No-parting-surface sand mold, manufacturing and casting method thereof and casting

Abstract

The invention discloses a parting-surface-free sand mold, a manufacturing and casting method thereof and a casting, and belongs to the technical field of casting. The method comprises the following steps: firstly, manufacturing an integral green sand blank by adopting a molding mixture, drying to obtain an integral sand blank, then machining the interior of the integral sand blank based on the idea of subtractive manufacturing, realizing parting-surface-free integral molding in a near-net shape on the basis, and casting by utilizing a parting-surface-free sand mold to obtain a casting. According to the invention, a mold sample and a core box are not required to be manufactured, parting and assembling procedures of a sand mold and a sand core are avoided, the casting process and the casting mold structure design are simplified, and the problem of casting size and shape deviation caused by assembly dislocation during mold assembly or core floating during casting is avoided. The formed casting is high in dimensional precision, accurate in shape, high in material utilization rate, small in follow-up machining allowance, short in casting production period and high in process yield, and the production cost is greatly reduced. The method is especially suitable for sand casting of precise castings with complex shapes.

Description

Technical Field

[0001] The invention belongs to the technical field of casting, and specifically relates to a sand mold without parting surface and a manufacturing and casting method and casting, and is particularly suitable for sand casting of precision castings with complex shapes. Background Art

[0002] Sand casting is the most widely used casting method at present, and more than 80% of castings are completed by sand casting. The main processes of traditional sand casting include making patterns, preparing molding mixtures, molding, demolding, core making, core setting, mold closing, smelting, pouring, sand dropping, cleaning, etc., and the molding demolding often involves factors such as demolding slope and sand digging. In traditional sand casting, in order to remove the pattern or core setting during molding, the complete sand mold is usually divided into two halves or multiple sand molds, and the surfaces where the two halves or multiple sand molds contact and match each other must be set, that is, the interface of the sand mold, that is, the parting surface. In addition, the mold closing is completed by assembling the two halves or multiple sand molds together at the parting surface. In the traditional sand casting process, casting defects and scraps are easily caused by factors such as demolding, core setting, and mold closing. Especially for sand casting of complex precision castings, problems such as misalignment, core deviation, or difficulty in closing are easily caused when closing the mold, resulting in low mold closing accuracy, causing defects such as misalignment or thickening of the casting, which seriously affects the dimensional accuracy and quality of the casting (such as uneven performance of each part). Therefore, due to the need to set the parting surface and other factors, traditional sand casting has prominent problems such as many processes, long mold making cycle, poor casting dimensional accuracy and quality, large waste of resources, and high production cost.

[0003] It can be seen that there is an urgent need to develop a new sand casting method that does not require setting a parting surface, so as to improve the dimensional accuracy and quality of sand castings, reduce the scrap rate, shorten the production cycle, and reduce manufacturing costs. Summary of the invention

[0004] The purpose of the present invention is to provide a sand mold without parting surface and its production and casting method and casting, which effectively solves the above-mentioned problems caused by the existence of parting surface in traditional sand casting, and is particularly suitable for sand casting of complex-shaped precision castings. First, a molding mixture is used to make an integral green sand blank, and the integral sand blank is dried to obtain the integral sand blank. Then, based on the idea of ​​subtractive manufacturing, the interior of the integral sand blank is machined, and on this basis, the overall modeling without parting surface is realized in a near-net shape, breaking through the traditional practice of selecting parting surface in sand casting, and subverting the traditional sand casting technology.

