Production method of high-cleanliness heavy rail steel

Abstract

The invention provides a production method of heavy rail steel. According to the method, through the converter-LF-RH-continuous casting full-process cleanliness control technology, especially through the combination of converter end point silicon-calcium alloy pre-deoxidation and LF silicon-calcium alloy gradient deoxidation, T [O] in steel can be greatly reduced, and stable control over the cleanliness of the steel rail can be achieved through inclusion removal dynamic conditions in the strengthening process. The internal defects of the steel rail caused by non-metallic inclusions can be remarkably reduced, the fatigue resistance, the wear resistance and the fracture resistance of the steel rail are enhanced, the steel rail T [O] is smaller than or equal to 0.0008%, the qualification rate is larger than or equal to 98% when the grades of the B type inclusions and the C type inclusions of the steel rail are smaller than or equal to 1.0 at the same time, and safe and high-speed development of the railway transportation industry is powerfully supported.

Description

Technical Field

[0001] This invention belongs to the field of heavy rail steel preparation technology, and relates to a method for producing heavy rail steel, and more particularly to a method for producing high-purity heavy rail steel. Background Technology

[0002] Railways are the lifeblood of my country's national economy, a key infrastructure project, and a major project for people's livelihood, playing a pivotal role in my country's economic and social development. Since the implementation of the "Medium and Long-Term Railway Network Plan" in 2004, my country's railway construction has achieved leapfrog development. As an important component of railway construction, high-quality steel rails have become the material foundation for high-quality development of railway transportation. Cleanliness, as an inherent foundation of high-performance steel materials, aims for low content of impurity elements (oxygen, sulfur, phosphorus, etc.) in the steel, low total amount of non-metallic inclusions, small size, and effective control of their composition and morphology. In recent years, users, represented by China Railway Corporation, have increasingly stringent requirements for the cleanliness of steel rails, especially with the accelerated development of high-speed passenger transport and heavy-haul freight transport, which has placed even higher demands on the cleanliness control of steel rails.

[0003] Existing technologies also disclose some corresponding research schemes. For example, CN114807779 discloses a heavy rail steel and its preparation process, which mainly adopts a combined deoxidation method based on slag surface diffusion deoxidation and vacuum carbon deoxidation to replace ferroalloy precipitation deoxidation. This method rationally distributes the deoxidation process across different reactors, enabling coordinated control of temperature, oxygen content, and alloy composition in the heavy rail steel. However, this method requires the addition of pre-melted alloy liquid to the ladle during smelting. This method affects the lifespan of refractory materials such as insertion tubes. If refractory material spalls off and enters the molten steel, it can negatively impact the cleanliness of the molten steel. Furthermore, the alloy yield in the vacuum process is affected by the vacuum level. Some heavy rail steels require high alloy content, and the pre-melted alloy liquid cannot stably achieve precise control of the molten steel composition. Moreover, this process distributes the deoxidation task, placing extremely high demands on equipment and operation, making it unsustainable in actual production. For example, CN108950119 discloses a smelting method to improve the cleanliness of heavy rail steel. This method includes hot metal pretreatment, converter smelting, LF refining, RH refining, and continuous casting. In the converter smelting process, active lime, quartz sand, high-magnesium lime, steelmaking sludge balls, and soda ash are used as slag-forming materials to blow hot metal, controlling the P content to within 0.003%. This invention can control T[O] ≤ 0.0010%. However, in actual production, due to fluctuations in carbon and temperature control at the converter endpoint, this process requires strict process control. Furthermore, the calcium treatment process after RH vacuum treatment, to some extent, worsens the Ds inclusions in the rails. For example, CN114058932 discloses a method for controlling silicate inclusions in heavy rail steel during its production. The method yields heavy rail steel with a sulfur content of less than or equal to 0.0008%. No silicon-containing alloys such as ferrosilicon or deoxidizers are added during the converter tapping process. Silicon-containing alloys such as ferrosilicon or deoxidizers are added during the LF refining process. Furthermore, high-basicity slag refining is used in the early stages of LF refining, and a certain amount of Al2O3-containing fluxing material is added to the refining slag. Because this method does not perform deoxidation at the converter endpoint, the oxygen activity of the molten steel is high, which significantly affects the alloy yield in subsequent alloying processes.

[0004] Therefore, finding a more suitable production process for heavy rail steel, further improving the cleanliness level of heavy rail steel, and reducing the impact of inclusions on the quality of heavy rail steel has become one of the urgent problems to be solved by many front-line researchers in the industry. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a method for producing heavy rail steel, particularly a method for producing high-cleanliness heavy rail steel. The production method provided by the present invention adopts a full-process cleanliness control process from converter to LF-RH to continuous casting, achieving stable production of heavy rail steel with T[O] ≤ 0.0008%, significantly reducing internal defects in the rails caused by non-metallic inclusions, enhancing the rails' fatigue resistance, wear resistance, and fracture resistance, and greatly improving the service life of the rails. Moreover, the preparation method is simple, highly controllable, and easy to operate, making it more suitable for industrial promotion and application.

