CN110747395A - Industrial ultra-pure iron and production method thereof - Google Patents
Industrial ultra-pure iron and production method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- C21C5/30—Regulating or controlling the blowing
- C21C5/34—Blowing through the bath
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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
- C21C7/06—Deoxidising, e.g. killing
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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
- C21C7/064—Dephosphorising; Desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/16—Remelting metals
- C22B9/18—Electroslag remelting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
Abstract
The invention belongs to the technical field of metal smelting, and particularly relates to industrial ultra-pure iron and a production method thereof. The industrial ultra-pure iron comprises the following components: less than or equal to 0.25 wt% of C, less than or equal to 0.005 wt% of Si, less than or equal to 0.005 wt% of Mn, less than or equal to 0.0008 wt% of S, less than or equal to 0.003 wt% of P, less than or equal to 0.005 wt% of Al, less than or equal to 0.003 wt% of Ti, Ce: 0.003-0.007 wt%, La: 0.001-0.004 wt%, trace Nd and Pr, and the balance of Fe and inevitable impurities; the preparation method comprises the following steps: sequentially carrying out KR molten iron pre-desulfurization, converter deep dephosphorization, LF deep desulfurization, RH deep deoxidation, continuous casting and electroslag remelting. The iron prepared by the method has high purity.
Description
Technical Field
The invention belongs to the technical field of metal smelting, and particularly relates to industrial ultra-pure iron and a production method thereof.
Background
Pure iron is an important raw material for producing magnetic materials, electrothermal alloys, precision alloys and special metal materials, and along with the increasing requirements on precision alloys and magnetic components, the purity requirements of sophisticated high-tech products are also increasing.
The raw materials of pure iron and industrial pure iron are produced by GB9971 and GB6983 in China, and the pure iron and the industrial pure iron are generally refined and manufactured outside a converter or a converter plus a furnace, but the purity is not high, the impurity elements of the pure iron are high, the quality purity of a real object is low, and particularly, carbon, sulfur and phosphorus are high, so that the pure iron and the industrial pure iron can only be used for manufacturing common parts. These pure irons are already unsuitable for the manufacture of high-end products, for the production of raw materials for maraging steels, high-strength stainless steels, advanced functional materials (soft magnetic alloys, etc.), in particular for advanced technologies and high-quality components.
The secondary hardening steel is a high-purity steel grade of Cr-Ni-Co-Mo series containing carbon, and is used for manufacturing parts of aircraft landing gear, beam, shaft and the like, and the chemical composition (wt%) of pure iron used in the steel is equal to or less than 0.25% of C, equal to or less than 0.05% of Si, equal to or less than 0.05% of Mn, equal to or less than 0.001% of S, equal to or less than 0.003% of P, equal to or less than 0.005% of Al and equal to or less than 0.005% of Ti. The purity is still the problem to be solved for the second hardening steel and the maraging steel at present, impurities in the pure iron are important reasons influencing the purity of the steel, and the high impurity content greatly influences the toughness of the material. In particular, secondary hardening steel in which S and easily oxidizable elements Al, Si, Ti and Mn have a great influence on the fracture toughness and impact toughness of the material is difficult to remove in double vacuum smelting, which requires that such elements in pure iron be as low as possible.
At present, high purity industrial pure iron is manufactured by electrolysis in japan and usa, and the purity can reach 99.9, but the price is very high, and the cost for producing secondary hardening steel, maraging steel, and high purity stainless steel is high. The alloy is generally manufactured by adopting a converter or an electric furnace plus external refining at home, and is manufactured by an AOD or VOD furnace in some cases, but the purity is not high, and particularly, the contents of sulfur, phosphorus and aluminum are high. With the progress of the external refining technology and the large-scale and intelligent control of the external refining equipment, the converter/electric furnace + external refining means are adopted to produce the pure iron, the pure iron can be classified and graded according to specific use requirements, and meanwhile, the refining and purifying process is further optimized.
At present, a lot of patents or articles exist in the aspects of purifying iron by converter/electric furnace + external refining, but the preparation method of the industrial ultra-pure iron which can be used for producing better low-alloy ultra-high-strength steel, secondary hardening ultra-high-strength steel, high-grade blade steel or low-medium-carbon high-purity stainless steel by adopting the long process of molten iron pretreatment, converter + external refining + continuous casting + electroslag remelting in a large batch mode belongs to the first example.
