A method for repairing surface cracks of a titanium alloy double-layer thin-wall part roll-welded seam

Abstract

In order to ensure reliable work of an actuator case of an aero-engine, to avoid problems such as post-welding oxidation, deformation and cracking of the base material of the actuator case and to reduce the failure rate, the application provides a repairing method for surface cracks of a double-layer thin-wall titanium alloy part by roll welding, which comprises the following steps: drilling a crack stopping hole at both ends of the crack; based on the patch repairing method, a titanium alloy plate with the same material and thickness as the base of the actuator case is used to make a patch to completely cover the damaged area, and then a manual tungsten argon arc welding device is used to weld the patch and the base of the actuator case. During the argon arc welding, argon is used as a protective gas to prevent the titanium alloy from being oxidized during the argon arc welding process, and at the same time, appropriate welding process parameters are selected to accurately control the welding heat input to prevent the material from being oxidized again and the base from being deformed. After welding, the surface of the weld is required to be smooth and the base material is required to be well fused, and the patch and the base surface should not have obvious deformation. The application has strong operability, simple operation process and good repairing effect.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a method for repairing surface cracks in roll welds of titanium alloy double-layer thin-walled parts using argon arc welding. Background Technology

[0002] Cracks are a harmful factor affecting the normal operation of aero-engine components and seriously threaten flight safety. The afterburner is designed to improve flight maneuverability, and its stable operation affects the overall performance of the engine. During operation, the afterburner of a certain type of aero-engine repeatedly experienced cracks in the actuator casing weld seam, which were repaired with argon arc welding but subsequently re-cracking. This fault severely compromised the integrity of the equipment and increased repair costs.

[0003] The actuator housing base material is titanium alloy Ti230-δ0.7mm, such as... Figure 1 , Figure 2 As shown, the main fault is a crack at the roll weld, which is currently being repaired using direct argon arc welding. However, due to incomplete cleaning of carbon deposits and oil stains within the roll weld interlayer of the actuator casing, the amount of TiH2 in the weld has increased. Since TiH2 has very low strength, its impact resistance is significantly reduced under the influence of its lamellar or needle-like structure, leading to delayed cracking at the weld joint. Repeated welding repairs alter the physical properties of the base material at the crack location, causing a decrease in plasticity and toughness, an increase in brittleness, and ultimately, a higher rate of post-weld cracking.

[0004] Patent document CN109175881A discloses a vacuum brazing method for repairing turbine stator blade patches in aero-engines. This method addresses turbine stator blade ablation faults by employing a patching approach, combining the removal of the ablated area, patch fabrication, and vacuum brazing. However, because aero-engine actuator housings are made of titanium alloys and high-temperature alloys, with numerous material grades and complex states, the impact of brazing temperature on different materials is difficult to assess. Therefore, this method is not suitable for repairing the double-layer structure of aero-engine actuator housings.

[0005] Patent document CN108145333A discloses a repair method for weld cracks in an aircraft afterburner actuator housing. Addressing the issue of numerous and long cracks in the actuator housing weld, it proposes a section-repair method involving the addition of replacement rings. This method reduces welding stress, effectively controls housing deformation, ensures weld strength meets usage requirements, and extends the housing's service life. However, this method is complex, requires sophisticated tooling and high precision in fitting clearances, and has a long repair cycle, making it unsuitable for application in aircraft repair shops.

[0006] A method for repairing cracks in the outer cylinder of an actuator is disclosed in patent document CN114102048A. The method completely eliminates the cracks in the outer cylinder of the actuator and repairs them by laser cladding. It can achieve metallurgical bonding between the cladding layer and the substrate, with a small heat-affected zone and small deformation. The repair material has a wall thickness of 8mm, which is not suitable for repairing thin-walled parts of the actuator casing.

[0007] A method for repairing a cracked and chipped casing shunt ring is disclosed in patent document CN102430889 B. The method involves first removing the faulty area, fabricating a patch of the same size, inserting the patch into the faulty area, and then welding it in place. However, this method can only repair single-layer structures and cannot be used to repair double-layer thin-walled components.

