WO2021235008A1

WO2021235008A1 - Method and apparatus for melting aluminum cutting chips

Info

Publication number: WO2021235008A1
Application number: PCT/JP2021/003027
Authority: WO
Inventors: 洋二青木; 雅之藤川; 晶中林; 英之川田; 慎山口; 孝明美濃
Original assignee: 株式会社広築
Priority date: 2020-05-22
Filing date: 2021-01-28
Publication date: 2021-11-25
Also published as: JP2021183712A; JP6975289B1

Abstract

[Problem] The present invention provides a method and an apparatus for melting aluminum cutting chips, in which the cutting chips that are dusts produced by cutting metal aluminum or an aluminum alloy are melted to produce an aluminum melt. [Solution] The method comprises: a preheating step for removing an oily water component from a cutting oil adhered to aluminum cutting chips by evaporation or decomposition; and a melting step for charging and diffusing the preheated cutting chips in an aluminum melt to melt the cutting chips. A melting apparatus is provided, which is configured such that the preheated aluminum cutting chips that are pushed and charged with a ceramic-made rotary cylindrical body arranged in the aluminum melt are diffused through a tip part while heating and melting the preheated aluminum cutting chips to melt the aluminum cutting chips.

Description

Aluminum chip melting method and melting device

The present invention relates to an aluminum chip melting method and a melting device, and more specifically, to obtain an aluminum molten metal by melting chips which are cutting chips of an aluminum metal or an alloy, the present invention produces an aluminum molten metal having good quality and a high yield. It also relates to a melting method and a melting device for aluminum chips that can achieve safe and stable operation while paying attention to environmental conservation.

Aluminum metal requires a large amount of electric power to manufacture, so its manufacturing cost is high. Therefore, as long as the scraps and scraps generated when processing aluminum products take the form of aluminum metal, their value is great considering the manufacturing cost. Therefore, aluminum scraps, cans, etc. are also recycled and melted to be used as raw materials for aluminum products. Cutting chips of aluminum-based metal, so-called aluminum chips, are treated in the same manner.

As the cutting oil used for cutting an aluminum-based metal, a water-containing cutting oil having a water-soluble cutting oil diluted with water having a content of 10% and a water content of about 90% is often used. Generally, aluminum chips discharged from a cutting machine are accompanied by cutting oil of 10 to 30 wt% by weight. Aluminum chips in this state are called wet chips. Since the oil content of water-soluble cutting oil usually contains many oxygen atoms in the form of hydroxyl groups (OH) and carbonyl groups (COOH) to ensure compatibility with water, wet chips are used. When charged into the molten aluminum and dissolved, oxygen atoms in the cutting oil oxidize the molten aluminum to generate aluminum oxide, and scum mixed with the molten aluminum is generated. As a result, there are problems that the melting yield is lowered, the quality of the molten metal is also deteriorated, and the scum removal work on the surface of the molten aluminum is required. Further, when the chips to which water is attached are allowed to enter the molten metal, an explosion occurs. Therefore, at a minimum, the water must be completely removed.

The end of the aluminum chip is in the state of a thin blade, and when it is moved, the end is destroyed to generate fine metallic aluminum powder. Since cutting oil is adsorbed on the chips of ordinary aluminum chips, they do not scatter in the atmosphere. However, when the wet chips are dried, the fine metallic aluminum powder is released from the cutting oil and scattered in the atmosphere, which causes a fire or a dust explosion. In addition, when handling aluminum chips in a dry state after being dried, metal aluminum powder is generated and scattered in the atmosphere, which causes a fire or a dust explosion. Therefore, if dry aluminum chips are present, they should be handled with great care, such as by completely burning the fine metallic aluminum powder in the surrounding atmosphere to convert it into harmless aluminum oxide and then dissipating it into the atmosphere. You have to be careful. In the following, wet aluminum chips are referred to as dry chips, and aluminum chips that have been dry preheated to remove the chips and cutting oil are referred to as dry chips.

It is desirable from the viewpoint of resource saving and energy saving that the chips are redissolved and recycled as aluminum. As an example, the chips are calcined in a rotary kiln so that aluminum is not oxidized to volatilize and remove oil and water, and then the dry chips are made into briquettes and charged into an aluminum melting furnace. There is one that obtains molten aluminum. This equipment is good in that the chips are reused, but the equipment is large-scale because it requires a wide variety of equipment, and dust collectors and ducts made of metallic aluminum powder generated from the rotary kiln during drying and calcination. There was a problem such as the danger of ignition and explosion.

In order to solve the above-mentioned problems, the chips are pretreated to remove water in the cutting oil to leave only the oil content, and then melted in an aluminum melting furnace to obtain an aluminum molten metal, and the oil content is used. As prior art, a melting device and a melting method for the chips, which are gasified in a melting furnace, attracted to a heating burner of the melting furnace and burned, and used as a substitute for fuel to save energy and prevent air pollution, are disclosed.

According to WO2017 / 051586 ([0008], [0028-0029], [FIG. 1]), which is the prior art, the cutting oil described in (0003) is charged into the molten metal together with chips, so that the cutting oil is charged. A large amount of aluminum oxide, so-called scum, is generated together with the smoke generated from the minute, which lowers the melting yield and causes quality deterioration due to the increase in the hydrogen content of the molten aluminum, which requires scum removal work on the surface of the molten metal. It caused many problems.

In order to solve these problems, a heat pretreatment (hereinafter referred to as the pretreatment) for drying the water content of the chips and decomposing and evaporating the oil content of the cutting oil was performed, and then the pretreatment was performed. The essence of this chip is to dissolve aluminum chips (hereinafter referred to as dry chips) in a molten aluminum (hereinafter referred to as holding molten metal) to obtain a high-yield, high-quality aluminum molten metal. There is a prior art that provided a melting method and melting equipment.

