CN113462965B - Steel for rolling 635 MPa-grade high-strength anti-seismic reinforcing steel bar in two-phase region and production method thereof - Google Patents

Steel for rolling 635 MPa-grade high-strength anti-seismic reinforcing steel bar in two-phase region and production method thereof Download PDF

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CN113462965B
CN113462965B CN202110675976.9A CN202110675976A CN113462965B CN 113462965 B CN113462965 B CN 113462965B CN 202110675976 A CN202110675976 A CN 202110675976A CN 113462965 B CN113462965 B CN 113462965B
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CN113462965A (en
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郭湛
汪开忠
于同仁
余良其
杨应东
姜婷
张晓瑞
徐雁
袁月
尹德福
龚梦强
丁雷
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Maanshan Iron and Steel 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
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C21C2007/0018—Boron
    • 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
    • C21D2211/004—Dispersions; Precipitations
    • 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

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Abstract

The invention discloses a steel for rolling 635 MPa-grade high-strength anti-seismic reinforcing steel bars in a two-phase region and a production method thereof, belonging to the technical field of hot-rolled ribbed reinforcing steel bars for concrete, wherein the steel for rolling 635 MPa-grade high-strength anti-seismic reinforcing steel bars in the two-phase region comprises the following chemical components in percentage by weight: c: 0.22-0.28%, Si: 0.40-0.80%, Mn: 1.40-1.60%, P: less than or equal to 0.035%, S: less than or equal to 0.035%, Nb: 0.010-0.020%, V: 0.100-0.150%, B: 0.0008-0.0035%, Cu: 0.10-0.20%, N: 0.010-0.020%, and the balance of Fe and inevitable impurity elements. The component range of the 635MPa steel bar and the two-phase region rolling process are designed by combining the existing process equipment conditions, and the strength grade reaches 635MPa on the premise of not reducing the ductility index, so that the requirements of high-rise and large-span building structures are met.

Description

Steel for rolling 635 MPa-grade high-strength anti-seismic reinforcing steel bar in two-phase region and production method thereof
Technical Field
The invention belongs to the technical field of hot-rolled ribbed steel bars for concrete, and particularly relates to steel for rolling 635 MPa-grade high-strength anti-seismic steel bars in a two-phase region and a production method thereof.
Background
Compared with the common hot rolled steel bar, the high-strength hot rolled steel bar has the advantages of high strength, excellent comprehensive performance (such as process performance, welding performance, ductility and earthquake resistance), energy conservation, environmental protection, long service life, high safety and the like. Low-strength-level steel bars are eliminated in developed countries abroad, 500 MPa-level steel bars are widely adopted, and 600 MPa-level steel bars are also widely applied. Compared with developed countries, the strength of the reinforcing steel bars in China is generally lower. In recent years, with the coming of a series of national high-strength steel bar popularization and application policies, the percentage of the use amount of the high-strength steel bars is increased year by year.
The research of engineering design shows that under the premise of not reducing the overall performance of a concrete structure, 635 MPa-level steel bars with small first-level specifications can be used for replacing 400 MPa-level steel bars, and if phi 25mm HRB630 can be used for replacing phi 28mm HRB400, the purpose of reducing the steel for the building is achieved. Calculated, the steel consumption can be reduced by more than 30%. In addition, the 635 MPa-grade high-strength steel bars can also solve the problems of 'fat beam and fat column' and the like in a building structure, increase the using area of the building, enable the structural design to be more reasonable, facilitate the promotion of the scientific development of engineering construction and the adjustment of the structure of products in the steel industry, and have important significance for eliminating out-of-date capacity and implementing the sustainable development strategy.
