CAST SHAPING METHOD AND CAST MATERIAL

Abstract

A molding method of molding a mold for producing iron castings includes generating mixed sand using engineered sand as an aggregate and a binder, filling the mold with the mixed sand, and solidifying the mixed sand filled in the mold.

Claims

1. A molding method of molding a mold for producing iron castings, the molding method comprising: generating mixed sand using engineered sand as an aggregate and a binder; filling the mold with the mixed sand; and solidifying the mixed sand filled in the mold.

2. The molding method according to claim 1, wherein the engineered sand comprises 60% or more of aluminum oxide (Al.sub.2O.sub.3) and 40% or less of silicon dioxide (SiO.sub.2), and the binder is either sodium silicate or potassium silicate.

3. The molding method according to claim 1, wherein the binder has a molar ratio of 1.8 or more.

4. The molding method according to claim 1, wherein the binder is 4 parts by weight or less relative to 100 parts by weight of the aggregate.

5. The molding method according to claim 1, wherein the engineered sand is produced by a melting method or a sintering method.

6. The molding method according to claim 1, wherein in the solidifying, the mixed sand is solidified by a dehydration condensation reaction.

7. The molding method according to claim 1, wherein in the solidifying, the mixed sand is solidified using carbon dioxide (CO.sub.2) gas.

8. The molding method according to claim 1, wherein the mixed sand is foamed mixed sand containing at least a surfactant.

9. A mold material for molding a mold for producing iron castings, the mold material comprising engineered sand as an aggregate, the engineered sand comprising 60% or more of aluminum oxide (Al.sub.2O.sub.3) and 40% or less of silicon dioxide (SiO.sub.2), and either sodium silicate or potassium silicate as a binder.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0019] FIG. 1 is a flowchart of a molding method according to one embodiment.

[0020] FIG. 2 is a graph showing the relationship between the amount of binder added and the bending strength for each aggregate.

[0021] FIG. 3 is a graph showing the relationship between the amount of binder added and the bending strength for each binder.

[0022] FIG. 4 is a graph showing the amount of sand adhering to the casting surface after sand removal for each aggregate.

[0023] FIG. 5 is a graph showing the amount of sand adhering to the casting surface after sand removal for each binder.

DESCRIPTION OF EMBODIMENTS

[0024] Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or equivalent parts are denoted by the same reference signs.

(Overview of the Molding Method)

[0025] A molding method according to one embodiment molds a mold. The mold is a master mold or a core for producing iron castings. Iron castings are castings produced using the molten metal containing iron oxide (FeO). Iron castings is, for example, cast iron.

[0026] FIG. 1 is a flowchart of a molding method according to one embodiment. As shown in FIG. 1, in the molding method, a mixing process (step S10) is first executed. In the mixing process (step S10), the aggregate and the binder are mixed in a mixing machine.

[0027] The aggregate is engineered sand containing 60% or more aluminum oxide (Al.sub.2O.sub.3) and 40% or less silicon dioxide (SiO.sub.2). The percentage notation (%) here represents the average value of the constituents of a single grain of sand. As a more specific example, the aggregate is engineered sand containing 61% or more and 72% or less aluminum oxide (Al.sub.2O.sub.3) and 20% or more and 36% or less silicon dioxide (SiO.sub.2). The engineered sand is in the form of particles, and as one example, spherical particles. The engineered sand is produced, for example, by a sintering method or a melting method.

[0028] The sintering method is a method in which fine particles are granulated with a spray dryer or an agitator mixer and then sintered with a rotary kiln. The melting method is a method in which fine particles are granulated and then melted, or a method in which materials are melted in an arc furnace and then atomized to form particles.

[0029] Engineered sand produced by the melting method tends to have a smaller specific surface area compared to engineered sand produced by the sintering method. Therefore, when molding is performed using engineered sand produced by the melting method, the amount of binder required to solidify the engineered sand can be reduced compared to when molding is performed using engineered sand produced by the sintering method. This molding method can reduce manufacturing costs.

[0030] The binder is either sodium silicate or potassium silicate. The binder is 4 parts by weight or less relative to 100 parts by weight of the aggregate. This means that the binder is 4 grams or less per 100 grams of the aggregate. As one example, the binder is 1 part by weight or more and 4 parts by weight or less relative to 100 parts by weight of the aggregate. The binder may have a molar ratio of 1.8 or more.

