CN116694847A - Method for producing low manganese molten steel by converter process - Google Patents
Method for producing low manganese molten steel by converter process Download PDFInfo
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- 239000011572 manganese Substances 0.000 title claims abstract description 75
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 70
- 239000010959 steel Substances 0.000 title claims abstract description 70
- 238000000034 method Methods 0.000 title claims abstract description 37
- 229910052748 manganese Inorganic materials 0.000 title claims abstract description 23
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 110
- 229910052742 iron Inorganic materials 0.000 claims abstract description 53
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 34
- 239000001301 oxygen Substances 0.000 claims abstract description 34
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 33
- 238000007664 blowing Methods 0.000 claims abstract description 30
- 238000010438 heat treatment Methods 0.000 claims abstract description 29
- 239000002893 slag Substances 0.000 claims abstract description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 22
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 20
- 230000001590 oxidative effect Effects 0.000 claims abstract description 14
- 238000007670 refining Methods 0.000 claims abstract description 13
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 12
- 230000003009 desulfurizing effect Effects 0.000 claims abstract description 12
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 10
- 239000007800 oxidant agent Substances 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims abstract description 10
- 230000000694 effects Effects 0.000 claims abstract description 9
- 239000008188 pellet Substances 0.000 claims abstract description 9
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 7
- 238000007599 discharging Methods 0.000 claims abstract description 4
- 238000003825 pressing Methods 0.000 claims abstract description 4
- 238000003723 Smelting Methods 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 5
- 238000010079 rubber tapping Methods 0.000 claims description 4
- 229910052717 sulfur Inorganic materials 0.000 claims description 4
- 238000005261 decarburization Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 230000000977 initiatory effect Effects 0.000 claims description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000006213 oxygenation reaction Methods 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 3
- 229910000617 Mangalloy Inorganic materials 0.000 description 3
- 235000011941 Tilia x europaea Nutrition 0.000 description 3
- 238000006477 desulfuration reaction Methods 0.000 description 3
- 230000023556 desulfurization Effects 0.000 description 3
- 239000004571 lime Substances 0.000 description 3
- 241001536352 Fraxinus americana Species 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- CSJDCSCTVDEHRN-UHFFFAOYSA-N methane;molecular oxygen Chemical compound C.O=O CSJDCSCTVDEHRN-UHFFFAOYSA-N 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000012840 feeding operation Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910001172 neodymium magnet Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000005502 peroxidation Methods 0.000 description 1
- 239000006187 pill Substances 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
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
-
- 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
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
-
- 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
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Carbon Steel Or Casting Steel Manufacturing (AREA)
Abstract
The invention discloses a method for producing low manganese molten steel by a converter process, which comprises the steps of folding molten iron into a blowing tank; performing blowing operation with nitrogen as blowing medium at flow rate of 60-80Nm 3 (h) discharging the molten iron from the gun to perform air stirring and air blowing for 10-20min; adding a desulfurizing agent to desulfurize molten iron and skim slag; 400-800kg of oxidant is added, nitrogen is stirred for 8-15min, slag is removed after the treatment is finished, and Mn content in molten steel is reduced to less than or equal to 0.15%; comprises the steps of converting to 25% -35% and carrying out first deslagging; blowing to 80% or more, and increasing oxygen supply strength to 3.3-3.7Nm 3 /(t.min), adding pellet ore 2.0% to the upper4.0 kg/ton steel; continuously converting for 30-90S after the lance is opened, pressing down the lance position of the oxygen lance to 700-850mm, and reducing the Mn content in the molten steel to be less than or equal to 0.03%; adding carbon powder in the heating process for moderate deoxidation; adding aluminum pellets or aluminum wires to deoxidize molten steel after heating, wherein the oxygen activity target range of the molten steel is 800-1200ppm, and the Mn content in the molten steel is reduced to less than or equal to 0.025%; RH refining.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a method for producing low manganese molten steel by a converter process.
Background
Some special purpose steels require lower Mn content in the steel, such as: the lower the Mn of the copper-clad steel is, the higher the conductivity of the steel wire is, the conductivity of the cable can be greatly improved, copper materials are saved, and the Mn in the steel is less than or equal to 0.03% in neodymium iron boron produced by taking industrial pure iron as a raw material.
Mn is a reducing element, in the converter production process, mn is firstly oxidized, reduced in the middle of converting, and oxidized again in the later stage, and the reaction formula is as follows:
[Mn]+1/2O2＝(MnO) ΔGθ＝－405250+125.411 (1)
after the blowing ignition, manganese element in the molten iron is directly oxidized by oxygen before carbon element to generate MnO which enters slag and gives off heat, the reaction (1) is facilitated at low temperature, and the generated MnO can promote early slag melting.
