A sand mold without parting surface, and a method for manufacturing and casting the same

Abstract

The application discloses a sand mold without parting surface and a manufacturing and casting method thereof and a casting, and belongs to the casting technical field. First, a modeling mixture is used to manufacture an integral green sand blank, and the integral sand blank is dried to obtain an integral sand blank, then the integral sand blank is machined based on the idea of subtractive manufacturing, and on the basis, the near net shape is realized to integrally model the sand mold without parting surface, and the casting is carried out by using the sand mold without parting surface to obtain the casting. The application does not need to manufacture a mold sample and a core box, and does not have the assembling process of the parting and the sand mold and the sand core, thereby simplifying the casting process and the mold structure design, avoiding the problems of the size and shape deviation of the casting caused by the assembling dislocation during the molding or the floating of the mold core during the casting. The formed casting has high size precision, accurate shape, high material utilization rate and small subsequent mechanical machining allowance, and the casting production cycle is short and the process yield is high, so that the production cost is greatly reduced. The application is especially suitable for the sand mold casting of the complex and precise casting.

Description

Technical Field

[0001] This invention belongs to the field of casting technology, specifically relating to a sand mold without a parting surface, its manufacturing and casting method, and castings, which is particularly suitable for sand casting of complex and precision castings. Background Technology

[0002] Sand casting is currently the most widely used casting method, with over 80% of castings completed using this method. The main processes of traditional sand casting include pattern making, preparation of the molding mixture, molding, mold removal, core making, core placement, mold assembly, melting, pouring, sand removal, and cleaning. Furthermore, the mold removal process often involves factors such as draft angle and sand removal. In traditional sand casting, to facilitate the removal of the pattern or core during molding, a complete sand mold is usually divided into two or more halves. Each half or multiple half-sand mold must have a contacting and mating surface, known as the parting line. The mold is then assembled by tightly fitting the two halves or multiple half-sand molds together at the parting line. In traditional sand casting, defects and scrap are easily caused by factors such as mold removal, core setting, and mold assembly. This is especially true for sand casting of complex and precision parts, where misalignment, core deviation, or difficulty in achieving a tight seal during mold assembly can occur, leading to low assembly accuracy. This results in defects such as misshapen parts or thickening in the casting, severely affecting the dimensional accuracy and quality of the casting (e.g., uneven performance of different parts). Therefore, traditional sand casting, due to the need for parting surfaces, suffers from numerous processes, long mold-making cycles, poor dimensional accuracy and quality of castings, significant resource waste, and high production costs.

[0003] Therefore, there is an urgent need to develop a new sand casting method that does not require setting a parting surface, in order to improve the dimensional accuracy and quality of sand castings, reduce scrap rate, shorten production cycle and reduce manufacturing cost. Summary of the Invention

[0004] The purpose of this invention is to provide a sand mold without a parting surface, its fabrication and casting method, and the resulting casting. This effectively solves the problems caused by the presence of a parting surface in traditional sand casting, and is particularly suitable for sand casting of complex and precision castings. First, a molding mixture is used to create a monolithic green sand billet, which is then dried to obtain the monolithic billet. Then, based on the concept of subtractive manufacturing, the interior of the monolithic billet is machined. Based on this, a near-net-shape monolithic molding without a parting surface is achieved, breaking through the traditional practice of selecting a parting surface in current sand casting, and revolutionizing traditional sand casting technology.

[0005] According to a first aspect of the present invention, a method for manufacturing a sand mold without a parting line is provided, the method comprising the following steps:

[0006] Step 1: Prepare the molding mixture;

[0007] Step 2: Use the aforementioned molding mixture to produce a complete raw sand blank;

[0008] Step 3: Dry the integral raw sand blank to obtain an integral sand blank;

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

[0010] Step 5: Based on the established strategy, plan the tool entry / exit positions, vent positions, riser positions, and external gate positions on the surface of the integral sand blank;

[0011] Step 6: Based on the planned positions of the tool inlet / outlet, the vent, the riser, and the external gate, machine the surface of the integral sand blank to form the tool inlet / outlet, the vent, the riser, and the external gate;

