JPWO2016208131A1 - Double-sided submerged arc welding method - Google Patents

Abstract

In a double-sided submerged arc welding method in which the ends of Ni steel plates (1) arranged vertically are covered with a flux (5) and welded from both sides, a first wire (21) and a second wire (22) made of a Ni-based alloy are used. The first torch (31) that is used as an electrode and feeds the first wire (21) toward the joining region where the ends are close to each other is moved along the joining region, and the first torch (31) is moved from the opposite side to the first torch (31). The second torch (32) that feeds the two wires (22) toward the joining region is kept behind the tip of the second wire (22) by a predetermined distance of 10 mm to 60 mm from the tip of the first wire (21). And move along the joining region (15).

Description

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

  As a method of butt welding (horizontal welding) between the steel plates lined up and down, first, welding is performed at one bottom of two grooves opened in one and the other in the thickness direction, and then the bottom of the other groove is gouged. There is a method of performing welding at the bottom of the groove after crushing the back side. On the other hand, there is also a method of welding from both sides at the same time in order to omit the back chip.

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

JP-A-61-206564

  By the way, in the low temperature tank which stores liquefied gas, such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas), Ni steel plate excellent in low temperature toughness may be used for a side wall. Since the low-temperature tank is huge, butt welding of Ni steel plates arranged in the upper and lower sides needs to be performed outdoors. Also, the welding work place is often a high place. From such a point of view, it is desirable to use a double-sided submerged arc welding method that does not use shield gas and welds from both sides while covering the ends with a flux, as a method of butt-welding Ni steel sheets arranged vertically.

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

  By the way, the inventors of the present invention have a sufficiently high joint strength when the base material is thick when using a dissimilar joint with a different base material (Ni steel plate) and welding material (wire) as described above. Although it can be obtained, it has been found that the joint strength decreases when the base material is thin.

  Therefore, an object of the present invention is to provide a double-sided submerged arc welding method capable of obtaining a sufficiently high joint strength even when the Ni steel plates to be abutted are thin.

  In order to solve the above-mentioned problem, the inventors of the present invention, as a result of intensive research, have found that the decrease in joint strength when the thickness of the base metal is small in the dissimilar joint is the amount of penetration of the base material into the weld ( We found out that this was caused by an increase in the dilution ratio. And it discovered that a dilution rate could be restrained low if the front-end | tip of the electrode arrange | positioned on both sides of a base material was shifted mutually. The present invention has been made from such a viewpoint.

  That is, the double-sided submerged arc welding method of the present invention is a double-sided submerged arc welding method of welding from both sides while covering ends of Ni steel plates arranged vertically with a flux, wherein the first wire and the second wire made of a Ni-based alloy are used. A wire is used as an electrode, and a first torch that feeds the first wire toward a joining region where the ends are close to each other is moved along the joining region, and the second wire is moved from the opposite side of the first torch. Moving the second torch extending toward the joining region along the joining region while keeping the tip of the second wire behind the tip of the first wire by a predetermined distance of 10 mm or more and 60 mm or less. It is characterized by.

  According to said structure, since the front-end | tip of a 2nd wire is arrange | positioned 10 mm or more back from the front-end | tip of a 1st wire, compared with the case where they are arrange | positioned in the same position, the range used as the high temperature in the edge part of Ni steel plate Narrow. Therefore, the amount of penetration of the Ni steel sheet into the welded portion is reduced, and the dilution rate can be kept low. Thereby, a sufficiently high joint strength can be obtained. On the other hand, since the tip of the second wire is not separated beyond 60 mm from the tip of the first wire, it is possible to suppress defects such as poor penetration in the welded portion.

  At least one of the end portions is formed with a root face that is pointed toward the other and has inclined surfaces on both sides in the thickness direction of the Ni steel plate, and the tip of the root face is at the center of the Ni steel plate. On the other hand, it may be located on the first wire side or the second wire side. When the tip of the root face is located at the center of the Ni steel plate, the upper Ni steel plate may fall to the second wire side by welding. On the other hand, if the tip of the root face is located on the first wire side or the second wire side with respect to the center of the Ni steel plate as in the above configuration, the upper Ni steel plate is prevented from falling. Can do.

