A 7 series aluminum alloy underwater friction stir welding method and auxiliary device

Abstract

The present invention discloses a method and auxiliary device for underwater friction stir welding of a 7-series aluminum alloy, relating to the field of underwater welding. The method comprises five steps: performing a zoned aging treatment on the aluminum alloy plate, maintaining the to-be-welded area in a solution quenched state, clamping and fixing the aluminum alloy plate, adding water and starting a heating device, performing underwater friction stir welding of the aluminum alloy plate, covering the plate, adjusting the water temperature to perform a high-temperature short-time pre-aging treatment on the weld, and adjusting the water temperature again to perform a low-temperature long-time aging treatment on the weld, thereby completing the underwater stir welding of the aluminum alloy plate and the heat treatment of the weld. The present invention realizes underwater friction stir welding of aluminum alloy equipment while performing post-weld heat treatment on the weld, obtaining a weld structure with fine grains and fine dispersed precipitates, and effectively improving the welding strength.

Description

Technical Field

[0001] The present invention relates to the field of underwater welding, and in particular to a method and an auxiliary device for underwater friction stir welding of a 7 series aluminum alloy. Background Art

[0002] Aluminum alloy has a large thermal conductivity and specific heat capacity. During welding, the heat energy generated will be quickly transferred to the matrix, causing the dissolution and growth of the precipitate phase near the weld of the 7 series aluminum alloy. The strength of the aluminum alloy in the area affected by the welding heat will be reduced, seriously affecting the performance of the component.

[0003] Although aging treatment or post-weld solution + aging treatment can enhance the welding strength of aluminum alloys, welding, as a connection process, is usually the last step in equipment manufacturing. It is difficult to perform post-weld heat treatment on the welds of aluminum alloy components or equipment separately during production.

[0004] Therefore, how to develop a 7 series aluminum alloy underwater friction stir welding method and auxiliary equipment to achieve underwater friction stir welding of aluminum alloy equipment while performing post-weld heat treatment on the weld to obtain a weld structure with fine grains and fine dispersed precipitates, and effectively improve welding strength, has become a technical problem that needs to be urgently solved by people in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a 7 series aluminum alloy underwater friction stir welding method and auxiliary device, which can realize underwater friction stir welding of aluminum alloy equipment while performing post-weld heat treatment on the weld to obtain a weld structure with fine grains and fine dispersed precipitates, thereby effectively improving the welding strength.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a 7 series aluminum alloy underwater friction stir welding method, comprising the following steps:

[0008] Step 1: Pre-treatment of the aluminum alloy plate: Use a segmented heating furnace to perform aging treatment on the aluminum alloy plate in different zones, so that the base material zone reaches the predetermined aging state and the area to be welded is in a solution quenching state;

[0009] Step 2: Clamp and fix the aluminum alloy plates. First, splice the ends of the two aluminum alloy plates to be welded together and place them on the pad. Fix the aluminum alloy plates with a stir friction welding fixture. Secondly, apply sealant to the connection positions of the water tank, baffle, and aluminum alloy plates to form a sealing strip to effectively improve the airtightness of the connection and prevent water seepage.

[0010] Step 3: Friction stir welding of aluminum alloy plates. First, water is poured into the water tank. When the water level covers the aluminum alloy plates by 10 to 50 mm, the water filling operation is stopped. Secondly, the heating device is turned on to heat the water in the water tank. At the same time, the water pump starts working to promote the circulation of water in the water tank. Thirdly, when the temperature measuring device detects that the water temperature reaches the set value, the PLC controller controls the heating device to stop heating and restarts heating when the water temperature drops. Finally, the underwater friction stir welding operation of the two aluminum alloy plates is performed through the stirring head.

[0011] Step 4: High-temperature pre-aging treatment: First, the cover plate is connected to the top of the water tank; second, the PLC controller controls the heating device to continue heating. After the water temperature reaches the set value, a short-term high-temperature pre-aging treatment operation is started on the welds of the two aluminum alloy plates;

[0012] Step 5, low-temperature aging treatment. After completing the high-temperature pre-aging treatment operation, the PLC controller controls the heating device to stop heating and sets the low-temperature aging temperature until the water temperature is lower than the preset temperature. After the water temperature reaches the preset temperature, the heating device starts intermittent heating to maintain the water temperature, and performs a long-term low-temperature aging treatment operation on the welds of the two aluminum alloy plates.

