JP6698441B2 - Radiation imaging apparatus and radiation imaging method - Google Patents

Description

  The present invention relates to a radiation imaging apparatus and a radiation imaging method for continuously nondestructively imaging a molten metal injection state and the like in a casting process of a mass-produced casting part having a complicated shape.

  Among the metal workings of various industrial products, the casting method is the oldest and most popular method and is a working method in which a metal is once melted and then the molten metal is poured into a mold to be solidified and molded. Compared with forging and pressing, the greatest feature of this processing method is that if a mold can be constructed, complex three-dimensional shapes can be formed at once in a short time. However, when the molten metal is poured into the mold, gas is entrained, and a part where the molten metal does not flow sufficiently occurs, which causes defects inside and outside the casting. These are collectively referred to as casting defects, and various methods have been researched and developed to establish a method in which these defects do not occur in the casting process, but the production of casting defects has not been completely suppressed in the mass production casting process. Therefore, in order to prevent these casting defects, the injection state of the molten metal at each time is measured in the process of injecting the molten metal into the mold, and bubbles are generated due to gas entrainment, and the area where the molten metal flows in is insufficient. Need to be identified. If the molten metal injection process inside the mold can be dynamically measured, various models used in the casting simulation can be verified and the accuracy can be improved, and the simulation accuracy can be improved from the current level. As a result, it becomes possible to manufacture a high-quality cast product without the above-mentioned casting defects by optimizing the mold shape and the casting process conditions.

JP2010-125465

"Visualization of decrease in mold-casting", Itsuo Ohnaka, Journal of Japan Society for Precision Engineering, Vol.73, No.2, 2007(p171-174)

  Conventionally, as described in Non-Patent Document 1, the inflow state of the metal melt inside the mold has been observed and measured by flowing a fluid simulating the metal melt into a transparent resin model mold. With these systems, the actual molten metal injection state inside the mold can be simulated to some extent, but it is difficult to simulate the flow characteristics of the molten metal, the detailed mold shape, and the surface condition of the mold. Therefore, there is a need for a method and an apparatus for continuously nondestructively imaging the state of molten metal injection in the process of casting a mass-produced casting part having a complicated shape, the state in which the actual molten metal is injected into an actual mold. There is.

  In Non-Patent Document 1, a mold model is installed in the middle of an X-ray tube and a detector (image intensifier), high-temperature molten metal is injected into a simple model mold, and X-ray transmission images are taken at regular time intervals. An apparatus for capturing an image has been introduced. In this device, the maximum tube voltage of the X-ray tube is 210 kV and the current is 10 mA, and the transmission capacity of the cast steel material is limited to about 2 mm. Therefore, it is difficult to perform transmission imaging of the injection state of the molten metal in the mold (sand mold, mold) for the actual product.

  Patent Document 1 proposes a casting analysis device including a cavity filled with molten metal, an X-ray source, an X-ray detection means (image intensifier), and an analysis mold. In this device, the metal solidification process after the molten metal is completely filled in the mold is measured from the transmission image. Therefore, it is not possible to take an image of the injection state of the molten metal into the mold. Further, since it is a basic analytical analysis of the solidification process, the target test specimen is not an actual product mold but an analysis mold having a thin cavity, and it is difficult to apply it to an actual product size mold.

  A high-energy X-ray source that penetrates a thick metal material is required in order to visualize non-destructively a state in which a molten metal is injected into a mold of an actual product size by a non-destructive X-ray transmission image. In that case, a detector having high sensitivity to high-energy X-rays is also required for the detector that detects attenuated X-rays after transmission. On the other hand, when high-energy X-rays are used to transmit and image a mold (sand mold, mold) of a real product size, many scattered rays are generated when the X-rays pass through the mold region. The scattered radiation becomes image noise in the transmission image, and when a transmission image when the molten metal is injected inside the mold is captured using a detector such as a general image intensifier, the image becomes very unclear. On the other hand, if the energy of the X-ray source is reduced in order to reduce the scattered radiation, the X-ray transmission ability becomes insufficient with respect to the thickness of the mold (sand mold, mold) of the actual product size, and an X-ray transmission image cannot be obtained. . The scattered radiation generated when the X-rays are transmitted through the metal is also generated in the molten metal region, but since the amount thereof is relatively small compared to the volume of the template region, the scattered radiation generated in the template region is the most visible in the image. It has a great influence.

