JPS59141380A - Automatic one side welding method of girth joint of pipe - Google Patents

Abstract

PURPOSE:To form a penetration bead having good quality at a high speed in butt welding of pipes by constituting a butt groove of an arc-shaped groove on the outside and a single Vee groove on the inside, disposing a backing copper strip having a refractory material in the inside groove part, joining the butt part by arc welding from the outside groove part. CONSTITUTION:The groove of steel pipes 11, 12 to be welded is made into double grooves, where an arc-shaped outside groove 27 having outside surfaces 16, 16' and a single Vee groove having <=4mm. depth by slopes 13, 13' are provided by bringing groove root faces 14, 14' into contact with each other. A backing copper strip 25 having a refractory coating layer 24 is disposed on the inside groove surface side 36. A welding wire W is fed from the outside groove 15, 15' side and shielding gas 71 by active gas such as 35-75% CO2 is supplied from a nozzle 70 and automatic one side arc welding is performed. A molten pool 57 by melting of the wire W and the base material fills the grooves 13, 13' and is cooled and solidified by the backing strip 25, by which a penetration bead 26 is formed.

Description

[Detailed Description of the Invention] The present invention relates to an automatic welding method for girth joints in on-site welding of pipelines, and in particular, girth joints for pipes aimed at creating back wave heat at girth m-joints during high-speed welding. This invention relates to a single-sided automatic welding method.

Conventionally, when constructing pipelines, etc., the spread construction method has been adopted, in which each layer is welded separately and then welded individually.

In this Spredde method, finishing the first layer of Uranami weld metal at a high speed affects the actual efficiency of the work, so the welding method uses the downward welding method to distribute the high speed. Generally, when these pipes are butt welded by automatic welding, it is carried out by a gas-shielded arc welding method using a so-called copper backing method in which a backing Nil band is pressed against the inner surface of the pipe. In downward welding at such a high speed, a t current is inevitably generated in order to ensure a sufficient underwave bead.

In such downward welding at high current and high speed, the arc runs along the tip of the molten pool, and the molten pool follows behind. Under such conditions, the arc may sometimes directly penetrate the backing button j band and melt the backing copper band, resulting in welding and welding the backing bead and the backing copper band. happens. As a result, you will not have to waste extra time removing the backing copper strip from the pipe.
This results in a severe decrease in efficiency. Furthermore, a portion of the backing copper band melts into the uranami bead and becomes alloyed, which causes high-temperature cracks in the weld metal part.

The copper deposition phenomenon in such welding conditions is caused by welding 't(
5. It can be avoided by slowing down the welding speed, but then))
It is not possible to achieve high performance welding in the R stage.

Furthermore, the faster the welding speed of Uranami welding performed by downward welding, the narrower the appropriate conditions and the narrower the welding area. This still means variations in the machining dimensions of the groove, misalignment due to alignment of the four pipes,
The tolerance for the variation in the conditions that occur in the field of gear shifting becomes narrower, making it more difficult to apply.

Conventionally, in automatic butt circumferential welding of fixed pipes, one-sided welding is performed by consumable electrode arc welding using a backing device, for example, as shown in Fig. 1, Fig. 21, 11. There are techniques as shown in FIG. 3 and FIG. 3 (both described in JP-A-50-23350). This technique uses a backing copper strip 25,
Groove root surface 14.1 of abutted fixed tubes 11 and 12
4' and the inner 111ii created by the 13.13'
This is a method in which a welding wire W guided from the outside through a contact tube 60 is fed into a double ■-shaped joint formed by a V groove on the outside with an introduction angle (advance angle) A≧15°.

In this case, welding is performed while injecting shielding gas 71 from the nozzle 70 at a very high speed in order to hold the molten pool 57, thereby forming the underwave bead 26.

Therefore, the above technology comprehensively ensures a number of factors, such as accurate wire speed and direction control at abnormally steep angles, CTWD (wire projection distance) adjustment, gas flow control, high bevel accuracy, etc. This seems like a good method. However, in actual on-site welding, it is extremely difficult to accurately ensure and guarantee these many factors. Furthermore, when the control means becomes complicated as described above, it is necessary to constantly maintain and manage the control means in order to operate the control means normally, which is really complicated. As a practical matter, even if one attempts to apply the above-mentioned technique to on-site welding while allowing for the variations in conditions that occur on-site, it is almost impossible to do so.

