JPH08206865A - Profiling device for laser welding of tube - Google Patents

Abstract

PURPOSE: To eliminate welding defects in manufacturing a small-diameter, thick tube. CONSTITUTION: In the equipment of continuously manufacturing and welding tubes with a power laser beam, the device is structured such that; by using the outer diameter of a tube Dp, detected value of a seam center Sc and offset quantity Sf of welding focus, the deflection quantity Lmd and the deflection angle Pc are computed on a reflection mirror 19 and a condensing convex lens 13; that the rotary phase quantity of a stepping motor is controlled so as to control the optical system 19, 13 through a reducer and a worm gear; and that a laser beam is emitted from the direction vertical 16 to the seam center.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pipe making, mainly metal pipes, and more particularly, to a pipe seam formed by molding a flat plate-like pipe material into a circular shape continuously by using a power laser. The present invention relates to a laser welding copying device for welding.

[0002]

2. Description of the Related Art Laser welding using a power laser is excellent because of excellent structural and mechanical properties of a welded portion and energy efficiency and productivity of welding work.
For example, it is used as a method for producing a metal pipe such as stainless steel.

In general, in a pipe making process, pipes having a plurality of specifications having different outer diameters and wall thicknesses are made by the same equipment by changing the forming rolls. In such a pipe-making line, the seam center meanders if there is a misalignment of the roll row. The meandering is also caused by unevenness in the width direction material and the size of the flat plate material. Since this meandering is an unavoidable phenomenon in the pipe making process, an optical or electromagnetic seam center detector is installed immediately before the welding point, and the laser beam irradiation position is controlled to follow this. There is. FIG. 1 shows a simplified diagram of a general configuration of a pipe manufacturing process by laser welding. In the figure, the material formed into a circular shape by the forming roll row of 5 has a beam from the laser welding torch of 12 at the position detected by the seam center detector and the irradiation direction of the beam is the pipe forming line. Welding is controlled by swinging at right angles.

FIG. 6 shows a conventional laser beam scanning control operation by displacement control of a condenser lens (convex lens). In FIG. 6A, the seam center deviation amount Sc is “0”.
When the laser beam is focused “when”, and FIG. 6B shows the focusing state when Sc is not “0”. The annular beam guided from the laser oscillator main body through the waveguide to the center axis of the pipe making process rotates the step motor through the controller based on the detected value of the seam center, and the worm gear. The convex lens is moved in the horizontal direction via to control the amount of focus displacement. Further, since the welding focal depth from the pipe surface may vary depending on the welding conditions, the vertical position of the lens is adjusted or controlled manually or by a control device to adjust the welding focal depth. In the control by such a conventional method, there is a problem that the welding disengagement occurs when the pipe diameter Dp is small and the pipe wall thickness tp is small.

FIG. 7 shows an irradiation diagram of the laser beam on the welded portion when "Sc is not 0" in FIG. 6B, and the occurrence of welding deviation will be described. 7A shows the beam divergence not taken into consideration, and FIG. 7B shows the beam divergence taken into consideration. Seam line 18 which is a butt line of the end faces of the original plate when the flat plate material is formed into a pipe shape
Is the line to be irradiated with the laser beam. The laser beam focus position is controlled so that the laser beam is focused at the intersection P between the distance Sc from the pipe center and the welding focus level Lwf, but the beam divergence is taken into consideration (Fig. 7). Also in (b)), the upper half is welded in the thickness direction of the pipe, but the lower half is not welded because the beam does not hit the seam line 18. When laser welding metal materials, the energy density near the beam focus becomes high, and the material in this area evaporates instantaneously to form holes, which is commonly called the "wall hole effect" in which the laser beam is reflected on the surface of the molten metal. As a result of this effect, there is a "keyhole" after the beam focus.
Needle-like plasmatized holes are formed in the direction of the beam center. Therefore, a welding failure phenomenon occurs more significantly than that shown in FIG. 7, but on the other hand, since the heat transfer phenomenon from the melting surface is also added, the keyhole has a bulge and this effect is mitigated. It will be. The effect of the wallhole effect cannot be generally discussed because it depends on the material to be welded and the welding conditions. According to the experience of the inventors of the present invention with a laser welding machine for stainless pipes, Lwf = 0 [mm], Sc ≧ 3 [mm], and Dp × tp ≦ 8.
It was found that welding failure may occur at 0 [mm ² ] Lwf: focus level, Sc: seam center offset amount, Dp: pipe diameter, tp: pipe wall thickness. Of course, this defect occurrence condition changes depending on the configuration of the welding machine and the operating conditions of the pipe making line, so it cannot be discussed uniquely.
This is a phenomenon that generally occurs in laser welding because the beam spread is small due to its characteristics.

