CN118006863A - Utilization method of ultralow-carbon steel casting residue direct-return ladle - Google Patents
Utilization method of ultralow-carbon steel casting residue direct-return ladle Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 65
- 229910000975 Carbon steel Inorganic materials 0.000 title claims description 7
- 239000010962 carbon steel Substances 0.000 title claims description 7
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 127
- 239000010959 steel Substances 0.000 claims abstract description 127
- 239000002893 slag Substances 0.000 claims abstract description 106
- 238000005261 decarburization Methods 0.000 claims abstract description 47
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 36
- 238000010079 rubber tapping Methods 0.000 claims abstract description 21
- 229910052786 argon Inorganic materials 0.000 claims abstract description 18
- 238000007664 blowing Methods 0.000 claims abstract description 18
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- 238000007872 degassing Methods 0.000 claims description 8
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- 239000007789 gas Substances 0.000 claims description 6
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 4
- 239000003595 mist Substances 0.000 claims description 4
- 230000008719 thickening Effects 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 3
- 229910001209 Low-carbon steel Inorganic materials 0.000 abstract description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 22
- 238000003723 Smelting Methods 0.000 description 12
- 229910052742 iron Inorganic materials 0.000 description 11
- CSJDCSCTVDEHRN-UHFFFAOYSA-N methane;molecular oxygen Chemical compound C.O=O CSJDCSCTVDEHRN-UHFFFAOYSA-N 0.000 description 7
- 238000007670 refining Methods 0.000 description 7
- 238000000926 separation method Methods 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
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- 239000001301 oxygen Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 230000007306 turnover Effects 0.000 description 5
- 238000012545 processing Methods 0.000 description 4
- 238000009628 steelmaking Methods 0.000 description 4
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- 238000012546 transfer Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241001062472 Stokellia anisodon Species 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The invention relates to a utilization method of an ultra-low carbon steel casting residue direct-return ladle, which comprises the following steps: step 1: the temperature of molten steel at the blowing end point of the converter is more than or equal to 1660 ℃, the temperature of the blowing end point [ C ] is 0.02% -0.06%, the temperature of molten steel at the argon station after entering the converter is more than or equal to 1620 ℃, a sliding plate or a slag stopper is adopted for slag stopping in the tapping process, the thickness of a ladle slag layer is controlled to be less than 100mm, and the steel ladle clearance is controlled to be more than 400mm; step 2: argon blowing treatment of molten steel: step 3: transferring molten steel to RH for vacuum decarburization treatment, and step 4: pouring slag before casting: after pouring of the big ladle is finished, the casting residue of the big ladle is lifted to a slag turning position by a crane, and the step 5: pouring the slag and adding the casting residue into the molten steel of the next full ladle by using a travelling crane, and step 6: transferring the fully-packaged molten steel after casting to RH for vacuum decarburization treatment, and step 7: after pouring of the big ladle, pouring slag before pouring the big ladle casting residue, adding the next full ladle of molten steel, and repeating the steps 4-6 to realize continuous casting residue direct recycling.
Description
Technical Field
The invention relates to a method, in particular to a method for utilizing ultra-low carbon steel casting scraps to directly return to a ladle, and belongs to a refining process in the field of ferrous metallurgy.
Background
In the traditional steelmaking process, the ladle casting residue is generally poured into a slag basin, cooled for more than 16 hours, transported to a steel slag treatment site through a ladle car, subjected to heavy hammer separation treatment, returned to a steel mill as scrap steel treatment through a part with high iron content by magnetic separation, added into a scrap steel tank through an electric sucking disc, and re-smelted into molten steel through a converter or an electric furnace. Some steelworks adopt a casting residue return ladle for use, the ladle of the bedding molten iron is poured into the ladle of the ladle casting residue, 3-6 ladle casting residues are added with the molten iron, and the molten iron is returned to a converter or an electric furnace for re-smelting. The two ladle casting residue treatment methods have long turnover period, and increase the processing cost of the steel slag separation treatment process and the smelting burden of the converter. The ladle casting residue direct return ladle is to mix the ladle casting residue into the next full ladle of molten steel, and then to perform secondary pouring on the ladle after being treated by different external refining processes such as argon blowing, LF, vacuum and the like. However, in the process of directly returning ladle from ladle casting residue, ladle slag foaming is very easy to cause due to carbon-oxygen return, an argon pipe and personal injury accidents are burnt out, and particularly, the non-deoxidized ultra-low carbon steel grade is obtained.
