Calculation method for theoretical addition amount of CaO-Al2O3 covering agent for continuous casting tundish and application of calculation method

Abstract

The invention provides a method for calculating the theoretical addition amount of a CaO-Al2O3 covering agent for a continuous casting tundish. The method comprises the following steps: S1) determining the source of Al2O3 inclusion in molten steel of IF steel; calculating the total amount of Al2O3 inclusions generated by the IF molten steel of the first furnace; (S2) in the IF steel continuous casting process, the adsorption capacity of the CaO-Al2O3 tundish covering agent on Al2O3 inclusion is calculated; s3) calculating the weight of a tundish covering agent required for adsorbing Al2O3 inclusions by the molten steel in the first heat; and calculating the weight of the tundish covering agent required for removing Al2O3 inclusions in the molten steel by continuously casting the tundish for N times. According to the calculation method provided by the invention, the theoretical adding weight of the tundish covering agent can be quickly calculated and determined, and the problem of poor component and inclusion adsorption effect caused by unreasonable adding amount of the tundish covering agent is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a method for calculating the theoretical addition amount of a CaO-Al2O3 series covering agent in a continuous casting tundish and its application. Background Art

[0002] The tundish covering agent plays an important metallurgical function in the continuous casting process. One of its main metallurgical functions is to adsorb and remove inclusions in the molten steel. Especially for steel grades such as automotive panels (IF steel) that have strict requirements on the cleanliness of the molten steel, the importance of the tundish covering agent in the adsorption and removal of inclusions becomes increasingly prominent.

[0003] In order to improve the metallurgical functions of the tundish covering agent, such as adsorption and removal of inclusions, researchers have proposed improvements to the tundish covering agent mainly from the aspects of composition and processing technology. For example: Chinese patent with publication number CN116987841A discloses a tundish covering agent and a preparation method thereof for the production of high-quality carbon structural steel. The disclosed covering agent can effectively adsorb inclusions and melt quickly, reduce the pollution to molten steel, and make full use of various waste materials; Chinese patent with publication number CN117920953A provides a tundish covering agent and a preparation method for electrical steel. The disclosed tundish covering agent effectively improves the slag-like physicochemical properties of the covering agent and enhances the ability to adsorb inclusions; Chinese patent with application number CN202310690778.9 provides a low-silicon, low-carbon, smokeless electric-melted hollow covering agent for tundish and a preparation method thereof. The disclosed covering agent has good spreadability, light specific gravity, small dosage, no ignition loss, and the ability to adsorb impurities. Strong advantages; Chinese patent with publication number CN117210641A provides a method for preparing a tundish covering agent for ultra-low sulfur steel, which can reduce production costs and effectively ensure that the molten steel does not increase S during casting by controlling the amount of lime added and reducing the initial S content of molten steel during refining; Chinese patent with publication number CN116041079A discloses a tundish covering agent with improved thermal insulation performance and a preparation method thereof, which improves the adsorption and removal ability of the covering agent for inclusions through higher basicity, and has the advantages of excellent slagging performance and low corrosion resistance of tundish refractory materials; Chinese patent with publication number CN116479212A discloses a new type of environmentally friendly ladle covering agent and its preparation method and application, and the disclosed covering agent has excellent thermal insulation and heat preservation effects, and significantly reduces dust pollution.

[0004] In the continuous casting process, the amount of covering agent added to the tundish is a key factor affecting its metallurgical function and production cost. If the amount of covering agent added is insufficient, the effect of purifying molten steel inclusions is poor, and it is difficult to ensure the cleanliness of the molten steel. If the amount of covering agent added to the tundish is too much, the production cost of the covering agent per ton of steel increases. At the same time, if too much covering agent is added, the risk of crusting of the covering agent in the tundish increases, affecting the smoothness of the continuous casting process. At present, the existing technology mainly improves the metallurgical function of the tundish covering agent by optimizing the composition and processing technology of the covering agent. However, no corresponding theoretical calculation method is proposed for the reasonable addition amount of the tundish covering agent. Summary of the invention

[0005] The technical problem solved by the present invention is to provide a method for calculating the theoretical addition amount of the CaO-Al2O3 series covering agent in the continuous casting tundish. The calculation method provided in the present application can quickly calculate and determine the theoretical addition weight of the tundish covering agent, thereby avoiding the problem of poor adsorption effect of components and inclusions caused by unreasonable addition amount of the tundish covering agent.

