JPH06246484A - Production of powder and granular material packed pipe - Google Patents

Abstract

PURPOSE:To produce the powder and granular material packed pipe which obviates cracking of a pipe shell by obtaining a defectless joined weld zone. CONSTITUTION:This process for production of the powder and granular material packed pipe consists in supplying powder and granular materials 25 into a tubular body 1 during the course of forming a metallic strip to the tubular body 1 and butt welding both edge surfaces 2L, 2R of the tubular body 1 by high-frequency welding, then reducing the diameter of the welded pipe. The wall thickness of the tubular body 1 is <=5mm and the outside diameter thereof is <=50mm. Both edge parts 19L, 19R formed to a groove opening upward and downward from the center in the thickness direction of the edges are butt welded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powder / granule-filled tube in which carbon steel, stainless steel, copper alloy, aluminum alloy or other metal tube is filled with the powder / granular material.

Here, the powder or granules mean powder or granules such as welding flux, oxide superconducting material, and additive for molten steel.

[0003]

2. Description of the Related Art A flux-cored seamless wire for welding is one type of powder-filled tube. In the production of this seamless wire, the strip steel is slit to the required width,
The strip steel after slitting is gradually formed from a U-shape to an O-shape by a forming roll. During this forming, the flux is supplied from the opening along the longitudinal direction of the U-shaped strip steel to the strip steel valley portion by the feeder. Then, while forming into an O-shape, the opposite edge surfaces of the opening are joined by welding, and the diameter is subsequently reduced. Further, after annealing if necessary, the tube filled with the flux is drawn into a desired diameter and wound up to obtain a product.

As a welding method in the production of the powder-filled tube, high-frequency welding such as high-frequency induction welding method and high-frequency resistance welding method is widely used. In all of these welding methods, when formed into a substantially O shape, the Joule heat generated by the high frequency current heats the edge surface of the opening to the melting temperature and presses the opposing edge surfaces with a pair of squeeze rolls.

By the way, when a pipe filled with flux and welded is reduced in diameter by rolling, wire drawing, or the like, cracks may occur in the outer skin of the pipe. And as the cause of this crack,
It is considered as follows. During welding, part of the flux such as oxides and silicates is adsorbed on the opening edge surface of the tubular body. That is, at the welding position, the opening edge of the tubular body becomes a magnetic pole due to the magnetic field generated by the welding current. Therefore, the ferromagnetic component of the flux is attracted to the opening edge portion by the magnetic force. At this time, the non-magnetic component is also attracted to the opening edge portion along with the ferromagnetic component. The flux adsorbed on the edge portions of the openings becomes inclusions in the welded joint, resulting in welding defects. Then, due to this welding defect, cracking occurs when the diameter is reduced. The cracks when the diameter is reduced are directly introduced into the product, that is, the flux-cored wire for welding, and deteriorate the welding workability.

One of the techniques for solving such a problem is "composite wire for welding" disclosed in Japanese Patent Laid-Open No. 234794/1985, which is a powder raw material having a non-permeability of 1.10 or less. Is filled with a non-magnetic powder to prevent the powder from being attracted to the opening edge by magnetic force. JP-A-63-58
There is a "composite pipe manufacturing method" disclosed in Japanese Patent Publication No. 97,
Fine powder finer than 48 mesh is removed when the powder is supplied to prevent the fine powder from adhering to the opening edge portion. Further, as another technique, there is a "method for producing a tube filled with powder" disclosed in JP-A-54-109040. This technique supplies powder so that it does not fill the tubular body, and creates a gap or distance between the joint weld and the surface of the powder layer that has been supplied. I try not to reach.

[0007]

However, even if the joint welding portion is improved by the above-mentioned conventional technique, the cracks as described above still occur when the diameter of the pipe is reduced, and the product yield is lowered. Once the cracks occur, even if the cracks are minute at first, the cracks extend in the longitudinal direction of the pipe as the reduced diameter size of the pipe becomes smaller, and the length becomes a length that cannot be ignored in the product size.

