JPH06155027A - Automatic welding equipment for square steel pipe - Google Patents

Abstract

PURPOSE:To provide an automatic welding equipment square steel pipes capable of welding continuously automatically a weld line consisting of a straight line part and a curved line part and with the bead thickness uniform in butt welding of the square steel pipes. CONSTITUTION:An L-shaped rail 18 is fixed on a square steel pipe 10 and the square steel 10 and 12 in an abutted state are welded continuously from the straight line part to the curved line part of the weld line by a welding torch 42 conveyed by a welding carriage while moving the welding carriage 30 and a traveling carriage 34 on this rail. The welding speed in the curved line part of the square steel pipes is controlled based on the welding speed of the straight line part and curvature of the rail of the curved line part and the weld line of the square steel pipes so that the bead thickness in the straight line part and the bead thickness in the curved line part are maintained constant. There are cases to obtain the curvature of the rail from acceleration obtained at the time of traveling by mounting an accelerometer simply by measuring and storing in advance only the curvature of the square steel pipe weld line in addition to the curvature of the rail in the curved line part and the weld line of the square steel pipes being measured and stored in a storage means in advance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic welding apparatus for square steel pipes for automatically butt-welding square steel pipes used as building materials in building construction and the like at a construction site.

[0002]

2. Description of the Related Art The conventional apparatus for butt welding square steel pipes used at a construction site is semi-automatic and requires skill of a skilled worker. In this case, first, the square steel pipes are butted against each other and temporarily fixed with an erection piece to secure them.
The entire welding operation is carried out by the procedure of first welding the straight line portion and a part of the curved portion of the welding line, and then cutting the erection piece and welding the remaining curved portion.
In this case, a bead splice is formed on the curved portion, and a process for smoothing this is performed.

[0003]

The conventional butt welding of square steel pipes, however, has a problem in that the work efficiency is low because the welding is semi-automatic, and it is difficult to promote the construction. Further, since the work is semi-automatic, the worker is required to have a high level of welding skill. Therefore, there is a problem that it is difficult for a beginner to perform the work.

Further, since the straight line portion of the welding line and a part of the curved portion are welded and then the remaining curved portion is welded, it is necessary to perform bead joining at the boundary portion of the curved portion. Therefore, it takes time to care for this joint with a grinder or the like. In addition, there is a problem that the corner portion which is a curved portion is apt to deteriorate the welding accuracy, is likely to cause a defect, and is apt to cause the quality deterioration due to the bead thickness being different between the straight portion and the curved portion.

The present invention has been made based on the above-mentioned circumstances, and by automatically performing butt welding of square steel pipes and controlling the speed of the carriage, the straight and curved portions of the square steel pipes have the same thickness continuously. It is an object of the present invention to provide an automatic welding device for square steel pipes which can improve welding accuracy and welding quality.

[0006]

[Means for Solving the Problems]
The first aspect of the present invention comprises a straight portion and an arc-shaped curved portion.
Welding in which square steel pipes with weld lines are butted against each other
In the device, a welding line consisting of the straight line portion and the curved line portion
Rail attached to square steel pipe along with welding torch
A truck that can move on the rail while transporting
And the curvature and square steel of the rail at each position of the rail
Storage means for storing in advance the curvature of the weld line of the pipe;
Position detecting means for detecting the position of the rail on the rail,
From the storage means and the position detection means,
The curvature of the weld line of steel and square steel pipe, and based on that value
The traveling speed of the carriage or the welding wire feeding speed or
And a control means for controlling both of these.
It is a characteristic.

The control means controls the welding speed of the carriage or the feeding speed of the welding wire or both of them so that the thicknesses of the welding beads at the straight line portion and the curved portion on the same welding line are continuously constant. It is characterized by.

[0008]

With the above construction, the present invention provides a rail that can be fixedly attached to a square steel pipe when the square steel pipes used at a construction site are butted against each other and welded to each other. Also, the square steel pipe can be automatically welded by moving the carriage carrying the control means and welding. Further, the control means appropriately controls the traveling speed of the carriage and the wire feeding speed in accordance with the curvature of the welding line of the square steel pipe, so that the bead thickness of the straight line portion and the curved portion can be adjusted to be constant. .

