Uniform cooling production method for high performance double-hole copper bars for large rotor windings

Abstract

The present invention relates to the field of metal processing, and provides a horizontal continuous casting production process for double-hole copper bars of large rotor windings, which significantly improves product quality and production efficiency through innovative design and optimization. The process mainly includes steps such as raw material preparation, smelting, heat preservation, horizontal continuous casting, ingot forming, cold rolling, drawing, post-processing and quality inspection. Among them, the raw material preparation stage optimizes the material properties by accurately controlling the alloy element ratio, such as adding 0.03-0.1% silver, 0.02-0.05% magnesium, 0.03-0.08% zirconium and 0.02-0.06% chromium. Dual-frequency induction technology is used in smelting to ensure uniformity. The innovation of the horizontal continuous casting link is particularly prominent. The crystallizer body made of high thermal conductivity copper alloy is combined with a high-purity isostatic graphite double-hole mold to achieve precise segmented cooling control. The most distinctive feature is the middle cooling structure, which effectively solves the problem of uneven cooling during the solidification process of the double-hole copper bar by setting a jet outlet in the rear half of the mold rod and using high-frequency pulse jet technology.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material processing, in particular to the manufacturing process of copper alloy materials for power equipment, and specifically to a horizontal continuous casting production method of double-hole copper bars for large rotor windings. The present invention also relates to related technical fields such as motor manufacturing, power generation equipment manufacturing, and high-performance conductive material production. Background Art

[0002] The double-hole copper busbars used in large rotor windings must meet a series of stringent performance requirements to ensure efficient, stable and long-term reliable operation of the generator. These requirements include extremely high conductivity (≥97% IACS), excellent mechanical strength (tensile strength ≥300MPa), outstanding fatigue resistance (fatigue strength ≥150MPa under 10^8 cycles), excellent high temperature stability and creep resistance, extremely high dimensional accuracy (section size tolerance ≤±0.1mm) and surface finish (Ra≤3μm), excellent oxidation and corrosion resistance, and good welding and bending properties. These comprehensive requirements ensure that the double-hole copper busbars can operate stably and for a long time in the harsh working environment of large rotor windings.

[0003] Existing technologies face many challenges in meeting these requirements, especially in solving the cooling uniformity problem caused by the special structure of the double-hole copper busbar. The following are several related technologies:

[0004] Authorization announcement number CN 102864329 B discloses a brass alloy suitable for horizontal continuous casting, easy cutting and easy hot forging, with the composition of 70-72wt% copper, 2-4wt% silicon, 0.2-0.5wt% tellurium, 0.05-0.15wt% phosphorus, 0.01-0.05wt% lead, and the rest is zinc and unavoidable impurities. The alloy is lead-free and environmentally friendly, easy to cut, and has good hot forging performance. The tensile strength can reach 530-560MPa, the yield strength can reach 480-500MPa, and the elongation is 10-13%. However, the electrical conductivity and high temperature performance of this alloy are difficult to meet the strict requirements of large rotor windings.

[0005] Authorization announcement number CN 110964943 B discloses a method for producing high-strength copper alloys by semi-continuous casting. This method increases the dispersion strengthening effect of the alloy by adding niobium and manganese elements to the copper-nickel-tin alloy, which is beneficial to improving the strength of the alloy. The use of semi-continuous casting solves the shrinkage and shrinkage defects in the model casting and horizontal continuous casting process, and also significantly reduces segregation defects and improves production efficiency. However, this method fails to solve the cooling problem caused by the special structure of the double-hole copper busbar.

[0006] Application publication number CN 116213661 A discloses a crystallizer and horizontal continuous casting method for preparing tin-phosphor bronze bars. This method achieves structural refinement of tin-phosphor bronze bars by precisely controlling various parameters, substantially eliminates reverse segregation of tin, solves the problem of wire drawing cracking, and significantly improves the tensile strength of the product. This method provides a useful reference in parameter control, but still does not solve the problem of cooling uniformity caused by the special structure of the double-hole copper bar.

[0007] The unique geometric structure of the double-hole copper bar brings additional challenges to the traditional continuous casting process, especially the difference in thickness between the middle part and the periphery leads to uneven cooling, which easily causes internal stress concentration and uneven structure. At the same time, the existing technology still has a lot of room for improvement in improving production efficiency, reducing resource consumption and improving equipment utilization.

[0008] In view of the above problems, developing a process that can overcome the challenges of existing technologies and is suitable for the production of double-hole copper busbars can not only ensure product quality, but also improve production efficiency and reduce resource consumption. It is of great significance to promote the localization and industrial upgrading of core components of large-scale power generation equipment in my country. Summary of the invention

[0009] The purpose of the present invention is to solve the shortcomings of the prior art. The present invention provides a horizontal continuous casting production process for double-hole copper bars of large rotor windings. The material properties are optimized by precisely controlling the alloy element ratio and a middle cooling structure with high-frequency pulse jetting is adopted to effectively solve the problems of uneven cooling and segregation during the solidification process of the double-hole copper bars.

