CN114700470A - Tundish covering agent for smelting rare earth steel and method for reducing rare earth loss - Google Patents
Tundish covering agent for smelting rare earth steel and method for reducing rare earth loss Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 154
- 239000010959 steel Substances 0.000 title claims abstract description 154
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 144
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 135
- 238000000034 method Methods 0.000 title claims abstract description 53
- 238000003723 Smelting Methods 0.000 title claims abstract description 21
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 91
- 238000009749 continuous casting Methods 0.000 claims abstract description 45
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 29
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229910052593 corundum Inorganic materials 0.000 claims abstract description 29
- 229910001845 yogo sapphire Inorganic materials 0.000 claims abstract description 29
- 229910000421 cerium(III) oxide Inorganic materials 0.000 claims abstract description 19
- 229910052681 coesite Inorganic materials 0.000 claims abstract description 16
- 229910052906 cristobalite Inorganic materials 0.000 claims abstract description 16
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 16
- 229910052682 stishovite Inorganic materials 0.000 claims abstract description 16
- 229910052905 tridymite Inorganic materials 0.000 claims abstract description 16
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum oxide Inorganic materials [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims abstract description 14
- KTUFCUMIWABKDW-UHFFFAOYSA-N oxo(oxolanthaniooxy)lanthanum Chemical compound O=[La]O[La]=O KTUFCUMIWABKDW-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000002893 slag Substances 0.000 claims description 128
- 238000007670 refining Methods 0.000 claims description 68
- 229910052760 oxygen Inorganic materials 0.000 claims description 32
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 29
- 239000001301 oxygen Substances 0.000 claims description 29
- GSVIBLVMWGSPRZ-UHFFFAOYSA-N cerium iron Chemical compound [Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Ce].[Ce] GSVIBLVMWGSPRZ-UHFFFAOYSA-N 0.000 claims description 15
- NNLJGFCRHBKPPJ-UHFFFAOYSA-N iron lanthanum Chemical compound [Fe].[La] NNLJGFCRHBKPPJ-UHFFFAOYSA-N 0.000 claims description 7
- 238000005266 casting Methods 0.000 claims description 4
- 230000008569 process Effects 0.000 abstract description 23
- 238000004519 manufacturing process Methods 0.000 abstract description 22
- 238000009851 ferrous metallurgy Methods 0.000 abstract description 2
- 229910052804 chromium Inorganic materials 0.000 description 42
- 229910052748 manganese Inorganic materials 0.000 description 33
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 24
- 238000002844 melting Methods 0.000 description 22
- 230000008018 melting Effects 0.000 description 22
- 229910052802 copper Inorganic materials 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 15
- 239000000126 substance Substances 0.000 description 15
- 229910000640 Fe alloy Inorganic materials 0.000 description 14
- 229910052759 nickel Inorganic materials 0.000 description 14
- 239000000463 material Substances 0.000 description 12
- 239000010935 stainless steel Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 7
- 229910052684 Cerium Inorganic materials 0.000 description 6
- 239000000203 mixture Substances 0.000 description 5
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 229910052746 lanthanum Inorganic materials 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 238000005273 aeration Methods 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910001021 Ferroalloy Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 238000010835 comparative analysis Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- -1 low density Chemical class 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
-
- 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
- C21C7/0006—Adding metallic additives
-
- 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
- C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/076—Use of slags or fluxes as treating agents
-
- 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
Abstract
The invention discloses a tundish covering agent for smelting rare earth steel and a method for reducing rare earth loss, belongs to the technical field of ferrous metallurgy, and solves the problem of low yield of rare earth elements in the existing rare earth steel smelting process. A tundish covering agent for smelting rare earth steel comprises the following components in percentage by mass: 55-65 of SiO2：5‑8，MgO：11‑15，Al2O3：15‑24，FeO+MnO＜0.5，Ce2O3+La2O3：0.1‑2.9，CaO/SiO2: 8.0-11. Aiming at the characteristic that the rare earth in the molten steel in the tundish is easy to oxidize in the continuous casting process of the rare earth steel, the minimum rare earth loss is obtained by optimizing the components of the tundish covering agent. The tundish covering agent and the method of the invention are adopted to lead secondary refiningThe yield in the continuous casting process is more than 40 percent, is improved by more than 8 percent compared with the prior rare earth yield, and reduces the production cost by 50 yuan per ton of steel.
Description
Technical Field
The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a tundish covering agent for smelting rare earth steel and a method for reducing rare earth loss.
Background
The action mechanism and the action effect of the rare earth in the steel are reported in a large number of documents, and the addition of the rare earth in the steel can obviously improve the structure of the steel and improve the performance of the steel. However, due to the special physical and chemical properties of rare earth metals, such as low density, easy volatilization, strong oxophilicity and the like, the rare earth steel is seriously oxidized and burned in the smelting process, and the rare earth yield is always low. In a laboratory or a single furnace test, the rare earth yield is controllable, or the rare earth yield is not a necessary and serious problem, but for continuous production of rare earth steel by adopting a continuous casting process, the stable addition of rare earth, the stable retention of rare earth in steel and the like become a key problem.
The yield of rare earth in the production practice of rare earth steel is about 30%, the fluctuation is large, and the rare earth component in the product is very unstable. Therefore, it is necessary to provide a control method for reducing the rare earth loss in the process of smelting rare earth steel.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a tundish covering agent for smelting rare earth steel and a method for reducing rare earth loss, so as to solve the problem of low rare earth element yield in the existing rare earth steel smelting process.
