195t refining furnace tt700l steel deep desulfurization low-nitrogen titanium control smelting process

Abstract

The application discloses a 195t refining furnace TT700L steel deep desulfurization low-nitrogen titanium control smelting process and belongs to the technical field of steel refining, which comprises the following steps: S1, station entry slagging: after molten steel enters a station, lime, pre-melting calcium aluminate refining slag, fluorite and aluminum particles are added, rapid slagging and deep deoxidation are carried out, and white slag is formed; S2, slag condition adjustment: after temperature measurement and sampling, lime and aluminum particles are supplemented according to the slag condition, FeO+MnO in the slag is controlled to be less than 1.0%, and the white slag is kept stable; S3, alloying: under the condition that the white slag is kept stable for more than 5min and Als is more than 0.025%, 60# niobium iron and 30# titanium iron are added according to the molten steel quantity of 195t; S4, station exit control: submerged arc heating is adopted throughout the whole process, only soft stirring is carried out after alloying and the molten steel surface is not exposed, and the station is exited until the composition and temperature reach the standards. The application has the characteristics of stable process and strong operability, can significantly improve the cleanliness of molten steel and the product qualified rate, and reduces the power consumption and refractory consumption.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking and refining technology, and in particular relates to a deep desulfurization, low nitrogen, and controlled titanium smelting process for TT700L steel in a 195t refining furnace. Background Technology

[0002] TT700L is a low-alloy high-strength steel specifically designed for automotive structural components and beams. The production of this steel involves extremely stringent requirements regarding the cleanliness and compositional stability of the molten steel. Specifically, in terms of steel composition control, the sulfur (S) content must be strictly controlled to no more than 0.008%, while the nitrogen (N) content must be controlled to no more than 50 parts per million (i.e., 50 ppm). Furthermore, to ensure the steel possesses the required properties, it is also necessary to maintain a stable recovery rate of microalloying elements such as titanium (Ti) and niobium (Nb) during the smelting process, and to prevent abnormal burn-off of these elements.

[0003] However, in actual production, the traditional LF refining process suffers from several significant technical drawbacks. First, the refining slag in this process often exhibits low basicity and high oxidizing properties, making it difficult to achieve deep and stable desulfurization during refining. This easily leads to excessive sulfur content or sulfur reversion, severely impacting steel quality. Second, due to poor submerged arc treatment, there is a high risk of nitrogen accumulation during refining, making it difficult to stably control the nitrogen content to no more than 50 parts per million (50 ppm), posing a significant challenge to product quality assurance. Furthermore, titanium is extremely susceptible to oxidation and burn-off under this process environment, resulting in significant fluctuations in composition and ultimately a low product yield. Additionally, the refining slag system has poor fluidity and slow slag formation, leading not only to excessive energy consumption but also severe corrosion of refractory materials, further increasing production costs and process control difficulties.

[0004] Currently, for LF furnaces with a steel output of 195 tons, the integrated refining process specifically designed for TT700L steel—characterized by high basicity, low oxidation, strong desulfurization capabilities, and stable control of titanium and nitrogen—is not yet fully developed. This imperfection directly hinders the ability to meet the actual needs of large-scale and stable production of high-end hot-rolled structural steel, becoming a bottleneck restricting the high-quality development of related steel products. Summary of the Invention

[0005] The main objective of this invention is to provide a deep desulfurization and low-nitrogen controlled titanium smelting process for TT700L steel in a 195t refining furnace. By optimizing the high-basicity, low-oxidizing refining slag system, and in conjunction with a special feeding system and alloy addition amount, deep desulfurization (S≤0.008%) and low-nitrogen control (N≤50ppm) of TT700L steel can be achieved, while ensuring stable recovery rates of Ti and Nb elements.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The purpose of this invention is to provide a deep desulfurization, low-nitrogen controlled titanium smelting process for TT700L steel in a 195t refining furnace, comprising: S1. Slag formation upon entering the station: After the molten steel enters the station, lime, pre-melted calcium aluminate refining slag, fluorite and aluminum particles are added to quickly slag and deeply deoxidize, forming white slag; S2. Slag Condition Adjustment: After temperature measurement and sampling, lime and aluminum particles are added according to the slag condition to control FeO+MnO in the slag to <1.0% and maintain the stability of white slag. S3, Alloying: Under the condition that the white slag is kept stable for ≥5 min and Als≥0.025%, add 60# ferroniobium and 30# ferrotitanium according to 195t of molten steel. S4. Outgoing control: Submerged arc heating is used throughout the process. After alloying, only soft stirring is performed and the molten steel surface is not exposed until the composition and temperature meet the standards before leaving the station.