[0010] In order to solve the above problems, the present invention adopts the following scheme: A horizontal continuous casting production process for double-hole copper bars of large rotor windings, comprising the following steps:

[0011] S1 Raw material preparation: Use high-quality electrolytic copper or oxygen-free copper with a purity of ≥99.99% as the base material and add alloy elements;

[0012] S2 melting: using dual-frequency induction melting technology, combined with medium-frequency and high-frequency power supplies, using a mixed gas of argon and nitrogen for protection, optimizing melt flow through a multi-frequency and multi-mode electromagnetic stirring system, and controlling the temperature within the range of 1150-1200°C;

[0013] S3 insulation: multi-zone temperature control in the insulation furnace, the temperature range is 1130-1160℃;

[0014] S4 horizontal continuous casting: Use horizontal continuous casting equipment including crystallizer, middle cooling structure and ingot drawing system: The ingot drawing system is equipped with a force sensor to monitor the ingot drawing force in real time and adopts a "pull, push, stop" cycle sequence;

[0015] S5 double-hole copper busbar casting;

[0016] S6 cold rolling: adopts asynchronous multi-roll rolling system;

[0017] S7 drawing: using composite intelligent die system;

[0018] S8 post-processing;

[0019] S9 quality inspection.

[0020] Beneficial effects:

[0021] The production process systematically integrates raw material preparation, smelting, insulation, horizontal continuous casting, ingot forming, cold rolling, drawing, post-processing and quality inspection to build a comprehensive production system for double-hole copper bars for large rotor windings. Among them, the use of dual-frequency induction melting technology and multi-frequency multi-mode electromagnetic stirring system ensures the uniformity and stability of the melt, the horizontal continuous casting technology and precise temperature control improve the molding quality of the product, and the asynchronous multi-roll rolling system and composite material intelligent mold system further optimize the product performance. This full-process process design not only significantly improves production efficiency, but also ensures the high quality and performance stability of the product, providing reliable technical support for the manufacture of large rotor windings.

[0022] Preferably, the alloying elements in the S1 step include: 0.03-0.1% silver; 0.02-0.05% magnesium; 0.03-0.08% zirconium; 0.02-0.06% chromium. Beneficial effect: By precisely controlling the ratio of alloying elements, the process effectively optimizes the comprehensive performance of the copper busbar. Adding 0.03-0.1% silver increases the softening temperature and high temperature strength of the material, 0.02-0.05% magnesium improves the oxidation resistance and refines the grain structure, 0.03-0.08% zirconium significantly increases the recrystallization temperature, ensuring the strength stability of the material in a high temperature working environment, and 0.02-0.06% chromium enhances the wear resistance and corrosion resistance of the material. This alloy formula not only improves the performance of the copper busbar in high temperature and high stress environments, but also extends its service life, providing a material basis for the long-term stable operation of large rotor windings.

[0023] Preferably, the crystallizer for horizontal continuous casting in the step S4 comprises: a main body, made of a copper alloy with high thermal conductivity, having a sleeve channel running through it, a spiral cooling water channel is arranged outside the main body, and a variable frequency pump is used to realize precise segmented cooling control; a mounting portion, located at one end of the sleeve channel, is convex, and is provided with a fastening portion and a first inlet, wherein the first inlet has a conical design; a double-hole mold, made of high-purity, high-density isostatic graphite material, tightly sleeved in the sleeve channel; comprising a crystallization channel and a mounting entity; the crystallization channel adopts an integral design, is hollow inside and has an open end; the mounting entity is located at one end of the crystallization channel and is fixed on the crystallizer; two mold rods are arranged in the double-hole mold, which are in the shape of a quadrangular pyramid and have a draft angle that gradually decreases from one end to the other end of the cross-sectional shape. Beneficial effect: the main body made of a copper alloy with high thermal conductivity, in conjunction with an external spiral cooling water channel and a variable frequency pump, realizes precise segmented cooling control and ensures the uniformity of the solidification process. The conical first inlet on the mounting part ensures the smooth introduction of molten copper, reduces turbulence and gas entrapment, and improves the internal quality of the casting. The double-hole mold made of high-purity, high-density isostatic graphite not only improves the molding accuracy, but its integral design and draft angle also facilitate product demoulding, significantly improving production efficiency.

