CN116288061A - 1000 MPa-level ultra-high strength corrosion-resistant steel bar and preparation method thereof - Google Patents

1000 MPa-level ultra-high strength corrosion-resistant steel bar and preparation method thereof Download PDF

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CN116288061A
CN116288061A CN202310241156.8A CN202310241156A CN116288061A CN 116288061 A CN116288061 A CN 116288061A CN 202310241156 A CN202310241156 A CN 202310241156A CN 116288061 A CN116288061 A CN 116288061A
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equal
steel
steel bar
high strength
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周和敏
柯雪利
王长城
黄玉鸿
蔡恒忠
曾智中
张俊
徐洪军
高俊哲
沈朋飞
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CISRI Sunward Technology Co Ltd
Guangxi Shenglong Iron and Steel Materials Research Institute
Guangxi Shenglong Metallurgical Co Ltd
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CISRI Sunward Technology Co Ltd
Guangxi Shenglong Iron and Steel Materials Research Institute
Guangxi Shenglong Metallurgical 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/36—Processes yielding slags of special composition
    • 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
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • 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
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Abstract

The invention discloses a 1000 MPa-level ultrahigh-strength corrosion-resistant steel bar and a preparation method thereof, belongs to the technical field of metal materials, and is used for solving the problems that the existing steel bar is low in strength level, lacks 1000 MPa-level hot-rolled steel bars and cannot be reasonably matched in yield strength, tensile strength and corrosion resistance. The problems that the carbon equivalent of the pre-stressed steel bar subjected to quenching-tempering heat treatment in the prior art is too high, the pre-stressed steel bar cannot be used for steel bar welding, the plastic index is low, and the pre-stressed steel bar cannot be used as a common reinforced concrete building structure are solved. The 1000 MPa-level ultra-high strength corrosion-resistant steel bar comprises the following components in percentage by mass: c:0.32 to 0.35 percent, si:0.55 to 0.85 percent, mn:1.40 to 1.60 percent of Ni:0.45 to 0.85 percent, cr:0.65 to 1.05 percent, V:0.140 to 0.180 percent, N:0.020% -0.050%, nb:0.020% -0.040%, ti:0.010% -0.025%, cu:0.20 to 0.60 percent, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, and the balance of Fe and unavoidable trace impurities. The 1000 MPa-level ultra-high strength corrosion-resistant steel bar has the advantages of excellent room temperature strength and toughness, high yield ratio, good shock resistance and excellent corrosion resistance.

Description

1000 MPa-level ultra-high strength corrosion-resistant steel bar and preparation method thereof
Technical Field
The invention relates to the technical field of metal materials, in particular to a 1000 MPa-level ultra-high strength corrosion-resistant steel bar and a preparation method thereof.
Background
According to the national requirements of controlling total quantity, eliminating the fall and accelerating the structural adjustment of the steel industry, the development and application of key steel varieties such as high strength, high corrosion resistance, high special performance and the like are increased by improving the quality and the performance of common products with wide range, and the high-strength, anti-seismic, weather-resistant, fire-resistant and corrosion-resistant steel bars and the like are developed. The strength of the existing reinforced bars is mainly 400MPa and 500MPa, and considering that destructive disasters such as earthquake, fire disaster and the like are often the most important aspect of the damage of the reinforced concrete building. Therefore, the earthquake-proof design, especially the strength of the steel bars, becomes the most important factor for the disaster-tolerant capability of the building. Considering the cost factor, namely the service life of reinforced concrete buildings, especially under special environments, such as harbor buildings, cross-sea bridges and the like, the corrosion resistance of steel becomes a necessary factor for the service life. The main chemical composition C of the existing 830 Mpa-level reinforcing steel bar (CN 103484780B) is as follows: 0.38 to 0.43 percent, mn:0.6 to 0.8 percent, cr:0.7 to 0.9 percent, ni:1.6 to 2 percent of Mo:0.15 to 0.25 percent. The carbon content is far higher than that of common steel bars, the carbon equivalent is too high, the steel bars cannot be used for welding the steel bars, the plastic index is low, the steel bars are quenched by high-pressure water spraying at 1100 ℃ through induction heating, then are tempered water cooled at 600 ℃ through induction heating, the structure is tempered martensite, the steel bars are heat-treated secondary processing prestressed steel bars, the steel bars cannot be used as common reinforced concrete building structures, and the heat-treated steel bars are high in production cost. Therefore, it is necessary to develop a 1000 Mpa-level high-strength high-corrosion-resistance steel bar, and reasonable matching of high strength and toughness and high corrosion resistance can be achieved without remarkably increasing cost.
Disclosure of Invention
In view of the above, the invention aims to provide a 1000MPa grade ultra-high strength corrosion-resistant steel bar and a preparation method thereof, which are used for solving the problem that the yield strength, tensile strength and corrosion resistance of the existing steel bar cannot be reasonably matched.
The aim of the invention is mainly realized by the following technical scheme:
on one hand, the invention provides a 1000 MPa-grade ultra-high strength corrosion-resistant steel bar, which comprises the following components in percentage by mass: c:0.32 to 0.35 percent, si:0.55 to 0.85 percent, mn:1.40 to 1.60 percent of Ni:0.45 to 0.85 percent, cr:0.65 to 1.05 percent, V:0.140 to 0.180 percent, N:0.020% -0.050%, nb:0.020% -0.040%, ti:0.010% -0.025%, cu:0.20 to 0.60 percent, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, and the balance of Fe and unavoidable trace impurities.
Further, the 1000MPa grade ultra-high strength corrosion resistant steel bar comprises the following components in percentage by mass: c:0.32 to 0.35 percent, si:0.55 to 0.8 percent of Mn:1.43 to 1.60 percent of Ni:0.45 to 0.83 percent, cr:0.65 to 1.03 percent, V:0.140 to 0.180 percent, N:0.0210% -0.045%, nb:0.020% -0.040%, ti:0.010% -0.025%, cu:0.20 to 0.60 percent, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, and the balance of Fe and unavoidable trace impurities.
Further, in the components of the 1000MPa grade ultra-high strength corrosion-resistant steel bar, the range of carbon equivalent is 0.83% -0.86%.
Further, in the components of the 1000MPa grade ultra-high strength corrosion-resistant steel bar, w (V)/w (N) is more than 5.3.
Further, the microstructure of the 1000MPa grade ultra-high strength corrosion-resistant steel bar is ferrite, pearlite and bainite, wherein the volume percentage of ferrite is 15-30%, the volume percentage of pearlite is 5-15%, and the volume percentage of bainite is 55-80%; the grain size is 10.5-12.5 grade.
