Liquid penetrant inspection method and liquid penetrant inspection device

Abstract

To provide a liquid penetrant inspection method and a liquid penetrant inspection device which achieve the reduction in time to the completion of an observation step.SOLUTION: A liquid penetrant inspection method sequentially includes a liquid penetrant step 31, a cleaning step 32, a development step 33, and an observation step 34. A liquid penetrant inspection device 1 for executing the liquid penetrant inspection method injects superheated steam with a steam injection unit 20 in the cleaning step 32, and takes still images with first and second automatic imaging units or makes a video with a third automatic imaging unit in the observation step 34.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a penetrant inspection method and apparatus, and more particularly to a method of penetrantly infiltrating a flaw on the surface of an object to be inspected with a penetrant and then cleaning the flaw, a method of observing the flaw, and an apparatus for carrying out these methods. [Background technology]

[0002] Penetrant testing has long been known as one of the non-destructive testing methods for detecting minute opening defects on the surfaces of products made of non-magnetic materials such as aluminum, titanium, stainless steel, and ceramics that are manufactured as industrial materials.

[0003] Penetrant testing is standardized in JIS Z2343-1 to 6. Conventionally known penetrant testing methods for penetrant testing include a penetrant step in which a penetrant is applied to the surface of the test object to allow the penetrant to penetrate into the open defects present on the surface of the test object, a cleaning step in which the excess penetrant that has not penetrated into the defects and remains on the surface of the test object is removed by a cleaning solution to leave the penetrant only in the defects, a development step in which a uniform thin layer of developer is formed on the surface of the test object after the cleaning solution has dried, and the penetrant that has penetrated into the defects is sucked out to reveal a defect indication pattern on the layer surface, and then an observation step in which the defect indication pattern is confirmed under visible light or ultraviolet light irradiation. If the surface of the test object has oil stains or the like before the penetrant step, a pre-cleaning step is performed to clean the surface using an organic solvent or the like. The penetrant is usually a non-volatile, highly penetrating liquid obtained by dissolving a red dye or a fluorescent dye in a petroleum-based mixed solvent, an aromatic solvent, or the like, and adding a plasticizer, a surfactant, or the like. Also, a method is known in which an organic solvent capable of dissolving the penetrant or water is used as a cleaning liquid for cleaning away the excess penetrant.

[0004] Patent Document 1 discloses a penetrant inspection method in which a cleaning operation is performed in which excess penetrant remaining on the surface of the test object is turned into fine oil droplets and removed by spraying steam onto the surface of the test object using a high-pressure jet in a penetrant inspection test. This technology is superior in that it uses steam, but the steam is thought to contain moisture, so there is room for reducing the amount of wastewater and the drying time can be long.

[0005] [Patent Document 1] Japanese Patent Application Publication No. 52-146291 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally known penetrant testing is a type of flaw detection testing that takes a relatively long time. Therefore, there was an issue of whether the time required for this test could be shortened. More specifically, there was an issue of whether it would be possible to move to the observation process in a short time after the cleaning process, and whether it would be possible to complete the observation process in a shorter time, since the conventional method of observing after the flaws have grown takes too much time in the observation process. Another issue was that the long time required for penetrant testing meant that a large space was required for penetrant testing.

[0007] In particular, when the object to be inspected is a relatively large billet, a storage space is required to wait for the growth of the indication pattern for a number of billets, and therefore, in factories with a large production volume, it is necessary to secure a large space to store a large number of large billets, which is also a problem. Therefore, the conventional penetrant inspection method is practically unable to target parts with a large production volume or parts that must be inspected in real time. In addition, if water is used in the cleaning process, it is safe without the risk of inhalation toxicity or ignition. However, if water is used, the water is contaminated, which imposes a large burden on wastewater treatment, which is also a problem. The present invention provides a penetrant inspection method and a penetrant inspection device used therefor to solve these problems. [Means for solving the problem]

[0008] A penetrant inspection method including a penetrant step of applying a penetrant liquid to a surface of an object to be inspected, a cleaning step of removing the penetrant liquid from the surface of the object to be inspected, and an observation step of observing an indication pattern, The cleaning step is characterized in that superheated steam having a temperature of 110° C. or higher immediately after being sprayed from the nozzle of a steam spraying device is sprayed onto the surface of the test object.

[0009] Furthermore, in the penetrant inspection method of the present invention, the cleaning step is characterized in that the superheated steam is sprayed from an oblique direction onto the surface of the object to be inspected using a steam injection device, and the penetrant liquid atomized by the superheated steam is sucked and collected by a suction and collection means from a direction in which the superheated steam is reflected by the surface of the object to be inspected.

[0010] Furthermore, the penetrant flaw detection method of the present invention is characterized in that the observation step is started within 20 seconds after the cleaning step.

[0011] Furthermore, in the present invention, the penetrant flaw detection equipment is equipped with a penetrating means, a cleaning means, and an observation means for carrying out each process, the cleaning means is equipped with a steam injection device and a suction recovery unit, the steam injection device is capable of injecting the superheated steam toward the surface of the object to be inspected, the temperature of the superheated steam immediately after being injected from the injection port of the nozzle of the steam injection device is 110 degrees or higher, the injection direction of the steam injection device is oblique to the surface of the object to be inspected, the suction recovery unit is equipped with an opening, and the opening is located in a reflection direction in which the superheated steam is reflected after being injected by the steam injection device and coming into contact with the surface of the object to be inspected.

