JP2016002574A - Manufacturing method of casting mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technique capable of easily optimizing a manufacturing condition of a casting mold, and capable of advantageously manufacturing the sound casting mold excellent in an appearance and a physical property, by reducing dying, reducing defective molding due to a dryness shortage, reducing a strength shortage, reducing wearing-out of a casting mold surface, and reducing a variation in a casting mold physical property.SOLUTION: A manufacturing method uses coated sand formed by covering casting sand with a binder which uses a water-soluble inorganic compound as a binder component, and after filling this in a molding cavity of a molding tool held at the temperature of 20°C-110°C, steam and carrier gas are simultaneously introduced into the molding tool by adjusting so that a rate of respective pressures becomes 1:1-1:20, and are ventilated between the coated sands filled in the molding tool, and the coated sand-covering binder is wetted thereby, and is held in the molding tool held at the temperature, and the coated sand is solidified and/or hardened thereby, and a casting mold is manufactured.

Description

  The present invention relates to a method for producing a mold, and more particularly to a method for producing a casting mold using dry coated sand having fluidity at room temperature.

  Conventionally, as one of the molds used for casting a molten metal, the object is to use a coated sand formed by coating mold sand made of refractory aggregate or casting sand with a predetermined binder. What was obtained by molding into a shape has been used. For example, “Casting Engineering Handbook” edited by the Japan Foundry Engineering Society, pages 78-90, such a binder is water glass. In addition to inorganic binders such as these, organic binders using resins such as phenolic resins, furan resins, and urethane resins have been clarified, and self-hardening molds are formed using these binders. The method is also clarified.

  Japanese Patent Laid-Open No. 2012-115870 discloses a caking that is formed by coating foundry sand with a caking agent selected from a water-soluble inorganic compound, a saccharide, and a water-soluble thermoplastic resin. One method for producing a mold using an agent-coated refractory (resin-coated sand) has been clarified. In this case, steam is blown into a mold filled with the resin-coated sand, and the resin-coated sand is heated with the latent heat of condensation of the steam, and the binder of the coating layer of the resin-coated sand with the condensed water of the steam. After moistening and giving tackiness, the target mold is produced by drying and solidifying the binder.

  However, when the binder of the resin-coated sand coating layer is moistened with water vapor condensate to give tackiness, it is difficult to uniformly vent the water vapor only by passing only the water vapor. There was a risk of unevenness in the dissolution of the binder. In particular, binders in places where a lot of moisture passes or where the temperature of the sand is low, such as vents, dissolves quickly, causing the binder to flow away, causing a squeaking phenomenon (casting sand adheres to the mold surface). However, there is a problem that the remaining mold may cause unevenness on the surface of the mold to be molded, or cause a decrease in mold strength or molding failure due to insufficient drying.

  On the other hand, in places where the mold temperature is high and the sand temperature is high, it is difficult for water vapor to condense. Therefore, it is necessary to ventilate more water vapor. However, in the above vents and places where the sand temperature is low, a lot of water vapor is consumed, so that the mold temperature is high, and in the places where the sand temperature is high, water vapor does not rotate, Dissolution cannot be performed, and problems such as a reduction in strength and poor molding due to the battering of the mold surface and insufficient dissolution of the binder occur. In addition, since molds manufactured under such unstable molding conditions vary in physical properties, the manufacturing method in which only water vapor is passed is relatively small and the mold has a simple shape. However, it does not cause a big problem, but when molding a mold with a large shape or a complex shape, the uneven dissolution of the binder and the variation in the physical properties of the mold become large, and the optimum manufacturing conditions are required. There are also problems such as difficulty in making them.

JP 2012-115870 A

"Casting Engineering Handbook" pages 78-90

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is to reduce stains, reduce molding defects due to insufficient drying, reduce insufficient strength, It is an object of the present invention to provide a method capable of advantageously producing a sound mold having good appearance and physical properties while facilitating optimization of mold production conditions by reducing stickiness and variation in mold physical properties.

  And, in order to solve the above-mentioned problems, the present invention can be suitably implemented in various aspects as listed below, and each aspect described below is adopted in any combination. Is possible. It should be noted that aspects or technical features of the present invention are not limited to those described below, and can be recognized based on the inventive concept that can be grasped from the description of the entire specification. Should be understood.

