JP2019061797A - Consumable electrode type arc melting furnace - Google Patents

Abstract

To provide a consumable electrode type arc melting furnace capable of easily separating a rod plug from a stub socket by effectively preventing unintended engagement of the rod plug into the stub socket while ensuring required electrical connectivity between the stinger rod's rod plug and the plug socket.SOLUTION: A tapered inner surface 2 of a stub socket 1 comprises two or more stages of tapered surface including a lower tapered surface 2a in contact with a tapered outer surface 5a of a truncated cone tip 5 of a rod plug 3 and an upper taper surface 2b, located above the lower tapered surface 2a, having a taper angle with respect to a plane orthogonal to a central axis line CL of the stub socket 1 being smaller than that of the lower tapered surface 2a. A cylindrical base 4 of the rod plug 3 is not in contact with the tapered inner surface 2 of the stub socket 1.SELECTED DRAWING: Figure 1

Description

  According to the present invention, the consumable electrode is held by the stinger rod through the stub attached to the upper end thereof, and the consumable electrode is suspended and supported in the crucible by the stinger rod and current flows, thereby casting the consumable electrode and the crucible. The present invention relates to a consumable electrode type arc melting furnace that melts a consumable electrode by arc heat generated between a lump and a molten metal pool, and in particular, may occur at an electrical connection between a stub and a stinger rod in use It proposes a technology that addresses the connection problem.

  For example, this type of arc melting furnace for producing ingots of high melting point active metals such as titanium, zirconium, tantalum, molybdenum or their alloys generates an arc under vacuum between molten metal in a water-cooled copper crucible It may be used for vacuum arc remelting (VAR) and the like.

  The consumable electrode type arc melting furnace 21 shown in FIG. 4 as one example of such an arc melting furnace mainly comprises a crucible 23 in which the consumable electrode 22 is disposed, and a stub 24 as an energizing jig attached to the upper end of the consumable electrode 22. And a stinger rod 25 for holding the stub 24 and suspending and supporting the consumable electrode 22 in the crucible 23 and for moving it up and down, and a clamp portion 25a for holding the stub 24 is provided at the lower end side of the stinger rod 25. It is provided. The consumable electrode type arc melting furnace 21 is further provided with a water cooling jacket 26 disposed around the crucible 23, a vacuum tank 27 disposed above the crucible 23 and partitioning the inside into a vacuum chamber, and not shown. It is equipped with a power supply, cables and other necessary equipment.

In order to perform vacuum arc remelting using the consumable electrode type arc melting furnace 21, one end of the power supply is connected to the stinger rod 25 and the other end is connected to the crucible 23, and the vacuum tank 27 is set. Into a vacuum chamber. In this state, the lower end of the consumable electrode 22 is brought close to the bottom of the crucible 23 based on the operation of the stinger rod 25 so that the consumable electrode 22 through which current flows from the stinger rod 25 through the stub 24 is used as one electrode. With the crucible 23 as the other electrode, an arc is generated under vacuum between the molten metal pool at the top of the ingot formed by melting and the tip of the consumable electrode 22. Then, the consumable electrode 22 can be heated and melted by the high heat locally generated by the arc.
As a technique regarding such an arc melting method, there exist a thing etc. which were described in patent documents 1-6 conventionally.

  In addition, the consumable electrode 22 is generally a bundle obtained by bundling and welding a compact obtained by compression molding of raw material powder such as particles, or an ingot which has been melted once or more, each time the arc melting method is performed. Because it is consumed, a new consumable electrode 22 is used each time. On the other hand, the stub 24 attached to the upper end of the consumable electrode 22 by welding or the like and used for physical and electrical connection with the stinger rod 25 has an unmelted residual portion of the consumable electrode 22 attached thereto after dissolution. And repeatedly used for the next dissolution.

U.S. Pat. No. 320,275. US Patent No. 3215974 U.S. Pat. No. 3,293,347 Patent No. 3005641 JP, 2006-66156, A JP, 2009-46715, A

  The electrical connection between the stub 24 and the stinger rod 25 is, as shown in FIG. 5, a concave stub socket 31 provided recessed from the upper end surface of the stub 24 and a clamp at the lower end of the stinger rod 25. It is comprised by the convex-shaped rod plug 32 located in the part 25a. In addition, illustration and description are abbreviate | omitted about the clamp mechanism of the clamp part 25a here.

