Nonferrous metal melting method

Abstract

To provide a nonferrous metal melting method with high efficiency.SOLUTION: A circulation type nonferrous metal melting furnace 1 is configured to: form a circulation passage of molten metal by juxtaposing a first temperature rise chamber 12 having a plurality of first electric heaters 30 and a second temperature rise chamber 13 having a plurality of second electric heaters 40 while sandwiching an intermediate wall 15; provide an input port 11 for a nonferrous metallic material on one end side of the intermediate wall 15 between the first temperature rise chamber 12 and the second temperature rise chamber 13; cause the other end side of the intermediate wall 15 to communicate with a molten metal delivery chamber 14 from which molten metal can be taken out; perform temperature control in each of the first temperature rise chamber 12 and the second temperature rise chamber 13; and circulate the molten metal via a circulation pump 20 provided in the second temperature rise chamber 13. In a method for melting the nonferrous metallic material by using the circulation type nonferrous metal melting furnace, rotational frequency of the circulation pump 20 is increased as an input amount per unit time of the nonferrous metallic material increases.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a non-ferrous metal melting method for melting non-ferrous metals such as aluminum alloys while circulating the molten metal for the purpose of using it in the production of various cast products such as die-cast casting.

Background Art

[0002] Conventionally, for melting non-ferrous metals such as aluminum alloys, melting furnaces using radiant flames from burners using fossil fuels such as petroleum and natural gas have been mainly adopted. However, since the radiant flames from 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 with a structure in which an electric heater is immersed in the molten metal has been disclosed (see, for example, Patent Document 1). As shown in FIG. 3, 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 heating chamber 52, and a dross removal chamber 53. The non-ferrous metal material charged into the melting chamber 51 is melted by an electric heater 56 provided in the heating chamber 52 and heated to a predetermined temperature, and then supplied from there to a hot water outlet chamber 55 through a calming chamber 54. The molten metal circulates from the dross removal chamber 53 to the heating chamber 52, but no electric heater is provided in this dross removal chamber 53.

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

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the inventors were not satisfied with such a situation and further advanced research and development. In order to miniaturize, they developed a circulating non-ferrous metal melting furnace that can more efficiently melt and raise the temperature of non-ferrous metal materials. Then, focusing on the temperature and flow rate of the molten metal obtained using this circulating non-ferrous metal melting furnace, they further developed a more efficient non-ferrous metal melting method.

[0007] Therefore, an object of the present invention is to provide a non-ferrous metal melting method capable of efficiently melting and raising the temperature of non-ferrous metal materials.

Means for Solving the Problems

[0008] To achieve the above object, the non-ferrous metal melting method of the present invention comprises a first heating chamber (12) provided with a plurality of first electric heaters (30) and a second heating chamber (13) provided with a plurality of second electric heaters (40), which are arranged side by side with an intermediate wall (15) therebetween to form a circulation path for the molten metal. An inlet (11) for non-ferrous metal materials is provided on one end side of the intermediate wall (15) between the first heating chamber (12) and the second heating chamber (13), and the other end side of the intermediate wall (15) is communicated with a tapping chamber (14) from which the molten metal can be taken out. Temperature control is performed in each of the first heating chamber (12) and the second heating chamber (13), and the molten metal is circulated through a circulation pump (20) provided in the first heating chamber (12) or the second heating chamber (13) or both. A method for melting the non-ferrous metal material using a circulating non-ferrous metal melting furnace (1) configured as described above, characterized in that the rotational speed of the circulation pump (20) is increased as the input amount of the non-ferrous metal material per unit time increases.

[0009] Further, the present invention is characterized in that the rotational speed of the circulation pump (20) is increased as the difference between the upstream molten metal temperature and the downstream molten metal temperature in the first heating chamber (12) increases.

[0010] Further, the present invention is characterized in that the rotational speed of the circulation pump (20) is increased as the difference between the molten metal temperature on the upstream side and the molten metal temperature on the downstream side of the second heating chamber (13) increases.

