Metal part and casting method thereof

Abstract

The invention relates to a metal piece and a casting method thereof.The casting method of the metal piece comprises the following steps that a wax mold module is obtained, and the wax mold module comprises a casting wax mold and a pouring wax mold connected with the casting wax mold; wherein a pouring gate in the pouring wax mold is in an hourglass shape, and the height of the pouring gate is 20-50 mm; slurry adhering and sand hanging are conducted on the wax mold module, and a mold shell is formed on the surface of the wax mold module; the wax mold module is removed; deoxidizing and deslagging the molten metal liquid, and introducing protective gas from the side surface of a container for bearing the molten metal liquid at the flow rate of 400L / min-500L / min; and molten metal liquid obtained after deoxidation and deslagging is poured into the mold shell obtained after the wax mold set is removed, the mold shell is filled with the molten metal liquid, cooling forming is conducted, and the metal part is obtained. The casting method of the metal part is beneficial to improving the surface defects of the metal part and improving the cleanliness.

Description

Technical Field

[0001] The present application relates to the field of casting, and in particular to a metal part and a casting method thereof. Background Art

[0002] Metals such as stainless steel have the advantages of strong corrosion resistance and high strength, and are the main materials for special-shaped parts. However, the structure of special-shaped parts is complex and cannot be formed by stamping, welding, etc., and needs to be formed by investment casting. However, the current stainless steel investment castings still have the following problems: the surface is prone to defects such as inclusions, cold shuts, and pores, and it is impossible to achieve high cleanliness. Summary of the invention

[0003] Based on this, the present application provides a casting method for metal parts, which is beneficial to improving surface defects and improving cleanliness.

[0004] In addition, another aspect of the present application provides a metal part.

[0005] A method for casting a metal part comprises the following steps:

[0006] Obtaining a wax mold set, the wax mold set comprising a casting wax mold and a pouring wax mold connected to the casting wax mold; wherein the gate in the pouring wax mold is hourglass-shaped and has a height of 20 mm to 50 mm;

[0007] The wax mold module is subjected to slurry gluing and sanding to form a mold shell on the surface of the wax mold module;

[0008] removing the wax model assembly;

[0009] Deoxidizing and deslagging the molten metal, while introducing a protective gas at a flow rate of 400 L / min to 500 L / min from the side of the container carrying the molten metal;

[0010] The molten metal liquid after deoxidation and slag removal is poured into the mold shell after the wax mold assembly is removed, so that the molten metal liquid fills the mold shell, and is cooled and formed to obtain a metal part.

[0011] Optionally, the maximum width of the gate is R1, the minimum width is R2, and R2 / R1 is 0.4-0.6.

[0012] Optionally, the inner wall of the gate is arc-shaped.

[0013] Optionally, the shielding gas comprises argon.

[0014] Optionally, the protective gas is introduced from two opposite sides of the container carrying the molten metal.

[0015] Optionally, the molten metal is heated by a medium frequency induction furnace, and air inlet pipes are provided on two opposite sides of the medium frequency induction furnace. While the molten metal is being heated, the protective gas is introduced into the molten metal through the air inlet pipes.

[0016] Optionally, the total thickness of the mold shell is 8 mm to 15 mm, and the total number of layers is 5 to 8 layers.

[0017] Optionally, after the step of removing the wax mold assembly and before the step of pouring the molten metal, the method further includes: calcining the mold shell at 1100° C. to 1200° C. for 40 min to 60 min.

[0018] Optionally, the mold shell is baked using far infrared rays.

[0019] Optionally, in the step of pouring the deoxidized and deslaged molten metal into the mold shell after the wax mold assembly is removed, the pouring speed is 50 cm / s to 80 cm / s.

[0020] Optionally, the wax model module is prepared by 3D printing.

[0021] Optionally, the metal member comprises stainless steel.

[0022] Optionally, the metal part is a special-shaped part.

[0023] Optionally, the area of ​​the metal piece is greater than or equal to 50 square decimeters.

[0024] A metal part is prepared by the above-mentioned metal part casting method.

[0025] The casting method of the metal parts mentioned above optimizes the shape and size of the gate during the metal parts investment casting process, and introduces a certain flow of protective gas from the side, which is beneficial to reducing the surface defects of the cast metal parts and improving the cleanliness. Specifically, by adopting an hourglass-shaped gate and controlling the height of the gate, the molten metal flows downward along the inner wall of the gate during the pouring process, and the gas in the mold shell moves upward and is discharged, thereby avoiding the occurrence of shrinkage holes, cold shuts and other defects on the surface of the metal parts. In the process of deoxidizing and deslagging the molten metal, the protective gas is introduced from the side, which is more beneficial to the formation of turbulence in the molten metal than the traditional method of introducing the protective gas from the top or bottom, thereby improving the reaction efficiency of the molten metal with the deoxidizer and the deslagging agent, significantly improving the purity of the molten metal and the deoxidation and deslagging effect. At the same time, combined with the precise control of the protective gas flow rate, the problem of surface defects such as pores and inclusions caused by excessive disturbance of the molten metal surface or insufficient deoxidation reaction is avoided.

