High-conductivity steel bar for aluminum electrolysis cell and manufacturing method of high-conductivity steel bar

Abstract

The invention discloses a high-conductivity steel bar for an aluminum electrolysis cell and a manufacturing method of the high-conductivity steel bar, and the steel bar comprises the following chemical components: less than or equal to 0.002% of C, less than or equal to 0.008% of Si, less than or equal to 0.02% of Mn, less than or equal to 0.005% of P, less than or equal to 0.003% of S, 0.01-0.02% of Al, 0.02-0.05% of Ti, 0.003-0.01% of B and less than or equal to 0.003% of O. The method comprises the steps of converter smelting, RH refining, slab continuous casting, slab longitudinal cutting processing, hot rolling and steel bar transverse fixed-length cutting. Through target component design, intermediate component control and hot rolling heating schedule innovation, the high-conductivity steel bar for the aluminum electrolysis cell with the tensile strength not lower than 265 MPa, the yield strength not lower than 140 MPa and the resistivity not larger than 11 mu omega.cm is manufactured. By innovatively designing product components and a hot rolling heating system, good conditions are created for improving the conductivity and the surface quality of the product, improving the mechanical property and improving the surface quality of the steel bar, and the steel bar for the aluminum electrolysis cell completely meets the performance requirement of the electrolytic aluminum industry for the steel bar.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel production for aluminum electrolytic cells, and in particular relates to a high-conductivity steel bar for aluminum electrolytic cells and a manufacturing method thereof. Background Art

[0002] China is the world's largest producer of electrolytic aluminum, with an output of 43.1 million tons in 2024, ranking first in the world for over 20 consecutive years. However, the electricity consumption per ton of aluminum produced by electrolytic aluminum production is between 13,000 and 13,300 kW / h, and this high power consumption has become a constraint on the industry's development. Cathode steel bars serve as the structural electrodes of the electrolytic aluminum cell and as the conductive connector between the carbon block and the busbar in the cathode system of the electrolytic aluminum cell. They are an important component of the electrolytic aluminum cell's conductive material and are required to have high electrical conductivity and excellent surface quality. The electrical conductivity of cathode steel bars directly affects the power consumption of electrolytic aluminum. Traditional materials are hot-rolled from low-carbon steel such as Q195. However, due to the high levels of residual elements such as carbon, silicon, and manganese, the conductivity fluctuates between 19.1 μΩ·cm and 50.3 μΩ·cm, and their electrical conductivity no longer meets the needs of industry development.

[0003] The difficulties in developing high-conductivity steel rod products for aluminum electrolytic cells are as follows: high-conductivity steel rods for aluminum electrolytic cells require the material to have good electrical conductivity and a resistivity of no more than 11μΩ·cm, and existing conventional materials cannot meet the above requirements; high-conductivity steel rods for aluminum electrolytic cells require the material to have a tensile strength of no less than 265MPa and a yield strength of no less than 140MPa, but in the existing technology, in order to reduce the resistivity, the alloy element content is usually reduced. However, reducing the alloy element content will reduce the material strength, and it is impossible to take into account both the conductivity and strength requirements. Moreover, aluminum electrolytic cell steel rods are usually manufactured by cutting continuous casting billets and hot rolling. Due to the small deformation, the mechanical properties of the material are further reduced, and the strength requirements cannot be met. Summary of the Invention

[0004] In order to solve the above technical problems existing in the prior art, the present invention provides a method for manufacturing a high-conductivity steel bar for an aluminum electrolytic cell, comprising the following steps:

[0005] S1, ingredient design

[0006] The chemical composition of the high-conductivity steel bar for aluminum electrolysis cells is optimized by mass percentage as follows: C≤0.002%, Si≤0.008%, Mn≤0.02%, P≤0.005%, S≤0.003%, Al: 0.01-0.02%, Ti: 0.02-0.05%, B: 0.003-0.01%, O≤0.003%, and the remainder is Fe and unavoidable impurities;

[0007] S2, converter smelting

[0008] The key components of the molten iron fed into the converter are controlled to be: Si≤0.50%, Mn≤0.06%, P≤0.06%, S≤0.0013%. During the converter smelting step, oxygen supply and slag making are used to make the molten steel meet the following composition requirements before tapping: C: 0.02-0.035%, Si≤0.005%, Mn≤0.02%, P≤0.004%, S≤0.0025%, with the remainder being Fe and unavoidable impurities.

[0009] S3, RH refining

[0010] First, decarburization is carried out under high vacuum conditions, the decarburization time is controlled to be 21-23 minutes, the vacuum pressure is controlled to be ≤65Pa, and after decarburization, 1.6-1.8 kg of aluminum is added per ton of molten steel for deoxidation. After the addition of aluminum, ferroboron and ferrotitanium are added for alloying, the amount of ferroboron added is controlled to be 40-45 kg per ton of molten steel, and the amount of ferrotitanium added is controlled to be 50-60 kg per ton of molten steel. After the addition of ferroboron and ferrotitanium, the steel is circulated for 10-15 minutes, and then the vacuum treatment is terminated. In the RH refining step, the RH outgoing station composition is controlled to be: C≤0.002%, Si≤0.008%, Mn≤0.02%, P≤0.005%, S≤0.003%, Al: 0.01-0.02%, Ti: 0.02-0.05%, B: 0.003-0.01%, O≤0.003%, and the rest is Fe and unavoidable impurities;

[0011] S4, slab continuous casting

[0012] Continuous slab casting according to target steel bar dimensions;

