KR20240170550A - V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures and its manufacturing method - Google Patents

Abstract

The present invention provides a V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures and a manufacturing method therefor. The steel plate of the present invention contains, in mass percentage, chemical components of C: 0.07 to 0.12%, Si: 0.35 to 0.45%, Mn: 1.30 to 1.40%, P≤0.020%, S≤0.008%, Cr: 0.60 to 0.70%, Ni: 0.25 to 0.35%, Cu: 0.30 to 0.40%, V: 0.08 to 0.12%, Als: 0.015 to 0.055%, N: 0.0200 to 0.0220%, the remainder being Fe and inevitable impurities, and is obtained by heating, rough rolling, finish rolling, laminar cooling, and coiling a slab containing the above components. The earthquake-resistant weather-resistant steel plate according to the present invention has excellent atmospheric corrosion resistance and earthquake resistance.

Description

V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures and its manufacturing method

The present invention relates to a V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures and a manufacturing method thereof, and belongs to the field of continuous hot-rolled belt technology, specifically, the field of earthquake-resistant weather-resistant steel plate technology.

Steel structures have the advantages of light weight, high strength, convenient installation, short construction cycle, and high recyclability, so the application of structural steel for building construction is developing rapidly. Existing structural steel for building construction, such as carbon structural steel and low-alloy high-strength steel, have poor corrosion resistance and are vulnerable to corrosion, which greatly shortens the life of steel structures. Therefore, rust must be removed and coated during use. This not only increases the cost of steel structures, but also causes environmental pollution. Therefore, high-performance structural steel for building construction must have excellent atmospheric corrosion resistance. In addition, China is an earthquake-prone area, and there are 101 seismic zones (level 7 or higher) that require earthquake preparedness, accounting for 32.5% of the country's total area. In order for buildings to achieve the goal of "withstanding small earthquakes, being repairable in large earthquakes, and not collapsing in even larger earthquakes", high-performance structural steel for building construction must have excellent seismic performance.

The "Structural Steel Part 6: Delivery Technical Conditions for Earthquake-Resistant Building Structural Steel" (GB/T 34560.6-2017) requires that the yield ratio of earthquake-resistant structural steel is ≤ 0.85, and the "Seismic Design Code for Buildings" (GB 50011-2010) requires that the yield ratio of earthquake-resistant structural steel is ≤ 0.85, has a distinct yield platform, a percentage elongation after fracture ≥ 20%, and good impact toughness. However, the yield point elongation Ae (percentage yield point extension) refers to the extension of the tensile gauge length from the initiation of yield to the initiation of uniform work hardening of a metal material that shows an obvious yield phenomenon, and the percentage of the tensile gauge length, and the larger the Ae value, the longer the yield platform length. In addition, buildings during earthquakes mainly withstand large alternating stress loads, and most of them have alternating cycles of less than 200, so it can be seen that the damage and failure process of architectural steel due to earthquakes is very similar to the high-strain, low-cycle fatigue behavior. Therefore, in order to realize excellent seismic performance, architectural structural steel should not only have excellent plasticity and toughness, but also have a small yield ratio, a large Ae value, and excellent high-strain, low-cycle fatigue performance.

Chinese published patents 107385324A, 107385239A, 107604248A, and 110184525A all disclose structural steel for construction with a yield strength of 500 MPa or more and a manufacturing method thereof, but they can only achieve a low yield ratio and fail to secure excellent atmospheric corrosion resistance, yield point elongation, high strain low-cycle fatigue performance, and other seismic performance indicators.

Based on the above technical problems, the technical problem to be solved by the present invention is to provide a V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures and a manufacturing method thereof.

The technical solution for achieving the purpose of the present invention is as follows.

One aspect of the present invention is to provide a V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures, the chemical composition including, in mass percentage, C: 0.07 to 0.12%, Si: 0.35 to 0.45%, Mn: 1.30 to 1.40%, P≤0.020%, S≤0.008%, Cr: 0.60 to 0.70%, Ni: 0.25 to 0.35%, Cu: 0.30 to 0.40%, V: 0.08 to 0.12%, Als: 0.015 to 0.055%, N: 0.0200 to 0.0220%, and the remainder is Fe and inevitable impurities.

The metal structure of the above earthquake-resistant weather-resistant steel plate for building structures is polygonal ferrite + pearlite, and the volume fraction is 75 to 80% ferrite and 20 to 25% pearlite.

In addition, the atmospheric corrosion resistance index of the earthquake-resistant weather-resistant steel plate for the above-mentioned building structure is I≥6.5.

In addition, the above earthquake-resistant weather-resistant steel plate for building structures has a yield strength of ≥550 MPa, a tensile strength of ≥600 MPa, an elongation at break of ≥20%, a yield ratio of ≤0.85, an elongation at yield point of Ae of ≥2.0%, a 180° bending test of D=2a, and an impact energy of full-size V-notch of -40°C of KV2 of ≥70J.

In addition, the relative corrosion rate of the earthquake-resistant weather-resistant steel plate for the above-mentioned building structure with respect to Q355B is ≤ 45%.

