Electric heater

Abstract

To provide a high-output electric heater for efficiently transferring a heat quantity to molten metal while suppressing disconnection.SOLUTION: A wholly-L-shaped electric heater 100 for heating molten metal M to be used for melting or temperature holding in a melting furnace 200 or a melting holding furnace includes a vertical pipe material 10 which extends in the vertical direction, of which the lower part is immersed in the molten metal M, and into which an electrical conduction material 40 is inserted, and a connection pipe material 30 which is connected to the lower end of the vertical pipe material 10, extends right and left horizontally, completely immersed in the molten metal M, and having a heating conductor 50 inside to be electrified by the electrical conduction material 40. At the vertical pipe material 10 side end of the connection pipe material 30, a spring material 61 is provided which horizontally expands and is electrically connected to the heating conductor 50. To the spring material 61, a thin plate piece 41 provided at the lower end of the electrical conduction material 40 is connected while being pushed against it downward.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electric heater for heating molten metal used for melting or maintaining the temperature. [Background technology]

[0002] Conventionally, as shown in FIG. 4, an L-shaped electric heater 6 has been known, which has a main body 6A having a heat generating portion 7 and immersed in molten metal and a support portion 6B supporting the main body 6A arranged so as to intersect with each other (for example, Patent Document 1). This electric heater 6 has a main body 6A and a support part 6B joined in an L-shape by a joining tube 6C, and the heating part 7 is a single nichrome wire tightly wound in a spiral shape inside the main body 6A to form a cylindrical shape. A lead wire 8 is inserted into the support part 6B from above, bent horizontally inside the joining tube 6C, and its tip is connected to the heating part 7 to supply electricity to the heating part 7.

[0003] This makes it possible to efficiently heat the molten metal even if it is shallow, without the need to make the molten metal deeper as in the vertical electric heater 1. Moreover, the weight of the main body 6A is set to provide a gravitational force that balances the buoyant force from the molten metal that the main body 6A immersed in the molten metal receives, thereby making it possible to suppress the occurrence of stress cracks in the bent portion where the main body 6A and the support part 6B are joined in an L-shape by the joining pipe 6C.

[0004] According to Patent Document 1, it is described that the tip of the lead wire 8 is electrically connected to the corresponding end of the heat generating part 7 (paragraph (0010)), but no specifics are given. This is considered to be a general connection method rather than a special one, since it describes a method of dealing with the case where the lead wire 8 breaks due to a long cumulative usage time or the like (paragraph (0023)). In the case of a general connection, there is a problem that the main body part 6A immersed in the molten metal thermally expands, putting a load on the connection part between the main body part 6A and the support part 6B, making the lead wire 8 prone to breakage. If the lead wire 8 breaks, the main body 6A, support part 6B and connecting tube 6C are disassembled, the lead wire 8 is removed, a new one is inserted and then reassembled. At this time, it is necessary to fill in only a specified amount of filler taking into account the balance with the buoyancy at the time of immersion, which requires precise work and makes the replacement work time-consuming and cumbersome. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-30226 Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an electric heater which has high output, is suppressed from breaking, and can efficiently transmit heat to molten metal. [Means for solving the problem]

[0007] In order to achieve the above object, the electric heater of the present invention is an electric heater (100) for heating molten metal (M) used for melting or temperature maintenance in a melting furnace (200) or a melting and holding furnace, comprising: a vertical pipe material (10) extending in the vertical direction, a lower portion of which is immersed in the molten metal (M), and a conductive material (40) is inserted therein; a connecting pipe material (30) which is connected to the lower end of the vertical pipe material (10), extends horizontally to the left and right, is completely immersed in the molten metal (M), and has a heating element (50) therein to which electricity is applied from the conductive material (40), and the whole is formed in an L-shape; A spring member (61) that expands and contracts left and right and is electrically connected to the heating element (50) is provided at the end of the connecting pipe member (30) on the side of the vertical pipe member (10), A thin plate piece (41) provided at the lower end of the conductive material (40) is connected to the spring material (61) in a state where it is pressed from above.