[0013] S5, slab longitudinal cutting process

[0014] Cut the continuous casting slab into billets longitudinally according to the hot rolling mill capacity and target steel bar size;

[0015] S6, hot rolled

[0016] The longitudinally cut billet is hot rolled into a steel bar of a specified cross-sectional size by a high-temperature constant temperature rapid rolling method, comprising: (1) first heating the billet to 1230-1250°C with a furnace, keeping the temperature for 2 hours, and then continuing to heat the billet to 1290-1310°C, keeping the temperature for 3 hours; (2) hot rolling the billet into shape according to the required cross-sectional size of the steel bar, controlling the hot rolling start temperature to 1280-1290°C, and controlling the time from the start of rolling to the end of rolling to be ≤3 minutes;

[0017] S7, horizontal cutting of steel bars

[0018] According to the length requirements of the finished steel bars, the hot-rolled steel bars are cut to length horizontally to produce high-conductivity steel bars for aluminum electrolytic cells.

[0019] Furthermore, in the above-mentioned method for manufacturing highly conductive steel bars for aluminum electrolytic cells, in the converter smelting step, no deoxidizer is added during converter tapping. After tapping is completed, a slag-forming agent is added to the ladle, and argon is blown into the ladle for stirring to prevent an increase in the phosphorus content of the molten steel. The main components of the slag-forming agent are controlled to be: CaO: 50-60%, FeO: 25-35%, and the rest are unavoidable impurities.

[0020] Furthermore, in the above-mentioned method for manufacturing a highly conductive steel bar for an aluminum electrolytic cell, when adding aluminum for deoxidation, the aluminum is fine-tuned according to the actual aluminum content in the molten steel with reference to the designed chemical composition of the steel bar.

[0021] Furthermore, in the above-mentioned method for manufacturing high-conductivity steel rods for aluminum electrolytic cells, the main components of ferroboron are controlled to be C≤0.05%, B: 18~21%, and the rest are Fe and inevitable impurities; the main components of ferrotitanium are controlled to be C≤0.03%, Ti: 65~70%, and the rest are Fe and inevitable impurities.

[0022] Furthermore, in the above-mentioned method for manufacturing a highly conductive steel bar for an aluminum electrolytic cell, in the slab continuous casting step, the thickness of the continuously cast slab is controlled to be 220-280 mm, the width is controlled to be 1000-1380 mm, and the length is controlled to be 2500-3600 mm.

[0023] Furthermore, in the above-mentioned method for manufacturing highly conductive steel bars for aluminum electrolytic cells, in the slab longitudinal cutting step, the continuously cast slab is longitudinally cut into 2 to 3 equal parts on average, and the width of the slab after cutting is 460 to 500 mm.

[0024] Furthermore, in the above-mentioned method for manufacturing a highly conductive steel bar for an aluminum electrolytic cell, the length of the highly conductive steel bar for an aluminum electrolytic cell obtained is 1600 to 3000 mm, and the cross-section is a rectangle or square with a side length of (60 to 220 mm) × (60 to 220 mm).

[0025] Furthermore, in the above-mentioned method for manufacturing high-conductivity steel bars for aluminum electrolytic cells, in the hot rolling step, cooling water is not used for cooling the hot rolling process, and an electromagnetic induction heating device is installed at the inlet of the rolling mill to ensure that the billet temperature during hot rolling is uniform and stable within the range of the starting rolling temperature of 1280 to 1290°C.

[0026] In addition, the present invention also provides a high-conductivity steel rod for an aluminum electrolytic cell, which is prepared by the above-mentioned method for manufacturing a high-conductivity steel rod for an aluminum electrolytic cell. The chemical composition of the high-conductivity steel rod for an aluminum electrolytic cell is as follows by mass percentage: C≤0.002%, Si≤0.008%, Mn≤0.02%, P≤0.005%, S≤0.003%, Al: 0.01-0.02%, Ti: 0.02-0.05%, B: 0.003-0.01%, O≤0.003%, and the remainder is Fe and unavoidable impurities. In addition, the high-conductivity steel rod for an aluminum electrolytic cell has a tensile strength of ≥265 MPa, a yield strength of ≥140 MPa, and a resistivity of ≤11 μΩ·cm.

[0027] Furthermore, the length of the high-conductivity steel rod for the aluminum electrolytic cell is 1600-3000 mm, and the cross section is a rectangle or square with a side length of (60-220 mm)×(60-220 mm).

[0028] The high-conductivity steel bar for aluminum electrolytic cells and the manufacturing method thereof of the present invention have the following advantages and beneficial effects:

[0029] (1) The product composition is innovatively designed. The present invention optimizes the chemical composition of the high-conductivity steel bar for aluminum electrolytic cells in terms of mass percentage to be: C≤0.002%, Si≤0.008%, Mn≤0.02%, P≤0.005%, S≤0.003%, Al: 0.01-0.02%, Ti: 0.02-0.05%, B: 0.003-0.01%, O≤0.003%. By strictly limiting the content of harmful elements such as carbon, silicon, manganese, and oxygen and rationally adding beneficial elements such as titanium and boron, good conditions are created for improving the product's electrical conductivity and surface quality as well as improving its mechanical properties. By strictly limiting the content of sulfur and oxygen and adding appropriate amounts of aluminum and titanium for deoxidation, the purity of the steel is improved and the surface quality of the steel bar after hot rolling is improved.

