A molding method and sand mold structure for a narrow cavity structure cylinder block casting
By using a split-core design and rigid connection, the problems of easy sand mold damage and difficult coating in casting of narrow cavity structures are solved, thus achieving high-quality production of castings.
Patent Information
- Application Number
- CN202610592837.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-30
- Publication Date
- 2026-08-04
AI Technical Summary
Existing casting processes for narrow cavity structures suffer from problems such as easy sand mold damage, difficulty in coating, and inability to demold complex structures, which severely limit the quality and yield of high-end cast steel parts.
The design employs a split-core structure, dividing the narrow cavity structure into a cavity core and a main sand mold. Through the rigid connection of the positioning core head, core seat, and standard core skeleton segment, a stable connection between the cavity core and the main sand mold is ensured, achieving uniform coating of the paint and preventing displacement.
The strength of sand molds with narrow cavities has been improved, solving the problems of easy damage during demolding and difficulty in coating, thus ensuring the dimensional accuracy and yield of castings.
Smart Images
Figure CN122500135A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of casting technology, and more specifically, to a molding method and sand mold structure for cylinder block castings with narrow cavity structures. Background Technology
[0002] Cast steel cylinders for steam turbines, gas turbines, compressors, and other energy equipment are core pressure-bearing components. Their internal structures are extremely complex, typically featuring multiple pipe openings, multiple chambers, and narrow oil grooves and gas passages with widths ranging from 25mm to 600mm. These intricate and complex internal features pose severe challenges and extremely high quality risks to the casting process, especially the molding operation.
[0003] Currently, the industry generally uses the traditional integral pattern sand casting method for such narrow cavity structures. The specific operation involves creating an integral pattern containing the narrow vortex structure. During molding, the core used to form the narrow vortex area is designed as a single unit with the core of the main sand core, and the sand is poured together to form an integral sand mold. However, this method suffers from problems in actual production, such as easy damage to the sand mold, difficulty in coating, and difficulty in demolding, severely limiting the design feasibility and casting feasibility of the structure.
[0004] Therefore, the production of narrow cavity sand molds in the existing technology has become a prominent bottleneck restricting the quality and yield of such high-end cast steel parts, and there is an urgent need for a molding method and sand mold structure for cylinder block castings with narrow cavity structures. Summary of the Invention
[0005] This application solves the problems of low sand mold strength in narrow cavities, easy damage during demolding, difficulty in coating leading to sand adhesion, and inability to demold complex structures when using integral pattern sand casting in the prior art.
[0006] The first aspect of this application provides a method for molding cast steel cylinder parts with narrow cavity structures, comprising: The cavity portion of the sand mold structure of the casting is designed as the cavity core, and the remaining part is designed as the main sand mold. A positioning core head is designed on the hollow core, and a core seat and a standard core hole penetrating the sand mold are designed at corresponding positions on the main sand mold; Prepare the hollow core such that the core skeleton of the hollow core has a standard core skeleton segment extending in the direction of the main sand mold; The hollow core is assembled with the main sand mold. The hollow core is placed on the core seat of the main sand mold through the positioning core head, and the standard core segment passes through the standard core hole on the main sand mold. On the back of the main sand mold, the core segment is fixedly connected to the skeleton or box of the main sand mold.
[0007] Preferably, before assembling the cavity core with the main sand mold, the method further includes: applying a coating to the vortex surface of the cavity core and drying it.
[0008] Preferably, the design of the cavity portion of the sand mold structure of the casting as a cavity core includes the cavity portion having a barbed structure, a deep and narrow gap, and a complex vortex structure with continuous distribution.
[0009] Preferably, the mating surfaces of the positioning core head and the core seat are provided with anti-misalignment cut corners.
[0010] Preferably, the standard core segment is fixedly connected to the skeleton or box of the main sand mold on the back side, including by welding, bolting and locking with special clamps.
[0011] Preferably, the core segment is made of round steel with a diameter of 10-12mm, and its length extends 50-100mm to the back of the main sand mold; a 30-50mm square tube is provided in the core hole and welded to the main core.