Disclosure of Invention
The invention aims to solve the technical problem of providing industrial ultra-pure iron and a production method thereof aiming at the specific use requirement of pure iron.
The invention relates to industrial ultra-pure iron, which comprises the following components: less than or equal to 0.25 wt% of C, less than or equal to 0.005 wt% of Si, less than or equal to 0.005 wt% of Mn, less than or equal to 0.0008 wt% of S, less than or equal to 0.003 wt% of P, less than or equal to 0.005 wt% of Al, less than or equal to 0.003 wt% of Ti, Ce: 0.003-0.007 wt%, La: 0.001 to 0.004 wt%, trace amounts of Nd and Pr, and the balance of Fe and inevitable impurities. The inevitable impurities are less than 0.001 wt%.
Furthermore, in the industrial ultra-pure iron, the number of the inclusions with the size less than or equal to 2um accounts for more than 80 percent.
The invention also provides a production method of the industrial ultra-pure iron. The production method comprises the following steps: sequentially carrying out KR molten iron pre-desulfurization, converter deep dephosphorization, LF deep desulfurization, RH deep deoxidation, continuous casting and electroslag remelting procedures; in the KR molten iron pre-desulfurization process, pre-desulfurization is carried out on molten iron with S less than 0.02%, and the molten iron S at the desulfurization end point is controlled to be less than 0.002%; in the converter deep dephosphorization procedure, a carbon block is adopted for deoxidation during tapping, and the addition amount of the carbon block is controlled so as to control the carbon content in molten iron to be not higher than 0.20 wt%; in the LF deep desulfurization process, firstly adding carbon powder to ensure that the carbon content in molten iron is 0.20-0.25 wt% in a reduction stage, then continuously adding the carbon powder to ensure that the carbon content in the molten iron is higher than 0.25 wt% in a deep desulfurization stage, and simultaneously controlling the alkalinity to be 5.0-7.0; in the RH deep deoxidation procedure, the mixed rare earth is added at the end of the vacuum deep deoxidation cycle, and the end point is when T [ O ] <15ppm is reached by blowing.
Preferably, in the method for producing industrial ultra-pure iron, the molten iron S is less than 0.01% in the KR molten iron pre-desulfurization step.
Specifically, in the production method of the industrial ultra-pure iron, the P removal end point is controlled to be P less than 0.0025% in the deep dephosphorization process of the converter.
Specifically, in the production method of the industrial ultra-pure iron, in the working procedures of converter deep dephosphorization, LF deep desulfurization and/or RH deep deoxidation, the slagging is carried out by adopting high-efficiency active metallurgical lime with low sulfur content and CaO content of more than 90%.
Specifically, in the production method of the industrial ultra-pure iron, in the RH deep deoxidation process, the misch metal includes 30% of La, 48% of Ce, 18% of Nd, and 3% of Pr. The remaining 1% is other rare earth elements.
Specifically, in the method for producing industrial ultra-pure iron, in the RH deep deoxidation step, the addition amount of the misch metal is 0.2kg/t molten iron.
Preferably, in the production method of the industrial ultra-pure iron, in the RH deep deoxidation process, before the mixed rare earth is added, the circulation deoxidation is adopted, and the argon blowing flow is 115-125 Nm3H, the time is 10-15 min; after the mixed rare earth is added, weak blowing is adopted for deoxygenation, and the flow rate of argon blowing is controlled to be 15-25 Nm3The time is controlled to be 12-18 min.
Specifically, in the above method for producing industrial ultra-pure iron, the continuous casting slab has a specification of 280mm 380mm, 320mm 410mm, 160mm square, 200mm square, Φ 240mm or Φ 360mm in the continuous casting step.
Specifically, in the production method of the industrial ultra-pure iron, in the electroslag remelting process, a slag system CaF is selected2-Al2O3-CaO。
Further, in the above method for producing industrial ultra-pure iron, the iron is produced by mass ratioMeter, CaF2﹕Al2O3﹕CaO＝65﹕25﹕10。
Specifically, in the above method for producing industrial ultra-pure iron, in the electroslag remelting step, the ingot shape is Φ 360mm or Φ 550 mm. Furthermore, the corresponding slag amount is 34 plus or minus 2kg and 115 plus or minus 5 kg.
