Method for solving in-hole shrinkage porosity of thick-wall rotor

Abstract

The invention relates to a method for solving in-hole shrinkage porosity of a thick-wall rotor, which comprises the following steps: sand core preparation: designing a main body sand core and a top surface sand core according to a casting structure, respectively presetting a first support piece cavity and a second support piece cavity in the main body sand core and the top surface sand core, and then manufacturing the sand cores; a mold is fastened to a core box bottom support, a positioning table is arranged in the middle of the core box bottom support, chilling core iron is arranged on the positioning table, chromium ore is added and compacted, and manufacturing of the rod-shaped sand core is completed; a first supporting piece and a second supporting piece are placed in the first supporting piece cavity and the second supporting piece cavity, the rod-shaped sand core is placed in the main body sand core, the top face sand core is assembled on the whole of the rod-shaped sand core and the main body sand core, and box assembling is completed. The method solves the problem that in the prior art, a thin and long hole in the middle of the thick-wall rotor is prone to shrinkage porosity during casting, and has the advantages of improving the casting yield and the cleaning efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of sand casting, in particular to a method for solving the problem of shrinkage in a shaft hole of a thick-walled rotor casting. Background Art

[0002] The rotor body of the screw compressor has a thick wall, and the middle ring has a small processing hole. The hole diameter is small and long, and the aspect ratio is greater than 10. In sand casting, it belongs to the hole diameter of super sand casting, which is very difficult to cast. In addition, the connection surface between the casting hole and the outside is extremely small, and the ratio of the surface area inside the hole to the heat dissipation area of ​​the two ends of the hole is extremely large. The heat dissipation condition in the hole is poor, the solidification in the hole is late, and the shrinkage is serious. Generally, graphite chilled iron is used instead of sand core to bring out the casting hole structure, while affecting the solidification temperature field and strengthening the cooling in the hole. However, due to the stone The lubricity and softness of the ink make it difficult to clean after casting. It cannot be directly polished and can only be removed bit by bit. The cleaning efficiency is low, and it may even be scrapped if it cannot be cleaned. Or resin sand is used to make the core. When making the core, a core iron is placed in the middle, but the position of the core iron is not fixed. During the pouring process, the core iron expands due to heat, causing the core iron to deform together with the sand core. The position of the core iron affects the deviation of the hole size and the quality of the casting around the hole. Finally, the casting is scrapped due to the deformation of the hole. Summary of the invention

[0003] Based on this, it is necessary to provide a method for solving the problem of shrinkage in thick-walled rotor holes, which is caused by the high difficulty in casting holes with a large aspect ratio, the difficulty in fixing the core iron position, and the easy deformation of the quenched core iron and sand core during the pouring process. The method effectively solves the problem of shrinkage in thick-walled rotor holes and greatly improves the yield rate of screw compressor castings and the cleaning efficiency of castings.

[0004] A method for solving shrinkage in a thick-walled rotor hole, characterized in that the method comprises the following steps:

[0005] Prefabricated sand core preparation: designing a main sand core and a top surface sand core according to the structure of the casting, respectively presetting a first support member cavity and a second support member cavity in the main sand core and the top surface sand core, and then manufacturing the sand core;

[0006] Making of rod-shaped sand core: fasten the mold on the core box base, a positioning platform is arranged in the middle of the core box base, the chilled core iron is arranged on the positioning platform, chromium ore sand is added and compacted, and the making of the rod-shaped sand core is completed;

[0007] Assembling the box: placing the first support member and the second support member in the first support member cavity and the second support member cavity, placing the rod-shaped sand core in the main sand core, assembling the top surface sand core on the rod-shaped sand core and the main sand core as a whole, and completing the assembly.

[0008] In one of the embodiments, in the prefabricated sand core preparation step, mutually cooperating positioning structures are provided on the top of the main sand core and the top surface sand core.

[0009] In one of the embodiments, in the rod-shaped sand core making step, the thickness of the chromium ore sand is 15 mm-25 mm.

[0010] In one of the embodiments, in the rod-shaped sand core manufacturing step, the chilled core iron is flush with the top surface of the rod-shaped sand core.

[0011] In one of the embodiments, in the step of making the rod-shaped sand core, a gap of 0.2 mm to 0.8 mm is left between the mold and the bottom surface of the core box base, and a gap of 0.8 mm to 1.5 mm is left on the side.

[0012] In one embodiment, in the box-closing step, the first support member and the second support member are made of lost foam.

[0013] In one embodiment, the positioning platform is a protrusion along the outer circumference, and a 3mm-5mm pit structure is arranged inside.

[0014] In one embodiment, the core box base is in a truncated cone shape, and a high convex ring of 15mm-25mm is provided on the outer side.

[0015] In one of the embodiments, a fastening device is provided on the mold.

[0016] In one embodiment, there are gaps between the positioning structures.