[0012] In addition, in the present invention, the penetrant flaw detection apparatus further includes a transport means, and the penetrant flaw detection apparatus forms a line along which the object to be inspected moves at a constant speed by the transport means, and the object to be inspected is transported sequentially to the penetrant means, the cleaning means, and the observation means, and is characterized in that the observation means includes, on the line, a first automatic imaging device capable of capturing still images and a second automatic imaging device capable of capturing still images, or a third automatic imaging device capable of capturing moving images. Effect of the Invention

[0013] The penetrant inspection method of the present invention is a penetrant inspection method which sequentially comprises a penetrating step of applying a penetrating liquid to the surface of the object to be inspected, a cleaning step of removing the penetrating liquid from the surface of the object to be inspected, and an observation step of observing an indication pattern, and is characterized in that the cleaning step involves injecting superheated steam having a temperature of 110 degrees or more immediately after injection from the nozzle outlet of a steam injection device onto the surface of the object to be inspected.Therefore, it is possible to provide a penetrant inspection method which can effectively remove the penetrating liquid in the cleaning step while accelerating the growth of the indication pattern.

[0014] Furthermore, in the penetrant inspection method of the present invention, the cleaning step is characterized in that superheated steam is sprayed from an oblique direction onto the surface of the object to be inspected using a steam injection device, and the penetrant liquid atomized by the superheated steam is sucked and collected by a suction recovery means from the direction in which the superheated steam is reflected off the surface of the object to be inspected. Therefore, it is possible to provide a penetrant inspection method that reduces the load on wastewater treatment in the cleaning step, reduces the risk of inhalation toxicity and ignition, and improves the working environment.

[0015] Furthermore, the penetrant inspection method of the present invention is characterized in that the observation step is started within 20 seconds after the cleaning step, making it possible to observe the growth of the indication pattern, thereby shortening the time required to complete the observation step of the penetrant inspection method.

[0016] Furthermore, the penetrant flaw detection apparatus of the present invention is equipped with a penetrant means, a cleaning means, and an observation means for carrying out each process, the cleaning means includes a steam injection device and a suction recovery unit, the steam injection device is capable of injecting superheated steam toward the surface of the object to be inspected, the superheated steam has a temperature of 110 degrees or more immediately after being injected from the nozzle of the steam injection device, the injection direction of the steam injection device is oblique to the surface of the object to be inspected, the suction recovery unit has an opening, and the opening is located in the reflection direction in which the superheated steam is reflected after being sprayed by the steam injection device and contacting the surface of the object to be inspected. Therefore, it is possible to provide a penetrant flaw detection apparatus that can effectively remove the penetrant liquid in the cleaning process and accelerate the growth of the indication pattern, reduce the load on wastewater treatment in the cleaning process, reduce the risk of inhalation toxicity and ignition, and improve the working environment.

[0017] Furthermore, in the present invention, the penetrant flaw detection apparatus further comprises a transporting means, and the object to be inspected is moved at a constant speed by the transporting means, forming a line along which the object to be inspected is sequentially transported to the penetrant means, the cleaning means, and the observation means, and the observation means is characterized in that it comprises, on the line, a first automatic imaging device capable of capturing still images and a second automatic imaging device capable of capturing still images, or a third automatic imaging device capable of capturing moving images, so that the growth of the indication pattern can be observed, and as a result, a penetrant flaw detection apparatus can be provided which can shorten the time required to complete the observation process of the penetrant flaw detection method. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a flowchart of a conventional penetrant inspection method. [Diagram 2] 1A and 1B are schematic cross-sectional views showing the transition of the state around the flaw 12 in a conventional penetrant inspection method, in which (W) is the state before the penetrating process 31 is performed, (X) is the state immediately after the penetrating liquid 21 is applied to the flaw 12 during the penetrating process 31, (Y) is the state around the flaw 12 when the penetrating time has elapsed from the state (X) during the penetrating process 31, and (Z) is a schematic diagram showing the state around the flaw 12 after the cleaning process 32'. [Diagram 3] FIG. 2 is a flowchart of a penetrant inspection method according to the present embodiment. [Figure 4] 13 is a schematic cross-sectional view showing the transition of the state around the flaw 12 in the penetrant inspection method of this embodiment, in which (W) is the state before the penetrant process 31 is performed, (X) is the state immediately after the penetrant liquid is applied to the flaw 12 during the penetrant process 31, (Y) is the state around the flaw 12 when the penetrant time has elapsed from the state (X) during the penetrant process 31, and (Z) is a schematic diagram showing the state around the flaw 12 after the cleaning process 32. [Diagram 5] 3 is a schematic diagram showing the state around a flaw 12 when a cleaning step 32 is performed in the penetrant inspection method according to the present embodiment. FIG. [Figure 6] 1 is a schematic diagram mainly showing flaws 12, 12', a first automatic imaging device 24, and a second automatic imaging device 25 during observation step 34 in the penetrant flaw detection device 1 and the penetrant flaw detection method according to the present embodiment. [Figure 7] 1 is a perspective view illustrating a penetrant flaw detection device 1 according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the details of the embodiment of the present invention will be described with reference to the drawings. First, the penetrant inspection method according to the present embodiment will be described. FIG. 1 is a flow chart of a conventional penetrant inspection method. FIG. 2 is a schematic cross-sectional view showing the transition of the state around the flaw 12 in the conventional penetrant inspection method, where the state transitions in the order of (W), (X), (Y), and (Z). Of these, (W) represents the initial state before the penetrant step 31 is performed. (X) represents the state immediately after the application of the penetrant to the flaw 12 in the penetrant step 31, (Y) represents the state around the flaw 12 when the penetrant time has elapsed from the state of (X) in the penetrant step 31, and (Z) represents the state around the flaw 12 after the cleaning step 32'. FIG. 3 is a flow chart of a penetrant inspection method as an example of an embodiment according to the present invention. FIG. 4 is a schematic cross-sectional view showing the transition of the state around the flaw 12 in the penetrant inspection method according to the present embodiment, where the state transitions in the order of (W), (X), (Y), and (Z). Among them, (W) represents the initial state before the penetration step 31 is performed. (X) represents the state immediately after the application of the penetrant to the flaw 12 during the penetration step 31, (Y) represents the state around the flaw 12 when a shorter penetration time than the conventional time has elapsed from the state of (X) during the penetration step 31, and (Z) represents the state around the flaw 12 after the cleaning step 32. FIG. 5 is a schematic diagram showing the state around the flaw 12 during the cleaning step 32 in the penetrant flaw detection device and penetrant flaw detection method according to this embodiment. FIG. 6 is a schematic diagram showing the transition of the flaw 12 when the observation step 34 is performed in the penetrant flaw detection device 1 and penetrant flaw detection method according to this embodiment. FIG. 7 is a perspective view and schematic diagram showing the penetrant flaw detection device 1 according to this embodiment for implementing the penetrant flaw detection method according to this embodiment. Therefore, some of the penetration means, developing means, means for generating superheated steam in the steam injection device 20, and suction recovery means are omitted from the illustration. In this disclosure, for the sake of convenience, when simply referring to the upper side, it refers to the upper side in FIGS. 2, 4, 5, and 6, and when simply referring to the lower side, it refers to the lower side in FIGS.

