A method for quickly identifying the types of cracks on the surface of a roll using eddy current flaw detection on a grinder
Through the improvement of the grinder vortex current flaw detection technology, the positioning function, damage value and soft point reflection characteristics are used to quickly identify the types of cracks on the surface of the roll and perform corresponding treatments, which solves the problem of long crack confirmation and treatment time in the existing technology, and achieves rapid and accurate identification and treatment of roll cracks.
Patent Information
- Application Number
- CN202210103171.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-01-27
- Publication Date
- 2025-03-11
- Estimated Expiration
- 2042-01-27
AI Technical Summary
The existing grinder vortex current flaw detection technology cannot quickly identify the types of cracks on the surface of the roll, resulting in long crack confirmation and treatment time, especially during night shift operation, which affects production preparation.
By utilizing the positioning function of the grinder vortex current flaw detection, the damage value and soft point reflection characteristics, combined with the position distribution characteristics of the rolling roll body, the types of cracks on the roll surface are quickly identified, and corresponding treatment methods are adopted according to the harm of different cracks.
It realizes the rapid and accurate identification and treatment of roll cracks, reduces the difficulty of operation, simplifies the crack identification and treatment process, and ensures that the roll rolls are quickly and accurately treated at night shifts.
Smart Images
Figure CN114609239B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of roller surface crack type identification, in particular to a method for rapidly identifying roller surface crack types by using a grinder eddy current flaw detection method. Background Art
[0002] During the use and production process of hot rolling mill rolls, various surface cracks often appear on the roll surface, especially some cracks caused by mechanical damage that are invisible to the naked eye. If they are not discovered and handled in time, they will expand during repeated use on the machine and cause roll accidents.
[0003] Mechanical cracks on the roll surface need to be completely removed, while thermal cracks on the front-end stand roll can be retained. If they are removed, it will increase roll consumption and costs. Therefore, during the use and maintenance of the roll, it is necessary to promptly detect various cracks, distinguish the types of cracks, and adopt different treatment methods according to the types of cracks to reduce consumption and costs and prevent accidents.
[0004] Roller grinder eddy current flaw detection is a major detection method for large-scale roll maintenance in modern steel enterprises. The grinder eddy current flaw detection uses the principle of electromagnetic induction. The advantages are that the grinder eddy current is an automated flaw detection method with fast detection speed, intuitive crack damage value and soft spot value amplitude display, and a recording function that can record the location of the damage value.
[0005] However, the disadvantage of eddy current flaw detection of grinders is that eddy current flaw detection does not have quantitative function, and cannot identify the type of cracks, crack depth, and crack hazard. Therefore, in actual production applications, after the eddy current flaw detection of the grinder finds the roll damage value, professional flaw detection personnel are required to use magnetic powder or penetration and other flaw detection methods to determine the shape and type of the crack, and use ultrasonic flaw detection to detect the crack depth. Finally, professional technicians can determine the crack treatment method. Therefore, the entire grinder eddy current flaw value re-inspection and identification process is cumbersome, and the confirmation and treatment time of cracked rolls is long, especially at night. The detection problem of the operating team is more prominent. The night shift operating team has a greater pressure on the standby roll. After the eddy current finds the roll damage value, it is impossible to perform normal exploitation because the state and nature of the crack are unknown. Therefore, the damaged rolls found by the night shift are all in the state of waiting for detection and treatment. If rolling accidents occur continuously, it will cause a backlog of damaged rolls to be treated, affecting production preparation. Summary of the invention
[0006] The purpose of the present invention is to provide a method for quickly identifying the type of cracks on the surface of a rolling mill using eddy current flaw detection on a grinder, so as to solve the problems raised in the above-mentioned background technology.
