JP5010344B2 - Surface treatment apparatus for cast steel pieces and surface treatment method for cast steel pieces - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform uniform melting treatment at an optional position in the width direction of a cast slab by adjusting distribution of alternating current magnetic fields thereby making an incident angle of a plasma arc on the surface of the cast slab always constant. <P>SOLUTION: A surface layer treatment apparatus 1 is provided with a plasma torch T generating the plasma arc P in a space between the cast slab H and the plasma torch T. Between the plasma torch T and the cast slab H, an alternating current magnetic field Mt reciprocating the plasma arc P in the width direction A of the cast slab H and an alternating current magnetic field Mh in a direction reverse to the magnetic field Mt below it are generated by alternating current generators (electromagnetic coils 21, 22). The plasma arc P reciprocated in the width direction A is rebent with electromagnetic force by the magnetic field Mh in the reverse direction immediately before it reaches the cast slab H, and the incident angle of the plasma arc P on the cast slab H can be controlled. <P>COPYRIGHT: (C)2009,JPO&amp;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 slab after continuous casting or the surface layer of 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 the surface layer of the cast steel slab is melted, it is necessary to uniformly heat and melt the cast steel slab by a plasma arc, and to melt the surface layer of the cast steel slab as uniformly as possible. That is, when heating a wide cast steel piece using the technique shown in Patent Document 1 or the like, it is necessary to heat the cast steel piece by applying a plasma arc to the entire width direction of the cast steel piece. For this reason, it has been proposed to reciprocate the plasma arc in the width direction of the cast steel piece using the electromagnetic force of the alternating magnetic field to heat the cast piece (see Patent Document 2). Thus, 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. In the present application, “cast steel slab” is a general term for “slab slab” and “steel slab”, “slab slab” is a steel material after casting, and “steel slab” is after rolling the slab. Means steel.

JP 2004-195512 A JP 54-142154 A

  In the prior art described above, for example, as shown in FIG. 13, two current paths 51, 52 made of metal wires, for example, are arranged in parallel with each other before and after the plasma torch T with respect to the conveying direction B of the cast steel slab H. , 53, 54 are provided to generate an alternating magnetic field M as indicated by a thick arrow in the figure, and the plasma arc is reciprocated in a direction perpendicular to the paper surface of FIG. It should be noted that the current direction shown in the figure indicates a state of a certain moment and is an alternating current, so the direction is changed over time. However, the current flowing in the current paths 51 and 52 is always in the same direction. The current flowing in the current paths 53 and 54 is in the opposite direction.

  When the plasma arc is reciprocated in the width direction of the slab H in this way, the plasma arc P is incident on the surface of the slab H in an oblique direction as shown in FIG. In such a case, the incident width b at the end is larger than the incident width a just below the plasma torch T, so the density of the incident heat at the end is lower than directly below the plasma torch T. Further, since the plasma gas diffuses by being incident obliquely, the amount of incident heat cannot be derived simply by the ratio of the area of the incident portion. Accordingly, if the plasma arc P is reciprocated at a constant plasma output and at a constant speed, the amount of heat input to the plasma arc P differs depending on the position in the width direction A of the slab H. May not be able to be processed properly.

  Thus, when the plasma arc P is incident at different angles depending on the position in the width direction A of the slab H, in order to make the melting depth of the molten slab surface layer uniform, The frequency must be changed. In addition, it is necessary to adjust different AC magnetic fields according to processing conditions such as the type of slab, processing speed, and plasma output. Therefore, it is necessary to perform a processing test for a plurality of processing conditions in advance and set an appropriate waveform and frequency of the alternating magnetic field, which takes a lot of time and effort.

  The present invention has been made in view of such points, and by adjusting the distribution of the alternating magnetic field, the angle of incidence of the plasma arc on the surface of the cast steel slab is always constant, and is uniform at any position in the width direction of the cast steel slab. The purpose is to perform a proper melting process.