[0008] Therefore, it is an object of the present invention to provide a powder-and-granule-filled pipe having no cracks in the pipe shell by obtaining a sound joint weld.

[0009]

The inventors have reiterated that cracks when the pipe diameter is reduced are welding defects due to magnetic particles magnetically adhering to the opening edge portion of the tubular body during welding. In addition to recognizing this, in order to prevent this, it is necessary to supply only substantially non-magnetic raw material powder, or to provide a gap or distance between the welded joint and the supplied powder layer surface. It was also confirmed that the effect is poor, that is, there is a limit to eliminating the magnetic sticking of the powder particles to the opening edge surface of the tubular body. Therefore, from the viewpoint that this magnetic sticking is unavoidable, the inventors have diligently studied a means for removing the magnetic sticking powdery particles from the welded joint to obtain a clean state without inclusions.

In the method for manufacturing a powder-filled tube according to the present invention, the powder is supplied to the tubular body while the metal strip is being formed into the tubular body, and both edge surfaces of the tubular body are butt-welded by high frequency welding. In the method for manufacturing a powder-filled tube for reducing the diameter of a welded pipe, the wall thickness of the tubular body is 5 mm or less, the pipe outer diameter is 50 mm or less, and the groove is opened vertically from the center in the edge thickness direction. It is characterized in that both formed edges are butt-welded. As the groove having such a shape, X, H, K or double-sided J groove is used.

Further, in the method for manufacturing a powder-filled tube according to the present invention, at least one of both edge portions is pressed by fins of a fin roll to form a groove that opens vertically from the center in the edge thickness direction. Is characterized by. That is, the edge surface is crushed and shaped to have a "V-shaped cross section" by the fins of the fin roll, and then butt-welded with an X groove or the like.

Further, when the vertex of the joining end shape of the edge surface of the tubular body is P, the outer end point is O, the inner end point is I, and the midpoint of the line segment OI is M, the distances L _PM , L _OI and the plate thickness are shown. L _PM / t = 0.5 to 7.0 L _OI / L _PM ≦ 1.0, where L _{PM is} the P-M distance in the tube axis direction L _OI is O- in the tube axis direction. It is characterized in that both edge surfaces of the tubular body are joined so as to form a mountain-shaped joining terminal shape in which the relationship of I distance is established.

Further, the V convergence angle θ is adjusted in the range of 3 to 15 ° so that the L _PM / t becomes a predetermined value.

In the present invention, machining or plastic working is used to form a groove (X groove, etc.) that opens vertically from the center in the edge thickness direction. However, since the tubular body has a small wall thickness of 5 mm or less and an outer diameter of 50 mm or less, it is relatively difficult to process. Therefore, it is economical and efficient to press down at least one of both edge portions with fins of a fin roll to form an X groove or the like. Here, the fin roll refers to a finned roll such as a fin pass roll or a seam guide roll installed between the powder and granular material supply position and the butt welding position. The fins of this fin roll crush and shape at least one edge surface of the tubular body opening into a "dogleg-shaped cross section". This state will be described with reference to a specific example shown in FIG. 1. The tubular body 1 containing the powdery particles 25 is sandwiched between a pair of rolls composed of a fin roll 35 and a support roll 36 and runs toward the squeeze roll. At this time, the fin roll 35 is placed in the opening of the tubular body 1.
Fins 37 are inserted and both edge surfaces 2L and 2R
Is crushed and shaped. That is, the side surfaces of the fins 37 are pressed against the upper and / or lower portions of the edge surfaces 2L and 2R, or the lower portion in the illustrated example, to crush the edge surfaces 2L and 2R from a flat shape to a "dogleg" cross section (mountain shape). Crush and shape the protruding surface of. The edge surfaces 2L and 2R after shaping are edge surfaces having a "V-shaped cross section" composed of the inner slopes 2iL and 2iR and the outer slopes 2oL and 2oR. After such a shaping process is applied to the edge surface, the contact of the center portion of the plate thickness precedes X.
Butt welding at the groove.