(1) Using a coated sand formed by coating casting sand with a binder containing a water-soluble inorganic compound as a binder component, this is kept in a molding cavity of a molding die maintained at a temperature of 20 ° C or higher and 110 ° C or lower. The water vapor and the carrier gas are adjusted so that the ratio of the pressure of the water vapor and the pressure of the carrier gas is 1: 1 to 1:20, and simultaneously introduced into the mold, The mold is made by aerating between the filled coated sands, moistening the binder that coats the coated sand in the mold, and then holding it in the mold held at the temperature. A method for producing a mold, characterized in that a coated sand filled therein is solidified or cured.
(2) The method for producing a mold according to the aspect (1), wherein the water-soluble inorganic compound is water glass.
(3) The aspect (1) or the aspect (2), wherein the water vapor and the carrier gas are individually supplied and introduced into the molding cavity through a vent provided in the molding die. Mold manufacturing method.
(4) The aspect (1) or the aspect (2), wherein the water vapor and the carrier gas are mixed in advance, and then introduced into the molding cavity through a vent provided in the mold. Mold manufacturing method.
(5) The aspect (1) or the aspect (4), wherein the water vapor is supplied to the mold under a pressure of 0.01 to 0.1 MPa at a temperature of less than 100 ° C. Mold manufacturing method.
(6) The method for producing a mold according to any one of the aspects (1) to (5), wherein the carrier gas is carbon dioxide, nitrogen, argon, or a mixed gas thereof.
(7) The method for producing a mold according to any one of the aspects (1) to (6), wherein an alkylene carbonate and / or an organic ester is contained as a curing agent in the carrier gas.
(8) The method for producing a mold according to any one of the aspects (1) to (7), wherein the water vapor is supplied to the mold for 1 second to 60 seconds.
(9) The method for producing a mold according to any one of the aspects (1) to (8), wherein the coated sand is a dry substance having fluidity at room temperature.
(10) The mold according to any one of the aspects (1) to (9), wherein the coated sand is preheated to a temperature of 30 ° C. or higher and then filled into a molding cavity of the mold. Manufacturing method.
(11) The modes (1) to (1), wherein when the water vapor and the carrier gas are introduced into the molding cavity of the molding die, the atmosphere in the molding cavity of the molding die is forcibly discharged out of the system. (10) The manufacturing method of the casting_mold | template as described in any one of.
(12) Manufacture of the mold according to any one of the aspects (1) to (11), wherein the water vapor and the carrier gas are introduced after the inside of the molding cavity of the mold is in a reduced pressure state. Law.
(13) The method for producing a mold according to any one of the aspects (1) to (12), wherein hot air or superheated steam is allowed to pass through the mold during the holding in the mold.

  As described above, according to the method for producing a mold according to the present invention, after filling a predetermined coated sand into a cavity of a mold having a temperature of 20 ° C. to 110 ° C., the water vapor and the carrier gas are mixed with the water vapor and the carrier gas. After moistening the binder that coats the coated sand by adjusting the pressure ratio to be within the predetermined range, introducing it into the mold, and venting between the filled coated sand By holding the coated sand in the mold so that the filled sand is solidified or hardened, the water vapor permeability into the mold cavity of the mold is remarkably improved when molding the target mold. Therefore, the appearance can be improved by suppressing or preventing solidification or curing unevenness in the mold to be molded. Excellent physical properties such as strength, a sound template is became possible to advantageously produced.

  By the way, the coated sand used in the method for producing a mold according to the present invention is obtained by coating molding sand with a binder containing a predetermined water-soluble inorganic compound as a binder component, and having a predetermined size. It is composed of casting sand made of refractory aggregate and a binder coating layer formed so as to cover the surface thereof.

  Such coated sand is generally obtained by mixing an aqueous solution of a binder containing a water-soluble inorganic compound as a binder component with heated refractory aggregate (casting sand), and further from the mixture. It can be easily manufactured by evaporating a medium such as moisture, in other words, by evaporating the medium such as moisture from an aqueous solution of a water-soluble inorganic compound, and is preferably a binder of a binder A dry coating layer formed of a water-soluble inorganic compound as a component is formed on the surface of the refractory aggregate, and is thus in a dry state, thereby having good room temperature fluidity. Particularly in the present invention, the moisture content of such coated sand is adjusted so as to be 0.5% by mass or less, preferably 0.3% by mass or less. In addition, it is recognized that the lower limit of such a moisture content is so good that it approaches 0 infinitely. Thus, by using the coated sand provided with a coating layer of a water-soluble inorganic compound in a dry state having an extremely low moisture content and no moisture, it becomes a smooth state and effective room temperature fluidity is imparted. Therefore, it is possible to effectively improve the filling property of the coated sand into the mold cavity of the mold for mold making, which makes a healthy mold advantageous. In addition to being able to be obtained, it can also contribute to the improvement of mold strength.

