Smelting method of national standard 43kg / m steel rail

Abstract

The invention discloses a smelting method of a national standard 43kg / m steel rail. A steel billet material of the steel rail comprises the following chemical components in percentage by mass: 0.50-0.60% of C; 0.20 to 0.60% of Si; 1.0 to 1.25 parts of Mn; p < = 0.025; s is less than or equal to 0.025; cr < = 0.15; al < = 0.010; the smelting method comprises the steps of molten iron pretreatment, converter smelting, LF furnace refining, RH refining, VD vacuum degassing, continuous casting and steel billet inspection. The sulfur mark of the casting blank is 0.5 grade, the low-power center porosity is 0.5 grade, the shrinkage cavity is 0.5 grade, the non-metallic inclusion is 0.5 grade, the rest is 0 grade, and the quality of the casting blank is good. The segregation indexes of the C element and the Mn element of the steel rail are basically between 0.95 and 1.05, segregation of the C element and segregation of the Mn element are relatively synchronous, and content fluctuation of all positions is small.

Description

Technical Field

[0001] The present invention relates to the technical field of smelting and continuous casting, and particularly relates to a smelting method for national standard 43 kg / m steel rails. Background Art

[0002] With the rapid development of China's railway industry, as an important part of railway tracks, the quality and specification requirements for steel rails are getting higher and higher. In practical applications, there are differences in performance and uses among steel rails of different standards. The appropriate type of steel rail should be selected according to specific needs and scenarios. Currently, iron standards, American standards, European standards, etc. are generally used as steel rail procurement standards, and there are relatively few purchases according to the national standard GB / T 2585. There are certain differences between the national standard and the iron standard in terms of composition and dimensional deviation, and there may be some quality fluctuations and unstable factors during the production process.

[0003] Therefore, in view of the above factors, in order to meet the actual needs, a smelting method for national standard 43 kg / m steel rails is developed. The segregation indices of C and Mn elements in the steel rails are basically between 0.95 and 1.05, the segregation of C and Mn elements is relatively synchronous, and the content fluctuations at each position are small. Summary of the Invention

[0004] The present invention aims to make up for the deficiencies of the prior art and provides a smelting method for national standard 43 kg / m steel rails to improve the overall quality and market competitiveness of the products.

[0005] The purpose of the present invention is to provide a smelting method for national standard 43 kg / m steel rails. The chemical composition of the steel billet material of the steel rail, by mass percentage, includes: C: 0.50 - 0.60; Si: 0.20 - 0.60; Mn: 1.0 - 1.25; P ≤ 0.025; S ≤ 0.025; Cr ≤ 0.15; Al ≤ 0.010; the balance is Fe and inevitable impurities;

[0006] The smelting method of the steel rail includes the following steps:

[0007] Hot metal pretreatment: Adopt a continuous treatment method in the hot metal trough, set a blowing and stirring gun or a powder injection gun on the hot metal trough, so that the pretreatment agent is in contact with the hot metal through blowing and stirring intensification, and spray the pretreatment agent into the hot metal in the hot metal ladle with a spray gun to make it fully react with the hot metal, so as to purify the hot metal and remove or extract relevant elements;

[0008] Converter smelting: The C content at tapping is C(%) ≥ 0.08, P(%) ≤ 0.015, and the tapping temperature is ≥ 1550 °C; and use silicomanganese, ferromanganese and ferrosilicon alloys for in-ladle deoxidation alloying, adopt an aluminum-free deoxidation process for smelting, use a combined blowing converter for smelting, adopt a single slag or double slag operation, control the final slag basicity at 3.0, and slag blocking must be carried out at tapping;

[0009] During the tapping process of the converter, the molten steel is pre-refined. By using a slag stopper to block the slag, the thickness of the ladle slag is controlled within 80 mm. During the tapping process, a high-alkalinity refining slag is added, and the addition amount is 4 - 6 kg / t of molten steel. Calcium silicate barium or aluminum reducing agent is used to deoxidize and modify the ladle slag, initially controlling the composition of the ladle slag and reducing the oxidability of the ladle slag, achieving the "pre-refining" purpose of desulfurization, deoxidation and removal of non-metallic inclusions in the molten steel, and can shorten the slag melting time of the LF furnace, extend the white slag refining time and improve the refining effect.

