Composite sand mold for frozen sand mold casting and preparation method thereof

Abstract

The invention belongs to the technical field of frozen sand mold casting, and particularly relates to a composite sand mold for frozen sand mold casting and a preparation method thereof.The preparation method of the composite sand mold for frozen sand mold casting comprises the steps that according to the size and shape of a casting and the structure and three-dimensional size of a frozen sand blank; frozen sand blanks are prepared according to the preset structure and the three-dimensional size; performing material reduction processing on the frozen sand blank according to a preset material reduction processing program to obtain a sand mold; wherein the sand mold comprises a freezing sand mold and a resin sand mold arranged on the surface of one side of the freezing sand mold; and the upper sand mold and the lower sand mold which are manufactured correspondingly are subjected to sand mold closing, so that the upper resin sand mold and the lower resin sand mold define a mold cavity, and the composite sand mold for frozen sand mold casting is obtained. The preparation method provided by the invention at least can improve the problem of floating sand in the blank making and die-free material reducing processes of the frozen sand mold, and meanwhile, improves the processing performance of the sand mold and improves the gas generation amount of the sand mold during pouring.

Description

Technical Field

[0001] The invention belongs to the technical field of frozen sand casting, and particularly relates to a composite sand mold used for frozen sand casting and a preparation method thereof. Background Art

[0002] Frozen sand casting is a revolutionary process in the casting field. The curing agent in traditional casting is replaced with pure water. The water and sand are fully mixed and then frozen to obtain a frozen sand mold. The use of frozen sand casting can accelerate the cooling rate of the casting after pouring and improve the performance of the casting. At the same time, no irritating gas is produced during the frozen casting process, which has the advantage of being green and environmentally friendly. After the sand mold is poured, the sand can be directly recovered without sand treatment, which can reduce production costs.

[0003] At present, frozen sand casting mainly adopts moldless subtractive molding, which first prepares frozen sand blanks, then performs subtractive processing on the frozen sand blanks, and finally puts the obtained frozen sand molds into boxes, and then freeze casting can be performed to obtain the corresponding castings. However, there are some problems in the preparation, subtractive processing and sand casting process of frozen sand molds:

[0004] First, the sand blank preparation and processing process will cause water loss, resulting in floating sand on the surface of the sand mold, which will affect the dimensional accuracy of the sand mold;

[0005] Secondly, the processability of frozen sand molds is poor. During the sand mold processing, the tool generates a lot of heat, which causes the sand mold to partially melt, and also affects the strength and size of the sand mold.

[0006] Finally, the vaporization of water in the sand casting process will produce a large amount of gas, some of which cannot be discharged in the mold cavity, which can easily cause defects such as pores in the casting.

[0007] Therefore, existing frozen sand casting still needs to be improved. Summary of the invention

[0008] The main purpose of the present invention is to propose a composite sand mold for frozen sand casting and a preparation method thereof. The preparation method of the present invention can at least improve the floating sand problem in the frozen sand mold blank making and moldless material reduction process, while improving the processing performance of the sand mold and improving the gas emission of the sand mold during pouring.

[0009] In order to achieve the above objectives, the present invention provides the following technical solutions.

[0010] According to a first aspect of the present invention, there is provided a method for preparing a composite sand mold for frozen sand casting, the method comprising the following steps: designing the structure and three-dimensional dimensions of an upper frozen sand blank and a lower frozen sand blank according to the size and shape of a casting; preparing the upper frozen sand blank and the lower frozen sand blank according to a preset structure and three-dimensional dimensions; performing subtractive processing on the upper frozen sand blank and the lower frozen sand blank according to a preset subtractive processing program to obtain an upper sand mold and a lower sand mold; wherein the upper sand mold comprises an upper frozen sand mold and an upper resin sand mold arranged on one side surface thereof; the lower sand mold comprises a lower frozen sand mold and a lower resin sand mold arranged on one side surface thereof; and performing sand mold clamping on the upper sand mold and the lower sand mold so that the upper resin sand mold and the lower resin sand mold are combined to form a mold cavity to obtain a composite sand mold for frozen sand casting.

