High-speed railway ballastless track plate steel wire used wire rod and production method thereof

Abstract

The application relates to the technical field of steel smelting processes, and particularly discloses a high-speed railway ballastless track plate steel wire used wire rod and a production method thereof. The wire rod comprises the following components in percentage by mass: C: 0.79%-0.84%, Si: 0.16%-0.23%, Mn: 0.75%-0.79%, P<=0.02%, S<=0.02%, Cr: 0.24%-0.28%, V: 0.04%-0.075%, Al: 0.005%-0.015%, and the rest is Fe and inevitable impurities. The tensile strength of the wire rod prepared by the application can reach 1204MPa-1230MPa, the reduction of area can reach 35%-40%, and the elongation after fracture can reach 12.5%-14.0%, so that the wire rod has high strength, high toughness and high plasticity, and the steel wire prepared from the wire rod can meet the requirements of high-speed railway construction.

Description

Technical Field

[0001] This application relates to the field of steel smelting technology, and more specifically, it relates to a wire rod for high-speed railway ballastless track slabs and its production method. Background Technology

[0002] High-speed rail refers to railway systems designed to high standards and capable of safe high-speed train operation. The world's first official high-speed rail system was the Tokaido Shinkansen in Japan, which opened in 1964 and had a design speed of 200 km / h. Now, with technological advancements, trains are even faster, and different eras and countries have developed different definitions of high-speed rail, establishing their own detailed technical standards for high-speed rail levels based on their national circumstances. These standards vary in terms of train speeds, railway types, and other factors.

[0003] China's high-speed railways generally use ballastless track, which refers to a track structure that uses a monolithic foundation of concrete, asphalt mixture, etc., instead of loose crushed stone ballast. Compared with ballasted track, ballastless track avoids ballast splashing, has better smoothness and stability, longer service life, better durability, requires less maintenance, and can achieve train speeds of over 350 km / h. It is currently one of the world's most advanced track technologies. The key to the construction of ballastless track lies in the use of ballastless track slabs. These slabs typically require high-strength and high-toughness steel wire for manufacturing. According to current standards, the tensile strength of the steel wire used in ballastless track slabs should not be less than 1860 MPa, the reduction of area should not be less than 35%, and the elongation should not be less than 3.5%.

[0004] Currently, Chinese patent CN 101705429A discloses a wire rod for high-speed railway ballastless track sleeper slabs and its production method. This method reduces the carbon content, increases the content of alloying elements such as silicon, manganese, and chromium, and adds trace amounts of boron, resulting in a tensile strength of 700-1000 MPa, a reduction of area greater than 30%, and an elongation greater than 18% for the wire rod, significantly improving its toughness and thus giving the steel wire made from it a high fatigue life. However, while this method greatly improves the toughness of the wire rod, the excessively low carbon content leads to insufficient strength, resulting in low tensile strength of the steel wire made from it, which in turn reduces the firmness of the connection between the ballastless track slab and the rail. Furthermore, the addition of boron in this method increases production costs and environmental pollution.

[0005] Therefore, how to make wire rods meet the requirements of both high strength and high toughness has become an important research issue in the industry. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a wire rod for high-speed railway ballastless track slabs and its production method.

[0007] Firstly, this application provides a wire rod for high-speed railway ballastless track slabs, which adopts the following technical solution:

[0008] A type of wire rod for high-speed railway ballastless track slabs comprises the following components by weight percentage: C: 0.79%-0.84%, Si: 0.16%-0.23%, Mn: 0.75%-0.79%, P≤0.02%, S≤0.02%, Cr: 0.24%-0.28%, V: 0.04%-0.075%, Al: 0.005%-0.015%, with the remainder being Fe and unavoidable impurities.

[0009] Preferably, the wire rod has a tensile strength of 1204MPa-1230MPa, a reduction of area of ​​35%-40%, and an elongation after fracture of 12.5%-14.0%.

[0010] By adopting the above technical solutions, in the wire rod of this application, C element can improve the strength and hardness of the wire rod, Si element can improve the plasticity and toughness of the wire rod, Mn element can improve the hardenability and wear resistance of the wire rod, Cr element can improve the oxidation resistance and corrosion resistance of the wire rod, V element can form fine compounds with C and N elements, thereby inhibiting the growth of austenite grains and the formation of continuous cementite in the wire rod, thus improving the overall mechanical properties of the wire rod, and Al element can be micro-alloyed during the production process to change the microstructure of the wire rod and refine the grain size, thereby improving the overall mechanical properties of the wire rod.

[0011] This application has rationally designed the alloy element composition of the wire rod and optimized the proportion of each alloy element. At the same time, Al and V elements have been added to the wire rod, so that the wire rod of this application can have high strength, as well as high toughness and plasticity. This allows the steel wire made from the wire rod of this application to have both high strength and high toughness, so as to ensure the firmness of the connection between the ballastless track slab and the rail. Furthermore, the steel wire can adapt to the length change when stretched and undergo uniform deformation, preventing brittle fracture or cracks caused by stress concentration, and preventing the fastening force between the ballastless track slab and the fastener from being affected by plastic deformation or relaxation.