[0006] In view of this, the present application provides a method for calculating the theoretical addition amount of a CaO-Al2O3 system covering agent for a continuous casting tundish, comprising the following steps:

[0007] S1) RH refining is performed on the molten steel of IF steel. After decarburization, aluminum is added to remove [O] in the molten steel. The weight of the obtained Al2O3 inclusion is recorded as Q i1 , kg, calculated as formula (Ⅰ):

[0008] Q i1 =W1×1000×a×10 -6 ×2.13 (Ⅰ);

[0009] S2) The molten steel in step S1) is transferred to the tundish. During this process, the [Al] in the molten steel undergoes a burning reaction, and the weight of the Al2O3 inclusion obtained is recorded as Q i2 , kg, calculated as formula (Ⅱ);

[0010] Q i2 =W1×1000×ΔAl×10 -6 ×1.89 (Ⅱ);

[0011] The total amount of Al2O3 inclusions generated in one batch of IF steel is denoted as Q i , kg, calculated as (III);

[0012] Q i =Q i1 +Q i2 (III);

[0013] S3) During the continuous casting of IF steel, based on the average temperature of molten steel during the continuous casting process and the contents of CaO and Al2O3 in the CaO-Al2O3 system tundish covering agent, the adsorption capacity of the CaO-Al2O3 system tundish covering agent for Al2O3 inclusions was calculated using formula (IV), denoted as I:

[0014] I=w 1C / (-8.195+0.01482×T-5.9497×10 -6 ×T 2 )-w 1A (IV);

[0015] S4) Calculate the weight of the tundish covering agent required for one batch of molten steel to adsorb Al2O3 inclusions, recorded as S1, kg, and the calculation formula is as shown in formula (V);

[0016] S1=Q i / I (V);

[0017] For each tundish continuous casting heat N, calculate the weight of the tundish covering agent required to remove Al2O3 inclusions in molten steel, denoted as S, kg, using the following formula (VI):

[0018] S = S1 × N (VI);

[0019] Where, W1 is the average weight of molten steel in the ladle, t;

[0020] a is the average oxygen activity of molten steel after decarburization, ppm;

[0021] ΔAl is the average acid-soluble aluminum loss from RH refining station to tundish; ppm;

[0022] w 1C is the CaO content in the coating agent of the CaO-Al2O3 system, wt%;

[0023] w 1A is the content of Al2O3 in the coating agent of CaO-Al2O3 system, wt%;

[0024] T is the average temperature of molten steel in the tundish, ℃.

[0025] Preferably, the adsorption capacity I is obtained specifically as follows:

[0026] S31) The adsorption capacity of the CaO-Al2O3 system covering agent for Al2O3 inclusions is defined as I, and the calculation formula of I is shown in (VII):

[0027]

[0028] S32) Detect the mass percentage of CaO and Al2O3 in the initial CaO-Al2O3 system covering agent, which are respectively recorded as w 1C 、w 1A , wt%;

[0029] S33) using the initial CaO-Al2O3 system covering agent to adsorb Al2O3 inclusions, and the ratio of CaO to Al2O3 when saturation is reached is defined as the calcium-aluminum ratio K, and the calculation formula of the ratio and the temperature of the molten steel in the continuous casting process is shown in formula (VIII):

[0030] K=-8.195+0.01482×T-5.9497×10 -6 ×T 2 (VIII);

[0031] S34) After the adsorption is saturated, the weight of Al2O3 inclusions in the CaO-Al2O3 system covering agent is obtained. I Calculate according to formula (IX):

[0032] Q I =W Al2O3 -W' Al2O3 =Q s ×(w 1C / Kw 1A ) (Ⅸ);

[0033] S35) combining the calculation formula (IX) and the calculation formula (VII) to obtain the adsorption capacity I of the CaO-Al2O3 system covering agent for inclusions;

[0034] Among them, Q s is the initial weight of CaO-Al2O3 system covering agent, kg; Q I is the weight of Al2O3 inclusions when they reach saturation in the covering agent, kg;

[0035] T is the average temperature of molten steel during continuous casting, °C;

[0036] W' Al2O3 is the weight of Al2O3 in the initial CaO-Al2O3 system covering agent, kg;

[0037] W Al2O3 It is the total weight of Al2O3 when the CaO-Al2O3 system covering agent is saturated with adsorption, kg.

[0038] Preferably, the formula (VIII) is obtained by the following method:

[0039] The calcium-aluminum ratios of different initial CaO-Al2O3 system covering agents at different temperatures when Al2O3 inclusions are adsorbed saturated are calculated using thermodynamic calculation software to obtain a curve of the calcium-aluminum ratio and temperature when the covering agent is adsorbed saturated; the calcium-aluminum ratios of the initial CaO-Al2O3 system covering agents are different;

[0040] The temperature and calcium-aluminum ratio when the covering agent is adsorbed to saturation are fitted.

[0041] Preferably, the detected amount of the initial CaO-Al2O3 based covering agent is ≥100g.

[0042] Preferably, K is 0.3 to 0.6.

[0043] Preferably, before obtaining formula (IX), the following steps are also included:

[0044] The CaO-Al2O3 system covering agent is adsorbed to saturation, and the total weight of Al2O3 in the saturated covering agent is W Al2O3 The calculation is carried out according to the following formula:

[0045] W Al2O3 =W' CaO / K=Q s × 1C / K.

[0046] Preferably, T is 1350-1550°C.

[0047] Preferably, the number of heats N is 8-12.

