JP2007029969A - Coating agent composition for sand mold casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating agent composition for sand mold casting, which is improved in good balance to the prevention of sulfurizing phenomenon, burning resistance and drying. <P>SOLUTION: This coating agent composition contains a basic refractory aggregate having sphericity of 0.88-1.00. <P>COPYRIGHT: (C)2007,JPO&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.

Organic self-hardening molds such as furan resins and phenolic resins are used in many small-scale, high-variety foundries because they have excellent features such as high productivity and easy recovery and recycling of used sand. However, since the organic acid undergoes thermal decomposition during casting and generates sulfur-based gases such as SO ₂ and H ₂ S, a sulfurization phenomenon occurs on the surface of the casting, and the various properties of the casting are remarkably deteriorated.

  As for the deterioration of various characteristics due to the sulfurization phenomenon, there is a decrease in weldability and toughness in ordinary cast iron, a decrease in corrosion resistance in stainless steel, and in ductile cast iron, a poorly spheroidized structure is formed in the surface layer, resulting in a decrease in strength and toughness. .

As a countermeasure for preventing this sulfurization phenomenon, it is known to formulate a substance having a high affinity with a sulfur-based gas (for example, Patent Document 1). Further, Patent Document 2 includes a coating agent containing a substance that expands by heating such as vermiculite and obsidian, and Patent Document 3 further includes a substance that forms a film by melting or reaction of low-melting glass or the like. A coating agent is described.
JP-A-1-15246 JP-A-3-226334 JP-A-11-309544

  In recent years, demands for shorter delivery times, higher productivity, lower costs, and environmental considerations have become stricter, and the required performance of coating agents has become higher. In particular, prevention of sulfurization phenomenon, prevention of seizure defects, and quick drying are indispensable performances for the aforementioned demands. However, the technique of Patent Document 1 relates to the prevention of the sulfurization phenomenon and cannot improve the necessary properties of the coating agent such as prevention of seizure defects and quick drying properties in a well-balanced manner. Further, the document 2 describes a mold method in which spheroidal sand and furan resin are combined, and does not give an effective suggestion for improving the coating agent.

  An object of the present invention is to provide a coating composition for sand mold casting which has improved the prevention of sulfurization phenomenon, seizure resistance and drying property in a well-balanced manner.

  The present invention relates to a coating composition for sand casting containing a basic refractory aggregate having a sphericity of 0.88 to 1.00 (hereinafter sometimes referred to as a spherical aggregate according to the present invention). .

  Further, the present invention provides a mold formed by applying the above-mentioned coating composition of the present invention to a sand mold surface, a casting produced using the mold, and a sphericity of 0.88 to 1.00, The present invention relates to a refractory aggregate for a sand casting casting agent that is basic.

  ADVANTAGE OF THE INVENTION According to this invention, the coating agent composition for sand mold castings for sand mold casting which improved the prevention of a sulfuration phenomenon, seizure resistance, and drying property with sufficient balance is obtained.

  The mold agent composition of the present invention is a mold agent composition for sand casting that has a sphericity of 0.88 to 1.00 and contains a basic refractory aggregate.

  In the present invention, the basic refractory aggregate is a refractory aggregate mainly composed of an alkaline earth metal oxide and MgO, and the total amount of the alkaline earth metal oxide and MgO is in the refractory aggregate. Is preferably contained in an amount of 25% by weight or more, more preferably 50% by weight or more, and still more preferably 80% by weight or more. The total amount of alkaline earth metal oxide and MgO in the refractory aggregate such as the spherical aggregate according to the present invention can be measured by an X-ray analyzer based on JIS R2216.

  As the basic fire-resistant aggregate, from the viewpoint of high affinity with sulfur, those containing at least one selected from the group consisting of magnesia, olivine, forsterite, spinel, talc, and calcia are preferable, olivine, Forsterite and spinel are more preferable, and olivine is more preferable.

In the present invention, a basic refractory aggregate having a sphericity of 0.88 to 1.00 is used. Here, the sphericity is calculated from the area of the projected cross section obtained by image analysis of an image (photograph) obtained by a scanning electron microscope of each refractory aggregate particle and the perimeter, [the area of the particle projected cross section (mm circumferential length of a true circle having the same area as ²⁾ (mm)] / [the circumferential length of a particle projected section of (mm)] determined, which is the average value for any 50 of the refractory aggregate particles . The sphericity of the spherical aggregate according to the present invention is preferably 0.95 to 1.00 because the effect of the present invention is more remarkable.

  As a method for spheroidizing the refractory aggregate, (1) a granulation firing method for obtaining an aggregate having a slightly porous surface with a porous surface by firing the granule obtained by spray-drying the raw material slurry with a rotary kiln, (2) Electrolytic atomization method to obtain an aggregate with a smooth surface and high sphericity obtained by blowing air to the molten raw material, and (3) Using fine powder as the raw material and melting it in a flame There is a flame melting method that obtains an aggregate with a smooth surface and a higher sphericity by spheroidizing.