[0026] Therefore, the above-mentioned casting method of metal parts is beneficial to improving the surface defects of metal parts and improving the cleanliness by optimizing the process parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 A schematic diagram of a process flow of a casting method for a metal part according to some embodiments of the present application;

[0029] Figure 2 A schematic diagram of a structure in which the inner wall of an hourglass-shaped gate is in an arc shape in some embodiments of the present application;

[0030] Figure 3 A schematic diagram of a structure in which the inner wall of an hourglass-shaped gate is in a broken line shape;

[0031] Figure 4 A schematic diagram of introducing a protective gas into a molten metal in some embodiments of the present application;

[0032] Figure 5 A schematic diagram of a process flow of a casting method for a metal part according to some other embodiments of the present application;

[0033] Figure 6 This is an ultra-depth-of-field microscope image of the stainless steel part prepared in Comparative Example 1;

[0034] Figure 7 This is a physical picture of the stainless steel part prepared in Comparative Example 1;

[0035] Figure 8 This is a polished appearance picture of the stainless steel part prepared in Comparative Example 1. DETAILED DESCRIPTION

[0036] In order to facilitate the understanding of the present application, the present application will be described more comprehensively below in conjunction with the specific embodiments. The preferred embodiments of the present application are provided in the specific embodiments. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0038] Unless otherwise specified or there is a contradiction, the terms and phrases used in this application have the following meanings:

[0039] In this application, "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0040] In the description of the present application, “plurality” means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined.

[0041] In this application, "one or several" refers to any one, any two or more of the listed items. Among them, "several" refers to any two or more of the listed items.

[0042] In this application, the percentage concentration involved, unless otherwise specified, refers to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of the component.

[0043] In this document, "further", "further", "particularly", "for example", "such as", "example", "for example", etc. are used for descriptive purposes, indicating that the previous and subsequent technical solutions are related in terms of the content covered, but should not be understood as a limitation on the previous technical solution, nor can it be understood as a limitation on the protection scope of this document. In this document, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0044] Herein, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If multiple "optional" items appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" item is independent of each other. In this application, descriptions such as "optionally contain", "optionally include", etc. mean "contain or not contain". "Optional component X" means that component X exists or does not exist, or means that component X is contained or not contained.

[0045] When a numerical range is disclosed in this application, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed in this application should be understood to include any and all subranges included therein.

[0046] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0047] The terms "including" and "having" and any variations thereof in the embodiments of the present application are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or components that are inherent to these processes, methods, products, or devices.

[0048] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0049] In order to overcome the various defects existing on the surface of metal parts in investment casting, traditional technology mainly adds deoxidizer and slag remover, and controls the time of deoxidizer and slag remover by experience. The products cast out by this method each time have different defects, such as pores, inclusions, segregation, etc.; especially for special-shaped parts, different parts have different problems. Another traditional technology discloses an investment casting process for a stainless steel pump casing. By performing multiple sandblasting treatments on the surface of the wax mold, the smoothness of the surface of the finished product can be greatly improved, and the quality of the finished product can be improved. At the same time, a proportioning solution and an ammonium chloride solution are added during pouring, so that the stainless steel solution can better adhere to the pores inside the pump casing, and take away the floating sand inside, further improving the precision of the finished product. However, the added ammonium chloride may decompose at high temperature to produce ammonia (NH3) and hydrogen chloride (HCl) gas. The primary hydrogen and ammonia produced when ammonia decomposes may dissolve in the molten steel to reach a saturated state, and quickly combine into hydrogen and nitrogen to form a large number of fine bubbles, which will cause more pores and inclusions on the surface of the casting.

[0050] Based on this, some embodiments of the present application provide a method for casting a metal part, see Figure 1 , including the following steps:

[0051] Step S110: obtaining a wax mold module set, the wax mold module set comprising a casting wax mold and a pouring wax mold connected to the casting wax mold; wherein the gate in the pouring wax mold is hourglass-shaped and has a height of 20 mm to 50 mm.

[0052] Step S120: applying slurry and sand to the wax mold module to form a mold shell on the surface of the wax mold module.

[0053] Step S130: removing the wax mold assembly.

[0054] Step S140: Deoxidize and remove slag from the molten metal, and at the same time, introduce protective gas from the side of the container carrying the molten metal at a flow rate of 400L / min to 500L / min.

