JP2670848B2 - Composite wire for gas shielded arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a gas shielded arc welding composite wire used for welding a steel structure, in which the arc is stable particularly in a small current region and the bead shape is good. Small leg length (3.0-4.0m
m) The present invention relates to a composite wire for gas shield arc welding, which gives a fillet weld metal.

[Conventional technology]

In recent years, in welding construction of various structures such as shipbuilding and bridges, the use of gas shield arc welding, which is advantageous for promoting efficiency improvement and labor saving of welding construction, is rapidly increasing. In particular, metal powder-based composite wires are characterized by a higher amount of welding and less slag generation than general titania-based composite wires, and are often used for butt welding and fillet welding of steel materials. The amount tends to increase more and more.

Furthermore, in recent years, a wide variety of welded structures, especially in the shipbuilding industry, even for plate thicknesses of about 3.2 mm to 6 mm that are often used for passenger ships, semi-automatic welding, small leg length with good bead shape 3.
There has been an increasing demand for the development of composite wires that can obtain fillet beads of 0 to 4.0 mm.

[Problems to be Solved by the Invention] By the way, it has been difficult for the conventional composite wire to meet these needs. That is, in order to obtain a bead with a long leg length of 3.0 to 4.0 mm by semi-automatic welding using a conventional wire, welding had to be done with a small current. However, when performing welding with a small current, for example, when using a 1.2 mmφ composite wire, the stability of the arc becomes extremely poor at 170 A or less, the beads are likely to be uneven, and problems such as undercut occur. there were. The wire diameter is 0.8mm
There is also a method of welding by increasing the current density with a small current by reducing the diameter to φ, 0.9 mm φ, 1.0 mm φ, but the stability of the arc is not improved so much and it is not possible to obtain a fillet bead with a small leg length by semi-automatic welding. The reality is that it has not been realized.

As a means for solving such a problem, for example, a technique described in JP-A-61-94175 is known. This technology aims to stabilize the arc in the high current region and improves the bead shape.However, the arc in the small current region is stable and the bead shape is good. I am not completely satisfied.

The present invention has been made in view of the above problems, and provides a composite wire for gas shield arc welding that improves arc stability at a small current and provides a small leg length fillet weld metal having a good bead shape.

[Means for solving the problem]

The composite wire of the present invention is composed of iron powder: 54 to 85% (same as below by weight%), deoxidizer: 10 to 45%, iron sulfide: 0.1 to 0.8%, carboxymethyl cellulose as a fixing agent (hereinafter abbreviated as CMC). ): 8 to 25% of the total weight of the wire is filled with a flux containing 0.3 to 6.0% in the steel shell,
Moreover, the carbon content in all the wires is limited to 0.09% or less.

[Action]

The present inventors observed various arc phenomena with a high-speed camera for the arc state at a small current, which is the greatest difficulty of the metal powder-based flux-cored wire, and made various studies. As a result, it was revealed that the arc instability factors were caused by the following two points: a. Droplet coarsening and b. Droplet explosion.

Therefore, in order to improve the transferability of the arc in the small current region, (1) stabilize the arc to transfer droplets into fine particles, and (2) suppress the explosion of CO (CO ₂ ) gas. We have found that measures such as reducing the amount of carbon in the wire, (3) making the arc as short as possible and stabilizing the arc by increasing the number of short circuits are effective.

 The present invention will be described in detail below based on these findings.

First, using the basic flux shown in Table 1 with various fluxes of iron sulfide and CMC, a metal powder wire was experimentally manufactured and tested. In this case, a 1.2 mmφ metal powder wire was prepared by varying the content of iron sulfide in the flux in the range of 0.1 to 0.8% by weight and CMC in the range of 0.3 to 0.6% by weight, and filling the outer surface of the mild steel with 10%.

Using this wire, the target leg length under the welding conditions shown below
Horizontal fillet welding was performed by semi-automatic welding with 3.0 to 4.0 mm, and the arc state and bead shape were evaluated.

Welding conditions Polarity: DC wire Welding current: 150A Welding voltage: 20V Wire protruding length: 10 to 15mm Shielding gas: CO ₂ 20l / min Steel plate: SM-41B material Thickness 6 ^t × 50 ^W × 500 ^L (mm) ( T type fillet) FIG. 1 shows the relationship between the iron sulfide content (%) in the flux, the arc state and the bead shape, and FIG. 2 shows the relationship between the iron sulfide content (%) and the number of short circuits.

