Smelting method for controlling total aluminum content of heavy rail steel

Abstract

The invention relates to the technical field of steel smelting, in particular to a smelting method for controlling the total aluminum content of heavy rail steel. The smelting method provided by the invention comprises the steps of converter smelting, LF refining, RH treatment and continuous casting treatment, a proper amount of low-aluminum ferrosilicon alloy is added for deoxidation through converter tapping, a magnesium-aluminum steel ladle is operated, the LF adopts a low-aluminum slag system and RH enhanced deoxidation to cooperatively control aluminum and oxygen, stable production of the heavy rail steel with [Al] less than or equal to 0.0020 wt% is realized, the average aluminum content can be reduced to below 0.0015 wt%, and the production cost is reduced. And meanwhile, T.[ O] in the steel is controlled to be 0.0008 wt% or below, and the molten steel cleanliness of the heavy rail steel can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and in particular to a smelting method for controlling the total aluminum content of heavy rail steel. Background Technology

[0002] In the smelting process of heavy rail steel, precise control of the total aluminum content is a core factor determining the cleanliness and fatigue resistance of the molten steel. As a strong deoxidizing element, aluminum's residual form (acid-soluble aluminum and total aluminum) directly affects the type and distribution of inclusions in the heavy rail steel. When the total aluminum content in the steel exceeds 0.0040 wt%, brittle Al2O3 inclusions are easily formed, leading to the initiation of fatigue cracks in the rail. However, in traditional processes, due to fluctuations in the oxygen content at the converter endpoint and the extensive use of aluminum alloys and auxiliary materials, it is often difficult to stably control the total aluminum content in the steel below 0.0040 wt%.

[0003] The limitation of existing technologies lies in the insufficient synergy of aluminum and oxygen content control throughout the entire process. For example, in the converter deoxidation stage, the oxygen content at the converter endpoint fluctuates significantly. Excessive addition of low-alumina deoxidation alloys can lead to increased aluminum content, while insufficient addition makes it difficult to control the oxygen content of the molten steel. In the LF refining stage, the traditional slag-forming process adds bauxite to the slag, resulting in an Al2O3 content in the slag exceeding 15wt%, which in turn increases the aluminum content in the molten steel. During RH vacuum treatment, if the slag basicity is not properly controlled, the increased activity of Al2O3 in the slag can also lead to aluminum reversion in the molten steel, thereby increasing the total aluminum content by 0.0005wt%-0.0010wt%. In addition, the prolonged contact between high-alumina castables as ladle refractory materials and molten steel can cause emulsification at the "molten steel-high-alumina ladle brick" interface, introducing exogenous Al2O3 into the molten steel and increasing both the total aluminum and total oxygen content.

[0004] Patent application CN111254248A discloses a method for controlling the total aluminum content in U75V heavy rail steel. However, due to the addition of 0.5~1.2 kg / t of bauxite slag in the LF furnace, the Al2O3 content in the LF refining slag is difficult to control, with the proportion of total Al ≤ 0.0040 wt% only reaching over 90%. Patent application CN118256671A discloses a method for controlling magnesium-aluminum spinel inclusions in heavy rail steel production by using deoxidizers and alloys with low total aluminum content during the converter tapping and refining processes. However, this method can only control the acid-soluble aluminum content in heavy rail steel to no more than 0.0050 wt%, and does not focus on controlling total oxygen content. Therefore, it is necessary to develop a process system for the coordinated control of aluminum and oxygen content throughout the entire heavy rail steel production process to simultaneously reduce the total aluminum and total oxygen content in heavy rail steel, providing a favorable guarantee for the high-quality production of heavy rail steel in the railway era. Summary of the Invention

[0005] In view of this, the present invention provides a smelting method for controlling the total aluminum content of heavy rail steel, which can effectively control the total aluminum content and oxygen content.

[0006] This invention provides a smelting method for controlling the total aluminum content of heavy rail steel, comprising the following steps:

[0007] (A) Converter smelting:

[0008] Steel is tapped when the converter smelting reaches the converter endpoint; the carbon content at the converter endpoint is controlled to be ≥0.05wt%, and the tapping temperature is 1640~1660℃; during the tapping process, when the steel amount is ≥1 / 4, low-aluminum ferrosilicon alloy is added for deoxidation, followed by low-aluminum ferrosilicon manganese alloy for alloying, active lime is added for slag formation, and finally a carbon raiser is added for carbon raising; after tapping, the ladle is sent to the furnace post-furnace argon blowing station for argon blowing.

[0009] The working layer of the ladle is constructed with magnesium-aluminum ladle bricks, and the slag line is constructed with magnesium-carbon ladle bricks.

