JP2007021578A - Structure for producing casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for producing a casting with which gas defect as the casting quality can be improved. <P>SOLUTION: On the surface of the structure (1) containing organic fiber, inorganic fiber and binder, the structure for producing the casting is made by sticking the inorganic grains having 1-800 nm average grain diameter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure such as a mold used in manufacturing a casting, a method for manufacturing the structure, and a method for manufacturing a casting using the structure.

In casting production, in general, a mold having a cavity (core if necessary) is formed with casting sand, and a receiving port, a gate, a runner and a weir (hereinafter referred to as “note”) for supplying molten metal to the cavity. (Also called hot water system)) is formed so as to lead to the cavity, and further, venting, hot water or filing to the outside is usually formed with a casting sand mold, or the pouring system is a refractory material. Molded using porcelain pipes, etc., but molded using a runner made of a structure containing organic fibers, inorganic fibers, inorganic particles and a binder as found in Patent Document 1 A method for producing a casting has been proposed. Patent Document 1 describes that a structure or the like is contained or impregnated before thermosetting the structure. This method has less heat loss of molten metal when casting compared to conventional porcelain pipes, is lightweight and has a fitting part, so the runner assembly work is simple, and dust generation and industrial waste are reduced. The improvement effect of these etc. is recognized.
JP2004-195547

  However, when used in the manufacture of castings such as thin-walled cast steel that is sensitive to gas generated from the runner made of the structure of Patent Document 1, there remains a problem that casting defects are relatively easy to generate gas defects. It had been.

  The subject of this invention is providing the structure for casting manufacture which can improve the gas defect which is casting quality.

  The present invention provides a casting comprising a structure (I) containing organic fibers, inorganic fibers and a binder, and inorganic particles having an average particle diameter of 1 to 800 nm attached to the surface of the structure (I). The present invention relates to a manufacturing structure.

  Moreover, this invention relates to the manufacturing method of the casting using the structure for casting manufacture of the said invention.

  Moreover, this invention relates to the manufacturing method of the structure for casting manufacture which has the process of making the inorganic particle of average particle diameter 1-800 nm adhere to the surface of structure (I) containing an organic fiber, an inorganic fiber, and a binder.

  Moreover, this invention is a manufacturing method of the structure for casting manufacture of the said invention, Comprising: The structure for casting manufacture which has a papermaking process using the raw material slurry which contains the said organic fiber, the said inorganic fiber, and the said binder at least It relates to a manufacturing method.

  ADVANTAGE OF THE INVENTION According to this invention, the structure for casting manufacture suitable as a casting_mold | template for casting which can improve the gas defect which is casting quality is provided.

  Hereinafter, the present invention will be described based on preferred forms thereof. The structure for producing a casting according to the present invention is formed by attaching inorganic particles having an average particle diameter of 1 to 800 nm to the surface of the structure (I) containing organic fibers, inorganic fibers and a binder. A preferable structure for producing a casting of the present invention contains organic fibers, inorganic fibers and a binder, and has an average particle size on the surface of the structure (I) [preferably the structure (I) heat-treated at 100 to 300 ° C.]. A layer containing inorganic particles having a diameter of 1 to 800 nm is formed. That is, it is preferable that the inorganic particles form a layer on the surface of the structure (I).

  The organic fiber forms a skeleton in the state before being used for casting in the structure (I), and a part or all of the organic fiber is burned by the heat of the molten metal at the time of casting. A cavity is formed.

  Examples of the organic fiber include wood pulp, fibrillated synthetic fiber, regenerated fiber (for example, rayon fiber) and the like, and these are used alone or in combination of two or more. Among these, paper fiber is preferable. The reason for this is that it can be formed into various forms by papermaking, the wet strength properties of the dehydrated and dried molded body are excellent, the availability of paper fibers is easy, stable and economical.

  In addition to wood pulp, cotton pulp, linter pulp, bamboo, straw and other non-wood pulp can be used for the paper fiber. Virgin pulp or waste paper pulp (collected product) can be used alone or in combination of two or more. Waste paper pulp is particularly preferred from the standpoints of availability, environmental protection, and reduction in production costs.

  The average fiber length of the organic fibers is preferably 0.8 to 2 mm, more preferably 0.9 to 1.8 mm. If the average fiber length of the organic fiber is 0.8 mm or more, the surface of the molded body will not be cracked, and mechanical properties such as impact strength will not be deteriorated. If the average fiber length is 2 mm or less, uneven thickness will occur. And the smoothness of the surface is improved.

  The content of the organic fiber is preferably 1 part by weight or more and less than 20 parts by weight, and more preferably 2 to 15 parts by weight, based on the ease of forming the structure and the effect of suppressing gas generation. In addition, in this specification, a weight part means the value with respect to a total of 100 weight part of an organic fiber, an inorganic fiber, and a binder (and other aggregates are also included). If the content of the organic fiber is 1 part by weight or more, the organic fiber forming the skeleton of the structure is sufficient, the moldability of the structure is good, and the strength of the structure after dehydration or drying is sufficient. Also, if it is less than 20 parts by weight, it is possible to prevent a large amount of combustion gas from being generated at the time of pouring, and blowing back from the pouring gate or raising (in a thin rod-like cavity provided at the upper part of the mold, the molten metal is cast into the mold. It is possible to prevent the flame from coming out from the portion that rises to the upper surface of the mold after satisfying the above. As a result, casting gas defects can be reduced and casting quality is improved. As the organic fiber species, it is preferable to use waste paper (newspaper, etc.) in view of the moldability, supplyability and economic efficiency of the structure.

