CN112176242A - Production method of 650 MPa-level ultrahigh-strength steel bar - Google Patents
Production method of 650 MPa-level ultrahigh-strength steel bar Download PDFInfo
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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
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
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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
- 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
- C21D8/08—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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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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- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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Abstract
The application discloses a production method of a 650 MPa-level ultrahigh-strength steel bar, which comprises smelting and rolling; the invention adopts a production process combining vanadium-nitrogen microalloying and controlled rolling and controlled cooling technologies, wherein a novel molten steel nitrogen increasing process is adopted for smelting, so that sufficient nitrogen is ensured to be combined with vanadium microalloy elements to generate sufficient amount of two-phase particles which are dispersedly distributed to play a stronger role in precipitation strengthening; the rolling adopts a new technology of full-flow high-precision temperature-control rolling and temperature-control cooling, so that the addition of precious micro-alloy elements is effectively reduced, the low-temperature toughness and the welding performance of the product are improved, the energy-saving, environment-friendly and green production of 650MPa grade ultrahigh-strength steel bars is realized, a new breakthrough in industrial production is realized on the basis of the existing 600MPa grade ultrahigh-strength steel bars, and the method has great significance in promoting the material-saving, energy-saving and sustainable development of the construction industry.
Description
Technical Field
The invention relates to the technical field of steel bar production, in particular to a production method of 650 MPa-level ultrahigh-strength steel bars.
Background
Building construction and civil engineering, mainly with reinforced concrete structure as the main material, wherein the hot rolling ribbed steel bar is the main raw material, its quality directly influences the quality of the engineering construction, relate to public safety and personal property safety, the building industry is the largest industry of consumption of steel, also is the largest industry of resource consumption at the same time; therefore, the popularization and application of the high-strength steel bars and the ultrahigh-strength steel bars and the reduction of the consumption of construction steel are development directions of metallurgical industry and construction industry, and in recent years, under the joint efforts of steel enterprises, government departments and scientific research institutes, the high-strength steel bars of 400MPa, 500MPa and 600MPa levels have been successively developed, so that the updating and upgrading of steel bar products are promoted.
According to calculation, in the construction project, the 650 MPa-grade steel bar is used for replacing the 400 MPa-grade steel bar, so that the using amount of steel can be saved by about 30 percent; the 650 MPa-grade steel bar is used for replacing the 500 MPa-grade steel bar, so that the use amount of steel can be saved by about 10 percent; the 650 MPa-grade reinforcing steel bar is used for replacing the 600 MPa-grade reinforcing steel bar, so that the use amount of steel can be saved by about 3%, the important significance is achieved for greatly promoting energy conservation and emission reduction and improving the energy-saving result of the construction industry, the reinforcing steel bar product with higher strength grade is developed, strategic resources such as ores, alloys and energy sources are saved, the environmental pollution is reduced, the inevitable requirements for the sustainable development of the steel industry and the construction industry are met, and therefore, the production method of the 650 MPa-grade ultrahigh-strength reinforcing steel bar is provided for solving the problems.
Disclosure of Invention
The application provides a production method of 650 MPa-level ultrahigh-strength steel bars, and solves the problems that traditional low-strength steel wastes steel when applied, traditional high-strength steel is high in production cost, iron ore, coke and lime are consumed greatly, and the service life of a converter is short.
