CN110172543B - Method for preventing steel flocculation in casting process of rare earth treated steel - Google Patents
Method for preventing steel flocculation in casting process of rare earth treated steel Download PDFInfo
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- CN110172543B CN110172543B CN201910435574.4A CN201910435574A CN110172543B CN 110172543 B CN110172543 B CN 110172543B CN 201910435574 A CN201910435574 A CN 201910435574A CN 110172543 B CN110172543 B CN 110172543B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/02—Dephosphorising or desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
Abstract
The invention discloses a method for preventing steel flocculation in the casting process of rare earth treated steel, which is suitable for stable and continuous casting production of the rare earth treated steel, wherein molten iron is pretreated by KR desulfurization, the sulfur content, the temperature and the slag carrying amount of the molten iron are well controlled, and conditions are created for converter steelmaking; the BOF converter controls the carbon drawing (C), (O) and the temperature well, ensures that the converter successfully draws carbon at one time, and carries out slag washing operation in the tapping process to promote the floating of impurities in molten steel; LF refining controls the rapid white slag making and holding time, the molten steel stirring condition in the process, calcium treatment and soft blowing control, and the contents of [ S ] and [ O ] discharged from a station; controlling the circular flow of the molten steel, the rare earth treatment time, the pure degassing time, the molten steel temperature and the steel passing time sequence by RH vacuum refining; the stable continuous casting of the rare earth treated steel is realized after the control points of the casting machine process such as protective casting, liquid level control, a drawing speed and superheat degree matching system and the like are well controlled.
Description
Technical Field
The invention relates to the technical field of ferrous metallurgy, in particular to a method for preventing steel flocculation in the casting process of rare earth treated steel.
Background
(1) Each steel mill lacks a stable rare earth element adding process;
(2) the molten steel [ RE ] atoms react with the refractory material (ladle wall/tundish wall/submerged nozzle) interface to generate high-density solid RE2O3 particles, and the high-density solid RE2O3 particles are deposited on the submerged nozzle wall to cause continuous casting nodulation accidents. The continuous casting of the rare earth treated steel cannot be realized, and continuous and stable production data of the rare earth treated steel is lacked.
Disclosure of Invention
The invention aims to provide a method for preventing steel flocculation in the casting process of rare earth treated steel, which solves the problem of steel flocculation stopping in the casting process of rare earth treated steel and realizes the stable and continuous casting of rare earth treated steel.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method of preventing steel from being flocculated during casting of rare earth treated steel comprising:
KR desulfurization step: after the KR is required to be subjected to molten iron treatment: the S content in the molten iron is less than or equal to 0.005 percent, the temperature of the molten iron is not less than 1280 percent, and the exposed area of the molten iron is more than or equal to 95 percent;
BOF converter process: the converter adopts single slag remaining operation, the carbon drawing is required to have the [ C ] more than or equal to 0.07 percent, the [ P ] less than or equal to 0.01 percent and the [ S ] less than or equal to 0.01 percent, the converter is required to be hit at one time, the tapping hole does not scatter flow in the tapping process, the tapping time is less than 5 minutes, the slag washing operation is carried out in the tapping process, the full aggregation and floating of impurities are ensured, the purity of molten steel is improved, and the terminal temperature of the molten steel implements the current operation standard;
an LF refining procedure: refining to produce white slag, wherein the slagging speed is high and the retention time is more than or equal to 15 minutes; during slagging, the diameter of the exposed area of the molten steel is not more than 1/3 of the diameter of the steel ladle; the deoxidation alloying of the molten steel is required to be completed in refining, and the components of the molten steel need to be added into a target range in advance in the refining; after the conventional refining task, Ca treatment is carried out, the slag surface is kept in a slight fluctuation state during soft blowing, the total content of O is required to be not more than 20ppm and the content of S is not more than 50ppm when the slag is discharged;
RH refining process: the vacuum refining requires pumping for no more than 4 minutes, the minimum vacuum degree reaches below 266Pa, the vacuum degree does not fluctuate and bounce in the vacuum treatment process, the flow of circulating argon is adjusted in the vacuum treatment process, the molten steel is ensured to be fully circulated, the purposes that [ H ] in the molten steel is less than or equal to 1.5ppm, [ O ] is less than or equal to 20ppm, and [ N ] is less than or equal to 50ppm, various inclusions are not higher than 1.0 grade, and the requirements of pure steel are completely met; adding rare earth alloy through a vacuum hopper at the later stage of refining, adding rare earth, circulating for 5 minutes, then repressing, and soft blowing for 5-6 minutes; and immediately supplying the molten steel to continuous casting;
and (3) continuous casting process: the casting machine is ensured to start casting within 20 minutes after RH refining treatment, the superheat degree of the tundish is improved by 10-15 ℃ compared with the prior art, and the stable constant drawing speed of the casting machine is ensured within the range that the superheat degree of the molten steel meets the requirement; the casting machine needs to make protective pouring work in the whole process, ensures that the nitrogen increase amount of the molten steel is no more than 5ppm, requires to close a ladle water gap before 30 seconds before ladle slag discharging, prevents ladle slag discharging, and simultaneously needs to make parameter adjustment of dynamic secondary cooling water distribution, electromagnetic stirring and dynamic light pressure to reduce the problems of slab center segregation and center porosity and improve the quality of a casting blank.
