JP2008114282A - Apparatus and method for surface treatment of cast steel billet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out a surface treatment uniformly in the width direction even when cast billets and steel billets have a variety of widths. <P>SOLUTION: In an apparatus having a plurality of plasma torches T1 to T7 arranged in parallel with each other so as to generate plasma arcs P between the cast billets H and the plasma torches, electromagnetic coils 22, 24 are arranged outside the respective plasma torches T1, T7 located at both ends so as to generate an AC magnetic field in the direction opposed to the direction of the AC magnetic field generated by an electromagnetic coil 12 in order to reciprocate the plasma arc P in the width direction A. The electromagnetic coils 22, 24 can move toward the central side along the parallel direction of the plasma torches T1 to T7. The outward amplitudes only of the plasma arcs P can be controlled by the AC magnetic fields of the electromagnetic coils 22, 24. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface layer processing apparatus and a surface layer processing method for heating or melting a surface layer of a cast steel slab such as a continuous cast slab of steel or a steel slab in the middle of rolling.

  For example, a plasma heating apparatus is used for the process of modifying the surface layer of a slab after continuous casting or a steel slab during rolling (see Patent Document 1).

  The plasma heating apparatus includes, for example, a direct current plasma plasma torch that is disposed opposite to a slab to be conveyed and has a torch as a cathode and a slab as an anode, and generates a plasma arc between the plasma torch and the slab. The slab is heated and melted by the heat of the plasma arc, and the surface layer is subjected to a modification treatment, for example.

  When heating a relatively wide slab using such a technique, it is necessary to heat the slab by applying a plasma arc to the entire width of the slab. For this reason, for example, it has been proposed to reciprocate the plasma arc in the width direction of the slab using electromagnetic force of an alternating magnetic field to heat the slab (see Patent Document 2). The method of reciprocating the plasma arc using the electromagnetic force of the alternating magnetic field is superior in that the number of mechanical parts can be reduced as compared with the method of scanning the plasma torch.

JP 2004-195512 A JP 54-142154 A

  Under the above prior art, in order to heat-treat a wider slab, a plurality of plasma torches are arranged in parallel along the width direction of the slab at equal intervals. In such a case, an appropriate pitch of the plasma torch is about 100 mm. The reason is as follows. That is, the diameter of the plasma torch used for this kind of heat treatment is about 60 mm, and furthermore, a space for installing the torch between the plasma torches is required to be about 20 mm or more. This is necessary. On the other hand, when trying to increase the torch output to increase the processing width per plasma torch, the flow rate of argon gas used for the arc increases, the flow transitions from laminar flow to turbulent flow, and the arc is disturbed. Since the unevenness of the melt-processed portion of the material becomes severe, the upper limit of the pitch of the plasma torch is about 120 mm. Therefore, in view of these circumstances, the pitch of the plasma torch is about 100 mm.

  Thus, when the pitch of the plasma torches is about 100 mm, the adjustment allowance of the plasma torches at both ends arranged in parallel by not igniting the torch is about 100 mm on one side.

  However, in continuous casting of a continuous cast slab, particularly a slab having a rectangular cross-section for a plate, a technique of changing the width during casting by mechanical movement of a short side is generally used, and from 1 m or less The width is changed in increments of several cm up to 2 m or more. Even in such a case, in order to produce a high-quality product, it is necessary to uniformly heat and melt the slab surface. That is, it is necessary to uniformly heat and melt the slab slab whose width changes in the range of several centimeters to 1 m by the plasma arc.

  In this regard, as described above, the adjustment allowance of the plasma torches at both ends arranged in parallel by not igniting the torch is about 100 mm on one side, so that it is conventionally impossible to adjust the width less than that. If the arc is formed by igniting the plasma torches at both ends without adjustment, the edge of the slab is excessively melted or the arc wraps around to the side of the slab, resulting in processing failure. There was a risk.

