A method of casting a complex valve body casting

Abstract

This invention relates to a casting method for complex valve body castings, comprising the following steps: an analysis step, in which the gating system is designed according to the valve body structure, and the heat distribution and heat dissipation during the casting process are analyzed to determine the heat dissipation location data and heat dissipation rate data; a chilling step, in which chills are fabricated based on the heat dissipation location data and heat dissipation rate data; a sand core preparation step, in which sand cores are fabricated based on the heat dissipation location data and heat dissipation rate data; a box-closing casting step, in which the sand core is placed in the sand box, the chills are inserted into the sand box, and then the box is closed, with the casting volume gradually increasing during the casting process; the casting temperature is 1610-1630℃; inert gas is introduced at the beginning of the casting process; the amount of inert gas is gradually reduced; and a box-opening and cleaning step, in which the sand box is slowly cooled to 300℃ before opening; after opening the box, the sand is cleaned and the gating system is cleaned. This method solves the problem in existing solutions where uneven valve body wall thickness leads to uneven heat dissipation, resulting in casting defects within the valve body.

Description

Technical Field

[0001] This invention relates to the field of casting, and more particularly to a casting method for complex valve body castings. Background Technology

[0002] Large cast stainless steel valve bodies often operate in environments characterized by high temperatures, high pressures, and corrosive conditions. Due to the complex internal structure and uneven wall thickness of the valve body, heat is concentrated in the thicker areas during casting, while heat dissipates more rapidly in the thinner areas. This thermal stress makes the areas with alternating thick and thin sections of the valve body prone to cracking.

[0003] Rapid solidification at the thin-walled sections of the valve body obstructs the feeding channels of the riser, leading to defects such as porosity in the valve body's inner wall. These internal defects significantly reduce the valve body's strength, making it prone to stress concentration during stress, which in turn promotes crack initiation and propagation. In corrosive media, surface defects in the valve body provide initial attachment points for pitting corrosion. These defects result in casting scrap, affecting delivery schedules and significantly increasing production costs.

[0004] Chinese invention patent application number 202211578807.4 proposes a method for controlling the temperature of castings through multi-point thermal control to achieve sequential solidification. However, this method is quite complex, and since it is used for key castings in aerospace high-temperature alloys, the cost of such a control method is not suitable for valve body casting.

[0005] Chinese invention patent application number 201210114617.7 proposes a method for setting up internal water channels in chills to promote heat dissipation. However, setting up pipes inside chills has the problems of complex structure and poor versatility. At the same time, adding internal circulating water channels can only enhance the cooling effect of chills, but cannot perform fine-grained heat control for different areas. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a casting method for complex valve body castings, so as to solve the problem that uneven valve body wall thickness leads to uneven heat dissipation, resulting in casting defects in the valve body.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A casting method for complex valve body castings; comprising the following steps:

[0009] The analysis steps include designing the gating system based on the valve body's structure, analyzing the heat distribution and heat dissipation during the casting process, and determining the heat dissipation location data and heat dissipation rate data.

[0010] The process of making a chiller involves fabricating the chiller based on data on the location and rate of heat dissipation.

[0011] The sand core making process involves creating sand cores based on data on heat dissipation location and heat dissipation rate.

[0012] The casting process involves placing the sand core in the sand box, inserting a chill into the sand box, and then closing the box. During the casting process, the casting volume gradually increases. The casting temperature is 1610-1630℃. Inert gas is introduced at the beginning of the casting process, and the amount of inert gas is gradually reduced.

[0013] The unpacking and cleaning process involves slowly cooling the sand box to 300°C before unpacking; after unpacking, the sand is removed and the pouring channel is cleaned.

[0014] A further technical solution is to include an opening step before the cooling iron step: making an opening in the sand box based on the heat dissipation location data.

[0015] A further technical solution is that the cooling iron step includes the following process:

[0016] Shell manufacturing process: The shell is manufactured according to the opening size;

[0017] Core manufacturing process: Determine the surface shape of the core based on heat dissipation rate data; Place the core into the outer shell;

[0018] Filling process: Paraffin wax is filled between the inner core and the outer shell.

[0019] A further technical solution is that the sand core includes guide protrusions in the sand core making step; the position of the guide protrusions is determined based on heat dissipation position data; and the extension angle of the guide protrusions is determined based on heat dissipation rate data.

