JP2018176194A - Electric-resistance weld pipe welding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric-resistance weld pipe welding device capable of making a heat value on an end face of an opening of an open pipe equal to that generated in a conventional method while preventing burning damage of an impeder.SOLUTION: An electric-resistance weld pipe welding device 100 for manufacturing an electric-resistance weld pipe, which melts both end face parts 2a and 2b of a pipe stock mutually facing from both sides to an opening 2 of an opening pipe 1 having the opening 2 extending in a travelling direction with an induction current generated on the surface of the open pipe 1, and which brings the end face parts 2a and 2b into contact with each other and welds them mutually at a welding point 5 while gradually narrowing a space of the opening 2, includes: an induction coil 3 turning around an outer peripheral side of the open pipe 1; an impeder 7 arranged inside the open pipe 1; and an electromagnetic shield material 10 disposed in a range of overlapping between itself and the opening 2 of the open pipe 1 located at least directly below the induction coil 3 in a space between the impeder 7 arranged inside the open pipe 1 and an inner peripheral surface of the open pipe 1.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a welded tube welding apparatus which bends in a cylindrical shape for induction heating while traveling a metal strip and welds between both end portions of the metal strip by a current induced in the metal strip.

  Generally, as a method of manufacturing a metal pipe, a seamless pipe manufactured by making a hole directly in a metal billet, an extruded pipe, etc., in addition to a welded tube or a spiral pipe which is formed into a pipe shape by welding while bending a metal strip. There is a manufacturing method, etc.

  ERW tubes are produced in large quantities, in particular because they have high productivity and can be manufactured inexpensively. Such a welded tube is formed into a cylindrical shape while traveling a metal band plate to form an open tube, and then an end surface portion (hereinafter simply referred to as In a state where high frequency current is supplied to the end of the open tube to increase the melting temperature, the end faces of both end faces of the open tube are welded by welding with a roll (squeeze roll) to form a tube (with the squeeze roll) The position of the end face to be pressure-welded is the welding point, including the heat-affected zone and the like in the vicinity of the welding point. Under the present circumstances, as a method of supplying an electric current to the edge part of an open pipe, for example, an induction coil (solenoid coil) is wound so that the outer periphery of an open pipe may be enclosed, and primary current is sent through this induction coil, for example. There is a method of generating an induced current directly in the open tube (see, for example, Patent Document 1), and another method is a method in which a metal electrode is pressed against the end of the open tube and current is directly supplied from a power supply. There is a part (hereinafter, a part that supplies a current to such an open tube is simply referred to as a power supply part). At this time, a high frequency current of about 100 to 400 kHz is generally used as a current leading to the induction coil or the electrode, and a ferromagnetic material called an impeder is often disposed on the inner surface side of the tube. The impedanceer is used to block an induced current (hereinafter also referred to as a reactive current) that does not contribute to welding that attempts to go around the inner circumference of the open tube.

International Publication No. 2014/027565

  However, as in the case of the induction coil described in Patent Document 1, when the conductor portion of the induction coil is disposed so as to straddle the opening of the open tube, the impeder burns out during welding when manufacturing the welded tube. However, the rod connecting the cutting bit for internal cutting may break or there is a problem that stable operation can not be performed for a long time. Such a problem is remarkable in the case of producing a small diameter tube, in particular a thick-walled tube by a method of manufacturing a welded tube.

  The present invention has been made in view of such a point, and it is possible to make the calorific value of the end face of the opening of the open pipe equal to that of the conventional welding method while preventing the burnout of the impeder. It aims at providing an apparatus.

  In order to achieve the above object, the present invention generates on the surface of an open pipe having an opening extending in the traveling direction, both end faces of the tube material facing each other from the both sides of the opening. An ERW welding apparatus for manufacturing a welded tube in which the end faces are brought into contact with each other at a welding point and welded while being melted by a high induction current while the distance between the openings is gradually narrowed. At least in the space between the induction coil around the outer periphery of the pipe, the impedancer disposed inside the open pipe, and the gap between the impedancer disposed inside the open pipe and the inner peripheral surface of the open pipe And an electromagnetic shield material provided in a range overlapping with the opening of the open tube located directly below the coil.

  According to the present invention, the electromagnetic shielding material is provided in a range overlapping at least the opening of the open pipe located immediately below the induction coil in the gap between the impeder disposed inside the open pipe and the inner peripheral surface of the open pipe. Thus, the magnetic flux from the induction coil directly entering the impedance can be avoided, and the influence of the magnetic field from the induced current flowing through the end face of the opening of the open tube can be avoided.

  In the seam welded tube welding apparatus, the electromagnetic shield material may be provided in a range facing a half circumference of an inner circumferential surface of the open tube with the opening as a center.

  Further, in the electric seam welded tube welding apparatus, the electromagnetic welding pipe may further include an impedance case that accommodates the impedance, and the electromagnetic shield material may be provided in the impedance case.

