Straight-rolled HRB500E straight aseismic steel bar and production method thereof

Abstract

The invention provides a direct-rolled HRB500E straight anti-seismic reinforcing steel bar and a production method thereof. The direct-rolled HRB500E straight anti-seismic reinforcing steel bar comprises the following chemical components in percentage by mass: more than or equal to 0.22 wt% and less than or equal to 0.25 wt% of C, more than or equal to 0.40 wt% and less than or equal to 0.60 wt% of Si, more than or equal to 1.20 wt% and less than or equal to 1.40 wt% of Mn, more than or equal to 0.045 wt% and less than or equal to 0.075 wt% of V, more than or equal to 0.015 wt% and less than or equal to 0.025 wt% of Nb, less than or equal to 0.045 wt% of P, less than or equal to 0.045 wt% of S and the balance of iron and other inevitable impurities. The steel bar prepared by the invention has high strength and high toughness, and has good comprehensive mechanical properties.

Description

Technical Field

[0001] The present invention relates to the field of earthquake-resistant steel bars, and in particular to a direct-rolled HRB500E straight bar earthquake-resistant steel bar and a production method thereof. Background Art

[0002] After the release of GB 1499.2-2024 standard, the composition, performance and metallographic requirements were further standardized, and the production of water-piercing steel bars was restricted. Since most steel mills produce HRB500E hot-rolled ribbed steel bars using micro-alloys such as Nb and V for strengthening, in order to ensure the solid solution of the alloy, the furnace temperature requirements for the production of HRB500E hot-rolled ribbed steel bars are high, resulting in high fuel consumption and high production costs.

[0003] However, HRB500E steel bars produced by the commonly used direct rolling technology without heating not only have insufficient plasticity and toughness, but also have large fluctuations in product performance, resulting in some products failing to meet earthquake resistance requirements.

[0004] Based on the above, it is urgent to study the direct-rolled HRB500E straight bar earthquake-resistant steel bars and their production methods to solve the above problems. Summary of the invention

[0005] The main purpose of the present invention is to provide an electric direct-rolled HRB500E straight bar earthquake-resistant steel bar and a production method thereof, so as to solve the technical problem of high furnace temperature requirement for the production of HRB500E hot-rolled ribbed steel bars in the above-mentioned common technology.

[0006] To achieve the above-mentioned purpose, the present invention provides a direct-rolled HRB500E straight seismic-resistant steel bar, the chemical composition and mass percentage of the direct-rolled HRB500E straight seismic-resistant steel bar are 0.22wt%≤C≤0.25wt%, 0.40wt%≤Si≤0.60wt%, 1.20wt%≤Mn≤1.40wt%, 0.045wt%≤V≤0.075wt%, 0.015wt%≤Nb≤0.025wt%, P≤0.045wt%, S≤0.045wt%, and the rest are iron and other inevitable impurities.

[0007] Furthermore, the carbon equivalent of the direct-rolled HRB500E straight seismic steel bar is ≤0.055wt%; the yield strength is 520-570Mpa; the tensile strength is 680-730Mpa; the strength-yield ratio is 1.26-1.35; the yield-yield ratio is 1.04-1.14; the elongation is 18%-22%; and the total elongation at maximum force is 10.5-13.5.

[0008] Furthermore, the metallographic phase of the direct-rolled HRB500E straight seismic steel bar is ferrite + pearlite; the average grain diameter of the ferrite is 8 to 13 μm, and the grain size is 11.0 to 12.0; wherein the proportion of the ferrite is 55% to 65%, and the proportion of the pearlite is 35% to 45%.

[0009] The present invention provides a method for producing the direct-rolled HRB500E straight seismic steel bars as described in any one of the above, comprising the steps of:

[0010] S1. Continuously cast a slab, controlling fluctuation ≤ 0.2 m / min; the chemical composition and mass percentage of the slab are 0.22wt% ≤ C ≤ 0.25wt%, 0.40wt% ≤ Si ≤ 0.60wt%, 1.20wt% ≤ Mn ≤ 1.40wt%, 0.045wt% ≤ V ≤ 0.075wt%, 0.015wt% ≤ Nb ≤ 0.025wt%, P ≤ 0.045wt%, S ≤ 0.045wt%, and the rest are iron and other inevitable impurities;

[0011] When the continuous casting speed is 3.2-3.6 m / min, the cutting temperature of the ingot is 1020-1100°C, a heat preservation cover is provided for the continuous casting, and the temperature is reduced by ≤100°C before the rolling mill, and the ingot is tapped by direct rolling;

[0012] S2. The cast slab is subjected to direct rough rolling to obtain a rough rolled material, wherein the direct rough rolling temperature is 920 to 980°C;

[0013] S3. The rough-rolled material is sequentially subjected to finish rolling, finished product unit processing and cooling on a cooling bed to obtain direct-rolled HRB500E straight bar earthquake-resistant steel bars.

