Device for casting large screw compressor rotor screw casting and working method thereof

Abstract

The application relates to a device for casting a large screw compressor rotor screw casting and a working method thereof, and belongs to the mechanical field. The application comprises a molten iron filtering device, a lock box screw, an iron type sand-coated casting cavity and a coated sand shell type cavity for forming a complete screw helical tooth surface casting cavity of the rotor screw casting, the rotor screw casting is arranged in an axial horizontal mode in the iron type casting; a gate cup and a straight gate cavity are arranged in an axial horizontal mode in the upper iron type casting and the lower iron type casting; a pouring system is arranged in the upper iron type casting and the lower iron type casting, and the pouring system is arranged in a bottom pouring mode. The application further provides a working method of the device for casting the large screw compressor rotor screw casting. The application has the advantages of reasonable structure design, safety and reliability, high casting process yield, simple production process control, guaranteed rotor screw axial dynamic balance performance, realized batch production of the large rotor screw casting and met the use requirement.

Description

Technical Field

[0001] This invention relates to an apparatus and its working method, and more particularly to an apparatus and its working method for casting large screw compressor rotor screw castings. It is applicable to the iron mold sand-shell composite mold casting method for axial vertical bottom pouring of large screw compressor rotor screw castings, and belongs to the field of machinery. Background Technology

[0002] The screw compressor uses two rotating rotors (hereinafter referred to as: rotor screws) with helical gear surfaces for forward and reverse rotation (see...). Figures 1-3 The screw compressor is a gas compression and refrigeration device that uses the meshing of two rotors to compress gas. It is characterized by its simple structure, low exhaust temperature, high gas compression ratio, and high efficiency. It is gradually developing from small rotor-screw compressors to large rotor-screw compressors and has a promising application prospect.

[0003] The production of large rotor screw castings still relies on sand casting (using wet molding sand or self-hardening resin sand). This involves using three- or multi-mold methods, with manual rotation or multiple movable blocks used to create the helical tooth surface of the rotor screw. The mold requires numerous chills, and risers are used to feed the molten iron. The production process is relatively complex, resulting in lower rotor screw quality and production efficiency, a high scrap rate, and high production costs. Furthermore, due to the slow heat transfer, poor mold rigidity, and other limitations of ordinary sand casting processes, the internal structure and mechanical properties of large rotor screw castings are difficult to meet product requirements. The existing production processes and methods for large rotor screw castings (weighing 400-600 kg, approximately 1000 mm in length, with a maximum diameter of 350-450 mm for the helical tooth surface) have become one of the bottlenecks in the development of large screw compressors.

[0004] Iron mold sand casting technology is an energy-saving, efficient, high-quality, and green casting production technology. It features fast cooling speed and high mold rigidity. Targeting the structural characteristics and process requirements of rotor screw castings, iron mold sand casting forming technology is used in combination with shell forming technology for the helical gear surface cavity of the rotor screw. By rationally planning the pouring form of large rotor screws, bottom-pouring axial vertical riserless casting production of large rotor screws can be realized in a single-mold casting process.

[0005] Therefore, it is particularly necessary to provide a production process mode for large rotor screw castings that uses iron mold sand-shell casting with axial horizontal molding and axial vertical pouring, so as to realize the high-quality and mass production of large rotor screw castings. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned shortcomings in the prior art and to provide a device and its working method for casting large screw compressor rotor screw castings that has a reasonable structural design, is safe and reliable, has a high casting yield, is simple to control in the production process, ensures the axial dynamic balance performance of the rotor screw, and realizes the mass production of large rotor screw castings.

[0007] The technical solution adopted by this invention to solve the above problems is as follows: The device for casting large screw compressor rotor screw castings includes an iron molten metal filtration device and a locking screw for locking and fixing the upper and lower iron molds. Its characteristic is that it further includes an upper support shaft, a lower support shaft mold cavity, a rotor screw helical tooth surface shell backing cavity, an iron mold sand-coated casting cavity for forming the rotor screw casting, and a coated sand shell cavity for forming the complete screw helical tooth surface casting cavity of the rotor screw casting. The rotor screw casting cavities are arranged axially and horizontally in the iron mold, with two parts per mold, and a circular rotor... Half of the rotor screw casting cavity is arranged in the upper mold and half in the lower mold. The gating system includes a connected pouring cup and a sprue. The pouring cup and sprue cavity are arranged horizontally in the upper and lower molds. The gating system is set in the upper and lower molds and adopts bottom pouring. During pouring, the rotor screw casting rotates 90°, and the axial arrangement of the rotor screw casting cavity changes from horizontal to vertical. Molten iron enters from the bottom surface of the lower support shaft at the bottom of the rotor screw casting cavity and flows from bottom to top along the axial direction of the rotor screw casting cavity to fill the mold.

