Rolling method for improving conductivity of cathode flat steel for electrolytic aluminum and application of rolling method

Abstract

The invention provides a rolling method of cathode flat steel, which comprises the following steps: firstly, heating a casting blank to obtain a heated blank, then carrying out surface descaling on the heated blank, and carrying out multi-pass rough rolling to obtain an intermediate blank; the heating treatment comprises a preheating section and a soaking section; the heating treatment is specifically a heating treatment process for controlling the austenite grain size of the casting blank; the multi-pass rough rolling comprises multi-pass rough rolling of which the reduction rate is sequentially reduced; and carrying out multi-pass finish rolling on the intermediate billet obtained in the previous step, carrying out on-line cooling, and then carrying out stacking slow cooling to obtain the rolled and formed cathode flat steel. According to the method, directional improvement of the conductivity of the electrolytic aluminum cathode flat steel is achieved through rolling process optimization, heating under a rolling path of a low-temperature ferrite area and rolling pass reduction distribution design are focused, the ferrite grain size and the conductive texture of a material are cooperatively regulated, the normal conductivity of the cathode flat steel is improved, and the conductivity of the cathode flat steel is improved. And a core material support is provided for reducing ineffective current loss in the electrolytic aluminum industry.

Description

Technical Field

[0001] This invention relates to the field of cathode flat steel rolling technology, specifically to a method for rolling cathode flat steel and its application, and more particularly to a method for rolling cathode flat steel for electrolytic aluminum to improve its conductivity and its application. Background Technology

[0002] The electrolytic aluminum industry is a high-energy-consuming basic industry, with electricity costs accounting for more than 40% of the total cost. The theoretical DC power consumption per ton of aluminum is 6300 kWh, while the current DC power consumption per ton of aluminum is as high as 13000 kWh, indicating significant potential for energy conservation and consumption reduction. In the electrolytic aluminum production process, the cathode flat steel, as a key conductive component, plays a crucial role in guiding the current from the cathode carbon block to the external busbar. However, due to the resistivity differences when the current is transmitted to the molten aluminum, the cathode carbon block, and the flat steel, the current is deflected in the molten aluminum layer, forming a horizontal current component. This horizontal current not only does not participate in the electrochemical reaction, causing ineffective energy loss, but also interacts with the magnetic field, causing fluctuations in the molten aluminum, leading to unstable electrode spacing and cell voltage fluctuations, severely restricting current efficiency and the lifespan of the electrolytic cell.

[0003] To reduce the horizontal current component, electrolytic aluminum companies often optimize the cathode structure (variable cross-section flat steel) or upgrade the material to higher conductivity cathode flat steel (high purification) to reduce the overall resistivity, thereby achieving energy saving and consumption reduction. However, these methods have certain shortcomings: structural optimization requires redesigning the structure of each component inside the electrolytic cell, which is particularly complex to operate and increases investment costs; high purification control of the composition can certainly improve the conductivity of the cathode flat steel, but the low manganese-sulfur ratio of the steel grade makes rolling prone to cracking risk, and the rolling temperature range is limited, generally using low-temperature ferrite rolling. Under this rolling condition, the internal defects and conductive texture of the material cannot be controlled from the perspective of current transmission, and the horizontal current suppression effect is limited.

[0004] Therefore, designing a more suitable production process to solve the aforementioned technical problems in existing technologies has become one of the urgent issues for many front-line researchers in the industry. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a rolling method and application for cathode flat steel, particularly a rolling method for improving the conductivity of cathode flat steel used in electrolytic aluminum. The innovative solution proposed in this invention, based on heating and rolling processes, controls the recrystallization conductive texture and ferrite grain size through low-temperature rolling in the ferrite region, thereby changing the defect density and anisotropy of the material, reducing electron scattering, improving conductivity stability, and achieving an improvement in vertical conductivity. This invention breaks through the traditional technical route that relies on high-purity control of components, achieving a targeted improvement in conductivity by utilizing the rolling path and the current transmission characteristics of the electrolytic cell. Moreover, the production method is simple, highly controllable, and easy to operate, making it more suitable for industrial promotion and application.

[0006] This invention provides a method for rolling cathode flat steel, comprising the following steps:

[0007] 1) The billet is heated to obtain a heated billet. Then, the heated billet is descaled and then subjected to multiple rough rolling passes to obtain an intermediate billet.

[0008] The heating process includes a preheating section and a homogenizing section;

[0009] The heat treatment specifically refers to a heat treatment process that controls the austenite grain size of the cast billet;

[0010] The multi-pass roughing includes multi-pass roughing with successively decreasing reduction rates;

[0011] 2) After the intermediate billet obtained in the above steps is subjected to multiple passes of precision rolling, it is first cooled online and then stacked for slow cooling to obtain the rolled cathode flat steel.

