US20210129210A1 - Method of reusing core sand - Google Patents
Method of reusing core sand Download PDFInfo
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- US20210129210A1 US20210129210A1 US17/149,897 US202117149897A US2021129210A1 US 20210129210 A1 US20210129210 A1 US 20210129210A1 US 202117149897 A US202117149897 A US 202117149897A US 2021129210 A1 US2021129210 A1 US 2021129210A1
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- Prior art keywords
- water glass
- core
- core sand
- water
- granules
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
- B22C5/04—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose by grinding, blending, mixing, kneading, or stirring
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
- B22C1/186—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents contaming ammonium or metal silicates, silica sols
- B22C1/188—Alkali metal silicates
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
- B22C5/04—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose by grinding, blending, mixing, kneading, or stirring
- B22C5/0409—Blending, mixing, kneading or stirring; Methods therefor
- B22C5/045—Devices having a horizontal stirrer shaft in a fixed receptacle
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
- B22C5/10—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose by dust separating
Definitions
- the present disclosure relates to a method of reusing core sand, for example, a method of reusing core sand in which water glass is used as a binder.
- JP 2013-111602 A discloses a method for forming a sand mold (core) in which water glass is used as a binder to prevent the production of gas from a core during casting.
- sand for forming a core is reused.
- core sand is mixed with a binder in order to make core sand grains adhere to each other.
- the core sand can be reused by collecting the core sand, which is not needed after casting, and removing impurities and the binder adhering to the core sand from the core sand.
- the disclosure provides a method of reusing core sand capable of improving the strength of a core which is formed by reusing core sand in which water glass is used as a binder.
- a method of reusing core sand including: crushing a core used for casting into granules; heating the granules at a temperature of 300° C. to 550° C.; causing the heated granules to collide against each other such that water glass used as a binder detaches from the core sand; and blowing air into a mixture of the water glass and the core sand, which are detached from each other, such that the core sand is separated and collected from the mixture due to a difference in specific gravity between the water glass and the core sand.
- the granules obtained by crushing the core after casting are heated at a temperature of 300° C. to 550° C. Therefore, the water glass included in the granules is inactivated (modified so as not to inhibit the hardening of water glass during reuse), and the strength of a core formed reusing the core sand can be improved.
- the strength of a core which is formed by reusing core sand in which water glass is used as a binder, can be improved.
- FIG. 1A is a diagram showing a mechanism according to an embodiment of the disclosure in which water glass is hardened
- FIG. 1B is a diagram showing the mechanism according to the embodiment of the disclosure in which water glass is hardened
- FIG. 2 is a diagram showing the mechanism according to the embodiment of the disclosure in which water glass is hardened
- FIG. 3A is a diagram showing the mechanism according to the embodiment of the disclosure in which water glass is hardened
- FIG. 3B is a diagram showing the mechanism according to the embodiment of the disclosure in which water glass is hardened
- FIG. 4 is a diagram showing a mechanism according to the embodiment of the disclosure in which the hardening of water glass is inhibited by sodium;
- FIG. 5 is a flowchart showing an example of a method of reusing core sand according to the embodiment of the disclosure
- FIG. 6 is a diagram showing a crushing device which crushes core sand in the method of reusing core sand according to the embodiment of the disclosure
- FIG. 7 is a graph showing the active amount and the total remaining amount of water glass which vary depending on a heating temperature in the method of reusing core sand according to the embodiment of the disclosure, in which the horizontal axis represents the heating temperature and the vertical axis represents a ratio of the mass of water glass to the mass of granules;
- FIG. 8 is a diagram showing a heating device which heats the core sand in the method of reusing core sand according to the embodiment of the disclosure
- FIG. 9A is a diagram showing a detaching device which detaches the water glass from the core sand in the method of reusing core sand according to the embodiment of the disclosure.
- FIG. 9B is a diagram showing an example of a state in which the water glass detaches from the core sand according to the embodiment of the disclosure.
- FIG. 10 is a diagram showing a separating and collecting device which separates and collects the core sand in the method of reusing core sand according to the embodiment of the disclosure.
- FIG. 11 is a graph showing an example of a strength of a core in the method of reusing core sand according to the embodiment of the disclosure, in which the horizontal axis represents the number of times of reuse and the vertical axis represents a transverse strength of a test piece (TP).
- TP test piece
- a method of reusing core sand according to the embodiment will be described.
- water glass is used as a binder. That is, in this method, core sand in which water glass is used as a binder is reused after forming a core using the core sand and using the core for aluminum casting at a casting temperature of 650° C. to 750° C.
- FIGS. 1A to 3B are diagrams showing the mechanism in which water glass is hardened.
- water and water glass 15 as a binder are mixed with core sand 9 , and the mixture is kneaded.
- the water glass 15 adhering to a surface of the core sand 9 is represented by the following molecular formula (1) and has a structure represented by the following formula (2).
- the water glass 15 is a mixture including silicon dioxide, sodium oxide, and water.
- an OH group is present at a molecular terminal of the water glass 15 .
- the kneaded mixture of the core sand 9 , water, and the water glass 15 is put into a mold and fixed.
- the water glass 15 is heated at a high temperature such that the molecules thereof react with and bind to each other.
- the OH group present at the molecular terminal of the water glass 15 causes a dehydration condensation reaction to occur.
- an O ion and a H ion in an OH group present at a terminal of one molecule react with and bind to a H ion in an OH group present at a terminal of another molecule to form one water molecule.
- the molecules of the water glass 15 adhering to the surface of the core sand 9 react with and bind to each other.
- a Si—O network 16 is formed on the surface of the core sand 9 .
- a core including the water glass 15 is hardened.
- the water glass 15 is used as the binder during the formation of the core.
- the formed core has a sufficient strength.
