CN114833437B - Synergistic double-sided near-net spot welding method - Google Patents
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- CN114833437B CN114833437B CN202210477458.0A CN202210477458A CN114833437B CN 114833437 B CN114833437 B CN 114833437B CN 202210477458 A CN202210477458 A CN 202210477458A CN 114833437 B CN114833437 B CN 114833437B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding
- B23K20/122—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding
- B23K20/1245—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding characterised by the apparatus
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding
- B23K20/122—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding
- B23K20/1245—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding characterised by the apparatus
- B23K20/125—Rotary tool drive mechanism
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/26—Auxiliary equipment
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Abstract
The invention relates to a cooperative double-sided near-net spot welding method, which adopts a needleless stirring tool, stirring heads at two sides move to a pressing position through displacement control or pressure control, continuously rub with a workpiece to be welded for welding time according to a set rotating direction and rotating speed, and finally the two stirring heads are pulled back away from the surface of the workpiece along a preset track to finish a spot welding process. The invention is characterized in that the thermodynamic cycle process at the left side and the right side is regulated by the design of welding specifications such as tool size (D/mm), process parameters (main shaft rotating speed omega/rpm and residence time t/s) and the like, so that double-sided synchronous forming is realized, micro-connection and macroscopic defects of a joint interface are expected to be synergistically improved, and the welding process can realize structures such as typical single-sided structures, symmetrical double-sided structures, asymmetrical double-sided structures and the like, and the controllability is greatly improved. Therefore, the cooperative double-sided needleless friction stir welding can improve the productivity while solving the defects of the conventional friction stir spot welding, and has great industrial application prospect.
Description
Technical Field
The invention belongs to a spot welding method, relates to a cooperative double-sided near-net spot welding method, and provides a novel near-net spot welding method based on a cooperative double-sided forming concept, which is mainly suitable for connecting light metal sheets or metal strips with ultrathin and easy deformation, no support in space, unequal thickness and the like. The method has the advantages of simple operation, strong controllability, high joint quality, good reliability, wide application range, low production cost and easy popularization and application.
Background
With the rapid development of the industrial fields of aviation, aerospace, automobiles, ships and the like, the innovation of advanced manufacturing technology is greatly promoted by the requirements of light structure and high reliability. Aiming at a plurality of problems existing in the existing metal point connecting structure, such as easy loosening and falling, poor ageing resistance and corrosion resistance, air holes and crack defects, and the like, the friction stir spot welding technology (Friction Stir Spot Welding, FSSW) effectively improves the defects by virtue of outstanding metallurgical advantages, has good process stability and economic benefit, and has wide application in metal material connection. However, the inherent post-weld "keyhole" defect severely affects the joint integrity and reliability, limiting the spread of the technology. Based on this, backfill friction stir spot welding (Refill Friction Stir Spot Welding, R-FSSW, US6722556B 2) and needleless friction stir spot welding techniques (Probless Friction Stir Spot Welding, P-FSSW, CN 200910238020.1) were developed successively. Backfill friction stir spot welding (R-FSSW) is a high strength spot welded joint free of keyhole defects obtained by controlling complex relative movements between the pin and sleeve such that the welded material is fully flowed and refilled into the keyhole, which has been reported by the Shanghai aerospace equipment manufacturing general factories to have achieved application of this process in rocket ribbon manufacturing. However, the process has high requirements on the precision of a motion control system, and the problem of easy blockage of component equipment gaps exists, so that the forming quality and efficiency are seriously affected. The needleless friction stir spot welding (P-FSSW) technology is a technology that achieves a reliable connection of thin-walled structures by achieving a viscoplastic flow of a material through a thermodynamic action of a shoulder, and is attracting attention by virtue of relatively simple welding tools and processes. However, the friction stir spot welding technology has the following characteristics: 1. the uncontrollable nature of macroscopic hook geometry defects (hook) makes it difficult to eliminate the hook geometry defects while improving the interface metallurgical connection due to the asymmetric thermodynamic cycle effect up and down during welding, so that the spot welded joint exhibits the characteristics of low strength, poor plasticity and the like. 2. The defect of local metallurgical bonding is difficult to eliminate, and as the single-sided welding is only carried out in one direction of the workpiece, the lower plate material is weaker under the action of heat, the material is not easy to generate plastic deformation and flow, interface bonding is not facilitated, local weak connection is caused, and the mechanical property of a welded joint is seriously affected. 3. The welding structure and the tool are limited, the applicable plate thickness and the process range are relatively narrow, and particularly, the forming is difficult when ultrathin, non-uniform thickness or heterostructure is connected, and the welding quality is difficult to control. 4. The need for a back rigid support, its support tooling and control is complex, which greatly limits the application of friction stir spot welding technology to unsupported curved structures.
