A crystallizer for horizontal continuous casting

Abstract

The present application relates to the technical field of horizontal continuous casting of copper cast billets, and specifically discloses a crystallizer for horizontal continuous casting, which comprises a copper sleeve and a cold water jacket sleeving the copper sleeve, a water inlet and a water return are connected to the cold water jacket, and an inner cylinder is fixedly installed between the copper sleeve and the cold water jacket, the inner cylinder sleeving the copper sleeve forms a cylindrical water gap between the inner cylinder and the copper sleeve, the water inlet is communicated with one end of the cylindrical water gap, the water return is communicated with the other end of the cylindrical water gap in the axial direction, and a threaded groove is arranged on the inner surface of the inner cylinder or the outer surface of the copper sleeve; the pitch of the threaded groove is 3-5 mm, and the depth of the threaded groove is 1-2.5 mm; the water inlet is close to the discharge end of the cast billet, and the water return is close to the feeding end of the cast billet. The present application is used to solve the problems of uneven color on the surface of the copper cast billet and uneven grain size after horizontal continuous casting in the prior art.

Description

Technical Field

[0001] This invention relates to the field of horizontal continuous casting technology for copper billets, and specifically to a crystallizer for horizontal continuous casting. Background Technology

[0002] In the precision copper tubing industry, horizontal continuous casting is an advanced technology for producing hollow copper billets. Compared to the previous methods of top drawing and extrusion, this process has advantages such as lower investment, higher production efficiency, higher yield, and lower energy consumption, and is therefore widely used in the production of master blanks for precision copper tubing casting.

[0003] The horizontal continuous casting process for copper billets refers to the production process in which molten copper is continuously injected into a water-cooled crystallizer (primary cooling crystallization). After the molten copper solidifies and forms a hard shell, it is pulled out from the crystallizer outlet, cooled a second time by a water spray cooler, and cut into billets after complete solidification.

[0004] In the entire process of producing hollow copper billets, the molten copper is heated and refined in an industrial frequency cored induction furnace, and then enters the casting furnace (also known as the holding furnace) through a diversion channel. A crystallizer with a graphite mold is installed at the outlet of the holding furnace (such as a graphite crystallization system for a horizontal continuous casting furnace with patent publication number CN200945523Y). The molten copper enters the graphite mold from the inlet of the graphite mold, and then the molten copper undergoes primary and secondary cooling to form a hard shell, which is then pulled out of the billet by a traction machine.

[0005] Specifically, the primary crystallization process includes a copper jacket and a cooling water jacket. The cooling water jacket completely encloses the copper jacket, forming a water flow cavity between them. The cooling water jacket is equipped with an inlet and an outlet, while the copper jacket contains a fixed graphite mold, thus achieving the cooling of the molten copper.

[0006] However, after the copper billet is produced, it often has problems such as uneven color and uneven grain size on the surface. Both uneven color and uneven grain size can easily lead to processing defects in the subsequent processing of the copper billet (hollow copper billets require subsequent processing such as rolling, continuous drawing, coil drawing, and heat treatment before small copper tube products can be obtained. If the quality of the copper billet itself is not good, defects such as cracks, spots, and color differences are likely to occur in the subsequent processing). Summary of the Invention

[0007] The present invention aims to provide a crystallizer for horizontal continuous casting to solve the problems of uneven surface color and uneven grain size of copper billets after horizontal continuous casting in the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A crystallizer for horizontal continuous casting includes a copper sleeve and a cooling water jacket that covers the copper sleeve. The cooling water jacket is connected to an inlet and an outlet. It also includes an inner cylinder that is fixedly installed between the copper sleeve and the cooling water jacket. The inner cylinder covers the copper sleeve, and a cylindrical water gap is formed between the inner cylinder and the copper sleeve. The inlet is connected to one end of the cylindrical water gap, and the outlet is connected to the other end of the cylindrical water gap along its axial direction. The inner surface of the inner cylinder or the outer surface of the copper sleeve is provided with a threaded groove.

[0010] The principle and advantages of this scheme are as follows: When this scheme is adopted, the threaded grooves are set on the inner or outer surface of the water gap (setting threaded grooves on the outer surface of the copper sleeve is equivalent to setting threaded grooves on the inner surface of the water gap; similarly, the threaded grooves on the inner surface of the inner cylinder are equivalent to the threaded grooves on the outer surface of the water gap). This allows the cooling water entering from the cold water jacket to be guided by the threaded grooves during the flow process, forming a spiral flow. This overcomes or reduces the influence of the cooling water's own weight, thereby improving the uniformity of the cooling water's flow rate and direction. This allows the copper billet to be heated evenly during the cooling process, achieving uniform cooling, uniform grain size, and uniform surface color of the billet.

