JP2013081985A - Submerged arc welding method for steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-electrode submerged arc welding method which performs internal-and-external one layer welding, capable of obtaining a beautiful bead appearance while obtaining sufficient penetration with low heat input.SOLUTION: In the internal-and-external one layer welding using the submerged arc welding of three electrodes or more, at least one of the internal surface welding and the external surface welding is made such that the current density Dof a first electrode is 220 (A/mm) or more, the current density Dof a second electrode is 85 (A/mm), the distance between the wire centers of the first electrode and the second electrode measured at the surface layer position of the steel plate is 21 mm or more, and the distance between the wire center of a rearmost electrode and one electrode just before the rearmost electrode measured at the surface layer position of the steel plate is set to be 19 mm or less. Here, current density (A/mm)=welding current (A)/wire cross section (mm). Further preferably, in the internal surface welding and the external surface welding of which the conditions are made as above, the electrode angle of the rearmost electrode is set to be 40° or more, the included angle is set to be 50° or more and 70° or less.

Description

  The present invention relates to a submerged arc welding method for steel materials, and more particularly to a method suitable for pipe making welding of large diameter steel pipes such as UOE steel pipes and spiral steel pipes.

  Submerged arc welding with two or more electrodes is applied to pipe making welding (seam welding) of large diameter steel pipes. From the viewpoint of improving pipe production efficiency, double-sided single-layer welding, in which the inner surface side of the steel pipe is welded in one pass and the outer surface side in one pass, is generally performed, and highly efficient welding is performed (for example, Patent Documents 1 and 2).

  In double-sided single-layer welding, in order to ensure a sufficient penetration depth so that the inner surface welding metal and the outer surface welding metal overlap and there is no unmelted portion, it is common to perform welding by applying a large current of 1000 A or more, By placing importance on efficiency and defect suppression, welding heat input tends to be excessive, and the toughness of the welded portion, particularly the welded heat affected zone, tends to deteriorate.

  In order to increase the toughness of welds, it is effective to reduce the heat input, especially in the case of steel pipe welding with thick steel pipes, the required heat input is increased, so the heat input is reduced as much as possible. This is an issue. However, when heat input is reduced, insufficient penetration tends to occur. Therefore, various submerged arc welding methods aiming to achieve both heat input reduction and deep penetration have been proposed.

  For example, Patent Document 3 proposes a submerged arc welding method for welding at a high current density, and by supplying arc energy in the plate thickness direction, the necessary penetration depth is ensured, but the base material in the steel width direction is secured. Describes a submerged arc welding method that suppresses melting and prevents excessive welding heat input and achieves both reduced heat input and deep penetration.

  Patent Document 4 and Patent Document 5 disclose a submerged arc welding method that suppresses a point at which a welding defect such as slag entrainment, which is a disadvantage of a high current density submerged arc welding method, is likely to occur by appropriately controlling the electrode arrangement. Have been described.

Japanese Patent Laid-Open No. 11-138266 JP-A-10-109171 JP 2006-272377 A JP 2009-195957 A JP 2009-208114 A

  By the way, in selecting welding conditions, it is necessary to consider the appearance of the bead in addition to the toughness of the welded portion and the penetration shape. In the submerged arc welding methods described in Patent Documents 4 and 5, the bead width is increased. There is a problem that undercut is likely to occur.

  Therefore, the present invention has an object to provide a multi-electrode submerged arc welding method capable of obtaining a beautiful bead appearance without undercut while obtaining deep penetration with low heat input, and welding steel materials in one layer on the inner and outer surfaces. And

  The inventors of the present invention made a single-layer welded joint on the inner and outer surfaces of a steel material by a submerged arc welding method using three or more electrodes under various welding conditions, and investigated the weld metal cross-sectional shape and the bead appearance.

  As a result, the current density of the first electrode, the current density of the second electrode, the distance between the centers of the wires between the first electrode and the second electrode, and the distance between the centers of the wires between the last electrode and the last electrode before the last It was found that by setting it appropriately, a beautiful bead appearance without undercut is obtained while obtaining deep penetration with low heat input.

