CN111074157A - Preparation method of low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bar - Google Patents

Preparation method of low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bar Download PDF

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CN111074157A
CN111074157A CN202010028735.0A CN202010028735A CN111074157A CN 111074157 A CN111074157 A CN 111074157A CN 202010028735 A CN202010028735 A CN 202010028735A CN 111074157 A CN111074157 A CN 111074157A
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steel
balance
inevitable impurities
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temperature
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CN111074157B (en
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陈伟
张卫强
陈必胜
武天寿
吴光耀
曹云
杨春雷
张瑜
王忠宇
刘林刚
陈爱林
李金柱
杨凯
苏灿东
舒云胜
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Wuhan Iron and Steel Group Kunming Iron and Steel Co Ltd
Yunnan Titanium Industry Co Ltd
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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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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
    • C21D2211/001—Austenite
    • 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
    • C21D2211/002—Bainite
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

The invention discloses a preparation method of a low-niobium microalloyed HRB400E ultrafine grain high-toughness anti-seismic steel bar, wherein the method adopts lower heating temperature and start rolling temperature for steel rolling, refines original austenite grains, promotes the refinement of ferrite grains when austenite is converted into ferrite, has grain size reaching more than 11.0 grade, has obvious fine grain strengthening effect and improves the ductility and toughness of steel; the ferrocolumbium is added into the steel, the lower initial rolling temperature is controlled, and the multi-section low-water-pressure grading controlled cooling process after rolling is adopted, so that the driving force for Nb (C, N) precipitation is increased, and a large amount of fine and dispersed second phases are precipitated on a low-temperature ferrite matrix, a crystal boundary and a dislocation line, so that the ferrite matrix is strengthened, the strength of the steel is obviously improved, and the performances of the steel, such as welding, aging and the like, are improved; granular bainite with the content of 2-5% is formed at the central part of the cross section of the steel bar, the dislocation density is higher, the tensile strength of the steel can be obviously improved, and the anti-seismic performance is improved; the process has the characteristics of low production cost, strong process applicability and controllability and the like.

Description

Preparation method of low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bar
Technical Field
The invention relates to a preparation method of a low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar, and also relates to a preparation method of a nitrogen-rich niobium microalloyed 400MPa ultrafine-grained anti-seismic steel bar.
Background
Hot rolled ribbed bars are the primary reinforcing material for reinforced concrete building structures, carrying stress and strain loads in the structure, such as tensile, compressive and strain loads. At present, the annual output of hot-rolled ribbed steel bars in China is about 2 hundred million tons, and the hot-rolled ribbed steel bars are steel materials which are most used for the construction of national economic building engineering structures. With the continuous development of buildings in China towards high-rise, large-span and anti-seismic structures, the development of fine-grained anti-seismic steel bars with high toughness and excellent comprehensive performance is one of the important tasks of improving the technical level and adjusting the product structure in the steel industry.
With the continuous upgrading of building structures in recent years, the strength of steel is continuously improved, and the upgrading and updating of the reinforcing steel bars for buildings and the modification and perfection of product standards are promoted. The national standard GB/T1499.2-2018 of the hot-rolled ribbed steel bar is formally implemented in 2018, 11/1.2018, the new standard adds metallographic structure inspection regulations and a matched macroscopic metallographic structure, section Vickers hardness and microstructure inspection method, makes stricter and more definite regulations on steel bar performance, quality inspection and judgment, puts higher and stricter requirements on the production process, and has a positive propulsion effect on improving the quality of the hot-rolled ribbed steel bar product, promoting energy conservation and emission reduction and eliminating the backward capacity.
After the GB/T1499.2-2018 standard is implemented, domestic main hot-rolled ribbed steel bar production enterprises basically adopt a vanadium microalloying process to produce straight ribbed steel bars, and simultaneously, through optimizing chemical component control and a rolling process, the Vickers hardness of macroscopic metallographic phase, microstructure and section of the steel bars is ensured to meet the new standard inspection requirements. The HRB400E is produced by adopting a vanadium microalloying process, a certain amount of vanadium-nitrogen alloy or nitrided ferrovanadium is added into steel, and the vanadium alloy is expensive, so that the production cost is higher, and the reduction of the production cost of a reinforcing steel bar enterprise and the improvement of the market competitiveness of a product are not facilitated.
At present, related research reports of HRB400E straight anti-seismic steel bar production technology after GB/T1499.2-2018 standard implementation exist in China, but a vanadium-nitrogen microalloying process is mainly adopted, the content of V in steel is controlled to be 0.025-0.035wt%, HRB400E steel bars with macroscopic metallographic phase, section Vickers hardness and microstructure meeting GB/T1499.2-2018 standard are obtained through a proper controlled rolling and controlled cooling process, and the grain size of the microstructure of the steel bars is mostly controlled to be 9.5-10.5 grade. At present, no research report of the preparation method of the low-niobium (Nb is less than or equal to 0.019wt%) microalloyed HRB400E ultrafine grain high-toughness anti-seismic reinforcing steel bar adopted by the invention exists in China, and no research report of the preparation method of the nitrogen-rich niobium microalloyed 400MPa ultrafine grain anti-seismic reinforcing steel bar adopted by the invention exists.
Disclosure of Invention
Aiming at the situation that the production cost of HRB400E steel bars produced by adopting a vanadium microalloying process after GB/T1499.2-2018 standard is implemented is high, the first purpose of the invention is to provide a preparation method of low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bars, and the second purpose of the invention is to provide a preparation method of nitrogen-rich niobium microalloyed 400MPa ultrafine-grain anti-seismic steel bars.
The first object of the present invention is achieved by:
a preparation method of a low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bar specifically comprises the following steps:
A. smelting molten steel: respectively processing the scrap steel, the pig iron and the molten iron according to the temperature of 120-Steel、20kg/tSteel915 and 940kg/t are added into an LD converter, then conventional top-bottom composite blowing is carried out, conventional lime, light-burned dolomite and magnesite balls are added for slagging, and the addition amount of the lime is 20-25kg/tSteelThe addition amount of light-burned dolomite is 15-20kg/tSteelThe adding amount of the magnesite balls is 0.5kg/tSteelControlling the end point carbon content to be more than or equal to 0.08wt% and the tapping temperature to be less than or equal to 1650 ℃; 1.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizer in mass ratio for slag washing: al (Al)2O321.5wt%，SiO25.2wt%, CaO 46.5wt%, Al 9.2wt%, MgO6.5wt%, and the balance Fe and inevitable impurities, wherein the tapping process adopts a whole-course bottom argon blowing process, and argon flowThe amount is controlled to be 10-15 NL/min; the chemical components of the scrap steel comprise 0.12-0.20wt% of C, 0.35-0.60wt% of Si, 0.45-0.70wt% of Mn, 0.035-0.046wt% of P, 0.028-0.039wt% of S, and the balance of Fe and inevitable impurities; 3.3-3.6wt% of pig iron chemical components C, 0.30-0.50wt% of Si, 0.32-0.55wt% of Mn, 0.058-0.075wt% of P, 0.018-0.027wt% of S, and the balance of Fe and inevitable impurities; the chemical components of the molten iron are C4.0-4.5 wt%, Si 0.15-0.35wt%, Mn 0.30-0.50wt%, P0.080-0.120 wt% and S less than or equal to 0.035wt%, and the temperature of the molten iron is more than or equal to 1280 ℃;
B. and (3) deoxidation alloying: tapping the molten steel, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → silicon carbide → ferrosilicon → silicomanganese → high carbon ferromanganese → high silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: 32.5wt% of Si, 16.8wt% of Ca, 10.6wt% of AlFe and the balance of inevitable impurities; at a rate of 1.8kg/tSteelAdding the following silicon carbide in mass ratio: 82.5wt% of SiC, 26.5wt% of C, 0.053wt% of P, 0.035wt% of S and the balance of inevitable impurities; according to 3.4-4.7 kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; according to the ratio of 10.2-12.2 kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.3wt% of Mn, 7.1wt% of C, and the balance of Fe and inevitable impurities; according to 0.24-0.32kg/tSteelAdding the following ferroniobium in percentage by mass: nb65.6wt%, Si 6.7wt%, C0.35 wt%, P0.214 wt%, S0.075 wt%, and the balance Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 3/4, the alloy is added; after tapping, hoisting the molten steel to an argon station for refining treatment;
C. refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting an argon band, starting argon, blowing the molten steel with argon at the flow rate of 15-25 NL/min for 4 minutes, and adding a molten steel covering agent, wherein the addition amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
D. casting molten steel: the temperature of the tundish is 1523-1535 ℃, the pulling speed is 2.5-2.7 m/min, and the flow of the cooling water of the crystallizer is 110-120 m3H, adopting an R9m straight-arc continuous straightening 5-machine 5-flow small square billet casting machine to cast the molten steel into a billet with the cross section of 150mm multiplied by 150mm under the condition that the secondary cooling specific water amount is 1.5-1.7L/kg;
E. heating a steel billet: and (3) feeding the steel billet into a heating furnace with the furnace temperature of 1060-1100 ℃ in a soaking section, heating for 70-80 minutes, tapping, and then pushing to a full-continuous bar mill for rolling.
F. Controlling rolling and cooling of steel billets: roughly rolling the steel billet for 6 passes under the rolling condition of the speed of 0.5-1.0 m/s; then, carrying out medium rolling for 4-6 passes under the rolling condition with the speed of 3.0-4.0 m/s; finally, finish rolling for 2-5 passes under the rolling condition with the speed of 9.0-13.5 m/s; performing controlled cooling on the finish-rolled steel through 1 long-pipe water cooling section device with the length of 4.5 meters and 1-3 short-pipe water cooling section devices with the length of 0.8 meter, wherein the number of water pumps in the long-pipe water cooling section is 1, and the pressure of the water pumps is 1.4-1.7 MPa; the number of water pumps in the water cooling section of the short pipe is 1-2, and the pressure of the water pumps is 1.0-1.5 MPa; and naturally cooling the steel bars to room temperature in a cooling bed after cooling control, and obtaining the target object.
