A method for returning molten steel residue to the hot metal ladle

Abstract

The present invention discloses a method for returning molten steel residue to hot metal ladle tilting, mainly solving the technical problems of slag overflow or even splashing during the process of returning molten steel residue to hot metal ladle tilting in the prior art. The technical solution is as follows: A method for returning molten steel residue to hot metal ladle tilting includes: 1) Turning over the bottom hot metal; 2) Transporting the hot metal ladle containing the bottom hot metal to the ladle slag turning area under the ladle turntable of the continuous casting machine; 3) Pouring out the molten steel residue in the ladle; 4) Deoxidizing the slag in the hot metal ladle; 5) Tilting the hot metal ladle; 6) Desulfurizing the hot metal; 7) Adding metal materials to the converter; 8) Blowing the converter; 9) Tapping the converter. The method of the present invention is simple to operate, safe and reliable, realizes the safe recycling of molten steel residue, and reduces the consumption of steel and iron materials by more than 52 kg / t on average.

Description

Technical Field

[0001] The present invention relates to a technology for recycling and utilization of molten steel remaining after casting, and particularly to a method for returning molten steel remaining after casting to a hot metal ladle, belonging to the technical field of iron and steel metallurgy. Background Art

[0002] During continuous casting, when the sub-ladle slag detector detects a large amount of slag flowing from the tundish, the slide gate is closed and the casting of the ladle of molten steel is completed. At this time, there is still 3 - 7t of molten steel in the remaining molten steel in the ladle. To utilize this part of molten steel, the original process was to pour the remaining molten steel into a slag pot with a grid. After cooling, the remaining slag was crushed and subjected to magnetic separation to screen out the steel slag with a high metal content, and then it was added to the converter in the form of scrap steel for recycling. This process completely loses the heat of the remaining molten steel, increases the cost of steel slag treatment, reduces the metal recovery rate in the remaining molten steel, and is not conducive to smelting with a high scrap ratio in the converter and cost reduction. Therefore, a process for directly returning the remaining molten steel after continuous casting to the ladle for hot recycling was developed. However, due to the strong oxidation of the steel slag in some heats, a relatively strong carbon-oxygen reaction occurs during the process of turning over the hot metal, resulting in a large amount of steel slag overflowing from the hot metal ladle, which easily causes the cable of the hot metal car to burn out and production interruption.

[0003] The Chinese patent application document with the application publication number CN103320576A discloses a "method for recycling and utilization of refining slag poured into a hot metal ladle". The remaining molten steel slag after continuous casting that has been refined by the LF furnace and has a ladle slag basicity > 6 is poured into the hot metal ladle and then the ladle is turned over to turn over the hot metal, thereby realizing 100% recovery of the molten steel remaining after casting and slag washing and desulfurization during the process of turning over the hot metal. The refining slag of this technology only circulates 2 times, and after the circulation ends, it still can only be poured into the slag pot for treatment; in response to slag overflow, the method of reducing the tapping speed or stopping tapping is used to prevent and control slag overflow. However, this technology does not fundamentally prevent or solve the problem of slag overflow, resulting in a long ladle turnover cycle and a slow production rhythm.

[0004] The Chinese patent application document with the application publication number CN110273047A discloses a "method for recovering molten steel by returning hot remaining molten steel slag to a hot metal ladle". A tilting reheating and heat preservation furnace is set up in the slag pot area of the steelmaking receiving bay, and a slag skimmer is configured. After continuous casting ends, the remaining molten steel slag in the ladle is poured into the reheating and heat preservation furnace for heating. The slag skimmer is used to skim the slag from the reheating and heat preservation furnace in a timely manner, and then the remaining molten steel is poured into a preheated hot metal ladle, and then hot metal is received and desulfurized. This method can effectively avoid splashing and slag overflow during the process of receiving hot metal in the hot metal ladle. However, it is necessary to be equipped with a reheating and heat preservation furnace and a slag skimmer. On the one hand, there is no space in the slag turning area under the continuous casting turntable to newly build a heat preservation furnace and a slag skimmer. On the other hand, in order to remove the steel slag, it has a relatively high requirement for fluidity, and it needs to be heated to a relatively high temperature and kept warm for a long time, resulting in a significant increase in energy consumption, greatly offsetting the value of recovering molten steel in the remaining molten steel. Summary of the Invention

