High-strength fatigue-resistant elastic-plastic damping steel, and manufacturing method and application thereof

Abstract

The application relates to a high-strength anti-fatigue elastic-plastic damping steel and a manufacturing method and application thereof, and the mass percentage of the chemical components is as follows: 30% < Mn <= 40%, 6.0% <= Al <= 11.0%, 0.6% <= C <= 1.2%, 0.6% < Si <= 3.0%, 1.0% < Cr <= 3.0%, Ti <= 1.0%, Nb <= 1.0%, V <= 1.0%, P <= 0.15%, S <= 0.03%, N <= 0.03%, and the rest is Fe and inevitable impurity elements. The elastic-plastic damping steel is manufactured through a melting and casting, hot rolling, annealing after hot rolling production process flow or a melting and casting, hot rolling, solid solution and aging heat treatment production process flow, the yield strength of the elastic-plastic damping steel is greater than 420 MPa; under the condition of cyclic tensile-compression loading, when the strain amplitude, strain ratio and loading frequency are 1%, -1.0 and 0.1-0.2 Hz respectively, the room-temperature fatigue life of the steel plate is greater than 2000 cycles.

Description

Technical Field

[0001] This invention relates to a steel material, and more particularly to a high-strength fatigue-resistant elastoplastic damping steel, its manufacturing method, and its application. Background Technology

[0002] Large-scale earthquakes can cause enormous damage to high-rise buildings and structures. Using elasto-plastic steel dampers placed within buildings can effectively absorb external seismic energy, minimizing damage to buildings and structures. Elaso-plastic steel dampers absorb seismic energy through the elasto-plastic hysteretic deformation of the damping unit steel under external reciprocating vibrations. Therefore, the damping unit steel used in dampers (hereinafter referred to as "elasto-plastic damping steel") needs to possess relatively stable hysteretic characteristics and good low-cycle fatigue performance.

[0003] Currently, the elastoplastic damping steels used to manufacture steel dampers are typically low-yield-point steels and high-yield-strength carbon structural steels (such as Q235 and Q355B). All of these steels are ferritic steels; under alternating loads, fatigue damage usually initiates and propagates early from stress and strain concentration points, lodged slip bands, and dislocation cellular structures within the ferritic steel material, ultimately leading to fatigue failure. Consequently, the fatigue life of these materials is often low. Furthermore, as the strength of ferritic steel increases, the fatigue life under repeated plastic deformation typically decreases accordingly. Therefore, steel dampers made from these ferritic steel materials often fail to meet fatigue resistance requirements under certain operating conditions.

[0004] Low-layer-fault-energy Fe-Mn-Si austenitic alloy steels possess excellent fatigue resistance and can be used to manufacture damping units for steel dampers, thereby extending the service life of the dampers. However, the yield strength of these low-layer-fault-energy Fe-Mn-Si austenitic alloy steels is relatively low (typically significantly lower than 350–400 MPa); when the damping unit needs to provide a large damping force, the design cross-sectional area of ​​the damping unit must also increase, leading to an increase in the installation space required for the damper. For some building structures with limited installation space (such as bridge structures), steel dampers are often unsuitable for design or their spatial layout is inflexible.

[0005] In summary, given the unfavorable properties of existing elastoplastic damping steels (low fatigue resistance of ferritic steels and low yield strength of low stacking fault energy Fe-Mn-Si austenitic alloy steels), there is an urgent need to develop elastoplastic damping steels with higher yield strength and better fatigue resistance. This would enable the manufacture of damping units and steel dampers that can provide greater damping force, have good fatigue performance, and have small structural dimensions. This would allow for the miniaturization and weight reduction of steel dampers, enhancing their installation and operational flexibility while still providing energy dissipation and vibration reduction. Summary of the Invention

[0006] The present invention provides a high-strength fatigue-resistant elastoplastic damping steel in a first aspect, a manufacturing method of the above-mentioned high-strength fatigue-resistant elastoplastic damping steel in a second aspect, and an application of the above-mentioned high-strength fatigue-resistant elastoplastic damping steel in a third aspect.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] The first aspect of this invention provides a high-strength fatigue-resistant elastoplastic damping steel.

