CN117758016A - Preparation method of ultrapure functional iron - Google Patents
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- CN117758016A CN117758016A CN202410028875.6A CN202410028875A CN117758016A CN 117758016 A CN117758016 A CN 117758016A CN 202410028875 A CN202410028875 A CN 202410028875A CN 117758016 A CN117758016 A CN 117758016A
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 94
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 46
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- 239000002893 slag Substances 0.000 claims abstract description 59
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 56
- 239000010959 steel Substances 0.000 claims abstract description 56
- 238000007670 refining Methods 0.000 claims abstract description 35
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 30
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 29
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 26
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 23
- 230000023556 desulfurization Effects 0.000 claims abstract description 23
- 238000004519 manufacturing process Methods 0.000 claims abstract description 15
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 14
- 238000003723 Smelting Methods 0.000 claims abstract description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000001301 oxygen Substances 0.000 claims abstract description 9
- 230000000694 effects Effects 0.000 claims abstract description 8
- 238000010891 electric arc Methods 0.000 claims abstract description 7
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 30
- 239000010436 fluorite Substances 0.000 claims description 30
- 239000005997 Calcium carbide Substances 0.000 claims description 26
- CLZWAWBPWVRRGI-UHFFFAOYSA-N tert-butyl 2-[2-[2-[2-[bis[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]amino]-5-bromophenoxy]ethoxy]-4-methyl-n-[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]anilino]acetate Chemical compound CC1=CC=C(N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)C(OCCOC=2C(=CC=C(Br)C=2)N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)=C1 CLZWAWBPWVRRGI-UHFFFAOYSA-N 0.000 claims description 26
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 25
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 25
- 239000004571 lime Substances 0.000 claims description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 24
- 239000011593 sulfur Substances 0.000 claims description 14
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 12
- 229910052782 aluminium Inorganic materials 0.000 claims description 12
- 239000000126 substance Substances 0.000 claims description 12
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 10
- 238000005070 sampling Methods 0.000 claims description 10
- 229910052710 silicon Inorganic materials 0.000 claims description 10
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 9
- 239000011574 phosphorus Substances 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 230000003647 oxidation Effects 0.000 claims description 7
- 238000007254 oxidation reaction Methods 0.000 claims description 7
- 238000010079 rubber tapping Methods 0.000 claims description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 6
- 238000004458 analytical method Methods 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 239000011572 manganese Substances 0.000 claims description 6
- 239000010703 silicon Substances 0.000 claims description 6
- 229910052786 argon Inorganic materials 0.000 claims description 5
- 229910052595 hematite Inorganic materials 0.000 claims description 5
- 239000011019 hematite Substances 0.000 claims description 5
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 claims description 5
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 5
- 230000033228 biological regulation Effects 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 3
- 229910052787 antimony Inorganic materials 0.000 claims description 3
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 238000009792 diffusion process Methods 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 2
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 2
- 229910052797 bismuth Inorganic materials 0.000 claims description 2
- 239000011575 calcium Substances 0.000 claims description 2
- 229910052791 calcium Inorganic materials 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 claims description 2
- 229910052718 tin Inorganic materials 0.000 claims description 2
- 229910052721 tungsten Inorganic materials 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 230000009467 reduction Effects 0.000 abstract description 3
- 238000002844 melting Methods 0.000 abstract description 2
- 230000008018 melting Effects 0.000 abstract description 2
- 239000011573 trace mineral Substances 0.000 abstract description 2
- 235000013619 trace mineral Nutrition 0.000 abstract description 2
- 230000003009 desulfurizing effect Effects 0.000 abstract 1
- 238000000034 method Methods 0.000 description 14
- 229910000797 Ultra-high-strength steel Inorganic materials 0.000 description 13
- 239000000203 mixture Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 238000007872 degassing Methods 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 230000008901 benefit Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000007123 defense Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000011031 large-scale manufacturing process Methods 0.000 description 2
- 230000033116 oxidation-reduction process Effects 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 241001442654 Percnon planissimum Species 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000012761 high-performance material Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 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 1
- 238000005272 metallurgy Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000007619 statistical method Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 238000009849 vacuum degassing Methods 0.000 description 1
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- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention relates to a preparation method of ultrapure functional iron, which comprises the following steps: smelting and melting high-quality steel in an electric arc furnace, introducing oxygen, and removing P, si, mn, C and trace elements; making new slag in the arc furnace into a reduction period; pouring a ladle in the middle, thoroughly removing reducing slag in the electric arc furnace and preventing P from returning; deoxidizing and desulfurizing in ladle refining furnace and vacuum refining furnace with carbide slag system; and secondly, carrying out deoxidation and desulfurization on the ladle refining furnace and the vacuum refining furnace by adopting a carbide slag system. The preparation method is reasonable, the production process is simple, the effect of preventing P return is good, the O and S removal efficiency is high, and the product quality is stable.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a preparation method of ultrapure functional iron.
