JP2008068301A - Arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform welding of high quality by obtaining sufficient bead width and bead height, and also by obtaining deep penetration into a base material. <P>SOLUTION: Welding is performed to the +Z direction along a boundary 34 between a first member 30 and a second member 32 of an upper plate by making a welding torch 14 go around while conducting a weaving motion. One period of the weaving is a one-round route designated by teaching points P1, P2, P3, P4. The welding is performed while switching the current during one period of weaving in such a manner that DC is applied in a first moving section 40a, AC is applied in a second moving section 40b, AC is applied in a third moving section 40c, and AC is applied in a fourth moving section 40d. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an arc welding method for performing welding by weaving that makes a welding torch go around.

  In recent vehicles, weight reduction has been achieved in response to demands for safety, economy, and low fuel consumption, and the use of high-strength aluminum is increasing. In addition, there is an increasing demand for applying an aluminum material to a place where a high load is applied in a vehicle or the like and arc welding the members with high strength. However, since aluminum material has high thermal conductivity, it has a large thermal effect, and advanced technology is required for welding.

  For example, Patent Literature 1 and Patent Literature 2 listed below can be cited as welding of an aluminum material.

  In Patent Document 1, it is proposed that the half cycle on the thick plate side is set to a high current, the half cycle on the thin plate side is set to a low current, and a high-frequency pulse current is applied to stabilize the arc during one cycle of weaving. .

  Patent Document 2 proposes an automatic welding apparatus for aluminum alloy pipes, which is automatic welding in which the outer circumference of the pipe is rotated once by a welding torch and is performed while switching between alternating current and direct current.

Japanese Patent Laid-Open No. 2004-9115 Japanese Patent No. 2922457

  In order to weld aluminum materials with sufficient strength at locations where particularly heavy loads are applied, such as in vehicles, using beading MIG welding, the bead width and bead height (also called throat thickness) are made larger than before. There is a need. Further, in order to obtain stable welding quality, sufficient penetration into the base material is necessary.

  On the other hand, in the technique of Patent Document 1, it seems that the melting on the thin plate side is stable, but the width and height of the beads are insufficient, and sufficient penetration into the base material cannot be obtained. In the apparatus of Patent Document 2 described above, only AC and DC are periodically switched by movement of the welding torch on the welding line, and arc welding by weaving is not used. Therefore, the bead width is very narrow and the welding strength is small.

  Thus, when the aluminum material is MIG welded by the conventional arc welding method, the strength may be insufficient, and reinforcement by TIG welding or the like is necessary to obtain a predetermined strength.

  The present invention has been made in consideration of such problems, and provides an arc welding method that can obtain a sufficient bead width and height and a deep penetration into a base material, thereby obtaining high-quality welding. For the purpose.

  An arc welding method according to the present invention is an arc welding method in which a welding torch is circulated by weaving to perform welding, and during one cycle in which the welding torch circulates, the current is changed between direct current and alternating current at least once. It is characterized by switching and welding.

  In this way, by switching the current between direct current and alternating current in one cycle, deep penetration into the base metal is obtained in the welded portion by direct current, and heat input is suppressed in the welded portion by alternating current, and the melting amount is reduced. As a result, a sufficient build-up is obtained, and as a result, a sufficient bead width and height are obtained, and a deep penetration into the base material is obtained, resulting in a high-quality weld.

  Note that weaving here is not a narrowly defined operation method that simply vibrates symmetrically with respect to the welding progress direction, but instead of vibrating in a laterally asymmetric manner with respect to the welding progress direction, it also moves in the backward direction, and the operation path Is a broad meaning including a method that operates to form a predetermined one-round route, a partially opened C-shaped route, or the like.

  In this case, if welding is started with direct current at the start of welding in one cycle of the weaving, appropriate penetration into the base material can be obtained.

  In addition, by setting the moving speed of the welding torch faster in the section where welding is performed with direct current than the section where welding is performed with alternating current, heat is not excessively applied to the base metal, and aluminum having high thermal conductivity. It can be suitably applied to materials and the like.

