JPH09206946A - Three electrode submerged arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain superior results in the corner joint welding of an extremely thick box column by welding while a gas blow phenomenon is generated from only the rear side of the third electrode and not from the rear side in the weld ing direction of the first and the second electrode. SOLUTION: The voids A, B of the arc of the first electrode L and the second M are maintained in a stable size and shape by avoiding a gas blow in the rear side of these electrodes. Consequently, the arc generating point of the third electrode T becomes a constant position, so that welding is performed stably without fluctuation in voltage. Then, with welding performed while a gas blow phenomenon is generated in the rear side of the third electrode T, a bead waveform is finely stabilized, making it possible to obtain the bead width sufficient to melt the groove width on the surface of a mesh plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-electrode submerged arc welding method applied to corner joint welding when manufacturing an extremely thick box column used for a building structure.

[0002]

2. Description of the Related Art In recent years, building construction using box pillars has become popular in urban areas, and the building is becoming higher and higher.
Along with this, the steel materials used have become increasingly thicker and have been put to practical use up to a plate thickness of 100 mm by multi-layer welding or the like. The box column is made by assembling four steel plates into a square column and welding the corner joint part by submerged arc welding which is high efficiency welding. At present, two-electrode submerged arc welding is generally adopted,
A method of welding one layer up to about 50 mm has been put into practical use.

Further, the three-electrode method has been put into practical use for the purpose of applying the submerged arc single-layer welding even to an extremely thick steel plate exceeding 50 mm. Examples of the three-electrode submerged arc welding method include, for example, the Welding Method Committee 67th document “Thick plate multi-electrode 1
An example in which a plate thickness of 40 mm is applied to "run submerged arc welding" (edited by Welding Society, May 23, 1978) is reported. Further, recently, application to a plate thickness of 70 to 80 mm by submerged arc single layer welding has been studied.

[0004]

However, in the corner joint three-electrode submerged arc one-layer welding of a box column of a thick plate whose plate thickness exceeds 50 mm, a large amount of gas is blown up because a high current is used, and As a result, irregularities in the slag and molten metal are likely to occur. Therefore, in order to obtain a good welded portion, it is not possible to deal with it only by setting normal welding conditions such as current and voltage, and there are cases in which a defective weld bead appearance or a weld defect occurs.

[0005]

Means for Solving the Problems As a result of various studies to solve this point, the present inventors have found that in three-electrode submerged arc one-layer welding of extremely thick steel plates having a plate thickness exceeding 50 mm, immediately after each electrode. It was found that a good weld can be obtained by controlling the gas blow-up phenomenon of. That is, the present invention does not generate a gas blow-up phenomenon from the rear side in the welding direction of the first electrode and the second electrode when welding one layer of the corner joint of the extremely thick box column by the three-electrode submerged arc welding method. A three-electrode submerged arc welding method is characterized in that welding is performed while generating a gas blowing phenomenon only from the rear of the three electrodes.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings along with the operation. FIG. 1 is a conceptual diagram showing a situation at the time of three-electrode submerged arc welding, FIGS. 2 (a) and 2 (b) are electrode arrangements and groove shapes at the time of three-electrode submerged arc welding, and FIGS. 3 (a) and 3 (b) are The bead appearance is shown.

In three-electrode submerged arc welding, conditions are set so that each of the three electrodes has a role. That is, the first electrode L sets conditions such as current and voltage so as to obtain a necessary penetration depth. As shown in FIGS. 1 and 2, the wire of the second electrode M generates an arc on the molten metal composed of the wire of the first electrode L and the base material, increases the amount of deposited metal, and is formed by the first electrode L. By forming the molten metal by the second electrode M above the weld metal composed of the metal in the wire 5, the steel plates 11 and 13 and the flux 6 in the plate thickness direction, and making the solidification structure of the weld metal upward, To prevent pear cracking that tends to occur at the center of the bead formed by one electrode L, the current, voltage and distance between the electrodes
Set conditions such as L _1-2 and L _2-3 .

Further, the bead waveform 14 of the third electrode T is stable and fine, does not cause an undercut, does not have a horse-back shape in which the center of the bead rises high, and has a bead width of 1
The conditions such as current, voltage, and distance between the electrodes L _1-2 and L _2-3 are set so that the bead appearance shown in FIG.

For example, the shape of the groove when performing three-layer submerged arc one-layer welding with a steel plate thickness of 70 to 80 mm is shown in FIG.
As shown in (b), the steel plates 11 and 13 are groove-processed, and the groove angle θ = 30 ° and the root face R = 2 mm are examples of proper shapes. If the groove angle θ is too large, the groove cross-sectional area becomes large, and the current welding power source capacity is 2 per electrode.
At 000 to 2500 A, the required amount of deposited metal cannot be obtained. On the other hand, if the groove angle θ is too small, the amount of deposited metal can be secured, but it is difficult to obtain a sufficient penetration depth. Even when the root face R is large, it is difficult to secure a sufficient penetration depth as in the case where the groove angle θ is too small.