That is, it was found that the addition of iron sulfide in an amount of 0.1% or more markedly increased the number of short circuits. It was confirmed that the large number of times per unit time means that the droplets become small, and that the arc at a small current is stable and a good fillet bead can be obtained. However, it was found that when the content exceeds 0.8%, this value shows a sharp decrease. That is, the droplets gradually become coarse and do not move smoothly to the base material side, resulting in a defective bead shape. From this, it was found that the appropriate range of iron sulfide is 0.1 to 0.8%.

Next, regarding CMC, if the content is less than 0.3%, the flux does not stick, so the dispersion of the filling flux is large, and the arc stability deteriorates. On the other hand, if it exceeds 6.0%, the arc becomes excessively strong and the bead shape is deteriorated, so that an undercut is likely to occur. That is, the range of CMC is 0.3-
It turned out that 6.0% is appropriate.

Further, in the arc state sputter amount, the bead shape is deteriorated as the carbon content in all the wires is increased, and the sputter amount is rapidly increased. That is, the carbon content in all wires is 0.
It has been clarified that if the content is suppressed to 09% or less, the arc state can be stabilized and the amount of spatter can be effectively suppressed.

To improve the transferability of the arc in the small current range of the metal powder flux-cored wire, a. Transfer droplets into fine particles, b. Reduce the amount of carbon in the wire, c. Shorten the arc length and reduce the number of short circuits. I said that it is essential to increase,
If any of these conditions are lacking, the purpose of improving the arc state and bead shape in the small current region cannot be achieved.

Therefore, as a feature of the present invention, it is necessary to satisfy all of the above-mentioned factors, whereby the arc state and bead shape of the metal powder flux-cored wire can be made good. Furthermore, in order to sufficiently achieve the object of the present invention, the following component restrictions are necessary.

Iron powder accounts for 54-85% of the total flux.
Set in the range of weight%. The reason is that the content of iron powder is
If it is less than 54%, the effect of improving the welding efficiency, which is the characteristic of the metal powder-based flux-cored wire, cannot be sufficiently achieved,
On the other hand, when it exceeds 85% by weight, components such as deoxidizer and arc stabilizer are insufficient, and defects such as pits and blowholes occur, or the arc becomes unstable, and the bead shape is deteriorated and spattering is prevented. It is not preferable because the number of occurrences increases.

The deoxidizer is 10 to 45 as a proportion of the total flux.
% By weight. The reason is that if the content of the deoxidizing agent is less than 10%, not only deoxidation becomes insufficient and the X-ray performance is significantly lowered, but also the fillet bead shape is deteriorated. On the other hand, if it exceeds 45%, the toughness and crack resistance of the weld metal are reduced. Further, the droplets become coarse, the arc becomes unstable, and many obstacles such as frequent occurrence of large-sized spatters, convex welding bead shape, and reduction of appropriate welding condition range appear.

Here, the deoxidizer also acts to remove oxygen by combining with oxygen in the weld metal, so specifically, Mn, Si, Al, Mg, T
Examples thereof include metal powders such as i and Zr, or alloys of these with iron. These may be used alone or in combination of two or more.

Iron sulfide accounts for 0.1-0.1% of the total flux.
0.8% The reason for this is that if the content of iron sulfide is less than 0.1%, the length of the arc becomes longer due to the coarsening of the droplets that migrate from the arc tip, and the stability of the arc deteriorates significantly, The weld bead has a convex shape because of poor conformability. On the other hand, if it exceeds 0.8%, the short-circuit time becomes extremely long and the weld metal intermittently solidifies, resulting in humping beads or forming a low melting point compound during solidification, which not only lowers the crack resistance but also It is not preferable because the migration of droplets is significantly reduced.

CMC is 0.3 to 6.0 as a percentage of the total flux.
%. The reason for this is that if it is less than 0.3%, the flux does not solidify and granulate, and therefore the flux does not stick, so the dispersion of the filling flux is large, and the welding workability, in particular the arc stability, becomes a problem. While 6.0
When the content exceeds%, the wire filled with the metal powder system becomes a gouging state because the arc becomes stronger than necessary due to the effect of C, which is a component of CMC, so that the amount of spatter frequently occurs and the bead-shaped unevenness becomes severe. Further, a large amount of C is retained in the weld metal, and the mechanical performance of the weld metal deteriorates.