  The inorganic fiber mainly forms a skeleton in a state before being used for casting in a structure, and maintains its shape without being burned by the heat of molten metal during casting. In particular, when an organic binder described later is used, the inorganic fiber can suppress thermal shrinkage caused by thermal decomposition of the organic binder due to the heat of the molten metal.

  Examples of the inorganic fibers include carbon fiber, artificial mineral fibers such as rock wool, ceramic fibers, and natural mineral fibers, which are used alone or in combination. Among these, it is preferable to use a carbon fiber having high strength even at a high temperature from the viewpoint of suppressing the heat shrinkage. Moreover, it is preferable to use rock wool from the viewpoint of reducing manufacturing costs.

The average fiber length of the inorganic fibers is preferably 0.2 to 10 mm, and more preferably 0.5 to 8 mm. If the average fiber length of the inorganic fibers is 0.2 mm or more, the drainage is good and there is no risk of poor dehydration during the production of the structure. Moreover, papermaking property becomes favorable at the time of manufacture of a thick structure (especially hollow three-dimensional shaped object like a bottle). On the other hand, if the average fiber length of the inorganic fibers is 10 mm or less, a structure with an equal thickness can be obtained, and the manufacture of a hollow structure is facilitated.

  The content of the inorganic fiber is preferably 1 to 80 parts by weight, and more preferably 2 to 40 parts by weight. If the content of the inorganic fiber is 1 part by weight or more, the strength of the structure manufactured using an organic binder is particularly strong at the time of casting, and due to carbonization of the binder, the structure is shrunk, cracked, There is no risk of peeling (a phenomenon in which the wall of the structure separates into an inner layer and an outer layer). Furthermore, it can suppress that a part of structure or casting sand mixes in a product (casting), and a defective product is manufactured. Moreover, if the content of the inorganic fiber is 80 parts by weight or less, the formability of the structure in the paper making process or the dehydration process is particularly good, leading to a reduction in fluctuations in raw material costs due to the fibers used.

  The ratio of the inorganic fiber to the organic fiber (inorganic fiber content / organic fiber content) is a weight ratio. For example, when the inorganic fiber is a carbon fiber, 0.1 to 50 is preferable and 0.2 to 30 is more preferable. preferable. When inorganic fiber is rock wool, 10-90 are preferable and 20-80 are more preferable. If this weight ratio is less than the upper limit of the above range, the structure has good formability in papermaking and dehydration molding, the structure after dehydration has sufficient strength, and the structure may crack when taken out from the papermaking mold. Can be prevented. Moreover, if this weight ratio is more than the lower limit of the said range, it can suppress that a structure shrink | contracts due to the thermal decomposition of an organic fiber or the below-mentioned organic binder.

  In the present invention, an organic binder and an inorganic binder can be used as the binder. Examples of the organic binder include thermosetting resins such as phenol resins, epoxy resins, and furan resins. Among these, it is particularly preferable to use a phenol resin from the viewpoints that the generation of combustible gas is small, there is a combustion suppressing effect, and the residual carbon ratio after pyrolysis (carbonization) is high. As the phenol resin, a novolak phenol resin that requires a curing agent as described below, or a resol type phenol resin that does not require a curing agent is used.

  When novolac phenolic resin is used, a curing agent is required. Since the curing agent is easily soluble in water, it is preferably applied to the surface of the structure after dehydration. It is preferable to use hexamethylenetetramine or the like as the curing agent. As the most preferable organic binder, a low free phenol resin such as a resol phenol resin or a cresol novolac phenol resin reacted with an alkali catalyst or a hydrochloric acid catalyst or an epoxy resin is most preferable from the viewpoint of working environment.

  Further, as the inorganic binder, a phosphoric acid binder, water glass such as silicate, gypsum, sulfate, silica binder, or silicon binder may be used. The organic binders may be used alone or in combination of two or more, and may be used in combination with an organic binder and an inorganic binder.

  The binder has a weight loss rate at 1000 ° C. in a nitrogen atmosphere (when measured by TG thermal analysis) by firmly bonding the organic fiber, the inorganic fiber and the inorganic particle when the paper-made part is dry-molded before casting. Is preferably 50% by weight or less, preferably 40% by weight or less.

  The content of the binder (solid content) is preferably 5 to 50 parts by weight and more preferably 10 to 30 parts by weight from the effect of maintaining strength and suppressing the amount of gas generated.

  As described above, the cause of the increase in the amount of gas generation is mainly the organic fiber and the organic binder. Therefore, the raw material species, the blending amount, and the weight ratio of both are the most important.

