A method for accurately controlling the aluminum content at the end point of LF furnace for medium and high carbon aluminum killed steel

Abstract

The present invention discloses a method for accurately controlling the aluminum content of the LF furnace end point of medium and high carbon aluminum killed steel, and belongs to the technical field of steelmaking and refining. The method of the present invention comprises the following operations: adding aluminum-iron alloy to perform deoxidation alloying treatment during the steel tapping process of a converter or an electric furnace; when the LF furnace enters the station, a certain amount of aluminum particles are sprinkled on the slag surface to deoxidize the slag according to the slag discharge situation during the steel tapping process; lime and pre-melted refined slag are used for slag making operation, SiC is used for diffusion deoxidation operation of the slag, and the temperature and composition are adjusted; after the formation of white slag and the adjustment of the composition other than aluminum element, the time from the molten steel to the station is estimated, and a certain amount of aluminum wire is fed into the molten steel according to the molten steel [Als] content and the station time. The present invention realizes that the number of aluminum adjustment times in the LF furnace refining process is ≤2 times, and the amount of aluminum adjustment in the middle and late stages of LF furnace refining is the least, under the premise of stable control of the aluminum content at the LF furnace station, thereby maximizing the cleanliness of the molten steel.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking and refining, and in particular relates to a method for accurately controlling the aluminum content at the end point of a medium- and high-carbon aluminum killed steel LF furnace. Background Art

[0002] Aluminum is a strong deoxidizer that can effectively reduce the oxygen content in steel, thereby improving the cleanliness of molten steel. At the same time, aluminum is an important alloying element. A certain amount of aluminum in steel can refine grains, improve toughness, and prevent failure. Since aluminum is easily oxidized during the molten steel smelting process, it is difficult to stabilize the acid-soluble aluminum content in steel within a narrow optimal range. Therefore, the precise control of aluminum content in the production process of aluminum-killed steel is a major difficulty. Too high or too low aluminum content in steel and downgrade or surface quality problems caused by repeated aluminum adjustments often occur.

[0003] At present, the problem is that aluminum is a strong deoxidizing element. During the steel-making process of the converter (or electric furnace), argon blowing treatment and LF furnace refining process, aluminum easily reacts with oxygen in molten steel, oxygen in steel slag and oxygen in the air to generate deoxidized products. That is, key indicators such as aluminum recovery rate and aluminum consumption are not only related to the active oxygen content in the steel and the oxidizability of the slag, but also affected by factors such as the amount of slag under the primary refining furnace, the slag-making process of the LF furnace, the amount of alloy added, the argon stirring intensity, the refining time, the permeability of the ladle, the refining cycle, and the amount of molten steel. The influence of these factors on the aluminum recovery rate and aluminum consumption in the production process has very complex nonlinear characteristics and is difficult to quantify. In the actual production process, the aluminum content can only be adjusted according to the experience of the operator, and the control ability is poor. It is easy to have the aluminum content at the end of the LF furnace fail to meet the requirements or repeatedly adjust the aluminum during the LF furnace refining process, thereby affecting the cleanliness of the molten steel and the precise control of the aluminum content in the steel at the end of refining.

[0004] At present, the metallurgical industry has two main strategies for controlling aluminum content in the production practice of medium and high carbon steel:

[0005] (1) A two-step method is adopted, that is, the total amount of aluminum to be added is divided into two parts, one part of the aluminum is added to the ladle with the steel flow in the form of aluminum blocks during steel tapping, and the remaining part of the aluminum is added to the ladle in the form of aluminum blocks or aluminum wires during the argon blowing process or LF furnace refining process to control the aluminum content. This method basically relies on production experience to control the amount of aluminum iron and aluminum particles added, and does not quantitatively consider the influence of factors such as the amount of slag under the primary refining furnace, the bottom blowing of the ladle, and the slag making conditions on the aluminum attenuation law. The amount of addition is basically determined by manual experience, which is prone to unstable aluminum content adjustment or repeated aluminum adjustment in the middle and late stages of LF furnace refining, thereby adversely affecting the cleanliness of the molten steel.

[0006] (2) Oxygenation of molten steel is performed before aluminum is added, and the amount of aluminum alloy or aluminum wire to be added is calculated based on the active oxygen content of the molten steel. This method does not take into account the effect of slag oxidizability on aluminum yield. At the same time, oxygenation of molten steel will also affect production rhythm and increase production costs.