  The object of the present invention has been made in view of the above circumstances, and in order to improve the quality of cast products and reduce the defective product generation rate, molten metal is injected into a mold of the actual product size. A radiation image pickup apparatus and a radiation image pickup method capable of performing high-quality dynamic image pickup by reducing image noise due to scattered rays generated from a mold region when the state is dynamically visualized by an X-ray transmission image in a non-destructive manner. To provide.

  The present invention is a two-dimensional array of a radiation generator that emits radiation, a first detector unit that has a plurality of detector elements that detect the radiation that has passed through an imaging target, and a collimator that blocks scattered radiation. A radiation detector having a second detector unit having a plurality of radiation detector elements for detecting radiation that has passed through an imaging target; and radiation that has passed through the imaging target for the first detector unit and the second detector unit. A detection device that is provided with a driving device that moves the imaging target or moves the first detector unit and the second detector unit so as to detect one of them, and outputs the first detector unit and the second detector unit. The above object can be achieved by a radiation imaging apparatus including a calculation device that creates a transmission image of an imaging target in consideration of the amount of scattered radiation using data.

  According to the present invention, it is possible to obtain a high-definition transmitted image that is nondestructive with respect to a mold of an actual product size and has small image noise.

FIG. 6 is a diagram showing a procedure of a radiation imaging method according to the first embodiment of the present invention. 1 is a schematic diagram of a radiation imaging apparatus according to a first embodiment of the present invention. It is a figure which shows the mold sample shape of an imaging target. FIG. 3 is a diagram showing an arrangement at the time of imaging only a mold part when a mold sample to be imaged is imaged by the radiation imaging apparatus according to Example 1 of the present invention. It is a figure which shows the transmission image simulation result at the time of imaging only the casting_mold|template part of the casting_mold|template sample of imaging object by the radiation imaging device by Example 1 of this invention. FIG. 3 is a diagram showing an arrangement in which a mold sample to be imaged is imaged with a radiation imaging apparatus according to the first embodiment of the present invention when a molten metal is injected into a mold part. FIG. 5 is a diagram showing a simulation result when a mold sample to be imaged is imaged in the radiation imaging apparatus according to the first embodiment of the present invention while a molten metal is being injected into the mold part. 6 is a schematic diagram of a radiation imaging apparatus according to a second embodiment of the present invention. FIG. It is a figure which shows the procedure of the radiation imaging method by Example 3 of this invention.

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

  FIG. 1 is a flow chart of a radiation imaging method for capturing a dynamic transmission image of the present embodiment, FIG. 2 shows a configuration of a radiation imaging apparatus 20 of the present embodiment, and FIG. 3 is a sample of a mold to be imaged. An example is shown, and FIG. 4 is a diagram showing a state when the mold sample of FIG. 3 is imaged by the radiation imaging method of the present embodiment.

  As shown in FIG. 2, the radiation imaging apparatus 20 fixes and supports the radiation generation apparatus 1, the first detector unit 2, the second detector unit 5, the first detector unit 2 and the second detector unit 5. The supporting device 7, the computing device 8, the memory and display device 9, the first detector unit 2 and the second detector unit 5 are laterally moved and a detector driving device 19 for setting them at a predetermined position is provided. The radiation imaging apparatus 20 of the present embodiment is a radiation imaging apparatus capable of capturing a dynamic transmission image.

  The radiation generation device 1 has a radiation source that generates radiation such as X-rays, γ-rays, and neutron rays. In this embodiment, a radiation generating apparatus including an X-ray source that generates X-rays will be described as an example. As the X-ray source, an X-ray tube can be used at a voltage of 600 kV or less and a linear accelerator (LINAC) at a voltage of 1 MV or more.

