Device for casting rotor screw rod casting of large screw rod compressor and working method of device

Abstract

The invention relates to a device for casting a rotor screw casting of a large screw compressor and a working method of the device, and belongs to the field of machinery. The device comprises a molten iron filtering device, a box locking screw rod, an iron mold sand-lined casting mold cavity and a precoated sand shell mold cavity used for forming a complete screw rod spiral tooth surface casting mold cavity of a rotor screw rod casting, wherein the rotor screw rod casting is axially and horizontally arranged in an iron mold casting mold; the sprue cup and the sprue cavity are axially and horizontally arranged in the upper iron mold casting mold and the lower iron mold casting mold; the pouring system is arranged in the upper iron mold casting mold and the lower iron mold casting mold, and the pouring system is arranged in a bottom pouring mode. The invention further provides a working method of the device for casting the rotor screw rod casting of the large screw rod compressor. The rotor screw axial dynamic balance device is reasonable in structural design, safe, reliable, high in casting process yield and simple in production process control, the rotor screw axial dynamic balance performance is guaranteed, batch production of large rotor screw castings is achieved, and use requirements are met.

Description

Technical Field

[0001] The present invention relates to a device and a working method thereof, and in particular to a device and a working method thereof for casting large screw compressor rotor screw castings, which is suitable for axial vertical bottom pouring of large screw compressor rotor screw castings in an iron mold covered with sand-shell composite mold casting form, and belongs to the field of machinery. Background Art

[0002] The screw compressor uses two forward and reverse rotors with helical gear surfaces (hereinafter referred to as: rotor screw) (see Figure 1-Figure 3 ) mesh with each other to compress the gas. The screw compressor is a high-efficiency, energy-saving, low-noise gas compression and refrigeration device with the characteristics of simple structure, low exhaust temperature, large gas compression ratio, high efficiency, etc. It has gradually developed from small rotor screw compressors to large rotor screw compressors and has a good application prospect.

[0003] The production of large rotor screw castings currently still uses sand casting (green sand or self-hardening resin sand), with three-open molds or multiple molds, and the spiral tooth surface casting cavity in the rotor screw is produced by manual rotary demolding or multi-block demolding. A large amount of chiller needs to be arranged in the mold, and the molten iron in the mold is fed by setting risers. The production process is relatively complicated, the quality and production efficiency of the rotor screw are relatively low, the scrap rate is high, and the production cost is high. In addition, due to the slow heat transfer of ordinary sand molds, poor mold rigidity, and some limiting factors in the sand casting process, it is difficult to meet the product requirements for the internal organization of large rotor screw castings and the mechanical properties of such castings. The existing production process and production form of large rotor screw castings (weight 400-600 kg, length of about 1000 mm, maximum diameter of screw spiral tooth surface of about 350-450 mm) have become one of the bottlenecks in the development of large screw compressors.

[0004] Iron mold sand-coated casting technology is an energy-saving, efficient, high-quality and green casting production technology with the characteristics of fast cooling speed and high casting mold rigidity. According to the structural characteristics and process requirements of rotor screw castings, the iron mold sand-coated casting forming technology is used, combined with the shell mold forming technology of the spiral gear surface cavity of the rotor screw. Through reasonable planning of the casting form of large rotor screws, the bottom-pouring axial vertical riser-free casting production of large rotor screws can be realized in single-open mold casting.

[0005] Therefore, it is particularly necessary to provide an iron mold sand-shell casting rotor screw casting production process mode suitable for axial horizontal molding and axial vertical pouring of large rotor screw castings to achieve high-quality and mass production of large rotor screw castings. Summary of the invention

