CN113388710A - Smelting control method of ultrahigh-strength cord steel - Google Patents
Smelting control method of ultrahigh-strength cord steel Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 112
- 239000010959 steel Substances 0.000 title claims abstract description 112
- 238000000034 method Methods 0.000 title claims abstract description 73
- 238000003723 Smelting Methods 0.000 title claims abstract description 36
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 60
- 239000002893 slag Substances 0.000 claims abstract description 57
- 238000010079 rubber tapping Methods 0.000 claims abstract description 48
- 238000007664 blowing Methods 0.000 claims abstract description 40
- 229910052742 iron Inorganic materials 0.000 claims abstract description 30
- 238000007670 refining Methods 0.000 claims abstract description 15
- 238000009749 continuous casting Methods 0.000 claims abstract description 12
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 9
- 230000023556 desulfurization Effects 0.000 claims abstract description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 56
- 229910052786 argon Inorganic materials 0.000 claims description 28
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 14
- 229910052717 sulfur Inorganic materials 0.000 claims description 14
- 239000011593 sulfur Substances 0.000 claims description 14
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 12
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 12
- 239000004571 lime Substances 0.000 claims description 12
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 11
- 229910052593 corundum Inorganic materials 0.000 claims description 11
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 11
- 230000002378 acidificating effect Effects 0.000 claims description 9
- 239000000498 cooling water Substances 0.000 claims description 9
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 8
- 229910052681 coesite Inorganic materials 0.000 claims description 8
- 229910052906 cristobalite Inorganic materials 0.000 claims description 8
- 239000010436 fluorite Substances 0.000 claims description 8
- 239000000843 powder Substances 0.000 claims description 8
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 8
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 8
- 239000000377 silicon dioxide Substances 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 8
- 229910052682 stishovite Inorganic materials 0.000 claims description 8
- 229910052905 tridymite Inorganic materials 0.000 claims description 8
- 235000012239 silicon dioxide Nutrition 0.000 claims description 7
- 239000006004 Quartz sand Substances 0.000 claims description 3
- 238000005266 casting Methods 0.000 claims description 3
- 238000002844 melting Methods 0.000 claims description 3
- 230000008018 melting Effects 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 238000002347 injection Methods 0.000 claims 2
- 239000007924 injection Substances 0.000 claims 2
- 239000000203 mixture Substances 0.000 claims 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract description 16
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 11
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 8
- 229910052799 carbon Inorganic materials 0.000 abstract description 6
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 abstract description 4
- 238000001514 detection method Methods 0.000 abstract description 2
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 238000004886 process control Methods 0.000 abstract description 2
- 238000009628 steelmaking Methods 0.000 abstract description 2
- 239000010936 titanium Substances 0.000 description 10
- 239000000956 alloy Substances 0.000 description 6
- 229910045601 alloy Inorganic materials 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 5
- 238000005275 alloying Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 230000003009 desulfurizing effect Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229910052719 titanium Inorganic materials 0.000 description 5
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 230000000638 stimulation Effects 0.000 description 1
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Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
-
- 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
-
- 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
- C21C5/30—Regulating or controlling the blowing
- C21C5/34—Blowing through the bath
-
- 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
- C21C5/36—Processes yielding slags of special composition
-
- 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
- C21C7/064—Dephosphorising; Desulfurising
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Carbon Steel Or Casting Steel Manufacturing (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention discloses a smelting control method of ultrahigh-strength cord steel. Belongs to the technical control field of steel making of steel ultrahigh-strength cord steel; the method comprises the following specific steps: KR desulfurization procedure is adopted; controlling before smelting in a converter; controlling converter blowing; controlling before converter tapping; controlling a deoxidation and slagging link of the LF furnace; a continuous casting process; and finally finishing the smelting of the ultrahigh-strength cord steel. According to the invention, by controlling aspects of KR molten iron desulphurization, converter double-slag operation, end point carbon content, tapping temperature, refining, deoxidation, slagging and the like, the nitrogen content of molten steel is reduced to the maximum extent, TiN inclusions in the molten steel are reduced, the purity of the molten steel is improved, the flow is shortened, and the processing time is reduced; the ultrahigh-strength cord steel produced by the method meets the requirements on detection of corresponding inclusions (the level of A, C-type inclusions is less than or equal to 1.0 grade, and the level of B, D-type inclusions is less than or equal to 0.5 grade), and meanwhile, the yield is improved by more than 5% by adopting short-process control, so that the ultrahigh-strength cord steel has higher economic, environmental and social benefits.
