A repair method for eliminating welding cracks of ZL205A alloy castings

Abstract

The application belongs to the technical field of welding, and particularly relates to a repair welding method for eliminating welding cracks of ZL205A alloy castings. The application provides a repair welding method for eliminating welding cracks of ZL205A alloy castings, which comprises the following steps: S1. high-temperature heat treatment is performed on the ZL205A alloy castings after defects are removed; S2. the castings are taken out when the castings are cooled to 100-150 DEG C in the furnace, and tungsten argon arc repair welding is performed; S3. the welding area is covered with heat preservation cotton, and the castings are cooled to normal temperature; S4. if defects need to be repaired again after the castings are subjected to the aforementioned high-temperature heat treatment and repair welding, only a local area is heated to 100-150 DEG C by using a torch, and then tungsten argon arc repair welding is performed; the tungsten argon arc repair welding is performed in a spiral line repair welding sequence and a layered overlaying manner. The application eliminates the root cause of thermal cracks through high-temperature heat treatment before welding, and controls welding process stress by using a spiral line repair welding sequence, so that the repair welding thermal cracks of super-large thin-walled ZL205A castings can be effectively eliminated, only one heat treatment is needed, the production efficiency is high, and the composition of welding wire is optimized to further reduce the thermal crack tendency.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, specifically relating to a welding repair method for eliminating welding cracks in ZL205A alloy castings. Background Technology

[0002] ZL205A alloy is a high-strength and high-toughness cast aluminum alloy, widely used in key fields such as aerospace and defense due to its excellent comprehensive mechanical properties. However, ZL205A alloy belongs to the Al-Cu alloy system, with a wide crystallization temperature range, a solid-liquid phase temperature difference of 115℃, and a pasty solidification process, making it highly prone to hot cracking. Castings, especially large, complex, thin-walled castings, inevitably produce defects such as shrinkage porosity, gas porosity, and cracks during the casting process, requiring welding repair.

[0003] However, when welding ZL205A alloy castings, the process itself involves rapid heating and solidification, which also presents a serious problem of hot cracking. This is especially true for ultra-large castings, such as those exceeding 3 meters in length, 5-10 mm in wall thickness, and with complex structures. These castings have high residual stress, high rigidity, and rapid heat dissipation, leading to more concentrated shrinkage stress during welding. This makes hot cracking defects more prominent, often resulting in the scrapping of valuable castings.

[0004] To suppress welding cracks, patent CN106425021A discloses a welding repair process for nickel-based cast high-temperature alloy castings. This process involves homogenization heat treatment at an extremely high temperature of no less than 1205℃ followed by rapid cooling. This temperature is far higher than the melting point of aluminum alloys and is unsuitable for ZL205A alloys. Patent CN109570711A discloses a welding method for cracks in aluminum-silicon-magnesium alloys. However, this method only uses low-temperature annealing at 300-350℃ for hot cracks, which cannot fundamentally eliminate the low-melting-point eutectic phase in ZL205A alloys. In particular, it cannot effectively and completely release the internal stress of ultra-large, complex, thin-walled castings, thus having limited effectiveness in suppressing hot cracks.

[0005] Therefore, developing a welding repair process specifically for ultra-large, thin-walled, complex ZL205A alloy castings that can effectively eliminate hot cracks during welding repair and is simple and reliable has significant engineering application value and economic benefits. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a welding repair method for eliminating welding cracks in ZL205A alloy castings, particularly for ultra-large, complex, thin-walled ZL205A alloy castings, effectively eliminating hot cracks generated during the welding repair process. This invention eliminates the root causes of hot cracks through pre-welding high-temperature heat treatment, and controls welding stress by combining a spiral welding repair sequence. This effectively eliminates welding hot cracks in ultra-large, thin-walled ZL205A castings, requiring only one heat treatment, resulting in high production efficiency; furthermore, optimized welding wire composition further reduces the tendency for hot cracking.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A welding repair method for eliminating welding cracks in ZL205A alloy castings includes the following steps: S1. Perform high-temperature heat treatment on the ZL205A alloy castings with the defects removed; S2. When the casting is cooled to 100-150℃ in the furnace, remove it and perform tungsten inert gas welding for repair. S3. Cover the welding area with insulating cotton and allow it to cool to room temperature; S4. If a defect that needs to be repaired is found again in a casting that has been repaired after the aforementioned high-temperature heat treatment, only a blowtorch is used to heat the local area to 100-150°C, and then tungsten inert gas welding is performed for repair. The tungsten inert gas welding repair is carried out using a spiral welding sequence and a layered surfacing method. The ZL205A alloy casting is a large, thin-walled, complex casting with a length exceeding 3 meters and a wall thickness of 5-10 mm.

