JP2009039767A - Method for making casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for making a casting mold, in which a coated film hardly peels even when burner drying, etc. are carried out. <P>SOLUTION: The method for making the casting mold includes a step (I) for making a sand mold from casting sand, a step (II) for applying an aqueous facing composition containing scale-like fireproof particles to the sand mold obtained by the step (I), and a step (III) for drying at least a part of the portion of the sand mold obtained by the step (II) and applied with the aqueous facing composition by bringing the part into contact with a flame. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a mold using an aqueous coating agent composition.

  The casting mold agent is applied or sprayed (including bukkake) to the mold surface where the molten metal comes into contact, and the coating surface is applied to protect the mold surface, and the chemical reaction between the molten metal and the mold surface It is used to prevent the occurrence of casting defects in castings. Such a coating agent is generally composed of refractory particles, a binder, a sintering agent, a dispersion medium (solvent) and the like. Among these, the refractory particles are a coating base material, mainly for preventing casting seizure, and powders (aggregates) such as zircon, silica, magnesia, chromite, and graphite are used.

Patent Document 1 discloses a coating composition containing at least one refractory particle selected from obsidian, pearlite and pinestone, and at least one refractory particle selected from unmo, feldspar and blast furnace slag. ing. Patent Document 2 discloses a coating composition containing refractory particles having 45% by weight or more of Al ₂ O ₃ and at least one refractory particle selected from obsidian, pearlite, and pinestone.
JP 2006-181579 A JP 2006-198677 A

  When an aqueous coating agent using water as a dispersion medium is used among the coating agents, burner drying may be performed in a factory or the like that does not have a drying facility. Also, even in factories that have drying equipment, when installing a sand mold coated with a coating agent in the drying equipment, it may be partially dried with a burner so that the coating mold does not adhere to the installation surface. is there. Since the burner drying is rapid drying, the coating film may be peeled off.

  The subject of this invention is providing the manufacturing method of the casting_mold | template which a coating film cannot peel easily even if it performs rapid drying, such as burner drying.

  The present invention includes a step (I) of producing a sand mold from casting sand, a step (II) of applying an aqueous coating composition containing scaly refractory particles to the sand mold obtained by the step (I), And a step (III) of drying at least a part of the portion coated with the water-based coating composition in the sand mold obtained in the step (II) by contact with a flame.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the casting_mold | template which includes the drying process by a flame like burner drying and a coating film cannot peel easily is provided.

  Step (I) is a step of producing a predetermined sand mold from foundry sand, and can be performed according to a normal method. A suitable binder is added to the foundry sand and cured to obtain a sand mold having a predetermined shape.

  Step (II) is a step of applying an aqueous coating composition containing scaly refractory particles to the sand mold obtained in step (I). Examples of the method for applying the composition to the sand mold include a flow coating method (bukkake method), a dipping method (a soaking method), a brush coating method, and a spray coating method. The bukkake method is a preferable method from the viewpoint of simplicity.

  The coating agent composition used in step (II) contains scaly refractory particles. Here, the scale-like refractory particles are scaly fine pieces and mean flat refractory particles.

  In addition, the scale-like refractory particles used in the present invention can use an aspect ratio as a scale indicating the degree of scale-like shape. The scaly refractory particles are preferably those having an aspect ratio in the range of 5 to 80, more preferably 10 to 70, and more preferably 20 to 50, from the viewpoint of preventing peeling of the coating film upon drying by contact with a flame such as a burner. Further preferred. The aspect ratio is closer to a sphere as the value is smaller, and the flatness of the particles is higher as the value is larger.

  Here, this aspect ratio is measured by taking a small amount of scaly refractory particles and expanding it 300 times with a microscope (VH-8000, manufactured by Keyence Corporation), in any 100 particles of scaly refractory particles. The maximum diameter in the surface direction and the thickness can be measured, and the respective average values can be obtained using the following formula [(average value in the maximum surface direction diameter) / (average value in thickness)].

  The aqueous coating composition used in the present invention contains at least scaly refractory particles, but preferably further contains refractory particles other than scaly refractory particles. In the present invention, the ratio of the scaly refractory particles to the total refractory particles is preferably 3.5% by weight or more, more preferably 7% by weight or more, and further preferably 9 to 25% by weight.

  As a preferred aqueous coating composition for use in the present invention, at least one refractory particle selected from refractory particles of mullite composition (a) (hereinafter referred to as component (a)), obsidian, pearlite, and pine sebumite (B) [hereinafter referred to as component (b)], and an aspect ratio of 5 to 80, and at least one scaly refractory particle (c) [hereinafter referred to as component (c) selected from corn, talc and graphite] An aqueous coating composition containing Hereinafter, these components (a) to (c) will be described.

