JP6086276B2 - Cold crucible melting furnace - Google Patents

Description

  The present invention relates to a melting furnace that melts a metal to be melted by induction heating, and particularly to a cold crucible melting furnace that performs induction heating melting while forming a skull by cooling.

  Conventionally, as an apparatus for melting a metal to be melted by induction heating, for example, a furnace main body formed of a metal such as copper and having a cooling water channel therein, and an induction heating coil arranged around the furnace main body are provided. There is a cold crucible melting furnace. When melting the metal to be melted accommodated in the furnace main body in this cold crucible melting furnace, the metal to be melted is inductively heated by an induction heating coil, and the furnace main body is cooled by passing cooling water through a cooling water channel. As a result, the metal to be melted accommodated in the furnace body is extracted by the furnace body on the outer peripheral side, so that the melted metal is cooled and solidified skull is formed on this outer peripheral side, and only the inside melts. Become. For this reason, the molten metal in which the metal to be melted is separated from the furnace body by the skull, thereby preventing contamination from the furnace body. Moreover, since the furnace body is made of metal as described above, there is no risk of damage such as cracking even if rapidly melted. For this reason, in a cold crucible melting furnace, it is possible to produce a high purity molten metal at a high speed.

  By the way, in recent years, the molten metal produced by the cold crucible melting furnace has a good molten metal flow to the mold, thereby improving the product quality and the yield. It is desired that the temperature is raised to over 150 ° C, preferably over + 150 ° C. However, in a conventional cold crucible melting furnace, the metal to be melted accommodated in the furnace body is removed by the furnace body with a heat removal amount corresponding to the thermal conductivity of the material (copper, etc.) forming the furnace body. Therefore, the temperature could be overheated only below + 100 ° C. with respect to the melting point of the metal to be dissolved.

  In view of the above circumstances, the invention according to Patent Document 1 has been made. A cold crucible melting furnace according to the present invention includes a furnace body having a housing recess for housing a metal to be melted, a cooling means for cooling the furnace body, an outer circumferential side of the furnace body, and a housing recess for the furnace body. A cold crucible melting furnace including an induction heating coil for induction heating of a metal to be melted contained in the furnace, wherein at least a bottom surface of the inner surface of the furnace body constituting the housing recess has a melting point higher than that of the metal to be melted. It is covered with a heat cushioning member formed of a high refractory material.

  According to this invention, the metal to be melted accommodated in the accommodating recess is induction-heated by the induction heating coil, and is also removed from the furnace body cooled by the cooling means, thereby forming a skull at the outer peripheral portion. The molten metal can be generated inside. Here, heat removal by the furnace body is performed from the inner surface of the furnace body facing the metal to be melted, but the bottom surface covered with the heat buffer member formed of refractory is removed through this heat buffer member. Heat is to be performed, and the amount of heat removal can be reduced as compared with direct heat removal. For this reason, a to-be-dissolved metal can be heated effectively and a to-be-dissolved metal can be melt | dissolved rapidly. Thereby, overheating of +150 degreeC or more is possible with respect to melting | fusing point of a to-be-dissolved metal.

JP 2009-85525 A

  By the way, such a cold crucible melting furnace is provided with a temperature measuring means for measuring the temperature of the molten metal in the housing recess. As an example of this temperature measuring means, a radiation thermometer is provided above the furnace body (not specified in Patent Document 1, see FIG. 3). By measuring the temperature with this radiation thermometer, it is detected that the molten metal has been heated to a desired temperature suitable for the hot water, and the next process, specifically, the hot water treatment (the process of removing the molten metal from the housing recess), or A process for reducing the power supplied to the induction heating coil is performed.

