JP2009119469A - Fluid sand self-curing mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid sand self-curing mold, wherein artificial sand is used, the additional amount of resin is reduced, and a surfactant is not required. <P>SOLUTION: As for the fluid sand self-curing mold, sand mixture is obtained by using the new sand of artificial sand produced by a melting process or a flame fusion process and having a sphericity of ≥0.8 or the recovered sand thereof or the regenerated sand thereof and adding furan resin whose coefficient of viscosity at 25°C is 5.5 to 50 mPa s and a hardener liquid to the artificial sand, so as to be kneaded, wherein the content of the furan resin is at least 0.1 mass% and the content of the hardening effective component of the hardener liquid is at least 0.01 mass%, the adding and kneading are performed in such a manner that the relation between the total additional amount (mass%) of the furan resin and the hardener liquid and the coefficient of the viscosity of the furan resin satisfies [the total additional amount (mass%) of the furan resin and the hardener liquid]≤-6.25×10<SP>-3</SP>×[the coefficient of the viscosity (mPa s) of the furan resin]+1.056, and the fluidity of the sand mixture satisfies that the diameter of a slump flow is ≥two times the diameter of a slump cone, in a slump test. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic self-hardening flow mold used for casting.

  One of the molds used for casting is an organic self-hardening mold. The organic self-hardening mold uses sand (hereinafter simply referred to as kneaded sand) kneaded by adding an organic resin and a resin curing agent to foundry sand as a mold material. As the organic resin, a furan resin, a phenol resin, an alkali phenol resin, or the like is used.

  In addition, a self-hardening fluid mold in which bubbles are interposed between sand grains by adding a surfactant and water to the kneaded sand and the kneaded sand has foaming fluidity is also used. This self-hardening flow mold has a great advantage that labor can be saved at the time of molding, but on the other hand, there is a problem that mold shrinkage (lowering of the mold) occurs due to bubble breakage. Therefore, Patent Document 1 and Patent Document 2 are disclosed as means for solving this problem. However, in the conventional self-hardening fluid mold, in order to obtain fluidity of the kneaded sand, addition of a surfactant is indispensable, and there is no example of a fluid mold that does not use a surfactant.

Silica sand produced in nature is mainly used for foundry sand, but chromite sand or zircon sand may be used to prevent seizure with molten metal. Seizure is a phenomenon in which molten metal enters between sand grains, and is classified into physical seizure and chemical seizure. Physical seizure is a phenomenon in which molten metal penetrates between sand grains by physical force. Chemical seizure means that a chemical change occurs between sand, molten metal, and air, and the wettability between the sand and molten metal changes, so that the molten metal penetrates between the sand grains. It is often caused mainly by firelite-based products (FeO.SiO ₂ ).

  Regardless of the self-hardening mold or self-hardening flow mold, when natural silica sand is used, the sand form is unstable and uneven, so that the amount of resin and curing agent above a certain level is required to cure the kneaded sand. is necessary. That is, there is a problem that there is a limit in reducing the addition amount of the resin and the curing agent. For example, when furan resin is used, 0.5% by mass or more of resin is necessary with respect to the mass of natural sand. If it is 0.5 mass% or less, the sand after kneading may not be cured or the strength may be insufficient, so that it becomes impossible to produce a stable self-hardening mold. Moreover, there is a problem that natural sand does not become fluid sand simply by reducing the amount of resin added due to the unevenness of the sand.

  In recent years, spherical artificial sand has been developed and put into practical use for the purpose of improving the fluidity, fire resistance and recovery rate of sand. For example, Patent Documents 3 to 5 disclose a method for producing artificial sand. Artificial sand production methods are mainly classified into three types: a sintering method, a melting method (atomizing method), and a flame melting method. Patent Document 3 discloses a method for producing mullite sand by a sintering method. In the sintering method, the raw material composition is granulated in a spherical shape and then fired in a rotary kiln or the like to produce artificial sand. However, this method has good sphericity, but there are problems such as unevenness on the surface during baking and the surface becomes porous, so that the strength cannot be obtained unless the amount of resin added is increased. In addition, if the amount of resin added is increased due to this surface problem, there will be a problem that it does not become fluid sand. In order to avoid the problem of the surface condition, fluidized sand by a sintering method in which the surface is reprocessed to increase the surface smoothness has been put into practical use.