[0006] This invention provides a method for producing heavy rail steel, comprising the following steps:

[0007] 1) Feed the raw material molten iron and / or semi-steel into the converter, use top and bottom combined blowing protective gas for converter smelting, control the carbon content at the end of the converter, tap the steel, use silicon-calcium alloy for deoxidation during the tapping process, and then end the tapping after alloying, and then blow protective gas into the ladle.

[0008] 2) First, add silicon-calcium alloy to the molten steel obtained in the above steps to raise the temperature, then add composite refining slag to refine and form slag, then add silicon-calcium alloy again to continue slag formation, then perform LF slag formation, and then heat up and perform LF refining.

[0009] 3) The LF-refined molten steel obtained in the above steps is subjected to RH vacuum treatment. During the treatment process, protective gas is blown throughout. After the vacuum is broken, the protective gas flow rate is increased and protective gas treatment is continued to obtain castable molten steel.

[0010] 4) The molten steel obtained in the above steps is continuously cast under high superheat, with full protection during the casting process, to obtain heavy rail steel billets.

[0011] Preferably, the sulfur content in the molten iron or semi-steel is ≤0.005 wt%;

[0012] The flow rate of the top and bottom composite blowing protective gas is 1000~1200 NL / min;

[0013] The carbon content at the final stage of the converter is 0.05wt%~0.08wt%;

[0014] The tapping temperature is 1640~1660℃

[0015] The tapping time is 4-5 minutes.

[0016] Preferably, the silicon-calcium alloy is added after the steel output is greater than or equal to 1 / 4;

[0017] The amount of silicon-calcium alloy added is 2.0~3.0 kg / t. 钢 ;

[0018] The silicon-calcium alloy has a silicon content of 55.0 wt% to 65.0 wt% and a calcium content of 26.0 wt% to 36.0 wt%.

[0019] The aluminum content of the silicon-calcium alloy is ≤1.5wt%;

[0020] The particle size of the silicon-calcium alloy in step 1) is 20~50mm.

[0021] Preferably, the alloying specifically involves adding silicon-manganese alloy and low-aluminum ferrosilicon for alloying;

[0022] After alloying, the process also includes adding active lime for slag formation and adding petroleum coke recarburizing agent for carbonization.

[0023] In step 1), the time for blowing protective gas is 6-8 minutes;

[0024] In step 1), the flow rate of the protective gas is 100~200 NL / min;

[0025] In step 1), the T[O] in the obtained molten steel is ≤0.0012%.

[0026] Preferably, the amount of silicon-calcium alloy added first is 1.5~2.5 kg / t. 钢 ;

[0027] The temperature for the heating is 40~60℃;

[0028] The method of adding the composite refining slag includes adding it in batches;

[0029] The amount of the composite refining slag added is 4.0~5.0 kg / t. 钢 ;

[0030] When adding the composite refining slag, cryolite is also added to create slag.

[0031] The amount of cryolite added is 0.1~1.0 kg / t. 钢 .

[0032] Preferably, the SiO2 content in the composite refining slag is 20.0 wt% to 30.0 wt%.

[0033] The CaO content in the composite refining slag is 50.0 wt%~60.0 wt%;

[0034] The addition of silicon-calcium alloy specifically refers to adding the silicon-calcium alloy 4 minutes after refining and slag formation.

[0035] The amount of silicon-calcium alloy added is 1.0~2.0 kg / t.钢 ;

[0036] The particle size of the silicon-calcium alloy in step 2) is 5~10mm.

[0037] Preferably, the LF slag-forming time is ≥16 min;

[0038] The FeO content in the refining slag of the LF refining process is ≤0.8wt%;

[0039] The LF refining pressure is a slightly positive pressure of 50~80kPa;

[0040] The refining temperature of the LF is 1560~1580℃.

[0041] Preferably, the LF refining process uses bottom-blown protective gas;

[0042] The flow rate of the bottom-blown protective gas is 100~200 NL / min;

[0043] The vacuum pressure of the RH vacuum treatment is ≤3mbar;

[0044] The RH vacuum treatment time is 13~18 minutes;

[0045] In step 3), the flow rate of the protective gas during the entire process is 50~80 NL / min.

[0046] Preferably, the flow rate of the protective gas during the continued blowing process is 120~150 NL / min;

[0047] The duration of the continued protective gas blowing process is 8-10 minutes.

