Additive repair method for damage defect of stepped hole in part

Abstract

The invention provides an additive repairing method for a stepped hole damage defect on a part, which comprises the following steps of: firstly, removing the stepped hole defect, and preparing a matched filling material according to the size of the removed stepped hole; filling a filling material into the stepped hole, welding and positioning the filling material and the top surface of the base material by adopting laser welding, and ensuring that the filling material does not slide relative to the base material or fly out of the base material during friction stir welding of the static shaft shoulder; then, a static shoulder friction stir welding method is adopted, the filler is extruded, the filler and the base metal are reliably combined, control over welding heat input is achieved, the influence of welding heat on the base metal is reduced, and the problems of air holes, slag inclusion, coarse grains, hot cracks and the like which are prone to occurring in conventional fusion welding repair are solved. And the welding quality is high, and the maintenance cost of parts is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal parts repair, and specifically relates to an additive repair method for stepped hole damage defects on parts. Background Art

[0002] The mounting ears with circular stepped holes are used in many parts of aircraft, mainly for mounting heavy objects. Due to the wear, impact and thermal fatigue between parts during long-term use, cracks, wear and corrosion will occur around the aircraft mounting ears. If the damaged parts are not repaired in time or the aircraft mounting ears are not replaced, the aircraft mounting ears will inevitably break, causing the aircraft to malfunction and cause huge economic losses. Aircrafts themselves pursue lightweight and high-strength characteristics, so aircraft mounting ears are often made of high-strength aluminum alloys.

[0003] At present, arc melting surfacing and laser cladding are commonly used to repair defects in light-weight aluminum alloys and magnesium alloys. The Chinese invention patent application with publication number CN113649700A discloses a method for additive repair and remanufacturing of magnesium alloys. The method mainly uses laser-arc composite forming equipment to accurately repair the damage after mechanical grinding, and the damaged parts need to be stress-relieved annealed after repair. The additive technologies of arc welding and laser powder feeding are both methods of melting base materials and filler metals. Due to the large heat input and difficulty in controlling, the mechanical properties and organizational properties of the repaired parts are easily greatly reduced. Therefore, it is generally necessary to heat treat the repaired components. However, for complex and non-disassembled parts or dissimilar metal assembly parts, the heat treatment process will affect other materials, so the heat treatment process cannot be used to restore the performance of the workpiece. Although the laser-arc composite forming equipment in this invention patent can repair damage to the step surface of parts, for parts made of high-strength aluminum alloy, due to the large heat input, it will inevitably lead to defects such as element burning, coarse structure and pores in the material, and thus cannot meet the high-strength use requirements of the parts.

[0004] At present, in addition to the repair methods of melting welding, there are also solid-phase additive repair methods, such as stir friction additive manufacturing technology. The Chinese invention patent application with publication number CN105171229 discloses a stir friction additive manufacturing method for metal materials; the Chinese invention patent with publication number CN113927151 discloses a stir friction additive manufacturing method and equipment for thin-walled cylindrical structural reinforcement ribs. Both patents are based on the technical principle of "layer-by-layer" accumulation of additive manufacturing. The stir friction head stirs two layers of metal to connect them. After a certain number of layers are accumulated layer by layer, the relevant mechanical processing is performed as required to achieve the repair or manufacture of parts. Although this scheme utilizes the characteristics of stir friction welding solid-state connection, it can ensure that the material does not have defects such as element burnout, coarse structure, and pores, but because the interlayer edge area of ​​layer-by-layer accumulation is prone to unconnected defects, it is more suitable for additive manufacturing of large parts, but not suitable for defect repair of structural parts with small damage area, shallow depth, complex structure, and small repair impact area. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the existing fusion welding and solid phase additive repair methods will reduce the strength of parts and are not suitable for the damage repair of stepped holes of complex small parts with small and shallow damage areas, and to provide an additive repair method for stepped hole damage defects on parts. This method utilizes the concentrated energy of laser welding to produce a small heat affected area, and the static shoulder stir friction welding can effectively avoid the thinning effect of traditional stir friction welding, so as to achieve rapid and high-quality repair of local area cracks, holes, wear, corrosion and other defects that appear in the service process of round hole stepped components of lightweight metal parts such as aluminum alloys, significantly improve the service time of the components, and save production costs.