[0055] Step S150: pouring the deoxidized and deslaged molten metal into the mold shell after the wax mold assembly is removed, so that the molten metal fills the mold shell, and cooling and molding to obtain a metal part.

[0056] In the present application, the hourglass-shaped gate means that the gate has large diameters at both ends and a small diameter in the middle, and the middle is the neck.

[0057] In some embodiments, the maximum width of the gate is R1, the minimum width is R2, and R2 / R1 is 0.4-0.6. It is understood that R2 / R1 refers to the ratio of R2 to R1. For example, R2 / R1 can be, but is not limited to, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, or a range consisting of any two of these values. Specifically, the maximum width of the gate corresponds to the diameter at both ends of the gate, and the minimum width of the gate corresponds to the diameter in the middle of the gate. In one example, the diameters at both ends of the gate are the same.

[0058] In some embodiments, the inner wall of the gate is rounded. Figure 2 , a schematic diagram of the structure of the gate in the casting wax model. Figure 2 In the figure, the downward black arrow indicates the flow direction of the molten metal during the pouring process, and the upward red arrow indicates the flow direction of the gas during the pouring process. The present application has found that the inner wall of the gate is in an arc shape. On the one hand, during the pouring process, the molten metal flows downward along the inner wall of the gate, and the gas in the mold shell moves upward and is discharged, thereby avoiding defects such as shrinkage cavities and cold shuts on the surface of the metal parts. On the other hand, it can also avoid the problem of the molten metal forming a large impact on the opposite side during the pouring process, causing the mold shell to rupture and the molten metal to leak out. If the inner wall of the gate is in a broken line shape, for example Figure 3As shown, during the pouring process, the molten metal may directly impact the opposite side from the oblique line at the upper end of the pouring gate. When the impact force is large, the mold shell may be broken, causing the molten metal to leak out. Therefore, in some embodiments of the present application, preferably, the inner wall of the pouring gate is in an arc shape.

[0059] In some of these embodiments, the inner wall of the gate is smooth to reduce flow resistance.

[0060] The gate is hourglass-shaped, and the height is controlled at 20mm~50mm to ensure the stability and controllability of the molten metal flow. Due to the special design of the hourglass-shaped gate, the molten metal will flow downward along the inner wall of the gate during the flow process, while driving the gas in the cavity to move upward and discharge. Specifically, the bottom diameter of the gate is enlarged and an R-angle diversion structure is provided, so that the molten metal can form a vacuum area when flowing through the gate, promoting the gas to be discharged upward from the bottom of the gate through the middle area, enhancing the gas discharge effect, and effectively reducing the pores and shrinkage defects inside the casting.

[0061] If the gate height is lower than 20mm, the molten metal cannot flow downward along the inner wall of the gate when pouring the molten metal, which will form turbulence in the runner, making it impossible for the gas in the mold to move upward and be discharged, causing shrinkage holes, cold shuts and other defects on the casting surface. If the gate height is higher than 50mm, the height of the middle neck will increase, causing neck shrinkage, and the molten metal will form turbulence at the neck, which will also make it impossible for the gas in the mold to move upward and be discharged, causing shrinkage holes, cold shuts and other defects on the casting surface.

[0062] Exemplarily, the height of the gate may be, but is not limited to, 20 mm, 22 mm, 25 mm, 28 mm, 30 mm, 32 mm, 35 mm, 38 mm, 40 mm, 42 mm, 45 mm, 48 mm, 50 mm, or a range consisting of any two of these values.

[0063] In some embodiments, the wax model module is prepared by 3D printing.

[0064] It is understood that the casting wax mold is a mold for the metal parts to be made later, and the shape of the casting wax mold is the same as the shape of the metal parts to be made. The pouring wax mold is a mold used to pour molten metal. The pouring wax mold includes structures such as a gate and a runner. The runner can adopt a structure commonly used in the art. It is understood that the materials of the casting wax mold and the pouring wax mold can be the same or different, and only need to use a material with a low melting point and easy to melt commonly used in the art.

[0065] In addition, in other embodiments, the wax mold set can also be obtained by other processes commonly used in the art, for example, separately obtaining a casting wax mold and a pouring wax mold, and then combining the two to obtain a wax mold set. This process can be commonly used in the art and will not be described in detail here.

[0066] Specifically, the steps of gluing and sanding the wax model module can be commonly used in the art, for example, using silica sol coating for gluing, using zircon sand for sanding, etc. In some embodiments, the steps of gluing and sanding the wax model module include: immersing the wax model module in silica sol coating, allowing the silica sol coating to wet the surface of the wax model module, and coating zircon sand on the surface of the silica sol.