[0012] Secondly, this application provides a method for producing wire rods for high-speed railway ballastless track slabs, which adopts the following technical solution:

[0013] A method for producing wire rod for high-speed railway ballastless track slabs includes S1. converter smelting, S2. LF refining, S3. continuous casting, and S4. high-speed wire rod rolling. In step S1, an alloy is added to the molten steel for deoxidation and alloying during tapping, and the steel is slag washed with quicklime. The alloy includes (0.33±0.01) kg / ton of aluminum ingots, (10.92±0.02) kg / ton of silicon manganese, and (0.60±0. The steel composition includes ferrosilicon (0.1) kg / ton steel, high-carbon ferrochrome (5.2±0.02) kg / ton steel, low-nitrogen carbon powder (9.93±0.01) kg / ton steel, and ferrovanadium (1.27±0.28) kg / ton steel; in step S2, slag formation is carried out by electric current at a temperature ≥1480℃ and the steel composition is adjusted, with bottom-blown argon stirring throughout the process. When the temperature reaches (1525±5)℃, the composition of the steel reaches C:(0.81±0.01) kg / ton steel. When the content of 0.2% (0.20±0.02)%, Si: (0.20±0.02)%, Mn: (0.78±0.01)%, P≤0.02%, S≤0.02%, Cr: (0.27±0.01)%, V: (0.058±0.018)%, and Al: (0.01±0.005)%, wire feeding is performed. When T[O]≤30ppm, the furnace is lifted out after stirring with soft-blown argon gas for more than 10 minutes; the step S3 In step S3, a fully protected casting process is adopted, controlling the liquidus temperature of the molten steel at 1466℃ and the casting superheat at 15℃-25℃. In step S4, the 250mm diameter round billet obtained in step S3 is heated, rough rolled, finish rolled, sizing reduced, wire rod drawn, and cooled to obtain a wire rod with a diameter of 15mm. The wire rod drawing temperature is controlled at 880℃-900℃, and the Morgan-Stelmore air-cooling line is used for cooling, controlling the minimum phase transformation temperature at 610℃.

[0014] Preferably, the roller speed in the Morgan-Stelmo air-cooled line in step S4 is set as follows: the initial roller speed is 0.65 m / s, and the lead rate of each roller speed is 10%, 10%, 10%, 10%, 6%, 0%, 0%, 0%, 0%, -18%, -5%, 0%.

[0015] Preferably, in step S4, the number of fans in the Morgan Stello air-cooled line that are turned on is 11, with the power of fans 1#-10# being turned on at 100% power and fan 11# being turned on at 60% power.

[0016] By adopting the above technical solution: First, in the steel tapping process of converter smelting, a specific amount of ferrovanadium and aluminum blocks are added to the molten steel, which can enable the V and Al elements to achieve microalloying in the next refining process, inhibit the growth of austenite grains and the formation of continuous cementite in the wire rod, refine the grain size, change the microstructure of the wire rod, and thus improve the strength, toughness, plasticity, fatigue resistance and stability of the wire rod. This application strictly controls the addition of each alloy, especially the addition of aluminum blocks and ferrovanadium, so that the alloy element composition of the molten steel entering the next step of LF furnace refining is: C: 0.70%-0.78%, Si: 0.10%-0.15%, Mn: 0.65%-0.75%, P≤0.02%, S≤0.02%, Cr: 0.20%-0.25%, V: 0.045-0.055%, Al: 0.003-0.008%, thereby ensuring that the content of each alloy element in the final wire rod is in the optimal ratio. Furthermore, the aluminum blocks in this application also act as a deoxidizer, reducing the oxygen and sulfur content in the molten steel, so that the T[O] in the molten steel entering the LF refining furnace is ≤50ppm, improving the purity and weldability of the molten steel.

[0017] Secondly, this application further adjusts the composition of the molten steel during LF furnace refining to achieve the following composition: C: (0.81±0.02)%, Si: (0.20±0.02)%, Mn: (0.78±0.01)%, P≤0.02%, S≤0.02%, Cr: (0.27±0.01)%, V: (0.058±0.018)%, Al: (0.01±0.005)%, thereby ensuring that the content of each alloying element in the final wire rod is in the optimal ratio; at the same time, the temperature and total oxygen content of the molten steel when it exits the LF refining furnace are controlled so that the final wire rod can have both high strength and high toughness.

[0018] Furthermore, this application also employs low superheat casting, which reduces the casting temperature, narrows the gap between the casting temperature and the liquidus temperature of the molten steel, and reduces the superheat of the molten steel, thereby reducing the formation of inclusions and porosity in the wire rod.

[0019] In addition, in existing technologies, smaller billets (e.g., 150mm × 150mm) are typically produced using a single-fire forming technique, where solidification and deformation are completed in a single cooling cycle. Larger billets, however, generally require two fires. Directly applying a single-fire forming technique to larger billets may negatively impact their microstructure uniformity and mechanical properties. This application, however, allows for the direct application of a single-fire forming technique to 250mm diameter round billets, producing wire rods that still exhibit good microstructure uniformity and mechanical properties. On the one hand, this application strictly controls the content of each alloying element in the wire rod, resulting in wire rods with high strength and toughness, capable of withstanding large temperature differences. On the other hand, this application controls the initial temperature of each process: the furnace exit temperature after billet heating is 1140℃-1200℃, the finishing rolling start temperature is 920℃-940℃, and the sizing reduction start temperature is 890℃-910℃, thereby controlling the wire drawing temperature to 880℃-900℃. Simultaneously, a Morgan-Steyrmo air-cooling line is used to achieve high-volume cooling, and during the cooling process, the roller speed and air volume in the Morgan-Steyrmo air-cooling line are controlled, i.e., precise control of the cooling rate, to control the minimum phase transformation temperature to 610℃. Phase transformation is a change in the crystal structure of a metal during cooling, playing a crucial role in the material's properties. By controlling the minimum phase transformation temperature to 610℃, this application can promote a more complete phase transformation of the wire rod during the cooling process, thereby forming a stable crystal structure within the wire rod and ensuring that the wire rod has good structural uniformity and mechanical properties.

[0020] In summary, the main challenges of this application are twofold: first, how to achieve high strength while maintaining high plasticity and toughness in the wire rod; second, the wire rod is produced by single-fire drawing from a 250mm diameter steel billet during high-speed wire rolling, and direct single-fire drawing from a large-diameter steel billet significantly impacts the uniformity of the billet's microstructure and mechanical properties. This application, however, optimizes the mechanical properties of the wire rod by controlling multiple key conditions, enabling the wire rod produced from a 250mm diameter round billet to simultaneously possess high strength, high toughness, and high plasticity.