[0024] Preferably, the middle cooling structure in the horizontal continuous casting step in the S4 step includes: a) injection inlet: opened on the outer wall of the crystallizer, specifically provided with two injection inlets, respectively corresponding to the positions of the two mold rods, to ensure uniform cooling of the middle part of the double-hole copper bar; b) injection outlet: arranged in the rear half of the mold rod, and located on the side wall of the mold rod close to the other mold rod, in a plurality of distributions; this design takes into account the temperature distribution characteristics of the molten copper during the crystallization process, the molten copper temperature in the first half is relatively high and mainly relies on peripheral cooling, the molten copper in the second half has solidified, and the cooling of the middle part becomes particularly important; c) pulse injection assembly: can spray the cooling medium into the injection inlet in a high-frequency pulse manner, using high-frequency pulse technology, and the specific frequency is synchronized with the frequency of the "pull, push, stop" cycle sequence of the double-hole copper bar; the assembly includes an intelligent control system, which can dynamically adjust the injection frequency, pressure and flow rate of the cooling medium according to the real-time monitored temperature data; wherein, a connected cooling channel is formed between the injection inlet and the injection outlet. Beneficial effects: By opening the injection inlet corresponding to the position of the two mold rods on the outer wall of the crystallizer, uniform cooling of the middle part of the double-hole copper bar is ensured. The injection outlet is set in the rear half of the mold rod, and high-frequency pulse injection technology is used, which not only takes into account the temperature distribution characteristics of the copper liquid during the solidification process, but also improves the cooling efficiency. The intelligent control system can dynamically adjust the injection frequency, pressure and flow rate of the cooling medium according to the real-time monitored temperature data, realizing precise control of the cooling process.

[0025] Preferably, the asynchronous multi-roller rolling system used in the S6 cold rolling step has a 4+4 roll configuration, and each roll is independently speed-regulated; the working roll is equipped with a high-frequency micro-vibration device, which applies a micro-vibration of 20-50kHz during the rolling process, and a cold-hot composite rolling process is adopted, and the surface layer 0.1-0.3mm is quickly heated and then rolled using high-frequency induction heating technology. Beneficial effect: The cold rolling process not only improves the rolling accuracy but also ensures the uniformity of the product cross section through the asynchronous multi-roller rolling system with a 4+4 roll configuration and the independent speed regulation function of each roll. The high-frequency micro-vibration device equipped with the working roll applies a micro-vibration of 20-50kHz during the rolling process, effectively reducing surface defects and improving the internal organizational structure of the material. The cold-hot composite rolling process is adopted, and the surface layer 0.1-0.3mm is quickly heated and then rolled using high-frequency induction heating technology, which not only optimizes the surface quality of the product, but also further improves the internal structure. This comprehensive cold rolling process not only improves the dimensional accuracy and surface quality of the product, but also optimizes the mechanical properties of the material.

[0026] Preferably, the composite intelligent mold system in the S7 drawing step includes: an outer mold, which uses a cemented carbide with a nano-ceramic coating; an inner mold, which uses a shape memory alloy to achieve temperature-adaptive size control. Beneficial effect: The outer mold uses a cemented carbide with a nano-ceramic coating, which greatly improves the wear resistance and service life of the mold, reduces the frequency of mold replacement, and improves production efficiency. The inner mold uses a shape memory alloy to achieve temperature-adaptive size control, and can automatically adjust the size according to the temperature change during the drawing process, ensuring high precision and consistency of product size.

[0027] Preferably, a multi-stage variable speed drawing system is used in the S7 drawing step. Beneficial effect: The use of a multi-stage variable speed drawing system significantly optimizes the drawing process and improves product quality. The system can flexibly adjust the speed during the drawing process, effectively optimize the stress distribution, and reduce the generation of surface defects. By accurately controlling the drawing speed at each stage, not only the dimensional accuracy of the product is improved, but also the internal organizational structure of the material is improved.

[0028] Preferably, the production process also includes an electromagnetic stirring step, and an electromagnetic stirring device is provided in the crystallizer and the secondary cooling zone to improve the solidification structure. Beneficial effect: The electromagnetic stirring device is provided in the crystallizer and the secondary cooling zone, which significantly improves the solidification structure of the double-hole copper bar. Electromagnetic stirring not only promotes the flow of the melt, but also effectively inhibits the growth of columnar crystals and promotes the formation of equiaxed crystals, thereby optimizing the crystal structure of the casting. This stirring effect also promotes the uniform distribution of alloy elements during the solidification process and reduces the occurrence of segregation.