Background
The functional iron is a special steel with extremely low content of S, P and other impurities, is widely applied to smelting various ultra-high strength steel, precise alloy and other aerospace, petrochemical, ocean engineering and civil materials, has higher and higher requirements on the ultra-high strength steel and other special alloy along with the continuous improvement of national defense and aerospace strength in China, effectively improves the cleanliness of the ultra-high strength steel by taking the functional iron as a raw material for mass use, greatly improves the toughness, fatigue strength and creep strength of the material, can reduce the coercive force of the magnetic material, improves the permeability and is the basis for improving the industrial strength and national defense capability in China. The functional iron mainly recycles the scrap steel, converts the scrap steel into pure iron with extremely low content of harmful elements and gases, and promotes the industrialization progress of the ultra-pure functional iron.
The high-performance material produced abroad benefits from the developed ultra-pure iron technology, and the quality of the domestic high-end ultra-high-strength steel is different from that of the foreign material to a certain extent, mainly because the purity of the iron-based raw material is not high. P, S, N is a harmful element in steel, often biased at grain boundaries, and although the strength of steel can be improved, tensile properties and creep properties and weldability are seriously lowered. For this reason, pure iron is prepared by adopting technologies such as an electrolytic method, electromagnetic suspension smelting and the like abroad, but the production cost is high; the method for smelting the ultrapure functional iron adopts an electric furnace for removing P, si, mn, C at home, has low production cost and high purity, adopts an LF furnace and a VD furnace for deoxidation and desulfurization, but adopts high-alkalinity slag as slag system, has low desulfurization speed, has high gas contents of O, N and the like, adopts rare earth elements and magnesium with strong oxidability, is easy to burn, and cannot reduce the content of sulfur and phosphorus in the pure iron to the limit. Is not suitable for producing high-purity low-segregation low S, P pure iron by a vacuum induction furnace.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method of ultrapure functional iron, which has the advantages of reasonable preparation method, simple production process, good effect of preventing P from returning, high O and S removal efficiency and stable product quality.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a method for preparing ultrapure functional iron, comprising the steps of:
s1, smelting high-quality scrap steel in an electric arc furnace, and adding lime, fluorite and hematite into 4-6 batches of the furnace burden after the furnace burden is completely smelted to form slag; when the oxidation period is entered, oxygen is introduced into the furnace, the temperature is controlled between 1510 ℃ and 1560 ℃, and oxidation treatment is carried out to remove phosphorus, silicon, manganese and carbon; when the phosphorus in the molten steel is less than or equal to 0.001 percent, the silicon is less than or equal to 0.01 weight percent, and the carbon is as follows: 0.1% -0.2% of slag skimming;
s2, after deslagging, new slag is produced, carbide slag system and aluminum white slag are added for deoxidization, slag amount is added according to 5% of molten steel, after large-voltage deslagging, electrode carbon is added for 1Kg/t, calcium carbide is added for 3Kg/t, aluminum ingot is added for 3Kg/t, slag is continuously added during the period, the effect of deoxidizer is fully exerted, the molten steel is deeply reduced, sampling analysis is carried out after the molten steel is kept for 20min, the aluminum content is less than or equal to 0.005%, the carbon content is 0.35% -0.45%, and deslagging is carried out again when the sulfur content is less than or equal to 0.005%; tapping steel at the temperature of molten steel of not less than 1670 ℃ and feeding the steel into a ladle refining furnace;
s3, molten steel flows into a second ladle refining furnace from the bottom of the first ladle refining furnace, so that reducing slag is left in the first ladle refining furnace, and the reducing slag in the electric arc furnace is thoroughly removed; after pouring, controlling the temperature to 1660-1690 ℃ and the oxygen content to 20-50ppm, and adding calcium carbide into a ladle refining furnace according to 3Kg/t for deoxidization and desulfurization;