Specifically, in the production method of the industrial ultra-pure iron, carbon powder is added in the smelting process to deoxidize the slag system in the electroslag remelting process.
The invention has the beneficial effects that: the KR molten iron pre-desulfurization can reduce the S of the molten iron fed into the furnace to a certain level; the converter dephosphorizes deeply, residual elements such as P, Si, Mn and the like can be removed to the maximum extent by adopting oxidizing slag, and the carbon block is adopted for deoxidation after the converter taps, so that the deoxidation by adopting deoxidizers such as aluminum, silicon, manganese and the like is avoided, and the content of aluminum, silicon and manganese in molten iron is avoided being increased; the medium and low carbon content in the molten iron controls the oxidizing quantity of the molten iron and slag, which is beneficial to LF deep removal of S and RH deep removal of O; through the series of procedures, the industrial ultra-pure iron produced by the method comprises the following components of less than or equal to 0.25 wt% of C, less than or equal to 0.005 wt% of Si, less than or equal to 0.005 wt% of Mn, less than or equal to 0.0008 wt% of S, less than or equal to 0.003 wt% of P, less than or equal to 0.005 wt% of Al, less than or equal to 0.003 wt% of Ti, Ce: 0.003-0.007 wt%, La: 0.001-0.004 wt%, trace Nd and Pr, less than 0.001 wt% of other impurities, and the balance Fe; the number of the inclusions with the size less than or equal to 2um accounts for more than 80 percent, the iron is low in S, O and P, the size of the inclusions is small, the number of the inclusions is small, trace rare earth is added, and the type of the inclusions is rare earth-containing inclusions. The pure iron produced by the invention can be used for producing high-quality low-alloy ultrahigh-strength steel, secondary hardening ultrahigh-strength steel, high-grade blade steel or low-medium-carbon high-purity stainless steel.
Detailed Description
The present invention will be described in detail with reference to specific embodiments, but the present invention is not limited thereto.
The invention relates to a production method of industrial ultra-pure iron, which adopts the long-flow production of KR molten iron pre-desulfurization → converter smelting → LF deep desulfurization → slag skimming → RH deep deoxidation → square billet or round billet continuous casting → electroslag remelting and comprises the following steps:
1) KR molten iron pre-desulfurization: the molten iron with the S less than 0.02 percent is adopted as a raw material, the molten iron with the S less than 0.01 percent is allowed to be selected under the condition, KR is desulfurized in a mechanical stirring and slagging mode, good thermodynamic and kinetic conditions of desulfurization are achieved, and the S is stably controlled to be less than 0.002 percent at the end point; after the molten iron is desulfurized, removing desulfurized slag;
2) deep dephosphorization in converter smelting: kinetic and thermodynamic conditions favoring dep: high oxidizability and high alkalinity, large slag amount, low-temperature smelting, bottom blowing nitrogen and stirring; oxygen blowing is adopted to oxidize residual elements such as Si, Mn and the like in the molten iron as much as possible, and the P of the molten iron is stably controlled to be less than 0.0025% at the end point; slag stopping and tapping are adopted in the tapping process, and slag is basically not discharged, so that rephosphorization in the subsequent process is reduced; the tapping deoxidation adopts the addition of a carbon block for deoxidation, the addition amount of the carbon block is controlled to control the concentration of C in the molten iron to be not higher than 0.20 wt%, and deoxidants such as aluminum, silicon, manganese and the like are not used for deoxidation, so that the increase of the content of aluminum, silicon and manganese in the molten iron is avoided; in the early stage of the step, residual elements such as P, Si, Mn and the like are removed by oxygen blowing in the converter, and carbon is added for deoxidation in the later converter tapping process;