[0005] According to a first aspect of the technical solution of the present invention, a method for making a sand mold without a parting surface is provided, and the method for making a sand mold without a parting surface comprises the following steps:

[0006] Step 1: Prepare modeling mixture;

[0007] Step 2: using the modeling mixture to make an integral green sand blank;

[0008] Step 3: drying the whole green sand blank to obtain a whole sand blank;

[0009] Step 4: formulating a strategy for machining the integral sand blank;

[0010] Step 5: planning the tool inlet and outlet positions, exhaust port positions, riser positions and external gate positions on the surface of the integral sand blank according to the formulated strategy;

[0011] Step 6: According to the planned positions of the tool inlet and outlet, the exhaust port, the riser and the outer gate, the surface of the integral sand blank is machined to form the tool inlet and outlet, the exhaust port, the riser and the outer gate;

[0012] Step 7: machining the interior of the integral sand blank through the tool inlet and outlet of the machining equipment to form an integral cavity, and machining an exhaust channel, a riser channel and a runner to achieve an integral shape of the integral sand blank without a parting surface;

[0013] Step 8: Seal the tool inlet and outlet to obtain a sand mold without a parting surface having the integral cavity inside.

[0014] Furthermore, the raw materials used for the molding mixture include at least raw sand, a binder and water, the raw sand is at least one of silica sand, quartz sand, resin sand, glass sand, clay sand, chromium ore sand, gem sand, water glass sand, limestone sand, vacuum zircon sand, coal gangue sand, Luo mineral sand, coated sand, white hard sand, corundum sand, magnesia sand, olivine sand or new sand; the binder is at least one of furan resin, alkaline phenolic resin or water glass.

[0015] Furthermore, the overall green sand blank has an outer shape of a cube, a cylinder, a sphere or a special-shaped body, and is manufactured by at least one of manual manufacturing, machine manufacturing or 3D printing.

[0016] Furthermore, the sand and slag generated by machining is removed by at least one of vacuum extraction, gas purging or mechanical dumping.

[0017] Furthermore, a layer of paint is brushed or sprayed on the surface of the integral cavity.

[0018] Furthermore, the modeling mixture is used to seal the tool inlet and outlet.

[0019] Furthermore, the machining is CNC machining, and the CNC machining is at least one of electric spark machining, laser machining, and CNC machining.

[0020] Further, a strategy for machining the integral sand blank is formulated according to the designed casting structure, exhaust structure, feeding riser structure and runner structure;

[0021] Among them, when formulating the strategy for machining the integral sand blank, the designed cooling structure is taken into consideration, the cooling opening positions on the surface of the integral sand blank are planned, and the surface and the interior of the integral sand blank are machined to form cooling openings and cooling channels.

[0022] According to a second aspect of the technical solution of the present invention, a sand mold without a parting surface is provided, and the sand mold without a parting surface is manufactured by the method for manufacturing a sand mold without a parting surface according to any of the above aspects.

[0023] According to a third aspect of the technical solution of the present invention, a method for sand casting without a parting surface is provided. The sand casting method without a parting surface is operated based on the sand mold without a parting surface described above, and the sand casting method without a parting surface comprises the following steps:

[0024] Step 1: Smelting metal raw materials to obtain metal melt;

[0025] Step 2: pouring the molten metal into the integral cavity of the sand mold without a parting surface through the outer gate and the runner to fill the integral cavity;

[0026] Step 3: After the metal melt solidifies and cools, the sand is removed and the casting is obtained after cleaning.

[0027] Furthermore, the cooling structure is used to regulate the solidification process of the metal melt in the integral cavity.

[0028] According to a fourth aspect of the technical solution of the present invention, there is provided a casting, wherein the casting is prepared by the sand casting method without parting surface according to any one of the above aspects.

[0029] Beneficial effects of the present invention:

[0030] (1) The sand mold without parting surface of the present invention is an integral molding sand mold, which greatly simplifies the sand mold design (such as no need to consider the design of parting surface, sand core and draft angle, etc.), saves sand mold design time, improves design flexibility, and provides sufficient freedom for casting structure design, so that highly complex castings can be designed. At the same time, casting defects and scrap problems such as uneven wall thickness and dimensional deviation of the casting caused by inaccurate sand core size or inaccurate core position and insufficient mold closing accuracy in traditional sand casting will not occur. It also avoids the problem of inconsistent quality of the sand molds combined together caused by the separate production of each sand mold in traditional sand casting.