[0008] To ensure the normal operation of aircraft engines and prevent the actuator casing cracks from expanding and breaking, which could lead to unsafe operating conditions such as leaks due to a lack of seal between the actuator casing and the aircraft nacelle tail seal, it is urgent to find a repair method to repair actuator casings with roll weld cracks while still meeting the product's performance requirements. Summary of the Invention

[0009] To ensure the reliable operation of the aero-engine actuator housing and avoid post-weld oxidation, deformation, and cracking of the base material (a 0.7mm thick double-layer thin-walled titanium alloy component) to reduce the failure rate, this invention proposes a method for repairing surface cracks in the roll weld seam of the titanium alloy double-layer thin-walled component. This invention combines patch repair methods with argon arc welding technology to achieve the repair of surface cracks in the roll weld seam of the double-layer thin-walled component.

[0010] The inventive concept of this invention is:

[0011] First, to prevent the expansion and extension of cracks in the roll weld, anti-crack holes are drilled at both ends of the crack.

[0012] Then, to prevent the cracks in the titanium alloy roll weld from reopening due to repeated welding repairs, a patch repair method was used. A patch made of the same material and thickness as the actuator housing substrate was fabricated to completely cover the damaged area. A manual tungsten inert gas (TIG) welding machine was then used to weld the patch to the actuator housing substrate. During TIG welding, argon gas was used as a shielding gas to prevent oxidation of the titanium alloy. Appropriate welding process parameters were selected to precisely control the welding heat input and prevent further oxidation and substrate deformation. Post-weld, the weld surface should have a smooth transition and good fusion with the substrate material; there should be no significant deformation on the patch or substrate surfaces.

[0013] The technical solution of this invention is:

[0014] A method for repairing surface cracks in the roll weld seam of a titanium alloy double-layer thin-walled component is characterized by being used to repair cracks with a single crack length of less than or equal to 50 mm on the surface of the roll weld seam of the titanium alloy double-layer thin-walled component, or to repair crack areas on the surface of the roll weld seam of the titanium alloy double-layer thin-walled component where multiple cracks exist locally, with each crack length not exceeding 10 mm, crack spacing not exceeding 20 mm, and crack area length less than or equal to 50 mm; the method includes the following steps:

[0015] Step 1: Create the patch

[0016] Based on the length of the crack in the roll weld, the oxidation and deformation of the base material at the crack, a patch is made. The patch material and thickness are the same as the base material and can completely cover the damaged area.

[0017] Step 2: Pre-welding treatment

[0018] 2.1 Drill anti-crack holes at both ends of the crack;

[0019] 2.2 Grind the weld seam crack to the level of the substrate, and grind the area to be welded and the area around the substrate until the metal luster is exposed.

[0020] 2.3 The alignment patch is made to match the surface of the area to be soldered and the fitting gap is no more than 1mm;

[0021] 2.4 Clean the area to be welded thoroughly;

[0022] 2.5 Seal the interlayer of the roll weld seam, leaving only two holes for the inflow and outflow of protective gas, respectively;

[0023] 2.6 Inert gas is introduced into the interlayer of the roll weld as a protective gas at a flow rate of 8-10 L / min;

[0024] Step 3: Tungsten Inert Gas Welding

[0025] First, perform multi-point tack welding on the patch, then weld the patch to the substrate using segmented, symmetrical welding. Each segment should be 15-20mm long. The welding process parameters for both tack welding and segmented, symmetrical welding are as follows:

[0026] Welding current 30-35A, argon gas flow rate of welding torch 10-12L / min, power supply is DC positive polarity;

[0027] During welding, before the weld has completely cooled, add a drag bucket and pass inert gas at a rate of 8-10 L / min to protect the weld and prevent oxidation of the titanium alloy.

[0028] When ending the arc, delay for 1 to 2 minutes before stopping the gas, and then remove the welding torch after stopping the gas.

[0029] Step 4: Visual inspection;

[0030] Step 5: Polish off any excess material;

[0031] Step 6: Non-destructive testing.

[0032] Furthermore, the patch mentioned in step 1 is a rectangular patch, with the length of each side being 5-10 mm longer than the crack damage area, the patch width being 20-30 mm, and the four corners of the patch being rounded with a radius of R16-20 mm.

