Circulating non-iron metal melting furnace

Abstract

Efficiently melts and heats non-ferrous metal materials. [Solution] The furnace body 10 has heating chambers 12 and 13 that communicate with an inlet 11 for non-ferrous metal material, a tapping chamber 14 that can receive a portion of the molten metal heated to a predetermined temperature in the heating chambers 12 and 13 and from which the molten metal can be removed, a circulation pump 20 provided in the heating chambers 12 and 13 to circulate the molten metal, a plurality of electric heaters 30 and 40 provided in the heating chambers 12 and 13 to heat the molten metal to a predetermined temperature, a cylindrical space 80 provided in the circulation path of the molten metal in the heating chambers 12 and 13, with an inlet 81 into which the molten metal discharged from the circulation pump 20 flows in and an outlet 82 formed at different height positions for the flowing molten metal to be discharged, a shaft 85 provided in the cylindrical space 80 and with blades 86 fixed to stir the molten metal inside and extending upward, a swivel device 91 that swivels the shaft 85 together with the blades 86, and a lifting device 92 that moves the shaft 85 up and down together with the blades 86.

Description

Technical Field

[0001] The present invention relates to a circulating non-ferrous metal melting furnace that melts non-ferrous metals such as aluminum alloys while circulating them for the purpose of using them in the production of various cast products such as die-castings.

Background Art

[0002] Conventionally, for melting non-ferrous metals such as aluminum alloys, melting furnaces using radiant flames from gas burners using fossil fuels such as petroleum have been mainly adopted. However, since radiant flames from gas burners using fossil fuels have problems in terms of thermal efficiency and the environment, improvement measures have been demanded.

[0003] As an improvement measure, a non-ferrous metal melting furnace having a structure in which an electric heater is immersed in molten metal has been disclosed (see, for example, Patent Document 1). As shown in FIG. 4, the non-ferrous metal melting furnace 50 described in this Patent Document 1 is provided with a plurality of chambers including a melting chamber 51, a temperature-raising chamber 52, and a dross-removing chamber 53. The non-ferrous metal material charged into the melting chamber 50 is melted by an electric heater 56 provided in the temperature-raising chamber 52 and heated to a predetermined temperature, and then supplied from there to a hot water chamber 55 through a calming chamber 54. The molten metal circulates from the dross-removing chamber 53 to the temperature-raising chamber 52, but no electric heater is provided in this dross-removing chamber 53.

[0004] This non-ferrous metal melting furnace 50 uses an electric heater to melt and heat the non-ferrous metal material, and thus has a great advantage of being superior in terms of thermal efficiency and the environment compared to the conventional melting furnace using a gas burner.

[0005] However, the present inventors did not satisfy with such a current situation and advanced further research and development, and developed a circulating non-ferrous metal melting furnace that can melt and heat non-ferrous metal materials more efficiently with a novel configuration that has not existed until now (Patent Document 2).

[0006] As shown in Figure 5, this circulating non-ferrous metal melting furnace 101 has a furnace body 110 that includes an inlet 111 for non-ferrous metal materials, a first heating chamber 112 communicating with the inlet 111, a second heating chamber 113 arranged parallel to the first heating chamber 112 via an intermediate wall 115 and forming a circulation path for the molten metal to circulate between the first heating chamber 112 and the second heating chamber 113, and a tapping chamber 114 that communicates with the downstream side of the first heating chamber 112 and can receive a portion of the molten metal heated to a predetermined temperature in the first heating chamber 112 and from which the molten metal can be removed. The system includes a circulation pump 120 for circulating the molten metal, a plurality of first electric heaters 130 installed in the first heating chamber 112 to raise the molten metal to a predetermined first temperature, and a plurality of second electric heaters 140 installed in the second heating chamber 113 to raise the molten metal, which has been heated to the first temperature in the first heating chamber 112, to a second temperature exceeding the first temperature. The molten metal, which has been heated to the second temperature in the second heating chamber 113, is circulated back to the first heating chamber 112, and its heat is transferred to the non-ferrous metal material introduced from the inlet 111. A partition wall 117 is provided between the first heating chamber 112 and the molten metal outlet chamber 114. A connecting passage 117a is formed in this partition wall 117, connecting the first heating chamber 112 to the molten metal outlet chamber 114. The molten metal outlet chamber 114 is equipped with a mechanism (not shown) for removing the received molten metal to the outside.

