WO2024119783A1 - Anti-seismic and weather-proof steel plate for v-series 550 mpa building structure, and manufacturing method therefor - Google Patents

Abstract

The present invention provides an anti-seismic and weather-proof steel plate for a V-series 550 MPa building structure, and a manufacturing method therefor. The steel plate comprises the following components in percentage by weight: C: 0.07-0.12%; Si: 0.35-0.45%; Mn: 1.30-1.40%; P ≤ 0.020%; S ≤ 0.008%; Cr: 0.60-0.70%; Ni: 0.25-0.35%; Cu: 0.30-0.40%; V: 0.08-0.12%; Als: 0.015-0.055%; N: 0.0200-0.0220%; and the balance being Fe and inevitable impurities. The steel plate is obtained by performing heating, rough rolling, finish rolling, laminar cooling and coiling on a slab having said components. The anti-seismic and weather-proof steel plate provided by the present invention has excellent atmospheric corrosion resistance and anti-seismic performance.

Description

V series 550MPa grade earthquake-resistant weathering steel plate for building structure and preparation method thereof Technical Field

The present invention relates to the technical field of hot-rolled plates and strips, specifically the technical field of earthquake-resistant and weather-resistant steel plates, and in particular to a V-series 550MPa-grade earthquake-resistant and weather-resistant steel plate for building structures and a preparation method thereof.

Background technique

Steel structure buildings have the advantages of light weight, high strength, convenient installation, short construction period, and high recycling rate. Therefore, the application of steel for building structures has developed rapidly. Traditional building structure steels such as carbon structural steel and low-alloy high-strength steel are prone to corrosion due to their poor corrosion resistance, which greatly shortens the service life of steel structure buildings. Therefore, they are rust-proofed and painted during use, which not only increases the cost of steel structure buildings, but also causes environmental pollution problems. Therefore, high-performance building structure steel needs to have excellent atmospheric corrosion resistance. In addition, my country is an earthquake-prone area, and there are as many as 101 earthquake zones (above magnitude 7) that should be fortified for earthquakes, accounting for 32.5% of the country's total area. Therefore, in order to achieve the goal of "small earthquakes are not damaged, heavy earthquakes can be repaired, and large earthquakes do not collapse", high-performance building structure steel also needs to have excellent seismic resistance.

"Structural Steel Part 6: Technical Delivery Conditions for Earthquake-Resistant Building Structural Steel" (GB/T 34560.6-2017) requires that the yield strength ratio of steel used in earthquake-resistant structures be ≤0.85, while "Code for Seismic Design of Buildings" (GB 50011-2010) requires that the yield strength ratio of steel used in earthquake-resistant structures be ≤0.85, and that it should have a clear yield platform, an elongation ≥20%, and good impact toughness. The yield point elongation Ae refers to the percentage of the ratio of the extension of the extensometer gauge length between the beginning of yielding and the beginning of uniform work hardening of metal materials that show obvious yielding to the extensometer gauge length. The larger the Ae value, the longer the yield platform length. In addition, buildings are mainly subjected to alternating large strain loads during earthquakes, and the number of alternations is mostly less than 200 times. It can be seen that the damage and fracture process of construction steel caused by earthquakes is very similar to high-strain low-cycle fatigue behavior. Therefore, in order to achieve excellent seismic performance for building structure steel, it is necessary not to In addition to having good plasticity and toughness, it is also necessary to have a small yield strength ratio, a large Ae value and good high strain low cycle fatigue performance.

Chinese patents with publication numbers 107385324A, 107385239A, 107604248A, and 110184525A all disclose steel for building structures with a yield strength of more than 500 MPa and a method for manufacturing the same, but can only achieve a relatively low yield strength ratio and cannot achieve excellent atmospheric corrosion resistance. At the same time, they cannot guarantee seismic performance indicators such as yield point elongation and high strain low cycle fatigue performance.

Summary of the invention

In view of the above technical problems, a V-series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structures and a preparation method thereof are provided.