[0009] A high-strength fatigue-resistant elastoplastic damping steel has the following chemical composition by mass percentage: 30% < Mn ≤ 40%, 6.0% ≤ Al ≤ 11.0%, 0.6% ≤ C ≤ 1.2%, 0.6% < Si ≤ 3.0%, 1.0% < Cr ≤ 3.0%, Ti ≤ 1.0%, Nb ≤ 1.0%, V ≤ 1.0%, P ≤ 0.15%, S ≤ 0.03%, N ≤ 0.03%, with the remainder being Fe and unavoidable impurity elements.

[0010] The microstructure of the high-strength fatigue-resistant elastoplastic damping steel includes austenite, ferrite with a volume fraction not exceeding 10%, and carbides with a volume fraction not exceeding 10%.

[0011] The average grain size of the austenitic structure is no greater than 250 μm.

[0012] The high-strength fatigue-resistant elastoplastic damping steel has a yield strength >420MPa; under cyclic tensile-compression loading conditions, when the strain amplitude, strain ratio and loading frequency are 1%, -1.0 and 0.1~0.2Hz respectively, the room temperature fatigue life of the elastoplastic damping steel is >2000 cycles.

[0013] In one embodiment of the present invention, preferably, the chemical composition of the high-strength fatigue-resistant elastoplastic damping steel is as follows (mass percentage): 30% < Mn ≤ 38.8%, 6.0% ≤ Al ≤ 10.0%, 0.6% ≤ C ≤ 0.88%, 0.62% ≤ Si ≤ 1.50%, 1.1% ≤ Cr ≤ 2.3%, Ti ≤ 0.2%, Nb ≤ 0.5%, V ≤ 0.5%, P ≤ 0.15%, S ≤ 0.03%, N ≤ 0.03%, with the remainder being Fe and unavoidable impurity elements.

[0014] In one embodiment of the present invention, more preferably, the chemical composition of the high-strength fatigue-resistant elastoplastic damping steel is as follows (mass percentage): 30% < Mn ≤ 37.3%, 7.8% ≤ Al ≤ 10.0%, 0.76% ≤ C ≤ 0.88%, 0.62% ≤ Si ≤ 1.50%, 1.1% ≤ Cr ≤ 2.3%, P ≤ 0.15%, S ≤ 0.03%, N ≤ 0.03%, with the remainder being Fe and unavoidable impurity elements.

[0015] In the composition design of this invention, the functions of each component are as follows.

[0016] Mn: Mn is the main alloying element in this invention. Mn can increase austenite stability, promote austenite formation, and increase austenite stacking fault energy. Increasing the Mn content is beneficial to promoting the activation of the dislocation plane slip mechanism in the austenitic matrix of alloy steel, thereby improving the fatigue resistance of alloy steel. When the Mn content is less than 30.0%, too much ferrite phase may appear in the alloy steel, which will affect the low-cycle fatigue life of the alloy steel; when the Mn content is greater than 40.0%, β-Mn brittle phase is prone to appear in the alloy steel matrix, which also reduces the plasticity, toughness and fatigue resistance of the alloy steel. Therefore, this invention controls the Mn content to be 30.0% to 40.0%.

[0017] Al: Al is the main alloying element in this invention. On the one hand, Al can significantly increase the stacking fault energy of austenite in steel, promote the activation of the dislocation plane slip mechanism in the austenitic matrix of alloy steel, and improve the fatigue resistance of alloy steel; Al can play a solid solution strengthening role, improving the yield strength of alloy steel. On the other hand, Al is a strong ferrite forming element. Adding excessive Al will form excessive ferrite in the matrix of alloy steel, thereby affecting the low-cycle fatigue life of alloy steel. Furthermore, Al is the main forming element of κ carbides in the austenitic matrix. Increasing the Al content promotes the formation of κ carbides in the austenitic matrix (thereby increasing the yield strength of alloy steel), but the presence of excessive Al and κ carbides will reduce the fatigue resistance of alloy steel (mainly manifested as: reduced low-cycle fatigue life of alloy steel, and a significant decrease in peak cyclic stress during fatigue deformation with increasing cyclic deformation cycles). Therefore, the Al content is controlled at 6.0% to 11.0% in this invention.