[0029] Preferably, the S9 quality inspection step includes: using a laser measurement system to detect dimensional tolerances; conducting process performance tests such as stretching, bending, and torsion; measuring technical indicators such as conductivity and hardness; using an endoscope to check the quality of the inner hole; and using ultrasonic flaw detection to detect internal defects. Beneficial effects: This multi-faceted, high-precision quality inspection not only ensures the quality of each product, but also provides feedback for the production process, helps to continuously improve the production process, and ultimately ensures the overall quality and reliability of the large rotor winding double-hole copper busbar.

[0030] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0031] The horizontal continuous casting production process of double-hole copper bars for large rotor windings provided by the present invention has achieved significant technological breakthroughs through systematic innovation, especially in the horizontal continuous casting link. The innovative crystallizer structure adopts a high thermal conductivity copper alloy body and a high-purity isostatic graphite double-hole mold, combined with precise segmented cooling control, which greatly improves the molding accuracy and efficiency. The most prominent is the innovation of the middle cooling structure. By setting the injection outlet in the rear half of the mold rod and adopting high-frequency pulse injection technology, the problem of uneven cooling during the solidification process of the double-hole copper bar in the traditional process is effectively solved. It is particularly noteworthy that the tiny vibrations generated by the pulse injection significantly promote the uniform distribution of solutes in the copper liquid and greatly reduce the segregation phenomenon. This innovation not only optimizes the internal structure of the product, but also significantly improves the uniformity and stability of the performance, laying a solid foundation for the production of high-quality double-hole copper bars, and is of great significance to improving the performance and reliability of large motors and power generation equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the figures required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the figures described below are only some embodiments of the present application. For ordinary technicians in this field, other figures can be obtained based on these figures without paying creative work.

[0033] Figure 1 It is a flowchart of the production process of the present invention;

[0034] Figure 2 It is a structural schematic diagram of the horizontal continuous casting equipment of the present invention;

[0035] Figure 3 It is a structural schematic diagram of the crystallizer of the present invention;

[0036] Figure 4 is a cross-sectional schematic diagram of the crystallizer of the present invention to show the internal structure;

[0037] Figure 5It is a structural schematic diagram of the double-hole mold of the present invention;

[0038] Figure 6 This is a schematic diagram of the cross-sectional structure of the product's double-hole copper busbar.

[0039] Figure numerals: fastener 001, flange funnel 002, insulation furnace 01, continuous casting table 1, crystallizer 2, main body 20, double-hole mold 21, sleeve channel 22, crystallization channel 021, installation entity 022, second inlet 25, installation part 23, first inlet 24, connecting sleeve 26, mold rod 211, middle cooling structure 3, injection inlet 31, injection outlet 32, pulse injection assembly 33, ingot guide table 91, ingot guide rod 92. DETAILED DESCRIPTION

[0040] The following will be combined Figure 1-Figure 6 The preferred embodiments of the present invention are described in detail. It should be noted that the following description is only a preferred embodiment of the present invention, rather than a limitation of the present invention. Those skilled in the art should understand that various modifications and variations can be made to the present invention without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0041] Embodiment 1:

[0042] The present invention provides a horizontal continuous casting production process for double-hole copper bars of large rotor windings, which adopts horizontal continuous casting technology to achieve efficient production of high-quality double-hole copper bars. The specific implementation of the present invention will be described in detail below.

[0043] Step 1. Raw material preparation

[0044] High-quality electrolytic copper or oxygen-free copper with a purity of ≥99.99% is selected as the basic material, and the comprehensive performance of the copper busbar is improved by adding alloy elements in appropriate proportions. For example, adding 0.03-0.1% silver can increase the softening temperature and high-temperature strength; adding 0.02-0.05% magnesium can improve the oxidation resistance and refine the grains; adding 0.03-0.08% zirconium can increase the recrystallization temperature and maintain the strength in high-temperature working environments; adding 0.02-0.06% chromium can enhance wear resistance and corrosion resistance.

[0045] If the product has higher requirements for high temperature stability, 0.01-0.03% of rare earth elements (such as cerium or lanthanum) can be added to further refine the grains. And the total amount of impurity elements such as phosphorus, sulfur, and iron should be strictly controlled not to exceed 0.01%.

[0046] When there are higher requirements for uniformity of element distribution, the product introduces pre-alloying technology to pre-alloy some alloy elements with copper into intermediate alloys. For elements that are difficult to distribute evenly through traditional smelting methods, consider using powder metallurgy technology to achieve more precise composition control. Finally, establish a complete raw material traceability system to record the source, composition and performance data of each batch of raw materials, providing a basis for quality control and continuous improvement.