- used water glass 15 the water glass 15 which has been used as a binder
- new water glass 15 the water glass 15 newly added as a binder
- the core sand 9 includes the used water glass 15 .
- the used water glass 15 loses its original adhesive force. Due to this reason, as described below, it is presumed that the used water glass 15 has sodium ions.
- the new water glass 15 has a structure represented by the following formula (3).
- FIG. 4 is a diagram showing a mechanism in which the hardening of water glass is inhibited by sodium.
- the reaction caused by the hardening mechanism of the water glass 15 shown in FIG. 2 is not likely to progress. That is, the dehydration condensation reaction of the water glass 15 is prevented. Accordingly, the Si—O network 16 cannot be formed using the water glass 15 adhering to the surface of the core sand 9 . Therefore, when the core sand 9 including the used water glass 15 is reused to form a core, the strength of the formed core cannot be maintained at a predetermined value.
- a core having a strength equivalent to that of the new core sand 9 cannot be formed using the core sand 9 including the used water glass 15 .
- the core sand 9 including the used water glass 15 can be reused.
- FIG. 5 is a flowchart showing an example of a method of reusing core sand according to the embodiment of the disclosure.
- the method of reusing the core sand 9 according to the embodiment includes a crushing step (Step S 1 ), a heating step (Step S 2 ), a detaching step (Step S 3 ), and a separation and collection step (Step S 4 ).
- a core used for casting is crushed into granules 14 .
- the core is crushed until the average grain size (D50) of the granules is 3 mm or less.
- the average grain size of the granules after crushing is not particularly limited as long as it is about 10 mm or less.
- Step S 5 a defective core 8 which cannot be used for casting (Step S 6 ) may be formed due to chipping or cracking. This defective core 8 is also crushed in the crushing step (Step S 1 ).
- FIG. 6 is a diagram showing a crushing device which crushes core sand in the method of reusing core sand according to the embodiment of the disclosure.
- the crushing device 10 includes a chamber 11 , a motor, 12 , a rotor 13 , and a mesh 17 .
- the chamber 11 is provided above the motor 12 .
- the rotor 13 provide in the chamber 11 is connected to the motor 12 . Due to the rotation of the motor 12 , the rotor 13 swings.
- the mesh 17 is provided on a top surface of the rotor 13 .
- a lump of core is put into the chamber 11 , and the rotor 13 swings due to the motor 12 . Due to the swinging of the rotor 13 , granules of the core collide against each other, or the rotor 13 collides against the core. As a result, the core is crushed.
- the granules 14 is sieved through the mesh 17 to have a grain size less than a pore size of the mesh 17 . As a result, the core is crushed into the granules 14 having a grain size of 3 mm or less.
- FIG. 7 is a graph showing the active amount and the remaining amount of the water glass 15 which vary depending on the heating temperature in the method of reusing core sand according to the embodiment, in which the horizontal axis represents the heating temperature and the vertical axis represents a ratio of the mass of the water glass 15 to the mass of the granules.
- the heating time at each temperature is 10 minutes or longer, for example, 10 minutes.
- the remaining amount of the water glass 15 is obtained based on the amount of the water glass 15 which is eluted into an acid by dipping the core sand 9 in the acid.
- the water glass 15 is dissolved in an acid. Therefore, using this method, the remaining amount of the water glass 15 in the core sand 9 can be measured.
- the active amount of the water glass 15 is obtained based on the amount of the water glass 15 eluted into water by dipping the core sand 9 in water.
- the active amount of the water glass 15 refers to the amount of active water glass 15 .
- the active water glass 15 refers to water-soluble water glass 15 . When dissolved in water, the water-soluble water glass 15 releases sodium ions. As described above, the sodium ions inhibit the hardening of the water glass 15 as a binder. Since the active water glass 15 is water-soluble, the active amount of the water glass 15 included in the core sand 9 can be measured.
- the amount of the water glass 15 added as a binder during the formation of the core is 0.6%.
- the amount of the water glass 15 added in a case where the new core sand 9 is used is the same as the amount of the water glass 15 added in a case where the core sand 9 after casting is reused. The reason is that the used water glass 15 loses its original adhesive force.
- the remaining amount of the water glass 15 included in the core sand 9 after the crushing step is about 0.53%.
- the remaining amount includes the amount of the active water glass 15 (water-soluble water glass 15 ) and the amount of inactive water glass 15 (water-insoluble water glass 15 ).
- the active amount of the water glass 15 is about 0.51%. In this way, in a case where the core sand 9 includes the used water glass 15 , most of the remaining water glass 15 is the active water glass 15 .
- the active amount of the water glass 15 is larger than 0.20%. That is, in a case where the heating temperature is lower than 300° C., most of the water glass 15 remaining in the core sand 9 is the active water glass 15 . In a case where the heating temperature is 300° C., the remaining amount of the water glass 15 is 0.43%, and the active amount thereof is 0.20%. Accordingly, the amount of the water-insoluble water glass 15 is 0.23%. In a case where the heating temperature is 350° C., the remaining amount of the water glass 15 is 0.52%, and the active amount thereof is 0.17% which is lower than 0.20%. Accordingly, the amount of the water-insoluble water glass 15 is 0.35%.
- the remaining amounts of the water glass 15 are 0.46%, 0.52%, 0.44%, and 0.67%, respectively. At all the heating temperatures, the active amounts are 0.12%, which is lower than 0.20%. Accordingly, the amounts of the water-insoluble water glass 15 are 0.34%, 0.40%, 0.32%, and 0.55%, respectively. In a case where the heating temperatures are 600° C. and 650° C., the remaining amounts of the water glass 15 are 0.44% and 0.45%. At all the heating temperatures, the active amounts are 0.06%, which are lower than 0.20%. Accordingly, the amounts of the water-insoluble water glass 15 are 0.38% and 0.39%, respectively.