[0031] (2) The method for making a sand mold without a parting surface of the present invention does not require the pre-production of the mold and core box required for traditional modeling, omits the processes of mold removal, core making, core setting and mold closing, greatly simplifies the modeling process, shortens the sand mold making process, improves the production efficiency, reduces the production cost, improves the dimensional accuracy of the sand mold cavity and the overall sand mold quality, and avoids the problems of the traditional sand mold combination, such as the trouble of making each sand mold separately, the long process and the high cost, as well as the complicated process and the difficulty of precise alignment caused by the machining of the front and back surfaces of the sand mold, the assembly misalignment during mold closing, and the lack of assembly accuracy.

[0032] (3) The parting surface-free sand casting method of the present invention is a new sand casting method with nearly zero margin and precise molding. It does not require mold removal, no parting surface, and no sand core, and realizes parting surface-free sand casting, that is, integral molding sand casting. The molded casting has no flash, burrs, and mold draft, and reduces the dimensional error or casting defects and waste caused by mold removal, mold closing, or core combination in traditional sand casting. Therefore, the casting has high dimensional accuracy and has the characteristics of precision castings. It can partially replace precision casting, greatly reduce the weight of the casting blank and the subsequent machining allowance is small (the machining allowance can be reduced by more than 60%), reduce the cost of casting machining, reduce the casting machining time by 40% to 50% compared with traditional sand casting, shorten the production cycle, and the process technology is easy to master, which is convenient for realizing mechanical automation production. The process yield rate can reach more than 95%, greatly reducing the production cost. It is particularly suitable for sand casting of complex-shaped precision castings.

[0033] (4) The casting of the present invention has no burrs, high dimensional accuracy and accurate shape, which reduces the workload of cleaning and polishing by more than 50%. The performance of each part is uniform, the overall internal and external quality is good, and the manufacturing cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 The present invention is a process flow chart for making a sand mold without a parting surface. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art may make non-essential improvements and adjustments based on the contents of the present invention.

[0037] The technical solution of the present invention first provides a method for making a sand mold without a parting surface, such as Figure 1 As shown, the following steps are included:

[0038] S1: Prepare modeling mixture.

[0039] In a preferred embodiment, in S1, the raw materials used for the molding mixture include at least raw sand, a binder and water, the raw sand is at least one of silica sand, quartz sand, resin sand, glass sand, clay sand, chromium ore sand, gem sand, water glass sand, limestone sand, vacuum zircon sand, coal gangue sand, Luo ore sand, coated sand, white hard sand, corundum sand, magnesia sand, olivine sand or new sand; the binder is at least one of furan resin, alkaline phenolic resin or water glass.

[0040] S2: using the modeling mixture to make an integral green sand blank.

[0041] In a preferred embodiment, in S2, the overall green sand blank has an outer shape of a cube, a cylinder, a sphere or a special shape, and is manufactured by at least one of manual manufacturing, machine manufacturing or 3D printing.

[0042] S3: Drying the whole green sand blank to obtain a whole sand blank.

[0043] S4: formulating a strategy for machining the integral sand blank.

[0044] In a preferred embodiment, a strategy for machining the integral sand blank is formulated according to the designed casting structure, exhaust structure, feeding riser structure and runner structure;

[0045] Among them, when formulating the strategy for machining the integral sand blank, the designed cooling structure is taken into consideration, the cooling opening positions on the surface of the integral sand blank are planned, and the surface and the interior of the integral sand blank are machined to form cooling openings and cooling channels.

[0046] In a preferred embodiment, the machining is CNC machining, and the CNC machining is at least one of electric spark machining, laser machining, and CNC machining.

[0047] S5: planning the tool inlet and outlet positions, exhaust port positions, riser positions and external gate positions on the surface of the integral sand blank according to the formulated strategy.

[0048] S6: According to the planned positions of the tool inlet and outlet, the exhaust port, the riser and the outer gate, the surface of the integral sand blank is machined to form the tool inlet and outlet, the exhaust port, the riser and the outer gate.

[0049] S7: machining the interior of the integral sand blank through the tool inlet and outlet with a tool of a machining device to form an integral cavity, and machining an exhaust channel, a riser channel and a runner to achieve an integral shape of the integral sand blank without a parting surface.

