Arc welding apparatus, arc welding method, arc welding system, and welded article

An arc welding apparatus includes: a detector configured to detect whether it is in a short state or an arc state between a consumable electrode and a welded article; a feed adjuster configured to apply a forward feed for feeding the consumable electrode when the arc state is detected and apply a reverse feed for feeding the consumable electrode when the short state is detected; a determiner configured to determine whether or not a predetermined period has elapsed after the detector has detected the short state; and an instructor configured to instruct the feed adjuster to continue the reverse feed even when the arc state is detected, until the determiner determines that the predetermined period has elapsed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2013-194109 filed with the Japan Patent Office on Sep. 19, 2013, the entire content of which is hereby incorporated by reference.

BACKGROUND

1. Technical Field

Disclosed embodiments relate to an arc welding apparatus, an arc welding method, an arc welding system, and a welded article.

2. Related Art

An arc welding apparatus disclosed in Japanese Patent No. 4807474 intends to improve the welding quality by controlling the feeding direction to the welding wire. Feeding the welding wire in the direction to the base metal (the work) is called as “forward feed” and feeding the welding wire in the direction opposite to the base metal is called as “reverse feed”. The arc welding apparatus of Japanese Patent No. 4807474 suppresses the increase of the spatter by reverse-feeding the welding wire until a short is opened regardless of the welding frequency.

SUMMARY

An arc welding apparatus includes: a detector configured to detect whether it is in a short state or an arc state between a consumable electrode and a welded article; a feed adjuster configured to adjust a feeding state of the consumable electrode so as to apply a forward feed for feeding the consumable electrode in a direction to the welded article when the detector detects the arc state and apply a reverse feed for feeding the consumable electrode in a direction opposite to the welded article when the detector detects the short state; a determiner configured to determine whether or not a predetermined period has elapsed after the detector has detected the short state; and an instructor configured to instruct the feed adjuster to continue the reverse feed even when the detector detects the arc state, until the determiner determines that the predetermined period has elapsed after the detector has detected the short state.

DETAILED DESCRIPTION

An arc welding apparatus according to one form of the embodiments includes a detector, a feed adjuster, a determiner, and an instructor. The detector detects whether it is in a short state or an arc state between a consumable electrode and a welded article. The feed adjuster adjusts a feeding state of the consumable electrode so as to apply a forward feed for feeding the consumable electrode in a direction to the welded article when the detector detects the arc state and apply a reverse feed for feeding the consumable electrode in a direction opposite to the welded article when the detector detects the short state. The determiner determines whether or not a predetermined period has elapsed after the detector has detected the short state. Until the determiner determines that the predetermined period has elapsed after the detector has detected the short state, the instructor instructs the feed adjuster to continue the reverse feed even when the detector detects the arc state.

According to one form of the embodiments, the welding quality can be improved.

Described below in detail will be embodiments of an arc welding apparatus, an arc welding method, an arc welding system, and a welded article disclosed by the present application with reference to accompanying drawings. It is noted that the following embodiments do not limit the present disclosure.

An arc welding apparatus1according to the first embodiment continues the reverse feed until at least a predetermined period has elapsed regardless of whether it is in a short state or an arc state. This allows for the improvement of the welding quality.

FIG. 1is a diagram illustrating a configuration of the arc welding apparatus1according to the first embodiment. The arc welding apparatus1has a primary rectifying circuit3, a welding controller4, a switching circuit5, a transformer6, a secondary rectifying circuit7, a reactor8, a current detector9, a voltage detector10, and a storage17. The arc welding apparatus1supplies electric power for the welding to a welding torch13and a welded article (a work) W.

The primary rectifying circuit3is connected to a source power supply2. Further, the primary rectifying circuit3rectifies alternating power supplied from the source power supply2. Further, the primary rectifying circuit3supplies the rectified power to the switching circuit5.

The switching circuit5applies a PWM control to the electric power supplied from the primary rectifying circuit3to generate power supply to be supplied to the welding torch13. Further, the switching circuit5outputs the generated power supply to the transformer6.

The transformer6transforms the power supply voltage. Further, the transformer6outputs the transformed power supply to the secondary rectifying circuit7. The secondary rectifying circuit7rectifies the power supply outputted from the transformer6. Further, the secondary rectifying circuit7is connected to the work W via an output terminal12.