[0030] (2) The hot rolling heating system is innovatively designed. The present invention adopts high-temperature constant-temperature rapid rolling to perform hot rolling processing, which effectively solves the problem of hot rolling cracking and further improves product quality.

[0031] (3) By implementing the present invention, the tensile strength of the steel rod for aluminum electrolytic cells produced is not less than 265 MPa, the yield strength is not less than 140 MPa, and the resistivity is not greater than 11 μΩ·cm. The product has good mechanical properties, good electrical conductivity and surface quality, and has no processing cracking defects. It fully meets the performance requirements of the electrolytic aluminum industry for steel rods for aluminum electrolytic cells. Promoting the present invention in the electrolytic aluminum industry can reduce the DC power consumption of aluminum liquid electrolysis and reduce carbon dioxide emissions, and has good social significance and application prospects. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] The purpose of the present invention is to develop a high-conductivity steel bar for aluminum electrolytic cells and a manufacturing method thereof that takes into account both conductivity and strength according to the needs of the electrolytic aluminum industry. To this end, the present invention adopts the process steps of "converter smelting → RH refining → slab continuous casting → slab longitudinal cutting processing → hot rolling → steel bar transverse fixed-length cutting". Through target composition design, intermediate composition control, and hot rolling heating system innovation, a high-conductivity steel bar for aluminum electrolytic cells with a cross-section of a rectangle or square with a side length of (60 to 220 mm) × (60 to 220 mm) and a length of 1600 to 3000 mm is manufactured. The tensile strength of the steel bar is ≥265 MPa, the yield strength is ≥140 MPa, and the resistivity is ≤11 μΩ·cm, which fully meets the performance requirements of the electrolytic aluminum industry for steel bars for aluminum electrolytic cells.

[0034] Specifically, the method for manufacturing a high-conductivity steel bar for an aluminum electrolysis cell of the present invention comprises the following steps:

[0035] S1, ingredient design

[0036] The chemical composition of high-conductivity steel bars for aluminum electrolytic cells is optimized by mass percentage as follows: C≤0.002%, Si≤0.008%, Mn≤0.02%, P≤0.005%, S≤0.003%, Al: 0.01~0.02%, Ti: 0.02~0.05%, B: 0.003~0.01%, O≤0.003%, and the rest is Fe and unavoidable impurities.

[0037] Chemical composition and product purity are important factors affecting the mechanical properties, electrical conductivity, and surface quality of high-conductivity steel bars for aluminum electrolytic cells. Among them, the content of residual elements such as carbon, silicon, and manganese affects the electrical conductivity of the material. Therefore, the content of the above elements is strictly controlled in the present invention. Low content of elements such as silicon and manganese will lead to low mechanical properties of the material. In order to ensure the mechanical performance indicators, trace amounts of titanium and boron are added in the present invention to improve the mechanical performance indicators by refining the grains and increasing the intergranular strength. Purity seriously affects the surface quality of the steel bar after hot rolling. Therefore, the sulfur and oxygen contents are strictly limited in the present invention, and an appropriate amount of aluminum is added for deoxidation. The trace amount of titanium added also has a certain deoxidation effect.

[0038] S2, converter smelting

[0039] The primary purpose of converter smelting is to remove harmful elements such as carbon, silicon, manganese, phosphorus, and gases from molten steel. The key components of the molten iron entering the converter are controlled to be: Si ≤ 0.50%, Mn ≤ 0.06%, P ≤ 0.06%, and S ≤ 0.0013%. During the converter smelting step, oxygen supply and slag formation are used to achieve the following compositional requirements for tapping: C: 0.02-0.035%, Si ≤ 0.005%, Mn ≤ 0.02%, P ≤ 0.004%, and S ≤ 0.0025%. The remainder is iron and unavoidable impurities.

[0040] No deoxidizer is added during converter tapping. After tapping, a slag-forming agent is added to the ladle, and argon is blown through the ladle to prevent the increase of phosphorus content in the molten steel. The main components of the slag-forming agent are controlled to be: CaO: 50-60%, FeO: 25-35%, and the rest are unavoidable impurities.

[0041] S3, RH refining

[0042] RH refining includes decarburization, deoxidation, and composition adjustment, specifically: (1) After the converter molten steel enters the RH step, it is first decarburized under high vacuum conditions, with the decarburization time controlled at 21 to 23 minutes and the vacuum pressure controlled at ≤65 Pa; (2) After decarburization, 1.6 to 1.8 kg of aluminum is added per ton of molten steel for deoxidation, and the aluminum addition can be fine-tuned according to the actual aluminum content in the molten steel with reference to the designed chemical composition of the steel bar; (3) 3 minutes after the aluminum addition is completed, ferroboron and ferrotitanium are added for alloying, with the amount of ferroboron added controlled at 40 to 45 kg per ton of molten steel and the amount of ferrotitanium added controlled at 50 to 60 kg per ton of molten steel, wherein the main components of ferroboron are controlled at C ≤ 0.05%, B: 18 to 21%, and the rest are Fe and unavoidable impurities; the main components of ferrotitanium are controlled at C ≤ 0.03%, Ti: 65 to 70%, and the rest are Fe and unavoidable impurities; (4) After adding ferroboron and ferrotitanium, the process is circulated for 10 to 15 minutes, and then the vacuum treatment is terminated.

[0043] In the RH refining step, the RH outgoing composition is controlled as follows: C≤0.002%, Si≤0.008%, Mn≤0.02%, P≤0.005%, S≤0.003%, Al: 0.01~0.02%, Ti: 0.02~0.05%, B: 0.003~0.01%, O≤0.003%, and the rest are Fe and unavoidable impurities.