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a side view of an automatic welding apparatus according to an embodiment of the present invention, and FIG. 2 is a front view thereof. FIG. 3 is a perspective view showing a state where square steel pipes to be welded are butted and temporarily fixed, and FIG. 4 is a plan view showing a state where rails for an automatic welding device are attached to the square steel pipes. Here, as shown in FIG. 3, a case will be described in which a square steel pipe 10 and a square steel pipe 12 used as building construction materials are butted against each other at a welded portion 14 and welded. The welding line of this square steel pipe has a straight line portion when welding a flat surface portion and a curved portion when welding a corner portion.

Prior to welding, the square steel pipe 10 and the square steel pipe 12 are first butted against each other, and both are temporarily fixed by an erection piece 16. The erection piece 16 is fixed with a bolt (not shown). After that, FIG.
The L-shaped moving rail 18 is fixed to the square steel pipe 10 as shown in FIG. The moving rails 18 are fixed by sandwiching the mutually facing surfaces of the square steel pipe 10 with fixing means 20 and holding the bolts 22 from both sides. Note that this L-shaped rail corresponds to a quarter of one square steel pipe, and in order to weld the entire circumference of the square steel pipe, it is necessary to remove and weld the L-shaped rail and the bogie 4 times. However, there is an advantage that it can be applied to a wide range of rectangular steel pipes.

As shown in FIGS. 1 and 2, a welding carriage 30 and a traveling carriage 34 are provided on the rail 18.
Each of the welding carriage 30 and the traveling carriage 34 is supported by four bearings 32 from above and below the rail 18,
This is provided on the other side, that is, another set in the depth direction of FIG. 1, and is supported by a total of eight bearings. Further, the traveling carriage 34 and the welding carriage 30 are joints 3
6 are connected to each other. A rack 38 is provided on the rail 18, and a drivable gear 40 of the traveling carriage 34 meshes with the rack 38. Therefore, by driving the gear 40, the traveling carriage 34 and the welding carriage 30 connected thereto can be moved along the rail at the same speed.

A welding torch 42 for feeding a welding wire 44 from the tip is provided at the lower portion of the welding carriage 30.
The welding torch 42 is a welding torch for gas metal arc welding. The welding torch 42 is moved along the rail 18 by the welding carriage 30 (this is the x direction), and also in the groove depth direction (y direction) as shown in FIG. ) And the groove width direction (z direction). Therefore, the tip portion of the welding torch 42 can be moved to any position of the workpiece. A plane including the y direction and the z direction is set to be perpendicular to the midpoint of a line connecting the bearing 32 and another set of bearings in the depth direction. By doing so, the torch tip can move in a substantially arc shape when the carriage travels along the arc portion of the rail. further,
It is also possible to swing the welding torch itself so that the tip portion performs a so-called weaving operation. The welding conditions are determined by the traveling speed of the welding carriage 30 and the feeding speed of the welding wire 44, and the welding voltage is selected to a value that maintains an appropriate arc state with respect to these values.

FIG. 5 is a block diagram showing the structure of the control means provided inside the welding carriage 30. This control operation is performed mainly by the CPU 50. Four control blocks are provided on the right side of the CPU 50, and these control blocks correspond to movements in the x direction, z direction, and y direction, and rotation of the welding torch (weaving operation). Taking the control of movement in the x direction as an example, the servo controller 52 generates a signal indicating the position and speed of the welding carriage on the rail based on a command from the CPU 50, and this signal drives the traveling carriage via the servo amplifier 54. It is sent to the motor 56 of the driving carriage. The motor rotates based on this signal to move the welding carriage to a predetermined position on the rail at a predetermined speed. With this operation, the position of this welding carriage is detected, this position information is returned from the encoder 58 to the servo controller 54, and the welding carriage is moved to a more accurate position by the servo operation. The CPU 50 further includes a storage device 6 described later.
0, the wire feeder 62, the welding power source 64, etc. are also controlled.

