JP2002178158A - Upset butt weldability judging device and judging method for aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an upset weldability judging device and a weldability judging method for an aluminum alloy which enable rapid and exact judgment at a real time of welding. SOLUTION: The upset butt weldability judging device for the aluminum alloy is provided with a welding current detecting means 11, a welding voltage detecting means 12, a current-carrying time detecting means 15, an electrode displacement detecting means 14, a pressurizing force detecting means 13, and a weldability judging means 17 which judges weldability of a joining boundary based on respective detected values from respective detecting means. Weldability of the joining boundary 3 is judged by calculating at least one or more of current density, pressurizing force density, a current integrated value, a carorific value, upset butt deforming speed, an upset butt displacement ratio and a unit carorific value which are obtained from respective detecting means to compare them with reference values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weldability judging apparatus and method for quantitatively judging the quality of upset butt weldability of an aluminum alloy.

[0002]

2. Description of the Related Art In recent years, upset butt welding, which is excellent in workability and efficiency, has been frequently used for welding aluminum alloys.

In the upset butt welding method, the joining end faces of the materials to be welded are butt-joined, a predetermined welding current is applied in a state where a predetermined pressing force is applied, and the butt end faces are contacted by the contact resistance of the butt end faces and Joule heat due to the specific resistance of the material. Is heated and softened, and the softened portion is extruded perpendicularly to the joining surface by a large pressing force to join the joints. Since a direct current is used, this is also called a DC butt welding method.

[0004] In order to monitor the weldability in the above-mentioned upset butt welding, factors that affect the weldability include:
Monitoring is performed focusing on three factors: a welding current flowing through a material to be welded, a pressing force applied to a butt end face of the material to be welded, and an energizing time during which the welding current flows.

[0005]

However, in the upset butt welding of aluminum alloys, there is a shortage of total heat input at the time of heat input to the joining interface, which is a butt end face, and a heat unbalance in the width direction of the welded material at the joining interface. With the conventional monitoring method of monitoring the welding current, pressing force, and energizing time described above, the actual state of upset butt welding is due to the complicated operation involving the occurrence of heat and the change in the amount of heat input due to the change in the thickness of the oxide film at the joint interface. Further, it is difficult to accurately grasp the weldability, and therefore, there is a problem in maintaining stable welding quality, and it is not always necessary that defective welding products do not flow to the subsequent process.

An object of the present invention is to provide an apparatus and a method for determining the upset butt weldability of an aluminum alloy, which can quickly and accurately determine the weldability of upset butt welding in real time.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a welding current is applied to a material to be welded through a welding electrode, and welding is performed on a joint interface of the material to be welded by resistance heating. In upset butt welding of aluminum alloy,
Welding current detecting means for detecting a welding current flowing through the material to be welded, welding voltage detecting means for detecting a welding voltage applied to the material to be welded, and detecting an energizing time to be applied to the material to be welded Energizing time detecting means, electrode displacement amount detecting means for detecting the displacement amount of the welding electrode, pressing force detecting means for detecting a pressing force applied to the joining interface, based on each detected value of each detecting means And weldability determining means for determining the weldability of the bonding interface.

According to the upset butt weldability judging device, a current density relating to heat input to the joining interface is obtained from the welding current detecting means, and a pressing force density relating to contact at the joining interface is detected by the pressing force detection. Means, a current integral value relating to the heat softening of the joint interface is obtained from the respective detection means of the welding current and the energizing time, and a calorific value relating to the appropriate heat input of the joint interface is the welding current, the welding voltage. And energization time.

[0009] The weldability judging means judges the quality of the weldability based on the weldability-related characteristics of the current density, the pressurized pressure density, the current integral value and the calorific value, so that an accurate judgment is made. .

In addition, an upset bat deformation period (hereinafter, referred to as an upset bat deformation period)
This is called the upset deformation period. In the step (1), the upset deformation rate related to the heat balance at the bonding interface and the upset displacement ratio related to the oxide discharge at the bonding interface are obtained from the electrode displacement detecting means, and the unit related to the required heat input at the bonding interface is obtained. A heat value is obtained from the electrode displacement amount detection means and the heat value.

Since the weldability is determined by the weldability determining means based on the weldability-related characteristics during the upset deformation period of the upset deformation speed, the upset displacement amount ratio, and the unit calorific value, a more accurate determination is made. Is performed.