The present inventors have already developed a pipeline welding automation technology in Japanese Patent Application Laid-Open No. 5-13301 that does not require these complicated controls and can produce a stable Uranami bead by a reliable method suitable for on-site welding.
No. 3-130246 and t1 "opening/closing 55-1391
I have proposed No. 94. In other words, the former relates to a single-sided welding strip in which a 0.1 to 1.2-thickness coating is provided on the surface of the backing copper strip, and the latter concerns the inner surface of the backing copper strip during automatic welding of pipe girth joints. This bolt has a V-groove on the side and a U-groove on the outer surface, and is used for the welding method that performs receding angle welding, and prevents welding of the front and back copper strips to the uranami bead. This technology provides pipeline automation technology that allows stable welding beads to be obtained in on-site welding without the need for special control, and although these technologies are highly effective, there is a problem with processing dimension fluctuations at the tip of the pipe. , Misalignment due to steel pipe alignment,
In terms of the accuracy of application to gap fluctuations and the adaptability to arc fluctuations sometimes caused by uncertain factors, it has not been possible to obtain sufficiently satisfactory results using each alone.

Therefore, the present inventors added shielding gas selection to both technologies and expected an excellent synergistic effect, thereby developing an erasing pipeline to obtain a reliable and stable Uranami bead to meet the strict demands of on-site welding. This was a successful development of a new welding technology. That is, the present invention is based on high-speed girth welding of pipes, and an Ir-shaped groove with a depth of 4 mm or less is provided on the inner surface of the tube, sandwiching the groove root surface, and the groove root is formed on the outer surface of the tube. A single layer or i/″3 with a narrow arc-shaped groove and a thickness of 0.1 to 1.2 mm.
: Girth'M method of pipe, which is characterized by arc welding from the outer surface of the pipe using a backing copper strip having multiple refractory coating layers and a shielding gas containing an active gas of 35 to 759 I+. This is a single-sided automatic welding method.

The present invention will be explained in detail below. First of all, FIGS. 4 and 5 are explanatory diagrams of the circumferential single-sided automatic welding method for fixed pipes according to the present invention, in which the grooves of the steel pipes (base metal) 11 and 12 are double grooves, and the groove root surface is 14° and 14' are brought into close contact, 16.16' and internal slope 13.13' are provided from the root 27 of the outer groove to the outer surface, and a backing copper strip 25 is pressed against the inner surface 36 of the groove. Hand device and external bevel side 15.1
The welding wire W is fed in from the 5' side, the shielding gas 7e is fed through the nozzle 70, and arc welding is performed.

In such cases, a good Uranami bead 2 is used for single-sided welding.
In order to obtain 6, the groove root 27 must be deep and the fluctuation of the welding arc 28 is small, the molten pool 57 is stable,
It is necessary to smoothly repeat the generation and hardening 1.

However, in order to form the uranami bead 26 by single-sided welding in a welded joint where the groove root surfaces 14.14' are in close contact, the welding arc 28 must move from the groove root 27 to the mating surface of the groove root surfaces 14.14'. I have to pass through it.

A molten pool 57 formed by this arc heat melts the base metal in the surrounding area and molten metal generated by melting the wire W fills the inner groove 13.13' and is cooled by the backing copper band 25. It solidifies to form a Uranami bead 26.

On the other hand, the groove on the outer surface must be arcuate for the following reasons. In other words, the arc-shaped groove 15.15' reaches the groove walls 16, 16' more gently than the V-shaped groove, so there is less variation in the arc length in the groove width direction, and the welding arc 28
becomes stable. Therefore, the molten shape of the molten pool 57 is stabilized, so that it fits well with the groove wall surface 16, 16', and the formed bead has no irregularities and is good. Furthermore, groove route 2
Since 7 is a circular arc, the welding arc 28 hits at a right angle, resulting in the deepest weld penetration.

If you make an inner groove of 13.13' on the inside of the sweet spot,
The arc passing through the groove root 14.14' is absorbed and weakened within the space of the inner groove 13.13', thereby preventing the refractory coating layer 24 and the backing m-band 25 from being melted and damaged by the arc. be able to. The reason why the groove depth h on the inner surface of the pipe is limited to 4 or less is as follows. Namely, when performing the above-mentioned welding, if the groove depth h on the inner surface shown in Fig. 4 exceeds 4, Since the molten pool does not completely fill the grooves 13 and 13', a shoulder of the inner V groove remains and an inner bead overgrowth cannot be obtained. Therefore, the pipe inner groove depth h
was set to 48 or less. For this reason, in the present invention, the groove shape is limited to the one described above.

