A safe and fast LF refining slagging method

Abstract

The application discloses a safe and fast LF refining slagging method, and particularly relates to the following steps: mixing fluorite, 80 vanadium-iron smelting lean slag and refining slag after crushing and drying treatment according to a proportion to form an auxiliary slagging agent; during LF refining treatment, the auxiliary slagging agent is added from a high-position stock bin after conventional slagging materials are added to form slag, and then qualified molten steel can be obtained through subsequent LF refining operation. The application effectively solves the problem of serious foaming of the refining slag during the process of simply using the 80 vanadium-iron smelting lean slag, realizes the recycling of part of the refining slag while achieving safe and fast slagging, and reduces resource waste.

Description

Technical Field

[0001] This invention belongs to the field of LF refining and steelmaking, and specifically relates to a safe and rapid LF refining slag-forming method. Background Technology

[0002] 80% vanadium ferrometallurgical lean slag is a byproduct of vanadium plant production. It can be added during refining to assist in slag formation and accelerate slag production. However, using 80% vanadium ferrometallurgical lean slag alone can lead to severe foaming of the refining slag, which can easily cause slag overflow during refining and create safety hazards. Summary of the Invention

[0003] To solve the above-mentioned technical problems, the present invention provides a safe and rapid LF refining slag-making method, which can not only eliminate the safety hazards caused by simply using 80 vanadium iron to smelt lean slag, but also achieve a high refining efficiency similar to that of simply using 80 vanadium iron to smelt lean slag.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A safe and rapid LF refining slag-forming method is as follows: Fluorite, 80 vanadium ferrometallurgical lean slag, and refining slag are crushed, dried, and then mixed in proportion to form an auxiliary slag-forming agent; during the LF refining process, after the conventional slag-forming material is added, the auxiliary slag-forming agent is added from the high-level silo to form slag, and then qualified molten steel can be obtained through subsequent LF refining operations.

[0005] Furthermore, the total amount of auxiliary slagging agent added to a single furnace according to the present invention is 500-800 kg.

[0006] Furthermore, in the auxiliary slag-forming agent of the present invention, the mass proportions of fluorite, 80 vanadium ferrometallurgical lean slag, and refining slag are 20%-25%, 20%-25%, and 50-60%, respectively.

[0007] Furthermore, the particle size requirement of the auxiliary slag-forming agent described in this invention is 10-30 mm.

[0008] Furthermore, the composition and mass content of the auxiliary slag-forming agent of the present invention satisfy the following: CaF2>10%, CaO>35%, SiO2<5%, MgO>8%, P<1%, S<1%, Al2O3>30%.

[0009] Furthermore, the auxiliary slag-forming agent described in this invention is added within 30 seconds after the addition of conventional slag-forming material.

[0010] Furthermore, the total amount of auxiliary slagging agent added in a single furnace according to the present invention shall not exceed 50% of the total amount of conventional slagging material added in a single furnace.

[0011] Furthermore, the final composition and percentage content of the qualified molten steel described in this invention are: C≤0.05%, S≤0.015%, with the balance being iron and other unavoidable elements.

[0012] The inventive principle of the technical solution of this invention lies in: The lean slag from 80% vanadium ferrometallurgical smelting can provide some Al2O3 to the slag. Al2O3, together with CaO and SiO2 in the slag, forms a low-melting-point slag system. This low-melting-point slag system can improve slag fluidity while inhibiting the formation of high-melting-point, high-viscosity calcium silicate minerals. The highly fluid slag can also provide favorable kinetic conditions for desulfurization. Fluorite contains a large amount of CaF2; its addition to the refining furnace can lower the melting point of 2CaO·SiO2, allowing CaO to quickly dissolve into the slag, and F... - Ions break down long silicate chains, breaking large molecules into smaller clusters, thus improving slag fluidity and promoting rapid slag formation. The CaO and Al2O3 in the refined slag promote CaO recycling and also enhance slag fluidity. Furthermore, the refined slag is a pre-melted slag material, melting more rapidly than raw materials and having less impact on temperature. Because the amount of lean 80V ferrovanadium smelting slag added is controlled by the mixed auxiliary slag-forming agent, its reaction is far less violent than using lean 80V ferrovanadium smelting slag alone, significantly increasing the safety factor while achieving the same auxiliary slag-forming effect.