[0008] Preferably, the molten iron filtration device of the present invention is provided with two ceramic filter screens, both of which are horizontally arranged in the sand-covered molding cavity of the lower iron mold.

[0009] Preferably, the gating system of the present invention further includes a horizontal gating, an inner gating, a venting riser, a riser gating, and a venting needle. The horizontal gating is connected to the sprue and includes an upper horizontal gating and a lower horizontal gating. The inner gating has a circular cross-sectional shape, with the upper iron mold and the lower iron mold each occupying half of the circle. The venting riser and the venting needle are both circular. The riser gating has a rectangular cross-section, with the upper iron mold and the lower iron mold each occupying half of the cavity.

[0010] Preferably, the pouring cup of the present invention is a conical pouring cup, which is made directly in the upper iron mold and the lower iron mold, with the parting surface of the iron mold as the boundary, and the cavity of the upper iron mold and the lower iron mold each occupy half.

[0011] Preferably, the pouring cup of the present invention has one half of its conical cavity arranged in the upper iron mold and the other half of its conical cavity arranged in the lower iron mold.

[0012] Preferably, the diameter of the vent riser in this invention is determined according to the size of the rotor screw casting, and the diameter of the vent needle is controlled to be between 15-20 mm, depending on the size of the rotor screw casting.

[0013] Preferably, when the mold is closed, the ceramic filter screen can be placed directly in the lower iron mold. After the mold is closed, the iron mold is rotated 90°, and the ceramic filter screen in the iron mold is arranged vertically, while the molten iron filling and filtering is a horizontal flow filtration.

[0014] This invention also provides a method for operating an apparatus for casting large screw compressor rotor screw castings, characterized by the following specific steps: First, the upper iron mold, lower iron mold cavity, and rotor screw helical tooth shell cavity of the large rotor screw are shaped separately; the two rotor screw helical tooth shell cavities are placed horizontally axially in the two corresponding iron mold sand-coated casting backing cavities in the lower iron mold; simultaneously, two ceramic filter screens are placed horizontally in the corresponding cavity positions of the molten iron filtration device in the lower iron mold; then, the upper iron mold of the rotor screw is assembled onto the lower iron mold, and the locking screw is tightened to form a complete large rotor screw composite mold; the entire iron mold is then flipped... Rotate 90° to flip the rotor screw mold cavity and gating system from their original horizontal axial arrangement to a vertical axial arrangement, with the molten iron inlet of the pouring cup above the sprue facing upwards. Molten iron can then be poured. The poured molten iron enters the runner through the pouring cup and sprue, and is filtered by a vertically arranged ceramic filter screen. The filtered molten iron continues to flow through the runner at the other end of the ceramic filter screen to the ingate located at the bottom plane of the rotor screw support shaft, entering the rotor screw mold cavity upwards. The molten iron continuously fills the rotor screw mold cavity from bottom to top, with a smooth flow until the entire rotor screw mold cavity is completely filled. During the filling process, the mold cavity... The generated gas is promptly discharged into the atmosphere through the venting needle on the venting riser at the top of the rotor screw. Then, the cooler molten iron in the upper part of the rotor screw cavity, along with the floating molten iron containing slag, continues to fill the mold cavity above the venting riser. When the filling height of this type of molten iron in the venting riser reaches the lower edge of the riser and gating system above the sprue, the molten iron in the rotor screw cavity stops filling upwards. The high-temperature molten iron directly fills the venting riser through the riser and gating system. The temperature of the molten iron in the venting riser is higher than that of the molten iron above the rotor screw, and the molten iron in the venting riser effectively compensates for the shrinkage of the molten iron above the rotor screw. Simultaneously, inclusions in the molten iron in the rotor screw casting mold cavity are removed during solidification. The molten iron rises into the vent riser, where it solidifies and cools, resulting in a high-quality rotor screw casting free of shrinkage cavities, porosity, and inclusions. After solidification and cooling, the upper and lower molds are flipped 90°, restoring their horizontal arrangement from vertical to horizontal. The locking screws are then loosened to separate the molds, removing the casting and completing one casting of a large rotor screw. This process yields a large rotor screw casting with a dense structure and fine grains, achieving as-cast production of large rotor screw castings. This cycle can be repeated to achieve mass production of this type of casting.

