Patent Publication Number: US-9903653-B2

Title: Melting furnace

Description:
FIELD OF THE INVENTION 
     The present invention relates to a melting furnace and, in particular, relates to a melting furnace in which metal is melted while moving a furnace shell. 
     BACKGROUND ART OF THE INVENTION 
     In an arc furnace as a kind of melting furnace for melting metal material, a so-called hot spot and cold spot are formed within an inner space of a furnace shell containing the metal material. The hot spot places close to electrodes and at which the metal material is likely to be melted. The cold spot places distant from the electrodes and at which the metal material is not likely to be melted. In the cold spot, there arise a problem that it takes a long period of time to melt the metal material and thus melting of the metal material proceeds uniformly as a whole. In order to solve this problem, Patent Literature 1 proposes a process in which a furnace shell is rotationally displaced around an axis line extending in an up-down direction with respect to electrodes, thereby exchanging between the cold spot and the hot spot. In such the electric arc furnace, thermal nonuniformity within the furnace can be eliminated and an amount of wasteful power consumption can be reduced by rotationally displacing the furnace shell, without consuming power for a pump at an extra water-cooled part like in a shaft furnace and without additionally supplying burner combustion energy or the like for a composition appropriating processing of exhaust gas. Patent Literature 2 discloses a concrete configuration of an arc furnace which can perform such a rotational displacement of a furnace shell and tilting of the furnace shell for pouring. 
     Patent Literature 1: JP-A-2014-40965 
     Patent Literature 2: JP-A-2015-48976 
     SUMMARY OF THE INVENTION 
     To a furnace shell of an arc furnace are attached many auxiliary facilities such as a water-cooled panel and a burner, and cooling water, air, gas and so on used in these facilities are supplied via pipes. Each of these pipes is in a state that one end thereof is fixed to the furnace shell. In a case of rotationally displacing entirety of the furnace shell in this state as disclosed in Patent Literatures 1 and 2, it is necessary to use the pipes each of which is formed by flexible material like a flexible hose or the like and has a sufficient length capable of following an entire rotating area of the furnace shell. However, a load is likely to be applied to respective portions of each of the pipes due to own weight of the each pipe and also due to deformation or the like of a halfway portion of the each pipe accompanied by the rotation of the furnace shell. As a result, each of the pipes itself or coupling members coupled to both ends of the each pipe may be damaged, and this damage may cause leakage of fluid flowing within the pipes. Further, a similar problem is assumed to occur also in electric wirings for supplying power for driving the auxiliary facilities provided at the furnace shell and in electric wirings for transmitting signals for controlling the auxiliary facilities. 
     Therefore, an object of the present invention is to provide a melting furnace which has a furnace shell being moved and can protect pipes and wirings attached to the furnace shell from damage accompanied by movement of the furnace shell. 
     In order to solve the above-mentioned problem, the present invention provides a melting furnace, containing: 
     a furnace shell; 
     a furnace shell moving mechanism that supports the furnace shell so as to be movable on an installation surface; 
     a pipe or a wiring that has one end fixed to the furnace shell and has at least partially a flexible portion; and 
     a stand that containing a supporting part that supports a halfway portion of the pipe or the wiring, and a stand moving part that is coupled to the supporting part and moves the supporting part on the installation surface with movement of the furnace shell, in which the stand is mounted on the installation surface so as to be movable in an up-down direction with respect to the furnace shell. 
     Here, it is preferable that the stand moving part contains a wheel that moves on the installation surface, and the supporting part is coupled to the furnace shell so as to be movable up and down by a coupling unit that transmits movement of the furnace shell induced by the furnace shell moving mechanism to the wheel. In this case, the coupling unit preferably has a pin structure that couples the stand to the furnace shell so as to make the stand rotatable within a plane containing the up-down direction. Further, the melting furnace preferably further contains a track installed in order to guide the movement of the wheel. 
     The stand moving part is preferably provided at halfway portion of the supporting part. 
     The melting furnace preferably further contains an insulation installed in at least one of a portion between the supporting part and the furnace shell, a portion between the supporting part and the stand moving part, and a portion between the furnace shell and the furnace shell moving mechanism. In this case, the furnace shell, the furnace shell moving mechanism and the supporting part are preferably independently grounded. 
     The installation surface is preferably tiltable in a state of supporting the furnace shell and the stand. 
     The melting furnace preferably further contains a lock mechanism in at least one of the furnace shell moving mechanism and the stand, which the lock mechanism inhibits movement of the furnace shell and the stand on the installation surface. 