[0007] After searching, Chinese patent CN 113174464 A discloses a method for accurately controlling the final aluminum content in the LF furnace. The method takes the process aluminum content, the amount of slag added, the heating time, the argon flow rate and the length of the aluminum wire in the production conditions of the LF furnace refining process as the influencing factors of the final aluminum content, and fits the regression formula of the aluminum wire adjustment through a large number of experiments, thereby achieving accurate control of the final aluminum content in the molten steel. However, the method has the following problems: (1) Only the effect of the amount of slag added on the aluminum content is considered, and the effect of the LF furnace slag making process on the aluminum content adjustment is not considered. Since the slag-making process requires strong stirring of bottom-blown argon, various slag-making materials are prompted to react with each other as quickly as possible to form slag, which has a more serious impact on aluminum attenuation during the slag-making process; (2) The amount of slag added is limited to 3-8 kg / t steel, and the slag-making materials are lime and fluorite. In the production practice of LF furnaces, the amount of slag added to LF furnaces is mostly above 15 kg / t steel. At the same time, due to environmental pressure and other factors, fluorite slag-making is no longer allowed. Therefore, the practicality of this application is not strong; (3) The bottom-blown argon flow rate is limited to a too narrow range and is not applicable to the heating process, slag-making and desulfurization process of the LF furnace. In this application, the bottom-blown argon flow rate is limited to 100-200 NL / min, which is only applicable to the soft blowing process of LF furnace refining. The bottom-blown argon flow rate in the heating process, slag-making and desulfurization process of the LF furnace is basically between 300 and 800 NL / min.

[0008] For another example, Chinese patent CN 112094985 A discloses a method for controlling aluminum content, which can achieve the purpose of reducing the number of inclusions in ultra-low sulfur steel and controlling the aluminum content in steel by optimizing and controlling the amount of slag in the primary furnace, the amount of LF furnace slag, the composition of the slag system, the [Als] content in the molten steel after slagging, the bottom argon stirring intensity, and the [Als] content after VD breaking. The technical paper "The Practice of Argon Blowing Oxygen and Aluminum Addition in Aluminum Killed Steel Ladle" discusses some key factors affecting the control of acid-soluble aluminum, and develops a new process of oxygenating and adding aluminum in molten steel at the argon blowing station, so that the qualified rate of aluminum content can be stabilized at more than 99.9%. However, the above studies did not mention how to achieve precise control of aluminum content during LF furnace refining. Summary of the invention

[0009] 1. Problem to be solved

[0010] The purpose of the present invention is to provide a method for accurately controlling the aluminum content at the end point of the LF furnace, thereby overcoming the shortcomings of the prior art that the amount of deoxidizers such as aluminum iron and aluminum particles added is mainly controlled by production experience, resulting in low accuracy in controlling the aluminum content and more complicated regulation.

[0011] 2. Technical solution

[0012] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0013] The method of the present invention for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace end point comprises:

[0014] The operation of adding aluminum-iron alloy to perform deoxidation alloying treatment during the steelmaking process of converter or electric furnace; and

[0015] When the LF furnace enters the station, according to the slag discharge during the steel-making process, a certain amount of aluminum particles is sprinkled on the slag surface to deoxidize the slag; the amount of aluminum particles added M 铝粒 The controls are as follows:

[0016] M 铝粒 =0.003ρ 渣 *ω FeO *[(ρ 钢 *(V 钢包 -V 净空 )-m 总 ) / (ρ 钢 -ρ 渣 )-m 渣料 ]

[0017] In the above formula:

[0018] ρ 渣 is the density of slag when the LF furnace enters the station;

[0019] ω FeO It is the FeO content in the slag at the end of smelting in the primary furnace;

[0020] ρ 钢 It is the density of molten steel when the LF furnace enters the station;

[0021] V 钢包 is the total volume of the ladle;

[0022] V 净空 The net volume of the ladle, i.e., the volume remaining after removing the molten steel and slag from the ladle, can be determined based on parameters such as the net height of the ladle and the number of layers of refractory bricks;

[0023] m 总 The total weight of the molten steel and slag in the ladle, which can be obtained by subtracting the weight of the empty ladle from the total weight of the ladle after tapping;

[0024] m 渣料 It is the weight of slag added during the steel tapping process.

