Method for accurately controlling titanium content in titanium reinforced steel

Abstract

The invention discloses a method for accurately controlling the titanium content in titanium reinforced steel, and belongs to the technical field of steel smelting. In order to solve the problems in the prior art, realize accurate control on the titanium content in the titanium-reinforced steel and improve the titanium yield, the invention provides a method for accurately controlling the titanium content in the titanium-reinforced steel, which comprises the procedures of converter-small platform-electric heating-continuous casting. According to the method, the slag composition is accurately controlled, meanwhile, the Als content in the molten steel is controlled to be 0.033%-0.05% before titanium alloying, the SiO2 content in the molten steel is controlled, meanwhile, the continuous casting process is controlled, the titanium yield stably reaches 85% or above, and titanium component precision control with the error being + / -0.004% is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting, and in particular relates to a method for accurately controlling the titanium content in titanium-reinforced steel. Background Art

[0002] While Nb and V are relatively scarce in the Earth's crust, Ti is relatively abundant. Furthermore, Ti exhibits excellent grain refinement and precipitation strengthening properties. Consequently, Ti-containing microalloyed steels are gaining increasing attention in the industry. With the continuous improvement of metallurgical, rolling, and cooling process control, the challenges previously encountered in the production of titanium microalloyed steels have been gradually addressed. Titanium microalloying technology has become increasingly important in the development of high-strength steels. To reduce costs, the development of high-strength steels that utilize Ti instead of Nb and V has become a research hotspot for steelmakers and research institutions.

[0003] The order of elemental deoxidizing capacity in molten steel at atmospheric pressure is: [Ca] > [Al] > [Ti] > [Si] > [C] > [Cr] > [Mn]. This indicates that titanium is highly reactive, with an affinity for oxygen second only to aluminum. This means it is easily oxidized during refining and continuous casting, resulting in unstable yields and wide fluctuations in composition. Therefore, the main problem with titanium-added steel is unstable strength. This is primarily due to titanium's active chemical properties, which easily combines with elements like [O], [N], and [S] in the steel to form large titanium-containing phases. These phases neither refine the grains nor provide precipitation strengthening. This ultimately results in an unstable effective titanium content in the TiC particles that produce the most significant precipitation strengthening effect. Consequently, fluctuations in the [O], [N], and [S] content in the steel can lead to fluctuations in the strength of the steel plate.

[0004] CN202410288252.2 discloses a method for titanium alloying of molten steel: by respectively performing front slag treatment, molten steel deoxidation treatment, molten steel preliminary alloying treatment, and rear slag treatment at different stages of converter tapping, the organizational structure and chemical composition of the molten steel are effectively improved, and the quality and performance of the molten steel are jointly improved. In the argon station stage, aluminum wire deoxidation treatment is first performed to reduce the oxygen content in the molten steel, and then titanium alloying is performed by feeding titanium-iron cored wire to the argon station molten steel, accompanied by argon stirring, thereby increasing the residence time of titanium element in the molten steel and achieving good mixing, thereby significantly improving the yield of titanium element. In addition, by feeding the wire at the argon station, the subsequent refining process can be eliminated, the process flow can be simplified, and the production cost can be reduced, thus solving the problems of low titanium yield and high production cost caused by titanium alloying in the refining stage. However, this method has the following problems: (1) The titanium yield is low, only in the range of 70-80%; (2) It uses titanium cored wire for titanium alloying, which has poor operability; (3) This method does not mention titanium precision control during implementation, but its accuracy is poor when deduced based on the yield fluctuation range.

[0005] CN202311434823.0 discloses a method for improving the recovery rate of Ti, a component of straight-up steel grades: it includes a converter smelting process, an argon station refining process, and a casting process; when the S content in the molten iron is ≤0.015%, the amount of iron-containing slag added is controlled to be ≤15kg / ton of steel; when the S content in the molten iron is 0.015-0.020%, the amount of iron-containing slag added is controlled to be ≤12kg / ton of steel; when the S content in the molten iron is 0.020-0.025%, the amount of iron-containing slag added is controlled to be ≤9kg / ton of steel; when the S content in the molten iron is ≥0.025%, no iron-containing slag is added; the S content in the iron-containing slag is 0.6%; ferrotitanium is added 3 minutes before soft blowing, Als before addition is ≥0.01%, the ferrotitanium is added above the argon flower, Ti is matched according to the internal control upper limit, and the recovery rate is converted to 75%. However, the titanium yield of this method is relatively low, and when converted to 75% based on the yield, it is difficult to achieve precise control of titanium.