  However, sometimes the temperature measurement by the temperature measuring means is not normally performed. In the case of a radiation thermometer, this is caused by the effect of smoke generated from the molten metal, the effect of dirt or cloudiness on the lens of the radiation thermometer, the effect of shielding, the displacement of the temperature measurement position due to the positional relationship with the furnace body, etc. It is. When such a situation occurs, the amount of heat removed from the bottom surface of the furnace body is reduced due to the presence of the heat buffer member, so that the residual amount of heat in the furnace body increases, and the conventional bottom surface is heat buffered. Compared to a cold crucible melting furnace that is not covered with a member, the temperature of the molten metal rises rapidly. If the temperature of the molten metal rapidly rises above the desired temperature, the furnace body is cooled by passing cooling water, and thus the furnace body is not overheated to the extent that the furnace body melts. However, since the heat buffer member is not cooled as in the furnace body, the heat buffer member can not withstand the abnormal overheating due to the rapid temperature rise and is damaged, or the skull is reduced (or disappeared) due to overheating. Due to the direct contact with the molten metal, there is a possibility that the molten metal is contaminated by the refractory material eluted in the molten metal, which may hinder casting. Therefore, even when the temperature measurement by the temperature measuring means is not normally performed, the next process is appropriately performed when the molten metal is heated to a desired temperature so that the heat buffer member is not overheated abnormally. A cold crucible melting furnace that can be used has been desired.

  Therefore, the present invention is to provide a cold crucible melting furnace capable of avoiding the thermal buffer member from being overheated and damaged by appropriately performing the next process when the molten metal is heated to a desired temperature. And

A reference example related to the present invention includes a furnace body having a housing recess for housing a metal to be melted, and a molten metal that is disposed on the outer peripheral side of the furnace body and induction-heated the metal to be melted accommodated in the housing recess. An induction heating coil, wherein at least a part of the inner surface of the furnace body is a cold crucible melting furnace covered with a thermal buffer member formed of a refractory having a melting point higher than that of the metal to be melted. A cold crucible melting furnace comprising: an electric energy indexing unit that determines an amount of electric power supplied to a heating coil; and a control unit that performs a next process process based on the electric energy determined by the electric energy indexing unit.

  According to this, since a control part performs a next process process appropriately based on the electric energy calculated | required by the electric energy calculating means, overheating of a thermal buffer member can be avoided.

As a further aspect of the reference example related to the present invention , the control unit performs the next process when the amount of power calculated by the power amount indexing unit reaches a set value.

  According to this aspect, it is possible to reliably avoid overheating of the heat buffer member by appropriately setting the set value of the electric energy.

And as a further aspect of the reference example related to the present invention , the control unit has reached the set value corresponding to the temperature of the molten metal in the housing recess, the power amount calculated by the power amount indexing means. In this case, the next process is performed.

  According to this aspect, since the control unit performs the next process process based on the set value of the electric energy corresponding to the temperature of the molten metal, it is possible to reliably avoid overheating of the heat buffer member.

Then, the present invention provides a furnace body having a housing recess that contains a metal to be melted, and induction heating that is arranged on the outer peripheral side of the furnace body and that inductively heats the metal to be melted that is housed in the housing recess. A cold crucible melting furnace covered with a heat buffer member formed of a refractory material having a melting point higher than that of the metal to be melted, wherein the inner surface of the furnace body includes a coil. A temperature measuring means for measuring the temperature of the molten metal, a power amount indexing means for determining the amount of power supplied to the induction heating coil, and a temperature of the molten metal measured by the temperature measuring means reaches a set value, or A control unit that performs a next process when the amount of power determined by the power amount indexing unit reaches a set value, and a setting value of the power amount determined by the power amount indexing unit Said the temperature A cold crucible melting furnace that will be greater than the value of electric energy corresponding to the temperature set value of the measured melt by measuring means.

  According to this, either when the temperature of the molten metal measured by the temperature measuring means reaches a set value or when the amount of power determined by the power amount indexing means reaches the set value, the control unit Performs the next process. For this reason, even if any of each means does not operate normally, overheating of the thermal buffer member can be avoided.

Further , the timing of the next process based on the amount of power determined by the power amount indexing means is later than the timing of the next process based on the temperature of the molten metal measured by the temperature measuring means. For this reason, the power amount indexing means complements the temperature measuring means to perform the next process, and even if the temperature measurement by the temperature measuring means is not performed normally, overheating of the heat buffer member can be avoided. Certainly done.

  As a further aspect of the present invention, the next process is a process of taking out the molten metal from the housing recess or a process of reducing the power supplied to the induction heating coil.