[0048] Specifically, the high superheat degree refers to a steel superheat degree of 30~40℃;

[0049] The casting speed of the continuous casting process is 0.60~0.70 m / min;

[0050] The T[O] in the heavy rail steel is ≤0.0008%.

[0051] Preferably, the heavy rail steel, based on elemental mass content, comprises: C: 0.72wt%~0.75wt%, Si: 0.39wt%~0.42wt%, Mn: 0.93wt%~0.97wt%, P≤0.015wt%, S≤0.006wt%, Al≤0.003wt%, and the balance Fe.

[0052] This invention provides a method for producing heavy rail steel, comprising the following steps: First, molten iron and / or semi-steel are fed into a converter, and top and bottom combined blowing protective gas is used for converter smelting. The carbon content at the converter endpoint is controlled, and steel is tapped. During tapping, silicon-calcium alloy is used for deoxidation. After alloying, tapping is completed, and protective gas is blown onto the ladle. Then, silicon-calcium alloy is added to the molten steel obtained in the above steps to raise the temperature, followed by the addition of composite refining slag for refining and slag formation. Silicon-calcium alloy is added again to continue slag formation, followed by LF slag formation. After heating, LF refining is performed. Then, the LF-refined molten steel obtained in the above steps is subjected to RH vacuum treatment, with protective gas blowing throughout the treatment process. After the vacuum is broken, the protective gas flow rate is increased to continue the protective gas treatment, resulting in castable molten steel. Finally, the castable molten steel obtained in the above steps is continuously cast under high superheat, with protective casting throughout the process, to obtain heavy rail steel billets. Compared with existing technologies, this invention creatively designs a production method for heavy rail steel with specific steps and parameter controls to further improve the cleanliness level of heavy rail steel and reduce the impact of inclusions on its quality. This is a high-cleanliness heavy rail steel production process suitable for large-scale industrial production. Compared with similar domestic heavy rail production processes, this invention achieves stable control of rail cleanliness through a full-process cleanliness control process from converter to LF-RH to continuous casting. In particular, the combination of silicon-calcium alloy pre-deoxidation at the converter endpoint and silicon-calcium alloy gradient deoxidation at LF significantly reduces T[O] in the steel. Furthermore, by strengthening the kinetic conditions for inclusion removal during the process, stable control of rail cleanliness can be achieved. This invention can significantly reduce internal defects in rails caused by non-metallic inclusions, enhance the fatigue resistance, wear resistance, and fracture resistance of rails, achieving a rail T[O] ≤ 0.0008%, and a pass rate of ≥ 98% for both Class B and Class C inclusion ratings ≤ 1.0, effectively supporting the safe and rapid development of the railway transportation industry.

[0053] This invention employs a full-process cleanliness control technology from converter to LF to RH to continuous casting. The converter process utilizes composite blowing and final C-level control. The final stage employs multi-stage deoxidation and alloying processes to control T[O] in the steel to ≤0.0012%. The LF process uses a gradient deoxidation process with silicon-calcium alloy and a composite refining slag + cryolite synergistic slag-forming process to control the FeO content in the slag to ≤0.8wt%. Subsequently, high-vacuum treatment and strong argon circulation are used in the RH process to reduce inclusions in the steel. Continuous casting employs protective casting and high superheat to further reduce inclusions, achieving stable production of heavy rail steel with T[O] ≤0.0008%. The pass rate for rails with B and C category inclusion ratings simultaneously ≤1.0 is ≥98%, significantly reducing internal defects in the rails caused by non-metallic inclusions, enhancing the rails' fatigue resistance, wear resistance, and fracture resistance, and greatly improving the service life of the rails. Detailed Implementation

[0054] 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 claims of the present invention.

[0055] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0056] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, this invention preferably uses industrial-grade pure steel or steel of the standard purity required in the field of heavy rail steel preparation.

[0057] All raw materials of this invention are conventional in the field, and each brand name and abbreviation is clear and distinct in its relevant application. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand name, abbreviation and corresponding application.

[0058] This invention provides a method for producing heavy rail steel, comprising the following steps:

[0059] 1) Feed the raw material molten iron and / or semi-steel into the converter, use top and bottom combined blowing protective gas for converter smelting, control the carbon content at the end of the converter, tap the steel, use silicon-calcium alloy for deoxidation during the tapping process, and then end the tapping after alloying, and then blow protective gas into the ladle.

[0060] 2) First, add silicon-calcium alloy to the molten steel obtained in the above steps to raise the temperature, then add composite refining slag + cryolite to refine and form slag, then add silicon-calcium alloy to continue slag formation, then perform LF slag formation, and then heat up and perform LF refining.

[0061] 3) The LF-refined molten steel obtained in the above steps is subjected to RH vacuum treatment. During the treatment process, protective gas is blown throughout. After the vacuum is broken, the protective gas flow rate is increased and protective gas treatment is continued to obtain castable molten steel.