Further, the filling rate is appropriately in the range of 8 to 25% with respect to the total weight of the wire. The reason is that if it is less than 8%, the arc becomes unstable and the familiarity with the base material deteriorates, so that the appearance of the fillet beads is impaired. On the other hand, if it exceeds 25%, the outer portion of the wire becomes too thin, which may cause problems such as disconnection during wire production, particularly during wire drawing, and may cause instability during welding work. Therefore, the flux filling rate is 25
% Or less.

The carbon content is 0.09% or less of the total wire. The reason is that as the carbon content increases, the directionality of the arc becomes unstable, the welding beads become uneven, and the beads become uneven, and the amount of spatter also increases. That is, if the carbon content in all the wires is suppressed to 0.09% or less, the arc state and the amount of spatter can be effectively suppressed.

By the way, the target steel types for which the composite wire of the present invention is used are mainly mild steel and high-strength steel, but are not particularly limited to these and may be applied to welding of low-alloy steel and high-strength steel. You can also In addition to carbon dioxide gas as a shield gas, it is also applicable to the case of mixing carbon dioxide gas with oxygen gas or argon gas.

The cross-sectional structure of the wire may be either an open seam wire having a seam on the outer circumference or a closed seam wire having no seam on the outer circumference, but a seamless wire considering automation and robotization. Is desirable.

〔Example〕

 Next, the present invention will be described more specifically with reference to examples.

Table 2 shows the flux composition of the composite wire of the present invention and the composite wire prototyped for comparison, and Table 3 shows the welding test results when these wires were used for welding.

In Table 2, wires No. 1 to No. 11 are examples of the present invention, and No.
12 to No. 19 are comparative examples. All of the composite wires were made of mild steel, filled with flux while vibrating the electric resistance welded pipe, annealed at 650 ° C during the drawing process, and the wire surface was Cu-plated to a diameter of 1.2 mm. The test is
The method described in the above (Operation section) was performed to evaluate variations in arc state, bead shape, mechanical properties of deposited metal, and filling rate.

As a result, since the wires No. 1 to No. 11 were within the range of the present invention, the arc was stable and a good bead could be obtained even with a small current.

On the other hand, No. 12 and No. 13 are examples in which the amount of iron powder is outside the range of the present invention, and No. 12 in which the amount of iron powder is insufficient deteriorates the arc state and the bead shape. No.13, which has an excessive amount of iron powder,
The absolute amounts of other components such as deoxidizers tend to be insufficient, and defects such as the toughness of the deposited metal, pits and blowholes occur.
In No. 14, the amount of iron sulfide was too small, so the arc stability was poor, spatter increased, and the bead appearance was poor. N
In o.15, since the amounts of iron sulfide, iron powder, deoxidizer, and flux filling rate are outside the scope of the present invention, arc state, bead shape,
The performance of the deposited metal was poor.

In No. 16, the flux filling rate was low, so the arc state and bead shape deteriorated. No. 17 has too much iron sulfide,
At the same time that the stability of the arc was significantly deteriorated, the number of short circuits was reduced, and a tendency of a medium convex bead was observed.

In No. 18, the amount of carboxymethyl cellulose was too large, so the arc state became excessively strong, and the familiarity of the base material deteriorated and the bead appearance became poor. In No. 19, the amount of carboxymethyl cellulose was too small, so that the filling rate was greatly varied, the arc was unstable, and the bead surface was uneven, and a good weld bead was not obtained.

(Effect of the invention) As described above, the composite wire for gas shielded arc welding of the present invention has a stable arc at a small current, and enables a bead shape with a small leg length fillet weld metal.
The practicality of this type of wire can be dramatically improved. It is also possible to fully cope with automation of welding, robotization, and high efficiency.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of iron sulfide in the flux, the arc state and the bead shape. FIG. 2 is a graph showing the relationship between the iron sulfide content and the number of short circuits.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeru Kurihara 5-10-1 Fuchinobe, Sagamihara-shi, Kanagawa Inside the Second Research Laboratory, Nippon Steel Corporation (56) Reference JP-A-62-199295 (JP, A) ) JP-A-49-39535 (JP, A)

Claims (1)

(57) [Claims] 1. Iron powder: 54 to 85% (weight%: same below), deoxidizer: 10 to 45%, iron sulfide: 0.1 to 0.8%, carboxymethylcellulose: 0.3 to 6.0% as a fixing agent, respectively. A composite wire for gas shield arc welding, characterized in that the steel shell is filled with 8 to 25% of the total amount of the flux with respect to the total weight of the wire, and the carbon content of the total wire is limited to 0.09% or less.