TWI629134B - Submerged arc welding method on both sides - Google Patents

Abstract

The two-sided submerged arc welding method of the present invention involves welding the ends of Ni steel plates arranged one above the other with a flux covering one side and welding from both sides. Among them, a first wire and a second wire made of a Ni-based alloy are used as welding. The electrode moves the first welding torch that successively sends the first wire toward the bonding area where the ends are close to each other, and causes the second welding torch that successively sends the second wire from the opposite side of the first welding torch toward the bonding area. The front end of the second lead is maintained at a predetermined distance from the front end of the first lead by 10 mm or more and 60 mm or less, while moving along the joint area.

Description

Submerged arc welding method on both sides

The invention relates to a double side submerged arc welding method.

As a method for butt welding (horizontal welding) of the steel plates arranged one above the other, there are the following methods: First, welding is performed on the bottom of one of the two grooves which are opened in one of the plate thickness directions and the other, and then After the back chipping of the bottom of another trench is performed by planing, welding is performed on the bottom of the trench. On the other hand, there is also a method of simultaneously welding from both sides in order to omit the back chiseling.

For example, Patent Document 1 discloses a welding method in which a leading electrode and a trailing electrode are respectively arranged on both sides of a base material, and a distance between the leading electrodes is set to 0 to 50 mm. Furthermore, in the embodiment of the welding method disclosed in Patent Document 1, the base material and the welding material (wire) are both mild steel, and a shielding gas is used when welding.

[Prior technical literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 61-206564

However, in a low-temperature tank storing a liquefied gas such as LNG (liquefied natural gas) or LPG (liquefied petroleum gas), a Ni steel plate having excellent low-temperature toughness is sometimes used as a sidewall. Low temperature tank Large, therefore, the butt welding of Ni steel plates arranged on top of each other must be carried out on-site. Moreover, the welding work place is often located at a high place. From this point of view, as a method of butt-welding Ni steel plates arranged one above the other at the site, it is desirable to use a two-sided submerged arc welding method in which no shielding gas is used and the ends are welded from both sides with flux to cover each other.

In addition, it is difficult to perform uniform welding operations outdoors. Therefore, in order to prevent the performance of the welded portion, that is, the joint, from being deteriorated due to uneven welding work, it is effective to use a lead made of a Ni-based alloy having a higher toughness than a Ni steel plate as the lead to be an electrode.

However, the inventors of the present invention have found that when using the above-mentioned dissimilar material joints in which the base material (Ni steel plate) is different from the welding material (wire), a sufficiently high joint strength can be obtained when the base material is thick, but When thin, joint strength decreases.

Therefore, an object of the present invention is to provide a two-sided submerged arc welding method capable of obtaining a sufficiently high joint strength even when a butted Ni steel sheet is thin.

In order to solve the above problems, the inventors of the present invention have found out after careful research that the decrease in joint strength when the plate thickness of the base metal in the dissimilar material joint is small due to the melting amount (dilution rate) of the base material into the welded portion becomes larger. Further, it was found that if the front ends of the electrodes arranged on both sides of the base material are staggered from each other, the dilution rate can be suppressed to be low. The present invention has been completed based on this viewpoint.

That is, the two-sided submerged arc welding method of the present invention is to weld the ends of the Ni steel plates arranged one above the other from the two sides with flux, and the two sides of the submerged arc welding method are characterized by using a Ni-based alloy The first conductive wire and the second conductive wire constituted are used as electrodes; the first welding torch which successively sends the first conductive wire toward the joining area where the ends are close to each other is moved along the joining area, and the opposite side of the first welding torch is moved Sending the above second to the above-mentioned junction area The second welding torch of the conducting wire keeps the front end of the second conducting wire at a predetermined distance of 10 mm or more and 60 mm or less from the leading end of the first conducting wire while moving along the joint area.