[0020] The steps shown in FIG. 1 are a flow chart showing the steps of a conventional penetrant inspection method. In the conventional penetrant inspection method, a penetrant step 31, a cleaning step 32', a developing step 33, and an observation step 34' are sequentially performed. This will be described in detail with reference to the state around the flaw 12 shown in FIG. 2. Each of (W) to (Z) in FIG. 2 is a cross-sectional view showing an enlarged view of the flaw 12, which is a target for detection in the penetrant inspection method, on the inspection object 10. First, FIG. 2(W) shows the state before the penetrant step 31 shown in FIG. 1. In the state shown in FIG. 2(W), the flaw 12 has a defect opening 13 and a defect interior 14. The flaw 12 is formed in a shape having the defect opening 13 on the surface 11, which is the surface of the inspection object 10.

[0021] Next, the penetrating step 31 shown in Fig. 1 will be described in detail. The penetrating step 31 is performed by applying the penetrating liquid 21 to the surface 11 of the object to be inspected 10. Methods of application include coating, immersion in the penetrating liquid, etc. The penetrating liquid 21 may be a liquid having a composition in which a fluorescent dye or a red visible dye is dissolved in an oily solvent and a surfactant is further added to the liquid to make it removable by washing with water, or a liquid in which a fluorescent dye or a red visible dye is dissolved in an oily solvent.

[0022] FIG. 2(X) shows the state immediately after the penetrant 21 is applied to the surface 11 in the penetrant step 31. Since the penetrant 21 is applied to the surface 11 immediately, the penetrant 21 has not yet penetrated into the defect interior 14, which is the inside of the flaw 12. In the conventional penetrant inspection method, the penetrant 21 does not penetrate sufficiently into the defect interior 14 from the defect opening 13 unless a certain long penetration time is passed after the penetrant step 31. FIG. 2(Y) shows the state after the long penetration time has passed. In FIG. 2(Y), the penetrant 21 has sufficiently penetrated and penetrated into the defect interior 14. However, since the penetrant 21 covers the surface 11, it is necessary to remove the penetrant 21 from the surface 11 by the cleaning step 32' shown in FIG. 1. Therefore, in the cleaning step 32', the cleaning liquid is applied to the surface 11 from, for example, the direction of the arrow in FIG. 2(Y) so as to wash away the penetrant 21. This causes a transition from the state of FIG. 2(Y) to the state of FIG. 2(Z).

[0023] Next, the state of Fig. 2(Z) will be described in detail. The state of Fig. 2(Z) is a state in which the penetrant liquid 21 that filled the surface 11 of the inspection object 10 has been washed away with a cleaning liquid in the cleaning step 32', and the penetrant liquid 21 has been removed. Although the penetrant liquid 21 has been removed from the surface 11, the penetrant liquid 21 remains inside the defect 14 as it has penetrated therein.

[0024] Next, the developing step 33 will be described. First, in the state shown in FIG. 2(Z), the penetrant 21 remains only inside the defect 14. In this state, the flaw 12 is so fine that the presence of the penetrant 21 is difficult to detect with the naked eye. Therefore, a white inorganic fine powder or a dispersion of the white inorganic fine powder in water or a solvent is applied to the surface 11 as a developer so as to form a uniform thin layer on the test object. Examples of the white inorganic fine powder include magnesium carbonate powder and calcium carbonate powder. Then, the uniform thin layer of the white inorganic fine powder formed on the surface 11 causes a capillary phenomenon, sucking out the penetrant 21 inside the defect 14, thereby forming a rainbow pattern (defect indication pattern). This defect indication pattern shows the defect opening 13 in an enlarged manner, making it easy to detect with the naked eye.