<(A) component>
Component (a) used in the aqueous coating composition of the present invention is refractory particles having a mullite composition. The refractory particles having a mullite composition are refractory particles in which mullite crystals are detected by X-ray diffraction, and include general synthetic mullite, banquets, pyroxene, Hakuyama, and the like. From the viewpoint of obtaining a beautiful cast skin with no white film attached, the component (a) is preferably mullite having an Al ₂ O ₃ content of 45 to 90% by weight and an Al ₂ O ₃ content of 60 More preferred is ˜70 wt% mullite.

  The component (a) used in the present invention is preferably in the form of a powder having an average particle size of 1 to 100 μm, and more preferably 5 to 60 μm.

  In the present invention, the average particle diameter of each refractory particle is a median diameter of a single particle diameter distribution measured by a laser diffraction scattering type particle diameter distribution measuring apparatus (LA-920 type manufactured by Horiba, Ltd.).

<(B) component>
The component (b) used in the aqueous coating composition of the present invention is obsidian, pearlite and pine stone. Typical compositions of these ores, SiO ₂ is 76 wt%, Al ₂ O ₃ is 12 wt%, Fe ₂ O ₃ is 1 wt%, CaO 0.5 _{wt%, K 2 O, Na 2} O Is 4% by weight. Obsidian is preferable from the viewpoint of smoothness of the casting surface.

  As the component (b) used in the present invention, it is preferable to use a powdery material having an average particle diameter of 1 to 100 μm, and more preferably 5 to 60 μm.

<(C) component>
The component (c) used in the aqueous coating composition of the present invention is scaly refractory particles, in particular, at least one scaly refractory particle selected from corns, talc and graphite is preferable. An aspect ratio of 5 to 80 is preferable, and at least one scale-like refractory particle selected from plums, talc and graphite is preferable.

  Among the components (c), the plums are also called the plum group, and are aluminosilicates containing alkali metals (Chemical Dictionary 1, Vol. 1, July 1, 1963, 6th edition, Kyoritsu Publishing Co., Ltd.). . There are two types of eels: natural eels and artificial eels. Examples of natural eels include white eels, gold eels and black eels, preferably white eels. Examples of artificial rumbling include fluorine hummon such as fluor gold gilmo, fluorine tetrasilicon ummo, and teniolite. Eunmo sericite is also a type of Eunmo.

  Of the components (c), talc is a mineral composed of magnesium hydroxide and silicate, and is a kind of clay mineral. In the present invention, talc is scaly, and further has an aspect ratio of 5 to 80. Used.

  Among the components (c), the graphite includes scaly graphite and scaly graphite.

  As the component (c), hums are preferable from the viewpoint of concealment of the mold in the coating operation or bright color of the coating mold and prevention of peeling of the coating film during drying due to contact with a flame such as a burner.

  As the component (c) used in the present invention, a powdery material having an average particle diameter of 50 to 150 μm, more preferably 60 to 120 μm is used from the viewpoint of preventing peeling of the coating film upon drying due to contact with a flame such as a burner. Is preferred.

  In such an aqueous coating agent composition, the weight ratio of the refractory particles (a) to the refractory particles (b) is (a) / (b) = 1-9, and more preferably 1-4. From the viewpoint of peeling of the coating film from.

  Further, in such an aqueous coating composition, the fire-resistant particles (a) and the fire-resistant particles are prevented from the viewpoint of coating film peeling at the time of drying due to contact with a flame such as a burner, and from the viewpoint of coating film strength and coating film smoothness. The weight ratio of the total weight of (b) to the scaly refractory particles (c) is preferably [(a) + (b)] / (c) = 1-25, and more preferably 9-12. More preferably.

  The mold agent composition used in the present invention is an aqueous composition containing water. The water is preferably 20 to 150 parts by weight, more preferably 50 to 130 parts by weight, based on 100 parts by weight of the total refractory particles.

  Moreover, the binder used for this invention can be mix | blended with a binder which is normally used. For example, there are organic binders such as gum arabic, phenol, rosin, and petroleum resin that can form a strong coating film at room temperature, and inorganic binders such as sodium silicate and aluminum phosphate. These may be used in combination depending on conditions. The addition amount of the binder is preferably 0.5 to 2 parts by weight with respect to 100 parts by weight of the total refractory particles.

  Examples of the sintering agent include bentonites such as sodium bentonite and calcium bentonite, clays such as kibushi clay and attapulgite, ethyl silicate, and colloidal silica. The addition amount of the sintering agent is preferably 3 to 10 parts by weight with respect to 100 parts by weight of the total refractory particles.

  In addition, surfactants, dispersants, thixotropy-imparting agents, and the like are listed as components that can be blended in the coating composition used in the present invention.

  In addition, casting sand can be used without adding a binder, in which case the filling property is good, but when mold strength is required, a binder is added and cured with a curing agent. It is preferable to do so.