  The first detector unit 2 includes a plurality of detector elements 3 (line detector elements) arranged at predetermined intervals in a one-dimensional direction, a collimator 4 provided in front of each detector element 3, a detector element 3 and a collimator. A first detector unit driving device 17 that moves the unit 4 in the height direction is provided. As the detector element 3, a semiconductor detector element or a scintillator type detector element can be used. The collimator 4 is arranged between the radiation generating device 1 and the detector element 3 and in contact with the detector element 3. The collimator 4 shields the scattered radiation and makes the radiation transmitted through the imaging target incident on the detector element 3. Instead of the line detector element 3 and the collimator 4, an image intensifier equipped with a front collimator may be used. The first detector unit driving device 17 moves the first detector unit 2 up and down in the height direction by moving the line detector element 3 and the collimator 4 integrally in the height direction.

  The second detector unit 5 includes a plurality of detector elements 6 (two-dimensional array detector elements) arranged in a two-dimensional plane. The two-dimensional array detector element is, for example, a plurality of detector elements 6 arranged in a two-dimensional plane in a square lattice.

  The arithmetic unit 8 has a first imaging mode in which an imaging target images a fixed area (for example, a mold area) that does not change with time, and a change area that changes with time (for example, by injecting a molten metal into a mold, The second imaging mode is for imaging an imaging target including a region that changes with time). The computing device 8 obtains the amount of scattered radiation using the detection data output from the first detector unit 2 and the second detector unit 5 in the first imaging mode, and includes the change region in the second imaging mode. The imaging target is imaged at a predetermined time interval using the second detector unit, and a fluoroscopic image considering the amount of scattered radiation is created. The predetermined time interval may be a predetermined time interval stored in the storage device, or may be information on the time interval set by the operator.

  The detector driving device 19 moves the first detector unit 2 and the second detector unit 5 in the lateral direction and installs them at a predetermined position.

  A radiation imaging method for capturing a dynamic transmission image using the radiation imaging apparatus 20 of this embodiment will be described. First, in step S100, the detector driving device 10 sets the radiation by moving the first detector unit 2 to a position facing the Celsius device (X-ray tube) 1 with respect to the mold 10 that is the imaging target.

  In step S101, the first detector unit 2 captures a transmission image of only the mold region 10 before pouring the molten metal into the casting shape frame 12 of the mold 10. The state at this time is shown in FIG. First, an X-ray is generated from the radiation generation device 1 and is applied to the mold 10 which is the imaging target. The first detector unit driving device 17 moves the line detector element 3 and the collimator 4 so as to capture an image from the bottom to the top of the projection surface of the mold 10. The line detector element 3 detects the X-rays transmitted through the mold 10 at predetermined intervals and outputs the X-ray transmission amount data to the arithmetic unit 8. When the arithmetic unit 8 acquires the X-ray transmission amount data photographed at a predetermined interval, it converts the measured X-ray transmission amount data at each position into digital data to create transmission image data, and a storage and display device. Output to 9. The storage and display device 9 stores the received transmission image data as transmission image data A of the template region acquired from the first detector unit 2.

  Next, in step S102, the detector driving device 19 moves and sets the second detector unit 5 to a position facing the X-ray tube 1 with respect to the mold 10. FIG. 2B shows the set state. The second detector unit 5 does not include the collimator 4 provided in the first detector unit 2, but since the number of detector elements 6 is large, all of the projection surface of the mold is a two-dimensional element array detector element. It is not necessary to move the detector element in the height direction, unlike the line detector 3, since the light can be received by.

  In step S103, a transmission image of only the mold 10 region is captured using the second detector unit 5, and transmission image data B of only the mold region by the second detector unit 5 is acquired. FIG. 5(a) shows transmission image data A of the mold region by the first detector unit 2 obtained by using a transmission image simulator, and FIG. 5(b) shows transmission image data B of the mold region by the second detector unit 5. Shown in b). In the transmission image 13 of the template region by the first detector unit 2, as shown in FIG. 5(a), the radiation scattered from the template region 10 by the collimator 4 provided in front of the line detector element 3 (scattered rays). ) Is cut, a clear transmitted image 13 with less image noise can be obtained. In the transmission image 14 of the template region by the second detector unit 5, as shown in FIG. 5B, scattered rays from the template region 10 are incident on the respective detector elements 6, so that the transmission image 14 with a lot of image noise. Becomes However, when the transmission image 13 of the casting mold region is captured by the first detector unit 2, the transmission line image detector 3 with a collimator is moved in the height direction, which requires a transmission image capturing time. On the other hand, when the transmission image 14 of the casting mold region is captured by the second detector unit 5, since the detector elements 6 are arranged in the entire projection surface region of the casting target mold 10, the transmission image is obtained in a short time.