The purpose of the invention is mainly realized by the following technical scheme:
on one hand, the invention provides a tundish covering agent for smelting rare earth steel, which comprises the following components in percentage by mass: 55-65 of SiO2：5-8，MgO：11-15，Al2O3：15-24，FeO+MnO＜0.5，Ce2O3+La2O3：0.1-2.9，CaO/SiO2：8.0-11。
Furthermore, the mass percentage content of the rare earth Ce and/or La in the rare earth steel is 0.002-0.05%.
In another aspect, the present invention further provides a method for reducing rare earth loss, comprising the following steps:
step 3, refining and then continuously casting;
and 3, allowing the molten steel to enter a continuous casting crystallizer through a tundish, covering the molten steel with a tundish covering agent to isolate air, wherein the tundish covering agent is used as the tundish covering agent.
Further, in the step 2, in the LF furnace refining, the ladle top slag comprises the following components in percentage by mass: 55-65 of SiO2：5-8，MgO：11-15，Al2O3：15-24，FeO+MnO＜0.5，Ce2O3+La2O3：0.1-2.9，CaO/SiO2：8.0-11；
Further, the thickness of the ladle top slag is 140-200 mm.
Further, in step 2, rare earth is added in the last step of refining.
Further, the rare earth is added in the form of cerium iron and/or lanthanum iron.
Further, in step 2, before adding rare earth, the mass percentage of dissolved oxygen [ O ] in the molten steel is controlled to be less than 1.5 ppm.
Further, the tundish covering agent is used after ladle top slag in refining is ground to below 200 meshes and dried.
Furthermore, the thickness of the tundish covering agent is 200-250 mm.
Compared with the prior art, the invention has the following beneficial effects:
1. by adopting the tundish covering agent and the method, the yield in the processes from refining to continuous casting is over 40 percent, the yield is improved by more than 8 percent compared with the prior rare earth yield, and the production cost is reduced by 50 yuan per ton of steel.
2. Aiming at the characteristic that the rare earth in the molten steel in the tundish is easy to oxidize in the continuous casting process of the rare earth steel, the minimum rare earth loss is obtained by optimizing the components of the tundish covering agent.
3. The top slag of the refining ladle can have the same components as the tundish covering agent, so that the tundish covering agent is processed by utilizing the refining slag, the recycling of wastes is realized, and the production cost is reduced to the maximum extent.
4. By the technical scheme, the utilization rate of rare earth metal which is a valuable resource is improved, and an example is provided for production of rare earth steel.
Drawings
FIG. 1 is the oxygen increasing amount of each link in the process from refining to continuous casting of rare earth steel before improvement;
FIG. 2 is the rare earth loss of the rare earth steel in each link from refining to continuous casting before improvement.
FIG. 3 is the oxygen increasing amount of each link from refining to continuous casting of rare earth steel after tundish covering agent and ladle top slag are improved;
FIG. 4 shows the rare earth loss of the rare earth steel in each link from refining to continuous casting after tundish covering agent and ladle top slag are improved.
Detailed Description
The tundish covering agent for smelting rare earth steel and the method for reducing rare earth loss are described in further detail with reference to specific examples, which are provided for illustrative purposes only and the present invention is not limited to these examples.
The rare earth yield in the production practice of rare earth steel is about 30%, the fluctuation is large, the rare earth components in the product are unstable, the research on the control method for reducing the rare earth loss in the process of smelting the rare earth steel is very necessary, and the factors influencing the rare earth yield are complex.
Therefore, the invention deeply studies the rare earth loss in the process of smelting the rare earth steel, and provides the tundish covering agent for smelting the rare earth steel and the method for reducing the rare earth loss.
The invention provides a tundish covering agent for smelting rare earth steel, and the mass percentage of the components of the tundish covering agent is shown in table 1.
TABLE 1 composition wt/% of tundish covering agent
| CaO | SiO2 | MgO | Al2O3 | FeO+MnO | Ce2O3+La2O3 | CaO/SiO2 |
| 56-65 | 5-8 | 11-15 | 15-24 | ＜0.5 | 0.1-2.9 | 8.0-11 |
It should be noted that, in the research, it was found that the tundish covering agent is one of the factors affecting the yield of rare earth. Therefore, the present invention has made intensive studies on the following tundish covering agent. Specifically, the tundish covering agent comprises the following components: 26.91 percent of CaO; SiO 22 6.79％；Al2O3 18.35％；MgO 16.91％；Fe2O3 0.57％；C 0.01％；H20.33 percent of O; alkalinity: 3.96, 25% of ash and 5% of volatile matter.
Aiming at the tundish covering agent, the inventor obtains the oxygen increasing amount of each link of the rare earth steel in the process from refining to continuous casting through thermodynamic equilibrium calculation to obtain a relational graph shown in a figure 1 and a figure 2. Through analysis, the rare earth loss of molten steel in the continuous casting process can be obviously reduced by controlling and optimizing the composition of the tundish covering agent, the composition of the ladle top slag, the material of the ladle lining, the material of the tundish, the material of the stopper rod, the material of the long nozzle, the material of the water immersion nozzle and the material of the water feeding nozzle.
Specifically, as can be seen from fig. 1, the aeration of molten steel is related to the inhaled air, the covering agent component of the tundish, the slag component of the ladle top, the lining material of the ladle, the material of the tundish, the material of the stopper rod, the material of the long nozzle, the material of the immersion nozzle and the material of the upper nozzle, wherein the aeration ratio of the inhaled air, the covering agent component of the tundish and the slag component of the ladle top is 80%. Accordingly, as can be seen from FIG. 2, at a rare earth addition of 50ppm, the total loss of rare earth metals in the process was 33.74ppm, which accounted for 67.5% of the rare earth addition, wherein the loss caused by the intake air, tundish covering agent component and ladle top slag component was 21.07ppm, which accounted for 62.4% of the total loss, which was 42% of the rare earth addition.