[0018] C: C is the main alloying element in this invention. On the one hand, C is an important solid solution strengthening element, which can significantly improve the strength of alloy steel; C is also an austenite stabilizing element, promoting austenite formation. On the other hand, C is the main forming element of κ carbides in the austenite matrix. Increasing the C content promotes the formation of κ carbides in the austenite matrix and increases the strength of alloy steel, but the presence of excessive C and κ carbides will significantly reduce the fatigue resistance of alloy steel. Therefore, the C content is controlled at 0.6% to 1.2% in this invention.

[0019] Si: Si is an important alloying element in this invention. On the one hand, the addition of Si can significantly improve the yield strength and work hardening rate of alloy steel, increase the fluidity of molten steel during alloy steel smelting, thereby increasing the manufacturability of Al-rich alloy steel, promote the activation of dislocation plane slip mechanism in the austenitic matrix of alloy steel, thus improving the fatigue resistance of alloy steel, and inhibit the formation of β-Mn brittle phase in alloy steel, thereby improving the ductility and toughness of alloy steel. When the Si content is less than 0.6%, the above-mentioned beneficial effects are not very obvious. In addition, when alloy steel contains Si, ferromanganese alloys can be used to smelt and prepare alloy steel (using less or no more expensive electrolytic manganese as a raw material for steelmaking), which helps to significantly reduce the manufacturing cost of alloy steel. On the other hand, Si is a ferrite-forming element that promotes the formation and coarsening of κ carbides in the austenitic matrix of alloy steel. Excessive Si addition leads to excessive formation and coarsening of κ carbides, resulting in the formation of excessive ferrite, B2, and DO3 phases in the alloy steel matrix. All of these factors significantly weaken the fatigue resistance of the alloy steel. When the Si content exceeds 3.0%, these adverse effects are more pronounced. Therefore, this invention limits the Si content to 0.6% < Si ≤ 3.0%.

[0020] Cr: Cr is an important alloying element in this invention. Adding Cr helps increase the work hardening degree of alloy steel, thereby increasing the deformation flow stress and inhibiting the formation and coarsening of κ carbides in the austenitic matrix, thus contributing to improved fatigue resistance. However, Cr is a ferrite-forming element; adding excessive Cr will form an excessive ferrite phase in the alloy steel matrix, thereby weakening its fatigue resistance. Therefore, this invention limits the Cr content to 1.0% < Cr ≤ 3.0%.

[0021] Ti, Nb, and V: Ti, Nb, and V are strong carbide-forming elements. Adding these elements generates fine, dispersed carbides in the matrix of alloy steel, thereby improving the yield strength of the alloy steel. However, excessive Ti, Nb, and V, and the resulting carbides, can weaken the plasticity and fatigue resistance of the alloy steel. This invention limits Ti ≤ 1.0%, Nb ≤ 1.0%, and V ≤ 1.0%.

[0022] P: P increases the hot brittleness of alloy steel (especially in high-Mn alloy steel), and this invention limits the P content in the steel to ≤0.15%.

[0023] Sulfur (S): Sulfur causes hot brittleness in steel, especially in high-Mn alloy steels, where it significantly increases hot brittleness and reduces ductility and toughness. Therefore, the sulfur content is limited to ≤0.03%.

[0024] Nitrogen (N) readily combines with Al to form AlN; when the N content is too high, the resulting coarse AlN particles affect the ductility of the steel plate. Therefore, the N content is limited to ≤0.03%.

[0025] In one embodiment of the present invention, without altering the original microstructure of the elasto-plastic damping steel matrix, its composition may further include small amounts of Cu and Ni elements. Considering alloy cost, the mass percentage of these two elements does not exceed 3.0%. That is, the mass percentage of its chemical composition is: 30% < Mn ≤ 40%, 6.0% ≤ Al ≤ 11.0%, 0.6% ≤ C ≤ 1.2%, 0.6% < Si ≤ 3.0%, 1.0% < Cr ≤ 3.0%, Ti ≤ 1.0%, Nb ≤ 1.0%, V ≤ 1.0%, P ≤ 0.15%, S ≤ 0.03%, N ≤ 0.03%, Cu ≤ 3.0%, Ni ≤ 3.0%, with the remainder being Fe and unavoidable impurity elements.

