JPH06312267A - 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 especially high in efficiency and excellent in pit resistance, in horizontal fillet welding of primer coated steel sheets which is used much in a field of shipbuilding, a bridge, etc. CONSTITUTION:A rutile-base flux-cored wire having the diffused hydrogen quantity of 15.0-40.0ml/100g of deposited metal 9 measured according to a JIS Z3118 standard is used for both or one side of preceding electrodes 1A and 1B and succeeding electrodes 2A and 2B, the distance between both electrodes is made to 20-50mm, one pool is formed substantially and horizontal fillet welding is performed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a high speed horizontal fillet gas shield arc welding method which is particularly efficient and has excellent pit resistance in horizontal fillet welding of primer-coated steel sheets, which is widely used in the fields of shipbuilding, bridges and the like. Regarding

[0002]

2. Description of the Related Art In recent years, a gas shielded arc welding method using a flux-cored wire has been remarkably popular at the construction site of various welded structures. This is because the flux-cored wire has good welding workability as well as high-efficiency welding because of its high welding property. Recently, there has been an increasing demand for a reduction in the total cost of welding, and particularly in the fields of shipbuilding, bridges, etc., the rate of horizontal fillet welding is high. In contrast,
JP-A-63-235077, JP-A-2-2809
No. 68, etc. proposes a high-speed horizontal fillet welding method performed at a welding speed of 1 m / min or more.

However, most of the steel sheets are coated with various kinds of primers (shop primers) to prevent rust generation during the construction period, and when horizontal fillet welding is performed as it is, hydrogen or monoxide is generated by the welding arc heat. When the primer pyrolysis gas such as carbon penetrates into the weld metal, pits are easily generated on the bead surface. The pits generated on the bead surface need to be reworked, which reduces work efficiency.
Various proposals have heretofore been made in order to prevent the occurrence of pits, which are defects in the bead surface. For example, in the above-mentioned JP-A-2-280968, an inorganic zinc primer-coated steel sheet which is frequently used in the field of shipbuilding is targeted,
It is shown that the flux-cored wire used for improving the pit resistance contains a metal fluoride or a metal carbonate to stir the molten metal to accelerate the release of the primer pyrolysis gas. However, if the welding speed exceeds 1.5 m / min, or if the coating thickness of the primer is large even with an inorganic zinc primer, or the primer is thickly accumulated on the end face of the upper plate, it is not always sufficient. Pit resistance cannot be obtained.

On the other hand, in horizontal fillet welding of wash primer-coated steel sheets, which are often used in the field of bridges, a large amount of primer pyrolysis gas is generated, and pits tend to form when low-hydrogen flux-cored wires are used. Is very large, the effect of supplying excess hydrogen into the molten metal is known. For example, Japanese Patent Laid-Open No. 1-26
No. 2096, JP-A-3-180298, etc.
It is proposed that hydrogen in the molten metal be supersaturated by using a flux-cored wire containing a hydrogen compound or water intentionally to accelerate the release rate of gas from the molten metal and prevent the formation of pits. .

[0005]

However, in the case of horizontal fillet welding of wash primer-coated steel sheet using the above-mentioned high hydrogen type flux-cored wire, in the field construction, single electrode welding is performed at a low welding speed of about 40 to 50 cm / min. It has been done, and there has been a strong demand for this speedup. Therefore, the present invention is a high-speed horizontal fillet gas shield arc welding method that can cope with the film thickness variation of the inorganic zinc primer-coated steel plate and that has good pit resistance even when the wash primer-coated steel plate is horizontally fillet welded at high speed. The purpose is to provide.

[0006]

Means for Solving the Problems The present invention is intended to solve the above problems, and in horizontal fillet welding of a primer-coated steel sheet, both the leading electrode and the trailing electrode, or one of them, conforms to JIS Z3118 standard. Using a rutile flux-cored wire having a measured amount of diffusible hydrogen of the deposited metal of 15.0 to 40.0 ml / 100 g, the distance between the electrodes was set to 20 to 50 mm, and substantially one pool was formed. This is a high-speed horizontal fillet gas shielded arc welding method characterized by being performed as follows. In addition, here, the amount of shift between the leading side and the trailing side on both sides of the horizontal fillet joint is 0 to 250 m.
It is also characterized in that it is made into m and welded at the same time.

[0007]

The present invention will be described in detail below. The present inventors first investigated in detail the pit generation situation when the welding conditions and the primer film thickness were changed in the two-electrode high-speed horizontal fillet welding of the steel sheet coated with an inorganic zinc primer. As a result, it was found that the number of pits tended to decrease when the current was increased to increase the leg length and the voltage was increased to increase the molten metal pool.

