Railway-specific 400MPa grade seismic-resistant steel bars and their preparation method
By designing appropriate chemical compositions and process parameters, the problem that existing railway-specific seismic steel bars could not meet the TB/T3432-2016 standard was solved, and high-strength, low-carbon equivalent, and small-weight deviation 400MPa grade seismic steel bars were prepared to meet the railway-specific requirements.
Patent Information
- Application Number
- CN202610417260.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-31
- Publication Date
- 2026-06-02
AI Technical Summary
Existing methods for preparing railway-specific seismic-resistant steel bars cannot meet the requirements of high carbon equivalent, weight deviation of less than 3.0%, and micro-alloying production processes, and therefore cannot meet the TB/T3432-2016 standard.
By employing appropriate chemical composition design, the Mn content in the steel is reduced, the V microalloying content is increased, and the weight deviation is ensured to be less than 3.0% through a negative deviation automatic control system. Combined with weak water penetration process and high temperature cooling bed treatment, the metallographic structure is refined to improve strength.
The 400MPa grade seismic steel bars that meet the TB/T3432-2016 standard were prepared. They have good surface quality and mechanical properties, weight deviation is controlled within ±2.5%, carbon equivalent is less than 0.50%, and welding performance is excellent.
Smart Images
Figure CN122128619A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of special steel reinforcement technology, and in particular relates to a railway-specific 400MPa grade seismic-resistant steel reinforcement and its preparation method. Background Technology
[0002] The standards for railway-specific seismic-resistant steel bars differ from those for hot-rolled ribbed steel bars: hot-rolled ribbed steel bars adhere to GB1499.2-2024, while railway-specific seismic-resistant steel bars adhere to TB / T3432-2016-《High-Speed Railway Precast Post-Tensioned Prestressed Concrete Simply Supported Beams》. The carbon equivalent and weight deviation requirements for railway-specific seismic-resistant steel bars are higher than those for ordinary hot-rolled ribbed steel bars, specifically: 1. In addition to meeting the requirements of GB1499.2-2024, the allowable deviation (negative deviation) of the actual weight of the steel bars should be less than 3.0%; 2. The carbon equivalent should not exceed 0.50%; 3. The production process is a micro-alloying process, and preheating treatment (high-pressure water piercing) is prohibited. Existing processes cannot meet these requirements. Therefore, there is an urgent need to develop a new method for preparing railway-specific seismic-resistant steel bars. Summary of the Invention
[0003] This application provides a method for preparing 400MPa grade seismic-resistant steel bars for railway use, which can meet the requirements of low carbon equivalent, the negative deviation of steel bar weight is less than 3.0%, and the product quality meets the requirements of TB / T3432-2016 standard.
[0004] In a first aspect, this application provides a method for preparing railway-specific 400MPa grade seismic-resistant steel bars, comprising: The steel billet is provided with a chemical composition that meets the specified mass percentages: C: 0.21wt.%~0.25wt.%, Si: 0.35wt.%~0.55wt.%, Mn: 0.80wt.%~1.00wt.%, S: ≤0.040%, P: ≤0.040%, V: 0.025wt.%~0.040wt.%, with the remainder being Fe and unavoidable impurities during smelting; The steel billet is heated to 950℃~1010℃ to obtain a heated steel billet; The heated steel billet is hot-rolled using a 19-stand alternating horizontal and vertical rolling mill to obtain the final rolled steel bar; the final rolling temperature is 960℃~1020℃. The surface of the final rolled steel bars is cooled using a weak water quenching process to ensure a smooth surface. The temperature of the cooled steel bars on the cooling bed is controlled at 880℃~930℃ to refine and precipitate the V microalloying compounds in the metallographic structure of the steel bars. The steel bars are sheared and air-cooled to obtain railway-specific 400MPa grade seismic-resistant steel bars.
[0005] In an embodiment of the first aspect of this application, the step of providing a steel billet with a chemical composition satisfying a defined mass percentage includes: Steel billets are formed by smelting and continuous casting, based on a percentage of their mass.
[0006] In the embodiment of the first aspect of this application, the dimensions of the steel billet are width × thickness × length = 165 × 165 × 12000 mm, and the drawing speed is 3.0 m / min to 3.6 m / min.
[0007] In the embodiments of the first aspect of this application, the heating time for heating the steel billet to 950°C to 1010°C is 50 min to 90 min.
[0008] In the embodiments of the first aspect of this application, the step of hot continuous rolling the heated steel billet using a 19-stand alternating horizontal and vertical rolling mill includes: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill, and the final rolling speed of the steel bars was 10.0 m / s to 12.5 m / s to obtain the final rolled steel bars.
[0009] In the embodiments of the first aspect of this application, in the step of cooling the surface of the final rolled steel bar using a weak water piercing process, the weak water piercing process refers to the cooling process where the temperature of the final rolled steel bar is higher than the austenite initiation transformation temperature Ar3, which is 810℃~830℃, the cooling water pressure is 0.8MPa~1.0MPa, and the cooling water flow rate is 60m³ / h. 3 / h~100m 3 / h.
[0010] In an embodiment of the first aspect of this application, the method for preparing railway-specific 400MPa grade seismic-resistant steel bars further includes: randomly cutting several 500mm long steel bars on a cooling bed and weighing them to determine and obtain steel bars with a negative weight deviation of less than 3.0%.