Preferably, in the step D, the straightening temperature of the casting blank discharged from the withdrawal and straightening machine is controlled to be 1020-1030 ℃.
Preferably, in the step E, the steel tapping temperature of the steel billet is 1010-1030 ℃.
Preferably, in the step F, the temperature of the steel bar on the cooling bed is controlled to be 850-880 ℃.
The secondary cooling specific water amount in the step D is as follows: the ratio of the total water consumption in unit time of the secondary cooling area of the continuous casting machine to the mass of the casting blank passing through the secondary cooling area in unit time is an index of the secondary cooling water spray intensity of continuous casting by taking L/kg as a unit.
Preferably, the steel prepared by the method comprises the following chemical components in percentage by weight: 0.20 to 0.24 wt% of C, 0.38 to 0.48wt% of Si, 1.30 to 1.50wt% of Mn, 0.014 to 0.019wt% of Nb, less than or equal to 0.040wt% of S, less than or equal to 0.045wt% of P, less than or equal to 0.0070wt% of O, less than or equal to 0.0075wt% of N, and the balance of Fe and inevitable impurities.
Compared with the prior art, the preparation method of the low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar provided by the invention has the following beneficial effects:
1. the method for rolling steel adopts lower heating temperature and start rolling temperature, original austenite grains are refined, the refinement of ferrite grains is promoted when austenite is converted into ferrite, the grain size reaches more than 11.0 grade, the fine grain strengthening effect is obvious, and the ductility and toughness of the steel are improved; the ferrocolumbium is added into the steel, the lower initial rolling temperature is controlled, and the multi-section low-water-pressure grading controlled cooling process after rolling is adopted, so that the driving force for Nb (C, N) precipitation is increased, and a large amount of fine and dispersed second phases are precipitated on a low-temperature ferrite matrix, a crystal boundary and a dislocation line, so that the ferrite matrix is strengthened, the strength of the steel is obviously improved, and the performances of the steel, such as welding, aging and the like, are improved; granular bainite with the content of 2-5% is formed in the center of the cross section of the steel bar, the dislocation density is high, the tensile strength of the steel can be obviously improved, and the anti-seismic performance is improved. The invention fully exerts various strengthening functions of fine grain strengthening, precipitation strengthening, multiphase structure composite strengthening and the like by integrating and innovating chemical component design, converter smelting, deoxidation alloying, continuous casting, steel rolling heating system, rolling temperature and controlled cooling process, and the produced steel bar has the advantages of excellent and stable process mechanical property, fine and uniform microstructure, good plasticity and toughness, low strain timeliness, excellent earthquake resistance and the like.
2. The method has the characteristics of low production cost, strong process applicability and controllability and the like, various indexes of the produced steel bar are comprehensively superior to GB/T1499.2-2018, and the production cost is reduced by 50 yuan/T compared with the existing vanadium microalloying processSteelBy the method, the production cost of the HRB400E steel bar is greatly reduced after GB/T1499.2-2018 is implemented, the market competitiveness of the product is improved, and the method has remarkable economic and social benefits.
The second object of the present invention is achieved by:
a preparation method of a nitrogen-rich niobium microalloyed 400MPa ultrafine grain anti-seismic reinforcing steel bar specifically comprises the following steps:
a. smelting molten steel: respectively processing the scrap steel and the molten iron at the temperature of 110-Steel、940-970kg/tSteelThe mixture ratio is added into an LD converter, then the conventional top and bottom composite blowing is carried out, the conventional lime, the light burned dolomite and the magnesite balls are added for slagging, and the adding amount of the lime is 22-26kg/tSteelThe addition amount of the light-burned dolomite is 18-22kg/tSteelThe adding amount of the magnesite balls is 1.0-2.0kg/tSteelControlling the end point carbon content to be more than or equal to 0.07wt% and the tapping temperature to be less than or equal to 1650 ℃; 1.0-1.5kg/t of steel ladle bottom before tappingSteelAdding the following slag washing materials in percentage by mass for slag washing: al (Al)2O323.5wt%，SiO24.6wt%, 48.5wt% of CaO, 7.8wt% of Al, 5.4wt% of MgO5, and the balance of Fe and inevitable impurities, wherein a whole bottom nitrogen blowing process is adopted in the tapping process, and the nitrogen flow is controlled to be 20-25 NL/min; the chemical components of the scrap steel comprise 0.12-0.20wt% of C, 0.35-0.60wt% of Si, 0.45-0.70wt% of Mn, 0.035-0.046wt% of P, 0.028-0.039wt% of S, and the balance of Fe and inevitable impurities; the molten iron comprises 4.0-4.5wt% of chemical components C, 0.15-0.35wt% of Si, 0.30-0.50wt% of Mn, 0.080-0.120wt% of P, less than or equal to 0.035wt% of S and the balance of Fe and inevitable impurities, and the temperature of the molten iron is more than or equal to 1290 ℃;
b. and (3) deoxidation alloying: tapping the molten steel, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → ferrosilicon → silicomanganese → high-carbon ferromanganese → high-carbon ferrochrome → silicon-nitrogen alloy → high-silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: 32.5wt% of Si, 16.8wt% of Ca16, 10.6wt% of Al, and the balance of Fe and inevitable impurities; according to 4.1-5.6 kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; according to the weight of 9.7-12.2 kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.3wt% of Mn, 7.1wt% of C, and the balance of Fe and inevitable impurities; according to the ratio of 1.9-2.9 kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 54.6wt% of Cr, 8.3wt% of C, 0.065wt% of P0.042 wt% of S, and the balance of Fe andinevitable impurities; at a rate of 0.10kg/tSteelAdding the following silicon-nitrogen alloy in mass ratio: 48.5 percent of Si, 35.2 percent of N, 0.75 percent of C, 0.020 percent of P, 0.018 percent of S and the balance of Fe and inevitable impurities; according to 0.17-0.23 kg/tSteelAdding the following ferroniobium in percentage by mass: 65.2 percent of Nb, 5.7 percent of Si, 0.85 percent of C, 0.195 percent of P, 0.085 percent of S, and the balance of Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; after tapping, hoisting the molten steel to an argon station for refining treatment;
c. refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting a nitrogen band, starting nitrogen, blowing argon at the flow rate of 15-20 NL/min for 4 minutes, and adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
d. casting molten steel: casting the molten steel in the step C into a billet with a cross section of 150mm multiplied by 150mm by adopting an R9m straight arc continuous straightening 5-flow small square billet casting machine under the conditions that the temperature of a tundish is 1528-1540 ℃, the pulling speed is 2.7-2.9 m/min, the flow rate of cooling water of a crystallizer is 105-115 m3/h and the secondary cooling specific water amount is 1.6-1.8L/kg;
e. heating a steel billet: feeding the steel billets into a heating furnace with the furnace temperature of a soaking section of 1070-1100 ℃, heating for 60-70 minutes, tapping the steel billets, and then pushing the steel billets to a full-continuous bar mill for rolling;
f. controlling rolling and cooling of steel billets: c, roughly rolling the billet in the step E for 6 passes under the rolling condition that the speed is 0.5-1.0 m/s; then, carrying out medium rolling for 4-6 passes under the rolling condition with the speed of 3.0-4.0 m/s; then, the steel bar is cooled in a pre-water cooling device before finish rolling, the cooling water amount is 50-60 m3/h, and the finish rolling temperature of the pre-cooled steel bar is controlled to be 930-960 ℃; finally, finish rolling for 4-5 passes under the rolling condition that the speed is 11.0-13.5 m/s; performing multi-stage grading and controlled cooling on the finish-rolled steel through 3-5 short pipe water cooling section devices (each short pipe water cooling section device is 850mm in length and 100mm in interval), wherein the number of water pumps is 2-3, and the pressure of each water pump is 1.0-1.4 MPa; and naturally cooling the steel bars to room temperature in a cooling bed after cooling control, and obtaining the target object.
Preferably, in the step d, the straightening temperature of the casting blank discharged from the withdrawal and straightening machine is controlled to be 1005-1020 ℃.
Preferably, in the step e, the steel tapping temperature of the billet is 1020-1040 ℃.
Preferably, the temperature of the steel bar on the cooling bed is controlled to be 810-850 ℃.
The secondary cooling ratio water quantity of the step d is as follows: the ratio of the total water consumption in unit time of the secondary cooling area of the continuous casting machine to the mass of the casting blank passing through the secondary cooling area in unit time is an index of the secondary cooling water spray intensity of continuous casting by taking L/kg as a unit.
Preferably, the steel prepared by the method comprises the following chemical components in percentage by weight: 0.21-0.25 wt% of C, 0.40-0.54 wt% of Si, 1.30-1.46 wt% of Mn, 0.14-0.20 wt% of Cr, 0.010-0.014 wt% of Nb, less than or equal to 0.042wt% of S, less than or equal to 0.045wt% of P, less than or equal to 0.0060wt% of O, 0.0085-0.0115 wt% of N, and the balance of Fe and inevitable impurities.
The preparation method of the nitrogen-rich niobium microalloyed 400MPa ultrafine grain anti-seismic reinforcing steel bar provided by the invention has the following beneficial effects:
1. according to the method, a small amount of silicon-nitrogen alloy is added in the steelmaking deoxidation alloying process, so that the nitrogen content in the molten steel is increased, the transfer of Nb from a solid solution state to a carbonitride precipitated phase in the rolling process is promoted, a large amount of fine and dispersed Nb (C, N) precipitated phases are formed and precipitated, the austenite stability is increased, the phase transition temperature is reduced, and the precipitation strengthening effect of the steel is obviously improved; the steel rolling adopts a lower initial rolling temperature, the lower finish rolling temperature is controlled by pre-water cooling before finish rolling and the multi-section grading controlled cooling process after rolling, original austenite grains are refined, the transformation from austenite to fine ferrite is promoted, the grain size of central ferrite of the cross section of the steel bar reaches more than 12.0 grade, the fine grain strengthening effect is obvious, and the plastic toughness of the steel is improved; a small amount of chromium is added into the steel, so that the hardenability and the secondary hardening effect are obviously improved, the improvement of the steel strength is promoted, and the passivation corrosion resistance of the steel is improved; granular bainite with the content of 1-2% is formed at the central part of the cross section of the steel bar, so that the tensile strength of the steel is improved, and the seismic performance is improved.