[0047] Step 2. Smelting

[0048] First, dual-frequency induction melting technology is introduced, combining medium frequency (1-10 kHz) and high frequency (100-400 kHz) power supplies to achieve a balance between rapid melting and precise temperature control, improve energy efficiency and ensure uniform distribution of alloy elements. Secondly, a precise feeding system assisted by computer simulation is used to dynamically adjust the amount of alloy elements added according to the real-time monitoring of the melt composition to ensure precise control of the composition. In terms of gas protection, a mixed gas of argon and nitrogen is used, and pulse ventilation technology is used to enhance the protection effect and reduce the formation of oxides. The electromagnetic stirring system adopts a multi-frequency and multi-mode design, and uses different stirring modes in the melting, insulation and pouring stages to optimize the melt flow and promote the full dissolution and uniform distribution of alloy elements. In terms of temperature control, a multi-point real-time temperature measurement network is constructed to control the temperature fluctuation at 1150-1200℃.

[0049] Step 3. Keep warm

[0050] The holding furnace 01 is divided into multiple independent temperature control areas to achieve precise temperature gradient distribution within the range of 1130-1160℃, promoting the homogenization and diffusion of alloy elements. Secondly, pulse electromagnetic field stirring technology is used to periodically apply variable frequency electromagnetic fields during the holding process to enhance the microscopic flow inside the melt, accelerate the homogenization process of alloy elements, and shorten the holding time to 30-60 minutes. To prevent oxidation, high-purity argon gas is used to cover and introduce trace addition technology of rare earth elements (such as cerium) to form a protective rare earth oxide film. And in the later stage of holding, the melt is subjected to short-term ultrasonic treatment to refine the grain structure and improve the strength and uniformity of the material.

[0051] Step 4. Horizontal continuous casting

[0052] 4.1 Continuous casting equipment structure

[0053] The horizontal continuous casting production line of the present invention mainly comprises: a horizontally arranged continuous casting table 1 and a crystallizer 2 (connected to the holding furnace 01 through a precisely temperature-controlled conveying channel). The specific structure of the crystallizer 2 is as follows:

[0054] a. Body 20: It is mainly a solid structure, made of a copper alloy with high thermal conductivity (such as CuCrZr alloy), and has a through-going sleeve channel 22. The inner wall of the sleeve channel 22 is precisely machined and specially surface treated (such as nano-scale titanium nitride coating) to improve wear resistance and thermal conductivity. The outside of the body 20 is provided with a spiral cooling water channel, which cooperates with a variable frequency pump to achieve precise segmented cooling control.

[0055] b. Mounting part 23: located at one end of the sleeve channel 22, convex, made of high-strength stainless steel (such as 17-4PH) to ensure structural stability in high temperature environments. The mounting part 23 is provided with: a fastening part 231; the first inlet 24: with a conical design, with a wear-resistant ceramic lining embedded inside to ensure smooth introduction of copper liquid and reduce turbulence and gas entrapment.

[0056] Among them, the connection between the main body 20 and the mounting portion 23 adopts an innovative composite material transition interface, which effectively solves the problem of differences in thermal expansion coefficients between different materials. This interface consists of a titanium alloy matrix and a gradient functional material (FGM) layer to ensure sealing and structural integrity at high temperatures. The FGM layer gradually transitions from a copper-based alloy to stainless steel. Starting from the side of the main body 20, the copper content gradually decreases, while the content of elements such as chromium and nickel gradually increases, and finally transitions to the stainless steel component of the mounting portion 23.

[0057] c. Double-hole mold 21: The double-hole mold 21 is made of high-purity, high-density isostatic graphite material, which is precisely sleeved on the sleeve channel 22 and is used to form a double-hole copper busbar. Its specific design is as follows:

[0058] Materials and structure: Made of high-purity (purity ≥ 99.99%) and high-density (density ≥ 1.85g / cm³) isostatic graphite. The shape is rectangular, divided into two main parts: a large crystal channel 021 and a small installation entity 022.

[0059] Crystallization channel 021: adopts an integral design, is hollow inside and has an open end, and is used in the process of converting copper liquid from liquid to solid. It is precisely inserted into the sleeve channel 22, and a second inlet 25 matching the first inlet 24 is provided at the position corresponding to the first inlet 24.

[0060] The mounting entity 022 is located at one end of the crystallization channel 021 , has a small volume, and is provided with a threaded structure. It fits with the mounting portion 23 and is fixed on the crystallizer 2 through the fastening portion and the fastener 001 .

[0061] Mold rod 211: Two mold rods 211 are arranged in the double-hole mold 21, corresponding to the double holes of the double-hole copper bar. It is in the shape of a quadrangular pyramid, with a draft angle that gradually decreases from one end to the other end, and the angle range is 1.0-1.5° / m. The front end of the mold rod 211 (the end with a larger cross section, i.e., the end where the copper liquid flows in) is fixedly sealed and connected to the mounting entity 022, or the two are an integral structure. The direction of the mold rod 211 from the front end to the rear end is consistent with the output direction of the double-hole copper bar, and the direction from the larger end to the smaller end is also consistent with this.