[0026] In this invention, for austenitic alloy steel with the above-mentioned alloy composition, tensile-compression cyclic deformation promotes the activation of the dislocation plane slip mechanism in the alloy steel, thereby significantly improving the fatigue resistance of the alloy steel. The microstructure of the alloy steel is limited to include ferrite with a volume fraction not exceeding 10% and carbides with a volume fraction not exceeding 10%. When the content of ferrite phase and carbides (including κ carbides and Ti, Nb, and V carbides) in the alloy steel matrix is ​​excessive, the fatigue life of the alloy steel will be significantly reduced. In particular, when the austenitic matrix contains excessive κ carbides, the peak cyclic stress during fatigue deformation decreases significantly with increasing cyclic deformation cycles, and the fatigue resistance of the alloy steel decreases.

[0027] In this invention, the average grain size of austenite is limited to no more than 250 μm. When the austenite grain size is too large, fatigue cracks will form and propagate prematurely from the austenite grain boundaries during cyclic deformation, thereby significantly weakening the fatigue resistance of the alloy steel.

[0028] In this invention, the alloy steel having the alloy composition and microstructure characteristics described above has the following mechanical properties: the yield strength of the alloy steel is >420MPa; under cyclic tensile-compression loading conditions, when the strain amplitude, strain ratio and loading frequency are 1%, -1.0 and 0.1~0.2Hz respectively, the room temperature fatigue life of the alloy steel is >2000 cycles.

[0029] In addition, the alloy steel with the alloy composition in this invention has a density that is more than 7% lower than that of existing carbon structural steel (thereby achieving lightweighting of the damping unit in terms of material specific gravity), and its corrosion resistance is significantly improved compared to that of existing carbon structural steel.

[0030] A second aspect of the present invention provides two methods for manufacturing high-strength fatigue-resistant elastoplastic damping steels.

[0031] The manufacturing method of the first type of high-strength fatigue-resistant elastoplastic damping steel includes the following steps:

[0032] 1) Smelt and cast the billet according to the following component ratio to obtain the billet.

[0033] The mass percentages of the chemical composition are as follows: 30% < Mn ≤ 40%, 6.0% ≤ Al ≤ 11.0%, 0.6% ≤ C ≤ 1.2%, 0.6% < Si ≤ 3.0%, 1.0% < Cr ≤ 3.0%, Ti ≤ 1.0%, Nb ≤ 1.0%, V ≤ 1.0%, P ≤ 0.15%, S ≤ 0.03%, N ≤ 0.03%, with the remainder being Fe and unavoidable impurity elements;

[0034] 2) Hot rolling

[0035] The billet is heated at 1000-1250℃ and held for 1-6 hours. The billet is then hot-rolled into a hot-rolled plate with a hot-rolling deformation of ≥40% and a final rolling temperature of ≥800℃.

[0036] 3) Annealing after hot rolling

[0037] The hot-rolled plate is heated to a uniform heating temperature of 800-1100℃ for 0.5-5 hours; after annealing, the steel plate is cooled to room temperature at a rate of not less than 5℃ / min.

[0038] In one embodiment of the present invention, preferably, during the annealing after hot rolling, the homogenization temperature is 900-1000°C and the homogenization time is 1.0-1.5h.

[0039] The second method for manufacturing the high-strength fatigue-resistant elastoplastic damping steel includes the following steps:

[0040] 1) Smelt and cast the billet according to the following component ratio to obtain the billet.

[0041] The mass percentages of the chemical composition are as follows: 30% < Mn ≤ 40%, 6.0% ≤ Al ≤ 11.0%, 0.6% ≤ C ≤ 1.2%, 0.6% < Si ≤ 3.0%, 1.0% < Cr ≤ 3.0%, Ti ≤ 1.0%, Nb ≤ 1.0%, V ≤ 1.0%, P ≤ 0.15%, S ≤ 0.03%, N ≤ 0.03%, with the remainder being Fe and unavoidable impurity elements;

[0042] 2) Hot rolling

[0043] The billet is heated at 1000-1250℃ and held for 1-6 hours. The billet is then hot-rolled into a hot-rolled plate with a hot-rolling deformation of ≥40% and a final rolling temperature of ≥800℃.

