Feeder space forming material

Abstract

To provide a molten metal-feeding space-forming member that forms a molten metal-filled space which a molten metal fills, in a state in which a molten metal is stored in a storage space provided in a sand mold, and that is easy to manufacture and has excellent heat-retaining properties.SOLUTION: This invention relates to a molten metal-feeding space-forming member that forms a molten metal-filled space which the molten metal fills in a state in which it is stored in a storage space provided in a sand mold, wherein the member is formed with a mixture of a casting sand and a lightweight aggregate, and comprises 20 vol.% or more and 50 vol.% or less of the lightweight aggregate based on 100 vol.% of a total of the casting sand and the lightweight aggregate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a feeder space forming member that forms a feeder space to be filled with molten metal when the member is housed in a housing space provided in a sand mold. [Background technology]

[0002] In casting, feeders have the effect of replenishing molten metal poured into a sand mold to counteract solidification shrinkage (feeder effect), and are essential for preventing casting defects such as shrinkage cavities. Although feeders are removed after casting, they can account for around 30% of the total cast weight, and the amount of feeder significantly affects the casting yield (product weight / total cast weight). For this reason, reducing the amount of feeder is one efficient way to improve casting yield.

[0003] The feeder effect is exerted until the feeder filled in the feeder space solidifies, and if the time until the feeder solidifies (solidification time) is shortened, the feeder effect may become insufficient. To prevent this, it is common to increase the amount of feeder to extend the solidification time of the feeder, but the increased amount of feeder reduces the casting yield. If the heat retention of the feeder can be improved so that the solidification time does not shorten even when the amount of feeder is reduced, it will be possible to reduce the amount of feeder and improve the casting yield.

[0004] Therefore, the applicant of the present application has proposed an air-insulated feeder sleeve with a double-wall structure, which has an outer wall that covers from the outside an inner wall that forms the feeder formation space, and has an air layer between the inner wall and the outer wall (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-159339 Summary of the Invention [Problem to be solved by the invention]

[0006] The air-insulated feeder sleeve proposed in Patent Document 1 can sufficiently improve the heat retention of the feeder, but because it has a double-wall structure, it is time-consuming to manufacture.

[0007] In view of the above circumstances, an object of the present invention is to provide a feeder space-forming member that is easy to manufacture and has excellent heat retention properties. [Means for solving the problem]

[0008] The feeder space forming member of the present invention which solves the above object comprises: A feeder space forming member that forms a feeder space to be filled with molten metal when housed in a housing space provided in a sand mold, It is molded from a mixture containing molding sand and lightweight aggregate, The lightweight aggregate is contained in an amount of 20% by volume or more and 50% by volume or less relative to a total of 100% by volume of the foundry sand and the lightweight aggregate, The lightweight aggregate is one selected from expanded perlite, diatomaceous earth and silica fume; The foundry sand is silica sand having a grain size index of 45 or more and 170 or less as specified in JIS Z 2601, The mixture contains 1% by weight or more and 5% by weight or less of a binder when the entire mixture is taken as 100% by weight. The bulk density is 1.4g / cm 3 It is the following: It is characterized by a bending strength of 3 MPa or more. Also, The lightweight aggregate has a bulk density of 0.315 g / cm 3 ~0.335g / cm 3 The foamed perlite may be characterized as being foamed perlite. Also, A feeder space forming member that forms a feeder space to be filled with molten metal when housed in a housing space provided in a sand mold, It is molded from a mixture containing molding sand and lightweight aggregate, The lightweight aggregate may be contained in an amount of 20% by volume or more and 50% by volume or less relative to a total of 100% by volume of the foundry sand and the lightweight aggregate.

[0009] According to the feeder space forming member of the present invention, the material is devised so that heat retention is ensured by the air space possessed by the lightweight aggregate. If the lightweight aggregate is less than 20% by volume, the air space becomes insufficient and good heat retention cannot be obtained. On the other hand, if the lightweight aggregate is more than 50% by volume, the feeder space forming member itself will lack strength and will be prone to cracking. The feeder space forming member of the present invention can be manufactured by a known ordinary shell core molding method, and is easy to manufacture yet has excellent heat retention.