2. The method integrates and innovates chemical component design, converter smelting, deoxidation alloying, continuous casting, steel rolling heating system, rolling temperature and controlled cooling process, fully exerts various strengthening effects of fine grain strengthening, precipitation strengthening and the like, and the produced steel bar has the advantages of excellent and stable process mechanical property, fine and uniform microstructure, good plastic toughness, excellent fire resistance and earthquake resistance and the like.
3. The process provided by the method has the characteristics of low production cost, strong process applicability and controllability and the like, all indexes of the produced steel bar are comprehensively superior to GB/T1499.2-2018, and the production cost is reduced by 65 yuan/T compared with the existing vanadium microalloying processSteelBy the method, the production cost of the HRB400E steel bar is obviously reduced after GB/T1499.2-2018 is implemented, the market competitiveness of the product is improved, and the method has obvious economic and social benefits.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to be limiting in any way, and any modifications or alterations based on the teachings of the present invention are intended to fall within the scope of the present invention.
The invention provides a preparation method of a low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bar, which specifically comprises the following steps:
A. smelting molten steel: respectively processing the scrap steel, the pig iron and the molten iron according to the temperature of 120-Steel、20kg/tSteel915 and 940kg/t are added into an LD converter, then conventional top-bottom composite blowing is carried out, conventional lime, light-burned dolomite and magnesite balls are added for slagging, and the addition amount of the lime is 20-25kg/tSteelThe addition amount of light-burned dolomite is 15-20kg/tSteelThe adding amount of the magnesite balls is 0.5kg/tSteelControlling the end point carbon content to be more than or equal to 0.08wt% and the tapping temperature to be less than or equal to 1650 ℃; 1.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizer in mass ratio for slag washing: al (Al)2O321.5wt%，SiO25.2wt%, 46.5wt% of CaO, 9.2wt% of Al, 6.5wt% of MgO6, and the balance of Fe and inevitable impurities, wherein a whole bottom argon blowing process is adopted in the tapping process, and the argon flow is controlled to be 10-15 NL/min; the chemical components of the scrap steel comprise 0.12 to 0.20 weight percent of C, 0.35 to 0.60 weight percent of Si, 0.45 to 0.70 weight percent of Mn, 0.035 to 0.046 weight percent of P,0.028-0.039wt% of S, and the balance of Fe and inevitable impurities; 3.3-3.6wt% of pig iron chemical components C, 0.30-0.50wt% of Si, 0.32-0.55wt% of Mn, 0.058-0.075wt% of P, 0.018-0.027wt% of S, and the balance of Fe and inevitable impurities; the chemical components of the molten iron are C4.0-4.5 wt%, Si 0.15-0.35wt%, Mn 0.30-0.50wt%, P0.080-0.120 wt% and S less than or equal to 0.035wt%, and the temperature of the molten iron is more than or equal to 1280 ℃;
B. and (3) deoxidation alloying: tapping the molten steel, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → silicon carbide → ferrosilicon → silicomanganese → high carbon ferromanganese → high silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: 32.5wt% of Si, 16.8wt% of Ca, 10.6wt% of AlFe and the balance of inevitable impurities; at a rate of 1.8kg/tSteelAdding the following silicon carbide in mass ratio: 82.5wt% of SiC, 26.5wt% of C, 0.053wt% of P, 0.035wt% of S and the balance of inevitable impurities; according to 3.4-4.7 kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; according to the ratio of 10.2-12.2 kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.3wt% of Mn, 7.1wt% of C, and the balance of Fe and inevitable impurities; according to 0.24-0.32kg/tSteelAdding the following ferroniobium in percentage by mass: nb65.6wt%, Si 6.7wt%, C0.35 wt%, P0.214 wt%, S0.075 wt%, and the balance Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 3/4, the alloy is added; after tapping, hoisting the molten steel to an argon station for refining treatment;
C. refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting an argon band, starting argon, blowing the molten steel with argon at the flow rate of 15-25 NL/min for 4 minutes, and adding a molten steel covering agent, wherein the addition amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
D. casting molten steel: at a tundish temperature of1523 to 1535 ℃, the pulling speed is 2.5 to 2.7m/min, and the flow of cooling water of the crystallizer is 110 to 120m3H, adopting an R9m straight-arc continuous straightening 5-machine 5-flow small square billet casting machine to cast the molten steel into a billet with the cross section of 150mm multiplied by 150mm under the condition that the secondary cooling specific water amount is 1.5-1.7L/kg; controlling the straightening temperature of the casting blank discharged from the withdrawal and straightening machine to be 1020-1030 ℃;
E. heating a steel billet: and (3) feeding the steel billet into a heating furnace with the furnace temperature of 1060-1100 ℃ in a soaking section, heating for 70-80 minutes, wherein the steel tapping temperature of the steel billet is 1010-1030 ℃, and then pushing the steel billet to a full-continuous bar mill for rolling.
F. Controlling rolling and cooling of steel billets: roughly rolling the steel billet for 6 passes under the rolling condition of the speed of 0.5-1.0 m/s; then, carrying out medium rolling for 4-6 passes under the rolling condition with the speed of 3.0-4.0 m/s; finally, finish rolling for 2-5 passes under the rolling condition with the speed of 9.0-13.5 m/s; performing controlled cooling on the finish-rolled steel through 1 long-pipe water cooling section device with the length of 4.5 meters and 1-3 short-pipe water cooling section devices with the length of 0.8 meter, wherein the number of water pumps in the long-pipe water cooling section is 1, and the pressure of the water pumps is 1.4-1.7 MPa; the number of water pumps in the water cooling section of the short pipe is 1-2, and the pressure of the water pumps is 1.0-1.5 MPa; controlling the temperature of the steel bars on a cooling bed to be 850-880 ℃ after controlled cooling, and then naturally cooling the steel bars in the cooling bed to room temperature to obtain the HRB400E ultrafine-grained high-toughness anti-seismic steel bars with the following chemical components in percentage by weight: 0.20 to 0.24 wt% of C, 0.38 to 0.48wt% of Si, 1.30 to 1.50wt% of Mn, 0.014 to 0.019wt% of Nb, less than or equal to 0.040wt% of S, less than or equal to 0.045wt% of P, less than or equal to 0.0070wt% of O, less than or equal to 0.0075wt% of N, and the balance of Fe and inevitable impurities.
The mechanical properties, the microstructure and the Vickers hardness difference of the low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar provided by the invention are shown in tables 1 and 2.
TABLE 1 mechanical properties of HRB400E ultra-fine grain high-toughness aseismic steel bar prepared by the present invention
Figure DEST_PATH_IMAGE001
TABLE 2 metallographic structure and Vickers hardness of HRB400E ultra-fine grain high-toughness aseismic steel bar prepared by the invention
Figure 653592DEST_PATH_IMAGE002
Example 1
A preparation method of a low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bar specifically comprises the following steps:
A. smelting molten steel: at 120kg/t respectivelySteel、20kg/tSteelThe cold charge of the process is loaded into an LD converter, and scrap steel (chemical components: C0.12 wt%, Si0.35wt%, Mn 0.45wt%, P0.035 wt%, S0.028 wt%, and the balance Fe and unavoidable impurities) and pig iron (chemical components: C3.3 wt%, Si 0.30wt%, Mn 0.32wt%, P0.058wt%, S0.018 wt%, and the balance Fe and unavoidable impurities) are added into the LD converter according to the following mass ratio; then 940kg/tSteelThe molten iron charging proportion is that molten iron with the following temperature and mass ratio is added into an LD converter: the temperature of molten iron is 1280 ℃, the components of the molten iron comprise 4.0wt% of C, 0.15wt% of Si, 0.30wt% of Mn, 0.080wt% of P, 0.020wt% of S, and the balance of Fe and inevitable impurities; after adding scrap steel, pig iron and molten iron into an LD converter, carrying out conventional top-bottom combined blowing, adding conventional lime, light-burned dolomite and magnesite balls for slagging, wherein the adding amount of the lime is 20kg/tSteelThe addition amount of light-burned dolomite is 15kg/tSteelThe adding amount of the magnesite balls is 0.5kg/tSteelControlling the final carbon content to be 0.08wt% and the tapping temperature to be 1635 ℃; 1.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizer in mass ratio for slag washing: Al2O321.5wt%, SiO25.2wt%, CaO 46.5wt%, Al 9.2wt%, MgO6.5wt%, and the balance Fe and inevitable impurities, wherein the whole bottom argon blowing process is adopted in the tapping process, and the argon flow is controlled to be 10 NL/min.
B. And (3) deoxidation alloying: tapping the molten steel smelted in the step A, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → silicon carbide → ferrosilicon → silicomanganese → high carbon ferromanganese → high silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: si32.5wt%, Ca16.8wt%, Al10.6wt%, the balance being Fe and inevitable impurities; at a rate of 1.8kg/tSteelAdding the following silicon carbide in mass ratio: 82.5wt% of SiC, 26.5wt% of C, 0.053wt% of P, 0.035wt% of S and the balance of inevitable impurities; at 3.4kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; at a rate of 10.2kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: mn75.3wt%, C7.1 wt%, and the balance Fe and inevitable impurities; according to the ratio of 0.24-0.32kg/tSteelAdding the following ferroniobium in percentage by mass: 65.6wt% of Nb, 6.7wt% of Si, 0.35wt% of C, 0.214wt% of P, 0.075wt% of S and the balance of Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 3/4, the alloy is added; and after tapping, hoisting the molten steel to an argon station for refining treatment.
C. Refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting an argon band, starting argon, blowing argon at the flow rate of 15NL/min for 4 minutes, adding a molten steel covering agent, and controlling the adding amount to be 1.0kg/tSteelAnd then hoisting the molten steel to a casting station.
D. Casting molten steel: c, under the conditions that the temperature of a tundish is 1535 ℃, the pulling speed is 2.5m/min, the flow of cooling water of a crystallizer is 120m3/h, and the secondary cooling specific water is 1.5L/kg, adopting an R9m straight arc-shaped continuous straightening 5-machine 5-flow small square billet casting machine to cast the molten steel in the step C into a billet with the section of 150mm multiplied by 150 mm; the straightening temperature of the casting blank discharged from the tension leveler is controlled to be 1030 ℃.
