A friction stir welding method for internal water-cooled bars suitable for solid-phase additive manufacturing

Abstract

The present invention relates to the field of friction stir welding, and in particular to a method for friction stir welding of rods with internal water cooling, which is suitable for solid-phase additive manufacturing. The method comprises the following steps: S1, installing a water cooling system inside a welding tool; S2, starting the welding tool and the water cooling system to ensure that the feeding speed v of the welding tool is constant. 送 The feed rate v of the additive 进 The present invention reduces the peak temperature of the welding tool outlet during the solid-phase additive manufacturing process, reduces the weakening effect of heat accumulation on the material, and prevents excessive heat accumulation from causing excessive residual stress.

Description

Technical Field

[0001] The present invention relates to the field of friction stir welding, in particular to an internal water-cooled rod friction stir welding method suitable for solid-phase additive manufacturing. Background Art

[0002] Friction stir welding is a solid-phase joining technology that uses the heat generated by friction between a high-speed rotating welding tool and the workpiece to partially melt the material being welded. As the welding tool moves forward along the weld interface, the plasticized material flows from the front to the back of the tool under the influence of the tool's rotational friction, forming a dense solid-phase weld under the pressure of the tool. Existing friction stir welding tools, such as those described in patent number "CN116408532B," utilize a spindle system to achieve friction addition and friction stir welding. The spindle system's spindle head provides torque to the parent material, which is pressed downward while rotating to complete the addition process.

[0003] During the solid-phase friction stir additive manufacturing process, existing friction stir welding tools experience a continuous increase in heat input due to the accumulation of castings in the upper layer of material. Simultaneously, the temperature of the lower layer of material is difficult to quickly reduce. Prolonged high temperatures can cause the state of the lower layer of material to change during the additive process, such as increasing grain size, stress, and deformation, leading to a decrease in the performance of the additive part. Furthermore, during the additive process, the mold constantly generates heat from friction with the material, and this heat is also accumulated in the newly input part, causing the peak temperature during the solid-phase additive process to exceed the set value. Due to the accumulated heat, the performance of the newly input part will directly decrease, further affecting the material forming parameters during the additive process. This urgent issue needs to be addressed. Summary of the Invention

[0004] To avoid and overcome the technical problems existing in the prior art, the present invention provides a method for internally water-cooled friction stir welding of rods suitable for solid-phase additive manufacturing. This method reduces the peak temperature at the welding tool outlet during the solid-phase additive manufacturing process, mitigates the weakening effect of heat accumulation on the material, and prevents excessive residual stress caused by excessive heat accumulation.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A friction stir welding method for internally water-cooled bars suitable for solid-phase additive manufacturing comprises the following steps:

[0007] S1. Install a water cooling system inside the welding tool;

[0008] S2, start the welding tool and water cooling system to ensure the feeding speed of the welding tool v 送 The feed rate v of the additive 进 The following relationship is satisfied:

[0009]

[0010] Where a represents the side length of the square rod of the welding tool;

[0011] t represents the additive time;

[0012] R represents the radius of the working end of the stirring head.

[0013] As a further solution of the present invention: the output pressure of the rod during the additive process is not less than 3500N; at the end of each additive stage, the stirring head needs to stay in place for 2 to 15 seconds.

[0014] As a further solution of the present invention: the welding tool includes a shell with an installation channel opened in the axial direction for the core shaft to be installed, and a cooling channel is opened in the shell and is spirally arranged and coaxially arranged around the installation channel, and the two ends of the cooling channel are respectively connected to the liquid inlet joint and the liquid outlet joint; the stirring head is coaxially fixed on the core shaft, and at least one set of bearings is installed in the shell, and is coaxially rotatably matched with the core shaft through the bearings; a sealing structure is provided between the cooling channel and the bearings.

[0015] As a further solution of the present invention: the top and bottom of the shell are respectively provided with an upper mounting cavity and a lower mounting cavity arranged coaxially with the core shaft, and the upper mounting cavity and the lower mounting cavity are respectively installed with an upper bearing and a lower bearing. After the upper bearing and the lower bearing cooperate, the core shaft is supported and positioned at two points.

[0016] As a further solution of the present invention: an upper positioning groove is coaxially opened in the upper mounting cavity, and the diameter of the upper positioning groove corresponds to the diameter of the upper bearing; the outer ring of the upper bearing abuts and fits with the upper positioning groove from top to bottom, and a positioning ring is coaxially convexly provided on the outer ring of the core shaft, and the positioning ring of the core shaft abuts and fits with the inner ring of the upper bearing from top to bottom.