Note that when the wire introduction angle is set to the advancing angle, the molten steel starts to advance in the vertical position, and the arc strikes the top surface of the molten pool.
The weld penetration of groove route 27 becomes shallower and inner groove 1
Since the molten pool cannot fill 3.13', it is desirable that the wire introduction angle be vertical or receding in order to drive the molten pool to the rear of the arc. Next, the purpose of using the backing copper strip 25 having the coating layer 24 of refractory material in the fighting jig is to widen the range of applicable conditions. In other words, due to the above-mentioned condition fluctuations that occur at the site, the groove route may deviate from the advancing conditions.
4. Even if the arc that penetrates through 14°' reaches the backing copper strip, it can be prevented by interposing the refractory material coating layer 24 between the inner surface of the groove 36 and the backing copper strip 25 in FIG. Backing copper band 25
It is possible to prevent the arc from coming into contact with the Iμ contact, and no welding of the joint occurs.

This allows a stable Uranami bead to be obtained at all times.

The reason why the thickness of the refractory material is 0.1 fin or more is that if it is less than 0.1 fin, it will not be possible to fully utilize its properties as a refractory material.
L<This is because the durability after repeated use is poor.

On the other hand, if the temperature exceeds 1.2, the unevenness of the refractory material surface after welding becomes large, the smooth surface cannot be reproduced, and the coated material peels off during handling, which impairs usability. A suitable commensurate thickness is 1.2 m or less. Based on the above, the thickness of the coating treatment for fireproof materials should be set to 0.
It was limited to 1 to 1.2 abilities.

The refractory material referred to in the present invention is AlxOs S 102
, MfO.

These are metal oxides such as Ti021, ZrO, etc., used alone or mixed in arbitrary proportions. All of these refractory materials have properties that can be used as slag-forming agents, so those that are relatively compatible with molten iron and have extremely high melting points are selected. Methods for coating the backing copper strip with refractory materials include applying a paste of refractory powder dissolved in water glass, baking at 700 to 800°C, and thermal spraying. It is the most practical. Even if the coated cutting tool is directly hit by the arc for a short period of time, it has a high melting point and is cooled from the back by the backing copper strip, so the melt will not fall off and a smooth surface will be reproduced. 4 benefits can be gained from the use of repeated welding.

Next, it is necessary to use a shielding gas containing an active gas to prevent the generation of blowholes. In the present invention, the active gas refers to CO2 gas and CO2 gas containing some 02 gas. Moreover, the shielding gas containing active gas refers to a mixture of an appropriate amount of active gas with an inert gas such as Ar or He. However, in general, blowholes are likely to occur in high-speed downward welding, and this
The lfi direction becomes especially noticeable in upward welding. This blohol is determined by the amount of active gas in the inert gas, and the more active gas there is, the less blohol is generated. - Practical Conditions: As the amount of gas increases, the arc required to obtain a stable Uranami bead becomes expensive, spatter increases, and the number of arc short circuits decreases, resulting in poor workability. If the active gas content in the shielding gas is less than 35%, blowholes cannot be prevented, especially in the upward welding part. Moreover, if it exceeds 75%, the number of short circuits will decrease, and welding workability will be poor. Based on the above, the ratio of active gas in the shielding gas was limited to 35 to 75%.

In this way, the present invention provides a groove in which a V-shaped groove is provided on the inner surface of the tube and the groove route on the outer surface of the tube is arc-shaped in high-J degree welding of a narrow groove using a single consumable pole. By adopting a bracing copper strip with a coating layer and selecting the shielding gas composition, a stable balance between the welding arc and the molten pool is maintained over all positions during pipeline girth welding, making it possible to weld from the outside of the pipe. It becomes possible to obtain a beautiful underwave bead.

Hereinafter, the effects of the present invention will be explained in more detail with reference to Examples.

Example (1) Pipe steel Type API 5LX X52 dimensions Outer diameter 324 tayh Chemical composition C0.11%, Si0.23%, M, n
l, 30% Mechanical properties Tensile strength 55.3ume/'IIJ
Yield point: 44.7 k/d Elongation: 36 inches (2) Welding method: Consumable electrode arc welding method (3) Welding wire Solid wire diameter: 0.9 m Chemical composition: CO, 11%, SiO, 70%, Mn
1.42% Mechanical properties Tensile strength 584 average/mA Yield point 45', 6 kq/mA (4) Groove shape, welding conditions, and backing copper strip First, the conventional groove shape shown in Fig. 3 was taken. , the groove size is tt: 12
．． 7m, h: 2w, RF: 1.5mm
, tt: 6 fights, θ,: 22.5°, θ, = 45°, θ
, Near ° Toshida.

The backing copper strip was removed as shown in Figure 2. (The dimensions are 10 inches wide, 40 inches wide, and the depth of the groove d = 0.5 square meters.