[0010] (B) LF Refining:

[0011] When the LF ladle enters the station, silicon-calcium alloy is added to the slag surface and then heated by electricity. Refining slag and cryolite are then added to form slag. After the LF slag formation is completed, silicon-calcium alloy is added again and the temperature is raised to 1550~1580℃ before heating is stopped.

[0012] (C) RH treatment:

[0013] When RH enters the station, the oxygen of the molten steel is determined. Based on the oxygen determination results, silicon-calcium alloy is added again. The molten steel in the ladle is then vacuumed, and alloy is added for alloying treatment. The system is circulated for more than 5 minutes to break the vacuum and then soft argon blowing is performed.

[0014] (D) Continuous casting process:

[0015] The molten steel from step (C) is subjected to continuous casting.

[0016] Preferably, in step (A), the chemical composition of the low-aluminum silicon-iron alloy includes: Si: 65.0~85.0wt%, Al: <0.5wt%, with the balance being Fe and unavoidable impurities;

[0017] The particle size of the low-aluminum silicon-iron alloy is 20~50mm.

[0018] Preferably, in step (A), the amount of low-aluminum ferrosilicon alloy added and the final carbon content satisfy the following relationship: added amount = 9 - 100X; wherein, when the final carbon content is 0.05wt%~0.07wt%, X = final carbon content; when the final carbon content is >0.07wt%, X = 0.07wt%.

[0019] Preferably, the magnesium-aluminum steel-clad brick contains MgO content ≥ 50 wt%, Al2O3 content ≤ 30 wt%, and C content ≥ 5 wt%.

[0020] Preferably, the chemical composition of the silicon-calcium alloy is: Si: 55.0~65.0wt%, Ca: 10.0~25.0wt%, Al: <1wt%, with the balance being Fe and unavoidable impurities;

[0021] The particle size of the silicon-calcium alloy is 5~30mm.

[0022] Preferably, in step (C), the amount of silicon-calcium alloy added is preferably 0.1~0.9 kg / t steel, and simultaneously satisfies the following classification relationship with the oxygen determination result:

[0023] Oxygen content ≤12ppm, silicon-calcium alloy addition amount is 0.1kg / t steel;

[0024] 12ppm < constant oxygen ≤ 14ppm, silicon-calcium alloy addition is 0.3kg / t steel;

[0025] 14ppm < constant oxygen ≤ 16ppm, silicon-calcium alloy addition is 0.5kg / t steel;

[0026] 16ppm < constant oxygen ≤ 18ppm, silicon-calcium alloy addition is 0.7kg / t steel;

[0027] 18ppm < constant oxygen < 20ppm, silicon-calcium alloy addition is 0.8kg / t steel;

[0028] Oxygen concentration ≥20ppm, silicon-calcium alloy addition amount is 0.9kg / t steel.

[0029] Preferably, in step (B), the amount of silicon-calcium alloy added before energizing and heating is 2 to 10 wt% of the total amount of refining slag; after the LF slag is completed, the amount of silicon-calcium alloy added again is 2 to 10 wt% of the total amount of refining slag.

[0030] Preferably, in step (B), the refining slag is a high-carbon steel refining slag; the chemical composition of the high-carbon steel refining slag includes: SiO2: 15~34wt%, CaO: 45~70wt%, MgO: 0~8wt%, Al2O3: ≤5wt%, FeO: ≤1.5wt%; its slag basicity is controlled at 1.6~2.5;

[0031] The amount of refining slag added is 3.0~6.5 kg / t steel;

[0032] The amount of cryolite added is 0.2~1.0 kg / t steel.

[0033] Preferably, in step (C), the vacuum degree of the vacuum treatment is controlled to be <300 Pa;

[0034] After vacuum treatment for 16-19 minutes, alloy is added for alloying treatment;

[0035] The argon flow rate for the soft blowing argon operation is 0.3~0.6 NL / (min·t steel), and the duration is more than 3 minutes.

[0036] Preferably, in step (A), the amount of active lime added is 3.0~4.6 kg / t steel.