[0017] As a further solution of the present invention: a lower positioning groove is coaxially opened in the lower mounting cavity, and the diameter of the lower positioning groove corresponds to the diameter of the lower bearing; the outer ring of the lower bearing abuts and fits with the lower positioning groove from bottom to top, and the shoulder of the core shaft abuts and fits with the inner ring of the lower bearing from bottom to top.

[0018] As a further solution of the present invention: an annular groove is coaxially opened on the core shaft, a retaining spring is installed in the groove, the retaining spring is arranged below the lower bearing so as to be staggered in height, and the projection of the inner ring of the lower bearing in the vertical direction intersects with the retaining spring.

[0019] As a further solution of the present invention: there is an annular gap between the core shaft and the outer shell, and a first sealing ring, a second sealing ring and a third sealing ring arranged with different heights are installed in the annular gap; the first sealing ring is located between the inlet and the outlet of the cooling channel, the second sealing ring is located between the lower mounting cavity and the inlet of the cooling channel, and the third sealing ring is located between the upper mounting cavity and the outlet of the cooling channel; the first sealing ring, the second sealing ring and the third sealing ring are Gray rings.

[0020] As a further solution of the present invention: the inlet and outlet of the cooling channel are arranged radially along the shell, and the liquid inlet joint and the liquid outlet joint are respectively fixed with the inlet and outlet of the cooling channel by threaded engagement.

[0021] As a further solution of the present invention: the inlet of the cooling channel is located below the outlet; the stirring head and the core shaft form a detachable fit.

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

[0023] 1. After introducing the water cooling system, the present invention establishes a relationship between the feed speed of the welding tool and the feed speed of the additive material, so that the feed speed of the welding tool under the internal water cooling condition can match the optimal additive material feed speed, reducing the peak temperature of the welding tool outlet during the solid-phase additive process, reducing the weakening effect of heat accumulation on the material, preventing excessive heat accumulation from causing excessive growth of the grain size of the structure, and being able to reduce the temperature difference between the upper and lower materials, thereby reducing residual stress.

[0024] 2. The present invention provides a spiral cooling channel arranged around the core shaft in the housing. After introducing cooling water into the channel, the core shaft can be annularly cooled, which greatly reduces the heat input in the solid-phase stir friction additive manufacturing process, avoids the degradation of the performance of various materials, and ensures that the material can be better formed during the additive process.

[0025] 3. The core shaft of the present invention is positioned at two points by two sets of bearings, and the bearings and the cooling channel are sealed by sealing rings. The arrangement of multiple sealing rings on the outer ring of the core shaft prevents leakage of the cooling medium between different areas; the arrangement of the mounting cavities on the upper and lower end surfaces of the shell allows the corresponding bearings to be directly placed into the opening of the mounting cavity, and are installed in place after abutting against the bottom surface of the positioning groove of the mounting cavity.

[0026] 4. An annular groove is provided at the bottom of the core shaft of the present invention for installing a retaining spring. The retaining spring and the lower bearing are staggered in height, so that when the lower bearing accidentally falls, the retaining spring can support the lower bearing and provide safety protection. The liquid inlet and outlet joints are directly threaded and fixed to the inlet and outlet of the cooling channel for easy disassembly and installation. The cooling medium in the cooling channel enters from the bottom and exits from the top, forming convection cooling on the core shaft, and the cooling efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention.

[0028] Figure 2a This is the finished product image when the internal water cooling structure is added but the welding tool feeding speed and the additive material feeding speed are not matched.

[0029] Figure 2bThe finished product after adding an internal water-cooling structure to match the welding tool feeding speed with the additive material feeding speed.

[0030] In the picture:

[0031] 1. Shell; 11. Cooling channel; 12. Liquid inlet connector; 13. Liquid outlet connector;

[0032] 14. Upper mounting cavity; 141. Upper positioning groove; 142. Upper bearing;

[0033] 15. Lower mounting cavity; 151. Lower positioning groove; 152. Lower bearing;

[0034] 2. Mandrel; 21. Slot; 22. Circlip;

[0035] 23. First sealing ring; 24. Second sealing ring; 25. Third sealing ring; 3. Stirring head. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] See also Figures 1-2b In an embodiment of the present invention, a friction stir welding method for internally water-cooled bars suitable for solid-phase additive manufacturing includes the following steps:

[0038] S1. Install a water cooling system inside the welding tool;

[0039] The welding tool comprises a hollow housing 1 with a mounting channel defined at its center for the passage of a core shaft 2. The top opening of the housing 1 forms an upper mounting cavity 14, while the bottom opening of the housing 1 forms a lower mounting cavity 15. The upper and lower mounting cavities 14 and 15 are coaxially arranged with the core shaft 2.

