JPH07314175A - High-speed horizontal fillet gas shielded arc welding method - Google Patents

Abstract

PURPOSE:To provide a high-speed horizontal fillet gas shielded arc welding method which prevents bit generation by a primer cracking gas at the time of welding primer coated steel sheets and makes it possible to stably obtain good bead shapes. CONSTITUTION:A flux cared wire having a flat section of a minor axis/major axis 0.05 to 0.40 and contg. TiO2 at 2.0 to 6.0wt.% by the total weight of the wire is used at least for a preceding electrode and welding is executed by arranging the wire in such a manner that its major axis direction is a weld line direction in the two-electrode horizontal fillet gas shielded arc welding method to be executed by forming one pool.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed horizontal fillet gas shield arc welding method for improving primer resistance in high-speed horizontal fillet welding of a primer-coated steel sheet and obtaining a stable and good bead shape.

[0002]

2. Description of the Related Art In recent years, in the fields of shipbuilding and bridges, there is a strong demand for speeding up horizontal fillet welding in order to reduce welding costs. On the other hand, a multi-electrode high-speed horizontal fillet welding method by a gas shield arc welding method using a flux-cored wire has been proposed, for example, in JP-A-63-235077 and JP-A-2-280968. The use of the flux-cored wire secures the bead leg length due to the high speed due to its high weldability, and the undercut of the slag forming agent typified by TiO ₂ contained as the filling flux composition easily occurs at the high speed. Because it is effective in prevention.

By the way, in high-speed horizontal fillet welding in a practical field, there is a strong demand for improving the primer resistance in addition to the above-mentioned bead forming property. This is because ship-primer coated steel sheets are generally used in the shipbuilding and bridge fields for rust prevention during the manufacturing of welded structures and for paintability after finishing, and pits, which are bead surface defects, tend to occur as speed increases. This is because In particular, the use of a primer with a relatively high hydrogen potential and the occurrence of pits are extremely sensitive to steel sheets with uneven coating film thickness, which not only impairs the quality of the welded portion but also requires a long repair time.

As a measure for preventing pits, it is necessary to remove the primer before welding or to thoroughly manage the primer (type, film thickness), but there are various improvements in the primer resistance from the welding method and welding material. Is being considered. For example, the proposal of JP-A-63-104783 is
The aim position of the wire is specified in order to reduce the influence of the primer in horizontal fillet welding of one-electrode welding. Further, JP-A-62-110873 proposes to precede the primer burning electrode in multi-electrode welding. However, applying the wire aiming position to two-electrode welding as it is deteriorates the bead forming property, and the installation of the combustion electrode complicates the apparatus.

Incidentally, the above-mentioned Japanese Patent Laid-Open No. 2-280968.
In the publication, it is proposed to use a TiO ₂ -based flux-cored wire containing a metal fluoride and a metal carbonate in order to prevent the formation of pits, and the effect is obtained practically. Occurrence can be a problem. Also, in practical use, the processing accuracy of welding members, especially the gap between the vertical plate and the lower plate (hereinafter referred to as the gap)
However, there is a demand for a welding method that is widely applicable in terms of bead formation.

[0006]

Therefore, the present invention improves the pit resistance, which is a problem with the increase in the speed of horizontal fillet welding of a primer-coated steel sheet, and can be applied in the field where a stable and good bead shape can be obtained. An object of the present invention is to provide a high-speed horizontal fillet gas shielded arc welding method with a wide range of properties.

[0007]

Means for Solving the Problems The present invention is to solve the above problems, and in a two-electrode horizontal fillet gas shielded arc welding method in which one pool is formed, at least the leading electrode has a minor axis / major axis. It has a flat cross section of 0.05 to 0.40 and TiO ₂ is 2.0 to 2.0 with respect to the total weight of the wire.
A high-speed horizontal fillet gas shield arc welding method characterized by using a flux-cored wire containing 6.0 wt% and arranging and welding the wire such that the major axis direction of the wire is the welding line direction.