  By making the binder content appropriate, it is possible to prevent the structure from sticking to the mold during dry molding after paper making, making it easier to separate the structure from the mold, and the surface of the cured binder mold Build-up (resin adhesion) can be reduced, the dimensional accuracy of the structure can be improved, and the frequency of cleaning the mold surface can also be reduced.

  In addition to the organic fiber, inorganic fiber, and binder described above in the composition of the structure used in the present invention, aggregate particles having an average particle diameter (median diameter) of 1 μm or more are used as the composition raw material of the intermediate molded body of the structure. May be. Examples of the aggregate particles include refractory aggregate particles such as obsidian, silica, alumina, mullite, magnesia, zircon, chromite, mica, and graphite. These aggregate particles may be used alone or in combination of two or more. The average particle diameter (median diameter) is preferably 1 to 100 μm, more preferably 1 to 60 μm. If the average particle diameter is 1 μm or more, the yield at the time of papermaking is good, and fluctuations in the composition of the structure can be suppressed. Further, when the average particle size is 100 μm or less, the dispersibility of the raw material slurry becomes good, the thickness variation of the finished structure becomes small, the unevenness of strength is suppressed, and the quality becomes good.

  Further, as the aggregate particles, two or more types having different melting points or thermal decomposition temperatures can be used in combination. In particular, from the standpoint of maintaining the shape of the structure when it is exposed to high temperature during casting from before casting at room temperature, and preventing carburization during casting, the low melting point aggregate particles and the high melting point The aggregate particles are preferably used in combination. In this case, the low melting point aggregate particles include clay, silicate, obsidian and the like, and the high melting point aggregate particles include silica, wollastonite, mullite, chamotte, alumina, magnesia, zircon, chromite, mica. And graphite.

  In addition to the organic fiber, the inorganic fiber, and the binder, a paper strength reinforcing material may be added to the structure (I) of the present invention. The paper strength reinforcing material has an action of preventing swelling of the intermediate molded body when the intermediate molded body of the structure (I) is impregnated with a binder (described later).

  The amount of the paper strength reinforcing material used is preferably 0.01 to 2%, particularly preferably 0.02 to 1% of the total weight of the fibers as a solid content. If the amount of the paper strength reinforcing material used is 0.01% or more, the above-mentioned swelling prevention is sufficient, and the added powder is properly fixed to the fiber. On the other hand, if it is 2% or less, it becomes difficult for the molded body of the structure to stick to the mold.

  Examples of the paper strength reinforcing material include latex, acrylic emulsion, polyvinyl alcohol, carboxymethyl cellulose (CMC), polyacylamide resin, and polyamidoamine epichlorohydrin resin.

  Components such as a flocculant and a colorant can be further added to the structure (I) of the present invention.

  The thickness of the structure (I) can be set according to the purpose of use and the like, but the thickness of at least the portion in contact with the molten metal is preferably 0.2 to 5 mm, more preferably 0.4 to 3 mm. If this thickness is 0.2 mm or more, the strength of the structure is sufficient, and the shape and function desired for the structure can be maintained without losing the pressure of the foundry sand. Moreover, if this thickness is 5 mm or less, air permeability becomes appropriate, raw material costs can be reduced, molding time can be shortened, and manufacturing costs can be suppressed.

  The structure (I) has a compressive strength in a state before being used for casting of preferably 10 N or more, and more preferably 30 N or more. When the compressive strength is 10 N or more, the structure is not deformed by being pushed by the foundry sand, and the function as a structure can be maintained.

  When the structure (I) is produced using a raw material slurry containing water, the weight moisture content before use of the structure (I) (before being used for casting) is preferably 10% or less. % Or less is more preferable. The reason is that the lower the water content, the lower the amount of gas generated due to the thermal decomposition (carbonization) of the organic binder during casting.

  The specific gravity before use of the structure (I) is preferably 1 or less, and more preferably 0.8 or less. The reason is that if the specific gravity is small, the weight becomes light and the structure can be handled and processed easily.

  Next, based on the example of a hollow structure inside, the manufacturing method of the structure (I) which concerns on this invention is demonstrated about the manufacturing method which has the papermaking process which is a preferable manufacturing method. In this manufacturing method, it is preferable that the binder is a thermosetting resin and includes a step of heat-treating the organic fiber, the inorganic fiber, and the fiber laminate including the binder at 100 to 300 ° C.

  First, a raw slurry containing the organic fiber, the inorganic fiber, and the binder in the predetermined ratio is prepared. The raw material slurry is prepared by dispersing the fibers and the binder in a predetermined dispersion medium. The binder may be impregnated without adding the binder.

  Examples of the dispersion medium include water, white water, and solvents such as ethanol and methanol. Water is particularly preferable from the viewpoints of stability of papermaking and dehydration molding, stability of the quality of the molded body, cost, and ease of handling.

  The total content of the fibers in the raw slurry is preferably 0.1 to 4% by weight, and more preferably 1 to 3% by weight. If the total content of the fibers in the raw material slurry is 4% by weight or less, unevenness in the thickness of the molded body hardly occurs, and in the case of a hollow product, the surface property of the inner surface is also good. Moreover, if this total content is 0.1 weight% or more, it can suppress that a local thin part generate | occur | produces in a molded object.