[0011] Furthermore, due to the uniform cooling of the copper billet during the horizontal continuous casting process, the graphite mold used in billet production is also heated more evenly. The average service life of the original graphite mold was about 120 hours. After the crystallizer was changed in this solution, the average service life of the graphite mold was increased to 160 hours. The service life of the graphite mold was increased by about 50% compared with the past, which greatly reduced the usage of graphite molds as consumables and reduced the production cost of enterprises.

[0012] Preferably, as an improvement, the pitch of the threaded groove is 3-5mm and the thread depth is 1-2.5mm.

[0013] Beneficial Effects: Through multiple research and development improvements, this solution has revealed that the pitch and depth of the threaded groove have a significant impact on the quality of copper billets produced by horizontal continuous casting. Due to the small size of the cylindrical water gap and the large water flow rate at the inlet, excessively deep threaded grooves and large pitches cause significant disturbance to the water flow, easily leading to uneven grain size and inconsistent surface quality and color of the copper billet. Conversely, small pitches and shallow threaded grooves result in weak guidance of the water flow, still failing to meet the production quality requirements of the copper billet. The threaded groove design of this invention ensures uniform cooling of the copper billet, resulting in billet with uniform surface color and grain size. Furthermore, it allows for a grain size of 1.4-1.8 mm, achieving a significant refinement compared to the existing average grain size of 2.8 mm.

[0014] With significantly refined grains, the holding time for refining molten copper can be greatly shortened from 10 minutes to 5 minutes, while still achieving the same machining effect on the billet. Although the reduced holding time may result in an increase in trace impurities in the molten copper, the increased surface area at grain boundaries due to the refined grains ensures that even these impurities are evenly dispersed within the billet, preventing impurity aggregation and ensuring that subsequent processing is identical to that of existing billets (i.e., no defects or defect numbers within the required range). The reduced holding time also significantly lowers energy consumption and contributes to energy conservation and environmental protection.

[0015] Preferably, as an improvement, the water inlet is located near the discharge end of the billet, and the water return is located near the feed end of the billet.

[0016] Beneficial effects: This scheme allows the cooling water to exchange heat at the discharge end of the copper billet first, so that the cooling water moves from the discharge end of the copper billet to the forming end of the copper billet. This not only ensures the cooling of the copper billet in the axial direction, but also maximizes the utilization of the cooling water.

[0017] Preferably, as an improvement, an annular water inlet cavity is provided between the cold water jacket and the inner cylinder to enclose the inner cylinder. The water inlet cavity is connected to the end of the cylindrical water slit, and the water inlet is located away from the end of the cylindrical water slit connected to the water inlet cavity.

[0018] Beneficial effects: Compared with the case where the water inlet is directly connected to the cylindrical water gap, this solution uses an annular water inlet cavity. On the one hand, the annular water inlet cavity buffers the water flow entering from the water inlet, preventing uneven water flow into the cylindrical water gap. On the other hand, the annular water inlet cavity ensures that the cooling water, after entering the water inlet cavity, will first completely fill the water inlet cavity before flowing into the cylindrical water gap at a uniform flow rate around the perimeter. This ensures the uniformity of the water inlet around the cylindrical water gap and provides a guarantee for the uniform cooling of the copper casting billet.

[0019] Preferably, as an improvement, an annular return water cavity is provided between the cold water jacket and the inner cylinder, and an annular return water groove is provided between the return water cavity and the end of the cylindrical water slit. The annular return water groove is located between the inner cylinder and the cold water jacket, and the return water cavity is located between the inlet cavity and the annular return water groove.

[0020] Beneficial effects: This solution, through the setting of an annular return water cavity and an annular return water groove, ensures that when the cooling water flows out from the cylindrical water gap, it overflows along the annular return water groove and flows into the annular return water cavity. This ensures that the cylindrical water gap is always completely filled with cooling water during the cooling process, and that the cooling water has a uniform and stable flow rate. This further contributes to the uniform cooling of the copper billet and the uniformity of the generated grain size.

[0021] Preferably, as an improvement, the inner cylinder is detachably connected to the cold water jacket to facilitate the replacement and maintenance of the inner cylinder and improve the service life of the equipment.

[0022] Preferably, as an improvement, the threaded groove is provided on the inner surface of the inner cylinder.