[0012] The second aspect of this application provides a sand mold structure for casting steel castings with narrow cavity structures, employing the molding method for cylinder castings with narrow cavity structures as described above, comprising a main sand mold and at least one cavity core; the cavity core forms a rigid connection structure with the skeleton on the back of the main sand mold through its extended core segment.
[0013] This application solves the problems of low sand mold strength in narrow parts, easy damage during demolding, difficulty in coating, and inability to demold complex structures by adopting a split-core design and rigid connection fixation. Attached Figure Description
[0014] Figure 1 A schematic flowchart illustrating the molding method for a narrow cavity structure cylinder casting steel part provided in an embodiment of this application; Figure 2A This is a schematic diagram of the turbine product prototype structure provided in the embodiments of this application; Figure 2B This is a schematic diagram of the sand mold structure of the upper casing of the steam turbine product provided in the embodiments of this application; Figure 3A This is a front view of the core-splitting structure of a steam turbine product provided in an embodiment of this application; Figure 3B This is a top view of the core structure of a steam turbine product provided in an embodiment of this application; Figure 4A The embodiment of this application provides a schematic diagram of the sand mold fabrication for the main body of the steam turbine product. Figure 1 ; Figure 4BThis application provides a schematic diagram of the main sand mold fabrication process for a steam turbine product; Figure 5A The embodiments of this application provide a schematic diagram of the fabrication of the hollow core of a steam turbine product. Figure 1 ; Figure 5B The embodiment of this application provides a schematic diagram of the fabrication of the hollow core of the steam turbine product, Part 2. Detailed Implementation
[0015] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.
[0016] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," "top," "bottom," "end," "top," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.
[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0018] Please refer to Figure 1 , Figure 1 This is a schematic flowchart of a molding method for a narrow cavity structure cylinder casting steel part provided in an embodiment of this application, including the following steps: S1: Design the cavity part of the sand mold structure of the casting as the cavity core, and design the remaining part as the main sand mold.
[0019] For irregular areas of narrow, hollow cylinder castings, traditional integral molding methods are difficult to use and prone to damage. This invention first decomposes the overall sand mold structure of the casting. The complex-shaped, narrow-sized portion is independently separated into a "hollow core," while the remaining part is designed as the "main sand mold."
[0020] Furthermore, the design of the cavity portion of the sand mold structure of the casting as a cavity core includes a complex vortex structure with barbed structure, deep and narrow gaps, and continuous distribution.
[0021] S2: A positioning core head is designed on the hollow core, and a core seat and a standard core hole that penetrates the sand mold are designed at the corresponding positions on the main sand mold.
[0022] In the design of the hollow core, a positioning core head is added. Furthermore, the mating surfaces of the positioning core head and the core seat are provided with anti-misalignment chamfers to ensure assembly accuracy. On the main sand mold, a core seat is designed at a corresponding position to accommodate the positioning core head, and a standard core hole penetrating the sand mold is pre-set above the core seat.
[0023] The main model is created and shaped (main sand mold). During the shaping process, a positioning core head for the hollow core needs to be placed on the main model, thus forming a corresponding core seat on the main sand mold. The key step is to pre-determine the position of the core hole on the main model, vertically place the core hole skeleton (which can be a section of square tubing), and fix it to the main core skeleton of the main sand mold to form an integral structure. Then, the sand is pounded and compacted, finally producing a main sand mold with core holes and core seats.
[0024] S3: Prepare the hollow core, so that the core of the hollow core has a core segment extending in the direction of the main sand mold.
[0025] In the core design of the hollow core, a standard core segment extending towards the main sand mold is specially designed. This standard core segment is preferably made of round steel with a diameter of 10~12mm. Its length needs to be determined according to the thickness of the sand mold and the amount of sand it can absorb, ensuring that it extends to the back of the main sand mold by 50~100mm and that its position matches the standard core hole on the main sand mold.
[0026] S4: The hollow core is assembled with the main sand mold. The hollow core is placed on the core seat of the main sand mold through the positioning core head, and the standard core segment passes through the standard core hole on the main sand mold.
