JP5372725B2 - Molding agent composition for sand casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating agent composition for sand mold casting which has high metal penetration resistance and satisfactory coating operability, and to provide a method for producing a casting using it. <P>SOLUTION: The coating agent composition for sand mold casting includes a refractory aggregate, binder grains and a solvent. The binder grains are insoluble in the solvent, the actual carbon ratio at 900&deg;C is &ge;20 wt.%, and also, sphericity is 0.90 to 1.00. Further, in the method for producing a casting, a sand mold for casting obtained by coating the surface 1 of the sand mold with a coating agent composition is used, as the coating agent composition, a coating agent composition for sand mold casting is used. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a coating composition for sand molds used for casting cast steel, cast iron, aluminum, copper and alloys thereof.

  As a casting coating agent used for a sand mold, an agent that protects the surface of a sand mold by applying a coating film on a sand mold (mold) surface in contact with a molten metal is known. Such a casting mold agent is used to prevent the chemical reaction between the molten metal and the sand mold surface and the occurrence of casting defects in the casting.

  As a conventional sand mold casting coating composition, Patent Document 1 discloses a coating composition containing spherical sand, an organic binder such as a phenolic organic polymer substance, and a solvent. According to the coating composition disclosed in Patent Document 1, a vacuum suction casting mold having a high air permeability can be produced.

  On the other hand, as a coating agent composition for disappearance model casting, Patent Documents 2 and 3 disclose a coating agent composition containing a foamed synthetic resin made of a spherical or cubic polystyrene resin or the like. According to the coating composition disclosed in Patent Documents 2 and 3, casting defects caused by thermal decomposition of the foamed synthetic resin can be prevented.

JP 2004-98134 A Japanese Patent Laid-Open No. 2001-1104 JP 2009-214126 A

  In the conventional sand mold casting coating composition, when the difficulty of the object is high, that is, when forming a casting having a complicated shape, it is difficult to reliably prevent the occurrence of a casting defect in the casting. Therefore, further improvement is desired for the seizure resistance.

  Further, in the conventional sand mold casting coating composition, it is desired to improve the coating workability when the coating composition is applied to the sand mold surface. For example, when the coating composition is applied to the sand mold surface by brush coating, the elongation (brush elongation) of the coating composition on the sand mold surface is not always good. If the coating workability is poor, the casting productivity is lowered and the cost is increased. With regard to such problems, conventional sand mold casting coating compositions have not been sufficiently studied.

  The present invention provides a mold casting composition for sand mold casting that has high seizure resistance and good coating workability, and a method for producing a casting using the same.

  The sand casting casting composition of the present invention is a sand casting casting composition containing refractory aggregate, binder particles and a solvent, wherein the binder particles are insoluble in the solvent, and 900 A sand casting casting composition having a residual carbon ratio of 20% by weight or more at 0 ° C. and a sphericity of 0.90 to 1.00.

  The casting production method of the present invention is a casting production method using a casting sand mold formed by applying a coating composition to a sand mold surface, and the sand mold of the present invention is used as the coating composition. It is the manufacturing method of the casting which uses the coating agent composition for casting.

  According to the coating composition for sand mold casting of the present invention, it is possible to provide a coating composition for sand mold casting that has high seizure resistance and good coating workability. In addition, according to the casting production method of the present invention, since the sand mold casting coating composition of the present invention is used, it is possible to suppress seizure defects and improve casting productivity.

It is a schematic perspective view of a sand mold (core).

  Hereinafter, components contained in the mold casting composition for sand casting of the present invention (hereinafter, also simply referred to as “coating composition”) will be described.

<Fireproof aggregate>
The refractory aggregate used in the present invention is not particularly limited, but from the viewpoint of fire resistance, economy, and resistance to reaction with molten metal, mullite, silica, alumina, magnesia, zircon, alumina silicate, graphite, It is preferably composed of one or more selected from obsidian, olivine, talc and mica, and more preferably one or more selected from talc, zircon and graphite (especially scaly graphite).

The fire resistant aggregate used in the present invention preferably has an average particle diameter of 0.5 to 100 μm, more preferably 1 to 30 μm, and more preferably 5 to 20 μm from the viewpoint of improving application workability. More preferably it is. Here, the average particle diameter of the refractory aggregate is a volume-median particle diameter (D50) measured using a laser diffraction particle size distribution analyzer (LA-920 manufactured by Horiba, Ltd.). The analysis conditions are as follows.
Measurement method: Flow method Dispersion medium: Solvent dispersion method in which sodium hexametaphosphate (0.1% by weight) is added to ion-exchanged water: Stirring, built-in ultrasonic irradiation (3 minutes)
Sample concentration: 2 mg / 100 ml

<Binder particles>
The binder particles have a function of bonding refractory aggregates or refractory aggregates and a mold at the time of casting, and can maintain hot strength. From the viewpoint of seizure resistance, the binder particles used in the present invention have a residual carbon ratio at 900 ° C. (hereinafter also simply referred to as “residual carbon ratio”) of 20% by weight or more.