The technical means adopted by the present invention are as follows:

V series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structure includes the following components by weight percentage: C: 0.07-0.12%, Si: 0.35-0.45%, Mn: 1.30-1.40%, P≤0.020%, S≤0.008%, Cr: 0.60-0.70%, Ni: 0.25-0.35%, Cu: 0.30-0.40%, V: 0.08-0.12%, Als: 0.015-0.055%, N: 0.0200-0.0220%, and the balance is Fe and unavoidable impurities.

Furthermore, the metallographic structure of the earthquake-resistant and weather-resistant steel plate for building structure is polygonal ferrite+pearlite; the volume fraction thereof is 75-80% for ferrite and 20-25% for pearlite.

Furthermore, the atmospheric corrosion resistance index I of the earthquake-resistant and weather-resistant steel plate for building structure is ≥ 6.5;

Furthermore, the seismic and weather-resistant steel plate for building structure has a yield strength of ≥550MPa, a tensile strength of ≥600MPa, an elongation after fracture of ≥20%, a yield strength ratio of ≤0.85, an elongation at yield point Ae of ≥2.0%, a 180° bending test of D=2a, and a full-size V-notch -40°C impact energy KV ₂ of ≥70J.

Furthermore, the corrosion rate of the earthquake-resistant and weather-resistant steel plate for the building structure relative to Q355B is ≤45%;

Furthermore, the fatigue life of the earthquake-resistant and weather-resistant steel plate for building structure in a high-strain low-cycle fatigue test with a strain amplitude range of ±2% is ≥200 weeks.

Furthermore, the thickness of the earthquake-resistant and weather-resistant steel plate for the building structure is 6.0 to 16.0 mm.

Functions and mechanisms of each element and main process in the present invention:

The influence law of yield strength ratio: grain refinement strengthening and dislocation strengthening make the increase of yield strength greater than the increase of tensile strength, thus significantly increasing the yield strength ratio; precipitation strengthening makes the increase of yield strength slightly greater than the increase of tensile strength, thus slightly affecting the yield strength ratio; solid solution strengthening makes the increase of yield strength slightly smaller than the increase of tensile strength, thus reducing the yield strength ratio.

The influence of yield point elongation: (1) The increase of interstitial atom content of C and N can make the yield phenomenon more obvious, thereby increasing the yield point elongation. The yield effect of low carbon steel is due to the pinning of dislocations by the Coriolis gas formed by interstitial atoms C and N. During deformation, the stress must be increased to a certain extent to allow the dislocations to break free from the pinning. At this time, an upper yield point is formed on the tensile curve; once the dislocation breaks free from the pinning, it can continue to move under a smaller stress. At this time, a lower yield point is formed on the stress-strain curve. (2) When the microstructure has a high dislocation density such as bainite and martensite, the yield point elongation will be reduced. When the dislocation density in the crystal is high, the strengthening effect is greater, the interaction between dislocations is strong when subjected to force, and the strain hardening behavior is prominent, which will lead to the yield phenomenon being not obvious, thereby reducing the yield point elongation. (3) Grain refinement can make the yield phenomenon more obvious, thereby increasing the yield point elongation. The theory of polycrystalline coordinated deformation can be used to explain the obvious improvement of grain refinement on the yield phenomenon. Unlike single crystals, polycrystallines must maintain the coordination of deformation between grains during deformation, and for this reason polycrystalline deformation requires five independent slip systems. Although ferrite with a body-centered cubic structure has more than five slip systems, when the grains are larger, the number of crystal orientations will decrease, and the number of slip systems that can be activated will be low, so that slip only occurs in large grains with low yield strength and favorable orientation. As stress increases, multiple slip and the initiation of slip in other grains will occur in large grains with favorable orientation, which ends the yield stage prematurely and enters the work hardening stage, resulting in low yield platform elongation. When the grain size decreases, the number of crystal orientations will increase significantly, increasing the number of slip systems that can be activated, resulting in the initial single slip occurring in more grains. In addition, fine grains have higher yield strength and shear stress. Once a dislocation breaks free from the pinning of interstitial atoms, more single slips on parallel slip planes can be activated successively because the applied shear stress is much higher than the critical shear stress for dislocation initiation, thus forming an almost Parallel slip bands lead to a macroscopically long yield platform. Similarly, as stress increases, multi-slip does not occur preferentially in large grains with favorable orientations like coarse-grained samples, but occurs simultaneously in most grains, thus not entering the work hardening stage early.