[0050] In a preferred embodiment, in S7, the sand and slag generated by machining are removed by at least one of vacuum extraction, gas purging or mechanical dumping.

[0051] In a preferred embodiment, in S7, a layer of paint is brushed or sprayed on the surface of the integral cavity.

[0052] S8: Seal the tool inlet and outlet to obtain a sand mold without a parting surface having the integral mold cavity inside.

[0053] In a preferred embodiment, in S8, the tool inlet and outlet are sealed with the molding mixture.

[0054] The technical solution of the present invention also provides a sand mold without a parting surface, and the sand mold without a parting surface is manufactured according to the method for manufacturing the sand mold without a parting surface described above.

[0055] The technical solution of the present invention further provides a sand casting method without a parting surface, the sand casting method without a parting surface is based on the operation according to the sand mold without a parting surface described above, and the sand casting method without a parting surface comprises the following steps:

[0056] Step 1: Smelting metal raw materials to obtain metal melt;

[0057] Step 2: pouring the molten metal into the integral cavity of the sand mold without a parting surface through the outer gate and the runner to fill the integral cavity;

[0058] Step 3: After the metal melt solidifies and cools, the sand is removed and the casting is obtained after cleaning.

[0059] In a preferred embodiment, the cooling structure is used to regulate the solidification process of the metal melt in the integral cavity.

[0060] The technical solution of the present invention further provides a casting, which is prepared by the sand casting method without parting surface described above.

[0061] Embodiment 1:

[0062] Sand mould and casting of engine cylinder block.

[0063] Step 1: Prepare a molding mixture by selecting 50 / 100 mesh quartz sand, furan resin, curing agent, silane and water;

[0064] Step 2: using the modeling mixture to make an integral green sand blank by a machine;

[0065] Step 3: drying the whole green sand blank to obtain a whole sand blank;

[0066] Step 4: formulating a strategy for CNC machining the integral sand blank according to the designed engine cylinder casting structure, exhaust structure, feeding riser structure, cooling structure and runner structure;

[0067] Step 5: planning the tool inlet and outlet positions, exhaust port positions, riser positions, cooling channel positions and external gate positions on the surface of the integral sand blank according to the formulated strategy;

[0068] Step 6: machining the surface of the integral sand blank to form tool inlets and outlets, exhaust ports, risers, cooling ports and external gates;

[0069] Step 7: CNC machining the interior of the integral sand blank through the tool inlet and outlet to form an integral cavity, spray alcohol-based graphite paint on the surface of the integral cavity, and machine out an exhaust channel, a riser channel, a cooling channel and a runner to achieve an integral shape of the integral sand blank without a parting surface;

[0070] Step 8: Seal the tool inlet and outlet to obtain a sand mold of an engine cylinder block without a parting surface and having the integral cavity inside.

[0071] The process steps of casting the engine cylinder block sand mold without parting surface are as follows:

[0072] Step 1: smelting gray cast iron HT250 to obtain gray cast iron HT250 melt;

[0073] Step 2: pouring the gray cast iron HT250 melt into the integral mold cavity of the sand mold without a parting surface through the external gate and the runner to fill the integral mold cavity;

[0074] Step 3: Using the cooling structure to regulate the solidification process of the gray cast iron HT250 melt in the integral cavity;

[0075] Step 4: After the gray cast iron HT250 melt solidifies and cools, the sand is removed and the engine cylinder block casting is obtained after cleaning.

[0076] Embodiment 2:

[0077] Automobile engine cylinder head sand mold and casting.

