Earthquake-resistant steel bar and method for manufacturing the same

Abstract

The application discloses an anti-seismic steel bar and a preparation method thereof. The anti-seismic steel bar comprises the following chemical components in percentage by mass: C: 0.22% to 0.25%, Si: 0.40% to 0.60%, Mn: 1.30% to 1.50%, P: less than or equal to 0.045%, S: less than or equal to 0.045%, and the balance of Fe and inevitable impurities. The anti-seismic steel bar has good yield strength and excellent strength-yield ratio. The preparation method can be used to prepare the anti-seismic steel bar with good yield strength and excellent strength-yield ratio.

Description

Technical Field

[0001] This application belongs to the field of steel smelting technology, specifically relating to an earthquake-resistant steel bar and its preparation method. Background Technology

[0002] Currently, steel mills often use microalloying of Nb, V, etc. to produce hot-rolled ribbed steel bars through high-strength wire rods, relying on precipitation strengthening to achieve the required properties of the steel bars. This results in higher costs for the same grade of steel bars using alloys, and Nb, V, and other elements require higher solid solution temperatures, leading to a higher metallographic structure in the steel bars and a 1.0 to 1.5 grade coarser wire rod, which increases the difficulty of rolling.

[0003] The yield strength of existing hot-rolled ribbed steel bars that do not employ microalloying is generally low, thus requiring improvement. Summary of the Invention

[0004] In view of this, this application provides a seismic-resistant steel bar and a method for preparing the same, aiming to provide a seismic-resistant steel bar with good yield strength and strength-to-yield ratio.

[0005] In a first aspect, embodiments of this application provide a seismic-resistant steel reinforcement, comprising the following chemical composition by mass percentage: C: 0.22%–0.25%, Si: 0.40%–0.60%, Mn: 1.30%–

[0006] 1.50%, P≤0.045%, S≤0.045%, balance is Fe and unavoidable impurities.

[0007] According to one embodiment of this application, the diameter of the seismic-resistant steel reinforcement is 12mm to 20mm.

[0008] According to one embodiment of this application, the metallographic structure of the seismic-resistant steel reinforcement comprises, by volume fraction: 40%–55% pearlite and 45%–60% ferritite.

[0009] According to one embodiment of this application, the average grain size of the seismic-resistant steel reinforcement is 5.5 to 8.5 μm, and the grain size is grade 11.0 to 12.0.

[0010] According to one embodiment of this application, the yield strength of the seismic-resistant steel reinforcement is 420-460 MPa, the tensile strength is 605-655 MPa, the strength-to-yield ratio is 1.38-1.47, and the total elongation at maximum force is 11.0%-14.9%.

[0011] Secondly, embodiments of this application provide a method for preparing seismic-resistant steel reinforcement, including:

[0012] Molten steel is continuously cast to produce a square billet, wherein the square billet comprises the following chemical composition by mass percentage: C: 0.22%–0.25%, Si: 0.40%–0.60%, Mn: 1.30%–1.50%, P≤0.045%, S≤0.045%, with the balance being Fe and unavoidable impurities;

[0013] The billet is rolled and cooled to produce earthquake-resistant steel bars, wherein the initial cooling temperature of the billet is 800℃~860℃.

[0014] According to one embodiment of this application, the initial cooling temperature of the billet is 800°C to 860°C.

[0015] According to an embodiment of one aspect of this application, 18 rolling mills are used, including 550mm closed-end rolling mills of No. 1-4, 450mm closed-end rolling mills of No. 5-8, 450mm short-stress rolling mills of No. 9-11, and 350mm short-stress rolling mills of No. 12-18.

[0016] According to one embodiment of this application, 18 rolling mills are used, wherein rolling mills 1-11 are arranged alternately in a horizontal and vertical configuration.

[0017] According to one embodiment of this application, 18 rolling mills are used, of which No. 12 is a flat roll mill, No. 13 is a vertical box mill, No. 14 is a first pre-cut mill, No. 15 is a second pre-cut mill, No. 16 is a slitting mill, No. 17 is a flat elliptical roll mill, and No. 18 is a finished product rolling mill.

[0018] According to one embodiment of this application, the casting speed of continuous casting is 3.4 to 3.6 m / min; the casting speed fluctuation of continuous casting is ≤0.2 m / min.

[0019] According to one embodiment of this application, the rolling process includes heating and homogenization, with the heating and homogenization temperatures being 1050–1150°C, respectively.

[0020] According to one embodiment of this application, the billet tapping temperature after rolling is 920°C to 980°C.

[0021] According to one embodiment of this application, the final rolling speed is 12.0 to 12.5 m / s.