[0048] The present application also provides the application of the calculation method in the design of coating agents in the CaO-Al2O3 system.

[0049] The present application provides a method for calculating the theoretical addition amount of CaO-Al2O3 series covering agent in a continuous casting tundish. The method first refines the molten steel of IF steel, adds aluminum to remove [O] in the molten steel after decarburization, and generates Al2O3 inclusions. The generated amount Q is calculated. i1 ; Then the molten steel is transferred to the tundish. During this process, the [Al] in the molten steel undergoes a burning reaction to produce Al2O3 inclusions. Calculate the amount of Al2O3 produced. i2 , then the total amount of Al2O3 inclusions generated in one batch of IF steel is Q i =Q i1 +Q i2; In the process of IF steel continuous casting, the calculation formula of adsorption capacity I can be determined based on the average temperature of molten steel during tundish continuous casting and the contents of CaO and Al2O3 in the CaO-Al2O3 system tundish covering agent. On the above basis, the weight of tundish covering agent required for one batch of molten steel to adsorb Al2O3 inclusions can be calculated. In actual production, the tundish covering agent required for tundish continuous casting batch N can be calculated. The calculation method provided in this application is based on the process parameters of IF steel in RH treatment, tundish continuous casting batches, and tundish covering agent composition. On the basis of determining the source of Al2O3 inclusions in molten steel, the theoretical amount of tundish covering agent added in the tundish to remove Al2O3 inclusions in IF steel is calculated, thereby avoiding problems such as composition and inclusion adsorption effect caused by unreasonable addition of tundish covering agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The calcium-aluminum ratio K curve diagram of the covering agent with different initial calcium-aluminum ratios at different temperatures when Al2O3 inclusion adsorption is saturated;

[0051] Figure 2 The graph is a curve showing the change of calcium-aluminum ratio under different amounts of covering agent added during the casting process of the embodiment of the present invention;

[0052] Figure 3 This is a curve diagram of the change of calcium-aluminum ratio of the coating agent during the coating casting process in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0054] In view of the lack of a method for calculating the theoretical amount of a tundish covering agent for adsorbing Al2O3 inclusions in the prior art, the present application provides a method for calculating the theoretical amount of a CaO-Al2O3-based covering agent for a continuous casting tundish, which is based on the composition of the tundish covering agent and process-related process data, and quickly and accurately calculates the theoretical amount of the tundish covering agent without affecting normal production. Specifically, an embodiment of the present invention discloses a method for calculating the theoretical amount of a CaO-Al2O3-based covering agent for a continuous casting tundish, comprising the following steps:

[0055] S1) RH refining is performed on the molten steel of IF steel. After decarburization, aluminum is added to remove [O] in the molten steel. The weight of the obtained Al2O3 inclusions is recorded as Q i1 , kg, calculated as formula (Ⅰ):

[0056] Q i1 =W1×1000×a×10 -6×2.13 (Ⅰ);

[0057] S2) The molten steel in step S1) is transferred to the tundish. During this process, the [Al] in the molten steel undergoes a burning reaction, and the weight of the obtained Al2O3 inclusions is recorded as Q i2 , kg, calculated as formula (Ⅱ);

[0058] Q i2 =W1×1000×ΔAl×10 -6 ×1.89 (Ⅱ);

[0059] The total amount of Al2O3 inclusions generated in one batch of IF steel is denoted as Q i , kg, calculated as (III);

[0060] Q i =Q i1 +Q i2 (III);

[0061] S3) During the continuous casting of IF steel, based on the average temperature of molten steel during the continuous casting process and the contents of CaO and Al2O3 in the CaO-Al2O3 system tundish covering agent, the adsorption capacity of the CaO-Al2O3 system tundish covering agent for Al2O3 inclusions was calculated using formula (IV), denoted as I:

[0062] I=w 1C / (-8.195+0.01482×T-5.9497×10 -6 ×T 2 )-w 1A (IV);

[0063] S4) Calculate the weight of the tundish covering agent required for one batch of molten steel to adsorb Al2O3 inclusions, recorded as S1, kg, and the calculation formula is as shown in formula (V);

[0064] S1=Q i / I (V);

[0065] For each tundish continuous casting heat N, calculate the weight of the tundish covering agent required to remove Al2O3 inclusions in molten steel, denoted as S, kg, using the following formula (VI):

[0066] S = S1 × N (VI);

[0067] Where, W1 is the average weight of molten steel in the ladle, t;

[0068] a is the average oxygen activity of molten steel after decarburization, ppm;

[0069] ΔAl is the average acid-soluble aluminum loss from RH refining station to tundish; ppm;

[0070] w1C is the CaO content in the coating agent of the CaO-Al2O3 system, wt%;

[0071] w 1A is the content of Al2O3 in the coating agent of CaO-Al2O3 system, wt%;

[0072] T is the average temperature of molten steel in the tundish, ℃.

