Friction stir welding stirring head capable of improving flowing efficiency of base metal

Abstract

The invention discloses a friction stir welding stirring head capable of improving the flowing efficiency of base metal, which is characterized by comprising a friction stir welding stirring head body, the friction stir welding stirring head body comprises a clamping part, one end of the clamping part is provided with a spiral stirring needle, and the other end of the clamping part is provided with a stirring rod; the spiral stirring needle spirally shrinks towards the end part of the stirring needle, and a shaft shoulder part is arranged outside the radial peripheral surface of the spiral stirring needle; the shaft shoulder part is a concave surface inner asymptote groove shaft shoulder part; the spiral stirring needle is of a conical thread equally-divided three-section-shaped structure. And the end part of the spiral stirring needle is provided with a convex end head structure. According to the design of the end part of the stirring needle, the overall flowability of workpiece base metal can be effectively improved, a smaller crystal grain structure is generated, the forming is more stable, and the quality of a welding seam is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of friction stir welding, and in particular to a friction stir welding stirring head capable of improving the flow efficiency of a parent metal. Background Art

[0002] As a green and new solid-phase connection technology, friction stir welding technology has great advantages in welding low-melting-point materials such as aluminum alloy, magnesium, copper, etc. In addition to low-melting-point materials, it can also weld aluminum-copper dissimilar materials, titanium metal, steel and other materials. This technology has the advantages of small welding deformation, no need for gas protection, few joint defects, and good mechanical properties. It has a large number of applications in new energy vehicles, aerospace, shipbuilding, power electronics, rail transportation and other fields. The stirring head is the core component of friction welding. The selection of its materials and the design of its structure directly determine its service life and the quality of the joint weld.

[0003] After development, friction stir welding technology has entered the stage of industrial application from the experimental theoretical research stage. Stir friction welding first relies on the local friction heat generated by the stirring head and the workpiece base material to soften the material. As the stirring head rotates at high speed, the stirring head and the base metal undergo plastic flow. When equilibrium is reached, the stirring head moves forward, and a weld is formed under the joint action of the shoulder control and the downward pressure. According to the whole process, the quality of the welded joint is mainly affected by two aspects: one is the heat generated by the stirring needle and the shoulder during high-speed rotation (friction heat and metal plastic deformation heat); the other is the plastic flow and mixing of the base metal material. The formation of the weld is the result of the interaction of these two aspects. Heat generation is conducive to metal flow, and the flow of metal causes the material to plastically deform and also provides heat. Therefore, the quality of the weld can be improved by designing and optimizing the shape of the stirring head to increase heat generation, thereby improving the fluidity of the base metal.

[0004] In the whole process of friction stir welding, the stirring head is an important component. The stirring head is composed of three parts: the stirring needle end, the stirring needle, and the shaft shoulder. The design optimization and improvement of the stirring head shape can improve the production quality and efficiency of friction stir welding industrial products. Obviously, the ability of traditional stirring heads to drive the base metal is limited. It is urgent to optimize the design of the stirring head to improve the fluidity of the base metal and then improve the quality of the weld. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, the purpose of the present invention is to provide a friction stir welding stirring head for improving the flow efficiency of the parent metal, aiming to solve the problems in the above-mentioned technology.

[0006] In order to achieve the purpose of the present invention, the technical solution adopted is:

[0007] A friction stir welding stirring head for improving the flow efficiency of a base metal, comprising:

[0008] A friction stir welding stirring head body, the friction stir welding stirring head body comprises a clamping part, a spiral stirring needle is arranged at one end of the clamping part,

[0009] The spiral stirring needle is spirally contracted toward the end of the stirring needle, and a shaft shoulder is provided outside the radial outer peripheral surface of the spiral stirring needle;

[0010] The shaft shoulder portion is a concave inner asymptotic groove shaft shoulder portion;

[0011] The spiral stirring needle is a structure in which a conical thread is divided into three sections;

[0012] The end of the spiral stirring needle is provided with an outwardly protruding end structure.

[0013] In a preferred embodiment of the present invention, the spiral stirring needle is a right-handed conical thread structure divided into three equal sections.

[0014] In a preferred embodiment of the present invention, the outwardly protruding end structure is an outwardly protruding arc-shaped end structure.

[0015] In a preferred embodiment of the present invention, the radial cross-section of the spiral stirring needle is a conical thread structure, and the conical thread structure spirally contracts toward the end of the stirring needle, and the contraction angle range is 20-40°. The pitch of the spiral stirring needle is 0.5-0.8mm, and the screw depth of the spiral stirring needle is 1-2mm.

[0016] In a preferred embodiment of the present invention, the asymptotes of the asymptote groove shoulder portion in the concave surface are evenly distributed on the shoulder portion with the central axis of the stirring needle as the center, and the number of the asymptote grooves is 3-4.

[0017] In a preferred embodiment of the present invention, the diameter of the shaft shoulder is 3-4 times the diameter of the spiral stirring needle.