The reactor8smoothes the power supply rectified by the secondary rectifying circuit7. Further, the reactor8is connected to the welding torch13via an output terminal11. The power supply smoothed by the reactor8is supplied to the welding torch13and the work W via the output terminals11and12.

The current detector9detects the current between the welding torch13and the work W (hereafter, referred to as “welding current”). Further, the current detector9outputs the detected result to the welding controller4. The voltage detector10detects the voltage between the welding torch13and the work W (hereafter, referred to as “welding voltage”). Further, the voltage detector10outputs the detected result to the welding controller4.

The welding controller4controls the switching circuit5and a feeding device15based on the detected result inputted from the current detector9and the voltage detector10and the instruction inputted from an external controller16. Further, the welding controller4outputs information regarding the welding such as the welding current, the welding voltage, and the like to the external controller16. The details of the welding controller4will be described later.

The welding torch13supplies the welding current to a welding wire (a consumable electrode)14. The feeding device15has an actuator such as a servo motor, for example. Further, the feeding device15applies a forward feed and a reverse feed of the welding wire14based on the instruction from the welding controller4. Here, the forward feed refers to the feeding of the welding wire14in the direction to the work W. The reverse feed refers to the feeding of the welding wire14in the direction opposite to the work W.

The external controller16has a user interface (not shown) such as a keyboard, a touch panel, or the like and/or a display (not shown) such as a liquid crystal panel or the like. Further the external controller16accepts the input of the welding condition via the user interface. Here, the welding condition may include, for example, the welding current value, the welding voltage value, and the feeding speed of the welding wire14.

Further, the external controller16outputs the inputted welding condition to the welding controller4. Further, the external controller16displays the information regarding the welding inputted from the welding controller4on the display.

The storage17is, for example, a nonvolatile memory and stores control patterns, parameters, and the like of the feeding of the welding wire14, the welding current, and the welding voltage.

Next,FIG. 2is a block diagram illustrating the configuration of the welding controller4. The welding controller4has a detector41, a feed adjuster42, a determiner43, an instructor44, and a current adjuster45.

The detector41detects whether it is in a short state or an arc state between the welding wire14and the work W. Further, when the voltage value detected by the voltage detector10is less than or equal to a predetermined value, the detector41detects (determines) that it is in the short state between the welding wire14and the work W (that is, at this time, the detector41detects the short state). On the other hand, when the voltage value detected by the voltage detector10is greater than the predetermined value, the detector41detects (determines) that it is in the arc state between the welding wire14and the work W (that is, at this time, the detector41detects the arc state). Further, the detector41outputs the detected result to the determiner43and the instructor44.

The feed adjuster42adjusts the feeding state of the welding wire14so that the welding wire14is forward-fed when the detector41detects the arc state and the welding wire14is reverse-fed when the detector41detects the short state. Further, the feed adjuster42controls the feeding device15to apply the forward feed and the reverse feed of the welding wire14based on the instruction from the instructor44.

The determiner43determines whether or not a predetermined period has elapsed after the detector41has detected the short state. It is noted that the determiner43has a timer. Upon receiving the notification from the detector41indicating that the short state has been detected, the determiner43starts timing. Further, when a predetermined period has elapsed after starting the timing, the determiner43notifies it to the instructor44.

The instructor44instructs the feed adjuster42to adjust the feeding state of the welding wire14based on the detected result of the detector41. Specifically, when the detector41detects the arc state, the instructor44instructs the feed adjuster42to forward-feed the welding wire14. When the detector41detects the short state, the instructor44instructs the feed adjuster42to reverse-feed the welding wire14.

Further, until the determiner43determines that the predetermined period has elapsed after the detector41has detected the short state, the instructor44instructs the feed adjuster42to continue the reverse feed even when the detector41has detected the arc state.

Further, even when the determiner43has determined that the predetermined period has elapsed, the instructor44instructs the feed adjuster42to continue the reverse feed until the detector41detects the arc state.

The instructor44notifies the current adjuster45of the welding state and the feeding state. Specifically, the instructor44notifies the current adjuster45of whether the reverse feed is being applied under the short state, the forward feed is being applied under the arc state, or the reverse feed is being applied in spite of the arc state.