Aiming at the analysis, the melting temperature of the tundish covering agent is 1380-1450 ℃, so that the content of CaO which is weakly reacted with rare earth is increased. The concentration of the rare earth oxide is increased, the activity of the rare earth oxide is further improved, the rare earth elements in the molten steel are prevented from being transferred to the tundish covering agent, and the yield of the rare earth is further improved.
Wherein, Ce is contained in the tundish covering agent2O3And La2O3The content of (B) is related to the rare earth content in the molten steel, i.e. if only Ce is contained in the molten steel, only Ce is contained in the tundish covering agent2O3(ii) a If only La is contained in the molten steel, only La is contained in the tundish covering agent2O3(ii) a If the molten steel contains both Ce and La, Ce is contained in the tundish covering agent2O3And La2O3。
It should be noted that since the rare earth element has strong reducibility, (b) at a temperature of molten steel>1500 ℃), would readily react with SiO in the intermediate cladding agent2、Fe2O3Oxidation-reduction reaction occurs, but the reaction with CaO is weak, so that the covering agent alkalinity (CaO/SiO) of the tundish is reduced2) From 3.96 to 8-11, SiO2The amount of the rare earth is reduced, the oxygen transfer amount is reduced, and the loss of the rare earth is further reduced. Tundish covering agent Ce2O3+La2O3Then the activity of the rare earth oxide in the tundish covering agent can be increased, so that the oxidation of the rare earth element in the steel can be inhibited, and the yield is ensured.
The invention also provides a method for reducing rare earth loss, which comprises the following steps:
step 3, refining and then continuously casting;
specifically, in the step 2, slag formation is required in the refining process of the LF furnace, namely ladle top slag, and the components of the tundish covering agent can be adopted, and the specific components are shown in Table 1.
It is understood from the above description that ladle top slag is also one of the factors affecting the rare earth yield. The present invention has studied the following ladle top slag. Specifically, the ladle top slag: the alkalinity is 5.5 to 6.0 percent, and the CaO is 55 to 60 percent; SiO 22 10-12％；Al2O3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO20.5-0.8%; the slag thickness is 138 mm; the melting point of the slag is 1400 ℃.
Comparative analysis of the tundish retarder of the present invention (see Table 1) and the above steel slags revealed that the tundish retarder increased the basicity, and thus SiO2The content is relatively reduced, and simultaneously, the content of MgO is properly increased, and the concentration of the rare earth oxide is increased.
It is known that rare earth elements have strong reducibility at a temperature of refining molten steel: (>1500 ℃), will easily mix with SiO in the top slag2MnO and FeO generating oxygenThe reduction reaction is weak with CaO if the alkalinity (CaO/SiO)2) From less than 6 to 8-11, SiO2The amount of the rare earth is reduced, the oxygen transfer amount is reduced, and the loss of the rare earth is further reduced. Addition of Ce2O3+La2O3And then the concentration and activity of rare earth oxide in the slag can be increased, so that the oxidation of rare earth elements in steel can be inhibited, the rare earth elements in molten steel are prevented from being transferred into the slag, and the yield is ensured. Meanwhile, the melting temperature of the tundish covering agent is 1380-1450 ℃, which is lower than the temperature of the refined molten steel (C)>1500 ℃) and is in liquid state during refining, thereby having good physical covering and chemical metallurgical effect.
Through the analysis, the tundish covering agent is suitable for the ladle top slag in refining. Specifically, the thickness of the ladle slag in the refining process is 140-200 mm.
The rare earth steel suitable for the invention is the rare earth steel added with Ce and/or La, the mass percentage of the rare earth Ce + La in the rare earth steel is between 0.002 and 0.05 percent, and the rare earth steel is added in the form of ferroalloy, such as cerium iron and/or lanthanum iron. The rare earth metal is added in the last step of refining in the step 2, namely when the refining process is LF furnace → RH furnace, the rare earth metal is added in the vacuum chamber of the RH furnace, and the rare earth metal is added in the final cyclic degassing of the RH vacuum, so that the rare earth metal is ensured to be not contacted with oxygen in the air and to be not reacted with slag under the vacuum condition, and the rare earth yield is favorably improved; when the refining process is an LF furnace, adding the refining agent into the LF furnace.
Before the rare earth alloy is added, the mass percentage of dissolved oxygen [ O ] in the molten steel is controlled to be less than 1.5 ppm.
The purpose of controlling the dissolved oxygen [ O ] in the molten steel before adding the rare earth alloy is to reduce the oxidation of free oxygen in the molten steel to rare earth, but in view of the limitation of the current smelting process level, the oxygen content can only be controlled to be 1.0ppm at the minimum, so the actual controlled level of the dissolved oxygen [ O ] in the molten steel of the invention is between 1.0 and 1.5 ppm.
And after refining, the steel ladle is operated to a continuous casting pouring platform, the molten steel enters a continuous casting crystallizer through a tundish, argon is blown into the tundish before casting the rare earth steel, the atmosphere of the tundish is kept to be inert atmosphere, the tundish covering agent is used for covering the molten steel to isolate air, and the molten steel is subjected to conventional slag protection and/or argon atmosphere protection in the process of pouring and flowing.
Specifically, in step 3, the tundish covering agent of the present invention is used.
Since the refining slagging is performed before and after the continuous casting in the actual production, a possible embodiment is to use the refining final slag as the tundish covering agent.
However, since the refined top slag is agglomerated and has a very large particle size, and good dispersibility is required as a tundish covering agent, it is necessary to grind and screen the refined top slag for use as the tundish covering agent.