[0014] Furthermore, when the continuous casting speed in step S2 is less than 3.2 m / min, the ingot is heated in a heating furnace after it is removed from the production line. The temperature of the rough rolling treatment of the steel discharged from the heating furnace is 1000-1060°C. The steel is then subjected to finishing rolling, finished product unit treatment and cooling on a cooling bed to obtain straight-rolled HRB500E straight seismic-resistant steel bars.

[0015] Furthermore, the finishing rolling temperature during the finishing rolling treatment is 920-980°C.

[0016] Furthermore, the temperature of the finished product during the finished product unit processing is 900-960°C.

[0017] Furthermore, the temperature of the cooling bed during the cooling treatment on the upper cooling bed is 880-940°C.

[0018] Furthermore, the cross-sectional dimension of the material to be rolled is 165 mm*165 mm; the length of the material to be rolled is 12000 mm.

[0019] Furthermore, the cooling treatment on the upper cooling bed also includes cold shearing to length treatment and sampling inspection treatment.

[0020] The beneficial effects of the present invention are as follows:

[0021] The present invention provides a straight HRB500E seismic steel bar with the contents of vanadium and niobium controlled as follows: 0.045wt%≤V≤0.075wt%, 0.015wt%≤Nb≤0.025wt%. On the one hand, by adding appropriate amounts of microalloying elements such as vanadium and niobium, the grain structure of the steel bar can be refined, thereby improving its strength. While ensuring the strength, the toughness of the steel bar is not reduced, so that the steel bar has better comprehensive mechanical properties.

[0022] On the other hand, as an earthquake-resistant steel bar, the optimization of its chemical composition helps to improve its earthquake resistance, making it more suitable for structures with high requirements for earthquake resistance, such as high-rise buildings and bridges. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0024] Figure 1 The metallographic structure diagram of HRB500E prepared in Example 1 of the present invention is

[0025] Figure 2 This is the metallographic structure diagram of HRB500E prepared in Example 3 of the present invention.

[0026] Figure 3 This is the metallographic structure diagram of HRB500E prepared in Example 5 of the present invention.

[0027] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that all directional indications (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0030] In addition, in the present invention, the descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0031] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0032] In order to solve the problem of high furnace temperature requirement in the production of direct-rolled HRB500E straight seismic steel bars in commonly used technologies, the present invention provides a direct-rolled HRB500E straight seismic steel bar, whose chemical composition and mass percentage are 0.22wt%≤C≤0.25wt%, 0.40wt%≤Si≤0.60wt%, 1.20wt%≤Mn≤1.40wt%, 0.045wt%≤V≤0.075wt%, 0.015wt%≤Nb≤0.025wt%, P≤0.045wt%, S≤0.045wt%, and the rest are iron and other inevitable impurities.

[0033] Among the commonly used technologies, heating in the heating furnace is a crucial link in the processing of HRB500E earthquake-resistant steel bars. The heating temperature range is between 1120℃ and 1250℃. Its necessity is mainly reflected in the following aspects:

[0034] Improve the plasticity of steel bars: By heating, the internal structure of the steel bars can be softened and its plasticity can be improved, making it easier to carry out subsequent processing such as rolling.

[0035] Uniform steel temperature: The heating furnace ensures that the temperature of the steel bar is uniform throughout its entire length, avoiding performance differences caused by uneven temperatures during the rolling process.

[0036] Removal of internal stress: During the heating process, the stress inside the steel bar is released, which helps to reduce deformation and cracks during processing.

[0037] Improve steel properties: Appropriate heating temperature and time can optimize the mechanical properties of steel bars, such as improving strength and toughness.

