JP2017199625A - Energizing heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energizing heating apparatus that can efficiently continue energizing and heating in a stable state by a simple structure.SOLUTION: A top electrode 16 is arranged at a top part of a crucible 11 having conductivity, and a bottom electrode 19 is arranged at a bottom part of the crucible 11. The crucible 11 is heated by flowing DC currents to a space between the top electrode 16 and the bottom electrode 19, so that objects 12 to be heated such as aluminum stored in the crucible 11 are heated. With respect to a cross section orthogonal to a center shaft line 22 of the crucible 11, a cross sectional area of a peripheral wall 14 at the bottom part side of the crucible 11 is set smaller than a cross sectional area of the peripheral wall 14 at the top part side of the crucible. Further, the top electrode 16 is placed on a top surface 14a of the peripheral wall 14 of the crucible 11 and thereby the top electrode 16 is connected to the crucible 11. Rates of thermal expansion of the top electrode 16 and the crucible 11 are set to 1×10-10×10/K at a temperature of 500°C.SELECTED DRAWING: Figure 1

Description

  In the present invention, when a heating container formed of a conductive material is energized and self-heats to heat an object to be heated such as aluminum accommodated in the heating container, the current heating is efficiently and stably performed. It is related with the electric heating apparatus which can be continued by.

  In general, in an electric heating device, a pair of electrodes is provided at the upper and lower parts of a conductive container, and the container is heated by energizing between both electrodes, and the object to be heated, such as metal or ceramics, contained in the container It is comprised so that it may heat. In this case, the object to be heated contained in the container is present on the lower side in the container and not on the upper side, so the lower side of the container is heated to raise the temperature and suppress the heating on the upper side. Is desirable.

  This type of electric heating apparatus is disclosed in, for example, Patent Document 1. This energization heating apparatus includes a conductive container, an upper electrode connected to the upper part of the container, and a lower electrode connected to the lower part of the container, and energizes between the upper electrode and the lower electrode to heat the container. And configured to heat the material in the container.

  The upper opening end of the container is provided with a concave portion that opens upward, and the upper electrode includes a convex portion that is inserted into the concave portion, and the conductive metal member that can be dissolved by the heat of the container in the concave portion. Is housed. According to this energization heating device, local heat generated between the upper electrode and the container is prevented, and the durability of the energization heating device is improved.

JP 2010-38376 A

  In the energization heating device having the conventional configuration described in Patent Document 1 described above, a concave portion is provided at the upper opening end of the container, a convex portion to be inserted into the concave portion is provided in the upper electrode, and the concave portion is further provided in the concave portion. A conductive metal member must be accommodated. For this reason, the connection configuration between the upper electrode and the container is complicated, and the manufacture of the electric heating device is troublesome. Therefore, there is a need for an energization heating device that can stably continue energization heating with good heat generation efficiency with a simple configuration.

  Accordingly, an object of the present invention is to provide an energization heating apparatus that can continue energization heating efficiently and stably with a simple configuration.

In order to achieve the above object, the energization heating apparatus of the present invention has a top electrode disposed on the top of a conductive heating container, a bottom electrode disposed on the bottom of the heating container, and the top electrode and the bottom. An energization heating apparatus configured to heat a heating object contained in a heating container by heating a heating container by passing a direct current between the electrode and a center axis of the heating container For the cross section orthogonal, the cross-sectional area of the peripheral wall on the bottom side of the heating vessel is formed smaller than the cross-sectional area of the peripheral wall on the top side, and the top electrode is placed on the top of the heating vessel and the top electrode is connected to the heating vessel. and it is obtained by setting the thermal expansion coefficient of the top electrode and the heating vessel to ^{1 × 10 -6 ~10 × 10 -6} / K at 500 ° C..

The peripheral wall of the heating container is preferably formed in a tapered shape so that its cross-sectional area gradually decreases as it reaches the bottom.
The inclination angle of the tapered peripheral wall is preferably set to 5 to 20 ° with respect to the central axis of the heating vessel.

When the sectional area of the peripheral wall at the top of the heating container is 1.0, the sectional area of the peripheral wall at the bottom is preferably 0.3 to 0.7.
The top electrode is preferably made of graphite, and the heating vessel is preferably made of conductive ceramics.