[0011] Secondly, embodiments of this application provide a railway-specific 400MPa grade seismic-resistant steel bar, which is prepared according to the preparation method of the railway-specific 400MPa grade seismic-resistant steel bar provided in the first aspect embodiment.
[0012] In the embodiments of the second aspect of this application, the nominal diameter of the railway-specific 400MPa grade seismic steel bar is 12mm to 32mm, and the yield strength is 400MPa to 480MPa.
[0013] In the embodiments of the first aspect of this application, the yield strength of the railway-specific 400MPa grade seismic-resistant steel bar is 435MPa to 475MPa, the tensile strength is 605MPa to 650MPa, the strength-to-yield ratio is 1.37 to 1.45, the elongation is 17% to 25%, and the maximum total elongation A gt The content is 12.3% to 14.8%. The above mechanical properties were obtained according to GB1499.2-2024 requirements and tested according to GB / T28900.
[0014] In the embodiments of the first aspect of this application, the metallographic structure of the railway-specific 400MPa grade seismic-resistant steel bar is ferrite and pearlite, with a grain size ≥10.5.
[0015] In the embodiments of the first aspect of this application, the carbon equivalent of the railway-specific 400MPa grade seismic steel bar is 0.36wt.% to 0.42wt.%.
[0016] In the embodiments of the first aspect of this application, the allowable deviation between the actual weight of railway-specific 400MPa grade seismic steel bars and the standard required weight is controlled within ±2.5%.
[0017] The method for preparing railway-specific 400MPa grade seismic-resistant steel bars provided in this application involves designing a suitable chemical composition to reduce the Mn content and increase the V microalloying content in the steel to meet the requirements of low carbon equivalent. An automatic negative deviation control system ensures that the negative deviation of the steel bars leaving the factory is less than 3.0%. A higher upper cooling bed temperature is designed to ensure qualified metallographic structure while increasing the precipitation of fine V precipitates, thereby improving strength. This method produces railway-specific 400MPa grade seismic-resistant steel bars with a diameter of 12mm to 32mm and a grade of HRB400E, and the product quality meets all the requirements of the TB / T3432-2016 standard. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a schematic flowchart of the preparation method of railway-specific 400MPa grade seismic-resistant steel bars provided in the embodiments of this application.
[0020] Figure 2 This is a metallographic image of the 400MPa grade seismic-resistant steel bar for railway use, magnified 500 times, provided in Embodiment 1 of this application.
[0021] Figure 3This is a metallographic image of the 400MPa grade seismic-resistant steel bar for railway use, provided in Embodiment 2 of this application, magnified 500 times.
[0022] Figure 4 This is a metallographic image of the 400MPa grade seismic-resistant steel bar for railway use, provided in Embodiment 3 of this application, magnified 500 times.
[0023] Figure 5 This is a metallographic image of the 400MPa grade seismic-resistant steel bar for railway use, provided in Embodiment 4 of this application, magnified 500 times.
[0024] Figure 6 This is a metallographic image of the 400MPa grade seismic-resistant steel bar for railway use, provided in Embodiment 5 of this application, magnified 500 times.
[0025] Figure 7 This is a panoramic view and a metallographic microstructure diagram of the base circle of a 400MPa grade hot-rolled ribbed steel bar, magnified 500 times, compared to Scale 1.
[0026] Figure 8 This is a panoramic view and a metallographic image of the base circle of a 400MPa grade hot-rolled ribbed steel bar, magnified 500 times, according to Comparative Scale 5. Detailed Implementation
[0027] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.
[0028] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.
[0029] To address the problems of the prior art, this application provides a railway-specific 400MPa grade seismic-resistant steel bar and its preparation method. The preparation method of the railway-specific 400MPa grade seismic-resistant steel bar provided in this application will be described below.
[0030] Figure 1 A schematic flowchart of a method for preparing railway-specific 400MPa grade seismic-resistant steel bars according to an embodiment of this application is shown.
[0031] like Figure 1 As shown, the preparation method of railway-specific 400MPa grade seismic-resistant steel bars includes: The steel billet is provided with a chemical composition that meets the specified mass percentages: C: 0.21wt.%~0.25wt.%, Si: 0.35wt.%~0.55wt.%, Mn: 0.80wt.%~1.00wt.%, S: ≤0.040%, P: ≤0.040%, V: 0.025wt.%~0.040wt.%, with the remainder being Fe and unavoidable impurities during smelting; The steel billet is heated to 950℃~1010℃ to obtain a heated steel billet; The heated steel billet is hot-rolled using a 19-stand alternating horizontal and vertical rolling mill to obtain the final rolled steel bar; the final rolling temperature is 960℃~1020℃. The surface of the final rolled steel bars is cooled using a weak water quenching process to ensure a smooth surface. The temperature of the cooled steel bars on the cooling bed is controlled at 880℃~930℃ to refine and precipitate the V microalloying compounds in the metallographic structure of the steel bars. The steel bars are sheared and air-cooled to obtain railway-specific 400MPa grade seismic-resistant steel bars.
