JP4243174B2 - Mg alloy coating scrap processing method - Google Patents

Description

  The present invention relates to a Mg alloy used in, for example, personal computers and household appliances, and particularly relates to a method for processing Mg alloy coated scrap.

  Portable home appliances, personal computers, televisions, lighting equipment, do-it-yourself tools, some parts of automobiles and motorcycles, etc., are replaced with difficult-to-recycle plastics, and Mg alloys have progressed. Remelted and reused. On the other hand, paint scraps that are considered defective in the manufacturing process and paint scraps generated from discarded household electrical appliances are stored without being recycled, and some are used for other purposes such as deoxidizers for iron refining. It was used.

  Therefore, in recent years, a technique has been proposed in which paint scrap is directly melted so as to regenerate the paint scrap without causing an increase in cost (for example, see Patent Document 1).

JP 2000-226622 A

  However, the following problems exist in the above-described conventional technology.

  That is, when the paint scrap of the Mg alloy coated product is melted, there is a risk of intense burning of the coating film and the generation of odors or toxic gases, and the regeneration work is not preferable in terms of the working environment. For scraps of poor quality, the flux method using a chloride-based refining agent had to be adopted, and not only the working environment was bad, but also dioxins could be generated.

  The objective of this invention is providing the processing method of the Mg alloy coating scrap which can perform a reproduction | regeneration process smoothly, without harming an environment.

  In order to achieve the above object, the first invention, while heating fluidized sand, keeps the temperature in a range of 350 ° C. or more and 410 ° C. or less, and supplies coated scrap made of Mg alloy in the fluid sand, The resin component of the paint scrap coating is vaporized and separated and removed.

  In the present invention, by utilizing the fact that plastics are thermally decomposed at a lower temperature and the decomposition products are combusted compared to general metals, coating scraps are supplied into high-temperature fluidized sand, so that The resin component can be vaporized without applying such strong heat that the base metal is oxidized. Thereby, the resin component of the coating film can be separated and removed without inhibiting the generation of unburned organic matter and dioxin and harming the environment. In particular, at this time, by setting the temperature of the fluidized sand to a temperature range of 350 ° C. to 410 ° C., it is possible to prevent the combustion due to overheating of the scrap base material (magnesium alloy) while ensuring the vaporization of the resin component and to perform the processing smoothly. be able to.

  In order to achieve the above object, the second invention is to heat the fluidized sand and maintain the temperature in the range of 350 ° C. or higher and 430 ° C. or lower, and supply Mg alloy coated scrap into the fluidized sand. The resin component of the paint scrap coating film is vaporized and separated and removed, and the scrap after the separation and removal is taken out from the fluidized sand while being kept in an incombustible gas atmosphere.

  For example, if the scrap is kept in a nonflammable gas atmosphere by covering it with a cover or the like and cooled, the temperature of the fluidized sand is further increased to 350 ° C. to 430 than in the first invention in which such measures are not taken. Even in the temperature range of ° C., combustion can be performed smoothly by preventing the combustion due to overheating of the scrap base material (magnesium alloy) while reliably vaporizing the resin component.

  A third invention is characterized in that, in the second invention, the scrap after taking out is further kept in an incombustible gas atmosphere for a predetermined period.

  Thereby, ignition and oxidation due to overheating of the scrap after taking out can be reliably prevented.

  According to a fourth invention, in the second or third invention, the scrap is covered with a flameproof cover, and the nonflammable gas is supplied to the inside of the cover, thereby holding the scrap in the nonflammable gas atmosphere. It is characterized by doing.

  Thereby, nonflammable gas is supplied to the space partitioned in the flameproof cover to form a nonflammable gas atmosphere, and it is possible to reliably prevent ignition and oxidation due to overheating of the scrap after removal.

  In a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, a continuous processing blast method (for example, a sand blast method, a shot blast method, a wet blast method, an oscillating blast method, etc.) is applied to the scrap. It is characterized by performing the cleaning process of the scrap surface.