[0040] An upper positioning groove 141 is coaxially defined in the cavity wall of the upper installation cavity 14 , and a lower positioning groove 151 is coaxially defined in the cavity wall of the lower installation cavity 15 .

[0041] The upper bearing 142 is installed in the upper positioning groove 141 from top to bottom. The diameter of the upper bearing 142 corresponds to the diameter of the upper mounting cavity 14. The outer ring of the upper bearing 142 abuts the bottom surface of the upper positioning groove 141 from top to bottom. A positioning ring is coaxially protruded on the outer ring of the core shaft 2, and the positioning ring of the core shaft 2 abuts the inner ring of the upper bearing 142 from top to bottom.

[0042] The lower bearing 152 is installed in the lower positioning groove 151 from bottom to top, and the diameter of the lower bearing 152 corresponds to the diameter of the lower mounting cavity 15. The outer ring of the lower bearing 152 abuts the bottom surface of the lower positioning groove 151 from bottom to top. The core shaft 2 has a shoulder that abuts the inner ring of the lower bearing 152 from bottom to top.

[0043] An annular groove 21 is coaxially opened on the core shaft 2, and a retaining spring 22 is installed in the groove 21. The retaining spring 22 is arranged below the lower bearing 152 so as to be staggered in height. The projection of the inner ring of the lower bearing 152 along the vertical direction intersects with the retaining spring 22. The retaining spring 22 is used to prevent the lower bearing 152 from falling and plays a supporting role.

[0044] After the core shaft 2 passes through the installation channel in the housing 1 from top to bottom, it is clamped and positioned by the upper bearing 142 and the lower bearing 152. The stirring head 3 is coaxially fixed to the bottom of the core shaft 2 and is detachably fixed to the core shaft 2 by screws.

[0045] The water cooling system includes a spiral cooling channel 11 within the housing 1. This channel 11 is coaxially arranged with the core shaft 2, thereby surrounding it. The water inlet of the cooling channel 11 is located at the bottom, and the water outlet is located at the top. Both the inlet and outlet are arranged radially along the housing 1. The inlet and outlet of the cooling channel 11 are threadedly secured to the liquid inlet connector 12 and the liquid outlet connector 13, respectively.

[0046] The outer ring of the mandrel 2 is coaxially defined with mounting grooves at different heights for mounting sealing rings. These sealing rings include a first sealing ring 23, a second sealing ring 24, and a third sealing ring 25. The first sealing ring 23 is located between the inlet and outlet of the cooling channel 11, the second sealing ring 24 is located between the lower mounting cavity 15 and the inlet of the cooling channel 11, and the third sealing ring 25 is located between the upper mounting cavity 14 and the outlet of the cooling channel 11. Each sealing ring is used to prevent coolant from leaking through the gap between the mandrel 2 and the housing 1. Each sealing ring is preferably a Gly ring.

[0047] S2, start the welding tool and water cooling system to ensure the feeding speed of the welding tool v 送 The feed rate v of the additive 进 The following relationship is satisfied:

[0048]

[0049] Where a represents the side length of the square rod of the welding tool;

[0050] t represents the additive time;

[0051] R represents the radius of the working end of the stirring head 3.

[0052] Before adding material, a certain distance of 0.5-2.5mm is set between the shoulder and the basic surface. This distance is the thickness of the single-layer addition. The rod size is smaller than the core shaft 2 size, and the single-side gap is 0-0.2mm to ensure that the rod can pass through the core shaft 2 smoothly.

[0053] The output pressure of the rod during the additive process is not less than 3500N to ensure the forming state during the additive process.

[0054] At the end of each additive stage, the stirring head 3 needs to stay in place for 2 to 15 seconds to ensure that the material fully fills the tail end of each additive layer, and the material at the end of the stirring head 3 is fully softened, and the plasticized material at the front end of the stirring head 3 is separated from the rod.

[0055] After adding the internal cooling system, the external water cooling environment will affect the forming of the material. When the original welding tool feeding speed and the additive material feeding speed are used, the surface of the component will be affected by the internal and external temperature difference. Figure 2a As shown, obvious furrow and crack defects are produced.

[0056] Under water cooling conditions, the welding tool feeding speed and the additive material feeding speed are improved. After the speed relationship between the two is matched by the formula, the material forming is as follows Figure 2b As shown, the molding is stable.

[0057] Along the longitudinal direction of the component, the grain size is relatively uniform and there is no obvious grain growth phenomenon.

[0058] The basic principles of the present application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this application are merely illustrative and not restrictive, and it should not be assumed that these advantages, strengths, and effects are required of each embodiment of this application. In addition, the specific details disclosed above are merely illustrative and facilitating understanding, and are not restrictive. The above details do not limit this application to necessarily being implemented using the above specific details.

