Low-carbon low-silicon steel converter semi-deoxidation argon-blowing direct-feeding non-calcium treatment process

Abstract

The invention relates to the technical field of steelmaking, in particular to a low-carbon low-silicon steel converter semi-deoxidation argon-blowing direct non-calcium treatment process which comprises the following steps: S1, molten iron pretreatment: after desulfurization, the sulfur content is less than or equal to 0.003%, and the molten iron consumption is more than or equal to 825kg / t; s2, converter smelting, wherein the final temperature is controlled to be 1625-1635 DEG C; the adding amount of the converter tapping aluminum deoxidizer is controlled according to the end-point oxygen content; the upper limit of the addition amount of the aluminum deoxidizer is 650 kg / furnace; and S3, argon blowing: steel ladle bottom blowing is carried out after tapping, the bottom blowing flow is controlled to be larger than or equal to 70 Nm < 3 > / h, large stirring is carried out, temperature measurement, oxygen determination and aluminum wire feeding are carried out after argon blowing arrives at a station, after aluminum feeding is finished, the bottom blowing flow is adjusted to be 10-20 Nm < 3 > / h, soft blowing is carried out, and soft blowing is larger than or equal to 5 min. The method can effectively improve the castability of the molten steel, shorten the treatment period of argon blowing straight upward feeding, and reduce the processing cost of the steelmaking procedure.

Description

Technical Field

[0001] This invention relates to the field of steelmaking technology, specifically to a non-calcium treatment process for semi-deoxidation argon blowing in a converter for low-carbon, low-silicon steel. Background Technology

[0002] Currently, the most common process route for producing hot-rolled low-carbon, low-silicon commercial coils is converter (BOF) - ladle refining furnace calcium treatment (LF) - continuous casting machine (CCM). However, this process often encounters numerous problems during the molten steel pouring process. For example, frequent occurrences of stopper rod stroke increases and decreases, and the significant changes in stopper rod stroke can lead to large fluctuations in the liquid level in the crystallizer. These problems not only affect the stability of the pouring process but also negatively impact the quality of subsequent products. Furthermore, the molten steel obtained using this process route has a high defect rate in the rolled product, primarily due to inclusions, resulting in a persistently high product rework rate. This high rework rate not only affects production line performance and reduces efficiency but also increases production costs, significantly negatively impacting the company's economic benefits.

[0003] CN101914652A discloses a deoxidation process for low-carbon, low-silicon steel, which is carried out according to the following operation procedure: a. Converter tapping: Steel is tapped when the oxygen content at the end of the converter is above 500 ppm; b. Adding carbon powder for coarse deoxidation at the beginning of tapping: Carbon powder is added at a rate of 0.15~0.25 kg / ton of steel for coarse deoxidation; c. Adding aluminum-iron for deoxidation and alloying at 1 / 2 or 2 / 3 of the tapping: Aluminum-iron is added at a rate of 1.5~2.5 kg / ton of steel for deoxidation and alloying; d. The ladle is opened to the argon blowing station; e. Adding aluminum-iron: The oxygen content in the ladle is measured with a constant oxygen probe, and aluminum-iron is added according to the measured oxygen content to adjust the oxygen content in the ladle to below 50 ppm; f. Argon blowing: Argon blowing is carried out from the beginning of tapping at a flow rate of 300~400 NL / min. When the ladle is opened to the argon blowing station, the bottom blowing argon flow rate is adjusted to 50~80 NL / min for soft argon blowing. This deoxidation process uses carbon powder for coarse deoxidation, reducing the amount of aluminum and iron used and solving the problem of large amounts of deoxidation products remaining in molten steel, which could easily cause turbulent production accidents or lead to serious surface quality issues in the final product. However, after implementing this deoxidation process, LF refining is still required, and the cost of the steelmaking process remains relatively high.