[0009] Furthermore, the welding repair process also includes preparation of the weld bevel: before or after high-temperature heat treatment, the defect is cleaned and the bevel is machined; the angle between one side of the bevel and the vertical line is not less than 30°.

[0010] Furthermore, the spiral welding sequence is as follows: within each weld layer, welding is performed along the perimeter of the bevel and gradually converges towards the center to form a spiral weld bead; when welding to the central area, vertical upward stacking welding is used and the arc is attenuated.

[0011] Furthermore, the thickness of each weld bead in the layered welding is 3-5 mm, and the time between each layer is 1-5 minutes.

[0012] Furthermore, the welding current of the tungsten inert gas welding is less than 150A, the diameter of the tungsten electrode is 2-4mm, and the diameter of the welding wire is 1.5-2.5mm.

[0013] Furthermore, the high-temperature heat treatment is performed at a temperature of 536-542℃, with a holding time of 14-18 hours, followed by furnace cooling.

[0014] Through the above technical solution, high-temperature heat treatment fully dissolves the continuous and coarse low-melting-point Al2Cu eutectic phase at the grain boundaries in the as-cast microstructure of ZL205A alloy into the α-Al matrix, thereby eliminating the root cause of intergranular liquid film formation during welding repair and significantly improving the material's resistance to hot cracking. Simultaneously, this heat treatment also fully releases the residual stress in the casting—a key condition for causing welding hot cracking—and increases the mechanical strength of the casting, which also plays a significant role in preventing welding hot cracking. Controlling the initial welding temperature at 100-150℃ avoids excessive temperature gradients and shrinkage stress caused by welding at room temperature, and also prevents the degradation or overheating of the base material in the adjacent heat-affected zone due to excessively high temperatures. For newly discovered defects after heat treatment, only local preheating is required for direct welding repair, eliminating the need for further overall heat treatment and significantly improving production efficiency. The spiral welding sequence allows the peripheral weld beads, which are initially welded and in contact with the base material, to contract freely, thereby dispersing and releasing welding stress and preventing stress concentration in a certain area that could lead to hot cracking. When welding to the central area, vertical upward surfacing and arc attenuation are used to make the weld zone dense, and the gradual shrinkage through the attenuation process effectively prevents hot cracking during arc termination. Layered surfacing controls the interpass temperature, preventing excessive welding heat input from causing hot cracking, and by using a smaller welding heat input and appropriate electrode / welding wire specifications, hot cracking caused by excessive molten pool and thermal shrinkage is avoided.

[0015] Furthermore, prior to the high-temperature heat treatment, the defect location is confirmed: the location of the defect is used to determine whether high-temperature heat treatment is required. If the defect is located in a position prone to hot cracking, then high-temperature heat treatment is required; otherwise, it is not required.

[0016] Furthermore, the welding wire used is ZL205A alloy welding wire. Furthermore, the chemical composition of the ZL205A alloy welding wire, by mass percentage, is: Cu: 4.6-5.0%, Mn: 0.35-0.5%, Ti: 0.2-0.3%, Zr: 0.15-0.20%, V: 0.15-0.3%, B: 0.005-0.06%, Cd: 0.15-0.25%, with the balance being Al. This welding wire composition reduces the tendency for hot cracking by controlling the Cu content to the lower limit of the standard range and controlling the refining elements such as Mn, Ti, Zr, and V to the upper limit of the standard range to enhance the refining effect of the weld metal, thereby further reducing the hot cracking tendency of the weld metal itself.