[0044] S4, slab continuous casting

[0045] During the continuous casting process of slabs, the nozzle connection should be well sealed to prevent the molten steel from absorbing air. The thickness of the continuous casting slab is controlled to be 220-280mm, the width is controlled to be 1000-1380mm, and the length is controlled to be 2500-3600mm. Of course, the specific size of the continuous casting slab can be appropriately adjusted according to the target size requirements of the steel bar.

[0046] S5, slab longitudinal cutting process

[0047] The primary purpose of longitudinal slab cutting is to meet the requirements of the hot rolling mill capacity and target bar dimensions. The continuously cast slab is longitudinally cut into two or three equal sections. After slicing, the resulting sections are 220-280 mm thick, 460-500 mm wide, and 2500-3600 mm long.

[0048] S6, hot rolled

[0049] The longitudinally cut billet is hot rolled into a steel bar of a specified cross-sectional size by a high-temperature constant temperature rapid rolling method, specifically comprising: (1) hoisting the longitudinally cut billet to a heating furnace for heating, first heating the billet to 1230-1250°C with the furnace, keeping it warm for 2 hours, and then continuing to heat it to 1290-1310°C, keeping it warm for 3 hours, to ensure that the temperature inside and outside the billet is uniform; (2) hot rolling the billet into shape according to the required cross-sectional size of the steel bar, controlling the hot rolling start temperature to 1280-1290°C, and controlling the time from the start of rolling to the end of rolling to ≤3 minutes, and not using cooling water for cooling during the hot rolling process.

[0050] Furthermore, in the hot rolling step, in order to compensate for the temperature drop loss of the billet after being heated out of the furnace, an electromagnetic induction heating device is installed at the entrance of the rolling mill to ensure that the billet temperature during hot rolling is uniform and stable within the range of the starting rolling temperature of 1280~1290℃.

[0051] S7, horizontal cutting of steel bars

[0052] According to the length requirements of the finished steel bars, the hot-rolled steel bars are cut to a fixed length horizontally by sawing to obtain high-conductivity steel bars for aluminum electrolytic cells with a cross section of a rectangle or square with a side length of (60 to 220 mm) × (60 to 220 mm) and a length of 1600 to 3000 mm.

[0053] Thus, a highly conductive steel bar for aluminum electrolytic cells produced using the above-described method for manufacturing a highly conductive steel bar for aluminum electrolytic cells has the following chemical composition by mass: C ≤ 0.002%, Si ≤ 0.008%, Mn ≤ 0.02%, P ≤ 0.005%, S ≤ 0.003%, Al: 0.01-0.02%, Ti: 0.02-0.05%, B: 0.003-0.01%, O ≤ 0.003%, with the remainder being Fe and unavoidable impurities. Performance testing has shown that the highly conductive steel bar for aluminum electrolytic cells of the present invention has a tensile strength of ≥ 265 MPa, a yield strength of ≥ 140 MPa, and a resistivity of ≤ 11 μΩ·cm.

[0054] Furthermore, the length of the high-conductivity steel rod for the aluminum electrolytic cell is 1600-3000 mm, and the cross section is a rectangle or square with a side length of (60-220 mm)×(60-220 mm).

[0055] The highly conductive steel rod for aluminum electrolysis cells and the method for manufacturing the same are further described below with reference to specific embodiments.

[0056] Example 1

[0057] In Example 1 of the present invention, the chemical composition of the highly conductive steel bar for aluminum electrolytic cells is optimized by mass percentage to be: C: 0.0019%, Si: 0.006%, Mn: 0.019%, P: 0.004%, S: 0.0025%, Al: 0.015%, Ti: 0.035%, B: 0.007%, O: 0.003%, with the remainder being Fe and unavoidable impurities. The highly conductive steel bar for aluminum electrolytic cells is manufactured using the process steps of "converter smelting → RH refining → slab continuous casting → slab longitudinal cutting → hot rolling → transverse cutting of steel bar to length" to produce a rectangular cross-section of 60 mm x 130 mm and a length of 3000 mm. The method for manufacturing the highly conductive steel bar for aluminum electrolytic cells of Example 1 comprises the following steps:

[0058] S11, converter smelting

[0059] The key components of the molten iron entering the converter are: Si: 0.45%, Mn: 0.05%, P: 0.06%, S: 0.0011%. In the converter smelting step, through oxygen supply and slag making, the molten steel composition meets the following requirements and steel is tapped: C: 0.03%, Si: 0.004%, Mn: 0.015%, P: 0.004%, S: 0.0025%, and the rest are Fe and unavoidable impurities.

[0060] No deoxidizer is added during converter tapping. After tapping, a slag-forming agent is added to the ladle, and argon is blown through the ladle to prevent the increase of phosphorus content in the molten steel. The main components of the slag-forming agent are: CaO: 56%, FeO: 30%, and the rest are unavoidable impurities.