The peripheral wall of the heating container is preferably formed to have a uniform thickness.
The electrical resistivity of the heating container is preferably 50 × 10 ⁻³ to 250 × 10 ⁻³ Ω · cm.

  According to the electric heating apparatus of the present invention, there is an effect that the electric heating can be continued efficiently and stably with a simple configuration.

Sectional drawing which shows the whole structure of the electric heating apparatus in embodiment. The top view which shows the crucible as a heating container. Sectional drawing in the 3-3 line of FIG. Sectional drawing in the 4-4 line | wire of FIG. The top view which shows a top electrode. The top view which shows a bottom part electrode. The graph which shows the relationship between temperature and a coefficient of thermal expansion about the material of a top electrode and a crucible. The partial expanded sectional view which shows a contact state with a top electrode and the top surface of the surrounding wall of a crucible. Sectional drawing which shows the crucible of another example of this invention. Sectional drawing which shows the crucible of the further another example of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.
As shown in FIGS. 1 and 2, a crucible (crucible) 11 as a heating container constituting the energization heating device 10 has an inverted frustoconical cross section, and an object to be heated made of a molten metal such as aluminum or zinc. 12 is accommodated, and a spout 13 is formed at the upper end so as to project the heated article 12 after being melted by heating. The crucible 11 is formed of a single material having conductivity. The entire peripheral wall 14 of the crucible 11 is formed with a constant thickness, and the bottom wall 15 of the crucible 11 is formed thicker than the peripheral wall 14.

  As shown in FIGS. 1 and 5, on the top surface 14 a of the peripheral wall 14 of the crucible 11, a planar annular top electrode 16 having the same planar shape as the top surface 14 a of the peripheral wall 14 is placed. Contact is made with the top surface 14 a of the peripheral wall 14, and electrical conduction is achieved between the top electrode 16 and the peripheral wall 14. A connection portion 18 for connecting one end of the conductive wire 17 is formed protruding from a part of the top electrode 16.

  As shown in FIGS. 1 and 6, a disc-shaped bottom electrode 19 having a plane shape substantially the same as the bottom wall 15 is disposed on the lower surface 15a of the bottom wall 15 of the crucible 11, and the upper surface 19a is the bottom wall. 15 is in contact with the lower surface 15 a of the electrode 15, and electrical conduction is achieved between the bottom electrode 19 and the bottom wall 15. One end of a conducting wire 17 is connected to the bottom electrode 19.

  As shown in FIG. 1, the other end of the conducting wire 17 having one end connected to the top electrode 16 is connected to a DC power source 20, and the other end of the conducting wire 17 having one end connected to the bottom electrode 19 is also connected to the DC power source 20. It is connected to the. Then, a DC current is passed from the DC power source 20 through the lead wire 17 between the top electrode 16 and the bottom electrode 19 to cause the peripheral wall 14 and the bottom wall 15 of the crucible 11 to self-heat and to be heated in the crucible 11. The object 12 is heated and melted or kept at a high temperature.

  As shown by a two-dot chain line in FIG. 1, an oxide film 21 for protecting the peripheral wall 14 and the surface of the bottom wall 15 is formed on the inner peripheral surface and the outer peripheral surface of the peripheral wall 14 and the inner surface of the bottom wall 15. ing. The oxide film 21 is not formed on the top surface 14a of the peripheral wall 14 with which the top electrode 16 contacts and the bottom surface 15a of the bottom wall 15 with which the bottom electrode 19 contacts, and the top electrode 16 and the top surface 14a of the peripheral wall 14 And the conductivity between the bottom electrode 19 and the bottom surface 15a of the bottom wall 15 is not hindered.

  The peripheral wall 14 of the crucible 11 is formed in a tapered shape so that its cross-sectional area gradually decreases as it reaches the bottom. Here, the cross-sectional area of the peripheral wall 14 represents an area in a cross section in the direction orthogonal to the central axis (vertical line) 22 of the crucible 11, that is, in the horizontal direction. Since the electrical resistance value increases as the cross-sectional area of the peripheral wall 14 decreases and the amount of heat generated when the peripheral wall 14 is energized increases, the temperature on the bottom side gradually increases from the temperature on the top side of the peripheral wall 14. A gradient is formed.