  The present invention has been made in view of such a point, and, even for cast pieces having different widths, by adjusting only one side of the reciprocating movement width of the plasma arc in addition to adjustment by not igniting the torch. For example, even if it is an adjustment width of 100 mm or less, this is suitably realized, and it is aimed to uniformly heat or melt a cast steel slab of various widths with a plasma arc to perform surface treatment .

  In order to achieve the above object, the present invention provides a plasma processing apparatus in which a plurality of plasma torches for generating a plasma arc between a cast steel piece and a parallel arrangement along the width direction of the cast steel piece are provided by an alternating magnetic field. A first AC magnetic field generator for reciprocating the plasma arc in the width direction of the cast steel piece; and a second AC magnetic field generator for generating a magnetic field opposite to the first AC magnetic field. .

  As described above, in the present invention, in addition to the first AC magnetic field generator for reciprocating the plasma arc in the width direction of the cast steel piece, the second AC magnetic field for generating a magnetic field opposite to the first AC magnetic field. Since it has a generator, for example, with respect to a plasma arc by a plasma torch at both ends, the second AC magnetic field generator is brought closer to the arc from both ends, so that the AC by the second AC magnetic field generator With the magnetic field, the magnetic field generated by the first AC magnetic field generator can be gradually canceled from both end sides, and the movement width (runout width) outside the arc can be adjusted. That is, it is possible to adjust only the outside portion of the arc swing width by the first AC magnetic field generator. Therefore, for example, even an adjustment width of 100 mm or less can cope with this.

  The magnetic field intensity by the second AC magnetic field generator may be variable. As a result, the touch width can be further finely adjusted.

  The first AC magnetic field generator is, for example, a first AC magnetic field coil arranged in the parallel direction of the plasma torch and arranged before and after the plasma arc generated by the plasma torch. The generator is, for example, a second AC magnetic field coil that is disposed outside at least one of the plasma torches at both ends and is positioned before and after the plasma arc generated by the plasma torch when viewed from the parallel direction of the plasma torch. You may make it a 2nd alternating current magnetic field coil move to the center side along the parallel direction of a plasma torch. Thereby, the touch width of the both ends of the plasma torch on the outside can be adjusted according to the degree of movement toward the center.

  You may have a control part which controls the number of the plasma torch which produces a plasma arc, and the position of the movement destination of the said 2nd alternating current magnetic field coil according to the width | variety of the cast steel piece used as a process target. Accordingly, the number of plasma torches to be ignited and the touch width can be automatically adjusted according to the width of the cast steel piece.

You may further provide the conducting wire which is arrange | positioned at the both sides of the parallel direction of these DC plasma torches, and flows an electric current in the same direction as the plasma arc by the said plasma torch.
When a plurality of plasma torches are arranged in parallel, an electromagnetic force in the central direction is generated in each plasma arc due to the interaction of the DC magnetic field formed by the currents of the plurality of plasma arcs, and the plasma arc is biased toward the center side. However, in this way, by providing a conducting wire that allows current to flow in the same direction as the plasma arc, the magnetic field caused by the plasma arc current is canceled out by the DC magnetic field generated thereby, and the electromagnetic force acting on the plasma arc is removed. In addition, the above-described bias can be corrected. Therefore, when processing the cast steel slabs having different widths, if the number of plasma torches to be ignited varies from the outside, each plasma arc is adjusted by adjusting the current value of the conducting wire and adjusting the magnetic field due to the conducting wire current, for example. The DC magnetic field at can be canceled out.

  The conducting wire may be movable toward the center along the parallel direction of the plasma torch. Thereby, for example, when the width of the cast steel piece changes, the distance between the conductive wire and the cast steel piece can be adjusted to cancel the DC magnetic field in the plasma arc.

  According to another aspect, the present invention provides a plurality of plasma torches for generating a plasma arc between a cast steel piece and a parallel arrangement along the width direction of the cast steel piece, and the surface of the cast steel piece is treated by the plasma arc. In the surface layer processing method, the plasma arc is reciprocated in the width direction of the cast steel slab by the first AC magnetic field, and the plasma arc at both ends in the width direction is driven by the second AC magnetic field opposite to the first AC magnetic field. It is characterized by controlling the movement width to the outside in the width direction.