Description
Technical Field
The invention relates to the technical control field of steel making of ultrahigh-strength cord steel, in particular to a smelting control method of the ultrahigh-strength cord steel.
Background
The steel cord is mainly used as the framework material of various tires and other rubber products, the demand of the steel cord is closely related to the output of tire structural varieties, the tire industry in China is rapidly developed under the promotion of economic stimulation policies, engineering machinery, automobile industry, highways and other beneficial factors in recent years, the consumption of the steel cord in China is continuously increased, and the rapid development of the wire rod industry for the steel cord is promoted. China becomes the first automobile market in the world, and the cord line industry is also rapidly developed, and the basic yield accounts for more than half of the global market. The 70-grade cord is imported for over ten years, the 80-grade high-strength cord is also made into a home (except for cutting steel wires), and advanced enterprises develop to high-end and ultrahigh-strength (little competition and high gross profit).
Because of the requirements of the working conditions and the safety performance of the ultra-high strength cord steel, the requirement on the purity of the ultra-high strength cord steel is very high, the existence of inclusions with the diameter of more than 15 mu m is not allowed, the plasticity of the inclusions is required, meanwhile, the width size of titanium inclusions is required to be less than or equal to 5 mu m, in addition, the requirement on the content of harmful gases is also strict, wherein [ O ] is less than or equal to 30ppm, and [ N ] is less than or equal to 50 ppm. (ii) a At present, few enterprises for producing the ultrahigh-strength cord steel (grade 90) in China exist, the inclusion control stability is poor, and particularly, the titanium inclusion control difficulty is high, so that the quality level of the cord steel is seriously influenced.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a smelting control method of ultra-high strength cord steel, which reduces the nitrogen content of molten steel to the maximum extent, reduces TiN inclusions in the molten steel, improves the purity of the molten steel, shortens the flow, reduces the treatment time and solves the problems that the inclusions cannot be controlled in a targeted manner in the existing production process, particularly the titanium inclusion control problem and the nitrogen content of the molten steel is higher by controlling the aspects of KR molten iron desulphurization, converter double-slag operation, end-point carbon content, tapping temperature, refining, deoxidation, slagging and the like.
The technical scheme is as follows: the invention relates to a smelting control method of ultrahigh-strength cord steel, which comprises the following specific operation steps:
(1.1) KR desulfurization: adding 8-10 kg/ton of lime powder and 0.8-1.2 kg/ton of fluorite into a ladle to remove the sulfur content in the molten iron, thereby obtaining molten iron with the sulfur content less than or equal to 30 ppm;
(1.2) controlling before converter smelting: adding scrap steel into molten iron subjected to sulfur content removal treatment, wherein before the scrap steel is added, bottom blowing of a converter body is adjusted to be in a full-process argon blowing mode;
(1.3) converter blowing control: carrying out double-slag process treatment on the molten iron added with the scrap steel, namely, carrying out gun lifting and deslagging after gun blowing is carried out for 3-5min, then adding slag charge again for slagging, and adopting a high carbon-drawing process at the end point; thereby obtaining a raw molten steel;
(1.4) controlling before converter tapping: opening a ladle bottom blowing before tapping, and filling argon to discharge air in the ladle;
(1.5) controlling the deoxidation and slagging link of the LF furnace: adding 10-12 kg/ton steel premelted acidic slag charge at the initial stage of LF refining, deoxidizing the slag surface for 6-10 times by adopting high-purity silicon carbide, and carrying out slagging and slag mixing by using lime and quartz sand to obtain molten steel with inclusions in a low melting point region;
(1.6) continuous casting step: controlling the superheat degree of a continuous casting tundish to be less than or equal to 35 ℃, automatically distributing water for cooling secondary cooling water in a weak cooling mode, keeping the specific water amount to be 0.23-0.25 kg/L and the steel amount of residual molten steel to be more than or equal to 4t, continuously casting the molten steel into a bloom, and finally finishing smelting the ultrahigh-strength cord steel.