In order to make the product obtain excellent comprehensive performance matching such as seismic resistance and corrosion resistance, based on the influence of yield strength ratio and yield point elongation, the present invention limits the content of each element and the process parameters of the main processes.

Carbon: Carbon is an effective strengthening element in steel. It can be dissolved into the matrix to play a role in solid solution strengthening, and can combine with V to form carbide precipitation particles, which play a role in fine grain strengthening and precipitation strengthening. Therefore, increasing the carbon content is beneficial to improving strength; at the same time, carbon can be used as an interstitial atom to pin dislocations, making the yield phenomenon more obvious and increasing the Ae value. However, too high a carbon content will form more coarse and brittle carbide particles in the steel, which is not good for plasticity and toughness. Too high a carbon content is also prone to form a segregation band in the center of the steel plate, which is not good for bending performance, forming performance, etc. At the same time, too high a carbon content will increase the welding carbon equivalent and welding crack sensitivity index, which is not conducive to welding processing; therefore, the value range of C in the present invention is set to 0.07-0.12%.

Silicon: Silicon can be dissolved in ferrite and austenite to increase the hardness and strength of steel, which is beneficial to refine the rust layer structure and reduce the overall corrosion rate of steel. However, too high a content will reduce the plasticity and toughness of the steel, making it difficult to remove scale during rolling and also leading to a decrease in welding performance; therefore, the value range of Si in the present invention is set to 0.35-0.45%.

Manganese: Manganese has a strong solid solution strengthening effect, can significantly reduce the phase transition temperature of steel, and refine the microstructure of steel. It is an important strengthening element. However, when the Mn content is too high, cracks in the ingot are likely to occur during the continuous casting process. At the same time, it may cause component segregation in the core of the steel plate and reduce the welding performance of the steel. Therefore, the value range of Mn in the present invention is set to 1.30-1.40%.

Phosphorus and sulfur: Phosphorus and sulfur elements will have an adverse effect on the microstructure and properties of steel plates. Although phosphorus can effectively improve the atmospheric corrosion resistance of steel, too high a phosphorus content will significantly reduce the plasticity and low-temperature toughness of steel, while sulfur will form sulfide inclusions that deteriorate the performance of steel; therefore, the value ranges of P and S in the present invention are set to P≤0.020%, S≤0.008%.

Chromium: Chromium has a significant effect on improving the passivation ability of steel and can promote the formation of a dense passivation film or protective rust layer on the steel surface. Its enrichment in the rust layer can effectively improve the selective permeability of the rust layer to corrosive media; however, too high a chromium content will increase the production cost; therefore, the value range of Cr in the present invention is set to 0.60-0.70%.

Nickel: Adding nickel to steel will significantly improve the corrosion resistance of the steel. At the same time, nickel and copper elements form a copper-rich phase containing Ni, and are retained in the outer oxide layer in a solid state, reducing the copper enrichment in the matrix and the chance of forming a liquid copper-rich phase, thereby avoiding the occurrence of hot brittle defects. Therefore, Ni/Cu in steel is generally controlled to be ≥1/2; but too high nickel will increase the adhesion of the oxide scale, and pressing it into the steel will form hot rolling defects on the surface. In addition, nickel is a precious metal, and too high a nickel content will significantly increase the alloy cost of the steel; therefore, the value range of Ni in the present invention is set to 0.25-0.35%.