3) LF deep desulfurization: in the reduction stage, namely the shallow desulfurization stage, carbon powder is added to ensure that the content of C is 0.20-0.25 wt%, the stage can reduce oxygen in the slag, the oxidability of the slag is reduced, and the desulfurization and deoxidation are facilitated, and the carbon powder is adopted because the carbon powder has better reaction kinetics; in the deep desulfurization stage, the deoxidation of the slag and the molten steel is strengthened, carbon powder is continuously added to add the carbon content in the molten iron to be slightly higher than 0.25 wt% (0.25-0.26 wt%), and the steel slag (FeO + MnO) is ensured to be less than or equal to 1.0%; high-alkalinity operation is carried out, and the alkalinity is controlled within the range of 5.0-7.0; adding lime in small batches and in multiple batches at the later stage in the desulfurization process, controlling the stability of molten iron at the end point to be less than 0.001%, removing desulfurization slag and transferring to an RH process;
4) RH deep deoxidation: in the degassing step, the vacuum degree is not higher than 100Pa, the holding time is not lower than 25min, at the end of the vacuum deep deoxidation cycle, 0.2kg/T of mixed rare earth (the components are 30% of La, 48% of Ce, 18% of Nd and 3% of Pr) is added through a vacuum bunker to carry out deep desulfurization, deep deoxidation and impurity denaturation in molten iron, the content of T [ O ] in the molten iron is reduced through two modes of circulation and weak blowing, and the end point is when the content of T [ O ] is less than 15 ppm; controlling the content of the end point C according to the use requirement of specific pure iron: 0.01-0.25 wt%;
5) continuous casting: continuous casting is carried out by adopting a full-protection pouring mode, and a rectangular billet, a square billet and a round billet can be selected;
6) electroslag remelting: the electroslag remelting process can deeply desulfurize and remove large-particle rare earth inclusions, and selects slag system CaF2﹕Al2O3CaO 65:25:10, purifying and proportioning the dregs, and then requiring SiO in the dregs2Not more than 1%.
In the step 3) of the method, because the reaction is always in progress and is dynamically changed, carbon powder cannot be added in place at one time, the carbon powder needs to be continuously added subsequently, and part of the carbon powder can be added to the slag surface in the actual production operation process, so the carbon powder needs to be added to adjust the carbon content in the reduction stage and the deep desulfurization stage.
In the step 4), before the mixed rare earth is added, the circular deoxidation is adopted, and the argon blowing flow is 115-125 Nm3H, the time is 10-15 min; after the mixed rare earth is added, weak blowing is adopted for deoxygenation, and the flow rate of argon blowing is controlled to be 15-25 Nm3The time is controlled to be 12-18 min.
In the method, the converter, LF furnace smelting and RH furnace smelting are conventional smelting and secondary refining processes, so that Mn and Si in the molten iron can be effectively removed, and the molten iron meets the requirements of the component content standard of industrial ultra-pure iron, and the method is not repeated.
In step 5) of the method, the specifications of the continuous casting blank can be selected as follows: 280mm 380mm, 320mm 410mm, 160mm square, 200mm square, phi 240mm or phi 360mm, and the self-electricity consumption of the continuous casting billet is extremely good when the continuous casting billet can be directly used as electroslag remelting after being peeled.
In the step 6) of the method, the ingot can be 360mm or 550mm, and the corresponding slag amount is 34 +/-2 kg or 115 +/-5 kg.
In the step 6) of the method, no deoxidizing agent such as aluminum silicon and the like is added in the smelting process, and only carbon powder is added to deoxidize the slag system to ensure the stability of the slag system, so that the consistency of the component purity of the arc starting end and the feeding end of the electroslag ingot is ensured.
Examples 1 to 5
The KR molten iron pre-desulfurization adopts molten iron raw materials with S less than 0.02 percent and P less than 0.012 percent, the condition allows the molten iron with S less than 0.01 percent to be selected, and the molten iron enters a converter after the desulfurization slag is removed, so that the sulfur content of the molten iron entering the converter is required to be ensured to be less than 0.002 percent.
Deep dephosphorization is carried out in a converter smelting process, oxygen blowing, high oxidizability, high alkalinity, large slag amount and low-temperature smelting are adopted, residual elements such as P, Si, Mn and the like are removed by stirring with bottom blowing nitrogen, and the P is stably controlled to be less than 0.0025% at the end point; and (3) stopping slag and tapping, reducing the slag amount, and deoxidizing by adding a carbon block without deoxidizing agents such as aluminum, silicon and manganese in the molten iron in the tapping deoxidization process so as to avoid increasing the contents of aluminum, silicon and manganese in the molten iron.