Further, in the step (1.1), the rotating speed of the stirring paddle in the ladle is more than 100r/min, and the time is more than or equal to 10 min.
Further, in the step (1.3), the obtained raw molten steel is: controlling the mass percentage content of the end point C of the converter to be more than or equal to 0.10 percent and the tapping temperature to be more than or equal to 1600 ℃.
Further, in the step (1.4), the flow rate of the argon filling is controlled to be more than 100NL/min, and the argon filling time is 0.5-2 min.
Further, in the step (1.5), the ratio of each component in the pre-melted acidic slag is as follows: CaO: 38.0-46.0% of Al2O3：≤2.0SiO2：46.0-54.0。
Further, in the step (1.5), the final slag component is controlled in a target slag system through a slag surface deoxidation process:
namely, the weight percentage of SiO2 in the target refining slag system components is 35-50%, the weight percentage of CaO is 30-45%, the weight percentage of Al2O3 is 3-8%, and the alkalinity R is 0.7-0.9.
Further, in the step (1.6), the degree of superheat, the specific water amount, and the steel retention operation are controlled.
Has the advantages that: compared with the prior art, the invention reduces the nitrogen content of the molten steel to the maximum extent, reduces TiN inclusions in the molten steel, improves the purity of the molten steel, shortens the flow and reduces the processing time by controlling the aspects of KR molten iron desulphurization, converter double-slag operation, end point carbon content, tapping temperature, refining deoxidation slagging and the like; the ultrahigh-strength cord steel produced by the method meets the requirements on detection of corresponding inclusions (the level of A, C-type inclusions is less than or equal to 1.0 grade, and the level of B, D-type inclusions is less than or equal to 0.5 grade), and meanwhile, the yield is improved by more than 5% by adopting short-process control, so that the ultrahigh-strength cord steel has higher economic, environmental and social benefits.
Drawings
FIG. 1 is a flow chart of the architecture of the present invention.
Detailed Description
The invention relates to a smelting control method of ultrahigh-strength cord steel, which comprises the following specific operation steps:
(1.1) KR desulfurization: adding 8-10 kg/ton of lime powder and 0.8-1.2 kg/ton of fluorite into a ladle to remove the sulfur content in the molten iron, thereby obtaining molten iron with the sulfur content less than or equal to 30 ppm;
(1.2) controlling before converter smelting: adding scrap steel into molten iron subjected to sulfur content removal treatment, wherein before the scrap steel is added, bottom blowing of a converter body is adjusted to be in a full-process argon blowing mode;
(1.3) converter blowing control: carrying out double-slag process treatment on the molten iron added with the scrap steel, namely, carrying out gun lifting and deslagging after gun blowing is carried out for 3-5min, then adding slag charge again for slagging, and adopting a high carbon-drawing process at the end point; thereby obtaining a raw molten steel;
(1.4) controlling before converter tapping: opening a ladle bottom blowing before tapping, and filling argon to discharge air in the ladle;
(1.5) controlling the deoxidation and slagging link of the LF furnace: adding 10-12 kg/ton steel premelted acidic slag charge at the initial stage of LF refining, deoxidizing the slag surface for 6-10 times by adopting high-purity silicon carbide, and carrying out slagging and slag mixing by using lime and quartz sand to obtain molten steel with inclusions in a low melting point region;
(1.6) continuous casting step: controlling the superheat degree of a continuous casting tundish to be less than or equal to 35 ℃, automatically distributing water for cooling secondary cooling water in a weak cooling mode, keeping the specific water amount to be 0.23-0.25 kg/L and the steel amount of residual molten steel to be more than or equal to 4t, continuously casting the molten steel into a bloom, and finally finishing smelting the ultrahigh-strength cord steel.
