JPH04228263A - Method for welding pipe with consumable electrode type welding - Google Patents

Abstract

PURPOSE:To weld a pipe having weld parts excellent in accuracy and quality with a consumable electrode type welder. CONSTITUTION:In penetration welding method for welding pipe couplers 1, 2 mutually or a pipe and a nozzle neck coupler, after uniform thin thickness parts 5, 6 are formed for forming the penetration at the tip part of grooves 3, 4 of the pipe couplers 1, 2 or a pipe and nozzle neck couplers 10, 11 and also the notched clearance used as starting and finishing ends of the penetration welding is formed on this thin wall parts 5, 6, these pipe couplings 1, 2 are butted mutually or the pipe and the nozzle neck coupling are butted to execute the penetration welding with the consumable electrode system welding method, and the penetration welding having soundness and good accuracy can be executed by melting the starting and the finishing ends.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of welding pipes by consumable electrode welding.

0002

[Prior Art] Consumable electrode welding (covered arc, CO2,
MAG, SAW, etc.) are used, but when performing Uranami welding by butting the grooves of pipe joints, the filler metal (welding wire) sent out at the start of welding as shown in Figure 8. Since the filler material is forcibly melted by the arc, there is a problem in that the filler material is thickly piled up only at the start and end portions y of the groove before the groove is sufficiently preheated. In other words, even if lap welding is performed at the starting point of uranami welding, insufficient preheating will reduce weld penetration and the weld root thickness will fluctuate, resulting in a healthy backing at the beginning and end. Wave welding is no longer performed.

[0003] Therefore, in the past, the starting and ending ends y at the start, which are an obstacle to Uranami welding, were ground down with a grinder as shown in Fig. 9, and lap welding was performed on this to generate Uranami.
This type of welding method is unfavorable in terms of work efficiency, so after machining the connection end of the pipe joint to form a V- or U-shaped groove, a piece is installed between the grooves of the pipe joint. A predetermined gap (root spacing) was created using Uranami welding. Another method is to form a predetermined gap between the pipe joints by temporary welding using TIG welding. In addition to welding pipe joints together, when welding a nozzle joint to a pipe, a restraining jig 12 is used to fix the nozzle joint 10 at a predetermined gap position relative to the pipe 11, as shown in FIG. Alternatively, like the pipe joint described above, a piece was used between the grooves.

0004

[Problems to be Solved by the Invention] However, although the welding method using a block or a restraint jig can perform uranami welding for the purpose of reducing welding distortion, the block or restraint jig becomes an obstacle to welding. There is a problem in that automatic uranami welding cannot be performed, while tack welding allows for automatic uranami welding, but as the welding progresses, the distance between the joints changes due to welding heat, so the tension Stress is generated, making it difficult to achieve dimensional accuracy, and there is a problem in that the nozzle joint in particular tends to collapse due to tensile stress.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of welding pipes using a consumable electrode, which achieves good welding accuracy and quality using a consumable electrode welding machine.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the present invention provides a method for welding pipe joints together or a pipe and a nozzle joint, in which the groove tips of the pipe joints or the nozzle joint are preliminarily welded together. After forming a thin part with a uniform wall thickness on the side to form an uranami and cutting out a gap part in the thin part to be used as the start and end of uranami welding, these pipe fittings are connected to each other or to the pipe. Uranami welding is performed using the consumable electrode welding method by butting the nozzle joint with the nozzle joint.

[0007]

[Operation] With the connecting ends of the pipe joints butted against each other, Uranami welding is performed using the consumable electrode welding method, starting and ending at approximately the center of the gap. The area of the thin part around the gap is smaller than other parts, and the arc directly heats the back surface. Therefore, the root portion tends to be rapidly heated. Therefore, as soon as welding starts, the thin wall portions near the start and end ends rapidly reach the melting temperature. Simultaneously with this heating near the beginning and end, the delivered filler metal (welding wire) is quickly melted by the arc,
Pipe joints are welded together over the entire circumference.

On the other hand, the nozzle joint, like the pipe joint, is welded to the pipe over its entire circumference.

[0009]

[Embodiment] A preferred embodiment of the present invention will be described below.

