JPH03238174A - One-side submerged arc welding method at high speed - Google Patents

Abstract

PURPOSE:To perform welding with high efficiency by specifying the wire diameter of first and second electrodes and specifying the relation between an electric current and the welding speed of both. CONSTITUTION:One-side multiple electrode submerged arc welding is performed by using >=3 electrodes of first, second and third electrodes 8, 9 and 10. The wire diameter of the first electrode 8 and the second electrode 9 is then made to >=4.0 mmphi. When a current and the welding speed of the first electrode 8 are then denoted by Iq1(A) and S(sm/min), respectively, 100<=S<=200 is formulated and the inequality 1 is satisfied. When the distance 14 between the second electrode 9 and the third electrode 10 is made to 150-300 mm and a current of the third electrode 10 is denoted by I3 (A), the inequality II is satisfied. The two welding wires having 1.2-2.4 mmphi diameter are made to a couple to form one-unit electrode. Consequently, both sound and fine back beads and front beads can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a single-sided submerged arc welding method using three or more multi-electrodes, and more specifically, a welding speed of 1
The present invention relates to a highly efficient single-sided submerged arc welding method that is performed at a high speed of 00 cm/min or higher.

(Prior Art) Conventionally, single-sided submerged arc welding has been widely applied as a high-efficiency welding method for thick plates, mainly in shipbuilding.

However, the level of pursuit of efficiency is becoming higher and higher, and there is a demand for welding methods that are 1.5 to 2 times faster than conventional welding speeds.

However, the conventional single-sided submerged arc welding method
Special Publication No. 48-22572 and Special Publication No. 49-3842
As disclosed in Publication No. 0, etc., the welding speed is less than 100 cm/min in all cases.

On the other hand, in conventional joint welding in which welding is performed from the front side and the back side, many multi-electrode welding methods with a welding speed of 100 cm/min or more have been disclosed, but it is not possible to directly apply this technology to single-sided submerged arc welding. Have difficulty. In normal multi-electrode welding, in order to ensure the penetration and amount of welding, even if the current is increased considerably, there is no fear of the melt coming off, and no special consideration is required for forming a back bead. , speeding up can be achieved relatively easily.

However, in single-sided submerged arc welding, it is required to form not only a front bead but also a healthy back bead at the same time. If it protrudes too much, the bead will become uneven, and in extreme cases, horizontal cracks will occur. Furthermore, if the welding speed is high, the bead becomes thinner and undercuts are likely to occur at the end of the back bead. In addition, due to the high speed, the weld metal solidifies quickly, and as shown in FIG. 6(a), the crystal growth directions (dendrites) are butted, resulting in a structure that is extremely susceptible to cracking.

Therefore, in single-sided submerged arc welding, the current state of the art is that a welding speed of 100 cm/min or higher has not yet been achieved.

In addition, the single-sided submerged arc welding method referred to here refers to the fifth
As shown in Figures (a) and (b), backing flux 4 is sprinkled in a layer on the copper dowel 2 from the back side of the welded materials 1.1' that have been butted together, or the backing flux 4 is placed in a refractory canvas. The backing flux 4 is pressed onto the back surface of the materials to be welded 1, 1' by a push-up mechanism such as an air hose 5, and submerged arc welding is performed from the front side using the wire 3 and the flux 6. This is a welding method that forms a bead at the same time.

(Problems to be Solved by the Invention) The first object of the present invention is to provide a welding method that forms a sound back bead in the above-mentioned high-speed single-sided submerged arc welding method, and also to provide a welding method that forms a satisfactory front bead. The object of the present invention is to provide a welding method that also forms.

(Means for Solving the Problems) In view of the above circumstances, the present inventors conducted various studies and obtained the following findings. That is, in order to obtain a healthy back bead in high current/high speed single-sided submerged arc welding, (1) the back bead should be Use a wire that is formed only by the second electrode and has a thickness greater than a predetermined value in order to soften the concentration of arcs caused by an increase in current density due to high current.

