Large screw expander rotor forming method

Abstract

The invention discloses a method for forming a rotor of a large screw expander. The method comprises the following steps: (1) mounting a profiling crystallizer; (2) casting a rotor spiral body; (3) dismounting the profiling crystallizer; (4) flattening the stub bar and processing step holes in two ends of the middle hole; (5) round cakes are arranged at the two ends of the inner hole of the rotor spiral body; (6) shaft head casting: sleeving a shaft head crystallizer outside the positioning circular truncated cone, completing shaft head casting by adopting a mode of melting, cooling and moving at the same time, and finally forming a screw rotor forming body; according to the forming method, electrode casting is matched with a corresponding profiling crystallizer manufacturing process, so that the forming precision of the screw rotor reaches or is close to the effect of the shape of a finished product, the comprehensive advantages of good forming, short machining period and high quality are obtained, the problem of long machining time of a large screw rotor is solved, and the production cost is reduced. Special rough milling, semi-finish milling and finish milling cutter discs and blades are not needed, and meanwhile a large number of alloy materials are saved.

Description

Technical Field

[0001] The invention relates to the technical field of screw rotor processing, and in particular to a large screw expander rotor molding method. Background Art

[0002] The general process flow for manufacturing existing large screw expander rotors is: forging blank → normalizing → rough turning → rough milling spiral → heat treatment → semi-finishing turning → grinding outer circle → semi-finishing spiral milling → flaw detection → fine turning → fine milling spiral → meshing inspection → fine turning bearing position → fine grinding → milling keyway → inspection → surface treatment (as needed).

[0003] The shortcomings of the existing large screw rotor processing methods mainly include the following four points:

[0004] 1) Among the existing large screw rotor processing methods, the most time-consuming and difficult process is spiral milling. When processing a cylinder into a spiral, the removal margin is more than 50%, which not only wastes processing time, but also wastes half of the material. Regardless of the rough milling spiral process, semi-finishing spiral milling process or fine milling spiral process, the processing equipment must use a special CNC screw milling machine and be equipped with special rough milling, semi-finishing and fine milling cutter discs and blades.

[0005] 2) Due to the limitation of the processing range of special CNC screw milling machines for screw rotors, the processing diameter of the special screw milling machines with a larger processing range and which are more commonly used is 650mm, and the processing diameter of the largest screw milling machine is 1000mm. There are very few of them at home and abroad, with no more than 2 in China, and the equipment prices are particularly high. The price of a domestic equipment is more than 15 million yuan, while the price of a foreign equipment is more than 30 million yuan, and the processing time is long. There is no method or equipment for the overall processing of screw rotors with a diameter of 1020mm or more. At present, it can only be done by moving mountains like ants, using large-scale turning and milling composite machining centers to perform cutting processing with a very small feed amount to eliminate 50% of the excess rotor raw material. The efficiency is very low and the cost is very high. The unit price of a large-scale turning and milling composite machining center is also more than 10 million yuan, and the corresponding machine hourly price is also high.

[0006] 3) The large screw rotor processed by the existing method is too heavy, which seriously affects the weight of the screw expander. The screw rotor processed by the existing method is solid, and the solid middle part not only increases the weight, reduces efficiency in all aspects, but also has no other benefits.

[0007] 4) The screw rotor processed by the existing method can only be made of the same material as a whole. The material of the rotor spiral part and the material of the shaft head part cannot be different. When facing special working conditions such as corrosion, the spiral material and the shaft head material cannot be separated. Highly corrosion-resistant materials need to be used as a whole, which increases material costs.

[0008] Therefore, the molding and processing of large screw rotors is a major technical problem to be solved urgently. The present invention is produced under such circumstances. Summary of the invention

[0009] The purpose of the present invention is to provide a large screw expander rotor forming method to solve the problem that the existing large screw expander rotor processing method is insufficient.

[0010] The above technical objectives of the present invention are achieved through the following technical solutions:

[0011] A large screw expander rotor forming method comprises the following steps:

[0012] (1) Installation of the contoured crystallizer: The contoured crystallizer consists of a split outer crystallizer and an inner crystallizer. The outer crystallizer is made of multiple pieces of the same structure, with a molding cavity in the middle that is the shape of a rotor spiral. Rings with positioning truncated cones are installed at both ends of the molding cavity. The inner crystallizer is inserted in the middle of the molding cavity, thereby forming a hollow structure in the middle of the spiral. The bottom of the entire contoured crystallizer is installed on the bottom water tank.

