CN111485068B - Smelting method of IF steel with high surface quality - Google Patents
Smelting method of IF steel with high surface quality Download PDFInfo
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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
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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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
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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
- 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
- C21C7/076—Use of slags or fluxes as treating agents
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Abstract
The smelting method of the IF steel with high surface quality adopts a manufacturing process of BOF-LF-RH-CC, solves the problem of insufficient semi-steel heat source by heating molten steel through an LF furnace, reduces the addition of slag materials except for adding submerged arc and absorbing necessary slag materials required by inclusion in the LF treatment heating process after the molten steel is processed and tapped and before RH treatment and deoxidation, avoids the transfer of oxygen in the molten steel to slag in the process, and transfers oxygen in the slag to the steel in the molten steel carrying and continuous casting pouring processes after the molten steel is decarburized and deoxidized to cause the secondary oxidation of the molten steel and generate endogenic inclusion to pollute the molten steel. By adopting the smelting method, the inclusion control level can be improved, and the production cost can be reduced.
Description
Technical Field
The invention belongs to the technical field of smelting, and particularly relates to a smelting method of IF steel with high surface quality.
Background
IF steel (Interstitial Free Stee1), also known as Interstitial Free steel, is known as the third generation extra deep drawing steel because of its excellent deep drawing properties, high plastic strain ratio, high elongation, high hardening index, low yield ratio, and excellent non-aging properties. IF steel is mainly used for inner plates and outer plates of automobiles in automobiles, and in recent years, automobile manufacturing enterprises have higher quality requirements on steel plates for automobiles, and IF steel used as automobile appearance parts has higher surface quality requirements on steel coils. Inclusion defects have always been the major defect causing surface quality problems in IF steels, typically accounting for over 60% of surface quality defects in IF steels. 05, each steel coil is required to have no inclusion defects with the length being more than 100mm, the width being more than 1mm and the number being more than 3 or no inclusion defects with the length being more than 50mm, the width being more than 1mm and the number being more than 10, and the highest grade of the 05 surface is even required to have no inclusion defects.
In 2017, in journal of vanadium and titanium iron (Vol. 38, 156-160 nd 2 nd page of IF steel cold-rolled plate surface strip defect cause and control method, Dengjian Jun et al), a method for controlling inclusion defects of Handy steel in molten iron smelting of IF steel strip is reported, and in journal of steelmaking, in 2019, in 12 th month (Vol. 35, 55-56 th page 6 th page of first Jingtang IF steel production process development practice, Anchao et al), a control method for inclusion defects of first Steel Jingtang adopting molten iron smelting IF steel is also reported. All the reports adopt a control method for smelting IF steel inclusions by molten iron. For semisteel (a product of vanadium-containing molten iron after vanadium slag extraction), the carbon content and the temperature of the semisteel are both lost to a certain extent after vanadium extraction treatment, and in addition, the vanadium-titanium-iron ore semisteel with high sulfur content (average content is more than or equal to 0.080 percent) needs long-time pre-desulfurization treatment, if a manufacturing process of BOF-RH-CC is still adopted,the proportion of the deep blowing at the end point of the converter is increased, so that the oxygen activity in molten steel and slag is increased, and Al is increased2O3The difficulty in controlling inclusions is very low in yield for IF steel for smelting panels and even for IF steel for internal plates of some host factories. The Chinese scientific and technological project innovation achievement identification suggestion database (known halftone) reports a steel climbing method for smelting low-oxygen low-carbon IF steel by using vanadium-titanium molten iron (2016, old and bright) and adopts a BOF-LF-RH-CC manufacturing process to produce low-carbon low-oxygen IF steel, the problem of insufficient heat source in semi-steel smelting IF steel is well solved by using the heating function of an LF furnace, the problem of nitrogen absorption in the heating process of an LF procedure is solved, the component control can reach the level of smelting IF steel by using molten iron in the same industry, but the process is applied to the present, the problem of inclusion control cannot be well solved, and the inclusion control level is different from that of smelting IF steel by using molten iron in the same industry. In 2020, 1, 17 days, a chinese patent database (zhizi) discloses a method for smelting IF steel at low cost by semisteel in climbing steel, chen lu et al (main classification number: C22C33/06, patent classification no: C22C 33/06; C21C 5/28; C21C 7/10; C22C 38/02; C22C 38/04; C22C 38/14; C22C 38/06; C22C38/12), the method uses the thought of smelting IF steel by molten iron, adopts a BOF-RH-CC manufacturing process, aims to solve the problem of insufficient heat source of semi-steel smelting IF steel by improving the tapping temperature of a converter and the heat preservation in the molten steel process, has not been verified in batch at present, it is expected that the problem of insufficient heat source still remains when the molten iron resources are insufficient or the production is unstable, and in this case, the temperature is raised by deep blowing in a converter or RH aluminum heating (aluminum oxidation heat release and generation of Al are accompanied by generation of Al) is employed.2O3Inclusions) to increase the temperature all present the problem of increasing the risk of inclusions, while increasing the tapping temperature also may cause a reduction in the life of the lining of the converter. Therefore, a technical breakthrough is still needed in the aspect of smelting high-surface-quality IF steel from semisteel after vanadium extraction treatment of high-sulfur vanadium-titanium molten iron.