The magnetic field generated in the pipe due to high frequency welding is
The magnetic powder particles present on the surface layer portion of the powder layer 25 are floated 22 and magnetically attached 23 to the edge surface 2. Since these magnetic particles cause welding defects and eventually cracking of the outer shell of the pipe, it is desirable to remove them from the edge surface 2 as much as possible. As a means for solving this, in the present invention, both edge portions 19 of the tubular body 1 are formed into X-grooves or the like and are configured with two slopes 2o, 2i (see FIG. 4).

A mechanism for discharging the powder particles which are magnetically attached to the edge surface 2 will be described with reference to FIGS. 2a and 2b. a ... Shaded parts 26L and 26R in FIG. 2a indicate heat affected parts of the edge parts 19L and 19R due to the Joule heat of the high frequency current. Left and right edge surfaces 2L of the tubular body at the welding position,
2R narrows the gap by the pressing force of a pair of squeeze rolls, and eventually comes into contact with each other to be in a pressure contact state. First, the vertices pL and pR of both edge surfaces 2L and 2R contact each other, and then the edges between the inner slopes 2iL, 2iR and the outer slopes 2oL and 2oR are pressed together, and finally the inner end points iL and iR and the outer end points oL and oR. Is pressed.

B ... When the edges between the inner slopes 2iL and 2iR and the outer slopes 2oL and 2oR are pressed together, the heat-affected zone 27 located in the shaded area in FIG.
8i moves to an overflow state, that is, a metal flow rising phenomenon occurs. At this time, on the edge surface 2,
In the illustrated example, an external force indicated by an arrow acts on the powder particles 23 magnetically adhered to the inner slope 2iL due to the rising of the metal flow, and as a result, they are completely discharged from the joint.

Since the metal flow rising phenomenon occurs in the heat-affected zones 26L and 26R having a substantially triangular shape which appears when a high-frequency current flows, it is possible to suppress the heating portion due to the high-frequency current to a necessary minimum, and therefore the welding is performed. The high-frequency current required for heating, that is, the heat input can be reduced, and extremely efficient welding becomes possible.

On the other hand, FIG. 3 shows a case of a conventional I-shaped groove having parallel edge surfaces. The shaded portions 32L and 32R in FIG. 3 are edge portions 29L and 2L due to the high frequency current.
The heat affected zone of 9R is shown. In this case, the edge surface 33L, 33R
Contact with each other almost at the same time to start the pressure contact, so that the granular material particles 2 sandwiched between the edge surfaces 33L and 33R by magnetic sticking
3 loses its escape and is confined inside the heated metal. After that, the granular particles 23 try to move toward the inside and outside of the edge due to the rising of the metal flow of the heat-affected zones 32L and 32R, but depending on the magnetic attachment position (initial position) of the granular particles 23 on the edge surface, the inside and outside of the edge. In some cases, the particles 23 are not discharged to the surface, and this state becomes conspicuous when the powder particles 23 are magnetically attached near the center of the plate thickness. Even if the amount of upset by squeeze roll is simply increased to eliminate this, a sufficient discharge effect cannot be obtained, and in order to do so, the amount of heat input must be increased to widen the heat effect width of the edge part. Therefore, this directly leads to an increase in power consumption, and an increase in heat input promotes the generation of spatter and increases the chance of scattering and mixing in the tube. If the upset amount is further increased, the bead amount on the inner and outer surfaces of the edge will increase, which will increase the consumption of the skin band plate, and the excessive bead protruding on the inner surface of the edge will cause disconnection at the time of pipe diameter reduction, similar to the spatter scattered inside the pipe. Will be triggered. Therefore, the amount of upset cannot be increased so much that there is a limit in completely discharging the powder particles 23 from the edge surface.