The application provides a production method of a 650 MPa-level ultrahigh-strength steel bar, which comprises smelting and rolling, wherein the smelting is carried out according to the following processes:
s1, obtaining blast furnace molten iron by blast furnace ironmaking;
s2, adding scrap steel into the converter, and adding dolomite and lime according to the content of P, S in blast furnace molten iron;
s3, injecting blast furnace molten iron into the converter, wherein the molten iron accounts for 89-91 parts, and the scrap steel accounts for 9.7-10.3 parts;
s4, smelting for 25-35 minutes, wherein the blowing time is 12-18 minutes, and obtaining molten steel;
s5, controlling molten steel components during tapping: c is more than or equal to 0.08 percent, S is less than or equal to 0.030 percent, and P is less than or equal to 0.030 percent;
s6, ensuring bottom blowing of Ar to the steel ladle in the tapping process, simultaneously adding silicon-manganese alloy, silicon-nitrogen alloy, carburant and vanadium-nitrogen alloy, ensuring that molten steel does not leak naked after Ar gas flow and pressure are discharged, and measuring and sampling after blowing Ar3 minutes after tapping; controlling the temperature to be 1570-1590 ℃ after argon blowing, adding vanadium-nitrogen alloy and silicon nitride for component adjustment according to the sampling analysis result of C0.22-0.25%, Si 0.40-0.60%, Mn 1.40-1.50%, P less than or equal to 0.030%, S less than or equal to 0.030%, V0.12-0.18% and N more than or equal to 0.0170%, and blowing Ar for less than 8 minutes while stirring weakly;
s7, tapping time is 3.0-5.0 minutes, oxygen content of molten steel is less than 30ppm, continuous casting flow number is 6 or 8, drawing speed is 2.5-3.0m/min, whole-process protective casting is adopted in the continuous casting process, and casting blank size is 165mm x 12000 mm;
the rolling is produced according to the following process:
s1, heating the casting blank to 1010-1130 ℃, wherein the casting blank is cooled to 1080 +/-50 ℃ and the casting blank is heated to 1060 +/-50 ℃;
s2, soaking to 1150 +/-50 ℃ after heating;
s3, roughly rolling the heated casting blank at 1050 +/-50 ℃ at the speed of 2-3 m/S, and then carrying out medium rolling;
s4, performing finish rolling on the medium-rolled casting blank at 950 +/-30 ℃ and at the speed of 12-17 m/S by controlling a cooling water tank;
and S5, cooling the finished steel bars after finish rolling to 850 +/-20 ℃ in a grading manner, and then air-cooling the finished steel bars on a cooling bed to room temperature.
Preferably, the molten iron comprises, by mass, 4.0-5.5% of C, 0.20-0.70% of Si, 0.20-0.40% of Mn, not more than 0.070% of P, not more than 0.040% of S, and the balance of Fe and inevitable impurities.
Preferably, the temperature of the molten iron is more than or equal to 1250 ℃.
Preferably, the rolling adopts a controlled rolling process.
Preferably, the cooling is a staged cooling control process.
Preferably, the converter oxygen lance for blowing adopts a 5-hole nozzle, and the included angle is 12.5-14 degrees.
Preferably, the staged cooling process is: strong cold-red return-medium cold-red return-weak cold-red return.
According to the technical scheme, the production method of the 650 MPa-grade ultrahigh-strength steel bar is characterized in that waste steel, dolomite and lime are added into a converter, blast furnace molten iron is added, impact and scouring on converter refractory materials are reduced, a smelting period is 30 minutes, a converter oxygen lance is used for blowing for 15 minutes, sampling analysis is carried out at the later stage of smelting, the end point components are controlled to be more than or equal to 0.08 percent of C, less than or equal to 0.030 percent of S and less than or equal to 0.030 percent of P, Ar blowing at the bottom of the steel ladle is ensured in the steel tapping process, the added alloy is ensured to be melted uniformly, the flow and pressure of Ar after steel tapping ensure that molten steel is not leaked in the air, temperature measurement and sampling are carried out after Ar blowing for 3 minutes after steel tapping, the temperature after Ar blowing is controlled to be 1570-1590.25 percent, 0.40-0.60 percent of Si, 1.40-1.50 percent of Mn, less than or equal to 0.030 percent of P, less than or equal to 0.030 percent of S, 0., n is more than or equal to 0.0170 percent, vanadium-nitrogen alloy and silicon nitride are added according to target components, a proper amount of vanadium-nitrogen alloy is adopted for microalloy strengthening, silicon nitride is added for nitrogen increasing at the same time, sufficient nitrogen and vanadium microalloy elements are guaranteed to be combined to generate enough dispersed and distributed two-phase particles to play a role in precipitation strengthening, the content of harmful elements such as P, S and the like is strictly controlled, the tapping time is 3.0-5.0 minutes, the continuous casting flow number is 6 or 8 flows, the drawing speed is 2.5-3.0m/min, the casting size is 165mm 12000mm, a stepping heating furnace is adopted to heat a casting blank to 1080 ℃, rough rolling and medium rolling are carried out at the speed of 2-3 m/s, a cooling process is controlled before finish rolling, the finish rolling inlet temperature is guaranteed to be 950 +/-30 ℃, finish rolling is carried out, the casting blank is cooled to 850 ℃ in a three-stage, and then an upper cooling bed is carried.