According to the above configuration, the front end of the second lead is disposed more than 10 mm from the front end of the first lead. Therefore, compared with the case where they are arranged at the same position, the range of the high temperature of the end portion of the Ni steel plate becomes narrower. . Accordingly, the amount of melting of the Ni steel sheet into the welded portion is reduced, and the dilution rate can be suppressed to be low. Thereby, a sufficiently high joint strength can be obtained. On the other hand, since the front end of the second lead is not more than 60 mm from the front end of the first lead, defects such as poor melting in the welded portion can be suppressed.

At least one of the end portions may have a root surface that is tapered toward the other side and has inclined surfaces on both sides in the thickness direction of the Ni steel plate, and the front end of the root surface is opposite to the Ni steel plate. The center is located on the first lead side or the second lead side. When the front end of the root surface is located at the center of the Ni steel plate, the Ni steel plate on the upper side may fall to the second lead side due to welding. On the other hand, if the front end of the root surface is positioned on the first lead side or the second lead side with respect to the center of the Ni steel plate as described above, it is possible to suppress the falling of the Ni steel plate on the upper side.

For example, the thickness of the Ni steel plate may be 20 mm or less.

A belt may be arranged on both sides of the Ni steel plate on the lower side so as to be in contact with the Ni steel plate, and the flux may be deposited on the belt so as to cover the joint area. According to this configuration, the deposition position of the flux can be easily changed in accordance with the welding position.

According to the present invention, a sufficiently high joint strength can be obtained even when the butted Ni steel sheet is thin.

1‧‧‧Ni steel plate

12‧‧‧ root surface

13‧‧‧ front

15‧‧‧ Junction area

21‧‧‧The first wire

22‧‧‧ 2nd wire

31‧‧‧The first welding torch

32‧‧‧ 2nd welding torch

4‧‧‧ belt

5‧‧‧Flux

FIG. 1 is a side view for explaining a submerged arc welding method on both sides of an embodiment of the present invention.

FIG. 2 is a plan view showing a positional relationship between a first welding torch and a second welding torch.

Fig. 3 is a side view showing the shape of another root surface.

FIG. 4 is a diagram showing joint structures of Examples 1 to 4 and Comparative Examples 1 and 2. FIG.

1 and 2, a submerged arc welding method on both sides of an embodiment of the present invention will be described. In this two-side submerged arc welding method, butt welding (lateral welding) of Ni steel plates 1 arranged one above the other is performed. Specifically, the upper end portion of the lower Ni steel plate 1 and the lower end portion of the upper Ni steel plate 1 are covered with a flux 5 while welding from both sides.

A first lead 21 and a second lead 22 serving as electrodes are arranged on both sides of the bonding region 15 (so-called welding wire) where the ends of the Ni steel sheet 1 are close to each other. The first lead 21 is for a person who performs welding on one side first, and the second lead 22 is for a person who performs welding later on the opposite side. The first lead 21 is successively sent toward the bonding region 15 by the first welding torch 31, and the second lead 22 is successively sent toward the bonding region 15 from the opposite side of the first welding torch 31 by the second welding torch 32.

First, the Ni steel plate 1 as a base material and the first and second leads 21 and 22 as a welding material will be described.

The Ni steel sheet 1 is an iron alloy containing Ni (nickel) as a main additive. Examples of additives other than nickel in the iron alloy include C (carbon), Si (silicon), and Mn (manganese) (for example, refer to Japanese Industrial Standard JIS G 3127). For example, the content of nickel in the Ni steel sheet 1 is 3% or more and 15% or less in terms of mass%. Among them, when used for a low-temperature tank for storing liquefied gas, as the Ni steel plate 1, it is preferable to use 7% Ni steel or 9% Ni steel. Ni steel plate 1 is typically structure.

The two-sided submerged arc welding method of this embodiment can also be used when the Ni steel plate 1 is thick. If it is used when the Ni steel plate 1 is thin (for example, the thickness of the Ni steel plate 1 is 20 mm or less), it can be prevented The effect of reducing the strength of the welded joint, that is, the joint. The thickness of the Ni steel plate 1 may be 18 mm or less, or 16 mm or less.

