Multilayer forged stirring tool for friction stir welding

Abstract

The invention discloses a multilayer forging type stirring head for friction stir welding, comprising a clamping part, a shaft shoulder part and a stirring needle connected in sequence, a spiral groove is arranged on the peripheral side of the stirring needle, and the top surface of the spiral groove forms a forging surface. The stirring head has the advantages of simple and reliable structure, improved uniformity of weld structure, and reduced pressure and welding flash thickness.

Description

Technical Field

[0001] The invention mainly relates to a friction stir welding technology, in particular to a multi-layer forging type stirring head used for friction stir welding. Background Art

[0002] During the friction stir welding process, the interaction between the stirring head and the workpiece material generates heat, heating the workpiece material around the stirring head to a plasticized state to form a weld. This heat mainly includes the friction heat between the shoulder and the stirring needle and the base material, and the plastic deformation heat generated by the stirring and extrusion of the workpiece material. During the friction stir welding process, the distribution of the workpiece temperature field is uneven, showing a pattern in which the temperature is highest at the shoulder of the stirring head and decreases gradually toward the end face of the stirring needle.

[0003] The stirring head is the core of the friction stir welding technology. It interacts with the workpiece to achieve the connection of the welded materials.

[0004] There is no mature theory for the design of stirring head size. Most of them are designed based on experience. The stirring head is mainly composed of a stirring needle, a shoulder and a clamping area. The stirring needle is located at the top of the stirring head and has different shapes. The stirring needle generates some heat energy through rotational friction. The main function of the stirring needle is similar to that of a pump. It can make the metal in a highly plasticized state flow from front to back along the stirring needle while maintaining up and down movement, and forge and cool through the stirring head shoulder to form a joint. The size of the stirring needle determines the size of the weld core zone organization and the welding speed of the weld; the shape of the stirring needle determines the heating method and the mode of plastic material being forged during the welding process, and directly affects the flow form of the softened material in the weld zone, which plays an important role in the joint forming. The shape and size of the stirring needle and the related welding process parameters jointly determine the heat generation and material flow during the welding process, and ultimately determine the quality of the stir friction welding joint.

[0005] The forging pressure of the existing ordinary stirring head on the weld metal mainly comes from the shaft shoulder. When stir friction welding is performed on thick plates, the forging pressure decreases from the weld surface to the weld root. In order to form a good weld structure, it is necessary to increase the top force by increasing the downward pressure, which causes the flash to increase and the weld structure to be uneven in the depth direction. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a multilayer forging stirring head which has a simple and reliable structure, improves the uniformity of the weld structure, and can reduce the amount of downward pressure and the thickness of the welding flash.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A multilayer forging type stirring head for friction stir welding comprises a clamping part, a shaft shoulder part and a stirring needle which are connected in sequence. A spiral groove is arranged on the circumference of the stirring needle, and the top surface of the spiral groove forms a forging surface.

[0009] As a further improvement of the above technical solution:

[0010] The forging surface is a flat surface, and during welding, the forging surface is horizontal and straight.

[0011] The axis of the stirring needle is defined as the rotation center line, and a forging angle a is formed between the forging surface and the rotation center line, and 76.5°≤a≤95°.

[0012] In the welding state, a welding inclination angle b is formed between the rotation center line and the vertical line, and 1.5°≤b≤5°.

[0013] In the welding state, an angle c is formed between the forging surface and the vertical line, and 75°≤c≤90°.

[0014] The tip diameter of the stirring needle is defined as L1, and the root diameter of the stirring needle is defined as L2, where L1<L2.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] The present invention discloses a multi-layer forging type stirring head for friction stir welding, comprising a clamping portion, a shoulder portion and a stirring needle connected in sequence, wherein a spiral groove is arranged on the peripheral side of the stirring needle, and the top surface of the spiral groove forms a forging surface. During welding, the clamping portion is used for clamping, and the stirring needle generates heat energy through rotational friction, and the shoulder portion is used for forging. Compared with the traditional structure, the stirring head forges a multi-layer spiral groove on the peripheral side of the stirring needle, and the top surface of the spiral groove forms a forging surface. The multi-layer forging pressure brought by the multi-layer forging surface of the stirring needle during the welding process realizes more uniform stirring, and the metal inside the weld flows up and down more fully, so that the weld structure is more uniform in the depth direction. At the same time, the forging pressure of the shoulder portion can be reduced, the downward pressure is reduced, and the thickness of the welding flash is reduced. The structure is simple and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a three-dimensional structural schematic diagram of the present invention.

[0018] Figure 2 It is a main structural schematic diagram of the present invention.