[0013] The beneficial effects of adopting the above technical solution are as follows: This invention effectively solves the problem of severe foaming of refining slag during the smelting of lean slag using only 80 vanadium ferroalloy, significantly improving the safety factor while achieving the same auxiliary slag-forming effect. The recycling of some refining slag reduces resource waste. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to the embodiments.

[0015] The method of this invention mainly optimizes and controls the processing and proportioning of auxiliary slag-forming agents, as well as their application methods, as follows: (1) Processing and proportioning of auxiliary slag-forming agents The dried fluorite, 80 vanadium ferrometallurgical lean slag, and refining slag are processed and crushed to achieve a particle size of 10-30mm. The raw materials are then fed into a mixing tank for mixing, with the proportions of fluorite, 80 vanadium ferrometallurgical lean slag, and refining slag being 20%-25%, 20%-25%, and 50-60%, respectively. The mixed auxiliary slag-forming agent is then transported via conveyor belt to the LF refining high-level silo for later use.

[0016] (2) Method of using auxiliary slag-forming agent In the LF refining process, the conventional slag-forming material is added in 2-3 batches depending on the molten steel. The main slag-forming material in the LF refining process is small-particle lime, and an aluminous deoxidizer is used for slag deoxidation. Before the first heating, the auxiliary slag-forming agent is added within 30 seconds after the addition of the small-particle lime. After the first slag conditioning after heating, the addition of auxiliary slag-forming agent can be determined within 30 seconds of the addition of the small-particle lime, depending on the slag melting situation. If auxiliary slag-forming agent is used, the amount added should not exceed 200 kg. After reheating, a second slag conditioning is performed, and no further auxiliary slag-forming agent is added after the addition of small-particle lime. The total amount of auxiliary slag-forming agent added in a single furnace should not exceed 50% of the total amount of small-particle lime added. The composition of the auxiliary slag-forming agent used must meet the following requirements: CaF2 > 10%, CaO > 35%, SiO2 < 5%, MgO > 8%, P < 1%, S < 1%, Al2O3 > 30%.

[0017] The following examples and comparative examples all involve LF refining in furnaces that did not undergo hot casting residue recovery.

[0018] The particle size of the auxiliary slag-forming agent used in each embodiment is 10-30mm, the composition meets the specified requirements, and it is transported to the LF refining high-level silo via the feeding belt for later use. Example 1

[0019] A steel plant's 150t production line uses an LF refining furnace to produce DD11-MD steel. The molten steel charge is 163t, and the composition of the molten steel entering the station is: C: 0.040%, Si: 0.001%, Mn: 0.154%, P: 0.010%, S: 0.043%. The temperature of the molten steel at the argon station is 1595℃.

[0020] After the ladle arrives at the station, 1000 kg of fine-grained lime is added, followed by 500 kg of auxiliary slagging agent within 30 seconds. Submerged arc heating is then initiated after the addition is complete. Following heating, the first slag adjustment is performed with the addition of 200 kg of fine-grained lime; no further auxiliary slagging agent is added. Refining takes approximately 17 minutes, resulting in good slag texture and color, indicating slag formation is complete. After temperature measurement and sampling, a second submerged arc heating is performed. A second slag adjustment is then conducted, with no further addition of fine-grained lime. Subsequent alloying, calcium treatment, and weak argon blowing operations are then carried out.

[0021] In this embodiment, the contents of fluorite, lean slag from 80 vanadium ferrometallurgical smelting, and refining slag in the auxiliary slag-forming agent are 20%, 20%, and 60%, respectively. The composition and mass content of the auxiliary slag-forming agent are as follows: CaF2: 12.5%, CaO: 37.4%, SiO2: 1.4%, MgO: 9.7%, P: 0.35%, S: 0.55%, Al2O3: 32.7%.

