JP5426923B2 - Friction stir welding tool and joining method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a fixed pin type welding tool for friction stir welding of overlapped materials to be joined and a joining method using the joining tool, and in particular, using a joining tool in which an annular groove is formed on a stirring shaft. The present invention relates to a joining tool and a joining method for improving the joining effect of the friction stir welding performed.

  In the friction stir welding for the joint portion where a set of materials to be joined is overlapped, the joining boundary surface is joined using a fixed pin type joining tool as shown in FIG. The joining tool 100 includes a cylindrical tool body 101 and a pin-shaped stirring shaft 102 protruding downward from a shoulder surface 110 at the lower end thereof. In the friction stir welding, the stirring shaft 102 of the welding tool 100 is inserted while being rotated into a joining portion 210 where the materials 201 and 202 are stacked. The shoulder surface 110 is pressed against the upper surface of the material to be joined 201, and the joining tool 210 advances while rotating while the joining portion 210 is pressurized. In the joining portions 210 of the materials to be joined 201 and 202, the material softened by the frictional heat of the stirring shaft 102 is plastically fluidized, and the plastic material mixed with each other behind the stirring shaft 102 loses frictional heat and rapidly cools and solidifies. Are joined.

  By the way, in the friction stir welding with respect to the materials 201 and 202 that are stacked one above the other, the flow of the material by the friction stir does not only flow parallel to the rotation direction of the stirring shaft 102 but also moves up and down via the joint boundary surface 220. It is preferable to generate a flow. In the following Patent Document 2, a spiral screw is specifically described on the surface of the stirring shaft, and other reference is made to the annular groove and the rough surface. If the softened material fluctuates in the vertical direction by devising the surface shape of the stirring shaft in this way, the oxide film on the bonding boundary surface 220 that hinders bonding is easily broken, and more stable bonding quality can be obtained. is there. In addition, the oxide film is not only destroyed, but also greatly affects the plastic flow of the material generated in the joint portion 210 and affects the joining efficiency.

JP 2006-192501 A JP 11-28581 A

  Friction stir welding is a joining method that does not use a filler metal, unlike fusion welding. Therefore, it is the material itself of the softened materials 201 and 202 that fills the gap between the bonding boundary surfaces 220. However, if the gap becomes large without filling the filler material from the outside, the softened material becomes the gap. Insufficient flow into the metal leads to poor bonding. As a countermeasure against this problem, in addition to bringing the joint boundary into close contact, it is possible to cause a plastic flow such that the softened material sufficiently flows into the joint boundary surface 220.

Therefore, the inventor of the present application paid attention to an annular groove that does not cause a material flow in one vertical direction, such as a screw, on the surface shape of the stirring shaft, but causes a material flow in both the vertical direction. According to the stirring shaft having an annular groove formed on the surface, in addition to causing a material flow in the rotation direction, a vertical flow along the axial direction is also generated. However, in the conventional welding tool and the joining method, with respect to the flow of such vertical material, it has not been considered until either partially of any flow varies with the position of the annular groove peaks and valleys occurs. Then, this inventor examined the relationship between the joining boundary surface of the to-be-joined materials overlapped, and the annular groove formed in a stirring shaft.

  An object of the present invention is to provide a joining tool and a joining method for friction stir welding having a high joining effect based on the relationship between the annular groove of the stirring shaft and the joining boundary surface.

A welding tool for friction stir welding according to the present invention is a tool in which a pin-shaped stirring shaft is projected from a shoulder surface of a tool body, and the shoulder surface is pressed against a joint portion in which materials to be joined are stacked. Friction stir welding is performed by plastically flowing the material of the joint portion by the stirring shaft, and the stirring shaft has a plurality of trough portions in the axial direction that are annular grooves in a direction perpendicular to the axial direction on the surface. And having a plurality of crests between the adjacent valleys, and in the state at the time of the friction stir welding, the joint boundary surface of the stacked materials to be joined is viewed from the tip of the stirring shaft. all SANYO only one mountain portion was positioned, characterized in that to the tip of the stirring shaft from the first crest in which the diameter of the stirring shaft is changed in the direction to become smaller.

