JPH07314176A - Seamless flux-cored wire for gas shield arc welding - Google Patents

Abstract

(57) [Abstract] [Purpose] In a seamless type cross-section structure that has various advantages in welding performance such as pit resistance, cold crack resistance, wire rust resistance, weld tip wear resistance, and wire feedability. Provided is a flux-cored wire which has a high wire melting rate and high weldability even when a low oxygen content outer coating material is used. A seamless flux-cored wire containing iron oxide powder having a grain size of 100 μm or less in an amount of 0.01 to 0.20% by weight based on the total weight of the outer shell in a recess on the inner surface of the outer shell that is continuously provided in the longitudinal direction of the wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux-cored wire for gas shielded arc welding used for automatic or semi-automatic welding of steel structures.

[0002]

2. Description of the Related Art In recent years, in the production of steel structures such as shipbuilding, steel frames and bridges, the demand for higher welding efficiency and labor saving has been further strengthened, and along with this, a small diameter centering on 1.0 to 2.0 mm. The flux-cored wire for gas shielded arc welding (hereinafter referred to as "flux-cored wire") is being used in an increased amount due to its advantages such as good welding workability and high efficiency weldability. As shown in FIG. 4, a cross-sectional structure of a conventionally used flux-cored wire is a butt type (a) or (b) having an opening 2 in the outer skin 1 and a seamless type (c) having no opening. , (D). In the figure, 3 is a flux and 4 is a welded portion. Butt wire type flux-cored wire is supplied with flux at the stage of forming a relatively small size steel strip into a tubular body,
Finished with both ends abutting. On the other hand, a seamless flux-cored wire is disclosed, for example, in Japanese Patent Laid-Open No. 61-1.
As shown in Japanese Patent No. 5930, a steel pipe prepared in advance is used to fill the flux from the end opening thereof, or a steel strip of a relatively large size is used as seen in Japanese Patent Laid-Open No. 234795/60, Similar to a butt type flux-cored wire, it is manufactured by welding and welding the seams at both ends after forming and supplying the flux.

By the way, comparing the effects of the difference in the cross-sectional structure of the two on the welding performance, the butt type flux-cored wire absorbs the flux through the opening of the outer skin, and the welding of pits, blow holes, low temperature cracks, etc. Defects are likely to occur. In addition, there is a problem that the straightness of the wire tip, which is important when used for robot welding, and the wire feeding property in a long length are inferior because of a wire tendency. On the other hand, since seamless flux-cored wire can be subjected to dehydrogenation annealing and copper plating on the wire surface in the manufacturing process, pit resistance, cold crack resistance, wire rust resistance, weld tip wear resistance It has excellent wire feedability.

However, when the seamless flux-cored wire is used at the same current, the wire melting rate tends to be slightly slower than that of the butt-type flux-cored wire, and there is a demand for improvement in terms of welding efficiency.
On the other hand, Japanese Laid-Open Patent Publication No. 59-150695 proposes a seamless flux-cored wire in which the melting rate of the wire is increased and a high weldability is obtained by using a sheath material having a high oxygen content. With continuous casting in the direction, strong deoxidized steel with a low oxygen content has come to be generally used as a shell material for welding materials. JP-A-60-223697 discloses a seamless flux-cored wire in which a scale layer is formed on the inner surface of the outer cover, Japanese Patent Publication No.
Japanese Patent No. 31992 proposes seamless flux-cored wires in which the inner surface roughness of a steel outer shell is specified, but the high weldability that is the object of the present invention cannot be obtained.

[0005]

SUMMARY OF THE INVENTION Therefore, in the present invention, in the seamless type cross-section structure having various advantages in the above-mentioned welding performance, the wire melting rate is high and the wire melting rate is high even when the outer sheath material having a low oxygen content is used. It is an object of the present invention to provide a flux-cored wire having weldability.

[0006]

That is, the gist of the present invention is to provide a flux-cored wire for gas shielded arc welding in which a steel outer sheath is filled with flux, and the inner surface of the outer sheath portion continuously provided in the longitudinal direction of the wire. A seamless flux-cored wire for gas shield arc welding, characterized in that the recess contains 0.01 to 0.20% by weight of iron oxide powder having a particle size of 100 μm or less based on the total weight of the outer shell.

