Low-cost deoxidation process for converter steelmaking

Abstract

The invention discloses a low-cost deoxidation process for converter steelmaking. The low-cost deoxidation process comprises the steps of converter deoxidation, ladle deoxidation, vacuum deoxidation and the like. According to the method, a segmented deoxidation process is adopted, the carbon powder is added firstly, then the composite deoxidizer is added, and the silicon-calcium-barium-aluminum composite deoxidizer is adopted, so that compared with an existing aluminum deoxidation process, the use amount of aluminum is reduced by 50-60%, the deoxidation cost is reduced, inclusions generated by aluminum deoxidation can be deformed through calcium and barium, the yield of aluminum is 75% or above, and the method is suitable for industrial production. Oxide inclusions in the steel are obviously reduced, and after vacuum deoxidation treatment, the total oxygen content in the steel is effectively reduced, and the quality of molten steel is improved. The method has the advantages of controllable inclusion in steel, good deoxidation effect, stable product quality and low deoxidation cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of converter smelting, and particularly relates to a low-cost deoxidization process for converter steelmaking. BACKGROUND

[0002] Steel is an iron-carbon alloy with a carbon content of less than 2%, and has excellent mechanical properties and wide industrial applications. Steelmaking is a process of converting iron ore or scrap steel and other raw materials into steel through a series of chemical reactions and physical treatments. Converter steelmaking is currently the main method of steelmaking. By blowing oxygen into high-temperature molten iron, carbon, silicon, phosphorus and other impurities are removed, and the molten iron is converted into steel. However, after the oxygen blowing is completed, the molten steel inevitably contains excess oxygen, which seriously affects the quality of the steel. Therefore, deoxidization is an essential refining step immediately after blowing.

[0003] Currently, the deoxidization methods used in domestic steelmaking production processes mainly include: aluminum deoxidization method, which adds metallic aluminum to the molten steel in the ladle at tapping. The deoxidization method is relatively simple, but the deoxidization effect is unstable, and aluminum oxide non-metallic inclusions are easily generated. These inclusions are easily mixed into the molten steel, causing an increase in non-metallic inclusions in the steel, and the price of aluminum is relatively high. Carbon deoxidization method, which adds carbon-containing materials to the ladle before tapping. The deoxidization method is also relatively simple, but there is still the problem of unstable deoxidization effect, which easily causes safety hazards of molten steel overturning, and also increases the carbon content of the molten steel. Secondly, there are silicon-calcium alloy deoxidization method, core wire deoxidization method and other methods. Although these methods have stable deoxidization effect, they still have the problem of high deoxidization cost. Therefore, it is an objective need to develop a low-cost deoxidization process for converter steelmaking with controllable inclusions, good deoxidization effect and stable product quality. SUMMARY

[0004] In order to solve the problems in the background art, the purpose of the present application is to provide a low-cost deoxidization process for converter steelmaking with controllable inclusions, good deoxidization effect and stable product quality.

[0005] The low-cost deoxidization process for converter steelmaking according to the present application comprises the following steps: ① Converter deoxidization: After the molten steel in the converter completes oxygen blowing and is lifted, elemental carbon powder is uniformly sprayed into the molten steel. The addition amount of elemental carbon powder is 0.15-0.45 kg / t, the deoxidization time is 3-8 min, and the bottom argon blowing flow rate is 300-400 NL / min. ② Ladle deoxidation: during tapping, 1.6-2.3 kg / t of composite deoxidizer is added to the ladle, 50% of the composite deoxidizer is added to the ladle with the steel flow, and the other 50% is blown into the ladle from the ladle bottom through the ladle bottom blowing system, and all the composite deoxidizer is added within 60-120 s after tapping, the argon flow rate of bottom blowing is 300-500 m³ / h, and after the addition of the composite deoxidizer is completed, the argon flow rate of bottom blowing is reduced to 200-300 m³ / h, and the composition of the composite deoxidizer includes 35-45% silicon, 20-30% calcium, 15-25% barium, and 10-20% aluminum.

[0006] ③ Vacuum deoxidation: after the molten steel is deoxidized in the ladle, vacuum deoxidation treatment is performed.

[0007] Further, in step ①, the mass percentage of each component of the elemental carbon powder is: C≥98.5%, ash≤1.0%, S≤0.05%, P≤0.05%, volatile matter≤1.0%, moisture≤0.5%, N≤0.25%, and the particle size is 1-6 mm.

[0008] Further, in step ①, after the elemental carbon powder is added to the molten steel, ultrasonic stirring is used to stir the molten steel and the elemental carbon powder, and the ultrasonic frequency range is 25-40 KHz.

