A method for detecting and evaluating the circumferential cracking depth of a crack bottom at a roll neck of a heavy plate work roll

Abstract

A kind of detection and evaluation method of circumferential cracking depth of crack elimination pit bottom at the neck of thick plate working roll, by measuring the total irradiation area of secondary reflection wave on the surface of roll neck, to realize the method of detecting and depth quantitative evaluation of circumferential cracking of pit bottom or pit wall at the neck of roll, by the relative direction relationship of auxiliary device fixed sensor A and B, and make sensor A and B can move along the circumferential direction of roll neck, after the secondary reflection signal containing cracking information appears, keep sensor A stationary, make sensor B move while detecting in the area where signal can be received, to determine whether there is circumferential crack depth of pit bottom or pit wall, and determine its crack depth.The technical method can comprehensively detect and evaluate the whole crack elimination pit, and ensure the consistency of all detection signals.

Description

Technical Field

[0001] This invention relates to non-destructive testing of large metallurgical rolling mill tools. Specifically, this invention relates to a method for detecting and evaluating the depth of circumferential cracks at the neck of a thick plate work roll. More specifically, this invention relates to a method for detecting and evaluating the depth of circumferential cracks at the bottom of the crack-removal pit at the neck of a thick plate work roll. Background Technology

[0002] The rolling mill rolls used in the production of heavy steel plates are relatively large (for example, work rolls can weigh hundreds of tons and have a diameter of about 10 meters). Figure 1 After a certain output of hot-rolled thick plates, cracks may develop at the neck of the work rolls due to the immense stress. This is a highly dangerous defect; if not addressed promptly, the cracks will expand further during subsequent use, potentially leading to destructive accidents.

[0003] To prevent problems before they occur, during the rolling process of thick steel plates, if cracks develop at the neck of the work rolls, the cracks are removed at the neck to avoid stress concentration at the crack tip during production and use, which could lead to crack propagation. However, this creates multiple artificially created pits around the neck, known as crack-removal pits, as shown in Figure 2. Simultaneously, to protect these pits from further external corrosion, heat-applied water-retaining rings are designed onto them, such as... Figure 3 As shown. However, because this is a hot-fitting assembly method, once the water-retaining ring is installed, it is not easy to remove it again.

[0004] On the other hand, precisely because the water-retaining ring completely covers the crack-reducing pit, and given the large overall size of the thick plate work roll, monitoring for subsequent defects such as cracking near the pit becomes objectively difficult. Furthermore, historically, if the thick plate work roll continues to operate with the crack-reducing pit in place, cracking due to high stress can easily occur around the pit. Thick plate work rolls are expensive and crucial production tools and are not easily replaced. Therefore, prolonged use creates hidden dangers for continued operation.

[0005] For example, since the crack-removing pits made in the circumferential direction at the neck of the thick plate work roll are covered by the water-retaining ring, conventional non-destructive testing methods used in the metallurgical industry do not have the feasibility or space to conduct detection above the water-retaining ring. In addition, the roll neck is usually a cylinder up to 1370 mm long. These two factors also make it difficult to detect whether new cracks have appeared around the crack-removing pits and to evaluate the severity of the cracks.

[0006] Although there are many existing non-destructive testing methods, there are also many non-destructive testing techniques for crack detection, such as dye penetrant testing, electromagnetic testing, ultrasonic testing, eddy current testing, and X-ray testing. For example, the following are the main non-destructive testing methods:

[0007] 1) Magnetic particle testing: Widely used in aerospace, metallurgical tools, machinery manufacturing, atomic energy, weaponry, and other military industries and special equipment, it is one of the most common and convenient routine inspection methods. Magnetic particle testing is mostly used for semi-finished products and raw materials, such as bars, billets, forgings, and castings. However, due to the obstruction caused by the water-retaining ring, and because magnetic particle testing is usually only used for surface defect detection.