[0013] (2) Casting of the rotor spiral: Multiple electrodes are inserted into the molding cavity of the spiral, and the electrodes are energized. The electrode feed speed is accurately controlled, and the electrodes are heated and melted into the molding cavity. After cooling, the rotor spiral is formed, and the positioning cone is cast at the positions where the circular rings are installed at both ends of the rotor spiral.

[0014] (3) Dismantling the contoured crystallizer: dismantle the inner crystallizer and the outer crystallizer, and take out the formed rotor spiral.

[0015] (4) The material head is flat and stepped holes are processed at both ends of the middle hole: The material heads at both ends of the rotor spiral body are sawed flat by a hacksaw or other means, and stepped holes are processed at both ends of the middle hole. The processing length is determined by the combined length of the shaft head and the rotor spiral body.

[0016] (5) Round cakes are installed at both ends of the inner hole of the rotor spiral: round cakes of a certain thickness and made of the same material as the spiral are pressed into the stepped holes that have been processed at both ends of the middle hole of the spiral. An interference fit is used to ensure that they are firmly combined with the rotor spiral body for the subsequent melting and casting of the shaft heads at both ends.

[0017] (6) Shaft head casting: An shaft head crystallizer is installed on the outside of the positioning truncated table, and an electrode is used to complete the first shaft head casting by melting, cooling and moving. The second shaft head casting is completed by the same method as the first shaft head casting, and finally a screw rotor molded body is formed.

[0018] Furthermore, the outer crystallizer is formed by splicing four pieces of the same structure, and the outside can be fixed with a bolt structure. Splicing multiple pieces of the same structure is conducive to removing the rotor spiral after melting and casting.

[0019] Furthermore, six electrodes are used for the melting and casting of the intermediate spiral body, and are driven by six identical servo motor mechanisms to keep the feed speed consistent, thereby ensuring that the internal texture of the rotor spiral body is uniform when it is formed, and reducing the occurrence of defects such as bubbles and cracks.

[0020] Furthermore, the electrodes of the rotor spiral body and the shaft head are made of different materials. For example, the rotor spiral part in contact with the medium is made of high-strength stainless steel, while the shaft heads at both ends are not in contact with the corrosive medium and can be made of conventional alloy steel.

[0021] Furthermore, after round cakes are pressed into the two ends of the middle hole of the spiral body, a hollow portion can be formed in the middle position of the middle hole, and the spiral body of a large rotor can be hollow-designed and processed to meet the lightweight requirements of the large rotor.

[0022] Furthermore, a processing allowance of 2 to 4 mm is reserved at each processing position of the screw rotor forming body formed by melt casting, and the processing allowance is mainly determined by referring to the size of the screw blank and the accuracy requirement after processing.

[0023] In summary, the present invention has the following beneficial effects:

[0024] 1. The forming method of the present invention adopts the manufacturing process of electrode melting and casting in conjunction with the corresponding profiling crystallizer, so that the forming accuracy of the screw rotor reaches or approaches the shape of the finished product, thereby obtaining the comprehensive advantages of good forming, short processing cycle and excellent quality, solving the problem of long processing time for large screw rotors, and no longer requiring pre-design and manufacturing of special rough milling, semi-finishing milling and finishing milling cutter discs and blades, while also saving a large amount of alloy materials.

[0025] 2. The molding method of the present invention is not limited by the diameter of the screw rotor of the screw expander, which is conducive to the large-scale diameter of the screw rotor. The steam intake of the corresponding screw expander can also be increased, so that a large amount of low-quality energy can be fully utilized.

[0026] 3. The present invention performs hollow design and processing on the screw rotor to meet the lightweight requirements of large rotors.