[0031] In the mixing process (step S10), the aggregate and the binder may be mixed while foaming. In this case, a surfactant may be added. The surfactant is, for example, an anionic surfactant. This produces foamed mixed sand with a whipped cream-like consistency. Foamed mixed sand is mixed sand of solid particles and foamed liquid. Foamed mixed sand is a mixture of the aggregate, the binder, and the surfactant. Foamed mixed sand may contain not only the aggregate, the binder, and the surfactant but also other materials. For example, foamed mixed sand may further contain at least one of poorly water-soluble inorganic compound particles and lithium salts. Poorly water-soluble means that the solubility is 100 milligram or less when dissolved in 1 liter of water at 25 C. The inorganic compound particles are, for example, carbonates or hydroxides, and as one example, calcium carbonate, magnesium carbonate, magnesium hydroxide, or aluminum hydroxide. Examples of lithium salts include lithium silicate, lithium oxide, lithium hydroxide, lithium carbonate, lithium bromide, lithium chloride, lithium nitrate, or lithium nitrite. Using foamed mixed sand improves the fillability of the sand.

[0032] When the preparation of the mixed sand is completed in the mixing process (step S10), a filling process (step S12) is executed. In the filling process (step S12), the mixed sand (an example of the mold material) is filled into the mold. The filling method is not particularly limited. The filling method may be changed according to the type of solidification method described later. Examples of the filling method include blow filling by air flow, injection such as pressure feeding, hand filling, vibration filling, or squeeze.

[0033] When the filling of the mixed sand is completed in the filling process (step S12), a solidifying process (step S14) is executed. In the solidifying process (step S14), the mixed sand filled in the mold is solidified. The solidification method is not particularly limited. Examples of the solidification method include a method using a dehydration condensation reaction, a method of hardening the binder with carbon dioxide (CO.sub.2) gas, a method of mixing 2 to 4% slag with the aggregate and using the slag as a hardening agent, a method of gelling by mixing an ester and an additive with the aggregate, and a method of hardening by reacting metal powder with an alkali of the additive. When the solidifying process (step S14) is completed, the flowchart shown in FIG. 1 ends. After solidification is completed, the master mold or core is removed from the mold.

[0034] When the dehydration condensation reaction is used in the solidifying process (step S14), in the filling process (step S12), the foamed mixed sand is filled into the heated mold. When the binder is hardened with carbon dioxide (CO.sub.2) gas in the solidifying process (step S14), in the filling process (step S12), the mixed sand is filled into a wooden mold, a resin mold, or a (heated) permanent mold. When solidification by dehydration condensation reaction is adopted, and when solidification using carbon dioxide (CO.sub.2) gas is adopted, a foundry with less odor and a better environment can be realized compared to other methods.

Summary of Embodiments

[0035] In the molding method according to the embodiments, the content of silicon dioxide (SiO.sub.2) in the aggregate is 40% or less, and compared to natural silica sand that contains more than 90% silicon dioxide (SiO.sub.2), the silicon dioxide (SiO.sub.2) content is significantly reduced. Therefore, the mold produced by the molding method according to the embodiments is less likely to generate fayalite (2FeO.Math.SiO.sub.2) compared to a mold produced using natural silica sand as the aggregate. Thus, the molding method according to the embodiments can suppress the occurrence of burn-on defects and penetration on the surface of the casting compared to when natural silica sand is used as the aggregate. Furthermore, since fayalite (2FeO.Math.SiO.sub.2) is less likely to be generated, there is no need to apply a coating to the mold. Therefore, the molding method according to the embodiments can suppress the occurrence of defects without reducing productivity.

[0036] Moreover, to ensure the strength of the mold, it is necessary to add a larger amount of binder. When natural silica sand is used as the aggregate, the binder is generally added in an amount greater than 4 parts by weight. However, when a larger amount of binder is added, the collapsibility of the mold deteriorates. In the molding method according to the embodiments, by using engineered sand as the aggregate, sufficient strength of the mold can be obtained even if the amount of binder added is 4 parts by weight or less. Therefore, the molding method according to the embodiments can improve the collapsibility of the mold while maintaining the strength of the mold.

EXAMPLES

[0037] Examples and comparative examples conducted by the inventors to confirm the effects of this disclosure will be described below.

