Calcium abnormal treatment method for low-carbon low-silicon aluminum-containing steel and production method for low-carbon low-silicon aluminum-containing steel

Abstract

The application discloses a calcium abnormal treatment method of low-carbon low-silicon aluminum-containing steel and a production method of the low-carbon low-silicon aluminum-containing steel. In a gas supply mode of bottom argon blowing, a calcium wire is fed to molten steel. Under normal circumstances, the amount of the calcium wire fed per ton of molten steel is 1.05 m-1.35 m, the feeding speed of the calcium wire is 150-250 m / min, and the calcium content in the molten steel is 15-25 ppm. By controlling the feeding speed and the amount of the calcium wire, the types and quantity of inclusions in the molten steel are effectively controlled, and the situation of the stopper rising caused by the clogging of the tundish nozzle is reduced.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, and more specifically, to a method for treating calcium abnormalities in low-carbon, low-silicon aluminum-containing steel and a method for producing low-carbon, low-silicon aluminum-containing steel. Background Technology

[0002] For low-carbon, low-silicon aluminum-containing steels, such as SWRCH22A, due to their low carbon and silicon content and high aluminum content, deoxidation is mainly achieved by aluminum. Therefore, such steels require high-quality calcium treatment. Current calcium treatment processes control the calcium feeding line speed and amount, taking into account basic parameters such as the carbon, aluminum, and sulfur content before feeding, to effectively control the types and quantities of inclusions in the molten steel. However, these are general measures under normal circumstances. There is almost no mention of how to anticipate and implement emergency measures when the calcium treatment effect in the molten steel may be poor, in order to reduce the rise of the stopper rod caused by tundish nozzle nodule formation, and thus ensure the smooth completion of multiple heats of continuous casting. In view of this, this invention is proposed. Summary of the Invention

[0003] The purpose of this invention is to provide a method for treating calcium abnormalities in low-carbon, low-silicon aluminum-containing steel and a method for producing low-carbon, low-silicon aluminum-containing steel, thereby mitigating the stopper rod rise caused by tundish nozzle nodule formation by adjusting the parameters of the calcium treatment step.

[0004] This invention is implemented as follows:

[0005] In a first aspect, the present invention provides a method for handling calcium anomalies in low-carbon, low-silicon, aluminum-containing steel, wherein calcium is fed into the molten steel in a bottom-blown argon gas supply mode, comprising normal production and anomaly handling:

[0006] During normal production, the amount of calcium wire fed into each ton of molten steel is 1.05m-1.35m, the feeding speed is 150-250m / min, and the calcium content in the molten steel leaving the station is 15-25ppm.

[0007] In case of any of the following abnormal situations, take a steel sample 2.5-3.5 minutes after feeding the calcium line to confirm the calcium content as A. If A is less than 15 ppm, determine whether to feed the calcium line again based on the expected soft blowing time after feeding the calcium line.

[0008] ① Adopting a production mode of non-aluminum steel + low-carbon, low-silicon aluminum steel, casting in the second batch;

[0009] ②The first batch after the new calcium wire is replaced, or the last two batches when the calcium wire is bundled;

[0010] ③ Heats where the distance between the outlet and the molten steel surface is greater than 800 mm;

[0011] ④ Furnaces in which there are ≤2 instances of obvious splashing during calcium wire feeding. The splashing refers to the phenomenon where calcium vapor rises and carries steel and slag out during calcium wire feeding, causing them to spray out from the ladle opening. The obvious splashing refers to the phenomenon where the distance between the scattered steel sparks and the ladle wall is ≥3m.

[0012] In an optional embodiment, the calcium wire is a pure calcium wire;

[0013] Preferably, after feeding the calcium thread, the calcium should be gently blown out for 15-25 minutes.

[0014] Preferably, the distance between the outlet of the calcium feed line and the surface of the molten steel is ≤800mm.

[0015] In an optional embodiment, the low-carbon, low-silicon aluminum-containing steel contains C ≤ 0.25 wt%, Si ≤ 0.10 wt%, S ≤ 0.015 wt%, and 0.020% ≤ Als ≤ 0.045%.

