RU2521920C1 - Method to weld pipelines without preliminary heating of joints - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method involves connection of two and more cylindrical metal pipes, pipe sections, pipe strings by welded ring joint using arc welding along the whole pipe perimeter. Each welded joint pass is performed by parallel overlapping of two string beads. The second string bead covers the first one completely and is an annealing pass.

EFFECT: invention allows for the increased load-carrying ability of pipelines made from butt-welded pipes, pipe sections, pipe strings.

1 tbl, 4 dwg

Description

The invention relates to the construction, in particular to the welding of pipelines of underground and elevated laying.

A known method of welding butt welded pipe joints, including connecting two pipes with cutting of the connected ends for welding and a tubular insert-lining in the weld zone, moreover, in the insert-lining is made at an angle to the insert axis a longitudinal slot, and adjacent to the slot sections of the insert-lining are offset along the slot of the insert-lining in different directions (see RF patent No. 112325 of January 10, 2012).

The disadvantage of this method is the possibility of fixing the insert inside the pipe only with the help of the root butt weld, which is a filler for insertion onto its surface, i.e. having low tensile strength. In addition, due to the ovality of the pipe and insert, it is impossible to assemble a joint without a gap or with a uniform gap around the perimeter of the pipe. As a result, the weld is of poor quality.

A known method of welding butt joints in several passes using rollers. In addition, each layer is performed in one pass (see Fig. 1). Starting from the 3rd pass, each layer is performed in two or more passes by applying individual rollers. The number of layers is not limited and depends on the thickness of the elements being welded.

The disadvantage of this method is that the welding of each layer in the passage leads to the appearance of significant deformations, both welding and after welding, which leads to the formation of hot (polyanization) and cold cracks. The formation of cracks is caused by the fact that the previous layer, before applying the next, manages to cool. Stresses that occur when cooling unevenly heated metal are concentrated in the weld metal, which leads to loss of ductility and crack formation (see Demyantsevich V.P. Metallurgical and technological fundamentals of arc welding. M.-L., 1962, 296 pp. Ill. )

There is a known method of welding corner joints, in which the welding of the weld beads is performed by sections in which 2 or 3 parallel beads are stacked one after the other (see FIG. 2). The rollers impose one after another on the length of the electrode. Each subsequent roller partially overlaps the previous roller. Filling of the welded joint is carried out sequentially with short sections equal to the length of the electrode burning (see RD-23.040.00-KTN-386-09 “Technology for repairing oil and gas pipelines with pressure up to 6.3 MPa”).

The disadvantage of this technical solution is the high cooling rate of the welded joint due to the relatively small length of the welded sections, which requires constant concomitant heating of the welded joint, and the associated low productivity of the welding process.

There is also a method of welding welded pipe joints, including welding two pipes in a special narrow cutting of the connecting ends of the pipes for welding (see figure 3). In this case, the application of rollers is performed sequentially - one on top of the other. Welding is carried out by automatic welding using automatic welding machines in the “on descent” way (see RD-25.160.00-KTN-011-10). This method is closest in its technical solution to the proposed invention and adopted as a prototype.

A sign of an analogue that coincides with the essential features of the claimed invention is the cutting of the connecting ends of the pipes for welding.

The reasons that impede the achievement of the technical result provided by the invention are the need to make special cutting, perform preliminary, concomitant and interlayer heating of the joints, maintain the height of the welding rollers at a level of no more than 1.5 mm, low resistance of the welded joint to the formation of hot, cold and fatigue cracks.

The problem to which the invention is directed,

- consists in obtaining a weld with high metallurgical quality and high visco-plastic properties, which increases its resistance to cracking; increases the bearing capacity of the pipeline;

- refusal to conduct preliminary and concurrent heating of the joints before welding and during welding, increasing the visco-plastic properties of the weld metal, reducing the level of residual welding stresses in the welded joint, obtaining an optimal weld structure that is resistant to cracking, increasing the bearing capacity of the pipe made using butt welded pipes and pipe sections.

The technical result that can be obtained by implementing the present invention is to obtain a weld with high metallurgical quality and high visco-plastic properties, which increases its resistance to cracking; increases the bearing capacity of the pipeline.

R&D and experimental studies have shown that the removal of residual welding stresses and the prevention of hardening structures with low resistance to cracking are ensured by the use of a multilayer annular butt welded joint of pipe billets, endurance of the interlayer temperature control between the applied weld beads, and the application of a heat-insulating belt providing cooling of the welded connections at a speed of 200 ° C per hour to a temperature of 80 ° C, by applying welded Alikov forming a welded seam with an overlap of 100%.