[0007] According to this, molten metal is circulated by a circulation pump 120 through a circulation path formed by the first heating chamber 112 and the second heating chamber 113. A portion of the molten metal, which has been heated to a predetermined temperature (first temperature) in the first heating chamber 112 by the first electric heater 130, is received in the tapping chamber 114. Furthermore, the molten metal from the first heating chamber 112 is heated to a temperature exceeding the predetermined temperature (second temperature) in the second heating chamber 113 by the second electric heater 140, and then circulated back to the first heating chamber 112. This allows non-ferrous metal material introduced into the first heating chamber 112 from the input port 111 to be effectively melted and heated.

[0008] However, the circulating non-ferrous metal melting furnace 101 shown in Figure 5 does not actively purify the molten metal or reduce oxides. Therefore, the inventors have come to the conclusion that if these processes could be successfully implemented, non-ferrous metal materials could be melted and heated more efficiently.

[0009] While there are known degassing devices that use inert gas bubbles to disperse into the molten metal, causing absorbed gases and impurities to be adsorbed onto the bubbles and float to the surface (see, for example, Patent Document 3), these are used in a quiet flow or in a ladle where the stirring flow is not obstructed, and are not placed inside a furnace where the molten metal is circulated. Furthermore, there is a known technique of adding flux to molten aluminum to reduce oxides and separate them (see, for example, Patent Document 4), but this is often done in a quiet flow, and chips and thin burrs are processed in a wide melting chamber while vortex entrainment is limited to a specific area, making it impossible to obtain a high melting rate throughout the entire melting chamber by taking advantage of the vortex characteristics. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2010-96401 [Patent Document 2] Patent No. 6997738 [Patent Document 3] Patent No. 4183732 [Patent Document 4] Patent No. 6572325 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Therefore, the object of the present invention is to provide a circulating non-ferrous metal melting furnace that can efficiently melt and heat non-ferrous metal materials. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides a circulating non-ferrous metal melting furnace (1) that melts non-ferrous metal materials using an immersion electric heater, A furnace body (10) having an inlet (11) for non-ferrous metal material, heating chambers (12, 13) communicating with the inlet (11), and a tapping chamber (14) communicating with the heating chambers (12, 13) that can receive a portion of the molten metal heated to a predetermined temperature in the heating chambers (12, 13) and from which the molten metal can be removed, A circulation pump (20) is provided in the aforementioned heating chambers (12, 13) for circulating the molten metal, The heating chambers (12, 13) are provided with a plurality of electric heaters (30, 40) for raising the temperature of the molten metal to a predetermined temperature, A cylindrical space (80) is provided in the circulation channel for molten metal in the heating chambers (12,13), and has an inlet (81) into which molten metal discharged from the circulation pump (20) flows, and an outlet (82) into which the flowing molten metal flows out, formed at different height positions. A blade (86) for stirring the molten metal inside is fixed to a shaft (85) that extends vertically within the cylindrical space (80), A rotating device (91) that rotates the shaft (85) together with the blade (86), The device is characterized by comprising a lifting device (92) that moves the shaft (85) up and down together with the blade (86).

[0013] Furthermore, the present invention is characterized in that the inlet (81) and outlet (82) are positioned such that the direction in which molten metal flows into the cylindrical space (80) and the direction in which molten metal flows out of the cylindrical space (80) are the same as the direction of agitation flow within the cylindrical space (80).

[0014] Furthermore, the present invention is characterized in that a plurality of holes (87) are formed in the blade (86), and a gas supply device (93) is provided that ejects an inert gas through the holes (87).

[0015] The present invention is also characterized in that a fluxing agent is introduced onto the molten metal surface in the cylindrical space (80).