According to a second aspect of the present invention, there is provided an aluminum alloy upset butt weldability judging apparatus according to the first aspect, wherein the current density, the pressure density,
At least one or more of the current integrated value and the calorific value is calculated and compared with a reference value to determine the weldability of the bonding interface. According to the second aspect of the present invention, the current density, the pressure density, the current integrated value, or the calorific value, which are important properties related to weldability, are calculated and compared with each reference value to determine the weldability. Judgments are made quickly in real time.

[0013] In order to improve the efficiency of the judgment, the above 4
It is also possible to selectively pick up any one of the characteristics that are particularly required among the characteristics, calculate the characteristics, and compare them with the corresponding reference values. Further, when there is enough time for the judgment and high judgment accuracy is required, it is desirable to take as many characteristics as possible, calculate, and compare with the corresponding reference value.

According to a third aspect of the present invention, there is provided an upset butt deformation speed, an upset butt displacement ratio and a unit heat value obtained from the displacement of the welding electrode in the aluminum alloy upset butt determination apparatus according to the first aspect. , At least one or more is calculated and compared with a reference value to determine the weldability of the joint interface. According to the third aspect of the invention, three characteristics of upset deformation speed, upset displacement ratio, and unit heat generation, which are important characteristics related to weldability during the upset deformation period, are calculated and compared with each reference value, and the weldability is determined. Since the quality is determined, the weldability during the upset deformation period is quickly determined in real time.

In order to improve the efficiency of the determination, one or more of the above three characteristics may be selectively selected and calculated, compared with a corresponding reference value, and a representative determination of the weldability during the upset deformation period. It is also possible to do it.

According to a fourth aspect of the present invention, in order to determine the weldability of the joint interface in more detail from the point of the heat input, each heat value in the preheating period and the heating period is compared with a reference value. Thereby, the weldability of the joining interface is determined in more detail in terms of the heat input.
The invention of claim 5 compares each pressure density in each period of the upset butt welding with a reference value in order to determine the weldability of the joining interface in more detail from the viewpoint of the pressure density. Thereby, the weldability of the joint interface is determined in more detail from the viewpoint of the pressure density.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, a case where an aluminum alloy disc wheel rim is upset butt-welded will be described below with reference to an embodiment shown in FIGS.

FIG. 1 shows a schematic configuration of an upset butt welding apparatus. In the vicinity of a joining interface 3 of a rim material 4 made of aluminum alloy as a material to be welded, a welding electrode 1 on a fixed side and a welding electrode on a moving side are shown. 2 clamped. Reference numeral 5 denotes a welding power supply for supplying a DC current between the welding electrodes 1 and 2, reference numeral 6 denotes a current control device for controlling the DC current supplied from the welding power supply 5, and reference numeral 7 denotes a hydraulic power source. By driving the welding electrode 2 by applying a hydraulic pressure from above, a pressing force is applied to the bonding interface 3. 9 is a pressure control device for controlling the pressure applied to the bonding interface 3.

FIG. 2 (a) shows a state before welding of the joint interface 3, and FIG. 2 (b) shows a state of the joint interface 3 during welding. As shown in FIG. 2, the welding electrode 2 is driven in the direction of arrow F to apply a pressing force to the joining interface 3.
Due to the heating and softening of the joining interface 3 during welding, the welding electrode 2
Move by the distance indicated by. The moving distance A corresponds to an electrode displacement described later, and the electrode displacement is an important parameter that determines the amount of heat input to the bonding interface 3.

Next, FIG. 3 shows the electrode displacement in upset butt welding of a rim for an aluminum alloy disk wheel.
FIG. 4 shows an example of a time chart relating to a pressing force density and a current density. The squeezing time T ₀ of the electrode displacement amount G and the pressing force density P ₁ , which are the idle distances until the initial butting, the pressing force density P ₁ , preheating time of density I ₁ and the electrode displacement amount L ₁ T ₁
And the heating time T _{2 of the} pressure density P ₂ , the current density I ₂ and the electrode displacement L ₂ , and the upset deformation time T _{3 of the} pressure density P ₃ and the electrode displacement L ₃ .