[0078] Step 1: Prepare a molding mixture by selecting 50 / 100 mesh silica sand, water glass, bentonite, disintegrator and water;

[0079] Step 2: using the modeling mixture to manually make an integral green sand blank;

[0080] Step 3: drying the whole green sand blank to obtain a whole sand blank;

[0081] Step 4: formulating a strategy for CNC machining the integral sand blank according to the designed automobile engine cylinder head casting structure, exhaust structure, feeding riser structure, cooling structure and runner structure;

[0082] Step 5: planning the tool inlet and outlet positions, exhaust port positions, riser positions, cooling channel positions and external gate positions on the surface of the integral sand blank according to the formulated strategy;

[0083] Step 6: machining the surface of the integral sand blank to form tool inlets and outlets, exhaust ports, risers, cooling ports and external gates;

[0084] Step 7: CNC machining the interior of the integral sand blank through the tool inlet and outlet to form an integral cavity, spray alcohol-based graphite paint on the surface of the integral cavity, and machine out an exhaust channel, a riser channel, a cooling channel and a runner to achieve an integral shape of the integral sand blank without a parting surface;

[0085] Step 8: Seal the tool inlet and outlet to obtain a sand mold of a car engine cylinder head without a parting surface having the integral cavity inside.

[0086] The casting is performed using the sand mold for the automobile engine cylinder head without parting surface, and the process steps are as follows:

[0087] Step 1: smelting the vermicular graphite cast iron RuT350 to obtain a vermicular graphite cast iron RuT350 melt;

[0088] Step 2: pouring the compacted graphite cast iron RuT350 melt into the integral mold cavity of the sand mold without a parting surface through the outer gate and the runner to fill the integral mold cavity;

[0089] Step 3: Using the cooling structure to regulate the solidification process of the compacted graphite cast iron RuT350 melt in the integral cavity;

[0090] Step 4: After the RuT350 melt solidifies and cools, the sand is removed and the automobile engine cylinder head casting is obtained after cleaning.

[0091] Embodiment 3:

[0092] Transmission housing sand mold and casting.

[0093] Step 1: Prepare a molding mixture by selecting 50 / 100 mesh silica sand, furan resin, curing agent and water;

[0094] Step 2: using the modeling mixture to make an integral green sand blank by a machine;

[0095] Step 3: drying the whole green sand blank to obtain a whole sand blank;

[0096] Step 4: formulating a strategy for CNC machining the integral sand blank according to the designed transmission housing casting structure, exhaust structure, feeding riser structure, cooling structure and runner structure;

[0097] Step 5: planning the tool inlet and outlet positions, exhaust port positions, riser positions, cooling channel positions and external gate positions on the surface of the integral sand blank according to the formulated strategy;

[0098] Step 6: machining the surface of the integral sand blank to form tool inlets and outlets, exhaust ports, risers, cooling ports and external gates;

[0099] Step 7: CNC machining the interior of the integral sand blank through the tool inlet and outlet to form an integral cavity, spray alcohol-based zircon powder coating on the surface of the integral cavity, and machine out exhaust channels, riser channels, cooling channels and runners to achieve integral shaping of the integral sand blank without parting surfaces;

[0100] Step 8: Seal the tool inlet and outlet to obtain a sand mold of a transmission housing without a parting surface and having the integral cavity inside.

[0101] The sand mold without parting surface is used for casting, and the process steps are as follows:

[0102] Step 1: smelting ductile iron QT500-7 to obtain ductile iron QT500-7 melt;

[0103] Step 2: pouring the ductile iron QT500-7 melt into the integral mold cavity of the sand mold without a parting surface through the external gate and the runner to fill the integral mold cavity;

[0104] Step 3: Using the cooling structure to regulate the solidification process of the ductile iron QT500-7 melt in the integral cavity;

[0105] Step 4: After the ductile iron QT500-7 melt solidifies and cools, the sand is removed and the transmission housing casting is obtained after cleaning.

[0106] In summary, the technical solution of the present invention provides a sand mold without parting surface, and its production and casting method and casting. First, a molding mixture is used to make an integral raw sand blank, and the integral sand blank is dried to obtain the integral sand blank. Then, based on the idea of ​​subtractive manufacturing, the interior of the integral sand blank is machined, and on this basis, the overall molding without parting surface is realized in a near-net shape, and the casting is obtained by casting using the sand mold without parting surface. The present invention does not require the production of a mold and a core box, and does not have the assembly process of parting and sand molds and sand cores, which simplifies the casting process and the mold structure design, and avoids the problem of casting size and shape deviation caused by assembly dislocation during mold closing or core floating during casting. The molded casting has high dimensional accuracy, accurate shape, high material utilization rate, small subsequent machining allowance, short casting production cycle, high process yield rate, and greatly reduces production costs. It is particularly suitable for sand casting of complex precision castings.