[0044] 3) Solution treatment and aging heat treatment

[0045] During the solution treatment process, the hot-rolled plate is heated to a homogenization temperature of 1000-1180℃ for 0.5-3 hours; after homogenization, the steel plate is cooled to room temperature at a rate of not less than 100℃ / min.

[0046] During the aging process, the solution-treated steel plate is heated to a homogenization temperature of 500-750℃ for 0.5-5 hours. After homogenization, the steel plate is cooled to room temperature at a rate of not less than 10℃ / min.

[0047] The rationale for the manufacturing process design of this invention is as follows:

[0048] (1) Hot rolling process

[0049] The heating temperature is 1000–1250℃. When the heating temperature exceeds 1250℃, the cast slab will be overheated, resulting in coarse grain structure and reduced hot workability. When the heating temperature is below 1000℃, after high-pressure water descaling and initial rolling, the finishing rolling temperature is too low, resulting in excessive deformation resistance of the slab, making it difficult to manufacture hot-rolled steel plates with no surface defects and the specified thickness.

[0050] The holding time during hot rolling in this invention is 1 to 6 hours. Holding time exceeding 6 hours will result in coarse grain structure inside the slab; holding time less than 1 hour will still result in high inhomogeneity of the casting structure inside the slab and severe segregation.

[0051] This invention requires controlling the hot rolling deformation to be no less than 40% in order to eliminate the inhomogeneity and defects in the internal structure of the billet; it also requires controlling the final rolling temperature to be above 800℃ to complete the hot rolling of the billet. If the final rolling temperature is too low, the deformation resistance of the slab will be too high, making it difficult to manufacture hot-rolled steel plates of the required thickness and without surface and edge defects.

[0052] (2) Hot rolling followed by annealing process

[0053] The hot-rolled steel sheet undergoes annealing heat treatment. In this invention, the homogenization temperature is 800–1100℃, and the homogenization time is 0.5–5 hours. After annealing, the steel sheet is cooled to room temperature at a rate not less than 5℃ / min. The purpose of this process is to eliminate hot-rolled deformed structures and control carbides in the alloy steel matrix. The annealing process conditions of this invention are closely related to the alloy composition of the steel. When the homogenization temperature is below 800℃, the hot-rolled deformed structures cannot be sufficiently eliminated; when the homogenization temperature is above 1100℃, the austenite grains in the alloy matrix become excessively coarse. Both of these situations will impair the low-cycle fatigue life of the alloy steel at room temperature. Therefore, this invention controls the homogenization temperature of the annealing after hot rolling to be 800–1100℃. In the annealing process, the homogenization time can be adjusted by appropriately changing the homogenization temperature. Excessive holding time affects production efficiency; therefore, this invention controls the homogenization time to not exceed 5 hours. In one embodiment of the present invention, preferably, during annealing after hot rolling, the soaking temperature is 900–1000°C, and the soaking time is 1.0–1.5 h. After annealing, the steel plate needs to be cooled to room temperature at a cooling rate of not less than 5°C / min. When the cooling rate is less than 5°C / min, excessive and excessively coarse κ carbides may form in the alloy steel matrix, thereby affecting the fatigue resistance of the alloy steel.

[0054] (3) Solution treatment and aging process after hot rolling

[0055] Hot-rolled steel sheets are subjected to solution-aging heat treatment. The solution-aging process conditions of this invention are closely related to the alloy composition of the steel. The solution-aging process is used to control the carbide content and size in the austenitic matrix to achieve a balance between high strength and good fatigue performance. During the solution treatment, the hot-rolled sheet is heated to a homogenization temperature of 1000–1180°C for 0.5–3 hours. After homogenization, the steel sheet is cooled to room temperature at a rate not less than 100°C / min. When the solution temperature is below 1000°C, the carbides in the hot-rolled sheet cannot be completely dissolved, and a supersaturated solid solution cannot be effectively formed in the austenitic matrix. When the solution temperature is above 1180°C, the austenitic grains in the hot-rolled sheet are too coarse. After homogenization, when the cooling rate of the steel sheet is below 100°C / min, the supersaturation of the austenitic matrix will be significantly reduced, which is not conducive to the control of carbide content and size during subsequent aging.