  If necessary, additives such as the paper strength reinforcing material, the flocculant, and the preservative can be added to the raw material slurry.

  Next, an intermediate formed body of the structure (I) is made using the raw material slurry.

  In the paper making process of the intermediate formed body, for example, the cavity for the paper forming / dehydration forming in which a cavity having a shape corresponding to the outer shape of the intermediate formed body is formed by abutting a pair of split molds formed by two pieces. Use a mold. Then, a predetermined amount of raw material slurry is injected under pressure from the upper opening of the mold into the cavity. Thereby, the inside of the cavity is pressurized to a predetermined pressure. Each split mold is provided with a plurality of communication holes that communicate the outside with the cavity, and the inner surface of each split mold is covered with a net having a mesh of a predetermined size. For example, a pressure feed pump is used for the pressure injection of the raw slurry. The pressure for pressure injection of the raw material slurry is preferably 0.01 to 5 MPa, more preferably 0.01 to 3 MPa.

  As described above, since the inside of the cavity is pressurized to a predetermined pressure, the dispersion medium in the raw material slurry is discharged out of the mold from the communication hole. On the other hand, the solid content in the raw material slurry is deposited on the net covering the cavity, and a fiber laminate is uniformly formed on the net. In the fiber laminate obtained in this way, organic fibers and inorganic fibers are intricately entangled and a binder is interposed between them, so that even if it has a complicated shape, it is highly retained even after dry molding. Formability is obtained. Further, since the inside of the cavity is pressurized to a predetermined pressure, even when a hollow intermediate molded body is formed, the raw material slurry flows in the cavity and the raw material slurry is stirred. Therefore, the slurry concentration in the cavity is made uniform, and the fiber laminate is uniformly deposited on the net.

  After the fiber laminate having a predetermined thickness is formed, the pressure injection of the raw material slurry is stopped, and air is injected into the cavity to pressurize and dehydrate the fiber laminate. Thereafter, the press-fitting of air is stopped, the inside of the cavity is sucked through the communication hole, and an elastic, expandable and hollow core (elastic core) is inserted into the cavity. The core is made of urethane, fluorine rubber, silicone rubber, elastomer, or the like excellent in tensile strength, impact resilience, stretchability, and the like.

  Next, a pressurized fluid is supplied into the elastic core inserted into the cavity to expand the elastic core, and the fiber laminate is pressed against the inner surface of the cavity by the expanded elastic core. Thereby, the fiber laminate is pressed against the inner surface of the cavity, the shape of the inner surface of the cavity is transferred to the outer surface of the fiber laminate, and the dehydration of the fiber laminate proceeds.

  As the pressurized fluid used to expand the elastic core, for example, compressed air (heated air), oil (heated oil), and various other liquids are used. Further, the supply pressure of the pressurized fluid is preferably 0.01 to 5 MPa in view of the production efficiency of the molded body, and preferably 0.1 to 3 MPa in terms of particularly efficient production. When the pressure is 0.01 MPa or more, the drying efficiency of the fiber laminate is good, the surface property and the transfer property are sufficient, and when it is 5 MPa or less, a good effect is obtained and the apparatus can be downsized.

  Thus, since the fiber laminate is pressed against the inner surface of the cavity from the inside, even if the shape of the inner surface of the cavity is complicated, the inner surface shape is accurately transferred to the outer surface of the fiber laminate. Moreover, even if the molded body to be manufactured has a complicated shape, the bonding step of each part is not necessary, and therefore the finally obtained component does not have joints and thick portions due to bonding.

  When the inner surface shape of the cavity is sufficiently transferred to the outer surface of the fiber laminate and the fiber laminate can be dehydrated to a predetermined moisture content, the pressurized fluid in the elastic core is removed, and the elastic core Automatically shrinks to the size of. Then, the contracted elastic core is taken out from the cavity, and the mold is opened to take out a wet fiber laminate having a predetermined moisture content. The pressing / dehydration of the fiber laminate using the elastic core described above can be omitted as necessary, and the fiber laminate can be dehydrated and molded only by pressurization / dehydration by press-fitting air into the cavity.

  The dehydrated fiber laminate is then transferred to a heating / drying process.

  In the heating / drying step, a dry molding die in which a cavity having a shape corresponding to the outer shape of the intermediate molded body is formed is used. Then, the mold is heated to a predetermined temperature, and the wet fiber laminate obtained by dehydration molding is loaded into the mold.

  Next, an elastic core similar to the elastic core used in the paper making process is inserted into the fiber laminate, and a pressurized fluid is supplied into the elastic core to expand the elastic core. The fiber core is pressed against the inner surface of the cavity with the elastic core. It is preferable to use an elastic core whose surface is modified with a fluorine resin, a silicone resin or the like. The supply pressure of the pressurized fluid is preferably the same pressure as in the dehydration step. Under this condition, the fiber laminate is heated and dried to dry-mold the intermediate molded body.