[0012] Step 7: The cutting tool of the machining equipment is used to machine and subtract material from the inside of the integral sand blank through the tool inlet and outlet to form an integral cavity, and the venting channel, riser channel and gating are machined to realize the integral shape of the integral sand blank without parting surface;

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

[0014] Furthermore, the raw materials used in the molding mixture include at least raw sand, binder, and water. The raw sand is at least one of silica sand, quartz sand, resin sand, glass sand, clay sand, chromite sand, alumina sand, water glass sand, limestone sand, vacuum zircon sand, coal gangue sand, Luoyang 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.

[0015] Furthermore, the shape of the integral raw sand blank is a cube, cylinder, sphere, or irregular shape, and the manufacturing method is at least one of handmade, machine-made, or 3D printed.

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

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

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

[0019] Furthermore, the machining is CNC machining, which is at least one of electrical discharge machining, laser machining, and CNC machining.

[0020] Furthermore, based on the designed casting structure, venting structure, feeding riser structure, and gating structure, a strategy for machining the integral sand billet is formulated;

[0021] In formulating the strategy for machining the integral sand blank, the designed cooling structure is taken into account, the location of the cooling inlets on the surface of the integral sand blank is planned, and the surface and interior of the integral sand blank are machined to form cooling inlets and cooling channels.

[0022] According to a second aspect of the present invention, a non-partitioned surface sand mold is provided, wherein the non-partitioned surface sand mold is manufactured using the non-partitioned surface sand mold manufacturing method described in any of the above aspects.

[0023] According to a third aspect of the present invention, a method for sand casting without a parting line is provided. The method is based on the operation described above using a sand casting without a parting line, and includes the following steps:

[0024] Step 1: Melt the metal raw materials to obtain molten metal;

[0025] Step 2: Pour the molten metal through the external gate and the runner into the integral cavity of the sand mold without a parting surface, filling the integral cavity;

[0026] Step 3: After the molten metal solidifies and cools, it is removed from the sand and cleaned to obtain a casting.

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

[0028] According to a fourth aspect of the present invention, a casting is provided, the casting being prepared by a sand casting method without parting lines as described in any of the preceding aspects.

[0029] The beneficial effects of this invention are:

[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 not having 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. It can design highly complex castings, and will not have casting defects and scrap problems such as uneven wall thickness and dimensional deviation caused by inaccurate sand core size or inaccurate core position and insufficient mold assembly accuracy in traditional sand casting. It also avoids the problem of inconsistent sand mold quality caused by the separate production of each sand mold in traditional sand casting.

[0031] (2) The sand mold making method of the present invention does not require the prior production of the pattern, core box, etc. required for traditional modeling. It omits the processes of mold taking, core making, core setting and mold assembly, 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 troublesome production of each sand mold, long process and high cost in traditional sand mold combination, as well as the cumbersome process and difficulty in accurate alignment caused by the machining of the front and back sides of the sand mold, and the misalignment and insufficient assembly accuracy during mold assembly.

[0032] (3) The sand casting method without parting line of the present invention is a new sand casting method with near-zero allowance and precise forming. It eliminates the need for mold removal, parting line, and sand core, realizing sand casting without parting line, i.e., integral molding sand casting. The formed castings are free of flash, burrs, and draft angles, and reduce dimensional errors, casting defects, and scrap caused by mold removal, mold assembly, or core combination in traditional sand casting. Therefore, the castings have high dimensional accuracy and the characteristics of precision castings. It can partially replace precision casting, greatly reducing the weight of the casting blank and the subsequent machining allowance is small (the machining allowance can be reduced by more than 60%), reducing the cost of casting machining. Compared with traditional sand casting, the casting machining time is reduced by 40% to 50%, shortening the production cycle. The process technology is easy to master and facilitates the realization of mechanized automated production. The process yield 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 castings of the present invention are free of flash and burrs, have high dimensional accuracy and accurate shape, reduce the amount of cleaning and grinding work by more than 50%, have uniform performance of each part, good overall internal and external quality, and low manufacturing cost. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart of the process for manufacturing sand molds without parting lines according to the present invention. Detailed Implementation

[0036] The present invention will be described in detail below with reference to the embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make non-essential improvements and adjustments based on the content of the present invention.

