JPH03238173A - One-side submerged arc welding method - Google Patents

Abstract

PURPOSE:To form a fine bead by arranging two welding wires having the specified diameter in parallel with a weld line to form one electrode, using this as a first electrode and making a root gap specified times the size of the wire diameter. CONSTITUTION:Square groove multiple electrode one-side submerged arc welding is performed by using a small diameter welding wire 1 and a large diameter welding wire 2. The two welding wires having 1.0-3.5mmphi diameter (d) are then arranged in parallel with the weld line. The same welding power source, a wire feed machine 3 of a wire feed mechanism and a feed roller 4 for the twin wires are then held commonly for these wires to form the one electrode. This is used as the first electrode and the root gap is made to 1.2-1.5 times the size of the wire 1 diameter. consequently, square grooves welding can be easily performed at high speed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an I-groove multi-electrode single-sided submerged arc welding method, particularly in single-sided single-layer welding of a plate thickness of 20 mm or less.
The present invention relates to a single-sided welding method that is fast and produces a good bead without welding defects.

(Conventional technology) Conventionally, flux copper backing or glass tape +
Single-sided submerged arc welding using a solidifying agent as a backing material has been recognized for its high efficiency and has been widely used, particularly in the field of shipbuilding, but further improvements in efficiency are desired.

A problem that must be solved in order to meet this requirement is the shape of the groove. That is, in single-sided welding, V, Y, U
It is customary to perform construction using a bevel, and therefore it is necessary to take the trouble to process the beveling. Cutting the end face of the workpiece vertically and butting it together ■Using single-sided groove welding not only omits the groove processing process but also makes it possible to reduce the weld cross-sectional area, significantly improving construction efficiency. be able to.

However, in conventional one-groove single-sided welding, the current density is low because a large diameter wire is used, and the arc is generated above the workpiece and becomes a surface heat source, so deep penetration cannot be achieved and a back bead appears. It is difficult to obtain a stable back bead. In addition, if the welding current is set to a high current to produce a back bead, excess buildup of the front bead will occur, and even if a back bead appears, the arc plasma air flow will increase due to the high current, resulting in undercuts, slag entrainment, etc. Defects are likely to occur, and the bead shape becomes a pear-shaped bead, resulting in poor cracking resistance.

Various construction methods have been tried to improve these problems. In Japanese Patent Application Laid-open No. 50-84133,
■In downward multi-electrode welding using open-type beams, a method has been proposed in which the position of the trailing electrode is shifted from the welding line, and the first electrode performs welding under high current and low voltage conditions, and the trailing electrode performs welding under the conditions of low current and high voltage. ing.

That is, by using the first electrode at high current and low voltage to obtain deep penetration, and by shifting the trailing electrode from the weld line, the height of the excess buildup created by the leading electrode is spread laterally and lowered, and the fusion line is straightened. This is a way to prevent it from becoming a mold.

However, when the welding current is set to a high current, not only does the range of suitable conditions for obtaining a well-balanced bead shape between the back bead and extra metal become extremely narrow, but also the position of the trailing electrode is shifted from the welding line, making it difficult to If the electrodes are not placed in the correct position, the problem of two-step beads may occur, which is not practical.

Furthermore, in JP-A-53-127348, an appropriate gap is provided in the I groove so that the melting tip of the leading electrode is submerged below the surface of the workpiece, and the leading electrode is operated under high current and low voltage conditions. A method of welding has been proposed. That is, a method has been proposed that uses an I groove with a gap and sets the welding conditions of the leading electrode to high current and low voltage so that the arc generation position is below the surface of the workpiece to achieve penetration. .

However, this method also uses a high leading electrode welding current, which not only extremely narrows the range of suitable conditions for obtaining a bead shape with a good balance between the back bead and the extra welding, but also causes the leading electrode voltage to become extremely high. Because of this, the conditions for obtaining a good bead appearance are extremely narrow, which poses a big problem in terms of practicality.

(Problems to be Solved by the Invention) The present invention relates to I-groove multi-electrode single-sided submerged arc welding, and particularly in single-sided, single-layer welding with a plate thickness of 20 mm or less.
The object of the present invention is to provide a submerged arc welding method that does not produce defects such as humping beads or undercuts and can obtain a good bead shape when performing high-speed welding at m/m1n or more.