A method using a laser welding robot can be considered as another laser welding mechanism for preventing welding defects, but it is difficult to apply the above-mentioned measures from the viewpoint of control accuracy, responsiveness, and equipment cost. is there.

[0007]

The above-described conventional laser beam control method has a problem that the above-mentioned welding failure occurs when welding a small-diameter, thick-walled pipe. The present invention has been made in order to solve this problem, and provides a laser beam copying apparatus for preventing a welding defect by correctly irradiating a laser beam on a butt portion of a material from a direction connecting a seam center and a pipe center. To do.

[0008]

The present invention comprises an optical system for adjusting an annular laser beam incident from a direction perpendicular to the pipe traveling direction (pipe forming line) in a direction connecting the seam portion and the center of the pipe. An embodiment of the present invention comprises a mirror for reflecting an annular laser beam transmitted from a laser oscillator through a waveguide and incident from a direction perpendicular to a pipe making line, and a convex lens for converging the reflected beam. See the optical system and the distance and angle from these pipe surfaces.
A control unit that calculates a control amount from the detection value of the center detector, the offset command value of the welding focus from the pipe surface, the specifications of the pipe to be piped, a step motor,
It consists of a drive unit consisting of a reduction gear and a worm gear.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows the outline of the configuration of an embodiment of the present invention
FIG. 3 shows a reflection mirror 19 and a convex lens 13 inside the optical system storage box 21 of the welding torch 12 shown in FIG.
Indicates. The welding torch 12 is used for welding in the mode shown in FIG. First, referring to FIG. In the figure, Db is the outer diameter of the annular laser beam transmitted from the laser oscillator through the waveguide, Dp is the outer diameter of the pipe, tp is the wall thickness of the pipe, and Sc is the seam center. The displacement amount and Sf represent the depth command value of the welding focus from the pipe surface. In addition, these units are [mm].
The reflection mirror 19 and the convex lens 13 are housed in a box 21 shown by a chain double-dashed line as an optical system.

What is controlled is the displacement amount Lmd [mm] of the optical system storage box 21 from the vertical center line of the pipe, point C.
Rotation angle Pm [radian] of the mirror 19 about m, and deflection angle P of the lens 13 about the point Cm.
c [radian], the distance Llm [mm] between the center Cm of the mirror 19 and the center C1 of the lens 13, and the distance Lpm [mm] between the pipe surface and the center Cm of the mirror 19, and the drive mechanism shown in FIG. 41 is operated. Using the focal length fl [mm] of the lens 13, the seam center offset amount Sc [mm], and the welding focal depth Sf [mm], the respective values are calculated from the following formulas (1) to (4).
Is calculated by

[0011]

[Equation 2]

The values (target values) of Pc, Lmd, Llm and Pm are fluctuation amounts Dp, Sc, Sf, fl peculiar to the welding torch, and fl during welding in the controller 40 shown in FIG. Is calculated using Lpm fixed to the set value.
In the formulas (1) to (4), when Sc << Dp, the formula (1) is the formula (5), the formula (2) is the formula (6), and the formula (3) is the formula (7). , Equation (4) is P approximated by Equation (8)
There is no practical problem even if c ', Lmd', Llm ', and Pm' are used.

[0013]

(Equation 3)

Further, the expressions (5) to (8) can be further simplified. By using the copying apparatus of the present invention, it is shown that there is no welding dislocation as in the conventional control method described with reference to FIG. As shown, the laser beam is a seam line 18
Irradiation is carried out from the direction of the extension line 16 from the center of the pipe, and the welding failure that half is not welded in the pipe wall thickness direction as in the conventional control method does not occur. Since the actual laser has a slight beam divergence, the focusing of the beam has a divergence instead of a point, but a diagram relating to this is omitted.