[0011] In some embodiments of the present invention, the upper frozen sand blank includes an upper molding sand blank and an upper resin sand blank arranged on one side thereof along a thickness direction thereof.

[0012] In some embodiments of the present invention, the preparation of the upper frozen sand blank includes: fully mixing water and molding sand, pouring into a first sand box, fully compacting and keeping the surface smooth, so that the thickness of the upper molding sand blank reaches the target thickness; fully mixing resin and molding sand, continuing to pour into the first sand box, and evenly laying it on the surface of the upper molding sand blank, fully compacting and keeping the surface smooth, so that the thickness of the upper resin sand blank reaches the target thickness; transporting the sand blank as a whole to a freezing environment for freezing to obtain the upper frozen sand blank.

[0013] In some embodiments of the present invention, the lower frozen sand blank includes a lower molding sand blank and a lower resin sand blank arranged on one side thereof along a thickness direction thereof.

[0014] In some embodiments of the present invention, the preparation of the lower frozen sand blank includes: fully mixing water and molding sand, pouring into a second sand box, fully compacting and keeping the surface smooth, so that the thickness of the lower molding sand blank reaches the target thickness; fully mixing resin and molding sand, continuing to pour into the second sand box, and evenly laying it on the surface of the lower molding sand blank, fully compacting and keeping the surface smooth, so that the thickness of the lower resin sand blank reaches the target thickness; transporting the sand blank as a whole to a freezing environment for freezing to obtain the lower frozen sand blank.

[0015] In some embodiments of the present invention, the ambient temperature of the freezing environment is -15°C to -10°C.

[0016] In some embodiments of the present invention, based on the total mass of the upper resin sand blank or the lower resin sand blank, the percentage of the resin in the mass of the molding sand is 1% to 2%.

[0017] In some embodiments of the present invention, the water content of the upper molding sand blank or the lower molding sand blank is 3% to 5% of the mass of the molding sand.

[0018] In some embodiments of the present invention, the resin includes at least one of an alkali phenolic resin and a furan resin.

[0019] In some embodiments of the present invention, the upper resin sand blank of the upper frozen sand blank and the lower resin sand blank of the lower frozen sand blank are subjected to subtractive processing according to a preset subtractive processing program, wherein the thickness of the subtractive processing is less than the thickness of the resin sand blank.

[0020] In some embodiments of the present invention, the preparation method further comprises rapidly freezing the upper frozen sand blank and the lower frozen sand blank before subtractive processing.

[0021] In some embodiments of the present invention, the rapid freezing environment temperature is ≤-30°C.

[0022] In some embodiments of the present invention, the upper frozen sand blank and the lower frozen sand blank each independently have a square shape.

[0023] The second aspect of the present invention provides a composite sand mold for frozen sand casting, which is prepared by the preparation method described in the first aspect. The composite sand mold includes an upper sand mold and a lower sand mold that cooperate with each other. The upper sand mold has an upper frozen sand mold and an upper resin sand mold arranged on one side of it, and the lower sand mold has a lower frozen sand mold and a lower resin sand mold arranged on one side of it. The upper resin sand mold and the lower resin sand mold together form a mold cavity.

[0024] Compared with the prior art, the present invention achieves the following technical effects:

[0025] 1. The present invention adopts a combination of frozen sand mold and resin sand mold for preparation. The thickness of the frozen sand mold is much greater than that of the resin sand mold, and it still has the green advantage of frozen sand mold casting. At the same time, since the frozen sand mold accounts for the largest proportion, the sand mold will collapse after pouring and can be directly recycled. The resin sand mold layer in contact with the casting is thinner, and cleaning is relatively simple.

[0026] 2. In the present invention, a layer of resin sand is covered on the surface of the frozen sand mold, thereby reducing the contact between the frozen sand mold and the air during the freezing molding process and the subtractive processing process, reducing the water loss in the whole process, and solving the floating sand problem in the frozen sand casting process.