[0017] The technical solution adopted by the present invention can achieve the following beneficial effects:

[0018] The present invention discloses a method for solving shrinkage in thick-walled rotor holes. By fixing the quenching core iron during core making, designing the amount of sand between the quenching core iron and the casting and placing a lost foam support, the problem of easy shrinkage in the thick-walled middle hole of the rotor in the prior art is overcome, which is difficult to solve. The yield rate of screw compressor castings and the cleaning efficiency of the castings are greatly improved. The method has the advantages of convenient and easy operation, controllable size, improved casting hole quality, and greatly improved cleaning efficiency and yield rate of castings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of sand core assembly;

[0020] Figure 2 Assemble the cross-section of the sand core;

[0021] Figure 3 Schematic diagram of the top sand core;

[0022] Figure 4 Schematic diagram of the main sand core;

[0023] Figure 5 Schematic diagram for making rod-shaped sand core;

[0024] Figure 6 This is a schematic diagram of the core box bottom support structure;

[0025] Figure 7 Schematic diagram of the mold.

[0026] Description of reference numerals:

[0027] 1-top sand core, 2-main body sand core, 3-rod-shaped sand core, 4-quenching core iron, 5-mold, 6-first support member, 7-second support member, 8-positioning platform, 9-core box bottom support. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0029] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a centered element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a centered element at the same time. The terms "vertical", "horizontal", "left", "right", "top", "bottom", "bottom end", "top end" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0031] An embodiment of the present invention discloses a method for solving shrinkage in a thick-walled rotor hole. In the embodiment of the present invention, a support is provided to provide space for core iron deformation, the sand intake between the diameter of the quenching core iron and the casting is designed to ensure good sand core strength and quenching effect, and a core box base with a positioning platform is designed to prevent the position of the quenching core iron from shifting. The method includes the following steps: prefabricated sand core preparation, rod-shaped sand core production and box assembly.

[0032] Prefabricated sand core preparation: In the embodiment of the present invention, according to the casting structure, the 3D printing models of the top sand core 1 and the main body sand core 2 are pre-designed, and the designed sand cores are printed out with a 3D printer to complete the production of the top sand core 1 and the main body sand core 2; wherein the main body sand core 2 is a 3D printed sand core with a casting structure, the top sand core 1 is arranged on the top of the main body sand core 2, and the first support member cavity and the second support member cavity are respectively preset on the top sand core 1 and the main body sand core 2, and mutually matching positioning structures are arranged on the top of the main body sand core 2 and the top sand core 1; specifically, as Figure 1-4 As shown, a first support member cavity and a protruding structure or a concave pit structure are provided at the bottom of the top sand core 1, a second support member cavity is provided at the bottom of the main body sand core 2, and a concave pit structure or a protruding structure matching the protruding structure or the concave structure at the bottom of the top sand core 1 is provided at the top of the main body sand core 2. When assembling, the top surface sand core 1 and the main body sand core 2 are positioned relative to each other using the concave pit and the protruding structure. Furthermore, in order to better assemble the top surface sand core 1 and the main body sand core 2, gaps are left between the positioning structures. Preferably, the gap size is 0.5mm-3mm.

[0033] Rod-shaped sand core production: In the embodiment of the present invention, when producing a rod-shaped sand core, the mold 5 is fastened to the core box base 9, a positioning platform 8 is provided in the middle of the core box base 9, the chilled core iron 4 is arranged on the positioning platform 8 in the middle of the core box base 9, chromium ore sand is added and compacted, and the rod-shaped sand core production is completed; specifically, as Figure 6 As shown, the core box base 9 is in the shape of a truncated cone, and a high convex ring of 15mm-25mm is arranged along the outer circumference for fixing the mold 5. Further, there is a gap between the mold 5 and the bottom and side of the core box base 9. Preferably, there is a gap of 0.2mm-0.8mm between the mold 5 and the bottom surface of the core box base 9, and a gap of 0.8mm-1.5mm is left on the side. A positioning platform 8 is arranged in the middle of the core box base 9. The positioning platform 8 is a 3mm-5mm concave structure arranged inside the convex periphery for fixing the quenching core iron 4. Further, there is a gap between the concave structure in the middle of the positioning platform 8 and the quenching core iron 4. Preferably, the gap size is 0.5mm-1.5mm. Figure 7 As shown, the mold 5 includes a first component and a second component, and the first component and the second component are connected by a plurality of fastening devices. When in use, the first component and the second component are fastened together by the fastening devices. After the sand core is made, the fastening devices between the two components are opened to take out the made sand core. More specifically, the mold 5 can be described as a split mold.

