CN110640296A

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

Info

Publication number: CN110640296A
Application number: CN201910915501.5A
Authority: CN
Inventors: 岳玉梅; 李清华; 姬书得; 牛士玉; 宋崎; 马琳; 杨康; 龚鹏; 熊需海
Original assignee: Shenyang Aerospace University
Current assignee: Shenyang Aerospace University
Priority date: 2019-09-26
Filing date: 2019-09-26
Publication date: 2020-01-03

Abstract

The invention relates to a stirring head for friction stir welding, which improves the flowing behavior of materials and comprises a stirring head shaft, a shaft shoulder and a stirring pin, wherein the left side and the right side of the surface of the stirring pin are respectively provided with a first inner concave grain and a second inner concave grain, and the first inner concave grain and the second inner concave grain are in mirror symmetry relative to the central axial surface of the stirring head. In the friction stir lap welding process, the material in a plastic state can be driven to do up-and-down secondary motion, so that the defects of hook-shaped structures and cold lap joint which are easy to appear at a lap joint interface can be reduced or even eliminated, and the mechanical interlocking of friction stir welding of medium-metallurgy or non-metallurgy dissimilar materials at a connection interface can be enhanced, so that the mechanical property of a friction stir lap welding joint can be effectively improved; meanwhile, the stirring head has the same effect when rotating clockwise and anticlockwise, so that the problem of poor joint quality caused by wrong setting of the rotation direction of the stirring head in the use process is solved.

Description

Friction stir welding stirring head capable of improving material flowing behavior

Technical Field

The invention belongs to the technical field of friction stir welding, and particularly relates to a stirring head for friction stir welding, which is used for improving the flowing behavior of materials.

Background

Friction Stir Welding (FSW) is a novel solid phase welding technique proposed in 1991 by the british welding institute, has the advantages of high quality, energy saving, no pollution and the like, and is widely applied to the fields of aviation, aerospace, automobiles, ships and the like. In the welding process, the stirring head generates heat through friction with the base metal to realize plastic flow of metal, so that the base metal is connected. Therefore, the stirring head is the core of the friction stir welding technology, and the structural design of the stirring head has an important influence on the flow behavior of the plasticized metal.

Currently, in Friction Stir Lap Welding (FSLW), a thread is placed on the surface of a conical pin to promote downward flow of material. However, when a commonly used stirring head with a single thread direction is used for welding, materials are continuously gathered at the lower part of a lapping interface on the advancing side to form a material gathering area, and an upward extrusion force is generated on the interface, so that a hook-shaped defect which bends upwards is formed at the position; and on the backward side, the upper plate material moves from the forward side to the backward side under the action of the rotating shaft shoulder so as to fill an instantaneous cavity left by the stirring head after passing through, and when the material concentration area upwards extrudes the interface, the downward flowing materials can also extrude the lap joint interface, so that the backward side finally forms a cold lap joint structure which is bent up and down. The larger hook-shaped structure and the cold lap joint structure can reduce the Effective lap joint width (ELW) and the Effective lap joint thickness (EST) of the joint, and influence the pull-shear performance of the joint; in addition, the single-handed thread can affect the material flow when the rotation direction (forward or reverse) of the stirring head is set to be wrong, so that the defects of holes, incomplete welding and large burrs are generated, the expected effect cannot be obtained, and the bearing capacity of the joint is greatly reduced.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the stirring head for friction stir welding, which improves the material flow behavior, improves the appearance characteristic of a lap joint interface and enhances the mixing degree between an upper plate material and a lower plate material by regulating and controlling the material flow, and simultaneously can overcome the defects of holes, incomplete welding and large flash caused by the error setting of the rotation direction of the stirring head.

The utility model provides an improve material flow behavior's friction stir welding and use stirring head, includes stirring head axle, shaft shoulder and stirring pin, and the stirring pin surface left and right sides sets up first indent line and second indent line respectively.

The first inner concave veins and the second inner concave veins are mirror-symmetrical about the central axial plane of the stirring head.

The first inner concave grains are obliquely arranged towards the upper left, and the second inner concave grains are obliquely arranged towards the upper right.

The inclination angles of the first inner concave grains and the second inner concave grains relative to the shaft shoulder surface are 5-85 degrees.

The invention has the beneficial effects that: through set up first indent line and second indent line on the pin, obtained following beneficial effect:

1. compared with the traditional threaded stirring pin, the first inner concave grains and the second inner concave grains which are symmetrically arranged on the stirring pin in a mirror image manner can drive materials to flow in an up-and-down cross mode in the stirring process, so that a material concentration area is prevented from being generated at the tip of the stirring pin, the defects of a hook-shaped structure and cold lap joint are reduced or even eliminated, meanwhile, the width of a welding core area can be widened, the effective lap joint width is favorably improved, and the pull-shear strength of a joint is further improved;

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

3. the threads arranged in the mirror symmetry mode enable the stirring pin to obtain the same material flowing behavior when rotating clockwise or anticlockwise, and the problem that the quality of a joint is poor due to the defects of holes, incomplete penetration and large burrs caused by the wrong setting of the rotating direction of the stirring pin in the using process of a traditional stirring head is solved;

4. according to the invention, the flowing mode of the material can be regulated and controlled by changing the parameters such as the length, the width, the position, the inclination angle and the like of the first concave line and the second concave line, so that the bending direction and the position of the hook-shaped structure can be regulated, the position of a violent material mixing area can be regulated, and the joint strength can be improved.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

FIG. 2 is a schematic view of a first indent in the present invention;

FIG. 3 is a schematic view of a second indent in the present invention;

FIG. 4 is a schematic material flow diagram of a welding process of 2024-T4/7075-T6 dissimilar aluminum alloys provided in example 1;

FIG. 5 is a schematic cross-sectional view of the 2024-T4/7075-T6 dissimilar aluminum alloy joint provided in example 1;

wherein the content of the first and second substances,

1 stirring head shaft, 2 shaft shoulders, 3 stirring needles, 4 first concave grains and 5 second concave grains.