  Patent Document 4 discloses a method for producing artificial sand by a melting method. In the melting method, artificial sand is produced by melting a raw material composition and blowing air onto the melt. Patent Document 5 discloses a method for producing artificial sand by a flame melting method. In the flame melting method, raw material powder dispersed in a carrier gas such as oxygen is melted by a flame generated by the combustion of fuel such as propane, butane, methane, natural gas and oxygen, and spheroidized.

  In patent document 5, fluidity | liquidity is evaluated by the passage time of the sand using a funnel. This evaluation is merely a measure of the ease of rolling of sand, and is not an evaluation of fluidity like cement. As described above, there are documents on sand with good fluidity using artificial sand and molds with good fluidity, but there are documents on kneaded sand that flows according to the amount of resin added and the properties of the resin, that is, fluid molds. Absent.

In mold making, self-hardening flow molds are not always completed with the flow characteristics of sand only. In consideration of application to an actual mold, not only the flow characteristics of sand itself but also the flow characteristics when kneaded with a resin and a curing agent are important. Since the present invention is an invention of flowing kneaded sand, that is, a fluid mold, the slump test is one index for evaluating the fluidity of the kneaded sand. However, the evaluation of the fluidity of the kneaded sand using the slump test has not been made.
JP 2003-10944 A JP 2003-230941 A JP-A-5-169184 JP 2003-251434 A JP 2004-202577 A

  In order to obtain casting sand that flows using artificial sand, it is necessary to examine various points such as the properties and addition amount of the resin, the surface properties of the sand used, and the sphericity.

  In addition, casting sand becomes easier to flow as the amount of resin added is smaller. However, if the amount of resin added is decreased, there is a problem that the mold strength after curing is lowered. For this reason, when producing a flowable mold using artificial sand, it is preferable to discover and combine molding techniques that do not require much mold strength.

  Several of the present inventors have invented a self-hardening flow mold that generates bubbles with a surfactant, but this method requires a lot of resin, and more surface activity to generate bubbles. There is a problem that requires an agent.

  Due to these large amounts of resins and surfactants, the amount of gas generated during pouring increases, causing problems such as gas defects and high costs. In order to solve the problem of the flow mold by these surfactants, it is necessary to develop a self-hardening flow mold by another method with a small amount of resin addition.

  For spherical artificial sand or spherical natural sand, there are many literatures that have improved the fluidity of sand itself, but there are no literatures on fluid molds in which casting sand with added binders such as resins flows. . Considering the relationship between artificial sand and resin, for example, in the case of mullite artificial sand that is made by sintering and has not been surface-treated, there are fine irregularities on the surface, and the resin is absorbed into the holes. There are problems such as. In addition, spherical natural sand also has problems such as adsorption of resin to scratches on the sand surface. Therefore, in order to develop a self-hardening fluid mold, it is necessary to discover artificial sand in which the resin is not adsorbed by the artificial sand defects.

  The present invention has been made in view of these problems to be solved, and uses artificial sand that does not adsorb resin, has a sphericity that does not form a bridge, and the composition of the sand does not cause seizure. The amount of the resin added corresponds to the viscosity of the resin to be added. The present invention is used in a molding method suitable for the product of the present invention.