  More specifically, as shown in FIG. 6, the stub socket 31 and the rod plug 32 are taken out and shown, the stub socket 31 has a tapered inner surface 31a whose inner diameter increases toward the upper side, and the rod plug 32 is generally A truncated conical tip 32c having a cylindrical base 32a and a tapered outer surface 32b located below the cylindrical base 32a and substantially aligned with the tapered inner surface 31a. In such a stub socket 31 and rod plug 32, the tapered inner surface 31a and the tapered outer surface 32b are in surface contact, and electricity is supplied from the stinger rod 25 to the stub 24 and eventually to the consumable electrode 22.

  Here, even when using a large current in vacuum arc remelting or the like of a large ingot represented by vacuum melting of a titanium ingot, enough of the tapered inner surface 31a of the stub socket 31 and the tapered outer surface 32b of the rod plug 32 are sufficient. As shown in FIG. 7, when using the arc melting furnace 21 to secure a large contact area, that is, a current-carrying area, and to prevent local heat generation and arcing phenomenon due to contact resistance that may occur when the contact area is small. The pressing force to the inside of the stub socket 31 is applied to the rod plug 32 through the inner pipe 29 of the stinger rod 25 by a pressing mechanism 28 such as an air cylinder disposed above the rod 25.

  However, unlike the rod plug 32 of the stinger rod 25 which is cooled by water cooling or the like, the stub socket 31 accumulates Joule heat generated at the contact surface with the rod plug 32 and becomes high heat, the magnitude of the current, etc. Depending on the condition of (3), it is heated too much and softens to cause creep deformation. Here, along with the creep deformation of the stub socket 31, in combination with the thermal expansion due to the high temperature, the action of the pressing force from the rod plug 32 by the pressing mechanism 28 causes as shown by the arrow in FIG. The rod plug 32 is embedded in the stub socket 31.

  Thereafter, when the melting is completed and the stub 24 is cooled, the stub socket 31 is thermally shrunk, so that the rod plug 32 embedded in the stub socket 31 is inserted into the stub socket 31 like a so-called shrink fit. There is a problem that the rod plug 32 is difficult to separate from the stub socket 31 because it is firmly fitted. In this case, if the rod plug 32 is forcibly separated from the stub socket 31, the rod plug 32 may come off from the lower end of the stinger rod 25, and the repair or replacement thereof takes time and cost. .

  SUMMARY OF THE INVENTION The present invention is intended to solve such a problem in a conventional consumable electrode arc melting furnace, and its object is to provide a required electrical connection between a rod plug of a stinger rod and a plug socket. Electrode arc melting which can easily separate the rod plug from the stub socket by effectively preventing the unintentional fitting of the rod plug into the stub socket at the time of melting of the consumable electrode while securing the conductivity It is to provide a furnace.

  As a result of intensive investigations by the inventor on the above problem in which the rod plug is fitted like a shrink fit into the stub socket after use, in the prior art, in particular the lower end of the cylindrical base forming the upper part of the rod plug The side edge is in contact with the tapered inner surface of the stub socket, and the lower end edge bites into the tapered inner surface of the stub socket which creeps and thermally expands in use, thereby allowing the rod plug into the stub socket to be strong. Was found to be a major cause of a good fit.

  Therefore, the truncated cone tip which makes the lower part of the rod plug is in contact with the tapered inner surface of the stub socket with a sufficiently large area to ensure the necessary current-carrying area, while the cylindrical base of the rod plug is the tapered inner surface By forming the tapered inner surface as two or more steps of taper angles with different taper angles so that it does not contact with the rod plug fits into the stub socket even when the stub is cooled after melting I thought that I could prevent things effectively. Further, this is because the taper angle of the lower taper surface of the stub socket and the taper angle of the taper outer surface of the truncated cone end of the rod plug are both in a predetermined range which is smaller than that of the conventional one. We also found that it would be more effective.