Searching patent document finds that Chinese patent application number: the hot utilization method of CN201210272881.3 stainless steel continuous casting pouring residue discloses that a ladle with the pouring residue is transported to an electric furnace charging working line, the electric furnace is stopped from transmitting power, and the electric furnace is started; II, transportation and utilization, wherein steel slag and molten steel in a ladle are poured into a dephosphorized ladle, and then are mixed with dephosphorized molten iron into an electric furnace to be used as raw materials for smelting stainless steel in the electric furnace, and the ratio of continuous casting pouring remainder to the dephosphorized molten iron is as follows: 2-5 tons of continuous casting residual materials; 80-120 tons of dephosphorized molten iron; III, turning back on the electric furnace, and transmitting power for smelting. The method has the following problems:
1. the casting waste heat state returns to the electric furnace to smelt and turn over the cycle length.
2. Casting residue is used as scrap steel to enter an electric furnace for smelting, so that the electric furnace cost is increased.
Chinese patent application No.: CN201210542865.1 discloses a method for treating and recycling molten steel casting residues, which comprises the steps of digestion, screening, magnetic separation and other cyclic treatment. The f-CaO in the casting residues is digested by the steam, so that the expansion pulverization of the casting residues is promoted, the difficult problem of separation of the casting residues and the tank body is solved, and the dust emission is reduced. The invention adopts the casting residue and the hot-closed steel slag to match with the material, and ensures that the f-CaO content of the final product meets the requirements of cement and building material industries by utilizing the advantage of low f-CaO content of the hot-closed steel slag. And a rod mill treatment process is adopted, so that the grinding effect is good, and the granularity of the product is uniform and stable. The slag steel with the grade higher than 80% produced by the invention can be returned to steelmaking, the purified steel particles with the grade higher than 42% and the magnetic separation powder can be used for sintering processes, and the steel tailings with the iron content lower than 2% and the f-CaO lower than 3% can be used for producing steel slag powder, steel slag cement, building material products and road materials. The method has the following problems:
1. the casting residue needs to be digested, screened and magnetically separated, so that the slag-steel separation cost is increased.
2. The casting residue is returned and utilized for a long treatment period.
3. Slag steel containing 80% of iron is returned to steelmaking, so that the smelting burden of the converter is increased.
Chinese patent application No.: 201810207217.8A molten steel recovery method of a hot casting residue return ladle discloses a molten steel recovery method of a hot casting residue return ladle, which is characterized in that a heat preservation furnace arranged on a molten steel receiving span is used for receiving and circulating a plurality of packages of casting residues, and the heat preservation furnace is used for supplementing heat to the casting residues so as to keep the casting residues in a molten state. The slag is treated by adopting a mature and advanced roller technology, the rest molten steel is received by a baked ladle, the molten steel is conveyed to a cross-over trolley to be received by cross-over fully-charged molten iron, and the molten steel is charged into a converter after desulfurization, so that the thermal recovery of the rest molten steel in casting slag is realized. The method has the following problems:
1. According to the method, the heat-preserving furnace is added to supplement heat to the casting residues, so that the smelting burden of the converter is reduced, and the heat-supplementing cost of the heat-preserving furnace is increased.
2. The casting residue after heat supplement is added into a ladle to be smelted in a converter after molten iron desulfurization, and the turnover period is long.
Patent application number: application number: 201510700821.0 a treatment method of ladle casting surplus molten steel discloses a process flow of directly pouring ladle casting surplus molten steel into a semisteel ladle and then adding a mixture of semisteel, casting surplus molten steel and steel slag in the semisteel ladle into a converter for smelting, thereby saving the process flow of pouring ladle casting surplus molten steel into a slag pot for solidification and returning to the converter for recycling after cutting (or screening), and reducing the treatment cost of ladle casting surplus molten steel. The carbon content of the semisteel in the semisteel ladle is controlled to be 2.0-3.5%, so that the violent reaction in the semisteel ladle can be avoided. The method has the following problems:
3. the method reduces the processing cost of the classification of the casting residual steel slag, but increases the smelting burden of the converter and increases the blowing loss.