Further, the 1000MPa grade ultra-high strength corrosion resistant steel bar has the following properties: the yield strength is more than or equal to 1000MPa, the tensile strength is more than or equal to 1250MPa, the strength-to-deflection ratio is more than or equal to 1.25, the elongation after breaking is more than or equal to 12%, and the total maximum force elongation is more than or equal to 6.5%.
The invention also provides a preparation method of the 1000 MPa-level ultra-high strength corrosion-resistant steel bar, which comprises the following steps:
step 1, smelting blast furnace molten iron and scrap steel serving as raw materials through a converter, wherein the content of C in the final component of molten steel is controlled to be more than or equal to 0.10%, and the content of P is controlled to be less than or equal to 0.015%; the converter controls tapping temperature to 1640-1655 ℃, and Si iron, mn iron, si-Mn alloy, ni iron, cr iron, V-N alloy, nb iron, ti iron and Cu are added when tapping;
LF refining: the electrode heats the molten steel, and alloy bulk Si iron, si-Mn alloy, carbon powder, V-N alloy, nb iron, ti iron and Si-Ca wire pair components are added for fine adjustment, and qualified molten steel is obtained by LF argon blowing; white slag making operation, wherein the standing time is ensured to be more than or equal to 38min; feeding a calcium silicate wire for 150-200 m, and performing soft argon blowing for more than or equal to 5min after the components and the temperature are qualified;
step 3, performing full-process protection continuous casting on LF refined qualified molten steel, controlling the upper stage temperature of the molten steel at 1550+/-5 ℃, starting electromagnetic stirring in the whole process, and controlling the tundish temperature at 1515-1525 ℃;
step 4, heating and preserving heat of the continuous casting blank in a steel rolling heating furnace, and then performing hot rolling and controlled cooling to obtain 1000MPa grade ultra-high strength corrosion resistant steel bars;
in step 4, parameters of heating and heat preservation are as follows: the heat preservation temperature is controlled to 1150-1175 ℃, the heat preservation time of the hot blank is 60-90 min, and the heat preservation time of the cold blank is: 90-120 min;
in the step 4, the initial rolling temperature of hot rolling, the temperature of a finishing mill feeding K2 and the finishing temperature of a finishing mill feeding K1 are respectively controlled to 1050+/-10 ℃, 960+/-10 ℃ and 980+/-10 ℃; and (5) after rolling, cooling by control.
Further, in the step 1, the final slag components in the converter smelting process are controlled as follows: the final slag alkalinity R is more than or equal to 3.0, mgO=6-10%, TFe is less than or equal to 20%.
In the step 3, the pulling speed is controlled to be 2.8-3.2 m/min.
In the step 3, D class inclusions are less than or equal to 2.0 level, and Ds class inclusions are less than or equal to 2.0 level.
Compared with the prior art, the invention has the following beneficial effects:
a) According to the invention, the components of the steel bar are precisely controlled, the content of elements such as Mn, ni, cr, V, nb, ti, cu and the like is precisely controlled, and the yield strength and the tensile strength of the steel are remarkably improved through the precipitation strengthening and fine-grain strengthening effects of microalloy elements; the microstructure of the obtained steel bar is ensured to be ferrite, pearlite and bainite by combining with the process detail parameter control of each step in the preparation method; further ensuring the following mechanical properties of the steel bar: the yield strength is more than or equal to 1000MPa, the tensile strength is more than or equal to 1250MPa, the strength-to-deflection ratio is more than or equal to 1.25, the elongation after breaking is more than or equal to 12%, and the total maximum force elongation is more than or equal to 6.5%; the steel reinforcement has a relative corrosion rate (compared to Q235 reference) within 50% for 144 hours.
b) The invention adopts the strict components and inclusion control of steelmaking and refining, the steel rolling process adopts weak water cooling, air water mist cooling, air cooling or air cooling after online rolling, and the temperature of a cooling bed is controlled to be 860-980 ℃ according to different specifications. According to different specifications and sizes, flexible cooling control means are adopted, and flexible production of 1000 Mpa-level hot-rolled corrosion-resistant steel bars is realized.
c) The steel bar disclosed by the invention has the advantages of excellent room-temperature strength and toughness, high yield ratio, good shock resistance and excellent corrosion resistance. The steel bar has the advantages of low manufacturing cost, economy, practicability, good strength and toughness and good corrosion resistance.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
Fig. 1 is a microstructure of reinforcing bars of Φ18mm in example 1, 500×;
FIG. 2 is a microstructure of reinforcing bars of Φ18mm in example 2, 500×;
FIG. 3 is a microstructure of reinforcing bars of Φ18mm in example 3, 500X;
fig. 4 is a microstructure of a steel bar of comparative example, which does not contain Ni, cr, cu elements, 500×.
Detailed Description
Preferred embodiments of the present invention are described in detail below with reference to the attached drawing figures, which form a part of the present invention and are used in conjunction with the embodiments of the present invention to illustrate the principles of the present invention.
The invention provides a 1000 MPa-level ultra-high strength corrosion-resistant steel bar, which comprises the following components in percentage by mass: c:0.32 to 0.35 percent, si:0.55 to 0.85 percent, mn:1.40 to 1.60 percent of Ni:0.45 to 0.85 percent, cr:0.65 to 1.05 percent, V:0.140 to 0.180 percent, N:0.020% -0.050%, nb:0.020% -0.040%, ti:0.010% -0.025%, cu:0.20 to 0.60 percent, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, and the balance of Fe and unavoidable trace impurities.
The following is a specific description of the action and the selection of the amounts of the components contained in the invention:
carbon (C): is the cheapest element for improving the strength index of the steel bar. The C content in the steel increases, the yield point and the tensile strength increase, but the plasticity and the impact property decrease, and the welding performance of the steel deteriorates. C can also form primary carbide (V, nb, ti) C with V, nb and Ti, refine the grain size and further improve the strength. Too high carbon content also reduces the atmospheric corrosion resistance of the steel, and high carbon steel in open-air yards is easy to rust; in addition, carbon increases the cold shortness and aging sensitivity of the steel. Therefore, the invention controls the content of C to be 0.32-0.35%.
Manganese (Mn): is a good deoxidizer and desulfurizing agent. Steels generally contain a certain amount of manganese, which eliminates or reduces the hot shortness of the steel due to sulfur, thereby improving the hot workability of the steel.
