Preparation method of steel 87Mn hot-rolled wire rod for cable

Abstract

The invention belongs to the technical field of metal material processing, and particularly relates to a preparation method of a steel 87Mn hot-rolled wire rod for a cable. Comprising the steps that alloy proportioning is conducted on 87Mn steel element components according to the mass percent, a mixed material is formed, primary smelting is conducted, molten steel is obtained, the mass percent content of C in 87M steel elements is 0.85%-0.87%, and the mass percent content of Mn is 0.78%-0.82%; after the molten steel is refined, the molten steel flows into a tundish from a steel ladle during pouring, secondary cooling is conducted after cooling is conducted through a crystallizer, and a square billet is obtained through billet drawing; the square billet is rolled, and a 87 Mn wire rod with the diameter being 12-15 mm is manufactured; in the rolling process, a Stelmor air cooling line is adopted for five-stage controlled cooling. According to the method, accurate control over the structure and performance of the steel hot-rolled wire rod 87Mn for the airport terminal cable is achieved through a whole-process technical system of accurate component control, continuous casting process optimization and rolling-controlled cooling coordinated regulation and control.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing technology, specifically relating to a method for preparing 87Mn hot-rolled wire rod for cable steel. Background Technology

[0002] As the core material for the terminal building's cables, 87Mn steel needs to withstand long-term dynamic loads and complex environmental corrosion. Its requirements for structural uniformity, mechanical property stability, and fatigue life are far higher than those for ordinary bridge cable steel. The existing production methods have four major technical bottlenecks: First, the composition control precision is low, with large fluctuations in C and Mn content (above ±0.03%), and the lack of a vacuum refining process results in high gas and inclusion content in the steel, which easily leads to stress corrosion cracking during cable service. Second, the continuous casting process relies on fixed parameters and does not consider the influence of superheat on the solidification process, resulting in large deviations in the prediction of liquid cavity length (≥10%). It only uses two-stage electromagnetic stirring, making it difficult to control the central carbon segregation index below 1.05, and the core porosity defect rate is relatively high. Third, the controlled cooling process is mostly three-stage or four-stage, and the cooling gradient is not optimized for the special requirements of terminal building cable steel for toughness and fatigue performance. This easily leads to incomplete sorbitization (sorbitity ≤93%) or residual stress concentration, resulting in tensile strength fluctuations ≥70MPa and unstable reduction of area. Fourth, incomplete descaling after rolling leaves residual iron oxide scale, which easily causes cracks during subsequent drawing, affecting the quality of the finished cable.

[0003] For example, existing technologies such as Li Linping et al. Control technology of high casting speed production of slabs in Shougang Jingtang [J] point out that the continuous casting speed is fixed at 2.5m / min without dynamic adjustment of superheat. When the superheat of molten steel fluctuates by ±10℃, the deviation of the liquid phase cavity length can reach more than 0.6m. F-EMS cannot accurately act on the key area of ​​the liquid core, and the central carbon segregation index rises to 1.08~1.15. In the controlled cooling stage, the cooling rate is controlled only by fixing the fan frequency, without setting an intermediate slow cooling section. The temperature difference between the core and the surface of the wire rod is ≥40℃. The core is prone to the appearance of 1-2 grade network carbides, and the fatigue life is reduced by 15%~20% compared with the design value. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing 87Mn hot-rolled wire rod for cable use. Through a comprehensive technical system encompassing precise composition control, continuous casting process optimization, and coordinated rolling-cooling regulation, the microstructure and properties of the 87Mn hot-rolled wire rod for terminal building cable use are precisely controlled, ultimately achieving superior performance in terms of increased martensite content, reduced tensile strength fluctuations, and improved fatigue life.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0006] The purpose of this invention is to provide a method for preparing 87Mn hot-rolled wire rod for cable use, comprising primary smelting, continuous casting, and rolling, including the following steps: S1. Preliminary smelting: The elemental composition of 87Mn steel is alloyed according to the mass percentage to form a mixture, which is then subjected to preliminary smelting to obtain molten steel. The mass percentage of C in 87M steel is 0.85% to 0.87%, and the mass percentage of Mn is 0.78% to 0.82%.

[0007] S2. Continuous Casting: After refining, the molten steel flows from the ladle into the tundish during casting. It undergoes secondary cooling in the crystallizer. During crystallizer cooling, the solidified billet shell thickness and temperature gradient at different casting speeds are measured using a nail-shooting experiment. The overall solidification coefficient of the casting machine is calculated, and a coupled model of liquid cavity length, casting speed, and superheat is established. This ensures that the three magnetic stirring sections (M-EMS, F-EMS, and S-EMS) in the crystallizer are located in the initial solidification zone, the critical liquid core zone, and the final solidification zone of the billet, respectively. During secondary cooling, a gradient water supply and a combined air-mist-water-mist cooling method are used. The gradient water supply uses a first-stage water flow of 0.36 m³ / s. 3 / h~0.39m 3 / h, second stage water volume 0.26m 3 / h~0.29m 3 / h, three sections of water volume 0.18m 3 / h~0.22m 3 / h; the billet is pulled to obtain a square billet.

[0008] S3. Rolling: The billet is rolled in 24 passes to produce 87Mn wire rods with a diameter of Φ12mm~Φ15mm. During the rolling process, a five-stage controlled cooling system is used on the Steyrmo air-cooling line: Stage 1: 0s~7s of wire drawing, cooling rate 10℃ / s~12℃ / s; Stage 2: 7s~22s of wire drawing, cooling rate 2.2℃ / s~2.8℃ / s; Stage 3: 22s~40s of wire drawing, cooling rate 0.6℃ / s~0.7℃ / s; Stage 4: 40s~60s of wire drawing, cooling rate 0.4℃ / s~0.5℃ / s; Stage 5: After 60s of wire drawing, cooling rate 0.2℃ / s~0.3℃ / s.

[0009] Furthermore, during the nail-shooting experiment, a test point was set every 0.05 m / min within the pulling speed range of 2.3 m / min to 2.7 m / min to create a temperature gradient; the overall solidification coefficient of the casting machine was calculated to be K = 28.3 mm / min based on the modified square root law. 1 / 2 ~28.8 mm / min 1 / 2 .

[0010] Furthermore, the coupled model of liquid cavity length-pulling speed-superheat is L = 0.032V + 0.005ΔT + 0.42, R 2 ≥0.99, where L is the length of the liquid phase cavity, m; V is the pulling speed, m / min; ΔT is the superheat, ℃.

[0011] Furthermore, in the three-stage magnetic stirring, the M-EMS current is 350A~370A and the frequency is 10Hz~12Hz, the F-EMS current is 390A~410A and the frequency is 7Hz~9Hz, and the S-EMS current is 320A~340A and the frequency is 12Hz~14Hz.

[0012] Furthermore, the cooling water volume of the crystallizer is 0.85m³. 3 / h~0.95m 3 / h, secondary cooling water flow rate is 1.32L / kg~1.38L / kg, atomization pressure is 0.32MPa~0.38MPa, and water mist particle size is 50μm~80μm.