  As shown in FIG. 3, specifically, the cross section at the top of the peripheral wall 14 of the crucible 11 has a substantially annular shape having a large diameter with a constant width. As shown by a two-dot chain line in FIG. 3, the cross section is cut out by the amount corresponding to the spout 13. On the other hand, as shown in FIG. 4, the cross section at the bottom of the peripheral wall 14 of the crucible 11 has an annular shape having a small diameter of the same constant width as the top. For this reason, the cross-sectional area of the peripheral wall 14 on the bottom side of the crucible 11 is reduced to, for example, about ½ of the cross-sectional area of the peripheral wall 14 on the top side, and the heat generation amount of the peripheral wall 14 on the bottom side is the heat generation of the peripheral wall 14 on the top side. It increases about twice as much as the amount.

  The ratio of the cross-sectional area of the peripheral wall 14 at the top and bottom of the crucible 11 is 0.3 to 0.7 when the cross-sectional area of the peripheral wall 14 at the top of the crucible 11 is 1.0. It is preferable to set to. When the cross-sectional area of the peripheral wall 14 at the bottom is less than 0.3, the internal volume on the bottom side of the crucible 11 is extremely reduced, and the temperature of the peripheral wall 14 on the bottom side of the crucible 11 rises rapidly, and the object is heated. It becomes difficult to heat and melt the object 12 in a stable state. On the other hand, when the cross-sectional area of the peripheral wall 14 at the bottom exceeds 0.7, the heat generation of the peripheral wall 14 on the bottom side is small, and the heating efficiency of the article to be heated 12 cannot be increased.

  Considering the heating efficiency of the object to be heated 12 accommodated in the crucible 11, the amount of the object to be heated 12, etc., the inclination angle α of the peripheral wall 14 formed in a tapered shape, that is, the central axis 22 of the peripheral wall 14 and the crucible 11. Is preferably 5 to 20 °, more preferably 7 to 15 °. When the inclination angle α of the peripheral wall 14 is smaller than 5 °, the significance of shaping the peripheral wall 14 in a tapered shape is reduced, and the heating efficiency of the article to be heated 12 is lowered. On the other hand, when the inclination angle α of the peripheral wall 14 is larger than 20 °, the temperature rise on the bottom side of the peripheral wall 14 increases, but the temperature gradient on the bottom side and the top side becomes too large, Since control of a heating rate becomes difficult, it is not preferable.

As shown in FIG. 8, the lower surface 16a of the top electrode 16 is in surface contact with the top surface 14a of the peripheral wall 14 of the crucible 11, but the top electrode 16 is formed in an annular shape as shown by a two-dot chain line in FIG. Therefore, deformation (warping) is likely to occur due to thermal expansion. Therefore, in order to maintain good surface contact between the lower surface 16a of the top electrode 16 and the top surface 14a of the peripheral wall 14 of the crucible 11, the thermal expansion coefficient (linear expansion coefficient) of the top electrode 16 and the crucible 11 is 500. It is set in the range of 1 × 10 ⁻⁶ to 10 × 10 ⁻⁶ / K at ° C. Within the range of the thermal expansion coefficient, it is desirable to set the thermal expansion coefficient of the top electrode 16 and the thermal expansion coefficient of the crucible 11 as close as possible.

When the coefficient of thermal expansion is smaller than 1 × 10 ⁻⁶ / K, it is not preferable because it is difficult to select a material having both good conductivity and a low coefficient of thermal expansion as the material of the top electrode 16 or the crucible 11. On the other hand, when the coefficient of thermal expansion is greater than 10 × 10 ⁻⁶ / K, the thermal expansion of the top electrode 16 and the crucible 11 increases, and the contact between the lower surface 16 a of the top electrode 16 and the top surface 14 a of the peripheral wall 14 of the crucible 11. Defects are likely to occur, and local heat generation at the contact portion and poor conduction occur, which is not preferable.

The top electrode 16 is preferably formed of graphite having a low coefficient of thermal expansion. As shown in the following Table 1 and FIG. 7, the coefficient of thermal expansion (coefficient of thermal expansion) of the graphite is 3.3 × 10 ⁻⁶ / K at 500 ° C. The coefficient of thermal expansion of this graphite shows substantially the same value in the temperature range of 30 ° C to 530 ° C. The coefficient of thermal expansion of copper as an electrode material is about 20 × 10 ⁻⁶ / K at 500 ° C., which is larger than that of graphite.