[0016] The present invention is also characterized in that the heating chambers (12, 13) are composed of a first heating chamber (12) and a second heating chamber (13) arranged side by side via an intermediate wall (15), and a plurality of electric heaters (30, 40) are provided in the first heating chamber (12), including a first electric heater (30) for heating the molten metal to a predetermined first temperature, and a plurality of electric heaters (40) are provided in the second heating chamber (13) for heating the molten metal heated to the first temperature in the first heating chamber (12) to a second temperature exceeding the first temperature, and the molten metal heated to the second temperature in the second heating chamber is circulated to the first heating chamber (12) to supply its heat to the non-ferrous metal material introduced from the charging port (11).

[0017] The present invention is also characterized in that the non-ferrous metal material is aluminum or an aluminum alloy.

[0018] The symbols in the parentheses above indicate corresponding elements or corresponding matters shown in the drawings and in the embodiments for carrying out the invention described later.

Advantages of the Invention

[0019] According to the present invention, in a circulation-type non-ferrous metal melting furnace that melts a non-ferrous metal material using an electric heater, a shaft with blades fixed thereto is provided in a cylindrical space provided in the circulation flow path of the molten metal in the heating chamber, and the shaft can rotate and move up and down together with the blades. Therefore, the molten metal in the cylindrical space in the molten metal circulation flow path of the heating chamber can be stirred. For example, when melting materials that tend to float on the molten metal such as skim, the rotating blades are raised to a height where vortices form on the surface of the molten metal in the cylindrical space and rotated, so that the floating skim can be efficiently melted. Materials that tend to float on the molten metal such as skim may be directly introduced onto the surface of the molten metal in the cylindrical space. Further, the height position and rotational speed of the rotating blades can be controlled in a pre-programmed time and order to perform degassing treatment, flux treatment, and melting of materials such as skim in a time-sharing manner. At this time, for the cylindrical space, the inlet through which the molten metal discharged from the circulation pump flows in and the outlet through which the molten metal flows out are formed at different height positions, and the molten metal flowing in from the inlet is prevented from immediately flowing out from the outlet, so that sufficient stirring can be performed within the cylindrical space.

[0020] Further, according to the present invention, since the direction in which the molten metal flows into the cylindrical space and the direction in which the molten metal flows out of the cylindrical space are provided at positions such that they are the same as the stirring flow direction within the cylindrical space, the stirring flow is not disturbed by the circulating flow of the molten metal.

[0021] Further, according to the present invention, inert gas is ejected from a plurality of holes formed in the blades, and the bubbles of the inert gas are blown out and diffused into the molten metal, and bubbling that adsorbs the gas and impurities absorbed in the molten metal onto the bubbles and causes them to float is performed within the cylindrical space provided in the molten metal circulation flow path of the heating chamber, so that the molten metal can be efficiently purified. Further, since the bubbles of the inert gas are blown into the molten metal while stirring is caused by the rotation of the blades, they can be sufficiently diffused.

[0022] Further, according to the present invention, a fluxing agent can be introduced onto the surface of the molten metal in the cylindrical space, so that the molten metal can be further purified in the molten metal circulation flow path of the heating chamber. During the flux treatment, for example, after raising the blades that rotate to a height where vortices form on the surface of the molten metal in the cylindrical space and then rotating them, the fluxing agent is submerged in the molten metal, and after the fluxing agent has sunk into the molten metal, the position of the rotating blades is lowered to efficiently diffuse it. Further, it is also possible to move the rotating blades up and down to shorten the diffusion time.

[0023] Furthermore, according to the present invention, bubbling of inert gas, diffusion of flux, and melting of chips can be efficiently performed by moving a single rotating blade up and down.

[0024] Furthermore, according to the present invention, the heating chamber consists of a first heating chamber and a second heating chamber arranged side by side with an intermediate wall in between. The first heating chamber and the second heating chamber are each provided with a first electric heater that raises the temperature to a predetermined first temperature and a second electric heater that raises the temperature to a second temperature exceeding the first temperature. The molten metal heated to the second temperature in the second heating chamber is circulated to the first heating chamber, and the heat is transferred to the non-ferrous metal material introduced from the inlet. As a result, the non-ferrous metal material can be melted and heated efficiently in a short time.