(2) First. A back bead can be formed only when the sum of currents of the second electrode and the welding speed satisfy a special relationship.

Two points are important.

That is, the gist of the present invention is to provide a single-sided multi-electrode submerged arc welding method using three or more electrodes.
The wire diameter of the electrode and the second electrode is 4.0 mmφ or more, and the current of the first electrode is I.

(A), the current of the second electrode is I2 (A), the welding speed is S
(am/m1n), 100≦S≦200, and 4 (S+575)≦II +I2≦4 (S+725
) is a high-speed single-sided submerged arc welding method.

In addition, if it is necessary to form a more satisfactory surface bead, the distance between the second electrode and the third electrode should be set to 150 to 300+ nm.
And when the current of the third electrode is 13 (A), ■
3≦0.85 (II + 12) or a pair of two welding wires with a wire diameter of 1.2 to 2.4 open φ and a parallel arc generated by the same wire feeding mechanism.
A high-speed single-sided submerged arc welding method characterized by using a single electrode as a unit electrode and using this electrode as at least one electrode after the third electrode.''

(Function) The present invention will be explained in detail below. First, in the present invention, it is necessary to use three or more electrodes.

As a result, the first. Form a back bead with the second electrode, and
A surface bead is formed after the electrode, making it possible to secure the required amount of welding.

[Reasons for limiting wire diameter]

First, 1. The wire diameter of the second electrode will be described. In order to increase the amount of welding, it is effective to increase the current density, and therefore it is possible to reduce the wire diameter,
In the case of high-speed single-sided welding as in the present invention, the bead tends to become very thin. Furthermore, if the diameter is small, the arc will concentrate, the bead will become convex, and undercuts will likely occur. Therefore,
The first step is to soften the arc and widen the bead. Second
It is necessary to increase the diameter of the electrode wire. In this case, 4.
If it is less than 0 mm, there is no effect, and it is necessary to make it 4.0 mm or more.

[Welding speed and 1. [Relationship between the sum of currents of the second electrode] Generally, as the current increases, the molten pool becomes larger, making it easier for back beads to appear, but in extreme cases, cracks are more likely to occur.

On the other hand, as the speed increases, the molten pool becomes elongated or the amount of welding decreases, resulting in an insufficient supply of molten metal, which makes it difficult to form a back bead, and in extreme cases, an undercut. Therefore, by simply increasing the current and increasing the speed, too much or no back bead appears, making it difficult to form a well-balanced bead.

As a result of intensive studies to solve such high-current, high-speed single-sided submerged arc welding problems, we found that the sum of the current II (A) of the first electrode and the current II (A) of the second electrode (
It has been found that a very good back bead can be formed only when Il+12) and welding speed S (cm/m1n) satisfy a special relationship.

Figure 1 is 1. This study investigated the effects of the second electrode current sum and welding speed on back bead formation.

Welding is performed with plate thickness t = I Bmm as shown in Figure 4.
% root face d = 5 mm, groove angle θ-50'. Also, 1st. The distance of the second electrode is 35+++++*
Closed.

In this case, a height of 1.5 to 3.5+nm was determined to be a good range, a height of less than 1.5 mto was determined to be insufficient, and a height of more than 3.5 mto was determined to be excessive. In FIG. 1, the number attached to O represents the extra height of the back bead, and . is the case where the back bead does not come out at all. When the welding speed exceeded 200 cm/min, no back bead could be produced regardless of the current. As a result, the present inventors found that 100≦S≦200, and 4 (S+575)≦1. +12≦4 (S+725)
If so, we newly discovered that a healthy back bead without undercuts or cracks can be obtained.

In the present invention, as described above, in high-speed single-sided submerged arc welding using three or more electrodes, a wire having a specific thickness is first welded. the second electrode, and the first electrode in this case. It is essential to specify the relationship between the current sum of the second electrode and the welding speed.

FIG. 2 shows an example of the arrangement of electrodes of the present invention.