JP-A-2019-183275 ([0006], [0014-0018], [0025-0032], [Fig. 4], [Fig. 5])

The prior art is a region in which the dry chips are blocked from the atmosphere to prevent the dry chips provided in the holding molten metal from floating on the surface of the holding molten metal (hereinafter referred to as the floating prevention region). It is pushed in and melted. In order to completely prevent the dry chips pushed into the holding molten metal, the floating prevention region is provided with a region having a ceiling (Jinkasa ceiling) surrounding a downwardly inclined surface, and the dry cutting region is provided. The powder is pushed into the floating prevention region to prevent the dry chips from short-circuiting and floating, and a circulating molten metal flow is formed at a place corresponding to the apex of the floating prevention region, and the dry chips are formed. A mechanical stirrer with blades was provided to destroy the oxide film covering the surface of the dry chips and disperse the molten aluminum inside the dry chips (hereinafter referred to as molten chips) into the holding molten metal to promote dissolution. It is a thing.

The prior art is that the dry chips are pushed into the floating prevention region and heated and melted in the holding molten metal, and the dry chips pushed into the floating prevention region float on the surface of the holding molten metal. It moves on the circulating molten metal flow generated by the stirring blade installed at the apex of the floating prevention region, and at that time, it destroys the oxide film covering the surface of the dry chips. Although it was an excellent technology in that respect, it had various drawbacks as shown below, and it was not possible to realize smooth and stable operation.

The first technical problem is that the dry chips pushed into the holding molten metal are deficient in the idea that they are heated and melted by the heat held by the holding molten metal. Since each of the dry chips moves freely in the holding molten metal according to the circulating molten metal flow, it has not been possible to regulate the individual residence time in the holding molten metal. Therefore, some of the dry chips were separated from the chip floating prevention region and floated on the surface of the holding molten metal in an undissolved state due to insufficient heat exchange. Not only did it reduce the melting yield, but it also generated the extra work of cleaning the surface of the retained molten metal.

The second technical problem was that in the pretreatment, it was considered that the dry chip temperature after the treatment should be higher. The reason is that it is difficult to control the contact time between the dry chips pushed into the holding molten metal and the holding molten metal, and due to the anxiety, a higher dry chip temperature may be advantageous for melting. It was from an idea. However, the higher the temperature of the dry chips after the pretreatment, the thicker the oxide film formed on the surface of the dry chips, and the more difficult the oxide film is to be destroyed, so that the shape of the dry chips is maintained. Some of them surfaced on the surface of the retained molten metal. This not only reduced the melting yield, but also caused extra work of cleaning the surface of the holding molten metal.

The third technical problem is that it was difficult to form this with ceramics due to the shape of the chip floating prevention region, and since iron-based materials were used, iron was eroded by the holding molten metal and could not be maintained. The problem occurred.

The present invention solves these problems, and melts the pretreated dry chips in an aluminum melting furnace to obtain a high-yield, high-quality molten aluminum, and operates stably for a long time. It is an object of the present invention to provide a possible dissolution method and dissolution equipment for the chips.

In order to achieve the above object, the aluminum chip melting method according to claim 1 of the present invention is a method of dissolving the chips to which water-containing cutting oil is attached to obtain an aluminum molten metal. The pretreatment step of drying and preheating the powder in a temperature range from at least the temperature at which the water content of the water-containing cutting oil finishes evaporating to the temperature at which the oil content decomposes and evaporates, and the pretreatment. A storage space for storing the dry chips later in a state of being shut off from the atmosphere and transferring them to the next step, and a melting step of obtaining the aluminum molten metal by pushing the dry chips into the holding molten metal and charging them to dissolve them. In the method for dissolving the chips, the pretreated dry chips are partially immersed in the holding hot water in the depth direction with the lower end open, and are not eroded by the holding hot water. The dry chips are transferred into a rotating cylindrical body made of ceramics, and the dry chips corresponding to the amount of melting at one time are charged into the holding molten metal by the push rod of the pushing device, and the dry chips are held. After heating to melt the aluminum inside the dry chips (hereinafter, the melted aluminum portion of the chips is referred to as the chip melt), the chip melt is poured from the tip of the rotating cylinder. At the time of discharge, the oxide film covering the dry chips is finely destroyed, and the finely divided oxide film and the chip melt are discharged into the holding molten metal to ensure the dissolution of the dry chips. It is characterized by homogenizing the chip molten metal and the holding molten metal.

Due to the configuration of claim 1, the prior art could not control the time of the dry chips in the holding molten metal in the chip floating prevention region in the holding molten metal, but in the present technology, as the chip floating prevention region. Using a cylindrical tube (hereinafter referred to as the cylindrical tube) manufactured of ceramics and rotating along the central axis of the cylinder, the lower part of the cylindrical tube is open and immersed in the holding molten metal. An input port for the dry chips was provided on the upper part of the cylindrical tube, and the dry chips were modified so as to float and pile up on the surface of the molten metal inside the cylindrical tube. After that, the dry chips inside the cylindrical tube can be pushed into the molten metal by a required amount with a push rod, and can be held as it is for the time required for melting. By doing so, the dry chips cannot move freely in the holding molten metal, and can be restrained in the holding molten metal only for the time required for heating and melting by the holding molten metal. This made it possible to completely dissolve 100% of the dry chips when they were discharged from the lower part of the cylindrical tube into the holding molten metal. Further, by rotating the cylindrical tube along the central axis of the cylinder, the holding molten metal temperature is made uniform, the holding molten metal component is made uniform, and the completely melted dry chips are held from the lower end of the cylindrical tube. It was possible to finely destroy the oxide film that covered the dry chips when they were discharged inside, and to discharge the molten metal inside.