The method specifically comprises the steps of grinding the refined final slag to be less than 200 meshes (<0.075mm), drying and using the refined final slag, and controlling the thickness of the tundish covering agent to be 200-250 mm. By refining the refining slag, the tundish covering agent has good dispersibility on the surface of the molten steel, can isolate air and reduce air suction, thereby reducing oxygen in the air from entering the molten steel and causing oxidation reaction with rare earth elements.
In view of the above, it is understood that if ladle top slag is used as a tundish covering agent, there are great restrictions in processes and operations because the refining slag of the present furnace cannot be used as a tundish covering agent of the present furnace, and because of the difference in the types of steel to be smelted, the ladle top slag of the previous batch cannot be fully applied to the type of steel of the present batch. Therefore, depending on the specific steel grade being produced, the tundish covering agent of the present invention needs to be manufactured separately to meet the actual production needs.
By the method, the comparison between figure 3 and figure 1 shows that the oxygen increasing amount is reduced by 18.7 percent compared with that before the improvement, and the comparison between figure 4 and figure 2 shows that the rare earth loss amount is reduced to 58.92 percent from the original 67.48 percent, and is reduced by 8.56 percent. Specifically, the loss caused by tundish covering agent is reduced by 2.3%, the loss caused by ladle top slag is reduced by 3.92%, and the loss caused by air suction is reduced by 2.34%. The yield of rare earth in steel from refining to continuous casting is improved from 32.52% to 41.08%, and is improved by 8.56%, and the production cost is reduced by 50 yuan/ton steel.
Comparative example
Producing 5-furnace wear-resistant steel NM400 by the process of converter → LF furnace → RH furnace → continuous casting. The target components are as follows: 0.19 to 0.21 percent of C; si 0.55-0.65%; 1.45 to 1.60 percent of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.005 percent; 0.35 to 0.45 percent of Cr; 0.01 to 0.02 percent of Ti; ce 0.02%.
In the RH furnace refining, the average mass percentage content of dissolved oxygen [ O ] in the molten steel before the addition of the cerium-iron alloy was 1.43 ppm.
After the RH is discharged, the average component content in the molten steel of the 5 furnaces is as follows: 0.19 percent of C; 0.62 percent of Si; 1.50 percent of Mn; p0.013%; 0.004 percent of S; 0.41 percent of Cr; 0.016 percent of Ti; ce 0.0357%.
The alkalinity of the slag of the steel ladle top slag is 5.5 to 6.0, and the alkalinity of the slag is 55 to 60 percent; SiO 22 10-12％；Al2O3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO20.5-0.8%; the slag thickness is 138 mm; the melting point of the slag is 1400 ℃.
The tundish covering agent comprises the following components: 26.91 percent of CaO; SiO 22 6.79％；Al2O3 18.35％；MgO 16.91％；Fe2O3 0.57％；C 0.01％；H20.33 percent of O; alkalinity: 3.96, ash content 25% and volatile matter 5%.
The average composition of the molten steel of 5 furnaces in the continuous casting crystallizer is as follows: 0.19 percent of C; 0.60 percent of Si; 1.52 percent of Mn; p0.014%; 0.002% of S; 0.38 percent of Cr; 0.015 percent of Ti and 0.0160 percent of Ce. The rare earth loss is 0.0332%. The loss amount accounts for 67.48 percent of the rare earth content after the RH furnace is out of the station.
Example 1
The produced steel is wear-resistant steel NM400, and the production process is converter → LF furnace → RH furnace → continuous casting. The target components are as follows: 0.19 to 0.21 percent of C; si 0.55-0.65%; 1.45 to 1.60 percent of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.005 percent; 0.35 to 0.45 percent of Cr; 0.01 to 0.02 percent of Ti; ce 0.02%.
In the RH furnace refining, before the cerium-iron alloy is added, the mass percentage content of dissolved oxygen [ O ] in the molten steel is 1.45 ppm.
After the RH is discharged, the chemical components of the molten steel are as follows: 0.19 percent of C; 0.58 percent of Si; 1.51 percent of Mn; p0.014%; 0.003 percent of S; 0.38 percent of Cr; 0.016 percent of Ti; ce 0.0445%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 5.5-6.0 and the CaO to be 55-60 percent; SiO 22 10-12％；Al2O3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO20.5-0.8%; the slag thickness is 138 mm; the melting point of the slag is 1400 ℃.
The alkalinity of the tundish covering agent is 11, and the CaO content is 56 percent; SiO 22 5.1％；Ce2O3 2.5％；Al2O322 percent; MgO is 14; FeO + MnO 0.3%, melting point 1450 deg.C. The particle size of the tundish covering agent is less than 200 meshes (<0.075mm), the thickness of the tundish covering agent is controlled to be 210 mm.
The molten steel in the continuous casting crystallizer comprises the following components: 0.19 percent of C; 0.60 percent of Si; 1.52 percent of Mn; p0.014%; 0.002% of S; 0.38 percent of Cr; 0.015 percent of Ti and 0.0165 percent of Ce. The loss of rare earth is 0.0280%. The loss amount accounts for 62.88 percent of the rare earth content after the RH furnace is out of service, and is reduced by 4.6 percent compared with the comparative example.
Example 2
The produced steel is corrosion-resistant steel Q450NRQ1, and the production process is converter → LF furnace → continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025 percent; s is less than or equal to 0.008 percent; 0.30 to 1.25 percent of Cr; cu 0.20-0.55%; ni 0.12-0.65%; 0.02 percent of La.
In the LH furnace refining, before the lanthanum-iron alloy is added, the mass percentage content of dissolved oxygen [ O ] in the molten steel is 1.41 ppm.