[Test 1: Evaluation of Mold Strength]

[0038] Examples and comparative examples were produced by varying the types of aggregates and the amounts of binder added, and the mold strength was evaluated.

(Types of Aggregates)

[0039] Two types of engineered sand and two types of natural silica sand were prepared as aggregates.

TABLE-US-00001 TABLE 1 Manufac- Al.sub.2O.sub.3 SiO.sub.2 Type of turing constit- constit- Aggregate Method Product Name uent uent Engineered Melting ESPEARL#60 72% 20% sand 1 Method (manufactured by YAMAKAWA SANGYO CO., LTD.) Engineered Sintering CERABEADS#650 61% 36% sand 2 Method (manufactured by ITOCHU CERATECH CORPORATION) Natural silica FLATTERY 0.05% 99.85% sand 1 (manufactured by MITSUBISHI SHOJI CONSTRUCTION MATERIALS CORPORATION) Natural silica MIKAWA SILICA SAND 0.66% 98.09% sand 2 NO. 6 (manufactured by MIKAWA KEISEKI CO., LTD.)

(Binder, Surfactant)

[0040] The binder was No. 1 water glass (manufactured by FUJI CHEMICAL CO., LTD.), and the surfactant was an anionic surfactant.

Example 1

[0041] Engineered sand 1 was used as the aggregate. Engineered sand 1 was 100 parts by weight, the binder was 1 part by weight, and the surfactant was 0.25 parts by weight. These materials were mixed and foamed at about 200 rpm for about 5 minutes using a mixing machine (tabletop mixer: manufactured by AICOHSHA MFG. CO., LTD.) to prepare foamed mixed sand. Next, this foamed mixed sand was filled into a mold heated to 250 C. using an injection filling device. The mold was a mold for producing bending strength test pieces and had a cavity with a volume of about 80 cm.sup.3. The foamed mixed sand was filled at a gate speed of about 1 m/sec and a cylinder surface pressure of 0.4 MPa. The foamed mixed sand filled in the heated mold was left for 2 minutes to solidify the foamed mixed sand by a dehydration condensation reaction due to the heat of the mold. After solidification was completed, the core was removed from the mold.

Examples 2 to 6

[0042] In Example 2, the binder was 2 parts by weight. Other conditions were the same as in Example 1. In Example 3, the binder was 4 parts by weight. Other conditions were the same as in Example 1. In Example 4, engineered sand 2 was used as the aggregate. Other conditions were the same as in Example 1. In Example 5, engineered sand 2 was used as the aggregate. Other conditions were the same as in Example 2. In Example 6, engineered sand 2 was used as the aggregate. Other conditions were the same as in Example 3.

Comparative Examples 1 to 6

[0043] In Comparative Example 1, natural silica sand 1 was used as the aggregate. Other conditions were the same as in Example 1. In Comparative Example 2, natural silica sand 1 was used as the aggregate. Other conditions were the same as in Example 2. In Comparative Example 3, natural silica sand 1 was used as the aggregate. Other conditions were the same as in Example 3. In Comparative Example 4, natural silica sand 2 was used as the aggregate. Other conditions were the same as in Example 1. In Comparative Example 5, natural silica sand 2 was used as the aggregate. Other conditions were the same as in Example 2. In Comparative Example 6, natural silica sand 2 was used as the aggregate. Other conditions were the same as in Example 3.

TABLE-US-00002 TABLE 2 Binder (parts by Type of Aggregate weight) Example 1 Engineered sand 1 1 Example 2 Engineered sand 1 2 Example 3 Engineered sand 1 4 Example 4 Engineered sand 2 1 Example 5 Engineered sand 2 2 Example 6 Engineered sand 2 4 Comparative Example 1 Natural silica sand 1 1 Comparative Example 2 Natural silica sand 1 2 Comparative Example 3 Natural silica sand 1 4 Comparative Example 4 Natural silica sand 2 1 Comparative Example 5 Natural silica sand 2 2 Comparative Example 6 Natural silica sand 2 4

[0044] Sand test pieces of 10 mm10 mm140 mm were produced from Examples 1 to 6 and Comparative Examples 1 to 6, and the bending strength was measured. The bending strength was measured according to JACT Test Method SM-1, Bending Strength Test Method. The results are shown in FIG. 2.