  Thereby, impurities, such as the residue of the heavy metal pigment and the inorganic additive contained in the paint and the chemical conversion film oxide layer on the substrate side, can be removed. Therefore, it is possible to prevent the corrosion resistance of the product and the hot water flow property during die casting from being affected during the circulation use of the magnesium alloy.

  A sixth invention is characterized in that, in any one of the first to fifth inventions, the scrap is melt-regenerated by a fluxless process.

  As a result, the scrap can be refined and melted to easily form a recycled mass.

  According to the present invention, it is possible to smoothly recycle Mg alloy-coated scrap without harming the environment.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  This embodiment is an embodiment in the case where the paint peeling of a magnesium alloy personal computer casing (with paint) is performed as an example of the Mg alloy.

  FIG. 1 is a diagram illustrating an overall schematic configuration of a heat treatment apparatus (peeling furnace) for carrying out the Mg alloy paint scrap heat treatment method according to the present embodiment.

  In FIG. 1, a porous or mesh-like bottom portion (including a gas blowing portion) 1 </ b> A in a heat-insulated container (furnace body container) 1 having an inner width of 1.5 m × depth of 0.7 m × depth of 1.0 m. Add silica sand 2 of size 60 mesh to 100 mesh (approximately 250 μ to 150 μ) to a depth of 0.6 m. The particle size of the silica sand 2 is preferably 100 to 1000 μm. Other than the silica sand 2, thermally stable alumina particles, magnesia particles, spinel particles, and the like may be used. Further, the container 1 is preferably an iron container lined with a refractory material or a heat insulating material in order to maintain the thermal uniformity in the furnace.

  LPG gas and air as flammable gas were blown into the silica sand 2 in the container 1 through the valve 3 and the valve 4 from the lower part of the heat insulating container 1 to make the silica sand 2 in a fluid state. The combustible gas and air are added in an amount sufficient to bring the sand into a fluidized state and an amount in which the combustion state at the upper part of the flowing silica sand 2 is good. The silica sand 2 is heated by igniting with a pilot burner (not shown) on the upper surface of the sand 2 thus flowed. Thus, heating was performed with high thermal efficiency, and control was performed so as to be within a predetermined temperature range. The temperature control of the fluid sand 2 at this time can be controlled by the amount of the combustible gas supplied to the upper part. Combustion in the upper part of the fluidized sand 2 is accomplished by supplying sufficient secondary air, and suppresses the generation of unburned organic matter and dioxins.

After the temperature is raised in this manner, alloy scrap (= magnesium alloy coated personal computer casing 150 to 200 pieces of about 23 to about 23 pieces) as a material to be heated put in a steel basket (net pallet, basket) 5 30 kg) S is inserted (supplied). Organic components, carbon, CO gas, etc. decomposed from the paint on the surface of the scrap S are burned together as part of the heating source above the fluidized sand. As a result, the resin component (organic component) in the paint is decomposed into a volatile component by about 350 ° C. and is vaporized and removed. The remaining carbon content and the inorganic substances in the pigment and filler are lifted from the surface of the coating scrap S by the decomposition of the organic components. If the oxygen partial in the gas to be heated driving source fluidized sand 2, carbon content is gasified is CO, and CO _2. Such treatment was performed for a predetermined time (basically 10 to 20 minutes), but the treatment time was appropriately adjusted depending on the quality and quantity of the coating scrap S.

  FIG. 2 is a diagram showing the various processing conditions and the results at this time. As shown in the figure, the processing was performed by changing various processing conditions for comparison. The example shown in the figure shows sample examples among them, a processing temperature of 400 ° C., a processing time of 25 minutes, a processing number of 150 sheets (case 1), a processing temperature of 430 ° C., a processing time of 15 minutes, and a processing number of sheets. 200 sheets (case 2), processing temperature 330 ° C., processing time 60 minutes, processing number 200 sheets (case 3), processing temperature 420 ° C., processing time 20 minutes, processing number 200 sheets (case) 4) and a processing temperature of 460 ° C., a processing time of 20 minutes, and a processing number of 200 sheets (case 5).