[0017] The beneficial effects of this invention are: (1) This invention provides a welding repair method for eliminating welding cracks in ultra-large, thin-walled, and complex ZL205A alloy castings. This invention achieves full solid solution of the low-melting-point Al2Cu eutectic phase in the ZL205A alloy through high-temperature heat treatment before welding, avoiding the formation of intergranular liquid film during welding repair. In particular, it can effectively and completely release the internal stress of ultra-large, complex, and thin-walled castings, thereby fundamentally eliminating the basic conditions for the generation of hot cracks. The spiral welding repair sequence and layered welding can maximize the release of shrinkage stress during the welding process and avoid stress concentration. Combined with a preheating temperature of 100-150℃ and a small welding heat input, a low-stress and uniform welding environment is constructed.

[0018] (2) The present invention only requires one high-temperature heat treatment to achieve stress release and low-melting-point phase solid solution. When welding repair is performed again, there is no need to perform overall heat treatment again, which significantly improves production efficiency.

[0019] (3) By controlling the Cu content of the welding wire to the lower limit of the standard and the refining agent elements (Mn, Ti, Zr, V) to the upper limit, the present invention further reduces the hot cracking tendency of the weld metal itself and improves the mechanical properties of the weld. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the preparation of the weld bevel for the present invention.

[0021] Figure 2 This is a schematic diagram of the welding repair process of the present invention.

[0022] Figure 3 This is an X-ray photograph of the welded area of ​​the casting after welding repair in Embodiment 1 of the present invention.

[0023] Figure 4 The image shows an X-ray photograph of the welded area of ​​the casting after welding in Comparative Example 3.

[0024] Figure 5 This is a schematic diagram of the ultra-large, complex, thin-walled ZL205A alloy casting of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] In some embodiments, before or after high-temperature heat treatment, before welding repair, the defects are cleaned, the weld area is ground clean with a pneumatic milling cutter and cleaned with chemical cleaning agents such as acetone.

[0027] In some embodiments, defects have been cleaned and beveling has been performed before heat treatment. The casting is then heated at 539±3℃ for 14-18 hours, and after cooling in the furnace to 100-150℃, it is removed and directly repaired by welding. In some embodiments, if defects are found again in a casting that has already undergone the above heat treatment, the defective areas are repaired by... Figure 1 After beveling, use a blowtorch to heat the local area to 100-150℃ before performing the repair welding.

[0028] In some embodiments, according to Figure 2 The process is carried out in a spiral and layered manner, with each layer of the weld repair using... Figure 2 In the spiral welding sequence of -a, welding is performed along the perimeter of the bevel and gradually moves towards the center; when welding reaches the central area, as follows... Figure 2 -b, adopt vertical upward stacking welding, attenuation arc termination, each weld layer is 3-5mm thick, and the time between each layer is 1-5min. Control the welding temperature so that it is not too high. Finally, complete the welding in layers as in 2-c and 2-d.

[0029] In some embodiments, the welding process parameters during the welding process are: welding current less than 150A, tungsten electrode diameter 3mm, and welding wire diameter 1.5mm.

[0030] In some embodiments, the welding wire alloy composition is as follows:

[0031] Example 1 Taking the ZL205A alloy casting as an example for repair welding, this casting is an ultra-large thin-walled complex structural part with external dimensions of 3200mm×388mm×256mm and a wall thickness of 9mm.