For the related patent application of the steel bar, the Chinese patent application numbers are as follows: 200910218247.X, published as: 2010-06-02 'HRB 500E niobium boron composite microalloy high performance aseismic steel bar and its controlled rolling and controlled cooling production method' comprises the following chemical components by mass ratio: c: 0.20 to 0.25 wt%, Si: 0.25 to 0.45 wt%, Mn: 1.35 to 1.57 wt%, Nb: 0.035-0.050 wt%, B: 0.0008 to 0.0025 wt%, less than or equal to 0.045 wt% of S, less than or equal to 0.045 wt% of P, and the balance of Fe and inevitable impurities. In the process, a small amount of ferrocolumbium and ferroboron are added in the steelmaking process to obtain a steel billet, the initial rolling temperature, the final rolling temperature, the rolling speed, the rolling pass and time and the rapid cooling and cooling control after rolling are controlled through the steel rolling process, the dual functions of Nb and B microalloy strengthening and cooling control fine grain strengthening are exerted, the strength of the steel bar is obviously improved, and meanwhile, better toughness and plasticity are kept; however, if the strength is further improved in this way, the impact of plasticity and toughness is encountered, and the seismic performance is affected.
The Chinese patent application numbers are: 201210252106.1, publication date is: 2012-10-17 of a 600MPa grade earthquake resistant rebar and a method for manufacturing the same, the rebar comprises the following components: basic components: 0.21-0.26% of C, 0.61-0.80% of Si, 1.30-1.60% of Mn and 0.15-0.21% of V; optional ingredients: any one or a combination of more than two of Nb0.001-0.050%, Ti0.001-0.050%, Cr0.10-0.50%, B0.0001-0.0050% and Mo0.001-0.010%; the balance of Fe and inevitable impurities. The manufacturing method of the twisted steel adopts a short-flow process of converter or electric furnace smelting, small square billet continuous casting and rolling and cooling bed cooling. The yield strength of the twisted steel produced by adopting the components and the method is more than 600MPa, and the requirement of national standard on the anti-seismic performance of the twisted steel is met.
The Chinese patent application numbers are: 201910804021.1, publication date is: 2019-12-20, which comprises 0.15-0.20 wt% of C, 0.7-0.9 wt% of Si, 0.5-1.0 wt% of Mn, 0.8-2.0 wt% of Ni + Cr + Mo, 0.1-0.25 wt% of Nb + V, 0.05-0.15 wt% of Ti, 0.0015-0.0025 wt% of B, less than or equal to 0.003 wt% of N, less than or equal to 0.003 wt% of O, and the balance of Fe and inevitable impurities; and refining the LF white slag for 5min, and then adding ferroniobium, ferrovanadium and ferrotitanium cored wires for alloying, wherein the room-temperature yield strength of the prepared hot-rolled reinforcing steel bar finished product is more than or equal to 650 MPa.
Disclosure of Invention
1. Problems to be solved
Aiming at the problems of poor elongation property and low strength of the existing anti-seismic reinforcing steel bar, the invention provides a steel for rolling a 635MPa grade high-strength anti-seismic reinforcing steel bar in a two-phase region; the component range of the 635MPa steel bar and the two-phase region rolling process are designed by combining the existing process equipment conditions, and the strength grade reaches 635MPa on the premise of not reducing the ductility index, so that the requirements of high-rise and large-span building structures are met.
The invention also aims to provide a production method of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the invention relates to a steel for rolling 635 MPa-grade high-strength anti-seismic reinforcing steel bars in a two-phase region, which comprises the following chemical components in percentage by weight: c: 0.22-0.28%, Si: 0.40-0.80%, Mn: 1.40-1.60%, P: less than or equal to 0.035%, S: less than or equal to 0.035%, Nb: 0.010-0.020%, V: 0.100 to 0.150%, B: 0.0008-0.0035%, Cu: 0.10-0.20%, N: 0.010-0.020%, and the balance of Fe and inevitable impurity elements. Besides conventional strengthening elements such as C, Si, Mn, V, Nb and the like, the hardenability of the steel is improved by adding B element, the eutectoid point of the steel is moved to the left by adding Cu element, the V/Nb ratio is controlled, and the ferrite content is reduced and the pearlite content is improved by combining the two-phase region rolling process, so that the strength and the yield ratio are improved.
As a further illustration of the invention, the V/Nb ratio is from 5 to 15.