  After the above treatment, the iron basket 5 was lifted. At this time, in a plurality of cases including the case 1 and the case 2, the cover (seal cover, umbrella member) 6 was set so as to cover the outer peripheral side of the iron basket 5.

  As shown in FIG. 1, the cover 6 has a side surface and an upper surface surrounded by a plate made of steel or SUS, and the bottom surface is open. There is a through hole for the main hoist 7 on the upper surface, and a spray nozzle 8 for dissipating non-combustible gas (seal gas) is disposed inside.

  During the lifting, the hoist 7 is sprayed with a non-flammable gas (inert gas) from the nozzle 8 into the cover 6 (to ensure a non-flammable gas curtain area in the cover 6), 9, the iron basket 5 is taken out from the heat insulating container 1. That is, first, the main hoist 7 is hung on the arm 5a of the iron basket 5 (in the drawing, provided on only one side of the substantially square shape, but may be provided on two opposite sides), and the arm 6a The auxiliary hoist 9 that suspends the cover 6 is lowered through (provided only on one side of the substantially rectangular shape in the figure, but may be provided on two opposite sides), and the nonflammable gas is put into the cover 6. The iron basket 5 is pulled into the cover 6 while charging. When the main hoist 7 is lifted, it moves parallel to the front as it is and lowers it to the floor. Instead of the cover 6, the gas nozzle may be arranged so that the iron basket 5 is always wrapped in a seal gas atmosphere. The type of non-combustible gas is one of argon gas, carbon dioxide gas, nitrogen gas, SF6 gas, and mixed gas thereof.

  The iron basket 5 taken out is placed on the floor with the cover 6 covered, and after sealing for a predetermined time (for example, 5 minutes), the cover 6 is removed and opened. When these covers 6 are provided, a non-combustible gas at a predetermined flow rate (for example, 30 L / min) is supplied into the cover 6 through the nozzle 8 during a predetermined time (for example, 3 minutes) at the end of the working time and until the opening after the floor is placed. Infuse. Thereby, it cools in nonflammable gas until the scrap S which is a processed product goes up from the fluid sand 2 and cools to some extent.

  After the opening, the scrap S was observed. In Case 1 and Case 2, the paint content was 100% removed, and the base Mg alloy was recovered in high yield. In Case 3, the treatment temperature was too low and about 20% of the paint remained.

  In the above process, the solidus of the Mg alloy is generally about 430 ° C., and then enters the solid-liquid coexistence region, partially starts softening and semi-dissolving, and becomes easy to oxidize and burn. As suggested by the results shown in the figure, when there is no cover, the base material hangs in the air while being hot, so when the temperature is too high, not only the paint but also the magnesium alloy Softened / collapsed, easily ignited when taken out, and chopped pieces remain in the sand, tending to cause loss and fire accidents (see results for cases 4 and 5).

  According to the study by the inventors of the present application, it has been found that even when the cover 6 is not provided, combustion does not occur if the temperature of the fluidized sand is set to 410 ° C. (see the results of cases 1 and 4). Further, when the temperature was raised by 50 ° C. (= 480 ° C.) above the solidus temperature, the Mg alloy easily burned, and once ignited, the ambient temperature increased, and the entire treatment material was ignited. In this case, the treatment materials were all oxides and nitrides, and sand that could be used repeatedly had to be replaced.

  On the other hand, when placed on the floor with the cover 6 covered and opened after 5 minutes, no problems of oxidation and combustion occurred, and no problem occurred even when the processing temperature was raised to 430 ° C. (case 2). See results). However, when the temperature is set to 430 ° C. or higher, the shape change of the scrap S is large, and it takes time to take out from the iron basket 5, which is not preferable.