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

[0007] The technical solution adopted by the present invention to solve the above-mentioned problem is: the device for casting a large screw compressor rotor screw casting includes a molten iron filtering device, a lock box screw for locking and fixing the upper iron mold casting and the lower iron mold casting, and is characterized in that it also includes an upper support shaft for forming the rotor screw casting, a lower support shaft casting cavity, a rotor screw spiral tooth surface shell backing cavity, an iron mold sand casting cavity for forming the entire casting system cavity, and a coated sand shell cavity for forming a complete screw spiral tooth surface casting cavity of the rotor screw casting. The rotor screw casting cavity is arranged axially and horizontally in the iron mold casting, one mold has two pieces, and the circular rotor Half of the sub-screw casting cavity is arranged in the upper iron mold, and the other half is arranged in the lower iron mold; the pouring system includes a connected pouring cup and a straight runner, and the pouring cup and the straight runner cavity are arranged axially horizontally in the upper iron mold and the lower iron mold; the pouring system is arranged in the upper iron mold and the lower iron mold, and the pouring system is arranged in the form of bottom pouring. During pouring, the rotor screw mold is flipped 90°, and the axial arrangement of the rotor screw casting mold cavity changes from horizontal to vertical. The molten iron enters from the bottom surface of the lower support shaft at the lower end of the rotor screw casting mold cavity, and flows from bottom to top along the axial direction of the rotor screw casting mold cavity to fill the mold.

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

[0009] Preferably, the pouring system of the present invention also includes a cross runner, an entgate, a gas riser, a riser runner and a gas vent needle. The cross runner is connected to the straight runner, and the cross runner includes an upper cross runner and a lower cross runner; the cross-sectional shape of the entgate is circular, and the upper iron mold casting and the lower iron mold casting each occupy a semicircle; the gas riser and the gas vent needle are both circular; the cross-sectional shape of the riser runner is rectangular, and the upper iron mold casting and the lower iron mold casting cavity each occupy half.

[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 iron mold parting surface as the boundary, and the upper iron mold and the lower iron mold cavity each occupying half.

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

[0012] Preferably, the diameter of the gas outlet riser of the present invention is determined according to the size of the rotor screw casting, and the diameter of the gas outlet needle is controlled to be between 15 and 20 mm according to the size of the rotor screw casting.

[0013] Preferably, when the present invention is closed, the ceramic filter can be directly placed on the lower iron mold. After the iron mold is turned 90° after closing, the ceramic filter is arranged vertically in the iron mold, and the molten iron filling and filtration is horizontal flow filtration.

[0014] The present invention also provides a working method of a device for casting a large screw compressor rotor screw casting, which is characterized by: the specific steps are as follows: first, the upper iron mold casting, the lower iron mold casting cavity of the large rotor screw are molded, and the rotor screw spiral tooth surface shell mold cavity is molded; the two rotor screw spiral tooth surface shell mold cavities are horizontally and axially placed one by one in two corresponding iron mold sand-coated casting backing cavities in the lower iron mold casting; at the same time, two ceramic filter screens are horizontally placed at the corresponding cavity positions of the molten iron filtering device in the lower iron mold casting; then the upper iron mold casting of the rotor screw is assembled onto the lower iron mold casting, and then the locking screw is tightened to form a complete large rotor screw composite casting; the entire iron mold casting is turned over Turn 90° to flip the rotor screw casting cavity and the pouring system from the original axial horizontal arrangement to an axial vertical arrangement, and make the molten iron inlet of the pouring cup above the sprue face upwards, and then the molten iron can be poured; the poured molten iron enters the cross runner through the pouring cup and the sprue, and is filtered through the vertically arranged ceramic filter device to block slag; the filtered molten iron passes through the cross runner at the other end of the ceramic filter, and continues to flow to the inner gate set at the bottom plane of the rotor screw support shaft, and enters the casting cavity of the rotor screw upward, and the molten iron continuously fills the rotor screw casting cavity from bottom to top, and the filling flow is smooth until the entire rotor screw casting cavity is completely filled; during the filling process, the molten iron in the casting cavity The generated gas is discharged into the atmosphere in time through the gas outlet needle on the gas outlet riser at the top of the rotor screw; then the colder 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 riser above the rotor screw casting cavity. When the filling height of this type of molten iron in the gas outlet riser reaches the height of the lower edge of the riser runner above the straight runner, the molten iron in the rotor screw cavity no longer fills upward, and the high-temperature molten iron directly fills the gas outlet riser through the riser runner. The temperature of the molten iron in the gas outlet riser is higher than the temperature of the molten iron above the rotor screw. The molten iron in the gas outlet riser can well compensate for the shrinkage of the molten iron above the rotor screw. At the same time, the slag inclusions in the molten iron in the casting cavity of the rotor screw casting are The molten iron in the mold cavity begins to solidify and cool, so as to finally obtain a high-quality rotor screw casting without shrinkage cavities, shrinkage porosity and slag inclusion defects; after the molten iron in the mold solidifies and cools, the upper and lower iron molds are turned over 90 degrees, so that the parting surfaces of the upper and lower iron molds are turned from a vertical arrangement to a horizontal arrangement when the original iron molds are closed, and then the locking screw is loosened to open and separate the upper and lower iron molds, and the casting is taken out, thereby completing the casting production of a large rotor screw casting, and finally obtaining a large rotor screw casting with dense structure and fine grains, realizing the as-cast casting production of large rotor screw castings; the cycle is repeated in sequence to realize mass production of such castings.