[0027] 4. The molding method of the present invention can meet the material requirements of different parts of the rotor. For example, when the screw expander is used in a corrosive gas medium, the spiral part of the rotor in contact with the medium must use high-strength stainless steel, while the two end shaft heads do not contact the corrosive medium and can use conventional alloy steel, saving a lot of material costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Attached Figure 1 This is the main cross-sectional view of the spiral part of the screw rotor;

[0029] Attached Figure 2 This is a top view of the casting of the spiral part of the screw rotor;

[0030] Attached Figure 3 This is a cross-sectional view of the spiral part of the screw rotor;

[0031] Attached Figure 4 This is the melting casting diagram of the spiral part of the screw rotor;

[0032] Attached Figure 5 This is a schematic diagram of the casting of the screw rotor shaft head;

[0033] Attached Figure 6 This is a schematic diagram of the casting of the shaft head at the other end of the screw rotor;

[0034] Attached Figure 7 This is the overall schematic diagram of the screw rotor after melting and casting.

[0035] In the figure, 1. electrode; 2. outer crystallizer; 3. inner crystallizer; 4. bottom water tank; 5. forming cavity; 6. rotor spiral body; 7. round cake; 8. step hole; 9. positioning frustum; 10. electrode 2; 11. shaft head crystallizer; 12. slag pool; 13. metal molten pool; 14. hollow part; 15. screw rotor forming body. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings, and the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] A large screw expander rotor forming method comprises the following steps:

[0038] (1) Installation of contoured crystallizer: Reference Figure 1 and Figure 2 As shown, the profiled crystallizer is composed of a split outer crystallizer 2 and an inner crystallizer 3. The outer crystallizer 2 is formed by splicing multiple pieces of the same structure, forming a molding cavity 5 in the middle with the shape of the rotor spiral body 6. Both ends of the molding cavity 5 are equipped with circular rings with positioning truncated cones 9 on the inner side. The inner crystallizer 3 is inserted in the middle position of the molding cavity 5, so as to form a hollow structure in the middle part of the spiral body. The bottom of the entire profiled crystallizer is installed on the bottom water tank 4. The inner shape of the outer crystallizer 2 corresponds to the outer shape of the rotor.

[0039] (2) Casting of rotor spiral body 6: Figure 1As shown, multiple electrodes 1 are inserted into the spiral forming cavity 5, the electrodes 1 are energized, and the feeding speed of the electrodes 1 is accurately controlled. The electrodes 1 are heated and melted into the forming cavity 5, and gradually form a rotor spiral body 6 after cooling. The positioning truncated cone 9 is formed by melting at the positions where the circular rings are installed at both ends of the rotor spiral body 6. The formation structure of the positioning truncated cone 9 is shown in FIG. Figure 3 shown.

[0040] (3) Dismantling the profiling crystallizer: dismantle the inner crystallizer 3 and the outer crystallizer 2, take out the formed rotor spiral body 6, and connect the dismantled rotor spiral body 6 as shown in the following figure: Figure 3 shown.

[0041] (4) Smooth the material head and process the two ends of the middle hole into stepped holes 8: Use a hacksaw or other method to saw the material heads at both ends of the rotor spiral body 6 to make them smooth, and use a milling machine to process the two ends of the middle hole into stepped holes 8. Figure 4 The machining length of the step hole 8 shown is determined by the combined length of the shaft head and the rotor spiral body 6.

[0042] (5) Insert round cakes 7 into the two ends of the inner hole of the rotor spiral body 6: Press round cakes 7 of a certain thickness and made of the same material as the spiral body into the stepped holes 8 that have been processed at the two ends of the middle hole of the spiral body 6. Use interference fit to ensure that it is firmly combined with the rotor spiral body 6 for the subsequent melting and casting of the shaft heads at the two ends.

[0043] (6) Shaft head casting: Figure 5 As shown, a shaft head crystallizer 11 is mounted outside the positioning truncated table 9, and an electrode 2 10 is used. The electrode 2 10 is energized to form a slag pool 12 and a molten metal pool 13 in the shaft head crystallizer 11, and the first shaft head casting is completed by melting, cooling and moving at the same time; Figure 6 As shown, the second shaft head is cast in the same way as the first shaft head, and finally formed as shown in Figure 7 The hollow portion 14 and the screw rotor molded body 15 are shown.