- the amount of the water-soluble water glass 15 is adjusted to be smaller than the amount of the water-insoluble water glass 15 in the water glass 15 included in the granules 14 .
- the inhibition of the hardening of the core sand 9 during reuse can be prevented.
- the core has a predetermined strength only when the active amount of the water glass 15 included in the core sand 9 is 0.20% or lower. Accordingly, it is preferable that the heating temperature is 300° C. or higher in consideration of the active amount of the water glass 15 included in the core sand 9 . In this way, in the heating step, the water glass 15 remaining in the core sand 9 is inactivated to obtain the water-insoluble water glass 15 . Due to the heating, the amount of the water-soluble water glass 15 in the water glass 15 included in the granules is adjusted to be 0.2% or lower with respect to the amount of the granules. As a result, the strength of the core can be improved.
- the heating temperature in the heating step is 300° C. to 550° C.
- FIG. 8 is a diagram showing the heating device which heats the core sand in the method of reusing core sand according to the embodiment.
- the heating device 20 includes a fluid tank 21 , an inlet 22 , an outlet 23 , tube heaters 24 , and panel heaters 25 .
- the fluid tank 21 has a tank shape.
- the inlet 22 is provided at an end of an upper region of the fluid tank 21 .
- the outlet 23 is provided at another end of the upper region of the fluid tank 21 .
- the upper region of the fluid tank 21 is covered with, for example, an upper cover.
- the inside of the fluid tank 21 is divided by a partition so as to have a labyrinthine structure. For example, air flows through the inside of the fluid tank 21 . As a result, a heating target in the fluid tank 21 flows from the inlet 22 to the outlet 23 .
- the plural tube heaters 24 are inserted into the inside of the fluid tank 21 from above.
- Each of the tube heaters 24 has a rod shape and has one end connected to a region of the fluid tank 21 near the bottom and the other end protruding from the upper cover of the fluid tank 21 .
- the tube heaters 24 are disposed in the fluid tank 21 at regular intervals.
- the panel heaters 25 are provided on wall surfaces and the bottom surface of the fluid tank 21 .
- the core sand 9 as the granules 14 is put into the inlet 22 of the heating device 20 .
- the granules 14 flow through the inside of the fluid tank 21 , which is divided by the partition, along with flowing air. For example, air is caused to flow at a flow rate of 1100 L/min in the fluid tank 21 .
- the granules 14 are uniformly heated by the tube heaters 24 , which are disposed at regular intervals, and the panel heaters 25 . Since the inside of the fluid tank 21 has a labyrinthine structure, the time during which the granules 14 remains in the fluid tank 21 is secured. Since the granules 14 flows along with air, the number of contacts between the granules 14 and impurities is reduced. After heating, the granules 14 is cooled to a polishing temperature of 100° C. or lower using an air-cooling heat exchange method.
- FIG. 9A is a diagram showing a detaching device which detaches the water glass from the core sand in the method of reusing core sand according to the embodiment.
- FIG. 9B is a diagram showing an example of a state in which the water glass detaches from the core sand of the granules.
- the detaching device 30 includes a chamber 31 , an inlet 32 , a rotor 34 , and a motor 35 .
- the chamber 31 is provided above the motor 35 .
- the inlet 32 is provided above the chamber 31 .
- the rotor 34 is provided in the chamber 31 .
- the rotor 34 rotates when the motor 35 rotates.
- the granules 14 incorporated from the inlet 32 rotates in a vertical direction when the rotor 34 rotates.
- the rotating speed is 2200 rpm (frequency: 72.0 Hz).
- the granules 14 are caused to collide against each other such that the active water glass 15 and the inactive water glass 15 adhering to the surface of the core sand 9 are detached from the surface of the core sand 9 .
- the treatment time is, for example, 200 seconds.
- the amount of the granules 14 treated per batch is, for example, 17.5 kg. Due to the detaching step, the proportion of the inactive water glass 15 and the proportion of the active water glass 15 in the used water glass 15 can be reduced. In the heating step, the water glass 15 is heated and thus is appropriately dried and detaches from the core sand 9 easily.
- FIG. 10 is a diagram showing a separating and collecting device which separates and collects the core sand in the method of reusing core sand according to the embodiment.
- the separating and collecting device 40 separates and collects the core sand 9 from the mixture of the water glass 15 and the core sand 9 by blowing air thereto.
- the separating and collecting device 40 includes a chamber 41 , an inlet 42 , an outlet 43 , an air blowing port 44 , and an air outlet port 45 .
- a duct (not shown) is provided above the air outlet port 45 .
- the mixture of the water glass 15 and the core sand 9 is put into the chamber 41 through the inlet 42 .
- the core sand 9 put into the chamber 41 is separated due to a difference in specific gravity by air blown from the air blowing port 44 .
- the water glass 15 having a low specific gravity is blown to the air outlet port 45 along with the air, and the core sand 9 having a high specific gravity is blown to the outlet 43 .
- the core sand 9 is separated and collected from the outlet 43 .
- the core sand 9 can be reused to form a core (Step S 5 ).
- the core sand 9 is put into a mold and is solidified by heating to form a core.
- the heating temperature is, for example, a temperature lower than a casting temperature.
- Step S 6 the formed core is used for casting.
- the core is used for aluminum casting at a casting temperature of 650° C. to 750° C.
- Step S 7 a post-treatment is performed. In the post-treatment, the used core is shaken off from a casting formed by casting. Next, in order to reuse the core sand 9 , the crushing step of Step S 1 is performed.
- FIG. 11 is a graph showing an example of a strength of a core formed in the method of reusing core sand according to the embodiment, in which the horizontal axis represents the number of times of reuse and the vertical axis represents a transverse strength of a test piece (TP).