  Based on such findings, the consumable electrode type arc melting furnace according to the present invention comprises a crucible in which the consumable electrode is disposed, a stub attached to the upper end of the consumable electrode, and a stub that holds the consumable electrode in the crucible. And a stinger rod capable of lifting and displacing the consumable electrode while suspending and supporting the stub, wherein the stub is recessed from the upper end surface thereof and has a concave stub socket having a tapered inner surface whose inner diameter increases toward the upper side. Said stub socket comprising a frusto-conical tip having at its lower end a cylindrical base and a tapered outer surface located below said cylindrical base and corresponding to said tapered inner surface Power to the consumable electrode through the stinger rod and the stub, and to the crucible. More specifically, an arc is generated between the consumable electrode and the molten metal pool in the crucible, and the heat causes the consumable electrode to melt, and the tapered inner surface of the stub socket is the taper of the truncated cone tip of the rod plug. A lower taper surface contacting the outer surface, and an upper taper surface located above the lower taper surface and having a small taper angle with respect to a plane orthogonal to the central axis of the stub socket, as compared to the lower taper surface. The cylindrical base of the rod plug is configured to be in non-contact with the tapered inner surface of the stub socket.

Here, the taper angle of the upper tapered surface of the stub socket is preferably 25 ° to 35 ° with respect to a plane orthogonal to the central axis of the stub socket.
Here, the taper angle of the lower tapered surface of the stub socket and the taper angle of the tapered outer surface of the truncated cone end of the rod plug are both 40 ° to 50 ° with respect to a plane orthogonal to the central axis of the stub socket. It is preferable to set it as °.

And also, the contact area of the apparent and the lower tapered surface of the stub sockets, and the tapered an outer surface of the frustoconical tip of the rod plug, it is particularly effective to 4400mm ² ~5000mm ^2.

  Preferably, the upper end side edge portion of the lower tapered surface of the stub socket and the lower end side edge of the cylindrical base portion of the rod plug in an arrangement posture of the consumable electrode holding the stub attached to the upper end of the consumable electrode by a stinger rod. The distance along the axial direction with the part is 2.7 mm to 5.3 mm.

  According to the consumable electrode type arc melting furnace of the present invention, the tapered inner surface of the stub socket is compared with the lower tapered surface contacting the tapered outer surface of the truncated cone end of the rod plug and the lower tapered surface above the lower tapered surface. Of the rod plug and the plug socket by making the cylindrical base of the rod plug not in contact with the tapered inner surface of the stub socket. Unintended engagement of the rod plug into the stub socket can be effectively prevented while ensuring the required electrical connectivity between them. As a result, it is possible to easily separate the rod plug from the stub socket.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing in alignment with a central axis which takes out the stub socket and rod plug of the consumable electrode type arc melting furnace of 1 embodiment of this invention, and shows it in the state before and behind melting. It is a perspective view which shows each of the stub socket of FIG. 1, and a rod plug. It is a partial expanded sectional view of Drawing 1 (a). It is sectional drawing in alignment with a central axis which shows an example of a consumable electrode type arc melting furnace. It is sectional drawing in alignment with a central axis which shows the principal part of the conventional consumable electrode type arc melting furnace. It is sectional drawing which takes out the stub socket and rod plug of the consumable-electrode-type arc melting furnace of FIG. 5, and shows it in the state before and behind melt | dissolution. It is a fragmentary sectional view which shows the stinger rod of the consumable electrode arc melting furnace of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The consumable electrode type arc melting furnace 21 according to one embodiment of the present invention overlaps with that described above, but as shown in FIG. 4, the crucible 23 in which the consumable electrode 22 is disposed; A substantially cylindrical stub 24 attached by welding or the like to a substantially central region of the upper end of the consumable electrode 22 and a clamp 25a for gripping the stub 24 at the lower end of the stinger rod 25, for example, are provided. Etc. by holding the stub 24 with the stub 24, the consumable electrode 22 to which the stub 24 is attached is suspended and supported in the crucible 23 and can be moved up and down, and a water cooler disposed around the crucible 23 It comprises a jacket 26 and a vacuum tank 27 disposed on the upper side of the crucible 23 and partitioning the inside into a vacuum chamber. Other further, a power supply (not shown), includes equipment such as a cable.