[0006] To achieve the above purpose, the technical solution provided by the present invention is:

[0007] A method for additively repairing a step hole damage defect on a part, wherein the damage defect is located on the inner wall of the large-diameter hole and the step surface of the step hole, and the method is special in that it comprises the following steps:

[0008] Step 1, remove the damage defects and remove the least amount of material while ensuring that the defects are completely removed; measure the size of the large diameter hole and the small diameter hole in the step hole after the damage defects are removed;

[0009] Step 2, preparing a first filler and a second filler respectively according to the sizes of the large-diameter hole and the small-diameter hole after the damage defect is removed, and the height of the first filler is greater than the height of the large-diameter hole;

[0010] Step 3, sequentially assembling the prepared second filling material and the first filling material into the stepped hole of the part;

[0011] Step 4, performing laser positioning welding between the first filler and the top surface of the part;

[0012] Step 5, performing static shoulder friction stir welding on the first filler, so that the first filler is completely bonded to the large diameter hole of the stepped hole;

[0013] Step 6, install the filled part on the lathe, process it according to the original design size of the stepped hole, and restore the stepped hole of the part.

[0014] Furthermore, in step 1, the part is fixed on a lathe and a turning tool is used to remove damage defects.

[0015] Furthermore, in step 4, the process of laser positioning welding between the first filler and the top surface of the part is as follows:

[0016] First, set multiple welding positioning points on the side wall of the first filler and close to the top surface of the part, then set the laser welding parameters, make the laser and the top surface of the part form an angle of 5°, and perform laser spot welding on the welding positioning points.

[0017] Furthermore, four welding positioning points are set, and an angle of 90° is formed between adjacent welding positioning points.

[0018] Furthermore, the process of performing static shoulder friction stir welding on the first filler in step 5 comprises the following steps:

[0019] Step 5.1, according to the size of the welding static shaft shoulder stirring head and the aperture of the large diameter hole, calculate the number of welds required for welding and the offset of the stirring needle of the static shaft shoulder stirring head between adjacent welds;

[0020] Step 5.2, installing the static shoulder stirring head on the friction stir welding machine, setting the working parameters of the static shoulder stirring head, the working parameters are: the static shoulder stirring head rotation speed is 1400r / min, the plunge speed is 2mm / min, the downward pressure is 0.2mm, and there is no inclination;

[0021] Step 5.3, place the stirring needle of the static shoulder stirring head at the first welding positioning point, start the friction stir welding machine, and when the downward pressure of the static shoulder stirring head reaches 0.2 mm, keep it for 3 seconds, then move the stirring needle at a speed of 300 mm / min, pass through other welding positioning points in turn, until it moves a circle, and completes the friction stir welding of the first weld;

[0022] Step 5.4, shifting the stirring needle of the static shoulder stirring head radially inward according to the offset amount calculated in step 5.1, entering the next weld pass, and always maintaining the welding working state during the offset process, and starting the friction stir welding from the starting position after the offset;

[0023] Step 5.5, following the process of step 5.4, complete the welding of all welds in sequence;

[0024] Step 5.6, move the stirring needle of the static shoulder stirring head from the end position of the last weld to the center position of the first filler material, so that the keyhole formed by the stirring needle welding is located at the center position of the part;

[0025] Step 5.7, lift the static shoulder stirring head upward until the stirring needle of the static shoulder stirring head is away from the surface of the first filler, and the friction welding is completed.

[0026] Furthermore, in step 5.1, the offset of the stirring needle of the static shoulder stirring head between adjacent welds is 1-1.5 times the diameter of the stirring needle.

[0027] Furthermore, in step 2, the height of the first filler is 0.2 mm higher than the height of the large-diameter hole.

[0028] Furthermore, in step 2, the material of the prepared first filler and the second filler is the same as the material of the part.

[0029] The advantages of the present invention are:

[0030] 1. During the welding repair of the method of the present invention, laser welding is first used to position the filler and the part base, and then the step hole is repaired by static shoulder friction stir welding. Laser positioning welding realizes reliable connection between the filler and the base material, ensuring that the filler does not slide relative to the base material or fly out during static shoulder friction stir welding in the later stage. At the same time, the heat affected area of ​​laser welding positioning is small, which maximizes the stability of the repair area organization; static shoulder friction stir welding has a small welding heat input, which realizes the welding and fixing of the filler and the base material, while reducing the influence of welding heat on the performance of the base material, ensuring the strength of the part, and overcoming the problems of pores, slag inclusions, coarse grains and thermal cracks that are prone to occur in conventional melting welding repairs; and because of the use of a static shoulder stirring head, the high-speed rotation of the stirring head and the shoulder during the static shoulder friction stir welding process will not cause the base material to be squeezed to produce flash, making the surface of the base material smooth, greatly improving the repair quality.

