JPS6044080B2 - Manufacturing method of flux-cored welding wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flux-cored welding wire (hereinafter referred to as "wire"), and specifically, to prevent the bridging phenomenon of magnetic flux caused by magnetization of the material to be welded (steel strip). This invention relates to a method for manufacturing a wire that can completely weld and seal the butt portions of steel strips.

FIG. 1 is a perspective view showing a conventional wire manufacturing situation, where 1 is a nozzle head, 2 is a welding torch, 3 is a wire, 4 is a control device,
5 indicates a welding power source, respectively.

The pipe making stand 1 is a support stand made of thick-walled steel plate, etc., and has grooved bending rolls 6 on its upper surface that rotate in a horizontal plane and are opposed to each other with the steel strip 7 sandwiched therebetween, along the running direction of the steel strip. Multiple pairs are provided. Each of the bent seven steps 6 has a hem that opens toward the steel strip introduction side (lower left side in the figure), and the distance between the rolls 6 that are disposed opposite each other with the wire 3 in between becomes wider. When manufacturing the wire 3, the steel strip 7 is continuously introduced between the bending rolls 6 along the direction of the arrow A and gradually curved to form a longitudinal cavity, and the flux F is applied to the cavity. is charged to form a tubular shape, and then the welding power source 5 is turned on via the control device 4.
The welding torch 2 connected to the butt part 7a of the steel strip 7
The wire 3 is obtained by continuously welding the butt portion 7a with a welding torch. A grounding point 8 is provided on the leg of the nozzle head 1 to form a circuit returning to the welding power source 5. In the above-mentioned wire manufacturing method, the flux F charged into the wire contains ferromagnetic raw materials such as iron powder and iron oxide for the purpose of improving arc resistance and slag removability during welding. Moreover, the steel strip 7 itself is naturally a magnetic material.

On the other hand, the ground current flows from the welding point P through the steel strip and wire, and further via the bending roll 6 to the ground point 8 of the nozzle head 1.

In addition, the wire 3 immediately after welding receives welding heat and reaches a high temperature state, so the wire 3 after the welding point "P" is extremely hot compared to the steel strip 7 before the welding point P, and as a result, the wire 3 side The electrical resistance is larger than that of the steel strip 7 upstream.Therefore, the ground current flows in large quantities into the steel strip 7 upstream of the welding point P, making the steel strip 7 strongly magnetized.In other words, the magnetic flux on the upstream side of the welding point P As the density increases and a part of the steel strip 7 and the flux are magnetized, the abutting portion 7 of the steel strip 7 as shown in FIG.
The above-mentioned ferromagnetic flux raw material is attracted to a, and a bridge F'' is formed. Therefore, if welding is performed in this state, welding defects such as pinholes and bits will occur in the seal welded part of the wire 3. There is a problem in that the sealing performance is impaired and, as a result, the quality of the wire is significantly deteriorated, such as the fact that the flux in the product wire tends to absorb moisture.The present invention focuses on these circumstances. The purpose of this invention is to provide a method that avoids the flux bridging phenomenon at the butt portions of the strips and reliably produces wires that are completely welded and sealed.

However, the method of the present invention is a method for manufacturing a flux-cored welding wire in which flux is charged into a cavity while a steel strip is curved into a tubular shape, and the butt portions of the steel strip are welded and sealed. The gist of this method is that the grounding point is located downstream of or directly below the welding point.

