JPH09314335A - Tandem submerged arc welding method - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To weld a butt-welded joint having a large plate thickness and a thick root face by deep penetration. SOLUTION: The root face R of the abutting portion of the base material 1 having a large plate thickness T has a groove shape having a thickness of 10 to 25 mm. For this groove shape, the leading electrode has a diameter of 3.2 mm ~
With a small diameter wire of 4.0 mm, the current density is 100
Welding is performed under the condition of 150 A / mm ² . A wire having the same or slightly larger diameter as the wire of the leading electrode is used for the trailing electrode that is separated from the leading electrode by a required distance, and the current density is made smaller than that of the leading electrode for welding. A deep penetration is obtained at the leading electrode and a weld 9 is obtained. Subsequently, the welded portion 10 is obtained by the trailing electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem submerged arc welding method, and more particularly to a tandem submerged arc welding method for welding butt joints of steel sheets having a large thickness.

[0002]

2. Description of the Related Art Conventionally, when welding a butt joint of a thick steel plate having a plate thickness of 50 to 60 mm, it has been known to perform one run by the tandem submerged arc welding method. 5 (a) and (b) show an outline of an example,
The groove shape of the V-shaped butt joint of the base material 1 having the plate thickness T of 50 to 60 mm is a relatively narrow groove with a groove angle θ of 30 to 35 degrees, and the root face R is 0 to 5 mm. The gap G is set to 0, and the two electrodes of the leading electrode 2 and the trailing electrode 3 using a large-diameter wire with a wire diameter of 6.4 mm are arranged at a constant interval in the welding method (direction of arrow a) to form the leading electrode 2. 2050-2300A
(Ampere) (current density 65-70 A / mm ² ), trailing electrode 3 1700-1800 A (current density 52.5-5)
A large current of 5 A / mm ² ) is made to flow, and 1 minute per minute
The welding was carried out at a speed of 9 to 20 cm. FIG.
In (a), 4 is a welding power source, 5 is a flux, 6 is a slag, 7 is a weld metal, and 8 is a backing metal.

In such a conventional two-pole submerged arc welding method, inside the groove covered with the flux 5, first, the leading electrode 2 melts the deep groove, and then the trailing electrode 3
Then, the upper part was melted and the base material 1 was welded and joined.

[0004]

However, in the case of the conventional tandem submerged arc welding method using two poles, a wire having a diameter of 6.4 mm and a large diameter of 2000 A is used for the leading electrode 2.
A large welding power source 4 is required for a large current welding that exceeds, and during welding conditions, especially the penetration shape, depth,
There is a tendency for the fluctuations in the arc voltage, etc., that affect the welding conditions, etc., to be large and unstable, and these also affect the welding quality. The main reason for this is that the current density is small and the droplet transfer type in the arc atmosphere is the globular type (short circuit transfer). The fluctuation range will increase.

Therefore, according to the present invention, even in a joint in which the root face of the groove portion is larger than the root face in the tandem submerged arc welding method which has been conventionally carried out, the base material is sprayed with a stable voltage by high current density construction. An object of the present invention is to provide a tandem submerged arc welding method capable of melting and performing deep penetration welding.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention employs welding of a butt joint of a thick plate base material having a root face of 10 to 25 mm thickness with a small wire diameter of the leading electrode. Welding current density is 100 to 150 A / mm ² , and the wire diameter of the trailing electrode is the same as or larger than that of the leading electrode, the welding current density is 70 to 135 A / mm ^2, and the distance between the electrodes is 50 to 100 mm, total welding Heat condition 270-5
The welding method is to weld under the condition of 20 KJ / cm.

Since the wire diameter of the leading electrode is small, its current density (minimum: 100 A / mm ² ) is high, and high current density construction is possible. As a result, the depth of penetration at the time of welding can be increased, and even with a joint having a thick root face, the base material of the root portion can be melted to enable deep penetration welding. Also, because of the high current density welding, the welding speed is increased, and high efficiency welding can be performed. Furthermore, since the root face is thick, high temperature cracking is likely to occur in the welded portion by the leading electrode, but high temperature cracking can be eliminated by setting the welding condition by the trailing electrode to an appropriate value.

Further, if the wire diameter of the trailing electrode is made slightly thicker than the wire diameter of the leading electrode, the current density of the trailing electrode can be reduced even if the same current condition is selected for the leading electrode and the trailing electrode. Furthermore, when the wire diameters of the leading and trailing electrodes are the same,
By lowering the current of the trailing electrode, the current density can be lowered, the penetration depth and the bead width can be adjusted, and the hot crack generated in the leading electrode can be effectively prevented in the trailing electrode.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a groove shape of a butt joint of a steel plate having a plate thickness T of 60 mm for carrying out the tandem submerged arc welding method of the present invention. The conventional tandem submerged arc welding method shown in FIG. Similarly to the above, two electrodes of the leading electrode 2 and the trailing electrode 3 are arranged with a required gap in the welding direction, and after welding with the leading electrode 2, welding is performed with the trailing electrode 3. 1 is characterized in that the groove angle θ is 30 to 45 degrees, the gap G is 0 to 1.5 mm, as shown in FIG.
Two-electrode submerged arc welding in which a joint having an excessively large root face R of the groove (R = 10 to 25 mm) is melted to obtain welded portions 9 and 10 having a penetration depth as shown by a two-dot chain line in FIG. The way is.

