A high-efficiency horizontal continuous casting process for copper billets

Abstract

This invention relates to the field of horizontal continuous casting technology, specifically disclosing a high-efficiency horizontal continuous casting process for copper billets. The process involves molten copper entering a crystallizer for primary cooling, followed by secondary cooling via a water spray cooler. The hollow copper billets are then horizontally pulled out by a traction machine. The traction machine simultaneously pulls four copper billets at a traction speed of 455-470 mm / min and an output frequency of 90-135 times / min. The crystallizer features a cylindrical water inlet with threaded grooves on its inner or outer surface. Water enters uniformly circumferentially from the end near the traction machine and returns uniformly from the end near the molten copper. This solution aims to improve production efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the horizontal continuous casting technical field, in particular to a high-efficiency copper casting blank horizontal continuous casting process. BACKGROUND

[0002] In the precision copper pipe industry, horizontal continuous casting is an advanced technology for producing red copper hollow casting blank. Compared with the original up-drawing method and extrusion method, this process has the advantages of low investment, high production efficiency, high material yield and low energy consumption, and is therefore widely used in the production process of precision copper pipe casting blank.

[0003] The copper casting blank horizontal continuous casting process refers to a production process in which copper liquid is continuously injected into a water-cooled crystallizer (primary cooling and crystallization), the copper liquid is pulled out from the crystallizer outlet after forming a hard shell, and the copper liquid is completely solidified after secondary cooling by a water spray cooler and then cut into a blank.

[0004] In the entire process of producing red copper hollow casting blank, the copper liquid is heated and refined by a power-frequency cored induction furnace, and then enters a casting furnace (also known as a holding furnace) through a flow guide groove. A water-cooled crystallizer with a graphite mold and a water spray cooler (such as the graphite crystallization system for horizontal continuous casting furnace disclosed in patent publication No. CN200945523Y) are installed at the outlet end of the holding furnace. The copper liquid enters the graphite mold from the liquid inlet of the graphite mold, and then the copper liquid is cooled once and twice to form a hard shell, and the hollow casting blank is pulled out by a traction machine.

[0005] In the current conventional production, horizontal continuous casting can form 3 copper casting blanks at the same time to improve production efficiency. However, with the increasing competition in the industry, it is particularly important to improve production efficiency and reduce enterprise production cost while ensuring product quality.

[0006] In addition, in the production process, the copper casting blanks produced often have problems of uneven surface color and uneven grain size. Whether the color is uneven or the grain size is uneven, processing defects are prone to occur in the subsequent processing of the copper casting blank (the hollow copper casting blank needs subsequent processing such as rolling, joint drawing, disc drawing, heat treatment, etc., and the copper pipe product with small size can be obtained after these processing. If the quality of the copper casting blank is not good, product cracks, spots, color differences and other defects are prone to occur in the subsequent processing. SUMMARY

[0007] The present application aims to provide a high-efficiency copper casting blank horizontal continuous casting process to solve the problem of how to improve production efficiency.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] The high-efficiency copper casting blank horizontal continuous casting process needs copper liquid to enter a crystallizer for primary cooling, then passes through a water spray cooler for secondary cooling, and then is horizontally pulled out by a traction machine; the traction machine simultaneously pulls four copper casting blanks, the pulling speed is 455-470 mm / min, and the output frequency of pulling is 90-135 times / min.

[0010] The principle and advantages of the scheme are that: through the setting of the specific pulling procedure, the cycle frequency of the pulling-stop-primary reverse pushing-stop-secondary reverse pushing-stop is higher, before the equipment is improved, three copper casting blanks are pulled, and the pulling frequency is 75-85 times / min, and after the pulling procedure is optimized through the scheme, the cycle frequency is greatly improved, and can be increased to 90-135 times / min, the relatively higher frequency pulling procedure is used to replace the low frequency procedure in the continuous casting, so that the disturbance degree of the copper liquid is improved, although the pulling speed of a single copper casting blank is smaller than that of the three copper casting blanks simultaneously pulled in the continuous casting (the pulling speed of the three copper casting blanks in the continuous casting can reach 480 mm / min, and the four copper casting blanks can reach 455-470 mm / min), but the total production length of the copper casting blank in unit time is greatly improved, and the improvement rate is 25-31%, and the production efficiency is greatly improved.