In conclusion, the technical personnel in the field need to solve the problem of how to provide an IF steel smelting method which can improve the inclusion control level and reduce the production cost.
Disclosure of Invention
The invention aims to provide a smelting method of IF steel with high surface quality, which can improve the inclusion control level and reduce the production cost.
In order to solve the technical problem, the invention provides a smelting method of IF steel with high surface quality, which comprises the following steps:
1) BOF treatment: smelting molten steel in a converter, and by oxygen blowing decarburization, molten steel heating and slagging dephosphorization, enabling the content of C in the molten steel to be less than or equal to 0.05%, the content of P to be less than or equal to 0.020%, the content of S to be less than or equal to 0.020%, controlling the oxygen activity of molten steel at the end point of the converter to be 500-800 ppm, and controlling the tapping temperature to be 1660 +/-20 ℃, wherein lime is not added for slag washing and pre-deoxidation is not carried out in the tapping process;
2) the small platform behind the furnace does not carry out slag regulation treatment on the ladle slag, and does not blow argon, measure temperature and fix oxygen;
3) and (3) LF treatment: directly conveying the steel from a small platform behind a furnace to an LF furnace for heating, adding 0.5-1.0 kg/t of steel slag foaming agent and 2.0-3.0 kg/t of steel active lime for slagging and arc burying in the heating process, adding necessary slag materials required by adsorption and inclusion on the premise of keeping Ca/Al of ladle slag to be 1.4-1.8, adding steel with the total amount of the slag materials being less than or equal to 4.0kg/t, and leaving the station without adding slag regulating agent;
4) RH treatment: sequentially carrying out decarburization, denitrification, deoxidation, alloying and ladle slag regulation treatment on molten steel at the RH station in sequence, adding 2.5-3.5 kg/t of steel by using an aluminum-containing slag regulator before leaving the station, and controlling the outbound components to be that the middle limit of the target component of the content of Als is + 0.0030%, the content of C is less than or equal to 0.0040%, the content of Mn is 0.05-0.30%, the content of P is less than or equal to 0.020%, the content of S is less than or equal to 0.020%, the content of N is less than or equal to 0.0040%, the content of Ti is 0.02-0.08%, and the content of O is less than or equal to 0.0020%;
5) and (3) CC treatment: and (5) continuous casting and pouring.
Preferably, in the smelting method, in the step 1), the sliding plate is used for blocking slag during the tapping process of the converter, and lime is not added into a ladle.
Preferably, in the smelting method, in the step 3), after the heating compensation temperature of the LF furnace reaches the target temperature of 1635 +/-15 ℃, no slag modifier is added after the LF furnace leaves the station; and (4) conveying to the RH station of the step 4).
Preferably, in the above smelting method, in the step 4), the outlet temperature is controlled to be 1595 ± 15 ℃.
Preferably, in the smelting method, in the step 4), 2.5-3.5 kg/t of slag modifier is added to modify the ladle slag, and after 15-40 minutes of sedation, continuous casting is carried out.
Preferably, in the above smelting method, in the step 1), the molten iron is subjected to vanadium pre-extraction and pre-desulfurization before the molten steel is smelted in the converter.
