CN113802059B - Steel for large-span high-strength cable core and preparation method thereof - Google Patents
Steel for large-span high-strength cable core and preparation method thereof Download PDFInfo
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- CN113802059B CN113802059B CN202110945225.4A CN202110945225A CN113802059B CN 113802059 B CN113802059 B CN 113802059B CN 202110945225 A CN202110945225 A CN 202110945225A CN 113802059 B CN113802059 B CN 113802059B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- B22D11/18—Controlling or regulating processes or operations for pouring
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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
- C22C33/06—Making ferrous alloys by melting using master alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention particularly relates to steel for a large-span high-strength cable core and a preparation method thereof, belonging to the technical field of steel preparation, wherein the steel comprises the following chemical components in parts by mass: c:0.54 to 0.56 percent of Si, 0.17 to 0.25 percent of Mn, less than or equal to 0.012 percent of P, S: less than or equal to 0.010 percent, less than or equal to 0.003 percent of N, and the balance of Fe and inevitable impurities; by improving the purity, reducing the contents of O, N, P and S in the wire rod and improving the deformability of the wire rod, a user can directly draw from phi 5.5mm to phi 1.0-1.3mm by forced large-deformation drawing without heat treatment, the tensile strength of a finished steel wire is improved, and the tensile strength of a galvanized steel stranded wire of a cable can reach 1600-1800MPa.
Description
Technical Field
The invention belongs to the technical field of steel preparation, and particularly relates to steel for a large-span high-strength cable core and a preparation method thereof.
Background
Copper, aluminum and aluminum alloy have the advantages of small density, low resistance, low power consumption in long-distance transmission and the like compared with steel, and are better materials for manufacturing cables, but copper has higher price, so the copper alloy is commonly used in some compact instruments, and the preferred material for manufacturing the cables is aluminum or aluminum alloy. But the tensile strength of aluminum alloy is limited, and when designing large-span high strength transmission cable, the cable is designed into combined material, and the outer aluminum alloy inlayer that uses the galvanized steel strand wires improves the tensile strength of whole cable.
The common cable core uses 55 and 60# hard wires, a wire rod with phi 5.5-6.0mm specification is directly drawn to phi 2.0-2.3 without heat treatment after acid cleaning (mechanical shelling) and phosphorization, and is twisted into a steel strand after galvanization for manufacturing the cable core, the tensile strength of the original wire rod is about 900MPa, and the strength is 1300-1500MPa after cold drawing deformation of about 75-85%.
In severe freezing disaster weather, many cable fractures and tower collapse accidents can occur, and huge loss is caused to the property safety of people. In order to avoid such accidents, it is urgently needed to improve the bearing capacity of the transmission cables and the line towers, so that the bearing capacity of the galvanized steel stranded wires for the cable cores is improved.
In order to improve the bearing capacity of the galvanized steel strand, the most direct mode is to increase the sectional area of the galvanized steel strand on the basis of the original strand, but the mode can cause the dead weight of the cable to increase; the other mode is to change the material of the stranded wire, and change 55-60# into 70# or even 80#, the strength can be naturally improved, but the hardness of the steel is also correspondingly improved, the drawing equipment of downstream processing enterprises can be correspondingly improved, and meanwhile, the transportation and the erection of the cable are correspondingly increased.
Disclosure of Invention
In view of the above problems, the present invention has been made in order to provide a steel for a large-span high-strength cable core and a method for manufacturing the same, which overcome or at least partially solve the above problems.
The embodiment of the invention provides steel for a large-span high-strength cable core, which comprises the following chemical components in parts by mass: c:0.54 to 0.56 percent of Si, 0.17 to 0.25 percent of Mn, less than or equal to 0.012 percent of P, S: less than or equal to 0.010 percent, less than or equal to 0.003 percent of N, and the balance of Fe and inevitable impurities.