In this embodiment, the upper end portion of the lower Ni steel plate 1 is flat, and the lower end portion of the Ni steel plate 1 on the upper side is formed with the upper end portion of the lower Ni steel plate 1 that is tapered and formed on the Ni steel plate 1. The root surface 12 has inclined surfaces on both sides in the thickness direction. As a result, two grooves 11 are formed between the ends of the Ni steel sheet 1 in one direction and the other in the thickness direction of the Ni steel sheet 1. However, the root surface 12 may also be formed at the upper end portion of the lower Ni steel plate. Alternatively, the root surface 12 may be formed only on the upper end portion of the lower Ni steel plate.

The root gap between the ends of the Ni steel plate is, for example, 1 to 3 mm.

In this embodiment, the flat front end 13 of the root surface 12 is located at the center CL of the Ni steel plate 1. However, as shown in FIG. 3, the front end 13 of the root surface 12 may be located on the second lead 22 side with respect to the center CL of the Ni steel plate 1. When the front end 13 of the root surface 12 is located at the center CL of the Ni steel plate 1, the Ni steel plate 1 on the upper side may fall down to the side of the second lead 22 that is backward by welding. On the other hand, if the front end 13 of the root surface 12 is positioned on the second lead 22 side with respect to the center CL of the Ni steel plate 1 as shown in FIG. 3, the falling of the Ni steel plate 1 on the upper side can be suppressed. This effect can be obtained even when the front end of the root surface is located on the first lead 21 side with respect to the center CL of the Ni steel plate 1. Alternatively, the flat front end 13 of the root surface 12 may be located on either side of the Ni steel plate 1 so that the root surface 12 has only one inclined surface.

The first lead 21 and the second lead 22 are made of Ni having higher toughness than the Ni steel sheet 1. Base alloy composition. For example, this Ni-based alloy contains 55% or more of Ni in mass%. Examples of components other than Ni in the Ni-based alloy include Cu (copper), Cr (chromium), Fe (iron), and Mo (molybdenum). Ni-based alloys typically have a Vosstian iron structure. The diameters of the first and second lead wires 21 and 22 are, for example, 1.0 to 3.2 mm.

For example, when the Ni steel plate 1 is 9% Ni steel, as the first and second wires 21 and 22, any wire based on Japanese Industrial Standard JIS G 3333 YS9Ni can be used. In this case, as the flux 5, for example, an arbitrary flux based on Japanese Industrial Standard JIS G 3333 FS9Ni-H can be used.

Next, the submerged arc welding method on both sides of this embodiment will be described in detail.

First, the belts 4 are arranged on both sides of the lower Ni steel plate 1 so as to be in contact with the Ni steel plate 1. This belt 4 is a part of the flux supplying device in which the drawing is omitted. Then, on the belt 4, the flux 5 is deposited in powder form so as to cover the joint area 15 from both sides, in other words, to fill the groove 11 on both sides with the flux 5.

After that, the first welding torch 31 and the second welding torch 32 are arranged so that the first lead 21 is inserted into the one groove 11 and the second lead 22 is inserted into the other groove 11. At this time, as shown in FIG. 2, the first welding torch 31 and the second welding torch 32 are arranged such that the first lead 31 is located in front of the welding direction and the second lead 32 is located behind the welding direction. In other words, the front end of the second lead 32 is located rearward from the front end of the first lead 31 by a predetermined distance L.

The predetermined distance L is preferably 10 mm or more and 60 mm or less. The reason is that if the predetermined distance L becomes too small or too large, the joint strength decreases. The predetermined distance L is more preferably 15 mm or more, and even more preferably 20 mm or more. The predetermined distance L is more preferably 50 mm or less, and even more preferably 40 mm or less.

Thereafter, the first welding torch 31 is moved along the bonding area 15 while applying voltage to the first and second conducting wires 21 and 22, and the second welding torch 32 is positioned so that the front end of the second conducting wire 22 is spaced from the first conducting wire 21 The front end is maintained at the rear by a predetermined distance L, and moves along the joint region 15 while being held. Thereby, a first layer 61 is formed on the bottoms of the trenches 11 on both sides. After the first layer 61 is formed, the second layer 62 is similarly formed. Furthermore, if only the first layer 61 is buried in the trench 11, it is not necessary to form the second layer 62.