[0027] 3. In the present invention, during the subtractive processing, the resin sand blank is mainly processed. The resin sand blank has good processing performance, which avoids the problem of local melting of the sand mold due to heat generated by the tool during the subtractive processing of the frozen sand mold, and ensures the overall strength of the sand mold.

[0028] 4. In the present invention, the surface of the frozen sand mold after subtractive processing is a resin sand mold. During pouring, the molten iron contacts the resin sand mold, which prevents a large amount of gas in the frozen sand mold from entering the casting, reduces the problem of air holes in the casting, and the frozen sand mold can still increase the cooling rate of the casting, refine the structure of the casting, and improve the performance of the casting.

[0029] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0031] Figure 1 It is a schematic structural diagram of an upper frozen sand blank according to some embodiments of the present invention;

[0032] Figure 2 Schematic diagram of subtractive processing of an upper frozen sand blank according to some embodiments of the present invention;

[0033] Figure 3 Schematic diagram of the structure of a composite sand mold for frozen sand casting according to some embodiments of the present invention.

[0034] Reference numerals

[0035] 100. Add frozen sand blanks;

[0036] 110, adding molding sand blank; 120, adding resin sand blank;

[0037] 200. Composite sand mold;

[0038] 210. Upper sand mold; 220. Lower sand mold; 230. Mold cavity;

[0039] 2110, upper frozen sand mold; 2120, upper resin sand mold;

[0040] 2210, lower frozen sand mold; 2220, lower resin sand mold. DETAILED DESCRIPTION

[0041] The exemplary embodiments of the present invention will be described in more detail below with reference to specific embodiments. It should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0043] In the description of the embodiments of the present invention, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0044] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0045] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this document generally indicates that the associated objects before and after are in an "or" relationship.

[0046] In the description of the embodiments of the present invention, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0047] In the description of the embodiments of the present invention, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention.

[0048] Explanation of terms

[0049] Frozen sand blank: refers to the sand mold obtained by fully mixing water and silica sand and then freezing. The sand mold does not contain resin, curing agent and other ingredients, and has the advantage of being green and environmentally friendly.

[0050] Frozen sand mold: A sand mold used for casting obtained by subtractive processing of frozen sand blanks.

[0051] Resin sand mold: refers to the alkaline phenolic resin sand mold used in traditional casting.

[0052] Subtractive processing: refers to a method in which the frozen sand blank is placed in a processing equipment and the desired sand mold shape and size is obtained through milling and other methods.

[0053] At present, in order to solve the problem of floating sand, a method and device for directional quantitative in-situ deposition remanufacturing of frozen sand mold surface is proposed in the prior art. This method is mainly used in the processing of sand molds. By spraying atomized water on the surface of the sand mold during the processing, and spraying atomized resin on the surface of the sand mold after the processing, the floating sand on the surface is reduced and the strength of the sand mold is improved. Although this method takes into account the problem of water loss during the processing, there is also obvious water loss in the early freezing molding process. If the sand mold size is large, the freezing molding time will exceed one day. The sand mold is in contact with the air in a freezing environment, which will cause the water in the sand mold to continue to sublime. Secondly, during the processing of frozen sand blanks, the method of spraying atomized water and atomized resin at a fixed time and in a quantitative manner will lead to a high local moisture content and increased gas emission.

[0054] The invention provides a method for preparing a composite sand mold for frozen sand casting, so as to reduce or even solve the floating sand problem in the frozen sand mold blank making and moldless material reduction process, and at the same time improve the processing performance of the sand mold and improve the problem of excessive gas emission of the sand mold during pouring.