[0021] Preferably, in step S2, the electrolytic slag formation specifically involves: first, under conditions of voltage level 6 and current of 25000A-35000A, adding slag material to form white slag, with the white slag refining time being >15min; then, using silicon carbide and calcium carbide for slag surface deoxidation; and then, under conditions of voltage level 4 and current of 30000A-35000A, raising the temperature for 10min-15min to bring the molten steel temperature to (1525±5)℃.

[0022] Preferably, the slag material includes quicklime and fluorite; the specific addition process is as follows: first add quicklime of ≥5.33 kg / ton of steel, then add fluorite, and adjust the basicity according to the amount of slag so that the total amount of slag reaches 10 kg / ton of steel-12 kg / ton of steel, the basicity is 2-3, and FeO+MnO<1.0%.

[0023] Preferably, the amount of silicon carbide used is 0.4 kg / ton of steel to 1.0 kg / ton of steel; and the amount of calcium carbide used is 0.9 kg / ton of steel to 1.1 kg / ton of steel.

[0024] By adopting the above technical solution, this application first performs slag formation under certain voltage and current conditions, then adds quicklime to produce white slag, adds fluorite appropriately according to the slag fluidity, and adjusts the basicity according to the amount of slag so that the total slag amount reaches 10kg / ton-12kg / ton-steel, the basicity is 2-3, and FeO+MnO<1.0%. Then, silicon carbide and calcium carbide are used as reducing agents to deoxidize the slag surface. After that, under certain voltage and current conditions, the temperature is raised for a certain time to fully homogenize the chemical composition of the molten steel, remove non-metallic inclusions in the molten steel, and adjust the temperature.

[0025] Preferably, in step S2, the bottom-blown argon gas includes online bottom-blown argon gas and argon gas blown during the electrostatic slag-forming process; the flow rate of the online bottom-blown argon gas is 100L / min-150L / min, and the pressure is 0.3MPa-0.4MPa.

[0026] Preferably, the argon blowing process in the electrostatic slag formation includes a first electrostatic slag formation argon blowing and a second electrostatic slag formation argon blowing; wherein, the flow rate of the first electrostatic slag formation argon blowing is 250L / min-350L / min and the pressure is 0.3MPa-0.4MPa, and the flow rate of the second electrostatic slag formation argon blowing is 50L / min-100L / min and the pressure is 0.3MPa-0.4MPa.

[0027] In summary, this application has the following beneficial technical effects:

[0028] 1. The wire rod produced by the method of this application has a tensile strength of 1204MPa-1230MPa, a reduction of area of ​​35%-40%, and an elongation after fracture of 12.5%-14.0%, which combines high strength, high toughness and high plasticity.

[0029] 2. The wire rod of this application can enable the steel wire made from it to achieve a tensile strength of 1860MPa-2060MPa, a reduction of area of ​​35%-50%, and an elongation of 3.5%-5.0%, which meets the requirements of high-speed railway construction.

[0030] 3. The production method of this application effectively reduces energy consumption in the wire rod production process, saves resources, and reduces production costs. Attached Figure Description

[0031] Figure 1 This is a schematic diagram showing the metallographic structure of the wire rods prepared in Examples 1-3 under a 500x metallographic microscope.

[0032] Figure 2 This is a schematic diagram showing the metallographic structure of the wire rod prepared in Comparative Example 1 under a 500x metallographic microscope. Detailed Implementation

[0033] The present application will be further described in detail below with reference to the accompanying drawings, embodiments and comparative examples.

[0034] <Material Source>

[0035] The aluminum block in this application contains 99% Al.

[0036] The silicon-manganese alloy in this application contains 17.50% Si and 65.70% Mn.

[0037] The silicon content in the ferrosilicon of this application is 73.01%;

[0038] The high-carbon ferrochrome in this application contains 8.00% carbon and 53.41% chromium.

[0039] The low-nitrogen carbon powder of this application contains 81.85% carbon.

[0040] The vanadium-iron alloy of this application contains 50.46% V.

[0041] <Example>

[0042] Example 1

[0043] A method for producing wire rod for high-speed railway ballastless track slabs includes the following steps:

[0044] S1. Converter smelting

[0045] 95 tons of molten iron and 30 tons of scrap steel are added to the converter. The temperature of the molten iron entering the converter is ≥1280℃, P≤0.12%, Ni<0.15%. Argon gas is used for bottom blowing throughout the smelting process, with an oxygen pressure ≥0.8MPa. The slag basicity is controlled between 3.0 and 3.8. High-pressure supplemental blowing is used for final control, maintaining C≥0.12% and P≤0.015%. The tapping temperature is 1600℃-1620℃. When the final control requirements are met, the molten steel is tapped into a ladle. The tapping amount is 112.55 tons. During tapping... Add 36.02kg-38.27kg of aluminum blocks, 1226.80kg-1231.30kg of ferrosilicon, 66.40kg-68.66kg of ferrosilicon, 583.01kg-587.51kg of high-carbon ferrochrome, 1116.50kg-1118.75kg of low-nitrogen carbon powder, and 111.42kg-123.81kg of ferrovanadium to the molten steel for deoxidation and alloying. Then, wash the slag with 337.65kg of quicklime. After that, hoist the ladle to the LF refining furnace.