[0032] The method for preparing railway-specific 400MPa grade seismic-resistant steel bars provided in this application involves designing a suitable chemical composition to reduce the Mn content and increase the V microalloying content in the steel, thereby meeting the requirement of low carbon equivalent (≤0.50wt.%). An automatic negative deviation control system ensures that the negative deviation of the steel bars leaving the factory is less than 3.0%. A higher upper cooling bed temperature is designed to ensure qualified metallographic structure while increasing the precipitation of fine V precipitates, thus improving strength. This method produces railway-specific 400MPa grade seismic-resistant steel bars with a diameter of 12mm to 32mm and a grade of HRB400E, and the product quality meets all the requirements of the TB / T3432-2016 standard.
[0033] In some embodiments, the step of providing a steel billet with a chemical composition satisfying a defined mass percentage includes: smelting and continuously casting the billet to form a steel billet by mass percentage. This steel billet is then used to manufacture hot-rolled ribbed steel bars.
[0034] The method for preparing 400MPa grade seismic-resistant steel bars for railways provided in this application reduces the manganese content in the steel bars by adding V microalloying for fine grain strengthening and precipitation strengthening, thereby effectively reducing alloy costs and carbon equivalent. The reduction in carbon equivalent, in turn, effectively improves the weldability of the steel bars.
[0035] In some embodiments, the dimensions of the steel billet are width × thickness × length = 165 × 165 × 12000 mm, and the drawing speed is 3.0 m / min to 3.6 m / min. Steel billets of this specification are produced at this drawing speed and then rolled to obtain hot-rolled ribbed steel bars, i.e., railway-specific 400 MPa grade seismic-resistant steel bars.
[0036] In some embodiments, the heating time for heating the steel billet to 950°C to 1010°C is 50 min to 90 min, so as to ensure that the steel billet is heated fully and uniformly.
[0037] The method for preparing 400MPa grade seismic-resistant steel bars for railways provided in this application involves heating the steel billet to a furnace temperature of 950℃~1010℃ at a relatively low temperature. This can refine the grains of the ferrite and pearlite structures in the steel billet, thereby improving the mechanical properties, processing performance, and weldability of the steel bars. At the same time, no additional alloys are required, which can effectively reduce the alloy cost of the steel bars.
[0038] In some embodiments, the step of hot continuous rolling the heated steel billet using a 19-stand alternating horizontal and vertical rolling mill includes: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill, and the final rolling speed of the steel bars was 10.0 m / s to 12.5 m / s to obtain the final rolled steel bars.
[0039] The method for preparing railway-specific 400MPa grade seismic-resistant steel bars provided in this application embodiment can produce railway-specific 400MPa grade seismic-resistant steel bars of the corresponding specifications using the aforementioned number of stands in a rolling mill. Furthermore, by employing the aforementioned suitable final rolling speed combined with a weak water-quenching process, railway-specific 400MPa grade seismic-resistant steel bars can be produced. Here, "horizontal and vertical staggered" refers to the alternating arrangement of stands with horizontally arranged rolls and stands with vertically arranged rolls.
[0040] In some embodiments, in the step of cooling the surface of the final rolled steel bar using a weak water piercing process, the weak water piercing process refers to cooling the final rolled steel bar at a temperature higher than the austenite initiation transformation temperature Ar3, where Ar3 is 810℃~830℃, the cooling water pressure is 0.8MPa~1.0MPa, and the cooling water flow rate is 60m³ / h. 3 / h~100m 3 / h, to ensure a smooth surface on the reinforcing bars.
[0041] The method for preparing railway-specific 400MPa grade seismic-resistant steel bars provided in this application adopts a weak water penetration process, which can uniformly and finely refine the steel bar structure and obtain steel bars with good surface quality.
[0042] The method for preparing railway-specific 400MPa grade seismic-resistant steel bars provided in this application embodiment controls the temperature of the cooled steel bars on the cooling bed at 880℃~930℃, ensuring that the metallographic structure meets the requirements of the TB / T3432-2016 standard, while also facilitating the precipitation of fine V microalloying compounds, improving the strength of the steel bars, and giving the steel bars good surface quality.
[0043] In some embodiments, the method for preparing railway-specific 400MPa grade seismic-resistant steel bars further includes: Several 500mm long steel bars were randomly cut from the cooling bed and weighed to determine whether the weight negative deviation was less than 3.0%. Understandably, the weight deviation after load-bearing can be automatically uploaded to the negative deviation control system, which automatically determines whether the negative deviation of the steel bar weight meets the requirements, thus ensuring that the manufactured steel bars meet the requirements for negative weight deviation of steel bars in the TB / T3432-2016 standard as much as possible.
[0044] In some embodiments, after shearing and air cooling, the reinforcing bars can be packaged and stored for later use.
[0045] The method for preparing railway-specific 400MPa grade seismic-resistant steel bars provided in this application, through control of key processes, ensures that the composition of molten steel meets the requirements to obtain steel billets with the corresponding composition and content. It also involves selecting appropriate continuous casting speeds and improving the heating and rolling temperatures of the continuously cast steel billets. This results in HRB400E steel bars, i.e., railway-specific 400MPa grade seismic-resistant steel bars, with a yield strength of 435MPa~475MPa, a tensile strength of 605MPa~650MPa, a strength-to-yield ratio of 1.37~1.45, an elongation of 17%~25%, and a maximum total elongation A. gt The carbon content is 12.3% to 14.8%; the metallographic structure is F phase + P phase, the grain size is ≥10.5 grade, and the carbon equivalent and weight deviation meet the requirements of TB / T3432-2016.