[0004] CN 112267000 A discloses a short-process technology for producing low-carbon, low-silicon aluminum-killed steel, which eliminates the LF furnace stage through the following five aspects: 1. Controlling the converter tapping temperature: The converter adopts a top-and-bottom combined blowing mode, with the tapping temperature controlled at 1660-1670℃ and the Ar station temperature controlled at 1615-1530℃; 2. Controlling the converter's final carbon content to be greater than 0.04%, calculating the oxygen content based on the carbon content, and adding an aluminum-iron alloy for deoxidation and alloying at 1 / 4 of the tapping time to ensure that the aluminum content is controlled at the target level. The limitations of this technical solution are: 1. No aluminum is added to the argon station; 2. After adding aluminum-iron, add 200-400 kg of lime, 100-200 kg of fluorite, and 100-200 kg of medium-aluminum slag balls when the steel is 1 / 3 tapped; 3. After tapping, increase the bottom-blowing argon flow rate, blow open the slag surface to a diameter of 600 mm for two minutes, and then feed in aluminum wire to achieve the target aluminum content; 4. After feeding in the wire, reduce the argon flow rate so that the argon blows open the slag surface to a diameter of 400 mm for about 5 minutes before tapping, and control the temperature above 1590℃. The disadvantages of this technical solution are that lime, fluorite, and medium-aluminum slag balls need to be added during tapping, resulting in high costs. Also, this technical solution does not clearly define a method for switching directly from LF / RH to argon blowing, resulting in low flexibility and narrow applicability. Summary of the Invention

[0005] To address the technical problems of unstable castability and limited casting length in traditional argon blowing direct process, this invention provides a non-calcium treatment process for semi-deoxidation argon blowing direct process in converter for low-carbon and low-silicon steel. This process can effectively improve the castability of molten steel, shorten the argon blowing direct process cycle, and reduce the processing cost of steelmaking.

[0006] The technical solution of this invention is as follows: A semi-deoxidation argon blowing direct non-calcium treatment process for low-carbon, low-silicon steel converters includes the following steps: S1. Hot metal pretreatment: Sulfur content after desulfurization ≤0.003%, hot metal consumption ≥825kg / t; S2. Converter smelting: Control the final temperature to 1625~1635℃; control the amount of aluminum-based deoxidizer added to the converter according to the final oxygen content. When the final oxygen content is <400ppm, the amount of aluminum-based deoxidizer added is controlled at 1.2kg / 1ppm; when the final oxygen content is ≥400ppm, the amount of aluminum-based deoxidizer added is controlled at 1.0kg / 1ppm; when the final oxygen content is ≥600ppm, first add 24~60kg / furnace of carbon powder for pre-deoxidation, and then add aluminum-based deoxidizer; the upper limit of the amount of aluminum-based deoxidizer added is 650kg / furnace. S3. Argon blowing: Bottom blowing of the ladle after tapping, with the bottom blowing flow rate controlled at ≥70 Nm³. 3 The system is subjected to vigorous stirring at a rate of / h. After argon arrives at the station, the temperature and oxygen levels are measured, and aluminum wire is fed. After aluminum feeding is completed, the bottom blowing flow rate is adjusted to 10~20 Nm. 3 Perform soft blowing for ≥5 minutes per hour.

[0007] Furthermore, in step S2, the aluminum-based deoxidizer is a high-aluminum iron with an aluminum content of 60%.

[0008] Furthermore, in step S3, when the oxygen content at the destination is <10ppm, 100m of aluminum wire is fed; when the oxygen content at the destination is 10ppm ≤ <50ppm, 200m of aluminum wire is fed; when the oxygen content at the destination is >50ppm, (200 + constant oxygen value)m of aluminum wire is fed, where constant oxygen value is the oxygen content at the destination; large stirring is maintained during the feeding of aluminum wire.

[0009] Furthermore, in step S3, if the stirring time is ≥10 min, or if the oxygen at the converter endpoint is >800 ppm or there are abnormal furnaces with a small amount of slag during tapping or sintering, the soft blowing time should be extended by 2-3 min; for furnaces with poor bottom blowing in the ladle, the stirring time should be extended by 3-5 min; and aluminum should be replenished by the secondary aluminum feeder according to the composition.