In order to solve the above-described problem, the present invention provides a surface treatment apparatus including a plasma torch that generates a plasma arc between a cast steel piece and the plasma arc between the plasma torch and the cast steel piece. plasma and alternating magnetic field for reciprocating in the width direction of the said alternating magnetic field thereunder have a alternating magnetic field generator for generating an AC magnetic field in the opposite direction, the alternating magnetic field generator is generated by the plasma torch A pair of electromagnetic coils arranged before and after the arc in the conveying direction of the cast steel piece, and an AC power supply for supplying an alternating current in the same direction to the pair of electromagnetic coils .

  As described above, the present invention has an AC magnetic field generator that generates both an AC magnetic field for reciprocating the plasma arc and an AC magnetic field in the opposite direction before the cast steel slab, which is a member to be processed. Therefore, for example, when the plasma arc is moved to the left along the width direction of the cast steel piece, the plasma arc can be bent back rightward just before entering the cast steel piece. That is, the incident angle to the cast steel piece can be adjusted so as not to heat the cast steel piece with the plasma arc tilted. Therefore, even if the plasma arc is moved in the width direction, the surface layer treatment can be performed by always inputting heat while maintaining a substantially right angle of incidence as in the case of heat input immediately below the plasma torch. Note that the heat input with the "substantially right angle" incident angle maintained here does not necessarily have to be exactly a right angle, because a right angle or an unavoidable error range thereof is obtained by such an operation of the present invention. It is. Therefore, hereinafter, even if there is a description that the plasma arc heats into the cast steel piece while maintaining a right angle of incidence with respect to the action of the present invention, it is not necessarily limited to being strictly right angle.

The AC magnetic field generator includes a pair of electromagnetic coils disposed before and after a cast steel slab of a plasma arc generated by the plasma torch, and an AC power source that supplies an alternating current in the same direction to the pair of electromagnetic coils. Thus, it is possible to generate both an alternating magnetic field for reciprocating the plasma arc and a magnetic field for bending back with a simple structure. In such a case, the pair of electromagnetic coils may be movable in the vertical direction.

Further, the AC magnetic field generator supplies four AC coils arranged in parallel vertically on the front and rear sides of the transport direction of the cast steel pieces of the plasma arc generated by the plasma torch, and supplies AC current to the electromagnetic coils. The two pairs of electromagnetic coils on the plasma torch side and the two pairs of electromagnetic coils on the cast steel piece side may form alternating magnetic fields opposite to each other. With such a structure, the AC magnetic field for reciprocating the plasma arc and the magnetic field for bending the plasma arc near the cast steel slab are formed by different electromagnetic coils, making it easier and more precise to enter the plasma arc. The corner can be adjusted.

  In the above case, AC currents may be supplied from different AC power sources to the two pairs of electromagnetic coils on the plasma torch side and the two pairs of electromagnetic coils on the cast steel piece side. As a result, fine adjustment can be made with respect to each of the deflection width and the incident angle of the plasma arc, so that more precise surface layer processing is possible.

According to another aspect, the present invention includes a plasma torch for generating a plasma arc between a cast steel piece and a surface layer treatment method for treating a surface layer of the cast steel piece with the plasma arc, the plasma torch and the By generating both an alternating magnetic field for reciprocating the plasma arc in the width direction of the cast steel piece and an alternating magnetic field opposite to the alternating magnetic field below the cast steel piece, The incident angle to the cast steel slab is controlled, and the alternating magnetic field and the alternating magnetic field opposite to the alternating magnetic field are applied to a pair of electromagnetic coils arranged before and after the plasma arc in the transport direction of the cast steel slab. It is characterized by being generated by supplying alternating current in the same direction .

In such a case, the angle of incidence of the plasma arc on the cast steel piece may be further controlled by moving the pair of electromagnetic coils in the vertical direction.
The plasma arc generated by the plasma torch is arranged in parallel above and below four electromagnetic coils on each side before and after the transport direction of the cast steel piece, and the alternating magnetic field and the alternating magnetic field opposite to the alternating magnetic field are: You may make it generate | occur | produce by supplying the alternating current of mutually opposite direction with respect to two pairs of electromagnetic coils by the side of the said plasma torch and two pairs of electromagnetic coils by the side of the said cast steel among these coils.