[0018] In a preferred embodiment of the present invention, the friction stir welding stirring head body is coated with a PVD coating.

[0019] The beneficial effects of the present invention are:

[0020] The end design of the stirring needle of the present invention is more conducive to driving the metal flow, increasing the friction area of ​​the end and increasing the temperature of the metal bottom; the design of the stirring needle increases the driving force of the metal, compresses the weld metal to the extrusion zone of the weld core zone, and reduces the area of ​​the loose zone; the design of the shaft shoulder enhances the force of the metal on the upper part of the weld to flow downward, increases the overall temperature of the weld, and increases the area of ​​the weld core zone. The above design can effectively improve the overall fluidity of the workpiece parent metal, produce a smaller grain structure, more stable molding, and enhance the quality of the weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0022] Figure 2 This is an enlarged view of 1-A of the present invention.

[0023] Figure 3 It is a structural schematic diagram of the prior art corresponding to the present invention.

[0024] Figure 4 It is a top view of the present invention.

[0025] Figure 5 It is a comparison diagram of the metallographic cross-section of the weld of a common stirring needle in the prior art and the stirring needle of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below through the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of the present invention. In addition, in the following structure, the description of the known structure and technology is omitted to avoid unnecessary confusion of the concept of the present invention.

[0027] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or component referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0028] like Figure 1 , 2Or a stir friction welding stirring head for improving the flow efficiency of base metal as shown in 4, includes a stir friction welding stirring head body 100, the stir friction welding stirring head body 100 includes a clamping part 1 for matching with the output shaft of the stirring motor (not shown in the figure), a spiral stirring needle 3 is arranged at one end of the clamping part 1, the spiral stirring needle 3 is spirally contracted toward the position of the stirring needle end 2, and a shoulder part 4 is arranged outside the radial outer peripheral surface of the spiral stirring needle 4.

[0029] The shaft shoulder portion 4 is a concave inner asymptotic groove shaft shoulder portion. The shaft shoulder design is conducive to continuous heat generation and is a guarantee for improving the restraint ability and fluidity of the stirring head on the base metal.

[0030] The spiral stirring needle 3 is a right-handed conical thread structure 5 divided into three equal sections. The right-handed conical thread is conducive to moving the metal material downward, and the three equally divided sections are also conducive to preventing aluminum from sticking during the stirring process.

[0031] The right-handed conical thread structure 5 that divides the three sections into equal parts increases the volume of the cavity around the stirring needle and the contact area between the stirring needle and the metal, thereby improving the ability of the weld metal to flow into the extrusion zone, thereby increasing the total amount of the parent metal flowing and the lateral migration distance.

[0032] The asymptotic grooves 41 of the concave inner asymptotic groove shoulder portion 4 are evenly distributed on the shoulder portion 4 with the central axis 31 of the stirring needle as the center, and the number of the asymptotic grooves 41 is three.

[0033] The asymptote groove 41 guides the metal flow and affects the flow behavior of the metal. Compared with the common concave shoulder, it enhances the driving force for the metal to flow toward the root of the stirring needle.

[0034] The angle α between the inner concave surface of the asymptotic groove 41 and the outer edge of the shaft shoulder 4 is 9°.

[0035] The radial cross section of the spiral stirring needle 3 is a conical thread structure, and the conical thread structure spirally contracts toward the end of the stirring needle. The contraction angle ranges from 20 to 40 degrees, and is 30 degrees in the embodiment.

[0036] The pitch of the thread 6 of the spiral stirring needle 3 is 0.5-0.8 mm, and the depth of the thread 6 of the spiral stirring needle 3 is 1-2 mm.

[0037] The end of the spiral stirring needle 3 is provided with an outwardly convex end structure 2, which is specifically an outwardly convex arc-shaped end structure. The design of the outwardly convex arc-shaped end structure is conducive to sufficient stirring of the bottom of the stirring needle and the workpiece.

[0038] It changes the driving force of the plasticized metal in the extrusion zone at the bottom of the weld, and the average grain size in the weld core zone will be reduced, thereby affecting the fluidity of the metal in the upper extrusion zone.

[0039] The diameter of the shaft shoulder 4 is 3-4 times the diameter of the spiral stirring needle 3. In the embodiment, it is 3 times.

[0040] When the friction stir welding stirring head body 100 is working, the angle between the friction stir welding stirring head body 100 and the horizontal plane is set to an inclination angle of 3°, and the downward pressure is 0.5 mm.

[0041] During welding, in order to prevent the spiral stirring pin 3 from breaking due to too much resistance when the friction stir welding stirring head body 100 is pressed down, a small hole smaller than the spiral stirring pin 3 is drilled at the starting point of the workpiece before welding.

[0042] The right-handed conical thread is divided into three equal-angled planes in the direction parallel to the taper, and the plane depth is 0.9mm.

