JP4240935B2 - Control method and control device for rotary tool for friction stir welding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotary tool speed control method and apparatus for friction stir welding, and more particularly to a friction stir control method and apparatus capable of adjusting the tool speed in response to a reaction force applied to the rotary tool during friction stir welding. .
[0002]
[Prior art]
For example, Japanese Patent Publication No. 7-505090 discloses a novel method for joining long materials as a solid-phase joining method by friction stirrer, and this joining method is made of a material substantially harder than a workpiece. By inserting the rotating tool into the joint of the workpiece and moving the rotating tool while rotating, the workpiece is joined by plastic flow caused by frictional heat generated between the rotating tool and the workpiece. The friction welding method is a joining method in which the joining member is in a solid phase state and can be joined while integrating the softened solid phase portion while rotating the rotating tool, so that there is no thermal distortion and the joining direction is reduced. On the other hand, there is an advantage that even a long material that is substantially infinitely long can be continuously solid-phase bonded in the longitudinal direction. Further, since the solid-phase bonding using the plastic flow of the metal by the frictional heat between the rotating tool and the bonding member, the bonding can be performed without melting. Further, since the heating temperature is low, deformation after joining is small. Since the joint is not melted, there are many advantages such as fewer defects.
[0003]
Next, a rotary tool used for friction stir welding will be described. As disclosed in JP-A-7-505090, friction stir welding includes probe-type and bobbin tool-type rotary tools, and the probe-type tool 20 includes a shoulder portion 21 as shown in FIG. And a probe 22 provided in the shoulder portion 21, and the shoulder portion 21 has a circular shoulder surface. Then, the rotating tool 20 is rotated from the surface of the joining line in a state where a plurality of mold materials are abutted or fitted, and the probe 21 is inserted into a hole (not shown) provided in the joining line of the workpiece, Frictional heat is applied to the work piece by the circular shoulder surface 21a that slides and rotates on the joining lines of a plurality of mold materials, and the periphery of the probe 22 is plastically fluidized. In this state, the rotary tool 20 is moved along the joining line. As a result, the two materials are agitated and kneaded while receiving pressure, while the periphery of the joint line is plastically fluidized, and moves to the rear side of the probe. As a result, the plastic flowed material loses frictional heat on the rear side and rapidly cools and solidifies, so that both panel plates are joined together with the materials mixed together.
[0004]
However, in such a joining method, in order to generate frictional heat at the time of joining, it is necessary to press the rotary tool 20 to the joining line side, and therefore a backing metal is used to cope with this reaction force. This backing metal is installed in close contact with the back surface of the face plate of the workpiece, and requires high rigidity.
[0005]
Therefore, in such friction stir welding, there is a case where a large load is applied to the machine spindle supporting the rotating tool, and particularly a large load (particularly a probe (pin)) of the tool is applied during the bonding, resulting in damage.
If the tool breaks during welding, the operator will immediately stop operation upon detecting a change in the sound of the drive motor, etc., but the tool will still move forward until that time, so the poorly welded part will have a certain length. In the case of automating the friction stir welding operation and monitoring a plurality of friction stir welding machines by one worker, such trouble becomes more prominent, especially after the pin breaks and the tool The part where T has advanced needs to be joined again, but it takes a lot of man-hours to repair this poorly joined part.
[0006]
In order to eliminate such drawbacks, in JP-A-2001-340977, the current value of the rotary drive motor of the friction stir welding tool is compared with a reference value, and the operation is performed when the current value becomes 80% or less of the reference value. Stop (rotating drive motor and forward drive motor, or pulling up the welding tool, or stopping forward movement, etc.), and other solution means that the current value of the forward drive motor of the friction stir welding tool is a reference value Compared to the above, a technique is proposed in which the operation is stopped (the forward drive motor and the forward drive motor are stopped) when the current value becomes 80% or less of the reference value.
[0007]
However, this technique is intended to facilitate early detection when a pin is damaged, and is not a device for preventing the pin from being damaged.
For this reason, in actual friction stir welding, the size of the friction stir welding tool is appropriately selected according to the thickness of the plate to be joined, and the spindle rotational speed is set so that the load on the rotary drive motor is substantially constant depending on the size of the tool. The drive control is performed with a constant feed rate. However, in actual joining, the feed rate is set to be low in consideration of the most loaded state in consideration of variations in material hardness and thickness.
For this reason, the friction stir welding has a problem that the joining time becomes unnecessarily long as compared with the joining ability of the tool.