[0010] Furthermore, during soft blowing in step S3, the molten steel surface fluctuates and the slag ring is less than 10 cm.

[0011] Furthermore, in step S3, the argon blowing temperature at the station is 1610~1620℃, the temperature at the station outlet is 1595~1605℃, and the superheat of the casting machine is 30~40℃.

[0012] Furthermore, when switching the LF route to the direct argon blowing route, the calcium treatment of the LF in the previous furnace is cancelled, the casting machine slag discharge is controlled, the tundish tonnage is controlled, and ≥150kg of top slag is added to the furnace during the switch.

[0013] Furthermore, when switching the RH route to the direct argon blowing route, the amount of aluminum added to the RH in the previous furnace before the switch is <300kg, and when the top slag added to the furnace during the switch is ≥150kg, and the RH casting stroke continues to rise, the nozzle should be replaced before switching.

[0014] Furthermore, after switching to the direct argon blowing route, no lime, slag modifier, or slag conditioner is added to the top slag during and after the steel tapping process in step S2.

[0015] Furthermore, in low-carbon, low-silicon steel, C ≤ 0.06% and Si ≤ 0.05%.

[0016] The beneficial effects of this invention are as follows: The present invention provides a non-calcium treatment process for low-carbon, low-silicon steel in a converter with semi-deoxidation and direct argon blowing. By employing semi-deoxidation at the converter tapping stage and high-volume argon stirring under low-alumina conditions at the argon blowing station, this process effectively promotes the collision, growth, and flotation of inclusions, thereby reducing the inclusion content in the molten steel. Furthermore, after stable operation following the switchover, this process requires no addition of ladle slag materials and does not involve calcium treatment of the molten steel. It successfully solves the problems of unstable castability and limited casting length in traditional direct argon blowing processes for low-carbon, low-silicon steel, enabling the molten steel to achieve the same casting availability and casting length as the BOF-LF-CCM route.

[0017] This invention directly reduces the LF processing step, thereby reducing the consumption of flux, electricity, alloys, argon, and refractory materials. Compared with the BOF-LF-CCM route, the cost per ton of steel is reduced by 38.6 yuan. Compared with the traditional argon blowing direct process with poor castability, by reducing the cost of ladle top slag and calcium treatment, and shortening the argon blowing direct process cycle, the cost per ton of steel is reduced by 9.8 yuan, significantly improving the economic benefits of enterprises.

[0018] Furthermore, this invention can also achieve stable switching between direct argon blowing and different process routes, completely solving the problem of order group casting and production scheduling for different routes, further reducing production costs, improving production efficiency and production flexibility, and bringing greater market competitiveness to enterprises. Attached Figure Description

[0019] Figure 1 This is a stroke diagram of the continuous casting stopper rod in Example 1.

[0020] Figure 2 This is the stroke diagram of the continuous casting stopper rod in Example 2.

[0021] Figure 3 This is the stroke diagram of the continuous casting stopper rod in Example 3. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0023] Low-carbon, low-silicon steel has a low carbon content, which easily leads to high oxygen levels at the converter endpoint, resulting in the formation of hard and brittle Al2O3 inclusions. The low silicon content also prevents the reduction of aluminum consumption through silicon deoxidation. Traditional processes often result in poor castability and short casting cycles due to inclusions clogging the nozzle. Based on these characteristics of low-carbon, low-silicon steel, this invention provides a converter semi-deoxidation argon blowing direct non-calcium treatment process suitable for low-carbon, low-silicon steel with C≤0.06% and Si≤0.05%, comprising the following steps: S1. Hot metal pretreatment: After desulfurization, the sulfur content is ≤0.003%, which reduces the risk of sulfur in molten steel reacting with manganese and aluminum to form MnS and Al2S3 inclusions, and avoids the problem of aggravated nozzle blockage caused by the formation of hard and brittle inclusions by these inclusions combined with Al2O3. Low-sulfur molten steel can also improve the fluidity of molten steel, reduce flow fluctuations caused by inclusion aggregation during casting, and directly improve castability.