  According to the arc welding method of the present invention, by switching the current between direct current and alternating current during one cycle, a deep penetration into the base material can be obtained in the welded portion by direct current, and heat input in the welded portion by alternating current. As a result, sufficient bead width and height are obtained, deep penetration into the base material is obtained, and high-quality welding is obtained.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an arc welding method according to the present invention will be described with reference to FIGS. The arc welding method according to the present embodiment is performed by a welding system 10 shown in FIG.

  As shown in FIG. 1, a welding system 10 in which a MIG (Metal Inert Gas arc welding) welding method according to the present embodiment is performed is a system for arc welding to a workpiece W, and is a robot (moving) Means) 12, a welding torch 14 provided at the tip of the robot 12, a positioner 16 for holding the workpiece W, and a main controller 18 for performing overall control.

  The robot 12 is an industrial 6-axis joint type, and can arrange the welding torch 14 in an arbitrary posture at an arbitrary position within an operation range. The robot 12 can perform a program operation and a teaching operation, and can operate the welding torch 14 to move via a plurality of teaching points previously taught.

  The welding torch 14 is for MIG welding, and has a torch main body and a consumable wire electrode fed to the torch main body. In MIG welding, a shield gas is supplied from a gas nozzle in the main body of the torch, and an electrode wire is supplied from the center of a tip provided on the axis of the gas nozzle to melt the electrode wire and weld the workpiece. The electrode wire is fed from a predetermined reel toward the tip end of the chip by a feed roller at a predetermined speed, and shield gas stored in a cylinder is supplied to the welding torch 14.

  The positioner 16 is a biaxial mechanism for moving the position of the workpiece W so that the robot 12 can easily approach the welding torch 14, and performs a synchronous operation with the robot 12. The positioner 16 includes a base 20a, a pair of arms 20b obliquely projecting from the base 20a, a main rotating portion 20c held at both ends by these arms 20b, and one end of the main rotating portion 20c. And a rotating disk 20d provided on the surface.

  The main rotation part 20c is rotatable in the pitch direction (see arrow A) under the action of the first motor 20e provided on the arm 20b. The rotating disk 20d can be rotated in the roll direction (see arrow B) under the action of the second motor 20f provided at the end of the main rotating portion 20c. That is, the rotating disk 20d can perform two-axis operation in the pitch direction and the roll direction under the action of the first motor 20e and the second motor 20f.

  The rotating disk 20d is provided with a workpiece holding table 20g, and the workpiece W is fixed at a specified position by a jig 20h on the workpiece holding table 20g. The workpiece W is subjected to a predetermined grounding process and is at 0V potential.

  As shown in FIG. 2, the main controller 18 includes a robot controller 22 that controls the robot 12, a positioner controller 24 that controls the positioner 16, and a welding torch controller 26 that controls the welding torch 14. Have The robot control unit 22, the positioner control unit 24, and the welding torch control unit 26 are connected to each other and can be controlled synchronously by exchanging predetermined information in real time.

  The robot control unit 22 and the positioner control unit 24 can perform synchronized program operations by accessing the teaching data 22a and the teaching data 24a previously taught (or set by calculation, analysis, etc.).

  The welding torch control unit 26 includes a timing control unit 26a, a DC drive unit 26b, and an AC drive unit 26c. The timing control unit 26a confirms the operation timing of the robot control unit 22 and the positioner control unit 24 in real time, and applies a DC voltage to the wire electrode of the welding torch 14 via the DC drive unit 26b at a predetermined timing, or An AC voltage is applied to the wire electrode via the AC driving unit 26c. The standard of direct current and alternating current is set to ground potential. Further, the timing control unit 26a stops the voltage application to the wire electrode at a predetermined timing.

  By applying a DC voltage to the wire electrode, a DC current flows from the wire electrode to the workpiece W, and welding is performed. In welding by direct current, the wire electrode can be deeply melted into the base material.