  In addition, as the refractory aggregate (casting sand) constituting such a coated sand, it is a refractory substance functioning as a base material of a mold, and various refractory granular materials conventionally used for molds. Can be used, specifically, silica sand, recycled silica sand, special sand such as alumina sand, olivine sand, zircon sand, chromite sand, ferrochrome slag, ferronickel slag, converter slag Porous particles such as slag particles such as alumina particles and mullite particles and regenerated particles thereof; alumina balls, magnesia clinker and the like. These refractory aggregates may be fresh sand, or reclaimed sand or recovered sand that has been used once or a plurality of times as casting sand for casting molds. Even mixed sand made by adding new sand to the collected sand and mixing it can be anything. Such a refractory aggregate generally has a particle size of about 40 to 80 in terms of AFS index, and preferably has a particle size of about 60 or less in order to facilitate the ventilation and drying of water vapor during mold molding. As a thing, it will be used.

  The binder contains a water-soluble inorganic compound as a main component as a binder component, and is used in the form of an aqueous solution. In the present invention, water glass is typically used as this water-soluble inorganic compound, but other water-soluble inorganic compounds known as water-soluble binders such as sodium chloride, Chloride such as potassium chloride, carbonate such as sodium carbonate and potassium carbonate, phosphate such as sodium phosphate, borate such as sodium borate, aluminate such as sodium aluminate, vanadium such as sodium vanadate Acid salts etc. can also be used, and it is also possible to incorporate such water-soluble inorganic compounds as the main component and, if necessary, other known additives such as lubricants to be incorporated. It is.

And as water glass which is such a water-soluble inorganic compound, it is a soluble silicate compound, for example, sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, ammonium silicate. , Colloidal silica, alkyl silicate, and the like. In the present invention, the coated sand obtained is difficult to block, and the formability is good, so sodium silicate (sodium silicate) is advantageous. Will be used. In addition, such sodium silicate is normally classified into the types of No. 1 to No. 5 and used according to the SiO ₂ / Na ₂ O molar ratio. Specifically, sodium silicate No. 1 has a SiO ₂ / Na ₂ O molar ratio of 2.0 to 2.3, and sodium silicate No. 2 is SiO ₂ / Na ₂ O The molar ratio is 2.4 to 2.5, and the sodium silicate No. 3 has a SiO ₂ / Na ₂ O molar ratio of 3.1 to 3.3. In addition, sodium silicate No. 4 has a SiO ₂ / Na ₂ O molar ratio of 3.3 to 3.5, and sodium silicate No. 5 has a SiO ₂ / Na ₂ O molar ratio. Is 3.6 to 3.8. Among these, sodium silicate Nos. 1 to 3 are also defined in JIS K1408. These sodium silicates may be used in combination as well as used alone, or by mixing or adding additives such as sodium hydroxide, SiO ₂ / Na ₂ It is also possible to adjust the molar ratio of O.

Furthermore, in the present invention, in order to obtain a coated sand that achieves a particularly high packing density and a high mold strength, sodium silicate used as a binder has a SiO ₂ / Na ₂ O molar ratio of 1. It is desirable that it is within the range of .5 to 4.0, and it is more desirable that it is within the range of 2.0 to 3.0. However, it goes without saying that a molar ratio outside the range of the sodium silicate classification described above can be formed and used.

  In addition, when producing a coated sand using a binder or foundry sand (fireproof aggregate) having a water-soluble inorganic compound as described above as a binder component, the production method is not particularly limited, Conventionally known methods such as a dry hot coat method, a semi-hot coat method, a cold coat method, and a powder solvent method can be employed. In the present invention, for example, a whirl mixer, a speed mixer, etc. After kneading the pre-cast foundry sand and the binder in the kneading machine, a curing agent such as an oxide or salt is added as necessary, and by cooling with air, the massive contents are disintegrated into particles, A so-called dry hot coating method in which a lubricant such as calcium stearate is added is usually employed.

  By the way, when forming the target mold according to the present invention using the coated sand obtained as described above, first, the coated sand is placed in the molding cavity of the mold that provides the target mold. Filling and then filling the water vapor and carrier gas by blowing them in with their water vapor pressure and carrier gas pressure adjusted, passing through the filled phase of the coated sand and holding in the mold until dry The coated sand is solidified or hardened.