[0013] Furthermore, during the rolling process, the roughing rolling consists of passes 1 to 6 at a rolling speed of 9 m / s to 11 m / s, the intermediate rolling consists of passes 7 to 14 at a rolling speed of 16 m / s to 19 m / s, and the finishing rolling consists of passes 15 to 24 at a rolling speed of 26 m / s to 27 m / s. The temperature entering the finishing rolling stage is 925℃ to 935℃, and the final rolling temperature is 895℃ to 905℃. After roughing rolling, high-pressure water at 19 MPa to 21 MPa is used for descaling, and after intermediate rolling, laser descaling with a power of 1000W to 1200W is used.

[0014] Furthermore, in the five-stage cooling process, each stage uses five fans. The fan outlets are at an angle of 30° to 45° to the direction of wire rod movement, and the distance between the outlets and the wire rod surface is 50mm to 80mm. The first stage: the frequency is 50Hz, cooling the wire rod temperature to 710℃ to 720℃; the second stage: the frequency is 32Hz to 34Hz, cooling the wire rod temperature to 600℃ to 620℃; the third stage: the frequency is 15Hz to 20Hz, cooling the wire rod temperature to 550℃ to 560℃; the fourth stage: cooling the wire rod temperature to 510℃ to 530℃; and the fifth stage: cooling the wire rod temperature to 490℃ to 510℃.

[0015] Furthermore, ultrasonic vibration is introduced to assist in impurity removal during the bottom blowing stage of refining, so that T[O]≤13ppm and inclusion size≤8μm; during the bottom blowing process of refining, the argon blowing rate during the heating stage is 240NL / min~260NL / min, the argon blowing rate during the slag addition and alloying stage is 290NL / min~310NL / min, the argon blowing rate during the soft blowing stage is 38NL / min~42NL / min, the soft blowing time is 12min~14min, and the power of ultrasonic vibration is 300W~500W.

[0016] Furthermore, 87Mn steel is composed of the following elemental components by mass percentage: C: 0.85%–0.87%, Si: 0.28%–0.32%, Mn: 0.78%–0.82%, P: ≤0.010%, S: ≤0.006%, Cr: 0.14%–0.16%, Ni: ≤0.06%, Cu: ≤0.12%, V: 0.060%–0.070%, Al: 0.022%–0.028%, with the balance being Fe and unavoidable impurity elements, totaling 100%.

[0017] Furthermore, the primary refining process includes LF refining and RH vacuum refining. The vacuum degree of RH vacuum refining is ≤50Pa, and the holding time is 15min~20min.

[0018] Compared with the prior art, the present invention has the following advantages: (0) This invention achieves precise control of the microstructure and properties of hot-rolled wire rod 87Mn for terminal building cable through a full-process technical system of precise component control, continuous casting process optimization, and rolling-cooling coordinated regulation. Specifically, by controlling the C and Mn content in 87M steel, the tendency for carbon segregation is further reduced. During the continuous casting process, a coupled model of liquid cavity length, casting speed, and superheat is established to predict the liquid cavity length and temperature gradient. The positions and parameters of the three-stage electromagnetic stirring are adjusted to ensure that M-EMS, F-EMS, and S-EMS act on the initial solidification zone, the critical liquid core zone, and the final solidification zone of the billet, respectively, effectively improving center segregation and porosity. Through the coordinated control of the three-stage electromagnetic stirring parameters and the precise matching of current and frequency, the solute enrichment layer during the billet solidification process is destroyed, reducing the center carbon segregation index from 1.08 to below 1.03, suppressing compositional segregation in the final solidification zone, and reducing core defects. Combined with the use of a "strong-medium-weak" gradient water supply and a combined air-mist-water-mist cooling method, the surface temperature of the billet is ensured to be uniform, reducing thermal stress cracks. During the coordinated control of rolling and controlled cooling, the first stage involves rapidly passing E within 7 seconds. The SG′ stage first eutectoid cementite precipitation zone inhibits the formation of network carbides. The second stage provides a suitable temperature window for the martensite transformation. The third stage promotes the uniform transformation of austenite to sorbite, ensuring complete transformation of austenite into sorbite and avoiding martensite precipitation. The fourth stage ensures complete sorbite transformation and eliminates residual austenite. The fifth stage combines natural cooling with a low cooling rate to eliminate internal stress and improve the material's toughness and fatigue performance. Through innovative design of continuous casting dynamic solidification monitoring and five-stage controlled cooling process, combined with online composition closed-loop control and multi-field coupled electromagnetic stirring technology, the network carbide level in the core of the wire rod is stably controlled at level 0 to 1, with a sorbite ratio ≥96%, the tensile strength fluctuation range is reduced to 1330MPa to 1390MPa, and the reduction of area is stabilized at 25% to 31%. This meets the high reliability and high fatigue life requirements of steel for terminal building cables, while reducing the production scrap rate by ≥3.5%, demonstrating significant technological innovation and economic benefits.

[0019] (1) The continuous casting speed of this invention can be dynamically adjusted in the range of 2.3m / min to 2.7m / min. Combined with the precision rolling process, the production efficiency is increased by 15% to 20% compared with fixed parameter production. The dual dephosphorization and intelligent cooling control greatly reduce the residual iron oxide scale and the rate of performance failure, and the scrap rate is reduced by ≥3.5%. The alloy cost is reduced by 5 yuan / ton to 8 yuan / ton, and the annual economic benefits are increased by ≥2 million yuan. Attached Figure Description

[0020] Figure 1 The image shows the metallographic structure of the 87Mn hot-rolled wire rod for cable preparation according to Example 1 of the present invention.

[0021] Figure 2 This is the CCT curve of the Stellmo controlled cooling process for 87Mn steel in this invention.

[0022] Figure 3 The TTT curve is shown in the Stellmo controlled cooling process of 87Mn steel in this invention.

[0023] Figure 4 The image shows the metallographic structure of the 87Mn hot-rolled wire rod for cable preparation according to Example 1 of the present invention.

[0024] Figure 5 The image shows the metallographic structure of the 87Mn hot-rolled wire rod for cable preparation in Example 3 of this invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0027] Existing technologies, such as those by Li Linping et al., "Control Technology for High-Speed ​​Casting of Slabs at Shougang Jingtang" [J], point out that when the continuous casting speed is fixed at 2.5 m / min without dynamic adjustment based on superheat, the deviation in the length of the liquid phase cavity can reach more than 0.6 m when the superheat of the molten steel fluctuates by ±10℃. F-EMS cannot accurately act on the key area of ​​the liquid core, and the central carbon segregation index rises to 1.08 to 1.15. In the controlled cooling stage, the cooling rate is controlled only by fixing the fan frequency without setting an intermediate slow cooling section. The temperature difference between the core and the surface of the wire rod is ≥40℃, and 1-2 grade network carbides are prone to appear in the core. The fatigue life is reduced by 15% to 20% compared with the design value.