[0037] The heavy rail steel production process provided by this invention includes converter smelting → LF refining → RH treatment → continuous casting. By adding an appropriate amount of low-aluminum ferrosilicon alloy for deoxidation at the converter tapping, operating a magnesium-aluminum ladle, using a low-aluminum slag system in the LF process, and strengthening deoxidation through RH treatment, aluminum and oxygen are controlled in a coordinated manner. This achieves stable production of heavy rail steel with [Al] ≤ 0.0020 wt%, reducing the average aluminum content to below 0.0015 wt%, while controlling the total oxygen (T.[O]) in the steel to below 0.0008 wt%, effectively improving the cleanliness of the molten steel. This invention provides a process system for the coordinated control of aluminum and oxygen content throughout the entire heavy rail steel production process, simultaneously reducing the total aluminum and total oxygen content in heavy rail steel, providing a favorable guarantee for high-quality production of heavy rail steel in the railway era. Detailed Implementation

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0039] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0040] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0041] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0042] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it means that the units for the left and right endpoints are the same. For example, 1550~1580℃ means that the units for the left endpoint "1550" and the right endpoint "1580" are both in degrees Celsius.

[0043] This invention provides a smelting method for controlling the total aluminum content of heavy rail steel, comprising the following steps:

[0044] (A) Converter smelting:

[0045] Steel is tapped when the converter smelting reaches the converter endpoint; the carbon content at the converter endpoint is controlled to be ≥0.05wt%, and the tapping temperature is 1640~1660℃; during the tapping process, when the steel amount is ≥1 / 4, low-aluminum ferrosilicon alloy is added for deoxidation, then low-aluminum ferrosilicon manganese alloy is added for alloying, active lime is added for slag formation, and finally a carbon raiser is added for carbon raising; after tapping, the ladle is sent to the furnace post-furnace argon blowing station for argon blowing.

[0046] The working layer of the ladle is constructed with magnesium-aluminum ladle bricks, and the slag line is constructed with magnesium-carbon ladle bricks.

[0047] (B) LF Refining:

[0048] When the LF ladle enters the station, silicon-calcium alloy is added to the slag surface and then heated by electricity. Refining slag and cryolite are then added to form slag. After the LF slag formation is completed, silicon-calcium alloy is added again and the temperature is raised to 1550~1580℃ before heating is stopped.

[0049] (C) RH treatment:

[0050] When RH enters the station, the oxygen of the molten steel is determined. Based on the oxygen determination results, silicon-calcium alloy is added again. The molten steel in the ladle is then vacuumed, and alloy is added for alloying treatment. The system is circulated for more than 5 minutes to break the vacuum and then soft argon blowing is performed.

[0051] (D) Continuous casting process:

[0052] The molten steel from step (C) is subjected to continuous casting.

[0053] Regarding step (A) :

[0054] In this invention, steel is tapped when the converter smelting reaches the converter endpoint, and the endpoint carbon content and tapping temperature are controlled. The endpoint carbon content is controlled to be ≥0.05wt%, preferably 0.05wt%~0.10wt%. The tapping temperature is 1640~1660℃, specifically 1640℃, 1641℃, 1642℃, 1643℃, 1644℃, 1645℃, 1646℃, 1647℃, 1648℃, 1649℃, 1650℃, 1651℃, 1652℃, 1653℃, 1654℃, 1655℃, 1656℃, 1657℃, 1658℃, 1659℃, and 1660℃.

[0055] In this invention, during the steel tapping process, a low-aluminum ferrosilicon alloy is added for deoxidation when the tapping amount is ≥1 / 4. The chemical composition of the low-aluminum ferrosilicon alloy includes: Si: 65.0~85.0 wt%, Al: <0.5 wt%, with the balance being Fe and unavoidable impurities. The preferred grade of the low-aluminum ferrosilicon alloy is DLSi75Al0.3. The preferred particle size of the low-aluminum ferrosilicon alloy is 20~50 mm. In this invention, the amount of low-aluminum ferrosilicon alloy added and the final carbon content satisfy the following relationship: Addition amount = 9 - 100X (9 minus 100X); wherein, when the final carbon content is 0.05wt%~0.07wt%, X = final carbon content; when the final carbon content > 0.07wt%, X = 0.07wt% (equivalent to X taking a value from the final carbon content of 0.05%~0.07%, and when the final carbon content exceeds the above range, X takes the limit value of 0.07% to ensure the alloy yield in subsequent processes). Therefore, the preferred addition amount of low-aluminum ferrosilicon alloy is 2.0~4.0 kg / t steel, specifically 2.0 kg / t steel, 2.1 kg / t steel, 2.2 kg / t steel, 2.3 kg / t steel, 2.4 kg / t steel, 2.5 kg / t steel, 2.6 kg / t steel, 2.7 kg / t steel, 2.8 kg / t steel, 2.9 kg / t steel, 3.0 kg / t steel, 3.1 kg / t steel, 3.2 kg / t steel, 3.3 kg / t steel, 3.4 kg / t steel, 3.5 kg / t steel, 3.6 kg / t steel, 3.7 kg / t steel, 3.8 kg / t steel, 3.9 kg / t steel, and 4.0 kg / t steel, which can be adjusted according to the converter endpoint carbon content of the steel grade being smelted.

