Core manufacturing method for inner cylinder sand core of steam turbine

Abstract

The invention relates to a core making method of a steam turbine inner cylinder sand core, which comprises the following steps: during 3D printing of a main body sand core, synchronously printing a core box on the surface of the main body sand core, filling the core box with resin sand with an anti-sand-sticking effect for manual core making of a runner sand core, and synchronously sticking the main body sand core and the runner sand core into a whole, so that on one hand, sand sticking at a runner position is effectively prevented; on one hand, the defects of size deviation and the like caused by core assembly are avoided, and in addition, the problems of cost increase, subsequent sand treatment and the like caused by large-area use of special sand can be effectively avoided. According to the core manufacturing method of the steam turbine inner cylinder sand core, the existing simple mode that a 3D printing sand core is combined with a manual core is broken through, the 3D + technology is optimized, the 3D sand core and the manual sand core are integrally formed, no gap exists between the 3D sand core and the manual sand core, cooperation between the sand cores does not need to be considered, and the method is wide in applicability and can be popularized and applied to manufacturing of other types of sand cores.

Description

Technical Field

[0001] This invention relates to the field of casting technology, and in particular to a method for making sand cores for steam turbine inner cylinders. Background Technology

[0002] 3D printing employs binder jetting technology to lay sand layer by layer, curing each layer to form a sand core. This method offers advantages such as high forming precision and the elimination of the need for molds. It is widely used for complex sand core structures, such as those for turbine inner cylinders. The flow channels of a turbine inner cylinder are semi-enclosed, with a small-opening tubular structure. The surrounding area has a relatively thick wall, and this flow channel region is located in an overheated area, making it particularly prone to sand adhesion defects.

[0003] In existing technologies, turbine inner cylinder sand cores are typically fabricated using a 3D+ method, where the main sand core and the runner sand core are made independently before being assembled. The main sand core is 3D printed, while the runner sand core is hand-made using special sand to address sand adhesion issues. However, during the assembly process, the fitting dimensions of the main sand core and the runner sand core must be precisely considered. Inappropriate gaps or deviations in the hand-made core dimensions can lead to problems such as excessively large filler seams and difficulty in core placement, while also increasing the risk of sand rubbing into the mold cavity. Furthermore, the runner sand core uses a suspended structure, resulting in a weak connection with the main sand core, which is prone to casting defects and reduces production efficiency. Summary of the Invention

[0004] Therefore, it is necessary to provide a core-making method for steam turbine inner cylinder sand cores to address the aforementioned technical problems.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] This invention discloses a method for making a sand core for a steam turbine inner cylinder. The steam turbine inner cylinder sand core includes a main sand core and a flow channel sand core. A main core box and an auxiliary core box are disposed on the surface of the main sand core. The main sand core, the main core box, and the auxiliary core box together form a core box cavity for accommodating the flow channel sand core. The core making method includes the following steps:

[0007] The main sand core is manufactured using 3D printing, and the main core box is printed and brought out together with it.

[0008] Assembly: The main core box and the auxiliary core box are assembled to form the core box cavity;

[0009] Core making involves filling the core box cavity with resin sand, and removing the main core box and the auxiliary core box after the resin sand has cured.

[0010] In one embodiment, the resin sand is an anti-sticking sand molded sand uniformly mixed with resin and curing agent.

[0011] In one embodiment, the anti-adhesion molding sand is ceramic sand, steel sand, or chromite sand.

[0012] In one embodiment, the surface of the main sand core is provided with a plurality of core holes; in the printing step, the core holes are printed out together; before the flow channel sand core making step, the core is inserted into the core holes.

[0013] In one embodiment, prior to the assembly step, a coating is applied to the surface of the main core box and / or the auxiliary core box, followed by a release agent.

[0014] In one embodiment, the coating is an alcohol-based coating for casting.

[0015] In one embodiment, the main core box and / or the auxiliary core box are sanded with sandpaper before the coating is applied to their surfaces.

[0016] In one embodiment, the auxiliary core box is provided with a positioning core head, and the main core box is provided with a positioning groove to accommodate the positioning core head.

[0017] In one embodiment, the cross-sectional area of ​​the positioning core head gradually decreases along the direction away from the auxiliary core box.

[0018] In one embodiment, a dry sand layer is provided inside the main core box and / or auxiliary core box.

[0019] The technical solution adopted in this invention can achieve the following beneficial effects:

[0020] The present invention discloses a core-making method for turbine inner cylinder sand cores. While 3D printing the main sand core, a core box is simultaneously printed on the surface of the main sand core. The core box is filled with resin sand with anti-sticking properties for manual core making of the flow channel sand core. The main sand core and the flow channel sand core are bonded together as a whole. This effectively prevents sand from sticking to the flow channel and eliminates defects such as dimensional deviations caused by core assembly. In addition, it can effectively avoid the increased cost and subsequent sand processing problems caused by the large-scale use of special sand.