  At that time, a mold such as a mold or a wooden mold, which is filled with dry coated sand, is preferably preheated by heating, and is held in the heated mold for a certain period of time. The coated sand moistened with water vapor can be dried to allow the solidification or hardening of the coated sand to proceed advantageously. In general, a temperature of 20 ° C. or higher and 110 ° C. or lower, preferably 50 ° C. or higher and 100 ° C. or lower, and more preferably 60 ° C. or higher and 90 ° C. or lower is employed as the heat retention temperature by heating the mold. It becomes. If this temperature is too high, it will be difficult for steam to pass to the surface of the mold and the strength will decrease. If the temperature is too low, it will take time to dry the molded mold. In addition, the resin adheres to the mold surface, and it becomes easy to cause a stain.

  In addition, the dry coated sand to be filled in such a mold is also preferably preheated. Generally, the bending strength of the obtained mold can be increased more advantageously by filling the molding die with the coated sand heated to a temperature of 30 ° C. or higher. The heating temperature of such a coated sand is preferably about 30 to 100 ° C., and particularly, the coated sand heated to a temperature of about 40 to 80 ° C. is advantageously used.

  The mold is heated as described above. Specifically, after the dry coated sand is filled into the mold cavity, the mold is provided in the filling phase formed there. Through the vents, water vapor and carrier gas are simultaneously ventilated under pressure, and the coated sand constituting such a filling phase is moistened to be connected and connected to each other. (Combined material) is formed. When water glass is used as the water-soluble inorganic compound, normally, if no additives are added, it is solidified by evaporation and drying of water, and an acid or salt is added as a curing agent. If it is, it will be cured. However, in the present invention, since the curing agent is practically added, the filling phase is hardened. However, as described above, it may be simply solidified. There is no problem.

  Further, the water vapor and the carrier gas as described above are ventilated by adjusting the water vapor pressure and the carrier gas pressure to a predetermined range. Thereby, since the viscosity of the water vapor is lowered, the air permeability of the water vapor between the coated sands filled in the cavity is improved, and the effect of reducing the uneven dissolution of the binder is exhibited. It is. In particular, some of the binder in the coated sand is quickly dissolved and washed away from places where uneven moisture adheres to places where a lot of moisture passes, such as vents. However, it is advantageously suppressed or prevented, so that the molding can be performed without any unevenness in physical properties of the entire mold. In addition, since there is no variation in moisture due to the flow of water vapor into the cavity, drying and curing are promoted. It should be noted that the water vapor pressure and the carrier gas pressure must be adjusted to a certain ratio and introduced and vented at the same time, as will be described later. It can be shown. Here, the simultaneous ventilation of water vapor and carrier gas means that the error in starting each ventilation is within 1 second, preferably within 0.5 seconds.

  It should be noted that the water vapor that is blown through the vent of such a mold and allows the inside of the coated sand filling phase to be vented must contain water, and is preferably saturated water vapor. As the temperature of the water vapor, saturated water vapor of about 70 to 150 ° C. is generally used. However, in the present invention, when a high temperature water vapor temperature is employed, a large amount of energy is required for production. In particular, a water vapor temperature of less than 100 ° C. is advantageously employed. As the water vapor pressure at this time, a value of about 0.01 to 0.1 MPa, more preferably about 0.05 to 0.1 MPa is advantageously employed as a gauge pressure.

  As the carrier gas blown together with the water vapor, air, a reactive gas such as carbon dioxide (carbon dioxide gas), an inert gas such as nitrogen or argon, or the like is used. Among these, oxygen is mixed in the air, and depending on the heating conditions, oxygen may react with the binder to cause oxidative degradation, which may reduce the strength. Carbon, nitrogen, argon gas or any mixture thereof will be advantageously used. By venting together with water vapor and any one of carbon dioxide, nitrogen, or argon gas, the oxygen in the cavity is reduced, so that the risk of deterioration of the mold strength can be avoided. In addition, as a pressure of this carrier gas, generally a value of about 0.01 to 0.6 MPa, more preferably about 0.05 to 0.4 MPa is advantageously employed as a gauge pressure.

  As described above, the carrier gas is allowed to be ventilated together with the water vapor, thereby reducing the viscosity of the water vapor and improving the water vapor permeability. However, the water-soluble inorganic compound as a binder component can be obtained. Accordingly, it is possible to accelerate hardening of the coated sand in addition to the above-described effect by venting the reactive gas together with the water vapor. For example, when the water-soluble inorganic compound is water glass, by using carbon dioxide as a reactive gas, the carbon dioxide neutralizes the water glass, so that solidification or curing can be further promoted. is there.