[0056] During the aging process, the solution-treated steel plate is heated to a homogenization temperature of 500–750℃ for 0.5–5 hours. After homogenization, the steel plate is cooled to room temperature at a rate not less than 10℃ / min. When the homogenization temperature is below 500℃, carbides cannot effectively precipitate from the austenitic matrix; when the homogenization temperature is above 750℃, the content and size of the precipitated carbides in the austenitic matrix are excessive. After homogenization, if the cooling rate of the aged steel plate is less than 10℃ / min, the formed carbides will further coarsen. The aforementioned austenitic matrix carbides mainly refer to κ carbides; when the alloy composition contains Ti, Nb, or V, the matrix carbides also include carbides of Ti, Nb, or V. Excessive κ carbides will significantly reduce the low-cycle fatigue performance of the alloy steel.

[0057] This invention employs the aforementioned composition design, rolling process, annealing process, or solution aging process to manufacture steel plates whose matrix microstructure includes austenite, ferrite with a volume fraction not exceeding 10%, and carbides with a volume fraction not exceeding 10%, with the austenite grain size not exceeding 250 μm. During tensile-compression cyclic loading or shear cyclic loading, the alloy composition design promotes the activation of dislocation plane slip mechanism to reduce the generation of crystal defects and delay the propagation of fatigue cracks, resulting in good room temperature low-cycle fatigue life. In this invention, the alloy steel with the aforementioned alloy composition and microstructure characteristics has the following mechanical properties: yield strength > 420 MPa; under cyclic tensile-compression loading, when the strain amplitude, strain ratio, and loading frequency are 1%, -1.0, and 0.1–0.2 Hz, respectively, the room temperature fatigue life of the alloy steel is > 2000 cycles.

[0058] A third aspect of the invention provides the application of high-strength fatigue-resistant elastoplastic damping steel.

[0059] The high-strength fatigue-resistant elastoplastic damping steel described in this invention is used to manufacture damping units or steel dampers for seismic isolation and reduction in buildings and bridges, so as to improve the seismic protection performance of buildings.

[0060] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0061] 1. Compared with traditional ferritic steels (such as low yield point steels and carbon structural steels such as Q235 and Q355B), the steel grade of this invention exhibits significantly improved low-cycle fatigue life at room temperature; compared with low stacking fault energy Fe-Mn-Si austenitic alloy steels, the steel grade of this invention exhibits significantly improved strength. Therefore, the steel grade of this invention has a good match between strength and fatigue resistance, which helps to achieve lightweighting and miniaturization of damping units and steel dampers.

[0062] 2. The steel grade of this invention can be produced using ferromanganese alloy as raw material, which can reduce the cost of alloy steel.

[0063] 3. The elasto-plastic damping steel of the present invention not only has good mechanical properties, but also has the characteristics of low density and good corrosion resistance.

[0064] 4. The manufacturing process involved in this invention can be completed on existing steel plate production lines without major adjustments. Therefore, this invention has excellent prospects for widespread application. Detailed Implementation

[0065] A high-strength fatigue-resistant elastoplastic damping steel has the following chemical composition by mass percentage: 30% < Mn ≤ 40%, 6.0% ≤ Al ≤ 11.0%, 0.6% ≤ C ≤ 1.2%, 0.6% < Si ≤ 3.0%, 1.0% < Cr ≤ 3.0%, Ti ≤ 1.0%, Nb ≤ 1.0%, V ≤ 1.0%, P ≤ 0.15%, S ≤ 0.03%, N ≤ 0.03%, with the remainder being Fe and unavoidable impurity elements.

[0066] The manufacturing method of the first type of high-strength fatigue-resistant elastoplastic damping steel includes the following steps:

[0067] 1) Smelt and cast the billet according to the following component ratio to obtain the billet.

