JP2009255140A - Surface melting treatment apparatus of cast steel slab - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the yield of a cast steel slab by subjecting even both end faces in the width direction of a cast steel slab to a surface melting treatment. <P>SOLUTION: A plasma torch 10 is arranged in the upper part of a cast piece H. On both sides in the width direction B of a position which is irradiated with plasma arc P from the plasma torch 10 in the cast piece H, there are arranged holding members 20, 21. The holding members 20, 21 are horizontally movable by a moving mechanisms 24, 25 and are able to come in contact with both sides in the width direction B of the cast piece H. The holding members 20, 21, in contact with both sides of the cast piece H, are able to hold the molten part M which is fused by the plasma arc P from the plasma torch 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface layer melting apparatus for melting a surface layer of a cast steel piece such as a continuous cast slab of steel or a rolled steel piece by a plasma arc.

  For example, a plasma heating apparatus is used for the process of melting and modifying the surface layer of a cast steel piece such as a cast piece after continuous casting or a rolled steel piece (Patent Document 1).

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

  When the surface layer of the cast steel slab is melted, it is necessary to uniformly heat and melt the surface layer of the cast steel slab by a plasma arc, and to melt the surface layer of the cast steel slab as uniformly as possible. Therefore, for example, when heating a wide cast steel piece using the technique shown in Patent Document 1 or the like, it is necessary to irradiate a plasma arc on the entire width direction of the cast steel piece to heat the cast steel piece. For this reason, the plasma arc is reciprocated in the width direction of the cast steel piece (perpendicular to the conveying direction of the cast steel piece) using the electromagnetic force of the alternating magnetic field, and the upper surface of the cast steel piece is heated and melted over the entire width direction. (Patent Document 2). 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. Each steel material is meant.

JP 2004-195512 A JP 54-142154 A

  However, the conventional technique is suitable for uniformly heating and melting the surface layer of the cast steel slab, but has not been melted to both end portions in the width direction. This is because when the surface layer part is irradiated with a plasma arc so as to melt both end faces in the width direction and heated, the melted part of the end face part hangs down from the cast steel piece ( The so-called “melt-off” phenomenon).

  However, if both end portions in the width direction are not melted, the surface properties remain rough, or inclusions present in the portions cannot be floated and removed. Therefore, if the rolling process is performed in this state, wrinkles may occur on the product surface. Therefore, conventionally, it has been necessary to cut off both end portions in the width direction that have not been subjected to the melting treatment after melting the surface layer inside the end portions in the width direction of the cast steel piece. For this reason, the yield of cast steel slabs has been reduced.

  The present invention has been made in view of such a point, and in performing the surface layer melting treatment of the cast steel piece, the melting phenomenon is prevented and the surface layer melting treatment can be performed up to both end portions in the width direction of the cast steel piece, The purpose is to improve the yield of cast steel pieces.

  In order to achieve the above-mentioned object, the present invention is an apparatus for melting a surface layer of a cast steel piece to be conveyed by a plasma arc from a plasma torch disposed above the cast steel piece, which is conveyed It has a pair of holding members which are arranged on both sides of the cast steel piece and are brought into contact with the end face in the width direction of the cast steel piece to hold the molten portion of the end face melted by the plasma arc.

  Since the surface layer melting treatment apparatus of the present invention has a pair of holding members that can contact the end surfaces in the width direction of the cast steel piece on both sides of the cast steel piece, it is retained when the surface layer of the cast steel piece is melted. By bringing the members into contact with each other, the melted portion is held without falling down. Thereby, the surface layer of the cast steel piece can be melted by irradiating the plasma arc to the both end portions in the width direction of the cast steel piece, that is, the entire width direction of the cast steel piece. Thus, since both end portions in the width direction can be effectively used as products, the yield of cast steel pieces can be improved.

  The holding member may be made of a refractory material. The holding member may be made of copper. Furthermore, the holding member may have a main body portion made of copper and a contact portion attached to the cast steel piece side with respect to the main body portion and made of a refractory material.

  In addition, when a cast steel piece is conveyed and passes the heating-melting area | region by a plasma arc, a heating temperature will fall gradually from both sides of the width direction in connection with it, and it will solidify and solidify. Therefore, in order to enhance this cooling effect, a cooling flow path for circulating a cooling medium may be provided inside the holding member.

  The holding member may be provided with a moving mechanism that horizontally moves the holding member in a direction perpendicular to the conveying direction of the cast steel piece.

  The moving mechanism may be controlled to move the one holding member to a predetermined position to center the cast steel piece. In such a case, for example, after moving one holding member to a predetermined position, the other holding member is moved and the cast steel piece is held by the pair of holding members, whereby the cast steel piece is centered.