[0010] LF refining: Control the composition and temperature adjustment after the furnace by means of argon blowing at the argon blowing station and the LF furnace, alloy fine-tuning and heating and temperature raising in the IF furnace;

[0011] According to the different values of the temperature before argon blowing, the argon blowing time and the feeding amount of aluminum wire are adjusted in a timely manner, which can reduce the active oxygen in the steel to about 15 - 30 ppm. At the same time, the inclusions in the steel can float up sufficiently, providing qualified molten steel for continuous casting;

[0012] RH refining desulfurization: After RH deoxidation and alloying, the desulfurizing agent is added to the vacuum chamber in 3 batches, stirred for 8 min, and the lifting gas flow rate is set at 120 m 3 / h. After the RH treatment, VD vacuum degassing is carried out;

[0013] VD vacuum degassing: The deep vacuum time ≥ 20 min; the vacuum degree is less than 0.10 KPa; after the vacuum treatment, the soft blowing time ≥ 20 min, standing for more than 10 min, and the molten steel shall not be exposed during the soft blowing period;

[0014] Continuous casting: During continuous casting, the molten steel in the tundish is more than 15 tons. During the casting process, the liquid level is automatically controlled, electromagnetic stirring is used, and soft reduction is used normally. The liquidus temperature of the steel grade is 1469 °C.

[0015] Furthermore, before the continuous casting starts, the aluminum-carbon semi-immersed nozzle and the tundish need to be baked. During the continuous casting process, the average superheat ΔT of the molten steel is controlled between 25 - 35 °C.

[0016] Furthermore, the superheat of the steel grade is controlled not to be greater than 30 °C, ΔT of the first furnace ≤ 35 °C, and constant casting speed production is adopted.

[0017] Furthermore, the final deoxidizer adopts low-aluminum calcium silicate barium.

[0018] Furthermore, for the finished rail after VD vacuum degassing, the hydrogen content ≤ 1.5 PPm, the oxygen content ≤ 20 PPm, and the nitrogen content ≤ 90 PPm.

[0019] Furthermore, after vacuum degassing, four-strand continuous casting or six-strand continuous casting is carried out. The continuous casting speed is 0.95 m / min, and the size of the continuous casting billet of the steel billet is 280 mm × 380 mm.

[0020] Smelting method for 43 kg / m steel rail of national standard. The chemical composition of the steel billet material for the steel rail, by mass percentage, includes: C: 0.50 - 0.60; Si: 0.20 - 0.60; Mn: 1.0 - 1.25; P ≤ 0.025; S ≤ 0.025; Cr ≤ 0.15; Al ≤ 0.010; the balance is Fe and unavoidable impurities.

[0021] Smelting method for 43 kg / m steel rail of national standard. The chemical composition of the steel billet material for the steel rail, by mass percentage, includes: C: 0.55; Si: 0.22; Mn: 1.12; P ≤ 0.025; S ≤ 0.025; Cr ≤ 0.15; Al ≤ 0.010; the balance is Fe and unavoidable impurities. Application of a smelting method for 43 kg / m steel rail of national standard, applying the smelting method for 43 kg / m steel rail of national standard to the smelting of 43 kg / m steel rail.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] The high-speed steel rail produced by the present invention using hot metal pretreatment - converter - refining - RH vacuum degassing - continuous casting of square billets meets the requirements of international 43 kg / m steel rail in terms of both internal quality and external quality.

[0024] For the steel rail of the present invention, the segregation indexes of C and Mn elements are basically between 0.95 and 1.05, the segregation of C and Mn elements is relatively synchronous, and the content fluctuations at each position are small.

[0025] The present invention can meet the needs of national economic development and can provide high-quality steel rails that meet the safety requirements of industrial applications. Detailed implementation manners

[0026] In order to enable those skilled in the art of the present technology to better understand the technical solutions in the embodiments of the present invention and make the above-mentioned objects, features, and advantages of the present invention more obvious and understandable, the following further explains the detailed implementation manners of the present invention.