  The heating temperature (mold temperature) of the mold for dry molding is preferably 100 to 300 ° C, more preferably 180 to 250 ° C, and still more preferably 200 to 240 ° C from the viewpoint of surface properties and drying time. Since the heat treatment time varies depending on the heating temperature, it cannot be generally described, but from the viewpoint of quality and productivity, it is preferably 10 to 60 minutes, and more preferably 20 to 40 minutes. If the heating temperature is 300 ° C. or lower, the surface property of the intermediate molded body is good, and if it is 100 ° C. or higher, the drying time of the intermediate molded body can be shortened.

  When the fiber laminate is sufficiently dried, the pressurized fluid in the elastic core is drawn out, the core is shrunk and taken out from the fiber laminate. And the said metal mold | die is opened and the said intermediate molded object is taken out. In this intermediate molded body, the thermosetting resin is cured by heat treatment and used as the structure (I).

  Since the structure (I) thus obtained is pressed by the elastic core, the smoothness of the inner surface and the outer surface is high. Therefore, the molding accuracy is high, and a highly accurate structure can be obtained even when the fitting portion and the screw portion are provided. Therefore, the structures connected by these fitting portions and screw portions can reliably suppress the leakage of hot water, and the hot water smoothly flows through the structure. Moreover, since the thermal contraction rate of the structure at the time of casting is less than 5%, it is possible to reliably prevent hot water leakage due to cracking or deformation of the structure.

  The obtained intermediate molded body can be further impregnated partially or entirely with a binder, if necessary.

  Examples of the binder impregnated in the intermediate molded body include a resol type phenol resin and a silica-based binder.

  When the intermediate molded body is impregnated with a binder and is not included in the raw material slurry, the raw material slurry and white water can be easily treated.

  After impregnating the thermosetting binder, the intermediate molded body is dried by heating at a predetermined temperature, and the thermosetting binder is thermoset to complete the manufacture of the structure (I).

  Next, a layer (hereinafter referred to as an adhesion layer) in which inorganic particles adhered, preferably containing inorganic particles, was formed on the surface of the structure (I) [preferably the structure (I) heat-treated at 100 to 300 ° C.]. The structure manufacturing method of the present invention will be described in detail.

  As a state in which inorganic particles are adhered to the surface of the structure (I), the surface of the structure (I) is 50% or more, more preferably 80% or more, particularly 90% or more, from the viewpoint of manifesting the effect of the present invention. It is preferably coated with particles.

  The average particle diameter of the inorganic particles used in the present invention is in the range of 1 to 800 nm, and the particle diameter of the inorganic particles is 1 to 600 nm from the covering performance (sagging due to dripping of the inorganic particle liquid) and the gas defect improving effect. Is preferable, further 5 to 300 nm, and the most preferable particle diameter is 10 to 30 nm. Usually, these solid contents are 10 to 60% by weight, and 30 to 50% by weight is preferable from the standpoint of liquidity as a covering performance. In addition, the average particle diameter of this inorganic particle used by this invention can be calculated | required with the measuring method of the below-mentioned Example description.

  Examples of the inorganic particles include silica and alumina. When the adhesion layer containing the inorganic particles is formed on the surface of the structure (I), the thickness of the adhesion layer (the thickness of the inorganic particles in the cross section where the inorganic particles are adhered to the surface of the structure after drying) Is preferably from 1 to 800 μm, more preferably from 5 to 500 μm, particularly preferably from 10 to 100 μm, from the suppression of the ability to prevent gas defects, which is a casting quality, and the drooping performance of the coating. In addition, the thickness of an adhesion layer can be calculated | required by the measuring method of the below-mentioned Example description.

  Further, as a method of forming an adhesion layer that adheres to the surface of the structure (I) and further contains inorganic particles, brush coating, spray coating, electrostatic coating, baking coating, using a dispersion containing the inorganic particles, Although methods such as splash coating and dip coating can be mentioned, dip coating is most preferable as a result of intensive studies on the uniformity of the thickness of the adhesive layer, efficiency and economy. The dip coating process will be described in detail. The structure (I) is immersed in a bath containing a predetermined amount of a dispersion containing the inorganic particles. The immersion temperature (dispersion temperature) is preferably in the range of 5 to 40 ° C., more preferably 15 to 30 ° C., more preferably 20 to 30 ° C., and most preferably set to have a constant temperature. Further, from the viewpoint of productivity, the immersion time is preferably in the range of 1 to 60 seconds, and can be immersed batchwise or continuously. As described above, a drying process is performed to make the structure (I) (preferably the structure (I) heat-treated in advance at 100 to 300 ° C.) with the inorganic particles adhered to a stronger adhesion state. It is preferable. Examples of the drying method include hot air drying with a heater, far infrared drying, microwave drying, superheated steam drying, and the like, but are not particularly limited. In the case of drying using a hot air dryer, the drying temperature in the center of the drying furnace is preferably in the range of 100 to 500 ° C. Furthermore, from the influence of thermal decomposition of organic fibers and binders and safety due to ignition, 150 to 230 ° C. The range of is most preferable.

  The structure of the present invention is arranged in casting sand and backup particles (shot balls and other particles instead of casting sand), and can be used as a runner (pouring system) or a hot runner. It is possible to manufacture a casting that improves a gas defect, which is a defect, and is particularly suitable for manufacturing a cast steel casting in which a gas defect is likely to occur.

