JP2011131258A - Submerged arc welding method of steel material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a submerged arc welding method capable of obtaining the beautiful bead appearance while obtaining the sufficient penetration at high welding speed with low heat input. <P>SOLUTION: At least one of the inner surface welding and the outer surface welding is executed with the one-layer welding at the welding speed of ≥180 cm/min under the condition that the current density of the first and second electrodes satisfy the inequalities (1), the first electrode and the welding speed satisfy the inequality (2), and the total of the thickness of the steel material and the total groove sectional area of the inner surface and the outer surface satisfy the inequality (3). Inequality (1) : 95≤D<SB>1</SB>≤3.3×D<SB>2</SB>, inequality (2) : v+0.1×I<SB>1</SB>≤310, and inequality (3) : 3.9×t-S<SB>total</SB>≤20, where D<SB>1</SB>: current density (A/mm<SP>2</SP>) of the first electrode, D<SB>2</SB>: current density (A/mm<SP>2</SP>) of the second electrode, v: welding speed (cm/min), I<SB>1</SB>: first electrode current (A), t: thickness (mm), S<SB>total</SB>: total groove sectional area (mm<SP>2</SP>) of inner and outer surfaces. Preferably, the distance between the wire centers of the first and second electrodes measured at the surface position of the steel plate is set to 15-45 mm. <P>COPYRIGHT: (C)2011,JPO&INPIT

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 with one pass and the outer surface side with one pass, is commonly 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 emphasis on efficiency and defect suppression, welding heat input tends to be excessive, and the toughness of the welded part, 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, since reducing the heat input increases the risk of inadequate penetration, various proposals have been made regarding submerged arc welding methods aimed at achieving both heat input reduction and deep penetration.

  For example, Patent Document 3 proposes a submerged arc welding method with a high current and a further high current density. By supplying arc energy in the plate thickness direction as much as possible, only the necessary penetration depth is ensured. By suppressing the melting of the base material in the width direction, the heat input by welding is prevented from becoming excessive, and both heat input reduction and deep penetration are achieved.

JP 11-138266 A JP-A-10-109171 JP 2006-272377 A

  However, in the selection of welding conditions, it is necessary to consider the bead appearance in addition to the toughness of the weld and the penetration shape. In the submerged arc welding method described in Patent Document 3, heat input reduction and deep penetration are achieved. Although both can be achieved, under high welding speed conditions, it tends to be a humping bead, and the surplus is likely to be higher, and the work such as shaving off the surplus after welding is required, which may reduce the production efficiency.

  Therefore, the present invention can obtain a beautiful bead appearance while obtaining sufficient penetration at a high welding speed and low heat input using a conventional thin wire when performing multi-electrode submerged arc welding of steel materials from the inner and outer surfaces. An object is to provide a submerged arc welding method.

  The inventors of the present invention made single-layer welded joints of steel materials under various welding conditions by submerged arc welding, and investigated the weld metal cross-sectional shape and weld defects.

As a result, by setting the groove shape, welding conditions, and electrode arrangement appropriately, it is possible to reduce the surplus height and suppress the humping bead while obtaining sufficient penetration at low heat input and high welding speed. It was found that a bead with a good appearance can be obtained. This invention is made | formed based on this knowledge, The summary is as follows.
1.2 Inner and outer surface single layer welding of steel materials using submerged arc welding of electrodes or more, wherein at least one of inner surface welding and outer surface welding satisfies the following:

The welding speed is 180 cm / min or more, the total thickness of the steel plate and the groove cross-sectional area of the inner surface and the outer surface satisfy the following formula (1), and the first electrode and the welding speed are the following formula (2). Furthermore, the current densities of the first electrode and the second electrode satisfy the following expression (3).

3.9 × t-S _total ≦ 20 (1)
v + 0.1 × I ₁ ≦ 310 (2)
95 ≦ D ₁ ≦ 3.3 × D ₂ (3)
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 ),
v: welding speed (cm / min), I ₁ : first electrode current (A), t: plate thickness (mm),
S _total : Sum of groove cross-sectional areas of inner surface and outer surface (mm ² )
2. 2. The submerged arc welding method according to 1, wherein the distance between the wire centers of the first electrode and the second electrode measured at the surface layer position of the steel sheet is 15 mm or more and 45 mm or less.

