LF (ladle furnace) refining method for non-hot-state casting residue recovery heat

Abstract

The LF refining method comprises the following steps that 80 ferrovanadium smelting lean slag is subjected to crushing and drying treatment, and then the 80 ferrovanadium smelting lean slag is conveyed to an LF refining overhead stock bin through a feeding belt for standby application; in the LF refining treatment process, after a conventional slagging material is added, a proper amount of 80 ferrovanadium smelting lean slag is added from an overhead bunker for auxiliary slagging, and qualified molten steel is obtained through subsequent LF refining desulfurization, temperature adjustment and component fine adjustment. The method effectively solves the problems of difficult slagging, high slagging cost and low desulfurization efficiency in the LF refining process of the heat without hot casting residue recovery, realizes recycling of the 80 ferrovanadium smelting lean slag, and reduces resource waste.

Description

Technical Field

[0001] This invention belongs to the field of LF refining steelmaking, specifically relating to an LF refining method for unheated casting residue recovery furnaces. Background Technology

[0002] Due to factors such as production rhythm, the matching degree between continuous casting speed and converter tapping time, and the efficiency of ladle hot repair, it is impossible to achieve 100% recovery of hot casting residue generated in continuous casting. For heats where hot casting residue recovery is not achieved, a series of problems often arise during LF refining, including high consumption of slag-forming materials, slow slag formation speed, and long refining cycles. Furthermore, expensive modifiers are required as auxiliary slag-forming raw materials, increasing slag-forming costs. Lean slag from 80 vanadium ferrovanadium smelting is a byproduct of vanadium plant production, mostly used for external sales or contract processing, resulting in resource waste and increased costs. Summary of the Invention

[0003] The purpose of this invention is to provide an LF refining method for unheated casting residue recovery furnaces, which utilizes 80 vanadium ferrometallurgical lean slag as an auxiliary raw material to improve LF refining slag formation efficiency, reduce slag material consumption, shorten the refining cycle, and save production costs.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An LF refining method for recovering unheated casting residue in furnaces includes the following steps: The 80 vanadium iron smelting lean slag is crushed and dried, and then transported to the LF refining high-level silo via a feeding belt for later use. During the LF refining process, after the addition of conventional slag-forming materials, an appropriate amount of 80 vanadium iron smelting lean slag is added from the high-level silo for auxiliary slag formation. Qualified molten steel is obtained through subsequent LF refining desulfurization, temperature adjustment, and fine-tuning of composition.

[0005] Furthermore, the total amount of lean slag added to a single furnace in the 80 vanadium ferrometallurgical process described in this invention is 800-1100 kg.

[0006] Furthermore, the maximum diameter of the crushed lean slag from the 80 vanadium ferrometallurgical smelting process described in this invention is <10 cm.

[0007] Furthermore, the composition and mass content of the 80 vanadium ferrometallurgical lean slag of the present invention meet the following requirements: CaO%>5%, SiO2%<3%, MgO%>10%, P%<1%, S%<1%, Al2O3>40%.

[0008] Furthermore, the 80 vanadium ferrometallurgical lean slag described in this invention is added within 60 seconds after the addition of conventional slag-forming materials.

[0009] Furthermore, the 80 vanadium ferrometallurgical lean slag described in this invention is added twice; the first addition accounts for 70%-80% of the total amount, and the second addition accounts for 20%-30% of the total amount.

[0010] Furthermore, the total amount of 80 vanadium ferrometallurgical lean slag added in a single batch according to the present invention shall not exceed 70% of the total amount of conventional slag-forming material added in a single batch.

[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:

[0013] The lean slag from 80% vanadium ferrometallurgical smelting can provide a large amount of Al2O3 to the slag. Al2O3 combines with CaO and SiO2 in the slag to form 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 also provides favorable kinetic conditions for desulfurization. Furthermore, the lean slag from 80% vanadium ferrometallurgical smelting achieves a superior modifier effect at a low price, thus reducing production costs.