[0022] During the charging process, the bottom-blown argon flow rate was controlled at 1100 NL / min, and during the heating process, the bottom-blown argon flow rate was controlled at 280 NL / min, with a total heating time of 7.5 min. The first sample of molten steel showed a sulfur content of 0.012% and a desulfurization rate of 72.1%. After refining, the steel sample composition was: C: 0.045%, S: 0.008%, with a refining cycle of 31 minutes. The process was safe and performed well, with no abnormalities observed. Example 2

[0023] A steel plant's 150t production line uses an LF refining furnace to produce DD11-MD steel. The molten steel charge is 160t, and the composition of the molten steel entering the station is: C: 0.037%, Si: 0.001%, Mn: 0.150%, P: 0.013%, S: 0.048%. The temperature of the molten steel at the argon station is 1590℃.

[0024] After the ladle arrived at the station, 1100 kg of fine-grained lime was added, followed by 600 kg of auxiliary slagging agent within 30 seconds. Submerged arc heating was then initiated after the addition was complete. Following heating, the first slag adjustment was performed, with 400 kg of fine-grained lime added; no further auxiliary slagging agent was added. Refining took approximately 18 minutes, resulting in good slag condition and color, indicating slag formation was complete. After temperature measurement and sampling, a second submerged arc heating was performed. A second slag adjustment was then conducted, with no further addition of fine-grained lime. Subsequent alloying, calcium treatment, and weak argon blowing operations were then carried out.

[0025] In this embodiment, the contents of fluorite, lean slag from 80 vanadium ferrometallurgical smelting, and refining slag in the auxiliary slag-forming agent are 25%, 20%, and 55%, respectively. The composition and mass content of the auxiliary slag-forming agent are as follows: CaF2: 13.4%, CaO: 38.4%, SiO2: 0.89%, MgO: 8.8%, P: 0.25%, S: 0.39%, Al2O3: 34.6%.

[0026] During the charging process, the bottom-blown argon flow rate was controlled at 1100 NL / min, and during the heating process, the bottom-blown argon flow rate was controlled at 300 NL / min, with a total heating time of 7 minutes. The first sample of molten steel showed a sulfur content of 0.011% and a desulfurization rate of 77.1%. After refining, the steel sample composition was: C: 0.040%, S: 0.009%, with a refining cycle of 32 minutes. The process was safe and performed well, with no abnormalities observed. Example 3

[0027] A steel plant's 150t production line uses an LF refining furnace to produce DD11-MD steel. The molten steel charge is 165t, and the composition of the molten steel entering the station is: C: 0.035%, Si: 0.001%, Mn: 0.151%, P: 0.011%, S: 0.042%. The temperature of the molten steel at the argon station is 1594℃.

[0028] After the ladle arrives at the station, 1000 kg of fine-grained lime is added, followed by 500 kg of auxiliary slagging agent within 30 seconds. Submerged arc heating is then initiated after the addition is complete. Following heating, the first slag adjustment is performed, adding another 500 kg of fine-grained lime and 200 kg of auxiliary slagging agent. Refining takes approximately 16 minutes, resulting in good slag texture and color, indicating slag formation is complete. Temperature measurement and sampling are then conducted, followed by a second submerged arc heating. A second slag adjustment is performed after this second heating, without further addition of fine-grained lime. Subsequent alloying, calcium treatment, and weak argon blowing operations are then carried out.

[0029] In this embodiment, the contents of fluorite, lean slag from 80 vanadium ferrometallurgical smelting, and refining slag in the auxiliary slag-forming agent are 20%, 25%, and 55%, respectively. The composition and mass content of the auxiliary slag-forming agent are as follows: CaF2: 12.8%, CaO: 37.6%, SiO2: 0.77%, MgO: 9.3%, P: 0.35%, S: 0.52%, Al2O3: 33.8%.