[0011] Preferably, as an improvement, the pulling-stop-primary reverse pushing-stop-secondary reverse pushing-stop cycle is adopted, wherein the pulling length in each cycle is 4-7 mm, the pulling time is 100-140 ms, the first stop time is 60-135 ms, the second stop time is 60-125 ms, and the third stop time is 50-105 ms.

[0012] Beneficial effects: the scheme reduces the pulling length and the stop time, so that the disturbance degree of the copper liquid is improved, and the rapid heat transfer and grain refinement are realized.

[0013] Preferably, as an improvement, the length of the primary reverse pushing in each cycle of pulling is 0.6-1.3 mm, the primary reverse pushing time is 80-115 ms, the length of the secondary reverse pushing is 0.2-0.5 mm, and the secondary reverse pushing time is 50-65 ms.

[0014] Preferably, as an improvement, the crystallizer is provided with a cylindrical water joint, the inner surface or the outer surface of the cylindrical water joint is provided with a thread groove, the cylindrical water joint uniformly introduces water from one end close to the traction machine in the circumferential direction, and uniformly returns water from one end close to the copper liquid.

[0015] Preferably, as an improvement, the pitch of the thread groove is 3-5 mm, and the thread depth is 1-2.5 mm.

[0016] Preferably, as an improvement, the water pressure in the cylindrical water gap during cooling crystallization is 0.4-0.6 MPa, the water inlet temperature of the cylindrical water gap is 25-30 DEG C, and the water return temperature of the cylindrical water gap is 55-65 DEG C.

[0017] Preferably, as an improvement, the water return temperature of the cylindrical water gap during cooling crystallization is 60-62 DEG C.

[0018] Beneficial effects: Before the improvement of the crystallizer, the cylindrical water gap is a water gap with smooth inner and outer surfaces, and after the cooling water flows through the water gap, the water flow around the water gap is not uniform, which causes the problems of uneven surface color and uneven cross-section grain size of the hollow copper cast blank after production.

[0019] The present scheme sets a threaded groove on the inner surface or the outer surface of the cylindrical water gap, so that the cooling water forms a spiral flow when flowing in the cylindrical water gap under the guidance of the threaded groove, thereby improving the flow rate and uniformity of the flow direction of the cooling water, allowing the copper cast blank to be uniformly heated during the cooling process, and achieving the effects of uniform cooling, uniform grain size, and uniform surface color of the cast blank.

[0020] In addition, due to the uniform cooling of the copper cast blank during the horizontal continuous casting process, the graphite mold used for the production of the cast blank is also heated more uniformly, and the average service life of the original graphite mold is about 120 hours. After the crystallizer is improved according to the present scheme, the average service life of the graphite mold is improved to 160 hours, which is about 50% higher than before, greatly reducing the usage amount of the graphite mold as a consumable, and reducing the production cost of the enterprise.

[0021] In addition, the present scheme is combined with the optimization of the pulling program, so that when four copper cast blanks are produced at the same time, not only the production efficiency is improved, but also the grain size of the copper cast blank is finer. The original grain size of three copper cast blanks is about 2.8 mm, while the grain size of the copper cast blank according to the present scheme can be 1.4-1.8 mm. Moreover, due to the refinement of the grain size of the copper cast blank, the requirement for copper liquid refining is reduced. The original copper liquid standing refining and heat preservation time is 10 min, and now only 4-6 min is needed to meet the production requirement. Although the heat preservation time is greatly shortened, more trace impurities are retained in the copper liquid, but in the case that the crystallizer can make the grain more refined, the grain boundary surface area of the grain size is increased, so that the trace impurities can be effectively and uniformly dispersed, reducing the aggregation of impurities, thereby ensuring that the subsequent processing process of the copper cast blank will not have defects / defect quantity within the required range. The shortening of the heat preservation time greatly reduces the energy consumption, and is also helpful for energy saving and environmental protection.

