JPH06646A - One-side gas shielded arc welding method - Google Patents

Abstract

(57) [Summary] [Object] To provide a single-sided gas shielded arc welding method with good slag removability, bead shape, and crack resistance in single-sided welding of a relatively short in-plane temporary tack joint. [Constitution] Metal flux (F conversion value: 0.001 to 0.030%), total amount of slag forming agent; And the flux area S _F occupying the wire cross-sectional area S
Using a flux-cored wire having a ratio S _F / S of 0.06 to 0.28, a receding angle of 5 to 30 ° and a welding current I of 8
00A or less and the ratio I / d of I to the wire diameter d is 220 to
Weld at 450. [Effect] One-sided gas shield welding with excellent slag releasability, front / back bead shape and crack resistance can be achieved, contributing to higher efficiency of one-sided welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas shielded arc welding method for producing a welded structure, and particularly in single-sided welding, a single-sided gas having good welding workability such as crack resistance and slag peeling property and capable of high-efficiency welding. Shield arc welding method.

[0002]

2. Description of the Related Art In recent years, in the construction of various welded structures, the gas shielded arc welding method has been rapidly applied to various fields because the welding efficiency can be improved. Among them, one-sided welding, especially one-sided welding of relatively short joints, is difficult to automate and highly efficient, so single-sided welding by gas shielded arc welding in the semi-automatic low current region is the mainstream, and the efficiency improvement is high. , From the perspective of reducing the total cost of welding, it is currently the biggest issue.

Conventionally, high efficiency single-sided welding has been put into practical use in many fields by a submerged arc welding method centered on long joints. It is rarely used because it is necessary to collect it and it is difficult to make it into a device. On the other hand, as a high-efficiency one-sided welding method using gas shield arc welding, a method using an iron powder-based flux-cored wire (Japanese Patent Laid-Open No. 1-233070) has been proposed, but it produces a small amount of slag and a high current. Due to the high heat input welding, the slag on the bead surface is seized and the slag removability deteriorates, and a large number of man-hours are required for the removal work. In particular, this problem is remarkable in the in-plane temporary attachment one-side welding of 1-pass finishing of a relatively thin plate having a plate thickness of about 16 mm or less.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and in the one-side welding of a relatively short in-plane temporary joint, the drawbacks of the prior art are solved,
An object of the present invention is to provide a high-efficiency one-sided gas shielded arc welding method which has good slag releasability, bead shape on the front and back sides, and crack resistance, and is simple and can be automated in the equipment.

[0005]

The single-sided gas shielded arc welding method according to the present invention has the following features. For the wire weight in the steel shell,
Metal fluoride (F conversion value); 0.001 to 0.030%,
Total amount of slag forming agent containing metal fluoride; 0.80-4.
90% of the required flux is filled and the ratio of the flux area (S _F ) to the wire cross-sectional area (S) S _F /
Using a flux-cored wire with S of 0.06 to 0.28, a receding angle of 5 to 30 ° and a welding current (I) of 800 A
Below and the ratio of welding current (I) to wire diameter (d) I / d
Of 220 to 450 for welding, single-sided gas shielded arc welding method.

[0006]

The inventors of the present invention have completed the present invention by obtaining the following knowledge as a result of various experiments conducted on the bead forming property of single-sided welding, particularly high-efficiency gas shield single-sided welding using a backing material. is there.

Generally, for high-efficiency construction, the joint shape is a groove of in-plane temporary tack without a gap as shown in FIG. 1, but the temporary tack bead is sufficiently melted to form a sound back bead. Therefore, it is necessary to increase the arc force to deepen the penetration.

The arc force is basically proportional to the welding current, and the higher the current, the deeper the penetration and the more easily the back bead is formed, but on the contrary, the high temperature cracking is likely to occur, so the working current is naturally limited. In addition, the receding angle welding is more likely to form the back bead, and thus the current can be reduced, which is advantageous in crack resistance.

Among the types of wire, the solid wire has the strongest arcing force, and the back bead is easily formed.
In CO ₂ welding, there are many spatters, and there is a problem in welding workability such as seizing of slag on the surface bead. From this point, it is preferable to use a flux-cored wire.

However, the conventional flux-cored wire has a weak arc force and a shallow penetration. In order to obtain a good front / back bead by strengthening the arc force at a relatively low current, a single-sided first-layer bead having good slag removability and stableness can be obtained by specifying the composition and composition of the flux-cored wire.