[0012] Preferably, the cathode flat steel is a cathode flat steel for electrolytic aluminum;

[0013] The grade of the cathode flat steel is HYT2;

[0014] The cathode flat steel, by element mass percentage, includes: C≤0.008%, Si≤0.015%, Mn≤0.03%, P≤0.012%, S≤0.007%, Al≤0.030%, with the remainder being Fe and unavoidable impurities;

[0015] In the cathode flat steel, T[O]≤0.008%.

[0016] Preferably, the billet comprises a continuously cast rectangular billet;

[0017] The cast billet is specifically a large-section rectangular billet;

[0018] The dimensions of the large-section rectangular billet are (320~360) mm × (410~450) mm;

[0019] The temperature of the preheating section is 800~1000℃.

[0020] Preferably, the temperature of the heat spreader is 920~980℃;

[0021] The soaking time is 100-200 minutes;

[0022] The total time for the heat treatment is 300~420 min;

[0023] Specifically, controlling the austenite grain size of the billet means controlling the austenite grain size to be 2.0~5.0 grade.

[0024] Preferably, the surface descaling method includes high-pressure water descaling;

[0025] The pressure of the high-pressure water is 22~24MPa;

[0026] The multi-pass roughing process involves 7 passes.

[0027] The initial rolling temperature of the multi-pass roughing mill is ≤900℃.

[0028] Preferably, the single-pass reduction rate of the 1-3 passes of the multi-pass roughing is ≥22%;

[0029] The first to third passes of rough rolling are specifically rough rolling processes in which the reduction rate decreases sequentially.

[0030] The single-pass reduction rate of the 4-7 pass roughing in the multi-pass roughing is ≤18%;

[0031] The 4-7 passes of roughing are specifically roughing processes with successively decreasing reduction rates.

[0032] Preferably, the final rolling temperature of the multi-pass roughing is 840~870℃;

[0033] The multi-pass finishing rolling process involves 3 passes.

[0034] The initial rolling temperature of the multi-pass finishing mill is ≤820℃;

[0035] The multi-pass finishing rolling includes multi-pass finishing rolling with successively decreasing reduction rates.

[0036] Preferably, the single-pass reduction rate of the multi-pass finishing mill is ≤12%;

[0037] The final rolling temperature of the multi-pass finishing rolling is 780~820℃;

[0038] The online cooling method includes natural cooling;

[0039] The final temperature of the online cooling is 550~650℃.

[0040] Preferably, the online cooling rate is ≤60℃ / min;

[0041] The initial stacking temperature for slow cooling is ≤550℃;

[0042] The stacking time for slow cooling is greater than or equal to 48 hours;

[0043] The ferrite grain size of the cathode flat steel is 2.0~4.0 grade;

[0044] The cathode flat steel {100} <011> The texture component accounts for ≥35%.

[0045] The present invention also provides the application of the rolling method described in any one of the above technical solutions in the preparation of electrolytic aluminum cathode flat steel.

[0046] This invention provides a rolling method for cathode flat steel, comprising the following steps: first, a cast billet is heated to obtain a heated billet; then, the heated billet is descaled and subjected to multiple rough rolling passes to obtain an intermediate billet; the heating treatment includes a preheating section and a soaking section; specifically, the heating treatment is a process of controlling the austenite grain size of the cast billet; the multiple rough rolling passes include multiple rough rolling passes with progressively decreasing reduction rates; then, the intermediate billet obtained in the above steps is subjected to multiple finish rolling passes, followed by online cooling and then slow stacking cooling to obtain the rolled cathode flat steel. Compared with the prior art, this invention suggests that electrolytic aluminum cathode flat steel needs to possess high conductivity to reduce current loss in electrolytic aluminum production. During its service life, electrons preferentially migrate along the direction of high conductivity. Although traditional cathode flat steel production processes reduce resistivity through high purity control of chemical composition, the rolling process lacks directional control over ferrite grain size and microstructure, leading to horizontal scattering of current transmission and the formation of ineffective horizontal current. This results in suboptimal current utilization efficiency and energy waste. Therefore, it is necessary to innovate the heating and rolling path to achieve anisotropic control of the coarse grains and conductivity of the cathode flat steel, thereby reducing ineffective horizontal current from the source and improving the utilization efficiency of the service current of the electrolytic aluminum cell.

[0047] Based on this, the present invention creatively designs a rolling method for cathode flat steel, which is a preparation method that achieves targeted improvement of the conductivity of electrolytic aluminum cathode flat steel through rolling process optimization. This method focuses on the heating and rolling pass reduction distribution design under the low-temperature ferrite region rolling path, synergistically controlling the ferrite grain size and conductive texture of the material, improving the normal conductivity of the cathode flat steel, and providing core material support for reducing ineffective current loss in the electrolytic aluminum industry.