[0008] 2) X-ray non-destructive testing: Currently, the main methods include computer-aided imaging (CR), digital radiography (DR), computed tomography (CT), Compton imaging, and neutron detection. These methods can be used for routine defect detection, material microstructure, structure, residual stress, cumulative damage of components, precision dimensional measurement, and component life assessment. However, X-ray testing is mostly a penetration method, which is not suitable for large-volume samples such as thick plate work rolls, and it is also very inconvenient to implement on-site.

[0009] 3) Penetrant testing: Widely used to detect surface opening defects in most non-absorbent materials, such as steel and non-ferrous metals. It was the earliest and most widely used conventional testing method. It can also comprehensively detect defects with complex shapes in one go, making it suitable for field environments. However, like magnetic particle testing, penetrant testing is constrained by the obstruction of a water-retaining ring and is only used for surface defect detection. Therefore, this method is also not feasible.

[0010] 4) Electromagnetic Testing: Early electromagnetic nondestructive testing mainly included eddy current testing and magnetic flux leakage testing, which are methods for detecting defects and performance in materials and components based on changes in their electromagnetic properties. Later developed techniques such as metal magnetic memory testing, pulsed eddy current testing, AC magnetic field testing, current disturbance testing, Barkhausen noise testing, and magnetoacoustic emission technology all fall under the scope of electromagnetic testing. Like magnetic particle testing, this method is constrained by the obstruction of water-retaining rings and is mostly used for detecting defects within a limited depth range on the surface.

[0011] 5) Acoustic emission detection: also known as stress wave emission, is the phenomenon of transient elastic waves (AE) generated by the rapid release of energy from local sources in a material. Acoustic emission is a natural phenomenon that occurs constantly in nature. Acoustic emission detection technology can detect this dynamically online, but it cannot be used to evaluate depth.

[0012] 6) Infrared detection: This technique obtains the surface temperature distribution by receiving infrared rays emitted by an object, reflecting the internal and external temperature conditions of the object, thereby determining the presence of defects. It is particularly valuable for detecting defects within non-metallic materials. Like the methods mentioned above, this method is impractical due to the constraint of a water-blocking ring, and it is also used for surface defect detection.

[0013] 7) Laser detection: Since the invention of the laser in 1960, laser holography technology has become practical. Laser detection is mainly divided into three types according to the imaging principle: laser holography, laser speckle interference, and laser misaligned speckle interference. The reasons why laser holographic detection is not applicable are the same as above.

[0014] 8) Ultrasonic Testing: There are many methods available. Conventional ultrasonic testing primarily aims to detect and evaluate defects. Significant advancements in ultrasonic technologies in recent years include: phased array technology, TOFT technology, laser ultrasonic technology, electromagnetic ultrasonic testing technology, ultrasonic guided wave testing technology, and nonlinear ultrasonic technology. However, the adaptability of the testing equipment to different workpiece shapes requires careful consideration and design.

[0015] Industry analysis generally suggests that, based on the working conditions of thick plate work rolls, surface fatigue originates from cracks in the roll neck. These fatigue cracks gradually develop under alternating stress. The large size of the roll and the water-retaining ring make it difficult to detect defects at the crack-retaining pit. Therefore, even with large-size thick plate work rolls and water-retaining rings, it is difficult to meet the practical requirements for detecting cracks and their depth around the crack-retaining pit; that is, it is difficult to achieve non-destructive testing of the depth of cracks near the crack-retaining pit at the roll neck of thick plate work rolls. Therefore, a new, economical, efficient, and feasible non-destructive testing method and equipment is needed to address the current situation regarding cracks around the crack-retaining pit. Summary of the Invention

[0016] To address the aforementioned issues, this invention proposes a method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a roll. This invention employs ultrasonic waves as a technical means and designs a method specifically for detecting and evaluating the crack depth around the crack-removing pit at the neck of a thick plate work roll.