  Here, when using the consumable electrode type arc melting furnace 21, the crucible 23 made of copper or the like having a cylindrical or other predetermined shape is airtightly attached to the upper side thereof so that the inside is divided into a vacuum chamber. In this state, the molten metal is stored by melting the consumable electrode 22 by execution of the arc melting method described later, and functions to cool and solidify the molten metal based on the cooling action by the water cooling jacket 26.

  In addition, here, as the consumable electrode 22, one obtained by bundling and welding a columnar or rod-like compact having a circular cross section obtained by compression-molding a raw material powder such as granular or the like or a similar shape which is melted once or more Ingots and the like can be used. The consumable electrode 22 is melted and then cooled after each execution of the arc melting method to become a desired ingot, and the new consumable electrode 22 is a consumable electrode type before the start of the arc melting method. The arc melting furnace 21 is disposed via a stub 24 held by a stinger rod 25.

On the other hand, the stub 24 can be used repeatedly, and is attached to the consumable electrode 22 by welding or the like before the start of the arc melting method, and after the termination of the consumable electrode 22 which is not dissolved It is separated from the upper end remainder.
As shown in FIG. 1, the stub 24 is provided with a concave stub socket 1 recessed from the upper end face of the stub 24. The stub socket 1 made of copper or other conductive metal material is on the upper side. And has a tapered inner surface 2 of which the inner diameter increases as it goes to the point, and is used for electrical connection with the stinger rod 25. The illustrated stub socket 1 is, as shown in FIG. 2, substantially in the center of one surface of a disk-like one, recessed from the circular opening on the surface side and having the inner surface of the tapered inner surface 2 described above It has a shape provided with a recess 1a having a bottom surface of Around the opening of the recess 1a, one or more connecting circular through holes are provided.

Also, the stinger rod 25 which is driven to hold the stub 24 and displace the consumable electrode 22 up and down is generally, as shown in FIG. 7, an outer tube 29a and an inner tube 29a with respect to the outer tube 29a. Relative displacement along the axial direction, and relative displacement of the inner tube 29 relative to the outer tube 29a relative to the outer tube 29a and the inner tube 29 provided at the lower end with the rod plug 3 in contact with the stub socket 1 described above And a pressing mechanism 28 such as an air cylinder for pressing the rod plug 3 toward the stub socket 1.
The rod plug 3 made of conductive metal such as copper is located below the cylindrical base 4 and the cylindrical base 4 as shown in FIG. It is composed of a truncated cone end 5 having a tapered outer surface 5 a corresponding to the tapered inner surface 2 and is electrically connected to the stub socket 1. At the center of the surface of the rod plug 3, one or more connecting circular through holes are provided as shown in FIG.

  In vacuum arc remelting using such a consumable electrode type arc melting furnace 21, the ingot melted one or more times is used as the consumable electrode 22, and one end of the power supply is connected to the stinger rod 25, and the other The end is connected to the crucible 23, the vacuum tank 27 is attached to the upper side of the crucible 23, and the inside of the crucible 23 is evacuated to be a vacuum chamber.

Then, the stinger rod 25 is operated, and the lower end of the consumable electrode 22 is placed between the start material (ignition sponge titanium particles or chips, etc. made of the same material as the consumable electrode 22) thinly spread on the bottom surface of the crucible 23 , Short circuit and ignited, and immediately pull up the electrode to generate an arc to melt the starting material, form a pool of molten metal, conduct electricity from the stinger rod 25 through the stub 24 to the consumable electrode 22, and Energize 23. Thus, the consumable electrode 22 becomes one of the electrodes, and the crucible 23 becomes the other electrode, so that an arc is generated between the consumable electrode 22 and the molten metal pool of the ingot in the crucible 23 in a vacuum atmosphere. Thus, the high heat of the arc heats and melts the consumable electrode 22 to bring the molten metal to the upper portion of the ingot in the crucible 23.
The molten metal is cooled and solidified by a water cooling jacket 26 disposed around the crucible 23 so that a desired ingot can be produced.

