JP2021157892A - Induction melting furnace, monitoring method thereof, and sleeve - Google Patents

Abstract

To provide an induction melting furnace including a sleeve, in which the penetration rate of molten metal into a furnace wall, the penetration points thereof and the like are accurately grasped and monitored so that a metal melting process can be stabilized and made more efficient.SOLUTION: An induction melting furnace is characterized to monitor the progressive status in deterioration of a refractory material by detecting changes in electrical resistance between an electrode and an outside antenna or changes in electrical resistance between an inside antenna and the outside antenna and also monitor the progressive status in deterioration of a sleeve by detecting changes in electrical resistance between the inside antenna and the electrode.SELECTED DRAWING: Figure 1A

Description

The present invention relates to an induction melting furnace used in a casting process and a monitoring method thereof, and more particularly to an induction melting furnace using a sleeve having excellent heat resistance as a furnace wall of a melting chamber, a monitoring method thereof, and a sleeve thereof.

When a metal product is produced by casting, an induction melting furnace is used to melt the metal-based material. However, when the material is melted by induction heating and the molten metal is heated, the molten metal becomes one of the furnace walls. A phenomenon may occur in which the furnace material permeates the part and loses its function (hot water leakage).

When melting an alloy containing a metal with a low boiling point such as zinc, zinc evaporates at a temperature lower than the melting temperature of the alloy and penetrates the furnace wall. The steam touches and cools, and metallic zinc precipitates at the interface with the furnace wall.

Therefore, it is important to monitor hot water leakage in the melting step, and various detection methods have been proposed.

JP-A-2018-155424

In Patent Document 1 described above, the applicant of the present application provides a first hot water leak detection network for detecting a change in current value and a second hot water leak detection network for detecting disconnection in the lining region for holding the molten metal. We proposed a detection method that can easily and reliably determine whether the change in the detected value is due to a leak in the molten metal or a leak in the molten metal such as zinc precipitation.

However, with the conventional method, it has not been possible to monitor the condition of the furnace wall or the like before the serious hot water leakage caused by the cracking of the furnace wall or the like.

An object of the present invention is to stabilize and streamline the metal melting process by accurately grasping and monitoring the permeation rate of the molten metal into the furnace wall and the permeation location thereof in the induction melting furnace provided with the sleeve. do.

The induction melting furnace of the first invention is an induction melting furnace provided with a cylindrical sleeve.
On the outer surface of the sleeve, a plurality of inside antennas divided into two or more in an arc shape in a plan view are provided.
An outside antenna formed at least at a position corresponding to the inside antenna is provided on the inner surface of the coil protection lining provided on the outside of the sleeve via a refractory material to hold the heating coil.
The bottom of the melting chamber has an electrode whose tip is exposed from the bottom of the refractory material.
By detecting a change in the electric resistance value between the electrode and the outside antenna or a change in the electric resistance value between the inside antenna and the outside antenna, the deterioration progress of the fireproof material is monitored. At the same time
It is characterized in that the deterioration progress state of the sleeve is monitored by detecting the change in the electric resistance value between the inside antenna and the electrode.

According to the induction melting furnace of the first invention, in the fireproof material, the change in the electric resistance value between the electrode and the outside antenna or the change in the electric resistance value between the inside antenna and the outside antenna is detected. Since the permeation rate of minor hot water leaks can be grasped and the replacement time of the fireproof material can be predicted, the metal melting process can be stabilized and made more efficient.

In addition, by detecting changes in the electrical resistance between the inside antenna provided on the outer surface of the sleeve and the electrode whose tip is exposed from the bottom of the refractory material, slight cracks in the sleeve, zinc penetration status, and their occurrence are detected. The position can be grasped.

As a result, it is possible to predict the replacement time of the sleeve, select an operation method in consideration of the location of the abnormality, and repair the location between the melting steps depending on the location of the abnormality.

As described above, according to the induction melting furnace of the first invention, since minor abnormalities can be detected in the refractory material and the sleeve which are the furnace wall materials, it is possible to predict the replacement time thereof, and accordingly, the replacement members are arranged and the personnel are arranged. Since it is possible to make arrangements for the production, it is possible to formulate a stable and efficient production plan.

The induction melting furnace of the second invention is the induction melting furnace of the first invention.
The inside antenna is characterized in that it is formed in a range from the lower end of the sleeve to the center of the cylindrical shape in the longitudinal direction.