[0033] Furthermore, in step 2.2, the area around the patch to be applied is polished to at least 15mm until a metallic luster is exposed.

[0034] Furthermore, in step 3, when performing multi-point positioning welding of the patch, the positioning welding points should be symmetrically distributed, and the spacing between the positioning points should be 15-20mm.

[0035] Furthermore, the diameter of the anti-crack hole described in step 2.1 is 1.6-2.0 mm.

[0036] Furthermore, the inert gas mentioned in steps 2 and 3 is argon.

[0037] This invention also provides a method for repairing surface cracks in the roll weld seam of a titanium alloy double-layer thin-walled component. Its key feature is that it is used to repair cracks with a single crack length greater than 50 mm on the surface of the roll weld seam of a titanium alloy double-layer thin-walled component, or to repair crack areas on the surface of the roll weld seam of a titanium alloy double-layer thin-walled component where multiple cracks exist locally, with each crack length not exceeding 10 mm, crack spacing not exceeding 20 mm, and the length of the crack area exceeding 50 mm. The method includes the following steps:

[0038] Step 1: Create the patch

[0039] Based on the length of the crack in the roll weld, the oxidation and deformation of the base material at the crack, a patch is made. The patch material and thickness are the same as the base material and can completely cover the damaged area.

[0040] Step 2: Pre-welding treatment

[0041] 2.1 Drill anti-crack holes at both ends of the crack;

[0042] 2.2 Grind the weld seam crack to the level of the substrate, and grind the area to be welded and the area around the substrate until the metal luster is exposed.

[0043] 2.3 The alignment patch is made to match the surface of the area to be soldered and the fitting gap is no more than 1mm;

[0044] 2.4 Clean the area to be welded thoroughly;

[0045] 2.5 Seal the interlayer of the roll weld seam, leaving only two holes for the inflow and outflow of protective gas, respectively;

[0046] 2.6 Inert gas is introduced into the interlayer of the roll weld as a protective gas at a flow rate of 8-10 L / min;

[0047] Step 3: Tungsten Inert Gas Welding

[0048] First, intermittent welding is performed on the original crack, with each segment welded 10-15mm and the interval between two adjacent segments 20-25mm; then, the patch is tack welded at multiple points, and then the patch is welded to the substrate using an intermittent welding method, with each segment welded 15-20mm in length and the interval between two adjacent segments 15-20mm, and the welds of opposite segments are staggered.

[0049] The welding process parameters for intermittent welding of the original crack, tack welding of patches, and staggered intermittent welding are as follows:

[0050] Welding current 30-35A, argon gas flow rate of welding torch 10-12L / min, power supply is DC positive polarity;

[0051] During welding, before the weld has completely cooled, add a drag bucket and pass inert gas at a rate of 8-10 L / min to protect the weld and prevent oxidation of the titanium alloy.

[0052] When ending the arc, delay for 1 to 2 minutes before stopping the gas, and then remove the welding torch after stopping the gas.

[0053] Step 4: Visual inspection;

[0054] Step 5: Polish off any excess material;

[0055] Step 6: Non-destructive testing.

[0056] Furthermore, the patch mentioned in step 1 is a rectangular patch, with the length of each side being 5-10 mm longer than the crack damage area, the patch width being 20-30 mm, and the four corners of the patch being rounded with a radius of R16-20 mm.

[0057] Furthermore, in step 2.2, the area around the patch to be applied is polished to at least 15mm until a metallic luster is exposed.

[0058] Furthermore, in step 3, when performing multi-point positioning welding of the patch, the positioning welding points should be symmetrically distributed, and the spacing between the positioning points should be 15-20mm.

[0059] Compared with the prior art, the present invention has the following advantages:

[0060] 1. This invention is highly operable, has a simple operating process, and provides excellent repair results. It effectively avoids problems such as oxidation, deformation, stress concentration, and cracking caused by repeated welding of roll weld seams in titanium alloy double-layer thin-walled parts, improves the quality of welding repair, ensures the normal delivery of engines, and fills the technical gap in the field of repairing roll weld seam cracks in engine titanium alloy thin-walled parts.