Optionally, the chemical composition of the steel comprises, in mass fraction: c:0.55 percent, 0.19 to 0.23 percent of Si, 0.53 to 0.57 percent of Mn, less than or equal to 0.012 percent of P, S: less than or equal to 0.010 percent, less than or equal to 0.003 percent of N, and the balance of Fe and inevitable impurities.
Optionally, the metallographic structure of the steel is, in terms of volume fraction: pearlite structure over 95% and ferrite structure 1-5%.
Optionally, the grain size control range of the steel for the large-span high-strength cable core is 0.08-0.35 μm.
Optionally, the grain size control range of the steel for the large-span high-strength cable core is 0.14-0.18 μm.
Based on the same inventive concept, the embodiment of the invention also provides a preparation method of the steel for the large-span high-strength cable core, which comprises the following steps:
smelting molten iron in a converter;
refining the molten iron smelted by the converter to obtain molten steel;
continuously casting the molten steel to obtain a steel billet;
and rolling the steel billet by a wire mill to obtain a wire rod of the steel for the large-span high-strength cable core.
Optionally, when the molten steel is continuously cast, the superheat degree of the molten steel is 20-30 ℃.
Optionally, the C segregation index of the steel billet is not more than 1.06, and the porosity and shrinkage requirement of the steel billet is controlled within 0.5 level.
Optionally, the sorbite rate of the wire rod is more than or equal to 95%.
Optionally, the surface size precision of the wire rod is controlled according to grade C.
Optionally, the fluctuation of the tensile strength of the head part and the tail part of the wire rod is controlled within 40MPa, and the tensile strength of the same circle of the wire rod is controlled within 30 MPa.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
the steel for the large-span high-strength cable core provided by the embodiment of the invention comprises the following chemical components in percentage by mass: c:0.54 to 0.56 percent of Si, 0.17 to 0.25 percent of Mn, less than or equal to 0.012 percent of P, S: less than or equal to 0.010 percent, less than or equal to 0.003 percent of N, and the balance of Fe and inevitable impurities; by improving the purity, reducing the contents of O, N, P and S in the wire rod and improving the deformability of the wire rod, a user can directly draw from phi 5.5mm to phi 1.0-1.3mm by forced large-deformation drawing without heat treatment, the tensile strength of a finished steel wire is improved, and the tensile strength of a galvanized steel stranded wire of a cable can reach 1600-1800MPa.
The above description is only an overview of the technical solutions of the present invention, and the present invention can be implemented in accordance with the content of the description so as to make the technical means of the present invention more clearly understood, and the above and other objects, features, and advantages of the present invention will be more clearly understood.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flow chart of a method provided by an embodiment of the invention.
Detailed Description
The present invention will be specifically explained below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented thereby. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
In order to solve the technical problems, the general idea of the embodiment of the application is as follows:
severe 'freezing' occurs someplace in a year, and a user reflects that the galvanized steel stranded wire for the high-voltage cable core manufactured by the 55# in the prior art has low strength, and accidents such as severe cable loosening and even breakage occur, and redesign is needed.
The applicant finds in the course of the invention that: the national standard requirement of the normal No. 55 steel is as follows: c:0.52% -0.60%; 0.17 to 0.37 percent of Si; 0.50 to 0.80 percent of Mn; p is less than or equal to 0.035%; s: less than or equal to 0.035%; the components are common raw materials for manufacturing high-pressure transmission cables, and the performance of steel wires manufactured after cold drawing and hardening has larger fluctuation due to large component fluctuation. Meanwhile, due to the fact that the contents of P and S are high and the plasticity of the wire rod is relatively low, downstream processing enterprises can only draw from phi 5.5mm to phi 2.0mm during processing and cannot continue drawing, and individual enterprises have to perform intermediate heat treatment for continuous drawing and perform sorbitizing again before continuing drawing, but the tensile strength of the steel wire is greatly lost due to heat treatment.