  As for the conduction between the bottom electrode 19 and the bottom wall 15 of the crucible 11, the bottom electrode 19 has a disk shape and is less deformed by thermal expansion. 15 is maintained even at a high temperature, and conduction between the upper surface 19a of the bottom electrode 19 and the lower surface 15a of the bottom wall 15 of the crucible 11 is maintained well over time. For this reason, the bottom electrode 19 is usually formed of copper or the like.

On the other hand, as the conductive material forming the crucible 11, for example, conductive ceramics formed from a mixture of carbon (C), silicon carbide (SiC), and mullite (Al ₂ O ₃ , SiO ₂ ) is preferable. Used.

  As the conductive ceramics, for example, conductive ceramics 1 to 4 having a composition as shown in Table 1 below, a thermal expansion coefficient at 500 ° C., and an electrical resistivity are used. Note that mullite is an aluminosilicate composed of a compound of alumina and silica.

As shown in Table 1, the thermal expansion coefficient at 500 ° C. of the conductive ceramics 1 to 4 is 3.49 × 10 ^{−6 to} 3.60 × 10 ⁻⁶ / K, both of which are the heat of graphite. A value approximating the expansion coefficient is shown. For this reason, the thermal expansion of the top electrode 16 and the peripheral wall 14 of the crucible 11 is equivalent, and the contact state of the lower surface 16a of the top electrode 16 and the top surface 14a of the peripheral wall 14 of the crucible 11 is maintained.

  On the other hand, as shown by a two-dot chain line in FIG. 8, when the top electrode 16 is formed of copper, the top electrode 16 is warped because the thermal expansion of the top electrode 16 is large, and the lower surface 16 a of the top electrode 16 is Point contact or line contact occurs between the top surface 14 a of the peripheral wall 14 of the crucible 11 and local heating occurs between the lower surface 16 a of the top electrode 16 and the top surface 14 a of the peripheral wall 14 of the crucible 11.

The electric resistivity (electric specific resistance) of the crucible 11 is preferably 50 × 10 ⁻³ to 250 × 10 ⁻³ Ω · cm in consideration of the conductivity and heat generation of the crucible 11. When the electrical resistivity of the crucible 11 is smaller than 50 × 10 ⁻³ Ω · cm, the conductivity of the crucible 11 can be increased, but the heat generation of the crucible 11 is lowered, and the temperature rise at the lower part of the peripheral wall 14 of the crucible 11 is reduced. This is not preferable because it tends to be insufficient. On the other hand, when the electrical resistivity of the crucible 11 is larger than 250 × 10 ⁻³ Ω · cm, the heat generation of the crucible 11 can be increased, but the amount of heat generation becomes excessive or the conductivity of the crucible 11 decreases. This is not preferable because it is difficult to sufficiently energize the crucible 11.

Next, an effect | action is demonstrated about the electrical heating apparatus 10 of embodiment comprised as mentioned above.
As shown in FIG. 1, when aluminum as the object to be heated 12 accommodated in the crucible 11 is heated and melted by the electric heating device 10, the bottom electrode 19 is disposed below the bottom wall 15 of the crucible 11. The top electrode 16 is placed on the top surface 14a of the peripheral wall 14 of the crucible 11 and brought into contact. The bottom electrode 19 and the top electrode 16 are each connected to a DC power source 20 via a conducting wire 17. Subsequently, aluminum is accommodated in the lower part of the crucible 11.

  In this state, when a direct current is passed between the top electrode 16 and the bottom electrode 19, the direct current flows from the top electrode 16 through the peripheral wall 14 and the bottom wall 15 of the crucible 11 to the bottom electrode 19, and The peripheral wall 14 and the bottom wall 15 self-heat. At this time, the crucible 11 is formed in a tapered shape with a diameter decreasing toward the lower portion, and the cross-sectional area of the peripheral wall 14 of the crucible 11 gradually decreases from the top side toward the bottom side. Since the electrical resistance of the direct current flowing through the peripheral wall 14 of the crucible 11 is inversely proportional to the cross-sectional area of the peripheral wall 14, the amount of heat generated by Joule heat gradually increases from the top side to the bottom side of the peripheral wall 14 of the crucible 11.