[0062] 4) The molten steel obtained in the above steps is continuously cast under high superheat, with full protection during the casting process, to obtain heavy rail steel billets.

[0063] The present invention first feeds raw material molten iron and / or semi-steel into a converter, uses top and bottom combined blowing protective gas for converter smelting, controls the carbon content at the end of the converter, and taps the steel. During the tapping process, silicon-calcium alloy is used for deoxidation, and then after alloying, the tapping is ended, and protective gas is blown into the ladle.

[0064] In this invention, the protective gas is preferably an inert gas, and more preferably argon.

[0065] In this invention, the sulfur content in the raw material molten iron or semi-steel is preferably ≤0.005wt%, more preferably ≤0.0045wt%, and even more preferably ≤0.004wt%.

[0066] In this invention, the flow rate of the top and bottom composite blowing protective gas is preferably 1000~1200NL / min, more preferably 1040~1160NL / min, and even more preferably 1080~1120NL / min.

[0067] In this invention, the carbon content at the converter endpoint is preferably 0.05wt%~0.08wt%, more preferably 0.055wt%~0.075wt%, and even more preferably 0.06wt%~0.07wt%.

[0068] In this invention, the tapping temperature is preferably 1640~1660℃, more preferably 1644~1656℃, and even more preferably 1648~1652℃.

[0069] In this invention, the tapping time is preferably 4-5 min, more preferably 4.2-4.8 min, and even more preferably 4.4-4.6 min.

[0070] In this invention, the silicon-calcium alloy is preferably added after the steel output is greater than or equal to 1 / 4, more preferably after greater than or equal to 1 / 3, and even more preferably after greater than or equal to 1 / 2.

[0071] In this invention, the preferred amount of silicon-calcium alloy added is 2.0~3.0 kg / t. 钢 More preferably, it is 2.2~2.8 kg / t 钢 More preferably, it is 2.4~2.6 kg / t 钢。

[0072] In this invention, the silicon content of the silicon-calcium alloy is preferably 55.0 wt% to 65.0 wt%, more preferably 57.0 wt% to 63.0 wt%, even more preferably 59.0 wt% to 61.0 wt%, and the calcium content is preferably 26.0 wt% to 36.0 wt%, more preferably 28.0 wt% to 34.0 wt%, even more preferably 30.0 wt% to 32.0 wt%.

[0073] In this invention, the aluminum content of the silicon-calcium alloy is preferably ≤1.5wt%, more preferably ≤1.4wt%, and even more preferably ≤1.3wt%.

[0074] In this invention, the particle size of the silicon-calcium alloy in step 1) is preferably 20-50 mm, more preferably 25-45 mm, and even more preferably 30-40 mm.

[0075] In this invention, the alloying is preferably carried out by adding silicon-manganese alloy and low-aluminum ferrosilicon.

[0076] In this invention, after alloying, it is preferable to further include the steps of adding active lime for slag formation and adding petroleum coke recarburizing agent for carbonization.

[0077] In this invention, in step 1), the time for blowing protective gas is preferably 6-8 min, more preferably 6.4-7.6 min, and even more preferably 6.8-7.2 min.

[0078] In this invention, in step 1), the flow rate of the protective gas is preferably 100~200NL / min, more preferably 120~180NL / min, and even more preferably 140~160NL / min.

[0079] In this invention, in step 1), the T[O] in the obtained molten steel is preferably ≤0.0012%, more preferably T[O] ≤0.0011%, and even more preferably T[O] ≤0.0010%.

[0080] In this invention, silicon-calcium alloy is first added to the molten steel obtained in the above steps to raise the temperature, then composite refining slag + cryolite is added to refine and form slag, silicon-calcium alloy is added again to continue slag formation, then LF slag formation is carried out, and then LF refining is carried out after heating.

[0081] In this invention, the amount of silicon-calcium alloy added first is preferably 1.5~2.5 kg / t. 钢 More preferably, it is 1.7~2.3 kg / t 钢 More preferably, it is 1.9~2.1 kg / t 钢 .

[0082] In this invention, the heating temperature is preferably 40~60℃, more preferably 44~56℃, and even more preferably 48~52℃.

[0083] In this invention, the preferred method of adding the composite refining slag is to add it in batches.

[0084] In this invention, the preferred addition amount of the composite refining slag is 4.0~5.0 kg / t. 钢 More preferably, it is 4.2~4.8 kg / t 钢 More preferably, it is 4.4~4.6 kg / t 钢 .

[0085] In this invention, cryolite is preferably added to form slag when adding the composite refining slag.

[0086] In this invention, the amount of cryolite added is preferably 0.1~1.0 kg / t. 钢More preferably, it is 0.3~0.8 kg / t 钢 More preferably, it is 0.5~0.6 kg / t 钢 .