Further, in the step (1.1), the rotating speed of the stirring paddle in the ladle is more than 100r/min, and the time is more than or equal to 10 min.
Further, in the step (1.3), the obtained raw molten steel is: controlling the mass percentage content of the end point C of the converter to be more than or equal to 0.10 percent and the tapping temperature to be more than or equal to 1600 ℃.
Further, in the step (1.4), the flow rate of the argon filling is controlled to be more than 100NL/min, and the argon filling time is 0.5-2 min.
Further, in the step (1.5), the ratio of each component in the pre-melted acidic slag is as follows: CaO: 38.0-46.0% of Al2O3：≤2.0SiO2：46.0-54.0。
Further, in the step (1.5), the final slag component is controlled in a target slag system through a slag surface deoxidation process:
namely, the weight percentage of SiO2 in the target refining slag system components is 35-50%, the weight percentage of CaO is 30-45%, the weight percentage of Al2O3 is 3-8%, and the alkalinity R is 0.7-0.9.
Further, in the step (1.6), the degree of superheat, the specific water amount, and the steel retention operation are controlled.
The specific embodiment is as follows:
example 1
A smelting control method of ultra-high strength cord steel (90 grade) comprises the following steps:
(1) adopts KR desulfurization procedure: adding 8 kg/ton of iron lime powder and 1 kg/ton of iron fluorite, stirring at 100r/min1 for 10min, and desulfurizing to obtain molten iron with sulfur content of 24 ppm.
(2) Controlling before smelting in a converter: before adding the scrap steel, the bottom blowing of the converter body is adjusted to be in a full-process argon blowing mode.
(3) And (3) converter blowing control: carrying out gun lifting and deslagging in the converter in the gun blowing process for 3min, and then adding slag charge again for slagging, wherein the end point C of the converter is 0.12%, and the tapping temperature is 1610 ℃;
(4) controlling before converter tapping: and opening the bottom blowing of the ladle before tapping, and filling argon at the flow rate of 110NL/min for 1 min.
(5) Controlling the converter tapping process: and after tapping for 20 seconds, alloy and carbon powder are added for deoxidation alloying, and argon is blown from the bottom in the whole tapping process.
(6) 11 kg/ton steel premelted acidic slag (CaO: 38.0-46.0% Al) is added in the initial stage of LF refining2O3：≤2.0SiO2: 46.0-54.0), adopting high-purity silicon carbide to deoxidize the slag surface for 7 times, wherein the weight percentage of SiO2, CaO, Al2O3 and the alkalinity R in the final-point refined slag system components are 46%, 40%, 5% and 0.87 respectively;
(7) and (3) continuous casting process: the superheat degree of the tundish is 24 ℃, secondary cooling water is automatically distributed with water and cooled by adopting a weak cooling mode, the specific water amount is 0.23kg/L, the steel amount of the residual molten steel is 5t, and the molten steel is continuously cast into a bloom (250mm multiplied by 300mm) to finish smelting.
Through the control of the key nodes by the method, the Ti content of the finished product corresponding to the heat in the embodiment is controlled to be 3ppm, the grades of A, C, B, D-class inclusions corresponding to the rolled material are all 0.5 grade, meanwhile, the [ O ] content is 24ppm, and the [ N ] content is 32ppm, so that various control requirements of the ultrahigh-strength cord steel (90 grade) are met.
Example 2
A smelting control method of ultra-high strength cord steel (90 grade) comprises the following steps:
(1) adopts KR desulfurization procedure: adding 9 kg/ton of iron lime powder and 1.1 kg/ton of iron fluorite, stirring at 110r/min1 for 12min, and desulfurizing to obtain molten iron with sulfur content of 28 ppm.
(2) Controlling before smelting in a converter: before adding the scrap steel, the bottom blowing of the converter body is adjusted to be in a full-process argon blowing mode.