[0048] The rolling method provided by this invention breaks through the traditional technical route that relies on high-purity control of components. It achieves targeted improvement of conductivity by utilizing the rolling path and the current transmission characteristics of the electrolytic cell. This directly responds to the urgent need of the electrolytic aluminum industry for energy-saving and consumption-reducing technology upgrades. Its core processes, such as BD1 rough rolling with large reduction and BD2 finishing rolling with locked texture, are all compatible with existing rolling mill equipment and have already achieved mass production of this product, verifying the feasibility of the method. This technology optimizes conductivity through microstructure regulation, without the need to redesign the electrolytic cell structure. It is simple to operate and has significant economic and social benefits.

[0049] The results show that the rolling method of this invention can produce HYT2 ultra-high conductivity cathode steel bars with dimensions ranging from (140~210mm) to (200~250mm). Microstructure and property testing revealed a ferrite grain size of 2.0~4.0 grade, and EBSD testing yielded {100}. <011> With a texture volume fraction of ≥35%, a normal resistivity of ≤10.5μΩ·cm for the flat steel, and a longitudinal resistivity between 10.6 and 11.0μΩ·cm, the resistance to electron transmission in the vertical direction of the cathode flat steel is reduced during use, thus reducing ineffective horizontal current and improving current utilization efficiency. Detailed Implementation

[0050] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0051] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0052] There are no particular restrictions on the purity of any raw materials used in this invention. Preferably, industrial-grade pure or conventionally pure materials used in the rolling of HYT2 cathode flat steel are sufficient.

[0053] This invention provides a method for rolling cathode flat steel, comprising the following steps:

[0054] 1) The billet is heated to obtain a heated billet. Then, the heated billet is descaled and then subjected to multiple rough rolling passes to obtain an intermediate billet.

[0055] The heating process includes a preheating section and a homogenizing section;

[0056] The heat treatment specifically refers to a heat treatment process that controls the austenite grain size of the cast billet;

[0057] The multi-pass roughing includes multi-pass roughing with successively decreasing reduction rates;

[0058] 2) After the intermediate billet obtained in the above steps is subjected to multiple passes of precision rolling, it is first cooled online and then stacked for slow cooling to obtain the rolled cathode flat steel.

[0059] The present invention first heat-treats the cast billet to obtain a heated billet, then descales the surface of the heated billet, and then performs multiple rough rolling passes to obtain an intermediate billet;

[0060] The heating process includes a preheating section and a homogenizing section;

[0061] The heat treatment specifically refers to a heat treatment process that controls the austenite grain size of the cast billet;

[0062] The multi-pass roughing includes multiple passes with successively decreasing reduction rates.

[0063] In this invention, the billet preferably comprises a continuously cast rectangular billet.

[0064] In this invention, the cast billet is preferably a large-section rectangular billet.

[0065] In this invention, the preferred size of the large-section rectangular blank is (320~360) mm × (410~450) mm, and more preferably 320 mm × 410 mm or 360 mm × 450 mm.

[0066] In this invention, the temperature of the preheating section is preferably 800~1000℃, more preferably 840~960℃, and even more preferably 880~920℃.

[0067] In this invention, the temperature of the heat spreader is preferably 920~980℃, more preferably 930~970℃, and even more preferably 940~960℃.

[0068] In this invention, the time of the heat spreader is preferably 100-200 min, more preferably 120-180 min, and even more preferably 140-160 min.

[0069] In this invention, the total time for the heat treatment is preferably 300-420 min, more preferably 320-400 min, and even more preferably 340-380 min.

[0070] In this invention, the control of the austenite grain size of the billet specifically refers to controlling the austenite grain size to preferably be 2.0~5.0 grade, more preferably 2.5~4.5 grade, and even more preferably 3.0~4.0 grade.

[0071] In this invention, the surface descaling method preferably includes high-pressure water descaling.

[0072] In this invention, the pressure of the high-pressure water is preferably 22~24MPa, more preferably 22.4~23.6MPa, and even more preferably 22.8~23.2MPa.

[0073] In this invention, the number of passes in the multi-pass roughing is preferably 7.

[0074] In this invention, the initial rolling temperature of the multi-pass roughing is preferably ≤900℃, more preferably ≤870℃, and even more preferably ≤850℃. Specifically, the initial rolling temperature is set between 850 and 900℃.

[0075] In this invention, the single-pass reduction rate of the 1 to 3 passes of the multi-pass roughing is preferably ≥22%, more preferably ≥23%, and even more preferably ≥25%.

[0076] In this invention, the roughing process of the first to third passes is preferably a roughing process in which the reduction rate decreases sequentially.

[0077] In this invention, the single-pass reduction rate of the 4-7 passes of the multi-pass roughing is preferably ≤18%, more preferably ≤17%, and even more preferably ≤16%.

[0078] In this invention, the 4 to 7 passes of roughing are preferably roughing processes with successively decreasing reduction rates.