After LF leaves the station, the molten steel comprises the following chemical components: c0.047%; 0.08 percent of Si; 1.34 percent of Mn; p is 0.009%; 0.001% of S; 0.73 percent of Cr; 0.42 percent of Cu; 0.31 percent of Ni; la 0.0537%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 5.5-6.0 and the CaO to be 55-60 percent; SiO 22 10-12％；Al2O3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO20.5-0.8%; the thickness of the slag is 138 mm; the melting point of the slag is 1400 ℃.
The alkalinity of the tundish covering agent is 11, and the CaO content is 56 percent; SiO 22 5.1％；La2O3 1.0％；Al2O3 24Percent; 13 percent of MgO; FeO + MnO of 0.4%; the slag thickness is 250 mm; the melting point of the slag is 1445 ℃.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; 0.08 percent of Si; 1.32 percent of Mn; p is 0.009%; 0.001% of S; 0.72 percent of Cr; 0.42 percent of Cu; 0.30 percent of Ni; la 0.0201%. The rare earth loss is 0.0336%. The loss amount accounts for 62.6 percent of the rare earth content after the LF furnace is out of the station, and is reduced by 4.9 percent compared with a comparative example.
Example 3
The produced steel is corrosion-resistant steel Q450NRQ1, and the production process is converter → LF furnace → continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025 percent; s is less than or equal to 0.008 percent; 0.30 to 1.25 percent of Cr; cu 0.20-0.55%; ni 0.12-0.65%; la + Ce 0.0298%.
In the LH furnace refining, before adding cerium iron and lanthanum iron alloy, the mass percentage content of dissolved oxygen [ O ] in the molten steel is 1.35 ppm.
After LF leaves the station, the molten steel comprises the following chemical components: c0.047%; 0.08 percent of Si; 1.34 percent of Mn; p is 0.009%; 0.001% of S; 0.73 percent of Cr; 0.42 percent of Cu; 0.31 percent of Ni; ce 0.0410%; la 0.0421%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 5.5-6.0 and the CaO to be 55-60 percent; SiO 22 10-12％；Al2O3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO20.5-0.8%; the slag thickness is 138 mm; the melting point of the slag is 1400 ℃.
The alkalinity of the tundish covering agent is 11, and the CaO content is 65%; SiO 22 5.9％；Ce2O3+La2O3 1.0％；Al2O316 percent; MgO accounts for 12 percent; FeO + MnO of 0.1%; the slag thickness is 230 mm; the melting point of the slag is 1445 ℃.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; 0.08 percent of Si; 1.32 percent of Mn; p is 0.009%; 0.001% of S; 0.72 percent of Cr; 0.42 percent of Cu; 0.30 percent of Ni; ce 0.0162; la 0.0148%. The rare earth loss is 0.0521%. The loss amount accounts for 62.7 percent of the rare earth content after the LF furnace is out of the station, and is reduced by 4.8 percent compared with a comparative example.
Example 4
The produced steel is wear-resistant steel NM400, and the production process is converter → LF furnace → RH furnace → continuous casting. The target components are as follows: 0.19 to 0.21 percent of C; si 0.55-0.65%; 1.45 to 1.60 percent of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.005 percent; 0.35 to 0.45 percent of Cr; 0.01 to 0.02 percent of Ti; ce 0.04%.
In the RH furnace refining, the mass percentage of dissolved oxygen [ O ] in the molten steel before the cerium-iron alloy is added is 1.23 ppm.
After the RH is discharged, the chemical components of the molten steel are as follows: 0.19 percent of C; 0.62 percent of Si; 1.50 percent of Mn; p0.013%; 0.004 percent of S; 0.41 percent of Cr; 0.016 percent of Ti; ce 0.1056%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 5.5-6.0 and the CaO to be 55-60 percent; SiO 22 10-12％；Al2O3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO20.5 to 0.8 percent; the thickness of the slag is 138 mm; the melting point of the slag is 1400 ℃.
The alkalinity of the tundish covering agent is 10 percent, and the CaO content is 60 percent; SiO 22 6％；Ce2O3 2％；Al2O319 percent; MgO is 12%; FeO + MnO is 0.4%; the slag thickness is 240 mm; the slag melting point was 1434 ℃.
The molten steel in the continuous casting crystallizer comprises the following components: 0.20 percent of C; 0.58 percent of Si; 1.51 percent of Mn; p0.013%; 0.002% of S; 0.41 percent of Cr; 0.016 percent of Ti; ce 0.0394%. The rare earth loss is 0.0662%, the loss accounts for 62.7% of the rare earth content after the RH furnace is out of service, and is reduced by 4.8% compared with the comparative example.
Example 5
The produced steel is corrosion-resistant steel Q450NRQ1, and the production process is converter → LF furnace → continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025 percent; s is less than or equal to 0.008 percent; 0.30 to 1.25 percent of Cr; 0.20 to 0.55 percent of Cu; ni 0.12-0.65%; ce is 0.008 percent.
In LH furnace refining, before adding cerium-iron alloy, the mass percentage of dissolved oxygen [ O ] in molten steel is 1.47 ppm.
After LF leaves the station, the molten steel comprises the following chemical components: 0.048% of C; 0.08 percent of Si; 1.31 percent of Mn; p is 0.01 percent; 0.004 percent of S; 0.39 percent of Cr; 0.33 percent of Cu; 0.036% of Ni; ce 0.0224%.
Controlling steelThe basicity of the slag of the ladle top slag is 5.5 to 6.0, and the basicity of CaO is 55 to 60 percent; SiO 22 10-12％；Al2O3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO20.5 to 0.8 percent; the slag thickness is 138 mm; the melting point of the slag is 1400 ℃.
