JP4364717B2 - Foundry sand composition - Google Patents

Description

The present invention relates to a foundry sand composition used for a mold or the like.

Conventional technology

Conventionally, as casting sand which is one of casting mold materials, there are silica sand, zircon sand, chromite sand, olivine sand, etc., especially silica sand having an average particle diameter of 0.4 to 0.5 mm is widely used. I came. In addition, the raw materials blended so as to have an aluminosilicate composition mainly composed of Al ₂ O ₃ and SiO ₂ are adjusted in slurry and granulated, and then mixed with fine powder for preventing fusion between the granulated particles. Baked at 1400-1750 ° C., and the pulverized artificial ceramic particles manufactured by removing the fine powder for preventing fusion are reduced in molding man-hours, excellent in crush resistance, and reduced in waste. It has been used gradually because of its excellent fire resistance. It has also been proposed to use artificial ceramic particles obtained by different production methods (Patent Document 1).
JP 2003-136187 A

  Since the sand such as silica sand described above is indefinite, it has been difficult to fill the thin portion such as the fin-shaped portion of the mold with sand. In addition, the artificial ceramic particles produced by the firing method described above (hereinafter referred to as fired artificial ceramic particles) have many irregularities on the surface of the particles depending on the production conditions. It was not enough.

  The moldability of foundry sand is thought to improve as the surface of the sand particles becomes smoother. On the other hand, sand coated with a spherical aggregate with a smooth surface of sand particles with a binder is similar to liquid. In order to show the properties obtained, there is stickiness due to improper liquid crosslinking. As a result, it adheres to the molding work tool, and it is necessary to reduce the sand yield during molding or to frequently clean the inside of the mixer. In addition, sticking to a wood mold or a resin mold for molding a mold is likely to occur.

  An object of the present invention is to provide foundry sand that is excellent in filling property, has no stickiness and no stickiness of coated sand, and can easily produce a mold having a complicated shape or a mold having high strength.

  The present inventor is able to fill a mold having a complex shape with excellent workability by mixing a specific spherical casting sand in a predetermined ratio with the conventional casting sand, and the coated sand is sticky. The present inventors have found that a molding sand composition having no sticking can be obtained and completed the present invention.

  In the present invention, spherical casting sand (A) having an average particle diameter of 0.05 to 1.5 mm produced by a flame melting method and casting sand (B) other than (A) are obtained by (A) / (B ) = Foundry sand composition contained at a volume ratio of 5/95 to 50/50. The present invention also relates to a foundry sand composition in which the foundry sand composition of the present invention is coated with a binder composition. Furthermore, the present invention relates to a mold using the foundry sand composition of the present invention, and a casting manufactured using the mold.

  Since the foundry sand composition of the present invention contains the specific spherical foundry sand (A), the filling property of the casting sand itself is high, and the coated sand coated with the binder is also less sticky, so that the filling property of the mold is also enhanced. Manufacture of a mold having a complicated shape is facilitated and the strength of the mold is increased. That is, according to the foundry sand composition of the present invention, the moldability of the mold can be improved and the mold strength can be increased.

<Spherical casting sand (A)>
The spherical foundry sand (A) of the present invention is obtained by a flame melting method, and has the structural features that the surface is smooth, the sphericity is high, and it is dense. The structural feature greatly contributes to improvement of mold strength and surface smoothness of a cast casting.

  The spherical casting sand (A) of the present invention preferably has a sphericity of 0.98 or more, more preferably 0.99 or more. The sphericity can be determined by observing the foundry sand with an optical microscope or a digital scope (for example, VH-8000, manufactured by Keyence Corporation).

  Moreover, the average particle diameter (mm) of the spherical foundry sand (A) of the present invention is in the range of 0.05 to 1.5 mm from the viewpoint of reduction of the binder amount, ease of regeneration, mold strength, and the like. From the viewpoint of improving the recycle efficiency of the foundry sand, 0.075 to 1.5 mm is preferable, and from the viewpoint of increasing the mold strength, 0.05 to 1 mm is preferable. From the viewpoint of increasing both the regeneration efficiency and the mold strength, 0.05 to 0.5 mm is more preferable, and 0.05 to 0.35 mm is more preferable.