[0027] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0028] A smelting method for a 43 kg / m national standard rail. The chemical composition of the steel billet material for the rail, by mass percentage, includes: C: 0.50 - 0.60; Si: 0.20 - 0.60; Mn: 1.0 - 1.25; P ≤ 0.025; S ≤ 0.025; Cr ≤ 0.15; Al ≤ 0.010; the balance is Fe and unavoidable impurities.

[0029] The smelting method for the rail includes the following steps:

[0030] Hot metal pretreatment: Adopt a continuous treatment method in the hot metal trough. Set a lance for blowing and stirring or a powder lance on the hot metal trough to strengthen the contact between the pretreatment agent and the hot metal through blowing and stirring. Spray the pretreatment agent into the hot metal in the hot metal ladle with a lance to make it fully react with the hot metal, so as to purify the hot metal and remove or extract relevant elements.

[0031] Converter smelting: The C content at tapping is C(%) ≥ 0.08, P(%) ≤ 0.015, and the tapping temperature is ≥ 1550 °C; and use silicomanganese, ferromanganese and ferrosilicon alloys for in-ladle deoxidation alloying. Adopt a non-aluminum deoxidation process for smelting, use combined blowing in the converter for smelting, adopt single slag or double slag operation, control the final slag basicity at 3.0, and slag blocking must be carried out during tapping.

[0032] Steel water pre-refining during the converter tapping process. Block the slag with a slag stopper, control the thickness of the ladle slag within 80 mm. Add high basicity refining slag during the tapping process, with an addition amount of 4 - 6 kg / t of steel. Use calcium silicate barium or aluminum reducing agent to deoxidize and modify the ladle slag, initially control the composition of the ladle slag and reduce the oxidability of the ladle slag, so as to achieve the purpose of pre-refining for desulfurization, deoxidation and removal of non-metallic inclusions in the steel water.

[0033] LF refining: Control the post-furnace composition and temperature adjustment by means of argon blowing through the argon blowing station and the LF furnace, wire feeding of alloys, and heating and temperature rising in the LF furnace.

[0034] And according to the different values of the temperature before argon blowing, timely adjust the argon blowing time and the feeding amount of aluminum wire, which can reduce the active oxygen in the steel to about 15 - 30 ppm, and at the same time make the inclusions in the steel fully float up, providing qualified steel water for continuous casting.

[0035] RH refining desulfurization: After RH deoxidation alloying, add the desulfurizing agent to the vacuum chamber in 3 batches, stir for 8 min, and set the lifting gas flow rate at 120 m 3 / h. After the RH treatment, carry out VD vacuum degassing.

[0036] VD vacuum degassing: The deep vacuum time ≥ 20 min; the vacuum degree is less than 0.10 KPa; after the vacuum treatment, the soft blowing time ≥ 20 min, stand for more than 10 min, and the steel water shall not be exposed during the soft blowing period.

[0037] Continuous casting: During continuous casting, the molten steel volume in the tundish is greater than 15 tons. Automatic liquid level control is achieved during the casting process, electromagnetic stirring is used, soft reduction is used normally, and the liquidus temperature of the steel grade is 1469°C. Specific Example 1:

[0039] The smelting method of the national standard 43kg / m steel rail. The chemical composition of the steel billet material of the steel rail includes, by mass percentage: C: 0.58; Si: 0.45; Mn: 1.10; P: 0.015; S: 0.023; Cr: 0.10; Al: 0.008; the balance is Fe and inevitable impurities.