The invention relates to a production method of steel for rolling 635 MPa-grade high-strength anti-seismic reinforcing steel bars in a two-phase region, which comprises the following steps:
s1, refining the molten steel in an LF furnace;
s2, continuous casting;
s3, rolling in a two-phase region; by adopting (gamma + alpha) two-phase region rolling, on one hand, crystal grains are refined, and on the other hand, a large amount of dislocation and subgrain are formed in the crystal grains, so that the toughness of the steel is improved.
And S4, quickly cooling after rolling, and putting on a cooling bed.
As a further explanation of the invention, the step S1 is preceded by tapping from the converter, the end point C of the converter is more than or equal to 0.06 percent, the steel is completely eradicated from being peroxidized, and the slag is blocked in the tapping process.
As a further illustration of the present invention, in step S1, ferroboron is added to the LF furnace.
As a further illustration of the present invention, in the step S1, after the LF furnace stops heating, sampling and checking are performed, and the B content can be increased by about 0.0001% for each B-Fe alloy added with 0.0065kg/t steel according to the residual B content in the steel.
As a further illustration of the present invention, in step S3, the two-phase zone rolling comprises:
(1) the heating temperature range is 1100-1200 ℃; the soaking temperature range is 1050-1150 ℃, and the soaking time range is 60-100 min; the method is beneficial to austenitizing the steel and promoting the dissolution of Si, Mn, V, Nb, B and Cu in austenite, the square billet is cooled on a conveying roller way by water spraying, V, Nb (the maximum solution temperature of Nb is at least heated to 1100 ℃) and B, Cu are effectively dissolved in the steel, and the effect is played in the subsequent rolling process.
(2) The initial rolling temperature range is 950-1050 ℃; compared with the conventional steel bar rolling at 1050 +/-30 ℃, the initial rolling temperature is reduced, on one hand, crystal grains cannot be coarsened, on the other hand, preparation is made for (gamma + alpha) two-phase area finish rolling, the deformation is 25% after the rolling of 6 frames of roughing mill sets, the deformation is 25% after the rolling of 6 frames of middle mill sets, and the temperature of the gamma → alpha phase transformation point is improved by more than 850 ℃ through deformation induced phase transformation.
(3) The temperature range of the finishing mill is 850-950 ℃; B. the addition of Cu raises the temperature of gamma → alpha phase transition, and the (gamma + alpha) two-phase region is rolled at 850-950 ℃. Compared with the conventional reinforcing steel bar finish rolling at 1000-1050 ℃, the finish rolling temperature is reduced, and pearlite transformation can be promoted through finish rolling with large deformation; the method is favorable for NbC precipitation, promotes deformation to induce ferrite transformation, and the ferrite is elongated and refined along the axial direction, so that a large amount of dislocation and subgrain are formed in crystal grains; finally, the strength and the yield ratio are improved, a water spray cooling device is arranged between the middle rolling and the finish rolling, the temperature of a finishing mill is controlled to be 850-950 ℃, the steel is rolled in a (gamma + alpha) two-phase region by 6 finishing mill groups, the deformation is 50%, crystal grains are greatly refined, and a large amount of dislocation and subgrain are formed in the crystal grains.
As a further explanation of the present invention, in step S3, a water jet cooling device is provided before finish rolling.