[0011] Further, the present invention provides a method for melting a non-ferrous metal material using a circulation type non-ferrous metal melting furnace (1) configured such that a first heating chamber (12) provided with a plurality of first electric heaters (30) and a second heating chamber (13) provided with a plurality of second electric heaters (40) are arranged side by side with an intermediate wall (15) therebetween to form a circulation path for molten metal, an inlet (11) for a non-ferrous metal material is provided at one end side of the intermediate wall (15) between the first heating chamber (12) and the second heating chamber (13), the other end side of the intermediate wall (15) is communicated with a hot water chamber (14) from which molten metal can be taken out, temperature control is performed in each of the first heating chamber (12) and the second heating chamber (13), and molten metal is circulated through a circulation pump (20) provided in the first heating chamber (12) or the second heating chamber (13) or both. The present invention is characterized in that the rotational speed of the circulation pump (20) is increased as the difference between the molten metal temperature on the upstream side and the molten metal temperature on the downstream side of the first heating chamber (12) increases.

[0012] Further, the present invention provides a method for melting a non-ferrous metal material using a circulation type non-ferrous metal melting furnace (1) configured such that a first heating chamber (12) provided with a plurality of first electric heaters (30) and a second heating chamber (13) provided with a plurality of second electric heaters (40) are arranged side by side with an intermediate wall (15) therebetween to form a circulation path for molten metal, an inlet (11) for a non-ferrous metal material is provided at one end side of the intermediate wall (15) between the first heating chamber (12) and the second heating chamber (13), the other end side of the intermediate wall (15) is communicated with a hot water chamber (14) from which molten metal can be taken out, temperature control is performed in each of the first heating chamber (12) and the second heating chamber (13), and molten metal is circulated through a circulation pump (20) provided in the first heating chamber (12) or the second heating chamber (13) or both. The present invention is characterized in that the rotational speed of the circulation pump (20) is increased as the difference between the molten metal temperature on the upstream side and the molten metal temperature on the downstream side of the second heating chamber (13) increases.

[0013] Further, the present invention is characterized in that the inlets (11, 21) for the non-ferrous metal material are provided on the upstream side of the first heating chamber (12) and the downstream side of the second heating chamber (13).

[0014] Further, the present invention is characterized in that the non-ferrous metal material can be introduced into the fast-flowing or slow-flowing portions according to the velocity distribution of the circulating molten metal.

[0015] Note that the symbols in the parentheses indicate the corresponding elements or corresponding matters shown in the drawings and the embodiments for carrying out the invention described later.

Advantages of the Invention

[0016] According to the present invention, a first heating chamber provided with a plurality of first electric heaters and a second heating chamber provided with a plurality of second electric heaters are arranged side by side with an intermediate wall therebetween to form a circulation path for the molten metal. An inlet for the non-ferrous metal material is provided on one end side of the intermediate wall, and the other end side of the intermediate wall is communicated with a hot water outlet chamber from which the molten metal can be taken out. Temperature control is performed in each of the first heating chamber and the second heating chamber, and the molten metal is circulated through a circulation pump. In the circulation type non-ferrous metal melting furnace configured as described above, as the input amount of the non-ferrous metal material per unit time increases, the rotation speed of the circulation pump is increased, so that the melting speed of the non-ferrous metal material is increased.

[0017] Further, according to the present invention, as the difference between the molten metal temperature on the upstream side and the molten metal temperature on the downstream side of the first heating chamber increases, or as the difference between the molten metal temperature on the upstream side and the molten metal temperature on the downstream side of the second heating chamber increases, the rotation speed of the circulation pump is increased, so that the temperature inside each electric heater can be suppressed.

[0018] Further, according to the present invention, since the inlets for the non-ferrous metal material are provided on the upstream side of the first heating chamber and the downstream side of the second heating chamber, a large surface area of the non-ferrous metal material in contact with the circulating molten metal can be ensured, and the non-ferrous metal material can be efficiently melted.

