A method for manufacturing electrolytic aluminum cathode flat steel

Abstract

The invention discloses a manufacturing method of electrolytic aluminum cathode flat steel, which can fully meet the aluminum plant's demand for high-conductivity cathode flat steel by pre-treating molten iron, selecting low-phosphorus, low-manganese, and low-sulfur refined scrap steel, smelting by converter double slag method, converter over-blowing treatment, double-stop slag tapping, refining oxide slag system, special covering agent and protective slag for low-carbon steel for continuous casting, reducing secondary oxidation, controlling the rolling temperature to avoid the red-brittle temperature range and other process guarantee measures. The DZ10 cathode flat steel manufactured by the method adopts reasonable chemical composition design and deep demanganese and deep dephosphorization core process technology, and its ingot component purity reaches 3.2N level, which can effectively reduce the resistivity of cathode steel bars; the content of non-metallic inclusions is low, and the purity of steel is high; the low-multiple organization, gas content, and mechanical properties of the finished steel meet the standards, and the stable production of low-cost ultra-pure electrolytic aluminum cathode flat steel is realized, thereby meeting the needs of the electrolytic aluminum industry.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical material production and processing, and specifically relates to a method for manufacturing electrolytic aluminum cathode flat steel. Background Art

[0002] Electrolytic aluminum cathode flat steel is also called cathode flat steel or cathode steel bar, which is mainly used as the cathode of the electrolytic cell in the electrolytic aluminum industry. Aluminum is produced by electrolysis, and the equipment is an aluminum electrolytic cell. The aluminum electrolytic cell includes a cell body, anode equipment, and cathode equipment. The cathode equipment is mainly composed of cathode carbon blocks and cathode flat steel. The cathode flat steel is embedded in the carbon block after processing, which can evenly distribute the current, improve the horizontal current of the aluminum liquid, achieve low-voltage production, and reduce the DC power consumption of electrolytic aluminum. Since the power consumption cost of the electrolytic aluminum industry accounts for a large proportion, accounting for about 40% of the total cost of electrolytic aluminum enterprises, with the increase of electrolytic aluminum production capacity, in order to further reduce the electricity cost of enterprises and the requirements of energy conservation, emission reduction and consumption reduction, electrolytic aluminum plants are gradually developing in the direction of large current and large trough. At the same time, in order to reduce consumption, materials with improved conductivity, high purity, and better conductive properties will be the future development trend. At present, the main materials of cathode steel bars produced are Q195 and SAE1006, with a resistivity of ≤0.13μΩ·m at 20℃, which cannot meet the needs of cost reduction and consumption reduction in the electrolytic aluminum industry. Summary of the invention

[0003] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a method for manufacturing electrolytic aluminum cathode flat steel. The electrolytic aluminum cathode flat steel DZ10 produced by the method is an ultra-low carbon, ultra-low manganese, ultra-low sulfur and phosphorus steel grade with high purity and excellent performance. The resistivity at 20°C is ≤0.10μΩ·m, which can effectively reduce the resistivity, thereby reducing the electricity consumption cost of electrolytic aluminum enterprises and meeting the needs of the electrolytic aluminum industry.

[0004] In order to achieve the above invention purpose, the present invention provides a manufacturing method for producing electrolytic aluminum cathode flat steel by converter smelting process. Through molten iron pretreatment, selection of low-phosphorus, low-manganese, low-sulfur refined scrap steel, converter "double slag method" smelting, converter "overblowing" treatment, double-stop slag tapping, refined oxide slag system, special covering agent and protective slag for low-carbon steel for continuous casting, reduction of secondary oxidation, control of rolling temperature to avoid red brittle temperature range and other process guarantee measures, the manufactured electrolytic aluminum cathode flat steel DZ10 can fully meet the aluminum plant's demand for high conductivity cathode flat steel.

[0005] A method for manufacturing electrolytic aluminum cathode flat steel, the method comprising the following steps: blast furnace molten iron → molten iron pretreatment → 180t converter smelting → LF external refining → RH vacuum degassing → continuous casting slab → slab cutting → walking beam heating furnace heating → high-pressure water descaling → rolling → cooling → finishing → inspection → warehousing.

[0006] The composition of the molten steel in the step is controlled by mass percentage to be [C]≤0.008%; [Mn]≤0.03%; [Si]≤0.006%; [P]≤0.012%; [S]≤0.030%; [Alt]≤0.020%; the remainder is iron and unavoidable impurities.

