JPH08229685A - Welding method for clad steel pipe - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a highly efficient latent arc welding method for the groove portion of the inner surface mating material of the clad steel pipe. [Structure] Two high-alloy welding wires connected to one welding power source are arranged as electrodes at right angles to the seam welding line direction, and another welding power source is placed at an intermediate position 5-20 mm behind the electrodes. A welding method for a clad steel pipe, which comprises arranging one high alloy welding wire to be connected as an electrode and performing latent arc welding. [Effect] The productivity can be remarkably improved when welding the groove portion of the inner surface mating material of the clad steel pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clad steel made of stainless steel having excellent corrosion resistance or a high Ni-based high alloy steel on the inside and a low alloy steel having excellent strength on the outside as a base material.
The present invention relates to a seam welding method when a clad steel pipe is manufactured by a method such as OE.

[0002]

2. Description of the Related Art Recently, the development environment of petroleum resources has become more severe, and line pipes to be laid are required to have excellent corrosion resistance.
Since the life of conventional low alloy steel is extremely short, use of highly corrosion resistant steel pipes such as stainless steel and high Ni-based high alloy steel tends to be considered. However, manufacturing such a steel pipe itself from the above-mentioned component materials not only entails a huge laying cost of the line pipe, but also because these component materials have low strength, the wall thickness of the structure is designed. The thickness has to be increased, which further increases the cost. Therefore, recently, a clad steel obtained by adhering a high corrosion resistant material to a low alloy steel has been gradually receiving attention.

As described above, the clad steel is extremely useful for the above purpose because it has both corrosion resistance, high strength and high toughness. However, in order to form a clad steel pipe by using this material. Causes various problems in welding. That is, since the clad steel is composed of layers of steel having different components in the plate thickness direction, double-sided one-pass welding by latent arc welding such as the UOE method using ordinary low alloy steel is highly efficient but highly efficient. Due to also the dilution factor, its application is possible only under very limited conditions.

A conventional method for welding a clad steel pipe by the UOE method will be described in Japanese Patent Publication No. 1-38597, in which in welding a stainless clad steel pipe, the butted portion is an X-shaped groove and the inside is a two-step groove. As a result, it is disclosed that the bead width is widened to facilitate levitation of the slag at the time of submerged arc welding, and band arc welding is performed using a strip electrode on the inner stainless steel portion to reduce the dilution rate. However, in arc welding using a strip electrode, the arc may not be uniform over the strip width, that is, a wavy arc is likely to be formed, and a uniform weld portion may not be obtained. On the other hand, in Japanese Unexamined Patent Publication No. 63-10095, the depth and angle of the X-shaped groove are specified and the inner carbon steel is MI.
G, it is disclosed that the high alloy removed portion can be one-run welded by submerged arc welding (SAW). That is, in this publication, a high welding speed is achieved by a combination of the MIG method and the SAW method on the premise that the dilution ratio at the time of welding is reduced by deleting a width that does not interfere with the inner groove of carbon steel in the butt portion of the steel. It is trying to make it. However, with the SAW method that has been conventionally used for welding high alloy steel parts, there still remains the problem that a reduction in the dilution ratio cannot be expected so much.

On the other hand, from the above-mentioned viewpoint, the inventors of the present invention have proposed a method of welding a high-alloy clad steel pipe in which the inner groove shape is 2
As a step groove, the gap between the two high alloy welding wires connected to one power source should be slightly wider than the groove width of the mating material when performing latent arc welding of the mating material on the inner surface, and the seam welding line direction Japanese Patent Publication No. 6-35067 proposes a method in which a latent arc welding with a low dilution rate is possible by arranging it so that it is at a right angle. However, in the case of this method, the welding speed is 10 to 10.
It was about 40 cm / min, which was superior to the TIG welding method, but there was a problem that the welding speed was slow.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and in the production of stainless steel or high Ni-based high alloy clad steel pipes, in particular, it is formed by the UOE method. A special electrode is used for butt welding of the welded pipe body, and when welding the groove part of the laminated material, it suppresses dilution of the low alloy steel and does not cause welding defects,
It is also an object of the present invention to provide a highly efficient method for manufacturing a clad steel pipe.