[0015] Compared with existing technologies, this invention has the following advantages and effects: 1) The overall structure is reasonably designed, safe and reliable, and suitable for the axial vertical bottom pouring casting of large screw compressor rotor screw castings using a sand-shell composite mold; it meets the high rigidity and good cooling performance of the sand-shell composite mold for large rotor screw castings, and combined with the graphitization self-feeding effect in sand casting technology, it can greatly reduce the liquid feeding amount of rotor screw castings. At the same time, the strong feeding effect of high-temperature molten iron in the riser results in a high yield in the casting process of rotor screw castings; 2) The large rotor screw casting mold adopts horizontal sand molding, with the rotor screw helical tooth shell mold and molten iron filter screen placed horizontally, and the mold is horizontally closed, resulting in a high casting yield; The molding and box-closing processes are convenient and quick, and easy to mechanize; 3) After the box is closed and locked, the mold is rotated 90°, which can realize vertical bottom pouring of large rotor screw castings. The molten iron poured into the mold flows from bottom to top in the rotor screw casting mold. The flow of molten iron is balanced, which greatly reduces casting defects such as iron slag, gas entrapment forming porosity, and slag inclusions during the pouring process, while ensuring the axial dynamic balance performance of the rotor screw; 4) This application has fewer production links and simple production process control, which makes it easy to realize the mechanized and mass production of large rotor screw castings; 5) Combined with the rapid heat transfer effect of the iron mold, the cooling speed of the mold is greatly improved, which can realize the high strength performance of large rotor screw castings in the as-cast state, and the energy saving effect of the production process is significant. Attached Figure Description

[0016] Figure 1 This is a three-dimensional structural schematic diagram of the rotor screw casting according to an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of the main structure of the rotor screw casting according to an embodiment of the present invention.

[0018] Figure 3 This is a top view of the rotor screw casting according to an embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram of the main structure of the casting mold box for casting large rotor screws according to an embodiment of the present invention.

[0020] Figure 5 This is a top view of the mold box for casting large rotor screw castings according to an embodiment of the present invention.

[0021] Figure 6 This is a side view of the mold box for casting large rotor screws according to an embodiment of the present invention.

[0022] Figure 7 This is a schematic diagram of the gating system structure for the horizontally constructed vertically cast screw casting of this invention. Figure 1 .

[0023] Figure 8 This is a schematic diagram of the gating system structure for the horizontally constructed vertically cast screw casting of this invention. Figure 2 .

[0024] Figure 9 This is a schematic diagram of the gating system structure for the horizontally constructed vertically cast screw casting of this invention. Figure 3 .

[0025] Figure 10 This is a schematic diagram of molten iron filtration during the horizontal casting and vertical pouring of the screw casting according to an embodiment of the present invention.

[0026] Figure 11 This is a schematic diagram of the helical tooth shell structure used for casting rotor screw castings according to an embodiment of the present invention.

[0027] Figure 12 This is a schematic diagram of the upper and lower iron molds after horizontal sand covering during the production process of the rotor screw casting according to an embodiment of the present invention.

[0028] Figure 13 This is a schematic diagram showing the placement of the shell mold and filter screen in a horizontally placed lower iron mold during the production process of the rotor screw casting according to an embodiment of the present invention.

[0029] Figure 14 This is a schematic diagram showing the upper and lower iron molds horizontally locked together during the production process of the rotor screw casting according to an embodiment of the present invention.

[0030] Figure 15 This is a schematic diagram of the mold being rotated 90° and erected during the production process of the rotor screw casting according to an embodiment of the present invention.