The welding carriage 30 shown in FIG. 1 or FIG.
While moving along the V-shaped rail 18, the curved portion and the straight portion of the welding line in the abutting surfaces of the square steel pipes 10 and 12 are continuously welded. In such continuous welding, there is no need to perform bead splicing at a curved portion, so that maintenance by a grinder is unnecessary and the efficiency of welding work can be improved. Further, if welding can be performed automatically, no skilled worker is required. However, when automatic welding is performed, if the welding conditions in the straight line portion and the curved portion of the welding line, that is, the traveling speed of the welding carriage and the wire feeding speed are exactly the same, the bead thickness varies depending on the location. This is square steel pipe 10
This is because the curvature of and the curvature of the locus of movement of the welding carriage differ depending on the location. If the bead thickness varies from place to place, the welding beat cannot be properly raised, and therefore the welding conditions must be controlled so that the bead thickness is constant. In the present embodiment, multi-layer welding is premised, and even when welding one place, the bead thickness for one layer is small in one pass, and a predetermined thickness is obtained by stacking the beads over a plurality of layers.

Next, with reference to FIGS. 6A to 6C, control of the welding speed (that is, the moving speed of the tip of the welding wire) or the wire feeding speed at the straight line portion and the curved line portion of the welding line of the square steel pipe. Will be described. The control here is basically a control as a function of "welding speed (or wire feeding speed) / welding speed" (that is, the welding area of each pass of the groove cross section). Here, FIG. 6 (A) is an enlarged view of the welding bead for one pass, which is laminated by one pass of the welding torch in the straight portion of the welding line of the square steel pipe, as viewed from the z direction of FIG. 1. Yes, FIG. 6 (B) is a view of the curved portion of the welding line of the square steel pipe.
It is a figure similar to (A). FIG. 6C is an enlarged view of the groove between the square steel pipes 10 and 12 as viewed from the x direction in FIG. 1.
In these figures, r _s (mm) is the inner radius of curvature of the weld beads that are laminated in one pass, and r _e (mm) is the outer radius of curvature. Thus (r _e -r _s) is a thickness one pass is. Although the radius of curvature of the straight line part is infinite,
(A) for convenience r _s, 6 the r _e (B), is shown to correspond to (C). In addition, in FIG.
(R) is the width of the groove at the position of r. Therefore, if the shape of the groove and the shape of the weld bead in each pass are known, this S (r) can be obtained.

Assuming that the wire welding speed in the straight line portion is v _m (mm ³ / sec) and the welding speed is v _t (mm / sec), the geometrical relationships shown in FIGS. 6 (A) and 6 (C) are obtained. ,

[Equation 1] Is derived. From equation (1) can be obtained r _e, that is, the thickness of the weld bead when determined to a certain value welding speed v _m and the welding speed v _t in the linear portion. Next, at the curved portion, the welding speed of the wire is changed to v _m '
(Mm ³ / sec), the position of the wire tip is r _p (mm), and the angular velocity of the welding carriage is ω _p (rad / sec), from the geometrical relationships of FIGS. 6B and 6C,

[Equation 2] Is derived. The (2) in the r _e (1) v _m 'by calculating the right side by substituting r _e determined by the formula
/ R _p · ω _p , that is, “welding speed / welding speed” can be obtained. This value is the ratio of the welding speed (which is proportional to the wire feeding speed) and the welding speed (that is, the moving speed of the welding wire tip) at the position where the radius of curvature of the curved portion of the welding line of the square steel pipe is r _p , If this is understood, it is possible to know how to set the speed of the tip portion of the welding wire or the wire feeding speed in the curved portion of the welding line of the square steel pipe. In the straight part of the rail, the traveling speed of the welding carriage is equal to the welding speed,
Since the welding carriage rotates in a plane perpendicular to the z direction at the curved portion, it is necessary to increase the traveling speed of the welding carriage with respect to the wire tip moving speed (ie, welding speed) r _p · ω _p obtained by the equation (2). is there. Since the CPU 50 actually instructs the moving speed v (mm / sec) of the truck, a procedure for obtaining v is necessary.