[0006] CN202110120756.X discloses a process for improving titanium alloying in steel: slag blocking during the converter tapping process; entering the CAS refining furnace after adding deoxidizer and modifier, titanium alloying is performed by feeding titanium iron wire during the refining process, and argon blowing and stirring are performed at a medium intensity; or entering the LF refining furnace, titanium alloying is performed by adding titanium iron alloy during the refining process, and argon blowing and stirring are performed at a medium intensity; soft argon blowing is used for calcium treatment, and after the soft argon blowing lasts for at least a first set time, a molten steel insulation agent is added and the steel is discharged. This method optimizes the process of feeding titanium iron wire or adding titanium iron alloy during the refining process, so that titanium alloying is performed in advance before soft blowing, and maintains argon blowing and stirring of appropriate intensity after titanium alloying, thereby promoting the melting and homogenization of titanium alloy, stabilizing the titanium yield, and reducing the risk of re-judgment of titanium-containing steel grades due to titanium out of order. However, this method also uses a cored wire method, which is relatively costly and has poor operability; its titanium yield is also relatively low, only in the range of 70-80%; and there is no mention of precise control of titanium.

[0007] CN201510243689.5 discloses a method for adding ferrotitanium during steelmaking: the key is to control the oxygen content in the refined molten steel between 0 and 20 ppm and the aluminum content by weight between 0.015% and 0.050%. Before vacuum treatment, aluminum wire is fed until the aluminum content in the molten steel reaches 0.050% to 0.080% by weight. Ferrotitanium is then added, ensuring that the interval between the addition of aluminum wire and the addition of ferrotitanium is 2 to 8 minutes. Vacuum treatment is then performed, with argon blowing and stirring during the process. The preconditions for titanium alloying in this method are primarily aluminum content control, and titanium alloying is performed at RH, which is too simple. Furthermore, the titanium yield of this method is over 75%, which is still relatively low, and precise titanium control is not mentioned.

[0008] It can be seen that it is difficult to achieve precise control of the titanium content in titanium-reinforced steel with existing technologies, and it is also difficult to achieve a high titanium yield. Therefore, it is urgent to develop a method for precisely controlling the titanium content in titanium-reinforced steel. Summary of the Invention

[0009] To solve the problems in the prior art, achieve precise control of the titanium content in titanium-reinforced steel, and improve titanium yield, the present invention provides a method for precisely controlling the titanium content in titanium-reinforced steel. The process is a converter (BOF) - small platform - electric heating (LF) - continuous casting (CC) process, specifically comprising the following steps:

[0010] A. Reblowing of converter is prohibited, and the final oxygen content is ≤0.08%;

[0011] B. Add high-aluminum ferroalloy to deoxidize the steel, and adjust the oxygen on the small platform after the furnace. The outgoing a[O] should be ≤20ppm;

[0012] C. Add lime 4-7kg / t steel and aluminum shot 0.5-2kg / t steel into the LF station for rapid slagging, so that after slagging, the steel slag (FeO+MnO) is ≤2.0%, (CaO / Al2O3): 1.5-2.2, (CaO / SiO2)>5;

[0013] D. Before titanium alloying, control the Als content in molten steel to 0.033-0.05%;

[0014] E. Use low nitrogen 70 titanium iron for titanium alloying, titanium alloying amount = target value + empirical burn-off value; wherein, the target value is 0.03wt%≤target value≤0.20wt%; the empirical burn-off value is: when 0.03wt%≤target value<0.08wt%, the empirical burn-off value is 0.003wt%; when 0.08wt%≤target value≤0.12wt%, the empirical burn-off value is 0.005wt%; when 0.12wt%<target value≤0.20wt%, the empirical burn-off value is 0.007wt%;

[0015] F. Reheating is prohibited after titanium alloying;

[0016] G. Calcium aluminate-based tundish covering agent is used in continuous casting, with the addition amount being 0.5-0.7 kg / t steel;

[0017] H. Monitoring of slag discharge from ladle, the remaining molten steel in the ladle should be ≥5t;

[0018] I. The argon blowing rate of the stopper rod is controlled at 3L / min to 5L / min, and the argon blowing rate of the long nozzle is controlled at 50L / min to 60L / min. After continuous casting and rolling, titanium-reinforced steel is obtained.