[0007] To achieve the above object, the present invention provides the following technical solution: a method for quickly identifying the type of cracks on the surface of a roll by using eddy current flaw detection of a grinder, comprising the following steps: step one, crack location; step two, crack discovery; step three, crack identification;
[0008] In the above step 1, the positioning function of the eddy current of the grinder is used to determine the different display positions of different surface cracks on the roller body, and the surface cracks mainly include mechanical cracks, stress cracks, fatigue cracks and thermal cracks;
[0009] In the above step 2, according to the reflection characteristics of the grinder eddy current on the damage values and soft spots of different surface cracks, it is found that the amplitude and peak value of the grinder eddy current flaw detection on different surface cracks and soft spots of the roll are different;
[0010] In the above step three, according to the position distribution characteristics of different surface cracks on the roller body, combined with the different display characteristics of different cracks by the grinder eddy current flaw detection, the type of cracks on the roller surface is judged and identified, and corresponding treatment methods are taken for the cracked roller according to the harmfulness of different cracks.
[0011] Preferably, in the step one, mechanical cracks are generated by mechanical damage and are randomly located at various positions on the roller body. The positions of mechanical damage values of the roller detected by eddy current also appear randomly at various positions on the roller body. Fatigue cracks are concentrated in the contact areas between the supporting rollers and the working rollers on both sides of the roller and the edge areas where the strip steels on both sides contact the roller. The damage values of the eddy current flaw detection positions of fatigue cracks appear in the corresponding fatigue and stress concentration areas of the roller, and the positions are fixed. Thermal cracks only occur in the contact area between the roller surface and the steel plate. The damage value area of the thermal cracks is the width area of the strip steel, and the position is fixed.
[0012] Preferably, in the step 2, the mechanical cracks generally extend obliquely, and the crack area is gradually exposed after grinding, forming an eddy current display damage value that increases with grinding. Its reaction characteristics under the eddy current of the grinder are that the eddy current damage value area is small, the eddy current damage value is high, and the damage value exists independently, accompanied by a higher soft spot value that coincides with the damage value position, and the phenomenon that the damage value increases with increasing grinding will appear; fatigue cracks are dense small cracks that exist in three dimensions. After grinding, the original small cracks are ground away, and fatigue cracks in other parts are exposed on the surface again, resulting in a phenomenon that the damage value peak value does not change significantly and the position changes slightly. Its reaction characteristics under the eddy current of the grinder are that the damage value amplitude is wide, the stress zones on both sides are crest-shaped, and the other areas are slowly declining in the form of troughs, accompanied by soft spot values, and the soft spot peak value fluctuates with the damage value, and the peak position of the damage value due to increasing grinding There will be slight changes; thermal cracks are mainly open cracks, and the opening gradually becomes smaller with the increase of grinding amount, forming a shape with an overall decrease in amplitude. Its reaction characteristics under the eddy current of the grinder are that there are eddy current damage values and soft spot values in the steel-passing area of the entire roller surface. Because the temperature on both sides will be relatively low, the damage values and soft spot values will also be slightly low. With grinding, the overall display shape of the damage values and soft spot values does not change much, and the amplitude gradually decreases; the reaction characteristics of stress cracks under the eddy current of the grinder are similar to the eddy current damage values of mechanical cracks. The damage values and soft spot values have a smaller area and a higher amplitude. The more grinding, the larger the damage value will be. However, the difference is that stress cracks only occur in the stress concentration areas on both sides of the roller, and the damage values in the stress areas on the left and right sides are symmetrical. Affected by the transmission factors, the damage value on the transmission side is slightly larger and the damage value on the operating side is slightly smaller.
[0013] Preferably, in the step three, during eddy current flaw detection on the grinder, if a high damage value, a small area, an independent damage value, and a soft spot value are found anywhere on the roller body, it can be judged as a mechanical crack, and according to the harmfulness of the mechanical crack, a thorough grinding and removal treatment method is adopted; during eddy current flaw detection on the grinder, if damage values are found on both sides of the roller body, and the eddy current damage amplitude is wide and there are peak-to-valley transition values, it is a fatigue crack, and according to the harmfulness of the fatigue crack, a grinding and removal treatment method is adopted; during eddy current flaw detection on the grinder, if a large area and width eddy current damage value is found in the steel rolling area of the roller surface, accompanied by a soft spot value, it can be judged as a thermal crack, and the mesh thermal crack is retained for use without taking any treatment method; during eddy current flaw detection on the grinder, if damage values and soft spot values are found at symmetrical positions on both sides of the roller, with a small area and a high amplitude, it can be judged as a stress crack, and its harmfulness is the same as that of a mechanical crack, and a thorough grinding and removal treatment method is adopted.
