JP2007268551A - Multi-electrode one side submerged arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-electrode one side submerged arc welding method capable of obtaining a weld joint having the excellent bead shape and the sound and excellent joint performance for an extensive joint thickness. <P>SOLUTION: A groove shape of a butted part of a member to be welded is a V-shape, and its groove angle is 30-60°C. The filling ratio of a filler in the groove to the groove sectional area is ≥2% and <25%. When the filling ratio of the filler in the groove to the groove sectional area is ≥2% and ≤15%, the current of a first electrode is 950-1,570A. When the filling ratio of the filler in the groove to the groove sectional area is >15% and ≤20%, the current of the first electrode is 1,000 to 1,580A. When the filling ratio of the filler in the groove to the groove sectional area is >20% and <25%, the current of the first electrode is 1.050 to 1,590A. In this multi-electrode one side submerged arc welding method, a backing plate is a flux-copper backing or a flux backing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to multi-electrode single-sided submerged arc welding, and in particular, multi-electrode single-sided submerged arc that performs submerged arc welding by a flux copper backing method using a flux and a copper plate as a backing material or a flux backing method using a flux as a backing material. It relates to a welding method.

  The submerged arc welding method has the advantage that welding can be performed at a high current and a high speed compared to the covering arc welding method and the gas shielded arc welding method, and it can be used for large steel structures such as shipbuilding, steel frames and bridges. It is a welding method that is heavily used from the viewpoint of efficiency in manufacturing.

  Among the submerged arc welding methods, the single-sided submerged arc welding method is widely used in the shipbuilding field for panel splicing of parallel blocks and other panels, and a bead is formed in 11 passes from the front side to the back side of the steel plate. It is a highly efficient welding method that can be performed. Moreover, the plate | board thickness range of a to-be-welded steel plate is utilized from 9 mm to about 35 mm. At present, an experimental study of a single-sided submerged arc welding method has been conducted even for a plate thickness of about 40 mm, and there is an increasing demand for improvement in welding workability, mechanical performance of welded joints, and bead appearance.

  Recently, fabricators in the shipbuilding industry, etc., have been carrying out a single-sided submerged arc welding method with the replacement of aging equipment and an increased number of welding electrodes for the purpose of high-efficiency construction. As compared with the above, higher current and higher speed are achieved.

  With the increase in current and speed, various proposals requiring a strict welding method have been made in order to ensure the performance and soundness of the welded joint. Patent Document 1 proposes a welding method in which the groove shape is a V shape, and the groove angle, the particle size configuration of the filler in the groove, and the filling rate are regulated to improve the stability of the back bead shape. ing.

  Further, in Patent Document 2 and Patent Document 3, the groove shape is a V shape, and the groove angle and the filler in the groove are regulated from 1/3 of the welded material plate thickness to the height of the welded material surface. Therefore, a welding method for preventing a high-temperature crack detected by a good bead shape and nondestructive inspection is proposed.

JP 2005-349407 A JP-A-2005-319507 JP-A-2005-246385

  However, the conventional techniques described above have the following problems.

  The performance and soundness of the welded joint are determined by various mechanical tests in accordance with welding construction approval test methods such as front and back bending tests and side bending tests. However, as the strength and thickness of welded joints increase, and the current and speed of welding work increase, the welded joints with a plate thickness exceeding 35 mm in the conventional welding construction are good in the welding construction approval test. There is a problem that the result cannot be obtained. Even in a welded joint having a plate thickness of about 20 mm, a crack may occur on the bent surface by a bending test.

  In Patent Document 1, under welding conditions where a good back bead shape is obtained, the filling rate of the filler in the groove with respect to the groove cross-sectional area is as high as 50% or more, and the current value must be set high. Thereby, a base material dilution rate becomes high, carbon of a base material mixes in a weld metal, and a micro hot crack may generate | occur | produce in the weld metal formed by a 1st electrode.

  In Patent Document 2 and Patent Document 3, the setting of the current value of the first electrode with respect to the filling rate of the filler in the groove is not clear, and hot cracking is not detected by a nondestructive inspection or the like, but is manifested by a bending test. There is a problem that a minute hot crack of the weld metal formed by one electrode occurs.

  The present invention has been made in view of such a problem, and is a multi-electrode single-sided submerged arc welding capable of obtaining a welded joint having a good bead shape and sound and good joint performance for a wide range of joint plate thicknesses. It aims to provide a method.