The present invention has been completed based on the above findings, and the reasons why the present invention is configured will be described in detail below. First, the reason for limiting the flux-cored wire in the present invention is to add a metal fluoride to the wire in order to enhance the arc force and form a good back bead. Fluorine (F) in the metal fluoride has a so-called thermal pinch effect of increasing the ionization voltage and contracting the cross section of the arc, and as a result, has the effect of concentrating the arc and deepening the penetration. Metal fluoride is 0.0 in terms of F based on the total weight of the wire
If it is less than 01%, the above effect cannot be obtained and the arc force is weak, so that the temporary bead cannot be completely melted in the in-plane temporary one-side welding, and the back bead is not formed. On the other hand, if it exceeds 0.030%, F becomes excessive, the arc becomes unstable, spatter frequently occurs, and as a result of excessive concentration of the arc, defects such as fusion failure easily occur, which is not preferable. Therefore, the metal fluoride content is 0.001 to 0.030% in terms of F.

Further, the total amount of the slag forming agent containing metal fluoride is regulated for the following reason. That is, in high-efficiency in-plane tack welding, since high current and high heat input welding is performed, slag is seized on the bead surface and slag peeling tends to be significantly deteriorated. This tendency becomes greater as the amount of slag produced becomes smaller. For example, in single-sided welding of a relatively thin plate having a plate thickness of about 10 to 16 mm, slag releasability greatly affects the number of steps in the post-treatment process because it is finished by one-pass welding. In the case of a small amount of solid wire or iron powder-based flux-cored wire, the slag peeling of the surface bead is particularly inferior, so that the welding cost is increased by increasing the number of processes.
If the total amount of the slag agent in the wire is 0.80% or more, the slag is almost entirely covered on the bead surface, and the slag does not seize even in high current / high heat input welding, and therefore the peelability is also good. . On the other hand, when the total amount of the slag agent is more than 4.9%, the slag releasability and the bead appearance are good, but the arc force tends to decrease due to the increase in the arc stabilizing effect of the slag agent, and the back bead is formed. It is hard to be done. Further, when the plate thickness exceeds 16 mm, two-pass welding is performed, but in this case, it is necessary to remove slag for each pass, and defects such as slag entrainment are likely to occur. Therefore, the total amount of slag agent in the wire is limited to 0.8 to 4.9%. The term "slag agent" as used herein means TiO ₂ , S in addition to the above metal fluorides.
The term refers to metal oxides such as iO ₂ , alkali metal oxides such as K and Na, and complex compounds thereof.

Next, the reason for limiting the ratio S _F / S of the flux area (S _F ) to the wire cross-sectional area (S) to 0.06 to 0.28 is as follows. That is, current limitation is required from the viewpoint of preventing hot cracking, but in order to obtain a good single-sided first layer bead with a relatively low current, it is necessary to strengthen the arc force of the wire itself. To achieve this, the smaller the flux area in the wire cross section, in other words, the larger the skin area and the closer to the solid wire, the stronger the arc force at the same current. However, when S _F / S is less than 0.06, the arc force is strong and the formation of the back bead is sufficient, but the absolute amount of the filling flux is small, so that the predetermined weld metal performance cannot be obtained. On the other hand, if S _F / S exceeds 0.28, the outer skin area becomes smaller and the current density increases, so the droplets become finer and the droplet transferability becomes better, but the arc force becomes weaker and temporary. The attached beads cannot be melted and a stable back bead is not formed. Thus the ratio S _F / S flux area occupied in the wire cross-sectional area (S) (S _F) is limited as 0.06 to 0.28.

The above is the essential constitution of the flux-cored wire used in the present invention. As long as these requirements are satisfied, the components usually added to the flux-cored wire, for example, S.
A deoxidizing agent such as i, Ti and Al, an alloying agent such as Mo and Ni, and iron powder can be added as necessary. The cross-sectional shape of the wire is not limited at all, but in view of automation and robotization, the seamless seamless type shown in FIG. 2d, which has good wire feeding property and straightness, is preferable.

Next, the reasons for limiting the welding conditions will be described. In order to sufficiently melt the in-plane temporary bead and form a stable back bead, the angle of the torch is important together with the electric current described later. In the present invention, the torch angle is 5 to 30.
The receding angle of ° was set in order to sufficiently melt the in-plane temporary bead to form a stable back bead. That is, when the torch angle is changed at the same current, the penetration becomes deeper as the advancing angle, the vertical angle, and the receding angle increase, and the in-plane tacky bead is melted to easily form the back bead. When the torch angle is a forward angle or a retreat angle of up to 5 °, the penetration is not sufficient, so the temporary bead cannot be completely melted at the same current and a stable back bead cannot be formed. That is, a higher current is required to form the back bead under this condition, and the crack resistance deteriorates. On the other hand, welding with a receding angle of more than 30 ° is not preferable because the spatter increases and the bead tends to be convex. Therefore, the torch angle is set to a receding angle of 5 to 30 °.

In order to melt the temporary bead to form the back bead, it is basically necessary to increase the current. However, if one-sided welding is performed with a high current, high temperature cracks are likely to occur and spatter and fumes are increased, which is naturally limited.
It was revealed from experiments that the current for forming a good back bead varies depending on the wire diameter, and that there is an appropriate current range depending on the wire diameter. That is, NaF 0.6% (0.
Slag forming agent containing 3.5% of TiO ₂ as a main component and containing S _F /
Prototype a flux-cored wire of 1.2 to 3.2 mmφ having a sectional shape of FIG.
One-sided one-pass welding was performed under the following welding conditions, and the bead formability and crack resistance were investigated.