The residual carbon ratio is the amount of fixed carbon in the binder particles. The measurement method is as follows. First, the weight (1) after drying 2 g of binder particles at 105 ° C. for 12 hours is measured. Next, the dried binder particles are hermetically heated in a muffle furnace at 900 ° C. for 7 minutes. Further, the muffle furnace cover is removed and heated at 900 ° C. for 4 hours, and the weight (2) of the residue after heating is measured. From the weight (1) and the weight (2), the residual carbon ratio is calculated by the following formula.
Residual charcoal ratio (% by weight) = weight (2) / weight (1) × 100

  The residual carbon ratio is an index of the hot strength of the coating film formed on the surface of the mold by binding the refractory aggregate with binder particles. That is, the residual carbon ratio serves as an index of a function for developing the hot strength as the binder, and the higher the carbon ratio, the more preferable. The reason why the seizure resistance is increased by setting the residual carbon ratio of the binder particles to 20% by weight or more is not clear, but since the pyrolysis gas generated from the coating film at the time of casting can be reduced, It is considered that the void portion is reduced and the seizure defect is suppressed.

  The residual carbon ratio of the binder particles is preferably 40% by weight or more and more preferably 50% by weight or more from the viewpoint of seizure resistance. Further, from the viewpoint of availability, the residual carbon ratio of the binder particles is preferably 80% by weight or less, and more preferably 70% by weight or less. In addition, what is necessary is just to select what consists of suitable resin mentioned later, for example as binder particle | grains, in order to control the residual carbon ratio of binder particle | grains in the said range. A suitable resin is a phenolic resin having excellent heat resistance. For example, a resin having a residual carbon ratio of 20% by weight or more may be selected from resins having a weight average molecular weight of 1000 or more.

  Further, the binder particles used in the present invention have a sphericity of 0.90 to 1.00 from the viewpoint of coating workability, particularly brush elongation.

The sphericity refers to the area of the particle projection cross section obtained by image analysis of the image (photograph) obtained by the scanning electron microscope of each binder particle and the perimeter, [the area of the particle projection cross section (mm ² ) and This is a value obtained by calculating the circumferential length of a perfect circle of the same area (mm)] / [circumferential length of particle projected cross section (mm)] and averaging this for any 50 binder particles.

  The reason why the coating workability is improved by setting the sphericity of the binder particles to 0.90 to 1.00 is not clear, but it is possible to impart appropriate fluidity to the coating composition, This is considered to improve the properties, particularly the brush elongation.

  The sphericity of the binder particles is preferably from 0.95 to 1.00, more preferably from 0.97 to 0.99, from the viewpoint of brush elongation. In order to control the sphericity of the binder particles within the above range, for example, a binder particle having a sphericity within the above range may be selected from suitable resins described later.

  The binder particles are not particularly limited as long as the residual carbon ratio and sphericity are within the above ranges, but are insoluble in solvents from the viewpoint of improving the coating workability by maintaining the shape during the coating work. Material is used. Here, “insoluble in a solvent” means that the solubility in 100 g (25 ° C.) of the solvent used in the coating composition is less than 10 g.

  When water and / or alcohol is used as the solvent, examples of the binder particles insoluble in the solvent include those made of resins such as phenol resins, vinyl resins, amide resins, imide resins, polyurethane resins, What consists of a phenol-type resin is preferable.

  Examples of the binder particles having a residual carbon ratio of 20% by weight or more include those made of a resin such as a phenol resin, a xylene resin, and a urethane resin, and those made of a phenol resin are preferable.

  Usable phenolic resins include phenol, cresol, 3,5-xylenol, nonylphenol, p-tert-butylphenol, isopropenylphenol, phenylphenol and other alkylphenols, novolac, resole, resorcinol, xylenol, catechol, hydroquinone, phlorog Examples thereof include phenolic resins using polyhydric phenols such as lucinol, bisphenols such as bisphenol A, bisphenol F, bisphenol C, and bisphenol E as raw materials. Of these, a phenol resin having a hydroxymethyl group bonded to a benzene ring is preferred from the viewpoint of seizure resistance.