  In the above-described arc melting method, the concave stub socket 1 of the stub 24 and the rod plug in the clamp portion 25 a of the stinger rod 25 to effectively flow current from the stinger rod 25 to the consumable electrode 22 through the stub 24. It is necessary to bring 3 into contact with a relatively large area. This is particularly true for large vacuum arc remeltings such as vacuum melting of titanium ingots using crucible 23 with internal diameter greater than 1000 mm and consumable electrode 22 weighing more than 10 ton for 8 hours with high currents of 35 KA to 50 KA When it flows over the above dissolution time, it becomes important in order to prevent local heat generation and arcing phenomenon by contact resistance which may arise due to the fault of the contact concerned.

  In order to secure the required contact area between the stub socket 1 and the rod plug 3 and the like, the inner pipe 29 of the stinger rod 25 is displaced toward the stub 24 by the pressing mechanism 28 when performing the arc melting method. The rod plug 3 at the lower end of the inner pipe 29 is pressed toward the stub socket 1.

  However, when the consumable electrode 22 is melted, the rod plug 32 on the stinger rod 25 side is cooled by water cooling or the like, but the stub socket 1 on the consumable electrode 22 side is not cooled. The rod plug 3 is pushed into the stub socket 1 due to the creep deformation and thermal expansion of the stub socket 1 resulting therefrom. And in the prior art, after completion | finish of melt | dissolution, the rod plug was firmly fitted in the cooled stub socket, and there existed a problem that isolation | separation of the rod plug from a stub socket became difficult.

  In order to address this problem, in the embodiment of the present invention, as shown in FIGS. 1 and 2, the lower end taper in which the tapered inner surface 2 of the stub socket 1 is in contact with the tapered outer surface 5a of the truncated cone tip 5 of the rod plug 3 The taper angle with respect to a plane (hereinafter referred to as an “axis orthogonal plane”) which is located above the surface 2a and the lower tapered surface 2a and is orthogonal to the central axis CL of the stub socket 1 with respect to the lower tapered surface 2a. Is composed of two or more stages of tapered surfaces including a small upper stage tapered surface 2b, whereby preferably the cylindrical base 4 of the rod plug 3 and at least the tapered inner surface 2 of the stub socket 1 are always non-conductive. Be in contact.

  According to this, when the tapered inner surface 2 of the stub socket 1 is the above-described tapered surface in two or more steps, and the cylindrical base 4 of the rod plug 3 is not in contact with the tapered inner surface 2 of the stub socket 1 Even if creep deformation or thermal expansion occurs in the stub socket 1 into which the rod plug 3 is pushed as shown by the arrow in FIG. 1 (b), the tapered inner surface of the stub socket 1 at the lower end side edge of the cylindrical base 4 in particular. Since the biting into 2 is suppressed, the firm fitting of the rod plug 3 into the stub socket 1 is effectively prevented. As a result, it is possible to easily separate the rod plug 3 from the stub socket 1, and it is possible to effectively eliminate the possibility of a failure such as the rod plug 3 dropping off from the stinger rod 25.

  Further, in this embodiment, the stub socket 1 can be brought into contact with the tapered outer surface 5a of the rod plug 3 with a sufficiently large area at the lower tapered surface 2a, so that vacuum arc re-sizing of large ingots such as vacuum melting of titanium ingots. Even when using a large current for melting or the like, it is possible to prevent the local heat generation and the arcing phenomenon due to the reduction of the current application area.

In the illustrated embodiment, although the tapered inner surface 2 of the stub socket 1 is formed in two stages of the lower tapered surface 2a and the upper tapered surface 2b, the angle is further changed in the middle of the upper tapered surface 2b, for example. It is also possible to use three or more steps of tapered surface.
Further, in this embodiment, although the lower tapered surface 2a and the upper tapered surface 2b of the stub socket 1 are both flat surfaces whose inner diameters change linearly in the cross section shown in the figure, at least one of the tapered surfaces It is also possible to make one of them a curved surface whose inner diameter changes in a curvilinear manner in the cross section. When the lower tapered surface to be in contact with the tapered outer surface of the rod plug is a curved surface, it is preferable that the tapered outer surface of the rod plug is also a curved surface following the lower tapered surface in order to ensure a sufficiently large contact area.

