Method for reducing air holes through repair welding of internal defects of thin-wall aluminum alloy casting

Abstract

The invention discloses a method for reducing pores by repair welding of internal defects of a thin-wall aluminum alloy casting. The method comprises the following steps: confirming and marking X-ray positions of the internal defects of the aluminum alloy casting; internal defects at the marked position are cleaned, the defects are required to be completely eliminated, and the cleaning position is smooth and has a certain groove angle; cleaning oil stains and oxidation films at the repair welding position of the casting; preheating the whole casting; welding a reverse support and adding a blowing protection tool; manual argon arc welding filling surfacing is carried out, arc surfacing is carried out from the periphery to the center, and excess weld metal is reserved; removing redundant weld joint materials of surfacing bulges of the casting; x-ray detection is conducted on the repaired casting, whether the pore defects generated after surfacing repair can meet related requirements or not is emphatically confirmed, and if pores gathered on the surface layer of a weld joint exist, the pores can be discharged through a hot pressing method. According to the method, through hole internal defect cleaning, reverse supporting, blowing protection increasing and arc drawing surfacing methods are adopted for conducting surfacing repairing on the internal defects of the casting, the quality of aluminum alloy casting products is guaranteed, and the rejection rate and the production cost are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy welding, and specifically relates to a method for repairing internal defects of thin-walled (2 mm ≤ wall thickness ≤ 8 mm) aluminum alloy castings by repair welding and protecting to reduce porosity defects. Background Art

[0002] With the increasing complexity of products, the number of aluminum alloy casting products has been increasing year by year, and the quality requirements for castings are getting higher and higher. Due to the fact that the surface of the casting itself is prone to defects such as pits, holes, and pinholes, while the interior is prone to defects such as porosity, gas holes, and sand inclusions, the aluminum alloy casting products after casting often cannot meet the quality requirements of customers. At the same time, problems such as an increase in the scrap rate, production cost, and production cycle also occur.

[0003] Currently, in the industry, repair welding is usually carried out by manual argon arc welding with wire filling. Since the aluminum alloy castings themselves have many defects, new gas holes and inclusion defects will be generated after repair welding, resulting in the inability to meet the quality requirements of the products even after multiple repairs. The problem of repair welding of aluminum alloy castings has always been a pain point for improving the quality delivery of casting products.

[0004] The applicant found in practice that the main source of gas holes in the repair welding of thin-walled perforated aluminum alloy castings is from the ambient air, and the situation of gas entering the weld pool is often ignored, resulting in the internal quality inspection of structural parts with high defect requirements not meeting the corresponding requirements. Summary of the Invention

[0005] The present invention aims to provide a method for reducing gas holes in the repair welding of internal defects of thin-walled aluminum alloy castings, and controlling the gas in the external environment from entering the weld of the repaired aluminum alloy casting to form defective gas holes. Specifically, the present invention is a repair method that mainly relies on the combination of a reverse blowing protection tooling and the arc surfacing and repair welding operation techniques, to ensure that the internal gas hole defects of the repaired aluminum alloy casting meet the relevant standard requirements, improve the quality of casting products, and the repair method is fast and effective for thin-walled aluminum alloy castings.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for reducing gas holes in the repair welding of internal defects of thin-walled aluminum alloy castings, where 2 mm ≤ the thickness of the aluminum alloy casting ≤ 8 mm, and the method includes the following steps:

[0008] Step 1: Determine the accurate position of the internal defects of the casting product;

[0009] Step 2: Machine a through hole at the position containing the internal defect, the through hole penetrates at least two surfaces of the casting product and makes the internal defect completely contained in the through hole, the inner wall surface of the through hole is smooth and forms a groove structure, and a root face is reserved at the end of the groove;

[0010] Step 3: Remove the surface oil stain and oxide film on the inner wall of the through-hole, preheat the casting product as a whole, and remove the surface oil stain and oxide film on the welding wire.

[0011] Step 4: Set up a casting product support tooling and a blowing protection tooling on one side of the casting product corresponding to the inner wall of the through-hole with a root face reserved.

[0012] Step 5: Use manual argon arc welding to perform filling surfacing on the smooth groove surface of the inner wall of the through-hole. During the surfacing process, draw an arc from the side of the smooth groove surface near the edge of the through-hole to the side of the smooth groove surface near the center of the through-hole until the through-hole is completely filled, and leave a weld reinforcement on the side with the root face.

[0013] Step 6: Remove the excess surfacing raised weld material on the surface of the casting product.

[0014] Furthermore, before the said Step 1, it also includes:

[0015] Design the support and blowing protection tooling used in Step 4 according to the structure and shape characteristics of the casting product.

