FIG. 2 (A) is a cross-sectional view showing the main part of the inspection device 20. 2B is a cross-sectional view showing the core 30 used when preparing the cast product 10, and FIG. 3 is a diagram showing an example of the waveform of the reflected wave. FIG. 4 is a cross-sectional view showing the main part of the inspection apparatus in a proportional manner.

  With reference to FIG. 1 and FIG. 2, the inspection apparatus 20 is provided for a cast product 10 including a cast body portion 11 and a hollow portion 12 formed in the cast body portion 11 using a core 30. Used to detect breakage of the core 30. In the illustrated example, the cast product 10 is an engine cylinder head, and the hollow portion 12 is a water jacket for flowing cooling water. The core 30 is, for example, a sand core, and includes a thin portion 31 that is thinner than other portions. Since the thin-walled portion 31 of the core 30 is likely to be broken or chipped, the inspection device 20 inspects whether the thin-walled portion 31 is broken before the engine cylinder head 10 is shipped as a product.

  The inspection device 20 uses the principle of a well-known ultrasonic flaw detection test. The inspection device 20 transmits and receives ultrasonic waves (corresponding to a transmission probe and a reception probe) and the probe 21. A connected pulse generator 24, a receiver 25 connected to the probe 21, an imaging processing device 26 connected to the receiver 25, and a control device 27 connected to the imaging processing device 26. Have. In the embodiment, one probe 21 that is used for both transmission and reception is used. The pulse generator 24 and the receiver 25 constitute a transmission / reception circuit.

  The illustrated probe 21 is an oblique probe that transmits and receives ultrasonic waves obliquely with respect to the flaw detection surface 10a, and is configured by attaching a vibrator 23 to a wedge 22 made of synthetic resin. The probe 21 transmits ultrasonic waves toward the inspection surface 14 to be inspected in the boundary surface 13 between the casting main body 11 and the water jacket 12. The frequency of the transmitted ultrasonic wave is set to a predetermined frequency based on the signal from the pulse generator 24. The ultrasonic wave emitted from the vibrator 23 is propagated into the casting body 11 with a predetermined refraction angle θ. The refraction angle θ is calculated from the positional relationship between the probe 21 and the inspection surface 14 based on the design data of the engine cylinder head 10. The oblique angle probe 21 is preferably configured so that the refraction angle can be adjusted. This is because it is possible to finely adjust the refraction angle and to inspect a plurality of types of engine cylinder heads 10.

  The receiver 25 receives a signal (echo signal) related to the ultrasonic wave received by the probe 21 and reflected from the inspection surface 14.

  The control device 27 includes a CPU, a display 28, and the like, controls the operation of the entire inspection device 20, and detects whether the core 30 is broken. The display 28 displays an imaged ultrasonic waveform, a detection result, and the like.

  In a general core, the tip of the thin portion is formed in an arc shape. For this reason, the inspection surface 41 of the engine cylinder head 40 is also formed in an arc shape as shown in FIG. If the inspection surface 41 has an arc shape, the ultrasonic wave reflected by the inspection surface 41 is dispersed and attenuated, resulting in an unclear echo signal from the reflection source. Therefore, the amplitude of the echo signal is reduced and the detection performance (S / N) is lowered.

  Therefore, in the present embodiment, the following means are taken in order to increase the amplitude of the echo signal and improve the detection performance (S / N).

  That is, when the engine cylinder head 10 is prepared, the core 30 provided with the flat portion 32 having a cross-sectional planar shape at the tip of the thin portion 31 is used (see FIG. 2B), and the inspection surface 14 is set to the flat portion 32. To form a planar shape (see FIG. 2A).

  The flat portion 32 is provided on the core 30 so that the normal line on the inspection surface 14 having a planar shape is directed toward the probe 21. The inclination angle of the flat portion 32 is calculated from the positional relationship between the probe 21 and the inspection surface 14 based on the design data of the engine cylinder head 10.

  The range for forming the flat portion 32 may be a partial range at the tip of the thin portion 31. That is, it suffices if the inspection surface 14 formed by the flat portion 32 is located within a range where the ultrasonic wave propagating through the casting main body 11 can be reflected. Furthermore, the inspection surface 14 is set to an area that does not affect the flow rate of the cooling water so as not to disturb the original function of the water jacket 12.

  By setting the shape of the reflection source to a planar shape as described above, it is possible to reduce the dispersion and attenuation of ultrasonic waves reflected by the inspection surface 14 and increase the reflection efficiency. Therefore, a stable and clear echo signal can be obtained from the reflection source, the amplitude of the echo signal can be increased, and the detection performance (S / N) can be improved (see FIG. 3). In FIG. 3, the symbol “3A” indicates a reflected wave on the flaw detection surface 10 a, and the symbol “3B” indicates a reflected wave on the inspection surface 14.

  Further, in the present embodiment, when the engine cylinder head 10 is prepared, the planar shape is inspected by using the core 30 in which the surface roughness of the flat portion 32 is smaller than the surface roughness of other portions. The surface roughness of the surface 14 is smaller than the surface roughness of the other boundary surface 13, that is, a smooth surface. Specifically, by applying a coating mold to the surface of the flat portion 32, the surface roughness of the flat portion 32 in the core 30 is made smaller than the surface roughness of other portions. Thereby, the coating layer 15 having a smaller surface roughness than the surface roughness of the other boundary surface 13 is formed on the inspection surface 14 formed by the flat portion 32 of the core 30 (FIG. 2A). reference). For the coating mold, a mixed liquid of a volatile binder containing flat particles and the like can be used.

  By setting the interface property of the reflection source to a smooth surface as described above, it is possible to further reduce the dispersion and attenuation of the ultrasonic waves reflected by the inspection surface 14 and further increase the reflection efficiency. Therefore, a stable and clear echo signal can be obtained from the reflection source, the amplitude of the echo signal can be increased, and the detection performance (S / N) can be improved.