[0013] Preferably, the preset value of the water temperature in step three is 5°C to 50°C; the backward inclination angle of the stirring head is 1° to 3°, the feed speed is 50mm / min to 250mm / min, and the rotation speed is 500r / min to 2500r / min.

[0014] Preferably, the preset value of the water temperature in step 4 is 100° C., and the high-temperature aging treatment operation time is 0.5 h to 3 h.

[0015] Preferably, the preset value of the water temperature in step 5 is 40° C. to 80° C., and the low-temperature aging treatment operation time is 10 days to 60 days.

[0016] Preferably, a 7 series aluminum alloy underwater stir friction welding auxiliary device includes a water tank, a pad, a baffle, an aluminum alloy plate, a heating device and a stirring head, a plurality of the heating devices are distributed at the bottom of the water tank, the pad is horizontally arranged in the inner cavity of the water tank and divides the water tank into an upper and a lower area, a water inlet and a water outlet are respectively opened on the side wall of the water tank corresponding to the upper and lower areas, the water inlet and the water outlet are connected to the water pump through pipes, the baffle is connected to the top of the water tank, and cooperates with the water tank to form two size grooves, two aluminum alloy plates are spliced ​​together in the middle of the pad through the two size grooves, the stirring head is screwed in from the splicing position and performs underwater stir friction welding on the two spliced ​​aluminum alloy plates, and the heating device and water pump are electrically connected to the PLC controller.

[0017] Preferably, a temperature measuring device for measuring water temperature is installed on the inner wall of the water tank near the water inlet, and the temperature measuring device is electrically connected to the PLC controller.

[0018] Preferably, the height and width of the size groove formed by the baffle and the water groove match the height and width of the aluminum alloy plate.

[0019] Preferably, sealing strips for improving the sealing effect are provided at the connection position of the baffle and the water tank and around the size groove.

[0020] Preferably, the length of the pad is smaller than the length of the water tank, and the upper and lower areas are connected at one end away from the water inlet and the water outlet.

[0021] Preferably, a cover plate is provided above the water tank, and the cover plate is used to fit together with the top of the water tank and the baffle.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] 1) Through underwater friction stir welding and post-weld aging treatment, a weld structure with fine grains and fine dispersed precipitates is obtained, which reduces the impact of welding heat on the aluminum alloy and improves the strength of the weld;

[0024] 2) The setting of the pad realizes the division of the upper and lower partitions of the water tank cavity, and cooperates with the water inlet and outlet and the water pump to complete the rapid flow circulation of water, so as to achieve the rapid neutralization and unification of the water temperature in the water tank, and avoid the phenomenon of excessive water temperature in the local area near the heating device;

[0025] 3) By adjusting the size of the baffle, 7 series aluminum alloy plates of different sizes can be subjected to underwater friction stir welding and post-weld heat treatment;

[0026] 4) The present invention has a simple structure and is easy to operate. It can perform underwater friction stir welding on large aluminum alloy equipment and perform post-weld heat treatment on the welds, and is easy to industrialize.

[0027] In general, the present invention realizes underwater friction stir welding of aluminum alloy equipment while performing post-weld heat treatment on the weld to obtain a weld structure with fine grains and fine dispersed precipitates, thereby effectively improving the welding strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings.

[0029] Figure 1 This is a schematic diagram of the overall structure of a 7 series aluminum alloy underwater friction stir welding auxiliary device according to the present invention;

[0030] Figure 2 Schematic diagram of the partitioning of the aluminum alloy plate of the present invention;

[0031] Figure 3 This is a hardness distribution diagram of the aluminum alloy prepared in Example 1 of the present invention;

[0032] Figure 4 This is a hardness distribution diagram of the aluminum alloy prepared in Comparative Example 1 of the present invention;

[0033] Figure 5 This is the microstructure diagram of the aluminum alloy prepared in Example 1 of the present invention;

[0034] Figure 6 This is the microstructure diagram of the aluminum alloy prepared in Comparative Example 1.