According to the second aspect, the stirring power of the holding molten metal can be strengthened by making unevenness on the outer side wall of the region immersed in the holding molten metal of the cylindrical tube or by attaching a protrusion. As a result, the temperature of the retained molten metal is made uniform, the components of the retained molten metal are made uniform, and the heat conduction from the retained molten metal to the inside of the cylindrical tube is promoted. In addition, by stirring the retained molten metal, the oxide film covering the dry chips is destroyed, and what is dispersed in the retained molten metal aggregates and coalesces to increase the size and become oxide-based defects. It was possible to prevent it and obtain an extremely high quality molten aluminum.

According to the configuration of claim 3, a serrated protrusion is provided at the outlet of the cylindrical tube, or a rod-shaped ceramic that rotates integrally with the cylindrical tube is provided in the vicinity of the outlet of the cylindrical tube in the radial direction. The oxide film covering the dry chips was destroyed, and it became possible to uniformly disperse the oxide as an extremely fine oxide in the holding molten metal. As described above, extremely fine oxides are not recognized as oxide-based defects in the molten metal, so that the quality of the obtained molten metal is excellent.

Further, as described above, for the purpose of evaporating the water content of the water-soluble cutting oil and decomposing and evaporating the oil content, the thermal weight of the chips accompanied by the water-soluble cutting oil-differential thermal analysis (TG-DTA analysis). ) Was performed. As a result, it was found that the water was removed by heating to around 135 ° C., and the oil content was oxidized and generated heat in the range of 200 to 400 ° C. (see FIG. 7). Further, according to the thermal weight-differential thermal analysis (TG-DTA analysis) when the chips were heated in the atmosphere, the chips rapidly generated heat at around 580 ° C and exhibited an increase in weight. It is determined that this is because the metallic aluminum portion of the chips has undergone an oxidation reaction. (See FIG. 8). Based on these analysis results, the pretreatment conditions for the chips accompanied by the hydrous cutting oil were set. Further, after heating the chips accompanied by the hydrous cutting oil to 400 ° C. to 500 ° C., 550 ° C. and 570 ° C. in the atmosphere, the color tone of the surface of the chips was observed. It had a metallic luster at 500 ° C. or lower, but became gray at 550 ° C. and brown at 570 ° C. This indicates that the oxide film on the surface of the chips becomes thicker as the temperature rises.

According to the configuration of claim 4, regarding the chip temperature after the treatment in the pretreatment, complete removal of water is an essential condition in the pretreatment step, and complete decomposition of cutting oil is a preferable condition. In the present technique, as described in (0019) and (0021), the following pretreatment conditions are set in order to prevent the formation of the dry chips having a thick oxide film. From the viewpoint of complete decomposition of cutting oil, 450 ° C or higher is preferable. On the other hand, when the chip temperature after the treatment exceeds 550 ° C., the surface of the chips is covered with a thick oxide film. Therefore, the chip temperature after the pretreatment is in the range of 400 ° C to 570 ° C, preferably in the range of 450 ° C to 550 ° C, and most preferably in the range of 490 ° C ± 30 ° C. It was found from the dissolution experiments described below that it is optimal in terms of both reduction. That is, according to a melting experiment on an actual scale of 100 kg / hr, when the chip temperature was lower than 450 ° C., it became necessary to suspend and wait for the pushing operation in order to increase the pushing resistance of the pushing device. .. Further, when the temperature was 550 ° C. or higher, the chips floated on the surface of the holding molten metal while partially maintaining the shape of the chips, and it was necessary to clean the surface of the molten metal. When the chips were controlled to 490 ° C., the pressing resistance of the pressing device did not increase, and there were no chips floating on the surface of the holding molten metal. Further, during the operation, the chip temperature fluctuated between 470 ° C and 510 ° C, but the melting operation was stable and no problem occurred during the operation for 6 hours.

According to the configuration of claim 5, as described in the dissolution experiment of (0022), by controlling the temperature of the gas for pretreatment to 550 ° C. or lower, the pretreatment apparatus can be used at all locations in the pretreatment apparatus. The possibility of exceeding the melting point of chips has been eliminated. As a result, the clogging accident in the pretreatment device was completely eliminated, and long-term operation was possible.

According to the sixth aspect, the ceramic tube can be used as a material by forming the chip floating prevention region into a cylindrical tube shape. As a result, the material forming the chip floating prevention region was not melted by the holding molten metal, and stable operation was realized.

According to the configuration of claim 7, when the dry chips are pushed into the holding molten metal, the pushing rod is operated so that the dry chips are always interposed between the holding molten metal in the rotating cylinder and the tip of the pushing rod. By controlling and preventing the tip of the push rod from coming into contact with the holding molten metal, it was possible to completely prevent the dry chip pushing device from being clogged, and stable operation was made possible.

According to the configuration of claim 8, the cylindrical tube rotates while holding the dry chips inside, and serves to supply the heat held by the external holding molten metal to the dry chips inside. Therefore, it is preferable that the material forming the cylindrical tube has high thermal conductivity. However, even when a material having low thermal conductivity is used, the inside and outside of the cylindrical tube can be provided by providing a plurality of through holes having a size that the dry chips cannot pass through on the side wall of the holding molten metal immersion region of the cylindrical tube. It became possible to promote heat conduction by directly contacting with the holding molten metal of No. 1 and realized smooth melting of the dry chips.