The voltages applied to the first lead 21 and the second lead 22 may be AC voltages, but are preferably DC voltages. When it is a DC voltage, the voltage value is, for example, 20 to 40V, and the current value is, for example, 200 to 400A. The moving speed of the first and second welding torches 31 and 32 is, for example, 20 to 70 cm / minute.

As described above, in the submerged arc welding method on both sides of the present embodiment, the front end of the second wire 2 is arranged at a distance of 10 mm or more from the front end of the first wire 21, so it is the same as the position where they are arranged at the same position. As compared with the case, the range in which the end portion of the Ni steel plate 1 reaches a high temperature becomes narrower. Accordingly, the amount of melting of the Ni steel sheet 1 into the welded portion is reduced, and the dilution rate can be suppressed to be low. Thereby, a sufficiently high joint strength can be obtained. On the other hand, since the front end of the second lead 22 does not exceed 60 mm from the front end of the first lead 21, defects such as poor melting in the welded portion can be suppressed.

In addition, in this embodiment, since the flux 5 is deposited on the belt 4, the deposition position of the flux 5 can be easily changed in accordance with the welding position.

[Example]

Hereinafter, examples of the present invention will be described in more detail. However, the present invention is not limited to the following examples.

(Example 1)

First, as two Ni steel plates arranged one above the other, a 9% Ni steel plate having a width of 500 mm, a height of 200 mm, and a thickness of 12 mm based on the Japanese Industrial Standard JIS G 3127 SL9N590 was prepared. The upper end portion of the lower Ni steel plate is flat, and the lower end portion of the upper Ni steel plate, as shown in FIG. 1, has a root surface that is 2 mm flat in the center and is inclined at 45 degrees on both sides. The root gap was set to 2 mm.

As the first and second lead wires for electrodes, US-709S manufactured by Kobe Steel Co., Ltd. with a diameter of 2.4 mm based on Japanese Industrial Standard JIS G 3333 YS9Ni is prepared. As a flux, Japanese Industrial Standard JIS G 3333 is prepared. FS9Ni-H is the standard PF-N4 manufactured by Kobe Steel.

A predetermined distance L between the front end of the first lead and the front end of the second lead was 40 mm, and a direct current voltage of 28 V and a current of 360 A was applied to the first and second leads for welding. The first and second welding torches move at a speed of 40 cm / min. Thereby, the joint structure 7 shown in FIG. 4 is obtained.

(Example 2)

First, as two Ni steel plates arranged one above the other, a 9% Ni steel plate having a width of 1500 mm, a height of 150 mm, and a thickness of 9.6 mm based on the ASTM A553 standard of the American Society for Testing Materials was prepared. On the upper end portion of the lower Ni steel plate, a root surface that is 2 mm flat on one surface side of the first lead side and is inclined at 15 degrees in the center and the other surface side is formed. On the upper end portion of the Ni steel plate on the upper side, a root surface that is 2 mm flat on one surface side of the first lead side and is inclined at 40 degrees in the center and the other surface side is formed. That is, only one groove is formed between the ends of the Ni steel plate at an angle of 55 degrees from one surface side to the other surface side.

As the first and second lead wires for electrodes, Techalloy 276 manufactured by Lincoln Electric Corporation with a diameter of 1.6 mm was prepared, and as a flux, a Techalloy 276 manufactured by Lincoln Electric Corporation was prepared. P2007.

A predetermined distance L between the front end of the first lead and the front end of the second lead was 25 mm, and a DC voltage of 28 V and a current of 300 A was applied to the first and second leads for welding. The first and second welding torches move at a speed of 35 cm / min. Thereby, the joint structure 7 shown in FIG. 4 is obtained.