[0087] In this invention, the SiO2 content in the composite refining slag is preferably 20.0wt%~30.0wt%, more preferably 22.0wt%~28.0wt%, and even more preferably 24.0wt%~26.0wt%.

[0088] In this invention, the CaO content in the composite refining slag is preferably 50.0wt%~60.0wt%, more preferably 52.0wt%~58.0wt%, and even more preferably 54.0wt%~56.0wt%.

[0089] In this invention, the addition of silicon-calcium alloy is preferably carried out after 4 minutes of refining and slag formation.

[0090] In this invention, the amount of silicon-calcium alloy added is preferably 1.0~2.0 kg / t. 钢 More preferably, it is 1.2~1.8 kg / t 钢 More preferably, it is 1.4~1.6 kg / t 钢。

[0091] In this invention, the particle size of the silicon-calcium alloy in step 2) is preferably 5-10 mm, more preferably 6-9 mm, and even more preferably 7-8 mm.

[0092] In this invention, the LF slag treatment time is preferably ≥16 min, more preferably ≥17 min, and even more preferably ≥18 min.

[0093] In this invention, the FeO content in the refining slag of the LF refining is preferably ≤0.8wt%, more preferably ≤0.7wt%, and even more preferably ≤0.6wt%.

[0094] In this invention, the pressure of the LF refining is preferably a slightly positive pressure of 50~80 kPa, more preferably a slightly positive pressure of 55~75 kPa, and even more preferably a slightly positive pressure of 60~70 kPa.

[0095] In this invention, the refining temperature of the LF is preferably 1560~1580℃, more preferably 1564~1576℃, and even more preferably 1568~1572℃.

[0096] In this invention, bottom-blown protective gas is preferred in the LF refining process.

[0097] In this invention, the flow rate of the bottom-blowing protective gas is preferably 100~200NL / min, more preferably 120~180NL / min, and even more preferably 140~160NL / min.

[0098] The present invention then subjectes the LF-refined molten steel obtained in the above steps to RH vacuum treatment. During the treatment process, protective gas is blown throughout. After the vacuum is broken, the protective gas flow rate is increased and protective gas treatment is continued until casting molten steel is obtained.

[0099] In this invention, the vacuum pressure of the RH vacuum treatment is preferably ≤3mbar, more preferably ≤2.5mbar, and even more preferably ≤2mbar.

[0100] In this invention, the RH vacuum treatment time is preferably 13-18 min, more preferably 14-17 min, and even more preferably 15-16 min.

[0101] In this invention, in step 3), the flow rate of the protective gas during the entire process is preferably 50~80NL / min, more preferably 55~75NL / min, and even more preferably 60~70NL / min.

[0102] In this invention, the flow rate of the protective gas used for the continued blowing of protective gas is preferably 120~150NL / min, more preferably 125~145NL / min, and even more preferably 130~140NL / min.

[0103] In this invention, the duration of the continued blowing of protective gas is preferably 8-10 min, more preferably 8.4-9.6 min, and even more preferably 8.8-9.2 min.

[0104] Finally, the molten steel obtained from the above steps is continuously cast under high superheat, with full protection during the casting process, to obtain heavy rail steel billets.

[0105] In this invention, the high superheat specifically refers to a steel superheat of preferably 30~40℃, more preferably 32~38℃, and even more preferably 34~36℃.

[0106] In this invention, the casting speed of the continuous casting process is preferably 0.60~0.70m / min, more preferably 0.62~0.68m / min, and even more preferably 0.64~0.66m / min.

[0107] In this invention, the T[O] in the heavy rail steel is preferably ≤0.0008%, more preferably ≤0.0007%, and even more preferably ≤0.0006%.

[0108] In this invention, the heavy rail steel, based on elemental mass content, preferably comprises: C: 0.72wt%~0.75wt%, Si: 0.39wt%~0.42wt%, Mn: 0.93wt%~0.97wt%, P≤0.015wt%, S≤0.006wt%, Al≤0.003wt%, and the balance Fe; more preferably, it comprises C: 0.725wt%~0.745wt%, Si: 0.395wt%~0.415wt%. t%, Mn: 0.935wt%~0.96wt%, P≤0.014wt%, S≤0.005wt%, Al≤0.002wt% and balance Fe, more preferably C: 0.73wt%~0.74wt%, Si: 0.40wt%~0.41wt%, Mn: 0.94wt%~0.95wt%, P≤0.013wt%, S≤0.004wt%, Al≤0.001wt% and balance Fe.