Furthermore, soft blowing is carried out for 5 minutes in the RH refining process, and the soft blowing flow is as small as possible.
Furthermore, soft blowing is carried out for 6 minutes in the RH refining process, and the soft blowing flow is as small as possible.
Furthermore, the superheat degree of the tundish in the continuous casting process is improved by 10 ℃ compared with the prior art.
Furthermore, the superheat degree of the tundish in the continuous casting process is improved by 15 ℃ compared with the prior art.
Furthermore, the superheat degree of the tundish in the continuous casting process is improved by 12 ℃ compared with the prior art.
Further, the diameter of a molten steel exposed area in the LF refining process is 1/3 of the diameter of a ladle.
Compared with the prior art, the invention has the beneficial technical effects that:
the optimization and improvement of the process are carried out on the basis of not changing the original process route, and the operation standard of the whole process of smelting the rare earth treated steel is worked out; the method is operated according to established operation standards of the whole process of smelting the rare earth treated steel, can realize continuous casting of the rare earth treated steel, and has high operability and good popularization.
Detailed Description
A method for preventing steel flocculation in the casting process of rare earth treated steel comprises the following steps: KR-BOF-LF-RH-CC.
KR desulfurization step: after the KR is required to be subjected to molten iron treatment: the S content in the molten iron is less than or equal to 0.005 percent, the temperature of the molten iron is not less than 1280 percent, and the exposed area of the molten iron is more than or equal to 95 percent.
BOF converter process: the converter adopts single slag remaining operation, the carbon drawing is required to be carried out by more than or equal to 0.07 percent for [ C ], [ P ] less than or equal to 0.01 percent and [ S ] less than or equal to 0.01 percent, the converter is required to be hit at one time, the tapping hole does not scatter during the tapping process, the tapping time is less than 5 minutes, the slag washing operation is carried out during the tapping process, the full aggregation and floating of impurities are ensured, the purity of molten steel is improved, and the terminal temperature of the molten steel implements the current operating standard.
An LF refining procedure: refining to produce white slag, wherein the slagging speed is high and the retention time is more than or equal to 15 minutes; during slagging, the diameter of a bright ring (a molten steel exposed area) does not exceed 1/3 of the diameter of a steel ladle; the deoxidation alloying of the molten steel is required to be completed in refining, and the components of the molten steel need to be added into a target range in advance in the refining; after the conventional refining task, Ca treatment is carried out (soft blowing is more than or equal to 5 minutes), and the slag surface is kept in a slightly fluctuating state during soft blowing. The total content of [ O ] is not more than 20ppm and [ S ] is not more than 50ppm when the aluminum alloy is discharged.
RH refining process: the vacuum refining requires pumping for no more than 4 minutes, the minimum vacuum degree reaches below 266Pa, the vacuum degree does not fluctuate and bounce in the vacuum treatment process, the flow of circulating argon is adjusted in the vacuum treatment process, the molten steel is ensured to be fully circulated, the purposes that [ H ] in the molten steel is less than or equal to 1.5ppm, [ O ] is less than or equal to 20ppm, and [ N ] is less than or equal to 50ppm, various inclusions are not higher than 1.0 grade, and the requirements of pure steel are completely met; rare earth alloy is added through a vacuum hopper in the later stage of refining (the addition amount is determined according to actual conditions), after rare earth is added, the mixture is subjected to circulation for 5 minutes and then is subjected to repression, and soft blowing is carried out for 5-6 minutes (the soft blowing flow is as small as possible); and immediately feeding the molten steel to continuous casting (the smaller the residence time, the better).