[0037] The technical solution of this invention first provides a method for making sand molds without parting lines, such as... Figure 1 As shown, it includes the following steps:

[0038] S1: Prepare the molding mixture.

[0039] In a preferred embodiment, in step S1, the raw materials used in 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, chromite sand, alumina sand, water glass sand, limestone sand, vacuum zircon sand, coal gangue sand, Luoyang ore sand, coated sand, bleached 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: Use the aforementioned molding mixture to make an integral raw sand blank.

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

[0042] S3: Dry the whole raw sand blank to obtain a whole sand blank.

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

[0044] In a preferred embodiment, a strategy for machining the integral sand billet is formulated based on the designed casting structure, venting structure, feeding riser structure, and gating structure.

[0045] In formulating the strategy for machining the integral sand blank, the designed cooling structure is taken into account, the location of the cooling inlets on the surface of the integral sand blank is planned, and the surface and interior of the integral sand blank are machined to form cooling inlets and cooling channels.

[0046] In a preferred embodiment, the machining is CNC machining, which is at least one of electrical discharge machining, laser machining, and CNC machining.

[0047] S5: Based on the established strategy, plan the tool entry / exit position, vent position, riser position, and external gate position on the surface of the integral sand blank.

[0048] S6: Based on the planned positions of the tool inlet / outlet, the vent, the riser, and the external gate, the surface of the integral sand blank is machined to form the tool inlet / outlet, the vent, the riser, and the external gate.

[0049] S7: The cutting tool of the machining equipment is used to machine and subtract material from the interior of the integral sand blank through the tool inlet and outlet to form an integral cavity, and the exhaust channel, riser channel and gating are machined to realize the integral sand blank without parting surface integral shape.

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

[0051] In a preferred embodiment, in step S7, a coating is brushed or sprayed onto the surface of the integral cavity.

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

[0053] In a preferred embodiment, in step S8, the shaping mixture is used to seal the tool inlet and outlet.

[0054] The present invention also provides a non-partitioned surface sand mold, which is manufactured using the non-partitioned surface sand mold manufacturing method described above.

[0055] The present invention further provides a method for sand casting without a parting surface, the method being based on the above-described sand casting without a parting surface, and comprising the following steps:

[0056] Step 1: Melt the metal raw materials to obtain molten metal;

[0057] Step 2: Pour the molten metal through the external gate and the runner into the integral cavity of the sand mold without a parting surface, filling the integral cavity;

[0058] Step 3: After the molten metal solidifies and cools, it is removed from the sand and cleaned to obtain a casting.

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

[0060] The present invention provides another casting, which is prepared by sand casting without parting surface as described above.

[0061] Example 1:

[0062] Engine cylinder block sand casting and casting.

[0063] Step 1: Select 50 / 100 mesh quartz sand, furan resin, curing agent, silane and water to prepare the molding mixture;

[0064] Step 2: Using the aforementioned molding mixture, integral raw sand blanks are produced by machine;

[0065] Step 3: Dry the integral raw sand blank to obtain an integral sand blank;

[0066] Step 4: Based on the designed engine cylinder block casting structure, exhaust structure, feeding riser structure, cooling structure, and gating structure, formulate a strategy for CNC machining of the integral sand blank;

[0067] Step 5: Based on the established strategy, plan the tool entry / exit position, vent position, riser position, cooling channel position, and external gate position on the surface of the integral sand blank;

[0068] Step 6: Machining the surface of the integral sand blank to form the tool inlet / outlet, vent, riser, cooling channel, and external gate;

[0069] Step 7: The CNC machining tool is used to perform CNC subtractive manufacturing on the interior of the integral sand blank through the tool inlet and outlet to form an integral cavity. Alcohol-based graphite coating is sprayed on the surface of the integral cavity, and exhaust channels, riser channels, cooling channels and gating are machined to achieve the integral shape of the integral sand blank without parting surface.