[0061] 2. This invention employs a patch-mounted argon arc welding repair method instead of traditional direct argon arc welding, avoiding the degradation of the base material properties caused by repeated welding and preventing weld re-cracking. This method can be extended to the repair of damage to thin-walled titanium alloy components in fields such as aircraft and ships.

[0062] 3. This invention employs manual tungsten inert gas (TIG) welding, using argon gas as a protective gas during welding, which effectively prevents oxidation on the weld surface and back side. Through extensive process experiments and parameter adjustments, the welding current and time are strictly controlled while ensuring welding quality. Segmented and symmetrical welding is adopted, and the next segment of the weld is welded only after the weld has cooled to room temperature, effectively reducing the welding heat input, temperature gradient, deformation, and residual stress.

[0063] 4. This invention sets the welding current to 30-35A and the argon gas flow rate of the welding torch to 10-12L / min, which avoids the problems of poor weld surface fusion due to insufficient welding current and post-weld deformation due to excessive welding current. This invention also allows the welding torch to remain on the weld for 2 minutes after arc termination, taking into account that as the actual temperature increases during welding, titanium's affinity for oxygen, nitrogen, and hydrogen continuously increases (titanium rapidly absorbs hydrogen above 300℃, reacts rapidly with oxygen above 600℃, and reacts with... above 700℃). Nitrogen reaction can affect the plasticity and toughness of titanium alloy welds. Therefore, by appropriately delaying the reaction, the adverse effects of oxygen, nitrogen, and hydrogen on the plasticity and toughness of the weld can be avoided. During welding, when the weld has not completely cooled, argon gas is introduced into the bucket to protect it. The flow rate of the protective gas in the bucket is set to 8-10 L / min. This not only prevents the titanium alloy from being oxidized after melting, but also avoids the situation where the protective gas flow rate is too small to provide protection or too large to cause the weld to cool too quickly and crack, thus ensuring the quality of the repair.

[0064] 5. This invention uses a combination of patch and argon arc welding for repair. The weld is a fillet weld, which does not require full penetration. This can effectively reduce the heat input during welding, reduce the probability of post-weld deformation and re-cracking, and improve the repair quality.

[0065] 6. For crack defects with multiple cracks in a localized area, where the length of a single crack is no greater than 10 mm, the crack spacing is no greater than 20 mm, and the length of the crack area is greater than 50 mm, or for a single crack greater than 50 mm: Before patching, the original crack is intermittently welded, with each weld segment being 10-15 mm long and the interval between two adjacent segments being 20-25 mm. This can prevent severe misalignment, substrate deformation, and crack propagation at the crack due to uneven stress. When patching, an intermittent welding method is used, with each weld segment being 15-20 mm long and the interval between two adjacent segments being 15-20 mm. This can prevent substrate deformation due to excessively long welds and high heat input.

[0066] 7. The present invention has a simple process, low requirements for tooling and equipment and fitting clearance, high repair efficiency and short cycle. Attached Figure Description

[0067] Figure 1 A three-dimensional model of the motor housing for a titanium alloy double-layer thin-walled component.

[0068] Figure 2 This is an example of a crack failure in a roll weld.

[0069] Figure 3 This is an example of a titanium alloy patch manufactured according to Embodiment 1 of the present invention.

[0070] Figure 4 This is an example of patch positioning soldering in Embodiment 1 of the present invention.

[0071] Figure 5 This is an example of the post-weld process of patch argon arc welding in Embodiment 1 of the present invention.

[0072] Figure 6 This is the morphology of the weld after grinding in Embodiment 1 of the present invention.

[0073] Figure 7 This is a post-weld image of the intermittent welding of the original weld seam in Embodiment 5 of the present invention.

[0074] Figure 8 This is a schematic diagram illustrating the principle of intermittent patch welding in Embodiment 5 of the present invention.

[0075] Figure 9 This is a post-soldering image of the intermittent welding of patches in Embodiment 5 of the present invention. Detailed Implementation

[0076] The present invention will be further described in detail below with reference to the accompanying drawings.