[0022] This application has at least the following beneficial effects:

[0023] According to the embodiments of this application, based on the composition system of silicon-manganese alloy, replacing V microalloying, without adding microalloying materials such as Nb and V, it can promote grain refinement, improve the strength and hardness of steel, improve the wear resistance and toughness of steel, and design and prepare products with mechanical properties and metallographic properties that meet the requirements of seismic steel bars, and have excellent seismic performance. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0025] Figure 1 The microstructure of the earthquake-resistant steel reinforcement provided in Embodiment 1 of this application is shown in the figure.

[0026] Figure 2 The microstructure of the earthquake-resistant steel reinforcement provided in Embodiment 2 of this application is shown in the figure.

[0027] Figure 3 The microstructure of the earthquake-resistant steel reinforcement provided in Embodiment 3 of this application is shown in the figure.

[0028] Figure 4 A metallographic micrograph of the earthquake-resistant steel reinforcement provided in Embodiment 4 of this application is shown. Detailed Implementation

[0029] To make the purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the implementation details described in this specification are merely for illustrative purposes and are not intended to limit the scope of this application.

[0030] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0031] In the description of this application, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.

[0032] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0033] In a first aspect, embodiments of this application provide a seismic-resistant steel bar, comprising the following chemical composition by mass percentage: C: 0.22%–0.25%, Si: 0.40%–0.60%, Mn: 1.30%–1.50%, P≤0.045%, S≤0.045%, with the balance being Fe and unavoidable impurities.

[0034] This application adopts a silicon-manganese alloy-based composition system to replace V microalloying, without adding Nb, V, or other microalloyers. Silicon is one of the important components in steel, which can promote grain refinement, improve the strength and hardness of steel, and improve the wear resistance and toughness of steel. Manganese has a strong deoxidizing effect, which can reduce the oxygen content in steel and improve the strength and toughness of steel. By controlling the appropriate silicon-manganese content and the initial cooling temperature, fine-grained ferrite can be obtained, and the yield strength, tensile strength, strength-to-yield ratio, and Ag of the steel bars can fully meet the requirements of GB / T 1499.2-2018 national standard.

[0035] According to the embodiments of this application, the seismic reinforcement is HRB400 grade steel bar with a yield strength of 400 MPa.

[0036] In some embodiments, the carbon equivalent is ≤0.54%.

[0037] Carbon equivalent is usually expressed by the following formula:

[0038] Carbon equivalent (CE) = C / 6 + Mn / 6 + Ni / 15 + Cr / 5 + Mo / 5 + V / 5

[0039] Where C is the percentage of carbon content, and Mn, Ni, Cr, Mo, and V are the percentages of manganese, nickel, chromium, molybdenum, and vanadium, respectively.

[0040] The higher the carbon equivalent value, the greater the hardening tendency of the steel, as it reflects the influence of alloying elements on the steel. Steels with low carbon equivalents are generally easier to cold and hot work and have better weldability. The seismic-resistant reinforcing steel of this application has the aforementioned suitable carbon equivalent, exhibiting better hardness and strength, and good weldability and machinability.

[0041] Carbon equivalent is an important engineering parameter, especially in material selection, heat treatment, and welding process determination, as it provides crucial information about the properties and behavior of steel.

[0042] According to the embodiments of this application, silicon is one of the important components in steel, which can promote grain refinement, improve the strength and hardness of steel, and improve the wear resistance and toughness of steel. Manganese, on the other hand, has a strong deoxidizing effect, which can reduce the oxygen content in steel and improve the strength and toughness of steel. Therefore, controlling the content of silicon and manganese in steel bars within the above range is beneficial to promoting grain refinement, improving the strength and hardness of steel, and improving the wear resistance and toughness of steel.

[0043] In some alternative implementations, the diameter of the seismic reinforcement is 12mm to 20mm.

[0044] In some embodiments, seismic-resistant steel bars with a diameter of ∮12mm can be prepared by five-slit rolling; seismic-resistant steel bars with a diameter of ∮14mm can be prepared by four-slit rolling; and seismic-resistant steel bars with a diameter of ∮18-20mm can be prepared by two-slit rolling.

[0045] In some alternative embodiments, the metallographic structure of the seismic reinforcement includes, by volume fraction, 40%–55% pearlite and 45%–60% ferritite.

[0046] According to the embodiments of this application, ferrite has low strength and good plasticity, which helps to improve the ductility and toughness of steel bars; although pearlite increases strength and hardness, enabling steel bars to withstand greater loads without fracture, excessive pearlite can reduce the ductility of the material. Therefore, this application has a suitable volume fraction of pearlite and ferrite, which gives the seismic steel bars good toughness and fracture resistance, which helps prevent the steel bars from suddenly breaking under extreme stress and enhances their seismic performance.

