JP2624560B2 - Flux-cored wire for gas shielded arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for construction of welded structures such as shipbuilding and steel frames, and is particularly a gas shielded arc having a stable arc and good welding workability. The present invention relates to a flux cored wire for welding.

[Prior art] Flux-cored wire for gas shielded arc welding (hereinafter referred to as flux-cored wire) is a mild steel or low alloy steel shell material made from various raw materials such as slag forming agents, deoxidizers, alloying agents, and arc stabilizers. The flux is encapsulated, the arc is stable and the amount of spatter is small compared to solid wire, and good beads can be obtained in various welding positions such as downward, horizontal, vertical, and easy to weld. In addition, the flux-cored wire has characteristics such as a higher wire melting speed and a higher welding speed, and the amount of use has been rapidly increased against the background of recent demands for higher welding efficiency. In particular, a flux-cored wire containing 4% or more of a slag forming agent such as TiO ₂ or SiO ₂ as a flux composition with respect to the total weight of the wire has good welding workability in the above-mentioned various welding positions and a high use ratio.

By the way, conventional methods for manufacturing a flux-cored wire can be roughly divided into two types, and their cross-sectional structures are different as shown in FIGS. 1 (a) and 1 (b). (A) is manufactured by supplying a flux to the groove while forming a relatively small size steel strip as a shell material into a tubular body, and abutting both edges by molding, and then reducing the diameter to a predetermined size. The joint is left in the cross section of the wire and has a minute opening. (B) Using a steel pipe prepared in advance as a skin material, for example, sequentially supplying flux from the edge of the steel pipe while applying vibration to the steel pipe to form a flux-filled pipe, and then reducing the diameter to a predetermined size. Manufactured
There is no opening in the wire cross section. However, since the flux-cored wire manufactured by the former method has a minute opening in the wire cross section, the wire is large and the target property (stability of the target position of the wire tip) when applied to robot welding is inferior. And the internal flux are likely to absorb moisture in the atmosphere, so that the amount of diffusible hydrogen increases, and there is a drawback that wet processing such as Cu plating for cleaning the surface and improving electric conductivity cannot be performed. On the other hand, the flux-cored wire manufactured by the latter method does not have the above-mentioned disadvantages and is excellent in terms of welding performance.However, since the flux is supplied from the end of the steel pipe, it takes a long time to fill the flux. There was a problem with productivity.

On the other hand, a new method of manufacturing a flux-cored wire as disclosed in JP-A-60-234794 and JP-A-60-234795 has recently attracted attention. That is, a relatively large-sized steel strip is continuously fed, a flux is supplied at a stage of forming into a tubular body, and then the upper edges of the tubular body are welded by butt welding. This is a production method in which a series of devices are continuously used to form a tube. In this case, there are various types of welding of the upper edge of the tubular body, and high frequency resistance welding or high frequency induction welding is generally used.

FIG. 2 schematically shows such a manufacturing apparatus. 2 is a flux, 3 is a flux feeder, 4 is a strip, 5 is a strip feeder, 6 is a forming device, 7 is a tubular body being formed, 8 is a high-frequency induction coil, 9 is a squeeze roll, and 10 is a squeeze roll. A diameter reducing device 11 is a device for winding a flux filling tube.

However, the welding performance of a flux-cored wire in which the upper edge of a tubular body is welded in a state where such a flux is supplied and the welded tube is used as an outer shell material has not been studied so far. According to the results of the study by the present inventors, spatter particles generated when the pipes are welded by abutting the upper edges of the tubular body are particularly problematic. The generation of spatter particles can be almost eliminated by selecting appropriate pipe-forming welding conditions that match the size of the steel strip to be fed and the pipe-forming welding speed, but the size of the steel strip during continuous operation can be reduced. When a small amount of change or a considerably large change in the particle size of the supplied flux (increase in the fine particle portion) occurs, the generation of sputter particles increases, and the individual particle size also tends to increase.
Some of them inevitably fall into the flux inside the tubular body,
When mixed, it becomes a factor that impairs arc stability, which is important as welding performance of a flux-cored wire, and causes deterioration of welding work. Further, regarding the adverse effect of the sputtered particles, even in the above-described conventional manufacturing method in which the flux is supplied from the end of the steel pipe, a problem arises similarly when sputtered particles are present in the pipe using a welded pipe.