According to an exemplary embodiment of the present invention, there is provided a steel for a long-span high-strength cable core, the steel having a chemical composition comprising, in mass fraction: c:0.54 to 0.56 percent of Si, 0.17 to 0.25 percent of Mn, less than or equal to 0.012 percent of P, S: less than or equal to 0.010 percent, less than or equal to 0.003 percent of N, and the balance of Fe and inevitable impurities.
The C is a main element for determining the structure and performance of the steel after slow cooling, the reason for controlling the mass fraction of the C to be 0.54% -0.56% is that the wire rod keeps 880-920MPa, the adverse effect of overlarge mass fraction value is that the structure form is difficult to control, and the adverse effect of undersize is that the performance of the base material is lower than 880MPa.
Si is used for increasing the fluidity of molten steel, the reason for controlling the mass fraction of Si to be 0.17-0.25% is to enhance the deoxidation of the molten steel and enhance the fluidity of the molten steel during casting, the adverse effect of overlarge mass fraction is to cause the reduction of the surface shrinkage of rolled steel, the adverse effect of undersize is to cause the poor deoxidation effect of the molten steel and the poor purity of the molten steel;
mn is added into steel as a deoxidizer for molten steel, and can improve the deoxidizing effect of silicon and aluminum and form sulfide with sulfur, thereby eliminating the harmful effect of sulfur in steel to a great extent. The reason why the mass fraction of Mn is controlled to 0.50% to 0.60% is to dissolve manganese into ferrite to cause solid solution strengthening and to maintain relatively fine pearlite having a high strength in a rolled material. An adverse effect of an excessively large mass fraction is that the pearlite lamellae are too fine, and an adverse effect of an excessively small mass fraction is that the pearlite lamellae are too large.
P is a harmful element, the reason that the mass fraction of P is controlled to be less than or equal to 0.012 percent is that the rolled stock keeps high plasticity and toughness and improves the cold brittleness of steel, and the adverse effect of overlarge mass fraction is that the wire breakage rate of the rolled stock is higher.
S is also a harmful element, the largest harm of sulfur is to cause the cracking of steel during hot processing, the reason for controlling the mass fraction of S to be less than or equal to 0.010 percent is to avoid hot brittleness during the processing of rolled stock, and the adverse effect of overlarge mass fraction is that the occurrence rate of broken wire is higher;
n is also a harmful element, which causes quenching aging and deformation aging of the steel, so that the hardness and strength of the steel are increased and the plasticity and toughness are reduced, particularly in the deformation process, the plasticity and toughness are reduced obviously. The reason for controlling the mass fraction of N to be less than or equal to 0.003 percent is to reduce the processing aging problem of the wire rod, and the adverse effect of overlarge mass fraction is that the wire rod breakage rate is increased.
By improving the purity, reducing the contents of O, N, P and S in the wire rod and improving the deformability of the wire rod, a user can directly draw the wire rod from phi 5.5mm to phi 1.0-1.3mm by forced large-deformation drawing without heat treatment, so that the tensile strength of the finished steel wire is improved, and the tensile strength of the galvanized steel stranded wire of the cable can reach 1600-1800MPa.
As an alternative embodiment, the chemical composition of the steel comprises, in mass fractions: c:0.55 percent, 0.19 to 0.23 percent of Si, 0.53 to 0.57 percent of Mn, less than or equal to 0.012 percent of P, S: less than or equal to 0.010 percent, less than or equal to 0.003 percent of N, and the balance of Fe and inevitable impurities.
As an alternative embodiment, the metallographic structure of the steel is, in volume fractions: more than 95% of pearlite structure and 1-5% of ferrite structure.
The volume fraction of the ferrite structure is controlled to be 1-5%, the adverse effect of excessively large volume fraction is that the cementite structure which is not beneficial to drawing is easy to produce, and the adverse effect of excessively small volume fraction is that the strength of the drawn material can not meet the requirements of users.