More specifically, as one embodiment of the present invention, the wire diameter of the leading electrode 2 is 4.0 mm, the current density condition is 100 to 150 A / mm ^2, and the leading electrodes 2 to 50 are used.
The wire diameter of the trailing electrode 3 installed -100 mm apart is 4.8.
mm, the current density condition is 70 to 100 A / mm ^2, and the total welding heat input condition of the leading electrode and the trailing electrode is 350.
Perform one pass under welding conditions of ~ 450KJ / cm. The welding current density condition of the preceding electrode 2 is 100 to 1
50 A / mm ² and the welding current density condition of trailing electrode 3 is 70
-100 A / mm ² is used because below these values, the melting of the groove root face portion due to the arc is insufficient, and above these values, there is no change in the effect and there is no need to exceed this value. Is.

In the present invention, even if the joint has a narrow groove with a groove angle θ of 35 degrees as shown in FIG. 1 and has a thick root face R, as described above, the leading pole 2 and the trailing pole are In total, the welding heat input condition is set to a minimum of 350 KJ / cm, and a wire having a diameter of 4.0 mm is used for the leading electrode 2 under the above welding conditions to achieve a high current density (100 A
/ Mm ^{2 to} 150 A / mm ² ), it is possible to perform submerged arc welding with high heat input and deep penetration. The arc caused by this is considered to be a spray transfer type, and particles with a molten metal diameter equal to or smaller than the wire diameter are sprayed at a high speed, the arc voltage is stabilized, the energy density of the arc column is increased, and the groove tip is increased. The action of melting and digging the base material of the root part is strong and the concentration is good, so that it is possible to perform welding with a deeper penetration depth, as in the welded portion 9 shown by the two-dot chain line in FIG. It is possible to perform penetration welding which penetrates the base material 1 and reaches the backing metal 8 completely. The wire melting speed of the leading electrode at this time is approximately in the range of 3.8 to 8.5 m / min.
Moreover, the total welding heat input condition is set to 350 to 4 as described above.
Since it is as large as 50 KJ / cm, the required amount of deposited metal can be filled in the groove.

When ultra-deep penetration welding is performed on the leading electrode 2, a high temperature crack 11 is generated in the welded portion 9 by the leading electrode 2 due to the relationship between the bead width and the penetration depth as shown in FIG. The high temperature crack 11 is eliminated by adjusting the penetration depth by the trailing electrode 3 arranged with the inter-electrode distance of 50 to 100 mm so as to achieve semi-one pool welding. Since the trailing electrode 3 uses a wire having a wire diameter of 4.8 mm and the welding current density is set to 70 to 90% of that of the leading electrode 2, the minimum current density is 70 A / mm ² and the leading electrode is Although it is lower than that of No. 2, since the energy density of the arc column is high and the concentration is good, a large penetration depth is obtained, and a deep penetration welded portion 10 as shown by the broken line in FIG. 1 is obtained. The hot crack 11 of the welded portion 9 due to the leading electrode 2 can be eliminated.

In the tandem submerged arc welding method of the present invention, as described above, the leading electrode 2 and the trailing electrode 3 each have a wire having a relatively small diameter so that they can be welded at a high current density. The speed increases (1-1.
5kg / min level), high efficiency welding can be performed.

In the above embodiment, the leading electrode 2 is a wire having a diameter of 4.0 mm, and the trailing electrode 3 is a wire having a diameter of 4.0 mm.
Use 8mm wire and set the current density condition of the leading electrode 2 to 100.
Up to 150 A / mm ² and set the current density of trailing electrode 3 to 70
~100A / mm ² in the but leading electrode 2 and the trailing electrode used as a small-diameter both diameter 4.0mm to 3 wires, and the current density of the leading electrode ² 100~150A / mm 2, the trailing electrode 3 to 70 to 135 A / mm with 10 to 30% reduction
It can be set to ² .

In this embodiment, the leading electrode 2 and the trailing electrode 3 are
Since both use a small diameter wire with a diameter of 4.0 mm,
It can be constructed with high current density, deep penetration welding is possible,
A joint as shown in FIG. 1 having an excessive root face can be completely penetration welded. At this time, both the leading electrode 2 and the trailing electrode 3 use a small diameter wire with a diameter of 4.0 mm,
In the trailing electrode 3, the current density is reduced in the range of 10 to 30% as compared with the leading electrode 2, so that the hot crack in the welded portion of the leading electrode 2 is eliminated in the welded portion of the trailing electrode 3. . In this case, the current density ratio between the leading electrode 2 and the trailing electrode 3 is set such that the leading electrode 2: the trailing electrode 3 is 1: 0.7 to 0.9.