[0007]

The present inventors have conducted various studies in order to increase the melting rate of the seamless flux-cored wire manufactured by using the outer sheath material having a low oxygen content to obtain a high weldability. As a result, the effect of increasing the flux filling rate, filling the flux containing a large amount of iron powder to reduce the thickness of the outer skin portion, or using an alloy steel outer skin having a high Si and Mn content is very effective. Turned out to be big. However, thinning of the outer skin causes problems in production due to frequent disconnection during the wire drawing process in the small diameter stage.Also, alloy steel outer skin has a large amount of work hardening, and in particular TiO ₂ , SiO ₂ , Al ₂ O
_In a flux-cored wire containing a large amount of high-melting point oxides such as ₃ , MgO and ZrO ₂ as a slag-forming agent, a so-called unmelted flux sticking out phenomenon occurs in which the outer shell portion melts earlier than the filling flux during welding. It was found that there is a problem in welding workability, such as frequent occurrence of spatter and slag inclusion defects.

[0008] Next, assuming that the melting state of the butt-type flux-cored wire and the seamless flux-cored wire may affect the wire melting rate, a flux-cored wire having the same composition and the same filling rate was manufactured as a trial. Then, the state of wire fusion was observed in detail with a high-speed video camera. FIG. 5 is a schematic view of the molten state of the wire tip observed by a high-speed video camera.
In the case of a butt type flux-cored wire, the droplet 5 at the tip of the wire does not grow so much and the number of droplets released per unit time is large. On the other hand, in the case of the seamless flux-cored wire, it was found that the droplet grows relatively large and the number of detachments becomes small.

Further, it was possible to observe that there was a clear difference in the manner of detachment of the droplets at the tips of the two wires. Figure 5
(A), (b), (c), (d) in order to move to orbit the tip of the wire to grow to a certain size,
(E) As shown in the figure, new droplets are formed after the separated droplets 6 are formed, and growth starts again. However, in the case of the butt type flux-cored wire, it grows greatly when it reaches the opening of the outer skin. Most of the wires will come off without doing this, whereas in the case of a seamless flux-cored wire having no opening in the outer skin, the winding distance and the time until it comes off are long. In addition, when the melting rate and the welding rate of both wires were compared, it was shown that the butt-type flux-cored wire was faster in spite of the same composition and the same flux filling rate. That is, by suppressing the growth of droplets at the wire tip and accelerating the detachment of the droplet, the wire melting speed is increased and high weldability is obtained.

From these investigation results, in order to improve the wire melting speed and the welding speed, it is necessary to provide a means for smoothly separating the droplets, and the opening of the outer skin of the butt type flux cored wire is extremely effective. I came to the conclusion that I was working for. However, the butt-type flux-cored wire having an opening in the outer skin has the above-mentioned problems such as moisture absorption of flux, wire straightness, and wire feedability. From such a viewpoint, the inventors of the present invention conducted a trial wire test including a manufacturing method in order to develop a seamless flux-cored wire having the respective advantages of the butt-type flux-cored wire and the seamless flux-cored wire. The object is achieved by obtaining a constitution of the present invention in which a concave portion is continuously provided in the inner surface of the portion in the longitudinal direction of the wire, and a minute amount of fine iron oxide powder is contained in the concave portion.

FIG. 1 shows a sectional structure of a seamless flux-cored wire according to the present invention. The recesses 7 provided on the inner surface of the outer cover 1 are continuous in the longitudinal direction of the wire. In the figure, (a) shows one recess and (b) shows two recesses. Iron oxide powder 8 is embedded in this recess
Is in contact with the skin metal.

In the present invention, the provision of the concave portion on the inner surface of the outer skin portion means that the iron skin powder is uniformly contained in the longitudinal direction of the wire, and a thin portion is formed on the outer skin portion and the melting of the portion is preceded. This is because the molten state is the same as that of the flux-cored wire having the butt type cross-sectional structure. That is, the seamless flux-cored wire of the present invention has the original advantages such as the moisture absorption resistance of the seamless flux-cored wire having no opening until immediately before melting, and after entering the molten state, the opening of the butt-type flux-cored wire This is so that the advantages of the molten state brought about by the parts can be utilized.

