A method of forming a volute casting

Abstract

The application belongs to the technical field of casting and mainly relates to a forming method of an austenite volute casting, which adopts pattern following parting according to the special structure of the volute casting, adopts the mode of upper box integral manual core making combined with lower box 3D printing block core making, effectively solves the problems of being unable to part and being difficult to take a mold due to the irregular shape of the volute casting, and avoids the defects that if the upper box adopts 3D printing, core separation design is needed, but after core separation, the sand core is difficult to guarantee the stability of the center of gravity. Further, positioning pieces matched with each other are arranged on each sand core matched with each other to guarantee the installation progress and stability. By adopting the forming method provided by the application, the operation is simple, the strength of the sand core can be effectively improved, the risk of core floating caused by insufficient pressure to suppress the steel liquid buoyancy in the pouring process is reduced, the production cost is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of casting technology and mainly relates to a forming method for austenitic volute-type castings. Background Technology

[0002] With the rapid development of industry, energy conservation has received increasing attention. Utilizing expanders to recover energy from processes in industries such as chemical engineering, metallurgy, building materials, and power generation not only improves energy efficiency but also protects the environment. Therefore, expanders, as a new type of device for recovering and reusing waste heat and waste gas, are being used more and more widely.

[0003] An expander is a machine that utilizes the principle of reducing gas temperature by outputting mechanical work when compressed gas expands and depressurizes, thereby obtaining energy. It is a type of heat engine that converts thermal energy into mechanical energy, and is a rapidly developing new type of power machinery. It can directly drive generators or directly drive pumps, fans, and other mechanical equipment. The volute is a key component of the expander's inlet, primarily responsible for smoothly changing the direction of high-temperature, high-pressure exhaust gas containing a certain degree of corrosiveness, and evenly distributing it to the nozzles to perform work in the expansion chamber and recover energy, achieving energy conservation and consumption reduction. The spiral-gradient structure of the expander volute's inner cavity makes the product difficult to design in terms of both casting process and molding method, especially for a special type of volute with a connection between the air passage and the main body of the inner cavity that is only 65mm thick. This makes it difficult to guarantee the strength of the sand core, resulting in a high risk of core drift. Unlike ordinary volutes, the center of the air passage opening and the center of the main flow channel are not on the same plane, resulting in a large portion of the opening being beveled during molding, further complicating the volute molding design. Therefore, how to mold the aforementioned special type of volute is an urgent problem to be solved. Summary of the Invention

[0004] Based on the above-mentioned challenges, it is necessary to propose a forming method for volute castings that overcomes the problems of insufficient sand core strength and high risk of core drift in existing technologies.

[0005] A method for forming a volute casting, the method comprising the following steps: The upper and lower boxes are combined for shaping. The parting surface is set along the center of the main air passage and the center of the nozzle of the volute, which is not a horizontal plane.

[0006] The upper box sand core, the lower box sand core, and the inner cavity sand core are made, and the upper box sand core, the lower box sand core, and the inner cavity sand core are assembled to form the casting cavity of the volute casting.

[0007] The inner cavity sand core includes a cylindrical sand core and an air passage sand core. A first positioning head is provided on the cylindrical sand core, and a second positioning head matching the first positioning head is provided on the air passage sand core. The cylindrical sand core and the air passage sand core are assembled through the cooperation of the first and second positioning heads. Dividing the inner cavity sand core into a cylindrical sand core and an air passage sand core simplifies the complex core box structure that is difficult to fill and remove using a monolithic inner cavity sand core, and also avoids the risk of breakage at weak points during the hoisting of the monolithic sand core.

[0008] To better realize the present invention, both the cylindrical sand core and the air duct sand core are made by hand to facilitate the laying of the core skeleton and ensure the strength of the sand core.

[0009] To better realize this invention, the upper sand core is integrally formed and made by hand. Due to the complex internal gas channel structure of the volute casting, with diameters ranging from coarse to fine, the finest part having a diameter of approximately 200mm, if the upper sand core were made using 3D printing, it would be impossible to place the core frame, thus compromising the core's strength. Furthermore, due to the limited printing size of the printer, the upper sand core cannot be printed as a single unit. Dividing the upper sand core into several smaller cores would result in instability at the core center, making it impossible to fix. Therefore, the upper sand core is made entirely by hand.

[0010] To better realize the present invention, the lower box sand core is divided into several lower box sand core modules and is formed by 3D printing.

[0011] To better realize the present invention, several hidden risers are provided on the cylindrical sand core.

[0012] To better realize the present invention, a third positioning core is provided between several of the aforementioned dark risers.

[0013] To better realize the present invention, the third positioning core is set as a plum blossom-shaped core.

[0014] To better realize the present invention, a fourth positioning core head matching the third positioning core head is provided on the sand core of the lower box.

[0015] To better realize the present invention, a pouring hole is provided on the lower box sand core.

[0016] To better realize the present invention, a plurality of air passage sand core marker points are set on the lower box sand core, and air passage sand core marker heads that match each air passage sand core marker point are set on the air passage sand core. When closing the box, a fastener is used to pass through the air passage sand core marker points and the air passage sand core marker heads and fix them; this can effectively prevent the air passage sand core from drifting.