In the present invention, the term "junction termination shape" means
It means the shape of the joining end line formed at the end of the welded joint when both edge surfaces 2 of the tubular body are joined by high frequency welding. As shown in FIG. 4, according to the present invention, the edge surface 2 is composed of two slopes, that is, the outer slope 2o and the inner slope 2i, and the apex of the joint end line 18 formed at the end of the joint weld 17 is P, Let O be the outer end point, I be the inner end point, and M be the middle point of the line segment OI formed by the end points O and I.
Tube axial distances L _PM , L _OI determined by the positions of these points
And the plate thickness t, the relational expression L _PM /t=0.5 to 7.0
And a junction termination shape that satisfies L _OI / L _PM ≦ 1.0. This is because when L _PM /t<0.5, the effect of discharging the granular particles from the edge surface is not sufficient, and L _PM / t> 7.
At 0, high-frequency current was concentrated near the apex of the junction termination shape, spatter frequently occurred, and good junction could not be expected.
_{This is because when OI} / L _PM > 1.0, the upset amount is excessively biased inside and outside the edge, so that good bonding cannot be expected.

This joining end shape (shown by a thick line) has a joining end line 18i inclined inward from the center of the edge surface.
And a joining end line 180 that inclines toward the outside. The shape of the cross section (perpendicular to the tube axis) of the edge portion 19 at this time is a "dogleg" (mountain shape) as shown in the dotted line frame 21 of FIG. 4, and as shown in FIG. The combined edges 19L and 19R form an X groove. An apex p, an outer end point o, an inner end point i, and an end point o of a “dogleg” formed by the edge portion 19 in the dotted line frame 21;
The midpoint m of the line segment oi formed by i corresponds to the apex P, the outer end point O, the inner end point I, and the middle point M of the junction termination shape, respectively, but the contact order between the opposing edge surfaces is p →
It becomes o → i (example shown), and the contact at the central portion of the plate thickness precedes not the simultaneous contact. That is, the point P of the joining end line 18,
O and I correspond to points p, o, and i of different edge cross-sections, respectively. The groove height H (distance between the apex p and the midpoint m in the pipe axis direction) corresponds to the distance L _PM in the joint termination shape.

5 (a), (b), (c) and (d) show specific examples of the junction termination shape. (a) ... L _PM /t=2.7, L _OI / L _PM = 0 (b) ... L _PM /t=2.6, L _OI / L _PM = 0.8 (V
Groove tendency) (c) ... L _PM /t=3.9, L _OI / L _PM = 0.8 (reverse V groove tendency) (d) ... L _PM /t=0.6, L _OI / L _PM = 0 FIG. 6 is a top view of the tubular body at the welding position, and FIGS. 7a and 7b are VIa-VIa and VIb-VIb diagrams of FIG. 6, respectively. Here, for simplicity, L _OI / L _PM = 0. The junction termination shape in the case of is shown. Opening angle of both edge surfaces 2L, 2R at the welding position, that is, V convergence angle θ, groove height H
And the P-M distance L _PM along the pipe axis are theoretically [L _PM ] = H · (sin θ / 2) ⁻¹ ∴, as is clear from the right-angled triangle shown by the hatched portion in FIG. [L _PM / t] = (H / t) · (sin θ / 2) ⁻¹ (where, [] indicates a theoretical value). Then, the measured value L _PM / t and the theoretical value [L _PM /
It has been experimentally confirmed that L _PM / t = α [L _PM / t] holds with the time t]. The coefficient α is determined by each pipe making condition (pipe size (wall thickness, pipe diameter), squeeze allowance, heat input, welding speed, etc.) and takes a range of approximately 1 to 5. FIG. 8 is a graph of the above theoretical formula [L _PM / t] −θ
A diagram, the larger H / t value when a constant V convergent angle θ is apparent from figure [L _PM / t] value increases, also the V convergent angle θ is increased [L _PM / The t] value gradually decreases. Therefore, when the H / t value is small, that is, near the I-groove, the V convergence angle θ is set small, and
When the value is large, that is, when the apex angle of the edge surface is close to 90 °, the theoretical value [L
_PM / t], and therefore the measured value L _PM / t, can be kept within an appropriate range. That is, it is possible to adjust the actual measurement value L _PM / t using the V convergence angle θ as a control variable. This V convergence angle θ is θ = 3 to 15 in order to form a good welded joint.
It is desirable to set within the range of °.

