Precision casting gating system for reducing slag inclusion defects

Abstract

This invention discloses a precision casting gating system for reducing inclusion defects, comprising: a pouring cup, a sprue, multiple runners, multiple casting molds, and risers connected to the top of each casting mold. The outlet end of each runner connects to the bottom end of the casting mold, forming a bottom-pouring gating system for upward filling from the bottom of the casting mold. Each runner connects to the sprue to form a gating channel. Multiple filters are sequentially installed within each gating channel to reduce the amount of inclusions entering the casting mold. The gating channel is a variable-diameter channel with multiple changes in inner diameter along the flow direction of the molten metal, allowing the molten metal to gradually form a stable laminar flow before being poured into the corresponding casting mold from the bottom end. This system improves the stability of molten metal filling, effectively reduces the amount of foreign matter entering the part, and avoids the risk of mold shell peeling and inclusions caused by high-speed molten metal impacting the mold.

Description

Technical Field

[0001] This invention relates to the field of precision casting technology for aero-engine or industrial gas turbine components, and in particular, to a precision casting gating system for reducing inclusion defects. Background Technology

[0002] Currently, the main method for producing turbine rotor blanks in China is investment casting. This involves creating a wax model, then wrapping it layer by layer with refractory material and drying it to form a mold shell with specific structural dimensions. Finally, the turbine rotor blank is cast using a vacuum melting furnace. Throughout the production process, foreign matter can easily be introduced at any stage, ultimately leading to inclusions on the surface and inside the turbine rotor blank casting. When the turbine rotor operates at high temperatures, the impact of these defects is further amplified, causing the casting to lose its structural function. Therefore, after the turbine rotor is cast, a series of non-destructive tests, including fluorescent testing and X-ray testing, are performed to ensure that the number and size of inclusions in the casting are within a controllable range.

[0003] The existing impeller rotor blank structure is shown in the attached figure. Figure 1 As shown, it mainly consists of a central hub and blades radially and evenly distributed on the outer side of the hub. The minimum thickness at the common impeller hub is approximately 10 mm, while the thickness at the blade exhaust edge is only about 0.4~0.6 mm. To ensure the complete filling of the turbine rotor blade section, a mainstream design scheme in current casting systems is the top-pouring casting system, as shown in the attached diagram. Figure 2 As shown, the molten metal is poured directly into the mold shell through the pouring cup, and sufficient pressure is provided through the large riser at the top to ensure that the molten metal completely enters the blade section.

[0004] There are certain shortcomings in using this top-pouring casting system, as follows: (1) Weak slag blocking effect: After the molten metal enters the pouring cup, it will directly enter the module. At the same time, the foreign slag will enter the module along with the molten metal. When the slag enters the thin-walled position such as the blade, the slag cannot continue to flow with the molten metal, resulting in slag inclusion defects at that part of the blade.

[0005] (2) Disorder in the process of molten metal filling: When molten metal is filled, it is not hindered by other factors, but only affected by gravity. The flow rate of molten metal during pouring is too fast. When it reaches the inside of the mold shell, it is in a turbulent state. On the one hand, it is not conducive to slag removal. On the other hand, it will cause molten metal to splash and churn in the mold, thus failing to fill the mold effectively and resulting in under-casting defects.

[0006] (3) The impact force of molten metal on the mold shell is large: When pouring, the molten metal directly enters the mold shell. The high-speed molten metal has a large impact force on the mold shell. The inner surface of the mold shell is impacted, resulting in chipping and defects, which further increases the risk of slag inclusions in the casting. Summary of the Invention

[0007] This invention provides a precision casting gating system for reducing slag inclusion defects, thereby solving the technical problems of existing top-pouring gating systems, such as weak slag-blocking effect, disordered molten metal filling process, and large impact force on the mold shell during molten metal filling process.