Also, the shielding gas is 100% CO, flow rate 3077ml
It's n.

Wire introduction angle A: advancement angle 15°, welding current 260A'.

At a welding voltage of 27 V, a welding speed of 110 cTn/min, and a wire frequency of 390 times/min, in the cross section of the steel pipe as shown in Fig. 6, we measured the position of the clock from the pupil position to the load position at TTI. The distribution of the welding direction 59 toward the time position was downward welding. The results showed that a small amount of copper was deposited at the pupil position, and in addition, some of the shoulders of the inner groove 13.13' remained at the pupil position and ■1 time position, and an uranami bead could not be obtained. Standard 1104 was not satisfied.

On the other hand, similar (11 steel pipes, (2) welding method, (3)
) Using a welding wire, take the groove shape shown in Figure 4, and the groove dimensions are θ, 26°, R: 2.75/, RF
: 1.5m+++, θ.

:225°, and h is 2 mm, 4 mm +
Assuming that the three levels of 5 mm and θ, , R, and RF' are the same dimensions, h
-0 m (lull V) without a groove.The backing copper strip 25 has a thickness of 10 gates, a width of 40 mm, and an uncoated one, and an A t20 s of 0.1 mm.
, 0.25tan, 0.5m, 1.2mm.

1.51, and ZrQ, and A4
The 03 layers were stacked and thermally sprayed to a thickness of 0 and 5 mm to form the refractory coating layer 24, respectively.

As shown in FIG. 4, the coating layer 24 was provided to have a uniform thickness up to both shoulders of the copper strip 250. By doing so, the depth of each groove was set to d=0.5. Shielding gas is 100% CO2, Ar475% 002
, Ar + 50%C02, 'Ar + 35
Attack C02*Ar+ 20% CO, flow rate 30t/m
It was set as in. Wire introduction angle 13: receding angle 5°, welded part,
The flow was 250 to 290 A, the welding pressure was 25 to 27 cm, the welding speed was 110 cm 7 min, and the wire frequency was 39.
Regarding the steel pipe cross section as shown in Fig. 6 at 0 times/min,
Downward welding was performed from the X [hour position of the clock] to the ■ o'clock position or passing through the ■ o'clock position to the ■ o'clock position.

The results are shown in Table 1. Items marked with ○ achieved JIS 3104 grade 2 or higher in the full-line xi transmission test of the welded part.

Table 1 ○ Good △ Small amount of copper welded or Uranami slightly unstable The backing copper strip has a coating layer of fireproof material 0.1 to 1.2 cm thick, and the shielding gas has a coating layer of 35 to 75 cm.
The results of welding using % of the non-toxic gas were significantly better than those welding using any of the oxidizing gases used alone. As is clear from the above embodiments, the present invention enables high-speed single-sided welding technology to obtain a sound underwave bead in the automatic welding method of the girth joint of a vibrator, and contributes to the development of industry. , there is something very big.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are explanatory diagrams of automatic welding on one side of the circumference of a fixed pipe according to the conventional method, and Figures 4 and 5 (Sil is an illustration of the automatic welding of one side of the circumference of a fixed pipe according to the present invention). Figure 6 is an explanatory diagram showing the welding direction. 11.12...Fixed tube base material, 13.13'...Internal slope, 14.14'...Group root surface (Mating face),
1.5. ．． 15'... External bevel root arc, 16.1
6'...Top slope of external bevel, 17.17'...
External groove lower stage slope, 24... Refractory material coating layer, 25... Toto copper band, 27... Bevel root, 36... Internal groove side, 26... Uranami bead, 28 ...welding arc, 57...molten pool,
59... Welding direction, 60... Contact tube, 7
0... Nozzle, 71... Shield gas, W.
-・Welding wire, A...Wire introduction angle advancement angle,
B... Wire introduction angle receding angle, d... Groove depth,
IIl,, )], LX, X[l... Clock position where the cross section of the steel pipe is aligned with the clock face to indicate the welding position. Applicant Nippon Steel Corporation Representative Patent Attorney Minoru Aoyagi Figure 1
Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In high-speed welding of pipe girth joints, a ■-shaped groove with a depth of 4 mm or less is provided on the inner surface of the pipe, sandwiching the groove root surface, and a narrow groove with an arcuate groove root is provided on the outer surface of the pipe. In addition, using a backing copper strip having a single layer or multiple layer coating layer with a thickness of 0.1 to 1.2 mm, further 3
Using shielding gas containing active gas of 5 to 75%
- A single-sided automatic welding method for pipe girth joints, which is characterized by performing arc welding from the outside side.