A device and method for friction stir welding of dissimilar metals with gap filling

Abstract

The application discloses a kind of gap filling wire's dissimilar metal friction stir welding device and welding method, belong to dissimilar metal friction stir welding technical field.It includes static axle shoulder, stirring needle, wire feeder, steps are as follows: milling workpiece to be welded, need to process harder alloy, the butt joint cross section is cut into L type.Softer alloy is not processed, and the two form J type groove with blunt edge after assembly.Blunt edge height is 10%-70% plate thickness, step width is 5%-50% plate thickness;Polish, assemble workpiece to workbench;Install stirring head, adjust welding machine coordinate;Set relevant parameters, start wire feeder, preheating device and friction stir welding machine, and weld;Cool after welding, and welding is completed.The application can avoid the uneven heat distribution problem caused by the heat production difference between upper and lower parts of workpiece during the process of dissimilar metal friction stir welding of large difference, and can adjust the composition inside weld, strengthen interface, reduce the generation of intermetallic compound, and improve joint strength.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of gap filling wire of dissimilar metal friction stir welding device and welding method, belong to dissimilar metal friction stir welding technical field. BACKGROUND

[0002] The statements herein are provided only to aid in the understanding of the present application, and do not necessarily constitute prior art.

[0003] With the continuous improvement of the requirement of the sustainable development of manufacturing industry and the objective need of building a conservation-minded society, the joining technology of dissimilar materials has become one of the main development directions in the field of welding. Dissimilar material composite joint is beneficial to save mineral resources, reduce structural weight, reduce production cost, and realize the complementary advantages between different materials. However, the material properties of dissimilar materials are quite different and are prone to react at high temperature, and after traditional fusion welding, large deformation and brittle intermetallic compounds of workpiece are easily produced, which seriously affects the service performance of the joint. Therefore, the solid-phase joining technology represented by friction stir welding has obvious advantages in avoiding the problems brought by traditional fusion welding (such as porosity, inclusion, hot crack, thick intermetallic compound, and large deformation after welding).

[0004] Friction stir welding has the advantages of high joint quality, small welding deformation, and green and environmentally friendly welding process. It is to insert a high-speed rotating stir head into the contact surface of the workpiece to be welded, generate heat through the friction of the shaft shoulder and the stir pin with the workpiece to be welded, and increase the temperature near the stir head. At the same time, a downward pressure is applied by the shaft shoulder, and when the stir head moves forward along the welding interface, the material in a plastic state flows from the front to the rear of the stir head, and under the joint action of heat and force, the material is connected to form a joint. Compared with traditional fusion welding, friction stir welding has small heat input, thin intermetallic compound of joint, and the material does not melt during welding, with small residual stress and deformation after welding.

[0005] According to existing research, when friction stir welding connects dissimilar materials with large differences in thermophysical properties (such as aluminum alloy and titanium alloy connection or aluminum alloy and steel connection), the metal with higher melting point and hardness is generally placed on the advancing side, and the stir pin should be biased to the side of the metal with lower melting point and hardness. The purpose is to avoid excessive contact with the harder metal, reduce heat generation, avoid the formation of a large amount of hard and brittle intermetallic compounds at the interface, and avoid the peak temperature of the weld seam close to or even reaching the melting point of the base material with lower melting point.

[0006] However, in the process of friction stir welding of dissimilar materials, the shaft shoulder produces about 70% of the heat, and the temperature gradually decreases from top to bottom along the thickness direction. The upper part of the workpiece is affected by the shaft shoulder, which produces a lot of heat and has a high temperature, making the upper part of the dissimilar metal interface react too violently, easily producing coarse overheated structure, and easily producing thick hard intermetallic compounds, which worsen the joint performance. The lower part of the workpiece is mainly affected by the stir pin, which produces less heat and has a lower temperature, which easily leads to insufficient material flow at the bottom of the workpiece, and easily forms holes and other defects in the weld.

[0007] To reduce the temperature gradient along the thickness direction of the workpiece and avoid overheating of the upper part of the workpiece, some researchers have proposed a static shoulder friction stir welding method. The tool of this method is composed of a static shoulder and a rotating pin. During welding, the pin rotates and moves along the welding direction, while the static shoulder slides on the surface of the workpiece, generating heat through the friction between the pin and the surrounding material to soften the surrounding material to a plastic state. Because the shoulder is static, there is no intense friction between the shoulder and the workpiece material, which greatly reduces the heat generated by the shoulder on the upper part of the workpiece, and can improve the uneven heat input distribution along the thickness direction of the plate to some extent. However, the static shoulder still slides on the upper surface of the workpiece, which still generates some heat, and in order to avoid material overflowing into the space between the shaft shoulder and the stir pin during welding, causing the welding machine to be stuck, the static shoulder of the stir head generally still has a small-sized concave shoulder, so the heat generated on the upper part of the workpiece is still higher than that on the lower part. In addition, the bottom of the workpiece is in direct contact with the rigid backing plate, and the lower part of the workpiece cools quickly, so the conventional static shoulder friction stir welding cannot completely solve the problem of uneven temperature distribution along the thickness direction of the plate.