[0008] The technical solution adopted in this invention is as follows: A precision casting gating system for reducing inclusion defects includes: a pouring cup, a vertically arranged sprue with its top end connected to the pouring cup, multiple horizontally arranged gating runners, multiple casting mold shells for separately filling the molds to form impeller rotor blanks, and risers connected to the top of each casting mold shell; the multiple gating runners are evenly spaced along the circumference of the sprue, and the inlet end of each gating runner is connected to the bottom end of the sprue, and the outlet end of each gating runner is connected to the bottom end of the vertically arranged casting mold shell, so that the gating system forms a bottom-pouring gating system for filling the mold shell from the bottom to the top, and each horizontal gating runner... The gating system connects to the sprue to form a pouring channel. Each pouring channel is equipped with multiple filters to filter the pouring liquid multiple times, thereby reducing the amount of inclusions that ultimately enter the casting mold. The pouring channel is a variable inner diameter channel with multiple changes in its inner diameter along the pouring liquid flow direction. Through the changes in the inner diameter of the variable inner diameter channel and the effect of the filters, the pouring liquid gradually forms a stable laminar flow during the filling process before being poured into the corresponding casting mold from the bottom end, further reducing the amount of inclusions that ultimately enter the casting mold.

[0009] Furthermore, the sprue includes an upper sprue section and a lower sprue section arranged sequentially and connected by an arc transition. The lower sprue section is a tapered section whose inner diameter gradually decreases along the direction of the pouring liquid flow. The top of the upper sprue section is connected to the bottom of the pouring cup by an arc transition. The bottom of the lower sprue section is connected to each of the horizontal runners. The tapered design of the lower sprue section is used to ensure that the pouring liquid can adhere tightly to the inner wall of the sprue mold shell during the downward pouring process, thereby avoiding gaps between the pouring liquid and the inner wall of the sprue mold shell, which would cause the pouring liquid to swirl and form turbulence.

[0010] Furthermore, the formula for calculating the radius of the cross-section at height h of the lower section of the straight girder is as follows: Where r is the radius of the section to be calculated, r0 is the radius of the inlet of the lower section of the sprue, v0 is the initial velocity of the sprue fluid at the inlet of the lower section of the sprue, h is the height of the section to be calculated, and g is the acceleration due to gravity.

[0011] Furthermore, the upper section of the sprue is a tapered section with an inner diameter that gradually decreases along the direction of the filling flow of the casting liquid, and the inner taper of the upper section of the sprue is greater than that of the lower section of the sprue, so as to cooperate with the function of the pouring cup and thus ensure the filling volume of the entire casting system.

[0012] Furthermore, the cross-sectional area Sdirect at the outlet end of the straight runner and the cross-sectional area Shorizontal at the inlet end of the horizontal runner are related by the following formula: Sdirect ≈ n S_horizontal; where n is the number of horizontal runners.

[0013] Furthermore, the sprue includes a front section and a rear section of the sprue that are sequentially arranged and connected along the filling flow direction of the pouring liquid. The inlet end of the front section of the sprue is connected to the outlet end of the sprue, and the outlet end of the rear section of the sprue is connected to the bottom end of the casting mold shell. Both the front section and the rear section of the sprue are equal diameter sections with a constant inner diameter along their length direction, and the inner diameter of the front section of the sprue is larger than that of the rear section of the sprue, so that the pouring liquid gradually forms a stable laminar flow during the filling flow process and then fills the casting mold shell.

[0014] Furthermore, the total flow rate of the grout in the front section, Qfront, and the total flow rate of the grout in the rear section, Qback, satisfy the following formula: Qfront≈Qback.

[0015] Furthermore, by combining the velocity of the sprue in the front and rear sections of the sprue, the cross-sectional areas of the front and rear sections of the sprue, and the lengths of the front and rear sections of the sprue, calculations and verifications show that when the ratio of the radius of the rear section to the radius of the front section of the sprue is 0.4 to 0.7, the sprue can achieve the best laminar flow effect under the action of the sprue.

[0016] Furthermore, each pouring channel has two filters. One filter is located at the junction of the outlet end of the sprue and the inlet end of the runner, and the other filter is located at the junction of the inlet end of the rear section of the runner and the outlet end of the front section of the runner.

[0017] Furthermore, the gating system also includes multiple first reinforcing ribs connecting each riser and the pouring cup, and multiple second reinforcing ribs connecting each riser and the sprue.