  The average particle diameter can be determined as follows. That is, the diameter (mm) is measured when the sphericity from the projected particle cross section of the foundry sand particle is 1, while the major axis diameter (mm) of the randomly oriented foundry sand particle when the sphericity <1. The major axis diameter (mm) is measured to obtain (major axis diameter + minor axis diameter) / 2, and the average particle diameter (mm) is obtained by averaging the values obtained for any 100 casting sand particles. And The major axis diameter and the minor axis diameter are defined as follows. When the particle is stabilized on a plane and the projected image of the particle on the plane is sandwiched between two parallel lines, the width of the particle that minimizes the distance between the parallel lines is called the minor axis diameter. The distance when a particle is sandwiched between two parallel lines in a direction perpendicular to the line is called the major axis diameter.

The major axis diameter and the minor axis diameter of the foundry sand particles are obtained by obtaining an image (photograph) of the particles with an optical microscope or a digital scope (for example, VH-8000, manufactured by Keyence Corporation), and image analysis of the obtained image is performed. Can be obtained. The sphericity is obtained by image analysis of the obtained image to determine the area of the particle projection cross section of the particle and the perimeter of the cross section, and then [the area of the same area as the area of the particle projection cross section (mm ² )] The circumference of the perfect circle (mm)] / [perimeter of the particle projection cross section (mm)] is calculated, and the obtained values are averaged for any 50 foundry sand particles.

  Further, the water absorption rate (% by weight) of the spherical casting sand (A) of the present invention is such that the increase in the amount of binder used due to absorption of the binder used in the production of the mold into the casting sand is suppressed, and the mold strength is reduced. From the viewpoint of improvement and the like, it is preferably 3% by weight or less, more preferably 0.6% by weight or less, and further preferably 0.3% by weight or less. The water absorption can be measured according to the method for measuring the water absorption of JIS A1109 fine aggregate. In addition, when it is coated with a binder or when the binder remains after casting, the water absorption rate after removing these components by an appropriate method such as heat treatment (for example, 1000 ° C. or higher). Measure.

  The water absorption rate of the spherical casting sand (A) is usually the same as the water absorption rate when the sand is prepared by a flame melting method, as long as it has the same sphericity as compared with the sand prepared by a firing method other than the method. Lower.

The components of the spherical casting sand (A) of the present invention are not particularly limited, but contain Al ₂ O ₃ or SiO ₂ or a mixture thereof as a main component, and the Al ₂ O ₃ / SiO ₂ weight ratio is 1 to 15. (Hereinafter referred to as spherical casting sand (A-1)) is preferred.

The spheroidal molding sand (A-1) of the present invention is mainly composed of Al ₂ O ₃ and SiO ₂ , where “main component” is the total amount of Al ₂ O ₃ and SiO ₂ in the total amount of the casting sand. It means that 80% by weight or more is contained in all components.

The content of Al ₂ O ₃ and SiO ₂ which are the main components of the spherical molding sand (A-1) of the present invention is, as a total amount thereof, spherical molding sand (A-1) from the viewpoint of improving fire resistance. ) Is preferably 85 to 100% by weight, more preferably 90 to 100% by weight.

Further, the Al ₂ O ₃ / SiO ₂ weight ratio of the spherical casting sand (A-1) is 1 to 15. From the viewpoint of improvement in fire resistance and casting sand regeneration efficiency, 1.2 to 12 is preferable, and 1.5 to 9 is more preferable.

Incidentally, the present invention as the spherical molding sand (A-1) may be included as a component other than the main component is, for _{example, CaO, MgO, Fe 2 O} 3, TiO 2, K 2 O, Na 2 O-such as A metal oxide is mentioned. These are used as starting materials, for example, derived from the materials described below. When CaO and MgO are contained, from the viewpoint of improving the fire resistance of the spherical casting sand (A), the total content thereof is preferably 5% by weight or less. When Fe ₂ O ₃ and TiO ₂ are contained, their content is preferably 5% by weight or less. Further, the content of Fe ₂ O ₃ is more preferably 2.5% by weight or less, and further preferably 2% by weight or less. When K ₂ O and Na ₂ O are contained, the total content is preferably 3% by weight or less, more preferably 1% by weight or less.