[0031] 2. The repair method of the present invention can realize additive welding repair of the same material or different materials. The repair process is simple and easy to operate. The filler and the matrix are metallurgically bonded. The interface after welding is complete and defect-free, ensuring the mechanical properties of the repaired parts during service, and having high reliability.

[0032] 3. The method of the present invention can achieve high-quality repair of defects such as cracks, holes, wear, corrosion, etc. that appear in the stepped holes of lightweight metal parts such as aluminum alloys and magnesium alloys during service, especially the defect repair of circular stepped holes. There is no need to perform heat treatment procedures to maintain the mechanical properties of the parts. The method of the present invention can restore the parent material performance to more than 70%, saving maintenance costs. The method of the present invention provides a new method for repairing the stepped surface of parts, avoiding the dilemma of having to scrap parts because they cannot be repaired due to defects.

[0033] 4. In the method of the present invention, the damage defect is removed first by removing the smallest material, and then the filling material is processed according to the size of the step hole after the defect is removed, so as to achieve the minimum damage repair of the base material at the defective part, thereby avoiding the situation where the affected area of ​​the base material is too large due to large-area damage repair, thereby causing the performance of the base material to be reduced.

[0034] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0036] Figure 1 It is a flowchart of the additive repair method of the present invention;

[0037] Figure 2 It is a schematic diagram of the damage defect location of a part with a stepped hole;

[0038] Figure 3 It is a schematic diagram of a half-section of the structure of the filler prepared according to the size of the step hole after removing defects;

[0039] Figure 4 It is a schematic diagram of the welding positioning points set during laser positioning welding, where A, B, C, and D are welding positioning points respectively;

[0040] Figure 5 This is a schematic diagram of the path of the stirring needle of the static shoulder stirring head during the static shoulder friction stir welding repair, where the red color is the weld track and the black arrow represents the welding direction;

[0041] Figure 6 It is a schematic diagram of static shoulder friction stir welding;

[0042] Figure 7 It is a schematic diagram of the structure of the parts after friction stir welding via the static shoulder;

[0043] Figure 8 It is a schematic diagram of the structure of a part that has been repaired after machining, and the size of the stepped hole has been restored to its original size.

[0044] Explanation of the reference numerals: 1-damage defect, 2-part, 3-first filler, 4-second filler, 5-stationary shoulder stirring head, 6-keyhole. DETAILED DESCRIPTION

[0045] Embodiments of the present invention are described in detail below. The embodiments are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0046] Reference Figure 1 , which is a schematic diagram of the damaged position of the aircraft mounting ear step hole to be repaired. Generally, the damage defect 1 of the aircraft mounting ear step hole is located on the inner wall of the large diameter hole and the step surface of the step hole. The following takes the repair of the aluminum alloy aircraft mounting ear step hole as an example to describe the specific process of the method of the present invention.

[0047] An additive repair method for a stepped hole damage defect on a part comprises the following steps:

[0048] Step 1: fix the aluminum alloy aircraft mounting ear to be repaired on a lathe, and use a turning tool to remove defects along the step surface of the step hole to be repaired.

[0049] The damage to the inner wall of a large diameter hole is usually the entire surface is worn or corroded. When a lathe is used for removal, the entire inner wall surface needs to be processed for defect removal. For the removal of corrosion and wear defects, it is necessary to ensure that the removed part can cover the entire position of the damage until the new metal surface of the original parent material appears. In addition, during processing, the minimum material is removed while ensuring that the defects are completely removed, and only the defects are processed to ensure that the shape of the trapezoidal hole remains unchanged.

[0050] In this embodiment, the dimensions of the stepped hole before removing the 2nd part are as follows: the height of the large diameter hole of the stepped hole is 2 mm, the diameter of the large diameter hole is 28 mm, the height of the small diameter hole of the stepped hole is 7.5 mm, and the diameter of the small diameter hole is 22 mm.

[0051] The dimensions of the step holes after removal are: the large diameter hole height of the step hole is 3mm, the large diameter hole diameter is 30mm, the small diameter hole height of the step hole is 6.5mm, and the small diameter hole diameter is 22mm.

[0052] Step 2, according to the size of the large diameter hole and the small diameter hole after the damage defect is removed, the first filler 3 and the second filler 4 are processed and prepared respectively. The first filler is used to fill and install in the large diameter hole, and the second filler is used to fill and install in the small diameter hole. In order to facilitate the static shoulder stir friction welding in the later stage, the first filler is effectively press-welded in the large diameter hole under the pressure of the stirring head, and the height of the first filler is greater than the height of the large diameter hole. In this embodiment, the height of the prepared first filler is 3.2mm, which is 0.2mm higher than the height of the large diameter hole after the damage defect is removed.