(3) And (3) converter blowing control: the converter is blown for 4min by a lance, lance lifting and slag pouring are carried out, then slag charge is added again for slagging, the end point C of the converter is 0.14%, and the tapping temperature is 1630 ℃;
(4) controlling before converter tapping: and opening the bottom blowing of the ladle before tapping, and filling argon at the flow rate of 110NL/min for 1.5 min.
(5) Controlling the converter tapping process: and after tapping for 20 seconds, alloy and carbon powder are added for deoxidation alloying, and argon is blown from the bottom in the whole tapping process.
(6) 10 kg/ton steel premelted acidic slag (CaO: 38.0-46.0% Al) is added in the initial stage of LF refining2O3：≤2.0SiO2: 46.0-54.0), adopting high-purity silicon carbide to deoxidize the slag surface for 8 times, wherein the weight percentage of SiO2, CaO, Al2O3 and the alkalinity R in the final-point refined slag system components are 48%, 35%, 4% and 0.73 respectively;
(7) and (3) continuous casting process: the superheat degree of the tundish is 28 ℃, secondary cooling water is automatically distributed with water and cooled by adopting a weak cooling mode, the specific water amount is 0.23kg/L, the steel amount of the residual molten steel is 4t, and the molten steel is continuously cast into a bloom (250mm multiplied by 300mm) to finish smelting.
Through the control of the key nodes by the method, the Ti content of the finished product corresponding to the heat in the embodiment is controlled to be 4ppm, the grades of A, C, B, D-class inclusions corresponding to the rolled material are all 0.5 grade, meanwhile, the [ O ] content is 18ppm, the [ N ] content is 30ppm, and various control requirements of the ultrahigh-strength cord steel (90 grade) are met.
Example 3
A smelting control method of ultra-high strength cord steel (90 grade) comprises the following steps:
(1) adopts KR desulfurization procedure: adding 10 kg/ton of iron lime powder and 0.9 kg/ton of iron fluorite, stirring at 120r/min1 for 10min, and desulfurizing to obtain molten iron with sulfur content of 20 ppm.
(2) Controlling before smelting in a converter: before adding the scrap steel, the bottom blowing of the converter body is adjusted to be in a full-process argon blowing mode.
(3) And (3) converter blowing control: the converter lifts the gun and pours the slag after blowing for 5min, then adds the slag charge again for slagging, the end point C of the converter is 0.16%, and the tapping temperature is 1608 ℃;
(4) controlling before converter tapping: and opening the bottom blowing of the steel ladle before tapping, and filling argon at the flow rate of 120NL/min for 1 min.
(5) Controlling the converter tapping process: and after tapping for 20 seconds, alloy and carbon powder are added for deoxidation alloying, and argon is blown from the bottom in the whole tapping process.
(6) 10 kg/ton steel premelted acidic slag (CaO: 38.0-46.0% Al) is added in the initial stage of LF refining2O3：≤2.0SiO2: 46.0-54.0), adopting high-purity silicon carbide to deoxidize the slag surface for 6 times, wherein the weight percentage of SiO2, CaO, Al2O3 and the alkalinity R in the final-point refined slag system components are 45%, 35%, 3.5% and 0.78 respectively;
(7) and (3) continuous casting process: the superheat degree of the tundish is 26 ℃, secondary cooling water is automatically distributed with water and cooled by adopting a weak cooling mode, the specific water amount is 0.24kg/L, the steel amount of the residual molten steel is 5t, and the molten steel is continuously cast into a bloom (250mm multiplied by 300mm) to finish smelting.
Through the control of the key nodes by the method, the Ti content of the finished product corresponding to the heat in the embodiment is controlled to be 3ppm, the grades of A, C, B, D-class inclusions corresponding to the rolled material are all 0.5 grade, meanwhile, the [ O ] is 21ppm, the [ N ] content is 28ppm, and various control requirements of the ultrahigh-strength cord steel (90 grade) are met.
Example 4
A smelting control method of ultra-high strength cord steel (90 grade) comprises the following steps:
(1) adopts KR desulfurization procedure: adding 10 kg/ton of iron lime powder and 1.2 kg/ton of iron fluorite, stirring at 110r/min1 for 10min, and desulfurizing to obtain molten iron with sulfur content of 18 ppm.
