Metal core disappearance method precoated sand casting process suitable for hollow metal casting

Abstract

The invention provides a metal core disappearance method precoated sand casting process suitable for a hollow metal casting. The metal core disappearance method precoated sand casting process comprises the following steps that a sand shell mold and a sand core mold of a hollow metal casting product are designed and manufactured according to the shape follow-up of the hollow metal casting product; according to the hollow position needed by the hollow metal casting, a metal core with a fixed point location is designed and manufactured in a shape follow-up mode; respectively manufacturing a precoated sand shell mold and a precoated sand core by using the sand shell mold mold and the sand core mold based on an injection molding machine; the precoated sand shell mold serves as a mold cavity, the metal core and the precoated sand core serve as a combined mold core, meanwhile, the metal core and the precoated sand core are arranged on the inner side and the outer side of the interior of the position needing to be hollow correspondingly, and the hollow metal casting is manufactured by pouring high-temperature molten steel, and the metal core is gradually melted and disappears to form an internal hollow structure after the high-temperature molten steel is poured. The problems that a metal mold core in a cast hollow metal casting is difficult to take out and complex and troublesome in treatment, and the cast hollow metal casting product is low in yield and has internal stress defects in quality can be solved; and meanwhile, the problems that the quality of a casting is damaged, the production efficiency is reduced and the environment is polluted due to the fact that the interior of the precoated sand mold core is cleaned in the later period can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of coated sand casting, and particularly to a metal core disappearing method coated sand casting process applicable to hollow metal castings. Background Art

[0002] Compared with solid structural parts, hollow structural parts often have better quality, lighter weight, lower internal stress of the product, and are not prone to serious problems of internal stress fracture when the load is large during use. For casting hollow structural parts, there are various methods, each with its own advantages and disadvantages. The coated sand casting of hollow metal castings has the advantage of low cost, but its process steps are complex, and the treatment of the core is crucial. The commonly used cores include metal cores and coated sand cores.

[0003] At present, when using a metal core to cast hollow metal castings, usually taking advantage of its high melting point characteristics, after casting is completed, the metal core is removed to form a hollow structure. However, there are problems such as difficult removal of the core and complex and troublesome treatment.

[0004] At present, when using a coated sand core to cast hollow metal castings, especially for a closed hollow structure, the core usually needs to be designed in the form of a core head so that after pouring is completed, the self-collapsing molding sand can be discharged from the position of the core head to form the required hollow structure. However, there are deficiencies such as damage to the quality of the casting, reduction in production efficiency, increase in operation difficulty, and environmental impact after the molding sand is washed and sucked out later.

[0005] In summary, there is an urgent need for a coated sand casting method that can cast high-quality hollow metal castings. Summary of the Invention

[0006] In view of the above problems, the embodiments of the present invention provide a metal core disappearing method coated sand casting process applicable to hollow metal castings, which can improve the yield rate of hollow metal casting products, eliminate internal stress defects in quality, improve the toughness and stability of products, and also has advantages such as low cost, high efficiency, energy conservation and environmental protection.

[0007] In order to achieve the above object, the embodiments of the present invention provide the following technical solutions: The embodiments of the present invention provide a metal core disappearing method coated sand casting process applicable to hollow metal castings, including the following steps: 1) Design and manufacture a sand shell mold and a sand core mold for the hollow metal casting product according to its shape; 2) Design and manufacture a metal core with fixed points according to the hollow position required for the hollow metal casting; 3) Use the sand shell mold and the sand core mold to respectively make a coated sand shell mold and a coated sand core based on a shot molding machine; 4) Use the coated sand shell mold as the cavity, and use the metal core and the coated sand core as a combined core. At the same time, arrange the metal core and the coated sand core inside and outside the required hollow position respectively. Pour high-temperature molten steel to obtain a hollow metal casting. Among them, the metal core gradually melts and disappears after the pouring of high-temperature molten steel is completed, forming an internal hollow structure.

[0008] As a further optional embodiment, in step 4), the melting point temperature of the metal core is 100 - 200 degrees Celsius lower than the temperature of the high-temperature molten steel / the melting point temperature of the hollow metal casting. The metal core is gradually melted and absorbed by the high-temperature molten steel wrapped around its outer periphery and disappears.