[0016] Furthermore, in the said Step 1, use X-ray inspection to mark the accurate positions of the internal defects of the casting product.

[0017] Furthermore, in the said Step 2, use a combined method of drilling first and then milling to machine the through-hole.

[0018] Furthermore, in the said Step 2, the angle of the groove is 50° - 70°, the length of the root face is not more than 2 mm, and the aperture of the through-hole is greater than or equal to 10 mm.

[0019] Furthermore, in the said Step 3, use chemical pickling to remove the surface oil stain and oxide film on the inner wall of the through-hole and the welding wire.

[0020] Furthermore, in the said Step 4, there is a gap between the support and blowing protection tooling and the surface of the casting product at the through-hole, which is used to form the weld reinforcement.

[0021] Furthermore, in the said Step 5, when performing filling surfacing by manual argon arc welding, wait for 2 - 3 s after the casting product in the through-hole melts to form a molten pool before filling the wire. The wire filling angle is 70° - 90°, and the weld reinforcement left is not less than 3 mm.

[0022] Furthermore, in the said Step 5, when performing filling surfacing by manual argon arc welding, the welding torch moves clockwise along the circumferential direction of the through-hole.

[0023] Furthermore, after the said Step 6, it also includes performing porosity defect detection. If the porosity does not meet the requirements and accumulates on the surface layer of the surfacing weld, it is discharged by hot pressing.

[0024] Furthermore, according to the casting product status and deformation conditions, decide whether to perform heat treatment (such as sandblasting + aging).

[0025] Compared with the prior art, the method for repairing welding of internal defects of thin-walled aluminum alloy castings of the present invention has the following characteristics: 1. The first-pass qualification rate of repairing welding is greatly improved;

[0026] 2. The repairing welding method is effective and efficient, with a short preparation cycle, good economy, and strong applicability;

[0027] 3. Through practical feedback, the improvement effect of repairing welding for thin-walled aluminum alloy castings is very obvious, and the repairing quality and qualification rate of casting products have been greatly improved. Description of the Drawings

[0028] Figure 1 and Figure 2 are schematic diagrams of the support blowing protection tooling on the reverse side of the casting product;

[0029] Figure 3 is a schematic diagram of the principle for controlling the gas in the external environment to enter the weld of the repaired aluminum alloy casting;

[0030] Figure 4 are the groove and root face structure features at the through-hole, as well as schematic diagrams of the welding torch angle and wire filling angle;

[0031] Figure 5 is a schematic diagram of the circular arc surfacing technique;

[0032] In the figures: 1 - side plate of the protection tooling, 2 - gas shunt plate, 3 - air outlet hole, 4 - air inlet joint, 5 - air inlet rubber hose, 6 - gas shunt screen, 7 - argon, 8 - welding torch, 9 - casting product, 10 - support blowing protection tooling, 11 - movement direction of the welding torch, 12 - welding wire, 13 - perforation, 14 - molten pool. Detailed Embodiments

[0033] The present invention will be further described below in conjunction with the drawings and specific embodiments. However, it should not be understood that the scope of the subject matter of the present invention is limited to the following embodiments. Without departing from the above technical idea of the present invention, all modifications, substitutions, and changes made according to ordinary technical knowledge and customary means in the art are included in the scope of the present invention.

[0034] In this embodiment, the thin-walled aluminum alloy casting product 9 to be repaired is flat as a whole. According to the structure of the casting product 9 and the spatial characteristics of the reverse side of the repair welding, the designs are as shown in Figure 1 and Figure 2The reverse support gas blowing protection tooling 10 shown. This support gas blowing protection tooling 10 simultaneously has the functions of reverse support for welding of the casting product 9 and gas blowing to protect the weld seam. The support gas blowing protection tooling 10 mainly consists of a protection tooling side plate 1, a gas shunt plate 2, air holes 3, an air inlet joint 4, and an air inlet rubber hose 5. Four protection tooling side plates 1 are sequentially connected end to end to form a circumferential closed structure of the support gas blowing protection tooling 10. At the upper end face of the formed circumferential closed structure, a gas shunt plate 2 is installed, and air holes 3 are opened on the gas shunt plate 2. At the lower end face of the formed circumferential closed structure, a bottom plate is installed. The bottom plate and the circumferential closed structure form an air flow collecting cavity. A gas shunt screen 6 is installed in the air flow collecting cavity. An air inlet joint 4 is installed on the bottom plate, and the air inlet joint 4 is connected to the argon gas 7 gas source through the air inlet rubber hose 5.