Here, in the squeeze period, uniform contact of the bonding interface is performed before the energization, and in the preheating period, the specific resistance of the aluminum alloy increases due to heat input by energization and pressurization, and the bonding interface accompanying the deformation. In the heating period, the pressure is reduced and the contact resistance is increased to increase the heat input.
The scattering of the molten aluminum alloy is suppressed by lowering the current density together with the lowering of the pressing force, and during the upset deformation period, the molten oxide is reliably discharged by applying a large pressing force without applying electricity, exposing the new surface at the joint interface Sound welding is performed.

FIG. 4 is a block diagram showing the basic structure of the upset butt weldability judging device according to the present invention. The weldability judging device 10 comprises welding current detecting means 11, welding voltage detecting means 12, pressing force detecting means 13. , An electrode displacement amount detecting means 14 and an energizing time detecting means 15, each characteristic value is calculated by a weldability calculating means 16 based on each detection value detected by each detecting means, When the weldability of the interface is determined and the reference value is not satisfied, a warning is issued by the warning means 18.

The current density, the current integrated value, and the calorific value are obtained by calculation in the preheating period and the heating period based on the detection values detected by the respective detecting means, and the squeezing period, the preheating period, and the heating period are calculated. During the period and the upset deformation period, the pressing force density is obtained by calculation, and the calculated values of these four characteristics are compared with the respective reference values to determine the weldability. The reason for taking up these four characteristics is as follows. Will be described.

The current density is obtained from the welding current detected by the welding current detecting means 11 and the sectional area of the workpiece (welding current / sectional area of the workpiece). This current density is important for maintaining a stable heat input to the bonding interface.If the current density is low, it is easy to cause poor welding due to insufficient heat input to the bonding interface. Since fusion failure is likely to occur due to melting and scattering due to excessive heat input to the bonding interface, it is determined whether or not the optimal current density is maintained for each period (in this example, the preheating period and the heating period).

The pressure density is obtained from the pressure detected by the pressure detecting means 13 and the sectional area of the workpiece. This pressure density is important for maintaining a stable contact resistance at the bonding interface, and it is necessary to control the pressure over time for efficient heat input at the bonding interface. The pressing force density varies in each period (squeezing period, preheating period,
The heating period and the upset deformation period include a case where the preheating period and the heating period are not distinguished from each other and are set as the heating period. It is determined whether or not each of them is maintained.

The current integrated value is obtained from the welding current waveform detected by the welding current detecting means 11 and the energizing time detected by the energizing time detecting means 15. This current integral value is important for maintaining a stable heat-softened state of the bonding interface.
That is, in the upset butt welding, it is necessary to monitor the change in the resistance value. However, since the change in the resistance value greatly changes depending on various factors, the optimum value surrounded by the current and time excluding the influence of these factors is used. It is determined whether a proper current integration value is maintained for each period (in this example, the preheating period and the heating period).

The heat value is obtained from the welding current detected by the welding current detecting means 11, the welding voltage detected by the welding voltage detecting means 12, and the energizing time detected by the energizing time detecting means 15. Since this heating value includes all factors relating to the heat input at the bonding interface and is important in maintaining a suitable heat input to the bonding interface, the optimum heating value is determined for each period (in this example, the preheating period). Is determined for each heating period).

It is general that all the four important characteristics are calculated and compared with their respective reference values to judge the weldability comprehensively. Is a problem, by calculating only the pressing force density and comparing it with a reference value to determine
The determination may be made on behalf of the weldability in each period.

Further, during the upset deformation period,
In order to obtain sound welding quality, the upset deformation speed, the upset displacement ratio and the unit calorific value are calculated, and the calculated values of these three characteristics are compared with the respective reference values to determine the weldability. The reasons for taking the three characteristics will be described below.

The upset deformation speed is obtained from the maximum value of the differential value of the upset deformation curve, based on the electrode displacement detected by the electrode displacement detector 14. Since this upset deformation speed is important in determining a uniform temperature distribution (heat balance) in the width direction of the material to be welded at the joining interface, it is determined whether or not the optimal upset deformation speed is maintained.

The upset displacement ratio is upset butt displacement of the electrode displacement amount detected from the electrode displacement amount detector 14 (hereinafter, referred to as upset displacement.) L ₃ and the ratio of the total amount of displacement L (L ₃ / L). If the upset displacement ratio is small, the oxide present at the joint interface and the oxide generated during heating are not sufficiently discharged, and this is important in terms of oxide discharge. It is determined whether the ratio is maintained.