  According to the present invention, it is possible to adjust the incident angle of the plasma arc to the cast steel piece subjected to the surface layer treatment, and to always make the incident angle substantially perpendicular to the surface of the cast steel piece. Surface treatment can be performed, and high-quality products can be manufactured.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 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.

  The surface layer processing apparatus 1 is provided on the conveyance line of the slab H conveyed in the horizontal direction. The surface layer processing apparatus 1 has, for example, one or a plurality of plasma torches T disposed above the slab H to be conveyed. In the case of a plurality of plasma torches T, the plasma torches T are arranged in parallel along the width direction A of the slab H, but the number of the plasma torches T itself is arbitrary. The plasma torch T forms a plasma arc P by DC plasma with the slab H by applying a voltage from the DC power source 2. In the plasma arc P, a current flows from the slab H side to the plasma torch side. The output control of the plasma torch T is controlled by the control device 3. The plasma gas for generating the plasma arc P is preferably a non-oxidizing gas such as nitrogen gas or argon gas.

  Below the plasma torch T and before and after the slab H transfer direction B, that is, before and after the transfer direction B of the plasma arc P formed by the plasma torch T, linear electromagnetic waves as an AC magnetic field generator Coils 21 and 22 are provided in parallel to face each other. These electromagnetic coils 21, 22 cause the Lorentz force to act periodically on the plasma arc P by supplying an alternating current from the AC power source 5, and the plasma arc P is cast according to the supplied AC frequency. Reciprocate in the width direction A of H.

  FIG. 3A shows an enlarged cross section viewed from the CC direction of FIG. 2, and the electromagnetic coils 21 and 22 are arranged at symmetrical positions with respect to the central axis of the plasma torch T and are shown in FIG. When an alternating current is supplied from the alternating current power source 5, the current flows through the electromagnetic coils 21 and 22 in the same direction. As a result, magnetic fields Mt and Mh in opposite directions are generated on the upper and lower sides of the electromagnetic coils 21 and 22 as indicated by arrows in FIG. FIG. 3B shows the distribution of magnetic flux density at this time. The figure shows the direction of the instantaneous current, and the direction is changed over time. The output of the AC power supply 5 is controlled by the main controller 4.

  The surface layer processing apparatus 1 according to the present embodiment has the above-described configuration, and when a voltage from the DC power source 2 is applied, a plasma arc P generated by DC plasma between the plasma torch T and the slab H is applied. When an alternating current is supplied to the electromagnetic coils 21 and 22 from the alternating current power source 5, the plasma arc P reciprocates in the width direction A of the slab H in response to the electromagnetic force.

  FIG. 4 shows a moving state of the plasma arc P according to the present embodiment. When an alternating current flows through the electromagnetic coils 21 and 22, as shown in FIG. 3, opposite magnetic fields Mt and Mh are formed on the upper and lower sides of the electromagnetic coils 21 and 22, respectively. Therefore, as shown in FIG. 4, the plasma arc P that has received a force moving in the left direction in the drawing near the plasma torch T, for example, receives a force that returns to the opposite right side when approaching the slab H. Therefore, the plasma arc P is applied to the surface of the slab H by adjusting the return amount of the plasma arc P by the alternating magnetic field of the electromagnetic coils 21 and 22 according to the distance from the plasma torch T to the slab H surface. The light can be incident at a substantially right angle. The adjustment of the incident angle can be performed according to the installation positions of the electromagnetic coils 21 and 22. That is, the magnetic force distribution is controlled by moving the installation height of the electromagnetic coils 21 and 22 in the vertical direction according to the plasma output amount, the distance between the plasma torch T and the slab H, etc. Adjust the incident angle.

  Thus, by always causing the plasma arc P to enter the slab H in the vertical direction, the incident width a of the plasma arc P is always constant regardless of the position in the width direction A. In order to make the heat input to the slab H uniform in this state, the residence time at each position in the width direction A of the surface of the slab H by the movement of the plasma arc P may be equalized. The AC supplied from the AC power supply 5 to the electromagnetic coils 21 and 22 may form a simple waveform magnetic field such as a triangular wave so that the speed is constant. Therefore, it is possible to cope with various melting processing conditions by adjusting only the output of the plasma arc P and the strength of the magnetic field. Therefore, it is easy to control, and it is not necessary to determine various settings by conducting a sample processing test in advance, and the labor can be greatly reduced. Moreover, it has a very simple configuration and can be implemented even in a narrow space.