In 2010, U.S. Pat. No. 6,9 discloses a friction stir spot welding method (CN 200910273444.1), wherein a technique of simultaneously performing friction stir spot welding on both sides is proposed, which aims at solving the problems of deep pressing pit and excessive surface extrudate after conventional spot welding process, but the method aggravates a great amount of material loss caused by a "keyhole" defect, and simultaneously the separated shoulder-stirring pin introduces a blocking problem, and the method cannot regulate macroscopic hook geometry defect, so that the irreconcilable contradiction between macroscopic defect and microscopic connection still exists, thus the technique flexibility is low. At present, a simple and effective method for solving the problems is not found, so that macro-micro coordinated forming of the spot welding joint is realized, and the application and popularization of the solid-phase spot welding technology in the advanced manufacturing field are severely restricted. Therefore, by taking the advantage of no 'keyhole' forming as a reference, the development of a novel double-sided controllable near-net forming process has important significance in eliminating the contradiction, improving the quality of the spot welding joint and simplifying the production process.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a cooperative double-sided near-net spot welding method, which solves the problem of irreconcilability between micro metallurgical bonding and macroscopic hook geometry defects of a spot welding joint interface. The joint obtained by the method has the advantages of smooth surface formation, compact structure, high joint quality, simple operation process and low production cost.
Technical proposal
A cooperative double-sided near-net spot welding method is characterized in that: the needleless stirring head is welded on two opposite sides of a weldment simultaneously, so that double-side synchronous controllable forming is realized, and the steps are as follows:
step 1: stacking the welded materials to the designed thickness in a lap joint mode; if the welding materials are equal-thickness or non-equal-thickness metal sheets, directly stacking the two welded materials to form a welding sample;
step 2: the method comprises the steps of fixing a material to be welded on a clamp of a horizontal friction stir spot welding device, and symmetrically arranging needleless stirring heads with involute groove characteristics on main shafts at two sides, wherein the diameter of a shaft shoulder of each needleless stirring head is 3-5 times of the whole thickness of a welded sample;
step 3: feeding the needleless stirring heads at two sides until the two sides are contacted with the surface of the material to be welded, and adjusting a welding reference surface, namely, seamlessly contacting the shaft shoulder of the stirring head with the material to be welded to be used as a welding starting position;
step 4: selecting welding parameters, namely spindle rotation speed, welding time and pressing amount, according to the welded material and the plate thickness; when welding is performed by adopting non-equal thickness plates or heterogeneous materials, setting one side of the thick plates or hard materials as a high rotating speed side;
step 5: and (3) welding according to the set welding parameters, moving the stirring head to the surface of the sample along the direction of the guide rail during welding, loading the stirring head to the set upsetting force, maintaining the stirring head motionless, and starting the spindle motor to enable the stirring head to rotate in the set direction.
Step 6: after the welding is finished, the stirring heads at the two sides stop loading and retract along the direction of the guide rail, and the stirring heads stop rotating.
In the step 1, when the welding material is a multi-layer ultrathin metal strip, the welding material is stacked to a required thickness.