[0008] In the static shoulder friction stir welding of large-difference dissimilar metals, the stir pin usually needs to be slightly biased towards the harder metal. If the biasing amount of the upper part and the lower part is the same, since the bottom of the workpiece is in contact with the backing plate, it cools quickly, which can also cause overheating of the upper part. How to further optimize the welding heat distribution based on static shoulder friction stir welding, avoid overheating of the upper part of the workpiece to form a thick intermetallic compound layer and coarse grain structure, and at the same time, increase the heat generation and welding temperature of the bottom of the workpiece, and reduce the insufficient material flow caused by the low temperature of the lower part of the workpiece is a key problem that needs to be solved in the welding of large-difference dissimilar metals.

[0009] The patent document CN202110160985.4 provides a static shaft shoulder wire filling system for welding and additive manufacturing, which can realize high-quality welding and additive of homogenous alloy. However, in the aspect of large-difference dissimilar metal connection, the device still has a lot of problems. The patent document CN 114985898 A discloses a friction stir welding method for dissimilar metal bevel butt joint, which can realize high-quality connection of aluminum / steel dissimilar metal friction stir welding. However, the method has high requirements for the groove angle range, and too large or too small angle is not conducive to the improvement of joint strength, so ordinary milling machines are difficult to realize processing, which seriously affects the improvement of welding efficiency. At the same time, the wire filling method has poor stability, and only welding wire is added inside the groove. Improper assembly can easily cause large internal gap in the weld, and lack of metal filling in the nugget zone causes defects. Therefore, higher requirements are put forward for the assembly of workpieces during friction stir welding. In order to solve these problems, the present application provides an improved method. SUMMARY

[0010] In view of the deficiencies of the prior art, the present application provides a large-difference dissimilar metal friction stir welding device with gap wire filling to solve the problems that the excessive high temperature of the upper part of the workpiece during the dissimilar material welding process easily leads to excessive severe interface reaction of the dissimilar metal, causing the weakening of the joint performance, and the excessive low temperature of the lower part of the workpiece easily leads to welding defects.

[0011] The technical scheme of the present application is as follows:

[0012] A large-difference dissimilar metal friction stir welding device with gap wire filling is obtained by modifying a conventional static shaft shoulder friction stir welding system, so that wire filling is realized during the friction stir welding process.

[0013] The device comprises a static shaft shoulder, a stirring needle and a wire feeding device. The stirring needle penetrates through the static shaft shoulder, and the stirring needle and the static shaft shoulder are in gap fit. A rotating motor is connected above the stirring needle. The static shaft shoulder does not rotate during the welding process. The static shaft shoulder is provided with a wire feeding hole. The wire feeding device extends the wire into the wire feeding hole. A threaded groove is arranged on the side below the stirring needle. The starting end of the threaded groove is higher than the wire feeding hole, and the terminal end of the threaded groove extends to the bottom end of the stirring needle. The starting end of the threaded groove is higher than the wire feeding hole to ensure that the wire fed can be completely plasticized and broken by the stirring needle and move downward through the threaded groove into the nugget zone.

[0014] The gap is a fit gap between the workpieces. The stirring needle and the static shaft shoulder are configured to be capable of synchronous movement along the machining track, and the stirring needle is capable of rotational movement around its own axis. The machining end of the stirring needle is provided with a threaded groove. Before welding, the harder alloy needs to be processed to cut the butt cross section into an L shape, and the softer alloy is not processed. After assembly, the two form a J-shaped groove with a blunt edge.

[0015] Preferably, the gap width between the stirring pin and the static shoulder is 1.1-1.5 times the diameter of the welding wire.

[0016] Preferably, when the thread groove is right-handed, the spindle rotation direction is counterclockwise; when the thread groove is left-handed, the spindle rotation direction is clockwise. The two cooperate to produce a downward rotating force on the wire entering the thread groove.