[0014] Compared with the prior art, the beneficial effects of the present invention are: the method of using grinder eddy current flaw detection to quickly identify the types of roll surface cracks simplifies the complex roll crack identification and processing process. The work originally completed by a few professional technicians can now be mastered by ordinary grinder operators, the operating difficulty is greatly reduced, and all problematic rolls on the night shift are quickly and accurately processed. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 is a flow chart of the method of the present invention;
[0016] Figure 2 This is the eddy current flaw detection stress detection diagram of Experimental Example 1 of the present invention;
[0017] Figure 3 and Figure 4 All of them are magnetic particle inspection images of Experimental Example 1 of the present invention;
[0018] Figure 5 This is the ERP usage record diagram of Experimental Example 1 of the present invention;
[0019] Figure 6 This is the eddy current flaw detection stress detection diagram of Experimental Example 2 of the present invention;
[0020] Figure 7 This is a magnetic particle inspection image of Experimental Example 2 of the present invention;
[0021] Figure 8 This is the ERP usage record diagram of Experimental Example 2 in the present invention. DETAILED DESCRIPTION
[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0023] See also Figure 1 , an embodiment of the present invention provides: a method for quickly identifying the type of cracks on the surface of a roll by using eddy current flaw detection of a grinder, comprising the following steps: step one, crack location; step two, crack discovery; step three, crack identification;
[0024] In the above step 1, the positioning function of the eddy current of the grinder is used to determine the different display positions of different surface cracks on the roller body. The surface cracks mainly include mechanical cracks, stress cracks, fatigue cracks and thermal cracks. Mechanical cracks are caused by mechanical damage and are randomly located at various parts of the roller body. The eddy current detection position of the mechanical damage value of the roller also appears randomly at various parts of the roller body. Fatigue cracks are concentrated in the contact area between the supporting rollers and the working rollers on both sides of the roller and the edge area where the strip steel and the roller are in contact on both sides. The eddy current flaw detection position damage value of fatigue cracks appears in the corresponding fatigue and stress concentration area of the roller, and the position is fixed. Thermal cracks only occur in the contact area between the roller surface and the steel plate. The damage value area of the thermal cracks is the width area of the strip steel, and the position is fixed.
[0025] Among them, in the above step 2, according to the response characteristics of the grinder eddy current to the damage values and soft spots of cracks on different surfaces, it is found that the amplitude and peak value of the damage values and soft spot values of the cracks on different surfaces of the roller by the grinder eddy current flaw detection are different. Mechanical cracks generally extend obliquely. After grinding, the crack area is gradually exposed, forming an eddy current display damage value that becomes larger and larger with grinding. Its reaction characteristics under the grinder eddy current are small eddy current damage value area, high eddy current damage value, independent existence of damage value, accompanied by a high soft spot value coincident with the damage value position, and the phenomenon of increasing grinding will increase the damage value with grinding. Fatigue cracks are dense small cracks that exist in three dimensions. After grinding, the original small cracks are ground away, and fatigue cracks in other parts are exposed on the surface again, forming a phenomenon that the damage value peak value does not change significantly and the position changes slightly. Its reaction characteristics under the grinder eddy current are wide damage value amplitude, the stress zones on both sides are crest-shaped, and other areas are slowly declining troughs, accompanied by There is a soft spot value, and the peak value of the soft spot fluctuates with the damage value, and the peak position of the damage value will change slightly with the increase in grinding. The thermal crack is mainly an open crack. With the increase in the grinding amount, the opening gradually becomes smaller, forming a shape with an overall decrease in amplitude. Its reaction characteristics under the eddy current of the grinder are that the steel-passing area of the entire roller surface has eddy current damage values and soft spot values. Because the temperature on both sides will be low, the damage value and soft spot value will also be slightly low. With grinding, the overall display shape of the damage value and soft spot value does not change much, and the amplitude gradually decreases. The reaction characteristics of stress cracks under the eddy current of the grinder are similar to the eddy current damage value of mechanical cracks. The damage value and soft spot value area are small and the amplitude is high. The increase in grinding will also result in a larger damage value with more grinding, but the difference is that stress cracks only occur in the stress concentration areas on both sides of the roller, and the damage values of the stress areas on the left and right sides are symmetrical. Affected by the transmission factors, the damage value on the transmission side is slightly larger and the damage value on the operating side is slightly smaller.