The alkalinity of the tundish covering agent is 9 percent, CaO is 63 percent and SiO is2 7％，Ce2O3 1.0％，Al2O317%, 11.5% of MgO, 0.35% of FeO + MnO, 240mm of slag thickness and 1458 ℃ of slag melting point.
The molten steel in the continuous casting crystallizer comprises the following components: 0.048% of C; 0.08 percent of Si; 1.31 percent of Mn; p is 0.01 percent; 0.004 percent of S; 0.39 percent of Cr; 0.33 percent of Cu; 0.36 percent of Ni; ce 0.0083%. The rare earth loss was 0.0141%. The loss amount accounts for 62.9 percent of the rare earth content after the LF furnace is out of the station, and is reduced by 4.6 percent compared with a comparative example.
Example 6
The produced steel grade is corrosion-resistant steel Q450NRQ1, and the production process is converter → LF furnace → continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025 percent; s is less than or equal to 0.008 percent; 0.30 to 1.25 percent of Cr; cu 0.20-0.55%; ni 0.12-0.65%; ce 0.03%.
In LH furnace refining, before adding cerium-iron alloy, the mass percentage of dissolved oxygen [ O ] in molten steel is 1.34 ppm.
After LF leaves the station, the molten steel comprises the following chemical components: c0.047%; 0.08 percent of Si; 1.34 percent of Mn; p is 0.009%; 0.001% of S; 0.73 percent of Cr; 0.42 percent of Cu; 0.31 percent of Ni; ce 0.084%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 8 and CaO 56 percent; SiO 22 7％；Ce2O3 1.0％；Al2O322 percent; 13 percent of MgO; FeO + MnO of 0.4%; the slag thickness is 170 mm; the slag melting point was 1477 ℃.
The tundish covering agent is the same as the comparative example, and comprises the following components: CaO 26.91%; SiO 22 6.79％；Al2O3 18.35％；MgO 16.91％；Fe2O3 0.57％；C 0.01％；H20.33 percent of O; alkalinity: 3.96, 25% of ash and 5% of volatile matter.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; 0.08 percent of Si; 1.32 percent of Mn; p is 0.009%; 0.001% of S; 0.72 percent of Cr; 0.42 percent of Cu; 0.30 percent of Ni; ce 0.0311%. The rare earth loss is 0.0530%. The loss amount accounts for 63 percent of the rare earth content after the LF furnace is out of the station, and is reduced by 4.5 percent compared with a comparative example.
Example 7
The produced steel is wear-resistant steel NM400, and the production process comprises a converter → an LF furnace → an RH furnace → continuous casting. The target components are as follows: 0.19 to 0.21 percent of C; si 0.55-0.65%; 1.45-1.60% of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.005 percent; 0.35 to 0.45 percent of Cr; 0.01 to 0.02 percent of Ti; ce 0.02%.
In the RH furnace refining, the mass percentage of dissolved oxygen [ O ] in the molten steel before the cerium-iron alloy is added is 1.45 ppm.
After the RH is discharged, the chemical components of the molten steel are as follows: 0.19 percent of C; 0.58 percent of Si; 1.51 percent of Mn; p0.014%; 0.003 percent of S; 0.38 percent of Cr; 0.016 percent of Ti; ce 0.0401%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 11 and CaO 56 percent; SiO 22 5.1％；Ce2O3 2.5％；Al2O322 percent; MgO is 14; FeO + MnO of 0.3%; the slag thickness is 140 mm; the melting point of the slag was 1450 ℃.
The tundish covering agent uses ladle top slag in RH furnace refining, the specific method is to grind the RH refining slag to be less than 200 meshes (<0.075mm), and the RH refining slag is used after being dried, and the thickness of the tundish covering agent is controlled to be 210 mm.
The molten steel in the continuous casting crystallizer comprises the following components: 0.19 percent of C; 0.60 percent of Si; 1.52 percent of Mn; p0.014%; 0.002% of S; 0.38 percent of Cr; 0.015 percent of Ti and 0.0165 percent of Ce. The rare earth loss is 0.0236 percent. The loss amount accounts for 58.9 percent of the rare earth content after the RH furnace is out of service, and is reduced by 8.58 percent compared with the comparative example.
Example 8
The produced steel is wear-resistant steel NM400, and the production process is converter → LF furnace → RH furnace → continuous casting. The target components are as follows: 0.19 to 0.21 percent of C; si 0.55-0.65%; 1.45 to 1.60 percent of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.005 percent; 0.35 to 0.45 percent of Cr; 0.01 to 0.02 percent of Ti; ce 0.02%.
In the RH furnace refining, the mass percentage of dissolved oxygen [ O ] in the molten steel before the cerium-iron alloy is added is 1.41 ppm.
After the RH is discharged, the chemical components of the molten steel are as follows: 0.19 percent of C; 0.58 percent of Si; 1.51 percent of Mn; p0.014%; 0.003 percent of S; 0.38 percent of Cr; 0.016 percent of Ti; ce 0.0381%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 11 and CaO 56 percent; SiO 22 5.1％；Ce2O32.5％；Al2O322 percent; MgO accounts for 14 percent; FeO + MnO of 0.3%; the slag thickness is 180 mm; the melting point of the slag was 1450 ℃.
The tundish covering agent uses ladle top slag in RH furnace refining, the specific method is to grind the RH refining slag to below 200 meshes (<0.075mm), and the RH refining slag is dried and used, and the thickness of the tundish covering agent is controlled to be 230 mm.
