JP3891315B2 - Crucible induction furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction melting furnace that melts metal by induction heating, and in particular, a casting crucible type having a gas bubbling nozzle for blowing gas into a cast iron melt and an extrusion plug for extruding the crucible from the bottom of the furnace. Related to induction furnace.
[0002]
[Prior art]
The cast iron melt melted in the crucible induction furnace often contains low melting point metals such as zinc and lead generated from the plated steel sheet in the scrap steel supplied as a raw material. When the content of the low melting point metal is increased, the quality of the cast iron is deteriorated, and in particular, zinc vapor penetrates into the refractory material forming the crucible and melts it, or damages the induction coil on the outside. As one method for removing the low melting point metal in the molten metal, there is known a method (gas bubbling) in which an inert gas such as argon is blown into the molten metal and the evaporated low melting point metal is discharged together with this gas. Generally, a means is used in which a lance pipe is inserted from above and gas is blown, or a gas bubbling nozzle is set on the furnace bottom and gas is blown.
[0003]
On the other hand, the crucible forming the melting chamber of the raw material is generally constructed by solidifying a powder refractory material called a stamp material and firing the surface. However, this crucible gradually wears with use. It is necessary to renew at a rate of about once a month. At that time, as a method of disassembling the used crucible, a rapid dismantling method in which an extrusion plug is built into the refractory brick below the crucible, and the crucible is lifted from the furnace bottom by lifting the extrusion plug with a hydraulic mechanism at the time of crucible disassembly. It has been known.
[0004]
FIG. 2 is a longitudinal sectional view showing a conventional example of a crucible induction furnace provided with the gas bubbling nozzle and the extrusion plug. In FIG. 2, a melting chamber 2 is formed by a crucible 1 made of a stamp refractory material, and a hot water outlet 3 is provided at the top. An induction coil 5 is disposed outside the crucible 1 via a coil cement insulating material 4, and a yoke 6 is disposed outside the induction coil 5. Each of the above parts is housed in a furnace frame 7 to constitute a furnace body. The crucible 1 is supported on the furnace frame 7 via a refractory brick 8, and the crucible 1 is surrounded by a refractory cement 9 at two locations on the upper and lower sides. It is fixed to. The illustrated furnace body is supported in a tiltable manner on a stand (not shown) provided with a hydraulic cylinder.
[0005]
A gas bubbling nozzle 10 made of a porous plug is incorporated at the bottom of the crucible 1, and an inert gas such as argon supplied through a flow rate adjusting valve 13 is blown into the molten metal through a gas pipe 12 connected by piping from a gas cylinder 11. The low melting point metal contained is promoted to be removed. In addition, the extrusion plug 14 is incorporated in the refractory brick 8 below the crucible 1, and when the worn crucible 1 is disassembled, the extrusion plug 14 is lifted by the hydraulic mechanism 15 as indicated by a chain line, and the crucible 1 is removed. Extrused from the bottom of the furnace.
[0006]
[Problems to be solved by the invention]
In such a conventional configuration, it is preferable that the extrusion plug 14 is positioned at the center of the crucible in view of the balance when the crucible is pushed out. Therefore, the gas bubbling nozzle 10 avoids the interference with the extrusion plug 14, so It is incorporated at a position off the center. However, if the gas bubbling nozzle 10 is located away from the crucible center, it is difficult to blow the gas uniformly into the molten metal, and the ability to remove the low melting point metal is inevitably reduced compared to the case where it is installed at the center. It was. Further, since the hole 8a through which the gas bubbling nozzle 10 is inserted must be provided in the refractory brick 8 separately from that for the extrusion plug 14, the processing is troublesome.
It is an object of the present invention to enable uniform gas blowing when a gas bubbling nozzle and an extrusion plug are provided, and to eliminate the processing of refractory bricks for installing the gas bubbling nozzle.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention includes a gas bubbling nozzle for blowing gas into the molten metal in the melting chamber, and an extrusion plug for extruding the crucible forming the melting chamber from the furnace bottom to disassemble it. In the crucible induction furnace, the gas bubbling nozzle and the extrusion plug are arranged concentrically, and a nozzle insertion hole is provided in the extrusion plug. The extrusion plug is incorporated in a refractory brick below the crucible, and the gas A bubbling nozzle is incorporated into the bottom of the crucible through the nozzle insertion hole .
[0008]
As a result, the gas bubbling nozzle can be incorporated into the bottom of the crucible through the nozzle insertion hole of the extrusion plug, so that hole processing for inserting the gas bubbling nozzle into the refractory brick becomes unnecessary. In addition, the gas bubbling nozzle and the extrusion plug are stacked one above the other at the optimum position such as the center of the furnace bottom, so that uniform gas blowing into the molten metal and balanced crucible extrusion can be achieved simultaneously.
[0009]
Furthermore, the present invention provides a crucible type induction furnace in which a cylindrical nozzle presser is inserted into the nozzle insertion hole, and a flange is detachably fixed to the lower surface of the extrusion plug, and the gas is passed through the nozzle presser by the flange. The bubbling nozzle shall be fixed to the bottom of the crucible. Accordingly, the gas bubbling nozzle can be easily replaced only by attaching and detaching the flange, and the gas pipe can be passed through the center hole of the cylindrical nozzle presser, so that piping is also simplified.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a longitudinal sectional view of an essential part of a crucible induction furnace showing an embodiment of the present invention. In FIG. 1, a sleeve 16 made of a porous hollow cone is embedded in the center of the bottom of the crucible 1 in advance when the crucible is constructed, and a conical gas bubbling nozzle 10 made of a porous plug is closely inserted inside the sleeve 16. Yes. The gas bubbling nozzle 10 is made of, for example, a high-alumina porous material that allows gas to pass but retains the molten metal, and a disk (not shown) is fixed to the bottom surface, and a gas pipe 12 is connected to the center hole. Yes.