The shape of the concave portion on the inner surface of the outer skin is not particularly limited as long as it is a size capable of containing a predetermined amount of iron oxide powder. From the viewpoint of productivity such as wire drawability, the depth of the recess is preferably about 10 to 60% of the thickness of the outer skin. If the width of the recess is too small, the pre-melting of the recess is unlikely to occur. On the contrary, if the width is too wide, even if a predetermined amount of iron oxide is contained in contact with the outer skin, molten metal that is effective for detaching the droplets is formed. Since the supply of oxygen is insufficient and the wire melting rate is not improved, it is preferably in the range of 0.05 to 0.3 mm.

Further, if the iron oxide powder is contained in the recesses, the iron oxide is melted in a state of being in contact with the outer skin, so that the amount of oxygen in the droplets formed at the tip of the wire is increased and the surface tension is reduced to reduce the droplets. This is to facilitate the departure of the. Here, the particle size of the iron oxide powder contained in the recess is 100 μm.
The limitation to fine particles of m or less means that iron oxide powder has a relatively small specific gravity, and in the case of coarse particles, large concave portions must be provided, which causes a problem in productivity and facilitates melting of iron oxide itself. This is because it is easy to supply oxygen to the droplets. 1
When a coarse iron oxide powder exceeding 00 μm is contained, the iron oxide is delayed in melting and oxygen is not supplied smoothly to the droplets, the arc state becomes unstable and spatter loss results in high weldability. I can't.

Further, limiting the content of the iron oxide powder to 0.01 to 0.20% by weight based on the total weight of the outer shell has a bad influence on the workability of welding and the mechanical properties of the weld metal in this range. This is because the above effect due to iron oxide is obtained. If the content of iron oxide powder is less than 0.01% by weight, the molten state is not improved and the effect of improving the amount of wire fusion is small. On the other hand, when the content exceeds 0.20% by weight, the viscosity of the molten metal becomes too small. For example, in the flux-cored wire for all-position welding of TiO ₂ system, metal sagging occurs in the vertical welding position and the amount of oxygen of the weld metal is increased. Weldability deteriorates, such as increased and stable low temperature impact toughness is not obtained.
Regarding the types of iron oxide, FeO, Fe ₂ O ₃ , Fe ₃ O ₄
There is no particular limitation as long as it has as a main component. For example, hematite or mill scale having a controlled particle size can be used.

By providing a recess on the inner surface of the outer skin continuously in the longitudinal direction of the wire to contain iron oxide, the effect of the recess and the iron oxide can be sufficiently exerted over the entire length of the wire,
This is because it is possible to obtain a high weldability by eliminating the arc during welding and the fluctuation of the wire melting state and increasing the wire melting rate under good welding workability. JP-A-60-223697 proposes that the arc can be stabilized and the amount of spatter generated can be reduced by forming a scale layer on the entire inner surface of the outer skin portion. However, the seamless flux-cored wire of the present invention is This is a technique in which a concave portion is provided on the inner surface of the outer skin portion and iron oxide powder is contained therein to increase the wire melting rate to obtain a high weldability by the synergistic effect.

FIG. 2 shows an example of an apparatus for manufacturing the seamless flux-cored wire of the present invention. What is indicated by an arrow in FIG. 2 is the state of the material at that location of the device. In FIG. 2, first, in the strip steel 10 supplied from the strip steel supply device 9, a recess 7 of a predetermined size is continuously provided in the longitudinal direction on the surface of the strip steel to be the inner surface of the outer skin by the recess forming device 11. Cutting is the easiest method to form the recess,
Alternatively, it may be plastically deformed by being strongly compressed with a pointed indenter. Next, the iron oxide powder 8 is filled in the recesses in a flat plate shape by the iron oxide supply apparatus 12, and then the flux supply apparatus 1 is formed in a U-shaped shape by the molding apparatus 13.
Flux 3 is supplied from 4.

After that, both ends of the steel strip are abutted to each other to form a tubular body, and the abutted portion is welded to the seam portion by a welding device 15 such as high frequency, TIG, or laser. Then, the diameter is reduced by the rolling device 16 until the internal flux does not move, and the bobbin 17 is wound. After that, the wire is drawn to a predetermined size for finishing, but if necessary, an intermediate annealing treatment for softening or dehydrogenation or a copper plating treatment is performed in the drawing process.