The interlayer spacing of pearlite plates in the steel is 0.08-0.035 μm, and the sheet thickness of the steel for the large-span high-strength cable core is 0.14-0.18 μm.
The space between the layers is too large, the strength of the finished product is low, the space between the layers is too small, the strength of the finished product is high, and the yarn breakage rate is high
According to another exemplary embodiment of the present invention, there is provided a method for preparing a steel for a long-span high-strength cable core, the method including: high-quality molten iron → smelting in an LD (80 ton) converter → slag-stopping and tapping in the converter → deoxidation alloying in a ladle → LF (80 ton) ladle refining furnace → Si-Ca wire feeding → soft blowing of argon blowing at the bottom of the ladle → 160mm × 160mm square billet continuous casting machine → casting blank → heating of casting blank → rough rolling → medium rolling → water passing (primary controlled cooling) → finish rolling (controlled rolling) → water passing (secondary controlled cooling) → wire spinning → air cooling (tertiary controlled cooling) → coil gathering → PF line transportation → bundling → packaging transportation.
In actual use, the LD converter smelting main process parameters are as follows: volume after bricking: 58.5m 3 (ii) a Volume ratio [ V/T]:0.83; diameter of tap hole [ D in ]]:150mm; included angle of the steel tapping hole: 10 ° nozzle type: four-hole laval; diameter of throat: 31.86mm; outlet diameter: 41.05mm; the included angle between the spray hole and the center line of the oxygen lance is as follows: 12 ° 40'; mach number: 1.98 of; the working pressure of oxygen is 0.75-0.95 MPa; oxygen flow rate: 13000 to 16000m3/h; steel ladleThe material is as follows: adopts alumina-magnesia-carbon bricks and spinel castable.
The LF ladle refining furnace has the main technological parameters: one bottom-blown air brick is adopted to carry out bottom-blown refining (argon is used totally). Baking a steel ladle: a heat accumulating type baking device (using coke oven gas) is adopted. A refining system: blowing argon and feeding wires on line after the furnace; an 80-ton double-station LF ladle refining furnace has the heating capacity of 3-5 ℃/min and the power of 14MVA.
The main technological parameters of continuous casting are as follows: 6 basic arc radius of machine 6 flow billet caster: r10m; casting the section: 150mm × 150mm; length to length: 3.8 to 12m. Section: 150mm by 150mm. Pulling speed: 1.5-3 m/min, average 2.5m/min. A crystallizer: the length of the copper pipe is 1000mm. Vibration type of crystallizer: and (4) performing sinusoidal vibration. Frequency: 60 to 240 times/min. Amplitude + -5 mm. Liquid level automatic control mode: ce137 radioactive source. And (3) detection precision: plus or minus 3mm. Water flow rate of the crystallizer: 160m3/h. Electromagnetic stirring specification parameters: rated current of electromagnetic stirrer: 350A; rated voltage: 380V. Apparent power: 230KVA active power: 40KW (max) frequency: 2-8 Hz (6 Hz). Insulation grade: and (4) H level. Water flow rate of the crystallizer: 150m3/h. Infrared scale control system: detecting the length of the fixed length to be 9-12 m; the dummy bar form: a flexible chain dummy bar.
The control is that the superheat degree is required to be controlled at 25 ℃ during steel-making production; the casting blank C segregation index is less than or equal to 1.06; the loosening and shrinkage are required to be controlled within 0.5 grade. Heating the continuous casting billet by a heating furnace, rolling the continuous casting billet into a wire rod with the diameter of 5.5mm by a high-speed wire rod rolling mill, wherein the sorbite rate is required to be more than or equal to 95 percent, and the surface size precision is controlled according to C grade; meanwhile, the fluctuation of the head and tail tensile strength of the wire rod is controlled within 40MPa, and the tensile strength of the same circle is controlled within 30 MPa. The wire rod must not have the behavior of scratching and the like which is harmful to the surface quality of the wire rod during the bundling transportation process.