  The holding member may be provided with a contact terminal for grounding the cast steel piece being melted.

  In the holding member, both end portions of the contact surface with the end surface in the width direction of the cast steel piece in the direction along the transport direction of the cast steel piece may have curved portions that are convexly curved toward the end surface side. .

  According to the present invention, in performing the surface layer melting treatment of the cast steel piece, the surface layer melting treatment can be performed up to both end portions in the width direction of the cast steel piece, so that the yield of the cast steel piece can be improved.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 is a schematic view of an outline of the configuration of the surface layer melting apparatus 1 according to the present embodiment as viewed from the front, and FIG. 2 is a schematic diagram of an outline of the configuration of the surface layer melting apparatus 1 as viewed from above. FIG. 3 is a schematic view of the outline of the configuration of the surface layer melting apparatus 1 as seen from the side. In the present embodiment, a slab H continuously cast is used as a cast steel slab.

  The surface layer melting apparatus 1 is provided on a conveying line (not shown) of the slab H that is conveyed in the horizontal direction. The surface layer melting apparatus 1 has one or a plurality of plasma torches 10 arranged above a slab H that is conveyed in the conveying direction A, for example. In the present embodiment, for convenience of illustration, four plasma torches 10 are drawn. In the case of a plurality of plasma torches 10, the plasma torches 10 are arranged in parallel along the width direction B (perpendicular to the conveying direction A) of the slab H, but the number of plasma torches 10 itself is arbitrary.

  The plasma torch 10 is connected to a DC power source 11, and a plasma arc P by DC plasma can be formed between the slab H and the slab H by applying a voltage due to a DC current from the DC power source 11. In the plasma arc P, a current I flows from the slab H side to the plasma torch 10 side. As the plasma gas for generating the plasma arc P, a non-oxidizing gas such as argon gas or a mixed gas of hydrogen and argon gas is preferable. The supply of the direct current from the direct current power supply 11 is controlled by, for example, the control unit 100 of the general-purpose computer.

  An AC magnetic field is generated for the plasma arc P below the plasma torch 10 and before and after the slab H transfer direction A, that is, before and after the plasma arc P transfer direction A formed by the plasma torch 10. Electromagnetic coils 12 and 13 are provided in parallel to face each other. The electromagnetic coils 12 and 13 have, for example, a loop shape and extend in the width direction B of the slab H. These electromagnetic coils 12, 13 cause the Lorentz force to act on the plasma arc P periodically by supplying an alternating current from an alternating current power source (not shown), thereby supplying the plasma arc P to the supplied alternating current. The slab H is reciprocated in the width direction B according to the frequency. Thereby, the plasma arc P can be irradiated over the entire upper surface of the slab H in the width direction B.

  An alloying for adding an alloying material 14 such as a metal or an alloy to the upper surface of the slab H at the position between the plasma torches 10 as viewed from the conveying direction A on the rear side of the plasma torch 10 in the conveying direction. A material supply unit 15 is arranged. An alloying material supply unit 15 for adding the alloying material 14 is also disposed near the end face in the width direction B on the upper surface of the slab H. A predetermined amount of the alloying material 14 serving as an alloying material is supplied to the alloying material supply unit 15 from an alloying material hopper (not shown). In addition, as an alloying material, nickel, ferronickel, etc. are used, for example.

  A pair of holding members 20 and 21 are arranged opposite to each other in the width direction B of the slab H where the plasma arc P from the plasma torch 10 is irradiated, that is, on both sides of the slab H being conveyed. Yes. The holding members 20 and 21 are provided with moving mechanisms 24 and 25 such as cylinders via shafts 22 and 23, respectively. By these moving mechanisms 24 and 25, the holding members 20 and 21 can horizontally move in the width direction B of the slab H, and can contact the end surface of the slab H in the width direction B. The operations of the moving mechanisms 24 and 25 are controlled by the control unit 100. In the control unit 100, after controlling one moving mechanism 24 to move one holding member 20 to a predetermined position, the other moving mechanism 25 is controlled to move another holding member 21 and a pair of holding members The slab H can be centered by holding the slab H with the members 20 and 21.

  Next, for example, the holding member 20 disposed on the right side in the transport direction A will be described in detail. As shown in FIG. 4, the holding member 20 includes a main body 30 and a contact portion 31 that contacts a side surface in the width direction B of the slab H, and the contact portion 31 is attached to the main body 30. . For example, copper having good thermal conductivity is used for the main body 30, and BN (ceramic) refractory is used for the contact portion 31, for example. The contact portion 31 may be made of other ceramic materials such as alumina, zirconia, nitriding boric acid, and aluminum nitride.