[0022] Preferably, as an improvement, the cooling water needs to first enter the annular water inlet cavity provided in the crystallizer for buffering and filling the annular water inlet cavity before entering the water inlet end of the cylindrical water gap.

[0023] Beneficial effects: because the water inlet is connected only at a position of the annular water inlet cavity, the water flow of the water inlet is large but the speed is low, and if the cooling water directly enters into the cylindrical water gap, the speed of the cooling water entering around is not uniform or the direction is irregular, thereby affecting the uniform flow of the cooling water in the cylindrical water gap.

[0024] The annular water inlet cavity is arranged, on one hand, the annular water inlet cavity buffers the water flow entering from the water inlet, and avoids the non-uniform water flow entering into the cylindrical water gap, and on the other hand, the annular water inlet cavity is arranged, after the cooling water enters into the water inlet cavity, the water inlet cavity is completely filled, and then the cooling water flows into the cylindrical water gap at a uniform speed around, thereby ensuring the uniformity of the inlet of the cylindrical water gap, and providing protection for the uniform cooling of the copper cast blank.

[0025] Preferably, as an improvement, when the cooling water is discharged from the cylindrical water gap during the cooling crystallization, the cooling water first flows reversely into the annular water return groove arranged on the crystallizer, then enters into the annular water return cavity arranged in the crystallizer, and finally is discharged.

[0026] Beneficial effects: the annular water return cavity and the annular water return groove are arranged, when the cooling water flows out from the cylindrical water gap, the cooling water flows into the annular water return cavity along the annular water return groove in a way of overflowing, thereby ensuring that the cylindrical water gap is completely filled with the cooling water with a uniform and stable flow speed during the cooling process, and further helping the uniform cooling of the copper cast blank and the uniformity of the grain size. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a top view schematic diagram of four copper cast blanks during the horizontal continuous casting of the embodiment one of the present application.

[0028] Figure 2 It is a cycle unit schematic diagram of the traction program of the embodiment one of the present application.

[0029] Figure 3 It is a front view sectional view of the embodiment one of the present application when the copper cast blank is drawn (for showing the relationship among the crystallizer, the water spray cooler and the graphite mold).

[0030] Figure 4 It is a longitudinal sectional structure schematic diagram of the crystallizer of the embodiment one of the present application.

[0031] Figure 5 It is Figure 4 It is a local enlarged schematic diagram of the cylindrical water gap.

[0032] Figure 6 It is an effect diagram of the copper cast blank produced by the test 1 of the embodiment two of the present application (the grain is coarse, and there is a transgranular on the right side).

[0033] Figure 7The copper casting billet produced by Example 2 Test 10 (grains are coarse).

[0034] Figure 8 The copper casting billet produced by Example 2 Test 3-7 (grains are fine and uniform). DETAILED DESCRIPTION

[0035] The following is further described in detail by specific embodiments:

[0036] The reference signs in the drawings of the specification include: holding furnace 10, graphite mold 201, crystallizer 20, water spray cooler 30, copper sleeve 1, inner cylinder 2, cold water sleeve 3, water inlet 31, water return 32, water inlet cavity 33, water return cavity 34, water inlet groove 35, water return groove 36, cylindrical water joint 12, and threaded groove 21.

[0037] Example 1

[0038] In combination Figures 1 to 5 A high-efficiency copper casting billet horizontal continuous casting process is needed for the copper liquid with a temperature of 1160-1230°C to enter the crystallizer 20 from the holding furnace 10 for primary cooling (the graphite mold 201 is installed in the crystallizer 20), then pass through the water spray cooler 30 for secondary cooling, and then be horizontally pulled out by the pulling machine; the pulling machine simultaneously pulls four copper casting billets, the pulling speed is 455-470 mm / min, the output frequency of the pulling is 90-135 times / min, and each copper casting billet corresponds to a crystallizer and a water spray cooler.