[0024] The hot metal consumption is ≥825kg / t. A high proportion of hot metal can stabilize the converter blowing rhythm and avoid fluctuations in the final temperature and oxygen content caused by excessive scrap steel.

[0025] S2, Converter smelting: The final temperature should be controlled at 1625~1635℃. If the temperature is too high, it will aggravate the over-oxidation of molten steel, causing the oxygen content at the final point to soar and generate excessive Al2O3 inclusions. If the temperature is too low, it will reduce the fluidity of molten steel, and the temperature drop during argon blowing will easily fall below the continuous casting requirements, leading to casting interruption.

[0026] The amount of aluminum-based deoxidizer added during converter tapping is controlled according to the final oxygen content. When the final oxygen content is <400ppm, the amount of aluminum-based deoxidizer added is controlled at 1.2kg / 1ppm to ensure basic deoxidation effect. When the final oxygen content is ≥400ppm, the amount of aluminum-based deoxidizer added is controlled at 1.0kg / 1ppm to avoid excessive Al2O3 formation. When the final oxygen content is ≥600ppm, 24~60kg / heat of carbon powder is added first for pre-deoxidation, followed by the addition of aluminum-based deoxidizer. Carbon powder pre-deoxidation avoids the explosive formation of inclusions caused by directly using a large amount of aluminum for deoxidation in high-oxygen molten steel, thus mitigating the risk of inclusions clogging the nozzle. The upper limit of the amount of aluminum-based deoxidizer added is 650kg / heat to prevent billet cracks caused by excessive aluminum content.

[0027] In some embodiments, the aluminum-based deoxidizer is a high-aluminum iron with an aluminum content of 60%.

[0028] S3. Argon blowing: Bottom blowing of the ladle after tapping, with the bottom blowing flow rate controlled at ≥70 Nm³. 3 The system is subjected to vigorous stirring at a rate of / h. After argon arrives at the station, the temperature and oxygen levels are measured, and aluminum wire is fed. After aluminum feeding is completed, the bottom blowing flow rate is adjusted to 10~20 Nm. 3 Soft blowing is performed at a rate of / h, lasting ≥5min. Vigorous agitation creates intense circulation in the molten steel, promoting the collision and growth of fine Al2O3 inclusions remaining after partial deoxidation, significantly increasing their flotation speed and reducing the number of inclusions clogging the nozzle at the source. Simultaneously, vigorous agitation homogenizes the steel's composition and temperature, preventing fluidity fluctuations caused by uneven local composition or temperature, and improving castability. Soft blowing, with its gentle intensity, avoids secondary oxidation caused by excessive turbulence after vigorous agitation. During soft blowing, residual micro-inclusions continue to float until they are adsorbed by the top slag, further improving the steel's cleanliness. The ≥5min soft blowing time ensures sufficient flotation of inclusions, preventing inclusion residue due to insufficient argon blowing, extending nozzle life, and providing assurance for continuous casting across multiple heats.

[0029] In some embodiments, after argon is blown into the station, the oxygen content is detected, and aluminum is added accordingly based on the actual oxygen content. This avoids excessive formation of Al2O3 inclusions and ensures that the molten steel has suitable fluidity. It also avoids the problem of excessively high or low oxygen content caused by the one-size-fits-all deoxidation process in traditional processes, thus solving the problem of unstable castability. When the oxygen level at the station is less than 10 ppm, feed in 100 m of aluminum wire to supplement a small amount of aluminum to ensure the calming effect of the molten steel. When the oxygen concentration at arrival is between 10ppm and 50ppm, feed in 200m of aluminum wire to ensure sufficient deoxygenation. When the oxygen content at the destination is greater than 50 ppm, feed in aluminum wire of (200 + constant oxygen value) m. The constant oxygen value here is the oxygen content at the destination. Maintain vigorous stirring during the aluminum wire feeding process. Vigorous stirring causes the molten steel to flow violently, which allows the aluminum wire to melt quickly and disperse evenly. This prevents the formation of clusters of Al2O3 inclusions caused by localized agglomeration of the aluminum wire, ensuring that the deoxidation products are fine and easy to float, further improving the cleanliness and castability of the molten steel.