  The granulation firing method (1) can be performed with reference to, for example, JP-A-5-169184. The electromelting atomization method (2) can be performed with reference to, for example, Japanese Patent Application Laid-Open No. 2001-64703. The flame melting method (3) can be performed with reference to, for example, Japanese Patent Application Laid-Open No. 2001-261328. In the present invention, the aggregate obtained by the flame melting method (3) from which an aggregate having high surface smoothness and high sphericity can be obtained is preferred from the standpoint of seizure resistance.

Further, the spherical aggregate according to the present invention preferably has an average particle size of 0.1 to 50 μm, more preferably 1 to 40 μm, and particularly preferably 5 to 35 μm from the viewpoint of coating film strength, surface smoothness, and anti-seizure. . Here, an average particle diameter is an average particle diameter of 50% of volume accumulation measured using the laser diffraction type particle size distribution measuring apparatus (LA-920 by Horiba, Ltd.). The analysis conditions are as follows.
・ Measurement method: Flow method ・ Dispersion medium: Ion exchange water + 0.1% sodium hexametaphosphate mixed ・ Dispersion method: Stirring, built-in ultrasonic wave 3 minutes ・ Sample concentration: 2 mg / 100 cc

  The mold casting composition for sand casting of the present invention is a refractory aggregate having a sphericity of less than 0.88 (hereinafter referred to as a non-spherical aggregate) for the purpose of improving sand removal and reducing raw material costs. Can be contained.

  The non-spherical aggregate is preferably composed of graphite, mica, talc, magnesia, olivine, zircon, zirconia, spinel, alumina, chamotte, alumina silicate, obsidian, silica, and mullite.

  The weight ratio of the spherical aggregate (A) to the non-spherical aggregate (B) according to the present invention is preferably 15/85 to 90/10 in (A) / (B), and more preferably (A) / (B). = 30/70 to 90/10, especially 50/50 to 90/10 is preferable in terms of improving the prevention of the sulfuration phenomenon, the seizure resistance, and the drying property in a well-balanced manner.

  The spherical aggregate and the non-spherical aggregate according to the present invention are preferably non-hollow.

  The mold casting composition for sand casting of the present invention contains a basic refractory aggregate having a sphericity of 0.88 to 1.00, a binder, and a solvent.

  The content of the refractory aggregate in the coating composition for sand casting of the present invention (the total content of the spherical aggregate according to the present invention and the other refractory aggregate) achieves the object of the present invention. From a viewpoint, Preferably it is 40 to 90 weight%, More preferably, it is 60 to 80 weight%.

  Examples of the binder used in the mold casting composition for sand casting of the present invention include, for example, organic binders such as sugars, phenols, rosins, and petroleum resins capable of forming a strong coating film at room temperature, and at the time of casting. There are inorganic binders such as bentonite, ethyl silicate, and sodium silicate for increasing the hot strength of the coating film. These may be used in combination depending on conditions. The content of the binder in the composition is 0.5 to 10 with respect to 100 parts by weight in total of the refractory aggregate (the other refractory aggregate such as the spherical aggregate and the non-spherical aggregate according to the present invention). Part by weight, more preferably 1 to 5 parts by weight are preferred.

  As a solvent used for the coating agent composition for sand mold casting of the present invention, either aqueous or oily may be used. Oily is advantageous in terms of permeability and drying, and aqueous is advantageous in terms of safety. In the case of an oil-based coating agent, lower alcohol solvents such as methanol, ethanol and isopropyl alcohol, aromatic solvents such as xylene and toluene, and hydrocarbon solvents such as mineral spirit can be used. A lower alcohol solvent is preferred, and methanol is particularly preferred. Aromatic solvents and hydrocarbon solvents may be used as auxiliary solvents. In the case of an aqueous coating agent, water is the main solvent. In any case, the content of the solvent in the composition is 10 to 10 parts by weight with respect to a total of 100 parts by weight of the refractory aggregate (the other refractory aggregates such as the spherical aggregate and the non-spherical aggregate according to the present invention). 500 parts by weight, more preferably 10 to 100 parts by weight are preferred.

  In addition to the above components, other additives such as a cellulose derivative such as hydroxyalkylated cellulose, a thickener such as polyvinyl alcohol and sodium alginate can be used in combination with the coating composition for sand mold casting of the present invention.

  The mold agent composition of the present invention is suitable for sand mold casting and exhibits a remarkable effect in preventing the sulfurization phenomenon. This is because the basic spherical particles are filled extremely high in the gap between sand and sand, and the film density on the sand mold surface is increased, so that the sulfur-based gas that causes the sulfurization phenomenon is physically blocked. In addition to this, the amount of chemical trapping is considered to be high.

  The method of applying the coating composition of the present invention to the mold may be any of the conventionally known methods such as flow coating (bukkake method), dipping (dipping method), brush coating, spray coating, etc. A flow coating method is preferred. Further, as the foundry sand used for the casting mold, new sand or reclaimed sand such as zircon sand, chromite sand, synthetic mullite sand, etc. is used in addition to quartz sand mainly composed of quartz. Casting sand can also be used without the addition of a binder, in which case the filling properties are good, but if mold strength is required, a binder is added and cured with a curing agent. Is preferred.