[0005] The object of the present invention is to provide a method for returning molten steel residue to the hot metal ladle, mainly solving the technical problem of slag overflow or even splashing during the process of returning molten steel residue to the hot metal ladle in the prior art; the method of the present invention realizes the safe recycling of molten steel residue and reduces the production cost of returning molten steel residue.

[0006] The technical solution adopted by the present invention is a method for returning molten steel residue to the hot metal ladle, including the following steps:

[0007] 1) Pour the bottom hot metal. When the steel grade in the steel ladle for steel casting is non-extra-low-carbon steel, non-copper-containing steel, non-nickel-containing steel or non-molybdenum-containing steel, pour the bottom hot metal into the hot metal ladle at the hot metal pouring station. The mass of the bottom hot metal is m 1 , with the unit of t. The minimum value of m 1 is calculated according to formulas (1) to (7),

[0008] T 0 = 1536 - (w[C] * 100 + w[Si] * 8.5 + w[Mn] * 5 + w[P] * 30) - 7 (1)

[0009]

[0010] T ≥ T 0 + ΔT 1 (3)

[0011]

[0012]

[0013]

[0014]

[0015] In formulas (1) to (7), T is the temperature of the hot metal in the hot metal ladle after pouring the molten steel residue, with the unit of °C. T 0 is the melting point of the hot metal in the hot metal ladle after pouring the molten steel residue, with the unit of °C. T 1 is the temperature of the hot metal in the hot metal ladle before pouring the molten steel residue, with the unit of °C. T 2 is the temperature of the molten steel residue, with the unit of °C. ΔT 1 is the superheat of the hot metal, with the unit of °C. k is the number of furnaces for recycling the molten steel residue in one hot metal ladle, 2 ≤ k ≤ 6. ΔT 2 is the temperature drop of the hot metal in the hot metal ladle during the period from the end of pouring the molten steel residue in the (k - 1)th furnace to the start of pouring the molten steel residue in the kth furnace, with the unit of °C. m 2The mass of the remaining molten steel poured into the ladle for each heat, in t. w[C], w[Si], w[Mn], and w[P] are the mass percentages of carbon, silicon, manganese, and phosphorus in the hot metal in the ladle after pouring the remaining molten steel, in %, and w[C] 铁 , w[Si] 铁 , w[Mn] 铁 , w[P] 铁 are the mass percentages of carbon, silicon, manganese, and phosphorus in the bottom hot metal in the ladle, in %, and w[C] 钢 , w[Si] 钢 , w[Mn] 钢 , w[P] 钢 are the mass percentages of carbon, silicon, manganese, and phosphorus in the remaining molten steel in the steel ladle, in %;

[0016] 2) Transport the ladle containing the bottom hot metal to the slag - turning area of the steel ladle under the ladle turret of the continuous caster;

[0017] 3) Pour out the remaining molten steel in the steel ladle. After the steel ladle finishes pouring, lift the steel ladle to directly above the ladle containing the bottom hot metal in the slag - turning area of the steel ladle, change the steel ladle from the vertical state to the horizontal state, and pour the remaining molten steel in the steel ladle into the ladle containing the bottom hot metal. The mass of the poured remaining molten steel is 40% - 60% of the total mass of the remaining molten steel and hot slag in the steel ladle after pouring; One ladle receives the remaining molten steel from k heats;