[0073] The calculation method for the theoretical addition amount of Cao-Al2O3 series covering agent in the continuous casting tundish provided in this application is aimed at the calculation of the addition amount of the tundish covering agent in the continuous casting process of IF steel; the calculation method provided in this application should not be separated from the actual production process, but the relevant parameters should be detected in the actual production process to calculate the addition amount of the tundish covering agent.

[0074] In the calculation method provided in this application, it is necessary to determine the source of Al2O3 inclusions in molten steel; first, the molten steel of IF steel is subjected to RH refining, and aluminum is added after decarburization to remove [O] in the molten steel. The weight of the obtained Al2O3 inclusions is recorded as Q i1 , kg, calculated as formula (Ⅰ):

[0075] Q i1 =W1×1000×a×10 -6 ×2.13 (Ⅰ);

[0076] After RH refining and decarburization (VCD), [O] is dissolved in the molten steel. It is necessary to add metallic aluminum to remove [O] in the molten steel. The reaction formula of the deoxidation process is: 2[Al]+3[O]=Al2O3, that is, 2 mol [Al] (54 g) can remove 3 mol [O] (48 g) of molten steel, forming 1 mol (Al2O3) inclusions (102 g). The weight ratio of the (Al2O3) inclusions formed in the deoxidation process to the weight of dissolved oxygen [O] in the molten steel is 102 / 48=2.13; the average oxidation degree of the molten steel after decarburization (VCD) is a, ppm, so the weight of dissolved oxygen [O] in a furnace of molten steel after RH process decarburization (VCD) is W1×1000×a×10 -6 , from which the weight Q of Al2O3 inclusions formed in the process of adding aluminum to remove oxygen from molten steel can be finally determined i1 :Q i1 =W1×1000×a×10 -6 ×2.13.

[0077] Furthermore, during the transfer of IF steel molten steel from RH refining to the tundish, [Al] in the molten steel undergoes a burning reaction, and the weight of the resulting Al2O3 inclusions is recorded as Q i2 , kg, calculated as formula (Ⅱ);

[0078] Qi2 =W1×1000×ΔAl×10 -6 ×1.89 (Ⅱ);

[0079] The sources of Al2O3 inclusions in the above process are as follows: during the transfer of IF steel molten steel from RH to the tundish, the [Al] in the molten steel undergoes a secondary oxidation reaction of oxygen in the air to form a burn reaction 2[Al]+3[O]=(Al2O3), i.e., 2 mol [Al] (54 g) is secondary oxidized to form 1 mol (Al2O3) inclusions (102 g), and the weight ratio of the (Al2O3) inclusions formed in the secondary oxidation process to the weight of aluminum burnt in the molten steel is 102 / 54=1.89; the average acid-soluble aluminum burnt from RH station to the tundish is ΔAl, in ppm, so the average acid-soluble aluminum burnt weight of 1 furnace of molten steel from RH station to the tundish is W1×1000×ΔAl×10 -6 , then the weight of Al2O3 inclusions formed by aluminum burning in this process is Q i2 :Q i2 =W1×1000×ΔAl×10 -6 ×1.89.

[0080] On the basis of the above, the total amount of Al2O3 inclusions generated by molten steel of 1 heat of IF steel is denoted as Q i , kg; it is Q i1 and Q i2 The sum of .

[0081] Based on this, a model of the adsorption amount of Al2O3 by the tundish covering agent is established, that is, in the process of IF steel continuous casting, based on the average temperature of molten steel during the tundish continuous casting process, and the contents of CaO and Al2O3 in the CaO-Al2O3 system tundish covering agent, a model of the adsorption capacity of Al2O3 inclusions by the CaO-Al2O3 system tundish covering agent is established, where the adsorption capacity is recorded as I. The specific process of establishing the model is as follows:

[0082] S31) The adsorption capacity of the CaO-Al2O3 system covering agent for Al2O3 inclusions is defined as I, and the calculation formula of I is shown in (VII):

[0083]

[0084] S32) Detect the mass percentage of CaO and Al2O3 in the initial CaO-Al2O3 system covering agent, which are respectively recorded as w 1C 、w 1A , wt%;

[0085] S33) using the initial CaO-Al2O3 system covering agent to adsorb Al2O3 inclusions, and the ratio of CaO to Al2O3 when saturation is reached is defined as the calcium-aluminum ratio K, and the calculation formula of the ratio and the temperature of the molten steel in the continuous casting process is shown in formula (VIII):

[0086] K=-8.195+0.01482×T-5.9497×10 -6 ×T 2 (VIII);

[0087] S34) After the adsorption is saturated, the weight of Al2O3 inclusions in the CaO-Al2O3 system covering agent is obtained. I Calculate according to formula (IX):

[0088] Q I =W Al2O3 -W' Al2O3 =Q s ×(w 1C / Kw 1A ) (Ⅸ);

[0089] S35) combining the calculation formula (IX) and the calculation formula (VII) to obtain the adsorption capacity I of the CaO-Al2O3 system covering agent for inclusions;

[0090] Among them, Q s is the initial weight of CaO-Al2O3 system covering agent, kg; Q I is the weight of Al2O3 inclusions when they reach saturation in the covering agent, kg;

[0091] T is the average temperature of molten steel during continuous casting, °C;

[0092] W' Al2O3 is the weight of Al2O3 in the initial CaO-Al2O3 system covering agent, kg;

[0093] W Al2O3 It is the total weight of Al2O3 when the CaO-Al2O3 system covering agent is saturated with adsorption, kg.