[0030] In some embodiments, the stirring time is ≥10 min.

[0031] For abnormal heats where the oxygen content at the converter endpoint is >800ppm or there is spot blowing or a small amount of slag falling during tapping, the soft blowing time should be extended by 2-3 minutes. By extending the soft blowing time, the floating of inclusions and the adsorption of top slag can be enhanced, which can compensate for the steel contamination caused by high oxygen or slag falling and avoid deterioration of castability.

[0032] For furnaces with poor bottom blowing in the ladle, the stirring time should be extended by 3-5 minutes. Extending the stirring time ensures that the inclusion removal rate meets the standard and avoids inclusion residue caused by bottom blowing problems.

[0033] In some embodiments, aluminum is added to the secondary aluminum feed wire according to the composition to ensure that the molten steel has sufficient calming and cleanliness, further stabilizes the castability, and supports extended casting cycles.

[0034] In some embodiments, the appropriateness of the soft blowing intensity can be determined by visual indicators such as the fluctuation of the molten steel surface and the slag ring being <10cm during soft blowing, thus avoiding fluctuations in castability caused by improper soft blowing parameters and providing visual assurance for extending the number of pours.

[0035] In some embodiments, the argon blowing temperature at the station in step S3 is 1610~1620℃, the outlet temperature is 1595~1605℃, and the superheat of the casting machine is 30~40℃. Full-process temperature control ensures stable steel fluidity, avoids fluctuations in castability due to temperature issues, and provides stable temperature conditions for continuous casting in multiple furnaces, extending the casting cycle length.

[0036] In some embodiments, when switching the LF route to the direct argon blowing route, the calcium treatment of the LF in the previous furnace is cancelled, the casting machine discharges slag, the tundish tonnage is controlled, and ≥150kg of top slag is added to the furnace in the current furnace.

[0037] In some embodiments, when switching the RH route to the direct argon blowing route, the amount of aluminum added to the RH in the previous furnace before the switch is <300kg, and when the top slag added to the furnace is ≥150kg and the RH casting stroke continues to rise, the nozzle is replaced before switching.

[0038] In some embodiments, after switching to the direct argon blowing route, no top slag such as lime, slag modifier, or slag conditioner is added during the tapping process and after the tapping is completed in step S2.

[0039] Example 1 SPCC and DX51D+Z steel grades (C≤0.06%, Si≤0.05%) were smelted using a 210t converter and the aforementioned low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process. 21 heats were smelted in a single casting (without changing the tundish). The specific implementation steps are as follows: S1. Hot metal pretreatment: The molten iron is desulfurized according to the process requirements to ensure that the sulfur content of the molten iron after desulfurization is ≤0.003% and the molten iron consumption is ≥825kg / t.

[0040] S2, Converter smelting: The converter's final temperature is controlled at 1625~1635℃, and the final oxygen content range for this casting cycle is 327ppm~692ppm. Specifically, for heats with a final oxygen content <400ppm, the aluminum-based deoxidizer addition is controlled at 1.2kg / 1ppm; for heats with a final oxygen content ≥400ppm and <600ppm, the aluminum-based deoxidizer addition is controlled at 1.0kg / 1ppm; for heats with a final oxygen content ≥600ppm, 24~60kg / heat of carbon powder is added for pre-deoxidation, followed by the addition of the aluminum-based deoxidizer, with an upper limit of 650kg / heat. The aluminum-based deoxidizer used is high-alumina ferroalloy with an aluminum content of 60%. Furthermore, this implementation example does not involve route switching, and no lime, slag modifiers, or slag conditioners are added during or after tapping.