According to the configuration of claim 9, if the holding molten metal temperature is maintained above the melting point of the chips in principle, it can be transmitted to the inside of the cylindrical tube over time to dissolve the dry chips inside. However, the higher the temperature of the molten metal, the shorter the time required to transfer the heat required for melting. On the other hand, there is another problem that the retained molten metal is oxidized when the temperature of the retained molten metal is high. According to the experiment, when the temperature of the retained molten metal exceeds 900 ° C., the oxide film on the surface of the molten metal continues to grow and forms a huge alumina deposit generally called "ghost". Therefore, it is generally preferable to handle the molten aluminum at 800 ° C. or lower. In the present invention, it is important that the cylindrical tube rotates stably, so it is important that the thickness of the molten metal surface oxide film is thin and does not hinder the rotation of the cylindrical tube. On the other hand, from the viewpoint of the melting capacity of the chip melting furnace, we want to melt the required amount in the shortest possible time. An optimum holding molten metal temperature satisfying both of these conditions was found in the range of 680 ° C to 750 ° C, but most preferably in the range of 700 ° C to 720 ° C.

The feature of the present invention is that the heat held by the holding molten metal heats and melts the chips pushed into the holding molten metal, and further destroys the oxide film covering the surface of the melted chips to make them finer and hold them. In the technique of dispersing in the molten metal, the time for heating the chips pushed into the holding molten metal can be controlled as much as necessary. What makes this possible is the use of a rotating cylindrical tube made of ceramics as a chip floating prevention region. Therefore, as a requirement for realizing the present invention, firstly, it is necessary to heat the holding molten metal. There are three methods for heating the holding molten metal: a method of heating the holding molten metal from the outside with a combustion flame like a crucible, a method of directly heating the holding molten metal with electric heating, and a method of heating the holding molten metal with radiant heat from the surface. As a second requirement, the pretreatment for drying and preheating wet chips is essential. Regarding the heat source at the time of the preheat treatment, there are a method using a gas combustion flame and a method of electrically heating. In the method of using a gas combustion flame for heating the holding molten metal, the exhaust gas can be used. However, when the holding molten metal is electrically heated, there are a method of newly providing a gas combustion chamber in which a gas having a target temperature is generated and flowing to the pretreatment apparatus, and a method of electrically heating the pretreatment apparatus. As a third requirement, graphite, silicon carbide, silicon nitride, alumina, and aluminum nitride can be used as the material of the ceramic cylindrical tube. Since the thermal conductivity of graphite is higher than that of molten aluminum, the heat of the holding molten metal can be easily transferred to the inside of the cylindrical tube. From the viewpoint of thermal conductivity, sintered reaction silicon carbide is also good. On the other hand, since graphite is easily oxidized at a high temperature, it is necessary to maintain a high temperature atmosphere of 800 ° C. to 900 ° C. on the surface of the holding molten metal, especially when the holding molten metal is radiated and heated by combustion gas. It is necessary to take appropriate measures to prevent oxidation of the surface of the graphite tube. Since the thermal conductivity of silicon nitride and alumina ceramics is lower than that of molten aluminum, in order to transfer the heat of the holding molten metal into the cylindrical tube, as described in claim 8, as described in claim 8. It is necessary to make a slit or a hole in the wall of the cylindrical tube to the extent that the strength can be maintained so that the holding molten metal comes into direct contact with the molten metal inside the cylindrical tube to improve the thermal conductivity.

Further, the aluminum chip melting device according to claim 10 is an device for obtaining a molten aluminum by implementing the method for melting aluminum chips according to claims 1 to 9, wherein the hydrous cutting oil is attached. A preheating device that shields the chips from the atmosphere and preheats the chips within a temperature range from the temperature at which the water content of the cutting oil containing water at least finishes evaporating to the temperature at which the oil decomposes and evaporates, and the dry chips are made of aluminum. Holding of a chip melting furnace In an aluminum chip melting device consisting of a melting device that is pushed into a molten metal and melted to obtain an aluminum molten metal, the melting device comprises an aluminum melting furnace and the dry chips. A rotating cylinder made of ceramics that is partially immersed in the holding molten metal in the depth direction and is not eroded by the holding molten metal, and the dry chip pushing cylinder that supplies the dry chips into the inside of the cylinder. It is characterized by being composed of.

With this configuration, a preheating device removes oil and moisture from the chips containing hydrous cutting oil, and then a melting device holds the dry chips by a preheating chip pushing cylinder. A rotating cylinder partially immersed in the molten metal. After heating and raising the temperature based on the atmospheric temperature of the upper part of the molten metal and the temperature of the retained molten metal in the rotating cylinder, the dry cutting is performed by diffusing and supplying from the tip of the rotating cylinder to a deep place in the retained molten metal. The dissolution of the powder can be performed quickly and completely without reoxidation, and the quality of the molten aluminum can be maintained and the dissolution capacity can be improved.

Further, according to the configuration of claim 11, the heat transfer area on the surface of the rotating cylinder is increased by providing the cylindrical portion of the rotating cylinder with irregularities along the axial direction or a plurality of protruding portions. By causing turbulence on the contact surface with the holding molten metal due to the unevenness or protruding part and increasing the amount of heat transfer from the holding molten metal, the temperature rise of the dry chips in the rotating cylinder is achieved, and the amount of dissolution is increased. Can be increased. It also has the effect of suppressing the amount of alumina generated. Further, by stirring and mixing the retained molten metal, undissolved alumina can be uniformly diffused, and the quality of the retained molten metal can be homogenized.