[0009] Further, in step ①, laser-induced breakdown spectroscopy or inductively coupled plasma spectroscopy is used to monitor and feedback the composition of the molten steel in real time.

[0010] Further, in step ②, the particle size of the composite deoxidizer is 15-40 mm.

[0011] Further, in step ③, during the vacuum deoxidation treatment, the vacuum pressure is 20-50 Pa, and the treatment time is 15-25 min.

[0012] The beneficial effects of the present application are: First, the deoxidation effect is good, the present application adopts a segmented deoxidation process, elemental carbon powder is added to the converter before tapping for basic deoxidation, the carbon addition amount is controlled to ensure that the carbon addition amount in the steel is less than 120 ppm, the deoxidation amount is maximized, the total oxygen content in the steel is less than 100 ppm, then, during the tapping process and the ladle bottom blowing process, a composite deoxidizer is added to further deoxidize the molten steel, the total oxygen content in the steel is reduced to less than 50 ppm, and finally, the molten steel is subjected to vacuum deep deoxidation treatment, and the final oxygen content in the steel is reduced to less than 20 ppm. In summary, after the above-mentioned segmented multi-stage deoxidation treatment of the molten steel, a good deoxidation effect can be obtained.

[0013] Second, the deoxidation cost is low. In the process of deoxidation in the converter, the deoxidizer used is elemental carbon powder, and the price of the elemental carbon powder is relatively low. In the process of deoxidation in the ladle, the composite deoxidizer is used. Compared with most of the deoxidizers at present, the composite deoxidizer in the present application has no iron component and greatly reduces the proportion of aluminum. Compared with the aluminum-iron deoxidizer in the prior art, the aluminum-iron deoxidizer produces a large amount of aluminum oxide dioxides deoxidation product which is difficult to remove, and the inclusions are difficult to float and remove in time and remain in the molten steel, affecting the purity of the molten steel. The use amount of the aluminum-iron deoxidizer is greatly reduced, the quality of the molten steel is improved, the casting machine flocculation probability is reduced, and the deoxidation cost is reduced.

[0014] Third, the inclusions in the steel are controllable. The proportions of silicon, calcium and barium in the deoxidizer are reasonable. The alkaline earth metals calcium and barium have low boiling points and are easy to volatilize and lose. Silicon can reduce the volatilization loss of calcium and barium and improve the utilization rate. The silicon, calcium deoxidation product CaO-SiO2, the presence of calcium increases the solubility of silicon, and at the same time, calcium can also deform non-metallic inclusions and make them easy to be removed, thereby improving the deoxidation utilization rate of calcium and silicon. Barium can improve the deoxidation effect and desulfurization capacity of calcium and silicon and refine the grain. In summary, the added deoxidizer in the present application can also well control the inclusions of the deoxidation product in the steel when the deoxidation process is completed.

[0015] Fourth, the quality of the molten steel after deoxidation is stable. In the present application, carbon powder is used for preliminary deoxidation, and argon is used for stirring the molten steel during the deoxidation process, so that the carbon powder is uniformly mixed into the molten steel. The deoxidizer is divided into two streams, one stream is added into the ladle together with the steel stream, and the other stream is blown into the ladle through the bottom blowing system. Both are completed within 60-120 seconds of tapping. The huge kinetic energy generated by the molten steel pouring down from the converter is fully utilized, and this turbulent steel stream is used as a "stirrer" to rapidly bring the composite deoxidizer into the bottom of the ladle and realize the violent and uniform mixing with the molten steel. In addition, the bottom blowing system of the ladle is used to make the deoxidizer fully mixed with the molten steel, and the chemical and physical effects are superimposed to fully play the desulfurization and inclusion deformation capacity of calcium and barium, effectively reducing the generation of deoxidation impurities and manganese sulfide. The above-mentioned adding method of the deoxidizer realizes the gradient deoxidation of the molten steel, and can ensure the deoxidation effect and the quality of the molten steel after deoxidation.

