Damping steel for building earthquake resistance and preparation method thereof

Abstract

This application relates to the field of steel technology, and more particularly to a damping steel for seismic resistance in buildings and its preparation method. The chemical composition of the damping steel includes: C, Si, Mn, Ti, and Fe; wherein the content of C is 0.06 wt% to 0.08 wt%, the content of Si is 0.15 wt% to 0.30 wt%, the content of Mn is 4.0 wt% to 4.9 wt%, and the content of Ti is 0.008 wt% to 0.025 wt%. This application solves the technical problem that existing damping steels for seismic resistance in buildings cannot simultaneously achieve both a low yield strength ratio and high plasticity.

Description

Technical Field

[0001] This application relates to the field of steel technology, and in particular to a damping steel for earthquake resistance in buildings and its preparation method. Background Technology

[0002] Building dampers are devices that protect the main load-bearing structure and effectively reduce the destructive effects of vibration on buildings. These seismic-resistant devices bear seismic loads before the main structural components, yielding first and absorbing seismic energy through repeated loading hysteresis, thus protecting the safety of the main building structure. They are simple in construction, easy to replace after an earthquake, and highly reliable.

[0003] Currently, low-yield-point steel is the main steel used in building damping structures. Domestically and internationally, mature strength grades of 100MPa, 160MPa, and 225MPa have been developed, with the highest grade of 295MPa also beginning to be used. To ensure early yielding for energy absorption and seismic resistance, its strength is generally lower than the design and application strength of the main building structural materials. This type of steel is characterized by a low yield point, high elongation, and low yield-to-strength ratio.

[0004] To meet the increasingly higher design loads internationally, it is necessary to further improve the strength and impact toughness of the steel products used, while ensuring a low yield strength ratio and excellent plasticity. Currently, however, damping steel used for seismic resistance in buildings has a low yield strength and poor plasticity. Summary of the Invention

[0005] This application provides a damping steel for seismic resistance of buildings and its preparation method, in order to solve the technical problem that existing damping steels for seismic resistance of buildings cannot simultaneously achieve both low yield strength ratio and high plasticity.

[0006] In a first aspect, this application provides a damping steel for earthquake resistance in buildings, wherein the chemical composition of the damping steel includes:

[0007] C, Si, Mn, Ti, and Fe; among which,

[0008] The C content is 0.06 wt% to 0.08 wt%, the Si content is 0.15 wt% to 0.30 wt%, the Mn content is 4.0 wt% to 4.9 wt%, and the Ti content is 0.008 wt% to 0.025 wt%.

[0009] Optionally, the metallographic structure of the damping steel includes:

[0010] The mixture comprises tempered martensite, reverse-transformed austenite, and ferrite; wherein the volume fraction of the reverse-transformed austenite is 40% to 54%.

[0011] Optionally, the yield strength ratio of the damping steel is 0.60 to 0.80, and the elongation after fracture A of the damping steel is... 50 >50%.

[0012] Optionally, the damping steel has a yield strength of 400MPa to 440MPa, and the damping steel has a low-temperature impact resistance of -60℃.

[0013] Work > 60J.

[0014] Optionally, the thickness of the damping steel is 20mm-60mm.

[0015] Secondly, this application provides a method for preparing damping steel for seismic resistance in buildings, used to prepare the damping steel described in any embodiment of the first aspect, the method comprising:

[0016] The slab is heated under a set temperature condition;

[0017] Under the condition of setting the final rolling temperature, the heated slab is rolled and then straightened to obtain a hot-rolled plate;

[0018] The hot-rolled plate is cooled, and the cooling process parameters are controlled.

[0019] The cooled hot-rolled plate is subjected to heat treatment, and the process parameters of the heat treatment are controlled to obtain damping steel for earthquake resistance in buildings.

[0020] Optionally, the process parameters for the heat treatment include: heating.

[0021] Temperature and holding time; wherein the heating temperature is 580℃~620℃, and the holding time is 2.0min / mm~2.5min / mm.