[0046] Secondly, embodiments of this application provide a railway-specific 400MPa grade seismic-resistant steel bar, which is prepared according to the preparation method of the railway-specific 400MPa grade seismic-resistant steel bar provided in the first aspect embodiment.
[0047] In some embodiments, the nominal diameter of the railway-specific 400MPa grade seismic steel bar is 12mm to 32mm, and the yield strength is 400MPa to 520MPa.
[0048] In some embodiments, the yield strength of the railway-specific 400MPa grade seismic steel bar is 435MPa to 475MPa, the tensile strength is 605MPa to 650MPa, the strength-to-yield ratio is 1.37 to 1.45, the elongation is 17% to 25%, and the maximum force total elongation is 12.3% to 14.8%.
[0049] In some embodiments, the metallographic structure of the railway-specific 400MPa grade seismic-resistant steel bars is ferrite and pearlite, with a grain size ≥10.5 grade, and the mechanical properties meet the requirements of GB / T11499.2 with a certain margin.
[0050] In some embodiments, the carbon equivalent of railway-specific 400MPa grade seismic-resistant steel bars is 0.36wt.% to 0.42wt.%, which meets the requirement of TB / T3432-2016 standard that the carbon equivalent should not exceed 0.50%. Furthermore, using a lower carbon equivalent is beneficial to the weldability and improves the toughness and plasticity of the steel bars.
[0051] In some embodiments, the allowable deviation between the actual weight of railway-specific 400MPa grade seismic-resistant steel bars and the standard required weight is controlled within ±2.5%, which meets the requirement of less than 3.0% negative deviation of steel bar weight in TB / T3432-2016 standard.
[0052] The technical solutions and effects of this application will be further illustrated below through specific embodiments and comparative examples.
[0053] Example 1 A method for preparing 400MPa grade seismic-resistant steel bars for railway use, used to produce 400MPa grade seismic-resistant steel bars with a nominal diameter of 12mm for railway use, having a yield strength of 445MPa~450MPa, a tensile strength of 625MPa~635MPa, a strength-to-yield ratio of 1.40, an elongation of 23%~24%, a maximum force total elongation of 14.2%~14.8%, and a negative weight deviation of -2.2%; the chemical composition and content of the 400MPa grade seismic-resistant steel bars for railway use are as follows (by mass percentage): C, 0.23wt.%, Si, 0.38wt.%, Mn, 0.85wt.%, S, 0.017%, P, 0.022%, V, 0.032wt.%, Ceq, 0.38%, with the remainder being Fe and unavoidable impurities during smelting.
[0054] The preparation method of the 400MPa grade seismic-resistant steel bar for railway use in this embodiment includes: according to the chemical composition ratio of steel bars, smelting and continuous casting to provide a steel billet with a chemical composition that meets the specified mass percentage: by mass percentage of the steel billet, C: 0.23wt.%, Si: 0.38wt.%, Mn: 0.85wt.%, S: 0.017%, P: 0.022%, V: 0.032wt.%, Ceq: 0.38%, with the remainder being Fe and unavoidable impurities during smelting; the continuous casting speed is 3.0m / min, and the dimensions of the steel billet are width × thickness × length = 165 × 165 × 12000mm; The steel billet was heated to a tapping temperature of 992℃ using a heating section and a soaking section at a temperature of 1180℃ for 60 minutes to obtain a heated steel billet. The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill. The final rolling temperature was 970℃ and the final rolling speed was 12.5m / s to obtain the finished steel bars. The surface of the final rolled steel bars is cooled using a weak water quenching process to ensure that the temperature of the final rolled steel bars is higher than the austenite transformation initiation temperature Ar3, which is 810℃~830℃. The cooling water pressure for the cooling process is 0.8MPa~1.0MPa, and the cooling water flow rate is 60m³ / h. 3 / h~80m 3 / h, to ensure a smooth surface on the reinforcing bars; The temperature of the cooled steel bars on the cooling bed is controlled at 898℃ to refine and precipitate the V microalloying compounds in the metallographic structure of the steel bars. The steel bars are sheared and air-cooled to obtain railway-specific 400MPa grade seismic-resistant steel bars.
[0055] Example 2 A method for preparing 400MPa grade seismic-resistant steel bars for railway use, used to produce nominal diameters of 16mm, yield strengths of 435MPa to 440MPa, tensile strengths of 610MPa to 615MPa, strength-to-yield ratios of 1.39 to 1.40, elongation of 22% to 24%, total elongation at maximum force of 14.2% to 14.9%, and negative weight deviation of -2.4%. The chemical composition and content of the 400MPa grade seismic-resistant steel bars for railway use are as follows (by mass percentage): C: 0.23wt.%, Si: 0.38wt.%, Mn: 0.85wt.%, S: 0.017%, P: 0.022%, V: 0.032wt.%, Ceq: 0.38%, with the remainder being Fe and unavoidable impurities during smelting.