  According to the present invention, in the submerged arc welding of two or more electrodes, a reduction in welding heat input and an increase in the penetration amount are achieved at a high welding speed, and an inner / outer surface single-layer weld with a beautiful bead appearance is achieved. It can be obtained and is extremely useful industrially.

The figure which shows a groove shape. The schematic diagram which shows an example of a welding part macro cross section.

In the present invention, 1. Influence of groove shape on welding result (height height: h in FIG. 2) 2. Influence of welding conditions on welding results (humping beads); The influence of the current density D ₁ (A / mm ² ) of the first electrode and the current density D ₂ (A / mm ² ) of the second electrode on the welding result is represented by the parameter formula for each, and a good weld The value is specified so that

First, the influence of the groove shape on the welding result (recess height: h in FIG. 2) is as follows: Parameter formula: 3.9 × t−S _total (where t: plate thickness (mm), S _total : Sum of groove cross-sectional areas of inner surface and outer surface (mm ² )), and if the groove cross-sectional area is too small, the surplus height tends to be excessive, so the following formula (1) is satisfied.

Next, the influence of the welding conditions on the welding result (humping bead) is expressed by a parameter formula consisting of the first electrode current and the welding speed: v + 0.1 × I ₁ (where v: welding speed (cm / min), I ₁ : defined by the first electrode current (A)), and the welding condition in which the current of the first electrode is large and the welding speed is high is likely to be a humping bead, and therefore satisfies the following formula (2).

Welding current density Results on the first electrode _D 1 (A / mm ²⁾ and the influence of current density _D ² (A / mm 2) of the second electrode, the current density of the first electrode _D 1 (A / mm ² ) And 3.3 times the current density D ₂ (A / mm ² ) of the ^second electrode. If the current density D ₁ of the first electrode is too low, the penetration depth tends to be insufficient. Further, if the current density of the second electrode is too low with respect to the current density of the first electrode, bead irregularity is likely to occur, so that the following expression (3) is satisfied.

3.9 × t-S _total ≦ 20 (1)
v + 0.1 × I ₁ ≦ 310 (2)
95 ≦ D ₁ ≦ 3.3 × D ₂ (3)
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 ),
v: welding speed (cm / min), I ₁ : first electrode current (A), t: plate thickness (mm),
S _total : Sum of groove cross-sectional areas of inner surface and outer surface (mm ² )
In the present invention, the distance between the first electrode and the second electrode (the distance between the wire centers of the first electrode and the second electrode measured at the surface layer position) is preferably 15 mm or more and 45 mm or less. This is because the distance between the first electrode and the second electrode is preferably 15 mm or more for suppressing the occurrence of pear-shaped cracks, and the distance between the first electrode and the second electrode is preferably 45 mm or less for suppressing the slag entrainment. .

  Since the present invention is configured as described above, a high welding speed is possible. The present invention can be applied to both inner surface welding and outer surface welding, and is preferably applied to both inner surface welding and outer surface welding.

  A steel plate having thicknesses of 6.4 mm, 19.1 mm, and 31.8 mm is subjected to groove processing of the groove shape shown in FIG. 1 and then subjected to inner or outer surface single layer 3 or 4-electrode submerged arc welding to weld joints. After the bead appearance was visually observed, three macro sections taken by equally dividing the bead steady portion were visually inspected for the penetration state and the presence or absence of welding defects. Table 1 shows the chemical composition of the steel sheet, Table 2 shows the groove dimensions, and Table 3 shows the welding conditions. FIG. 2 shows a schematic diagram of a macro cross section.

  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 conditions, the current density and welding speed of the first electrode and the second electrode in each of the inner and outer surface welding. Changed. In addition, some welding was performed by changing the distance between the first electrode and the second electrode.