[0041] S3, Argon blowing: After tapping, bottom blowing is performed on the ladle, with the bottom blowing flow rate controlled at ≥70 Nm³. 3 Agitation is performed at a rate of 10.5-14 minutes per hour, meeting the requirement of agitation time ≥ 10 minutes. After argon arrives at the station, temperature and oxygen levels are measured. The arrival temperature is 1610-1620℃, and the arrival oxygen content ranges from 57ppm to 164ppm. Aluminum wire is fed according to the arrival oxygen content: for furnaces with arrival oxygen > 50ppm, (200 + constant oxygen value) m of aluminum wire is fed. The constant oxygen value is the arrival oxygen content value. Agitation is maintained during aluminum wire feeding. After aluminum feeding is completed, the bottom blowing flow rate is adjusted to 10-20 Nm. 3Soft blowing was performed at a rate of 5-7 minutes per hour, meeting the requirement of ≥5 minutes. During soft blowing, the molten steel surface fluctuated and the slag ring was <10cm. No abnormalities were observed in this casting cycle, such as converter endpoint oxygen >800ppm, spot blowing, small amount of slag falling during tapping, or poor bottom blowing in the ladle. The molten steel outlet temperature was controlled at 1595-1605℃, and the casting machine superheat was 30-40℃. The castability was stable throughout the entire casting cycle. The tundish nozzle was changed in the 13th heat of continuous casting, but not in the remaining heats. The rolling quality was satisfactory.

[0042] like Figure 1 As shown by the brown curve, under the semi-deoxidized argon blowing direct non-calcium treatment process in this embodiment, the stopper rod stroke did not fluctuate frequently and drastically, and no casting abnormalities occurred due to the quality of the molten steel.

[0043] Example 2 A 210t converter was used to smelt DX51D+Z steel (C≤0.06%, Si≤0.05%) using a low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct-flow non-calcium treatment process. Fifteen heats were smelted in a single casting (without changing the tundish). Tundishes 1 to 5 used a single-run RH route, while tundish 6 and above switched to an argon blowing direct-flow route. The specific implementation steps are as follows: S1. Hot metal pretreatment: Complete the desulfurization of molten iron according to the process requirements, ensuring that the sulfur content of the molten iron after desulfurization is ≤0.003% and the molten iron consumption is ≥825kg / t.

[0044] S2, Converter smelting: The converter's final temperature is controlled at 1625~1635℃, and the final oxygen content range for heats 6 to 15 of the tundish is 370ppm~705ppm. Specifically, for heats with a final oxygen content <400ppm, the amount of aluminum-based deoxidizer added is controlled at 1.2kg / 1ppm; for heats with a final oxygen content ≥400ppm and <600ppm, the amount of aluminum-based deoxidizer added is controlled at 1.0kg / 1ppm; for heats with a final oxygen content ≥600ppm, 24~60kg / heat of carbon powder is added for pre-deoxidation, followed by the addition of the aluminum-based deoxidizer. The maximum addition of the aluminum-based deoxidizer is 650kg / heat, and the aluminum-based deoxidizer used is high-alumina ferroaluminum with an aluminum content of 60%.

[0045] Because the RH route is switched to the direct argon blowing route, the amount of aluminum added to the RH in the previous heat (Tundish 5) before the switching heat (Tundish 6) is 235kg~266kg. When switching heat (Tundish 6), 150kg of top slag lime is added. In the other heats (Tundish 7~Tundish 15), no lime, slag modifier, slag conditioner or other top slag is added during the tapping process and after the tapping is completed. And there is no continuous increase in the RH pouring stroke. The switch can be performed without changing the nozzle.

