Friction stirring coupling device

Abstract

To provide a friction stir welding device using a bobbin type welding tool which can measure a temperature in real time over a thickness direction of a welding part by measuring the temperatures on a front face side and a rear face side of a welding object member.SOLUTION: A friction stir welding device according to the present invention measures a temperature during processing in real time by using a bobbin type welding tool. The bobbin type welding tool comprises: a plurality of channels in a hollow probe which extends to different positions in a vertical direction from at least an upper end to the vicinity of a lower end of the inside of the probe; a channel in a lower shoulder which extends to a position in the vicinity of an upper surface height in a lower shoulder part. Temperature measurement elements are arranged in the vicinity of the lower end of the channels in the probe and the channel in the lower shoulder. The tool further includes transmission means which transmits a temperature measurement result generated by using temperature measurement means from the respective temperature measurement elements.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a friction stir welding apparatus that uses a bobbin - type joining tool capable of measuring the temperature on the front and back surfaces of a joined member having a generally planar shape, thereby enabling real - time temperature measurement over the thickness direction of the joint part.

Background Art

[0002] There is known a friction stir welding apparatus (hereinafter, also referred to as an "FSW (Friction Stir Welding) apparatus") that applies frictional heat with a rotating joining tool to generate a plastic flow phenomenon in a joined member, stirs the joined member, and joins it. Friction stir welding (hereinafter, also referred to as "FSW") is known to have a refined structure and excellent mechanical properties at the joint part because it is a solid - phase joining, unlike ordinary fusion welding, and is used for joining metals that soften at relatively low temperatures, such as aluminum, copper, iron, and their alloys.

[0003] In a general FSW apparatus, processing conditions such as the specifications (material, shape, etc.) of an optimal joining tool, rotation speed (rotational speed), joining speed which is the feed speed, and insertion depth, which are determined in advance according to the material and wall thickness of the joined member, are set in advance, and joining is carried out while maintaining these processing conditions from the start to the end of joining. When examining whether the joining is appropriate and considering the joining conditions, the heat input to the joined member is the most important, and it has been found that it is necessary to achieve uniform and stable plastic flow in the joint part by stirring at an early stage.

[0004] Conventionally, after joining, it is confirmed retrospectively whether the joining is appropriate, and almost no consideration is given to managing the joining temperature from the start point to the end point of joining and the influence of fluctuations in the joining temperature on the joining quality. In contrast, in recent years, FSW apparatuses have been provided that can monitor in real - time and continuously the detailed temperature measurement of the joint part in an ordinary joining tool (see Patent Documents 1 - 3), enabling detection and management of uniform and stable plastic flow in the joint part during joining and obtaining a joining quality over the entire joint part.

[0005] In a typical FSW (Fiber Stabilization Welding) device, the joining tool consists of a shoulder portion that is gripped at the tip of the tool holder and rotates coaxially, and a stirring probe (hereinafter also simply referred to as "probe") that protrudes below the center of the shoulder portion to agitate the joint. In real-time temperature measurement in the conventional FSW device described above, multiple measurement points (measurement channels) are provided within the probe of such a typical joining tool in the thickness direction, and the temperature during joining is measured at each measurement point.

[0006] On the other hand, some FSW devices use a so-called bobbin-type joining tool (spool-type), which, in addition to a shoulder section (upper shoulder section) and probe similar to conventional joining tools, has a lower shoulder section on the back side that sandwiches the member to be joined. This bobbin-type joining tool (hereinafter also simply referred to as "bobbin tool") is characterized by the fact that it can join without requiring a backing jig, and can also follow variations in the thickness of the member to be joined (self-reacting) by changing the amount of tightening of the lower shoulder section, which is tightened and joined with a screw to the lower end of the probe.

[0007] The inventors have discovered the advantages of using this bobbin tool in the process of analyzing the bonding state by FSW in real time and afterward. Specifically, when using a conventional bonding tool, observation of the bonded cross-section of the bonded members reveals that plastic flow progresses in a wine glass-like shape that spreads out on the surface side (the contact side of the upper shoulder), whereas when using the bobbin tool, it has been found that stable and sufficient plastic flow occurs at an early stage, even on the back side of the bonded cross-section (the contact side of the lower shoulder). This is due to the effect of the bobbin tool having a lower shoulder, and it has been inferred that when using the bobbin tool, adjusting the clamping strength between the upper and lower shoulders (and the feed rate during processing), which is set before bonding, is an important factor in obtaining stable plastic flow.