[0109] This invention aims to complete and refine the overall technical solution, better ensure the composition and structure of heavy rail steel, further improve the cleanliness level and service life of heavy rail steel, and increase the fatigue resistance, wear resistance, and fracture resistance of the rails. The production method of the aforementioned high-cleanliness heavy rail steel may specifically include the following:

[0110] The present invention provides a method for producing high-purity heavy rail steel, comprising the following steps:

[0111] 1) Converter smelting: The sulfur content of the molten iron or semi-steel entering the furnace is ≤0.005%. The converter adopts a top-bottom combined blowing method, with bottom blowing of argon gas throughout the process. The argon gas flow rate is 1000~1200 NL / min. The carbon content at the end of the converter is 0.05~0.08wt%. The tapping temperature is 1640~1660℃. The tapping time is controlled at 4~5 minutes. When the tapping amount is ≥1 / 4, 2.0~3.0 kg / t of sulfur dioxide is added. 钢 The silicon-calcium alloy is deoxidized, followed by the addition of silicon-manganese alloy and low-aluminum ferrosilicon for alloying. 300 kg of active lime is added for slag formation, and petroleum coke is added as a carbon raiser for carbonization. After tapping, the ladle is sent to the furnace back argon blowing station for 6-8 minutes of argon blowing at a flow rate of 100-200 NL / min.

[0112] Specifically, the silicon-calcium alloy has a silicon content of 55.0~65.0 wt%, a calcium content of 26.0~36.0 wt%, an aluminum content of ≤1.5 wt%, and a particle size of 20~50 mm.

[0113] 2) LF Refining: The molten steel is hoisted to the LF furnace refining station, and 1.5~2.5 kg / t is added. 钢 After the silicon-calcium alloy is heated by electricity, it is added in batches at a rate of 4.0~5.0 kg / t.钢 Composite refining slag, 0~1.0 kg / t 钢 Add 1.0~2.0 kg / t of cryolite slag after 4 minutes of refining and slag formation. 钢 For silicon-calcium alloys, the LF slag formation time is ≥16 min.

[0114] Specifically, the furnace is kept under a slight positive pressure of 50~80kPa, and submerged arc heating is used. At the same time, argon gas is blown from the bottom at a flow rate of 100~200NL / min.

[0115] Specifically, the silicon content of the silicon-calcium alloy is 55.0~65.0 wt%, the calcium content is 26.0~36.0 wt%, the aluminum content is ≤1.5 wt%, and the particle size is 5~10 mm.

[0116] Specifically, the SiO2 content in the composite refining slag is 20.0~30.0 wt%, and the CaO content in the composite refining slag is 50.0~60.0 wt%.

[0117] 3) RH vacuum treatment: After the steel from the converter is refined by LF, it is vacuum treated in an RH vacuum furnace. After the molten steel enters the station, the vacuum degree is reduced to ≤3mbar within 3 minutes, and the treatment is carried out for 13~18 minutes under a vacuum degree of ≤3mbar.

[0118] Specifically, the entire vacuum treatment process involves argon blowing, with the argon flow rate controlled at 50~80 NL / min; after venting, the argon flow rate is switched to 120~150 NL / min for argon blowing for 8~10 minutes.

[0119] 4) Billet continuous casting: Molten steel is sent to the continuous casting platform. Argon gas is used to clean the tundish before casting. The casting process is protected throughout. The superheat of the molten steel is controlled at 30~40℃ and the casting machine speed is 0.60~0.70m / min.

[0120] The present invention provides a method for producing high-purity heavy rail steel. This method, with its specific steps and parameter controls, is a high-purity heavy rail steel production process suitable for large-scale industrial production. Compared to similar domestic heavy rail production processes, this invention utilizes a full-process cleanliness control technology from converter to LF-RH to continuous casting. In particular, the combination of silicon-calcium alloy pre-deoxidation at the converter endpoint and silicon-calcium alloy gradient deoxidation at the LF stage significantly reduces total oxygen (T[O]) in the steel. Furthermore, by strengthening the kinetics of inclusion removal during the process, stable control of rail cleanliness can be achieved. This invention can significantly reduce internal defects in rails caused by non-metallic inclusions, enhance the rail's fatigue resistance, wear resistance, and fracture resistance. Rail T[O] ≤ 0.0008%, and the pass rate for rails with both Class B and Class C inclusion ratings ≤ 1.0 is ≥ 98%, strongly supporting the safe and rapid development of the railway transportation industry.

[0121] This invention employs a full-process cleanliness control technology from converter to LF to RH to continuous casting. The converter process utilizes composite blowing and final C-level control. The final stage employs multi-stage deoxidation and alloying processes to control T[O] in the steel to ≤0.0012%. The LF process uses a gradient deoxidation process with silicon-calcium alloy and a composite refining slag + cryolite synergistic slag-forming process to control the FeO content in the slag to ≤0.8wt%. Subsequently, high-vacuum treatment and strong argon circulation are used in the RH process to reduce inclusions in the steel. Continuous casting employs protective casting and high superheat to further reduce inclusions, achieving stable production of heavy rail steel with T[O] ≤0.0008%. The pass rate for rails with B and C category inclusion ratings simultaneously ≤1.0 is ≥98%, significantly reducing internal defects in the rails caused by non-metallic inclusions, enhancing the rails' fatigue resistance, wear resistance, and fracture resistance, and greatly improving the service life of the rails.