[0017] To better realize the present invention, matching positioning platforms and positioning grooves are respectively provided on the upper box sand core and the lower box sand core to ensure the core assembly accuracy of the upper box sand core and the lower box sand core.

[0018] The molding method for volute castings provided by this invention utilizes a mold-following process based on the unique structure of the volute casting. It employs a combination of manual core-making for the upper mold box and 3D-printed segmented core-making for the lower mold box, effectively solving problems such as difficulty in mold separation and demolding caused by the irregular shape of the volute casting. Simultaneously, it avoids the drawback of 3D printing equipment size limitations, where 3D printing of the upper mold box requires a segmented design, but the sand cores after segmentation are difficult to stabilize. Furthermore, matching positioning components are set on each cooperating sand core to ensure installation progress and stability.

[0019] The molding method provided by this invention is simple to operate, can effectively improve the strength of the sand core, reduce the risk of core floating due to insufficient pressure to suppress the buoyancy of molten steel during the casting process, reduce production costs, and improve production efficiency. Attached Figure Description

[0020] Appendix Figure 1 Schematic diagram of the volute casting structure; Appendix Figure 2 Schematic diagram of the upper sand core structure; Appendix Figure 3 Schematic diagram of the lower chamber sand core structure; Appendix Figure 4 : Schematic diagram of the first angle of the cylindrical sand core structure; Appendix Figure 5 Schematic diagram of the second angle structure of a straight cylindrical sand core; Appendix Figure 6 Schematic diagram of airway sand core structure.

[0021] 100 - Airway inlet; 200 - Airway body; 300 - Upper chamber sand core; 400 - Lower chamber sand core; 500 - Straight cylindrical sand core; 600 - Airway sand core; 310 - Positioning platform; 410 - Positioning groove; 420 - Airway sand core marker point; 430 - Fourth positioning core head; 440 - Sprue hole; 510 - Third positioning core head; 520 - First positioning core head; 610 - Airway sand core marker core head; 620 - Second positioning core head. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0023] This embodiment mainly relates to a molding method for an irregularly shaped volute casting. The center deviation between the air passage inlet 100 and the air passage body 200 is approximately 270mm. The air passage has a spirally tapered structure. The maximum diameter of the air passage inlet 100 is 820mm, and the minimum diameter is 200mm. Therefore, an innovative and reasonable molding method needs to be designed based on these factors. See the attached document for details. Figure 1 To be continued Figure 6 As shown, the specific steps include: Step 01: The upper and lower boxes are combined to form the shape. The parting surface is set along the center of the main air passage 200 of the volute and the center of the pipe opening. That is, the parting surface is not a horizontal plane.

[0024] It should be noted that the parting line design follows the center of the gas duct inlet 100 of the volute casting, transitioning from the geometric center of the inclined inlet to the center of the gas duct body 200. The part above the parting line is the upper box, and the part below is the lower box. The lower box sand core 400 can still be stably placed on the molding platform after being disassembled, without any issues of support difficulties after disassembly.

[0025] Step 02: Fabricate the upper mold sand core 300, lower mold sand core 400, and inner cavity sand core. Assemble the upper mold sand core 300, lower mold sand core 400, and inner cavity sand core to form the mold cavity for the volute casting. The upper mold sand core 300 is formed by integral hand-making; the lower mold sand core 400 is divided into several lower mold sand core 400 modules and formed by 3D printing.

[0026] Step 03: The inner cavity sand core includes a cylindrical sand core 500 and an airway sand core 600; the cylindrical sand core 500 is provided with a first positioning head 520, and the airway sand core 600 is provided with a second positioning head 620 that matches the first positioning head 520. The cylindrical sand core 500 and the airway sand core 600 are assembled by the cooperation of the first positioning head 520 and the second positioning head 620.

[0027] Specifically, a fourth positioning core head 430 matching the third positioning core head 510 is provided on the lower box sand core 400. A gate hole 440 is provided on the lower box sand core 400. Several air duct sand core marker points 420 are provided on the lower box sand core 400, and air duct sand core marker core heads 610 matching each air duct sand core marker point 420 are provided on the air duct sand core 600. When closing the box, a fastener is used to pass through the air duct sand core marker points 420 and the air duct sand core marker core heads 610 and fix them; this can effectively prevent the air duct sand core 600 from drifting. Matching positioning platforms 310 and positioning grooves 410 are respectively provided on the upper box sand core 300 and the lower box sand core 400 to ensure the core assembly dimensional accuracy of the upper box sand core 300 and the lower box sand core 400.