(Means for Solving the Problems) The gist of the present invention is as follows: (1) In the groove multi-electrode single-sided submerged arc welding method, the wire diameter d is 1.0 to 3.
Two welding wires with a diameter of 5 mm are placed parallel to the welding line, and the same welding power source and wire feeding mechanism are shared.
The single-sided submerged arc welding method is characterized in that the two electrodes are used as at least the first electrode, and the groove gap is set to 1.2 to 1.5 times the wire diameter.

(for production) The operation of the present invention will be explained in detail below.

FIG. 1 is a side view schematically showing a three-electrode submerged arc welding method, which is an example of the present invention, and a part of the welded part is shown in a cross-sectional view for easy understanding.

In the figure, 1 is a small diameter wire of 1, B to 3.5 mm φ that constitutes the first electrode, and is fed at high speed by a twin wire feed roller 4 directly connected to a high-speed rotating wire feeder 3. The predetermined wire spacing 7 is determined by the electrode tip 5 for twin wires.
A parallel arc 8 is generated while maintaining the parallel arc 8.

The distance between the twin wires affects the formation of a stable and soft welding arc, and if this distance is too small, the arc becomes highly concentrated and unstable, making it impossible to form a good back bead. On the other hand, if this interval is too large, each becomes an independent welding arc, which is undesirable because the back bead formation tends to be narrow and convex.

Appropriate spacing varies depending on welding conditions, but the wire diameter is d
If mm, the appropriate distance between the wire centers is 2d to 5d. On the other hand, the welding wire 2 used for the second electrode and the third electrode is a single large diameter wire similar to the conventional method. In this case, a parallel arc method may be used in which the second and third electrodes are made of two small diameter wires similar to those of the first electrode.

As a result of various studies on arc phenomena, the present inventors obtained the following knowledge. The strength of the plasma airflow per unit arc is considered to be proportional to the welding current, and parallel arcs soften the arc plasma airflow.

This is because the current applied to the unit electrode is divided into each welding wire and parallel arcs are ignited, resulting in a less concentrated plasma airflow and the overall arc plasma airflow is smaller than that for large diameter wires. This is because the arc becomes soft, so when forming a back bead, it is less likely to have a convex tendency, and a good back bead shape without defects such as undercuts can be obtained.

In addition, since two small-diameter wires are used, when compared at the same welding current value, the wire melting efficiency is higher than that of a large-diameter wire, and a sufficient amount of welding can be obtained. A lower current value is required to obtain a sufficient amount of welding, which also has the effect of suppressing arc plasma airflow to a lower level.

The reason why the diameter of the twin wire is 1.0 to 3.5 mm is 1.
．． If it is less than 0 mm, the Joule heat effect at the protruding part of the wire will be significant, a wire fuse phenomenon will occur between the welding tip and the base metal, the arc length will not be constant, the welding voltage will fluctuate greatly, and stable welding cannot be maintained. In addition, when the twin wire is fed at high speed because the wire is too thin, feeding defects such as full bending of the wire are likely to occur, making stable welding difficult.

On the other hand, if the wire exceeds 3.5 m, the current density in each wire becomes small because the wire is thick, which not only makes it difficult to maintain a stable parallel arc, but also reduces the wire melting efficiency, resulting in a high amount of welding at the same welding current. The effect of securing is lost.

A good back bead shape can be obtained by using the method that provides the above-mentioned effects for the first electrode.

FIG. 2 is a front view showing the groove shape of the present invention.

The wire 1 of the first electrode is ■Workpieces 12-1 on the left and right sides of the groove
．． 1.2 times to 1.2 times the diameter of the wire provided between 12-2.
The arc is located in a gap with 5 times the spacing, and the arc is in this gap,
Occurs below the surface of the workpiece.

By having a gap in the groove and generating the arc of the first electrode below the surface of the workpiece in this gap, deep penetration can be obtained. In this case, the gap provided in the groove is set to 1.2 to 1.5 times the wire diameter, because if it is less than 1.2 times, the gap will become narrow and the arc will occur above the workpiece, resulting in deep penetration. will not be obtained.