[0079] In this invention, the final rolling temperature of the multi-pass roughing is preferably 840~870℃, more preferably 845~865℃, and even more preferably 850~860℃.

[0080] Finally, the intermediate billet obtained in the above steps is subjected to multiple passes of precision rolling, then cooled online and then stacked for slow cooling to obtain the rolled cathode flat steel.

[0081] In this invention, the multi-pass finishing rolling preferably involves 3 passes.

[0082] In this invention, the initial rolling temperature of the multi-pass finishing mill is preferably ≤820℃, more preferably ≤810℃, and even more preferably ≤800℃. Specifically, the initial rolling temperature of the multi-pass finishing mill can be 780~820℃.

[0083] In this invention, the multi-pass finishing rolling preferably includes multi-pass finishing rolling with successively decreasing reduction rates.

[0084] In this invention, the single-pass reduction rate of the multi-pass finishing mill is preferably ≤12%, more preferably ≤11%, and even more preferably ≤10%.

[0085] In this invention, the final rolling temperature of the multi-pass finishing rolling is preferably 780~820℃, more preferably 785~815℃, more preferably 790~810℃, and even more preferably 795~805℃.

[0086] In this invention, the online cooling method preferably includes natural cooling.

[0087] In this invention, the endpoint temperature of the online cooling is preferably 550~650℃, more preferably 570~630℃, and even more preferably 590~610℃.

[0088] In this invention, the cooling rate of the online cooling is preferably ≤60℃ / min, more preferably ≤50℃ / min, and even more preferably ≤40℃ / min.

[0089] In this invention, the initial stacking temperature for slow cooling is preferably ≤550℃, more preferably ≤540℃, and even more preferably ≤530℃. Specifically, the initial stacking temperature can be 490~530℃.

[0090] In this invention, the stacking time for slow cooling is preferably greater than or equal to 48 hours, more preferably greater than or equal to 49 hours, and even more preferably greater than or equal to 50 hours.

[0091] In this invention, the ferrite grain size of the cathode flat steel is preferably 2.0 to 4.0 grade, and can be 2.0 grade, 2.5 grade, 3 grade, 3.5 grade or 4 grade.

[0092] In this invention, the {100} of the cathode flat steel <011> The proportion of the texture component is preferably ≥35%, more preferably ≥40%, and even more preferably ≥35%.

[0093] In this invention, the cathode flat steel is preferably a cathode flat steel for electrolytic aluminum.

[0094] In this invention, the preferred grade of the cathode flat steel is HYT2.

[0095] In this invention, the cathode flat steel, by elemental mass percentage, preferably comprises: C≤0.008%, Si≤0.015%, Mn≤0.03%, P≤0.012%, S≤0.007%, Al≤0.030%, with the remainder being Fe and unavoidable impurities; more preferably, it comprises C≤0.007%, Si≤0.012%, Mn≤0.02%, P≤0.010%, S≤0.006%, Al≤0.020%, with the remainder being Fe and unavoidable impurities; even more preferably, it comprises C≤0.005%, Si≤0.006%, Mn≤0.015%, P≤0.007%, S≤0.005%, Al≤0.010%, with the remainder being Fe and unavoidable impurities.

[0096] In this invention, the cathode flat steel preferably has a T[O] ≤ 0.008%. More preferably, T[O] ≤ 0.006%, and even more preferably, T[O] ≤ 0.004%.

[0097] This invention provides the application of the rolling method described in any one of the above technical solutions in the preparation of electrolytic aluminum cathode flat steel.

[0098] This invention aims to complete and refine the overall technical solution, better ensure the stability and continuity of the rolling process, further improve the composition, microstructure, and properties of the rolled cathode flat steel, and thereby enhance the conductivity stability and vertical conductivity of the cathode flat steel. The rolling method for improving the conductivity of cathode flat steel used in electrolytic aluminum and its application may specifically include the following:

[0099] The electrolytic aluminum cathode flat steel in this invention is grade HYT2. The initial cross-sectional dimensions of the continuously cast billet are 320mm×410mm or 360mm×450mm, and it is finally rolled into a specification of (140~210mm)×(200~250mm). The initial cross-sectional dimensions are selected with a total compression ratio ≥3.0.

[0100] Specifically, the chemical composition (mass fraction) of the HYT2 cathode flat steel is: C≤0.008%, Si≤0.015%, Mn≤0.030%, P≤0.012%, S≤0.007%, Al≤0.030%, T[O]≤0.008%, with the balance being Fe and unavoidable impurities.

[0101] Specifically, it has better electrical conductivity, and its chemical composition (mass fraction) is: C≤0.006%, Si≤0.006%, Mn≤0.020%, P≤0.007%, S≤0.007%, Al≤0.015%, T[O]≤0.005%, with the balance being Fe and unavoidable impurities.