[0068] The mass percentages of the chemical composition are as follows: 30% < Mn ≤ 40%, 6.0% ≤ Al ≤ 11.0%, 0.6% ≤ C ≤ 1.2%, 0.6% < Si ≤ 3.0%, 1.0% < Cr ≤ 3.0%, Ti ≤ 1.0%, Nb ≤ 1.0%, V ≤ 1.0%, P ≤ 0.15%, S ≤ 0.03%, N ≤ 0.03%, with the remainder being Fe and unavoidable impurity elements;

[0069] 2) Hot rolling

[0070] The billet is heated at 1000-1250℃ and held for 1-6 hours. The billet is then hot-rolled into a hot-rolled plate with a hot-rolling deformation of ≥40% and a final rolling temperature of ≥800℃.

[0071] 3) Annealing after hot rolling

[0072] The hot-rolled plate is heated to a uniform heating temperature of 800-1100℃ for 0.5-5 hours; after annealing, the steel plate is cooled to room temperature at a rate of not less than 5℃ / min.

[0073] The second method for manufacturing the high-strength fatigue-resistant elastoplastic damping steel includes the following steps:

[0074] 1) Smelt and cast the billet according to the following component ratio to obtain the billet;

[0075] The mass percentages of the chemical composition are as follows: 30% < Mn ≤ 40%, 6.0% ≤ Al ≤ 11.0%, 0.6% ≤ C ≤ 1.2%, 0.6% < Si ≤ 3.0%, 1.0% < Cr ≤ 3.0%, Ti ≤ 1.0%, Nb ≤ 1.0%, V ≤ 1.0%, P ≤ 0.15%, S ≤ 0.03%, N ≤ 0.03%, with the remainder being Fe and unavoidable impurity elements;

[0076] 2) Hot rolling

[0077] The billet is heated at 1000-1250℃ and held for 1-6 hours. The billet is then hot-rolled into a hot-rolled plate with a hot-rolling deformation of ≥40% and a final rolling temperature of ≥800℃.

[0078] 3) Solution treatment and aging heat treatment

[0079] During the solution treatment process, the hot-rolled plate is heated to a homogenization temperature of 1000-1180℃ for 0.5-3 hours; after homogenization, the steel plate is cooled to room temperature at a rate of not less than 100℃ / min.

[0080] During the aging process, the solution-treated steel plate is heated to a homogenization temperature of 500-750℃ for 0.5-5 hours. After homogenization, the steel plate is cooled to room temperature at a rate of not less than 10℃ / min.

[0081] The present invention will now be described in detail with reference to specific embodiments.

[0082] Table 1 shows the alloy composition of the steel grades in the embodiments and comparative examples of the present invention. The contents of S, N and P are as follows: S is between 0.008% and 0.02%, N is between 0.006% and 0.02%, and P is between 0.009% and 0.15%. The Fe element content is the balance. Table 2 shows the manufacturing process of the steel grades in the embodiments and comparative examples of the present invention. Table 3 shows the microstructure and mechanical properties of the steel plates in the embodiments and comparative examples of the present invention.

[0083] The content ratios of each component in Examples 1-15 and Comparative Examples 1-5 are designed according to Table 1.

[0084] Table 1 (Unit: wt%)

[0085]

[0086]

[0087] Steel grades with the composition shown in Table 1 are slabs produced by smelting and casting. The slabs are heated at 1200°C and held for 2 hours before hot rolling. The hot rolling finish is completed at a final rolling temperature of 860°C, with a cumulative deformation of over 40%.

[0088] After hot-rolled steel sheets are treated by hot rolling followed by annealing or solution aging (see Table 2 for specific process conditions), they are cooled to room temperature to obtain the target damping steel sheet.

[0089] Table 2

[0090]

[0091]

[0092] The microstructure and mechanical properties of the steel plates in Examples 1-15 and Comparative Examples 1-5 of this invention are shown in Table 3. In Table 3, if the steel matrix of all examples contains ferrite and carbides, the volume fraction of ferrite does not exceed 10% and the volume fraction of carbides does not exceed 10%. The test conditions for low-cycle fatigue life at room temperature are: strain amplitude, strain ratio, and loading frequency of 1%, -1.0, and 0.1 to 0.2 Hz, respectively.