[0046] S2.LF Refining

[0047] The ladle inlet temperature is controlled to be ≥1480℃, the ladle hoisting temperature to be (1525±5)℃, and the liquidus temperature to be 1466℃. Molten steel is poured into the LF refining furnace. During tapping, argon gas is blown online from the bottom at a flow rate of 100L / min and a pressure of 0.3MPa. Under conditions of voltage level 6 and current 25000A, quicklime is added in 2-3 batches to form white slag. Argon gas is continuously blown and stirred during this process at a flow rate of 250L / min and a pressure of... The pressure is 0.3 MPa, the amount of quicklime added is ≥5.33 kg / ton of steel, and fluorite is added according to the slag fluidity. The white slag refining time is >15 min. The basicity is adjusted according to the slag amount to make the total slag amount reach 10 kg / ton of steel, the basicity is 2-3, and FeO+MnO <1.0%. After the composition is uniform, samples are taken and the composition is analyzed. After the test results are obtained, alloys are added to adjust the composition of the molten steel according to the target composition. Then, silicon carbide and calcium carbide are used for further processing. Deoxidation was performed on the slag surface, with silicon carbide at a dosage of 0.4 kg / ton of steel and calcium carbide at a dosage of 0.9 kg / ton of steel. The steel was then heated for 10 minutes under voltage level 4 and current of 30000 A, with continuous argon gas stirring at a flow rate of 50 L / min and a pressure of 0.3 MPa. When the molten steel temperature reached (1525±5)℃, the composition of the molten steel was C: (0.81±0.02)% and Si: (0.20±0.02). When the content of Mn: (0.78±0.01)%, P≤0.02%, S≤0.02%, Cr: (0.27±0.01)%, V: (0.042±0.003)%, and Al: (0.01±0.005)%, 200m of pure calcium wire is fed at a speed of 3m / s. When T[O]≤30ppm, the furnace is lifted out after stirring with soft blowing argon gas for more than 10min. The entire refining cycle is (45±5)min.

[0048] S3. Continuous casting

[0049] For round billets with a diameter of 250mm, to ensure billet quality and smooth continuous casting, the following aspects should be carefully controlled:

[0050] Temperature control: The temperature of the tundish is (1525±5)℃, the temperature of the intermediate tundish is 1481℃-1491℃, and the liquidus temperature is 1466℃.

[0051] Casting control: During continuous casting, protective sleeves are used throughout the process from the ladle to the tundish and from the tundish to the crystallizer to prevent secondary oxidation of the molten steel and ensure its purity; the casting speed (ΔT) (≤25℃) is controlled at 1.05 m / min, and the crystallizer water flow rate is 120 m³ / min. 3 / h-125m 3 / h, the secondary cooling water ratio is 0.6L / kg, the secondary cooling water distribution ratio is 27% for the first stage, 48% for the second stage, and 25% for the third stage, the electromagnetic stirring of the crystallizer is 3Hz, 450A, and the electromagnetic stirring of the end is 10Hz, 500A; the superheat is strictly controlled at 15℃; when the molten steel level in the tundish is ≥300mm, the molten steel level in the tundish is ≥400mm, and when the molten steel is poured from the upper and lower furnaces, the molten steel level in the tundish is ≥250mm; when the molten steel in the tundish reaches 2 / 3 of its height after the tundish starts pouring, 240kg of tundish covering agent is added first, followed by 70kg of rice husks;

[0052] S4. High-speed wire rolling

[0053] The 250mm diameter round billet obtained in step S3 above is heated, rough rolled, finish rolled, sizing reduced, wired, and cooled to obtain a wire rod with a diameter of 15mm. The wire rod contains C: 0.84%, Si: 0.23%, Mn: 0.79%, P: 0.02%, S: 0.02%, Cr: 0.28%, V: 0.040%, Al: 0.005%, with the remainder being Fe and unavoidable impurities.

[0054] The heating temperature control during the round billet heating process is as follows: preheating section ≤900℃, first heating section 900℃-1080℃, second heating section 1170℃-1250℃, soaking section 1170℃-1250℃; the billet exit temperature after heating is 1140℃; the finishing rolling start temperature is 920℃; the sizing reduction start temperature is 890℃; and the wire drawing temperature is 880℃.

[0055] The entire process utilizes the Morgan-Stelmo air-cooled line to achieve high-volume controlled cooling, ensuring a minimum phase change temperature of 610℃. Within the Morgan-Stelmo air-cooled line, the initial roller conveyor speed is 0.65 m / s, and the lead rates for each roller conveyor section are set sequentially as follows: 10%, 10%, 10%, 10%, 6%, 0%, 0%, 0%, 0%, -18%, -5%, 0%. Eleven fans are activated, with fans #1-#10 operating at 100% power and fan #11 operating at 60% power.

[0056] Example 2

[0057] A method for producing wire rod for high-speed railway ballastless track slabs includes the following steps:

[0058] S1. Converter smelting

[0059] 95 tons of molten iron and 30 tons of scrap steel are added to the converter. The temperature of the molten iron entering the converter is ≥1280℃, P≤0.12%, Ni<0.15%. Argon gas is used for bottom blowing throughout the smelting process, with an oxygen pressure ≥0.8MPa. The slag basicity is controlled between 3.0 and 3.8. High-pressure supplemental blowing is used for final control, maintaining C≥0.12% and P≤0.015%. The tapping temperature is 1600℃-1620℃. When the final control requirements are met, the molten steel is tapped into a ladle. The tapping amount is 112.55 tons. During tapping... Add 36.02kg-38.27kg of aluminum blocks, 1226.80kg-1231.30kg of ferrosilicon, 66.40kg-68.66kg of ferrosilicon, 583.01kg-587.51kg of high-carbon ferrochrome, 1116.50kg-1118.75kg of low-nitrogen carbon powder, and 111.42kg-123.81kg of ferrovanadium to the molten steel for deoxidation and alloying. Then, wash the slag with 393.93kg of quicklime. After that, hoist the ladle to the LF refining furnace.