[0025] The present invention first adds aluminum-iron alloy to perform deoxidation alloying treatment during the steel-tapping process of the converter (or electric furnace), and then sprinkles a certain amount of aluminum particles on the slag surface according to the slag discharge during the steel-tapping process when the LF furnace enters the station, thereby effectively preventing the oxidizing slag in the primary refining furnace from diffusing oxygen into the molten steel during the subsequent refining process. In the current prior art, the amount of aluminum particles added is usually determined by manual experience, and the control of the amount of aluminum particles added is inaccurate, and it is often necessary to add multiple times to adjust the aluminum, and the operation is relatively complicated. However, the present application can directly quantify the amount of aluminum particles added according to the slag discharge during the steel-tapping process, thereby effectively ensuring the accurate control of the amount of aluminum particles added and improving the deoxidation effect, while also saving time and cost, and the operation is relatively simple.

[0026] Furthermore, the amount of aluminum-iron alloy added during the steelmaking process of the converter or electric furnace is:

[0027] M 铝铁合金 =10×([Als] 成品目标 +0.027+X*[C] 成品 ) / (0.54*[C] 出钢 +0.10)

[0028] In the above formula, [Als] 成品目标 The target aluminum content of the finished product, [C] 出钢 is the carbon content at the time of steel production, [C] 成品 is the carbon content of the molten steel in the middle package. All contents are expressed as 1% by weight as 1 unit. For example, 0.5% is substituted into 0.5. X represents the effect of the molten steel composition on the aluminum yield. Its value range is 0.015-0.035. The higher the [C] and [Si] contents in the molten steel, the higher the yield. X takes the lower limit, otherwise, it takes the upper limit.

[0029] The present invention quantitatively controls the amount of aluminum-iron alloy added during the steel-making process of a converter or an electric furnace according to the composition of the molten steel, thereby facilitating accurate control of the amount of addition, which is beneficial to ensuring the deoxidation effect of steel-making and is easy to operate. Furthermore, the inventor of the present invention, based on long-term production experience, quantitatively optimizes the value of X according to the [C] and [Si] contents in the molten steel, thereby facilitating further ensuring the deoxidation effect of the steel-making process. Specifically,

[0030] When [C] ≥ 0.70%, X = 0.015 ~ 0.017;

[0031] When 0.4≤[C]<0.7, X=0.016~0.030;

[0032] When [C]<0.40%, X=0.028~0.035.

[0033] Furthermore, the value of X is further controlled as follows:

[0034] When [C]≥0.70%, 0.6≤[Si]≤0.9, X is 0.015;

[0035] When [C]≥0.70%, 0.3≤[Si]<0.6, X is 0.016;

[0036] When [C]≥0.70%, [Si]<0.30%, X is 0.017;

[0037] When 0.4≤[C]<0.7, 0.6≤[Si]≤0.9, X=0.016~0.017;

[0038] When 0.4≤[C]<0.7, 0.3≤[Si]<0.6, X=0.018~0.022;

[0039] When 0.4≤[C]<0.7, [Si]<0.30, X=0.022~0.030;

[0040] When [C]<0.40%, 0.6≤[Si]≤0.9, X=0.028~0.033;

[0041] When [C]<0.40% and [Si]<0.6%, X=0.033~0.035.

[0042] Furthermore, lime and pre-melted refined slag are used for slag making, and SiC and other siliceous reducing agents are used for diffusion deoxidation of the slag. At the same time, the temperature and composition are adjusted to control the main composition of the LF furnace slag as follows: CaO: 45% to 60%, Al 2 O 3 :20%~35%,SiO 2 :5%~20%, (TFe+MnO)≤1.0%.

[0043] Furthermore, after slag making and adjustment of components other than aluminum are completed, aluminum wire is continuously fed into the molten steel.