E. Heating a steel billet: and D, feeding the steel billet obtained in the step D into a heating furnace with the furnace temperature of a soaking section of 1060 ℃, heating for 70 minutes, wherein the steel tapping temperature of the steel billet is 1030 ℃, and then pushing the steel billet to a full-continuous bar mill for rolling.
F. Controlling rolling and cooling of steel billets: roughly rolling the billet steel obtained in the step E for 6 passes under the rolling condition of the speed of 1.0 m/s; then, carrying out medium rolling for 6 passes under the rolling condition with the speed of 4.0 m/s; finally, finish rolling is carried out for 5 passes under the rolling condition with the speed of 13.5 m/s; performing controlled cooling on the rolled steel through 1 long-pipe water cooling section device (with the length of 4.5 meters) and 1 short-pipe water cooling section device (with the length of 0.8 meter), wherein the number of long-pipe water cooling section water pumps is 1, and the pressure of the water pumps is 1.4 MPa; 1 water pump is started at the water cooling section of the short pipe, and the pressure of the water pump is 1.0 MPa; controlling the temperature of the steel bars on a cooling bed to 850 ℃ after controlled cooling, and then naturally cooling the steel bars in the cooling bed to room temperature to obtain the HRB400E ultrafine-grain high-toughness anti-seismic steel bars with the following chemical components in percentage by weight: 0.20wt% of C, 0.38wt% of Si, 1.30wt% of Mn, 0.014wt% of Nb, 0.025wt% of S, 0.030wt% of P0.0070 wt% of O, and 5wt% of N0.0075wt% of N, and the balance of Fe and inevitable impurities.
The mechanical properties, the microstructure and the difference in Vickers hardness of the low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar provided by the embodiment 1 are shown in tables 3 and 4.
Table 3 mechanical properties of the HRB400E ultra-fine grain high-toughness anti-seismic steel bar prepared in example 1
Figure DEST_PATH_IMAGE003
Table 4 the metallographic microstructure and vickers hardness of the HRB400E ultra-fine grain high-toughness anti-seismic steel bar prepared in example 1
Figure 238288DEST_PATH_IMAGE004
Example 2
A preparation method of a low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bar specifically comprises the following steps:
A. smelting molten steel: at 130kg/t respectivelySteel、20kg/tSteelThe cold charge charging ratio of the process is that scrap steel (chemical components: C0.17 wt%, Si 0.48wt%, Mn 0.58wt%, P0.040 wt%, S0.034 wt%, and the balance Fe and unavoidable impurities) and pig iron (chemical components: C3.4 wt%, Si0.40 wt%, Mn 0.39wt%, P0.065wt%, S0.023 wt%, and the balance Fe and unavoidable impurities) are added into an LD converter according to the following mass ratio; then according to 928kg/tSteelThe molten iron charging proportion is that molten iron with the following temperature and mass ratio is added into an LD converter:the temperature of the molten iron is 1295 ℃, the components of the molten iron are 4.3wt%, Si0.25wt%, Mn 0.40wt%, P0.100 wt% and S0.030 wt%, and the balance is Fe and inevitable impurities; after waste steel, pig iron and molten iron are added into an LD converter, conventional top-bottom combined blowing is carried out, conventional lime, light-burned dolomite and magnesite balls are added for slagging, and the addition amount of the lime is 23kg/tSteelThe addition amount of the light-burned dolomite is 18kg/tSteelThe adding amount of the magnesite balls is 0.5kg/tSteelControlling the end point carbon content to be 0.09wt% and the tapping temperature to be 1640 ℃; 1.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizer in mass ratio for slag washing: Al2O321.5wt%, SiO25.2wt%, CaO 46.5wt%, Al 9.2wt%, MgO6.5wt%, and the balance of Fe and inevitable impurities, wherein the whole bottom argon blowing process is adopted in the tapping process, and the argon flow is controlled to be 15 NL/min.
B. And (3) deoxidation alloying: tapping the molten steel smelted in the step A, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → silicon carbide → ferrosilicon → silicomanganese → high carbon ferromanganese → high silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: si32.5wt%, Ca16.8wt%, Al10.6wt%, and the balance Fe and inevitable impurities; according to the amount of 1.8kg/t steel, the following silicon carbide is added in mass ratio: 82.5wt% of SiC, 26.5wt% of C, 0.053wt% of P, 0.035wt% of S and the balance of inevitable impurities; at 3.4kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; at a rate of 10.2kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: mn75.3wt%, C7.1 wt%, and the balance Fe and inevitable impurities; at a rate of 0.24kg/tSteelAdding the following ferroniobium in percentage by mass: 65.6wt% of Nb, 6.7wt% of Si, 0.35wt% of C, 0.214wt% of P, 0.075wt% of S and the balance of Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 3/4, the alloy is added; after tapping, hoisting the molten steel to an argon station for refiningAnd (6) processing.
C. Refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting an argon band, starting argon, blowing the molten steel with argon at the flow rate of 20L/min for 4 minutes, and then adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelAnd then hoisting the molten steel to a casting station.
D. Casting molten steel: under the conditions that the temperature of a tundish is 1530 ℃, the pulling speed is 2.6m/min, the flow of cooling water of a crystallizer is 115m3/h, and the secondary cooling specific water amount is 1.6L/kg, the molten steel in the step C is cast into a billet with the section of 150mm multiplied by 150mm by a small billet casting machine with a R9m straight arc-shaped continuous straightening 5 machine 5 flow; the straightening temperature of the casting blank discharged from the withdrawal and straightening machine is controlled to be 1025 ℃.
E. Heating a steel billet: and D, feeding the steel billets obtained in the step D into a heating furnace with the furnace temperature of the soaking section of 1080 ℃, heating for 75 minutes, wherein the steel tapping temperature of the steel billets is 1020 ℃, and then pushing the steel billets to a full-continuous bar mill for rolling.
F. Controlling rolling and cooling of steel billets: roughly rolling the billet steel obtained in the step E for 6 passes under the rolling condition of the speed of 1.0 m/s; then, carrying out medium rolling for 5 passes under the rolling condition with the speed of 4.0 m/s; finally, finish rolling is carried out for 4 passes under the rolling condition with the speed of 11.5 m/s; performing controlled cooling on the rolled steel through 1 long-pipe water cooling section device (with the length of 4.5 meters) and 2 short-pipe water cooling section devices (with the length of 0.8 meter), wherein the number of long-pipe water cooling section water pumps is 1, and the pressure of the water pumps is 1.6 MPa; 2 water pumps of the water cooling section of the short pipe are started, and the pressure of the water pumps is 1.2 MPa; controlling the temperature of the steel bars on a cooling bed to 870 ℃ after controlled cooling, and then naturally cooling the steel bars in the cooling bed to room temperature to obtain the HRB400E ultrafine-grain high-toughness anti-seismic steel bars with the following chemical components in percentage by weight: 0.22wt% of C, 0.44wt% of Si, 1.40wt% of Mn, 0.017wt% of Nb, 0.035wt% of S, 0.038wt% of P, 0.0050wt% of O, 0.0070wt% of N, and the balance of Fe and inevitable impurities.
The mechanical properties, the microstructure and the difference in Vickers hardness of the low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar provided by the embodiment 2 are shown in tables 5 and 6.
TABLE 5 mechanical properties of HRB400E ultra-fine grain high-toughness aseismic steel bar produced in example 2 of the present invention
Figure DEST_PATH_IMAGE005
TABLE 6 metallographic microstructure and Vickers hardness of HRB400E ultra-fine grain high-toughness aseismic steel bar produced in example 2 of the present invention
Figure 251243DEST_PATH_IMAGE006
Example 3
A preparation method of a low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bar specifically comprises the following steps:
A. smelting molten steel: according to 135kg/t respectivelySteel、20kg/tSteelThe cold charge charging ratio of (1) adding scrap steel (chemical components: C0.20 wt%, Si 0.60wt%, Mn 0.70wt%, P0.046 wt%, S0.039 wt%, and the balance Fe and unavoidable impurities) and pig iron (chemical components: C3.6 wt%, Si 0.50wt%, Mn 0.55wt%, P0.075wt%, S0.027 wt%, and the balance Fe and unavoidable impurities) in the following mass ratio into an LD converter; then according to 915kg/tSteelThe molten iron charging proportion is that molten iron with the following temperature and mass ratio is added into an LD converter: the temperature of molten iron is 1310 ℃, the components of the molten iron are C4.5 wt%, Si0.35wt%, Mn 0.50wt%, P0.120 wt%, S0.035wt%, and the balance of Fe and inevitable impurities; after waste steel, pig iron and molten iron are added into an LD converter, conventional top-bottom combined blowing is carried out, conventional lime, light-burned dolomite and magnesite balls are added for slagging, and the addition amount of the lime is 25kg/tSteelThe addition amount of light-burned dolomite is 20kg/tSteelThe adding amount of the magnesite balls is 0.5kg/tSteelControlling the end point carbon content to be 0.10wt% and the tapping temperature to be 1650 ℃; 1.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizer in mass ratio for slag washing: Al2O321.5wt%, SiO25.2wt%, CaO 46.5wt%, Al 9.2wt%, MgO6.5wt%, and the balance Fe and inevitable impurities, wherein a whole bottom argon blowing process is adopted in the tapping process, and the argon flow is controlled to be 15 NL/min.
B. And (3) deoxidation alloying: tapping the molten steel smelted in the step A, and when the molten steel amount in a ladle is more than 1/4, carrying out the following stepsAnd (3) deoxidizing and alloying sequence: silico-aluminum-calcium deoxidizer → silicon carbide → ferrosilicon → silicomanganese → high carbon ferromanganese → high silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: si32.5wt%, Ca16.8wt%, Al10.6wt%, and the balance Fe and inevitable impurities; at a rate of 1.8kg/tSteelAdding the following silicon carbide in mass ratio: 82.5wt% of SiC, 26.5wt% of C, 0.053wt% of P, 0.035wt% of S and the balance of inevitable impurities; at 4.7kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; at 12.2kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: mn75.3wt%, C7.1 wt%, and the balance Fe and inevitable impurities; at a rate of 0.32kg/tSteelAdding the following ferroniobium in percentage by mass: 65.6wt% of Nb, 6.7wt% of Si, 0.35wt% of C, 0.214wt% of P, 0.075wt% of S and the balance of Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 3/4, the alloy is added; and after tapping, hoisting the molten steel to an argon station for refining treatment.
C. Refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting an argon band, starting argon, blowing the molten steel with the argon with the flow of 25NL/min for 4 minutes, and then adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelAnd then hoisting the molten steel to a casting station.
D. Casting molten steel: under the conditions that the temperature of a tundish is 1523 ℃, the pulling speed is 2.7m/min, the flow of cooling water of a crystallizer is 110m3/h, and the secondary cooling specific water is 1.7L/kg, adopting an R9m straight arc-shaped continuous straightening 5-machine 5-flow small square billet casting machine to cast the molten steel in the step C into a billet with the section of 150mm multiplied by 150 mm; the straightening temperature of the casting blank discharged from the withdrawal and straightening machine is controlled to be 1020 ℃.
E. Heating a steel billet: and D, feeding the steel billet obtained in the step D into a heating furnace with the furnace temperature of the soaking section of 1100 ℃, heating for 80 minutes, wherein the steel tapping temperature of the steel billet is 1010 ℃, and then pushing the steel billet to a full-continuous bar mill for rolling.
F. Controlling rolling and cooling of steel billets: roughly rolling the billet steel obtained in the step E for 6 passes under the rolling condition of the speed of 0.5 m/s; then, rolling for 4 passes under the rolling condition with the speed of 3.0 m/s; finally, finish rolling is carried out for 2 passes under the rolling condition with the speed of 9.0 m/s; performing controlled cooling on the rolled steel through 1 long-pipe water cooling section device (with the length of 4.5 meters) and 3 short-pipe water cooling section devices (with the length of 0.8 meter), wherein the number of long-pipe water cooling section water pumps is 1, and the pressure of the water pumps is 1.7 MPa; 2 water pumps of the water cooling section of the short pipe are started, and the pressure of the water pumps is 1.5 MPa; controlling the temperature of the steel bar on a cooling bed to 880 ℃ after controlled cooling, and then naturally cooling the steel bar in the cooling bed to room temperature to obtain the HRB400E ultrafine-grain high-toughness anti-seismic steel bar with the following chemical components in percentage by weight: 0.24 wt% of C, 0.48wt% of Si, 1.50wt% of Mn, 0.019wt% of Nb, 0.040wt% of S, 0.045wt% of P, 0.0050wt% of O, and N0.0060wt% of Nb, and the balance of Fe and inevitable impurities.
The mechanical properties, the microstructure and the difference in Vickers hardness of the low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar provided by the embodiment 3 are shown in tables 7 and 8.
TABLE 7 mechanics performance of HRB400E ultra-fine grain high-toughness aseismic steel bar produced in example 3 of the present invention
Figure DEST_PATH_IMAGE007
TABLE 8 mechanical properties of HRB400E ultra-fine grain high-toughness aseismic steel bar produced in example 3
Figure 946798DEST_PATH_IMAGE008
The invention also provides a preparation method of the nitrogen-rich niobium microalloyed 400MPa ultrafine grain anti-seismic steel bar, which specifically comprises the following steps:
a. smelting molten steel: respectively processing the scrap steel and the molten iron at the temperature of 110-Steel、940-970kg/tSteelThe mixture ratio is added into an LD converter, then the conventional top and bottom composite blowing is carried out, the conventional lime, the light burned dolomite and the magnesite balls are added for slagging, and the adding amount of the lime is 22-26kg/tSteelAdding light-burned dolomiteThe amount is 18-22kg/tSteelThe adding amount of the magnesite balls is 1.0-2.0kg/tSteelControlling the end point carbon content to be more than or equal to 0.07wt% and the tapping temperature to be less than or equal to 1650 ℃; 1.0-1.5kg/t of steel ladle bottom before tappingSteelAdding the following slag washing materials in percentage by mass for slag washing: al (Al)2O323.5wt%，SiO24.6wt%, 48.5wt% of CaO, 7.8wt% of Al, 5.4wt% of MgO5, and the balance of Fe and inevitable impurities, wherein a whole bottom nitrogen blowing process is adopted in the tapping process, and the nitrogen flow is controlled to be 20-25 NL/min; the chemical components of the scrap steel comprise 0.12-0.20wt% of C, 0.35-0.60wt% of Si, 0.45-0.70wt% of Mn, 0.035-0.046wt% of P, 0.028-0.039wt% of S, and the balance of Fe and inevitable impurities; the molten iron comprises 4.0-4.5wt% of chemical components C, 0.15-0.35wt% of Si, 0.30-0.50wt% of Mn, 0.080-0.120wt% of P, less than or equal to 0.035wt% of S and the balance of Fe and inevitable impurities, and the temperature of the molten iron is more than or equal to 1290 ℃;
b. and (3) deoxidation alloying: tapping the molten steel, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → ferrosilicon → silicomanganese → high-carbon ferromanganese → high-carbon ferrochrome → silicon-nitrogen alloy → high-silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: 32.5wt% of Si, 16.8wt% of Ca16, 10.6wt% of Al, and the balance of Fe and inevitable impurities; according to 4.1-5.6 kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; according to the weight of 9.7-12.2 kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.3wt% of Mn, 7.1wt% of C, and the balance of Fe and inevitable impurities; according to the ratio of 1.9-2.9 kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 54.6wt% of Cr, 8.3wt% of C, 0.065wt% of P0.042 wt% of S, and the balance of Fe and inevitable impurities; at a rate of 0.10kg/tSteelAdding the following silicon-nitrogen alloy in mass ratio: 48.5 percent of Si, 35.2 percent of N, 0.75 percent of C, 0.020 percent of P, 0.018 percent of S and the balance of Fe and inevitable impurities; according to 0.17-0.23 kg/tSteelAdding the following ferroniobium in percentage by mass: 65.2 percent of Nb, 5.7 percent of Si, 0.85 percent of C, 0.195 percent of P, 0.085 percent of S, and the balance of Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; after tapping, hoisting the molten steel to an argon station for refining treatment;
c. refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting a nitrogen band, starting nitrogen, blowing argon at the flow rate of 15-20 NL/min for 4 minutes, and adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
d. casting molten steel: casting the molten steel in the step C into a billet with a cross section of 150mm multiplied by 150mm by adopting an R9m straight arc continuous straightening 5-flow small square billet casting machine under the conditions that the temperature of a tundish is 1528-1540 ℃, the pulling speed is 2.7-2.9 m/min, the flow rate of cooling water of a crystallizer is 105-115 m3/h and the secondary cooling specific water amount is 1.6-1.8L/kg;
e. heating a steel billet: feeding the steel billets into a heating furnace with the furnace temperature of a soaking section of 1070-1100 ℃, heating for 60-70 minutes, tapping the steel billets, and then pushing the steel billets to a full-continuous bar mill for rolling;
f. controlling rolling and cooling of steel billets: c, roughly rolling the billet in the step E for 6 passes under the rolling condition that the speed is 0.5-1.0 m/s; then, carrying out medium rolling for 4-6 passes under the rolling condition with the speed of 3.0-4.0 m/s; then, the steel bar is cooled in a pre-water cooling device before finish rolling, the cooling water amount is 50-60 m3/h, and the finish rolling temperature of the pre-cooled steel bar is controlled to be 930-960 ℃; finally, finish rolling for 4-5 passes under the rolling condition that the speed is 11.0-13.5 m/s; performing multi-stage grading and controlled cooling on the finish-rolled steel through 3-5 short pipe water cooling section devices (each short pipe water cooling section device is 850mm in length and 100mm in interval), wherein the number of water pumps is 2-3, and the pressure of each water pump is 1.0-1.4 MPa; and naturally cooling the steel bars to room temperature in a cooling bed after cooling control, and obtaining the target object.
Further, in the step d, the straightening temperature of the casting blank discharged from the withdrawal and straightening machine is controlled to be 1005-1020 ℃.
Further, in the step e, the steel tapping temperature of the steel billet is 1020-1040 ℃.
Further, the temperature of the steel bar on a cooling bed is controlled to be 810-850 ℃.
The mechanical property, the microstructure and the Vickers hardness difference of the nitrogen-enriched niobium microalloyed 400MPa ultrafine crystal anti-seismic reinforcing steel bar provided by the invention are shown in tables 9-11.