[0016] In summary, the present application adopts a segmented deoxidation process, carbon powder is added first, and then a composite deoxidizer is added. The composite deoxidizer of silicon, calcium, barium and aluminum is used. Compared with the existing aluminum deoxidation process, the aluminum usage is reduced by 50-60%, the deoxidation cost is reduced, and the inclusions generated by aluminum deoxidation are deformed by calcium and barium. The aluminum recovery rate is more than 75%, the oxide inclusions in the steel are significantly reduced, and after vacuum deoxidation treatment, the total oxygen content in the steel is effectively reduced and the quality of the molten steel is improved. The present application has the advantages of controllable inclusions in the steel, good deoxidation effect, stable product quality and low deoxidation cost. DETAILED DESCRIPTION

[0017] The application will be further described in conjunction with the following examples, but not in any way limited to the application, any transformation or replacement based on the teaching of the application, all examples belong to the protection scope of the application. Example

[0018] The low-cost deoxidization process of converter steelmaking described in this embodiment 1 includes the following steps: ①Converter deoxidization: After the completion of oxygen blowing and the removal of the converter, elemental carbon powder is uniformly sprayed into the molten steel, the addition amount of elemental carbon powder is 0.15 kg / t, the deoxidization time is 3 min, and the argon bottom blowing flow is 300 NL / min. The mass percentage of each component of the elemental carbon powder is: C≥98.5%, ash≤1.0%, S≤0.05%, P≤0.05%, volatile matter≤1.0%, moisture≤0.5%, N≤0.25%, and particle size is 1-6 mm. After the elemental carbon powder is added into the molten steel, ultrasonic stirring is used to stir the molten steel and the elemental carbon powder. The ultrasonic frequency range is 25 KHz. Traditional mechanical stirring and bottom blowing stirring can promote the distribution of elemental carbon powder, but the energy consumption of traditional mechanical stirring and bottom blowing stirring is high, and it causes wear to the equipment, the stirring effect is limited, and it cannot guarantee the uniform distribution of elemental carbon powder in the molten steel, which affects the deoxidization effect. In order to solve this problem, ultrasonic stirring can be used to stir the molten steel and the elemental carbon powder. Ultrasonic stirring significantly enhances the distribution and reaction effect of elemental carbon powder through cavitation effect, further improves the deoxidization efficiency and effect, and real-time monitoring and feedback of the composition of the molten steel is carried out by using laser-induced breakdown spectroscopy or inductively coupled plasma spectroscopy. Through online analysis technology, the composition of the molten steel can be monitored in real time, providing fast feedback, timely adjusting process parameters, and ensuring accurate control of the deoxidization process.

[0019] ② Ladle deoxidization: During tapping, 1.6 kg / t of composite deoxidizer is added to the ladle, 50% of the composite deoxidizer is added to the ladle with the steel flow, and the other 50% is blown into the ladle from the bottom of the ladle through the ladle bottom blowing system, and all the composite deoxidizer is added within 60 seconds after tapping. The flow of argon bottom blowing is 300 m³ / h, and after the addition of the composite deoxidizer is completed, the flow of argon bottom blowing is reduced to 200 m³ / h. The composition of the composite deoxidizer includes 35% silicon, 30% calcium, 25% barium, and 10% aluminum. The particle size of the composite deoxidizer is 15 mm. The composite deoxidizer with appropriate particle size can effectively sink into the interior of the molten steel, and at the same time, it can quickly dissolve and react to achieve high element yield, good deoxidization effect, better molten steel purity, and lower production cost.

[0020] ③ Vacuum deoxidation: After the deoxidation of the molten steel in the ladle, vacuum deoxidation treatment is carried out. During the vacuum deoxidation treatment, the vacuum pressure is 20 Pa, and the treatment time is 15 min.

[0021] In this embodiment, a segmented deoxidation process is adopted, carbon powder is added first, and then a composite deoxidizer is added. The composite deoxidizer of silicon, calcium, barium and aluminum is used. Compared with the existing aluminum deoxidation process, the aluminum consumption is reduced by 50-60%, the deoxidation cost is reduced, and the calcium and barium can deform the inclusions generated by aluminum deoxidation. The oxide inclusions in the steel are significantly reduced. After vacuum deoxidation treatment, the final oxygen content in the steel is 16 ppm, and the quality of the molten steel is improved. Embodiment