In order to solve the above problems, the present invention has the following configuration. The foundry sand used was artificial sand having a sphericity of 0.8 or more, or recovered sand or recycled sand thereof. In addition, the furan resin to be used is used in the range where the viscosity at 25 ° C. is 5.5 to 50 mPa · s. Further, in the kneaded sand obtained by adding and kneading furan resin and a curing agent liquid to foundry sand, the resin content of at least 0.1% by mass or more of the furan resin and at least 0.01% by mass or more of the curing agent liquid. The relational expression between the addition amount (mass%) of the furan resin and the addition amount (mass%) of the furan resin containing the active ingredient of the curing agent is [the total addition amount (mass%) of the furan resin and the curing agent liquid]
≦ −6.25 × 10 ⁻³ × [viscosity of furan resin (mPa · s)] + 1.056
The kneaded sand was prepared by adding so as to satisfy the above conditions. Furthermore, regarding the fluidity of the prepared kneaded sand, the diameter of the slump flow in the slump test of the kneaded sand was more than twice the diameter of the slump cone.

  More preferably, the furan resin is at least one selected from the group consisting of furfuryl alcohol, a condensate of furfuryl alcohol and aldehydes, a condensate of phenols and aldehydes, a condensate of urea and aldehydes, It was decided to consist of two or more cocondensates selected from the above group.

  More desirably, the compression strength of the mold after curing is 0.3 MPa or more.

  The fluid mold in the present invention is an effective molding means in the full mold method that does not require a particularly high mold strength. In addition, the mold of the present invention having a compressive strength of 0.3 MPa or more is used as a substitute for green sand having a low moisture flow and a poor fluidity due to a large amount of moisture and clay and having a mold compressive strength of only 0.03 to 0.25 MPa. As a result, the product yield can be improved.

  The present invention enables the sand to be hardened and obtained the required strength with a small amount of resin added, and has a great effect that fluidity can be obtained without using a surfactant. is there.

  Hereinafter, the present invention will be described in detail.

  Since spherical artificial sand is used in the present invention, the sand itself has good fluidity. Therefore, there are advantages such that the sand is finely packed and the amount of resin added to the sand may be small. Furthermore, there is also an advantage that casting sand can be made without depending on the surfactant.

  Artificial sand can be used as fresh sand, recovered sand or recycled sand. Artificial sand produced by a melting method or flame melting method is desirable, but artificial sand produced by a sintering method can also be used if it has been subjected to a surface treatment to smooth the surface. In addition, the sphericity of the artificial sand is preferably 0.8 or more for the purpose of improving the packing property and rolling property of the sand itself. The sphericity of artificial sand can be obtained from the following equation.

[Perimeter of a perfect circle having the same area as the projected area of sand particles (mm)] / [Perimeter of the projected surface of sand particles (mm)]
The two perimeters in the equation can be obtained by taking an enlarged (close-up) photograph of the artificial sand and then applying the photograph to an image analyzer. Calculation was performed on any 30 or more sand particles, and the average value was defined as the sphericity of the artificial sand.

  The furan resin has a viscosity of 60 mPa · s or less at 25 ° C., which is lower than that of other resins, and the resin itself does not impair the fluidity of the kneaded sand. Therefore, it is suitable for the self-hardening fluid mold of the present invention. Since acid-cured phenol resins and alkali phenol resins have a high viscosity of 100 to 300 mPa · s at 25 ° C., it has been difficult as a result of experiments to produce flowing kneaded sand. However, if a resin having a viscosity as low as that of furan resin can be developed in the future, these low-viscosity resins can be applied to the self-curing fluid mold of the present invention.

  The furan resin that can be used is at least one selected from the group consisting of furfuryl alcohol, a condensate of furfuryl alcohol and aldehydes, a condensate of phenols and aldehydes, and a condensate of urea and aldehydes. A furan resin comprising two or more cocondensates selected from: The curing effective component is not particularly limited as long as it promotes the curing of the furan resin at room temperature. It is also possible to mix and use a plurality of curing active ingredients.