[0094] In the process of establishing the above model, the adsorption capacity of the CaO-Al2O3 system covering agent for Al2O3 inclusions is first defined as I, and the calculation formula of I is shown in (Ⅰ):

[0095]

[0096] Among them, Q s is the initial weight of CaO-Al2O3 system covering agent, kg; Q I It is the weight of Al2O3 inclusions when they reach saturation in the covering agent, kg.

[0097] When the CaO-Al2O3 system covering agent is saturated with adsorption, only the weight of Al2O3 inclusions increases. Therefore, the ratio of the weight of the covering agent at saturated adsorption to the weight of the initial adsorbent has a high accuracy in characterizing the adsorption amount of Al2O3 inclusions by the covering agent.

[0098] The mass percentage of CaO and Al2O3 in the initial CaO-Al2O3 coating agent is detected and recorded as w 1C 、w 1A , wt%; example, w 1C 30~60wt% 1A In order to test accurately and facilitate sampling, the weight of the initial CaO-Al2O3 system covering agent to be tested is ≥100g. s The weight of CaO contained in W' CaO =Q s × 1C , containing Al2O3 weight W' Al2O3 =Q s × 1A .

[0099] According to the present invention, the Al2O3 inclusions are adsorbed by the CaO-Al2O3 system covering agent. When saturation is reached, the ratio of CaO to Al2O3 is defined as the calcium-aluminum ratio K, which is calculated by the temperature of the molten steel during the continuous casting process as shown in formula (VIII):

[0100] K=-8.195+0.01482×T-5.9497×10 -6 ×T 2 (VIII);

[0101] The determination of the calcium-aluminum ratio K is specifically as follows: the final calcium-aluminum ratio K of the CaO-Al2O3 system covering agent with different initial calcium-aluminum ratios at different temperatures when the Al2O3 inclusions are adsorbed saturated is calculated using thermodynamic calculation software. The results are as follows: Figure 1 As shown by Figure 1 It can be seen that the calcium-aluminum ratio K when the covering agent is saturated with inclusion adsorption has nothing to do with the initial calcium-aluminum ratio, but is closely related to the temperature; and as the temperature rises, the calcium-aluminum ratio K decreases continuously when the adsorption is saturated. A quadratic fit was performed on the K value when the covering agent is saturated with inclusion adsorption at different temperatures and different initial calcium-aluminum ratios. The fitting formula is formula (VIII), and the fitting result is the solid line in the figure. The fitting result is consistent with the thermodynamic calculation result. Formula (VIII) and the covering agent use temperature can be used to quickly calculate and determine the K value. Figure 1 At the same time, the relationship between the theoretical calculated value and the fitting value was compared. The fitting value was consistent with the thermodynamic calculated value, indicating that the fitting formula can be used to accurately calculate and determine K.

[0102] In the present application, the temperature range of T is 1350-1550°C, which also represents the average temperature of the molten steel in the actual continuous casting process and can be detected during the continuous casting process.

[0103] After the CaO-Al2O3 system covering agent is saturated with Al2O3 inclusions, the mass of CaO is conserved, and the Al2O3 weight W at the time of saturated adsorption of the covering agent is obtained by using the calcium-aluminum ratio K at the time of saturated adsorption Al2O3 =W' CaO / K=Q s × 1C / K.

[0104] Since the initial CaO-Al2O3 system covering agent contains Al2O3, the above W Al2O3 It is not the weight of the adsorbed Al2O3 inclusions. The weight of Al2O3 adsorbed when the CaO-Al2O3 coating agent adsorbs Al2O3 inclusions to saturation is Q I =W Al2O3 -W' Al2O3 =Q s ×(w 1C / Kw 1A ), namely Q I It's Q s Substituting the relationship into the expression of I, we get I = w 1C / Kw 1A =w 1C / (-8.195+0.01482×T-5.9497×10 -6 ×T 2 )-w 1A The adsorption capacity of the CaO-Al2O3 system covering agent for Al2O3 inclusions is obtained, which represents the maximum weight of Al2O3 inclusions that can be adsorbed by 1 kg of the CaO-Al2O3 system covering agent.

[0105] Therefore, after obtaining the adsorption capacity of the tundish covering agent for Al2O3 inclusions and the weight of Al2O3 inclusions in one furnace of molten steel, the theoretical weight of the tundish covering agent required to adsorb and remove Al2O3 inclusions during the casting process of one furnace of molten steel is calculated, which is recorded as S1=Q i / I.