[0025] As for the observation step 34', in addition to visual observation, the indication pattern is observed using a method in which a fluorescent penetrant is used and then a black light is used in a dark room, or an image is generated using an imaging device or the like and then inspected.

[0026] Next, the penetrant inspection method according to the present invention and the penetrant inspection device 1 using this method will be described in detail with reference to Figs. 3 and 4. The steps shown in Fig. 3 are a flow chart showing steps of the penetrant inspection method as an example of an embodiment according to the present invention. Fig. 4 is a cross-sectional view showing an enlarged view of the periphery of a flaw 12, which is a detection target in the penetrant inspection method, on an object 10 in each of Figs. (W) to (Z). Unlike the conventional method, the penetrant inspection method according to the present embodiment includes a heating step 40 shown in Fig. 3. In the heating step 40, heating is performed toward the surface 11 shown in Fig. 4(X) by a heating means. The heating means may be a method using high-frequency induction heating, a method using steam or dry steam, a method using hot air, or a method using infrared heating, or other known means may be used. By heating the surface 11 and the surface vicinity 16 by the heating means, the air inside the defect 14 expands, making it easier to draw in the penetrant liquid 21.

[0027] The penetrant inspection method according to an embodiment of the present invention will be described in more detail with reference to Figs. 3 and 4. The penetrant inspection method according to an embodiment of the present invention shown in Fig. 3 is a method in which a heating step 40, a penetrant step 31, a cooling step 41, a cleaning step 32, a developing step 33, and an observation step 34 are sequentially performed. In this manner, the penetrant inspection method according to this embodiment first performs the heating step 40. In the heating step 40, the surface 11 is heated by a heating means in the initial state shown in Fig. 4(W), and then the penetrant step 31 is performed. In the heating step, it is preferable to heat the surface 11 to 20 degrees Celsius or more in absolute temperature. This means that the penetrant inspection is usually performed at room temperature, and therefore the surface 11 is heated to 20 degrees Celsius or more from room temperature. By heating in this manner, the penetration time is significantly reduced.

[0028] In this disclosure, the penetration time refers to the time required from the end of the process of applying the penetrant liquid 21 to the surface 11 of the object to be inspected 10 in the penetration step 31 until the penetrant liquid 21 has sufficiently penetrated into the interior 14 of the defect for penetrant testing and the state becomes ready for moving on to the next cleaning step 32, 32'.

[0029] In the heating step 40, it is preferable to raise the absolute temperature of the surface 11 by 20 degrees Celsius or more, and it is even more preferable to raise the absolute temperature of the surface 11 by 50 degrees Celsius or more by the heating means. When the absolute temperature of the surface 11 is raised by the heating means by 50 degrees Celsius or more in this manner, it is preferable that the penetrant liquid 21 can penetrate into the defect interior 14 to such an extent that a relatively large flaw of about 10 to 50 microns in size can be detected in a penetration time of about 5 to 10 seconds in a penetrant inspection of a billet or the like.

[0030] The penetrant step 31 in the penetrant inspection method according to this embodiment shown in Fig. 3 is performed by applying the penetrant liquid 21 to the surface 11 of the object 10 to be inspected. This results in a transition to the state shown in Fig. 4(X). The penetrant liquid 21 may be applied by a known method such as application by spraying or immersion in a penetrant liquid tank. Examples of the penetrant liquid 21 include a liquid having a composition in which a fluorescent dye or a red visible dye is dissolved in an oily solvent and a surfactant is further added to the liquid to make it removable by washing with water, or a liquid in which a fluorescent dye or a red visible dye is dissolved in an oily solvent, but other known liquids may also be used.

[0031] In the penetration step 31, after the penetrant liquid 21 is applied, the penetrant liquid 21 is left attached to the surface 11 and the cleaning step 32 is not started until the penetration time has elapsed. This allows the penetrant liquid 21 to penetrate into the defect interior 14. By going through the heating step 40 of the penetrant flaw detection method according to the present embodiment, this penetration time can be made shorter than usual. Specifically, what previously required 5 to 10 minutes or more is reduced to about 5 to 15 seconds. The use of a heating means is preferable because it allows the penetrant liquid 21 to sufficiently penetrate into the defect interior 14 even if the penetration time is shortened.

[0032] Next, the cooling step 41 shown in FIG. 3 will be described in detail. The cooling step 41 is preferably performed during the permeation time after the application of the permeation liquid 21 in the permeation step 31. However, the cooling step 41 may not be provided. In that case, as another example of this embodiment, a permeation time in which the cooling step 41 is not performed may be provided between the permeation step 31 and the cleaning step 32. The specific content of the cooling step 41 is performed by blowing cold air or pouring room temperature water or cold water toward the vicinity of the surface 11 to which the permeation liquid 21 is attached in the state of (X) in FIG. 4 after the permeation step 31. This generates a cooling effect that cools the surface 11 and the surface vicinity 16. The cooling effect also cools the air inside the defect 14 and causes it to contract. As a result, the permeation liquid 21 is drawn into the defect 14. By performing the cooling step 41, such a cooling effect is generated, so that the permeation time from the cooling step 41 to the transition to the cleaning step 32 can be shortened. As causes of the cooling effect in the vicinity of the surface 11 and the surface vicinity portion 16, cooling from the inside portion of the test object 10 and cooling by the penetrant 21 are also important.