And (3) continuous casting process: the casting machine is ensured to start casting within 20 minutes after RH refining treatment, the superheat degree of a tundish is improved by 10-15 ℃ compared with the prior art (the prior art is generally 23-33 ℃), and the stable constant drawing speed of the casting machine is ensured within the range that the superheat degree of molten steel meets the requirement; the casting machine needs to make protective casting work in the whole process, ensures that the nitrogen increase of the molten steel is not more than 5ppm, and requires that a ladle nozzle is closed before 30 seconds before ladle slag discharging to prevent ladle slag discharging. Meanwhile, the casting machine needs to make parameter adjustment of dynamic secondary cooling water distribution, electromagnetic stirring and dynamic light pressure to reduce the problems of slab center segregation, center porosity and the like, and the quality of the casting blank is improved.
And the other production process operation parameters execute the relevant standards of the steel-clad quality system.
Example 1
The rare earth steel treatment experiment is carried out on a wide and thick plate production line of a thin plate factory in 7 months and 7 days in 2017, and the experimental steel is wind power steel series. The adopted process route is KR-LD-LF-RH-CC-HR. The casting schedule of 8 furnaces and the rare earth treatment test of 6 furnaces were carried out in total from the 3 rd furnace of the casting schedule, and the addition amount of the rare earth was not less than 30 kg/furnace. The pouring process of the rare earth treated steel produced by the method for preventing the rare earth treated steel from flocculating steel in the pouring process of the rare earth treated steel in our factory is smooth, the continuous pouring of the rare earth treated steel in the 5-furnace is smoothly realized, and all indexes meet the planned requirements.
Example 2
In 2018, 6 and 11 months, rare earth treated steel tests are carried out on a wide and thick plate production line in a sheet mill, and the test steel is a high-strength steel series. The adopted process route is KR-LD-LF-RH-CC-HR. The casting schedule of 9 furnaces, the rare earth treatment test was carried out from the 1 st furnace in the casting schedule, and the rare earth treatment test of 9 furnaces was carried out in total, and the addition amount of the rare earth was not less than 60 kg/furnace. This wide and thick board production line of sheet mill successfully realizes that 9 stoves of rare earth steel are watered in succession, and 153 pieces 1885 tons of once output rare earth steel billet, the process is stable, and the index all reaches the plan requirement, realizes three technological breakthroughs at one stroke: firstly, the technical problem of direct casting of rare earth steel is broken through; secondly, the whole-casting long continuous casting of the rare earth steel is realized, and the continuous casting time is over 600 minutes; thirdly, the adding amount of the rare earth breaks through the highest historical level of the plant.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (7)
1. A method for preventing steel flocculation in the casting process of rare earth treated steel is characterized in that: the method comprises the following steps:
KR desulfurization step: after the KR is required to be subjected to molten iron treatment: the S content in the molten iron is less than or equal to 0.005 percent, the temperature of the molten iron is not less than 1280 percent, and the exposed area of the molten iron is more than or equal to 95 percent;
BOF converter process: the converter adopts single slag remaining operation, the carbon drawing is required to have the [ C ] more than or equal to 0.07 percent, the [ P ] less than or equal to 0.01 percent and the [ S ] less than or equal to 0.01 percent, the converter is required to be hit at one time, the tapping hole does not scatter flow in the tapping process, the tapping time is less than 5 minutes, the slag washing operation is carried out in the tapping process, the full aggregation and floating of impurities are ensured, the purity of molten steel is improved, and the terminal temperature of the molten steel implements the current operation standard;
an LF refining procedure: refining to produce white slag, wherein the slagging speed is high and the retention time is more than or equal to 15 minutes; during slagging, the diameter of the exposed area of the molten steel is not more than 1/3 of the diameter of the steel ladle; the deoxidation alloying of the molten steel is required to be completed in refining, and the components of the molten steel need to be added into a target range in advance in the refining; after the conventional refining task, Ca treatment is carried out, the slag surface is kept in a slight fluctuation state during soft blowing, the total content of O is required to be not more than 20ppm and the content of S is not more than 50ppm when the slag is discharged;