[0056] In this invention, after deoxidation with a low-aluminum ferrosilicon alloy, a low-aluminum ferrosilicon manganese alloy is added for alloying. The chemical composition of the low-aluminum ferrosilicon manganese alloy is: Si: 25.0wt%~28.0wt%, Mn: 60.0wt%~67.0wt%, Al≤1wt%, S≤0.05wt%, with the remainder being unavoidable impurities. The amount of ferrosilicon manganese alloy used needs to be adjusted according to the target composition requirements of the steel grade being smelted to meet production needs.

[0057] In this invention, after alloying with low-aluminum silicon-manganese alloy, active lime is added to form slag, further inhibiting the oxidation of the slag surface and preventing phosphorus reversion. The preferred amount of active lime added is 3.0~4.6 kg / t steel, specifically 3.0 kg / t steel, 3.1 kg / t steel, 3.2 kg / t steel, 3.3 kg / t steel, 3.4 kg / t steel, 3.5 kg / t steel, 3.6 kg / t steel, 3.7 kg / t steel, 3.8 kg / t steel, 3.9 kg / t steel, 4.0 kg / t steel, 4.1 kg / t steel, 4.2 kg / t steel, 4.3 kg / t steel, 4.4 kg / t steel, 4.5 kg / t steel, and 4.6 kg / t steel.

[0058] In this invention, after adding active lime to form slag, a recarburizing agent is added for carbonization. The recarburizing agent is preferably a petroleum coke recarburizing agent. The amount of the recarburizing agent is adjusted according to the target composition requirements of the steel grade being smelted to meet production needs.

[0059] In this invention, after steel tapping is completed, the ladle is sent to the furnace post-furnace argon blowing station for argon blowing. The preferred argon flow rate is 1000~1200 NL / min, specifically 1000 NL / min, 1100 NL / min, or 1200 NL / min. The preferred argon blowing time is 6~8 minutes, specifically 6 minutes, 7 minutes, or 8 minutes.

[0060] In this invention, the working layer (i.e., the lining) of the ladle is constructed entirely of magnesia-alumina steel ladle bricks, while the slag line section uses magnesia-carbon steel ladle bricks. The magnesia-alumina steel ladle bricks contain MgO content ≥ 50 wt%, Al2O3 content ≤ 30 wt%, and C content ≥ 5 wt%. A steel ladle typically consists of a three-layer structure: a thermal insulation layer, a permanent layer, and a working layer (lining). This invention improves the material of the working layer (i.e., the lining) by using the aforementioned materials.

[0061] Regarding step (B) :

[0062] In this invention, a silicon-calcium alloy is added to the slag surface when the LF ladle enters the station. The chemical composition of the silicon-calcium alloy is: Si: 55.0~65.0 wt%, Ca: 10.0~25.0 wt%, Al: <1 wt%, with the balance being Fe and unavoidable impurities. The preferred grade of the silicon-calcium alloy is Ca24Si60. The particle size of the silicon-calcium alloy is preferably 5~30 mm. The preferred amount of silicon-calcium alloy added is 2~10 wt% of the total refining slag, specifically 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, and 10 wt%.

[0063] In this invention, a silicon-calcium alloy is added and then energized to raise the temperature. The preferred energizing and heating time is 5 to 15 minutes, specifically 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, and 15 minutes.

[0064] In this invention, after the above-mentioned heating by electricity, refining slag and cryolite are added to form slag. The refining slag is a special refining slag for high-carbon steel, and its chemical composition includes: SiO2: 15~34wt%, CaO: 45~70wt%, MgO: 0~8wt%, Al2O3: ≤5wt%, FeO: ≤1.5wt%. Its slag basicity is controlled between 1.6 and 2.5, specifically 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, and 2.5. In this invention, the preferred addition amount of the refining slag is 3.0~6.5 kg / t steel, specifically 3.0 kg / t steel, 3.5 kg / t steel, 4.0 kg / t steel, 4.5 kg / t steel, 5.0 kg / t steel, 5.5 kg / t steel, 6.0 kg / t steel, and 6.5 kg / t steel. The preferred addition amount of the cryolite is 0.2~1.0 kg / t steel, specifically 0.2 kg / t steel, 0.3 kg / t steel, 0.4 kg / t steel, 0.5 kg / t steel, 0.6 kg / t steel, 0.7 kg / t steel, 0.8 kg / t steel, 0.9 kg / t steel, and 1.0 kg / t steel.