[0014] The beneficial effects of adopting the above technical solution are as follows:

[0015] The method of this invention effectively solves the problems of difficult slag formation, high slag production cost, and low desulfurization efficiency in the LF refining process of furnaces that have not undergone hot casting residue recovery. At the same time, it realizes the recycling of lean slag from 80 vanadium ferrometallurgical smelting, reducing resource waste. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to the embodiments.

[0017] The method of this invention mainly focuses on optimizing and controlling two aspects: the proportion and timing of adding slag-forming materials for LF refining in furnaces that have not undergone hot casting residue recovery, and the LF refining process. The details are as follows: (1) LF refining slag-forming feed addition ratio and timing The crushed and dried 80% vanadium ferroalloy slag is transported via conveyor belt to the high-level silo for LF refining. During the LF refining process, the 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 80% vanadium ferroalloy slag is added for the first time within 60 seconds after the addition of the small-particle lime, at a rate of 70%-80% of the total amount added, and this amount must not exceed 70% of the first batch of small-particle lime added. After the first slag conditioning after heating, the 80% vanadium ferroalloy slag is added again within 60 seconds after the addition of the small-particle lime, at a rate of 20%-30% of the total amount added, and this amount must not exceed 70% of the second batch of small-particle lime added. No more 80% vanadium ferroalloy slag is added after the third batch of small-particle lime. The composition of the lean slag used in the 80 vanadium ferrometallurgical smelting process meets the following requirements: CaO%>5%, SiO2%<3%, MgO%>10%, P%<1%, S%<1%, Al2O3>40%.

[0018] (2) LF refining process The argon pre-blowing flow rate for the ladle is 800–1200 NL / min, operating under slight positive pressure. Based on the composition of the molten steel sample from the preceding argon blowing station, 400–1200 kg of fine-grained lime and an appropriate amount of lean 80% vanadium ferroalloy smelting slag are added. After addition, the argon flow rate is adjusted to 200–350 NL / min, and submerged arc heating is initiated, heating for 4–8 minutes depending on the argon blowing station temperature. After heating, the first slag adjustment is performed. Based on the slag appearance and color, 200–600 kg of fine-grained lime and an appropriate amount of lean 80% vanadium ferroalloy smelting slag are added, and the argon flow rate is adjusted to 600–1200 NL / min for desulfurization. After temperature measurement and sampling, a second heating operation is performed based on the molten steel temperature. After the second heating, based on the molten steel composition test results, a series of operations are performed, including a second slag adjustment, desulfurization, fine-tuning of alloy composition, calcium treatment, temperature measurement and sampling, and weak argon blowing, to obtain molten steel with qualified composition. The final composition and percentage content of qualified molten steel are: C≤0.05%, S≤0.015%, with the balance being iron and other unavoidable elements.

[0019] The following examples and comparative examples all involve LF refining in furnaces that did not undergo hot casting residue recovery.

[0020] All 80 vanadium iron smelting lean slag used in each embodiment were crushed and dried. The maximum diameter of the crushed 80 vanadium iron smelting lean slag was <10cm, and it was transported to the LF refining high-level silo for later use via a feeding belt. Example 1

[0021] 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: 0.032%, Si: 0.001%, Mn: 0.150%, P: 0.011%, S: 0.045%. The temperature of the molten steel at the argon station is 1592℃.

[0022] After the ladle arrives at the station, 1100 kg of fine-grained lime is added, followed by 700 kg of lean 80% vanadium smelting slag within 60 seconds. Submerged arc heating is then initiated after the addition is complete. Following heating, the first slag adjustment is performed with 400 kg of fine-grained lime added, followed by 200 kg of lean 80% vanadium smelting slag within 60 seconds. Refining takes approximately 15 minutes, resulting in good slag condition and acceptable color, indicating slag formation is complete. Temperature measurement and sampling are then performed, followed by a second submerged arc heating. A second slag adjustment is then conducted, but no further addition of fine-grained lime is made. Subsequent alloying, calcium treatment, and weak argon blowing operations are then carried out.