     In the melting furnace according to the present invention, a pipe or wiring is supported at its halfway portion by a stand and the stand moves in synchronous with the movement of a furnace shell. Thus, when the furnace shell moves, the pipe or wiring moves together with the furnace shell in a state where its halfway portion is supported by the stand. As a result, a load of its own weight of the pipe or wiring and a load accompanied by the movement of the furnace shell are unlikely to be applied to the pipe or wiring. Thus, the pipe or wiring is prevented from being damaged by these loads. Further, since the stand is movable up and down with respect to the furnace shell, even if there is an irregularity on a locus along which the stand moves on the installation surface, up/down vibration of the stand at the time when the stand moves in synchronous with the movement of the furnace shell is suppressed. Thus, the pipe or wiring is suppressed from being damaged by the up/down vibration of the stand accompanied by the movement of the stand. 
     Here, in the case where the stand moving part contains a wheel that moves on the installation surface and the supporting part is coupled to the furnace shell so as to be movable up and down by a coupling unit that transmits movement of the furnace shell induced by the furnace shell moving mechanism to the wheel, the stand can be made to move in synchronism with the movement of the furnace shell with a simple configuration. 
     In the case where the coupling unit has a pin structure that couples the stand to the furnace shell so as to make the stand rotatable within a plane containing the up-down direction, the stand can be coupled to the furnace shell in a state of being movable up and down, with a simple configuration. 
     In the case where the installation surface is provided with a track for guiding movement of the wheel, the stand can be moved smoothly in synchronism with the movement of the furnace shell. 
     In the case where the stand moving part is provided at a halfway portion of the supporting part, the pipe or wiring can be stably supported by the stand and hence highly protected from application of a load. 
     In the case where the melting furnace further contains: an electrode provided in the furnace shell; and an insulation member provided in at least one of a portion between the supporting part and the furnace shell, a portion between the supporting part and the stand moving part, and a portion between the furnace shell and the furnace shell moving mechanism, the following effect can be provided. That is, even when current flows in the furnace shell due to current flowing in the electrodes, this current flowing in the furnace shell is prevented from negatively affecting the supporting part of the stand, the stand moving part and the furnace shell moving mechanism by flowing in respective portions. 
     In the case where the furnace shell, the furnace shell moving mechanism and the supporting part are independently grounded, such a phenomenon can be highly prevented from occurring that, when current flows in the furnace shell, this current flows in the above-mentioned respective portions and negatively affects thereon. 
     In the case where the installation surface is tiltable in a state of supporting the furnace shell and the stand, at a time of tilting the installation surface, even if a large rotation torque is applied to the furnace shell from the pipe or wiring which one end is fixed, since the pipe or wiring is supported by the stand that tilts together with the furnace shell, the rotation torque applied to the furnace shell can be reduced. 
     In the case where on at least one of the furnace shell moving mechanism and the stand is provided a lock mechanism which inhibits movement of the furnace shell and the stand on the installation surface, the furnace shell can be stably held on the installation surface while the furnace shell is not moved. In particular, in the case where the installation surface is tiltable in a state of supporting the furnace shell and the stand, a tilting operation can be performed stably by placing the furnace shell in a movement-inhibited state by the lock mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view illustrating an electric arc furnace according to an embodiment of the present invention. 
         FIG. 2  is a side view illustrating the electric arc furnace of  FIG. 1 . 
         FIG. 3  is a side view illustrating a stand of the electric arc furnace of  FIG. 1 . 
         FIG. 4  is a side view illustrating a coupling unit between the stand and the furnace shell of the electric arc furnace of  FIG. 1 . 
         FIG. 5  is a top view schematically illustrating a support frame in a furnace shell moving mechanism of the electric arc furnace of  FIG. 1 . 
         FIGS. 6A and 6B  are diagrams illustrating a state where the electric arc furnace of  FIG. 1  is tilted on a slag discharging side;  FIG. 6A  is a side view; and  FIG. 6B  is a sectional view along a direction connecting a tapping hole and a slag door. 
         FIG. 7  is a top view illustrating a modified embodiment of the electric arc furnace of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Explanation will be made with reference to the drawings as to an electric arc furnace as an example of a blast furnace according to an embodiment of the present invention. 
     (Configuration of Electric Arc Furnace) 
       FIG. 1  to  FIG. 3  illustrate an electric arc furnace  1  according an embodiment of the present invention. The electric arc furnace  1  is installed on a platform (installation surface)  90 . The platform  90  is supported by supporting bases  95  fixed on a floor surface F. The electric arc furnace  1  has a configuration, as a main body part, similar to that of the electric arc furnace (arc furnace) described in Patent Literature 1, and includes a furnace shell  10 , a furnace roof  20  and electrodes  25 . Further, a stand  30  is installed on the common platform  90  where the electric arc furnace  1  is installed. The electric arc furnace  1  further includes pipes  40  and a furnace shell moving mechanism  50 . 