Manganese and iron form solid solution, so that the hardness and strength of ferrite and austenite in steel are improved; manganese is also a carbide forming element, and enters cementite to replace a part of iron atoms. Manganese plays a role in refining pearlite in steel due to the fact that the critical transition temperature is reduced, and indirectly plays a role in improving the strength of the pearlite steel; manganese's ability to stabilize austenitic structure is inferior to nickel, and also strongly increases the hardenability of steel.
Manganese and sulfur form MnS with a high melting point, and thermal embrittlement due to FeS can be prevented. Manganese has a tendency to increase steel grain coarsening and temper embrittlement susceptibility. If the cooling is improper after smelting casting and forging, white spots are easily generated on the steel. Effect of Mn on microstructure and mechanical properties of steel: manganese is dissolved in ferrite and austenite in a solid way, so that an austenite region is enlarged; manganese strongly reduces Ar1 and martensite transformation temperature (the effect of which is inferior to that of carbon) of steel and the speed of transformation in steel, improves hardenability of steel, increases the content of retained austenite, makes the quenched and tempered structure of steel uniform and refined, avoids aggregation of carbide in carburized layer into blocks, but increases overheat sensitivity and tempering brittleness tendency of steel. The effect of manganese to strengthen ferrite or austenite is inferior to that of carbon, phosphorus and silicon, and the strength is improved, and meanwhile, the strength of the low-carbon and medium-carbon pearlite steel is obviously improved due to the refinement of pearlite, so that the ductility is reduced; manganese does not reduce the toughness of the steel under the precondition of strictly controlling the heat treatment process, avoiding grain growth during overheating and tempering brittleness. Therefore, the Mn content is controlled to be 1.40-1.60%.
Silicon (Si): can be dissolved in ferrite and austenite to improve the hardness and strength of steel, and the effect is inferior to that of phosphorus, but when the silicon content exceeds 3%, the plasticity and toughness of steel are obviously reduced. Action of Si on microstructure and mechanical Properties of Steel: exists in ferrite or austenite in solid solution form, reduces the austenite phase region, improves the hardness and strength of ferrite and austenite, and has stronger action than Mn, ni, cr, W, mo, V and the like. Comprehensive research shows that the Si content is controlled to be 0.55-0.85%.
Phosphorus (P): the alloy element is added into low alloy structural steel, so that the strength and the atmospheric corrosion resistance of the steel can be improved, phosphorus is dissolved in ferrite, the strength and the hardness of the steel can be improved, the biggest harm is serious segregation, the tempering brittleness is increased, the plasticity and the toughness of the steel are obviously reduced, and the steel is easy to crack. Phosphorus also has a detrimental effect on weldability. Phosphorus is a harmful element and is controlled strictly, and the content of phosphorus in the steel bar is generally not more than 0.045%. In the present invention, P is controlled to be within 0.025%.
Sulfur (S): the machinability of the steel can be improved except that sulfur is added as a beneficial element in free-cutting steel. In other steel types, sulfur is seriously segregated in the steel, the quality of the steel is deteriorated, the sulfur is a harmful element, the sulfur is strictly controlled, and the sulfur is generally controlled below 0.045% in the steel bar. In order to prevent brittleness due to sulfur, sufficient manganese should be added to form MnS having a higher melting point. In the present invention, S is controlled to be within 0.025%.
Chromium (Cr): can increase the hardenability of steel and has secondary hardening effect. The hardness and wear resistance of the high-carbon steel can be improved without embrittling the steel; chromium has good corrosion resistance, can improve the strength and hardness of carbon steel in a rolled state, and reduces the elongation and the reduction of area. When other alloy elements are added in the process of improving the strength and the hardness of the steel, the effect is obvious. In the invention, the Cr addition is controlled within the range of 0.65-1.05%.
Nickel (Ni): the solution can be infinitely dissolved in austenite, the solubility in ferrite is not influenced by the carbon content, the solution can reach 10%, the austenitic structure of steel can be maintained in the solid solution state, the austenitic temperature zone is enlarged, and the hardenability of austenite can be slightly improved. Nickel dissolved in ferrite can improve the strength and toughness of steel. In addition, nickel can improve corrosion resistance, but nickel is expensive. In the invention, the Ni addition is controlled within the range of 0.45-0.85%.
Copper (Cu): copper has the outstanding effect of improving the atmospheric corrosion resistance of common low alloy steels, and particularly when used with phosphorus, the addition of copper can also improve the strength and yield ratio of the steel without adversely affecting the welding performance. The corrosion-resistant life of the steel containing 0.20 to 0.50 percent of copper is 2 to 5 times that of the common carbon steel. When the copper content exceeds 0.75%, the aging strengthening effect can be generated after solution treatment and aging. At low copper levels, the effect is similar to nickel, but weaker. When the copper content is high, the heat distortion is not easy, and the copper embrittlement phenomenon is caused during the heat distortion. In the invention, the Cu addition is controlled within the range of 0.2-0.60%.
Vanadium (V): microalloying elements act in the steel by forming carbon and nitride. As the nitride in the steel has higher stability than carbide, the precipitated phase is finer and dispersed, and the strengthening effect is obviously improved. A large number of research results show that nitrogen is a very effective alloy element in vanadium-containing steel, and the nitrogen is added into the steel by about 0.01 percent, so that the yield strength can be improved by 120MPa, and the tensile strength can be improved by 135MPa. Therefore, the nitrogen can obviously improve the strengthening effect of the vanadium steel. Vanadium is mainly precipitated in the form of V (C, N) strengthening phase, and only 20% of vanadium is dissolved in the matrix. The nitrogen increase in the steel promotes the transformation of vanadium from a matrix to a V (C, N) precipitation phase, so that the vanadium in the steel plays a role in precipitation strengthening to the greatest extent. The strengthening effect of the vanadium steel can be obviously improved by fully utilizing the cheap nitrogen element, and the purposes of saving alloy content and reducing cost are achieved. Vanadium mainly plays a role in precipitation strengthening in the low-alloy hot-rolled ribbed steel bar, and the effect of precipitation strengthening depends on the quantity and the dispersity of precipitated phases, and the more and finer particles are dispersed, the greater the effect of precipitation strengthening is. The precipitation phase of V is related to the mass fraction of N and C in the steel, in particular to w (N), when the ratio w (V)/w (N) is greater than or equal to 4:1, vanadium can effectively combine with active nitrogen in steel, and V (C, N) is stably formed and precipitated in large amounts. In the invention, the V addition is controlled within the range of 0.140-0.180%.