  Here, the taper angle β on the acute angle side of the upper stage tapered surface 2b with respect to the plane orthogonal to the axis is smaller than the taper angle α on the acute angle side of the lower stage tapered surface 2a with respect to the plane orthogonal to the axis as shown in FIG. For example, in an extreme example, it may be 0 ° or less, for example, −15 ° to 0 °, but preferably 25 ° to 35 °. If the taper angle β of the upper tapered surface 2b is below the lower limit of this range, there is a risk of welding of the rod plug 3 due to point contact and creep softening, while if it exceeds the upper limit of this range, the rod plug 3 Buckling is a concern. From this viewpoint, the taper angle β on the acute angle side of the upper tapered surface 2 b is preferably 25 ° to 35 °.

  Here, the taper angle α of the lower taper surface 2a of the stub socket 1 is equal to the taper angle θ of the taper outer surface 5a of the rod plug 3 as in the illustrated embodiment, from the viewpoint of securing the conduction area. It is suitable. Specifically, it is preferable that the taper angle α of the lower tapered surface 2a of the stub socket 1 and the taper angle θ of the tapered outer surface 5a of the rod plug 3 both be 40 ° to 50 ° with respect to the plane perpendicular to the axis. . In the prior art, the taper angle of such a conducting surface is 60 °, but by setting it within the above-mentioned range smaller than that, in combination with the tapered inner surface 2 having two or more steps, a stub socket The separation of the rod plug 3 from 1 can be made easier. If the taper angles α and θ are below the lower limit of this range, the contact stress on the crimped surface becomes excessive and there is a concern that the creep deformation may be accelerated, and if it exceeds the upper limit of this range, cooling There is a risk that the shrinkage fit phenomenon of the More preferably, the taper angles α and θ are set to 40 ° to 50 °.

In the stub socket 1 having such two or more stages of tapered surfaces, the lower tapered surface 2a is brought into contact with the tapered outer surface 5a of the rod plug 3 with a large area to secure a required conduction area. and the lower tapered surface 2a, the contact area of the apparent the tapered outer surface 5a of the frustoconical tip 5 of the rod plug 3 is preferably set to 4400mm ² ~5000mm ^2. When the apparent contact area between the lower tapered surface 2a and the tapered outer surface 5a is less than 4400 mm ² , the effective conduction area is small at the time of energization of the maximum current 35KA to 50KA when melting a large ingot. There is a possibility that a part which becomes extremely high temperature may be generated due to local heat generation or arcing phenomenon, and in this case, the stub 24 creep-deforms, and the consumable electrode 22 separates from the clamp part 25a by its own weight. There is a risk of falling. On the other hand, when the apparent contact area between the lower tapered surface 2a and the tapered outer surface 5a is larger than 5000 mm ^2, there is a concern that the contact stress by the pressing mechanism 28 may be reduced. Therefore, the contact area of the apparent and lower tapered surface 2a and the tapered outer surface 5a, it is more preferable to 4400mm ² ~4700mm ^2. The apparent contact area is the arrangement posture of the consumable electrode 22 in which the stinger rod 25 grips the stub 24 attached to the upper end of the consumable electrode 22 before the start of energization, so that the appearance does not take into account surface irregularities. It can be calculated by determining the area where it is recognized that the tapered inner surface 2 of the socket 1 and the tapered outer surface 5a of the rod plug 3 are in contact.
Here, both the stub socket 1 and the rod plug 3 are preferably made of copper, in particular, oxygen free copper defined in JIS C1020 from the viewpoint of conductivity.

  However, when a pressing force into the stub socket 1 acts on the rod plug 3 based on the operation of the pressing mechanism 28 at the time of energization, the rod plug 3 is pushed into the stub socket 1 by the pressing force. Even from the viewpoint of more reliably preventing biting of the lower end side portion of the cylindrical base 4 of the rod plug 3 into the tapered inner surface 2 of the stub socket 1 as described above until the end of the arc melting method. Preferably, the cylindrical base 4 is located as far as possible from the tapered inner surface 2.