[0040] The smelting method of the steel rail includes the following steps:

[0041] Hot metal pretreatment: Adopt a continuous treatment method in the hot metal trench, set a lance for blowing and stirring or a powder lance on the hot metal trench, so that the pretreatment agent is strengthened in contact with the hot metal through blowing and stirring, and the pretreatment agent is sprayed into the hot metal in the hot metal ladle with a lance to make it fully react with the hot metal, so as to purify the hot metal and remove or extract relevant elements;

[0042] Converter smelting: The C content at tapping is C(%) ≥ 0.08, P(%) ≤ 0.015, and the tapping temperature is ≥ 1550°C; and silicon manganese, ferromanganese and ferrosilicon alloys are used for in-ladle deoxidation alloying, smelting is carried out by an aluminum-free deoxidation process, combined blowing converter smelting is adopted, single slag or double slag operation is used, and the final slag basicity is controlled at 3.0. Tapping must be slagged off; The converter smelting process is as follows.

[0043]

[0044]

[0045] During the tapping process of the converter, the molten steel is pre-refined. The slag in the ladle is controlled within 80mm in thickness by a slag stopper. During the tapping process, a high basicity refining slag is added, and the addition amount is 4-6kg / t of steel. And calcium silicate barium or aluminum reducing agent is used to deoxidize and modify the ladle slag, initially controlling the ladle slag components and reducing the oxidability of the ladle slag, achieving the purpose of pre-refining for desulfurization, deoxidation and removal of non-metallic inclusions in the molten steel;

[0046] LF refining: Control the post-furnace composition and temperature adjustment by means of blowing argon through the argon blowing station and the LF furnace, feeding wires, alloy fine-tuning and heating up the IF furnace;

[0047] And according to the different pre-argon temperature values, the blowing argon time and the feeding amount of aluminum wire are adjusted in a timely manner, so that the active oxygen in the steel can be reduced to about 15-30ppm, and at the same time, the inclusions in the steel can fully float up, providing qualified molten steel for continuous casting;

[0048] RH refining desulfurization: After RH deoxidation and alloying, the desulfurizer is added to the vacuum chamber in three batches, stirred for 8 minutes, and the lifting gas flow rate is set at 120 m 3 / h. After the RH treatment, VD vacuum degassing is carried out;

[0049] VD vacuum degassing: The deep vacuum time ≥ 20 minutes; the vacuum degree is less than 0.10 KPa; after the vacuum treatment, the soft blowing time ≥ 20 minutes, standing for more than 10 minutes, and the molten steel shall not be exposed during soft blowing;

[0050] Among them, before the continuous casting starts, the aluminum-carbon semi-immersed nozzle and the tundish need to be baked, and during the continuous casting process, the average superheat ΔT of the molten steel is controlled between 25 - 35 °C.

[0051] Among them, the final deoxidizer uses low-aluminum calcium-silicon-barium.

[0052] For the finished rail steel after VD vacuum degassing, the hydrogen content ≤ 1.5 PPm, the oxygen content ≤ 20 PPm, and the nitrogen content ≤ 90 PPm.

[0053] The specific VD process is shown in the following table:

[0054]

[0055] After vacuum degassing, four-strand continuous casting or six-strand continuous casting is carried out, the continuous casting speed is 0.95 m / min, and the specification of the continuous casting billet of the steel billet is 280 mm × 380 mm.

[0056] During continuous casting, the molten steel volume in the tundish is greater than 15 tons. The liquid level is automatically controlled during casting, electromagnetic stirring is used normally, and soft reduction is used normally. The liquidus temperature of the steel grade: 1469 °C. The superheat of the steel grade is controlled not to be greater than 30 °C, and ΔT of the first furnace ≤ 35 °C. Production is carried out at a constant casting speed of 0.62 - 0.67 m / min. The specification of the continuous casting billet is 280 mm × 380 mm, and the quality of the cast billet is good.

[0057] Composition % of the billet of the national standard 43 kg / m rail steel

[0058]

[0059] Since rail steel belongs to high-carbon steel, the shrinkage rate is large during solidification of molten steel, and serious porosity, shrinkage cavities and segregation are likely to form in the center. In addition, corner defects are also likely to occur. In order to obtain high-quality continuous casting billets of rail steel, it is necessary to reduce or eliminate its center segregation, shrinkage cavities and corner defects, etc.

[0060] Therefore, in the above-mentioned embodiments, during the continuous casting production process of rail steel, technologies such as full-protection casting, low superheat and low casting speed, low specific water volume, and light reduction at the solidification end are adopted to control its center segregation and shrinkage cavities.