[0038] The present invention provides a straight HRB500E seismic steel bar with the contents of vanadium and niobium controlled as follows: 0.045wt%≤V≤0.075wt%, 0.015wt%≤Nb≤0.025wt%. On the one hand, by adding appropriate amounts of microalloying elements such as vanadium and niobium, the grain structure of the steel bar can be refined, thereby improving its strength. While ensuring the strength, the toughness of the steel bar can be maintained, so that the steel bar has better comprehensive mechanical properties.

[0039] On the other hand, as an earthquake-resistant steel bar, the optimization of its chemical composition helps to improve its earthquake resistance, making it more suitable for structures with high requirements for earthquake resistance, such as high-rise buildings and bridges.

[0040] By adjusting the chemical composition of the steel bars (i.e., direct-rolled HRB500E straight bar earthquake-resistant steel bars, the same below), and then optimizing the suitable processing technology, the chemical composition and the technology are coordinated to obtain direct-rolled HRB500E straight bar earthquake-resistant steel bars with good strength in a way of low fuel consumption and high production efficiency.

[0041] In some embodiments, the steel bar processing process is as follows:

[0042] Includes steps:

[0043] S1. Continuously cast the ingot, and control the fluctuation ≤0.2m / min; the chemical composition and mass percentage of the ingot are 0.22wt%≤C≤0.25wt%, 0.40wt%≤Si≤0.60wt%, 1.20wt%≤Mn≤1.40wt%, 0.045wt%≤V≤0.075wt%, 0.015wt%≤Nb≤0.025wt%, P≤0.045wt%, S≤0.045wt%, and the rest are iron and other inevitable impurities.

[0044] For example, the cross-sectional dimensions of the ingot may be 165 mm*165 mm, and the length may be 12000 mm.

[0045] When the continuous casting speed is 3.2-3.6 m / min, the cutting temperature of the ingot is 1020-1100°C, a heat preservation cover is provided for the continuous casting, and the temperature is reduced by ≤100°C before the rolling mill, and the ingot is tapped by direct rolling.

[0046] S2. The ingot produced by direct rolling is subjected to direct rough rolling treatment to obtain rough rolled material, wherein the direct rough rolling treatment temperature is 920-980°C.

[0047] In the case that the continuous casting speed in step S1 is less than 3.2 m / min, the ingot is heated in a heating furnace after it is removed from the production line, and the temperature of the heating rough rolling treatment is 1000-1060°C.

[0048] Heating rough rolling is a process of heating in a heating furnace + rough rolling, wherein the heating time in the heating furnace can be 50-100 minutes and the temperature can be 1100-1200°C.

[0049] The use of a model in which direct rolling and heating furnace steelmaking complement each other can effectively avoid the impact of steelmaking and rolling line failures on process production, effectively improve production efficiency and reduce fuel costs.

[0050] The above-mentioned direct rolling temperature can be nearly 100°C lower than the steel-out temperature of the heating furnace because the ingot precipitates less at high temperature, and the core temperature of the ingot is maintained at about 1000°C, which can achieve the same effect as heating in a heating furnace to re-dissolve the alloy elements. In addition, the two different steel-out methods of direct rolling and heating furnace can adjust the amount of cooling water before finishing rolling to ensure that the finishing rolling temperature, the finished product temperature and the cooling bed temperature are consistent.

[0051] In some embodiments, the production specification of hot rolling can be ∮12mm to ∮25mm.

[0052] High-speed bar technology can be used to roll the material to be rolled efficiently and accurately to produce bar products that meet the requirements. High-speed bar production lines usually use advanced rolling technology and equipment, such as full short stress torsion-free rolling, multi-wire slitting technology, etc., to improve production efficiency and product quality.

[0053] S3. The rough-rolled material is sequentially subjected to finishing treatment, finished product unit treatment and cooling treatment on a cooling bed to obtain straight-rolled HRB500E straight seismic steel bars;

[0054] In some embodiments, the finishing rolling temperature during the finishing rolling process is 920-980° C. A temperature above the upper limit is not conducive to grain refinement, while a temperature below the lower limit will cause premature precipitation of microalloys.

[0055] It should be noted that different cooling degrees can be used to ensure that the finishing rolling temperature, the temperature of the finished product and the temperature of the cooling bed are consistent for the two different steel-out methods of direct rolling and heating furnace.