  Below, an example of the manufacturing method of the spherical foundry sand (A-1) of this invention by a flame melting method is demonstrated.

The production method of the spherical casting sand (A-1) according to the present invention comprises Al ₂ O ₃ and SiO ₂ as main components, an Al ₂ O ₃ / SiO ₂ weight ratio of 0.9 to 17, and an average particle size of 0. The method includes a step of using 0.05 to 2 mm powder particles as a starting material and melting the powder particles in a flame to spheroidize.

Here, “having Al ₂ O ₃ and SiO ₂ as main components” means that Al ₂ O ₃ and SiO ₂ are contained in a total amount of 80% by weight or more in all components in the powder particles as a starting material. It means that Therefore, as long as “mainly composed of Al ₂ O ₃ and SiO ₂ ”, the powder particle is composed of a mixture of a raw material as an Al ₂ O ₃ source and a raw material as a SiO ₂ source as described later. Even if it consists of the raw material alone as the (Al ₂ O ₃ + SiO ₂ ) source, the raw material as the Al ₂ O ₃ source and / or the raw material as the SiO ₂ source and (Al ₂ O ₃ + SiO _{2) 2} ) It may be a mixture with raw materials as a source.

In the powder particles as the starting material, the content of the total amount of Al ₂ O ₃ and SiO ₂ as the main component, the total amount of Al ₂ O ₃ and SiO ₂ in the resulting molding sand is all components in From the viewpoint of achieving 80% by weight or more, it is preferably 75% by weight or more, more preferably 80% by weight or more, still more preferably 85 to 100% by weight, particularly preferably 90 to 100% by weight. . Al The ₂ O ₃ / SiO ₂ weight ratio, from the viewpoint of Al ₂ O ₃ / SiO ₂ weight ratio in the resulting molding sand is made to be 1 to 15, is 0.9 to 17, preferably 1 ~ 15. The average particle size is 0.05 mm or more from the viewpoint of obtaining monodispersed foundry sand, 2 mm or less from the viewpoint of obtaining foundry sand having a desired sphericity, and 0.05 to 2 mm. Moreover, from a viewpoint of the improvement of the sphericity of the obtained foundry sand, 0.05-1.5 mm is preferable.

The reason why the Al ₂ O ₃ / SiO ₂ weight ratio differs between the raw material powder particles and the obtained foundry sand is that the lost amount of Al ₂ O _{3 and} the lost amount of SiO ₂ differ depending on the raw material. The average particle size of the raw material powder particles may be in the above-mentioned range because the amorphous powder has a spherical shape and the particle size is reduced.

In order to obtain the spherical molding sand (A-1) of the present invention, the powder particles as the starting material take into account the component evaporation at the time of melting, and the Al ₂ O ₃ / SiO ₂ weight ratio and average particle size are in the above range. Prepare and use inside.

  When melting the powder particles that are the starting material, if the particles contain moisture, the moisture evaporates, so that a large number of holes are formed in the resulting casting sand as the moisture evaporates. Become. The formation of the apertures results in an increase in water absorption rate of casting sand and a decrease in sphericity. Accordingly, the water content (% by weight) of the starting material is preferably 10% by weight or less, more preferably 3% by weight or less, from the viewpoint of adjusting the water absorption and sphericity of the resulting casting sand to an appropriate range. More preferably, it is not more than% by weight. The water content is measured by weight loss when 10 g of powder particles are heated at 800 ° C. for 1 hour.