4. The molten steel after casting is added into the semi-ladle and then is smelted by a converter, and the turnover period is long.
The patent application number 202010239300.0 discloses an energy-saving and emission-reduction method for recycling hot casting residues, and a set of feasible hot casting residues recycling method is prepared by comprehensively carding and summarizing the hot casting residues through analysis of recycling feasibility, flow design, point and cheating analysis of recycling procedures, process standard formulation, process operation formulation, effect analysis after recycling and the like. After the casting residue is recycled, the molten steel receiving rate is improved, the auxiliary material consumption is reduced, the rapid slag formation of refining is promoted, the refining treatment time is shortened, and the refining efficiency is improved. And before and after the casting residue is recovered, the inclusions in the molten steel are basically equivalent, the gas content is slightly reduced, and the quality of the molten steel is stable. The recycling rate of the casting residues in the factory can reach more than 60%, the cost is obviously reduced after the casting residues are recycled, the energy-saving and emission-reducing effects are obvious, and good economic and social benefits are obtained. The method has the following problems:
1. The method does not determine the converter endpoint control temperature and endpoint oxygen content.
2. The ladle casting residue is added into the ladle by the method, and LF refining treatment is needed, so that the process treatment cost is increased for steel grades which do not need LF refining treatment. The method does not treat the molten steel before casting, and slag overflow accidents caused by carbon-oxygen reaction are easy to occur, so that a new scheme is urgently needed to solve the technical problems.
Disclosure of Invention
The invention provides a utilization method of an ultralow-carbon steel casting residue direct-return ladle, which aims at the problems in the prior art. The method reduces the traditional ladle casting residue cooling separation and furnace return smelting processes, and avoids the problems of long ladle casting residue turnover period, steel slag separation processing cost and converter smelting heat burden. Meanwhile, the method is used for carrying out the ladle slag exhaust treatment in the tapping process, namely, the ladle slag deoxidization, the casting residue adding and the vacuum decarburization process, so that the occurrence of ladle residue steel return blowing loss and slag overflow accidents is reduced.
In order to achieve the above purpose, the technical scheme of the invention is as follows, and the method for utilizing the ultra-low carbon steel casting steel ladle is characterized by comprising the following steps:
Step 1: the temperature of molten steel at the blowing end point of the converter is more than or equal to 1660 ℃, the temperature of the blowing end point [ C ] is 0.02% -0.06%, the temperature of molten steel at the argon station after entering the converter is more than or equal to 1620 ℃, a sliding plate or a slag stopper is adopted for slag stopping in the tapping process, the thickness of a ladle slag layer is controlled to be less than 100mm, and the steel ladle clearance is controlled to be more than 400mm;
Step 2: argon blowing treatment of molten steel: the molten steel enters a station and is stirred for 3min under strong stirring, the argon flow is 200-400L/min, and the steel tapping is ensured to be completely melted by adding ladle slag modified materials;
step 3: transferring molten steel to RH for vacuum decarburization treatment, controlling the vacuum degree to be less than 0.27KPa during decarburization, controlling the decarburization time to be more than 12min, spraying gas mist to cover the slag surface of a steel ladle during the decarburization period of 5-8min, adding aluminum for deoxidization alloying after decarburization, and ensuring the pure degassing time to be more than 5min, and performing continuous casting and pouring on the molten steel;
Step 4: pouring slag before casting: after pouring of the big ladle is finished, the casting residue of the big ladle is lifted to a residue turning position by a crane,
Step 5: pouring slag and adding the casting residue into the molten steel in the next full ladle by using a travelling crane, wherein the casting residue time is controlled within 8 min;
Step 6: transferring the fully-packed molten steel after casting to RH for vacuum decarburization treatment,
Step 7: after pouring of the big ladle, pouring slag before pouring the big ladle casting residue, adding the next full ladle of molten steel, and repeating the steps 4-6 to realize continuous casting residue direct recycling.