  Even when a furan resin having a low viscosity is used, if the addition amount of the furan resin and the curing agent liquid is large, the wetness of the kneaded sand increases and the fluidity of the sand is lost. Therefore, the fluidity of the kneaded sand was investigated in detail by a slump test often used as an index representing fluidity. The slump test is a fluidity evaluation method that measures the spread of the object or the drop in the height of the top when the object is filled in a cup called a slump cone and the slump cone is lifted from the plate. 1). The spread of the object when the slump cone is pulled up is called slump flow. The larger the diameter, the more fluid. The slump test is usually used for evaluating the fluidity of concrete, but by applying it to the kneaded sand, the fluidity of the kneaded sand can be evaluated.

  If the diameter of the slump flow in the slump test is more than twice the diameter of the slump cone, the present inventors can obtain the necessary and sufficient fluidity even for sanding in complex parts in actual molding operations. It was made clear that

Furthermore, the present inventors changed the addition amounts of the furan resin and the curing agent and examined the fluidity of the kneaded sand in detail, and as a result, the total addition amount (mass%) of the furan resin and the curing agent liquid and the viscosity of the furan resin. The relationship of rate (mPa · s) is the following formula [total addition amount (mass%) of furan resin and curing agent liquid]
≦ −6.25 × 10 ⁻³ × [viscosity of furan resin (mPa · s)] + 1.056
By satisfying the above, a large finding was obtained that the diameter of the slump flow is more than twice the diameter of the slump cone. If this relational expression is used, stable fluidity can be obtained even when, for example, the viscosity of the resin is changed in order to adjust the curing speed or compressive strength.

  It has been found that the flow mold in the present invention has an excellent effect particularly in the full mode method. In the full mold method, a foamed polystyrene model with the same shape as the product is produced, and this is embedded in sand, mold casting is performed, and the casting is cast by replacing the molten polystyrene without removing the foamed polystyrene model. Is the method. The full mold method can cast a casting having a complicated shape without using a core as in the wood mold method. Further, there is an advantage that the mold strength may be low because the wooden mold is not extracted. By using the self-hardening fluid mold according to the present invention, the mixing capacity of the kneaded sand is greatly improved, it is possible to reduce the labor of molding work, simplify and provide a stable mold that does not have insufficient loading even in complicated parts. became.

  Considering buoyancy generated during casting and deformation of the mold due to the pressure of the molten metal, it is desirable that the mold strength is a compressive strength described in JISZ2601 of 0.3 MPa or more. In particular, even when producing a casting with a high yield as an alternative to a green mold, it is desirable that the mold be a mold of 0.3 MPa or more that can withstand the molten metal pressure. According to the investigation by the inventors, in order to obtain a mold strength of 0.3 MPa or more, at least 0.1% by mass of furan resin is required, and at least 0. It has been found that a curing agent active ingredient in a curing agent liquid of 01% by mass or more is necessary.

  By using artificial sand in this manner, a self-hardening fluid mold can be produced with a small amount of furan resin. When natural silica sand or artificial sand with irregular shapes is used for casting sand, the required strength cannot be obtained unless the resin addition amount is 0.5% by mass or more. With this resin addition amount, the diameter of the slump flow is not obtained. Was never more than twice the diameter of the slump cone. In addition, since the present invention has a mold configuration that does not require a surfactant, the problem of mold shrinkage due to bubble breakage, which is observed in conventional flow molds, has been completely solved.

  In addition, the amount of resin used can be greatly reduced compared to the case of using conventional natural silica sand, which makes it possible to reduce casting defects caused by gas generated during pouring, and at the same time, molding At the same time, the odor at the time of casting is reduced, so the effect of improving the working environment was also obtained.

  We have invented a self-hardening flow mold that uses spherical artificial sand and does not require a surfactant by adding a small amount of low viscosity resin. According to the present invention, both the effect of greatly reducing the required amount of resin addition and the effect of enabling flow without the need for a surfactant are combined. Therefore, the gas defect of the casting resulting from gasification of the resin and the curing agent liquid can be reduced, and further, the odor at the time of mold making and molten metal pouring can be reduced. Furthermore, since a self-hardening fluid mold can be provided without adding a surfactant, the problem of mold shrinkage due to bubble breakage can be solved. In particular, for the molding of complex parts in the full molding method that does not require mold strength, there was a great effect on simplification of operations and stabilization of sand filling during molding. In addition, by producing the spheroidal graphite cast iron produced in the green mold with the mold of the present invention, the non-pushing hot water method that does not require the hot water has doubled the product yield to 40-80%.