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

  A belt may be disposed on both sides of the lower Ni steel plate so as to contact the Ni steel plate, and the flux may be deposited on the belt so as to cover the joining region. According to this configuration, the flux accumulation position 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 Ni steel plates to be abutted are thin.

It is sectional drawing for demonstrating the both-sides submerged arc welding method which concerns on one Embodiment of this invention. It is a top view which shows the positional relationship of a 1st torch and a 2nd torch. It is sectional drawing which shows the shape of another route face. It is a figure which shows the joint structure of Examples 1-4 and Comparative Examples 1 and 2. FIG.

  With reference to FIG. 1 and FIG. 2, the both-sides submerged arc welding method which concerns on one Embodiment of this invention is demonstrated. This double-sided submerged arc welding method involves butt welding (lateral welding) of Ni steel plates 1 arranged vertically. Specifically, welding is performed from both sides while covering the upper end portion of the lower Ni steel plate 1 and the lower end portion of the upper Ni steel plate 1 with the flux 5.

  A first wire 21 and a second wire 22 used as electrodes are disposed on both sides of a joining region 15 (so-called welding line) where the ends of the Ni steel plate 1 are close to each other. The first wire 21 is for performing welding in advance on one side, and the second wire 22 is for performing welding on the opposite side with a slight delay. The first wire 21 is drawn out by the first torch 31 toward the bonding region 15, and the second wire 22 is drawn out by the second torch 32 toward the bonding region 15 from the side opposite to the first torch 31.

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

  The Ni steel plate 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, see Japanese Industrial Standard JIS G 3127). For example, the nickel content of the Ni steel sheet 1 is 3% or more and 15% or less in mass percent. Among them, it is preferable to use 7% Ni steel or 9% Ni steel as the Ni steel plate 1 for a low temperature tank for storing liquefied gas. The Ni steel sheet 1 typically has a ferrite structure.

  The both-side submerged arc welding method of the present embodiment can be used even when the Ni steel plate 1 is thick, but if the Ni steel plate 1 is thin (for example, when the thickness of the Ni steel plate 1 is 20 mm or less), The effect that the fall of the intensity | strength of the joint which is a welding part can be prevented is acquired. In addition, the plate | board thickness of the Ni steel plate 1 may be 18 mm or less, and may be 16 mm or less.

  In the present embodiment, the upper end of the lower Ni steel plate 1 is flat, but the thickness of the Ni steel plate 1 sharpened toward the upper end of the lower Ni steel plate 1 at the lower end of the upper Ni steel plate 1. A root face 12 having inclined surfaces on both sides in the direction is formed. Thereby, between the edge parts of the Ni steel plate 1, the two groove | channels 11 opened to one side and the other of the plate | board thickness direction of the Ni steel plate 1 are formed. However, the root face 12 may also be formed at the upper end of the lower Ni steel plate. Or the root face 12 may be formed only in the upper end part of the lower Ni steel plate.

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

  In the present embodiment, the flat tip 13 of the root face 12 is located at the center CL of the Ni steel plate 1. However, as shown in FIG. 3, the tip 13 of the root face 12 may be located on the second wire 22 side with respect to the center CL of the Ni steel plate 1. When the tip 13 of the root face 12 is located at the center CL of the Ni steel plate 1, the upper Ni steel plate 1 may fall down to the second wire 22 side that is followed by welding. On the other hand, if the tip 13 of the root face 12 is positioned on the second wire 22 side with respect to the center CL of the Ni steel plate 1 as shown in FIG. can do. This effect can be similarly obtained even when the tip of the root face is located on the first wire 21 side with respect to the center CL of the Ni steel plate 1. Alternatively, the root face 12 may have only one inclined surface so that the flat tip 13 of the root face 12 is located on one surface side of the Ni steel plate 1.