[0028] Patent CN120591517A discloses a controlled cooling method for 87Mn steel wire rod used in bridge cables. This method employs a Stellmore air-cooling controlled cooling process by precisely controlling the rolling temperature, wire drawing temperature, and roller speed to ensure uniform temperature distribution during cooling and prevent localized excessively rapid or slow cooling. A segmented controlled cooling process is used: the first stage involves rapid cooling to prevent the formation of network cementite; the second stage involves slow cooling to ensure uniform microstructure transformation; and the third stage involves natural cooling to stabilize the microstructure. The process design is reasonable and the operation is simple. The resulting 87Mn hot-rolled wire rod has no martensite or network cementite in its core, and the sorbite content is ≥93%. However, this method only focuses on the controlled cooling stage and lacks a comprehensive process design, resulting in lower precision and insufficient performance limits for the 87Mn hot-rolled wire rod.

[0029] Based on this, this invention fills the gaps in CN120591517A regarding refining and impurity removal, continuous casting solidification control, and five-stage refined controlled cooling through the coordinated regulation of the entire process from composition to continuous casting to rolling and controlled cooling. Through a comprehensive technical system encompassing precise composition control, optimized continuous casting process, and coordinated regulation of rolling and controlled cooling, it achieves precise control of the microstructure and properties of 87Mn hot-rolled wire rod for terminal building cables, ultimately resulting in superior performance with increased sorbite content, reduced tensile strength fluctuations, and improved fatigue life. Details are as follows:

[0030] A method for preparing 87Mn hot-rolled wire rod for cable use includes the following steps: S1. Refining: The elemental composition of 87Mn steel is alloyed according to the mass percentage to form a mixture, which is then subjected to primary refining to obtain molten steel. The mass percentage of C in 87M steel is 0.85% to 0.87%, and the mass percentage of Mn is 0.78% to 0.82%.

[0031] In this invention, by controlling the content of C and Mn elements in 87M steel, the tendency for carbon segregation is further reduced compared to the prior art (C: 0.86%~0.90%, Mn: 0.80%~0.90%). The 87Mn steel is composed of the following elemental components by mass percentage: C: 0.85%~0.87%, Si: 0.28%~0.32%, Mn: 0.78%~0.82%, P: ≤0.010%, S: ≤0.006%, Cr: 0.14%~0.16%, Ni: ≤0.06%, Cu: ≤0.12%, V: 0.060%~0.070%, Al: 0.022%~0.028%, with the balance being Fe and unavoidable impurity elements, totaling 100%. By strictly controlling the content of harmful elements (P≤0.010%, S≤0.006%), the impact of sulfide and phosphide inclusions on plasticity can be reduced.

[0032] In this invention, the primary refining process employs dual refining methods: LF refining and RH vacuum refining. The RH furnace vacuum treatment effectively reduces the gas content in the steel. Combined with real-time monitoring by an online composition analysis system (accuracy ±0.003%), the composition fluctuation is ensured to be ≤±3%, laying the foundation for subsequent process stability and performance improvement.

[0033] S2. Continuous Casting: After refining, the molten steel forms a ladle, which flows into the tundish. It undergoes secondary cooling after being cooled in the crystallizer. During the crystallizer cooling process, the solidified billet shell thickness and temperature gradient at different casting speeds are measured using a nail-shooting experiment. The overall solidification coefficient of the casting machine is calculated, and a coupled model of liquid cavity length-casting speed-superheat is established. This ensures that the M-EMS, F-EMS, and S-EMS in the three-stage magnetic stirring are located in the initial solidification zone, the critical liquid core zone, and the final solidification zone of the billet, respectively. During the secondary cooling process, a gradient water supply and a combined air-mist-water-mist cooling method are used. The gradient water supply uses a first-stage water flow of 0.36m³. 3 / h~0.39m 3 / h, second stage water volume 0.26m 3 / h~0.29m 3 / h, three sections of water volume 0.18m 3 / h~0.22m 3 / h; the billet is pulled to obtain a square billet of 150mm×150mm.

[0034] In this invention, ultrasonic vibration is introduced to assist in impurity removal during the bottom blowing stage of refining, resulting in T[O] ≤ 13 ppm and inclusion size ≤ 8 μm. During the bottom blowing process of refining, the argon blowing rate is 240 NL / min to 260 NL / min during the heating stage, 290 NL / min to 310 NL / min during the slag addition and alloying stage, and 38 NL / min to 42 NL / min during the soft blowing stage. The soft blowing time is 12 min to 14 min, and the ultrasonic vibration power is 300 W to 500 W. Compared with the prior art (T[O] ≥ 20 ppm), the purity is improved by 35%.

[0035] In this invention, before the nail-shooting experiment, the surface of the solidified billet is polished. After nailing, an ultrasonic flaw detector is used to check for cracks around the nail hole to ensure the validity of the experimental data. During the nail-shooting experiment, a Φ4mm tungsten alloy nail is used, and a test point is set every 0.05m / min within the range of drawing speed 2.3m / min to 2.7m / min. Combined with an infrared thermal imager, the surface temperature field of the billet is monitored in real time. The thickness of the solidified billet shell and the temperature gradient are measured at different drawing speeds. The comprehensive solidification coefficient of the casting machine is calculated according to the modified square root law, K = 28.3mm / min. 1 / 2 ~28.8 mm / min 1 / 2Therefore, a coupled model of liquid cavity length-pulling speed-superheat is established as L = 0.032V + 0.005ΔT + 0.42, R 2 ≥0.99, where L is the length of the liquid phase cavity, m; V is the pulling speed, m / min; and ΔT is the superheat, ℃. This improves the prediction accuracy to ±2%, a significant improvement over existing technologies (±10%).

[0036] In this invention, based on the liquid cavity length and temperature gradient predicted by the coupled model, the positions and parameters of the three-stage electromagnetic stirring are adjusted to ensure that M-EMS, F-EMS, and S-EMS act on the initial solidification zone, the critical liquid core zone, and the final solidification zone of the billet, respectively, effectively improving center segregation and porosity. Specifically, in the three-stage magnetic stirring, the M-EMS current is 350A–370A with a frequency of 10Hz–12Hz, the F-EMS current is 390A–410A with a frequency of 7Hz–9Hz, and the S-EMS current is 320A–340A with a frequency of 12Hz–14Hz. Through the coordinated control of the three-stage electromagnetic stirring parameters and the precise matching of current and frequency, the solute enrichment layer during the billet solidification process is destroyed, reducing the center carbon segregation index from 1.08 to below 1.03, a reduction of 4.6% compared to existing technologies. The introduction of S-EMS further suppresses component segregation in the final solidification zone, reducing core defects.

[0037] In this invention, the cooling water volume of the crystallizer is 0.85m³. 3 / h~0.95m 3 The secondary cooling process employs a "strong-medium-weak" gradient water supply combined with an air-mist-water-mist composite cooling method to ensure uniform surface temperature of the cast billet and reduce thermal stress cracks. The water flow rate is 0-3m in the first stage, 3-6m in the second stage, and 6-9m in the third stage. During the secondary cooling process, the cooling water flow rate is 1.32L / kg to 1.38L / kg, the atomization pressure is 0.32MPa to 0.38MPa, and the water mist particle size is 50μm to 80μm.