[0008] The present invention is also characterized in that the spring material (61) is made up of a plurality of disc springs (63) connected together, and the thin plate piece (41) is pressed between and connected to adjacent disc springs (63, 63).

[0009] In the present invention, an inert gas is sealed in the vertical pipe material (10) from above.

[0010] It should be noted that the symbols in parentheses above indicate corresponding elements or items described in the drawings and in the detailed description of the invention described below. Effect of the Invention

[0011] According to the present invention, an electric heater for heating molten metal, such as molten aluminum, used for melting or maintaining temperature in a melting furnace or melting and holding furnace is formed in an L-shape consisting of a vertical pipe material and a connecting pipe material connected to it, and the connecting pipe material is completely immersed in the molten metal and has a heating element provided therein, so that the electric heater can be used even if the molten metal is shallow.

[0012] Furthermore, according to the present invention, a spring material which expands and contracts left and right and is electrically connected to the heating element is provided at the side end of the vertical pipe material of the connecting pipe material, so that even if the connecting pipe material moves left and right due to thermal expansion and a load is applied to the connection part with the vertical pipe material, the left and right movement of the connecting pipe material is mitigated by the expansion and contraction of the spring material, and the thermal expansion is absorbed. This prevents the power supplied from the conductive material to the heating element from being cut off due to a break in the wire or the like. Furthermore, the conductive material is connected to the spring material with a thin plate piece attached to the lower end of the conductive material pressed from above, so that the connection is stable and the possibility of disconnection is minimized.

[0013] Furthermore, according to the present invention, the spring material is made up of a plurality of disc springs connected together, and the thin plate piece is connected so as to be pressed between adjacent disc springs. Therefore, when the spring material compresses, the thin plate piece is held in place by being sandwiched between the disc springs on both sides, further increasing the connection strength.

[0014] Furthermore, according to the present invention, since an inert gas is sealed in the vertical pipe from above, the molten metal is prevented from entering through the connection portion between the vertical pipe and the connecting pipe.

[0015] An electric heater formed in an overall L-shape like this, which has a configuration in which a spring material absorbs the thermal expansion of the connecting pipe material, has never been adopted in a melting furnace or a melting and holding furnace, so this is unique and is not mentioned at all in the above-mentioned patent documents. [Brief description of the drawings]

[0016] [Figure 1] 1 is a side view showing an electric heater according to an embodiment of the present invention. [Diagram 2] 2 is a partial cross-sectional view showing a main part of a melting furnace to which the electric heater shown in FIG. 1 is attached. [Diagram 3] FIG. 2 is an enlarged side view showing a main part of the electric heater shown in FIG. [Figure 4] FIG. 11 is a partial cross-sectional side view showing an electric heater according to a conventional example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] An electric heater according to an embodiment of the present invention will be described with reference to FIGS.

[0018] As shown in FIG. 1, the electric heater 100 of this embodiment is formed by connecting a vertical pipe material 10 and a connecting pipe material 30 to form an overall L-shape, and as shown in FIG. 2, it heats molten metal M used for melting or temperature maintenance in a melting furnace 200 (which may be a melting and holding furnace) for non-ferrous metals such as aluminum.

[0019] The melting furnace 200 is composed of a side wall 201 and a bottom wall 202, and the opening at the top is covered by a ceiling lid 300, into which the electric heater 100 is attached so as to be inserted. The ceiling lid 300 is a lid in its entirety, but it may be a lid that is only partially formed.

[0020] As shown in Fig. 2, the electric heater 100 is composed of a vertical pipe 10 and a connecting pipe 30 that is connected to the lower end of the vertical pipe 10 and extends in the left-right direction. Note that the left-right direction here refers to the left-right direction in Fig. 2 (the left-right direction when viewed from the front side of the paper) for the sake of convenience and is not particularly limited. The vertical pipe material 10 is made of a ceramic pipe with low thermal conductivity, and the connecting pipe material 30 is made of a ceramic pipe with high thermal conductivity.