The present invention has been made based on the above findings, and the gist thereof is as follows.
1.3. A steel submerged arc welding method characterized in that at least one of inner surface welding and outer surface welding satisfies the following conditions in single-layer inner and outer surface welding of steel materials using submerged arc welding of at least electrodes.
The current density of the first electrode satisfies the following formula (1), the current density of the second electrode satisfies the following formula (2), and the first electrode and the second electrode measured at the surface layer position of the steel plate The distance between the wire centers is 21 mm or more, and the distance between the wire centers of the last electrode measured at the surface layer position of the steel sheet and the electrode immediately before the last is 19 mm or less.
D ₁ ≧ 220 (1)
D ₂ ≧ 85 (2)
here,
Current density (A / mm ² ) = Welding current (A) ÷ Wire cross-sectional area (mm ² )
D ₁ : Current density of the first electrode (A / mm ² ), D ₂ : Current density of the second electrode (A / mm ² )
2. Furthermore, the electrode angle of the last electrode is 40 degree | times or more, The submerged arc welding method of the steel materials of 1 characterized by the above-mentioned.
3. Furthermore, groove angle is 50 degree or more and 70 degrees or less, The submerged arc welding method of the steel materials of 1 or 2 characterized by the above-mentioned.

  According to the present invention, it is possible to obtain a beautiful welded inner and outer surface single-layer welded portion excellent in welded portion toughness, which is extremely effective industrially. Further, since this effect can be obtained even when the groove angle is small, there is an effect of reducing the welding wire consumption.

The figure explaining the name of each part of groove shape. The schematic diagram explaining the macro cross section of an inner and outer surface single layer welding part. It is a figure explaining an electrode angle, (a) is an advancing angle, (b) A figure explaining a receding angle.

In the present invention, In order to obtain deep penetration, the current density of the first electrode and the second electrode is defined. The current density (A / mm ² ) is obtained by welding current (A) ÷ wire cross-sectional area (mm ² ).

  2. In order to prevent welding defects such as pear-shaped cracks and slag entrainment, the distance (mm) between the wire centers of the first electrode and the second electrode is defined.

  3. In order to obtain a beautiful bead appearance without undercut, the distance between the center of the wire (mm) between the last electrode and the electrode immediately before the last tail is specified, and the tail electrode is used to improve the bead appearance. The electrode angle is defined.

  4). Furthermore, when obtaining the effects of heat input reduction and welding wire usage reduction, the groove angle is set to 50 degrees or more and 70 degrees or less. By reducing the groove angle, the amount of wire welding required is reduced. However, if the groove angle is too small, large heat input is required to obtain the penetration, so the angle is set to 50 degrees or more and 70 degrees or less. Hereinafter, the present invention will be described by way of specific examples.

  After performing groove processing on steel plates with a thickness of 25.4 mm, 31.8 mm, and 38.1 mm (length 1000 mm), 3 or 4 electrode submerged arc welding of inner and outer surface single layer welding is performed to produce a welded joint. The penetration state, the presence or absence of weld defects, and the bead appearance were investigated.

  The investigation of the bead appearance was performed by visually observing the bead appearance of the welded joint and measuring the bead width in the steel sheet surface layer. The penetration state and the weld defect were investigated by visually observing three macro sections taken by equally dividing the bead steady portion. Table 1 shows the chemical composition of the steel sheet, Table 2 shows the dimensions of each part of the groove shape used for welding (see FIG. 1), and Table 3 shows the welding conditions. In Table 3, the electrode angle indicates the angle formed between the vertical direction and the electrode, and the forward angle is positive and the backward angle is negative (see FIG. 3).

  For each plate thickness, in the groove shape, the groove angle and groove depth are changed on the inner and outer surfaces, and in the welding condition, between the wire centers of the first electrode and the second electrode in each of the inner and outer surface welding. The distance between the center of the wire between the distance, the last electrode, and the electrode one before the last (in the case of three electrodes, the third electrode and the second electrode, and in the case of four electrodes, the fourth electrode and the third electrode) Changed. Moreover, the current density and welding speed of each electrode of the 1st electrode and the 2nd electrode were changed.

  Table 4 shows the welding results. In the table, a value L (see FIG. 2) obtained by measuring the distance in the plate thickness direction from the meeting portion between the inner surface weld metal and the outer surface weld metal to the penetration tip of the outer surface weld metal is less than 0.05 times the plate thickness. In some cases, the penetration was insufficient. The inner bead width was less than 0.65 times the plate thickness, and the outer bead width was less than 0.80 times the plate thickness.