[0067] Furthermore, the mold shell is multi-layered, and the steps of gluing and sanding the wax mold module include: immersing the wax mold module in silica sol coating, allowing the silica sol coating to wet the surface of the wax mold module, applying zircon sand on the surface of the silica sol, and repeating the gluing and sanding steps after air drying to obtain a multi-layer mold shell.

[0068] In some of the embodiments, the total number of layers of the mold shell is 5 to 8 layers, and the total thickness of the mold shell is 8 mm to 15 mm.

[0069] For example, the total number of layers of the formwork may be, but is not limited to, 5, 6, 7, 8, or a range consisting of any two of these values. The total thickness of the formwork may be, but is not limited to, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, or a range consisting of any two of these values.

[0070] By optimizing the number of layers and thickness of the mold shell, it is helpful to further improve surface defects and improve cleanliness. Specifically, the number of mold shell layers is 5 to 8 layers, and the total thickness is 8mm to 15mm, which is helpful to improve the structural density of the mold shell, and is more conducive to effectively resisting the impact force and high temperature of the molten metal during the casting process, thereby reducing the risk of the mold shell breaking or deforming during the pouring process, and making the mold shell surface have a suitable roughness to reduce surface defects, thereby reducing defects such as sand holes and pores in metal parts caused by the filling of molten metal liquid due to surface defects of the mold shell. In addition, the number of layers and thickness of the mold shell are appropriate, which reduces the risk of shrinkage holes, shrinkage and other defects in metal parts due to the slow cooling speed of the molten metal liquid due to the increase in the thickness of the mold shell, and is conducive to the smooth discharge of gas during the pouring process, reducing the risk of defects such as pores inside the casting.

[0071] In some embodiments, the step of removing the wax mold assembly is performed in a dewaxing machine. The specific temperature can be adjusted according to the material of the wax mold, for example, 70° C. to 100° C.

[0072] In some embodiments, after the step of removing the wax mold assembly and before the step of pouring molten metal into the mold shell, the step further includes: baking the mold shell at 1100°C to 1200°C for 40min to 60min. Baking the mold shell is beneficial to improving the strength of the mold shell and avoiding the decrease in strength and deformation of the mold shell during the subsequent pouring process. Precise control of baking temperature and time further improves the performance and stability of the mold shell.

[0073] For example, the calcination temperature may be, but is not limited to, 1100° C., 1120° C., 1120° C., 1120° C., 1120° C., 1120° C., 1120° C., or a range consisting of any two of these values. The calcination time may be, but is not limited to, 40 min, 42 min, 44 min, 45 min, 46 min, 48 min, 50 min, 52 min, 54 min, 55 min, 58 min, 60 min, or a range consisting of any two of these values.

[0074] Specifically, the mold shell is baked using far infrared rays. The far infrared rays can be evenly distributed around the mold shell, ensuring that the mold shell is heated in all directions, reducing defects in subsequent casting due to incomplete baking of parts of the mold shell. It can be understood that the wavelength range of far infrared rays is usually between 3μm and 1000μm.

[0075] In some embodiments, the metal is stainless steel, for example, the metal is 304 stainless steel. The molten metal is obtained by heating the metal at 1670° C. to 1690° C. It is understood that in other embodiments, the metal is not limited to stainless steel, and the heating and melting temperature can be adjusted according to the material of the metal.

[0076] In some embodiments, before the step of pouring the molten metal, the composition of the molten metal is tested, and corresponding element alloys are added according to the composition of the molten metal. By testing the composition of the molten metal and adding corresponding metal elements according to the difference between the composition of the molten metal and the composition of the workpiece to be cast, it can be ensured that its chemical composition meets the requirements of the casting process, thereby ensuring the quality of the casting and avoiding problems such as reduced mechanical properties and reduced corrosion resistance due to uneven composition.

[0077] In some of the embodiments, the metal is heated by a medium frequency induction furnace to obtain molten metal. The medium frequency induction furnace refers to an induction furnace with an operating frequency in the range of 150HZ to 10000Hz, which has the advantages of fast melting speed, high production efficiency, strong adaptability, flexible use, good electromagnetic stirring effect, and easy startup and operation.

[0078] In some embodiments, a deoxidizer and a slag remover are added to the molten metal for deoxidation and slag removal. The specific deoxidizer and slag remover can be commonly used in the art and are not particularly limited here. For example, in some embodiments, the primary deoxidizer is a manganese alloy, and the final deoxidizer is a composite iron alloy.