Copper: copper added to steel is conducive to forming a dense, well-adhesive amorphous oxide (hydrocarbon oxide) protective layer on the surface of the steel, which has a significant corrosion resistance effect; in addition, copper and sulfur form insoluble sulfides, thereby offsetting the harmful effects of S on the corrosion resistance of steel; however, when the copper content is too high, due to the low melting point of copper, which is lower than the heating temperature of the steel billet, the precipitated copper is in liquid and aggregates at the austenite grain boundary. When the precipitated copper content reaches a certain level, cracks are easily generated during heating or hot rolling; in addition, according to the calculation formula of the atmospheric corrosion resistance index I, too little or too much copper content will reduce the calculated value of I; therefore, the value range of Cu in the present invention is set to 0.30-0.40%.

Vanadium and nitrogen: Vanadium is dissolved in austenite to inhibit static and dynamic recrystallization during hot deformation, thereby expanding the unrecrystallized zone of austenite, increasing the strain in the unrecrystallized zone during fine rolling, promoting the transformation of austenite to ferrite, and refining the ferrite grains; at the same time, vanadium, carbon and nitrogen can form tiny carbonitrides to pin the grain boundaries, delay recrystallization, inhibit the growth of austenite grains, produce fine grain strengthening and precipitation strengthening effects, but increase the yield strength ratio; increasing the nitrogen content in steel is conducive to the precipitation of the second phase of vanadium, and when the nitrogen content is high, there is still a surplus after fixing the vanadium element, so that the remaining nitrogen element can be used as an interstitial atom to pin dislocations, making the yield phenomenon more obvious and improving the Ae value; however, if the nitrogen content is too high, it will increase the aging tendency, cold brittleness and hot brittleness of the steel, and damage the welding performance and cold bending performance of the steel; therefore, the value range of V in the present invention is set to 0.08-0.12%, and the value of N is set to 0.08-0.12%. The value range is set to 0.0200～0.0220%.

Aluminum: Aluminum is added to steel to play a deoxidizing role and improve the steel quality. However, if the aluminum content is too high, its nitrogen oxides are easily precipitated at the austenite grain boundaries, causing cracks in the ingot. Therefore, the value range of Als in the present invention is set to 0.015-0.055%.

The present invention also discloses a method for preparing a V-series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structures, comprising the following steps: heating, rough rolling, finish rolling, laminar cooling and coiling a slab containing the above components to obtain the earthquake-resistant and weather-resistant steel plate for building structures.

In the heating step, the slab is heated in a regenerative heating furnace. The purpose of heating the slab is to homogenize the as-cast structure and component segregation and to dissolve the alloy elements. However, if the heating temperature is too high or the heating time is too long, problems such as burning, overheating, and overburning may occur. Therefore, in the present invention, the heating temperature is set to 1180-1220°C and the heating time is set to 180-400 minutes in the heating step.

Further specifically, in the rough rolling step, the rough rolling needs to achieve sufficient deformation to ensure austenite recrystallization, refine austenite grains, and prevent the appearance of mixed crystal structure; if the thickness of the intermediate billet is too large, the rough rolling deformation may be insufficient, and the finishing rolling load increases; if the thickness of the intermediate billet is too small, the finishing rolling deformation may be insufficient. Therefore, the present invention sets the rough rolling step to undergo 6 rough rolling passes, with a deformation of ≥18% per pass; when the finished product thickness is 6.0-10.0mm, the intermediate billet thickness is 48-52mm; when the finished product thickness is >10.0-16.0mm, the intermediate billet thickness is 53-57mm.

