CN112090956B - Production control method of wire rod for low-segregation high-torsion bridge cable - Google Patents
Production control method of wire rod for low-segregation high-torsion bridge cable Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
Abstract
The invention discloses a production method of a wire rod for a low-segregation high-torsion bridge cable, which mainly comprises the following three stages: 1) steelmaking and continuous casting, 2) soaking and cogging, 3) rolling and controlled cooling. The carbon element segregation control difficulty is different due to the fact that the carbon content of the bridge cable steel is different, and a certain gap exists between main technological parameters of each stage according to the carbon content of the wire rod. The invention determines the implementation range of main technological parameters of each stage, can stably control the torsion performance of the steel billet and the wire rod by reducing the segregation degree of the steel billet and the wire rod on the premise of ensuring the strength of the material, and is suitable for bridge cable steel with high torsion performance requirement.
Description
Technical Field
The technical scheme belongs to the field of steel materials, and particularly relates to a production method of a wire rod for a low-segregation high-torsion bridge cable.
Background
The bridge cable is regarded as a 'life line' of bridge engineering, and the strength and toughness of the bridge cable are strictly required due to the changeable service environment of the bridge cable, wherein the requirement on the torsion (the time/360 DEG) of the steel wire is more than or equal to 12 times, and the requirement on the structural and performance uniformity of the bridge cable is extremely high.
The bridge cable steel wire rod is a raw material for manufacturing bridge cable steel wires, is typical hypereutectoid steel, and has the carbon content of 0.82-0.98% and the size of 12.0-15.5mm. In order to improve the strength of the steel wire and further achieve the purposes of reducing the dead weight of bridge engineering, improving the safety and saving the construction and maintenance cost, the bridge cable steel wire rod is generally subjected to carburetion treatment. The addition of carbon element is one of the main and conventional means for reinforcing steel, but as the carbon content of the wire rod increases, the gap between the carbon-lean region and the carbon-rich region of the wire rod is increased due to the uneven distribution of the carbon element, the segregation degree is greatly increased, and the control difficulty of the netlike carbide is further increased: for an average of 0.01% carbon increase, the grade of 0.045 of the network carbide can be correspondingly increased. When the segregation degree of the wire rod exceeds the standard, the steel wire is subjected to genetic influence, segregation in the aspects of composition and structure occurs, deformation stress of the steel wire is concentrated in the torsion process, the steel base is torn, torsion failure is accelerated, and the torsion performance is poor.
The more serious the segregation degree, the greater the impact on the torsional properties, the more stringent the requirements (no more than 2.0 levels) are imposed on the grade of network cementite of the bridge cable. The growth of the network cementite depends on carbon fluctuation caused by carbon element diffusion, and homogenization of the carbon element can effectively inhibit precipitation of the network carbon. In order to control the grade of the network cementite in the bridge cable, the maximum central carbon segregation in the bridge cable steel billet is generally required to be less than or equal to 1.10, and is preferably controlled to be less than or equal to 1.05, so that the maximum central carbon segregation of the wire rod is ensured to be less than or equal to 1.18, and the wire rod network carbon control difficulty is obviously reduced.
The key control difficulty of the existing bridge cable steel is that the strength and the torsion performance of the coated steel wire are simultaneously met, the strength is improved inevitably depending on the improvement of the carbon content of the wire rod, the control difficulty of steel billet and wire rod segregation is increased, the torsion performance of the steel wire is deteriorated, and the steel wire is also a bottleneck for limiting the further improvement of the strength of the bridge cable steel.
CN107299280a discloses a heat treatment wire rod for a 2000mpa cable wire and a production method, the weight percentage of the components is: c0.85-1.0%; si:0.80 to 1.5 percent; mn 0.30-0.80%; cr 0.20-0.80%; p is less than or equal to 0.015 percent; s is less than or equal to 0.010 percent; 0.01 to 0.08 percent of Al, and the balance of Fe and unavoidable impurities. The invention is produced by special design of components and by smelting-continuous casting-casting blank grinding-steel rolling-off-line heat treatment process, the sorbite rate of the obtained wire rod exceeds 95%, the structure is uniform, and quenching structures such as reticular carbide, martensite and the like are avoided. After the wire rod is subjected to drawing, galvanization (aluminum) and stabilization treatment, the strength of the steel wire is more than or equal to 2000MPa, and the wire rod can be used for producing 2000 MPa-level bridge cable galvanization (aluminum) steel wires, and is suitable for bridges with ultra-large span and ultra-high strength requirements. The patent adopts a hot forming process for rolling, and an isothermal salt bath off-line heat treatment process is adopted after rolling, which is also one of methods for improving the segregation of the finished wire rod.