[0060] S2.LF Refining

[0061] The ladle inlet temperature is controlled to be ≥1480℃, the ladle hoisting temperature to be (1525±5)℃, and the liquidus temperature to be 1466℃. Molten steel is poured into the LF refining furnace. During tapping, argon gas is blown online from the bottom at a flow rate of 125 L / min and a pressure of 0.35 MPa. Under conditions of voltage level 6 and current 30000 A, quicklime is added in 2-3 batches to form white slag. Argon gas is continuously blown and stirred during this process at a flow rate of 300 L / min and a pressure of... The pressure is 0.35 MPa. The amount of quicklime added is ≥5.33 kg / ton of steel. Fluorite is then added depending on the slag's fluidity. The refining time for the quicklime is >15 min. The basicity is adjusted according to the slag quantity to achieve a total slag quantity of 11 kg / ton of steel, a basicity of 2-3, and FeO+MnO <1.0%. After the composition is homogeneous, samples are taken and analyzed. Based on the test results, alloys are added to adjust the steel composition according to the target composition. Then, silicon carbide and calcium carbide are used for further refining. Deoxidation was performed on the slag surface using 0.7 kg / ton of silicon carbide and 1.0 kg / ton of calcium carbide. The steel was then heated for 12 minutes under voltage level 4 and current of 32000 A, with continuous argon gas stirring at a flow rate of 75 L / min and a pressure of 0.35 MPa. When the molten steel temperature reached (1525±5)℃, the steel composition was: C: (0.81±0.02)%, Si: (0.20±0.02)%. When the content of Cr: (0.27±0.01)%, Mn: (0.78±0.01)%, P≤0.02%, S≤0.02%, Cr: (0.27±0.01)%, V: (0.042±0.003)%, and Al: (0.01±0.005)%, 210m of pure calcium wire is fed at a speed of 4m / s. When T[O]≤30ppm, the furnace is lifted out after stirring with soft blowing argon gas for more than 10min. The entire refining cycle is (45±5)min.

[0062] S3. Continuous casting

[0063] For round billets with a diameter of 250mm, to ensure billet quality and smooth continuous casting, the following aspects should be carefully controlled:

[0064] Temperature control: The temperature of the tundish is (1525±5)℃, the temperature of the intermediate tundish is 1481℃-1491℃, and the liquidus temperature is 1466℃.

[0065] Casting control: During continuous casting, protective sleeves are used throughout the process from the ladle to the tundish and from the tundish to the crystallizer to prevent secondary oxidation of the molten steel and ensure its purity; the casting speed (ΔT) (≤25℃) is controlled at 1.05 m / min, and the crystallizer water flow rate is 120 m³ / min. 3 / h-125m 3 / h, the secondary cooling water ratio is 0.6L / kg, the secondary cooling water distribution ratio is 27% for the first stage, 48% for the second stage, and 25% for the third stage, the electromagnetic stirring of the crystallizer is 3Hz, 450A, and the electromagnetic stirring of the end is 10Hz, 500A; the superheat is strictly controlled at 20℃; when the molten steel level in the tundish is ≥300mm, pouring begins; when pouring steel from the upper and lower furnaces is connected to the transfer ladle, the molten steel level in the tundish is ≥400mm; when pouring stops, the molten steel level in the tundish is ≥250mm; after pouring begins in the tundish, when the molten steel in the tundish reaches 2 / 3 of the height, first add 240kg of tundish covering agent, then add 70kg of rice husks;

[0066] S4. High-speed wire rolling

[0067] The 250mm diameter round billet obtained in step S3 above is heated, rough rolled, finish rolled, sizing reduced, wired, and cooled to obtain a wire rod with a diameter of 15mm. The wire rod contains C: 0.81%, Si: 0.20%, Mn: 0.76%, P: 0.015%, S: 0.0015%, Cr: 0.25%, V: 0.045%, Al: 0.010%, with the remainder being Fe and unavoidable impurities.

[0068] The heating temperature control during the round billet heating process is as follows: preheating section ≤900℃, first heating section 900℃-1080℃, second heating section 1170℃-1250℃, soaking section 1170℃-1250℃; the billet exit temperature after heating is 1170℃; the finishing rolling start temperature is 930℃; the sizing reduction start temperature is 900℃; and the wire drawing temperature is 890℃.

[0069] The entire process utilizes the Morgan-Stelmo air-cooled line to achieve high-volume controlled cooling, ensuring a minimum phase change temperature of 610℃. Within the Morgan-Stelmo air-cooled line, the initial roller conveyor speed is 0.65 m / s, and the lead rates for each roller conveyor section are set sequentially as follows: 10%, 10%, 10%, 10%, 6%, 0%, 0%, 0%, 0%, -18%, -5%, 0%. Eleven fans are activated, with fans #1-#10 operating at 100% power and fan #11 operating at 60% power.

[0070] Example 3

[0071] A method for producing wire rod for high-speed railway ballastless track slabs includes the following steps:

[0072] S1. Converter smelting: 95t of molten iron and 30t of scrap steel are added to the converter. The temperature of the molten iron entering the converter is ≥1280℃, P≤0.12%, Ni<0.15%. Argon gas is used for bottom blowing throughout the smelting process, with an oxygen pressure ≥0.8MPa. The slag basicity is controlled between 3.0 and 3.8. High-pressure supplemental blowing is used for endpoint control, controlling C≥0.12% and P≤0.015%. The tapping temperature is 1600℃-1620℃. When the endpoint control requirements are met, the molten steel is tapped into a ladle. The tapping amount is 112.55t. During tapping, 36.02kg-38.27kg of aluminum blocks, 1226.80kg-1231.30kg of ferrosilicon, 66.40kg-68.66kg of ferrosilicon, 583.01kg-587.51kg of high-carbon ferrochrome, 1116.50kg-1118.75kg of low-nitrogen carbon powder, and 123.81kg-142.94kg of ferrovanadium are added to the molten steel for deoxidation and alloying. The steel is then washed with 450.2kg of quicklime before being hoisted to the LF refining furnace.