[0020] A further technical solution is to adjust the depth of the chill inserted into the sand box during the casting process according to the heat dissipation rate data.

[0021] A further technical solution is that the casting process of the box assembly and casting step includes the following steps:

[0022] First step: Determine the basic casting speed and basic ventilation speed;

[0023] Second process: Cast at 10-15% of the basic casting speed; Inert gas is introduced at the basic ventilation speed;

[0024] Third process: Cast at 60-65% of the basic casting speed; Inert gas is introduced at 6-9% of the basic ventilation speed;

[0025] Fourth step: Cast at the basic casting speed; stop the introduction of inert gas.

[0026] A further technical solution is to: during the casting process:

[0027] The second process accounts for 3-5% of the total casting process;

[0028] The third process accounts for 7-10% of the casting process;

[0029] The third process accounts for the remaining portion of the casting process.

[0030] Compared with the prior art, the beneficial technical effects of the present invention are as follows: (1) The casting medium can be continuously cooled by the chiller, and by moving the chiller, the rapid cooling zone, the gradual cooling zone and the slow cooling zone correspond to different thicknesses of the casting medium accumulation, avoiding overcooling or overheating of the casting medium accumulation, and the casting medium achieves uniform heat dissipation, avoiding casting defects; (2) In the second process, casting and ventilation are carried out simultaneously. At this time, the casting volume is small and the inert gas is introduced in large quantities. The inert gas is affected by the temperature of the casting medium, and the temperature of the inert gas rises rapidly. When the inert gas flows along the gating system, it completes the heating of the gating system; due to the large amount of inert gas introduced, the inert gas drives the casting medium to be distributed on the flow path, so that the gating system is heated evenly; due to the flow of gas, the temperature of the casting medium can be distributed quickly; (3) In the third process, casting and ventilation are carried out simultaneously. At this time, the casting volume increases and the inert gas is introduced in small quantities. In the second process, after the gating system is heated, the sand core and sand box will be heated and dried. Since the second process is short, if the local part is not thoroughly dried, the casting medium will bubble and jump. In the third process, a small amount of inert gas is introduced, which will cause the casting medium to shake, thereby eliminating the bubbling. The inert gas flows along the casting medium to suppress the jumping of the casting medium, thereby eliminating the defects caused by casting. (4) When the casting medium flows along the gating system, the casting medium first contacts the first protrusion 7. The casting medium flows along the first protrusion 7 and approaches the chill, completing the cooling of the casting medium. The casting medium gradually accumulates in the gating system and gradually submerges the second protrusion 8 and the first protrusion 7. Through the guidance of the casting medium by the second protrusion 8, the formation of cavities near the guide protrusion is gradually avoided, thus preventing defects. Attached Figure Description

[0031] Figure 1 A schematic flowchart of the casting method for complex valve body castings according to an embodiment of the present invention is shown.

[0032] Figure 2 A schematic diagram of the chill structure according to an embodiment of the present invention is shown.

[0033] Figure 3 A schematic diagram of the guide protrusion in an embodiment of the present invention is shown.

[0034] The following labels are used in the attached diagram: 1. Outer shell; 2. Inner core; 21. Gradual cooling block; 22. Slow cooling block; 23. Contact surface; 3. Paraffin wax; 4. Rapid cooling zone; 5. Gradual cooling zone; 6. Slow cooling zone; 7. First protrusion; 8. Second protrusion. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the device proposed by this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, only for the purpose of conveniently and clearly illustrating the embodiments of this invention. Please refer to the accompanying drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0036] Figure 1 A schematic flowchart of the casting method for complex valve body castings according to an embodiment of the present invention is shown. (Combined with...) Figure 1 As shown, this invention discloses a casting method for complex valve body castings.

[0037] The casting method for complex valve body castings includes the following steps:

[0038] The analysis steps involve designing the gating system based on the valve body's structure, analyzing the heat distribution and heat dissipation during the casting process, and determining the heat dissipation location and rate data.

[0039] The chiller process involves fabricating a chiller based on data on the location and rate of heat dissipation.

[0040] The sand core making process involves creating sand cores based on data on heat dissipation location and heat dissipation rate.