  In such a case, when controlling the movement width of the plasma arc at both ends in the width direction to the outside in the width direction, the output of the plasma arc when the plasma arc is moving outside may be controlled. By doing this, the amount of movement of the outer side in the width direction is reduced, so that the output of the plasma arc is reduced, and a more uniform amount of heat per unit area can be applied, so that uniform processing is possible as a whole. .

  According to the present invention, even if the width of a cast steel piece to be processed changes, the irradiation width of the arc on both ends thereof can be adjusted and heated uniformly to process, and a high-quality product is manufactured. be able to.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 is a schematic diagram of a schematic configuration of a surface processing apparatus 1 according to the present embodiment as viewed from the front, and FIG. 2 is a schematic diagram of the same from a plane.

  This surface layer processing apparatus 1 is provided on the conveyance line of the slab H conveyed in a horizontal direction. The surface layer processing apparatus 1 has, for example, a plurality of, for example, seven plasma torches T <b> 1 to T <b> 7 arranged above the slab H to be conveyed in parallel along the width direction A of the slab H. The number of plasma torches is arbitrary. These plasma torches T <b> 1 to T <b> 7 form a plasma arc P by DC plasma between each of the slabs H by application of a voltage from the DC power source 2. In each plasma arc P, a current flows from the slab H side to the plasma torch side. The number of ignitions and the output of the plasma torches T1 to T7 are controlled by the control device 3.

  A first AC magnetic field is generated below the plasma torches T1 to T7 and before and after the slab H in the transfer direction B, that is, before and after the transfer direction B of the plasma arc P formed by the plasma torches T1 to T7. As an apparatus, electromagnetic coils 11 and 12 are provided so as to be parallel to each other. These electromagnetic coils 11, 12 cause the Lorentz force to act periodically on each plasma arc P by supplying an AC current from an AC power supply 13, and cast each plasma arc P in accordance with the supplied AC frequency. Reciprocate in the width direction A of the piece H. More precisely, the reciprocal movement is close to the movement in which the plasma arc P reciprocates around the lower end of the plasma torch.

  Among the plasma torches T1 to T7, outside the plasma torch T1 positioned at one end, electromagnetic coils 21 and 22 as second magnetic field generators are arranged in parallel to each other, and positioned at the other end. Outside the plasma torch T7, electromagnetic coils 23 and 24 as a second magnetic field generator are arranged so as to be parallel to each other. Therefore, the electromagnetic coils 21 and 22 and the electromagnetic coils 23 and 24 are disposed to face each other. The electromagnetic coils 21, 22, 23, and 24 have loop shapes of the same type and the same size. When the alternating current is supplied from the alternating current power supply 25, the electromagnetic coils 21, 22, 23, and 24 are electromagnetic The magnetic fields opposite to the coils 11 and 12 are generated in synchronization. The magnetic field strength of the electromagnetic coils 21, 22, 23, 24 is the same as that of the electromagnetic coils 11, 12. The output of the AC power supply 25 is controlled by the main controller 31. The main controller 31 performs phase control between the AC power supply 13 of the electromagnetic coils 11 and 12 and the AC power supply 25 of the electromagnetic coils 21, 22, 23, and 24.

  Two sets of electromagnetic coils 21 and 22 are supported by a support member 26, and the support member 26 is attached to a horizontal movement mechanism 27 such as a cylinder. The electromagnetic coils 21 and 22 are plasma torches. It can move to the center side (plasma torch T4 side) along the parallel direction of T1 to T7, that is, the width direction A. The electromagnetic coils 23 and 24 are also supported by a support member 28, and the support member 28 is attached to a horizontal movement mechanism 29, and is arranged along the parallel direction of the plasma torches T 1 to T 7, that is, along the width direction A. It can be moved to the (plasma torch T4 side). The amount of movement of these horizontal movement mechanisms 27 and 29 is controlled by the main controller 31.