[0016] In an optional implementation, if A < 10 ppm, calcium wire is immediately added, and the amount of calcium wire added per furnace of molten steel is B = 60 / A + 150m.

[0017] In an optional implementation, if 10≤A≤12ppm and the expected soft blowing time after the calcium wire is fed is ≥13min, then the amount of calcium wire fed per furnace of molten steel is B=40-60m;

[0018] If 10≤A≤12ppm, and the expected softening time after supplementing with calcium thread is <13min, then do not supplement with calcium thread.

[0019] In an optional implementation, if 12 < A ≤ 15 ppm and the expected soft blowing time after the calcium wire is replenished is ≥ 13 min, then the amount of calcium wire replenished per furnace of molten steel is B = 20-40 m.

[0020] If 12 < A ≤ 15 ppm, and the expected softening time after supplementing with calcium thread is < 13 minutes, then do not supplement with calcium thread, and focus on maintaining the softening time.

[0021] In an optional implementation, if the above-mentioned abnormal situation occurs in the Nth heat (N≥2), and the stopper rises by more than 2mm after the continuous casting feedback ladle is opened, then the amount of calcium wire fed into the N+1th heat of molten steel is 190-210m.

[0022] Secondly, the present invention provides a method for producing low-carbon, low-silicon aluminum-containing steel, comprising sequentially performing primary steelmaking, deoxidation, refining, and calcium treatment of the steel as described in any one of the aforementioned embodiments.

[0023] The present invention has the following beneficial effects:

[0024] By controlling the calcium feeding rate and amount, combined with abnormal handling methods, the types and quantities of inclusions in the molten steel can be effectively controlled, thereby reducing the occurrence of stopper rod rise caused by tundish nozzle nodule formation. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0026] This application provides a method for handling calcium anomalies in low-carbon, low-silicon aluminum-containing steel, wherein calcium is fed into the molten steel in a bottom-blown argon gas supply mode, including normal production and anomaly handling:

[0027] During normal production, the amount of calcium wire fed into each ton of molten steel is 1.05m-1.35m, the feeding speed is 150-250m / min, and the calcium content in the molten steel leaving the station is 15-25ppm.

[0028] In case of any of the following abnormal situations, take a steel sample 2.5-3.5 minutes after feeding the calcium line to confirm the calcium content as A. If A is less than 15 ppm, determine whether to feed the calcium line again based on the expected soft blowing time after feeding the calcium line.

[0029] ① Adopting a production mode of non-aluminum steel + low-carbon, low-silicon aluminum steel, casting in the second batch;

[0030] ②The first batch after the new calcium wire is replaced, or the last two batches when the calcium wire is bundled;

[0031] ③ Heats where the distance between the outlet and the molten steel surface is greater than 800 mm;

[0032] ④ Furnaces in which there are ≤2 instances of obvious splashing during calcium wire feeding. The splashing refers to the phenomenon where calcium vapor rises and carries steel and slag out during calcium wire feeding, causing them to spray out from the ladle opening. The obvious splashing refers to the phenomenon where the distance between the scattered steel sparks and the ladle wall is ≥3m.

[0033] The amount of calcium wire fed is closely related to the calcium content of the molten steel leaving the station. For low-carbon, low-silicon, aluminum-containing steel, the amount of calcium wire fed per ton of molten steel is 1.05m-1.35m. Under normal circumstances, the mass of a furnace of molten steel is 130-145 tons, and the amount of calcium wire fed is 155-175m, with a typical value of 170m / 140t.

[0034] Furthermore, the feeding speed of the calcium wire is closely related to calcium loss. If the feeding speed is too high, the calcium wire will be fed into the molten steel to a greater depth, resulting in greater splashing intensity and reduced steel quality. If the feeding speed is too low, the calcium wire will be fed into the molten steel to a shallow depth and will remain in the molten steel for too short a time, increasing calcium loss.