[0079] The molten metal is deoxidized and deslaged, and at the same time, a protective gas is introduced from the side of the container carrying the molten metal at a flow rate of 400L / min~500L / min, which is conducive to better deoxidation, so that the molten metal forms turbulence, so that the deoxidizer can quickly react with the molten metal and the oxide can quickly float on the surface of the molten metal, and the slag is removed by the deslag remover. Specifically, the protective gas is introduced from the side, which is more conducive to the molten metal forming turbulence than the traditional method of introducing the protective gas from the top or bottom, and improves the mixing effect of the molten metal and the deoxidizer and deslag remover. If the flow rate of the protective gas is lower than 400L / min, the reduction in turbulence intensity will directly affect the mixing efficiency between the deoxidizer and the molten metal, making the deoxidation reaction insufficient, and part of the deoxidizer fails to effectively contact the oxide in the molten metal, resulting in a high oxygen content in the molten metal, affecting the quality of the final casting. In addition, the dispersion state of oxides in the molten metal will also deteriorate, which is not conducive to subsequent slag removal operations, will increase the amount of slag, increase production costs, and may affect the purity of the molten metal. When the flow rate of the shielding gas is higher than 500L / min, it will cause violent disturbances on the surface of the molten metal and even cause splashing. Too high a shielding gas flow rate may also cause uneven distribution of the deoxidizer in the molten metal, thereby affecting the stability of the deoxidation effect, and will also cause the oxides to form finer particles in the molten metal, which are difficult to effectively remove with a slag remover, increasing the difficulty of slag removal.

[0080] For example, the flow rate of the shielding gas may be, but is not limited to, 400 L / min, 420 L / min, 440 L / min, 450 L / min, 460 L / min, 480 L / min, 500 L / min, or a range consisting of any two of these values.

[0081] In one example, the shielding gas includes argon. It is understood that in other embodiments, the shielding gas is not limited to argon, but may also be other gases, such as inert gases such as helium. The above shielding gas can not only protect the molten metal from oxidation, but also does not introduce other elements into the molten metal. In addition, if the metal part to be obtained requires a high nitrogen content, such as high-nitrogen stainless steel, the shielding gas may also include nitrogen. If the metal part to be obtained does not need to contain nitrogen, the shielding gas is argon, helium, etc., and does not contain nitrogen.

[0082] Furthermore, protective gas is introduced from two opposite sides of the container carrying the molten metal. In some embodiments, a medium frequency induction furnace is used to heat the molten metal. Two opposite sides of the medium frequency induction furnace are provided with air inlet pipes. While the molten metal is being heated, protective gas is introduced into the molten metal through the air inlet pipes. For details, please refer to Figure 4 , the protective gas is introduced into the molten metal through the air inlet pipes on both sides. Figure 4 In the figure, the direction of the arrow indicates the direction of the shielding gas introduction.

[0083] In some embodiments, in the step of pouring the molten metal liquid after deoxidation and deslagging into the mold shell after removing the wax mold module, the pouring speed is 50cm / s~80cm / s. By optimizing the pouring speed, it is beneficial to further improve the surface defects of metal parts and improve the cleanliness. Specifically, the pouring speed is 50cm / s~80cm / s, which is beneficial to reduce the risk of increased cracking of castings due to the large thermal stress generated by the high pouring speed, and at the same time, reduce the risk of insufficient pouring. If the pouring speed is higher than 80cm / s, defects such as shrinkage cavities and shrinkage porosity are prone to occur on the surface, which may produce large thermal stresses and increase the risk of cracking of the casting; if the pouring speed is lower than 50cm / s, the temperature drops too fast during the pouring process, the fluidity deteriorates, and the cavity may not be completely filled, resulting in insufficient pouring defects; too long pouring time may also cause large thermal stresses inside the casting.

[0084] For example, the pouring speed may be, but is not limited to, 50 cm / s, 55 cm / s, 60 cm / s, 65 cm / s, 70 cm / s, 75 cm / s, 80 cm / s or a range consisting of any two of these values.

[0085] It can be understood that in the step of pouring the deoxidized and deslaged molten metal into the mold shell after the wax mold module is removed, the molten metal fills the space previously formed by the wax mold module until it is completely filled, including the middle mold head part.

[0086] In some embodiments, the metal part includes stainless steel. It is understood that in other embodiments, the metal part is not limited to stainless steel, but can also be other commonly used metal parts capable of investment casting, such as carbon steel, alloy steel, heat-resistant alloy, precision alloy, permanent magnet alloy, bearing alloy, copper alloy, aluminum alloy, titanium alloy and ductile iron.

[0087] In some embodiments, the metal part is a special-shaped part. Special-shaped parts refer to parts with irregular shapes or complex structures, and their shapes, sizes and structures are very different from common standard parts. Special-shaped parts are more likely to have surface defects than standard parts due to their complex structures. The use of the metal part casting method of some embodiments of the present application to prepare special-shaped parts is conducive to reducing surface defects. It can be understood that in other embodiments, the metal part casting method of the present application can also be used to prepare standard parts.