[0035] Explanation of the accompanying symbols: 1. Water tank; 2. Pad; 3. Baffle; 4. Aluminum alloy plate; 41. Area to be welded; 42. Base material area; 5. Heating device; 6. Stirring head; 7. Water pump; 8. Water inlet; 9. Water outlet; 10. Size groove; 11. Temperature measuring device; 12. Sealing strip; 13. Cover plate; 14. Stir friction welding fixture. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] like Figure 1-6 As shown, a method for underwater friction stir welding of 7 series aluminum alloy includes the following steps:

[0038] Step 1: Pre-treat the aluminum alloy plate by using a segmented heating furnace to perform aging treatment on the aluminum alloy plate 4 so that the base material area 42 reaches a predetermined aging state and the area to be welded 41 is in a solution quenching state;

[0039] Step 2: Clamp and fix the aluminum alloy plates. First, splice the ends of the two aluminum alloy plates at the areas to be welded 41 together and place them on the backing plate 2. Fix the aluminum alloy plates 4 using a stir friction welding fixture 14. Secondly, apply sealant to the connection positions of the water tank 1, the baffle 3, and the aluminum alloy plates 4 to form a sealing strip 12, which effectively improves the airtightness of the connection and prevents water seepage.

[0040] Step 3: Friction stir welding of the aluminum alloy plates. First, water is poured into the water tank 1. When the water level covers the aluminum alloy plates by 10 to 50 mm, the water filling operation of the water tank is stopped. Secondly, the heating device 5 is turned on to heat the water in the water tank. At the same time, the water pump 7 starts working to promote the circulation of water in the water tank. Thirdly, when the temperature measuring device 11 detects that the water temperature reaches the set value, the PLC controller controls the heating device 5 to stop heating and starts heating again when the water temperature drops. Finally, the underwater friction stir welding operation of the two aluminum alloy plates 4 is performed by the stirring head 6.

[0041] Step 4: High-temperature pre-aging treatment. First, the cover plate 13 is covered and connected to the top of the water tank 1. Then, the PLC controller controls the heating device 5 to continue heating. After the water temperature reaches the set value, a short-term high-temperature pre-aging treatment operation is started on the welds of the two aluminum alloy plates.

[0042] Step 5, low-temperature aging treatment. After completing the high-temperature pre-aging treatment operation, the PLC controller controls the heating device 5 to stop heating and sets the low-temperature aging temperature. When the water temperature is lower than the preset temperature, the heating device 5 starts intermittent heating to maintain the water temperature, and performs a long-term low-temperature aging treatment operation on the welds of the two aluminum alloy plates.

[0043] Specifically, in step 1, the aluminum alloy plate 4 is divided into a to-be-welded area 41 and a base material area 42, and a segmented heating furnace is used to perform zone aging treatment on the to-be-welded area 41 and the base material area 42 of the aluminum alloy plate 4, so that the base material area 42 of the aluminum alloy plate 4 is in a predetermined aging state, and the to-be-welded area 41 is in a solution quenching state.

[0044] Specifically, the sum of the widths of the to-be-welded areas 41 of the two aluminum alloy plates 4 is equal to the width of the water tank 1 .

[0045] Specifically, the friction stir welding fixture 14 in this application is a prior art, that is, the corresponding structure for fixing the aluminum alloy plate 4 when the friction stir welding operation is performed by the stirring head 6, which will not be described in detail here.

[0046] Specifically, the preset value of the water temperature in step three is 5°C to 50°C; the backward inclination angle of the stirring head is 1° to 3°, the feed speed is 50mm / min to 250mm / min, and the rotation speed is 500r / min to 2500r / min.

[0047] Specifically, the preset value of the water temperature in step 4 is 100° C., and the high-temperature aging treatment operation time is 0.5 h to 3 h.

[0048] Specifically, the preset value of the water temperature in step 5 is 40° C. to 80° C., and the low-temperature aging treatment operation time is 10 days to 60 days.

[0049] Specifically, a 7-series aluminum alloy underwater friction stir welding auxiliary device includes a water tank 1, a pad 2, a baffle 3, an aluminum alloy plate 4, a heating device 5 and a stirring head 6. Multiple heating devices 5 are evenly distributed at the bottom of the water tank 1. The pad 2 is horizontally arranged in the inner cavity of the water tank 1 and divides the water tank 1 into an upper and a lower area. A water inlet 8 and a water outlet 9 are respectively opened on the side wall of the water tank 1 corresponding to the upper and lower areas. The water inlet 8 and the water outlet 9 are both connected to the water pump 7 through pipes. The baffle 3 is connected to the top of the water tank 1 and cooperates with the water tank 1 to form two size grooves 10. Two aluminum alloy plates 4 are spliced ​​together in the middle of the pad 2 through the two size grooves 10. The stirring head 6 is screwed in from the splicing position and performs underwater friction stir welding on the two spliced ​​aluminum alloy plates 4. The heating device 5 and the water pump 7 are both electrically connected to the PLC controller. Specifically, the heating device 5 can be a ring-shaped heating tube, a heating plate or other heating devices.