[0077] The following Examples 1-4 and Comparative Examples 1-4 are as follows: Figure 2 The surface crack of the roller weld seam of the actuator housing shown is used as an example for repair. There is a 20mm long crack at the 3 o'clock position of the second roller weld seam of the actuator housing. The crack has been directly repaired by welding once. The base material has dark blue oxidation, but the base material has not been deformed. The base material and thickness are Ti230-δ0.7mm.

[0078] Example 1:

[0079] The specific repair method in this embodiment is as follows:

[0080] Step 1: Create the patch:

[0081] 1.1 Based on the length of the roll weld crack, the oxidation and deformation of the base material at the crack, a titanium alloy patch Ti230-δ0.7mm was made. The patch length was 30mm, the patch width was 25mm, and the four corners of the patch were rounded to R20mm.

[0082] 1.2 Use a grinding wheel to remove burrs around the surface mount, such as... Figure 3 As shown.

[0083] Step 2: Pre-welding treatment:

[0084] 2.1 Drill at both ends of the crack Crack arrestor hole;

[0085] 2.2 Using a dental grinding wheel (or dental abrasive wheel), grind the area where the patch needs to be applied at the crack of the roll weld until it is flush with the substrate. In this embodiment, the area where the patch needs to be applied is the original weld repair area of ​​the roll weld crack.

[0086] 2.2 Grind the area to be soldered and the area around the patch within 15mm using a dental grinding wheel until the metal shines through;

[0087] 2.3 Use a steel hammer to reshape the patch to match the profile of the part to be welded in the actuator housing, with a maximum clearance of 0.8mm;

[0088] 2.4 Use a white cloth dampened with anhydrous ethanol or other organic solvent cleaning solution to wipe the surface around the patch to be soldered and the surface of the actuator housing crack to be soldered clean;

[0089] 2.5 Use high-temperature tape to seal the holes in the interlayer of the roller weld of the actuator casing, leaving only two small holes, one for argon gas to flow in and one for argon gas to discharge.

[0090] 2.6 Argon gas is introduced into the interlayer of the roller weld of the actuator casing for protection, so that argon gas (other inert gases can also be used, argon gas is low cost) fills the entire interlayer to prevent oxidation on the back of the titanium alloy weld and can also accelerate cooling and reduce deformation. The required argon gas flow rate is 8-10 L / min.

[0091] Step 3: Tungsten Inert Gas Welding:

[0092] 3.1 Clean the welding wire:

[0093] Select welding wire Before welding, sand the oxide film on the surface of the welding wire with sandpaper, and wipe the surface of the welding wire clean with a white cloth dipped in anhydrous ethanol or other organic solvent cleaning solution.

[0094] 3.2 Tack Welding Patch:

[0095] A patch is fixed to the crack area (each side of the patch is 5mm longer than the crack damage area). Argon arc welding is used for tack welding. The tack welds should be symmetrically distributed, with a spacing of 15-20mm between them. The number of tack welds depends on the size of the patch; the larger the patch, the more tack welds are needed. In this embodiment, the patch has 6 tack welds. Figure 4 As shown; Argon arc welding positioning parameters: welding current 30A, argon gas flow rate of welding torch 10L / min, power supply is DC positive polarity;

[0096] 3.3 Welding Patch:

[0097] Considering the oxidation problem of titanium alloy after melting, during welding, argon gas should be added to the bucket to protect the weld before it is completely cooled to prevent oxidation of the titanium alloy after melting. The argon gas flow rate in the bucket should be 8L / min. When finishing the arc, the welding torch should not be removed from the weld immediately; the argon gas should be stopped after a delay of 1-2 minutes. After the gas is stopped, the welding torch should be removed. To reduce residual welding stress and deformation, a segmented, symmetrical welding method should be adopted, with each segment being 15mm in length. The welding heat input should be strictly controlled by controlling the welding current. The welding parameters are the same as the argon arc welding positioning parameters in 3.2. The welding current and arc termination time should be precisely controlled to ensure that the welding current for arc initiation, welding, and arc termination are 30-35A and the welding current is 30A. The weld between the patch and the actuator housing base should have a smooth transition and good fusion with the base material, without cracks or undercut. Figure 5 As shown. To reduce the temperature gradient at the weld, the next section of the weld can be welded after the weld has cooled to room temperature.