The reason for controlling the degree of superheat to be 25 ℃ is to obtain a casting blank with small carbon segregation degree, the adverse effect of overlarge temperature value is that the carbon segregation degree of the center of the casting blank is larger, the adverse effect of undersize is that the liquidity of molten steel is poor, and the freezing flow accident is easy to occur in the pouring process;
the reason for controlling the casting blank C segregation index to be less than or equal to 1.06 is to control the uniformity of carbon element, and the adverse effect of overlarge index value is that the performance fluctuation of the wire rod is too large.
The reason for controlling the porosity and the shrinkage cavity within the level of 0.5 is to ensure the compactness of the casting blank;
the reason for controlling the fluctuation of the head and tail tensile strength of the wire rod within 40MPa is to keep the performance of the wire rod stable, the adverse effect of overlarge fluctuation is that the structure control is unstable, the reason for controlling the same-circle tensile strength within 30MPa is to keep the performance consistency of the wire rod to the maximum, and the adverse effect of overlarge fluctuation is that the performance stability of a finished product is poor.
Specifically, a casting-time (full 18 furnace) DX55 is produced:
1. composition control
2. Quality control requirement and actual control in steel-making and continuous casting process
The method comprises the following steps: degree of superheat: less than or equal to 25 ℃; the casting blank C segregation index is less than or equal to 1.06; shrinkage and loosening: grade less than or equal to 0.5.
The actual production situation is as follows: in the smelting process, judging 2 furnaces because the superheat degree does not reach the standard, and judging 3 furnaces because the casting blank is unqualified; and sending the qualified 13 furnaces to a high-speed wire rod factory for rolling.
3. Steel rolling and cold control requirement and actual control
The method comprises the following steps: the fluctuation of the head and tail tensile strength of the wire rod is controlled within 40MPa, and the tensile strength of the same circle is controlled within 30 MPa; the sorbite rate is required to be more than or equal to 95 percent, and the surface size precision is controlled according to C grade.
Actually: the temperature control fluctuation of each link is within +/-5 ℃, the temperature difference between the edge part and the center part of the wire rod on the cooling control line is controlled within 10 ℃, and the phase change temperature rise is controlled within 10 ℃. The fluctuation of the head and tail tensile strength of the wire rod is controlled to be 20-36MPa, and the tensile strength of the same coil is controlled to be 18-27MPa.
The steel for a large-span high-strength cable core and the preparation method thereof according to the present invention will be described in detail with reference to examples, comparative examples and experimental data.
Example 1
The preparation method of the steel for the large-span high-strength cable core provided by the embodiment has the following conditions:
smelting in a converter:
molten iron conditions C of 4.25%, si of 0.56%, mn of 0.51%, P of 0.12%, S of 0.022%, temperature: 1318 deg.C.
The furnace charge structure: the adding amount of molten iron is 68.4 tons, and the adding amount of scrap steel is 4.4 tons.
Consumption of the first batch of dephosphorization residues: 850kg of lime and 1099kg of light-burned dolomite; 1900kg of Oryza glutinosa; the oxygen consumption is 880m3/N; blowing time: 238 seconds; semi-steel temperature: 1320 deg.C. Semi-steel slag sample: caO:42.09%, siO2:21.46%, TFe:11.71%, R:1.96. and (3) converter end point: c:0.14%, P:0.014%, S:0.018 percent. End point slag sample: caO:46.43%, siO2:13.44%, TFe:17.82%, R:3.46. the tapping temperature was 1610 ℃. Tapping time is 5 minutes and 21 seconds, and slag is 34mm later. And (3) deoxidation alloying: 6kg of micro-nitrogen carburant per ton of steel; 2kg of silicon, calcium and barium per ton of steel; 450kg of ferromanganese, 150kg of ferrosilicon and 110kg of carbon ferrochromium.