The current adjuster45adjusts the current value to be supplied to the welding wire14according to the notification from the instructor44. Specifically, the current adjuster45generates the current adjustment signal according to the notification from the instructor44and the control pattern of the welding current. Further, the current adjuster45outputs the current adjustment signal to the switching circuit5.

After the detector41has detected the arc state and until the determiner43determines that the predetermined period has elapsed after the detection of the short state, the current adjuster45adjusts the switching circuit5so that the current value supplied to the welding wire14is set smaller than the maximum value of the current that is supplied to the welding wire14in the case of the arc state.

Next, the operation of the arc welding apparatus1will be described. First, the normal operation of the arc welding apparatus1will be described.

FIG. 3illustrates graphs representing temporal changes of the welding current, the welding voltage, and the feeding speed of the welding wire14according to the present embodiment. The vertical axes of the graphs represent the welding current, the welding voltage, and the feeding speed, respectively. The horizontal axes of the graphs all represent time. It is noted that, in the present embodiment, the graph (the waveform) of the feeding speed has a form of trapezoidal waves as illustrated inFIG. 3. However, not limited to it, the waveform of the feeding speed may be a form of sinusoidal waves, a form of square waves, or a form of triangular waves.

It is assumed that the short state is detected by the arc welding apparatus1(the detector41) at time T1indicated inFIG. 3. Upon the detection of the short state, the arc welding apparatus1(the instructor44, the feed adjuster42) controls the feeding device15so as to change the feeding state of the welding wire14from the forward feed to the reverse feed. Further, the arc welding apparatus1(the current adjuster45, the switching circuit5) gradually increases the welding current.

In response that the welding wire14is reverse-fed, the short is then opened and the arc is regenerated, and the welding voltage rises. Then, at the time when the welding voltage exceeds a predetermined value (see, for example, time T2ofFIG. 3), the arc welding apparatus1detects the arc state. Upon detecting the arc state, the arc welding apparatus1controls the feeding device15to change the feeding state of the welding wire14from the reverse feed to the forward feed.

Further, upon detecting the arc state, the arc welding apparatus1supplies the welding current having the maximum current value to the welding wire14for a predetermined period. The arc welding apparatus1then gradually reduces the welding current.

In response that the welding wire14is forward-fed, the short then occurs and the welding voltage decreases. Then, at the time when that welding voltage falls below the predetermined value (see, for example, time T3ofFIG. 3), the arc welding apparatus1detects the short state. Since the operation of the arc welding apparatus1after the detection of such the short state is similar to the operation on and after the time T1, the description thereof will be omitted.

In this way, the arc welding apparatus1detects the short state and the arc state, and adjusts the forward feed and the reverse feed of the welding wire14based on the detected result.

It is noted that, as illustrated inFIG. 3, the short state and the arc state typically occur at a period close to constant. Therefore, the switching between the forward feed and the reverse feed of the welding wire14is done at a predetermined period. As a result, the distance between the tip end of the welding wire14and the work W (hereafter, referred to as “arc length”) is maintained to a proper length. The arc length is maintained to a proper length, so that the arc welding apparatus1is able to reduce the spatter to improve the welding quality.

Here, there is a case where the period of the occurrence of the arc state and the short state significantly changes due to the disturbance such as the change in the state of the melting pool or the environment. In particular, when the period of the short state is reduced, if the reverse feed were applied during the short state only as usual, the reverse feed period would also be reduced. Thus, the welding wire14would be insufficiently reverse-fed resulting in the reduced arc length. If the operation entered the arc state with the arc length being reduced, the spatter would increase and thus the poor welding quality would be caused.

In contrast, the arc welding apparatus1according to the present embodiment is configured to be able to improve the welding quality even when the short state (the short-state period) is reduced while typically applying the forward feed and the reverse feed depending on the arc state and the short state. Specifically, the arc welding apparatus1according to the present embodiment continues the reverse feed for a predetermined period even when the arc state is detected. This allows the proper arc length to be maintained, so that the welding quality can be improved. This point will be described in detail by usingFIG. 4.

FIG. 4illustrates graphs representing temporal changes of the welding current, the welding voltage, and the feeding speed of the welding wire14according to the present embodiment. The vertical axes of the graphs represent the welding current, the welding voltage, and the feeding speed, respectively. The horizontal axes of the graphs all represent time.