In the figure, 8 is the first electrode, 9 is the second electrode, lO is the third electrode, 1
1 is the bottom surface of the groove of the material to be welded 1, 12 is the surface of the material to be welded 1,
13 indicates the distance between the first and second electrodes, and 14 indicates the distance between the second and third electrodes.

[Reason for limiting the conditions of the third electrode] Next, the third and subsequent electrodes responsible for forming the surface bead were examined.

The third and subsequent electrodes are used to prevent internal defects such as poor fusion and slag entrainment, and to ensure the necessary amount of welding.At the same time, the weld metal formed by the first and second electrodes is melted. However, as shown in FIG. 6(b), it also has the role of controlling the direction of the dendrites upward. However, the first
．． When the third electrode is placed in the molten pool formed by the second electrode, it becomes a so-called one pool, and the arc caused by the third electrode reaches the lower end of the back bead, causing the bead to protrude too much and the punch line also butts. This results in a tissue that is extremely fragile. Therefore, the third electrode is the first. It must be placed outside the pool formed by the second electrode.

The inventors of the present invention firstly. As a result of examining the length of the pool formed by the second electrode in the area surrounded by diagonal lines in FIG. 1, the maximum length of the pool was about 140 mm.

Therefore, the distance between the second electrode and the third electrode must be 150 cm or more. However, if this length exceeds 800 m+++, the molten slag will completely solidify, making it impossible to generate a stable arc. Therefore, the distance between the second electrode and the third electrode was limited to 150 to 300 mm. In this case, the distance between the electrodes refers to the distance 14 between the wire centers at the bottom surface 11 of the groove, as shown in FIG.

Moreover, in order to ensure the amount of welding, if the current of the third electrode becomes too high, the weld penetration becomes deep, which adversely affects the back bead formed by the first and second electrodes. In this case, the current of the third electrode is the same as that of the first electrode. If it exceeds 65% of the total current of the second electrode, too much back bead will appear or cracks will occur. Therefore,
When the current of the third electrode is I3 (A), ■3≦0.
85 (II +12).

[Reason for applying small diameter wire]

By the way, there are many different plate thicknesses to which single-sided welding can be applied, and as the plate thickness increases, it becomes extremely difficult to ensure a sufficient amount of welding. It would be possible to increase the number of electrodes, but this increases the size of the device and increases the cost, so there is a limit to this. Therefore, it is necessary to devise ways to ensure the amount of welding as efficiently as possible.

Therefore, in order to increase the current density and increase the amount of welding, it is possible to use a small diameter wire. However, the front bead needs to be spread to a certain extent, and if a mere small diameter wire is used, the bead will be too thin, causing undercuts and poor fusion at both ends of the bead.

Therefore, as a result of considering a method that would ensure a shallow weld penetration, a wide bead, and a sufficient amount of welding, it was found that it is effective to generate parallel arcs using the same wire feeding mechanism using two small-diameter wires as a pair. did.

1 This wire feeding mechanism, as shown in FIG. 3(a), uses one electric motor 16 to feed two wires 15 and 15' through a pressure roller (not shown) and a feeding roller 17 to a nozzle 18.
is being sent to. According to this feeding mechanism, the current is distributed over the two wires, resulting in a soft arc and no deeper penetration even when the current is increased. FIG. 3(b) shows a specific example in which the present invention is applied to the third electrode 101 and the fourth electrode 19. Two wires are placed parallel to the weld line. In this case, if the wire diameter is less than 1.2 mm, sufficient bead salting cannot be obtained, and conversely, if it exceeds 2.4 mm, the current density becomes low and it is difficult to secure a sufficient amount of welding. Therefore, the wire diameter was limited to 1.2 to 2.4n+m.

By the way, the welding method of the present invention is a single-sided submerged arc welding method, and requires front side flux, backing flux, and electrode wire as welding materials.
The composition of these welding materials is not particularly limited as long as it is possible to obtain a weld metal appropriate for the purpose.