In the step 1, when the welding materials are metal sheets with equal thickness or unequal thickness, two welded materials are stacked to form a welding material sample.
The rotation directions of the stirring heads at the two sides are the same or opposite.
The rotation speed and the welding time of the stirring heads at the two sides are the same or different.
The pressure is controlled to be 5-10kN.
The rotation is 1500-2000rpm.
Advantageous effects
The cooperative double-sided near-net spot welding method provided by the invention uses the advantage of no keyhole in needleless friction stir spot welding to combine with the novel concept of double-sided forming, adopts a needleless stirring tool, and realizes double-sided synchronous controllable forming by adjusting the technological parameters of double-sided welding. In the processing process, the stirring heads at two sides move to a pressing position through displacement control or pressure control (5-10 kN), and continuously rub with a workpiece to be welded for a certain welding time according to a set rotating direction and rotating speed (1500-2000 rpm), and finally the two stirring heads are pulled back away from the surface of the workpiece along a preset track to finish the spot welding process. The invention is characterized in that the thermodynamic cycle process at the left side and the right side is regulated by the design of welding specifications such as tool size (D/mm), process parameters (main shaft rotating speed omega/rpm and residence time t/s) and the like, so that double-sided synchronous forming is realized, micro-connection and macroscopic defects of a joint interface are expected to be synergistically improved, and the welding process can realize structures such as typical single-sided structures, symmetrical double-sided structures, asymmetrical double-sided structures and the like, and the controllability is greatly improved. Therefore, the cooperative double-sided needleless friction stir welding can improve the productivity while solving the defects of the conventional friction stir spot welding, and has great industrial application prospect.
Compared with other forms of friction stir spot welding, the invention has the beneficial effects that: 1. in the symmetrical forming process, the technology can synchronously increase the thermodynamic action on the upper plate and the lower plate, improve the temperature and the strain in the plate thickness direction, reduce the gradient of the change of the upper plate and the lower plate, simultaneously intensify the metal flow behavior, strengthen the thermodynamic action on an interface, facilitate the crushing and the metallurgical bonding of an interface oxide layer, and simultaneously shorten the welding time (the welding time of the invention can be 1-3 s). 2. In the asymmetric forming process, the rotation speed and the rotation direction of stirring heads at two sides are adjusted to cause non-uniformity of temperature and plastic strain in upper and lower plates, so that macroscopic hook-shaped geometric defects deflect towards one side with better fluidity, interface adjustment characteristics are realized, the mechanical properties of the joint are affected, and the method is suitable for spot welding of non-uniform thickness or heterostructures. 3. And the welding of the unsupported curved surface structure can be realized without back rigid support. 4. The double-sided welding has high heat production, the welding heat input can be accurately controlled by adjusting the technological parameters of the stirring head, the technological window is wide, and the double-sided welding is suitable for welding an ultra-thin plate to a thick plate (0.5-3 mm). 5. The flexible rotating two-shaft shoulder structure is adopted to replace a back rigid support, and the flexible combined back rigid support has the advantages of reducing mechanical vibration, increasing welding plate thickness and realizing flexible combined process.