[0030] During the charging process, the bottom-blown argon flow rate was controlled at 1200 NL / min, and during the heating process, the bottom-blown argon flow rate was controlled at 300 NL / min, with a total heating time of 7 minutes. The first sample of molten steel showed a sulfur content of 0.011% and a desulfurization rate of 73.8%. After refining, the steel sample composition was: C: 0.039%, S: 0.008%, with a refining cycle of 30 minutes. The process was safe and performed well, with no abnormalities observed. Example 4

[0031] A steel plant's 150t production line uses an LF refining furnace to produce DD11-MD steel. The molten steel charge is 162t, and the composition of the molten steel entering the station is: C: 0.040%, Si: 0.001%, Mn: 0.154%, P: 0.014%, S: 0.049%. The temperature of the molten steel at the argon station is 1592℃.

[0032] After the ladle arrives at the station, 1200 kg of fine-grained lime is added, followed by 600 kg of auxiliary slagging agent within 30 seconds. Submerged arc heating is then initiated after the addition is complete. Following heating, the first slag adjustment is performed, with 500 kg of fine-grained lime and 200 kg of auxiliary slagging agent added. Refining takes approximately 18 minutes, resulting in good slag texture and color, indicating slag formation is complete. Temperature measurement and sampling are then conducted, followed by a second submerged arc heating. A second slag adjustment is performed after this second heating, without further addition of fine-grained lime. Subsequent alloying, calcium treatment, and weak argon blowing operations are then carried out.

[0033] In this embodiment, the contents of fluorite, lean slag from 80 vanadium ferrometallurgical smelting, and refining slag in the auxiliary slag-forming agent are 25%, 25%, and 50%, respectively. The composition and mass content of the auxiliary slag-forming agent are as follows: CaF2: 13.1%, CaO: 38.5%, SiO2: 0.61%, MgO: 8.7%, P: 0.29%, S: 0.54%, Al2O3: 34.1%.

[0034] During the charging process, the bottom-blown argon flow rate was controlled at 1100 NL / min, and during the heating process, the bottom-blown argon flow rate was controlled at 300 NL / min, with a total heating time of 8 minutes. The first sample of molten steel showed a sulfur content of 0.012% and a desulfurization rate of 75.5%. After refining, the molten steel sample composition was: C: 0.045%, S: 0.010%, with a refining cycle of 31 minutes. The process operated safely and smoothly, without any abnormalities.

[0035] Comparative Example 1 (using only 80 smelting lean slag) A steel plant's 150t production line uses an LF refining furnace to produce DD11-MD steel. The molten steel charge is 162t, and the composition of the molten steel entering the station is: C: 0.041%, Si: 0.001%, Mn: 0.151%, P: 0.012%, S: 0.043%. The temperature of the molten steel at the argon station is 1590℃.

[0036] After the ladle arrives at the station, the first batch consists of 1000 kg of fine-grained lime, followed by 600 kg of lean 80% vanadium ferrometallurgical slag within 60 seconds. Submerged arc heating is then initiated. After heating, the first slag adjustment is performed with the addition of 400 kg of fine-grained lime, followed by 200 kg of lean 80% vanadium ferrometallurgical slag within 60 seconds. Temperature measurement and sampling are then conducted, followed by a second submerged arc heating. After heating, a second slag adjustment is performed, but no further fine-grained lime is added. Subsequent alloying, calcium treatment, and weak argon blowing operations are then carried out.

[0037] The composition and mass content of the lean slag used in the 80 vanadium ferrometallurgical smelting are as follows: CaO: 5.8%, SiO2: 1.6%, MgO: 12.1%, P: 0.15%, S: 0.22%, Al2O3: 62.9%.

[0038] During the charging process, the bottom-blown argon flow rate was controlled at 1100 NL / min, and during the heating process, the bottom-blown argon flow rate was controlled at 300 NL / min, with a total heating time of 10 minutes. The first sample of molten steel showed a sulfur content of 0.011% and a desulfurization rate of 74.4%. After refining, the steel sample composition was: C: 0.045%, S: 0.008%, with a refining cycle of 32 minutes. Approximately 12 minutes into the refining process, the refining slag exhibited significant foaming, accompanied by slag overflow.