[0019] Figure 3 It is a main cross-sectional structural schematic diagram of the present invention.

[0020] Figure 4 It is a schematic diagram of the structure of the present invention in use state.

[0021] The symbols in the figure represent:

[0022] 1. Clamping part; 2. Shoulder part; 3. Stirring needle; 31. Spiral groove; 32. Forging surface; 33. Rotation center line; 34. Needle tip; 35. Needle root; 4. Vertical line. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Figures 1 to 4 An embodiment of a multilayer forging type stirring head for friction stir welding of the present invention is shown, comprising a clamping part 1, a shoulder part 2 and a stirring needle 3 connected in sequence, a spiral groove 31 is provided on the peripheral side of the stirring needle 3, and a forging surface 32 is formed on the top surface of the spiral groove 31. During welding, the clamping part 1 is used for clamping, the stirring needle 3 generates heat energy through rotational friction, and forging is formed by the shoulder part 2. Compared with the traditional structure, the stirring head forms a multilayer spiral groove 31 on the peripheral side of the stirring needle 3, and a forging surface 32 is formed on the top surface of the spiral groove 31. The multilayer forging pressure brought by the multilayer forging surface 32 of the stirring needle 3 during the welding process is used to achieve more uniform stirring, and the metal inside the weld flows up and down more fully, so that the weld structure is more uniform in the depth direction. At the same time, the forging pressure of the shoulder part 2 can be reduced, the amount of downward pressure is reduced, and the thickness of the welding flash is reduced. Its structure is simple and reliable, and it is suitable for welding thick plates, large thick plates, products requiring small downward pressure, and products requiring relatively uniform mechanical properties.

[0025] In this embodiment, the forging surface 32 is a flat surface, and during welding, the forging surface 32 is horizontal and straight. This arrangement can increase the contact area between the forging surface 32 and the workpiece, and further improve the stability of the welding pressure.

[0026] In this embodiment, the axis of the stirring needle 3 is defined as the rotation center line 33, and a forging angle a is formed between the forging surface 32 and the rotation center line 33, 76.5°≤a≤95°. In this embodiment, in the welding state, a welding inclination angle b is formed between the rotation center line 33 and the vertical line 4, 1.5°≤b≤5°. In this embodiment, in the welding state, an angle c is formed between the forging surface 32 and the vertical line 4, 75°≤c≤90°. During welding, the stirring welding inclination angle b increases by 1°, and the forging angle a increases by 1°-3°; similarly, when the stirring welding inclination angle b remains unchanged, the forging angle a decreases, and the angle c between the forging surface 32 and the vertical line 4 decreases, and vice versa; when the welding inclination angle b decreases, the forging angle a increases, and the angle c between the forging surface 32 and the vertical line 4 increases, and vice versa. The conventional stirring head spiral angle is 55°-65°. In order to increase the welding temperature and welding speed at the same time, it is necessary to increase the stirring intensity, that is, to increase the stirring speed and increase the upsetting force to increase the heat converted from mechanical energy per unit time. However, the increase in stirring intensity will bring two negative effects: first, the surface plastic metal overflows from the edge of the stirring head shoulder under the action of pressure and centrifugal force to form flash; second, the metal in the weld zone forms loose structure or even voids due to metal loss and insufficient filling. In this embodiment, a=80, b=4°, and c=75°.

[0027] In this embodiment, the diameter of the tip 34 of the stirring needle 3 is defined as L1, and the diameter of the root 35 of the stirring needle 3 is defined as L2, where L1<L2. This arrangement makes the stirring needle 3 have a cone-shaped structure as a whole, thereby increasing the forging pressure.

[0028] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. A multilayer forged stirring head for friction stir welding, comprising a clamping portion (1), a shoulder portion (2) and a stirring needle (3) connected in sequence, characterized in that: The stirring needle (3) is provided with a spiral groove (31) on its circumference, and the top surface of the spiral groove (31) forms a forging surface (32); the forging surface (32) is a straight surface, and during welding, the forging surface (32) is horizontal and straight; the axis of the stirring needle (3) is defined as the rotation center line (33), and a forging angle a is formed between the forging surface (32) and the rotation center line (33), and the angle is 76.5°≤a≤95°; in the welding state, a welding inclination angle b is formed between the rotation center line (33) and the vertical line (4), and the angle is 1.5°≤b≤5°; in the welding state, an angle c is formed between the forging surface (32) and the vertical line (4), and the angle is 75°≤c≤90°; the diameter of the needle tip (34) of the stirring needle (3) is defined as L1, and the diameter of the needle root (35) of the stirring needle (3) is defined as L2, and L1<L2; wherein, a=80°, b=4°, c=75°.

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