[0098] Step 4: Visual inspection:

[0099] Visual inspection using a magnifying glass of at least 10x magnification should be performed. The weld should have a smooth transition and good fusion with the base material. There should be no cracks or undercuts in the weld and heat-affected zone (if there are cracks or undercuts in the weld and heat-affected zone, the above welding method can be used for repair welding). The surface of the weld and heat-affected zone should be bright silver-white or light yellow, without dark blue or golden purple.

[0100] Step 5: Polishing allowance:

[0101] The weld excess on the patch surface is ground down using a dental grinding wheel. Multiple passes of grinding are performed to reduce stress and ensure a smooth finish and a seamless transition to the substrate material. Figure 6 As shown.

[0102] Step 6: Non-destructive testing:

[0103] Fluorescent inspection was performed on the ground weld, and no defects such as cracks or undercut were found in the weld and heat-affected zone.

[0104] Example 2:

[0105] The only difference between this embodiment and Embodiment 1 is that:

[0106] The patch made in step 1 is 40mm long (i.e., each side is 10mm longer than the crack damage area) and 30mm wide.

[0107] Step 2: After patch alignment, the maximum clearance between the patch and the part to be soldered in the actuator housing is 1mm.

[0108] The welding parameters for locating the patch and for segmented and symmetrical welding in step 3 are: welding current 35A, argon flow rate of welding torch 12L / min, and argon flow rate of trailer 10L / min; when welding in segments, the length of each segment is 20mm.

[0109] Example 3:

[0110] The only difference between this embodiment and Embodiment 1 is that:

[0111] The patch made in step 1 is 36mm long (i.e., each side is 8mm longer than the crack damage area) and 20mm wide.

[0112] Step 2: After patch alignment, the maximum clearance between the patch and the part to be soldered in the actuator housing is 0.9mm.

[0113] The welding parameters for locating the patch and for segmented, symmetrical welding in step 3 are: welding current 32A, argon flow rate 11L / min, and argon flow rate for the bucket 9L / min; for segmented welding, each segment is 20mm long.

[0114] Example 4:

[0115] The only difference between this embodiment and Embodiment 1 is that:

[0116] Step 2: After patch alignment, the maximum clearance between the patch and the part to be soldered in the actuator housing is 1mm.

[0117] In step 3, when welding in sections, each section is 20mm long.

[0118] Comparative Example 1:

[0119] The only difference between this embodiment and Embodiment 1 is that:

[0120] In step 3, protective argon gas is introduced through the bucket only after the weld has completely cooled.

[0121] Post-weld inspection results: The weld showed severe oxidation (dark blue and golden purple), which did not meet the requirements for visual inspection.

[0122] Comparative Example 2:

[0123] The only difference between this embodiment and Embodiment 1 is that:

[0124] When ending the arc in step 3, the welding torch should be removed from the weld immediately without delay.

[0125] Post-weld inspection results: The weld showed severe oxidation (dark blue and golden purple), which did not meet the requirements for visual inspection.

[0126] Comparative Example 3:

[0127] The only difference between this embodiment and Embodiment 1 is that:

[0128] The welding parameters for positioning the patch and segmented, symmetrical welding in step 3 are: welding current 29A, argon flow rate of welding torch 9L / min, and argon flow rate of trailer bucket 7L / min.

[0129] Post-weld inspection results: The weld surface fusion was poor, and the weld showed severe oxidation (dark blue and golden purple), which did not meet the requirements for visual inspection.

[0130] Comparative Example 4:

[0131] The only difference between this embodiment and Embodiment 1 is that:

[0132] The welding parameters for locating the patch and for segmented, symmetrical welding in step 3 are: welding current 36A, argon flow rate 13L / min, and shielding argon flow rate 11L / min.

[0133] Post-weld inspection results: The weld has deformed and cracks have appeared, which does not meet the requirements.