[0093] Table 3

[0094]

[0095]

[0096] As shown in Table 3, the present invention can obtain a high-strength fatigue-resistant elastoplastic damping steel plate through reasonable composition and process design. The yield strength of the elastoplastic damping steel plate is >420MPa. Under cyclic tensile-compression loading, when the strain amplitude, strain ratio and loading frequency are 1%, -1.0 and 0.1~0.2Hz respectively, the room temperature fatigue life of the alloy steel is >2000 cycles.

[0097] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A high-strength, fatigue-resistant, elastoplastic damping steel for manufacturing damping units or steel dampers for seismic isolation and vibration reduction in buildings and bridges, characterized in that, Its chemical composition by mass percentage is as follows: 36.1%≤Mn≤38.8%, 6.6%≤Al≤10.5%, 0.60%≤C≤0.91%, 0.80%≤Si≤2.50%, 1.1%≤Cr≤1.6%, 0.008%≤S≤0.02%, 0.006%≤N≤0.02%, 0.009%≤P≤0.15%, with Fe content as the balance. The microstructure of the elastoplastic damping steel includes austenite, ferrite with a volume fraction not exceeding 10%, and carbides with a volume fraction not exceeding 10%; the average grain size of the austenite is not greater than 250 μm. The yield strength of the elastoplastic damping steel is >420MPa; under cyclic tensile-compression loading conditions, when the strain amplitude, strain ratio and loading frequency are 1%, -1.0 and 0.1~0.2Hz respectively, the room temperature fatigue life of the elastoplastic damping steel is >2000 cycles. The damping unit or steel damper absorbs vibration energy by undergoing elastoplastic hysteresis deformation of the elastoplastic damping steel under external reciprocating vibration.

2. The method for manufacturing the high-strength fatigue-resistant elastoplastic damping steel according to claim 1, characterized in that, Includes the following steps: 1) Smelt and cast the billet according to the following component ratio to obtain the billet. The chemical composition by mass percentage is as follows: 36.1%≤Mn≤38.8%, 6.6%≤Al≤10.5%, 0.60%≤C≤0.91%, 0.80%≤Si≤2.50%, 1.1%≤Cr≤1.6%, 0.008%≤S≤0.02%, 0.006%≤N≤0.02%, 0.009%≤P≤0.15%, with Fe content as the balance. 2) Hot-rolled The billet is heated at 1000~1250℃ and held for 1~6 hours. The billet is then hot-rolled into a hot-rolled plate with a hot-rolling deformation of ≥40% and a final rolling temperature of ≥800℃. 3) Hot rolling followed by annealing The hot-rolled plate is heated to a uniform temperature of 800~1100℃ for 0.5~5 h; after annealing, the steel plate is cooled to room temperature at a rate of not less than 5℃ / min.

3. The method for manufacturing high-strength fatigue-resistant elastoplastic damping steel according to claim 2, characterized in that, During annealing after hot rolling, the soaking temperature is 900~1000℃ and the soaking time is 1.0~1.5h.

4. The method for manufacturing the high-strength fatigue-resistant elastoplastic damping steel according to claim 1, characterized in that, Includes the following steps: 1) Smelt and cast the billet according to the following component ratio to obtain the billet. The chemical composition by mass percentage is as follows: 36.1%≤Mn≤38.8%, 6.6%≤Al≤10.5%, 0.60%≤C≤0.91%, 0.80%≤Si≤2.50%, 1.1%≤Cr≤1.6%, 0.008%≤S≤0.02%, 0.006%≤N≤0.02%, 0.009%≤P≤0.15%, with Fe content as the balance. 2) Hot-rolled The billet is heated at 1000~1250℃ and held for 1~6 hours. The billet is then hot-rolled into a hot-rolled plate with a hot-rolling deformation of ≥40% and a final rolling temperature of ≥800℃. 3) Solution treatment and aging heat treatment During the solution treatment process, the hot-rolled plate is heated to a homogenization temperature of 1000~1180℃ for 0.5~3 hours; after homogenization, the steel plate is cooled to room temperature at a rate of not less than 100℃ / min. During the aging process, the solution-treated steel plate is heated to a homogenization temperature of 500~750℃ for 0.5~5 h; after homogenization, the steel plate is cooled to room temperature at a rate of not less than 10℃ / min.

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