     The furnace shell  10  is formed as a circular cylindrical bottomed vessel having an opening at its top part. The furnace roof  20  is a member capable of closing the opening of the furnace shell  10  by being driven by a furnace roof moving mechanism (not illustrated). Specifically, the furnace roof  20  performs an up/down movement and a rotation movement above the furnace shell  10 , thereby moving between a state of closing the opening of the furnace shell  10  and a state of opening the opening. Furthermore, three electrodes  25  penetrate the furnace roof  20  without contacting the furnace shell  10  and the furnace roof  20 , and reach a space inside the furnace shell  10 . The three electrodes  25  are arranged to form vertexes of an almost equilateral triangle around a center axis of the furnace shell  10 . When a metal material such as iron scrap material is contained in the furnace shell  10  and the three electrodes  25  are supplied with current such as three-phase alternate current to perform discharge, the metal material can be molten. The electric arc furnace  1  is configured as an electric arc furnace of an eccentric bottom tapping (EBT) type, and thus, the electric arc furnace  1  is provided with a tapping hole  11  for tapping molten steel and a slag door  12  for discharging slag as molten residue, at respective opposed positions of side wall of the furnace shell  10  (omitted in  FIG. 2 ). 
     The furnace shell  10  is supported by the platform  90  via the furnace shell moving mechanism  50 . As the furnace shell moving mechanism  50 , use can be made of one similar to that disclosed in Patent Literature 2. The configuration of the furnace shell moving mechanism  50  will be explained briefly. An annular support frame  51 , which is provided with a gear member formed along an inner periphery  51  a thereof as illustrated in  FIG. 5 , is supported by a bearing member  52 . The furnace shell  10  is fixed to the support frame  51 . 
     Gear boxes  53  and  53  are provided at two opposed portions of the inside of the support frame  51 . Two gears, a first gear  54  and a second gear  55 , are housed within each of the gear boxes  53 . The first gear  54  is rotatable within a plane parallel to a plane of the platform  90 , and the rotation shaft thereof is connected to a motor. The second gears  55  is also arranged to be rotatable within a plane parallel to the plane of the platform  90 , and the second gear meshes with the corresponding first gear  54  and also meshes with the gear member provided at the inner periphery  51   a  of the support frame  51 . When the first gear  54  is rotated by the motor, the support frame  51  is made to rotate around a center axis thereof via the second gear  55 . Thus, the furnace shell  10  fixed on the support frame  51  rotates (circles) around a center axis thereof extending up-down direction. At the time when the furnace shell  10  rotates, respective positions of the electrodes  25  along the plane of the platform  90  do not change. Thus, relative arrangement between the furnace shell  10  and the electrodes  25  changes according to the rotation of the furnace shell  10 . 
     Further, inside of the support frame  51 , a lock mechanism  56  is provided at an intermediate between the positions where gear boxes  53 ,  53  are arranged along the inner periphery of the support frame  51 . The lock mechanism  56  includes a plug member  56   a  provided so as to face to the inner periphery  51   a  of the support frame  51  and a driving cylinder  56   b  which can move the plug member  56   a  inward and outward along a radial direction of the support frame  51 . The support frame  51  is provided with a sheath member (not illustrated). In a state where a rotation position of the furnace shell  10 , that is, a rotation position of the support frame  51 , is at an original position, the plug member  56   a  of the lock mechanism  56  can enter into and be held by the sheath member. The original position of the support frame  51  means a rotation position of the furnace shell at which the furnace shell  10  can be tilted together with the platform  90  by using a tilting mechanisms  80  described later and both the tapping of molten metal from the tapping hole  11  and the discharging of slag from the slag door  12  can be performed. During the support frame  51  rotates the furnace shell  10 , the plug member  56   a  of the lock mechanism  56  is retracted inward from the support frame  51  so as not to interfere the rotation of the support frame  51 . In contrast, during the support frame  51  is stopped at the original position, the driving cylinder  56   b  moves the plug member  56   a  outward to the support frame  51  side, to thereby make the plug member  56   a  enter into and be held by the sheath member provided at the support frame  51 . As a result, the rotation of the support frame  51  can be inhibited. 