[0041] The casting process involves placing the sand core in the sand box, inserting a chill into the sand box, and then closing the box. During casting, the casting volume gradually increases. The casting temperature is 1610-1630℃. Inert gas is introduced at the beginning of the casting process, and the amount of inert gas is gradually reduced.

[0042] Unpacking and cleaning steps: Allow the sand box to cool slowly to 300℃ before unpacking. After unpacking, remove the sand and clean the gating system.

[0043] In the analysis step, the shape and dimensions of the gating system are determined based on the valve body drawings. The flow distribution of the casting medium during the casting process is simulated based on the shape and dimensions of the gating system. The heat distribution and dissipation during the casting process are analyzed based on the flow distribution, ultimately determining the heat dissipation location and rate data.

[0044] In a gating system, areas with a thicker accumulation of casting medium experience slower heat dissipation. Similarly, areas with complexly shaped channels in the gating system also experience slower heat dissipation.

[0045] The cooling process includes an opening step: making an opening in the sandbox based on the heat dissipation location data.

[0046] The heat dissipation locations are where the casting medium accumulates thickly in the gating system and in complexly shaped channels within the system. During the casting process, chills need to be inserted into the sand box. Openings are made in the sand box during the opening process to facilitate chill insertion. These openings allow for the chills to be inserted at different locations within the sand box, achieving a discrete distribution of chills.

[0047] The steps for cooling iron include the following:

[0048] Shell manufacturing process: The shell is manufactured according to the size of the opening.

[0049] Core manufacturing process: Determine the surface shape of the core based on heat dissipation rate data. Place the core into the outer shell.

[0050] Filling process: Paraffin wax is filled between the inner core and the outer shell.

[0051] Figure 2 A schematic diagram of the chill structure according to an embodiment of the present invention is shown. (Combined with...) Figure 1 and Figure 2 As shown.

[0052] The refrigeration system includes paraffin wax 3, a housing 1, and an inner core 2 placed inside the housing 1. One end of the housing 1 is sealed, and the other end is open. One end of the housing 1 is inserted into a sand box. The inner core 2 is placed inside the housing 1 from the other end.

[0053] The inner core 2 includes a gradually cooling block 21 and a slow cooling block 22. A gradually expanding or narrowing contact surface 23 is formed around the gradually cooling block 21. The contact surface 23 and the slow cooling block 22 are connected by a rounded transition. When the inner core 2 is installed inside the outer casing 1, the contact surface 23 does not contact the inner surface of the outer casing 1, the slow cooling block 22 conforms to the inner surface of the outer casing 1, and the end face of the inner core 2 does not contact the inner surface of the outer casing 1.

[0054] Since the end face and contact surface 23 of the inner core 2 do not contact the inner surface of the outer shell 1, a space is formed between the outer shell 1 and the inner core 2. The paraffin wax 3 fills the space.

[0055] The space between the end face of the inner core 2 and the inner surface of the outer shell 1 forms a rapid cooling zone 4. The space between the contact surface 23 and the inner surface of the outer shell 1 forms a gradual cooling zone 5. The area where the slow cooling block 22 contacts the inner surface of the outer shell 1 is the slow cooling zone 6.

[0056] The rapid cooling zone 4 is entirely composed of paraffin wax 3, resulting in good cooling. The slow cooling zone 6 is entirely composed of slow cooling blocks 22, resulting in poor cooling. The gradual cooling zone 5 includes both paraffin wax 3 and gradual cooling blocks 21, with a cooling effect between that of the rapid cooling zone 4 and the slow cooling zone 6. The cooling effect of the gradual cooling zone 5 also changes with the change in the contact surface 23.

[0057] In the core-making process, the sand core includes guide protrusions. The position of the guide protrusions is determined based on heat dissipation location data. The extension angle of the guide protrusions is determined based on heat dissipation rate data.

[0058] The rapid cooling zone 4, gradual cooling zone 5, and slow cooling zone 6 produce different cooling effects, giving the chills the ability to cool in a gradient manner to adapt to different cooling conditions and achieve precise temperature control of the gating system. By controlling the temperature of different locations of the casting medium, sequential solidification of the casting is achieved, improving the quality of the casting and preventing shrinkage porosity and gas porosity.