[0009] As a further optional embodiment, in step 4), when using the coated sand shell mold for casting, first load the coated sand core into the corresponding half of the coated sand shell mold, then fix the prefabricated metal core in this half of the coated sand shell mold, then combine the other half of the coated sand shell mold to form a complete cavity and tie and fix it. After that, pour the high-temperature molten steel slowly and evenly through the gating riser until the high-temperature molten steel reaches the top of the riser, and the pouring is completed.

[0010] As a further optional embodiment, in step 4), the metal core is installed at the central position corresponding to the internal closed cavity of the hollow metal casting.

[0011] As a further optional embodiment, the ratio range of the metal core to the circumferential dimension of the closed cavity is 0.4:1 - 0.8:1.

[0012] As a further optional embodiment, the size of the metal core is calculated and derived from the following heat formula In the formula, is the heat absorbed by the metal core from the high-temperature molten steel (unit: joule), is the mass of the metal core (unit: kilogram), is the specific heat capacity of the metal core (unit: joule / kilogram · degree Celsius), is the final temperature after the metal core melts (usually equal to the temperature of the high-temperature molten steel, unit: degree Celsius), is the initial temperature of the metal core (unit: degree Celsius), is the mass of the melted part of the metal core (unit: kilogram), which depends on the material and initial state of the metal core, is the latent heat of fusion of the metal core (unit: joule / kilogram), that is, the heat required for the metal to change from solid state to liquid state.

[0013] As a further optional embodiment, in step 1), when manufacturing the mold, a sand core fixing position and a metal core fixing position are reserved inside the sand shell mold for fixing and assembling the coated sand core at the sand core fixing position and connecting the metal core to the metal core fixing position through its fixing points in step 4).

[0014] As a further optional embodiment, in step 2), the material of the metal core is configured to be close to the material of the hollow metal casting, and the melting point temperature of the metal core is 100 - 200 degrees Celsius lower than that of the hollow metal casting, and it is manufactured by a modeling-based cutting and / or forging method.

[0015] As a further optional embodiment, in step 3), the sand shell mold and the sand core mold are respectively installed on a shot blasting molding machine, and then preheated, sand shot, and cured respectively, and then the prepared coated sand shell mold and coated sand core can be taken out for use.

[0016] Compared with the related technology, the metal core disappearing method coated sand casting process for hollow metal castings provided by the embodiments of the present invention uses a metal core that can automatically disappear, expands the proportion space range of the internal hollow structure of the hollow metal casting, and can minimize the overall weight while ensuring the external rigidity and strength of the product, avoid internal stress defects, improve the overall toughness and stability, improve the quality of the cast hollow metal casting products, especially the quality and yield of large-scale casting products. At the same time, it avoids the secondary processing and cleaning of the metal core, has higher casting efficiency, and is more energy-saving and environmentally friendly.

[0017] In addition to the technical problems solved by the embodiments of the present disclosure described above, the technical features constituting the technical solutions, and the beneficial effects brought by these technical features of the technical solutions, the other technical problems that can be solved by the metal core disappearing method coated sand casting process for hollow metal castings provided by the embodiments of the present disclosure, the other technical features included in the technical solutions, and the beneficial effects brought by these technical features will be further described in detail in the specific implementation manner. Brief Description of the Drawings

[0018] The present invention will be further described below with reference to the drawings and embodiments.

[0019] Figure 1 It is a schematic flow chart of the metal core disappearing method coated sand casting process for hollow metal castings provided by the embodiments of the present invention.

[0020] Figures 2-6 It is a schematic structural diagram of the bucket tooth coated sand shell mold in the metal core disappearing method coated sand casting process for hollow metal castings provided by the embodiments of the present invention, mainly showing the usage effect diagram of half of the bucket tooth coated sand shell mold; The meanings of the reference numerals in the drawings: 1 - Die tooth coated sand shell mold; 2 - Die tooth combined core; 21 - Die tooth metal core; 22 - Die tooth sand core.

[0021] Figures 7-10 It is a schematic structural diagram of a rough die tooth casting prepared by the metal core disappearing method coated sand casting process for hollow metal castings provided by an embodiment of the present invention; Meanings of the reference numerals in the figure: 3 - Rough die tooth casting; 31 - Die tooth internal hollow structure; 311 - Die tooth internal closed hollow structure; 312 - Die tooth internal open hollow structure. Detailed implementation manners

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] In the related art, when casting a hollow metal casting using a coated sand inner core, after pouring is completed, a hole will be left at the core head. After the internal cavity is cleaned by high pressure, the internal sand is then sucked out. After that, the hole needs to be sealed by welding or other methods (this will also increase the additional cost and risk of processing), and finally the casting of the hollow object is completed. However, during the process of cleaning and sucking out the sand in the metal hollow part, there are disadvantages such as damaged casting quality, reduced production efficiency, increased operation difficulty, and environmental impact. Specifically: 1) Damaged casting quality Surface defects: During the process of cleaning and sucking out the sand, if the operation is improper, it may cause scratches, depressions, or other damages on the casting surface, thus affecting the appearance quality of the casting.