  Further, according to the present invention, in an open tube having an opening extending in the traveling direction, both end surfaces of the tube material facing each other from the opening are melted by the induced current generated on the surface of the open tube. In addition, the welded tube welding apparatus for manufacturing a welded tube in which the end faces are brought into contact with each other at a welding point and welding is performed while gradually narrowing the gap between the openings, and circling the outer peripheral side of the open tube Induction coil, a plurality of impedances disposed in a substantially circular shape along the inner circumferential surface of the open pipe, and an electromagnetic wave provided in a range overlapping at least the opening of the open pipe located immediately below the induction coil And a shield material, wherein a part of the plurality of impedances located on the opening side among the plurality of impedances is replaced with the electromagnetic shield material. It may be.

  According to the present invention, in the case where the conductor portion of the induction coil is arranged to straddle the opening of the open pipe, particularly when manufacturing a small diameter pipe, particularly a thick-walled pipe by the method of manufacturing a welded tube. By providing an electromagnetic shield material in the gap between the impeder and the inner circumferential surface of the open pipe at least overlapping the opening of the open pipe located directly below the induction coil, the impeding problem of impedinger burnout becomes noticeable. The magnetic flux density can be reduced and advantageously prevented.

It is a schematic plan view which shows the electric seam welded tube welding apparatus which concerns on a prior art using the induction coil by which the closed circuit was formed so that the outer peripheral surface of the metal strip plate shape | molded by cylindrical shape might be enclosed. It is a schematic side view of the welded tube welding device shown in FIG. It is a schematic sectional side view of the welded tube welding apparatus shown to FIG. 1 and FIG. It is a sectional side view which shows the magnetic flux distribution in the electric resistance welding of a small diameter pipe. It is a sectional side view which shows the magnetic flux distribution in arc-tube welding of a comparatively large diameter pipe. It is a top view showing typically a welded tube welding device concerning a 1st embodiment of the present invention. It is sectional drawing of the welded tube welding apparatus shown in FIG. 6, (a) shows the AA cross section of FIG. 6, (b) shows the BB cross section of FIG. It is a sectional view showing a welded tube welding device concerning a 2nd embodiment of the present invention. It is sectional drawing which shows the welded tube welding apparatus which concerns on 3rd Embodiment of this invention. It is sectional drawing which shows the welded tube welding apparatus which concerns on 4th Embodiment of this invention. It is a top view which shows the structure and dimension of a welded tube welding device used in the Example. It is a graph which shows the relationship between the total calorific value [W / m < ³ >] of the end surface part of the open pipe in Example 1, Example 2 and Comparative Example 1, and the electric current [A] which flowed through the induction coil. It is a graph which shows the relationship between the maximum magnetic flux density [T] of the impeder in Example 1, Example 2, and the comparative example 1, and the electric current [A] which flowed through the induction coil.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

(Conventional ERW pipe welding equipment)
First, with reference to FIGS. 1 to 3, a conventional ERW welding apparatus as described in Patent Document 1 will be described. In FIG. 1, an induction coil 3 is wound around the outer periphery of an open tube 1 and high frequency electrical resistance welding is performed by induction currents 4a to 4d generated in the open tube 1 by the primary current supplied to the induction coil 3 to manufacture a welded tube. It is a schematic plan view explaining the welded tube for welding pipe, and FIG. 2 is a schematic side view of FIG. FIG. 3 is a schematic side sectional view of the apparatus shown in FIGS. 1 and 2. Here, most of the current flowing through the end of the open pipe 1 flows through the end face portions 2a and 2b facing each other, but in order to simplify the explanation, in FIG. 1, the end face portions 2a and 2b of the open pipe 1 for convenience. The upper surface side (peripheral surface side) of is drawn and shown as a current flows. Further, the impeller 7 is usually housed in a resin case and is cooled by the cooling water flowing in the case. In addition, the impeder case 9 (see FIG. 9) is also used to prevent the impeder 7 from being destroyed by hitting it during mounting. In the following description, the illustration of the impeder case 9 is omitted because it is difficult to understand the figure of the explanation except when it is desired to particularly explain the imperder case 9.

  In general, the ERW tube is formed by opening a metal strip plate, which is slit to a width matched to the diameter to be produced, gradually with a multistage roll into a circular tubular shape with both end faces in the width direction facing each other. Form into a tube. Thereafter, an induction current is supplied to the open tube by an induction current generated by the induction coil, and the end surface portion (end surface portion facing the opening) of the open tube is heated and melted. Thereafter, in the downstream of the process, the opposing end faces of the open pipe are pressed with a squeeze roll to complete welding while discharging the melted and softened portion out of the front and back sides together with the oxide which is likely to be a defect. Thereafter, the welded bead portion discharged is cut off to obtain a welded tube having a defect-free sound weld. Here, the “downstream” described in the present specification means the downstream side in the traveling direction of the metal strip or the open pipe, and in the following, “upstream” and “downstream” refer to the metal strip or It refers to "upstream" and "downstream" in the direction of travel of the open pipe.