[0021] The method for making sand cores for turbine inner cylinders disclosed in this invention breaks through the existing simple 3D printed sand core combination and handmade core method. It optimizes the 3D+ process, and the 3D sand core and the handmade sand core are integrally formed without gaps between them. There is no need to consider the fit between sand cores. This method has wide applicability and can be promoted to other types of sand core production. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view of the turbine inner cylinder sand core disclosed in an embodiment of the present invention.

[0023] Explanation of reference numerals in the attached figures:

[0024] 10-Main sand core, 11-Main core box, 21-First auxiliary core box, 22-Second auxiliary core box, 23-Third auxiliary core box, 24-Fourth auxiliary core box, 25-Fifth auxiliary core box, 30-Flow channel sand core, 40-Core skeleton, 50-Dry sand layer. Detailed Implementation

[0025] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the 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 invention.

[0026] 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.

[0027] 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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] This invention discloses a method for making sand cores for steam turbine inner cylinders, such as... Figure 1 As shown, the turbine inner cylinder sand core includes a main sand core 10 and a runner sand core 30. During the casting process, the runner sand core 30 is used to form the runner structure of the turbine inner cylinder casting, while the main sand core 10 is used to form other parts of the turbine inner cylinder casting. For this turbine inner cylinder sand core, this invention designs a 3D+ molding process. To improve the molding efficiency and accuracy of the main sand core 10 and reduce its core-making cost, the main sand core 10 is made using ordinary sand 3D printing. To improve the anti-sticking performance of the runner sand core 30, the runner sand core 30 is hand-made using resin sand made from special sand. To improve the fitting accuracy between the main sand core 10 and the runner sand core 30, during the hand-making process of the runner sand core 30, the main sand core 10 and the runner sand core 30 are molded as a single unit, eliminating the need for subsequent core assembly.

[0029] Specifically, the core-making method for the turbine inner cylinder sand core may include the following steps:

[0030] Core box design, such as Figure 1 As shown, a main core box 11 and an auxiliary core box assembly are designed at corresponding locations on the surface of the main sand core 10. The main core box 11, the auxiliary core box assembly, and the main sand core 10 together form a cavity that can accommodate the flow channel sand core 30. In this embodiment, the auxiliary core box assembly may include a first auxiliary core box 21, a second auxiliary core box 22, a third auxiliary core box 23, a fourth auxiliary core box 24, and a fifth auxiliary core box 25. The main core box 11, the first auxiliary core box 21, the second auxiliary core box 22, the third auxiliary core box 23, the fourth auxiliary core box 24, and the fifth auxiliary core box 25 can be assembled by splicing them together. Preferably, the main core box 11 and the first auxiliary core box 21 / fifth auxiliary core box 25 can be positioned by a positioning core head. The first auxiliary core box 21 / fifth auxiliary core box 25 is designed with a positioning core head, and the main core box 11 is designed with a positioning groove that matches the positioning core head. The positioning core head can be designed with a reverse slope so that the positioning core head can be inserted into the positioning groove.

[0031] The main sand core 10 is made by printing the main sand core 10 using a 3D printer. During the printing process, the main core box 11 is also printed out. That is, the main sand core 10 and the main core box 11 are printed together using a 3D printer.

[0032] In this embodiment, the first auxiliary core box 21, the second auxiliary core box 22, the third auxiliary core box 23, the fourth auxiliary core box 24 and the fifth auxiliary core box 25 can also be formed by 3D printing. They can be printed separately or printed together with the main sand core 10 and brought out together.

[0033] After cleaning the sand, the main core box 11 is sanded with fine sandpaper to remove surface texture. Then, two coats of casting alcohol-based coating are applied to the working surface of the main core box 11. After the coating dries, it is sanded again with fine sandpaper. Finally, a layer of release agent is applied. To improve the accuracy of the sand core fabrication, the overall thickness of the coating and release agent should be controlled within 0.8 mm.

[0034] The treatment of each auxiliary core box can be the same as that of the main core box 11. In both cases, the box is first sanded, then two layers of paint are applied, and then it is sanded again before applying a release agent.

[0035] It should be noted that in this embodiment, during the processing of the main core box 11 and each auxiliary core box, the positioning core head and positioning groove are not coated with paint and release agent.