  Moreover, by applying an AC voltage to the wire electrode, an AC current flows from the wire electrode to the workpiece W, and welding is performed. In welding with an alternating current, heat input is suppressed, a melting amount is secured, and a sufficient build-up is obtained.

  Here, DC means a state in which a positive or negative polarity voltage is applied with reference to the workpiece potential, and is not limited to the application of a constant voltage. Including the state of applying a voltage.

  AC is a state in which positive and negative polarities are alternately applied with respect to the potential (0V) of the workpiece W and energized. The positive and negative voltages are equal to each other. The present invention includes, but is not limited to, application of a voltage in which the positive side voltage and the negative side voltage are different, and a state of applying a pulsed voltage.

  For example, as shown in FIG. 3, the direct current generated by the direct current drive unit 26b is a direct current pulse, and a small positive base current Idb and a large positive pulse current Idp are alternately and repeatedly supplied every minute time. Is set to In this case, for example, the magnitude of the pulse current Idp may be variable, and the current value may be adjustable.

  For example, as shown in FIG. 4, the alternating current generated by the alternating-current drive unit 26c includes a negative current Ian having a small absolute value, a small positive base current Iab, and a large positive pulse current Iap in order, and for a minute time. It is set so that it is energized repeatedly every time. In this case, for example, the magnitudes of the pulse current Iap and the negative current Ian may be made variable so that the current value can be adjusted.

  As another example of the alternating current generated by the alternating current drive unit 26c, as shown in FIG. 5, a negative current Ian having a small absolute value, a small positive base current Iab, and a large positive change current Iav are provided. The power is set to be repeatedly energized in order and every minute time. The change current Iav is a section in which the first half of the first half is a section where the current is increased with a constant slope, and the first half of the middle section is a section in which a constant large current is held. The section / 3 is set as a section in which the current is decreased at a constant slope. In this case, for example, the maximum value of the pulse current Iap and the magnitude of the negative current Ian may be made variable so that the current value can be adjusted.

  In this welding system 10, as shown in FIG. 1, the boundary 34 between the first member (upper plate) 30 and the second member (lower plate) 32 of the workpiece W, and the first member 30 ′ and the second member 32, This is performed on the fillet portion provided along the boundary 34 '. Hereinafter, welding that is typically performed on the boundary 34 will be described. The boundary 34 may be a straight line or a curved line. The surface of the first member 30 is disposed slightly above the surface of the second member 32, and an appropriate level difference is provided (see FIG. 7).

  Next, teaching performed prior to actual welding will be described with reference to FIG.

  As indicated by a coordinate Z in FIG. 6, the welding progress direction is a positive direction from right to left. Further, the Y coordinate orthogonal to the Z coordinate is defined, and the downward direction in FIG. 6 is defined as plus and the upward direction is defined as minus. In other words, the negative range of the Y coordinate corresponds to the first member 30, and the positive range corresponds to the second member 32.

  Teaching for this welding is performed by recording four teaching points P1, P2, P3 and P4 in the teaching data 22a in the order of the weaving operation. These teaching points P1 to P4 are recorded as relative points with respect to predetermined reference points B1, B2,... Bn, and teaching points P1 to P4 are set for the respective reference points B1, B2,. Is equivalent to Reference points B1, B2,... Bn are set at equal intervals on the boundary 34 in the welding progress direction.

  When the reference point B1 is set as the origin of the YZ coordinates, the teaching point P1, which is the starting point of the weaving, is set to a position slightly more positive than the reference point B1 on the Z coordinates (Y = 0). The second teaching point P2 is set at a position where the Z coordinate is slightly negative and the Y coordinate is large in the positive direction. The third teaching point P3 is set at a position where the Z coordinate is further displaced in the minus direction from the teaching point P2 and the Y coordinate is about half the teaching point P2. The last teaching point P4 is set at a position that is substantially symmetric with respect to the teaching point P3 with respect to the Y coordinate and is substantially equal to the teaching point P2 with respect to the Z coordinate.