[0028] It should be noted that due to the irregular structure of the volute casting, the center deviation between the air passage opening 100 and the air passage body 200 is large, and the air passage has a spiral gradient structure. The diameter of the volute air passage is only 200mm from the largest point of the opening (820mm) to the smallest point of the end. Correspondingly, the diameter of the end of the internal sand core is also only 200mm. If the 3D printing method is used, it is impossible to place the core in the sand core, which would result in the inability to guarantee the strength of the sand core end. Therefore, it is necessary to use the traditional molding method to place the core to ensure its strength. Furthermore, due to the limited size of the printer, it is impossible to print the entire upper mold sand core 300. If the upper mold sand mold is divided into multiple sand cores for printing, the upper mold sand core 300 cannot be stably fixed to the lower mold sand core 400 after being separated because there is no support point above the cavity. A core head support point needs to be designed on the inner cavity sand core for the upper mold sand core 300 to be stable. However, the upper mold sand core 300 and the lower mold sand core 400 are in conjunction with the inner cavity sand core at the same time, which is complicated and increases the risk of dimensional deviation due to the splicing of multiple sand cores. Therefore, the upper mold sand core 300 cannot be 3D printed and needs to be formed by integral manual core making. Based on the above reasons, a method of integral manual core making of the upper mold combined with 3D printing and segmented core making of the lower mold is proposed to complete the forming of this special volute casting.

[0029] Specifically, both the cylindrical sand core 500 and the air duct sand core 600 are handmade to facilitate core reinforcement and ensure core strength. Furthermore, several concealed risers are provided on the cylindrical sand core 500; a third positioning core head 510 is positioned between these concealed risers. The third positioning core head 510 is configured as a quincunx (or quincunx) shaped core head.

[0030] The inner cylindrical section and the venting section of the volute casting have only a 65mm thick cavity. The inner sand core is a cylindrical section connected to a circular venting channel, and the connection is only 65mm thick. In addition, the inner sand core of the volute is equipped with a hidden riser, the bottom surface of which is flush with the bottom surface of the casting. The ingate enters from the bottom of the neck of the hidden riser. In the design of the inner cavity, a protruding core head is set to ensure that the inner sand core is fixed in the lower box sand core 400. This results in the ingate below the neck of the hidden riser being located in the inner sand core. When closing the box, the gate positions of the inner manual sand core and the lower box 3D printed sand core are prone to misalignment during core setting. Therefore, a reliable docking installation method needs to be designed for the straight cylindrical sand core 500 and the lower box sand core 400. Thus, a quincunx-shaped core head is used for positioning to avoid sand flushing problems caused by inaccurate docking.

[0031] Furthermore, the straight cylindrical sand core 500 uses a split core box on the left and right sides for core making; the air channel sand core 600 uses a split core box on the top and bottom sides for core making; this makes sand filling and mold removal simple and convenient.

[0032] It should be noted that the internal structure of the volute casting is complex. If the inner cavity sand core adopts a monolithic sand core structure, that is, the cylindrical sand core 500 and the air passage sand core 600 are monolithic sand cores, manual core making would make it difficult to fill the irregular air passage area inside the core box with sand and would make it impossible to remove the mold. The core box design would be very complex. In addition, the risk of breakage at the weak connection between the middle main body and the outer air passage during hoisting is high when the sand core is made as a monolithic sand core. Therefore, it is necessary to divide the inner cavity sand core into cylindrical sand cores 500 and air passage sand cores 600 for core making. This simplifies the core box structure and makes the operation easier. At the same time, fixing the cylindrical sand cores 500 and the air passage sand cores 600 separately avoids the risk of breakage at the weak connection between the air passage and the middle main body when using monolithic sand cores. Setting a positioning core head can ensure the accurate positioning of each sand core during the box assembly process.

[0033] 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.

[0034] 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 method for forming a volute casting, characterized in that, The volute casting is an irregularly structured volute casting; the forming method includes the following steps: The upper and lower boxes are combined for shaping, and the parting surface is set along the center of the main air passage and the center of the nozzle of the volute. The upper mold sand core, lower mold sand core, and inner cavity sand core are fabricated, and the upper mold sand core, lower mold sand core, and inner cavity sand core are assembled to form the casting cavity of the volute casting. The upper mold sand core is integrally formed by hand core making. The lower mold sand core is divided into several lower mold sand core modules and is formed by 3D printing. The inner cavity sand core includes a cylindrical sand core and an airway sand core, both of which are handmade. The cylindrical sand core is provided with a first positioning head, and the airway sand core is provided with a second positioning head that matches the first positioning head. The cylindrical sand core and the airway sand core are assembled by the cooperation of the first positioning head and the second positioning head. A plurality of concealed risers are provided on the cylindrical sand core; a third positioning core head is provided between the plurality of concealed risers; a fourth positioning core head matching the third positioning core head is provided on the sand core of the lower box; a plurality of air passage sand core marker points are provided on the sand core of the lower box, and air passage sand core marker core heads matching each of the air passage sand core marker points are provided on the air passage sand core. When closing the box, a fastener is used to pass through the air passage sand core marker points and the air passage sand core marker core heads and fix them.

2. The forming method for the volute casting according to claim 1, characterized in that, The third positioning core is configured as a plum blossom-shaped core.

3. The forming method for the volute casting according to claim 1, characterized in that, A pouring hole is provided on the lower sand core.

4. The forming method for the volute casting according to claim 1, characterized in that, Matching positioning platforms and positioning grooves are respectively provided on the upper and lower sand cores.

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