CN101157156A - A welding tool for friction stir welding - Google Patents

Abstract

The invention relates to a welding tool for friction stir welding of double-layer aluminum alloy materials. The welding tool includes a rear cylindrical connecting body, a middle cylinder, and a stirring pin at the front; the middle cylinder has a heat dissipation spiral groove; the front of the welding tool The stirring needle at the top is conical, and the conical surface is made with spiral grooves; the shoulder connected between the end of the middle cylinder and the bottom of the stirring needle is a concave conical surface, and at least three spiral grooves are evenly distributed on the conical surface of the stirring needle , the tip of the stirring needle is made with a hemispherical groove. The helical groove on the stirring needle intersects with the hemispherical groove, and at least three notches are formed on the edge of the semicircular groove at the top of the conical stirring needle. The friction stir welding tool of this structure strengthens the plastic flow of the aluminum alloy during friction stir welding, and solves the problem of insufficient heat and unevenness of the lower plate caused by poor heat transfer of the double-layer plate.

Description

A welding tool for friction stir welding

technical field

The invention relates to a welding tool, in particular to a welding tool used for friction stir welding of double-layer aluminum alloy plates, and belongs to the technical field of material connection.

Background technique

Friction stir welding (FSW) is a new low-temperature solid-phase joining technology, which is suitable for welding low-melting point alloys. It was invented by The Welding Institute (TWI) in 1991 (US5460317). The principle of this technology is to use a high-speed rotating stirring head to insert into the seam, and use the strong friction and stirring effect of the stirring head to make the welding joint The seam area is in a thermoplastic state and is crushed, mixed, and connected together under a certain pressure. The stirring head rotates and squeezes at a high speed in the direction of welding, and a weld seam is formed behind the stirring head, thus completing the solid state connection. . At present, all countries are competing to develop it, and it has been widely used in aerospace, ships, high-speed trains, armored combat vehicles and other fields. Since the friction stir welding completes the solid-state connection at a temperature lower than the melting point of the alloy material to be welded, the metal material does not melt, the welding shrinkage deformation is small, and the loss of mechanical properties is low, which has outstanding advantages.

Aluminum alloy materials are widely used in industrial and civil fields. In recent years, aluminum alloy materials with special shapes have been more and more widely used as the supporting frame of products. At present, with the increasing size of LCD TVs, the original engineering plastics used in TV frames It can no longer meet the requirements of strength and rigidity, and it is necessary to use high-strength aluminum alloy profiles to manufacture the frame of the LCD TV. However, since the aluminum alloy profile used in the frame of the LCD TV is a special-shaped aluminum alloy profile with a small boss on the inside of the long and short sides, traditional aluminum alloy welding methods such as TIG welding (tungsten inert welding) are used. Gas arc welding), MIG welding (melting inert gas shielded welding) cannot guarantee the shape and size of the boss after welding, and the welding deformation of aluminum alloy profiles after fusion welding is also unacceptable for household appliances, so friction stir welding is used The above-mentioned problems can be effectively solved by utilizing the advantages of small welding shrinkage deformation and low loss of mechanical properties. During friction stir welding, it is necessary to inlay auxiliary pads on the inside and outside of the aluminum alloy profile to be welded to form a double-layer aluminum alloy material structure, and when the existing friction stir welding stirring head is welding the above-mentioned double-layer aluminum alloy material, especially for The welding of aluminum alloy materials with special shapes has the problem that the lower plate cannot be welded due to the heat transfer problem of the double-layer plate. Patent No. CN200310116992.6 introduces a device and method for friction stir welding using grooved pins. Patent No. 200610010553.0 introduces a welding tool for friction stir welding of copper and copper alloys. None of the tools are suitable for friction stir welding of double-layer aluminum alloy materials.

Contents of the invention

The technical problem to be solved by the present invention is: when performing stir welding for aluminum alloy profiles with special shapes, the existing welding tools for friction stir welding are difficult to solve the problem that the lower plate cannot be welded due to the heat transfer problem of the double-layer plate, and the material The technical difficulties caused by problems such as uneven thickness and special shape make it difficult for friction stir welding to achieve the desired effect.