[0034] When making rod-shaped sand cores, Figure 5As shown, the first part and the second part of the mold 5 are fastened together by a fastening device to form a whole, the mold 5 is placed in a convex ring arranged along the outer circumference of the core box base 9, and fastened to the core box base 9, the quenching core iron 4 is placed in a positioning platform 8 arranged in the middle of the core box base 9 to prevent the position of the quenching core iron 4 from shifting, and then the chromium ore sand is started to flow, and the chromium ore sand is compacted to form a rod-shaped sand core 3. The quenching core iron 4 is flush with the top surface of the rod-shaped sand core 3, and the quenching core iron 4 is concentric with the center of the rod-shaped sand core 3, and the core making of the rod-shaped sand core 3 is completed, wherein the chromium sand ore has a guide The thermal effect is good, which is convenient for enhancing the cooling advantage in the hole; further, the thickness of the chromium ore sand is 15mm-25mm, that is, the distance between the quenching core iron 4 and the outer surface of the rod-shaped sand core 3 is maintained at 15mm-25mm, and the minimum distance is 15mm. This distance can not only ensure that the rod-shaped sand core 3 has a certain strength, but also can play the role of the quenching core iron 4 as a sand-isolating cold iron. The maximum distance of 25mm is to ensure that the quenching core iron 4 can have a good quenching effect as a sand-isolating cold iron. During pouring, the molten iron around the sand core close to the quenching core iron 4 is solidified first to ensure the quality of the hole.

[0035] Closing: In the embodiment of the present invention, Figure 1-2 As shown, the first support member 6 and the second support member 7 are placed in the first support member cavity and the second support member cavity preset by the top sand core 1 and the main body sand core 2 in the prefabricated sand core preparation step, and the rod-shaped sand core 3 with the quenching core iron 4 made in the rod-shaped sand core making step is placed in the main body sand core 2 to form a whole, and the top surface sand core 1 is assembled on the rod-shaped sand core 3 and the main body sand core 2 as a whole. During assembly, the top surface sand core 1 and the main body sand core 2 are positioned with each other using pits and protrusions to complete the installation. Furthermore, the material of the first support member 6 and the second support member 7 is lost foam. After pouring, as the quenching core iron 4 is deformed by heat, the lost foam can reserve space for elongation and deformation for the expansion of the quenching core iron 4. Preferably, the first support member 6 and the second support member 7 are lost foam materials with the same structure and can be used interchangeably. Furthermore, the first support member 6 and the second support member 7 are provided with a gap with the corresponding preset cavity to prevent the risk of not being able to be put in and falling off.

[0036] The method for solving shrinkage in the hole of a thick-walled rotor described in the present invention solves the problem of easy shrinkage in the casting of the slender hole in the middle of the thick-walled rotor by fixing the quenching core iron 4 when making the rod-shaped sand core 3, designing the sand intake between the quenching core iron 4 and the casting and the method of placing the lost foam support, thereby improving the yield rate and cleaning efficiency of the casting, and having the advantages of convenient and easy operation, controllable size, high casting quality, high cleaning efficiency and high casting yield rate.

[0037] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0038] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for solving shrinkage in thick-walled rotor holes, characterized in that: The method comprises the following steps: Prefabricated sand core preparation: designing a main sand core and a top surface sand core according to the structure of the casting, respectively presetting a first support member cavity and a second support member cavity in the main sand core and the top surface sand core, and then manufacturing the sand core; Making of rod-shaped sand core: fasten the mold on the core box base, a positioning platform is arranged in the middle of the core box base, the chilled core iron is arranged on the positioning platform, chromium ore sand is added and compacted, and the making of the rod-shaped sand core is completed; Assembling the box: placing the first support member and the second support member in the first support member cavity and the second support member cavity, placing the rod-shaped sand core in the main sand core, assembling the top surface sand core on the rod-shaped sand core and the main sand core as a whole, and completing the assembly.

2. The method for solving the shrinkage in the hole of thick-walled rotor according to claim 1 is characterized in that: In the prefabricated sand core preparation step, mutually cooperating positioning structures are provided on the top of the main sand core and the top surface sand core.

3. The method for solving shrinkage in the hole of thick-walled rotor according to claim 1, characterized in that: In the rod-shaped sand core manufacturing step, the thickness of the chromium ore sand is 15mm-25mm.

4. The method for solving the shrinkage in the hole of thick-walled rotor according to claim 1, characterized in that: In the rod-shaped sand core manufacturing step, the chilled core iron is flush with the top surface of the rod-shaped sand core.

5. The method for solving shrinkage in the hole of thick-walled rotor according to claim 1, characterized in that: In the step of making the rod-shaped sand core, a gap of 0.2 mm to 0.8 mm is left between the mold and the bottom surface of the core box base, and a gap of 0.8 mm to 1.5 mm is left on the side.

6. The method for solving shrinkage in the hole of thick-walled rotor according to claim 1, characterized in that: In the box closing step, the first support member and the second support member are made of lost foam.

7. The method for solving shrinkage in the hole of thick-walled rotor according to claim 1, characterized in that: The positioning platform is convex along the outer circumference and has a 3mm-5mm concave pit structure arranged inside.

8. The method for solving shrinkage in the hole of thick-walled rotor according to claim 1, characterized in that: The core box base is in a truncated cone shape, and a high convex ring of 15mm-25mm is arranged on the outer side.

9. The method for solving shrinkage in the hole of thick-walled rotor according to claim 1, characterized in that: The mold is provided with a fastening device.

10. The method for solving shrinkage in the hole of thick-walled rotor according to claim 2, characterized in that: There are gaps between the positioning structures.

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