     As illustrated in  FIG. 1  to  FIG. 3 , the furnace shell  10  is provided with various kinds of pipes  40  (two in the drawings). In the pipe  40 , a fixed end  41  as one end thereof is fixed to the platform  90 , or to an equipment which is fixed to a floor F where the platform  90  is installed, such as a wall of a building. In the drawings, each of the pipes  40  is fixed at its fixed end  41  to the wall of the building. A movable end  42  as the other end of each of the pipes  40  is fixed to the furnace shell  10 . Each of the pipes  40  is at least partially formed of a flexible material like a flexible hose or the like and allows various fluids such as water, gas or air to pass through a hollow part thereinside. The flexible portion of each of the pipes  40  has a sufficient length so that the pipes  40  can follow the rotation of the furnace shell  10  induced by the furnace shell moving mechanism  50 , in a state of being supported by the stand  30  as described below. This kind of pipes  40  are used for supplying fluid to various kinds of auxiliary facilities attached to the furnace shell  10 , and examples thereof include pipes used for flowing water in order to circulate the water within a water-cooled panel for cooling the furnace shell  10 , or pipes used for supplying fuel gas to a burner for assisting melting of the metal material within the furnace shell  10 . 
     The platform  90  is provided with the stand  30  in adjacent to the furnace shell  10 . The stand  30  includes a supporting part  31  and a wheel  32  acting as a stand moving part. The stand  30  has a frame structure in which a plurality of long metal members are arranged crosswise so as to extend in a direction substantially parallel to and in a direction substantially orthogonal to the plane of the platform  90 . The supporting part  31  is connected to the wheel  32  via a wheel connecting part  33 . The wheel connecting part  33  and the wheel  32  are provided in the vicinity of a center of the supporting part  31  along a direction connecting the stand  30  and the furnace shell  10 . A halfway portion of each of the pipes  40  is placed on the supporting part  31  in such a way that the each pipe is passed over the crossed metal members. In order to avoid vibration of the stand  30  being transmitted to the pipes  40 , the pipes  40  are not fixed to the stand  30  but merely placed on the metal members constituting the supporting part  31 . When the wheel  32  rotates, the stand  30  can move in a state of supporting the halfway portions of the pipes  40  by the supporting part  31 . In the present embodiment, the stand  30  is arranged at an almost center position between the tapping hole  11  and the slag door  12  along an outer periphery of the furnace shell  10  so as not to interfere the tapping of molten metal and the discharging of slag. 
     A coupling unit  60  for coupling the stand  30  to the furnace shell  10  is provided between the stand  30  and the furnace shell  10 . The coupling unit  60  couples the stand  30  to the furnace shell  10  by a pin structure. Specifically, as illustrated in  FIG. 4 , the coupling unit  60  includes a furnace shell side-coupling member  61  fixed to the furnace shell  10 , a stand side-coupling member  62  fixed to the stand  30 , and a coupling shaft  63  coupling between the furnace shell side-coupling member  61  and the stand side-coupling member  62 . The furnace shell side-coupling member  61  and the stand side-coupling member  62  are each constituted mainly by a substantially flat plate part, and are fixed to the furnace shell  10  and the stand  30 , respectively, by screw connection in a state of standing the flat plate parts substantially vertically. The furnace shell side-coupling member  61  is provided so as to protrude upward from an outer side of an outer wall of the furnace shell  10 . The stand side-coupling member  62  is provided so as to protrude toward the furnace shell  10  side from an end portion of the supporting part  31  of the stand  30  facing to the furnace shell  10 . That is, the furnace shell side-coupling member  61  and the stand side-coupling member  62  protrude substantially orthogonally to each other. The flat plate parts of the furnace shell side-coupling member  61  and the stand side-coupling member  62  are overlapped with each other substantially in parallel at respective portions near their tips. The respective overlapped portions of the flat plate parts are provided with through holes (not illustrated) in an overlapped manner. The rod-shaped coupling shaft  63  is unremovably inserted so as to penetrate both of the through hole provided in the furnace shell side-coupling member  61  and the through hole provided in the stand side-coupling member  62 . The coupling shaft  63  is not fixed to at least one of the furnace shell side-coupling member  61  and the stand side-coupling member  62 , thereby being rotatable around the axis thereof. In other words, the stand  30  including the stand side-coupling member  62  is arranged in a state of being coupled with the furnace shell  10  including the furnace shell side-coupling member  61  via the coupling shaft  63  so as to be rotatable within a vertical plane. Thus, the stand  30  is movable up and down with respect to the furnace shell  10 . 
     As illustrated in  FIG. 1  to  FIG. 3 , the platform  90  is provided with a groove-shaped rail (track)  91  along which the wheel  32  can move without running off, and the wheel  32  contacts the platform  90  within the rail  91 . Since the stand  30  is coupled to the furnace shell  10  via the coupling unit  60  as described above, when the furnace shell  10  is rotated by the furnace shell moving mechanism  50 , a force is applied to the stand  30  in a circumferential direction of the furnace shell  10  via the coupling unit  60 , and the stand  30  moves in synchronous with the rotation of the furnace shell  10  so as to follow the movement of the furnace shell  10 . The rail  91  is formed substantially in an arc-shape at a position corresponding to a locus along which the wheel  32  is to pass when the furnace shell  10  moves in this manner. 