[0036] The core box assembly and flow channel sand core 30 core making process involves sequentially assembling the main core box 11, the first auxiliary core box 21, and the second auxiliary core box 22 on the left side; similarly, the main core box 11, the fifth auxiliary core box 25, and the fourth auxiliary core box 24 on the right side are also assembled sequentially. Resin sand made from special sand is filled into the core box cavity, and the cavity is sealed using the third auxiliary core box 23. After the resin sand has cured, all auxiliary core boxes and the main core box 11 are removed, thus obtaining the flow channel sand core 30. Simultaneously, the flow channel sand core 30 and the main sand core 10 are cured and bonded together. The resin sand made from special sand can be a uniformly mixed anti-sticking sand molding sand containing resin and curing agent, such as ceramic sand, steel sand, or chromite sand.

[0037] In the embodiments disclosed in this invention, to improve the strength of the flow channel sand core 30 and the bonding strength between the flow channel sand core 30 and the main body sand core 10, a core rib 40 can be provided in the flow channel sand core 30 and at the bonding portion between the flow channel sand core 30 and the main body sand core 10. During the printing process of the main body sand core 10, multiple core rib holes can be formed on the surface of the main body sand core 10. After sand removal, the core rib 40 can be inserted into the core rib holes, with a portion of each core rib 40 inside the core rib hole and another portion inside the core box cavity. When sand is filled into the core box cavity to make the flow channel sand core 30, the core rib 40 is simultaneously implanted into the flow channel sand core 30 and the main body sand core 10. In this embodiment, the core rib 40 is rod-shaped. Of course, depending on the structure of the flow channel sand core 30, the core rib 40 can also be designed with various structures and various connection methods, such as welding connections between core ribs 40. This embodiment of the invention does not impose specific limitations on this.

[0038] In the embodiments disclosed in this invention, such as Figure 1 As shown, a dry sand layer 50 can be provided inside the main core box 11, the first auxiliary core box 21, the second auxiliary core box 22, the third auxiliary core box 23, the fourth auxiliary core box 24, and / or the fifth auxiliary core box 25. In this embodiment, the thickness of the main core box 11 and each auxiliary core box is approximately 30 mm, and the dry sand layer 50 can be provided at a distance of 10 mm to 15 mm from the surface of the casting. This dry sand layer 50 can be directly fabricated during the 3D printing process; that is, during the printing process, only sand is laid in this area without spraying adhesive. When the dry sand layer 50 is provided inside the main core box 11 and / or each auxiliary core box, the main core box 11 and / or each auxiliary core box can be removed by quickly breaking them apart.

[0039] 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.

[0040] 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 making a sand core for a steam turbine inner cylinder, characterized in that, The turbine inner cylinder sand core includes a main sand core and a flow channel sand core; the surface of the main sand core is provided with a main core box and an auxiliary core box, and the main sand core, the main core box and the auxiliary core box together form a core box cavity for accommodating the flow channel sand core; The core-making method includes the following steps: The main sand core is manufactured using 3D printing, and the main core box is printed and brought out together with it. Assembly: The main core box and the auxiliary core box are assembled to form the core box cavity; Core making involves filling the core box cavity with resin sand, and removing the main core box and the auxiliary core box after the resin sand has cured.

2. The core-making method for turbine inner cylinder sand cores according to claim 1, characterized in that, The resin sand is an anti-sticking sand molded sand uniformly mixed with resin and curing agent.

3. The core-making method for turbine inner cylinder sand cores according to claim 1, characterized in that, The anti-adhesion molding sand is ceramic sand, steel sand, or chromite sand.

4. The core-making method for turbine inner cylinder sand cores according to claim 1, characterized in that, The surface of the main sand core is provided with multiple core holes; In the printing step, the core hole is printed out along with the core. Before the core-making step of the flow channel sand core, the core is inserted into the core hole.

5. The method for making a sand core for a steam turbine inner cylinder according to claim 1, characterized in that, Before the assembly step, a coating is applied to the surface of the main core box and / or the auxiliary core box, followed by a release agent.

6. The method for making a sand core for a steam turbine inner cylinder according to claim 5, characterized in that, The coating is an alcohol-based coating for casting.

7. The method for making a sand core for a steam turbine inner cylinder according to claim 5, characterized in that, Before applying paint to the surface of the main core box and / or the auxiliary core box, sand the main core box and / or the auxiliary core box with sandpaper.

8. The method for making a sand core for a steam turbine inner cylinder according to claim 1, characterized in that, The auxiliary core box is provided with a positioning core head, and the main core box is provided with a positioning groove to accommodate the positioning core head.

9. The method for making a sand core for a steam turbine inner cylinder according to claim 1, characterized in that, The cross-sectional area of ​​the positioning core head gradually decreases along the direction away from the auxiliary core box.

10. The method for making a sand core for a steam turbine inner cylinder according to any one of claims 1 to 9, characterized in that, A dry sand layer is provided inside the main core box and / or auxiliary core box.

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