JP2017094338A - Build-up welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a build-up welding method capable of shortening both a construction period and manhours, when executing build-up welding to an inner surface of a pipe connecting cylindrical part, for example, in a pressure vessel.SOLUTION: As a torch, when executing build-up welding to an inner surface Wa of a pressure vessel base material W by a submerged arc welder 1 equipped with two wire torches 8 capable of simultaneously feeding a thin diameter welding wire 6 by two pieces, the two wire torches 8 are inserted into the inside of the pressure vessel base material W with electrode polarity of the two wire torches 8 as a DC wire minus, and while rotating the pressure vessel base material W around the axis C, the build-up welding is executed to the inner surface Wa of the pressure vessel base material W by weaving the two wire torches 8 in the direction along the axis C.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an overlay welding method suitable for overlay welding, for example, on the inner surface of a tubular portion (including a case where the preform itself forms a cylinder) of a base material.

  Conventionally, for example, pressure vessels that handle high-temperature and high-pressure gases and liquids are required to have corrosion resistance. Therefore, overlay welding using a corrosion-resistant metal as a welding material can be performed on a pressure vessel base material made of low alloy steel. Are known.

At this time, electroslag arc welding is usually used for overlay welding on the inner surface when the base material itself has a cylindrical shape. For example, the inner surface of a cylindrical portion for pipe connection formed on the base material Instead of electroslag arc welding, which is difficult to reduce in size, automatic build-up welding by TIG welding that can be improved in quality is employed for build-up welding on the inner surface of the cylindrical portion of the base material.
This TIG welding is described in detail in Non-Patent Document 1.

2nd Edition Welding and Joining Handbook Japan Welding Society, 237-251

  However, since TIG welding is conventionally used for overlay welding on the inner surface of the cylindrical portion of the base material, for example, the above-described cylindrical portion for pipe connection, it is possible to improve the quality, but a melting electrode such as MIG welding. Due to the nature of TIG welding, which has a slow welding speed compared to the type arc welding, there is a problem in that welding cannot be performed efficiently, and both the work period and the number of man-hours are increased. It was an issue.

  The present invention has been made by paying attention to the above-described conventional problems. For example, when performing build-up welding on the inner surface of a cylindrical portion for pipe connection in a base material of a pressure vessel, high quality is ensured. An object of the present invention is to provide a build-up welding method capable of realizing a shortening of the work period and a reduction in the number of man-hours.

  The inventors of the present invention focused on submerged arc welding in which the arc is blocked from the outside air and stabilized as a welding electrode type arc welding capable of increasing the welding speed. In this submerged arc welding, since the amount of penetration into the base metal usually increases, it is not suitable for build-up welding on the above-mentioned pressure vessel base material, but 2 welding wires can be fed simultaneously. It has been found that by using a wire torch, the amount of penetration into the base material can be controlled to improve the welding quality, and the present invention has been achieved.

  That is, according to the first aspect of the present invention, the inner surface of the cylindrical portion of the base material having the cylindrical portion is formed by a submerged arc welding machine equipped with a two-wire torch capable of simultaneously feeding two welding wires as a torch. When performing overlay welding, the electrode polarity of the two-wire torch is set to DC, wire minus, and the two-wire torch is weaved in a direction perpendicular to or along the axis of the cylindrical portion of the base material, It is set as the structure which performs overlay welding on the inner surface of the said cylindrical part of this base material.

  In the second aspect of the present invention, a thin welding wire is used as the welding wire. Here, the small-diameter welding wire refers to a welding wire having a wire diameter of 1.6 mm or less.

  The third aspect of the present invention is configured to switch the electrode polarity of the two-wire torch between direct current and wire plus when at least the second layer is built up.

  According to a fourth aspect of the present invention, the two-wire torch is inserted inside the cylindrical portion of the base material, and the base material is rotated around the axis of the cylindrical portion (the base material itself is a cylinder). (When the base material itself is rotated around its axis), the two-wire torch is weaved in a direction along the axial center of the cylindrical part, and the inner surface of the cylindrical part of the base material It is configured to perform overlay welding.