Referring to FIG. Copying device control device 40
In PLC (Programmable Controller) 22, the outer diameter Dp, the wall thickness tp, and the welding focus offset amount set value Sf of the pipe made by the operator are input.
Seam sensor detector 11 allows seam center detection value S
c is input. The PLC 22 uses Pc, Lmd, Llm, and Pm by using the arithmetic expressions (1) to (4) described above.
Is calculated, and the control command value to the step motors 30, 28, 29, 31 is calculated from the reduction ratios of the reduction gears 35, 33, 34, 36 and the movement amounts / rotation ratios of the worm gears 38, 39, and the motors are calculated. Data to the driver 25, 23, 24, 26.
Lmd and Llm are converted into movement amounts via a speed reducer and a worm gear. Pc and Pm are converted into rotation angles via a speed reducer. The controller 40 comprises 5 sets of drive mechanisms, 4 sets being controlled during welding as described above.
In this embodiment, the remaining one set (27, 32, 37)
Is to set the torch position (distance of the box 21) with respect to the pipe 10. Operator set value Lpm
If you enter, PLc22 will save it to memory,
A control command value for the step motor 32 is calculated and given to the motor driver 27. Lpm is converted into a moving amount via a reduction gear and a worm gear. Unless a new Lpm is input, the PLC 22 holds the next input LPm value and does not drive the motor 32. That is, LPm
(FIG. 3) is fixed to the set value. The displacement gauge detects the displacement of the pipe 10 in the height direction (the direction along the straight line 17), and the control command value to the motor 32 is fed back so that Lpm is maintained at the set value according to the detected value. Alternatively, the detected value of the displacement gauge may be used as Lpm in the above equation to calculate Pc, Lmd, Llm, and Pm, and Lp
You may make it control Pc, Lmd, Llm, and Pm according to the change of m.

In FIG. 5, each control amount is entered. The optical system storage box 21 is moved along the Lpm movement axis according to Dp,
It is adjusted to the height of Lpm (operator input value). In the examples of the inventors, Lpm is uniquely determined by the outer diameter of the pipe to be piped, and the adjustment frequency is low. Therefore, Lpm is set to an input value only when an operator input is made. Hereinafter, this height Lpm is treated as a fixed value.

In this embodiment, the Lmd moving shaft is a shaft for moving the optical system storage box in the horizontal direction according to Sc. In conjunction with the movement of Lmd, Pm with Cm as the swing center
The angles of c and Pm are controlled. Further, Lpm is controlled along the Lpm movement axis according to the set value of Sf. The effective diameter of the reflecting mirror is 127 [mm] (5 [inch]), the effective diameter of the convex lens is 76.2 [mm] (3 [inch]), and the focal length is 254.
[Mm] (10 [inch]). The diameter Db of the laser beam transmitted via the waveguide is 50.8 [mm] (2
[Inch]). Sc is based on the actual results of the applicable lines-
3 to +3 [mm]. Sf was set to -1 to +3 [mm] according to the specifications of the pipe to be piped.

Lpm is 330.2 based on Dp = 50.
± 50 [mm], Pc is ± 20 [deg] based on 0 [deg]
Lmd is ± 120 [mm] based on 0 [mm], Llm
Is 85 [mm] and ± 10 [mm], and Pm is 45 [de]
The maximum movement amount was set to ± 10 [deg] with a margin with reference to g].

The inventors of the present invention have implemented the above laser welding copying apparatus
It was assembled to the welding torch 21 shown in FIG. 1 and applied to a continuous welding line for stainless steel and titanium pipes (FIG. 1). The outer diameter Dp of the pipe manufactured in this line is from 21.7
The thickness is 89.1 [mm] and the thickness tp is 1.5 to 4.0 [mm]. The power laser source is an unstable 5 [k] installed in the electric room.
w] A CO2 laser oscillator is used to guide a beam from the horizontal direction directly above the welding line via a waveguide with an optical path length of about 9 [m] to perform laser welding. Conventionally, this type of pipe It was installed in place of the TIG welding machine used to manufacture the. In the line,
Various seam center twist countermeasures were implemented, but maximum ± 3
It turns out that a seam twist of [mm] is unavoidable. Due to this seam twist, the conventional laser beam copying mechanism originally installed was used, and if a small-diameter, thick-walled pipe is manufactured, the above-described welding failure occurs and the product yield decreases. However, by applying the above-mentioned embodiment,
Welding defects were reduced and product yield was improved.

That is, there were the following effects.

1) Welding defects that have occurred in welding small-diameter, thick-walled pipes no longer occur. After welding, the weld was cut off and the seam center and weld center were measured from the inner surface, and it was confirmed that all pipe specifications were welded with an accuracy of ± 50 [μm].

2) As a result, the product yield is improved.

3) Copy control with fast response characteristics could be achieved. The mirror, lens, and step motor for driving are lightweight, and the maximum moving speed of the seam center is 3 [mm / s
ec] was fully satisfied.

4) The equipment could be inexpensively constructed. Initially, the laser beam incident direction was from above the line, but by modifying it from the lateral direction of the line, and by modifying the conventional copying mechanism to the arc-shaped copying according to the present invention, the equipment could be inexpensively installed.