  Next, the detection procedure of the core break will be described.

  First, an engine cylinder head 10 including a casting main body 11 and a water jacket 12 formed in the casting main body 11 using a core 30 including a thin wall portion 31 that is thinner than other portions is prepared. (Step of preparing the engine cylinder head 10).

  In the step of preparing the engine cylinder head 10, a core 30 having a flat portion 32 having a cross-sectional planar shape at the tip of the thin portion 31 is used (see FIG. 2B), and the inspection surface 14 is set to a flat portion. 32 is formed into a planar shape (see FIG. 2A). Further, by applying a coating mold to the surface of the flat portion 32, the surface roughness of the flat portion 32 of the core 30 is made smaller than the surface roughness of other portions, and the inspection surface 14 has other boundary surfaces. A coating layer 15 having a surface roughness smaller than the surface roughness 13 is formed (see FIG. 2A).

  Next, ultrasonic waves are transmitted from the probe 21 toward the inspection surface 14 to be inspected in the boundary surface 13 between the casting main body 11 and the water jacket 12 (step of transmitting ultrasonic waves). The ultrasonic wave emitted from the vibrator 23 is propagated into the casting body 11 with a predetermined refraction angle θ. The refraction angle θ is calculated from the positional relationship between the probe 21 and the inspection surface 14 based on the design data of the engine cylinder head 10.

  Next, the ultrasonic waves reflected on the inspection surface 14 are received by the probe 21 (step of receiving ultrasonic waves). In the present embodiment, by setting the shape of the reflection source to a planar shape and further setting the interface property of the reflection source to a smooth surface, the dispersion and attenuation of the ultrasonic waves reflected by the inspection surface 14 are reduced. The reflection efficiency can be increased. Therefore, a stable and clear echo signal can be obtained from the reflection source, the amplitude of the echo signal can be increased, and the detection performance (S / N) can be improved.

  Next, the breakage of the core 30 is detected based on the received ultrasonic waves (step of detecting the breakage of the core). When the core breakage does not occur, an echo appears at the design position because the position of the inspection surface 14 is in accordance with the design data. Therefore, whether or not the core 30 is broken can be determined based on the position where the echo appears. The detection position of the inspection surface 14 is obtained from the propagation speed (sound speed) of the ultrasonic wave and the time required for the reflected wave to return. The display 28 displays an imaged ultrasonic waveform, a detection result, and the like.

  As a result of measurement using the selected sensor, the amplitude of the echo signal increased, the detection performance (S / N) was improved, and the effectiveness of the method of the present invention was confirmed. The specifications of the selected sensor are as follows.

Vibrator material: Lead niobate with matching layer Vibrator diameter: φ8
Damper: Tungsten epoxy resin (with lateral vibration eliminating coil)
Delay material: Polystyrene Delay material shape: 20 mm square Ultrasonic incident point: Center Sound absorbing material: Yes.

(Modification example)
Although the embodiment has been described in which the shape of the reflection source is set to a planar shape and the interface property of the reflection source is set to a smooth surface, at least the object of the present invention is set by setting the shape of the reflection source to a planar shape. Can be achieved.

  Although the transmission probe and the reception probe are shared by the single probe 21, the transmission probe and the reception probe can be provided separately and independently.

It is a schematic block diagram which shows the inspection apparatus which actualized the core breakage inspection method of the cast molded product which concerns on this invention. 2A is a cross-sectional view showing the main part of the inspection apparatus, and FIG. 2B is a cross-sectional view showing a core used when preparing a cast product. It is a diagram which shows an example of the waveform of a reflected wave. It is sectional drawing which shows the principal part of the inspection apparatus in contrast.

Explanation of symbols

10 Engine cylinder head (cast product),
11 Cast body part,
12 Water jacket (hollow part),
13 interface,
14 Inspection surface,
15 coating layer,
20 inspection equipment,
21 probes (transmission probes, reception probes),
22 Wedge,
23 vibrator,
24 pulse generator,
25 receiver,
26 imaging processing device,
27 control device,
28 display,
30 core,
31 Thin part,
32 Flat part.

Claims (5)

Preparing a cast molded article comprising a casting main body part and a hollow part formed in the casting main body part using a core including a thin part whose wall thickness is thinner than other parts;
Transmitting ultrasonic waves from the transmission probe toward the inspection surface to be inspected among the boundary surfaces between the casting main body portion and the hollow portion;
Receiving ultrasonic waves reflected on the inspection surface by a receiving probe;
Detecting breakage of the core based on the received ultrasonic wave, and
In the step of preparing the cast molded product, a cast molded product obtained by using a core provided with a flat portion having a cross-sectional planar shape at the tip of the thin portion, and molding the inspection surface into a planar shape by the flat portion. Core breakage inspection method.   2. The cast molded product according to claim 1, wherein the flat portion is provided on the core so that a normal line on the inspection surface having a planar shape is directed toward the reception probe. 3. Core breakage inspection method.   In the step of preparing the cast product, the surface roughness of the inspection surface having a planar shape is reduced by using a core in which the surface roughness of the flat portion is smaller than the surface roughness of other parts. The core breakage inspection method according to claim 1 or 2, wherein the core breakage inspection method is smaller than the surface roughness of the other boundary surface.   The casting according to claim 3, wherein the surface roughness of the flat portion in the core is made smaller than the surface roughness of other portions by applying a coating mold to the surface of the flat portion. Inspection method for core breakage of molded products.   The core breakage inspection method according to any one of claims 1 to 4, wherein the cast product is an engine cylinder head, and the hollow portion is a water jacket for flowing cooling water.

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