[0010] The foundry sand may be silica sand.

[0011] The lightweight aggregate is specified in JIS A 5002 (2003). In terms of unit volume weight, it is 25 kN / m 3 However, if we want to distinguish it more clearly from ordinary aggregate (in terms of air space retention rate), it is 23kN / m 3 It becomes something less than.

[0012] The mixture may contain a binder in addition to the foundry sand and the lightweight aggregate, or may contain a binder and a hardener.

[0013] It is more preferable that the lightweight aggregate is contained in an amount of 30% by volume or more and 45% by volume or less. If the amount is 30% by volume or more, the air space contained in the lightweight aggregate becomes more sufficient, resulting in better heat retention, and if the amount is 45% by volume or less, more sufficient strength can be obtained.

[0014] Also, The lightweight aggregate may be mainly composed of SiO2.

[0015] Lightweight aggregates that are primarily composed of SiO2 tend to have a porous structure.

[0016] moreover, The lightweight aggregate may be one selected from the group consisting of expanded perlite, diatomaceous earth, and silica fume.

[0017] In particular, expanded perlite is preferable because it is an expanded foam and therefore has a sufficient air layer.

[0018] In addition, The mixture has a bulk density of 1.4 g / cm 3 The invention may be characterized in that:

[0019] The air space occupancy rate is indirectly determined by this bulk density value. 3 If the temperature exceeds this range, there will be insufficient air space and good heat retention will not be achieved.

[0020] on the other hand, It is preferable that the bending strength is 3 MPa or more.

[0021] The flexural strength can be used to manage any insufficient strength of the feeder space forming member itself. If the bulk density of the mixture is too high, there will be an excess of air spaces, which will tend to reduce the flexural strength. The flexural strength is preferably 3 MPa or more. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a feeder space forming member that is easy to manufacture and has excellent heat retention properties. [Brief explanation of the drawings]

[0023] [Figure 1] Figure 1 shows an example of a feeder sleeve according to an embodiment of the present invention. [Figure 2] FIG. 1(A) is a diagram showing the feeder sleeve of Example 1 used in the performance evaluation of the feeder sleeve shown in FIG. 1(A), and FIG. 1(B) is a graph showing the cooling curves of the feeder sleeve of Example 1 and the feeder sleeve of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0024] An embodiment of the present invention will now be described with reference to the drawings. A feeder sleeve, which is one embodiment of a feeder space forming member of the present invention, forms a feeder space to be filled with molten metal when contained in a receiving space provided in a sand mold, and improves the heat retention of the feeder, which replenishes the molten metal as it solidifies and shrinks after being cast into the sand mold. The molten metal referred to here is not particularly limited, and may be iron or a non-ferrous metal such as an aluminum alloy or a magnesium alloy. The state in which the feeder space forming member is contained in the receiving space of the sand mold will hereinafter be referred to as the "contained state".

[0025] Figure 1 shows an example of a feeder sleeve according to one embodiment of the present invention, where (A) is a perspective view of the feeder sleeve 1, and (B) is a cross-sectional view showing the feeder sleeve 1 shown in (A) placed in the containing space of a sand mould.

[0026] As shown in Figure 1(A), the feeder sleeve 1 has a cylindrical outer shape. In this embodiment, a shell mold is described as an example, which is made by firing and hardening a mixture containing resin-coated sand (hereinafter abbreviated as "RCS"), which is foundry sand coated with a thermosetting resin, a type of binder, lightweight aggregate, and a hardener. The RCS of this embodiment uses silica sand as the foundry sand. Furthermore, a phenolic resin is used as the thermosetting resin binder. The amount of phenolic resin added is 1 to 5 wt%, with the total mixture taken as 100 wt%. Furthermore, hexamine or the like is used as a hardener. The feeder sleeve 1 of this embodiment is manufactured using the same molding method as a known ordinary shell core molding method.