The current density D ₁ of the first electrode was 220 (A / mm ² ) or more by inner surface welding and / or outer surface welding, and the current density D ₂ of the second electrode was 85 (A / mm ² ). The distance between the wire centers of the first electrode and the second electrode is 21 mm or more, and the distance between the wire centers of the last electrode measured at the steel sheet surface layer position and the electrode immediately before the last is 19 mm or less, No. in which inner surface welding and / or outer surface welding was performed. 1-5, no. 10 to 12 inner surface welds and / or outer surface welds have no pear-shaped cracks or slag entrainment welding defects, and a beautiful bead appearance is obtained. No. 10 to 12, those welded with an electrode angle (advance angle) of 40 ° or more of the last electrode were particularly good in bead appearance.

No. In No. 6, the distance between the wire centers of the first electrode and the second electrode was less than 21 mm for both inner surface welding and outer surface welding, slag was generated in inner surface welding, and pear-shaped cracks were generated in outer surface welding.
No. No. 7 is a case where the distance between the center of the wire between the last electrode and the immediately preceding electrode exceeds 19 mm in both the inner surface welding and the outer surface welding, and the bead width was small in both the inner surface welding and the outer surface welding.

No. No. 8 is a case where the current density of the first electrode is less than 220 A / mm ^{2 for} both the inner surface welding and the outer surface welding, resulting in insufficient penetration.
No. No. 9 is a case where the current density of the second electrode is less than 85 A / mm ^{2 in} both the inner surface welding and the outer surface welding, resulting in insufficient penetration.

No. 13 is a current density _{D 1} of the first electrode only the outer surface welding is 220 (A / mm ²⁾ or more, the current density _{D 2} of the second electrode 85 (A / ^mm 2), the first electrode as measured by the steel sheet surface position The distance between the wire center between the first electrode and the second electrode is 21 mm or more, and the distance between the wire center between the last electrode measured at the surface layer position of the steel sheet and the electrode immediately before the last is 19 mm or less. In the case of inner surface welding, the bead width was small because the distance between the center of the wire between the last electrode and the previous electrode exceeded 19 mm.

No. Although 14 is the first electrode ² below the current density is 220A / mm of inner surface welding, at a current density _{D 1} of the outer surface welding first electrode 220 (A / mm ²⁾ or more, the current density D of the second electrode ₂ is 85 (A / mm ² ), the distance between the wire centers of the first electrode and the second electrode measured at the steel plate surface layer position is 21 mm or more, and 1 from the last electrode and the last tail measured at the steel plate surface layer position Since the distance between the wire center and the previous electrode was 19 mm or less, a large bead width was obtained on both the inner surface and the outer surface while obtaining deep penetration without generating defects with low heat input.

From the above, in the present invention, the inner and outer surfaces further welding steel with submerged arc welding of three or more electrodes, the current density D ₁ of the first electrode at least one of the inner surface weld and the outer surface welding 220 (A / mm ²⁾ Thus, the current density D ₂ of the second electrode is 85 (A / mm ² ), the distance between the wire centers of the first electrode and the second electrode measured at the steel plate surface layer position is 21 mm or more, and at the steel plate surface layer position. The distance between the wire centers of the measured last electrode and the electrode immediately before the last is 19 mm or less. However, current density (A / mm ² ) = welding current (A) ÷ wire cross-sectional area (mm ² ).

1 Steel 2 Internal weld 3 External weld L Distance t Thickness

Claims (3)

A steel submerged arc welding method characterized in that at least one of inner surface welding and outer surface welding satisfies the following conditions in single-layer inner and outer surface welding of a steel material using submerged arc welding of three or more electrodes.
The current density of the first electrode satisfies the following formula (1), the current density of the second electrode satisfies the following formula (2), and the first electrode and the second electrode measured at the surface layer position of the steel plate The distance between the wire centers is 21 mm or more, and the distance between the wire centers of the last electrode measured at the surface layer position of the steel sheet and the electrode immediately before the last is 19 mm or less.
D ₁ ≧ 220 (1)
D ₂ ≧ 85 (2)
here,
Current density (A / mm ² ) = Welding current (A) ÷ Wire cross-sectional area (mm ² )
D ₁ : Current density of the first electrode (A / mm ² ), D ₂ : Current density of the second electrode (A / mm ² )   Furthermore, the electrode angle of the last electrode is 40 degrees or more, The submerged arc welding method of the steel materials of Claim 1 characterized by the above-mentioned.   Furthermore, a groove angle is 50 degree or more and 70 degrees or less, The submerged arc welding method of the steel materials of Claim 1 or 2 characterized by the above-mentioned.

Images