Preferably, in the smelting method, the vanadium pre-extraction process is as follows: and extracting vanadium from the molten iron to obtain semisteel, wherein the content of C in the semisteel is controlled to be 3.50 +/-0.30%, and the temperature is 1350 +/-30 ℃.
The smelting method of the IF steel with high surface quality adopts a manufacturing process of BOF-LF-RH-CC, solves the problem of insufficient semi-steel heat source by heating molten steel through an LF furnace, reduces the addition of slag materials except for adding submerged arc and absorbing necessary slag materials required by inclusion in the LF treatment heating process after the molten steel is processed and tapped and before RH treatment and deoxidation, avoids the transfer of oxygen in the molten steel to slag in the process, and transfers oxygen in the slag to the steel in the molten steel carrying and continuous casting pouring processes after the molten steel is decarburized and deoxidized to cause the secondary oxidation of the molten steel and generate endogenic inclusion to pollute the molten steel. By adopting the smelting method, the inclusion control level can be improved, and the production cost can be reduced.
Detailed Description
The core of the invention is to provide a smelting method of IF steel with high surface quality, which can improve the inclusion control level and reduce the production cost.
In order to make those skilled in the art better understand the technical solutions provided by the present invention, the present invention will be further described in detail with reference to specific embodiments.
The invention provides a smelting method of IF steel with high surface quality, which adopts a BOF-LF-RH-CC process and specifically comprises the following steps:
1) BOF treatment: smelting molten steel in a converter, and controlling the content of C in the molten steel to be less than or equal to 0.05%, the content of P to be less than or equal to 0.020%, the content of S to be less than or equal to 0.020%, the oxygen activity of the molten steel at the end point of the converter to be 500-800 ppm and the tapping temperature of the converter to be 1660 +/-20 ℃ by blowing oxygen for decarburization, heating the molten steel and slagging and dephosphorizing. Wherein, lime is not added for slag washing and pre-deoxidation are not carried out in the tapping process; before decarburization and deoxidation in RH treatment, because the oxygen activity of the molten steel is at a high oxygen level of 500-800 ppm, the addition of slag is reduced, and the possibility that oxygen absorption and nitrogen absorption pollute the molten steel and influence the control of the nitrogen content of the molten steel is avoided.
2) The small platform behind the furnace does not carry out slag regulation treatment on the ladle slag, and does not blow argon, measure temperature and fix oxygen;
3) and (3) LF treatment: directly conveying the steel from a small platform behind a furnace to an LF furnace for heating, adding 0.5-1.0 kg/t of steel slag foaming agent and 2.0-3.0 kg/t of steel active lime for slagging and arc burying in the heating process, adding necessary slag materials required by adsorption and inclusion on the premise of keeping Ca/Al of ladle slag to be 1.4-1.8, adding steel with the total amount of the slag materials being less than or equal to 4.0kg/t, and leaving the station without adding slag regulating agent; the slag mainly comprises a slag foaming agent and lime.
4) RH treatment: the molten steel is sequentially subjected to decarburization, denitrification, deoxidation, alloying and ladle slag regulation treatment at an RH station, 2.5-3.5 kg/t of steel is added with an aluminum-containing slag regulator before leaving the station, and the outbound components are controlled to have the middle limit of Als content target components of + 0.0030%, C content of less than or equal to 0.0040%, Mn content of 0.05-0.30%, P content of less than or equal to 0.020%, S content of less than or equal to 0.020%, N content of less than or equal to 0.0040%, Ti content of 0.02-0.08% and O content of less than or equal to 0.0020%;
5) and (3) CC treatment: and (5) continuous casting and pouring.