In step S4, the temperature range of the upper cooling bed for returning red is 800 to 900 ℃. The temperature is too high, the structure is coarse, the temperature is too low, a tempered martensite structure is formed, and the use is influenced. And a rapid water cooling device is arranged behind the finishing mill, the temperature of red returning on the cooling bed is controlled to be 800-900 ℃ after the finish rolling, an ideal fine grain structure mainly comprising ferrite and pearlite is obtained, the grain size reaches 9 grades and above, and the precipitation of second phase particles of V (C, N) and NbC is promoted, so that the toughness of the steel bar is improved.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region, the 635 MPa-grade high-strength anti-seismic reinforcing steel bar with high strength and high plasticity is produced by composition design and combining a two-phase region rolling process, the yield strength is more than or equal to 635MPa, the tensile strength is more than or equal to 795MPa, the elongation after fracture is more than or equal to 15%, the total elongation at maximum force is more than or equal to 9.0%, the strength-to-yield ratio is more than or equal to 1.25, and the yield-to-yield ratio is less than or equal to 1.30, so that the alloy composition of the 635 MPa-grade high-strength anti-seismic reinforcing steel bar is provided, resources are saved, and the requirement of the market on the 635 MPa-grade high-strength anti-seismic reinforcing steel bar is met by improving the rolling performance of the two-phase region;
(2) the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region is designed by adopting B, Cu components, is combined with a (gamma + alpha) two-phase region rolling method, comprehensively utilizes solid solution and precipitation of microalloy elements and comprehensive strengthening means such as rolling fine grains in the two-phase region to improve the strength and toughness of the reinforcing steel bar and meets the requirement on the performance of the 635 MPa-grade high-strength anti-seismic reinforcing steel bar;
(3) the invention relates to a production method of steel for rolling 635MPa grade high-strength anti-seismic reinforcing steel bar in a two-phase region, which comprises the following steps of controlling the heating temperature to be 1100-1200 ℃, controlling the soaking temperature to be 1050-1150 ℃, controlling the soaking time to be 60-100min, facilitating austenitizing the steel and promoting the dissolution of Si, Mn, V, Nb, B and Cu in austenite, cooling a square billet on a conveying roller bed by spraying water, controlling the initial rolling temperature to be 950-1050 ℃, rolling the square billet by a 6-frame rough rolling unit, controlling the deformation amount to be 25%, rolling the square billet by a 6-frame medium rolling unit, controlling the deformation amount to be 25%, increasing the temperature of gamma → alpha phase transition point to be more than 850 ℃ by deformation induction phase transition, arranging a water spraying cooling device between the medium rolling and the finish rolling, controlling the temperature of a finishing mill to be 850-950 ℃, rolling the square billet by the 6-frame finishing rolling unit in a (gamma + alpha) two-phase region, controlling the deformation amount to be 50%, greatly refining crystal grains, and forming a large amount of dislocation and subgrain the crystal grains, and a rapid water cooling device is arranged behind the finishing mill, after rolling, rapid cooling is carried out, the temperature of red returning on an upper cooling bed is controlled to be 800-900 ℃, an ideal fine-grain structure mainly comprising ferrite and pearlite is obtained, the grain size reaches 9 grades or above, and the precipitation of second-phase particles of V (C, N) and NbC is promoted, so that the toughness of the steel bar is improved.
Drawings
The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and examples, but it should be understood that these drawings are designed for illustrative purposes only and thus do not limit the scope of the present invention. Furthermore, unless otherwise indicated, the drawings are intended to be illustrative of the structural configurations described herein and are not necessarily drawn to scale.
Fig. 1 is a schematic diagram of a 500-time metallographic structure of a steel for rolling a 635 MPa-grade high-strength anti-seismic reinforcing steel bar in a two-phase region, wherein the metallographic structure is white: ferrite, gray: pearlite, grade 11.5 grain size.
Detailed Description
The following detailed description of exemplary embodiments of the invention refers to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration exemplary embodiments in which the invention may be practiced. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that various changes to the invention may be made without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is presented for purposes of illustration only and not limitation to describe the features and characteristics of the invention, to set forth the best mode of carrying out the invention, and to sufficiently enable one skilled in the art to practice the invention. Accordingly, the scope of the invention is to be limited only by the following claims.
The steel for rolling 635 MPa-grade high-strength anti-seismic reinforcing steel bars in the two-phase region comprises the following chemical components in percentage by weight as shown in Table 1:
TABLE 1 chemical element composition and weight percentages (weight percentage%, balance Fe and unavoidable impurities) of each example
Figure BDA0003120607740000041
Figure BDA0003120607740000051
The ingredients of the above examples satisfy the following ranges: c: 0.22-0.28%, Si: 0.40-0.80%, Mn: 1.40-1.60%, P: less than or equal to 0.035%, S: less than or equal to 0.035%, Nb: 0.010-0.020%, V: 0.100 to 0.150%, B: 0.0008-0.0035%, Cu: 0.10-0.20%, N: 0.010-0.020%, and the balance of Fe and inevitable impurity elements.