[Problems to be Solved by the Invention] Therefore, the present invention improves the arc stability by adjusting the sputter particles that are inevitably mixed into the flux at the stage of manufacturing the flux-cored wire, thereby improving the welding stability. The purpose is to provide a cored wire.

[Means for Solving the Problems] That is, the gist of the present invention is to provide a gas shielded arc welding in which a flux containing 4% or more of a slag forming agent with respect to the total weight of a wire is encapsulated in a sheath material made of a welded pipe. A flux-cored wire for gas-shielded arc welding, wherein the maximum particle diameter of sputtered particles mixed in the flux is 0.2 mm or less.

[Operation] Hereinafter, the present invention will be described in detail.

First, the present inventors manufactured a flux-cored wire using a steel strip having the size and chemical composition shown in Table 1 and a flux having a raw material composition mainly composed of TiO ₂ , and welded the upper edge portion of the tubular body. In addition to the observation of the state of generation of the sputtered particles during the sputtering, a method of adjusting the sputtered particles mixed into the flux was examined.

As a result, it was recognized that a small amount of spatter particles generated at the time of pipe welding were generated even when the flux was not supplied at all, and that the spatter particles adhered to the inside or the inner wall of the welded pipe. In addition, when pipe welding was performed by supplying a flux, it was observed that, in the particle size distribution of the flux, the generation of spatter particles tended to increase as the fine powder portion increased. Furthermore, some of the sputtered grains generated at this time could detect Ti and TiO ₂ not contained in the components of the metal strip, inside. It is clear that the Ti source is due to the flux component rutile (TiO ₂ ) powder, which means that the flux had already adhered to the upper edge of the tubular body before the upper edge of the tubular body was butted. Means The present inventors have found that the adhesion of the flux to the upper edge of the tubular body is caused by the soaring phenomenon of the fine powder portion when the flux is supplied from the flux supply device into the tubular body, and the welding of the tubular body by the high-frequency induction coil in the vicinity of the welding point. As the flux temperature in the tubular body increases with heating, the bonding force between the flux particles is weakened, and this is combined with the micro-vibration generated by the molding and transfer of the tubular body, which causes both the soaring phenomenon of the fine powder part. It was considered that the occurrence of spatter could be suppressed by preventing the above, and various measures were taken to address the problem.

Japanese Patent Application Laid-Open No. 60-234795 proposes removing fine powder adhering to the upper edge of the tubular body by sucking the powder from outside the tubular body in front of the welding point (flux supply side). According to these experiments, when the suction force is increased, the fine powder adhering to the upper edge of the tubular body can be almost removed by the former flux supply, but the amount of spatter generated tends to increase.
This is because the strong air flow was generated in the tubular body by applying sufficient suction force to remove the fine powder attached to the upper edge of the steel strip in accordance with the size of the steel strip. In addition to the fact that the rising of the fine powder portion of the flux was promoted, and that the upper edge was in a semi-molten state in the immediate vicinity of the welding point, so that the oxidation of the molten iron was promoted by the effect of the strong air current, so-called It is considered that the same state as the case where the excess oxide was interposed in the V-shaped edge portion in the high-frequency welding became the same, and stable pipe-forming welding was not performed.