[0015] Compared with the prior art, the present invention has the following advantages and effects: 1) The overall structural design is reasonable, safe and reliable, and is suitable for the iron mold sand-shell composite casting form of axial vertical bottom pouring of large screw compressor rotor screw castings; it meets the high rigidity of the iron mold sand-shell composite casting of large rotor screw castings and good casting cooling performance, combined with the graphitization self-shrinkage compensation effect in the iron mold sand-covered casting technology, it can greatly reduce the liquid shrinkage compensation amount of the rotor screw casting, and at the same time, the strong shrinkage compensation effect of the high-temperature molten iron in the gas outlet riser, the casting process of the rotor screw casting production has a high yield rate; 2) The large rotor screw casting mold adopts horizontal sand-covered molding, the rotor screw spiral tooth surface shell mold and the molten iron filter are placed horizontally, the box is closed horizontally, and the mold is made The mold and box closing process is convenient and fast, and it is easy to realize mechanized operation; 3) After the box is closed and locked, the mold is flipped 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. The molten iron flows balanced, which greatly reduces the generation of iron beans, gas entrapment to form pores, slag inclusions and other casting defects 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, and is easy to realize 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, and the high-strength performance of the cast state of large rotor screw castings can be achieved, and the energy-saving effect of the production process is significant. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

[0020] Figure 5 It is a schematic diagram of the top view of the structure of the casting mold assembly for casting a large rotor screw casting according to an embodiment of the present invention.

[0021] Figure 6 The present invention is a schematic diagram of the side view of a casting mold assembly for casting a large rotor screw casting according to an embodiment of the present invention.

[0022] Figure 7 Schematic diagram of the pouring system structure of the screw casting in the embodiment of the present invention Figure 1 .

[0023] Figure 8 Schematic diagram of the pouring system structure of the screw casting in the embodiment of the present invention Figure 2 .

[0024] Fig. 9 Schematic diagram of the pouring system structure of the screw casting in the embodiment of the present invention Figure 3 .

[0025] Fig.10 It is a schematic diagram of molten iron filtration when the screw casting according to an embodiment of the present invention is poured into a horizontal vertical casting mold.

[0026] Fig.11 It is a schematic diagram of the spiral tooth surface shell structure for casting a rotor screw casting according to an embodiment of the present invention.

[0027] Fig.12 It is a schematic diagram of the upper and lower iron molds after horizontal sand coating molding in the production process of the rotor screw casting according to the embodiment of the present invention.

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

[0029] Fig.14 It is a schematic diagram of the upper and lower iron molds being horizontally closed and locked during the production process of the rotor screw casting according to an embodiment of the present invention.

[0030] Fig.15 It is a schematic diagram of a casting mold flipped 90 degrees and erected during the production process of the rotor screw casting according to an embodiment of the present invention.

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

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

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

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

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

[0036] Fig.21 It is a schematic diagram of taking out the screw casting from the lower iron mold during the production process of the rotor screw casting in an embodiment of the present invention.