[0059] Figure 3 A schematic diagram of the guide protrusion according to an embodiment of the present invention is shown. (In conjunction with...) Figures 1-3 As shown.

[0060] Guide protrusions are formed on the outer surface of the sand core. Each guide protrusion includes a first protrusion 7 extending outward along the flow direction of the casting medium and a second protrusion 8 extending inward along the flow direction of the casting medium. The first protrusion 7 and the second protrusion 8 are rounded off. The extension angle of the first protrusion 7 is smaller than the extension angle of the second protrusion 8. The extension angle of the first protrusion 7 is the angle between its surface and the outer surface of the sand core. The extension angle of the second protrusion 8 is the angle between its surface and the outer surface of the sand core.

[0061] As the casting medium flows along the gating system, it first contacts the first protrusion 7, flows along it, and approaches the chill, thus cooling the medium. The casting medium gradually accumulates within the gating system, eventually submerging the second protrusion 8 and the first protrusion 7. The second protrusion 8 guides the flow of the casting medium, gradually preventing the formation of cavities and defects near the guide protrusion.

[0062] During the casting process, the depth of the chill inserted into the sand box is adjusted according to the heat dissipation rate data.

[0063] During the casting process, as the amount of casting medium gradually increases, the thickness of the accumulated casting medium gradually increases, and the heat dissipation rate gradually decreases. Therefore, it is necessary to adjust the insertion depth of the chill according to the changes.

[0064] During the initial casting process, when the thickness of the casting medium is relatively thin, the depth to which the chill is inserted into the sand box ensures that the slow cooling zone 6 comes into contact with the casting medium. As the casting medium gradually accumulates, the depth of the chill inserted into the sand box is adjusted so that the gradual cooling zone 5 comes into contact with the casting medium. When the casting medium accumulates to a thicker thickness, the depth of the chill inserted into the sand box is adjusted so that the rapid cooling zone 4 comes into contact with the casting medium. By adjusting the depth of the chill inserted into the sand box at different stages of the casting process, the rapid cooling zone 4, gradual cooling zone 5, and slow cooling zone 6 come into contact with different thicknesses of the accumulated casting medium.

[0065] The chiller continuously cools the areas where the casting medium accumulates. By moving the chiller, the rapid cooling zone 4, gradual cooling zone 5, and slow cooling zone 6 correspond to different thicknesses of the casting medium accumulation. This avoids overcooling or overheating of the areas where the casting medium accumulates, ensuring uniform heat dissipation and preventing casting defects.

[0066] The casting process of the box assembly and casting step includes the following steps:

[0067] The first step: Determine the basic casting speed and the basic ventilation speed.

[0068] Second process: Cast at 10-15% of the basic casting speed. Inert gas is introduced at the basic ventilation speed.

[0069] Third process: Cast at 60-65% of the basic casting speed. Introduce inert gas at 6-9% of the basic ventilation speed.

[0070] Fourth step: Cast at the basic casting speed. Stop introducing inert gas.

[0071] During the casting process:

[0072] The second process accounts for 3-5% of the total casting process.

[0073] The third process accounts for 7-10% of the casting process.

[0074] The third process accounts for the remaining portion of the casting process.

[0075] In the first process, the total casting time is determined based on the size of the casting. The basic casting speed is determined by the total casting time and the volume of the casting. The basic aeration speed is determined based on the flow path of the inert gas along the gating system.

[0076] In the second process, casting and venting occur simultaneously. At this stage, the casting volume is smaller, while the inert gas flow rate is larger. Influenced by the temperature of the casting medium, the inert gas temperature rises rapidly. As the inert gas flows along the gating system, it heats the system. Due to the larger flow rate of inert gas, it distributes the casting medium along the flow path, resulting in uniform heating within the gating system. The gas flow also allows for rapid temperature distribution within the casting medium. This second process is relatively short, accounting for only 3-5% of the total casting process. Once the inert gas has completed heating, the second process ends.

[0077] In the third process, casting and aeration occur simultaneously. At this stage, the casting volume increases while the amount of inert gas introduced decreases. In the second process, the gating system, after heating, dries the sand core and sand box. Due to the short duration of this second process, if any areas are not thoroughly dried, bubbling and agitation of the casting medium can occur. The introduction of a small amount of inert gas in the third process causes this agitation, thus eliminating bubbling. The inert gas flows along the casting medium, suppressing agitation and eliminating casting defects. The third process is therefore longer, accounting for 7-10% of the total casting process.