  The best mode for carrying out the present invention will be described below. However, the present invention is not limited to these embodiments.

  In the kneaded sand for a self-curing fluid mold prepared by adding a furan resin and a curing agent solution to artificial sand, the fluidity and mold strength were evaluated as follows. Tables 1 and 2 show the chemical composition and particle size distribution of the artificial sand used in this example.

また、フラン樹脂は、２５℃での粘性率を９、１７、２９、４１ｍＰａ・ｓに調整したＡ、Ｂ、Ｃ、Ｄの４種類を用いた。

Moreover, four types of A, B, C, and D whose viscosity at 25 ° C. was adjusted to 9, 17, 29, and 41 mPa · s were used as furan resins.

  The fluidity of the kneaded sand was evaluated by measuring the diameter of the slump flow by a slump test. FIG. 1 shows the method of the slump test. The slump flow refers to the spread of the sand 2 when the cup 2 called the slump cone 1 is filled with the sand 2 and the slump cone is pulled up from the surface plate 3. In this example, a slump cone having an opening diameter of 70 mm, a bottom surface diameter of 50 mm, and a height of 80 mm was used. Here, the diameter of the opening is the diameter d of the slump cone. The fluidity of the kneaded sand is determined by measuring the slump flow when the slump cone is pulled up vertically, that is, the diameter D of the spread of the kneaded sand, and the ratio of the slump flow diameter D to the slump cone diameter (D / d). It was evaluated by seeking.

  In the relationship between the slump flow and the fluidity in the sanding operation at the actual site, if the ratio (D / d) of the diameter of the slump flow to the diameter d of the slump cone 1 is twice or more, in the actual molding operation. We confirmed by field work that there was no problem with sanding in complex parts.

  The slump flow changes depending on the wet feeling of sand, and the factors that change the wet feeling depend on the total amount of liquid to be added (furan resin and hardener liquid) and the viscosity of the resin to be used.

  Therefore, kneaded sand was prepared by changing the amounts of furan resin and hardener solution added to the artificial sands listed in Tables 1 and 2, and a slump test was conducted with these kneaded sands. The ratio (D / d) to the diameter d was measured. The measurement results were arranged in a graph in which the vertical axis represents the total addition amount of the furan resin and the curing agent liquid and the horizontal axis represents the viscosity of the furan resin, and the range in which D / d is doubled or more was obtained. FIG. 2 shows the measurement results. When D / d is 2 times or more, it is plotted with a circle symbol, and when it is less than 2 times, it is plotted with a square symbol, and the obtained D / d value is written in each symbol.

From FIG. 2, the total addition amount (mass%) of the furan resin and the curing agent liquid and the viscosity coefficient (mPa · s) of the furan resin with respect to the range of 5.5 to 50 mPa · s of the furan resin. The relationship is the following formula [total addition amount of furan resin and curing agent liquid (mass%)]
≦ −6.25 × 10 ⁻³ × [viscosity of furan resin (mPa · s)] + 1.056
Is satisfied, the ratio (D / d) of the slump flow diameter D to the slump cone diameter d becomes twice or more. In other words, it was found that the conditions for obtaining good fluidity are within the hatched area in FIG.

  Next, the mold strength was evaluated by a compression test. The resin content of the furan resin was changed in the range of 0.05 to 0.5% by mass, and the compression test was performed based on JISZ2601. FIG. 3 shows the measurement results of the mold strength.

  Considering buoyancy generated during casting and deformation of the mold due to the pressure of the molten metal, it is desirable that the mold strength is a compressive strength described in JISZ2601 of 0.3 MPa or more. As shown in FIG. 3, it can be seen that at least 0.1% by mass or more of the resin content of furan resin is required to obtain a compressive strength of 0.3 MPa or more.