To be more specific, in the finishing step, the slabs on the last three passes of the finishing rolling are basically rolled in the austenite non-recrystallization zone. By adopting a large deformation rate, the austenite grains that have been rolled in the recrystallization zone and refined to a certain extent can be flattened and elongated, increasing the grain boundary area of austenite per unit volume. At the same time, a large number of deformation bands and high-density dislocations will be generated in the grains, thereby increasing the ferrite nucleation rate and obtaining a fine structure after phase transformation; if the finishing rolling start temperature is too high, the deformation amount in the austenite non-recrystallization zone during the finishing rolling process is insufficient, which is not conducive to structure refinement; if the final rolling temperature is too low, the difference from the start rolling temperature is too large, resulting in too fast cooling rate during the finishing rolling process, and there is a risk that the last few stands after finishing rolling are rolled in the two-phase zone, resulting in poor overall product performance; if the final rolling temperature is too high, the deformation amount in the non-recrystallization zone is insufficient, which is not conducive to the final Therefore, the present invention sets the finishing rolling step to be 7 passes of finishing rolling, the reduction rates of the last three stands are ≥17%, ≥13% and ≥10% respectively, the finishing rolling start temperature is ≤1030°C, and the final rolling temperature is 840-880°C.

Specifically in the laminar cooling step, the front-stage cooling mode can achieve a larger degree of supercooling to refine the final structure, and the use of a larger cooling rate can improve the core band structure to a certain extent, and is conducive to the precipitation of a small dispersed second phase to enhance the fine grain strengthening and precipitation strengthening effects, but too high a cooling rate can easily lead to the formation of medium and low temperature structures such as bainite and martensite, resulting in an increase in the yield strength ratio and a decrease in the yield point elongation. Therefore, the present invention adopts the front-stage cooling mode with a cooling rate of 40 to 80 ° C / s.

Specifically, in the coiling step, if the coiling temperature is too low, the cooling rate during the cooling process will be too high, resulting in the formation of medium-low temperature structures such as bainite and martensite, resulting in an increase in the yield strength ratio and a decrease in the yield point elongation; if the coiling temperature is too high, the grains and second phase particles will be coarse, resulting in a decrease in strength and toughness. Therefore, the coiling temperature is set to 650-690°C in the present invention.

Compared with the prior art, the present invention has the following advantages:

The present invention adds a certain amount of Si, Cr, Ni, Cu and other elements to make the atmospheric corrosion resistance index I≥6.5, thereby improving the atmospheric corrosion resistance of the product; the VN microalloying method is used to exert the fine grain strengthening and precipitation strengthening effects, so that the product obtains good strength, plasticity and toughness matching, and at the same time, the microstructure and performance of the product are regulated by combining the controlled rolling and controlled cooling process. The metallographic structure of the product is uniform polygonal ferrite+pearlite, the yield strength ratio is low, and the yield point elongation and high strain low cycle fatigue performance are high. The steel for building structure prepared by using the composition and the preparation method of the present invention has a yield strength of ≥550MPa, a tensile strength of ≥600MPa, an elongation after fracture of ≥20%, a yield strength ratio of ≤0.85, an elongation at the yield point of Ae of ≥2.0%, a 180° bending test of D=2a, a full-size V-notch impact energy of -40°C of KV ₂ of ≥70J, a relative corrosion rate of Q355B of ≤45%, a fatigue life of ≥200 weeks in a high-strain low-cycle fatigue test with a strain amplitude range of ±2%, and achieves excellent atmospheric corrosion resistance and seismic resistance.

Based on the above reasons, the present invention can be widely promoted in the fields of earthquake-resistant and weather-resistant steel plates.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1 is a metallographic structure diagram of a V-series 550MPa grade seismic and weather-resistant steel plate for building structures in Example 1 of the present invention.

Detailed ways

It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail with reference to the accompanying drawings and in combination with the embodiments. In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described in combination with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

In order to facilitate the understanding of the present invention, the present invention is further described below in conjunction with embodiments and comparative examples.

The V-series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structure disclosed by the present invention comprises the following components by weight percentage: C 0.07-0.12%, Si 0.35-0.45%, Mn 1.30-1.40%, P≤0.020%, S≤0.008%, Cr 0.60-0.70%, Ni 0.25-0.35%, Cu 0.30-0.40%, V 0.08-0.12%, Als 0.015-0.055%, N 0.0200-0.0220%, and the balance is Fe and unavoidable impurities.