  As shown in FIGS. 1 to 3, the open pipe (metal strip) 1 which is a material to be welded is rolled into a cylindrical shape while being gradually bent by a forming roll (not shown) during traveling from a flat plate state. The surface portions 2 a and 2 b are formed in the form of a cylindrical open pipe 1 facing each other, and then both end surface portions 2 a and 2 b are pressed by a squeeze roll 6 and passed through to contact at a welding point (welding portion) 5. An induction coil (solenoid coil) 3 as shown in FIGS. 1 to 3 is provided upstream of the squeeze roll 6 in order to melt the opposite end surface portions 2a and 2b and join them at the welding point 5. By flowing a high frequency current (usually in the order of 100 kHz) through the coil 3, an induced current is generated in the surface layer of the cylindrical open tube 1 immediately below the induction coil. Although this induction current circulates along the outer peripheral surface of the open tube 1 along the induction coil 3 which goes around the open tube 1, the opening 2 is present between the end surface portions 2a and 2b of the open tube 1 in the middle, In this portion, the induced current can not flow directly under the induction coil, and roughly tries to flow in two directions. That is, as shown in FIG. 1, the current flowing in the first direction is the currents 4a and 4b passing through the welding point 5 along the end face portions 2a and 2b of the open tube 1, and the current flowing in the second direction is , Current 4c and 4d that rotate around the outer peripheral surface from the opening of the open tube 1. Among these currents, the currents 4a and 4b passing through the welding point 5 flow through the surface layers of both end faces 2a and 2b facing the opening 2 of the open tube 1 by the proximity effect by the high frequency current to heat and melt the relevant point The welding is completed by being pressure-welded by the squeeze roll at the welding point 5.

  In addition, in FIG. 1, the illustration is abbreviate | omitted about the electric current (reactive current) which does not contribute to welding which tries to turn the inner peripheral surface of the open pipe | tube 1. As shown in FIG. The reason is that a core of a ferromagnetic substance called ferrite, such as an impeder 7, is disposed inside the open tube 1, and the impedance of the inner circumferential surface of the open tube 1 is increased to allow current to flow through the inner circumferential surface. It is because it can prevent. Alternatively, when the diameter of the welded tube to be manufactured is larger than the reciprocation length to the welding point 5 and the inner circumference of the open pipe 1 is sufficiently long, the impedance of the inner peripheral surface is obtained without arranging the impeder 7 This is because the current may be sufficiently large and the current flowing around the inner circumferential surface may be suppressed.

  Further, a cutting tool (not shown) for cutting the inner surface bead (welding bead) after welding is disposed downstream of the impeder 7 inside the open pipe 1, for example, in the case of a small diameter pipe An impeder 7 is disposed in the middle of a rod 8 disposed substantially at the center of the open pipe 1. The rod 8 is disposed, for example, so as to penetrate a substantially central portion of the substantially cylindrical impider 7.

  Here, as described above, the induction coil 3 in the conventional ERW welding apparatus revolves along the outer peripheral surface of the open pipe 1, and the conductor portion of the induction coil 3 is the opening 2 of the open pipe 1. It is arranged to straddle. In such a case, the impeder 7 may be burnt out during welding when manufacturing a welded tube, or the rod 8 for connecting a cutting tool (not shown) for cutting the inner surface bead may be broken. There was a problem that time stable operation was not possible.

  According to the present inventor's investigation, the cause of the burnout of the impeder 7 is (1) the high magnetic flux density flux generated by the induction coil 3 disposed so as to straddle the opening 2 of the open tube 1 is directly permeable. Impeller 7 is subjected to magnetic flux saturation due to entry into high impedance 7 and (2) magnetic flux generated by the induced current (welding current) flowing through end faces 2 a and 2 b of opening 2 causing flux saturation and heat generation. It turned out that it was due to burning out. When the welded tube manufactured as shown in FIG. 4 is a small diameter tube, for example, a tube having an inner diameter of 40 mm or less, particularly in the case of a thick walled tube, the space between the induction coil 3 and the impeder 7 is narrow. As a result, a strong magnetic flux directly enters the impedance 7 having high permeability and easy to collect magnetic flux from the opening 2 between the end surfaces 2a and 2b, and the end surfaces 2a and 2b of the open tube 1 and the impedance 7 The welding current of a large current flows through the end face portions 2a and 2b in the vicinity of the impeder 7 due to the short distance between them, and the impeder 7 is further exposed to the superimposed strong magnetic field by the magnetic flux generated by this large current. In the state of (2), the magnetic flux saturates easily, and heat generation and severe damage are difficult to avoid.

  On the other hand, when the diameter of the open tube 1 is relatively large, as shown in FIG. 5, the magnetic flux from the induction coil 3 and the magnetic flux from the welding current flowing through the end surfaces 2a and 2b are attenuated. The amount of magnetic flux entering 7 decreases and it is difficult to saturate the magnetic flux.