  According to this aspect, overheating of the thermal buffer member can be avoided by performing a process in which the control unit extracts the molten metal from the housing recess or a process of reducing the power supplied to the induction heating coil.

  And as a further aspect of the present invention, the set value of the electric energy includes the type and amount of the metal to be melted accommodated in the housing recess and the induction heating coil until the amount of the metal to be melted becomes molten metal. It is determined by the relationship with the amount of power supplied to.

  According to this aspect, the set value of the electric energy can be appropriately determined.

  According to the present invention, since the control unit can appropriately perform the next process based on the amount of electric power, the thermal buffer member can be prevented from being overheated and damaged.

It is the side view which showed the outline of the cold crucible melting furnace of 1st Embodiment, and displayed a partial cross section view. It is the side view which carried out the cross section display of the part which shows the case where the to-be-melted metal is melt | dissolved using the cold crucible melting furnace of 1st Embodiment. It is explanatory drawing which shows the structure including the circumference | surroundings of the furnace main body of the cold crucible melting furnace of 1st Embodiment. It is a graph which shows the temperature change of the molten metal at the time of induction heating, and the time change of supply electric power of the cold crucible melting furnace of 1st Embodiment. It is the side view which showed the outline of the cold crucible melting furnace of 2nd Embodiment, and partially displayed the cross section. It is explanatory drawing which shows the structure including the circumference | surroundings of the furnace main body of the cold crucible melting furnace of 2nd Embodiment. It is a graph which shows temporal changes, such as the temperature of the molten metal at the time of induction heating, of the cold crucible melting furnace of the second embodiment.

-First embodiment-
1 and 2 show the cold crucible melting furnace of the first embodiment. The basic configuration of this cold crucible melting furnace is the same as that described in Patent Document 1. That is, as shown in FIG. 1, the cold crucible melting furnace 1 is disposed on the outer peripheral side of the furnace body 10, the furnace body 10 that houses the metal W to be melted, the cooling means 20 that cools the furnace body 10. And an induction heating coil 30. Examples of the metal W to be melted include cast iron and iron oxide, but various other metals can be applied. The cold crucible melting furnace 1 of the present embodiment may be installed in the atmosphere to melt the metal W to be melted, or installed in a vacuum chamber (not shown) and melted in a vacuum atmosphere. The metal W may be melted.

  The furnace body 10 includes a base body 11 formed so as to constitute a bottom wall, and a plurality of conductive segments 12 arranged on the base body 11 in a substantially circular shape in plan view so as to constitute a side wall. Have. The base body 11 and the conductive segment 12 that are fixed to each other form an accommodation recess 10 a that opens at the top and accommodates the metal W to be melted.

  The base body 11 includes a columnar portion 13 formed in a substantially columnar shape, and a flange portion 14 projecting from the lower end portion of the columnar portion 13 to the outer peripheral side. The upper surface of the columnar portion 13 forms a bottom surface 15a of the inner surface 15 constituting the housing recess 10a, and the bottom surface 15a is covered with a heat buffer member 40 (described later). The flange portion 14 is formed with a plurality of fastening holes 11a and cooling water passages 11b communicating with each other in the vertical direction at positions corresponding to the respective conductive segments 12.

  The conductive segment 12 is formed in a substantially L-shaped longitudinal section by a side wall portion 16 erected in the vertical direction and a mounting portion 17 bent from the lower end of the side wall portion 16. The material of the conductive segment 12 is resistant to thermal shock, has a necessary mechanical strength, and has a high thermal conductivity necessary for forming a skull by cooling by the cooling means 20, for example, copper, chromium copper And beryllium copper are selected.

  The side wall portion 16 is in contact with the columnar portion 13 of the base body 11 at the lower inner surface, and the upper portion protrudes upward from the columnar portion 13 to form a wall surface 15b of the inner surface 15 constituting the housing recess 10a. A plurality of fastening holes 12a and cooling water passages 12b are formed in the attachment portion 17 so as to communicate with the fastening holes 11a and the cooling water passages 11b of the flange portion 14 of the base body 11, respectively. A fixing bolt 18 is inserted through the flange portion 14 of the base body 11 and the fastening holes 11a and 12a of the mounting portion 17 of the conductive segment 12 which are in communication with each other, and is tightened by a nut 18a. 12 and the base body 11 are united.

