Method for repairing metal cracks

Abstract

The application provides a metal crack repairing method. The metal crack repairing method comprises the following steps: S1, obtaining a workpiece to be repaired; S2, obtaining a welding gun, and baking the workpiece to be repaired at a first temperature and for a first time by using the welding gun; S3, polishing the crack area and performing ray and coloring detection; S4, perforating the end point of the crack; S5, polishing the crack area to form a pit; S6, coating the workpiece to be repaired with a heat preservation material, and heating the surface of the workpiece to be repaired with the pit by using a heat source; S7, obtaining a metal liquid, pouring the metal liquid into the pit, and heating the metal liquid at a second temperature by using the welding gun, so that the metal liquid penetrates into the grain boundary of the base material, and the step is repeated until the pit is filled after the metal liquid and the pit form an integral whole. The application solves the problem that the crack repairing of the metal workpiece in the prior art is repeatedly cracked and the crack spreads.

Description

Technical Field

[0001] The present invention relates to the technical field of casting equipment, and in particular to a metal crack repairing method. Background Art

[0002] During the use of highly brittle materials, especially those exposed to high temperatures, hazardous media, or cast components such as the housings, bases, cylinders, and connecting rods of large rotating equipment, these components can be subject to vibration, erosion by harmful elements in the media, or significant fluctuations in pressure and temperature. This can lead to cracking in the workpiece or metal peeling off, impacting its use. To ensure normal operation, repair is essential. However, due to the large size of these components and the brittleness of the parent material, the existing high-temperature melting fusion repair technology often results in repeated cracking, crack propagation, and even the appearance of severe new cracks, ultimately leading to repair failure and forced replacement, exponentially increasing production costs and labor intensity, and delaying production.

[0003] Current melting fusion repair techniques require the use of high temperatures to completely melt a portion of the metal workpiece and fuse it with the filler metal to form a closed joint. This process is then rapidly cooled in air, causing the base metal grains to rapidly grow and then rapidly shrink, ultimately creating gaps between the grain boundaries. Under the influence of welding stress, these gaps between the grain boundaries continue to expand, forming cracks that are difficult to repair. This is particularly true for extremely brittle materials, such as high-alloy steels and castings. Inadequate heat treatment conditions after insulation and preheating can easily lead to widespread cracking, ultimately rendering the workpiece or even the entire device useless.

[0004] That is to say, the crack repair of metal workpieces in the prior art has the problems of repeated cracking and crack propagation. Summary of the Invention

[0005] The main purpose of the present invention is to provide a metal crack repair method to solve the problems of repeated cracking and crack propagation in crack repair of metal workpieces in the prior art.

[0006] In order to achieve the above-mentioned objectives, the present invention provides a metal crack repair method, comprising the following steps: Step S1: Obtain a workpiece to be repaired and clean the workpiece to be repaired; Step S2: Obtain a welding gun and use the welding gun to bake the workpiece to be repaired at a first temperature and a first time; Step S3: Polish the crack area of ​​the workpiece to be repaired, and perform X-ray and coloring detection; Step S4: Punch the endpoints of the cracks in the crack area; Step S5: Grind the crack area of ​​the workpiece to be repaired to form a pit; Step S6: Use an insulating material to cover at least part of the surface of the workpiece to be repaired so that the surface of the workpiece to be repaired with the pit is exposed, and use a heat source to heat the surface of the workpiece to be repaired with the pit; Step S7: Obtain molten metal, pour the molten metal into the pit, and use a welding gun to continuously heat the molten metal in the pit at a second temperature so that the molten metal penetrates into the grain boundary of the base material of the workpiece to be repaired, and repeat this step after the molten metal and the pit form a whole until the pit is filled.

[0007] Furthermore, the metal crack repair method also includes steps located after step S6: a temperature measuring step: setting the surface opposite to the surface with the pit of the workpiece to be repaired as a temperature measuring surface, and using a temperature measuring gun to measure the temperature of the temperature measuring surface; a prefabricated metal liquid step: melting the metal material with a melting point lower than that of the workpiece to be repaired to form a metal liquid.

[0008] Furthermore, in step S7, a welding gun is used to continuously heat the molten metal in the pit at a second temperature so that the temperature of the pit reaches above 1312°C, so that the molten metal penetrates into the grain boundary of the base material of the workpiece to be repaired, and the welding gun is moved to cool the molten metal and form a whole with the workpiece to be repaired.