The starting material can be selected from, for example, mineral raw materials and synthetic raw materials having fire resistance. Examples of the raw material as the Al ₂ O ₃ source include bauxite, van earth shale, aluminum oxide, aluminum hydroxide and the like. Examples of the raw material as the SiO ₂ source include silica, silica sand, quartz, cristobalite, amorphous silica, feldspar, and pyrophyllite. Moreover, examples of the raw material as the (Al ₂ O ₃ + SiO ₂ ) source include kaolin, bangshale shale, bauxite, mica, sillimanite, andalusite, mullite, zeolite, montmorillonite, and hyrosite. These raw materials can be used alone or in admixture of two or more. The selected starting material is preferably used after calcining in order to reduce its moisture content or to facilitate its melting. Examples of the calcined raw material powder particles include calcined van pages, calcined mullite, calcined bauxite, a mixture of calcined aluminum hydroxide and kaolin, and the like.

  In the step of melting and spheroidizing powder particles as a starting material in a flame, the starting material as described above is dispersed in a carrier gas such as oxygen and melted by being introduced into a flame, and spheroidized ( Flame melting method). In a preferred embodiment, it is introduced into the following flame.

  The flame to be used is generated by burning fuel such as propane, butane, methane, natural liquefied gas, LPG, heavy oil, kerosene, light oil, pulverized coal and the like with oxygen. The fuel to oxygen ratio is preferably 1.01 to 1.3 in terms of volume ratio from the viewpoint of complete combustion. From the viewpoint of generating a high-temperature flame, an oxygen / gas burner is preferable. Although the structure of the burner is not particularly limited, the burners disclosed in JP-A-7-48118, JP-A-11-132421, JP-A-2000-205523, or JP-A-2000-346318 are disclosed. Illustrated.

  The following method is suitable for spheroidizing the above refractory raw material powder having a large average particle diameter in the range of 0.05 to 2 mm used in the production method of the present invention.

The powder particles are introduced into the flame by being dispersed in a carrier gas. As the carrier gas, oxygen is preferably used. In this case, there is an advantage that oxygen of the carrier gas can be consumed for fuel combustion. The powder concentration in the gas is preferably from 0.1 to 20 kg / Nm ³ , and more preferably from 0.2 to 10 kg / Nm ³ from the viewpoint of ensuring sufficient dispersibility of the powder particles.

  Furthermore, when thrown into the flame, it is more preferable to pass through a mesh, a static mixer or the like to improve dispersibility.

From the viewpoint of promptly spheroidizing in a flame and obtaining monodispersed spherical casting sand, it is preferable to select the shape and composition of the raw material powder particles. As the shape, it is preferable that the ratio of the major axis diameter / minor axis diameter of the raw material powder particles is 9 or less, more preferably 4 or less, from the viewpoint of ensuring residence time in the flame, melting, and spheroidization quickly. More preferably, it is 2 or less. On the other hand, as the composition, from the viewpoint of obtaining monodispersed spherical particles that are not fused, it is particularly preferable that the Al ₂ O ₃ / SiO ₂ weight ratio is 1.5 to 10.

Further, the powder particles can be suitably melted and spheroidized even in a plasma jet flame generated by ionizing N ₂ inert gas or the like.

  By the above method, the desired spheroidal sand (A-1) of the present invention can be obtained. The spherical casting sand (A-1) is very excellent in filling properties and is suitable as the spherical casting sand (A) of the present invention.

<Casting sand (B)>
In the present invention, the casting sand (B) other than the spherical casting sand (A) is appropriately mixed so that the spherical casting sand (A) is contained at a predetermined ratio, and the filling property and the reduction in stickiness are excellent. The foundry sand composition of the present invention is obtained.

As casting sand (B), what was conventionally used for manufacture of a casting mold can be used, and it can choose from silica sand, zircon sand, chromite sand, olivine sand, etc. Further, for example, aluminosilicate foundry sand (baked mullite sand) obtained by a baking granulation method, or baking artificial ceramic particles as described in JP-A No. 2003-136187 can also be used. A mixture of these foundry sands may also be used. As the sintered artificial ceramic particles, for example, the raw material blended so as to have a composition of aluminosilicate mainly composed of Al ₂ O ₃ and SiO ₂ is adjusted to a slurry, granulated, and then prevention of fusion between the granules For example, artificial ceramic particles produced by a firing method prepared by mixing fine powder for use and firing at 1400 to 1750 ° C. and removing fine powder for preventing fusion at the same time as crushing can be mentioned. As the foundry sand (B), from the viewpoint of reducing stickiness and smudge, foundry sand selected from quartz sand and calcined mullite, in particular, quartz sand having a sphericity of 0.90 or less and calcination having a sphericity of 0.90 or more. Foundry sand selected from mullite sand is preferably used. The water absorption of the foundry sand (B) is preferably 0.8% by weight or more, and more preferably 1.0 to 2.0% by weight, and the water absorption of the foundry sand (A) in that case is 0. More preferably, it is 6% by weight.