[0031] Figure 16 This is a schematic diagram of the filling process of molten iron in a vertical mold during the production of the rotor screw casting according to an embodiment of the present invention. Figure 1 .

[0032] Figure 17 This is a schematic diagram of the filling process of molten iron in a vertical mold during the production of the rotor screw casting according to an embodiment of the present invention. Figure 2 .

[0033] Figure 18 This is a schematic diagram of the filling process of molten iron in a vertical mold during the production of the rotor screw casting according to an embodiment of the present invention. Figure 3 .

[0034] Figure 19 This is a schematic diagram of molten iron solidifying in a vertical mold during the production process of the rotor screw casting according to an embodiment of the present invention.

[0035] Figure 20 This is a schematic diagram of the process of loosening the locking device and opening the upper mold during the production of the rotor screw casting according to an embodiment of the present invention.

[0036] Figure 21 This is a schematic diagram illustrating the removal of the screw casting from the lower mold during the production process of the rotor screw casting according to an embodiment of the present invention.

[0037] In the diagram: Rotor screw casting L; screw helical tooth surface L1; upper support shaft L2; lower support shaft L3; upper iron mold 1; lower iron mold 2; helical tooth shell 3; ceramic filter screen 4; locking screw 5; gating system 6; pouring cup 61; sprue 62; gating runner 63; ingate 64; vent riser 65; riser gating 66; vent needle 67; upper gating runner 631; lower gating runner 632; molten iron flow direction F. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0039] Example

[0040] See Figures 1 to 21 The apparatus for casting large screw compressor rotor screw castings in this embodiment includes a locking screw 5 for locking and fixing the upper iron mold 1 and the lower iron mold 2, an upper support shaft L2 and a lower support shaft L3 for forming the rotor screw casting L, a rotor screw helical tooth shell 3 for backing cavity, an iron mold sand-coated casting cavity for all the cavities of the gating system 6, and a coated sand shell cavity for forming the complete screw helical tooth surface L1 of the rotor screw casting L.

[0041] In this embodiment, the large rotor screw casting L mold adopts a one-mold-two-piece design. The mold cavities in the upper and lower iron molds are arranged axially and horizontally. That is, half of the circular rotor screw cavity is placed in the lower iron mold, and the other half of the circular cavity is placed in the upper iron mold. The upper and lower iron molds are respectively completed with sand covering. The screw helical tooth shell mold is placed in the lower iron mold with sand covering. Then the upper iron mold with sand covering is put into the lower iron mold with sand covering, thus forming a complete large rotor screw casting.

[0042] In this embodiment, the mold cavity structure is a composite mold cavity, mainly composed of two parts: an iron mold with sand coating and a coated sand shell cavity. Specifically, the iron mold with sand coating mainly forms the mold cavities for the two end support shafts of the rotor screw, the shell-type backing cavity for the rotor screw helical tooth surface, and the cavity for the entire gating system; the shell-type cavity for the coated sand screw helical surface mainly forms the complete rotor helical tooth surface mold cavity for the rotor screw (see...). Figure 11 The rotor screw of this shell type has no parting surface and no draft angle on the helical surface cavity, and is a single complete helical surface cavity, which can greatly reduce the amount of machining work on the helical surface.

[0043] In this embodiment, two ceramic filter screens 4 are provided in the molten iron filtration device. Both ceramic filter screens 4 are horizontally arranged in the sand-covered molding cavity of the lower iron mold 2.

[0044] See Figures 7-9 In this embodiment, the gating system 6 includes a gating cup 61, a straight gating 62, a horizontal gating 63, an inner gating 64, an air vent riser 65, a riser gating 66, and an air vent needle 67 connected together. The horizontal gating 63 is connected to the straight gating 62 and includes an upper horizontal gating 631 and a lower horizontal gating 632.

[0045] The entire gating system 6 is made directly in the upper iron mold 1 and the lower iron mold 2. The arrangement of the pouring cup 61 and the sprue 62 cavity in the gating system 6 in the upper iron mold 1 and the lower iron mold 2 is the same as the arrangement of the cavity in the rotor screw casting L mold, which is axially horizontal. That is, half of the sprue 62 cavity is arranged in the upper iron mold 1, and the other half of the sprue cavity is arranged in the lower iron mold 2.