[0043] When using a three-cut plane conical stirring needle for welding, the friction heat generation formula is: q = τ.v.cost, and the following tolerance dimensions are used:

[0044] The shoulder tolerance dimensions are:

[0045] Diameter ±0.1, angle and groove depth ±0.05, width and pitch ±0.05, root radius 1°.

[0046] The tolerance size of stirring needle is:

[0047] Three sections: length ±0.1, angle / depth ±0.05, uniform distribution ±0.1°;

[0048] The tolerances of the spiral groove of the spiral stirring needle 3 are: number of turns and depth ±0.05, tooth shape and groove width ±0.05;

[0049] The thread tolerances of the spiral stirring needle 3 are as follows: pitch and thread depth ±0.05, thread angle ±2°.

[0050] When the hardness of the friction stir welding stirring head body 100 is less than 50HRC, the outer circle rough machining, heat treatment and fine machining mode is adopted.

[0051] When the hardness is ≥50HRC, the external cylindrical rough machining, fine machining, heat treatment and external cylindrical grinding processing modes are adopted.

[0052] The thread, inner hole and outer circle precision in turning and milling finishing is 0.01-0.05mm. The dimensional precision of finishing grinder is required to be 1 micron-5 microns.

[0053] Because of the above structure, the working principle of the present invention is:

[0054] Before welding, the workpiece surface is cleaned to ensure that there is no oxide scale, oil stains and other impurities on the surface to be welded. The surface roughness of the welding plate is guaranteed to be 6.3 microns, the flatness is 0.5mm / m, the straightness of the weld is 0.6mm / , and the verticality (relative to the weldment surface) is 0.2mm.

[0055] Install the stirring head on the corresponding friction welding machine and follow the tool handle tightening requirements to ensure that the stirring head will not fall off when rotating at high speed.

[0056] Carry out process tool setting according to the drawings and perform dry run to ensure that no interference occurs.

[0057] Operators should be in a safe area and wear protective glasses, earplugs and dust masks.

[0058] During welding, the rotation of the stirring head needs to be observed.

[0059] During welding, it is strictly forbidden for personnel to touch the stirring head and weld.

[0060] After welding is completed, wait for the stirring needle to stop working, turn off the power, and wear heat-insulating gloves to remove the parts and disassemble the stirring head.

[0061] After welding, observe whether there is welding residue on the surface of the stirring needle. If there is residue, it needs to be removed by mechanical or chemical methods.

[0062] Detection method: The flow of metal materials is detected by the marking material method. During the rotation process, the forward-measured material will be brought to the backward-measured material. After processing, the slices are observed under a scanning electron microscope for detection.

[0063] Compared with the prior art, the present invention produces a smaller grain structure (e.g. Figure 5 The molding is more stable.

[0064] The basic principles and main features of the invention and the advantages of the invention are shown and described above.

[0065] Those skilled in the art should understand that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A friction stir welding stirring head for improving the flow efficiency of the parent metal, characterized in that: include: A friction stir welding stirring head body, the friction stir welding stirring head body comprises a clamping part, a spiral stirring needle is arranged at one end of the clamping part, The spiral stirring needle is spirally contracted toward the end of the stirring needle, and a shaft shoulder is provided outside the radial outer peripheral surface of the spiral stirring needle; The shaft shoulder portion is a concave inner asymptotic groove shaft shoulder portion; The spiral stirring needle is a structure in which a conical thread is divided into three sections; The end of the spiral stirring needle is provided with an outwardly protruding end structure.

2. A friction stir welding stirring head for improving the flow efficiency of the parent metal as claimed in claim 1, characterized in that: The spiral stirring needle is a right-handed conical thread structure divided into three equal sections.

3. A friction stir welding stirring head for improving the flow efficiency of the parent metal as claimed in claim 1, characterized in that: The outwardly protruding end structure is an outwardly protruding arc-shaped end structure.

4. A friction stir welding stirring head for improving the flow efficiency of the parent metal as claimed in claim 1, characterized in that: The radial cross-section of the spiral stirring needle is a conical thread structure, and the conical thread structure spirally contracts toward the end of the stirring needle. The contraction angle range is 20-40°, the pitch of the spiral stirring needle is 0.5-0.8mm, and the thread depth of the spiral stirring needle is 1-2mm.

5. A friction stir welding stirring head for improving the flow efficiency of the parent metal as claimed in claim 1, characterized in that: The asymptotes of the asymptote groove shoulder portion in the concave surface are evenly distributed on the shoulder portion with the central axis of the stirring needle as the center, and the number of the asymptote grooves is 3-4.

6. A friction stir welding stirring head for improving the flow efficiency of the parent metal as claimed in claim 1, characterized in that: The diameter of the shaft shoulder is 3-4 times the diameter of the spiral stirring needle.

7. A friction stir welding stirring head for improving the flow efficiency of the parent metal as claimed in claim 1, characterized in that: The friction stir welding stirring head body is coated with a PVD coating.

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