[0078] In the fourth process, casting is carried out at the basic casting speed and the inert gas supply is stopped until casting is completed.

[0079] After casting is completed, the unpacking and cleaning process begins. The sand box is slowly cooled to 300°C before unpacking. After unpacking, the sand is removed, and the gating system is cleaned.

[0080] The sand box acts as a heat insulator for the casting, slowing down the cooling process. This slow cooling ensures a uniform temperature throughout the casting, resulting in a more even distribution of its internal microstructure.

[0081] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0082] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A casting method for a complex valve body casting, characterized in that, Includes the following steps: The analysis steps include designing the gating system based on the valve body's structure, analyzing the heat distribution and heat dissipation during the casting process, and determining the heat dissipation location data and heat dissipation rate data. Opening procedure: Make an opening in the sandbox according to the heat dissipation location data; The process of making a chiller involves fabricating the chiller based on data on the location and rate of heat dissipation. The steps for cooling iron include the following: Shell manufacturing process: The shell is manufactured according to the opening size; Core manufacturing process: Determine the surface shape of the core based on heat dissipation rate data; Place the core into the outer shell; Filling process: Paraffin wax is filled between the inner core and the outer shell; The chilled iron consists of paraffin wax, an outer shell, and an inner core placed inside the outer shell; one end of the outer shell is sealed, and the other end of the outer shell is open; one end of the outer shell is inserted into a sand box, and the inner core is placed inside the outer shell from the other end of the outer shell. The inner core includes a gradually cooling block and a slow cooling block; a gradually expanding or narrowing contact surface is provided around the gradually cooling block; the contact surface and the slow cooling block are rounded; when the inner core is installed inside the outer shell, the contact surface does not contact the inner surface of the outer shell, the slow cooling block fits against the inner surface of the outer shell, and the end face of the inner core does not contact the inner surface of the outer shell. Since the end face and contact surface of the inner core do not contact the inner surface of the outer shell, a space is formed between the outer shell and the inner core, and the paraffin wax fills the space. The space between the end face of the inner core and the inner surface of the outer shell forms the rapid cooling zone; the space between the contact surface and the inner surface of the outer shell forms the gradual cooling zone; the area where the slow cooling block contacts the inner surface of the outer shell is the slow cooling zone. The sand core making process involves creating sand cores based on data on heat dissipation location and heat dissipation rate. The casting process involves placing the sand core in the sand box, inserting a chill into the sand box, and then closing the box. During the casting process, the casting volume gradually increases. The casting temperature is 1610-1630℃. Inert gas is introduced at the beginning of the casting process, and the amount of inert gas is gradually reduced. Unpacking and cleaning steps: Slowly cool the sand box to 300℃ before unpacking; after unpacking, clean the sand and clean the pouring channel; The casting process of the box assembly and casting step includes the following steps: First step: Determine the basic casting speed and basic ventilation speed; In the first process, the total casting time is determined based on the size of the casting; the basic casting speed is determined based on the total casting time and the volume of the casting; and the basic ventilation speed is determined based on the flow path of the inert gas along the gating system. Second process: Cast at 10-15% of the basic casting speed; Inert gas is introduced at the basic ventilation speed; Third process: Cast at 60-65% of the basic casting speed; Inert gas is introduced at 6-9% of the basic ventilation speed; Fourth step: Cast at the basic casting speed; stop the introduction of inert gas.

2. The casting method for complex valve body castings as described in claim 1, characterized in that: In the sand core making process, the sand core includes guide protrusions; the position of the guide protrusions is determined based on the heat dissipation position data; the extension angle of the guide protrusions is determined based on the heat dissipation rate data.

3. The casting method for complex valve body castings as described in claim 1, characterized in that: During the casting process, the depth of the chill inserted into the sand box is adjusted according to the heat dissipation rate data.

4. The casting method for complex valve body castings as described in claim 3, characterized in that: During the casting process: The second process accounts for 3-5% of the total casting process; The third process accounts for 7-10% of the casting process; The fourth process accounts for the remaining portion of the casting process.

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