  Next, in step S104, the difference amount between the transmission image data B of the template region by the second detector unit 5 and the transmission image data A of the template region by the first detector unit 2 is calculated. The difference amount data at each inspection element position obtained here becomes the amount of scattered ray components generated from the template region 10.

  Further, in the next step, in step S105, the injection of the molten metal is started. In the mold sample shown in FIG. 3, the molten metal is injected from the uppermost surface portion 11 of the injection region 12 of the molten metal inside the mold 10. FIG. 6 shows an imaging situation when the molten metal is being injected.

  After the injection of the molten metal is started, in step S106, the second detector unit 5 captures a transmission image at each time t in the process of injecting the molten metal into the mold. Since the injection speed of the molten metal and the speed at which the molten metal flows into the mold 12 and flows into the mold are fast, it is difficult to take an instantaneous one-section image by moving the line detector 3 with a collimator, and the moment when the second detector unit 5 is used. It is necessary to capture the transmission image of

  The steps S106 and S107 of FIG. 1 are repeated to capture an instantaneous transmission image at fixed time intervals until the molten metal is completely filled in the inner mold region 12 of the mold.

  Next, in step S107, when all of the internal mold region 12 of the mold is filled, in the next step S108, the arithmetic unit 8 starts the calculation for subtracting the scattered radiation component amount. In step S109, the difference between the detector element positions obtained in steps S101 to S104 is calculated from the transmission image pickup data C obtained by using the second detector unit 5 in the state where the molten metal is injected into the mold. Subtract the quantity data 103. The calculation device 8 obtains the transmission image data E at each time by repeating step S109 and step S110 with respect to the captured transmission image data at all calculation times.

  7A to 7D show a part of the transmission image data E at each time obtained by performing the process of steps S105 to S110 using the transmission image simulation. It can be seen that the scattered radiation component from the region of the mold 10 is removed from the image at each time, so that a situation in which the molten metal is gradually injected into the region 12 inside the mold can be clearly obtained as a transmission image.

  According to the present embodiment, when a transmission image is taken of a mold (sand mold, mold) of an actual product size, the amount of scattered radiation generated when X-rays penetrate the mold region is determined by the collimator 4 before the molten metal injection. Calculated from the transmission imaging obtained using the first detector unit 2 in which is installed and the transmission imaging obtained using the second detector unit 5 of the two-dimensional element array, and at the time of pouring the molten metal, By capturing a transmission image with the two-detector unit 5 and subtracting the scattered dose from the template region from the transmission image captured image at each time, a high-definition dynamic transmission image with small image noise can be obtained. That is, it is possible to generate and visualize a dynamic transmission image of the molten metal injection state inside the mold.

  Further, according to the present embodiment, the first detection unit 2 having the collimator 4 and the line detector element 3 and the second detector unit 5 having the two-dimensional array of detector elements are used as the X-ray generator 1 and the imaging device. It has a structure in which it can be installed independently at a position where a transmission image can be captured with respect to the target mold. With such a configuration, each transmission image in each process can be acquired, and the amount of scattered radiation generated when radiation passes through the template region can be accurately obtained.

  According to the present example, by analyzing the dynamic transmission image of the molten metal injection state inside the obtained mold, it becomes possible to set the mold shape and casting mold process conditions that can prevent the occurrence of casting defects, and cast products It becomes possible to prevent the occurrence of casting defects and improve the quality.