  At this time, the curing agent solution needs to be at least 20 parts with respect to 100 parts of the resin, and at least 50% of the curing effective component in the curing agent. Therefore, in terms of the amount added relative to the weight of the foundry sand, at least 0.01% by mass of an effective curing ingredient is required to cure the kneaded sand containing 0.1% by mass of the furan resin. I understand.

  Examples in which the self-hardening fluid mold according to the present invention is applied to the full mold method and the green mold are shown below.

  As shown in FIG. 4, a “U” -shaped casting having a concave shape in the lateral direction was produced by a full molding method. In this example, the lateral recess is referred to as a “lateral strip”, and a casting having a lateral recess is referred to as a “lateral strip casting”. In FIG. 4, (a) represents a state in the middle of molding, and (b) represents a state after completion of molding. Specifically, molding is performed according to the following procedure.

  The kneaded sand 6 is put into the casting frame 5 from the kneading mixer, and when the predetermined height is reached, the polystyrene foam model 7 and the runner 8 are set. Thereafter, the kneaded sand 6 is further introduced, and the foamed polystyrene model 7 and the runner 8 are buried. At this time, when there is a possibility that the horizontal stripes are floated, the cored bar 9 is applied. After the filling of the casting frame 5 with the sand is completed, the casting port is finally attached to the upper end of the runner to complete the molding.

  In a horizontal sill type casting having an opening of 200 mm × 200 mm, the length L was changed, and the filling property in the horizontal slab of flowing kneaded sand according to the present invention was investigated. The length of L was set to five types of 200, 400, 600, 800, and 1000 mm.

  In this example, the mold strength of the self-hardening flow mold in the present invention was adjusted to 1.0 MPa. For comparison, the same investigation was also conducted with a self-hardening mold in which the mold strength was adjusted to 1.0 MPa with natural silica sand. The particle size of the sand used was 35 in the AFS particle size index.

  The evaluation of the filling property of the kneaded sand at the time of molding is ◎ when the sand dropped from the kneading mixer is naturally filled in the horizontal stripe without any modification, and the part A in FIG. If it is stepped on, it will be filled in the horizontal stripe due to the fluidity of the kneaded sand, △ if it is necessary to push it slightly in the depth direction by hand, △, it is necessary to extend the hand into the horizontal stripe The case was marked with x.

表３に評価結果を示す。本発明の自硬性流動鋳型では、横シマの奥行きが６００ｍｍまでは、手による介助を必要としなくても、自然に、もしくは混練砂を足で垂直方向に踏み込むだけで、横シマ内を混練砂で充填することができた。一方、天然砂を用いた比較品では２００ｍｍの奥行きに対しても、横シマ内に手を伸ばして込め付けることを必要とした。

Table 3 shows the evaluation results. In the self-hardening fluid mold according to the present invention, when the width of the horizontal stripe is up to 600 mm, the sand is mixed naturally or just by stepping the mixed sand vertically with a foot, without the need for manual assistance. Could be filled with. On the other hand, in the comparative product using natural sand, it was necessary to extend the hand into the horizontal stripe even for a depth of 200 mm.

  Thus, it has been found that the self-hardening fluid mold according to the present invention has extremely excellent fluidity filling properties as compared with the conventional self-hardening mold made of natural sand, and can greatly reduce the labor of placing.

  Next, when the mold strength is low, there is a possibility that the horizontal stripes may be floated by the buoyancy generated during casting or the pressure of the molten metal. Adjust the mold strength of the self-hardening flow mold to 0.1, 0.2, 0.3, 0.4, 0.5 MPa, and make the casting shown in FIG. 3 by the full mold method. investigated. At this time, a metal core usually used for preventing floating in the horizontal stripe was applied. In the evaluation, a case where no sand collapsed or floated in the horizontal strip was indicated as “◯”, and a case where sand collapsed or floated occurred was indicated as “X”.