Drawings
Fig. 1: schematic of cooperative double-sided needleless friction stir spot welding: a needleless stirring head (II) welds lap surfaces of a sample (III) in a rotating direction (IV);
fig. 2: an involute profile schematic diagram of the stirring head;
fig. 3: schematic diagram of a cooperative double-sided needleless friction stir spot welding forming device;
fig. 4: schematic drawing of a welding plate;
fig. 5: and (I) a lens panoramic view of the cross section of the joint of the cooperative double-sided needleless friction stir spot welding: (II) a portion of the metallurgical bonding zone (III) a bonding surface central region;
fig. 6: the simulation results of the double-sided friction spot welding process comprise the temperature (I) of 0.2s, (II) of 1.0s, the strain (III) of 0.2s, (IV) of 1.0s, the material distribution (V) of 0.2s and (VI) of 1.0s;
Detailed Description
The invention will now be further described with reference to examples, figures:
the technical scheme of the invention is as follows: a cooperative double-sided near-net spot welding method adopts double-sided forming, and the left side and the right side of a welding piece are subjected to the thermal action of an additional stirring head at the same time, so that the symmetry of temperature, strain and metal flow at the two sides is realized, the deformation and connection at the joint surface are promoted, and the specific technical characteristics are as follows: a horizontal welding machine is adopted, and a workpiece is required to be positioned before welding; during welding, the stirring head moves the surface of the sample along the direction of the guide rail, is kept motionless after being loaded to a set upsetting force, and starts the spindle motor, so that the stirring head rotates at a high speed according to the set direction; the left stirring head and the right stirring head have the functions that: the stirring pin is not needed, so that the defect of a key hole is effectively avoided; the grooves on the surface of the shaft shoulder increase the contact area with the metal to be welded, so that friction heat generation is increased; the involute shape groove promotes the surface metal to gather inwards and flow downwards along the thickness direction, so that the stirring range is enlarged, and a good joint is formed. During welding, the pressing degree can be controlled by displacement control or upsetting pressure, the left stirring head and the right stirring head can rotate in a certain direction, the rotation directions of the two sides of the left stirring head and the right stirring head can be the same or opposite, the rotation speed and the welding time of the left stirring head and the right stirring head can be the same or different, for example, when the rotation speed of one stirring head is 0, the joint presents a typical single-sided needleless friction stir spot welding appearance. When the left stirring head and the right stirring head are inserted into the material to be welded to rotate and maintain for a period of time, heat is generated through friction between the end face of the shaft shoulder of the stirring head and the surface of the workpiece to be welded and is transferred into the weldment, so that the contact surface of the weldment is reliably connected under the action of thermal coupling, after welding, the stirring heads on two sides stop loading and retract along the direction of the guide rail, and the stirring heads stop rotating.
The symmetrical forming process is adopted, 2198-T8 high-strength aluminum lithium alloy with the thickness of 1.8mm is used as a research object, and near-net spot welding is carried out. The following is a specific embodiment example of the present invention, and it should be noted that this example is a typical example of the present invention, but the present invention is not limited to this example.
Implementation example:
as shown in FIG. 2, the end face of the shaft shoulder of the stirring head is provided with an involute groove, the diameter size of the involute groove is 20mm, and the involute groove is made of H13 hot work grinding tool steel with wider application and the brand of the involute groove is 4Cr5MoSiV1. FIG. 3 is a schematic diagram of a cooperative double-sided needleless friction stir spot welding forming apparatus including a hold down system, a holding device, a securing device, a stepping system, and a servo system. The test clamping device adopts 45# steel, and plays roles in fixing and transmitting torque. The fixing device is used for fixing the whole tool through the two ends of the welding plate, so that shaking is avoided, and torque influence caused by rotation of the main shaft in the welding process is prevented. The left stirring head is driven by a servo motor, the right stirring head is driven by a stepping motor, and the two motors are respectively provided with a limit rotation speed of 2500rpm which is close to that of the stepping motor and the servo motor in order to avoid vibration of a mechanical system, and the actual use is estimated to be 900-2000rpm. The hold down system may provide impact pressure to the welding tool during welding, through displacement control or pressure control, and is expected to be used at 5-10kN. The left-right movement travel of the stirring heads at the two sides is generally related to the plates to be welded, the thickness of the welding material used in the experiment is 1.8mm, the distance between the stirring heads before welding is larger than 20mm according to the rule, and the distance can be increased by about 2mm when the distance can be increased, so that the distance between the stirring heads is 1-26mm, namely the left-right travel distance of the stirring heads at the two sides is selected to be 13mm. The welding process is controlled by program setting parameters, parameters such as the pressing amount, the pressing speed, the stirring head rotating speed, the rotating direction, the welding time and the like in the welding process are adjusted by corresponding programs of the PC end, and the welding process has the advantages of high control precision, simplicity in operation and the like, and effectively reduces operation errors.