[0027] Additionally, expanded perlite is used as the lightweight aggregate. The amount of expanded perlite added is between 20% and 50% by volume, with the total of silica sand and expanded perlite being 100% by volume. The silica sand referred to here is silica sand alone that is not coated with a thermosetting resin. Expanded perlite is obtained by heating perlite ore, a natural mineral, to expand and foam. An air layer is formed in the expanded perlite due to the expansion and foaming. This air layer is used to ensure the heat retention of the feeder sleeve 1. If the expanded perlite is less than 20% by volume, the air layer will be insufficient and good heat retention will not be achieved. Looking at the above mixture, the bulk density is 1.4 g / cm 3 The bulk density of the mixture is indirectly determined by the air space occupancy rate. 3 If the bulk density of the mixture exceeds 50%, there will be insufficient air spaces, and good heat retention will not be achieved. On the other hand, if the expanded perlite exceeds 50% by volume, the proportion of air spaces will be too high, and the feeder sleeve 1 itself will lack strength and be prone to cracking. Looking at the feeder sleeve 1 solidified with a binder, it is necessary that the bending strength be 3 MPa or more. If the bulk density of the above mixture is too high, there will be an excessive number of air spaces, and bending strength will tend to decrease. For this reason, strength deficiencies can be managed by the bending strength of the finished feeder sleeve 1.

[0028] When perlite ore is heated to expand and foam, it expands and foams by four to several tens of times. If the heating conditions of the perlite ore are adjusted to promote expansion and foaming, the bulk density of the foamed perlite will decrease. Furthermore, if foamed perlite with a low bulk density is used, the bending strength of the feeder sleeve 1 tends to decrease. In other words, heat retention and strength are contradictory, and when the bulk density of the above mixture is 1.4 g / cm 3 In addition to controlling the amount of expanded perlite added so that the bending strength of the feeder sleeve 1 is 3 MPa or more, it is also preferable to adjust the heating conditions of the expanded perlite to control the degree of expansion and foaming.

[0029] The feeder sleeve 1 of this embodiment can be manufactured using the same molding method as the well-known normal shell core molding method, and while it is easy to manufacture, it has excellent heat retention properties due to the air layer of the expanded perlite.

[0030] The feeder sleeve 1 shown in Figure 1(A) has a simple shape having a peripheral wall 11 and a bottom wall 12. The space enclosed by the peripheral wall 11 and the bottom wall 12 forms the feeder formation space S. A communication hole 121 is provided in the centre of the bottom wall 12.

[0031] As shown in Figure 1(B), the sand mould 2 is a green sand mould consisting of an upper mould 2A and a lower mould 2B, and is provided with a sprue cup 21, a sprue 22, a runner 23 and a product section 24. Furthermore, a storage space capable of accommodating a feeder sleeve 1 is provided in the upper mould 2A above the product section 24 of the lower mould 2B, and the feeder sleeve 1 is accommodated in this storage space. The molten metal supplied to the sprue cup 21 flows from the sprue 22 through the runner 23 and through a weir into the product section 24. Once the product section 24 is filled with molten metal, the molten metal flows from the through holes 121 in the feeder sleeve 1 into the feeder formation space S, filling the feeder formation space S with molten metal. The molten metal filled in the feeder formation space S corresponds to the feeder.

[0032] The thickness (wall thickness) of each of the peripheral wall 11 and the bottom wall 12 is preferably 10 mm or more and 30 mm or less. If the thickness exceeds 30 mm, heat will be absorbed by the lightweight aggregate, resulting in poor heat retention, and conversely, if the thickness is less than 10 mm, there is a risk that the feeder sleeve 1 will crack due to the pressure of the molten metal. Furthermore, the wall thickness is more preferably 20 mm or more and 27 mm or less.