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

[0071] The casting process using the aforementioned parting-free engine cylinder block sand mold involves the following steps:

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

[0073] Step 2: Pour the gray cast iron HT250 molten metal through the external gate and the runner into the integral cavity of the sand mold without parting surface, filling the integral cavity;

[0074] Step 3: Utilize 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, it is removed from the sand and cleaned to obtain the engine cylinder block casting.

[0076] Example 2:

[0077] Sand casting and casting of automobile engine cylinder heads.

[0078] Step 1: Select 50 / 100 mesh silica sand, water glass, bentonite, dispersant and water to prepare the molding mixture;

[0079] Step 2: Using the aforementioned molding mixture, create a complete raw sand blank by hand;

[0080] Step 3: Dry the integral raw sand blank to obtain an integral sand blank;

[0081] Step 4: Based on the designed cylinder head casting structure, exhaust structure, feeding riser structure, cooling structure, and gating structure of the automobile engine, formulate a strategy for CNC machining of the integral sand blank;

[0082] Step 5: Based on the established strategy, plan the tool entry / exit position, vent position, riser position, cooling channel position, and external gate position on the surface of the integral sand blank;

[0083] Step 6: Machining the surface of the integral sand blank to form the tool inlet / outlet, vent, riser, cooling channel, and external gate;

[0084] Step 7: The CNC machining tool is used to perform CNC subtractive manufacturing on the interior of the integral sand blank through the tool inlet and outlet to form an integral cavity. Alcohol-based graphite coating is sprayed on the surface of the integral cavity, and exhaust channels, riser channels, cooling channels and gating are machined to achieve the integral shape of the integral sand blank without parting surface.

[0085] Step 8: Seal the tool inlet and outlet to obtain a sand mold for an automotive engine cylinder head without parting surface, which has the integral cavity inside.

[0086] The casting process for the automotive engine cylinder head using the aforementioned sand mold without parting surface is as follows:

[0087] Step 1: Melt vermicular graphite cast iron RuT350 to obtain vermicular graphite cast iron RuT350 melt;

[0088] Step 2: Pour the vermicular graphite cast iron RuT350 melt through the external gate and the gating system into the integral cavity of the sand mold without parting surface, filling the integral cavity;

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

[0090] Step 4: After the vermicular graphite cast iron RuT350 melt solidifies and cools, it is removed from the sand and cleaned to obtain the automobile engine cylinder head casting.

[0091] Example 3:

[0092] Transmission housing sand mold and casting.

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

[0094] Step 2: Using the aforementioned molding mixture, integral raw sand blanks are produced by machine;

[0095] Step 3: Dry the integral raw sand blank to obtain an integral sand blank;

[0096] Step 4: Based on the designed transmission housing casting structure, exhaust structure, feeding riser structure, cooling structure, and gating structure, formulate a strategy for CNC machining of the integral sand blank;

[0097] Step 5: Based on the established strategy, plan the tool entry / exit position, vent position, riser position, cooling channel position, and external gate position on the surface of the integral sand blank;

[0098] Step 6: Machining the surface of the integral sand blank to form the tool inlet / outlet, vent, riser, cooling channel, and external gate;

[0099] Step 7: The CNC machining tool is used to perform CNC subtractive manufacturing on the interior of the integral sand blank through the tool inlet and outlet to form an integral cavity. Alcohol-based zircon powder coating is sprayed on the surface of the integral cavity, and exhaust channels, riser channels, cooling channels and gating are machined to achieve the integral sand blank without parting surface integral shaping.

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

[0101] The casting process for the gearbox housing using the aforementioned sand mold without a parting line is as follows:

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

[0103] Step 2: Pour the molten ductile iron QT500-7 through the external gate and the runner into the integral cavity of the sand mold without parting surface, filling the integral cavity;

[0104] Step 3: Utilize 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, it is removed from the sand and cleaned to obtain the gearbox housing casting.