  In the multi-electrode single-sided submerged arc welding method according to the present invention, the groove shape of the butt portion of the material to be welded is V-shaped, the groove angle is 30 to 60 °, and the groove filler in the groove cross-sectional area is When the filling rate is 2% or more and less than 25% and the filling rate of the filler in the groove with respect to the groove cross-sectional area is 2 to 15%, the current value of the first electrode is 950 to 1570A, and the opening with respect to the groove cross-sectional area is When the filling rate of the inner filler exceeds 15% and 20% or less, the current value of the first electrode is 1000 to 1580A, and the filling rate of the inner filler relative to the groove cross-sectional area exceeds 20% and less than 25%. In this case, the current value of the first electrode is 1050 to 1590A.

  In this multi-electrode single-sided submerged arc welding method, welding is preferably performed by a flux copper backing method or a flux backing method.

  According to the present invention, by regulating the filling rate of the filler in the groove with respect to the groove shape and the groove cross-sectional area, and further regulating the current value of the first electrode with respect to the filling rate, the thickness and thickness are reduced. In the meat joint, an appropriate base material dilution ratio and back bead shape can be obtained, deterioration of toughness can be prevented, and hot cracking can be prevented. As a result, a welded joint having a good bead shape and sound and good joint performance can be obtained for a wide range of joint plate thicknesses of 9 to 40 mm.

  Next, embodiments of the present invention will be specifically described with reference to the accompanying drawings. As a result of conducting various experimental studies to achieve the above object, the present inventors have found that hot cracks that are manifested by side bending tests occur mainly in the weld metal formed by the first electrode. It was. Moreover, even in a wide range of single-sided submerged arc welding with a plate thickness of 9 to 40 mm, a good bead appearance and minute hot cracks that are not detected even in nondestructive inspection are prevented, and a welded joint having sound and good performance is obtained. Therefore, the groove shape is V-shaped, the filling rate of the filler in the groove with respect to the groove cross-sectional area is restricted, and the filling rate of the filler in the groove with respect to the groove cross-sectional area is first. It has been found that it is essential to regulate the current value of the electrode. That is, a wide range of joints with a plate thickness of 9 to 40 mm is provided by providing a precise construction method and welding conditions that regulate the current value of the first electrode suitable for the groove shape and the filling rate of the filler in the groove. A weld joint having a good bead shape and sound and good performance with respect to the plate thickness can be obtained.

  Hereinafter, the reasons for restricting the welding conditions of the multi-electrode single-sided submerged arc welding method according to the present invention will be described.

"Groove shape: V shape"
Mainly, it is necessary to lower the dilution rate of the base material component in order to prevent minute hot cracks generated in the weld metal formed by the first electrode. A U-shaped groove or the like can be cited as the method, but U-shaped groove machining is unsuitable because it results in machine cutting and increases costs. In addition, the Y shape with a shorter root face compared to conventional construction has a range of conditions that can ensure sufficient performance in a thick joint, but the processing cost increases. Therefore, the groove shape is a V shape.

"Bevel angle: 30 to 60 degrees"
The groove angle changes the formability of the back bead and the groove cross-sectional area. When the angle is less than 30 °, it is difficult to form the back bead, and it is not possible to obtain an appropriate height of the back bead and a bead width. Moreover, when the base material dilution rate is increased, minute hot cracks are generated, and cracks are generated on the bending surface by a bending test. On the other hand, if it exceeds 60 °, the back bead becomes excessive, the possibility that the weld metal melts from the back surface side of the base material increases, and the surplus height of the front bead becomes excessive. Moreover, since an appropriate base material dilution rate cannot be obtained, toughness deteriorates. Therefore, the groove angle is set to 30 to 60 °.

“Filling ratio of filler in groove relative to groove cross-sectional area: 2% or more and less than 25%”
The filling rate of the filler in the groove with respect to the groove cross-sectional area changes the formability of the back bead and the base material dilution rate. If it is less than 2%, the possibility that the weld metal melts from the back side of the base metal during welding increases. Moreover, since the application amount of the filler in the groove is small, the base material dilution rate is increased, minute hot cracks are generated, and cracks are generated on the bending surface by a bending test. On the other hand, if it exceeds 25%, the formability of the back bead is extremely lowered, and the surplus height is too small. Further, since an appropriate base material dilution rate cannot be obtained, the mechanical performance of the weld metal is deteriorated. Therefore, the filling rate of the filler in the groove with respect to the groove cross-sectional area is set to 2% or more and less than 25%.