[0019] Further, according to the present invention, by using a non-ferrous metal material, for example, a robot arm, etc., it can be introduced into a fast-flowing or slow-flowing portion according to the velocity distribution of the circulating molten metal. Therefore, while increasing the circulation amount of the molten metal, the flow velocity of the molten metal on the surface of the introduced non-ferrous metal material can be reduced to suppress the melting rate. As a result, the difference between the upstream molten metal temperature and the downstream molten metal temperature in the first heating chamber and the difference between the upstream molten metal temperature and the downstream molten metal temperature in the second heating chamber can be made as small as possible.

[0020] As described above, according to the present invention, since the thermal resistance from each electric heater to the non-ferrous metal material to be melted can be reduced, the output of each electric heater can be maximally exerted, and it is also possible to miniaturize the entire circulating non-ferrous metal melting furnace. As a result, a circulating non-ferrous metal melting furnace capable of exhibiting an extremely large melting capacity that has never existed before can be installed in the area of a holding furnace that has no melting power.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0022] With reference to the drawings, a non-ferrous metal melting method using a circulating non-ferrous metal melting furnace 1 according to an embodiment of the present invention will be described.

[0023] As shown in Fig. 1, the cyclic non-ferrous metal melting furnace 1 according to this embodiment circulates molten metal while immersing an electric heater, except for its upper end portion, in the molten metal and utilizes its heat to melt and heat up non-ferrous metal materials. It includes a furnace body 10, a circulation pump 20, a first electric heater 30, a second electric heater 40, thermometers T1 to T11, and a control unit 100 for controlling the entire electrical system.

[0024] The furnace body 10 has a substantially rectangular planar shape with an outer shell formed by a furnace wall 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 taken out. Note that the planar shape of the furnace body 10 is not limited to a rectangular shape.

[0025] The inlet 11 is provided on the upstream side of the second heating chamber 13. The first heating chamber 12 is provided in communication with the inlet 11 and receives non-ferrous metal materials introduced from the inlet 11. The second heating chamber 13 is arranged in parallel with the first heating chamber 12 via an intermediate wall 15, and forms a circulation path in which molten metal circulates with the first heating chamber 12.

[0026] The tapping chamber 14 is provided at a position opposite to the inlet 11 via a diversion channel 18 provided to communicate with the upstream side of the second heating chamber 13. The first heating chamber 12 and the second heating chamber 13 are partitioned by a partition wall 17 except for a gap channel 17a that communicates with the upstream side of the second heating chamber 13 between them and the diversion channel 18. A degassing device 70 that generates an inert gas to adsorb aluminum dross and make it float on the upper surface of the molten metal is attached to the diversion channel 18. Note that the aluminum dross is scraped out manually. This tapping chamber 14 is provided with a mechanism (not shown) for taking out the received molten metal to the outside. The inlet 11 is provided at one end side of the intermediate wall 15 between the first heating chamber 12 and the second heating chamber 13, and the other end side of the intermediate wall 15 between the first heating chamber 12 and the second heating chamber 13 is communicated with the tapping chamber 14.

[0027] Between both ends of the intermediate wall 15 and the furnace wall 10a and the partition wall 17 facing them, gap passages 16 (a first gap passage 16a and a second gap passage 16b) are respectively formed. Therefore, the circulation path is formed in the order of the first gap passage 16a, the first heating chamber 12, the second gap passage 16b, and the second heating chamber 13 from the upstream side (the inlet 11).

[0028] The circulation pump 20 is provided on the downstream side of the second heating chamber 13 and circulates the molten metal along the circulation path. Note that the installation location and number of the circulation pump 20 are not limited. Therefore, it can be provided in the first heating chamber 12, or can also be provided in both the first heating chamber 12 and the second heating chamber 13.

[0029] The first electric heater 30 is provided in the first heating chamber 12 and heats the molten metal to a predetermined first temperature. A total of 11 first electric heaters 30 are provided in the present embodiment, but this number is not limited. The second electric heater 40 is provided in the second heating chamber 13 and heats the molten metal heated to the first temperature in the first heating chamber 12 to a second temperature exceeding the first temperature. A total of 6 second electric heaters 40 are provided in the present embodiment, but this number is also not limited.

[0030] The thermometers T1 to T11 are thermocouple type sensors and are respectively provided in the first heating chamber 12, the second heating chamber 13, and the hot water outlet chamber 14 to measure the temperature of the molten metal. This number is also not limited.