[0035] In this embodiment, the calcium wire is typically fed at the above-mentioned feeding rate and amount. After completion, a sample is taken before the molten steel leaves the station to determine the calcium content in the molten steel. The calcium content in the molten steel leaving the station is 15-25 ppm. If the Ca content in the molten steel leaving the station is <15 ppm, then there is a high probability that the molten steel in this furnace will be damaged due to insufficient calcium treatment, resulting in insufficient floating of Al2O3 inclusions in the molten steel. This will lead to the accumulation of Al2O3 inclusions at the nozzle, the rise of the stopper rod, fluctuation of the liquid level in the crystallizer, and a deterioration in the quality of the cast billet.

[0036] In the exception handling steps:

[0037] ① The production mode of non-aluminum steel + low-carbon, low-silicon aluminum steel is adopted, and the second heat is poured. In the existing technology, when producing low-carbon, low-silicon aluminum steel, the production mode of HPB300 steel (non-aluminum steel) + multiple heats of SWRCH22A steel (low-carbon, low-silicon aluminum steel) may be adopted. In this case, since the first heat is generally non-aluminum deoxidized steel, that is, Si and Mn deoxidized steel, if the molten steel in this heat has strong oxidizing properties and the calcium treatment of the second heat (i.e. the first heat of low-carbon, low-silicon aluminum steel) is not sufficient, the aluminum in the molten steel of the second heat is easily oxidized to Al2O3 in the tundish, which may eventually lead to nozzle blockage.

[0038] ② The first batch after replacing the calcium wire or the last two batches of the calcium wire bundle; in these two cases, due to the different tightness of the end closure of each bundle of calcium wire during production, and the powder falling off when the operator inserts the calcium wire into the wire feeder, the hardness of the wire and the weight of calcium core powder per unit length of wire will change, thus affecting the amount of calcium wire fed.

[0039] ③ Heats where the distance between the outlet and the molten steel surface is greater than 800mm; When the converter occasionally has insufficient steel output, the large clearance distance will reduce the vertical downward velocity of the calcium wire when feeding it, and the force of the wire penetrating the steel-slag interface will be weaker, which may prevent the calcium wire from being fed into the molten steel.

[0040] ④ Heats in which there are ≤2 instances of noticeable splashing during calcium wire feeding. Splashing refers to the phenomenon where calcium vapor rises and carries steel and slag out of the ladle during calcium wire feeding; noticeable splashing means that the distance between the landing point of the scattered steel sparks and the ladle wall is ≥3m. The inventors discovered that if there is no noticeable splashing or the number of splashes is too low during calcium wire feeding, it may be due to insufficient calcium core powder per unit length of wire or insufficient deoxidation of the molten steel before calcium wire feeding, resulting in insufficient calcium vapor production per unit time and inadequate calcium treatment.

[0041] The aforementioned abnormal situations may result in low calcium content in the steel strand, thus affecting the quality of the cast billet. Therefore, when these abnormal situations occur, it is necessary to take samples in advance to confirm the calcium content in the molten steel. In this embodiment, sampling is carried out approximately 3 minutes after the calcium wire is fed. On the one hand, at this time, the calcium wire has reacted relatively fully with the molten steel, and the calcium content is representative. On the other hand, it is necessary to ensure that there is sufficient time for replenishing the calcium wire before the molten steel leaves the station. Therefore, sampling needs to be carried out as soon as possible.

[0042] In an optional embodiment, the calcium wire is a pure calcium wire.

[0043] In an optional implementation, after feeding the calcium wire, a soft blowing process is performed for 15-25 minutes to stir the molten steel.

[0044] In an optional implementation, the distance between the outlet and the molten steel surface is ≤800mm when feeding calcium wire, which is conducive to the smooth feeding of calcium wire into the molten steel.

[0045] In an optional embodiment, the low-carbon, low-silicon aluminum-containing steel contains C ≤ 0.25 wt%, Si ≤ 0.10 wt%, S ≤ 0.015 wt%, and 0.020% ≤ Als ≤ 0.045%.

[0046] In an optional implementation, if A < 10 ppm, calcium wire is immediately added, and the amount of calcium wire added per furnace of molten steel is B = 60 / A + 150m; if A < 10 ppm, due to the low calcium content, calcium wire must be added immediately regardless of how much time is expected between the time of adding calcium wire and the time before the molten steel leaves the station. This may shorten the soft blowing time, but the soft blowing time will generally be ≥ 9 min.