The effects of the elements in the steel for the anti-seismic reinforcing steel bar are basically as follows:
c is a main element for strengthening the steel, can form solid solution and carbide in the steel to improve the strength and is beneficial to improving the yield ratio. The higher the C content, the higher the strength, but the lower the plasticity and toughness. Therefore, the content of C should be reduced as much as possible while ensuring that the strength of the steel can meet the use requirements. The content of C in the invention is 0.22-0.28%.
Si plays a role in solid solution strengthening, and mainly forms solid solution in ferrite to improve the strength of the steel, which is beneficial to improving the yield ratio, but can reduce the plasticity of the steel. The Si content of the invention is 0.40-0.80%.
Mn acts as solid solution strengthening, forms a solid solution mainly in pearlite to improve the strength of steel, and contributes to the improvement of the yield ratio, but at higher contents, it coarsens grains, increases brittleness, and also affects the weldability of steel. The Mn content of the invention is 1.40-1.60%.
Nb and V have the functions of fine grain strengthening and precipitation strengthening, the strength of the steel can be obviously improved, and the extensibility of the steel can be ensured, wherein Nb mainly plays a role in fine grain strengthening, and V mainly plays a role in precipitation strengthening. When Nb or V is used alone, the yield ratio of the steel cannot be improved, and when Nb and V are combined and the V/Nb ratio is 5-15, especially the V/Nb ratio is 10, the yield ratio of the steel is improved. In the invention, the Nb content is 0.010-0.020%, and the V content is 0.100-0.150%.
N can improve the strength of steel, particularly in V-containing steel, N can promote precipitation of V and refine grains, VN steel has a precipitation strengthening effect which is nearly 2 times that of V steel, but aging hardening can be caused by the fact that the content of N is too high. The content of N in the invention is 0.010-0.020%.
B is a key element for improving the hardenability of the steel, can increase the hardenability size of the steel, and improves the uniformity of the structure and performance in the section of the steel after quenching. In the invention, the content of B is 0.0008-0.0035%.
Cu can be dissolved in austenite to form a solid solution, and the eutectoid point of the steel is moved to the left, so that the pearlite content is increased, and the strength of the steel is improved, but the brittleness is increased when the Cu content is too high. The Cu content in the invention is 0.10-0.20%.
Among the elements, except for conventional strengthening elements such as C, Si, Mn, V, Nb and the like, the hardenability of the steel is improved by adding B element, the eutectoid point of the steel is moved to the left by adding Cu element, the V/Nb ratio is controlled, and the ferrite content is reduced and the pearlite content is improved by combining the two-phase region rolling process, so that the strength and the yield ratio are improved. The V/Nb ratio is 5 to 15, preferably 10.
The invention relates to a production method of steel for rolling 635 MPa-grade high-strength anti-seismic reinforcing steel bars in a two-phase region, which comprises the following steps:
s1, the end point C of the converter is more than or equal to 0.06 percent, the steel is completely eradicated from peroxidation tapping, and slag is blocked in the tapping process. (non-converter steelmaking systems such as arc furnaces can be used, and adaptive adjustment is required).
S2, refining the molten steel in an LF furnace; after the LF furnace stops heating, sampling and checking are carried out, and the B content can be increased by about 0.0001 percent for each B-Fe alloy added with 0.0065kg/t steel according to the residual B content in the steel.
S3, continuous casting;
s4, rolling in a two-phase region; by adopting (gamma + alpha) two-phase region rolling, on one hand, crystal grains are refined, and on the other hand, a large amount of dislocation and subgrain are formed in the crystal grains, so that the toughness of the steel is improved. The two-phase region rolling comprises the following steps:
(1) the heating temperature range is 1100-1200 ℃; the soaking temperature range is 1050-1150 ℃, and the soaking time range is 60-100 min; the method is beneficial to austenitizing the steel and promoting the dissolution of Si, Mn, V, Nb, B and Cu in austenite, the square billet is cooled by spraying water on a roller conveyor, V, Nb (the solid solution temperature of Nb is the highest and is at least heated to 1100 ℃) and B, Cu are effectively dissolved in the steel, and the effect is played in the subsequent rolling process.