[0033] Furthermore, in the feeder sleeve 1, the thickness of the bottom wall 12 may be thinner than the thickness of the peripheral wall 11. Because heat is transferred to the feeder sleeve 1 from the product portion 24 through the bottom wall 12, the thickness of the bottom wall 12 may be made relatively thin so that the air layer in the foamed perlite does not provide insulation. On the other hand, the thickness of the peripheral wall 11 may be made relatively thick to thicken the air layer in the foamed perlite so that the heat of the molten metal filled in the feeder formation space S does not escape. In other words, the wall provided with the communication hole 121 connecting to the product portion 24 may be made thinner than the other walls.

[0034] In this embodiment, expanded perlite is used as the lightweight aggregate, but it is not limited to expanded perlite. Lightweight aggregate is specified in JIS A 5002 (2003). In terms of unit volume weight, it is 25 kN / m 3 However, if we want to distinguish it more clearly from ordinary aggregate (in terms of air space retention rate), it is 23kN / m 3 The lightweight aggregate may be one whose main component is SiO2. Lightweight aggregates whose main component is SiO2 tend to have a porous structure. More specifically, diatomaceous earth or silica fume may be used. Alternatively, two or three of expanded perlite, diatomaceous earth, and silica fume may be used in combination.

[0035] The foundry sand may be artificial sand such as mullite, alumina, or zircon, or may be special sand such as zircon, olivine, or slag.The binder may also be furan resin, phenol urethane resin, alkali phenol resin, or water glass.

[0036] Furthermore, the feeder sleeve 1 may be manufactured by the same molding method as the well-known normal shell core molding method, or may be manufactured by gas hardening, for example by the cold box method, or may be made of a self-hardening (self-reactive) material, provided that this is easy to manufacture.

[0037] Figure 2(A) shows the feeder sleeve 1E of Example 1 used in the performance evaluation of the feeder sleeve shown in Figure 1(A).

[0038] The feeder sleeve 1E of Example 1 shown in Figure 2(A) was manufactured using a mixture containing silica sand, expanded perlite, and phenolic resin, using the same molding method as the well-known normal shell core molding method. The compounding ratio of silica sand to expanded perlite was 60% by volume and 40% by volume of expanded perlite, where the total of silica sand and expanded perlite was 100% by volume. Hardlite B-04 manufactured by Showa Chemical Industry Co., Ltd. was used as the expanded perlite. The bulk density of Hardlite B-04 alone was 0.315g / cm 3 ~0.335g / cm 3 The amount of phenol resin added was 3% by weight, taking the entire mixture as 100% by weight. In the feeder sleeve 1E of Example 1, the bottom wall 12E had no communicating hole 121 but was closed, and a K-type thermocouple 12s was fitted. The capacity of the feeder formation space SE enclosed by the peripheral wall 11E and bottom wall 12E was approximately 220 cc.

[0039] On the other hand, as Comparative Example 1, a feeder sleeve was also produced which was the same as Example 1 above except that the silica sand was 100% by volume and the expanded perlite was 0% by volume.

[0040] Approximately 700g of aluminium alloy (AC4C) was placed in a No. 5 graphite crucible and melted in an electric furnace by heating to approximately 780°C. The melt was allowed to cool outside the furnace so that the pouring temperature reached 770°C, and the melt was poured from above into the feeder sleeve 1E of Example 1 and the feeder sleeve of Comparative Example 1. Temperature measurements were taken using a thermocouple attached to the bottom wall of the feeder sleeve, and the cooling curves were recorded using a data logger. Multiple units of both the feeder sleeve 1E of Example 1 and the feeder sleeve of Comparative Example 1 were prepared, and multiple experiments were carried out.

[0041] Figure 2(B) is a graph showing the cooling curves for feeder sleeve 1E of Example 1 and the feeder sleeve of Comparative Example 1. This graph represents the average value of multiple experimental results recorded by a data logger.