[0008]

The present inventors have improved the bead formability and primer resistance considering the gap resistance when performing horizontal fillet welding of a primer-coated steel sheet at a high welding speed of 1.5 to 3.0 m / min. It was examined by various experiments. First, in order to obtain a stable fillet bead shape without undercut at a high welding speed of 1.5 m / min or more,
Even if a flux-cored wire with a fast wire melting rate is used so that the amount of deposited metal commensurate with the leg length can be secured, 2
It was found that electrodeization is necessary, and when both electrodes are arranged so that the molten pool becomes one pool, smooth beads can be obtained.

Regarding the pit generation condition, when the types of the primers were the same and the film thickness was almost constant, the pits tended to be generated more as the penetration of the corners of the standing plate and the lower plate by the leading electrode increased. It also tends to occur when the arc becomes unstable due to changes in the wire aiming position and the gap during welding. It was confirmed by fracture surface observation. However, when the gap is increased, pits hardly occur. It is clear that the main cause of pit formation in high-speed horizontal fillet welding is the gas produced by burning or thermal decomposition of the primer applied to the steel plate during welding. It was concluded that it is effective to reduce the gas generation from the primer, that is, to weld without increasing the penetration at the corners so much.

The inventors of the present invention have previously disclosed Japanese Patent Laid-Open No. 4-284974.
Paying attention to the melting form of the flux-cored wire with a flat cross section proposed in Japanese Patent Publication No.
As a result of diligent study on application to electrode high-speed horizontal fillet welding, it was found that the primer resistance of high-speed horizontal fillet welding performed at a welding speed of 1.5 m / min or more can be remarkably improved.

In two-electrode high-speed horizontal fillet welding performed in one pool, the leading electrode has a flat cross section T as shown in FIG.
By arranging and welding the io ₂ -based flux-cored wire such that the major axis direction is the welding line direction,
The amount of gas generated from the primer can be reduced as compared with the case of using a conventional flux-cored wire having a circular cross section as shown in FIG. In the wire sectional views of FIGS. 1 and 5, 1 is an outer skin portion, 2
Is flux. This is an effect due to the melting form of the flux-cored wire having a flat cross section in which the arc is dispersed in the welding line direction and the digging of the molten pool due to the arc force is alleviated. Reducing the depth of the molten pool also works effectively for stabilizing the molten pool, and it is possible to prevent an increase in penetration at the corners where the arc becomes unstable. Further, stabilization of the molten pool also promotes smooth floating and release of gas from the molten metal, which improves primer resistance.

Furthermore, it has been found that the use of a flux-cored wire having a flat cross section is extremely effective in stabilizing the bead shape. 2 and 3 are conceptual views showing an example of a welding situation according to the present invention, FIG. 2 is a side view seen from a direction perpendicular to a welding line, and FIG. 3 is a view seen from a welding line direction.
Is weld metal, 9 is generated slag, 10 is a standing plate, and 11 is a lower plate. In the two-electrode one-pool welding method, in order to obtain fillet high-speed weldability, it is necessary to stabilize the pool 5 formed between the leading electrode 3 and the trailing electrode 4. That is,
The molten metal 6 generated by the leading electrode is blown backward by the strong plasma flow of the leading electrode, but a forward force is applied by the arc 7 of the trailing electrode 4 to form a pool of molten metal between the trailing electrodes. The point of two-electrode high-speed fillet welding is to control the rearward movement of the molten pool to obtain fillet beads without defects such as undercut. However, when aiming for higher speed, the welding current must be set high in order to obtain the amount of welding commensurate with the target leg length. When a conventional flux-cored wire with a circular cross-section is used for this, the arc is concentrated, so the digging action of the arc directly below the electrode is strong, and the powerful plasma air flow increases the arc force between the leading and trailing electrodes. Moreover, the stability of the molten metal pool between the two electrodes is lost, and a good bead shape cannot be obtained.