<Casting sand composition>
The casting sand composition of the present invention is obtained by combining spherical casting sand (A) and foundry sand (B) with (A) / (B) from the viewpoint of both excellent filling properties and reduced stickiness of the coated sand. ) = 5/95 to 50/50, preferably 10/90 to 40/60, more preferably 10/90 to 30/70. Further, in the foundry sand composition of the present invention, particularly in the total foundry sand, the sum of the spherical foundry sand (A) and the foundry sand (B) is 80 to 100% by weight, more preferably 90 to 100% by weight, and particularly 95 to 100%. It is preferable that it is weight%.

  Both the spherical foundry sand (A) and the foundry sand (B) of the present invention may be reclaimed sand such as machine regeneration by roasting regeneration and surface polishing, and regeneration by washing with water or solvent.

  The foundry sand composition of the present invention can be suitably used for casting applications such as cast steel, cast iron, aluminum, copper and alloys thereof.

  The foundry sand composition of the present invention is a molding foundry sand, the surface of which is coated with a resin capable of maintaining the mutual binding of the sand during pouring and disrupting the mutual binding of the sand after pouring. Can be used as

  For the binder composition, conventionally known binders for molds are used. For example, an alkali phenol ester curing method in which a phenol resin and an organic ester are cured with an alkali metal, a phenol resin and a polyisocyanate are present in the presence of a tertiary amine. An iso-cure method in which a phenol-urethane resin is prepared and cured, an alkali phenol methyl formate gas curing method using a phenol resin and methyl formate, a hepset method in which a phenol resin and a polyisocyanate are prepared and cured in the presence of a basic catalyst, and furan Examples thereof include an organic binder composition used in a furan mold method using a resin and an acidic catalyst, an inorganic binder composition such as water glass, and the like. At that time, in addition to the foundry sand composition of the present invention, additives commonly used in the production of molds such as organic binders and lubricants may be added. In the case of using an organic binder composition containing a resin, the amount of resin added may be the minimum amount necessary for binding between foundry sands. Specifically, the addition amount of the resin is preferably 3 to 0.5 parts by weight per 100 parts by weight in total of the spherical foundry sand (A) and the foundry sand (B) in the foundry sand composition of the present invention. The amount is preferably 2.5 to 0.5 parts by weight.

  The foundry sand composition of the present invention can be used as a mold material for producing a casting. Further, since there is little stickiness, it can be suitably used in the case of lamination by a lamination molding method (for example, JP-T-2004-508941 and JP-A-2000-24750). As the obtained casting, it can be used even for the one having the most complicated structure. 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 1-2 and Comparative Examples 1-3
96% by weight of Al ₂ O ₃ and SiO ₂ produced by flame melting method as spherical casting sand (A) are contained in a total amount, the Al ₂ O ₃ / SiO ₂ weight ratio is 2.7, and the average particle size is 0 Table 1 shows a spherical aggregate A1 having a diameter of .16 mm, a sphericity of 0.99, and a water absorption rate of 0% by weight, and flattery sand (water absorption rate of 0.9% by weight) as casting sand (B). It was mixed at a ratio to obtain a foundry sand composition.