  The welding torch 14 operates along a route that passes through these four teaching points P1, P2, P3, and P4 (hereinafter also referred to as weaving), and between the teaching point P1 and the teaching point P2. The first movement section 40a, the second movement section 40b between the teaching point P2 and the teaching point P3, the third movement section 40c between the teaching point P3 and the teaching point P4, and the teaching point P3 and the teaching point P4. A round motion is performed so that a quadrangular closed region is formed by the fourth movement section 40d between the two. The welding torch 14 basically moves linearly between the teaching points, but may be moved in a curved line using a predetermined operation mode.

  As is clear from FIG. 6, the one-round route formed by the teaching points P <b> 1 to P <b> 4 is longer in the Y direction than the Z direction, and is second than the first member 30 side (the range where the Y coordinate is negative). It is set so as to be offset toward the side of the member 32 (the range where the Y coordinate is positive). In addition, the weaving that passes through the teaching points P1 to P4 is an operation in the counterclockwise direction, and the teaching point P1 that starts the circulation is provided at a position closest to the welding progress direction (+ Z direction) among the four teaching points. ing. Further, the first movement section 40a at the start of welding in one cycle is set from the first member 30 side of the upper plate toward the second member 32 side of the lower plate.

  The welding torch 14 is taught to circulate via the necessary and sufficient four teaching points P1 to P4, the teaching number is not excessively large, teaching is easy, and the degree of freedom of setting is high. A large and appropriate weaving path can be constructed. Note that the weaving route is not necessarily a one-round route, and may be a C-shaped route or the like that is partially open.

  With the teaching of the teaching points P1 to P4, the type of the welding current in each of the moving sections 40a to 40d and the moving speeds V1, V2, V3, and V4 in each of the moving sections 40a to 40d are set. That is, the first moving section 40a and the fourth moving section 40d on the welding progress direction (+ Z direction) side are set to direct current, and the second moving section 40b and the third moving section 40c on the reverse direction (−Z direction) side are set to alternating current. Set to. Furthermore, the moving speeds V1 and V4 of the first moving section 40a and the fourth moving section 40d set to DC are higher than the moving speeds V2 and V3 of the second moving section 40b and the third moving section 40c set to AC. Set fast. The speeds V1 and V4 may be set to 1.1 to 2.0 times the speeds V2 and V3, for example.

  For convenience of explanation, the teaching points P1 to P4 are shown on the same plane. However, in actuality, coordinate values in the height direction (X direction) are set in accordance with the shapes of the first member 30, the second member 32, and the fillet portion. It is good to set individually. Further, the angle of the welding torch 14 is preferably set to be about 5 to 15 ° with respect to the surface of the workpiece W, for example.

  Each of the above settings is merely an example, and it is needless to say that the setting may be appropriately changed according to the material and shape of the workpiece W.

  Next, a method for performing MIG welding on the workpiece W using the welding system 10 configured as described above will be described.

  First, the workpiece W is fixed at a specified position of the workpiece holding table 20g of the positioner 16, and then the robot 12 and the positioner 16 are operated synchronously based on the teaching data 22a and 24a.

  Next, the positions of the teaching points P1 to P4 are obtained with the first reference point B1 as a reference, and the tip of the welding torch 14 is brought close to the teaching point P1.

  Next, the welding torch 14 is moved at the speed V1 to the teaching point P2 along the first movement section 40a. At this time, a direct voltage is applied to the wire electrode under the action of the direct current drive unit 26b to apply a direct current to perform welding, thereby forming the first bead 60 (see FIG. 6).

  In the first movement section 40a, since welding is performed by direct current, deep penetration into the base material is obtained. In particular, the first moving section 40a is a section on the welding progress direction side, and has not yet been welded by weaving, and is a portion where a bead is not formed, so that a current flows easily and deeper penetration into the base material. Is obtained. In addition, since the speed V1 is set relatively fast, it is not excessively heat input to the base material, and since there is little thermal influence, it can be suitably applied to aluminum materials having high thermal conductivity. It is.