(2) Controlling before smelting in a converter: before adding the scrap steel, the bottom blowing of the converter body is adjusted to be in a full-process argon blowing mode.
(3) And (3) converter blowing control: carrying out gun lifting and deslagging in the converter in gun blowing for 3min, and then adding slag charge again for slagging, wherein the end point C of the converter is 0.11%, and the tapping temperature is 1625 ℃;
(4) controlling before converter tapping: and opening the bottom blowing of the steel ladle before tapping, and filling argon at the flow rate of 120NL/min for 2 min.
(5) Controlling the converter tapping process: and after tapping for 20 seconds, alloy and carbon powder are added for deoxidation alloying, and argon is blown from the bottom in the whole tapping process.
(6) The pre-melted acid slag (CaO: 38.0-46.0% Al) of 12 kg/ton steel is added in the initial stage of LF refining2O3：≤2.0SiO2: 46.0-54.0), adopting high-purity silicon carbide to deoxidize the slag surface for 8 times, wherein the weight percentage of SiO2, CaO, Al2O3 and the alkalinity R in the final-point refined slag system components are 48%, 43%, 6% and 0.90 respectively;
(7) and (3) continuous casting process: the superheat degree of the tundish is 29 ℃, secondary cooling water is automatically distributed with water and cooled by adopting a weak cooling mode, the specific water amount is 0.25kg/L, the steel amount of the residual molten steel is 5t, and the molten steel is continuously cast into a bloom (250mm multiplied by 300mm) to finish smelting.
Through the control of the key nodes by the method, the Ti content of the finished product corresponding to the heat in the embodiment is controlled to be 3ppm, and the grades of A, C-class inclusions corresponding to the rolled material are all 1.0 grade; B. the grade of the D-type inclusions is 0.5 grade, meanwhile, the [ O ] content is 22ppm, the [ N ] content is 20ppm, and various control requirements of the ultrahigh-strength cord steel (90 grade) are met.
Comparative example
To further illustrate the process of the present invention, a set of production scenarios not heretofore employed with the process of the present invention is provided below as a comparison. The comparative example does not adopt the relevant measures, and the specific steps are as follows:
1. adopts KR desulfurization procedure: adding 11 kg/ton of iron lime powder and 1 kg/ton of iron fluorite, stirring at a rotating speed of 110r/min1 for 10min, and desulfurizing to obtain molten iron with sulfur content of 25 ppm.
2. Controlling before smelting in a converter: before adding the scrap steel, the bottom blowing of the converter body is in a full-process nitrogen blowing mode.
3. Controlling the carbon content at the end point of the converter: a double-slag process is not adopted, the end point carbon content of the converter is 0.06 percent, and the tapping temperature is 1589 ℃;
2. controlling the tapping temperature of the converter: the tapping temperature of the converter is 1590 ℃;
3. adding time of the aluminum blocks in the tapping process: adding the alloy added with the tapping into an aluminum block;
4. controlling before converter tapping: and the ladle is not filled with argon before tapping.
5. Controlling the converter tapping process: and after tapping for 20 seconds, alloy and carbon powder are added for deoxidation alloying, and argon is blown from the bottom in the whole tapping process.
6. And in the LF refining process, lime and refining slag are adopted for slagging, SiC is adopted for slag surface diffusion deoxidation in the power supply smelting process, and CaO in the end-point slag: 45% SiO2：32％、Al2O3:9％，R：1.4；
7. And (3) continuous casting process: the superheat degree of the secondary cooling water is 33 ℃, the secondary cooling water is cooled by automatic water distribution in a weak cooling mode, the specific water amount is 0.27kg/L, and steel retaining operation is not adopted.