In the joining method of friction stir welding according to the present invention, a pin-like stirring shaft protrudes from the shoulder surface of the tool body, and a plurality of troughs that are annular grooves in the direction perpendicular to the axial direction are formed in the axial direction on the stirring shaft surface. A plurality of peaks are formed between the adjacent valleys, and the diameter of the stirring shaft decreases from the first peak to the tip of the stirring shaft when viewed from the tip of the stirring shaft. Using the welding tool that changes to the above, the shoulder surface is pressed against the joint portion where the materials to be joined are stacked, and the material of the joint portion is plastically flowed by the stirring shaft to perform friction stir welding. The welding tool in a state where the shoulder surface is pressed against the material to be joined and only the first peak portion of the stirring shaft is positioned on the joining boundary surface between the materials to be joined. And rotate in the specified direction along the joint. Characterized in that to the row.

  According to the present invention, since the position of the peak portion due to the annular groove is aligned with the joint boundary surface, during friction stir welding, the material gathers from above and below the joint boundary surface of the overlapped materials to be joined. Even if there is a gap in the surface, the material flows into the surface, and the bonding with the bonding strength secured becomes possible. In addition, the lower part of the joint boundary surface can be obtained by making the peak part located at the joint boundary surface the first peak part when viewed from the tip of the stirring shaft, or by further changing the diameter from the peak part to the tip. Then, the material moves greatly up and down, and by effectively destroying the oxide film on the bonding interface that hinders bonding, bonding with more stable quality becomes possible.

It is the side view which showed the stirring axis | shaft with the joining tool of embodiment and another joining tool. It is the figure which showed the simulation result of the friction stir welding by the welding tool of embodiment about the flow of the material of the stirring axis vicinity in the graph. It is the figure which showed the simulation result of the friction stir welding by the other welding tool about the flow of the material of the stirrer shaft vicinity. It is the figure which visualized and showed the simulation result about the flow of the material of the joining boundary surface by friction stir welding. It is the perspective view which showed the friction stir welding with respect to the lap joint using the fixing tool of a fixed pin type | mold.

  Next, an embodiment of a welding tool and a joining method for friction stir welding according to the present invention will be described below with reference to the drawings. The joining tool of the present embodiment is a cylindrical tool body and a fixed pin type with a stirring shaft protruding from the shoulder surface at the lower end thereof, similar to the conventional example shown in FIG. Friction stir welding is performed with respect to the joint portion 210 of the overlapped workpieces 201 and 202. FIG. 1 is a view showing the joining tool of the present embodiment compared with other joining tools, and in particular, only the stirring shaft which is a characteristic of the tool main body is omitted.

  The agitation shafts 1 and 2 of the welding tool shown in FIGS. 1 (a) and 1 (b) are formed with a plurality of upper and lower annular grooves 10 on the surface thereof. 12 alternately exist in the axial direction (up and down). In FIG. 1, the height position of the shoulder surface 5 is aligned for both the joining tools of the stirring shafts 1 and 2, and a joining boundary surface 21 (not shown) between the materials to be joined (corresponding to the joining boundary surface 220 shown in FIG. 5). Are shown to be the same height. And both the stirring shafts 1 and 2 are the same shaft diameter and length, Comprising: The pitch of the annular groove 10 is also formed by the same dimension.

  However, the annular groove 10 formed in the stirring shafts 1 and 2 is different in the axial position of the valley portion 11 and the mountain portion 12 due to this, so that the connecting portions 15 and 25 to the shoulder surface 5 and the lower end The shapes of the parts 16 and 26 are different. The agitation shaft 1 shown in FIG. 1A is the present embodiment, and the agitation shaft 2 shown in FIG. 1B is a comparative example. The difference is that the agitation shaft 1 is located at the position of the joining interface 21. The crest 12 by the annular groove 10 is located, and the stirring shaft 2 is that the trough 11 is located at the joining boundary surface 21.

The joining tool of the present embodiment is formed so that the crest 12 formed on the stirring shaft 1 can be adjusted to the height of the joining interface 21. In particular, among the crests 12 formed by the plurality of annular grooves 1, the first crest 12 a is formed so as to match the height of the joint boundary surface 21 when viewed from the lower end surface 17. Therefore, the stirring shaft 1 has the thickness dimension of the upper material to be joined from the shoulder surface 5 to the center of the peak portion 12a, and the portion from the center to the tip of the peak portion 12a enters the lower material to be joined. . One of the stirring shaft 2, and the middle position of the height valley 11 of the bonding interface 21, the lower end portion 26 is shaped having a diameter spread toward the lower end face 27.