[0045] FIG. 2 is a graph showing the relationship between the amount of binder added and the bending strength for each aggregate. In FIG. 2, the horizontal axis represents the amount of binder added (parts by weight), and the vertical axis represents the bending strength (MPa). Cores used in casting require a strength that prevents them from breaking during transportation or when being placed in the mold. Therefore, the required strength was set to a bending strength of 3 MPa or more, and the measurement results were evaluated. The dashed line in the figure is the regression curve. As shown in FIG. 2, in the case of engineered sand 1 in Examples 1 to 3, it was confirmed that a bending strength of 3 MPa or more was achieved when the binder was 1 part by weight. In the case of engineered sand 2 in Examples 4 to 6, it was confirmed that a bending strength of 3 MPa or more was achieved when the binder was 4 parts by weight (estimated to be about 2.5 parts by weight from the regression curve). In contrast, in the case of natural silica sand 1 in Comparative Examples 1 to 3, although a bending strength of 3 MPa or more was achieved when the binder was 4 parts by weight (estimated to be about 3.5 parts by weight from the regression curve), the bending strength was found to be lower than that of engineered sand 2 in Examples 4 to 6. In the case of natural silica sand 2 in Comparative Examples 4 to 6, a bending strength of 3 MPa or more was not achieved even when the binder was 4 parts by weight. In Comparative Examples 4 to 6 with natural silica sand 2, it is estimated from the regression curve that 5.0 parts by weight of binder are required to achieve a bending strength of 3 MPa or more. Thus, it was confirmed that by using engineered sand as the aggregate, the required strength can be secured with a smaller amount of binder compared to natural silica sand. This difference in measurement results is considered to be influenced by the differences in shape and specific surface area between engineered sand and natural silica sand. Engineered sand has a smooth surface, while natural silica sand has many surface irregularities, so engineered sand has a smaller specific surface area and can achieve the desired strength with a smaller amount of binder.

[Test 2: Evaluation of Mold Strength]

[0046] Examples were produced by varying the types of binders and the amounts of binder added, and the mold strength was evaluated.

(Types of Binders)

[0047] Sodium silicate and potassium silicate with different molar ratios were prepared as binders.

TABLE-US-00003 TABLE 3 Aqueous Solution Type of Molar Concen- Binder Ratio Product Name tration Binder Sodium 2.0 No. 1 water glass 45% 1 Silicate (manufactured by FUJI CHEMICAL CO., LTD.) Binder Sodium 3.1 No. 3 water glass 38% 2 Silicate (manufactured by FUJI CHEMICAL CO., LTD.) Binder Potassium 1.8 1K Potassium Silicate 50% 3 Silicate (manufactured by NIPPON CHEMICAL INDUSTRIAL CO., LTD.) Binder Potassium 3.4 2K Potassium Silicate 29% 4 Silicate (manufactured by NIPPON CHEMICAL INDUSTRIAL CO., LTD.)

(Aggregate, Surfactant)

[0048] The aggregate was engineered sand 1 from Table 1, and the surfactant was an anionic surfactant.

Example 7

[0049] Engineered sand 1 was used as the aggregate. Engineered sand 1 was 100 parts by weight, the binder 1 was 1 part by weight, and the surfactant was 0.25 parts by weight. The production conditions were the same as in Example 1.

Examples 8 to 18

[0050] In Examples 8 and 9, the binder 1 was 2 parts by weight and 4 parts by weight, respectively. Other conditions were the same as in Example 7. In Examples 10 to 12, the binder 2 was 1, 2, and 4 parts by weight, respectively. Other conditions were the same as in Example 7. In Examples 13 to 15, the binder 3 was 1, 2, and 4 parts by weight, respectively. Other conditions were the same as in Example 7. In Examples 16 to 18, the binder 4 was 1, 2, and 4 parts by weight, respectively. Other conditions were the same as in Example 7.