TABLE 9 mechanical properties of 400MPa superfine crystal anti-seismic reinforcing steel bar produced by the present invention
Figure DEST_PATH_IMAGE009
TABLE 10 high-temp. (600 deg.C) mechanical properties of 400MPa superfine crystal aseismic reinforcing bar produced by the present invention
Figure 627178DEST_PATH_IMAGE010
TABLE 11 metallographic structure and Vickers hardness of 400MPa ultrafine crystal anti-seismic reinforcing bar produced by the invention
Figure DEST_PATH_IMAGE011
Example 4
A preparation method of a nitrogen-rich niobium microalloyed 400MPa ultrafine grain anti-seismic reinforcing steel bar specifically comprises the following steps:
a. smelting molten steel: according to 110kg/tSteelCharging cold charge into the converter, adding scrap steel (chemical components: C0.12 wt%, Si0.35wt%, Mn 0.45wt%, P0.035 wt%, S0.028 wt%, and the balance Fe and inevitable impurities) into LD converter; then 970kg/tSteelThe molten iron charging proportion is that molten iron with the following temperature and mass ratio is added into an LD converter: the temperature of molten iron is 1290 ℃, the components of the molten iron are 4.0wt percent of C, 0.15wt percent of Si, 0.30wt percent of Mn, 0.080wt percent of P, 0.020wt percent of S and the balance of Fe and inevitable impurities; after waste steel, pig iron and molten iron are added into an LD converter, conventional top-bottom combined blowing is carried out, conventional lime, light-burned dolomite and magnesite balls are added for slagging, and the addition amount of the lime is 22kg/tSteelThe addition amount of the light-burned dolomite is 18kg/tSteelThe adding amount of the magnesite balls is 1.0kg/tSteelControlling the end point carbon contentThe amount is 0.07wt%, and the tapping temperature is 1635 ℃; 1.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing materials in percentage by mass for slag washing: al (Al)2O323.5wt%，SiO24.6wt%, CaO48.5wt%, Al 7.8wt%, MgO5.4wt%, and the balance Fe and inevitable impurities, wherein the whole bottom blowing process is adopted in the tapping process, and the nitrogen flow rate is controlled to be 20 NL/min.
b. And (3) deoxidation alloying: tapping the molten steel smelted in the step a, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → ferrosilicon → silicomanganese → high-carbon ferromanganese → high-carbon ferrochrome → silicon-nitrogen alloy → high-silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: 32.5wt% of Si, 16.8wt% of Ca, 10.6wt% of Al and the balance of Fe and inevitable impurities; at 4.1kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; at 9.7kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.3wt% of Mn, 7.1wt% of C, and the balance of Fe and inevitable impurities; at a rate of 1.9kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 54.6wt% of Cr, 8.3wt% of C, 0.065wt% of P, 0.042wt% of S, and the balance of Fe and inevitable impurities; at a rate of 0.10kg/tSteelAdding the following silicon-nitrogen alloy in mass ratio: 48.5 percent of Si, 35.2 percent of N, 0.75 percent of C, 0.020 percent of P, 0.018 percent of S and the balance of Fe and inevitable impurities; at a rate of 0.17kg/tSteelAdding the following ferroniobium in percentage by mass: 65.2wt% of Nb, 5.7wt% of Si, 0.85wt% of C, 0.195wt% of P, 0.085wt% of S, and the balance of Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; and after tapping, hoisting the molten steel to an argon station for refining treatment.
c. Refining in a molten steel argon station: the molten steel is lifted to an argon station to be connected with a nitrogen band, the nitrogen is started, argon with the flow rate of 15NL/min is adopted to carry out argon blowing treatment on the molten steel, and the argon blowing time is4 minutes later, the molten steel covering agent is added, and the adding amount is controlled to be 1.0kg/tSteelAnd then hoisting the molten steel to a casting station.
d. Casting molten steel: the temperature of the tundish is 1540 ℃, the pulling speed is 2.7m/min, and the cooling water flow of the crystallizer is 115m3H, adopting an R9m straight-arc continuous straightening 5-machine 5-flow small square billet casting machine to cast the molten steel in the step c into a billet with the cross section of 150mm multiplied by 150mm under the condition that the secondary cooling specific water amount is 1.8L/kg; the straightening temperature of the casting blank discharged from the withdrawal and straightening machine is controlled to be 1005 ℃.
e. Heating a steel billet: and d, feeding the steel billet obtained in the step d into a heating furnace with the furnace temperature of the soaking section of 1100 ℃, heating for 60 minutes, wherein the steel tapping temperature of the steel billet is 1040 ℃, and then pushing the steel billet to a full-continuous bar mill for rolling.
f. Controlling rolling and cooling of steel billets: rough rolling the billet steel obtained in the step e for 6 passes under the rolling condition of the speed of 1.0 m/s; then, carrying out medium rolling for 6 passes under the rolling condition with the speed of 4.0 m/s; then the steel plate enters a pre-water cooling device before finish rolling to carry out controlled cooling before finish rolling, wherein the cooling water amount is 50m3The finish rolling temperature of the steel bar after pre-water cooling is controlled to be 960 ℃; finally, finish rolling is carried out for 5 passes under the rolling condition with the speed of 13.5 m/s; performing multi-section grading and controlled cooling on the finish-rolled steel through 3 short pipe water cooling section devices (each short pipe water cooling section device is 850mm in length and 100mm in interval), wherein 2 water pumps are started, and the pressure of each water pump is 1.0 MPa; controlling the temperature of the steel bars on a cooling bed to be 810 ℃ after controlled cooling, and then naturally cooling the steel bars in the cooling bed to room temperature to obtain the ultrafine crystal anti-seismic steel bars with the nominal diameter of 12mm and 400MPa, which have the following chemical components in percentage by weight: 0.21wt% of C, 0.40wt% of Si, 1.30wt% of Mn, 0.14wt% of Cr0.1010 wt% of Nb, 0.022wt% of S, 0.025wt% of P0.0060 wt% of O, 0.0085wt% of N, and the balance of Fe and inevitable impurities.
The mechanical properties, the microstructure and the difference in Vickers hardness of the nitrogen-enriched niobium microalloyed 400MPa ultrafine crystal anti-seismic reinforcing steel bar provided in the embodiment 4 are shown in tables 12 to 14.
TABLE 12 mechanical Properties of 400MPa ultra-fine grain anti-seismic reinforcing bar produced in example 4
Figure 639566DEST_PATH_IMAGE012
TABLE 13 high-temp. (600 deg.C) mechanical properties of 400MPa ultra-fine grained aseismic steel bar produced in example 4
Figure DEST_PATH_IMAGE013
TABLE 14 metallographic structure and Vickers hardness of 400MPa ultrafine crystal anti-seismic reinforcing bar produced in example 4
Figure 546342DEST_PATH_IMAGE014
Example 5
A preparation method of a nitrogen-rich niobium microalloyed 400MPa ultrafine grain anti-seismic reinforcing steel bar specifically comprises the following steps:
a. smelting molten steel: at 130kg/tSteelCharging cold charge into the converter, adding scrap steel (chemical components: C0.18 wt%, Si 0.48wt%, Mn 0.58wt%, P0.040 wt%, S0.033 wt%, and the balance Fe and inevitable impurities) into an LD converter according to the following mass ratio; then 955kg/tSteelThe molten iron charging proportion is that molten iron with the following temperature and mass ratio is added into an LD converter: the temperature of molten iron is 1305 ℃, the components of the molten iron are C4.2 wt%, Si0.25wt%, Mn 0.40wt%, P0.110 wt% and S0.030 wt%, and the balance is Fe and inevitable impurities; after waste steel, pig iron and molten iron are added into an LD converter, conventional top-bottom combined blowing is carried out, conventional lime, light-burned dolomite and magnesite balls are added for slagging, and the addition amount of the lime is 24kg/tSteelThe addition amount of light-burned dolomite is 20kg/tSteelThe adding amount of the magnesite balls is 2.0kg/tSteelControlling the end point carbon content to be 0.09wt% and the tapping temperature to be 1645 ℃; 1.5kg/t of steel ladle bottom before tappingSteelAdding the following slag washing materials in percentage by mass for slag washing: al (Al)2O323.5wt%，SiO24.6wt%, CaO48.5wt%, Al 7.8wt%, MgO5.4wt%, and the balance Fe and inevitable impurities, wherein the whole bottom blowing process is adopted in the tapping process, and the nitrogen flow is controlled to be 25 NL/min.
b. And (3) deoxidation alloying: tapping the molten steel smelted in the step a, and when the amount of the molten steel in the ladle is more than 1/4The following deoxidation alloying sequence is followed: silico-aluminum-calcium deoxidizer → ferrosilicon → silicomanganese → high-carbon ferromanganese → high-carbon ferrochrome → silicon-nitrogen alloy → high-silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: 32.5wt% of Si, 16.8wt% of Ca, 10.6wt% of Al and the balance of Fe and inevitable impurities; at 4.8kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; at a rate of 10.9kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.3wt% of Mn, 7.1wt% of C, and the balance of Fe and inevitable impurities; at a rate of 2.4kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 54.6wt% of Cr, 8.3wt% of C, 0.065wt% of P, 0.042wt% of S, and the balance of Fe and inevitable impurities; at a rate of 0.10kg/tSteelAdding the following silicon-nitrogen alloy in mass ratio: 48.5 percent of Si, 35.2 percent of N, 0.75 percent of C, 0.020 percent of P, 0.018 percent of S and the balance of Fe and inevitable impurities; at a rate of 0.20kg/tSteelAdding the following ferroniobium in percentage by mass: 65.2 percent of Nb, 5.7 percent of Si, 0.85 percent of C, 0.195 percent of P, 0.085 percent of S, and the balance of Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; and after tapping, hoisting the molten steel to an argon station for refining treatment.
c. Refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting a nitrogen band, starting nitrogen, blowing argon with the flow of 20NL/min for 4 minutes, adding a molten steel covering agent, and controlling the adding amount to be 1.0kg/tSteelAnd then hoisting the molten steel to a casting station.
d. Casting molten steel: the temperature of the tundish is 1535 ℃, the pulling speed is 2.8m/min, and the flow of cooling water of the crystallizer is 110m3H, adopting an R9m straight-arc continuous straightening 5-machine 5-flow small square billet casting machine to cast the molten steel in the step C into a billet with the cross section of 150mm multiplied by 150mm under the condition that the secondary cooling specific water amount is 1.7L/kg; the straightening temperature of the casting blank discharged from the tension leveler is controlled to be 1010 ℃.
e. Heating a steel billet: and d, feeding the steel billets obtained in the step d into a heating furnace with the furnace temperature of a soaking section of 1080 ℃, heating for 60 minutes, wherein the steel tapping temperature of the steel billets is 1030 ℃, and then pushing the steel billets to a full-continuous bar mill for rolling.
f. Controlling rolling and cooling of steel billets: rough rolling the billet steel obtained in the step e for 6 passes under the rolling condition of the speed of 1.0 m/s; then, carrying out medium rolling for 5 passes under the rolling condition with the speed of 4.0 m/s; then the steel plate enters a pre-water cooling device before finish rolling to carry out controlled cooling before finish rolling, wherein the cooling water amount is 55m3The finish rolling temperature of the steel bar after pre-water cooling is controlled to be 950 ℃; finally, finish rolling is carried out for 5 passes under the rolling condition with the speed of 12.0 m/s; performing multi-section grading and controlled cooling on the finish-rolled steel through 4 short pipe water cooling section devices (each length is 850mm, and the interval between every two water cooling sections is 100mm), starting 2 water pumps, wherein the pressure of each water pump is 1.2 MPa; controlling the temperature of the steel bar on a cooling bed to be 830 ℃ after controlled cooling, and then naturally cooling the steel bar in the cooling bed to room temperature to obtain the ultrafine crystal anti-seismic steel bar with the nominal diameter of 16mm and 400MPa, wherein the ultrafine crystal anti-seismic steel bar comprises the following chemical components in percentage by weight: 0.22wt% of C, 0.48wt% of Si, 1.38wt% of Mn, 0.17wt% of Cr0.17wt% of Nb, 0.012wt% of S, 0.035wt% of P0.037wt% of O, 0.0052wt% of N, 0.0100wt% of N, and the balance of Fe and inevitable impurities.