[0061] In order to prevent secondary oxidation caused by the contact between the molten steel of the rail and air, a long nozzle is used to protect the molten steel flow between the ladle and the tundish, and a refractory mortar is used to seal between the long nozzle and the sliding nozzle of the ladle. The molten steel surface in the tundish is covered with a double-layer covering agent. At the same time, the tundish is filled to full and the weight is controlled to be above 35t.

[0062] Between the tundish and the mold, a porous submerged nozzle is used for protected casting, and its insertion depth is ensured.

[0063] The sulfur printing and hot acid inspection of the continuous casting billets of high-carbon steel rail billets are shown in the following table:

[0064] Sulfur printing inspection results (grade) of 43kg / m rail steel continuous casting billets

[0065]

[0066] Hot acid inspection results (grade) of national standard 43kg / m continuous casting billets

[0067]

[0068] The sulfur printing of the continuous casting billet is grade 0.5, the low-magnification central porosity is 0.5, the shrinkage cavity is grade 0.5, the non-metallic inclusions are grade 0.5, and the rest are grade 0. The quality of the continuous casting billet is good. Specific embodiment two:

[0070] The smelting method of national standard 43kg / m rail. The chemical composition of the steel billet material of the rail includes, by mass percentage: C: 0.50 - 0.60; Si: 0.26 - 0.60; Mn: 1.181; P: 0.018; S: 0.015; Cr: 0.1; Al: 0.008; the balance is Fe and unavoidable impurities.

[0071] The smelting method of the rail includes the following steps:

[0072] Hot metal pretreatment: Adopt a continuous treatment method in the hot metal trough, set a lance or a powder injection lance on the hot metal trough, so that the pretreatment agent is strengthened in contact with the hot metal through injection and stirring, and the pretreatment agent is sprayed into the hot metal in the ladle with a lance to make it fully react with the hot metal, so as to purify the hot metal and remove or extract relevant elements;

[0073] Converter smelting: The C content at tapping is C(%) ≥ 0.08, P(%) ≤ 0.015, and the tapping temperature is ≥ 1550°C; and silicon manganese, ferromanganese and ferrosilicon alloys are used for in-ladle deoxidation alloying, smelting is carried out by an aluminum-free deoxidation process, combined blowing converter smelting is adopted, single slag or double slag operation is used, and the final slag basicity is controlled at 3.0. Tapping must be slagged off;

[0074] During the tapping process of the converter, the molten steel is pre-refined. By using a slag stopper to block the slag, the thickness of the ladle slag is controlled within 80 mm. During the tapping process, a high-alkalinity refining slag is added, with an addition amount of 4 - 6 kg / t of molten steel. Calcium silicate barium or aluminum reducing agent is used to deoxidize and modify the ladle slag, initially controlling the composition of the ladle slag and reducing the oxidizability of the ladle slag, achieving the purpose of pre-refining for desulfurization, deoxidation, and removing non-metallic inclusions in the molten steel;

[0075] LF refining: Control the post-furnace composition and temperature adjustment by means of argon blowing and wire feeding in the argon blowing station and LF furnace, alloy fine-tuning, and heating and temperature rising in the IF furnace;

[0076] According to the different pre-argon temperatures, the argon blowing time and the feeding amount of aluminum wire are adjusted in a timely manner, which can reduce the active oxygen in the steel to about 15 - 30 ppm. At the same time, the inclusions in the steel can fully float up, providing qualified molten steel for continuous casting;

[0077] RH refining desulfurization: After RH deoxidation and alloying, the desulfurizing agent is added to the vacuum chamber in 3 batches, stirred for 8 min, and the lifting gas flow rate is set at 120 m 3 / h. After the RH treatment, VD vacuum degassing is carried out;

[0078] VD vacuum degassing: The deep vacuum time ≥ 20 min; the vacuum degree is less than 0.10 KPa; after the vacuum treatment, the soft blowing time ≥ 20 min, and it is static for more than 10 min. During the soft blowing period, the molten steel shall not be exposed;

[0079] Continuous casting: During continuous casting, the molten steel amount in the tundish is greater than 15 tons. During the casting process, automatic liquid level control is achieved, electromagnetic stirring is used, and soft reduction is used normally. The liquidus temperature of the steel grade is: 1469 °C.