(MnO)+[C]＝[Mn]+CO ΔGθ＝287440－170.081 (2)
In the middle stage of converting, the reaction rate of carbon and oxygen is gradually accelerated, feO in slag is reduced, the temperature of a molten pool is increased, the reaction (2) is carried out towards the positive direction, and MnO part entering the slag in the early stage is reduced and returns to molten steel again.
[Mn]+[O]＝(MnO) ΔGθ＝－288100+128.31 (3)
[Mn]+(FeO)＝(MnO)+Fe ΔGθ＝－174314+77.491 (4)
In the later stage of blowing, the mass fraction of molten steel carbon is reduced, and the oxidizing property of molten steel and FeO in slag are increased due to the slow consumption. Manganese in the molten steel is re-oxidized into slag, and the reactions are as in (3), and as in formula (4).
However, the demanganization capacity of the converter is limited, and the Mn of the end point of the converter is between 0.05 and 0.15 percent between 60 and 80 percent, and other measures are needed to further reduce the Mn.
In the patent CN113774277A, low-sulfur molten iron is obtained through KR desulfurization in molten iron pretreatment, and then is added into a converter, and a series of technical measures such as flux addition amount, molten steel temperature, oxygen lance position, free oxygen content in molten steel and the like are controlled through one-time deslagging in converter smelting, so that the molten steel can obtain high-purity molten steel with carbon content less than or equal to 0.002% and manganese content less than or equal to 0.035%.
Patent CN108998614A adopts a production process route of molten iron pretreatment-converter-LF furnace-RH, adopts a duplex process, adopts a full slag-remaining and double slag-making technology, adopts a special oxygen supply technology, controls the oxygen value of the end point of the converter to be 600 ppm-800 ppm, controls the temperature of the end point of the converter to be 1660-1680 ℃ and controls the mass percentage content of molten iron manganese to be less than 0.16%; slag is discharged after oxidation periods of Si and Mn, and boiling tapping is carried out; adding lime to dephosphorize and burn manganese under the oxidizing condition, so that the steel grade refining rate is greatly improved, and low manganese steel with Mn mass percent content less than or equal to 0.025% is produced. The method has high requirement (less than 0.16%) on molten iron, has weak adaptability, is large in slag quantity due to the fact that the total amount of lime added into an LF furnace is 6.4-8kg/t, is unfavorable for the stable control of the oxygen content in steel, and has no limitation on the condition of adding white ash and burning manganese, such as the oxygen content of molten steel, and the Mn content can be increased when adding white ash in a reducing atmosphere.
Patent CN111440916a discloses a method for producing low manganese steel by using a high manganese molten iron converter, comprising: s1, adjusting smelting conditions of a converter, selecting a furnace number with higher carbon-oxygen area for smelting, adjusting a bottom blowing control mode according to the carbon-oxygen area, adjusting the ratio of molten iron to scrap steel into the converter, creating conditions for slag formation, and using a reasonable oxygen lance control mode; s2, controlling the smelting process of the converter in stages, adding head batch materials after normal ignition in the earlier stage of converter blowing, carefully observing the reaction condition in the converter, and preventing splashing; the melting condition of slag and the temperature of a molten pool are well controlled in the middle period of converting, and a sublance is used for measuring the temperature of the molten pool and the carbon content in the middle and later periods of converting; and in the later stage of blowing, feeding operation is carried out according to the measurement condition of 1SC, the terminal temperature and the oxygen content are controlled, and finally molten steel with the manganese content lower than 0.03% is smelted by taking high-manganese molten iron as a raw material. The method focuses on the reduction of Mn in the converter process, does not relate to the whole process flow, and does not reach the requirement that the Mn content is less than or equal to 0.025 percent.
The related database is searched, and the process practice of producing the ultra-low Mn content is developed in China, wherein the manganese is controlled mainly by adjusting the oxidability, slag and temperature of converter smelting. In order to increase the purity of the pure iron, the Mn content requirement is in a trend of lower and lower, and the effect of Mn content of less than or equal to 0.025% is not achieved in the prior patents. By limiting the Mn content of molten iron and improving the Mn removal efficiency of a converter, mass production is difficult to realize, and the blowing loss of the converter is increased by about 20-50kg/t. Therefore, the converter process is used for producing the ultra-low Mn molten steel, the upward and downward working procedures (Mn removal of molten iron and Mn reduction of LF) are needed, and the Mn is comprehensively reduced in the whole process.