[0061] S12, RH refined

[0062] After the converter molten steel enters the RH step, it is first decarburized under high vacuum conditions. The decarburization time is 21 minutes and the vacuum pressure is 50Pa. After decarburization, 1.8 kg of aluminum is added per ton of molten steel for deoxidation. The aluminum can be fine-tuned according to the actual aluminum content in the molten steel with reference to the design chemical composition of the steel bar. 3 minutes after the addition of aluminum, ferroboron and ferrotitanium are added for alloying. The amount of ferroboron added is 45 kg per ton of molten steel and the amount of ferrotitanium added is 60 kg per ton of molten steel. Among them, the main components of ferroboron are C: 0.043% and B: 18%, and the rest are Fe and unavoidable impurities. The main components of ferrotitanium are C: 0.03% and Ti: 65%, and the rest are Fe and unavoidable impurities. After adding ferroboron and ferrotitanium, the cycle is 13 minutes, and then the vacuum treatment is terminated. The RH outgoing composition is: C: 0.0018%, Si: 0.006%, Mn: 0.015%, P: 0.004%, S: 0.0025%, Al: 0.01%, Ti: 0.04%, B: 0.008%, O: 0.003%, and the rest is Fe and unavoidable impurities.

[0063] S13, slab continuous casting

[0064] During the continuous casting process of slabs, the nozzle connection should be well sealed. The thickness of the continuous casting slab is 220mm, the width is 1380mm, and the length is 2500.

[0065] S14, slab longitudinal cutting process

[0066] The continuous casting slab is cut into three equal parts longitudinally. After cutting, the slab has a thickness of 220 mm, a width of 460 mm and a length of 2500 mm.

[0067] S15, hot rolled

[0068] The longitudinally cut billet is hot rolled into a steel bar of specified cross-sectional dimensions by means of high-temperature constant-temperature rapid rolling, specifically comprising: (1) hoisting the longitudinally cut billet to a heating furnace for heating, first heating the billet to 1250°C with the furnace, holding it for 2 hours, then continuing to heat it to 1310°C, holding it for 3 hours, to ensure uniform temperature inside and outside the billet; (2) hot rolling the billet into the required 60mm×130mm rectangular cross-sectional steel bar, with the hot rolling start temperature of 1290°C and the rolling time from the start to the end of the rolling being two minutes and fifty seconds. No cooling water is used for cooling during the hot rolling process. In addition, in order to compensate for the temperature drop loss of the billet after it is heated out of the furnace, an electromagnetic induction heating device is installed at the rolling mill entrance to ensure that the billet temperature is uniform and stable at the start rolling temperature of 1290°C during hot rolling.

[0069] S16, horizontal cutting of steel bars

[0070] According to the requirement of 3000mm finished steel bar length, the hot-rolled steel bars are cut to length horizontally by sawing.

[0071] Thus, using Example 1, a highly conductive steel bar for aluminum electrolytic cells was produced, having a cross-sectional length of 60 mm x 130 mm and a length of 3000 mm. The chemical composition, by mass, was as follows: C: 0.0019%, Si: 0.006%, Mn: 0.019%, P: 0.004%, S: 0.0025%, Al: 0.015%, Ti: 0.035%, B: 0.007%, O: 0.003%, with the remainder being Fe and unavoidable impurities. Performance testing showed that the highly conductive steel bar for aluminum electrolytic cells of Example 1 had a tensile strength of 265 MPa, a yield strength of 140 MPa, and a resistivity of 11 μΩ·cm.

[0072] Example 2

[0073] In Example 2 of the present invention, the chemical composition of the highly conductive steel bar for aluminum electrolytic cells is optimized by mass percentage to be: C: 0.0018%, Si: 0.007%, Mn: 0.02%, P: 0.005%, S: 0.003%, Al: 0.02%, Ti: 0.049%, B: 0.003%, O: 0.0019%, with the remainder being Fe and unavoidable impurities. The highly conductive steel bar for aluminum electrolytic cells is manufactured using the process steps of "converter smelting → RH refining → slab continuous casting → slab longitudinal cutting → hot rolling → steel bar transverse cutting to length" to produce a rectangular cross-section of 110 mm x 180 mm and a length of 1600 mm. The method for manufacturing the highly conductive steel bar for aluminum electrolytic cells of Example 2 comprises the following steps:

[0074] S21, converter smelting

[0075] The key components of the molten iron entering the converter are: Si: 0.5%, Mn: 0.06%, P: 0.053%, S: 0.0013%. In the converter smelting step, through oxygen supply and slag making, the molten steel composition meets the following requirements and steel is tapped: C: 0.035%, Si: 0.005%, Mn: 0.02%, P: 0.0035%, S: 0.0023%, and the rest are Fe and unavoidable impurities.

[0076] No deoxidizer is added during converter tapping. After tapping, a slag-forming agent is added to the ladle, and argon is blown through the ladle to stir the steel to prevent the increase of phosphorus content in the molten steel. The main components of the slag-forming agent are: CaO: 50%, FeO: 35%, and the rest are unavoidable impurities.

[0077] S22, RH refined

[0078] After the converter molten steel enters the RH step, it is first decarburized under high vacuum conditions. The decarburization time is 22 minutes and the vacuum pressure is 59 Pa. After decarburization, 1.6 kg of aluminum is added per ton of molten steel for deoxidation. The aluminum can be fine-tuned according to the actual aluminum content in the molten steel with reference to the design chemical composition of the steel bar. 3 minutes after the addition of aluminum, ferroboron and ferrotitanium are added for alloying. The amount of ferroboron added is 40 kg per ton of molten steel and the amount of ferrotitanium added is 50 kg per ton of molten steel. Among them, the main components of ferroboron are C: 0.045% and B: 21%, and the rest are Fe and unavoidable impurities. The main components of ferrotitanium are C: 0.025% and Ti: 70%, and the rest are Fe and unavoidable impurities. After adding ferroboron and ferrotitanium, the cycle is 10 minutes, and then the vacuum treatment is terminated. The RH outgoing composition is: C: 0.0015%, Si: 0.008%, Mn: 0.02%, P: 0.005%, S: 0.003%, Al: 0.02%, Ti: 0.05%, B: 0.003%, O: 0.0019%, and the rest is Fe and unavoidable impurities.