  According to a fifth aspect of the present invention, the two-wire torch is inserted inside the cylindrical portion of the base material, and the inserted two-wire torch is used as an axis of the cylindrical portion of the base material (the base material itself is In the case of a cylindrical shape, while weaving in a direction orthogonal to the axis of the base material), it advances along the axis of the cylindrical part and builds up on the inner surface of the cylindrical part of the base material It is configured to perform welding.

  In the overlay welding method according to the present invention, when overlay welding is performed on the cylindrical portion of the base material, the base material mounting table that supports the base material rotatably around the axis of the cylindrical portion, and this It is desirable to use a positioner that rotates the base material set on the base material mounting table at an appropriate angle as an aid for overlay welding by the submerged arc welding machine. It is desirable to use it as an aid for overlay welding.

  In the overlay welding method according to the first aspect of the present invention, since two welding wires are simultaneously fed by a two-wire torch, when a small-diameter welding wire is used, one welding wire is used. Compared with the one-wire torch that feeds the wire, the amount of resistance heat generation is increased, so that it is possible to suppress the penetration into the base material while obtaining a welding speed equivalent to that of the one-wire torch at a low current.

  Further, in the overlay welding method according to the first aspect of the present invention, when performing overlay welding by the submerged arc welding machine equipped with the two-wire torch as described above, the electrode polarity of the two-wire torch is set to DC and wire minus. Therefore, a large welding amount can be obtained while suppressing the amount of penetration into the base material.

  Furthermore, in the build-up welding method according to the first aspect of the present invention, the 2-wire torch is made to weave when performing build-up welding. Therefore, by adjusting the weaving width and speed, the width can be increased. A flat weld bead with a low height is obtained.

  That is, in the overlay welding method according to the first aspect of the present invention, it is possible to increase the welding quality by suppressing the amount of penetration into the base material, and further, to form a wide flat weld bead without reducing the welding speed. Therefore, the number of passes can be reduced, and as a result, the work period can be shortened and the number of steps can be reduced by the amount that the number of passes can be reduced.

  Furthermore, in the overlay welding method according to the second aspect of the present invention, since a thin welding wire having a wire diameter of 1.6 mm or less is used, a thick welding wire having a wire diameter exceeding 1.6 mm is used. As compared with a 1-wire torch that feeds a single wire, resistance heat generation is further increased, and accordingly, it is possible to suppress the penetration into the base material while obtaining a welding speed equivalent to that of a 1-wire torch at a low current. It becomes.

  Furthermore, in the overlay welding method according to the third aspect of the present invention, for example, in a case where two layers of stainless steel, which is a different metal as a corrosion-resistant metal, are stacked on a base material made of low alloy steel, first, a two-wire torch In addition to being able to suppress the amount of penetration into the base metal when overlaying stainless steel containing a large amount of ferrite-forming elements (Si, Cr, Nb, etc.) as the first layer, with the electrode polarity of DC being negative and wire minus When the appropriate amount of ferrite is generated, cracks are hardly generated in the built-up portion.

Next, when the electrode polarity of the two-wire torch is switched between direct current and wire plus, and the stainless steel having excellent corrosion resistance and containing an appropriate amount of ferrite-forming element is overlaid on the first layer as the second layer, the first layer of the second layer The amount of penetration with respect to increases, and the thickness of the first layer decreases.
In other words, the thickness of the second layer of stainless steel, which has excellent corrosion resistance, increases. When machining is performed after this build-up, stainless steel with sufficient machining allowance and poor corrosion resistance of the first layer is machined. This avoids exposure.

  That is, in the overlay welding method according to the third aspect of the present invention, for example, in the case where two layers of stainless steel, which are different metals as corrosion resistant metals, are stacked on a base material made of low alloy steel, the amount of penetration into the base material It is possible to reduce the number of passes because it is possible to form a wide flat weld bead without reducing the welding speed after controlling the welding quality of the first layer and the second layer by controlling As a result, the work period can be shortened and the man-hours can be reduced by the amount that can reduce the number of passes.

