CN110640296A - Friction stir welding stirring head capable of improving material flowing behavior - Google Patents

Abstract

The invention relates to a stirring head for friction stir welding with improved material flow behavior, comprising a stirring head shaft, a shaft shoulder and a stirring needle. The first inner groove and the second inner groove are mirror-symmetrical about the central axis plane of the stirring head. In the process of friction stir lap welding, the invention can drive the material in a plastic state to move up and down, which can not only reduce or even eliminate the hook-like structure and cold lap defects that are easy to appear at the lap interface, but also can strengthen the medium Metallurgical or non-metallurgical dissimilar materials friction stir welding is mechanically interlocked at the connection interface, so the mechanical properties of the friction stir lap welding joint can be effectively improved; at the same time, the stirring head of the present invention has the same effect when rotating clockwise and counterclockwise, avoiding It solves the problem of poor quality of the joint caused by the wrong setting of the rotation direction of the stirring head during use.

Description

A stirring head for friction stir welding with improved material flow behavior

technical field

The invention belongs to the technical field of friction stir welding, and in particular relates to a stirring head for friction stir welding with improved material flow behavior.

Background technique

Friction stir welding (FSW) is a new type of solid phase welding technology proposed by the Welding Research Institute in the United Kingdom in 1991. It has the advantages of high quality, energy saving, and no pollution. field. During the welding process, the stirring head generates heat through friction with the base metal and realizes the plastic flow of the metal, thereby achieving the connection to the base metal. Therefore, the stirring head is the core of friction stir welding technology, and its structural design has an important influence on the flow behavior of plasticized metal.

At present, in the process of friction stir lap welding (FSLW), the way of arranging threads on the surface of the conical stirring head is often used to promote the downward flow of the material. However, when the commonly used agitator head with a single thread direction is welded, the material will continue to accumulate at the lower part of the lap interface on the advancing side to form a material concentration area, which will produce upward extrusion force on the interface, resulting in the formation of an upwardly curved hook. On the backward side, the material of the upper plate migrates from the forward side to the backward side under the action of the rotating shoulder to fill the transient cavity left by the passing of the stirring head. The flowing material also squeezes the lap interface, resulting in a cold lap that bends up and down on the receding side. The larger hook structure and cold lap structure will reduce the effective lap width (ELW) and effective lap thickness (EST) of the joint, which will affect the tensile and shear performance of the joint; in addition, a single rotation direction When the rotation direction (forward or reverse) of the agitator head is set incorrectly, it will affect the flow of the material, resulting in the generation of holes, incomplete penetration, and large flash defects. The expected effect cannot be obtained, and the bearing capacity of the joint is greatly reduced.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the present invention provides a friction stir welding stirrer for improving the flow behavior of materials, which can improve the morphological characteristics of the lap interface and enhance the mixing degree between the upper and lower plate materials by regulating the flow of the material, and at the same time, the The stirring head proposed by the invention can also overcome the defects of holes, incomplete penetration and large flash caused by wrong setting of the rotating direction of the stirring head.

A stirring head for friction stir welding with improved material flow behavior comprises a stirring head shaft, a shaft shoulder and a stirring needle. The left and right sides of the stirring needle surface are respectively provided with a first inner groove and a second inner groove.

The first inner groove and the second inner groove are mirror-symmetrical about the central axis plane of the stirring head.

The first inner indentations are arranged obliquely to the upper left, and the second inner indentations are arranged obliquely to the upper right.

The inclination angle of the first inner groove and the second inner groove relative to the shaft shoulder surface is 5°˜85°.

The beneficial effects of the present invention are: by arranging the first inner indentation and the second inner indentation on the stirring needle, the following beneficial effects are obtained:

1. Compared with the traditional threaded stirring needle, the mirror-symmetrically arranged first and second internal grooves on the stirring needle in the present invention can drive the material to flow alternately up and down during the stirring process, avoiding the generation of material at the tip of the stirring needle The concentrated area reduces or even eliminates the hook-like structure and cold lap defects, and at the same time can widen the width of the weld nugget area, which is beneficial to increase the effective lap width, thereby improving the tensile and shear strength of the joint;

2. The present invention can improve the internal forming of the joint, effectively enhance the mechanical interlocking effect of friction stir welding of medium metallurgical or non-metallurgical dissimilar materials near the lap interface, and is beneficial to improve the strength of the lap joint;

3. The mirror-symmetrical arrangement of threads in the present invention enables the stirring needle to obtain the same material flow behavior when it rotates clockwise or counterclockwise, which avoids holes, Incomplete penetration and large flash defects, resulting in poor joint quality;

4. The present invention can adjust the flow mode of the material by changing the parameters such as the length, width, position, and inclination angle of the first inner groove and the second inner groove, not only the bending direction and position of the hook-shaped structure can be adjusted, but also The adjustment of the position of the intense material mixing zone is realized, which is beneficial to improve the strength of the joint.

Description of drawings

Fig. 1 is the overall structure schematic diagram of the present invention;

Fig. 2 is the schematic diagram of the first inner concave pattern in the present invention;

3 is a schematic diagram of a second inner concave pattern in the present invention;

4 is a schematic diagram of material flow during welding of 2024-T4/7075-T6 dissimilar aluminum alloys provided in Example 1;

5 is a schematic diagram of the cross-sectional morphology of the 2024-T4/7075-T6 dissimilar aluminum alloy joint provided in Example 1;

in,

1 stirring head shaft, 2 shaft shoulder, 3 stirring needle, 4 first inner groove, 5 second inner groove.