[0017] Based on the characteristics of crack conditions and operable space at the neck of a thick plate work roll, this invention calculates the total irradiation area of ​​the secondary reflected wave on the surface of the neck to detect and quantitatively evaluate the circumferential crack depth at the bottom of the crack-removing pit at the neck.

[0018] The technical solution of the present invention for a method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll is as follows:

[0019] A method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removal pit at the neck of a thick plate work roll, characterized in that...

[0020] An auxiliary device is installed on the thick plate work roll near the roll neck, which can move and be fixed upward around the outer circumference of the work roll. This device allows the ultrasonic transmitting sensor A and the ultrasonic receiving sensor B to move circumferentially along the work roll near the roll neck, with a relative direction and positional relationship.

[0021] Ultrasonic transmitter A emits ultrasonic transverse waves at a certain position on the outer periphery of the work roll near the roll neck. The ultrasonic transverse waves enter the body of the thick plate work roll, pass through the pit wall and pit bottom, and will produce two reflections when they reach the inner wall of the outer periphery of the work roll diameter. After detecting the crack, the ultrasonic transverse waves reflected in the second reflection contain the signal of the circumferential crack at the bottom or wall of the crack.

[0022] After the secondary ultrasonic transverse wave reflection signal containing crack signals is detected, the ultrasonic transmitting sensor A remains stationary, while the ultrasonic receiving sensor B moves and continues to detect in the area of ​​the outer periphery of the work roller where the signal can be received, in order to discover and measure the circumferential crack area information of the crack-removing pit bottom or pit wall detected by the secondary ultrasonic transverse wave reflection.

[0023] Using an ultrasonic flaw detector, the depth of circumferential cracks at the bottom edge of the pit is evaluated based on the detected area of ​​circumferential cracks at the bottom or wall of the pit.

[0024] Sensor A emits an ultrasonic transverse wave that enters the body of the thick plate working roll. When the wave reaches the wall and bottom of the crack elimination pit, it is reflected for the first time. After passing through the pit wall and bottom, the ultrasonic transverse wave is reflected for the second time when it reaches the inner wall of the outer circumference of the working roll. The above two reflected waves are fixed. If a crack is detected, the crack signal is superimposed on the inherent signal state.

[0025] The present invention provides a method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll, characterized in that...

[0026] The ultrasonic transverse wave emitted by ultrasonic sensor A at a certain position on the outer periphery of the work roll near the roll neck enters the body of the thick plate work roll and produces two reflections, including the following two forms and their paths:

[0027] (1) The case where the transverse wave beam is reflected by the bottom of the pit: the reflected longitudinal wave is reflected by the bottom plane of the pit and propagates into the inside of the roller body with a small reflection angle with the bottom plane of the pit as the reflecting surface. The reflected transverse wave continues to propagate towards the circumferential crack of the bottom of the pit and takes effect with the bottom plane of the pit as the reflecting surface, along the direction of 45° with the normal. The transverse wave after being reflected by the bottom of the pit continues to propagate and interacts with the circumferential crack surface of the bottom of the pit or the edge of the pit wall. It is reflected again by the circumferential crack surface and propagates towards the receiving sensor B.

[0028] (2) The case where the sound beam first reflects the circumferential crack surface of the pit bottom or pit wall: Since most of the cracks near the pit bottom surface extend inward along the direction of passing through the inner edge of the bottom surface and perpendicular to the axial direction of the roll, the angle between the propagating sound beam and the circumferential crack surface of the pit bottom is also 45°. The transverse wave sound beam is reflected by the circumferential crack surface, and the resulting reflected longitudinal wave propagates into the roll body with a small reflection angle with the circumferential crack surface as the reflecting surface. The reflected transverse wave continues to propagate towards the pit bottom plane and takes effect with the circumferential crack surface as the reflecting surface, along the direction of 45° with the normal. The transverse wave reflected by the circumferential crack surface of the pit bottom edge continues to propagate and is reflected again by the pit bottom plane, and then propagates towards the receiving sensor B.

[0029] The present invention provides a method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll, characterized in that...