  A coated sand obtained by adding and mixing 1.2 parts by weight of an alkali phenol resin (Kaoh Step S-660) and 0.24 parts by weight of a curing agent (Kaoh Step QX-130) to 100 parts by weight of the foundry sand composition. A test piece frame of 50 mmφ × 50 mmh was filled and cured at 25 ° C., and the compressive strength of the test mold was measured after 24 hours. The compressive strength was measured by the method described in JIS Z 2604-1976. The kneaded foundry sand composition was tacky, smudged and filled with fine molds by observing when it was formed using a wood mold for producing a fin-shaped mold shown in FIG. At that time, the stickiness was evaluated for the adhesion to the protective equipment (work gloves) used for the work by the feel at the time of molding, and the blotch was evaluated for the resistance to pulling from the fin-shaped mold by the feel. FIG. 1 is a schematic plan view of a wooden shape, the colored portion is a wooden shape, and the depth (filling height) is 250 mm. The results are shown in Table 1.

Example 3 and Comparative Example 4
It contains 93% by weight of Al ₂ O ₃ and SiO ₂ produced by flame melting method as spherical casting sand (A), the Al ₂ O ₃ / SiO ₂ weight ratio is 1.9, and the average particle size is 0 .15 mm, sphericity is 0.99, water absorption is 0.1% by weight, and spherical aggregate A2 having a water absorption rate of 0.1% by weight is used. Using a mullite spherical aggregate having a weight of 1.4% by weight (in the table, expressed as calcined mullite), the mixture was mixed at the ratio shown in Table 1 to obtain a foundry sand composition. The casting sand composition was manufactured and evaluated in the same manner as in Example 1.

Example 4
Except for the use of silica (spherical aggregate A3) having an average particle size of 0.09 mm, a sphericity of 0.99, and a water absorption of 0.1% by weight, produced by the flame melting method as spherical casting sand (A). A mold was produced and evaluated in the same manner as in Example 3.

Comparative Examples 5-6
Electrolytic fusion with an average particle diameter of 0.24 mm, spherical degree of 0.96, and water absorption of 0.6% by weight, having the same composition as that of Example 1 produced by electrofusion atomization method as spherical casting sand (B) Spherical mullite foundry sand (in the table, indicated as electrofused mullite) and the above-mentioned calcined mullite were mixed at a ratio shown in Table 1 to obtain a foundry sand composition. The casting sand composition was manufactured and evaluated in the same manner as in Example 1.

The evaluation criteria in the table are as follows.
-Stickiness (adhesiveness to protective equipment (work gloves) used for work): 5 = not sticky, 4 = almost sticky, 3 = slightly sticky, 2 = sticky, 1 = very sticky Resistance when mold is released): ○ = There is almost no resistance, △ = Low resistance, × = High resistance ・ Detailed mold filling property: ◎ = Good filling to tip, ○ = Rough filling at tip , △ = The part which is not filled in the tip part remains, x = The tip part is not filled

  As shown in the results of Table 1, when the molding sand composition containing the spherical molding sand (A) of the present invention at a predetermined volume ratio is used, the filling property of the coated sand into the mold is increased and the compression strength of the mold is also improved. It was high. In addition, there was little stickiness or stickiness when the coated sand was filled into the mold.

FIG. 3 is a schematic plan view of a wooden pattern for producing a fin-shaped mold used in an example.

Claims (8)

Spheroidal foundry sand (A) having an average particle size of 0.05 to 1.5 mm produced by the flame melting method and foundry sand (B) other than (A) are (A) / (B) = 5 / Foundry sand composition contained at a volume ratio of 95-50 / 50. _2. The foundry sand composition according to claim 1, wherein the spherical foundry sand (A) contains Al ₂ O ₃ and SiO ₂ as main components and has an Al ₂ O ₃ / SiO ₂ weight ratio of 1 to 15. ₃ . The foundry sand composition according to claim 1 or 2, wherein the water absorption of the spherical sand (A) is 0.6% by weight or less, and the water absorption of the foundry sand (B) is 0.8% by weight or more. 4. The foundry sand composition according to claim 1, wherein the spherical sand (A) has a sphericity of 0.98 or more. The foundry sand composition according to claim 1, wherein the foundry sand (B) is selected from quartz sand and calcined mullite. A foundry sand composition obtained by coating the foundry sand composition according to any one of claims 1 to 5 with a binder composition. The casting_mold | template using the foundry sand composition of any one of Claims 1-6. A casting produced using the mold according to claim 7.

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