[0050] Specifically, a temperature measuring device 11 for measuring water temperature is installed on the inner wall of the water tank 1 near the water inlet 8. The temperature measuring device 11 is electrically connected to the PLC controller. Specifically, the temperature measuring device 11 can be a water temperature sensor.

[0051] Specifically, the height and width of the dimension groove 10 formed by the baffle 3 and the water groove 1 match the height and width of the aluminum alloy plate 4 .

[0052] Specifically, sealing strips 12 for improving the sealing effect are provided at the connection position between the baffle 3 and the water tank 1 and around the size groove 10 .

[0053] Specifically, the length of the pad 2 is shorter than the length of the water tank 1, and the upper and lower areas are connected at the end away from the water inlet 8 and the water outlet 9. Specifically, the water inlet 8, the water outlet 9 and the water pump 7 arranged on one side of the water tank 1 are used to accelerate the circulation of water in the upper and lower areas.

[0054] Specifically, a cover plate 13 is further provided above the water tank 1 , and the cover plate 13 is used to be fitted and connected with the top of the water tank 1 and the baffle 3 .

[0055] Example 1:

[0056] The 8 mm thick 7A52 aluminum alloy plate 4 was subjected to underwater friction stir welding according to the above steps 1 to 5:

[0057] 1) A sectional aging treatment is performed on the 7A52 aluminum alloy plate 4 using a segmented heating furnace, so that the base metal area 42 of the 7A52 aluminum alloy plate 4 is in a T6 state and the area to be welded 41 is in a solution quenched state. The total width of the area to be welded 41 of the two aluminum alloy plates 4 is 50 mm.

[0058] 2) Clamp and fix the 7A52 aluminum alloy plate 4, and apply sealant at the connection position of the water tank 1, the baffle 3, and the 7A52 aluminum alloy plate 4 to form a sealing strip 12, which effectively improves the air tightness of the connection and prevents water seepage;

[0059] 3) Underwater friction stir welding of two 7A52 aluminum alloy plates 4 was performed at a water temperature of 20° C., with a stirring head 6 having a rotation speed of 1500 rpm, a feed speed of 100 mm / min, and a stirring head inclination angle of 2°;

[0060] 4) After completing the welding operation of the 7A52 aluminum alloy plate 4, cover the cover plate 13 and perform a high-temperature pre-aging treatment operation on the weld at 100°C / 2h;

[0061] 5) Perform low-temperature aging treatment on the weld at 50℃ / 240h.

[0062] Comparative Example 1:

[0063] According to the existing technology, an 8 mm thick T6 state 7A52 aluminum alloy plate 4 is subjected to underwater friction stir welding operation.

[0064] The comparison results of Example 1 and Comparative Example 1 are as follows:

[0065] 1) Figure 3 is the aluminum alloy hardness distribution diagram at the weld and the base material area 42 in Example 1, Figure 4 For comparison of the aluminum alloy hardness distribution diagrams at the weld and the base material in Example 1, Figure 3 and Figure 4 It can be seen from the comparison that the hardness of the weld of the aluminum alloy plate in Example 1 is higher than that of the base material area;

[0066] 2) Figure 5 This is a microstructure photo of the aluminum alloy near the weld in Example 1. Figure 6 For the microstructure photo of the aluminum alloy near the weld in Example 1, Figure 5 and Figure 6 It can be seen from the comparison that the aluminum alloy in Example 1 is less affected by the welding heat input and the precipitated phase is relatively fine; while the heat-affected zone of the aluminum alloy in Comparative Example 1 is more affected by the welding heat input and the precipitated phase is larger;

[0067] 3) The mechanical properties of the weld were tested. The tensile strength of the aluminum alloy weld in Example 1 was 412 MPa, while the tensile strength of the aluminum alloy weld in Example 1 was 475 MPa. The welding strength was greatly improved compared with the ordinary underwater friction stir welding.