CN109468530a discloses a hot-rolled wire rod for a galvanized steel wire of a large bridge cable with the grade of more than 2000mpa and a production method, and the chemical components of the product are as follows by weight percentage: 0.90-1.10%, si:0.20-0.60%, mn:0.30-0.90%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, cr:0.10-0.40%, al:0.010-0.070%, V:0.02-0.15%, cu: less than or equal to 0.05 percent, ca:20-40ppm, N:20-90ppm, the others being Fe and unavoidable residual elements; the sorbite tissue content of the wire rod is more than or equal to 95%, the pass range of the tensile strength is less than or equal to 70MPa (uniformity), the tensile strength of the galvanized steel wire is more than or equal to 2000MPa after the wire rod is drawn and galvanized, and the torsion times are more than or equal to 12 times. The technological process of the wire rod comprises molten iron pretreatment, converter or electric furnace steelmaking, LF refining, RH degassing treatment, 390 x 510 bloom continuous casting, blank reheating, blank rolling, intermediate bloom surface finishing, intermediate bloom reheating, intermediate bloom rolling, wire rod online EDC water bath toughening treatment and wire rod collecting and packaging. The key technology for controlling wire rod segregation in the patent is an online EDC water bath toughening treatment technology, and is a theoretically feasible method.
CN102936688A discloses a wire rod for bridge cable with tensile strength more than or equal to 2000mpa and a production method, the wire rod comprises the following components in percentage by weight: c:0.95 to 1.2 percent, si:0.1 to 0.48 percent, mn:0.6 to 1.0 percent, cr:0.1 to 0.5 percent, V:0.01 to 0.05 percent, cu is less than or equal to 0.05 percent, al:0.05 to 0.15 percent, N:0.01 to 0.03 percent, P is less than or equal to 0.025 percent, and S is less than or equal to 0.015 percent; the production steps are as follows: smelting and continuously casting to form a blank; heating the casting blank; rolling; heating again; high-speed rolling; spinning; air-cooling to room temperature; and (5) standby application. According to the invention, as the continuous casting bloom is adopted, the bloom is rolled into the small bloom and then is rolled by a high-speed wire, so that the metallographic structure and the like of the wire for the bridge cable are uniform, and the crystal grains are better refined; and because of adopting the processes of rapid cooling with large air quantity and the like, the tensile strength of the steel wire for the final bridge cable is more than or equal to 2000MPa and is stable, the torsion value is more than or equal to 15 times, and the phenomenon of wire breakage caused by the quality problem of the steel wire in cold drawing is avoided. The patent can achieve the effect of improving the strength of the wire rod by adopting large air quantity for rapid cooling, but the control of segregation is not explained excessively.
CN109628837a discloses an ultra-fine bainite bridge cable steel and a preparation method thereof, and the invention adopts a deformation heat treatment and isothermal quenching process to obtain the cable steel. The pre-deformation and low temperature bainite isothermal are combined, and refining technologies such as micro alloy refining, rolling control and cooling control refining, pre-deformation, low temperature bainite isothermal and the like are comprehensively utilized to obtain an ultra-fine bainitic structure consisting of non-carbonized bainite and residual austenite, wherein the tensile strength is 1800-2100 MPa, and the elongation is 12-20%. The preparation process flow of the ultra-fine bainitic bridge cable steel comprises the following steps: smelting continuous casting hot rolling cutting austenitizing pre-deformation low-temperature bainite isothermal temperature; during pre-deformation, firstly, the cut hot rolling is reheated to Ac+50 ℃ to carry out austenitizing, the temperature is kept for 0.5-1h, then the hot rolling is rapidly cooled (the cooling speed is higher than 10 ℃/s) to 220-280 ℃, the progress is Wen Za, the reduction is 20-30%, and then the hot rolling is put into a salt bath furnace at 220-280 ℃ to carry out isothermal temperature for 3-5h, and isothermal bainite transformation is carried out; and then taking out the mixture and air cooling the mixture to room temperature. The main innovation point of the patent is that the metallographic structure of the bridge cable steel is ultra-fine bainite, the bainite transformation time is too long, the process control difficulty is high, the current application condition is not met, the bainite can ensure the torsion performance required by the material, and the problem exists, which is not confirmed at present.