[0023] The composition and mass content of the lean slag used in the 80 vanadium ferrometallurgical smelting of this embodiment are as follows: CaO%: 6.5%, SiO2%: 1.2%, MgO%: 13.2%, P%: 0.25%, S%: 0.10%, Al2O3: 55.3%.

[0024] During the charging period, the bottom-blown argon flow rate was controlled at 1000 NL / min, and during the heating period, 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 had an S content of 0.012% and a desulfurization rate of 73.3%. After refining, the molten steel sample composition was: C: 0.037%, S: 0.010%, and the refining cycle was 31 minutes. The consumption of small-particle lime and 80 vanadium ferroalloy smelting lean slag resulted in a total slag-making cost of 960 yuan. (The unit price of small-particle lime was 735 yuan / ton, and the unit price of 80 vanadium ferroalloy smelting lean slag was 250 yuan / ton. The subsequent examples and comparative examples will use this unit price to calculate the cost.) Example 2

[0025] 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: 0.149%, P: 0.012%, S: 0.040%. The temperature of the molten steel at the argon station is 1590℃.

[0026] After the ladle arrives at the station, 1000 kg of fine-grained lime is added, followed by 650 kg of lean 80 vanadium ferrometallurgical slag within 60 seconds. Submerged arc heating is then initiated after the addition is complete. Following heating, the first slag adjustment is performed with 400 kg of fine-grained lime added, followed by 200 kg of lean 80 vanadium ferrometallurgical slag within 60 seconds. Refining takes approximately 18 minutes, resulting in good slag condition and acceptable color, indicating slag formation is complete. Temperature measurement and sampling are then performed, followed by a second submerged arc heating. A second slag adjustment is then conducted, but no further addition of fine-grained lime is made. Subsequent alloying, calcium treatment, and weak argon blowing operations are then carried out.

[0027] The composition and mass content of the lean slag used in the 80 vanadium ferrometallurgical smelting in this embodiment are as follows: CaO%: 5.9%, SiO2%: 1.7%, MgO%: 12.8%, P%: 0.17%, S%: 0.23%, Al2O3: 62.1%.

[0028] 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 72.5%. After refining, the steel sample composition was: C: 0.045%, S: 0.008%, with a refining cycle of 32 minutes. The consumption of small-particle lime and lean slag from 80 vanadium ferrometallurgy resulted in a slag-making cost of 899 yuan. Example 3

[0029] 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: 0.039%, Si: 0.001%, Mn: 0.151%, P: 0.013%, S: 0.045%. The temperature of the molten steel at the argon station is 1595℃.

[0030] After the ladle arrives at the station, 1100 kg of fine-grained lime is added, followed by 700 kg of lean 80% vanadium ferrometallurgical slag within 60 seconds. Submerged arc heating is then initiated after the addition is complete. Following heating, the first slag conditioning is performed with 500 kg of fine-grained lime added, followed by 300 kg of lean 80% vanadium ferrometallurgical slag within 60 seconds. Refining takes approximately 16 minutes, resulting in good slag condition and acceptable color, indicating slag formation is complete. Temperature measurement and sampling are then performed, followed by a second submerged arc heating. After heating, a second slag conditioning is performed with 100 kg of fine-grained lime added, and subsequent alloying, calcium treatment, and weak argon blowing operations are carried out.

[0031] The composition and mass content of the 80 vanadium ferrometallurgical lean slag used in this embodiment are as follows: CaO%: 5.9%, SiO2%: 1.4%, MgO%: 11.9%, P%: 0.21%, S%: 0.20%, Al2O3: 55.9%.

[0032] 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, with a total heating time of 9 minutes. The first sample of molten steel had a sulfur content of 0.009% and a desulfurization rate of 80.0%. After refining, the molten steel sample composition was: C: 0.042%, S: 0.007%, and the refining cycle was 32 minutes. The consumption of small-particle lime and lean slag from 80 vanadium ferrometallurgy resulted in a total slag-making cost of 1083 yuan. Example 4

[0033] A steel plant's 150t production line uses an LF refining furnace to produce DD11-MD steel. The molten steel charge is 166t, and the composition of the molten steel entering the station is: C: 0.045%, Si: 0.001%, Mn: 0.152%, P: 0.014%, S: 0.053%. The temperature of the molten steel at the argon station is 1589℃.