  The above embodiment can be similarly implemented even when there are a plurality of plasma torches T. Since the horizontal movement width of the plasma arc P generated by the plasma torch T used in this type of apparatus is normally about 100 mm, a plurality of plasma torches T are provided when the width of the slab H exceeds 100 mm. This is arranged, and each plasma torch T is similarly reciprocated to perform surface layer processing.

  In addition, when controlling the incident angle to the slab H to be processed, it can be suitably controlled by a method such as imaging the surface portion with a CCD camera and using the image processing data in addition to visual observation. .

  5 and 6 show different embodiments of the present invention. FIG. 5 is a schematic view of an outline of the configuration of the surface processing apparatus 11 as seen from the front, and FIG. 6 is a schematic view of the same as seen from the plane.

  The surface layer processing apparatus 11 has a plurality (seven in the figure) of plasma torches T1 to T7 arranged in parallel along the width direction A of the slab H arranged above the slab H to be conveyed. 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 T1 to T7 side. The number of ignitions and the output of the plasma torches T1 to T7 are controlled by the control device 3.

  Below the plasma torches T1 to T7 and before and after the slab H 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, The electromagnetic coils 23, 24, 25, and 26 are provided so as to be parallel to each other. These electromagnetic coils 23, 24, 25, 26 are supplied with each plasma arc P by periodically applying a Lorentz force to each plasma arc P by supplying alternating current from AC power sources 15, 16. The slab H is reciprocated in the width direction A according to the AC frequency.

  The electromagnetic coils 23, 24, 25, and 26 (see FIG. 7) are symmetrically arranged on both sides of the plasma torches T1 to T7. The electromagnetic coils 23 and 24 and the electromagnetic coils 25 and 26 are loop-shaped of the same type and the same size, respectively. It has a shape. The electromagnetic coils 23 and 24 and the electromagnetic coils 25 and 26 generate reverse magnetic fields in synchronism when supplied with AC current from the AC power sources 15 and 16, respectively. The magnetic field strength and direction of the electromagnetic coil 23 are the same as those of the electromagnetic coil 24, and the magnetic field strength and direction of the electromagnetic coil 25 are the same as those of the electromagnetic coil 26. The main controller 4 performs output and phase control of the AC power supply 15 of the electromagnetic coils 23 and 24 and the AC power supply 16 of the electromagnetic coils 25 and 26.

  FIG. 7A shows an enlarged cross section viewed from the DD direction in FIG. 6. The electromagnetic coils 23 and 24 and the electromagnetic coils 25 and 26 are respectively symmetrical with respect to the central axis of the plasma torch T1. Has been placed. Then, as shown in FIG. 5, when the alternating current is supplied from the electromagnetic power sources 15 and 16 to the electromagnetic coils 23, 24, 25, and 26, the electromagnetic coils 23 and 24 and the electromagnetic coils 25 and 26 are reversed in direction. Current flows. As a result, magnetic fields Mt and Mh in opposite directions are generated between the electromagnetic coils 23 and 24 and between the electromagnetic coils 25 and 26 as shown by arrows in FIG. FIG. 7B shows the distribution of magnetic flux density at this time. The figure shows the direction of the instantaneous current, and the direction changes with the passage of time.

  FIG. 8 shows a moving state of the plasma arc P according to the present embodiment. When an alternating current flows, magnetic fields Mt and Mh in opposite directions are formed near the plasma torch T1 and the slab H as shown in FIG. 7 due to the influence of the electromagnetic coils 23, 24, 25, and 26. Therefore, as in the embodiment of FIG. 4 described above, as shown in FIG. 8, the plasma arc P that has received a force moving in the left direction of the figure in the vicinity of the plasma torch T1, for example, on the right side opposite to the slab H Receive the power to return to.