“Current value of the first electrode relative to the filling rate of the filler”
Regulating the current value of the first electrode after making the groove shape a V shape of 30 to 60 ° and optimizing the filling rate of the filler in the groove with respect to the groove cross-sectional area is the base material dilution rate, And optimize the back bead shape. If the current value of the first electrode with respect to the filling rate of the filler in the groove is less than the specified value of the present invention, the surplus height of the back bead becomes too small and an appropriate base material dilution rate cannot be obtained. To do. On the other hand, when the specified value is exceeded, the base material dilution rate becomes high, minute hot cracks of the weld metal are generated, and the amount of heat input is large, so that the toughness deteriorates. Therefore, when the filling rate of the filler in the groove with respect to the groove cross-sectional area is 2 to 15%, the current value of the first electrode is 950 to 1570A, and the filling ratio of the filler in the groove with respect to the groove cross-sectional area is 15%. Exceeding 20% or less, the current value of the first electrode is 1000 to 1580A, and the filling rate of the filler in the groove with respect to the groove cross-sectional area exceeds 20%, and when it is less than 25%, the current of the first electrode The value is 1050 to 1590A.

  Appropriate base material dilution ratio and back bead shape can be obtained, and by preventing high temperature cracks that are manifested by bending strain in the bending test, the soundness of the welded joints constituting the steel structure can be stably obtained. . In addition, although the flux copper backing welding method and the flux backing welding method are mentioned as the multi-electrode single-sided submerged arc welding method, the present invention can stably obtain the soundness of the welded joint regardless of the number of electrodes and the welding method. This is a single-sided submerged arc welding method.

  Next, examples and comparative examples for demonstrating the effects of the present invention will be described.

  Tables 1, 2 and 3 below show the steel plates used in the test, the main components of the wires, and the wire diameters of the electrodes. A wire corresponding to JIS Z3351 YS-S6 and a surface flux corresponding to JIS Z3352 FS-BN1 were used. In the electrode arrangement shown in FIG. 1, four electrodes (L, T1, T2, T3) are arranged in a line at electrode intervals of 30 mm, 170 mm, and 30 mm along the welding direction. L is a receding angle inclined by 10 ° from the normal direction of the welding surface with respect to the welding direction, T1 is an advancing angle inclined by 5 °, T2 is an advancing angle inclined by 3 °, and T3 is an advancing angle inclined by 13 °. ing. The groove shape of the steel plate used in the test shown in FIG. 2 is a steel plate having a plate thickness of 20 mm or 40 mm. The groove shape is V-shaped, and the groove angle is 30 to 60 °. The root gap is 0 to 3 mm. Under these welding conditions, four-electrode FCB submerged arc welding was performed.

  The welding workability during welding is evaluated, and the back bead shape is visually confirmed after welding, and the presence or absence of defects is confirmed by an ultrasonic flaw detection test. In the defect, the defect form was investigated with an electron microscope. Furthermore, in order to evaluate the soundness and mechanical performance of the welded joint, a joint with a plate thickness of 20 mm was subjected to a front / back bending test with a bending radius of 2 t and a bending angle of 180 ° using the test piece described in JIS Z2122. Investigate the presence or absence of defects on the bending surface. In addition, a No. 4 test piece described in JIS Z3111 was used, a 7 mm notch process was performed from the surface side of the steel plate to the center of the weld metal, and a Charpy impact test was performed at -20 °. On the other hand, a joint with a plate thickness of 40 mm is subjected to a side bending test with a bending radius of 2 t and a bending angle of 180 ° using a test piece described in JIS Z2122, and the presence or absence of defects on the bending surface is investigated. In addition, a No. 4 test piece described in JIS Z3111 was used, a 7 mm notch process was applied to the center of the weld metal from the back side of the steel plate, and a Charpy impact test was performed at -20 °. The test results are shown in Table 4, Table 5 and Table 6 below.