[0034] After the ladle arrives at the station, 1200 kg of fine-grained lime is added, followed by 750 kg of lean 80 vanadium ferrometallurgical slag within 60 seconds. Submerged arc heating is then initiated after the addition is complete. Following heating, the first slag conditioning is performed with 400 kg of fine-grained lime added, followed by 250 kg of lean 80 vanadium ferrometallurgical slag within 60 seconds. Refining takes approximately 17 minutes, resulting in good slag condition and acceptable color, indicating slag formation is complete. Temperature measurement and sampling are then performed, followed by a second submerged arc heating. After this second heating, a second slag conditioning is performed with 200 kg of fine-grained lime added, and subsequent alloying, calcium treatment, and weak argon blowing operations are carried out.

[0035] The composition and mass content of the 80 vanadium ferrometallurgical lean slag used in this embodiment are as follows: CaO%: 6.1%, SiO2%: 1.2%, MgO%: 13.2%, P%: 0.19%, S%: 0.18%, Al2O3: 60.2%.

[0036] During the charging period, the bottom-blown argon flow rate was controlled at 1200 NL / min, and during the heating period, the bottom-blown argon flow rate was controlled at 300 NL / min, with a total heating time of 11 minutes. The first sample of molten steel had a sulfur content of 0.013% and a desulfurization rate of 75.5%. After refining, the molten steel sample composition was: C: 0.049%, S: 0.011%, and the refining cycle was 32 minutes. The consumption of small-particle lime and lean slag from 80 vanadium ferrometallurgy resulted in a total slag-making cost of 1132 yuan. Example 5

[0037] 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: 0.040%, Si: 0.001%, Mn: 0.150%, P: 0.011%, S: 0.042%. The temperature of the molten steel at the argon station is 1591℃.

[0038] After the ladle arrives at the station, 1000 kg of fine-grained lime is added, followed by 600 kg of lean 80% vanadium smelting slag within 60 seconds. Submerged arc heating is then initiated after the addition is complete. Following heating, the first slag adjustment is performed by adding 300 kg of fine-grained lime, followed by 200 kg of lean 80% vanadium smelting slag within 60 seconds. Refining takes approximately 15 minutes, resulting in good slag condition and acceptable color, indicating slag formation is complete. Temperature measurement and sampling are then performed, followed by a second submerged arc heating. A second slag adjustment is then conducted, but no further addition of fine-grained lime is made. Subsequent alloying, calcium treatment, and weak argon blowing operations are then carried out.

[0039] The composition and mass content of the lean slag used in the 80 vanadium ferrometallurgical process in this embodiment are as follows: CaO%: 5.8%, SiO2%: 1.7%, MgO%: 12.1%, P%: 0.23%, S%: 0.25%, Al2O3: 57.6%.

[0040] 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 300 NL / min, with a total heating time of 9 minutes. The first sample of molten steel had a sulfur content of 0.011% and a desulfurization rate of 73.8%. After refining, the molten steel sample composition was: C: 0.045%, S: 0.010%, and the refining cycle was 32 minutes. The consumption of small-particle lime and lean slag from 80 vanadium ferrometallurgy resulted in a total slag-making cost of 837 yuan.

[0041] Comparative Example 1 (Standard Operation) 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: 0.038%, Si: 0.001%, Mn: 0.152%, P: 0.013%, S: 0.040%. The temperature of the molten steel at the argon station is 1590℃.

[0042] After the ladle arrives at the station, 1100 kg of fine-grained lime and 200 kg of modifier are added. Submerged arc heating is then initiated. After heating, the first slag conditioning is performed, with the addition of 500 kg of fine-grained lime and 100 kg of modifier. Refining takes approximately 20 minutes, resulting in good slag condition and acceptable color, indicating slag formation is complete. Temperature measurement and sampling are then conducted, followed by a second submerged arc heating. After heating, a second slag conditioning is performed, with the addition of 300 kg of fine-grained lime. Subsequent alloying, calcium treatment, and weak argon blowing are then carried out.