[0055] The key to the preparation method of the present invention is that when preparing a sand blank, a frozen sand blank is first prepared, and then a layer of resin sand blank is covered on the surface of the frozen sand blank, and the thickness of the resin sand blank is greater than the maximum subtractive processing thickness of the sand mold. When the sand mold is frozen, the resin sand can effectively reduce the sublimation of water in the bottom sand mold, thereby preventing the generation of floating sand on the surface; and in the moldless subtractive process, since the thickness of the resin sand blank is greater than the maximum subtractive processing thickness of the sand mold, the resin sand blank is mainly processed, and the frozen sand blank at the lower layer will not be processed. Since the processing performance of the resin sand blank is better than that of the frozen sand blank, the sand mold will not have the problem of water loss and reduced strength.

[0056] The preparation method of the present invention is specifically carried out according to the following steps.

[0057] (1) Determine the structure and three-dimensional dimensions of the frozen sand blank.

[0058] In the embodiment of the present invention, the structures and three-dimensional dimensions of the upper frozen sand blank and the lower frozen sand blank are designed respectively according to the size and shape of the casting.

[0059] In some embodiments of the present invention, the shape of the upper frozen sand blank includes but is not limited to a square, and can be set according to actual needs.

[0060] In some embodiments of the present invention, the shape of the lower frozen sand blank includes but is not limited to a square, and can be set according to actual needs.

[0061] Figure 1 A cubic upper frozen sand blank 100 is shown, and the overall thickness of the upper frozen sand blank 100 is h.

[0062] Continue to see Figure 1 As shown, the upper frozen sand blank 100 is composed of two parts, including an upper molding sand blank 110 and an upper resin sand blank 120 arranged on one side thereof along its thickness direction.

[0063] In some embodiments of the present invention, the thickness h1 of the upper molding sand blank 110 and the thickness h2 of the upper resin sand blank 120 are set according to actual needs, and the overall thickness of the upper frozen sand blank 100 satisfies h=h1+h2.

[0064] In some embodiments of the present invention, the lower frozen sand blank includes a lower molding sand blank and a lower resin sand blank disposed on one side thereof along a thickness direction thereof.

[0065] In some embodiments of the present invention, the thickness of the upper molding sand blank and the lower molding sand blank are each independently greater than or equal to the thickness of the lower resin sand blank.

[0066] (2) Determine the maximum processing thickness of subtractive processing.

[0067] In the embodiment of the present invention, before the subtractive processing of the sand blank, the subtractive processing procedure of the frozen sand blank is determined in advance through processing simulation, and the maximum subtractive processing thickness is determined. Figure 2 The maximum subtractive machining thickness h0 is shown in .

[0068] (3) Prepare frozen sand blanks.

[0069] In an embodiment of the present invention, an upper frozen sand blank and a lower frozen sand blank are prepared respectively according to a preset structure and three-dimensional dimensions.

[0070] In some embodiments of the present invention, the preparation processes of the upper frozen sand blank and the lower frozen sand blank are the same, that is, the upper frozen sand blank and the lower frozen sand blank are respectively prepared according to the same procedure.

[0071] In some embodiments of the present invention, in the upper frozen sand blank, the upper molding sand blank is a sand blank formed by pressing after mixing water and molding sand, and its thickness is set to h1, and the upper resin sand blank is a resin blank formed by pressing after mixing resin and molding sand, and its thickness is set to h2, and the overall thickness of the upper frozen sand blank satisfies h=h1+h2.

[0072] In some embodiments of the present invention, the preparation of the upper frozen sand blank includes: after fully mixing water and molding sand, pouring them into the first sand box, fully compacting and keeping the surface smooth, when the thickness of the upper molding sand blank reaches the target thickness, such as reaching the preset thickness h1, stop adding sand, and scrape the surface flat; after fully mixing the resin and molding sand, continue to pour them into the first sand box, and evenly lay them on the surface of the upper molding sand blank, also fully compacting and keeping the surface smooth, when the thickness of the upper resin sand blank reaches the target thickness, such as reaching the preset thickness h2, and at this time the overall thickness of the sand blank reaches h, stop adding sand, and scrape the sand blank flat; transport the sand blank as a whole to a freezing environment for freezing to obtain the target upper frozen sand blank.