[0065] In this invention, after the addition of refining slag and cryolite for slag formation and the completion of LF slag formation, a silicon-calcium alloy is added again. The type and particle size characteristics of the silicon-calcium alloy are consistent with those described above and will not be repeated here. The preferred amount of silicon-calcium alloy added is 2-10 wt% of the total refining slag, specifically 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, and 10 wt%.

[0066] In this invention, after adding the silicon-calcium alloy again, the temperature is raised to 1550~1580℃ and then heating is stopped. The specific temperature can be 1550℃, 1555℃, 1559℃, 1560℃, 1565℃, 1570℃, 1575℃, or 1580℃.

[0067] Regarding step (C) :

[0068] In this invention, after step (B) is completed, the ladle is sent to the RH station for RH treatment. During RH treatment, the molten steel undergoes an oxygen determination operation. This oxygen determination involves measuring the oxygen content in the molten steel, and the process can be adjusted based on the results. In this invention, based on the oxygen determination results, a silicon-calcium alloy is added again to the slag surface. The type and particle size of the silicon-calcium alloy are consistent with those described above and will not be repeated here. The preferred addition amount of the silicon-calcium alloy is 0.1~0.9 kg / t steel, and simultaneously satisfies the following classification relationship with the oxygen determination result: oxygen determination ≤ 12 ppm, silicon-calcium alloy addition amount is 0.1 kg / t steel; 12 ppm < oxygen determination ≤ 14 ppm, silicon-calcium alloy addition amount is 0.3 kg / t steel; 14 ppm < oxygen determination ≤ 16 ppm, silicon-calcium alloy addition amount is 0.5 kg / t steel; 16 ppm < oxygen determination ≤ 18 ppm, silicon-calcium alloy addition amount is 0.7 kg / t steel; 18 ppm < oxygen determination < 20 ppm, silicon-calcium alloy addition amount is 0.8 kg / t steel; oxygen determination ≥ 20 ppm, silicon-calcium alloy addition amount is 0.9 kg / t steel.

[0069] In this invention, molten steel contained in a ladle is subjected to vacuum treatment. The vacuum level is controlled to be <300 Pa. After vacuum treatment for 16-19 minutes, an alloy is added for alloying. The type and amount of alloy added are adjusted according to the target composition requirements of the steel being smelted to meet production needs. The alloying treatment is cyclically treated for at least 5 minutes to break the vacuum and perform soft argon blowing. The preferred argon flow rate for the soft argon blowing operation is 0.3-0.6 NL / (min·t steel), specifically 0.3 NL / (min·t steel), 0.4 NL / (min·t steel), 0.5 NL / (min·t steel), or 0.6 NL / (min·t steel). The preferred duration of the soft argon blowing operation is at least 3 minutes.

[0070] Regarding step (D) :

[0071] In this invention, after step (C) is completed, the molten steel leaving the station in step (C) is subjected to continuous casting.

[0072] The heavy rail steel production process provided by this invention achieves stable production of heavy rail steel with [Al] ≤ 0.0020 wt%, and the average aluminum content can be reduced to below 0.0015 wt%, while the total oxygen (T.[O]) in the steel is controlled below 0.0008 wt%, effectively improving the cleanliness of the molten steel. This process involves adding an appropriate amount of low-aluminum ferrosilicon alloy for deoxidation during converter tapping, operating a magnesium-aluminum ladle, using a low-aluminum slag system in the LF (sulfuric acid) process, and enhanced deoxidation by RH (hydrogenation).

[0073] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0074] Example 1

[0075] (A) Converter smelting:

[0076] At the point of tapping from the converter, the final carbon content is 0.074 wt%. During tapping, when the steel volume is ≥1 / 4, 2.0 kg / t of low-aluminum ferrosilicon alloy is added for deoxidation, followed by low-aluminum ferrosilicon manganese alloy for alloying, and then 4.6 kg / t of active lime is added for slag formation to further inhibit slag oxidation and prevent phosphorus reversion. Finally, petroleum coke is added to increase carbon content. After tapping, the ladle is sent to the furnace for argon blowing, and the tapping temperature is 1644℃.

[0077] The low-aluminum ferrosilicon grade is DLSi75Al0.3, with a particle size of 20~50mm. The chemical composition of the low-aluminum silicon-manganese alloy is Si: 76wt%, Al: <0.5wt%, with the balance being Fe and unavoidable impurities.

[0078] The working layer (i.e., the lining) of the ladle is constructed entirely of magnesia-alumina steel ladle bricks, while the slag line section is constructed of magnesia-carbon steel ladle bricks. The magnesia-alumina steel ladle bricks contain 75.18 wt% MgO, 16.23 wt% Al2O3, and 6.28 wt% C, with the remainder being common impurities found in refractory materials.