  That is, the temperature rise is large on the bottom side of the crucible 11, and the temperature rise is suppressed on the top side. In other words, the aluminum accommodated in the lower part in the crucible 11 is heated quickly, while heating in the upper part in the crucible 11 in which no aluminum is accommodated is suppressed.

  When the energization heating is continued, the temperature of the top electrode 16 in contact with the top surface 14a of the peripheral wall 14 of the crucible 11 also rises, and the peripheral wall 14 and the top electrode 16 of the crucible 11 reach a high temperature. For this reason, both the peripheral wall 14 and the top electrode 16 of the crucible 11 are thermally expanded.

At this time, the thermal expansion coefficients of the peripheral wall 14 of the crucible 11 and the top electrode 16 are both set within a range of 1 × 10 ⁻⁶ to 10 × 10 ⁻⁶ / K. For example, the thermal expansion coefficient of the peripheral wall 14 formed by the conductive ceramic is about 3.5 × 10 -6 ^{/ K,} the thermal expansion coefficient of the top electrode 16 formed of graphite about 5.0 × 10 ^{- 6} / K, which is set to be approximately the same. Therefore, the thermal expansion difference between the thermal expansion of the peripheral wall 14 and the thermal expansion of the top electrode 16 is within an allowable range, and the surface contact between the lower surface 16a of the top electrode 16 and the top surface 14a of the peripheral wall 14 is maintained well. In addition, local heat generation (abnormal heat generation) due to point contact or line contact is suppressed, and electrical continuity between the two is well maintained over time. As a result, the heating of the peripheral wall 14 of the crucible 11 can be continued in a stable state.

The effect exhibited by the above embodiment is described collectively below.
(1) In the electric heating apparatus 10 of this embodiment, the crucible 11 is formed so that the cross-sectional area of the peripheral wall 14 on the bottom side of the crucible 11 is smaller than the cross-sectional area of the peripheral wall 14 on the top side. For this reason, the cross-sectional area of the peripheral wall 14 on the bottom side can be easily reduced by the shape of the diameter of the bottom side of the crucible 11, and the temperature of the peripheral wall 14 on the bottom side necessary for heating the article to be heated 12. Can be easily increased.

Furthermore, the thermal expansion coefficients of the top electrode 16 and the crucible 11 were set in a range of 1 × 10 ⁻⁶ to 10 × 10 ⁻⁶ / K. Therefore, the thermal expansion of the top electrode 16 and the top of the crucible 11 can be made equal, and the electrical conductivity between the lower surface 16a of the top electrode 16 and the top surface 14a of the peripheral wall 14 of the crucible 11 is improved over a long period of time. Can be held.

Therefore, according to the electric heating apparatus 10 of this embodiment, electric heating can be continued efficiently and stably with a simple configuration.
(2) The peripheral wall 14 of the crucible 11 is formed in a tapered shape so that its cross-sectional area gradually decreases as it reaches the bottom. For this reason, the crucible 11 can be easily manufactured, and the temperature can be gradually increased toward the bottom side of the peripheral wall 14 of the crucible 11, so that temperature control can be clearly performed.

  (3) The inclination angle α of the peripheral wall 14 formed in the tapered shape is set to 5 to 20 °. Therefore, the temperature gradient from the bottom side to the top side of the peripheral wall 14 of the crucible 11 can be made appropriate, and the object to be heated 12 can be heated smoothly.

  (4) When the cross-sectional area of the peripheral wall 14 at the top of the crucible 11 is 1.0, the cross-sectional area of the peripheral wall 14 at the bottom is 0.3 to 0.7. In this case, the temperature rise of the peripheral wall 14 at the bottom of the crucible 11 can be set appropriately, and the object to be heated 12 can be heated quickly.

  (5) The top electrode 16 is made of graphite, and the crucible 11 is made of the conductive ceramic. At this time, the difference in thermal expansion between the top electrode 16 and the peripheral wall 14 of the crucible 11 can be suppressed as much as possible, and the contact between the lower surface 16a of the top electrode 16 and the top surface 14a of the peripheral wall 14 of the crucible 11 can be satisfactorily maintained. The conduction between them can be maintained for a long time.