[0019] Among them, in the above method for accurately controlling the titanium content in titanium-reinforced steel, in step B, the aluminum content of the high-aluminum aluminum iron is 75-85wt%, the iron content is 15-25wt%, and the rest is irremovable trace impurities.

[0020] Among them, in the above method for accurately controlling the titanium content in titanium-reinforced steel, in step B, the amount of high-aluminum aluminum iron added is 2 to 2.5 kg / t steel.

[0021] Among them, in the above-mentioned method for accurately controlling the titanium content in titanium-reinforced steel, in step B, if the high-aluminum aluminum iron is deoxidized, the outgoing a[O] is greater than 20ppm, and the oxygen is determined on the small platform behind the furnace, and aluminum wire is fed according to the oxygen content to make the outgoing a[O] ≤ 20ppm.

[0022] In the above method for precisely controlling the titanium content in titanium-reinforced steel, in step D, when the Als content is lower than 0.033%, aluminum wire is used to supplement the content, and after feeding the aluminum wire, argon is soft-blown for ≥3 minutes before titanium alloying is performed.

[0023] Wherein, in the above method for accurately controlling the titanium content in titanium-reinforced steel, in step D, the amount of low-nitrogen 70 ferrotitanium added is 0.5-3.0 kg / t steel.

[0024] Among them, in the above-mentioned method for accurately controlling the titanium content in titanium-reinforced steel, in step G, the calcium aluminate-based coating agent contains the following components in mass percentage: CaO 40-50%, P≤0.2%, S≤0.2%, Al2O3 25-35%, Na2O32-4%, MgO≤10%, FeO≤2.0%, SiO2≤8.0%, N≤0.5%, H2O≤2.0%; and the CaO / Al2O3 ratio is 1.6-2.2, the main raw materials CaO and Al2O3 are pre-melted calcium aluminate (the use of a partial pre-melted material + partial raw material process is strictly prohibited), the ignition loss at 900°C is ≤10%, and the sodium shall not be configured with industrial NaCl.

[0025] Beneficial effects of the present invention:

[0026] The present invention deeply analyzes the main factors that affect the titanium yield and the precise control of titanium, accurately controls the slag composition, and ensures that after slag making, the steel slag (FeO+MnO) is ≤2.0%, (CaO / Al2O3): 1.5-2.2, and (CaO / SiO2)>5. At the same time, before titanium alloying, the Als content in molten steel is controlled to 0.033-0.05% to ensure that the molten steel is in a low oxygen state and avoid burning aluminum and titanium. The continuous casting process is controlled to improve its protective casting effect, and ultimately the titanium yield is stably achieved at more than 85%, and the titanium component precision control with an error of ±0.004% is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1This is the Gibbs free energy spectrum of titanium and aluminum oxidation at 1873K.

[0028] Figure 2 This is the relationship between Als in molten steel and titanium yield. DETAILED DESCRIPTION

[0029] Specifically, a method for accurately controlling the titanium content in titanium-reinforced steel includes a process of converter (BOF) - small platform - electric heating (LF) - continuous casting (CC), specifically comprising the following steps:

[0030] A. Reblowing of converter is prohibited, and the final oxygen content is ≤0.08%;

[0031] B. Add high-aluminum ferroalloy to deoxidize the steel, and adjust the oxygen on the small platform after the furnace. The outgoing a[O] should be ≤20ppm;

[0032] C. Add lime 4-7kg / t steel and aluminum shot 0.5-2kg / t steel into the LF station for rapid slagging, so that after slagging, the steel slag (FeO+MnO) is ≤2.0%, (CaO / Al2O3): 1.5-2.2, (CaO / SiO2)>5;

[0033] D. Before titanium alloying, control the Als content in molten steel to 0.033-0.05%;