The junction termination shape is L _PM /t=0.5-
In order to obtain a mountain shape _satisfying 7.0 and L _OI / L _PM ≦ 1.0, a molding schedule is determined in advance by experiments so as to obtain a desired shape, and a pipe is molded according to the molding schedule. When deciding the forming schedule, ... the degree of end bending of both edges of the hoop (band plate) by the preforming rolls ... the degree of forming by the forming rolls ... the open pipe (tubular body) by the fins of the fin rolls
Degree of shaping of edge surface ... Degree of upset by squeeze roll ... Distance between seam guide roll and squeeze roll ... Adjust fin width of seam guide roll, etc. to obtain desired joining end shape. The V convergence angle θ is mainly set by adjusting.

The determination of the joint end shape is carried out by a spread test of the welded pipe. To explain the procedure, first stop the welding and put a test piece (at the position where the squeeze roll has passed) of an appropriate length (for example, 2 to 5 times the outer diameter of the tube) across both the open pipe and the welded pipe. Sampling from the welding position, the pipe end on the open pipe side of this test piece is angled
It is pressed with a press (about 10 tons) on a cone-shaped tool of ° to spread it into a trumpet shape, and the fractured surface of the obtained sample is observed to determine the joining end shape.

[0025]

In the present invention, both edge portions formed in the groove that opens vertically from the center in the edge thickness direction are butt welded. When both edge surfaces with a groove of this shape are abutted, a space that expands toward both ends of the edge part is formed in the groove, and due to the existence of this space, it occurs in the process of pressing the edge part. The rising phenomenon of the metal flow from the center of the thickness of the edge surface toward the both ends of the thickness becomes more prominent. At this time, the powder particles attached to the edge surface are almost completely discharged from the joint due to the rise of the metal flow of the heated metal. That is, even if the granular particles adhere to the edge surface, the self-cleaning action of discharging the adhered granular particles (so-called dirt) to the inside and outside of the pipe in the process of pressing the edge portion.

Further, according to the present invention, at least one of the both edge portions is crushed by the fins of the fin roll to form a "dogleg-shaped cross section", and then butt welding is performed at the X groove or the like. In this case, since it is crushed by the fins of the fin roll, it is not necessary to separately provide a processing device for the edge surface, and the shaping process can be continuously performed in-line.

The self-cleaning effect can be effectively exhibited by butt-welding both edge surfaces of the tubular body with the X groove so that the joint end shape becomes the above-mentioned specific mountain shape.

Further, the above-mentioned metal flow rising phenomenon is
Since it occurs in the heat-affected zone of the substantially triangular edge that appears when a high-frequency current flows, it is possible to minimize the heating portion due to the high-frequency current, thus reducing the high-frequency current required for welding, that is, the heat input. As a result, extremely efficient welding is possible.

In this way, according to the present invention, the cracking of the tube due to the adhesion of the powder or granular material to the edge surface of the tubular body due to magnetic attachment or the like is eliminated. Further, efficient and stable welding can be realized in a relatively low heat input (low power amount) region.

[0030]

EXAMPLES The manufacturing of flux-cored wires for welding will be described below as examples. FIG. 9 is a configuration diagram of a main part of the welding flux-cored wire manufacturing apparatus.