[0056] In some embodiments, the inlet temperature of the finished product during the finished product unit processing is 900-960° C. A temperature above the upper limit is not conducive to grain refinement, and a temperature below the lower limit will cause premature precipitation of microalloys.

[0057] In some embodiments, the cooling bed temperature during the upper cooling bed cooling treatment is 880-940° C. A temperature above the upper limit is not conducive to grain refinement, while a temperature below the lower limit will result in excessive cooling of the outer ring to form a semi-closed loop structure.

[0058] In some embodiments, the cooling process on the cooling bed may also include cold shearing to length processing and sampling and inspection processing.

[0059] The carbon equivalent of the straight-rolled HRB500E straight seismic steel bar produced through steps S1 to S3 is ≤0.055wt%; the yield strength is 520-570Mpa; the tensile strength is 680-730Mpa; the strength-yield ratio is 1.26-1.35; the yield-yield ratio is 1.04-1.14; the elongation is 18%-22%; and the total elongation at maximum force is 10.5-13.5.

[0060] Exemplarily, the metallographic structure is F+P, and both the mechanical properties and the metallographic structure meet the GB 1499.2-2024 standard and the seismic requirements.

[0061] The metallographic structure of the direct-rolled HRB500E straight seismic steel bar is ferrite + pearlite; the average grain diameter of the ferrite is 10-13 μm, and the grain size is 11.0-12.0; wherein the proportion of the ferrite is 55%-65%, and the proportion of the pearlite is 35%-45%.

[0062] According to the advantages of high-speed bars and direct rolling production line configuration, the present invention proposes a production method of direct-rolled HRB500E straight bar earthquake-resistant steel bars. Through continuous casting speed matching, bar direct rolling, controlled rolling and cooling, high-speed bar rolling technology, etc., on the premise of ensuring that the mechanical properties and metallographic structure meet the HRB500E hot-rolled ribbed earthquake-resistant steel bars, the production specifications of ∮12mm~∮25mm can achieve reduced fuel consumption and improved production efficiency, thereby improving product competitiveness.

[0063] For easier understanding, here is an example:

[0064] The invention provides a production method of direct-rolled HRB500E straight bar earthquake-resistant steel bars, the process comprising steelmaking-continuous casting-high-speed bar direct rolling-controlled rolling and controlled cooling-cooling on a cooling bed-cold shearing and sizing-sampling and inspection-packaging and storage.

[0065] The present invention is further described below by specific embodiments 1 to 6:

[0066] Example 1, Example 3, and Example 1 respectively produce three specifications of HRB500E hot-rolled ribbed steel bars of ∮14mm, ∮20mm, and ∮25mm. The chemical composition mass percentage (wt%) is shown in Table 1, and the rest are residual elements in molten steel. The drawing speed, temperature control, and final rolling speed are shown in Table 2. The mechanical properties and plate shape measurement results are shown in Table 3:

[0067] Table 1 Chemical composition of each example (wt%, balance Fe)

[0068] Example C Si Mn P S Nb V Ceq 1 0.23 0.50 1.38 0.028 0.020 0.018 0.055 0.50 3 0.24 0.52 1.28 0.020 0.035 0.020 0.068 0.48 5 0.23 0.48 1.34 0.025 0.022 0.019 0.070 0.49

[0069] Table 2 Parameters of rolling speed + rough rolling temperature + finishing rolling temperature + finished product temperature + cooling bed temperature + final rolling speed of each embodiment

[0070]

[0071] The other steps in Example 2 are the same as those in Example 1, except that the continuous casting speed is adjusted to less than 3.2 m / min, and direct rolling is replaced by the heating furnace steelmaking method.

[0072] The other steps in Example 4 are the same as those in Example 3, except that the continuous casting speed is adjusted to <3.2 m / min. 时 , replacing direct rolling with the method of tapping steel from a heating furnace.

[0073] The other steps in Example 6 are the same as those in Example 5, except that the continuous casting speed is adjusted to less than 3.2 m / min, and direct rolling is replaced by steel tapping from a heating furnace.

[0074] Table 3 Mechanical properties of each embodiment

[0075]

[0076] Examples 1, 3 and 5 show that HRB500E produced by direct rolling without heating has stable temperature control, good surface quality, and its mechanical properties and metallographic structure fully meet the requirements of GB 1499.2-2024.