[0073] In some embodiments of the present invention, the preparation of the lower frozen sand blank includes: after fully mixing water and molding sand, pouring them into the second sand box, fully compacting and keeping the surface smooth, when the thickness of the lower molding sand blank reaches the target thickness, such as reaching the preset thickness h1, stop adding sand, and scrape the surface flat; after fully mixing the resin and molding sand, continue to pour them into the second sand box, and evenly lay them on the surface of the lower molding sand blank, also fully compacting and keeping the surface smooth, when the thickness of the lower resin sand blank reaches the target thickness, such as reaching the preset thickness h2, and at this time the overall thickness of the sand blank reaches h, stop adding sand, and scrape the sand blank flat; transport the sand blank as a whole to a freezing environment for freezing to obtain the lower frozen sand blank.

[0074] In an embodiment of the present invention, the ambient temperature of the freezing environment is in the range of -15°C to -10°C. The ambient temperature of the freezing environment should meet the following conditions, that is, the sand blank should have initial strength after freezing, the tensile strength of the frozen sand blank should not be less than 0.5MPa, and the compressive strength should be higher than 1MPa. According to this requirement, the ambient temperature of the freezing environment should be lower than -10°C. At the same time, in order to reduce energy waste during the freezing process, the ambient temperature should not be too low. Considering comprehensively, the ambient temperature is set in the range of -15°C to -10°C. Exemplarily, the freezing environment temperature can be one of -15°C, -14°C, -13°C, -12°C, -11°C, -10°C, or any value that meets the above range. In an embodiment of the present invention, the resin can be, but is not limited to, alkaline phenolic resin and furan resin.

[0075] In the embodiment of the present invention, the molding sand may be, but is not limited to, silica sand.

[0076] In some embodiments of the present invention, based on the total mass of the resin sand blank, the percentage of the resin to the mass of the molding sand is 1% to 2%. Exemplarily, the percentage of the resin to the mass of the molding sand can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or any value that meets the above range.

[0077] In some embodiments of the present invention, based on the total mass of the resin of the lower resin sand blank, the percentage of the resin to the mass of the molding sand is 1% to 2%. Exemplarily, the percentage of the resin to the mass of the molding sand can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or any value that meets the above range.

[0078] In some embodiments of the present invention, the water content of the upper molding sand blank is 3% to 5% of the mass of the molding sand. For example, the water content of the upper molding sand blank can be 3%, 3.2%, 3.4%, 3.5%, 3.6%, 3.8%, 4.2%, 4.4%, 4.5%, 4.6%, 4.8%, 5% or any value that meets the above range.

[0079] In some embodiments of the present invention, the water content of the lower molding sand blank is 3% to 5% of the mass of the molding sand. For example, the water content of the lower molding sand blank can be 3%, 3.2%, 3.4%, 3.5%, 3.6%, 3.8%, 4.2%, 4.4%, 4.5%, 4.6%, 4.8%, 5% or any value that meets the above range.

[0080] (5) Frozen sand blanks are quickly frozen.

[0081] In an embodiment of the present invention, the frozen sand blanks including the upper frozen sand blanks and the lower frozen sand blanks are rapidly frozen before subtractive processing to make them meet processing conditions, wherein the tensile strength of the frozen sand blanks should be higher than 1MPa, and the compressive strength should be higher than 2MPa. Taking all factors into consideration, the ambient temperature for rapid freezing should be lower than -30°C, such as -50°C to -30°C.

[0082] In some embodiments of the present invention, liquid nitrogen may be used to rapidly freeze the frozen sand blank.

[0083] It is worth mentioning that, according to actual needs, the frozen sand blank can be frozen and stored before the rapid freezing treatment, that is, stored in an ambient temperature of -15°C to -10°C, and then the frozen sand blank can be rapidly frozen when the subtractive processing is required. (5) Subtractive processing and molding.

[0084] In an embodiment of the present invention, the frozen sand blank after freeze forming is transferred to a subtractive processing device, and the subtractive processing program obtained by simulation in the above step (2) is executed.