[0035] In the present invention, first, through holes are opened at the positions of the thin-walled aluminum alloy casting product 9 containing internal defects to remove the internal defects, and then manual argon arc welding is used for filling and surfacing according to the size of the repair area of the internal defects on the thin-walled aluminum alloy casting product 9. The key point is to control the wire filling time and the wire filling angle. As Figure 4 and Figure 5 shown, when filling the wire, an arc surfacing is performed by drawing an arc from the four perimeters of the through hole ( Figure 5 the outer edge of the through hole in ) to the center (that is, the starting point of the arc trajectory is at the outer edge of the through hole, and the end point of the arc is at one side edge of the center of the through hole). Finally, a weld seam reinforcement is left on the reverse side of the casting product 9, and then the excess weld seam material on the surface of the thin-walled aluminum alloy casting product 9 is removed.

[0036] In the present invention, the method for reducing pores in the repair welding of internal defects of the aluminum alloy casting product 9 includes the following steps: 1. Design and process a support gas blowing protection tooling 10 for the reverse side of the casting product 9 according to the structure of the casting product 9 and the characteristics of the reverse side space for repair welding;

[0037] 2. Confirm and exclude internal defects: Use X-ray to detect the positions of internal defects and confirm and mark them. Use drilling and milling in combination to clean and exclude the internal defects at the marked positions. It is required that the defects are completely excluded and the cleaned positions are smooth with a certain bevel angle (that is, a perforation 13 is made, and the perforation 13 includes a bevel and a root face), and then use X-ray to confirm again whether the internal defects are excluded;

[0038] 3. Use chemical pickling to remove the oil stains and oxide films on the surfaces of the casting product 9 and the welding wire 12, and preheat the casting product 9 as a whole;

[0039] 4. Install the support gas blowing protection tooling 10 for the reverse side of welding at the repair welding position of the casting product 9;

[0040] 5. Use manual argon arc welding for filling and surfacing. The key point is to control the wire filling time and the wire filling angle. Perform an arc surfacing by drawing an arc from the four perimeters of the perforation 13 to the center, and leave a weld seam reinforcement;

[0041] 6. Remove the redundant weld material of the surfacing bulge on the surface of the cast product 9; conduct X-ray inspection on the repaired cast product 9, and focus on confirming whether the porosity defects generated after surfacing repair can meet the relevant requirements. For the pores aggregated on the weld surface layer, they can be discharged by hot pressing method. Decide whether to perform heat treatment (blasting + aging) according to the repaired state and deformation condition of the cast product 9.

[0042] Taking the repair by welding of a thin-walled structure cast with the cast grade of F357.0 as an example, the specific process is as follows:

[0043] In the first step, according to the flat structure characteristics of the cast product 9 and the characteristic that the space on the reverse side of the repair welding is a plane, a support blowing protection tooling 10 for the reverse side of the cast product 9 as shown in Figure 1 and Figure 2 is designed and processed. The material of the support blowing protection tooling 10 is recommended to be stainless steel;

[0044] In the second step, defect confirmation and elimination: Through the X-ray position confirmation mark, use a combination of drilling and milling (drill through holes first, and then mill the groove and root face) to clean and eliminate the internal defects at the marked position. It is required that the defects are completely eliminated and the cleaned position is smooth with a certain groove angle (as shown in Figure 4 , punch through hole 13, the diameter of the punch through hole 13 ≥ 10 mm, the groove angle is 50° - 70°, and the root face is reserved 0 - 2 mm. In special cases, the root face can be not reserved), and use X-ray to confirm again whether the internal defects are eliminated;

[0045] In the third step, use chemical pickling to remove the oil stains and oxide films on the surface of the cast product 9 and the welding wire 12; and preheat the cast product 9 as a whole, and control the time within 1 - 2 hours. Complete the subsequent repair welding operation within 4 hours after pickling;

[0046] In the fourth step, wear clean gloves to add the welding reverse side support blowing protection tooling 10 at the repair welding position, and reserve a gap of 3 - 4 mm for forming the weld reinforcement at the punch through hole 13 on the reverse side of the cast product 9. Here, the 3 - 4 mm gap refers to the distance from the gas diverter plate 2 to the reverse side of the cast product 9, corresponding to the upper end surface of the gas diverter plate 2 in Figure 1 and Figure 2 needs to be offset downward by a certain distance from the upper end of the protection tooling side plate 1. During surfacing, the upper end surface of the protection tooling side plate 1 can be closely attached to the reverse side surface of the cast product 9, so as to isolate the root face side of the punch through hole 13 from the outside air;

[0047] In the fifth step, use manual argon arc welding for filling and surfacing, and key control the wire filling time and wire filling angle. After the aluminum alloy (i.e., the cast product 9) at the punch through hole 13 melts to form a molten pool 14, stay for 2 - 3 s, and then fill the wire. The wire filling angle is 70° - 90°. Pay attention to observing the defects, and according to Figure 5The welding torch 8 is moved clockwise in the welding torch movement direction 11 in []. At each position of the clockwise movement, an arc surfacing is drawn from the periphery to the center, leaving a weld reinforcement of not less than 3 mm.