  In addition, when the water vapor and the carrier gas are simultaneously ventilated, if necessary, an alkylene carbonate and / or an organic ester are both aerated or introduced as a curing agent, whereby a water-soluble inorganic compound as a binder component is introduced. It is also effective to achieve a more rapid curing. And introduction | transduction of the alkylene carbonate and / or organic ester as such a hardening | curing agent will generally be implemented in the form made to contain in carrier gas, However, these alkylene carbonate and organic ester are to the last. It is used in an auxiliary manner, and in its use, it is necessary to pay particular attention not to adversely affect the environment due to the leakage. Such alkylene carbonates and organic esters are generally used at a ratio of about 1 to 10 parts by mass with respect to 100 parts by mass of the carrier gas.

  Here, all of these alkylene carbonates and organic esters are known as water glass curing agents, and are appropriately selected and used from the various known ones. Among them, examples of the alkylene carbonate include ethylene carbonate, propylene carbonate, 4-ethyldioxolone, 4-butyldioxolone, 4,4-dimethyloxolone, 4,5-dimethyldioxolone, and the like. Organic esters include methyl formate, ethyl formate, ethyl acetate, ethyl lactate, triethyl citrate, dimethyl succinate, dimethyl malonate, dimethyl sebacate, dimethyl oxalate, methyl acrylate, ethylene glycol Examples thereof include carboxylic acid esters such as acetate, diacetin, and triacetin, and lactones such as γ-butyrolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, β-propiolactone, and ε-caprolactone. Among these, methyl formate, triacetin, γ-butyrolactone, ethylene carbonate, propylene carbonate and the like are preferably used.

  By the way, when the water vapor and the carrier gas are simultaneously introduced into the molding die as described above, the ratio of the water vapor pressure and the carrier gas pressure is set to 1: On the other hand, when the ratio of the pressure of the water vapor and the carrier gas becomes too high when the water vapor is passed and dried by heating in the mold, the water vapor becomes thin and the water vapor is coated sand. The ratio between the water vapor pressure and the carrier gas pressure needs to be 1:20 or less from the point where the water is dried faster than the water is moistened. Preferably, the ratio between the water vapor pressure and the carrier gas pressure is in the range of 1: 1 to 1:10, and more preferably in the range of 1: 1.2 to 1: 5. When the mold to be molded is large or has a complicated shape, it is desirable to lower the temperature of the mold and increase the ratio of the carrier gas to vent.

  In addition, about the pressure of these gas, it is not the partial pressure at the time of sand mold molding, but the pressure value of each gas when the piping is closed before molding. By allowing water vapor and carrier gas to flow within the range of these pressure ratios, water vapor can be evenly supplied to the mold formed in the mold, and the water vapor ventilation time and the mold The drying time is short and the molding speed can be shortened. Further, when the temperature of the water vapor is less than 100 ° C., the water vapor pressure is 0.1 MPa or less, but the carrier gas can be vented at a pressure equal to or higher than this water vapor pressure, so that the pressure of the aeration can be increased. Even if the coated sand has poor air permeability, there is an advantage that molding is possible, and even with large molds or molds with complicated shapes, unevenness of ventilation and variation in physical properties are prevented, and the appearance is good Thus, a mold having stable physical properties can be advantageously obtained.

  In addition, as a method of venting water vapor and carrier gas as described above, generally, the coated sand (filled into the molding cavity of the molding die) is blown together with water vapor and carrier gas from a common vent provided in the molding die. A method is used in which the inside of the phase is vented. Furthermore, as the aeration time, water vapor is supplied to the surface of the coated coated sand so that the water-soluble inorganic compound (binder component) as the binder is sufficiently moistened, and the coated sand is mutually bonded. The time that can be joined (joined) is appropriately selected depending on the size of the mold, the number of vents, and the like. The ventilation of water vapor at this time generally adopts an aeration time of about 1 second to about 60 seconds, preferably 3 to 40 seconds, more preferably about 5 to 30 seconds. This is because it becomes difficult to sufficiently wet the coated sand surface when the water vapor ventilation time is too short. When the water vapor ventilation time is too long, the binder on the coated sand surface dissolves and flows out. This is because there is a risk that the mold will be stained. The carrier gas may be vented at the same time as the water vapor, and the same ventilation time as that of the water vapor may be used. In order to accelerate the drying of the wet binder, the air flow time is longer than that of the water vapor. Also good.