The molten steel in the continuous casting crystallizer comprises the following components: 0.19 percent of C; 0.55 percent of Si; 1.52 percent of Mn; p0.014%; 0.002% of S; 0.38 percent of Cr; 0.015 percent of Ti and 0.0160 percent of Ce. The rare earth loss is 0.0221%. The loss amount accounts for 58 percent of the rare earth content after the RH furnace is out of service, and is reduced by 9.48 percent compared with the comparative example.
Example 9
The produced steel is corrosion-resistant steel Q450NRQ1, and the production process is converter → LF furnace → continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025 percent; s is less than or equal to 0.008 percent; 0.30 to 1.25 percent of Cr; cu 0.20-0.55%; ni 0.12-0.65%; ce 0.03%.
In LH furnace refining, before adding cerium-iron alloy, the mass percentage of dissolved oxygen [ O ] in molten steel is 1.34 ppm.
After LF leaves the station, the molten steel comprises the following chemical components: c0.047%; 0.08 percent of Si; 1.34 percent of Mn; p is 0.009%; 0.001% of S; 0.73 percent of Cr; 0.42 percent of Cu; 0.31 percent of Ni; ce 0.0759%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 8 and CaO 56 percent; SiO 22 7％；Ce2O3 1.0％；Al2O322 percent; 13 percent of MgO; FeO + MnO of 0.4%; the slag thickness is 150 mm; the slag melting point was 1477 ℃.
The tundish covering agent uses LF refining slag, the specific method is to grind the LF refining slag to be less than 200 meshes (<0.075mm), and the LF refining slag is used after being dried, and the thickness of the tundish covering agent is controlled to be 220 mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; 0.08 percent of Si; 1.32 percent of Mn; p is 0.009%; 0.001% of S; 0.72 percent of Cr; 0.42 percent of Cu; 0.30 percent of Ni; ce 0.0311%. The rare earth loss is 0.0448%. The loss amount accounts for 59 percent of the rare earth content after the LF furnace is out of the station, and is reduced by 8.48 percent compared with a comparative example.
Example 10
The produced steel is corrosion-resistant steel Q450NRQ1, and the production process is converter → LF furnace → continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025 percent; s is less than or equal to 0.008 percent; 0.30 to 1.25 percent of Cr; cu 0.20-0.55%; ni 0.12-0.65%; 0.02 percent of La.
In LH furnace refining, before lanthanum-iron alloy is added, the mass percentage of dissolved oxygen [ O ] in the molten steel is 1.41 ppm.
After LF leaves the station, the molten steel comprises the following chemical components: c0.047%; 0.08 percent of Si; 1.34 percent of Mn; p is 0.009%; 0.001% of S; 0.73 percent of Cr; 0.42 percent of Cu; 0.31 percent of Ni; la 0.0481%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 11 and 56 percent of CaO; SiO 22 5.1％；La2O3 1.0％；Al2O324 percent; 13 percent of MgO; FeO + MnO of 0.4%; the slag thickness is 200 mm; the melting point of the slag is 1445 ℃.
The tundish covering agent uses LF refining slag, the specific method is to grind the LF refining slag to be less than 200 meshes (<0.075mm), and the LF refining slag is used after being dried, and the thickness of the tundish covering agent is controlled to be 250 mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; 0.08 percent of Si; 1.32 percent of Mn; p is 0.009%; 0.001% of S; 0.72 percent of Cr; 0.42 percent of Cu; 0.30 percent of Ni; la 0.0201%. The loss of rare earth is 0.028%. The loss amount accounts for 58.2 percent of the rare earth content after the LF furnace is out of the station, and is reduced by 9.28 percent compared with a comparative example.
Example 11
The produced steel grade is corrosion-resistant steel Q450NRQ1, and the production process is converter → LF furnace → continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025 percent; s is less than or equal to 0.008 percent; 0.30 to 1.25 percent of Cr; cu 0.20-0.55%; ni 0.12-0.65%; la + Ce 0.0298%.
In the LH furnace refining, before adding cerium iron and lanthanum iron alloy, the mass percentage content of dissolved oxygen [ O ] in the molten steel is 1.35 ppm.
After LF leaves the station, the molten steel comprises the following chemical components: c0.047%; 0.08 percent of Si; 1.34 percent of Mn; p is 0.009%; 0.001% of S; 0.73 percent of Cr; 0.42 percent of Cu; 0.31 percent of Ni; ce 0.0368%; 0.0375% of La.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 11 and CaO 65 percent; SiO 22 5.9％；Ce2O3+La2O3 1.0％；Al2O316 percent; MgO accounts for 12 percent; FeO + MnO of 0.1%; the slag thickness is 190 mm; the melting point of the slag is 1445 ℃.
The tundish covering agent uses LF refining slag, the specific method is to grind the LF refining slag to be less than 200 meshes (<0.075mm), and the LF refining slag is used after being dried, and the thickness of the tundish covering agent is controlled to be 240 mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; 0.08 percent of Si; 1.32 percent of Mn; p is 0.009%; 0.001% of S; 0.72 percent of Cr; 0.42 percent of Cu; 0.30 percent of Ni; ce 0.0162; la 0.0148%. The rare earth loss is 0.0433%. The loss amount accounts for 58.3 percent of the rare earth content after the LF furnace is out of the station, and is reduced by 9.38 percent compared with a comparative example.
Example 12
The produced steel is wear-resistant steel NM400, and the production process is converter → LF furnace → RH furnace → continuous casting. The target components are as follows: 0.19 to 0.21 percent of C; si 0.55-0.65%; 1.45 to 1.60 percent of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.005 percent; 0.35 to 0.45 percent of Cr; 0.01 to 0.02 percent of Ti; ce 0.04%.