  Furthermore, in the first movement section 40a, the weld pool is prevented from being advanced by slightly retreating in the direction opposite to the welding progress direction with respect to the Z axis, and the welding quality is improved.

  Conventionally, welding has been performed from the lower plate side to the upper plate side at the welding portion corresponding to the first moving section 40a. However, in the method according to the present embodiment, the upper portion of the first moving section 40a is Welding is performed from the first member 30 side of the plate toward the second member 32 side of the lower plate. Thereby, when the first member 30 is a casting, welding is performed while melting the casting, and the arc jump is difficult to be dispersed by taking out the arc to the stepped portion, and the remaining shape of the stepped portion is significantly reduced. The necessary weld strength requirements are met.

  After the welding torch 14 reaches the teaching point P2, the welding torch 14 is moved at the speed V2 to the teaching point P3 along the second movement section 40b. At this time, welding is performed by applying an AC voltage to the wire electrode and applying an AC current to the wire electrode under the action of the AC driving unit 26c. That is, at the teaching point P2, the current for performing welding is switched from direct current to alternating current. In the welding in this section, the second bead 62 is formed.

  In the second moving section 40b, since welding is performed by alternating current, heat input is suppressed, a melting amount is ensured, and a sufficient overlay is obtained. In particular, the second movement section 40b is a section on the opposite side to the welding progress direction, and is a place that substantially overlaps the first bead 60 welded with a direct current by the first movement section 40a of the previous weaving. Therefore, a certain amount of beads have already been formed, and the current is slightly less likely to flow, so that the overlay is formed more effectively than the penetration into the base material. Further, since the speed V2 is set to be relatively low, the time for performing the build-up becomes longer, and a higher build-up is formed.

  Further, in the second movement section 40b, the upper plate moves toward the first member 30 side, so that the height of the upper plate is kept stable by using the step of the boundary 34, and sufficient build-up is compensated. The

  After the welding torch 14 reaches the teaching point P3, the welding torch 14 is moved at the speed V3 to the teaching point P4 along the third movement section 40c. At this time, welding is performed by applying an AC voltage to the wire electrode and applying an AC current to the wire electrode under the action of the AC driving unit 26c. In the third movement section 40c, substantially the same effect as that of the second movement section 40b is obtained.

  After the welding torch 14 reaches the teaching point P4, the welding torch 14 is moved at the speed V4 to the teaching point P1 along the fourth movement section 40d. At this time, welding is performed by applying a direct current to the wire electrode by applying a direct current under the action of the direct current drive unit 26b. That is, at the teaching point P4, the current for welding is switched from AC to DC.

  In the fourth movement section 40d, substantially the same effect as that of the first movement section 40a is obtained. Further, in the fourth moving section 40d, the welding is proceeded in the welding direction with respect to the Z axis, but the distance is shorter than that of the first moving section 40a, the molten pool is hardly preceded, and the welding quality is maintained. Be drunk.

  When the welding of the fourth moving section 40d is finished, the welding of one cycle by weaving is finished, and the circumferential bead 64 is formed. The weaving path is set longer in the Y direction than in the Z direction, and the width D of the bead 70 (see FIG. 7) made up of the plurality of circumferential beads 64 is formed sufficiently long.

  Thereafter, the welding current is stopped once and the welding torch 14 is moved to a preparation position for performing the next weaving. That is, as the second weaving, teaching points P1 ′, P2 ′, P3 ′, and P4 ′ (see FIG. 6) that are paths based on the reference point B2 are determined, and the robot 12 and the positioner 16 cooperate with each other. The welding torch 14 is moved to a new teaching point P1 ′. Here, the teaching points P1 'to P4' are equivalent to those obtained by moving the teaching points P1 to P4 in the welding progress direction. Thereafter, similar welding is sequentially performed on the reference points B2, B3,... Bn along the welding progress direction.

  As described above, in the arc welding method according to the present embodiment, the current is switched between direct current and alternating current during one weaving cycle. Thereby, while deep welding to a base material is obtained in the welding part by direct current, heat input is suppressed in the welding part by alternating current, and the amount of melting is secured, and sufficient overlaying is obtained.