[0026] In the above step three, according to the position distribution characteristics of different surface cracks on the roll body, combined with the different display characteristics of different cracks by the grinder eddy current flaw detection, the type of cracks on the roll surface is determined and identified, and corresponding treatment methods are taken for the cracked roll according to the harmfulness of different cracks. During the grinder eddy current flaw detection, if a high damage value, small area, independent damage value, and soft point value are found anywhere on the roll body, it can be judged as a mechanical crack, and according to the harmfulness of the mechanical crack, a thorough grinding and removal treatment method is taken. During the grinder eddy current flaw detection, if a high damage value, small area, independent damage value, and soft point value are found anywhere on the roll body, it can be judged as a mechanical crack, and according to the harmfulness of the mechanical crack, a thorough grinding and removal treatment method is taken. If damage values are found on both sides of the body, and the eddy current damage amplitude is wide and has peak-to-valley transition values, it is a fatigue crack. According to the harmfulness of the fatigue crack, the treatment method of grinding and removal is adopted. When the grinder eddy current flaw detection is performed, if a large area and width eddy current damage value is found in the rolling area of the roller surface, accompanied by a soft spot value, it can be judged as a thermal crack. The network thermal crack is retained for use without any treatment method. When the grinder eddy current flaw detection is performed, if damage values and soft spot values are found in symmetrical positions on both sides of the roller, the area is small, and the amplitude is high, it can be judged as a stress crack. Its harmfulness is the same as that of mechanical cracks, and the treatment method of thorough grinding and removal is adopted.
[0027] See also Figure 2-8 The present invention uses the above-mentioned implementation method to conduct a verification experiment: the support rollers of Bengang's 1700 line production line began to show collective fatigue in 2017, and the fatigue problem had been completely solved by the end of 2019; during this period, 27 support rollers were found to have cracks. This method was used to separate the mechanical cracks and fatigue cracks, and the mechanical cracks were removed by turning or digging, and the fatigue cracks were ground. The minimum number of support roller turnovers in the country was used to meet the roller needs of the largest number of stands; after more than three years of continuous implementation and application of this invention, it was determined that the judgment was accurate and the technology was reliable.
[0028] Experimental Example 1:
[0029] On September 20, 2017, during the grinding process of the hot rolling 1700 line support roller Y09-04, it was found that the damage value of 0.5 and the soft spot value of 0.4 appeared on both sides. This method was used to determine that they were fatigue cracks on both sides. After verification by magnetic particle testing, it was proved that they were fatigue cracks. For details of the experiment, please refer to the attached Figure 2 , 3 , 4 and 5.
[0030] Experimental Example 2:
[0031] On July 23, 2018, the 1700 line support roller Y09-009 was found to have a damage value of 2.2 and a soft spot value of 2.9 after grinding. This method was used to determine that it was a mechanical crack and needed to be removed. After confirmation by magnetic particle inspection, it was verified that the eddy current damage value was indeed a mechanical crack and was turned. For experimental details, see the attached Figure 6 , 7 and 8.
[0032] Based on the above, the advantage of the present invention is that the type of roll crack can be accurately and quickly identified based on the different positions and different damage value displays displayed when the eddy current damage value is soft, and the crack nature and treatment method can be determined based on the type of crack, thereby simplifying the complex roll crack identification and treatment process. The work that was originally done by a few professional technicians can now be mastered by ordinary grinder operators, and the operating difficulty is greatly reduced. All problem rolls of the night shift are quickly and accurately handled.
[0033] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.