[0017] Preferably, the lower end surface of the static shoulder is provided with a shoulder boss, the shoulder boss is coaxial with the static shoulder, the diameter of the shoulder boss is smaller than that of the static shoulder, and the wire feeding hole is arranged on the shoulder boss. To avoid material overflow between the shoulder and the stirring pin during welding, causing the welding machine to be stuck.

[0018] Further preferably, the number of wire feeding holes is at least one and at most six, and the wire feeding holes are uniformly distributed axially. The number of wire feeding holes to be used is calculated according to the amount of filler metal required during actual welding and the actual wire feeding speed.

[0019] Further preferably, the diameter of the wire feeding hole is 1.1-1.5 times the diameter of the welding wire.

[0020] Preferably, the welding device further comprises a hot wire power source, and the welding wire passes through the hot wire power source for preheating before entering the wire feeding hole. Additional heat is provided to make it easier to deform plastically when processing inside the static shoulder, reducing and preventing the phenomenon of the welding machine being stuck.

[0021] Preferably, the welding wire includes aluminum alloy welding wire, nickel alloy welding wire, high-entropy alloy welding wire, and zinc alloy welding wire. The welding wire with different chemical composition than the plate to be welded can be selected, which aims to adjust the interfacial metallurgical reaction and strengthen the interface to improve the joint strength.

[0022] A dissimilar metal friction stir welding method with gap wire filling, comprising the following steps:

[0023] Step one: the upper half of the butt joint surface of the plate to be welded with higher hardness is processed into L shape, and the plate to be welded with lower hardness is not processed, so that a J-shaped groove with a blunt edge is formed after the two plates are butt jointed;

[0024] Step two: during welding, the stirring pin is deviated to the side of the metal with lower hardness (softer metal), and only a small part of the stirring pin is on the side of the metal with higher hardness; the plate with higher hardness should be placed on the advancing side of the stirring pin, and the plate with lower hardness should be placed on the retreating side of the stirring pin; when the stirring pin starts to rotate and gradually presses down, due to the existence of the J-shaped groove with a blunt edge, the side of the stirring pin is not in contact with the metal with higher hardness in the upper half of the joint, so only the metal with lower hardness is frictional to produce heat and plasticize the surrounding metal; when the stirring pin continues to press down to the lower half of the joint, the stirring pin is in contact with both the metal with higher hardness and the metal with lower hardness, and they are frictional to produce heat and soften the metal together;

[0025] Step three: after the completion of the pressing process under the stirring head, the wire is sent into the wire feeding hole, the wire is pushed through the wire feeding hole by the pushing force of the wire feeding mechanism connected thereto, the end thereof is in contact with the threaded groove of the stirring needle, and plasticization occurs under the action of friction and preheating, the hot plasticized wire is broken and extruded into the threaded groove under the cutting action of the threaded groove of the stirring needle, and the plastic softened wire moves along the threaded groove under the rotation of the stirring needle, enters the nugget zone, and is mixed with the plastic material in the stirring zone;

[0026] Step four: after the pressing force of the stirring needle reaches the preset value, the stirring needle rotates and advances, the static shaft shoulder does not rotate with the stirring needle, a weld is formed to complete the welding process.

[0027] Preferably, in step one, the groove is a stepped groove, the stepped width is 5%-50% of the plate thickness, and the root face height is 10%-70% of the plate thickness.

[0028] Further preferably, in step two, in order to avoid excessive insertion of hard metal and generate a large amount of heat, when the stirring needle is pressed to the bottom of the J-shaped groove, part of the stirring needle is inserted into the hard alloy, and the pressing amount is 10%-80% of the stepped width.

[0029] Preferably, in step four, the stirring needle is inclined in the opposite direction of the welding direction during the welding process.

[0030] Further preferably, in step four, the inclination angle of the stirring needle is 2°-2.5°.

[0031] Preferably, in step four, the process parameters during the welding process can be: the stirring needle rotating speed is 300-1000 rpm, and the welding speed is 15-300 mm / min.

[0032] The beneficial effects of the present application are:

[0033] The gap referred to in the title of the present application refers to the stepped width of the J-shaped groove, by adopting a J-shaped groove with a root face, the stirring needle only rubs against the metal with lower hardness in the upper half during the welding process, and rubs against the metal on both sides in the lower half. This joint form makes the heat input of the upper and lower parts uniform, avoids excessive temperature in the upper part, reduces interfacial reaction and inhibits abnormal grain growth, and improves the joint performance. At the same time, the flowability of the root material is improved to avoid weld hole defects. It is especially suitable for different materials with large differences in physical and chemical properties such as aluminum copper, aluminum magnesium, aluminum titanium, aluminum steel, copper steel, etc.