According to the induction melting furnace of the second invention, the abnormality can be detected in the lower half portion of the sleeve and the refractory material, which are more prone to abnormality.

The induction melting furnace of the third invention is the induction melting furnace of the first or second invention.
The inside antenna is characterized in that it is formed in a comb shape having a comb tooth electrode extending in the longitudinal direction in a cylindrical shape of the sleeve.

According to the induction melting furnace of the third invention, it is possible to grasp the range in which the abnormality occurs in the sleeve and the refractory material.

The fourth invention is a method for monitoring an induction melting furnace provided with a cylindrical sleeve.
Inside a plurality of inside antennas provided on the outer surface of the sleeve, which are divided into two or more in an arc shape in a plan view, and a coil protection lining provided on the outside of the sleeve via a fireproof material to hold a heating coil. Changes in electrical resistance between the outside antenna provided on the surface and formed at least at a position corresponding to the inside antenna, or the outside antenna and the bottom of the melting chamber provided at the bottom of the fireproof material. By detecting the change in the electrical resistance value between the antenna and the antenna whose tip is exposed, the deterioration progress of the fireproof material can be monitored, and at the same time.
It is characterized in that the deterioration progress state of the sleeve is monitored by detecting the change in the electric resistance value between the inside antenna and the electrode.

According to the method for monitoring the induction melting furnace of the fourth invention, the change in the electric resistance value between the electrode and the outside antenna or the change in the electric resistance value between the inside antenna and the outside antenna is detected. Since the permeation rate of slight hot water leakage in the fireproof material can be grasped and the replacement time of the fireproof material can be predicted, the metal melting process can be stabilized and made more efficient.

In addition, by detecting changes in the electrical resistance between the inside antenna provided on the outer surface of the sleeve and the electrode whose tip is exposed from the bottom of the refractory material, slight cracks in the sleeve, zinc penetration status, and their occurrence are detected. The position can be grasped.

As a result, it is possible to predict the replacement time of the sleeve, select an operation method in consideration of the location of the abnormality, and repair the location between the melting steps depending on the location of the abnormality.

As described above, according to the monitoring method of the induction melting furnace of the fourth invention, since minor abnormalities can be detected in the refractory material and the sleeve which are the furnace wall materials, the replacement time of them can be predicted, and the replacement member can be replaced accordingly. Since it is possible to make arrangements and personnel arrangements, it is possible to formulate a stable and efficient production plan.

The fifth invention is a cylindrical sleeve for an induction melting furnace.
The outer surface of the sleeve is characterized by having a plurality of inside antennas divided into two or more in an arc shape in a plan view.

According to the sleeve of the fifth invention, in the metal melting step using this sleeve, it is possible to grasp the slight cracking of the sleeve, the permeation state of zinc, the generation position thereof, and the like.

The whole block diagram which shows the structure of the induction melting furnace of this embodiment. The plan view explanatory view of the induction melting furnace of this embodiment. The perspective view of the sleeve used for the induction melting furnace of this embodiment. The figure which shows the wear of the sleeve in this embodiment. The figure which shows the breakage of a sleeve in this embodiment. The figure which shows zinc penetration into a sleeve in this embodiment. The figure which shows the deterioration of the refractory material in this embodiment.

The induction melting furnace of the present embodiment, a monitoring method thereof, and a sleeve thereof will be described with reference to FIGS. 1A, 1B and 2.

As shown in FIG. 1A, the induction melting furnace of the present embodiment has a sleeve 2 forming the outer wall of the melting chamber 1, a refractory material 3 forming the bottom of the melting chamber 1 and surrounding the sleeve 2, and a coil having a heating coil. It includes a protective lining 4, an iron core 5, and a furnace frame 6.

Further, as a monitoring system for monitoring the deterioration progress of the sleeve 2 and the refractory material 3, an inside antenna 7 provided on the outer surface of the sleeve 2 and an outside antenna 8 provided on the inner surface of the coil protection lining 4 are used. An electrode 9 whose tip is exposed from the bottom of the refractory material 3 at the bottom of the melting chamber 1, a DC power supply 10, a detector 11, and a recorder 12 are provided.

The induction melting furnace of the present embodiment has a structure in which a cylindrical sleeve 2 having excellent heat resistance is incorporated, and when the furnace wall is worn out, only the sleeve 2 manufactured in advance needs to be replaced. Unlike the conventional melting furnace, it is not necessary to replace the furnace wall over a long period of time, and the operation stop time and the repair cost can be significantly reduced.