LF deep desulfurization, in which carbon powder is added in a reduction stage to ensure that the content of C is 0.20-0.25 wt%, and in a deep desulfurization stage, the deoxidation of slag and molten steel is strengthened, the carbon content in molten iron can be added to be slightly higher than 0.25 wt%, and the steel slag (FeO + MnO) is ensured to be less than or equal to 1.0%; high alkalinity operation, alkalinity control in the range of 5.0-7.0; and (3) adding lime in small batches and in multiple batches at the later stage in the desulfurization process, stably controlling the S of the molten iron at the end point to be less than 0.001%, and transferring the desulfurized slag to an RH process.
RH deep deoxidation, wherein the vacuum degree in the degassing step is not higher than 100Pa, the holding time is not lower than 25min, at the end of the vacuum deep deoxidation cycle, 0.2kg/T mixed rare earth (the components are 30% La, 48% Ce, 18% Nd and 3% Pr) is added through a vacuum bunker to carry out deep desulphurization, deep deoxidation and modification of inclusions in molten iron, and the content of T [ O ] in steel is reduced through two modes of circulation and weak blowing to reach T [ O ] less than 15 ppm. Controlling the content of the end point C according to the use requirement of specific pure iron: 0.01-0.25 wt%.
Continuous casting is carried out by adopting a full-protection pouring mode, wherein the phi of the round billet is 240mm in the embodiment 1-3, and the phi of 360mm is selected in the embodiment 4-5.
The electroslag remelting process can deeply desulfurize and remove large-particle rare earth inclusions, and selects slag system CaF2：Al2O3: CaO 65:25:10 (wt%), after purifying slag, SiO in slag is required2Not more than 1%. In the embodiment 1-3, the ingot type phi 360mm is selected, and the corresponding slag quantity is 34 +/-2 kg; example 4-5, the ingot form of phi 550mm is selected, and the corresponding slag quantity is 115 +/-5kg。
TABLE 1 component contents (wt%) of industrial ultra-pure iron continuous casting slabs of examples 1 to 5
| C | Si | Mn | S | P | Al | Ti | Ce | La | |
| 1 | 0.25 | 0.006 | 0.022 | 0.0007 | 0.0024 | 0.003 | 0.0020 | 0.005 | 0.004 |
| 2 | 0.24 | 0.006 | 0.021 | 0.0009 | 0.0026 | 0.004 | 0.0017 | 0.006 | 0.003 |
| 3 | 0.23 | 0.006 | 0.022 | 0.0008 | 0.0027 | 0.003 | 0.0015 | 0.009 | 0.004 |
| 4 | 0.24 | 0.006 | 0.023 | 0.0009 | 0.0025 | 0.002 | 0.0018 | 0.008 | 0.004 |
| 5 | 0.24 | 0.006 | 0.020 | 0.0007 | 0.0020 | 0.0025 | 0.0017 | 0.007 | 0.005 |
TABLE 2 content (wt%) of corresponding electroslag ingot component in industrial ultra-pure iron of examples 1 to 5
| C | Si | Mn | S | P | Al | Ti | Ce | La | |
| Require that | ≤0.25 | ≤0.005 | ≤0.005 | ≤0.0008 | ≤0.003 | ≤0.005 | ≤0.003 | 0.003-0.007 | 0.001-0.004 |
| 1 | 0.22 | ≤0.0050 | ≤0.0050 | 0.0005 | 0.0020 | ≤0.0050 | 0.0015 | 0.003 | 0.002 |
| 2 | 0.23 | ≤0.0050 | ≤0.0050 | 0.0007 | 0.0019 | ≤0.0050 | 0.0016 | 0.004 | 0.002 |
| 3 | 0.20 | ≤0.0050 | ≤0.0050 | 0.0006 | 0.0022 | ≤0.0050 | 0.0013 | 0.006 | 0.003 |
| 4 | 0.22 | ≤0.0050 | ≤0.0050 | 0.0007 | 0.0020 | ≤0.0050 | 0.0015 | 0.004 | 0.003 |
| 5 | 0.23 | ≤0.0050 | ≤0.0050 | 0.0006 | 0.0017 | ≤0.0050 | 0.0015 | 0.005 | 0.004 |
As can be seen from tables 1 and 2, the contents of Si, Mn, Al, Ti, S and P are reduced by the electroslag remelting process, and pure iron is further purified. As can be seen from Table 2, the contents of the elements of the electroslag ingots in the embodiments 1 to 5 all meet the technical requirements, particularly, the sulfur content can be controlled below 0.0008%, and the rare earth content ranges from 0.005 to 0.011%.