  The mold is mixed with an organic binder such as furan resin or alkali phenol resin or an inorganic binder such as water glass into the casting sand, filled around the same shape as the product, then cured and removed. This is a sand mold in which the product shape obtained is reversed, and the molten metal is poured into the void (cavity) to obtain a product.

  In general, the coating mold is initially used as a composition having a low solvent concentration and a high solid content (preservation composition), and is further diluted to an appropriate slurry viscosity at the time of use. Such a high solids composition is usually adjusted to about 200 penetration by adjusting the amount of the solvent, etc., and is further diluted with a solvent at the time of use and used as an appropriate viscosity. The appropriate slurry viscosity at the time of application is 5 to 50 baume for alcohol-based coating agents and 30 to 80 baume for aqueous coating agents.

  As a casting manufactured using the mold of the present invention, a casting having a beautiful cast surface with little influence of sulfurization can be obtained. Therefore, it is suitable for a casting that requires a complicated structure and a beautiful casting surface. is there. 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.

[I] Preparation of coating agent composition 2 parts by weight of bentonite, 2 parts by weight of natural polysaccharide resin (gum arabic) and water (water having a penetration of 200) with respect to 100 parts by weight of the fireproof aggregate shown in Table 1 For 30 minutes in a kneader to obtain a paste-form (penetration degree 200, 800S-01, manufactured by Ransha Co., Ltd.) coating agent composition.

[II] Evaluation (1) Sulfuration prevention test Furan reclaimed sand (AFS45) is cooled to 5 ° C, which is a condition where sulfurization is likely to occur, and then Kao Quaker furan resin 340B (furfuryl alcohol, urea, formaldehyde condensation) A square test piece of 150 mm × 100 mm was prepared from 0.8% by weight of the product) to foundry sand and 40% by weight of Kao Quaker curing agent US-3 (organic sulfonic acid curing agent) to the resin. The test piece composition was further diluted with water and adjusted to the concentration (Baume degree) shown in Table 1 (bukkake method), and sufficiently dried naturally. Thereafter, hot water was poured under conditions of material FCD450 and casting temperature of 1380 ° C. The test piece was cooled to ambient temperature, the casting was taken out, and the metal structure of the corner portion of the casting was observed. The determination of the evaluation is based on the image taken using a metal microscope, and the depth from the casting surface of the abnormal structure generated from the casting surface (graphite spheroidization ratio calculated based on JISG5502 is 80% or less) ( mm).

(2) Seizure resistance test Using regenerated furan sand (AFS45), Kao Quaker furan resin 340B (furfuryl alcohol / urea / formaldehyde condensate) is 0.8% by weight of the casting sand, cured by Kao Quaker A mold having a cylindrical space portion having a diameter of 350 mm and a height of 370 mm obtained by curing the agent TK-3 (organic sulfonic acid curing agent) with 40% by weight of the resin was produced. The above coating composition was further diluted with water and adjusted to the concentration (Baume degree) shown in Table 1 (coating method), and sufficiently dried naturally. Then, hot water was poured under the conditions of FC-250, casting temperature 1450 ° C., and weight 250 kg. The test piece was cooled to the ambient temperature, and the casting was taken out and a seizure resistance test was performed. Judgment of the seizure resistance test was performed according to the following criteria.
[Evaluation criteria]
○: No seizure occurred Δ: Mild seizure with small volume ×: Strong seizure with large volume

(3) Drying test Furan regenerated sand (AFS45) is used, and Kao Quaker furan resin 340B (furfuryl alcohol / urea / formaldehyde condensate) is 0.8% by weight with respect to foundry sand, Kao Quaker hardener. A test piece having an inner diameter of 100 mm and a height of 100 mm obtained by curing TK-3 (organic sulfonic acid curing agent) with 40% by weight of the resin was further diluted with water to obtain the concentration shown in Table 1. What was adjusted to (Baume degree) was apply | coated. The test piece was allowed to stand at 25 ° C./50% RH, and the weight was measured every 15 minutes. When the weight loss was 0.2% or less with respect to the applied coating weight, the drying was finished. The shorter the time until completion of drying, the better the drying property.

  In Table 1, the refractory aggregates of Examples 1 to 3 and Comparative Example 4 are manufactured by the flame melting method.

Claims (7)

  A sand casting casting composition containing a basic refractory aggregate having a sphericity of 0.88 to 1.00.   The sand casting casting coating composition according to claim 1, wherein the basic refractory aggregate is at least one selected from the group consisting of magnesia, olivine, forsterite, spinel, talc and calcia.   The coating composition for sand mold casting according to claim 1 or 2, wherein the average particle size of the refractory aggregate is 0.1 to 50 µm.   The coating composition for sand mold casting according to any one of claims 1 to 3, wherein the refractory aggregate is produced by a flame melting method.   The casting_mold | template formed by apply | coating the coating agent composition in any one of Claims 1-4 to the sand type | mold surface.   A casting produced using the mold according to claim 5.   A refractory aggregate for sand casting, which has a sphericity of 0.88 to 1.00 and is basic.