[0044] Further, such as Figure 4 As shown, the outer crystallizer 2 is formed by splicing four pieces of the same structure, and the outside can be fixed with a bolt structure. Splicing multiple pieces of the same structure is conducive to taking out the rotor spiral 6 after melting and casting.

[0045] Further, such as Figure 2 As shown, the intermediate spiral body is melt-casted using six electrodes 1 and is driven by six identical servo motor mechanisms to keep the feed speed consistent, thereby ensuring that the internal texture of the rotor spiral body 6 is uniform when it is formed and reducing defects such as bubbles and cracks.

[0046] Furthermore, the rotor spiral body 6 and the electrode 2 10 of the shaft head are made of different materials. For example, the spiral part in contact with the medium should use high-strength stainless steel, while the two ends of the shaft head are not in contact with the corrosive medium, and the electrode 2 10 can use conventional alloy steel.

[0047] Further, such as Figure 4 As shown, after the round cakes 7 are pressed into the two ends of the middle hole of the spiral body, a hollow part is formed in the middle position of the middle hole. The spiral body of a large rotor is hollowed out and processed to meet the requirements of lightweighting of large rotors.

[0048] Furthermore, a processing allowance of 2 to 4 mm is reserved at each processing position of the screw rotor forming body 15 formed by melt casting, and the processing allowance is mainly determined by referring to the size of the screw blank and the precision requirement after processing.

[0049] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. After reading this specification, those skilled in the art can make non-creative modifications to this embodiment as needed, but they are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A large screw expander rotor forming method, characterized in that: The following steps are involved: (1) Installation of the contoured crystallizer: The contoured crystallizer consists of a split outer crystallizer and an inner crystallizer. The outer crystallizer is made of multiple pieces of the same structure, with a forming cavity in the middle that is in the shape of a rotor spiral. Both ends of the forming cavity are provided with circular rings that form a positioning truncated cone on the inner side. The inner crystallizer is inserted in the middle of the forming cavity, thereby forming a hollow structure in the middle of the spiral. The bottom of the entire contoured crystallizer is installed on the bottom water tank. (2) Casting of the rotor spiral body: multiple electrodes are inserted into the spiral body forming cavity, the electrodes are energized, and the electrode feeding speed is accurately controlled. The electrodes are heated and melted into the forming cavity. After cooling, the rotor spiral body is formed, and the positioning truncated cones are cast at the positions where the circular rings are installed at both ends of the rotor spiral body; (3) Dismantling the contoured crystallizer: dismantle the inner crystallizer and the outer crystallizer, and take out the formed rotor spiral; (4) The material head is flat and the two ends of the middle hole are processed into stepped holes: the material heads at both ends of the rotor spiral body are sawed flat by a hacksaw or other means, and stepped holes are processed at both ends of the middle hole. The processing length is determined by the combined length of the shaft head and the rotor spiral body; (5) Insert round cakes at both ends of the inner hole of the rotor spiral: Press round cakes of a certain thickness and made of the same material as the spiral into the stepped holes that have been processed at both ends of the middle hole of the spiral. Use interference fit to ensure that it is firmly combined with the rotor spiral for subsequent melting and casting of the shaft heads at both ends; (6) Shaft head casting: An shaft head crystallizer is installed on the outside of the positioning truncated table, and an electrode is used to complete the first shaft head casting by melting, cooling and moving. The second shaft head casting is completed by the same method as the first shaft head casting, and finally a screw rotor molded body is formed.

2. A large screw expander rotor forming method according to claim 1, characterized in that: The outer crystallizer is formed by splicing four identical structures.

3. A large screw expander rotor forming method according to claim 2, characterized in that: The intermediate spiral casting uses six electrodes and is driven by six identical servo motor mechanisms to keep the feed speed consistent.

4. A large screw expander rotor forming method according to claim 3, characterized in that: The electrodes of the rotor spiral body and the shaft head are made of different materials.

5. A large screw expander rotor forming method according to claim 1, characterized in that: In the step (5), after the round cakes are pressed into the two ends of the middle hole of the spiral body, a hollow part is formed in the middle position of the middle hole.

6. A large screw expander rotor forming method according to claim 1, characterized in that: A processing allowance of 2 to 4 mm is left at each processing position of the screw blank formed by melt casting.

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