[0008] However, conventional FSW devices that measure temperature in real time, such as those described in Patent Documents 1-3, analyze plastic flow based only on temperature measurements at multiple points with different depths within the probe. Applying this directly to bobbin tools does not measure the temperature of the contact area on the back side (lower shoulder side), making it difficult to optimize the surface contact strength (contact force on the back side) of the lower shoulder and predict processing accuracy and speed. In particular, in bobbin tool FSW, which is useful for joining thick plates and cylindrical shapes that are difficult with conventional FSW, the analysis and optimization of joining conditions are considered to be extremely important, and temperature measurement on the lower shoulder side is essential. The inventors intended to propose this and provide a specific configuration. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] International Publication No. WO2016 / 111336 [Patent Document 2] Japanese Patent Publication No. 2016-42761 [Patent Document 3] Japanese Patent Publication No. 2017-035702 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention was created in view of the above circumstances, and aims to provide a specific configuration for a friction stir welding apparatus that can perform precise temperature measurement in real time over the entire thickness direction of the joined members in friction stir welding using a so-called bobbin-type joining tool, in order to obtain sufficient and stable plastic flow at the joint early on, and can optimize joining conditions such as the tightening strength and amount of the lower shoulder and the feed rate. [Means for solving the problem]

[0011] The present invention, provided to solve the above-mentioned problems, The present invention provides a friction stir welding apparatus that measures the temperature during processing in real time using a bobbin-type joining tool comprising: an upper shoulder portion that rotates around a rotation axis while its lower surface is in contact with the upper surface of the workpiece; a cylindrical probe portion that protrudes downward from the lower surface of the upper shoulder portion; and a lower shoulder portion that is connected to the lower end of the probe and rotates around the same rotation axis while its upper surface is in contact with the lower surface of the workpiece.

[0012] Furthermore, the friction stir welding apparatus of the present invention described above is The bobbin-type joining tool includes at least Within the probe, there are multiple hollow channels extending to different positions in the vertical direction, from the upper end to near the lower end, The lower shoulder portion includes an internal channel that extends within the lower shoulder portion to a position near the height of its upper surface, A temperature measuring element is placed near the lower end of each of the aforementioned probe channels and lower shoulder channels. Furthermore, it includes a transmission means for transmitting the temperature measurement results generated from each temperature measuring element using the temperature measuring means.

[0013] The friction stir welding apparatus of the present invention is a temperature measurement device for FSW using the bobbin tool type welding tool described above. Specifically, similar to conventional welding tools, multiple temperature measurement points are provided at different depths (different positions in the vertical direction) from the upper end to the lower end of the probe, and a temperature measurement point is also provided near the boundary with the member to be joined within the lower shoulder portion on the back side of the member to be joined (near the height of its upper surface within the lower shoulder portion). Temperature information from the multiple temperature measurement points in the probe and the temperature measurement point in the lower shoulder is transmitted wirelessly or by other means, enabling real-time monitoring of the plastic flow during welding across the entire thickness direction of the member to be joined.

[0014] In this way, not only the temperature inside the probe but also the temperature at the top surface height inside the lower shoulder can be determined. This allows for monitoring of plastic flow across the entire thickness direction, and because temperature measurement is based on the lower shoulder side, which fluctuates according to the amount and strength of clamping, the temperature near the bottom surface of the joined member can be monitored regardless of the thickness of the joined member (reducing losses such as estimation calculations). Furthermore, it is possible to precisely monitor the plastic flow according to joining conditions such as the clamping strength and feed rate of the lower shoulder. As a result, it is possible to precisely analyze and optimize the effects of clamping strength and feed rate on joining, which previously relied on empirical rules and past post-hoc data.

[0015] In this specification, "top," "bottom," "front," and "back" refer to the drive side that contacts the member to be joined as "top" and "front," and the opposite side as "bottom" and "back." The case where the main shaft, which acts as the drive shaft, is above the member to be joined is described as a representative example.