[0102] The rolling forming method provided by the present invention includes: billet heating → high-pressure water descaling → rolling on BD1 reversible rolling mill → rolling on BD2 reversible rolling mill → sawing → online cooling → stacking and slow cooling.

[0103] Billet heating: Place the billet in a walking beam furnace. The preheating temperature is 800~1000℃, the soaking temperature is 920~980℃, and the total heating time in the furnace is 300~420min, of which the soaking time is 100~200min. Control the austenite grain size to be 2.0~5.0.

[0104] High-pressure water descaling: High-pressure water at 22~24MPa is used to remove the iron oxide scale from the surface of the heated billet.

[0105] Roughing on the BD1 reversible mill: The descaled billet enters the BD1 reversible mill for 7 passes of roughing. The initial rolling temperature is ≤900℃. The single-pass reduction rate of passes 1 to 3 is ≥22%, with a pressure reduction distribution mode. The reduction rate of passes 4 to 7 is ≤18%, with a pressure reduction distribution mode. The final rolling temperature of BD1 is 840~870℃.

[0106] BD2 reversible mill finishing: The intermediate billet enters the BD2 reversible mill for 3 passes of rolling, with an initial rolling temperature ≥820℃, a single pass reduction rate ≤12%, a pressure reduction distribution mode, and a final rolling temperature of 780~820℃.

[0107] Online cooling: After rolling, the ends of the cathode flat steel are sawn and naturally cooled to 550~650℃, with a cooling rate ≤60℃ / min.

[0108] Slow cooling during stacking: initial stacking temperature ≤550℃, stacking time 48h.

[0109] Specifically, the rolling method uses low-temperature ferrite region rolling to avoid corner cracking defects caused by low manganese-sulfur ratio.

[0110] The rolling method provided by this invention controls the grain size of cathode flat steel to grade 2.0~4.0, which is achieved by the following conditions: (1) the heating furnace is heated for a long time, and the original austenite grains are coarsened; (2) the rolling is carried out with a large reduction in the rough rolling stage, so that the rolling force penetrates to the core, improves the uniformity of the whole cross section, and the reduction rate is distributed in a decreasing manner. The deformation process is dominated by dynamic recovery rather than recrystallization, which inhibits grain refinement (the critical temperature of dynamic recrystallization is about 650℃); (3) natural cooling is adopted after rolling, and water or spray is strictly prohibited on the surface to reduce the defect density.

[0111] The rolling method provided by this invention performs {100} <011> The texture composition is controlled to be ≥35%, which is achieved by the following conditions: (1) rough rolling with large reduction to form austenite grains along the rolling direction with {100} <011> Dominant texture, low temperature suppresses grain boundary migration; (2) The pass reduction rate gradually decreases to avoid deformation-induced γ texture {111} <112> (3) The final rolling temperature is controlled at 780~820℃. If the temperature is too low, it is easy to form a texture with poor electrical conductivity.

[0112] The stacking slow cooling method provided by this invention is to reduce the density of point defects in steel by using residual heat, thereby improving the electrical conductivity of the steel.

[0113] Performance: The ferrite grain size of the finished cathode flat steel is 2.0~4.0 grade, {100} <011> With a texture component ratio of ≥35%, the normal resistivity of the cathode flat steel is ≤10.5μΩ·cm, and the longitudinal resistivity is 10.6~11.0μΩ·cm. During use, it reduces the resistance of electron transmission in the vertical direction of the cathode flat steel, reduces ineffective horizontal current, and improves current utilization efficiency.

[0114] The present invention provides a rolling method for improving the conductivity of cathode flat steel for electrolytic aluminum and its application. The rolling method for cathode flat steel designed in this invention is a preparation method that achieves targeted improvement of the conductivity of electrolytic aluminum cathode flat steel through optimized rolling process. This method focuses on the heating and rolling pass reduction distribution design under the low-temperature ferrite region rolling path, synergistically controlling the ferrite grain size and conductive texture of the material, improving the normal conductivity of the cathode flat steel, and providing core material support for reducing ineffective current loss in the electrolytic aluminum industry.

[0115] The rolling method provided by this invention breaks through the traditional technical route that relies on high-purity control of components. It achieves targeted improvement of conductivity by utilizing the rolling path and the current transmission characteristics of the electrolytic cell, directly responding to the urgent need of the electrolytic aluminum industry for energy-saving and consumption-reducing technology upgrades. Its core processes, such as BD1 rough rolling with large reduction and BD2 finishing rolling with locked texture, are compatible with existing rolling mill equipment and have already achieved mass production of this product, verifying the feasibility of the method. This technology optimizes conductivity through microstructure control, eliminating the need to redesign the electrolytic cell structure. It is simple to operate and has significant economic and social benefits.