[0027] The core with the core segment is placed into the core box, filled with sand and pounded to complete the preparation of the hollow core.
[0028] Furthermore, since the hollow core is manufactured independently, operators can easily apply coating to the entire surface of the volutes (i.e., the forming surface of the casting) of the hollow core during this step. Uniform coating can be achieved on both narrow right angles and complex curved surfaces. After coating, the hollow core is sent to a drying oven for drying to ensure the coating layer adheres firmly.
[0029] S5: On the back of the main sand mold, the core segment is fixedly connected to the skeleton or box of the main sand mold.
[0030] By positioning the core head and core seat together, the hollow core is precisely placed on the main sand mold. At this time, the core marker segment on the hollow core will naturally pass through the core marker hole on the main sand mold and extend to the back of the main sand mold.
[0031] Then, a rigid connection is established: on the back of the main sand mold (i.e., the exposed end of the core hole), the core segment is securely connected to the core hole square tube (or box block) on the main sand mold using welding, bolting, or special clamps. This rigid connection ensures that the hollow core will not shift, sink, or float due to the impact or buoyancy of the molten metal during subsequent mold assembly and pouring processes.
[0032] The core segment of the standard mold can be fixedly connected to the frame or box of the main sand mold by welding, bolting, or locking with special clamps.
[0033] Furthermore, the core segment is made of round steel with a diameter of 10-12mm, and its length extends 50-100mm to the back of the main sand mold; a 30-50mm square tube is provided in the core hole and welded to the main core.
[0034] Based on the same inventive concept, this application also provides a sand mold structure for casting steel parts with narrow cavity structures, employing the molding method for cylinder block steel parts with narrow cavity structures as described above, including a main sand mold and at least one cavity core; the cavity core forms a rigid connection structure with the skeleton on the back of the main sand mold through its extended core segment. For details, refer to steps S1-S5 and any optional embodiments thereof; this embodiment will not repeat them further. The molding method for cast steel cylinder parts with narrow cavity structures provided in this application will be described below with reference to a specific embodiment. Please refer to Figures 2-5.
[0035] In this embodiment, taking the manufacture of a certain type of high-pressure cylinder for a steam turbine as an example, such as... Figure 2A and Figure 2B The image shows the product pattern 1 and the upper sand mold 2. The mold opening has two consecutive vortex grooves 3, with an irregular annular shape and a width of 35-60mm. The specific implementation steps are as follows: Core-splitting design: Based on the sand mold structure, the overall sand mold is designed in sections. Complex shapes, narrow dimensions, and difficult-to-form or demold vortex and cavity sections are independently designed as one or more "cavity cores." This product has two continuous vortex sections, which need to be split into two different "cavity cores"4. The remaining main body is designed as the "main body sand mold"5. Each cavity core is designed with a positioning core head6 and anti-misalignment cutting angles, and a corresponding core seat7 is designed on the main body sand mold, such as... Figure 3A and Figure 3B As shown.
[0036] Fabrication of the main sand mold: Based on the above core-splitting design, fabricate and shape the main body pattern. A positioning core head 6 for the hollow core needs to be placed on the main body pattern to form a corresponding core seat 7 on the main sand mold. A core guide hole 8 penetrating the sand mold is pre-set. A 30-50mm square tube is placed perpendicular to the core head positioning hole and welded to the main core frame 9 to form a whole. The main sand mold with the core guide hole and core seat is then produced. Figure 4A and Figure 4B As shown.
[0037] Fabrication of the hollow core: The hollow core 4 is fabricated separately. Its core frame is designed with a standard core frame segment 10 extending towards the main sand mold. This standard core frame segment can be made of Φ10~12 round steel, depending on the sand mold thickness and sand intake. Its length is 50~100mm from the back of the high-pressure main sand mold, and its position matches the standard core hole on the main sand mold. The hollow core is then pounded within the core box 11, as follows: Figure 5A and Figure 5B As shown.