[0022] Optionally, the set temperature is 1100℃~1150℃.

[0023] Optionally, the final rolling temperature is set to 860℃~920℃.

[0024] Optionally, the cooling process parameters include: the starting temperature of cooling, the ending temperature of cooling, and the cooling temperature.

[0025] The cooling rate is 18℃ / s to 30℃ / s. The starting temperature of the cooling is 720℃ to 800℃, the ending temperature of the cooling is ≤250℃, and the cooling rate is 18℃ / s to 30℃ / s.

[0026] The technical solutions provided in this application have the following advantages compared with the prior art:

[0027] The seismic damping steel for buildings provided in this application aims to obtain a microstructure containing a target amount of reverse-transformed austenite after heat treatment by controlling the chemical composition of the damping steel. This steel possesses a reverse-transformed austenite morphology, which enables the steel plate to achieve a phase transformation-induced plasticity mechanism. The reverse-transformed austenite in the microstructure undergoes phase transformation under load, providing the steel plate with a high balance of strength, toughness, and plasticity. This product can be used to manufacture building seismic damping devices and is a replacement for low-yield-point steel suitable for higher-grade building structural steels. It has a lower yield strength ratio than other structural steels used in structural components, a very narrow yield point fluctuation range, and excellent low-temperature impact toughness, providing a new solution for adapting to the large-scale upgrading and replacement of high-performance building steels both domestically and internationally. It solves the technical problem that existing seismic damping steels for buildings cannot simultaneously achieve both a low yield strength ratio and high plasticity, and achieves excellent comprehensive performance as described above. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A schematic flowchart illustrating a method for preparing earthquake-resistant damping steel for buildings, provided in an embodiment of this application;

[0031] Figure 2 A scanning electron microscope image of structural steel for seismic damping in buildings, provided in Embodiment 1 of this application;

[0032] Figure 3 A scanning electron microscope image of structural steel for seismic damping in buildings, provided in Embodiment 2 of this application;

[0033] Figure 4 A scanning electron microscope image of a structural steel for seismic damping in buildings, provided in Embodiment 3 of this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0036] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." 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. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0038] In a first aspect, this application provides a damping steel for earthquake resistance in buildings, wherein the chemical composition of the damping steel includes:

[0039] C, Si, Mn, Ti, and Fe; among which,

[0040] The C content is 0.06 wt% to 0.08 wt%, the Si content is 0.15 wt% to 0.30 wt%, the Mn content is 4.0 wt% to 4.9 wt%, and the Ti content is 0.008 wt% to 0.025 wt%.

[0041] The positive effects of controlling the carbon content to 0.06 wt% to 0.08 wt% include: carbon expands the austenite phase region and has a strong solid solution strengthening effect. Simultaneously, carbon can form precipitates with Nb and Ti to create a second phase, resulting in precipitation strengthening and improving the strength of the steel plate. If the carbon content is too high, it will deteriorate the weldability and low-temperature toughness of the steel plate to some extent; if the carbon content is too low, it will result in lower steel plate strength to some extent. Specifically, the carbon content can be 0.06 wt%, 0.07 wt%, or 0.08 wt%, etc.

[0042] The positive effects of controlling the Si content to 0.15 wt% to 0.30 wt% include: Si does not form carbides with C, but exists in steel in a solid solution state. Through interaction with the stress field of mobile dislocations, it hinders dislocation movement and improves the strength of the steel plate. If the Si content is too high, it will inhibit the formation of second phases such as carbides to a certain extent, and the precipitation strengthening effect will not be effectively exerted; if the Si content is too low, it will weaken the interaction between solid solution atoms and dislocations to a certain extent, resulting in lower strength. Specifically, the Si content can be 0.15 wt%, 0.25 wt%, 0.20 wt%, 0.30 wt%, etc.