CN105107848A discloses "a method for producing a high strength bridge cable steel wire rod", which method comprises: during continuous casting, the liquidus line of the tundish temperature is controlled at 10-20 ℃, the pulling speed is controlled at 0.3-0.5 m/min, and a bloom with 280-320-380 x 420mm is obtained through continuous casting; cogging the large square billet into small square billets 150-200 mm by two fires; rolling the small square billet into a high line with the diameter of 11-14 mm; wherein, in the process of cogging by two fires, the temperature of a heating section, the temperature of a soaking section, the air consumption coefficient, the time of a billet in a furnace, the furnace pressure, the atmosphere in the furnace, the starting rolling temperature and the cooling mode are controlled; in the rolling process of the high line, the temperature difference between the upper section and the lower section of a heating section, a soaking section, a casting blank, the time of a furnace, the initial rolling temperature, the inlet temperature of a finishing mill and the like are controlled. In the technical scheme, the technical problem that the martensitic structure grade of the high-strength bridge cable steel wire rod in the prior art is high is solved by combining the control of the continuous casting process with the control of the heating process and the cooling process of the two-fire cogging and rolling high line, the martensitic structure grade is reduced, and the torsion performance and the segregation control method are not involved.
Disclosure of Invention
The invention aims to solve the technical problem of providing a production method of the wire rod for the low-segregation high-torsion bridge cable, which aims at the defects in the prior art, can stably control the torsion performance of the wire rod by reducing the segregation degree of a steel billet and the wire rod on the premise of ensuring the strength of materials, and is suitable for bridge cable steel with high torsion performance requirement.
The invention adopts the technical proposal for solving the problems that:
a production control method of a wire rod for a low-segregation high-torsion bridge cable mainly comprises three stages: 1) steelmaking and continuous casting, 2) soaking and cogging, 3) rolling and controlled cooling. Because the carbon content of bridge cable steel can cause different control difficulties of carbon element segregation, certain gaps exist among main technological parameters of each stage according to the different carbon content of wire rods, and the specific procedures, specific processes and parameters included in each stage are as follows:
1) Steelmaking and continuous casting: desulphurizing molten iron, smelting in a converter, blowing argon, LF refining, vacuum treatment, soft blowing, continuous casting, casting blank finishing and the like; wherein the vacuum treatment time is more than or equal to 9min;
in the continuous casting step, the superheat degree of the ladle molten steel in continuous casting is less than or equal to 30 ℃ (when the carbon content of the wire rod is more than or equal to 0.9 percent and the superheat degree of the ladle molten steel is less than or equal to 25 percent), and the pulling speed is 0.35-0.65m/min; the secondary cooling water is 0.8-1.2L/kg, the light rolling reduction is more than or equal to 8.5mm (when the carbon content of the wire rod is more than or equal to 0.9%, the light rolling reduction is more than or equal to 11.0 mm); continuous casting bloom cross section size: 300mm. Gtoreq.300 mm, preferably 320 mm. Gtoreq.420 mm;
2) Soaking (or heating) and cogging: soaking or heating the billet, cogging and rolling, surface grinding and the like; wherein, the liquid crystal display device comprises a liquid crystal display device,
A. when the carbon content of the wire rod is more than or equal to 0.9%, soaking treatment is adopted for the bloom: the heating temperature is controlled to 1250-1320 ℃, the soaking heat preservation time is more than or equal to 8 hours, the micro-positive pressure of 30-35MPa is kept in the soaking pit, and the atmosphere in the pit is kept at O 2 Less than 1.1% CO less than 2.6% weak reducibility; when the carbon content of the wire rod is less than 0.9%, the bloom is directly heated conventionally without soaking treatment: the heating temperature is 1200-1250 ℃, the heating and heat preserving time is 200-250min, and the section temperature difference is less than or equal to 30 ℃;
B. the bloom is subjected to soaking or heating and then is directly subjected to cogging and rolling, the initial rolling temperature is 1180-1280 ℃, and the bloom is a square bloom, and the size range of the square bloom is: 160mm x 160mm to 220mm x 220mm (wherein, when the carbon content of the wire rod is more than or equal to 0.9%, the square billet size is 160mm x 160mm, and when the carbon content of the wire rod is less than 0.9%, the square billet size is 220mm x 220 mm);