In order to eliminate the above-mentioned drawbacks, the present inventors have proposed that near the welding point,
Especially the steel strip 7 and flux F on the upstream side of the welding point
We considered it necessary to prevent the magnetization of

In other words, in a region extremely close to the welding point, even the magnetic material described above is considered to be in a high temperature state due to the influence of welding heat, exceeding the Curie point of the magnetic material. It is determined that magnetization does not occur at . However, in areas upstream from the welding point where the influence of welding heat is small and the temperature of the magnetic material does not exceed the Curie point, the magnetic field generated by the ground current is applied to the steel strip 7 and the flange. It is thought that the flux F is magnetized, thereby forming a bridge F'' at the butt part of the steel strip.Flux F becomes bridge-like and enters the cavity when it reaches the non-magnetized part directly below the welding point. Even though it should have fallen to 7
At the stage of squeezing into a tube, it is squeezed from both sides and held between the abutting parts. That is, even if the temperature reaches a portion extremely close to the welding point and is raised above the Curie point, the bridging cannot be eliminated and the above-mentioned drawbacks will be exposed. Therefore, it was inferred that in order to obtain a good condition, it is necessary to suppress or prevent the generation of the magnetic field itself upstream of the welding point as much as possible. And since the magnetic field is generated by the earth current as mentioned above,
It was concluded that the earth current upstream of the welding point should be reduced or eliminated as much as possible. The present invention is the result of intensive research aimed at embodying this idea, and was completed by adopting the configuration described above. A detailed description will be given below with reference to the drawings.

FIG. 3 is an explanatory diagram of main parts showing a specific embodiment of the method of the present invention, in which an energized roller 10 is provided downstream from the welding point P,
A welding current circuit is formed using the energizing roller 10 as a grounding point.

In order to eliminate leakage current from sources other than the energizing roller 10, insulation is provided between the bending roll 6 and the main body 1''. Alternatively, the bending roll may be formed of an insulating material such as ceramics. When a voltage is applied to the welding torch 2 via the control device 4, an arc current 12a flows between the welding torch 2 and the wire 3, and the arc current 2
Further, a passes through the wire 3 as a ground current 12 and returns from the energizing roller 10 to the welding power source 5. That is, under such an energizing method, the energizing roller 10 constituting the ground point is located downstream of the welding point P, and most of the ground current 12 is at the welding point P.
The detour current 12b (two-dot chain line) flows approximately linearly between the current supply roller 10 and the current-carrying roller 10 as shown by the one-dot chain line, and the detour current 12b (two-dot chain line) is extremely small.

Therefore, almost no earth current flows in the vicinity of the area upstream from the welding point P where the bridging phenomenon may occur.
Magnetic flux and magnetization of the steel strip at this location can be avoided. Concerns about the magnetization of the magnetic material due to the influence of a slight detour current generated near the welding point P can be ignored as the temperature rises above the Curie point due to welding heat, as mentioned earlier, and the bridging phenomenon There is no fear that this will happen. The basic configuration of the present invention is as described above, but as a configuration other than the above, for example, even if the current-carrying roller is attached at a position directly below the welding point P, the present invention is satisfied.

In other words, there is no problem even if the current is a little closer to the upstream side as long as the range affected by the ground current is within the range exceeding the Curie point. The present invention is roughly configured as described above, and as a result of being able to avoid the bridging phenomenon of magnetic flux at the butt portion of the strip steel, it is possible to obtain a high quality flux-cored welding wire without welding defects.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the conventional wire manufacturing method, Fig. 2 is an explanatory diagram of the bridging phenomenon of flux at the butt part of the steel strip, and Fig. 3 is a partially broken side view of the main part of the wire manufacturing apparatus to which the method of the present invention is applied. There is a diagram. 1... Nozzle head, 2... Welding torch, 3
...Wire, 4...Control device, 5...
... Welding power source, 7... Band TM (non-welding material)
, 8... Grounding point, 10... Current-carrying roller,
F...Flux, P...Welding point.

Claims (1)

[Claims] 1. A method for manufacturing a flux-cored welding wire, in which a steel strip is curved into a tubular shape to form a sheath pipe, and flux is charged into a cavity, and the butt portions of the steel strip are welded and sealed,
A method for manufacturing a flux-cored welding wire, characterized in that a grounding point is established on a traveling workpiece to be welded and on the downstream side or directly below the welding point.