[0080] Among them, before the start of continuous casting, the aluminum-carbon semi-immersed nozzle and the tundish need to be baked. During the continuous casting process, the average superheat ΔT of the molten steel is controlled between 25 - 35 °C.

[0081] Among them, the superheat of the steel grade is controlled not to be greater than 30 °C, the first furnace ΔT ≤ 35 °C, and constant casting speed production is adopted.

[0082] Among them, the final deoxidizer adopts low-aluminum calcium silicate barium.

[0083] For the finished rail after VD vacuum degassing, the hydrogen content ≤ 1.5 PPm, the oxygen content ≤ 20 PPm, and the nitrogen content ≤ 90 PPm.

[0084] After vacuum degassing, four-strand continuous casting or six-strand continuous casting is carried out. The continuous casting speed is 0.95 m / min, and the size of the continuous casting billet of the steel billet is 280 mm × 380 mm.

[0085] Therefore, in the above embodiments, during the continuous casting production process of rail steel, technologies such as full-process protected casting, low superheat and low casting speed, low specific water volume, and light reduction at the solidification end are adopted to control its central segregation and shrinkage cavity.

[0086] To prevent secondary oxidation caused by the contact between rail molten steel and air, a long nozzle is used to protect the molten steel flow between the ladle and the tundish, and a mudding material is used for sealing between the long nozzle and the sliding nozzle of the ladle. The molten steel surface in the tundish is covered with a double-layer covering agent. At the same time, the tundish is filled with molten steel for casting, and the weight is controlled to be above 35t.

[0087] Protected casting is carried out by using a porous submerged nozzle between the tundish and the mold, and its insertion depth is ensured. Specific Embodiment Three:

[0088] The smelting method of the national standard 43kg / m rail. The chemical composition of the steel billet material of the rail includes, by mass percentage: C: 0.55; Si: 0.22; Mn: 1.12; P≤0.025; S≤0.025; Cr≤0.15; Al≤0.010; the balance is Fe and unavoidable impurities.

[0089] The smelting method of the rail includes the following steps:

[0090] Hot metal pretreatment: Adopt a continuous treatment method in the hot metal trough. A blowing and stirring gun or a powder injection gun is set on the hot metal trough to strengthen the contact between the pretreatment agent and the hot metal through blowing and stirring. The pretreatment agent is sprayed into the hot metal in the ladle by a spray gun to fully react with the hot metal, so as to purify the hot metal and remove or extract relevant elements;

[0091] Converter smelting: The C content at tapping is C(%)≥0.08, P(%)≤0.015, and the tapping temperature is ≥1550°C; Silicon manganese, ferromanganese and ferrosilicon alloys are used for in-ladle deoxidation alloying. The non-aluminum deoxidation process is adopted for smelting. A combined blowing converter is used for smelting, and a single slag or double slag operation is adopted. The basicity of the final slag is controlled at 3.0, and slag blocking must be carried out during tapping;

[0092] Molten steel pre-refining during the converter tapping process. The slag in the ladle is blocked by a slag stopper, and the thickness of the ladle slag is controlled within 80mm. High-basicity refining slag is added during the tapping process, and the addition amount is 4-6kg / t of steel. Silicon-calcium-barium or aluminum reducing agent is used to deoxidize and modify the ladle slag, initially controlling the composition of the ladle slag and reducing the oxidability of the ladle slag, achieving the purpose of pre-refining for desulfurization, deoxidation and removal of non-metallic inclusions in the molten steel;

[0093] LF refining: Control the post-furnace composition and temperature adjustment by means of argon blowing and wire feeding in the argon blowing station and LF furnace, alloy fine-tuning, and heating and temperature rising in the IF furnace;