The industrial ultra-pure iron prepared by the method can be applied to producing high-quality low-alloy ultra-high-strength steel, secondary hardening ultra-high-strength steel, high-grade blade steel and low-medium-carbon high-purity stainless steel.
Claims (10)
1. The industrial ultra-pure iron is characterized in that: the components are as follows: less than or equal to 0.25 wt% of C, less than or equal to 0.005 wt% of Si, less than or equal to 0.005 wt% of Mn, less than or equal to 0.0008 wt% of S, less than or equal to 0.003 wt% of P, less than or equal to 0.005 wt% of Al, less than or equal to 0.003 wt% of Ti, Ce: 0.003-0.007 wt%, La: 0.001 to 0.004 wt%, trace amounts of Nd and Pr, and the balance of Fe and inevitable impurities.
2. The industrial ultra-pure iron of claim 1, wherein: the number of the inclusions with the size less than or equal to 2um accounts for more than 80 percent.
3. The method for producing industrial ultra-pure iron according to claim 1 or 2, characterized in that: the method comprises the following steps: sequentially carrying out KR molten iron pre-desulfurization, converter deep dephosphorization, LF deep desulfurization, RH deep deoxidation, continuous casting and electroslag remelting procedures; in the KR molten iron pre-desulfurization process, pre-desulfurization is carried out on molten iron with S less than 0.02%, and the molten iron S at the desulfurization end point is controlled to be less than 0.002%; in the converter deep dephosphorization procedure, a carbon block is adopted for deoxidation during tapping, and the addition amount of the carbon block is controlled so as to control the carbon content in molten iron to be not higher than 0.20 wt%; in the LF deep desulfurization process, firstly adding carbon powder to ensure that the carbon content in molten iron is 0.20-0.25 wt% in a reduction stage, then continuously adding the carbon powder to ensure that the carbon content in the molten iron is higher than 0.25 wt% in a deep desulfurization stage, and simultaneously controlling the alkalinity to be 5.0-7.0; in the RH deep deoxidation procedure, the mixed rare earth is added at the end of the vacuum deep deoxidation cycle, and the end point is when T [ O ] <15ppm is reached by blowing.
4. The method for producing industrial ultra-pure iron according to claim 3, characterized in that: in the KR molten iron pre-desulfurization process, the S content of the molten iron is less than 0.01 percent.
5. The method for producing industrial ultra-pure iron according to claim 3, characterized in that: in the deep dephosphorization process of the converter, the P removal end point is controlled to be P less than 0.0025 percent.
6. The method for producing industrial ultra-pure iron according to claim 3, characterized in that: in the working procedures of deep dephosphorization of the converter, deep desulfurization of LF and/or deep deoxidation of RH, slagging is carried out by adopting high-efficiency active metallurgical lime with low sulfur content and CaO content of more than 90 percent.
7. The method for producing industrial ultra-pure iron according to claim 3, characterized in that: in the RH deep deoxidation procedure, the mixed rare earth comprises 30% of La, 48% of Ce, 18% of Nd and 3% of Pr; further, the addition amount of the mixed rare earth is 0.2kg/t molten iron.
8. The method for producing industrial ultra-pure iron according to claim 3, characterized in that: in the RH deep deoxidation procedure, before the mixed rare earth is added, the circular deoxidation is adopted, and the argon blowing flow is 115-125 Nm3H, the time is 10-15 min; after the mixed rare earth is added, weak blowing is adopted for deoxygenation, and the flow rate of argon blowing is controlled to be 15-25 Nm3The time is controlled to be 12-18 min.
9. The method for producing industrial ultra-pure iron according to claim 3, characterized in that: in the electroslag remelting process, a slag system CaF is selected2-Al2O3-CaO; further, CaF in mass ratio2﹕Al2O3﹕CaO＝65﹕25﹕10。
10. The method for producing industrial ultra-pure iron according to claim 3, characterized in that: in the electroslag remelting process, carbon powder is added in the smelting process to deoxidize a slag system.
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