In order to solve the above technical problems, the technical solution of the present invention is: a welding tool for friction stir welding, including a rear cylindrical connecting body, a middle cylinder, and a stirring needle at the front; The platform is loosely fastened, and the middle cylinder has a heat-dissipating spiral groove; the stirring needle at the front of the welding tool is conical, and the conical surface is shaped with a spiral groove; the end of the middle cylinder and the bottom of the stirring needle The connected shaft shoulder is a concave conical surface, at least three spiral grooves are evenly distributed on the conical surface of the stirring needle, and a hemispherical groove is formed on the top of the stirring needle.

The helical groove on the stirring needle intersects with the hemispherical groove, and at least three notches are formed on the edge of the semicircular groove at the top of the conical stirring needle.

The included angle between the normal of the concave conical surface of the shaft shoulder and the axis of the stirring needle is 5-15 degrees.

The helix angle of the helical groove is 55-65 degrees.

The depth of the hemispherical groove is 3-4mm.

The shape of the spiral groove is a concave semicircle with a depth of 2-3mm.

The spiral groove may also have a triangular cross-section, the triangular cross-section is 54 degrees, and the depth is 2-3 mm.

In the present invention, the friction surface of the stirring head with a special shape is in contact with the outer surface (or inner surface) of the L-shaped aluminum alloy profile. During welding, since at least three spiral grooves are added on the stirring pin of the stirring head, the top of the stirring head increases A groove is formed, which is partly circular or partly elliptical, so that it can strengthen the plastic flow of the aluminum alloy during friction stir welding, and use the specially increased metal flow to generate heat, which improves the stirring of the L-shaped aluminum alloy profile. Due to the insufficient heat of the lower layer caused by the heat transfer problem of the double-layer plate during friction welding, the high-quality connection of L-shaped aluminum alloy profiles is realized.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is a schematic diagram of the application of the present invention.

Fig. 2 is a structural diagram of a welding tool for friction stir welding of the present invention.

Detailed ways

The schematic diagram of the special-shaped L-shaped aluminum alloy profile of the embodiment of the present invention is shown in sequence 1 in FIG. 1 , which is used to make a large-size LCD TV frame. There is a small boss 5 on the inside of the long and short sides of the profile. After welding the L-shaped aluminum alloy profile frame of a large-size LCD TV, it is required to ensure the shape and size of the boss, and the welding deformation requirements of the aluminum alloy profile after fusion welding Also very small.

As shown in Figure 1, in this embodiment, the L-shaped aluminum alloy profile 1 is reversed, that is, the friction surface of the stirring head contacts the inner surface of the L-shaped aluminum alloy profile 1, and the inner surface of the L-shaped aluminum alloy profile 1 to be welded The outer side is inlaid and spells auxiliary cushion block 3,4 respectively.

The structure of the stirring head 2 of the present invention shown in Fig. 2 comprises the stirring pin 10 of rear cylindrical connecting body 7, middle cylinder 8, front; Cylindrical connecting body 7 is shaped on anti-loose fastening platform 6, The middle cylinder 8 is provided with a heat-dissipating spiral groove 9; the stirring needle 10 at the front of the welding tool is conical, and the conical surface is formed with a spiral groove 12; the end of the middle cylinder 8 is connected to the bottom of the stirring needle 10. 14 is a concave conical surface, and at least three spiral grooves 13 are evenly distributed on the conical surface of the stirring needle 10. The top of the stirring needle 10 is shaped on a hemispherical groove 11, and the spiral groove 13 on the stirring needle is connected with the hemispherical groove. 11 intersect, at least three notches are formed on the edge of the semicircular groove 11 at the top of the conical stirring needle 10. The included angle between the normal of the concave tapered surface of the shaft shoulder 14 and the axis of the stirring needle 10 is 5-15 degrees, and the helix angle of the helical groove 13 is 55-65 degrees. The depth of the hemispherical groove 11 is 3-4mm. The shape of the spiral groove 12 is a concave semicircle with a depth of 2-3mm. The spiral groove 12 can also be a triangular cross-section, the triangular cross-section is 54 degrees, and the depth is 2-3 mm.