[0032] X-ray inspection revealed shrinkage defects in the center of the casting. The shrinkage defects were thoroughly cleaned using a pneumatic milling cutter and machined into a V-shaped bevel, ensuring that the angle between one side of the bevel and the vertical line was 30°. The casting was then placed in a heat treatment furnace, and the furnace temperature was controlled at 539°C for 14 hours. When the furnace cools to 150℃, the casting is removed and placed on a welding platform. The area to be welded is brushed until bright with a wire brush, and then tungsten inert gas (TIG) welding is performed. The TIG diameter is 3mm, and ZL205A welding wire (Cu 4.8%, Mn 0.4%, Ti 0.25%, Zr 0.18%, V 0.2%, B 0.03%, Cd 0.2%, balance Al) with a diameter of 1.5mm is used. The welding current is controlled at 140A. For the first layer of welding, welding starts from the perimeter of the bevel, and the welding wire gradually converges towards the center of the bevel in a spiral trajectory. After reaching the center, welding is carried out vertically upwards, controlling the first layer of weld to 3mm. The welding current is gradually reduced from 140A to 0A to complete the arc termination. After 3 minutes, the second layer is applied, and a total of 4 layers of welding are completed. Immediately after welding, cover the entire welded area with insulating cotton to allow it to cool slowly to room temperature. After removing and grinding off any excess weld material, perform an X-ray inspection on the welded area. The results are as follows: Figure 3 As shown, the welded area is well formed, and there are no welding cracks in the casting.

[0033] Example 2 Taking the ZL205A alloy casting as an example for repair welding, this casting is an ultra-large thin-walled complex structural part with external dimensions of 3200mm×388mm×256mm and a wall thickness of 9mm.

[0034] X-ray inspection revealed porosity defects at the casting end, which did not require high-temperature heat treatment. The porosity defects were thoroughly cleaned using a pneumatic milling cutter, and a V-shaped bevel was machined, ensuring that the angle between each side of the bevel and the vertical line was 35°. The casting was placed on a welding platform, and the weld repair area was locally heated to 120°C using a blowtorch. The surface of the weld repair area was then brushed with a wire brush until it achieved a metallic luster. TIG welding was performed using a 2.5mm diameter tungsten electrode and ZL205A welding wire (Cu 4.8%, Mn 0.4%, Ti 0.25%, Zr 0.18%, V 0.2%, B...). The filler material consisted of 0.03% Cd, 0.2% Cd, and the balance Al. The welding wire diameter was 2.0 mm, and the welding current was controlled at 130 A. For the first layer of welding, welding began around the bevel perimeter, with the welding wire gradually converging towards the center of the bevel in a spiral trajectory. After reaching the center, welding was carried out vertically upwards, controlling the first weld bead to 4 mm. The welding current was gradually reduced from 130 A to 0 A to complete the arc termination. After a 2-minute pause, the second layer was applied, for a total of three layers. After welding, the entire welded area was immediately covered with insulating cotton to allow it to cool slowly to room temperature. After removing and grinding the excess weld, the welded area underwent X-ray inspection. The welded area showed good formation, and no welding cracks were found in the casting.

[0035] Example 3 Taking the ZL205A alloy casting as an example for repair welding, this casting is an ultra-large thin-walled complex structural part with external dimensions of 3200mm×388mm×256mm and a wall thickness of 9mm.

[0036] X-ray inspection revealed a crack defect in the lower center of the casting. The crack defect was thoroughly cleaned using a pneumatic milling cutter and machined into a V-shaped bevel, ensuring that the angle between one side of the bevel and the vertical line was 40°. The casting was then placed in a heat treatment furnace, and the furnace temperature was controlled at 539°C for 16 hours. When the furnace cools to 120℃, the casting is removed and placed on a welding platform. The area to be welded is brushed until bright with a wire brush, and then tungsten inert gas (TIG) welding is performed. The TIG diameter is 3.5mm, and ZL205A welding wire (Cu 4.8%, Mn 0.4%, Ti 0.25%, Zr 0.18%, V 0.2%, B 0.03%, Cd 0.2%, balance Al) with a diameter of 2.2mm is used. The welding current is controlled at 140A. For the first layer of welding, welding starts from the perimeter of the bevel, and the welding wire gradually converges towards the center of the bevel in a spiral trajectory. After reaching the center, welding is carried out vertically upwards, controlling the first layer of weld to 5mm. The welding current is gradually reduced from 140A to 0A to complete the arc termination. After 4 minutes, the second layer is applied, and a total of 4 layers of welding are completed. Immediately after welding, cover the entire welded area with insulating cotton to allow it to cool slowly to room temperature. After removing and grinding off any excess weld material, perform an X-ray inspection on the welded area. The results are as follows: Figure 3 As shown, the welded area is well formed, and there are no welding cracks in the casting.