As shown in FIG. 9, an open tube (tubular body)
The forming roll group 24, the side rolls 3, and the flux supply device 4 are arranged along the feeding direction of 1. A preforming roll (not shown) is provided on the upstream side of the forming roll 24.
Is provided. The flux 25 is supplied from the space 5 between the side rolls 3 to the open tube 1 in the middle of molding. Open pipe 1 supplied with flux 25
Passes through the fin pass roll 6 and the seam guide roll 7 and enters the welding zone. The high frequency induction welding device 8 includes a work coil 9 and a squeeze roll 10. A high frequency welding current is supplied to the work coil 9 from a power source 12. The welded pipe 11 has an extra bead 14 on the outer surface side cut by a cutting tool 13 and is rolled by a rolling roll group 16, and while being annealed, has an outer diameter of 1 by a rolling device and a wire drawing device (neither is shown). 0.0 to 2.0 m
Reduced to a product size of m. The extra bead 15 on the inner surface side remains as it is up to the product size.

By such high frequency induction welding, the width w = 3
A steel strip with a thickness of 0 to 150 mm and a thickness t of 1 to 5 mm has an outer diameter D =
Pipes are made into tubes of about 10 to 50 mm. As welding conditions at this time, the frequency of the high-frequency current ... f = 300 to 800 kHz Heat input (electric energy = EpIp) ... P = 50 to 500 kVA Work coil to V convergence point distance ... L = 10 to 100 mm V convergence angle ... θ = 3 to 15 ° is adopted, welding speed (pipe forming speed) V = 10
Pipe forming is performed at a speed of about 200 m / min.

When such high frequency welding is carried out, a magnetic field is generated in the open pipe 1. This magnetic field is generated by the granular layer 25.
The magnetic powder particles present in the surface layer of the above are soared and magnetically attached to the edge surface 2. Since these magnetic particles cause welding defects and eventually cracking of the outer shell of the pipe, it is desirable to remove them from the edge surface 2 as much as possible. As a means for solving this problem, in the present invention, the edge surface 2 of the tubular body is crushed and shaped by the fins of the fin roll to form a "V-shaped cross section". That is, in the manufacturing method of the present invention, the edge surface 2 (2L, 2R) of the open pipe 1 running toward the squeeze roll 10 is finned by the fin pass roll 6 and the seam guide roll 7 in the manufacturing method of the wire shown in FIG. The side surface of the fin 37 is pressed against the upper portion and / or the lower portion of the edge surface 2 by means of 37 to crush it, and the edge surface 2 is crushed and shaped from a planar shape to a projecting surface having a “dogleg” cross section (mountain shape). Then, the squeeze roll 10 is pressed and butt-welded at the X groove (see FIG. 1). In the process of this pressure welding, the metal flow rising phenomenon from the center of the thickness of the edge surface 2 toward the both ends of the thickness becomes more prominent, which causes the particulate particles magnetically adhered to the edge surface to be almost completely discharged from the joint. can do.

Next, the result of cracking of the flux-cored wire for welding manufactured by the manufacturing method of the present invention will be described. Steel strip with a plate thickness of 2.2 mm and a width of 65.5 mm (SPH
C, C = 0.05%), outer diameter 22.4 mm, inner diameter 18.
Mold into a 0 mm tube. Filling rate of flux is 1 during molding
It was supplied at 5% and the open tubes were continuously butt-joined.
At this time, the frequency of the high frequency current supplied to the work coil was 510 kHz, the welding speed V was 30 m / min, and the distance between the work coil and the V convergence point was 15 mm. The tube after welding was annealed once with a group of rolling rolls to reduce the outer diameter to 3.2 mm, annealed and plated, and wound into a coil.
Then, finish drawing and reducing the diameter to a product size of 1.2 mm in outer diameter and 0.6 mm in inner diameter were examined for crack occurrence in the product wire.