[0044] Furthermore, the amount of aluminum wire fed into the molten steel is:

[0045] M 铝线 =A×[[Als] 成品目标 +0.027+X*[C] 成品 -[Als] 实时 +Z{0.25Y[Als] 实时 -0.003}], in meters

[0046] Among them, [Als] 成品目标 is the target aluminum content of the finished product; [Als] 实时 is the aluminum content when feeding aluminum wire, X represents the effect of molten steel composition on aluminum recovery rate, and its value is 0.015-0.035, Y represents the effect of molten steel composition on aluminum attenuation rate before leaving the station after the formation of white slag, and its value is 0.3-1.6; Z represents the effect of soft blowing time from the last aluminum adjustment to the exit process on the amount of additional aluminum wire fed, and its value is 0.9-1.3; A represents the effect of aluminum wire specifications on the amount of aluminum fed. Among them, the higher the [C] and [Si] contents, the lower the aluminum attenuation rate and the higher the recovery rate. X and Y take the lower limit, otherwise, take the upper limit.

[0047] Furthermore, when the diameter of the feed aluminum wire changes, the coefficient A is calculated as follows:

[0048] A=2000×10^2 / d^2

[0049] In the above formula, d is the diameter of the feed aluminum wire, in meters. For example, when the diameter d = 10 mm, A = 2000; when the diameter d = 20 mm, the coefficient A = 2000 × (10 × 10) / (20 × 20) = 500 meters.

[0050] Furthermore, in the aluminum feeding amount calculation formula, the specific formula for determining the values ​​of X and Y is as follows:

[0051] When [C] ≥ 0.70%, X = 0.015 ~ 0.017, Y = 0.3 ~ 1;

[0052] When 0.4≤[C]<0.7, X=0.016~0.030, Y=1~1.4;

[0053] When [C]<0.40%, X=0.028~0.035, Y=1.4~1.6.

[0054] Furthermore, in the aluminum feeding amount calculation formula, the values ​​of X and Y are further determined as follows:

[0055] When [C]≥0.70%, 0.6≤[Si]≤0.9, X=0.015, Y=0.3;

[0056] When [C]≥0.70%, 0.3≤[Si]<0.6, X=0.016, Y=0.6;

[0057] When [C]≥0.70%, [Si]<0.30%, X=0.017, Y=1;

[0058] When 0.4≤[C]<0.7, 0.6≤[Si]≤0.9, X=0.016~0.017, Y=1;

[0059] When 0.4≤[C]<0.7, 0.3≤[Si]<0.6, X=0.018~0.022, Y=1.2;

[0060] When 0.4≤[C]<0.7, [Si]<0.30, X=0.022~0.030, Y=1.4;

[0061] When [C]<0.40%, 0.6≤[Si]≤0.9, X=0.028~0.033, Y=1.4;

[0062] When [C]<0.40%, [Si]<0.6%, X=0.033~0.035, Y=1.6.

[0063] Furthermore, in the formula for determining the amount of aluminum wire fed, Z is determined by the time of exiting the station, which represents the effect of the soft blowing time on the amount of additional aluminum wire fed during the last aluminum adjustment to the exiting station. The shorter the soft blowing time, the smaller the aluminum attenuation, the less the additional aluminum wire fed, and Z takes the lower limit, otherwise it takes the upper limit. The specific value selection principle is:

[0064] ① When the departure time is less than 20 minutes, Z = 0.9;

[0065] ② When the departure time is between 20 and 30 minutes, Z = 1.0;

[0066] ③ When the departure time is between 30 and 40 minutes, Z = 1.2;

[0067] ④ When the exit time is greater than 40 minutes, Z=1.3.

[0068] 3. Beneficial effects

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] (1) The present invention provides a method for accurately controlling the aluminum content at the end point of the LF furnace of medium and high carbon aluminum killed steel. According to the slag-discharging situation during the steel-discharging process, a certain amount of aluminum particles are sprinkled on the slag surface for deoxidation. By quantitatively controlling the amount of aluminum particles added, the accurate control of the amount of aluminum particles added can be effectively guaranteed. The control method is simple to operate, which overcomes the shortcomings of the traditional method of adding aluminum particles mainly relying on manual experience.

[0071] (2) The method of the present invention for accurately controlling the aluminum content at the end point of the LF furnace of medium and high carbon aluminum killed steel further quantifies the amount of aluminum iron added during the steelmaking process and the amount of aluminum wire fed after slag making and before leaving the station, thereby facilitating further ensuring the accurate control of the aluminum content at the end point of the LF furnace and improving product quality.