     A tilting mechanism  80  may be provided at the platform  90  on which the furnace shell  10  and the stand  30  are installed. The tilting mechanism  80  tilts the furnace shell  10  and the stand  30  in a predetermined direction so as to facilitate the tapping and the discharging of slag from the furnace shell  10 . In this case, although a relative arrangement between the fixed ends  41  of the pipes  40  and the platform  90  changes in accordance with the tilt movement of the platform  90 , this change can be absorbed by the flexibility of the pipes  40 . 
     As a concrete configuration of the tilting mechanism  80 , use can be made of one similar to that disclosed in Patent Literature 2. The configuration will be explained briefly herein. As illustrated in  FIG. 2 ,  FIG. 6A  and  FIG. 6B , the tilting mechanism  80  includes a gear (supporting base-side gear)  81  provided at the supporting base  95  and a gear (platform-side gear)  82  which meshes with the gear  81  of the supporting base  95  side. The gear  82  is provided at a bottom part of the platform  90  which is formed to have a convex curved surface along a direction connecting the tapping hole  11  and the slag door  12  in the original position. A cylinder  83  is rotatably connected to the platform  90  at an outside position of one end of the gear  82 . When a force is applied in an upward or downward direction to one end of the platform  90  by the cylinder  83 , the platform  90  is made to roll on the supporting base  95  while maintaining the meshed state between the supporting base-side gear  81  and the platform-side gear  82 . Thus, the platform  90  can be tilted in the direction connecting the tapping hole  11  and the slag door  12  in the original position while keeping the furnace shell  10  and the stand  30  vertically supported on the plane of the platform  90 . The tapping of molten metal from the tapping hole  11  and the discharging of slag from the slag door  12  can be assisted by this tilting movement. FIG.  6 A and  FIG. 6B  illustrate a state where the downward force is applied to the slag door  12 -side portion of the platform  90  by the cylinder  83  and thus the platform  90  is tilted to a direction (direction T) lowering the position of the slag door  12 . In this state, the discharging of slag from the slag door  12  is assisted. During the platform  90  is tilted by the tilting mechanisms  80 , the rotation of the furnace shell  10  on the platform  90  by the furnace shell moving mechanism  50  is inhibited by the lock mechanism  56 . 
     Further, insulating members are provided at respective portions of the present electric arc furnace  1 . Specifically, a coupling unit insulation plate  71  ( FIG. 4 ) is provided between the furnace shell side-coupling member  61  and the furnace shell  10 . A wheel part insulation plate  72  ( FIG. 3 ) is provided between the wheel connecting part  33  of the stand  30  and the wheel  32 . Further, a furnace shell part insulation plate  73  ( FIG. 2 ) is provided between a bottom portion of the furnace shell  10  and the support frame  51  of the furnace shell moving mechanism  50 . Each of these insulation plates  71  to  73  electrically insulates between members disposed at both sides thereof. Further, the furnace shell  10 , the stand  30  and the bearing member  52  of the furnace shell moving mechanism  50  are independently grounded by ground connection ports E 1  to E 3 , respectively. 
     (Characteristics of Electric Arc Furnace) 
     As described above, in the electric arc furnace  1  according to the present embodiment, a positional relation between the furnace shell  10  and the electrodes  25  can be changed by rotating the furnace shell  10  with respect to the electrodes  25 . By changing the positional relation, uniformity of heating and melting of the metal material within the furnace shell  10  can be enhanced. That is, as the electrodes  25  arranged to form an almost equilateral-triangle shape at the center of the furnace shell  10  having an almost circular cylindrical shape are inserted, a hot spot, which is close to the electrodes  25  and likely to be a high temperature, and a cold spot, which is distant from the electrodes  25  and unlikely to be a high temperature, are inevitably generated within the furnace shell  10 . However, by rotating the furnace shell  10  to change the positional relation between the furnace shell  10  and the electrodes  25  during the melting process of the metal material, respective positions of the hot spot and the cold spot in the furnace shell  10  can be also changed, whereby the uniformity of heating and melting of the metal material can be attained. In terms of necessarily and sufficiently changing the respective positions of the hot spot and the cold spot, a rotatable angle of the furnace shell  10  is preferably in a range of substantially from 50° to 60° in the case where the number of electrodes is three. 