[0037] In the figure: rotor screw casting L: screw spiral tooth surface L1, upper support shaft L2, lower support shaft L3; upper iron mold casting mold 1, lower iron mold casting mold 2, spiral tooth surface shell mold 3, ceramic filter screen 4, lock box screw 5, pouring system 6, pouring cup 61, straight runner 62, cross runner 63, inner runner 64, air outlet riser 65, riser runner 66, air outlet needle 67, upper cross runner 631, lower cross runner 632; molten iron flows to F. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and by way of examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0039] Example

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

[0041] The large rotor screw casting L mold in this embodiment adopts one mold and two parts, and the arrangement of the mold cavity in the upper and lower iron molds is axially horizontal, that is: a semicircular cavity in the rotor screw cavity of the two screws is arranged in the lower mold of the iron mold casting, and the other semicircular cavity is arranged in the upper mold of the iron mold casting. The upper and lower iron molds are respectively completed with sand covering molding, and the screw spiral tooth surface shell mold is placed on the lower iron mold sand covering casting, and then the upper iron mold sand covering casting is assembled onto the iron mold sand covering casting of the lower iron mold to form a complete large rotor screw casting.

[0042] The casting cavity structure of this embodiment is a composite casting cavity, which is mainly composed of two parts, namely: an iron mold covered sand casting cavity and a coated sand shell cavity. Among them: the iron mold covered sand casting cavity mainly forms the two end support shaft casting cavity of the rotor screw, the shell backing cavity of the rotor screw spiral tooth surface, and the cavity of the entire casting system; the shell cavity of the coated sand screw spiral surface mainly forms the complete rotor spiral tooth surface casting cavity of the rotor screw (see Fig.11 ), there is no parting surface on the spiral surface cavity of the rotor screw of this shell type, and there is no mold draft. It is a single spiral surface complete cavity, which can greatly reduce the processing workload of the spiral surface.

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

[0044] See also Figure 7-Figure 9 In this embodiment, the pouring system 6 includes a connected pouring cup 61, a straight runner 62, a cross runner 63, an inner runner 64, a gas outlet riser 65, a riser runner 66 and a gas outlet needle 67. The cross runner 63 is connected to the straight runner 62, and the cross runner 63 includes an upper cross runner 631 and a lower cross runner 632.

[0045] The entire pouring 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 pouring system 6 in the upper iron mold 1 and the lower iron mold 2 is the same as the arrangement of the rotor screw casting L mold cavity, that is, one semicircular cavity of the sprue 62 is arranged in the upper iron mold 1, and the other semicircular cavity is arranged in the lower iron mold 2.

[0046] According to the structural characteristics, process requirements, and performance requirements of the rotor screw casting, the pouring system 6 of this embodiment is arranged in the form of bottom pouring. During pouring, the rotor screw casting is flipped 90°, and the axial arrangement of the rotor screw casting L casting cavity is changed from horizontal to vertical. The molten iron enters from the bottom surface of the lower support shaft L3 at the lower end of the rotor screw casting L casting cavity, and flows from bottom to top along the axial direction of the rotor screw casting L casting cavity to fill the mold.

[0047] In this embodiment, the runner 62 for filling the mold with unfiltered molten iron begins to occupy half of the upper iron mold 1 and the lower iron mold 2 respectively, and then gradually transitions upward to the cavity of the upper iron mold 1; the mold cavity for placing the ceramic filter screen 4 is bounded by the parting surface, and is entirely set in the lower iron mold 2. The lower runner 632 below the ceramic filter screen 4 is set in the lower iron mold 2, and then gradually transitions upward to the upper iron mold 1, until the cavities of the upper iron mold 1 and the lower iron mold 2 each occupy half.

[0048] In this embodiment, the cross-sectional shape of the inner runner 64 is circular, and the upper iron mold 1 and the lower iron mold 2 each occupy a semicircle; the air outlet riser 65 and the air outlet needle 67 are both circular; the riser diameter is determined according to the size of the rotor screw casting, and the air outlet needle diameter is also controlled to be between 15 and 20 mm according to the size of the rotor screw casting; the cross-sectional shape of the riser runner 66 is rectangular, and the upper iron mold 1 and the lower iron mold 2 cavity each occupy half.