[0038] S3. Rolling: The billet is rolled in 24 passes to produce 87Mn wire rods with a diameter of Φ12mm~Φ15mm. During the rolling process, a five-stage controlled cooling system is used on the Steyrmo air-cooling line: Stage 1: 0s~7s of wire drawing, cooling rate 10℃ / s~12℃ / s; Stage 2: 7s~22s of wire drawing, cooling rate 2.2℃ / s~2.8℃ / s; Stage 3: 22s~40s of wire drawing, cooling rate 0.6℃ / s~0.7℃ / s; Stage 4: 40s~60s of wire drawing, cooling rate 0.4℃ / s~0.5℃ / s; Stage 5: After 60s of wire drawing, cooling rate 0.2℃ / s~0.3℃ / s.

[0039] In this invention, the rolling process includes roughing, intermediate rolling, and finishing rolling. Roughing consists of passes 1 to 6 at a speed of 9 to 11 m / s; intermediate rolling consists of passes 7 to 14 at a speed of 16 to 19 m / s; and finishing rolling consists of passes 15 to 24 at a speed of 26 to 27 m / s. The temperature entering the finishing mill is 925°C to 935°C, and the final rolling temperature is 895°C to 905°C. After roughing, descaling is performed using high-pressure water at 19 MPa to 21 MPa, and after intermediate rolling, descaling is performed using a laser with a power of 1000W to 1200W. By increasing the number of intermediate and finishing rolling passes, the deformation uniformity is improved by 20%. The finishing mill uses a gradual speed increase to avoid temperature fluctuations (≤±5°C) caused by sudden speed changes, ensuring a stable final rolling temperature. Furthermore, an innovative dual descaling process using high-pressure water and laser is employed to thoroughly remove iron oxide scale and prevent cracks during subsequent drawing processes.

[0040] In this invention, a total of 20 fans are used in the five-stage cooling process. Five fans are used in each stage of cooling, and the fans numbered 1 to 20 from the first stage to the fifth stage. The air outlet of each fan is at an angle of 30° to 45° with the direction of wire movement. The distance between the air outlet and the surface of the wire is 50mm to 80mm. Before entering the fan, the wire temperature is 875±5℃.

[0041] The first stage is rapid cooling, which occurs from 0 to 7 seconds after spinning. Fans 1 to 4 are activated at a frequency of 50Hz. A bidirectional top blower (total air volume 30,000 m³ / h) is added to the outlet of the spinning machine. 3 / h~50,000m 3 / h), the insulation covers of fans 1 to 4 are opened; the cooling rate is 10℃ / s~12℃ / s, cooling the wire rod temperature from the coiling temperature (875±5℃) to 710℃~720℃. With the assistance of the top blower, it quickly passes through the ESG′ preeutectoid cementite precipitation zone within 7s, inhibiting the formation of network carbides.

[0042] The second stage is the preparation for phase transformation, which is the spinning process from 7s to 22s. Fans No. 5 to No. 8 are turned on at a frequency of 32Hz to 34Hz. The opening of the insulation cover of fans No. 5 to No. 8 is 40% to 60%, and the cooling rate is 2.2℃ / s to 2.8℃ / s, cooling the spinning temperature to 600℃ to 620℃, providing a suitable temperature window for the sorbite transformation.

[0043] The third stage is a slow phase transformation, where the wire spinning process takes 22 to 40 seconds. Fans No. 9 to No. 12 operate at a low frequency of 15 to 20 Hz, and the insulation cover of fans No. 9 to No. 12 is opened at 20% to 30%. The cooling rate is 0.6℃ / s to 0.7℃ / s, cooling the wire spinning temperature to 550℃ to 560℃. This promotes the uniform transformation of austenite to sorbite, ensuring that austenite is completely transformed into sorbite and preventing martensite precipitation.

[0044] The fourth stage is the completion of heat preservation, that is, when the wire is spinning for 40s to 60s, fans No. 13 to No. 16 are turned off and the heat preservation covers of fans No. 13 to No. 16 are completely closed. The cooling rate is 0.4℃ / s to 0.5℃ / s, cooling the wire spinning temperature to 510℃ to 530℃ to ensure that the sorbite transformation is complete and to eliminate residual austenite.

[0045] The fifth stage is slow cooling. After 60 seconds of wire spinning, fans 17 to 20 are turned off and their insulation covers are opened for natural cooling at a rate of 0.2℃ / s to 0.3℃ / s. The wire spinning temperature is then cooled to 490℃ to 510℃. This combination of natural cooling and slow cooling rate eliminates internal stress, improves the material's toughness and fatigue performance, and increases the section reduction rate by 5 to 7 percentage points compared to existing technologies, resulting in 87Mn hot-rolled wire rod for cable use.

[0046] In this invention, an 18-segment roller conveyor is used during the rolling process, and the roller conveyor speed is controlled. The speed of segments 1 to 6 is 0.48 m / s to 0.52 m / s, segments 7 to 12 are 0.62 m / s to 0.68 m / s, and segments 13 to 18 are 0.82 m / s to 0.88 m / s. Combining infrared temperature measurement and electromagnetic induction speed measurement, the roller conveyor speed is adjusted in real time using a PID algorithm, with a deviation ≤ ±0.02 m / s. Infrared temperature measurement points (accuracy ±1℃) are set at 3m, 9m, 16m, 26m, and 40m on the Steyrmo air-cooling line to monitor the wire rod temperature in real time. When the deviation between the measured temperature and the target temperature exceeds ±10℃, the frequency of the corresponding section fan, the opening of the insulation cover, and the roller conveyor speed are automatically adjusted, with a feedback response time ≤0.8s. By combining intelligent control with multi-node temperature feedback and using PID algorithm to achieve real-time adjustment, the response time is ≤0.8s and the temperature deviation is controlled within ±10℃, which improves the accuracy by 50% compared with the existing technology (±20℃) and ensures uniform organization along the entire length.

[0047] In summary, this invention achieves precise control over the microstructure and properties of 87Mn hot-rolled wire rod for terminal building cable steel through a comprehensive technical system encompassing precise composition control, continuous casting process optimization, and coordinated rolling-cooling regulation. By innovatively designing dynamic solidification monitoring and a five-stage controlled cooling process for continuous casting, combined with online closed-loop composition control and multi-field coupled electromagnetic stirring technology, the core network carbide level of the wire rod is stably controlled between grade 0 and 1, with a sorbite content ≥96%, a tensile strength fluctuation range reduced to 1330MPa–1390MPa, and a reduction of area stabilized between 25% and 31%. This meets the high reliability and long fatigue life requirements for terminal building cable steel while reducing the scrap rate by ≥3.5%, demonstrating significant technological innovation and economic benefits. Among them, the continuous casting speed can be dynamically adjusted in the range of 2.3-2.7m / min. Combined with the precision rolling process, the production efficiency is increased by 15-20% compared with fixed parameter production. The dual dephosphorization and intelligent cooling control greatly reduce the residual iron oxide scale and the performance failure rate, and the scrap rate is reduced by ≥3.5%.

[0048] The following specific examples will provide further explanation.