[0072] (3) The method of the present invention provides a method for accurately controlling the final aluminum content of the LF furnace of medium and high carbon aluminum killed steel. Through the coordination of each step of deoxidation operation, it can adapt to the influence of changes in various factors such as the active oxygen content in the steel, the oxidizability of the slag, the slag-making process, the amount of alloy added, the argon stirring intensity, the refining time, the air permeability of the ladle, the refining cycle, and the difference in the amount of molten steel on the final aluminum content. There is no need to set oxygen or repeatedly adjust aluminum. Under the premise of stable control of the aluminum content at the LF furnace outlet, the number of aluminum adjustments during the LF furnace refining process is ≤2 times, and the amount of aluminum adjustment in the middle and late stages of LF furnace refining is minimized, thereby maximizing the cleanliness of the molten steel. DETAILED DESCRIPTION

[0073] The method provided by the present invention provides a method for accurately controlling the aluminum content at the end point of the LF furnace of medium and high carbon steel, which can adapt to the changes of factors such as the active oxygen content in the steel, the oxidizability of the slag, the slag making process, the amount of alloy added, the argon stirring intensity, the refining time, the air permeability of the ladle, the refining cycle, and the difference in the amount of molten steel. Compared with the prior art, the main innovations of the present invention are:

[0074] (1) A method for simply, quickly and accurately calculating the amount of slag in the primary furnace during steelmaking is provided. The amount of aluminum particles added and the method for accurately controlling the aluminum content are provided for different slag amounts and slag oxidizability. However, the prior art does not consider the effects of the oxidizability of the slag at the end of converter / electric furnace smelting and the amount of slag on the oxygen content and aluminum content of molten steel.

[0075] (2) In view of the fact that the influence of factors such as the slag-making process, alloy addition, argon stirring intensity, ladle permeability, etc. on aluminum attenuation in the early stage of LF furnace refining varies greatly and cannot be quantified, the present invention makes full use of the metallurgical transmission principle, metallurgical dynamics and metallurgical thermodynamics theory, combines the characteristics of LF furnace refining and the attenuation law of aluminum content, and achieves the consistency of the influence of factors such as slag amount, LF furnace slag-making process, alloy addition, argon stirring intensity, ladle permeability, etc. on aluminum attenuation between different furnaces in the middle stage of LF furnace refining, providing a basis for the standardized adjustment of aluminum content in the middle and late stages. The existing technology is easily affected by factors such as slag-making process, alloy addition, argon stirring intensity, ladle permeability, etc. during aluminum adjustment, and the influence degree varies greatly between furnaces, resulting in large fluctuations in aluminum content.

[0076] (3) Based on the consistent influence of LF furnace slag making process, alloy addition amount, argon stirring intensity, ladle permeability and other factors on aluminum attenuation, the influence of molten steel composition, outlet temperature, soft blowing time and other factors on the aluminum content of molten steel was quantitatively analyzed, and the adjustment method of aluminum content in molten steel with different molten steel composition, outlet temperature and soft blowing time was given.

[0077] The present invention is further described below in conjunction with specific embodiments. However, it should be noted that due to limited space here, only some embodiments are listed to illustrate the LF furnace endpoint aluminum content control method of the present invention, but in fact it is not limited to the following specific embodiments.

[0078] Example 1

[0079] The two-step method of this embodiment to accurately control the aluminum content of the LF furnace endpoint is applied to a 120-ton electric furnace-LF furnace process in a certain factory, smelting steel: 50Mn, [Als] 成品目标 =0.022%, the target value of aluminum content at the end of LF furnace is 0.032%, [C] 成品 =0.52, [Si] = 0.28%, molten steel volume is 120 tons, total slag volume is 2.0 tons, and the specific control method is as follows:

[0080] (1) During the steelmaking process of the electric furnace, aluminum-iron alloy is added for deoxidation and alloying operation. The amount of aluminum-iron added is:

[0081] M 铝铁合金 =10×([Als] 成品目标 +0.027+X*[C] 成品 ) / (0.54*[C] 出钢 +0.10)

[0082] (2) When the LF furnace enters the station, a certain amount of aluminum particles is sprinkled on the slag surface according to the slag discharge during the steel-making process to deoxidize the slag. The more slag is discharged during the steel-making process, the more aluminum particles are added. Specifically:

[0083] M 铝粒 =0.003ρ 渣 *ω FeO *[(ρ 钢 *(V 钢包 -V 净空 )-m 总 ) / (ρ 钢 -ρ 渣 )-m 渣料 ]