  A second embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 8, the radiation imaging apparatus 20A of the present embodiment includes a radiation generation apparatus 1, a first detector unit 2, a second detector unit 5, a first detector unit 2 and a second detector unit 5. A support device 21, a computing device 8, a storage and display device 9, a table (for example, a turntable) 16 on which an imaging target is placed, and a table drive device for vertically moving the table 16 in a height direction. 18 is provided. The structure of the radiation imaging apparatus 20A according to the present exemplary embodiment and the method of capturing a dynamic transmission image using the radiation imaging apparatus 20A will be described below, focusing on the differences from the first exemplary embodiment.

  The radiation imaging apparatus 20A has a configuration in which the first detector unit 3 is arranged below the second detector unit 5. The table drive device 18 moves the table 15 in the height direction, thereby moving the mold 10 to be imaged on the table 15 in the height direction. In the first embodiment, the first detector unit driving device 17 moves the first detector unit 2 and the second detector unit 5 in the height direction, so that the first detector unit 2 or the second detector unit 5 is moved. Is positioned so as to be arranged at a position facing the radiation generating apparatus 1 with respect to the imaging target, but in the present embodiment, the table driving device 18 moves the table 15 in the height direction to thereby move the first detector unit. This is a configuration in which any one of the second and second detector units 5 is positioned so as to be arranged at a position facing the imaging device 1 with respect to the imaging target.

  The radiation imaging method for capturing a dynamic transmission image using the radiation imaging apparatus 20A of the present embodiment will be described below while focusing on differences from the radiation imaging method of the first embodiment. By carrying out step S101 of FIG. 1, transmission image data A of the template region by the first detector unit 2 is obtained. Further, the table driving device 18 moves the turntable 15 to the position of the second detector unit 5 and executes step S103 of FIG. 1 to obtain transmission image data B of the mold region by the second detector unit 5. In the subsequent processing steps, the same processing as that in and after step S104 of the first embodiment is performed.

  According to this embodiment, the same effect as that of the first embodiment can be obtained.

  A third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a flow chart showing a method for capturing a radiation image of a dynamic transmission image according to this embodiment.

  In the first embodiment, the case where the molten metal is injected into the mold is shown, but in the present embodiment, it is also used for the dynamic transmission image capturing when the state change partially occurs in the general fixed region. An example will be described. In FIG. 9, as compared with FIG. 1 of Example 1, the mold portion is a fixed region, and the molten metal injection region is a region where a state change occurs inside the fixed region. As such a system, for example, a fluid flow state at actual temperature/actual pressure inside a movable part inside a mechanical part, inside a pipe or a reactor is assumed.

  According to this embodiment, the same effect as that of the first embodiment can be obtained.

  Further, according to the present embodiment, it is possible to non-destructively visualize the internal fluctuation situation that could not be visualized from the outside conventionally.

  Furthermore, according to the present embodiment, it is possible to observe the change state of the movable part inside the fixed region for each time point in a general mechanical part from the outside without destructing, and the internal operating state can be confirmed from the outside. When the object to be photographed is the flow state of pipes and reactors, the internal flow state at actual temperature and pressure can be visualized from the outside.

1: Radiation generator,
2: First detector unit 3: Line detector element 4: Collimator 5: Second detector unit 6: Two-dimensional array detector element 7: Support device 8: Arithmetic device 9: Memory and display device 10: Mold 11: Molten metal inflow surface 12 of the mold: molten metal inflow region 15 in the mold: molten metal inflow part 16: turntable 17: first detector unit drive device 18: table drive device 19: detector drive device 20, 20A: radiation Imaging device

Claims (11)