Through the control of the key nodes by the method, the corresponding heat in the embodiment is obtained
The comparative example corresponds to the furnace finished product Ti content of 8ppm, and corresponds to A, C types of rolled stock, the grades are all 1.5 grades; B. the grade of the D-type inclusions is 1.0 grade, and meanwhile, the [ O ] content is 28ppm and the [ N ] content is 46ppm, so that the quality control requirement of the ultrahigh-strength cord steel (90 grade) cannot be met.
By comparing and analyzing the comparative example and the method of the invention, the end point carbon content of the converter of the comparative example is lower, the oxygen content is high, and the burden of subsequent inclusion removal is increased; the converter adopts single slag smelting, the titanium content is reduced from converter slag back to molten steel in the later stage of blowing, the titanium content of the molten steel is higher, and the quantity of TiN inclusions is increased; in the converter blowing process, nitrogen and argon switching is carried out by converter bottom blowing, and ladle argon filling operation is not carried out before tapping, so that the possibility of nitrogen increase of molten steel is increased, and finally, the nitrogen content of the molten steel is higher.
Claims (6)
1. A smelting control method of ultrahigh-strength cord steel is characterized by comprising the following specific operation steps:
(1.1) KR desulfurization: adding 8-10 kg/ton of lime powder and 0.8-1.2 kg/ton of fluorite into a ladle to remove the sulfur content in the molten iron, thereby obtaining molten iron with the sulfur content less than or equal to 30 ppm;
(1.2) controlling before converter smelting: adding scrap steel into molten iron subjected to sulfur content removal treatment, wherein before the scrap steel is added, bottom blowing of a converter body is adjusted to be in a full-process argon blowing mode;
(1.3) converter blowing control: carrying out double-slag process treatment on the molten iron added with the scrap steel, namely, carrying out gun lifting and deslagging after gun blowing is carried out for 3-5min, then adding slag charge again for slagging, and adopting a high carbon-drawing process at the end point; thereby obtaining a raw molten steel;
(1.4) controlling before converter tapping: opening a ladle bottom blowing before tapping, and filling argon to discharge air in the ladle;
(1.5) controlling the deoxidation and slagging link of the LF furnace: adding 10-12 kg/ton steel premelted acidic slag charge at the initial stage of LF refining, deoxidizing the slag surface for 6-10 times by adopting high-purity silicon carbide, and carrying out slagging and slag mixing by using lime and quartz sand to obtain molten steel with inclusions in a low melting point region;
(1.6) continuous casting step: controlling the superheat degree of a continuous casting tundish to be less than or equal to 35 ℃, automatically distributing water for cooling secondary cooling water in a weak cooling mode, keeping the specific water amount to be 0.23-0.25 kg/L and the steel amount of residual molten steel to be more than or equal to 4t, continuously casting the molten steel into a bloom, and finally finishing smelting the ultrahigh-strength cord steel.
2. The method for controlling smelting of an ultra-high strength cord steel according to claim 1, wherein in the step (1.1), the rotating speed of the stirring paddle in the ladle is more than 100r/min, and the time is more than or equal to 10 min.
3. The method for controlling smelting of an ultra-high strength cord steel according to claim 1, wherein in the step (1.3), the obtained raw molten steel is: controlling the mass percentage content of the end point C of the converter to be more than or equal to 0.10 percent and the tapping temperature to be more than or equal to 1600 ℃.
4. The method for controlling smelting of an ultra-high strength cord steel according to claim 1, wherein in the step (1.4), the flow rate of argon injection is controlled to be more than 100NL/min, and the argon injection time is 0.5-2 min.
5. The method for controlling smelting of ultra-high strength cord steel according to claim 1, wherein in step (1.5), the ratio of each component in the pre-melted acidic slag is: CaO: 38.0-46.0% of Al2O3：≤2.0SiO2：46.0-54.0。
6. The method for controlling smelting of an ultra-high strength cord steel according to claim 1, wherein in the step (1.5), the final slag composition is controlled to a target slag system by a slag surface deoxidation process:
namely, the weight percentage of SiO2 in the target refining slag system components is 35-50%, the weight percentage of CaO is 30-45%, the weight percentage of Al2O3 is 3-8%, and the alkalinity R is 0.7-0.9.
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