It is to be noted that the main purpose of adding lime slag washing in the steel ladle in the converter tapping process is as follows: 1) promoting the polymerization of the deoxidation product, thereby promoting the floating of the inclusion; 2) certain P is removed by utilizing the dynamic condition of the tapping process; 3) and covering and insulating molten steel. The IF steel does not deoxidize in the converter tapping process, and does not generate a deoxidized product, so that the task of promoting the deoxidized product to polymerize and float does not exist; secondly, the content of P in the vanadium-titanium molten iron is low, and the control of P is not a main contradiction for IF steel; thirdly, IF steel is undeoxidized steel, the covering effect of molten steel is slightly poor, and the problem of nitrogen absorption is not worried about, theoretical research shows that the molten steel is easier to absorb nitrogen in a deoxidized state, the nitrogen absorption amount is extremely low in the undeoxidized state, and the temperature loss can be compensated by accelerating the transfer speed of the molten steel (small platform does not measure temperature and fix oxygen). Therefore, the technical analysis that lime is not added into a steel ladle in the process of converter tapping is considered to be feasible, and the aim of reducing the addition of the lime is to reduce the total slag amount in the steel ladle before RH treatment decarburization and deoxidation, further reduce the oxygen capacity of slag and avoid the transmission of oxygen in steel slag after RH treatment decarburization and deoxidation to steel so as to cause secondary oxidation of molten steel.
The smelting method of the IF steel with high surface quality adopts a manufacturing process of BOF-LF-RH-CC, solves the problem of insufficient semi-steel heat source by heating molten steel through an LF furnace, reduces the addition of slag materials except for adding submerged arc and absorbing necessary slag materials required by inclusion in the LF treatment heating process after the molten steel is processed and tapped and before RH treatment and deoxidation, avoids the transfer of oxygen in the molten steel to slag in the process, and transfers oxygen in the slag to the steel in the molten steel carrying and continuous casting pouring processes after the molten steel is decarburized and deoxidized to cause the secondary oxidation of the molten steel and generate endogenic inclusion to pollute the molten steel.
By adopting the smelting method, the Als loss (an index for representing secondary oxidation and mainly caused by the secondary oxidation of molten steel) from the vacuum station-out of the IF steel to the continuous casting is averagely 25ppm, the average loss is reduced by 30ppm compared with the prior art, the inclusion generated by the secondary oxidation is greatly reduced, the discovery rate of the inclusion of the steel coil is reduced by 10-20% in a same ratio, meanwhile, lime is not added in the tapping process, the temperature and oxygen measurement of a small platform behind the furnace are not carried out, a slag regulating agent is not added in the LF furnace, the aluminum wire addition can be reduced due to the reduction of the Als loss from the vacuum station-out to the continuous casting, the water gap is not changed in the continuous casting pouring process due to the improvement of the purity of the molten steel, and the like, and the production cost can be averagely reduced by 13.2 yuan/ton. Therefore, the inclusion control level can be improved, and the production cost can be reduced.
Because the molten steel is pretreated before being smelted by the converter, vanadium is extracted and desulfurization is carried out. The process of pre-extracting vanadium comprises the following steps: extracting vanadium from the molten iron to obtain semisteel, wherein the content of C in the semisteel is controlled to be 3.50 +/-0.30%, and the temperature is 1350 +/-30 ℃.
In a specific embodiment, a sliding plate is used for blocking slag in the converter tapping process to prevent converter slag from entering a steel ladle, and lime is not added into the steel ladle.
In the specific implementation mode of the LF treatment process, the small platform behind the furnace does not carry out slag regulation treatment on ladle slag, and argon blowing, temperature measurement and oxygen fixing are not carried out.
For semi-steel smelting IF steel, the main function of the LF treatment station is to compensate temperature. Meanwhile, the prior art also carries out slag conditioning treatment on the steel slag in the working procedure, and aims to reduce the oxidability of the slag and prevent the secondary oxidation of molten steel. But the molten steel is not deoxidized at this time, even if a part of oxygen in the steel slag is removed, the oxygen of the molten steel in the subsequent process is transferred to the slag to achieve new balance, but the oxygen for RH process natural decarburization is lost, meanwhile, the slag regulating agent is added to increase the slag amount and correspondingly increase the oxygen capacity of the slag, and the oxygen in the slag is transferred to the molten steel after RH deoxidation alloying, but the secondary oxidation of the molten steel is increased. Therefore, the slag can be adjusted in the LF procedure without adding a ladle slag adjusting agent.
The molten steel refining task of IF steel is mainly in RH processing procedure, small platform temperature measurement and oxygen determination have no substantive significance, and the consumption of temperature measurement and oxygen determination probes is increased, so that the production cost is increased, and the method can also be cancelled.
In a specific embodiment, since the LF treatment process aims at adopting an electric heating compensation temperature, in order to improve the heating efficiency, the LF furnace is transported to the RH station in step 4) after the heating compensation temperature reaches the target temperature of 1635 ± 15 ℃.