<Welding conditions> Welding voltage; Appropriate welding speed; 10 to 35 cm / min (changed according to welding current to keep the welding cross-section area constant) Shielding gas; 100% CO ₂ <Steel plate used> Steel type; SM-50B, plate thickness; 14 mm, groove shape; root gap G = 0 in FIG. 1, groove angle θ
= 50 ° <Backing material> Ceramic backing material

From FIG. 3, when the welding current (I) exceeds 800 A, hot cracking occurs regardless of the wire diameter. When the ratio I / d of the welding current (I) to the wire diameter (d) is 220 or less, the arc force is weak and a stable back bead is not formed. On the other hand, when the I / d exceeds 450, the back bead formation is good, but hot cracking tends to occur. Therefore, the welding current (I) is 800 A or less and the I / d is 220 to 450.
It is necessary to control and weld.

Although the flux-cored wire and welding conditions in the present invention have been described above, the type of backing material in the single-sided gas shielded arc welding method of the present invention is not particularly limited. For example, solid flux type, ceramic type and Any glass tape backing material can be used. Further, in order to improve the welding efficiency, an appropriate amount of a filler such as a cut wire may be sprayed in the groove for welding. Further, the type of shield gas is mainly CO ₂ gas, but an Ar / He based mixed gas may be used in order to reduce sputtering.

[0020]

EXAMPLES Next, the present invention will be described more specifically based on examples. Table 1 shows the composition of the flux-cored wire and the single-sided welding conditions. Figure 2 for all flux cored wires
(D) of the sectional shape. Using these wires, single-sided welding was performed under the welding conditions shown in Table 1, and the stability of the back bead, the slag peeling property of the front bead, and the presence or absence of cracks were investigated. The results are shown in Table 2. If the plate is thick, 2
Although the finish was a pass, the welding conditions were the same for one pass and two passes.

Other welding conditions are as follows. Welding method; downward automatic welding, shield gas; CO ₂ (25L /
min), welding voltage; appropriate, steel plate used; SM-50B, plate thickness 9 to 25 mm x width 250 mm x length 600 mm (2 with restraint plate
Restraint in place), groove shape; θ = 50 ° G = 0mm in Fig. 1, 2 in-plane temporary beads (bead height approx. 6mm, length 50m)
m), backing material; ceramic backing material

No. 1-No. 10 is an example of the present invention,
In each case, a good back bead was formed, and the slag removability, spatter amount, and crack resistance of the front bead were also good. On the other hand, No. No. 11 has a small flux area ratio of the wire cross section and does not contain a predetermined flux, so that there are many spatters. In No. 12, the amount of F was too large and spatter frequently occurred. No. No. 13 had a small amount of slag agent, and the slag was seized especially on the surface beads, and the releasability was remarkably deteriorated.
Since No. 14 has a large amount of slag and a large flux area ratio, the in-plane temporary bead cannot be melted and the stability of the back bead is poor. In addition, No. 15, No. 16 and No. 16 No. 20 has a torch angle outside the scope of the present invention. 15 and N
o. No. 20 has no back bead formed, and No. 20 No. 16 had a large amount of spatter and the bead had a convex shape. No. in which the ratio of the welding current to the wire diameter (I / d) exceeds the present invention. No. 17 was cracked and was less than the present invention. No back bead was formed in No. 18. Furthermore, No. Since No. 19 had a high welding current, there were many spatters and cracks occurred.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

As described in detail above, the present invention overcomes the drawbacks of the prior art in single-sided welding of relatively short in-plane temporary joints, and provides slag releasability, front / back bead shapes, and crack resistance. The present invention provides a single-sided gas shielded arc welding method that has good performance and can be automated, and can greatly contribute to the improvement of efficiency of single-sided welding in the future.

[Brief description of drawings]

FIG. 1 is a view showing an example of a groove shape.

FIG. 2 is a view showing a cross-sectional shape of a flux-cored wire.

FIG. 3 is an experimental diagram showing the effects of wire diameter and welding current on bead formation in single-sided one-pass welding.

Claims (1)

[Claims] 1. A metal fluoride (F-converted value); 0.001 to 0.030%, and a total amount of a slag-forming agent containing a metal fluoride; 0.80 to 4. 90%
The flux was loaded as an essential and using the flux-cored wire ratio S _F / S flux area occupied in the wire cross-sectional area (S) (S _F) is 0.06 to 0.28, receding angle of 5 -30 °, welding current (I) is 800 A or less, and ratio I / d of welding current (I) and wire diameter (d) is 2
A single-sided gas shielded arc welding method characterized by welding at 20 to 450.