[0088] In some embodiments, the area of ​​the metal part is greater than or equal to 50 square decimeters. Large-area metal parts such as those with an area greater than or equal to 50 square decimeters are more likely to have surface defects. The casting method of metal parts in some embodiments of the present application can be used to prepare large-area metal parts and reduce surface defects of large-area metal parts. It can be understood that in other embodiments, the casting method of metal parts in some embodiments of the present application can also be used to prepare small-area metal parts.

[0089] In some embodiments, during the cooling step, the casting is placed in water or the surface of the casting is sprayed with water, and the high thermal conductivity of water is used to quickly remove heat.

[0090] In some of these examples, see Figure 5 , the casting method of the metal part comprises the following steps:

[0091] Step S210: Prepare a wax mold module by 3D printing, wherein the wax mold module includes a casting wax mold and a pouring wax mold connected to the casting wax mold; wherein the gate in the pouring wax mold is hourglass-shaped and has a height of 20 mm to 50 mm.

[0092] Step S220: slurry and sand are applied to the wax mold module to form a multi-layer mold shell on the surface of the wax mold module. The total number of layers of the mold shell is 5 to 8 layers, and the total thickness is 8 mm to 15 mm.

[0093] Step S230: removing the wax mold assembly.

[0094] Step S240: calcining the mold shell after removing the wax mold assembly at 1100° C. to 1200° C. for 40 min to 60 min.

[0095] Step S250: Deoxidize and remove slag from the molten metal, and at the same time, introduce protective gas from two opposite sides of the container carrying the molten metal at a flow rate of 400L / min to 500L / min.

[0096] Step S260: pouring the deoxidized and deslagging molten metal into the calcined mold shell at a pouring speed of 50 cm / s to 80 cm / s, so that the molten metal fills the mold shell, and cooling and molding to obtain a metal part.

[0097] Figure 5 This is a schematic diagram of a process for casting a metal part according to an embodiment of the present application. It should be understood that although Figure 5 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and they can be performed in other orders. Figure 5 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The order of execution is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of other sub-steps or stages.

[0098] The above-mentioned casting method of metal parts has at least the following advantages:

[0099] (1) The above-mentioned pouring wax mold adopts an hourglass-shaped gate, and its height is controlled within the range of 20mm~50mm, which effectively ensures the stability and controllability of molten steel flow. The enlarged diameter and diversion structure at the bottom of the gate promote the upward discharge of gas from the bottom of the gate, significantly reducing defects such as pores, shrinkage cavities and shrinkage porosity inside the casting.

[0100] (2) The wax mold is made using 3D printing technology, and after multiple slurry sticking and sand hanging processes, a dense mold shell with 5 to 8 layers and a total thickness of 8 mm to 15 mm is formed. This mold shell design not only ensures the structural strength of the mold shell, but also avoids the problems of slow cooling speed and poor gas discharge caused by excessive thickness, thereby improving the quality and surface finish of the casting.

[0101] (3) Far infrared calcining technology ensures that the mold shell is heated evenly in all directions, reducing casting defects caused by incomplete calcining. Precise control of calcining temperature and time further improves the performance and stability of the mold shell.

[0102] (4) Use high temperature to melt the metal quickly, and add alloys to adjust the composition in time during the smelting process. When the temperature of the molten metal reaches 1670℃~1690℃, add protective gas to form turbulence, which enhances the reaction efficiency of the deoxidizer and slag remover with the molten metal, and significantly improves the purity of the molten metal and the deoxidation and slag removal effect. Precise control of the protective gas flow rate avoids the problem of excessive disturbance on the surface of the molten metal or insufficient deoxidation reaction.

[0103] (5) During the pouring process, the pouring speed is controlled within the range of 50 cm / s to 80 cm / s, which not only ensures that the molten metal can quickly fill the mold cavity, but also avoids defects such as shrinkage cavities and shrinkage caused by too fast pouring speed or insufficient pouring caused by too slow speed. In addition, accurate pouring speed control can also help reduce thermal stress and crack risks inside the casting.

[0104] A second aspect of the present application provides a metal part, which is prepared by the casting method of the metal part of the first aspect.

[0105] In order to make the purpose and advantages of the present application clearer, the casting method of the metal parts of the present application and its effects are further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and shall not be used to limit the present application. The following embodiments do not include other components except for unavoidable impurities unless otherwise specified. The drugs and instruments used in the embodiments are conventionally selected in the art unless otherwise specified. The experimental methods for which specific conditions are not specified in the embodiments are implemented according to conventional conditions, such as the conditions described in the literature and books or the methods recommended by the manufacturer.