  In addition, when the impinger 7 burns out, the induced current circulates along the inner peripheral surface of the open tube 1 without flowing through the end surface portions 2a and 2b of the opening 2, and therefore flows through the end surface portions 2a and 2b. The electric current necessary for welding should not be ensured, and the calorific value at the end face portions 2a and 2b may be reduced, which may make welding impossible. Furthermore, the rod 8 may be inductively heated by the induction current circulating along the inner circumferential surface of the open tube 1 and may be broken. Further, the resin-made impeder case (not shown) housing the impeder 7 is easily deformed by the radiant heat from the heat-generating end face portions 2a and 2b in the upper part, and further holes are opened, and the cooling water is In some cases, the impeller 7 can not be cooled and eventually can not be operated.

  Therefore, the inventor of the present invention reduces the magnetic flux density of the impeder 7 by preventing the magnetic flux generated from the induced current flowing through the induction coil 3 and the end faces 2a and 2b of the open tube 1 from directly entering the impeder 7, We examined a method that can be used stably for a long time without flux saturation of 7.

  As a result, it is found that the present inventor can stably use the impeder 7 for a long time without magnetic flux saturation by directly shielding the impeder 7 to be a strong magnetic field in order to lower the magnetic flux density of the impeder 7. I got More specifically, in the present invention, at least the opening 2 of the open pipe 1 located directly below the induction coil 3 in the gap between the impeder 7 disposed inside the open pipe 1 and the inner peripheral surface of the open pipe 1. It was decided to provide an electromagnetic shielding material in the overlapping range. Thus, the magnetic flux from the induction coil 3 directly entering the impedanceer 7 can be avoided, and the influence of the magnetic field from the induced current flowing through the end face portions 2a and 2b of the opening 2 of the open tube 1 can be avoided. Hereinafter, preferred embodiments of the present invention completed by the above findings will be described.

First Embodiment
First, the configuration of a welded tube welding apparatus 100 according to a first embodiment of the present invention will be described with reference to FIGS. 6 and 7. In the figure, although the impeder is drawn as it is, the impeder is actually stored in the impeder case. However, it is difficult to understand the drawing in a narrow place, so the impedance case is not shown in the drawing of this embodiment. FIG. 6 is a plan view schematically showing a welded tube welding apparatus 100 according to the present embodiment. 7 is a cross-sectional view of the ERW tube welding apparatus 100 shown in FIG. 6, where (a) shows an AA cross section of FIG. 4 and (b) shows a BB cross section of FIG.

  As shown in FIGS. 6 and 7, in the seam welded tube welding apparatus 100 according to the present embodiment, the metal strip 1 traveling in the traveling direction R is in the width direction of the metal strip 1 by multistage forming rolls (not shown). The induction heating means disposed in the vicinity of the opening 2 of the open tube 1 after being bent into a cylindrical shape and formed into the open tube 1 so that both end face portions (end face portions) 2a and 2b face each other at an interval. The high frequency current is passed through the induction coil 3 as an induction coil, and the both ends 2a and 2b are melted by the generated induction current. That is, the electric resistance welded tube welding apparatus 100 causes the induction coil 3 to induce a high frequency current which is an induced current in the vicinity of the opening 2 of the open pipe 1. Normally, an induced current is generated and flows directly below the induction coil, but when a high frequency current flows, the high frequency current tends to flow so that the space surrounded by the currents of different polarities narrows so as to reduce the inductance. In the case of the present embodiment, both end surface portions 2a and 2b of the open tube 1 are in close proximity to each other, and thus the end surfaces 2a and 2b become spaces surrounded by induced currents of different polarities. The induction current generated outside is branched and flows on the surfaces of the end surface portions 2a and 2b, and the current heats and melts the end surface portions 2a and 2b. The gap between the openings 2 is made by bringing the both end surface portions 2 a and 2 b into contact with each other at the welding point 5 while the width of the opening 2 is gradually narrowed by pressing the both sides of the open tube 1 by the squeeze roll 6.

  More specifically, the welded tube welding apparatus 100 according to the present embodiment is an end surface portion of a tube material of the open tube 1 having the opening 2 extending in the traveling direction, which faces the opening 2 from both sides (in other words, And the end faces 2a and 2b opposite to each other across the opening 2 are melted by the induction current generated by the induction heating means, and while the distance between the openings 2 is gradually narrowed, the end faces 2a and 2b Are brought into contact at the welding point 5 and welded, for producing a welded tube. The electric seam welded tube welding apparatus 100 at least includes an induction coil 3 as an induction heating means according to the present embodiment, an impider 7 and an electromagnetic shield material 10.

  The induction coil 3 is a solenoid coil disposed so as to be separated from the outer peripheral surface of the open pipe 1 so as to circulate along the outer peripheral surface of the open pipe 1. Both ends of the induction coil 3 are connected to a high frequency power supply (not shown).