  Next, FIG. 2 and FIG. 3 are diagrams showing simulation results of friction stir welding using the welding tools for the stirring shafts 1 and 2. In particular, FIG. 2 shows the flow of the material to be joined generated in the vicinity of the stirring shafts 1 and 2, FIG. 2 shows the case of the stirring shaft 1 of the present embodiment, and FIG. 3 shows the stirring shaft 2 of the comparative embodiment. Shows the case. In each graph, the vertical axis indicates the position of the material to be joined, and the horizontal axis indicates the speed of the material. As for the position of the vertical axis, the zero point is the position of the lower end surfaces 17 and 27 of the stirring shafts 1 and 2, and the position indicated by the two-dot chain line located above is the joint boundary surface 21. As for the velocity on the horizontal axis, a positive value indicates an upward flow, and a negative value indicates a downward flow.

The solid line and the broken line shown in the graphs of FIG. 2 and FIG. 3 correspond to the side shapes of the stirring shafts 1 and 2 shown in FIG. A thick broken line indicates a minimum diameter position of the valley portion 11. By the way, in FIG.2 and FIG.3, the direction of the material flow of the to-be-joined material corresponding to the side shape of the stirring shafts 1 and 2 is typically shown by the arrow.
In the friction stir welding by the stirring shafts 1 and 2 having the annular groove 10, a flow from the vertical direction occurs toward the peak portion 12, and conversely, in the valley portion 11, the material flows from the portion in the vertical direction. ing. Accordingly, it can be seen from this that the surrounding material tends to be drawn from the vertical direction to the mountain portion 12 while the material tends to be separated from the valley portion 11.

  Moreover, the thin line of the vertical axis | shaft zero position shown to the graph of FIG.2 and FIG.3 has shown the position corresponding to the lower end surfaces 17 and 27 of the stirring shafts 1 and 2. FIG. Comparing the stirring shafts 1 and 2 with respect to the flow of the material generated at the positions of the lower end surfaces 17 and 27, it can be seen that both values are positive and an upward flow is generated. And the flow has a larger value in the stirring shaft 1 of this embodiment, and it turns out that the strong flow has arisen upwards rather than the stirring shaft 2 of a comparison form.

Here, FIG. 4 is a visualization of the plastic flow of the material in the joint portion of the material to be joined by simulation, and the result of the particles arranged on the joining boundary surface of the material to be joined moved by agitation is shown by particle trace. Is. FIG. 4 (a) shows the result of friction stirring with the welding tool provided with the stirring shaft 1 of the present embodiment, and FIG. 4 (b) shows the result of friction stirring with the welding tool provided with the stirring shaft 2 of the comparative embodiment. It is. And in any case, the two-dot chain line shown in the figure has shown the position of the joining boundary surface 21 by a to-be-joined material.

  From the simulation results shown in FIG. 4, the particles in the case of the stirring shaft 1 shown in FIG. 4A are more distributed below the bonding interface 21 than the stirring shaft 2 in FIG. Yes. This is considered to be caused by the downward flow caused by the counter flow accompanying the strong upward flow occurring near the lower end surface 17 shown in FIG. From this, the stirring shaft 2 in FIG. 4B has a small movement of the material of the joining boundary surface 21, whereas the stirring shaft 1 shown in FIG. You can see that it is moving.

  Next, as shown in P1 and P2 in FIGS. 2 and 3, the material flow at the joining interface 21 has a large upward flow rate on the stirring shaft 2, and the stirring shaft 1 has a flow rate close to zero. Show. Therefore, the material in the upper and lower ranges sandwiching the joining boundary surface 21 moves upward on the stirring shaft 2 as a whole. Then, as shown in FIG. 4B, the particles flow to the upper side of the bonding boundary surface 21 and are distributed, and the material flows into the bonding boundary surface 21 from the lower material to be bonded. On the other hand, although the particles are slightly raised in the stirring shaft 1, it is considered that the material is gathered near the joint boundary surface 21 corresponding to the peak portion 12.