C. the square billet after the cogging is subjected to full peeling and polishing treatment, the polishing depth is more than or equal to 1.5mm, and the polishing depth can be properly increased to ensure that the oxide layer on the surface of the billet is completely removed; after grinding, corners of the small square billets have no sharp corners, and the plane is totally flat and free of concave and convex;
3) Rolling and cooling control: square billet heating, multi-pass rolling, spinning, stelmor controlled cooling, coil collecting and the like; wherein, the liquid crystal display device comprises a liquid crystal display device,
A. the heating temperature of the square billet is 1180+/-30 ℃, the temperature difference of the section is less than or equal to 30 ℃, the steel billet is in the furnace time of 180-250min (wherein, when the carbon content of a wire rod is more than or equal to 0.9%,160mm x 160mm square billet is in the furnace time range of 180-220min, and when the carbon content of the wire rod is less than 0.9%,220mm x 220mm square billet is in the furnace time range of 210-250 min);
B. the initial rolling temperature of high-speed wire rolling is 1150+/-25 ℃, the inlet temperature of a finishing mill is 900+/-20 ℃, the inlet temperature of a reducing sizing mill is 910+/-20 ℃, the spinning temperature is 920+/-20 ℃, and the outlet speed of 20-frame pre-finish rolling is 8.0m/s; the diameter of the finished wire rod is 12.0-15.5mm;
C. the length of the Steyr air cooling line is 97 meters, the total number of the fans is 14, and the air quantity of the 1 # fan and the 4# fan is 210000m 3 The air quantity of the 5-10# fan is 154000m 3 The air quantity of the 11 # 14 fan is 125000m 3 And/h. The initial speed of the Steyr air-cooled roller way is 45m/min, the fans are all fully opened, the roller way speed range of the 1 # fan to the 8# fan is 1.03,9-14# fan, and the roller way speed range of the 0.97,8# fan reaches the maximum value. The stelmor air cooling line is key equipment for controlling cooling, and the wire rod structure can be optimally controlled by adopting the set parameters, namely, the sorbite rate in the wire rod metallographic structure is more than or equal to 95 percent, no abnormal structures such as martensite are generated, and otherwise, the structure type and the proportion can be influenced.
D. When the carbon content of the wire rod is more than or equal to 0.9%, pit slow cooling is carried out after the wire rod is collected, so that direct wind blowing is avoided, the internal stress of the wire rod is reduced, and the wire rod is cooled to below 300 ℃ and then is subjected to PF line air cooling; for the wire rod with the carbon content less than 0.9%, the wire rod can be directly air-cooled by the PF line.
Compared with the prior art, the invention has the beneficial effects that:
the process treatment is carried out in the bridge cable steel production process, and the segregation degree of the bloom can be ensured by controlling the superheat degree and the soft reduction of molten steel; performing two-fire forming and soaking treatment on the steel billet to ensure that carbon elements in the steel billet are fully diffused, the steel billet is compact, the holes and cracks in the steel billet are reduced, and the carbon segregation degree of the steel billet is reduced; aiming at the serious decarburization problem possibly caused in the soaking process, the square billet after cogging is subjected to full peeling and grinding, so that the decarburization degree caused in the carbon diffusion process is effectively reduced; the decarburization risk of the square billets in the rolling and heating process is further reduced by controlling the heating process of the square billets, and the qualified metallographic structure of the wire rods is ensured and the segregation degree is low by controlling the starting rolling temperature, the finishing rolling temperature, the reducing sizing rolling temperature, the spinning temperature and the stelmor air cooling process, so that the method is suitable for trial production of steel wires with high torsion performance.
In addition, main process control parameters of each stage are controlled in a classified key mode according to different bridge cable steel carbon content, and in the process of producing the 12.0-15.5mm wire rod through the process, the maximum central carbon segregation of a square billet is less than or equal to 1.12, the maximum central carbon segregation of the square billet is less than or equal to 1.07, the maximum central carbon segregation of the wire rod is less than or equal to 1.15, the wire rod net carbide is less than or equal to 2.0, the depth of a wire rod decarburized layer is less than or equal to 1.0 percent D (D is the diameter of the wire rod), the sorbite rate in a wire rod metallographic structure is more than or equal to 95 percent, and abnormal structures such as martensite are avoided. The control method can optimize the uniformity of carbon elements of the material, reduce the grade of the netlike carbide, ensure the tissue uniformity of the wire rod, and further stably ensure the torsion performance of the trial-manufactured steel wire.
