JPH05161971A - Method for welding inside of spiral steel pipe and device therefor - Google Patents

Abstract

PURPOSE:To prevent the occurrence of the defect of seam disconnection by performing inside welding with the amount of travel of an outside welding torch as the profile reference of an inside welding torch. CONSTITUTION:When the seam B of a steel sheet formed spirally continuously is moved from the specified position, an operator observes the deviation between the seam and the outside welding torch 1 and operates the driving motor 2 of the outside welding torch 1 by a manual operation to correct the positional deviation. The amount of travel of the outside welding torch 1 at this time is measured by a detector 7 and based on the amount of travel, the positional feedback of the inside welding torch 3 is controlled by a controller 8. The amount of travel of the inside welding torch 3 is set in accordance with the travel of a regular formed steel pipe on the controller 8. When the outside welding torch 1 is moved, the amount of travel is inputted to the controller 8 and the travel in the amount adjusted by this input is carried out by a driving device 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying method for welding the inner surface of a seam when a steel strip is formed into a spiral shape and then the seam is welded to manufacture a spiral steel pipe.

[0002]

2. Description of the Related Art A method of manufacturing a welded steel pipe by continuously welding the seams after forming a steel strip into a spiral shape is a conventional method of welding the inner surface by submerged welding and then the outer surface. Instead, a composite welding is performed in which a formed steel sheet is welded by resistance welding, the outer seam is welded by submerged welding, and then the inner surface is welded.
No. 91 publication.

By adopting this composite welding method, it is possible to heat at high density and high speed by electric resistance welding, and since the heat input is large, it is possible to weld the majority of the parts, and for submerged welding that enables high-speed core wire feeding, the whole The welding speed is almost twice as fast as before, and it is extremely promising as an efficient method for manufacturing spiral steel pipes.

However, for welding the inner surface, for example, Japanese Patent Laid-Open Nos. 50-57933 and 53-761.
As disclosed in Japanese Patent No. 41, etc., the operator recognizes the deviation between the welding torch reference needle and the inner seam by the monitoring camera installed on the inner surface of the pipe,
The displacement was manually corrected.

[0005]

However, since the shape of the seam itself is unclear and the surveillance camera is located on the inner surface of the pipe, the seam is not sufficiently illuminated, and the seam and the reference are determined depending on the camera position. Since the needle is misaligned, the welding line is misaligned, and the welding torch is manually adjusted, the operation that can follow the seam fluctuation cannot be performed, and not only the work efficiency is low, but also the seam dislocation defect occurs. was there.

An object of the present invention is to form a steel strip into a spiral shape,
It is an object of the present invention to provide a method for accurately performing inner surface welding when welding the joint to manufacture a spiral steel pipe.

[0007]

According to the present invention, the outer surface is first welded to the seam of the steel sheet after the steel strip is spirally formed,
Then, in the method for manufacturing a spiral steel pipe in which inner surface welding is performed, inner surface welding is performed by using the movement amount of the outer surface welding torch as a reference for copying the inner surface welding torch.

As an apparatus for carrying out the present invention, an apparatus for detecting the amount of movement of a drive unit used to move the outer surface welding torch, and the amount of movement detected by this detection apparatus for moving the inner surface welding torch. The device may be a device provided with a control device which is a control input amount to the device.

[0009]

[Function] Since the outer surface welding welds the outer surface of the pipe, the operator visually imitates the welding torch on the seam, and the variation of the seam is detected by the outer surface welding torch. Is used as a seam position signal. That is, since the movement amount of the welding torch at the time of outer surface welding is directly used as a control factor of the movement amount of the inner surface welding torch, the inner surface welding torch reliably follows the change in movement of the outer surface welding torch. If the torch for welding for outer surface welding is accurately aligned,
Inner surface welding can be performed automatically and reliably.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an outline of equipment to which the present invention is applied.

In the figure, 1 is a series heating type submerged arc outer surface welding torch for welding the outer surface of a spirally formed steel pipe, and 2 is a seam B of continuously formed steel sheets A. Is visually confirmed, and a drive motor for aligning the outer surface welding torch 1 with the joint B is shown. Reference numeral 3 denotes a series-heating type submerged arc inner surface welding torch, and 4 is a moving base for aligning the inner surface welding torch 3 with the inner surface of the steel plate seam B, and the moving base 4 and a drive unit. 5 is the operating rod 6
Are connected so that the attached operation rod 6 can be moved in the direction of the arrow to align the inner surface welding torch 3 attached to the tip of the operation rod 6 with the steel plate joint B. Reference numeral 7 represents a detector for detecting the movement amount of the outer surface welding torch 1, and reference numeral 8 represents a control device for converting the movement amount from the detector 7 into the movement amount of the inner surface welding torch 3.

FIG. 2 shows the operating principle. Referring to FIG. 1 and FIG. 1, when the seam B of the steel sheet S continuously formed in a spiral shape moves from the specified position, the operator visually checks the deviation between the seam and the outer surface welding torch 1. ,
Driving motor 2 for torch 1 for external welding by manual operation
To correct the misalignment. The movement amount of the outer surface welding torch 1 at this time is measured by the detector 7, and the position feedback control of the inner surface welding torch 3 is performed by the controller 8 based on the movement amount. The movement amount of the inner surface welding torch 3 is set in the control device 8 in accordance with the movement of the normal formed steel pipe. The drive device 5 performs the movement of the input amount adjusted by the input.

The amount of seam deviation in the conventional manual copying method is ±
Although it was about 3.3 mm, by adopting this copying method, it was reduced to ± 1.05 mm, and about twice the copying accuracy could be obtained.

[0014]

According to the present invention, the following effects can be obtained.

(1) When manufacturing a spiral steel pipe, a copying system of a welding torch can be constructed, and since highly accurate copying welding can be performed, a seam deviation defect can be eliminated.

(2) In terms of equipment, automation can be achieved by adopting a relatively simple apparatus in which a moving amount detector is simply attached to the conventional welding equipment.

(3) Since the control amount is the movement amount of the torch for external surface welding by direct visual inspection, no deviation occurs.

(4) Since the movement amount detector is attached to the outer surface of the pipe, heat and welding current noise are not adversely affected, so that highly reliable equipment can be provided.

(5) The automatic seam copying eliminates the need for an internal welding operator, thus saving labor.

[Brief description of drawings]

FIG. 1 shows an outline of an apparatus according to an embodiment of the present invention.

2 shows an actuation system of the embodiment of FIG.

[Explanation of symbols]

 1 torch for external welding 2 drive motor 3 torch for internal welding 4 moving table 5 driving device 6 operating rod 7 detector 8 controller

Claims (2)

[Claims] 1. A method for manufacturing a spiral steel pipe in which outer surface welding is first performed on the seam of a steel sheet after a steel strip is formed into a spiral shape, and then inner surface welding is performed, and the amount of movement of the outer surface welding torch is changed to the inner surface welding torch. Inner surface welding method for spiral steel pipes, where inner surface welding is performed as a copy reference. 2. A device for detecting the amount of movement of a drive unit used to move the outer surface welding torch, and the amount of movement detected by this detection unit is used as a control input amount to a unit for moving and driving the inner surface welding torch. Inner welding device for spiral steel pipe with control device.