[0018] 4) Deoxidize the slag in the ladle. According to the LF refining furnace treatment ratio of the remaining molten steel recovered by a single ladle, add high - alumina slag deoxidizer to the ladle for deoxidation treatment. When the LF refining furnace treatment ratio is 60% - 100%, no high - alumina slag deoxidizer is added; When the LF refining furnace treatment ratio is 30% - 60%, the added mass of the high - alumina slag deoxidizer is 0.04 - 0.12 kg / t; When the LF refining furnace treatment ratio is 0% - 30%, the added mass of the high - alumina slag deoxidizer is 0.12 - 0.20 kg / t;

[0019] 5) Pour the hot metal from the ladle. Transport the ladle containing the remaining molten steel to the pouring station for receiving hot metal. The received mass is m 3 , in t, m 3 = m 4 - m 1 - k×m 2 ×a. In the formula, m 1 is the mass of the bottom hot metal in the ladle, in t, m 2 is the mass of the remaining molten steel poured into the ladle for each heat, in t, m 4The mass of the bottom layer of hot metal in the ladle for the current heat standard, with the unit of t, a is a constant, and its value ranges from 60% to 90%;

[0020] 6) Desulfurize the hot metal. Lift the ladle filled with hot metal from the hot metal tipping station to the desulfurization station for hot metal desulfurization and slag skimming;

[0021] 7) Add metallic materials to the converter. Add scrap steel to the converter in sequence and pour in the hot metal after desulfurization and slag skimming;

[0022] 8) Blow the converter;

[0023] 9) Tap the converter.

[0024] In step 1) of the present invention, when pouring the bottom layer of hot metal into the ladle at the hot metal tipping station, the starting time of the ladle receiving hot metal should be controlled within s to (s + 10) min before the end of steel casting of the molten steel to be recycled, where s = s 0 + m 1 / v, in the formula, s 0 is the time for the ladle to transport from the hot metal tipping station to the ladle slag turning area, with the unit of min; m 1 is the mass of the bottom layer of hot metal in the ladle, with the unit of t; v is the hot metal receiving speed of the ladle at the tipping station, with the unit of t / min.

[0025] In step 1) of the present invention, the mass m of the bottom layer of hot metal 1 is 12% - 16% of the nominal capacity of the ladle, and the effect is good.

[0026] In step 4) of the present invention, the mass percentage content of the chemical composition of the high-aluminum slag deoxidizer is: CaO 20% - 30%, Al 2 O 3 5% - 10%, SiO 2 0% - 5%, Al ≥ 41%, CaF 2 2% - 6%.

[0027] Basis for the selection of the process parameters of the method of the present invention:

[0028] 1. In step 1), on the one hand, increasing the mass of the bottom layer of hot metal in the ladle can reduce the melting point of the liquid metal after the hot metal is mixed with the molten steel of the casting residue, so as to ensure that the temperature of the liquid metal after the hot metal is mixed with the molten steel of the casting residue is higher than its melting point and has a certain degree of superheat, prevent solidification, and increase the number of recycling furnaces of the molten steel of the casting residue; but on the other hand, the mass of the bottom layer of hot metal cannot be too much, which is not conducive to increasing the number of recycling furnaces of the molten steel of the casting residue in a single ladle, increasing the heat loss of the hot metal during the waiting process, and is not conducive to increasing the scrap ratio of the converter; the number of recycling furnaces of the molten steel of the casting residue in a single ladle cannot be too many, otherwise it will greatly reduce the heat of the converter, increase the consumption of steel materials and heating agents, and is not conducive to reducing the cost of the converter; the number of recycling furnaces of the molten steel of the casting residue in a single ladle cannot be too few, otherwise it will affect the production efficiency and cannot increase the casting residue recovery ratio.