[0094] According to the different values of the pre-argon temperature, the argon blowing time and the feeding amount of aluminum wire are adjusted in a timely manner, so that the activity oxygen in the steel can be reduced to about 15-30 ppm, and at the same time, the inclusions in the steel can float up sufficiently, providing qualified molten steel for continuous casting;

[0095] RH refining desulfurization: After RH deoxidation alloying, the desulfurizing agent is added to the vacuum chamber in 3 batches, stirred for 8 min, and the lifting gas flow rate is set at 120 m 3 / h. After the RH treatment, VD vacuum degassing is carried out;

[0096] VD vacuum degassing: The deep vacuum time ≥ 20 min; the vacuum degree is less than 0.10 KPa; after the vacuum treatment, the soft blowing time ≥ 20 min, standing for more than 10 min, and the molten steel shall not be exposed during soft blowing;

[0097] Continuous casting: During continuous casting, the molten steel volume in the tundish is greater than 15 tons. During the casting process, the liquid level is automatically controlled, electromagnetic stirring is used, and soft reduction is used normally. The liquidus temperature of the steel grade is 1469 °C.

[0098] Among them, before the continuous casting pouring starts, the aluminum-carbon semi-immersed nozzle and the tundish need to be baked. During the continuous casting process, the average superheat ΔT of the molten steel is controlled between 25-35 °C.

[0099] Among them, the superheat of the steel grade is controlled not to be greater than 30 °C, and for the first furnace, ΔT ≤ 35 °C, and constant casting speed production is adopted.

[0100] Among them, the final deoxidizer uses low-aluminum calcium-silicon-barium.

[0101] For the finished rail after VD vacuum degassing, the hydrogen content ≤ 1.5 PPm, the oxygen content ≤ 20 PPm, and the nitrogen content ≤ 90 PPm.

[0102] After vacuum degassing, four-strand continuous casting or six-strand continuous casting is carried out. The continuous casting speed is 0.95 m / min, and the specifications of the continuously cast billet of the steel billet are 280 mm × 380 mm.

[0103] Therefore, in the above embodiments, during the continuous casting production process of rail steel, technologies such as full protection casting, low superheat and low casting speed, low specific water volume, and light soft reduction at the solidification end are adopted to control its center segregation and shrinkage cavity.

[0104] In order to prevent the molten rail steel from contacting with air and causing secondary oxidation, a long nozzle is used to protect the molten steel flow between the ladle and the tundish, and the long nozzle and the sliding nozzle of the ladle are sealed with mud. The molten steel surface in the tundish is covered with a double-layer covering agent. At the same time, the tundish is filled with molten steel for casting, and the weight is controlled above 35 t.

[0105] Between the tundish and the mold, a porous immersed nozzle is used for protected casting, and its insertion depth is ensured. Specific Example Four:

[0106] Application of a smelting method for national standard 43 kg / m steel rails. The smelting method for national standard 43 kg / m steel rails is applied to the smelting of 43 kg / m steel rails, so as to achieve that the segregation indexes of C and Mn elements in the national standard 43 kg / m steel rails are basically between 0.95 and 1.05, the segregation of C and Mn elements is relatively synchronous, and the content fluctuations at each position are small.