[0034] In order to avoid the reduction of mechanical properties caused by the thickness reduction of the joint after welding due to the opening of the groove, the present application adopts a wire filling static shaft shoulder structure to compensate for the missing volume at the groove by feeding the wire.

[0035] The application can avoid the problem that too much upper stirring needle is stirred into dissimilar metal, which causes deformation, incoordination and micro-cracks and holes.

[0036] The application uses wire as feeding material, has low cost, and can improve welding speed by arranging multiple wire feeding holes.

[0037] The application reduces and avoids the problem of wire jamming in the welding process, adds a welding wire preheating device, and improves the wire feeding efficiency.

[0038] The application uses a wire feeder to fill wire, can adjust the wire feeding amount and wire feeding speed according to the parameters in the welding process, and can ensure that the internal metal of the weld is fully filled. Compared with the angle groove, the groove in the application only needs to be processed by a common milling machine, which can effectively improve the welding efficiency. The application uses a static shaft shoulder stirring needle, which has obvious advantages in improving the problem of too large temperature difference in the thickness direction compared with the conventional friction stir welding stirring needle.

[0039] The structure of the application does not need to make large-scale modification to the existing friction stir welding equipment, is beneficial to technology upgrading and equipment replacement, and is easy to quickly industrialize and apply. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The application is a dissimilar metal friction stir welding device structure with gap filling wire;

[0041] Figure 2 The application is a dissimilar metal friction stir welding device structure with gap filling wire;

[0042] Figure 3 The application is a dissimilar metal friction stir welding device structure with gap filling wire;

[0043] 1, stirring needle; 2, static shaft shoulder; 3, high-hardness pre-processed metal plate; 4, low-hardness un-pre-processed metal plate; 5, wire; 6, weld; 7, hot wire device. DETAILED DESCRIPTION

[0044] The application will be further described below by examples and in conjunction with the drawings, but is not limited thereto.

[0045] It should be pointed out that the following detailed description is exemplary and is intended to provide further description of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0046] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0047] For the convenience of description, if the terms "upper", "lower", "left", "right" are used in the present application, they only mean the same direction as the upper, lower, left and right directions of the drawings themselves, and do not limit the structure, but only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0048] As introduced in the background, the existing dissimilar material friction stir welding method has the problem of uneven heat input and temperature distribution in the thickness direction of the workpiece, which is easy to produce welding defects. In view of the above problems, the present application proposes a large difference dissimilar metal friction stir welding method with gap.

[0049] Example 1:

[0050] A dissimilar metal friction stir welding device with gap filling wire, which is modified from a conventional static shaft shoulder friction stir welding system, realizes wire filling during the friction stir welding process. It includes a static shaft shoulder, a stirring needle, and a wire feeding device. The stirring needle penetrates the static shaft shoulder, and the stirring needle and the static shaft shoulder are gap fitted. The stirring needle is connected to a rotating motor above it. The rotating motor is located in the welding machine shell. The static shaft shoulder is fixedly connected to the bottom of the welding machine shell and does not rotate during the welding process. The static shaft shoulder is provided with a wire feeding hole, and the wire feeding device extends the wire into the wire feeding hole. A threaded groove is provided on the side below the stirring needle. The starting end of the threaded groove is higher than the wire feeding hole, and the terminal end of the threaded groove extends to the bottom end of the stirring needle. The starting end of the threaded groove is higher than the wire feeding hole to ensure that the wire fed can be completely plasticized and broken by the stirring needle and move downward through the threaded groove into the weld nugget zone.

[0051] The gap is a fitting gap between the workpieces. The stirring needle and the static shaft shoulder are configured to be able to move synchronously along the machining trajectory, and the stirring needle is able to rotate around its own axis. The machining end of the stirring needle is provided with a threaded groove. Before welding, the harder alloy needs to be processed to cut the butt cross section into an L shape. The softer alloy is not processed, and the two form a J-shaped groove with a blunt edge after assembly.

[0052] When the thread groove is right-handed (right-handed thread is the conventional term, the helix line inclines to the right and up), the spindle rotation direction is counterclockwise; when the thread groove is left-handed, the spindle rotation direction is clockwise. The two cooperate to make the wire entering the thread groove produce a resultant force of downward rotation.