[0046] Based on the structural characteristics, process requirements, and performance requirements of the rotor screw casting mold, the gating system 6 in this embodiment adopts a bottom-pouring method. During pouring, the rotor screw casting mold is rotated 90°, and the axial arrangement of the rotor screw casting L mold cavity changes from horizontal to vertical. Molten iron enters from the bottom surface of the lower support shaft L3 at the lower end of the rotor screw casting L mold cavity and flows from bottom to top along the axial direction of the rotor screw casting L mold cavity to fill the mold.

[0047] In this embodiment, the unfiltered molten iron filling horizontal runner 62 initially occupies half in the upper iron mold 1 and the lower iron mold 2, and then gradually transitions upwards to the upper iron mold 1 cavity. The mold cavity where the ceramic filter screen 4 is placed is entirely located in the lower iron mold 2, with the parting surface as the boundary. The lower horizontal runner 632 below the ceramic filter screen 4 is located in the lower iron mold 2, and then gradually transitions upwards to the upper iron mold 1 until the upper iron mold 1 and the lower iron mold 2 cavities each occupy half.

[0048] In this embodiment, the ingate 64 has a circular cross-sectional shape, with the upper iron mold 1 and the lower iron mold 2 each occupying half of the circle; the vent riser 65 and the vent needle 67 are both circular; the riser diameter is determined according to the size of the rotor screw casting, and the vent needle diameter is also controlled between 15-20 mm according to the size of the rotor screw casting; the riser gate 66 has a rectangular cross-section, with the upper iron mold 1 and the lower iron mold 2 each occupying half of the cavity.

[0049] In this embodiment, the overheated vent riser 65 plays a good role in feeding the molten iron in the rotor screw mold cavity; the vent riser 65 also helps to float the slag in the molten iron in the rotor screw mold cavity.

[0050] In this embodiment, the ceramic filter screen 4 in the molten iron filtration device is horizontally arranged in the sand-coated molding cavity of the lower iron mold 2. When the iron mold needs to be poured, it needs to be rotated 90°, that is, the mold cavity, which was originally arranged horizontally along the axis of the large screw casting, is rotated to a vertical arrangement. At this time, the originally horizontally arranged ceramic filter screen 4 also becomes vertically arranged. This vertical ceramic filter screen 4 filtration method during molten iron pouring is completely different from the traditional horizontal arrangement of ceramic filter screens. Figure 10 As can be seen, when molten iron enters the sprue 62 from top to bottom through the pouring cup 61, it splits to the left and right and enters the left and right upper horizontal runners 631 cavities in the upper iron mold 1 respectively. The molten iron flows horizontally through the vertically arranged ceramic filter screen 4 to filter the molten iron, and then flows from the lower horizontal runner 632 cavity in the lower iron mold to fill the inner runner 64. Through the inner runner 64, the molten iron fills upward and enters the mold cavity of the rotor screw casting L.