[0033] Next, the cleaning step 32 shown in FIG. 3 and FIG. 4(Y) will be described. In the cleaning step 32, as shown in FIG. 4(Y), the penetrant 21 has sufficiently penetrated into the defect interior 14 from the defect opening 13. In other words, the penetrant 21 has sufficiently penetrated into the defect interior 14. However, the penetrant 21 covers the surface 11, so it is necessary to remove it. For this reason, the penetrant 21 is removed from the surface 11 by the cleaning step 32 shown in FIG. 3. For this reason, the penetrant flaw detection device 1 according to this embodiment is provided with a cleaning means. The cleaning means includes a steam injection device 20 and a suction recovery unit 22. The suction recovery unit 22 is not shown in FIG. 4(Y) and (Z). In the cleaning step 32, a method is used in which the cleaning liquid is injected from the steam injection device 20 in FIG. 4(Y) as superheated steam toward the surface 11 to remove the penetrant 21. By carrying out this, the state of FIG. 4(Y) transitions to the state of FIG. 4(Z).

[0034] Next, the developing step 33 will be described. First, the state in FIG. 4(Z) is a state in which the cleaning step 32 is completed and the penetrant 21 remains only inside the defect 14. In this state, the presence of the penetrant 21 is difficult to detect with the naked eye. Therefore, as a developer, a white inorganic fine powder or a powder obtained by dispersing the white inorganic fine powder in water or a solvent is applied to the surface 11 so as to form a uniform thin layer on the test object. As the white inorganic fine powder, a powder known to be used as a developer, such as magnesium carbonate powder or calcium carbonate powder, may be used. Then, the uniform thin layer of the white inorganic fine powder formed on the surface 11 causes a capillary phenomenon, sucking out the penetrant 21 inside the defect 14, thereby forming a rainbow pattern (defect indication pattern). This defect indication pattern shows the defect opening 13 in an enlarged manner, making it easier to detect with the naked eye and improving the detection accuracy.

[0035] However, the penetrant inspection method of the present invention may be performed by a known method such as a non-developing method without the development step 33. In the case of the non-developing method, the development step 33 is not performed to apply a developer, and the indication pattern of the penetrant is observed as is. For this reason, it is preferable to use a fluorescent penetrant from the viewpoint of convenience of observation in the observation step 34, but the present invention is not limited to this.

[0036] As for the observation step 34 shown in FIG. 3, the indication pattern can be observed by visual inspection or by using known means such as a method of using a fluorescent penetrant and then a black light in a dark room, or a method of generating an image using an imaging device and inspecting it.

[0037] FIG. 5 shows an example of the penetrant inspection method and penetrant inspection device 1 according to the present embodiment, for carrying out the cleaning step 32. The steam injection device 20 injects superheated steam in the direction of the arrow α toward the surface 11 of the test object 10 from the upper right direction. Then, the superheated steam hits the penetrant 21, mixes with the condensed water, turns into fine oil droplets, and the penetrant 21 turns into mist, or the superheated steam condenses into water, mixes with the penetrant 21, and flows down. It is preferable to use superheated steam that has a temperature of 110 degrees Celsius or more immediately after being injected from the nozzle of the steam injection device 20. It is also preferable that the pressure of the superheated steam inside the nozzle of the steam injection device 20 is 0.1 to 1.0 megapascals. If the pressure is lower than 0.1 MPa, the penetrant 21 cannot be effectively removed, and if the pressure exceeds 1.0 MPa, when a fluorescent penetrant is used as the penetrant 21, the fluorescent brightness of the fluorescent penetrant decreases, and the indication pattern may become unrecognizable. The cleaning process 32 is preferably performed in a booth surrounded by a shielding plate so that the mist of the penetrant 21 does not scatter, but this is not a limitation. Also, when the cleaning process is performed in a booth, a suction recovery section may not be provided because the penetrant does not scatter to the outside.

[0038] Furthermore, it is more preferable that the temperature of the superheated steam injected by the steam injection device 20 immediately after being injected from the injection port of the nozzle provided in the steam injection device 20 is 130 degrees Celsius or more and 180 degrees Celsius or less. At 130 degrees Celsius, there is a 30 degree margin before condensation, so that the amount of water that condenses when the superheated steam is sprayed onto the surface 11 and becomes waste water can be reduced, and the drying of the surface 11 can be accelerated. This is preferable because the drying of the surface 11 does not hinder the growth of the indication pattern, in which the penetrant 21 oozes out of the flaw 12 and forms an indication pattern. Furthermore, if the superheated steam exceeds 180 degrees Celsius, when a fluorescent penetrant is used as the penetrant 21, the fluorescent substance contained in the fluorescent penetrant is an organic substance, and there is a risk of the composition changing and the quality being altered.

[0039] As shown in FIG. 5, the opening of the suction recovery unit 22 is provided in the direction of the arrow β, which is the direction in which the superheated steam incident from the direction α is reflected. The suction recovery unit 22 is composed of an opening, a pipe, and a suction recovery means, and the suction recovery means 22 may be a known means such as a mist collector or a local exhaust device combined with a filter. The suction recovery unit 22 may also be equipped with a ventilator 23. If a motor is used to configure the suction recovery means, there is a risk of malfunction when high-temperature mist is sucked. Therefore, in addition to suction from the opening in the β direction, the ventilator 23 also takes in gas from the ventilator 23, which is preferable because it can lower the temperature of the sucked gas when it reaches the suction recovery means. The ventilator 23 may be equipped with a damper with an adjustable air volume (not shown). This damper with an adjustable air volume is preferable because it can adjust the temperature inside the pipe of the suction recovery means 22.