[0007]

In order to achieve the above object, the present invention has the following structures. When manufacturing a clad steel pipe by clad welding clad steel consisting of low alloy steel on the outside and stainless steel or high Ni-based high alloy steel on the inside (hereinafter referred to as the laminated material), the width of the laminated material of the inner seam is It is removed until the low alloy steel is exposed to 14 to 16 mm, and the inside low alloy steel of the removed portion has a depth of 35 to 50% of the low alloy steel thickness and a groove width of the surface of the low alloy steel. Is provided with a V-groove that is smaller than the deleted width of the laminated material by 4 to 6 mm, and a weld bead is formed in the groove portion of the low alloy steel by using a low alloy wire so as not to melt the laminated material. After that, when welding the groove portion of the remaining mating material, two high alloy welding wires connected to one power source are used as electrodes, and the distance between the two welding wires is set to be 4 times larger than the removal width of the mating material. ~ 8mm wide and seam welding line direction And at right angles to further the electrode behind 5
A welding method for a clad steel pipe, characterized in that one high alloy welding wire is used as an electrode to perform a latent arc welding at an intermediate position of ˜20 mm.

Hereinafter, the present invention will be described in detail. The clad steel targeted by the present invention is made of a low alloy steel as a base material and has stainless steel or high Ni-based high alloy steel (for example, SUS3) on its surface.
No. 04, Incoloy 825, etc.) is bonded as a joining material, and this itself is manufactured by the conventional rolling compression bonding, explosive bonding method or the like.

The clad steel plate is formed into a tubular body after a groove is formed at the end portion in the longitudinal direction of the steel plate to be a seam welded portion by the UOE method. FIG. 1 shows an example of a basic groove shape according to the present invention. Outer low alloy steel 1 and inner laminated material 2
The clad steel consisting of the low alloy steel 1 has a width of 14 to 16 mm for the inner laminated material 2 in the state where the seams are butted.
The cutout portion 3 is provided until the exposed portion. Further, the outer low alloy steel 1 is provided with a groove 4 having a V-shaped seam portion butt shape. There is no particular problem if this shape is the same as the outer shape of the normal low alloy steel by the UO process. On the other hand, in the low alloy steel 1 of the inner laminated material removed portion, the depth is 35% to 50% of the low alloy steel thickness, and the groove width on the surface of the low alloy steel is 4 than the aforementioned laminated material deleted width. The V groove 5 is provided so as to be smaller by ˜6 mm. Here, the reason why the inside groove shape is set within the above range is to make the weld bead shape and the quality of the welded portion appropriate.

FIG. 2 shows the welding process of the present invention. First, a temporary welding bead 6 is formed on the outer groove 4 by using a welding wire for low alloy steel (FIG. 2 (a)). . Next, a welding bead 7 is formed in the groove 5 of the inner low alloy steel portion using a welding wire for low alloy steel (FIG. 2 (b)).
In the welding of the inner low alloy steel portion, it is important not to melt the notch 3 of the laminated material 2 and to form a smooth weld bead. In the present invention, the reason why the groove width of the low alloy steel is narrowed by 4 to 6 mm with respect to the width of the laminated material is that the laminated material is not melted when the weld bead 7 is formed. After the inner welding, the bead 8 is formed by latent arc welding on the groove 4 which is temporarily tack-welded on the outer side (FIG. 2 (c)), and the welding of the inner and outer low alloy steel portions is completed. After that, as shown in FIG. 2D, the latent arc welding bead 9 is attached to the groove of the notch 3 of the inner laminated material 2.
However, the present invention is characterized by the method of obtaining this weld bead.

FIG. 3 is a diagram showing an outline of a welding device for the groove portion of the notch 3 of the laminated material inside the clad steel pipe according to the present invention. That is, the welding tip 10 has a welding power source 1
A wire feeder 17 for holding two welding wires 13 and 14 for high alloy steel fed from a wire feeder 12 connected to 1 and a welding tip 15 connected to a welding power source 16 Welding wire 18 for high alloy steel sent from Japan
, And set the tip of each wire so that the wire protrudes above the surface of the mating material and the length is in the range of 15 to 25 mm. At this time, the distance between the two wires 13 and 14 fed from the welding tip 10 is set to be 4 to 8 mm wider than the notch width of the above-mentioned mating material and set at right angles to the welding line. Further, the wire 18 fed from the welding tip 15 has a wire projection length of 15 to 20 mm at an intermediate position behind the welding lines of the wires 13 and 14 and 5 to 20 mm behind the welding line.
It is set so as to have a range of 25 mm, and the latent arc welding of the cutout portion 3 of the laminated material 2 is performed.