(1) Before welding, the welding plate is processed into a size of 30X 65X 1.8mm according to the standardization of the welding test 3 As shown in fig. 4, the surface of the welding plate is cleaned by using alcohol and acetone, the welding plate is clamped according to a lap joint structure, the lap joint width is 30mm, and the welding plate interface is ensured to be tightly attached through a rib plate fixing device; moving the stirring head to a position 13mm away from the surface of the weldment; inputting instruction programs such as welding parameters and the like through a PC end;
(2) During welding, the stirring heads at the two sides move the surface of the sample along the direction of the guide rail at 20mm/min, the sample is kept still after being loaded to the set 5kN, the welding starts, the left stirring head and the right stirring head rotate at 950rpm in opposite directions as shown in the figure 1, simultaneously press down according to the preset 0.3mm, and after the welding time reaches 2s, the stirring is stopped;
(3) After the welding is finished, the left stirring head and the right stirring head stop loading and rotating, retract along the direction of the guide rail at the original speed, loosen the fixing device and take out the weldment;
(4) And (3) carrying out OM observation on the welded product obtained in the step (3), wherein the obtained joint morphology is shown in fig. 5, the joint surface is smooth and flat, other subsequent processing processes are not required, the welding spots are almost symmetrical in structural characteristics, the structure is compact, the hook-shaped geometric defects are not remarkably deteriorated, and the weak deviation can be attributed to slight vibration in the welding process. At the same time, the interfacial metallurgical bond is significantly improved due to the enhanced thermodynamic cycle effect, microscopic hole defects are not observed, and reliable joints are formed (II and III in FIG. 5). In addition, through numerical simulation analysis, it can be seen that in the double-sided spot welding process, the upper plate and the lower plate are quickly heated by double-sided synchronous heat input, the joint temperature is characterized by central symmetrical distribution, the high-temperature zone is gradually expanded along with the progress of the welding process, and the temperature gradient in the thickness direction of the final plate is reduced (I and II in fig. 6), which is just because the double-sided welding increases the friction stir area, so that the heat generation quantity is improved. The plastic strain distribution of the joint cross section is consistent with temperature (III and VI in figure 6), and the strain fields of the upper and lower plates which are approximately symmetrically distributed are less likely to cause one-sided warping of the interface in theory, so that obvious hook-shaped geometric defects are prevented from being formed to deteriorate the joint strength. As can be seen from fig. 6 v and iv, the metal flow behavior on both sides of the interface during symmetric formation of the spot welds exhibits a high degree of symmetry, indirectly demonstrating the precise reliability of the near net spot welding process of the present invention. Therefore, the spot welding process of the invention can improve the temperature and the strain in the plate thickness direction by synchronously increasing the thermodynamic effect on the lower plate material, so that the gradient of the change is reduced, the metal flow behavior is enhanced, the thermodynamic effect on the interface is enhanced, and the interface oxide layer is favorably crushed and metallurgically bonded.