[0077] The metallographic organization diagrams obtained in Example 1, Example 3 and Example 5 are shown in the attached drawings. Figure 1 , Attachment Figure 2 And attached Figure 3 shown.

[0078] The above technical solutions of the present invention are only preferred embodiments of the present invention, and the patent scope of the present invention is not limited thereto. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A direct-rolled HRB500E straight bar seismic steel bar, characterized in that: The chemical composition and mass percentage of the direct-rolled HRB500E straight seismic steel bars are 0.22wt%≤C≤0.25wt%, 0.40wt%≤Si≤0.60wt%, 1.20wt%≤Mn≤1.40wt%, 0.045wt%≤V≤0.075wt%, 0.015wt%≤Nb≤0.025wt%, P≤0.045wt%, S≤0.045wt%, and the rest are iron and other inevitable impurities.

2. The direct-rolled HRB500E straight seismic steel bar according to claim 1 is characterized in that: The carbon equivalent of the direct-rolled HRB500E straight bar earthquake-resistant steel bar is ≤0.055wt%; the yield strength is 520-570Mpa; the tensile strength is 680-730Mpa; the strength-yield ratio is 1.26-1.35; the yield-yield ratio is 1.04-1.14; the elongation is 18-22%; and the total elongation at maximum force is 10.5-13.

5.

3. The direct-rolled HRB500E straight seismic steel bar according to claim 1 is characterized in that: The metallographic structure of the direct-rolled HRB500E straight seismic steel bar is ferrite + pearlite; the average grain diameter of the ferrite is 10-13 μm, and the grain size is 11.0-12.0; wherein the proportion of the ferrite is 55%-65%, and the proportion of the pearlite is 35%-45%.

4. A method for producing direct-rolled HRB500E straight seismic steel bars according to any one of claims 1 to 3, characterized in that: Includes steps: S1. Continuously cast a slab, controlling fluctuation ≤ 0.2 m / min; the chemical composition and mass percentage of the slab are 0.22wt% ≤ C ≤ 0.25wt%, 0.40wt% ≤ Si ≤ 0.60wt%, 1.20wt% ≤ Mn ≤ 1.40wt%, 0.045wt% ≤ V ≤ 0.075wt%, 0.015wt% ≤ Nb ≤ 0.025wt%, P ≤ 0.045wt%, S ≤ 0.045wt%, and the rest are iron and other inevitable impurities; When the continuous casting speed is 3.2-3.6 m / min, the billet is tapped by direct rolling, the billet cut-off temperature is 1020-1100° C., a heat preservation cover is provided in the continuous casting area, and the billet is cooled by ≤100° C. before reaching the rolling mill; S2. The cast slab is subjected to direct rough rolling to obtain a rough rolled material, wherein the direct rough rolling temperature is 920 to 980°C; S3. The rough-rolled material is sequentially subjected to finish rolling, finished product unit processing and cooling on a cooling bed to obtain direct-rolled HRB500E straight bar earthquake-resistant steel bars.

5. The production method according to claim 4, characterized in that: When the continuous casting speed in step S1 is less than 3.2 m / min, the ingot is heated in a heating furnace after it is removed from the production line. The temperature of the rough rolling treatment of the steel discharged from the heating furnace is 1000-1060°C. The steel is then subjected to finishing rolling, finished product unit treatment and cooling on a cooling bed to obtain straight-rolled HRB500E seismic-resistant steel bars.

6. The method for producing the direct-rolled HRB500E straight seismic steel bars according to claim 4, characterized in that: The finishing rolling temperature during the finishing rolling treatment is 920 to 980°C.

7. The method for producing direct-rolled HRB500E straight seismic steel bars according to claim 4, characterized in that: The temperature of the finished product when the finished product unit is processed is 900-960°C.

8. The method for producing the direct-rolled HRB500E straight seismic steel bar according to claim 4, characterized in that: The temperature of the cooling bed during the upper cooling bed cooling treatment is 880-940°C.

9. The method for producing the direct-rolled HRB500E straight seismic steel bar according to claim 4, characterized in that: The cross-sectional dimension of the ingot is 165 mm*165 mm; the length of the ingot is 12000 mm.

10. The method for producing the direct-rolled HRB500E straight seismic steel bar according to claim 4, characterized in that: The cooling process on the upper cooling bed also includes cold shearing to length processing and sampling and inspection processing.

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