[0084] Where: M 铝粒 is the amount of aluminum particles added;

[0085] ρ 渣The density of the slag at 1600℃ is 3100kg.m -3 ;

[0086] ω FeO It is the FeO content in the slag at the end of smelting in the primary furnace;

[0087] ρ 钢 The density of molten steel at 1600℃ is 7120kg.m -3 ;

[0088] V 钢包 is the total volume of the ladle; V 净空 The net volume of the ladle, i.e., the volume remaining after removing the molten steel and slag from the ladle, can be determined based on parameters such as the net height of the ladle and the number of layers of refractory bricks;

[0089] m 总 The total weight of the molten steel and slag in the ladle, which can be obtained by subtracting the weight of the empty ladle from the total weight of the ladle after steel is tapped. When substituted into the formula for calculation, the unit is converted to tons;

[0090] m 渣料 It is the weight of slag added in the steel-making process, which is converted into tons when substituted into the calculation formula.

[0091] (3) Use lime and pre-melted refined slag for slag making, use SiC for diffusion deoxidation of slag, and adjust the temperature and composition. LF furnace slag composition: CaO: 60%, Al 2 O 3 : 30%, SiO 2 : 5%.

[0092] (4) After the formation of white slag and the adjustment of components other than aluminum, the time before the molten steel leaves the station is estimated, and a certain amount of aluminum wire is fed into the molten steel according to the molten steel [Als] content and the time before the molten steel leaves the station. The formula for aluminum wire is:

[0093] 2000×[[Als] 成品目标 +0.027+X*[C] 成品 -[Als] 实时 +Z{0.25Y[Als] 实时 -0.003}](m)

[0094] Where: The content in the formula is 1% (weight) as 1 unit, such as 0.5%, substitute 0.5; [Als] 实时is the aluminum content when feeding aluminum wire; the specific parameters of aluminum wire are: Al content ≥ 99.5%, diameter 10mm. X represents the influence of molten steel composition on aluminum recovery rate. The higher the [C] and [Si] content, the lower the aluminum attenuation rate and the higher the recovery rate. X takes the lower limit, otherwise, the upper limit is taken. Y represents the influence of molten steel composition on the aluminum attenuation rate before leaving the station after the formation of white slag and the last feeding of aluminum wire. The higher the [C] and [Si] content, the smaller the attenuation amount. Y takes the lower limit, otherwise the upper limit is taken. Z is determined by the time of leaving the station, and represents the influence of the soft blowing time from the last aluminum adjustment to the process of leaving the station on the amount of additional aluminum wire fed. The shorter the soft blowing time, the smaller the aluminum attenuation amount and the less aluminum wire fed. Z takes the lower limit, otherwise the upper limit is taken. The parameter values ​​in each step of the operation in this embodiment are specifically shown in Table 1 below. After the aluminum content is adjusted according to the technical scheme of this embodiment, the aluminum content of the LF furnace leaving the station is 0.033%.

[0095] Table 1 Partial process parameters of Examples 1-2 and Comparative Example 1

[0096]

[0097] Example 2

[0098] The method for accurately controlling the aluminum content at the end point of the LF furnace in Example 2 is basically the same as that in Example 1, except that some parameters are different from those in Example 1, as shown in Table 1. The slag composition of the LF furnace in this example is: CaO: 55%, Al 2 O 3 : 25%, SiO 2 After the aluminum content is adjusted according to the technical solution of this embodiment, the aluminum content of the LF furnace when it leaves the station is 0.032%.

[0099] Comparative Example 1

[0100] In the LF furnace endpoint aluminum content control method of this comparative example, aluminum-iron alloy is added to perform deoxidation and alloying operation according to production experience during the electric furnace steelmaking process. After the LF furnace enters the station, 20 kg of aluminum particles are added to make reducing slag. After the white slag is formed and the components other than aluminum are adjusted, the time from the molten steel to the station is estimated. According to the molten steel [Als] content, the station-out time and production experience, a certain amount of aluminum wire is fed into the molten steel, wherein the feeding amounts of aluminum-iron alloy and aluminum wire are shown in Table 1.