  As described above, the electromagnetic coils 21 and 22 are arranged to be parallel to each other, and the electromagnetic coils 23 and 24 are also arranged to be parallel to each other. As shown by the broken line in FIG. 2, the distance between the coils 23 and 24 is between the electromagnetic coil 11 and the plasma torch T when moving to the center side (plasma torch T4 side) along the width direction A. The electromagnetic coils 22 and 24 enter, and the electromagnetic coils 21 and 23 enter between the electromagnetic coil 12 and the plasma torch T. That is, in the present embodiment, the electromagnetic coils 21, 22, 23, and 24 are arranged to be able to enter inside the electromagnetic coils 11 and 12 with the plasma arc generated by the plasma torch T interposed therebetween. In addition, not only this but the space | interval between the electromagnetic coils 21, 22 and the electromagnetic coils 23, 22 so that the electromagnetic coils 21, 22, 23, 24 can enter the outside of the electromagnetic coils 11, 12 across the plasma arc. You may set the space | interval between 24, respectively.

  The surface layer processing apparatus 1 according to the present embodiment has the above-described configuration. When a voltage from the DC power source 2 is applied, plasma generated by DC plasma between the plasma torches T1 to T7 and the slab H is applied. When the arc P is formed and an alternating current is supplied to the electromagnetic coils 11 and 12 from the alternating current power supply 13, the formed plasma arc P reciprocates in the width direction A of the slab H. However, in this embodiment, since the loop-shaped electromagnetic coils 11 and 12 are used, the reciprocation of the plasma arc P in this embodiment is the lower end of the plasma torch T as shown in FIG. This movement is close to reciprocating rotation around the vicinity of the part. Accordingly, in this specification, for convenience of explanation, the reciprocating movement is referred to as swinging, and the moving distance on the surface of the slab H at that time is referred to as a swing width. That is, in FIG. 3, the length D in the width direction A where the plasma arc P is irradiated on the surface of the slab H is the runout width. For example, referring to the plasma torch T2, the deflection width inside the plasma torch center line C (plasma torch T4 side) is Din, and the deflection width outside the torch center line C (plasma torch T1 outside) is Dout. To do.

  Under the influence of the AC magnetic field of only the electromagnetic coils 11 and 12 by the AC current from the AC power source 13, the distribution of the magnetic flux density is centered on the center line C of the torch as shown in the lower diagram of FIG. Therefore, in the formed plasma arc P, the inner deflection width Din = the outer deflection width Dout. In this type of processing, the deflection width D is usually about 100 mm, and as described above, the pitch of the parallel arrangement of the plasma torches T1 to T7 (the distance between the centers of the torches) is 100 mm. When the seven plasma torches T1 to T7 are provided as in the surface layer processing apparatus 1 according to the embodiment, the upper limit of the width M of the slab H that can be appropriately processed is 700 mm, and the plasma torches are sequentially formed from both ends. The adjustment allowance by not igniting T is 100 mm on one side.

  Therefore, for example, when the width M of the slab H to be processed is 500 mm, the seven plasma torches T1 and T7 at both ends need not be ignited. The slab H having a width of 500 mm can be uniformly processed by the plasma arc over the entire width direction A by the plasma arc by the five torches of the plasma torches T2 to T6.

  However, for example, in the case of a slab H having a width of 650 mm, on the premise that the center of the slab H is not shifted, that is, when the adjustment margin is less than 100 mm on one side, it is not possible to appropriately deal with the ignition control of the plasma torches T1 to T7 alone. . That is, for example, when processing is performed with the seven plasma torches T1 to T7 as in the previous example, the outer deflection width Dout in the plasma arc of the plasma torches T1 and T7 at both ends at that time becomes excessive, and the width direction of the slab H There is a possibility that the edge portion of the steel will be in an excessively melted state, and the arc itself may wrap around the side surface of the slab or the molten portion may fall off. Moreover, if it processes with five plasma torches T2-T6, the area | region of 75 mm will each be unprocessed from the both ends of a slab.