[0046] S3, Argon blowing: Bottom blowing of the ladle after tapping, with a bottom blowing flow rate ≥70 Nm³.3 The furnace is stirred vigorously for 11-15 minutes per hour, meeting the requirement of a stirring time ≥ 10 minutes. After argon arrives at the station, temperature and oxygen levels are measured. The arrival temperature is 1610-1620℃, and the arrival oxygen content ranges from 56ppm to 129ppm. Aluminum wire is fed according to the arrival oxygen content: for furnaces with arrival oxygen > 50ppm, (200 + constant oxygen value) m of aluminum wire is fed. The constant oxygen value is the arrival oxygen content. Vigorous stirring is maintained during aluminum wire feeding. After aluminum feeding is completed, the bottom blowing flow rate is adjusted to 10-20 Nm. 3 Soft blowing was performed at a rate of 5-8 minutes per hour, meeting the requirement of ≥5 minutes. During soft blowing, the molten steel surface fluctuated, and the slag ring was <10cm. There were no abnormal heats in this casting run. The molten steel outlet temperature was controlled at 1595-1605℃, and the casting machine superheat was 30-40℃. The castability of all heats was stable. The tundish nozzle was changed in the 9th heat of continuous casting, while the nozzles of the rest were not changed. The rolling quality was all qualified.

[0047] like Figure 2 As shown by the brown curve, under the semi-deoxidized argon blowing direct non-calcium treatment process in this embodiment, the stopper rod stroke did not fluctuate frequently and drastically, and no casting abnormalities occurred due to the quality of the molten steel.

[0048] Example 3 SPCC steel (C≤0.06%, Si≤0.05%) was smelted using a 210t converter and a low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct-up non-calcium treatment process. 22 heats were smelted in a single casting (without changing the tundish). Tundishes 1 to 18 used a single-line LF route, while tundish 19 and above switched to an argon blowing direct-up route. The specific implementation steps are as follows: S1. Hot metal pretreatment: Complete the desulfurization of molten iron according to the process requirements, ensuring that the sulfur content of the molten iron after desulfurization is ≤0.003% and the molten iron consumption is ≥825kg / t.

[0049] S2, Converter smelting: The converter endpoint temperature is controlled at 1625~1635℃, and the endpoint oxygen content range for heats 19 to 22 of the tundish is 407ppm~508ppm. For heats with endpoint oxygen ≥400ppm and <600ppm, the amount of aluminum-based deoxidizer added is controlled at 1.0kg / 1ppm.

[0050] Because the LF route is switched to the direct argon blowing route, the calcium treatment of the LF in the previous heat (18th tundish) before the switching heat (19th tundish) is cancelled. The casting machine adopts slag discharge and tundish tonnage control operation. 150kg of top slag lime is added in the switching heat (19th tundish). No lime, slag modifier, slag conditioner and other top slag are added during the tapping process and after the tapping of the other heats (20th to 22nd tundish).

[0051] S3, Argon blowing: Bottom blowing of the ladle after tapping, with a bottom blowing flow rate ≥70 Nm³. 3 A vigorous stirring process is performed at a rate of / h, with a vigorous argon stirring time of 10-15 minutes, meeting the requirement of a vigorous stirring time ≥10 minutes. After the argon arrives at the station, the temperature and oxygen content are measured. The arrival temperature is 1610-1620℃, and the arrival oxygen content ranges from 57ppm to 184ppm. Aluminum wire is fed according to the arrival oxygen content: if the arrival oxygen is >50ppm, feed (200 + the determined oxygen value) m of aluminum wire. The determined oxygen value is the arrival oxygen content value. Vigorous stirring is maintained during aluminum wire feeding. After aluminum feeding is completed, the bottom blowing flow rate is adjusted to 10-20 Nm. 3 Soft blowing was performed at a rate of 5.5-6.5 minutes per hour, meeting the requirement of ≥5 minutes. During soft blowing, the molten steel surface fluctuated and the slag ring was <10cm. There were no abnormal heats in this casting run. The molten steel outlet temperature was controlled at 1595-1605℃, and the casting machine superheat was 30-40℃. The castability of all heats was stable. The tundish nozzle was changed in the 16th heat of continuous casting, while the nozzles of the others were not changed, and the rolling quality was qualified. At the same time, depending on the composition of the molten steel, secondary aluminum feeding wire supplementation was performed as necessary.