[0116] The results show that the rolling method of this invention can produce HYT2 ultra-high conductivity cathode steel bars with dimensions ranging from (140~210mm) to (200~250mm). Microstructure and property testing revealed a ferrite grain size of 2.0~4.0 grade, and EBSD testing yielded {100}. <011> With a texture volume fraction of ≥35%, a normal resistivity of ≤10.5μΩ·cm for the flat steel, and a longitudinal resistivity between 10.6 and 11.0μΩ·cm, the resistance to electron transmission in the vertical direction of the cathode flat steel is reduced during use, thus reducing ineffective horizontal current and improving current utilization efficiency.

[0117] To further illustrate the present invention, the following describes in detail a method for rolling cathode flat steel and its application, in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0118] Example 1

[0119] The HYT2 cathode flat steel with a specification of 140mm×200mm was prepared by the method provided in this invention. The initial cross-sectional size of the continuously cast billet was 320mm×410mm, and the total rolling compression ratio was 4.68.

[0120] The chemical composition (mass fraction) of the raw material is: C 0.004%, Si 0.006%, Mn 0.020%, P 0.005%, S 0.005%, Al 0.010%, T[O]=41ppm, with the balance being Fe and unavoidable impurities.

[0121] The rolling forming process of cathode flat steel includes billet heating → high-pressure water descaling → rolling on BD1 reversible rolling mill → rolling on BD2 reversible rolling mill → sawing → online cooling → stacking slow cooling.

[0122] Billet heating: The billet is placed in a walking beam furnace. The preheating zone temperature is 800~1000℃, with an average of 922℃. The soaking zone temperature is 920~980℃, with an average of 968℃. The total heating time in the furnace is 300~420min, with an average of 350min. The soaking zone time is 100~200min, with an average of 120min. The austenite grain size is grade 3.0.

[0123] High-pressure water descaling: High-pressure water at 22~24MPa is used to remove the iron oxide scale from the surface of the heated billet.

[0124] Roughing on the BD1 reversible mill: The descaled billet enters the BD1 reversible mill for 7 passes of roughing. The initial rolling temperature is ≤900℃. The single-pass reduction rate of passes 1-3 is ≥22%, the reduction rate of the first pass is 35%, and the pressure reduction distribution mode is used. The reduction rate of passes 4-7 is ≤18%, the reduction rate of the fourth pass is 15%, and the pressure reduction distribution mode is used. The final rolling temperature of BD1 is 840-870℃.

[0125] BD2 reversible mill finishing: The intermediate billet enters the BD2 reversible mill for 3 passes of rolling. The initial rolling temperature is ≥820℃, the single pass reduction rate is ≤12%, the first pass reduction rate is 10%, the pressure reduction distribution mode is used, and the final rolling temperature is 780~820℃.

[0126] Online cooling: After rolling, the ends of the cathode flat steel are sawn and naturally cooled to 550~650℃, with a cooling rate ≤60℃ / min.

[0127] Slow cooling during stacking: initial stacking temperature ≤550℃, stacking time 48h.

[0128] Performance testing: The ferrite grain size of the cathode flat steel is grade 2.0, {100} <011> The texture component accounts for 36%, and the normal resistivity of the cathode flat steel is 10.3 μΩ·cm, while the longitudinal resistivity is 10.7 μΩ·cm.

[0129] Example 2

[0130] The HYT2 cathode flat steel with a specification of 180mm×220mm was prepared by the method provided in this invention. The initial cross-sectional size of the continuously cast billet was 320mm×410mm, and the total rolling compression ratio was 3.31.

[0131] The chemical composition (mass fraction) of the raw material is: C 0.005%, Si 0.008%, Mn 0.030%, P 0.010%, S 0.007%, Al 0.006%, T[O]=61ppm, with the balance being Fe and unavoidable impurities.

[0132] The rolling forming process of cathode flat steel includes billet heating → high-pressure water descaling → rolling on BD1 reversible rolling mill → rolling on BD2 reversible rolling mill → sawing → online cooling → stacking slow cooling.

[0133] Billet heating: The billet is placed in a walking beam furnace. The preheating temperature is 800~1000℃, with an average of 942℃. The soaking temperature is 920~980℃, with an average of 975℃. The total heating time in the furnace is 300~420min, with an average of 410min. The soaking time is 100~200min, with an average of 160min. The austenite grain size is grade 2.0.

[0134] High-pressure water descaling: High-pressure water at 22~24MPa is used to remove the iron oxide scale from the surface of the heated billet.

[0135] Roughing on the BD1 reversible mill: The descaled billet enters the BD1 reversible mill for 7 passes of roughing. The initial rolling temperature is ≤900℃. The single-pass reduction rate of passes 1-3 is ≥22%, the reduction rate of the first pass is 32%, and the pressure reduction distribution mode is used. The reduction rate of passes 4-7 is ≤18%, the reduction rate of the fourth pass is 16%, and the pressure reduction distribution mode is used. The final rolling temperature of BD1 is 840-870℃.