TABLE-US-00004 TABLE 4 Binder Type of (parts by Aggregate Binder weight) Example 7 Engineered sand 1 Binder 1 1 Example 8 Engineered sand 1 Binder 1 2 Example 9 Engineered sand 1 Binder 1 4 Example 10 Engineered sand 1 Binder 2 1 Example 11 Engineered sand 1 Binder 2 2 Example 12 Engineered sand 1 Binder 2 4 Example 13 Engineered sand 1 Binder 3 1 Example 14 Engineered sand 1 Binder 3 2 Example 15 Engineered sand 1 Binder 3 4 Example 16 Engineered sand 1 Binder 4 1 Example 17 Engineered sand 1 Binder 4 2 Example 18 Engineered sand 1 Binder 4 4

[0051] Sand test pieces of 10 mm10 mm140 mm were produced from Examples 7 to 18, and the bending strength was measured. The bending strength was measured according to JACT Test Method SM-1, Bending Strength Test Method. The results are shown in FIG. 3.

[0052] FIG. 3 is a graph showing the relationship between the amount of binder added and the bending strength for each binder. In FIG. 3, the horizontal axis represents the amount of binder added (parts by weight), and the vertical axis represents the bending strength (MPa). As in Test 1, the required strength was set to a bending strength of 3 MPa or more, and the measurement results were evaluated. The dashed line in the figure is a regression curve. As shown in FIG. 3, in the case of binder 1 of Examples 7 to 9 (Examples 1 to 3), it was confirmed that a bending strength of 3 MPa or more was achieved when the binder was 1 part by weight. In the case of binder 2 of Examples 10 to 12, it was confirmed that a bending strength of 3 MPa or more was achieved when the binder was 4 parts by weight (estimated to be about 2.5 parts by weight from the regression curve). In the case of binder 3 of Examples 13 to 15, it was confirmed that a bending strength of 3 MPa or more was achieved when the binder was 2 parts by weight (estimated to be about 1.5 parts by weight from the regression curve). In the case of binder 4 of Examples 16 to 18, it was confirmed that a bending strength of 3 MPa or more was achieved when the binder was 4 parts by weight. Thus, it was confirmed that a bending strength of 3 MPa or more was achieved when the binder was 1 to 4 parts by weight. Furthermore, it was confirmed that a bending strength of 3 MPa or more was achieved with at least 4 parts by weight of any binder.

[Test 3: Evaluation of Collapsibility]

[0053] The collapsibility of molds (cores, master molds) produced using each aggregate was evaluated.

[0054] The parts by weight of binder 1 required to achieve a bending strength of 3 MPa or more, estimated from the results of Test 1, are shown in Table 5.

TABLE-US-00005 TABLE 5 Engineered sand 1 1.0 part by weight Engineered sand 2 2.5 parts by weight Natural silica sand 1 3.5 parts by weight Natural silica sand 2 5.0 parts by weight

<Core> (Examples 19, 20, Comparative Examples 7, 8)

[0055] In Example 19, a core was produced using 100 parts by weight of engineered sand 1, 1 part by weight of binder 1, and 0.25 parts by weight of anionic surfactant. In Example 20, a core was produced using 100 parts by weight of engineered sand 2, 2.5 parts by weight of binder 1, and 0.25 parts by weight of anionic surfactant. In Comparative Example 7, a core was produced using 100 parts by weight of natural silica sand 1, 3.5 parts by weight of binder 1, and 0.25 parts by weight of anionic surfactant. In Comparative Example 8, a core was produced using 100 parts by weight of natural silica sand 2, 5.0 parts by weight of binder 1, and 0.25 parts by weight of anionic surfactant. The production conditions for Examples 19, 20, and Comparative Examples 7, 8 were the same as in Example 1, and cores of 10 mm10 mm140 mm were obtained.

<Master Mold> (Example 21)

[0056] A material consisting of 100 parts by weight of engineered sand 1 and 1 part by weight of binder 1 was mixed at about 200 rpm for about 5 minutes using a mixing machine (tabletop mixer: manufactured by AICOHSHA MFG. CO., LTD.) to prepare wet mixed sand. Next, this mixed sand was hand-filled into a wooden mold. A wooden mold capable of casting a 30 mm30 mm100 mm casting and accommodating a 10 mm10 mm140 mm core was used. Carbon dioxide (CO.sub.2) was blown into the mixed sand filled in the wooden mold for 30 seconds to solidify the mixed sand. After solidification was completed, the master mold was removed from the wooden mold.