The set of essential features characterizing the invention, ensuring the receipt of the specified technical result in all cases that apply to the requested amount of legal protection and are in a causal connection with the specified result, the method of welding pipelines without preliminary and concomitant heating of the joints, including cutting the connecting pipe ends for welding according to the invention, the assembly of the welding elements is carried out, the edges of the welded elements of the welded joints are prepared They perform welding of elements with a circular butt using arc welding around the entire perimeter of the pipe, with each passage forming a weld being parallel to the application of two rollers, with each second roller being annealing and completely overlapping the first roller, observing the interlayer temperature control between by applied weld beads, and cooling the weld at a speed of 200 ° C per hour is ensured by covering with heat-insulating belts, the removal of which is carried out after reaching t the joint temperature of 80 ° C, with the possibility of removing residual welding stresses and preventing the formation of quenching structures with low resistance to cracking that occurs when the joint is cooled.

The method is illustrated in the drawing (see figure 4), which shows a diagram of the superposition of the welded beads of the annular weld. The following notation is used in the figure: 1-1, 2-1, n-1 - numbers of the main rollers; 1-2, 2.2, n-2 - numbers of annealing rollers; E is the width of the facing layer of the seam; δ is the thickness of the welded element.

This invention is used for welding pipes in the construction of aboveground and underground pipelines at low ambient temperatures.

Conducted research work at LLC NII TNN and subsidiaries of Transneft, as well as route tests when laying a route in the Far North with air temperatures up to minus 50 ° C showed that it is necessary to apply welded rollers forming weld, with overlap of 100%, with observance of the interlayer temperature control between the applied rollers of the weld, and the possibility of cooling the weld at a speed of 200 ° C per hour is ensured by covering with heat-insulating belts and, removal of which produces seam after reaching a temperature of 80 ° C, which ensures removal of residual welding stresses and prevent the formation of hardening structures with low resistance to cracking.

Work.

A method of welding pipelines without preheating the joints includes cutting the joined ends of the pipes for welding, assembling the elements for welding, preparing the edges of the welded elements of the welded joints, applying welds that form the weld, 100% overlap, observing the interlayer temperature control between the weld beads weld, providing cooling of the welded joint at a speed of 200 ° C per hour due to covering with heat-insulating belts, removing the heat-insulating belt after reaching the pace Joint temperatures 80 ° С. The proposed welding method allows to reduce residual welding stresses in the welded joint, to increase its visco-plastic properties by preventing the formation of quenching structures, and to increase resistance to the formation of cold cracks.

Welding is performed by electrodes of type E50A, E60 according to GOST 9466-75, GOST 9467-75.

Welding of butt welds is performed by applying at least 4 main and 4 annealing rollers, with each subsequent roller overlapping the previous 100%.

In order to determine the operability of the structure and its optimal characteristics, full-scale experimental work was carried out in production conditions at temperatures up to minus 50 ° C inclusive. A scourge of 72 m long from pipes with a diameter of 1220 mm and a wall thickness of 14 mm from a pipe of strength class K56 was welded in aerial design on inventory supports. Non-destructive testing showed the absence of defects of welding origin, as well as mechanical damage and cracks.

As a result, the welding technology parameters specified in table 1 were set.

Table 1 Parameter Designation Value, mm Pipe strength class according to GOST R 52079-2003 TO K60, up Type of welding electrodes according to GOST 9466-75, GOST 9467-75 E E50A, E60 Edging options: - bevel angle, degrees α 16-52 - blunting c 1.8 ± 0.8 The degree of overlap of the main roller annealing,% N one hundred Thickness range of welded elements, mm S 8-32 The minimum number of overlapping main and annealing rollers n four Range of interlayer temperature, ° С T 150-250 Maximum joint cooling rate after welding, ° C / hour V 200 Ambient temperature during welding T minus 50 to

The minimum temperature at which the joint can be cooled in air without protective shelters T 80

Application of the proposed method provides a weld with high metallurgical quality and high visco-plastic properties, which increases its resistance to cracking; increases the bearing capacity of the pipeline.

Claims (1)

A method of welding pipelines without preheating the joints, including cutting the connecting ends of the pipes for welding, characterized in that they assemble the welding elements, prepare the edges of the welded elements of the welded joints, weld the elements with a ring joint using arc welding around the entire perimeter of the pipe and cooling the welded joint, in this case, each passage forming the weld is performed by parallel application of two rollers with control of the interlayer temperature between the applied rollers a weld, in this case every second roller is annealing and completely covers the first roller, and the welded joint is cooled at a rate of 200 ° C per hour by covering with heat-insulating belts, which are removed after reaching a joint temperature of 80 ° C to remove residual welding stresses and preventing the formation of quenching structures with low resistance to cracking occurring upon cooling of the joint.

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