[0106] Example 1

[0107] This embodiment provides a casting method for a stainless steel part, comprising the following steps:

[0108] (1) According to the shape of the stainless steel part, a low melting point and easily fusible material is used to print and shape it on a 3D printer to obtain a casting mold and a pouring mold. The gate of the pouring mold is designed to be an hourglass-shaped gate, as shown in the figure. Figure 2 As shown, the height is controlled at 20 mm, the ratio of the minimum width to the maximum width of the gate is 0.5, and the casting wax mold and the pouring wax mold tree are assembled to obtain the wax mold module.

[0109] (2) Immerse the wax mold module in silica sol coating, allow the silica sol coating to wet the surface of the wax mold module, evenly apply zircon sand on the surface of the silica sol and air dry. After air drying, repeat the above steps, perform multiple slurry sticking and sand hanging to obtain a multi-layer mold shell. The number of mold shell layers is 5, and the total thickness of the mold shell is 8mm~10mm.

[0110] (3) Dewaxing is performed in a dewaxing machine to remove the wax mold module, and the mold shell after the wax mold module is removed is baked using far infrared rays. The baking temperature is controlled at 1100°C and the time is controlled at 40 minutes.

[0111] (4) Use a medium frequency induction furnace to quickly melt the 304 stainless steel plate at high temperature, and continuously add materials into the furnace to raise the temperature of the molten steel to 1670℃ for smelting. When the temperature reaches 1670℃, test the composition of the molten steel, and add the corresponding alloy according to the results of the molten steel composition. Deoxidation and slag removal are carried out at a temperature of 1670℃. Electrolytic manganese alloy is used for initial deoxidation, and composite iron alloy is used for final deoxidation. Two inlet pipes are added in the middle of the medium frequency induction furnace. Argon gas enters the molten steel through the inlet pipes. The argon gas flow rate is controlled at 400L / min to form turbulent flow in the molten steel, so that the deoxidizer can quickly react with the molten steel and the oxide can quickly float on the surface of the molten steel, and the slag is removed by the slag remover.

[0112] (5) Pour the stainless steel water that has been dissolved into liquid at high temperature into the mold shell after the wax is removed. The liquid stainless steel water fills the space previously formed by the wax mold until it is completely filled. The pouring speed is controlled at 50cm / s.

[0113] (6) Place the casting in water or spray the casting surface with water, and use the high thermal conductivity of water to quickly remove heat to obtain a stainless steel part.

[0114] Embodiment 2~6

[0115] Embodiments 2 to 6 respectively provide a casting method for a stainless steel part, and the preparation steps are similar to those of Embodiment 1, except that the process parameters are different. The process parameters of Embodiments 2 to 6 are shown in Table 1 below. The rest are the same as those of Embodiment 1 and will not be repeated.

[0116] Comparative Example 1

[0117] Comparative Example 1 provides a method for casting a stainless steel part, referring to the method in CN 110090921A, comprising the following steps:

[0118] (1) According to the shape of the stainless steel part, a low-melting-point, easily-melted material is used to print and shape it on a 3D printer to obtain a casting module and a pouring module, wherein the gate of the pouring module is a straight cylinder with a height of 30 mm, and the casting wax mold and the pouring wax mold are placed together to obtain a wax mold module.

[0119] (2) Immerse the wax mold module in silica sol coating, allow the silica sol coating to wet the surface of the wax mold module, evenly apply zircon sand on the surface of the silica sol and air dry. After air drying, repeat the above steps, perform multiple slurry sticking and sand hanging to obtain a multi-layer mold shell. The number of mold shell layers is 6, and the total thickness of the mold shell is 12 mm.

[0120] (3) Dewaxing to obtain a mold shell.

[0121] (4) Firing the mold shell at a temperature of 1150°C for 40 minutes.

[0122] (4) Pouring: the pouring temperature is 1640°C and the pouring speed is ≤3 seconds. Then the casting is cooled naturally and a large-area thin-walled part is obtained after demolding.

[0123] Comparative Examples 2~3

[0124] Comparative Examples 2 and 3 respectively provide a method for casting a stainless steel part, and the preparation steps are similar to those of Example 1, except that the gate heights in step (1) are different. The gate heights of Comparative Examples 2 and 3 are shown in Table 2 below. The remaining steps and parameters are the same as those of Example 1 and will not be repeated here.

[0125] Comparative Example 4

[0126] Comparative Example 4 provides a method for casting a stainless steel part. The preparation steps are similar to those of Example 1, except that the shape of the gate in step (1) is different. In Comparative Example 4, the gate shape is a straight cylinder, that is, the width of the gate at different positions is the same, which is the same as the maximum width of the gate in Example 1. The other steps and parameters are the same as those in Example 1 and will not be repeated.