[0034] E. Use low nitrogen 70 titanium iron for titanium alloying, titanium alloying amount = target value + empirical burn-off value; wherein, the target value is 0.03wt%≤target value 0.20wt%; the empirical burn-off value is: when 0.03wt%≤target value<0.08wt%, the empirical burn-off value is 0.003wt%; when 0.08wt%≤target value≤0.12wt%, the empirical burn-off value is 0.005wt%; when 0.12wt%<target value≤0.20wt%, the empirical burn-off value is 0.007wt%;

[0035] F. Reheating is prohibited after titanium alloying;

[0036] G. Calcium aluminate-based tundish covering agent is used in continuous casting, with the addition amount being 0.5-0.7 kg / t steel;

[0037] H. Monitoring of slag discharge from ladle, the remaining molten steel in the ladle should be ≥5t;

[0038] I. The argon blowing rate of the stopper rod is controlled at 3L / min to 5L / min, and the argon blowing rate of the long nozzle is controlled at 50L / min to 60L / min. After continuous casting and rolling, titanium-reinforced steel is obtained.

[0039] In step B of the present invention, the high-aluminum aluminum iron has an aluminum content of 75-85wt%, an iron content of 15-25wt%, and the rest is irremovable trace impurities.

[0040] In step B of the present invention, the addition amount of the high-aluminum ferroaluminum is 2 to 2.5 kg / t steel.

[0041] In step B of the present invention, if the outlet a[O] is greater than 20 ppm after deoxidation of the high-aluminum ferroaluminum, aluminum wire is fed according to the oxygen content after oxygen is determined on the small platform behind the furnace to ensure that the outlet a[O] is less than or equal to 20 ppm.

[0042] The inventors have found that the main factors affecting titanium yield and precise control of titanium are slag composition, molten steel oxygen content, and slag composition.

[0043] Among them, in the control of molten steel oxygen content, the oxidation thermodynamic reaction of [Ti] and [Al] in the molten steel is as follows:

[0044] 2[Ti]+3[O]=Ti2O3(s), lgK=56060 / T-18.08 (1);

[0045] 2[Al]+3[O]=Al2O3(s), lgK=64000 / T-20.57 (2).

[0046] From equations (1) and (2), we can get the free energy comparison of Ti2O3 and Al2O3, as shown in Figure 1 .

[0047] Depend on Figure 1 It can be seen that under the same [Ti] and [Al] content conditions, the formation free energy of Ti2O3 is always greater than the formation free energy of Al2O3, indicating that the affinity between [Al] and [O] is stronger than the affinity between [Ti] and [O]. Therefore, when [Al] is contained in the molten steel, [Al] reacts preferentially with [O]. In order to reduce the consumption of [Ti] due to deoxidation and improve the yield of [Ti], it is necessary to ensure that there is a certain [Al] content in the molten steel. In addition, when the [O] content decreases sharply, [Al] in the steel may react with [Ti] oxide, reducing [Ti] to form Al2O3. The reaction equation is shown in Equation (3), which can further improve the yield of [Ti].

[0048] 2[Al]+Ti2O3(s)=2[Ti]+Al2O3(s), ΔG 0 =-356072+137.7T, J / mol -1 (3).

[0049] Figure 2 The influence of Als content in molten steel on titanium yield. Figure 2As can be seen, as the Als content in the molten steel increases, the [Ti] yield also increases accordingly. When the Als content in the molten steel is above 0.033%, the [Ti] yield is generally above 85%. However, the current price of aluminum has exceeded 20,000 yuan / ton. To control costs, too high an aluminum content will lead to increased burnout, which will produce more Al2O3 inclusions and contaminate the molten steel. Therefore, the present invention implements cost control by controlling the Als content in the molten steel to 0.033-0.05% before titanium alloying in step D. In step D, when the Als content is less than 0.033%, aluminum wire is added to supplement the content. After feeding the aluminum wire, soft argon blowing is performed for ≥3 minutes before titanium alloying.

[0050] In step D of the present invention, the addition amount of the low-nitrogen 70 ferrotitanium is 0.5-3.0 kg / t steel.