[0025] Furthermore, according to the present invention, since the non-ferrous metal material is aluminum or an aluminum alloy, various cast products using aluminum can be manufactured successfully. [Brief explanation of the drawing]

[0026] [Figure 1] This is a schematic plan view showing an embodiment of a circulating non-ferrous metal melting furnace according to the present invention. [Figure 2] This is an enlarged perspective view showing the configuration around the cylindrical space in Figure 1. [Figure 3] This is an enlarged cross-sectional view showing the configuration around the cylindrical space in Figure 1. [Figure 4] This is a schematic plan view showing a conventional circulating non-ferrous metal melting furnace. [Figure 5] This is a schematic plan view showing a circulating non-ferrous metal melting furnace according to another conventional example. [Modes for carrying out the invention]

[0027] A circulating non-ferrous metal melting furnace 1 according to an embodiment of the present invention will be described with reference to the drawings.

[0028] As shown in Figure 1, the circulating non-ferrous metal melting furnace 1 according to this embodiment melts and raises the temperature of non-ferrous metal materials by circulating molten metal and immersing an immersion-type electric heater in the molten metal, with the portion of the heater excluding its upper end submerged in the molten metal. The furnace comprises a furnace body 10, a circulation pump 20, a first electric heater 30, a second electric heater 40, a cylindrical space 80 with a shaft 85 equipped with blades 86 in the center, a swivel device 91, a lifting device 92, a gas supply device 93, and a control unit 100 that controls the entire electrical system.

[0029] The furnace body 10 has a roughly rectangular shape in plan view, with its outer shell formed by the furnace walls 10a, and includes an inlet 11 for non-ferrous metal materials, a first heating chamber 12, a second heating chamber 13, and a tapping chamber 14 from which molten metal can be removed. However, the planar shape of the furnace body 10 is not limited to a rectangular shape.

[0030] The input port 11 is located upstream of the second heating chamber 13. The first heating chamber 12 is connected to the input port 11 and receives non-ferrous metal materials introduced from the input port 11. The second heating chamber 13 is installed alongside the first heating chamber 12 via an intermediate wall 15, forming a circulation path for the molten metal to circulate between the two chambers.

[0031] The hot water outlet chamber 14 is located in a position accessible via a guide channel 18 that is connected to the downstream side of the first heating chamber 12. This molten metal outlet chamber 14 is equipped with a mechanism (not shown) for removing the received molten metal to the outside.

[0032] The circulation pump 20 is installed downstream of the second heating chamber 13 and circulates the molten metal along the circulation path. The location and number of the circulation pumps 20 are not limited. Therefore, they can be installed in the first heating chamber 12, or they can be installed in both the first heating chamber 12 and the second heating chamber 13.

[0033] The first electric heater 30 is installed in the first heating chamber 12 and heats the molten metal to a predetermined first temperature. The number of first electric heaters 30 is not limited. The second electric heater 40 is installed in the second heating chamber 13 and raises the molten metal, which has been heated to the first temperature in the first heating chamber 12, to a second temperature that exceeds the first temperature. The number of second electric heaters 40 is not limited. The sensors are thermocouple type, and thermometers, which are thermocouple type sensors (not shown), are installed in the first heating chamber 12, the second heating chamber 13, and the molten metal outlet chamber 14, respectively, to measure the temperature of the molten metal.

[0034] The cylindrical space 80 is located at the corner on the first heating chamber 12 side of the molten metal circulation path, between the downstream side of the circulation pump 20 and the upstream side of the first heating chamber 12. As shown in Figures 2 and 3, the cylindrical space 80 has an inlet 81 through which molten metal discharged from the circulation pump 20 flows in via the inlet 11, and an outlet 82 through which the flowing molten metal flows out.

[0035] The inlet 81 and outlet 82 are formed at different heights, with the outlet 82 positioned higher than the inlet 81 within the cylindrical space 80. Furthermore, the inlet 81 and outlet 82 are positioned such that the direction in which the molten metal flows into the cylindrical space 80 and the direction in which the molten metal flows out of the cylindrical space 80 are the same as the direction of agitation flow within the cylindrical space 80.

[0036] A shaft 85 is provided within the cylindrical space 80, extending upward from the center of the bottom surface, and a blade 86 for stirring the molten metal inside is fixed to the lower end of the shaft 85. The shaft 85, together with the blades 86, is rotatable by the slewing device 91 and is also movable vertically by the lifting device 92. Multiple holes 87 are formed in the blade 86, and an inert gas is ejected from the holes 87 by a gas supply device 93.