  In the methods of Examples 1 to 72 of the present invention, welding workability, bead shape, ultrasonic flaw detection test, bending test, and Charpy absorbed energy at −20 ° were good. In the methods of Comparative Example 73 and Comparative Example 74, since the groove angle is less than 30 °, the formability of the back bead is deteriorated, the backfill height of the back bead is too small, and the base material dilution rate is high. As a result, cracks occurred on the bending surface by the bending test. In Comparative Example 75, since the filling rate of the filler in the groove with respect to the groove cross-sectional area was less than 2%, the weld metal was melted from the back side of the steel plate. In addition, the base material dilution rate increased, and cracks occurred on the bending surface in the bending test. In Comparative Example 76, since the filling rate of the filler in the groove with respect to the groove cross-sectional area exceeds 25%, the surplus height of the back bead is too small and an appropriate base material dilution rate cannot be obtained. As a result, the toughness deteriorated. In Comparative Example 77, since the current of the first electrode was less than 950 A, the surplus height of the back bead was too small, and an appropriate base material dilution rate could not be obtained, so the toughness deteriorated. In Comparative Example 78, since the current of the first electrode exceeds 1590A, the height of the back bead is excessive, and a hot crack occurs in the final solidified portion of the weld metal formed by the first electrode, As a result of the bending test, cracks occurred on the bending surface, and an appropriate base material dilution rate could not be obtained, so the toughness deteriorated. In Comparative Example 79 and Comparative Example 80, since the groove angle exceeded 60 °, the formation of the back bead was excessive and the weld metal was melted. Further, the surplus height of the front bead was too small, and an appropriate base material dilution rate could not be obtained, so that the toughness deteriorated. In Comparative Example 81 and Comparative Example 82, since the groove angle is less than 30 °, the formability of the back bead is deteriorated, the extra height of the back bead is excessively small, and the base material dilution rate is increased. Cracks occurred on the bending surface by the bending test. In Comparative Example 83, since the filling rate of the filler in the groove with respect to the groove cross-sectional area was less than 2%, the weld metal was melted from the back side of the steel plate. In addition, the base material dilution rate increased, and cracks occurred on the bending surface in the bending test. In Comparative Example 84, since the filling rate of the filler in the groove with respect to the groove cross-sectional area exceeds 25%, the surplus height of the back bead is too small and an appropriate base material dilution rate cannot be obtained. As a result, the toughness deteriorated. In Comparative Example 85, since the current of the first electrode was less than 950 A, the surplus height of the back bead was too small, and an appropriate base material dilution rate could not be obtained, so the toughness deteriorated. In Comparative Example 86, since the current of the first electrode exceeds 1590A, the height of the back bead is excessive, and a hot crack is generated in the final solidified portion of the weld metal formed by the first electrode, As a result of the bending test, cracks occurred on the bending surface, and an appropriate base material dilution rate could not be obtained, so the toughness deteriorated. In Comparative Example 87 and Comparative Example 88, since the groove angle exceeded 60 °, the formation of the back bead was excessive, and the weld metal was melted. Moreover, since the surplus height of the front bead was too small and an appropriate base material dilution rate could not be obtained, the toughness deteriorated.

  The present invention can be suitably used in single-sided submerged arc welding with a plate thickness of 9 to 40 mm.

It is a figure which shows arrangement | positioning of an electrode. It is a figure which shows a groove shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrode 2 ... Arrow which shows welding direction 3 ... Steel plate

Claims (3)

The groove shape of the butt portion of the welded material is V-shaped, the groove angle is 30 to 60 °, and the filling rate of the filler in the groove with respect to the groove cross-sectional area is 2% or more and less than 25%. When the filling rate of the filler in the groove with respect to the tip cross-sectional area is 2 to 15%, the current value of the first electrode is 950 to 1570A, and the filling rate of the filler in the groove with respect to the groove cross-sectional area exceeds 15% and 20 % Or less, the current value of the first electrode is 1000 to 1580A, and when the filling rate of the filler in the groove with respect to the groove cross-sectional area is more than 20% and less than 25%, the current value of the first electrode is 1050 to 1590A. A multi-electrode single-sided submerged arc welding method, characterized in that: The multi-electrode single-sided submerged arc welding method according to claim 1, wherein welding is performed by a flux copper backing method. The multi-electrode single-sided submerged arc welding method according to claim 1, wherein welding is performed by a flux backing method.

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