[0136] BD2 reversible mill finishing: The intermediate billet enters the BD2 reversible mill for 3 passes of rolling. The initial rolling temperature is ≥820℃, the single pass reduction rate is ≤12%, the first pass reduction rate is 12%, the pressure reduction distribution mode is used, and the final rolling temperature is 780~820℃.

[0137] Online cooling: After rolling, the ends of the cathode flat steel are sawn and naturally cooled to 550~650℃, with a cooling rate ≤60℃ / min.

[0138] Slow cooling during stacking: initial stacking temperature ≤550℃, stacking time 48h.

[0139] Performance testing: The ferrite grain size of the cathode flat steel is grade 2.0, {100} <011> The texture component accounts for 40%, and the normal resistivity of the cathode flat steel is 10.3 μΩ·cm, while the longitudinal resistivity is 10.6 μΩ·cm.

[0140] Example 3

[0141] The HYT2 cathode flat steel with a specification of 160mm×230mm was prepared by the method provided in this invention. The initial cross-sectional size of the continuously cast billet was 320mm×410mm, and the total rolling compression ratio was 3.56.

[0142] The chemical composition (mass fraction) of the raw material is: C 0.006%, Si 0.009%, Mn 0.022%, P 0.006%, S 0.006%, Al 0.029%, T[O]=23ppm, with the balance being Fe and unavoidable impurities.

[0143] The rolling forming process of cathode flat steel includes billet heating → high-pressure water descaling → rolling on BD1 reversible rolling mill → rolling on BD2 reversible rolling mill → sawing → online cooling → stacking slow cooling.

[0144] Billet heating: The billet is placed in a walking beam furnace. The preheating zone temperature is 800~1000℃, with an average of 945℃. The soaking zone temperature is 920~980℃, with an average of 980℃. The total heating time in the furnace is 300~420min, with an average of 300min. The soaking zone time is 100~200min, with an average of 100min. The austenite grain size is grade 4.0.

[0145] High-pressure water descaling: High-pressure water at 22~24MPa is used to remove the iron oxide scale from the surface of the heated billet.

[0146] Roughing on the BD1 reversible mill: The descaled billet enters the BD1 reversible mill for 7 passes of roughing. The initial rolling temperature is ≤900℃. The single-pass reduction rate of passes 1-3 is ≥22%, the reduction rate of the first pass is 25%, and the pressure reduction distribution mode is used. The reduction rate of passes 4-7 is ≤18%, the reduction rate of the fourth pass is 17%, and the pressure reduction distribution mode is used. The final rolling temperature of BD1 is 840-870℃.

[0147] BD2 reversible mill finishing: The intermediate billet enters the BD2 reversible mill for 3 passes of rolling. The initial rolling temperature is ≥820℃, the single pass reduction rate is ≤12%, the first pass reduction rate is 9%, the pressure reduction distribution mode is used, and the final rolling temperature is 780~820℃.

[0148] Online cooling: After rolling, the ends of the cathode flat steel are sawn and naturally cooled to 550~650℃, with a cooling rate ≤60℃ / min.

[0149] Slow cooling during stacking: initial stacking temperature ≤550℃, stacking time 48h.

[0150] Performance testing: The ferrite grain size of the cathode flat steel is grade 2.0, {100} <011> The texture component accounts for 35%, and the normal resistivity of the cathode flat steel is 10.5 μΩ·cm, while the longitudinal resistivity is 10.8 μΩ·cm.

[0151] Example 4

[0152] The HYT2 cathode flat steel with a specification of 210mm×250mm was prepared by the method provided in this invention. The initial cross-sectional size of the continuously cast billet was 360mm×450mm, and the total rolling compression ratio was 3.08.

[0153] The chemical composition (mass fraction) of the raw material is: C 0.004%, Si 0.007%, Mn 0.015%, P 0.005%, S 0.005%, Al 0.008%, T[O]=40ppm, with the balance being Fe and unavoidable impurities.

[0154] The rolling forming process of cathode flat steel includes billet heating → high-pressure water descaling → rolling on BD1 reversible rolling mill → rolling on BD2 reversible rolling mill → sawing → online cooling → stacking slow cooling.

[0155] Billet heating: The billet is placed in a walking beam furnace. The preheating zone temperature is 800~1000℃, with an average of 820℃. The soaking zone temperature is 920~980℃, with an average of 955℃. The total heating time in the furnace is 300~420min, with an average of 300min. The soaking zone time is 100~200min, with an average of 105min. The austenite grain size is grade 5.0.

[0156] High-pressure water descaling: High-pressure water at 22~24MPa is used to remove the iron oxide scale from the surface of the heated billet.