An LF ladle refining furnace:
910kg of lime; 112kg of refining slag; 145kg of submerged arc slag; 180kg of fluorite; 100kg of bauxite; 100kg of ferrosilicon powder; 1m of silicon-calcium line per ton of steel; the soft argon blowing flow is 65NL/min, and the time is 12 minutes and 30 seconds; and a [ o ] after refining is finished: 9.8ppm.
The continuous casting process comprises the following steps:
electromagnetic stirring parameters of the crystallizer: 380A, 4Hz; the water flow of the crystallizer is 120t/h, and the specific water amount of 0.75L/kg is selected for secondary cooling; the superheat degree of the tundish molten steel is 25 ℃; the pulling speed is 1.80m/min.
The carbon and nitrogen content of each station of DX55 is changed: converter (C: 0.15%; N: 0.0016%) → entering the LF furnace (C: 0.50%; N: 0.0017%) → exiting the LF furnace (C: 0.54%; N: 0.002%) → middle ladle (C: 0.54%; N: 0.0021%) → rolled bar (C: 0.54%; N: 0.0022%).
Example 2
The preparation method of the steel for the large-span high-strength cable core provided by the embodiment has the following conditions:
smelting in a converter:
molten iron conditions C4.15%, si 0.43%, mn 0.36%, P0.129%, S0.011%, temperature: 1288 ℃ is adopted.
The furnace charge structure: the adding amount of the molten iron is 69.1 tons, and the adding amount of the scrap steel is 5.1 tons.
Consumption of the first batch of dephosphorization residues: 1800kg of lime and 475kg of light-burned dolomite; 807kg of austenite ore; oxygen consumption is 900m3/N; blowing time: 242 seconds; the semisteel temperature: 1399 ℃. Semi-steel slag sample: caO:47.50%, siO2:20.41%, TFe:11.05%, R:2.31. and (3) finishing the converter: c:0.16%, P:0.012%, S:0.015 percent. End point slag sample: caO:52.53%, siO2:14.94%, TFe:13.42%, R:3.52. the tapping temperature was 1612 ℃. Tapping time is 5 minutes and 25 seconds, and 30mm is left after slag. Deoxidizing and alloying: 6kg of micro-nitrogen carburant per ton of steel; 2kg of silicon, calcium and barium per ton of steel; 440kg of ferromanganese, 155kg of ferrosilicon and 115kg of carbon ferrochrome.
An LF ladle refining furnace:
912kg of lime; 110kg of refining slag; 135kg of submerged arc slag; 150kg of fluorite; 110kg of bauxite; 90kg of ferrosilicon powder; 1m of silicon-calcium line per ton of steel; the soft argon blowing flow is 60NL/min, and the time is 11 minutes and 45 seconds; 7.8ppm of alpha [ o ] is discharged after refining.
The continuous casting process comprises the following steps:
electromagnetic stirring parameters of the crystallizer: 380A, 4Hz; the water flow of the crystallizer is 120t/h, and the specific water amount of 0.75L/kg is selected for secondary cooling; the superheat degree of the tundish molten steel is 29 ℃; the pulling speed is 1.82m/min.
Change of nitrogen content of DX55 stations: converter (C: 0.16%, N: 0.0018%) → into the LF (C: 0.53%, N: 0.0020%) → out of the LF (C: 0.54%, N: 0.0022%) → middle ladle (C: 0.55%, N: 0.0016%) → rolled product (C: 0.55%, N: 0.0025%).
Example 3
The preparation method of the steel for the large-span high-strength cable core provided by the embodiment has the following conditions:
smelting in a converter:
the molten iron conditions comprise 4.23% of C, 0.56% of Si, 0.51% of Mn, 0.12% of P, 0.025% of S and the following temperature: 1320 deg.C.
The furnace charge structure: the adding amount of the molten iron is 68.4 tons, and the adding amount of the scrap steel is 4.4 tons.