[0062] Connection method: a connection sleeve 26 is provided between the first inlet 24 and the second inlet 25. A flange funnel 002 is provided on the connection sleeve 26 and communicated with the copper liquid conveying channel of the holding furnace 01.

[0063] 4.2 Ingot starter system: The ingot starter system consists of an ingot starter table 91 that can be translated along the output direction of the double-hole copper bar and an ingot starter rod 92 arranged thereon. The advance and retreat of the ingot starter rod is controlled by a precision screw mechanism driven by a servo motor. The system follows the cyclic sequence of "pull, push, stop". This periodic motion mode is crucial to controlling the solidification speed and quality of the copper bar. In order to accurately control the ingot starter process, the system integrates a force sensor to monitor the ingot starter force in real time to prevent excessive stress. Based on the force sensor data, the intelligent control system can dynamically adjust the ingot starter speed and force, optimize the rhythm of "pull, push, stop", and adapt to the solidification state at different stages.

[0064] 4.3 Cooling system

[0065] The body 20 is provided with a cooling medium channel 27 surrounding the crystallization channel 021. Multi-zone cooling: 3-4 independently controlled cooling zones along the length of the crystallizer. Water flow design: spiral flow channel to ensure uniform cooling. Cooling water temperature control: each zone is independently controlled, with an inlet temperature of 20-25°C.

[0066] 4.4 Middle cooling structure

[0067] In order to solve the problem of uneven cooling of the middle part of the double-hole copper bar crystallizer 2 due to thin outer walls and thick middle, the present invention designs an innovative middle cooling structure 3. This structure not only ensures uniform cooling of the middle part of the double-hole copper bar, but also accurately controls the cooling process.

[0068] The middle cooling structure 3 mainly includes three key components: a) injection inlet 31: opened on the outer wall of the crystallizer 2. b) injection outlet 32: opened on the side wall of the mold rod 211 close to another mold rod 211, distributed in a plurality of patterns. c) pulse injection component 33: capable of injecting cooling medium into the injection inlet 31 in a high-frequency pulsed manner.

[0069] Cooling channel design: A connected cooling channel is formed between the injection inlet 31 and the injection outlet 32 ​​.

[0070] There are two schemes for designing the cooling channel: a) one cooling channel in the installation entity 022 and then independently separated in the two mold rods 211. b) one cooling channel from the installation entity 022 to the two mold rods 211. This design ensures that the cooling medium can effectively flow from the injection inlet 31 to the injection outlet 32.

[0071] Uniform cooling design: There are two injection inlets 31, which respectively correspond to the positions of the two mold rods 211. This design ensures uniform cooling of the middle part of the double-hole copper bar.

[0072] Precise cooling control: The jet outlet 32 ​​is specially set in the rear half of the mold rod 211. This design takes into account the temperature distribution characteristics of the copper liquid during the crystallization process: a) The front half: The copper liquid temperature is relatively high, and it mainly relies on peripheral cooling. b) The rear half: The copper liquid has solidified, and the cooling of the middle part becomes particularly important.

[0073] Through this design, the cooling rate of the middle part of the double-hole copper busbar can be controlled more accurately.

[0074] Pulse jet technology: The pulse jet assembly 33 uses high-frequency pulse technology, which has the following advantages:

[0075] a) Allow the cooling medium to pass through the front section quickly to avoid being affected by the high temperature of the front section. b) Take into account the temperature gradient of the double-hole copper busbar during the crystallization process. c) Ensure that the cooling medium can effectively reach the second half of the area that needs to be cooled.

[0076] Intelligent control system: The pause phase in pulse technology plays an important role: a) allowing the system to dynamically adjust the injection frequency, pressure and flow rate of the cooling medium based on real-time monitored temperature data. b) providing the necessary time window for heat transfer and temperature equalization.

[0077] Through this innovative middle cooling structure design, the present invention effectively solves the problem of insufficient cooling and uneven cooling of the middle part of the double-hole copper bar in the traditional continuous casting process. It realizes precise control of the cooling process, which not only ensures that the cooling medium can effectively reach the area that needs cooling, but also avoids the negative effects that may be caused by overcooling. The accuracy and flexibility of this cooling method provide key technical support for the production of high-quality, stable performance double-hole copper bars for large rotor windings. High-frequency pulse technology is adopted to ensure that the cooling medium passes through the front section quickly and effectively reaches the rear half area that needs cooling. The tiny vibration generated by the pulse jet promotes the uniform distribution of solutes in the copper liquid and reduces segregation. The jet outlet 32 ​​adopts a special nozzle design to atomize the cooling medium into fine water droplets to increase the heat exchange efficiency. The pulse frequency of the pulse nozzle is synchronized with the frequency of the "pull, push, stop" cycle sequence of the double-hole copper bar, and jet cooling is performed in the "stop" stage.