[0040] The moving direction Σ indicated by an arrow in Fig. 5 indicates the direction in which the inspection object 10 is moved along the inspection line by the conveying means. It is preferable that the inspection object 10 is moved along the moving direction Σ by the conveying means at a predetermined speed, which contributes to the automation of the inspection line. In this embodiment, the conveying means is rollers 61 shown in Fig. 7, but any known means such as straight conveying or skew conveying may be used as the conveying means. In the case of skewed transport, fewer peripheral devices are required, but since there is a possibility that the indication pattern will disappear if transport rollers are provided before the observation process, it is more preferable not to provide transport rollers before the observation process.

[0041] Next, the observation step 34 in the penetrant inspection method and penetrant inspection device 1 according to this embodiment will be described in more detail with reference to Fig. 6. After the cleaning step 32 shown in Fig. 5 is completed, the test object 10 that has moved in the traveling direction Σ reaches the observation means of the penetrant inspection device 1. As the observation means, Fig. 6 shows a configuration including a first automatic imaging device 24 capable of capturing still images and a second automatic imaging device 25 also capable of capturing still images, but a configuration including a third automatic imaging device capable of capturing moving images may also be used. Fig. 6 shows a flaw 12 and a flaw 12', but the flaw that has changed state when the flaw 12 moves in the traveling direction is shown as flaw 12'.

[0042] 6, a case where the observation step 34 is started by using a non-developing method after the cleaning step 32 is completed will be described in more detail. The penetrant flaw detection device 1 and the penetrant flaw detection method according to the present invention include the first automatic imaging device 24 and the second automatic imaging device 25, or the third automatic imaging device, as an observation means. After the cleaning step 32 is completed, imaging by the first automatic imaging device 24 or imaging of a moving image by the third automatic imaging device is started in the observation step 34 between 1 second and 20 seconds. In the case of the embodiment shown in FIG. 6, a portion of the surface of the inspection object 10 cleaned in the cleaning step 32 moves in the direction of travel Σ into the imaging range of the first automatic imaging device 24 capable of capturing still images. Then, the portion of the surface of the object 10 cleaned in the cleaning step 32 reaches the imaging range 26 of the first automatic imaging device 24 one second after the completion of the cleaning step 32, and reaches the imaging range 26' of the second automatic imaging device 25 by 20 seconds after the completion of the cleaning step 32, and is imaged by the second automatic imaging device 25. However, from the viewpoint of time saving, it is fully possible and preferable to perform this within 1 to 10 seconds from the completion of the cleaning step 32.

[0043] The first automatic imaging device 24 and the second automatic imaging device 25 capture images at regular intervals that are appropriately designed according to the transport speed of the transport means traveling in the traveling direction Σ. It is preferable that the interval between the first automatic imaging device 24 and the second automatic imaging device 25 is set to a predetermined interval depending on the transport speed, which is the speed at which the transport means travels in the traveling direction Σ, after a specific part enters the imaging range 26 and before it enters the next imaging range 26', so that the growth of the indication pattern can be observed by the first and second automatic imaging devices to distinguish pseudo patterns, etc.

[0044] In the case of capturing a moving image by the third automatic imaging device, the portion of the surface of the object 10 cleaned in the cleaning step 32 reaches the imaging range of the third automatic imaging device one second after the completion of the cleaning step 32, and the portion of the surface of the object 10 cleaned in the cleaning step 32 is imaged for a predetermined period of time. By capturing images in this manner, the growth of the indication pattern can be captured and a false pattern or the like can be distinguished, which is preferable.

[0045] Next, referring to FIG. 6, the penetrant inspection method and penetrant inspection device 1 according to this embodiment will be described in detail with a focus on the state of the flaw 12. The flaw 12 shown in FIG. 6 has reached the imaging range 26. The flaw 12 is at a stage where the penetrant 21 has started to come out from the flaw opening 13 onto the surface 11 and has started to form an indication pattern. Next, the flaw 12' that has reached the imaging range 26' will be described. The flaw 12' has more penetrant 21 coming out from the flaw opening 13 onto the surface 11 than the flaw 12, forming an indication pattern. The indication pattern formed by the flaw 12' is wider than that formed by the flaw 12. This is called the growth of the indication pattern in this disclosure, and since the presence of the flaw can be observed by observing the growth of the indication pattern, a configuration in which the first automatic imaging device 24, the second automatic imaging device 25, or the third automatic imaging device is provided is preferable. This configuration is preferable because it reduces the time required to complete the observation process compared to when the observation process is performed after the indication pattern has grown sufficiently.

[0046] Next, referring to FIG. 6, the spraying of superheated steam onto the surface 11 by the steam spraying device 20 in the cleaning means will be described to accelerate the growth of the indication pattern. The flaw 12 in FIG. 6 is in a state in which the penetrant 21 has oozed a small amount onto the surface 11 to form an indication pattern, and at this time, the temperature inside the defect 14 and the surface vicinity 16 is increased by heating with the superheated steam. As a result, the air pressure inside the defect 14 is increased, and a pressure difference is generated between the inside of the defect 14 and the atmospheric pressure, so that this pressure generates a force pushing the penetrant 21 onto the surface 11. This force increases the speed at which the penetrant 21 oozes onto the surface 11. In addition, the viscosity of the penetrant 21 is reduced by heating with the superheated steam, and the surface 11 dries quickly, which also contribute to the increase in the speed at which the penetrant 21 oozes onto the surface 11. This accelerates the growth of the indication pattern.