[0051] The working process of the device for casting large screw compressor rotor screw castings in this embodiment is as follows: First, the upper iron mold 1 and lower iron mold 2 of the large rotor screw are shaped, as well as the rotor screw helical tooth shell 3. The two rotor screw helical tooth shell 3 cavities are placed horizontally in the two corresponding iron mold sand-coated casting backing cavities in the lower iron mold 2 of the large rotor screw. At the same time, two ceramic filter screens 4 are placed horizontally in the corresponding cavity positions of the molten iron filtration device in the lower iron mold 2. Then, the upper iron mold (1) of the rotor screw is closed onto the lower iron mold 2, and the locking screw 5 is tightened to form a complete large rotor screw composite mold. The entire iron mold is rotated 90° so that the rotor screw mold is shaped. The cavity and gating system 6 are flipped from their original horizontal axial arrangement to a vertical axial arrangement, with the molten iron inlet of the pouring cup 61 above the sprue 62 facing upwards, allowing for molten iron pouring. The poured molten iron enters the runner 63 through the pouring cup 61 and the sprue 62, and is filtered for slag by the vertically arranged ceramic filter screen 4. The filtered molten iron continues to flow through the runner 63 at the other end of the ceramic filter screen 4, continuing to fill the mold to the ingate located at the bottom plane of the rotor screw support shaft, and enters the casting cavity of the rotor screw upwards. The molten iron continuously fills the rotor screw casting cavity from bottom to top, with a smooth filling flow, until the entire rotor screw casting cavity is completely filled. During the filling process, the gas generated in the casting cavity passes through the top of the rotor screw. The vent needle 67 on the vent riser 65 promptly discharges the molten iron into the atmosphere; then, the cooler molten iron in the upper part of the rotor screw cavity and the floating molten iron containing slag continue to fill the mold upwards into the vent riser 65 above the rotor screw mold cavity. When the filling height of this type of molten iron in the vent riser 65 reaches the lower edge height of the riser gating 66 above the sprue 62, the molten iron in the rotor screw cavity stops filling upwards. The high-temperature molten iron directly fills the vent riser 65 through the riser gating 66. In this way, the temperature of the molten iron in the vent riser 65 is higher than that of the molten iron above the rotor screw. The molten iron in the vent riser 65 can effectively compensate for the shrinkage of the molten iron above the rotor screw. At the same time, the inclusions in the molten iron in the rotor screw casting L mold cavity can be released by floating before solidification. The molten iron enters the vent riser 65, and then the molten iron in the mold cavity begins to solidify and cool, thus finally obtaining a high-quality rotor screw casting L without shrinkage cavities, shrinkage porosity, or slag inclusions. After the molten iron in the mold has solidified and cooled, the upper and lower iron molds are flipped 90°, so that the parting surface of the upper and lower iron molds changes from a vertical arrangement back to the horizontal arrangement when the iron molds are closed. Then, the locking screw 5 is loosened to open and separate the upper and lower iron molds, and the casting is taken out (the casting is a semi-circular shaft shape in both the upper and lower iron molds, and the casting is easily separated from the iron mold). This completes the casting production of a large rotor screw casting, and finally obtains a large rotor screw casting with a dense structure and fine grains, realizing the as-cast production of large rotor screw castings.By repeating this process, mass production of this type of casting can be achieved.

[0052] The technological principle of the composite casting device in this embodiment is as follows: To ensure the axial dynamic balance of the rotor screw casting, the rotor screw casting L must be vertically arranged in the mold during the casting process. For large rotor screw castings, with the rotor screw casting L arranged vertically axially, the height of the inner cavity of the casting in the mold is over 1000 mm. For such a high mold, the molten iron pouring process must adopt a bottom-pouring method. This pouring process ensures that the molten iron poured into the mold fills the mold smoothly from bottom to top, while also allowing inclusions in the molten iron to float to the surface, thus obtaining a defect-free casting. For large rotor screw castings, each casting typically weighs 400-600 kg, is approximately 1000 mm long, and has a maximum diameter of approximately 350-450 mm for the screw helical teeth. If such castings are arranged perpendicular to the parting surface of the iron mold in a sand-coated iron mold, the thickness of a single iron mold exceeds 600 mm, and it is small at both ends and large in the middle, which will cause great difficulty in sand molding of the iron mold, or require a sand molding machine with a larger stroke and demolding force; in addition, it is difficult to achieve a completely bottom pouring method in large rotor screws with this arrangement; at the same time, in the production process of large rotor screw castings with this arrangement, after the large rotor screw casting has solidified and cooled, the separation between the casting and the iron mold will be difficult due to the cooling shrinkage of the casting. The large rotor screw casting of this application adopts a one-mold two-piece large rotor screw casting mold, and the cavity of the large rotor screw casting is arranged axially horizontally in the iron mold; the sprue 62, gating 63, ingate 64, and molten iron filtering device flow channel of the gating system 6 are all made on the iron mold sand-coated iron mold on the parting surface of the upper and lower iron molds ( Figures 7-9 ); 3. Place the rotor screw helical tooth shell 3 horizontally in the lower iron mold sand-coated casting cavity; 4. Place the molten iron ceramic filter screen horizontally in the lower iron mold sand-coated casting cavity; 5. Horizontally close the mold box, and then lock the upper and lower molds. Figures 4-6 Then, the mold, after being locked in place, is vertically rotated 90°, so that the rotor screw mold cavity, originally arranged horizontally, is now arranged vertically. Pouring the mold in this state allows for bottom-pouring filling of molten iron within the large rotor screw casting mold, ensuring that the large rotor screw casting mold fills, solidifies, and cools under relatively ideal conditions, ultimately achieving high-quality casting production of large screw castings. In this embodiment, during the cooling process, the molten iron in the large rotor screw mold cavity can fully utilize the expansion caused by the graphite precipitated during solidification to offset the liquid shrinkage caused by cooling. Simultaneously, the strong feeding effect of the high-temperature molten iron at the riser 65° above the screw casting cavity makes the molten iron utilization rate in this embodiment far higher than that of traditional sand casting.