On the other hand, if it exceeds 1.5 times, the width of the gap becomes too wide, which not only causes one-sided melting where an arc occurs on the other side of the workpiece across the gap, but also causes instability such as fluctuation of the arc, resulting in poor backing. I can't get a bead.

In addition, when starting, steel wool, cut wire, etc. shall be inserted into the gap and then started.

The welding method of the present invention is an I-groove single-sided submerged arc welding method, which requires front side flux, backing flux, and electrode wire as welding materials. The composition is not particularly limited. That is, as the front side flux, S 102 and A D 20
s 1 M g O.

Metal oxides such as MnO and TiO, metal fluorides such as CaF2, metal carbonates such as CaCOMgCOa, deoxidizers such as St and Mn, alloying agents such as Ni and Mo, or iron powder. It is sufficient to use a flux made by suitably blending the following, and the form thereof may be either a melt type or a bond type flux. The same applies to backing flux.

Regarding the electrode wire, it is selected according to the target performance, but Mn: 0.3 to 3.2%, MO20, 1
A wire containing 5 to 0.75% of one or more types is preferable in order to ensure strength.

(Example) Using the steel plates shown in Table 1, wires shown in Table 2,
Using the front side flux shown in the table and the backing flux shown in Table 4, submerged arc welding was performed on one side of the groove.

The flux shown in Tables 3 and 4 is a bonded flux obtained by granulating raw material powder with water glass and then firing it, and the flux particle size is 12×100 mesh. In addition, the back flux shown in Table 4 is a back flux that is combined with a copper dome, and the phenol resin is dissolved in alcohol as a solvent.
After making it into a mucilage, it was coated on flux particles.

0 Table 5 shows welding conditions and results.

Table 1 Table 1 (wt, %) S102CaOCaF2 102102M12O3 Iron powder Alloy Others Table Other 2C02°Fed.

N a 20° K2O, etc. 1 Good welds could be obtained in all cases 1 to 5 using the present invention.

On the other hand, in Comparative Example 6, the conditions were the same as in Invention Example 2, but due to the use of a large diameter wire, penetration was insufficient and the back bead was sufficiently exposed, and the surface bead had a large excess. Ta. In Comparative Example 7, when a large diameter wire was used and the first electrode was set to high current and low voltage in order to obtain sufficient penetration, the back bead became convex and an undercut occurred. Comparative Example 8 was under the same conditions as Inventive Example 4, but because the groove gap was narrow, an arc was generated above the workpiece, and the back bead produced a large excess on the front bead. Comparative Example 9 was under the same conditions as Inventive Example 5, but because the groove gap was wide, arcing occurred only on one side of the groove, resulting in a bead rather than a piece.

(Effects of the Invention) The present invention is configured as described above, and it is possible to easily perform high-speed welding of an I-groove, which was difficult in the conventional multi-electrode single-sided submerged arc welding method, and to form a good bead. It has great industrial value.

[Brief explanation of drawings]

Fig. 1 is a schematic partial cross-sectional side view of the method of the present invention;
The figure is a front view showing the groove shape of the present invention. 1: Small diameter welding wire 2: Large diameter welding wire 3: Wire feeder 4; Feed roller for twin wires 5: Electrode tip for twin wires 6: Electrode tip for large diameter wires 7: Wire spacing of twin wires 8: Parallel arc 9; Conventional arc 10: Welding flux 11; Back flux 12, 12-],,
]12-2: Object to be welded 13: Copper dowel 1.
4.15 Varnish slag 16: Back slag 17.1
8: Molten pool 19. 20: Weld metal 21: Air hose W: Welding direction Agent Patent attorney Tatsuo Chanoki 3 4 5

Claims (1)

[Claims] In the I-bevel multi-electrode single-sided submerged arc welding method, two welding wires with a wire diameter d of 1.0 to 3.5 mmφ are arranged in parallel to the welding line, and the same welding power source and wire feeding mechanism are shared. This is used as at least the first electrode, and the groove gap is set to 1.2 times to 1 times the wire diameter.
．． A single-sided submerged arc welding method characterized by a 5x welding process.