  According to the present embodiment, it is possible to perform appropriate processing even for such a slab H having a width of, for example, 650 mm. That is, the electromagnetic coils 21, 22 and the electromagnetic coils 23, 24 arranged outside the plasma torches T1, T7 at both ends are moved to the center side (plasma torch T4 side), and the plasma torches T1, T1, The runout width Dout outside T7 can be reduced according to the width of the slab H.

  This will be described with reference to the plasma torch T1. As shown in FIGS. 4 and 5, the horizontal moving mechanism 27 causes the tips of the electromagnetic coils 21 and 22 to enter from the outside of the plasma torch T1 to the vicinity of the plasma torch T1. Let Then, since the alternating magnetic field of the electromagnetic coils 21 and 22 is a magnetic field opposite to the alternating magnetic field of the electromagnetic coils 11 and 12 that oscillate the plasma arc P, as shown in FIG. , 22, the AC magnetic fields of the electromagnetic coils 11, 12 can be canceled out gradually from the end side. As the AC magnetic fields of the electromagnetic coils 11 and 12 are canceled out in this way, the end side, that is, the outer deflection width Dout becomes smaller. If the degree of cancellation by the alternating magnetic field of the electromagnetic coils 11 and 12, that is, the degree of entry of the electromagnetic coils 21 and 22 (movement distance to the center side) is adjusted according to the adjustment width of the width of the slab H, the slab H An appropriate outer deflection width Dout can be set with respect to the width. For example, in the case of the slab H having a width of 650 mm as described above, the electromagnetic coils 21 and 22 and the electromagnetic coils 21 and 22 are set so that the outer deflection width Dout of the plasma arc of the plasma torches T2 and T6 at both ends is 25 mm. What is necessary is just to control the movement distance to the center side of the coils 23 and 24. FIG.

  Therefore, according to the present invention, even if the width of the slab H to be processed fluctuates, it is always possible to appropriately melt by controlling the moving distances of the electromagnetic coils 21 and 22 and the electromagnetic coils 23 and 24 to the center side. Processing can be performed.

  In addition to controlling the moving distance of the electromagnetic coils 21 and 22 and the electromagnetic coils 23 and 24 toward the center, the AC power supplied to the electromagnetic coils 21 and 22 and the electromagnetic coils 23 and 24 is also adjusted. Thus, finer control of the outer deflection width Dout is also possible.

  The moving distances of the electromagnetic coils 21 and 22 and the electromagnetic coils 23 and 24 toward the center side are the deflection width Dout outside the plasma arc of the ignited plasma torch T and the slab H to be processed. It may be controlled by looking at the state of the edge portion. For example, the width M of the slab H obtained in advance by experiments, the number of plasma torches T to be ignited, and the centers of the electromagnetic coils 21 and 22 and the electromagnetic coils 23 and 24 Correlation data with the moving distance to the side is acquired, and based on the data, the main controller 31 may automatically control these according to the width M of the slab H to be processed. Good.

  When controlling the situation of the edge portion of the slab H to be processed, for example, the edge portion of the slab H is imaged by using a CCD camera, and the image processing data of the edge portion of the slab H is preferably used. it can. That is, in an image captured by a CCD camera using a filter generally used for welding, an area where plasma heat input is sufficient emits white and high luminance. Therefore, using the image processing data of the end of the slab H to be processed, the corner position of the end of the slab H is compared with the outside of the line with high brightness and the contact of the material (slab H). When the contact is inside the end, the plasma amplitude can be moved outward by feedback control so that the contact overlaps the end.

  By the way, as described above, when the outer deflection width Dout of the plasma arc is made smaller than the inner deflection width Din, the inner deflection width Din is increased in the surface layer of the slab H corresponding to the outer deflection width Dout. When the input heat amount per unit area is larger than that of the corresponding surface layer, and the outer deflection width Dout is controlled to be considerably smaller than the inner deflection width Din, the melted state is increased between the outer deflection width Dout and the inner deflection width Dout. In the portion of the runout width Din, non-uniformity that cannot be ignored may occur.