It is assumed that the short state is detected by the arc welding apparatus1(the detector41) at time T4indicated inFIG. 4. Upon the detection of the short state, the arc welding apparatus1(the instructor44, the feed adjuster42) controls the feeding device15so as to change the feeding state of the welding wire14from the forward feed to the reverse feed.

Then, at time T5, the arc state is detected. As this time, it is assumed that the short-state period indicated by the period from the time T4to the time T5is shorter than the normal short-state period (for example, the period from the time T1to the time T2). In this case, the arc welding apparatus1according to the present embodiment (the instructor44) continues the reverse feed of the welding wire14for a predetermined period. Specifically, even when detecting the arc state at the time T5, the arc welding apparatus1reverse-feeds the welding wire14until time T6at which the predetermined period has elapsed from the detection of the short state.

That is, at the time T6, the arc welding apparatus1(the determiner43) determines that the predetermined period has elapsed from the detection of the short state. Then, the arc welding apparatus1(the instructor44and the feed adjuster42) controls the feeding device15to change the feeding state of the welding wire14from the reverse feed to the forward feed.

Further, while the reverse feed is being applied under the arc state (between the time T5to the time T6), the arc welding apparatus1(the current adjuster45, the switching circuit5) reduces the value of the welding current supplied to the welding wire14to be smaller than the maximum value Imax of the welding current supplied to the welding wire14in the case of the arc state. This allows for the suppression of vibration in the melting pool and thus allows for the stable welding.

It is noted that, inFIG. 4, the value of the welding current during the reverse feed being applied under the arc state (between the time T5and the time T6) is set to a constant value between the maximum value Imax and the minimum value Imin of the welding current. This value of the welding current is not limited to it, but may be set to substantially the same as the minimum value Imin of the welding current, or may be set so as to increase at a constant increasing rate, for example.

Described below will be the above-described predetermined period (the period from the time T4to the time T6) that is the reverse feed period in the case where the period of the short state is reduced as illustrated inFIG. 4. For example, this predetermined period is set to be substantially the same as the reverse feed period in the case where the short state and the arc state occur at a period close to constant. For example, in the present embodiment, the predetermined period is set to substantially the same as the period from the time T1to the time T2ofFIG. 3. It is noted that the setting method of the predetermined period may include, for example, the method of deriving the proper value in advance by the experiment and the like.

Further, the determiner43may change the predetermined period depending on the welding current value inputted from the external controller16. This is because the period at which the short state and the arc state occur changes when the welding current value is changed. Therefore, the predetermined period is changed depending on the welding current value, so that the predetermined period can be the proper value regardless of the welding current value. This allows for the improvement of the welding quality regardless of the welding current value.

Next, by referring toFIG. 5and already illustratedFIG. 1andFIG. 2, a welding process of the arc welding apparatus1according to the present embodiment will be described.FIG. 5is a flowchart illustrating the welding process according to the present embodiment.

First, the detector41detects whether or not it is in the short state between the welding wire14and the work W (step S101). Here, if the detector41detects the short state (step S101, Yes), the feed adjuster42adjusts the feeding state of the welding wire14to reverse-feed the welding wire14(step S102). On the other hand, if the detector41does not detect the short state (step S101, No), step S105is performed (that is, the welding wire14is forward-fed).

After the step S102, the detector41detects whether or not it is in the arc state between the welding wire14and the work W (step S103). Here, if the detector41detects the arc state (step S103, Yes), step S104is performed. If the detector41does not detect the arc state (step S103, No), the process returns to the step S102.

Then, at the step S104, the determiner43determines whether or not a predetermined period has elapsed. Here, if the determiner43determines that the predetermined period has elapsed (step S104, Yes), the feed adjuster42adjusts the feeding state of the welding wire14to forward-feed the welding wire14(step S105).

On the other hand, if the determiner43determines that the predetermined period has not elapsed (step S104, No), the instructor44instructs the feed adjuster42to continue the reverse feed (step S106), and the process returns to the step S104. Further, at the step S106, the current adjuster45reduces the value of the welding current supplied to the welding wire14to be smaller than the maximum value Imax of the welding current supplied to the welding wire14in the case of the arc state.