[0029] 2. In step 3), according to the characteristics that the density of molten steel is significantly greater than that of ladle slag and the viscosity of molten steel is significantly less than that of ladle slag, the molten steel is always located below the ladle slag. After the ladle changes from the vertical state to the horizontal state, the molten steel flows out before the ladle slag and enters the torpedo ladle, realizing the separation of steel and slag, thus greatly reducing the amount of ladle slag entering the torpedo ladle and avoiding the slag overflow and splashing problems caused by the relatively intense carbon-oxygen reaction during the process of pouring the remaining molten steel and the process of receiving molten iron again. By using the change in the mass of the ladle during the process of pouring the remaining molten steel, the amount of slag poured out is judged. Through a large number of studies, it is found that when the reduction in the mass of the ladle is controlled within 40% - 60% of the total mass of the remaining molten steel and hot ladle slag in the ladle after the steel pouring is completed, the amount of molten steel poured out can be maximized while the amount of ladle slag poured out is reduced. When it is greater than 60%, the amount of ladle slag poured out increases significantly.

[0030] 3. In step 4), selecting to add a high-alumina slag deoxidizer can achieve a good deoxidation effect on the slag in the torpedo ladle. Since the ladle slag brought into the torpedo ladle has a certain oxidizing property, if it is not deoxidized, splashing or a large amount of slag overflow will occur during the process of adding molten iron, which will affect safety. However, too much deoxidizer cannot be added, otherwise the cost will increase significantly. The oxidizing property of the ladle slag treated by the LF refining furnace is weak, and the oxidizing property of the ladle slag not treated by the LF refining furnace is strong. Through a large number of studies, according to the refining path composition of the remaining molten steel recovered from a single torpedo ladle, taking the proportions of passing through the LF refining furnace of 30% and 60% as the boundaries, different masses of high-alumina slag deoxidizer are added to deoxidize the slag in the torpedo ladle to avoid splashing or slag overflow during the process of adding molten iron and reduce the production cost.

[0031] The present invention has the following positive effects compared with the prior art: 1. The method of the present invention is simple to operate, safe and reliable. According to the cycle of the torpedo ladle receiving molten iron from the ladle turntable station to the ladle slag turning area and the continuous casting pouring cycle, the starting time of turning the bottom molten iron in the torpedo ladle is reasonably controlled, thereby reducing the waiting time of the torpedo ladle in the ladle slag turning area, reducing the temperature drop of the molten iron, solving the problems of solidification and splashing of the molten iron during the process of returning the remaining molten steel to the ladle turntable station, and realizing that one torpedo ladle can recycle the remaining molten steel of multiple furnaces, with high production efficiency. 2. The method of the present invention reduces the steel slag treatment cost, the consumption of iron and steel materials and the heat loss, and on average reduces the consumption of iron and steel materials by 52 kg / t. Detailed Embodiments

[0032] The present invention will be further described below in conjunction with specific Examples 1 - 5, as shown in Tables 1 - 2.

[0033] In Examples 1 - 5, the molten iron receiving speed of the torpedo ladle is 6 t / min, the time for the torpedo ladle to be transported from the ladle turntable station to the slag turning area is 16 min, the converter with a nominal capacity of 250 t, and the continuous casting pouring cycle is 40 min.

[0034] A method for returning molten steel in the casting residue to molten iron and pouring it into a ladle, comprising the following steps:

[0035] 1) Pour the bottom molten iron. When the steel grade in the steel ladle for steel casting is non-extra-low-carbon steel, non-copper-containing steel, non-nickel-containing steel or non-molybdenum-containing steel, pour the bottom molten iron into the molten iron ladle at the molten iron pouring station 21 - 32.7 minutes before the end of steel casting. The mass of the bottom molten iron is 12% - 16% of the nominal capacity of the molten iron ladle;

[0036] 2) Transport the molten iron ladle containing the bottom molten iron to the slag turning area of the ladle turntable under the continuous caster;

[0037] 3) Pour out the molten steel in the casting residue in the ladle. After the steel ladle finishes casting, hoist the steel ladle to directly above the molten iron ladle containing the bottom molten iron in the slag turning area of the ladle, change the steel ladle from the vertical state to the horizontal state, and pour the molten steel in the casting residue in the steel ladle into the molten iron ladle containing the bottom molten iron. The pouring mass of the molten steel in the casting residue is 40% - 60% of the total mass of the molten steel in the casting residue and the hot slag in the ladle after the end of casting; One molten iron ladle can receive the molten steel in the casting residue of 2 - 6 furnaces;