[0007] A manufacturing method of the above-mentioned electrolytic aluminum cathode flat steel, further, the raw and auxiliary materials require that the molten iron temperature is ≥1300°C, and the main components of the molten iron are [Mn]≤0.15%; [S]≤0.035%; [Ti]≤0.050%. Low-sulfur scrap steel or hanging rolled material is used, with a total scrap steel amount of 20 to 25 tons, and low-carbon steel or ultra-low-carbon steel is produced in one batch before converter smelting for furnace washing.

[0008] In the above technical solution, further, in the molten iron pretreatment process, the molten iron [S] after the pretreatment is ≤ 0.0025%, and the slag is skimmed off.

[0009] In the above technical scheme, further, in the converter smelting process, the converter double blowing smelting adopts the double slag method for dephosphorization and demanganese operation, the first slag making and slag discharge volume is greater than 2 / 3, after the normal oxygen blowing is completed, the spot blowing is carried out after calming for 2 minutes, the spot blowing time is 40 seconds to 60 seconds, the converter end oxygen ≥ 0.0700%, the end temperature > 1670℃, the end [C] ≤ 0.04%, [Mn] ≤ 0.04%, [P] ≤ 0.008%, [S] ≤ 0.005%. Pay attention to the cleaning of the ladle, there must be no residual steel and residue in the ladle, use ultra-low carbon ladle, the front and rear slide blocks are used for steel tapping, slag is strictly prohibited, and steel tapping is not deoxidized.

[0010] In the above technical scheme, further, in the LF refining process, the temperature is raised to slag, the temperature meets the RH requirements, and 6-10 kg / t of lime is added for deep manganese removal without deoxidation. The LF argon post-temperature is 1630±5°C, and the RH argon pre-temperature is 1620±5°C. RH decarburization is performed after [Mn], [P], and [S] meet the internal control requirements.

[0011] In the above technical scheme, further, in the RH refining process, the last batch of materials in the RH tank washing heat is aluminum balls (manganese alloy is not allowed), deep decarburization for 10 to 15 minutes, and aluminum particles are used for deoxidation after decarburization to ensure that the free oxygen content in the steel is less than 0.0060%, the temperature after RH argon is 1610±5℃, and other components are not adjusted. The cycle time is ≥15 minutes, the net cycle is ≥6 minutes, and no calcium treatment is performed.

[0012] In the above technical solution, further, in the continuous casting process, the tundish superheat is controlled at 35±5℃, and the casting speed is 1.0 m / min. The whole process is protected casting, the mold protection slag uses ultra-low carbon protection slag, and the tundish slag uses carbon-free tundish slag. The head and tail of the ingot are cut, each 2 meters.

[0013] In the above technical solution, further, in the heating process, heating is carried out by a step-beam heating furnace, and the heating temperature is 1170-1190° C.; the total heating time is ≥180 minutes.

[0014] In the above technical solution, further, in the rolling process, the cooling water strength of the rolling mill groove is adjusted before rolling to avoid the cracks caused by too fast cooling of the corners of the billet during rolling. The starting rolling temperature is ≥1130℃, and the final rolling temperature is ≥960℃. The heating temperature is adjusted at any time according to the starting rolling temperature during the production process.

[0015] In the above technical solution, further, in the cooling process, the steel cooling bed is air-cooled, and the temperature of the lower cooling bed is ≤200°C.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] ① The purity of the ingot composition reaches 3.2N level (i.e. 99.92%), which can effectively reduce the resistivity of the cathode steel bar, thereby reducing the electricity consumption cost of the electrolytic aluminum enterprise and meeting the needs of the electrolytic aluminum industry.

[0018] ②The content of non-metallic inclusions is low and the steel purity is high.

[0019] ③The macrostructure, gas content and mechanical properties of the finished steel meet the user's requirements. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific examples, but the present invention is not limited in any way. To avoid redundant description, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0021] Example

[0022] A method for manufacturing electrolytic aluminum cathode flat steel DZ10, the method comprising the following steps: blast furnace molten iron→molten iron pretreatment→180t converter smelting→LF refining outside the furnace→RH vacuum degassing→continuous casting slab→slab cutting→walking beam heating furnace heating→high-pressure water descaling→rolling→cooling→finishing→inspection→warehousing.

[0023] The composition of the molten steel in the step is controlled by mass percentage to be [C]≤0.008%; [Mn]≤0.03%; [Si]≤0.006%; [P]≤0.012%; [S]≤0.030%; [Alt]≤0.020%; the remainder is iron and unavoidable impurities.

[0024] The specific implementation steps of manufacturing electrolytic aluminum cathode flat steel DZ10 using the technical solution of the present invention are as follows:

[0025] 1. Molten iron into the furnace

[0026] Molten iron temperature: 1322℃, main molten iron components are [C]: 4.25%, [Mn]: 0.149%, [Si]: 0.39%, [P]: 0.097%, [S]: 0.041%, [Ti]: 0.022%.