[0107] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0108] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0109] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for making a sand mold without a parting surface, characterized in that: The method for making a sand mold without a parting surface comprises the following steps: Step 1: Prepare modeling mixture; Step 2: using the modeling mixture to make an integral green sand blank; Step 3: drying the whole green sand blank to obtain a whole sand blank; Step 4: formulating a strategy for machining the integral sand blank; Step 5: planning the tool inlet and outlet positions, exhaust port positions, riser positions and external gate positions on the surface of the integral sand blank according to the formulated strategy; Step 6: According to the planned positions of the tool inlet and outlet, the exhaust port, the riser and the outer gate, the surface of the integral sand blank is machined to form the tool inlet and outlet, the exhaust port, the riser and the outer gate; Step 7: machining the interior of the integral sand blank through the tool inlet and outlet of the machining equipment to form an integral cavity, and machining an exhaust channel, a riser channel and a runner to achieve an integral shape of the integral sand blank without a parting surface; Step 8: Seal the tool inlet and outlet to obtain a sand mold without a parting surface having the integral cavity inside.

2. The method for making a sand mold without a parting surface according to claim 1, characterized in that: The raw materials used for the modeling mixture at least include raw sand, a binder and water. The raw sand is at least one of silica sand, quartz sand, resin sand, glass sand, clay sand, chrome ore sand, gem sand, water glass sand, limestone sand, vacuum zircon sand, coal gangue sand, Luo ore sand, coated sand, white hard sand, corundum sand, magnesia sand, olivine sand or new sand; the binder is at least one of furan resin, alkaline phenolic resin or water glass; the shape of the overall raw sand blank is a cube, a cylinder, a sphere or an irregular body, and the production method is at least one of manual production, machine production or 3D printing production.

3. The method for making a sand mold without a parting surface according to claim 1, characterized in that: The sand and slag generated by machining is removed by at least one of vacuum extraction, gas purging or mechanical dumping.

4. The method for making a sand mold without a parting surface according to claim 1, characterized in that: A layer of coating is brushed or sprayed on the surface of the integral cavity.

5. The method for making a sand mold without a parting surface according to claim 1, characterized in that: The machining is CNC machining, and the CNC machining is at least one of electric spark machining, laser machining, and CNC machining; the modeling mixture is used to seal the tool inlet and outlet.

6. The method for making a sand mold without a parting surface according to claim 1, characterized in that: Formulate a strategy for machining the integral sand blank according to the designed casting structure, exhaust structure, feeding riser structure and runner structure; Among them, when formulating the strategy for machining the integral sand blank, the designed cooling structure is taken into consideration, the cooling opening positions on the surface of the integral sand blank are planned, and the surface and the interior of the integral sand blank are machined to form cooling openings and cooling channels.

7. A sand mold without parting surface, characterized in that: The sand mold without a parting surface is manufactured by the method for manufacturing a sand mold without a parting surface according to any one of claims 1 to 6.

8. A sand casting method without parting surface, characterized in that: The sand casting method without a parting surface is operated based on the sand mold without a parting surface according to claim 7, and the sand casting method without a parting surface comprises the following steps: Step 1: Smelting metal raw materials to obtain metal melt; Step 2: pouring the molten metal into the integral cavity of the sand mold without a parting surface through the outer gate and the runner to fill the integral cavity; Step 3: After the metal melt solidifies and cools, the sand is removed and the casting is obtained after cleaning.

9. A parting surface-free sand casting method according to claim 8, characterized in that: The cooling structure is used to regulate the solidification process of the metal melt in the integral cavity.

10. A casting, characterized in that: The casting is prepared by the sand casting method without parting surface according to any one of claims 8 to 9.

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