[0073] S2.LF Refining

[0074] The ladle temperature is controlled to be ≥1480℃, the ladle hoisting temperature is (1525±5)℃, and the liquidus temperature is 1466℃. Molten steel is poured into the LF refining furnace. During tapping, argon gas is blown online at a flow rate of 150L / min and a pressure of 0.4MPa. Under voltage level 6 and current of 35000A, quicklime is added in 2-3 batches to create white slag. Argon gas is continuously blown and stirred at a flow rate of 350L / min and a pressure of 0.4MPa. The amount of quicklime added is ≥5.33kg / ton of steel. Fluorite is then added depending on the slag's fluidity. The white slag refining time is >15min. The basicity is adjusted according to the slag volume to achieve a total slag volume of 12kg / ton of steel, a basicity of 2-3, and FeO+MnO <1.0%. After the composition is homogeneous, samples are taken and analyzed. Based on the test results, alloys are added to adjust the molten steel composition according to the target composition. Then, silicon carbide and calcium carbide are used for further processing. The slag surface is deoxidized, with silicon carbide used at a rate of 1 kg / ton of steel and calcium carbide used at a rate of 1.1 kg / ton of steel. Then, the temperature is increased for 15 minutes under conditions of voltage level 4 and current of 35000 A, with continuous argon gas stirring at a flow rate of 100 L / min and a pressure of 0.4 MPa. When the molten steel temperature reaches (1525±5)℃, the composition of the molten steel is C: (0.81±0.02)% and Si: (0.20±0.02). When the content of Mn: (0.78±0.01)%, P≤0.02%, S≤0.02%, Cr: (0.27±0.01)%, V: (0.06±0.015)%, and Al: (0.01±0.005)%, 220m of pure calcium wire is fed at a speed of 5m / s. When T[O]≤30ppm, the furnace is lifted out after stirring with soft blowing argon gas for more than 10min. The entire refining cycle is (45±5)min.

[0075] S3. Continuous casting

[0076] For round billets with a diameter of 250mm, to ensure billet quality and smooth continuous casting, the following aspects should be carefully controlled:

[0077] Temperature control: The temperature of the tundish is (1525±5)℃, the temperature of the intermediate tundish is 1481℃-1491℃, and the liquidus temperature is 1466℃.

[0078] Casting control: During continuous casting, protective sleeves are used throughout the process from the ladle to the tundish and from the tundish to the crystallizer to prevent secondary oxidation of the molten steel and ensure its purity; the casting speed (ΔT) (≤25℃) is controlled at 1.05 m / min, and the crystallizer water flow rate is 120 m³ / min. 3 / h-125m 3 / h, the secondary cooling water ratio is 0.6L / kg, the secondary cooling water distribution ratio is 27% for the first stage, 48% for the second stage, and 25% for the third stage, the electromagnetic stirring of the crystallizer is 3Hz, 450A, and the electromagnetic stirring of the end is 10Hz, 500A; the superheat is strictly controlled at 20℃; when the molten steel level in the tundish is ≥300mm, pouring begins; when pouring steel from the upper and lower furnaces is connected to the transfer ladle, the molten steel level in the tundish is ≥400mm; when pouring stops, the molten steel level in the tundish is ≥250mm; after pouring begins in the tundish, when the molten steel in the tundish reaches 2 / 3 of the height, first add 240kg of tundish covering agent, then add 70kg of rice husks;

[0079] S4. High-speed wire rolling

[0080] The 250mm diameter round billet obtained in step S3 above is heated, rough rolled, finish rolled, sizing reduced, wired, and cooled to obtain a wire rod with a diameter of 15mm. The wire rod contains C: 0.79%, Si: 0.16%, Mn: 0.75%, P: 0.02%, S: 0.02%, Cr: 0.24%, V: 0.075%, Al: 0.015%, with the remainder being Fe and unavoidable impurities.

[0081] The heating temperature control during the round billet heating process is as follows: preheating section ≤900℃, first heating section 900℃-1080℃, second heating section 1170℃-1250℃, soaking section 1170℃-1250℃; the billet exit temperature after heating is 1200℃; the finishing rolling start temperature is 940℃; the sizing reduction start temperature is 910℃; and the wire drawing temperature is 900℃.

[0082] The entire process utilizes the Morgan-Stelmo air-cooled line to achieve high-volume controlled cooling, ensuring a minimum phase change temperature of 610℃. Within the Morgan-Stelmo air-cooled line, the initial roller conveyor speed is 0.65 m / s, and the lead rates for each roller conveyor section are set sequentially as follows: 10%, 10%, 10%, 10%, 6%, 0%, 0%, 0%, 0%, -18%, -5%, 0%. Eleven fans are activated, with fans #1-#10 operating at 100% power and fan #11 operating at 60% power.

[0083] <Comparative Example>

[0084] Comparative Example 1

[0085] The difference from Example 2 is that during the tapping process of the converter smelting, the amount of aluminum blocks used is 11.26 kg and the amount of ferrovanadium used is 56.28 kg. In addition, during the refining in the LF furnace, the Al content in the molten steel is 0.0002% and the V content is 0.02%, while the rest are the same as in Example 2.

[0086] Comparative Example 2

[0087] The difference from Example 2 is that during the tapping process of the converter smelting, the amount of aluminum blocks used is 56.28 kg, the amount of ferrovanadium used is 225.1 kg, and during the refining in the LF furnace, the Al content in the molten steel is 0.025%, the V content is 0.10%, and the rest are the same as in Example 2.

[0088] Comparative Example 3

[0089] The difference from Example 2 is that the casting superheat is 30°C during the continuous casting process.