Claims
1. A method for quickly identifying the type of cracks on the surface of a roll using eddy current flaw detection on a grinder, comprising the following steps: Step 1, crack location; Step 2, crack discovery; Step 3, crack identification; It is characterized by: In the above step 1, the positioning function of the eddy current of the grinder is used to determine the different display positions of different surface cracks on the roller body, and the surface cracks include mechanical cracks, stress cracks, fatigue cracks and thermal cracks; In the above step 2, according to the reflection characteristics of the grinder eddy current on the damage values and soft spots of different surface cracks, it is found that the amplitude and peak value of the grinder eddy current flaw detection on different surface cracks and soft spots of the roll are different; In the above step 3, according to the position distribution characteristics of different surface cracks on the roll body, combined with the different display characteristics of different cracks by the grinder eddy current flaw detection, the types of cracks on the roll surface are judged and identified, and corresponding treatment methods are taken for the cracked roll according to the harmfulness of different cracks; In the step 1, mechanical cracks are generated by mechanical damage, and the positions are random, and they are generated at various parts of the roller body. The positions of mechanical damage values of the rollers detected by eddy current also appear randomly at various parts of the roller body. Fatigue cracks are concentrated in the contact areas between the support rollers and the working rollers on both sides of the rollers and the edge areas where the strip steels on both sides contact the rollers. The damage values of the eddy current flaw detection positions of fatigue cracks appear in the corresponding fatigue and stress concentration areas of the rollers, and the positions are fixed. Thermal cracks only occur in the contact area between the roller surface and the steel plate. The damage value area of thermal cracks is the width area of the strip steel, and the position is fixed. In the step 2, the mechanical cracks are inclined to expand, and the crack area is gradually exposed after grinding, forming an eddy current display damage value that is larger and larger with grinding. Its reaction characteristics under the eddy current of the grinder are that the eddy current damage value area is small, the eddy current damage value is high, and the damage value exists independently, accompanied by a higher soft spot value that coincides with the damage value position, and the phenomenon that the damage value becomes larger with increasing grinding will appear; fatigue cracks are dense small cracks that exist in three dimensions. After grinding, the original small cracks are ground away, and the fatigue cracks in other parts are exposed on the surface again, forming a phenomenon that the damage value peak value does not change significantly and the position changes slightly. Its reaction characteristics under the eddy current of the grinder are that the damage value amplitude is wide, the stress zones on both sides are crest-shaped, and the other areas are slowly declining in the form of troughs, accompanied by soft spot values, and the soft spot peak value fluctuates with the damage value, and the peak position of the damage value with increasing grinding will slightly change. There are changes; thermal cracks are open cracks, and the opening gradually becomes smaller with the increase of grinding amount, forming a shape with an overall decrease in amplitude. Its reaction characteristics under the eddy current of the grinder are that there are eddy current damage values and soft spot values in the steel-passing area of the entire roller surface. Because the temperature on both sides will be relatively low, the damage values and soft spot values will also be slightly lower. With grinding, the overall display shape of the damage values and soft spot values does not change much, and the amplitude gradually decreases; the reaction characteristics of stress cracks under the eddy current of the grinder are similar to the eddy current damage values of mechanical cracks, and the damage values and soft spot values have a smaller area and a higher amplitude. The more grinding, the larger the damage value will be. However, the difference is that stress cracks only occur in the stress concentration areas on both sides of the roller, and the damage values of the stress areas on the left and right sides are symmetrical. Affected by the transmission factors, the damage value on the transmission side is slightly larger and the damage value on the operating side is slightly smaller. In the step three, when the grinder eddy current flaw detection is performed, if a high damage value, a small area, an independent damage value, and a soft spot value are found anywhere on the roller body, it can be judged as a mechanical crack, and according to the harmfulness of the mechanical crack, a thorough grinding and removal treatment method is adopted; when the grinder eddy current flaw detection is performed, if damage values are found on both sides of the roller body, and the eddy current damage amplitude is wide and there are peak-to-valley transition values, it is a fatigue crack, and according to the harmfulness of the fatigue crack, a grinding and removal treatment method is adopted; when the grinder eddy current flaw detection is performed, if a large area and width eddy current damage value is found in the steel rolling area of the roller surface, accompanied by a soft spot value, it can be judged as a thermal crack, and the mesh thermal crack is retained for use without taking any treatment method; when the grinder eddy current flaw detection is performed, if damage values and soft spot values are found at symmetrical positions on both sides of the roller, the area is small, and the amplitude is high, it can be judged as a stress crack, and its harmfulness is the same as that of a mechanical crack, and a thorough grinding and removal treatment method is adopted.