  Therefore, as shown in FIG. 1, the welding tool of the present embodiment has a plurality of annular grooves 10 formed on the stirring shaft 1 protruding from the shoulder surface 5 of the tool body. In particular, the first peak 12a from the lower end surface 17 of the stirring shaft 1 is formed so as to be positioned on the joining boundary surface 21 of the overlapped materials to be joined. Therefore, the dimension h1 from the shoulder surface 5 to the center of the peak portion 12a is formed in accordance with the thickness dimension of the materials to be joined that are stacked from above. In addition, the dimension h2 below the peak portion 12a may be at any position on the valley portion 11 as long as the peak portion 12a becomes the first peak portion, but the lower end surface 17 as in the present embodiment. Is preferably the smallest diameter. That is, it is preferable that the diameter of the stirring shaft 1 changes so as to decrease toward the lower end surface 17.

Then, the friction stir welding performed by the welding tool having the stirring shaft 1 is performed while rotating the welding tool with respect to the bonding portion 210 of the workpieces 201 and 202 stacked vertically as shown in FIG. The stirring shaft 1 is inserted from the upper side, and the shoulder surface 5 is pressed against the upper surface of the upper material to be joined 201. At this time, the lower end portion 16 of the stirring shaft 1 enters the lower material to be joined 202, and the first peak portion 12a as seen from the lower end surface 17 becomes the joining boundary surface 220 (the joining boundary surface 21 in FIG. 1). To position. Then, the joining tool advances along the joining portion 210 while rotating. At that time, while applying a load to the material to be joined 201 and 202 through the shoulder surface 5, a stirring shaft 1 junction 210 material is softened plastically fluidized by frictional heat, intermingled with one another at the rear of the stirring shaft 1 The plastic material loses frictional heat and rapidly cools and solidifies.

  Therefore, in the friction stir welding by the joining tool and the joining method of the present embodiment, the flow of collecting the material in the vicinity of the joining boundary surface 21 is created by positioning the peak portion 12a by the annular groove 10 with respect to the joining boundary surface 21. . For this reason, even if there is a gap in the bonding boundary surface 21, the material flows into the gap and fills the gap, thereby enabling stable bonding with ensuring bonding strength. In addition to the material gathering on the bonding interface 21, the material moves greatly up and down below the bonding interface 21, thereby effectively destroying the oxide film on the bonding interface 21 that hinders bonding. , More stable quality bonding becomes possible.

Above, although the embodiments the bonding tool and a bonding method of friction stir welding according to the present invention, the present invention is not limited thereto, Ru can der various changes without departing the spirit .
Moreover, although the some annular groove 10 was formed in the stirring shaft 1 of the said embodiment, for example, the shape which left only the 1st peak part 12a seeing from the lower end surface 17, and abbreviate | omitted the other peak part 12 was used. A stirring shaft may be used.

DESCRIPTION OF SYMBOLS 1 Stirring shaft 5 Shoulder surface 10 Annular groove 11 Valley part 12, 12a Mountain part 16 Lower end part 17 Lower end surface 21 Joining interface surface 201,202 Joined material 210 Joining part 220 Joining interface surface

Claims (2)

A pin-shaped stirring shaft is protruded from the shoulder surface of the tool body, and the shoulder surface is pressed against the joint portion where the materials to be joined are stacked, and the material of the joint portion is plastically flowed by the stirring shaft. In a welding tool for friction stir welding,
The stirring shaft has a plurality of troughs in the axial direction on the surface in a direction perpendicular to the axial direction, and has a plurality of crests between the adjacent troughs, during the friction stir welding in the state state, and are those that only the first crest watching the superimposed on the bonding interface between the bonding material from the tip of the stirring shaft is located, said from the first crest A welding tool for friction stir welding, wherein the diameter of the stirring shaft changes in a direction of decreasing toward the tip of the stirring shaft . A pin-shaped stirring shaft protrudes from the shoulder surface of the tool body, and a plurality of valleys that are annular grooves are formed in the axial direction in the direction orthogonal to the axial direction on the surface of the stirring shaft. Using a welding tool that changes in a direction in which the diameter of the stirring shaft decreases from the first peak portion to the tip of the stirring shaft when viewed from the tip of the stirring shaft. A method of pressing the shoulder surface against a joint portion where materials are stacked, and friction stir welding by plastically flowing the material of the joint portion with the stirring shaft,
The shoulder surface is pressed against the material to be joined, and the joining tool is rotated in a state where only the first peak portion of the stirring shaft is positioned on the joining boundary surface between the materials to be joined. And a friction stir welding method characterized in that the method proceeds in a predetermined direction along the joint.

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