[0122] To further illustrate the present invention, the following describes in detail a method for producing heavy rail steel provided by the present invention with reference to embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0123] Examples and Comparative Examples

[0124] 1) Converter smelting: The sulfur content of the molten iron or semi-steel entering the furnace is ≤0.005%. The converter adopts a top-bottom combined blowing method, with bottom blowing of argon gas throughout the process. The argon gas flow rate is 1500 NL / min. The carbon content at the end of the converter is 0.08 wt%. The tapping temperature is 1640℃. The tapping time is controlled at 4~5 min. When the tapping amount is ≥1 / 4, 2.0~3.0 kg / t of sulfur dioxide is added. 钢The silicon-calcium alloy is deoxidized, followed by the addition of silicon-manganese alloy and low-aluminum ferrosilicon for alloying. 300 kg of active lime is added for slag formation, and petroleum coke is added as a carbon raiser for carbonization. After tapping, the ladle is sent to the furnace back argon blowing station for argon blowing for 7 minutes at a flow rate of 150 NL / min.

[0125] The silicon-calcium alloy has a silicon content of 60.0 wt%, a calcium content of 30.0 wt%, an aluminum content of 1.1 wt%, and a particle size of 20 mm.

[0126] 2) LF Refining: The molten steel is hoisted to the LF furnace refining station, and 1.5~2.5 kg / t is added. 钢 After the silicon-calcium alloy is heated by electricity, it is added in batches at a rate of 4.5 kg / t. 钢 Composite refining slag, 0.5 kg / t 钢 Add 1.0~2.0 kg / t of cryolite slag after 4 minutes of refining and slag formation. 钢 For silicon-calcium alloys, the LF slag formation time is ≥16 min. The furnace is maintained at a slight positive pressure of 50 kPa, and submerged arc heating is used, while bottom blowing of argon gas is carried out at a flow rate of 150 NL / min.

[0127] The silicon-calcium alloy has a silicon content of 60.0 wt%, a calcium content of 30.0 wt%, an aluminum content of 1.1 wt%, and a particle size of 5 mm. The composite refining slag has a SiO2 content of 25.0 wt% and a CaO content of 55.0 wt%.

[0128] 3) RH Vacuum Treatment: After the steel from the converter is refined by LF, it is vacuum treated in an RH vacuum furnace. After the molten steel enters the station, the vacuum degree is evacuated to ≤3mbar within 3 minutes, and the treatment is carried out at a vacuum degree of ≤3mbar for 13~18 minutes. Argon blowing is carried out throughout the vacuum treatment process, and the argon flow rate is controlled at 50~80NL / min. After the vacuum is broken, the argon flow rate is switched and controlled at 150NL / min for argon blowing treatment for 9 minutes.

[0129] 4) Billet Continuous Casting: Molten steel is sent to the continuous casting platform. Before casting, the tundish is cleaned with argon gas. The casting process is protected throughout, and the superheat of the molten steel is controlled at 30~40℃. The casting machine speed is 0.60~0.70m / min. The production methods of the comparative examples and embodiments of this invention are shown in Table 1, which adopt the converter-LF-RH-continuous casting process.

[0130] See Table 1, which shows the smelting process parameters in the embodiments and comparative examples of the present invention.

[0131] Table 1

[0132]

[0133] The FeO content in the slag, the T[O] of the rail, and the inclusion rating of the comparative examples and embodiments of the present invention are shown in Table 2. Table 2 shows the FeO content in the slag, the T[O] of the rail, and the inclusion rating in the embodiments and comparative examples of the present invention. Specifically, X-ray fluorescence spectrometry was used to detect the FeO content in the slag, GB / T 10561 2023 was used to evaluate Class B and C inclusions in the rail, and TB / T 2344.1-2020 was used to process the gas samples of the rail and detect the T[O] of the rail.

[0134] Table 2

[0135]

[0136] As can be seen from the production data of the embodiments and comparative examples of the present invention, the FeO content in the heavy rail refining slag of the present invention is ≤0.8wt%, the rail T[O] is ≤0.0008%, and the pass rate of rail B and C inclusion ratings ≤1.0 is ≥98%. This not only significantly improves the cleanliness control level of molten steel and reduces the rail B / C inclusion rating, but also significantly enhances the fatigue resistance, wear resistance and fracture resistance of the rail, thereby improving the service life of the rail.