Niobium (Nb): nb microalloying is widely applied to the production of high-strength plate strip steel. The addition of a trace amount of Nb into the low-carbon steel generally has the addition of 0.05 percent, the alloy cost is very low, and the strength and the toughness and plasticity of the steel are obviously improved by virtue of fine grain strengthening in combination with a rolling control and cooling control process of low-temperature deformation. However, the stringent requirements of niobium-containing steels on the production process are difficult to achieve under the conditions of the steel bar production. The wire rod rolling mill for producing the steel bars is fixed hole rolling, the existing continuous rod production line realizes high-efficiency rolling, the speed is very high, the temperature is generally increased during the steel bar production process, the outlet temperature of the steel bars in the final rolling stand is higher than 1100 ℃, and therefore, the steel bar production is difficult to reach the low-temperature large-deformation process condition required by niobium-containing steel. The solubility of Nb (CN), which requires a high heating temperature, is only 0.02% by mass of Nb that can be solutioned into steel at 1200 c, is another reason that Nb is limited in the use of steel bars. Although the production process conditions of the steel bar are difficult to exert the effect of strengthening the fine crystals of the niobium-containing steel, the precipitation of Nb (CN) also has a strong precipitation strengthening effect. The key point of the niobium-containing reinforcing steel bar is to reduce the precipitation temperature of Nb (CN) as much as possible, so as to obtain fine Nb (CN) precipitated phase particles. By accelerating cooling after rolling and micro Ti treatment, adding a trace amount of Nb into steel, and combining the technological measures of quick cooling after rolling, the performance of the niobium-containing steel bar is improved. In the invention, the adding amount of Nb is controlled within the range of 0.020-0.040 percent.
Titanium (Ti): ti is the micro-alloying element which is applied to steel at the earliest, tiC has strong precipitation strengthening effect in the steel, and trace Ti can obviously improve the strength of the steel. However, ti has a strong binding force with O, S, N in steel, and before TiC is formed, ti will first form oxides, sulfides and nitrides of Ti with O, S, N and other elements in steel, resulting in difficulty in stable control of titanium content in steel, thereby causing great fluctuation in steel strength level. Oxides and sulfides of Ti are formed in molten steel, and TiN is precipitated during solidification of molten steel, and is liable to become coarse inclusions. For the above reasons, the process route for improving strength by Ti microalloying has been essentially abandoned. Ti microalloying technology has been shifted to the micro titanium treatment and oxide metallurgy, and the weldability of steel is improved by adding a trace amount of Ti to the steel and utilizing the formed fine TiO and TiN. In the invention, ti is controlled to be in the range of 0.010-0.025%.
In order to further improve the comprehensive performance of the 1000 MPa-grade ultra-high strength corrosion-resistant steel bar, the 1000 MPa-grade ultra-high strength corrosion-resistant steel bar comprises the following components in percentage by mass: c:0.32 to 0.35 percent, si:0.55 to 0.8 percent of Mn:1.43 to 1.60 percent of Ni:0.45 to 0.83 percent, cr:0.65 to 1.03 percent, V:0.140 to 0.180 percent, N:0.0210% -0.045%, nb:0.020% -0.040%, ti:0.010% -0.025%, cu:0.20 to 0.60 percent, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, and the balance of Fe and unavoidable trace impurities.
Specifically, the carbon equivalent Ceq of the 1000MPa grade ultra-high strength corrosion-resistant steel bar is in the range of 0.83-0.86%.
Specifically, in the 1000MPa grade ultra-high strength corrosion-resistant steel bar, w (V)/w (N) is more than 5.3.
The invention also provides a preparation method of the 1000 MPa-level ultra-high strength corrosion-resistant steel bar, which comprises the following steps:
step 1, smelting blast furnace molten iron and scrap steel serving as raw materials through a converter, wherein the content of C in the final component of molten steel is controlled to be more than or equal to 0.10%, and the content of P is controlled to be less than or equal to 0.015%; the converter controls tapping temperature to 1640-1655 ℃, and Si iron, mn iron, si-Mn alloy, ni iron, cr iron, V-N alloy, nb iron, ti iron, cu and the like which are required are added during tapping;
step 2, LF refining: the electrode heats the molten steel, and alloy bulk Si iron, si-Mn alloy, carbon powder, V-N alloy, nb iron and Si-Ca wire pair components are added for fine adjustment, and the qualified molten steel with low gas content and inclusion content is obtained by LF argon blowing; white slag making operation, wherein the standing time is ensured to be more than or equal to 38min; feeding a calcium silicate wire for 150-200 m, and performing soft argon blowing for more than or equal to 5min after the components and the temperature are qualified;
step 3. The whole-process protection continuous casting of the LF refined qualified molten steel, controlling the upper stage temperature of the molten steel at 1550+/-5 ℃, starting electromagnetic stirring in the whole process, controlling the tundish temperature at 1515-1525 ℃, controlling the pulling speed at 2.8-3.2 m/s, and reducing the pulling speed by 0.1m/min when the superheat degree is increased by 3 ℃ when the molten steel temperature exceeds 1525 ℃;
and 4, heating and preserving heat of the continuous casting blank in a steel rolling heating furnace, and then performing hot rolling and controlled cooling to obtain the 1000 MPa-level ultrahigh-strength corrosion-resistant steel bar.
Specifically, in the step 1, considering that the reduction of the Si content in the molten iron of the blast furnace not only can reduce the fuel ratio of the blast furnace and improve the utilization coefficient of the blast furnace, energy saving and emission reduction are realized, under normal conditions, si per reduction unit is 8 times of the heat consumption required for reducing one unit of iron, so that silicon reduction is to save coke; and the method can realize the slag-less smelting in the steelmaking process, shorten the steelmaking time, reduce the energy consumption and the material cost and create good conditions for steelmaking. In general, the P, S content has adverse effects on the performance of steel, particularly on plastic indexes, and belongs to the field of elements needing to be strictly controlled, and the low-P and low-S molten iron of a blast furnace can reduce the burden of P and S removal in the subsequent steelmaking process and reduce the steelmaking cost. Thus, the control of the molten iron of the blast furnace is required to satisfy the following table 1.
Table 1 blast furnace hot metal conditions
Figure BDA0004124180320000111
Specifically, in the step 1, the converter steelmaking relies on oxygen blowing to react with carbon in the blast furnace molten iron to generate a large amount of heat, and the scrap steel is added to serve as a cooling agent, so that the steel yield is increased, and the steelmaking cost is reduced. However, the steel scrap cannot be excessively added, which results in a decrease in the temperature of molten steel, and the steel making cannot be completed. Therefore, the scrap ratio is controlled to 35% or less.
Specifically, in the above step 1, the composition of the V-N alloy can be shown in Table 2 below.