     When the furnace shell  10  rotates in this manner, the movable ends  42  of the pipes  40  move together with the furnace shell  10  in a state where the fixed ends  41  are kept to be fixed to the platform  90 . Since the pipe  40  has the at least partially flexible portion, the pipe  40  can change and deform so as to follow the movement of the furnace shell  10 . However, if the portion between the fixed end  41  and the movable end  42  of the pipe  40  is not supported by the stand  30 , the pipe  40  is applied with a large load due to its own weight. Further, a force such as a tension may be applied to the pipe  40  even due to the movement of the furnace shell  10 , and hence an excessive load may be applied to the pipe. Such the loads may cause various kinds of damages such as breakage of the material constituting the pipe  40  or looseness of coupling structure of the pipe such as a joint of the fixed end  41  or the movable end  42 . These damages may result in a situation such as leakage of the fluid flowing within the pipe  40 . However, in the electric arc furnace  1 , the halfway portion of each of the pipes  40  is supported by the stand  30 , and further the stand  30  moves in synchronous with the rotation of the furnace shell  10 . Thus, an excessive load due to the change and deformation is unlikely to be applied to each of the pipes  40  even when the furnace shell  10  rotates. In this manner, the pipes  40  and the coupling structure thereof are suppressed from being damaged with the rotation of the furnace shell  10 . 
     The stand  30  moves so as to follow the rotation of the furnace shell  10  in a manner that the wheel  32  rotates and moves along the rail  91  provided on the platform  90 . If the platform  90  or the rail  91  has an irregularity, the irregularity is transmitted to the stand  30  as an up/down vibration. If the stand  30  vibrates up and down, this vibration may be transmitted to the pipes  40 . The vibration of the stand  30  may also cause damages at respective portions of the pipes  40  such as the breakage of the material constituting the pipes  40  or the looseness of coupling structure of the pipes such as joints, which may result in the situation such as leakage of the fluid flowing within the pipes  40 . However, in the electric arc furnace  1  according to the present embodiment, the furnace shell  10  and the stand  30  are connected so as to be movable up and down by the coupling unit  60  having the pin structure. Thus, even when the stand  30  vibrates up and down due to the irregularity on the rail  91 , this vibration is absorbed by up/down movement of the coupling unit  60 . As a result, the vibration of the stand  30  can be avoided being transmitted to the pies  40  via the fixed ends  41 . The stand  30  can be used for supporting not only the pipes  40  for flowing the fluid but also halfway portions of various members each having at least partially flexible portion and being fixed at its one end to the electric arc furnace  1 , such as electric wirings for driving and controlling various auxiliary facilities attached to the furnace shell  10 . 
     A range within which the coupling unit  60  is movable up and down only has to be substantially the same as or more than a height difference of the irregularity on the rail  91 . In terms of typical irregularity of the platform capable of supporting this kind of the electric arc furnace  1 , the movable range of the coupling unit  60  may be in a range of from 1 mm to 50 mm. In the case of using the pin structure described above, if the movable range is converted into a rotation angle around the coupling shaft  63 , the rotation angle may be substantially in a range of from 1° to 10° assuming that the furnace shell  10  has a diameter of almost from several meters to 10 meters. 
     Concrete structure of the coupling unit  60  may be any type so long as the coupling unit can couple the stand  30  to the furnace shell  10  so as to be movable up and down and can transmit a movement of the furnace shell  10  within the plane of the platform  90  to the wheel  32  as the stand moving part, thereby moving the stand  30  so as to follow the furnace shell  10 . In the case where the coupling unit  60  contains the pin structure as described above, the stand  30  can be moved on the platform  90  so as to follow the rotation of the furnace shell  10  while securing the up/down movement of the stand  30 , with a simple configuration. As other coupling structures than the pin structure, which is capable of moving the stand  30  on the plane of the platform  90  so as to follow the movement of the furnace shell  10  while making the stand  30  movable up and down, there may be mentioned a structure which can couple the stand  30  to the furnace shell  10  via a member that is expandable up and down, such as a bellows, a spring or an elastic member. 
     In the case where the stand  30  is configured to be movable on the platform  90  by the wheel  32 , the stand  30  can be moved so as to automatically follow the movement of the furnace shell  10  with a simple configuration. Further, when the rail  91 , along which the wheel  32  moves, is provided on the platform  90 , the movement of the stand  30  following the furnace shell  10  can be guided smoothly. However, the stand moving part is not necessarily limited to the wheel  32 , and may be a structure using a roller or a bearing, for example. In addition, in the case where the stand  30  is configured to automatically follow the rotation of the furnace shell  10  via the coupling structure provided between the furnace shell  10  and the stand  30 , such as the coupling unit  60  as in the above-described embodiment, the movement of the stand  30  can be easily synchronized with the movement of the furnace shell  10  without driving the movement of the stand  30  by any active mechanism. However, the stand  30  may be made to be moved by an independent active mechanism without coupling the stand  30  to the furnace shell  10  while ensuring the synchronization therebetween. 