[0107] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0108] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for smelting national standard 43kg / m rails, characterized in that; The chemical composition of the steel billet material of the rail includes, by mass percentage: C: 0.50-0.60; Si: 0.20-0.60; Mn: 1.0-1.25; P≤0.025; S≤0.025; Cr≤0.15; Al≤0.010; the balance is Fe and unavoidable impurities; The smelting method of the rail includes the following steps: Hot metal pretreatment: adopt the hot metal ditch continuous treatment method to set a spray stirring gun or powder spray gun on the hot metal ditch, so that the pretreatment agent can strengthen the contact with the hot metal through spray stirring, and spray the pretreatment agent into the hot metal in the hot metal tank with a spray gun to make it fully react with the hot metal, so as to purify the hot metal and remove or extract related elements; Converter smelting: the C content of the steel is C (%) ≥ 0.08, P (%) ≤ 0.015, and the tapping temperature is ≥ 1550 ° C; silicon manganese, ferromanganese and ferrosilicon alloys are used for in-tank deoxidation and alloying, and aluminum-free deoxidation process is used for smelting, double-blowing converter smelting, single slag or double slag operation, the final slag basicity is controlled at 3.0, and slag blocking is required for steel tapping; During the converter steel-tapping process, the molten steel is pre-refined. The slag thickness of the ladle slag is controlled within 80mm by using a slag dart. High-basicity refined slag is added during the steel-tapping process. The amount added is 4-6kg / t steel. Silicon calcium barium or aluminum reducing agent is used to deoxidize and modify the ladle slag. The ladle slag composition is preliminarily controlled and the oxidizability of the ladle slag is reduced, so as to achieve the pre-refining purpose of desulfurization, deoxidation and removal of non-metallic inclusions in the molten steel. LF refining: Control the post-furnace composition and temperature adjustment through the argon blowing station and LF furnace argon blowing wire feeding, alloy fine-tuning and IF furnace heating and temperature rise; According to the different argon pre-temperature values, timely adjust the argon blowing time and the feeding amount of aluminum wire, which can reduce the active oxygen in the steel to about 15-30ppm, and make the inclusions in the steel float fully, providing qualified molten steel for continuous casting; RH refining desulfurization: After RH deoxidation and alloying, add the desulfurizer into the vacuum chamber in three batches, stir for 8 minutes, and increase the gas flow rate to 120m 3 / h, after RH treatment, VD vacuum degassing is performed; VD vacuum degassing: deep vacuum time ≥ 20min; vacuum degree less than 0.10KPa; soft blowing time ≥ 20min after vacuum treatment, let stand for more than 10min, molten steel shall not be exposed during soft blowing; Continuous casting: The amount of molten steel in the tundish is greater than 15 tons during continuous casting. The liquid level is automatically controlled during the casting process. Electromagnetic stirring is used and it works normally under light pressure. The liquidus temperature of the steel grade is 1469℃.

2. The smelting method of the national standard 43kg / m rail according to claim 1, characterized in that; Before continuous casting begins, the aluminum-carbon semi-submerged nozzle and the tundish need to be baked, and the average superheat ΔT of the molten steel during the continuous casting process is controlled between 25-35°C.

3. The smelting method of the national standard 43kg / m rail according to claim 2, characterized in that: The superheat of the steel grade is controlled to be no more than 30℃, the first furnace ΔT≤35℃, and constant drawing speed is adopted for production.

4. The smelting method of the national standard 43kg / m rail according to claim 3, characterized in that; The final deoxidizer is low-aluminum silicon calcium barium.

5. The smelting method of the national standard 43kg / m rail according to claim 4, characterized in that ; The hydrogen content of VD vacuum degassed finished rail is ≤1.5PPm, the oxygen content is ≤20PPm, and the nitrogen content is ≤90PPm.

6. The smelting method of the national standard 43kg / m rail according to claim 5, characterized in that; After vacuum degassing, four-strand continuous casting or six-strand continuous casting is carried out, the continuous casting speed is 0.95m / min, and the specifications of the steel continuous casting billet are 280mm×380mm.

7. The smelting method of the national standard 43kg / m rail according to claim 6, characterized in that: The chemical composition of the steel billet material of the rail includes, by mass percentage: C: 0.50-0.60; Si: 0.20-0.60; Mn: 1.0-1.25; P≤0.025; S≤0.025; Cr≤0.15; Al≤0.010; the remainder is Fe and unavoidable impurities.

8. The smelting method of the national standard 43kg / m rail according to claim 7, characterized in that; The chemical composition of the steel billet material of the rail includes, by mass percentage, C: 0.55; Si: 0.22; Mn: 1.12; P≤0.025; S≤0.025; Cr≤0.15; Al≤0.010; the remainder is Fe and unavoidable impurities.

9. An application of the smelting method of the national standard 43kg / m rail according to any one of claims 1 to 8, characterized in that; The smelting method of the national standard 43kg / m rail according to any one of claims 1 to 8 is applied to the smelting of the 43kg / m rail.

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