TABLE 2 vanadium-nitrogen alloy composition (%)
Number plate V N C Si Al P S
VN12 77.79 16.31 3.74 0.11 0.15 0.008 0.013
Specifically, in the step 1, the Si iron, mn iron, si-Mn alloy, ni iron, cr iron, V-N alloy, nb iron, ti iron and Cu are required to be clean and dried.
Specifically, in the step 1, the converter smelting is required to accurately control the content of the endpoint C to be 0.10-0.15%, the content of P to be less than or equal to 0.015% and the content of S to be less than or equal to 0.025%, so that the peroxidation of molten steel is avoided. The number of times of post-blowing is strictly controlled to be no more than 2 times.
Specifically, in the step 1, if the content of the end point C does not meet the control requirement, performing spot-blowing treatment; and if the content of the end point P, S does not meet the control requirement, lime is added for spot blowing treatment.
Specifically, in the step 1, the lime addition amount is calculated according to the following formula in the blowing process of converter smelting:
lime addition = 2.14 x Si content in molten iron x basicity x molten iron addition/(CaO content in lime-basicity x SiO in lime) 2 Content).
Specifically, in the above step 1, the deoxidizing agent may be Si-Al-Ba, si-Ca-Ba or the like.
Specifically, in the step 1, lime: caO is more than or equal to 88 percent.
Specifically, in the step 1, the end point temperature is controlled to be 1650 ℃ or higher, otherwise, the spot-blowing treatment is performed.
Specifically, in the step 1, the final slag components in the converter smelting process are controlled as follows: the final slag alkalinity R is more than or equal to 3.0, mgO=6-10%, TFe is less than or equal to 20%.
Specifically, in the step 1, slag stopping tapping is required to be adopted during tapping, and the slag thickness is controlled to be less than or equal to 50mm, so that slag can be controlled to be involved in molten steel, molten steel rephosphorization is avoided, the inclusion content in the steel is reduced, and the quality of the molten steel is improved.
Before tapping, opening bottom blowing, and controlling the blowing diameter of the ladle to be 300-500 mm. The arrangement can strengthen the stirring of the molten pool, so that the molten pool is more uniform, the inclusions float upwards, the inclusions are reduced, and the quality is improved.
The deoxidizer is added manually before tapping 1/4, other alloys are added when tapping 1/4, and the deoxidizer is added when tapping 3/4, so as to perform deoxidization alloying.
Specifically, in the step 1, the control of the converter components requires that Mn is controlled according to 0.95% -1.05%, si is controlled according to 0.35%, and C, si, mn, nb, V, ti, cu is finely adjusted in a refining furnace through bulk materials of alloys such as carbon powder, ferrosilicon, ferroniobium, vanadium-nitrogen alloy, ferrotitanium, copper plates and the like and wire feeding of calcium silicate wires.
Specifically, in the step 2, three groups of slag samples are taken for detection in the front, middle and later stages of the LF furnace, and a pinhole sample is taken for detection in the outlet of the LF furnace. The molten steel composition requirement of the outgoing LF furnace must be within an internal control range.
Specifically, in the step 2, the addition amount of the alloy is adjusted according to the requirement of the internal control component, and the specific addition amount is according to the following formula:
alloy addition= (inner control component middle limit-molten steel residual component)/(alloy grade×alloy absorptivity) ×steel tapping amount.
And determining whether to continue adjusting according to the analysis of the molten steel after each alloy addition, if the lower limit of the internal control requirement is lower than the lower limit, continuing adjusting, and if the upper limit of the internal control requirement is higher than the upper limit, continuing normal processing.
Specifically, in the step 2, when the LF furnace is out, siCa or SiCaBa wires are fed for 150-200 m, and soft argon blowing is carried out for more than or equal to 5 minutes.
Specifically, in the step 2, if the alloy is added or the argon blowing time is not less than 2 minutes after temperature adjustment.
Specifically, in the step 3, the pulling speed must be performed according to the pulling curve, and the pulling speed must not be frequently and greatly changed; therefore, the pulling speed is controlled to be 2.8-3.2 m/min. In order to ensure the quality of the continuous casting billet, the superheat degree of the tundish is controlled between 15 and 20 ℃.
Specifically, in the step 3, D class inclusions (spherical oxides) in the produced continuous casting blank are less than or equal to 2.0 levels, and Ds class inclusions (single spherical oxides) are less than or equal to 2.0 levels; the low-power defect meets the following requirements of qualified continuous casting billets;
table 3 low power level
General porosity Center porosity Center crack Intermediate crack Segregation of Subcutaneous crack Equiaxed crystal rate
Grade less than or equal to 2.0 Grade less than or equal to 2.0 Not more than 1.0 level Not more than 1.0 level Not more than 1.0 level Not more than 1.0 level ≥30％
Specifically, in the step 4, the casting blank must be strictly and carefully inspected before being charged into the furnace; if the surface of the casting blank has defects such as inclusion, scab, crack, subcutaneous bubble, fold, overlap and the like, the casting blank can be put into the furnace only by flame cleaning.
Specifically, in the step 4: the heat preservation temperature of the continuous casting blank in the steel rolling heating furnace is controlled to 1150-1175 ℃.
Specifically, in the step 4, the heat preservation time of the hot blank is 60-90 min, and the heat preservation time of the cold blank is: 90-120 min.
Specifically, in the step 4, the heating furnace is a walking beam type side-in side-out three-section heating furnace, and the temperatures of the preheating section, the heating section and the soaking section in the hearth are all automatically controlled and adjusted by a computer.
Specifically, in the step 4, according to the production requirement of the hot rolled straight bar, the initial rolling temperature, the temperature of the feeding K2 finishing mill (water cooling adjustment) and the final rolling temperature of the K1 finishing mill are respectively controlled to 1050+/-10 ℃, 960+/-10 ℃ and 980+/-10 ℃; after rolling, strong water cooling (when cooling, 1-4 sections are opened and are strong cooling), weak water cooling (1 section is opened, low water pressure and small water quantity) air water mist cooling (compressed air is used for atomizing and cooling water), air cooling (cooling bed blast cooling) and air cooling (natural cooling in air) are adopted, and the cooling bed temperature is controlled to be 860-980 ℃ according to different specifications (the upper limit of the cooling bed temperature on small-specification steel bars and the lower limit of the cooling bed temperature on large-specification steel bars).
Specifically, in the step 4, the microstructure of the 1000MPa grade ultra-high strength corrosion-resistant steel bar is ferrite, pearlite and bainite, wherein the volume percentage of ferrite is 15-30%, the volume percentage of pearlite is 5-15%, and the volume percentage of bainite is 55-80%; the grain size is 10.5-12.5 grade.