[0049] In this embodiment, the overheated gas outlet riser 65 plays a good role in compensating the shrinkage of the molten iron in the rotor screw casting cavity; the gas outlet riser 65 has a floating effect on the slag of the molten iron in the rotor screw casting cavity.

[0050] The ceramic filter screen 4 in the molten iron filtering device of this embodiment is arranged horizontally in the sand-coated mold cavity in the lower iron mold 2. When the iron mold needs to be poured, the iron mold needs to be flipped 90°, that is, the original horizontal axial arrangement of the large screw casting mold cavity is flipped to a vertical arrangement, and the original horizontal arrangement of the ceramic filter screen 4 is also changed to a vertical arrangement. This vertical ceramic filter screen 4 filtering method of molten iron during molten iron pouring is completely different from the horizontal arrangement of the traditional ceramic filter screen. Fig.10 It can be seen that: when the molten iron enters the sprue 62 from top to bottom through the pouring cup 61, and after entering the bottom of the sprue 62, it separates to the left and right and respectively enters the left and right upper cross runners 631 cavities in the upper iron mold 1, the molten iron flows horizontally through the vertically arranged ceramic filter 4 to filter the molten iron, and then flows from the lower cross runner 632 cavity in the lower iron mold to fill the mold to the entrapment 64, and the molten iron fills upward through the entrapment 64 and enters the mold cavity of the rotor screw casting L.

[0051] The working process of the device for casting a large screw compressor rotor screw casting of this embodiment is as follows: first, the upper iron mold casting 1, the lower iron mold casting 2, and the rotor screw spiral tooth surface shell mold 3 are respectively molded; the two rotor screw spiral tooth surface shell mold 3 cavities are horizontally and axially placed one by one in the two corresponding iron mold sand casting backing cavities in the lower iron mold casting 2 of the large rotor screw; at the same time, two ceramic filter screens 4 are horizontally placed at the corresponding 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 assembled onto the lower iron mold casting 2, and then the locking screw 5 is tightened to form a complete large rotor screw composite casting; the entire iron mold casting is turned over 90 degrees to make the rotor screw casting The cavity and the pouring system 6 are flipped from the original axial horizontal arrangement to an axial vertical arrangement, and the molten iron inlet of the pouring cup 61 above the sprue 62 is facing 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 sprue 62, and the molten iron is filtered by the vertically arranged ceramic filter 4 device to block slag; the filtered molten iron passes through the cross runner 63 at the other end of the ceramic filter 4, and continues to flow to the inner gate set at the bottom plane of the rotor screw support shaft, and enters the casting cavity of the rotor screw upward, and the molten iron continuously fills the rotor screw casting cavity from bottom to top, and the filling flow is smooth until the entire rotor screw casting cavity is completely filled; the gas generated in the casting cavity during the filling process passes through the top of the rotor screw The air outlet needle 67 on the air outlet riser 65 is discharged into the atmosphere in time; then the colder molten iron in the upper part of the rotor screw cavity and the floating slag-containing molten iron continue to fill upward into the air outlet riser 65 above the rotor screw casting cavity. When the filling height of this type of molten iron in the air outlet riser 65 reaches the lower edge height of the riser runner 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 air outlet riser 65 through the riser runner 66. In this way, the temperature of the molten iron in the air outlet riser 65 is higher than the temperature of the molten iron above the rotor screw. The molten iron in the air outlet riser 65 can well compensate for the shrinkage of the molten iron above the rotor screw. At the same time, the slag inclusions in the molten iron in the L casting cavity of the rotor screw casting can be floated before solidification. After entering the air outlet riser 65, the molten iron in the mold cavity begins to solidify and cool, thereby finally obtaining a high-quality rotor screw casting L without shrinkage cavities, shrinkage porosity, and slag inclusion defects; after the molten iron in the mold solidifies and cools, the upper and lower iron molds are turned over by 90 degrees, so that the parting surfaces of the upper and lower iron molds are turned from a vertical arrangement to a horizontal arrangement when the original iron molds are closed, and 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 in a semicircular shaft shape in the upper and lower iron molds, and the casting and the iron mold are easily separated), thereby completing a large rotor screw casting casting production, and finally obtaining a large rotor screw casting with a dense structure and fine grains, and realizing the as-cast casting production of large rotor screw castings;By cycling in sequence, batch production of this type of castings can be achieved. ;