  That is, sufficient penetration is secured by direct current welding at the welding progress direction side. Next, on the opposite side, switching to alternating current and changing the EN ratio can control only the amount of penetration without decreasing the supply amount (current), and it can be accumulated without flowing the bead of the built-in part, enough A bead 70 having a high height H (see FIG. 8) is obtained.

  Here, the EN ratio is a current waveform at the time of AC welding, and is a ratio of the negative side width S2 to the total amplitude S1 (see FIG. 5). When the wire side has a negative potential with respect to the workpiece W, the melting of the wire proceeds more than the case of the positive potential. Therefore, the amount of penetration can be adjusted by changing the EN ratio by controlling the welding power source. Therefore, when the EN ratio increases (when the total amplitude S1 is reduced or the width S2 is increased), the wire can be melted with a small current even at the same wire feed speed, the welding average current is lowered, and the workpiece W is melted. Less. That is, when the EN ratio is increased, a bead with a shallower penetration and a larger surplus is obtained.

  As a result of the above welding, as shown in FIGS. 7 and 8, a bead 70 having a sufficiently large width D and height H is obtained, and a deep penetration 72 with respect to the base material is obtained, so that high-quality welding is obtained. Therefore, the first member 30 and the second member 32 are connected with high strength and can be used for high load applications. Moreover, there is no need to reinforce by TIG welding or the like when used for high load applications. In addition, since the melted portion cannot accurately indicate the boundary portion, it is schematically illustrated by a broken line in FIG.

  In addition, the above weaving is not a narrowly defined operation method that simply vibrates symmetrically with respect to the welding progress direction, but asymmetrically vibrates with respect to the welding progress direction and moves in the backward direction, and the movement path is It has a broad meaning including a method that operates to form a predetermined closed region.

  Furthermore, appropriate penetration into the base material can be obtained by welding with DC at the start of welding in one cycle of weaving.

  Furthermore, the teaching point P1 for starting the circulation is provided at a position closest to the welding progress direction among the four teaching points P1 to P4, and the portion that has not yet been welded is reliably welded with a direct current. This will be done and sufficient penetration is obtained.

  The location where the current is switched from direct current to alternating current, or where alternating current is switched to direct current does not necessarily need to be completely coincident with the teaching point P1 and the teaching point P3, and may be appropriately shifted depending on the design conditions. The weaving that is performed a plurality of times is not necessarily performed by an individual round route, but may be performed by a series of continuous routes.

  Of course, the arc welding method according to the present embodiment can be applied to various locations such as a lap joint, a butt having a different thickness, and a fillet portion.

  The arc welding method according to the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations and processes can be adopted without departing from the gist of the present invention.

It is a perspective view of a welding system. It is a block block diagram of a welding system. It is a time chart of direct current. It is a time chart of an alternating current. It is a time chart of the alternating current which concerns on a modification. It is a schematic diagram which shows the teaching point of the welding with respect to a workpiece | work. It is a perspective view of a work and a bead. It is sectional drawing of a workpiece | work and a bead.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Welding system 12 ... Robot 14 ... Welding torch 16 ... Positioner 30 ... 1st member (upper board) 32 ... 2nd member (lower board)
40a ... 1st movement section 40b ... 2nd movement section 40c ... 3rd movement section 40d ... 4th movement section 70 ... Beads B1, B2, Bn ... Reference point P1-P4 ... Teaching point W ... Workpiece

Claims (3)

An arc welding method for performing welding by turning a welding torch by weaving,
An arc welding method characterized in that welding is performed by switching the current between direct current and alternating current one or more times during one cycle of the welding torch. The arc welding method according to claim 1,
An arc welding method comprising welding at the start of welding in one cycle of the weaving with a direct current. In the arc welding method according to claim 1 or 2,
An arc welding method characterized in that a speed at which the welding torch is moved is set faster in a section where welding is performed with direct current than a section where welding is performed with alternating current.

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