Specifically, the mechanical properties of the 1000 MPa-level ultra-high strength corrosion-resistant steel bar are as follows: the yield strength is equal to or greater than 1000MPa (such as 1014-1084 MPa), the tensile strength is equal to or greater than 1250MPa (1272-1495 MPa), the strength-to-flex ratio is equal to or greater than 1.25 (such as 1.25-1.42), the Qu Qu ratio is less than 1.3 (such as 1.01-1.07), the elongation after break is equal to or greater than 12% (such as 16-21.5%), and the maximum total elongation is equal to or greater than 6.5% (such as 7-11%).
Specifically, in the step 4, the relative corrosion rate (compared with the Q235 reference) of the 1000MPa grade ultra-high strength corrosion-resistant steel bar within 144 hours is within 50%, such as 23.95% -45.45%. The corrosion resistance is good.
According to the invention, the components of the 1000 MPa-level ultra-high strength corrosion-resistant steel bar are precisely controlled, the content of elements such as Mn, ni, cr, V, nb, ti, cu is precisely controlled, and the yield strength and the tensile strength of the steel are remarkably improved through the precipitation strengthening and fine grain strengthening effects of microalloy elements; the microstructure of the obtained steel bar is ensured to be ferrite, pearlite and bainite by combining with the process detail parameter control of each step in the preparation method; further ensuring the following mechanical properties of the steel bar: the yield strength is equal to or greater than 1000MPa, the yield strength is equal to or greater than 1000MPa (such as 1014-1084 MPa), the tensile strength is equal to or greater than 1250MPa (1272-1495 MPa), the strength-to-flex ratio is equal to or greater than 1.25 (such as 1.25-1.42), the Qu Qu ratio is less than 1.3 (such as 1.01-1.07), the elongation after break is equal to or greater than 12% (such as 16.0-21.5%), and the maximum total elongation is equal to or greater than 6.5% (such as 7.0-11.0%); the steel reinforcement has a relative corrosion rate (compared to Q235 reference) within 50% for 144 hours. The steel bar disclosed by the invention has the advantages of excellent room-temperature strength and toughness, high yield ratio, good shock resistance and excellent corrosion resistance. The steel of the invention has low cost, economy, practicability, good strength and toughness and good corrosion resistance.
Example 1-example 3:
the invention provides a 1000MPa grade ultra-high strength corrosion resistant steel bar and a preparation method thereof, and the components of the steel of the embodiment 1 to the embodiment 3 are shown in the following table 7.
The preparation method of the high-strength high-corrosion-resistance steel bar in the embodiment 1-3 comprises the following steps:
step 1, using blast furnace molten iron and scrap steel as raw materials (molten iron 107.4t and scrap steel 15.24 t), smelting by a converter, wherein the content of C in the final component of molten steel is controlled to be 0.10-0.15%, P is less than or equal to 0.015% and S is less than or equal to 0.025%; the converter controls the tapping temperature to 1640-1655 ℃, and Si iron, mn iron, si-Mn alloy, ni iron, cr iron, V-N alloy, nb iron and the like which are required are added during tapping;
step 2, LF refining: the electrode carries out temperature raising on molten steel, adds alloy bulk Si iron, si-Mn alloy, carbon powder, V-N alloy, nb iron and Si-Ca wire pair components to carry out fine adjustment, and carries out LF argon blowing to obtain qualified molten steel with low gas content and inclusion content; white slag making operation, wherein the standing time is ensured to be more than or equal to 38min; feeding Si-Ca wire 150-200 m, and soft argon blowing time is more than or equal to 5min after the component temperature is qualified;
step 3. The whole-process protection continuous casting of the LF refined qualified molten steel, controlling the upper stage temperature of the molten steel at 1550+/-5 ℃, starting electromagnetic stirring in the whole process, controlling the current at 320A, controlling the frequency at 3Hz, controlling the tundish temperature at 1515-1525 ℃, controlling the pulling speed at 2.8-3.2 m/s, and reducing the pulling speed by 0.1m/min when the superheat degree is increased by 3 ℃ when the molten steel temperature exceeds 1525 ℃;
and 4, heating and preserving heat of the continuous casting blank in a steel rolling heating furnace, and then carrying out hot rolling and cooling to obtain the high-strength high-corrosion-resistance steel bar.
Specifically, in the above step 1, the blast furnace molten iron satisfies the following table 4.
Table 4 blast furnace hot metal conditions
Figure BDA0004124180320000151
Figure BDA0004124180320000161
Specifically, in the step 1, the scrap ratio is controlled to be 35% or less.
Specifically, in the above step 1, the composition of the V-N alloy can be shown in the following Table 5-1.
TABLE 5-1 vanadium nitrogen alloy composition (%)
Number plate V N C Si Al P S
VN12 77.79 16.31 3.74 0.11 0.15 0.008 0.013
Specifically, in the step 1, the alloys such as Si iron, mn iron, si-Mn alloy, ni iron, cr iron, V-N alloy, nb iron, ti iron, cu and the like are cleaned and dried.
Specifically, in the step 1, the converter smelting requires accurate control of the endpoint C content to be 0.10% -0.15%.
Specifically, in the above step 1, the deoxidizer may be Si-Al-Ba, si-Ca-Ba, or the like.
Specifically, in the step 1, lime: caO is more than or equal to 88 percent.
Specifically, in the step 1, the final slag components in the converter smelting process are controlled as follows: the final slag alkalinity R is more than or equal to 3.0, mgO=6-10%, TFe is less than or equal to 20%.
Specifically, in the step 1, slag blocking tapping is required to be adopted during tapping, and the slag thickness is controlled to be less than or equal to 50mm;
before tapping, opening bottom blowing, and controlling the blowing diameter of the ladle to be 300-500 mm.
The deoxidizer is added manually before tapping 1/4, other alloys are added when tapping 1/4, and the deoxidizer is added when tapping 3/4, so as to perform deoxidization alloying. The converter determines the alloy addition according to the conditions of the steel water quantity, the molten steel oxidizing property, the alloy components and the like.
Specifically, in the step 1, the control of the converter components requires that Mn is controlled according to 0.95% -1.05%, si is controlled according to 0.35%, and C, si, mn, nb, V, ti, cu is finely adjusted in a refining furnace through bulk materials of alloys such as carbon powder, ferrosilicon, ferroniobium, vanadium-nitrogen alloy, ferrotitanium, copper plates and the like and wire feeding of calcium silicate wires.