Example 22, Comparative Examples 9, 10

[0057] In Example 22, a master mold was produced using 100 parts by weight of engineered sand 2 and 2.5 parts by weight of binder 1. In Comparative Example 9, a master mold was produced using 100 parts by weight of natural silica sand 1 and 3.5 parts by weight of binder 1. In Comparative Example 10, a master mold was produced using 100 parts by weight of natural silica sand 2 and 5.0 parts by weight of binder 1. The production conditions for Example 22 and Comparative Examples 9, 10 were the same as in Example 21.

TABLE-US-00006 TABLE 6 Cast- ing Binder Num- Type of (parts by ber Core Master mold Aggregate Binder weight) 1 Example 19 Example 21 Engineered Binder 1 1.0 sand 1 2 Example 20 Example 22 Engineered Binder 1 2.5 sand 1 3 Comparative Comparative Natural silica Binder 1 3.5 Example 7 Example 9 sand 1 4 Comparative Comparative Natural silica Binder 1 5.0 Example 8 Example 10 sand 1

[0058] Using the core and the master mold from Casting Number 1, cast iron FC200 was cast. The casting was performed without applying a coating to the core and the master mold. After casting, the sprue was hammered 10 times to remove the sand from the casting, and the collapsibility of the core was visually checked, and the weight of the sand adhering to the casting was measured. The same conditions were used to visually check the collapsibility of the cores and measure the weight of the sand adhering to the casting for Casting Numbers 2 to 4.

<Visual Results of the Collapsibility of Cores>

[0059] In the engineered sand of Casting Numbers 1 and 2, the cores collapsed, and the core parts became through-holes. In contrast, in the natural silica sand of Casting Numbers 3 and 4, the cores did not collapse and remained inside the casting. Thus, it was confirmed that it is difficult to achieve both the strength and collapsibility of the cores when natural silica sand is used as the aggregate. Furthermore, it was confirmed that both the strength and collapsibility of the cores can be achieved by using engineered sand as the aggregate.

<Sand Adhering to the Casting>

[0060] FIG. 4 is a graph showing the amount of sand adhering to the casting surface after sand removal for each aggregate. The horizontal axis represents the casting number, and the vertical axis represents the amount of sand adhering. As shown in FIG. 4, in Casting Number 1, where the aggregate was engineered sand, the amount of sand adhering was about 2 grams, and in Casting Number 2, where the aggregate was also engineered sand, the amount of sand adhering was about 6 grams. Thus, when the aggregate was engineered sand, the sand adhered to the casting only slightly. In contrast, in Casting Number 3, where the aggregate was natural silica sand, the amount of sand adhering was about 36 grams, and in Casting Number 4, where the aggregate was also natural silica sand, the amount of sand adhering was about 32 grams. The natural silica sand solidified around the casting. Since natural silica sand caused burn-on defects, the weight of the natural silica sand that could be removed from the casting with a metal file was measured. Thus, it was confirmed that it is difficult to achieve both the strength and collapsibility of the master mold when natural silica sand is used as the aggregate. Furthermore, it was confirmed that both the strength and collapsibility of the master mold can be achieved by using engineered sand as the aggregate.

[Test 4: Evaluation of Collapsibility]

[0061] The collapsibility of cores and master molds produced using each binder was evaluated.

[0062] The parts by weight of each binder required to achieve a bending strength of 3 MPa or more in engineered sand 1, estimated from the results of Test 2, are shown in Table 7.

TABLE-US-00007 TABLE 7 Binder 1 1.0 part by weight Binder 2 2.5 parts by weight Binder 3 1.5 parts by weight Binder 4 4.0 parts by weight

<Core> (Examples 23 to 26)

[0063] In Example 23, a core was produced using 100 parts by weight of engineered sand 1, 1 part by weight of binder 1, and 0.25 parts by weight of anionic surfactant. In Example 24, a core was produced using 100 parts by weight of engineered sand 1, 2.5 parts by weight of binder 2, and 0.25 parts by weight of anionic surfactant. In Example 25, a core was produced using 100 parts by weight of engineered sand 1, 1.5 parts by weight of binder 3, and 0.25 parts by weight of anionic surfactant. In Example 26, a core was produced using 100 parts by weight of engineered sand 1, 4.0 parts by weight of binder 4, and 0.25 parts by weight of anionic surfactant. The production conditions for Examples 23 to 26 were the same as in Example 1.