[0039] Each crystallizer 20 includes a fixedly installed copper sleeve 1, an inner cylinder 2, and a cold water sleeve 3 from inside to outside, the inner cylinder 2 covers the copper sleeve 1, the cold water sleeve 3 covers the inner cylinder 2, the cold water sleeve 3 is connected with two water inlets 31 and two water returns 32, the two water inlets 31 are symmetrically arranged about the inner cylinder 2, the two water returns 32 are symmetrically arranged about the inner cylinder 2, the inner cylinder 2 is fixedly installed in the cooling water sleeve by a detachable connection, and an annular water inlet cavity 33 and an annular water return cavity 34 are formed between the inner cylinder 2 and the cooling water sleeve, the water inlet cavity 33 is in communication with the water inlet 31, and the water return cavity 34 is in communication with the water return 32.

[0040] The inner cylinder 2 and the copper sleeve 1 form a cylindrical water joint 12, the water inlet cavity 33 is in communication with one end of the cylindrical water joint 12, and the water outlet cavity is in communication with the other end of the cylindrical water joint 12 in the axial direction, in this embodiment, the water inlet cavity 33 is close to the discharge end of the crystallizer, and the water return cavity 34 is close to the feeding end of the crystallizer.

[0041] In order to ensure the uniformity of the cooling water entering the cylindrical water joint 12, the water inlet 31 is arranged away from the end of the water inlet cavity 33 in communication with the cylindrical water joint 12, and the water inlet cavity 33 is in communication with the annular water inlet groove 35 formed between the end face of the inner cylinder 2 and the cold water sleeve 3.

[0042] To ensure that the cylindrical water gap 12 is filled with cooling water, an annular water return groove 36 is formed between the water return cavity 34 and the end of the cylindrical water gap 12, the annular water return groove 36 is located between the inner cylinder 2 and the cooling water jacket 3, the cross section of the annular water return groove 36 is U-shaped, the water return cavity 34 is located between the water inlet cavity 33 and the annular water return groove 36, so that when the cooling water flows out of the cylindrical water gap 12, it moves in the reverse direction in a flooding manner, and the moving process flows into the annular water return cavity 34 along the annular water return groove 36, and the U-shaped structure of the annular water return groove 36 makes the water return path longer, thereby ensuring that the cylindrical water gap 12 is always completely filled with cooling water during the cooling process, and the cooling water is uniform and stable, which helps the uniform cooling of the copper cast billet and the uniformity of the generated grain size.

[0043] The inner surface of the inner cylinder 2 is processed with a threaded groove 21. The pitch of the threaded groove 21 is 3-5mm, the threaded depth is 1-2.5mm, and the cross section of the threaded groove 21 is triangular.

[0044] When the crystallizer 20 is used, the water inlet temperature is 28℃±2℃, the water return temperature is 60℃±2℃, and the water pressure of the cylindrical water gap 12 is 0.5Mpa±0.1Mpa;

[0045] The water temperature of the secondary water cooling of the water spray cooler 30 is 28℃±2℃, and the water flow is 240L / min±20L / min.

[0046] When the copper cast billet is cooled, the cooling water of the water-cooled crystallizer 20 enters the water inlet cavity 33 of the water-cooled crystallizer 20 from the water inlet 31, and then uniformly flows into the cylindrical water gap 12 from the water inlet groove 35. Under the guidance of the threaded groove 21, the cooling water entering the cylindrical water gap 12 flows spirally, and finally flows out of the annular water return groove 36 into the water return cavity 34, and finally is discharged from the water return port 32. The cooling water on the water spray cooler 30 enters from the side close to the crystallizer 20, and then the sprayed water is discharged from the end away from the crystallizer 20, realizing the cooling of the copper cast billet.

[0047] The specification of each copper cast billet produced is an outer diameter of 90±2mm and a wall thickness of 25mm.

[0048] When pulling, the cycle of pull-stop-onetime reverse push-stop-second time reverse push-stop is adopted, wherein the length of each cycle is 4-7mm, the length of the pull is 100-140ms, the length of the first stop is 60-135ms, the length of the second stop is 60-125ms, the length of the third stop is 50-105ms, the length of the first reverse push is 0.6-1.3mm, the length of the first reverse push is 80-115ms, the length of the second reverse push is 0.2-0.5mm, and the length of the second reverse push is 50-65ms.