s4, lime, fluorite and calcium carbide are added into the ladle refining furnace in two batches for slagging, the slag amount is added according to 2% of molten steel, the electrode carbon is 1-2Kg/t, and the electrode carbon content is adjusted according to the analysis of the carbon content by sampling; slag formation and heating, wherein the temperature range is 1660-1690 ℃, argon is introduced and stirred, the diffusion reaction kinetics condition is improved, and when sulfur is less than or equal to 0.001wt%, carbon: transferring into a vacuum refining furnace after 0.1% -0.3%, vacuum degree is less than 40-67 Pa, temperature is above 1540 ℃, holding for 15-29 min, sampling, and performing secondary deoxidation and desulfurization;
s5, transferring molten steel into a ladle refining furnace, adding lime, fluorite and calcium carbide into the ladle refining furnace in two batches for slagging, increasing the slag by 10Kg/t, increasing the temperature of the molten steel by 1670-1690 ℃, introducing argon and stirring, and carrying out secondary deoxidation and desulfurization; sampling and fully analyzing, transferring the sample into a vacuum refining furnace after sulfur is less than or equal to 0.0008wt%, and tapping after the vacuum degree is less than 40-67 Pa, the temperature is above 1540 ℃ and the sulfur is kept for 15-27 min;
s6, pouring the molten steel to obtain the ultrapure functional iron, wherein the pouring temperature is 1570-1580 ℃.
In the above method for preparing ultrapure functional iron, in step S1, the scrap steel used is high-quality low-sulfur and phosphorus flat steel, and the composition requirements are that carbon: 0.30-0.7wt%, phosphorus: less than or equal to 0.040 weight percent and less than or equal to 0.030 weight percent of sulfur.
In the above preparation method of ultrapure functional iron, in step S1, the mass ratio of lime, fluorite and hematite is 1.8-2.5: 1:0.2; wherein lime is required to be carefully selected, fluorite is required to be specially classified, and crushed to less than 8mm.
In the above preparation method of ultrapure functional iron, in step S2, the mass ratio of the carbide slag system to the aluminum is 50:3, wherein the mass ratio of lime, fluorite and carbide is 1.8-2: 1:0.2 to 0.4; the deoxidization reaction is 5CaO+2[ Al]+3[S]＝3CaS+(2CaO.Al 2 O 3 )。
In the preparation method of the ultrapure functional iron, in the step S4, the mass ratio of lime to fluorite to calcium carbide is 4-5: 1 to 3:1 to 2.5; and fluorite requires high-purity superfine fluorite to prevent Si increase, and the chemical components of the fluorite meet the regulations: caF (CaF) 2 ≥94％，SiO 2 ≤2.5％，S≤0.02％，H 2 O is less than or equal to 0.3 percent; the lime is dried before use, and the chemical components of the lime accord with the regulations: caO is more than or equal to 95 percent, siO 2 ≤2％，S≤0.05％，H 2 O is less than or equal to 0.3 percent; the granularity of the calcium carbide is less than 8mm.
In the preparation method of the ultrapure functional iron, in the step S5, the mass ratio of lime to fluorite to calcium carbide is 4-5: 1 to 3:1 to 3; the secondary ladle refining furnace needs to increase the addition amount of calcium carbide, improve the fluidity of slag, 1-3Kg/t of calcium carbide and 1-3Kg/t of fluorite, and strengthen desulfurization.
The ultrapure functional iron prepared by the preparation method comprises the following elements in percentage by mass: less than or equal to 0.25 weight percent of C, less than or equal to 0.02 weight percent of Si, less than or equal to 0.04 weight percent of Mn, less than or equal to 0.0008 weight percent of S, less than or equal to 0.003 weight percent of P, less than or equal to 0.005 weight percent of Al, less than or equal to 0.006 weight percent of Ti, less than or equal to 0.002 weight percent of O, less than or equal to 0.003 weight percent of N, less than or equal to 0.08 weight percent of Cu, less than or equal to 0.5 weight percent of Co, less than or equal to 0.0005 weight percent of B, less than or equal to 0.0001 weight percent of Bi, less than or equal to 0.008 weight percent of Sn, less than or equal to 0.005 weight percent of Sb, less than or equal to 0.004 weight percent of Ca, less than or equal to 0.003 weight percent of W, less than or equal to 0.004 weight percent of V, and the balance of Fe and other unavoidable impurities.