[0079] (B) LF Refining:

[0080] When the LF ladle enters the station, 8 wt% of silicon-calcium alloy (based on the total amount of refining slag) is added to the slag surface, and the temperature is increased for 11 minutes. Subsequently, 4.0 kg / t of high-carbon steel refining slag and 0.5 kg / t of cryolite are added to form the slag. After the LF slag formation is completed, 8 wt% of silicon-calcium alloy (based on the total amount of refining slag) is added again, and the temperature is increased to 1550℃ before heating is stopped.

[0081] The silicon-calcium alloy is designated as Ca24Si60, with a particle size of 5-30 mm. The chemical composition of the high-carbon steel refining slag includes: SiO2: 33.07 wt%, CaO: 59.51 wt%, MgO: 4.56 wt%, Al2O3: 1.48 wt%, FeO: 0.23 wt%; the slag leaving the terminal contains 4.1 wt% Al2O3, has a basicity of 2.2, and contains 1.1 wt% FeO, with the remainder being common phases in slag systems.

[0082] (C) RH treatment:

[0083] Upon arrival at the RH station, the molten steel underwent an oxygen determination process, achieving an oxygen content of 13.1 ppm. Based on the previously described classification relationship, 0.3 kg / t of silicon-calcium alloy (same type and size as in step B) was added to the slag surface. The molten steel in the ladle was then subjected to vacuum treatment, with the vacuum level controlled at <300 Pa. After 16 minutes of vacuum treatment, alloying was added for alloying. The vacuum was broken after 8 minutes of circulation treatment, and the argon flow rate was adjusted to 0.5 NL / (min·t steel) for soft argon blowing for 6 minutes.

[0084] (D) Continuous casting treatment: The molten steel leaving the station in step (C) is subjected to continuous casting treatment.

[0085] The finished heavy rail steel rolled in this embodiment was tested and found to have [Al]=0.0012wt% and T.[O]=0.0006wt%.

[0086] Example 2

[0087] (A) Converter smelting:

[0088] At the point of tapping from the converter, the final carbon content is 0.058 wt%. During tapping, when the steel volume is ≥1 / 4, 3.2 kg / t of low-aluminum ferrosilicon alloy is added for deoxidation, followed by the addition of low-aluminum ferrosilicon manganese alloy for alloying, and then 3.8 kg / t of active lime is added for slag formation to further inhibit slag oxidation and prevent phosphorus reversion. Finally, petroleum coke is added to increase carbon content. After tapping, the ladle is sent to the furnace for argon blowing, and the tapping temperature is 1656℃.

[0089] The materials used for low-aluminum ferrosilicon, low-aluminum silicon-manganese alloy, and steel ladle are the same as in Example 1.

[0090] (B) LF Refining:

[0091] When the LF ladle enters the station, 8 wt% of silicon-calcium alloy (based on the total amount of refining slag) is added to the slag surface, and the temperature is increased for 10 minutes. Subsequently, 4.0 kg / t of high-carbon steel refining slag and 0.5 kg / t of cryolite are added to form the slag. After the LF slag formation is completed, 8 wt% of silicon-calcium alloy (based on the total amount of refining slag) is added again, and the temperature is increased to 1580℃ before heating is stopped.

[0092] The silicon-calcium alloy is the same as in Example 1. The high-carbon steel refining slag is the same as in Example 1. The slag leaving the station contains 3.9 wt% Al2O3, 2.3 basicity, and 1.1 wt% FeO.

[0093] (C) RH treatment:

[0094] Upon arrival at the RH station, the molten steel underwent an oxygen determination process, maintaining an oxygen content of 15.7 ppm. Based on the previously described classification relationship, 0.5 kg / t of silicon-calcium alloy (same type and size as in step B) was added to the slag surface. The molten steel in the ladle was then subjected to vacuum treatment, with the vacuum level controlled at <300 Pa. After 19 minutes of vacuum treatment, alloying was added for alloying. The vacuum was broken after 8 minutes of circulation treatment, and the argon flow rate was adjusted to 0.6 NL / (min·t steel) for soft argon blowing for 5 minutes.

[0095] (D) Continuous casting treatment: The molten steel leaving the station in step (C) is subjected to continuous casting treatment.

[0096] The finished heavy rail steel rolled in this embodiment was tested and found to have [Al]=0.0015wt% and T.[O]=0.0006wt%.