[0085] In an embodiment of the present invention, the upper frozen sand blank and the lower frozen sand blank are subjected to subtractive processing according to a preset subtractive processing program to obtain an upper sand mold and a lower sand mold. The upper sand mold includes an upper frozen sand mold and an upper resin sand mold arranged on one side surface thereof; the lower sand mold includes a lower frozen sand mold and a lower resin sand mold arranged on one side surface thereof.

[0086] In the embodiment of the present invention, the subtractive processing process is mainly performed on the resin sand blank area, wherein the maximum processing thickness h0 of the subtractive processing is slightly smaller than the thickness h2 of the resin sand blank, see Figure 2 As shown, the remaining resin sand blank area is formed into a resin sand mold.

[0087] In some embodiments of the present invention, the upper resin sand blank of the upper frozen sand blank and the lower resin sand blank of the lower frozen sand blank are subjected to subtractive processing according to a preset subtractive processing program, wherein the thickness of the subtractive processing is less than the thickness of the resin sand blank.

[0088] In some embodiments of the present invention, the thickness of the upper frozen sand mold and the lower frozen sand mold are independently much greater than the thickness of the upper resin sand mold and the lower resin sand mold. It can be understood that a thin layer of upper resin sand mold is covered on the surface of the upper frozen sand mold, and a thin layer of lower resin sand mold is covered on the surface of the lower frozen sand mold.

[0089] In some embodiments of the present invention, the thickness of the upper resin sand mold can be 1mm to 5mm, for example, the thickness of the upper resin sand mold can be one of 1mm, 2mm, 3mm, 4mm, 5mm or any value that satisfies the above range. The thickness of the lower resin sand mold can be 1mm to 5mm, for example, the thickness of the lower resin sand mold can be one of 1mm, 2mm, 3mm, 4mm, 5mm or any value that satisfies the above range. Of course, the specific thickness of the upper resin sand mold and the lower resin sand mold at different positions can be set according to actual conditions, without specific limitation.

[0090] In some cases, according to actual needs, the thickness of a certain area in the upper resin sand mold is 0, that is, the frozen sand mold corresponding to this part of the area is exposed and directly contacts with the melt during pouring.

[0091] (6) Sand mold assembly.

[0092] In the embodiment of the present invention, after the frozen sand blank is subjected to moldless material reduction, the desired target frozen sand mold is obtained, and after the upper and lower frozen sand molds are combined into a mold, a composite sand mold is obtained, which meets the conditions for casting.

[0093] In some embodiments of the present invention, the upper sand mold and the lower sand mold are sand molded together so that the upper resin sand mold and the lower resin sand mold are surrounded by each other to form a mold cavity, thereby obtaining a composite sand mold for frozen sand casting.

[0094] Another aspect of the present invention provides a composite sand mold for frozen sand casting, which is prepared by the above-mentioned preparation method.

[0095] join Figure 3 As shown, the composite sand mold 200 includes an upper sand mold 210 and a lower sand mold 220 that cooperate with each other. The upper sand mold 210 has an upper frozen sand mold 2110 and an upper resin sand mold 2120 arranged on one side thereof, and the lower sand mold 220 has a lower frozen sand mold 2210 and a lower resin sand mold 2220 arranged on one side thereof. The upper resin sand mold 2120 and the lower resin sand mold 2220 together form a mold cavity 230.

[0096] Another aspect of the present invention provides a casting method, specifically, casting is performed based on the composite sand mold for frozen sand casting.

[0097] In an embodiment of the invention, the composite sand mold is transported to a casting area, and then casting and subsequent cleaning processes can be performed.

[0098] It is worth mentioning that before being transported to the pouring area, the obtained composite sand mold can be stored in a frozen state, that is, stored in an ambient temperature of -15°C to -10°C, and before pouring, the composite sand mold can be quickly frozen as appropriate, and the quick freezing temperature is lower than -30°C, such as -50°C to -30°C.