  That is, the gas of the casting is obtained by optimizing the raw material of the structure (I) and the composition ratio thereof according to the structure of the present invention and forming an adhesion layer preferably containing inorganic particles on the surface of the structure (I). A casting manufacturing structure capable of improving defects can be provided. Although it is not clear as a reason why the gas defect of the casting is improved by the present invention, the gas is generated by controlling the gas generation amount of the structure itself exposed to the molten metal and attaching inorganic particles to the surface of the structure. It is estimated that the generation timing is delayed and the gas intrusion into the molten metal is slow.

  Furthermore, from the viewpoint of producing a casting that improves gas defects, it is desirable to adhere the inorganic particles to the surface side of the structure (I) that contacts the molten metal, preferably to form an adhesion layer. At that time, the inorganic particles are not adhered to the surface side of the structure (I) that does not contact the molten metal, that is, the inorganic particles are adhered only to the surface side of the structure (I) that contacts the molten metal, preferably It is preferable to form an adhesion layer.

  In this case, as a method of attaching the inorganic particles to the surface of the structure (I) in contact with the molten metal, and further forming an adhesion layer containing inorganic particles, a brush application using a dispersion containing the inorganic particles, Spray application is preferred.

  A structure in which the inorganic particles adhere to the surface of the structure (I) that contacts the molten metal, preferably an adhesion layer is formed, and the inorganic particles do not adhere to the surface of the structure (I) that does not contact the molten metal By using, the gas defect of the casting is further improved. The reason for this is not clear, but it adheres to the surface side in contact with the molten metal, preferably the surface of the inorganic particles forming the adhesion layer barriers the gas entering the molten metal side and does not contact the molten metal This is presumably due to the result of gas being removed from the mold to the mold side.

  The total weight of the organic fiber, inorganic fiber and binder (including other aggregates) in the structure of the present invention is preferably 50% by weight or more, more preferably 80% by weight, and further 90% by weight. preferable.

  The weight of the inorganic particles having an average particle diameter of 1 to 800 nm in the structure of the present invention is preferably 0.1 to 20% by weight, and more preferably 1 to 10% by weight.

  As a use of the structure of the present invention, a so-called full mold casting method using a mold having a cavity as described above or a foamed polystyrene model, or a disappearing model casting method without using a binder, or a main mold or core as a mold, etc. The structure of the present invention can be used in the field of casting or other fields where heat resistance is required, and the use is not particularly limited, but for runners for runners, runners for frying or cores in particular Is preferred.

The evaluation methods used in the following examples and comparative examples will be described.
<Measurement of gas generation amount of casting structure>
The amount of gas generated was measured using a gas generation amount measuring device (measuring device name: No.682 GAS PRESSURE TESTER HARRY W. DIETERT CO.). That is, the temperature in the furnace is set to 1000 ° C., the measurement sample weight of 0.1 g is accurately measured to the last three digits (in mg), the sample to be measured is placed on the sample stage, and the measuring instrument Measure gas generation according to the manual. The gas generation amount is calculated by the program with the integral value of the gas generation rate, and the gas generation amount after 30 seconds is calculated. As a computer for analyzing the gas generation rate and gas generation amount, Chromatopack C-R4A manufactured by Shimadzu Corporation was used.

<Measuring method of average particle diameter of inorganic particles>
The average particle diameter D (nm) of the inorganic particles is calculated as D = 2720 / S from the specific surface area S (m ² / g) obtained by measurement by the nitrogen adsorption method (BET method).

<Gas defects in castings>
In order to determine the occurrence of gas defects in a flat casting part cast by the method described later, the gas defects inside the casting were determined according to the following criteria by photographing with X-rays.
Judgment criteria ◎: No occurrence of gas defects in flat cast parts ○: Some occurrences of gas defects in flat cast parts but no repair required △: Some occurrence of gas defects in flat cast parts X: Those that require repair ×: Many gas defects are found in flat cast parts and cannot be repaired

<Measurement of adhesion layer thickness>
The thickness of the adhesion layer containing inorganic particles was measured by conducting EPMA analysis (surface analysis and line analysis of inorganic particle elements) on the cross section of the casting structure.

[Examples 1 to 4]
After making a predetermined fiber laminate using the following raw material slurry, the fiber laminate was dehydrated and dried to obtain a runner for a gate (equivalent to a straight pipe and an elbow pipe, the structure (I)). The composition of the structure (I) was as shown in Table 1.

<Preparation of raw material slurry>
An organic fiber and an inorganic fiber having the following composition are dispersed in water to prepare a slurry of about 1% (the total weight of the organic fiber and the inorganic fiber is 1% by weight with respect to water), and then aggregate particles and a binder are added to the slurry. And the following flocculant were added, and organic fibers, inorganic fibers, a binder, and the like were blended so as to obtain the structure (I) shown in Table 1, and respective raw material slurries were prepared.