[0021] The vertical pipe 10 extends in the vertical direction, with its lower portion immersed in the molten metal M, and has a conductive material 40 inserted therein. 3, the conductive material 40 is an electrode bar 40 made of a material capable of absorbing thermal expansion (e.g., nickel), and has a thin plate piece 41 provided at its lower end. The thin plate piece 41 is conductive and may be integral with the electrode bar 40 and have a thin plate-like lower end, or may be separate from the electrode bar 40. An insulating pipe 11 (e.g., an alumina pipe) is inserted into the vertical pipe material 10 so as to surround the electrode rod 40. The electrode rod 40 is simply inserted into the insulating pipe 11, but is not fixed thereto, so that thermal expansion can be absorbed. The upper end of the electrode rod 40 is connected to a single-phase AC power source via a control device (not shown). 1 to 3, the insides of the vertical pipes 10 and the connecting pipes 30 are shown by solid lines.

[0022] The connecting pipe material 30 is connected to the right side of the lower end of the vertical pipe material 10 and extends horizontally from left to right. The connecting pipe material 30 is completely immersed in the molten metal M, and a heating element 50 that is energized by a conductive material 40 is provided inside the connecting pipe material 30. The heating element 50 is a plurality of nichrome wires (not shown) wound in a spiral shape, and the periphery of the nichrome wires is filled with a mixture of aluminum oxide or magnesium oxide and boron nitride.

[0023] A spring material 61 that expands and contracts laterally and is electrically connected to the heating element 50 is provided at the left end of the connecting pipe material 30. The spring material 61 is made up of a plurality of disc springs 63 connected laterally.

[0024] The connection between the vertical pipe member 10 and the connecting pipe member 30 will now be described. As shown in Fig. 3, the spring material 61 is provided so as to protrude further leftward from the left end of the connecting pipe material 30. A cover 31 made of an insulating material is attached to the left end of the connecting pipe material 30 to prevent the mixture of aluminum oxide or magnesium oxide and boron nitride filled inside from spilling out, and a holed electrode plate 32 is attached to the left side of the cover 31. The right end of the spring material 61 is connected to the left end of the electrode plate 32. A nichrome wire constituting the heating element 50 is passed through the hole in the electrode plate 32 and is electrically connected to the spring material 61. The left end of the spring material 61 is housed and fixed in a recessed receiving portion 33 made of an insulating material. At this time, the thin plate piece 41 provided at the lower end of the electrode rod 40 is inserted between adjacent disc springs 63, 63 and is tightly clamped by the disc springs 63, 63 from the left and right, and the thin plate piece 41 is connected between the disc springs 63, 63 so as to be pressed downward from above.

[0025] The vertical pipe material 10 is then arranged so that its lower end is located directly above the receiving portion 33 and the spring material 61, and the vertical pipe material 10 and the connecting pipe material 30 are connected by an L-shaped ceramic elbow 35 with low thermal conductivity. The lower part of the vertical pipe material 10 is fixed to the upper part 35a of the elbow 35, which opens upward, by a screw type, and the space between them is sealed with mortar. At this time, the lower end of the vertical pipe material 10 is arranged so that it is placed on the upper surface of the receiving portion 33. The left side of the connecting pipe material 30 is fixed to the lower part 35b of the elbow 35 that opens toward the right side by a screw, and the space between them is sealed with mortar. It can also be fixed using a heat-resistant adhesive such as Sumiceram. At this time, the left end of the receiving part 33 is positioned so that it abuts against the left inner surface of the elbow 35.

[0026] In addition, an inert gas (nitrogen gas or argon gas) is sealed inside the vertical pipe material 10 from above to prevent the infiltration of molten metal.