In particular, the length of joints such as aluminum molds used for the floor and side panels of railway vehicles where friction stir welding is used is very long, around 25m. Correspondingly, how to shorten the joining time within a range where the tool is not damaged is a very important problem.
[0008]
Now, in order to eliminate the drawbacks of the probe type rotary tool, a rotary tool called a bobbin tool 10 has been proposed as shown in FIG. 4B.
Such a tool is provided with a pair of shoulders 10A and 10B spaced apart so as to sandwich both front and back surfaces of a metal plate to be joined, and a probe 11 is provided between the pair of upper and lower shoulders 10A and 10B. Therefore, frictional heat can be generated on both sides of the joint surface, and not only the back side is not poorly bonded, but also because the mutual reaction force is received between the pair of upper and lower shoulders 10A and 10B. No gold or support is required.
However, since the distance between the pair of upper and lower shoulders 10A and 10B is fixed by the probe 11 in this prior art, if the member to be joined is deformed or the thickness varies, this cannot be absorbed and smooth. Unable to perform friction stir welding. In particular, considering the gap (gap) generated in the joint in the joining process (manufacturing process), if the gap varies, the load fluctuates due to variations in the thickness of the gap or joint even if the transport speed is constant. Again, the feed rate must be set lower than the maximum load.
[0009]
[Problems to be solved]
In view of such a problem, the present invention maintains a good joint surface without damaging the friction stir welding tool in any of the probe type and bobbin type tools, and maximizes the joining ability of the tool to achieve the joining time. The purpose is to solve the problem of unnecessarily long.
[0010]
[Means for Solving the Problems]
The present invention is a method for controlling the speed of a friction stir welding rotary tool comprising a small diameter portion that penetrates into a joining portion and a large diameter portion that is pressed against a joining surface.
The reaction force (hereinafter referred to as reaction force) of the tool received during the movement of the tool during the joining operation is detected and measured, the measured reaction force is compared with a reference value, and the tool is moved in the joining direction based on the reference value. and controlling the welding speed and velocity as a variable.
[0011]
The focus of the present invention is that in the case of friction stir welding, there is a proportional relationship between the reaction force of the rotating tool received from the joining surface and the moving speed of the tool, and the higher the moving speed of the tool, the more likely the tool will be broken. It pays attention to the possibility that it becomes higher and the unevenness is formed on the bonding surface.
Accordingly, the present invention obtains in advance the maximum moving speed capable of maintaining a good joining surface, sets the reaction force corresponding to it as a reference value, and moves the tool in the joining direction so that the reaction force measured during operation approaches the reference value. The gist is to perform the joining operation by controlling the speed.
[0012]
According to this invention, the thickness and hardness of the base metal on the joining side vary, and in response to this, even in the case of any probe of the probe type bobbin type, the reaction force corresponding to the pressing force varies. Correspondingly, the tool moving speed in the welding direction can be increased or decreased, so that the rotating tool can be joined at a speed that is always close to the joining ability of the tool without being damaged, so that no joining time is required. Can solve the problem of lengthening.
[0013]
As an apparatus for suitably carrying out the invention, means for detecting a reaction force (reaction force) of a tool received during movement of a tool during a joining operation, means for comparing the measured reaction force and a reference value, It is comprised from the means to calculate the moving speed (joining speed) of the tool in a joining direction based on a comparison value, and the means to set to the tool moving speed corresponding to reaction force by this calculating means.
[0014]
In this case, the reference value does not need to be set to a constant value such as 90% of the maximum load value, and is set to a level zone such as 90 to 98% as described in claim 2. Also good. That is, the reference value is recognized as a level zone, the reaction force (reaction force) of the tool received during the movement of the tool during the joining operation is detected and measured, the measured reaction force is compared with the reference level zone, and the measurement is performed. When the reaction force is lower than the reference level zone lower limit value, the tool moving speed in the welding direction is increased, and when the measured reaction force is higher than the reference level zone upper limit value, the tool moving speed in the welding direction is reduced. It is also one aspect of the present invention that the moving speed of the tool is maintained when is within the reference level zone.
[0015]
By performing zone control in this way, stable and high-quality friction stir welding can be performed without frequently changing the tool speed.