[0106] Based on the number of tundish continuous casting furnaces N, the weight S of the tundish covering agent required to remove Al2O3 inclusions in molten steel during the steel casting process is calculated: S=S1×N, where N is 8-12.

[0107] This application proposes a method for calculating the theoretical amount of CaO-Al2O3 covering agent added to the IF steel continuous casting tundish. Based on the process parameters such as IF steel RH treatment, the number of tundish continuous casting furnaces, and the composition of the tundish covering agent, the theoretical amount of covering agent added to remove Al2O3 inclusions from IF molten steel in the tundish can be accurately calculated, thereby improving the cleanliness of molten steel for automobile panels and other types of steel, reducing the inclusion degradation rate, and is expected to create an annual profit of at least 500,000 yuan. This invention can be promoted and applied in the industry.

[0108] In order to further understand the present invention, the calculation method of the theoretical addition amount of the CaO-Al2O3 series covering agent for the continuous casting tundish provided by the present invention is described in detail below in conjunction with the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0109] Example IF Calculation of the theoretical weight of the tundish covering agent required to remove Al2O3 inclusions from molten steel by continuous casting of 10 furnaces of tundish steel

[0110] (1) Based on the actual industrial production, the relevant process parameters of the IF steel process are determined, including: the average molten steel weight of the ladle W1 = 220 tons, the average oxygen activity of the molten steel after vacuum decarburization (VCD) a = 260 ppm, the average acid-soluble aluminum loss ΔAl from RH exit to tundish = 70 ppm, the number of tundish continuous casting furnaces N = 10 furnaces, and the average molten steel temperature of the tundish during continuous casting T = 1550 °C;

[0111] (2) Take 150g of the CaO-Al2O3-based middle coating agent before initial use and test to determine its CaO and Al2O3 contents, which are w 1C =58.3%, w 1A =23.1%;

[0112] (3) Based on the average temperature of molten steel during the tundish casting process and the CaO and Al2O3 contents of the tundish covering agent, the adsorption and removal capacity of the covering agent for Al2O3 inclusions I is calculated:

[0113] I=w 1C / (-8.195+0.01482×T-5.9497×10 -6 ×T 2 ) -w 1A =58.3% / (-8.195+0.01482×T-5.9497×10 -6 ×T 2 ) -w 1A =58.3% / (-8.195+0.01482×1550-5.9497×10 -6 ×1550 2 )-23.1%=0.98(E1);

[0114] In formula (1), I is defined as:

[0115]

[0116] In formula (E2), Q s is the weight of the covering agent before initial use, kg; Q I is the dissolved weight of inclusions when they reach saturation in the covering agent liquid slag, kg; I means that 1 kg of the covering agent can adsorb and remove 0.98 kg of Al2O3 inclusions;

[0117] (4) Calculate the amount of Al2O3 inclusions Q formed by adding aluminum to remove oxygen from a batch of molten steel after decarburization (VCD) in the RH process. i1 :

[0118] Q i1 =W1×1000×a×10 -6 ×2.13=220×1000×260×10 -6 × 2.13 = 121.8 kg (E3);

[0119] Where, is the amount of Al2O3 inclusions formed in the process of adding aluminum to remove oxygen from molten steel, kg;

[0120] (5) Calculate the amount of Al2O3 inclusions Q formed by the average acid-soluble aluminum burning from the exit of 1 furnace of molten steel RH to the tundish i2 :

[0121] Q i2 =W1×1000×ΔAl×10 -6 ×1.89=220×1000×70×10 -6 × 1.89 = 29.1 kg (E4);

[0122] In the formula, Q i2 The weight of Al2O3 inclusions formed by secondary oxidation and burning of acid-soluble aluminum in molten steel during the process from RH exit to continuous casting tundish, kg;

[0123] (6) The Al2O3 inclusions in the IF steel in the continuous casting tundish come from the Al2O3 inclusions generated by the aluminum deoxidation of the steel after RH decarburization (VCD), and the Al2O3 inclusions formed by the secondary oxidation and burning of the acid-soluble aluminum in the steel during the process from RH to the continuous casting tundish. The total amount of Al2O3 inclusions generated in the production of one furnace of steel is Q i for:

[0124] Q i =Q i1 +Q i2 =121.8kg+29.1kg=150.9kg (E5);

[0125] In the formula, Q i The total amount of Al2O3 inclusions generated in one furnace of molten steel, kg;

[0126] (7) Calculate the weight of the tundish covering agent S1 required to adsorb and remove Al2O3 inclusions in the tundish during the casting process of molten steel in one furnace:

[0127] S1=Q i / I=150.9kg / 0.98=154.0kg (E6);

[0128] Where S1 is the theoretical weight of the middle coating agent required to adsorb the Al2O3 inclusions contained in one furnace of molten steel during the casting process, kg;

[0129] (8) Based on the number of tundish continuous casting furnaces N, determine the weight S of the tundish covering agent required to remove Al2O3 inclusions in the molten steel during the steel casting process:

[0130] S = S1 × N = 154.0 kg / furnace × 10 furnaces = 1540.0 kg (E7);

[0131] That is, to adsorb Al2O3 inclusions in molten steel, theoretically 1540.0 kg of middle bag covering agent is needed.