Specifically, in the step 2, three groups of slag samples are taken for detection in the front, middle and later stages of the LF furnace, and a pinhole sample is taken for detection in the outlet of the LF furnace. The molten steel composition requirement of the outgoing LF furnace must be within an internal control range.
Specifically, in the step 2, the addition amount of the alloy is adjusted according to the requirement of the internal control component, and the specific addition amount is according to the following formula:
alloy addition amount= (inner control component middle limit-molten steel residual component)/(alloy grade×alloy absorptivity) ×steel tapping amount
And determining whether to continue adjusting according to the analysis of the molten steel after each alloy addition, if the lower limit of the internal control requirement is lower than the lower limit, continuing adjusting, and if the upper limit of the internal control requirement is higher than the upper limit, continuing normal processing.
Specifically, in the step 2, slag materials in the refining of the LF furnace are shown in Table 5-2.
TABLE 5-2 slag charge
Figure BDA0004124180320000171
Specifically, in the step 2, the refining process requires white slag making operation, sampling and temperature measurement are performed after 8 minutes of power transmission, the power transmission time of molten steel refining is more than 15 minutes, and the standing time of an LF furnace is more than or equal to 38 minutes.
TABLE 5-3 refining electrode energizing time for LF furnace
Figure BDA0004124180320000172
Specifically, in the step 3, the pulling speed is controlled to be 2.8-3.2 m/min, and the superheat degree of the tundish is controlled to be 15-20 ℃.
Specifically, in the step 3, D class inclusions (spherical oxides) in the produced continuous casting square billet steel are less than or equal to 2.0 levels, and D class inclusions (single spherical oxides) are less than or equal to 2.0 levels; the low-power defect meets the following requirements of qualified continuous casting billets;
table 6 low power level
Figure BDA0004124180320000173
Figure BDA0004124180320000181
Specifically, in the step 4, the casting blank must be strictly and carefully inspected before being charged into the furnace; if the surface of the casting blank has defects such as inclusion, scab, crack, subcutaneous bubble, fold, overlap and the like, the casting blank can be put into the furnace only by flame cleaning.
Specifically, in the step 4, the heating furnace is a walking beam type side-in side-out three-section heating furnace, and comprises a preheating section, a heating section and a soaking section in a hearth. The temperature of each section of the heating furnace is automatically controlled and adjusted by a computer.
Specifically, in the step 4: the heat preservation temperature of the continuous casting blank in the steel rolling heating furnace is controlled to 1150-1175 ℃.
Specifically, in the step 4, the heat preservation time of the hot blank is 60-90 min, and the heat preservation time of the cold blank is: 90-120 min.
Specifically, in the step 4, according to the production requirement of the straight hot rolled steel bar, the initial rolling temperature, the temperature of the entering K2 finishing mill (water cooling adjustment) and the final rolling temperature of the K1 finishing mill are respectively controlled to 1050+/-10 ℃, 960+/-10 ℃ and 980+/-10 ℃; after rolling, strong water cooling (1-4 sections are opened and are strong cooling) is not needed, weak water cooling (1 section is opened, low water pressure and small water quantity) air water mist cooling (compressed air is used for carrying out atomization cooling on water), air cooling (cooling bed blast cooling) and air cooling (natural cooling in air) are adopted, and the temperature of the cooling bed is controlled to be 860-980 ℃ according to different specifications.
Specific components of the reinforcing bars of examples 1 to 3 are shown in the following Table 7, the microstructure of the reinforcing bars of examples 1 to 3 is shown in Table 8 to 1, the microstructure of the reinforcing bars of examples 1 to 3 is shown in Table 8 to 2, and the mechanical properties of the reinforcing bars are shown in tables 9 to 1,9 to 2, and 9 to 3.
TABLE 7 Main chemical Components (%)
Figure BDA0004124180320000182
Figure BDA0004124180320000191
TABLE 8-1 Low power tissue of examples 1-3
General porosity Center porosity Center crack Intermediate crack Segregation of Subcutaneous crack Equiaxed crystal rate
Grade less than or equal to 2.0 Grade less than or equal to 2.0 Not more than 1.0 level Not more than 1.0 level Not more than 1.0 level Not more than 1.0 level ≥30％
TABLE 8-2 microstructure of the rebars of examples 1-3
Sequence number Microstructure of microstructure Grain size of
Example 1 About 15% ferrite +5% pearlite +80% bainite 11.0 to 12.5 grades
Example 2 About 20% ferrite +10% pearlite +70% bainite 10.5 to 12.0 grade
Example 3 About 30% ferrite +15% pearlite +55% bainite 10.5 to 11.5 grades
Contrast sample About 55% ferrite +45% pearlite 8.0 to 10.0 grade
Table 9-1 mechanical properties of the reinforcing bars of example 1 in different sizes and different cooling processes
Figure BDA0004124180320000192
Figure BDA0004124180320000201
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Remarks: the aerosol is cold (small amount of water atomization) and weakly water-cooled (low pressure small amount of water), as follows.
Table 9-2 mechanical properties of the reinforcing bars of example 2 in different sizes and different cooling processes
Figure BDA0004124180320000202
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Figure BDA0004124180320000211
Table 9-3 mechanical properties of the reinforcing bars of example 3 in different sizes and different cooling processes
Figure BDA0004124180320000212
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Figure BDA0004124180320000221
As can be seen from the above tables 9-1,9-2 and 9-3:
the room temperature yield strength of the reinforcing steel bar is more than or equal to 1000MPa (for example, 1:1015 MPa-1073 MPa; example, 2:1014 MPa-1069 MPa; example, 3:1011 MPa-1084 MPa), the tensile strength is more than or equal to 1250MPa (for example, 1:1300 MPa-1495 MPa; example, 2:1272 MPa-1478 MPa; example, 3:1274 MPa-1425 MPa), the strength-to-flex ratio is more than or equal to 1.25 (for example, 1:1.27-1.42; example, 2:1.25-1.40; example, 3:1.25-1.34), the elongation after break is more than or equal to 12% (for example, 1:17.5-20.5; example, 2:16.0-21.0%, example, 16.0-21.5%), the maximum total elongation is more than or equal to 6.5% (for example, 1:7.5-10%, example, 7.0-11.0%, and example, 3:7.5-10.5% of the total elongation after breaking is more than or equal to 6.5% (for example, 1:7.5-10.0%), and the mechanical property meets the requirement of HR1000-class B.