[0016] Furthermore, a suitable friction stir welding apparatus of the present invention, The distance between the upper shoulder portion and the lower shoulder portion is determined by a tightening mechanism that allows the position of the lower shoulder portion to be adjusted according to the thickness of the workpiece. The channel within the probe has at least its lower end, The upper probe includes an internal channel located near the boundary between the upper shoulder portion and the probe, and a internal channel located below the internal channel of the upper probe and above a predetermined upper limit position of the fluctuation of the lower shoulder portion. The temperature measurement results from the temperature measuring elements installed in each are transmitted by the transmission means.

[0017] As described above, the temperature measurement point at the lowest point in the thickness direction of the joined member is set inside the lower shoulder portion. This is to set the "temperature measurement point at the lowest point inside the probe" as the "temperature measurement point of the lower probe" that varies in the vertical direction with respect to the probe, and to be "located above the upper surface of the lower shoulder portion assumed in advance" from the thickness of the joined member. Thus, at least the position (1) on the upper end side inside the probe, the position on the lower end side inside the probe (including the intermediate position (2)) that is below this and above the upper surface of the lower shoulder portion, and the position (3) on the upper surface side of the lower shoulder portion can be used for temperature measurement. With such a configuration, even if the variation position and strength when the lower shoulder portion is tightened and abutted against the back surface (lower surface) of the joined member change, the position of the measurement lowest point is determined based on the lower shoulder portion standard, and temperature measurement can be performed over the entire depth direction of the probe (i.e., the entire thickness direction of the joined member), and the progress of plastic flow can be monitored. Also, joining conditions (e.g., the amount of variation (tightening amount) of the lower shoulder portion, the contact force (tightening strength), the feed rate) sufficient to obtain early and stable plastic flow can be optimally designed.

Advantages of the Invention

[0018] According to the friction stir welding apparatus of the present invention, in friction stir welding using a bobbin-type joining tool that does not require a backing jig, the temperature over the entire thickness direction of the joining portion of the joined member, particularly the temperature on the lower shoulder portion side, can be precisely measured. Therefore, the influence of plastic flow from the back surface side can also be monitored, and early, sufficient, and stable plastic flow can be obtained at the joining portion regardless of the variation of the lower shoulder portion. As a result, joining conditions such as the tightening strength and tightening amount of the lower shoulder portion, and the feed rate of the tool can be optimized.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic diagram showing the general principle of self-acting friction stir welding performed using a bobbin-type joining tool. [Figure 2] It is a photographic view showing a state where the upper part of an embodiment of the bobbin-type joining tool used in the friction stir apparatus of the present invention is used as a tool holder. [Figure 3] This is an enlarged photograph of the photograph in FIG. 2 showing from below the tool holder to the bobbin-type joining tool. [Figure 4] This is a photograph showing the entire bobbin-type joining tool shown in FIGS. 2 to 3.

Best Mode for Carrying Out the Invention

[0020] 《Regarding the Structure and Principle of FSW of Bobbin-Type Joining Tool》 FIG. 1 is a schematic diagram showing the general principle of self-acting friction stir welding performed using a bobbin-type joining tool.

[0021] The bobbin-type joining tool is a joining tool used for self-acting friction stir welding that can follow the variation in the thickness of the joined members without requiring a backing jig on the back surface (lower surface) of the joined members. As shown in FIG. 1, a general bobbin-type joining tool has an inner tool 11 inserted in a nested manner inside a hollow upper shoulder portion 12, and a cylindrical probe 14 extending downward from the lower end of the inner tool 11 protrudes from the lower surface of the lower shoulder portion 12. The probe 14 penetrates the joined member 20 from the upper surface (front surface) to the lower surface (back surface) and is inserted into a lower shoulder 16 installed on the lower surface side and fixed with a tightening nut 22.