  The first wire 21 and the second wire 22 are made of a Ni-based alloy having higher toughness than the Ni steel plate 1. For example, such a Ni-based alloy contains 55% or more of Ni by mass percentage. Components other than Ni in the Ni-based alloy include, for example, Cu (copper), Cr (chromium), Fe (iron), Mo (molybdenum), and the like. Ni-based alloys typically have an austenite structure. The diameters of the first and second 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, any wire that conforms to the Japanese Industrial Standard JIS G 3333 YS9Ni can be used as the first and second wires 21 and 22. In this case, as the flux 5, for example, any flux that conforms to the Japanese Industrial Standard JIS G 3333 FS9Ni-H can be used.

  Next, the double-sided submerged arc welding method of this embodiment will be described in detail.

  First, the belt 4 is disposed 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 an unillustrated flux supply device. Next, the flux 5 that is powder is deposited on the belt 4 so as to cover the joining region 15 from both sides, in other words, so that the flux 5 is filled in both the grooves 11.

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

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

  Thereafter, while applying a voltage to the first wire 21 and the second wire 22, the first torch 31 is moved along the joining region 15, and the second torch 32 is moved to the tip of the second wire 22. It moves along the joining area | region 15, keeping only the predetermined distance L back from the front-end | tip. As a result, the first layer 61 is formed at the bottom of both the grooves 11. After the formation of the first layer 61, the second layer 62 is formed in the same manner. If the inside of the groove 11 is filled only with the first layer 61, the formation of the second layer 62 is unnecessary.

  The voltage applied to each of the first wire 21 and the second wire 22 may be an AC voltage, but is preferably a DC voltage. In the case of a DC voltage, the voltage value is 20 to 40 V, for example, and the current value is 200 to 400 A, for example. Moreover, the moving speed of the 1st and 2nd torch 31, 32 is 20-70 cm / min, for example.

  As described above, in the double-sided submerged arc welding method of the present embodiment, the tip of the second wire 22 is disposed 10 mm or more rearward from the tip of the first wire 21, so that compared to the case where they are disposed at the same position. The range of high temperature at the end of the Ni steel sheet 1 is narrowed. Therefore, the amount of penetration of the Ni steel sheet 1 into the welded portion is reduced, and the dilution rate can be kept low. Thereby, a sufficiently high joint strength can be obtained. On the other hand, since the tip of the second wire 22 is not separated from the tip of the first wire 21 by more than 60 mm, defects such as poor penetration in the welded portion can be suppressed.

  Moreover, in this embodiment, since the flux 5 is deposited on the belt 4, the deposition position of the flux 5 can be easily changed according to the welding position.

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

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

  US-709S made by Kobe Steel Co., Ltd. with a diameter of 2.4 mm conforming to Japanese Industrial Standard JIS G 3333 YS9Ni is prepared as the first and second wires used as electrodes, and the Japanese Industrial Standard JIS G 3333 FS9Ni- is used as the flux. PF-N4 manufactured by Kobe Steel, which complies with H, was prepared.

  The predetermined distance L between the tip of the first wire and the tip of the second wire was 40 mm, and welding was performed by applying a DC voltage of voltage 28V and current 360A to the first and second wires. The first and second torches were moved at 40 cm / min. Thereby, the joint structure 7 as shown in FIG. 4 was obtained.

(Example 2)
First, a 9% Ni steel plate having a width of 1500 mm, a height of 150 mm, and a plate thickness of 9.6 mm was prepared as two Ni steel plates arranged vertically. At the upper end of the lower Ni steel plate, a root face having a flat surface of 2 mm on one side of the first wire and an inclination of 15 degrees on the center and the other surface side was formed. On the upper end portion of the upper Ni steel plate, a root face having a flat surface of 2 mm on the first wire side and an inclination of 40 degrees on the center and the other surface side was formed. That is, only one groove opened at an angle of 55 degrees from one surface side to the other surface side was formed between the ends of the Ni steel plates.

  Lincoln Techalloy 276 having a diameter of 1.6 mm was prepared as the first and second wires used as the electrodes, and Lincoln P2007 was prepared as the flux.

  The predetermined distance L between the tip of the first wire and the tip of the second wire was 25 mm, and welding was performed by applying a direct current voltage of 28V and 300A to the first and second wires. The first and second torches were moved at 35 cm / min. Thereby, the joint structure 7 as shown in FIG. 4 was obtained.