  Step (III) is a step of drying at least a part of the portion coated with the sand-type aqueous coating agent composition obtained in the above-described step (II) by contact with a flame. Specifically, it is dried by contact with a flame until the gloss of water on the surface of the coated film is lost. The drying time is about 30 seconds to 10 minutes, depending on the size of the portion to be dried. The flame temperature is preferably 800 to 1900 ° C. (the flame temperature is obtained by measuring the temperature of the outer flame), and it is preferable to use a burner as a means for developing the flame. Examples of the drying device for the burner include TRUSCO NAKAYAMA Co., Ltd., part number TB-L10, Shinfuji Co., part number RE-7, etc. connected to the LP cylinder.

  Since the water-based coating agent composition is water as the dispersion medium, drying is slow at room temperature. The sand mold coated with this is installed when it is used for the next process, for example, the gentle drying process of the entire sand mold. It takes time to secure the contact area with the instrument. For this reason, forced drying such as burner drying is often performed. However, for example, when mullite and obsidian are blended as a coating agent as a fireproof aggregate of a coating agent, a large cohesive force between particles is generated. Therefore, the coating film is easily peeled off when burner drying is performed and rapid drying occurs. On the other hand, in the present invention, by using scaly refractory particles such as plums, it is possible to obtain a coating mold in which the coating film does not easily peel off even when dried by contact with flame such as a burner. The reason for this is not clear, but it is thought that the scaly refractory particles strongly protect the surface of the coating film, and it is considered that the effect is more pronounced with the hummo having a high hydrogen bonding force.

  It is preferable that the casting_mold | template which passed through process (III) is further used for the drying process at 100-200 degreeC.

  As a casting manufactured using the mold obtained in the present invention, a casting having a beautiful casting surface is obtained, and therefore, it is suitable for a casting that requires a complicated structure and a beautiful casting surface. 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.

  The components having the composition shown in Table 1 were kneaded at 250 rpm for 10 minutes with a KTM-10 mixer manufactured by Kanto Blender Kogyo Co., Ltd. The resulting paste was diluted to 60 baume. This was used as an aqueous coating composition.

  For 100 parts by weight of free mantle sand, 1.0 part by weight of furan resin (Kaolitener 340B, Kao Quaker Co., Ltd.) as a binder and 0.4 part by weight of its curing agent (TK-3, Kao Quaker Co., Ltd.) In addition, a plate-shaped (shape 80 mm × 80 mm × 10 mm) mold was produced. Aqueous coating composition is applied to the mold by brushing (applyed so that the coating film becomes 0.5 mm), and immediately after that, burner drying (flame temperature: 1000 ° C.) with a PRINCE GAS torch burner (crater type: GT-5000). ) And image analysis of paint film peeling by burner (analysis software: WinROOF, digital camera: Panasonic DMC-FX1), the area of the peeling part is a percentage of the total area where the coating composition was applied (%). The results are shown in Table 1.

  Further, the five flat molds are placed flat on the donut-shaped bottom part of a cylindrical mold (with a circular weir 40 mm in diameter in the center) having an inner diameter of 350 mm and a height of 380 mm and bonded. (The dimensional unit in FIGS. 1 and 2 and FIG. 1 is mm). At that time, the inner wall of the mold and the flat mold were arranged uniformly so that one side of 80 mm of the mold was directed in the circumferential direction of the mold, and the maximum distance between the one side and the side wall was 20 mm (FIG. 2). In addition, for bonding the mold bottom to the flat mold, a plastic seal for Nissin Sangyo, a plastic seal for Nissin mold, and Mane One Touch was used, and the adhesive was sufficiently dried by allowing it to stand for 24 hours. Into this mold, FC-250, 250 kg of molten metal was cast at 1400 ° C., and the baked state of the cast product after the dispersion was observed. The results are shown in Table 1.

It is the schematic which shows the casting_mold | template used for evaluation of the baking state in the Example. FIG. 2 is a schematic plan view of the mold of FIG. 1.

Claims (6)

  Step (I) for producing a sand mold from foundry sand, Step (II) for applying an aqueous coating composition containing scaly refractory particles to the sand mold obtained by Step (I), and Step (II) And a step (III) of drying at least a part of a portion of the sand mold obtained by the above-mentioned application of the aqueous coating composition by contact with a flame.   The water-based coating agent composition has a mullite composition refractory particles (a), at least one refractory particles (b) selected from obsidian, nacre and pine sebite, and an aspect ratio of 5 to 80. The manufacturing method of the casting_mold | template of Claim 1 containing the at least 1 type of scaly refractory particle (c) chosen from a kind, talc, and graphite.   The weight ratio of the total weight of the refractory particles (a) and the refractory particles (b) to the scaly refractory particles (c) in the aqueous coating composition is [(a) + (b)] / (C) The manufacturing method of the casting_mold | template of Claim 1 or 2 which is 1-25.   The method for producing a mold according to any one of claims 1 to 3, wherein the refractory particles (b) are obsidian.   The method for producing a mold according to any one of claims 1 to 4, wherein the scaly refractory particles (c) are eels.   The method for producing a mold according to any one of claims 1 to 5, wherein the flame is supplied by a burner.

Images