[0031] Although not shown in the figure, the control unit 100 includes a storage unit such as a CPU, a ROM, and a RAM, and controls the circulation pump 20, the first electric heater 30, and the second electric heater 40 based on the temperature information from the input thermometers T1 to T11 and the information of the non-ferrous metal material.

[0032] In addition, the non-ferrous metal in this embodiment is an aluminum alloy. The first temperature is set to 650°C to 720°C, which is suitable for casting the casting product, for the molten aluminum alloy. The second temperature is set to 750°C, and the heat of the molten metal, which is about 100°C higher than the first temperature, is utilized to efficiently melt and raise the temperature of the non-ferrous metal introduced from the inlet 11 in a short time. Note that the first temperature and the second temperature can be changed depending on the type of non-ferrous metal to be melted and heated.

[0033] According to the circulation type non-ferrous metal melting furnace configured as described above, the control unit 100 increases the rotation speed of the circulation pump 20 as the input amount per unit time of the non-ferrous metal material introduced from the inlet 11 increases. Accordingly, the melting rate of the non-ferrous metal material increases, and the internal temperature of each of the electric heaters 30 and 40 can be suppressed.

[0034] In addition, the control unit 100 increases the rotation speed of the circulation pump 20 as the difference between the upstream molten metal temperature and the downstream molten metal temperature in the first heating chamber 12 increases, based on the temperatures detected by the thermometers T1 and T3. Also by this, the circulation amount of the molten metal increases, and the internal temperature of each of the electric heaters 30 and 40 can be suppressed. Furthermore, the control unit 100 increases the rotation speed of the circulation pump 20 as the difference between the upstream molten metal temperature and the downstream molten metal temperature in the second heating chamber 13 increases, based on the temperatures detected by the thermometers T5 and T7, not only on the first heating chamber 12 side but also on the second heating chamber 13 side, and similarly, the internal temperature of each of the electric heaters 30 and 40 can be suppressed.

[0035] In the embodiment of the present invention, the inlet 11 for the non-ferrous metal material provided on the downstream side of the second heating chamber 13 (the first inlet 11) can also have a second inlet 21 provided on the upstream side of the first heating chamber 12, as shown in FIG. 1. If the inlets 11 and 21 for the non-ferrous metal material are provided at two locations, the surface area of the non-ferrous metal material in contact with the circulating molten metal can be ensured to be large, and the non-ferrous metal material can be efficiently melted.

[0036] Alternatively, instead of or in combination with the inlets 11 and 21 for non-ferrous metal materials, as shown in FIG. 2, the non-ferrous metal materials can be freely introduced into the portions with high or low flow rates according to the velocity distribution of the circulating molten metal by using, for example, robot arms R1 and R2. According to this, the difference between the molten metal temperature on the upstream side and the downstream side of the first heating chamber 12 and the difference between the molten metal temperature on the upstream side and the downstream side of the second heating chamber 13 can be made as small as possible.

[0037] In the embodiment of the present invention, the gap passage 17a is provided on the upstream side of the second heating chamber 13, and the molten metal is caused to flow into the tapping chamber 14 through the flow guide passage 18. However, the present invention is not limited to this. As shown in FIG. 2, the gap passage 17a can be provided on the downstream side of the first heating chamber 12, and the molten metal can be caused to flow into the tapping chamber 14 through the flow guide passage 18. Further, the flow guide passage 18 provided with the degassing device 70 can be omitted, and the gap passage 17a can be directly communicated with the tapping chamber 14.

[0038] In the above embodiment of the present invention, the aluminum alloy is the object of melting and heating, but other non-ferrous alloys can be the object. Further, the first temperature and the second temperature can be appropriately changed according to the non-ferrous metal or the like to be treated.