In order to obtain the speed of the traveling carriage (welding carriage) (that is, welding speed) from r _p · ω _p obtained by the equation (2),

[Equation 3] You can use the formula Here, v is the speed of the traveling carriage (mm / sec), ρ is the radius of curvature (mm) of the moving trajectory of the on-rail carriage speed management position, and y is the on-rail carriage speed management position (two sets in the x direction of the welding carriage). The distance (mm) from the middle point of the line connecting the bearings to the tip of the wire is calculated from the encoder value of the y-direction movement motor.

In the actual welding work, the wire welding speed (that is, the wire feeding speed) is constant at both the curved portion and the straight portion, and only the welding speed (that is, a value determined by the traveling speed of the welding carriage and the curvature of the rail) is used. Since it is easy to control if changed, v _{m in} equation (1) and v _m 'in equation (2) are often made equal as long as the welding speed is within an appropriate range determined by the welding wire type.

By the way, in reality, since two bearings of the welding dolly before and after the traveling direction individually come into contact with the curved portion, ρ does not always match the radius of curvature at the dolly speed control position on the rail. The solid line in FIG. 7 (A) is the vehicle speed of the welding carriage until the straight line portion of the welding line of the square steel pipe reaches the straight line portion again (the situation is shown in FIGS. 7 (B) to (D)). It is a figure showing the change of the curvature of the locus of the management position, and the state of the change of the curvature with respect to the position of the dolly draws a trapezoid as shown in the figure. On the other hand, the wavy line shows how the rail curvature changes. The part corresponding to the hypotenuse of this trapezoid is the curvature of the locus of the vehicle speed control position when only one of the two pairs of bearings with the centers 90 mm apart is approaching the curved part of the weld line of the square steel pipe. Changes rapidly as the dolly progresses. On the other hand, the portion corresponding to the upper side of the trapezoid is the curvature of the locus of the vehicle speed control position in the state where both bearings are passing over the curved portion, and this value is constant and matches the rail curvature 1/150.

In the equation (3), ρ and r _e are determined from the curvature of the rail and the curvature of the welding line of the square steel pipe, respectively, so they are measured in advance before welding work, and S (r) and v _t ,
_{v m, v m ', (} r p -r e) is determined in advance to appropriate values for groove shape, and stored in the internal storage device 60 of FIG. 5. Although these values depend on the size of the square steel pipe, they are generally measured in 10 mm intervals in the x direction on the rail and stored in the storage device 60 in advance. Then, when performing the welding operation, the corresponding values are read out at the respective positions of the welding line of the square steel pipe under the control of the CPU 50, and the values of the welding carriage corrected from the above equations (1), (2) and (3) are read. The speed is calculated to control the speed of the traveling carriage, and the wire feeding speed is further controlled as necessary. By performing such control, the thickness of the weld bead can be kept constant even when continuously welding the welding line of the square steel pipe consisting of the straight portion and the curved portion, and the laminated welding is automatically performed. It will be possible to do.

By the way, the center of curvature of the rail and the center of curvature of the square steel pipe do not necessarily coincide. 8 (A) to (C)
This figure shows this state. In the same figure (A), when the center of curvature O of the rail 18 and the center of curvature O ′ of the square steel pipe 10 coincide, in the same figure (B), the center of curvature O ′ of the square steel pipe 10 is In the case of being on the inner side, FIG. 6C shows the case where the center of curvature O of the rail 18 is on the inner side. Even in such a case, the above-mentioned calculation procedure can be used as it is, but if the torch target angle at the moment of transition from the straight line portion to the curved portion, that is, the angle Δφ in FIGS. 8B and 8C is too large, The corrected value becomes inaccurate, and the bead thickness cannot be kept constant. This torch aiming angle becomes maximum at the boundary between the straight line portion and the curved portion, and becomes minimum (ideally zero) near the center of the curved portion. Therefore, as a practical allowable range | Δ
It is desirable that the maximum value of φ | be 20 ° or less.