  (6) The peripheral wall 14 of the crucible 11 is formed with a uniform thickness. In this case, the amount of heat generated by the crucible 11 can be controlled by the tapered shape of the crucible 11 regardless of the thickness of the peripheral wall 14 of the crucible 11.

(7) The electric resistivity of the crucible 11 is 50 × 10 ⁻³ to 250 × 10 ⁻³ Ω · cm. For this reason, it is possible to achieve good conduction in the peripheral wall 14 and the bottom wall 15 of the crucible 11 and at the same time, appropriate heat generation of the peripheral wall 14 can be achieved.

It should be noted that the embodiment described above can be modified and embodied as follows.
As shown in FIG. 9, you may comprise the lower part of the crucible 11 with the bottomed cylindrical part 23, and may comprise the taper part 24 which diameter-expands an upper part as the top part side. In this case, the article to be heated 12 is accommodated in the bottomed cylindrical portion 23 on the lower side of the crucible 11. And since the cross-sectional area of the lower peripheral wall 14 of the crucible 11 is set smaller than the cross-sectional area of the upper peripheral wall 14, the to-be-heated object 12 can be heated efficiently.

  As shown in FIG. 10, the lower part of the crucible 11 may be constituted by a bottomed cylindrical part 23, and the upper part may be constituted by a large-diameter cylindrical part 25 having a larger diameter than the bottomed cylindrical part 23 on the lower side. Also in this case, the article to be heated 12 is accommodated in the bottomed cylindrical portion 23 on the lower side of the crucible 11. And since the cross-sectional area of the lower peripheral wall 14 of the crucible 11 is set smaller than the cross-sectional area of the upper peripheral wall 14, the heating efficiency of the to-be-heated object 12 can be improved.

The heating container may be formed in a square tube shape such as a square tube shape so that the cross-sectional area of the peripheral wall 14 on the bottom side is smaller than the cross-sectional area of the peripheral wall 14 on the top side.
A heat shield plate may be disposed between the bottom electrode 19 and the DC power source 20 or between the top electrode 16 and the DC power source 20.

  DESCRIPTION OF SYMBOLS 10 ... Current heating apparatus, 11 ... Crucible as a heating container, 12 ... To-be-heated object, 14 ... Perimeter wall, 16 ... Top electrode, 19 ... Bottom electrode, 22 ... Center axis, (alpha) ... Inclination angle.

Claims (7)

A top electrode is disposed at the top of the conductive heating container, a bottom electrode is disposed at the bottom of the heating container, and a direct current is passed between the top electrode and the bottom electrode to cause the heating container to generate heat. An energization heating device configured to heat an object to be heated contained in a heating container,
The cross section perpendicular to the central axis of the heating container is formed such that the cross sectional area of the peripheral wall on the bottom side of the heating container is smaller than the cross sectional area of the peripheral wall on the top side, and the top electrode is placed on the top of the heating container. An electric heating apparatus in which an electrode is connected to a heating container, and a coefficient of thermal expansion of the top electrode and the heating container is set to 1 × 10 ⁻⁶ to 10 × 10 ⁻⁶ / K at 500 ° C.   The energization heating apparatus according to claim 1, wherein the peripheral wall of the heating container is formed in a tapered shape so that the cross-sectional area gradually decreases toward the bottom.   The electric heating apparatus according to claim 2, wherein an inclination angle of the tapered peripheral wall is set to 5 to 20 degrees with respect to a central axis of the heating container.   The energization heating apparatus according to claim 2 or 3, wherein the cross-sectional area of the peripheral wall at the bottom is 0.3 to 0.7 when the cross-sectional area of the peripheral wall at the top of the heating container is 1.0.   The energization heating apparatus according to any one of claims 1 to 4, wherein the top electrode is made of graphite, and the heating container is made of conductive ceramics.   The energization heating device according to any one of claims 1 to 5, wherein the peripheral wall of the heating container is formed to have a uniform thickness. The electrical heating device according to any one of claims 1 to 6, wherein the heating container has an electric resistivity of 50 x ^10-3 to 250 x ^10-3 Ω · cm.