[0039] Comparative Example 2 (using only 80 smelting lean slag) A steel plant's 150t production line uses an LF refining furnace to produce DD11-MD steel. The molten steel charge is 164t, and the composition of the molten steel entering the station is: C: 0.040%, Si: 0.001%, Mn: 0.153%, P: 0.012%, S: 0.044%. The temperature of the molten steel at the argon station is 1595℃.

[0040] After the ladle enters the station, the first batch of 1100 kg of fine-grained lime is added, followed by 700 kg of lean 80 vanadium ferrometallurgical slag within 60 seconds. After the addition is complete, submerged arc heating is performed. After heating, the first slag adjustment is performed by adding 500 kg of fine-grained lime, followed by 300 kg of lean 80 vanadium ferrometallurgical slag within 60 seconds. After temperature measurement and sampling, a second submerged arc heating is performed. After heating, a second slag adjustment is performed by adding 100 kg of fine-grained lime, followed by subsequent alloying, calcium treatment, and weak argon blowing operations.

[0041] The composition and mass content of the lean slag used in the 80 vanadium ferrometallurgical smelting are as follows: CaO: 5.9%, SiO2: 1.42%, MgO: 11.93%, P: 0.24%, S: 0.17%, Al2O3: 58.9%.

[0042] During the charging period, the bottom-blown argon flow rate was controlled at 1100 NL / min, and during the heating period, the bottom-blown argon flow rate was controlled at 290 NL / min. The total heating time was 9 minutes. The first sample of molten steel had an S content of 0.010% and a desulfurization rate of 77.3%. After refining, the molten steel sample composition was: C: 0.045% and S: 0.006%. The refining cycle was 32 minutes. About 10 minutes into the refining process, the refining slag showed obvious foaming, accompanied by slag overflow.

[0043] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that various modifications and changes can be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined by the claims.

Claims

1. A safe and rapid LF refining slag-forming method, characterized in that, Fluorite, 80 vanadium ferrometallurgical lean slag, and refining slag are crushed, dried, and then mixed in proportion to form an auxiliary slag-forming agent. During the LF refining process, after the conventional slag-forming material is added, the auxiliary slag-forming agent is added from the high-level silo to form slag. Then, qualified molten steel can be obtained through subsequent LF refining operations.

2. The safe and rapid LF refining slag-forming method according to claim 1, characterized in that, The total amount of the auxiliary slag-forming agent added per furnace is 500-800 kg.

3. The safe and rapid LF refining slag-forming method according to claim 1, characterized in that, The mass percentages of fluorite, lean slag from 80 vanadium ferrometallurgy, and refining slag in the auxiliary slag-forming agent are 20%-25%, 20%-25%, and 50-60%, respectively.

4. The safe and rapid LF refining slag-forming method according to claim 1, characterized in that, The particle size requirement for the auxiliary slag-forming agent is 10-30mm.

5. The safe and rapid LF refining slag-forming method according to claim 1, characterized in that, The composition and mass content of the auxiliary slag-forming agent meet the following requirements: CaF2>10%, CaO>35%, SiO2<5%, MgO>8%, P<1%, S<1%, Al2O3>30%.

6. The safe and rapid LF refining slag-forming method according to claim 1, characterized in that, The auxiliary slag-forming agent is added within 30 seconds after the conventional slag-forming material is added.

7. The safe and rapid LF refining slag-forming method according to claim 1, characterized in that, The total amount of the auxiliary slagging agent added in a single furnace shall not exceed 50% of the total amount of conventional slagging material added in a single furnace.

8. A safe and rapid LF refining slag-forming method according to claim 1, characterized in that, The final composition and percentage content of the qualified molten steel are: C≤0.05%, S≤0.015%, with the balance being iron and other unavoidable elements.