[0016]
As a preferred apparatus of such an invention, there are means for detecting a reaction force (reaction force) of the tool received during movement of the tool during the joining operation, and means for comparing the detected reaction force with a reference level zone. When the detected reaction force is lower than the reference level zone lower limit value, the moving speed of the tool in the welding direction is increased, and when the detected reaction force is higher than the reference level zone upper limit value, the tool moving speed in the welding direction is reduced, When the detected reaction force is within the reference level zone, it can be configured to include a tool moving speed setting means for maintaining the moving speed of the tool.
[0017]
In any of the above-described inventions, the maximum moving speed in the joining direction capable of maintaining a good joining surface is obtained in advance, the reaction force corresponding thereto is set as a reference value or a level zone (hereinafter referred to as a reference value), and sequentially measured during operation. It is preferable to perform the joining operation by controlling the tool moving speed so that the reaction force that is applied approaches the reference value.
[0018]
The rotary tool may be either a probe type tool or a bobbin tool type tool.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, unless otherwise specified, the dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention.
[0020]
FIG. 1 is a schematic diagram showing a control configuration of the friction welding apparatus according to the first embodiment of the present invention.
In the figure, reference numeral 1 denotes a workpiece to be joined, for example, a structure in which single skin panels are butted together and joined.
The rotary tool 20 is a probe-type rotary tool in which a pin 22 projects from the central axis of the cylindrical shoulder 21, and a reaction force detection sensor 3 such as a load cell or a strain sensor is interposed between the rotary tool 20 and the main shaft 2 that chucks the tool 20. is doing. Reference numeral 4 denotes a measuring instrument for receiving a signal from the reaction force detection sensor 3 and converting the tool reaction force into a digital value and measuring it. Here, the tool reaction force is a reaction force received during the movement of the tool during the joining operation, and changes according to the moving speed of the tool 20 during the joining.
[0021]
Reference numeral 5 denotes a reference data storage database. In this database, the types of aluminum plates to be joined and the types of joining tools to be selected corresponding to the thicknesses are recorded on a map, and the pin 1 of the joining tool is stored in the memory. The diameter, the reference rotation speed, the reference advance speed, and the standard current value of the rotary drive motor that performs friction stir welding are stored.
The reaction force reference value is within the range of the standard voltage ± 10%, and the maximum reaction force value that does not cause motor burnout or pin breakage is determined in advance through experiments.
[0022]
For example, when joining a base material of an A6N01-T5 aluminum alloy with a thickness t = 4 mm by butt joining,
Using a rotating tool having a cylindrical shoulder diameter of 14 mm, a pin diameter of 6 mm, and a pin length of 3.7 mm, the tool reaction force / joining speed / joining state was examined at a constant tool rotation speed of 400 rpm.
as a result,
(1) When the tool reaction force was 800 kgf with a joining speed of 250 mm / min, the joining condition was good.
(2) Even when the welding speed was increased to 350 mm / min and the tool reaction force increased to 900 kgf, the bonding condition was good.
(3) Next, when the welding speed was further increased to 450 mm / min and the tool reaction force increased to 1100 kgf, irregularities were formed on the surface of the joint and the joining state was poor.
From this experiment, if the reference value of the tool reaction force is set to 900 kgf, it is possible to join at the maximum speed at which good joining can be obtained.
[0023]
An arithmetic processing unit 6 performs arithmetic processing based on the flow of FIG.
Reference numeral 7 denotes an NC apparatus that performs a joining operation while moving a tool based on the joining speed calculated by the arithmetic processing unit 6.
[0024]
A flow operation in the apparatus configuration will be described with reference to FIG.
First, a reference value suitable for the base material and the tool is detected by reading the reference value from the reference data storage database 5 (S0), and then welding is performed at a joining speed of about 300 mm / min, which is slightly lower than the reference maximum joining speed. A signal from the sensor 3 is captured (S1), and the reaction force measured by the measuring instrument 4 is compared with the reference value. (S2)
If the measured value is lower than the reference value of 900 kgf, the joining speed is increased. (S3)
If the measured value is higher than the standard value of 900 kgf, the joining speed is reduced. (S4)
Then, the above operation is repeated (S5), and the friction stir welding is performed by controlling the joining speed (tool moving speed) so that the tool reaction force substantially coincides with the reference value.
As a result, the rotating tool 20 can be joined at a speed that is always close to the joining ability of the tool without being damaged, leading to a reduction in joining time.
[0025]
FIG. 3 is an example of a flow chart corresponding to FIG. 2 in which the reference value is leveled. In FIG. 3, the reference value is frequently zoned by setting the level zone in the range of (860 to 900 kgf) and performing zone control. Stable and high-quality friction stir welding can be performed without changing the tool speed.