  Therefore, as shown in FIG. 3, in the disposition attitude of the consumable electrode 22 in which the stub 24 attached to the upper end of the consumable electrode 22 is gripped by the stinger rod 25 before the start of energization, the upper end of the lower tapered surface 2 a of the stub socket 1 The distance DL between the side edge Ue and the lower end edge Le of the cylindrical base 4 of the rod plug 3 along the direction of the central axis CL is preferably 2.5 mm to 5.5 mm. More preferably, the distance DL along the axial direction is 2.7 mm to 5.3 mm. If the distance DL along the axial direction is too short, the cylindrical base 4 of the rod plug 3 may come into contact with the tapered inner surface 2 of the stub socket 1 as the stub socket 1 becomes hot when energized. On the other hand, if the distance DL along the axial direction is too long, there is a concern that the required contact area between the lower tapered surface 2a of the stub socket 1 and the tapered outer surface 5a of the rod plug 3 can not be secured.

The axial distance from the bottom of the concave portion 1a of the stub socket 1 to the upper edge Ue of the lower tapered surface 2a of the stub socket 1 (that is, the axial direction in which the lower tapered surface 2a is formed) Can be, for example, 22.5 mm to 25.1 mm. The axial distance from the upper end side edge Ue of the lower tapered surface 2a of the stub socket 1 to the upper end surface of the stub (that is, the axial length at which the upper tapered surface 2b is formed) is, for example, 27 It can be set to .3 mm to 29.9 mm.
The rod plug 3 is generally separated by a distance of, for example, 9.0 mm to 11.7 mm between the tip of the truncated cone tip 5 and the bottom of the recess 1 a of the stub socket 1 when the consumable electrode arc melting furnace 21 is used. It is arranged to be positioned.

  Next, the stub socket and rod plug of the consumable electrode type arc melting furnace according to the present invention were produced on a trial basis and their effects were confirmed, which will be described below. However, the description herein is for the purpose of illustration only and is not intended to be limiting.

(Invention example)
As shown in FIGS. 1 to 3, rod plugs and stub sockets each made of oxygen free copper defined in JIS C1020 were produced.
Here, in the rod plug, the taper angle θ of the tapered outer surface is 45 °, the diameter of the circular tip end face of the truncated cone portion is 95.5 mm, and the diameter of the outer peripheral surface of the cylindrical base is 125.5 mm, The axial length of the cylindrical base is 15 mm. Here, in the stub socket, the taper angle α of the lower tapered surface is 45 °, the diameter at the bottom of the circle is 74.8 mm, and the diameter at the upper edge of the lower tapered surface is 115.5 mm. The axial distance from the bottom surface to the upper end side edge of the lower tapered surface is 10.35 mm. The contact area between the tapered outer surface of the rod plug and the tapered inner surface of the plug socket was 4687 mm ² .

The above rod plug and stub socket are attached to a consumable electrode type arc melting furnace having a structure as shown in FIGS. 4 and 7, and the maximum current during melting is set to a direct current of 42 KA using the consumable electrode type arc melting furnace. Under the condition that the retention time of the maximum current is 8 hours or more, the primary dissolution of pure titanium equivalent material (oxygen content (% O) = 0.10) consumable electrode (weight: about 15 tons) Did. In this consumable electrode type arc melting furnace, the crucible has an inner diameter of 1185 mm. Here, the current density obtained by dividing the above-mentioned maximum current by the contact area is 8.96 A / mm ² .

  Such primary melting was repeated using the same rod plug and stub socket for a total of 20 meltings. After completion of each melting, the contact portion of the rod plug and the stub socket was confirmed, and no firm fit such as shrink fitting had occurred. Thus, it has been found that the rod plug and the stub socket can easily separate the rod plug from the stub socket after melting.