[0099] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a composite sand mold for frozen sand casting, characterized in that: The preparation method comprises the following steps: According to the size and shape of the casting, the structure and three-dimensional size of the upper frozen sand blank and the lower frozen sand blank are designed respectively; The upper frozen sand blank and the lower frozen sand blank are prepared respectively according to the preset structure and three-dimensional size; According to a preset subtractive processing program, the upper frozen sand blank and the lower frozen sand blank are subjected to subtractive processing to obtain an upper sand mold and a lower sand mold; wherein the upper sand mold includes an upper frozen sand mold and an upper resin sand mold arranged on one side surface thereof; and the lower sand mold includes a lower frozen sand mold and a lower resin sand mold arranged on one side surface thereof; The upper sand mold and the lower sand mold are sand molded together so that the upper resin sand mold and the lower resin sand mold are surrounded by each other to form a mold cavity, thereby obtaining a composite sand mold for frozen sand casting.

2. The preparation method according to claim 1, characterized in that The upper frozen sand blank comprises an upper molding sand blank and an upper resin sand blank arranged on one side thereof along a thickness direction thereof.

3. The preparation method according to claim 2, characterized in that: The preparation of the upper frozen sand blank comprises: Pour the water and molding sand into the first sand box after mixing them thoroughly, compact them thoroughly and keep the surface flat, so that the thickness of the upper molding sand blank reaches the target thickness; After the resin and the molding sand are fully mixed, continue to pour them into the first sand box and evenly spread them on the surface of the upper molding sand blank, fully compact and keep the surface flat, so that the thickness of the upper resin sand blank reaches the target thickness; The sand blank is transferred as a whole to a freezing environment for freezing to obtain the upper frozen sand blank.

4. The preparation method according to claim 2, characterized in that: The lower frozen sand blank comprises a lower molding sand blank and a lower resin sand blank arranged on one side thereof along a thickness direction thereof.

5. The preparation method according to claim 4, characterized in that: The preparation of the lower frozen sand blank comprises: Pour the water and molding sand into the second sand box after mixing them thoroughly, compact them thoroughly and keep the surface flat, so that the thickness of the lower molding sand blank reaches the target thickness; After the resin and the molding sand are fully mixed, continue to pour them into the second sand box and evenly spread them on the surface of the lower molding sand blank, fully compact and keep the surface flat, so that the thickness of the lower resin sand blank reaches the target thickness; The sand blank is transported as a whole to a freezing environment for freezing to obtain the lower frozen sand blank.

6. The preparation method according to claim 3 or 5, characterized in that: The ambient temperature of the freezing environment is -15°C to -10°C.

7. The preparation method according to claim 3 or 5, characterized in that: Based on the total mass of the upper resin sand blank or the lower resin sand blank, the percentage of the resin in the mass of the molding sand is 1% to 2%; Preferably, the water content of the upper molding sand blank or the lower molding sand blank is 3% to 5% of the mass of the molding sand; Preferably, the resin includes at least one of an alkaline phenolic resin and a furan resin.

8. The preparation method according to claim 4, characterized in that: The upper resin sand blank of the upper frozen sand blank and the lower resin sand blank of the lower frozen sand blank are subjected to subtractive processing according to a preset subtractive processing program, wherein the thickness of the subtractive processing is less than the thickness of the resin sand blank.

9. The preparation method according to claim 1, characterized in that: The preparation method further comprises rapidly freezing the upper frozen sand blank and the lower frozen sand blank before the subtractive processing; Preferably, the rapid freezing environment temperature is ≤-30°C; Preferably, the upper frozen sand blank and the lower frozen sand blank are each independently shaped like a square.

10. A composite sand mold for frozen sand casting prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The composite sand mold includes an upper sand mold and a lower sand mold that cooperate with each other. The upper sand mold has an upper freezing sand mold and an upper resin sand mold arranged on one side of it. The lower sand mold has a lower freezing sand mold and a lower resin sand mold arranged on one side of it. The upper resin sand mold and the lower resin sand mold are combined to form a mold cavity.

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