Example 2: by adopting an asymmetric forming process of unequal thick plates, 2198-T8 high-strength aluminum lithium alloy with the thickness of 1.8mm and 1.5mm is taken as a research object, and the following specific implementation examples are as follows:
before welding, processing according to the standardization of welding test to obtain 30×65X1.8 mm 3 And 30X 65X 1.5mm 3 Cleaning the surface of the welded plate by using alcohol and acetone, clamping according to a structure with the lap joint width of 30mm, respectively placing the two plates on the left side and the right side of a rib plate fixing device, and finally moving a stirring head to a position 13mm away from the surface of a weldment; inputting instruction programs such as welding parameters and the like through a PC end;
(2) During welding, the stirring heads at the two sides load samples to a preset value of 5kN along the direction of a guide rail at 20mm/min, the left stirring head and the right stirring head respectively run at different welding parameters, the left stirring head rotates at 950rpm and presses down at a preset value of 0.3mm, the right stirring head runs at 900rpm and presses down at a preset value of 0.2mm, and stirring is stopped after the welding time reaches 2 s;
(3) After the welding is finished, the left stirring head and the right stirring head stop loading and rotating, retract along the direction of the guide rail at the original speed, loosen the fixing device and take out the weldment;
by adopting an asymmetric forming process, the left welding plate is subjected to a strong thermodynamic cycle effect due to the relatively high process parameters of the left stirring head, so that the plastic flow degree and the strain field of the left metal are relatively large. But because the flow capacity of the right side metal is relatively weak, the flow metal of the left side solder plate will be constrained to spread to the right and thus spread back out. Meanwhile, the central interface is bearing the extrusion effect caused by asymmetric metal flow, and the metal on the right side is forced to flow outwards to the left, so that the interface hook shape warps at a thicker position on the left side. The hook shape warps towards a thicker part, so that the loss degree of the effective thickness of the joint can be controlled, and the hook shape is embedded into the thicker plate to play a certain mechanical jogging role to increase the overall mechanical property of the joint, so that the optimal solution of the hook shape adjusting effect is realized.
Example 3: by adopting an asymmetric forming process of a dissimilar welding plate, 2198-T8 high-strength aluminum lithium alloy and 6061 aluminum alloy with the thickness of 1.8mm are taken as research objects, and the following specific implementation examples are as follows:
(1) Before welding, processing according to the standardization of welding test to obtain 30×65X1.8 mm 3 The 2198-T8 aluminum lithium alloy and 6061 aluminum alloy welding plates are cleaned by alcohol and acetone, clamped according to a structure with the lap joint width of 30mm, the two plates are respectively arranged on the left side and the right side of a rib plate fixing device, and finally a stirring head is moved to a position 13mm away from the surface of a welding piece; inputting instruction programs such as welding parameters and the like through a PC end;
(2) During welding, the stirring heads at the two sides load samples to a preset value of 5kN along the direction of a guide rail at 20mm/min, the left stirring head and the right stirring head respectively run at different welding parameters, the left stirring head rotates at 1000rpm, the right stirring head runs at 950rpm, the stirring heads at the two sides simultaneously press down at a preset value of 0.2mm, and after the welding time reaches 2s, stirring is stopped;
(3) After the welding is finished, the left stirring head and the right stirring head stop loading and rotating, retract along the direction of the guide rail at the original speed, loosen the fixing device and take out the weldment;
by adopting a cooperative double-sided needleless friction stir spot welding process, on one hand, the stirring heads on the left side and the right side simultaneously generate friction heat and plastic deformation in the spot welding process, so that more energy can be generated in a limited time, and the welding quality is improved; on the other hand, the strength of the left side 22198-T8 aluminum alloy is higher than that of the right side 6061 aluminum alloy, and the plastic fluidity of the left side metal can be increased by adopting higher process parameters, so that the consistency of plastic flow of the two sides of the metal is realized. The symmetrical plastic strain fields on two sides enable the hook shape to be kept flat with the interface, so that the effective plate thickness invariance of the spot welding joint is ensured, and high-strength spot welding is realized.
The near net spot weld joint strength measured at present is as high as 8-12kN, which is higher than the R-FSSW joint strength (7-10 kN) and the P-FSSW joint strength (5-7 kN) under the same existing conditions. Compared with the prior FSSW technology, the spot welding method has more flexibility, for example, when ultra-thin plate welding is carried out, the same parameters can be set for the stirring heads on two sides so as to avoid forming hook-shaped geometric defects; the hook geometry defect profile can be purposefully biased when performing slab welding, and mechanical nesting is used to increase joint strength. Therefore, the weldable plate thickness of the spot welding method realizes breakthrough from 0.5 to 3mm (the weldable plate thickness range of the prior FSSW technology is limited to 1 to 2 mm). In conclusion, the cooperative double-sided needleless friction stir spot welding technology further improves the realization of joint performance by virtue of excellent forming controllability and flexibility. Therefore, the process developed by the invention is feasible and has good application prospect.