[0023] Preferably, as an improvement, the number of water inlets and water outlets is greater than or equal to 2, all water inlets are evenly distributed around the circumference of the copper sleeve, and all water outlets are evenly distributed around the circumference of the copper sleeve.

[0024] Beneficial effects: The multiple inlets and outlets in this design can further improve the uniformity of the cooling water flow rate and direction, thereby improving the cooling uniformity and quality of the billet. Attached Figure Description

[0025] Figure 1 This is a longitudinal section diagram of Embodiment 1 of the present invention.

[0026] Figure 2 for Figure 1 The image in the middle is a magnified view of a section of the cylindrical water slit.

[0027] Figure 3 This is a schematic diagram illustrating the relationship between the crystallizer, the water spray cooler, and the graphite mold, as shown in Embodiment 1 of the present invention.

[0028] Figure 4 This is an image showing the effect of the copper billet produced in Experiment 1 of this embodiment (coarse grains, with transgranular grains on the right).

[0029] Figure 5 This is a rendering of the copper billet produced in Experiment 10 of Example 1 (coarse grains).

[0030] Figure 6 The image shows the effect of the copper billet produced in Experiments 3-7 of Example 1 (with fine and uniform grains). Detailed Implementation

[0031] The following detailed description illustrates the specific implementation method:

[0032] The reference numerals in the accompanying drawings include: copper sleeve 1, inner cylinder 2, cold water jacket 3, water inlet 31, water outlet 32, water inlet cavity 33, water outlet cavity 34, water inlet groove 35, water outlet groove 36, cylindrical water slit 12, threaded groove 21, graphite mold 10, and water spray cooler 20.

[0033] Example 1

[0034] Combination Figure 1 and Figure 2A crystallizer for horizontal continuous casting includes, from the inside out, a fixedly installed copper sleeve 1, an inner cylinder 2, and a cooling water jacket 3. The inner cylinder 2 covers the copper sleeve 1, and the cooling water jacket 3 covers the inner cylinder 2. The cooling water jacket 3 is connected to two water inlets 31 and two water outlets 32. The two water inlets 31 are symmetrically arranged about the inner cylinder 2, and the two water outlets 32 are symmetrically arranged about the inner cylinder 2. The inner cylinder 2 is fixed inside the cooling water jacket by a detachable connection. An annular water inlet cavity 33 and an annular water return cavity 34 are formed between the inner cylinder 2 and the cooling water jacket. The water inlet cavity 33 is connected to the water inlet 31, and the water return cavity 34 is connected to the water return outlet 32.

[0035] A cylindrical water slit 12 is formed between the inner cylinder 2 and the copper sleeve 1. The water inlet chamber 33 is connected to the end of the cylindrical water slit 12, and the water outlet chamber is connected to the other end of the cylindrical water slit 12 along the axial direction. In this embodiment, the water inlet chamber 33 is close to the discharge end of the crystallizer, and the water return chamber 34 is close to the feed end of the crystallizer.

[0036] In this embodiment, to ensure the uniformity of cooling water entering the cylindrical water gap 12, the water inlet 31 is positioned away from the end of the water inlet cavity 33 that connects to the cylindrical water gap 12. The water inlet cavity 33 is connected to the annular water inlet groove 35 formed between the end face of the inner cylinder 2 and the cold water jacket 3.

[0037] In this embodiment, to ensure that the cylindrical water slit 12 is filled with cooling water, an annular return water groove 36 is formed between the return water cavity 34 and the end of the cylindrical water slit 12. The annular return water groove 36 is located between the inner cylinder 2 and the cooling water jacket 3. The cross-section of the annular return water groove 36 is U-shaped. The return water cavity 34 is located between the inlet cavity 33 and the annular return water groove 36, so that when the cooling water flows out of the cylindrical water slit 12, it moves in the opposite direction in a flooding manner. During the movement process, it flows into the annular return water cavity 34 along the annular return water groove 36. The U-shaped structure of the annular return water groove 36 makes the return water path longer, thereby ensuring that the cylindrical water slit 12 is always completely filled with cooling water during the cooling process, and that the cooling water has a uniform and stable flow rate, which helps to achieve uniform cooling of the copper casting billet and uniformity of the generated grain size.

[0038] The inner surface of the inner cylinder 2 is machined with a threaded groove 21. The thread pitch of the threaded groove 21 is 3-5mm, the thread depth is 1-2.5mm, and the cross-section of the threaded groove 21 is triangular.