  Furthermore, the improvement in the breathability of water vapor and carrier gas between the coated sands filled in such a mold allows the water vapor and carrier gas to be vented while sucking the atmosphere in the mold from the exhaust port of the mold. This can be further enhanced by doing so. It is also an effective technique to introduce the water vapor and the carrier gas after the inside of the molding cavity of the mold is previously depressurized. In addition, it is important for the production of complex shaped cores and the like to appropriately set the positions of the vents and exhaust ports and optimize the length of the gas flow path. In some cases, it is also effective to use a plurality of vents and exhausts and perform simulation of gas ventilation.

  The method of venting the water vapor and the carrier gas is not particularly limited as long as it can be vented into the mold, but before the gas is passed through the mold, the water vapor and the carrier gas are simultaneously vented in a mixed state. It is desirable. By mixing before aeration to the mold, the water vapor can be uniformly diluted with the carrier gas, so that the water vapor can be uniformly and evenly supplied to the mold. In the flow path communicating with the vent of the mold, the flow path of the water vapor and the flow path of the carrier gas are merged to form a flow path for venting to the mold, and a space is provided in the merged portion. A method in which carrier gas is mixed in such a space, or a method in which a water vapor vent and a carrier gas vent are provided at positions facing each other so that the gases collide with each other and then mixed. Alternatively, a method of providing a mixing means such as a static mixer in the flow path can be employed.

  In the present invention, after aeration with water vapor and carrier gas, the coated sand filled in the mold is dried and, in order to solidify or harden, in the heated mold, The filled phase of the coated sand is retained, thereby advantageously forming a mold having the desired properties. The holding time in such a mold is appropriately selected depending on the type of the water-soluble inorganic compound, the temperature of the mold, the ventilation condition of water vapor or carrier gas, the presence or absence of the use of a curing agent, and the like. However, generally, about 30 seconds to 20 minutes, preferably about 1 minute to 10 minutes, and more preferably about 1 minute to 5 minutes are employed.

  In particular, in the present invention, hot air such as heated dry air or superheated steam is blown in order to actively dry the filling phase of the coated sand moistened by such steam during holding in such a mold. Therefore, a method of allowing the filling phase to be ventilated is preferably employed. The temperature of such hot air is 50 ° C to 200 ° C, preferably 80 ° C to 180 ° C, and the temperature of the superheated steam is 100 ° C to 300 ° C, preferably 110 ° C to 220 ° C. By such hot air or superheated steam ventilation, the coated sand is quickly dried to the inside of the filled phase, and the solidification or curing of the filled phase is further advantageously promoted. In addition to improving the properties, it is possible to advantageously improve the properties such as the bending strength of the obtained mold, and it can also contribute to shortening the molding time of the mold.

  Hereinafter, the configuration of the present invention will be more specifically clarified by using some examples of the present invention. However, the present invention is interpreted in a limited manner by the description of such examples. It should be understood that it is not done. In the following examples and comparative examples, all parts and percentages are shown on a mass basis unless otherwise specified. Moreover, the state of the molds obtained in Examples and Comparative Examples and the measurement of the bending strength of the molds were respectively performed as follows.

−Measurement of bending strength (kgf / cm ² ) −
About the test piece of width: 25.4 mm x height: 25.4 mm x length: 200 mm obtained in each of the following Examples and Comparative Examples, the breaking load was measured using a measuring instrument (manufactured by Takachiho Seiki Co., Ltd.). : Digital casting sand strength tester), and the bending strength was calculated by the following formula using the measured breaking load.
Bending strength = 1.5 × LW / ab ²
[However, L: distance between fulcrums (cm), W: breaking load (kgf), a: width of test piece (cm), b: thickness of test piece (cm)]

―Observation of mold appearance―
The appearance when a test piece having the above-mentioned width: 25.4 mm × height: 25.4 mm × length: 200 mm was molded was visually observed and evaluated. That is, ten panelists evaluated the appearance of the molded specimens (molds) according to the following criteria, and evaluated at the average level. In the present invention, level 3 or higher is regarded as acceptable. Further, at level 1, since the test piece collapsed, the bending strength could not be measured.
Level 1: A state where the shape collapses.
Level 2: Partially missing but in a certain shape.
Level 3: Although there is sand adherence to the mold and surface roughness, it is almost in shape.
Level 4: The completed shape can be taken.

-Production example of CS-
First, as casting sand, commercially available flattery sand No. 6 (trade name: manufactured by Cape Flattery Silica Mines) is prepared as fresh sand, and commercially available sodium silicate No. 1 (product) Name: manufactured by Fuji Chemical Co., Ltd.), diluted with water, and added with sodium hydroxide, the non-volatile content (ratio excluding water content from water glass aqueous solution) was 25.6% by mass A water glass aqueous solution having a ratio of 2.0 was prepared as a binder.