[0022] Before joining, the inner tool 11 can move vertically within the upper shoulder portion 12, and the nut 22 is tightened by a predetermined amount according to the thickness (δ: refer to FIG. 2) of the joined member 20, and adjusted by applying a tightening strength load, so that the upper and lower surfaces of the joined member 20 are respectively abutted against the lower surface of the upper shoulder portion 12 and the 6 upper surface of the lower shoulder portion 1 (FIG. 1(See arrows A and B). In this state, the upper shoulder portion 12 is rotated axially (see arrow b in Figure 1), and the integrally connected probe 14 and lower shoulder portion 16 are also rotated coaxially with the axial rotation of the upper shoulder portion 12 (see arrow a in Figure 1), moving in the joining direction at a predetermined speed (feed rate). With this bobbin-type joining tool 10, the lower shoulder portion 16 also contacts and rotates the lower surface (back surface) of the member to be joined 20. Therefore, in FSW using a normal joining tool in which only the upper shoulder portion 12 contacts and rotates, there was a possibility of incompleteness due to the instability of the plastic flow. However, when using the bobbin-type joining tool 10, it was inferred that the lower shoulder portion 16 achieves heating of the lower surface (back surface) of the member to be joined 20, thereby stabilizing the plastic flow at an early stage.

[0023] Based on these assumptions, it was thought that in FSW using the bobbin-type joining tool 10, it would be necessary to measure the temperature of the underside (back side) of the member to be joined 20 and monitor the heat input state in real time in order to ensure its superiority. However, as mentioned above, conventional products that do not provide such assumptions do not measure the temperature of the back side of the member to be joined 20.

[0024] [Embodiment of a bobbin-type joining tool used in the friction stir welding apparatus of the present invention] Figures 2 to 4 are photographic diagrams showing an example of a bobbin-type joining tool used in the friction stirring apparatus of the present invention. Figure 2 is a photograph showing the upper part of the bobbin-type joining tool connected to the tool holder, Figure 3 is a magnified photograph of the photograph in Figure 2 showing the lower part of the tool holder and the bobbin-type joining tool, and Figure 4 is a photograph showing the entire bobbin-type joining tool as shown in Figures 1 and 2. Note that in Figures 2 to 4, the workpiece 20 is not shown and is indicated as an arrangement position (reference numeral 20).

[0025] The bobbin-type joining tool 10 is connected to a spindle (not shown) at its upper end and to a tool holder 11. While rotating coaxially with the spindle and tool holder 11, it grips the upper and lower surfaces (front and back surfaces) of the member to be joined 20 and joins the member to be joined 20 in the joining direction at a predetermined feed amount (feed speed).

[0026] This bobbin-type joining tool 10 has a cylindrical upper shoulder portion 12 with a flat, smooth lower surface 12a, and rotates downwards while contacting the upper surface (not shown) of the joining portion of the member to be joined 20. Similarly, the lower shoulder portion 16 is cylindrical with approximately the same diameter as the upper shoulder portion 12 and has a flat, smooth upper surface 12, and contacts the lower surface (not shown) of the joining portion of the member to be joined 20 during joining, and rotates while sandwiching the member to be joined 20 in the thickness direction between the upper shoulder portion 12 and the lower shoulder portion 16.

[0027] The probe 14 tapers outward from the lower surface 12a of the upper shoulder portion 12 toward the upper surface 16a of the lower shoulder portion 16, and extends through the thickness direction at the joint of the joined member 20. It then penetrates the inside of the lower shoulder portion 16 and protrudes from the lower surface 16b of the lower probe 16. The probe 14 also has a screw groove 14a along its outer circumference, and the lower shoulder portion 16 is fixed by screw fastening with nuts 22 and 24 below the lower shoulder portion 16. The nuts 22 and 24 are a so-called double nut system, and the tightening amount and tightening force of the nut 22 are adjusted according to the thickness δ of the joined member 20 and the contact force of the lower shoulder 16, which is one of the joining conditions. In this example, loosening of the nut 22 is prevented by tightening the nut 24 with a washer 23 in between.

[0028] Next, we will explain the temperature measurement points of the bobbin-type bonding tool 10. As shown in Figures 4(1) to (3), the bobbin-type joining tool 10 allows temperature measurement during joining at least in the depth direction at the upper end position (1) inside the probe 12, an intermediate position (2) below the upper end position (1) inside the probe 12, and the lower end position (3) near the upper surface 16a of the lower shoulder portion 16.