  As described above, when the cover 6 is not provided, the temperature at which the resin component is substantially vaporized (350 ° C.) is set as the lower limit of the low temperature, 410 ° C. at which the scrap S did not burn is set as the upper limit, and the temperature range of 350 ° C. to 410 ° C. When the cover 6 is present, it has been found that the upper limit can be further set to 430 ° C.

  As described above, no organic content remains on the surface of the coating scrap S subjected to the treatment process in the above temperature range (350 ° C. to 410 ° C. without cover 6 and 350 ° C. to 430 ° C. with cover 6). Although there are no heavy metal pigments or inorganic additives contained in the paint, they remain in an ash-like or film-like form (for example, the Cu content is 5 times that of the die-cast component before coating, and the Fe content is 10). Times, Cr content is 30 times higher). Further, on the metal side, there is a chemical conversion treatment film before coating, and an oxide layer is formed. If only the ash-like material is removed, it can be removed by high-pressure water spraying, steam washing, water washing treatment, etc., but the chemical conversion treatment film cannot be removed. Further, since magnesium alloy is circulated, the concentration of the above elements may have a great adverse effect on the corrosion resistance of the product and the hot water flow during die casting.

  Accordingly, the inventors of the present application have examined that, as a removal method suitable for industrial and mass processing, a sand blast shot blast method, a wet blast method, a swing shot, and the like, in which material supply and extraction are automated using a belt conveyor. It has been found that continuous processing blasting methods such as blasting are preferred. If these methods are used to insert a fixed amount into the blasting device and remove ash, oxide film, base treatment film, etc., a cleaner scrap can be obtained. In the case of wet blasting, the blasting material is preferably alumina, glass beads, plastic powder or the like. For swing shot blasting, use zinc shot or steel grid. One peeling time is about 1 to 3 minutes and may be adjusted according to the shape and amount of scrap.

  As an example performed by the inventors of the present application, 20 pieces of the scraps S after the above-described treatment are put into a swing type shot blasting apparatus (inner dimensions 80 cm × 80 cm × 60 cm) using a Zn shot and a steel grid, When each 3 minute treatment was performed, it was found that the above-mentioned impurities could be removed to the level of the die casting component before coating. In addition, although the coating scrap which did not pass through the above-mentioned method by this invention was processed with the same blasting apparatus, even if it processed for 20 minutes, it was about 1/2 that the coating | coated peeled and the foundation | substrate was exposed.

  Further, according to the study by the inventors of the present application, the scrap S that has undergone the above process is an ultra-high-quality scrap (grade-1 scrap) that does not have a surface oxide layer attached to the high-quality scrap generated in the normal die casting process. Therefore, it was found that it can be purified and dissolved by fluxless processing without using chloride, etc., and can easily be regenerated.

In the fluxless treatment method, scrap is melted under a seal gas atmosphere, and inclusions are floated and separated (excluded) by argon gas bubbling treatment, and then the hot water partially separated and cleaned is cast into an ingot case. . As an example performed by the inventors of the present application, 450 kg of scrap S was put into a 500 kg magnesium alloy melting and refining furnace and subjected to non-flux melting and refining treatment using a seal gas. Argon gas was blown into the molten metal at a rate of 10 liters / minute for 20 minutes, and the molten oxygen was precipitated and floated and cast, sampled and analyzed for oxygen, and the oxygen content before dissolution was 120 ppm. The average was 7 ppm, and the oxide was sufficiently removed.
By passing through all the above processes, the recycling process which does not by-produce dioxin and other harmful substances is completed.

  As described above, according to the processing method of the Mg alloy coated scrap according to the present embodiment, the plastic is thermally decomposed at a lower temperature than the general metal and the decomposition product burns, and the coating is performed. By supplying the scrap S into the high-temperature fluidized sand 2, the resin component in the paint can be vaporized without applying heat that is strong enough to oxidize the metal of the base material (Mg alloy). Thereby, the resin component of the coating film can be separated and removed without inhibiting the generation of unburned organic matter and dioxin and harming the environment.