On the other hand, when a flux-cored wire having a flat cross section is used, the arc is dispersed and generated in the longitudinal direction of the welding line, so that the arc force can be alleviated, a stable pool of water is maintained, and a good bead shape is obtained. To be Furthermore, in practical use, there are welded members with uneven gaps and rounded end plate end faces, and conventional circular cross-section wires are used for horizontal fillet welding at high speeds of 1.5 to 3.0 m / min. In such a case, if the gap or the roundness of the end face of the standing plate becomes a little larger, the wire will sneak into the gap, and problems such as arc instability, frequent spattering, and defective bead shape are likely to occur.

In contrast to this problem, when a flux-cored wire having a flat cross section is used, arcs are generated in a dispersed manner, so that even if the gap is insensitive to about 0.5 to 1.5 mm, a good bead is obtained. The shape is obtained. The welding speed of the present invention can be 3.0 m / min when applied to a leg length of 4 to 5 mm, which has a high ratio in longge pre-welding for shipbuilding. However, if it exceeds 3.0 m / min, the total current of the two electrodes becomes 1100 A or more in order to obtain the required amount of welding, and the molten metal pool becomes unstable and undercut easily occurs.

The size of the flux-cored wire having a flat cross section has a great influence on the penetration of the corner portion, and as shown in FIG. 1, its major axis (L ₁ ) is 1.5 to 15 mm and its minor axis (L ₂ ). Is 0.5 to 2.4 mm, L ₂ / L ₁ is 0.05
The range of .about.0.40 is preferable, and in this size, the penetration at the corner can be made smaller than that in the case of using the conventional flux-cored wire having a circular cross section. That is, when L ₂ / L ₁ is less than 0.05, the electrode shape becomes too flat, resulting in poor contact with the contact tip and increased contact resistance during electrode feeding, resulting in an unstable arc and between the two electrodes. The pool is not stable and the bead shape deteriorates. On the other hand, when L ₂ / L ₁ exceeds 0.40, arcs are generated in a vertical direction with respect to the welding line direction, undercuts occur on both sides of the standing plate and the lower plate, and the pool Becomes unstable and the bead shape deteriorates.

As for the composition of the filling flux, a TiO ₂ system is the best because it requires a slag-forming agent component from the viewpoint of bead forming property and can obtain good arc stability and bead appearance. By using a flux-cored wire containing TiO ₂ in an amount of 2.0 to 6.0% by weight based on the total weight of the wire,
A stable arc is maintained, and a slag having good fluidity uniformly covers the entire bead to adjust the bead shape. If the content of TiO ₂ is less than 2.0% by weight, this effect cannot be obtained. If it exceeds 6.0% by weight, the slag encapsulation property and bead shape are improved, but the slag viscosity is increased and the slag generation amount is also increased. Since the amount is too large, the gas generated from the primer and entering the molten pool is prevented from being released to the outside, resulting in frequent occurrence of pits and gas grooves.

Other components contained in the flux-cored wire used in the present invention include Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , FeO, other than TiO ₂ .
Oxides such as Fe ₂ O ₃ , K ₂ O and Na ₂ O (1 to 6% by weight), deoxidizing agents such as Si, Mn, Al, Ti and Mg (1 to 6% by weight)
5% by weight), fluoride for improving pit resistance (0.01
.About.0.5% by weight) is preferably contained within the range shown in (). In addition, Ni, Cr, Mo, V, N
Alloying components such as b and Cu and iron powder may be appropriately added to the flux.

As for the sheath material of the flux-cored wire, mild steel (C; 0.06% by weight or less, Si; 0.2% by weight or less, Mn; 0.5% by weight or less, P; 0) which is easily processed into a flat cross section. 0.020% by weight or less, S; 0.020% by weight
Or less), or alloy steel (C; 0.06 wt% or less, Si;
0.3-1.5% by weight, Mn; 0.5-2.0% by weight,
P; 0.020 wt% or less, P; 0.020 wt% or less) can be used. Flux filling rate is 10
The range of -30% is preferable from the viewpoint of welding speed and workability. Although CO ₂ gas is generally used as the shield gas during welding, the above effect can be obtained even when Ar—CO ₂ system gas is used.