  The induction coil 3 used in the present embodiment is made of a pipe, wire, plate or the like of a good conductor such as copper, and is used as a generic name of an induction coil forming a closed circuit on the open pipe 1. It is not limited. Also, the shape of the induction coil 3 is not particularly limited. For example, the induction coil 3 may go around the outer circumferential surface of the open tube 1 and may be shaped to draw a circular turn (circular coil) or may be shaped to draw a rectangular turn (rectangular coil) Good. The number of turns is not limited.

  In addition, the configuration and effects of the induction coil 3 are the same as those of the induction coil 3 in the above-described conventional ERW welding apparatus.

  The imperator 7 is disposed inside the open tube 1 and, as described above, is a core of a ferromagnetic material made of ferrite or the like. The impedance of the inner peripheral surface of the open pipe 1 can be increased by arranging the impeller 7 inside the open pipe 1, and current can be prevented from flowing in the inner peripheral surface. Further, the impeder 7 is usually accommodated in an impeder case (not shown, see FIG. 9) made of resin, and is cooled by the cooling water flowing in the impeder case. Further, as the impeller 7, one having a structure in which the impiders, which are usually a plurality of round rod-like ferromagnetic cores, are arranged in a substantially circular shape (see FIG. 10 (b)) or a cylindrical one (see FIG. 9) used. Since each round rod-like impeller is as thin as several mm in diameter, it is likely to be broken or broken by hitting the inside of the open pipe 1 when attaching the impeder 7 inside the open pipe 1 or the like. Therefore, the impeder case covers the impeder 7 to protect the impeder 7 from being broken or broken.

  In addition, the configuration and effects of the impeder 7 are the same as the impeder 7 in the above-described conventional ERW welding apparatus.

  As shown in FIGS. 6 and 7, the electromagnetic shield material 10 is open at least immediately below the induction coil 3 in the gap between the impeder 7 disposed inside the open tube 1 and the inner peripheral surface of the open tube 1. It is provided in the range which overlaps with the opening 2 of the tube 1. More specifically, the electromagnetic shielding material 10 includes at least a region overlapping the opening 2 of the open tube 1 (a region covering the opening 2 from the inner peripheral side of the open tube 1), and both end surfaces 2a of the opening 2 , And 2b in the circumferential direction of the open pipe 1 along the inner circumferential surface of the open pipe 1. That is, the shape of the electromagnetic shielding material 10 is a curved plate along the inner circumferential surface of the open tube 1.

  In order to sufficiently reduce the magnetic flux density of the impeder 7, as shown in FIG. 7, the circumferential region of the open tube 1 on which the electromagnetic shielding material 10 is installed is centered on the central portion of the opening 2. It is preferable that the region be 45 ° apart on both sides in the circumferential direction (that is, a region extended in a circular arc shape along the inner circumferential surface of the open tube 1 by 1⁄4 circumference). Further, as shown in FIG. 6, the area in the longitudinal (tube axis) direction of the open pipe 1 in which the electromagnetic shield material 10 is installed should include at least the area directly below the induction coil 3, but it is more reliable In order to shield the magnetic flux entering the impeller 7, it is preferable to install the electromagnetic shield material 10 over the area near the induction coil 3, ie, the area to the welding point 5 near the induction coil 3. Accurately, it is better to analyze the electromagnetic field, calculate the distribution of the magnetic field, and shield only the appropriate range.

  Moreover, when the thickness of the electromagnetic shielding material 10 is too thin, the reduction effect of the magnetic flux density of the impedance 7 becomes insufficient. On the other hand, if the thickness of the electromagnetic shield material 10 is too thick, the small diameter tube (especially thick tube) having a narrow distance between the inner peripheral surface of the open tube 1 and the impedance 7 enters the open tube 1 of the electromagnetic shield material 10 Insertion is difficult. Therefore, the thickness of the electromagnetic shielding material 10 is preferably about 1 mm.

  The material of the electromagnetic shielding material 10 is not particularly limited as long as it is a material having a function of avoiding the magnetic flux entering the impeder 7 and reducing the magnetic flux density of the impeder 7, for example copper, aluminum, carbon fiber etc. It can be used.

  As described above, in the present embodiment, since the electromagnetic shielding material 10 having the above-described configuration is used, (1) the magnetic flux of high magnetic flux density generated by the induction coil 3 directly enters the high permeability permeability needle 7 And (2) it is possible to suppress that the magnetic flux generated by the induced current flowing through the end face portions 2 a and 2 b of the opening 2 enters the impedanceer 7. As a result, the impedances 7 will not cause magnetic flux saturation, and neither heat nor burnout will occur. Therefore, according to the present embodiment, the amount of heat generated at the end face portions 2a and 2b of the opening 2 is substantially equal to the amount of heat generated by the ERW welding device for large diameter pipes, and the maximum magnetic flux density of the It becomes possible to keep stable below the saturation magnetic flux density. Therefore, it is not necessary to stop the production of the electric welded tube and replace the impedanceer 7 due to the burnout of the impedanceer 7, thereby improving the productivity and improving the yield.