The arrangement of the electrodes and the distance between the electrodes are indicated by the arrow D in the welding progress direction in FIG. 2, and the inclination angles θ ₁ , θ ₂ , θ _{3 of} the first electrode L, the second electrode M and the third electrode T are shown. Is determined in consideration of bead shape and melting. First electrode L and second
The distance L _1-2 between the electrode M and the electrode M is 100 to 140 mm, and the distance L _2-3 between the second electrode M and the third electrode T is 120 to 160.
Normally set to mm. If the inter-electrode distance L _1-2 is too small or too large, the solidification structure of the weld metal does not face upward as described above, and pear cracking occurs in the weld metal. If the inter-electrode distance L _2-3 is too small, the bead width 15 is likely to be too large. On the contrary, if the inter-electrode distance L _2-3 is too large, the slag has already solidified at the arc generation point by the third electrode T. As shown in FIG. 3A, the arc becomes unstable and it becomes difficult to form the bead waveform 14 and the bead width 15 in a stable shape.

Regarding the current, voltage and speed, the maximum usable current is limited by the capacity of the current welding power source, and the welding heat input is determined in order to obtain the required amount of deposited metal for the above groove shape. , Voltage and speed are also determined automatically.

FIG. 1 is a conceptual diagram assuming a situation during welding under the above conditions. This is the normal state of the invention.
At the time of welding, the arc cavities A, B and C of the electrodes L, M and T are considered to exist by connecting directly under the flux 6. This is because gas G such as CO ₂ and CO generated when the flux 6 is melted or the wires 5 and the base materials 11 and 13 are melted is caused to flow backward by a strong arc force, but the cavities A and B on the molten pool 8 are It is considered that a thin slag shell 3 is generated in the upper part of C. Therefore, the blowing of the gas G occurs behind the welding proceeding direction D of the electrode. The bead appearance as a result of this normal welding according to the present invention is shown in FIG.

In this case, when the gas G is blown up behind the first electrode L, the arc cavity A is crushed by the first electrode L, and the unmelted flux 6 falls into the arc cavity A accordingly, so that the slag is slagged. Is not stable and causes non-uniformity. That is, the change in the amount of slag generated by the first electrode L generated in the narrow groove 12 also affects the stability of the molten pool 8 and causes a large fluctuation in the depth direction of the molten metal in the groove. For this reason, the arc generation point of the second electrode M largely changes up and down, and the voltage fluctuates, causing irregularities in the amount of deposited metal and the amount of slag generated. Further, although an arc due to the third electrode T is generated on this, it becomes more and more unstable, and finally, as shown in FIG. 3A, the welding bead meanders or the unmelted residue of the groove 12 occurs. To do.

Even if the gas blowing up behind the first electrode L does not occur, if the gas blowing up occurs behind the second electrode M, the gas blowing up occurs behind the first electrode L as well. The variation of the molten metal in the molten pool 8 due to the change in the amount of slag generated becomes large, and the arc generated at the third electrode T becomes unstable similarly. That is, the position of the molten metal in the molten pool behind the second electrode M is not stable, the arc generation point of the third electrode T generated on the molten metal changes, and the amount of deposited metal and the amount of slag produced become irregular. Finally, the weld bead becomes defective as shown in FIG.

By preventing gas from being blown up behind the first electrode L and the second electrode M, the first electrode L and the second electrode
The cavities A and B of the arc of the electrode M can be maintained in a stable size and shape, so that the arc generation point of the third electrode T becomes a fixed position and stable welding without voltage fluctuation proceeds.

At this time, when the gas is not blown up behind the third electrode T as in the case of the first electrode L and the second electrode M, the bead waveform 14 is rough and the bead width 15 as shown in FIG. 3A. The appearance becomes narrower and the groove 12 on the surface of the steel sheet may become unmelted. This phenomenon is seen when the flux dispersion thickness is increased. The reason for this is considered to be that the arc cavity C formed by the third electrode T is balanced at a very high pressure, so that the spread of the arc is limited and narrowed.

On the other hand, the first electrode L and the second electrode M
When the welding is performed while generating the gas blow-up phenomenon G behind the third electrode T and not generating the gas blow-up phenomenon G behind the third electrode T, the bead waveform 14 is stable and fine, and the steel plates 11, 13 It is possible to obtain a sufficient bead width 15 that melts the groove width of the surface of the.

As described above, even if the gas blow-up G occurs behind the third electrode T, the arc generation point is the first electrode L or the second electrode.
Since it is not in the groove like the electrode M but above the surface of the steel plate, the pressure in the arc cavity C is released not only in the upward direction but also in the lateral direction, so that the amount of deposited metal and the amount of slag produced are irregular. It is considered that the problem does not occur. Therefore, a good weld bead can be obtained. The gas blow-up phenomenon G may be intermittent or continuous, and may cause gas blow-up to reduce the pressure in the arc cavity. The smaller the flux distribution thickness, the more the gas is blown up continuously behind the electrode. On the other hand, as the thickness of the flux is increased, the position where the gas is blown up moves to the rear of the electrode and is intermittently generated. Furthermore, if the flux dispersion thickness is too large, it will not be observed as a blow-up phenomenon, the gas will remain at the solidification interface between the slag and the molten metal, and will remain as bubbles in the solidified slag, or a circular or rectangular shape will appear on the surface of the weld bead. To form a pock mark, which is one of so-called welding defects.