[0018] The present invention has the following beneficial effects: The pouring process of the precision casting gating system for reducing inclusion defects in this invention is as follows: First, the molten metal enters the pouring cup after melting, and then flows into the sprue in a turbulent state. After passing through the sprue, it enters multiple runners from the bottom end of the sprue. After passing through the runners, it flows upwards from the bottom end of the casting mold shell, forming a bottom-pouring pouring process. Finally, after filling the casting mold shell, it flows upwards from the top end of the casting mold shell into a connected riser, thus completing the synchronous pouring of multiple impeller rotor blanks in this batch. Throughout the pouring process, the molten metal is affected by the varying inner diameter of the pouring channels in the sprue and runners, thereby reducing the degree of turbulence in the molten metal until it becomes a stable laminar flow before filling the casting mold shell from the bottom end. At the same time, during the flow of the molten metal during filling, it is also subjected to multiple filters to ultimately reduce the amount of inclusions entering the casting mold shell, thereby achieving the goal of reducing the proportion of inclusions inside the casting.

[0019] In the casting system of this invention, (1) it is beneficial to improve the stability of molten metal filling: after passing through the sprue, multiple filter screens and the horizontal sprue, the molten metal enters the interior of the casting mold shell in a stable laminar flow. During the whole process, the flow of molten metal gradually tends to a stable laminar flow, and the excess material will float on the top layer of the molten metal and enter the riser, thus achieving the purpose of avoiding the entry of excess material into the interior of the part; (2) it can effectively reduce the amount of excess material entering the interior of the part: before the molten metal enters the casting mold shell, it has already passed through the action of multiple filter screens, and most of the slag inclusions have been blocked outside the filter screens, thus greatly reducing the proportion of slag inclusions in the molten metal and ultimately reducing the defect of slag inclusions in the blades; (3) it can avoid the risk of mold shell peeling and slag inclusion caused by high-speed molten metal impacting the mold shell: before the molten metal enters the casting mold shell, it will first impact multiple filter screens to reduce the speed, thus greatly reducing the speed and avoiding the phenomenon of mold shell peeling and slag inclusion caused by impacting the mold shell.

[0020] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 It is an existing impeller rotor-like blank structure; Figure 2 This is a schematic diagram of an existing top-casting system. Figure 3 This is a top view schematic diagram of a precision casting gating system for reducing inclusion defects according to a preferred embodiment of the present invention; Figure 4 yes Figure 3 A partial sectional front view schematic diagram of a precision casting gating system for reducing inclusion defects.

[0022] Legend: 1. Pouring cup; 2. Sprue; 21. Upper section of sprue; 22. Lower section of sprue; 3. Horizontal pouring runner; 31. Front section of horizontal pouring runner; 32. Rear section of horizontal pouring runner; 4. Casting mold shell; 5. Riser; 6. Filter screen; 7. First reinforcing rib. Detailed Implementation

[0023] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0024] Those skilled in the art will understand that, unless specifically stated otherwise, the term "comprising" as used in this specification means the presence of the stated features, integers, steps, operations, components, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, components, and / or combinations thereof. It should be understood that when we say a component is "connected" to another component, it can be directly connected to the other component or connected via an intermediate component. The term "and / or" as used herein includes all or any unit and all combinations of one or more associated listed items. The terms "first" and "second," etc., in this specification and claims are used to distinguish different objects, not to describe a particular order.

[0025] Reference Figure 3 and Figure 4A preferred embodiment of the present invention provides a precision casting gating system for reducing inclusion defects, comprising: a pouring cup 1, a vertically arranged sprue 2 with its top end connected to the pouring cup 1, multiple horizontally arranged gating runners 3, multiple casting mold shells 4 for separately filling the mold to form impeller rotor blanks, and risers 5 connected to the top of each casting mold shell 4. The multiple gating runners 3 are evenly spaced along the circumference of the sprue 2, and the inlet end of each gating runner 3 is connected to the bottom end of the sprue 2, and the outlet end of each gating runner 3 is connected to the bottom end of the vertically arranged casting mold shell 4, so that the gating system forms a bottom-pouring gating system for filling the mold shell 4 from the bottom end upwards. Each gating runner 3 connects to the sprue 2 to form a pouring channel, and multiple filter screens 6 are sequentially arranged in each pouring channel to filter the pouring liquid multiple times through the multiple filter screens 6, thereby reducing the amount of inclusions that ultimately enter the casting mold shell 4. The pouring channel is a variable inner diameter channel with multiple changes in the inner diameter along the pouring flow direction of the pouring liquid. Through the change in the inner diameter of the variable inner diameter channel and the action of the filter screen 6, the pouring liquid gradually forms a stable laminar flow during the pouring process and is then poured into the corresponding casting mold 4 from the bottom end of each casting mold 4, so as to further reduce the amount of inclusions that finally enter the casting mold 4.