[0053] On the one hand, the outer surface of the stirring needle is processed with a thread groove, in order to prevent friction damage to the stirring needle and the static shaft shoulder, on the other hand, considering the reason why the static shaft shoulder does not rotate, so the cooperation between the inside of the static shaft shoulder and each part of the stirring needle is a clearance fit; if the cooperation clearance is too large, the stirring needle will be unstable and will vibrate, which will affect the welding precision, and in severe cases, the stirring needle may be damaged, and if the cooperation clearance is too small, the stirring needle and the inside of the static shaft shoulder will be excessively rubbed, which will also damage the device, therefore, a suitable clearance is slightly larger than the diameter of the welding wire, and the clearance width is 1.1-1.5 times the diameter of the welding wire. The diameter of the wire feeding hole is the same as the clearance width.

[0054] The lower end surface of the static shaft shoulder is provided with a shaft shoulder boss, the shaft shoulder boss is coaxial with the static shaft shoulder, the diameter of the shaft shoulder boss is smaller than that of the static shaft shoulder, the number of wire feeding holes is one, and the wire feeding hole is arranged on the shaft shoulder boss and penetrates the thickness of the shaft shoulder boss and is perpendicular to the axis of the static shaft shoulder, as shown in Figure 2 , which is used to feed the external wire to the stirring needle in the shaft shoulder boss. In order to avoid the overflow of materials between the shaft shoulder and the stirring needle during welding, causing the welding machine to be stuck.

[0055] The welding device also includes a hot wire power source, and the welding wire passes through the hot wire power source for preheating before entering the wire feeding hole. Additional heat is provided to make it easier to deform plastically when machining in the static shaft shoulder, reducing and preventing the phenomenon of welding machine sticking.

[0056] The wire is used as the feedstock, which is low in cost, and the performance of the weld can be adjusted by different wire compositions, and the welding speed can be improved by arranging multiple wire feeding holes.

[0057] Example 2:

[0058] A kind of gap filling wire dissimilar metal friction stir welding device, its structure is as described in example 1, the difference is that the number of wire feeding holes is two, and is symmetrically distributed on the shaft shoulder boss, and the number of wire feeding holes used can be calculated according to the amount of metal needed to be filled and the actual wire feeding speed during actual welding.

[0059] Example 3:

[0060] This embodiment discloses a friction welding method using the gap filling wire dissimilar metal friction stir welding device described in example 1, as shown in Figure 1 , Figure 2 , comprising the following steps:

[0061] Step one: insert the stirring needle into the static shaft shoulder, connect the wire to the wire feeding mechanism; the upper half of the butt joint surface of the higher hardness material to be welded is processed into L shape, and the lower hardness material to be welded is not processed, so that a J groove with a blunt edge is formed after the butt joint of the two plates. The groove is a stepped groove, the step width is 5%-50% of the plate thickness, and the blunt edge height is 10%-70% of the plate thickness.

[0062] Step two: during welding, the material with higher hardness is placed on the advancing side, the left edge of the stirring needle is adjusted to coincide with the edge of the lower melting point aluminum alloy, and the stirring needle offset is adjusted so that it moves a small amount to the harder alloy side, mostly above the softer metal part. When the stirring needle starts to rotate and gradually press down, due to the existence of the J groove with a blunt edge, the stirring needle side in the upper half of the joint does not contact the higher hardness metal, so it only produces heat and plasticizes the surrounding metal by friction with the lower hardness metal; when the stirring needle is pressed down to the bottom of the J groove, part of the stirring needle is inserted into the harder alloy, and the pressing amount is 0.1-0.8 times the step width, i.e. the horizontal width of the stirring needle covering the harder metal part is 0.1-0.8 times the step width, as shown by the dashed line in the stirring needle, the stirring needle starts to contact the harder metal plate when pressed down to the bottom of the groove, but does not completely cover the entire step width, generally the horizontal width of the stirring needle inserted into the harder metal part is 0.3-1.2mm. The stirring needle is biased to the side of the lower hardness alloy plate, the stirring needle rotates and inserts into the area to be welded. In the upper part of the joint, the stirring needle only rubs with the softer metal and the wire; in the lower part of the joint, the stirring needle rubs with both the harder metal and the softer metal, producing heat and softening the metal by friction. Figure 2

[0063] Step three: after the stirring head pressing process is completed, the wire is fed into the wire feeding hole, the wire is pushed through the wire feeding hole by the pushing force of the wire feeding mechanism connected to it, and the end of the wire is in contact with the thread groove of the stirring needle. Under the action of friction and preheating, the wire is plasticized, the plasticized wire is broken and extruded into the thread groove under the action of the thread groove of the stirring needle, and the plasticized wire metal moves downward along the thread groove under the action of the stirring needle rotation, and enters the stirring zone and mixes with the plastic material in the stirring zone.