  And after throwing the above-mentioned flattery sand heated to a temperature of about 140 ° C. into a kneader (speed muller manufactured by Enshu Iron Works Co., Ltd.), the aqueous water glass solution was further added to 100 parts of the flattery sand. It was added at a ratio of 0.75 part in terms of solid content, kneading was carried out for 60 seconds to evaporate water, and stirring and mixing were performed until the sand granule collapsed. Thereafter, the obtained mixture was taken out from the kneader to obtain dry coated sand (CS1) having free flow at room temperature.

-Molding example 1 (Example 1)-
After filling CS1 having a temperature of 20 ° C. obtained in the above CS production example into a mold heated to 75 ° C. at a gauge pressure of 0.3 MPa, a 0.025 MPa gauge Steam with a pressure of about 81 ° C. was blown for 30 seconds, and simultaneously with the blowing of this steam, nitrogen gas with a gauge pressure of 0.05 MPa was blown for 30 seconds at a flow rate of 5 L / min. Then, the coated sand phase filled in the molding die (specifically, in the molding cavity) was aerated. Nitrogen gas was blown in simultaneously with the water vapor, and the blowing was completed simultaneously with the completion of the water vapor blowing. Then, after such a flow of water vapor and nitrogen gas is completed, hot air (apparatus display temperature 300 ° C.) is blown in for 120 seconds, and heating is performed for 2 minutes in the mold, so that CS1 filled in the mold is By making it harden | cure, the casting_mold | template used as a test piece [25.4mmx25.4mmx200mm] was produced. And about this obtained test piece, according to the test method mentioned above, bending strength and the external appearance of a casting_mold | template were measured, and the result is shown in following Table 1.

-Molding examples 2 to 5 (Examples 2 to 5)-
In Example 1, except that steam with a gauge pressure of 0.03 MPa was blown, while nitrogen gas with a gauge pressure of 0.05 MPa, 0.1 MPa, 0.2 MPa, or 0.3 MPa was blown, and Example 1 Similarly, a test piece was produced. The measurement results for the obtained test pieces are shown in Table 1 below.

-Example 6 of mold casting (Example 6)-
In Example 1, a test piece was prepared in the same manner as in Example 1 except that steam with a gauge pressure of 0.02 MPa was blown and nitrogen gas with a gauge pressure of 0.4 MPa was blown. The measurement results for the obtained test pieces are shown in Table 1 below.

-Example 7 of mold casting (Example 7)-
In Example 1, the temperature of the mold was set to 100 ° C., and water vapor with a gauge pressure of 0.04 MPa was blown, while nitrogen gas with a gauge pressure of 0.2 MPa was blown in the same manner as in Example 1, A test piece was prepared. The measurement results for the obtained test pieces are shown in Table 1 below.

-Examples 8 to 10 of mold casting (Examples 8 to 10)-
In Example 1, the temperature of the mold was set to 85 ° C., 65 ° C., or 55 ° C., and water vapor of 0.03 MPa gauge pressure was blown, while nitrogen gas of 0.3 MPa gauge pressure was blown. A test piece was prepared in the same manner as in Example 1. And the measurement result about those obtained test pieces is shown in Table 1 below.

-Examples of mold making 11-12 (Examples 11-12)-
In Example 1, water vapor with a gauge pressure of 0.03 MPa was blown for 10 seconds or 50 seconds, while nitrogen gas with a gauge pressure of 0.3 MPa was blown in the same manner as in Example 1, and the test piece was Produced. And the measurement result about the obtained test piece is shown in the following Table 1.

-Example 13 of mold casting (Example 13)-
In Example 1, the temperature of the mold was set to 30 ° C., and water vapor was blown at a gauge pressure of 0.02 MPa, while nitrogen gas was blown at a gauge pressure of 0.4 MPa, as in Example 1, A test piece was prepared. And the measurement result about those obtained test pieces is shown in Table 1 below.

-Mold casting examples 14-15 (Comparative Examples 1-2)-
In Example 1, a test piece was prepared in the same manner as in Example 1 except that water vapor with a gauge pressure of 0.025 MPa or 0.03 MPa was blown and nitrogen gas was not blown. The measurement results for the obtained test pieces are shown in Table 1 below.