[0008] Furthermore, the content of each component in the refining slag, by weight percentage, is as follows: CaO: 58%–65%; Al2O3: 20%–28%, SiO2: ≤8%, CaF2: 5%~10%, MgO: 3%–6%, FeO+MnO≤1.0%, Among them, the alkalinity R = CaO / SiO2 ≥ 7.0.

[0009] Furthermore, the smelting process controls the sulfur content S in the finished molten steel to be ≤0.008%.

[0010] Furthermore, the smelting process controls the nitrogen content (N) in the finished molten steel to be ≤50ppm.

[0011] Furthermore, the recovery rate of titanium in the smelting process is ≥75%, and the recovery rate of niobium is ≥90%.

[0012] Furthermore, the recovery rate of niobium in the smelting process is ≥90%.

[0013] Furthermore, in S3, after alloying is completed, only a soft stirring and homogenization operation is performed, and no slag adjustment or material addition operation is performed.

[0014] Furthermore, add 108 kg of 60# ferroniobium and 910 kg of 30# ferrotitanium to 195 tons of molten steel.

[0015] Furthermore, S1 includes: immediately after the molten steel enters the station, adding 800kg to 1000kg of lime, 600kg to 800kg of pre-melted calcium aluminate refining slag, 100kg to 150kg of fluorite, and 50kg to 100kg of aluminum granules.

[0016] Furthermore, the target finished product composition: C: 0.05%~0.09%, Si<0.20%, Mn: 1.40%~1.50%, P<0.020%, S<0.008%, Al s: 0.020%~0.045%, Nb: 0.025%~0.035%, Ti: 0.100%~0.115%, N<50ppm.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention optimizes the high-alkalinity, low-oxidizing refining slag system, combined with a special feeding regime and alloy addition amount, to achieve deep desulfurization (S≤0.008%) and low nitrogen control (N≤50ppm) of TT700L steel, while ensuring stable recovery rates of Ti and Nb elements. It features stable process and strong operability, which can significantly improve the cleanliness of molten steel and the product qualification rate, and reduce power consumption and refractory material consumption. Attached Figure Description

[0018] Figure 1 This is a flowchart of a preferred embodiment of the present invention. Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0020] The purpose of this invention is to achieve: (1) Deep desulfurization, S stability ≤0.008%, no sulfur reversion; (2) Low nitrogen control, N stable ≤50ppm; (3) Ti recovery rate ≥75%, Nb recovery rate ≥90%, and small composition fluctuation; (4) The molten steel has high cleanliness, good submerged arc effect, and reduced power consumption and refractory material consumption.

[0021] like Figure 1 As shown, a deep desulfurization, low-nitrogen, and controlled-titanium smelting process for TT700L steel in a 195t refining furnace mainly includes: S1. Slag formation upon entering the station: After the molten steel enters the station, lime, pre-melted calcium aluminate refining slag, fluorite and aluminum particles are added to quickly slag and deeply deoxidize, forming white slag; Specifically, immediately after the molten steel enters the station, add 800-1000 kg of lime, 600-800 kg of pre-melted calcium aluminate refining slag (if available, the amount of fluorite can be reduced), 100-150 kg of fluorite, and 50-100 kg of aluminum granules to quickly slag, deeply deoxidize, and form white slag.

[0022] S2. Slag Condition Adjustment: After temperature measurement and sampling, lime and aluminum particles are added according to the slag condition to control FeO+MnO in the slag to <1.0% and maintain the stability of white slag. Specifically, after temperature measurement and sampling, 200kg to 400kg of lime and an appropriate amount of aluminum granules are added according to the slag condition to ensure that the slag is pure white and has good fluidity, and to control the FeO+MnO content in the slag to be less than 1.0%. S3, Alloying: Under the condition that the white slag is kept stable for ≥5 min and Als≥0.025%, add 60# ferroniobium and 30# ferrotitanium according to 195t of molten steel. Specifically, the white slag should be kept stable for ≥5 minutes and Als≥0.025%. After meeting the conditions, microalloying should be carried out. 108 kg of 60% ferroniobium and 910 kg of 30% ferrotitanium should be added in sequence and gently stirred evenly. Slag adjustment, material addition and high-flow-rate stirring are prohibited. S4. Outgoing control: Submerged arc heating is used throughout the process. After alloying, only soft stirring is performed and the molten steel surface is not exposed until the composition and temperature meet the standards before leaving the station. Specifically, the entire process involves submerged arc heating and soft stirring without exposing the molten steel surface. The steel is then removed from the station once the composition and temperature meet the standards.

[0023] The refining slag, by weight percentage, contains the following components: CaO: 58%–65%; Al2O3: 20%–28%, SiO2: ≤8%, CaF2: 5%~10%, MgO: 3%–6%, FeO+MnO≤1.0%, Among them, the alkalinity R = CaO / SiO2 ≥ 7.0.

[0024] The smelting process controls the sulfur content (S) in the finished molten steel to be ≤0.008%.