[0052] The process principle of the composite casting device of this embodiment: In order to ensure the axial dynamic balance performance of the rotor screw casting, in the casting production process of the rotor screw casting L, the rotor screw casting L needs to be arranged vertically in the casting mold. For large rotor screw castings, the rotor screw casting L is arranged vertically in the axial direction, and the height of the casting cavity in the casting mold is more than 1000 mm. For such a high casting mold, the molten iron pouring process must adopt the form of bottom pouring. This molten iron pouring process can well make the molten iron poured into the casting mold smoothly fill the mold from bottom to top, and at the same time make the inclusions in the molten iron float well, so as to obtain a defect-free quality casting. For large rotor screw castings, each casting generally weighs 400-600 kg, is about 1000 mm long, and the maximum diameter of the screw spiral tooth surface is about 350-450 mm. If this type of casting is arranged perpendicular to the iron mold parting surface in the iron mold sand-coated casting, the thickness of a single iron mold will exceed 600 mm, and it will be small at both ends and large in the middle, which will cause great difficulty in the sand-coated molding of the iron mold sand-coated casting, or require a sand-coated molding machine with a larger stroke and demolding force; in addition, it is difficult to achieve a complete bottom pouring method in a large rotor screw using this arrangement; at the same time, when this arrangement is used for the production of large rotor screw castings, when the large rotor screw casting is solidified and cooled, the separation between the casting and the iron mold will be difficult due to the cooling and shrinkage of the casting, etc. The large rotor screw casting of the present application adopts a one-mold and two-piece large rotor screw casting mold, and the large rotor screw casting cavity is arranged axially and horizontally in the iron mold; the straight runner 62, the cross runner 63, the inner runner 64, the molten iron filter device flow channel, etc. of the pouring system 6 are all made on the iron mold sand-coated casting on the upper and lower iron mold parting surfaces ( Figure 7-Figure 9 ); Place the rotor screw helical tooth surface shell mold 3 axially and horizontally in the lower iron mold sand casting cavity, place the molten iron ceramic filter 4 horizontally in the lower iron mold sand casting, close the box horizontally, and then lock the upper and lower molds ( Figure 4-Figure 6 ); then the mold after the box is closed and locked is flipped vertically by 90°, so that the rotor screw casting cavity, which was originally arranged horizontally in the axial direction, is flipped to be arranged vertically in the axial direction. In this state, the casting mold is poured, and the bottom injection filling mode of molten iron in the large rotor screw casting mold can be realized, so that the large rotor screw casting mold can be filled, solidified, and cooled in a relatively ideal state, and finally the high-quality casting production of large screw castings can be realized. During the cooling process, the molten iron in the large rotor screw casting cavity of this embodiment can make full use of the expansion caused by the graphite precipitated during the solidification process of the molten iron to offset the liquid contraction caused by the cooling of the molten iron. At the same time, the strong shrinkage compensation effect of the high-temperature molten iron in the air outlet riser 65 above the screw casting cavity makes the molten iron utilization rate of this embodiment much higher than that of the traditional sand casting.