[0048] In the sixth step, the excess weld material of the surfacing protrusion of the casting product 9 is removed. The repaired casting product 9 is subjected to X-ray inspection; it is mainly confirmed whether the porosity defects generated after the surfacing repair can meet the relevant requirements. If the pores gathered on the surface layer of the weld can be discharged by the hot pressing method.

[0049] Repair is carried out according to the above method, and the first-pass qualification rate of the repair welding of the thin-walled aluminum alloy casting is increased from the original 10% to 80%.

[0050] As described above, it is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for reducing pores in repair welding of internal defects of thin-walled aluminum alloy castings, characterized in that, 2 mm ≤ thickness of aluminum alloy casting ≤ 8 mm, and the method includes the following steps: Step 1: Determine the exact position of internal defects in the casting product (9); Step 2: Machine a through-hole at the position containing the internal defect. The through-hole penetrates at least two surfaces of the casting product (9) and completely encloses the internal defect within the through-hole. The inner wall surface of the through-hole is smooth and forms a bevel structure, and a root face is reserved at the end of the bevel; Step 3: Remove the surface oil stain and oxide film on the inner wall of the through-hole, preheat the casting product (9) as a whole, and remove the surface oil stain and oxide film on the welding wire; Step 4: Set up the support blowing protection tooling (10) of the casting product (9) on the side of the casting product (9) corresponding to the root face reserved on the inner wall of the through-hole; Step 5: Use manual argon arc welding to perform filling surfacing on the smooth bevel surface of the inner wall of the through-hole. During the surfacing process, draw an arc from the side of the smooth bevel surface at the edge of the through-hole towards the side of the smooth bevel surface at the center of the through-hole until the through-hole is completely filled, and a weld reinforcement is left on the root face side; Step 6: Remove the excess surfacing raised weld material on the surface of the casting product (9).

2. A method for reducing porosity in the repair welding of internal defects of thin-walled aluminum alloy castings according to claim 1, characterized in that, Before the said Step 1, it further includes: Design the support blowing protection tooling (10) used in Step 4 according to the structure and shape characteristics of the casting product (9).

3. A method for reducing pores in the repair welding of internal defects of thin-walled aluminum alloy castings according to claim 1, characterized in that: In the said Step 1, use X-ray inspection to mark the exact position of internal defects in the casting product (9).

4. A method for reducing pores in the repair welding of internal defects of a thin-walled aluminum alloy casting according to claim 1, characterized in that: In the said Step 2, use a combination of drilling and milling to machine the through-hole.

5. A method for reducing pores in the repair welding of internal defects of thin-walled aluminum alloy castings according to claim 1, characterized in that: In the said Step 2, the angle of the bevel is 50° - 70°, the length of the root face is not greater than 2 mm, and the diameter of the through-hole is greater than or equal to 10 mm.

6. A method for reducing pores in the repair welding of internal defects of thin-walled aluminum alloy castings according to claim 1, characterized in that: In the said Step 3, use chemical pickling to remove the surface oil stain and oxide film on the inner wall of the through-hole and the welding wire.

7. A method for reducing porosity in the repair welding of internal defects of thin-walled aluminum alloy castings according to claim 1, characterized in that: In the said Step 4, there is a gap between the support blowing protection tooling (10) and the surface of the casting product (9) at the through-hole for forming the weld reinforcement.

8. A method for reducing pores in the repair welding of internal defects of thin-walled aluminum alloy castings according to claim 1, characterized in that: In the said Step 5, when performing manual argon arc welding filling surfacing, wait for 2 - 3 s after the casting product (9) in the through-hole melts to form a molten pool (14) and then fill the wire. The wire filling angle is 70° - 90°, and the weld reinforcement left is not less than 3 mm.

9. A method for reducing pores in repair welding of internal defects of thin-walled aluminum alloy castings according to claim 1, characterized in that: In the said Step 5, when performing manual argon arc welding filling surfacing, the welding torch (8) moves clockwise along the circumferential direction of the through-hole.

10. A method for reducing porosity in the repair welding of internal defects of thin-walled aluminum alloy castings according to claim 1, characterized in that: After the said Step 6, it further includes performing porosity defect detection. If the porosity does not meet the requirements and accumulates on the surface layer of the surfacing weld, it is discharged by hot pressing method.

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