Compared with the prior art, the invention has the beneficial effects that:
1. a proper amount of vanadium-nitrogen alloy is adopted for microalloy strengthening, and silicon nitride is added for nitrogen increasing, so that sufficient nitrogen is ensured to be combined with vanadium microalloy elements to generate sufficient dispersed two-phase particles for precipitation strengthening, and the content of harmful elements such as P, S and the like is strictly controlled;
2. by adopting the design of the controlled rolling and controlled cooling process, the effects of dispersion precipitation strengthening and fine grain strengthening of two-phase particles such as carbonitride and the like are fully exerted, the strength of the steel bar is further improved, and the design target requirements of various mechanical property indexes of the steel bar are met;
3. fully refining austenite grains through heating, repeated deformation recrystallization for multiple times in a high-temperature deformation recrystallization region;
4. in the non-recrystallization zone, the refined austenite grains are fully deformed through multi-pass rolling so as to generate a large amount of dislocation substructures and deformation zones in the austenite grains, thereby creating conditions for a large amount of nucleation of ferrite grains in gamma → alpha phase transition and achieving the purpose of fully refining the ferrite grains;
5. in a (gamma + alpha) two-phase region in the phase transformation process, on one hand, ferrite grains generated by phase transformation are fully deformed, a large number of dislocation substructures are introduced, and the strengthening effect of the dislocation substructures is improved; on the other hand, the microalloy elements are subjected to strain-induced dispersion precipitation on ferrite grains through deformation, so that the precipitation strengthening effect of V-carbonitride precipitated particles is improved.
In conclusion, the invention adopts a production process combining vanadium-nitrogen microalloying and controlled rolling and controlled cooling technologies, wherein a novel molten steel nitrogen increasing process is adopted for smelting, so that sufficient nitrogen is ensured to be combined with vanadium microalloying elements to generate enough amount of two-phase particles which are dispersedly distributed to play a stronger role in precipitation strengthening; the rolling adopts a new technology of full-flow high-precision temperature-control rolling and temperature-control cooling, so that the addition of precious micro-alloy elements is effectively reduced, the low-temperature toughness and the welding performance of the product are improved, the energy-saving, environment-friendly and green production of 650MPa grade ultrahigh-strength steel bars is realized, a new breakthrough in industrial production is realized on the basis of the existing 600MPa grade ultrahigh-strength steel bars, and the method has great significance in promoting the material-saving, energy-saving and sustainable development of the construction industry.
Detailed Description
In order to make the technical solutions in the present application better understood by those skilled in the art, the technical solutions in the embodiments of the present application are clearly and completely described below.