[Combination of raw slurry]
Organic fiber: used newspaper (average fiber length 1mm, freeness 150cc)
・ Inorganic fiber: Carbon fiber (trade name “Treka chop” manufactured by Toray Industries, Inc., fiber length: 3 mm) ・ Binder: Phenolic resin (Asahi Organic Materials Co., Ltd., SP1006LS)
・ Aggregate particles (obsidian, average particle size 30μm)
Flocculant: polyacrylamide flocculant (Mitsui Cytec Co., Ltd., A110)
-Paper strength enhancer: 1% aqueous solution of carboxymethyl cellulose-Dispersion medium: water The above components were applied to a beater to obtain a water slurry so that the organic fibers, inorganic fibers, aggregate particles and binder had the weight mixing ratio shown in Table 1. The freeness of the fiber laminate made from the slurry was 300 cc. The flocculant and the paper strength enhancer are added to the slurry so that the total amount of organic fibers, inorganic fibers, binders and aggregate particles is 100 parts by weight (in terms of solid content) and 1 part by weight (in terms of solid content). Blended.

<Paper making and dehydration process>
As the papermaking mold, a mold having a cavity forming surface corresponding to the structure (straight pipe and elbow pipe) was used. A net having a predetermined opening is arranged on the cavity forming surface of the mold, and a plurality of communication holes are formed to communicate the cavity forming surface with the outside. In addition, this metal mold | die consists of a pair of split mold. The raw slurry is circulated by a pump, and a predetermined amount of slurry is pressurized and injected into the papermaking mold, while water in the slurry is removed through the communication hole, and a predetermined fiber laminate is deposited on the surface of the net. I let you. When injection of a predetermined amount of the raw material slurry was completed, pressurized air was injected into the papermaking mold to dehydrate the fiber laminate. The pressure of the pressurized air was 0.2 MPa, and the time required for dehydration was about 30 seconds.

<Curing agent coating process>
A curing agent (hexamethylenetetramine) in an amount corresponding to 15% (weight ratio) of the binder was dispersed in water, and the resulting fiber laminate was uniformly coated on the entire surface.

<Drying process>
As the drying mold, a mold having a cavity forming surface corresponding to the structure (straight pipe and elbow pipe) was used. The mold is formed with a large number of communication holes that communicate the cavity forming surface with the outside. The mold is composed of a pair of split molds. The fiber laminate coated with the curing agent was taken out from the papermaking mold and transferred to a dry mold heated to 220 ° C. Then, a bag-shaped elastic core is inserted from the upper opening of the dry mold, and pressurized fluid (pressurized air, 0.2 MPa) is put into the elastic core in the sealed dry mold. The elastic core was inflated to inflate, and the fiber laminate was pressed against the inner surface of the dry mold with the elastic core, and dried while transferring the inner shape of the dry mold onto the surface of the fiber laminate. After performing pressure drying for a predetermined time (180 seconds), the pressurized fluid in the elastic core is removed, the elastic core is contracted and taken out from the drying mold, and the molded body is taken out from the drying mold and cooled. did.

<Formation of adhesion layer>
Subsequently, in order to produce a structure in which an adhesion layer containing inorganic particles (manufactured by Nissan Chemical Industries, Ltd .: Snowtex 40, average particle size 15 nm) is formed on the surface of the heat-cured structure, a 30 L container is produced. 20 kg of inorganic particle dispersion liquid (dispersion liquid containing 40 parts by weight of Snowtex 40 and 60 parts by weight of water) is put in, and the thermoset structure (straight pipe and elbow pipe) is dip-coated (liquid) After a temperature of 20 ° C. for 30 seconds, the structure with the inorganic particles attached was taken out and drained for 15 minutes. Then, it was dried with a hot air dryer at 180 ° C. for 30 minutes to obtain a structure on which an adhesion layer containing inorganic particles was formed.

<Runner assembly process and mold production and casting process>
In order to assemble as a runner (runner) for casting using the obtained structure, one straight pipe with a fitting part (diameter φ50 mm / length 300 mm) and an elbow pipe with a fitting part (diameter φ50 mm / Cavity that fits two runners with a length of 100 mm and becomes a flat cast part (flat cast is 500 mm long x 300 mm wide x 30 mm thick, and the top is equipped with a heat retaining material to prevent shrinkage) A furan resin mold provided with the runner was formed. After 24 hours, a cast steel casting (material: SC-830, casting temperature 1600 ° C.) was cast.

[Comparative Example 1]
Comparative Example 1 is the same as Example 2 (Table 1) except that the inorganic particles are not attached to the surface of the structure.

[Examples 5 to 7 and Comparative Example 2]
In Example 2, a structure was produced in the same manner except that the inorganic particles shown in Table 2 were used as the inorganic particles, and the same evaluation was performed. The results are shown in Table 2. The results of Example 2 are also shown in Table 2.

[Examples 8 to 12]
In Example 2, “Snowtex 40” (average particle size: 15 nm) manufactured by Nissan Chemical Industries, Ltd. was used as the inorganic particles, and the inorganic particle concentration in the dispersion (the balance was water) was as shown in Table 3, and The structure was manufactured in the same manner except that the number of immersions in the dispersion was as shown in Table 3. At that time, drying was repeated for each dip coating. Drying conditions were 180 ° C. and 30 minutes at a time. Evaluation similar to Example 2 was performed about the gas generation amount using the obtained structure. The results are shown in Table 3. The results of Comparative Example 1 in which no adhesion layer was formed are also shown in Table 3.