Claims (7)
1. A cooperative double-sided near-net spot welding method is characterized in that: the needleless stirring head is welded on two opposite sides of a weldment simultaneously, so that double-side synchronous controllable forming is realized, and the steps are as follows:
step 1: stacking the welded materials to the designed thickness in a lap joint mode; if the welding materials are equal-thickness or non-equal-thickness metal sheets, directly stacking the two welded materials to form a welding sample;
step 2: the method comprises the steps of fixing a material to be welded on a clamp of a horizontal friction stir spot welding device, and symmetrically arranging needleless stirring heads with involute groove characteristics on main shafts at two sides, wherein the diameter of a shaft shoulder of each needleless stirring head is 3-5 times of the whole thickness of a welded sample;
step 3: feeding the needleless stirring heads at two sides until the two sides are contacted with the surface of the material to be welded, and adjusting a welding reference surface, namely, seamlessly contacting the shaft shoulder of the stirring head with the material to be welded to be used as a welding starting position;
step 4: selecting welding parameters, namely spindle rotation speed, welding time and pressing amount, according to the welded material and the plate thickness; when welding is performed by adopting non-equal thickness plates or heterogeneous materials, setting one side of the thick plates or hard materials as a high rotating speed side;
step 5: welding according to the set welding parameters, moving the stirring head to the surface of the sample along the direction of the guide rail during welding, loading the stirring head to the set upsetting force, maintaining the stirring head still, starting the spindle motor, and enabling the stirring head to rotate in the set direction
Step 6: after the welding is finished, the stirring heads at the two sides stop loading and retract along the direction of the guide rail, and the stirring heads stop rotating.
2. The cooperative double-sided near-net spot welding method of claim 1, wherein: in the step 1, when the welding material is a multi-layer ultrathin metal strip, the welding material is stacked to a required thickness.
3. The cooperative double-sided near-net spot welding method of claim 1, wherein: in the step 1, when the welding materials are metal sheets with equal thickness or unequal thickness, two welded materials are stacked to form a welding material sample.
4. The cooperative double-sided near-net spot welding method of claim 1, wherein: the rotation directions of the stirring heads at the two sides are the same or opposite.
5. The cooperative double-sided near-net spot welding method of claim 1, wherein: the rotation speed and the welding time of the stirring heads at the two sides are the same or different.
6. The cooperative double-sided near-net spot welding method of claim 1, wherein: the pressure is controlled to be 5-10kN.
7. The cooperative double-sided near-net spot welding method of claim 1, wherein: the rotation is 1500-2000rpm.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0456967A2 (en) * | 1990-05-16 | 1991-11-21 | Akio Hirane | Spot welder and method for using |
| CN101722360A (en) * | 2009-12-29 | 2010-06-09 | 湖北工业大学 | Friction stir spot welding method |
| CN109551095A (en) * | 2018-11-15 | 2019-04-02 | 江苏理工学院 | A kind of no keyhole agitating friction overlap joint spot welding method |
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2022
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|---|---|---|---|---|
| EP0456967A2 (en) * | 1990-05-16 | 1991-11-21 | Akio Hirane | Spot welder and method for using |
| CN101722360A (en) * | 2009-12-29 | 2010-06-09 | 湖北工业大学 | Friction stir spot welding method |
| CN109551095A (en) * | 2018-11-15 | 2019-04-02 | 江苏理工学院 | A kind of no keyhole agitating friction overlap joint spot welding method |
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| Title |
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| 工艺参数对铝合金双面搅拌点焊力学性能的影响;孙世烜;李延民;郝云飞;贺佳誉;红亮;赵燕;;铝加工(01);第15-24页 * |
| 搅拌摩擦点焊技术及其研究现状;傅田;李文亚;杨夏炜;李锦锋;高大路;;材料工程(04);第102-114页 * |
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| CN114833437A (en) | 2022-08-02 |
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