[0049] To verify the influence of the above traction program on the production, the following 7 groups of tests are carried out, wherein the original production and test A-test F are different in two points, the first point is that the original production produces 3 copper cast blanks each time, and the corresponding traction machine can pull 3, the number of crystallizers and water sprayers is 3 sets, while test A-test F produces 4 copper cast blanks each time, and the corresponding traction machine can pull 4, the number of crystallizers and water sprayers is 4 sets; the second point is that the crystallizer used in the original production does not have a threaded groove in the cylindrical water joint, while test A-test F all use the above crystallizer with threaded groove, wherein the specific pitch of the crystallizer is 3mm, and the threaded depth is 1mm. The 7 groups of test parameter tables and test result tables of the change of traction program action are as follows table 1 and table 2.

[0050] Table 1: 7 groups of test parameter tables of the change of traction program action

[0051]

[0052] Table 2: 7 groups of test result tables of the change of traction program action

[0053]

[0054] Note: The copper liquid temperature used in the above 7 groups of test groups is 1175℃±10℃.

[0055] From the above 7 groups of tests, it can be seen that test A to test D of the present application can ensure that the surface color of the cast blank is uniform, and the grain size is uniform, which shows that through the optimization design of the traction program, the traction is more frequent, the high-frequency program is replaced by the low-frequency program, the length of the first drawing is reduced, the pause time is reduced, the degree of disturbance of the copper liquid is increased, so as to realize the rapid heat transfer and the refinement of the grain, ensure the realization of the production of 4 copper cast blanks, improve the production efficiency by 26-31%, and greatly reduce the production cost.

[0056] In addition, test A to test D can make the grain size more refined, and the average grain size can reach 1.4-1.8mm. Because the copper cast blank grain size of test A to test D is refined, the requirement for copper liquid refining is reduced, the original copper liquid standing refining holding time is 10min, and now only 5min can meet the production requirement. Although the holding time is greatly shortened, more trace impurities in the copper liquid are retained, but in the case that the crystallizer can make the grain more refined, the grain boundary surface area of the grain size is increased, so as to ensure that the trace impurities can be effectively and uniformly dispersed, reduce the aggregation of impurities, and thus ensure that the subsequent processing process of the copper cast blank will not have defects / defect quantity within the requirement range. The shortening of the holding time greatly reduces the energy consumption, and is helpful to energy saving and environmental protection.

[0057] In addition, the average service life of the graphite mold in the original production crystallizer is about 120 hours after use, and the average service life of the graphite mold is increased to 160 hours after the crystallizer is changed in the test A-test D. The service life of the graphite mold is increased by about 50% compared with the past, which greatly reduces the use amount of the graphite mold as a consumable and further reduces the production cost of the enterprise.

[0058] It should be noted that although the above tests E and F can improve the production quality and obtain qualified casting quality, the frequency exceeds 135 times / min, the output action of the servo motor of the traction machine changes too fast, the engagement precision of the transmission structure in the traction machine is too high, and the action is unstable, so it is not suitable for practical use.

[0059] Example two

[0060] To verify the effect of the present application under different size thread grooves, ten groups of test groups for producing red copper hollow casting blanks were set based on example one, the different test parameters of the test groups are shown in table three below, and the test results are shown in table four below.

[0061] Table three test parameters of ten groups of test groups

[0062]

[0063]

[0064] Among the above ten test groups, other parameters are: the inner diameter of the cylindrical water joint is 138mm, the water pressure is 0.5Mpa±0.1Mpa; the water temperature of the secondary water cooling is 28℃±2℃, the water flow is 240L / min; the length of the crystallizer used is 175-210mm, and the specification of the red copper hollow casting blank produced is 90±2mm in outer diameter and 25mm in wall thickness.

[0065] Table four test results of ten groups of test groups

[0066]

[0067] Note: The above casting surface temperature is the casting surface temperature after cooling by the water spray cooler.