The average particle size of the binder particles used in the present invention is preferably 1 to 80 μm, more preferably 2 to 50 μm, and more preferably 5 to 30 μm from the viewpoints of coating workability, dispersibility, and seizure resistance. More preferably, it is more preferably 5 to 20 μm. Here, the average particle diameter of the binder particles is a volume-median particle diameter (D50) measured using a laser diffraction particle size distribution analyzer (LA-920 manufactured by Horiba, Ltd.). The analysis conditions are as follows.
Measurement method: Wet method Dispersion medium: Water dispersion method: Stirring, built-in ultrasonic irradiation (3 minutes)
Sample concentration: 200 mg / 100 ml

  The content of the binder particles in the coating composition is 0 with respect to 100 parts by weight of the refractory aggregate from the viewpoint of improving the coating film strength and reducing the amount of pyrolysis gas to improve the seizure resistance. 5 to 10 parts by weight is preferable, and 1 to 5 parts by weight is more preferable.

<Solvent>
Although the solvent used by this invention is not specifically limited, Water and / or alcohol etc. can be used. Water is preferable in terms of safety and economy. Examples of the alcohol include methanol, ethanol, propanol, butanol, hexanol and the like, and ethanol is preferable from the viewpoint of cost and coating workability. The content of the solvent in the coating composition is 10 to 500 parts by weight with respect to 100 parts by weight of the refractory aggregate from the viewpoint of maintaining the thickness of the coating film in an appropriate range and from the viewpoint of reducing dripping. Preferably, 10 to 100 parts by weight is more preferable.

<Other ingredients>
Other components that can be blended in the coating composition of the present invention include binders such as gum arabic, sintering agents such as attapulgite and bentonite, colorants such as pigments and dyes, and rheology modifiers that improve coating workability. Additives such as anti-settling agents and surfactants can be used. In addition, additives such as thickeners and preservatives such as cellulose derivatives such as hydroxyalkylated cellulose, polyvinyl alcohol and sodium alginate can also be used.

  The mold agent composition of the present invention is suitable for a casting production method using a casting sand mold formed by applying a mold agent composition to a sand mold surface. That is, the casting manufacturing method of the present invention is a casting manufacturing method using a casting sand mold formed by applying the above-described coating agent composition of the present invention to a sand mold surface.

  The method for applying the coating composition of the present invention to the sand mold (mold) is not particularly limited, and is conventionally known, for example, flow coating (bukkake method), dipping (dipping method), brush coating, spray coating, and the like. The method you can use is available. Among these, it is preferable to apply the coating composition of the present invention by brush coating because the effect of the present invention (improvement of brush elongation) is effectively exhibited. Further, as the foundry sand used for the sand mold, silica sand mainly composed of quartz, new sand such as zircon sand, chromite sand, synthetic mullite sand, or regenerated sand thereof is used. Foundry sand can also be used without the addition of a binder, in which case the filling property is good, but when high sand mold strength is required, a binder is added and a hardener is used. It is preferable to cure.

  In addition, the above sand molds are generally mixed with molding binders such as organic binders such as furan resin and alkali phenol resin and inorganic binders such as water glass. After being filled in, it is obtained by curing and die cutting.

  In general, the coating agent composition is kept as a composition (preservation composition) in a state where the solvent concentration is low (solid content concentration is high) during storage so that an appropriate viscosity can be obtained during use. And diluted with a solvent. The composition having a high solid content (preservation composition) may be adjusted to the amount of solvent and the like, and usually has a penetration of about 200. The appropriate viscosity (concentration) at the time of use is 30 to 80 baume.

  When a casting is produced using the mold composition of the present invention, a casting having few seizure defects and a beautiful casting surface is obtained, so that a complicated structure and a beautiful casting surface are required. It is suitable for. Specific examples of castings include members, parts, and the like used for hydraulic valves, motors, molds, engine frames, machine tools, building members, and the like of construction machines.

  Examples and the like specifically showing the present invention will be described below.