[0056] The preparation method of the 400MPa grade seismic-resistant steel bar for railway use in this embodiment includes: according to the chemical composition ratio of steel bars, smelting and continuous casting to provide a steel billet with a chemical composition that meets the specified mass percentage: by mass percentage of the steel billet, C: 0.23wt.%, Si: 0.38wt.%, Mn: 0.85wt.%, S: 0.017%, P: 0.022%, V: 0.032wt.%, Ceq: 0.38%, with the remainder being Fe and unavoidable impurities during smelting; the continuous casting speed is 3.4m / min, and the dimensions of the steel billet are width × thickness × length = 165 × 165 × 12000mm; The steel billet was heated to a tapping temperature of 962℃ using a heating section and a soaking section at a temperature of 1180℃ for 50 minutes to obtain a heated steel billet. The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by a 7-stand finishing mill. The final rolling temperature was 975℃ and the final rolling speed was 12.5m / s to obtain the finished steel bars. The surface of the final rolled steel bars is cooled using a weak water quenching process to ensure that the temperature of the final rolled steel bars is higher than the austenite transformation initiation temperature Ar3, which is 810℃~830℃. The cooling water pressure for the cooling treatment is 0.8MPa~1.0MPa, and the cooling water flow rate is 60m³ / h. 3 / h~80m 3 / h, to ensure a smooth surface on the reinforcing bars; The temperature of the cooled steel bars on the cooling bed is controlled at 900℃ to refine and precipitate the V microalloying compounds in the metallographic structure of the steel bars. The steel bars are sheared and air-cooled to obtain railway-specific 400MPa grade seismic-resistant steel bars.
[0057] Example 3 A method for preparing 400MPa grade seismic-resistant steel bars for railway use, used to produce nominal diameters of 20mm, yield strengths of 440MPa to 445MPa, tensile strengths of 625MPa to 630MPa, strength-to-yield ratios of 1.42, elongation of 22% to 23%, total elongation at maximum force of 13.8% to 14.3%, and negative weight deviation of -2.0%; the chemical composition and content of the 400MPa grade seismic-resistant steel bars for railway use are as follows (by mass percentage): C: 0.22wt.%, Si: 0.45wt.%, Mn: 0.88wt.%, S: 0.013%, P: 0.025%, V: 0.028wt.%, Ceq: 0.36%, with the remainder being Fe and unavoidable impurities during smelting.
[0058] The preparation method of the 400MPa grade seismic-resistant steel bar for railway use in this embodiment includes: according to the chemical composition ratio of steel bars, smelting and continuous casting to provide a steel billet with a chemical composition that meets the specified mass percentage: by mass percentage of the steel billet, C: 0.22wt.%, Si: 0.45wt.%, Mn: 0.88wt.%, S: 0.013%, P: 0.025%, V: 0.028wt.%, Ceq: 0.37%, with the remainder being Fe and unavoidable impurities during smelting; the continuous casting speed is 3.5m / min, and the dimensions of the steel billet are width × thickness × length = 165 × 165 × 12000mm; The steel billet was heated to a tapping temperature of 980℃ using a heating section and a soaking section at a temperature of 1185℃ for 80 minutes to obtain a heated steel billet. The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill. The final rolling temperature was 1000℃ and the final rolling speed was 11.8m / s to obtain the finished steel bars. The surface of the final rolled steel bars is cooled using a weak water quenching process to ensure that the temperature of the final rolled steel bars is higher than the austenite transformation initiation temperature Ar3, which is 810℃~830℃. The cooling water pressure for the cooling process is 0.8MPa~1.0MPa, and the cooling water flow rate is 60m³ / h. 3 / h~80m 3 / h, to ensure a smooth surface on the reinforcing bars; The temperature of the cooled steel bars on the cooling bed is controlled at 922℃ to refine and precipitate the V microalloying compounds in the metallographic structure of the steel bars. The steel bars are sheared and air-cooled to obtain railway-specific 400MPa grade seismic-resistant steel bars.
[0059] Example 4 A method for preparing 400MPa grade seismic-resistant steel bars for railway use, used to produce nominal diameters of 25mm, yield strengths of 445MPa to 450MPa, tensile strengths of 630MPa to 635MPa, strength-to-yield ratios of 1.41 to 1.42, elongation of 20% to 22.5%, total elongation at maximum force of 12.8% to 14.1%, and negative weight deviation of -2.5%. The chemical composition and content of the 400MPa grade seismic-resistant steel bars for railway use are as follows (by mass percentage): C: 0.22wt.%, Si: 0.45wt.%, Mn: 0.88wt.%, S: 0.013%, P: 0.025%, V: 0.028wt.%, Ceq: 0.37%, with the remainder being Fe and unavoidable impurities during smelting.
[0060] The preparation method of the 400MPa grade seismic-resistant steel bar for railway use in this embodiment includes: according to the chemical composition ratio of the steel bar, smelting and continuous casting to provide a steel billet with a chemical composition that meets the specified mass percentage: by mass percentage of the steel billet, C: 0.22wt.%, Si: 0.45wt.%, Mn: 0.88wt.%, S: 0.013%, P: 0.025%, V: 0.028wt.%, Ceq: 0.37%, with the remainder being Fe and unavoidable impurities during smelting; the continuous casting speed is 3.5m / min, and the dimensions of the steel billet are width × thickness × length = 165 × 165 × 12000mm; The steel billet was heated to a tapping temperature of 1000℃ using a heating section and a soaking section at a temperature of 1185℃ for 90 minutes to obtain a heated steel billet. The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill. The final rolling temperature was 1015℃ and the final rolling speed was 11.5m / s to obtain the finished steel bars. The surface of the final rolled steel bars is cooled using a weak water quenching process to ensure that the temperature of the final rolled steel bars is higher than the austenite transformation initiation temperature Ar3, which is 810℃~830℃. The cooling water pressure for the cooling process is 0.8MPa~1.0MPa, and the cooling water flow rate is 60m³ / h. 3 / h~80m 3 / h, to ensure a smooth surface on the reinforcing bars; The temperature of the cooled steel bars on the cooling bed is controlled at 930℃ to refine and precipitate the V microalloying compounds in the metallographic structure of the steel bars. The steel bars are sheared and air-cooled to obtain railway-specific 400MPa grade seismic-resistant steel bars.