Disclosure of Invention
Aiming at the problem that the Mn removing efficiency of a converter is difficult to meet the requirement of steel grade components, the invention aims to provide a method for producing low manganese molten steel by a converter process, which is used for solving the limitation requirement on the Mn content of molten iron, implementing the Mn removing operation in a molten iron pretreatment stage, and not intentionally deoxidizing in an LF furnace to form a high-oxygen environment, reducing the Mn content of the obtained molten steel from less than or equal to 0.06% to less than or equal to 0.025%, improving the refining rate from 20% to 76.3%, and simultaneously widening the Mn content of the molten iron of a blast furnace entering a factory from less than or equal to 0.15% to less than or equal to 0.25%.
In order to achieve the above purpose, the following technical scheme is adopted:
a method for producing low manganese molten steel by a converter process comprises the following steps:
(1) Pretreating the blast furnace molten iron entering a factory;
comprises the steps of folding molten iron into a blowing tank; performing blowing operation with nitrogen as blowing medium at flow rate of 60-80Nm 3 (h) discharging the molten iron from the gun to perform air stirring and air blowing for 10-20min; adding a desulfurizing agent to desulfurize molten iron and skim slag; 400-800kg of oxidant is added, nitrogen is stirred for 8-15min, slag is removed after the treatment is finished, and Mn content in molten steel is reduced to less than or equal to 0.15%;
(2) Smelting in a converter;
comprises the steps of converting to 25% -35% and carrying out first deslagging; blowing to 80% or more, and increasing oxygen supply strength to 3.3-3.7Nm 3 V (t.min), adding 2.0-4.0 kg of pellet ore per ton of steel; continuously converting for 30-90S after the lance is opened, pressing down the lance position of the oxygen lance to 700-850mm, and reducing the Mn content in the molten steel to be less than or equal to 0.03%;
(3) Refining in an LF furnace;
adding carbon powder in the heating process for moderate deoxidation; adding aluminum pellets or aluminum wires to deoxidize molten steel after heating, wherein the oxygen activity target range of the molten steel is 800-1200ppm, and the Mn content in the molten steel is reduced to less than or equal to 0.025%;
(4) RH refining.
According to the scheme, mn in the blast furnace molten iron entering the factory in the step 1 is less than or equal to 0.25%, si is more than or equal to 0.1% and less than or equal to 0.6%; the temperature is 1250 ℃ to 1 ℃ to 1400 ℃.
According to the scheme, the step 1 comprises adding 1-2 tons of iron oxide scale, folding and standing for 3-5min.
According to the scheme, the tapping temperature in the step 2 is 1600-1620 ℃, and the C content in the molten steel is controlled to be less than or equal to 0.045%.
According to the scheme, the step 3 comprises stopping oxygen, and adjusting a heating gear according to the arrival temperature, wherein the total heating time of the LF furnace is 15-30min.
According to the scheme, the carbon powder adding amount in the step 3 is calculated according to the following formula:
W carbon powder ＝([O] Initial + 1 Heating time × 15-800)*0.16；
W Carbon powder ＝([O] Initial + 1 Heating time × 15-800)*0.16；
W Carbon powder -adding the weight of carbon powder, kg;
[O] initial initiation -to station oxygen activity, ppm;
1 heating time Heating time, min.
According to the scheme, the step 4 comprises vacuum decarburization and aluminum addition deoxidization.
According to the scheme, the molten steel obtained in the step 4 comprises the following main chemical components in percentage by weight: c is less than or equal to 0.003%, mn is less than or equal to 0.025%, si is less than or equal to 0.010%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, and the balance is Fe and unavoidable impurities.
The main task of the invention in the molten iron pretreatment process is to reduce the Mn content of molten iron, and the molten iron in the iron folding process is strongly stirred and the nitrogen of a desulfurization spray gun is stirred to react with the added oxidant so as to oxidize Mn, and the product MnO is scraped off. In the molten iron pretreatment stage, firstly, stirring for 10-20min, and then desulfurizing, mainly because strong reducibility is needed for desulfurizing, the oxidant can be reduced after stirring, and the desulfurizing efficiency of the desulfurizing agent is improved. Si is limited to be more than or equal to 0.1% and less than or equal to 0.6%, and Si is oxidized preferentially to Mn, so that the added oxidant is consumed due to the fact that Si in molten iron is too high, and Mn removing efficiency is affected.