[0106] In summary, the technical solution of this invention provides a sand mold without a parting surface, its fabrication and casting method, and the resulting casting. First, a monolithic green sand billet is made using a molding mixture and dried to obtain the monolithic sand billet. Then, based on the concept of subtractive manufacturing, the interior of the monolithic sand billet is machined. Based on this, a near-net-shape monolithic molding without a parting surface is achieved. The casting is then obtained using the sand mold without a parting surface. This invention eliminates the need for pattern making and core box making, and avoids the assembly processes of parting, sand mold, and sand core, simplifying the casting process and mold structure design. It avoids problems such as misalignment during mold assembly or core floating during casting, which can cause dimensional and shape deviations in the casting. The resulting castings have high dimensional accuracy, accurate shape, high material utilization, small subsequent machining allowance, short casting production cycle, and high process yield, significantly reducing production costs. It is particularly suitable for sand casting of complex and precision castings.

[0107] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0108] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0109] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method of making a sand mold without parting surface, characterized by, The non-parting surface sand mold is a whole molding sand mold without a parting surface, and the non-parting surface sand mold manufacturing method does not need to make a mold sample and a core box, and omits the mold taking, core making, core setting and mold closing processes; the non-parting surface sand mold manufacturing method comprises the following steps: Step 1: preparing a molding mixture; Step 2: using the molding mixture to make a whole 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 whole sand blank; Step 5: planning the tool access position, exhaust port position, riser position and sprue position of the surface of the whole sand blank according to the formulated strategy; Step 6: machining the surface of the whole sand blank according to the planned tool access position, exhaust port position, riser position and sprue position to form a tool access, exhaust port, riser and sprue; Step 7: machining the inside of the whole sand blank through the tool access to form a whole cavity by subtractive manufacturing of the machining equipment, and machining an exhaust passage, riser passage and sprue to realize the whole molding of the whole sand blank without a parting surface; Step 8: sealing the tool access to obtain a non-parting surface sand mold with the whole cavity inside.

2. A method of making a split-free sand mold according to claim 1, wherein The raw materials used in the molding 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, chromium ore sand, pearl sand, water glass sand, limestone sand, vacuum zircon sand, coal gangue sand, lo ore sand, precoated 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 whole green sand blank is at least one of a cube, a cylinder, a sphere or a special-shaped body, and the manufacturing method is at least one of hand making, machine making or 3D printing.

3. The method of claim 1, wherein The sand slag generated by machining is removed by at least one of vacuum extraction, gas purging or mechanical pouring.

4. The method of claim 1, wherein A layer of paint is brushed or sprayed on the surface of the whole cavity.

5. The method of claim 1 wherein, The machining is numerical control machining, and the numerical control machining is at least one of electric spark machining, laser machining and numerical control machining; the tool access is sealed by using the molding mixture.

6. The method of making a sand mold without parting line according to claim 1, wherein According to the structure of the designed casting, exhaust structure, riser structure and sprue structure, a strategy for machining the whole sand blank is formulated; In formulating the strategy for machining the whole sand blank, the cooling channel position of the surface of the whole sand blank is planned by taking into account the designed cooling structure, and the surface and the inside of the whole sand blank are machined to form a cooling channel and a cooling passage.

7. A split-free sand mold characterized by comprising: The non-parting surface sand mold is manufactured by using the non-parting surface sand mold manufacturing method according to any one of claims 1 to 6.

8. A no-flash sand mold casting method characterized by, The non-parting surface sand mold casting method is operated based on the non-parting surface sand mold according to claim 7, and comprises the following steps: Step 1: smelting a metal raw material to obtain a metal melt; Step 2: pouring the metal melt into the integral cavity of the non-parting sand mold through the outer sprue and the runner, filling the integral cavity; Step 3: after the metal melt is solidified and cooled, the sand is shaken out, and the casting is obtained after cleaning.

9. A no-parting-face sand mold casting method according to claim 8, characterized by, The cooling structure is used to regulate the solidification process of the metal melt in the integral cavity.

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