- the transverse strength of a core formed using new core sand is 1.8 to 4.0 MPa. Even in a case where the core sand is reused 48 times to form cores, the strengths of the cores is maintained at the same strength as that of the core formed using new core sand.
- the granules obtained by crushing the core after casting are heated at a temperature of 300° C. to 550° C. Therefore, the water glass 15 included in the granules 14 is inactivated, and the strength of a core formed reusing the core sand can be improved.
- the core is crushed into the granules 14 .
- the granules 14 can be uniformly heated.
- the water glass 15 can be uniformly detached from the core sand 9 .
- the amount of the water-soluble water glass 15 is adjusted to be smaller than the amount of the water- insoluble water glass 15 in the water glass 15 included in the granules 14 .
- the amount of the water-soluble water glass 15 is adjusted to be 0.2% or lower with respect to the amount of the granules 14 .
- the water glass 15 can be appropriately dried. As a result, the water glass 15 can be easily detached from the core sand 9 . In the detaching step, not only the water-soluble water glass 15 but also the water-insoluble water glass 15 can be detached from the core sand 9 . Therefore, in the separation and collection step, the amount of the used water glass 15 included in the core sand 9 can be reduced.
- the method of reusing core sand in which the water glass 15 is used as a binder has been described.
- this reuse method is applicable to not only sand used for forming a core but also sand used for casting.
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Abstract
Description
- This application is a Division of application Ser. No. 16/851,274 filed Apr. 17, 2020, which is allowed and is a Division of U.S. patent application Ser. No. 15/949,394 filed Apr. 10, 2018, which is patented and is a Continuation of U.S. patent application Ser. No. 15/287,479, filed on Oct. 6, 2016, which is patented and claims priority to Japanese Patent Application No. 2015-205849, filed on Oct. 19, 2015. The disclosure of each of the prior applications is hereby incorporated by reference herein in its entirety.
- The present disclosure relates to a method of reusing core sand, for example, a method of reusing core sand in which water glass is used as a binder.
- Japanese Patent Application Publication No. 2013-111602 (JP 2013-111602 A) discloses a method for forming a sand mold (core) in which water glass is used as a binder to prevent the production of gas from a core during casting.
- In general, sand (core sand) for forming a core is reused. During the formation of a core for casting, core sand is mixed with a binder in order to make core sand grains adhere to each other. The core sand can be reused by collecting the core sand, which is not needed after casting, and removing impurities and the binder adhering to the core sand from the core sand.
- However, regarding a core in which water glass is used as a binder, it is difficult to separate the core into core sand and water glass. In a case where a sand mold (core) is formed using core sand in which water glass remains, it is difficult to harden the core sand so as to have a sufficient strength. Therefore, a method of reusing core sand in which water glass is used as a binder has yet to be established.
- The disclosure provides a method of reusing core sand capable of improving the strength of a core which is formed by reusing core sand in which water glass is used as a binder.
- According to an aspect of the disclosure, there is provided a method of reusing core sand including: crushing a core used for casting into granules; heating the granules at a temperature of 300° C. to 550° C.; causing the heated granules to collide against each other such that water glass used as a binder detaches from the core sand; and blowing air into a mixture of the water glass and the core sand, which are detached from each other, such that the core sand is separated and collected from the mixture due to a difference in specific gravity between the water glass and the core sand.
- According to the aspect, the granules obtained by crushing the core after casting are heated at a temperature of 300° C. to 550° C. Therefore, the water glass included in the granules is inactivated (modified so as not to inhibit the hardening of water glass during reuse), and the strength of a core formed reusing the core sand can be improved.
- According to the aspect of the disclosure, the strength of a core, which is formed by reusing core sand in which water glass is used as a binder, can be improved.
- Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
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FIG. 1A is a diagram showing a mechanism according to an embodiment of the disclosure in which water glass is hardened; -
FIG. 1B is a diagram showing the mechanism according to the embodiment of the disclosure in which water glass is hardened; -
FIG. 2 is a diagram showing the mechanism according to the embodiment of the disclosure in which water glass is hardened; -
FIG. 3A is a diagram showing the mechanism according to the embodiment of the disclosure in which water glass is hardened; -
FIG. 3B is a diagram showing the mechanism according to the embodiment of the disclosure in which water glass is hardened; -
FIG. 4 is a diagram showing a mechanism according to the embodiment of the disclosure in which the hardening of water glass is inhibited by sodium; -
FIG. 5 is a flowchart showing an example of a method of reusing core sand according to the embodiment of the disclosure; -
FIG. 6 is a diagram showing a crushing device which crushes core sand in the method of reusing core sand according to the embodiment of the disclosure; -
FIG. 7 is a graph showing the active amount and the total remaining amount of water glass which vary depending on a heating temperature in the method of reusing core sand according to the embodiment of the disclosure, in which the horizontal axis represents the heating temperature and the vertical axis represents a ratio of the mass of water glass to the mass of granules; -
FIG. 8 is a diagram showing a heating device which heats the core sand in the method of reusing core sand according to the embodiment of the disclosure; -
FIG. 9A is a diagram showing a detaching device which detaches the water glass from the core sand in the method of reusing core sand according to the embodiment of the disclosure; -
FIG. 9B is a diagram showing an example of a state in which the water glass detaches from the core sand according to the embodiment of the disclosure; -
FIG. 10 is a diagram showing a separating and collecting device which separates and collects the core sand in the method of reusing core sand according to the embodiment of the disclosure; and -
FIG. 11 is a graph showing an example of a strength of a core in the method of reusing core sand according to the embodiment of the disclosure, in which the horizontal axis represents the number of times of reuse and the vertical axis represents a transverse strength of a test piece (TP). - Hereinafter, an embodiment of the disclosure will be described in detail with reference to the accompanying drawings. However, the disclosure is not limited to the following embodiment. In order to clarify the description, the following description and the drawings are appropriately simplified.