-Mold making examples 16-17 (Comparative Examples 3-4)-
In Example 1, the temperature of the mold was set to 30 ° C. or 120 ° C., and water vapor of 0.02 MPa or 0.04 MPa gauge pressure was blown, while nitrogen gas of 0.5 MPa or 0.2 MPa gauge pressure was blown. Except that, a test piece was prepared in the same manner as in Example 1. The measurement results for the obtained test pieces are shown in Table 1 below.

-Example 18 of mold casting (Comparative Example 5)-
In Example 2, it was carried out except that water vapor and nitrogen gas were not simultaneously vented, water vapor of 0.03 MPa gauge pressure was blown for 30 seconds, and then nitrogen gas of 0.05 MPa gauge pressure was bubbled for 30 seconds. A test piece was prepared in the same manner as in Example 2. And the measurement result about the obtained test piece is shown in the following Table 1.

  As is apparent from the results of Table 1, the heating and holding temperature of the mold is within the range defined by the present invention even when the pressure of water vapor or nitrogen gas as the carrier gas that is passed through the mold is changed. By making the ratio of the pressure of water vapor and nitrogen gas be within a range of 1: 1 to 1:20, the carrier gas is not vented, compared with the case where the carrier gas is not vented, It can be seen that a healthy mold having an excellent appearance and good physical properties such as strength can be advantageously obtained without causing problems such as spots and boroughs.

On the other hand, as shown in Comparative Examples 1 and 2, when only water vapor is ventilated and nitrogen gas as a carrier gas is not vented, problems such as spots and bolsters are caused and necessary for measurement. In Comparative Example 3 in which the pressure was too high with respect to the water vapor pressure even when nitrogen gas was vented, In the case of Comparative Example 4 in which the appearance is not sufficient and the heating and holding temperature of the mold is 120 ° C., problems such as spots are caused even if nitrogen gas is vented, and the intended test is performed. I couldn't get a piece. In addition, it is clear that water vapor and nitrogen gas are not simultaneously ventilated, and in Comparative Example 5 in which nitrogen gas is ventilated after the aeration of water vapor, the appearance deteriorates and the mold strength is not sufficient. became.

Claims (13)

  Using a coated sand formed by coating foundry sand with a binder containing a water-soluble inorganic compound as a binder component, this was filled into a molding cavity of a mold maintained at a temperature of 20 ° C. or higher and 110 ° C. or lower. Thereafter, the water vapor and the carrier gas were adjusted so that the ratio of the pressure of the water vapor and the pressure of the carrier gas was 1: 1 to 1:20, and simultaneously introduced into the mold and filled. Fill the mold by holding it in the mold held at the temperature after moistening the binder that coats the coated sand in the mold by aeration between the coated sands. A method for producing a mold, wherein the coated sand is solidified or cured.   The method for producing a mold according to claim 1, wherein the water-soluble inorganic compound is water glass.   The method for producing a mold according to claim 1 or 2, wherein the water vapor and the carrier gas are separately supplied and introduced into the molding cavity through a vent provided in the molding die.   The method for producing a mold according to claim 1 or 2, wherein the water vapor and the carrier gas are mixed in advance and then introduced into the molding cavity through a vent provided in the mold.   The method for producing a mold according to any one of claims 1 to 4, wherein the water vapor is supplied to the mold under a pressure of 0.01 to 0.1 MPa at a temperature of less than 100 ° C.   The method for producing a mold according to any one of claims 1 to 5, wherein the carrier gas is carbon dioxide, nitrogen, argon, or a mixed gas thereof.   The method for producing a mold according to any one of claims 1 to 6, wherein an alkylene carbonate and / or an organic ester is contained as a curing agent in the carrier gas.   The method for producing a mold according to any one of claims 1 to 7, wherein the water vapor is supplied to the mold for 1 second to 60 seconds.   The method for producing a mold according to any one of claims 1 to 8, wherein the coated sand is in a dry state having fluidity at room temperature.   The method for producing a mold according to any one of claims 1 to 9, wherein the coated sand is preheated to a temperature of 30 ° C or higher and then filled into a molding cavity of the mold.   The atmosphere in the molding cavity of the mold is forcibly discharged out of the system when the water vapor and the carrier gas are introduced into the molding cavity of the mold. The manufacturing method of the casting_mold | template as described in a term.   The method for producing a mold according to any one of claims 1 to 11, wherein the water vapor and the carrier gas are introduced after the inside of the molding cavity of the mold is in a reduced pressure state. The method for producing a mold according to any one of claims 1 to 12, wherein hot air or superheated steam is allowed to pass through the mold during holding in the mold.