[0026] The casting process of the precision casting gating system for reducing inclusion defects of the present invention is as follows: First, the casting liquid (molten metal) enters the pouring cup 1 after melting, and then enters the sprue 2 in a turbulent state. After passing through the sprue 2, it enters multiple horizontal runners 3 from the bottom end of the sprue 2. After passing through the horizontal runners 3, it enters the casting mold 4 from the bottom end of the casting mold 4 to form bottom pouring of the casting mold 4. Finally, after filling the casting mold 4, it enters the connected riser 5 from the top end of the casting mold 4, thereby completing the synchronous casting of multiple impeller rotor blanks in this batch. Throughout the pouring process, the molten metal is affected by the varying inner diameter of the pouring channels in the sprue 2 and the runner 3, which reduces the turbulence of the molten metal until it becomes a stable laminar flow before being poured into the casting mold 4 from the bottom. At the same time, during the flow of the molten metal, it is also subjected to the action of multiple filters 6 to ultimately reduce the amount of slag entering the casting mold 4, thereby achieving the goal of reducing the proportion of slag inside the casting.

[0027] In the casting system of the present invention, (1) it is beneficial to improve the stability of the molten metal filling: after the molten metal passes through the sprue 2, multiple filter screens 6 and the horizontal sprue 3 and other multi-stage structures, the molten metal enters the interior of the casting mold shell 4 in a stable laminar flow. During the whole process, the flow of the molten metal gradually tends to a stable laminar flow, and the excess will float on the top layer of the molten metal and enter the interior of the riser 5, thus achieving the purpose of avoiding the excess from entering the interior of the part; (2) it can effectively reduce the amount of excess entering the interior of the part: before the molten metal enters the casting mold shell 4, it has already passed through the multi-stage filter screens 6, and most of the slag has been blocked outside the filter screens 6, so the proportion of slag in the molten metal is greatly reduced, and the defect of slag inclusion in the blade is ultimately reduced; (3) it can avoid the risk of mold shell peeling caused by high-speed molten metal impacting the mold shell and thus generating slag inclusion: before the molten metal enters the casting mold shell 4, it will first impact multiple filter screens 6 to reduce the speed, so the speed is greatly reduced, avoiding the phenomenon of impacting the mold shell and causing slag inclusion.

[0028] Optionally, such as Figure 4 As shown, the sprue 2 includes an upper sprue section 21 and a lower sprue section 22, which are arranged sequentially and connected by an arc transition. The lower sprue section 22 is a tapered section whose inner diameter gradually decreases along the direction of the pouring liquid flow. The top of the upper sprue section 21 is connected to the bottom of the pouring cup 1 by an arc transition. The bottom of the lower sprue section 22 is connected to each of the horizontal runners 3. The tapered design of the lower sprue section 22 is designed to ensure that the pouring liquid can adhere tightly to the inner wall of the sprue 2 mold shell during the downward pouring process. This avoids gaps between the pouring liquid and the inner wall of the sprue 2 mold shell, which would cause the pouring liquid to swirl and form turbulence. This facilitates slag removal and reduces the defects caused by splashing and churning of molten metal in the casting, which could prevent filling and result in under-casting.

[0029] In this optional scheme, the lower section 22 of the sprue is not a conventional cylinder, but a cone with an incline. By calculating the flow rate of the molten metal and the work done by gravity on the molten metal, the cross-sectional radius of the lower section 22 of the sprue at height h can be calculated, as shown in the following calculation formula: .

[0030] Where r is the radius of the section to be calculated, r0 is the radius of the inlet of the lower section 22 of the sprue, v0 is the initial velocity of the sprue fluid at the inlet of the lower section 22 of the sprue, h is the height of the section to be calculated, and g is the acceleration due to gravity.

[0031] Using the aforementioned inclined conical sprue lower section 22 ensures that the molten metal can fit completely with the sprue mold shell during filling, without causing turbulence due to molten metal swirl caused by gaps. This not only facilitates slag removal but also promotes the formation of laminar flow of molten metal in the subsequent horizontal sprue 3.