[0011]
On the other hand, an extrusion plug 14 is incorporated in the refractory brick 8 below the crucible 1 concentrically with the gas bubbling nozzle 10. The extrusion plug 14 made of refractory cement is formed in an inverted conical shape so that the refractory brick can be pulled out upward from the nozzle 8, and a nozzle insertion hole 17 having a circular cross section having the same diameter as the lower inner diameter of the sleeve 15 is provided at the center. On the lower surface, there is an annular reinforcing plate 18 in which a hole having the same diameter as the nozzle insertion hole 17 is punched. The reinforcing plate 18 is made of an iron plate, and hooks 18 a welded to several places on the surface facing the extrusion plug 14 are inserted into the extrusion plug 14 and fixed. In the case of the illustrated embodiment, the reinforcing plate 18 is aligned with the bottom plate 7a of the furnace frame 7, and the bottom plate 7a has a circular hole having an inner diameter that is slightly larger than its outer shape so as to escape the reinforcing plate 18 portion. ing.
[0012]
A flange 19 made of an iron plate having the same diameter as the reinforcing plate 18 is fixed to the lower surface of the extrusion plug 14. The flange 19 has a small hole through which the gas pipe 12 passes, and is fastened and fixed by several screws (not shown) that are screwed into screw holes (not shown) provided in the reinforcing plate 18. The flange 19 presses the gas bubbling nozzle 10 from below via a nozzle presser 20 inserted into the nozzle insertion hole 17 of the extrusion plug 14, and fixes it in the sleeve 16. The nozzle retainer 20 is formed into a hollow cylindrical shape by fireproof cement, and the gas pipe 12 connected to the gas bubbling nozzle 10 is drawn out through the hollow hole and the center hole of the flange 19. A leg portion 19a made of an annular body is also fixed to the lower surface of the flange 19 by welding in order to uniformly apply a pushing force to the peripheral edge portion of the push plug 14.
[0013]
In the above-described embodiment, when a melting material is introduced into the melting chamber 2 and the induction coil 5 is energized, the melting material is melted by heat generated by the induced current. The melted material melts at 1250 to 1300 ° C., but is further heated to 1500 to 1550 ° C. and then discharged. In the meantime, zinc and lead contained in the molten metal melt and evaporate at a temperature much lower than that of iron. Therefore, argon gas is blown into the molten metal from the gas bubbling nozzle 10, and the vapor is blown into the molten metal outside the furnace. To discharge. In that case, since the gas bubbling nozzle 10 is located at the center of the furnace bottom in spite of the presence of the extrusion plug 14, the blown gas is uniformly dispersed in the melting chamber 2, and the low melting point metal vapor in the molten metal is discharged uniformly. can do. Further, since the gas bubbling nozzle 10 can be incorporated into the bottom of the crucible through the nozzle insertion hole 17 of the extrusion plug 10, it is not necessary to provide a dedicated hole in the refractory brick 8 separately from that for the extrusion plug 14.
[0014]
Since the gas bubbling nozzle 10 is consumed due to contact with the molten metal, it is necessary to replace the gas bubbling nozzle 10 more frequently than the crucible 1. In that case, the flange 19 is removed by loosening the screw, and the gas bubbling nozzle 10 is extracted together with the nozzle presser 20. The new gas bubbling nozzle 10 is installed in the reverse order.
[0015]
On the other hand, the inner wall surface of the crucible 1 is exposed to a high temperature close to 1600 ° C. and wears due to mechanical wear and impact due to the stirring of the molten metal by electromagnetic force. Therefore, it is necessary to update at an appropriate interval as described above. In this case, the extrusion plug 14 is lifted through the flange 19 by the hydraulic mechanism 15, and the crucible 1 is extracted upward and disassembled. At this time, the push-up force from the hydraulic mechanism 15 is uniformly applied to the peripheral edge of the push plug 14 due to the presence of the leg 19a made of an annular body, and the push plug 14 is not cracked due to the uneven push-up force.
[0016]
【The invention's effect】
According to the present invention, when the gas bubbling nozzle and the extrusion plug are provided together, it is not necessary to drill holes for incorporating the gas bubbling nozzle in the refractory brick, and the gas bubbling nozzle and the extrusion plug are stacked one above the other in the furnace. The nozzle can be arranged at the optimum position on the bottom, and the nozzle can be easily replaced through the nozzle insertion hole of the extrusion plug.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a main part of a crucible induction furnace showing an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of a crucible induction furnace showing a conventional example.
[Explanation of symbols]
1 crucible 2 melting chamber 5 induction coil 8 refractory brick 10 gas bubbling nozzle 14 extrusion plug 17 nozzle insertion hole 18 reinforcing plate 19 flange 20 nozzle presser

Claims (2)

In a crucible induction furnace provided with a gas bubbling nozzle for blowing gas into the molten metal in the melting chamber, and an extrusion plug for extruding the crucible forming the melting chamber from the furnace bottom,
The gas bubbling nozzle and the extrusion plug are arranged concentrically, and a nozzle insertion hole is provided in the extrusion plug, the extrusion plug is incorporated in a refractory brick below the crucible , and the gas bubbling nozzle is installed in the nozzle insertion hole. A crucible induction furnace, which is incorporated into the bottom of the crucible. A cylindrical nozzle presser is inserted into the nozzle insertion hole, and a flange is detachably fixed to the lower surface of the extrusion plug, and the gas bubbling nozzle is fixed to the bottom of the crucible through the nozzle presser by the flange. The crucible induction furnace according to claim 1, wherein:

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