[0047] In an optional implementation, if 10≤A≤12ppm and the expected soft blowing time after the calcium wire is fed is ≥13min, then the amount of calcium wire fed per furnace of molten steel is B=40-60m;

[0048] If 10≤A≤12ppm, and the expected softening time after supplementing with calcium thread is <13min, then do not supplement with calcium thread.

[0049] If 10 ≤ A ≤ 12 ppm, prioritize ensuring sufficient soft blowing time. Provided the soft blowing time is not less than 13 minutes, supplement with calcium thread. The time for supplementing with calcium thread in this application can be calculated based on the amount and speed of calcium thread supplementation, and by considering the sampling time, the time required to complete the calcium thread supplementation can be estimated.

[0050] In an optional implementation, if 12 < A ≤ 15 ppm and the expected soft blowing time after the calcium wire is replenished is ≥ 13 min, then the amount of calcium wire replenished per furnace of molten steel is B = 20-40 m.

[0051] If 12 < A ≤ 15 ppm, and the expected softening time after supplementing with calcium thread is < 13 minutes, then do not supplement with calcium thread, and focus on maintaining the softening time.

[0052] If 12 < A ≤ 15 ppm, prioritize ensuring the soft blowing time. Provided that the soft blowing time is not less than 13 minutes, supplement with calcium thread.

[0053] In an optional implementation, if A > 15 ppm, calcium supplementation is not required.

[0054] In an optional implementation, if the above-mentioned abnormal situation occurs in the Nth heat (N≥2), and the stopper rises by more than 2mm after the continuous casting feedback ladle is opened, then the amount of calcium wire fed into the N+1th heat of molten steel is 190-210m.

[0055] If the above abnormality occurs during the Nth heat, accompanied by the stopper rod rising by more than 2mm, the calcium wire feed rate should be increased to 190-210mm to allow the Al2O3 inclusions in the molten steel to float to the surface, reduce the accumulation of Al2O3 inclusions at the nozzle, and reduce the rise of the stopper rod.

[0056] Secondly, the present invention provides a method for producing low-carbon, low-silicon aluminum-containing steel, comprising sequentially performing primary steelmaking, deoxidation, refining, and calcium treatment of the steel as described in any one of the aforementioned embodiments.

[0057] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0058] Comparative Example 1

[0059] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22A steel) under normal conditions: In the second heat of casting 61134, under the bottom-blown argon gas supply mode, 170m of pure calcium wire is fed into 140t of molten steel. The calcium wire fed is when about half of the whole bundle of calcium wire is used. The distance between the outlet of the calcium wire and the surface of the molten steel is 400mm. The feeding speed of the calcium wire is 200m / min. During the feeding, there are 3 obvious splashes. After the calcium wire is fed, soft blowing is performed for 15min.

[0060] The calcium content in the molten steel leaving the station was 14 ppm. Subsequently, the stopper rod rose by -0.5 mm (i.e. fell by 0.5 mm), and the number of fluctuations in the liquid crystallization level was 0.

[0061] Comparative Example 2

[0062] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22A steel). The main difference from Example 1 before the technical modification is that the last batch of calcium wire bundled is used when feeding calcium wire.

[0063] In the second heat of 61148 SWRCH22A, under the bottom-blown argon gas supply mode, 170m of pure calcium wire was fed into 138t of molten steel. The calcium wire was a whole bundle of calcium wire, and when about 200m was used, the distance between the outlet of the calcium wire and the surface of the molten steel was 380mm. The feeding speed was 200m / min. During the feeding, there were 3 obvious splashes. After the calcium wire was fed, soft blowing was carried out for 15min.

[0064] The calcium content in the molten steel leaving the station was 7 ppm. Subsequently, the stopper rod rose by 9.3 mm, and the number of fluctuations in the liquid crystallization level was 8.

[0065] Comparative Example 3

[0066] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22A steel). The main difference from Example 1 before the technical modification is that the distance between the outlet and the molten steel surface is 900mm.