[0079] S23, slab continuous casting

[0080] During the continuous casting process of slabs, the nozzle connection should be well sealed. The thickness of the continuous casting slab is 250mm, the width is 1000mm, and the length is 3600.

[0081] S24, slab longitudinal cutting process

[0082] The continuous casting slab is cut into two equal parts longitudinally. After cutting, the slab has a thickness of 250 mm, a width of 500 mm and a length of 3600 mm.

[0083] S25, hot rolled

[0084] The longitudinally cut billet is hot rolled into a steel bar of specified cross-sectional dimensions by means of high-temperature constant-temperature rapid rolling, specifically including: (1) hoisting the longitudinally cut billet to a heating furnace for heating, first heating the billet to 1230°C with the furnace, keeping it warm for 2 hours, and then continuing to heat it to 1290°C and keeping it warm for 3 hours to ensure that the temperature inside and outside the billet is uniform; (2) hot rolling the billet into the required 110mm×180mm rectangular cross-sectional steel bar, with the hot rolling start temperature of 1283°C and the rolling time from the start to the end of the rolling being three minutes. No cooling water is used for cooling during the hot rolling process. In addition, in order to compensate for the temperature drop loss of the billet after it is heated out of the furnace, an electromagnetic induction heating device is installed at the rolling mill entrance to ensure that the billet temperature is uniform and stable at the start rolling temperature of 1283°C during hot rolling.

[0085] S26, horizontal cutting of steel bars

[0086] According to the requirement of 1600mm finished steel bar length, the hot-rolled steel bars are cut to length horizontally by sawing.

[0087] Thus, using Example 2, a highly conductive steel bar for aluminum electrolytic cells was produced, having a cross-sectional length of 110 mm x 180 mm and a length of 1600 mm. The chemical composition, by mass percentage, was as follows: C: 0.0018%, Si: 0.007%, Mn: 0.02%, P: 0.005%, S: 0.003%, Al: 0.02%, Ti: 0.049%, B: 0.003%, O: 0.0019%, with the remainder being Fe and unavoidable impurities. Performance testing showed that the highly conductive steel bar for aluminum electrolytic cells of Example 2 had a tensile strength of 280 MPa, a yield strength of 153 MPa, and a resistivity of 10.8 μΩ·cm.

[0088] Example 3

[0089] In Example 3 of the present invention, the chemical composition of the highly conductive steel bar for aluminum electrolysis cells is optimized by mass percentage to be: C: 0.002%, Si: 0.008%, Mn: 0.018%, P: 0.004%, S: 0.0029%, Al: 0.018%, Ti: 0.02%, B: 0.009%, O: 0.0023%, with the remainder being Fe and unavoidable impurities. The highly conductive steel bar for aluminum electrolysis cells is manufactured using the process steps of "converter smelting → RH refining → slab continuous casting → slab longitudinal cutting → hot rolling → steel bar transverse cutting to size" to produce a rectangular cross-section of 110 mm x 220 mm and a length of 2100 mm. The method for manufacturing the highly conductive steel bar for aluminum electrolysis cells of Example 3 comprises the following steps:

[0090] S31, converter smelting

[0091] The key components of the molten iron entering the converter are: Si: 0.4%, Mn: 0.05%, P: 0.056%, S: 0.0012%. In the converter smelting step, through oxygen supply and slag making, the molten steel composition meets the following requirements and steel is tapped: C: 0.02%, Si: 0.004%, Mn: 0.019%, P: 0.0038%, S: 0.0022%, and the rest are Fe and unavoidable impurities.

[0092] No deoxidizer is added during converter tapping. After tapping, a slag-forming agent is added to the ladle, and argon is blown through the ladle to prevent the increase of phosphorus content in the molten steel. The main components of the slag-forming agent are: CaO: 60%, FeO: 25%, and the rest are unavoidable impurities.

[0093] S32, RH refined

[0094] After the converter molten steel enters the RH step, it is first decarburized under high vacuum conditions. The decarburization time is 23 minutes and the vacuum pressure is 65Pa. After decarburization, 1.75 kg of aluminum is added per ton of molten steel for deoxidation. The aluminum addition can be fine-tuned according to the actual aluminum content in the molten steel with reference to the design chemical composition of the steel bar. 3 minutes after the addition of aluminum, ferroboron and ferrotitanium are added for alloying. The amount of ferroboron added is 43 kg per ton of molten steel and the amount of ferrotitanium added is 55 kg per ton of molten steel. Among them, the main components of ferroboron are C: 0.05% and B: 19%, and the rest are Fe and unavoidable impurities. The main components of ferrotitanium are C: 0.029% and Ti: 68%, and the rest are Fe and unavoidable impurities. After adding ferroboron and ferrotitanium, the cycle is 15 minutes, and then the vacuum treatment is terminated. The RH outgoing composition is: C: 0.002%, Si: 0.007%, Mn: 0.019%, P: 0.004%, S: 0.0028%, Al: 0.016%, Ti: 0.02%, B: 0.01%, O: 0.0025%, and the rest is Fe and unavoidable impurities.

[0095] S33, slab continuous casting

[0096] During the continuous casting process of slabs, the nozzle connection should be well sealed. The thickness of the continuous casting slab is 280mm, the width is 1000mm, and the length is 3000.