In a specific embodiment, in the LF treatment process, before RH decarburization and deoxidation, steel with the total amount of slag materials less than or equal to 4.0kg/t is added into a steel ladle, specifically, 2.0-3.0 kg/t of steel lime and 0.5-1.0 kg/t of steel slag foaming agent are added. The method is also suitable for smelting IF steel by molten iron with less slag added into the steel ladle before RH decarburization and deoxidation.
In a specific embodiment, after decarburization and deoxidation alloying are completed in an RH treatment station, oxygen balance between slag and metal is broken, oxygen potential in slag is higher than that in molten steel, oxygen in slag is transferred to the molten steel, so that secondary oxidation of the molten steel is caused, a slag modifier is required to be added in time for slag adjustment, and the addition amount is enough and is 2.5-3.5 kg per ton of steel. The RH outbound component is controlled to have the middle limit of Als content target component of + 0.0030%, C content of less than or equal to 0.0040%, Mn content of 0.05-0.30%, P content of less than or equal to 0.020%, S content of less than or equal to 0.020%, N content of less than or equal to 0.0040%, Ti content of 0.02-0.08% and O content of less than or equal to 0.0020%.
In addition, the outbound temperature was controlled at 1595 ± 15 ℃. Adding 2.5-3.5 kg/t slag modifier to carry out slag modification on the ladle slag, and carrying out continuous casting and pouring after 15-40 minutes of sedation.
The method has no difference from other methods in the control requirement of continuous casting pouring, mainly performs protection pouring, liquid level stability control and the like, and is not described again here.
The complete smelting process is 'molten iron pretreatment → converter smelting molten steel → molten steel LF furnace heating → molten steel RH refining → molten steel continuous casting pouring'.
According to the IF steel smelting process, the method specifically comprises the following steps:
pretreating molten iron
The molten iron is vanadium-titanium molten iron, and is mainly characterized by containing a certain vanadium element, high sulfur content and low temperature, so that the vanadium pre-extraction and the pre-desulfurization treatment are carried out firstly. The vanadium pre-extraction is to blow oxygen to molten iron through an oxygen top-blowing converter, vanadium oxide elements enter vanadium slag, carbon elements in the molten iron are oxidized to a certain degree while vanadium is oxidized, the temperature is increased to a certain degree, the molten iron after vanadium extraction is called semi-steel, the C of the semi-steel after vanadium extraction is controlled to be 3.50 +/-0.30 percent, the temperature is 1350 +/-30 ℃, and the semi-steel is further subjected to pre-desulfurization treatment and then added into a steel-making converter for steel making.
(II) preliminary smelting of molten steel-smelting molten steel in converter
The steelmaking converter continues to blow oxygen, decarbonize, heat, slag and dephosphorize, and the converter end point controls the molten steel components as follows: c is less than or equal to 0.05 percent, P is less than or equal to 0.020 percent, S is less than or equal to 0.020 percent, O is less than or equal to 500ppm and less than or equal to 800ppm, the temperature is controlled at 1660 +/-20 ℃, then molten steel is poured into a ladle, and a sliding plate is adopted for stopping slag in the converter tapping process to prevent converter slag from entering the ladle. The process of washing the slaked lime slag is adopted in the process of tapping of the converter, no other slag charge is added, the deoxidation is not carried out, the operations of argon blowing, temperature measurement, oxygen determination and the like of a small platform behind the converter are cancelled after tapping, and the molten steel is directly hoisted to an LF station.
(III) refining of molten Steel
The refining of the molten steel is carried out in two procedures, the molten steel is firstly heated by adopting electric arc in an LF procedure to compensate the deficiency of a semi-steel steelmaking heat source, and then the molten steel is hung to an RH station to be subjected to decarburization, deoxidation, final component control, slag regulation and other treatments.