[0157] Roughing on the BD1 reversible mill: The descaled billet enters the BD1 reversible mill for 7 passes of roughing. The initial rolling temperature is ≤900℃. The single-pass reduction rate of passes 1-3 is ≥22%, the reduction rate of the first pass is 23%, and the pressure reduction distribution mode is used. The reduction rate of passes 4-7 is ≤18%, the reduction rate of the fourth pass is 15%, and the pressure reduction distribution mode is used. The final rolling temperature of BD1 is 840-870℃.

[0158] BD2 reversible mill finishing: The intermediate billet enters the BD2 reversible mill for 3 passes of rolling. The initial rolling temperature is ≥820℃, the single pass reduction rate is ≤12%, the first pass reduction rate is 10%, the pressure reduction distribution mode is used, and the final rolling temperature is 780~820℃.

[0159] Online cooling: After rolling, the ends of the cathode flat steel are sawn and naturally cooled to 550~650℃, with a cooling rate ≤60℃ / min.

[0160] Slow cooling during stacking: initial stacking temperature ≤550℃, stacking time 48h.

[0161] Performance testing: The ferrite grain size of the cathode flat steel is grade 2.0, {100} <011> The texture component accounts for 42%, and the normal resistivity of the cathode flat steel is 10.2 μΩ·cm, while the longitudinal resistivity is 10.6 μΩ·cm.

[0162] The foregoing has provided a detailed description of a rolling method for improving the conductivity of cathode flat steel for electrolytic aluminum and its application. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for rolling cathode flat steel, characterized in that, Includes the following steps: 1) The billet is heated to obtain a heated billet. Then, the heated billet is descaled and then subjected to multiple rough rolling passes to obtain an intermediate billet. The heating process includes a preheating section and a homogenizing section; The heat treatment specifically refers to a heat treatment process that controls the austenite grain size of the cast billet; The multi-pass roughing includes multi-pass roughing with successively decreasing reduction rates; 2) After the intermediate billet obtained in the above steps is subjected to multiple passes of precision rolling, it is first cooled online and then stacked for slow cooling to obtain the rolled cathode flat steel.

2. The rolling method according to claim 1, characterized in that, The cathode flat steel is specifically a cathode flat steel for electrolytic aluminum; The grade of the cathode flat steel is HYT2; The cathode flat steel, by element mass percentage, includes: C≤0.008%, Si≤0.015%, Mn≤0.03%, P≤0.012%, S≤0.007%, Al≤0.030%, with the remainder being Fe and unavoidable impurities; In the cathode flat steel, T[O]≤0.008%.

3. The rolling method according to claim 1, characterized in that, The cast billet includes a continuously cast rectangular billet; The cast billet is specifically a large-section rectangular billet; The dimensions of the large-section rectangular billet are (320~360) mm × (410~450) mm; The temperature of the preheating section is 800~1000℃.

4. The rolling method according to claim 1, characterized in that, The temperature of the heat spreader is 920~980℃; The soaking time is 100-200 minutes; The total time for the heat treatment is 300~420 min; Specifically, controlling the austenite grain size of the billet involves controlling the austenite grain size to be 2.0~5.0 grade.

5. The rolling method according to claim 1, characterized in that, The surface descaling method includes high-pressure water descaling; The pressure of the high-pressure water is 22~24MPa; The multi-pass roughing process involves 7 passes. The initial rolling temperature of the multi-pass roughing mill is ≤900℃.

6. The rolling method according to claim 5, characterized in that, The single-pass reduction rate of the 1-3 pass roughing in the multi-pass roughing is ≥22%; The first to third passes of rough rolling are specifically rough rolling processes in which the reduction rate decreases sequentially. The single-pass reduction rate of the 4-7 pass roughing in the multi-pass roughing is ≤18%; The 4-7 passes of roughing are specifically roughing processes with successively decreasing reduction rates.

7. The rolling method according to claim 1, characterized in that, The final rolling temperature of the multi-pass roughing is 840~870℃; The multi-pass finishing rolling process involves 3 passes. The initial rolling temperature of the multi-pass finishing mill is ≤820℃; The multi-pass finishing rolling includes multi-pass finishing rolling with successively decreasing reduction rates.

8. The rolling method according to claim 1, characterized in that, The single-pass reduction rate of the multi-pass finishing mill is ≤12%; The final rolling temperature of the multi-pass finishing rolling is 780~820℃; The online cooling method includes natural cooling; The final temperature of the online cooling is 550~650℃.

9. The rolling method according to claim 1, characterized in that, The cooling rate of the online cooling system is ≤60℃ / min; The initial stacking temperature for slow cooling is ≤550℃; The stacking time for slow cooling is greater than or equal to 48 hours; The ferrite grain size of the cathode flat steel is 2.0~4.0 grade; The cathode flat steel {100} <011> The texture component accounts for ≥35%.

10. The application of the rolling method according to any one of claims 1 to 9 in the preparation of electrolytic aluminum cathode flat steel.