[0042] The horizontal axis of the graph shown in Figure 2(B) represents elapsed time (seconds) and the vertical axis represents temperature (°C) measured by the thermocouple. The solid line represents the cooling curve for feeder sleeve 1E of Example 1, and the dotted line represents the cooling curve for the feeder sleeve of Comparative Example 1.

[0043] First, there was a difference in the average time until the primary crystals began to appear, which is the start of solidification (tL = 152 seconds, tL' = 97 seconds), with this average time being approximately 1.6 times longer in Example 1 compared to Comparative Example 1. There was also a difference in the average time until the eutectic reaction began (tE1 = 703 seconds, tE1' = 473 seconds), with this average time being approximately 1.5 times longer in Example 1 compared to Comparative Example 1. There was also a difference in the average time until the eutectic solidification completed (tE2 = 1330 seconds, tE2' = 985 seconds), with this average time being approximately 1.4 times longer in Example 1 compared to Comparative Example 1. Furthermore, the average length of time from the time the primary crystals began to appear to the time the eutectic solidification completed (hereinafter referred to as the "average solidification time") was approximately 1.3 times longer in Example 1 compared to Comparative Example 1. From these findings, it can be seen that the feeder sleeve 1E of Example 1 has better heat retention than the feeder sleeve of Comparative Example 1.

[0044] In addition to Example 1, feeder sleeves were also manufactured for Examples 2 to 5. In addition to Comparative Example 1, a feeder sleeve for Comparative Example 2 was also manufactured. Examples 2 to 5 and Comparative Example 2 were the same as Example 1 except that the compounding ratio of silica sand and expanded perlite was changed.

[0045] The bending strength (transverse rupture strength) of the feeder sleeve in each example was measured in accordance with the method specified in JACT Test Table SM-1 Bending Strength Test Method.

[0046] The bulk density of the mixtures used in Examples 1 to 5 and Comparative Examples 1 and 2 was also calculated.

[0047] The results are summarized in Table 1.

[0048] [Table 1] The grain size index of the silica sand used in each of Examples 1 to 5 and Comparative Examples 1 and 2 was in the range of JIS grain size index of 45 or more and 170 or less (AFS grain size index of 30 or more and 100 or less). The JIS grain size index is based on the method for determining the grain size index specified in JIS Z 2601 (1993), and the AFS grain size index is a grain size index specified by the American Foundry Society.

[0049] First, in the case of the feeder sleeve 1E of Example 1, the bending strength was 4.7 MPa and the bulk density of the mixture was 1.281 g / cm 3 As described above, it was confirmed that Example 1 had approximately 1.5 times the heat retention effect compared to Comparative Example 1. From this, it can be seen that the bulk density was 1.281 g / cm 3 On the other hand, in Comparative Example 1, the bulk density was 1.501 g / cm 3 Furthermore, when handling the feeder sleeve 1E of Example 1 normally, it did not chip or crack, and there was no sense of insufficient strength. The bending strength was measured to be 4.7 MPa. The bending strength of the feeder sleeve of Comparative Example 1 was 9.2 MPa.

[0050] In Example 2, the blending ratio of foamed perlite was increased to 50% by volume. The feeder sleeve of Example 2 may chip slightly during normal handling, and this is thought to be the limit of its strength. The measured bending strength was 2.9 MPa. As a result, it was concluded that the upper limit of the blending ratio of silica sand to foamed perlite is 50% by volume, and that a bending strength of 3 MPa is necessary.

[0051] In Example 3, the blend ratio of expanded perlite was reduced to 20% by volume, and in Comparative Example 2 it was reduced further to 10% by volume. The feeder sleeve of Example 3 had an average solidification time length slightly less than 1.2 times longer than that of Comparative Example 1, and the feeder sleeve of Comparative Example 2 had an average solidification time length slightly less than 1.1 times longer than that of Comparative Example 1. As some variation in the average solidification time length was observed in multiple experiments, it was determined that a blend ratio slightly less than 1.1 times was insufficient, and that a blend ratio slightly less than 1.2 times was necessary to achieve good heat retention, and as a result it was determined that a blend ratio of expanded perlite of at least 20% by volume was necessary. Furthermore, the bulk density of the mixture of Example 2 was 1.396 g / cm 3 Therefore, the upper limit of the bulk density of the mixture was set at 1.4 g / cm 3 It was decided.