In order to further understand the present invention, three groups of embodiments of the composition and preparation method of the earthquake-resistant and weather-resistant steel plate for building structure of the present invention and two groups of comparative examples are provided for comparative explanation.

The atmospheric corrosion resistance index of the earthquake-resistant and weather-resistant steel plate for building structure is I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P)-7.29(%Cu)(%Ni)-9.10(%Ni)(%P)-33.39(%Cu) ² .

The yield strength, tensile strength and elongation after fracture of the earthquake-resistant weathering steel plate for building structure are tested according to "Metallic Material Tensile Test Part 1: Room Temperature Test Method" (GB/T 228.1); the bending performance is tested according to "Metallic Material Bending Test Method" (GB/T 232); the impact performance is tested according to "Metallic Material Charpy Pendulum Impact Test Method" (GB/T 229); the corrosion resistance is tested for 72 hours according to "Railway Weathering Steel Cyclic Immersion Corrosion Test Method" (TB/T 2375); the high strain low cycle fatigue performance is tested according to "Metallic Material Fatigue Test Axial Strain Control Method", the strain amplitude range is ±2%, the strain ratio R=-1, the deformation rate is 2× ^10-3 , the load is 3kN, and the failure of the sample is judged as fracture or the stress value drops to 30% of the stable stress value.

Example 1

A V-series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structure, the chemical composition of which is shown in Table 1, and the remainder is Fe and unavoidable impurities.

A method for preparing a V-series 550MPa grade seismic and weather-resistant steel plate for building structures, wherein the plate is smelted into a slab by a conventional method according to the composition, and the smelted slab is further processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling are performed in sequence. The specific processing technology is as follows: the heating temperature is 1190°C, and the heating time is 220min; after 6 rough rolling passes, the deformation amount of each pass is ≥18%, and the thickness of the intermediate slab is 51mm; after 7 finishing rolling passes, the reduction rates of the last three stands are ≥17%, ≥13% and ≥10% respectively, the finishing rolling start temperature is 1010-1020°C, and the final rolling temperature is 850-860°C; the front-stage cooling mode is adopted, and the plate is cooled to the target coiling temperature, the cooling rate is about 70°C/s, and the coiling temperature is 650-660°C. The metallographic structure is uniform polygonal ferrite + pearlite, as shown in FIG1, the volume fraction of ferrite is 75%, and the volume fraction of pearlite is 25%.

Example 2

A V-series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structure, the chemical composition of which is shown in Table 1, and the remainder is Fe and unavoidable impurities.

A method for preparing a V-series 550MPa grade seismic and weather-resistant steel plate for building structures, wherein the plate is smelted into a slab by a conventional method according to the composition, and the smelted slab is further processed, and heating, rough rolling, finish rolling, laminar cooling and coiling are performed in sequence. The specific processing technology is as follows: the heating temperature is 1210°C, and the heating time is 250min; after 6 rough rolling passes, the deformation amount of each pass is ≥18%, and the thickness of the intermediate slab is 54mm; after 7 finish rolling passes, the reduction rates of the last three stands are ≥17%, ≥13% and ≥10% respectively, the start rolling temperature of the finish rolling is 1010-1030°C, and the final rolling temperature is 860-870°C; the front-stage cooling mode is adopted, and the plate is cooled to the target coiling temperature, the cooling rate is about 65°C/s, and the coiling temperature is 660-690°C. The metallographic structure is uniform polygonal ferrite + pearlite, the volume fraction of ferrite is 78%, and the volume fraction of pearlite is 22%.

Example 3

A V-series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structure, the chemical composition of which is shown in Table 1, and the remainder is Fe and unavoidable impurities.