  Furthermore, in the overlay welding method according to the fourth aspect of the present invention, for example, when the base material itself has a cylindrical shape, a two-wire torch is inserted inside the base material, If the 2-wire torch is weaved in the direction along the axis of the base material while rotating around the axis, the required weld bead is piled up along the circumferential direction on the inner surface of the base material. By sequentially depositing the weld beads in a direction along the axis of the base material, overlay welding on the inner surface of the base material is efficiently performed.

  On the other hand, in the overlay welding method according to the fifth aspect of the present invention, for example, when the base material is heavy and it is difficult to perform welding while continuously rotating, the inside of the cylindrical portion of the base material If a two-wire torch is inserted into the base and the inserted two-wire torch is weaved in a direction perpendicular to the axis of the cylindrical portion of the base material, the two-wire torch is advanced in a direction along the axis of the cylindrical portion. The weld bead having the required width is piled up along the axial direction on the inner surface of the base material, and the base material is rotated by a predetermined amount so that the weld beads are sequentially arranged in the circumferential direction of the base material. Thus, build-up welding on the inner surface of the cylindrical portion of the base material is efficiently performed.

  In the overlay welding method according to the present invention, when performing overlay welding on the inner surface of the cylindrical portion of the base material, for example, the inner surface of the cylindrical portion for pipe connection in the pressure vessel, after ensuring high quality, A very excellent effect that it is possible to shorten the work period and reduce the number of man-hours is brought about.

It is side explanatory drawing of the submerged arc welding machine used for the overlay welding method which concerns on one Example of this invention. It is plane explanatory drawing of the submerged arc welding machine shown in FIG. It is an external appearance photograph which shows the condition of the build-up part on the test base material at the time of performing a build-up welding test using the submerged arc welding machine in FIG. FIG. 2 is a partial cross-sectional explanatory diagram at the initial layer build-up stage at the position in the circle in FIG. 2 when overlay welding is performed by the overlay welding method according to another embodiment of the present invention using the submerged arc welder in FIG. It is partial sectional explanatory drawing (b) of a 2nd pile-up stage, and partial sectional explanatory drawing (c) after machining.

Hereinafter, the present invention will be described with reference to the drawings.
1 and 2 show a submerged arc welding machine used in a build-up welding method according to an embodiment of the present invention. In this embodiment, build-up welding is performed on the inner surface of a cylindrical pressure vessel base material. A case will be described as an example.

  As shown in FIGS. 1 and 2, the submerged arc welding machine 1 includes a base 2 installed on a foundation E, a column 3 disposed on the left end of the base 2 in the drawing, and a vertical direction on the column 3. A horizontal beam 4 supported so as to be movable, a slider 5 supported by the horizontal beam 4 and sliding in the horizontal direction (arrow direction in FIG. 1), and a wire diameter fixed to the horizontal beam 4 of 1.6 mm or Two reels 7 and 7 each holding a welding wire 6 having a small diameter of 1.2 mm in a wound state, and the tip portions of the two welding wires 6 and 6 arranged at the tip of the slider 5 are simultaneously fed. A two-wire torch 8 that can be held, a feeder 10 that is supported by the horizontal beam 4 via the bar 9, pulls out the welding wires 6 and 6 from the two reels 7 and 7, and sends them to the two-wire torch 8; The control unit 12 is provided.

  In this case, the two-wire torch 8 is attached to the tip of the slider 5 via the weaver 13, and the two-wire torch 8 is weaved by the weaver 13 in the direction of the arrow in FIG. Yes.

On the other hand, at the right end portion of the base 2 in FIG. 1, a base material mounting table 14 that supports a cylindrical pressure vessel base material W so as to be rotatable around its axis C, and a pressure set on the base material mounting table 14. A positioner 15 that rotates the container base material W by an appropriate angle is disposed, and the base material mounting table 14 and the positioner 15 constitute auxiliary equipment for overlay welding of the submerged arc welding machine 1.
The digital power supply 11 of the submerged arc welder 1 is connected to the control unit 12 and is connected to a weaver 13 and the like as indicated by a broken line in FIG. The digital power source 11 is connected to the two-wire torch 8 and the pressure vessel base material W so that the electrode polarity can be switched.