Further, according to the configuration of claim 12, a plurality of rack-shaped tooth molds are provided at the tip discharge portion of the rotating cylinder, and the oxide film covering the molten aluminum in the dry chips is destroyed to be fine. The quality of the retained molten metal is further improved by diffusing and discharging it as an oxide. In addition, the dry chips containing molten aluminum are crushed from the tip of the rotating cylinder, discharged into the holding molten metal, and diffused well to promote the dissolution of the dry chips and completely dissolve them. Contribute to.

Further, according to the configuration of claim 13, a single or a plurality of crossed ceramic rod-shaped portions are provided inside near the discharge end of the rotating cylinder, and aluminum melted inside the dry chips inside the cylinder is included. After breaking the oxide film and making it finer, it is charged into the holding molten metal to promote the dissolution in the holding molten metal and contribute to the improvement of the molten metal quality.

Further, according to the configuration of claim 14, by providing a plurality of through holes in the tubular portion of the rotating cylinder, the holding molten metal comes into contact with or invades the dry chips inside the rotating cylinder through the through holes. It promotes heat exchange between the dry chips inside and the retained molten metal outside, and contributes to promoting the melting of aluminum in the dry chips.

Further, according to the configuration of claim 15, the rotating cylinder can be made of graphite, silicon carbide, silicon nitride, alumina, or aluminum nitride, which is a material that is not eroded by the holding molten metal, and is a rotating cylinder. Since the life of the silicon is not eroded by the retained molten metal, it can be extended, which contributes to the improvement of the capacity and operating rate of the aluminum chip melting device. Further, in the case of graphite or silicon carbide as a material having high thermal conductivity, it contributes to rapid heating of the dry chips of the rotating cylinder. It was

According to the aluminum chip melting method according to claims 1 to 9 of the present invention, when the preheated aluminum chips are pushed into the molten aluminum and melted, the rotating cylinder immersed in the molten aluminum is used. It is a melting method that can obtain a high-quality molten aluminum with almost no alumina scum, and has a high yield of melting aluminum chips by charging the aluminum chips via the route. Further, according to the aluminum chip melting apparatus according to claims 10 to 15 of the present invention, aluminum chips are melted by adopting a rotating cylindrical body of ceramics which is immersed in the molten aluminum and is not eroded by the molten aluminum. It is possible to improve the operating rate of the device and the processing capacity, improve the aluminum melting yield, and improve the quality of the molten aluminum. In this way, the present invention contributes to the utilization of resources and energy saving.

FIG. 1 is a schematic overall layout of an aluminum chip melting device according to the present invention. FIG. 2 is a schematic state diagram in which the preheated aluminum chips according to the present invention are charged into the chip pushing device. FIG. 3 is a schematic phase diagram of pushing the preheated aluminum chips according to the present invention into the molten metal from the chip pushing device. FIG. 4 is a schematic phase diagram showing the behavior of the preheated aluminum chips according to the present invention in the chip pushing device. FIG. 5 is a schematic perspective view of a rotating cylinder of the chip pushing device according to the present invention. FIG. 6 is a flow chart showing a method for melting aluminum chips of the present invention. FIG. 7 is a representative example of a thermal weight-differential thermal analysis chart of hydrous cutting oil of aluminum chips. FIG. 8 is a representative example of a thermogravimetric-differential thermal analysis chart in which aluminum powder is heated in the atmosphere.

The process of the method for dissolving the chips accompanied by the water-containing cutting oil according to the present invention will be described with reference to the flow chart of FIG. The chips accompanied by a water-containing cutting oil consisting of an emulsion state oil and water reduce the amount of the water-containing cutting oil via a centrifuge. After that, a sizing step for adjusting the particle size of the chips can be added (a). Next, the chips accompanied by the hydrous cutting oil go through the pretreatment step (b) for the purpose of complete removal of water, decomposition and evaporation of oil under the condition of air shutoff, and under the condition of air shutoff. The chips are transferred to a storage space for storage and transfer, charged into the inside of a rotating cylindrical body made of ceramics by a pushing device under the condition of air shutoff, and pushed into the holding molten metal by the required amount to melt. The state is maintained for the required time, and when the time to complete the dissolution elapses, the next required amount of the chips is pushed into the holding molten metal, and at the same time, the oxide film covering the chips at the lower end of the rotating cylinder. It is composed of a chip indentation melting step (c) in which the powder is broken down into fine particles and then discharged into the holding molten metal.

As the aluminum chip melting furnace used in the method for melting aluminum chips and the melting device of the present invention, a rutsubo furnace, a immersion heater type electric heating furnace, a gas combustion type radiant heating furnace and the like can be applied. These aluminum chip melting furnaces include a rutsubo furnace for indirectly heating the molten aluminum, an electric heating furnace with a dip heater, and a gas combustion type radiant heating furnace for directly radiating and heating the molten aluminum from the surface of the molten metal.

Considering the heat transfer to the rotating cylinder, in the former case, only the molten metal is heated and the heat transfer from the molten metal is the main, but in the latter case, the place outside the molten metal at the top of the rotating cylinder is , There is radiation from the flame and convection heat transfer from the atmosphere, and the part in the molten metal receives the heat transfer from the molten metal. In this way, the preheated aluminum chips in the rotating cylinder are shielded from the outside air, efficiently heated and heated, and the contained metallic aluminum portion melts without increasing the oxide film of the chips.