[0053] This embodiment is aimed at the casting process requirements of the axial vertical bottom pouring of the large screw compressor rotor screw casting L, and the forming process characteristics of the iron mold covered with sand casting mold. In the single-open mold iron mold covered with sand casting mold with upper and lower horizontal parting, a half-iron mold covered with sand and arranged along the axial direction of the rotor screw is horizontally made in the upper and lower iron mold cavities, and a corresponding pouring system 6. After the upper and lower halves of the mold are horizontally combined with the screw spiral tooth surface shell mold 3, a large rotor screw casting cavity with a complete horizontal arrangement and a matching pouring system 6 can be formed. After the combined box is locked, the parting surface of the mold of the large rotor screw casting L is flipped 90° from the horizontal position, so that the straight gate in the casting system of the casting is vertically upward and the casting parting surface is perpendicular to the horizontal plane. In this way, the casting cavity of the rotor screw in the entire composite casting can be arranged vertically. In this state, molten iron is poured in, and the molten iron smoothly enters the casting cavity of the rotor screw casting through the bottom of the lower support shaft of the rotor screw casting cavity, such as the pouring cup 61, the straight runner 62, the cross runner filter device, and the inner runner 64, from bottom to top until the entire rotor screw casting cavity is filled. The molten iron is poured and filled smoothly. By utilizing the characteristics of good rigidity and fast cooling speed of the iron mold covered with sand casting, by reasonably setting the cross-sectional dimensions of the pouring system, small riser casting of large rotor screw castings can be achieved. The casting has fine grains, dense internal structure, excellent comprehensive mechanical properties and good dynamic balance performance. At the same time, casting defects such as iron bean splashing, air entanglement, slag inclusion, shrinkage and shrinkage holes in the rotor screw casting during the molten iron pouring process are avoided.

[0054] Through the above description, those skilled in the art can already implement it.

[0055] In addition, it should be noted that the shapes and names of the parts and components of the specific embodiments described in this specification may be different, and the above content described in this specification is only an example of the structure of the present invention. All equivalent changes or simple changes made based on the structure, features and principles described in the patent concept of the present invention are included in the protection scope of the patent of the present invention. Technicians in the technical field to which the present invention belongs can make various modifications or supplements to the specific embodiments described or replace them in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A device for casting a large screw compressor rotor screw casting, comprising a molten iron filtering device, a lock box screw (5) for locking and fixing an upper iron mold (1) and a lower iron mold (2), characterized in that: It also includes an upper support shaft (L2) and a lower support shaft (L3) casting cavity for forming a rotor screw casting (L), a rotor screw spiral tooth surface shell mold (3) backing cavity, an iron mold covered sand casting cavity for the entire casting system (6) cavity, and a coated sand shell mold cavity for forming a complete screw spiral tooth surface (L1) casting cavity of the rotor screw casting (L). The rotor screw casting (L) cavity is axially arranged horizontally in the iron mold, one mold has two pieces, and the circular rotor screw casting (L) cavity is half arranged in the upper iron mold and half arranged in the lower iron mold; the casting system (6) includes a connected pouring cup (61) and a straight runner (62), the pouring cup (61) and the sprue (62) cavity are arranged in an axially horizontal arrangement 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 the pouring system (6) is arranged in a bottom pouring manner. During pouring, the rotor screw mold is flipped 90 degrees, and the axial arrangement of the rotor screw casting (L) mold cavity changes from a horizontal arrangement to a vertical arrangement. The 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.

2. The device for casting a large screw compressor rotor screw casting according to claim 1, characterized in that: Two ceramic filter screens (4) are arranged in the molten iron filtering device, and the two ceramic filter screens (4) are both horizontally arranged in the sand-covered molding cavity in the lower iron mold (2).

3. The device for casting a large screw compressor rotor screw casting according to claim 1, characterized in that: The pouring system (6) further comprises a runner (63), an entgate (64), a gas outlet riser (65), a riser runner (66) and a gas outlet needle (67); the runner (63) is connected to the sprue (62); the runner (63) comprises an upper runner (631) and a lower runner (632); the cross-sectional shape of the entgate (64) is circular, with the upper iron mold (1) and the lower iron mold (2) each occupying a half of the circle; the gas outlet riser (65) and the gas outlet needle (67) are both circular; the riser runner (66) is rectangular in cross-sectional shape, with the upper iron mold (1) and the lower iron mold (2) each occupying a half of the cavity.