[0053] Since the aircraft ear material in this embodiment is 2A12-T6 aluminum alloy, the prepared filler is also made of 2A12-T6 aluminum alloy, and of course, a material close to the aircraft ear material can also be selected. In this embodiment, the prepared first filler has a height of 3.2 mm and a diameter of 30 mm, and the second filler has a height of 6.5 mm and a diameter of 22 mm.

[0054] Step 3: sequentially install the second filler and the first filler into the small diameter hole and the large diameter hole of the stepped hole, and the second filler and the first filler are in a tight fit relationship with the small diameter hole and the large diameter hole respectively. The second filler installed in the small diameter hole is used to support the first filler when the static shoulder stir friction welding is performed later to prevent the first filler from collapsing during welding.

[0055] Step 4: To prevent the first filler from sliding or flying out relative to the lug base during the subsequent static shoulder friction stir welding, the first filler is laser positioned and welded to the upper surface of the aircraft lug base:

[0056] First, set multiple welding positioning points on the side wall of the first filler and close to the top surface of the lug, then set the laser welding parameters, make the laser and the top surface of the part form a 5° angle, and perform laser spot welding on the welding positioning points. On the basis of ensuring reliable connection between the first filler and the lug base interface, the size of the formed welding positioning point should be as small as possible.

[0057] In this embodiment, four welding positioning points are set at the edge of the first filler, namely positioning point A, positioning point B, positioning point C and positioning point D, and the angle between adjacent positioning points is 90 degrees. The parameters of the laser welding equipment are: laser power 3kW, laser spot diameter 0.5mm, focal length 0mm, and an angle of 5° between the laser and the top surface of the part. The laser welding parameters can be adjusted according to the type and thickness of the filler material.

[0058] Step 5: Perform static shoulder friction stir welding on the first filler so that the first filler is completely bonded to the large diameter hole of the stepped hole. The specific process is:

[0059] Step 5.1, according to the size of the welding static shoulder stirring head 5 and the aperture of the large diameter hole, determine the number of welds required for welding and the offset of the stirring needle of the static shoulder stirring head between adjacent welds.

[0060] It is necessary to ensure that the subsequent weld bead overlaps the previous weld bead by 30%, so that the filler material and the part matrix can achieve metallurgical bonding under sufficient heat input during the friction stir welding process of the stirring head. The general offset is 1-1.5 times the diameter of the stirring needle. In this embodiment, the diameter of the stirring needle is 2mm, the number of welds is 4, and the offset is 3mm.

[0061] Step 5.2, installing the static shoulder stirring head on the friction stir welding machine, setting the working parameters of the static shoulder stirring head, the working parameters are: the static shoulder stirring head rotation speed is 1400r / min, the plunge speed is 2mm / min, the downward pressure is 0.2mm, and there is no inclination;

[0062] Step 5.3, place the stirring needle of the static shoulder stirring head at the welding positioning point A, start the friction stir welding machine, and when the downward pressure of the static shoulder stirring head reaches 0.2 mm, keep it for 3 seconds, and then move the stirring needle along the arc curve where the ABCD positioning point is located at a speed of 300 mm / min until it moves a circle, completing the friction stir welding of the first weld;

[0063] Step 5.4, shifting the stirring needle of the static shoulder stirring head radially inward according to the offset amount calculated in step 5.1, entering the next weld pass, and always maintaining the welding working state during the offset process, and starting the friction stir welding from the starting position after the offset;

[0064] Step 5.5, following the process of step 5.4, complete the welding of all welds in sequence;

[0065] Step 5.6, in order to prevent the keyhole 6 formed by the rotation of the stirring needle after the welding is completed from causing new defects, the stirring needle of the static shoulder stirring head is moved from the end position of the last weld to the center position of the first filler material, so that the keyhole formed by the stirring needle welding is located at the center position of the hanging ear, which is convenient for the later processing to remove the keyhole 6 and avoid new defects caused by the keyhole being located at the edge position;

[0066] Step 5.7, move the stirring head upward at a speed of 4 mm / min until the stirring needle of the static shoulder stirring head is away from the surface of the first filler, and the friction welding is completed.