However, in high-speed welding, pits are very sensitive to fluctuations in the primer film thickness, and it is difficult to control the primer film thickness especially on the end face of the upper plate, which is the largest pit generation factor in field work. At this time, almost no pit was found in the first bead of the fillet joint, and it was found in the second bead. This is because when welding the second bead, the first bead blocked the escape path of the gas, so a large amount of gas entered the molten metal, and this gas could not be released before solidification of the molten metal. . In other words, it is clear that the formation of pits in horizontal fillet welding is caused by the thermal decomposition gas of the primer, and in order to improve the pit resistance, it is necessary to promptly release the gas that has entered the molten metal to the outside. is there.

The present inventors cannot expect much about the effect of preventing pit generation by adjusting the welding conditions, and it is also unavoidable that the film thickness of the primer fluctuates to some extent in the on-site construction. As a result of various studies on means for promptly releasing the primer pyrolysis gas to the outside, the present invention based on two-electrode welding in which one pool is formed by using a flux-cored wire of high hydrogen type with a large hydrogen generation amount. It was found that the occurrence of pits in high-speed horizontal fillet welding can be significantly reduced.

FIG. 1 is a sectional view parallel to the welding advancing direction showing an embodiment of the present invention. In FIG. 1, a flux-cored wire having a hydrogen generation amount within a range to be described later is used for both or one of the leading electrode 1 and the trailing electrode 2.
Hydrogen generated in the atmosphere of the arcs 3 and 4 of both electrodes penetrates into the molten metal pool 5, and the hydrogen is excessively supplied together with the stirring effect of the molten metal, whereby bubbles grow and separate,
Promotes ascent rate.

However, in high speed horizontal fillet welding,
Since the solidification rate of the molten metal becomes faster, the above-mentioned bubble separation,
Floating is insufficient and pits are likely to occur. Therefore, in the present invention, in order to delay the solidification of the molten metal and sufficiently release the gas, the amount of heat input is increased by two-electrode welding, and the molten metal forms one pool. Forming this one pool is extremely effective for lengthening the length 6 of the molten metal pool and ensuring the gas release time. The electrodes are arranged so that the distance 7 between the electrodes is 20 to 50 mm in order to stably form one pool state of the molten metal. If the distance between the electrodes is less than 20 mm, it is difficult to stabilize the molten metal pool due to the arc interference of both electrodes, and the length of the molten metal pool is shortened to cause insufficient gas release and pits are generated. On the other hand, when the distance between the electrodes exceeds 50 mm, the slag generated by the preceding electrode starts to solidify and a stable one pool cannot be formed.

The rutile flux-cored wire is used in order to form the molten slag layer 8 to delay the solidification of the molten metal and to improve welding workability such as bead shape / appearance and slag removability. . The wire diameter may be 1.2 to 2.0 mm. In FIG. 1, 9 is a weld metal (bead), 10 is a solidified slag, and 11 is a base material (steel plate).

Further, as shown in FIG. 2 which is a plan view of the welding condition from above, the shift distance 12 between the leading side torches 1A and 1B and the trailing side torches 2A and 2B is set on both sides of the horizontal fillet joint. The effect of improving the pit resistance of the present invention can be further exerted by simultaneous welding with a thickness of 250 mm or less. This is because the solidification of the molten metal on the trailing side is delayed by the welding heat on the leading side after the welding is completed, and the gas can be easily released.

Next, horizontal fillet welding of wash primer-coated steel sheets is conventionally performed with a single electrode at a slow welding speed. This is because the amount of pyrolysis gas generated by the wash primer is remarkably large as compared with the inorganic zinc primer, so that the gas is sufficiently released from the molten metal by performing the low speed welding. The present invention takes advantage of the two-electrode welding performed by forming one pool as described above, and even with a wash primer coated steel plate, the welding speed is 1.0 m / m.
It is possible to prevent the occurrence of pits when it is in or more.

Here, for the flux-cored wire used in the present invention, the amount of diffusible hydrogen of the weld metal measured according to JIS Z3118 standard is 15.0 to 40.0 ml.
The reason for limiting to / 100 g is as follows.