[0067] In the second heat of casting 61187, SWRCH22A, under the bottom-blown argon gas supply mode, 170m of pure calcium wire was fed into 141t of molten steel. The calcium wire was a whole bundle of calcium wire used to the middle section. The distance between the outlet of the calcium wire and the surface of the molten steel was 900mm. The feeding speed was 200m / min. During the feeding, there were 3 obvious splashes. After the calcium wire was fed, soft blowing was carried out for 15min.

[0068] The calcium content in the molten steel leaving the station was 12 ppm. Subsequently, the stopper rod rose by 4 mm, and the number of fluctuations in the liquid crystallization level was 4.

[0069] Comparative Example 4

[0070] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22A steel). The main difference from Example 1 before the technical modification is that the number of obvious splashes during the calcium feeding line is 1.

[0071] In the second heat of 61245 SWRCH22A, under the bottom-blown argon gas supply mode, 170m of pure calcium wire was fed into 143t of molten steel. The calcium wire was a whole bundle and used to the middle section. The distance between the outlet of the calcium wire and the surface of the molten steel was 410mm. The feeding speed was 200m / min. Because the molten steel may not have been sufficiently deoxidized before feeding the calcium wire, there was only one obvious splash during the feeding period. After feeding the calcium wire, soft blowing was carried out for 16min.

[0072] The calcium content in the molten steel leaving the station was 9 ppm. Subsequently, the stopper rod rose by 6.5 mm, and the number of fluctuations in the liquid crystallization level was 5.

[0073] For the third heat of SWRCH22A in casting batch 61245, the influence of the stopper rod curve of the second heat was disregarded. Under the bottom-blown argon gas supply mode, 170m of pure calcium wire of normal length was still fed into 140t of molten steel. The calcium wire fed was a whole bundle of calcium wire used to the middle section. The distance between the outlet of the calcium wire and the surface of the molten steel was 400mm. The feeding speed of the calcium wire was 200m / min. During the feeding, there were 3 obvious splashes. After the calcium wire was fed, soft blowing was carried out for 15min.

[0074] The calcium content in the molten steel leaving the station was 16 ppm. Subsequently, the stopper rod rose by 2.2 mm, and the liquid surface fluctuated twice.

[0075] Example 1

[0076] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22A steel), which differs from Comparative 2 only in that: the calcium content is confirmed by sampling in advance and abnormal treatment measures are adopted.

[0077] Three minutes after feeding the calcium wire, a sample was taken to confirm the calcium content. It was found that the calcium content was only 9 ppm. Calcium wire B = (60 / 9 + 150) m ≈ 157 m was immediately added. After feeding the calcium wire, the temperature was measured and a sample was taken after 13 minutes of soft blowing. The molten steel was then discharged from the station.

[0078] The calcium content in the molten steel leaving the station was 14 ppm. Subsequently, the stopper rod rose by 1.3 mm, and the number of fluctuations in the liquid crystallization level was 2.

[0079] Results: By taking samples in advance to confirm the calcium content and adopting abnormal handling measures, the results were significantly improved compared to the previous results (calcium content in the molten steel leaving the station was 7 ppm, the stopper rod rose by 9.3 mm, and the number of fluctuations in the liquid crystallization surface was 8).

[0080] Example 2

[0081] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22A steel), which differs from Comparative Example 3 only in that: the calcium content is confirmed by sampling in advance and abnormal treatment measures are adopted.

[0082] Three minutes after feeding the calcium wire, a sample was taken to confirm the calcium content. It was found that the calcium content was only 14 ppm. Calcium wire B=30m was immediately fed again. After feeding the calcium wire, the temperature was measured and a sample was taken after 15 minutes of soft blowing. The molten steel was then discharged from the station.

[0083] The calcium content in the molten steel leaving the station was 16 ppm. Subsequently, the stopper rod rose by 0.8 mm, and the number of fluctuations in the liquid crystallization level was 1.

[0084] Results: By taking samples in advance to confirm the calcium content and adopting abnormal handling measures, the results were significantly improved compared to the previous results (calcium content in the molten steel leaving the station was 12 ppm, the stopper rod rose by 4 mm, and the number of fluctuations in the liquid crystallization level was 4).