  The main body 30 has a substantially rectangular parallelepiped shape, and the upper surface of the main body 30 is disposed higher than the upper surface of the slab H. Further, the length L of the main body 30 in the transport direction A is long enough to hold the melted portion M in which the surface layer of the cast steel piece H is melted during the melting process, that is, the cast piece as shown in FIG. It is set to a length sufficient to solidify the melted portion M at the end in the width direction B of H.

  The contact portion 31 has a flat plate shape and is fixed to the upper portion of the side surface of the main body portion 30 on the slab H side, as shown in FIG. The upper surface of the contact part 31 is arranged higher than the upper surface of the slab H. The vertical length D of the contact portion 31 is set to a length sufficient to hold the melted portion M during the melting process, that is, the lower surface of the contact portion 31 is lower than the lower surface of the melted portion M. Is set to As shown in FIG. 5, the length of the contact portion 31 in the transport direction A is set to the same length L as the main body portion 30 described above. With such a configuration, when the contact portion 31 comes into contact with the side surface in the width direction B of the slab H during the melting process, the melting portion M can be held so as not to hang down.

  Inside the main body 30, for example, a cooling passage 32 through which cooling water as a cooling medium flows is provided. The cooling flow path 32 communicates with a cooling water supply source 33 provided outside the main body 30. The cooling flow path 32 is provided with a supply device group 34 including a valve for controlling the flow of the cooling water, a flow rate adjusting unit, and the like. The cooling water circulates in the cooling flow path 32, the cooling water supply source 33, and the supply device group 34. For example, the cooling water in the cooling water supply source 33 is supplied to the cooling flow path 32 in the main body 30 by the supply device group 34 and circulates, and then flows into the cooling water supply source 33.

  Below the contact portion 31 and on the side surface of the main body 30 on the slab H side, a ground terminal 35 is provided as a contact terminal that contacts the side surface in the width direction B of the slab H. The ground terminal 35 is connected to the DC power supply 11 via a conducting wire 36 passing through the main body 30. The ground terminal 35 can ground the slab H to the DC power source 11 when contacting the side surface in the width direction B of the slab H during the melting process. The ground terminal 35 and the conductive wire 36 are insulated from the main body 30. The ground terminal 35 may have a rotating roller configuration that can rotate in the conveyance direction A of the slab H.

  The configuration of the holding member 21 is the same as that of the holding member 20 described above, and a description thereof will be omitted.

  The surface layer melting apparatus 1 according to the present embodiment has the above-described configuration. Next, the melting process of the slab H performed in the surface layer melting apparatus 1 will be described.

  First, the slab H is transported, and the transport of the slab H is stopped when the tip portion is transported to a position below the plasma torch 10 (positions of the holding members 20 and 21). Thereafter, as shown in FIG. 6A, the control unit 100 controls the one moving mechanism 24 to move the one holding member 20 to a predetermined position. The predetermined position is a position where the slab H is centered when the slab H comes into contact with the holding member 20. Next, as shown in FIG. 6B, the other moving mechanism 25 is controlled to move the other holding member 21 to the slab H side and move until the slab H comes into contact with the holding member 20. Accordingly, at this time, the holding members 20 and 21 are in contact with both side surfaces of the slab H in the width direction B, and the slab H is held by the holding members 20 and 21. In this way, the slab H is centered.

  When the slab H is centered, a voltage is applied to the plasma torch 10 by the DC power source 11 to generate DC plasma in the plasma torch 10. 6C, a plasma arc P is formed between the plasma torch 10 and the slab H by DC plasma. At this time, by operating the electromagnetic coils 12 and 13, the plasma arc P receives electromagnetic force due to an alternating magnetic field and reciprocates in the width direction B of the slab H as shown by the reciprocal arrows in FIG. Moving. Simultaneously with the formation of the plasma arc P, as shown in FIG. 3, the slab is continuously supplied to the slab H with the alloying material 14 such as a predetermined metal or alloy from the alloying material supply unit 15. Transport H.

  Then, the surface layer of the slab H is melted together with the alloying material 14 by the heat of the plasma arc P, and a molten portion M is formed on the surface layer of the slab H. The melting part M is formed over the entire width direction B of the slab H by the reciprocating movement of the plasma arc P. However, since the melting part M is held by the holding members 20 and 21, it droops from the slab H. It wo n’t fall.

  Further, when the surface layer of the slab H is melted by the plasma arc P, cooling water is circulated from the cooling water supply source 33 into the holding members 20 and 21. Then, as shown in FIG. 2, both ends of the melt direction M in the width direction B are cooled and solidified by the cooling water. Thereafter, during the conveyance of the slab H, the inner part of the melting portion M is also naturally cooled and solidified, and a series of melting processes for modifying the surface layer of the slab H is completed.