- A method of reusing core sand according to the embodiment will be described. In the method of reusing core sand according to the embodiment, water glass is used as a binder. That is, in this method, core sand in which water glass is used as a binder is reused after forming a core using the core sand and using the core for aluminum casting at a casting temperature of 650° C. to 750° C.
- Here, first, a mechanism in which the water glass used as the binder during the formation of the core is hardened will be described. Next, a mechanism in which water glass which has been used as a binder inhibits the hardening of water glass newly added as a binder will be described. Next, the method of reusing core sand in which water glass is used as a binder will be described.
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FIGS. 1A to 3B are diagrams showing the mechanism in which water glass is hardened. During the formation of a core, water andwater glass 15 as a binder are mixed withcore sand 9, and the mixture is kneaded. As shown inFIG. 1A , thewater glass 15 adhering to a surface of thecore sand 9 is represented by the following molecular formula (1) and has a structure represented by the following formula (2). As shown in the formula (1), thewater glass 15 is a mixture including silicon dioxide, sodium oxide, and water. As shown in the formula (2), an OH group is present at a molecular terminal of thewater glass 15. - Next, the kneaded mixture of the
core sand 9, water, and thewater glass 15 is put into a mold and fixed. As shown inFIG. 2 , for example, during the formation of a core or casting, thewater glass 15 is heated at a high temperature such that the molecules thereof react with and bind to each other. The OH group present at the molecular terminal of thewater glass 15 causes a dehydration condensation reaction to occur. At this time, an O ion and a H ion in an OH group present at a terminal of one molecule react with and bind to a H ion in an OH group present at a terminal of another molecule to form one water molecule. - As shown in
FIGS. 3A and 3B , due to the above-described dehydration condensation reaction, the molecules of thewater glass 15 adhering to the surface of thecore sand 9 react with and bind to each other. A Si—O network 16 is formed on the surface of thecore sand 9. As a result, a core including thewater glass 15 is hardened. At this time, a large number of water molecules are formed. Thewater glass 15 is used as the binder during the formation of the core. The formed core has a sufficient strength. - Next, a mechanism in which the
water glass 15 which has been used as a binder (hereinafter, referred to as “usedwater glass 15”) inhibits the hardening of thewater glass 15 newly added as a binder (hereinafter, referred to as “new water glass 15”) will be described. Even when thecore sand 9 is reused, water and thenew water glass 15 are mixed with thecore sand 9, and the mixture is kneaded. Thecore sand 9 includes the usedwater glass 15. The usedwater glass 15 loses its original adhesive force. Due to this reason, as described below, it is presumed that the usedwater glass 15 has sodium ions. When thecore sand 9 including the usedwater glass 15, water, and thenew water glass 15 are mixed with each other, the sodium ions are eluted from the usedwater glass 15 into water. The sodium ions eluted into water are substituted with hydrogen ions in thenew water glass 15. Thenew water glass 15 has a structure represented by the following formula (3). -
FIG. 4 is a diagram showing a mechanism in which the hardening of water glass is inhibited by sodium. As shown inFIG. 4 , when thewater glass 15 has the structure represented by the above-described formula (3), the reaction caused by the hardening mechanism of thewater glass 15 shown inFIG. 2 is not likely to progress. That is, the dehydration condensation reaction of thewater glass 15 is prevented. Accordingly, the Si—O network 16 cannot be formed using thewater glass 15 adhering to the surface of thecore sand 9. Therefore, when thecore sand 9 including the usedwater glass 15 is reused to form a core, the strength of the formed core cannot be maintained at a predetermined value. In this way, in the related art, a core having a strength equivalent to that of thenew core sand 9 cannot be formed using thecore sand 9 including the usedwater glass 15. In the method of reusing thecore sand 9 described below, thecore sand 9 including the usedwater glass 15 can be reused. -
FIG. 5 is a flowchart showing an example of a method of reusing core sand according to the embodiment of the disclosure. As shown inFIG. 5 , the method of reusing thecore sand 9 according to the embodiment includes a crushing step (Step S1), a heating step (Step S2), a detaching step (Step S3), and a separation and collection step (Step S4). In the crushing step, a core used for casting is crushed intogranules 14. For example, the core is crushed until the average grain size (D50) of the granules is 3 mm or less. The average grain size of the granules after crushing is not particularly limited as long as it is about 10 mm or less. However, the less the average grain size, the better. In a case where thecore sand 9 is reused to form a core (Step S5), adefective core 8 which cannot be used for casting (Step S6) may be formed due to chipping or cracking. Thisdefective core 8 is also crushed in the crushing step (Step S1). - In the crushing step, for example, a crushing
device 10 is used.FIG. 6 is a diagram showing a crushing device which crushes core sand in the method of reusing core sand according to the embodiment of the disclosure. As shown inFIG. 6 , the crushingdevice 10 includes achamber 11, a motor, 12, arotor 13, and amesh 17. Thechamber 11 is provided above themotor 12. Therotor 13 provide in thechamber 11 is connected to themotor 12. Due to the rotation of themotor 12, therotor 13 swings. Themesh 17 is provided on a top surface of therotor 13. - A lump of core is put into the
chamber 11, and therotor 13 swings due to themotor 12. Due to the swinging of therotor 13, granules of the core collide against each other, or therotor 13 collides against the core. As a result, the core is crushed. Thegranules 14 is sieved through themesh 17 to have a grain size less than a pore size of themesh 17. As a result, the core is crushed into thegranules 14 having a grain size of 3 mm or less. - Next, in the heating step shown in Step S2 of