(Example 3)

First, as two Ni steel plates arranged vertically, a 9% Ni steel plate having a width of 500 mm, a height of 200 mm, and a thickness of 12 mm was prepared based on Japanese Industrial Standard JIS G 3127 SL9N590. The upper end portion of the lower Ni steel plate is flat, and the lower end portion of the upper Ni steel plate, as shown in FIG. 1, has a root surface that is flat 2 mm in the center and is inclined at 45 degrees on both sides. The root gap is 2mm.

As the first and second leads used as electrodes, US-709S manufactured by Kobe Steel Co., Ltd. with a diameter of 2.4 mm based on Japanese Industrial Standard JIS G 3333 YS9Ni is prepared. As a flux, Japanese Industrial Standard JIS G 3333 is prepared. FS9Ni-H is based on PF-N4 manufactured by Kobe Steel Co., Ltd.

A predetermined distance L between the front end of the first lead and the front end of the second lead was 30 mm, and a DC voltage of 29 V and a current of 300 A was applied to the first and second leads for welding. The first and second welding torches move at a speed of 40 cm / min. Thereby, the joint structure 7 shown in FIG. 4 is obtained.

(Example 4)

A joint structure 7 was obtained in the same manner as in Example 3 except that the predetermined distance L between the front end of the first lead and the front end of the second lead was set to 50 mm.

(Comparative example 1)

A joint structure 7 was obtained in the same manner as in Example 1 except that the front end of the first lead and the front end of the second lead were set to the same position (that is, a predetermined distance L = 0 mm).

(Comparative example 2)

A joint structure 7 was obtained in the same manner as in Example 3 except that the predetermined distance L between the front end of the first lead and the front end of the second lead was set to 80 mm.

(Stretching test)

As shown in FIG. 4, from the joint structure 7 of Examples 1 to 4 and Comparative Examples 1 and 2, two samples 71 in a band shape extending in a direction orthogonal to the welding direction were cut, and these samples 71 were drawn. Extension test. In the tensile test, each sample 71 was stretched in the longitudinal direction, and the stress when the welded portion of each sample 71 was broken was measured as the tensile strength. The tensile strength of the Ni steel sheet itself is about 750 MPa.

The manufacturing conditions and tensile strength of the joint structure 7 of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Tables 1 and 2.

As can be seen from Table 2, in Comparative Example 1 in which the front end of the first lead and the front end of the second lead were located at the same position, the tensile strength was lower than 600 MPa, and the joint strength was reduced. On the other hand, in Examples 1 to 4 in which the front end of the second lead is separated from the front end of the first lead to a certain extent backward, the tensile strength exceeds 690 MPa, and a higher joint strength can be obtained. However, in Comparative Example 2 in which the front end of the second lead was largely separated from the front end of the first lead to the rear, the tensile strength was lower than 680 MPa (650 MPa in the same sample), and the joint strength decreased.

Claims (3)

A two-sided submerged arc welding method, in which the ends of Ni steel plates with a thickness of 20 mm or less arranged one above the other is welded from both sides with the flux covering one side, the two-sided submerged arc welding method is characterized in that: Using the first lead and the second lead made of Ni-based alloy as electrodes, the first welding torch that successively sends the first lead toward the bonding area where the ends are close to each other moves along the bonding area, and moves from the first The opposite side of the welding torch successively sends out the second welding torch of the second wire to the front side of the second wire so that the front end of the second wire is kept behind at a predetermined distance of 10mm to 60mm from the front end of the first wire. The joint area moves. For example, the method of submerged arc welding on both sides of the scope of patent application, wherein at least one of the ends is formed with a tapered surface toward the other side and inclined surfaces on both sides of the thickness direction of the Ni steel plate. The front end of the root surface is located on the first lead side or the second lead side with respect to the center of the Ni steel plate. For example, the two-sided submerged arc welding method of the scope of application for patents 1 or 2, wherein a belt is arranged on both sides of the above-mentioned Ni steel plate so as to be in contact with the above-mentioned Ni steel plate, and the belt is covered to cover the above. The above-mentioned flux is deposited in the form of a bonding area.