The joint termination shape of each experiment No. was formed by experimentally determining a molding schedule so as to obtain a desired shape and molding a tube according to the molding schedule. The method of adjusting the molding schedule is as described above. In the experimental example according to the present invention, the edge surface of the opening portion of the open pipe was crushed by the fins of the fin roll to be shaped into a "V-shaped cross section" and then butt-welded with the X groove. At this time, the L _PM / t value was set by adjusting the V convergence angle θ in the range of 5 to 10 °.

The amount of heat input P (= EpIp) is the same as in Experiment Nos. 1 to 10.
In the case of the present invention, P = 130 to 150 kVA is set, and in Experiment Nos. 11 to 13 (comparative example), P = 165.
High-frequency welding was performed with kVA set.

Table 1 shows the composition of the supplied flux.
After mixing the raw material powders, a binder (water glass) was added, and the mixture was granulated and classified to prepare a supply flux.

[0038]

[Table 1]

The results of cracking are shown in Table 2. The crack was evaluated by conducting an eddy current flaw detection test (ECT) on the wire sheath over the entire length of 100 km of the product wire having an outer diameter of 1.2 mmφ after wire drawing (20 kg winding spool × 37) to confirm the presence and position of the crack, It was carried out by observing the corresponding portion with a magnifying glass when a cracking signal was output and confirming the presence of cracks in the longitudinal direction of the wire. When the presence of cracks could not be confirmed at all, this was regarded as good. Also, if there is a crack, the treatment liquid tends to infiltrate into the wire during surface treatment or wire drawing from the opening of the crack and deteriorate the quality of the product. I made this a defect.

[0040]

[Table 2]

In Table 2, Experiment Nos. 1 to 10 are experimental examples of the present invention, and the shapes of the end ends of the welded joints are all the joint end shapes specified in the present invention. In any of these experimental examples, cracking of the tube skin was not confirmed,
The quality of the product wire was good, and when welding was performed using this flux-cored wire for welding, good welding workability was realized.

On the other hand, Experiment Nos. 11 to 13 are comparative examples, and the shape of the end of the welded joint is not the shape of the terminal end of the joint specified in the present invention. That is,
In Experiment No. 11, the L _PM / t value is less than the lower limit value (0.5). In Experiment No. 12, the L _PM / t value exceeds the upper limit value (7.0). Experiment No. 13 is an I-shaped groove. After all, in these comparative examples, the magnetic particles existing in the flux surface layer part were soared by the magnetic field and magnetically attached to the edge part of the open tube, and as a result, cracks were generated in the tube outer layer and the product yield was lowered.

[0043]

According to the present invention, powder particles are supplied to the tubular body while the metal strip is formed into the tubular body, both edge surfaces of the tubular body are joined by high frequency welding, and the powder particles are filled. In the method for producing a powder-granular-filled pipe for reducing the diameter of the welded pipe, both edge portions formed into a groove (X groove, etc.) that opens vertically from the center in the edge thickness direction are butt welded. Further, the edge surface is crushed by the fins of the fin roll to be shaped into a "V-shaped cross section" and then butt-welded with an X groove or the like. Further, the edge surface of the tubular body is butt-welded with an X groove or the like so that the joining end shape becomes the above-mentioned specific mountain shape. From these facts: -Particle particles adhering to the edge surface are almost completely discharged from the joint due to the rise of the metal flow of the heated metal.
That is, even if powdery or granular particles adhere to the edge surface, it has a self-cleaning action of discharging the adhered powdery or granular particles (so-called dirt) into and out of the pipe in the process of pressing the edge portion.

Since the metal flow rising phenomenon occurs in the heat-affected zone of the "V-shaped cross section" of the edge portion, it is possible to minimize the heating portion due to the high frequency current.
Therefore, the high frequency current necessary for welding, that is, the heat input can be reduced, and extremely efficient welding can be performed.

The edge surface can be continuously shaped in-line into a "V-shaped cross section". Therefore, there is no complexity of shaping the edge surface by a processing device separately provided in another process.