  Here, the adjacent conductive segments 12 fixed to the base body 11 are arranged with a gap therebetween. Thereby, each conductive segment 12 is electrically insulated. In each conductive segment 12, a slit 12 c communicating in the thickness direction is formed at a substantially central portion in the width direction. Although not shown, the slit 12c is also formed in the attachment portion 17 and is formed in the side wall portion 16 from the lower end portion to the upper side (however, it does not reach the upper end portion). And the cooling water channel 12b is formed in the both sides of the width direction which pinches | interposes the slit 12c in the side wall part 16, respectively. One and the other cooling water passages 12 b and 12 b in the side wall portion 16 are connected to each other by a communication hole 12 d formed in the upper end portion of the side wall portion 16. Each cooling water channel 12 b communicates with the cooling water channel 11 b of the base body 11.

  As a result, if cooling water is supplied from a cooling water supply source (not shown) to the cooling water channel 11b of the base body 11, the supplied cooling water is used to cool one of the cooling water channel 11b of the base body 11 and the conductive segment 12. The water channel 12b, the communication hole 12d, the other cooling water channel 12b of the conductive segment 12, and the cooling water channel 11b of the base body 11 are sequentially discharged to the outside. For this reason, the electroconductive segment 12 and the base body 11 are cooled by this cooling water. That is, the cooling means 20 is constituted by the cooling water supply source, the cooling water channels 11b and 12b, and the communication hole 12d. The cooling capacity of the cooling means 20 is required to be the cooling capacity at which the entire furnace main body 10 is equal to or lower than the melting temperature of the metal W to be melted. It has become.

  The heat buffer member 40 is a substantially disk-shaped member corresponding to the shape of the columnar portion 13 of the base body 11 and covers the entire bottom surface 15a. The thermal buffer member 40 is formed of a refractory having a melting point higher than that of the metal W to be melted, has a lower thermal conductivity than the material forming the furnace body 10, has a mechanical strength equivalent to that of the furnace body 10, A material having thermal shock resistance required when the metal W to be melted is heated and melted is selected. More specifically, the refractory forming the heat buffer member 40 is preferably made of an oxide such as aluminum oxide, magnesium oxide, silicon oxide, or zirconium oxide. Further, it may contain silicon carbide or the like. Further, the heat buffer member 40 may cover a part of the wall surface 15b in addition to the bottom surface 15a.

  The induction heating coil 30 is wound around the outer periphery of the furnace body 10 and is supplied with predetermined high-frequency AC power by the melting power supply device 50 shown in FIG. It is possible to generate an alternating magnetic field by this AC power and to inductively heat the melted metal W accommodated in the accommodating recess 10a.

  As shown in FIG. 3, the cold-crucible melting furnace 1 having the above-described configuration is arranged at a high place by being supported by a gantry 71. The gantry 71 is provided with a hot water supply mechanism 72. The hot water discharge mechanism 72 includes a drive shaft 72a driven by a motor, and thereby the cold crucible melting furnace 1 can be tilted with respect to the pedestal portion 71 as illustrated by arrows and a two-dot chain line. Thereby, the molten metal can be poured into the mold M from the inclined housing recess 10a. Control of the hot water for the hot water mechanism 72 is performed by a hot water control unit 62 (described later). Moreover, in this embodiment, the radiation thermometer 73 as a temperature measurement means is located above the accommodation recessed part 10a in the cold crucible melting furnace 1, and this radiation thermometer 73 measures the temperature of the molten metal in the accommodation recessed part 10a. . In addition to the radiation thermometer, a temperature sensor such as a thermocouple can be used as the temperature measuring means.