[0037] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that after removing the defects, the casting is not subjected to high-temperature heat treatment, but is directly repaired by welding under as-cast conditions.

[0038] Taking the ZL205A alloy casting as an example for repair welding, this casting is an ultra-large thin-walled complex structural part with external dimensions of 3200mm×388mm×256mm and a wall thickness of 9mm.

[0039] X-ray inspection revealed shrinkage porosity defects in the center of the casting. These defects were thoroughly cleaned using a pneumatic milling cutter, and a V-shaped bevel was machined, ensuring that the angle between each side of the bevel and the vertical line was 30°. Without high-temperature heat treatment, tungsten inert gas (TIG) welding was performed directly at room temperature. The TIG welding electrode was 3mm in diameter, and ZL205A welding wire (Cu 4.8%, Mn 0.4%, Ti 0.25%, Zr 0.18%, V 0.2%, B 0.03%, Cd 0.2%, balance Al) with a diameter of 1.5mm was used. The welding current was controlled at 140A. For the first layer of repair, welding began along the perimeter of the bevel, with the welding wire gradually converging towards the center in a spiral trajectory. After reaching the center, welding was performed vertically upwards, controlling the first weld bead to 3mm. The welding current was gradually reduced from 140A to 0A to complete the arc termination, and the second layer was applied after a 3-minute pause. A total of four layers of repair were completed. After welding, the entire welded area was immediately covered with insulating cotton to allow it to cool slowly to room temperature. After removing and grinding the excess weld, the welded area was inspected by X-ray. The results showed that the welded area had obvious hot crack defects and could not meet the service performance requirements.

[0040] Because of the presence of continuous, coarse, low-melting-point Al2Cu eutectic phases at the grain boundaries in the as-cast microstructure, the high-temperature heating during welding causes these eutectic phases to remelt and form intergranular liquid films, which are then pulled apart under the action of welding shrinkage stress, resulting in hot cracks.

[0041] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the conventional straight reciprocating weld sequence is used during the repair welding, instead of a spiral weld sequence.

[0042] Taking the ZL205A alloy casting as an example for repair welding, this casting is an ultra-large thin-walled complex structural part with external dimensions of 3200mm×388mm×256mm and a wall thickness of 9mm.

[0043] X-ray inspection revealed shrinkage porosity defects in the center of the casting. These defects were thoroughly cleaned using a pneumatic milling cutter, and a V-shaped bevel was machined, ensuring that the angle between each side of the bevel and the vertical line was 30°. The casting was then placed in a heat treatment furnace at 539°C for 14 hours. After cooling to 150°C, the casting was removed and placed on a welding platform. The area to be welded was brushed until bright with a wire brush, and then tungsten inert gas (TIG) welding was performed. The TIG welding electrode was 3mm in diameter, and ZL205A welding wire (Cu 4.8%, Mn 0.4%, Ti 0.25%, Zr 0.18%, V 0.2%, B 0.03%, Cd 0.2%, balance Al) with a diameter of 1.5mm was used. The welding current was controlled at 140A. Welding was performed in a straight line in one direction, then back in the opposite direction, repeating this process. After welding, the entire welded area was immediately covered with insulating cotton to allow it to cool slowly to room temperature. After removing and grinding the excess weld, the welded area was inspected by X-ray. The welded area showed hot cracking defects and could not meet the service performance requirements.

[0044] Because the linear reciprocating welding sequence prevents the effective release of welding stress, the stress accumulates in the weld and causes hot cracks under the action of shrinkage stress in the weld zone.