[0039] Combination Figure 3 In this embodiment, when the crystallizer is in use, a graphite mold 10 is assembled inside the copper sleeve, and a water spray cooler 20 with surrounding water spray is fixedly installed at the discharge end of the crystallizer. When cooling the copper billet, the cooling water enters the water inlet chamber of the crystallizer from the water inlet and then flows evenly into the cylindrical water gap from the water inlet groove. Under the guidance of the threaded groove, the cooling water entering the cylindrical water gap flows in a spiral shape and finally overflows from the annular return water groove into the return water chamber and is finally discharged from the return water outlet.

[0040] To verify the effectiveness of this embodiment under different threaded groove sizes, ten test groups were set up to produce hollow copper billets. The different test parameters of the test groups are shown in Table 1 below, and the test results are shown in Table 2 below.

[0041] Table 1. Experimental parameters of ten groups of experiments

[0042]

[0043] The other parameters for the ten test groups mentioned above are as follows: the inner diameter of the cylindrical water slit is 138 mm, the water pressure is 0.5 MPa ± 0.1 MPa; the inlet water temperature for secondary water cooling is 28℃ ± 2℃, and the water flow rate is 240 L / min; the length of the crystallizer used is 175-210 mm, and the specifications of the produced hollow copper billet are an outer diameter of 90 ± 2 mm and a wall thickness of 25 mm.

[0044] Table 20 shows the results of the experiments.

[0045]

[0046]

[0047] Note: The above-mentioned billet surface temperature is the billet surface temperature after being cooled by a water spray cooler.

[0048] From the above ten test groups, it can be seen that Test 1 has a large pitch and thread depth, resulting in uneven surface color and grain size of the cast billet. In particular, there are individual instances of transgranularity, and the casting effect is as follows: Figure 4 As shown in the figure; after setting the pitch and thread depth to a very small value in Experiment 2, the surface temperature of the billet decreased, resulting in a more uniform surface quality. However, the phenomenon of uneven grain size was observed, with one side of the grains being normal and the other side being larger. Although the phenomenon of grain penetration was no longer observed compared to Experiment 1, there were at least 2 to 3 large grains covering the cross section. Therefore, Experiment 2 is still not feasible.

[0049] While the pitch of Experiment 10 was large, the thread depth was too small, resulting in weak water flow guidance and producing billets with defects such as… Figure 5 The test showed that the billet surface had problems with uneven color and coarse grain size; while in test 8, although the billet surface color was uniform, there was still a problem with uneven grain size.

[0050] Only experiments 3 to 7, through the design of the thread groove depth and pitch, enabled the return water temperature to be increased to 60-62℃ under the same inlet water temperature of 28℃ and inlet water flow rate of 45L / min. This ensured the uniformity of the surface color and grain size of the cast billet, achieving the desired uniformity. Figure 6The results shown indicate that the copper billet grains in Tests 3-7 are finer (the cylindrical water gap of the billet before the improvement had no thread grooves and the average grain size was about 2.8 mm, while the average grain size in Tests 3-7 was 1.4-1.8 mm).

[0051] When the grain size of the copper billet is fine, the surface area of ​​the grain boundaries increases, allowing the trace impurities that were originally present in the molten copper to be distributed more evenly and to accumulate less. On the one hand, this greatly improves the material properties of the copper billet, thereby improving its machinability in subsequent processes and facilitating rolling and coiling. On the other hand, the improved material properties of the copper billet also result in better heat treatment performance after it is made into copper tubes, thereby improving the overall quality of the product and enhancing the competitiveness of the enterprise.

[0052] On the other hand, when using a crystallizer without a threaded groove structure to produce copper billets, the holding time for the copper liquid in the previous process needs to be set longer (holding time 10 minutes). This results in better removal of trace impurities in the copper liquid (trace impurities accumulate at the grain boundary edges during copper liquid cooling and crystallization). Because there are fewer trace impurities, the produced billets will not have defects in subsequent processing (or the probability of defects will be within the production requirements, generally achieving an average grain size of 2.8 mm, and an average of 1.2 defects per 100 kg when the subsequent copper billets are processed into 7 mm internally threaded copper tubes). Furthermore, if the methods described in experiments 3 to 7 of this embodiment are used, it is possible to utilize… After the copper molten metal is transformed into a copper billet using a crystallizer, the grain size becomes finer. The finer grain size greatly increases the area of ​​the grain boundaries. This means that even if the holding time for refining the copper molten metal is shortened (holding time is 5 minutes), and the content of trace impurities increases relatively, the finer grain size (1.4-1.8 mm) makes the trace impurities more uniform, thus reducing the aggregation effect. As a result, the billet will not have defects in subsequent processing (or the probability of defects will be within the production requirements; the average number of defects per 100 kg when the copper billet is processed into a 7 mm internally threaded copper pipe is 1.18). The shortened holding time also greatly reduces energy consumption and contributes to energy conservation and environmental protection.