(2) The initial rolling temperature range is 950-1050 ℃; compared with the conventional steel bar rolling at 1050 +/-30 ℃, the initial rolling temperature is reduced, on one hand, crystal grains cannot be coarsened, on the other hand, preparation is made for (gamma + alpha) two-phase area finish rolling, the deformation is 25% after the rolling of 6 frames of roughing mill sets, the deformation is 25% after the rolling of 6 frames of middle mill sets, and the temperature of the gamma → alpha phase transformation point is improved by more than 850 ℃ through deformation induced phase transformation.
(3) The temperature range of the finishing mill is 850-950 ℃; B. the addition of Cu increases the temperature of gamma → alpha phase transition, and the rolling enters a (gamma + alpha) two-phase region at 850-950 ℃. Compared with the conventional reinforcing steel bar finish rolling at 1000-1050 ℃, the finish rolling temperature is reduced, and pearlite transformation can be promoted through finish rolling with large deformation; the method is favorable for NbC precipitation, promotes deformation to induce ferrite transformation, and the ferrite is elongated and refined along the axial direction, so that a large amount of dislocation and subgrain are formed in crystal grains; finally, the strength and the yield ratio are improved, a water spray cooling device is arranged between the middle rolling and the finish rolling, the temperature of a finishing mill is controlled to be 850-950 ℃, the steel is rolled in a (gamma + alpha) two-phase region by 6 finishing mill groups, the deformation is 50%, crystal grains are greatly refined, and a large amount of dislocation and subgrain are formed in the crystal grains.
S5, rapidly cooling after rolling, and feeding the steel plate to a cooling bed, wherein the temperature range of the red returning of the cooling bed is 800-900 ℃. The temperature is too high, the structure is coarse, the temperature is too low, a tempered martensite structure is formed, and the use is influenced. And a rapid water cooling device is arranged behind the finishing mill, the temperature of red returning on the cooling bed is controlled to be 800-900 ℃ after the rapid cooling after the rolling, as shown in figure 1, an ideal fine-grain structure mainly comprising ferrite and pearlite is obtained, the grain size reaches 9 grades and above, and the precipitation of second-phase particles of V (C, N) and NbC is promoted, so that the toughness of the steel bar is improved.
Example 1
The chemical composition and the weight percentage content of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region are shown in example 1 in Table 1.
The production method of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region in the embodiment comprises the following steps of:
and S1, the end point C of the converter is 0.06 percent, steel is completely tapped through peroxidation, and slag is blocked in the tapping process.
S2, refining the molten steel in an LF furnace; and after the LF furnace stops heating, sampling and inspecting, and adding 0.065kg/t ferroboron into the LF furnace.
S3, continuously casting into 150mm2And (5) square billet.
S4, rolling in a two-phase region; by adopting (gamma + alpha) two-phase region rolling, on one hand, crystal grains are refined, and on the other hand, a large amount of dislocation and subgrain are formed in the crystal grains, so that the toughness of the steel is improved. The two-phase region rolling comprises the following steps:
(1) the heating temperature is 1100 ℃; the soaking temperature is 1050 deg.C, and the soaking time is 100 min.
(2) The initial rolling temperature range is 950 ℃; the deformation is 25% after rolling by a 6-frame roughing mill, and the deformation is 25% after rolling by a 6-frame medium mill.
(3) The temperature range of the finishing mill is 850 ℃; rolling in the (gamma + alpha) two-phase region by a 6-frame finishing mill group, wherein the deformation is 50%.
S5, rapidly cooling after rolling, and feeding the steel plate to a cooling bed with the temperature range of going back to red of 800 ℃.
The mechanical properties of the obtained steel for the anti-seismic reinforcing steel bar are shown in table 2 after three tests:
table 2 mechanical properties of steel for earthquake resistant reinforcing bar of example 1
ReL(MPa) Rm/MPa) High yield ratio (R)m/ReL) Yield ratio (R)eL/635) A(％) Agt(％)
662 854 1.29 1.04 18.5 10.6
660 845 1.28 1.04 19.5 11.5
665 857 1.29 1.05 20.0 9.5
Example 2
The chemical composition and the weight percentage content of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region are shown in example 2 in Table 1.