[0052] In Example 4, the foamed perlite content was set to 45% by volume, which is intermediate between Examples 1 and 2. As mentioned above, the feeder sleeve of Example 2 was subject to slight chipping during normal handling, but this did not occur with the feeder sleeve of Example 4. As a result, it can be said that an upper limit for the foamed perlite content is 45% by volume rather than 50% by volume. Furthermore, since the flexural strength of the feeder sleeve of Example 4 was 3.6 MPa, it can be said that a lower limit for the flexural strength of the feeder sleeve is preferably 3.6 MPa.

[0053] In Example 5, the blending ratio of expanded perlite was set to 30% by volume, which is intermediate between Examples 1 and 3. The feeder sleeve of Example 5 had an average solidification time lengthened by approximately 1.25 times compared to the feeder sleeve of Comparative Example 1, so it can be said that the lower limit of the blending ratio of expanded perlite is preferably 30% by volume rather than 20% by volume. In addition, the bulk density of the mixture of Example 5 was 1.349 g / cm 3 Therefore, the upper limit of the bulk density of the mixture is 1.35 g / cm 3 It can be said that it is preferable that:

[0054] To summarise the above, the mixing ratio of silica sand to expanded perlite is such that increasing the proportion of expanded perlite improves heat retention, but if it is too high the strength of the feeder sleeve will be insufficient, so the proportion of expanded perlite must be between 20% and 50% by volume, and more preferably between 30% and 45% by volume. Also, looking at the bulk density of the mixture, it is 1.4 g / cm 3 It must be less than or equal to 1.35g / cm 3 Furthermore, in terms of bending strength of the feeder sleeve, it is necessary that it be 3 MPa or more, and more preferably 3.6 MPa or more.

[0055] In addition, although expanded perlite was used in each example, lightweight aggregates containing SiO2 as the main component are likely to have a porous structure and can be expected to have the same effects as expanded perlite. In particular, diatomaceous earth and silica fume can be used instead of expanded perlite. Alternatively, two types of lightweight aggregates selected from expanded perlite, diatomaceous earth, and silica fume may be mixed together, or all three types may be mixed together.

[0056] The present invention is not limited to the embodiments and examples described above, and various modifications can be made within the scope of the claims. For example, the molten metal is not limited to aluminum alloy, but may be iron or a non-ferrous metal such as a magnesium alloy. The foundry sand is not limited to silica sand. [Explanation of symbols]

[0057] 1,1E Feeder sleeve 11,11E Surrounding wall 12,12E Bottom wall S, SE riser forming space

Claims

1. A feeder space forming member that forms a feeder space to be filled with molten metal when housed in a housing space provided in a sand mold, It is molded from a mixture containing molding sand and lightweight aggregate, The lightweight aggregate is contained in an amount of 20% by volume or more and 50% by volume or less relative to a total of 100% by volume of the foundry sand and the lightweight aggregate, The lightweight aggregate is one selected from the group consisting of expanded perlite, diatomaceous earth, and silica fume; The foundry sand is silica sand having a grain size index specified in JIS Z 2601 of 45 or more and 170 or less, The mixture contains 1% by weight or more and 5% by weight or less of a binder when the entire mixture is taken as 100% by weight, and has a bulk density of 1.4 g / cm 3 or less; A feeder space forming member having a bending strength of 3 MPa or more.

2. The feeder space forming member according to claim 1, characterized in that the lightweight aggregate is expanded perlite having a bulk density of 0.315 g / cm 3 to 0.335 g / cm 3 .

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