[0134] The repair methods described in the above embodiments are applicable to the repair of circumferential cracks with only a single crack and a crack length of 50 mm or less, as well as crack defects with multiple cracks, where the length of a single crack is no greater than 10 mm, the crack spacing is no greater than 20 mm, and the length of the crack area is no greater than 50 mm. In practice, crack defects with multiple local cracks, where the length of a single crack is no greater than 10 mm, the crack spacing is no greater than 20 mm, and the length of the crack area is greater than 50 mm, or circumferential crack defects with only a single crack but a crack length greater than 50 mm, may also occur. When repairing these two types of cracks, fine adjustments need to be made to the above methods. Specifically, before patch repair, intermittent welding is performed on the crack using tungsten inert gas welding to prevent severe misalignment, substrate deformation, and crack propagation due to uneven stress at the crack. Then, staggered intermittent welding is performed between the patch and the substrate to prevent deformation due to excessively long welds and high heat input. Detailed descriptions are provided below using specific embodiments.

[0135] Example 5:

[0136] During repair, a crack measuring 70mm in length was found at the 6 o'clock position of the second roll weld seam of the actuator housing. The crack had been repaired twice at the original weld seam, and the base material showed dark blue oxidation, but no deformation was observed. This embodiment describes the repair of this crack defect, using a titanium alloy Ti230-δ0.7mm with the same material and thickness as the actuator housing base material, and rounding the sharp edges of the patch to R20mm. The specific repair method differs from Embodiment 1 above only in that:

[0137] The patch made in step 1 has a length of 90mm and a width of 30mm.

[0138] In step 3 of tungsten inert gas welding:

[0139] (1) Before applying the tack weld, perform intermittent welding on the crack, with each weld segment being 10-15mm long and the interval between adjacent segments being 20-25mm. Figure 7 As shown.

[0140] (2) When welding the patch, use staggered intermittent welding, with each weld segment being 15-20mm long and the interval between adjacent segments being 15-20mm, and the welds of opposite segments being staggered. Figure 8 , 9 As shown.

[0141] After the repair was completed, both visual inspection and non-destructive testing met the requirements.

[0142] Example 6:

[0143] This embodiment is for repairing crack defects in which there are multiple cracks in a local area, with each crack not exceeding 10 mm in length, the crack spacing not exceeding 20 mm, and the length of the crack area exceeding 50 mm. The specific method is the same as in Embodiment 5, and will not be repeated here.

[0144] As can be seen from the above embodiments and comparative examples, only by following the process parameters of this invention can the integrity of the substrate structure and the stability of the repair quality be guaranteed, based on the combination of patch repair method and argon arc welding technology.

Claims

1. A method for repairing surface cracks in a double-layer thin-walled titanium alloy part roll-welded seam, characterized in that, This material is used to repair cracks with a single crack length of 50 mm or less on the surface of the roll weld seam of a titanium alloy double-layer thin-walled component, or to repair crack areas with multiple cracks on the surface of the roll weld seam of a titanium alloy double-layer thin-walled component, where the length of each crack is no greater than 10 mm, the crack spacing is no greater than 20 mm, and the length of the crack area is 50 mm or less; it includes the following steps: Step 1: Create the patch Based on the length of the crack in the roll weld, the oxidation and deformation of the base material at the crack, a patch is made. The patch material and thickness are the same as the base material and can completely cover the damaged area. Step 2: Pre-welding treatment 2.1 Drill anti-crack holes at both ends of the crack; 2.2 Grind the weld seam crack to the level of the substrate, and grind the area to be welded and the area around the substrate until the metal luster is exposed. 2.3 The alignment patch is made to match the surface of the area to be soldered and the fitting gap is no more than 1mm; 2.4 Clean the area to be welded thoroughly; 2.5 Seal the interlayer of the roll weld seam, leaving only two holes for the inflow and outflow of protective gas, respectively; 2.6 Inert gas is introduced into the interlayer of the roll weld as a protective gas at a flow rate of 8-10 L / min; Step 3: Tungsten Inert Gas Welding First, perform multi-point tack welding on the patch, then weld the patch to the substrate using segmented, symmetrical welding. Each segment should be 15-20mm long. The welding process parameters for both tack welding and segmented, symmetrical welding are as follows: Welding current 30-35A, argon gas flow rate of welding torch 10-12L / min, power supply is DC positive polarity; During welding, before the weld has completely cooled, add a drag bucket and pass inert gas at a rate of 8-10 L / min to protect the weld and prevent oxidation of the titanium alloy. When ending the arc, delay for 1 to 2 minutes before stopping the gas, and then remove the welding torch after stopping the gas. Step 4: Visual inspection; Step 5: Polish off any excess material; Step 6: Non-destructive testing.