[0053] This embodiment addresses the casting process requirements of axial vertical bottom pouring for the large screw compressor rotor casting L. It utilizes the forming process characteristics of sand-coated iron mold casting. In a single-mold sand-coated iron mold with upper and lower horizontal parting, half of the sand-coated iron mold, arranged axially along the rotor screw, and a corresponding gating system 6 are horizontally fabricated in each of the upper and lower iron mold cavities. After the upper and lower half of the mold are horizontally joined with the screw helical tooth shell mold 3, a complete large rotor screw casting cavity with a horizontal arrangement and its matching gating system 6 are formed. By rotating the parting surface of the large rotor screw casting L mold 90° from the horizontal position after locking the mold, the sprue in the casting system faces vertically upwards, and the parting surface of the mold is perpendicular to the horizontal plane. In this way, the rotor screw's mold cavity can be arranged vertically in the entire composite mold. When molten iron is poured in this state, it smoothly enters the rotor screw casting mold cavity through the bottom of the lower support shaft of the rotor screw casting cavity, such as the pouring cup 61, the sprue 62, the horizontal runner filter device, and the ingate 64, from bottom to top until the entire rotor screw casting mold cavity is filled. The molten iron pouring and filling is stable. Utilizing the good rigidity and fast cooling speed of the iron mold with sand coating, by reasonably setting the cross-sectional dimensions of each section of the gating system, it is possible to achieve small riser casting of large rotor screw castings. The castings have fine grains, dense internal structure, excellent comprehensive mechanical properties, and good dynamic balance performance. At the same time, it avoids casting defects such as iron splashing, air entrapment, slag inclusions, shrinkage cavities, etc. during the molten iron pouring process.

[0054] Based on the above description, those skilled in the art are already able to implement it.

[0055] Furthermore, it should be noted that the specific embodiments described in this specification may differ in the shape and name of their parts and components. The above description is merely illustrative of the structure of the present invention. All equivalent or simple variations made based on the structure, features, and principles described in this patent concept are included within the protection scope of this patent. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to substitute them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in these claims, all of which should fall within the protection scope of this invention.

Claims

1. A device for casting a large screw compressor rotor screw casting, comprising a molten iron filtering device, a locking box screw (5) for locking and fixing an upper iron mold casting mold (1) and a lower iron mold casting mold (2), characterized in that: The application also discloses an iron-coated sand mold cavity for forming an upper supporting shaft (L2), a lower supporting shaft (L3) mold cavity of a rotor screw casting (L), a rotor screw helical tooth surface shell mold (3) back lining cavity, a complete pouring system (6) cavity, and a coated sand shell mold cavity for forming a complete screw helical tooth surface (L1) of the rotor screw casting (L), wherein the rotor screw casting (L) cavity is arranged in an axial horizontal mode in the iron mold, one mold two pieces, and the half of the round rotor screw casting (L) cavity is arranged in the upper iron mold and the other half is arranged in the lower iron mold; the pouring system (6) comprises a connected sprue cup (61) and a straight runner (62), the sprue cup (61) and the straight runner (62) are arranged in an axial horizontal mode in the upper iron mold (1) and the lower iron mold (2); the pouring system (6) is arranged in the upper iron mold (1) and the lower iron mold (2) and is arranged in a bottom pouring mode, the rotor screw casting mold is turned by 90 degrees during pouring, the rotor screw casting mold cavity is changed from horizontal arrangement to vertical arrangement, and the molten iron flows into the rotor screw casting mold cavity from the bottom surface of the lower supporting shaft (L3) at the lower end of the rotor screw casting mold cavity and flows from the bottom to the top along the axial direction of the rotor screw casting mold cavity.