1. LF furnace heating of molten steel
And (3) adopting electric heating to compensate temperature: after the molten steel is subjected to an electric heating process, argon blowing and heating are immediately started, 0.5-1.0 kg/t of steel slag foaming agent and 2.0-3.0 kg/t of steel active lime are added in the heating process to make slag and bury foxes so as to improve the heating efficiency and prevent nitrogen absorption, slag is added as little as possible on the premise that the Ca/Al of ladle slag is kept 1.4-1.8 so as to ensure the adsorption capacity of slag inclusion, and finally the temperature of the molten steel is controlled at 1635 +/-15 ℃ in an LF station. In order to reduce the slag amount, an aluminum-containing slag modifier is not added in the LF procedure.
2. RH refining
The main tasks of RH refining are decarburization, deoxidation and final molten steel alloying, and simultaneously, the oxidizability of steel slag is reduced so as to reduce the secondary oxidation of molten steel after the molten steel is deoxidized and alloyed. The molten steel decarburization is carried out by natural decarburization or forced oxygen decarburization according to the oxygen content of the steel, and the molten steel composition is adjusted according to the composition requirement of the target steel grade after deoxidation. Wherein the content of Als is controlled to be +0.0030 percent (about 0.0020 percent lower than that of the prior art) of the target component middle limit so as to compensate Als loss caused by secondary oxidation, and other outbound components are controlled as follows: less than or equal to 0.0040 percent of C, 0.05 to 0.30 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, less than or equal to 0.0040 percent of N, 0.02 to 0.08 percent of Ti and less than or equal to 0.0020 percent of O. The outlet temperature is controlled to be 1595 +/-15 ℃. 2.5-3.5 kg/t of steel containing an aluminum slag modifier is added before leaving the station, oxygen in part of steel slag is removed, and secondary oxidation of molten steel caused by transfer of oxygen in slag to molten steel is reduced.
(IV) continuous casting
After RH treatment of the molten steel is finished, the molten steel is calmed for 15-40 minutes, and then continuous casting is carried out, the method has no difference from other methods in the control requirement of continuous casting, and mainly has the advantages of protective casting, liquid level stability control and the like, and is not described again here.
The following examples 1-3 prove that the IF steel obtained by the smelting method of the invention has a technical effect obviously superior to that of the original process.
Example 1:
smelting a steel seed M3A35, wherein after vanadium extraction and desulfurization of molten iron, the semi-steel enters a steel converter, the content of C is 3.7 percent, the content of S is 0.0037 percent, the steel converter is blown for 22 minutes and 19 seconds, the content of C at the end point of the converter is 0.04 percent, the activity of O is 655ppm, the temperature is 1656 ℃, lime is not added in the tapping process, and a slag modifier is not added in a small platform behind the converter; heating the LF furnace for 8 minutes at 1622 ℃ before heating, adding 481kg of lime and 164kg of slag foaming agent in the heating process, not adding a slag adjusting agent when leaving the station, and keeping the leaving temperature at 1642 ℃; RH processing is carried out for 32 minutes and 56 seconds, O activity after cyclic decarburization is 306.35ppm, 404kg of slag modifier is added before leaving the station, the leaving temperature is 1598 ℃, the Als content of the molten steel leaving the station is 0.0353 percent, and the Als content of the finished molten steel is 0.038 percent.
The actual implementation effect is as follows: 1. 645kg of slag charge is added into the ladle before the molten steel enters the RH process, which is reduced by about 2.43kg/t steel compared with the slag amount in the prior art; 2. als hardly has oxidation loss in the process from RH station leaving to continuous casting pouring, which indicates that the secondary oxidation of molten steel is very slight and is obviously superior to the original process; 3. the N content of the finished molten steel is 17ppm, the standard component requirements of steel grades are met, and the risk of nitrogen absorption of the molten steel due to reduction of slag amount is avoided; 4. the castability of the molten steel is good in the continuous casting process, and the ladle is continuously cast for the second time; 5. the LF furnace does not replace a tundish immersion nozzle, and the time for replacing the nozzle is prolonged by about 60 minutes compared with the original process; 6. the inclusion discovery rate 41.17 percent of Al in the shape of short strips (the length is less than or equal to 100mm and the width is less than or equal to 1mm) after the continuous casting billet is rolled into a cold-rolled steel coil3O2The existence rate of fine impurities and large impurities is 0 percent, which is superior to the original process level.