[0090] Comparative Example 4

[0091] The difference from Example 2 is as follows: during the high-speed wire rolling process, the wire drawing temperature is 890℃; in the Morgan-Stelmo air-cooled line, the speed of the first section of the roller conveyor is 0.8m / s, and the speeds of each section of the roller conveyor are 0.88m / s, 0.97m / s, 1.06m / s, 1.17m / s, 1.24m / s, 1.24m / s, 1.24m / s, 1.24m / s, 1.24m / s, 1.02m / s, 0.97m / s, and 0.97m / s respectively; the fans are turned on at 100% power for fans #1-#16; and the minimum phase change temperature is 590℃.

[0092] Comparative Example 5

[0093] The difference from Example 2 is as follows: During the high-speed wire rolling process, the wire drawing temperature is 890℃. In the Morgan-Stelmo air-cooled line, the speed of the first section of the roller conveyor is 0.60m / s, and the speeds of each section of the roller conveyor are 0.66m / s, 0.73m / s, 0.80m / s, 0.88m / s, 0.93m / s, 0.93m / s, 0.93m / s, 0.93m / s, 0.76m / s, 0.73m / s, and 0.73m / s respectively. The fans are turned on at 80% power for fans 1#-6#, 100% power for fans 7#-10#, and 60% power for fan 11#. The minimum phase change temperature is 630℃.

[0094] Performance Testing

[0095] 1. The wire rods prepared in Examples 1-3 and Comparative Examples 1-7 were tested for elongation after fracture, reduction of area and tensile strength according to GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". The results are shown in Table 1.

[0096] 2. After the wire rods obtained in Examples 1-3 undergo post-treatment processes such as cold drawing, annealing, and galvanizing, steel wire for high-speed railway ballastless track slabs with a diameter of 3mm is obtained. The elongation, reduction of area, and tensile strength of the above steel wire are tested according to GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". The results are as follows: the tensile strength of the steel wire is 1860MPa-2060MPa, the reduction of area is 35%-50%, and the elongation is 3.5%-5.0%.

[0097] Table 1. Results of Wire Rod Performance Test

[0098] project Tensile strength (MPa) Elongation after fracture (%) Reduction of area (%) Example 1 1204 12.5 35 Example 2 1211 13.3 35 Example 3 1230 14.0 40 Comparative Example 1 1205 8.2 20 Comparative Example 2 1225 14.5 32 Comparative Example 3 1205 11.1 28 Comparative Example 4 1196 10.5 30 Comparative Example 5 1203 9.5 20

[0099] As shown in Table 1, the wire rods obtained in Examples 1-3 of this application have a tensile strength of 1204 MPa-1230 MPa, an elongation after fracture of 12.5%-14.0%, and a reduction of area of ​​35%-40%. This indicates that by rationally designing the content of each alloying element in the wire rod, adding V and Al elements, controlling the overheating during casting to a low range, and controlling the temperature at each stage during high-speed wire rolling and using dynamic control cooling technology to precisely control the cooling rate, the minimum phase transformation temperature is controlled to 610℃. This allows this application to directly process 250mm diameter round billets into finished products in a single firing during high-speed wire rolling, resulting in wire rods with high strength, toughness, and plasticity. Furthermore, referencing... Figure 1 In the wire rods prepared in Examples 1-3 of this application, the network carbide level is grade 0, which is relatively low. Lower-grade network carbides are generally associated with a more uniform grain boundary structure. Therefore, this indicates that the wire rods of this application have better strength, toughness, and plasticity, and can perform better under stress loading.

[0100] Compared to the wire rod obtained in Example 2, the wire rod prepared in Comparative Example 1 showed a 0.50% decrease in tensile strength, a 38.35% decrease in elongation after fracture, and a 42.86% decrease in reduction of area. Compared to the wire rod prepared in Example 2, the wire rod prepared in Comparative Example 2 showed a 1.15% increase in tensile strength and a 9.02% increase in elongation after fracture, but a 8.57% decrease in reduction of area. These data further demonstrate the importance of controlling the content of V and Al elements for wire rod performance. This application comprehensively optimizes the mechanical properties of wire rod by controlling the content of V and Al elements, enabling wire rods obtained directly from 250mm diameter round billets to simultaneously possess high strength, high toughness, and high plasticity. Furthermore, referring to… Figure 2In Comparative Example 1, the wire rod has a network carbide level of 3, which is relatively high. Network carbides can cause the grain boundaries of the material to become discontinuous, weakening the strength and toughness of the material. Therefore, higher-level network carbides will have a significant negative impact on the mechanical properties of the wire rod, reducing its mechanical properties.

[0101] Compared with the wire rod prepared in Example 2, the wire rod prepared in Comparative Example 3 had a 0.50% decrease in tensile strength, a 16.54% decrease in elongation after fracture, and a 20% decrease in reduction of area. This indicates that the casting overheating has a certain impact on the performance of the wire rod. Therefore, based on the data from Comparative Examples 1-2, this application can optimize the mechanical properties of the wire rod by controlling the content of V and Al elements, and further improve the performance of the wire rod by controlling the casting overheating.

[0102] Compared with the wire rod prepared in Example 2, the wire rod prepared in Comparative Example 4 had a 1.24% lower tensile strength, a 21.05% lower elongation after fracture, and a 14.29% lower reduction of area. This indicates that by precisely controlling the cooling rate, this application can increase the minimum phase transformation temperature from 590°C to 610°C, making the phase transformation during the wire rod cooling process more complete, resulting in a more stable crystal structure and comprehensively improving the mechanical properties of the wire rod.