  Here, in the present embodiment, as shown in FIG. 7, the electromagnetic shield material 10 is installed in a region which is expanded in a circular arc shape for 1⁄4 circumference along the inner peripheral surface of the open tube 1. In this case, in the region outside the circumferential end of the open tube 1 of the electromagnetic shielding material 10, the magnetic flux entering the impeder 7 becomes difficult to shield.

  Therefore, in the resistance welded tube welding apparatus according to the second embodiment of the present invention described below, the impeding device can be more reliably ensured by extending the installation region of the electromagnetic shield material in the circumferential direction of the open tube 1 compared to the first embodiment. The magnetic flux is prevented from entering 7 and the shielding effect of the magnetic flux of the electromagnetic shielding material, that is, the reduction effect of the magnetic flux density of the impedance 7 is enhanced. Hereinafter, a welded tube welding apparatus according to a second embodiment of the present invention will be described.

Second Embodiment
Next, the configuration of a welded tube welding apparatus according to a second embodiment of the present invention will be described with reference to FIGS. 6 and 8. FIG. 8 is a cross-sectional view showing a welded tube welding apparatus according to the present embodiment, and shows a cross section cut along the line AA of FIG. The impeller case is the same as the above-described first embodiment in that it is not shown.

  As shown in FIG. 8, the welded tube welding apparatus according to the present embodiment differs from the welded tube welding apparatus 100 according to the first embodiment described above in the installation area of the electromagnetic shield material. Specifically, the electromagnetic shielding member 20 according to the present embodiment is a range facing the half circumference of the inner peripheral surface of the open pipe 1 with the opening 2 of the open pipe 1 as a center, that is, the opening of the open pipe 1 It is provided in the area which spreads 90 degrees on both sides in the circumferential direction centering on the center part of 2.

  By providing the electromagnetic shielding material 20 in the above region, the magnetic flux can be more reliably prevented from entering the impedance 7 and the shielding effect of the magnetic flux of the electromagnetic shielding material, that is, the reduction effect of the magnetic flux density of the impedance 7 can be enhanced. Can.

  In addition, about another structure of the welded tube welding device which concerns on this embodiment, since it is the same as that of the case of 1st Embodiment mentioned above, detailed description is abbreviate | omitted.

Third Embodiment
Next, the configuration of a welded tube welding apparatus according to a third embodiment of the present invention will be described with reference to FIGS. 6 and 9. FIG. 9 is a cross-sectional view showing a welded tube welding apparatus according to the present embodiment, where (a) shows a cross section taken along the line A-A of FIG. 6, and (b) shows B- of FIG. The cross section cut | disconnected by B line is shown. In addition, in this embodiment, since the positional relationship of an electromagnetic shielding material and an impedance case is important, in FIG. 9, the impedance case is illustrated.

  As shown in FIG. 9, in the seam welded tube welding apparatus according to the present embodiment, the electromagnetic shielding material 10 is provided in the inside of an impeder case 9 in which the impeder 7 is accommodated. More specifically, in the present embodiment, the electromagnetic shielding material 10 is provided in the gap between the impeder 7 disposed inside the open tube 1 and the inner circumferential surface of the impeder case 9.

  In the first embodiment described above, the positional relationship between the electromagnetic shielding material 10 and the impeder case 9 is not particularly defined. However, if the electromagnetic shielding material 10 is disposed outside the impeder case 9, the electromagnetic shielding is temporarily performed. Since the distance between the material 10 and the impedance 7 is large, the magnetic field of the impedance 7 is more likely to be higher than in the case where the electromagnetic shielding material 10 is provided in the impedance case 9 as in the present embodiment. Also, if the welded tube is a small diameter tube (especially a thick-walled tube), the distance between the outer circumferential surface of the impeder case 9 and the inner circumferential surface of the open tube 1 (about a small diameter tube with an outer diameter of 40 mm or less Depending on the thickness and the shape of the electromagnetic shielding material 10, the electromagnetic shielding material 10 may not be arranged outside the impedance case 9 because the width is about 2 mm.

  Therefore, by providing the electromagnetic shield material 10 in the impeder case 9 as in the present embodiment, the magnetic field of the impeder 7 can be suppressed to improve the magnetic flux density reduction effect, and a small diameter pipe (particularly, thick walled pipe) Even in the case of the above, the electromagnetic shielding material 10 can be easily installed.

  In FIG. 9, an example in which the electromagnetic shield material is installed in a region extending in an arc shape of 1⁄4 circumference along the inner peripheral surface of the open tube 1 with the opening 2 of the open tube 1 as the center ( That is, although the example using the electromagnetic shielding material 10 which concerns on 1st Embodiment is shown, it is not restricted to this. For example, in the present embodiment, the electromagnetic shield material is disposed in a range facing the half circumference of the inner circumferential surface of the open tube 1 with the opening 2 of the open tube 1 as the center (that is, in the second embodiment) Such electromagnetic shielding material 20 may be used).