[0049] Example 1 A method for preparing 87Mn hot-rolled wire rod for cable use includes primary smelting, continuous casting, and rolling, comprising the following steps: S1. Initial Refining: 87Mn steel is composed of the following elemental components by mass percentage: C: 0.86%, Si: 0.3%, Mn: 0.80%, P: 0.009%, S: 0.005%, Cr: 0.15%, Ni: 0.04%, Cu: 0.07%, V: 0.065%, Al: 0.025%, with the balance being Fe and unavoidable impurity elements, totaling 100%. The elemental composition of the 87Mn steel is alloyed according to the mass percentage, and the elements are mixed evenly to form a mixture. After rough adjustment in an LF refining furnace, it enters an RH vacuum refining furnace at a vacuum degree of 40 Pa for 18 min, with composition fluctuations ≤ ±2%, yielding molten steel.

[0050] S2. Continuous casting: After refining, the molten steel flows from the ladle into the tundish during casting. After being cooled in the crystallizer, it undergoes secondary cooling and is then pulled to obtain a 150mm×150mm square billet.

[0051] In the refining bottom blowing stage, ultrasonic vibration is introduced to assist in impurity removal, so that T[O]=12ppm and the inclusion size is 7μm. In the refining bottom blowing process, the argon blowing rate in the heating stage is 25NL / min, the argon blowing rate in the slag addition and alloying stage is 300NL / min, the argon blowing rate in the soft blowing stage is 40NL / min, the soft blowing time is 13min, and the power of ultrasonic vibration is 40W.

[0052] After the crystallizer cools: Before the nail-shooting test, the surface of the solidified billet is polished. After nailing, an ultrasonic flaw detector is used to check for cracks around the nail hole to ensure the validity of the experimental data. During the nail-shooting test, a Φ4mm tungsten alloy nail is used. A test point is set every 0.05m / min within the drawing speed range of 2.3m / min to 2.7m / min. The surface temperature field of the billet is monitored in real time using an infrared thermal imager. The thickness of the solidified billet shell and the temperature gradient are measured at different drawing speeds. The overall solidification coefficient of the casting machine is calculated according to the modified square root law, K = 28.3mm / min. 1 / 2 ~28.8 mm / min 1 / 2 Therefore, a coupled model of liquid cavity length-pulling speed-superheat is established as L = 0.032V + 0.005ΔT + 0.42, R 2 ≥0.99, where L is the length of the liquid phase cavity, m; V is the pulling speed, m / min; ΔT is the superheat, ℃.

[0053] The molten steel superheat ΔT = 15℃, the casting speed is 2.5m / min, and the liquid phase cavity length L = 0.032 × 2.5 + 0.005 × 15 + 0.42 = 1.295m is calculated according to the coupled model. In the three-stage magnetic stirring, M-EMS, F-EMS, and S-EMS are located in the initial solidification zone of the billet, the critical liquid core zone, and the final solidification zone, respectively. F-EMS is positioned 13.2m from the liquid surface of the crystallizer, S-EMS is positioned 18.5m from the liquid surface of the crystallizer, and M-EMS is positioned at the lower part of the crystallizer. The current of M-EMS is set to 360A and the frequency to 11Hz, the current of F-EMS to 400A and the frequency to 8Hz, and the current of S-EMS to 330A and the frequency to 13Hz. Crystallizer cooling: Crystallizer water volume 0.9m³. 3 / h.

[0054] Secondary cooling: A gradient water supply and a combined air-mist-water-mist cooling method are adopted, wherein the secondary cooling specific water flow rate is 1.35L / kg, and the primary water flow rate is 0.38m³. 3 / h, second stage water volume 0.28m 3 / h, three-stage water volume 0.20m 3 / h; gas-water mist composite cooling, atomization pressure 0.35MPa, water mist particle size 60μm.

[0055] S3. Rolling: The billet is rolled in 24 passes. Roughing passes 1-6 are rolled at a speed of 10 m / s; intermediate rolling passes 7-14 are rolled at a speed of 18 m / s; and finishing rolling passes 15-24 are rolled at a speed of 26.5 m / s. The temperature entering the finishing rolling mill is 930℃, and the final rolling temperature is 900℃. After roughing, descaling is performed using 20 MPa high-pressure water, and after intermediate rolling, laser descaling is performed using a power of 1000W. This produces 87Mn wire rods with a diameter of Φ14 mm.

[0056] During the rolling process, a five-stage controlled cooling system, using the Stellmore air-cooling line, is employed: In the first stage, from 0 to 7 seconds after spinning, fans 1 through 4 are turned on at a frequency of 50Hz, and a bidirectional top blower (total air volume 40,000 m³) is added to the outlet of the spinning machine. 3 / h), the insulation covers of fans 1 to 4 are opened; the cooling rate is 11℃ / s, cooling the wire rod temperature from the wire spinning temperature (875℃) to 715℃.

[0057] In the second stage, during the 7s to 22s of filament spinning, fans No. 5 to No. 8 are turned on at a frequency of 33Hz, the insulation cover of fans No. 5 to No. 8 is opened to 50%, and the cooling rate is 2.5℃ / s, cooling the filament spinning temperature to 610℃.

[0058] In the third stage, during the 22s to 40s of filament spinning, fans 9 to 12 operate at a low frequency of 18Hz, with the insulation covers of fans 9 to 12 open at 25%; the cooling rate is 0.65℃ / s, cooling the filament spinning temperature to 550℃.

[0059] In the fourth stage, which is 40s to 60s when the silk is being spun, fans 13 to 16 are turned off and their insulation covers are fully closed. The cooling rate is 0.45℃ / s, cooling the silk-spun temperature to 510℃.

[0060] In the fifth stage, 60 seconds after the silk is spun, fans 17 to 20 are turned off and their insulation covers are opened for natural cooling at a rate of 0.25℃ / s, cooling the silk-spun temperature to 500℃.

[0061] During the rolling process, an 18-segment roller conveyor is used, with roller speed control: 0.5 m / s for segments 1-6, 0.65 m / s for segments 7-12, and 0.85 m / s for segments 13-18. Combining infrared thermography and electromagnetic induction speed measurement, a PID algorithm is used to adjust the roller speed in real time, with a deviation ≤ ±0.02 m / s. Infrared thermography points (accuracy ±1℃) are set at 3m, 9m, 16m, 26m, and 40m on the Steyrmo air-cooling line to monitor the wire rod temperature in real time, with a maximum deviation of 7℃.

[0062] The final product is 87Mn hot-rolled wire rod for cable use.

[0063] Figure 1 The image shows the metallographic structure of the 87Mn hot-rolled wire rod for cable preparation according to Example 1 of this invention. Figure 1 As shown, the metallographic structure is a uniform sorbite and pearlite, with no obvious network structure.

[0064] Figure 2 This is the CCT curve of the Stellmo controlled cooling process for 87Mn steel in this invention. Figure 3This is the TTT curve of the Stellmo controlled cooling process for 87Mn steel in this invention. Figure 2 and Figure 3 As shown, the CCT and TTT curves provide data support for the Stellmore controlled cooling process, namely: after water cooling, the wire is spun to reduce the growth of austenite grains; in the air cooling stage, it is first rapidly cooled to the pre-phase transformation temperature of 700℃ at a cooling rate of 10℃ / s to prepare for the phase transformation and reduce the amount of secondary iron oxide scale formation. Then, the optimal cooling rate should be controlled at 1~3℃ / s to ensure that the wire obtains the required microstructure and properties.