[0045] Comparative Example 3 The difference between Comparative Example 1 and Example 1 is that the casting was taken out for welding after cooling to room temperature in the furnace, rather than being taken out at 100-150°C.

[0046] Taking the ZL205A alloy casting as an example for repair welding, this casting is an ultra-large thin-walled complex structural part with external dimensions of 3200mm×388mm×256mm and a wall thickness of 9mm.

[0047] X-ray inspection revealed shrinkage defects in the center of the casting. The shrinkage defects were thoroughly cleaned using a pneumatic milling cutter and machined into a V-shaped bevel, ensuring that the angle between one side of the bevel and the vertical line was 30°. The casting was then placed in a heat treatment furnace, and the furnace temperature was controlled at 539°C for 14 hours. After the furnace cools to room temperature, the casting is removed and placed on a welding platform. The area to be welded is brushed until shiny with a wire brush, and then tungsten inert gas (TIG) welding is performed. The TIG diameter is 3mm, and ZL205A welding wire (Cu 4.8%, Mn 0.4%, Ti 0.25%, Zr 0.18%, V 0.2%, B 0.03%, Cd 0.2%, balance Al) with a diameter of 1.5mm is used. The welding current is controlled at 140A. For the first layer of welding, welding starts from the perimeter of the bevel, and the welding wire gradually converges towards the center of the bevel in a spiral trajectory. After reaching the center, welding is carried out vertically upwards, controlling the first layer of weld to 3mm. The welding current is gradually reduced from 140A to 0A to complete the arc termination. After 3 minutes, the second layer is applied, and a total of 4 layers of welding are completed. After welding, the entire welded area was immediately covered with insulating cotton to allow it to cool slowly to room temperature. After removing and grinding the excess weld, the welded area was inspected by X-ray. The welded area showed obvious hot cracking defects and could not meet the service performance requirements.

[0048] Because the temperature gradient between the casting and the weld pool is greater after the casting cools to room temperature, the shrinkage stress generated during welding is also greater. Furthermore, welding at room temperature lacks preheating, leading to faster heat dissipation and solidification shrinkage in the weld area, thus exacerbating the formation of hot cracks.

[0049] Comparative Example 4 The difference between Comparative Example 1 and Example 1 is that the welding wire used is a conventional ZL205A welding wire with a Cu content at the upper limit of the standard range (Cu 5.3%) and a refining agent element content at the lower limit of the standard range (Mn 0.3%, Ti 0.15%, Zr 0.05%, V 0.05%).

[0050] Taking the ZL205A alloy casting as an example for repair welding, this casting is an ultra-large thin-walled complex structural part with external dimensions of 3200mm×388mm×256mm and a wall thickness of 9mm.

[0051] X-ray inspection revealed shrinkage defects in the center of the casting. The shrinkage defects were thoroughly cleaned using a pneumatic milling cutter and machined into a V-shaped bevel, ensuring that the angle between one side of the bevel and the vertical line was 30°. The casting was then placed in a heat treatment furnace, and the furnace temperature was controlled at 539°C for 14 hours. When the furnace cools to 150℃, the casting is removed and placed on a welding platform. The area to be welded is brushed until bright with a wire brush, and then tungsten inert gas (TIG) welding is performed. The TIG diameter is 3mm, and ZL205A welding wire (Cu 5.3%, Mn 0.3%, Ti 0.15%, Zr 0.05%, V 0.05%, B 0.03%, Cd 0.2%, balance Al) with a diameter of 1.5mm is used. The welding current is controlled at 140A. For the first layer of welding, welding starts from the perimeter of the bevel, and the welding wire gradually converges towards the center of the bevel in a spiral trajectory. After reaching the center, welding is carried out vertically upwards, controlling the first layer of weld to 3mm. The welding current is gradually reduced from 140A to 0A to complete the arc termination. After 3 minutes, the second layer is applied, and a total of 4 layers of welding are completed. After welding, the entire welded area was immediately covered with insulating cotton to allow it to cool slowly to room temperature. After removing and grinding the excess weld, the welded area was inspected by X-ray. A small number of microcracks were found in the welded area. Performance testing showed that the tensile strength of the welded area was only 72% of that of the base material, which did not meet the service performance requirements.