In addition, the fatigue life of the earthquake-resistant weather-resistant steel plate for building structures in a high-strain, low-cycle fatigue test with a deformation amplitude range of ±2% is 200 cycles or more.

Additionally, the thickness of the earthquake-resistant weather-resistant steel plate for the above-mentioned building structure is 6.0 to 16.0 mm.

Action and mechanism of each element and main process of the present invention:

Yield ratio effect law: Washing strengthening and dislocation strengthening can significantly increase the yield ratio by making the increase in yield strength greater than the increase in tensile strength; precipitation strengthening can have a small effect on the yield ratio by making the increase in yield strength slightly greater than the increase in tensile strength; and solid solution strengthening can decrease the yield ratio by making the increase in yield strength slightly smaller than the increase in tensile strength.

The effect law of yield point elongation: (1) The increase in the content of C, N self-interstitial atoms can make the yield phenomenon more obvious and increase the yield point elongation. The yield effect of low carbon steel is that the Cottrell atmosphere formed by the interstitial atoms C, N pins dislocations, so the stress must increase to a certain extent during deformation so that the dislocations can escape from pinning, at which time the upper yield point is formed on the tensile curve, and once the dislocations escape from pinning, they can continue to move even under small stresses, at which time the lower yield point is formed on the stress-strain curve. (2) If a high-density microstructure such as bainite or martensite appears, the yield point elongation decreases. When the dislocation density in the crystal is high, the strengthening effect is greater, the interaction between dislocations is strong when force is applied, and the behavior of strain hardening is prominent, so the yield phenomenon is not obvious and the yield point elongation decreases. (3) The refinement of the crystal grains can make the yield phenomenon more obvious and increase the yield point elongation. The obvious improvement effect of grain refinement on the yield phenomenon can be explained by the polycrystal harmonic deformation theory. Unlike single crystals, polycrystals must maintain the strain harmony between crystal grains during the deformation process, so polycrystal deformation requires five independent slip lines. There are more than five slip lines in body-centered cubic structure ferrite, but when the crystal grains are large, the number of crystal orientations is reduced and the number of movable slip lines is small, so slip occurs only in large crystal grains with low yield strength and favorable orientation. As the stress increases, multiple slips and other grain slips begin in large crystal grains with favorable orientation, which causes the yield stage to end early and enters the working and hardening stage, resulting in low elongation of the yield platform. When the crystal grains decrease, the number of crystal orientations increases greatly, and the number of movable slip lines increases accordingly, so that initial single slip can occur in more crystal grains. In addition, fine grains have higher yield strength and fracture stress, and once a dislocation escapes the pinning of an interstitial atom, the fracture stress applied is much higher than the critical fracture stress at which the dislocation initiates, so that more single slips on parallel slip planes are sequentially operated to form nearly parallel slip bands, forming a macroscopically longer yield platform. Similarly, as stress increases, multiple slips do not occur preferentially in large grains with favorable orientations as in coarse-grained samples, but rather simultaneously in most grains, thus avoiding the early entry into the working-hardening stage.

In order to achieve comprehensive performance matching of the product, including excellent earthquake resistance and corrosion resistance, the present invention limited the content of each element and the process parameters of the main process based on the influence law of yield ratio and yield point elongation.

Carbon: Carbon is an effective strengthening element in steel, which can be dissolved in the matrix to play a role of solid solution strengthening, and can also combine with V to form carbide precipitation particles to play a role of microcrystal strengthening and precipitation strengthening, so increasing the carbon content is beneficial to improving the strength, and at the same time, carbon can fix dislocations as interstitial atoms, which makes the yield phenomenon more obvious and increases the Ae value. However, if the carbon content is too high, larger and brittle carbide particles will be formed in the steel, which is not good for plasticity and toughness, and if the carbon content is too high, a segregation belt is easily formed in the center of the steel plate, which is disadvantageous for bending performance, formability, etc., and if the carbon content is too high, the welding carbon equivalent and the welding crack sensitivity index will increase, which is disadvantageous for welding processing, so the C content of the present invention is set to 0.07 to 0.12%.

Silicon: Silicon can be dissolved in ferrite and austenite, which can improve the hardness and strength of steel, and help to refine the rust layer structure and reduce the overall corrosion rate of steel, but if the content is too high, the plasticity and toughness of steel will decrease, descaling during rolling will be difficult, and the welding performance will be reduced, so the Si content of the present invention is set to 0.35 to 0.45%.

Manganese: Manganese has a strong solid solution strengthening effect, can greatly reduce the phase transition temperature of steel, and refine the microstructure of steel, and is an important toughening element. However, if the Mn content is too high, cracks in the casting blank are likely to occur during the continuous casting process, and at the same time, the core component of the steel plate may segregate, thereby reducing the welding performance of the steel. Therefore, the Mn content of the present invention is set to 1.30 to 1.40%.

Phosphorus and Sulfur: Phosphorus and sulfur elements have a negative effect on the structural performance of steel plates, and phosphorus can effectively improve the atmospheric corrosion resistance of steel, but if the phosphorus content is too high, the plasticity and low-temperature toughness of steel will be greatly reduced, and sulfur will form sulfide impurities, thereby worsening the performance of steel, so the P and S contents of the present invention are set to P≤0.020% and 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, and the concentration in the rust layer can effectively improve the selective penetration property of the rust layer for corrosive media, but if the chromium content is too high, the production cost will increase, so the Cr content of the present invention is set at 0.60~0.70%.