<Master Mold> (Examples 27 to 30)

[0064] In Example 27, a master mold was produced using 100 parts by weight of engineered sand 1 and 1 part by weight of binder 1. In Example 28, a master mold was produced using 100 parts by weight of engineered sand 1 and 2.5 parts by weight of binder 2. In Example 29, a master mold was produced using 100 parts by weight of engineered sand 1 and 1.5 parts by weight of binder 3. In Example 30, a master mold was produced using 100 parts by weight of engineered sand 1 and 4.0 parts by weight of binder 4. The production conditions for Examples 27 to 30 were the same as in Example 21.

TABLE-US-00008 TABLE 8 Cast- ing Binder Num- Type of (parts by ber Core Master Mold Aggregate Binder weight) 5 Example 23 Example 23 Engineered Binder 1 1.0 sand 1 6 Example 24 Example 20 Engineered Binder 2 2.5 sand 1 7 Example 25 Example 19 Engineered Binder 3 1.5 sand 1 8 Example 36 Example 20 Engineered Binder 4 4.0 sand 1

[0065] Using the core and the master mold from Casting Number 5, cast iron FC200 was cast. The casting was performed without applying a coating to the core and the master mold. After casting, the sprue was hammered 10 times to remove the sand from the casting, and the collapsibility of the cores was visually checked, and the weight of the sand adhering to the casting was measured. The same conditions were used to visually check the collapsibility of the core and measure the weight of the sand adhering to the casting for Casting Numbers 6 to 8.

<Visual Results of the Collapsibility of Cores>

[0066] In the engineered sand of Casting Numbers 5 to 8, the cores collapsed, and the core parts became through-holes. Thus, it was confirmed that both the strength and collapsibility of the cores can be achieved by using engineered sand as the aggregate, regardless of the type of binder.

<Sand Adhering to the Casting>

[0067] FIG. 5 is a graph showing the amount of sand adhering to the casting surface after sand removal for each binder. The horizontal axis represents the casting number, and the vertical axis represents the amount of sand adhering. As shown in FIG. 5, in Casting Numbers 5 to 8, where the aggregate was engineered sand, the amount of sand adhering was 4 grams or less, regardless of the type of binder. Thus, it was confirmed that when the aggregate was engineered sand, the sand adhered to the casting only slightly, regardless of the type of binder. Furthermore, it was confirmed that both the strength and collapsibility of the master mold can be achieved by using engineered sand as the aggregate, regardless of the type of binder.

[0068] While various illustrative embodiments have been described above, this disclosure is not limited to the above-described illustrative embodiments and various omissions, substitutions, and changes may be made.

[0069] Various illustrative embodiments included in this disclosure include the following clauses:

[Clause 1] A molding method of molding a mold for producing iron castings, the molding method comprising: [0070] generating mixed sand using engineered sand as an aggregate and a binder; [0071] filling the mold with the mixed sand; and [0072] solidifying the mixed sand filled in the mold.
[Clause 2] The molding method according to clause 1, wherein the engineered sand comprises 60% or more of aluminum oxide (Al.sub.2O.sub.3) and 40% or less of silicon dioxide (SiO.sub.2), and the binder is either sodium silicate or potassium silicate.
[Clause 3] The molding method according to clause 1 or 2, wherein the binder has a molar ratio of 1.8 or more.
[Clause 4] The molding method according to any one of clauses 1 to 3, wherein the binder is 4 parts by weight or less relative to 100 parts by weight of the aggregate.
[Clause 5] The molding method according to any one of clauses 1 to 4, wherein the engineered sand is produced by a melting method or a sintering method.
[Clause 6] The molding method according to any one of clauses 1 to 5, wherein in the solidifying, the mixed sand is solidified by a dehydration condensation reaction.
[Clause 7] The molding method according to any one of clauses 1 to 6, wherein in the solidifying, the mixed sand is solidified using carbon dioxide (CO.sub.2) gas.
[Clause 8] The molding method according to any one of clauses 1 to 7, wherein the mixed sand is foamed mixed sand containing at least a surfactant.
[Clause 9] A mold material for molding a mold for producing iron castings, the mold material comprising engineered sand as an aggregate, the engineered sand comprising 60% or more of aluminum oxide (Al.sub.2O.sub.3) and 40% or less of silicon dioxide (SiO.sub.2), and either sodium silicate or potassium silicate as a binder.