[0053] In addition, due to the uniform cooling of the copper billet during the horizontal continuous casting process, the graphite mold used in billet production is also heated more evenly. The average service life of the original graphite mold was about 120 hours. After the crystallizer was changed in this solution, the average service life of the graphite mold was increased to 160 hours. The service life of the graphite mold was increased by about 50% compared with the past, which greatly reduced the usage of graphite molds as consumables and reduced the production cost of enterprises.

[0054] Example 2

[0055] This second embodiment provides a method for using a crystallizer for horizontal continuous casting. It requires the use of the crystallizer for horizontal continuous casting in the first embodiment. The steps are as follows: When cooling the copper billet, cooling water enters the cylindrical water gap from the inlet. Guided by the threaded groove, the cooling water entering the cylindrical water gap flows in a spiral shape and is finally discharged from the return port.

[0056] During the cooling process, the crystallizer used for horizontal continuous casting is used as the primary water cooler. The inlet flow rate of the primary water cooler is controlled at 42-48 L / min, the primary inlet temperature is set at 26-30℃, the cylindrical water gap pressure of the primary water cooler is 0.4-0.6 MPa, and the primary return water temperature is controlled at 60-62℃.

[0057] During the cooling process, a water spray cooler is used as a secondary water cooler. The inlet water temperature of the secondary water cooler is 26-30℃, and the water flow rate is 220-260L / min. The cooling water on the water spray cooler enters from the side closest to the crystallizer, and then the sprayed water is discharged from the end furthest from the crystallizer, thereby cooling the copper casting billet.

[0058] This embodiment ensures that the produced hollow copper billet with an outer diameter of 90±2mm and a wall thickness of 25mm can achieve uniform surface color and fine and uniform grain size.

[0059] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A crystallizer for horizontal continuous casting, used to produce hollow copper billets, comprising a copper sleeve and a cooling water jacket that covers the copper sleeve, wherein an inlet and an outlet are connected to the cooling water jacket, characterized in that: It also includes an inner cylinder that is fixedly installed between the copper sleeve and the cold water sleeve. The inner cylinder covers the copper sleeve, and a cylindrical water gap is formed between the inner cylinder and the copper sleeve. The water inlet is connected to one end of the cylindrical water gap, and the water outlet is connected to the other end of the cylindrical water gap along the axial direction. The inner surface of the inner cylinder is provided with a threaded groove. The thread pitch of the threaded groove is 3-5mm, and the thread depth is 1-2.5mm; the cross-section of the threaded groove is triangular. An annular water inlet cavity is provided between the cold water jacket and the inner cylinder to enclose the inner cylinder. The water inlet cavity is connected to the end of the cylindrical water slit, and the water inlet is located away from the end of the water inlet cavity that is connected to the cylindrical water slit. An annular return water chamber is provided between the cooling water jacket and the inner cylinder. An annular return water groove is provided between the return water chamber and the end of the cylindrical water slit. The annular return water groove is located between the inner cylinder and the cooling water jacket, and the return water chamber is located between the inlet chamber and the annular return water groove, so that when the cooling water flows out from the cylindrical water slit, it moves in the opposite direction in a flooding manner. When cooling the copper billet, the cooling water enters the cylindrical water gap from the inlet. Guided by the threaded groove, the cooling water entering the cylindrical water gap flows in a spiral shape and finally exits from the return port. The inlet flow rate is controlled at 42-48 L / min, the inlet temperature is set at 26-30℃, the cylindrical water slit pressure is 0.4-0.6 MPa, and the return water temperature is 60-62℃.

2. A crystallizer for horizontal continuous casting according to claim 1, characterized in that: The water inlet is located near the discharge end of the billet, and the water return outlet is located near the feed end of the billet.

3. A crystallizer for horizontal continuous casting according to claim 1, characterized in that: The inner cylinder is detachably connected to the cold water jacket.

4. A crystallizer for horizontal continuous casting according to any one of claims 1-3, characterized in that: The number of inlets and outlets is greater than or equal to 2. All inlets are evenly distributed around the circumference of the copper bushing, and all outlets are evenly distributed around the circumference of the copper bushing.

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