[0009] Furthermore, in step S7, the molten metal is formed in the pit layer by layer in multiple times.

[0010] Furthermore, the metal crack repair method also includes a cooling step located after step S7. The cooling step is to remove the heat source and cool the workpiece to be repaired at a first cooling rate until the temperature of the workpiece to be repaired drops to 757.5°C. The workpiece to be repaired is completely covered with an insulating material and cooled at a second cooling rate. The second cooling rate is less than the first cooling rate until the workpiece to be repaired is cooled to room temperature and the insulating material is removed.

[0011] Furthermore, the metal crack repair method also includes a detection step located after the cooling step, and the detection step is to perform ultrasonic detection, color detection, and water pressure testing on the repaired part of the workpiece to be repaired and the surrounding area of ​​the repaired part.

[0012] Furthermore, in step S5, the pit is a U-shaped pit.

[0013] Furthermore, the length of the U-shaped pit is equal to the length of the crack, and the depth of the U-shaped pit is less than the depth of the crack.

[0014] Furthermore, in step S2, the first temperature is less than or equal to 150°C, and the first time is greater than or equal to 62 hours.

[0015] Furthermore, in step S6, there are multiple heat sources, and multiple heat sources are arranged at intervals on both sides of the pit.

[0016] Applying the technical solution of the present invention, the metal crack repair method includes the following steps S1 to S7, step S1: obtaining a workpiece to be repaired and cleaning the workpiece to be repaired; step S2: obtaining a welding gun and using the welding gun to bake the workpiece to be repaired at a first temperature and a first time; step S3: polishing the crack area of ​​the workpiece to be repaired, and performing radiographic and coloring detection; step S4: punching the end points of the cracks in the crack area; step S5: grinding the crack area of ​​the workpiece to be repaired to form a pit; step S6: using an insulating material to cover at least part of the surface of the workpiece to be repaired so that the surface of the workpiece to be repaired with the pit is exposed, and using a heat source to heat the surface of the workpiece to be repaired with the pit; step S7: obtaining molten metal, pouring the molten metal into the pit, and using a welding gun to continuously heat the molten metal in the pit at a second temperature so that the molten metal penetrates into the grain boundary of the base material of the workpiece to be repaired, and repeating this step after the molten metal and the pit form a whole until the pit is filled.

[0017] By using a welding gun to bake the workpiece to be repaired at a first temperature and for a first time in step S2, harmful gases and moisture inside the workpiece to be repaired can be removed, preventing them from entering the molten pool and causing defects such as pores, white spots, and cracks, thereby ensuring that subsequent processes can be carried out stably. By polishing the crack area of ​​the workpiece to be repaired in step S3, the workpiece to be repaired presents a metallic luster, and at the same time confirms the state of the crack gap and the situation of impurities in the gap so as to take cleaning measures, and then performs radiographic and coloring detection to determine the direction and size of the crack so as to determine the direction in which the crack may expand. In step S4, the endpoints of the cracks in the crack area are punched, that is, positioning holes are machined at the endpoints of the cracks to prevent the cracks from expanding infinitely during the grinding or repair process, which is conducive to preventing the cracks from spreading. In step S5, the crack area of ​​the workpiece to be repaired is polished to form pits, leaving storage space for the subsequent molten metal and a channel for the metal to penetrate into the grain boundaries of the parent material of the workpiece to be repaired, which is conducive to ensuring good subsequent bonding. In step S6, a heat source is used to heat the surface of the workpiece to be repaired with the pit, ensuring that the overall temperature of the workpiece to be repaired is evenly increased, so that the temperature point at which the grains of the base material of the workpiece to be repaired swell and produce tiny gaps is reached, which is beneficial to prevent the rapid dissipation of heat during the subsequent repair process, so that it cools slowly to prevent the generation of new cracks. In step S7, molten metal is obtained and poured into the pit. The molten metal in the pit is continuously heated at a second temperature using a welding gun so that the molten metal penetrates into the grain boundary of the base material of the workpiece to be repaired. After the molten metal and the pit form a whole, this step is repeated until the pit is filled, thereby completing the repair work of the crack area on the workpiece to be repaired. The metal crack repair method of the present application can effectively avoid repeated cracking, crack propagation, and the appearance of new cracks, thereby ensuring that the workpiece can continue to be used, avoiding the need to replace the workpiece, and greatly saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 A flow chart showing a metal crack repair method according to an optional embodiment of the present invention;

[0020] Figure 2 Shown Figure 1 A state diagram of the metal crack repair method in the repair process.