When the seamless flux-cored wire of the present invention is manufactured using a steel pipe, the seam portion is welded and rolled by the manufacturing apparatus shown in FIG. 2 without supplying the flux, and the outer skin portion as shown in FIG. A steel pipe having a cross-sectional structure in which iron oxide is densely contained on the inner surface is obtained, and is disclosed in JP-A-59-3589.
After filling the flux from the end opening of the steel pipe by the vibration filling method as disclosed in Japanese Patent No. 8, the wire is drawn to a small diameter and finished. The seamless flux-cored wire of the present invention exerts its effect well in the TiO ₂ composition which is frequently used for all-position welding or fillet welding of mild steel, high-strength steel, low-temperature steel, etc. Even in a composition system containing a large amount of metal powder such as, the effect of improving the wire melting rate is recognized. The flux filling rate is preferably in the range of 8 to 25% by weight in terms of wire melting rate and productivity.

[0020]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples. Using the steel strip shown in Table 1 and the TiO ₂ -based flux shown in Table 2, a seamless flux-cored wire having a finished size of 1.2 mm was manufactured by a manufacturing apparatus schematically shown in FIG. Flux filling rate is 13.5% by weight,
The content of the iron oxide powder was adjusted by changing the shape of the recess on the inner surface of the outer skin in the wire cross section.

[0021]

[Table 1]

[0022]

[Table 2]

After welding the seam portion by high frequency induction heating,
Subsequently, cold rolling, cassette roller, and wire drawing with a drawing die were performed. In this wire drawing process, intermediate annealing (700 ° C.) and copper plating treatment were performed twice for dehydrogenation and softening. Table 3 shows the welding test method, and Table 4 shows the welding workability evaluation by semi-automatic welding and the welding speed measurement value (average value of three times) by automatic welding, which are the results of the welding test. The wire symbol W8 is shown in FIG. 4 (a) manufactured using the steel strip H2 shown in Table 1.
It is a conventional butt type flux cored wire shown in FIG.

[0024]

[Table 3]

[0025]

[Table 4]

The seamless flux-cored wires W1, W2, W3 according to the present invention have no manufacturing problems, have good welding workability, and have a welding speed equal to or higher than that of the butt type flux-cored wire (W8). ing. On the other hand, W4 to W8 are comparative examples.

W4 is a case where the content of the iron oxide powder contained in the recess is too small, and the effect of improving the welding speed is small.
In W5, when the iron oxide particle size was too coarse, the wire melting rate increased, but the arc became unstable, and the deposition rate rather decreased due to spatter loss. W6 was a case where the content of iron oxide powder was too large, the arc state was unstable, coarse particles of spatter were generated, and the metal was liable to droop during vertical downward welding. W7 is a conventional seamless flux-cored wire having no recess on the inner surface of the outer skin, and has a slow welding speed. W8 has good welding workability and welding speed, but the presence of the openings caused the flux to absorb moisture, resulting in pits in horizontal fillet welding.

[0028]

As described above, according to the present invention, when the outer skin material having a low oxygen content is used in the seamless type sectional structure having various advantages such as the moisture absorption resistance of the flux, the straightness of the wire, and the wire feeding property. However, the present invention provides a flux-cored wire for gas shielded arc welding, which has a high wire melting rate and high weldability.

[Brief description of drawings]

1A and 1B are views showing an example of a cross-sectional structure of a seamless flux-cored wire according to the present invention.

FIG. 2 is a conceptual diagram of a seamless flux-cored wire manufacturing apparatus of the present invention.

FIG. 3 is an example of an outer coat for producing the seamless flux-cored wire of the present invention.

4A to 4D are views showing examples of cross-sectional structures of flux-cored wires.

FIG. 5 is a diagram for explaining a molten state of the flux-cored wire, in which (a) to (e) sequentially show changes in state over time.

[Explanation of symbols]

 1 Outer Skin 2 Opening 3 Flux 4 Weld 5 Droplet 6 at the tip of wire 6 Dropped droplet 7 Recess on inner surface of outer skin 8 Iron oxide powder 9 Steel strip feeder 10 Steel strip 11 Recess forming device 12 Iron oxide feeder 13 Forming device 14 Flux supply device 15 Welding device 16 Rolling device 17 Bobbin

Claims (1)

[Claims] 1. A flux-cored wire for gas shielded arc welding, comprising a steel outer shell filled with flux, wherein iron oxide powder having a grain size of 100 μm or less is formed in a recess on the inner surface of the outer shell which is continuously provided in the longitudinal direction of the wire. A seamless flux-cored wire for gas shielded arc welding, characterized by containing 0.01 to 0.20% by weight based on the total weight of the outer skin.