  In the present embodiment, electromagnetic coils 23 and 24 that generate a magnetic field Mt for moving the plasma arc P to the left and right, and a magnetic field Mh for returning the plasma arc P in the reverse direction near the surface of the slab H are generated. Since the electromagnetic coils 25 and 26 are provided separately, the incident angle of the plasma arc P can be finely adjusted more accurately. The speed of the plasma flow of the plasma arc P is the fastest immediately after exiting the plasma torch T and gradually decelerates. Therefore, in order to move the plasma arc P in the portion close to the plasma torch T1, the magnetic field Mt is strengthened to give a sufficient curvature, and in the vicinity of the slab H, the magnetic field Mh is slightly weakened to give a reverse force to bend back. It is preferable to adjust as follows. In the present embodiment, the magnetic field is freely controlled by independently controlling the current supplied to the electromagnetic coils 23 and 24 and the electromagnetic coils 25 and 26 without changing the installation positions of the electromagnetic coils 23 to 26. Adjustments can be made. Therefore, the present embodiment can be freely adapted by simple adjustment according to the plasma current, the distance between the plasma torch T and the slab H, the change in oxygen or nitrogen concentration in the atmosphere, and the like.

  In this way, the plasma arc P can be easily adjusted so that the plasma arc P bends back and is always incident at right angles to the slab H. Therefore, the incident width a of the plasma arc P is always constant regardless of the position in the width direction A. Become. Therefore, in order to make the heat input to the slab H uniform in this state, it is possible to form a simple waveform magnetic field such as a triangular wave so that the moving speed of the plasma arc P is constant. Easy.

  Furthermore, in the present embodiment, since the magnetic field Mt for moving the plasma arc P and the magnetic field Mh for bending back can be controlled independently, it is possible to freely adjust the left and right swing width of the plasma arc P. it can. Therefore, even if the width of the slab H varies, it can be easily handled.

  The surface layer processing apparatus of each embodiment described above is used when, for example, 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.

  With the above surface layer processing apparatus, the surface layer reforming process by plasma heating and melting was performed on the slab. The cast slab used as a sample was 0.2% mass C steel having a thickness of 100 mm, a width of 100 mm, and a length of 500 mm, and the surface layer was melt-treated at a conveying speed of 3 mm / s and 5 mm / s. The number of plasma torches was one, and the plasma current was 300A and 500A.

  FIG. 9 is a partial cross-sectional view of the surface layer processing apparatus in the present embodiment. The distance h between the tip of the plasma torch T and the slab H is 100 mm, and the magnetic flux density is at a height h1 that is 1/4 of the distance h from the slab H to the plasma torch T and at a height h2 that is 3/4. The maximum positive and negative values were set to 6 mT and 10 mT, respectively. A total of two electromagnetic coils, each carrying a current of 710 A in the same direction, were arranged at positions symmetrical with respect to the conveyance direction B from the central axis of the plasma torch T, one by one. A horizontal distance d from the central axis to each electromagnetic coil is 40 mm. When the height h3 in the vertical direction from the surface of the slab H of the electromagnetic coil was 38.3 mm, a magnetic field having the predetermined magnetic flux density was obtained. FIG. 9 shows the direction of the instantaneous current, and the direction is changed over time. The waveform of the alternating current that generates the magnetic field was a triangular wave as shown in FIG. 10, and the frequency was 100 Hz.

  Moreover, the surface modification process was performed by the conventional method with the same material. In the conventional example, the AC magnetic field was a sine wave of 100 Hz, and the maximum value of the magnetic flux density was 3 mT at the intermediate height (1/2 h) between the plasma torch and the slab. Furthermore, the same material was used when the alternating magnetic field waveform was trapezoidal. For the trapezoidal wave, the ratio of the portion where the magnetic field becomes a constant value, that is, the value of the width E with respect to the width F of the waveform in FIG.

  After performing the surface modification treatment under each of the above conditions, the side surface of the melt-treated portion of each material was investigated.

  According to the embodiment of the present invention, the melt depth at the central portion of the processing portion is 5 mm, the melt depth at the 1/4 and 3/4 positions of the total treatment width of 100 mm is also 5 mm, and the melt depth over the entire width direction. Was uniform.