[0032] In this optional solution, such as Figure 4As shown, the upper section 21 of the sprue is a tapered section whose inner diameter gradually decreases along the direction of the pouring liquid filling flow. The inner taper of the upper section 21 of the sprue is greater than that of the inner taper of the lower section 22 of the sprue. This is to cooperate with the function of the pouring cup 1 to ensure the filling volume of the entire pouring system and to effectively prevent the molten metal from overflowing from the pouring cup 1, thus ensuring the safety of the filling process.

[0033] Preferably, such as Figure 3 and Figure 4 As shown, when molten metal enters the sprue 3 from the sprue 2, it should be ensured that the molten metal can completely enter multiple sprues 3. Therefore, the cross-sectional area S at the outlet end of the sprue 2 is... 直 The cross-sectional area S at the inlet end of the horizontal runner 3 横 Formula 2 should be satisfied as follows: S 直 ≈n S 横 Where n is the number of horizontal sprues 3. In this preferred embodiment, the number of n is 3.

[0034] Optionally, such as Figure 3 and Figure 4 As shown, the sprue 3 includes a front section 31 and a rear section 32, which are sequentially arranged and connected along the filling flow direction of the molten metal. The inlet end of the front section 31 is connected to the outlet end of the sprue 2, and the outlet end of the rear section 32 is connected to the bottom end of the casting mold shell 4. Both the front section 31 and the rear section 32 are sections with a constant inner diameter along their length, and the inner diameter of the front section 31 is larger than that of the rear section 32, so that the molten metal gradually forms a stable laminar flow before entering the casting mold shell 4 during the filling flow process. In this optional scheme, the difference in length and radius between the front section 31 and the rear section 32 is used to ensure that the molten metal reaches a stable laminar flow before entering the casting mold shell 4.

[0035] When specifically setting the front section 31 and rear section 32 of the horizontal runner, the two should first satisfy the following relationship: the total flow rate Q of the pouring liquid in the front section 31 of the horizontal runner. 前 The total flow rate Q of the grout in the rear section 32 of the horizontal runner 后 It satisfies the following formula three: Q 前 ≈Q 后 This ensures that the molten metal can completely enter the rear section 32 of the sprue from the front section 31, and then enter the casting mold shell 4 from the rear section 32, thus avoiding problems such as blockage and poor flow in the entire sprue 3.

[0036] Then, considering the velocity of the sprue fluid in the front section 31 and the rear section 32 of the horizontal runner, the cross-sectional areas of the front section 31 and the rear section 32, and the lengths of the front section 31 and the rear section 32 (theoretically, a longer rear section 32 is more conducive to the formation and stability of laminar flow; however, in actual production, given the actual layout of the production site, the rear section 32 cannot be of arbitrary length. Therefore, in actual design, based on the site conditions, the lengths of the front section 31 and the rear section 32 of the horizontal runner are first rationally arranged, and then the specific cross-sectional radii of the front section 31 and the rear section 32 are specifically calculated and analyzed), in this optional scheme, based on the actual site layout, calculations and verification show that when the ratio of the radius of the rear section 32 to the radius of the front section 31 is 0.4 to 0.7, the sprue fluid can achieve the best laminar flow effect under the action of the horizontal runner 3.

[0037] Optionally, such as Figure 3 and Figure 4 As shown, each casting channel has two filters 6. One filter 6 is located at the junction of the outlet end of the sprue 2 and the inlet end of the runner 3, and the other filter 6 is located at the junction of the inlet end of the rear section 32 of the runner and the outlet end of the front section 31 of the runner. In this optional scheme, two filters 6 are installed in each casting channel to reduce the degree of turbulence in the molten metal and block most of the inclusions outside the part. Specifically, the filter 6 at the outlet end of the sprue 2 can initially reduce the flow velocity of the molten metal, filter the turbulent fluid to a direction closer to the flow direction, and prevent high-speed molten metal from impacting the bottom of the mold shell. It can also prevent large-sized foreign matter from entering the subsequent casting system, thereby reducing the risk of inclusions in the product. The addition of a second-stage filter 6 at the inlet of the rear section 32 of the runner can concentrate the flow direction of the molten metal to a greater extent, thereby achieving the purpose of laminar flow of the molten metal. At the same time, the use of two-stage filters 6 can also block most of the foreign inclusions outside the part, thereby effectively reducing the proportion of inclusions in the casting.