[0097] Example 3

[0098] (A) Converter smelting:

[0099] At the point of tapping from the converter, the final carbon content is 0.062 wt%. During tapping, when the steel volume is ≥1 / 4, 2.8 kg / t of low-aluminum ferrosilicon alloy is added for deoxidation, followed by the addition of low-aluminum ferrosilicon manganese alloy for alloying, and then 4.6 kg / t of active lime is added for slag formation to further inhibit slag oxidation and prevent phosphorus reversion. Finally, petroleum coke is added to increase carbon content. After tapping, the ladle is sent to the furnace for argon blowing, and the tapping temperature is 1646℃.

[0100] The materials used for low-aluminum ferrosilicon, low-aluminum silicon-manganese alloy, and steel ladle are the same as in Example 1.

[0101] (B) LF Refining:

[0102] When the LF ladle enters the station, 8 wt% of a silicon-calcium alloy (based on the total amount of refining slag) is added to the slag surface, and the temperature is increased for 11 minutes. Subsequently, 4.0 kg / t of high-carbon steel refining slag and 1.0 kg / t of cryolite are added to form the slag. After the LF slag formation is completed, another 8 wt% of the silicon-calcium alloy (based on the total amount of refining slag) is added, and the temperature is increased to 1570℃ before heating is stopped.

[0103] The silicon-calcium alloy is the same as in Example 1. The high-carbon steel refining slag is the same as in Example 1. The slag leaving the station contains 4.6 wt% Al2O3, 2.2 basicity, and 1.0 wt% FeO.

[0104] (C) RH treatment:

[0105] Upon arrival at the RH station, the molten steel underwent a constant oxygen level of 11.5 ppm. Based on the previously described classification relationship, 0.1 kg / t of silicon-calcium alloy (same type and size as in step B) was added to the slag surface. The molten steel in the ladle was then subjected to vacuum treatment, with the vacuum level controlled at <300 Pa. After 17 minutes of vacuum treatment, alloying was added for alloying. The vacuum was broken after 7 minutes of circulation treatment, and the argon flow rate was adjusted to 0.4 NL / (min·t steel) for soft argon blowing for 6 minutes.

[0106] (D) Continuous casting treatment: The molten steel leaving the station in step (C) is subjected to continuous casting treatment.

[0107] The finished heavy rail steel rolled in this embodiment was tested and found to have [Al]=0.0013wt% and T.[O]=0.0005wt%.

[0108] Comparative Example 1

[0109] The implementation follows Example 1, with the following differences: the working layer of the ladle is constructed entirely of alumina-magnesia steel ladle bricks, while the slag line area uses magnesia-carbon steel ladle bricks. The alumina-magnesia steel ladle bricks contain 12.33 wt% MgO, 80.62 wt% Al2O3, and 6.17 wt% C, with the remainder being common impurity phases found in refractory materials. Furthermore, in step (C), instead of oxygen determination and the addition of silicon-calcium alloys to the molten steel upon arrival at the RH station, the molten steel in the ladle undergoes vacuum treatment and subsequent operations directly.

[0110] The finished heavy rail steel rolled in this comparative example was tested and found to have [Al]=0.0033wt% and T.[O]=0.0007wt%.

[0111] Comparative Example 2

[0112] The implementation was carried out according to Example 1, except that: in step (A), the final carbon content was controlled to be 0.032wt%, the amount of low-aluminum ferrosilicon alloy added was 4.0kg / t steel, and the tapping temperature was 1668℃; the ladle was selected in the same way as in Comparative Example 1; in step (C), when the RH entered the station, the oxygen was not determined and the silicon-calcium alloy was not added to the molten steel, but the molten steel in the ladle was directly subjected to vacuum treatment and subsequent operations.

[0113] The finished heavy rail steel rolled in this comparative example was tested and found to have [Al]=0.0038wt% and T.[O]=0.0010wt%.

[0114] Comparative Example 3

[0115] The implementation was carried out according to Example 1, except that: in step (A), the final carbon content was controlled to be 0.042 wt%, the amount of low-aluminum ferrosilicon alloy added was 4.0 kg / t steel, and the tapping temperature was 1663℃; in step (C), the oxygen content was determined to be 14.8 ppm, and the amount of silicon-calcium alloy added was 0.7 kg / t steel (that is, the amount of silicon-calcium alloy added and the oxygen determination result did not meet the grading system specified above).

[0116] The finished heavy rail steel rolled in this comparative example was tested and found to have [Al]=0.0040wt% and T.[O]=0.0007wt%.