The mechanical properties, the microstructure and the Vickers hardness difference of the nitrogen-enriched niobium microalloyed 400MPa ultrafine-grained anti-seismic reinforcing steel bar provided by the embodiment 4 are shown in tables 15 to 17.
TABLE 15 mechanics performance of 400MPa ultra-fine grain aseismic reinforcing bar process produced in example 5
Figure DEST_PATH_IMAGE015
TABLE 16 high-temp. (600 deg.C) mechanical properties of 400MPa ultra-fine grain aseismic steel bar produced in example 5
Figure 294855DEST_PATH_IMAGE016
TABLE 17 metallographic structure and Vickers hardness of 400MPa ultrafine crystal anti-seismic reinforcing bar produced in example 5
Figure DEST_PATH_IMAGE017
Example 6
A preparation method of a nitrogen-rich niobium microalloyed 400MPa ultrafine grain anti-seismic reinforcing steel bar specifically comprises the following steps:
a. smelting molten steel: at 140kg/tSteelCharging cold charge into the converter, adding scrap steel (chemical components: C0.20 wt%, Si 0.60wt%, Mn 0.70wt%, P0.046 wt%, S0.039 wt%, and the balance Fe and inevitable impurities) into the LD converter according to the following mass ratio; then 940kg/tSteelThe molten iron charging proportion is that molten iron with the following temperature and mass ratio is added into an LD converter: the temperature of molten iron is 1310 ℃, the components of the molten iron are C4.5 wt%, Si0.35wt%, Mn 0.50wt%, P0.120 wt% and S0.035wt%, and the balance is Fe and inevitable impurities; after waste steel, pig iron and molten iron are added into an LD converter, conventional top-bottom combined blowing is carried out, conventional lime, light-burned dolomite and magnesite balls are added for slagging, and the addition amount of the lime is 26kg/tSteelThe addition amount of the light-burned dolomite is 22kg/tSteelThe adding amount of the magnesite balls is 2.0kg/tSteelControlling the end point carbon content to be 0.09wt% and the tapping temperature to be 1650 ℃; 1.5kg/t of steel ladle bottom before tappingSteelAdding the following slag washing materials in percentage by mass for slag washing: al (Al)2O323.5wt%，SiO24.6wt%, CaO48.5wt%, Al 7.8wt%, MgO5.4wt%, and the balance Fe and inevitable impurities, wherein the whole bottom blowing process is adopted in the tapping process, and the nitrogen flow is controlled to be 25 NL/min.
b. And (3) deoxidation alloying: tapping the molten steel smelted in the step a, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → ferrosilicon → silicomanganese → high-carbon ferromanganese → high-carbon ferrochrome → silicon-nitrogen alloy → high-silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: 32.5wt% of Si, 16.8wt% of Ca, 10.6wt% of Al and the balance of Fe and inevitable impurities; at 5.6kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; at 12.2kg/tSteelThe amount of (a) to (b) is,adding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.3wt% of Mn, 7.1wt% of C, and the balance of Fe and inevitable impurities; at a rate of 2.9kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 54.6wt% of Cr, 8.3wt% of C, 0.065wt% of P, 0.042wt% of S, and the balance of Fe and inevitable impurities; at a rate of 0.10kg/tSteelAdding the following silicon-nitrogen alloy in mass ratio: 48.5 percent of Si, 35.2 percent of N, 0.75 percent of C, 0.020 percent of P, 0.018 percent of S and the balance of Fe and inevitable impurities; at a rate of 0.23kg/tSteelAdding the following ferroniobium in percentage by mass: 65.2 percent of Nb, 5.7 percent of Si, 0.85 percent of C, 0.195 percent of P, 0.085 percent of S, and the balance of Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; and after tapping, hoisting the molten steel to an argon station for refining treatment.
c. Refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting a nitrogen band, starting nitrogen, blowing argon with the flow of 20NL/min for 4 minutes, adding a molten steel covering agent, and controlling the adding amount to be 1.0kg/tSteelAnd then hoisting the molten steel to a casting station.
d. Casting molten steel: the temperature of the tundish is 1528 ℃, the pulling speed is 2.9m/min, and the flow of cooling water of the crystallizer is 105m3H, adopting an R9m straight-arc continuous straightening 5-machine 5-flow small square billet casting machine to cast the molten steel in the step c into a billet with the cross section of 150mm multiplied by 150mm under the condition that the secondary cooling specific water amount is 1.6L/kg; the straightening temperature of the casting blank discharged from the withdrawal and straightening machine is controlled to be 1020 ℃.
e. Heating a steel billet: and d, feeding the steel billets obtained in the step d into a heating furnace with the furnace temperature of a soaking section of 1070 ℃, heating for 70 minutes, wherein the steel tapping temperature of the steel billets is 1020 ℃, and then pushing the steel billets to a full-continuous bar mill for rolling.
f. Controlling rolling and cooling of steel billets: rough rolling the billet steel obtained in the step e for 6 passes under the rolling condition of the speed of 0.5 m/s; then, rolling for 4 passes under the rolling condition with the speed of 3.0 m/s; then the steel plate enters a pre-water cooling device before finish rolling to carry out controlled cooling before finish rolling, wherein the cooling water amount is 60m3The finish rolling temperature of the steel bar after pre-water cooling is controlled to be 930 ℃; finally, finish rolling is carried out for 4 passes under the rolling condition with the speed of 11.0 m/s; performing multi-stage grading and controlled cooling on the finish-rolled steel through 5 short pipe water cooling section devices (each short pipe water cooling section device is 850mm in length and 100mm in interval), starting 3 water pumps, and controlling the pressure of the water pumps to be 1.4 MPa; controlling the temperature of the steel bars on a cooling bed to 850 ℃ after controlled cooling, and then naturally cooling the steel bars in the cooling bed to room temperature to obtain the ultrafine-grained anti-seismic steel bars with the nominal diameter of 20mm and 400MPa, which have the following chemical components in percentage by weight: 0.25wt% of C, 0.54wt% of Si, 1.46wt% of Mn, 0.20wt% of Cr0.20wt% of Nb, 0.014wt% of S, 0.042wt% of P0.045wt% of O, 0.0045wt% of N, and the balance of Fe and inevitable impurities.
The mechanical properties, the microstructure and the difference in Vickers hardness of the nitrogen-enriched niobium microalloyed 400MPa ultrafine crystal anti-seismic reinforcing steel bar provided in the embodiment 6 are shown in tables 18 to 20.
TABLE 18 mechanics performance of 400MPa ultra-fine grain aseismic reinforcing bar process produced in example 6
Figure 846053DEST_PATH_IMAGE018
TABLE 19 mechanical properties at high temperature (600 deg.C) of the ultra-fine grain anti-seismic reinforcing steel bar of 400MPa produced in example 6
Figure DEST_PATH_IMAGE019
TABLE 20 metallographic structure and Vickers hardness of 400MPa ultrafine crystal anti-seismic reinforcing bar produced in example 6
Figure 287399DEST_PATH_IMAGE020
。

Claims (10)

1. A preparation method of a low-niobium microalloyed HRB400E ultrafine-grain high-toughness anti-seismic steel bar is characterized by comprising the following steps:
A. smelting molten steel: respectively processing the scrap steel, the pig iron and the molten iron according to the temperature of 120-Steel、20kg/tSteel915 + 940kg/t of the mixture ratio is added into the LD converterIn the furnace, the conventional top-bottom composite blowing is carried out, the conventional lime, the light-burned dolomite and the magnesite balls are added for slagging, the addition amount of the lime is 20-25kg/t steel, the addition amount of the light-burned dolomite is 15-20kg/t steel, and the addition amount of the magnesite balls is 0.5kg/t steelSteelControlling the end point carbon content to be more than or equal to 0.08wt% and the tapping temperature to be less than or equal to 1650 ℃; 1.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizer in mass ratio for slag washing: al (Al)2O321.5wt%，SiO25.2wt%, 46.5wt% of CaO, 9.2wt% of Al, 6.5wt% of MgO6, and the balance of Fe and inevitable impurities, wherein a whole bottom argon blowing process is adopted in the tapping process, and the argon flow is controlled to be 10-15 NL/min; the chemical components of the scrap steel comprise 0.12-0.20wt% of C, 0.35-0.60wt% of Si, 0.45-0.70wt% of Mn, 0.035-0.046wt% of P, 0.028-0.039wt% of S, and the balance of Fe and inevitable impurities; 3.3-3.6wt% of pig iron chemical components C, 0.30-0.50wt% of Si, 0.32-0.55wt% of Mn, 0.058-0.075wt% of P, 0.018-0.027wt% of S, and the balance of Fe and inevitable impurities; the chemical components of the molten iron are C4.0-4.5 wt%, Si 0.15-0.35wt%, Mn 0.30-0.50wt%, P0.080-0.120 wt% and S less than or equal to 0.035wt%, and the temperature of the molten iron is more than or equal to 1280 ℃;
B. and (3) deoxidation alloying: tapping the molten steel, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → silicon carbide → ferrosilicon → silicomanganese → high carbon ferromanganese → high silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: 32.5wt% of Si, 16.8wt% of Ca, 10.6wt% of AlFe and the balance of inevitable impurities; at a rate of 1.8kg/tSteelAdding the following silicon carbide in mass ratio: 82.5wt% of SiC, 26.5wt% of C, 0.053wt% of P, 0.035wt% of S and the balance of inevitable impurities; according to 3.4-4.7 kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; according to the ratio of 10.2-12.2 kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.3wt% of Mn, 7.1wt% of C and the balance of Fe and FeUnavoidable impurities; according to 0.24-0.32kg/tSteelAdding the following ferroniobium in percentage by mass: nb65.6wt%, Si 6.7wt%, C0.35 wt%, P0.214 wt%, S0.075 wt%, and the balance Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 3/4, the alloy is added; after tapping, hoisting the molten steel to an argon station for refining treatment;
C. refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting an argon band, starting argon, blowing the molten steel with argon at the flow rate of 15-25 NL/min for 4 minutes, and adding a molten steel covering agent, wherein the addition amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
D. casting molten steel: the temperature of the tundish is 1523-1535 ℃, the pulling speed is 2.5-2.7 m/min, and the flow of the cooling water of the crystallizer is 110-120 m3H, adopting an R9m straight-arc continuous straightening 5-machine 5-flow small square billet casting machine to cast the molten steel into a billet with the cross section of 150mm multiplied by 150mm under the condition that the secondary cooling specific water amount is 1.5-1.7L/kg;
E. heating a steel billet: feeding the steel billet into a heating furnace with the furnace temperature of 1060-1100 ℃ at a soaking section, heating for 70-80 minutes, tapping, and then pushing to a full-continuous bar mill for rolling;
F. controlling rolling and cooling of steel billets: roughly rolling the steel billet for 6 passes under the rolling condition of the speed of 0.5-1.0 m/s; then, carrying out medium rolling for 4-6 passes under the rolling condition with the speed of 3.0-4.0 m/s; finally, finish rolling for 2-5 passes under the rolling condition with the speed of 9.0-13.5 m/s; performing controlled cooling on the finish-rolled steel through 1 long-pipe water cooling section device with the length of 4.5 meters and 1-3 short-pipe water cooling section devices with the length of 0.8 meter, wherein the number of water pumps in the long-pipe water cooling section is 1, and the pressure of the water pumps is 1.4-1.7 MPa; the number of water pumps in the water cooling section of the short pipe is 1-2, and the pressure of the water pumps is 1.0-1.5 MPa; and naturally cooling the steel bars to room temperature in a cooling bed after cooling control, and obtaining the target object.