[0047] In some alternative embodiments, the average grain size of the seismic-resistant steel bars is 5.5–8.5 μm, and the grain size is grade 11.0–12.0.

[0048] According to the embodiments of this application, the seismic-resistant steel reinforcement composition system of this application exhibits superior mechanical properties compared to other seismic-resistant steel reinforcement systems that do not use microalloying, particularly demonstrating higher tensile strength and smaller grain size. The reasons for this may be attributed to the matching process and composition system of this application, the higher silicon and manganese content resulting in finer original austenite grains, the use of a low-temperature rolling process for the billet, and the appropriate temperature cooling bed.

[0049] Compared with other microalloyed seismic steel bars containing elements such as Nb and V, the seismic steel bar composition system of this application exhibits superior mechanical properties and smaller grains. The reason for this may be that elements such as Nb and V require higher solution temperatures, resulting in coarser grains (approximately 1.0-1.5 grade larger) compared to other steel bars of the same specification, thus contributing to the superior mechanical properties of the seismic steel bar.

[0050] In some alternative embodiments, the yield strength of the seismic reinforcement is 420-460 MPa, the tensile strength is 605-655 MPa, the strength-to-yield ratio is 1.38-1.47, the yield-to-yield ratio is 1.05-1.15, and the total elongation at maximum force is 11.0%-14.9%.

[0051] Methods for preparing earthquake-resistant steel reinforcement

[0052] Secondly, embodiments of this application provide a method for preparing seismic-resistant steel reinforcement, including:

[0053] Molten steel is continuously cast to produce a square billet, wherein the square billet comprises the following chemical composition by mass percentage: C: 0.22%–0.25%, Si: 0.40%–0.60%, Mn: 1.30%–1.50%, P≤0.045%, S≤0.045%, with the balance being Fe and unavoidable impurities;

[0054] The billet is rolled and cooled to produce earthquake-resistant steel bars, wherein the initial cooling temperature of the billet is 800℃~860℃.

[0055] According to the embodiments of this application, by designing the composition of silicon and manganese, it is possible to promote grain refinement, improve the strength and hardness of steel, and improve the strength, wear resistance and toughness of steel. By controlling the appropriate silicon and manganese content and the initial cooling temperature, fine-grained ferrite can be obtained, and the yield strength, tensile strength, strength-to-yield ratio and maximum force elongation (Agt) of the steel bars can fully meet the requirements of GB / T1499.2-2018 national standard.

[0056] The preparation methods for earthquake-resistant steel bars generally include the following processes: blast furnace molten iron smelting, converter molten steel smelting, LF refining, billet continuous casting, heating furnace heating, rolling, (bar) controlled cooling, multiple length shearing, cooling bed cooling, cold shearing to length, finishing, packaging, weighing, and warehousing.

[0057] In some embodiments, a single-pass pre-cutting production process is adopted to achieve rolling production with different cutting lines of ∮12mm to ∮20mm specifications.

[0058] In some embodiments, the method for preparing earthquake-resistant steel bars includes: blast furnace molten iron smelting, converter molten steel smelting, LF refining, billet continuous casting, heating furnace heating, rolling, (bar) controlled cooling, multiple length shearing, cooling bed cooling, cold shearing to length, finishing, packaging, weighing, and warehousing.

[0059] In some alternative embodiments, the initial cooling temperature of the billet is 800°C to 860°C.

[0060] The billet is in its state after rolling and before the cooling process begins. The billet temperature can be between 800℃ and 860℃, and cooling begins in this state. Cooling can be carried out at room temperature under a cooling bed, which is beneficial for reducing the grain size in the billet.

[0061] According to the embodiments of this application, the billet contains an appropriate amount of silicon and manganese, and by combining specific rolling temperatures and initial cooling temperatures, a fine-grained ferrite metallographic structure is obtained, so that the mechanical properties of the seismic steel reinforcement can fully meet the national standard requirements.

[0062] In some alternative implementations, 18 rolling mills are used, including 550mm closed-end rolling mills of No. 1-4, 450mm closed-end rolling mills of No. 5-8, 450mm short-stress rolling mills of No. 9-11, and 350mm short-stress rolling mills of No. 12-18.

[0063] According to one embodiment of this application, 18 rolling mills are used, wherein rolling mills 1-11 are arranged alternately in a horizontal and vertical configuration.