  On the other hand, in the conventional example, when the alternating magnetic field is a sine wave, the state of the processing part is deepest when the melting depth at the center in the width direction is 6 mm, and gradually becomes shallower toward the end, and the total processing width is 100 mm. At the 1/4 and 3/4 positions, the melt depth was 4 mm.

  In the conventional example, when the alternating magnetic field is a trapezoidal wave, the conditions of the trapezoidal wave when the entire melting depth in the width direction is uniform differ depending on the magnitude of the plasma current. That is, when the plasma current is 300 A, the ratio of the trapezoidal wave constant magnetic field part is 50%, and when the plasma current is 500 A, the ratio of the constant magnetic field part is 70%. It was 5 mm. However, in this case, since the optimum magnetic field waveform differs depending on the plasma output, the optimum waveform must be examined beforehand by experiment for each plasma output. Therefore, in addition to requiring extra time and cost, the trapezoidal wave control requires a complicated control mechanism. Therefore, the embodiment of the present invention in which a uniform melting depth is obtained even with a triangular wave that is easy to control is suitable.

  A surface layer reforming process by plasma heating and melting was performed on examples having different electromagnetic coil arrangements under the same conditions using the same materials as in Example 1.

  FIG. 12 is a partial cross-sectional view of the surface layer processing apparatus in the present embodiment. As in the first embodiment, the distance h between the tip of the plasma torch T and the slab H is 100 mm, and the height h1, 3/4 of the distance h from the slab H to the plasma torch T is 1/4. At h2, the maximum positive and negative values of the magnetic flux density were set to 6 mT and 10 mT, respectively. Four electromagnetic coils were arranged at positions symmetrical with respect to the conveyance direction B from the central axis of the plasma torch T. A horizontal distance d from the central axis to each electromagnetic coil is 40 mm. The heights h4, h5, h6, and h7 in the vertical direction of each electromagnetic coil were 5 mm, 45 mm, 55 mm, and 95 mm, respectively. Currents in the same direction were supplied to the electromagnetic coils at the symmetrical positions. The current in the same direction was supplied to the electromagnetic coil closest to the plasma torch T and the electromagnetic coil closest to the slab H, and the current in the opposite direction was supplied to the electromagnetic coil arranged therebetween. When a current of 430 A was passed through the four electromagnetic coils near the plasma torch T and 260 A was passed through the four electromagnetic coils near the slab H, the predetermined magnetic field was obtained. FIG. 12 shows the direction of the instantaneous current, and the direction is changed over time. The waveform of the alternating current that generates the magnetic field was a triangular wave as in Example 1.

  After performing the surface modification treatment under these conditions, the side surface of the melt-treated portion of each material was examined. As in Example 1, the melt depth at the center of the treated portion was 5 mm and the total treatment width was 100 mm. The melt depth at the positions of / 4 and 3/4 was also 5 mm, and the melt depth was uniform over the entire width direction. In the case of the present embodiment, since the adjustment of the magnetic field can be controlled by the current supplied to the electromagnetic coil, it is not necessary to change the height of the electromagnetic coil once installed.

  The present invention is useful when a cast steel slab is uniformly surface-treated 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 state of the magnetic field in 1st Embodiment, (A) is explanatory drawing of the magnetic field by the expanded cross section seen from CC direction of FIG. 2, (B) is a distribution map of magnetic flux density. . It is explanatory drawing which looked at the movement state of the plasma arc by the alternating current magnetic field of FIG. 3 from the front. 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. It is explanatory drawing which shows the state of the magnetic field in 2nd Embodiment, (A) is explanatory drawing of the magnetic field by the expanded cross section seen from the DD direction of FIG. 6, (B) is a distribution map of magnetic flux density. . It is explanatory drawing which looked at the movement state of the plasma arc by the alternating current magnetic field of FIG. 7 from the front. 1 is a cross-sectional view showing Example 1. FIG. It is a wave form diagram of the triangular wave used in the Example. It is a waveform diagram of the trapezoidal wave used in the conventional example. 6 is a cross-sectional view showing Example 2. FIG. It is explanatory drawing which shows the state of the magnetic field of a prior art example, (A) is explanatory drawing of the magnetic field by a cross section, (B) is a distribution map of magnetic flux density. It is explanatory drawing which looked at the movement state of the plasma arc by the alternating current magnetic field of FIG. 13 from the front.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 Surface processing apparatus 2 DC power supply 3 Control apparatus 4 Main control apparatus 5, 15, 16 AC power supply 21, 22, 23, 24, 25, 26 Electromagnetic coil A Width direction B Conveyance direction H Slab Mt, Mh Magnetic field P Plasma arc T, T1, T2, T3, T4, T5, T6, T7 Plasma torch