[0064] Step four: after the pressing force of the stirring needle reaches the preset value, the stirring needle rotates and advances, and the stirring needle is inclined in the opposite direction of the welding direction during welding. As the stirring head moves, it is deposited under the extrusion of the static shaft shoulder behind it, forming a weld, realizing the welding of dissimilar materials; the static shaft shoulder does not rotate during welding, only applies pressure and constraint to the plasticized material. After a welding is completed, a weld bead is formed to complete the welding process, and the welding surface does not need to be cut and polished, avoiding the generation of machining allowance, improving the utilization rate of materials and the welding efficiency. After welding is completed, stop feeding the wire, at the same time, gradually reduce the stirring needle speed to complete stop, move the stirring head upwards, and finally obtain a weld with no internal defects and good external shape.​

[0065] Experimental Example 1

[0066] This experimental example utilizes a device and process for friction stir welding of dissimilar metals with a gap filler as described in Examples 1 and 3. In this experimental example, the material of the higher hardness plate is TA1 titanium alloy plate with a thickness of 7 mm, which is pre-processed to be cut into a stepped shape to form a J-shaped groove with a root face after butt joining, the root face height is 3 mm, and the stepped width is 1 mm; the material of the lower hardness plate is 2024-T4 aluminum alloy with a thickness of 7 mm, which is not pre-processed; the material of the filler wire is 2024 aluminum alloy with a diameter of 0.2 mm; the diameter of the wire feeding hole is 0.3 mm, and the length is 4 mm; the horizontal height of the wire feeding hole is 3 mm from the lower end surface of the static shoulder; the material of the stirring pin is H13 tool steel, and the diameter of the stirring pin is 6 mm; the thread groove is right-handed; the material of the static shoulder is H13 tool steel; the process parameters used can be: the stirring pin speed is 500 rpm, the welding speed is 60 mm / min, and the stirring pin inclination angle is 2.5°.

[0067] The welding method comprises the following steps:

[0068] Step 1, the joint surface of the TA1 titanium alloy plate is pre-processed into a stepped shape before welding;

[0069] Step 2, clean the two metal plates to remove surface oil and oxide scale;

[0070] Step 3, place the TA1 titanium alloy plate on the advancing side and the 2024-T4 aluminum alloy on the retreating side, butt join the two plates to form a J-shaped joint with a root face;

[0071] Step 4, insert the stirring pin with a right-handed thread groove into the static shoulder, and connect the wire to the wire feeding device;

[0072] Step 5, connect the clamping handle of the stirring pin to the main shaft of the friction stir welding machine, adjust the X-axis, Y-axis and Z-axis coordinates of the welding machine, adjust the left edge of the stirring pin to coincide with the edge of the 2024-T4 plate, and then adjust the stirring pin offset, moving 0.5 mm to the TA1 alloy side (TA1 alloy indentation is 0.5 mm);

[0073] Step 6, set the welding parameters (main shaft speed, welding speed, stirring head inclination angle, stirring pin rotation direction, etc., in this experimental example, the preferred stirring pin speed is 500 rpm, the welding speed is 60 mm / min, the stirring head inclination angle is 2.5°, and the stirring pin rotation direction is counterclockwise), and start the friction stir welding machine;

[0074] Step 7, at this time, place the wire into the wire feeding hole and start the wire feeder;

[0075] Step 8, after the welding is completed, stop the wire feeding, and the welding is completed.

[0076] Experimental Example 2

[0077] This experimental example utilizes a kind of inter-band gap filling wire dissimilar metal friction stir welding device and process based on the described in examples 1 and 3. In this experimental example, the material of the higher hardness plate is TC4 plate, the thickness is 4mm, it is pre-processed, cut into a step shape to form a J type groove with a blunt edge after butt joint, the height of the blunt edge is 1mm, and the step width is 0.5mm; the material of the lower hardness plate is 6061-T6 aluminum alloy, the thickness is 4mm, and it is not pre-processed; the material of the wire is pure nickel welding wire, the diameter is 0.2mm; the diameter of the wire feeding hole is 0.3mm, the length is 4mm, and the horizontal height of the wire feeding hole is 3mm away from the lower end surface of the static shaft shoulder; the material of the stirring needle is H13 tool steel, the diameter of the stirring needle is 6mm; the thread groove rotation direction is right-handed; the material of the static shaft shoulder is H13 tool steel; the process parameters used can be: the stirring needle speed is 700rpm, the welding speed is 50mm / min, and the stirring head inclination angle is 2°.