This structure strengthens the plastic flow of metal during friction stir welding of L-shaped aluminum alloy profiles, and uses the specially increased heat generation of metal flow to improve the heat shortage of the lower plate caused by the heat transfer problem of double-layer plates during friction stir welding. It solves the special requirements of friction stir welding process on the welding parts that need contact friction. After the L-shaped aluminum alloy profile is added with auxiliary pads 3 and 4, the heat transfer problem of the double-layer plate is improved, and the high-quality connection of the L-shaped profile is realized. The heat generated by the plastic flow of metal during the welding process is mainly produced by the extrusion of the special-shaped stirring pin 10 in front of the stirring head 5 during the welding process, and at least 3 spiral grooves 13 processed on the conical stirring pin 10 , which increases the flow of plastic metal from bottom to top. When the flowing metal flows upward, it encounters the concave shoulder 14. Under the resistance of the concave shoulder 14, the metal moves downward again. At this time, the flow The metal forms a flow field that is closed from bottom to top and from top to bottom, causing the plastic metal to form a violent movement. According to the principle of plastic metal processing, the violent movement of plastic metal will generate a lot of heat. At the same time, the top of the conical stirring pin 10 is processed into a semicircular groove 11, and intersects with the spiral groove 13, and 3 gaps are formed on the edge of the semicircular groove 11 at the top of the conical stirring pin 10, which is convenient for Plastic metal flows out and in through the gap.

During welding, the L-shaped aluminum alloy profile 1 and the auxiliary pads 3 and 4 are clamped on the welding workbench by a special clamp, the stirring head 2 rotates from point C and inserts the auxiliary pad 3, and then starts welding. At this time, the L-shaped aluminum alloy profile 1 and the auxiliary pads 3 and 4 form an integral structure in the thickness direction, and the heat transfer of the heat generated by the rotational friction of the shaft shoulder 14 of the stirring head 2 can be carried out continuously. When the stirring head 2 reaches At point A, there are already two layers in the thickness direction, that is, the L-shaped aluminum alloy profile and the auxiliary pad 3, because there is an air layer interface at the joint between the L-shaped profile 1 and the auxiliary pad 3, and the air is A poor conductor of heat, so heat transfer between two layers of metal is difficult. The auxiliary pad 3 at the bottom is prone to the problem of not being welded due to insufficient heat, but the auxiliary pad 3 below is a process pad, which needs to be removed by machining after welding, so the welding quality of the pad is not good or bad. relation. After the stirring head 2 reaches point D, the L-shaped aluminum alloy profile has been welded.

Below is a practical application example that adopts device of the present invention to carry out welding:

Through experimental verification, when welding, after adopting the stirring head of the present invention, when the rotating speed of the stirring head is at a lower rotating speed of 600 rpm, a weld seam with good welding quality can be obtained, while the rotating speed of the existing stirring head must reach 1000 rpm, and the welding effect is not satisfactory.

In addition to the above-mentioned embodiments, the present invention can also have other implementations, such as the direction of rotation of the spiral groove, etc. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims (7)

1. A welding tool for friction stir welding, comprising a rear cylindrical connector (7), a middle cylinder (8), a stirring pin (10) at the front; the cylindrical connector (7) is shaped on The anti-loose fastening platform (6), the middle cylinder (8) is made with a heat dissipation spiral groove (9); it is characterized in that: the stirring pin (10) at the front part of the welding tool is conical, and the conical The surface is shaped with a spiral groove (12); the shoulder (14) where the end of the middle cylinder (8) is connected to the bottom of the stirring needle (10) is a concave conical surface, and the conical surface of the stirring needle (10) At least three helical grooves (13) are uniformly distributed on the top, and a hemispherical groove (11) is formed on the top of the stirring needle (10). 2. A welding tool for friction stir welding according to claim 1, characterized in that: the spiral groove (12) on the stirring needle (10) intersects with the hemispherical groove (11), and the conical At least three notches are formed on the edge of the top semicircular groove of the stirring needle (10). 3. A welding tool for friction stir welding according to claim 1, characterized in that: the included angle between the normal line of the concave conical surface of the shoulder (13) and the axis of the stirring needle (10) is 5-15 Spend. 4. A welding tool for friction stir welding according to claim 1 or 2, characterized in that: the helix angle of the helical groove (13) is 55-65 degrees. 5. A welding tool for friction stir welding according to claim 1, characterized in that: the depth of the hemispherical groove (11) is 3-4mm. 6. A welding tool for friction stir welding according to claim 1, characterized in that: the shape of the spiral groove (9) is a concave semicircle, and the depth is 2-3 mm. 7. A welding tool for friction stir welding according to claim 6, characterized in that: the spiral groove (9) may also have a triangular cross-section, the triangular cross-section is 54 degrees, and the depth is 2-3mm.

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