[0037] The control unit 100, although not shown in the figure, includes a CPU, ROM, RAM, and other memory units, and controls the circulation pump 20, first electric heater 30, second electric heater 40, swivel device 91, lifting device 92, and gas supply device 93 based on temperature information from the thermometer and information on non-ferrous metal materials.

[0038] In this embodiment, the non-ferrous metal is an aluminum alloy. The first temperature is set to 650°C to 720°C, which is suitable for casting molten aluminum alloy products. The second temperature is set to 690°C to 750°C, and is set to efficiently melt and heat up the non-ferrous metal introduced from the inlet 11 in a short time by utilizing the heat of the molten metal, which is about 10°C higher than the first temperature. The first and second temperatures can be varied depending on the type of non-ferrous metal being melted and heated.

[0039] In the circulating non-ferrous metal melting furnace 1 configured in this way, which melts non-ferrous metal materials using electric heaters 30 and 40, a shaft 85 to which blades 86 are fixed is provided in a cylindrical space 80 provided in the molten metal circulation channel formed to pass through the first heating chamber 12 and the second heating chamber 13, and the shaft 85 together with the blades 86 can rotate and move up and down via a swivel device 91 and a lifting device 92, so that the molten metal in the cylindrical space 80 can be stirred in the molten metal circulation channel of the heating chambers 12 and 13.

[0040] For example, when dissolving materials that tend to float in molten metal, such as metal chips, the floating material is introduced into the cylindrical space 80 from above. Then, the blades 86 are raised and rotated to a height that creates a vortex on the surface of the molten metal within the cylindrical space 80, thereby efficiently dissolving the floating metal chips. Time-division processing can also be performed by controlling the height position and rotation speed of the rotating blades 86 according to a pre-programmed time and sequence. In this configuration, the inlet 81 through which the molten metal discharged from the circulation pump 20 flows into the cylindrical space 80, and the outlet 82 through which the molten metal flows out, are formed at different heights. This prevents the molten metal flowing in from the inlet 81 from immediately flowing out from the outlet 82, thus allowing for sufficient stirring within the cylindrical space 80. Here, the outlet 82 is positioned higher than the inlet 81 in the cylindrical space 80, but the opposite may also be true: the inlet 81 may be positioned higher than the outlet 82.

[0041] Furthermore, since the cylindrical space 80 is positioned such that the direction in which the molten metal flows into and out of the cylindrical space 80 is the same as the direction of the agitated flow within the cylindrical space 80 (clockwise in Figure 1), the agitated flow is not disturbed by the circulating flow of the molten metal.

[0042] Furthermore, by ejecting inert gas from multiple holes 87 formed in the blade 86, and diffusing the inert gas bubbles into the molten metal, bubbling occurs within the cylindrical space 80 provided in the molten metal circulation channel of the heating chambers 12 and 13. This process adsorbs gases and impurities absorbed into the molten metal onto the bubbles and causes them to float to the surface, thus efficiently purifying the molten metal. In addition, since the inert gas bubbles are ejected into the molten metal while stirring by the rotation of the blade 86, sufficient diffusion can be achieved.

[0043] Furthermore, by introducing a fluxing agent to the surface of the molten metal in the cylindrical space 80, the molten metal can be purified in the molten metal circulation channels of the heating chambers 12 and 13. During flux treatment, for example, the rotating blades 86 can be raised to a height that creates vortices on the surface of the molten metal in the cylindrical space 80, and then rotated to submerge the flux into the molten metal. After the flux has submerged in the molten metal, the position of the rotating blades 86 can be lowered to efficiently diffuse it. It is also possible to move the rotating blades 86 up and down to shorten the diffusion time.

[0044] Furthermore, by dividing the process into time segments, the bubbling of the inert gas, the diffusion of the flux, and the melting of the chips can be efficiently performed by moving a single rotating blade 86 up and down.