  The melting power supply device 50 includes a melting power supply device control unit 51 and a power amount calculation unit 52 as a power amount indexing unit. The melting power supply device control unit 51 controls the high-frequency AC power supplied to the induction heating coil 30. As this control, thyristor phase control can be exemplified, but various other controls for increasing and decreasing high-frequency AC power can be employed. The power amount calculation unit 52 is connected to the melting power supply device control unit 51, detects a command value of power supplied to the induction heating coil 30 in the melting power supply device 50, and uses the supplied power and the accumulated supply time. The amount of power supplied to the induction heating coil 30 is calculated. As shown in FIG. 3, the power amount calculation unit 52 of the present embodiment is provided in the melting power supply device 50 separately from the melting power supply device control unit 51, but is integrated with the melting power supply device control unit 51. Also good. In addition to the above, the power amount calculation unit 52 may calculate the power amount by measuring at least one of current and voltage on the path from the melting power supply device 50 to the induction heating coil 30. The aspect of the amount calculation unit 52 is not limited. Moreover, you may calculate electric energy using various methods other than calculation.

  The control unit 60 includes a determination unit 61 and a hot water control unit 62. The determination unit 61 makes a determination regarding the hot water based on the measured temperature value of the molten metal by the radiation thermometer 73 and the electric energy calculated by the electric energy calculation unit 52. The hot water control unit 62 operates the hot water mechanism 72 when the determination unit 61 determines that a predetermined condition (described later) corresponding to a state in which hot water is available is reached, and performs a hot water operation as the next process. In addition, this control part 60 also performs control which supplies a cooling water to the cooling water path 12b of the electroconductive segment 12 (detailed description is abbreviate | omitted).

  In the determination unit 61 of the present embodiment, a hot water temperature setting value for the temperature measurement value of the radiation thermometer 73 is set. This hot water temperature set value is a threshold value of the temperature measurement value of the radiation thermometer 73 for the determination unit 61 to make a determination of the hot water work. The determination unit 61 determines whether or not the temperature measurement value of the radiation thermometer 73 is equal to or higher than the hot water temperature set value, and if it is determined that the temperature measurement value is equal to or higher than the hot water temperature set value, the hot water control unit 62 is The hot water discharge mechanism 72 is operated.

  Further, the correlation between the amount of electric power supplied to the induction heating coil 30 and the molten metal temperature, which is grasped in advance (when the type of the metal W to be melted is the same and the amount is equal, the relationship between the electric energy and the molten metal temperature is substantially constant. Based on the above, a limit power amount (the power amount at time t2 in FIG. 4 / corresponding to the area of the hatched portion in FIG. 4) is set. This limit power amount is a threshold value of the amount of power supplied to the induction heating coil 30 for the determination unit 61 to determine the hot water work, and is not directly related to the temperature measurement value of the radiation thermometer 73. Further, in the present embodiment, this limited power amount depends on the relationship between the type and amount of the metal W to be melted and the amount of power supplied to the induction heating coil 30 until the amount of the metal W to be melted becomes molten metal. Determined. This power limit is determined by a table or a mathematical formula based on the relationship. In some cases, the limit power amount may be fixed without changing.

  The limit power amount in the present embodiment is a set value in which a margin (amount of surplus power) is further added to the amount of power when the temperature of the molten metal reaches the tapping temperature set value (the amount of power at time t1 in FIG. 4). . That is, the set value of the limited power amount is set larger than the amount of power corresponding to the tapping temperature setting value by the margin. The margin is determined based on the heat resistant temperature of the heat buffer member 40.

  Here, FIG. 4 is a graph showing the time change of the temperature of the molten metal (temperature measurement value) and the time change of the supplied power during induction heating. The vertical axis represents temperature and power, and the horizontal axis represents time. Regarding temperature, the tapping temperature setting value (horizontal line in the figure), radiation temperature measurement temperature value (solid line rising to the right in the figure), radiation temperature measurement temperature value (during temperature measurement failure) (two points to the right in the figure) A chain line) is shown. Regarding power, supply power (a solid line rising to the right in the drawing and a horizontal line continuous to the right) is shown. In addition, although the radiation temperature measurement temperature value is shown as a straight line on the figure for the sake of simplicity of explanation, the actual temperature measurement time change is not linear because the dissolution conditions change, It fluctuates in a complicated manner (the same applies when the temperature measurement is good or bad). In addition, the notation on the figure of the radiation temperature measurement temperature value (during temperature measurement failure) is merely an example, and is not limited to the illustrated time change.