The unit heat value is obtained from the heat input amount (the heat value described above) with respect to the upset displacement amount (unit heat value = heat input amount / upset displacement amount). This unit heat generation is important in maintaining the heat input to secure the welding quality at the joint interface because the upset displacement is substantially constant and determined by the heat input if the heat balance is secured. It is determined whether or not the optimal unit heat generation is maintained.

Generally, all three important characteristics during the upset deformation period are calculated and compared with their respective reference values to determine weldability comprehensively. However, in order to increase the efficiency of the determination, For example, when the heat balance is a problem, the weldability during the upset deformation period may be determined by calculating only the upset deformation speed and comparing it with a reference value.

Next, FIG. 5 is a block diagram showing a basic circuit of the upset butt weldability judging device. The memory (ROM) 21, the memory (RAM) 22, and the memory (ROM) 21 are interconnected via a processing unit (CPU) 20. A controller 26 containing an input interface 23, an output interface 24, and a peripheral device 25 having a keyboard, a display, a printer, and the like is provided. The controller 26 has a welding current detection circuit 31, an A / D converter 30, and a welding voltage. Detection circuit 32, pressure detection circuit 3
3. Electrode displacement amount detection circuit 34 and conduction time detection circuit 35
Is connected.

The output signal of each of the detection circuits is input from an input interface 23 to a processing unit (CPU) 20 via an A / D converter 30 and is processed by the processing unit (CPU) 20 to calculate the above-mentioned important characteristics. The values are compared with the respective reference values.
6 is driven, and an alarm is issued from the alarm means 18 described above.

The memory (ROM) 21 of the controller 26 stores programs to be used for various processes including a flowchart described later, and executes the programs while the processing unit (CPU) 20 is running. The memory (RAM) 22 temporarily stores variable data necessary for executing the program.

FIG. 6 is a flowchart showing the outline processing of the above-described important characteristics. Sampling starts when welding is started (steps S1 and S2), and sampling ends when welding is completed (steps S3 and S4). Next, the above-mentioned important characteristics are calculated for each corresponding period (steps S5 to S11), and the quality of the weldability is determined based on the calculation results (step S12). If "no", an abnormal signal is output (step S12). Step S13).

Next, the calculation of each of the important characteristics (steps S5 to S11) shown in FIG. 6 will be specifically described from each sampling to the calculation using each flowchart.

FIG. 7 is a flowchart relating to the current density and the current integrated value. First, sampling of the welding current, the pressing force and the electrode displacement is started (step 101), and it is determined whether or not the energization is started (step 102). If so, the measurement of the welding current during the preheating period is started (step 1).
03). Next, it is determined whether the differential value of the pressurization curve is negative (step 104). If the differential value is negative, the pressing force decreases, that is, the preheating period ends, and the measurement of the welding current during the preheating period ends (step 104). Step 105).

Next, the measurement of the welding current during the heating period is started (step 106), and it is determined whether or not the differential value of the displacement curve is positive (step 107). Since the heating time has ended, the measurement of the welding current is ended (step 108). Next, it is determined whether the time is up (step 109). If the time is up, the current density and the current integrated value in the preheating period and the heating period are calculated (steps 110 and 111). Here, “time-up” means the end of the sampling time (the same applies hereinafter).

In the above-described example, the timing of terminating the measurement of the welding current is set at the time of “positive” conversion of the differential value of the displacement curve, but this is for accurately separating the end of the heating period. That is, generally, the end of the preheating period is determined by the pressing force density P ₁ → P ₂
The welding current measurement may be terminated when the pressure density rises from P _{2 to} P ₃ as set at the time of the change of the pressure. Since a slight time lag occurs inevitably from the rise of the pressing force detected by the pressing force detecting means 13, the end of the heating period is decided by increasing the electrode displacement. Note that the end of the heating period may be separated when the current density I ₂ suddenly decreases.

FIG. 8 is a flowchart relating to the pressing force density. First, sampling of the pressing force and the electrode displacement is started (step 201), and it is determined whether or not the pressing is started (step 202). The measurement of the pressure during the period is started (step 203). Next, it is determined whether or not the energization has been started (step 204). If it has been started, the measurement of the pressing force during the squeeze period is terminated (step 205), and the measurement of the pressing force during the preheating period is started (step 206). Next, it is determined whether the differential value of the pressurization curve is negative (Step 207). If the differential value is negative, the measurement of the pressing force during the preheating period is terminated (Step 208).
The measurement of the pressure during the heating period is started (step 20).
9).