[0078] 4.5 Electromagnetic stirring

[0079] An electromagnetic stirring device is installed in the crystallizer and the secondary cooling zone to improve the solidification structure.

[0080] Step 5. Double-hole copper busbar casting

[0081] Use high-speed cutting machine to cut off. Perform light milling on the surface to remove surface defects.

[0082] Step 6. Cold rolling (key process 2)

[0083] First, an asynchronous multi-roll rolling system with a 4+4 roll configuration is used, and each roll is independently regulated to reduce surface defects and improve the uniformity of internal structure. On this basis, the working roll is equipped with a high-frequency micro-vibration device, which applies 20-50kHz micro-vibration during the rolling process, which not only reduces the rolling force, but also improves the material fluidity and grain structure. The innovative hot and cold composite rolling process uses high-frequency induction heating technology to quickly heat the surface layer of 0.1-0.3mm after cold rolling in the first stage, and then rolls, effectively reducing surface cracks and enhancing material plasticity. To ensure product quality, an ultrasonic probe is installed in the last pass to achieve real-time detection of internal defects and dynamic adjustment of rolling parameters, and a closed-loop quality control system is constructed. Pulse current auxiliary technology is introduced in the intermediate heat treatment stage, and high-density pulse current is superimposed on the traditional solution treatment, which significantly shortens the processing time and optimizes the distribution of alloy elements. Finally, the temperature distribution of the rolled piece is monitored in real time through an infrared array, precise temperature field control is achieved, and the cooling system is dynamically adjusted, effectively reducing deformation caused by thermal stress and improving the dimensional stability of the product.

[0084] Step 7. Pulling (Key Process 3)

[0085] A composite intelligent mold system is used, with the outer mold made of cemented carbide with nano-ceramic coating and the inner mold made of shape memory alloy to achieve temperature-adaptive dimensional control; electromagnetic-assisted drawing technology is introduced to improve material fluidity and reduce surface defects through an adjustable pulsed electromagnetic field; a multi-stage variable-speed drawing system uses independently controlled servo motors to achieve speed gradient control and optimize stress distribution; a high-precision laser is installed at the drawing exit for local rapid annealing to reduce residual stress; an intelligent fluid containing nanoparticles is used as a lubricant, and the viscosity is regulated by an external magnetic field to optimize the lubrication effect; an integrated eddy current flaw detection, laser diameter measurement and mechanical property online detection system is used; a flexible clamping device with a pneumatic microneedle array is introduced to dynamically adjust the clamping force and reduce surface damage; finally, an intelligent cooling system combining multi-point precision injection and infrared monitoring is used to adjust the cooling intensity and position according to the real-time temperature distribution.

[0086] Step 8. Post-processing

[0087] Use a multi-roller straightening machine for leveling and straightening. Use a high-precision CNC sawing machine for sawing to ensure the flatness of the end surface.

[0088] Step 9. Quality Inspection

[0089] Dimensional tolerance testing: using laser measurement systems. Process performance testing: conducting tests such as stretching, bending, and torsion. Technical index testing: measuring parameters such as conductivity and hardness. Endoscopic inspection: checking the quality of the inner hole. Ultrasonic flaw detection: detecting internal defects.

[0090] Step 10. Finished product processing

[0091] Surface cleaning: alkaline cleaning or sandblasting of the inner surface.

[0092] Warehousing: Stored in a dedicated warehouse with controlled temperature and humidity.

[0093] Through the application of the above process flow and innovative technology, the present invention realizes high-quality and high-efficiency production of double-hole copper bars for large rotor windings. This process not only solves the problems of uneven cooling and internal defects existing in traditional production methods, but also significantly improves the performance and consistency of the product through a number of innovative designs.

[0094] Although the present invention has been disclosed in conjunction with certain embodiments shown and described in detail, various modifications and improvements thereto will be readily apparent to those skilled in the art having benefit of the disclosure herein. Therefore, the spirit and scope of the present invention will not be limited by the foregoing examples, but will be understood in the broadest sense permitted by law.

[0095] All documents cited herein are hereby incorporated by reference in their entirety for all purposes.