[0038] 4) Deoxidize the slag in the molten iron ladle. According to the LF refining furnace treatment ratio of the molten steel in the casting residue recovered by a single molten iron ladle, add a high-alumina slag deoxidizer to the molten iron ladle for deoxidation treatment. When the LF refining furnace treatment ratio is 60% - 100%, no high-alumina slag deoxidizer is added. When the LF refining furnace treatment ratio is 30% - 60%, the added mass of the high-alumina slag deoxidizer is 0.04 - 0.12 kg / t. When the LF refining furnace treatment ratio is 0% - 30%, the added mass of the high-alumina slag deoxidizer is 0.12 - 0.20 kg / t;

[0039] 5) Pour the molten iron into the ladle. Transport the molten iron ladle containing the molten steel in the casting residue to the pouring station for iron supplementation. The iron supplementation mass m 3 =m 4 -m 1 -k*m 2 *0.9, where m 1 is the mass of the bottom molten iron in the molten iron ladle, with the unit of t, m 2 is the mass of the molten steel in the casting residue poured into the molten iron ladle per furnace, with the unit of t, m 4 is the mass of the poured molten iron for the current furnace standard, with the unit of t;

[0040] 6) Desulfurize the molten iron. Hoist the molten iron ladle filled with molten iron from the pouring station to the desulfurization station for molten iron desulfurization and slag skimming

[0041] 7) Add metal materials to the converter. Add scrap steel to the converter in sequence and pour in the molten iron after desulfurization and slag skimming;

[0042] 8) Blow the converter;

[0043] 9) Tap the converter.

[0044] Table 1 Control parameters of the embodiments of the present invention

[0045]

[0046] Table 2 Steel material consumption parameters of the embodiments of the present invention

[0047]

[0048] Table 1 shows the control parameters of Embodiments 1-5 of the present invention, and Table 2 shows the implementation effects after the casting residue is returned to the ladle in Embodiments 1-5 of the present invention, which are reflected in the change of steel material consumption. The calculation formula is The average steel material consumption of Embodiments 1-5 is 1032.49 kg / t, which is 52 kg / t lower than the average steel material consumption of 1085 kg / t in the conventional process, thus greatly reducing the production cost of steelmaking and having a wide application prospect.