As shown in FIGS. 1 to 3, first, a pipe joint 1,
After machining the connecting ends of the two to form grooves 3 and 4 at a predetermined groove angle, the outer peripheral surfaces of the tips of the grooves 3 and 4 are further machined to make the wall thickness uniform. thin wall portion 5,
6 are respectively formed, and the end faces of the connecting ends of these pipe joints 1 and 2 are machined flat along the radial direction. As shown in FIG. 3, the thickness t and depth L of the thin parts 5 and 6 are as follows:
It is formed to a size that produces a healthy back wave when automatic back wave welding is performed using the consumable electrode welding method. Next, cutouts 8 and 9 of a predetermined length are formed along the circumferential direction at any one location of the thin walled portions 5 and 6 of each pipe joint 1 and 2, respectively. After this, the notches 8 and 9 are aligned, and the end faces of these pipe joints 1 and 2 are butted together to form notches 8 and 9 several millimeters wide, and in this butt state, the consumable electrode welding method is used to open the pipe joints 1 and 2. Ahead 3
, 4 performs Uranami automatic welding. To start welding, an arc is first generated between the base metal (tube) and the electrode near the notch, and immediately after the welding wire is melted, the electrode is immediately moved to the notch. Welding is performed with the starting and ending ends x approximately at the center of the notches 8 and 9. Here, the thin-walled parts 5, 6 near the notches 8, 9 are easily heated because their area is small compared to other parts, and for this reason, the thin-walled parts 5, 6 near the start and end ends are extremely short at the same time as welding starts. Melting temperature is reached in time. At the same time, the delivered filler metal (welding wire) is quickly melted by the arc, so that a sound uranami weld is performed at the welding start position, and the pipe fittings 1 and 2 have a sound uranami welding all around the circumference. Welding begins to take place. After the first layer of Uranami welding is completed, multiple layers of welding are successively built up using a consumable electrode welder.

[0011] As described above, the welding method of the present invention
, 2 are brought into contact with each other to ensure welding accuracy, and by setting the vicinity of the center of the notches 8 and 9 as the starting end of welding, a sound Uranami welding at the beginning and end is completed.

FIGS. 4 to 6 show an example in which the thin wall portion 5 having the groove 3 and notch 8 formed in the pipe joints 1 and 2 is similarly formed in the nozzle joint 10, and the pipe 11 is This figure shows an example in which automatic Uranami welding was performed using a consumable electrode welding method similar to the welding method described above. However, the basic shape of the connection end of this nozzle joint 10 is the same as that of the pipe joints 1 and 2 above, but in order to make a good butt against the pipe 11, the groove 3 and The thin wall portion 5 is formed into a saddle shape to be stably placed on the tube 11.

[0013]

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

(1) In consumable electrode welding, it is possible to perform sound back wave welding at the beginning and end of a pipe joint, significantly improving the welding quality, and creating close contact over the entire circumference of the joint except for the beginning and end treated areas. Therefore, welding distortion can be significantly reduced and highly accurate welding can be performed.

(2) Uranami welding can be performed automatically by the consumable electrode welding method.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a state in which pipe joints according to the present invention are butted against each other.

FIG. 2 is a cross-sectional view taken along line AA in FIG. 1;

FIG. 3 is a sectional view taken along line BB in FIG. 1;

FIG. 4 is a side view showing a butt state of a nozzle joint and a pipe according to the present invention.

FIG. 5 is a cross-sectional view taken along line CC in FIG. 4;

6 is a cross-sectional view taken along the line DD in FIG. 4; FIG.

FIG. 7 is a side view showing the relationship between a conventional nozzle joint and a restraint jig.

FIG. 8 is a schematic diagram showing a conventional welding state of starting and ending parts using a consumable electrode welding machine.

FIG. 9 is a schematic diagram illustrating a welding state when a conventional welding start and end portion is processed using a consumable electrode welding machine.

[Explanation of symbols]

1 Pipe fitting 2 Pipe fitting 3 Bevel 4 Bevel 5 Thin wall part 6 Thin wall part 8 Notch forming the gap 9 Notch forming gap x beginning and end

Claims (1)

[Claims] Claim 1: In a method for welding pipe fittings together or between a pipe and a nozzle joint, welding of uniform thickness is performed in advance on the groove end side of the pipe joints or on the groove end side of the nozzle joint. After forming a thin-walled part and cutting out a gap in the thin-walled part to be used as the start and end of Uranami welding, the pipe fittings or the pipe and the nozzle joint are butted together and the Uranami welding is performed using a consumable electrode welding machine. A method for welding pipes by consumable electrode welding, characterized by applying welding.