FIG. 1 shows a microstructure of 1000MPa grade corrosion resistant steel bar of 18mm in example 1; FIG. 2 shows a microstructure of 1000MPa grade corrosion resistant steel bar of 18mm in example 2; FIG. 3 shows a microstructure of 1000MPa grade corrosion resistant steel bar of 18mm in example 3; fig. 4 shows a microstructure of a 600Mpa plain steel bar without Ni, cr, cu elements of the comparative example, the microstructure of the comparative example being ferrite + pearlite, the grain size being 8.0-10 grade, the ferrite and pearlite grains of the comparative example being coarser in size and lower in strength.
The invention also researches the corrosion resistance of the steel bar, and the test solution adopts sodium chloride solution with the initial concentration of (0.34+/-0.09) mol.L -1 Sodium chloride solution (mass fraction of 2.0% ± 0.05%) with corrosion test time of 24 hours, 72 hours and 144 hours, respectively. The results of corrosion-resistant steel bar corrosion test using Q235 as a reference are shown in Table 10. As can be seen from the test results in Table 10, the relative corrosion rates are all within 50% (for example, the average relative corrosion rate for 144 hours is 23.95% in example 1, 48.04% in example 2 and 45.45% in example 3), and the requirement that the relative corrosion rate of the corrosion-resistant steel bars is less than 70% is met.
Table 10 corrosion resistance of the bars of examples and comparative examples
Figure BDA0004124180320000241
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.

Claims (10)

1. The 1000 MPa-level ultra-high strength corrosion-resistant steel bar is characterized by comprising the following components in percentage by mass: c:0.32 to 0.35 percent, si:0.55 to 0.85 percent, mn:1.40 to 1.60 percent of Ni:0.45 to 0.85 percent, cr:0.65 to 1.05 percent, V:0.140 to 0.180 percent, N:0.020% -0.050%, nb:0.020% -0.040%, ti:0.010% -0.025%, cu:0.20 to 0.60 percent, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, and the balance of Fe and unavoidable trace impurities.
2. The 1000 MPa-grade ultra-high strength corrosion-resistant steel bar according to claim 1, wherein the 1000 MPa-grade ultra-high strength corrosion-resistant steel bar comprises, in mass percent: c:0.32 to 0.35 percent, si:0.55 to 0.80 percent of Mn:1.43 to 1.60 percent of Ni:0.45 to 0.83 percent, cr:0.65 to 1.03 percent, V:0.140 to 0.180 percent, N:0.0210% -0.045%, nb:0.020% -0.040%, ti:0.010% -0.025%, cu:0.20 to 0.60 percent, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, and the balance of Fe and unavoidable trace impurities.
3. The ultra-high strength corrosion resistant reinforcement of 1000MPa grade according to claim 1, wherein the carbon equivalent of the composition of the ultra-high strength corrosion resistant reinforcement of 1000MPa grade is in the range of 0.83% to 0.86%.
4. The 1000 MPa-grade ultra-high strength corrosion-resistant reinforcing bar according to claim 1, wherein w (V)/w (N) is 5.3 or more in the composition of the 1000 MPa-grade ultra-high strength corrosion-resistant reinforcing bar.
5. The 1000MPa grade ultra-high strength corrosion resistant steel bar according to claim 1, wherein the microstructure of the 1000MPa grade ultra-high strength corrosion resistant steel bar is ferrite + pearlite + bainite, wherein the volume percentage of ferrite is 15-30%, the volume percentage of pearlite is 5-15%, and the volume percentage of bainite is 55-80%; the grain size is 10.5-12.5 grade.
6. The 1000MPa grade ultra-high strength corrosion resistant rebar of any one of claims 1 to 5, wherein the 1000MPa grade ultra-high strength corrosion resistant rebar has the following properties: the yield strength is more than or equal to 1000MPa, the tensile strength is more than or equal to 1250MPa, the strength-to-deflection ratio is more than or equal to 1.25, the elongation after breaking is more than or equal to 12%, and the total maximum force elongation is more than or equal to 6.5%.
7. The preparation method of the 1000 MPa-level ultra-high strength corrosion-resistant steel bar is characterized by comprising the following steps:
step 1, smelting blast furnace molten iron and scrap steel serving as raw materials through a converter, wherein the content of C in the final component of molten steel is controlled to be more than or equal to 0.10%, and the content of P is controlled to be less than or equal to 0.015%; the converter controls tapping temperature to 1640-1655 ℃, and Si iron, mn iron, si-Mn alloy, ni iron, cr iron, V-N alloy, nb iron, ti iron and Cu are added when tapping;
step 2, LF refining: the electrode heats the molten steel, and alloy bulk Si iron, si-Mn alloy, carbon powder, V-N alloy, nb iron and Si-Ca wire pair components are added for fine adjustment, and qualified molten steel is obtained by LF argon blowing; white slag making operation, wherein the standing time is ensured to be more than or equal to 38min; feeding a calcium silicate wire for 150-200 m, and performing soft argon blowing for more than or equal to 5min after the components and the temperature are qualified;
step 3, performing full-process protection continuous casting on LF refined qualified molten steel, controlling the upper stage temperature of the molten steel at 1550+/-5 ℃, starting electromagnetic stirring in the whole process, and controlling the tundish temperature at 1515-1525 ℃;
step 4, heating and preserving heat of the continuous casting blank in a steel rolling heating furnace, and then performing hot rolling and controlled cooling to obtain 1000MPa grade ultra-high strength corrosion resistant steel bars;
in the step 4, the parameters of heating and heat preservation are as follows: the heat preservation temperature is controlled to 1150-1175 ℃, the heat preservation time of the hot blank is 60-90 min, and the heat preservation time of the cold blank is: 90-120 min;
in the step 4, the initial rolling temperature of hot rolling, the temperature of a finishing mill feeding K2 and the finishing temperature of a finishing mill feeding K1 are respectively controlled to 1050+/-10 ℃, 960+/-10 ℃ and 980+/-10 ℃; and (5) cooling after rolling.
8. The method according to claim 7, wherein in the step 1, the final slag composition in the converter smelting process is controlled as follows: the final slag alkalinity R is more than or equal to 3.0, mgO=6-10%, TFe is less than or equal to 20%.
9. The method according to claim 7, wherein in the step 3, the pulling speed is controlled to be 2.8-3.2 m/min.
10. The method according to any one of claims 7 to 9, wherein in the continuous casting slab produced in the step 3, the D-class inclusion is no more than 2.0 grade and the Ds-class inclusion is no more than 2.0 grade.
CN202310241156.8A 2023-03-14 2023-03-14 1000 MPa-level ultra-high strength corrosion-resistant steel bar and preparation method thereof Pending CN116288061A (en)

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