[0137] The above provides a detailed description of a method for producing high-purity heavy rail steel according to the present invention. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope 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 the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method of producing heavy rail steel, characterized by, The method comprises the following steps: 1) feeding raw molten iron and / or semi-steel into a converter, adopting top and bottom combined blowing refining protection gas, carrying out converter smelting, controlling the carbon content of the converter endpoint, carrying out tapping, adopting silicon-calcium alloy for deoxidation during the tapping process, then ending the tapping after alloying, and then blowing protection gas to the ladle; 2) adding silicon-calcium alloy to the molten steel obtained in the above step to increase the temperature, then adding a composite refining slag to refine and form slag, and then adding silicon-calcium alloy to continue slagging, and then performing LF slagging, and then heating and increasing the temperature, and then performing LF refining; 3) performing RH vacuum treatment on the molten steel obtained after the above step of LF refining, blowing protection gas throughout the treatment process, and then obtaining casting molten steel after breaking the vacuum and continuing to blow protection gas at an increased flow rate; 4) continuously casting the casting molten steel obtained in the above step at a high superheat, and continuously protecting the casting to obtain heavy rail steel billets.

2. The production method according to claim 1, characterized by, The S content in the raw molten iron or semi-steel is ≤0.005wt%; The flow rate of the top and bottom combined blowing refining protection gas is 1000-1200 NL / min; The carbon content of the converter endpoint is 0.05wt%-0.08wt%; The temperature of the tapping is 1640-1660℃ The time of the tapping is 4-5min.

3. The production method according to claim 1, characterized by, The silicon-calcium alloy is added after the tapping amount is greater than or equal to 1 / 4; The silicon calcium alloy is added in an amount of 2.0-3.0 kg / t 钢 ; The silicon content of the silicon-calcium alloy is 55.0wt%-65.0wt%, and the calcium content is 26.0wt%-36.0wt%; The aluminum content of the silicon-calcium alloy is ≤1.5wt%; The particle size of the silicon-calcium alloy in step 1) is 20-50mm.

4. The production method according to claim 1, characterized by, The alloying specifically comprises adding silicon-manganese alloy and low-aluminum ferrosilicon for alloying; After the alloying, the steps of adding active lime for slagging and adding petroleum coke carbonizer for carbonization are further included; In step 1), the time of blowing protection gas is 6-8min; In step 1), the flow rate of blowing protection gas is 100-200 NL / min; In step 1), the T[O] in the obtained molten steel is ≤0.0012%.

5. The production method according to claim 1, characterized by, The first added silicon-calcium alloy is added in an amount of 1.5-2.5 kg / t 钢 ; The temperature of the heating is 40-60℃; The way of adding the composite refining slag comprises batch adding; The composite refining slag is added in an amount of 4.0-5.0 kg / t 钢 ; The ice crystal is further added when the composite refining slag is added; The cryolite is added in an amount of 0.1 to 1.0 kg / t 钢 .

6. The production method according to claim 1, characterized by, The SiO2 content in the composite refining slag is 20.0wt%-30.0wt%; The CaO content in the composite refining slag is 50.0wt%-60.0wt%; The silicon-calcium alloy is added after 4min of refining and slagging; The added amount of the silicon-calcium alloy is 1.0-2.0 kg / t 钢 ; The particle size of the silicon-calcium alloy in step 2) is 5-10mm.

7. The production method according to claim 1, characterized by, The time of the LF slagging is ≥16min; The FeO content in the refining slag of the LF refining is ≤0.8wt%; The pressure of the LF refining is 50-80kPa of micro-positive pressure; The temperature of the LF refining is 1560-1580℃.

8. The production method according to claim 1, characterized by, Protection gas is blown at the bottom during the LF refining process; The flow rate of the bottom blowing protection gas is 100-200 NL / min; The vacuum pressure of the RH vacuum treatment is ≤3mbar; The time of the RH vacuum treatment is 13-18min; The protection gas flow rate in the step 3) is 50-80 NL / min.

9. The production method according to claim 1, characterized by, The protection gas flow rate in the continuous protection gas treatment is 120-150 NL / min. The time of the continuous protection gas treatment is 8-10 min. The high superheat degree is specifically that the superheat degree of the molten steel is 30-40 DEG C. The casting speed of the continuous casting process is 0.60-0.70 m / min. T[O] in the heavy rail steel is less than or equal to 0.0008%.

10. The production method according to claim 1, characterized by, The heavy rail steel contains, in terms of element mass content, C: 0.72wt%-0.75wt%, Si: 0.39wt%-0.42wt%, Mn: 0.93wt%-0.97wt%, P: less than or equal to 0.015wt%, S: less than or equal to 0.006wt%, Al: less than or equal to 0.003wt%, and the balance of Fe.

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