[0078] The welding method comprises the following steps:

[0079] Step 1, before welding, the joint surface of the TC4 titanium alloy plate is pre-processed into a step shape;

[0080] Step 2, clean the two metal plates to remove surface oil and scale;

[0081] Step 3, place the TC4 titanium alloy plate on the advancing side and the 6061-T6 aluminum alloy on the retreating side, butt joint the two plates to form a J type joint with a blunt edge;

[0082] Step 4, insert the stirring needle with right-handed thread groove into the static shaft shoulder, and connect the wire to the wire feeding device;

[0083] Step 5, connect the clamping handle of the stirring needle to the main shaft of the friction stir welding machine, adjust the X axis, Y axis and Z axis coordinates, adjust the left edge of the stirring needle to coincide with the edge of the 6061-T6 plate, and then adjust the stirring needle offset, move 0.3mm to the TC4 alloy side (TC4 alloy indentation is 0.3mm);

[0084] Step 6, set the welding parameters (main shaft speed, welding speed, stirring head inclination angle, stirring needle rotation direction, etc., in this experimental example, the preferred stirring needle speed is 700rpm, the welding speed is 50mm / min, the stirring head inclination angle is 2.5°, and the stirring needle rotation direction is counterclockwise), and start the friction stir welding machine;

[0085] Step 7, at this time, put the wire into the wire feeding hole, start the wire feeder, and start the wire preheating system;

[0086] Step 8, after the completion of welding, stop the wire feeding and close the wire preheating system, and the welding is completed.

[0087] Experimental Example 3

[0088] In this experimental example, the material of the plate with higher hardness is Q345 plate with a thickness of 3 mm, which is pre-processed to be stepped to form a J-shaped groove with a blunt edge after butt joint, the height of the blunt edge is 1 mm, and the width of the step is 1 mm; the material of the plate with lower hardness is ZK61 magnesium alloy with a thickness of 3 mm, which is not pre-processed; the material of the wire is 5356 aluminum alloy wire with a diameter of 0.2 mm; the diameter of the wire feeding hole is 0.3 mm, and the length is 4 mm; the horizontal height of the wire feeding hole is 3 mm away from the lower end surface of the static shoulder; the material of the stirring pin is H13 tool steel, and the diameter of the stirring pin is 6 mm; the thread groove is right-handed; the material of the static shoulder is H13 tool steel; the process parameters used can be: the stirring pin speed is 800 rpm, the welding speed is 100 mm / min, and the stirring head inclination angle is 2°.

[0089] The welding method comprises the following steps:

[0090] Step 1, before welding, the joint surface of the Q345 steel plate is pre-processed to be stepped;

[0091] Step 2, clean the two metal plates to remove surface oil and oxide scale;

[0092] Step 3, place the Q345 steel plate on the advancing side and the ZK61 magnesium alloy on the retreating side, butt joint the two plates to form a J-shaped joint with a blunt edge;

[0093] Step 4, insert the stirring pin with a right-handed thread groove into the static shoulder, and connect the wire to the wire feeding device;

[0094] Step 5, connect the clamping handle of the stirring pin to the main shaft of the friction stir welding machine, adjust the X-axis, Y-axis and Z-axis coordinates of the welding machine, adjust the left edge of the stirring pin to coincide with the edge of the ZK61 magnesium alloy, and then adjust the stirring pin offset, move 0.5 mm to the Q345 steel plate side (the Q345 steel plate is pressed in by 0.5 mm);

[0095] Step 6, set the welding parameters (main shaft speed, welding speed, stirring head inclination angle, stirring pin rotation direction, etc., in this experimental example, the preferred stirring pin speed is 800 rpm, the welding speed is 100 mm / min, the stirring head inclination angle is 2.5°, and the stirring pin rotation direction is counterclockwise), and start the friction stir welding machine;

[0096] Step 7, at this time, put the wire into the wire feeding hole, start the wire feeder, and start the wire preheating system.

[0097] Step 8, after the welding is completed, stop the wire feeding and close the wire preheating system, and the welding is completed.

[0098] In addition, in some other application experimental examples, the friction stir welding device of the embodiment can be used in the fields of automobiles, high-speed trains, aerospace, etc. It can be understood that, based on the above description, since the static shaft shoulder can be designed into any shape to adapt to different joint forms, and the material of the wire is variable, the device and method can be applicable to the welding between different materials and the same material.