Next, it is determined whether the differential value of the displacement curve is positive (step 210). If the differential value is positive, the measurement of the pressing force during the heating period is terminated (step 211), and Start measuring the applied pressure (step 2
12). Then upset deformation time T ₃ is determined whether the time is up (step 213), and terminates the measurement of the pressure of upsetting deformation period if the time is up (Step 214). Next, it is determined whether the time is up (step 215). If the time is up, the pressing force density in each of the squeezing, preheating, heating and upset deformation periods is calculated (step 216).

FIG. 9 is a flowchart relating to the heat value.
First, sampling of the welding current / voltage, pressing force, electrode displacement, and energizing time is started (step 301), and it is determined whether energization has been started (step 302). Then, the measurement of the energization time is started (step 303). Next, it is determined whether or not the differential value of the pressurization curve is negative (step 304). If the differential value is negative, the measurement of the welding current / voltage and the energizing time during the preheating period is terminated (step 305), and the heating period is determined. Of the welding current / voltage and the energizing time is started (step 30).
6).

Next, it is determined whether or not the differential value of the displacement curve is positive (Step 307). If the differential value is positive, the measurement of the welding current / voltage and the energizing time during the heating period is terminated (Step 308). . The other partitioning method at the end of the heating period is as described above. Next, it is determined whether the time is up (step 309). If the time is up, the average resistance value and the heat value during the preheating period are calculated (steps 310 and 311), and the average resistance value and the heat value during the heating period are calculated. The calculation is performed (steps 312 and 313).

FIG. 10 is a flowchart relating to the upset deformation speed and the upset displacement ratio. First, sampling of the pressing force and the electrode displacement is started (step 401), and it is determined whether or not the pressurization is started (step 402). If so, measurement of the electrode displacement during the squeeze period is started (step 403). Next, it is determined whether the energization has been started (step 404). If the energization has been started, the measurement of the electrode displacement amount during the squeeze period is ended (step 40).
5), measurement of the electrode displacement during the preheating period is started (step 406). Next, it is determined whether the differential value of the pressurization curve is negative (step 407). If the differential value is negative, the measurement of the electrode displacement during the preheating period is completed (step 40).
8), measurement of the electrode displacement amount during the heating period is started (step 409).

Next, it is determined whether or not the differential value of the displacement curve is positive (step 410). If it is positive, the measurement of the electrode displacement during the heating period is terminated (step 411).
The measurement of the electrode displacement during the upset deformation period is started (step 412). The other partitioning method at the end of the heating period is as described above. Next, it is determined whether the time is up (step 413). If the time is up, the measurement of the electrode displacement during the upset deformation period is completed (step 414), and after the measurement is completed, the electrode displacement during the squeezing, preheating and heating periods is completed. After calculating (Step 4
15, 416, 417), and calculates the upset deformation speed and the upset displacement amount ratio during the upset deformation period (step 418).

FIG. 11 is a flowchart relating to the unit heat value. Steps 501 to 508 correspond to those in FIG.
Steps 301 to 308 of FIG.

That is, when the measurement in step 508 is completed, measurement of the amount of electrode displacement during the upset deformation period is started (step 509), and it is determined whether the time is up (step 510). The measurement of the current displacement amount during the upset deformation period ends (step 511). Next, an average resistance value and a calorific value in the preheating period and the heating period are calculated (steps 512 and 513),
The electrode displacement amount during the upset deformation period is calculated (step 514), and finally the unit heat value is calculated from the calculated value (step 515).

The value of each important characteristic calculated according to the above-described procedure is compared with the respective reference value to determine whether the weldability is good or not, and if it is determined to be “No”, an alarm is issued as described above. Be emitted. In this case, the operation of the welding line is immediately stopped so that defective welding products are not flowed to the subsequent process, inspection and adjustment of abnormal parts of the welding equipment are performed, and when the treatment is completed, the welding line is restarted. Is done.