[0043] The positive effects of controlling the Mn content to 4.0 wt%–4.9 wt% include: Mn is an element that expands austenite and effectively stabilizes supercooled austenite, allowing the steel plate to obtain a high content of reverse-transformed austenite at room temperature. If the Mn content is too high, it can cause severe Mn segregation in the core of the steel plate, reducing the uniformity of its properties; if the Mn content is too low, it can lead to insufficient reverse-transformed austenite content, resulting in poor plasticity and toughness. Specifically, the Mn content can be 4.0 wt%, 4.2 wt%, 4.4 wt%, 4.6 wt%, 4.9 wt%, etc.

[0044] The positive effects of controlling the Ti content to 0.008 wt% to 0.025 wt% include: Ti microalloying elements can combine with C to form TiC, which refines the grain size of the steel plate and further ensures its low-temperature toughness. If the Ti content is too high, it will cause the TiC precipitate to be too large, failing to effectively refine the grains; if the Ti content is too low, the precipitation strengthening effect of the steel plate will be weak, resulting in insufficient strength. Specifically, the Mn content can be 0.008 wt%, 0.010 wt%, 0.015 wt%, 0.020 wt%, 0.025 wt%, etc.

[0045] In some embodiments, the metallographic structure of the damping steel includes:

[0046] Tempered martensite, reverse-transformed austenite, and ferrite; please refer to Figures 2-4 The volume fraction of the reverse-transformed austenite is 40% to 54%.

[0047] In this metallographic structure, the role of tempered martensite is as follows: Tempered martensite forms the matrix and, through dislocation strengthening and lath strengthening mechanisms, ensures the steel plate strength meets the requirement of 400MPa~440MPa. The role of reverse-transformed austenite is as follows: Through the phase transformation-induced plasticity mechanism, reverse-transformed austenite undergoes a phase transformation under load, providing the steel plate with high toughness and meeting the low-temperature toughness requirement of -60℃. The role of ferrite is as follows: Ferrite is a softening phase, providing the steel plate with a lower yield strength ratio and excellent plasticity, meeting the yield strength ratio requirement of 0.60~0.80 and A... 50 >50%.

[0048] The positive effects of controlling the volume fraction of reverse-transformed austenite to be 40%–54% are as follows: Through the transformation-induced plasticity mechanism, the reverse-transformed austenite undergoes a phase transformation under load, providing the steel plate with high toughness and meeting the low-temperature toughness requirement of -60℃. If the volume fraction is too high, it will reduce the stability of the reverse-transformed austenite to some extent, causing the phase transformation to occur before loading, resulting in poor toughness of the steel plate. If the volume fraction is too low, it will result in poor phase transformation-induced plasticity of the steel plate, also leading to lower toughness. Specifically, the volume fraction of reverse-transformed austenite can be 40%, 44%, 48%, 52%, 54%, etc.

[0049] In some embodiments, the yield strength ratio of the damping steel is 0.60 to 0.80, and the elongation after fracture A of the damping steel is... 50 >50%.

[0050] In the embodiments of this application, the above-mentioned damping steel has a low yield strength ratio and excellent plasticity.

[0051] In some embodiments, the damping steel has a yield strength of 400 MPa to 440 MPa, and the damping steel has a -60℃...

[0052] The low-temperature impact energy is >60J.

[0053] In the embodiments of this application, the damping steel described above has a low yield strength ratio, excellent plasticity, and excellent mechanical properties.

[0054] In some embodiments, the thickness of the damping steel is 20mm-60mm.

[0055] The positive effects of controlling the thickness of damping steel to 20mm-60mm: High-temperature rolling of the cast billet into steel plates of 20mm-60mm results in a higher compression ratio, more complete recrystallization, and better grain refinement, which is beneficial for the steel plate to achieve excellent strength and toughness. Specifically, the thickness of this damping steel can be 20mm, 30mm, 40mm, 50mm, 60mm, etc.

[0056] Secondly, this application provides a method for preparing damping steel for seismic resistance in buildings, used to prepare the damping steel described in any embodiment of the first aspect. Please refer to [link to relevant documentation]. Figure 1 The method includes:

[0057] S1. Heating the slab at a set temperature;

[0058] S2. Under the condition of setting the final rolling temperature, the heated slab is rolled and then straightened to obtain a hot-rolled plate.