Detailed Description
For a better understanding of the present invention, the following examples are set forth to illustrate the invention further, but are not to be construed as limiting the invention.
The bridge cable steel comprises different strength grades, raw materials (wire rods) required by the different strength grades are different and are mainly reflected in the original strength of the wire rods, and the strength of the wire rods depends on the carbon content of the wire rods, so that the wire rods with different carbon contents are adopted for trial production according to the strength requirements of the bridge cable steel. The segregation control difficulty in the trial production process of materials with different carbon contents is different, and the higher the carbon content is, the greater the segregation control difficulty is, so that different control means are adopted for different carbon contents, and unnecessary waste caused by excessive control is avoided. In the following embodiments, the components and mass percentages of the wire rod are: 0.82 to 0.98 percent of C, 0.3 to 1.2 percent of Si, 0.3 to 0.9 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, less than or equal to 0.2 percent of Cu, less than or equal to 0.4 percent of Cr, less than or equal to 0.05 percent of Nb, less than or equal to 0.07 percent of V, less than or equal to 0.05 percent of Ti, and the balance of Fe and unavoidable impurities.
Examples 1 to 5
A production control method of a wire rod for a low-segregation high-torsion bridge cable mainly comprises three stages: 1) steelmaking and continuous casting, 2) soaking and cogging, 3) rolling and controlled cooling. Because the carbon content of bridge cable steel can cause different control difficulties of carbon element segregation, certain gaps exist among main technological parameters of each stage according to the different carbon content of wire rods, and the specific main working procedures, specific processes and parameters of each stage are as follows:
1) Steelmaking and continuous casting: molten iron desulfurization, converter smelting, argon blowing, LF refining, vacuum treatment, soft blowing, continuous casting, casting blank finishing and the like; wherein the vacuum treatment time is more than or equal to 9min;
A. the vacuum treatment time is more than or equal to 9min;
B. the superheat degree of the ladle molten steel is less than or equal to 30 ℃ (when the carbon content of the wire rod is more than or equal to 0.9 percent, the superheat degree of the ladle molten steel is less than or equal to 25 ℃);
C. pulling speed: 0.35-0.65m/min;
D. second cold water: 0.8-1.2L/kg;
E. the light reduction is more than or equal to 8.5mm (when the carbon content of the wire rod is more than or equal to 0.9 percent, the light reduction is more than or equal to 11.0 mm.);
F. continuous casting bloom cross section size: 320mm 420mm.
2) Soaking (or heating) and cogging: soaking or heating the billet, cogging, rolling, surface grinding and the like; wherein, the liquid crystal display device comprises a liquid crystal display device,
A. when the carbon content of the wire rod is more than or equal to 0.9%, soaking treatment is adopted for the bloom: the heating temperature is controlled to 1250-1320 ℃, the soaking heat preservation time is more than or equal to 8 hours, the micro-positive pressure of 30-35MPa is kept in the soaking pit, and the atmosphere in the pit is kept at O 2 Less than 1.1% CO less than 2.6% weak reducibility; when the carbon content of the wire rod is less than 0.9%, the bloom is directly heated conventionally without soaking treatment: the heating temperature is 1200-1250 ℃, the heating and heat preserving time is 200-250min, and the section temperature difference is less than or equal to 30 ℃;
B. the bloom is subjected to soaking or heating and then is directly subjected to cogging and rolling, the initial rolling temperature is 1180-1280 ℃, and the bloom is a square bloom, and the size range of the square bloom is: 160mm x 160mm to 220mm x 220mm (wherein, when the carbon content of the wire rod is more than or equal to 0.9%, the square billet size is 160mm x 160mm, and when the carbon content of the wire rod is less than 0.9%, the square billet size is 220mm x 220 mm);