  According to the above embodiment, since the holding members 20 and 21 are brought into contact with both side surfaces in the width direction B of the slab H during the melting process, the surface layer of the slab H is melted over the entire width direction B. Even if it processes, the fusion | melting part M is hold | maintained by the holding members 20 and 21, without dripping down. In this way, since the surface layer melting treatment can be performed up to both end surface portions in the width direction B of the slab H, both end surface portions in the width direction B can be effectively used as products, and the yield of the slab H can be increased. Can be improved.

  Further, during the surface layer melting process of the slab H, the melted part M can be cooled by the cooling water flowing through the holding members 20 and 21, so that the melted part M can be solidified in a short time, The surface layer melting treatment can be performed in a short time. Thus, when the fusion | melting part M solidifies in a short time, the length L of the conveyance direction A of the holding members 20 and 21 can be shortened, and the surface layer melting processing apparatus 1 can be reduced in size.

  In addition, since the holding members 20 and 21 can be moved in the width direction of the slab H by the moving mechanisms 24 and 25, the holding members 20 and 21 can appropriately contact the side surface of the slab H according to the width of the slab H. Furthermore, since the control part 100 can center the slab H by controlling the moving mechanisms 24 and 25 and moving the holding members 20 and 21, the entire slab H in the width direction B can be processed during the melting process. Thus, the plasma arc P can be reliably formed.

  By the way, for the ground contact of the slab H during the conventional melting process, for example, a separate dedicated contact member has been used so as to contact the lower surface of the slab H. In this regard, the holding members 20 and 21 of the present embodiment are provided with the ground terminal 35, so that it is not necessary to provide a separate contact member as in the prior art. Further, since the ground terminal 35 can be moved in the width direction B of the slab H by the moving mechanisms 24 and 25, the slab H can be appropriately grounded according to the width of the slab H.

  In addition, since copper having good thermal conductivity is used for the main body 30 of the holding members 20 and 21, the melted part M can be efficiently cooled by the cooling water flowing through the main body 30.

  Furthermore, since a refractory is used for the contact portion 31 of the holding members 20 and 21, maintenance can be easily performed even if the contact portion 31 is worn due to contact with the slab H. Further, such a refractory is inexpensive, and the production of the holding members 20 and 21 can be reduced. Furthermore, when the alloying material 14 is added and the melting process is performed, the alloying material 14 is uniformly diffused into the melting part M, that is, the melting part M is prevented from solidifying before the alloying material 14 is diffused. It is preferable that the part M is not rapidly cooled. In such a case, the refractory used for the contact part 31 also has an effect of relaxing the cooling rate of the melting part M. In addition, the adjustment of the cooling rate of the melting part M is performed by controlling the cooling water supply source 33 and the supply device group 34 described above, and adjusting the temperature and flow rate of the cooling water flowing through the holding members 20 and 21. It can also be done.

  In the above embodiment, the main body 30 and the contact portion 31 of the holding members 20 and 21 are respectively made of copper and refractory. However, both the main body 30 and the contact portion 31 may be made of copper. Alternatively, both may use a refractory. For example, when the surface layer of the slab H is melted without adding the alloying material 14 such as metal or alloy, the molten part M can be rapidly cooled, so that copper is used for the main body part 30 and the contact part 31. Can do.

  In the above embodiment, the planar shape of the holding members 20 and 21 is rectangular, but as shown in FIG. 7, both end portions in the direction along the conveying direction A on the contact surface with the slab H are cast. You may have the curved parts 40 and 40 curved convexly on the side surface side of the width direction B of the piece H (it curves in convex shape, but does not protrude on the cast piece H side). In such a case, even if the slab H is conveyed obliquely with respect to the longitudinal direction of the holding members 20 and 21, the impact received by the holding members 20 and 21 can be reduced.

  Hereinafter, the quality of the slab after the surface melting process will be described in an example in which the surface layer of the slab is melt-processed. As the apparatus for melting the surface layer of the slab, the surface melting apparatus 1 previously shown in FIGS. 1 to 5 is used, and copper is used for the main body part 30 and the contact part 31 of the holding members 20 and 21. It was.