Although FIG. 4 shows the arrangement of the wires 13, 14 and 18, as shown in FIG.
3 and 14 are arranged at right angles to the seam welding direction (arrow), and the wire 18 is located 5 to 20 mm behind the wires 13 and 14 and at an intermediate position between the wires 13 and 14 with respect to the welding line. Being arranged (isosceles triangle)
It is the basis of the present invention. That is, by arranging in this way, the welding material is melted so that the welding arc of the preceding two wires 13 and 14 does not directly act on the welding portion of the low alloy steel portion, and the welding material is fused and welded. The molten pool 19 is formed by filling both ends of the cutout portion of the material. further,
One trailing welding wire 18 acts to increase the amount of welding of the weld pool 19 formed of the leading wire and facilitates the improvement of the welding speed. However, as shown in FIG. 3B, when the leading electrode and the trailing electrode are arranged too far apart, the molten pool formed by the leading electrode and the molten pool formed by the trailing electrode are respectively separated. Formed, and welding defects such as slag inclusion easily occur. On the other hand, when the arrangement distance is made extremely close, there is only one molten pool as shown in FIG. 7C, but since the welding arc of the trailing electrode directly acts on the weld metal of the low alloy steel part, The dilution ratio of the low alloy portion increases, and the corrosion resistance, which is a main characteristic of the weld metal, is impaired.

According to the present invention, since the welding arc of the leading electrode does not act directly on the low alloy steel portion in this manner, and the welding arc of the trailing electrode acts on the molten pool formed by the leading electrode, the dilution ratio is low. The weld metal can be obtained, and a higher amount of welding can be secured, so that the welding speed can be improved.
On the other hand, as the welding wire, a high alloy welding wire containing a larger amount of alloying elements than the laminating material is used. For example, the laminating material component is Incoloy 825 (40% Ni-20% Cr).
-3% Mo), the welding material is Inconel 625 (60% Ni-20% C) in consideration of dilution from the low alloy steel part.
The use of the r-9% Mo) system is preferred.

In addition, in order to effectively carry out the present invention, the following conditions are preferably adopted. 1) The diameter of the welding wire is preferably a fine system and is preferably in the range of 0.9 to 1.6 mm in order to stabilize the wire feeding and the welding arc. 2) Welding current of 400 to 6 is used as the welding condition of the leading electrode.
00A, welding voltage 25 to 42V, and welding conditions for the trailing electrode include welding current 200 to 300A and welding voltage 25.
It is not preferable that the voltage is set to ˜42 V, that is, on the high current side outside this condition range, the penetration depth increases and the dilution rate of the welded portion of the low alloy steel increases. On the other hand, on the other hand, on the low current side outside this condition range, the dilution rate is small, but the welding speed must be extremely slowed down in order to obtain a proper amount of welding, resulting in inefficiency.

3) A welding speed of 30 to 60 cm / min makes it possible to obtain a good weld. 4) Welding wires (electrodes) are arranged at right angles to the seam welding line direction, but an allowable range of up to 5 ° is acceptable. If this angle is too large, the welding arc becomes unstable and the bead shape deteriorates.

5) The flux for latent arc welding may be either melt type or bond type.

[0017]

Example A high alloy clad steel plate having the components shown in Table 1 was used, and the test piece had a total thickness of 20 mm (including a laminated material thickness of 3 mm, the laminated material was Incoloy 825), a width of 400 mm, and a length of 1000 mm.

[0018]

[Table 1]

As shown in FIG. 5, a groove was machined on the inside and outside of the low alloy steel of the above sample, and on the inside laminated material (the numerical value in the figure is a numerical value in degrees, and the simple numerical value is in mm). For the low alloy steel part of the base metal part, temporary welding (carbon dioxide gas arc welding, heat input 3000 J / c) to the outer groove part
m), the inner welding was performed by two-electrode latent arc welding, and the outer welding was performed by three-electrode latent arc welding. The outline is shown in FIG.