[0024] Internal defects: If the sand is not completely cleaned, the remaining sand may form inclusions or pores inside the casting, resulting in unstable internal quality of the casting and reducing its mechanical properties and service life.

[0025] The above defects lead to a low finished product rate of the cast hollow metal casting products and problems with internal stress defects in the quality.

[0026] 2) Reduced production efficiency Cleaning time-consuming: Cleaning the sand in the metal hollow part takes a certain amount of time. Especially when the casting structure is complex or the sand is difficult to remove, the cleaning time may be longer, thus reducing the production efficiency.

[0027] Difficulty in suction: For some hollow parts made of metal, especially those with complex shapes or small sizes, it may be difficult to effectively suck out the molding sand, which will also increase the operation difficulty and time consumption.

[0028] 3) Increased operation difficulty High technical requirements: Cleaning and sucking out the molding sand require a certain technical level and operation experience to ensure the quality of castings and production efficiency. If the operator is unskilled or lacks experience, it may lead to operation errors or a decrease in the quality of castings.

[0029] Strong equipment dependence: Cleaning and sucking out the molding sand usually rely on specific equipment, such as cleaning machines, sand suction machines, etc. If these equipment malfunction or are not properly maintained, it may affect the cleaning effect and production efficiency.

[0030] 4) Environmental impact: Wastewater treatment: The wastewater generated during the cleaning process may contain harmful substances and needs to be properly treated to meet environmental protection requirements. If not treated properly, it may cause environmental pollution.

[0031] Waste treatment: The molding sand removed by cleaning and other possible wastes also need to be properly treated to avoid adverse effects on the environment.

[0032] In related technologies, when casting hollow metal castings using a metal core, during the casting process, the metal core may get stuck or deformed due to various reasons such as thermal expansion and casting pressure, resulting in difficulty in removing it from the casting. Therefore, there are problems such as difficult removal of the core and complex and troublesome processing.

[0033] In view of this, the embodiments of the present invention provide a metal core disappearing method coated sand casting process applicable to hollow metal castings. By setting a combined core with a metal core that can be absorbed and disappeared by high-temperature molten steel, and using the asynchronous melting of temperature differences, an internal hollow structure with a smooth interior is formed. This round and regular internal hollow structure will have greater advantages in casting large metal hollow components. Therefore, it can improve the quality of cast hollow metal products, especially the quality and yield of large casting products. Furthermore, many originally solid products can, according to needs, utilize the metal core disappearing method coated sand casting process of the embodiments of the present invention, combine and exert the performance of "chill", add a closed hollow structure inside, and make an internal hollow structure with a larger spatial range, achieving the purpose of improving the toughness of metal casting products while ensuring rigidity and strength, having better stability, saving materials, and making the products lighter. Since the metal core is absorbed and disappears after casting, there is no need for secondary processing and cleaning, nor for hole sealing treatment. Therefore, the metal core disappearing method coated sand casting process of the embodiments of the present invention can also make the casting cost lower, the casting efficiency higher, and more energy-saving and environmentally friendly.

[0034] As Figure 1 shown, an embodiment of the present invention provides a metal core lost method coated sand casting process applicable to hollow metal castings, including the following steps: 1) Design and manufacture a sand shell mold and a sand core mold according to the shape of the hollow metal casting product; 2) Design and manufacture a metal core with fixed points according to the required hollow position of the hollow metal casting; 3) Use the sand shell mold and the sand core mold to make coated sand shells and coated sand cores respectively based on a shot blasting molding machine; 4) Use the coated sand shell as the cavity, and use the metal core and the coated sand core as a combined core. At the same time, arrange the metal core and the coated sand core on the inner and outer sides of the required hollow position respectively. Pour high-temperature molten steel to obtain a hollow metal casting. Among them, the metal core gradually melts and disappears after the pouring of high-temperature molten steel is completed, forming an internal hollow structure.