FIG. 5 , thegranules 14 are heated at a temperature of 300° C. to 550° C.FIG. 7 is a graph showing the active amount and the remaining amount of thewater glass 15 which vary depending on the heating temperature in the method of reusing core sand according to the embodiment, in which the horizontal axis represents the heating temperature and the vertical axis represents a ratio of the mass of thewater glass 15 to the mass of the granules. The heating time at each temperature is 10 minutes or longer, for example, 10 minutes. Here, the remaining amount of thewater glass 15 is obtained based on the amount of thewater glass 15 which is eluted into an acid by dipping thecore sand 9 in the acid. Thewater glass 15 is dissolved in an acid. Therefore, using this method, the remaining amount of thewater glass 15 in thecore sand 9 can be measured. - On the other hand, the active amount of the
water glass 15 is obtained based on the amount of thewater glass 15 eluted into water by dipping thecore sand 9 in water. The active amount of thewater glass 15 refers to the amount ofactive water glass 15. Theactive water glass 15 refers to water-soluble water glass 15. When dissolved in water, the water-soluble water glass 15 releases sodium ions. As described above, the sodium ions inhibit the hardening of thewater glass 15 as a binder. Since theactive water glass 15 is water-soluble, the active amount of thewater glass 15 included in thecore sand 9 can be measured. - As shown in
FIG. 7 , the amount of thewater glass 15 added as a binder during the formation of the core is 0.6%. The amount of thewater glass 15 added in a case where thenew core sand 9 is used is the same as the amount of thewater glass 15 added in a case where thecore sand 9 after casting is reused. The reason is that the usedwater glass 15 loses its original adhesive force. - The remaining amount of the
water glass 15 included in thecore sand 9 after the crushing step is about 0.53%. The remaining amount includes the amount of the active water glass 15 (water-soluble water glass 15) and the amount of inactive water glass 15 (water-insoluble water glass 15). The active amount of thewater glass 15 is about 0.51%. In this way, in a case where thecore sand 9 includes the usedwater glass 15, most of the remainingwater glass 15 is theactive water glass 15. - In a case where the heating temperature is lower than 300° C., the active amount of the
water glass 15 is larger than 0.20%. That is, in a case where the heating temperature is lower than 300° C., most of thewater glass 15 remaining in thecore sand 9 is theactive water glass 15. In a case where the heating temperature is 300° C., the remaining amount of thewater glass 15 is 0.43%, and the active amount thereof is 0.20%. Accordingly, the amount of the water-insoluble water glass 15 is 0.23%. In a case where the heating temperature is 350° C., the remaining amount of thewater glass 15 is 0.52%, and the active amount thereof is 0.17% which is lower than 0.20%. Accordingly, the amount of the water-insoluble water glass 15 is 0.35%. - In a case where the heating temperatures are 400° C., 450° C., 500° C., and 550° C., the remaining amounts of the
water glass 15 are 0.46%, 0.52%, 0.44%, and 0.67%, respectively. At all the heating temperatures, the active amounts are 0.12%, which is lower than 0.20%. Accordingly, the amounts of the water-insoluble water glass 15 are 0.34%, 0.40%, 0.32%, and 0.55%, respectively. In a case where the heating temperatures are 600° C. and 650° C., the remaining amounts of thewater glass 15 are 0.44% and 0.45%. At all the heating temperatures, the active amounts are 0.06%, which are lower than 0.20%. Accordingly, the amounts of the water-insoluble water glass 15 are 0.38% and 0.39%, respectively. - By heating the
granules 14 at a temperature of 300° C. or higher in the heating step, the amount of the water-soluble water glass 15 is adjusted to be smaller than the amount of the water-insoluble water glass 15 in thewater glass 15 included in thegranules 14. As a result, the inhibition of the hardening of thecore sand 9 during reuse can be prevented. - As the amount of the
water glass 15 eluted into water which is added during the formation of a core decreases, the strength of the formed core is improved. In a case where thecore sand 9 is reused to form a core, the core has a predetermined strength only when the active amount of thewater glass 15 included in thecore sand 9 is 0.20% or lower. Accordingly, it is preferable that the heating temperature is 300° C. or higher in consideration of the active amount of thewater glass 15 included in thecore sand 9. In this way, in the heating step, thewater glass 15 remaining in thecore sand 9 is inactivated to obtain the water-insoluble water glass 15. Due to the heating, the amount of the water-soluble water glass 15 in thewater glass 15 included in the granules is adjusted to be 0.2% or lower with respect to the amount of the granules. As a result, the strength of the core can be improved. - On the other hand, in a case where the heating temperature is higher than 550° C., the
core sand 9 is solidified. Thecore sand 9 and the binder are solidified in the heating device, and thus thecore sand 9 cannot be separated from the binder. Accordingly, it is preferable that the heating temperature in the heating step is 300° C. to 550° C. - In the heating step, for example, a
heating device 20 is used.FIG. 8 is a diagram showing the heating device which heats the core sand in the method of reusing core sand according to the embodiment. As shown inFIG. 8 , theheating device 20 includes afluid tank 21, aninlet 22, anoutlet 23,tube heaters 24, andpanel heaters 25. Thefluid tank 21 has a tank shape. Theinlet 22 is provided at an end of an upper region of thefluid tank 21. Theoutlet 23 is provided at another end of the upper region of thefluid tank 21. - The upper region of the
fluid tank 21 is covered with, for example, an upper cover. The inside of thefluid tank 21 is divided by a partition so as to have a labyrinthine structure. For example, air flows through the inside of thefluid tank 21. As a result, a heating target in thefluid tank 21 flows from theinlet 22 to theoutlet 23. Theplural tube heaters 24 are inserted into the inside of thefluid tank 21 from above. - Each of the
tube heaters 24 has a rod shape and has one end connected to a region of thefluid tank 21 near the bottom and the other end protruding from the upper cover of thefluid tank 21. Thetube heaters 24 are disposed in thefluid tank 21 at regular intervals. Thepanel heaters 25 are provided on wall surfaces and the bottom surface of thefluid tank 21. - The
core sand 9 as thegranules 14 is put into theinlet 22 of theheating device 20. Thegranules 14 flow through the inside of thefluid tank 21, which is divided by the partition, along with flowing air. For example, air is caused to flow at a flow rate of 1100 L/min in thefluid tank 21. Thegranules 14 are uniformly heated by thetube heaters 24, which are disposed at regular intervals, and thepanel heaters 25. Since the inside of thefluid tank 21 has a labyrinthine structure, the time during which thegranules 14 remains in thefluid tank 21 is secured. Since thegranules 14 flows along with air, the number of contacts between thegranules 14 and impurities is reduced. After heating, thegranules 14 is cooled to a polishing temperature of 100° C. or lower using an air-cooling heat exchange method. - Next, in the detaching step shown in Step S3, the