表４に評価結果を示す。この結果に示されるように、鋳型強度を０．３ＭＰａ以上とすることで、横シマ内に砂の崩れや浮かされのない健全な鋳物を作製できることがわかった。

Table 4 shows the evaluation results. As shown in this result, it was found that by setting the mold strength to 0.3 MPa or more, it is possible to produce a sound casting in which no sand collapses or floats in the horizontal stripes.

  Next, an example in which the self-hardening fluid mold according to the present invention is used as an alternative mold for a green mold will be described. 100 mm × 100 mm × 100 mm (shape factor 2), 100 mm × 100 mm × 50 mm (shape factor 4), 100 mm × 100 mm × 33 mm (shape factor 6), 100 mm × 100 mm × 25 mm (shape factor 8), 100 mm × 100 mm A test piece of × 20 mm (shape factor 10) was prepared, and a molten FCD450 was cast into the test piece, and the shrinkage of the test piece was compared. The shape factor is a value obtained by dividing the sum of the lengths of the two sides other than the shortest side of the rectangular parallelepiped by the length of the shortest side. As the mold, a green mold having a compressive strength of 0.25 MPa and a mold of the present invention of 0.3 MPa, 0.5 MPa, 1 MPa, 2 MPa, and 3 MPa were used. The grain size of the sand was No. 6 sand. Table 5 shows the results where no sink marks are generated and the results are shown with crosses.

この実験より、本発明の鋳型は生型より引けづらく、硬度が高くなるほど引けが発生しづらくなることがわかる。

From this experiment, it can be seen that the mold of the present invention is harder to draw than the green mold, and the higher the hardness, the harder the shrinkage occurs.

It is a figure which shows the measuring method of the angle of repose of kneaded sand. It is a figure which shows the measurement result of the angle of repose in the relationship between the resin part of furan resin, the total addition amount (mass%) of the hardening active ingredient in a hardening | curing agent, and the viscosity (mPa * s) of furan resin. It is a figure which shows the relationship between the resin content addition amount of furan resin, and compressive strength. It is a figure which shows the mode of molding in a full mold method, (a) is a mode in the middle of molding, (b) shows the mode after completion of molding.

Explanation of symbols

1 Slump cone 2 Kneaded sand 3 Surface plate 4 [Total addition amount (mass%) of furan resin and curing agent liquid]
= −6.25 × 10 ⁻³ × [Viscosity of furan resin (mPa · s)] + 1.056
5 Casting frame 6 Kneaded sand 7 Styrofoam model 8 Runway 9 Core metal 10 Casting port

Claims (4)

A new type of artificial sand with a sphericity of 0.8 or more prepared by the melting method or flame melting method, or its recovered sand or its reclaimed sand is made of a furan resin having a viscosity of 5.5 to 50 mPa · s at 25 ° C. A resin component of at least 0.1% by mass or more and a curing active ingredient of at least 0.01% by mass of a curing agent liquid, a total addition amount (% by mass) of the furan resin and the curing agent liquid, and the furan The relationship with the viscosity (mPa · s) of the resin is [total addition amount (mass%) of furan resin and curing agent liquid]
≦ −6.25 × 10 ⁻³ × [viscosity of furan resin (mPa · s)] + 1.056
A self-hardening fluidized mold, wherein a kneaded sand obtained by adding and kneading so as to satisfy the above conditions is used, and the diameter of the slump flow in the slump test of the kneaded sand is at least twice the diameter of the slump cone.   The furan resin may be one or more selected from the group consisting of furfuryl alcohol, furfuryl alcohol and aldehyde condensates, phenols and aldehyde condensates, urea and aldehyde condensates, or selected from the above group 2. The self-hardening fluid mold according to claim 1, comprising two or more kinds of cocondensates.   The self-hardening fluid mold according to claim 1 or 2, wherein the mold compressive strength after molding is 0.3 MPa or more.   The self-hardening fluid mold according to any one of claims 1 to 3, which is used in a full mold method.

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