[0065] The mechanical properties of the 87Mn hot-rolled wire rod for cable preparation in Example 1 were tested. The test results were as follows: carbon grade 0, sorbite content 97%, tensile strength 1365MPa, reduction of area 29%, performance dispersion 1.8%, scrap rate 1.9%, and fatigue life 22% higher than the existing technology (control technology for high-speed production of slabs at Shougang Jingtang).

[0066] Example 2 A method for preparing 87Mn hot-rolled wire rod for cable use includes smelting, continuous casting, and rolling, comprising the following steps: S1. Initial Refining: 87Mn steel is composed of the following elemental components by mass percentage: C: 0.85%, Si: 0.28%, Mn: 0.78%, P: 0.008%, S: 0.004%, Cr: 0.14%, Ni: 0.03%, Cu: 0.06%, V: 0.060%, Al: 0.022%, with the balance being Fe and unavoidable impurity elements, totaling 100%. The elemental composition of the 87Mn steel is alloyed according to the mass percentage, and the elements are mixed evenly to form a mixture. After rough adjustment in an LF refining furnace, it enters an RH vacuum refining furnace at a vacuum degree of 35 Pa for 15 min, with composition fluctuations ≤ ±2%, yielding molten steel.

[0067] S2. Continuous casting: After refining, the molten steel flows from the ladle into the tundish during casting. After being cooled in the crystallizer, it undergoes secondary cooling and is then pulled to obtain a 150mm×150mm square billet.

[0068] In the refining bottom blowing stage, ultrasonic vibration is introduced to assist in impurity removal, resulting in T[O]=11ppm and inclusion size of 6μm. During the refining bottom blowing process, the argon blowing rate is 240NL / min in the heating stage, 290NL / min in the slag addition and alloying stage, 38NL / min in the soft blowing stage, and the soft blowing time is 12min. The power of ultrasonic vibration is 300W.

[0069] After the crystallizer cools: Before the nail-shooting test, the surface of the solidified billet is polished. After nailing, an ultrasonic flaw detector is used to check for cracks around the nail hole to ensure the validity of the experimental data. During the nail-shooting test, a Φ4mm tungsten alloy nail is used. A test point is set every 0.05m / min within the drawing speed range of 2.3m / min to 2.7m / min. The surface temperature field of the billet is monitored in real time using an infrared thermal imager. The thickness of the solidified billet shell and the temperature gradient are measured at different drawing speeds. The overall solidification coefficient of the casting machine is calculated as K = 28.3mm / min based on the modified square root law. 1 / 2 ~28.8 mm / min 1 / 2 .

[0070] A coupled model of liquid phase cavity length-pulling speed-superheat is then established as L=0.032V+0.005ΔT+0.42, R²≥0.99, where L is the liquid phase cavity length, m; V is the pulling speed, m / min; and ΔT is the superheat, ℃.

[0071] The molten steel superheat ΔT = 12℃, the casting speed is 2.3m / min, and the length of the liquid phase cavity is calculated to be L = 0.032×2.3 + 0.005×12 + 0.42 = 1.226m according to the coupled model. In the three-stage magnetic stirring, M-EMS, F-EMS, and S-EMS are located in the initial solidification zone of the billet, the critical liquid core zone, and the final solidification zone, respectively. Among them, F-EMS is set at 12.8m from the liquid surface of the crystallizer, S-EMS is set at 18.0m from the liquid surface of the crystallizer, and M-EMS is set at the lower part of the crystallizer. The current of M-EMS is set to 350A and the frequency to 10Hz, the current of F-EMS is set to 390A and the frequency to 7Hz, and the current of S-EMS is set to 320A and the frequency to 12Hz. Crystallizer cooling: crystallizer water flow rate is 0.85m³ / h.

[0072] Secondary cooling: A gradient water supply and a combined air-mist-water-mist cooling method are adopted, wherein the secondary cooling specific water flow rate is 1.32L / kg, and the primary water flow rate is 0.36m³. 3 / h, second stage water volume 0.26m 3 / h, three-stage water volume 0.18m 3 / h; gas-water mist composite cooling, atomization pressure 0.32MPa, water mist particle size 50μm.

[0073] S3. Rolling: The billet is rolled in 24 passes. Roughing passes 1-6 are rolled at a speed of 9 m / s; intermediate rolling passes 7-14 are rolled at a speed of 16 m / s; and finishing rolling passes 15-24 are rolled at a speed of 26 m / s. The temperature entering the finishing rolling mill is 925℃, and the final rolling temperature is 895℃. After roughing, descaling is performed using 19 MPa high-pressure water, and after intermediate rolling, laser descaling is performed using a power of 1000W. This produces 87Mn wire rods with a diameter of Φ14 mm.

[0074] During the rolling process, a five-stage controlled cooling system, using the Stellmore air-cooling line, is employed: In the first stage, from 0 to 7 seconds after spinning, fans 1 through 4 are turned on at a frequency of 50Hz, and a bidirectional top blower (total air volume 30,000 m³) is added to the outlet of the spinning machine. 3 / h), the insulation covers of fans 1 to 4 are opened; the cooling rate is 10℃ / s, cooling the wire rod temperature from the wire spinning temperature (870℃) to 710℃.

[0075] In the second stage, during the 7s to 22s of filament spinning, fans No. 5 to No. 8 are turned on at a frequency of 32Hz, the insulation cover of fans No. 5 to No. 8 is opened to 40%, and the cooling rate is 2.2℃ / s, cooling the filament spinning temperature to 600℃.

[0076] In the third stage, during the 22s to 40s of filament spinning, fans 9 to 12 operate at a low frequency of 15Hz, with the insulation covers of fans 9 to 12 open at 20%; the cooling rate is 0.6℃ / s, cooling the filament spinning temperature to 550℃.

[0077] In the fourth stage, which is 40s to 60s when the silk is being spun, fans 13 to 16 are turned off and their insulation covers are fully closed. The cooling rate is 0.4℃ / s, cooling the silk-spun temperature to 510℃.

[0078] In the fifth stage, 60 seconds after the silk is spun, fans 17 to 20 are turned off and their insulation covers are opened for natural cooling at a rate of 0.2℃ / s, reducing the silk-spun temperature to 490℃.

[0079] During the rolling process, an 18-segment roller conveyor is used, with roller speed control: 0.48 m / s for segments 1-6, 0.62 m / s for segments 7-12, and 0.82 m / s for segments 13-18. Combining infrared thermography and electromagnetic induction speed measurement, a PID algorithm is used to adjust the roller speed in real time, with a deviation ≤ ±0.02 m / s. Infrared thermography points (accuracy ±1℃) are set at 3m, 9m, 16m, 26m, and 40m on the Steyrmo air-cooling line to monitor the wire rod temperature in real time, with a maximum deviation of 6℃.

[0080] The final product is 87Mn hot-rolled wire rod for cable use.