[0025] The smelting process controls the nitrogen content (N) in the finished molten steel to be ≤50ppm.

[0026] The recovery rate of titanium in the smelting process is ≥75%, and the recovery rate of niobium is ≥90%.

[0027] The recovery rate of niobium in the smelting process is ≥90%.

[0028] Target finished product ingredients: C: 0.05%~0.09%, Si<0.20%, Mn: 1.40%~1.50%, P<0.020%, S<0.008%, Al s: 0.020%~0.045%, Nb: 0.025%~0.035%, Ti: 0.100%~0.115%, N<50ppm.

[0029] This invention optimizes the high-basicity, low-oxidizing refining slag system, combined with a specialized feeding regime and alloy addition amount, to achieve deep desulfurization (S≤0.008%) and low nitrogen control (N≤50ppm) of TT700L steel, while ensuring stable recovery rates of Ti and Nb elements. This solves problems such as Ti burn-off, nitrogen increase, and unstable desulfurization in traditional processes. This invention is suitable for batch production in a 195t LF furnace, offering stable processes, strong operability, and significantly improving steel cleanliness and product qualification rate while reducing power consumption and refractory material consumption. It possesses high production application and promotion value.

[0030] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A deep desulfurization, low-nitrogen, controlled titanium smelting process for TT700L steel in a 195t refining furnace, characterized in that, include: S1. Slag formation upon entering the station: After the molten steel enters the station, lime, pre-melted calcium aluminate refining slag, fluorite and aluminum particles are added to quickly slag and deeply deoxidize, forming white slag; S2. Slag Condition Adjustment: After temperature measurement and sampling, lime and aluminum particles are added according to the slag condition to control FeO+MnO in the slag to <1.0% and maintain the stability of white slag. S3, Alloying: Under the condition that the white slag is kept stable for ≥5 min and Als≥0.025%, add 60# ferroniobium and 30# ferrotitanium according to 195t of molten steel. S4. Outgoing control: Submerged arc heating is used throughout the process. After alloying, only soft stirring is performed and the molten steel surface is not exposed until the composition and temperature meet the standards before leaving the station.

2. The 195t refining furnace TT700L steel deep desulfurization and low-nitrogen controlled titanium smelting process according to claim 1, characterized in that, The refining slag, by weight percentage, contains the following components: CaO: 58%–65%; Al2O3: 20%–28%, SiO2: ≤8%, CaF2: 5%~10%, MgO: 3-6%, FeO+MnO≤1.0%, Among them, the alkalinity R = CaO / SiO2 ≥ 7.

0.

3. The 195t refining furnace deep desulfurization and low-nitrogen controlled titanium smelting process for TT700L steel according to claim 1, characterized in that, The smelting process controls the sulfur content (S) in the finished molten steel to be ≤0.008%.

4. The 195t refining furnace TT700L steel deep desulfurization, low-nitrogen controlled titanium smelting process according to claim 1, characterized in that: The smelting process controls the nitrogen content (N) in the finished molten steel to be ≤50ppm.

5. The 195t refining furnace deep desulfurization and low-nitrogen controlled titanium smelting process for TT700L steel according to claim 1, characterized in that, The recovery rate of titanium in the smelting process is ≥75%, and the recovery rate of niobium is ≥90%.

6. The 195t refining furnace deep desulfurization and low-nitrogen controlled titanium smelting process for TT700L steel according to claim 1, characterized in that, The recovery rate of niobium in the smelting process is ≥90%.

7. The 195t refining furnace TT700L steel deep desulfurization and low-nitrogen controlled titanium smelting process according to claim 1, characterized in that: In S3, after alloying is completed, only a soft stirring operation is performed to achieve uniformity; no slag adjustment or material addition is performed.

8. The 195t refining furnace deep desulfurization and low-nitrogen controlled titanium smelting process for TT700L steel according to claim 1, characterized in that, Add 108 kg of 60# ferroniobium and 910 kg of 30# ferrotitanium to 195 tons of molten steel.

9. The 195t refining furnace deep desulfurization and low-nitrogen controlled titanium smelting process for TT700L steel according to claim 1, characterized in that, S1 includes: Immediately after the molten steel enters the station, add 800-1000 kg of lime, 600-800 kg of pre-melted calcium aluminate refining slag, 100-150 kg of fluorite, and 50-100 kg of aluminum granules.

10. The 195t refining furnace TT700L steel deep desulfurization, low-nitrogen controlled titanium smelting process according to claim 1, characterized in that: Target finished product ingredients: C: 0.05%~0.09%, Si<0.20%, Mn: 1.40%~1.50%, P<0.020%, S<0.008%, Al s: 0.020%~0.045%, Nb: 0.025%~0.035%, Ti: 0.100%~0.115%, N<50ppm.

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