heated granules 14 are caused to collide against each other such that thewater glass 15 detaches from thecore sand 9.FIG. 9A is a diagram showing a detaching device which detaches the water glass from the core sand in the method of reusing core sand according to the embodiment.FIG. 9B is a diagram showing an example of a state in which the water glass detaches from the core sand of the granules. As shown inFIG. 9A , the detachingdevice 30 includes achamber 31, aninlet 32, arotor 34, and amotor 35. Thechamber 31 is provided above themotor 35. Theinlet 32 is provided above thechamber 31. Therotor 34 is provided in thechamber 31. Therotor 34 rotates when themotor 35 rotates. - The
granules 14 incorporated from theinlet 32 rotates in a vertical direction when therotor 34 rotates. The rotating speed is 2200 rpm (frequency: 72.0 Hz). As shown inFIG. 9B , in the detachingdevice 30, thegranules 14 are caused to collide against each other such that theactive water glass 15 and theinactive water glass 15 adhering to the surface of thecore sand 9 are detached from the surface of thecore sand 9. The treatment time is, for example, 200 seconds. The amount of thegranules 14 treated per batch is, for example, 17.5 kg. Due to the detaching step, the proportion of theinactive water glass 15 and the proportion of theactive water glass 15 in the usedwater glass 15 can be reduced. In the heating step, thewater glass 15 is heated and thus is appropriately dried and detaches from thecore sand 9 easily. - Next, in the separation and collection step shown in Step S4, air is blown into a mixture of the
water glass 15 and thecore sand 9, which are detached from each other, such that thecore sand 9 is separated and collected from the mixture due to a difference in specific gravity between thewater glass 15 and thecore sand 9.FIG. 10 is a diagram showing a separating and collecting device which separates and collects the core sand in the method of reusing core sand according to the embodiment. As shown inFIG. 10 , the separating and collectingdevice 40 separates and collects thecore sand 9 from the mixture of thewater glass 15 and thecore sand 9 by blowing air thereto. The separating and collectingdevice 40 includes achamber 41, aninlet 42, anoutlet 43, anair blowing port 44, and anair outlet port 45. A duct (not shown) is provided above theair outlet port 45. - The mixture of the
water glass 15 and thecore sand 9 is put into thechamber 41 through theinlet 42. Thecore sand 9 put into thechamber 41 is separated due to a difference in specific gravity by air blown from theair blowing port 44. Thewater glass 15 having a low specific gravity is blown to theair outlet port 45 along with the air, and thecore sand 9 having a high specific gravity is blown to theoutlet 43. As a result, thecore sand 9 is separated and collected from theoutlet 43. - In this way, by treating the used
core sand 9 in the crushing step (Step S1), the heating step (Step S2), the detaching step (Step S3), and the separation and collection step (Step S4) in this order, thecore sand 9 can be reused to form a core (Step S5). During the formation of a core, thecore sand 9 is put into a mold and is solidified by heating to form a core. The heating temperature is, for example, a temperature lower than a casting temperature. As a result, the used core sand can be reused such that the formed core has the same strength as that of a core formed using new core sand. - Next, as shown in Step S6, the formed core is used for casting. For example, the core is used for aluminum casting at a casting temperature of 650° C. to 750° C. Next, as shown in Step S7, a post-treatment is performed. In the post-treatment, the used core is shaken off from a casting formed by casting. Next, in order to reuse the
core sand 9, the crushing step of Step S1 is performed. -
FIG. 11 is a graph showing an example of a strength of a core formed in the method of reusing core sand according to the embodiment, in which the horizontal axis represents the number of times of reuse and the vertical axis represents a transverse strength of a test piece (TP). As shown inFIG. 11 , the transverse strength of a core formed using new core sand is 1.8 to 4.0 MPa. Even in a case where the core sand is reused 48 times to form cores, the strengths of the cores is maintained at the same strength as that of the core formed using new core sand. - In the method of reusing core sand according to the embodiment, the granules obtained by crushing the core after casting are heated at a temperature of 300° C. to 550° C. Therefore, the
water glass 15 included in thegranules 14 is inactivated, and the strength of a core formed reusing the core sand can be improved. - Since even a core in which the
water glass 15 is used as a binder can be reused, the manufacturing costs can be reduced. - In the crushing step, the core is crushed into the
granules 14. As a result, in the heating step, thegranules 14 can be uniformly heated. Further, in the detaching step, thewater glass 15 can be uniformly detached from thecore sand 9. - In the heating step, it is preferable that, due to the heating, the amount of the water-
soluble water glass 15 is adjusted to be smaller than the amount of the water-insoluble water glass 15 in thewater glass 15 included in thegranules 14. In particular, it is preferable that the amount of the water-soluble water glass 15 is adjusted to be 0.2% or lower with respect to the amount of thegranules 14. With the above-described configuration, the inhibition of the hardening of thewater glass 15 by sodium ions can be reduced, and the strength of a core formed by reusing the core sand can be further improved. - In the heating step, the
water glass 15 can be appropriately dried. As a result, thewater glass 15 can be easily detached from thecore sand 9. In the detaching step, not only the water-soluble water glass 15 but also the water-insoluble water glass 15 can be detached from thecore sand 9. Therefore, in the separation and collection step, the amount of the usedwater glass 15 included in thecore sand 9 can be reduced. - Hereinabove, the embodiment of the method of reusing the
core sand 9 according to the disclosure has been described. However, the disclosure is not limited to the above-described configuration, and various modifications can be made. - For example, in the embodiment, the method of reusing core sand in which the
water glass 15 is used as a binder has been described. However, this reuse method is applicable to not only sand used for forming a core but also sand used for casting.