[0027] 2. Hot metal pretreatment

[0028] 177.7kg magnesium powder, 694.6kg desulfurization powder, 2.3 tons of slag removal, after treatment [S]: 0.002%.

[0029] 3. Converter smelting

[0030] The scrap steel used is low-sulfur scrap steel with an addition amount of 24 tons. Converter double blowing smelting, large flow oxygen blowing, oxygen flow rate is 40000Nm 3 / h. 3 tons of lime are added in the first blowing, and the slag is discharged after 3 minutes and 25 seconds of blowing. 3.5 tons of lime are added in the second blowing, and the blowing is repeated for 9 minutes and 20 seconds. After the blowing is completed, the temperature is measured and samples are taken, and then the spot blowing is performed for 58 seconds. 500kg of ladle ash is added during the steelmaking process. Double-block slag steelmaking. The binary basicity R of the slag is 4.3. The final oxygen of the converter is 0.0609%, the final temperature is 1644℃, the final [C]: 0.048%, [Mn]: 0.066%, [P]: 0.012%, [S]: 0.0027%.

[0031] 4. LF refining outside the furnace

[0032] The LF treatment cycle was 52 minutes. Before LF treatment, the temperature of the molten steel was 1558°C and the oxygen content of the molten steel was 0.0809%. During the first heating process, 1000 kg of lime was added in batches, and the temperature was 1559°C after heating. During the second and third heating processes, 200 kg of lime was added, and the slag was sticky. After LF treatment, the temperature of the molten steel was 1626°C, the oxygen content of the molten steel was 0.0663%, the binary basicity R of the slag was 12, and the RH vacuum decarburization was performed.

[0033] 5. RH refining

[0034] The RH treatment cycle is 35 minutes. Before RH treatment, the temperature of the molten steel is 1626℃ and the oxygen content is 0.0569%. After the valve is opened, it enters the deep decarburization stage. After 13 minutes, the temperature of the molten steel is 1579℃ and the oxygen content is 0.05064%. The temperature rise oxygen content is 120Nm 3 After heating, the temperature was measured at 1598℃, oxygen 0.0326%, and the secondary heating oxygen 40Nm 3 After direct deoxidation, the temperature was measured at 1610°C and the aluminum value was 0.004%. 34kg of aluminum was added and the net circulation was repeated after 6 minutes. After RH treatment, the temperature of the molten steel was 1602°C and the aluminum value was 0.014%.

[0035] 6. Continuous casting

[0036] The average overheating degree of the tundish is 35℃, the temperature of the ladle is 1611℃, the water content of the secondary cooling is 1.1NL / Kg, the casting cycle is 40 minutes, the pulling speed is 0.8m / min, the specifications of the continuous casting billet are 230mm×1290mm, the billet cutting length is 7600mm, and the head and tail of the billet are cut off by 2 meters each. The whole process is protected casting, and the crystallizer protective slag uses ultra-low carbon protective slag. The billet cutting adopts flame cutting. After the continuous casting billet is piled and cooled, it is longitudinally cut into strips and transferred to the rolling process.

[0037] 7. Heating

[0038] The heating was carried out in a walking beam heating furnace at a temperature of 1180°C and a total heating time of 330 minutes.

[0039] 8. Rolling

[0040] The 1150mm BD billet mill was used for billet opening, high-pressure water dephosphorization was put into normal operation, and the billet was rolled for 3 passes, with the starting rolling temperature of 1130-1170℃, and then passed through 3 850 large bar continuous rolling mills, and then entered 3 480 medium bar continuous rolling mills for rolling, the mill cooling water was closed by 50%, the medium bar inlet temperature was 1090℃, the final rolling temperature was 980℃, and the production specification was 180mm×130mm. No crack defects were found during the production process.

[0041] 9. Cooling

[0042] The steel is air-cooled, and the lower cooling bed temperature is 130℃.

[0043] The chemical composition of the electrolytic aluminum cathode flat steel DZ10 produced in the embodiment is C: 0.002%, Mn: 0.02%, Si: 0.002%, P: 0.004%, S: 0.004%, Cr: 0.012%, Mo: 0.003%, Ti: 0.0003%, Cu: 0.006%, Ni: 0.004%, Nb: 0.0011%, Alt: 0.014%, V: 0.0016%, B: 0.0003%, Ca: 0.0001%, W: 0.0026%.

[0044] The macroscopic inspection results of the finished product of the embodiment are shown in Table 1. As can be seen from Table 1, the steel structure has good density.