[0059] The block diagrams of the devices, devices, equipment, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, devices, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "include," "comprise," "have," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

Claims

1. A friction stir welding method for internal water cooling rods suitable for solid phase additive manufacturing, characterized in that: The steps include: S1. Install a water cooling system inside the welding tool; S2, start the welding tool and water cooling system to ensure the feeding speed of the welding tool v 送 The feed rate v of the additive 进 The following relationship is satisfied: Where a represents the side length of the square rod of the welding tool; t represents the additive time; R represents the working end radius of the stirring head (3).

2. The internal water-cooled friction stir welding method for solid-phase additive manufacturing according to claim 1, characterized in that: The output pressure of the rod during the additive process is not less than 3500N; at the end of each additive stage, the stirring head (3) needs to stay in place for 2 to 15 seconds.

3. The internal water-cooled friction stir welding method for solid-phase additive manufacturing according to claim 1 or 2, characterized in that: The welding tool comprises a housing (1) with an installation channel opened along the axial direction for the core shaft (2) to be installed, a cooling channel (11) is opened in the housing (1) and is arranged coaxially around the installation channel in a spiral shape, and the two ends of the cooling channel (11) are respectively connected to a liquid inlet joint (12) and a liquid outlet joint (13); the stirring head (3) is coaxially fixed on the core shaft (2), at least one set of bearings is installed in the housing (1), and is coaxially rotatably matched with the core shaft (2) through the bearings; a sealing structure is provided between the cooling channel (11) and the bearings.

4. The internal water-cooled friction stir welding method for solid-phase additive manufacturing according to claim 3, characterized in that: The top and bottom of the housing (1) are respectively provided with an upper mounting cavity (14) and a lower mounting cavity (15) coaxially arranged with the core shaft (2); an upper bearing (142) and a lower bearing (152) are respectively installed in the upper mounting cavity (14) and the lower mounting cavity (15); the upper bearing (142) and the lower bearing (152) cooperate to support and position the core shaft (2) at two points.

5. The internal water-cooled friction stir welding method for solid-phase additive manufacturing according to claim 4, characterized in that: An upper positioning groove (141) is coaxially provided in the upper mounting cavity (14), and the diameter of the upper positioning groove (141) corresponds to the diameter of the upper bearing (142); the outer ring of the upper bearing (142) abuts and fits with the upper positioning groove (141) from top to bottom, and a positioning ring is coaxially provided on the outer ring of the core shaft (2), and the positioning ring of the core shaft (2) abuts and fits with the inner ring of the upper bearing (142) from top to bottom.

6. The internal water-cooled friction stir welding method for solid-phase additive manufacturing according to claim 4, characterized in that: A lower positioning groove (151) is coaxially provided in the lower mounting cavity (15), and the diameter of the lower positioning groove (151) corresponds to the diameter of the lower bearing (152); the outer ring of the lower bearing (152) abuts against the lower positioning groove (151) from bottom to top, and the shaft shoulder of the core shaft (2) abuts against the inner ring of the lower bearing (152) from bottom to top.

7. The internal water-cooled friction stir welding method for solid-phase additive manufacturing according to claim 6, characterized in that: An annular groove (21) is coaxially provided on the core shaft (2), a retaining spring (22) is installed in the groove (21), and the retaining spring (22) is arranged below the lower bearing (152) so as to be staggered in height. The projection of the inner ring of the lower bearing (152) in the vertical direction intersects with the retaining spring (22).

8. The internal water-cooled friction stir welding method for solid-phase additive manufacturing according to claim 3, characterized in that: An annular gap exists between the core shaft (2) and the housing (1), and a first sealing ring (23), a second sealing ring (24) and a third sealing ring (25) arranged at different heights are installed in the annular gap; the first sealing ring (23) is located between the inlet and the outlet of the cooling channel (11), the second sealing ring (24) is located between the lower mounting cavity (15) and the inlet of the cooling channel (11), and the third sealing ring (25) is located between the upper mounting cavity (14) and the outlet of the cooling channel (11); the first sealing ring (23), the second sealing ring (24) and the third sealing ring (25) are Gley rings.

9. The internal water-cooled friction stir welding method for solid-phase additive manufacturing according to claim 3, characterized in that: The inlet and outlet of the cooling channel (11) are arranged radially along the outer shell (1), and the liquid inlet joint (12) and the liquid outlet joint (13) are respectively threadedly fixed to the inlet and outlet of the cooling channel (11).

10. The internal water-cooled friction stir welding method for solid-phase additive manufacturing according to claim 3, characterized in that: The inlet of the cooling channel (11) is located below the outlet; the stirring head (3) and the core shaft (2) form a detachable fit.

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