Claims (3)
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US17/149,897 US20210129210A1 (en) | 2015-10-19 | 2021-01-15 | Method of reusing core sand |
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JP2015205849A JP6354728B2 (en) | 2015-10-19 | 2015-10-19 | Reuse method and reuse device for core sand |
JP2015-205849 | 2015-10-19 | ||
US15/287,479 US10183322B2 (en) | 2015-10-19 | 2016-10-06 | Method of reusing core sand |
US15/949,394 US10668525B2 (en) | 2015-10-19 | 2018-04-10 | Method of reusing core sand |
US16/851,274 US10967421B2 (en) | 2015-10-19 | 2020-04-17 | Method of reusing core sand |
US17/149,897 US20210129210A1 (en) | 2015-10-19 | 2021-01-15 | Method of reusing core sand |
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US16/851,274 Division US10967421B2 (en) | 2015-10-19 | 2020-04-17 | Method of reusing core sand |
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US15/287,479 Active US10183322B2 (en) | 2015-10-19 | 2016-10-06 | Method of reusing core sand |
US15/949,394 Active 2037-04-29 US10668525B2 (en) | 2015-10-19 | 2018-04-10 | Method of reusing core sand |
US16/851,274 Active US10967421B2 (en) | 2015-10-19 | 2020-04-17 | Method of reusing core sand |
US17/149,897 Abandoned US20210129210A1 (en) | 2015-10-19 | 2021-01-15 | Method of reusing core sand |
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US15/287,479 Active US10183322B2 (en) | 2015-10-19 | 2016-10-06 | Method of reusing core sand |
US15/949,394 Active 2037-04-29 US10668525B2 (en) | 2015-10-19 | 2018-04-10 | Method of reusing core sand |
US16/851,274 Active US10967421B2 (en) | 2015-10-19 | 2020-04-17 | Method of reusing core sand |
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JP6354728B2 (en) | 2015-10-19 | 2018-07-11 | トヨタ自動車株式会社 | Reuse method and reuse device for core sand |
CN108723287B (en) * | 2018-06-11 | 2020-01-07 | 重庆长江造型材料(集团)股份有限公司 | Thermal regeneration method of silicate inorganic coating wet waste sand |
EP3620244B1 (en) * | 2018-09-07 | 2021-06-30 | HÜTTENES-ALBERTUS Chemische Werke Gesellschaft mit beschränkter Haftung | Method of preparing a particulate refractory composition for use in the manufacture of foundry moulds and cores, corresponding uses, and reclamation mixture for thermal treatment |
CN111283139B (en) * | 2018-12-27 | 2021-01-15 | 李秀英 | Casting raw sand screening method |
CN112122546B (en) * | 2020-09-08 | 2021-08-03 | 扬州胜宁信息技术有限公司 | Processing equipment and processing technology for recycling casting waste sand solid waste |
CN112264577A (en) * | 2020-10-20 | 2021-01-26 | 秦庭东 | Energy-concerving and environment-protective misce bene device when being favorable to casting mulling |
JP2023144031A (en) * | 2023-07-25 | 2023-10-06 | 大阪硅曹株式会社 | Method for regenerating casting sand |
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DE1806842A1 (en) * | 1968-11-04 | 1970-05-27 | Wilhelm Schwiese | Foundry sand regeneration |
JPS51140823A (en) * | 1975-05-30 | 1976-12-04 | Komatsu Mfg Co Ltd | Method of regenerating and processing casting sand |
JPS5677045A (en) * | 1979-11-26 | 1981-06-25 | Yozo Ishizuka | Technique of recycling casting waste sand containing alkali seed to neutral resource through hot air treatment |
DE3103030C2 (en) * | 1981-01-30 | 1984-05-03 | Klöckner-Humboldt-Deutz AG, 5000 Köln | Process for the extraction of foundry sand from used foundry sand |
ES2034025T3 (en) * | 1988-05-26 | 1993-04-01 | Pohl Giessereitechnik | PROCEDURE FOR THE RECOVERY OF USED SAND FROM FOUNDRY AND ITS CORRESPONDING EQUIPMENT. |
JP4679937B2 (en) * | 2005-03-10 | 2011-05-11 | 花王株式会社 | Manufacturing method of foundry sand |
DE102007008149A1 (en) * | 2007-02-19 | 2008-08-21 | Ashland-Südchemie-Kernfest GmbH | Thermal regeneration of foundry sand |
DE102011081530A1 (en) * | 2011-08-25 | 2013-02-28 | Bayerische Motoren Werke Aktiengesellschaft | Process for the regeneration of the sand from sand molds and cores |
JP5734818B2 (en) | 2011-11-28 | 2015-06-17 | トヨタ自動車株式会社 | Sand mold making method and sand mold |
JP6354728B2 (en) * | 2015-10-19 | 2018-07-11 | トヨタ自動車株式会社 | Reuse method and reuse device for core sand |
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US10967421B2 (en) | 2021-04-06 |
US20180221939A1 (en) | 2018-08-09 |
US20170106433A1 (en) | 2017-04-20 |
JP6354728B2 (en) | 2018-07-11 |
US10183322B2 (en) | 2019-01-22 |
US10668525B2 (en) | 2020-06-02 |
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