The invention has the technical effects and advantages that:
according to the preparation method of the ultrapure functional iron, provided by the invention, high-quality scrap steel is adopted for smelting, so that the preparation cost is saved; by adopting two ladle refining furnaces for pouring, the slag system in the oxidation-reduction stage can be thoroughly removed, and a large amount of Si0 in the slag in the oxidation stage can be prevented 2 And P 2 O 5 Si and P are reduced; the desulfurization speed can be increased by deoxidizing molten steel by adopting a carbide slag system and an aluminum white slag making process; the ladle refining furnace and the vacuum refining furnace are subjected to deoxidation and desulfurization by using the carbide slag system for the second time, so that the deoxidation and desulfurization effects are greatly improved; the ultra-pure functional iron and the functional iron produced by the preparation method reach the level of ultra-low impurity elements, ensure that Si is less than or equal to 0.02wt percent, mn is less than or equal to 0.04wt percent, S is less than or equal to 0.0008wt percent, and the content of residual elements is less than 0.001wt percent, and the preparation method is simple in process, suitable for large-scale production and capable of completely meeting the production requirements of ultra-high strength steel.
Detailed Description
The examples given below illustrate the invention in further detail.
As the element C is an indispensable grain boundary strengthening element in the ultra-high strength steel, the ultra-pure functional iron produced by adopting the technical scheme of the invention can contain less than 0.25 percent of carbon, silicon, manganese, oxygen and nitrogen are easier to form nonmetallic inclusions, and as the raw material of the ultra-high strength steel, the high strength of the ultra-high strength steel can be reduced, sulfur can reduce the plasticity of the steel, and meanwhile, the mechanical property of the ultra-high strength steel is greatly influenced by oxides, so that the chemical components of the ultra-pure functional iron produced by adopting the technical scheme of the invention are controlled to be less than or equal to 0.25 percent by weight of C, less than or equal to 0.02 percent by weight of Si, less than or equal to 0.04 percent by weight of Mn, less than or equal to 0.0008 percent by weight of S, less than or equal to 0.003 percent by weight of P, less than or equal to 0.005 percent by weight of Al, less than or equal to 0.006 percent by weight of Ti, less than or equal to 0.002 percent by weight of O, less than or equal to 0.003 percent by weight of N, less than or equal to 0.08 percent by weight of Cu, less than or equal to 0.5 percent by weight of Co, less than or equal to 0.0005 percent by Bi, less than or equal to 0.008 percent by weight, less than or equal to 0.0.008 percent of Sb, less equal to 0.0.0 percent of equal to 0 and 0.004, and the balance of V and unavoidable impurities. The functional iron reaches the level of ultra-low impurity elements, ensures that Si is less than or equal to 0.02wt percent, mn is less than or equal to 0.04wt percent, S is less than or equal to 0.0008wt percent, and residual element content is less than 0.001wt percent, and has simple process, is suitable for large-scale production, and can completely meet the production requirement of ultra-high strength steel.
The process route adopted for preparing the ultrapure functional iron comprises the steps of removing P, si, mn, C by an electric arc furnace EAF and trace elements, pouring a ladle to prevent non-return P, performing external refining LF+vacuum refining furnace VOD deoxidization desulfurization, performing external refining LF+vacuum refining furnace VOD secondary deoxidization desulfurization; the method specifically comprises the following steps:
s1, an EAF oxidation period; carrying out EAF smelting on high-quality scrap steel, wherein the used scrap steel is high-quality low S, P flat steel, and the component requirements are C:0.30-0.7wt%, P: less than or equal to 0.040wt%, S less than or equal to 0.030wt% and graphite carbon; lime, fluorite and hematite=1.8 to 2.5 are added in 4 to 6 batches after the furnace burden is fully melted: 1:0.2, oxidizing by oxygen blowing to remove P, si, mn, C; when P is less than or equal to 0.001%, si is less than or equal to 0.01% by weight, C:0.1% -0.2%, and low-temperature P removal is carried out at 1510-1560 ℃; oxygen is supplied after slag is added, the temperature is controlled to 1620-1660 ℃, the slag is removed by Wen Huazha and 100%, and P, si and Mn are prevented from returning.