On the other hand, the present inventors have found that the suction of the fine powder portion of the flux changes the composition of the flux-cored wire, making it impossible to obtain the designed welding performance. In view of this, we paid attention to adjusting the water content of the flux to make the fine powder portion hard to soar. That is, when the supplied flux is given a water content of a certain value or more by moisture absorption or water addition in advance, the soaring of fine powder at the time of supply from the flux supply device to the tubular body, and the temperature rise of the flux near the welding point. Both the rising of the accompanying fine powder are hardly recognized,
It was found that the generation of spatter particles could be reduced to the same level as in the case of welding without supplying flux. In particular, it is difficult to prevent soaring of the fine powder near the welding point by the suction, and this effect is extremely large. It is considered that the moisture in the flux at this time acts as follows. The high-frequency induction coil heats the side and bottom of the tubular body to a high temperature of about 300 to 500 ° C, but the flux temperature inside the tubular body that is in contact with it also rises, and the flux located on the side that is in contact with the inner wall The contained water vaporizes instantaneously, and becomes a state in which the space between the flux particles is filled with water vapor, so that the bonding force between the flux particles is strengthened and acts to make the fine powder portion hard to soar.
Therefore, the amount of water contained in the flux may be a very small amount necessary for this. If the amount is too large, it will not only hinder stable supply of the flux, but also easily cause defects in the welded portion of the flux-filled pipe. The residual moisture in the flux deviates from the dry state by the initial stage of the subsequent diameter reduction, and is also removed during the intermediate annealing performed in the diameter reduction process of the flux-filled pipe, thereby impairing the welding performance as a flux-cored wire. Never.

Next, the effects of spatter particles mixed in the flux on the welding performance of the wire, which were generated when pipe welding was performed while changing the moisture content of the flux, were investigated. The pipe-forming welding conditions were set to appropriate conditions capable of minimizing the generation of spatter particles, and the flux filling rate was set to 13.5% by weight. The particle size of the sputter was measured by drawing the flux-filled tube formed by the above manufacturing apparatus, observing the cross-section of the wire with the final finished size (1.2 mmφ) in the longitudinal direction or orthogonal, or taking out the flux and collecting the sputtered particles. Went directly.

The discrimination between the sputtered particles and other flux raw material powders that is a problem of the present invention is based on the fact that the sputtered particles are formed by rapid solidification of droplets and are hard and do not spread even by compression during wire drawing like iron powder. Therefore, it is almost spherical in shape, leaving almost the shape at the time of occurrence, so that it is easily possible in appearance. In addition, it can be distinguished from other raw materials by analyzing the hardness test and the composition. Fig. 3 shows the moisture content of the supplied flux (measured by the gravimetric method by heating and holding at 200 ° C), the maximum grain size of the sputtered grains observed in the cross section of the final finished wire diameter of 1.2mmφ, and the The results of the investigation on arc stability are shown. As is clear from FIG. 3, the water content of the supplied flux was 0.15.
By setting the content to about 1.0% by weight, the maximum grain size of the sputtered grains can be made 0.2 mm or less, and at this time, the arc stability also becomes good. If the moisture content of the flux exceeds 1.0% by weight, the arc became unstable even though the maximum grain size of the sputtered grains was 0.2 mm or less. This is because the supply of metal was not smooth, and the variation of the flux filling rate in the longitudinal direction of the wire became large.

In the present invention, the reason why the maximum particle size of the sputtered particles mixed in the flux is limited to 0.2 mm or more is that, as shown in FIG. 3, the arc stability which is important as the welding performance of the flux-cored wire is good. In order to keep. If the maximum particle size of the spatter particles exceeds 0.2 mm, the transfer of droplets at the tip of the wire during welding is disturbed and the arc becomes unstable, resulting in frequent occurrence of welding spatter and deterioration of the bead shape. In addition, the adverse effect of such spatter particles mixed in the flux also appears in a flux-cored wire manufactured by a conventional method of supplying a flux from an end port using a welding pipe to form a flux-filled pipe. Before the selection or use of appropriate pipe-forming welding conditions, a cleaning treatment for removing spatter particles in the welded pipe should be performed. In the composition of the slacks-cored wire of the present invention, the reason why the slag forming agent is limited to 4% or more based on the total weight of the wire is to maintain good welding workability in various welding positions. Insufficient amount, especially in the shape of the bead in the vertical position.

Hereinafter, the effects of the present invention will be described in more detail with reference to examples.