An example in which a rutsubo-type aluminum chip melting furnace is used as an embodiment of the aluminum chip melting apparatus 1 to which the method of the present invention is applied will be described with reference to FIG. The aluminum chip melting device 1 includes a drying preheating device 3 that removes water and oil in the cutting oil to which aluminum chips adhere, and a melting furnace combustion burner 2-for melting the preheated aluminum chips in the molten metal M. The rutsubo-type aluminum chip melting furnace 2 having the third, the chip pushing-out device 5 for charging the preheated aluminum chips into the molten metal M of the rutsubo-type melting furnace 2, and the chip pushing-out device 5 are preheated aluminum. It is composed of a chip pushing charging device 4 for charging chips.

Further, as shown in FIGS. 1, 2, 3, and 4, between the drying preheating device 3 and the rutsubo-type aluminum chip melting furnace 2, the chip pushing-in device 4 which is a feature of the present invention A chip pushing / discharging device 5 is installed. The chip intrusion device 4 and the chip intrusion / discharge device 5 have a cylindrical shape having substantially the same diameter, and the chip intrusion device 4 having the chip intrusion piston 4-2 is fixed, but the powder intrusion device 4 is fixed. The discharge device 5 includes a rotary cylinder 5-1 that rotates around the axis, and a cylinder rotation drive device 5-6 is provided in the structure on the furnace lid 7-2. Since 1/2 to 1/3 of the total length of the rotating cylindrical body 5-1 is immersed in the molten aluminum M and heated from the molten aluminum M, graphite and silicon carbide are ceramics that are not eroded by the molten aluminum M. It can be selected from quality, silicon nitride, alumina, and aluminum nitride. Among them, graphite and silicon carbide are materials having high thermal conductivity and are suitable.

Further, as shown in FIG. 5, the rotating cylinder 5-1 is a relatively elongated cylinder having a total height: diameter of 4 to 2.5, and the outlet end forms a tooth-shaped discharge portion 5-2. The inlet end 5-6 is connected to a rotation driving device 5-6 that rotationally drives the rotating cylinder. Further, it is preferable to provide as many cylindrical body side projecting portions 5-3 as the number of tooth molds 5-2 on the surface of the rotating cylindrical body 5-1 in the length direction, and the projecting portions 5-3 in the molten metal M. A turbulent flow is generated in the molten metal M due to the rotation of the molten metal M, and the heat transfer from the molten metal M to the rotating cylinder 5-1 can be promoted and the molten metal M can be stirred and mixed. Further, since a circulating flow is generated in the molten metal M, the heat transfer of the combustion heat of the chip melting furnace burner 2-3 from the furnace wall to the molten metal M is also improved with respect to the aluminum molten metal M whose thermal conductivity is lower than that of the solid. Further, on the surface of the rotating cylindrical body 5-1, a cylindrical body through hole 5-4 is provided at a position close to the surface of the molten metal M between the protruding portions 5-3 on the side of the cylindrical body, and the molten metal M and the molten metal M are provided. It promotes the melting of aluminum in the chips by allowing contact with the preheated aluminum chips inside to improve heat transfer. Further, a single or a plurality of stirring rods 5-5 are provided at positions near the discharge end of the rotating cylinder 5-1, and the preheated aluminum chips inside are covered with an oxide film of the outer capsule by stirring. Is crushed to promote the dissolution of chips in the molten metal M and the dispersion of the oxide film. Further, the tooth-shaped discharge portion 5-2 at the discharge end described above is a molten state in which the preheated aluminum chips are heated and heated by the molten metal M in the rotating cylinder 5-1 and covered with an oxide film of the chips. Aluminum can be crushed and diffused and discharged into the molten metal M to produce a high-quality molten aluminum. The rotary cylinder 5-1 is preferably made of a material that does not erode the molten aluminum M, and graphite, silicon carbide, silicon nitride, alumina, or aluminum nitride can be used. Of these, graphite (110 W / M / K) and silicon carbide (155 W / M / K), which have high thermal conductivity, are preferable.

Further, as shown in FIG. 4, a chip pushing and discharging device 4 is mounted on the chip pushing and discharging device 5, and the preheated aluminum chips are pushed by the chip pushing and discharging device 4. It is sent to the discharge device 5 and supplied into the molten metal M. In the chip pushing piston loading device 4, the chip pushing piston 4-2 is inscribed inside the chip pushing cylinder cylinder 4-1 and the chip pushing piston rod from the upper chip pushing drive cylinder unit 4-4 is provided. 4-3 is connected to the chip pushing piston inner cylinder 4-2b, and the fireproof piston head 4-2a fastened to the tip of the chip pushing piston inner cylinder 4-2b can be moved up and down. Further, the lower end of the stroke of the piston head 4-2a is spaced from the level of the molten aluminum in the rotating cylinder 5-1 with chips interposed therebetween to prevent melting damage of the piston head 4-2a. ing. In addition, as a quantitative buffer for the preheated aluminum chips 6 that are intermittently charged into the rotating cylinder 5-1, an air-blocked storage space 4 composed of a discharge chute 3-2c and a chip inlet chute 4-5. -6 is provided.