[0043] During the charging period, the bottom-blown argon flow rate was controlled at 1200 NL / min, and during the heating period, the bottom-blown argon flow rate was controlled at 350 NL / min, with a total heating time of 11 minutes. The first sample of molten steel had a sulfur content of 0.015% and a desulfurization rate of 62.5%. After refining, the molten steel sample composition was: C: 0.048%, S: 0.012%, and the refining cycle was 34 minutes. The consumption of small-particle lime and modifier resulted in a total slag-making cost of 1771 yuan. (The modifier's unit price was 2800 yuan / ton, and this unit price will be used for subsequent comparative cost calculations.) Comparative Example 2 (Standard Operation) 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: 0.149%, P: 0.010%, S: 0.039%. The temperature of the molten steel at the argon station is 1592℃.

[0044] After the ladle arrives at the station, 1200 kg of fine-grained lime and 200 kg of modifier are added. Submerged arc heating is then initiated. After heating, the first slag conditioning is performed, with 400 kg of fine-grained lime and 100 kg of modifier added. Refining takes approximately 19 minutes, resulting in good slag condition and acceptable color, indicating slag formation is complete. Temperature measurement and sampling are then conducted, followed by a second submerged arc heating. After heating, a second slag conditioning is performed, with 200 kg of fine-grained lime added, before subsequent alloying, calcium treatment, and weak argon blowing operations.

[0045] During the charging period, the bottom-blown argon flow rate was controlled at 1200 NL / min, and during the heating period, the bottom-blown argon flow rate was controlled at 00 NL / min, with a total heating time of 11 minutes. The first sample of molten steel had an S content of 0.016% and a desulfurization rate of 59.0%. After refining, the molten steel sample composition was: C: 0.048%, S: 0.014%, and the refining cycle was 35 minutes. The consumption of small-particle lime and modifiers resulted in a total slag-making cost of 1722 yuan.

[0046] 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 method for LF refining in unheated casting residue recovery furnaces, characterized in that, Includes the following steps: The 80 vanadium iron smelting lean slag is crushed and dried, and then transported to the LF refining high-level silo via a feeding belt for later use. During the LF refining process, after the addition of conventional slag-forming materials, an appropriate amount of 80 vanadium iron smelting lean slag is added from the high-level silo for auxiliary slag formation. Qualified molten steel is obtained through subsequent LF refining desulfurization, temperature adjustment, and fine-tuning of composition.

2. The LF refining method for recovering unheated casting residue in furnaces according to claim 1, characterized in that, The total amount of lean slag added to a single furnace for the 80 vanadium ferrometallurgical smelting process is 800-1100 kg.

3. The LF refining method for recovering unheated casting residue in furnaces according to claim 1, characterized in that, The maximum diameter of the crushed lean slag from the 80 vanadium ferrometallurgical smelting process is <10 cm.

4. The LF refining method for recovering unheated casting residue in furnaces according to claim 1, characterized in that, The composition and mass content of the 80 vanadium ferrometallurgical lean slag meet the following requirements: CaO%>5%, SiO2%<3%, MgO%>10%, P%<1%, S%<1%, Al2O3>40%.

5. The LF refining method for recovering unheated casting residue in a furnace according to claim 1, characterized in that, The 80 vanadium ferrometallurgical lean slag is added within 60 seconds after the conventional slag-forming material is added.

6. The LF refining method for recovering unheated casting residue in furnaces according to claim 1, characterized in that, The 80 vanadium ferrometallurgical lean slag is added in two batches: the first batch contains 70%-80% of the total amount, and the second batch contains 20%-30% of the total amount.

7. The LF refining method for recovering unheated casting residue in furnaces according to claim 1, characterized in that, The total amount of the 80 vanadium ferrometallurgical lean slag added in a single batch shall not exceed 70% of the total amount of conventional slag-forming material added in a single batch.

8. The LF refining method for recovering unheated casting residue in furnaces 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.