The invention aims to pour out the deoxidized products of silicon and manganese for the first time in the converter stage, and prevent the deoxidized products from being reduced in the're-drying' stage. In the stage of converting to 80% or more in converter, oxygen supply strength is raised, and pellet ore is added to further reduce carbon content in molten steel and raise slag oxidizing property. The continuous blowing after the gun is carried out is that the molten steel is in a peroxidized state.
The total heating time of the LF refining is controlled to be 15-30min, and the oxygenation speed in the heating process is 10-15ppm/min, and the oxygenation is controlled to be 200-450ppm by the heating time. The LF furnace mainly aims at increasing the oxygen activity in molten steel, so that no reducing substances are added, and the slag layer is thinned to promote oxygen absorption.
Compared with the prior art, the invention has the following beneficial effects:
the Mn content of the low manganese steel molten steel is reduced from less than or equal to 0.06 percent to less than or equal to 0.025 percent, and the refining rate is improved from 20 percent to 76.3 percent.
The technical standard of raw materials is relaxed, and the Mn content of the blast furnace molten iron entering a factory is relaxed from less than or equal to 0.15 percent to less than or equal to 0.25 percent.
Detailed Description
The following examples further illustrate the technical aspects of the present invention, but are not intended to limit the scope of the present invention.
The specific embodiment provides a method for producing low manganese molten iron by a converter process, which comprises the steps of blast furnace molten iron, molten iron pretreatment, converter, LF, RH and pouring. The method comprises the following steps:
the composition and the temperature of the molten iron of the blast furnace in the factory are as follows: mn is less than or equal to 0.25%, si is less than or equal to 0.1% and less than or equal to 0.6%, and the temperature is less than or equal to 1250 ℃ and less than or equal to 1 ℃ and less than or equal to 1400 ℃; the invention relaxes the technical standard of raw materials, and the Mn content of the blast furnace molten iron entering the factory is relaxed from less than or equal to 0.15 percent to less than or equal to 0.25 percent.
And (3) a molten iron pretreatment process. Comprising S1: folding molten iron into a blowing tank, adding 1-2 tons of iron oxide scale in the iron folding process, folding and standing for 3-5min, and S2: performing blowing operation with nitrogen as blowing medium at flow rate of 60-80Nm 3 And (h) discharging the molten iron from the gun, and performing air stirring and air blowing for 10-20min. S3: adding a desulfurizing agent to desulfurize molten iron and skim slag; s4: 400-800kg of oxidant and nitrogen are added, stirring is carried out for 8-15min, and slag skimming is carried out after the treatment is finished. Mn is less than or equal to 0.15 percent after treatment. In the molten iron pretreatment process, the main task is to reduce the Mn content of molten iron, and the molten iron is strongly stirred in the iron folding process and the nitrogen of a desulfurization spray gun is stirred to react with the added oxidant so as to oxidize Mn, and the product MnO is scraped off. In the molten iron pretreatment stage, firstly, stirring for 10-20min, and then desulfurizing, mainly because strong reducibility is needed for desulfurizing, the oxidant can be reduced after stirring, and the desulfurizing efficiency of the desulfurizing agent is improved. Si is limited to be more than or equal to 0.1% and less than or equal to 0.6%, because Si is oxidized preferentially to Mn, and the added oxidant is consumed due to the excessively high Si in molten iron, so that Mn removing efficiency is affected
Smelting in a converter. Comprising S1: blowing to 25% -35% stage to make first deslagging; s2: blowing to be more than or equal to 80%, increasing oxygen supply strength to be 3.3-3.7Nm3/(t.min), adding 2.0-4.0 kg of pellet ore per ton of steel, continuously blowing for 30-90S after 'current gun', pressing down the gun position of an oxygen gun to be 700-850mm, and controlling the tapping temperature target to be 1600-1620 ℃, wherein the C content in molten steel is less than or equal to 0.045%, and the Mn is less than or equal to 0.03%. The purpose of the first deslagging in the converter stage is to pour out the deoxidized products of silicon and manganese, and prevent the deoxidized products from being reduced in the're-drying' stage. In the stage of converting to 80% or more in converter, oxygen supply strength is raised, and pellet ore is added to further reduce carbon content in molten steel and raise slag oxidizing property. The continuous blowing after the gun is operated to ensure that the molten steel is in a peroxidation state
Refining in an LF furnace. Comprising S1: stopping oxygen, adjusting a heating gear according to the temperature at the stop, and LF, total heating time of the furnace is 15-30min, S2: adding a certain amount of carbon powder in the heating process to perform moderate deoxidation, W Carbon powder ＝([O] Initial + 1 Heating time × 15-800) 0.16, lime addition 0-1kg/t, S3: and (3) adding an aluminum pill or an aluminum wire to deoxidize molten steel after heating, wherein the oxygen activity of the molten steel is 800-1200ppm, and a high-aluminum refining agent cannot be added in the stirring process. The Mn content in the molten steel is reduced to less than or equal to 0.025 percent. The total heating time of LF refining is controlled to be 15-30min, and the oxygenation speed in the heating process is 10-15ppm/min, and the oxygenation is controlled to be 200-450ppm through the heating time. The LF furnace mainly aims at increasing the oxygen activity in molten steel, so that no reducing substances are added, and the slag layer is thinned to promote oxygen absorption.