[0068] From the above ten test groups, it can be seen that the pitch and thread depth of test 1 are both large, resulting in uneven surface color and grain size of the casting blank, especially there is an individual transgranular phenomenon, and the casting effect is as follows: Figure 6As shown; test 2 after setting the pitch and thread depth to be small, the surface temperature of the casting blank is reduced, making the surface quality of the casting blank uniform, but the phenomenon of normal grain on one side and large and uneven grain on the other side appears, although compared with test 1, the transgranular phenomenon no longer appears, but there are at least 2 to 3 large grains covering the cross section, it can be seen that test 2 is still not feasible.

[0069] And the pitch of test 10 is large, but the thread depth is too small, resulting in weak water flow guiding effect, and the casting blank produced has the problems of uneven surface color and coarse grain size as shown; and test 8 can achieve uniform surface color of the casting blank, but there is a problem of uneven grain. Figure 7

[0070] Only test 3 to test 7, by designing the thread groove depth and pitch, the water inlet temperature is 28℃, the water inlet flow is 45L / min, the return water temperature is increased to 60-62℃, which ensures the uniformity of the surface color and grain size of the casting blank, achieves the effect as shown, and the copper casting blank grain is smaller (the average grain size of the original production before improvement is about 2.8mm, and the average grain size under test 3-7 is 1.4-1.8mm). Figure 8

[0071] The above is only an embodiment of the present application, and the specific technical solutions and / or common knowledge of the scheme are not described in detail. It should be noted that for those skilled in the art, without departing from the technical solutions of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, which will not affect the effect and practicality of the patent. The protection scope of the present application should be subject to the content of its claims, and the specific implementation mode and the like in the specification can be used to explain the content of the claims.​​

Claims

1. A high-efficiency copper casting billet horizontal continuous casting process, which requires the copper liquid to enter the crystallizer for primary cooling, then passes through the water spray cooler for secondary cooling, and then the hollow copper casting billet is horizontally pulled out by the traction machine; characterized in that: The traction machine simultaneously pulls 4 copper cast slabs, the pulling speed is 455-470 mm / min, and the output frequency of pulling is 90-135 times / min; ​ During pulling, the pulling-stopping-onetime reverse-stopping-twice reverse-stopping cycle is adopted, wherein the length of pulling in each cycle is 4-7 mm, the time of pulling is 100-140 ms, the time of the first stop is 60-135 ms, the time of the second stop is 60-125 ms, and the time of the third stop is 50-105 ms; In each cycle of pulling, the length of one-time reverse is 0.6-1.3 mm, the time of one-time reverse is 80-115 ms, the length of twice reverse is 0.2-0.5 mm, and the time of twice reverse is 50-65 ms; The crystallizer is provided with a cylindrical water joint, the inner surface or the outer surface of the cylindrical water joint is provided with a thread groove, the cylindrical water joint uniformly inputs water from one end close to the traction machine in the circumferential direction, and uniformly returns water from one end close to the copper liquid, the pitch of the thread groove is 3-5 mm, and the thread depth is 1-2.5 mm.

2. A high efficiency copper slab horizontal continuous casting process as claimed in claim 1 wherein: During cooling crystallization, the water pressure in the cylindrical water joint is 0.4-0.6 Mpa, the water temperature of the cylindrical water joint is 25-30℃, and the return water temperature of the cylindrical water joint is 55-65℃.

3. A high efficiency copper slab horizontal continuous casting process as claimed in claim 1 wherein: During cooling crystallization, the return water temperature of the cylindrical water joint is 60-62℃.

4. A high efficiency copper slab horizontal continuous casting process as claimed in claim 1 wherein: During cooling crystallization, the cooling water needs to enter the annular water inlet cavity provided in the crystallizer for buffering and filling the annular water inlet cavity before entering the water inlet end of the cylindrical water joint.

5. A high efficiency copper slab horizontal continuous casting process as claimed in claim 1 wherein: During cooling crystallization, when the cooling water is discharged from the cylindrical water joint, it first surges into the annular water return groove provided in the crystallizer in the reverse direction, then enters the annular water return cavity provided in the crystallizer, and finally is discharged.

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