[0021] The above drawings include the following reference numerals:

[0022] 10. Workpiece to be repaired; 20. U-shaped pit; 30. Temperature measuring gun; 40. Temperature measuring point; 50. Molten metal; 60. Welding gun; 70. Heat source. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0025] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity direction; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above directional words are not used to limit the present invention.

[0026] In order to solve the problems of repeated cracking and crack propagation in crack repair of metal workpieces in the prior art, the present invention provides a metal crack repair method.

[0027] like Figure 1 and Figure 2 As shown, the metal crack repair method includes the following steps S1 to S7:

[0028] Step S1: obtaining a workpiece 10 to be repaired and cleaning the workpiece 10 to be repaired;

[0029] Step S2: Obtain a welding gun 60 and use the welding gun 60 to bake the workpiece 10 to be repaired at a first temperature and for a first time;

[0030] Step S3: polishing the cracked area of ​​the workpiece 10 to be repaired, and performing radiographic and colorimetric inspections;

[0031] Step S4: punching the end points of the cracks in the crack area;

[0032] Step S5: grinding the cracked area of ​​the workpiece 10 to be repaired to form a pit;

[0033] Step S6: using a heat-insulating material to cover at least a portion of the surface of the workpiece 10 to be repaired, so that the surface of the workpiece 10 to be repaired with the pit is exposed, and using a heat source 70 to heat the surface of the workpiece 10 to be repaired with the pit;

[0034] Step S7: Obtain molten metal 50, pour the molten metal 50 into the pit, and use a welding gun 60 to continuously heat the molten metal 50 in the pit at the second temperature so that the molten metal 50 penetrates into the grain boundary of the base material of the workpiece 10 to be repaired. After the molten metal 50 and the pit form a whole, repeat this step until the pit is filled.

[0035] By using a welding gun 60 to bake the workpiece 10 to be repaired at a first temperature and for a first time in step S2, harmful gases and moisture inside the workpiece 10 to be repaired can be removed, and the harmful gases and moisture can be prevented from entering the molten pool to cause defects such as pores, white spots, and cracks, thereby ensuring that subsequent processes can be carried out stably. By polishing the crack area of ​​the workpiece 10 to be repaired in step S3, the workpiece 10 to be repaired presents a metallic luster, and at the same time, the state of the crack gap is confirmed, and the situation of impurities in the gap is confirmed so that cleaning measures can be taken, and then X-ray and coloring detection are performed to determine the direction and specifications of the crack, so as to determine the direction in which the crack may expand. In step S4, the endpoints of the cracks in the crack area are punched, that is, positioning holes are processed at the endpoints of the cracks to prevent the cracks from expanding infinitely during the grinding or repair process, which is conducive to preventing the cracks from spreading. In step S5, the cracked area of ​​the workpiece 10 to be repaired is polished to form a pit, so as to leave storage space for the subsequent molten metal 50 and a channel for penetrating into the grain boundary of the parent material of the workpiece 10 to be repaired, which is conducive to ensuring good subsequent bonding. In step S6, the surface of the workpiece 10 to be repaired with the pit is heated by using a heat source 70 to ensure that the overall temperature of the workpiece 10 to be repaired is evenly increased, so that the temperature point at which the parent material grains of the workpiece 10 to be repaired expand and tiny gaps are generated is reached, which is conducive to preventing the rapid dissipation of heat during the subsequent repair process, so that it cools slowly to prevent the generation of new cracks. In step S7, the molten metal 50 is obtained and poured into the pit. The welding gun 60 is used to continuously heat the molten metal 50 in the pit at a second temperature so that the molten metal 50 penetrates into the grain boundary of the parent material of the workpiece 10 to be repaired. After the molten metal 50 and the pit form a whole, this step is repeated until the pit is filled, thereby completing the repair work of the cracked area on the workpiece 10 to be repaired. The metal crack repair method of the present application can effectively avoid repeated cracking, crack propagation and the appearance of new cracks, thereby ensuring that the workpiece can continue to be used, avoiding the need to replace the workpiece, and greatly saving costs.