  When performing the overlay welding on the inner surface Wa of the cylindrical pressure vessel base W using the submerged arc welding machine 1 and the base material mounting table 14 and the positioner 15 as auxiliary equipment for the overlay welding, The electrode polarity of the two-wire torch 8 is set to DC and wire minus, and the slider 5 is slid to insert the two-wire torch 8 inside the pressure vessel base material W as shown by a one-dot chain line in FIG.

  Next, the pressure vessel base material W set on the base material mounting table 14 is rotated around the axis C by the positioner 15, and at the same time, the two-wire torch 8 is moved by the weaver 13 on the basis of the command of the control unit 12. If weaving is performed in a direction along the axis C of W with a swing width of 25 to 40 mm, the weld bead B corresponding to 1 Pass of the required width is formed of the pressure vessel base material W as shown by a two-dot chain line in FIG. It will be piled up along the circumferential direction on the inner surface Wa.

  Subsequently, the welding bead B is aligned in the direction along the axis C of the pressure vessel base material W while the two-wire torch 8 is advanced deeply (rightward in the drawing) inside the pressure vessel base material W. The first layer build-up welding with respect to the inner surface Wa of the pressure vessel base material W is performed by sequentially increasing the number of passes.

  And if this build-up welding operation is repeated by the number of layers determined, build-up welding of a plurality of layers with respect to the inner surface Wa of the pressure vessel base material W will be performed.

  Thus, in overlay welding by the submerged arc welding machine 1 described above, two welding wires 6 and 6 having a diameter of 1.6 mm or 1.2 mm are simultaneously fed by the 2-wire torch 8. Therefore, as compared with a one-wire torch that feeds a welding wire having a large wire diameter, a welding speed equivalent to that of the one-wire torch can be obtained at a low current by an amount corresponding to an increase in resistance heat generation.

  Further, in the overlay welding by the submerged arc welding machine 1 described above, since the electrode polarity of the two-wire torch 8 is set to DC and wire minus, a large amount of welding is obtained while suppressing the amount of penetration of the first layer into the pressure vessel base material W. Will be.

  Further, in the overlay welding by the submerged arc welding machine 1 described above, the two-wire torch 8 having the electrode polarity as the DC positive electrode is weaved in the direction along the axis C of the pressure vessel base material W. By adjusting the weaving width and speed, a flat weld bead B having a wide width and a low surplus is obtained.

  That is, in the overlay welding by the submerged arc welding machine 1 described above, the welding amount of the submerged arc welding machine 1 is increased without reducing the welding amount of the submerged arc welding machine 1 while suppressing the amount of penetration into the pressure vessel base material W to be small. Therefore, it is possible to reduce the number of passes, and as a result, it is possible to shorten the work period and reduce the number of steps by the amount that can reduce the number of passes.

  Therefore, in order to confirm the effect of the overlay welding method according to the above-described embodiment, as shown in FIG. 3, on the test base material We having a flat plate shape using the above-described submerged arc welding machine 1, A built-up portion Be having a length l = 300 mm × width w = 200 mm was formed. For comparison, a built-up portion corresponding to the built-up portion was similarly formed on the test base material by TIG welding (not shown).

  In overlay welding using the submerged arc welding machine 1, the weaving width is about 40 mm, the welding speed is 80 mm / min, the welding speed is 80 g / min, and the arc time is 18.8 min. Welding is performed with a weaving width of about 15 mm at 13 Pass, a welding speed of 80 mm / min, a welding speed of 30 g / min, an arc time of 48.8 min, and the weld quality of the built-up part Be is a built-up part formed by TIG welding. It was almost equivalent.

  Therefore, in the overlay welding method according to the above-described embodiment using the submerged arc welding machine 1, a wide flat welding bead is formed without reducing the welding speed of the submerged arc welding machine 1 while ensuring the welding quality. As a result, it was proved that it was possible to fill the meat very efficiently as much as the number of passes could be reduced.

  In the above-described embodiment, the pressure vessel base material W itself has a cylindrical shape, and the 2-wire torch 8 is rotated around the axis C of the pressure vessel base material W while the axis of the pressure vessel base material W is rotated. By weaving in the direction along C, build-up welding in the circumferential direction is performed on the inner surface Wa of the pressure vessel base material W.