[0081] Figure 4 The image shows the metallographic structure of the 87Mn hot-rolled wire rod for cable preparation according to Example 1 of this invention. Figure 4 As shown, the metallographic structure is a uniform sorbite and pearlite, with no obvious network structure.

[0082] The mechanical properties of the 87Mn hot-rolled wire rod for cable preparation in Example 2 were tested. The test results were as follows: carbon grade 0, sorbite content 96%, tensile strength 1330MPa, reduction of area 25%, performance dispersion 1.6%, scrap rate 2.1%, and fatigue life 20% higher than that of the existing technology (control technology for high-speed production of slabs at Shougang Jingtang).

[0083] Example 3 A method for preparing 87Mn hot-rolled wire rod for cable use includes primary smelting, continuous casting, and rolling, comprising the following steps: S1. Initial Refining: 87Mn steel is composed of the following elemental components by mass percentage: C: 0.87%, Si: 0.32%, Mn: 0.82%, P: 0.010%, S: 0.006%, Cr: 0.16%, Ni: 0.05%, Cu: ≤0.10%, V: 0.070%, Al: 0.028%, with the balance being Fe and unavoidable impurity elements, totaling 100%. The elemental composition of the 87Mn steel is alloyed according to the mass percentage, and the elements are mixed evenly to form a mixture. After rough adjustment in an LF refining furnace, it enters an RH vacuum refining furnace at a vacuum degree of 50 Pa for 20 min, with composition fluctuations ≤±2%, yielding molten steel.

[0084] S2. Continuous casting: After refining, the molten steel flows from the ladle into the tundish during casting. After being cooled in the crystallizer, it undergoes secondary cooling and is then pulled to obtain a 150mm×150mm square billet.

[0085] In the refining bottom blowing stage, ultrasonic vibration is introduced to assist in impurity removal, resulting in T[O]=13ppm and inclusion size of 8μm. During the refining bottom blowing process, the argon blowing rate is 260NL / min in the heating stage, 310NL / min in the slag addition and alloying stage, 42NL / min in the soft blowing stage, and the soft blowing time is 14min. The power of ultrasonic vibration is 500W.

[0086] After the crystallizer cools: Before the nail-shooting test, the surface of the solidified billet is polished. After nailing, an ultrasonic flaw detector is used to check for cracks around the nail hole to ensure the validity of the experimental data. During the nail-shooting test, a Φ4mm tungsten alloy nail is used. A test point is set every 0.05m / min within the drawing speed range of 2.3m / min to 2.7m / min. The surface temperature field of the billet is monitored in real time using an infrared thermal imager. The thickness of the solidified billet shell and the temperature gradient are measured at different drawing speeds. The overall solidification coefficient of the casting machine is calculated as K = 28.3mm / min based on the modified square root law. 1 / 2 ~28.8 mm / min 1 / 2 .

[0087] A coupled model of liquid phase cavity length-pulling speed-superheat is then established as L=0.032V+0.005ΔT+0.42, R²≥0.99, where L is the liquid phase cavity length, m; V is the pulling speed, m / min; and ΔT is the superheat, ℃.

[0088] The molten steel superheat ΔT = 18℃, the casting speed is 2.7 m / min, and the length of the liquid phase cavity is calculated to be L = 0.032 × 2.7 + 0.005 × 18 + 0.42 = 1.384 m according to the coupled model. In the three-stage magnetic stirring, M-EMS, F-EMS, and S-EMS are located in the initial solidification zone of the billet, the critical liquid core zone, and the final solidification zone, respectively. Among them, F-EMS is set at 13.5 m from the liquid surface of the crystallizer, S-EMS is set at 19.0 m from the liquid surface of the crystallizer, and M-EMS is set at the lower part of the crystallizer. The current of M-EMS is set to 370 A and the frequency to 12 Hz, the current of F-EMS is set to 410 A and the frequency to 9 Hz, and the current of S-EMS is set to 340 A and the frequency to 14 Hz. Crystallizer cooling: crystallizer water flow rate is 0.95 m³ / h.

[0089] Secondary cooling: A gradient water supply and a combined air-mist-water-mist cooling method are adopted, wherein the secondary cooling specific water flow rate is 1.38L / kg, and the primary water flow rate is 0.39m³. 3 / h, second stage water volume 0.29m 3 / h, three-stage water volume 0.22m 3 / h; gas-water mist composite cooling, atomization pressure 0.38MPa, water mist particle size 80μm.

[0090] S3. Rolling: The billet is rolled in 24 passes. Roughing passes 1-6 are rolled at a speed of 11 m / s; intermediate rolling passes 7-14 are rolled at a speed of 19 m / s; and finishing rolling passes 15-24 are rolled at a speed of 27 m / s. The temperature entering the finishing rolling mill is 935℃, and the final rolling temperature is 905℃. After roughing, descaling is performed using 21 MPa high-pressure water, and after intermediate rolling, laser descaling is performed using a power of 1200W. This produces 87Mn wire rods with a diameter of Φ14 mm.

[0091] During the rolling process, a five-stage controlled cooling system, using the Stellmore air-cooling line, is employed: In the first stage, from 0 to 7 seconds after spinning, fans 1 through 4 are turned on at a frequency of 50Hz, and a bidirectional top blower (total air volume 50,000 m³) is added to the outlet of the spinning machine. 3 / h), the insulation covers of fans 1 to 4 are opened; the cooling rate is 12℃ / s, cooling the wire rod temperature from the wire spinning temperature (880℃) to 720℃.

[0092] In the second stage, which is from 7s to 22s when the silk is being spun, fans No. 5 to No. 8 are turned on at a frequency of 34Hz. The insulation cover of fans No. 5 to No. 8 is opened to 60%, and the cooling rate is 2.8℃ / s, cooling the silk-spun temperature to 620℃.

[0093] In the third stage, during the 22s to 40s of filament spinning, fans 9 to 12 operate at a low frequency of 20Hz, with the insulation covers of fans 9 to 12 open at 30%; the cooling rate is 0.7℃ / s, cooling the filament spinning temperature to 550℃.

[0094] In the fourth stage, which is 40s to 60s when the silk is being spun, fans 13 to 16 are turned off and their insulation covers are fully closed. The cooling rate is 0.5℃ / s, cooling the silk-spun temperature to 510℃.

[0095] In the fifth stage, 60 seconds after the silk is spun, fans 17 to 20 are turned off and their insulation covers are opened for natural cooling at a rate of 0.3℃ / s, reducing the silk-spun temperature to 510℃.

[0096] During the rolling process, an 18-segment roller conveyor is used, with roller speed control: 0.52 m / s for segments 1-6, 0.68 m / s for segments 7-12, and 0.88 m / s for segments 13-18. Combining infrared thermography and electromagnetic induction speed measurement, a PID algorithm is used to adjust the roller speed in real time, with a deviation ≤ ±0.02 m / s. Infrared thermography points (accuracy ±1℃) are set at 3m, 9m, 16m, 26m, and 40m on the Steyrmo air-cooling line to monitor the wire rod temperature in real time, with a maximum deviation of 8℃.

[0097] The final product is 87Mn hot-rolled wire rod for cable use.