Claims (7)

In the surface treatment apparatus equipped with a plasma torch that generates a plasma arc between cast steel pieces,
Between the plasma torch and the cast steel slab, an alternating magnetic field that reciprocates the plasma arc in the width direction of the cast steel slab, and an alternating current that generates an alternating magnetic field opposite to the alternating magnetic field below the alternating magnetic field. have a magnetic field generating device,
The AC magnetic field generator includes a pair of electromagnetic coils disposed before and after a cast steel slab of a plasma arc generated by the plasma torch, and an AC power source that supplies an alternating current in the same direction to the pair of electromagnetic coils. A surface layer processing apparatus for cast steel pieces, comprising: The surface treatment apparatus for cast steel pieces according to claim 1 , wherein the pair of electromagnetic coils is movable in the vertical direction. In the surface treatment apparatus equipped with a plasma torch that generates a plasma arc between cast steel pieces,
Between the plasma torch and the cast steel slab, an alternating magnetic field that reciprocates the plasma arc in the width direction of the cast steel slab, and an alternating current that generates an alternating magnetic field opposite to the alternating magnetic field below the alternating magnetic field. have a magnetic field generating device,
The AC magnetic field generation device supplies AC current to each of the four electromagnetic coils arranged in parallel one above the other in front and rear of the transport direction of the cast steel piece of the plasma arc generated by the plasma torch, and the electromagnetic coil. AC power supply,
The surface treatment apparatus for cast steel pieces, wherein the two pairs of electromagnetic coils on the plasma torch side and the two pairs of electromagnetic coils on the cast steel piece side form alternating magnetic fields opposite to each other. The surface layer of a cast steel slab according to claim 3 , wherein an alternating current is supplied from different AC power sources to the two pairs of electromagnetic coils on the plasma torch side and the two pairs of electromagnetic coils on the cast steel piece side. Processing equipment. In the surface layer processing method comprising a plasma torch for generating a plasma arc between the cast steel pieces and processing the surface layer of the cast steel pieces by the plasma arc,
By generating an alternating magnetic field for reciprocating the plasma arc in the width direction of the cast steel piece between the plasma torch and the cast steel piece, and generating an alternating magnetic field opposite to the alternating magnetic field below the alternating magnetic field. Controlling the angle of incidence of the plasma arc on the cast steel slab ,
The alternating magnetic field opposite to the alternating magnetic field supplies an alternating current in the same direction to a pair of electromagnetic coils arranged before and after the plasma arc in the conveying direction of the cast steel slab. The surface layer processing method of the cast steel piece characterized by the above-mentioned. 6. The surface treatment method for a cast steel piece according to claim 5 , wherein the pair of electromagnetic coils are moved in the vertical direction to further control an incident angle of the plasma arc to the cast steel piece. In the surface layer processing method comprising a plasma torch for generating a plasma arc between the cast steel pieces and processing the surface layer of the cast steel pieces by the plasma arc,
By generating an alternating magnetic field for reciprocating the plasma arc in the width direction of the cast steel piece between the plasma torch and the cast steel piece, and generating an alternating magnetic field opposite to the alternating magnetic field below the alternating magnetic field. Controlling the angle of incidence of the plasma arc on the cast steel slab ,
The plasma arc generated by the plasma torch is arranged in parallel above and below four electromagnetic coils on each side before and after the cast steel piece conveying direction, and the alternating magnetic field and the alternating magnetic field opposite to the alternating magnetic field are arranged in these coils. 7, wherein the plasma torch side two pairs of electromagnetic coils and the cast steel piece side two pairs of electromagnetic coils are generated by supplying alternating currents in opposite directions to each other. Surface treatment method for cast steel pieces.

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