[0101] According to Table 1, after the aluminum content is adjusted according to the technical solution of the present invention, the aluminum content when the LF furnace leaves the station is distributed around the target value of 0.032%, and the difference is ≤0.001%, which is much smaller than 0.003% of the control example. The control level of the aluminum content when the LF furnace leaves the station is significantly improved.

[0102] Embodiment 3-4

[0103] The two-step method of Examples 3 and 4 for accurately controlling the aluminum content at the end point of the LF furnace was applied to a 150-ton converter-LF furnace process in a certain factory, smelting steel grades: 82A, [Als] 成品目标 =0.015%, the target value of aluminum content at the end of LF furnace is 0.018%, [C] 成品 =0.81, [Si] =0.35%, molten steel volume is 150 tons, total slag volume is 2.5 tons, and specific control process parameters are shown in Table 2 below. LF furnace slag composition in Example 3: CaO: 48%, Al 2 O 3 : 33%, SiO 2 : 13%, the LF furnace slag composition in Example 4: CaO: 45%, Al 2 O 3 : 35%, SiO 2 : 15%.

[0104] Comparative Example 2

[0105] In the LF furnace endpoint aluminum content control method of this comparative example, aluminum-iron alloy is added to perform deoxidation and alloying operation according to production experience during the electric furnace steelmaking process. After the LF furnace enters the station, 20 kg of aluminum particles are added to make reducing slag. After the white slag is formed and the components other than aluminum are adjusted, the time from the molten steel to the station is estimated. According to the molten steel [Als] content, the station-out time and production experience, a certain amount of aluminum wire is fed into the molten steel, wherein the feeding amounts of aluminum-iron alloy and aluminum wire are shown in Table 2.

[0106] Table 2 Partial process parameters of Examples 3-4 and Comparative Example 2

[0107]

[0108] It can be seen from the data in Table 2 that after the aluminum content is adjusted by the technical solutions in Examples 3 and 4, the aluminum content when the LF furnace leaves the station is distributed around the target value of 0.018%, and the difference is ≤0.001%, which is less than 0.003% of Comparative Example 2. The control level of aluminum content when the LF furnace leaves the station is significantly improved.

Claims

1. A method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace end point, characterized in that: include, The operation of adding aluminum-iron alloy to perform deoxidation alloying treatment during the steelmaking process of converter or electric furnace; as well as When the LF furnace enters the station, according to the slag discharge during the steel-making process, a certain amount of aluminum particles are sprinkled on the slag surface to deoxidize the slag; the amount of aluminum particles added M 铝粒 The controls are as follows: M 铝粒 =0.003ρ 渣 *oh FeO *[(r 钢 *(V 钢包 -V 净空 )-m 总 ) / (ρ 钢 -r 渣 )-m 渣料 ] In the above formula: M 铝粒 The unit is Kg; ρ 渣 It is the density of slag when LF furnace enters the station, in kg.m -3 ; ω FeO It is the FeO content in the slag at the end of the primary smelting furnace, in %, and needs to be converted into a decimal when substituted into the formula; ρ 钢 It is the density of molten steel when the LF furnace enters the station, in kg.m -3 ; V 钢包 is the total volume of the ladle, in m 3 ; V 净空 is the net volume of the ladle, in m 3 ; m 总 is the total weight of molten steel and slag in the ladle, which is converted into tons when substituted into the calculation formula; m 渣料 It is the weight of slag added in the steel-making process, which is converted into tons when substituted into the calculation formula.

2. The method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace endpoint according to claim 1, characterized in that: The amount of aluminum-iron alloy added during the steelmaking process of the converter or electric furnace is: M 铝铁合金 =10×([Als] 成品目标 +0.027+X*[C] 成品 ) / (0.54*[C] 出钢 +0.10) In the above formula, [Als] 成品目标 The target aluminum content of the finished product, [C] 出钢 is the carbon content at the time of steel production, [C] 成品 is the target carbon content of the molten steel in the middle package, and each content is expressed as 1% by weight as 1 unit. X represents the effect of the molten steel composition on the aluminum yield, and its value range is 0.015 to 0.

035.

3. The method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace endpoint according to claim 2, characterized in that: The value of X is inversely correlated with the actual [C] content in the molten steel, where: When [C] ≥ 0.70%, X = 0.015 ~ 0.017; When 0.4≤[C]<0.7, X=0.016~0.030; When [C]<0.40%, X=0.028~0.