[0061] Example 5 A method for preparing 400MPa grade seismic-resistant steel bars for railway use, used to produce nominal diameters of 32mm, yield strengths of 435MPa to 440MPa, tensile strengths of 610MPa to 615MPa, strength-to-yield ratios of 1.40 to 1.41, elongation of 20% to 22%, total elongation at maximum force of 13.2% to 13.5%, and a negative weight deviation of -1.5%. The chemical composition and content of the 400MPa grade seismic-resistant steel bars for railway use are as follows (by mass percentage): C: 0.21wt.%, Si: 0.51wt.%, Mn: 0.92wt.%, S: 0.010%, P: 0.018%, V: 0.030wt.%, Ceq: 0.36%, with the remainder being Fe and unavoidable impurities during smelting.
[0062] The preparation method of the 400MPa grade seismic-resistant steel bar for railway use in this embodiment includes: according to the chemical composition ratio of steel bars, smelting and continuous casting to provide a steel billet with a chemical composition that meets the specified mass percentage: by mass percentage of the steel billet, C: 0.21wt.%, Si: 0.51wt.%, Mn: 0.92wt.%, S: 0.010%, P: 0.018%, V: 0.030wt.%, Ceq: 0.36%, with the remainder being Fe and unavoidable impurities during smelting; the continuous casting speed is 3.2m / min, and the dimensions of the steel billet are width × thickness × length = 165 × 165 × 12000mm; The steel billet was heated to a tapping temperature of 1005℃ using a heating section and a soaking section at a temperature of 1188℃ for 70 minutes to obtain a heated steel billet. The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill. The final rolling temperature was 1010℃ and the final rolling speed was 10.2m / s to obtain the finished steel bars. The surface of the final rolled steel bars is cooled using a weak water quenching process to ensure that the temperature of the final rolled steel bars is higher than the austenite transformation temperature Ar3. The austenite transformation initiation temperature Ar3 is 810℃~830℃. The cooling water pressure for the cooling treatment is 0.8MPa~1.0MPa, and the cooling water flow rate is 60m³ / h. 3 / h~80m 3 / h, to ensure a smooth surface on the reinforcing bars; The temperature of the cooled steel bars on the cooling bed is controlled at 928℃ to refine and precipitate the V microalloying compounds in the metallographic structure of the steel bars. The steel bars are sheared and air-cooled to obtain railway-specific 400MPa grade seismic-resistant steel bars.
[0063] Comparative Example 1 Comparative Example 1 produces a 400MPa grade hot-rolled ribbed steel bar with a nominal diameter of 12mm. According to the chemical composition ratio of the steel bar, a steel billet is produced by smelting and continuous casting to provide the chemical composition meeting the following mass percentage requirements: C: 0.23wt.%, Si: 0.38wt.%, Mn: 1.25wt.%, S: 0.017%, P: 0.028%, Ceq: 0.45%, with the remainder being Fe and unavoidable impurities during smelting; the continuous casting speed is 3.2m / min, and the billet dimensions are width × thickness × length = 165 × 165 × 12000mm. The steel billet is heated to 1025℃ for 60 minutes to obtain a heated steel billet; The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill. The final rolling temperature was 1040℃ and the final rolling speed was 12.5m / s to obtain the finished steel bars. The final rolled steel bars are cooled using a water-cooling process. The temperature of the cooled steel bars on the cooling bed is controlled at 850℃. The steel bars are sheared and air-cooled to obtain 400MPa grade seismic-resistant steel bars.
[0064] Comparative Example 2 Comparative Example 2 produces a 400MPa grade hot-rolled ribbed steel bar with a nominal diameter of 16mm. According to the chemical composition ratio of the steel bar, a steel billet was produced by smelting and continuous casting to provide the chemical composition meeting the following mass percentage requirements: C: 0.22wt.%, Si: 0.38wt.%, Mn: 1.30wt.%, S: 0.027%, P: 0.028%, Ceq: 0.44%, with the remainder being Fe and unavoidable impurities from smelting. The continuous casting speed was 3.0m / min, and the billet dimensions were width × thickness × length = 165 × 165 × 12000mm. The steel billet is heated to 1015℃ for 60 minutes to obtain a heated steel billet; The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill. The final rolling temperature was 1025℃ and the final rolling speed was 12.0m / s to obtain the finished steel bars. The final rolled steel bars are cooled using a water-cooling process. The temperature of the cooled steel bars on the cooling bed is controlled at 860℃. The steel bars are sheared and air-cooled to obtain 400MPa grade seismic-resistant steel bars.