[0047] Distinguishing between indications and pseudo indications cannot be generalized because there are various patterns depending on the condition of surface 11, but as the growth of the indications accelerates, the change in the indications becomes more noticeable, and by capturing this with an observation means it may be possible to determine the presence or absence of scratches, so it is preferable to make the growth of the indications observable between 1 and 20 seconds after the end of cleaning step 32. However, from the standpoint of saving time, it is fully possible and preferable to do this between 1 and 10 seconds from the completion of cleaning step 32.

[0048] Next, the penetrant inspection device 1 and the penetrant inspection method according to the present invention will be described with reference to FIG. 7. FIG. 7 is a perspective view of the schematic diagrams of FIG. 5 and FIG. 6. The penetrant inspection device 1 shown in FIG. 7 forms a line, and the suction and recovery means 22, the steam injection device 20, the first automatic imaging device 24, and the second automatic imaging device 25 are arranged from the left front side toward the traveling direction Σ. As another example of this embodiment, in the case of a configuration in which a third automatic imaging device is provided, the third automatic imaging device is arranged at the position of the first automatic imaging device 24 shown in FIG. 6 and FIG. 7. The inspected object 10 is transported by the rollers 61 at a predetermined speed in the traveling direction Σ. This transport speed is the transport speed. Since the transport speed is constant, it is necessary to perform continuous observation in the observation process 34. Therefore, when the transport speed is constant, the burden on the inspector is large when the inspector visually checks. For this reason, it is preferable to configure the observation means as the first automatic imaging device 24, the second automatic imaging device 25, or the third automatic imaging device and automate it, but the present disclosure is not limited to this and it may also be by known means such as visual inspection.

[0049] The penetrant flaw detection device 1 of the present invention is provided with a cleaning means and an observation means in addition to the heating means. A developing means for carrying out the developing step 33 may also be provided. However, since there is a development-free method, the developing means does not have to be provided. The developing means is preferably a spraying or coating device for applying a developer or developing solution to the surface 11 of the inspected object 10, and the observation means is preferably composed of a recording medium, a display medium, etc. in addition to the first to third automatic imaging devices, although any known means may be used for each of them as appropriate.

[0050] Next, the heating means in the penetrant inspection method and penetrant inspection device 1 of this embodiment will be described in more detail. As the heating means, a high-frequency induction heating method, a steam or dry steam method, a hot air method, and an infrared heating method can be used. When using hot air, it is preferable to use dry air, and known means can be used as devices for implementing these heating means. Moreover, the heating means is configured to be able to implement the heating step 40.

[0051] As an example of an embodiment of the penetrant inspection device and penetrant inspection method of the present invention, the operation when high-frequency induction heating is used as the heating means will be described in detail below. In the heating step 40 performed in the state of FIG. 4(W), the range from the surface 11 to the penetration depth δ shown in the figure is the surface vicinity 16. The penetration depth δ in this case is an arbitrary value when an arbitrary penetration depth δ is set in advance in the design of the heating step 40. When high-frequency induction heating is performed as the heating means in the heating step 40, the surface vicinity 16 is heated first. Next, the air on the surface 11 adjacent to the surface vicinity 16 and the air inside the defect 14 are heated. By heating the air, the air remaining inside the defect 14 is heated when the state of FIG. 4(X) is reached in the penetrant step 31 shown in FIG. 3. During the penetration time, the heated air is cooled and contracted by the cooling effect of the cooling from the part inside the surface vicinity 16 of the test object 10, the cooling by the penetrant 21, and the cooling by the cooling step 41. As the air inside the defect 14 contracts, a force acts to draw the penetrant liquid 21 into the defect 14, and the time it takes for the penetrant liquid 21 to permeate into the defect 14 is shortened.

[0052] Next, the penetrant inspection method and penetrant inspection device of the present invention are applicable to materials in which eddy currents do not easily flow, and the case where the heating means is steam or, among steam, dry steam will be described in detail. In the case of dry steam, although not shown, as an example of this embodiment, the penetrant inspection device 1 is provided with one or more steam injection units. The steam injection unit is composed of an injection nozzle, a hose, a steam supply source, etc., but as long as it can inject steam onto the surface 11, it may be by any suitable known means. Dry steam or steam is injected toward the surface 11 by the steam injection unit. At this time, it is preferable that the steam or dry steam has a steam pressure of 0.03 megapascals or more. As a result, the air on the surface 11 becomes heated steam. And the steam penetrates into the inside 14 of the defect. In addition, by heating not only the surface 11 but also the surface vicinity 16 as a target, the air inside the defect 14 is prevented from cooling immediately. By heating in this way, the air remaining inside the defect 14 is heated when the state of FIG. 4(X) is reached in the penetration step 31 shown in FIG. 3. After the permeation step 31, the heated air is cooled during the permeation time by the cooling effect of the cooling from the portion inside the surface vicinity portion 16 of the object 10, the cooling by the permeation liquid 21, and the cooling step 41, and the steam is condensed. As the steam inside the defect 14 condenses, a pressure difference occurs between the air inside the defect 14 and the atmospheric pressure, and the permeation liquid 21 is drawn into the defect 14. In this way, the permeation time required for the permeation of the permeation liquid 21 into the defect 14 is shortened.