2. The preparation method of the low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar as claimed in claim 1, wherein in the step D, the straightening temperature of a casting blank taken out of a withdrawal and straightening machine is controlled to be 1020-1030 ℃.
3. The preparation method of the low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar as claimed in claim 1, wherein in the step E, the steel tapping temperature of the steel billet is 1010-1030 ℃.
4. The preparation method of the low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar as claimed in claim 1, wherein in the step F, the temperature of the steel bar on a cooling bed is controlled to be 850-880 ℃.
5. The preparation method of the low-niobium microalloyed HRB400E ultrafine-grained high-toughness anti-seismic steel bar as claimed in claim 1, wherein the steel comprises the following chemical components in parts by weight: 0.20-0.24 wt% of C, 0.38-0.48 wt% of Si, 1.30-1.50 wt% of Mn1.014-0.019 wt% of Nb, less than or equal to 0.040wt% of S, less than or equal to 0.045wt% of P, less than or equal to 0.0070wt% of O, less than or equal to 0.0075wt% of N, and the balance of Fe and inevitable impurities.
6. A preparation method of a nitrogen-rich niobium microalloyed 400MPa ultrafine grain anti-seismic reinforcing steel bar is characterized by comprising the following steps:
a. smelting molten steel: respectively processing the scrap steel and the molten iron at the temperature of 110-Steel、940-970kg/tSteelThe mixture ratio is added into an LD converter, then the conventional top and bottom composite blowing is carried out, the conventional lime, the light burned dolomite and the magnesite balls are added for slagging, and the adding amount of the lime is 22-26kg/tSteelThe addition amount of the light-burned dolomite is 18-22kg/tSteelThe adding amount of the magnesite balls is 1.0-2.0kg/tSteelControlling the end point carbon content to be more than or equal to 0.07wt% and the tapping temperature to be less than or equal to 1650 ℃; 1.0-1.5kg/t of steel ladle bottom before tappingSteelAdding the following slag washing materials in percentage by mass for slag washing: Al2O323.5wt%, SiO24.6wt%, CaO48.5wt%, Al 7.8wt%, MgO5.4wt%, and the balance Fe and inevitable impurities, wherein a whole-process bottom nitrogen blowing process is adopted in the tapping process, and the nitrogen flow is controlled to be 20-25 NL/min; the chemical components of the scrap steel comprise 0.12 to 0.20 weight percent of C, 0.35 to 0.60 weight percent of Si, 0.45 to 0.70 weight percent of Mn, 0.035 to 0.046 weight percent of P, 0.028 to 0.039 weight percent of S,the balance of Fe and inevitable impurities; the molten iron comprises 4.0-4.5wt% of chemical components C, 0.15-0.35wt% of Si, 0.30-0.50wt% of Mn, 0.080-0.120wt% of P, less than or equal to 0.035wt% of S and the balance of Fe and inevitable impurities, and the temperature of the molten iron is more than or equal to 1290 ℃;
b. and (3) deoxidation alloying: tapping the molten steel, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: silico-aluminum-calcium deoxidizer → ferrosilicon → silicomanganese → high-carbon ferromanganese → high-carbon ferrochrome → silicon-nitrogen alloy → high-silicon ferroniobium, the following substances are added into the steel ladle in sequence: at a rate of 1.0kg/tSteelAdding the following silicon-aluminum-calcium deoxidizer in mass ratio: 32.5wt% of Si, 16.8wt% of Ca16, 10.6wt% of Al, and the balance of Fe and inevitable impurities; according to 4.1-5.6 kg/tSteelAdding the following ferrosilicon in percentage by mass: 73.5wt% of Si, and the balance of Fe and inevitable impurities; according to the weight of 9.7-12.2 kg/tSteelAdding the following silicon-manganese alloy in mass ratio: 65.2wt% of Mn, 17.3wt% of Si, 1.8wt% of C, and the balance of Fe and inevitable impurities; at 9.1kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.3wt% of Mn, 7.1wt% of C, and the balance of Fe and inevitable impurities; according to the ratio of 1.9-2.9 kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 54.6wt% of Cr, 8.3wt% of C, 0.065wt% of P0.042 wt% of S, and the balance of Fe and inevitable impurities; at a rate of 0.10kg/tSteelAdding the following silicon-nitrogen alloy in mass ratio: 48.5 percent of Si, 35.2 percent of N, 0.75 percent of C, 0.020 percent of P, 0.018 percent of S and the balance of Fe and inevitable impurities; according to 0.17-0.23 kg/tSteelAdding the following ferroniobium in percentage by mass: 65.2 percent of Nb, 5.7 percent of Si, 0.85 percent of C, 0.195 percent of P, 0.085 percent of S, and the balance of Fe and inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; after tapping, hoisting the molten steel to an argon station for refining treatment;
c. refining in a molten steel argon station: hoisting the molten steel to an argon station, connecting a nitrogen band, starting nitrogen, blowing argon at the flow rate of 15-20 NL/min for 4 minutes, and adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
d. casting molten steel: casting the molten steel in the step C into a billet with a cross section of 150mm multiplied by 150mm by adopting an R9m straight arc continuous straightening 5-flow small square billet casting machine under the conditions that the temperature of a tundish is 1528-1540 ℃, the pulling speed is 2.7-2.9 m/min, the flow rate of cooling water of a crystallizer is 105-115 m3/h and the secondary cooling specific water amount is 1.6-1.8L/kg;
e. heating a steel billet: feeding the steel billets into a heating furnace with the furnace temperature of a soaking section of 1070-1100 ℃, heating for 60-70 minutes, tapping the steel billets, and then pushing the steel billets to a full-continuous bar mill for rolling;
f. controlling rolling and cooling of steel billets: carrying out rough rolling on the billet obtained in the step e for 6 passes under the rolling condition that the speed is 0.5-1.0 m/s; then, carrying out medium rolling for 4-6 passes under the rolling condition with the speed of 3.0-4.0 m/s; then, the steel bar is cooled in a pre-water cooling device before finish rolling, the cooling water amount is 50-60 m3/h, and the finish rolling temperature of the pre-cooled steel bar is controlled to be 930-960 ℃; finally, finish rolling for 4-5 passes under the rolling condition that the speed is 11.0-13.5 m/s; performing multi-stage grading and controlled cooling on the finish-rolled steel through 3-5 short pipe water cooling section devices (each short pipe water cooling section device is 850mm in length and 100mm in interval), wherein the number of water pumps is 2-3, and the pressure of each water pump is 1.0-1.4 MPa; and naturally cooling the steel bars to room temperature in a cooling bed after cooling control, and obtaining the target object.
7. The preparation method of the nitrogen-enriched niobium microalloyed 400MPa ultrafine grain anti-seismic steel bar as claimed in claim 6, wherein in the step d, the straightening temperature of a casting blank out of a withdrawal straightening machine is controlled to be 1005-1020 ℃.
8. The method for preparing the ultra-fine grain aseismic steel bar with the nitrogen-enriched niobium microalloyed pressure of 400MPa according to claim 6, wherein in the step e, the steel tapping temperature of the billet is 1020-1040 ℃.
9. The method for preparing the nitrogen-enriched niobium microalloyed 400MPa ultrafine grain anti-seismic steel bar according to claim 6, wherein in the step f, the temperature of a steel bar upper cooling bed is controlled to be 810-850 ℃.
10. The preparation method of the nitrogen-enriched niobium microalloyed 400MPa ultrafine grain anti-seismic steel bar according to claim 6, characterized in that the steel comprises the following chemical components in parts by weight: 0.21-0.25 wt% of C, 0.40-0.54 wt% of Si, 1.30-1.46 wt% of Mn, 0.14-0.20 wt% of Cr, 0.010-0.014 wt% of Nb, less than or equal to 0.042wt% of S, less than or equal to 0.045wt% of P, less than or equal to 0.0060wt% of O, 0.0085-0.0115 wt% of N, and the balance of Fe and inevitable impurities.
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