Example 2:
smelting a steel seed M3A30, wherein after vanadium extraction and desulfurization of molten iron, the semi-steel enters a steel converter, the content of C is 3.3 percent, the content of S is 0.0053 percent, the steel converter is blown for 17 minutes and 34 seconds, the content of C at the end point of the converter is 0.03 percent, the activity of O is 713ppm, the temperature is 1640 ℃, lime is not added in the tapping process, and a slag modifier is not added in a small platform behind the converter; heating for 17 minutes at 1580 ℃ before heating in an LF (ladle furnace), adding 650kg of lime and 116kg of slag foaming agent in the heating process, leaving station without adding slag modifier, and leaving station at 1645 ℃; RH processing is carried out for 28 minutes and 29 seconds, O activity after cyclic decarburization is 312.18ppm, 600kg of slag modifier is added before leaving the station, the leaving temperature is 1583 ℃, the Als content of the leaving molten steel is 0.036 percent, and the Als content of the finished molten steel is 0.037 percent.
The actual implementation effect is as follows: 1. 766kg of slag is added into a steel ladle before molten steel enters an RH process, and the amount of slag is reduced by about 1.85kg/t steel compared with that of the slag in the prior art; 2. als hardly has oxidation loss in the process from RH station leaving to continuous casting pouring, which indicates that the secondary oxidation of molten steel is very slight and is obviously superior to the original process; 3. the N content of the finished molten steel is 23ppm, the standard component requirements of steel grades are met, and the risk of nitrogen absorption of the molten steel due to reduction of slag amount is avoided; 4. the castability of the molten steel is good in the continuous casting process, and the ladle is continuously cast for the second time; 5. the LF furnace does not replace a tundish immersion nozzle, and the time for replacing the nozzle is prolonged by about 50 minutes compared with the original process; 6. the inclusion discovery rate of the continuously cast bloom after being rolled into cold-rolled steel coils is 40 percent, wherein one steel coil has 1 large-scale inclusion with the length of 1300mm, and the rest are short-strip Al3O2The existence rate of fine impurities and large impurities is 6.67 percent, which is superior to the original process level.
Example 3:
smelting a steel seed M3A30, wherein after vanadium extraction and desulfurization of molten iron, the semi-steel enters a steel converter, the content of C is 3.7 percent, the content of S is 0.0051 percent, the steel converter is blown for 15 minutes and 10 seconds, the content of C at the end point of the converter is 0.05 percent, the activity of O is 575ppm, the temperature is 1657 ℃, lime is not added in the tapping process, and a slag modifier is not added in a small platform behind the converter; the LF furnace is heated at 1647 ℃ for 10 minutes before heating, lime 383kg and a slag foaming agent 200kg are added in the heating process, no slag regulating agent is added when the LF furnace leaves the station, and the leaving temperature is 1622 ℃; RH processing is carried out for 30 minutes and 14 seconds, O activity after cyclic decarburization is 334.507ppm, 505kg of slag modifier is added before leaving the station, the leaving station temperature is 1593 ℃, the content of Als in the molten steel leaving the station is 0.0314 percent, and the content of Als in the finished molten steel is 0.031 percent.
The actual implementation effect is as follows: 1. 645kg of slag charge is added into the ladle before the molten steel enters the RH process, which is reduced by about 2.73kg/t steel compared with the slag amount in the prior art; 2. als hardly has oxidation loss in the process from RH station leaving to continuous casting pouring, which indicates that the secondary oxidation of molten steel is very slight and is obviously superior to the original process; 3. the N content of the finished molten steel is 24ppm, the standard component requirements of steel grades are met, and the risk of nitrogen absorption of the molten steel due to reduction of slag amount is avoided; 4. the castability of the molten steel is good in the continuous casting process, and the ladle is continuously cast for the second time; 5. the LF furnace does not replace a tundish immersion nozzle, and the time for replacing the nozzle is prolonged by about 50 minutes compared with the original process;6. the inclusion discovery rate of the continuously cast bloom after being rolled into a cold-rolled steel coil is 31.25 percent, and the Al is in a short strip shape3O2The existence rate of fine impurities and large impurities is 0 percent, which is superior to the original process level.
The method can be used for smelting IF steel by using semisteel and can also be used for smelting IF steel by using molten iron, and the method belongs to the protection scope of the invention.