[0068] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0069] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A 7 series aluminum alloy underwater friction stir welding auxiliary device, characterized by: The invention comprises a water tank (1), a pad (2), a baffle (3), an aluminum alloy plate (4), a heating device (5) and a stirring head (6), wherein a plurality of the heating devices (5) are uniformly distributed at the bottom of the water tank (1), the pad (2) is horizontally arranged in the inner cavity of the water tank (1) and divides the water tank (1) into an upper area and a lower area, and a water inlet (8) and a water outlet (9) are respectively opened on the side wall of the water tank (1) corresponding to the upper area and the lower area, and the water inlet (8) and the water outlet (9) are both connected by a The pipeline is connected to the water pump (7), the baffle (3) is connected to the top of the water tank (1), and cooperates with the water tank (1) to form two size grooves (10), the two aluminum alloy plates (4) are respectively spliced ​​together at the middle of the backing plate (2) through the two size grooves (10), the stirring head (6) is screwed into the splicing position and performs underwater stir friction welding on the two spliced ​​aluminum alloy plates (4), and the heating device (5) and the water pump (7) are both electrically connected to the PLC controller; A temperature measuring device (11) for measuring water temperature is installed at a position near the water inlet (8) on the inner wall of the water tank (1), and the temperature measuring device (11) is electrically connected to the PLC controller; Sealing strips (12) are provided at the connection position between the baffle (3) and the water tank (1) and around the size groove (10) for improving the sealing effect; A cover plate (13) is also provided above the water tank (1), and the cover plate (13) is used to be fitted and connected with the top of the water tank (1) and the baffle (3).

2. The 7 series aluminum alloy underwater friction stir welding auxiliary device according to claim 1, characterized in that: The height and width of the dimension groove (10) formed by the cooperation of the baffle (3) and the water groove (1) match the height and width of the aluminum alloy plate (4).

3. The underwater friction stir welding auxiliary device for 7 series aluminum alloy according to claim 2, characterized in that: The length of the pad (2) is smaller than the length of the water tank (1), and the upper and lower areas are connected at an end away from the water inlet (8) and the water outlet (9).

4. A method for underwater friction stir welding of 7 series aluminum alloys, characterized by: An underwater friction stir welding auxiliary device for 7 series aluminum alloy according to any one of claims 1 to 3 comprises the following steps: Step 1: Pre-treatment of the aluminum alloy plate: Use a segmented heating furnace to perform aging treatment on the aluminum alloy plate in different zones, so that the base material zone reaches the predetermined aging state and the area to be welded is in a solution quenching state; Step 2: Clamp and fix the aluminum alloy plates. First, splice the ends of the two aluminum alloy plates to be welded together and place them on the pad. Fix the aluminum alloy plates with a stir friction welding fixture. Secondly, apply sealant to the connection positions of the water tank, baffle, and aluminum alloy plates to form a sealing strip to effectively improve the airtightness of the connection and prevent water seepage. Step 3: Friction stir welding of aluminum alloy plates. First, water is poured into the water tank. When the water level covers the aluminum alloy plates by 10 to 50 mm, the water filling operation is stopped. Secondly, the heating device is turned on to heat the water in the water tank. At the same time, the water pump starts working to promote the circulation of water in the water tank. Thirdly, when the temperature measuring device detects that the water temperature reaches the set value, the PLC controller controls the heating device to stop heating and restarts heating when the water temperature drops. Finally, the underwater friction stir welding operation of the two aluminum alloy plates is performed through the stirring head. Step 4: High-temperature pre-aging treatment: First, the cover plate is connected to the top of the water tank; second, the PLC controller controls the heating device to continue heating. After the water temperature reaches the set value, a short-term high-temperature pre-aging treatment operation is started on the welds of the two aluminum alloy plates; Step 5, low-temperature aging treatment. After completing the high-temperature pre-aging treatment operation, the PLC controller controls the heating device to stop heating and sets the low-temperature aging temperature. When the water temperature is lower than the preset temperature, the heating device starts intermittent heating to maintain the water temperature, and performs a long-term low-temperature aging treatment operation on the welds of the two aluminum alloy plates.

5. The underwater friction stir welding method for 7 series aluminum alloy according to claim 4, characterized in that: The preset value of the water temperature in step three is 5°C to 50°C; the backward inclination angle of the stirring head is 1° to 3°, the feed speed is 50mm / min to 250mm / min, and the rotation speed is 500r / min to 2500r / min.

6. The underwater friction stir welding method for 7 series aluminum alloy according to claim 4, characterized in that: The preset value of the water temperature in step 4 is 100° C., and the high-temperature aging treatment operation time is 0.5 h to 3 h.

7. The underwater friction stir welding method for 7 series aluminum alloy according to claim 4, characterized in that: The preset value of the water temperature in step 5 is 40° C. to 80° C., and the low-temperature aging treatment operation time is 10 days to 60 days.

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