Subsequently, the welding controller4determines whether or not to finish the welding (step S107). Here, if it is determined to finish the welding (step S107, Yes), the arc welding apparatus1finishes the welding of the work W. On the other hand, if it is not determined to finish the welding (step S107, No), the process returns to the step S101and the welding is continued.

Here, the welding controller4may determine whether or not to finish the welding based on the time from the start of the welding or the instruction from the external controller16, for example. It is noted that, in the welding process ofFIG. 5, whether or not to finish the welding is determined when the forward feed is being applied. However, whether or not to finish the welding may be determined when the reverse feed is being applied. Alternatively, the welding controller4may accept the welding completion instruction as an interrupt instruction while executing the welding process.

Further, in the welding process ofFIG. 5, whether or not it is in the short state between the welding wire14and the work W is detected at the step S101. In this step, however, detected may be whether or not it is in the arc state between the welding wire14and the work W. Alternatively, in the step S101, the detector41may compare the welding voltage with a predetermined value. In this case, the detector41may detect (determine) that it is in the short state between the welding wire14and the work W if the welding voltage is less than or equal to the predetermined value, or may detect (determine) that it is in the arc state between the welding wire14and the work W if the welding voltage is greater than the predetermined value. In this way, the process of the step S101and the process of the step S103may be performed together in one step.

Further, in the welding process ofFIG. 5, whether or not the predetermined period has elapsed from the detection of the short state is determined after the arc state has been detected. This results in that, even when the determiner43determines that the predetermined period has elapsed, the instructor44instructs the feed adjuster42to continue the reverse feed until the detector41detects the arc state.

As having been described above, the arc welding apparatus according to the first embodiment has the detector, the feed adjuster, the determiner, and the instructor. The detector detects whether it is in the short state or the arc state between the consumable electrode (the welding wire14) and the welded article (the work W).

The feed adjuster adjusts the feeding state of the consumable electrode so as to apply the forward feed for feeding the consumable electrode in the direction to the welded article when the detector detects the arc state and apply the reverse feed for feeding the consumable electrode in the direction opposite to the welded article when the detector detects the short state.

The determiner determines whether or not a predetermined period has elapsed after the detector has detected the short state. Until the determiner determines that the predetermined period has elapsed after the detector has detected the short state, the instructor instructs the feed adjuster to continue the reverse feed even when the detector detects the arc state.

Therefore, according to the arc welding apparatus according to the first embodiment, the reverse feed is continued until at least a predetermined period has elapsed regardless of whether it is in the short state or the arc state between the consumable electrode and the welded article. Therefore, even when the short state is reduced, the spatter can be reduced and thus the welding quality can be improved. That is, the welding quality can be further improved.

In the second embodiment, an arc welding system100will be described. In the arc welding system100, the arc welding apparatus1according to the first embodiment and a robot20having the welding torch13attached to its tip end are combined. This allows for further improvement of the welding quality in the arc welding system100.

FIG. 6is a diagram illustrating the arc welding system100according to the second embodiment. It is noted that, in the second embodiment, the same components as those in the first embodiment are provided with the same reference numerals and the description thereof will be omitted.

The arc welding system100has the arc welding apparatus1according to the first embodiment and the robot20. The robot20moves the tip end of the welding wire14relatively with respect to the work W. The arc welding system100further has the welding torch13, the welding wire14, the feeding device15, the external controller16, a gas cylinder18, and a welding wire supplier19.

In the present embodiment, the external controller16functions also as a controller of the robot20. That is, the external controller16controls the robot20and changes the position and attitude of the welding torch13. For example, the external controller16moves the welding torch13so that the tip end of the welding torch13traces a desired welding line with respect to the work W.

The welding wire supplier19supplies the incorporated welding wire14to the feeding device15. The gas cylinder18supplies a shield gas to the welding torch13.

In the second embodiment, the arc welding apparatus1according to the first embodiment is mounted to the arc welding system100. This allows for further improvement of the welding quality in the arc welding system100.

Further advantages and modified examples can be readily derived by those skilled in the art. Thus, a broader form of the present disclosure is not limited by the specific details and the exemplary embodiments that have been illustrated and described above. Therefore, various modifications are possible without departing from the spirit and scope of the concept of the extensive disclosure defined by the appended claims and their equivalents.