Consumption of dephosphorization residues in the first batch: 850kg of lime and 1099kg of light-burned dolomite; 1900kg of Oryza glutinosa; the oxygen consumption is 880m3/N; blowing time: 238 seconds; the semisteel temperature: 1320 deg.C. Semi-steel slag sample: caO:44.66%, siO2:20.16%, TFe:13.36%, R:2.22. and (3) converter end point: c:0.15%, P:0.012%, S:0.018 percent. End point slag sample: caO:48.78%, siO2:15.22%, TFe:13.01%, R:3.21. the tapping temperature was 1615 ℃. Tapping time is 5 minutes and 09 seconds, and slag is 39mm later. And (3) deoxidation alloying: 6kg of micro-nitrogen carburant per ton of steel; 2kg of silicon, calcium and barium per ton of steel; 450kg of ferromanganese, 150kg of ferrosilicon and 110kg of carbon ferrochromium.
An LF ladle refining furnace:
880kg of lime; 1102kg of refining slag; 150kg of submerged arc slag; 170kg of fluorite; 110kg of bauxite; 120kg of ferrosilicon powder; 1m of silicon-calcium line per ton of steel; the soft argon blowing flow rate is 66NL/min, and the time is 11 minutes and 23 seconds.
The continuous casting process comprises the following steps:
electromagnetic stirring parameters of the crystallizer: 380A, 4Hz; the water flow of the crystallizer is 120t/h, and the specific water amount of 0.75L/kg is selected for secondary cooling; the superheat degree of the tundish molten steel is 25 ℃; the pulling speed is 1.81m/min.
Change of nitrogen content of DX55 stations: a converter (C: 0.15%, N: 0.0022%) → into an LF furnace (C: 0.54%, N: 0.0025%) → out of the LF furnace (C: 0.54%, N: 0.0026%) → middle ladle (C: 054%, N: 0.0028%) → rolled stock (C: 0.54%, N: 0.0030%).
Example 4
The preparation method of the steel for the large-span high-strength cable core provided by the embodiment has the following conditions:
smelting in a converter:
molten iron conditions C of 4.2%, si of 0.56%, mn of 0.51%, P of 0.12%, S of 0.022%, temperature: 1318 ℃.
The furnace charge structure: the adding amount of molten iron is 68.4 tons, and the adding amount of scrap steel is 4.4 tons.
Consumption of the first batch of dephosphorization residues: 850kg of lime and 1099kg of light-burned dolomite; 1810kg of Orite; oxygen consumption is 870m3/N; blowing time: 238 seconds; the semisteel temperature: 1320 deg.C. Semi-steel slag sample: caO:42.09%, siO2:21.46%, TFe:11.71%, R:1.96. and (3) converter end point: c:0.14%, P:0.014%, S:0.018 percent. End point slag sample: caO:46.43%, siO2:13.44%, TFe:17.82%, R:3.46. the tapping temperature was 1618 ℃. Tapping time is 5 minutes and 21 seconds, and slag is 34mm later. Deoxidizing and alloying: 6kg of micro-nitrogen carburant per ton of steel; 2kg of silicon, calcium and barium per ton of steel; 450kg of ferromanganese, 150kg of ferrosilicon and 110kg of carbon ferrochromium.
An LF ladle refining furnace:
910kg of lime; 112kg of refining slag; 145kg of submerged arc slag; 180kg of fluorite; 100kg of bauxite; 100kg of ferrosilicon powder; 1m of silicon-calcium line per ton of steel; the soft argon blowing flow rate is 65NL/min, and the time is 12 minutes and 30 seconds.
The continuous casting process comprises the following steps:
electromagnetic stirring parameters of the crystallizer: 380A, 4Hz; the water flow of the crystallizer is 120t/h, and the secondary cooling adopts 0.75L/kg of specific water; the superheat degree of the tundish molten steel is 35 ℃; the pulling speed is 1.85m/min.