  In order to prevent such a situation, when the plasma arc swings outward, the output of the plasma arc may be controlled to be reduced in synchronization therewith. For example, when the slab H having a width of 650 mm is processed, the outer deflection width Dout of the plasma arc of the plasma torches T1 and T7 at both ends that are ignited is controlled to be 25 mm, that is, outside When the deflection width Dout is ½ of the inner deflection width Din, the output of the plasma arc may be reduced to ½ when the plasma arc swings outward. As a result, the same amount of heat is input per unit area between the outer deflection width Dout and the inner deflection width Din, and the outer deflection width Dout portion and the inner deflection width Din portion. The portion can be uniformly melt-processed.

  Such control is performed, for example, by the main control device 31 controlling the DC power supply 2 based on the ratio of the outer deflection width Dout and the inner deflection width Din and the synchronization signal based on the frequency signals of the AC power supplies 13 and 25. This can be realized by controlling the control device 3 to be controlled.

  By the way, when a plurality of plasma torches T are arranged in parallel, an electromagnetic force in the central direction acts on each plasma arc due to the interaction of magnetic fields formed by the currents of the plurality of plasma arcs, and the plasma arc is formed on the slab H. May be biased toward the center. In such a case, when the deviation is large, the slab H is heated unevenly in the width direction A or melted, and for example, the surface modification process of the slab may be uneven.

  The surface processing apparatus 51 according to the second embodiment shown in FIGS. 7 and 8 corrects this. That is, in the surface layer processing apparatus 51, in addition to the electromagnetic coils 11, 12 as the first alternating magnetic field generator and the electromagnetic coils 21, 22, 23, 24 as the second alternating magnetic field generator, Metal rods 61, 62, 63, and 64 serving as conducting wires, which are mechanisms for canceling the electromagnetic force in the center direction generated by the direct current plasma.

  More specifically, for example, on the plasma torch T1 side, the metal rods 61 and 62 formed of, for example, a copper cylindrical tube are perpendicular to the plasma arc P in the vertical direction (the normal direction of the surface of the slab H). It is provided for. The metal rods 61 and 62 are disposed at a height similar to that of the plasma arc P formed between the plasma torch T and the slab H, and the total length thereof is set longer than that of the plasma arc P. The metal bars 61 and 62 are arranged in parallel.

  The metal rods 61 and 62 are attached to a horizontal movement mechanism 72 such as a cylinder via a support member 71, move to the center side along the parallel direction of the plasma torch T, that is, the width direction A, and the metal rod 61. , 62 can advance and retreat with respect to the end of the slab H in the width direction A. The metal rods 61 and 62 are arranged at positions symmetrical with respect to a straight line L in which the plasma torches T are arranged as viewed from above. Further, the metal rods 61 and 62 are arranged at a predetermined distance from the straight line L so as not to contact the plasma torch T and the plasma arc P when moved to the slab H side.

  The metal bars 63 and 64 disposed on the outer side on the plasma torch T7 side are also disposed in the same manner as the metal bars 61 and 62 and attached to the horizontal movement mechanism 74 via the support member 73. Inside the metal rods 61, 62, 63, 64, there are formed refrigerant flow paths through which water serving as refrigerant flows. Thereby, the temperature rise by the heat_generation | fever of the metal rods 61, 62, 63, and 64 is suppressed.

  In the present embodiment, these metal rods 61, 62, 63, 64 are in front of and behind the conveying direction B across the plasma torch T arranged in parallel, as viewed from the side, and with the electromagnetic coils 11, 12, It arrange | positions so that it may be located between the plasma torch T arrange | positioned in parallel. The distance between the electromagnetic coils 21 and 22 and the distance between the electromagnetic coils 23 and 24 are set to be larger than those of the previous surface layer processing apparatus 1 and are along the conveyance direction B with respect to the electromagnetic coils 11 and 12. Are arranged outside.