[0064] According to one embodiment of this application, 18 rolling mills are used, of which No. 12 is a flat roll mill, No. 13 is a vertical box mill, No. 14 is a first pre-cut mill, No. 15 is a second pre-cut mill, No. 16 is a slitting mill, No. 17 is a flat elliptical roll mill, and No. 18 is a finished product rolling mill.

[0065] According to the embodiments of this application, by using a suitable rolling mill, specific grooves are created on the surface of the seismic-resistant steel reinforcement. Furthermore, the rolling process alters the cross-sectional shape and size of the steel, significantly impacting its microstructure, mechanical properties, and surface characteristics. This facilitates grain refinement and phase transformation control, achieving a balance between strength and toughness, increasing the yield strength of the reinforcement, and improving its mechanical properties.

[0066] In some optional embodiments, the casting speed is 3.4 to 3.6 m / min; the casting speed fluctuation is ≤0.2 m / min.

[0067] In some alternative embodiments, heating and homogenization are performed before rolling, with the heating and homogenization temperatures ranging from 1050 to 1150°C.

[0068] According to the embodiments of this application, the billet contains a suitable amount of silicon and manganese, and a fine-grained ferrite metallographic structure is obtained by using specific heating temperature, soaking temperature and initial cooling temperature, so that the mechanical properties of the seismic steel reinforcement can fully meet the national standard requirements.

[0069] In some alternative implementations, the billet tapping temperature after rolling is 920°C to 980°C.

[0070] According to the embodiments of this application, the billet contains a suitable amount of silicon and manganese, and a fine-grained ferrite metallographic structure is obtained through specific rolling temperature and tapping temperature, so that the mechanical properties of the seismic steel reinforcement can fully meet the national standard requirements.

[0071] In some alternative implementations, the final rolling speed is 11.0 to 12.5 m / s.

[0072] According to the embodiments of this application, controlling the final rolling speed within the above-mentioned range can optimize the microstructure of the reinforcing steel, improve its strength and seismic performance, and optimize the plasticity and toughness of the material.

[0073] Example

[0074] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0075] Examples 1-4

[0076] This embodiment provides a method for producing earthquake-resistant steel bars, the process of which includes steelmaking, continuous casting, heating furnace, rolling, cooling bed cooling, cold shearing to length, sampling and inspection, and packaging and warehousing.

[0077] The square billet obtained by continuous casting has the following chemical composition by mass percentage: C: 0.22%–0.25%, Si: 0.40%–0.60%, Mn: 1.30%–1.50%, P≤0.045%, S≤0.045%, with the balance being Fe and unavoidable impurities; the casting speed fluctuation of the continuous casting is ≤0.2 m / min;

[0078] The initial temperature of the billet during cooling on the cooling bed (i.e., the temperature of the upper cooling bed) is 800℃~860℃.

[0079] The mass percentage (wt%) of the chemical composition of Examples 1-4 is shown in Table 1, and the casting speed, cooling bed temperature control, and final rolling speed of the continuous casting are shown in Table 2.

[0080] Table 1. Chemical composition (wt%, balance Fe) of each embodiment.

[0081] Furnace number C Si Mn P S Furnace 1 0.2448％ 0.5608％ 1.4371％ 0.0335％ 0.0328％ Furnace 2 0.2393％ 0.5448％ 1.3885％ 0.0201％ 0.0356％ Furnace 3 0.2346％ 0.5402％ 1.4212％ 0.0398％ 0.0074％ Furnace 4 0.2268％ 0.5551％ 1.45022％ 0.0193％ 0.0216％

[0082] Table 2

[0083]

[0084]

[0085] Comparative Examples 1-4

[0086] The comparative example differs from the embodiment in the following aspects: tapping temperature, upper cooling bed temperature, final rolling speed, and continuous casting speed. The continuous casting speed of the comparative example is 3.4 m / min, with a fluctuation of ±0.2 m / min.

[0087] project tapping temperature / ℃ upper cooling bed temperature / ℃ Final rolling speed (m / s) Comparative Example 1 1022 894 12.64 Comparative Example 2 1018 890 12.34 Comparative Example 3 1015 884 10.6 Comparative Example 4 1010 889 10.2

[0088] Performance testing

[0089] The seismic-resistant steel bars prepared in the examples and comparative examples were sampled according to GB / T 2975 "Sampling location and specimen preparation for mechanical property testing of steel and steel products"; the mechanical properties were measured according to GB / T228.1-2010 "Metallic materials, tensile testing - Part 1: Room temperature test method".

[0090] The test standard for cold bending performance is GB / T 1499.2-2018, and the results are shown in Table 3.

