JPH071129A - Welding method for seam of inside surface of metallic pipe having bent part - Google Patents

Abstract

PURPOSE:To smoothly weld a gap on the inside surface at a seam from inside in the welded piping of a metallic pipe having a bent part. CONSTITUTION:In the shielding gas 2 that is poured for filling inside a bent pipe 9 from the welding equipment including a driving device which is attached to the end part of a piping parts, an insulated flexible tube 3 is inserted which is provided with a guiding plate 7 and capable of freely passing the curve of the pipe; an arc is generated from an electrode 6, which is attached to a core bar 5 at the tip end of a built-in inner wire 4, and a revolution is transmitted to smoothly perform the welding-all-around of a seam part 10.

Description

Description: TECHNICAL FIELD The present invention relates to a method for smoothly welding a gap in the inner surface of a seam portion from the inner surface, which has been impossible in the past, in the welding of a metal pipe having a bend. Is. (A) (Prior art) In the conventional welding and piping technology, welding is mainly performed from the outer peripheral portion regardless of high pressure and low pressure, except for those with a large diameter, but corrosion due to rust etc. generated from the inner surface joint portion Deterioration of pipes due to cracks has serious consequences such as pipe damage accidents. As a measure to improve this drawback of welded pipe, the technique of back-side welding with a groove angle and a root interval has already been established, but the roughness and unevenness of the inner surface after welding is small in the fluid. If the inner surface cannot be ground, such as pipes with irregular bends, it will be a serious obstacle to the fluid. In vacuum equipment, gas is generated from the scale, and if the fluid is liquid, it becomes a dead point due to pressure loss and retention. Even in hydraulic equipment, air traps and drifts cause subtle errors in the accuracy of the equipment, which can cause accidents. (B) (Problems to be solved by the invention) In non-ferrous metal pipes, internally-polished stainless steel welded pipes are used in food, chemical, fiber-related industries due to their advantages such as corrosion resistance and chemical resistance. Although widely used, in these cases as well, the joint portion of the inner surface of the pipe is a major obstacle to the fluid. In terms of food products, from the standpoint of countermeasures against the generation of microorganisms and spoilage due to residues during cleaning, liquids that remain in the gaps in chemicals, etc. In the case of a flange joint, such as a flange joint, it is not possible to pipe the back seam from the outside, and it is very difficult to finish the grinding of the back seam of the bent pipe seam.
In the textile industry, internally polished stainless steel pipes are used for the resin passages of the spinning head of synthetic fibers and various resin passages based on petrochemicals. Very slight steps and gaps on the inner surface seam cause burns and scaling due to high temperatures, which is a major problem in quality maintenance. In order to deal with various diversified products, external pipes of heat medium containers are becoming mainstream for each company for the purpose of easy exchange and cleaning of resin passages, but grinding deep pipes and small-diameter back-end pipes However, the polishing finish is difficult, and at present, it is limited to only a part that can be visually observed. (C) (Means for Solving the Problems) In addition to the conventional welding technique, the present invention provides a shield which is injected and filled into a pipe having a bend from a welding device including a driving device set at the pipe end or the flange surface. Insert an insulated flexible tube that can hold the guide plate and freely pass through the curve of the pipe into the gas,
An arc is generated from the electrode attached to the shaft rod at the tip of the built-in inner wire to transmit rotation, and the entire circumference of the pipe-to-pipe and pipe-to-flange inner surface joints that are bent are smoothly welded. By integrating the parts, obstacles to fluid such as pipe gaps are removed. SUS304 x Sch80 x 8A to 25A
In the inner surface welding test with a flexible welder inserted from the end of the pipe, the penetration depth of 1.5-2.
3mm, weld bead height is (+-) 0.1-0.3m
At m, no bead cracks due to shrinkage, etc., or other phenomena of welding defects are observed in the entire circumference welded portion. (D) (Effect of the Invention) The present invention is a small-diameter pipe, which was a defect of the conventional welded pipe,
Or, it enables smooth inner circumference welding in the deep portion of the pipe with bends, eliminates all obstacles of various fluids caused by steps, gaps, etc., and always provides stable and high-quality products and highly reliable equipment parts. Can contribute to the production of.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a structural diagram of a flexible shaft, which is a flexible tube having a built-in conductor inner wire, and a flexible tube covered with an insulating tube. The rotation is transmitted through the inner wire by the axis rod of. Fig. 2 shows the installation of welding equipment at the end of the pipe ~ Drive unit ~ Shield gas ~ Insulation tube
~ Inner wire ~ Shaft rod ~ Electrode ~ Guide plate (8) ~ Flexible tube ~ Pipe ▲ 10 ▼ ~
welded part

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[Procedure Amendment] [Date of submission] December 13, 1993 [Procedure Amendment 1] [Document name for amendment] Specification [Item name for amendment] Invention title [Amendment method] Change [Amendment content] Name: Welding method for joints on the inner surface of metal pipes that have bends

Claims (1)

Claims: (1) In welding the inner surface seam of a metal pipe-to-metal pipe and a connection part such as a flange in contact with the metal pipe, while injecting the shield gas into the pipe, Welding method performed from the inside in the atmosphere. (2) Insert the flexible tube wrapped with the insulator that contains the inner wire into the shielding gas that is injected and filled into the pipe, and attach it to the shaft rod with the guide plate at the tip of the inner wire inside the tube. A welding device that welds a circumferential seam portion of an inner surface of a pipe by rotating an inner wire connected to a shaft by generating an arc from an attached electrode.