C. the square billet after the cogging is subjected to full peeling and polishing treatment, the polishing depth is more than or equal to 1.5mm, and the polishing depth can be properly increased to ensure that the oxide layer on the surface of the billet is completely removed; after grinding, corners of the small square billets have no sharp corners, and the plane is totally flat and free of concave and convex;
3) Rolling and cooling control: square billet heating, multi-pass rolling (generally rough rolling, middle rolling, pre-finish rolling, reducing sizing), spinning, stelmor controlled cooling, coil collecting and the like; wherein, the liquid crystal display device comprises a liquid crystal display device,
A. the heating temperature of the square billet is 1180+/-30 ℃, the temperature difference of the section is less than or equal to 30 ℃, the steel billet is in the furnace time of 180-250min (wherein, when the carbon content of a wire rod is more than or equal to 0.9%,160mm x 160mm square billet is in the furnace time range of 180-220min, and when the carbon content of the wire rod is less than 0.9%,220mm x 220mm square billet is in the furnace time range of 210-250 min);
B. the initial rolling temperature of high-line rolling is 1150+/-25 ℃; the inlet temperature of the finishing mill is 900+/-20 ℃; reducing the inlet temperature of the sizing mill to 910+/-20 ℃; the spinning temperature is 920+/-20 ℃;20 pre-finish rolling outlet speeds are 8.0m/s; the diameter of the finished wire rod is 12.0-15.5mm;
C. the length of the Steyr air cooling line is 97 meters, the total number of the fans is 14, and the air quantity of the 1 # fan and the 4# fan is 210000m 3 The air quantity of the 5-10# fan is 154000m 3 The air quantity of the 11 # 14 fan is 125000m 3 And/h. The initial speed of the Steyr air-cooled roller way is 45m/min, the fans are all fully opened, the roller way speed range of the 1-8# fan is 1.03,9-14# fan, and the roller way speed range of the 0.97,8# fan reaches the maximum value;
D. when the carbon content of the wire rod is more than or equal to 0.9%, pit slow cooling is carried out after the wire rod is collected, so that direct wind blowing is avoided, the internal stress of the wire rod is reduced, and the wire rod is cooled to below 300 ℃ and then is subjected to PF line air cooling. For the wire rod with the carbon content less than 0.9%, the wire rod can be directly air-cooled by the PF line.
The compositions of the components and the specific processes and parameters in examples 1-5 are shown in tables 1-4. Table 5 shows the results of performance tests of the cast slabs and wire rods obtained in each example.
TABLE 1 composition of ingredients
| C/％ | Si/％ | Mn/％ | P/％ | S/％ | Cu/％ | Cr/％ | Nb/％ | V/％ | Ti/％ | |
| Requirements for | 0.82-0.98 | 0.3-1.2 | 0.3-0.9 | ≤0.025 | ≤0.025 | ≤0.2 | ≤0.4 | ≤0.05 | ≤0.07 | ≤0.05 |
| Example 1 | 0.87 | 0.35 | 0.85 | 0.012 | 0.009 | 0.05 | 0.25 | - | 0.05 | - |
| Example 2 | 0.92 | 0.90 | 0.32 | 0.010 | 0.008 | 0.007 | 0.26 | 0.02 | 0.04 | - |
| Example 3 | 0.83 | 0.33 | 0.78 | 0.012 | 0.008 | 0.006 | 0.32 | - | 0.06 | 0.04 |
| Example 4 | 0.88 | 0.50 | 0.81 | 0.013 | 0.007 | 0.005 | 0.28 | 0.03 | - | 0.03 |
| Example 5 | 0.97 | 0.95 | 0.40 | 0.008 | 0.009 | 0.008 | 0.30 | - | 0.05 | - |
TABLE 2 steelmaking and continuous casting parameters
TABLE 3 soaking and cogging parameters
TABLE 4 Rolling and controlled Cooling Main parameters
TABLE 5 results of properties of casting and wire rods
In summary, the main process control parameters of each stage are controlled in a classified mode according to different carbon content of bridge cable steel, and in the process of producing the 12.0-15.5mm wire rod through the process, the maximum center carbon segregation of a square billet is less than or equal to 1.12, the maximum center carbon segregation of a square billet is less than or equal to 1.07, the maximum center carbon segregation of the wire rod is less than or equal to 1.15, the mesh carbide of the wire rod is less than or equal to 2.0, the decarburized layer depth of the wire rod is less than or equal to 1.0% D (D is the diameter of the wire rod), the sorbite rate in the metallographic structure of the wire rod is more than or equal to 95%, and abnormal structures such as martensite are avoided, so that the produced wire rod is ensured to be qualified in metallographic structure and low in segregation degree and suitable for trial production of the steel wire with high torsion performance.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and changes can be made by those skilled in the art without departing from the inventive concept and remain within the scope of the invention.