[0022] The low-cost deoxidation process for converter steelmaking according to the embodiment 2 comprises the following steps: ① Converter deoxidation: After the completion of oxygen blowing and the removal of the molten steel in the converter, elemental carbon powder is uniformly sprayed into the molten steel. The addition amount of elemental carbon powder is 0.35 kg / t, the deoxidation time is 5 min, and the argon bottom blowing flow is 350 NL / min. The mass percentage of each component of the elemental carbon powder is: C≥98.5%, ash≤1.0%, S≤0.05%, P≤0.05%, volatile matter≤1.0%, moisture≤0.5%, N≤0.25%, and particle size is 4 mm. After the elemental carbon powder is added into the molten steel, ultrasonic stirring is used to stir the molten steel and the elemental carbon powder. The ultrasonic frequency range is 35 KHz. Traditional mechanical stirring and bottom blowing stirring can promote the distribution of elemental carbon powder, but the energy consumption of traditional mechanical stirring and bottom blowing stirring is high, and it causes wear to the equipment. The stirring effect is limited, and it cannot guarantee the uniform distribution of elemental carbon powder in the molten steel, which affects the deoxidation effect. In order to solve this problem, ultrasonic stirring can be used to stir the molten steel and the elemental carbon powder. Ultrasonic stirring significantly enhances the distribution and reaction effect of elemental carbon powder through cavitation effect, further improves the deoxidation efficiency and effect, and uses laser-induced breakdown spectroscopy or inductively coupled plasma spectroscopy to monitor and feedback the composition of the molten steel in real time. Through online analysis technology, the composition of the molten steel can be monitored in real time, and rapid feedback can be provided to timely adjust the process parameters and ensure accurate control of the deoxidation process.

[0023] ② Ladle deoxidation: In the tapping process, 2.0 kg / t of composite deoxidizer is added to the ladle, 50% of the composite deoxidizer is added to the ladle with the steel stream, and the other 50% is blown into the ladle from the bottom of the ladle through the ladle bottom blowing system, and all the composite deoxidizer is added within 80s after tapping, the flow rate of bottom blowing argon is 400 m³ / h, and after the addition of the composite deoxidizer is completed, the flow rate of bottom blowing argon is reduced to 250 m³ / h, the composition of the composite deoxidizer includes 45% silicon, 20% calcium, 15% barium, and 20% aluminum. The particle size of the composite deoxidizer is 30mm, and the composite deoxidizer with appropriate particle size can effectively sink into the interior of the molten steel and quickly dissolve and react to achieve higher element yield, better deoxidation effect, better molten steel purity, and lower production cost.

[0024] ③ Vacuum deoxidation: After the molten steel is deoxidized in the ladle, vacuum deoxidation treatment is carried out. During the vacuum deoxidation treatment, the vacuum pressure is 35 Pa, and the treatment time is 20 min.

[0025] In this embodiment, a segmented deoxidation process is used, carbon powder is added first, and then composite deoxidizer is added, and a silicon-calcium-barium-aluminum composite deoxidizer is used. Compared with the existing aluminum deoxidation process, the aluminum consumption is reduced by 50-60%, the deoxidation cost is reduced, and the calcium and barium can deform the inclusions generated by aluminum deoxidation, the oxide inclusions in the steel are significantly reduced, and after vacuum deoxidation treatment, the final oxygen content in the steel is 15 ppm, and the molten steel quality is improved. Embodiment

[0026] The low-cost deoxidation process for converter steelmaking described in Embodiment 3 includes the following steps: ① Converter deoxidation: After the completion of oxygen blowing in the converter, elemental carbon powder is uniformly sprayed into the molten steel, the addition amount of elemental carbon powder is 0.45 kg / t, the deoxidation time is 8 min, and the argon bottom blowing flow is 400 NL / min. The mass percentage of each component of the elemental carbon powder is: C≥98.5%, ash≤1.0%, S≤0.05%, P≤0.05%, volatile matter≤1.0%, moisture≤0.5%, N≤0.25%, and the particle size is 6 mm. After the elemental carbon powder is added to the molten steel, ultrasonic stirring is used to stir the molten steel and the elemental carbon powder. The ultrasonic frequency range is 40 KHz. Traditional mechanical stirring and bottom blowing stirring can promote the distribution of elemental carbon powder, but the energy consumption of traditional mechanical stirring and bottom blowing stirring is high, and it causes wear to the equipment. The stirring effect is limited, and it cannot guarantee the uniform distribution of elemental carbon powder in the molten steel, which affects the deoxidation effect. In order to solve this problem, ultrasonic stirring can be used to stir the molten steel and the elemental carbon powder. Ultrasonic stirring significantly enhances the distribution and reaction effect of elemental carbon powder through cavitation effect, further improves the deoxidation efficiency and effect, and uses laser-induced breakdown spectroscopy or inductively coupled plasma spectroscopy to monitor and feedback the composition of the molten steel in real time. Through online analysis technology, the composition of the molten steel can be monitored in real time, and fast feedback can be provided to timely adjust the process parameters and ensure accurate control of the deoxidation process.