[0045] Furthermore, the heating chambers 12 and 13 consist of a first heating chamber 12 and a second heating chamber 13 arranged side by side with an intermediate wall 15 in between. The first heating chamber 12 and the second heating chamber 13 are each equipped with a first electric heater 30 that raises the temperature to a predetermined first temperature and a second electric heater 40 that raises the temperature to a second temperature exceeding the first temperature. The molten metal heated to the second temperature in the second heating chamber 13 is circulated back to the first heating chamber 12, and its heat is transferred to the non-ferrous metal material introduced from the inlet 11. This allows for the efficient melting and heating of the non-ferrous metal material in a short amount of time.

[0046] In the above embodiments of the present invention, aluminum alloys are used for melting and heating, but other non-ferrous alloys can also be used. Furthermore, the first and second temperatures can be appropriately changed depending on the non-ferrous metal being targeted. [Explanation of Symbols]

[0047] 1 Circulating non-ferrous metal melting furnace 10 Furnace body 10a Furnace wall 11 Inlet 12 First Temperature-Boosting Chamber 13. Second Temperature-Boosting Chamber 14 Hot spring room 15 Intermediate wall 18 Channel 20 Circulation pump 30-inch Daiichi Electric Heater 40 Second Electric Heater 50 Circulating non-ferrous metal melting furnace 51 Melting chamber 52 Warming room 53 Debris Removal Room 54 Sedation Room 55 Hot spring room 56 Electric heater 80 Cylindrical space 81 Inlet 82 Outlet 85 axis 86 feathers 87 holes 91 Swivel device 92 Lifting device 93 Gas supply equipment 100 Control Unit 101 Circulating non-ferrous metal melting furnace 110 Furnace body 110a Furnace wall 111 Inlet 112 First Temperature-Boosting Room 113 Second Temperature-Boosting Room 114 Hot Spring Room 115 Intermediate wall 117 Bulkhead 117a Gap passage 120 Circulation pump 130 Daiichi Electric Heater 140 Second Electric Heater

Claims

1. A circulating non-ferrous metal melting furnace that melts non-ferrous metal materials using an immersion-type electric heater, A furnace body having an inlet for non-ferrous metal material, a heating chamber communicating with the inlet, and a tapping chamber communicating with the heating chamber, which receives a portion of the molten metal heated to a predetermined temperature in the heating chamber and from which the molten metal can be removed. A circulation pump is provided in the aforementioned heating chamber for circulating the molten metal, The aforementioned heating chamber is provided with a plurality of electric heaters for raising the temperature of the molten metal to a predetermined temperature, A cylindrical space is provided in the circulation channel for molten metal in the heating chamber, with an inlet into which molten metal discharged from the circulation pump flows in and an outlet for which the flowing molten metal flows out, both located at different heights. A shaft extending upward is fixed to a blade that stirs the molten metal inside the cylindrical space, A rotating device that rotates the shaft together with the blade, A non-ferrous metal melting furnace characterized by comprising a lifting device that moves the shaft up and down together with the blades.

2. The non-ferrous metal melting furnace according to claim 1, characterized in that the inlet and outlet are positioned such that the direction in which molten metal flows into the cylindrical space and the direction in which molten metal flows out of the cylindrical space are the same as the direction of agitation flow within the cylindrical space.

3. The non-ferrous metal melting furnace according to claim 1 or 2, characterized in that a plurality of holes are formed in the blades, and a gas supply device is provided for ejecting inert gas through the holes.

4. The non-ferrous metal melting furnace according to claim 1 or 2, characterized in that a fluxing agent is introduced into the surface of the molten metal in the cylindrical space.

5. The aforementioned heating chamber consists of a first heating chamber and a second heating chamber arranged side by side with an intermediate wall in between, The electric heaters consist of a plurality of first electric heaters provided in the first heating chamber to raise the molten metal to a predetermined first temperature, and a plurality of second electric heaters provided in the second heating chamber to raise the molten metal, which has been heated to the first temperature in the first heating chamber, to a second temperature exceeding the first temperature. The non-ferrous metal melting furnace according to claim 1 or 2, characterized in that the molten metal heated to the second temperature in the second heating chamber is circulated to the first heating chamber, and the heat is supplied to the non-ferrous metal material introduced from the inlet.

6. The circulating non-ferrous metal melting furnace according to claim 5, characterized in that the non-ferrous metal material is aluminum or an aluminum alloy.

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