[0038] During operation, after the molten metal is melted, it first enters the pouring cup 1, and then enters the sprue 2 in a turbulent state. The molten metal is constrained by the gradually narrowing lower section 22 of the sprue to reduce the degree of turbulence. When the molten metal comes into contact with the first-stage filter screen 6, the speed of the molten metal entering the front section 31 of the runner is significantly reduced. At the same time, larger inclusions are blocked inside the sprue 2 to prevent them from entering the subsequent parts. After the velocity direction of the molten metal is turned to horizontal in the front section 31 of the runner, the flow speed is further reduced after passing through the second-stage filter screen 6. At the same time, medium-sized inclusions are blocked outside the parts again. After passing through the longer rear section 32 of the runner, the molten metal is basically in a laminar flow state. As the molten metal enters the casting mold shell 4, the inclusions will float to the riser 5, ultimately achieving the purpose of reducing the proportion of inclusions inside the casting.

[0039] Preferably, such as Figure 3 and Figure 4 As shown, the gating system also includes multiple first reinforcing ribs 7 connecting each riser 5 to the pouring cup 1, and multiple second reinforcing ribs connecting each riser 5 to the sprue 2. In this preferred embodiment, the first reinforcing ribs 7 and the second reinforcing ribs are used to improve the strength of the module and reduce the risk of module damage due to center of gravity shift during production.

[0040] The system of this invention has been put into production verification in integral casting impellers for aero engines. The product gating system design and technical solution are consistent. After considering the yield, shell manufacturing process, and module counterweight, the final design consists of 3 blanks per group, as shown in the attached figure. Figure 3 As shown. The gating system should be designed according to the aforementioned method: The conical inclination angle of the lower section 22 of the sprue is calculated according to Formula 1. The radius of the inlet end of the upper section 21 of the sprue is designed to be Φ53~Φ57mm, and the corresponding pouring cup 1 is selected according to the size of the inlet end of the upper section 21 of the sprue. Then, considering the pouring speed and the overall height of the module, the diameter of the outlet end of the lower section 22 of the sprue is calculated to be Φ47~49mm. Then, according to Formula 2, Formula 3, and the actual layout of the site, further calculations determine that the inner diameter of the front section 31 of the horizontal sprue is approximately Φ28~Φ29mm, and the inner diameter of the rear section 32 of the horizontal sprue is approximately Φ20~Φ21mm (the ratio of the inner diameter of the rear section 32 of the horizontal sprue to the inner diameter of the front section 31 of the horizontal sprue is approximately 0.7). Finally, a primary filter screen 6 is designed at the outlet end of the sprue 2, and a secondary filter screen 6 is set in each of the three horizontal sprues 3. The mesh density of the two-stage filter screens 6 is 10~20ppi. After verification in actual production, non-destructive testing results showed that the slag inclusion situation of the product was significantly improved, and this solution is effective in improving the slag inclusion problem in castings.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A precision casting gating system for reducing inclusion defects, characterized in that, include: The pouring cup (1), the vertically arranged sprue (2) connected to the pouring cup (1) at the top, the multiple horizontally arranged sprues (3), the multiple casting mold shells (4) used to form impeller rotor blanks after filling the molds separately, and the risers (5) connected to the top of each casting mold shell (4). Multiple horizontal runners (3) are evenly spaced along the circumference of the sprue (2), and the inlet end of each horizontal runner (3) is connected to the bottom end of the sprue (2), and the outlet end of each horizontal runner (3) is connected to the bottom end of the vertically arranged casting mold (4), so that the gating system forms a bottom-pouring gating system for filling the casting mold (4) from the bottom end upwards, and each horizontal runner (3) is connected to the sprue (2) to form a gating channel. Multiple filter screens (6) are arranged in sequence in each gating channel so that the gating liquid is filtered multiple times through multiple filter screens (6) to reduce the amount of slag that finally enters the casting mold (4); The pouring channel is a variable inner diameter channel with multiple changes in the inner diameter along the pouring flow direction of the pouring liquid. Through the change in the inner diameter of the variable inner diameter channel and the action of the filter screen (6), the pouring liquid gradually forms a stable laminar flow during the filling process and is then poured into the corresponding casting mold shell (4) from the bottom end of each casting mold shell (4) to further reduce the amount of slag that finally enters the casting mold shell (4).