  During normal operation of the cold crucible melting furnace 1, when the point A on FIG. 4, that is, the temperature measurement value by the radiation thermometer 73 (“radiation temperature measurement temperature value” in FIG. 4) reaches the tapping temperature setting value, Hot water is discharged by the hot water control unit 62.

  However, when the temperature measurement by the radiation thermometer 73 is not normally performed due to the effect of smoke generated from the molten metal, the radiation thermometer is measured despite the fact that the molten metal has actually reached the tapping temperature setting value. The temperature measurement value by 73 (“radiation temperature measurement temperature value (when temperature measurement is poor)” in FIG. 4) is at point B on FIG. 4, and the temperature measurement value has not reached the tapping temperature setting value. Not done. In this case, since the induction heating is continued, the molten metal is heated to a temperature exceeding the temperature suitable for the hot water due to the continuation of the induction heating.

  In the present embodiment, when the supplied power reaches the point C in FIG. 4, that is, when the power amount calculated by the power amount calculation unit 52 reaches the limit power amount, the measurement by the radiation thermometer 73 is performed. Regardless of the temperature, hot water is used. That is, even if the hot water supply mechanism 72 is not operated based on the temperature measurement value of the radiation thermometer 73, the determination unit 61 determines whether the power amount calculated by the power amount calculation unit 52 is equal to or greater than the limit power amount. If it is determined whether or not the calculated power amount is equal to or greater than the limit power amount, the hot water discharge mechanism 72 is operated via the hot water control unit 62. For this reason, it is possible to prevent the molten metal from being overheated abnormally beyond the margin of the electric energy. In addition, when the electric energy calculated by the electric energy calculation part 52 reaches the said limit electric energy, the control part 60 may alert | report an alarm while performing hot water.

  Next, the operation of the cold crucible melting furnace 1 of the present embodiment will be described with reference to FIGS. First, the molten metal W that is in the form of a lump or powder is introduced into the housing recess 10 a of the furnace body 10. Next, high-frequency AC power is supplied to the induction heating coil 30 while driving the cooling means 20 to cool the furnace body 10. As a result, an alternating magnetic field is generated around the induction heating coil 30. The generated alternating magnetic field reaches the melted metal W by passing through the furnace body 10 and into the housing recess 10a, whereby the melted metal W is heated by induction heating. For this reason, the metal W to be melted starts melting from the surface side heated to the melting temperature to become a molten metal and touches the inner surface 15 of the furnace body 10. Then, the molten metal is removed by the cooling by the cooling means 20 to the furnace body 10 which is below the melting point of the metal W to be melted, cooled and solidified at the outer peripheral portion, and as shown in FIG. Skull W1 is formed so as to cover a part on the wall surface 15b side. If the skull W1 has a thickness greater than or equal to a predetermined value and the heating capability by induction heating exceeds the cooling capability by the furnace body 10, the molten metal stays on the inner peripheral side from the skull W1. And when the retention amount of the molten metal in the accommodation recessed part 10a increases, a molten metal will receive the interaction of the said alternating magnetic field and an induced electric current, and the effect | action of gravity, and will become a dome shape rising toward the inner peripheral part from the outer peripheral part. Stir while forming.

  Since the metal W to be melted is separated from the furnace main body 10 by the skull W1, impurities in the furnace main body 10 are not transferred to the metal W to be melted and are generated as molten metal. Here, heat removal by the furnace body 10 is performed from the inner surface 15 of the furnace body 10 facing the metal W to be melted as described above, but the bottom surface 15a covered with the heat buffer member 40 formed of a refractory material. Since the molten metal and the heat buffer member 40 are in contact with each other through the skull W1, heat is removed through the heat buffer member 40, and the amount of heat removed is smaller than that in which direct heat removal is performed. Can be reduced. For this reason, the molten metal produced | generated by induction heating, forming the skull W1 and preventing the contamination by the furnace main body 10, can be further heated, and can be effectively overheated. That is, the temperature of the generated molten metal can be increased rapidly (for example, 10 ° C./second) until it reaches + 150 ° C. or higher with respect to the melting point of the metal W to be melted. Product quality and yield can be improved. In addition, a molten metal suitable for precision casting can be generated.