Nitrogen content variation of DX55 stations: a converter (C: 0.14%, N: 0.0023%) → entering an LF furnace (C: 0.53%, N: 0.0026%) → exiting the LF furnace (C: 0.53%, N: 0.0028%) → middle ladle (C: 0.54%, N: 0.0030%) → rolled stock (C: 0.55%, N: 0.0030%).
Comparative examples 1 to 3
Three types of steel for cable cores are randomly available from the market.
Examples of the experiments
The steels obtained in examples 1 to 4 and comparative examples 1 to 2 were examined and the results are shown in the following tables.
From the above table, the wire rod prepared by the method provided by the embodiment of the invention can be directly drawn from phi 5.5mm to phi 1.0-1.3mm without heat treatment in the middle, and the tensile strength of the galvanized steel strand of the cable can reach 1600-1800Mpa.
One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:
(1) According to the steel provided by the embodiment of the invention, the purity is improved, the contents of O, N, P and S in the wire rod are reduced, and the deformability of the wire rod is improved, so that a user can perform forced large-deformation drawing without heat treatment, the steel can be directly drawn from phi 5.5mm to phi 1.0-1.3mm, the tensile strength of a finished steel wire is improved, and the tensile strength of a galvanized steel strand of a cable can reach 1600-1800MPa;
(2) The method provided by the embodiment of the invention improves the quality of the original steel wire rod and the machinability, the produced wire rod can be directly drawn from phi 5.5mm to phi 1.0-1.3mm without heat treatment in the middle, and the tensile strength of the wire rod can reach 1600-1800MPa. The bearing capacity of the cable is improved, the weight cannot be increased, and meanwhile, the steel material is designed and is medium-high carbon steel. On the premise of not upgrading and reconstructing downstream user processing equipment, the steel stranded wire for the cable core of the large-span high-voltage transmission line can be produced.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (5)
1. The utility model provides a large-span high strength steel for cable core which characterized in that, the chemical composition of steel includes with mass fraction: c:0.54 to 0.56 percent of Si, 0.17 to 0.25 percent of Mn, less than or equal to 0.012 percent of P, S: not more than 0.010 percent, not more than 0.003 percent of N, and the balance of Fe and inevitable impurities, wherein the metallographic structure of the steel is calculated by volume fraction: more than 95% of pearlite structure, 1-5% of ferrite structure and 0.08-0.35 mu m of pearlite interlamellar spacing, wherein in the preparation process of the steel, the C segregation index of a billet is controlled to be less than or equal to 1.06, the loose shrinkage cavity of the billet is controlled within 0.5 grade, the sorbite rate of a wire rod is controlled to be more than or equal to 95%, the fluctuation of the tensile strength of the head part and the tail part of the wire rod is controlled to be within 40MPa, and the same-circle tensile strength of the wire rod is controlled to be within 30 MPa.
2. The steel for a large-span high-strength cable core according to claim 1, wherein the chemical composition of the steel comprises, in mass fraction: c:0.55 percent of Si, 0.19 to 0.23 percent of Mn, less than or equal to 0.012 percent of P, S: less than or equal to 0.010 percent, less than or equal to 0.003 percent of N, and the balance of Fe and inevitable impurities.
3. A method for preparing the steel for the large-span high-strength cable core according to any one of claims 1 to 2, wherein the method comprises:
smelting molten iron in a converter;
refining the molten iron smelted by the converter to obtain molten steel;
continuously casting the molten steel to obtain a steel billet;
and rolling the steel billet by a wire mill to obtain the wire rod of the steel for the large-span high-strength cable core.
4. The method for preparing the steel for the large-span high-strength cable core according to claim 3, wherein the superheat degree of the molten steel is 20-30 ℃ when the molten steel is continuously cast.
5. The method for preparing the steel for the large-span high-strength cable core according to claim 3, wherein the surface dimensional accuracy of the wire rod is controlled according to C grade.
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