Further, when the behavior of the preheated aluminum chips 6 is explained with reference to FIGS. 2, 3 and 4, the bulk specific gravity (0.3) of the preheated aluminum chips 6 is higher than that of the molten metal M (specific density 2.3). It is considered that buoyancy is generated with respect to the molten metal M even if it is low and filled and the specific gravity is high, and the inside of the rotating cylinder 5-1 is accumulated and clogged from the tip portion. Therefore, the preheated aluminum chips 6 are deposited from the vicinity of the lower part of the chip pushing cylinder cylinder 4-1 to the tip end of the rotary cylinder 5-1 via the discharge chute 3-2c from the preheated screw feeder (not shown). ing. On the other hand, the chip pushing piston 4-2 intermittently moves up and down by the stroke ST, and accumulates in the air-blocked storage space 4-6 composed of the discharge chute 3-2c and the chip inlet chute 4-5. The preheated aluminum chips 6 are pushed toward the preheated aluminum chips 6 deposited on the rotating cylinder 5-1 and the preheated aluminum chips 6 corresponding to the pushing amount are discharged from the tip of the rotating cylinder 5-1. It is diffused and discharged from 5-2 into the molten metal M and completely melted to generate the molten metal M. Therefore, the aluminum chips 6 supplied from the rotary cylinder 5-1 into the molten metal M are discharged with the intermittent pushing down of the chip pushing piston 4-2. Further, the aluminum chips 6 staying in the rotating cylinder 5-1 are short-circuited and rarely move up and down during the suspension of the pressing cycle, and are sufficiently heated and raised by the molten metal M through the wall surface of the rotating cylinder 5-1. The aluminum portion covered with the oxide film on the surface of the hot chips 6 is considered to be melted. Further, the supply amount of the preheated aluminum chips 6 to the rotating cylinder 5-1, in other words, the dissolution amount can be adjusted by the pressing frequency of the chip pushing piston 4-2.

Further, as shown in FIG. 1, the rutsubo-type melting furnace 2 of the aluminum chip melting device 1 is surrounded by a furnace wall refractory 2-4, a furnace lid refractory 2-5, and a furnace bottom refractory 2-6. It is installed on the furnace mounting table 2-2 in the melting furnace combustion chamber 2-7. The melting furnace combustion burner 2-3 is provided in the corner near the bottom of the melting furnace combustion chamber 2-7, and the combustion exhaust gas outlet is at the upper part of the melting furnace combustion chamber 2-7, with the combustion burner 2-3. Since the axis is offset, the flame of the combustion burner 2-3 becomes a swirling flow that licks the outer wall of the rutsubo-type melting furnace 2 from the bottom to the top, and heats the rutsubo-type melting furnace 2. The crucible type melting furnace 2 is mainly formed of a carbon refractory material in the shape of a pot, holds an aluminum molten metal M having a melting point of about 660 ° C. inside, and swirls the outer wall from the bottom to the top of the melting furnace combustion burner 2-3. Since it is heated by the flow flame, the melting furnace 2 is indirectly heated by the combustion burner 2-3. Usually, the combustion chamber temperature of the melting furnace is in the range of 700 ° C. to 1000 ° C.

(Example)
Using the method and equipment of the present invention, 700 kg of aluminum chips having an oil content of 2.2 to 3.0 is dried and preheated at 450 to 470 ° C. in a graphite crucible type melting furnace 2 (diameter 900 mm, height 1000 mm), and then dried and preheated. It was melted with a molten aluminum solution at 700 ° C. to obtain an aluminum ingot (Al purity 99.8%) of about 690 kg. The charge of aluminum chips was 200 kg / hr. The graphite rotary cylinder 5-1 has an inner diameter of 300 mm, a height of 900 mm (immersion depth in molten metal 650 mm), a rotation speed of about 20 rpm, a chip pushing piston stroke of about 700 mm, a speed of about 700 mm, a speed of 20 sec, and a speed of 9 sec. It was operated in. The melting operation was stable, and the quality of the molten metal obtained the following results.

In order to investigate the cleanliness of the obtained molten metal, a comparative survey was conducted between a commercially available ADC12 standard ingot and an ingot obtained from the molten metal after 3 hours and 6 hours of continuous chip operation. As the evaluation method, evaluation by PoDFA and K mold evaluation were performed. These evaluations were requested from a specialized evaluation organization. The results are shown in Tables 1 and 2.

From the results in Table 1 above, the quality of the ingot obtained in operation is equivalent to that of a commercially available ingot. Further, from the results in Table 2, the cleanliness is a clean molten metal having Rank A of A, which is a level at which casting is acceptable.

Not only can it be used in the field of processing aluminum chips, but it can also be applied in the field of processing zinc, magnesium metals and their alloy chips.

1: Aluminum chip melting device
2: Aluminum chip melting furnace 2-1: Melting furnace body 2-2: Furnace mounting table
2-3: Melting furnace combustion burner 2-4: Furnace chamber refractory 2-5: Furnace lid refractory 2-6: Pot bottom refractory 2-7: Combustion chamber
3: Drying preheating device 3-1: Chip hopper 3-2: Screw conveyor 3-2a: Screw blade 3-2b: Conveyor outer cylinder
3-2c: Discharge part chute 3-3: Preheating duct 3-4: Drive motor 4: Chip pushing charging device 4-1: Chip pushing cylinder cylinder 4-2: Chip pushing piston 4-2a: Piston head 4-2b: Piston inner cylinder 4-3: Chip push-in piston rod 4-4: Chip push-in drive cylinder unit 4-5: Chip entry / exit chute 4-6: Storage space 5: Chip push-in / discharge device 5 -1: Rotating cylinder 5-2: Cylindrical tooth-shaped discharge part 5-3: Cylindrical side protruding part 5-4: Cylindrical through hole 5-5: Stirring rod
5-6: Rotary cylinder rotary drive device 6: Preheated aluminum chips M: molten metal