2 That is, the front side flux is 5iO3An)203
, metal oxides such as TiO7, MnO, MgO, Ca
F 2 + M g Metal fluorides such as F2, CaCO3
A flux prepared by suitably blending metal carbonates such as, deoxidizing agents such as St, Mn, alloying agents such as Ni, Mo, or iron powder may be used.

The flux type may be either melt type or bond type flux. The same applies to backing flux.

The electrode wire is selected in relation to the flux composition, Mn: 0, 3-8, 2%, MO:
A wire containing 0.15 to 0.75% of one or more types is preferable in order to ensure strength and toughness.

The present invention has been described in detail above, but in order to further clarify the effects of the present invention, examples will be described below.

(Example) For the steel plate shown in Table 1, using the wire shown in Table 2, the flux shown in Table 3, and the backing flux shown in Table 4,
Two types of single-sided submerged arc welding were performed.

The flux shown in Table 3 is a bonded flux in which raw material powder is granulated using water glass and then fired in a rotary kiln at 400° C. and 120 ml, and the particle size of the finished flux is sized to a 12×100 mesh. Further, the backing flux shown in Table 4 is a backing flux combined with a copper dome shown in FIG. 5(a) and is a bond type black. The phenol resin was dissolved in water and alcohol as solvents to form a slime, which was then coated on the flux particles.

Table 5 shows the welding results in Examples of the present invention.

Invention examples Nos. 1 to 8 all formed good back beads and excellent welds were obtained in all cases, but on the other hand, comparative examples Nos. 9 to 14 had poor welding results. As shown in the column, a satisfactory back bead could not be formed.

In Table 5, the groove shape shown in FIG. 4 was used. t is the thickness of the test plate, d is the root face, and θ is the groove angle.

(Effects of the Invention) As explained above, the present invention uses a high-speed single-sided submerged arc welding method to obtain an extremely sound and good back bead, and also to form a good front bead, making it possible to perform highly efficient welding and to put it into practical use. The value is extremely large.

[Brief explanation of drawings]

Figure 1 shows 1. A diagram for explaining the influence of the current sum of the second electrode and the welding speed on back bead formation, FIGS. 2 and 3 (a) and (b) are side views showing an embodiment of the welding method of the present invention, FIG. 4 is a front view showing the groove shape used in the embodiment of the present invention, FIGS. 5(a) and (b) are front views for explaining the single-sided submerged arc welding method, and FIG. 6(a)
, (b) is a front view for explaining the direction of dendrites of weld metal. 1, 1': Material to be welded 2: Copper weld 3: Electrode wire 4: Packing blacks 5: Air hose 6: Flux 7; Fireproof canvas

Claims (1)

[Scope of Claims] (1) In a single-sided multi-electrode submerged arc welding method using three or more electrodes, the wire diameters of the first and second electrodes are 4.0 mmφ or more, and the current of the first electrode is I, (
A), the current of the second electrode is I_2(A), and the welding speed is S(
cm/min), 100≦S≦200 and 4 (S+575)≦I_1+I_2≦4 (S+725)
A high-speed single-sided submerged arc welding method that satisfies the following. (2) The distance between the second electrode and the third electrode is 150 to 300 m.
The high-speed single-sided submerged arc welding method according to claim 1, wherein I_3≦0.65 (I_1+I_2) where m is the current of the third electrode and I_3 (A). (3) The wire diameter is 1.
A pair of two welding wires with a diameter of 2 to 2.4 mm and parallel arcs generated by the same wire feeding mechanism are used as one unit electrode, and this electrode is used as at least one electrode after the third electrode. A high-speed single-sided submerged arc welding method according to claim 1. (4) The distance between the second electrode and the third electrode is 150 to 300 m.
m and the current of the third electrode is I_3 (A), I_3≦0.65 (I_1+I_2) and a pair of two welding wires with a wire diameter of 1.2 to 2.4 mmφ. The high-speed single-sided submerged arc according to claim 1, characterized in that parallel arcs generated by the same wire feeding mechanism are used as one unit of electrode, and this electrode is used as at least one electrode after the third electrode. Welding method.