[0059] S3. Cool the hot-rolled plate and control the cooling process parameters;

[0060] S4. The cooled hot-rolled plate is subjected to heat treatment, and the process parameters of the heat treatment are controlled to obtain damping steel for earthquake resistance in buildings.

[0061] The straightening process, specifically heated straightening, aims to eliminate residual stress within the steel plate, prevent secondary plate deformation during cooling, and reduce pressure on downstream hot straighteners. "Set temperature" refers to the heating temperature, and "Set final rolling temperature" refers to the final rolling temperature.

[0062] In some embodiments, the process parameters of the heat treatment include: heating temperature and holding time; wherein, the

[0063] The heating temperature is 580℃~620℃, and the holding time is 2.0min / mm~2.5min / mm.

[0064] Under the given steel composition and rolling process, by adjusting the austenite reversal heat treatment process, a suitable thin-film reversed austenite morphology is obtained, achieving the aforementioned excellent comprehensive properties. In this heat treatment process, controlling the heating temperature to 580℃~620℃ and the holding time to 2.0min / mm~2.5min / mm has the following positive effects: heat treatment within this temperature range and holding time can obtain the target content of reversed austenite. If the heating temperature is too high, the stability of the reversed austenite will decrease to some extent, making it impossible to obtain the target content of reversed austenite at room temperature; if the heating temperature is too low, the element diffusion rate and the formation rate of reversed austenite will decrease to some extent, making it impossible to obtain the target content of reversed austenite at room temperature. If the holding time is too long, the stability of the reversed austenite will decrease to some extent, making it impossible to obtain the target content of reversed austenite at room temperature; if the holding time is too short, the element diffusion rate and the formation rate of reversed austenite will decrease to some extent, making it impossible to obtain the target content of reversed austenite at room temperature. Specifically, the heating temperature can be 580℃, 590℃, 600℃, 610℃, 620℃, etc.; the holding time can be 2.0min / mm, 2.1min / mm, 2.2min / mm, 2.3min / mm, 2.4min / mm, 2.5min / mm, etc.

[0065] In some embodiments, the set temperature is 1100℃~1150℃.

[0066] The positive effects of controlling the heating temperature to 1100℃~1150℃ include: higher compositional uniformity in the billet and the acquisition of fine, uniform austenite grains, which is beneficial for subsequent grain refinement after rolling. If the heating temperature is too high, it can lead to significant austenite grain growth in the billet, resulting in larger austenite grains after rolling and lower strength and toughness in the steel plate. Conversely, if the heating temperature is too low, it can result in poor compositional uniformity in the billet, deteriorating the steel plate's properties. Specifically, the heating temperature can be 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, 1150℃, etc.

[0067] In some embodiments, the set final rolling temperature is 860°C to 920°C.

[0068] The positive effects of controlling the final rolling temperature to 860℃~920℃ are: It allows the steel plate to be rolled within the temperature range of the non-recrystallization region of austenite, resulting in a more uniform austenite grain size and a phase transformation structure dominated by refined martensite laths. If the final rolling temperature is too high, the steel plate may enter part of the recrystallization region during rolling, leading to mixed austenite crystals, which is detrimental to the strength and toughness of the steel plate. If the final rolling temperature is too low, the steel plate may be rolled in the two-phase region or the ferrite region, resulting in excessive mill load and poor steel plate strength and toughness. Specifically, the final rolling temperature can be 860℃, 880℃, 900℃, 920℃, etc.

[0069] In some embodiments, the cooling process parameters include: the starting temperature of cooling, the ending temperature of cooling, and so on.

[0070] The cooling rate is 18℃ / s to 30℃ / s. The starting temperature of the cooling is 720℃~800℃, the ending temperature of the cooling is ≤250℃, and the cooling rate is 18℃ / s~30℃ / s.