  At this time, for example, when the pressure vessel base material W is heavy and it is difficult to perform welding while continuously rotating, the two-wire torch 8 inserted inside the pressure vessel base material W is used. By moving the two-wire torch 8 along the axis C while weaving in a direction orthogonal to the axis C of the W, the meat along the axis C direction with respect to the inner surface Wa of the pressure vessel base material W is increased. A prime welding can be performed.

Next, the overlay welding method according to another embodiment of the present invention will be described.
In this embodiment, the inner surface Wa of the cylindrical pressure vessel base material W made of low alloy steel using the submerged arc welding machine 1 and the base material mounting table 14 and positioner 15 as auxiliary equipment for overlay welding. Next, the case where two layers of stainless steel, which is a dissimilar metal, are stacked as a corrosion resistant metal will be described as an example.

  First, the electrode polarity of the two-wire torch 8 using a stainless steel welding wire 6 containing a large amount of ferrite-forming elements (ferritizing elements such as Si, Cr, Nb, etc.) having a small diameter of 1.6 mm or 1.2 mm. Is a direct current and wire minus, the slider 5 is slid and the two-wire torch 8 is inserted inside the pressure vessel base material W.

  Next, the pressure vessel base material W set on the base material mounting table 14 is rotated around the axis C by the positioner 15, and at the same time, the two-wire torch 8 is moved by the weaver 13 on the basis of the command of the control unit 12. If weaving is performed in a direction along the axis C of W with a swing width of 25 to 40 mm, build-up welding for 1 Pass in the circumferential direction with respect to the inner surface Wa of the pressure vessel base material W is performed.

  Subsequently, if this welding operation is repeated by the predetermined number of passes while advancing the two-wire torch 8 inside the pressure vessel base material W, as shown in FIG. Overlay welding of the first layer L1 is performed.

  As described above, when the electrode polarity of the two-wire torch 8 is DC and wire minus and stainless steel containing a large amount of ferrite-forming elements is built up as the first layer L1, the amount of penetration of stainless steel into the pressure vessel base material W (FIG. 4 (a )) (Amount of penetration from the inner surface Wa of the pressure vessel base material W indicated by a broken line) d1 is suppressed to a small amount, and an appropriate amount of ferrite makes it difficult to cause cracks in the built-up portion.

  Following the build-up of the first layer L1, a stainless steel welding wire 6 having excellent corrosion resistance and containing a suitable amount of a ferrite-forming element and having a wire diameter of 1.6 mm or 1.2 mm is used. After the electrode polarity of the two-wire torch 8 is switched between direct current and wire plus, the two-wire torch 8 that has been retracted outside the pressure vessel base material W is inserted into the pressure vessel base material W again.

  Then, while the pressure vessel base material W is rotated around the axis C by the positioner 15, the 2-wire torch 8 is weaved by the weaver 13 in a direction along the axis C of the pressure vessel base material W with a swing width of 25 to 40 mm. For example, overlay welding for 1 Pass in the second layer is performed.

  Subsequently, if the welding operation is repeated by the predetermined number of passes while the two-wire torch 8 is advanced deeply, as shown in FIG. 4 (b), a stainless steel containing an appropriate amount of ferrite-forming element having excellent corrosion resistance. Steel is piled up on the first layer L1 as the second layer L2.

  As described above, when the electrode polarity of the two-wire torch 8 is set to DC and wire plus, and the stainless steel having excellent corrosion resistance and containing an appropriate amount of ferrite-forming elements is overlaid on the first layer L1 as the second layer L2, the second layer is obtained. The amount of penetration of the L2 stainless steel into the first layer L1 (the amount of penetration from the build-up height of the first layer L1 indicated by a two-dot chain line in FIG. 4B) d2 increases, and the thickness of the stainless steel of the first layer L1 ( The height t1 from the inner surface Wa of the pressure vessel base material W is reduced.