Claims

1. A horizontal continuous casting production process for double-hole copper bars of large rotor windings, characterized in that: The following steps are involved: S1 Raw material preparation: Use high-quality electrolytic copper or oxygen-free copper with a purity of ≥99.99% as the base material and add alloy elements; S2 melting: using dual-frequency induction melting technology, combined with medium-frequency and high-frequency power supplies, using a mixed gas of argon and nitrogen for protection, optimizing melt flow through a multi-frequency and multi-mode electromagnetic stirring system, and controlling the temperature within the range of 1150-1200°C; S3 insulation: multi-zone temperature control in the insulation furnace, the temperature range is 1130-1160℃; S4 horizontal continuous casting: Use horizontal continuous casting equipment including crystallizer, middle cooling structure and ingot drawing system: The ingot drawing system is equipped with a force sensor to monitor the ingot drawing force in real time and adopts a "pull, push, stop" cycle sequence; S5 double-hole copper busbar casting; S6 cold rolling: adopts asynchronous multi-roll rolling system; S7 drawing: using composite intelligent die system; S8 post-processing; S9 quality inspection; The middle cooling structure in the horizontal continuous casting step in the S4 step comprises: a) Injection inlet: It is opened on the outer wall of the crystallizer. Specifically, there are two injection inlets, which correspond to the positions of the two mold rods respectively, to ensure uniform cooling of the middle part of the double-hole copper bar; b) Injection outlet: It is set in the rear half of the mold rod and located on the side wall of the mold rod close to the other mold rod, and is distributed in several patterns. This design takes into account the temperature distribution characteristics of the copper liquid during the crystallization process. The temperature of the copper liquid in the first half is relatively high and mainly relies on peripheral cooling. The copper liquid in the second half has solidified, so cooling the middle part becomes particularly important. c) Pulse jet assembly: The cooling medium is sprayed into the jet inlet in a high-frequency pulse manner, using high-frequency pulse technology, and the specific frequency is synchronized with the frequency of the "pull, push, stop" cycle sequence of the double-hole copper busbar; this assembly includes an intelligent control system, which dynamically adjusts the cooling medium spray frequency, pressure and flow rate according to the real-time monitored temperature data; Wherein, a cooling channel connected to the injection inlet and the injection outlet is formed; The composite material intelligent mold system in the S7 drawing step includes: For the outer mold, use cemented carbide with nano-ceramic coating; The inner mold adopts shape memory alloy to achieve temperature adaptive size control.

2. The horizontal continuous casting production process of large rotor winding double-hole copper bars according to claim 1 is characterized in that: The alloying elements in step S1 include: 0.03-0.1% silver; 0.02-0.05% magnesium; 0.03-0.08% zirconium; 0.02-0.06% chromium.

3. The horizontal continuous casting production process of large rotor winding double-hole copper bars according to claim 1 is characterized in that: The crystallizer for horizontal continuous casting in step S4 comprises: The main body is made of copper alloy with high thermal conductivity, with a through-hole sleeve channel. The outside of the main body is equipped with a spiral cooling water channel, which cooperates with the frequency conversion pump to achieve precise segmented cooling control; The mounting portion is located at one end of the sleeve channel and is convex. The mounting portion is provided with a fastening portion and a first inlet, wherein the first inlet has a conical design; The double-hole mold is made of high-purity, high-density isostatic graphite material and is tightly fitted into the sleeve channel; it includes a crystallization channel and a mounting entity; the crystallization channel adopts an integral design, is hollow inside and has an open end; the mounting entity is located at one end of the crystallization channel and is fixed on the crystallizer; two mold rods are arranged in the double-hole mold, which are in the shape of a quadrangular pyramid and have a draft angle that gradually decreases from one end to the other end.

4. The horizontal continuous casting production process of large rotor winding double-hole copper bar according to claim 1 is characterized in that: The asynchronous multi-roller rolling system used in the S6 cold rolling step has a 4+4 roll configuration, and each roll has an independent speed adjustment; the working rolls are equipped with a high-frequency micro-vibration device, which applies 20-50kHz micro-vibration during the rolling process, and adopts a cold and hot composite rolling process, using high-frequency induction heating technology to quickly heat the surface layer 0.1-0.3mm before rolling.

5. The horizontal continuous casting production process of large rotor winding double-hole copper bars according to claim 4 is characterized in that: The S7 drawing step adopts a multi-stage variable speed drawing system.

6. The horizontal continuous casting production process of large rotor winding double-hole copper bar according to claim 1 is characterized in that: The method also includes an electromagnetic stirring step, in which an electromagnetic stirring device is arranged in the crystallizer and the secondary cooling zone to improve the solidification structure.

7. The horizontal continuous casting production process of large rotor winding double-hole copper bar according to claim 1 is characterized in that: The S9 quality inspection step includes: Dimensional tolerance inspection using laser measurement systems; Conduct tensile, bending, torsion and other process performance tests; Measure technical indicators such as conductivity and hardness; Use an endoscope to check the quality of the inner hole; Ultrasonic testing is used to detect internal defects.

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