[0097] S34, slab longitudinal cutting process

[0098] The continuous casting slab is cut into two equal parts longitudinally. After cutting, the slab has a thickness of 280 mm, a width of 500 mm and a length of 3000 mm.

[0099] S35, hot rolled

[0100] The longitudinally cut billet is hot rolled into a steel bar of specified cross-sectional dimensions by means of high-temperature constant-temperature rapid rolling, specifically including: (1) hoisting the longitudinally cut billet to a heating furnace for heating. First, the billet is heated to 1235°C with the furnace, kept at this temperature for 2 hours, and then continued to be heated to 1300°C and kept at this temperature for 3 hours to ensure that the temperature inside and outside the billet is uniform; (2) the billet is hot rolled into a 110mm×220mm rectangular cross-sectional steel bar according to the requirements. The hot rolling start temperature is 1280°C, and the rolling time from the start to the end of the rolling is 2 minutes and 30 seconds. No cooling water is used for cooling during the hot rolling process. In addition, in order to compensate for the temperature drop loss of the billet after it is heated out of the furnace, an electromagnetic induction heating device is installed at the rolling mill entrance to ensure that the billet temperature is uniform and stable at the start rolling temperature of 1280°C during hot rolling.

[0101] S36, horizontal cutting of steel bars

[0102] According to the requirement of 2100mm finished steel bar length, the hot-rolled steel bars are cut to length horizontally by sawing.

[0103] Thus, using Example 3, a highly conductive steel bar for aluminum electrolytic cells was produced, having a cross-sectional length of 110 mm x 220 mm and a length of 2100 mm. The chemical composition, by mass percentage, was as follows: C: 0.002%, Si: 0.008%, Mn: 0.018%, P: 0.004%, S: 0.0029%, Al: 0.018%, Ti: 0.02%, B: 0.009%, O: 0.0023%, with the remainder being Fe and unavoidable impurities. Performance testing showed that the highly conductive steel bar for aluminum electrolytic cells of Example 3 had a tensile strength of 270 MPa, a yield strength of 150 MPa, and a resistivity of 10.3 μΩ·cm.

[0104] In summary, the present invention utilizes the following process steps: converter smelting → RH refining → slab continuous casting → slab longitudinal cutting → hot rolling → steel bar transverse cutting to length. Through target composition design, intermediate composition control, and innovative hot rolling heating systems, a highly conductive steel bar for aluminum electrolysis cells is manufactured that balances conductivity and strength. Compared to the prior art, the present invention provides the following advantages and benefits:

[0105] (1) The product composition is innovatively designed. The present invention optimizes the chemical composition of the high-conductivity steel bar for aluminum electrolytic cells in terms of mass percentage to be: C≤0.002%, Si≤0.008%, Mn≤0.02%, P≤0.005%, S≤0.003%, Al: 0.01-0.02%, Ti: 0.02-0.05%, B: 0.003-0.01%, O≤0.003%. By strictly limiting the content of harmful elements such as carbon, silicon, manganese, and oxygen and rationally adding beneficial elements such as titanium and boron, good conditions are created for improving the product's electrical conductivity and surface quality as well as improving its mechanical properties. By strictly limiting the content of sulfur and oxygen and adding appropriate amounts of aluminum and titanium for deoxidation, the purity of the steel is improved and the surface quality of the steel bar after hot rolling is improved.

[0106] (2) An innovative hot rolling heating system is designed. The present invention adopts a high-temperature constant-temperature rapid rolling method for hot rolling processing, which effectively solves the problem of hot rolling cracking and further improves product quality.

[0107] (3) By implementing the present invention, the tensile strength of the steel rod for aluminum electrolytic cells produced is ≥265MPa, the yield strength is ≥140MPa, and the resistivity is ≤11μΩ·cm. The product has good mechanical properties, good electrical conductivity and surface quality, and has no processing cracking defects. It fully meets the performance requirements of the electrolytic aluminum industry for steel rods for aluminum electrolytic cells. Promoting the present invention in the electrolytic aluminum industry can reduce the DC power consumption of aluminum liquid electrolysis and reduce carbon dioxide emissions, and has good social significance and application prospects.