[0067] Step 6: Fix the friction welded aircraft mounting lug on the lathe, use the lathe tool to process the stepped hole according to the size of the original stepped hole, and remove the excess filler. The repair of the aircraft mounting lug stepped hole is completed.

[0068] During welding, the repair method of the present invention first spot-welds the first filler to the part base through laser welding, ensuring reliable static shoulder stir friction welding in the later stage while maximizing the stability of the repair area structure; then static shoulder stir friction welding is used to weld the filler in the stepped hole to be repaired, and the advantages of static shoulder solid phase welding are used to control the welding heat input, reduce the influence of welding heat on the parent material, improve the welding quality, and ensure the strength of the repaired part.

[0069] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. An additive repair method for a stepped hole damage defect on a part, wherein the damage defect is located on the inner wall of the large diameter hole and the step surface of the stepped hole, characterized in that: The following steps are involved: Step 1, remove the damage defects and remove the least amount of material while ensuring that the defects are completely removed; measure the size of the large diameter hole and the small diameter hole in the step hole after the damage defects are removed; Step 2, preparing a first filler and a second filler respectively according to the sizes of the large-diameter hole and the small-diameter hole after the damage defect is removed, and the height of the first filler is greater than the height of the large-diameter hole; Step 3, sequentially assembling the prepared second filler and the first filler into the stepped hole of the part; Step 4, performing laser positioning welding between the first filler and the top surface of the part; Step 5, performing static shoulder friction stir welding on the first filler, so that the first filler is completely bonded to the large diameter hole of the stepped hole; Step 6, install the filled part on the lathe, process it according to the original design size of the stepped hole, and restore the stepped hole of the part.

2. According to claim 1, a method for additively repairing a step hole damage defect on a part is characterized in that: In step 1, the part is fixed on a lathe and a turning tool is used to remove damage defects.

3. According to claim 1, the additive repair method for step hole damage defects of a part is characterized in that: In step 4, the process of laser positioning welding between the first filler and the top surface of the part is as follows: First, set multiple welding positioning points on the side wall of the first filler and close to the top surface of the part, then set the laser welding parameters, make the laser and the top surface of the part form an angle of 5°, and perform laser spot welding on the welding positioning points.

4. According to claim 3, the additive repair method for step hole damage defects of a part is characterized in that: There are four welding positioning points set, and the angle between adjacent welding positioning points is 90°.

5. The additive repair method for step hole damage defects of a part according to claim 3, characterized in that: The process of performing static shoulder friction stir welding on the first filler in step 5 comprises the following steps: Step 5.1, according to the size of the welding static shoulder stirring head and the aperture of the large diameter hole, calculate the number of welds required for welding and the offset of the stirring needle of the static shoulder stirring head between adjacent welds; Step 5.2, installing the static shoulder stirring head on the friction stir welding machine, setting the working parameters of the static shoulder stirring head, the working parameters are: the static shoulder stirring head rotation speed is 1400r / min, the plunge speed is 2mm / min, the downward pressure is 0.2mm, and there is no inclination; Step 5.3, place the stirring needle of the static shoulder stirring head at the first welding positioning point, start the friction stir welding machine, and when the downward pressure of the static shoulder stirring head reaches 0.2 mm, keep it for 3 seconds, then move the stirring needle at a speed of 300 mm / min, pass through other welding positioning points in turn, until it moves a circle, and completes the friction stir welding of the first weld; Step 5.4, shifting the stirring needle of the static shoulder stirring head radially inward according to the offset amount calculated in step 5.1, entering the next weld pass, and always maintaining the welding working state during the offset process, and starting the friction stir welding from the starting position after the offset; Step 5.5, following the process of step 5.4, complete the welding of all welds in sequence; Step 5.6, move the stirring needle of the static shoulder stirring head from the end position of the last weld to the center position of the first filler material, so that the keyhole formed by the stirring needle welding is located at the center position of the part; Step 5.7, lift the static shoulder stirring head upward until the stirring needle of the static shoulder stirring head is away from the surface of the first filler, and the friction welding is completed.

6. The additive repair method for step hole damage defects of a part according to claim 5, characterized in that: In step 5.1, the offset of the stirring needle of the static shoulder stirring head between adjacent welds is 1-1.5 times the diameter of the stirring needle.

7. The additive repair method for step hole damage defects of a part according to claim 1, characterized in that: In the step 2, the height of the first filler is 0.2 mm higher than the height of the large-diameter hole.

8. The additive repair method for step hole damage defects of a part according to claim 1, characterized in that: In step 2, the material of the prepared first filler and the second filler is the same as the material of the part.

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