[0035] In step 1) of the embodiment of the present invention, during mold manufacturing, a sand core fixing position and a metal core fixing position are designed and reserved inside the sand shell mold for fixing and assembling the coated sand core at the sand core fixing position and connecting the metal core to the metal core fixing position through its fixing points in step 4).

[0036] In step 2) of the embodiment of the present invention, the material of the metal core is configured to be close to the material of the hollow metal casting, and the melting point temperature of the metal core is 100 - 200 degrees Celsius lower than the melting point temperature of the hollow metal casting, and it is manufactured by a cutting and / or forging method based on modeling.

[0037] Specifically, when implementing, the selection of the metal core should consider the material, quality and size. In terms of material, according to the material of the casting, the material of the metal core that conforms to the casting material can be selected. The basic principle is that the material of the metal core is close to the casting material. For example, when the material of the hollow metal casting is cast steel, the material of the metal core can be selected as ductile iron, so that its melting point is slightly lower than the melting point temperature of the casting, generally 100 - 200 degrees Celsius lower. After pouring high-temperature molten steel, the entire cavity will be filled. This temperature difference can make the metal core and the hollow metal casting out of sync during the melting process. The metal inner core is wrapped and melted by the molten steel and is gradually absorbed, thereby forming an internal space with a smooth inner wall, not only reducing the overall quality, but also improving the toughness of the product.

[0038] In terms of quality and size, the quality and size parameters of the metal inner core can be deduced and calculated through the following heat calculation formula.

[0039]

[0040] In the formula, is the heat absorbed by the metal core from the high-temperature molten steel (unit: joule), is the mass of the metal core (unit: kilogram), is the specific heat capacity of the metal core (unit: joule / (kilogram·degree Celsius)), is the final temperature after the metal core melts (usually equal to the temperature of the high-temperature molten steel, unit: degree Celsius), is the initial temperature of the metal core (unit: degree Celsius), is the mass of the melted part of the metal core (unit: kilogram), which depends on the material and initial state of the metal core, is the latent heat of fusion of the metal core (unit: joule / kilogram), that is, the heat required for the metal to change from solid state to liquid state.

[0041] The above heat calculation formula represents the heat absorbed by the metal core from the high-temperature molten steel. Since the melting of the metal core is achieved through the heat exchange between the metal core and the poured high-temperature molten steel, that is, through heat conduction. Considering that in shell molding casting, it is generally slowly and stably poured in a certain closed space, the influence of heat radiation and convection can be ignored. Also, since the thermophysical properties (such as thermal conductivity, density, specific heat capacity) of the metal core and the high-temperature molten steel are known, according to the characteristic of the fixed melting point of the metal core, the heat required for its complete melting is fixed, thus the above formula is obtained.

[0042] The calculation formula for the heat released by the required high-temperature molten steel is as follows: Wherein: is the heat released by the high-temperature molten steel (unit: joule), is the mass of the high-temperature molten steel in contact with the metal core (unit: kilogram), is the specific heat capacity of the high-temperature molten steel (unit: joule / (kilogram·degree Celsius)), is the initial temperature of the high-temperature molten steel (unit: degree Celsius).

[0043] Therefore, the heat released by the high-temperature molten steel should be greater than or equal to so that the internal metal core can completely absorb heat and melt.

[0044] In step 4) of the embodiment of the present invention, the metal core is preferably installed at the central position corresponding to the internal closed cavity of the hollow metal casting. Further preferably, the ratio range of the metal core to the surrounding of the closed cavity is 0.4:1 - 0.8:1. After such design, the closed hollow structure prepared after the metal core is absorbed is exactly at the appropriate central position of the hollow metal casting, and the outer edges have symmetrical thicknesses, and the best toughness and rigidity effects can be obtained, and the effect of ensuring that the overall quality is very light can be taken into account.

[0045] In step 3) of the embodiment of the present invention, the pre-coated sand shell mold and the sand core mold are respectively installed on a shot-pressure molding machine, and then respectively pre-heated, sand-shot, and cured, and then the prepared pre-coated sand shell and pre-coated sand core can be taken out for standby.

[0046] In step 4) of the embodiment of the present invention, the melting point temperature of the metal core is 100-200 degrees Celsius lower than the temperature of the high-temperature molten steel / the melting point temperature of the hollow metal casting, and the metal core is gradually melted and absorbed by the high-temperature molten steel wrapped around its outer periphery and disappears.