RH refining process: the vacuum refining requires pumping for no more than 4 minutes, the minimum vacuum degree reaches below 266Pa, the vacuum degree does not fluctuate and bounce in the vacuum treatment process, the flow of circulating argon is adjusted in the vacuum treatment process, the molten steel is ensured to be fully circulated, the purposes that [ H ] in the molten steel is less than or equal to 1.5ppm, [ O ] is less than or equal to 20ppm, and [ N ] is less than or equal to 50ppm, various inclusions are not higher than 1.0 grade, and the requirements of pure steel are completely met; adding rare earth alloy through a vacuum hopper at the later stage of refining, adding rare earth, circulating for 5 minutes, then repressing, and soft blowing for 5-6 minutes; and immediately supplying the molten steel to continuous casting;
and (3) continuous casting process: the casting machine is ensured to start casting within 20 minutes after RH refining treatment, the superheat degree of the tundish is improved by 10-15 ℃ compared with the prior art, the temperature of the prior art is 23-33 ℃, and the stable constant drawing speed of the casting machine is ensured within the range that the superheat degree of molten steel meets the requirement; the casting machine needs to make protective pouring work in the whole process, ensures that the nitrogen increase amount of the molten steel is no more than 5ppm, requires to close a ladle water gap before 30 seconds before ladle slag discharging, prevents ladle slag discharging, and simultaneously needs to make parameter adjustment of dynamic secondary cooling water distribution, electromagnetic stirring and dynamic light pressure to reduce the problems of slab center segregation and center porosity and improve the quality of a casting blank.
2. The method for preventing steel from being flocculated during casting of rare earth treated steel according to claim 1, wherein: in the RH refining process, soft blowing is carried out for 5 minutes, and the soft blowing flow is as small as possible.
3. The method for preventing steel from being flocculated during casting of rare earth treated steel according to claim 1, wherein: in the RH refining process, soft blowing is carried out for 6 minutes, and the soft blowing flow is as small as possible.
4. The method for preventing steel from being flocculated during casting of rare earth treated steel according to claim 1, wherein: the superheat degree of the tundish in the continuous casting process is improved by 10 ℃ compared with the prior art.
5. The method for preventing steel from being flocculated during casting of rare earth treated steel according to claim 1, wherein: the superheat degree of the tundish in the continuous casting process is improved by 15 ℃ compared with the prior art.
6. The method for preventing steel from being flocculated during casting of rare earth treated steel according to claim 1, wherein: the superheat degree of the tundish in the continuous casting process is improved by 12 ℃ compared with the prior art.
7. The method for preventing steel from being flocculated during casting of rare earth treated steel according to claim 1, wherein: the diameter of a molten steel exposed area in the LF refining process is 1/3 of the diameter of a ladle.
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| CN110512051B (en) * | 2019-09-05 | 2021-07-23 | 首钢集团有限公司 | Rare earth alloying method for avoiding continuous casting nozzle nodulation |
| CN111057948A (en) * | 2019-12-14 | 2020-04-24 | 石家庄钢铁有限责任公司 | Narrow-range production control method for rare earth elements La and Ce in rare earth bearing steel |
| CN111363890A (en) * | 2020-03-23 | 2020-07-03 | 首钢集团有限公司 | Rare earth treatment method for RH refining |
| CN111809018A (en) * | 2020-06-17 | 2020-10-23 | 包头钢铁（集团）有限责任公司 | Method for improving hydrogen cracking resistance and hydrogen sulfide corrosion resistance of steel blank for 16MnHIC flange |
| CN111593252B (en) * | 2020-06-30 | 2021-03-16 | 新余钢铁股份有限公司 | Smelting method of rare earth steel |
| CN111545717B (en) * | 2020-06-30 | 2022-05-17 | 新余钢铁股份有限公司 | Pouring method of rare earth steel |
| CN112226578A (en) * | 2020-09-15 | 2021-01-15 | 包头钢铁（集团）有限责任公司 | Rare earth addition control method for high-strength rare earth girder steel |
| CN113828749A (en) * | 2021-08-13 | 2021-12-24 | 包头钢铁（集团）有限责任公司 | Method for realizing continuous casting castability of rare earth steel by adjusting superheat degree |
| CN113832380A (en) * | 2021-09-24 | 2021-12-24 | 重庆钢铁股份有限公司 | Smelting method of ultralow-aluminum-content low-sulfur non-oriented silicon steel |
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