[0052] like Figure 3 As shown by the brown curve, under the semi-deoxidized argon blowing direct non-calcium treatment process in this embodiment, the stopper rod stroke did not fluctuate frequently and drastically, and no casting abnormalities occurred due to the quality of the molten steel.

[0053] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A non-calcium treatment process for semi-deoxidation argon blowing directly onto a converter to process low-carbon, low-silicon steel, characterized in that... Includes the following steps: S1. Hot metal pretreatment: Sulfur content after desulfurization ≤0.003%, hot metal consumption ≥825kg / t; S2. Converter smelting: Control the final temperature to 1625~1635℃; control the amount of aluminum-based deoxidizer added to the converter according to the final oxygen content. When the final oxygen content is <400ppm, the amount of aluminum-based deoxidizer added is controlled at 1.2kg / 1ppm; when the final oxygen content is ≥400ppm, the amount of aluminum-based deoxidizer added is controlled at 1.0kg / 1ppm; when the final oxygen content is ≥600ppm, first add 24~60kg / furnace of carbon powder for pre-deoxidation, and then add aluminum-based deoxidizer; the upper limit of the amount of aluminum-based deoxidizer added is 650kg / furnace. S3. Argon blowing: Bottom blowing of the ladle after tapping, with the bottom blowing flow rate controlled at ≥70 Nm³. 3 The system is subjected to vigorous stirring at a rate of / h. After argon arrives at the station, the temperature and oxygen levels are measured, and aluminum wire is fed. After aluminum feeding is completed, the bottom blowing flow rate is adjusted to 10~20 Nm. 3 Perform soft blowing for ≥5 minutes per hour.

2. The low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process as described in claim 1, characterized in that, In step S2, the aluminum-based deoxidizer is high-aluminum iron with an aluminum content of 60%.

3. The low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process as described in claim 1, characterized in that, In step S3, when the oxygen level at the destination is <10ppm, feed in 100m of aluminum wire; when the oxygen level at the destination is 10ppm ≤ <50ppm, feed in 200m of aluminum wire; when the oxygen level at the destination is >50ppm, feed in (200 + constant oxygen value)m of aluminum wire.

4. The low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process as described in claim 1, characterized in that, The stirring time in step S3 shall be ≥10 min.

5. The low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process as described in claim 1, characterized in that, In step S3, during soft blowing, the molten steel surface fluctuates and the slag ring is less than 10cm.

6. The low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process as described in claim 1, characterized in that, In step S3, the argon blowing temperature at the station is 1610~1620℃, the temperature at the station outlet is 1595~1605℃, and the superheat of the casting machine is 30~40℃.

7. The low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process as described in claim 1, characterized in that, When switching the LF route to the direct argon blowing route, the calcium treatment of the LF in the previous furnace should be cancelled, the casting machine should discharge slag, the tundish tonnage should be controlled, and ≥150kg of top slag should be added to the furnace in the switching phase.

8. The low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process as described in claim 1, characterized in that, When switching the RH route to the direct argon blowing route, the amount of aluminum added to the RH in the previous furnace before the switch should be less than 300 kg. When the top slag added to the furnace during the switch is ≥150 kg and the RH casting stroke continues to rise, the nozzle should be replaced before switching again.

9. The low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process as described in claim 7 or 8, characterized in that, After switching to the direct argon blowing route, no top slag is added during the steel tapping process and after the steel tapping is completed in step S2.

10. The low-carbon, low-silicon steel converter semi-deoxidation argon blowing direct non-calcium treatment process as described in claim 1, characterized in that, Low-carbon, low-silicon steel contains C ≤ 0.06% and Si ≤ 0.05%.

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