[0030] The ultrasonic transmitting sensor A and the ultrasonic receiving sensor B are arranged on both sides of the outer periphery of the work roll near the neck, relative to the crack-removing pit. The transmitting sensor A, the crack-removing pit, and the receiving sensor B are in a triangular positional relationship on the axial projection of the work roll.

[0031] The present invention provides a method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll, characterized in that...

[0032] The emission path of ultrasonic transmitting sensor A and the receiving path of ultrasonic receiving sensor B form a 45° angle with the projection of the bottom plane of the crack-removing pit onto the vertical plane of the working roller axis.

[0033] The present invention provides a method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll, characterized in that...

[0034] The incident angle of the ultrasonic transmitting sensor A relative to the crack-removing pit is in the range of 45°±10°.

[0035] The present invention provides a method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll, characterized in that...

[0036] The straight-line distance from the ultrasonic transmitting sensor A to the incident path of the crack-removing pit is 1-1.2m.

[0037] The present invention provides a method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll, characterized in that...

[0038] If, apart from the inherent reflection signals reflected from the bottom or wall of the crack-removing pit and the inner wall of the outer periphery near the neck of the work roll, there is no superposition of crack signals, it is determined that no cracking has occurred.

[0039] If the ultrasonic transverse wave secondary reflection signal received by ultrasonic receiver sensor B has a superposition of crack signal, it is determined that cracking has occurred, and the size and depth of the crack can be determined by the ultrasonic flaw detector.

[0040] like Figures 7-10 Under normal circumstances, the cracks near the bottom of the pit extend inward along the inner edge of the bottom surface, perpendicular to the axial direction of the roll. Although the sound beam is deformed by reflection on the roll surface, it is still a pulsed sound wave with a certain width and the highest central intensity. It will be reflected twice in two ways: once by the bottom plane of the pit and once by the circumferential cracks at the bottom of the pit (if they already exist).

[0041] One scenario involves initial reflection from the pit bottom: Since the angle between the propagating sound beam and the pit bottom plane is also 45°, the sound beam will be reflected by the pit bottom plane. Because we are using transverse waves, the resulting reflected longitudinal waves will propagate into the roller body at a small reflection angle with the pit bottom plane as the reflecting surface. Meanwhile, the reflected transverse waves will continue to propagate circumferentially towards the pit bottom with the pit bottom plane as the reflecting surface, along a direction at a 45° angle to the normal, and thus have an effect. Figures 8-10 The three angle views. The transverse wave, after being reflected by the bottom of the pit, continues to propagate and interacts with the circumferential cracked surface of the pit bottom or the edge of the pit wall. It is reflected again by the circumferential cracked surface and propagates in the direction of the receiving sensor B.

[0042] Another scenario involves initial reflection from the circumferential cracks at the bottom or wall of the pit. Since most cracks near the bottom extend inwards along the inner edge of the bottom surface, perpendicular to the roll axis, the angle between the propagating sound beam and the circumferential cracks at the bottom is also 45°. Because we are using transverse waves, the sound beam is reflected by the circumferential cracks. The resulting reflected longitudinal wave will propagate into the roll body at a smaller reflection angle with the circumferential cracks as the reflecting surface. Meanwhile, the reflected transverse wave will continue to propagate towards the bottom plane at a 45° angle to the normal, also with the circumferential cracks as the reflecting surface, thus exerting its effect. This differs from the sequential order of the two reflections from the circumferential reflecting surface and the bottom plane. Figures 8-10 The situation is similar in the three angle views. The transverse wave, after being reflected by the circumferential cracked surface at the bottom of the pit, continues to propagate and is reflected again by the bottom plane of the pit, thus propagating towards the receiving sensor B.

[0043] In both of the aforementioned forms of double reflection, the final effect is that, after two reflections, the secondary reflected transverse wave is projected onto the receiving sensor B on the other side of the roll neck, corresponding to the transmitting sensor A on one side of the roll neck. Figure 7 Based on the above detection method, the presence and depth of circumferential cracks in the pit bottom or wall can be determined by the area in the region where the receiving sensor B can receive transverse wave signals.