Here, in this embodiment, the weldability was determined in the case of the upset butt welding method including four periods of the squeeze period, the preheating period, the heating period, and the upset deformation period. The present invention is not limited to the case, and can be similarly applied to all the welding methods used for upset butt welding of an aluminum alloy.

[0052]

The apparatus and method for judging the upset butt weldability of an aluminum alloy according to the present invention use the above-described means, and therefore have the following effects.

According to the weldability judging device of the present invention, the detection means and the judgment means for detecting each important characteristic for judging the weldability of the aluminum alloy are provided. Can be accurately determined.

According to the method for determining weldability according to the second and third aspects, each important characteristic is quickly calculated to determine the quality of the weldability. It is performed quickly in real time, thereby preventing outflow of defective welding products to subsequent processes. In addition, since the result of the measure at the time of occurrence of a defect is immediately known, early measures can be easily performed.

According to the method for judging weldability according to the fourth aspect, since each heat value in the preheating period and the heating period is compared with the reference value, the weldability of the joining interface is judged in more detail in terms of the heat input. be able to.

According to the weldability determining method of the present invention, each pressing force density in each period of upset butt welding (for example, a squeeze period, a preheating period, a heating period, and an upset deformation period) is compared with a reference value. Therefore, the weldability of the joining interface can be determined in more detail from the viewpoint of the pressing force density.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration of a welding device.

FIGS. 2A and 2B are cross-sectional views illustrating an electrode displacement amount, and FIG.
Is a sectional view before welding, and (b) is a sectional view during welding.

FIG. 3 is an example of a time chart showing a relationship among an electrode displacement amount, a pressing force density, and a current density.

FIG. 4 is a block diagram showing a basic configuration of a weldability determination device.

FIG. 5 is a block diagram showing a basic circuit of the weldability determination device.

FIG. 6 is a flowchart showing a schematic process of the weldability determination device.

FIG. 7 is a flowchart regarding a current density and a current integration value.

FIG. 8 is a flowchart relating to a pressing force density.

FIG. 9 is a flowchart relating to a heat generation amount.

FIG. 10 is a flowchart regarding an upset deformation speed and an upset displacement amount ratio.

FIG. 11 is a flowchart relating to a unit heat value.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 (fixed side) welding electrode 2 (moving side) welding electrode 3 Joining interface 4 Workpiece 10 Weldability judging device 11 Welding current detecting means 12 Welding voltage detecting means 13 Pressure detecting means 14 Electrode displacement detecting means 15 Energizing time Detecting means 17 Weldability determining means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B23K 11/25 513 B23K 11/25 513

Claims (5)

[Claims] In an upset butt welding of an aluminum alloy in which a welding current is applied to a material to be welded through a welding electrode and welding is performed on a joining interface of the material to be welded by resistance heating, a welding current applied to the material to be welded is used. Welding current detecting means for detecting, welding voltage detecting means for detecting a welding voltage applied to the material to be welded, energizing time detecting means for detecting an energizing time to be applied to the material to be welded, An electrode displacement amount detecting means for detecting a displacement amount, a pressing force detecting means for detecting a pressing force applied to the joining interface, and determining weldability of the joining interface based on each detection value of each detecting means. An upset butt weldability determination device for an aluminum alloy, comprising: weldability determination means. 2. A current density, a pressing force density, a current integral value and a heat generation value obtained from each detection value of each of the detection means of the aluminum alloy upset butt weldability judging device according to claim 1. A method for determining the upset butt weldability of an aluminum alloy, wherein one or more operations are calculated and compared with a reference value to determine the weldability of the joint interface. 3. An upset butt deformation speed (hereinafter referred to as an upset deformation speed) and an upset butt displacement amount ratio (hereinafter, referred to as an upset deformation speed) obtained from the displacement amount of the welding electrode of the aluminum alloy upset butt determination device according to claim 1. An upset butt made of an aluminum alloy, wherein at least one of the upset displacement ratio and the unit calorific value is calculated and compared with a reference value to determine the weldability of the bonding interface. Method for determining weldability. 4. The method for judging the upset butt weldability of an aluminum alloy according to claim 2, wherein the respective calorific values during the preheating period and the heating period are compared with a reference value to determine the weldability of the joint interface. 5. The method for judging the upset butt weldability of an aluminum alloy according to claim 2, wherein each welding force density in each period of the upset butt welding is compared with a reference value to determine the weldability of the joint interface. .