A method for preparing a V-series 550MPa grade seismic and weather-resistant steel plate for building structures, wherein the plate is smelted into a slab by a conventional method according to the composition, and the smelted slab is further processed, and heating, rough rolling, finish rolling, laminar cooling and coiling are performed in sequence. The specific processing technology is as follows: the heating temperature is 1185°C, and the heating time is 235min; after 6 rough rolling passes, the deformation amount of each pass is ≥18%, and the thickness of the intermediate slab is 56mm; after 7 finish rolling passes, the reduction rates of the last three stands are ≥17%, ≥13% and ≥10% respectively, the start rolling temperature of the finish rolling is 1010-1030°C, and the final rolling temperature is 850-870°C; the front-stage cooling mode is adopted, and the plate is cooled to the target coiling temperature, the cooling rate is about 50°C/s, and the coiling temperature is 670-680°C. The metallographic structure is uniform polygonal ferrite + pearlite, the volume fraction of ferrite is 80%, and the volume fraction of pearlite is 20%.

Comparative Example 1 (Comparative Example 1 specifically refers to Example 2 in "A Large Thickness Q500GJCD High Strength Steel Plate for Building Structure and Its Manufacturing Method" (CN107385324A))

A steel for building structure, the chemical composition of which is shown in Table 1, and the balance is Fe and inevitable impurities.

A method for preparing steel for building structures comprises the following steps: smelting the steel into slabs by conventional methods according to the composition, further processing the smelted slabs by a wide and thick plate rolling mill, and sequentially performing heating, rough rolling, finishing rolling, laminar cooling and coiling. The specific processing technology comprises the following steps: heating temperature is 1200-1220°C, heating time is 375min; rough rolling, waiting thickness is 50mm, after waiting, the starting rolling temperature of the finishing mill is 900°C, and finishing rolling is performed, the final rolling temperature is ≥796°C; after rolling, the rolled piece is directly sent to an ACC equipment for watering to accelerate cooling, the cooling rate is 6-7°C/s, and the final cooling temperature is 690-710°C; the rolled piece is then leveled by a hot leveling machine; and then the rolled piece is sent to a cooling bed for natural cooling to 320°C and then slowly cooled by a stack offline for 24h.

Comparative Example 2 (Comparative Example 2 specifically refers to Example 2 in "A high-strength Q500GJD quenched and tempered steel plate for building structures and its manufacturing method" (CN107604248A))

A steel for building structure, the chemical composition of which is shown in Table 1, and the balance is Fe and inevitable impurities.

A preparation method for building structure steel comprises the following steps: smelting into slabs by conventional methods according to the composition, further processing the smelted slabs by a wide and thick plate rolling mill, and sequentially performing heating, rough rolling, finishing rolling, laminar cooling and coiling. The specific processing technology comprises the following steps: heating temperature is 1180-1220°C, and heating time is 220min; rough rolling is performed to a thickness of 65mm, and the slabs are sent to a finishing mill for rolling, and the final rolling temperature is 795°C; after rolling, the rolled pieces are directly sent to a hot leveling machine for leveling; the rolled pieces are then sent to a cooling bed for natural cooling; qualified plates are transferred to a heat treatment process, with a quenching temperature of 905°C, a furnace time of 25min, water cooling, a tempering temperature of 660°C, a furnace time of 27min, and air cooling to room temperature.

Table 1 Mass percentage of chemical components of Examples and Comparative Examples (wt%)

The specific mechanical property test results of the embodiments and comparative examples are shown in Table 2.

Table 2 Performance test results of embodiments and comparative examples

Note 1: The diameter of the bending indenter is D, and the thickness of the specimen is a;

Note 2: For the impact test, half-size specimens were used in Example 1, and full-size specimens were used in Examples 2, 3 and Comparative Examples 1 and 2; the impact test temperature of the example was -40°C, and the impact test temperature of Comparative Examples 1 and 2 was -20°C.