[0117] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A smelting method for controlling the total aluminum content of heavy rail steel, characterized in that, Includes the following steps: (A) Converter smelting: Steel is tapped when the converter smelting reaches the converter endpoint; the carbon content at the converter endpoint is controlled to be ≥0.05wt%, and the tapping temperature is 1640~1660℃; during the tapping process, when the steel amount is ≥1 / 4, low-aluminum ferrosilicon alloy is added for deoxidation, followed by low-aluminum ferrosilicon manganese alloy for alloying, active lime is added for slag formation, and finally a carbon raiser is added for carbon raising; after tapping, the ladle is sent to the furnace post-furnace argon blowing station for argon blowing. The working layer of the ladle is constructed with magnesium-aluminum ladle bricks, and the slag line is constructed with magnesium-carbon ladle bricks. (B) LF Refining: When the LF ladle enters the station, silicon-calcium alloy is added to the slag surface and then heated by electricity. Refining slag and cryolite are then added to form slag. After the LF slag formation is completed, silicon-calcium alloy is added again and the temperature is raised to 1550~1580℃ before heating is stopped. (C) RH treatment: When RH enters the station, the oxygen of the molten steel is determined. Based on the oxygen determination results, silicon-calcium alloy is added again. The molten steel in the ladle is then vacuumed, and alloy is added for alloying treatment. The system is circulated for more than 5 minutes to break the vacuum and then soft argon blowing is performed. (D) Continuous casting process: The molten steel from step (C) is subjected to continuous casting.

2. The smelting method according to claim 1, characterized in that, In step (A), the chemical composition of the low-aluminum silicon-iron alloy includes: Si: 65.0~85.0wt%, Al: <0.5wt%, with the balance being Fe and unavoidable impurities; The particle size of the low-aluminum silicon-iron alloy is 20~50mm.

3. The smelting method according to claim 1, characterized in that, In step (A), the amount of low-aluminum ferrosilicon alloy added and the final carbon content satisfy the following relationship: added amount = 9 - 100X; wherein, when the final carbon content is 0.05wt%~0.07wt%, X = final carbon content; when the final carbon content is >0.07wt%, X = 0.07wt%.

4. The smelting method according to claim 1, characterized in that, The magnesium-aluminum steel-clad bricks contain MgO content ≥ 50 wt%, Al2O3 content ≤ 30 wt%, and C content ≥ 5 wt%.

5. The smelting method according to claim 1, characterized in that, The chemical composition of the silicon-calcium alloy is: Si: 55.0~65.0wt%, Ca: 10.0~25.0wt%, Al: <1wt%, with the balance being Fe and unavoidable impurities; The particle size of the silicon-calcium alloy is 5~30mm.

6. The smelting method according to claim 1, characterized in that, In step (C), the preferred amount of silicon-calcium alloy added is 0.1~0.9 kg / t steel, and simultaneously satisfies the following classification relationship with the oxygen determination results: Oxygen content ≤12ppm, silicon-calcium alloy addition amount is 0.1kg / t steel; 12ppm < constant oxygen ≤ 14ppm, silicon-calcium alloy addition is 0.3kg / t steel; 14ppm < constant oxygen ≤ 16ppm, silicon-calcium alloy addition is 0.5kg / t steel; 16ppm < constant oxygen ≤ 18ppm, silicon-calcium alloy addition is 0.7kg / t steel; 18ppm < constant oxygen < 20ppm, silicon-calcium alloy addition is 0.8kg / t steel; Oxygen concentration ≥20ppm, silicon-calcium alloy addition amount is 0.9kg / t steel.

7. The smelting method according to claim 1, characterized in that, In step (B), the amount of silicon-calcium alloy added before powering on and heating up is 2 to 10 wt% of the total amount of refining slag; after the LF slag is completed, the amount of silicon-calcium alloy added again is 2 to 10 wt% of the total amount of refining slag.

8. The smelting method according to claim 1, characterized in that, In step (B), the refining slag is a special refining slag for high-carbon steel; the chemical composition of the special refining slag for carbon steel includes: SiO2: 15~34wt%, CaO: 45~70wt%, MgO: 0~8wt%, Al2O3: ≤5wt%, FeO: ≤1.5wt%; its slag basicity is controlled at 1.6~2.5; The amount of refining slag added is 3.0~6.5 kg / t steel; The amount of cryolite added is 0.2~1.0 kg / t steel.

9. The smelting method according to claim 1, characterized in that, In step (C), the vacuum level of the vacuum treatment is controlled to be <300 Pa; After vacuum treatment for 16-19 minutes, alloy is added for alloying treatment; The argon flow rate for the soft blowing argon operation is 0.3~0.6 NL / (min·t steel), and the duration is more than 3 minutes.

10. The smelting method according to claim 1, characterized in that, In step (A), the amount of active lime added is 3.0~4.6 kg / t steel.