[0091] The maximum force elongation (Agt) fully meets the requirements of GB / T 1499.2-2018 national standard, and the results are shown in Table 3.

[0092] The yield-to-yield ratio is calculated as: yield strength / standard yield strength of the steel bar of that grade. For the seismic steel bars in this application, the standard yield strength is 400 MPa.

[0093] Table 3 shows the mechanical properties of the three groups of samples in each embodiment.

[0094]

[0095]

[0096] Examples 1-4 show that the HRB400E seismic-resistant steel bars produced in this application have good surface quality, mechanical properties, and cold bending performance. The metallographic structure consists of ferritic and pearlitic materials, with no closed-loop abnormal structures at the edges. Specifically, the average grain size of the φ12mm steel bars is approximately 5.6µm, with a grain size grade of 12.0; the average grain size of the φ14mm steel bars is approximately 6.2µm, with a grain size grade of 11.5; the average grain size of the φ18mm steel bars is approximately 7.2µm, with a grain size grade of 11.0+; and the average grain size of the φ20mm steel bars is approximately 8.1µm, with a grain size grade of 11.0-. The metallographic structure fully meets the requirements of GB / T1499.2-2018.

[0097] The metallographic structures of the seismic-resistant steel bars in Examples 1-4 are as follows: Figures 1 to 4 As shown. - The image of the metallographic structure was obtained by observing 1 / 4 of the structure under a 500× microscope, indicating that the seismic-resistant steel reinforcement has a small grain size.

[0098] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions made by those skilled in the art should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A type of earthquake-resistant reinforcing steel bar, characterized in that, The chemical composition, by mass percentage, includes the following: C: 0.22%–0.25%, Si: 0.40%–0.60%, Mn: 1.30%–1.50%, P ≤ 0.045%, S≤0.045%, balance is Fe and unavoidable impurities.

2. The earthquake-resistant reinforcing steel according to claim 1, characterized in that, The diameter of the earthquake-resistant steel bars is 12mm to 20mm.

3. The earthquake-resistant reinforcing steel according to claim 1, characterized in that, The metallographic structure of the earthquake-resistant steel reinforcement comprises, by volume fraction: 40%–55% pearlite and 45%–60% ferritite.

4. The earthquake-resistant reinforcing steel according to claim 1, characterized in that, The average grain size of the earthquake-resistant steel bars is 5.5–8.5 μm, and the grain size is grade 11.0–12.

0.

5. The seismic-resistant reinforcing steel according to any one of claims 1 to 4, characterized in that, The seismic-resistant steel bars have a yield strength of 420–460 MPa, a tensile strength of 605–655 MPa, a strength-to-yield ratio of 1.38–1.47, and a maximum total elongation of 11.0%–14.9%.

6. A method for preparing earthquake-resistant steel reinforcement, characterized in that, include: Molten steel is continuously cast to obtain a square billet, wherein the square billet comprises the following chemical composition by mass percentage: C: 0.22%~0.25%, Si: 0.40%~0.60%, Mn: 1.30%~1.50%, P≤0.045%, S≤0.045%, with the balance being Fe and unavoidable impurities; The square billet is rolled and cooled to obtain the earthquake-resistant steel bar, wherein the temperature of the square billet before cooling is 800℃~860℃.

7. The method according to claim 6, characterized in that, The temperature of the billet before cooling is 800℃~860℃.

8. The method according to claim 6, characterized in that, The rolling process satisfies at least one of the following conditions: 1) 18 rolling mills are used, including 550mm closed rolling mills of No. 1-4, 450mm closed rolling mills of No. 5-8, 450mm short stress rolling mills of No. 9-11, and 350mm short stress rolling mills of No. 12-18. 2) 18 rolling mills are used, with mills 1-11 arranged alternately in a horizontal and vertical configuration; 3) 18 rolling mills are used, of which No. 12 is a flat roll mill, No. 13 is a vertical box mill, No. 14 is the first pre-cut mill, No. 15 is the second pre-cut mill, No. 16 is the slitting mill, No. 17 is the flat oval mill, and No. 18 is the finished product mill.

9. The method according to claim 6, characterized in that, The method satisfies at least one of the following conditions: 1) The casting speed of the continuous casting is 3.4 to 3.6 m / min; the casting speed fluctuation of the continuous casting is ≤0.2 m / min; 2) The rolling process includes heating and homogenization, wherein the heating and homogenization temperatures are 1050–1150°C; 3) The billet tapping temperature after rolling is 920℃~980℃.

10. The method according to claim 6, characterized in that, The final rolling speed is 12.0 to 12.5 m / s.

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