2. The apparatus for casting large screw compressor rotor screw casting according to claim 1, characterized in that: The sprue cup (61) is a conical sprue cup (61) which is directly formed in the upper iron mold (1) and the lower iron mold (2) and is divided by the iron mold parting surface, and the upper iron mold (1) and the lower iron mold (2) each occupy half of the cavity.

3. The apparatus of claim 1, wherein: The diameter of the gas outlet (65) is determined according to the size of the rotor screw casting (L), and the diameter of the gas outlet needle (67) is determined according to the size of the rotor screw casting (L), and is controlled within 15-20 mm.

4. The apparatus of claim 1, wherein: When the mold is closed, the ceramic filter screen (4) can be directly placed in the lower iron mold casting (2), and after the mold is closed, the ceramic filter screen (4) in the iron mold casting is vertically arranged after the iron mold casting is turned over by 90°, and the molten iron filling the mold is filtered in a horizontal flow.

5. A method of operation of a device for casting a large screw compressor rotor screw casting, using a device for casting a large screw compressor rotor screw casting according to any one of claims 1 to 4, characterized in that: The specific steps are as follows: first, the mold cavities of the upper iron mold casting (1) and the lower iron mold casting (2) of the large rotor screw, and the mold cavity of the rotor screw helical tooth surface shell mold (3) are respectively molded; the two rotor screw helical tooth surface shell molds (3) are placed horizontally and axially in the two corresponding iron mold sand-coated casting back lining cavities of the lower iron mold casting (2); at the same time, the two ceramic filter screens (4) are placed horizontally in the corresponding mold cavity positions of the molten iron filtering device in the lower iron mold casting (2); then the upper iron mold casting (1) of the rotor screw is closed on the lower iron mold casting (2), and then the locking screw (5) is tightened to form a complete large rotor screw composite mold; The entire iron mold casting is turned over by 90°, so that the rotor screw casting mold cavity and the pouring system (6) are turned over from the original axial horizontal arrangement to an axial vertical arrangement, and the molten iron inlet at the top of the pouring cup (61) above the sprue (62) faces upward, and then the molten iron can be poured; the poured molten iron enters the cross runner (63) through the pouring cup (61) and the straight runner (62), and the molten iron is subjected to slag blocking and filtering through the ceramic filter screen (4) device which has been vertically arranged; the filtered molten iron passes through the cross runner (63) at the other end of the ceramic filter screen (4) and continues to flow to the ingate arranged at the bottom of the rotor screw support shaft to enter the casting mold cavity of the rotor screw upward, and the molten iron continuously fills the rotor screw casting mold cavity from bottom to top, and the filling flow is stable until the entire rotor screw casting mold cavity is completely filled; the gas generated in the mold cavity during the filling process is discharged into the atmosphere in a timely manner through the gas outlet needle (67) on the gas outlet (65) at the top of the rotor screw; then the relatively cold molten iron in the upper part of the rotor screw cavity and the floating molten iron containing slag continue to fill upward into the gas outlet (65) above the rotor screw casting mold cavity, and when the filling height of this kind of molten iron in the gas outlet (65) reaches the lower edge height of the riser (66) above the straight runner (62), the molten iron in the rotor screw cavity no longer fills upward, and the high-temperature molten iron directly fills the gas outlet (65) through the riser (66), and the temperature of the molten iron in the gas outlet (65) is higher than that of the molten iron above the rotor screw, so that the molten iron in the gas outlet (65) can well compensate the shrinkage of the molten iron above the rotor screw, and at the same time, the slag in the molten iron in the rotor screw casting (L) mold cavity can enter the gas outlet (65) by floating before solidification, and then the molten iron in the mold cavity begins to solidify and cool, thereby finally obtaining a high-quality rotor screw casting (L) without shrinkage, porosity and slag defects; After the molten iron in the mold is solidified and cooled, the upper and lower molds are turned over by 90°, the parting surface of the upper and lower molds is turned over from vertical arrangement to horizontal arrangement as in the original mold, then the locking screw (5) is loosened, the upper and lower molds are separated, the casting is taken out, and thus the casting production of the large rotor screw casting is completed, and the large rotor screw casting with compact structure and small grain is obtained, and the as-cast casting production of the large rotor screw casting is realized; the cycle is repeated, and the batch production of the casting can be realized.

Images