  In particular, when there is no cover 6, the temperature of the fluidized sand 2 is set to a temperature range of 350 ° C. to 410 ° C., so that the combustion of the scrap base material (magnesium alloy) due to overheating is performed while the resin component is reliably vaporized. And can be processed smoothly. Further, if the scrap S is kept in a non-combustible gas atmosphere by the cover 6 and cooled, the resin component can be reduced even in a temperature range of 350 ° C. to 430 ° C. in which the temperature of the fluidized sand 2 is further expanded to a higher temperature than the above. While being reliably vaporized, combustion due to overheating of the scrap base material (magnesium alloy) can be prevented and smooth processing can be performed.

  Further, the scrap S after the smooth processing as described above is subjected to a cleaning process on the surface of the scrap using an oscillating shot blasting device, thereby further adding a heavy metal pigment contained in the paint. -Impurities such as residual inorganic additives and the chemical conversion film oxide layer on the substrate side can be removed. Therefore, it is possible to prevent the corrosion resistance of the product and the hot water flow property during die casting from being affected during the circulation use of the magnesium alloy. Furthermore, the scrap S can be refined and melted to form a reclaimed lump easily by melting and regenerating by fluxless processing.

  In addition, for a manufacturer that manufactures parts made of Mg alloy, it is possible to adopt a fluxless method that has a lower cost and a better working environment in the regeneration method by improving the quality of the scrap S by a paint peeling operation. In addition, since it is not necessary to purchase new materials for the amount of discarded paint, there is a cost reduction effect.

  Furthermore, in general, the following effects can also be obtained.

  That is, by regenerating the magnesium alloy according to the present invention, it is possible to eliminate the step of generating harmful substances such as dioxin, which has not been achieved in the past, so that a clean circulation circuit is completed. For the coming recycling society, materials can be recycled by using magnesium alloys instead of plastics for components such as portable home appliances, televisions, and automobile parts. Can provide a method for eliminating the occurrence of environmental problems, and can greatly contribute to the conservation of the global environment. Moreover, the significance of using a magnesium alloy becomes clear, and if the amount of the alloy used inevitably increases, the global environment will be improved at an accelerated rate.

It is a figure showing the whole schematic structure of the heat processing apparatus which implements one Embodiment of this invention. It is a figure showing the example of the result of having processed in various process conditions in the heat processing by one Embodiment of this invention.

Explanation of symbols

1 Insulated container 2 Silica sand (fluidized sand)
3 Flammable gas supply valve 5 Iron basket 6 Cover (flameproof cover)
S Paint scrap

Claims (6)

While heating the fluidized sand, the temperature is maintained in the range of 350 ° C or higher and 410 ° C or lower
Supply Mg alloy paint scrap into the fluid sand,
A method for treating Mg alloy coated scrap, characterized in that the resin component of the coating film of the coated scrap is vaporized and separated and removed. While maintaining the fluidized sand, the temperature is maintained in the range of 350 ° C or higher and 430 ° C or lower,
Supply Mg alloy paint scrap into the fluid sand,
Evaporate and remove the resin component of the paint scrap coating,
A method for treating Mg alloy-coated scrap, wherein the scrap after separation and removal is taken out of the fluidized sand while being maintained in an incombustible gas atmosphere. In the processing method of the Mg alloy coating scrap of Claim 2,
The scrap after the take-out is further maintained in a nonflammable gas atmosphere for a predetermined period. In the processing method of the Mg alloy coating scrap of Claim 2 or 3,
A method for treating Mg alloy coated scrap, wherein the scrap is covered with a flameproof cover, and the scrap is held in the nonflammable gas atmosphere by supplying the nonflammable gas into the cover. In the processing method of the Mg alloy coating scrap of any one of Claims 1-4,
A method for treating Mg alloy-coated scrap, wherein the scrap surface is subjected to a cleaning process using a continuous processing blasting method for the scrap. In the processing method of the Mg alloy coating scrap of any one of Claims 1-5,
A processing method for Mg alloy coated scrap, wherein the scrap is melted and regenerated by fluxless processing.

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