[0029] The upper position (1) and the intermediate position (2) are defined as follows, similar to a standard joining tool that does not have a lower shoulder portion 16: channels (not shown) extending to the upper position (1) and the intermediate position (2) are provided within the probe 14, respectively. A thermocouple is inserted and fixed into the channel, and the temperature at the upper position (1) and the intermediate position (2) is measured. This data is then digitally converted by an electronic circuit board in the tool holder 11, which is electrically connected to the thermocouple, and transmitted wirelessly or otherwise to an external PC or other device for monitoring.

[0030] The lower end position (3) is the upper end position of the lower shoulder portion 16, and as the connecting boundary between the probe 14 and the lower shoulder portion 16, it measures the temperature near the upper surface 16a of the lower shoulder portion 16 regardless of fluctuations in the lower shoulder portion 16. Specifically, a channel (not shown) is provided within the lower shoulder portion 16 that extends to the lower end position (3), similar to the upper end position (1) and intermediate position (2) described above. A thermocouple is inserted and fixed within this channel to measure the temperature at the lower end position (3). This temperature is then digitally converted by an electronic circuit board in the tool holder 11, which is electrically connected to the thermocouple, and transmitted wirelessly or otherwise to an external PC or the like for monitoring.

[0031] As described above, by setting up temperature measurement points, it is possible to monitor the temperature of the joint over the entire thickness direction of the joined member 20, regardless of fluctuations due to the position adjustment of the lower shoulder portion 16, as well as the influence of the lower shoulder portion 16, which is unique to the bobbin-type joining tool 10, on the plastic flow on the back side. Through this monitoring, it is also possible to monitor the tightening amount and tightening strength of the lower shoulder portion 16 by the nut 22 as joining conditions, the relationship between the feed rate of the probe 14 in the joining direction and stable plastic flow, and to optimize the joining conditions for each joined member 20 and joining tool 10, taking into account the balance between joining time and joining accuracy.

[0032] In Figure 4, three temperature measurement points are shown as examples: the upper end (1), the middle (2), and the lower end (3). However, in order to precisely measure the temperature across the entire thickness of the joined member 20, even more temperature measurement points can be provided at different positions in the thickness direction within the probe 14.

[0033] Although embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments. The scope of the present invention is indicated by the claims rather than the above description of embodiments, and all modifications within the meaning and scope equivalent to the claims are further included. [Explanation of symbols]

[0034] 10…Bobbin-type joining tool 11…Tool holder 12… Upper shoulder section 14…Probe 16... Lower shoulder area 20…Part to be joined 22... Nut 23... Washer 24... Nut

Claims

1. A friction stir welding apparatus for real-time temperature measurement during processing, comprising a bobbin-type joining tool having an upper shoulder portion that rotates around a rotation axis while its lower surface is in contact with the upper surface of the workpiece, a cylindrical probe portion that protrudes downward from the lower surface of the upper shoulder portion, and a lower shoulder portion that is connected to the lower end of the probe and rotates around the same rotation axis while its upper surface is in contact with the lower surface of the workpiece, The bobbin-type joining tool includes at least Within the probe, there are multiple hollow channels extending to different positions in the vertical direction, from the upper end to near the lower end, The lower shoulder portion includes an internal channel that extends within the lower shoulder portion to a position near the height of its upper surface, The channel within the probe has at least its lower end, The upper probe includes an internal channel located near the boundary between the upper shoulder portion and the probe, and a internal channel located below the internal channel of the upper probe and above a predetermined upper limit position of the fluctuation of the lower shoulder portion. Each of the above-mentioned channels within the upper probe, the lower probe, and the lower shoulder has a temperature measuring element located near its lower end. Furthermore, the friction stir welding apparatus includes a transmission means for transmitting temperature measurement results generated from each temperature measuring element using a temperature measuring means.

2. The friction stir welding apparatus according to claim 1, wherein the distance between the upper shoulder portion and the lower shoulder portion is determined by a tightening mechanism that allows the position of the lower shoulder portion to be adjusted according to the thickness of the workpiece.

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