When the metal is melted, the melting chamber 1 is filled with the molten metal Y, the inner side surface of the melting chamber 1 is made of a sleeve 2, and the bottom surface is made of a refractory material 3.

The sleeve 2 is made of cylindrical and heat-resistant ceramics, and as shown in FIG. 2, a plurality of recesses 21 for hanging a transport belt or the like during transportation are provided at the lower end portion, and the molten metal Y is taken out at the upper end portion. It has a sprue 22. Further, a linear recess 24 in which a temperature measuring unit 23 for continuously measuring the temperature of the molten metal Y is housed is formed in a part of the inner surface surface in the longitudinal direction of the cylinder.

The refractory material 3 is also made of other ceramics having heat resistance, and has a form in which the sleeve 2 can be stored.

The coil protection lining 4 is also made of another ceramic having heat resistance, and is integrally molded by embedding a water-cooled heating coil. The heating coil is fixed at a distance of at least about 20 mm or more from the inner surface of the coil protection lining 4.

Iron cores 5, which are return magnetic circuit cores, are vertically attached to the outer periphery of the coil protection lining 4 at predetermined intervals, and the outside thereof is surrounded by a furnace frame 6.

In the melting step, the melting material is put into the melting chamber 1 and an alternating current is applied to the heating coil to heat the melting material in the melting chamber 1 by induction heating, and finally the molten metal Y is formed.

The inside antenna 7 is formed by dividing a wire rod obtained by linearly processing a high melting point material such as a nichrome wire or a stainless steel wire into four parts on the outer surface of the lower half of the sleeve 2 in an arc shape in a plan view. The sleeve 2 is formed in a comb shape having a cylindrical comb tooth electrode 71 extending in the longitudinal direction. The wire has a thickness of 1.0 to 1.5 mm and is fixed to the sleeve 2 with a fireproof tape. Here, if the electrode spacing of the comb tooth electrode 71 is changed too fine, it tends to malfunction, and if it is too rough, it does not react to the hot water splinter generated by hot water leakage. In the present embodiment, in the sleeve 2 having a diameter (outer diameter) of 900 mm, the electrode spacing of the comb tooth electrodes 71 is 80 mm, and the number of electrodes is four.

The number of comb tooth electrodes 71 in one division range can be 2 to 10, and these are grouped at the lower end of the sleeve 2 and electric signals are drawn from the terminals 72 at the upper end of the sleeve 2.

The outside antenna 8 is formed on the inner surface of the coil protection lining 4, and is formed at a position corresponding to at least the inside antenna 7 on the inner surface.

The outside antenna 8 can also be a wire obtained by processing a high melting point material such as a nichrome wire or a stainless wire into a linear shape, and when it is formed on the entire inner surface of the coil protection lining 4, it is formed in a spiral shape or a wavy shape. do. The thickness of the wire is 1.0 to 1.5 mm, and it is fixed to the coil protection lining 4 by an embedded type.

The electrode 9 is a needle-shaped electrode embedded so that the tip is exposed on the inner bottom surface of the melting chamber 1 and the bottom surface of the fireproof material 3, and one end is connected to the electrode 9 and the other end is an inside antenna 7. A DC power supply 10, a detector 11, and a recorder 12 connected to the above constitute one monitoring circuit. The outside antenna 8 is also connected to the DC power supply 10, the detector 11, and the recorder 12.

This monitoring circuit changes (decreases) the electrical resistance values between the electrode 9 and the inside antenna 7, between the electrode 9 and the outside antenna 8, and between the outside antenna 8 and the inside antenna 7, respectively. It is detected numerically as a change (increase) in the current value flowing through the antenna.

In detecting the change in the electric resistance value between the inside antenna 7 and the outside antenna 8, as shown in FIGS. 1B and 2, the inside antenna 7 is formed in a range divided into four, so that the inside antenna 7 is divided inside. Each of the antennas 7A to 7D is provided with a DC power supply 10, a detector 11, and a recorder 12, and an independent monitoring circuit is formed for each of the divided inside antennas 7A to 7D.

Here, in a general-purpose monitoring circuit, changes in individual electric resistance values are monitored in a switchable manner, but in a high-end monitoring circuit, all changes in electric resistance values are measured and recorded fully automatically.