[0036] It should be noted that the metal crack repair method of the present application is significantly effective in repairing various cracks in highly brittle materials. It can prevent crack propagation and the formation of new cracks during the repair process, and can also prevent repeated cracking after repair, thus ensuring the high efficiency of crack repair. It can also improve the applicability and processability of the repaired area and the surrounding parent material, avoid the scrapping of various equipment due to improper crack repair, and effectively reduce production costs and labor intensity.

[0037] Furthermore, the workpiece 10 to be repaired in the metal crack repair method of this application can be a highly brittle material. This metal crack repair method of this application is designed based on the actual conditions of on-site crack repair of highly brittle materials, as well as the characteristics of metal grain expansion at high temperatures and the strong permeability of heavy metal liquids at 50°C. This method is designed to overcome the drawbacks of melt-type fusion repair techniques for repairing extremely brittle materials, which can lead to unlimited crack expansion, ultimately rendering the workpiece or even the entire device useless.

[0038] It should also be noted that during the repair process, the base material of the workpiece 10 to be repaired is not melted, but the filling metal liquid 50 penetrates into the body through the grain boundaries of the base material, and is slowly cooled for a long time by heat preservation to form a whole, thereby achieving the purpose of repair.

[0039] Specifically, in step S1, cleaning the workpiece 10 to be repaired includes: comprehensively cleaning the oil, dirt, paint and other harmful substances inside and outside the workpiece 10 to be repaired that are likely to cause rapid cooling and affect the repair quality, so as to avoid aggravated cooling during the repair process or causing cracks and other defects in the repaired part.

[0040] Specifically, in step S2, the first temperature is less than or equal to 150°C, and the first time is greater than or equal to 62 hours. In a specific embodiment of the present application, the first temperature is 150°C and the first time is 62 hours. That is, the workpiece 10 to be repaired is baked at a low temperature of 150°C using the welding torch 60 for 62 hours to remove harmful gases and moisture from the workpiece 10 to be repaired, preventing them from entering the molten pool and causing defects such as pores, white spots, and cracks.

[0041] like Figure 2 As shown, the metal crack repair method further includes a temperature measurement step and a metal liquid prefabrication step after step S6:

[0042] Temperature measurement step: set the surface opposite to the surface with the pit of the workpiece 10 to be repaired as the temperature measuring surface, set a plurality of spaced temperature measuring points 40 on the temperature measuring surface, and use a temperature measuring gun 30 to continuously measure the temperature of the temperature measuring points 40 on the temperature measuring surface to ensure that the overall temperature of the workpiece 10 to be repaired is uniform, and monitor the workpiece 10 to be repaired to reach a temperature of about 1312°C at which the base material grains expand and tiny gaps are generated.

[0043] Preparing molten metal step: melt a metal material having a melting point lower than the base material of the workpiece 10 to be repaired by 420° C. to form molten metal 50, and store it in a small container for future use.

[0044] Specifically, in step S5, the cracked area of ​​the workpiece 10 to be repaired is ground to form a U-shaped pit 20, specifically a U-shaped groove. The length of the U-shaped pit 20 is equal to the total length of the crack, and the depth of the U-shaped pit 20 is 1.5 mm to 2.5 mm less than the crack depth. This provides storage space for the molten metal 50 and a channel for infiltration into the grain boundaries of the parent material of the workpiece 10 to be repaired, ensuring good subsequent bonding.

[0045] Specifically, the above-mentioned thermal insulation material is thermal insulation cotton. In step S6, the thermal insulation material is used to cover at least part of the surface of the workpiece 10 to be repaired, leaving only the position of the heat source 70 in the U-shaped pit 20 for heating. There are multiple heat sources 70, and multiple heat sources 70 are respectively provided on both sides of the pit. In a specific embodiment of the present application, the number of heat sources 70 is four, and two heat sources 70 are respectively provided on both sides of the U-shaped pit 20. The heat sources 70 are used to continuously heat the surface around the U-shaped pit 20 to ensure the uniformity of the temperature near the U-shaped pit 20, so as to prevent the rapid dissipation of heat during the repair process and ensure the effect of constant temperature.

[0046] refer to Figure 2 Two heat sources 70 are used to fully heat the left side of the U-shaped pit 20, and the other two heat sources 70 are used to fully heat the right side of the U-shaped pit 20, ensuring that the average heating rate is 150°C / h, ensuring that the overall temperature of the workpiece 10 to be repaired is evenly increased.