[0085] Example 3

[0086] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22A steel), which differs from Comparative Example 4 only in that: the second furnace is poured, samples are taken in advance to confirm the calcium content, and abnormal treatment measures are adopted.

[0087] Three minutes after feeding the calcium wire, a sample was taken to confirm the calcium content. It was found that the calcium content was only 11 ppm. Calcium wire B=50m was immediately fed again. After feeding the calcium wire, the temperature was measured and a sample was taken after 15 minutes of soft blowing. The molten steel was then discharged from the station.

[0088] The calcium content in the molten steel leaving the station was 17 ppm. Subsequently, the stopper rod rose by 0.2 mm, and the number of fluctuations in the liquid crystallization level was 1.

[0089] Results: By taking samples in advance to confirm the calcium content and adopting abnormal handling measures, the results were significantly improved compared to the previous results (calcium content in the molten steel leaving the station was 9 ppm, the stopper rod rose by 6.5 mm, and the number of fluctuations in the liquid crystallization surface was 5).

[0090] Example 4

[0091] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22A steel), which differs from Comparative Example 4 only in that: the third furnace is cast, and abnormal treatment measures are adopted in advance.

[0092] Considering the poor stopper rod curve of the second heat of steel, under the bottom blowing argon gas supply mode, 195m of pure calcium wire was fed into 140t of molten steel (normally 170m). The calcium wire was fed in a whole bundle and was used to the middle section. The distance between the outlet of the calcium wire and the surface of the molten steel was 400mm. The feeding speed was 200m / min. During the feeding, there were 4 obvious splashes. After the calcium wire was fed, soft blowing was carried out for 15min.

[0093] The calcium content in the molten steel leaving the station was 18 ppm. Subsequently, the stopper rod rose by -0.1 mm (i.e., fell by 0.1 mm), and the number of fluctuations in the liquid crystallization level was 1.

[0094] Results: By adopting abnormal handling measures in advance, the results were significantly better than before (calcium content in the molten steel leaving the station was 16 ppm, the stopper rod rose by 2.2 mm, and the number of fluctuations in the liquid crystallization surface was 2).

[0095] As can be seen from Examples 1-4, the corresponding method of the present invention effectively solves the abnormalities during molten steel pouring.

[0096] Comparative Example 5

[0097] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22A steel), which differs from Embodiment 2 only in that: after supplementing with calcium wire, the soft blowing time is <13min.

[0098] Three minutes after feeding the calcium wire, a sample was taken to confirm the calcium content. Because the laboratory produced the steel sample composition late, it was later found that the calcium content was only 14 ppm. Calcium wire B=30m was immediately fed again. After feeding the calcium wire, it was only enough to blow softly for 10 minutes before the temperature was measured and the sample was taken. The molten steel was then discharged from the station.

[0099] The calcium content in the molten steel leaving the station was 15 ppm. Subsequently, the stopper rod rose by 1.5 mm, and the number of fluctuations in the liquid crystallization level was 2.

[0100] Results: Due to the failure to properly calculate the remaining soft blowing time after supplementing with calcium wire, the soft blowing time should have been maintained, but the decision was made to continue supplementing with calcium wire. As a result, the final outcome was worse than the previous one (calcium content in the molten steel leaving the station was 16 ppm, the stopper rod rose by 0.8 mm, and the number of fluctuations in the crystallization liquid level was 1).

[0101] Comparative Example 6

[0102] This embodiment provides a calcium treatment method for low-carbon, low-silicon aluminum-containing steel (SWRCH22 steel). The only difference from Embodiment 3 is that after discovering that the calcium content is low, no calcium line is added; only the soft blowing time is guaranteed.

[0103] Three minutes after feeding the calcium line, a sample was taken to confirm the calcium content, which was found to be only 11 ppm. No additional calcium line was fed. After feeding the calcium line, the temperature was measured and a sample was taken 19 minutes after the soft blowing was completed. The molten steel was then discharged from the station.