[Example] (Example 1) Using a steel strip having a size and a chemical composition shown in Table 1 and a flux having a raw material composition shown in Table 2 (a fine powder portion of 100 mesh or less is about 15% by weight) A flux-filled tube (outer diameter 12.0 mmφ) is formed by the manufacturing apparatus schematically shown in FIG. 2 and subsequently reduced in diameter by wire drawing (intermediate annealing 2).
Time) A flux-cored wire having a final finished size of 1.2 mmφ was trial manufactured. The feeding speed of the steel strip is 25.0m / min,
The pipe welding conditions were constant at 520 KHz and 130 KVA, and the spatter particles generated by changing the water content in the flux were adjusted. Welding workability of the obtained prototype wire was investigated by semi-automatic welding under welding conditions of 270A-30V, CO ₂ gas flow rate 20 / min. Table 3 shows the test wire and the results of the welding workability test. In Table 3, in Test Nos. 1, 2, and 4 (W1, 2, 4), the maximum particle size of the sputtered particles mixed in the flux was 0.
The welding workability was good because it was 2 mm or less, but in Test No. 3 (W3), the arc became unstable because the maximum particle size of the sputtered particles exceeded 0.2 mm.

(Example 2) Strips of the sizes and chemical components shown in Table 1 were fed,
A welding pipe (outer diameter 12.5 mmφ, wall thickness 2.2 mm) is manufactured without supplying flux by the manufacturing apparatus schematically shown in FIG. 2, and a flux having a raw material composition shown in Table 2 is produced using this welding pipe. The welded pipe was supplied from the end while being vibrated to form a flux-filled pipe, which was subsequently reduced in diameter by wire drawing (intermediate annealing twice) to produce a trial production of a flux-cored wire having a final finished size of 1.2 mmφ. Table 4 shows the results of the test wire and the welding workability test. The welding conditions for the prototype wire
300A-31V, CO ₂ gas flow rate 20 / min, semi-automatic welding.

In Table 4, test Nos. 5 and 6 (W5 and 6), in which the welding conditions used for the welded pipes were optimized and the maximum particle size of the spatter particles mixed in the flux was 0.2 mm or less, were arc stable. On the other hand, in Test No. 7 (W7), the arc became unstable because the pipe welding conditions were inappropriate and the maximum grain size of the sputtered grains exceeded 0.2 mm.

[Effects of the Invention] As described above, the present invention is generated at the manufacturing stage when a flux-cored wire having no opening on the wire surface is manufactured by using a welded pipe as a shell material, and the flux is generated during the manufacturing process. The present invention provides a flux-cored wire in which the stability of the arc is increased by adjusting the amount of sputter particles mixed in the wire, and good welding workability can be obtained in various welding positions.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are views showing the cross-sectional structure of a flux-cored wire, FIG. 2 is a schematic view showing a continuous production apparatus for a flux-cored wire, and FIG. It is a figure which shows the relationship between the amount, the maximum particle size of the sputtered particle mixed in the flux, and arc stability. DESCRIPTION OF SYMBOLS 1 ... Outer shell material, 2 ... Flux, 3 ... Flux supply device, 4 ... Strip steel, 5 ... Strip steel feeder, 6 ... Molding device, 7 ... Tubular body in molding stage, 8 ... ... High frequency induction coil, 9 ... Squeeze roll, 10 ... Diameter, 11 ... Flux filling tube winding device

Continuation of the front page (56) References JP-A-3-169499 (JP, A) JP-A-3-294098 (JP, A) JP-A-4-55088 (JP, A) JP-A-6-238486 (JP) , A) Tokiko Hei 7-108475 (JP, B2)

Claims (1)

(57) [Claims] 1. A flux-cored wire for gas shielded arc welding wherein a flux containing 4% or more of a slag forming agent with respect to the total weight of the wire is covered by a sheath material made of a welded pipe, which is mixed into the flux. A flux-cored wire for gas shielded arc welding, wherein the maximum particle size of the sputtered particles is 0.2 mm or less.