(Comparative example)
Dissolution tests under the same conditions were carried out in the same consumable electrode type arc melting furnace as in the invention example except that rod plugs and stub sockets of the shape as shown in FIG. 6 were used.
Here, in the rod plug, the taper angle θ of the tapered outer surface is 60 °, the diameter of the circular tip end face of the truncated cone portion is 110.3 mm, and the diameter of the outer peripheral surface of the cylindrical base is 122.3 mm, The axial length of the cylindrical base is 10.3 mm. Here, the stub socket has a taper surface taper angle α of 60 ° and a circular bottom diameter of 98.5 mm, and the bottom surface of the stub socket and the leading edge of the rod plug when the rod plug is arranged The distance between the surface and the surface is 13 mm, and the diameter of the tapered inner surface of the stub socket at the position where the front end surface of the rod plug is 110.3 mm. The contact area between the tapered outer surface of the rod plug and the tapered inner surface of the plug socket was 4342 mm ² . The current density is 9.67 A / mm ² when the current density is calculated from the contact area and the maximum current 42 KA.

  When the same primary melting as in the invention example was repeatedly performed using a consumable electrode type arc melting furnace equipped with such a rod plug and a stub socket, the rod plug was firmly attached to the stub socket when the sixth melting was completed. After fitting, it was difficult to separate them, and it took 2 hours to repair them.

DESCRIPTION OF SYMBOLS 1 stub socket 1a recessed part 2 taper inner surface 2a lower taper surface 2b upper taper surface 3 rod plug 4 cylindrical base 5 cone truncated end 5a taper outer surface 21 consumable electrode type arc melting furnace 22 consumable electrode 23 crucible 24 stub 25 stinger rod 25a clamp part 26 water cooling jacket 27 vacuum tank 28 pressing mechanism (air cylinder)
29 inner pipe 29a outer pipe CL central axis Ue lower end of lower tapered surface Le lower end of cylindrical base α lower tapered surface taper angle β upper tapered surface taper angle θ taper of tapered cone outer surface taper Angle DL Distance along the axial direction between top edge and bottom edge

Claims (5)

A stinger rod capable of suspending and supporting the consumable electrode in the crucible and vertically displacing the consumable electrode by holding the stub and holding the stub in the crucible in which the consumable electrode is disposed, the stub attached to the upper end of the consumable electrode Equipped with
The stub has a concave stub socket having a tapered inner surface which is recessed from the upper end surface and whose inner diameter increases toward the upper side, and the stinger rod has a cylindrical base at its lower end and a lower side than the cylindrical base Comprising a frusto-conical tip having a tapered outer surface corresponding to the tapered inner surface and having a convex rod plug electrically connected to the stub socket;
A consumable electrode arc melting furnace that generates an arc between the consumable electrode and the molten metal pool in the crucible by energizing the consumable electrode through the stinger rod and the stub and energizing the crucible, and the heat causes the consumable electrode to melt. And
The stub socket is located above the lower taper surface, the lower taper surface contacting the taper outer surface of the truncated cone end portion of the rod plug, and the taper inner surface of the stub socket, relative to the lower taper surface. Consumable electrode type in which the cylindrical base of the rod plug is not in contact with the tapered inner surface of the stub socket, which is composed of two or more stages of tapered surfaces including an upper tapered surface having a small taper angle with respect to a plane orthogonal to the central axis of Arc melting furnace.   The consumable electrode type arc melting furnace according to claim 1, wherein a taper angle of the upper tapered surface of the stub socket is set to 25 ° to 35 ° with respect to a plane orthogonal to a central axis of the stub socket.   The taper angle of the lower tapered surface of the stub socket and the taper angle of the tapered outer surface of the truncated cone end of the rod plug are both 40 ° to 50 ° with respect to a plane orthogonal to the central axis of the stub socket. The consumable electrode type arc melting furnace according to Item 1 or 2. And the lower tapered surface of the stub socket, the contact area between the apparent and the tapered outer surface of the truncated cone tip of the rod plug, a consumable electrode type according to claim 1 comprising as 4400mm ² ~5000mm ² Arc melting furnace.   In the disposition attitude of the consumable electrode in which the stub attached to the upper end of the consumable electrode is gripped by the stinger rod, the axis line between the upper edge of the lower tapered surface of the stub socket and the lower edge of the cylindrical base of the rod plug The consumable electrode type arc melting furnace according to any one of claims 1 to 4, wherein the distance along the direction is 2.7 mm to 5.3 mm.

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