  Further, in order to prevent the trouble of replacing the electromagnetic shielding material 10, the electromagnetic shielding material 10 may be disposed outside the impedance case 9.

  In addition, about another structure of the welded tube welding device which concerns on this embodiment, since it is the same as that of the case of 1st Embodiment mentioned above, detailed description is abbreviate | omitted.

Fourth Embodiment
Next, the configuration of a welded tube welding apparatus according to a fourth embodiment of the present invention will be described with reference to FIGS. 6 and 10. FIG. 10 is a cross-sectional view showing a welded tube welding apparatus according to the present embodiment, where (a) shows a cross section taken along the line A-A of FIG. 6, and (b) shows B- of FIG. The cross section cut | disconnected by B line is shown. The impeller case is the same as the above-described first embodiment in that it is not shown.

  As shown in FIG. 10, the welded tube welding device according to the present embodiment has substantially the same configuration as the welded tube welding device 100 according to the first embodiment described above, but the impedancer 7 and the electromagnetic shield material 10 The arrangement is different from that of the first embodiment. That is, in the present embodiment, the impeder 7 is configured of a plurality of round rod-like ferromagnetic cores, and each round rod-like impeller is disposed in a substantially circular shape along the inner circumferential surface of the open tube 1 In this case, among the plurality of round rod-like impedances, a part of the round rod-like impedances located on the opening 2 side of the open tube 1 is replaced with the electromagnetic shield material 10. Therefore, in the present embodiment, as in the welded seam welding apparatus according to the first to third embodiments described above, the electromagnetic shield material is disposed on the inside of the open pipe 1 and the inner periphery of the impeder 7 and the open pipe 1 It is not necessarily provided in the gap with the surface.

  In addition, in the case where the plurality of round rod-like impellers constituting the impider 7 are arranged side by side along the longitudinal direction of the open tube 1, only the impeders located at least in the region directly under the induction coil 3 and having a concern of magnetic flux saturation. Can be replaced with the electromagnetic shield material 10, thereby reducing the effect of blocking the reactive current trying to rotate the inner peripheral surface of the open tube 1 which was borne by the portion of the impeding rod by being replaced with the magnetic shield material. Can be minimized.

  In FIG. 10, an example in which the electromagnetic shield material is installed in a region extending in an arc shape of 1⁄4 circumference along the inner peripheral surface of the open tube 1 with the opening 2 of the open tube 1 as the center ( That is, although the example using the electromagnetic shielding material 10 which concerns on 1st Embodiment is shown, it is not restricted to this. For example, in the present embodiment, the electromagnetic shield material is disposed in a range facing the half circumference of the inner circumferential surface of the open tube 1 with the opening 2 of the open tube 1 as the center (that is, in the second embodiment) Such electromagnetic shielding material 20 may be used).

  In the case of the present embodiment, the heating efficiency of the end face portions 2a and 2b of the opening 2 is slightly deteriorated because the number of impedances is reduced compared to the case of the first to third embodiments described above (however, Although there is no problem in production), the installation space of the electromagnetic shield material 10 can be secured with enough space inside the open pipe 1 by the reduction of the number of impedances, stable operation without damage to the impedances. Can continue.

  In addition, about another structure of the welded tube welding device which concerns on this embodiment, since it is the same as that of the case of 1st Embodiment mentioned above, detailed description is abbreviate | omitted.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that those skilled in the art can conceive of various modifications or alterations within the scope of the idea described in the claims, and they are naturally within the technical scope of the present invention. It is understood that.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

A steel pipe made of ordinary steel and having a pipe diameter of 31.8 mm and a wall thickness of 6.3 mm was subjected to an electric current of 3000 A using the electric resistance welded tube welding apparatus of Example 1, Example 2 and Comparative Example 1 shown below. The total calorific value [W / m ³ ] of the end face of the steel pipe in the range of 700 mm upstream from the welding point in the case of seam welding was calculated. The results are shown in FIG. Moreover, the result of having calculated the maximum magnetic flux density [T] of an impeder by FEM (Finite Element Method: finite element method) analysis on the conditions of such a welded tube is shown in FIG. FIG. 12 is a graph showing the relationship between the total calorific value [W / m ³ ] of the end face portion of the open pipe in Example 1 and Example 2 and Comparative Example 1 and the current [A] applied to the induction coil. FIG. 13 is a graph showing the relationship between the maximum magnetic flux density [T] of the impeder in Example 1, Example 2 and Comparative Example 1 and the current [A] applied to the induction coil.