Explanation of reference numerals

[0039] 1 Circulating non-ferrous metal melting furnace 10 Furnace body 10a Furnace wall 11 Inlet (first inlet) 12 First heating chamber 13 Second heating chamber 14 Tapping chamber 15 Intermediate wall 16 Gap passage 16a First gap passage 16b Second gap passage 17 Partition wall 17a Gap passage 18 Flow guide passage 20 Circulation pump 21 Second input port 30 First electric heater 40 Second electric heater 50 Circulating non-ferrous metal melting furnace 51 Melting chamber 52 Heating-up chamber 53 Dross removal chamber 54 Calming chamber 55 Hot water outlet chamber 56 Electric heater 70 Degassing device 100 Control unit R1, R2 Robot arms T1~T11 Thermometers

Claims

1. A method for melting a non-ferrous metal material using a circulation type non-ferrous metal melting furnace configured as follows: A first temperature raising chamber provided with a plurality of first electric heaters and a second temperature raising chamber provided with a plurality of second electric heaters are arranged side by side with an intermediate wall therebetween to form a circulation path for the molten metal. An inlet for the non-ferrous metal material is provided on one end side of the intermediate wall between the first temperature raising chamber and the second temperature raising chamber, and the other end side of the intermediate wall is communicated with a hot water outlet chamber from which the molten metal can be taken out. Temperature control is performed in each of the first temperature raising chamber and the second temperature raising chamber, and the molten metal is circulated through a circulation pump provided in the first temperature raising chamber, the second temperature raising chamber, or both. The method is characterized in that: As the input amount of the non-ferrous metal material per unit time increases, the rotational speed of the circulation pump is increased.

2. The method for melting a non-ferrous metal according to claim 1, characterized in that as the difference between the upstream molten metal temperature and the downstream molten metal temperature in the first temperature raising chamber increases, the rotational speed of the circulation pump is increased.

3. The method for melting a non-ferrous metal according to claim 1, characterized in that as the difference between the upstream molten metal temperature and the downstream molten metal temperature in the second temperature raising chamber increases, the rotational speed of the circulation pump is increased.

4. A method for melting a non-ferrous metal material using a circulation type non-ferrous metal melting furnace configured as follows: A first temperature raising chamber provided with a plurality of first electric heaters and a second temperature raising chamber provided with a plurality of second electric heaters are arranged side by side with an intermediate wall therebetween to form a circulation path for the molten metal. An inlet for the non-ferrous metal material is provided on one end side of the intermediate wall between the first temperature raising chamber and the second temperature raising chamber, and the other end side of the intermediate wall is communicated with a hot water outlet chamber from which the molten metal can be taken out. Temperature control is performed in each of the first temperature raising chamber and the second temperature raising chamber, and the molten metal is circulated through a circulation pump provided in the first temperature raising chamber, the second temperature raising chamber, or both. The method is characterized in that: As the difference between the upstream molten metal temperature and the downstream molten metal temperature in the first temperature raising chamber increases, the rotational speed of the circulation pump is increased.

5. A first heating chamber provided with a plurality of first electric heaters and a second heating chamber provided with a plurality of second electric heaters are arranged side by side with an intermediate wall therebetween to form a molten metal circulation path. An inlet for a non-ferrous metal material is provided on one end side of the intermediate wall between the first heating chamber and the second heating chamber, and the other end side of the intermediate wall is communicated with a hot water outlet chamber from which the molten metal can be taken out. Temperature control is performed in each of the first heating chamber and the second heating chamber, and the molten metal is circulated through a circulation pump provided in the first heating chamber, the second heating chamber, or both. A method for melting a non-ferrous metal material using a circulation type non-ferrous metal melting furnace configured as described above, A method for melting a non-ferrous metal, characterized in that the rotational speed of the circulation pump is increased as the difference between the upstream molten metal temperature and the downstream molten metal temperature in the second heating chamber increases. Claim 6 The method for melting a non-ferrous metal according to any one of claims 1 to 5, characterized in that the inlet for the non-ferrous metal material is provided on the upstream side of the first heating chamber and the downstream side of the second heating chamber. Claim 7 The method for melting a non-ferrous metal according to any one of claims 1 to 5, characterized in that the non-ferrous metal material can be introduced into a portion with a high flow rate or a low flow rate according to the velocity distribution of the circulating molten metal.

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