[0027] In the case of the melting furnace (electric furnace) 200 according to this embodiment, the height from the hearth 202A required to immerse the connecting pipe material 30 provided with the heating element 50 in the molten metal M can be kept small compared to the case of a vertical electric heater, and therefore the effective amount of molten aluminum tapped is determined by the distance from the surface of the molten metal M to the top of the connecting pipe material 30. This allows the effective amount of molten aluminum to be made larger compared to the case of a vertical electric heater, and correspondingly, the amount of remaining molten aluminum can be significantly reduced.

[0028] The electric heater 100 configured in this manner is formed into an L-shape consisting of a vertical pipe material 10 and a connecting pipe material 30 connected to it, and the connecting pipe material 30 is completely immersed in the molten metal M with the heating element 50 provided thereon, so that the electric heater 100 can be used even if the molten metal M is shallow. Furthermore, when a higher output electric heater 100 is used, there is no restriction on the depth of the molten metal M as in the case of a vertical electric heater, and the molten metal M can be efficiently heated. The temperature of the molten metal M can also be easily raised to 1200 degrees (°C) or higher in a short period of time.

[0029] In addition, a spring material 61 which expands and contracts left and right and is electrically connected to the heating element 50 is provided at the left end of the connecting pipe material 30. Therefore, even if the connecting pipe material 30 moves left and right due to thermal expansion and a load is applied to the connection part with the vertical pipe material 10, the left and right movement of the connecting pipe material 30 is mitigated by the expansion and contraction of the spring material 61, and the thermal expansion is absorbed. This prevents the power supplied from the conductive material 40 to the heating element 50 from being cut off due to a break in the wire or the like. Moreover, the conductive material 40 is connected to the spring material 61 with the thin plate piece 41 at the lower end of the conductive material 40 pressed from above, so that the connection is stable and the possibility of disconnection is minimized.

[0030] In addition, the spring material 61 is made up of a plurality of disc springs 63 connected together, and the thin plate piece 41 is connected so as to be pressed between adjacent disc springs 63, 63. Therefore, when the spring material 61 contracts, the thin plate piece 41 is held in such a manner that it is sandwiched between the disc springs 63, 63 from the left and right, further increasing the connection strength.

[0031] In this embodiment, a nichrome wire is used for the heating element 50, but the present invention is not limited to this. Also, although the spring material 61 is formed by connecting disc springs 63, other materials may be used. [Explanation of symbols]

[0032] 6 Electric heater 6A Main unit 6B Support part 6C joint pipe 7 Heating Part 8 Lead Wire 10 Vertical pipe material 11 Insulated pipe 30 Connecting pipe material 31 Lid 32 Electrode Plate 33 Receiving part 35 Elbow 35a upper part 35b bottom 40 Conductive materials 41 Thin plate piece 50 Heating element 61 Spring material 63 Disc Spring 100 Electric heater 200 Melting furnace 201 Side wall 202 Bottom wall 202A hearth 300 Ceiling Cover M Molten metal

Claims

1. An electric heater for heating molten metal used for melting or maintaining temperature in a melting furnace or a melting and holding furnace, A vertical pipe member having a lower portion immersed in the molten metal and a conductive material inserted therein, the vertical pipe member extending in a vertical direction; a connecting pipe material connected to the lower end of the vertical pipe material, extending horizontally to the left and right, completely immersed in the molten metal, and having a heating element inside that is energized by the conductive material, the connecting pipe material being formed into an L-shape as a whole; A spring member that expands and contracts left and right and is electrically connected to the heating element is provided at the side end of the vertical pipe member of the connecting pipe member, 2. An electric heater comprising: a thin plate member provided at a lower end of the conductive material and connected to the spring material in a state where the thin plate member is pressed from above.

2. 2. The electric heater according to claim 1, wherein the spring member is a plurality of coned disc springs connected together, and the thin plate piece is pressed between adjacent coned disc springs to connect them.

3. 3. The electric heater according to claim 1, wherein an inert gas is sealed in the vertical pipe from above.

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