[0051] In slag composition control, in addition to [O] in the molten steel, [Ti] and [Al] also react with FeO, MnO, and SiO2 in the slag in equations (4) to (9), resulting in secondary oxidation of [Ti] and [Al], reducing the yield of [Ti]. At the same time, the deoxidation products entering the molten steel will also cause deterioration of steel quality. Equations (4) to (9) are as follows:

[0052] 2[Al]+3(FeO)=Al2O3(s)+3[Fe] (4);

[0053] 2[Al]+3(MnO)=Al2O3(s)+3[Mn] (5);

[0054] 4[Al]+3(SiO2)=2Al2O3(s)+3[Si] (6);

[0055] 2[Ti]+3(FeO)=Ti2O3(s)+3[Fe] (7);

[0056] 2[Ti]+3(MnO)=Ti2O3(s)+3[Mn] (8);

[0057] 4[Ti]+3(SiO2)=2Ti2O3(s)+3[Si] (9).

[0058] Based on the above analysis, to ensure a high [Ti] yield, the slag's oxidizing properties (FeO + MnO) and SiO2 content must be reduced during the refining process. Furthermore, to improve the slag's ability to adsorb Al2O3 inclusions, the slag's C / A (CaO / Al2O3) and R (CaO / SiO2) ratios must also be controlled. (FeO + MnO) represents oxidizing properties; a lower ratio indicates lower oxidizing properties, taking into account cost considerations. R (CaO / SiO2) also, to a certain extent, controls the SiO2 content. C / A (CaO / Al2O3) primarily describes inclusion adsorption and slag fluidity, with a (CaO / Al2O3) range of 1.5-2.2 indicating excellent fluidity and inclusion adsorption. Taking all these factors into consideration, in Step C of the present invention, the slag's (FeO + MnO) after slag formation is maintained at ≤2.0%, (CaO / Al2O3) 1.5-2.2, and (CaO / SiO2) >5.

[0059] In step G of the present invention, the calcium aluminate-based coating agent contains the following components in percentage by mass: CaO 40-50%, P≤0.2%, S≤0.2%, Al2O3 25-35%, Na2O 2-4%, MgO≤10%, FeO≤2.0%, SiO2≤8.0%, N≤0.5%, and H2O≤2.0%; and the CaO / Al2O3 ratio is 1.6-2.2. The main raw materials CaO and Al2O3 are pre-melted calcium aluminate (the use of a partial pre-melted material + partial raw material process is strictly prohibited), the ignition loss at 900°C is ≤10%, and the sodium shall not be configured with industrial NaCl.

[0060] During protective casting, factors such as slag encapsulation, shroud sealing, stopper rods, and argon blowing in the shroud all significantly impact titanium secondary oxidation during continuous casting, requiring careful consideration. This invention controls the SiO2 content in the molten steel before continuous casting to prevent aluminum and titanium burns. This minimizes aluminum and titanium burnout while ensuring proper spreadability, enhancing protective casting effectiveness.

[0061] The present invention is further described in detail below through examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0062] Example 1

[0063] Titanium content requirement for steel grades: 0.060~0.070%.

[0064] Specific steps:

[0065] (1) Nominal 120t converter, converter not reblown, end point oxygen 0.072%;

[0066] (2) High-aluminum aluminum iron is added for deoxidation (the addition amount is 2.1kg / t steel) (the aluminum content is 84%, the iron content is 15.8%, and the rest are trace impurities that cannot be removed). After the oxygen is determined on the small platform behind the furnace, the aluminum wire is fed according to the oxygen content, and the a[O] content out of the station is 18ppm;

[0067] (3) LF enters the station and adds 4.2kg / t steel of lime and 1.8kg / t steel of aluminum shot for rapid slagging, so that after slagging, the steel slag (FeO+MnO): 1.3%, (CaO / Al2O3): 1.8, (CaO / SiO2): 6;

[0068] (4) The Als content in the steel before titanium alloying was 0.033%, and no aluminum was added;

[0069] (5) Titanium alloying amount = target value (0.065%) + empirical burn-off value (0.003%), totaling 0.068%; low nitrogen 70 titanium iron is used for titanium alloying, and the addition amount is 0.78 kg / t steel;

[0070] (6) No reheating after titanium alloying;

[0071] (7) Calcium aluminate-based coating agent is used in continuous casting. Its technical indicators are shown in Table 1, and the addition amount is controlled at 0.52 kg per ton of steel;

[0072] Table 1 Technical indicators of the covering agent in the package / wt%

[0073]

[0074] (8) Monitoring of slag discharge from ladle, the remaining molten steel in the ladle is 5.2t;

[0075] (9) The argon blowing rate of the stopper rod is controlled at 3.2L / min, and the argon blowing rate of the long nozzle is controlled at 53L / min. After continuous casting and rolling, the finished titanium-reinforced steel is obtained.