[Reference example]
As described above, the thickness of the adhesion layer containing inorganic particles was measured by performing EPMA analysis (Si element surface analysis and line analysis) on the cross section of the casting structure. 1 and Comparative Example 1 are schematically shown in FIGS. In Example 10, from the line analysis (Si K nucleus) by EPMA (Electron Probe Micro-Analysis) in the lower left of FIG. 1, the thickness of the silica component of the adhesion layer containing inorganic particles on the surface of the structure is about 24 μm. From the surface analysis by EPMA in the lower right, it can be seen that an adhesion layer is formed on the surface of the structure by the silica component which is inorganic particles.

Example 13
In the same manner as in Example 1, the structure (I) (straight pipe and elbow pipe) was obtained with the composition shown in Table 4. A structure was obtained in the same manner except that the method for forming the adhesion layer in Example 2 was changed to the following method.

<Formation of adhesion layer>
Subsequently, a structure in which an adhesion layer containing inorganic particles (manufactured by Nissan Chemical Industries, Ltd .: Snowtex 40, average particle size 15 nm) is formed on the surface of the heat-cured structure in contact with the molten metal is manufactured. Therefore, a 20 kg inorganic particle dispersion (dispersion containing 40 parts by weight of Snowtex 40 and 60 parts by weight of water) is placed in a 30 L container, and the thermoset structure (straight pipe and elbow pipe) ) The inside of the cavity (surface in contact with the molten metal) was sprayed with an inorganic particle dispersion liquid at a flow rate of 1 L / min. The structure was removed and drained for 15 minutes. Then, it was dried with a hot air dryer at 180 ° C. for 30 minutes to obtain a structure in which an adhesion layer (thickness: 24 μm) containing inorganic particles was formed on the surface in contact with the molten metal.

<Runner assembly process and mold production and casting process>
The resulting structure is used to assemble as a casting runner (runner) as shown in FIG. 3 and consists of two elbow pipes (diameter: 50 mm) with fitting parts and straight pipes (diameter: 50 mm diameter) with fitting parts. , 150mm in length) Fits a single runner 31 and becomes a donut-shaped casting part Cavity 32 (outer diameter 240mm, inner diameter 140mm, thickness 30mm, with lift) A phenolic resin mold was formed. After 24 hours, a cast steel casting (SCS-13 casting temperature 1600 to 1540 ° C.) was cast.

The sand used for molding was fresh Fremantle sand, the casting weight was 20kg, the mold weight was 100kg. 20% by weight (based on resin) was used.

<X-ray photography of cast specimen and image analysis of area of internal gas defect>
After cutting off the runner part and the lift part of the casting test piece, the X-ray transmission device “6MeV linac” was used for photography. In order to measure the internal gas defect area of the cast specimen, the transmission photograph was used, and the internal gas defect area was calculated by “Winroof” in image analysis software. The smaller the internal gas defect area, the higher the quality of the casting. The results are shown in Table 4. In addition, the result of having performed the same evaluation also about the casting obtained using the structure obtained in Example 2 (The surface which is not in contact with a molten metal is also formed with the adhesion layer of an inorganic particle) was written together.

Sectional SEM photograph of the structure of Example 10, line analysis chart and surface analysis image by EPMA Cross-sectional SEM photograph, EPMA line analysis chart and surface analysis image of structure of Comparative Example 1 Schematic which shows the casting process in Example 13.

Claims (9)

  A structure for casting production comprising a structure (I) containing organic fibers, inorganic fibers and a binder, and inorganic particles having an average particle diameter of 1 to 800 nm attached to the surface of the structure (I). .   The structure for casting production according to claim 1, wherein the binder is a thermosetting resin, and the thermosetting resin is cured by heat treatment in the structure (I).   The structure for casting production according to claim 1 or 2, wherein the inorganic particles are at least one selected from silica and alumina.   The structure for casting production according to any one of claims 1 to 3, wherein a layer containing the inorganic particles is formed on the surface of the structure (I), and the thickness of the layer is 1 to 800 µm.   The manufacturing method of the casting using the structure for casting manufacture in any one of Claims 1-4.   The casting production according to any one of claims 1 to 4, further comprising a step of attaching inorganic particles having an average particle diameter of 1 to 800 nm to the surface of the structure (I) containing organic fibers, inorganic fibers and a binder. Manufacturing method of structure.   The said binder is a thermosetting resin, The manufacturing method of the structure for casting manufacture of Claim 6 which has the process of heat-processing the fiber laminated body containing the said organic fiber, the said inorganic fiber, and this binder at 100-300 degreeC. .   The method for producing a structure for casting production according to claim 6 or 7, wherein the inorganic particles are adhered by bringing the structure (I) into contact with a dispersion in which the inorganic particles are dispersed.   The manufacturing method of the structure for casting manufacture of any one of Claims 6-8 which has a papermaking process using the raw material slurry which contains the said organic fiber, the said inorganic fiber, and the said binder at least.