Since the X groove or the like is formed immediately before the work roll, the shape of the groove can be easily adjusted and the processing becomes easy.

In this way, according to the present invention, the cracking of the tube caused by the adhesion of the powder or granular material to the edge surface of the tubular body by magnetic attachment or the like is eliminated. As a result, the product yield can be improved, and a powder-filled tube with good quality can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state of shaping an edge surface by fins of a fin roll.

2 (a) and 2 (b) are explanatory views showing a discharge state of powder particles attached to an edge surface according to the present invention.

FIG. 3 is an explanatory diagram showing a state where the edge surfaces of a conventional groove shape (I groove) are butted.

FIG. 4 is an explanatory diagram of a joint termination shape.

5 (a), (b), (c) and (d) are explanatory views showing a specific example of the junction termination shape.

FIG. 6 is a top view of the tubular body in the welding position.

7 (a) is a sectional view taken along line VIIa-VIIa of FIG. 6, (b).
FIG. 7 is a sectional view taken along line VIIb-VIIb in FIG.

FIG. 8 is a [L _PM / t] -θ diagram showing the relationship between the theoretical value [L _PM / t] and the V convergence angle θ.

FIG. 9 is a configuration diagram of a main part of a manufacturing apparatus for a flux-cored wire for welding.

[Explanation of symbols]

1 Open Pipe (Tubular Body) 2 Edge Surface 3 Side Roll 4 Flux Supply Device 6 Fin Pass Roll 7 Seam Guide Roll 8 High Frequency Welding Device 9 Work Coil 10 Squeeze Roll 11 Welded Pipe 12 Power Supply 16 Rolling Roll Group 17 Joint Welding Part 18 Joining end line 18o Outer joining end line 18i Inner joining end line 19 Edge part 22 Soaring magnetic particles 23 Magnetic particles magnetically adhered to the edge surface 25 Flux (powder) 26L Heat-affected zone 26R Heat-affected zone 27 Heat-affected zone 35 Fin roll 37 Fin of fin roll P P apex of joining end line O Outer end point of joining end line I Inner end point of joining end line M Midpoint of line segment OI formed by end points O, I _{PM PM} axial direction P-M distance L _OI O-I distance in the axial direction of the pipe p Apex of "V-shape" at the edge o " Outer end point of "V-shape" i Inner end point of "V-shape" at edge part m Middle point of line segment oi made by end points o and i H P-m distance (groove height) in the pipe axis direction

Claims (4)

[Claims] 1. A powdery or granular material filling method for supplying a powdery or granular material to a tubular body while forming a metal strip into a tubular body, and butt-welding both edge surfaces of the tubular body by high-frequency welding to reduce the diameter of the welded pipe. In the method for producing a pipe, butt welding is performed on both edges of a groove having a wall thickness of 5 mm or less, an outer diameter of 50 mm or less, and a groove that opens vertically from the center of the edge thickness direction. A method of manufacturing a powder-filled tube characterized by the above. 2. The method of manufacturing a powder- or granular-material filling pipe according to claim 1, wherein at least one of the both edge portions is pressed by a fin of a fin roll to form a groove that opens vertically from the center in the edge thickness direction. . 3. The distance L _PM , L _OI and the plate thickness, where P is the apex of the joint termination shape of the edge surface of the tubular body, O is the outer end point, I is the inner end point, and M is the midpoint of the line segment OI. L _PM / t = 0.5 to 7.0 L _OI / L _PM ≦ 1.0, where L _{PM is} the P-M distance in the tube axis direction L _OI is O- in the tube axis direction. 2. A mountain-shaped junction termination shape in which the relationship of I distance is established.
A method for producing a powder-filled tube according to the description. 4. The L _PM / t is set to a predetermined value,
The method for producing a powder / granular filled tube according to claim 3, wherein the V convergence angle θ is adjusted within a range of 3 to 15 °.