[0044] 1) If there are no circumferential cracks at the bottom or edge of the pit, there will be no secondary reflected transverse wave signal in the area where the receiving sensor B is located, because the transverse wave incident from sensor A will propagate towards the roller body after being reflected by the bottom surface of the pit.

[0045] 2) If a circumferential crack of a certain depth appears at the bottom or edge of the pit, then within a certain area of ​​the receiving sensor B, the transverse wave signal generated by the secondary reflection of the transverse wave incident from sensor A at the bottom of the pit can be received. Moreover, as the depth of the circumferential crack at the bottom edge of the pit increases, the area where the secondary reflected transverse wave signal can be detected gradually increases. This is because the transverse wave incident at the bottom of the pit does not converge after being acted upon by the two reflecting surfaces, but rather gradually expands the surface area of ​​the roller neck covered by the secondary reflected transverse wave.

[0046] Based on the above principle, in the actual evaluation of the circumferential crack depth at the bottom edge of the pit, it is only necessary to fix the relative orientation of sensors A and B through an auxiliary device, and enable sensors A and B to move circumferentially along the roller neck. After the secondary reflection signal appears, sensor A is kept stationary, and sensor B moves and detects in the area where the signal can be received. The size of the area where the secondary reflection signal can be received is measured to determine the corresponding circumferential crack depth.

[0047] According to the present invention, a method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll is characterized in that...

[0048] Transmitting sensor A and receiving sensor B are arranged on both sides of the outer periphery of the work roll neck, relative to the crack elimination pit. Transmitting sensor A, crack elimination pit, and receiving sensor B are arranged on the work roll neck and are in a triangular positional relationship on the projection of the work roll axial plane.

[0049] In another embodiment, the transmitting sensor A, the crack-removing sensor B, and the receiving sensor B are arranged on the neck of the work roll and are in a right-angled triangle position on the projection of the work roll axial plane.

[0050] That is, the projection of the line connecting the transmitting sensor A and the receiving sensor B to the crack-removing pit on the vertical plane of the work roll forms a 45° angle with the radial plane of the work roll, and the line connecting the transmitting sensor A and the receiving sensor B to the crack-removing pit forms a 90° angle.

[0051] This invention specifically designs a method for detecting and quantitatively evaluating the depth of circumferential cracks at the bottom of anti-crack pits at the roll neck by measuring the total irradiation area of ​​secondary reflected waves on the roll neck surface. This provides a technical means for quantitatively assessing the "health status" of expensive and important production tools such as thick plate work rolls at the relatively vulnerable roll neck. With the assistance of a specially designed device capable of continuous movement along the circumference of the roll neck, detection can be attempted at different circumferential positions. This method can comprehensively detect and evaluate the entire anti-crack pit while ensuring the consistency of conditions for all detection signals. Attached Figure Description

[0052] Figure 1 A schematic diagram of the work rolls used in the production of thick steel plates.

[0053] Figure 2(a) and (b) are schematic diagrams of crack elimination at the neck of the thick plate work roll, respectively.

[0054] Figure 3 This is a schematic diagram of the crack-removing pits and water-retaining ring at the neck of a thick plate work roll.

[0055] Figure 4 This is a top view showing the relative spatial position of a pair of ultrasonic sensors and the anti-crack pit of the roll neck, as well as the ultrasonic propagation path, according to an embodiment of the present invention.

[0056] Figure 5 This is a front view of the relative spatial position of a pair of ultrasonic sensors and the anti-crack pit of the roll neck, and the ultrasonic propagation path, according to an embodiment of the present invention.

[0057] Figure 6 This is a side view of the relative spatial position of a pair of ultrasonic sensors and the anti-crack pit of the roll neck, as well as the ultrasonic propagation path, according to an embodiment of the present invention.