  And in this embodiment, in addition to performing the hot water control based on the temperature measurement value of the radiation thermometer 73, the hot water control part 62 controls the hot water based on the electric energy calculated by the electric energy calculation part 52. Take control. That is, the basic control using the radiation thermometer 73 is supplemented as the control using the power amount calculation unit 52 as backup control. This back-up control is calculated by the electric energy calculation unit 52 without being based on the temperature measurement value of the radiation thermometer 73 when the temperature measurement of the radiation thermometer 73 is not normally performed (at the time of abnormality). It is the control which performs the hot water discharge based on the amount of electric power which has been. For this reason, by setting the limit electric energy for performing hot water discharge beforehand, even if temperature measurement of the radiation thermometer 73 is not normally performed, the molten metal greatly exceeds the temperature suitable for hot water supply. Therefore, the hot water can be discharged properly without overheating. Therefore, it can avoid that the thermal buffer member 40 is overheated and damaged. In addition, it is possible to prevent the mold M from being damaged due to an abnormally hot molten metal being poured. For this reason, the stable operation can be performed and the quality of the casting can be stabilized.

-Second Embodiment-
Next, a second embodiment will be described. In addition, description is abbreviate | omitted about the structure which overlaps with 1st Embodiment.

  In the present embodiment, a thermocouple 80 as a temperature sensor is provided in the thermal buffer member 40. Specifically, as shown in FIG. 5, the thermocouple 80 is embedded in the thermal buffer member 40 so that the temperature measuring unit (temperature measuring contact) in the thermocouple 80 is located inside the thermal buffer member 40. . The position of the temperature measuring unit in the thermal buffer member 40 is not particularly limited, but due to the relationship with the temperature distribution or temperature gradient in the thermal buffer member 40 (the upper surface of the thermal buffer member 40 is the highest temperature), the thermal buffer member 40. A position close to the upper surface of is desirable. However, the position of the side temperature portion may be a position close to the bottom surface of the heat buffer member 40, and the temperature on the upper surface of the heat buffer member 40 may be obtained by performing calculation in the control unit 60, for example.

  The control part 60 of this embodiment is provided with the judgment part 61 and the hot water control part 62 similar to 1st Embodiment, as shown in FIG. The determination unit 61 obtains the temperature measurement value (first tapping temperature setting value) of the molten metal by the radiation thermometer 73 and the temperature measurement value (second tapping temperature setting value) of the heat buffer member 40 obtained by the thermocouple 80. Based on this, make judgments regarding hot springs. Specifically, when the determination unit 61 determines that one of the temperature measurement values has reached a predetermined condition (described later) corresponding to a state in which hot water can be discharged, the hot water control unit 62 is the first embodiment. Similarly to the above, the hot water discharge mechanism 72 is operated to perform the hot water discharge operation as the next process.

  The first hot water temperature setting value for the radiation thermometer 73 set in the determination unit 61 of the present embodiment is the same as the hot water temperature setting value of the first embodiment. The second hot water temperature setting value for the thermocouple 80 is determined based on the heat resistant temperature of the heat buffer member 40, and the temperature measurement value of the heat buffer member 40 at the same time is the temperature measurement of the molten metal by the radiation thermometer 73. Since it becomes lower than a value (when temperature measurement is favorable), the 2nd hot water temperature setting value is set lower than the 1st hot water temperature setting value (refer FIG. 7). However, depending on the case, the second hot water temperature set value may be set higher than the first hot water temperature set value. As in the first embodiment, the determination unit 61 has a limited power amount.

  FIG. 7 is a graph showing changes over time in the temperature of the molten metal and the heat buffer member 40 (temperature measurement values) during induction heating. As in FIG. 4, the vertical axis indicates temperature and power, and the horizontal axis indicates time. Regarding the temperature, the first and second tapping temperature setting values (horizontal line in the figure), radiation temperature measurement temperature value (solid line extending upward from the origin in the figure), radiation temperature measurement temperature value (during temperature measurement failure) ( 2 shows a thermocouple temperature measurement value (a solid line rising to the right extending below the radiation temperature measurement temperature value). Regarding power, supply power (a solid line rising to the right in the drawing and a horizontal line continuous to the right) is shown. Note that the radiation temperature measurement temperature value and the thermocouple temperature measurement value are shown as straight lines in the figure for the sake of simplicity, but the actual temperature measurement time change is a straight line because the dissolution conditions change. It does not become a shape, and it varies in a complicated manner.