After the above-mentioned base material low alloy steel portion was welded, the groove portion of the inner laminated material was welded. As a welding method,
For comparison with the method of the present invention shown in FIG. 3, a 1-power 2-wire latent arc welding method was adopted as a conventional method. The welding materials used are shown in Table 2, and the welding conditions and the results obtained are evaluated and shown in Table 3. In addition, in the electrode (welding wire) arrangement as a welding condition, the wire interval when two welding wires of the preceding electrode are arranged at right angles to the welding direction is a parallel interval (m
m), and the distance between the leading electrode and the trailing electrode is described as the distance between the electrodes. The evaluation of welding results is indicated by a circle when the bead shape is practical, and by a cross when the bead shape is judged to be impractical. Furthermore, the base metal dilution ratio is a low alloy steel occupying in the weld metal of the laminated material part measured by the area method by collecting the penetration cross-section macro from the welding test material, sketching the penetration shape with a projector after polishing and corrosion The percentage of penetration is shown.

In the comparative method of 1 power source and 2 wires, the welding speed is increased from 25 cm / min to 30 cm by increasing the current from 400 A to 500 A as indicated by symbols H to I.
/ J, the welding current is further increased and the welding speed is set to 40 cm / min. The symbol J indicates that the weld metal of the welded material of the joining material is not completely connected and a practical weld bead shape is secured. Was difficult. On the other hand, 1 power source 2 wires (leading electrode) to 1 power source 1 wire (backward electrode)
In the method of the present invention, the welding amount can be secured by the trailing electrode, and the welding speed is 35 cm / min.
From 60 to 60 cm / min, a bead shape and a base metal dilution rate of practical results were obtained, and it was confirmed that the welding speed of the present invention can be significantly improved as compared with the comparative method (conventional method).

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

As described above, according to the present invention,
When welding a clad steel pipe, it is possible to obtain a welded part of the inner laminated material that is uniform and has no defects due to component dilution, etc., and enables stable and highly efficient production in line with pipe manufacturing such as the UOE method. it can.

[Brief description of drawings]

FIG. 1 is a view showing a groove shape of clad steel.

FIG. 2 is a diagram showing a welding process of the present invention.

FIG. 3 is a diagram showing an outline of a welding device for an inner laminated material of a clad steel pipe according to the present invention.

FIG. 4 is a diagram showing an arrangement of welding wires according to the present invention.

FIG. 5 is a diagram showing a groove shape used in Examples.

FIG. 6 is a diagram showing a welding example of a base material (low alloy steel) portion.

[Explanation of symbols]

 1 Low alloy steel 2 Laminated material 3 Laminated material notch of inner seam 4 Outer groove 5 Inner groove low alloy steel groove 6 Outer temporary bead 7 Inner low alloy steel latent arc weld 8 Outer latent arc welding Part 9 Inner laminated material arc welding part 10 Welding tip of leading electrode 11 Welding power source of leading electrode 12 Wire feeding mechanism of leading electrode 13 Welding wire of leading electrode 14 Welding wire of leading electrode 15 Welding tip of trailing electrode 16 Welding power source for trailing electrode 17 Wire feeding mechanism for trailing electrode 18 Welding wire for trailing electrode 19 Weld pool

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B23K 33/00 B23K 33/00 A // B23K 9/00 501 8315-4E 9/00 501P

Claims (1)

[Claims] 1. When manufacturing a clad steel pipe by seam-welding a clad steel consisting of a low alloy steel on the outer side and a stainless steel or a high Ni-based high alloy steel (hereinafter referred to as a laminated material) on the inner side, The width of the laminated material is 14-16 mm
Until the low alloy steel is exposed, and the inside of the removed low alloy steel has a depth of 35 to 35 of the low alloy steel thickness.
50%, V groove is provided such that the groove width of the surface of the low alloy steel is 4 to 6 mm smaller than the deleted width of the laminated material, and the groove portion of the low alloy steel is combined by using the low alloy wire. After forming the welding bead so as not to melt the material, when welding the groove part of the remaining mating material, two high alloy welding wires connected to one power source are used as electrodes, and these two welding wires The spacing is 4 to 8 mm wider than the width of the material removed.
It should be wide and placed at right angles to the direction of the seam welding line, and 1 at the intermediate position 5 to 20 mm behind the electrode.
A method for welding a clad steel pipe, which comprises performing a submerged arc welding using the high alloy welding wire as an electrode.