Combining the preparation methods of the three groups of embodiments and the three groups of comparative examples, according to the chemical composition in Table 1 and the performance test results of the embodiments and comparative examples obtained in Table 2, it can be known that the embodiments achieve excellent atmospheric corrosion resistance by adding a certain amount of Si, Cr, Ni, Cu and other elements; the V-N microalloying method exerts the effect of fine grain strengthening and precipitation strengthening, so that the product obtains a good match of strength, plasticity and toughness, and at the same time, the microstructure and properties of the product are regulated by combining the controlled rolling and controlled cooling process, and the product has a low yield strength ratio, and a high yield point elongation and high strain low cycle fatigue performance. Therefore, the V-series 550MPa grade seismic and weather-resistant steel plate for building structures disclosed in the present invention and its preparation method achieve excellent atmospheric corrosion resistance and seismic performance and other comprehensive performance matching, and have a good application prospect.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. V series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structure is characterized in that it includes the following components by weight percentage: C: 0.07-0.12%, Si: 0.35-0.45%, Mn: 1.30-1.40%, P≤0.020%, S≤0.008%, Cr: 0.60-0.70%, Ni: 0.25-0.35%, Cu: 0.30-0.40%, V: 0.08-0.12%, Als: 0.015-0.055%, N: 0.0200-0.0220%, and the balance is Fe and unavoidable impurities.
2. The V-series 550MPa grade seismic and weather-resistant steel plate for building structures according to claim 1 is characterized in that the metallographic structure of the seismic and weather-resistant steel plate for building structures is polygonal ferrite + pearlite; the volume fraction thereof is 75-80% ferrite and 20-25% pearlite.
3. The V-series 550MPa grade seismic and weather-resistant steel plate for building structures according to claim 1, characterized in that the atmospheric corrosion resistance index I of the seismic and weather-resistant steel plate for building structures is ≥ 6.5;

   The seismic weathering steel plate for building structure has yield strength ≥550MPa, tensile strength ≥600MPa, elongation after fracture ≥20%, yield strength ratio ≤0.85, yield point elongation Ae ≥2.0%, 180° bending test D=2a, full-size V-notch -40°C impact energy KV ₂ ≥70J.
4. The V-series 550MPa grade seismic and weather-resistant steel plate for building structures according to claim 1 is characterized in that the corrosion rate of the seismic and weather-resistant steel plate for building structures relative to Q355B is ≤45%; the fatigue life of the seismic and weather-resistant steel plate for building structures in a high-strain low-cycle fatigue test with a strain amplitude range of ±2% is ≥200 weeks.
5. The V-series 550MPa grade seismic and weather-resistant steel plate for building structures according to claim 1 is characterized in that the thickness of the seismic and weather-resistant steel plate for building structures is 6.0 to 16.0 mm.
6. A method for preparing a V-series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structures, characterized in that it comprises the following steps: heating, rough rolling, finish rolling, laminar cooling and coiling a slab containing the components described in any one of claims 1 to 5 to obtain the earthquake-resistant and weather-resistant steel plate for building structures.
7. A V-series 550MPa grade earthquake-resistant weathering steel plate for building structures according to claim 6 The preparation method is characterized in that in the heating step, the heating temperature is 1180-1220° C. and the heating time is 180-400 min.
8. The method for preparing a V-series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structures according to claim 6 is characterized in that in the rough rolling step, six rough rolling passes are performed, and the deformation amount of each pass is ≥18%; when the thickness of the finished product is 6.0-10.0mm, the thickness of the intermediate blank is 48-52mm; when the thickness of the finished product is >10.0-16.0mm, the thickness of the intermediate blank is 53-57mm;

   In the finishing rolling step, 7 finishing rolling passes are performed, wherein the rolling ratios of the last three passes are ≥17%, ≥13% and ≥10% respectively, the finishing rolling start temperature is ≤1030°C, and the final rolling temperature is 840-880°C.
9. The method for preparing a V-series 550MPa grade earthquake-resistant and weather-resistant steel plate for building structures according to claim 6 is characterized in that in the laminar cooling step, a front-stage cooling mode is adopted and the cooling rate is 40 to 80°C/s.
10. The method for preparing a V-series 550MPa grade seismic and weather-resistant steel plate for building structure according to claim 6 is characterized in that in the coiling step, the coiling temperature is 650-690°C.