[0047] In a specific embodiment of the present application, the heat source 70 may be a spray gun or other tools for heating.

[0048] Specifically, in step S7, after pouring the molten metal 50 into the pit, a welding torch 60 is used to continuously heat the molten metal 50 in the pit and the pit walls on both sides of the pit at a second temperature, so that the temperature of the pit reaches above the temperature point of 1312°C. This causes the grains of the parent material of the workpiece 10 to be repaired to continue to expand, the grain boundary gaps to expand, and the fluidity of the molten metal 50 to increase. The flowing molten metal 50 is then gradually infiltrated into the grain boundaries of the parent material of the workpiece 10 to be repaired. Continuous heating increases its fluidity and gradually infiltrates the tiny gaps between the expanded grains. The welding torch 60 is then slowly moved, allowing the molten metal 50 that has infiltrated the grain boundaries of the parent material of the workpiece 10 to be repaired to slowly cool and form a single unit with the workpiece 10 to be repaired. The above-mentioned second temperature can be set according to actual conditions, as long as the temperature of the pit reaches above the temperature point of 1312°C.

[0049] Specifically, in step S7, the molten metal 50 is deposited layer by layer into the recess. This means that the molten metal 50 penetrates layer by layer into the grain boundaries of the parent material of the workpiece 10 to be repaired. After the molten metal 50 and the recess have formed a single, integrated whole, the next layer of molten metal 50 is added, and this process is repeated until the recess is completely filled. This ensures grain refinement, reduces the likelihood of defect formation, and further enhances the structural strength of the repaired area.

[0050] Specifically, after the pit is filled, the metal crack repair method also includes a cooling step located after step S7. The cooling step is that multiple heat sources 70 are slowly removed in sequence, so that the workpiece to be repaired 10 is cooled at a first cooling rate to ensure that the overall temperature of the workpiece to be repaired 10 drops evenly and slowly until the temperature of the workpiece to be repaired 10 drops to 757.5°C. The workpiece to be repaired 10 is completely wrapped with insulation cotton, and the workpiece to be repaired 10 is cooled at a second cooling rate to slowly cool the workpiece to be repaired 10. The second cooling rate is less than the first cooling rate. After 72 hours, until the workpiece to be repaired 10 is cooled to room temperature or normal temperature, the insulation material is removed.

[0051] In a specific embodiment of the present application, the first cooling rate is an average of 20°C / h, and the second cooling rate is an average of 5°C / h.

[0052] Specifically, the metal crack repair method further includes a testing step after the cooling step. The testing step comprises performing ultrasonic testing, colorimetric testing, and a hydrostatic test on the repaired portion of the workpiece 10 and its surroundings. A pass is achieved if the ultrasonic testing result is Class I, the colorimetric testing result is Class I, and a hydrostatic test at 1.25 times the design pressure shows no leakage.

[0053] The advantages of the metal crack repair method of the present application will be described below in conjunction with specific applications, taking a reciprocating compressor cylinder base as an example. The cylinder base has a thickness of 55mm, a height of 856mm, and a diameter of 1216mm. During operation, the cooling water channel is blocked, preventing normal circulation and discharge. When it is shut down in winter, it freezes and cracks. The cracks are penetrating cracks with a length of 684mm. In order to save costs, crack repair was arranged. Previously, a melting fusion repair technology was used for repair, but because the melting temperature was too high and the parent material was gray cast iron, which was highly brittle, the repair process repeatedly cracked and eventually failed. In order to solve the problem as quickly as possible, a metal crack repair method using grain boundary infiltration of molten metal 50 was developed. After it was put into use, the effect was significantly improved. Although there are still some micro defects, there is no crack propagation phenomenon, and no new cracks have appeared. The repaired cylinder base is still in operation to this day. The cost savings are approximately 6.775 million yuan.

[0054] Obviously, the above-described embodiments are only some, but not all of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the protection scope of the present application.

[0055] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments consistent with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, devices, components and / or combinations thereof, but do not preclude the presence or addition of one or more other features, steps, operations, devices, components and / or combinations thereof.

[0056] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments consistent with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, devices, components and / or combinations thereof, but do not preclude the presence or addition of one or more other features, steps, operations, devices, components and / or combinations thereof.