[0019]

[Examples] Two types of SM490B steel having a plate thickness of 70 mm and 80 mm shown in Table 1 were formed into a shape shown in FIG.
Create a box column corner joint with 0 °, 2 mm when the root face R has a plate thickness of 70 mm and 4 mm when the plate thickness is 80 mm,
In the electrode arrangement shown in FIG. 2, each electrode has an electrode inclination angle θ ₁ = 8.
Inclination at θ, θ ₂ = 0 °, θ ₃ = 5 °, wire protrusion length Ex ₁ = 50 mm, Ex ₂ = 60 mm, Ex ₃ = 60
mm, the gap between the 1st and 2nd electrodes L _1-2 = 130mm, 2nd
-Three-electrode submerged arc single-layer welding was carried out under the welding conditions shown in Table 4 with the gap between the electrodes of the third electrode L _2-3 = 130 mm.

As the welding material, the wire is the JIS shown in Table 2.
Wire diameter 6.4 specified as YS-S1 of Z3351
mm is used for all electrodes, and JIS Z 33 shown in Table 3 is used.
No. 52 FS-BT1 was combined with a specified iron powder bond flux (particle size 12 × 100 mesh).

For the flux distribution, a flux distribution nozzle is installed at a position 50 mm forward of each electrode in the welding direction, and the height of each nozzle is adjusted and whether or not the flux is distributed is shown in Table 5.
The flux dispersion thickness was changed for each electrode as shown in FIG. Welding was performed with the same dispersion thickness for both 70 mm and 80 mm plate thickness.

After welding, the bead appearance was observed, and then a macroscopic test piece of the cross section of the welded portion was sampled to observe the presence or absence of internal defects such as slag inclusion. Table 6 shows the welding results.
For the symbols in the table, for example, A1-70 is the symbol A1 shown in Table 5 for the flux distribution thickness, which represents welding with a plate thickness of 70 mm, and A1-80 represents welding with a plate thickness of 80 mm.

In each of A1-70 to A6-80 of the present invention, good weld beads without defects were obtained. On the other hand, in the comparative example, the welding results that caused the same problems with the plate thicknesses of 70 mm and 80 mm were not satisfactory. That is,
In Comparative Examples B1-70 and B1-80, since gas was blown up behind the second electrode, meandering of the bead occurred. In Comparative Examples B2-70 and B2-80, since gas was not blown up behind the third electrode, a pock mark was generated on the bead surface, and unmelted residue was also generated at the groove.
In Comparative Examples B3-70 and B3-80, since gas was blown up behind the first electrode, slag entrainment occurred. In Comparative Examples B4-70 and B4-80, since gas was blown up behind the first electrode and behind the second electrode,
The bead meandered and slag was involved. In Comparative Examples B5-70 and B5-80, the gas was blown up behind the first electrode and the second electrode, and the gas was not blown up behind the third electrode. The remaining unmelted portion occurred.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

[Table 5]

[0029]

[Table 6]

[0030]

According to the welding method of the present invention, it is possible to obtain a good weld portion without welding defects in the submerged arc single layer welding of an extremely thick box column corner joint, which greatly contributes to the improvement of welding efficiency. , Can contribute to the development of industry in this field.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a situation at the time of three-electrode submerged arc welding.

FIG. 2A is an explanatory view showing an electrode arrangement during three-electrode submerged arc welding, and FIG. 2B is an explanatory view showing a groove shape.

FIG. 3A is a view showing a bad bead appearance, and FIG. 3B is a view showing a good bead appearance.

[Explanation of symbols]

1 ---- Groove bottom 2 ---- Steel plate surface 3 ---- Slug shell 4 ---- Contact tip 5 ---- Wire 6 ---- Flux 7 ---- Slug 8-- --- Molten pool 9 ---- Weld metal 10 ---- Backing metal A, B, C ---- Arc cavity D ---- Welding direction G ---- Gas blow-up phenomenon L- --- First electrode M ---- Second electrode T ---- Third electrode R ---- Root face t ---- Plate thickness, 11, 13 ---- Steel plate 12 ---- Groove surface θ ---- Groove angle θ ₁ , θ ₂ , θ ₃ ---- Electrode inclination angle Ex ₁ , Ex ₂ , Ex ₃ ---- Wire protrusion length L _1-2 --- -Between first electrode and second electrode L _2-3 ---- Between second electrode and third electrode 14 ---- Bead waveform 15 ---- Bead width

Claims (1)

[Claims] 1. When a corner joint of an extremely thick box column is welded in one layer by a three-electrode submerged arc welding method, a gas blow-up phenomenon does not occur from the rear side in the welding direction of the first electrode and the second electrode. A three-electrode submerged arc welding method, wherein welding is performed while generating a gas blowing phenomenon only from the rear of the three electrodes.