That is, first, after reading the reference level zone from the reference data storage database 5 (S9), the welding is performed at a joining speed of about 300 mm / min, which is slightly lower than the reference maximum joining speed, and the signal from the detection sensor 3 is captured ( S10) The reaction force measured by the measuring instrument is compared with the reference level zone (860 to 900 kgf) value stored in the reference value data. (S11)
If the measured value is within the reference level zone (860 to 900 kgf), the joining speed is maintained (S12).
When the reference level zone (860 to 900 kgf) is below the lower limit value, the moving speed of the tool is increased. (S13)
If the measured value is equal to or higher than the reference level zone upper limit value, the moving speed of the tool is reduced. (S14)
The above operation is repeated (S15), and the friction stir welding is performed by controlling the joining speed (tool moving speed) so that the tool reaction force enters the reference level zone.
[0026]
【The invention's effect】
As described above, according to the present invention, in the case of both a probe type and a bobbin type tool, the friction stir welding tool is maintained without a breakage, and the joining ability of the tool is maximized and the joining is performed to the maximum. The problem of unnecessarily long time can be solved.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a control configuration of a friction welding apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing the control operation of FIG. 1;
FIG. 3 is a flowchart corresponding to FIG. 2 in which the reference value is leveled into zones.
FIG. 4 is a basic configuration diagram of a friction stir welding probe tool and a bobbin tool according to the prior art.
[Explanation of symbols]
3 Reaction force detection sensor 4 Measuring instrument 5 Reference data storage database 6 Arithmetic processing device 7 NC device 10 Bobbin tool 20 Probe type rotary tool

Claims (6)

In the speed control method of the rotary tool for friction stir welding comprising a small diameter part that penetrates into the joining part and a large diameter part that is pressed against the joining surface,
The reaction force (hereinafter referred to as reaction force) of the tool received during the movement of the tool during the joining operation is detected and measured, the measured reaction force is compared with a reference value, and the tool is moved in the joining direction based on the reference value. the method of friction stir welding rotary tool and controlling the welding speed and velocity as a variable. In the method of controlling the speed of the tool according to claim 1,
The reaction force of the tool experienced during movement of the tool is detected measured at the time of bonding operation, compares the said measured reaction force and the reference level zone, in the welding direction if the measured reaction force is below the reference level zone lower limit Increase the moving speed of the tool, reduce the moving speed of the tool when the measured reaction force exceeds the upper limit of the reference level zone, and maintain the moving speed of the tool when the measured reaction force is within the reference level zone A control method of a rotary tool for friction stir welding characterized by the above. In the method of controlling the speed of the tool according to claim 1,
The maximum moving speed that can maintain a good bonding surface is obtained in advance, the reaction force corresponding to it is set as a reference value or level zone (hereinafter referred to as the reference value), and bonding is performed so that the reaction force measured sequentially during operation approaches the reference value. A control method of a rotary tool for friction stir welding, characterized in that a welding operation is performed by controlling a tool moving speed in a direction . In the control device of the rotary tool for friction stir welding comprising a small diameter portion that penetrates into the joining portion and a large diameter portion that is pressed against the joining surface,
Means for detecting the reaction force (reaction force) of the tool received during the movement of the tool during the joining operation, means for comparing the measured reaction force with a reference value, and the tool in the joining direction based on the comparison value means for calculating a moving speed, the control device of the friction stir welding rotary tool, characterized in that it comprises means for setting the tool movement speed corresponding to the reaction force by the computing means. The tool speed control apparatus according to claim 4, wherein
Means for detecting the reaction force (reaction force) of the tool received during the movement of the tool during the joining operation, means for comparing the detected reaction force with the reference level zone, and the detected reaction force is a reference level zone lower limit value When the moving speed of the tool in the joining direction is increased in the following cases, and when the detected reaction force is greater than or equal to the upper limit of the reference level zone, the moving speed of the tool in the joining direction is reduced, and the detected reaction force is within the reference level zone And a speed control device for a rotary tool for friction stir welding, characterized by comprising tool moving speed setting means for maintaining the moving speed of the tool. 6. The friction stir welding according to claim 4 or 5, wherein the reference value (including the level zone) is obtained in advance as a maximum moving speed in a joining direction capable of maintaining a good joining surface, and a corresponding reaction force is set as a reference value. Rotary tool control device.

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