[0047] In step 4) of the embodiment of the present invention, when casting using the pre-coated sand shell mold, first install the pre-coated sand core into the corresponding half of the pre-coated sand shell mold, then fix the pre-prepared metal core in this half of the pre-coated sand shell mold, then combine the other half of the pre-coated sand shell mold together to form a complete cavity and tie and fix it. After that, slowly and evenly pour the high-temperature molten steel through the pouring riser until the high-temperature molten steel reaches the top of the riser, and the pouring is completed. Embodiment 1

[0048] Figure 2 is a perspective view of half of the pre-coated sand shell mold 1 for the bucket tooth, Figure 3 is a front view of half of the pre-coated sand shell mold 1 for the bucket tooth, Figure 4 is a side view of half of the pre-coated sand shell mold 1 for the bucket tooth, Figure 5 is a top view of half of the pre-coated sand shell mold 1 for the bucket tooth, Figure 6 is a bottom view of half of the pre-coated sand shell mold 1 for the bucket tooth; Figure 7 is a perspective view of the rough casting 3 of the bucket tooth, Figure 8 is a front view of the rough casting 3 of the bucket tooth, Figure 9 is a half-sectional view of the rough casting 3 of the bucket tooth, Figure 10 Figure 8 The sectional view at A-A in

[0049] Referring to Figures 2 to 10 , in this Embodiment 1, the hollow metal casting is a cast steel bucket tooth to specifically introduce the metal core disappearing method pre-coated sand casting process of the present invention, which is as follows: Step 1) According to the actual product size of the cast steel bucket tooth, design the bucket tooth sand shell mold and the bucket tooth sand core 22 mold in a shape-following manner; when manufacturing the mold, design and reserve the structure of the sand core fixing position and the metal core fixing position in the bucket tooth sand shell mold, so that the metal core can be stably fixed inside during the later assembly after the bucket tooth pre-coated sand shell mold 1 is completed; Step 2) Through the hollow position required by the cast steel bucket tooth product, design the shape-following size (for example, a uniform ratio can be formed in the surrounding solid space and a predetermined thickness can be maintained) and the fixing points (such as the top fixing of the metal core inside the bucket tooth and the metal core fixing column, and the flat conical design of the metal core) of the bucket tooth metal core 21 according to the spatial ratio of its hollow position.

[0050] For the material of the installed metal core 21 of the bucket tooth, according to the material of the cast steel bucket tooth, ductile iron material with performance close to it can be selected. Its melting point temperature is slightly lower than the temperature of the high-temperature molten steel, which is beneficial for the metal core 21 of the bucket tooth to absorb heat and melt better and be absorbed.

[0051] Step 3): Install the bucket tooth sand shell mold on the injection molding machine, heat it using the electric heating tube of the equipment itself. After reaching the set temperature, inject the coated sand into the mold cavity for curing. The curing time is determined according to the size of the sand shell. After curing is completed, take out the bucket tooth coated sand shell mold 1 for standby; replace the bucket tooth sand shell mold with the bucket tooth sand core 22 mold, and the preparation of the bucket tooth sand core 22 can be completed.

[0052] Step 4): Casting: Refer to Figures 2-6 , when using the bucket tooth coated sand shell mold 1 for casting, first install the bucket tooth sand core 22 into the corresponding half of the coated sand shell mold (i.e., corresponding to the non-closed cavity of the casting), then fix the previously set metal core 21 of the bucket tooth at the set fixed position in this half of the coated sand shell mold (i.e., corresponding to the center part of the closed cavity inside the casting). Thus, the installation of the combined core 2 of the bucket tooth is completed. Then, combine the other half of the bucket tooth coated sand shell mold 1 to form a complete cavity, then carry out bundling and fixing. After that, pour high-temperature molten steel (such as 1650 degrees) through the gating riser until the molten steel reaches the top of the riser. The pouring is completed. During the operation, the injection of high-temperature molten steel cannot be too fast, and it should gradually and continuously evenly wrap the entire metal core 21 of the bucket tooth, so that the metal core 21 of the bucket tooth gradually absorbs heat to reach the melting point and melts and is absorbed.