[0103] Compared to the wire rod prepared in Example 2, the wire rod prepared in Comparative Example 5 exhibited a 0.66% decrease in tensile strength, a 28.57% decrease in elongation after fracture, and a 42.86% decrease in reduction of area. This indicates that while increasing the minimum phase transformation temperature can improve performance to some extent, excessively increasing the minimum phase transformation temperature leads to a significant decrease in the cooling rate. This affects the rearrangement of metal crystals during the phase transformation, resulting in increased interlamellar spacing in the sorbite and consequently, poor crystal structure uniformity, thus reducing the mechanical properties of the wire rod. In contrast, this application comprehensively considers the adjustment of various parameters, controlling them within an optimal range and balancing the requirements of material plasticity, crystal structure stability, and tensile strength. This results in the wire rod prepared in this application possessing higher mechanical properties.

[0104] In summary, the comparison between the data of Comparative Examples 1-4 and the data of Example 2 further proves that this application achieves high strength, high toughness, and high plasticity by simultaneously controlling multiple key nodes and comprehensively regulating these factors. If any key node fails to meet the requirements of this application, the resulting wire rod will not achieve good performance.

[0105] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for producing wire rod for high-speed railway ballastless track slabs, comprising S1. converter smelting, S2. LF refining, S3. continuous casting and S4. high-speed wire rod rolling, characterized in that: In step S1, an alloy is added to the molten steel during tapping for deoxidation and alloying, and then washed with quicklime. The alloy includes aluminum blocks at 0.33±0.01 kg / ton of steel, silicon manganese at 10.92±0.02 kg / ton of steel, ferrosilicon at 0.60±0.01 kg / ton of steel, high-carbon ferrochrome at 5.2±0.02 kg / ton of steel, low-nitrogen carbon powder at 9.93±0.01 kg / ton of steel, and ferrovanadium at 1.27±0.28 kg / ton of steel. In step S2, slag formation and steel composition are carried out at a temperature of ≥1480℃, with bottom-blown argon stirring throughout. When the temperature reaches 1525±5℃ and the steel composition reaches C:0.81±0.02%, Si:0.20±0.02%, Mn:0.78±0.01%, P≤0.02%, S≤0.02%, Cr:0.27±0.01%, V:0.058±0.018%, Al:0.01±0.005%, wire feeding is performed. When T[O]≤30ppm, the steel is stirred with soft-blown argon for more than 10 minutes before being lifted out of the furnace. In step S3, full protective casting is adopted, and the liquidus temperature of the molten steel is controlled at 1466℃, and the casting superheat is 15℃-25℃. In step S4, the 250mm diameter round billet obtained in step S3 is heated, rough rolled, finish rolled, sizing reduced, wired, and cooled to obtain a wire rod with a diameter of 15mm; wherein the wired temperature is controlled at 880℃-900℃, and Morgan-Stelmore air-cooling line is used for cooling, and the minimum phase transformation temperature is controlled at 610℃. The wire rod for high-speed railway ballastless track slabs comprises the following components by mass percentage: C: 0.79%-0.84%, Si: 0.16%-0.23%, Mn: 0.75%-0.79%, P≤0.02%, S≤0.02%, Cr: 0.24%-0.28%, V: 0.04%-0.075%, Al: 0.005%-0.015%, with the remainder being Fe and unavoidable impurities; The wire rod has a tensile strength of 1204MPa-1230MPa, a reduction of area of ​​35%-40%, and an elongation after fracture of 12.5%-14.0%. The roller conveyor speed in the Morgan Stellmore air-cooled line in step S4 is set as follows: the initial roller conveyor speed is 0.65 m / s, and the lead rate of each roller conveyor speed is 10%, 10%, 10%, 10%, 6%, 0%, 0%, 0%, -18%, -5%, 0% respectively. In step S4, the number of fans in the Morgan Stello air-cooled line that are turned on is 11, with the power of fans 1#-10# turned on at 100% power and fan 11# turned on at 60% power.

2. The method for producing wire rod for high-speed railway ballastless track slabs according to claim 1, characterized in that, The electrolytic slag formation in step S2 is as follows: First, under the conditions of voltage level 6 and current of 25000A-35000A, slag material is added to form white slag, and the white slag refining time is >15min. Then, silicon carbide and calcium carbide are used for slag surface deoxidation. Then, under the conditions of voltage level 4 and current of 30000A-35000A, the temperature is raised for 10min-15min to make the molten steel temperature reach 1525±5℃.

3. The method for producing wire rod for high-speed railway ballastless track slabs according to claim 2, characterized in that, The slag material includes quicklime and fluorite; the specific addition process is as follows: first add quicklime of ≥5.33 kg / ton of steel, then add fluorite, and adjust the basicity according to the amount of slag so that the total amount of slag reaches 10 kg / ton of steel-12 kg / ton of steel, the basicity is 2-3, and FeO+MnO<1.0%.

4. The method for producing wire rod for high-speed railway ballastless track slabs according to claim 2, characterized in that, The amount of silicon carbide used is 0.4 kg / ton of steel to 1.0 kg / ton of steel; the amount of calcium carbide used is 0.9 kg / ton of steel to 1.1 kg / ton of steel.

5. The method for producing wire rod for high-speed railway ballastless track slabs according to claim 1, characterized in that, The bottom-blowing argon gas in step S2 includes online bottom-blowing argon gas and argon gas blown during the electrostatic slag-forming process; the flow rate of the online bottom-blowing argon gas is 100L / min-150L / min, and the pressure is 0.3MPa-0.4MPa.

6. A method for producing wire rod for high-speed railway ballastless track slabs according to claim 5, characterized in that, The argon blowing process in the electrostatic slag formation includes a first argon blowing and a second argon blowing. The flow rate of the first argon blowing is 250 L / min-350 L / min, and the pressure is 0.3 MPa-0.4 MPa. The flow rate of the second argon blowing is 50 L / min-100 L / min, and the pressure is 0.3 MPa-0.4 MPa.

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