S2, an EAF reduction period; the new slag is subjected to reduction stage, and the carbide slag system and the Al white slag are used for deoxidization, wherein the mass ratio of the carbide slag system to the Al is 50:3, and the mass ratio of lime, fluorite and calcium carbide is 1.8-2: 1:0.2 to 0.4, slag is added according to 5 percent of molten steel, 1Kg/t of electrode carbon, 3Kg/t of calcium carbide and 3Kg/t of aluminum ingot are added after large-voltage slagging, and the continuous slag dropping during the period fully plays the role of deoxidizer. The deoxidization reaction is 5CaO+2[ Al]+3[S]＝3CaS+(2CaO.Al 2 O 3 ) The molten steel is deeply reduced, and is sampled and analyzed after being kept for 20min, so that the Al content is less than or equal to 0.005%, the C content is 0.35% -0.45%, and 100% slag is removed when the S content is less than or equal to 0.005%; tapping the slag after new slag making, wherein the tapping temperature is more than or equal to 1670 ℃, and charging into an LF ladle.
S3, pouring; pouring the molten steel into two iron-washed LF bags, thoroughly removing reducing slag in an electric furnace, and preventing the return P, si; after the ladle is reversed, adding calcium carbide into the LF ladle according to the ratio of 3Kg/t for advanced deoxidation and desulfurization.
S4, primary LF refining and VD degassing; carrying out LF+VD deoxidation and desulfurization by using a carbide slag system, wherein fluorite, lime and calcium carbide are added into an LF furnace in two batches for slagging, and the mass ratio of the lime to the fluorite to the calcium carbide is 4-5: 1 to 3:1 to 2.5, adding slag according to 2 percent of molten steel, and adjusting the carbon content of an electrode according to the content of C in the sample analysis according to the carbon content of the electrode of 1-2 Kg/t; slag formation and temperature rising are carried out, the temperature range is 1660-1690 ℃, argon stirring is increased, the diffusion reaction dynamics condition is improved, S is removed by less than or equal to 0.001wt%, C: transferring 0.1% -0.3% into a VD smelting furnace, maintaining the vacuum degree at less than 40-67 Pa for 15-29 min, sampling at above 1540 ℃, and performing secondary refining and degassing;
s5, the oxygen content is still higher after the primary vacuum degassing, secondary LF+VD degassing is needed, and according to the ion reaction formula of desulfurization: [ S ]]+[O 2- ]＝[S 2- ]+[O]O concentration is reduced by secondary LF feeding, which is beneficial to S removal. The carbide slag system lime is used: fluorite: calcium carbide according to the proportion of 4 to 5:1 to 3: the ratio of 1 to 2.5 is increased by 10Kg/t, and deoxidation and desulfurization are carried out. Raising the temperature of molten steel by 1670-1690 ℃, sampling and fully analyzing, transferring into a VD smelting furnace after S removal is less than or equal to 0.0008wt%, and tapping after vacuum degree is less than 40-67 PaPa and 15-29 min. The CaC needs to be improved for the secondary LF furnace 2 The addition amount of the calcium carbide is 1-3Kg/t, fluorite is 1-3Kg/t, and desulfurization is enhanced.
S6, pouring the molten steel to obtain the ultrapure functional iron, wherein the pouring temperature is 1570-1580 ℃.
The preparation process route of the embodiment adopts an LF tundish, can thoroughly remove the slag system in the oxidation-reduction period and prevent a large amount of Si0 in the slag in the oxidation period 2 And P 2 O 5 Si and P are reduced; AI is adopted to deoxidize the molten steel, so that the desulfurization speed can be increased; the secondary LF+VD degassing is adopted, so that the deoxidization, desulfurization and denitrification effects are greatly improved.
The production specific parameters of examples 1, 2, 3 and comparative example 1 are shown in table 1 below, wherein the comparative example 1 process adopts the no-rewind mode, the vacuum pressure is high, and other processes are the same as examples 1, 2, 3, and the specific steps are as follows:
TABLE 1 production specific parameters of inventive and comparative examples
The slag ratios in examples 1, 2 and 3 in Table 1 are changed, the produced ultra-pure iron components meet the requirements, the VD furnace pressure in comparative example 1 is larger, the vacuum degree is smaller, and the deoxidizing effect is poor.