[0058] Figure 7 This is a schematic diagram showing the relative spatial positions of the transmitting sensor A, the small crack pit, and the receiving sensor B on the neck of the work roll, as well as the propagation path of the incident transverse wave inside the neck of the work roll, according to an embodiment of the present invention.

[0059] Figure 8 This is a front view of the ultrasonic transverse wave emitted by sensor A into the crack-removing pit and the secondary reflection of the pit bottom and the circumferential crack at the edge of the pit bottom, according to an embodiment of the present invention.

[0060] Figure 9 This is a side view of the ultrasonic transverse wave emitted by sensor A towards the crack elimination pit and the secondary reflection of the pit bottom and the circumferential crack at the edge of the pit bottom, according to an embodiment of the present invention.

[0061] Figure 10 This is a top view of the ultrasonic transverse wave emitted by sensor A towards the crack elimination pit and the secondary reflection of the pit bottom and the circumferential cracks at the edge of the pit bottom, according to an embodiment of the present invention. Detailed Implementation

[0062] Example 1

[0063] An auxiliary device is installed about 400-500 mm from the neck of a thick plate work roll weighing tens to hundreds of tons and several meters in diameter. This auxiliary device allows the ultrasonic transmitting sensor A and the ultrasonic receiving sensor B to move along the outer circumference of the work roll from the neck, with relative orientation and positional relationship.

[0064] The work roll had a crack at its neck, which was subsequently removed to prevent stress concentration at the crack tip and further crack propagation. This resulted in several crack-removal pits, as shown in Figure 2. Additionally, to protect these pits from further external erosion, heat-applied water-retaining rings were designed onto them.

[0065] According to this embodiment, ultrasonic transmitting sensor A and ultrasonic receiving sensor B are moved along the circumference of the roll neck. Sensor A emits an ultrasonic transverse wave at a certain position on the outer periphery of the work roll near the roll neck and enters the body of the thick plate work roll. When the ultrasonic transverse wave entering the body of the thick plate work roll detects the bottom of the crack elimination pit and the circumferential crack at the bottom of the pit, it will generate two reflections.

[0066] After a secondary ultrasonic transverse wave reflection signal containing a crack signal appears, sensor A remains stationary while sensor B moves and continues to detect in the area around the outer periphery of the working roller where the signal can be received. The size of the area of ​​the secondary ultrasonic transverse wave reflection detection is measured to evaluate the actual circumferential crack depth at the bottom edge of the pit.

[0067] like Figures 4-10 The cracks near the bottom of the pit extend inward along the inner edge of the bottom surface, perpendicular to the axial direction of the roll. Although the sound beam is deformed by reflection on the roll surface, it is still a pulsed sound wave with a certain width and the highest central intensity. It will be reflected twice in two ways: once by the bottom plane of the pit and once by the circumferential cracks at the bottom of the pit (if they already exist).

[0068] One scenario involves initial reflection from the pit bottom: Since the angle between the propagating sound beam and the pit bottom plane is also 45°, the sound beam will be reflected by the pit bottom plane. Because a transverse wave is used, the resulting reflected longitudinal wave will propagate into the roller body with a small reflection angle using the pit bottom plane as the reflecting surface. Meanwhile, the reflected transverse wave will continue to propagate circumferentially towards the pit bottom with the pit bottom plane as the reflecting surface, along a direction at a 45° angle to the normal, and take effect.

[0069] like Figures 8-10 The three angle views. The transverse wave, after being reflected by the bottom of the pit, continues to propagate and interacts with the circumferential cracked surface at the bottom edge of the pit. It is reflected again by the circumferential cracked surface and propagates towards the receiving sensor B.