RH refining. Performing conventional operations such as vacuum decarburization, aluminum addition deoxidization and the like, wherein the obtained molten steel comprises the following main chemical components in percentage by weight: c is less than or equal to 0.003%, mn is less than or equal to 0.025%, si is less than or equal to 0.010%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, and the balance is Fe and unavoidable impurities.
Examples 1-6 were performed according to the methods described above and the process conditions in tables 1-3. Wherein, table 1 describes the technological parameters of the molten iron pretreatment process; table 2 describes the converter process parameters; table 3 describes the LF process parameters.
TABLE 1
TABLE 2
TABLE 3 Table 3
Claims (8)
1. A method for producing low manganese molten steel by a converter process is characterized by comprising the following steps:
(1) Pretreating the blast furnace molten iron entering a factory;
comprises the steps of folding molten iron into a blowing tank; performing blowing operation with nitrogen as blowing medium at flow rate of 60-80Nm 3 (h) discharging the molten iron from the gun to perform air stirring and air blowing for 10-20min; adding a desulfurizing agent to desulfurize molten iron and skim slag; 400-800kg of oxidant is added, nitrogen is stirred for 8-15min, slag is removed after the treatment is finished, and Mn content in molten steel is reduced to less than or equal to 0.15%;
(2) Smelting in a converter;
comprises the steps of converting to 25% -35% and carrying out first deslagging; blowing to 80% or more, and increasing oxygen supply strength to 3.3-3.7Nm 3 V (t.min), adding 2.0-4.0 kg of pellet ore per ton of steel; continuously converting for 30-90S after the lance is opened, pressing down the lance position of the oxygen lance to 700-850mm, and reducing the Mn content in the molten steel to be less than or equal to 0.03%;
(3) Refining in an LF furnace;
adding carbon powder in the heating process for moderate deoxidation; adding aluminum pellets or aluminum wires to deoxidize molten steel after heating, wherein the oxygen activity target range of the molten steel is 800-1200ppm, and the Mn content in the molten steel is reduced to less than or equal to 0.025%;
(4) RH refining.
2. The method for producing low-manganese molten steel by using the converter process according to claim 1, wherein Mn in the in-plant blast furnace molten iron in the step 1 is less than or equal to 0.25%, si is more than or equal to 0.1% and less than or equal to 0.6%; the temperature is 1250 ℃ to 1 ℃ to 1400 ℃.
3. The method for producing molten steel with low manganese content by using a converter process according to claim 1, wherein the step 1 comprises adding 1-2 tons of iron scale, folding and standing for 3-5min.
4. The method for producing molten steel with low manganese content by using the converter process according to claim 1, wherein the tapping temperature in the step 2 is 1600-1620 ℃, and the C content in the molten steel is controlled to be less than or equal to 0.045%.
5. The method for producing molten steel with low manganese by using the converter process according to claim 1, wherein the step 3 comprises stopping oxygen supply, adjusting a heating gear according to the temperature at the stop, and the total heating time of the LF furnace is 15-30min.
6. The method for producing low-manganese molten steel by using a converter process according to claim 1, wherein the carbon powder addition amount in the step 3 is calculated according to the following formula:
W carbon powder ＝([O] Initial + 1 Heating time × 15-800)*0.16；
W Carbon powder ＝([O] Initial + 1 Heating time × 15-800)*0.16；
W Carbon powder -adding the weight of carbon powder, kg;
[O] initial initiation -to station oxygen activity, ppm;
1 heating time Heating time, min.
7. The method for producing molten steel of claim 1, wherein step 4 includes vacuum decarburization and aluminum deoxidation.
8. The method for producing molten steel with low manganese by using the converter process according to claim 1, wherein the molten steel obtained in the step 4 comprises the following main chemical components in percentage by weight: c is less than or equal to 0.003%, mn is less than or equal to 0.025%, si is less than or equal to 0.010%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, and the balance is Fe and unavoidable impurities.
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