The following statistics are shown in table 2 for the chemical compositions of the embodiments and comparative cases of the present application, and are specifically as follows:
TABLE 2 statistical analysis of chemical compositions of examples of the present invention and examples thereof
The contents of the ultrapure functional iron chemical components obtained by the preparation methods of examples 1, 2 and 3 are all in the standard range, however, the content of P, S element in the ultrapure functional iron chemical component obtained by the preparation method of comparative example 1 is too high to meet the requirement, and through analysis, the P element is too high mainly due to the lack of the ladle-down procedure, the slag returns to P, the S element content is too high mainly due to insufficient vacuum degree, deoxidization air accident and the ladle is not deeply S-removed.
Application example 1
The ultra-pure functional iron obtained by the preparation methods of examples 1, 2 and 3 is used as a raw material to produce two furnaces (the furnace numbers are V323-480 and V323-481 respectively) 30Ni10Co7Mo2CrWV steel, and the chemical compositions and the gas contents of the two furnaces 30Ni10Co7Mo2CrWV steel are shown in Table 3;
table 330 chemical composition of Ni10Co7Mo2CrWV Steel
TABLE 3 continuity
As shown in Table 3, the gas content of the 30Ni10Co7Mo2CrWV ultra-high strength steel prepared by the method is only about 4 ppm, and S, P and other harmful elements are strictly controlled, so that the mechanical properties of the 30Ni10Co7Mo2CrWV ultra-high strength steel are greatly improved, the vacuum melting and degassing time is reduced, and the production efficiency is improved.
Application example 2
The ultra-pure functional iron obtained by the preparation methods of examples 1, 2 and 3 is used as a raw material to produce one furnace (furnace number V323-487) 23Co14Ni12Cr3MoE steel, and the steel composition and the gas content of the obtained one furnace 23Co14Ni12Cr3MoE steel are shown in Table 4;
TABLE 423Co14Ni12Cr3MoE chemical composition
Table 4 continuation
As shown in Table 4, the gas content of the 23Co14Ni12Cr3MoE ultra-high strength steel prepared by the method is only about 9 ppm, and the S element meets the standard requirement.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and improvements could be made by those skilled in the art without departing from the inventive concept, which falls within the scope of the present invention.
Claims (7)
1. The preparation method of the ultrapure functional iron is characterized by comprising the following steps:
s1, smelting high-quality scrap steel in an electric arc furnace, and adding lime, fluorite and hematite into 4-6 batches of the furnace burden after the furnace burden is completely smelted to form slag; when the oxidation period is entered, oxygen is introduced into the furnace, the temperature is controlled between 1510 ℃ and 1560 ℃, and oxidation treatment is carried out to remove phosphorus, silicon, manganese and carbon; when the phosphorus in the molten steel is less than or equal to 0.001 percent, the silicon is less than or equal to 0.01 weight percent, and the carbon is as follows: 0.1% -0.2% of slag skimming;
s2, after deslagging, new slag is produced, carbide slag system and aluminum white slag are added for deoxidization, slag amount is added according to 5% of molten steel, after large-voltage deslagging, electrode carbon is added for 1Kg/t, calcium carbide is added for 3Kg/t, aluminum ingot is added for 3Kg/t, slag is continuously added during the period, the effect of deoxidizer is fully exerted, the molten steel is deeply reduced, sampling analysis is carried out after the molten steel is kept for 20min, the aluminum content is less than or equal to 0.005%, the carbon content is 0.35% -0.45%, and deslagging is carried out again when the sulfur content is less than or equal to 0.005%; tapping steel at the temperature of molten steel of not less than 1670 ℃ and feeding the steel into a ladle refining furnace;
s3, molten steel flows into a second ladle refining furnace from the bottom of the first ladle refining furnace, so that reducing slag is left in the first ladle refining furnace, and the reducing slag in the electric arc furnace is thoroughly removed; after pouring, controlling the temperature to 1660-1690 ℃ and the oxygen content to 20-50ppm, and adding calcium carbide into a ladle refining furnace according to 3Kg/t for deoxidization and desulfurization;
s4, lime, fluorite and calcium carbide are added into the ladle refining furnace in two batches for slagging, the slag amount is added according to 2% of molten steel, the electrode carbon is 1-2Kg/t, and the electrode carbon content is adjusted according to the analysis of the carbon content by sampling; slag formation and heating, wherein the temperature range is 1660-1690 ℃, argon is introduced and stirred, the diffusion reaction kinetics condition is improved, and when sulfur is less than or equal to 0.001wt%, carbon: transferring into a vacuum refining furnace after 0.1% -0.3%, vacuum degree is less than 40-67 Pa, temperature is above 1540 ℃, holding for 15-29 min, sampling, and performing secondary deoxidation and desulfurization;
s5, transferring molten steel into a ladle refining furnace, adding lime, fluorite and calcium carbide into the ladle refining furnace in two batches for slagging, increasing the slag by 10Kg/t, increasing the temperature of the molten steel by 1670-1690 ℃, introducing argon and stirring, and carrying out secondary deoxidation and desulfurization; sampling and fully analyzing, transferring the sample into a vacuum refining furnace after sulfur is less than or equal to 0.0008wt%, and tapping after the vacuum degree is less than 40-67 Pa, the temperature is above 1540 ℃ and the sulfur is kept for 15-27 min;
s6, pouring the molten steel to obtain the ultrapure functional iron, wherein the pouring temperature is 1570-1580 ℃.