[0019]

EXAMPLES The effects of the present invention will be described in detail below with reference to examples. Mild steel pipe (C; 0.05% by weight, Si;
0.01% by weight, Mn; 0.25% by weight, P; 0.01
0 wt%, S; 0.005 wt%) was filled with flux, reduced in diameter by wire drawing, and then rolled into a flux having a flat cross section in which the major axis (L ₁ ) and the minor axis (L ₂ ) were changed. A wire was prototyped. For comparison, a flux-cored wire having a circular cross-section with a wire diameter of 1.6 mm was also manufactured by using the same mild steel pipe and flux. Table 1 and Table 2 show the details of the prototype wire.

[0020]

[Table 1]

[0021]

[Table 2]

Using these trial wires, a T-shaped fillet test piece (SM490B, plate thickness 12 mm, inorganic zinc primer coating, film thickness 25 μm) having the shape shown in FIG. A welding test (same welding condition without shift, 1 pool welding, target leg length 4 to 5 mm) was performed. In FIG. 4, 12 is a primer and 13 is a gap. Further, the torch angles θ ₁ and θ in Table 3 are
₂ , θ ₃ and θ ₄ are as described in FIGS. 2 and 3. Table 4 shows the welding test results. In Table 4, the test No. Test Nos. 1 to 5 are according to the present invention. 6-8
Is a comparative example.

[0023]

[Table 3]

[0024]

[Table 4]

Test No. Nos. 1 to 4 use a flux-cored wire (A1 to A3) having a flat cross section for the leading electrode and a flux-cored wire (A5) having a circular cross section for the trailing electrode, and the welding speed is 1.5 to 1.8 m / min (target). When the leg length was 5 mm), no pit was generated and the bead shape was also good. No. No. 5 is a case where the flux-cored wire (A3) having a flat cross section is used for both the leading electrode and the trailing electrode, and the welding speed is 2.5 m / min (target leg length 4 mm). ing.

No. In No. 6, the flux distribution wire with a flat cross section used had a minor axis / major axis of more than 0.40, so the arc dispersion effect was not sufficient, and pits were generated, and arcs were also generated on the base metal side and undercut There has occurred. No.
Nos. 7 and 8 used a flux-cored wire having a circular cross-section for both electrodes, so that pits were generated at a high welding speed of 1.5 m / min or more, and the bead shape was deteriorated due to poor gap resistance.

[0027]

As described above, the present invention provides a high-speed horizontal fillet gas shielded arc welding method in which the flux-cored wire having a flat cross section is arranged at least on the leading electrode to enhance the primer resistance and the bead forming property. The present invention can greatly contribute to high efficiency and low cost of welding at a practical site.

[Brief description of drawings]

FIG. 1 is a view showing a cross section of a flux-cored wire having a flat cross section used in the present invention.

FIG. 2 is a side view as seen from a direction perpendicular to the welding line, which is a conceptual diagram for explaining the welding situation according to the present invention.

FIG. 3 is a conceptual diagram for explaining a welding situation according to the present invention, as viewed from the welding line direction.

FIG. 4 is a diagram showing a shape of a test plate in an example.

FIG. 5 is a view showing a cross section of a conventional wire with flacks.

[Explanation of symbols]

 1 Outer Skin 2 Flux 3 Leading Electrode 4 Trailing Electrode 5 Hot Water Pool 6 Molten Metal 7 Arc 8 Weld Metal 9 Generated Slag 10 Standing Plate 11 Lower Plate 12 Primer 13 Gap

Claims (1)

[Claims] 1. A two-electrode horizontal fillet gas shielded arc welding method for forming one pool, in which at least the leading electrode has a flat cross section with a minor axis / major axis of 0.05 to 0.40 TiO ₂ is added to the weight of 2.0 to 6.
A high-speed horizontal fillet gas shielded arc welding method characterized by using a flux-cored wire containing 0% by weight and arranging the wire so that the major axis direction of the wire is the welding line direction.