[0052] The higher Cu content in the wire increases the amount of low-melting-point eutectic phase, which increases the tendency for hot cracking; while the lower content of refining agent leads to coarse weld structure and reduced crack resistance.

[0053] This invention eliminates the root cause of hot cracks by pre-welding high-temperature heat treatment and releases stress by spiral welding sequence, which can effectively eliminate welding hot cracks in ultra-large thin-walled ZL205A castings. Moreover, it can be completed in one heat treatment, resulting in high production efficiency. Furthermore, the optimized welding wire composition further reduces the tendency for hot cracking.

[0054] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A welding repair method for eliminating welding cracks in ZL205A alloy castings, characterized in that, Includes the following steps: S1. Perform high-temperature heat treatment on the ZL205A alloy castings with the defects removed; S2. When the casting is cooled to 100-150℃ in the furnace, remove it and perform tungsten inert gas welding for repair. S3. Cover the welding area with insulating cotton and allow it to cool to room temperature; S4. If a defect that needs to be repaired is found again in a casting that has been repaired after the aforementioned high-temperature heat treatment, only a blowtorch is used to heat the local area to 100-150°C, and then tungsten inert gas welding is performed for repair. The tungsten inert gas welding repair is carried out using a spiral welding sequence and a layered surfacing method. The ZL205A alloy casting is a large, thin-walled, complex casting with a length exceeding 3 meters and a wall thickness of 5-10 mm.

2. The welding repair method for eliminating welding cracks in ZL205A alloy castings according to claim 1, characterized in that, The welding repair process also includes beveling preparation: before or after high-temperature heat treatment, the defect is cleaned and the bevel is machined; the angle between one side of the bevel and the vertical line is not less than 30°.

3. The welding repair method for eliminating welding cracks in ZL205A alloy castings according to claim 1, characterized in that, The spiral welding sequence is as follows: within each weld layer, welding is performed along the perimeter of the bevel and gradually converges towards the center to form a spiral weld bead; when welding to the central area, vertical upward stacking welding is used and the arc is attenuated.

4. The welding repair method for eliminating welding cracks in ZL205A alloy castings according to claim 1, characterized in that, The thickness of each weld bead in the layered welding is 3-5 mm, and the time between each layer is 1-5 minutes.

5. The welding repair method for eliminating welding cracks in ZL205A alloy castings according to claim 1, characterized in that, The welding current for the tungsten inert gas (TIG) welding is less than 150A, the diameter of the tungsten electrode is 2-4mm, and the diameter of the welding wire is 1.5-2.5mm.

6. The welding repair method for eliminating welding cracks in ZL205A alloy castings according to claim 1, characterized in that, The high-temperature heat treatment is performed at a temperature of 536-542℃, with a holding time of 14-18 hours, followed by furnace cooling.

7. The welding repair method for eliminating welding cracks in ZL205A alloy castings according to claim 1, characterized in that, Before the high-temperature heat treatment, the defect location is confirmed: the location of the defect is used to determine whether high-temperature heat treatment is required. If the defect is located in a position where hot cracks are likely to occur, then high-temperature heat treatment is required; otherwise, it is not required.

8. The welding repair method for eliminating welding cracks in ZL205A alloy castings according to claim 1, characterized in that, The welding wire used is ZL205A alloy welding wire.

9. The welding repair method for eliminating welding cracks in ZL205A alloy castings according to claim 8, characterized in that, The chemical composition of the ZL205A alloy welding wire by mass percentage is as follows: Cu: 4.6-5.0%, Mn: 0.35-0.5%, Ti: 0.2-0.3%, Zr: 0.15-0.20%, V: 0.15-0.3%, B: 0.005-0.06%, Cd: 0.15-0.25%, with the balance being Al.

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