2. The method for producing ultrapure functional iron according to claim 1, characterized in that: in the step S1, the used scrap steel is high-quality low-sulfur and phosphorus flat steel, and the components of the scrap steel are required to be carbon: 0.30 to 0.7 weight percent, less than or equal to 0.040 weight percent of phosphorus and less than or equal to 0.030 weight percent of sulfur.
3. The method for producing ultrapure functional iron according to claim 1, characterized in that: in the step S1, the mass ratio of the lime to the fluorite to the hematite is 1.8-2.5: 1:0.2; wherein lime is required to be carefully selected, fluorite is required to be specially classified, and crushed to less than 8mm.
4. The method for producing ultrapure functional iron according to claim 1, characterized in that: in the step S2, the mass ratio of the carbide slag system to the aluminum is 50:3, wherein the mass ratio of lime to fluorite to calcium carbide is 1.8-2: 1:0.2 to 0.4; the deoxidization reaction is 5CaO+2[ Al]+3[S]＝3CaS+(2CaO.Al 2 O 3 )。
5. The method for producing ultrapure functional iron according to claim 1, characterized in that: in the step S4, the mass ratio of lime to fluorite to calcium carbide is 4-5: 1 to 3:1 to 2.5; and fluorite requires high-purity superfine fluorite to prevent silicon increase, and the chemical components of the fluorite meet the regulations: caF (CaF) 2 ≥94％，SiO 2 ≤2.5％，S≤0.02％，H 2 O is less than or equal to 0.3 percent; the lime is dried before use, and the chemical components of the lime accord with the regulations: caO is more than or equal to 95 percent, siO 2 ≤2％，S≤0.05％，H 2 O is less than or equal to 0.3 percent; the granularity of the calcium carbide is less than 8mm.
6. The method for producing ultrapure functional iron according to claim 1, characterized in that: in the step S5, the mass ratio of lime to fluorite to calcium carbide is 4-5: 1 to 3:1 to 3; the secondary ladle refining furnace needs to increase the addition amount of calcium carbide, improve the fluidity of slag, 1-3Kg/t of calcium carbide and 1-3Kg/t of fluorite, and strengthen desulfurization.
7. The ultrapure functional iron produced by the method for producing ultrapure functional iron as claimed in any one of claims 1 to 6, characterized by comprising, in mass percent: less than or equal to 0.25 weight percent of C, less than or equal to 0.02 weight percent of Si, less than or equal to 0.04 weight percent of Mn, less than or equal to 0.0008 weight percent of S, less than or equal to 0.003 weight percent of P, less than or equal to 0.005 weight percent of Al, less than or equal to 0.006 weight percent of Ti, less than or equal to 0.002 weight percent of O, less than or equal to 0.003 weight percent of N, less than or equal to 0.08 weight percent of Cu, less than or equal to 0.5 weight percent of Co, less than or equal to 0.0005 weight percent of B, less than or equal to 0.0001 weight percent of Bi, less than or equal to 0.008 weight percent of Sn, less than or equal to 0.005 weight percent of Sb, less than or equal to 0.004 weight percent of Ca, less than or equal to 0.003 weight percent of W, less than or equal to 0.004 weight percent of V, and the balance of Fe and other unavoidable impurities.
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