(Example 3)
First, a 9% Ni steel plate having a width of 500 mm, a height of 200 mm, and a thickness of 12 mm, which conforms to Japanese Industrial Standard JIS G 3127 SL9N590, was prepared as two Ni steel plates arranged one above the other. The upper end of the lower Ni steel plate was flat, and a root face having a flat center of 2 mm and inclined at 45 degrees on both sides was formed at the lower end of the upper Ni steel plate as shown in FIG. The root gap was 2 mm.

  US-709S made by Kobe Steel Co., Ltd. with a diameter of 2.4 mm conforming to Japanese Industrial Standard JIS G 3333 YS9Ni is prepared as the first and second wires used as electrodes, and the Japanese Industrial Standard JIS G 3333 FS9Ni- is used as the flux. PF-N4 manufactured by Kobe Steel, which complies with H, was prepared.

  The predetermined distance L between the tip of the first wire and the tip of the second wire was 30 mm, and welding was performed by applying a direct current voltage of 29V and 300A to the first and second wires. The first and second torches were moved at 40 cm / min. Thereby, the joint structure 7 as shown in FIG. 4 was 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 tip of the first wire and the tip of the second wire was 50 mm.

(Comparative Example 1)
A joint structure 7 was obtained in the same manner as in Example 1 except that the tip of the first wire and the tip of the second wire were at the same position (that is, the 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 tip of the first wire and the tip of the second wire was 80 mm.

(Tensile test)
As shown in FIG. 4, two strip-shaped samples 71 extending in a direction orthogonal to the welding direction are cut out from the joint structures 7 of Examples 1 to 4 and Comparative Examples 1 and 2, and are pulled against these samples 71. A test was conducted. In the tensile test, each sample 71 was pulled in the longitudinal direction, and the stress when the welded portion of each sample 71 broke was measured as the tensile strength. The tensile strength of the Ni steel sheet itself is about 750 MPa.

  Production conditions and tensile strength of the joint structures 7 of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Tables 1 and 2.

  From Table 2, it can be seen that in Comparative Example 1 in which the tip of the first wire and the tip of the second wire are in the same position, the tensile strength is less than 600 MPa and the joint strength is low. On the other hand, in Examples 1 to 4 in which the tip of the second wire is separated from the tip of the first wire to some extent, the tensile strength exceeds 690 MPa, and high joint strength is obtained. However, in Comparative Example 2 in which the tip of the second wire is greatly separated backward from the tip of the first wire, the tensile strength is less than 680 MPa (650 MPa in one sample), and the joint strength is low.

DESCRIPTION OF SYMBOLS 1 Ni steel plate 12 Root face 13 Tip 15 Joining region 21 1st wire 22 2nd wire 31 1st torch 32 2nd torch 4 Belt 5 Flux

Claims (4)

It is a double-sided submerged arc welding method of welding from both sides while covering the ends of Ni steel plates lined up and down with flux,
Using the first wire and the second wire made of Ni-based alloy as electrodes,
The first torch that feeds the first wire toward the joining region where the ends are close to each other is moved along the joining region, and the second wire is directed to the joining region from the side opposite to the first torch. A two-sided submerged arc welding method in which the second torch that is fed out is moved along the joining region while maintaining the tip of the second wire behind the tip of the first wire by a predetermined distance of 10 mm to 60 mm.   At least one of the end portions is formed with a root face that is pointed toward the other and has inclined surfaces on both sides in the thickness direction of the Ni steel plate, and the tip of the root face is at the center of the Ni steel plate. 2. The double-sided submerged arc welding method according to claim 1, wherein the two-sided submerged arc welding method is located on the first wire side or the second wire side.   The double-sided submerged arc welding method according to claim 1 or 2, wherein a thickness of the Ni steel plate is 20 mm or less.   The belt is disposed on both sides of the lower Ni steel plate so as to contact the Ni steel plate, and the flux is deposited on the belt so as to cover the joining region. Double-sided submerged arc welding method described in 2.

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