[0057] The preferred embodiments of the present application have been described above with the aid of drawing figures, and are not limited to those embodiments; instead, they will include, in general, any modifications of more or less than the specific details of the embodiments. Accordingly, the application is not limited, except as by the appended claims.

Claims

1. A metal crack repair method, characterized in that: The steps include: Step S1: obtaining a workpiece (10) to be repaired, and cleaning the workpiece (10) to be repaired; Step S2: obtaining a welding gun (60), and using the welding gun (60) to bake the workpiece (10) to be repaired at a first temperature and for a first time; Step S3: polishing the cracked area of ​​the workpiece (10) to be repaired, and performing radiographic and colorimetric testing; Step S4: performing a punching process on the end points of the cracks in the crack region; Step S5: grinding the cracked area of ​​the workpiece (10) to be repaired to form a pit; Step S6: using a heat-insulating material to cover at least a portion of the surface of the workpiece to be repaired (10), so that the surface of the workpiece to be repaired (10) having the pit is exposed, and using a heat source (70) to heat the surface of the workpiece to be repaired (10) having the pit to ensure the overall temperature of the workpiece to be repaired (10), so that the base material grains of the workpiece to be repaired (10) expand and generate small gaps; Step S7: obtaining molten metal (50), pouring the molten metal (50) into the pit, and continuously heating the molten metal (50) in the pit at a second temperature using the welding gun (60), so that the grains of the parent material of the workpiece (10) to be repaired continue to expand and the grain boundary gaps are enlarged, so that the molten metal (50) penetrates into the grain boundaries of the parent material of the workpiece (10) to be repaired, and repeating this step after the molten metal (50) is slowly cooled by heat preservation for a long time to form a whole with the pit, until the pit is filled; During the above-mentioned repair process, the base material of the workpiece (10) to be repaired is not melted.

2. The metal crack repair method according to claim 1, characterized in that: The metal crack repairing method further comprises the following steps after step S6: Temperature measurement step: setting a surface opposite to the surface of the workpiece (10) to be repaired having the pit as a temperature measurement surface, and measuring the temperature of the temperature measurement surface using a temperature measuring gun (30); Prefabrication of molten metal step: melting a metal material having a melting point lower than that of the workpiece (10) to be repaired to form the molten metal (50).

3. The metal crack repairing method according to claim 1, characterized in that: In step S7, the welding gun (60) is used to continuously heat the molten metal (50) in the pit at a second temperature so that the temperature of the pit reaches above 1312° C., so that the molten metal (50) penetrates into the grain boundary of the parent material of the workpiece to be repaired (10), and the welding gun (60) is moved to cool the molten metal (50) and form a whole with the workpiece to be repaired (10).

4. The metal crack repair method according to claim 1, characterized in that: In the step S7, the molten metal (50) is formed in the pit layer by layer in multiple times.

5. The metal crack repairing method according to claim 1, characterized in that: The metal crack repair method further includes a cooling step after step S7. The cooling step is to remove the heat source (70) and cool the workpiece to be repaired (10) at a first cooling rate until the temperature of the workpiece to be repaired (10) drops to 757.5°C, and then completely cover the workpiece to be repaired (10) with a heat-insulating material, and cool the workpiece to be repaired (10) at a second cooling rate, which is lower than the first cooling rate, until the workpiece to be repaired (10) cools to room temperature, and then remove the heat-insulating material.

6. The metal crack repairing method according to claim 5, characterized in that: The metal crack repair method further comprises a detection step after the cooling step, The detection step comprises performing ultrasonic detection, color detection, and water pressure testing on the repaired portion of the workpiece (10) to be repaired and the surrounding area of ​​the repaired portion.

7. The metal crack repairing method according to claim 1, characterized in that: In step S5, the pit is a U-shaped pit (20).

8. The metal crack repairing method according to claim 7, characterized in that: The length of the U-shaped pit (20) is equal to the length of the crack, and the depth of the U-shaped pit (20) is less than the depth of the crack.

9. The metal crack repairing method according to claim 1, characterized in that: In the step S2, the first temperature is less than or equal to 150° C., and the first time is greater than or equal to 62 hours.

10. The metal crack repairing method according to claim 1, characterized in that: In step S6, the heat sources (70) are multiple, and the two sides of the pit are respectively provided with multiple heat sources (70) arranged at intervals.

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