[0070] Another scenario involves initial reflection from the circumferential cracked surface at the bottom of the pit. Since most cracks near the bottom extend inwards along the inner edge of the bottom surface, perpendicular to the roll axis, the angle between the propagating sound beam and the circumferential cracked surface is also 45°. Because a transverse wave is used, the sound beam is reflected by the circumferential cracked surface. The resulting reflected longitudinal wave will propagate into the roll body at a smaller reflection angle with the circumferential cracked surface as the reflecting surface. Meanwhile, the reflected transverse wave will continue to propagate towards the bottom plane at a 45° angle to the normal, also with the circumferential cracked surface as the reflecting surface, thus exerting its effect. This differs from the sequential order of the two reflections from the circumferential reflecting surface and the bottom plane. Figures 8-10 The situation is similar in the three angle views. The transverse wave, after being reflected by the circumferential cracked surface at the bottom of the pit, continues to propagate and is reflected again by the bottom plane of the pit, thus propagating towards the receiving sensor B.

[0071] In both of the aforementioned forms of double reflection, the final effect is that, after two reflections, the secondary reflected transverse wave is projected onto the receiving sensor B on the other side of the roll neck, corresponding to the transmitting sensor A on one side of the roll neck. Figure 7 .

[0072] Transmitting sensor A and receiving sensor B are arranged on both sides of the outer periphery of the work roll neck, relative to the crack elimination pit. Transmitting sensor A, crack elimination pit, and receiving sensor B are arranged on the work roll neck and are in a triangular positional relationship on the projection of the work roll axial plane.

[0073] That is, the projection of the line connecting the transmitting sensor A and the receiving sensor B to the crack-removing pit on the vertical plane of the work roll forms a 45° angle with the radial plane of the work roll, and the line connecting the transmitting sensor A and the receiving sensor B to the crack-removing pit forms a 90° angle.

[0074] exist Figure 7 The image shows the spatial relationship between the transmitting sensor A, the crack-removing pit, and the receiving sensor B on the neck of the work roll, as well as the propagation path of the incident shear wave. After being emitted from sensor A, the ultrasonic shear wave propagates to the crack-removing pit along a direction where its projection on both the horizontal and vertical planes is 45°.

[0075] According to this embodiment, the incident path distance from the transmitting sensor A to the crack elimination pit is 1m, and the incident angle of the transmitting sensor A relative to the crack elimination pit is in the range of 45°±10°.

[0076] The propagation path of the incident transverse wave. After being emitted from sensor A, the ultrasonic transverse wave propagates along a direction with projections of 45° on both the horizontal and vertical planes to the crack-removing pit.

[0077] In this embodiment, the area of ​​the crack-removing pit measured by the ultrasonic transverse wave emitted by sensor A is 50*100*50mm, that is, the bottom surface of the crack-removing pit is 50mm deep, 100mm long, and 50mm wide.

[0078] According to the present invention, a quantitative assessment technique is provided for thick plate work rolls to determine whether cracks have occurred at the relatively weak location of the roll neck, and to quantitatively evaluate the "health status" of the cracks. Specifically, by calculating the total irradiation area of ​​the secondary reflected wave on the roll neck surface, a method is used to detect and quantitatively evaluate the depth of circumferential cracks at the bottom of the crack-reducing pit at the roll neck. Detection can be performed at different circumferential locations, comprehensively detecting and evaluating the entire crack-reducing pit, and ensuring the consistency of conditions for all detection signals.