[0127] Comparative Examples 5-6

[0128] Comparative Examples 5 and 6 respectively provide a casting method for a stainless steel part, and the preparation steps are similar to those of Example 1, except that the argon flow rate in step (4) is different. The argon flow rates of Comparative Examples 5 and 6 are specifically shown in Table 2 below. The remaining steps and parameters are the same as those of Example 1 and will not be repeated here.

[0129] Comparative Example 7

[0130] Comparative Example 7 provides a method for casting a stainless steel part. The preparation steps are similar to those of Example 1, except that the method of introducing argon gas in step (4) is different. In Comparative Example 7, an air inlet pipe is provided at the bottom of the medium frequency induction furnace, and argon gas enters the molten steel through the air inlet pipe at the bottom. The remaining steps are the same as those of Example 1 and will not be described in detail.

[0131] Table 1 Process parameters of the casting method of stainless steel parts in various embodiments

[0132]

[0133] Table 2 Process parameters of the casting method of stainless steel parts in each comparative example

[0134]

[0135] The surface appearance of the stainless steel casting special-shaped parts of Examples 1 to 6 and Comparative Examples 1 to 7 was tested, and the results are shown in Table 3.

[0136] Table 3 Surface appearance results of special-shaped castings

[0137]

[0138] Among them, the ultra-depth-of-field microscope of the stainless steel part prepared in Comparative Example 1 is as follows: Figure 6 As shown in the actual picture Figure 7 As shown, the polished appearance is Figure 8 As shown. Figure 6 It can be seen from the figure that the surface inclusions of the stainless steel part prepared in Comparative Example 1 are relatively large. Figure 7 It can be seen that the stainless steel parts of comparative example 1 have insufficient pouring and cold shut defects. Figure 8 It can be seen that the stainless steel part of comparative example 1 has a cold shut defect.

[0139] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0140] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solution of the present application in detail, but it cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the contents of the attached claims, and the description and drawings can be used to explain the contents of the claims.

Claims

1. A method for casting a metal part, characterized in that: The steps include: Obtaining a wax mold set, the wax mold set comprising a casting wax mold and a pouring wax mold connected to the casting wax mold; wherein the gate in the pouring wax mold is hourglass-shaped and has a height of 20 mm to 50 mm; The wax mold module is subjected to slurry gluing and sanding to form a mold shell on the surface of the wax mold module; removing the wax model assembly; Deoxidizing and deslagging the molten metal, while introducing a protective gas at a flow rate of 400 L / min to 500 L / min from the side of the container carrying the molten metal; The molten metal liquid after deoxidation and slag removal is poured into the mold shell after the wax mold assembly is removed, so that the molten metal liquid fills the mold shell, and is cooled and formed to obtain a metal part.

2. The method for casting a metal part according to claim 1, characterized in that: The maximum width of the gate is R1, the minimum width is R2, and R2 / R1 is 0.4-0.6; and / or, The inner wall of the gate is in an arc shape.

3. The method for casting a metal part according to claim 1, characterized in that: introducing the protective gas from two opposite sides of the container carrying the molten metal; Optionally, the molten metal is heated by a medium frequency induction furnace, and air inlet pipes are provided on two opposite sides of the medium frequency induction furnace. While the molten metal is being heated, the protective gas is introduced into the molten metal through the air inlet pipes.

4. The method for casting a metal part according to claim 1 or 3, characterized in that: The shielding gas includes argon.

5. The method for casting a metal part according to claim 1, characterized in that: The total thickness of the mold shell is 8mm~15mm, and the total number of layers is 5~8 layers.

6. The method for casting a metal part according to claim 1 or 5, characterized in that: After the step of removing the wax mold assembly and before the step of pouring the molten metal, the method further comprises: baking the mold shell at 1100° C. to 1200° C. for 40 min to 60 min; Optionally, the mold shell is baked using far infrared rays.

7. The method for casting a metal part according to any one of claims 1 to 3 and 5, characterized in that: In the step of pouring the deoxidized and deslaged molten metal into the mold shell after the wax mold assembly is removed, the pouring speed is 50 cm / s to 80 cm / s.

8. The method for casting a metal part according to any one of claims 1 to 3 and 5, characterized in that: The wax model module is prepared by 3D printing.

9. The method for casting a metal part according to any one of claims 1 to 3 and 5, characterized in that: The metal part comprises stainless steel; and / or, The metal part is a special-shaped part; and / or, The area of ​​the metal piece is greater than or equal to 50 square decimeters.

10. A metal part, characterized in that: The metal part is prepared by the casting method of any one of claims 1 to 9.

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