In the above-mentioned embodiment, it is necessary to measure the curvature values of the weld line and the rail of the square steel pipe in advance by some method. On the other hand, a sensor for measuring the acceleration in the y direction is mounted at the carriage speed control position of the welding carriage,
By measuring the acceleration in the plane including the welding line with this sensor, the curvature of the trajectory of the bogie speed control position is automatically calculated.

[Equation 4] It is also possible to implement a configuration in which the value of ρ is obtained from the relationship of Here, a (mm / s ² ) is the acceleration in the y direction, which is obtained from the output of the sensor, and v (mm / s) is the traveling speed of the truck, C
It is managed by the PU 50. With such a configuration, an appropriate acceleration sensor can be selected and used from the commercially available general acceleration sensors, and automatic measurement can be performed by preparing a predetermined program executed by the CPU 50. . The value of ρ thus obtained can be substituted into the above equation (3) to obtain the speed of the carriage to be controlled. In the embodiment in which the acceleration sensor is mounted as described above, there is an advantage that the labor of previously measuring the curvature of the rail and traveling of the cart for the curvature measurement can be omitted.

As another embodiment, a voltage is applied between the welding wire and a square steel pipe which is the object to be welded, and the energization is detected from an increase in current or a decrease in voltage to detect contact between the two, The curvature of the rail can also be obtained from this. Figure 9
(A) shows that the welding carriage 30 is moved along the rail so that the welding wire does not contact the surface of the square steel pipe, and stopped at predetermined positions a, b, c, d, and e on the rail.
It shows how the wire 44 at the tip of the welding torch 42 is repeatedly moved in the y direction so as to come into contact with the surface of the square steel pipe 10.

At this time, when the current flowing between the square steel pipe and the wire exceeds a certain threshold value, it is considered that the wire has come into contact with the square steel pipe, and the movement in the y direction is stopped. The distance d (mm) from the bogie speed control position to the surface of the square steel pipe is measured from the value, and the horizontal axis represents the x direction and the vertical axis d represents FIG. 9. The contact between the wire and the square steel pipe can also be detected from the fact that the voltage value has dropped below the predetermined value from the applied voltage. Approximating the part where d changes in the form of this graph with an isosceles triangle, the length of the base of the triangle is L (mm), and the distance between the two wheels of the carriage in the x direction is k (mm)

[Equation 5] The curvature of the curved portion of the rail 18 can be calculated by the relationship of The curvature thus obtained is calculated as above (3)
By substituting into the equation, the speed of the truck to be controlled can be obtained.

Although the rails have been described as L-shaped in the above embodiments, any of the above embodiments can be applied to the case of a closed rail surrounding the entire square steel pipe. In the case of such a closed rail, there is no need to remove the rail and there is an advantage that the automatic welding operation only needs to be performed once.

[0026]

As described above, according to the present invention, in butt welding of square steel pipes, a welding line consisting of a straight line portion and a curved portion can be continuously and automatically welded, so that a bead splicing treatment in the curved portion is unnecessary. Therefore, it is possible to perform highly accurate welding even by an unskilled worker, and the bead of the curved portion can be controlled by controlling the welding speed in the curved portion based on the bead thickness of the linear portion and the curvature of the curved portion. Since the thickness can be set to the same uniform thickness as that of the straight line portion, it is possible to provide an automatic welding apparatus for square steel pipes that does not cause uneven welding strength and enables highly accurate welding work.

[Brief description of drawings]

FIG. 1 is a side view of an automatic welding apparatus according to an embodiment of the present invention.

FIG. 2 is a front view of the automatic welding device shown in FIG.

FIG. 3 is a perspective view showing a state where square steel pipes, which are objects to be welded, are butted.

FIG. 4 is a plan view showing a state in which a rail through which a welding carriage and a traveling carriage pass is fixed to a square steel pipe.

FIG. 5 is a block diagram of a control system of the automatic welding apparatus.