[0027] ② Ladle deoxidation: During tapping, 2.3 kg / t of composite deoxidizer is added to the ladle. 50% of the composite deoxidizer is added to the ladle with the steel flow, and the other 50% is blown into the ladle from the bottom of the ladle through the ladle bottom blowing system. All the composite deoxidizer is added within 120 seconds after tapping. The argon bottom blowing flow is 500 m³ / h. After the addition of the composite deoxidizer is completed, the argon bottom blowing flow is reduced to 300 m³ / h. The composition of the composite deoxidizer includes 40% silicon, 25% calcium, 20% barium, and 15% aluminum. The particle size of the composite deoxidizer is 40 mm. The composite deoxidizer with appropriate particle size can effectively sink into the interior of the molten steel and quickly dissolve and react to achieve high element yield, good deoxidation effect, better molten steel purity, and lower production cost.

[0028] ③ Vacuum deoxidation: After the molten steel completes deoxidation in the ladle, vacuum deoxidation treatment is performed. During the vacuum deoxidation treatment, the vacuum pressure is 50 Pa, and the treatment time is 25 min.

[0029] In this embodiment, a segmented deoxidation process is used, elemental carbon powder is added first, and then a composite deoxidizer is added. The composite deoxidizer is composed of silicon, calcium, barium, and aluminum. Compared with the existing aluminum deoxidation process, the use of the composite deoxidizer reduces the aluminum consumption by 50-60%, reduces the deoxidation cost, and deforms the inclusions generated by aluminum deoxidation through calcium and barium. The oxide inclusions in the steel are significantly reduced. After vacuum deoxidation treatment, the final oxygen content in the steel is 12 ppm, and the quality of the molten steel is improved.

[0030] The present application first carries out preliminary basic deoxidation in the converter with elemental carbon powder, and the composition and usage amount of the subsequent composite deoxidizer are different from those of the prior art, the content of aluminum in the composite deoxidizer is reduced, calcium and barium can also play the roles of desulfurization and inclusion deformation, the deoxidation impurities can be reduced, barium can improve the deoxidation effect and desulfurization capacity of calcium and silicon, refine the grain, and improve the purity of molten steel, the composite deoxidizer is added in the early stage of tapping, and the composite deoxidizer is added in two streams, the cooperation of chemical reaction and physical disturbance is fully utilized, and the deoxidation effect in the ladle is effectively ensured, and the cost is saved.

Claims

1. A low cost deoxidation process for converter steelmaking, characterized in that: The method comprises the following steps: ① Converter deoxidation: After the completion of oxygen blowing in the converter, elemental carbon powder is uniformly sprayed into the molten steel, the addition amount of the elemental carbon powder is 0.15-0.45 kg / t, the deoxidation time is 3-8 min, and the argon bottom blowing flow rate is 300-400 NL / min; ② Ladle deoxidation: During tapping, 1.6-2.3 kg / t of composite deoxidizer is added into the ladle, 50% of the composite deoxidizer is added into the ladle along with the steel stream, and the other 50% is blown into the ladle from the bottom of the ladle through the ladle bottom blowing system, and all the composite deoxidizer is added within 60-120 s after tapping, the argon bottom blowing flow rate is 300-500 m³ / h, after the addition of the composite deoxidizer, the argon bottom blowing flow rate is reduced to 200-300 m³ / h, and the composition of the composite deoxidizer comprises 35-45% silicon, 20-30% calcium, 15-25% barium and 10-20% aluminum; ③ Vacuum deoxidation: After the completion of deoxidation in the ladle, vacuum deoxidation treatment is performed.

2. A low cost deoxidation process for converter steel making as claimed in claim 1 wherein: In step ①, the mass percentage of each component of the elemental carbon powder is as follows: C≥98.5%, ash≤1.0%, S≤0.05%, P≤0.05%, volatile matter≤1.0%, moisture≤0.5%, N≤0.25%, and the particle size is 1-6 mm.

3. A low cost deoxidation process for converter steel making as claimed in claim 1 wherein: In step ①, after the addition of the elemental carbon powder into the molten steel, the molten steel and the elemental carbon powder are stirred by using ultrasonic stirring, and the ultrasonic frequency range is 25-40 KHz.

4. A low cost deoxidation process for converter steel making as claimed in claim 1 wherein: In step ①, the composition of the molten steel is monitored and fed back in real time by using laser-induced breakdown spectroscopy or inductively coupled plasma spectroscopy.

5. A low cost deoxidation process for converter steel making as claimed in claim 1 wherein: In step ②, the particle size of the composite deoxidizer is 15-40 mm.

6. A low cost deoxidation process for converter steel making as claimed in claim 1 wherein: In step ③, during the vacuum deoxidation treatment, the vacuum pressure is 20-50 Pa, and the treatment time is 15-25 min.