[0065] Comparative Example 3 Comparative Example 3 produced a 400MPa grade hot-rolled ribbed steel bar with a nominal diameter of 20mm. According to the chemical composition ratio of the steel bar, a steel billet was produced by smelting and continuous casting to provide a chemical composition meeting the following mass percentage requirements: C: 0.22wt.%, Si: 0.45wt.%, Mn: 1.30wt.%, S: 0.020%, P: 0.021%, Ceq: 0.44%, with the remainder being Fe and unavoidable impurities from smelting. The continuous casting speed was 3.0m / min, and the billet dimensions were width × thickness × length = 165 × 165 × 12000mm. The steel billet is heated to 1035℃ for 70 minutes to obtain a heated steel billet; The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill. The final rolling temperature was 1050℃ and the final rolling speed was 11.5m / s to obtain the finished steel bars. The final rolled steel bars are cooled using a water-cooling process. The temperature of the cooled steel bars on the cooling bed is controlled at 865℃. The steel bars are sheared and air-cooled to obtain 400MPa grade seismic-resistant steel bars.
[0066] Comparative Example 4 Producing 400MPa grade hot-rolled ribbed steel bars with a nominal diameter of 25mm. According to the chemical composition ratio of the steel bars, steel billets are produced through smelting and continuous casting to provide the chemical composition meeting the following mass percentage requirements: C: 0.21wt.%, Si: 0.49wt.%, Mn: 1.35wt.%, S: 0.020%, P: 0.021%, Ceq: 0.44%, with the remainder being Fe and unavoidable impurities from smelting. The continuous casting speed is 3.3m / min, and the billet dimensions are width × thickness × length = 165 × 165 × 12000mm. The steel billet is heated to 1045℃ for 70 minutes to obtain a heated steel billet; The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill. The final rolling temperature was 1058℃ and the steel bar conveying speed after final rolling was 11.0m / s to obtain the finished steel bar. The final rolled steel bars are cooled using a water-cooling process. The temperature of the cooled steel bars on the cooling bed is controlled at 840℃; The steel bars are sheared and air-cooled to obtain 400MPa grade seismic-resistant steel bars.
[0067] Comparative Example 5 Comparative Example 5 produced a 400MPa grade hot-rolled ribbed steel bar with a nominal diameter of 32mm. According to the chemical composition ratio of the steel bar, a steel billet was produced by smelting and continuous casting to provide the chemical composition meeting the following mass percentage requirements: C: 0.23wt.%, Si: 0.5wt.%, Mn: 1.38wt.%, S: 0.020%, P: 0.029%, Ceq: 0.46%, with the remainder being Fe and unavoidable impurities from smelting; the continuous casting speed was 3.5m / min, and the billet dimensions were width × thickness × length = 165 × 165 × 12000mm. The steel billet is heated to 1050℃ for 70 minutes to obtain a heated steel billet; The heated steel billets are hot-rolled using a 19-stand alternating horizontal and vertical rolling mill, including: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill. The final rolling temperature was 1055℃ and the steel bar conveying speed after final rolling was 10.0m / s to obtain the finished steel bar. The final rolled steel bars are cooled using a water-cooling process. The temperature of the cooled steel bars on the cooling bed is controlled at 870℃. The steel bars are sheared and air-cooled to obtain 400MPa grade seismic-resistant steel bars.
[0068] Five specifications of HRB400E 400MPa grade seismic steel bars for railway special use with diameters of 12mm, 16mm, 20mm, 25mm and 32mm were produced for Examples 1-5, respectively. Five specifications of 400MPa grade hot-rolled ribbed steel bars with diameters of 12mm, 16mm, 20mm, 25mm and 32mm were also produced for Comparative Examples 1-5. The chemical composition and carbon equivalent (%) are shown in Table 1. The pulling speed, temperature control and final rolling speed are shown in Table 2. The mechanical property measurement and results are shown in Table 3.
[0069] Table 1 Chemical composition of each embodiment (wt.%, balance Fe) Note: In Table 1, "-" indicates that the heat does not contain that metal element. It should be noted that the composition and content of the molten steel in heats 1-5 in Table 1 correspond to the composition of the steel billets prepared in Examples 1-5, and the composition and content of the molten steel in heats 6-10 correspond to the composition of the steel billets prepared in Comparative Examples 1-5.
[0070] Table 2 Specifications, tapping temperature, upper cooling bed temperature, and final rolling speed parameters for each embodiment. It should be noted that the tapping temperature refers to the temperature at which the steel billet is output from the heating furnace.
[0071] Table 3. Test results of the mechanical properties of steel bars in Examples 1-5 and Comparative Examples 1-5 Table 3 shows the performance test results and some indicator requirements of Examples 1-5. The HRB400E railway-specific 400MPa grade seismic-resistant steel bars produced using the preparation method of this application for railway-specific 400MPa grade seismic-resistant steel bars have surface quality, mechanical properties, and a steel bar metallographic structure of F+P, all meeting the requirements of GB / T1499.2; among them, as... Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, these are the metallographic structures of the steel bars in Examples 1-5 magnified 500 times. The metallographic structures of the steel bars are all F+P, which means that the metallographic structures of the steel bars are mainly ferrite and pearlite. Martensite should not appear on the base circle. The carbon equivalent and weight deviation fully meet the requirements of TB / T3432-2016.