  In this example, the plasma heating and melting described in the above embodiment is performed after cutting a slab H having a thickness of 250 mm and a width of 1200 mm of 0.2% C steel (unit: mass%) that has been continuously cast. The surface layer 5 mm of the continuous cast slab H was melted at a speed of 10 mm / s by adding nickel as the alloying material 14 using the method of melting by the above. At this time, the interval between the plasma torches 10 was 100 mm, and twelve torches were used. Further, the position of the upper surface of the contact portion 31 of the holding members 20 and 21 arranged on both sides of the slab H is 10 mm above the upper surface of the slab H, and the position of the lower surface of the contact portion 31 is the upper surface of the slab H. 10 mm below. That is, the vertical length D of the contact portion 31 is 20 mm.

  As a result of this melting treatment, a uniform molten state having a melting depth of 5 mm ± 0.5 mm is obtained in the entire width direction B of the slab H, and the end portion of the slab H in the width direction B is burned off. Didn't happen either. In addition, the concentration of nickel as the alloying material 14 added with the target of a nickel concentration of 1% by mass in the cant back analysis was also as good as 1 ± 0.2%.

  In the embodiment, even when the surface layer melting treatment of the slab H is performed using the BN refractory for the contact portion 31 of the holding members 20 and 21, the end of the slab H in the width direction B is the same as described above. The melt-out phenomenon of the part did not occur, and the concentration of the alloying material 14 was also good.

  Further, in the above embodiment, even if the width of the slab H is 800 mm and the number of the plasma torches 10 is reduced to 8, the above-mentioned and the end portion in the width direction B of the slab H do not occur and the alloying is not performed. The density of the material 14 was also good. Furthermore, even if the width of the slab H was changed, it was confirmed that the slab H was properly centered.

  The present invention is useful, for example, when a surface layer of a cast steel slab such as a continuous cast slab of steel or a steel slab after rolling is melted by a plasma arc.

It is explanatory drawing which showed typically the outline of the structure of the surface layer melting | dissolving processing apparatus 1 concerning this Embodiment from the front. It is explanatory drawing which showed typically the outline of the structure of the surface layer melting | dissolving processing apparatus 1 concerning this Embodiment from the upper direction. It is explanatory drawing which showed typically the outline of the structure of the surface layer fusion processing apparatus 1 concerning this Embodiment from the side. It is a longitudinal cross-sectional view of a holding member. It is a top view of a holding member. It is explanatory drawing which showed the process of the surface layer melting process of slab, (a) shows the state which moved one holding member to the predetermined position, (b) shows the state which centered the slab, (C) has shown the state which has melt-processed the surface layer of slab. It is a top view of the holding member concerning other embodiments.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface melting processing apparatus 10 Plasma torch 11 DC power supply 12, 13 Electromagnetic coil 14 Alloying material 15 Alloying material supply part 20, 21 Holding member 22, 23 Shaft 24, 25 Moving mechanism 30 Main part 31 Contact part 32 Cooling flow path 33 Cooling Water supply source 34 Supply device group 35 Ground 36 Conductor 40 Bending part 100 Control part H Cast piece A Transport direction B Width direction D Length of contact part in the vertical direction L Length of main part in the transport direction M Melting part P Plasma arc

Claims (9)

An apparatus for melting a surface layer of a cast steel piece to be conveyed by a plasma arc from a plasma torch disposed above the cast steel piece,
It is disposed on both sides of the cast steel piece to be conveyed, and has a pair of holding members that hold the molten portion of the end face melted by the plasma arc in contact with the end face in the width direction of the cast steel piece. A surface layer melting apparatus for cast steel pieces. The surface layer melting apparatus according to claim 1, wherein the holding member is made of a refractory material. The surface layer melting apparatus according to claim 1, wherein the holding member is made of copper. 2. The surface layer melting apparatus according to claim 1, wherein the holding member includes a main body portion made of copper and a contact portion made of a refractory and attached to the cast steel piece side with respect to the main body portion. The apparatus for melting a surface layer of a cast steel piece according to any one of claims 1 to 4, wherein a cooling flow path for circulating a cooling medium is provided inside the holding member. The cast member according to any one of claims 1 to 5, wherein the retaining member is provided with a moving mechanism that horizontally moves the retaining member in a direction perpendicular to the conveying direction of the cast steel piece. Surface melt processing equipment. The apparatus for melting a surface layer of a cast steel piece according to claim 6, further comprising a control unit that controls the moving mechanism to move the one holding member to a predetermined position to center the cast steel piece. The apparatus for melting a surface layer of a cast steel piece according to any one of claims 1 to 7, wherein the holding member is provided with a contact terminal for grounding the cast steel piece being melted. In the holding member, both end portions in a direction along the conveying direction of the cast steel piece at a contact surface with the end surface in the width direction of the cast steel piece have curved portions that are convexly curved toward the end surface side. A surface layer melting apparatus for cast steel pieces according to any one of claims 1 to 8.

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