  Points A to C on FIG. 7 are the same as those in FIG. In this embodiment, in addition to this, when the point D on FIG. 7, that is, the temperature measurement value by the thermocouple 80 (“thermocouple temperature measurement value” in FIG. 7) reaches the second hot water temperature setting value, Regardless of the temperature measured by the radiation thermometer 73 and the amount of power calculated by the power amount calculation unit 52, the hot water is discharged. For this reason, it can prevent that a molten metal is overheated abnormally.

  Further, in the present embodiment, the hot water control unit 62 controls the hot water based on the temperature measurement value of the radiation thermometer 73, the electric energy calculated by the electric energy calculation unit 52, and the thermocouple 80. The hot water is controlled based on the measured temperature value. That is, both the control using the electric energy calculation unit 52 and the control using the thermocouple 80 complement the basic control using the radiation thermometer 73 as backup control. That is, in this embodiment, since two systems are backed up, a cold crucible melting furnace with further improved reliability compared to the first embodiment can be obtained. Note that the backup control may be performed by giving priority to one of the electric energy calculated by the electric energy calculator 52 and the temperature measurement value of the thermocouple 80 over the other.

  Note that the temperature sensor in the second embodiment is not limited to the thermocouple, and various types of temperature sensors can be used. Further, the temperature measuring unit is not limited to the configuration in which the temperature measuring unit is positioned in the thermal buffer member 40 as in the present embodiment, and the temperature is directly measured. The temperature of the buffer member 40 may be measured.

  As mentioned above, although two embodiment was picked up and demonstrated per this invention, this invention is not limited to said each embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

  For example, in each of the above embodiments, the control unit 60 performs the hot water treatment by the hot water control unit 62, but instead of the hot water processing, the electric power supplied to the induction heating coil 30 by the melting power supply device control unit 51 is, for example, You may perform other process processes other than what was mentioned above, such as the heat retention process reduced to the minimum value which can hold | maintain the state of a molten metal (the state stirred in the dome shape).

  In addition, it does not include the power amount indexing means (for example, the power amount calculation unit 52 in the first embodiment), and the temperature value of the radiation thermometer 73 and the temperature value of the temperature sensor (for example, the thermocouple 80 in the second embodiment). Thus, the determination unit 61 may make a determination regarding hot water.

DESCRIPTION OF SYMBOLS 1 Cold crucible melting furnace 10 Furnace main body 10a Housing recessed part 15 Inner surface of a furnace main body 30 Induction heating coil 40 Thermal buffer member 52 Electric power amount indexing means, Electric energy calculation part 60 Control part 73 Temperature measuring means, Radiation thermometer W Melted metal

Claims (3)

A furnace body having a housing recess for housing the metal to be melted, and an induction heating coil disposed on the outer peripheral side of the furnace body and inductively heating the metal to be melted housed in the housing recess to form a molten metal, At least a part of the inner surface of the furnace body is a cold crucible melting furnace covered with a thermal buffer member formed of a refractory having a melting point higher than the melting metal,
Temperature measuring means for measuring the temperature of the molten metal in the housing recess;
Power amount indexing means for determining the amount of power supplied to the induction heating coil;
When the temperature of the molten metal measured by the temperature measuring unit reaches a set value, or when the amount of power calculated by the power amount indexing unit reaches a set value, a control unit that performs next process processing and, with a,
The set value of the indexed amount of power by the electric energy indexing means, cold crucible melting furnace that will be greater than the value of electric energy corresponding to the temperature set value of the molten metal measured by said temperature measuring means. 2. The cold crucible melting furnace according to claim 1 , wherein the next process is a process of taking out the molten metal from the housing recess or a process of reducing power supplied to the induction heating coil. The set value of the amount of power depends on the relationship between the type and amount of the metal to be melted accommodated in the housing recess and the amount of power supplied to the induction heating coil until the amount of the metal to be melted becomes molten metal. cold crucible melting furnace according to claim 1 that is determined.

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