[0104] The calcium content in the molten steel leaving the station was 9 ppm. Subsequently, the stopper rod rose by 5.5 mm, and the number of fluctuations in the liquid crystallization level was 4.

[0105] Results: The attempt to remove inclusions in the molten steel by extending the soft blowing time did not achieve the desired effect, and the final result was worse than the previous result (calcium content in the molten steel leaving the station was 17 ppm, the stopper rod rose by 0.2 mm, and the number of crystallization liquid level fluctuations was 1).

[0106] Comparative examples 5 and 6 show that a balance needs to be struck between continuing to supplement calcium feed (to fully denature inclusions in the molten steel) and ensuring sufficient soft blowing time (to allow inclusions to float to the surface), otherwise both will have adverse effects.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating calcium abnormalities in low-carbon, low-silicon aluminum-containing steel, wherein calcium wire is fed into the molten steel under bottom-blown argon gas supply mode, characterized in that, Includes normal production and abnormal handling: During normal production, the amount of calcium wire fed into each ton of molten steel is 1.05m - 1.35m, the feeding speed is 150-250m / min, and the calcium content in the molten steel leaving the station is 15-25ppm. In case of any of the following abnormal situations, take a steel sample 2.5-3.5 minutes after feeding the calcium line to confirm the calcium content as A. If A is less than 15 ppm, determine whether to feed the calcium line again based on the expected soft blowing time after feeding the calcium line. ① Adopting a production mode of non-aluminum steel + low-carbon, low-silicon aluminum steel, casting in the second batch; ②The first batch after the new calcium wire is replaced, or the last two batches when the calcium wire is bundled; ③ Heats where the distance between the outlet and the molten steel surface is greater than 800 mm; ④ Furnaces in which there are ≤2 instances of obvious splashing during calcium wire feeding. Splashing refers to the phenomenon where calcium vapor rises and carries steel and slag out of the ladle opening during calcium wire feeding; obvious refers to splashing where the distance between the falling steel sparks and the ladle wall is ≥3m. If A < 10 ppm, then immediately supplement with calcium wire. The amount of calcium wire supplemented per furnace of molten steel is B = 60 / A + 150m. If 10≤A≤12ppm and the expected soft blowing time after the calcium wire is replenished is ≥13min, then the amount of calcium wire replenished per furnace of molten steel is B=40-60m; If 10≤A≤12ppm, and the expected soft blowing time after supplementing with calcium thread is <13min, then do not supplement with calcium thread; If 12 < A ≤ 15 ppm and the expected soft blowing time after the calcium wire is replenished is ≥ 13 min, then the amount of calcium wire replenished per furnace of molten steel is B = 20-40 m. If 12 < A ≤ 15 ppm, and the expected softening time after supplementing with calcium thread is < 13 minutes, then do not supplement with calcium thread, and focus on maintaining the softening time.

2. The method for treating calcium abnormalities in low-carbon, low-silicon aluminum-containing steel according to claim 1, characterized in that, The calcium wire is pure calcium wire; After feeding the calcium thread, perform a gentle blowing process for 15-25 minutes. When feeding calcium wire, the distance between the outlet and the surface of the molten steel should be ≤800mm.

3. The method for treating calcium abnormalities in low-carbon, low-silicon aluminum-containing steel according to claim 1, characterized in that, The low-carbon, low-silicon aluminum-containing steel contains C ≤ 0.25 wt%, Si ≤ 0.10 wt%, S ≤ 0.015 wt%, and 0.020% ≤ Als ≤ 0.045%.

4. The method for treating calcium abnormalities in low-carbon, low-silicon aluminum-containing steel according to claim 1, characterized in that, If the above-mentioned abnormal situation occurs in the Nth heat (N≥2), and the stopper rod rises more than 2mm after the continuous casting feedback ladle opens, then the amount of calcium wire fed into the N+1th heat of molten steel is 190-210m.

5. A method for producing low-carbon, low-silicon aluminum-containing steel, characterized in that, The method includes sequentially performing primary steelmaking, deoxidation, refining, and calcium abnormality treatment of the steel as described in any one of claims 1-4 for low-carbon, low-silicon aluminum-containing steel.