Claims (5)
1. A production control method of a wire rod for a low-segregation high-torsion bridge cable mainly comprises three stages: 1) steelmaking and continuous casting, 2) soaking and cogging, 3) rolling and cooling control; the wire rod is characterized by comprising the following components in percentage by mass: 0.92 to 0.98 percent of C, 0.9 to 1.2 percent of Si, 0.3 to 0.40 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, less than or equal to 0.2 percent of Cu, less than or equal to 0.4 percent of Cr, less than or equal to 0.05 percent of Nb, less than or equal to 0.07 percent of V, less than or equal to 0.05 percent of Ti, and the balance of Fe and unavoidable impurities;
the specific procedures, specific processes and parameters included in each stage are as follows:
1) Steelmaking and continuous casting: desulphurizing molten iron, smelting in a converter, blowing argon, LF refining, vacuum treatment, soft blowing, continuous casting and casting blank finishing; wherein, in the continuous casting step, the superheat degree of the ladle molten steel is less than or equal to 25 ℃, and the light reduction is more than or equal to 11.0mm;
2) Soaking and cogging: soaking steel billet, cogging and rolling, and grinding the surface; wherein, soaking treatment is adopted for the bloom: the heating temperature is controlled to 1250-1320 ℃, the soaking heat preservation time is more than or equal to 8 hours, the micro-positive pressure of 30-35MPa is kept in the soaking pit, and the atmosphere in the pit is kept at O 2 Weak reducibility of less than 1.1 percent and CO of less than 2.6 percent, and the square billet is obtained after cogging;
3) Rolling and cooling control: heating square billets, carrying out multi-pass rolling, spinning, carrying out stelmor controlled cooling and collecting coils; wherein, the liquid crystal display device comprises a liquid crystal display device,
A. the heating temperature of the square billet is 1180+/-30 ℃, the section temperature difference is less than or equal to 30 ℃, and the time range of the square billet in a furnace is 180-220min;
B. the diameter of the finished wire rod is 12.0-15.5mm;
C. the coil rod is collected and then slowly cooled in a pit, so that direct wind blowing is avoided, internal stress of the coil rod is reduced, and the coil rod is cooled to below 300 ℃ and then is air cooled on a PF line;
in the process of producing the wire rod, the maximum center carbon segregation of the bloom is less than or equal to 1.12; the maximum center carbon segregation of the square billet is less than or equal to 1.07; the maximum central carbon segregation of the wire rod is less than or equal to 1.15; the wire rod net carbide is less than or equal to 2.0 grade; the depth of the decarburized layer of the wire rod is less than or equal to 1.0 percent D, and D is the diameter of the wire rod; the sorbite rate in the metallographic structure of the wire rod is more than or equal to 95 percent and no martensite abnormal structure exists.
2. The production control method of the wire rod for the low-segregation high-torsion bridge cable, which is characterized in that in the steelmaking and continuous casting stages, the vacuum treatment time is more than or equal to 9min; the pulling speed in continuous casting is 0.35-0.65m/min, the secondary cooling water is 0.8-1.2L/kg, and the section size of the continuous casting bloom is: 300mm.
3. The production control method of the wire rod for the low-segregation high-torsion bridge cable, which is characterized in that in the soaking and cogging stage, the initial rolling temperature is 1180-1280 ℃, square billets are formed after cogging, and the square billets are 160mm in size.
4. The production control method of the wire rod for the low-segregation high-torsion bridge cable, which is characterized in that in the soaking and cogging stages, the square billet after cogging is subjected to full-skinning grinding treatment, and the grinding depth is more than or equal to 1.5mm.
5. The production control method of the wire rod for the low-segregation high-torsion bridge cable according to claim 1, wherein in the rolling and cooling control stage, the stelmor air cooling line is 97 m long, 14 groups of fans are used, and the number of fans is 1-4#The air volume is 210000m 3 The air quantity of the 5-10# fan is 154000m 3 The air quantity of the 11 # 14 fan is 125000m 3 /h; the initial speed of the Steyr air-cooled roller way is 45m/min, the fans are all fully opened, the roller way speed range of the 1 # fan to the 8# fan is 1.03,9-14# fan, and the roller way speed range of the 0.97,8# fan reaches the maximum value.
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