2. The precision casting gating system for reducing inclusion defects according to claim 1, characterized in that, The sprue (2) includes an upper section (21) and a lower section (22) of the sprue, which are arranged sequentially and connected by an arc transition. The lower section (22) of the sprue is a tapered section whose inner diameter gradually decreases along the direction of the filling flow of the casting liquid. The top of the upper section (21) of the sprue is connected to the bottom of the pouring cup (1) by a rounded transition. The bottom end of the lower section (22) of the sprue is connected to each of the horizontal sprues (3), and the tapered setting of the lower section (22) of the sprue is used to ensure that the sprue liquid can be closely attached to the inner wall of the sprue (2) mold shell during the downward filling process, thereby avoiding the gap between the sprue liquid and the inner wall of the sprue (2) mold shell, which would cause the sprue liquid to roll and form turbulence.

3. The precision casting gating system for reducing inclusion defects according to claim 2, characterized in that, The formula for calculating the radius of the cross section at height h of the lower section (22) of the straight girder is as follows: ； Where r is the radius of the section to be calculated, r0 is the radius of the inlet of the lower section (22) of the straight sprue, v0 is the initial velocity of the sprue at the inlet of the lower section (22), h is the height of the section to be calculated, and g is the acceleration due to gravity.

4. The precision casting gating system for reducing inclusion defects according to claim 2, characterized in that, The upper section (21) of the sprue is a tapered section whose inner diameter gradually decreases along the direction of the filling flow of the pouring liquid, and the inner taper of the upper section (21) of the sprue is greater than that of the inner taper of the lower section (22) of the sprue, so as to cooperate with the function of the pouring cup (1) and thus ensure the filling volume of the entire pouring system.

5. The precision casting gating system for reducing inclusion defects according to claim 1, characterized in that, The cross-sectional area S at the outlet end of the straight gating (2) 直 The cross-sectional area S at the inlet end of the horizontal runner (3) 横 The relationship satisfies the following formula: S 直 ≈n S 横 ; Where n is the number of horizontal runners (3).

6. The precision casting gating system for reducing inclusion defects according to claim 1, characterized in that, The horizontal runner (3) includes a front section (31) and a rear section (32) of the horizontal runner arranged sequentially and connected along the filling flow direction of the pouring liquid. The inlet end of the front section (31) of the horizontal runner is connected to the outlet end of the straight runner (2), and the outlet end of the rear section (32) of the horizontal runner is connected to the bottom end of the casting mold shell (4). Both the front section (31) and the rear section (32) of the sprue are equal diameter sections with an unchanged inner diameter along their length direction. The inner diameter of the front section (31) of the sprue is larger than that of the rear section (32) of the sprue, so that the pouring liquid gradually forms a stable laminar flow during the filling process and then fills the casting mold shell (4).

7. The precision casting gating system for reducing inclusion defects according to claim 6, characterized in that, The total flow rate Q of the grout in the front section (31) of the horizontal runner 前 The total flow rate Q of the grout in the rear section (32) of the horizontal runner 后 It satisfies the following formula three: Q 前 ≈Q 后 。 8. The precision casting gating system for reducing inclusion defects according to claim 7, characterized in that, Based on the velocity of the grout in the front section (31) and the rear section (32) of the horizontal runner, the cross-sectional area of ​​the front section (31) and the cross-sectional area of ​​the rear section (32) of the horizontal runner, the length of the front section (31) and the length of the rear section (32) of the horizontal runner, the calculation and verification results show that when the ratio of the radius of the rear section (32) of the horizontal runner to the radius of the front section (31) of the horizontal runner is 0.4 to 0.7, the grout can achieve the best laminar flow effect under the action of the horizontal runner (3).

9. The precision casting gating system for reducing inclusion defects according to claim 1, characterized in that, Each pouring channel has two filters (6). One filter (6) is located at the junction of the outlet end of the straight pouring channel (2) and the inlet end of the horizontal pouring channel (3). The other filter (6) is located at the junction of the inlet end of the rear section (32) of the horizontal pouring channel and the outlet end of the front section (31) of the horizontal pouring channel.

10. The precision casting gating system for reducing inclusion defects according to claim 1, characterized in that, The gating system also includes multiple first reinforcing ribs (7) connecting each riser (5) to the pouring cup (1), and multiple second reinforcing ribs connecting each riser (5) to the sprue (2).

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