It is noted that the welding wire14is an example of the consumable electrode. The work W is an example of the welded article. The detector41is an example of the detection means. The feed adjuster42is an example of the feed adjustment means. The determiner43is an example of the determination means. The instructor44is an example of the instruction means.

Further, the arc welding apparatus, the arc welding method, the arc welding system, and the welded article may be the following first to fourth arc welding apparatus, first to third arc welding methods, first arc welding system, and first welded article. The first arc welding apparatus has: a detector configured to detect whether it is in a short state or an arc state between a consumable electrode and a welded article; a feed adjuster configured to adjust a feeding state of the consumable electrode so as to apply a forward feed for feeding the consumable electrode in a direction to the welded article when the detector detects the arc state and apply a reverse feed for feeding the consumable electrode in a direction opposite to the welded article when the detector detects the short state; a determiner configured to determine whether or not a predetermined period has elapsed after the detector has detected the short state; and an instructor configured to instruct the feed adjuster to continue the reverse feed even when the detector detects the arc state, until the determiner determines that the predetermined period has elapsed after the detector has detected the short state.

In the second arc welding apparatus in the first arc welding apparatus, when the determiner determines that the predetermined period has elapsed, the instructor instructs the feed adjuster to continue the reverse feed until the detector detects the arc state.

In the first or second arc welding apparatus, the third arc welding apparatus has a current adjuster configured to reduce a current value supplied to the consumable electrode to be smaller than the maximum value of a current supplied to the consumable electrode in a case of the arc state until the determiner determines that the predetermined period has elapsed after the detector has detected the arc state.

In the fourth arc welding apparatus in any one of the first to third arc welding apparatus, the determiner changes the predetermined period depending on a welding current.

The first arc welding method includes: a detection step for detecting whether it is in a short state or an arc state between a consumable electrode and a welded article; a feed adjustment step for adjusting a feeding state of the consumable electrode so as to apply a forward feed for feeding the consumable electrode in a direction to the welded article when the detection step detects the arc state and apply a reverse feed for feeding the consumable electrode in a direction opposite to the welded article when the detection step detects the short state; a determination step for determining whether or not a predetermined period has elapsed after the detection step has detected the short state; and an instruction step for instructing the feed adjustment step to continue the reverse feed even when the detection step detects the arc state, until the determination step determines that the predetermined period has elapsed after the detection step has detected the short state.

In the second arc welding method in the first arc welding method, when the determination step determines that the predetermined period has elapsed, the instruction step instructs the feed adjustment step to continue the reverse feed until the detection step detects the arc state.

In the first or second arc welding method, the third arc welding method includes a current adjustment step for reducing a current value supplied to the consumable electrode to be smaller than the maximum value of a current supplied to the consumable electrode in a case of the arc state until the determination step determines that the predetermined period has elapsed after the detection step has detected the arc state.

The first arc welding system has: an arc welding apparatus having a detector configured to detect whether it is in a short state or an arc state between a consumable electrode and a welded article, a feed adjuster configured to adjust a feeding state of the consumable electrode so as to apply a forward feed for feeding the consumable electrode in a direction to the welded article when the detector detects the arc state and apply a reverse feed for feeding the consumable electrode in a direction opposite to the welded article when the detector detects the short state, a determiner configured to determine whether or not a predetermined period has elapsed after the detector has detected the short state, and an instructor configured to instruct the feed adjuster to continue the reverse feed even when the detector detects the arc state, until the determiner determines that the predetermined period has elapsed after the detector has detected the short state; and a robot configured to move a tip end of the consumable electrode with respect to the welded article.

The first welded article is welded by an arc welding method including a detection step for detecting whether it is in a short state or an arc state between a consumable electrode and a welded article, a feed adjustment step for adjusting a feeding state of the consumable electrode so as to apply a forward feed for feeding the consumable electrode in a direction to the welded article when the detection step detects the arc state and apply a reverse feed for feeding the consumable electrode in a direction opposite to the welded article when the detection step detects the short state, a determination step for determining whether or not a predetermined period has elapsed after the detection step has detected the short state, and an instruction step for instructing the feed adjustment step to continue the reverse feed even when the detection step detects the arc state, until the determination step determines that the predetermined period has elapsed after the detection step has detected the short state.