In the step 1, modified lime 5kg/t is added along with the steel flow to carry out slag thickening, and 1.2kg/t of high-alumina slag balls are added to the molten steel surface after tapping. Modified lime is added for 5kg/t in the tapping process to improve the alkalinity of ladle slag, reduce the fluidity of ladle slag and reduce oxygen transfer between steel slag; after tapping, adding 1.2kg/t high-aluminum deoxidizer to the molten steel surface to reduce the oxidizing property of ladle slag and avoid foaming slag overflow caused by carbon-oxygen reaction in the casting process due to high oxygen content.
In the step 4, the casting ladle is tilted to a horizontal angle of 85 degrees, and the ladle is aligned after the first casting surplus heat is subjected to slag-finding and waiting for 10 seconds and then aligned after the second casting surplus heat is subjected to slag-finding and waiting for 15 seconds;
the invention relates to pouring slag before casting residue in the step 4, which aims to avoid slag suction accidents in the RH vacuum treatment process caused by large molten steel slag amount after casting residue is added. Ladle alignment after 10 seconds of first casting residue waiting, ladle alignment after 15 seconds of casting residue returning to the furnace number after casting residue adding, and the purpose of controlling total slag quantity is achieved by controlling slag pouring time according to the number of times of casting residue utilization.
In the step 6, the vacuum degree is controlled to be less than 0.27KPa, the decarburization time is more than 12min, the ladle slag surface is covered by aerosol spraying in the decarburization period of 5-8min, aluminum is added for deoxidization alloying after decarburization, the pure degassing time is ensured to be more than 5min, and continuous casting and pouring are carried out on molten steel. Covering the ladle slag surface by aerosol spraying in the decarburization period of 5-8min to promote the shrinkage of the ladle slag surface and the generation of cracks, promote the removal of carbon-oxygen reaction products in the decarburization period and reduce the foaming of the slag layer and burn out the circulating argon pipe.
Compared with the prior art, the invention has the advantages that 1) the technical scheme can ensure the safety of the ladle returning process and the RH vacuum treatment process of the casting residue through the control steps, realize the shortest recycling period of the casting residue, the highest heat efficiency, reduce the smelting burden of the converter and simultaneously well reduce the consumption of steel materials; 2) According to the scheme, the front deslagging operation is carried out on the ladle casting residues, the thickness of a ladle slag layer is reduced, the risk of slag suction accidents of an RH furnace is avoided, the slag surface of the ladle is covered by aerosol injection in a decarburization period of 5-8min, forced cooling shrinkage is carried out, the risk of splashing caused by the fact that gas generated by a carbon-oxygen reaction is not discharged in time is avoided, the recoverable slag and steel are treated through the scheme, 60% of molten steel is contained in normal casting residue molten steel for measuring and calculating, and the consumption of 2.2 kg/ton of steel by steel materials can be reduced.
Detailed Description
The present invention will be described in detail with reference to examples.
Example 1: a method for utilizing ultra-low carbon steel casting residue direct return ladle, comprising the following steps:
Step 1: the temperature of molten steel at the blowing end point of the converter is more than or equal to 1660 ℃, the temperature of the blowing end point [ C ] is 0.02% -0.06%, the temperature of molten steel at the argon station after entering the converter is more than or equal to 1620 ℃, a sliding plate or a slag stopper is adopted for slag stopping in the tapping process, the thickness of a ladle slag layer is controlled to be less than 100mm, and the steel ladle clearance is controlled to be more than 400mm; in the step 1, modified lime 5kg/t is added along with the steel flow in the tapping process to carry out slag thickening, and 1.2kg/t of high-alumina slag balls are added to the molten steel surface after tapping. Modified lime is added for 5kg/t in the tapping process to improve the alkalinity of ladle slag, reduce the fluidity of ladle slag and reduce oxygen transfer between steel slag; after tapping, adding 1.2kg/t high-aluminum deoxidizer to the molten steel surface to reduce the oxidizing property of ladle slag and avoid foaming slag overflow caused by carbon-oxygen reaction in the casting process due to high oxygen content.