As described above, the present invention enriches the molten metal with hydrogen and utilizes the advantages of two-electrode welding to easily release the gas from the molten metal and improve the pit resistance. The diffusible hydrogen content of the flux-cored wire is 1
If the amount is less than 5.0 ml / 100 g, the amount of hydrogen supplied to the molten metal is too small, so that the growth / desorption rate of bubbles is slower than the solidification rate of the molten metal, and the formation of pits cannot be prevented. On the other hand, when a flux-cored wire with a diffusible hydrogen content of more than 40 ml / 100 g is used, hydrogen is actively released in the arc atmosphere, the arc is rough, and spatter frequently occurs, and the molten metal pool also undergoes a severe boiling phenomenon to form a bead shape Is disturbed. It should be noted that supplying a predetermined amount of hydrogen from the flux-cored wire into the molten metal means that hydrogen compounds such as TiH ₂ , cellulose, organic substances such as wood powder, mica,
It is easy by adding an inorganic compound such as talc to the flux or filling a flux that has absorbed moisture.

Although CO ₂ gas is usually used as the shield gas, when a flux-cored wire having a diffusible hydrogen content of 35 ml / 100 g or more is used, an Ar--CO ₂ -based mixed gas for enhancing arc safety is used. Preferably.

[0018]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples. The fillet joint of the primer-coated steel sheet shown in FIG. 3 was prepared by using the flux-cored wire shown in Table 1 and Table 2,
Horizontal fillet welding was performed under the welding conditions shown in Table 4. In addition,
FIG. 3A shows an inorganic zinc primer steel plate (plate thickness 12.7).
mm, the film thickness of the lower plate 11B is 20 to 30 μm, and the upper plate 11A.
The end surface is 20 to 40 μm, and the same figure (b) shows a wash primer steel plate (plate thickness 12.7 mm, film thickness 20 to 30 μm).
m, the end surface of the upper plate 11A was degassed), and the gap between the upper plate 11A and the lower plate 11B was set to 0.1 mm or less by temporary pressing. In the figure, 13 is a coating film. The test results are summarized in Tables 3 and 4. The conditions other than those shown in Tables 3 and 4 are 12.7t × 75w of JIS SM490B as a steel plate.
* 1200 l (mm) is used, the welding wire diameter is 1.6 mm, the power source is DC-DC, and the wire protrusion length is 2
5 mm, shield gas flow rate 25 liter / m for each electrode
In, the leg length of the bead is 5 to 6 mm. The test results are for a total welding length of 3 m (3 for each test body).

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

Test No. 1-4, 9-11, 13, 14
Is according to the present invention and has good welding workability and pit resistance. No. 5-8, No. 12 is a comparative example.
No. In No. 5, when a low hydrogen type flux-cored wire was used, pits were generated on the second bead side. No. 6 and No. No. 12 had many pits due to insufficient hydrogen supply. No. No. 7 is No. 7 when the supply amount of hydrogen is excessive. In No. 8, when the distance between the electrodes was too large, the arc became unstable, the spatter frequently occurred, and the bead shape was deteriorated, and pits were generated.

[0024]

INDUSTRIAL APPLICABILITY As described above, the present invention significantly improves the pit resistance, which is a problem in accelerating horizontal fillet welding of a primer-coated steel sheet. This can greatly contribute to higher welding efficiency.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an implementation situation of the present invention.

FIG. 2 is a plan view showing an example of a welding situation of the present invention.

FIG. 3 is a schematic view showing the fillet joint shapes of the primer-coated steel sheets used in the examples (a) and (b), respectively.

[Explanation of symbols]

 1, 1A, 1B Leading electrode 2, 2A, 2B Trailing electrode 3 Leading electrode arc 4 Trailing electrode arc 5 Molten metal pool 6 Molten metal pool length 7 Interelectrode distance 8 Molten slag layer 9 Weld metal 10 Welding Slag 11 Base material 11A Upper plate 11B Lower plate 12 Shift distance in case of simultaneous welding on both sides 13 Coating film

Claims (2)

[Claims] 1. In horizontal fillet welding of a primer-coated steel sheet, JI is applied to both or one of the leading electrode and the trailing electrode.
Using a rutile flux-cored wire in which the amount of diffusible hydrogen of the deposited metal measured according to the SZ3118 standard is 15.0 to 40.0 ml / 100 g, the distance between the electrodes is set to 20 to 50 mm, and A high-speed horizontal fillet gas shielded arc welding method, which is characterized in that one pool is formed as a whole. 2. The high-speed horizontal fillet gas shielded arc welding method according to claim 1, wherein both sides of the horizontal fillet joint are welded at the same time with the shift amounts of the leading side and the trailing side set to 0 to 250 mm. .