035.

4. The method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace endpoint according to claim 3, characterized in that: The value of X is further controlled as follows: When [C]≥0.70%, 0.6≤[Si]≤0.9, X is 0.015; When [C]≥0.70%, 0.3≤[Si]<0.6, X is 0.016; When [C]≥0.70%, [Si]<0.30%, X is 0.017; When 0.4≤[C]<0.7, 0.6≤[Si]≤0.9, X=0.016~0.017; When 0.4≤[C]<0.7, 0.3≤[Si]<0.6, X=0.018~0.022; When 0.4≤[C]<0.7, [Si]<0.30, X=0.022~0.030; When [C]<0.40%, 0.6≤[Si]≤0.9, X=0.028~0.033; When [C]<0.40% and [Si]<0.6%, X=0.033~0.

035.

5. A method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace endpoint according to any one of claims 1 to 4, characterized in that: Lime and pre-melted refined slag are used for slag making, and a siliceous reducing agent is used to diffuse and deoxidize the slag. At the same time, the temperature and composition are adjusted to control the main components of the LF furnace slag as follows: CaO: 45% to 60%, Al2O3: 20% to 35%, SiO2: 5% to 20%, (TFe+MnO)≤1.0%.

6. A method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace endpoint according to any one of claims 1 to 4, characterized in that: After slag making and adjustment of components other than aluminum are completed, aluminum wire is continued to be fed into the molten steel.

7. The method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace endpoint according to claim 6, characterized in that: The amount of aluminum wire that is continuously fed into the molten steel is: M 铝线 =A×{[Als] 成品目标 +0.027+X*[C] 成品 -[Als] 实时 +Z[0.25Y[Als] 实时 -0.003]}, in meters Among them, [Als] 成品目标 is the target aluminum content of the finished product; [Als] 实时 is the aluminum content when feeding aluminum wire, X represents the influence of molten steel composition on aluminum recovery rate, and its value is 0.015-0.035; Y represents the influence of molten steel composition when feeding aluminum wire for the last time after white slag is formed on the aluminum attenuation rate before leaving the station, and its value is 0.3-1.6; Z represents the influence of soft blowing time from the last aluminum adjustment to the exit process on the amount of additional aluminum wire fed, and its value is 0.9-1.3; A represents the influence of aluminum wire specifications on the amount of aluminum fed; wherein the content of each element in the calculation formula is 1% by weight as 1 unit.

8. The method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace endpoint according to claim 7, characterized in that: When the diameter of the feed aluminum wire changes, the coefficient A is calculated as follows: A=2000×10^2 / d^2 In the above formula, d is the diameter of the feed aluminum wire, in millimeters.

9. The method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace endpoint according to claim 7, characterized in that: In the calculation formula for aluminum feeding amount, the values ​​of X and Y are inversely correlated with the [C] and [Si] contents in molten steel. The specific determination formula is as follows: When [C] ≥ 0.70%, X = 0.015 ~ 0.017, Y = 0.3 ~ 1; When 0.4≤[C]<0.7, X=0.016~0.030, Y=1~1.4; When [C]<0.40%, X=0.028~0.035, Y=1.4~1.

6.

10. The method for accurately controlling the aluminum content of medium and high carbon aluminum killed steel at the LF furnace endpoint according to claim 9, characterized in that: In the aluminum feeding amount calculation formula, the values ​​of X and Y are further determined as follows: When [C] ≥ 0.70%, 0.6 ≤ [Si] ≤ 0.9, X = 0.015, Y = 0.3; When [C]≥0.70%, 0.3≤[Si]<0.6, X=0.016, Y=0.6; When [C]≥0.70%, [Si]<0.30%, X=0.017, Y=1; When 0.4≤[C]<0.7, 0.6≤[Si]≤0.9, X=0.016~0.017, Y=1; When 0.4≤[C]<0.7, 0.3≤[Si]<0.6, X=0.018~0.022, Y=1.2; When 0.4≤[C]<0.7, [Si]<0.30, X=0.022~0.030, Y=1.4; When [C]<0.40%, 0.6≤[Si]≤0.9, X=0.028~0.033, Y=1.4; When [C]<0.40%, [Si]<0.6%, X=0.033~0.035, Y=1.6.

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