Claims

It is a method to obtain a molten aluminum by dissolving aluminum chips to which water-containing cutting oil is attached (hereinafter referred to as the chips), and the chips are at least from the temperature at which the water content of the water-containing cutting oil finishes evaporating. , A preheating step (hereinafter referred to as the pretreatment) in which the chips are shielded from the atmosphere to dry and preheat within a temperature range up to the temperature at which the oil decomposes and evaporates, and aluminum chips after the pretreatment (hereinafter referred to as the pretreatment). Hereinafter, the storage space for transferring the dry chips to the next step in a state of being shut off from the atmosphere, and the dry chips in the aluminum molten metal of the aluminum chip melting furnace (hereinafter referred to as holding molten metal). The dry chips are partially immersed in the holding molten metal in the depth direction in the melting step of pressing and charging into (referred to as) to melt and obtaining the molten aluminum, and the method of melting the aluminum chips. , It is pushed into a rotating cylinder made of ceramics that is not eroded by the holding molten metal, and the dry chips are heated to the holding molten metal temperature to melt the aluminum inside the dry chips, and then the tip of the rotating cylinder. When the dry chips are discharged from the aluminum, the oxide film covering the surface of the dry chips is destroyed and made finer, and then discharged into the holding molten metal to promote the dissolution of the dry chips. A method for melting aluminum chips, which comprises homogenizing a holding molten metal and detoxifying the oxides in the obtained molten aluminum to obtain an extremely high quality molten aluminum.
By providing unevenness along the axial direction or a plurality of projecting portions on the outer side wall of the holding molten metal immersion region of the rotating cylinder, the stirring force of the holding molten metal is strengthened, and the holding molten metal moves into the inside of the rotating cylinder. By improving heat transfer, the dissolution of the dry chips pushed into the rotating cylinder is promoted, the temperature and components of the holding molten metal are made uniform, and the oxide film covering the surface of the dry chips is aggregated. The method for dissolving aluminum chips according to claim 1, wherein the quality of the retained molten metal is maintained at a high level by preventing coalescence and dispersing the retained molten metal in a fine state.
The oxide film covering the dry chips is formed by providing a plurality of serrated irregularities on the tip discharging portion of the rotating cylinder, or by installing a ceramic rod in the vicinity of the tip discharging portion in the radial direction. The method for dissolving aluminum chips according to claim 1 or 2, further improving the quality of the molten aluminum obtained by breaking it into fine oxides and discharging it into the holding molten metal.
In the method for melting aluminum chips according to any one of claims 1 to 3, the preheating temperature of the dry chips is set to 400 ° C. to 570 ° C., preferably 450 ° C. to 550 ° C., most preferably 490 ° C. ± 20 ° C. A method for dissolving aluminum chips, which comprises controlling to.
The aluminum chip according to claim 4, wherein in the preheat treatment of the chip, the gas temperature for the pretreatment is regulated to 550 ° C. or lower so that the chip is heated so as not to exceed the melting point of the chip. Dissolution method.
The invention according to any one of claims 1 to 5, wherein the rotating cylinder is made of a ceramic that is not easily attacked by a holding molten metal of graphite, silicon carbide, silicon nitride, alumina, or aluminum nitride. How to dissolve aluminum chips.
When the dry chips are charged into the holding molten metal from the rotating cylinder, the tip of the dry chip pushing device that moves up and down inside the rotating cylinder is in the holding molten metal inside the rotating cylinder. Claim 1 is characterized in that the dry chips are charged into the holding molten metal with a layer of the dry chips interposed between the holding molten metal and the tip of the pressing device so as not to touch the holding molten metal. The method for dissolving aluminum chips according to any one of 1 to 6.
A plurality of through holes are provided in the side wall of the holding molten metal immersion region of the rotating cylinder to promote heat exchange between the dry powder inside the rotating cylinder and the external holding molten metal to promote the dissolution of the dry chips. The method for dissolving aluminum chips according to any one of claims 1 to 7, wherein the aluminum chips can be melted.
The temperature of the holding molten metal used in the method for dissolving chips is controlled in the range of 650 ° C to 800 ° C, preferably in the range of 680 ° C to 750 ° C, and most preferably in the range of 700 ° C to 720 ° C. The method for dissolving aluminum chips according to any one of claims 1 to 8.
A device for obtaining molten aluminum by carrying out the method for melting aluminum chips according to claims 1 to 9, wherein the chips to which water-containing cutting oil is attached are at least from a temperature at which the water content of the water-containing cutting oil finishes evaporating. A preheating device that shields the chips from the atmosphere and preheats them within the temperature range up to the temperature at which the oil decomposes and evaporates, and the dry chips are pushed into the holding molten metal of the aluminum chip melting furnace and melted. In a melting device for aluminum chips, which comprises a melting device for obtaining molten aluminum, the melting device partially immerses the aluminum melting furnace and the dry chips in the depth direction for supplying the dry chips into the holding molten metal. A device for melting aluminum chips, which comprises a rotating cylinder made of ceramics that is not eroded by the holding molten metal, and a dry chip pushing cylinder that supplies the dry chips to the inside of the cylinder. ..
The aluminum chip melting device according to claim 10, wherein the cylindrical portion of the rotating cylinder is provided with irregularities along the axial direction or a plurality of protruding portions.
The aluminum chip melting device according to claim 10 or 11, wherein a plurality of rack-shaped tooth molds are provided at the tip discharging portion of the rotating cylinder.
The aluminum chip melting apparatus according to any one of claims 10 to 12, wherein a rod-shaped portion of ceramics crossed at a single point or a plurality of places is provided inside near the discharge end of the rotating cylinder.
The aluminum chip melting device according to any one of claims 10 to 13, wherein the tubular portion of the rotating cylinder is provided with a through hole through which a plurality of holding molten metal can come into contact with or enter.
13. Aluminum chip melting device