A radiation generator for irradiating radiation,
A first detector unit having a plurality of detector elements for detecting the radiation transmitted through the imaging target and a collimator for shielding the scattered radiation, and detecting the radiation transmitted through the imaging target in a two-dimensional array A radiation detector having a second detector unit having a plurality of radiation detector elements for
The imaging target is moved, or the first detector unit and the second detection are performed so that the radiation transmitted through the imaging target is detected by either the first detector unit or the second detector unit. Equipped with a drive to move the vessel unit,
Radiation, comprising: a calculation device that creates a transmission image of the imaging target in consideration of the amount of scattering of the radiation, using detection data output from the first detector unit and the second detector unit. Imaging device. The radiation imaging apparatus according to claim 1,
The radiation imaging apparatus, wherein the detector element of the first detector unit is a line-arranged detector element composed of a plurality of one-dimensionally arranged detector elements. The radiation imaging apparatus according to claim 1 or 2, wherein
A detector driving device that moves the first detector unit so as to capture an image from the lower end to the upper end of the projection surface of the imaging target;
The arithmetic unit is
A radiation imaging apparatus, wherein the amount of scattering is obtained from a difference between first fluoroscopic image data obtained by moving the first detector unit and second fluoroscopic image data obtained by the second detector unit. The radiation imaging apparatus according to claim 1 or 2, wherein
A table, which is arranged between the radiation generator and the radiation detector, on which the imaging target is placed,
A table drive device that moves the table in the height direction so as to capture an image from the lower end to the upper end of the projection surface of the imaging target,
The arithmetic unit is
The scattering amount of the radiation is obtained from the difference between the first fluoroscopic image data obtained from the first detector unit obtained by moving the table and the second fluoroscopic image data obtained from the second detector unit. Radiation imaging device. The radiation imaging apparatus according to any one of claims 1 to 4,
The arithmetic unit is
The imaging target has a first imaging mode for imaging a fixed area that does not change with time, and a second imaging mode for imaging a changing area that changes with time,
In the first IMAGING mode, determine the amount of scattering of the radiation by using the detection data output from the first detector unit and said second detector unit,
In the second imaging mode, imaging the imaging target including the change region at a predetermined time interval using the second detector unit to create a plurality of fluoroscopic images in consideration of the radiation scattering amount. A characteristic radiation imaging apparatus. The radiation imaging apparatus according to any one of claims 1 to 5,
The radiation imaging apparatus, wherein the first detector unit and the second detector unit are semiconductor detectors or scintillator type detectors. A radiation generator for irradiating radiation,
A first detector unit having a plurality of detector elements for detecting the radiation transmitted through the imaging target and a collimator for shielding the scattered radiation, and detecting the radiation transmitted through the imaging target in a two-dimensional array A radiation detector having a second detector unit having a plurality of radiation detector elements for
The imaging target is moved, or the first detector unit and the second detection are performed so that the radiation transmitted through the imaging target is detected by either the first detector unit or the second detector unit. Drive for moving the vessel unit,
Based on the detection data output from the radiation detector, a radiation imaging method by a radiation imaging device including a calculation device that creates a fluoroscopic image of the imaging target,
Determining the amount of scattering of the radiation using the detection data output from the first detector unit and the second detector unit;
A radiation imaging method comprising the step of creating a transmission image of the imaging target in consideration of the amount of scattered radiation. The radiation imaging method according to claim 7,
The radiation imaging method, wherein the detector element of the first detector unit is a line array detector element including a plurality of one-dimensionally arranged detector elements. The radiation imaging method according to claim 7 or 8,
Moving the first detector unit so as to image from the lower end to the upper end of the projection surface of the imaging target;
Radiation imaging, comprising the step of obtaining the amount of scattering from the difference between the first fluoroscopic image data obtained by moving the first detector unit and the second fluoroscopic image data obtained from the second detector unit. Method. The radiation imaging method according to claim 7 or 8,
Moving the imaging target disposed between the radiation generator and the radiation detector so as to capture an image from a lower end to an upper end of a projection surface of the imaging target;
The scattering amount of the radiation is obtained from the difference between the first fluoroscopic image data obtained from the first detector unit and the second fluoroscopic image data obtained from the second detector unit while moving the imaging target. A radiation imaging method, comprising: a step. The radiation imaging method according to any one of claims 7 to 10,
The imaging target has a first imaging mode for imaging a fixed area that does not change with time, and a second imaging mode for imaging a changing area that changes with time,
In the first IMAGING mode, a step of using a detection data output from the first detector unit and said second detector unit determining the amount of scattering of the radiation,
In the second imaging mode, the method includes the step of imaging the imaging target including the change region at a predetermined time interval using the second detector unit to create a fluoroscopic image in consideration of the radiation scattering amount. And a radiation imaging method.

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