Claims

1. A method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removal pit at the neck of a thick plate work roll, characterized in that, An auxiliary device is installed on the thick plate work roll near the roll neck, which can move and be fixed upward around the outer circumference of the work roll. This device allows the ultrasonic transmitting sensor A and the ultrasonic receiving sensor B to move circumferentially along the work roll near the roll neck, with a relative direction and positional relationship. Ultrasonic transmitting sensor A emits ultrasonic transverse waves at a certain position on the outer periphery of the work roll near the roll neck. The ultrasonic transverse waves enter the body of the thick plate work roll, pass through the pit wall and pit bottom, and will produce two reflections when they reach the inner wall of the outer periphery of the work roll diameter. After detecting the crack, the ultrasonic transverse waves reflected in the second reflection contain signals of the circumferential cracks at the bottom or wall of the pit. After the secondary ultrasonic transverse wave reflection signal containing crack signals is detected, the ultrasonic transmitting sensor A remains stationary, while the ultrasonic receiving sensor B moves and continues to detect in the area of ​​the outer periphery of the work roller where the signal can be received, in order to discover and measure the crack bottom and the circumferential crack area information of the secondary ultrasonic transverse wave reflection detection. Using an ultrasonic flaw detector, the depth of the circumferential crack at the bottom edge of the pit is assessed based on the detected crack area at the bottom of the pit and the area of ​​the crack in the circumferential direction at the bottom of the pit. The ultrasonic transmitting sensor A and the ultrasonic receiving sensor B are arranged on both sides of the outer periphery of the work roll near the neck, relative to the crack-removing pit. The transmitting sensor A, the crack-removing pit, and the receiving sensor B are in a triangular positional relationship on the axial projection of the work roll.

2. The method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll according to claim 1, characterized in that, When ultrasonic transmitter A emits an ultrasonic transverse wave at a certain position on the outer periphery of the work roll near the roll neck, the wave enters the body of the thick plate work roll and detects a crack signal, resulting in two reflections, including the following two forms and their paths: (1) The case where the transverse wave beam is reflected by the bottom of the pit: the reflected longitudinal wave is reflected by the bottom plane of the pit and propagates into the roller body with a small reflection angle with the bottom plane of the pit as the reflecting surface. The reflected transverse wave continues to propagate towards the circumferential crack of the bottom of the pit and takes effect with the bottom plane of the pit as the reflecting surface, along the direction of 45° with the normal. The transverse wave after being reflected by the bottom of the pit continues to propagate and takes effect with the circumferential crack surface of the bottom edge of the pit. It is reflected again by the circumferential crack surface and propagates towards the receiving sensor B. (2) The case where the sound beam first reflects the circumferential cracked surface of the pit bottom or pit wall: Since most of the cracks near the pit bottom or pit wall extend inward along the direction perpendicular to the axial direction of the roll through the inner edge of the bottom surface, the angle between the propagating sound beam and the circumferential cracked surface of the pit bottom or pit wall is also 45°. The transverse sound beam is reflected by the circumferential cracked surface, and the resulting reflected longitudinal wave propagates into the inside of the roll body with a small reflection angle with the circumferential cracked surface as the reflecting surface. The reflected transverse wave continues to propagate towards the pit bottom plane and takes effect with the circumferential cracked surface as the reflecting surface, along the direction of 45° with the normal. The transverse wave reflected by the circumferential cracked surface of the pit bottom edge continues to propagate and is reflected again by the pit bottom plane, and then propagates towards the receiving sensor B.

3. The method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll according to claim 1, characterized in that, The angle between the emission path of ultrasonic transmitting sensor A and the receiving path of ultrasonic receiving sensor B and the bottom plane of the crack-removing pit is 45° when projected onto the vertical plane of the working roller axis.

4. The method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll according to claim 1, characterized in that, The incident angle of the ultrasonic transmitting sensor A relative to the crack-removing pit is in the range of 45°±10°.

5. The method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll according to claim 1, characterized in that, The straight-line distance from the ultrasonic transmitting sensor A to the incident path of the crack-removing pit is 1-1.2m.

6. The method for detecting and evaluating the circumferential crack depth at the bottom of the crack-removing pit at the neck of a thick plate work roll according to claim 1, characterized in that, If, apart from the inherent reflection signals reflected from the bottom or wall of the crack elimination pit and the inner wall of the outer periphery near the neck of the work roll, there is no superposition of crack signals, it is determined that no cracking has occurred. If the ultrasonic transverse wave secondary reflection signal received by ultrasonic receiver sensor B has a superposition of crack signal, it is determined that cracking has occurred, and the size and depth of the crack can be determined by the ultrasonic flaw detector.

Images