[0132] In order to verify the accuracy of the calculation method of the present application, three tundishes were tested continuously. Each tundish had 10 continuous castings of IF steel and the working conditions were the same: the average molten steel weight of the large ladle W1 = 220 tons, the average oxygen activity of the molten steel after vacuum decarburization (VCD) a = 260ppm, the average acid-soluble aluminum loss ΔAl from RH station to tundish = 70ppm, the number of continuous casting furnaces for the tundish N = 10 furnaces, and the average temperature of the molten steel in the tundish during continuous casting T = 1550℃; the same composition of covering agents (CaO and Al2O3 contents were w 1C =58.3%, w 1A =23.1%), wherein 900kg of covering agent was added to the first tundish (comparison), 1200kg of covering agent was added to the second tundish (comparison), and 1540kg of covering agent was added to the third tundish (test). During the test, the covering agent of each tundish was taken for testing to determine the change of calcium-aluminum ratio (CaO / Al2O3), such as Figure 2 shown by Figure 2It can be seen that as the casting process proceeds, the Al2O3 inclusions in the molten steel continuously float up into the tundish covering agent, resulting in a continuous decrease in the calcium-aluminum ratio (CaO / Al2O3) in the covering agent. Among them, the calcium-aluminum ratio of the first tundish and the second tundish decreased to 0.48 in the 7th and 9th furnaces, respectively, and then stopped decreasing. The calcium-aluminum ratio of the tundish covering agent of the third tundish did not decrease to 0.48 until the last furnace (the 10th furnace of the tundish) was cast. It can be seen from steps S31 to S35 in the calculation method of the present application that when the tundish covering agent reaches saturation in adsorption of Al2O3 inclusions, Al2O3 inclusions will be difficult to dissolve into the tundish covering agent. At this time, the calcium-aluminum ratio of the covering agent will reach a stable value, and this value is only related to the temperature, and has nothing to do with the initial calcium-aluminum ratio of the covering agent. Based on the calculation formula (VIII), it can be calculated that under the condition of the middle package temperature of 1550°C, when the adsorption of Al2O3 inclusions by the middle package covering agent reaches saturation, the calcium-aluminum ratio K=0.48, which coincides with the final calcium-aluminum ratio of 0.48 of the three middle packages. In the test, the calcium-aluminum ratio of the first package and the second package in the 7th and 9th furnaces dropped to 0.48 and then stopped decreasing, indicating that the amount of covering agent added was insufficient, causing the covering agent to reach saturation state for Al2O3 inclusions in advance. From the third package to the last furnace of the middle package (the 10th furnace), the calcium-aluminum ratio of the middle package covering agent just reached 0.48 when the adsorption was saturated, indicating that the amount of covering agent added in the third package just met the adsorption requirements for Al2O3 inclusions, thereby proving the accuracy of the calculation method of the present application.

[0133] Furthermore, in order to verify the accuracy of the above calculation method, w 1C =58.3%, w 1A =23.1% calcium aluminum-based tundish covering agent was tested. The tundish was continuously cast for 10 batches. 160 kg of the calcium aluminum-based tundish covering agent was added to the tundish casting area. The temperature of the tundish covering agent was 1550°C during the continuous casting process. Samples of the tundish covering agent were taken from the casting area for each batch during the casting process to test the composition. The change of the calcium aluminum ratio in the casting area during the casting process was obtained as follows: Figure 3 As shown; with the increase in casting heats, Al2O3 in the molten steel continuously floats up into the tundish covering agent, resulting in a continuous decrease in the calcium-aluminum ratio in the covering agent; when the tundish is cast to the 7th and subsequent heats, the calcium-aluminum ratio is basically maintained at 0.47 and no longer decreases, indicating that the tundish covering agent has reached saturation in adsorbing Al2O3 inclusions; from step (3) of the embodiment, it can be seen that at 1550°C, K=0.48 determined by the formula calculation is in good agreement with the actual measured value of 0.47 during the test process, which verifies the accuracy of the K value calculation formula proposed in this application. Substituting the measured K value of 0.47 into formula (Ⅳ) can finally determine the measured inclusion adsorption capacity I=w 1C / Kw 1A=58.3% / 0.47-23.1%=1.00; the measured value 1.00 is in good agreement with the calculated value 0.98, thus verifying the reliability of the calculation method of the present application.