The production method of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region in the embodiment comprises the following steps of:
and S1, the converter end point C is 0.07 percent, steel is completely tapped through peroxidation, and slag is blocked in the steel tapping process.
S2, refining the molten steel in an LF furnace; after the LF furnace stops heating, sampling and checking are carried out, and 0.2175kg/t ferroboron is added into the LF furnace.
S3, continuously casting into 150mm2And (5) square billet.
S4, rolling in a two-phase region; by adopting (gamma + alpha) two-phase region rolling, on one hand, crystal grains are refined, and on the other hand, a large amount of dislocation and subgrain are formed in the crystal grains, so that the toughness of the steel is improved. The two-phase region rolling comprises the following steps:
(1) the heating temperature is 1200 ℃; soaking temperature is 1150 deg.C, and soaking time is 60 min.
(2) The initial rolling temperature range is 1050 ℃; the deformation is 25% after rolling by a 6-frame roughing mill set, and the deformation is 25% after rolling by a 6-frame medium mill set.
(3) The temperature range of the finishing mill is 950 ℃; rolling in the (gamma + alpha) two-phase region by a 6-frame finishing mill group, wherein the deformation is 50%.
S5, rapidly cooling after rolling, and feeding the steel plate to a cooling bed with the temperature range of returning red of 900 ℃.
The mechanical properties of the obtained steel for the anti-seismic reinforcing steel bar are shown in table 3 after three tests:
table 3 mechanical properties of steel for earthquake resistant reinforcing bar of example 2
ReL(MPa) Rm/MPa) High yield ratio (R)m/ReL) Yield ratio (R)eL/635) A(％) Agt(％)
689 870 1.26 1.09 18.0 9.0
679 850 1.25 1.07 19.0 9.5
675 850 1.26 1.06 20.6 12.0
Example 3
The chemical composition and the weight percentage content of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region are shown in example 3 in Table 1.
The production method of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region in the embodiment comprises the following steps of:
and S1, setting the converter end point C to be 0.08 percent, completely eradicating steel tapping through peroxidation, and pushing off slag in the steel tapping process.
S2, refining the molten steel in an LF furnace; after the LF furnace stops heating, sampling and checking are carried out, and 0.1105kg/t ferroboron is added into the LF furnace.
S3, continuously casting into 150mm2And (5) square billet.
S4, rolling in a two-phase region; by adopting (gamma + alpha) two-phase region rolling, on one hand, crystal grains are refined, and on the other hand, a large amount of dislocation and subgrain are formed in the crystal grains, so that the toughness of the steel is improved. The two-phase region rolling comprises the following steps:
(1) the heating temperature is 1150 ℃; the soaking temperature is 1100 deg.C, and the soaking time is 80 min.
(2) The initial rolling temperature range is 1000 ℃; the deformation is 25% after rolling by a 6-frame roughing mill set, and the deformation is 25% after rolling by a 6-frame medium mill set.
(3) The temperature range of the finishing mill is 900 ℃; rolling in the (gamma + alpha) two-phase region by a 6-frame finishing mill group, wherein the deformation is 50%.
And S5, rapidly cooling after rolling, and feeding the steel plate to a cooling bed, wherein the temperature range of the red returning of the cooling bed is 850 ℃.
The mechanical properties of the obtained steel for the anti-seismic reinforcing steel bar are shown in table 4 after three tests:
table 4 mechanical properties of steel for earthquake resistant reinforcing bar of example 3
ReL(MPa) Rm/MPa) High yield ratio (R)m/ReL) Yield ratio (R)eL/635) A(％) Agt(％)
684 868 1.27 1.08 18.2 9.3
674 848 1.26 1.06 19.2 9.8
670 848 1.27 1.06 20.8 12.3
Example 4
The chemical composition and the weight percentage content of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region are shown in example 4 in the table 1.
The production method of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region in the embodiment comprises the following steps of:
and S1, the end point C of the converter is 0.09 percent, steel is completely tapped through peroxidation, and slag is blocked in the steel tapping process.
S2, refining the molten steel in an LF furnace; after the LF furnace stops heating, sampling and checking are carried out, and 0.1406kg/t ferroboron is added into the LF furnace.
S3, continuously casting into 150mm2And (5) square billet.