[0053] Refer to Figures 7-10 , after the pouring is completed, open the mold to obtain the roughcast 3 of the bucket tooth casting. Experiments prove that the roughcast 3 of the bucket tooth casting prepared by the process of Embodiment 1 of the present invention forms a hollow structure 31 inside the bucket tooth. This hollow structure 31 inside the bucket tooth includes both a closed hollow structure 311 inside the bucket tooth and an open hollow structure 312 inside the bucket tooth. Among them, the open hollow structure 312 inside the bucket tooth corresponds to the bucket tooth slot forming the bucket tooth casting, and the position of the original solid structure innovatively forms a closed hollow structure 311 inside the bucket tooth, solving the problem of low toughness caused by the overall weight being too heavy and the defect of internal stress, and at the same time ensuring the external rigidity and strength of the product.

[0054] The above is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Any simple modification and equivalent change made to the above embodiments based on the technical essence of the present invention all fall within the protection scope of the present invention.

Claims

1. A lost metal core furan resin sand casting process applicable to hollow metal castings, characterized in that, It includes the following steps: 1) Design and manufacture the sand shell mold and the sand core mold according to the shape of the hollow metal casting product; 2) Design and manufacture a metal core with fixed points according to the hollow position required for the hollow metal casting; 3) Use the sand shell mold and the sand core mold to make a coated sand shell mold and a coated sand core respectively based on a shot-pressure molding machine; 4) Use the coated sand shell mold as the cavity, and use the metal core and the coated sand core as a combined core. At the same time, arrange the metal core and the coated sand core on the inner side and the outer side of the required hollow position respectively, and obtain the hollow metal casting by pouring high-temperature molten steel. Among them, the metal core gradually melts and disappears after the pouring of the high-temperature molten steel is completed, forming an internal hollow structure.

2. The lost metal core coated sand casting process applicable to hollow metal castings according to claim 1, characterized in that, In step 4), the melting point temperature of the metal core is 100 - 200 degrees Celsius lower than the temperature of the high-temperature molten steel, and the metal core is gradually melted and absorbed by the high-temperature molten steel wrapped around its outer periphery and disappears.

3. The lost metal core resin coated sand casting process for hollow metal castings according to claim 1 or 2, characterized in that, In step 4), when casting using the coated sand shell mold, first install the coated sand core into the corresponding half of the coated sand shell mold, then fix the prefabricated metal core in this half of the coated sand shell mold, then combine the other half of the coated sand shell mold to form a complete cavity and bind and fix it. After that, pour the high-temperature molten steel slowly and evenly through the pouring riser until the high-temperature molten steel reaches the top of the riser, and the pouring is completed.

4. The metal core lost method coated sand casting process applicable to hollow metal castings according to claim 3, characterized in that, In step 4), the metal core is installed at the central position corresponding to the internal closed cavity of the hollow metal casting.

5. The lost metal core coated sand casting process applicable to hollow metal castings according to claim 4, characterized in that, The ratio of the circumferential dimension of the metal core to the closed cavity ranges from 0.4:1 to 0.8:

1.

6. The lost metal core coated sand casting process applicable to hollow metal castings according to claim 5, characterized in that, The size of the metal core is derived by calculating according to the following heat formula Wherein, is the heat absorbed by the metal core from the high-temperature molten steel (unit: joule), is the mass of the metal core (unit: kilogram), is the specific heat capacity of the metal core (unit: joule / (kilogram·degree Celsius)), is the final temperature after the metal core melts (usually equal to the temperature of the high-temperature molten steel, unit: degree Celsius), is the initial temperature of the metal core (unit: degree Celsius), is the mass of the melted part of the metal core (unit: kilogram), which depends on the material and initial state of the metal core, is the latent heat of fusion of the metal core (unit: joule / kilogram), that is, the heat required for the metal to change from solid state to liquid state.

7. The lost metal core coated sand casting process for hollow metal castings according to claim 1, characterized in that, In step 1), during mold manufacturing, design and reserve a sand core fixing position and a metal core fixing position inside the sand shell mold for fixing and assembling the coated sand core at the sand core fixing position and connecting the metal core to the metal core fixing position through its fixing points in step 4).

8. The lost metal core coated sand casting process applicable to hollow metal castings according to claim 1, characterized in that, In step 2), the material of the metal core is configured to be close to the material of the hollow metal casting, and the melting point temperature of the metal core is 100 - 200 degrees Celsius lower than the melting point temperature of the hollow metal casting, and it is manufactured by a cutting and / or forging method based on modeling.

9. The lost metal core coated sand casting process for hollow metal castings according to claim 1, characterized in that, In step 3), install the sand shell mold and the sand core mold on the shot-pressure molding machine respectively, and after preheating, sand shooting, and curing respectively, the made coated sand shell mold and coated sand core can be taken out for use.

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