  That is, the thickness (the height from the inner surface Wa of the pressure vessel base material W shown by the broken line in FIG. 4B) t2 of the stainless steel of the second layer L2 having excellent corrosion resistance is increased, and is shown in FIG. 4C. Thus, when machining is performed after this build-up, a machining allowance (the amount of penetration from the build-up height of the second layer L2 shown by the one-dot chain line in FIG. 4C) is sufficiently secured. Thus, it is avoided that the stainless steel having poor corrosion resistance of the first layer L1 is exposed on the machined surface Ma by machining.

  Therefore, in the overlay welding method according to this embodiment, in the case where two layers of stainless steel, which is a dissimilar metal, are deposited on the inner surface Wa of the cylindrical pressure vessel base material W made of low alloy steel, the pressure vessel mother It is possible to form a wide and flat weld bead without reducing the welding speed of the submerged arc welding machine 1 after controlling the amount of penetration into the material W to ensure the welding quality of the first layer L1 and the second layer L2. Therefore, the work period can be shortened and the man-hours can be reduced by the amount that can reduce the number of passes.

  In this embodiment, the case where two layers of stainless steel, which is a dissimilar metal, are stacked on the inner surface Wa of the cylindrical pressure vessel base material W made of low alloy steel has been described as an example. You may employ | adopt the overlay welding method which concerns on, for example, when three or more layers of stainless steel are built.

  As described above, when three or more layers of stainless steel are stacked, the electrode polarity of the two-wire torch 8 is switched between direct current and wire plus in at least the second layer build-up. The electrode polarity of 8 may be any of DC, wire minus, DC, and wire plus.

  Further, for example, the overlay welding method according to the present invention may be employed for overlaying various alloys such as a Ni-based alloy that is highly susceptible to cracking and is desired to suppress the first layer from being melted into the base material.

  In the above embodiment, the case where the pressure vessel base material W itself has a cylindrical shape and the welding is performed on the inner surface Wa of the cylindrical pressure vessel base material W will be described as an example. However, the present invention is not limited to this, and this cylinder is formed when the base material has a tubular part that the base material has the overlay welding method according to the present invention, that is, when the cylindrical part is formed in a part of the base material. You may employ | adopt to perform overlay welding to the inner surface of a shape part.

  Moreover, although the above-mentioned Example showed the case where build-up welding was performed to the inner surface Wa of the pressure vessel base material W with the submerged arc welding machine 1 equipped with 1 pole of the 2-wire torch 8, it is not limited to this. Alternatively, for example, overlay welding may be performed on the inner surface Wa of the pressure vessel base material W by a submerged arc welding machine equipped with two two-wire torches 8.

  The configuration of the overlay welding method according to the present invention is not limited to the configuration of the above-described embodiment.

DESCRIPTION OF SYMBOLS 1 Submerged arc welding machine 6 Welding wire 8 2 wire torch C Base material axis L2 2nd layer W Pressure vessel base material (base material)
Wa Inside surface of base material

Claims (5)

When performing overlay welding on the inner surface of the cylindrical part of the base material having a cylindrical part by a submerged arc welding machine equipped with a two-wire torch capable of simultaneously feeding two welding wires as a torch,
While the electrode polarity of the two-wire torch is direct current and wire minus, the two-wire torch is weaved in a direction orthogonal to or along the axis of the cylindrical portion of the base material, and the cylindrical shape of the base material Overlay welding method in which overlay welding is performed on the inner surface of the part.   The build-up welding method according to claim 1, wherein a thin-diameter welding wire is used as the welding wire.   The build-up welding method according to claim 1 or 2, wherein the electrode polarity of the two-wire torch is switched between direct current and wire plus when at least the second layer is built up.   Inserting the two-wire torch inside the cylindrical part of the base material, rotating the base material around the axis of the cylindrical part, and moving the two-wire torch along the axis of the cylindrical part The build-up welding method according to any one of claims 1 to 3, wherein overlay welding is performed on the inner surface of the cylindrical portion of the base material by weaving.   Inserting the two-wire torch inside the cylindrical portion of the base material, and weaving the inserted two-wire torch in a direction perpendicular to the axis of the cylindrical portion of the base material, The build-up welding method according to any one of 1 to 3, wherein the welding is made on the inner surface of the cylindrical portion of the base material by being advanced along an axis.

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