In the RH furnace refining, the mass percentage of dissolved oxygen [ O ] in the molten steel before the cerium-iron alloy is added is 1.23 ppm.
After the RH is discharged, the chemical components of the molten steel are as follows: 0.19 percent of C; 0.62 percent of Si; 1.50 percent of Mn; p is 0.013%; 0.004 percent of S; 0.41 percent of Cr; 0.016 percent of Ti; ce 0.0961%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 10 and CaO to be 60 percent; SiO 22 6％；Ce2O3 2％；Al2O319 percent; MgO is 12%; FeO + MnO is 0.4%; the slag thickness is 150 mm; the slag melting point was 1434 ℃.
The tundish covering agent uses ladle top slag used in RH furnace in refining, the specific method is to grind the RH refining slag to less than 200 meshes (<0.075mm), and use the RH refining slag after drying, and the thickness of the tundish covering agent is controlled to be 220 mm.
The molten steel in the continuous casting crystallizer comprises the following components: 0.20 percent of C; 0.58 percent of Si; 1.51 percent of Mn; p0.013%; 0.002% of S; 0.41 percent of Cr; 0.016 percent of Ti; ce 0.0394%. The rare earth loss is 0.0567%, the loss accounts for 58.98% of the rare earth content after the RH furnace is out of station, and the rare earth loss is reduced by 8.9% compared with a comparative example.
Example 13
The produced steel is corrosion-resistant steel Q450NRQ1, and the production process is converter → LF furnace → continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025 percent; s is less than or equal to 0.008 percent; 0.30 to 1.25 percent of Cr; cu 0.20-0.55%; ni 0.12-0.65%; ce 0.008%.
In LH furnace refining, before adding cerium-iron alloy, the mass percentage of dissolved oxygen [ O ] in molten steel is 1.47 ppm.
After LF leaves the station, the molten steel comprises the following chemical components: 0.048% of C; 0.08 percent of Si; 1.31 percent of Mn; p is 0.01 percent; 0.004 percent of S; 0.39 percent of Cr; 0.33 percent of Cu; 0.036% of Ni; ce 0.0201%.
Controlling the alkalinity of the slag of the top slag of the steel ladle to be 9, CaO 63 percent and SiO2 7％，Ce2O3 1.0％，Al2O317%, 11.5% of MgO, 0.35% of FeO + MnO, 150mm of slag thickness and 1458 ℃ of slag melting point.
The tundish covering agent is refined slag used by an LF furnace, the specific method is to grind the LF refined slag to be less than 200 meshes (<0.075mm), and the LF refined slag is dried and used, and the thickness of the tundish covering agent is controlled to be 220 mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.048%; 0.08 percent of Si; 1.31 percent of Mn; p is 0.01%; 0.004 percent of S; 0.39 percent of Cr; 0.33 percent of Cu; 0.36 percent of Ni; ce 0.0083%. The rare earth loss is 0.0118%. The loss amount accounts for 58.78 percent of the rare earth content after the LF furnace is out of the station, and is reduced by 8.7 percent compared with a comparative example.
From the above examples, it can be seen that the improvement of the tundish covering agent reduces the rare earth loss by about 4%, and the use of the tundish covering agent in the ladle top slag also reduces the rare earth consumption by about 4%. The alkalinity of the tundish covering agent is improved to be beneficial to improving the rare earth yield, but the fluidity is reduced when the alkalinity is too high, the covering effect of molten steel is influenced, and the probability of air suction is increased. The use of the tundish covering agent and the ladle top slag will increase the beneficial effect, which is particularly important for higher basicity slag, but the thickness exceeds a certain value, the effect is reduced and the cost is increased therewith.
Claims (10)
1. The tundish covering agent for smelting rare earth steel is characterized by comprising the following components in percentage by mass: 55-65 of SiO2：5-8，MgO：11-15，Al2O3：15-24，FeO+MnO＜0.5，Ce2O3+La2O3：0.1-2.9，CaO/SiO2：8.0-11。
2. The tundish covering agent according to claim 1, wherein the rare earth Ce and/or La is contained in the rare earth steel in an amount of 0.002-0.05% by mass.
3. A method for reducing rare earth loss, comprising the steps of:
step 1, smelting in a converter or an electric furnace;
step 2, refining in an LF furnace or an LF furnace → an RH furnace;
and 3, refining and then continuously casting.
In the step 3, the molten steel enters the continuous casting crystallizer through a tundish, and the molten steel is covered by a tundish covering agent to isolate air, wherein the tundish covering agent disclosed in the claim 1 is used as the tundish covering agent.
4. The method of claim 3, wherein the ladle top slag component in the LF furnace refining is in mass percent in the step 2The number is CaO: 55-65 of SiO2：5-8，MgO：11-15，Al2O3：15-24，FeO+MnO＜0.5，Ce2O3+La2O3：0.1-2.9，CaO/SiO2：8.0-11。
5. The method as claimed in claim 4, wherein the ladle top slag thickness is 140-200 mm.
6. The method of claim 3, wherein in step 2, rare earth is added in the last step of refining.
7. The method of claim 6, wherein the rare earth is added as cerium iron and/or lanthanum iron.
8. The method according to claim 6, wherein in the step 2, before the addition of the rare earth, the mass percentage of dissolved oxygen [ O ] in the molten steel is controlled to be less than 1.5 ppm.
9. The method according to claim 3, wherein the tundish covering agent is used after the slag on the top of the ladle in refining is ground to below 200 meshes and dried.
10. The method of claim 9, wherein the tundish covering agent has a thickness of 200 to 250 mm.
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Citations (6)
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