[0076] After testing, the finished product contains 0.062% to 0.068% titanium, and the titanium yield is 86 to 88%, achieving the target value of ±0.003% titanium component precision control.

[0077] Example 2

[0078] Titanium content requirement for steel grades: 0.08-0.12%.

[0079] Specific steps:

[0080] (1) Nominal 120t converter, converter not reblown, end point oxygen 0.063%;

[0081] (2) High-aluminum aluminum iron is added for deoxidation (the addition amount is 2.4kg / t steel) (the aluminum content is 78%, the iron content is 21.7%, and the rest are trace impurities that cannot be removed). After the oxygen is determined on the small platform behind the furnace, the aluminum wire is fed according to the oxygen content, and the a[O] out of the station is 14ppm;

[0082] (3) LF enters the station and adds 5.7kg / t steel of lime and 1.2kg / t steel of aluminum shot for rapid slagging, so that after slagging, the steel slag (FeO+MnO): 1.5%, (CaO / Al2O3): 1.8, (CaO / SiO2): 9;

[0083] (4) The Als content in the steel before titanium alloying is 0.028%, and the content is increased to 0.035% by aluminum;

[0084] (5) After feeding the wire, soft blowing for 3.2 minutes is carried out for titanium alloying. The titanium alloying amount = target value (0.10%) + empirical burn-off value (0.005%), totaling 0.105%. Low nitrogen 70 titanium iron is used for titanium alloying, and the addition amount is 1.24 kg / t steel.

[0085] (6) No reheating after titanium alloying;

[0086] (7) Calcium aluminate-based coating agent is used in continuous casting. Its technical indicators are shown in Table 2, and the addition amount is controlled at 0.61 kg per ton of steel;

[0087] Table 2 Technical indicators of the covering agent in the package / wt%

[0088]

[0089] (8) Monitoring of slag discharge from ladle, the remaining molten steel in the ladle is 5.1t;

[0090] (9) The argon blowing rate of the stopper rod is controlled at 3.3L / min, and the argon blowing rate of the long nozzle is controlled at 55L / min. After continuous casting and rolling, the finished titanium-reinforced steel is obtained.

[0091] After testing, the finished product titanium content was 0.097% to 0.102%, and the titanium yield was 85% to 87%, achieving the titanium component precision control of the target value of ±0.003%.

[0092] Example 3

[0093] Titanium content requirement for steel: 0.15~0.20%.

[0094] Specific steps:

[0095] (1) Nominal 120t converter, converter not reblown, end point oxygen 0.053%;

[0096] (2) High-aluminum aluminum iron is added for deoxidation (the addition amount is 2kg / t steel) (the aluminum content is 76%, the iron content is 23.4%, and the rest are trace impurities that cannot be removed). After the oxygen is determined on the small platform behind the furnace, the aluminum wire is fed according to the oxygen content, and the outgoing a[O] is 9ppm;

[0097] (3) LF enters the station and adds 6.7kg / t steel of lime and 0.7kg / t steel of aluminum shot for rapid slagging, so that after slagging, the steel slag (FeO+MnO): 1.2%, (CaO / Al2O3): 2.2, (CaO / SiO2): 11;

[0098] (4) The Als content in the steel before titanium alloying was 0.034%, and no aluminum was added;

[0099] (5) Titanium alloying amount = target value (0.175%) + empirical burn-off value (0.007%), totaling 0.182%; low nitrogen 70 titanium iron is used for titanium alloying, and the addition amount is 2.06 kg / t steel;

[0100] (6) No reheating after titanium alloying;

[0101] (7) Calcium aluminate-based coating agent is used in continuous casting. Its technical indicators are shown in Table 3, and the addition amount is controlled at 0.61 kg per ton of steel;

[0102] Table 3 Technical indicators of the covering agent in the package / wt%

[0103]

[0104] (8) Monitoring of slag discharge from ladle, the remaining molten steel in the ladle is 5.5t;

[0105] (9) The argon blowing rate of the stopper rod is controlled at 4.3L / min, and the argon blowing rate of the long nozzle is controlled at 57L / min. After continuous casting and rolling, the finished titanium-reinforced steel is obtained.