Detailed Description

For better understanding of the present invention, the technical solutions and effects of the present invention will be described in detail by the following embodiments with reference to the accompanying drawings.

Example 1

As shown in figures 1-3, the stirring head for friction stir welding for improving the material flow behavior comprises a stirring head shaft 1, a shaft shoulder 2 and a stirring pin 3, wherein the left side and the right side of the surface of the stirring pin 3 are respectively provided with a first concave texture 4 and a second concave texture 5, and the first concave texture 4 and the second concave texture 5 are in mirror symmetry with respect to the central axial plane of the stirring head. As shown in fig. 2, the first inner concave grains 4 are composed of a plurality of concave grains, the concave grains are mutually parallel and obliquely arranged towards the upper left, and the inclination angle of the first inner concave grains 4 relative to the shaft shoulder surface is 5-85 degrees; as shown in fig. 3, the second concave veins 5 are composed of a plurality of concave veins which are parallel to each other and obliquely arranged towards the upper right, and the inclination angle of the second concave veins 5 relative to the shaft shoulder surface is 5-85 degrees. In this embodiment, the number of the first concave grains 4 and the second concave grains 5 is 4, and the inclination angle with the shaft shoulder surface is 45 °.

A friction stir lap welding test was conducted on a 2024-T4/7075-T6 dissimilar aluminum alloy using the friction stir welding tip for friction stir welding provided in this example to improve the flow behavior of the material, with the upper and lower plate thicknesses both being 3 mm. As shown in fig. 4, during welding using the counterclockwise rotating pin 3, the second dimples 5 drive the material to flow downward, and the first dimples 4 drive the material to flow upward.

The driving form of the stirring pin 3 for rotating one circle to the material can be divided into two stages: as shown in fig. 4(a), when the pin 3 starts to rotate from the 0 ° orientation in the first stage, the second concave ridges 5 and the first concave ridges 4 are respectively located on the advancing side and the retreating side, the material on the advancing side flows downward under the heading force of the shoulder 2 and the second concave ridges 5, the material reaches the retreating side from the advancing side at the bottom of the pin 3, most of the material which is supposed to be gathered on the retreating side flows upward under the driving of the first concave ridges 4, and the remaining material forms a small upward squeezing effect on the lapping interface. As shown in fig. 4(b), when the pin 3 is rotated to 90 °, the second concave veins 5 of the pin 3 gradually transition from the forward side to the backward side, the first concave veins 4 transition from the backward side to the forward side, and during this process, the second concave veins 5 drive the material to flow downward, and in addition, the material on the forward side is transferred from the bottom of the pin 3 to the backward side, the material gathered on the backward side reaches a peak, and the bending degree of the cold lap joint structure reaches a maximum. The stirring pin 3 continues to rotate, the material flow of the advancing side and the retreating side is respectively dominated by the second concave grains 5 and the first concave grains 4 in the previous stage and gradually transits to be dominated by the first concave grains 4 and the second concave grains 5 respectively, and at the moment, the stirring pin 3 drives the material to enter the next stage.

In the second stage, after the stirring pin 3 rotates to 180 degrees gradually, the material on the advancing side of the joint is driven by the first concave grains 4 to flow upwards completely, the material transferred from the advancing side to the retreating side at the bottom of the nugget is reduced, the extrusion force of the retreating side interface for bearing the material to flow upwards is reduced, and the material on the upper part of the retreating side of the nugget is driven by the second concave grains 5 and the shaft shoulder 2 to flow downwards to extrude the cold lap joint structure. After the stirring pin 3 further rotates to 270 degrees, the first inner concave grains 4 gradually transit from the advancing side to the retreating side, the second inner concave grains 5 gradually transit from the retreating side to the advancing side, finally, half of the first inner concave grains 4 and half of the second inner concave grains 5 are located on the advancing side and half of the second inner concave grains 5 are located on the retreating side, and at the moment, the retreating side cold lap joint structure only presents a slightly upward bending shape.

In the welding process, the lapping interface is continuously bent up and down along with the continuous rotation of the stirring pin 3 to finally form a serrated combined interface; the first inner concave grains 4 and the second inner concave grains 5 which are in mirror symmetry in the welding process are continuously alternated on the advancing side and the retreating side, materials do not continuously flow in the same form, and an obvious material concentration area cannot be formed, so that the situation that the materials extrude and overlap the interface upwards does not occur on the advancing side of the joint, and the interface is finally in a straight shape. As shown in the cross-sectional profile of the 2024-T4/7075-T6 dissimilar aluminum alloy joint in FIG. 5, the hook-like structure is eliminated, the cold lap joint structure is shortened, and the lap joint interface presents good mechanical interlocking characteristics.

Claims

1. The utility model provides an improve material flow behavior's friction stir welding and use stirring head, includes stirring head axle, shaft shoulder and stirring pin, its characterized in that: the left side and the right side of the surface of the stirring pin are respectively provided with a first concave grain and a second concave grain.

2. The friction stir welding tool for improving material flow behavior of claim 1, wherein: the first inner concave veins and the second inner concave veins are mirror-symmetrical about the central axial plane of the stirring head.

3. The friction stir welding tool for improving material flow behavior of claim 1, wherein: the first inner concave grains are obliquely arranged towards the upper left, and the second inner concave grains are obliquely arranged towards the upper right.

4. The friction stir welding tool for improving material flow behavior of claim 2, wherein: the inclination angles of the first inner concave grains and the second inner concave grains relative to the shaft shoulder surface are 5-85 degrees.