[0134] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0135] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calculating the theoretical addition amount of a CaO-Al2O3-based covering agent for a continuous casting tundish, comprising the following steps: S1) RH refining is performed on the molten steel of IF steel. After decarburization, aluminum is added to remove [O] in the molten steel. The weight of the obtained Al2O3 inclusion is recorded as Q i1 , kg, calculated as formula (Ⅰ): Q i1 =W1×1000×a×10 -6 ×2.13 (Ⅰ); S2) The molten steel in step S1) is transferred to the tundish. During this process, the [Al] in the molten steel undergoes a burning reaction, and the weight of the Al2O3 inclusion obtained is recorded as Q i2 , kg, calculated as formula (Ⅱ); Q i2 =W1×1000×ΔAl×10 -6 ×1.89 (Ⅱ); The total amount of Al2O3 inclusions generated in one batch of IF steel is denoted as Q i , kg, calculated as (III); Q i =Q i1 +Q i2 (Ⅲ); S3) During the continuous casting of IF steel, based on the average temperature of molten steel during the continuous casting process and the contents of CaO and Al2O3 in the CaO-Al2O3 system tundish covering agent, the adsorption capacity of the CaO-Al2O3 system tundish covering agent for Al2O3 inclusions was calculated using formula (IV), denoted as I: I=w 1C / (-8.195+0.01482×T-5.9497×10 -6 ×T 2 )-w 1A (Ⅳ); S4) Calculate the weight of the tundish covering agent required for one batch of molten steel to adsorb Al2O3 inclusions, recorded as S1, kg, and the calculation formula is as shown in formula (V); S1=Q i / I (Ⅴ); For each tundish continuous casting heat N, calculate the weight of the tundish covering agent required to remove Al2O3 inclusions in molten steel, denoted as S, kg, using the following formula (VI): S = S1 × N (VI); Where, W1 is the average weight of molten steel in the ladle, t; a is the average oxygen activity of molten steel after decarburization, ppm; ΔAl is the average acid-soluble aluminum loss from RH refining station to tundish; ppm; w 1C is the CaO content in the coating agent of the CaO-Al2O3 system, wt%; w 1A is the content of Al2O3 in the coating agent of CaO-Al2O3 system, wt%; T is the average temperature of molten steel in the tundish, ℃.

2. The calculation method according to claim 1, characterized in that: The adsorption capacity I is obtained specifically as follows: S31) The adsorption capacity of the CaO-Al2O3 system covering agent for Al2O3 inclusions is defined as I, and the calculation formula of I is shown in (VII): S32) Detect the mass percentage of CaO and Al2O3 in the initial CaO-Al2O3 system covering agent, which are respectively recorded as w 1C 、w 1A , wt%; S33) using the initial CaO-Al2O3 system covering agent to adsorb Al2O3 inclusions, and the ratio of CaO to Al2O3 when saturation is reached is defined as the calcium-aluminum ratio K, and the calculation formula of the ratio and the temperature of the molten steel in the continuous casting process is shown in formula (VIII): K=-8.195+0.01482×T-5.9497×10 -6 ×T 2 (Ⅷ); S34) After the adsorption is saturated, the weight of Al2O3 inclusions in the CaO-Al2O3 system covering agent is obtained. I Calculate according to formula (IX): Q I =W Al2O3 -W’ Al2O3 =Q s ×(w 1C / K-w 1A ) (Ⅸ); S35) combining the calculation formula (IX) and the calculation formula (VII) to obtain the adsorption capacity I of the CaO-Al2O3 system covering agent for inclusions; Among them, Q s is the initial weight of CaO-Al2O3 system covering agent, kg; Q I is the weight of Al2O3 inclusions when they reach saturation in the covering agent, kg; T is the average temperature of molten steel during continuous casting, °C; W' Al2O3 is the weight of Al2O3 in the initial CaO-Al2O3 system covering agent, kg; W Al2O3 It is the total weight of Al2O3 when the CaO-Al2O3 system covering agent is saturated with adsorption, kg.

3. The calculation method according to claim 2, characterized in that: The formula (VIII) is obtained by the following method: The calcium-aluminum ratios of different initial CaO-Al2O3 system covering agents at different temperatures when Al2O3 inclusions are adsorbed saturated are calculated using thermodynamic calculation software to obtain a curve of the calcium-aluminum ratio and temperature when the covering agent is adsorbed saturated; the calcium-aluminum ratios of the initial CaO-Al2O3 system covering agents are different; The temperature and calcium-aluminum ratio when the covering agent is adsorbed to saturation are fitted.

4. The calculation method according to claim 2, characterized in that: The detected amount of the initial CaO-Al2O3 system covering agent is ≥100g.

5. The calculation method according to claim 2, characterized in that: K is 0.3~0.

6.

6. The calculation method according to claim 2, characterized in that: Before obtaining the formula (IX), the following is also included: The CaO-Al2O3 system covering agent is adsorbed to saturation, and the total weight of Al2O3 in the saturated covering agent is W Al2O3 The calculation is carried out according to the following formula: W Al2O3 =W’ CaO / K=Q s ×w 1C / K。 7. The calculation method according to claim 1, characterized in that: T is 1350~1550℃.

8. The calculation method according to claim 1, characterized in that: The heat number N is 8-12.

9. Application of the calculation method according to any one of claims 1 to 8 in the design of coating agents in the CaO-Al2O3 system.

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