  Of course, the present invention is not limited to these, and the metal bars 61, 62, 63, 64 may also be disposed outside the electromagnetic coils 11, 12 along the transport direction B as viewed from the side. 63, 64 and the electromagnetic coils 21, 22, 23, 24 may be disposed inside the electromagnetic coils 11, 12 along the conveyance direction B as viewed from the side. Furthermore, the state opposite to that shown in FIG. 8, that is, the electromagnetic coils 21, 22, 23, 24 are arranged inside the electromagnetic coils 11, 12 along the conveying direction B as viewed from the side, and the metal rod 61 , 62, 63, 64 may also be arranged on the outside.

  The metal bars 61 and 62 are connected to a DC power source 75, and the metal bars 63 and 64 are connected to a DC power source 76. With this configuration, a current in the same direction as the direct current plasma arc P can be passed through the metal rods 61, 62, 63, 64 at a desired current value. A DC magnetic field is formed in the region on the slab H by the DC current flowing through these metal rods 61, 62, 63, 64, and the magnetic field formed by the interaction of the currents of the plasma arc P generated in parallel is canceled out. be able to. By canceling out the magnetic field in this way, each plasma arc P is not subjected to the electromagnetic force attracting each other, that is, the above-described force toward the center.

  The DC power supplies 75 and 76 and the horizontal movement mechanisms 72 and 74 are controlled by the main controller 31. For example, a plasma torch T to be ignited (the number of plasma torches forming a plasma arc) is selected according to the width M of the slab H, and when the plasma torch T is used, the magnetic field in each plasma arc P is used. The position and current value of the movement destination of the metal rods 61, 62, 63, 64 are selected so that is canceled.

  Since the surface processing apparatus 51 has the above-described configuration, the current of the plasma arc P is generated by the DC magnetic field according to the movement of the metal bars 61, 62, 63, and 64 along the center direction along the width direction A. As a result, it is possible to prevent the phenomenon that the plasma arc on the slab H is biased toward the center as described above. Therefore, a surface layer process that is more uniform in the width direction than the surface layer processing apparatus 1 according to the first embodiment can be performed on the slab H.

  In the above embodiment, the metal rods 61, 62, 63, 64 are movable, but may be fixed. In such a case, the magnetic field in the plasma arc P can be canceled out by adjusting the current values of the metal bars 61, 62, 63, 64. When the metal rods 61, 62, 63, 64 are fixed as described above, the metal rods 61, 62, 63, 64 are arranged on the straight line L of the row of plasma torches T as viewed from the side. May be.

  The surface layer processing apparatus of the above-described embodiment is used, for example, when the slab H is heated or an additive such as carbon is supplied to the slab H to perform the surface layer melt reforming process. The present invention can also be applied to a surface layer reforming process performed by adding an additive element other than carbon or an alloy thereof to the slab H. Furthermore, the object to be treated of the present invention is not limited to a cast slab, and may be a steel slab.

  After cutting the slab for which continuous casting was completed, the surface layer reforming process by plasma heating and melting was performed on the slab using the surface layer processing apparatus 1 described above. The cast slab as a sample has a thickness of 250 mm, and the thickness of the continuous cast slab of 0.2 mass% C steel, which is reduced to 1,150 mm from the width of 1200 mm during casting, conveys 5 mm of the surface layer of 10 mm / s. Melt processing at speed. The number of plasma torches T in the apparatus used is 12, and the pitch of each torch is 100 mm.

  First, as a result of processing without operating the electromagnetic coils 21, 22, 23, and 24 as the second AC magnetic field generator, for the first slab with a width of 1200 mm, the edge is sufficiently uniform in the slab width direction. A good melted state was also obtained in the portion, but in the latter half of the 1150 mm wide slab, the edge portion was excessively melted, causing a problem that the melted portion dripped from the end portion.