[0053] Next, the relationship between performing the heating step 40 and the faster penetration time will be described. When the surface 11 is heated to 50 degrees Celsius in absolute temperature by the heating means in the heating step 40, theoretically, when air at 25 degrees is raised by 50 degrees in the heating step 40, for example, the volume expands and increases by 17 percent. In this state, the penetration step 31 is performed and the penetrating liquid 21 is applied to the surface 11. Then, in addition to the force of the penetrating liquid 21 itself trying to enter the inside 14 of the defect, the volume of the air inside the defect 14, which expanded by 17 percent, returns to its original state as the temperature approaches normal temperature, and the volume decreases by about 17 percent. This makes it possible to instantly draw a large amount of the penetrating liquid 21 into the inside 14 of the defect.

[0054] As an example of an embodiment of the penetrant inspection device and penetrant inspection method according to the present invention, the case where the heating means is only hot air or only infrared heating will be described. When only these means are used, the heating time, which is the time required to heat the surface 11 to 20 degrees Celsius or more in absolute temperature, may take about one minute or more. Therefore, even if the surface vicinity 16 is heated, thermal diffusion occurs, and the inner part of the object 10, which is closer to the surface vicinity 16, also becomes hot. In this case, the cooling effect on the surface vicinity 16 due to the inner part of the object 10 being at room temperature is weakened. Therefore, it is particularly preferable to provide a cooling process 41.

[0055] Next, as an example of an embodiment of the penetrant inspection device and penetrant inspection method according to the present invention, the case where the heating means is only steam or only high-frequency induction heating will be described. When the heating means is only hot air or only infrared heating, it is difficult to heat the surface 11 to 20 degrees Celsius or more in absolute temperature within 10 seconds, whereas when the heating means is only steam or only high-frequency induction heating, it is fully possible to heat the surface 11 to 20 degrees Celsius or more in absolute temperature even if the heating time is within 10 seconds. Therefore, when the heating means is only steam or only high-frequency induction heating, the heating time can be kept within 10 seconds, and as a result, thermal diffusion is sufficiently suppressed. Therefore, when the heating means is only steam or only high-frequency induction heating, it is preferable to provide the cooling process 41, but the cooling process 41 may not be provided.

[0056] Next, the penetrant inspection device 1 of the present invention will be further described. The penetrant inspection device 1 of the present invention may include a heating means for performing the heating step 40, a penetrating means for performing the penetrating step 31, a cooling means for performing the cooling step 41, a cleaning means for performing the cleaning step 32, a developing means for performing the developing step 33, and an observation means for performing the observation step 34. As the penetrating means, a known means such as a means for applying the penetrating liquid 21 to the object to be inspected 10 by a spraying device may be used, as the cooling means, a known device for blowing cold air, as the developing means, a device for applying the developing liquid to the object to be inspected 10, and the like, each of which may be a known device. In addition, the penetrant inspection device 1 of the present invention may be appropriately designed so as to be able to carry out the penetrant inspection method of the present invention.

[0057] The present disclosure can be suitably used for the purpose of inspecting defects in billets and the like made of non-magnetic materials as the inspection subject 10. However, the present disclosure is not limited to this, and can be widely used in the inspection of products that require flaw detection. [Explanation of symbols]

[0058] 1, Penetrant testing equipment 10. Test object 11, surface 12. Damage 13. Defective opening 14. Defect inside 16. Near surface 20. Steam injection device 21, Penetration liquid 22, Suction recovery section 23. Ventilator 24, the first automatic imaging device 25, second automatic imaging device 26, 26´ Imaging range 31, Penetration process 32. Cleaning process 33, Development process 34. Observation process 40,Heating process 41, Cooling process 61, Roller δ Penetration depth

Claims

1. A penetrant inspection method including a penetrant step of applying a penetrant liquid to a surface of an object to be inspected, a cleaning step of removing the penetrant liquid from the surface of the object to be inspected, and an observation step of observing an indication pattern, The cleaning step comprises injecting superheated steam having a temperature of 110° C. or higher immediately after being ejected from an ejection port of a nozzle of a steam ejection device onto the surface of the object to be inspected.

2. 2. The penetrant inspection method according to claim 1, wherein the cleaning step comprises using a steam injection device to inject the superheated steam from an oblique direction onto the surface of the test object, and suctioning and recovering the penetrant atomized by the superheated steam from a direction in which the superheated steam is reflected by the surface of the test object by a suction and recovery means.

3. 2. The penetrant inspection method according to claim 1, wherein the observation step is started within 20 seconds after the cleaning step.

4. A penetrant inspection device for carrying out the penetrant inspection method according to claim 1, The penetrant flaw detector is provided with a penetrant means, a cleaning means, and an observation means for carrying out each step, the cleaning means includes a steam injection device and a suction recovery unit, the steam injection device is capable of injecting the superheated steam toward the surface of the object to be inspected, The superheated steam has a temperature of 110° C. or higher immediately after being sprayed from the nozzle of the steam spraying device, The penetrant flaw detection device is characterized in that the spray direction of the steam spray device is oblique to the surface of the test object, the suction recovery section has an opening, and the opening is located in a reflection direction in which the superheated steam is sprayed by the steam spray device and reflected after coming into contact with the surface of the test object.

5. The penetrant flaw detection apparatus according to claim 4, further comprising a transport means, the penetrant flaw detection apparatus forming a line along which the test object is moved at a constant speed by the transport means, and the test object is transported in sequence to the penetrant means, the cleaning means, and the observation means, the observation means comprising on the line a first automatic imaging device capable of capturing still images and a second automatic imaging device capable of capturing still images, or a third automatic imaging device capable of capturing video.

Images