A production method of 650 MPa-level ultrahigh-strength steel bars comprises smelting and rolling, wherein the smelting is produced according to the following processes:
s1, obtaining blast furnace molten iron by blast furnace ironmaking, sampling and detecting the blast furnace molten iron after obtaining the blast furnace molten iron to obtain the contents of C, Si, Mn, P and S in the molten iron, wherein the temperature of the molten iron is more than or equal to 1250 ℃;
s2, adding scrap steel into the converter, adding dolomite and lime according to the content of P, S in blast furnace molten iron, reducing the scouring of the converter when the molten iron is directly added, and prolonging the service life of the converter body, wherein the absorptivity of Mn element is 90-95%, the absorptivity of Si element is 75-80%, and the absorptivity of V element is 95%;
wherein the lime is added in an amount of [ Si ═ Si]％Molten iron2.14R (yield strength) iron water charge 1000/CaO%Effective in treating lime；
Wherein the silicon manganese alloy addition amount is (target value-residual value) 1000 tapping amount/(alloy content) alloy recovery rate;
s3, injecting blast furnace molten iron into the converter, wherein the molten iron is 135 +/-2 t, and the scrap steel is 15 +/-1 t;
s4, carrying out a smelting period of 30 minutes, wherein the converting time is 15 minutes, the converter oxygen lance for converting adopts a 5-hole nozzle, the included angle is 12.5-14 degrees, slag is generated during slag splashing, impurities are oxidized into gas to escape or into oxides to form slag with added flux, and the purity is improved to obtain molten steel;
s5, controlling molten steel components during tapping: c is more than or equal to 0.08 percent, S is less than or equal to 0.030 percent, P is less than or equal to 0.030 percent, and the content of harmful elements such as P, S and the like is strictly controlled;
s6, ensuring bottom blowing of Ar to the steel ladle in the tapping process, simultaneously adding silicon-manganese alloy, silicon-nitrogen alloy, carburant and vanadium-nitrogen alloy, ensuring that molten steel does not leak naked after Ar gas flow and pressure are discharged, and measuring and sampling after blowing Ar3 minutes after tapping; controlling the temperature to be 1570-1590 ℃ after argon blowing, supplementing vanadium-nitrogen alloy and silicon nitride powder into an argon blowing station for component adjustment according to the sampling analysis result of C0.22-0.25%, Si 0.40-0.60%, Mn 1.40-1.50%, P less than or equal to 0.030%, S less than or equal to 0.030%, V0.12-0.18% and N more than or equal to 0.0170%, blowing Ar for weak stirring for more than 3 minutes, and simultaneously requiring the Ar blowing time to be not less than 8 minutes, fully playing the roles of dispersion precipitation strengthening and fine grain strengthening of two-phase particles such as carbonitride and the like, further improving the strength of the steel bar, and meeting the design target requirements of various mechanical property indexes of the steel bar;
s7, tapping time is 3.0-5.0 minutes, oxygen content of molten steel is less than 30ppm, continuous casting flow number is 6 or 8, pulling speed is 2.5-3.0m/min, whole-process protective casting is adopted in the continuous casting process, covering agents are added into a steel ladle and a middle ladle, protective slag is added into a crystallizer, a steel ladle sleeve and a crystallizer submerged nozzle are adopted to prevent molten steel from being oxidized, purity of the molten steel is ensured, and size of a casting blank is 165mm, 12000 mm;
| heat of furnace | Temperature of continuous casting ladle | The temperature of the middle ladle is lower | Pulling speed (m/min) |
| Number of start-up heat | 1610-1625 | 1540-1560 | 2.5-2.8 |
| Normal heat number | 1570-1585 | 1525-1540 | 2.6-3.0 |
The rolling is produced according to the following process:
s1, heating the casting blank to 1010-; when the hot charging is 1060 +/-50 ℃ and the temperature of the billet is above 400 ℃, the continuous casting billet is normally and continuously sent to a steel rolling heating furnace for production;
s2, soaking to 1150 +/-50 ℃ after heating, and fully refining austenite grains through multi-pass repeated deformation recrystallization in a high-temperature deformation recrystallization zone, wherein large-amplitude fluctuation is not allowed, and the highest furnace temperature is not allowed to exceed 1200 ℃;
s3, roughly rolling the heated casting blank at 1080 ℃ and 2-3 m/S, then carrying out medium rolling, and in a non-recrystallization region, fully deforming the refined austenite grains through multi-pass rolling so as to generate a large amount of dislocation substructures and deformation bands in the austenite grains, creating conditions for a large amount of nucleation of the ferrite grains in gamma → alpha phase transition, and achieving the purpose of fully refining the ferrite grains; on the other hand, the microalloy elements are subjected to strain-induced dispersion precipitation on ferrite grains through deformation, the precipitation strengthening effect of V carbonitride precipitated particles is improved, and head cutting treatment is carried out in the rolling process;