[0071] The positive effects of controlling the cooling start temperature to 720℃~800℃, the cooling end temperature to ≤250℃, and the cooling rate to 18℃ / s~30℃ / s are: It ensures proper cooling of the steel plate, allowing for sufficient martensitic transformation and obtaining a complete lath martensite microstructure. If the starting cooling temperature is too high, it can lead to coarse grains; if the starting cooling temperature is too low, it can result in prolonged air cooling before controlled cooling, preventing the formation of a complete lath martensite microstructure. If the cooling end temperature is too high, it can result in only partial martensitic transformation, also preventing a complete lath martensite microstructure. If the cooling end temperature is too low, it can lead to excessive cooling, resulting in poor plate shape and flatness. Similarly, an excessively high cooling rate can also lead to excessive cooling, resulting in poor plate shape and flatness; an excessively low cooling rate can prevent the formation of a complete lath martensite microstructure. Specifically, the starting temperature of the cooling can be 720℃, 740℃, 760℃, 780℃, 800℃, etc., the ending temperature of the cooling can be 250℃, 240℃, 230℃, etc., and the cooling rate can be 18℃ / s, 22℃ / s, 26℃ / s, 30℃ / s, etc.

[0072] The preparation method of the building earthquake-resistant damping steel is based on the above-mentioned building earthquake-resistant damping steel. The specific steps of the building earthquake-resistant damping steel can be referred to the above embodiments. Since the preparation method of the building earthquake-resistant damping steel adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0073] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0074] Table 1 Chemical composition (wt%) and microstructure of damping steel for seismic resistance in buildings

[0075]

[0076] Table 2. Manufacturing process parameters for damping steel for seismic resistance in buildings.

[0077]

[0078] Table 3 Mechanical properties of damping steel for seismic resistance in buildings

[0079]

[0080] By designing the reasonable chemical composition in Table 1 and controlling the preparation process parameters of the damping steel for seismic resistance in Table 2, the yield strength ratio of the damping steel was achieved to be 0.60–0.80, and the elongation after fracture A was also achieved. 50 >50%. However, by altering the chemical composition or preparation process parameters, the volume fraction of reverse-transformed austenite decreases, resulting in poorer overall mechanical properties of the final damping steel.

[0081] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A damping steel for building earthquake resistance, characterized by, The chemical composition of the damping steel is as follows: It is composed of C, Si, Mn, Ti, and Fe; among which, The content of C is 0.06 wt% to 0.08 wt%, the content of Si is 0.15 wt% to 0.30 wt%, the content of Mn is 4.0 wt% to 4.9 wt%, the content of Ti is 0.008 wt% to 0.025 wt%, and the balance is Fe. The metallographic structure of the damping steel includes: The material comprises tempered martensite, reverse-transformed austenite, and ferrite; wherein the volume fraction of the reverse-transformed austenite is 40%–54%. The damping steel has a yield strength ratio of 0.60 to 0.80, and the damping steel has an elongation after fracture A. 50 >50%; The damping steel has a yield strength of 400MPa to 440MPa and a low-temperature impact energy of -60℃ > 60J. The thickness of the damping steel is 20mm-60mm; The method for preparing the earthquake-resistant damping steel for buildings includes: The slab is heated under a set temperature condition; Under the condition of setting the final rolling temperature, the heated slab is rolled and then straightened to obtain a hot-rolled plate; The hot-rolled plate is cooled, and the cooling process parameters are controlled. The cooled hot-rolled plate is subjected to heat treatment, and the process parameters of the heat treatment are controlled to obtain damping steel for seismic resistance in buildings; The process parameters for the heat treatment include: heating temperature and holding time; wherein, the heating temperature is 580℃~620℃, and the holding time is 2.0min / mm~2.5min / mm; The set temperature is 1100℃~1150℃; The set final rolling temperature is 860℃~920℃; The cooling process parameters include: The cooling start temperature, cooling end temperature, and cooling rate are specified; wherein the cooling start temperature is 720℃~800℃, the cooling end temperature is ≤250℃, and the cooling rate is 18℃ / s~30℃ / s.

Images