4. The device for casting a large screw compressor rotor screw casting according to claim 1, characterized in that: The pouring cup (61) is a conical pouring cup (61) which is directly made in the upper iron mold (1) and the lower iron mold (2), with the iron mold parting surface as the boundary, and the upper iron mold (1) and the lower iron mold (2) each occupying half of the mold cavity.

5. The device for casting a large screw compressor rotor screw casting according to claim 3, characterized in that: The diameter of the gas outlet riser (65) is determined according to the size of the rotor screw casting (L), and the diameter of the gas outlet needle (67) is controlled to be between 15 and 20 mm according to the size of the rotor screw casting (L).

6. The device for casting a large screw compressor rotor screw casting according to claim 2, characterized in that: When the box is closed, the ceramic filter screen (4) can be directly placed on the lower iron mold (2). After the box is closed, the iron mold is turned 90 degrees, and the ceramic filter screen (4) in the iron mold is arranged vertically, and the molten iron is filled and filtered in a horizontal flow.

7. A method for operating a device for casting a large screw compressor rotor screw casting, using the device for casting a large screw compressor rotor screw casting as claimed in any one of claims 1 to 6, characterized in that: The specific steps are as follows: First, the upper iron mold (1) and the lower iron mold (2) cavities of the large rotor screw are molded, as well as the rotor screw spiral tooth surface shell mold (3) cavity; the two rotor screw spiral tooth surface shell mold (3) cavities are horizontally and axially placed one by one in two corresponding iron mold sand casting backing cavities in the lower iron mold (2); at the same time, two ceramic filter screens (4) are horizontally placed at the corresponding cavity positions of the molten iron filter device in the lower iron mold (2); then the upper iron mold (1) of the rotor screw is assembled onto the lower iron mold (2), and then the locking screw (5) is tightened to form a complete large rotor screw composite mold; The entire iron mold is turned over 90 degrees, so that the rotor screw 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 of the pouring cup (61) above the sprue (62) is facing 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 sprue (62), and is filtered by the vertically arranged ceramic filter (4) device to block slag; the filtered molten iron passes through the cross runner (63) at the other end of the ceramic filter (4), continues to flow to the inner gate set at the bottom plane of the rotor screw support shaft, and enters the mold cavity of the rotor screw upward, and the molten iron continuously fills the rotor screw mold cavity from bottom to top, and the filling flow is smooth until the entire rotor screw mold cavity is completely filled; the gas generated in the mold cavity during the filling process is discharged in time through the gas outlet needle (67) on the gas outlet riser (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 riser (65) above the rotor screw casting cavity. When the filling height of such molten iron in the gas outlet riser (65) reaches the height of the lower edge of the riser runner (66) above the sprue (62), the molten iron in the rotor screw cavity no longer fills upward, and the high-temperature molten iron directly fills the gas outlet riser (65) through the riser runner (66), and the gas outlet The temperature of the molten iron in the riser (65) is higher than the temperature of the molten iron above the rotor screw. The molten iron in the gas outlet riser (65) can effectively compensate for the shrinkage of the molten iron above the rotor screw. At the same time, the slag inclusions in the molten iron in the casting mold cavity of the rotor screw casting (L) can enter the gas outlet riser (65) by floating before solidification. Then, the molten iron in the casting mold cavity begins to solidify and cool, so as to finally obtain a high-quality rotor screw casting (L) without shrinkage cavities, shrinkage porosity, and slag inclusion defects. After the molten iron in the casting mold is solidified and cooled, the upper and lower iron molds are turned over by 90 degrees, so that the parting surfaces of the upper and lower iron molds are turned from a vertical arrangement to a horizontal arrangement when the iron molds are originally closed, and then the locking screw (5) is loosened to open and separate the upper and lower iron molds, and the casting is taken out, thereby completing the casting production of a large rotor screw casting, and finally obtaining a large rotor screw casting with a dense structure and fine grains, thereby realizing the as-cast casting production of large rotor screw castings; the cycle is repeated in sequence, and mass production of such castings can be realized.

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