Table 4 shows the welding results. No. 1-No. 10 is a parameter formula: 3.9 × t−S _{total with} a value of 20 or less, a parameter formula: v + 0.1 × I _{1 with} a value of 310 or less, and the current density D of the first electrode in inner surface welding and / or outer surface welding. ₁ (A / mm ² ) is 95 or more, and the current density D ₁ (A / mm ² ) of the first electrode is 3.3 times the current density D ₂ (A / mm ² ) or less of the second electrode. A beautiful bead appearance is obtained at the inner surface welded portion and / or the outer surface welded portion even when the inner surface welding and / or the outer surface welding is performed and the welding speed is 180 (cm / min) or higher.

No. The inner surface welding of No. 3 has a parameter formula: v + 0.1 × I ₁ exceeding 310, and the absolute value of the current density D ₁ (A / mm ² ) of the first electrode is less than 95. Met.

No. 5, the current density D ₁ (A / mm ² ) of the first electrode exceeds the current density D ₂ (A / mm ² ) of the second electrode multiplied by 3.3. min) Even below, the bead was irregular.

No. No. 11 had a current density of the first electrode of inner surface welding and outer surface welding of less than 95, and poor penetration occurred. No. No. 12 had a small sum of the inner face groove cross-sectional area and the outer face groove cross-sectional area, and the value of the parameter formula: 3.9 × t- _Total was more than 20, and the surplus was increased in the inner surface welding and the outer surface welding.

No. 13 is an inner surface welding and an outer surface welding, and the current density D ₁ (A / mm ² ) of the first electrode exceeds 3.3 times the current density D ₂ (A / mm ² ) of the second electrode, and the bead is irregular. It was.

No. 14 is a case where the value of the parameter formula: v + 0.1 × I ₁ exceeds 310 in both the inner surface welding and the outer surface welding, and both the inner surface welding and the outer surface welding became humping beads.

No. 15 is a humping bead when the value of the parameter formula: v + 0.1 × I ₁ exceeds 310 in the inner surface welding, and the outer surface welding is an example in which the welding speed is less than 180 cm / min.

No. No. 16 shows that the bead irregularity occurs when the current density D ₁ (A / mm ² ) of the first electrode exceeds 3.3 times the current density D ₂ (A / mm ² ) of the second electrode in the inner surface welding. Is an example where the welding speed is less than 180 cm / min.

  In addition, although sufficient penetration and a beautiful bead appearance were obtained, no. In the outer surface welding of No. 9, the interelectrode distance between the first electrode and the second electrode (the distance between the wire centers measured at the surface layer position) was 13 mm, and a pear-shaped crack occurred. No. In the outer surface welding No. 10, the distance between the first electrode and the second electrode was 47 mm, and slag entrainment occurred. Moreover, the welding speed of both welding is less than 180 cm / min.

DESCRIPTION OF SYMBOLS 1 Steel material 2 Inner surface welded part 3 Outer surface welded part h Extra height t Plate thickness

Claims (2)

A steel submerged arc welding method characterized in that at least one of inner surface welding and outer surface welding satisfies the following in single-layer inner and outer surface welding of a steel material using submerged arc welding of two or more electrodes.
The welding speed is 180 cm / min or more, the total thickness of the steel plate and the groove cross-sectional area of the inner surface and the outer surface satisfy the following formula (1), and the first electrode and the welding speed are the following formula (2). Furthermore, the current densities of the first electrode and the second electrode satisfy the following expression (3).
3.9 × t-S _total ≦ 20 (1)
v + 0.1 × I ₁ ≦ 310 (2)
95 ≦ D ₁ ≦ 3.3 × D ₂ (3)
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 ),
v: welding speed (cm / min), I ₁ : first electrode current (A), t: plate thickness (mm),
S _total : Sum of groove cross-sectional areas of inner surface and outer surface (mm ² )   The submerged arc welding method according to claim 1, wherein the distance between the wire centers of the first electrode and the second electrode measured at the surface layer position of the steel sheet is 15 mm or more and 45 mm or less.

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