  On the other hand, the electromagnetic coils 21, 22, 23, 24 as the second AC magnetic field generator are operated, and when the plasma arc swings outward in the width direction, the plasma output is halved in synchronization with this. As a result, even with a slab having a width of 1150 mm, a uniform molten state having a melting depth of 5 mm ± 0.5 mm was obtained as a whole, and the phenomenon of the end portion being melted down could be suppressed.

  INDUSTRIAL APPLICABILITY The present invention is useful when uniformly treating a cast steel piece having a varying width in the width direction.

It is a schematic diagram which shows the outline seen from the front of the structure of the surface layer processing apparatus concerning 1st Embodiment. It is a schematic diagram which shows the outline seen from the plane of the structure of the surface layer processing apparatus concerning 1st Embodiment. It is explanatory drawing which shows the rocking | fluctuation state of the alternating magnetic field and plasma arc by an electromagnetic coil. It is explanatory drawing seen from the front which shows the state which moved the electromagnetic coil to the center side. It is explanatory drawing seen from the plane which shows the state which moved the electromagnetic coil to the center side. It is explanatory drawing which shows the rocking | fluctuation state of the alternating current magnetic field and plasma arc at the time of moving an electromagnetic coil to the center side. It is a schematic diagram which shows the outline seen from the front of the structure of the surface layer processing apparatus concerning 2nd Embodiment. It is a schematic diagram which shows the outline seen from the plane of the structure of the surface layer processing apparatus concerning 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface processing apparatus 2 DC power supply 11, 12, 21, 22, 23, 24 Electromagnetic coil 13, 25 AC power supply 27, 29 Horizontal movement mechanism 31 Main controller H Slab P Plasma arc A Width direction B Conveyance direction

Claims (8)

In the surface treatment apparatus in which a plurality of plasma torches that generate a plasma arc between the cast steel pieces are arranged in parallel along the width direction of the cast steel pieces,
A first AC magnetic field generator for reciprocating the plasma arc in the width direction of the cast steel piece by an AC magnetic field;
A surface layer processing apparatus for cast steel pieces, comprising: a second AC magnetic field generator that generates a magnetic field opposite to the first AC magnetic field. The surface treatment apparatus for cast steel pieces according to claim 1, wherein the magnetic field intensity by the second AC magnetic field generator is variable. The first AC magnetic field generator is a first AC magnetic field coil disposed in the parallel direction of the plasma torch and disposed before and after the plasma arc generated by the plasma torch,
The second AC magnetic field generator is a second AC magnetic field coil disposed outside each of the plasma torches at both ends and positioned before and after the plasma arc generated by the plasma torch when viewed from the parallel direction of the plasma torch. ,
The surface treatment apparatus for cast steel pieces according to claim 1 or 2, wherein the second AC magnetic field coil is movable toward the center side along the parallel direction of the plasma torch. It has a control part which controls the number of plasma torches which produce a plasma arc, and the position of the move place of the 2nd exchange field coil according to the width of the cast steel piece used as a candidate for processing. The surface layer processing apparatus of the cast steel piece of 3. 5. The cast steel slab according to claim 1, wherein the cast steel slab is provided on both sides of the plurality of plasma torches in a parallel direction, and has a conducting wire that allows a current to flow in the same direction as a plasma arc by the plasma torches. Surface processing equipment. The surface treatment apparatus for cast steel pieces according to claim 5, wherein the conducting wire is movable toward the center side along a parallel direction of the plasma torch. In the surface layer processing method of arranging a plurality of plasma torches for generating a plasma arc between the cast steel pieces in parallel along the width direction of the cast steel pieces and processing the surface layer of the cast steel pieces by the plasma arc,
The first AC magnetic field causes the plasma arc to reciprocate in the width direction of the cast steel piece,
A method for treating a surface layer of a cast steel slab, comprising controlling a movement width of plasma arcs at both ends outward in the width direction by a second AC magnetic field opposite to the first AC magnetic field. The control of the plasma arc output when the plasma arc is moving to the outside when controlling the movement width of the plasma arc at the both ends to the outside in the width direction. The surface layer processing method of the cast steel piece of description.

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