Similarly, in order to detect a change in the electric resistance value between the inside antenna 7 and the outside antenna 8, one end is connected to the outside antenna 8 and the other end is connected to the inside antenna 7. The detector 11 and the recorder 12 constitute another monitoring circuit.

Again, since the inside antenna 7 is formed in a range divided into four, each of the divided inside antennas 7A to 7D is provided with a DC power supply 10, a detector 11, and a recorder 12, respectively. An independent monitoring circuit is formed every 7A to 7D.

Again, in a general-purpose monitoring circuit, changes in individual electrical resistance values are monitored in a switchable manner, but in a high-end monitoring circuit, all changes in electrical resistance values are measured and recorded fully automatically.

Further, also in detecting the change in the electric resistance value between the electrode 9 and the outside antenna 8, a monitoring circuit is formed according to the installation state of the outside antenna 8 to monitor the change in the electric resistance value.

The sleeve 2 in this embodiment is provided with a temperature sensor 25 on its outer surface. In the melting step, by comparing the temperature information from the temperature measuring unit 23 and the temperature sensor 25 described above, it is possible to monitor the melting damage of the sleeve 2, that is, the change in the average thickness of the sleeve 2.

Hereinafter, an example of a method for monitoring deterioration over time of the sleeve 2 and the refractory material 3 in the induction melting furnace of the present invention will be described.

FIG. 3 shows a change in the current value between the electrode 9 and the inside antenna 7 when the sleeve 2 is consumed in the melting process while the induction melting furnace is operated daily. Here, the change in the current value is shown as a value indicating the change in the electric resistance value (the same applies hereinafter).

As the sleeve 2 is consumed and the wall thickness becomes thinner, the electric resistance value becomes smaller. Since the electric resistance value becomes small, the current easily flows and the current value rises. Since the electric resistance value is inversely proportional to the thickness, the residual thickness can be estimated from the current value. As a result, if the upper limit of the current value is determined, it is possible to know how many days later the dangerous state will occur from the consumption rate, and the sleeve 2 can be replaced in a planned manner.

Here, it is shown that the dissolution step was carried out without any major abnormality until the 30th day.

FIG. 4 shows the change in the current value between the electrode 9 and the inside antenna 7 when the sleeve 2 is broken on the 15th day.

Since the sleeve 2 was broken on the 15th day from the start of operation, the molten metal leaked and was in contact (short circuit) with the inside antenna 7, so that the current value was the upper limit of 100 mA.

In this case, the melting process can be interrupted and the sleeve 2 can be replaced or repaired, or if the refractory material 3 is maintained, the melting process can be continued.

FIG. 5 shows a change in the current value between the electrode 9 and the inside antenna 7 when a component such as zinc that adversely affects the insulation and the life of the furnace body permeates and accumulates in the sleeve 2. In such a case, since the discharge phenomenon is accompanied, the current value rises while swinging in small steps.

In this case as well, the melting step can be interrupted to replace or repair the sleeve 2, and if the refractory material 3 is maintained, the melting step can be continued.

FIG. 6 is a change in the current value between the electrode 9 and the outside antenna 8 when the sleeve 2 is broken in FIG. 4 described above.

On the 15th day from the start of operation, the electric resistance value decreases and the current value gradually increases as the sleeve 2 cracks and the molten metal jet pieces permeate the refractory material 3. Then, on the 30th day, when the hot water bottle reaches the outside antenna 8, it is short-circuited and reaches the upper limit of 100 mA.

In this monitoring example, when the current value exceeds approximately 40 mA, it is judged to be a dangerous level, and the melting process should be stopped on the 29th day from the start of operation.

In this way, it is easy to estimate what is happening by combining the degree of increase in the current value and the measurement site.

Further, in the conventional hot water leakage detection device, the detection is performed only between the electrode 9 and the outside antenna 8 in the present invention. Therefore, the behavior of the change in the current value at the time of hot water leakage rises sharply just before it becomes unusable as shown in FIG. In this case, it is possible to safely discontinue use (stop the furnace), but it is not possible to replace the sleeve 2 in a planned manner in advance. As a result, there is an operation loss in which the operation is suddenly stopped and the replacement work is performed. On the other hand, when the inside antenna 7 is present, it can be recognized that the sleeve is broken on the 15th day as shown in FIG. 4, so that the preparation for replacement can be started with a margin.