Detailed ways

In order to better explain the present invention and facilitate understanding, the technical solutions and effects of the present invention will be described in detail below with reference to the accompanying drawings and through specific embodiments.

Example 1

As shown in Figure 1-3, a stirrer for friction stir welding that improves material flow behavior includes a stirrer shaft 1, a shaft shoulder 2 and a stirrer pin 3. The left and right sides of the stirrer pin 3 are respectively provided with first inner grooves 4 and the second inner groove 5, the first inner groove 4 and the second inner groove 5 are mirror-symmetrical about the central axis of the stirring head. As shown in Fig. 2, the first concave pattern 4 is composed of several concave lines, and the concave lines are parallel to each other and are arranged obliquely to the upper left. The inclination angle of the first concave pattern 4 relative to the shaft shoulder surface is 5°～85°; as shown in FIG. 3 , the second concave pattern 5 is composed of several concave lines, and the concave lines are parallel to each other and arranged obliquely upward to the right, and the second concave pattern 5 is relative to the shaft. The inclination angle of the shoulder surface is 5° to 85°. In this embodiment, there are four concave lines in the first concave groove 4 and the second concave groove 5, and the inclination angle with the shoulder surface is 45°.

The friction stir lap welding test was performed on 2024-T4/7075-T6 dissimilar aluminum alloys using a friction stir welding stirrer with improved material flow behavior provided in this example, and the upper and lower plate thicknesses were both 3 mm. As shown in FIG. 4 , during the welding process using the counterclockwise rotating stirring pin 3 , the second indentation 5 drives the material to flow downward, while the first indentation 4 drives the material to flow upward.

The driving form of the stirring needle 3 for one rotation of the material can be divided into two stages: as shown in Figure 4(a), in the first stage, when the stirring needle 3 starts to rotate from the 0° orientation, the second inner groove 5 and the first An inner groove 4 is located on the advancing side and the retreating side respectively. At this time, the material on the advancing side flows downwards driven by the upsetting force of the shaft shoulder 2 and the second inner indentation 5, and the material reaches the backward at the bottom of the stirring needle 3 from the forward side. On the lap side, most of the materials that should be gathered on the retreating side flow upwards driven by the first inner concave grooves 4, and the remaining materials form a small upward extrusion effect on the overlapping interface. As shown in Figure 4(b), when the stirring needle 3 rotates to the 90° orientation, the second inner groove 5 of the stirring needle 3 gradually transitions from the forward side to the backward side, and the first inner groove 4 moves from the backward side to the forward side. During the transition, the second inner groove 5 drives the material to flow downward, and the material on the front advancing side is transferred from the bottom of the stirring needle 3 to the retreating side, the material gathered on the retreating side reaches the peak, and the bending degree of the cold lap structure reaches the maximum. The stirring needle 3 continues to rotate, and the material flow on the forward side and the backward side is respectively dominated by the second indentation 5 and the first indentation 4 in the previous stage, and gradually transitions to being dominated by the first indentation 4 and the second indentation respectively. The inner concave grooves 5 are dominant, and at this time, the driving of the material by the stirring needle 3 enters the next stage.

In the second stage, after the stirring needle 3 is gradually rotated to 180°, the material on the forward side of the joint is completely driven by the first inner groove 4 to flow upward, and the material transferred at the bottom of the weld nugget from the forward side to the backward side is also reduced, and the backward side The upward extrusion force of the interface bearing material becomes smaller, and the material on the upper part of the retreating side of the weld nugget flows downward under the driving of the second inner groove 5 and the shaft shoulder 2 to squeeze the cold lap structure. After the stirring needle 3 is further rotated to 270°, the first inner groove 4 gradually transitions from the forward side to the backward side, and the second inner groove 5 transitions from the backward side to the forward side. Half of the concave grooves 5 are located on the forward side and half are located on the backward side. At this time, the cold lap joint structure on the backward side only exhibits a slightly upward curved shape.

During the welding process, with the continuous rotation of the stirring needle 3, the overlapping interface is continuously bent up and down to form a zigzag bonding interface; The advancing side and the retreating side are constantly alternated, and the material does not flow continuously in the same form, and no obvious material concentration area can be formed. Therefore, there is no material pressing upward on the lap interface on the advancing side of the joint, and the interface finally presents a flat appearance. As shown in the cross-sectional morphology of the 2024-T4/7075-T6 dissimilar aluminum alloy joint in Figure 5, the hook-like structure is eliminated, the cold lap structure is shortened, and the lap interface presents a good mechanical interlocking feature.

Claims (4)

1. a stirring head for friction stir welding for improving material flow behavior, comprising a stirring head shaft, a shaft shoulder and a stirring needle, it is characterized in that: the left and right sides of the stirring needle surface are respectively provided with the first indentation and the second indentation . 2 . The stirrer for friction stir welding with improved material flow behavior according to claim 1 , wherein the first indentation and the second indentation are mirror-symmetrical about the central axis of the stirrer. 3 . 3 . The friction stir welding stirrer for improving material flow behavior according to claim 1 , wherein the first inner indentations are arranged obliquely to the upper left, and the second inner indentations are arranged obliquely to the upper right. 3 . . 4 . The friction stir welding stirring head for improving material flow behavior according to claim 2 , wherein the inclination angle of the first inner groove and the second inner groove relative to the shaft shoulder surface is 5. 5 . °～85°.

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