[0106] After testing, the finished product contained 0.173% to 0.179% titanium, and the titanium yield was 85% to 86%, achieving the target value of ±0.004% titanium component precision control.

Claims

1. A method for accurately controlling the titanium content in titanium-reinforced steel, characterized in that: The process is converter-small platform-electric heating-continuous casting, which specifically includes the following steps: A. Reblowing of converter is prohibited, and the final oxygen content is ≤0.08%; B. Add high aluminum iron to deoxidize the steel, and determine the oxygen on the small platform behind the furnace, and the outgoing a[O]≤20ppm; C. Add lime 4-7kg / t steel and aluminum shot 0.5-2kg / t steel into the LF station for rapid slag making, so that after slag making, the steel slag (FeO+MnO) is ≤2.0%, (CaO / Al2O3): 1.5-2.2, (CaO / SiO2)>5; D. Before titanium alloying, the Als content in molten steel should be controlled at 0.033-0.05%; E. Use low nitrogen 70 titanium iron for titanium alloying, titanium alloying titanium content = target value + empirical burn-off value; wherein, the target value is 0.03wt%≤target value≤0.20wt%; the empirical burn-off value is: when 0.03wt%≤target value<0.08wt%, the empirical burn-off value is 0.003wt%; when 0.08wt%≤target value≤0.12wt%, the empirical burn-off value is 0.005wt%; when 0.12wt%<target value≤0.20wt%, the empirical burn-off value is 0.007wt%; F. Reheating is prohibited after titanium alloying; G. Calcium aluminate-based coating agent is used in continuous casting, and the addition amount is 0.5-0.7 kg / t steel; H. Monitoring of slag discharge from ladle, the remaining molten steel in the ladle should be ≥5t; I. The argon blowing of the stopper rod is controlled at 3L / min-5L / min, and the argon blowing of the long nozzle is controlled at 50L / min-60L / min. After continuous casting and rolling, titanium-reinforced steel is obtained.

2. The method for accurately controlling the titanium content in titanium-reinforced steel according to claim 1, characterized in that: In step B, the aluminum content of the high-aluminum aluminum iron is 75-85wt%, the iron content is 15-25wt%, and the rest is irremovable trace impurities.

3. The method for accurately controlling the titanium content in titanium-reinforced steel according to claim 1, characterized in that: In step B, the amount of high-aluminum aluminum iron added is 2-2.5 kg / t steel.

4. The method for accurately controlling the titanium content in titanium-reinforced steel according to claim 1, characterized in that: In step B, if the high-aluminum aluminum iron is deoxidized and the outgoing a[O] is greater than 20ppm, the aluminum wire is supplemented according to the oxygen content after the oxygen is determined on the small platform behind the furnace to ensure that the outgoing a[O] is ≤20ppm.

5. The method for accurately controlling the titanium content in titanium-reinforced steel according to claim 1, characterized in that: In step D, when the Als content is lower than 0.033%, aluminum wire is used to supplement it, and after feeding the aluminum wire, argon is soft-blown for ≥3 minutes before titanium alloying.

6. The method for accurately controlling the titanium content in titanium-reinforced steel according to claim 1, characterized in that: In step D, the addition amount of the low nitrogen 70 titanium iron is 0.5-3.0 kg / t steel.

7. The method for accurately controlling the titanium content in titanium-reinforced steel according to any one of claims 1 to 6, characterized in that: In step G, the calcium aluminate-based coating agent contains the following components in percentage by mass: CaO 40-50%, P≤0.2%, S≤0.2%, Al2O3 25-35%, Na2O 2-4%, MgO≤10%, FeO≤2.0%, SiO2≤8.0%, N≤0.5%, H2O≤2.0%; and CaO / Al2O3 is 1.6-2.2, the main raw materials CaO and Al2O3 are pre-melted calcium aluminate, the ignition loss at 900°C is ≤10%, and sodium shall not be configured with industrial NaCl.

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