[0045] Table 1 Results of macroscopic examination of finished product of Example

[0046]

[0047] The non-metallic inclusion test results of the finished product of the embodiment are shown in Table 2. As can be seen from Table 2, the steel material has high purity.

[0048] Table 2 Test results of non-metallic inclusions in finished products of the embodiment

[0049]

[0050]

[0051] The mechanical properties test results of the finished product of the embodiment are shown in Table 3. As can be seen from Table 3, the mechanical properties meet the standard requirements.

[0052] Table 3 Mechanical properties test results of finished products of the embodiment

[0053]

[0054] The gas test results of the finished product of the embodiment are shown in Table 4. As can be seen from Table 4, the harmful elements in the steel are low.

[0055] Table 4 Gas test results of finished products of the embodiment

[0056]

[0057] The resistivity test result of the finished product of the embodiment is: 20°C resistivity: 0.10 μΩ·m. It can meet the cost reduction and consumption reduction needs of the electrolytic aluminum industry.

[0058] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for manufacturing electrolytic aluminum cathode flat steel, characterized in that: The method comprises the following steps: blast furnace molten iron→molten iron pretreatment→180t converter smelting→LF refining outside the furnace→RH vacuum degassing→continuous casting slab→slab cutting→walking beam heating furnace heating→high pressure water descaling→rolling→cooling→finishing→inspection→warehousing; In the converter smelting process, the converter double blowing smelting adopts the double slag method for dephosphorization and demanganese operation. The first slag making and slag discharge volume is greater than 2 / 3. After the normal oxygen blowing is completed, the spot blowing is carried out after calming for 2 minutes. The spot blowing time is 40 to 60 seconds. The converter end oxygen ≥ 0.0700%, the end temperature > 1670℃, the end [C] ≤ 0.04%, [Mn] ≤ 0.04%, [P] ≤ 0.008%, [S] ≤ 0.005%; In the LF refining process, the temperature is raised to slag, and when the temperature meets the RH requirements, 6-10 kg / t of lime is added for deep manganese removal without deoxidation; the temperature after LF argon is 1630±5℃, and the temperature before RH argon is 1620±5℃; RH decarburization is carried out after [Mn], [P], and [S] meet the internal control requirements; In the RH vacuum degassing process, the last batch of materials in the RH tank washing furnace is aluminum balls, and manganese alloy is not allowed to be used; deep decarburization takes 10 to 15 minutes, and aluminum particles are used for deoxidation after decarburization to make the free oxygen content in the steel less than 0.0060%, the temperature after RH argon is 1610±5℃, the cycle time is ≥15min, the net cycle is ≥6min, and no calcium treatment is performed; In the continuous casting process, the tundish superheat is controlled at 35±5℃, and the casting speed is 1.0m / min; the whole process is protected casting, the mold protection slag uses ultra-low carbon protection slag, and the tundish slag uses carbon-free tundish slag; the head and tail of the ingot are cut, each 2m; In the heating process, a walking beam heating furnace is used for heating, the heating temperature is 1170℃~1190℃, and the total heating time is ≥180min; In the rolling and cooling process, the starting rolling temperature is ≥1130℃, and the final rolling temperature is ≥960℃; the steel cooling bed is air-cooled, and the lower cooling bed temperature is ≤200℃; The chemical composition of the electrolytic aluminum cathode flat steel manufactured by the method is C: 0.002%, Mn: 0.02%, Si: 0.002%, P: 0.004%, S: 0.004%, Cr: 0.012%, Mo: 0.003%, Ti: 0.0003%, Cu: 0.006%, Ni: 0.004%, Nb: 0.0011%, Alt: 0.014%, V: 0.0016%, B: 0.0003%, Ca: 0.0001%, W: 0.0026%; Mechanical properties of the electrolytic aluminum cathode flat steel R eH Not less than 170MPa, R m Not less than 380MPa; resistivity at 20℃ ≤0.10μΩ·m.

2. The manufacturing method according to claim 1, characterized in that: The composition of the molten steel in the method steps is controlled by mass percentage to be [C]≤0.008%; [Mn]≤0.03%; [Si]≤0.006%; [P]≤0.012%; [S]≤0.030%; [Alt]≤0.020%; the remainder is iron and unavoidable impurities.

3. The manufacturing method according to claim 1, characterized in that: Requirements for raw and auxiliary materials: molten iron temperature ≥1300℃, main components of molten iron: [Mn]≤0.15%; [S]≤0.035%; [Ti]≤0.050%.

4. The manufacturing method according to claim 1, characterized in that: In the molten iron pretreatment process, after pretreatment, the molten iron [S] is ≤ 0.0025%, and the slag is skimmed off.

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