6 (A) and 6 (B) are enlarged views of a bead for one layer in a straight line portion viewed from the z direction, and FIG. 6 (C) is a cross-sectional view of a weld bead for one layer at the groove of the square steel pipe.

FIG. 7 is a graph showing a change in curvature from when the carriage reaches the straight line portion through the straight line portion to the curved line portion.

FIG. 8 (A) is a plan view showing an example in which the center of curvature of the rail and the center of curvature of the curved portion of the square steel pipe match, and FIG. 8 (B) is the center of curvature of the curved portion of the square steel pipe. FIG. 4C is a plan view showing an example in the case of being inside, and FIG. 6C is a plan view showing an example in the case where the center of curvature of the curved portion of the square steel pipe is outside the center of curvature of the rail.

FIG. 9A is a plan view showing a state in which the wire at the tip of the welding torch is brought into contact with the surface of a square steel pipe at a predetermined bogie position on a rail to move the welding torch, and FIG. 9B is a horizontal axis. 2 is a measurement graph in which the position of the dolly is taken and the vertical axis is the distance from the center of the wheels before and after the dolly to the surface of the square steel pipe.

[Explanation of symbols]

 10, 12 Square steel pipe 16 Erection beads 18 Rail 30 Welding trolley 32 Bearing 34 Traveling trolley 42 Welding torch 44 Welding wire 50 CPU 60 Storage device

Claims (4)

[Claims] 1. A welding device for welding square steel pipes having a welding line composed of a straight line portion and an arc-shaped curved line portion by abutting each other, wherein a corner is formed along a welding line formed by the straight line portion and the curved line portion of the square steel pipe. A rail attached to the steel pipe, a carriage that is movable on the rail while transporting the welding torch, a storage unit that stores in advance the curvature of the rail and the curvature of the welding line of the square steel pipe at each position of the rail, Position detecting means for detecting the position of the carriage on the rail, and the curvature of the welding line of the rail and the square steel pipe at each position of the rail from the storage means and the position detecting means, and the carriage based on the value An automatic welding apparatus for square steel pipes, comprising: a control means for controlling the traveling speed of the welding wire, the welding wire feeding speed, or both. 2. A welding device for welding square steel pipes having a welding line consisting of a straight line portion and an arc-shaped curved line portion by abutting each other, wherein a corner is formed along the welding line formed by the straight line portion and the curved line portion of the square steel pipe. A rail attached to the steel pipe; a carriage that is movable on the rail while transporting the welding torch; a storage unit that stores the curvature of the welding line of the square steel pipe in advance; Acceleration detection means for detecting the acceleration, the curvature of the rail at each position of the rail from the acceleration detection means, the value of the curvature of the welding line of the square steel pipe stored in the storage means of the truck An automatic welding apparatus for square steel pipes, comprising: a control means for controlling a traveling speed, a welding wire feeding speed, or both. 3. A welding device for abutting and welding square steel pipes each having a welding line composed of a straight portion and an arc-shaped curved portion, the rail being attached to the square steel pipe along the straight portion and the curved portion of the square steel pipe. A carriage that is movable on the rail while transporting a welding torch; a storage unit that stores in advance the curvature of the welding line of the square steel pipe; and a carriage that passes the carriage on the rail before welding work. At this time, contact detection means for detecting contact between the welding torch and the square steel pipe by applying a voltage between the welding torch and the square steel pipe to detect energization from an increase in current or a decrease in voltage. , The curvature of the rail at each position of the rail is obtained from the contact detection means, and the traveling speed of the carriage or the welding wire feed is calculated based on the value and the curvature of the welding line of the square steel pipe stored in the storage means. Automatic welding apparatus corner steel pipe, characterized in that it comprises a speed or control means for controlling both of these, the. 4. The control means controls the traveling speed of the carriage or the welding wire feeding speed or both of them so that the thickness of the welding bead of the straight line portion and the curved portion on the same welding line is continuously constant. The automatic welding device for square steel pipes according to claim 1, 2 or 3, which is controlled.