According to the above embodiment, the change in the electric resistance value between the electrode 9 and the outside antenna 8 whose tip is exposed from the bottom of the fireproof material 3, or the electricity between the inside antenna 7 and the outside antenna 8. By detecting the change in the resistance value, the permeation rate of slight hot water leakage in the fireproof material 3 can be grasped, and the replacement time of the fireproof material 3 can be predicted, so that the metal melting process is stabilized and made efficient. be able to.

Further, by detecting a change in the electric resistance value between the inside antenna 7 provided on the outer surface of the sleeve 2 and the electrode 9 whose tip is exposed from the bottom of the refractory material 3, slight cracks in the sleeve 2 and zinc can be detected. It is possible to grasp the infiltration situation and its occurrence position. As a result, it is possible to predict the replacement time of the sleeve 2, select the operation method in consideration of the location where the abnormality occurs, and repair the location between the melting steps depending on the location where the abnormality occurs. ..

In this way, since minor abnormalities can be detected in the refractory material 3 and the sleeve 2 which are the furnace wall materials, the replacement time can be predicted, and the replacement members and personnel can be arranged accordingly, which is stable. You can make an efficient production plan.

In this embodiment, an example in which the deterioration progress of the fireproof material 3 is monitored by detecting a change in the electric resistance value between the electrode 9 whose tip is exposed from the bottom of the fireproof material 3 and the outside antenna 8. As shown, it is clear that the deterioration progress status of the fireproof material 3 can be monitored by detecting the change in the electric resistance value between the inside antenna 7 and the outside antenna 8.

Further, the inside antenna 7 is formed on the outer surface of the lower half of the sleeve 2 in a range divided into four in an arc shape in a plan view. There may be.

Further, in the present embodiment, the inside antenna 7 is a comb tooth electrode 71 made of a wire rod, but a thin film-shaped electrode may be used.

1 ... Melting chamber, 2 ... Sleeve, 3 ... Refractory material, 4 ... Coil protection lining, 5 ... Iron core, 6 ... Furnace frame, 7 ... Inside antenna, 8 ... Outside antenna, 9 ... Electrode, 10 ... DC power supply, 11 ... detector, 12 ... recorder, 71 ... comb tooth electrode, Y ... molten metal.

Claims (5)

An induction melting furnace with a cylindrical sleeve.
On the outer surface of the sleeve, a plurality of inside antennas divided into two or more in an arc shape in a plan view are provided.
An outside antenna formed at least at a position corresponding to the inside antenna is provided on the inner surface of the coil protection lining provided on the outside of the sleeve via a refractory material to hold the heating coil.
The bottom of the melting chamber has an electrode whose tip is exposed from the bottom of the refractory material.
By detecting a change in the electric resistance value between the electrode and the outside antenna or a change in the electric resistance value between the inside antenna and the outside antenna, the deterioration progress of the fireproof material is monitored. At the same time
An induction melting furnace characterized in that the progress of deterioration of the sleeve is monitored by detecting a change in the electric resistance value between the inside antenna and the electrode. The induction melting furnace according to claim 1, wherein the inside antenna is formed in a range from the lower end of the sleeve to the center of the cylindrical shape in the longitudinal direction. The induction melting furnace according to claim 1 or 2, wherein the inside antenna is formed in a comb shape having a comb-tooth electrode extending in the longitudinal direction in a cylindrical shape of the sleeve. A method of monitoring an induction melting furnace with a cylindrical sleeve.
Inside a plurality of inside antennas provided on the outer surface of the sleeve, which are divided into two or more in an arc shape in a plan view, and a coil protection lining provided on the outside of the sleeve via a fireproof material to hold a heating coil. Changes in electrical resistance between the outside antenna provided on the surface and formed at least at a position corresponding to the inside antenna, or the outside antenna and the bottom of the melting chamber provided at the bottom of the fireproof material. By detecting the change in the electrical resistance value between the antenna and the antenna whose tip is exposed, the deterioration progress of the fireproof material can be monitored, and at the same time.
A method for monitoring an induction melting furnace, which comprises monitoring the progress of deterioration of the sleeve by detecting a change in an electric resistance value between the inside antenna and the electrode. Cylindrical sleeve for induction melting furnace
The sleeve is characterized in that the outer surface of the sleeve has a plurality of inside antennas divided into two or more in an arc shape in a plan view.

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