Example 1
The case where the copper tube induction coil having an outer diameter of 10 mm was provided as the electric welded tube welding device of Example 1 was calculated. Here, as shown in FIG. 11, the induction coil is located 60 mm away from the welding point in the running direction and 50 mm upstream from the welding point at a position 10 mm away from the open pipe (steel pipe) in the radial direction. In the range of position, it arranged so that it might turn around in the perimeter direction and it calculated. Further, the impeder, which is a ferromagnetic core made of ferrite, was disposed in the range of a position of 25 mm on the upstream side in the traveling direction from the welding point and a position of 300 mm upstream from the position. Furthermore, assuming a copper plate of 1 mm thickness as an electromagnetic shielding material, this copper plate is expanded by 45 ° circumferentially on both sides around the central portion of the opening (that is, 1/1 along the inner circumferential surface of the open tube The calculation was made on the assumption that it was installed in an arc-shaped area of 4 cycles. The installation range of the electromagnetic shield material (copper plate) in the longitudinal direction of the open tube includes a part of the area directly under the induction coil and a part of the area directly below the end face through which the large current welding current flows. A position of 40 mm on the upstream side in the traveling direction from the welding point and a position of 50 mm on the upstream side from the position were set. The width of the opening of the open tube was 6.5 mm, and the angle of the opening at the welding point was 6 °.

(Example 2)
A region where the electromagnetic shielding material (copper plate of 1 mm thickness) is expanded by 90 ° circumferentially on both sides around the central portion of the opening (that is, the inner periphery of the open tube 1 around the opening 2 of the open tube 1) Electric resistance tube welding was performed in the same manner as in Example 1 except that it was installed in a range facing the half circumference of the surface).

(Comparative example 1)
Electric resistance tube welding was performed in the same manner as in Example 1 except that the electromagnetic shielding material was not installed.

  As shown in FIG. 12 and FIG. 13, the amount of heat generated at the end face of the opening when welded by the seam welded tube using the welded tube welding apparatus provided with the electromagnetic shield material of the first embodiment and the second embodiment is The amount of heat generated was slightly lower than the amount of heat generated when welded using ERW tube welding equipment not equipped with the electromagnetic shielding material of Comparative Example 1 but heat generation was sufficient to perform ERW tube welding. Amount. Further, as for the magnetic flux (that is, the maximum magnetic flux density of the impeder) entering the imperder in the case where the welded tube is welded using the welded tube welding apparatus provided with the electromagnetic shielding material of Example 1 and Example 2, the impeder saturates It has been found that the magnetic flux density (saturation magnetic flux density) decreases to a point smaller than that.

  In particular, in the second embodiment in which the electromagnetic shield material is installed in a range facing the half circumference of the inner circumferential surface of the open tube 1, the electromagnetic shield material is installed in a range of 1⁄4 circumference of the inner circumferential surface of the open tube 1 Since the maximum magnetic flux density can be further lowered than in Example 1, it is found that welding can be performed more efficiently.

  INDUSTRIAL APPLICABILITY The present invention is useful for a welded tube welding apparatus which bends in a cylindrical shape for induction heating while traveling a metal strip and welds between both end portions of the metal strip by an electric current induced in the metal strip. The welded tube manufactured in this manner is used, for example, as a pipe that is required to be reduced in weight, such as an oil well pipe, a pipe for two-wheelers and four-wheel vehicles, and the like.

1 Open tube (metal strip)
2 opening 2a, 2b end face 5 weld point (weld)
6 squeeze roll 7 impeder 8 rod 9 impeder case 10, 20 electromagnetic shielding material 100 welded tube welding device R traveling direction

Claims (4)

An open tube having an opening extending in the traveling direction, both end surfaces of the tube material facing each other from both sides of the opening are melted by an induced current generated on the surface of the open tube, and A welded tube welding apparatus for manufacturing a welded tube, wherein the end faces are brought into contact with each other at a welding point and welding is performed while gradually narrowing the gap,
An induction coil around the outer circumference of the open tube;
An imperator located inside the open tube;
An electromagnetic shield material provided in a range overlapping at least the opening of the open pipe located immediately below the induction coil in the gap between the impedancer disposed inside the open pipe and the inner circumferential surface of the open pipe ,
An ERW tube welding apparatus comprising:   The ERW welding apparatus according to claim 1, wherein the electromagnetic shielding material is provided in a range facing the half circumference of the inner peripheral surface of the open pipe centering on the opening. It further comprises an impedance case for storing the impedance,
The ERW welding device according to claim 1 or 2, wherein the electromagnetic shield material is provided in the impedance case. An open tube having an opening extending in the traveling direction, both end surfaces of the tube material facing each other from both sides of the opening are melted by an induced current generated on the surface of the open tube, and A welded tube welding apparatus for manufacturing a welded tube, wherein the end faces are brought into contact with each other at a welding point and welding is performed while gradually narrowing the gap,
An induction coil around the outer circumference of the open tube;
A plurality of impedances arranged in a substantially circular shape along the inner circumferential surface of the open pipe;
An electromagnetic shield material provided in a range overlapping at least the opening of the open tube located immediately below the induction coil;
Equipped with
Among the plurality of impedances, a part of the impedances located on the side of the opening is replaced with the electromagnetic shield material,

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