The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (7)
1. A smelting method of IF steel with high surface quality is characterized by comprising the following steps:
1) BOF treatment: smelting molten steel in a converter, and by oxygen blowing decarburization, molten steel heating and slagging dephosphorization, enabling the content of C in the molten steel to be less than or equal to 0.05%, the content of P to be less than or equal to 0.020%, the content of S to be less than or equal to 0.020%, controlling the oxygen activity of molten steel at the end point of the converter to be 500-800 ppm, and controlling the tapping temperature of the converter to be 1660 +/-20 ℃, wherein lime is not added for slag washing and pre-deoxidation is not carried out in the tapping process;
2) the small platform behind the furnace does not carry out slag regulation treatment on the ladle slag, and does not blow argon, measure temperature and fix oxygen;
3) and (3) LF treatment: directly conveying the steel from a small platform behind a furnace to an LF furnace for heating, adding 0.5-1.0 kg/t of steel slag foaming agent and 2.0-3.0 kg/t of steel active lime for slagging and arc burying in the heating process, adding necessary slag materials required by adsorption and inclusion on the premise of keeping Ca/Al of ladle slag to be 1.4-1.8, adding steel with the total amount of the slag materials being less than or equal to 4.0kg/t, and leaving the station without adding slag regulating agent;
4) RH treatment: sequentially carrying out decarburization, denitrification, deoxidation, alloying and ladle slag regulation treatment on molten steel at the RH station in sequence, adding 2.5-3.5 kg/t of steel by using an aluminum-containing slag regulator before leaving the station, and controlling the outbound components to be that the middle limit of the target component of the content of Als is + 0.0030%, the content of C is less than or equal to 0.0040%, the content of Mn is 0.05-0.30%, the content of P is less than or equal to 0.020%, the content of S is less than or equal to 0.020%, the content of N is less than or equal to 0.0040%, the content of Ti is 0.02-0.08%, and the content of O is less than or equal to 0.0020%;
5) and (3) CC treatment: and (5) continuous casting and pouring.
2. The method for smelting the IF steel with high surface quality according to claim 1, wherein in step 1), the converter tapping process uses a sliding plate for slag blocking, and lime is not added into the ladle.
3. The method for smelting the IF steel with high surface quality as recited in claim 1, wherein in the step 3), no slag modifier is added when the LF furnace is out of the station, and the LF furnace is transported to the RH station in the step 4) after the heating compensation temperature is up to the target temperature of 1635 +/-15 ℃.
4. The method for smelting IF steel with high surface quality according to claim 1, wherein the temperature of the tapping in step 4) is controlled to 1595 ± 15 ℃.
5. The smelting method of the IF steel with high surface quality as claimed in claim 1, wherein in the step 4), 2.5-3.5 kg/t of slag modifier is added to carry out slag modification on the ladle slag, and continuous casting is carried out after 15-40 minutes of sedation.
6. The method for smelting the IF steel with high surface quality according to claim 1, wherein in the step 1), the molten iron is subjected to vanadium pre-extraction and pre-desulfurization before the molten steel is smelted in the converter.
7. The smelting method of the IF steel with high surface quality as claimed in claim 6, wherein the pre-vanadium extracting process is: and extracting vanadium from the molten iron to obtain semisteel, wherein the content of C in the semisteel is controlled to be 3.50 +/-0.30%, and the temperature is 1350 +/-30 ℃.
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| CN113564449A (en) * | 2021-07-28 | 2021-10-29 | 攀钢集团攀枝花钢铁研究院有限公司 | Semi-steel smelting method of phosphorus-containing high-strength IF steel |
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| CN101550475A (en) * | 2009-05-15 | 2009-10-07 | 首钢总公司 | Method for producing ultra-low-carbon steel |
| CN110468257A (en) * | 2019-09-12 | 2019-11-19 | 马鞍山钢铁股份有限公司 | It is a kind of suitable for low-carbon, the ladle top slag method for modifying of ultra-low-carbon steel |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101550475A (en) * | 2009-05-15 | 2009-10-07 | 首钢总公司 | Method for producing ultra-low-carbon steel |
| CN110468257A (en) * | 2019-09-12 | 2019-11-19 | 马鞍山钢铁股份有限公司 | It is a kind of suitable for low-carbon, the ladle top slag method for modifying of ultra-low-carbon steel |
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