Step 2: argon blowing treatment of molten steel: the molten steel enters a station and is stirred for 3min under strong stirring, the argon flow is 200-400L/min, and the steel tapping is ensured to be completely melted by adding ladle slag modified materials;
step 3: transferring molten steel to RH for vacuum decarburization treatment, controlling the vacuum degree to be less than 0.27KPa during decarburization, controlling the decarburization time to be more than 12min, spraying gas mist to cover the slag surface of a steel ladle during the decarburization period of 5-8min, adding aluminum for deoxidization alloying after decarburization, and ensuring the pure degassing time to be more than 5min, and performing continuous casting and pouring on the molten steel;
Step 4: pouring slag before casting: after pouring of the large ladle, hoisting the casting residue of the large ladle to a residue turning position by using a crane, in the step 4, tilting the casting residue ladle to a horizontal angle of 85 degrees, waiting 10 seconds after residue finding of the primary casting residue, and returning the ladle to the right after residue finding of the secondary casting residue and waiting 15 seconds after residue finding of the secondary casting residue;
the invention relates to pouring slag before casting residue in the step 4, which aims to avoid slag suction accidents in the RH vacuum treatment process caused by large molten steel slag amount after casting residue is added. Ladle alignment after 10 seconds of first casting residue waiting, ladle alignment after 15 seconds of casting residue returning to the furnace number after casting residue adding, and the purpose of controlling total slag quantity is achieved by controlling slag pouring time according to the number of times of casting residue utilization.
Step 5: pouring slag and adding the casting residue into the molten steel in the next full ladle by using a travelling crane, wherein the casting residue time is controlled within 8 min;
Step 6: and (3) transferring the fully-packed molten steel after casting to RH for vacuum decarburization treatment, wherein in the step (6), the vacuum degree is controlled to be less than 0.27KPa during decarburization, the decarburization time is more than 12min, the slag surface of the steel ladle is covered by aerosol spraying during the decarburization period of 5-8min, aluminum is added for deoxidization alloying after decarburization, and the pure degassing time is ensured to be more than 5min, so that continuous casting and pouring are performed on the molten steel. Covering the ladle slag surface by aerosol spraying in the decarburization period of 5-8min to promote the shrinkage of the ladle slag surface and the generation of cracks, promote the removal of carbon-oxygen reaction products in the decarburization period and reduce the foaming of the slag layer and burn out the circulating argon pipe.
Step 7: after pouring of the big ladle, pouring slag before pouring the big ladle casting residue, adding the next full ladle of molten steel, and repeating the steps 4-6 to realize continuous casting residue direct recycling.
Example 2: a method for utilizing ultra-low carbon steel casting residue direct return ladle, comprising the following steps:
step 1: the temperature of molten steel at the blowing end point of the converter is more than or equal to 1660 ℃, the temperature of molten steel at the blowing end point [ C ] is 0.02% -0.06%, and the temperature of molten steel is more than or equal to 1620 ℃ when entering an argon station after the converter. And a sliding plate or a slag blocking plug is adopted for blocking slag in the tapping process, the thickness of a ladle slag layer is controlled to be less than 100mm, the clearance of the ladle is controlled to be greater than 400mm, modified lime is added with the steel flow in the tapping process for carrying out slag thickening, and 1.2kg/t of high-alumina slag balls are added to the molten steel surface after tapping is finished.
Step 2: argon blowing treatment of molten steel: the molten steel enters a station and is stirred strongly for 3min, the argon flow is 200-400L/min, and the steel tapping is ensured to be completely melted by adding ladle slag modified materials.
Step 3: transferring molten steel to RH for vacuum decarburization treatment, controlling the vacuum degree to be less than 0.27KPa during decarburization, controlling the decarburization time to be more than 12min, spraying gas mist to cover the slag surface of a steel ladle during the decarburization period of 5-8min, adding aluminum for deoxidization alloying after decarburization, and ensuring the pure degassing time to be more than 5 min.
Step 4: pouring slag before casting: after pouring of the large ladle, hoisting the large ladle casting residue to a residue turning position by using a crane, turning over the casting residue ladle to a horizontal angle of 85 degrees, waiting for 10 seconds after the first casting residue furnace residue is found, and returning the ladle after the second casting residue furnace residue is found for 15 seconds or more.
Step 5: pouring slag and adding the casting residue into the molten steel in the next full ladle by using a travelling crane, wherein the casting residue time is controlled within 8 min.