5) Further, it is possible to manufacture pipes of large diameter, thin wall to small diameter, thick wall by one laser welding line, and productivity is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a general process configuration of a line for producing a pipe by continuously performing laser welding. Illustration of equipment such as a cutting machine after the welded portion is omitted.

FIG. 2 is a block diagram showing an overall outline of an embodiment of the present invention.

FIG. 3 is a block diagram showing a cross section of the inside of the optical system storage box 21 shown in FIG. 2 and the pipe 10 to be welded.

FIG. 4 is an enlarged cross-sectional view showing a part of the pipe 10 of FIG.

5 is a block diagram showing an enlarged interior of the optical system storage box 21 of FIG.

FIG. 6 is an explanatory view for explaining the laser beam scanning control only by the displacement amount control of the convex lens, which has been conventionally used in the line of the laser welding machine, and the pipe to be welded 1
0 and the cross section of the laser irradiation lens 13 are shown.
(A) shows the case where the seam center offset Sc is 0 and the welding line is above the center of the pipe conveying line, and (b) shows S.
The following shows how the laser beam is focused and copied when c moves.

FIG. 7 is a view for explaining that welding deviation occurs according to conventional copying control when the seam center changes, and shows a cross section of the pipe to be welded 10; (A) shows the irradiation state of the laser beam in the pipe thickness direction when the divergence of the laser beam is not taken into consideration and (b) is taken into consideration.

[Explanation of symbols]

1: Leveler 2: Shear 3: Welder 4: Pinch roll 5: Forming roll row 6: Input side pressing roll 7: Output side pressing roll 8: Slit coil 9: Plate material 10: Pipe 11: Seam center detector 12 : Laser welding torch 13: Convex lens (converging lens) 14: Annular laser beam 15: Laser beam during focusing 16: Optical axis center line 17: Pipe forming line center line 18: Seam line 19: Horizontal movement of lens 20: arrow indicating vertical movement of the lens 21: optical system storage box 22: PLC 23-27: step motor driver 28-32: step motor 33-37: speed reducer 38-39: worm gear 40: control device 41 : Drive device 42: Waveguide 43: Lpm moving axis 44: Lm
d moving axis 45: Lpm moving axis 46: Pm
Runout movement Sc: Seam center offset amount Sf: Welding focus offset amount fl: Condenser lens focal length Dp: Pipe outer diameter tp: Pipe wall thickness Lps: Pipe surface level Lwf: Welding focal light level Lpc: Pipe center level P : Laser beam focusing point Lpm: distance between pipe surface and reflecting mirror Lmd: amount of movement of reflecting mirror Llm: distance between reflecting mirror and focusing lens Pc: deflection angle of focusing lens Pm: deflection angle of reflecting mirror Dc: laser Beam diameter Cm: central axis of rotation of the reflection mirror Cl: center of condenser lens Cp: center of pipe

Claims (3)

[Claims] 1. A laser welding copying apparatus for a pipe, wherein a seam portion of a pipe, which is formed by shaping a flat tubular material into a circular shape, is continuously copied and welded by using a power laser. A laser welding copying apparatus for pipes, comprising: an optical system for adjusting a circular laser beam in a direction connecting the seam portion and the center of the pipe. 2. The adjusting optical system includes a plane mirror that reflects an incident annular laser beam and a condenser lens that collects the laser beam reflected by the plane mirror; the laser welding copying apparatus further includes a pipe mirror. 2. A means for detecting a seam center position, and means for controlling a position and a rotation angle of the plane mirror and a position of the condenser lens based on the detected seam center position. Laser welding copying device for pipes. 3. A laser welding copying apparatus for pipes, in which a seam portion of a pipe formed by forming a flat plate-shaped pipe material into a circular shape is continuously copied and welded by using a power laser, through a waveguide from a laser transmitter. An optical system including a reflection mirror for reflecting a parallel circular beam transmitted from the direction perpendicular to the pipe making line and a condenser lens for condensing the reflected circular beam; the pipe outer diameter Dp, which changes every moment during pipe making. The seam center detection value Sc, the depth command value Sf of the beam focusing point from the pipe surface, the focal length Fl of the focusing lens, and the distance Lpm from the pipe surface to the optical system moving center predetermined by the size of Fl are used. Then, using the following equations (1) to (4) or their approximate solutions, the movement amount Lmd from the movement center of the reflection mirror, the distance Llm between the condensing lens and the reflection mirror, and the light condensing Computing means for computing the deflection angle Pc from the center of the reflecting mirror of the lens and the rotation angle Pm of the reflecting mirror that is interlocked with the deflection angle of the condenser lens; control means for determining a control amount based on the computation result of the computing device; Driving means for driving the optical system based on the control amount;