[0098] Figure 5 The metallographic diagram of the 87Mn hot-rolled wire rod for cable preparation in Example 3 of this invention is shown below. Figure 5 As shown, the metallographic structure is a uniform sorbite and pearlite, with no obvious network structure.

[0099] The mechanical properties of the 87Mn hot-rolled wire rod for cable preparation in Example 3 were tested. The results showed that the wire rod had a carbon grade of 1, a sorbite content of 98%, a tensile strength of 1390 MPa, a reduction of area of ​​31%, a performance dispersion of 2.0%, a scrap rate of 1.7%, and a fatigue life that was 25% higher than that of the existing technology (the control technology for high-speed production of slabs at Shougang Jingtang).

[0100] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0101] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing 87Mn hot-rolled wire rod for cable use, comprising refining, continuous casting, and rolling, characterized in that, Includes the following steps: Preliminary smelting: The elemental composition of 87Mn steel is alloyed according to the mass percentage to form a mixture, which is then subjected to preliminary smelting to obtain molten steel. In this mixture, the mass percentage of C in 87M steel is 0.85% to 0.87%, and the mass percentage of Mn is 0.78% to 0.82%. Continuous casting: After refining, the molten steel flows from the ladle into the tundish during pouring. It undergoes secondary cooling in the crystallizer. During crystallizer cooling, the solidified billet shell thickness and temperature gradient at different casting speeds are measured using a nail-shooting experiment. The overall solidification coefficient of the casting machine is calculated, and a coupled model of liquid cavity length, casting speed, and superheat is established. This ensures that the three magnetic stirring sections (M-EMS, F-EMS, and S-EMS) in the crystallizer are located in the initial solidification zone, the critical liquid core zone, and the final solidification zone, respectively. During secondary cooling, a gradient water supply and a combined air-mist / water-mist cooling method are used. The gradient water supply uses a first-stage water flow of 0.36 m³ / s. 3 / h~0.39m 3 / h, second stage water volume 0.26m 3 / h~0.29m 3 / h, three sections of water volume 0.18m 3 / h~0.22m 3 / h; The billet is pulled to obtain a square billet; Rolling: The billet is rolled in 24 passes to produce 87Mn wire rods with a diameter of Φ12mm~Φ15mm. During the rolling process, a five-stage controlled cooling system is used on the Steyrmo air-cooling line: Stage 1: 0s~7s of wire drawing, cooling rate 10℃ / s~12℃ / s; Stage 2: 7s~22s of wire drawing, cooling rate 2.2℃ / s~2.8℃ / s; Stage 3: 22s~40s of wire drawing, cooling rate 0.6℃ / s~0.7℃ / s; Stage 4: 40s~60s of wire drawing, cooling rate 0.4℃ / s~0.5℃ / s; Stage 5: After 60s of wire drawing, cooling rate 0.2℃ / s~0.3℃ / s.

2. The method for preparing 87Mn hot-rolled wire rod for cables according to claim 1, characterized in that, During the nail-shooting experiment, a test point was set every 0.05 m / min within the pulling speed range of 2.3 m / min to 2.7 m / min to create a temperature gradient. The overall solidification coefficient of the casting machine was calculated to be K = 28.3 mm / min based on the modified square root law. 1 / 2 ~28.8 mm / min 1 / 2 .

3. The method for preparing 87Mn hot-rolled wire rod for cables according to claim 1, characterized in that, The coupled model of liquid cavity length-pulling speed-superheat is L = 0.032V + 0.005ΔT + 0.42, R 2 ≥0.99, where L is the length of the liquid phase cavity, m; V is the pulling speed, m / min; and ΔT is the superheat, ℃.

4. The method for preparing 87Mn hot-rolled wire rod for cables according to claim 1, characterized in that, M-EMS current is 350A~370A, frequency is 10Hz~12Hz; F-EMS current is 390A~410A, frequency is 7Hz~9Hz; S-EMS current is 320A~340A, frequency is 12Hz~14Hz.

5. The method for preparing 87Mn hot-rolled wire rod for cables according to claim 1, characterized in that, Cooling water flow rate for the crystallizer: 0.85 m³ 3 / h~0.95m 3 / h, secondary cooling water flow rate is 1.32L / kg~1.38L / kg, atomization pressure is 0.32MPa~0.38MPa, and water mist particle size is 50μm~80μm.

6. The method for preparing 87Mn hot-rolled wire rod for cables according to claim 1, characterized in that, During the rolling process, rough rolling consists of passes 1 to 6 at a rolling speed of 9 m / s to 11 m / s, intermediate rolling consists of passes 7 to 14 at a rolling speed of 16 m / s to 19 m / s, and finish rolling consists of passes 15 to 24 at a rolling speed of 26 m / s to 27 m / s. The temperature entering the finish rolling stage is 925℃ to 935℃, and the final rolling temperature is 895℃ to 905℃. After rough rolling, high-pressure water at 19 MPa to 21 MPa is used for descaling, and after intermediate rolling, laser descaling with a power of 1000W to 1200W is used.

7. The method for preparing 87Mn hot-rolled wire rod for cables according to claim 1, characterized in that, In the five-stage cooling process, five fans are used in each stage. The fan outlets are at an angle of 30° to 45° to the direction of wire rod movement, and the distance between the outlets and the wire rod surface is 50mm to 80mm. The first stage: the frequency is 50Hz, cooling the wire rod temperature to 710℃ to 720℃; the second stage: the frequency is 32Hz to 34Hz, cooling the wire rod temperature to 600℃ to 620℃; the third stage: the frequency is 15Hz to 20Hz, cooling the wire rod temperature to 550℃ to 560℃; the fourth stage: cooling the wire rod temperature to 510℃ to 530℃; and the fifth stage: cooling the wire rod temperature to 490℃ to 510℃.

8. The method for preparing 87Mn hot-rolled wire rod for cables according to claim 1, characterized in that, Ultrasonic vibration is introduced to assist in impurity removal during the bottom blowing stage of refining, so that T[O]≤13ppm and inclusion size≤8μm. During the bottom blowing process of refining, the argon blowing rate during the heating stage is 240NL / min~260NL / min, the argon blowing rate during the slag addition and alloying stage is 290NL / min~310NL / min, the argon blowing rate during the soft blowing stage is 38NL / min~42NL / min, the soft blowing time is 12min~14min, and the power of ultrasonic vibration is 300W~500W.

9. The method for preparing 87Mn hot-rolled wire rod for cables according to claim 1, characterized in that, 87Mn steel is composed of the following elemental components by mass percentage: C: 0.85%~0.87%, Si: 0.28%~0.32%, Mn: 0.78%~0.82%, P: ≤0.010%, S: ≤0.006%, Cr: 0.14%~0.16%, Ni: ≤0.06%, Cu: ≤0.12%, V: 0.060%~0.070%, Al: 0.022%~0.028%, with the balance being Fe and unavoidable impurity elements, totaling 100%.

10. The method for preparing 87Mn hot-rolled wire rod for cables according to claim 1, characterized in that, The refining process includes LF refining and RH vacuum refining. The vacuum degree of RH vacuum refining is ≤50Pa, and the holding time is 15min~20min.

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