Step 6: transferring the fully-packed molten steel after casting to RH for vacuum decarburization treatment, controlling the vacuum degree to be less than 0.27KPa during decarburization, controlling the deep decarburization time to be more than 12min, spraying aerosol to cover the slag surface of the steel ladle during the decarburization period of 5-8min, adding aluminum for deoxidization alloying after decarburization, and ensuring the pure degassing time to be more than 5 min.
Step 7: after pouring of the big ladle, pouring slag before pouring the big ladle casting residue, adding the next full ladle of molten steel, and repeating the steps 4-6 to realize continuous casting residue direct recycling.
The converter in the embodiment of the invention is a 150t converter, and the steel grade is DN0140E1. The process parameters of the examples of the present invention are shown in table 1.
TABLE 1 specific process parameters for the method embodiment of the invention
After the scheme is adopted, the casting residue molten steel is directly cast after thermal state circulation treatment, the casting residue treatment period is shortened, the temperature drop is reduced, and the casting blank yield is greatly improved. The steel ladle is returned to the casting ladle to directly recycle slag steel generated in steelmaking, so that the processing cost is reduced, the emission is reduced, and the method has very important practical significance for improving the recycling level of enterprise resources.
It should be noted that the above-mentioned embodiments are not intended to limit the scope of the present invention, and equivalent changes or substitutions made on the basis of the above-mentioned technical solutions fall within the scope of the present invention as defined in the claims.
Claims (4)
1. The method for utilizing the ultralow-carbon steel casting residue direct-return ladle is characterized by comprising the following steps of:
Step 1: the temperature of molten steel at the blowing end point of the converter is more than or equal to 1660 ℃, the temperature of the blowing end point [ C ] is 0.02% -0.06%, the temperature of molten steel at the argon station after entering the converter is more than or equal to 1620 ℃, a sliding plate or a slag stopper is adopted for slag stopping in the tapping process, the thickness of a ladle slag layer is controlled to be less than 100mm, and the steel ladle clearance is controlled to be more than 400mm;
Step 2: argon blowing treatment of molten steel: the molten steel enters a station and is stirred for 3min under strong stirring, the argon flow is 200-400L/min, and the steel tapping is ensured to be completely melted by adding ladle slag modified materials;
step 3: transferring molten steel to RH for vacuum decarburization treatment, controlling the vacuum degree to be less than 0.27KPa during decarburization, controlling the decarburization time to be more than 12min, spraying gas mist to cover the slag surface of a steel ladle during the decarburization period of 5-8min, adding aluminum for deoxidization alloying after decarburization, and ensuring the pure degassing time to be more than 5min, and performing continuous casting and pouring on the molten steel;
Step 4: pouring slag before casting: after pouring of the big ladle is finished, the casting residue of the big ladle is lifted to a residue turning position by a crane,
Step 5: pouring slag and adding the casting residue into the molten steel in the next full ladle by using a travelling crane, wherein the casting residue time is controlled within 8 min;
Step 6: transferring the fully-packed molten steel after casting to RH for vacuum decarburization treatment,
Step 7: after pouring of the big ladle, pouring slag before pouring the big ladle casting residue, adding the next full ladle of molten steel, and repeating the steps 4-6 to realize continuous casting residue direct recycling.
2. The method for utilizing the ultralow-carbon steel casting residue direct-return ladle according to claim 1, wherein in the step 1, modified lime 5kg/t is added along with a steel flow in the tapping process to carry out slag thickening, and 1.2kg/t of high-alumina slag balls are added to the molten steel surface after tapping is finished.
3. The method for utilizing the ultralow-carbon steel casting residue direct-return ladle according to claim 2, wherein in the step4, the casting residue ladle is tilted to a horizontal angle of 85 degrees, and the ladle is aligned after waiting for 10 seconds after the first casting residue heat sees slag and is aligned after waiting for 15 seconds after the second casting residue heat sees slag.
4. The method for utilizing the ultralow-carbon steel casting residue direct-return ladle according to claim 3, wherein in the step 6, the vacuum degree is controlled to be less than 0.27KPa during decarburization, the decarburization time is more than 12min, the ladle slag surface is covered by aerosol spraying during the decarburization period of 5-8min, the decarburization is finished, aluminum is added for deoxidization alloying, the pure degassing time is ensured to be more than 5min, and the molten steel is cast continuously.
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