s4, performing finish rolling on the medium-rolled casting blank through a controlled cooling water tank at 950 +/-30 ℃ and at the speed of 12-17 m/S, wherein the rolling process adopts a controlled rolling process, and the controlled rolling and controlled cooling process design is adopted, so that the effects of dispersion precipitation strengthening and fine grain strengthening of two-phase particles such as carbonitride and the like are fully exerted, the strength of the steel bar is further improved, and the design target requirements of various mechanical property indexes of the steel bar are met;
sizing and multiple length parameters:
s5, cooling finished steel bars after finish rolling to 850 +/-20 ℃ in a grading manner, then cooling the finished steel bars to room temperature in an air cooling mode on a cooling bed, wherein the cooling process adopts a grading cooling control process, the detail steps of grading cooling include 3 grades, strong cooling, red returning, middle cooling, red returning, weak cooling and red returning, the temperature range and time of each grade (due to continuous production, the time is determined by the length of a water tank and the rolling speed, the length of the water tank of each grade can be adjusted according to parameters such as the amount of water of a switch nozzle and the like required), and the temperature of the cooling bed is accurately controlled to 850 +/-20 ℃;
when the chemical components of the steel billet or the mechanical property of the finished product is lower, the temperature is controlled according to the middle and lower limits;
after the reinforcing steel bar is cooled to normal temperature in air, detecting;
metallographic structure: ferrite, pearlite and a small amount of bainite which is dispersedly distributed, the grain size is 10-12 grade, and no martensite and other hard phase harmful tissues exist; the Vickers hardness of the section is uniform, and the range is not more than 40 HV;
the yield strength Rel 665-715 MPa, the tensile strength Rm 820-1000 MPa, the elongation after fracture A15-25%, the maximum total force elongation Agt 10-13%, Rm0/Rel0≥1.30，Rel0Rel is less than or equal to 1.15 (note: Rm)0Measured tensile strength, Rel, for the reinforcement0The yield strength of the steel bar under actual measurement) completely meets the requirements of the design target value of the mechanical property and each index of the seismic performance of the steel bar.
In the invention, the molten iron comprises the following components, by mass, 4.0-5.5% of C, 0.20-0.70% of Si, 0.20-0.40% of Mn, less than or equal to 0.070% of P, less than or equal to 0.040% of S, and the balance of Fe and inevitable impurities, wherein molten iron with the impurity content exceeding P, S and the like is subjected to molten iron pretreatment in advance.
According to the technical scheme, during production, waste steel, dolomite and lime are added into a converter, blast furnace molten iron is added, impact and scouring on refractory materials of the converter are reduced, a smelting period is 30 minutes, blowing time is 15 minutes by using an oxygen lance of the converter, sampling analysis is carried out at the later smelting stage, end-point components are controlled to be more than or equal to 0.08 percent of C, less than or equal to 0.030 percent of S and less than or equal to 0.030 percent of P, bottom blowing Ar to steel ladle in the tapping process is guaranteed, the added alloy is guaranteed to be melted uniformly, the flow and pressure of Ar after tapping ensure that molten steel does not leak in air, temperature measurement and sampling are carried out after blowing Ar for 3 minutes after tapping, the temperature after blowing Ar is controlled to 1570-1590 ℃, according to the primary sampling analysis result, C is controlled to be 0.22-0.25 percent, Si is controlled to be 0.40-0.60 percent, Mn is controlled to be 1.40-1.50 percent, P is less than or equal to 0.030 percent, S is less than or equal to 0.030 percent, silicon nitride, a proper amount of vanadium-nitrogen alloy is adopted for microalloy strengthening, and simultaneously silicon nitride is added for nitrogen increase to ensure that sufficient nitrogen is combined with vanadium microalloy elements to generate enough dispersed and distributed two-phase particles to play a role in precipitation strengthening, the content of harmful elements such as P, S and the like is strictly controlled, the tapping time is 3.0-5.0 minutes, the number of continuous casting flows is 6 or 8, the continuous casting flows are heated to 1080 ℃ at the drawing speed of 2.5-3.0m/min, the casting size is 165mm x 12000mm, the casting blank is roughly and intermediately rolled at the speed of 2-3 m/s by adopting a stepping heating furnace, a cooling process is controlled before finish rolling to ensure the finish rolling inlet temperature to be 950 +/-30 ℃, finish rolling is carried out, three-stage cooling is carried out to 850 ℃ after finishing rolling, and then the casting blank is air-cooled to room temperature on a cooling bed.
Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims.
It will be understood that the present application is not limited to the precise arrangements that have been described above and that various modifications and changes may be made without departing from the scope thereof. The above-described embodiments of the present application do not limit the scope of the present application.
Claims (6)
1. The production method of the 650 MPa-grade ultrahigh-strength steel bar is characterized by comprising smelting and rolling, wherein the smelting is produced according to the following processes:
s1, obtaining blast furnace molten iron by blast furnace ironmaking;
s2, adding scrap steel into the converter, and adding dolomite and lime according to the content of P, S in blast furnace molten iron;
s3, injecting blast furnace molten iron into the converter, wherein the molten iron accounts for 89-91 parts, and the scrap steel accounts for 9.7-10.3 parts;
s4, smelting for 25-35 minutes, wherein the blowing time is 12-18 minutes, and obtaining molten steel;
s5, controlling molten steel components during tapping: c is more than or equal to 0.08 percent, S is less than or equal to 0.030 percent, and P is less than or equal to 0.030 percent;
s6, ensuring bottom blowing of Ar to the steel ladle in the tapping process, simultaneously adding silicon-manganese alloy, silicon-nitrogen alloy, carburant and vanadium-nitrogen alloy, ensuring that molten steel does not leak naked after Ar gas flow and pressure are discharged, and measuring and sampling after blowing Ar3 minutes after tapping; controlling the temperature to be 1570-1590 ℃ after argon blowing, adding vanadium-nitrogen alloy and silicon nitride for component adjustment according to the sampling analysis result of C0.22-0.25%, Si 0.40-0.60%, Mn 1.40-1.50%, P less than or equal to 0.030%, S less than or equal to 0.030%, V0.12-0.18% and N more than or equal to 0.0170%, and blowing Ar for less than 8 minutes while stirring weakly;
s7, tapping time is 3.0-5.0 minutes, oxygen content of molten steel is less than 30ppm, continuous casting flow number is 6 or 8, drawing speed is 2.5-3.0m/min, whole-process protective casting is adopted in the continuous casting process, and casting blank size is 165mm x 12000 mm;
the rolling is produced according to the following process:
s1, heating the casting blank to 1010-1130 ℃, wherein the casting blank is cooled to 1080 +/-50 ℃ and the casting blank is heated to 1060 +/-50 ℃;
s2, soaking to 1150 +/-50 ℃ after heating;
s3, roughly rolling the heated casting blank at 1050 +/-50 ℃ at the speed of 2-3 m/S, and then carrying out medium rolling;
s4, performing finish rolling on the medium-rolled casting blank at 950 +/-30 ℃ and at the speed of 12-17 m/S by controlling a cooling water tank;
and S5, cooling the finished steel bars after finish rolling to 850 +/-20 ℃ in a grading manner, and then air-cooling the finished steel bars on a cooling bed to room temperature.
2. The method for producing the 650 MPa-grade ultrahigh-strength steel bar according to claim 1, wherein the molten iron comprises, by mass, 4.0-5.5% of C, 0.20-0.70% of Si, 0.20-0.40% of Mn, 0.070% or less of P, 0.040% or less of S, and the balance of Fe and inevitable impurities.
3. The method for producing the 650MPa grade ultra-high strength steel bar according to claim 2, wherein the temperature of the molten iron is more than or equal to 1250 ℃.
4. The method of claim 1, wherein said rolling is performed by a controlled rolling process.
5. The method of claim 1, wherein the cooling is performed by a staged cooling control process.
6. The method for producing the 650MPa grade ultra-high strength steel bar according to claim 1, wherein the converter oxygen lance for blowing adopts a 5-hole nozzle, and the included angle is 12.5-14 degrees.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113416884A (en) * | 2021-06-07 | 2021-09-21 | 宁夏建龙龙祥钢铁有限公司 | Production method of high-ductility corrosion-resistant steel bar |
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