     In the electric arc furnace  1  according to the present embodiment, the wheel  32  as the stand moving part is arranged to place near the center of the supporting part  31 . In the case where the stand moving part is provided at a halfway portion of the supporting part  31 , that is, at a position of the supporting part along the direction connecting the stand  30  and the furnace shell  10  except for both ends, the pipes  40  can be supported by the stand  30  in a well-balanced state. And thus, each of the pipes  40  can be effectively protected from a load due to the own weight of the each pipe  40 , the movement of the stand  30  and vibration accompanied by this movement. The stand moving part is preferably provided at a portion of the supporting part almost in a range from ⅓ to ⅔ of the entire length of the supporting part  31  from the furnace shell  10  side, along the direction connecting the stand  30  and the furnace shell  10 . Although the only one wheel  32  is provided at the stand  30 , from a viewpoint of stability and security of support and movement of the stand  30 , two or more wheels may be provided at positions passing on the same rail  91 . 
     The tilting mechanisms  80  are not necessarily provided in the electric arc furnace  1 . However, in an electric arc furnace of a type for tapping molten metal from a position deviated from the center of the furnace shell, such as the EBT type furnace, usually some kind of a tilting mechanism is provided. In the case where the fixed end  41  of the pipe  40  is fixed to a facility which is fixed with respect to the floor F, such as a wall of a building, if the pipe  40  is not supported by the stand  30 , a rotation torque due to weight of the pipe  40  is directly applied to the furnace shell  10  via the movable end  42  at the time when the furnace shell  10  is tilted. Thus, the tilting of the platform  90  may also cause damage of the furnace shell  10  or looseness of the coupling structure of the pipe or the like, like the rotation of the furnace shell  10 . However, as described above, in the case where the pipe  40  is supported by the stand  30  which tilts together with the furnace shell  10 , the rotation torque applied from the pipe  40  can be received by the stand  30 , thereby reducing a load applied to the furnace shell  10  and the coupling structure of the pipe. In the present embodiment, the stand  30  is provided at the almost center position between the tapping hole  11  and the slag door  12  along an outer periphery of the furnace shell  10  so that the stand  30  does not interfere the tapping of molten metal and the discharging of slag. Thus, the tilting direction of the platform  90  at the original position is substantially orthogonal to an arrangement direction of the stand  30  with respect to the furnace shell  10 . This directional relation also contributes to reduction of the rotation torque applied to the furnace shell  10  at the time of tilting the furnace shell  10 . 
     As a method of reducing influence of a load applied to the furnace shell  10  from the pipes  40  accompanied with the rotation of the furnace shell  10  on the platform  90  and the tilting of the platform  90 , it is considered to design the furnace shell  10  firmly in place of providing the stand  30 . However, because a total weight of both the pipes  40  and contents thereof sometimes exceeds 10 tons, in order to sufficiently reduce the influence of such the heavy members, it is necessary to extremely enlarge or increase a weight of the furnace shell  10 . In contrast, in the case where the stand  30  is provided so as to support the pipe  40  as described above, a load applied to the furnace shell  10  can be reduced without designing the furnace shell  10  excessively firmly. 
     As described above, when the platform  90  is tilted by the tilting mechanisms  80 , the rotation of the support frame  51  in the furnace shell moving mechanism  50  is inhibited by the lock mechanism  56 . Therefore, rotation of the furnace shell  10  on the platform  90  is inhibited and further, movement of the stand  30  on the platform  90  is inhibited via the coupling unit  60 . As a result, the furnace shell  10  and the stand  30  are stably kept in a state of being supported by the platform  90  during the platform  90  is being tilted. Since the furnace shell  10  and the stand  30  are coupled by the coupling unit  60 , if a lock mechanism capable of inhibiting the movement on the platform  90  is provided in at least one of the furnace shell moving mechanism  50  and the stand  30 , both movement of the furnace shell  10  and the stand  30  can be inhibited. However, as described above, in the case of employing the lock mechanism  56 , which acts on the support frame  51  itself serving as a driving source of the movement of the furnace shell  10  and the stand  30 , to thereby inhibit the rotation of the support frame  51 , both the movement of the furnace shell  10  and the stand  30  can be effectively inhibited. In a case where the movement of the stand  30  cannot be inhibited sufficiently only by the lock mechanism  56  provided at the furnace shell moving mechanism  50 , such as a case where a weight of the stand  30  is large, a lock mechanism, for example, for inhibiting the rotation of the wheel  32  may be provided on the stand  30  in addition to the lock mechanism  56  of the furnace shell moving mechanism  50 . 