<Preparation of coating agent composition>
In a weight ratio shown in Table 1 (Example) and Table 2 (Comparative Example), refractory aggregate, binder, water, ethanol and additives are mixed, and kneaded at 25 ° C. for 30 minutes in a kneader, paste A shaped coating composition was obtained. All of the above refractory aggregates include talc (average particle size 22 μm), zircon (average particle size 7 μm) and scaly graphite (average particle size 39 μm), talc: zircon: scale graphite = 45: 25: A mixture with a weight ratio of 30 was used. Moreover, all of the above additives are a binder (gum arabic), a sintering agent 1 (attapulgite), a sintering agent 2 (bentonite), an anionic surfactant (sodium naphthalene sulfonate), Brominated preservatives, binder: sintering agent 1: sintering agent 2: anionic surfactant: brominated preservative = 8.8: 14.6: 70.2: 3.5: 2. What was mixed by the weight ratio of 9 was used. When the obtained coating agent composition was measured with a needle penetration measuring device 800S-01 manufactured by Koiso Co., Ltd., the penetration was 200 in all cases. In addition, "solubility with respect to a solvent" of the binder in Table 1 and Table 2 is a water-ethanol mixed solvent (weight ratio is water: ethanol = 25.0: 2.0 or 25.6: 2.0) 100 g (25 ℃)) After adding 10g of binder and dispersing ultrasonically, when processing for 10 minutes at 3000rpm in a centrifuge, the case where the precipitate is generated is considered "insoluble" and the precipitate is generated The case where it did not exist was defined as “soluble”.

<Burning test>
Using furan reclaimed sand (AFS45) as foundry sand, adding 0.8 parts by weight of furan resin (340B) manufactured by Kao Quaker to 100 parts by weight of foundry sand, and further adding a curing agent (TK-3 manufactured by Kao Quaker) ) Was added to 40 parts by weight of 100 parts by weight of furan resin, and kneaded sand was molded to prepare eight pentagonal cores 1 shown in FIG. And after diluting the said coating agent composition with water so that it may become the density | concentration (baume) at the time of application | coating shown in Table 1 and Table 2, eight cores 1 are each added to this diluted coating agent composition. It was pickled and dried with hot air at 105 ° C. for 1 hour. Next, on the bottom surface of the main mold for forming a casting having a diameter of 350 mm and a height of 400 mm, the eight cores after the drying are equally arranged on the same circumference (diameter 250 mm) as shown in FIG. . Molten metal (material FC-250) was poured into this mold at 1420 ° C. and left for 24 hours. Thereafter, the casting mold was taken out, the casting was taken out, the area of the inner surface of the void portion where the core was placed in the obtained casting was measured, and the burning rate was calculated by the following formula. The results are shown in Tables 1 and 2.
Burning rate (%) = (Area deposited on the inner surface of the void where the core was disposed / Total area of the inner surface of the void where the core was disposed) × 100

<Application test>
Using furan reclaimed sand (AFS45) as foundry sand, adding 0.8 parts by weight of furan resin (340B) manufactured by Kao Quaker to 100 parts by weight of foundry sand, and further adding a curing agent (TK-3 manufactured by Kao Quaker) ) Was added to 40 parts by weight of 100 parts by weight of furan resin, and kneaded sand was molded to prepare a plate-shaped test piece having a length of 300 mm, a width of 200 mm, and a thickness of 30 mm. And after diluting the said coating agent composition with water so that it may become the density | concentration (baume) at the time of application | coating shown in Table 1 and Table 2, the said diluted coating agent composition is brushed on the surface of the said test piece. It was applied by painting. The ease of application with a brush at that time (brush elongation) was evaluated in the following three stages. The results are shown in Tables 1 and 2.

(Brush elongation evaluation criteria)
1: Elongation is bad.
2: Elongation is good.
3: Very good elongation.

  As shown in Table 1, in Examples 1 to 4, good results were obtained for both the baking test and the coating test. On the other hand, as shown in Table 2, Comparative Examples 1 to 14 were significantly inferior to Examples 1 to 4 in at least one of the baking test and the coating test. From this result, it was confirmed that according to the present invention, it is possible to provide a coating composition having excellent anti-seizure properties and good workability (particularly brush elongation).

1 core

Claims (5)

A sand casting casting composition containing refractory aggregate, binder particles and solvent,
The binder particles are insoluble in the solvent, have a residual carbon ratio at 900 ° C. of 20% by weight or more, and have a sphericity of 0.90 to 1.00.   The sand mold casting coating composition according to claim 1, wherein the binder particles are made of a phenolic resin.   The sand mold casting coating composition according to claim 1 or 2, wherein the binder particles have an average particle size of 1 to 80 µm.   The sanding casting coating composition according to any one of claims 1 to 3, wherein a content of the binder particles is 0.5 to 10 parts by weight with respect to 100 parts by weight of the refractory aggregate. A casting manufacturing method using a casting sand mold formed by applying a coating agent composition to a sand mold surface,
The manufacturing method of a casting whose said coating agent composition is the coating agent composition for sand mold casting of any one of Claims 1-4.

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