S4, rolling in a two-phase region; by adopting (gamma + alpha) two-phase region rolling, on one hand, crystal grains are refined, and on the other hand, a large amount of dislocation and subgrain are formed in the crystal grains, so that the toughness of the steel is improved. The two-phase region rolling comprises the following steps:
(1) the heating temperature is 1170 ℃; the soaking temperature is 1120 ℃, and the soaking time is 85 min.
(2) The initial rolling temperature range is 1020 ℃; the deformation is 25% after rolling by a 6-frame roughing mill set, and the deformation is 25% after rolling by a 6-frame medium mill set.
(3) The temperature range of the finishing mill is 920 ℃; rolling in the (gamma + alpha) two-phase region by a 6-frame finishing mill group, wherein the deformation is 50%.
S5, rapidly cooling after rolling, and feeding the steel plate to a cooling bed, wherein the temperature range of the red return of the cooling bed is 870 ℃.
The mechanical properties of the obtained steel for the anti-seismic reinforcing steel bar are shown in table 5 after three tests:
table 5 mechanical properties of steel for earthquake resistant reinforcing bar of example 4
ReL(MPa) Rm/MPa) High yield ratio (R)m/ReL) Yield ratio (R)eL/635) A(％) Agt(％)
682 871 1.28 1.07 18.1 9.5
672 870 1.29 1.06 19.1 9.7
667 864 1.30 1.05 19.8 11.9
In the above examples, ReLThe yield strength; rmIs tensile strength; high yield ratio (R)m/ReL)，RmTo measure tensile strength, ReLMeasured yield strength; yield ratio (R)eL635) is the characteristic value of the yield strength of the steel bar, and the unit is MPa; a is elongation after fracture; a. thegtElongation at maximum force.

Claims (5)

1. The steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region is characterized by comprising the following chemical components in percentage by weight: c: 0.22-0.28%, Si: 0.40-0.80%, Mn: 1.40-1.60%, P: less than or equal to 0.035%, S: less than or equal to 0.035%, Nb: 0.010-0.020%, V: 0.100-0.150%, B: 0.0035%, Cu: 0.10-0.20%, N: 0.010-0.020% of Fe and inevitable impurity elements in balance; wherein the V/Nb ratio is 10;
the production method of the steel for rolling the 635 MPa-grade high-strength anti-seismic reinforcing steel bar in the two-phase region comprises the following steps: s1, refining the molten steel in an LF furnace; s2, continuous casting; s3, rolling in a two-phase region; s4, rapidly cooling after rolling, and putting on a cooling bed;
before the step S1, converter tapping is also included, the end point C of the converter is more than or equal to 0.06%, and slag is blocked in the tapping process;
in step S3, the two-phase zone rolling includes:
(1) the heating temperature range is 1100-1200 ℃; the soaking temperature range is 1050-1150 ℃, and the soaking time range is 60-100 min;
(2) the initial rolling temperature range is 950-1050 ℃;
(3) the temperature range of the finishing mill is 850-950 ℃;
in step S3, a water spray cooling device is provided before finish rolling.
2. The production method of the steel for the two-phase zone rolled 635MPa grade high-strength anti-seismic reinforcing steel bar according to the claim 1 is characterized by comprising the following steps:
s1, refining the molten steel in an LF furnace;
s2, continuously casting;
s3, rolling in a two-phase region;
and S4, quickly cooling after rolling, and putting on a cooling bed.
3. The method for producing the steel for the 635MPa grade high-strength aseismic reinforcement rolled in the two-phase region according to claim 2, wherein in the step S1, ferroboron is added into the LF furnace.
4. The method for producing the steel for the 635MPa grade high-strength anti-seismic reinforcing steel bar rolled in the two-phase region according to claim 3, wherein in the step S1, after the LF furnace stops heating, sampling is performed, and a ferroboron alloy is added according to the residual B content in the steel.
5. The method for producing the steel for the 635MPa grade high-strength anti-seismic reinforcing steel bar rolled in the two-phase region according to claim 2, wherein the temperature range of the upper cooling bed red returning in the step S4 is 800-900 ℃.
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