[0038] Sand mold assembly: The surface of the cavity core volute is coated and dried, and the core head is precisely placed on the core seat of the main sand mold using this coating. Simultaneously, the standard core segment extending from the cavity core is inserted into the pre-set standard core hole on the main sand mold. On the back of the main sand mold, at the exposed end of the standard core hole, the standard core segment is rigidly connected and fixed to the square tube of the standard core hole in the main sand mold using welding, fasteners, or special clamps, ensuring that the cavity core will not shift or float during subsequent mold assembly and pouring processes.
[0039] Mold assembly and casting: After all the cavity cores are installed and fixed, the entire surface is brushed and dried before the mold is assembled to form a complete mold.
[0040] Based on the technical solution provided in this application, the most vulnerable narrow groove section is independently cored, avoiding direct pulling on this fragile sand mold during the demolding process, fundamentally eliminating sand mold cracking and detachment defects. The hollow core is made in an independent core box, with all surfaces (including the narrowest curved surface) exposed, allowing for convenient and uniform brushing or dipping with coatings, completely solving the coating problem and effectively preventing sand adhesion to the casting. Any complex and narrow structure that is difficult to demold can be solved by designing an independent hollow core. The core box can be designed as a detachable or special structure to ensure the core can be removed from the core box, thus greatly freeing the design constraints of the casting's internal structure. Precise positioning is achieved through the positioning core head and core seat, and the rigid connection of the standard core core frame and standard core hole doubles the guarantee of the hollow core's positional accuracy in the mold, preventing displacement or sinking under the buoyancy of the molten metal, and ensuring the accuracy of the casting dimensions. It can be widely used in the production of various medium and large cast steel and cast iron parts with internal narrow cavities and complex channels.
[0041] 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.
[0042] The embodiments described above are merely illustrative of several implementation methods of this application, 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 this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A molding method for a steel casting of a cylinder block of a narrow cavity structure, characterized by, include: The cavity portion of the sand mold structure of the casting is designed as the cavity core, and the remaining part is designed as the main sand mold. A positioning core head is designed on the hollow core, and a core seat and a standard core hole penetrating the sand mold are designed at corresponding positions on the main sand mold; Prepare the hollow core such that the core skeleton of the hollow core has a standard core skeleton segment extending in the direction of the main sand mold; The hollow core is assembled with the main sand mold. The hollow core is placed on the core seat of the main sand mold through the positioning core head, and the standard core segment passes through the standard core hole on the main sand mold. On the back of the main sand mold, the core segment is fixedly connected to the skeleton or box of the main sand mold.
2. The molding method for a cast steel member for a narrow cavity structure cylinder according to claim 1, characterized by, Before assembling the cavity core with the main sand mold, the process further includes: applying a coating to the vortex surface of the cavity core and drying it.
3. The molding method for a cast steel member for a narrow cavity structure cylinder according to claim 1, characterized by, The design of the cavity portion of the sand mold structure of the casting as a cavity core includes the cavity portion having a barbed structure, a deep and narrow gap, and a complex vortex structure with continuous distribution.
4. The molding method for a cast steel member for a narrow cavity structure cylinder according to claim 1, characterized by, The mating surfaces of the positioning core and the core seat are provided with anti-misalignment cut corners.
5. The molding method for a cast steel member for a narrow cavity structure cylinder according to claim 1, characterized by, On the back of the main sand mold, the standard core segment is fixedly connected to the skeleton or box of the main sand mold, including by welding, bolting and locking with special clamps.
6. The molding method for a cast steel member for a narrow cavity structure cylinder according to claim 1, characterized by The core segment is made of round steel with a diameter of 10-12mm, and its length extends 50-100mm to the back of the main sand mold; a 30-50mm square tube is provided in the core hole and welded to the main core.
7. A sand mold structure for casting a cast steel member having a narrow cavity structure, characterized by, The molding method for cylinder block castings with narrow cavity structures as described in any one of claims 1-6 includes a main sand mold and at least one cavity core; the cavity core forms a rigid connection structure with the skeleton on the back of the main sand mold through its extended core core segment.