As another embodiment of the present invention, a wire having a diameter of 3.2 mm is used for both the leading electrode 2 and the trailing electrode 3, and the current density of the leading electrode 2 is 100 to 150 A / m.
m ² and the trailing electrode 3 may be 70 to 135 A / mm ^2, and the wire of the leading electrode 2 may have a diameter of 4.0 mm, and the wire of the trailing electrode 3 may have the same diameter of 6.4 mm as the conventional one. The current density may be 40 to 55 A / mm ² .

In any of these cases, the current density of the leading electrode 2 can be increased, high current density construction can be adopted, and a joint with an excessively large root face (10 to 25 mm thick) can be melted to achieve an ultra-deep depth. Penetration welding is possible.

[0019]

EXAMPLES Next, experimental results of the present inventors will be shown. (1) In the groove shape as shown in FIG. 1, the thickness of the base material 1 is 60 mm, the groove angle θ is 35 degrees, and the root face R is 1
The joint of 4 mm and the gap G of 0 mm is a single pole construction with only the leading pole, the leading pole wire has a diameter of 4.0 mm, the current density is 100 to 130 A / mm ² , and the welding heat input for the single pole is 180.
Welded at ~ 240 KJ / cm. As a result, in the welding with the leading electrode 2, as shown in FIG. 2, the base material of the root face portion was melted, and the high temperature crack 11 was generated in the welded portion 9 due to the relationship between the bead width and the penetration depth. (2) In order to prevent the hot cracking, the wire of the leading electrode has a diameter of 4.0 mm, the current density is 100 to 130 A / mm ² , the welding heat input of only the leading electrode is 180 to 240 KJ / cm, and the trailing electrode is Diameter wire is 4.8mm, current density is 70 ~ 90A
/ Mm ² , welding heat input of only trailing electrode 170-230KJ /
cm, and further, welding was performed under welding conditions in which the distance between the electrodes was 70 mm to 100 mm, and as a result, as shown in FIG. 4, a welded portion 10 by the trailing electrode was formed on the welded portion 9 by the leading electrode. Good penetration without hot cracking was confirmed. (3) With the groove-shaped joint shown in (1) above, the wire of the leading electrode has a diameter of 4.0 mm and a current density of 100 to 130 A / mm ² ,
Welding heat input of only the leading electrode is 180-240KJ / cm,
The trailing electrode wire has a diameter of 4.8 mm and a current density of 70 to 90.
A / mm ² , welding heat input of trailing electrode only 170-230KJ
/ Cm and the welding condition was such that the distance between the electrodes was 50 mm to less than 70 mm, and as a result, good penetration was confirmed as shown in FIG.

[0020]

As described above, according to the tandem submerged arc welding method of the present invention, a wire having a small diameter (diameter 3.2 to 4.0 mm) is used as the leading electrode and the current density thereof is 100 to 150 A /. since then higher than mm ² and traditional method for welding at high current densities, (i) the included angle is narrow and the root face is even joint groove shape such that even 10 to 25 mm, the thickness A certain root face part can be melted, deep penetration welding can be performed, and high temperature cracks that occur in the weld part due to the leading electrode can be determined by determining the welding conditions that are the optimum bead width and penetration depth as the trailing electrode. Can be prevented, and because the penetration depth is large,
It is possible to significantly reduce the joint cross-sectional area by narrowing the groove, and (ii) the welding speed is very high (1 to 1.5 kg / min) due to welding at high current density, and therefore high efficiency is achieved. Welding is possible. (Iii) Since it is a tandem system, various improvements such as prevention of hot cracking of the welded portion by the leading electrode, shaping of the bead shape of the surface, improvement of the penetration shape, etc. are necessary to grasp the appropriate value of the welding condition of the trailing electrode It is possible to achieve excellent effects such as the fact that it can be carried out.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a groove shape for applying a welding method of the present invention.

FIG. 2 is a cross-sectional view showing a state where hot cracking occurs in a welded portion of the excessive joint of the root face as shown in FIG. 1 welded by the leading electrode in the welding method of the present invention.

FIG. 3 is a cross-sectional view showing an example when an excessive joint having a root face as shown in FIG. 1 is welded by the welding method of the present invention.

FIG. 4 is a cross-sectional view showing an example when welding is performed with slightly different welding conditions.

FIG. 5 is a perspective view showing how to perform a tandem submerged arc welding method, in which (a) is a perspective view showing a state at the time of welding;
(B) is a view showing a groove shape.

[Explanation of symbols]

 1 Base material 2 Leading electrode 3 Trailing electrode 8 Backing metal 9 Welded portion 10 Welded portion 11 Hot cracking

Claims (2)

[Claims] 1. Welding of a butt joint of a thick plate base material having a root face of 10 to 25 mm thickness is performed by setting a wire diameter of a leading electrode to a small value and a welding current density of 100 to 150 A / mm ² and a trailing electrode. The wire diameter is the same as or larger than that of the leading electrode, the welding current density is 70 to 135 A / mm ² , the distance between the electrodes is 50 to 100 mm, and the total welding heat input condition is 270 to 5
Tandem submerged arc welding method characterized by welding under conditions of 20 KJ / cm. 2. The wire diameter of the leading electrode is 3.2 to 4.0.
The tandem submerged arc welding method according to claim 1, wherein the wire diameter of the trailing electrode is 3.2 to 6.4 mm.