2. The method of claim 1, wherein: The patch mentioned in step 1 is a rectangular patch, with each side being 5-10 mm longer than the crack damage area, a patch width of 20-30 mm, and the four corners of the patch rounded to R16-20 mm.

3. The method of claim 1 or 2, wherein: In step 2.2, polish the area around the patch to be applied for at least 15mm until a metallic luster is exposed.

4. The method of claim 3, wherein: In step 3, when performing multi-point positioning welding of the patch, the positioning welding points should be symmetrically distributed, and the spacing between the positioning points should be 15-20mm.

5. The method of claim 1 or 2, wherein: The diameter of the anti-crack hole mentioned in step 2.1 is 1.6-2.0 mm.

6. The method of claim 1 or 2, wherein: The inert gas mentioned in steps 2 and 3 is argon.

7. A method for repairing surface cracks of a double-layer thin-walled titanium alloy part by roll welding, characterized in that, This material is used to repair cracks with a single crack length greater than 50 mm on the surface of the roll weld seam of a titanium alloy double-layer thin-walled component, or to repair crack areas on the surface of the roll weld seam of a titanium alloy double-layer thin-walled component where multiple cracks exist locally, with a single crack length not exceeding 10 mm, a crack spacing not exceeding 20 mm, and a crack area length greater than 50 mm; it includes the following steps: Step 1: Create the patch Based on the length of the crack in the roll weld, the oxidation and deformation of the base material at the crack, a patch is made. The patch material and thickness are the same as the base material and can completely cover the damaged area. Step 2: Pre-welding treatment 2.1 Drill anti-crack holes at both ends of the crack; 2.2 Grind the weld seam crack to the level of the substrate, and grind the area to be welded and the area around the substrate until the metal luster is exposed. 2.3 The alignment patch is made to match the surface of the area to be soldered and the fitting gap is no more than 1mm; 2.4 Clean the area to be welded thoroughly; 2.5 Seal the interlayer of the roll weld, leaving only two holes for the inflow and outflow of protective gas, respectively; 2.6 Inert gas is introduced into the interlayer of the roll weld as a protective gas at a flow rate of 8-10 L / min; Step 3: Tungsten Inert Gas Welding First, intermittent welding is performed on the original crack, with each segment welded 10-15mm and the interval between two adjacent segments 20-25mm; then, the patch is tack welded at multiple points, and then the patch is welded to the substrate using an intermittent welding method, with each segment welded 15-20mm in length and the interval between two adjacent segments 15-20mm, and the welds of opposite segments are staggered. The welding process parameters for intermittent welding of the original crack, tack welding of patches, and staggered intermittent welding are as follows: Welding current 30-35A, argon gas flow rate of welding torch 10-12L / min, power supply is DC positive polarity; During welding, before the weld has completely cooled, add a drag bucket and pass inert gas at a rate of 8-10 L / min to protect the weld and prevent oxidation of the titanium alloy. When ending the arc, delay for 1 to 2 minutes before stopping the gas, and then remove the welding torch after stopping the gas. Step 4: Visual inspection; Step 5: Polish off any excess material; Step 6: Non-destructive testing.

8. The method of claim 7, wherein: The patch mentioned in step 1 is a rectangular patch, with each side being 5-10 mm longer than the crack damage area, a patch width of 20-30 mm, and the four corners of the patch rounded to R16-20 mm.

9. The method of claim 7 or 8, wherein: In step 2.2, polish the area around the patch to be applied for at least 15mm until a metallic luster is exposed.

10. The method of claim 9, wherein: In step 3, when performing multi-point positioning welding of the patch, the positioning welding points should be symmetrically distributed, and the spacing between the positioning points should be 15-20mm.

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