Claims

1. A welding method for a dissimilar metal friction stir welding apparatus with gap filler wire, characterized in that, The dissimilar metal friction stir welding apparatus with gap filler wire includes a stationary shoulder, a stirring pin, and a wire feeding device. The stirring pin passes through the stationary shoulder, and there is a gap fit between the stirring pin and the stationary shoulder. A rotary motor is connected above the stirring pin. The stationary shoulder does not rotate during welding. The stationary shoulder has a wire feeding hole, and the wire feeding device inserts the wire into the wire feeding hole. A threaded groove is provided on the lower side of the stirring pin. The starting end of the threaded groove is higher than the wire feeding hole, and the end of the threaded groove extends to the bottom end of the stirring pin. The welding method includes the following steps: Step 1: Machin the upper half of the butt joint surface of the plates with higher hardness into an L-shape, and leave the plates with lower hardness unmachined, so that after the two plates are butt jointed, a J-shaped bevel with a blunt edge is formed. Step 2: During welding, the stirring pin is tilted towards the side with lower hardness metal, with only a small portion of the stirring pin on the side with higher hardness metal. The plate with higher hardness is placed on the forward side of the stirring pin, and the plate with lower hardness is placed on the backward side of the stirring pin. When the stirring pin starts to rotate and gradually presses down, due to the presence of the blunt-edged J-shaped bevel, the side of the stirring pin does not contact the higher hardness metal in the upper part of the joint. Therefore, it only rubs against the lower hardness metal to generate heat and plasticize the surrounding metal. When the stirring pin continues to press down to the lower part of the joint, the stirring pin contacts both the higher hardness metal and the lower hardness metal at the same time, and they rub together to generate heat and soften the metal. Step 3: After the stirring head presses down, the wire is fed into the wire feeding hole. Under the thrust of the wire feeding mechanism connected to it, the wire passes through the wire feeding hole and its end contacts the thread groove of the stirring needle. Under the action of friction and preheating, it is plasticized. The thermoplasticized wire is broken and squeezed into the thread groove after being cut by the thread groove of the stirring needle. Under the action of the rotation of the stirring needle, the plasticized and softened wire moves along the thread groove and enters the weld nugget area to mix with the plastic material in the stirring area. Step 4: After the downward pressure of the stirring needle reaches the preset value, the stirring needle rotates and moves forward, while the stationary shoulder does not rotate with the stirring needle, forming a weld bead and completing the welding process.

2. The welding method of the dissimilar metal friction stir welding apparatus with gap filler wire according to claim 1, characterized in that, In step one, the bevel is a stepped bevel, with a step width of 5%-50% of the plate thickness and a blunt edge height of 10%-70% of the plate thickness.

3. The welding method of the dissimilar metal friction stir welding apparatus with gap filler wire according to claim 2, characterized in that, In step two, when the stirring pin is pressed down to the bottom of the J-shaped bevel, part of the stirring pin is inserted into the harder plate to be welded, with an insertion amount of 0.1-0.8 times the step width.

4. The welding method of the dissimilar metal friction stir welding apparatus with gap filler wire according to claim 1, characterized in that, In step four, the stirring pin is tilted in the opposite direction of the welding process.

5. The welding method of the dissimilar metal friction stir welding apparatus with gap filler wire according to claim 4, characterized in that, In step four, the tilt angle of the stirring needle is 2°~2.5°.

6. The welding method of the dissimilar metal friction stir welding apparatus with gap filler wire according to claim 1, characterized in that, When the thread groove is right-handed, the spindle rotates counterclockwise; when the thread groove is left-handed, the spindle rotates clockwise.

7. The welding method of the dissimilar metal friction stir welding apparatus with gap filler wire according to claim 1, characterized in that, The gap width between the stirring needle and the stationary shaft shoulder is 1.1-1.5 times the diameter of the welding wire.

8. The welding method of the dissimilar metal friction stir welding apparatus with gap filler wire according to claim 1, characterized in that, The lower end face of the stationary shaft shoulder is provided with a shoulder boss, which is integral and coaxial with the stationary shaft shoulder. The diameter of the shoulder boss is smaller than that of the stationary shaft shoulder, and the wire feeding hole is located on the shoulder boss.

9. The welding method of the dissimilar metal friction stir welding apparatus with gap filler wire according to claim 4, characterized in that, The number of wire feeding holes is at least one and at most six, and the wire feeding holes are evenly distributed axially; the diameter of the wire feeding holes is 1.1-1.5 times the diameter of the welding wire.

10. The welding method of the dissimilar metal friction stir welding apparatus with gap filler wire according to claim 1, characterized in that, The welding apparatus also includes a hot wire power source, through which the welding wire passes before entering the wire feed hole.

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