     In the electric arc furnace  1  according to the present embodiment, since the coupling unit insulation plate  71  is provided between the furnace shell side-coupling member  61  of the coupling unit  60  and the furnace shell  10 , the furnace shell  10  and the stand  30  are electrically insulated to each other. Further, since the wheel part insulation plate  72  is provided between the wheel connecting part  33  of the stand  30  and the wheel  32 , the supporting part  31  of the stand  30  and the wheel  32  are electrically insulated to each other. The furnace shell  10  and the stand  30  are independently grounded. Since alternate current of  10  kA order may flow to the electrodes  25  inserted into the furnace shell  10 , an induction current in a range of from several amperes to several hundred amperes may also flow in the surface of the furnace shell  10  made of metal. If such the large current flows to the wheel  32  via the coupling unit  60  and the supporting part  31  of the stand  30 , a spark may be generated at the wheel  32 , and smooth movement of the wheel  32  may be interfered or the wheel  32  may be irreversibly damaged. If this situation occurs at the wheel  32 , the up/down vibration of the stand  30  becomes large and such the vibration may not be absorbed sufficiently by the up/down movement of the coupling unit  60 . Then, as described above, this current flowing to the wheel  32  from the furnace shell  10  can be prevented by insulating between the furnace shell  10  and the stand  30  and further insulating between the supporting part  31  of the stand  30  and the wheel  32 , and by independently grounding the furnace shell  10  and the stand  30 . 
     In addition, the furnace shell  10  and the furnace shell moving mechanism  50  are electrically insulated by providing the furnace shell part insulation plate  73  therebetween. Further, the furnace shell  10  and the furnace shell moving mechanism  50  are independently grounded. Therefore, the induction current flowing in the furnace shell  10  is prevented from flowing to the furnace shell moving mechanism  50 . If current flows to the furnace shell moving mechanism  50 , the bearing member  52  may be damaged. In this case, not only smooth rotation of the furnace shell  10  may be interfered but also up/down vibration is likely to be applied to the pipe  40  due to the rotation itself of the furnace shell  10 . 
     (Other Embodiments) 
     In the electric arc furnace  1 , various modified embodiments other than the above-described embodiment are conceivable. For example, although only the single coupling unit  60  for coupling the furnace shell  10  and the stand  30  is provided in the above-described embodiment, a plurality of coupling units each similar to the coupling unit  60  may be provided in a viewpoint of stabilizing the coupling. For example, as in a modified embodiment illustrated in  FIG. 7 , two coupling units  60 ,  60  may be provided at respective positions corresponding to both ends of the stand  30  along a circumferential direction of the furnace shell  10 . A coupling beam  62 a may couple between stand side-coupling members  62 ,  62  of the two coupling units  60 ,  60  as U-shape. 
     A furnace to which the furnace shell  10  is applied is not limited to the electric arc furnace such as an arc furnace, but may be any principle type so long as it is a melting furnace which can promote uniform melting of metal material by moving a furnace shell. The movement of the furnace shell is not limited to a rotation (revolution) around the center axis thereof but may be any movement on the surface of the platform. Further, the electric arc furnace is not limited to the EBT type furnace but may be another type such as a molten delivery trough type furnace. However, in a case of providing the tilting mechanism as described above, a centric bottom tapping (CBT) type furnace not required to be tilted is removed. 
     As described above, although the embodiments according to the present invention are explained in detail, the present invention is not limited to the above-described embodiments and may be changed and modified in various manners within a range not departing from the gist of the present invention. 
     The present application is based on the Japanese patent applications No. 2014-225147 filed on Nov. 5, 2014 and No. 2015-146742 filed on Jul. 24, 2015, which contents are incorporated herein by reference. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1  electric arc furnace (melting furnace) 
           10  furnace shell 
           20  furnace roof 
           30  stand 
           31  supporting part 
           32  wheel (stand moving part) 
           33  wheel connecting part 
           40  pipe 
           41  fixed end 
           42  movable end 
           50  furnace shell moving mechanism 
           54  first gear 
           55  second gear 
           56  lock mechanism 
           60  coupling unit 
           61  furnace shell side-coupling member 
           62  stand side-coupling member 
           63  coupling shaft 
           80  tilting mechanism 
           81  supporting base-side gear 
           82  platform-side gear 
           83  cylinder 
           90  platform (installation surface) 
           91  rail (track) 
           95  supporting base