[0072] And such Figure 7 As shown in (a), in the HRB400E railway-specific 400MPa grade seismic steel bars produced by the preparation method of Comparative Example 1, tempered martensite structure, as indicated by the blue arrow, appeared on the base circle section of the steel bar. Figure 7 The metallographic structure in (b) also differs significantly from that of the seismic-resistant steel reinforcement in Examples 1-5. For example... Figure 8 As shown in (a), in the HRB400E railway-specific 400MPa grade seismic steel bars produced by the preparation method of Comparative Example 5, tempered martensite structure, as indicated by the blue arrow, also appeared on the base circle section of the steel bars. Figure 8 The metallographic structure in (b) is also significantly different from that of the seismic steel reinforcement in Examples 1-5.
[0073] Furthermore, as shown in Table 3, the performance test results of Examples 1-5 and the test results of some index requirements indicate that, under the conditions of using higher billet heating and tapping temperatures, final rolling temperatures, and lower upper cooling bed temperatures, the yield strength, tensile strength, strength-to-yield ratio, and elongation of the 400MPa grade hot-rolled ribbed steel bars prepared under these conditions are all lower than those of the railway-specific 400MPa grade seismic steel bars in the embodiments of this application.
[0074] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.
Claims
1. A method for preparing 400MPa grade seismic-resistant steel bars for railway use, characterized in that, include: Provide steel billets that meet the specified chemical composition by mass percentage: C: 0.21wt.%~0.25wt.%, Si: 0.35wt.%~0.55wt.%, Mn: 0.80wt.%~1.00wt.%, S: ≤0.040%, P: ≤0.040%, V: 0.025wt.%~0.040wt.%, with the remainder being Fe and unavoidable impurities during smelting; The steel billet is heated to 950℃~1010℃ to obtain a heated steel billet; The heated steel billet is hot-rolled using a 19-stand alternating horizontal and vertical rolling mill to obtain the final rolled steel bar; the final rolling temperature is 960℃~1020℃. The surface of the final rolled steel bars is cooled using a weak water quenching process to ensure a smooth surface. The temperature of the cooled steel bars on the cooling bed is controlled at 880℃~930℃ to refine and precipitate the V microalloying compounds in the metallographic structure of the steel bars. The steel bars are sheared and air-cooled to obtain railway-specific 400MPa grade seismic-resistant steel bars.
2. The method for preparing railway-specific 400MPa grade seismic-resistant steel bars according to claim 1, characterized in that, The step of providing a steel billet with a chemical composition that meets the specified mass percentage includes: Steel billets are formed by smelting and continuous casting, based on a percentage of their mass. Optionally, the dimensions of the steel billet are width × thickness × length = 165 × 165 × 12000 mm, and the drawing speed is 3.0 m / min to 3.6 m / min.
3. The method for preparing railway-specific 400MPa grade seismic-resistant steel bars according to claim 1, characterized in that, The heating time for heating the steel billet to 950℃~1010℃ is 50min~90min.
4. The method for preparing railway-specific 400MPa grade seismic-resistant steel bars according to claim 1, characterized in that, The step of hot continuous rolling the heated steel billet using a 19-stand alternating horizontal and vertical rolling mill includes: A six-stand roughing mill is used to rough-roll the heated steel billet to obtain a rough-rolled steel billet; The rough-rolled steel billet is subjected to intermediate rolling treatment using a 6-stand intermediate rolling mill to obtain an intermediate-rolled steel billet; The steel billet was finished by 7 stands of a finishing mill, and the final rolling speed of the steel bars was 10.0 m / s to 12.5 m / s to obtain the final rolled steel bars.
5. The method for preparing railway-specific 400MPa grade seismic-resistant steel bars according to claim 1, characterized in that, In the step of cooling the surface of the final rolled steel bar using a weak water-cooling process, the weak water-cooling process refers to the cooling process where the temperature of the final rolled steel bar is higher than the austenite initiation transformation temperature Ar3, which is 810℃~830℃, the cooling water pressure is 0.8MPa~1.0MPa, and the cooling water flow rate is 60 m³ / s. 3 / h~100m 3 / h.
6. The method for preparing railway-specific 400MPa grade seismic-resistant steel bars according to claim 1, characterized in that, The method for preparing the railway-specific 400MPa grade seismic-resistant steel reinforcement also includes: Several 500mm long steel bars were randomly cut from the cooling bed and weighed to determine and obtain steel bars with a negative weight deviation of less than 3.0%.
7. A railway-specific 400MPa grade seismic-resistant steel bar, characterized in that, The steel bar is prepared according to any one of claims 1-6. It is a 400MPa grade seismic-resistant steel bar for railway use.
8. The railway-specific 400MPa grade seismic-resistant steel bar according to claim 7, characterized in that, The nominal diameter of the railway-specific 400MPa grade seismic-resistant steel bars is 12mm to 32mm, the yield strength is 400MPa to 480MPa, the tensile strength is 605MPa to 650MPa, the strength-to-yield ratio is 1.37 to 1.45, the elongation is 17% to 25%, and the maximum total elongation A is... gt The percentages ranged from 12.3% to 14.8%.
9. The railway-specific 400MPa grade seismic-resistant steel bar according to claim 7, characterized in that, The yield strength of the railway-specific 400MPa grade seismic steel bar is 435MPa to 475MPa.
10. The railway-specific 400MPa grade seismic-resistant steel bar according to claim 7, characterized in that, The metallographic structure of the railway-specific 400MPa grade seismic steel bar is ferrite and pearlite, with a grain size ≥10.5 and a carbon equivalent of 0.36wt.%~0.42wt.%.