[0108] It should be noted that, unless otherwise specified, the noun terms herein have the meanings commonly understood by those skilled in the art. Moreover, when a numerical range is disclosed herein, the above range is deemed to be continuous and includes the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. In addition, when multiple range description features are provided, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0109] It should also be noted that, in this article, the term "comprise" or any other variation thereof is intended to cover non-exclusive inclusion, so that an article or device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such article or device.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method for manufacturing a high-conductivity steel bar for an aluminum electrolytic cell, characterized in that: The steps include: S1, ingredient design The chemical composition of the high-conductivity steel bar for aluminum electrolysis cells is optimized by mass percentage as follows: C≤0.002%, Si≤0.008%, Mn≤0.02%, P≤0.005%, S≤0.003%, Al: 0.01-0.02%, Ti: 0.02-0.05%, B: 0.003-0.01%, O≤0.003%, and the remainder is Fe and unavoidable impurities; S2, converter smelting The key components of the molten iron fed into the converter are controlled to be: Si≤0.50%, Mn≤0.06%, P≤0.06%, S≤0.0013%. During the converter smelting step, oxygen supply and slag making are used to make the molten steel meet the following composition requirements before tapping: C: 0.02-0.035%, Si≤0.005%, Mn≤0.02%, P≤0.004%, S≤0.0025%, with the remainder being Fe and unavoidable impurities. S3, RH refining First, decarburization is carried out under high vacuum conditions, the decarburization time is controlled to be 21-23 minutes, the vacuum pressure is controlled to be ≤65Pa, and after decarburization, 1.6-1.8 kg of aluminum is added per ton of molten steel for deoxidation. After the addition of aluminum, ferroboron and ferrotitanium are added for alloying, the amount of ferroboron added is controlled to be 40-45 kg per ton of molten steel, and the amount of ferrotitanium added is controlled to be 50-60 kg per ton of molten steel. After the addition of ferroboron and ferrotitanium, the steel is circulated for 10-15 minutes, and then the vacuum treatment is terminated. In the RH refining step, the RH outgoing station composition is controlled to be: C≤0.002%, Si≤0.008%, Mn≤0.02%, P≤0.005%, S≤0.003%, Al: 0.01-0.02%, Ti: 0.02-0.05%, B: 0.003-0.01%, O≤0.003%, and the rest is Fe and unavoidable impurities; S4, slab continuous casting Continuous slab casting according to target steel bar dimensions; S5, slab longitudinal cutting process Cut the continuous casting slab into billets longitudinally according to the hot rolling mill capacity and target steel bar size; S6, hot rolled The longitudinally cut billet is hot rolled into a steel bar of a specified cross-sectional size by a high-temperature constant temperature rapid rolling method, comprising: (1) first heating the billet to 1230-1250°C with a furnace, keeping the temperature for 2 hours, and then continuing to heat the billet to 1290-1310°C, keeping the temperature for 3 hours; (2) hot rolling the billet into shape according to the required cross-sectional size of the steel bar, controlling the hot rolling start temperature to 1280-1290°C, and controlling the time from the start of rolling to the end of rolling to be ≤3 minutes; S7, horizontal cutting of steel bars According to the length requirements of the finished steel bars, the hot-rolled steel bars are cut to length horizontally to produce high-conductivity steel bars for aluminum electrolytic cells.

2. The method for manufacturing a high-conductivity steel bar for an aluminum electrolytic cell according to claim 1, wherein: In the converter smelting step, no deoxidizer is added during converter tapping. After tapping, a slag-forming agent is added to the ladle, and argon is blown into the ladle for stirring to prevent the increase of the phosphorus content of the molten steel. The main components of the slag-forming agent are controlled to be: CaO: 50-60%, FeO: 25-35%, and the rest are unavoidable impurities.

3. The method for manufacturing a high-conductivity steel bar for an aluminum electrolytic cell according to claim 1, wherein: In the RH refining step, when adding aluminum for deoxidation, aluminum is added for fine adjustment according to the actual aluminum content in the molten steel with reference to the designed chemical composition of the steel bar.

4. The method for manufacturing a high-conductivity steel bar for an aluminum electrolytic cell according to claim 1, wherein: In the RH refining step, the main components of ferroboron are controlled to be C≤0.05%, B: 18~21%, and the rest are Fe and inevitable impurities; the main components of ferrotitanium are controlled to be C≤0.03%, Ti: 65~70%, and the rest are Fe and inevitable impurities.

5. The method for manufacturing a high-conductivity steel bar for an aluminum electrolytic cell according to claim 1, wherein: In the slab continuous casting step, the thickness of the continuously cast slab is controlled to be 220-280 mm, the width is controlled to be 1000-1380 mm, and the length is controlled to be 2500-3600 mm.

6. The method for manufacturing a high-conductivity steel bar for an aluminum electrolytic cell according to claim 5, wherein: In the slab longitudinal cutting process step, the continuous casting slab is longitudinally cut into 2 to 3 equal parts on average, and the width of the slab after cutting is 460 to 500 mm.

7. The method for manufacturing a high-conductivity steel bar for an aluminum electrolytic cell according to claim 6, wherein: The length of the prepared high-conductivity steel rod for aluminum electrolytic cell is 1600-3000 mm, and the cross section is a rectangle or square with a side length of (60-220 mm)×(60-220 mm).

8. The method for manufacturing a high-conductivity steel bar for an aluminum electrolytic cell according to claim 1, wherein: During the hot rolling step, cooling water is not used for cooling, and an electromagnetic induction heating device is installed at the rolling mill entrance to ensure that the billet temperature is uniform and stable within the range of the starting rolling temperature of 1280 to 1290°C during hot rolling.

9. A high-conductivity steel bar for aluminum electrolysis cell, characterized in that: The highly conductive steel rod for an aluminum electrolytic cell is prepared by the method for manufacturing a highly conductive steel rod for an aluminum electrolytic cell according to any one of claims 1 to 8. The chemical composition of the highly conductive steel rod for an aluminum electrolytic cell is as follows, by mass percentage: C ≤ 0.002%, Si ≤ 0.008%, Mn ≤ 0.02%, P ≤ 0.005%, S ≤ 0.003%, Al: 0.01-0.02%, Ti: 0.02-0.05%, B: 0.003-0.01%, O ≤ 0.003%, and the remainder is Fe and unavoidable impurities. The highly conductive steel rod for an aluminum electrolytic cell has a tensile strength ≥ 265 MPa, a yield strength ≥ 140 MPa, and a resistivity ≤ 11 μΩ·cm.

10. The high-conductivity steel bar for aluminum electrolysis cell according to claim 9, characterized in that: The length of the high-conductivity steel rod for the aluminum electrolytic cell is 1600-3000 mm, and the cross section is a rectangle or square with a side length of (60-220 mm)×(60-220 mm).