[0049] In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A method for returning molten steel from continuous casting residue to a hot metal ladle for tilting, characterized in that, it includes the following steps: 1) Pour the bottom-lining hot metal. When the steel grade in the ladle for steel pouring is non-extra-low-carbon steel, non-copper-containing steel, non-nickel-containing steel or non-molybdenum-containing steel, pour the bottom-lining hot metal into the hot metal ladle at the hot metal transfer station. The mass of the bottom-lining hot metal is m 1 , with the unit of t. The minimum value of m 1 is calculated according to formulas (1) to (7). T 0 = 1536 - (w[C] * 100 + w[Si] * 8.5 + w[Mn] * 5 + w[P] * 30) - 7 (1) T≥T 0 +ΔT 1 (3) In Formulas (1) to (7), T is the temperature of the molten iron in the ladle after pouring the remaining molten steel, in °C, T 0 is the melting point of the molten iron in the ladle after pouring the remaining molten steel, in °C, T 1 is the temperature of the molten iron in the ladle before pouring the remaining molten steel, in °C, T 2 is the temperature of the remaining molten steel, in °C, ΔT 1 is the superheat of the molten iron, in °C, k is the number of furnaces in which the remaining molten steel in a ladle is recycled, 2 ≤ k ≤ 6, ΔT 2 is the temperature drop of the molten iron in the ladle during the period from the end of pouring the remaining molten steel in the (k - 1)-th furnace to the start of pouring the remaining molten steel in the k-th furnace, in °C, m 2 is the mass of the remaining molten steel poured into the ladle per furnace, in t, w[C], w[Si], w[Mn], and w[P] are the mass percentages of carbon, silicon, manganese, and phosphorus in the molten iron in the ladle after pouring the remaining molten steel, in %, w[C] 铁 , w[Si] 铁 , w[Mn] 铁 , w[P] 铁 are the mass percentages of carbon, silicon, manganese, and phosphorus in the bottom molten iron in the ladle, in %, w[C] 钢 , w[Si] 钢 , w[Mn] 钢 , w[P] 钢 are the mass percentages of carbon, silicon, manganese, and phosphorus in the remaining molten steel in the steel ladle, in %; 2) Transport the hot metal ladle containing the bottom hot metal to the ladle slag-turning area under the ladle turret of the continuous caster; 3) Pour out the molten steel residue in the ladle. After the ladle casting is completed, hoist the ladle to directly above the hot metal ladle containing the bottom hot metal in the ladle slag-turning area, change the ladle from a vertical state to a horizontal state, and pour the molten steel residue in the ladle into the hot metal ladle containing the bottom hot metal. The pouring mass of the molten steel residue is 40% - 60% of the total mass of the molten steel residue and hot slag in the ladle after casting; One hot metal ladle receives the molten steel residue from k furnaces; 4) Deoxidize the slag in the hot metal ladle. According to the LF refining furnace treatment ratio of the molten steel residue recovered in a single hot metal ladle, add high-alumina slag deoxidizer to the hot metal ladle for deoxidation treatment. When the LF refining furnace treatment ratio is 60% - 100%, no high-alumina slag deoxidizer is added; When the LF refining furnace treatment ratio is 30% - 60%, the added mass of the high-alumina slag deoxidizer is 0.04 - 0.12 kg / t; When the LF refining furnace treatment ratio is 0% - 30%, the added mass of the high-alumina slag deoxidizer is 0.12 - 0.20 kg / t; 5) Pour the molten iron. Transport the ladle containing the remaining molten steel after casting to the ladle turntable station for receiving molten iron. The received molten iron mass is m 3 , with the unit of t, m 3 = m 4 - m 1 - k × m 2 × a. In the formula, m 1 is the mass of the bottom molten iron in the ladle, with the unit of t, m 2 is the mass of the remaining molten steel poured into the ladle per heat, with the unit of t, m 4 is the standard ladle turntable molten iron mass for the current heat, with the unit of t, and a is a constant, with a value ranging from 60% to 90%; 6) Desulfurize the hot metal. Hoist the hot metal ladle filled with hot metal from the tilting station to the desulfurization station for hot metal desulfurization and slag skimming; 7) Add metal materials to the converter. Add scrap steel to the converter in sequence and then charge the hot metal after desulfurization and slag skimming; 8) Blow the converter; 9) Tap the converter.

2. The method for returning molten steel from continuous casting residue to a hot metal ladle for tilting according to claim 1, characterized in that, In step 1), when pouring the bottom molten iron into the ladle at the hot metal tapping station, the starting time for the ladle to receive hot metal should be controlled within s to (s + 10) minutes before the end of steel casting of the molten steel to be recycled, where s = s 0 + m 1 / v, where s 0 is the time for the ladle to be transported from the hot metal tapping station to the slag turning area of the ladle, in minutes; m 1 is the mass of the bottom molten iron in the ladle, in tons; and v is the hot metal receiving speed of the ladle at the tapping station, in tons per minute.

3. The method for returning molten steel from continuous casting residue to a hot metal ladle for tilting according to claim 1, characterized in that, In step 1), the mass m of the bottom padding molten iron 1 is 12% to 16% of the nominal capacity of the ladle.

4. The method for returning molten steel from continuous casting residue to a hot metal ladle for tilting according to claim 1, characterized in that, In step 4), the mass percentage of the chemical components of the high-alumina slag deoxidizer is as follows: CaO 20% - 30%, Al 2 O 3 5% - 10%, SiO 2 0% - 5%, Al ≥ 41%, CaF 2 2% - 6%.

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