Nickel: When nickel is added to steel, the corrosion resistance of the steel is greatly improved, and at the same time, nickel and copper elements form a copper-rich phase containing Ni, which remains in the outer oxide layer in a solid state, thereby reducing the concentration of copper in the gas and reducing the opportunity of forming a liquid copper phase, thereby preventing the occurrence of heat embrittlement defects, so that Ni/Cu≥1/2 in the steel is generally controlled, but too high a nickel content will increase the adhesion of the oxide layer, and when pressed into the steel, hot-rolling defects will be formed on the surface, and in addition, nickel is a precious metal, and if the nickel content is too high, the cost of the steel alloy will greatly increase, so the Ni content of the present invention is set to 0.25% to 0.35%.

Copper: The addition of copper element is beneficial to form a dense and highly adhesive amorphous oxide (hydrocarbon-based oxide) protective layer on the steel surface, and has obvious corrosion resistance. In addition, copper can produce sulfur and insoluble sulfides to offset the harmful effect of S on the corrosion resistance of steel. However, when the copper content is too high, since the melting point of copper is lower than the heating temperature of the steel billet, the precipitated copper will accumulate in the austenite grain boundary in a liquid state, and when the precipitated copper content reaches a certain level, cracks are likely to occur during heating or hot rolling. In addition, according to the calculation formula of the atmospheric corrosion resistance index I, if the copper content is too little or too much, the calculated value of I will decrease, so the Cu content of the present invention is set to 0.30 to 0.40%.

Vanadium, Nitrogen: The dissolution of vanadium element in austenite suppresses the static and dynamic recrystallization during the thermal deformation process, expands the non-recrystallized region of austenite, increases the amount of deformation of the non-recrystallized region during the finishing rolling process, and promotes the conversion of austenite to ferrite, thereby refining the ferrite grains. At the same time, vanadium combines with carbon and nitrogen to form fine carbonitride pinning grain boundaries, delays recrystallization, suppresses the growth of austenite grains, and produces microcrystal strengthening and precipitation strengthening effects, but increases the yield ratio. Increasing the nitrogen element content of steel is beneficial to the second phase precipitation of vanadium, and when the nitrogen content is high, the residue remains after the fixation of vanadium element, which can use the remaining nitrogen as interstitial atoms to pin dislocations, so the yield phenomenon becomes more obvious and the Ae value can be increased. However, if the nitrogen content is too high, it increases the aging tendency and cold embrittlement and hot embrittlement of the steel, thereby damaging the weldability and cold bending performance of the steel. Therefore, the V content of the present invention is set to 0.08 to 0.12%, and the N content is set to 0.0200 to 0.0220%.

Aluminum: Aluminum can be added to steel to perform a deoxidizing effect and improve the quality of the steel. However, if the aluminum content is too high, nitrogen oxides are likely to precipitate at the austenite grain boundary, causing cracks in the cast billet. Therefore, the Als content of the present invention is set to 0.015 to 0.055%.

The present invention also provides a method for manufacturing a V-type 550 MPa grade earthquake-resistant weather-resistant steel plate for building structures, comprising the steps of heating, rough rolling, finish rolling, laminar cooling, and coiling a slab containing the above components to obtain an earthquake-resistant weather-resistant steel plate for building structures.

In addition, in the heating step, heating the slab in a regenerative heating furnace and heating the slab uniformizes the cast structure and segregation of components while dissolving alloy elements, but if the heating temperature is too high and the heating time is too long, problems such as combustion loss, overheating, and over-burning occur. Therefore, in the present invention, the heating temperature is set to 1180 to 1220°C in the heating step, and the heating time is set to 180 to 400 minutes.

In addition, in the rough rolling stage, the rough rolling should achieve sufficient deformation to ensure the recrystallization of austenite and refine the austenite grains to prevent the occurrence of a mixed grain structure. If the thickness of the intermediate billet is too thick, the rough rolling deformation may be insufficient and the finish rolling load may also increase. If the thickness of the intermediate billet is too small, the finish rolling deformation may be insufficient. Therefore, in the present invention, 6 passes of rough rolling are performed in the rough rolling stage, and the deformation of each pass is 18% or more. When the thickness of the finished product is 6.0 to 10.0 mm, the thickness of the intermediate billet is 48 to 52 mm, and when the thickness of the finished product is 10.0 to 16.0 mm, the thickness of the intermediate billet is 53 to 57 mm.

In addition, in the finishing rolling stage, the slab on the frame of the last three passes of the finishing rolling is basically rolled in the austenite non-recrystallized region, and the austenite grains that have already been rolled and refined to a certain extent in the recrystallized region can be rolled and extended by using a large strain rate, and the grain boundary area of austenite per unit volume can be increased, and at the same time, many deformation bands and high-density dislocations can be generated in the crystal, so as to increase the nucleation rate of ferrite and obtain the microstructure after the phase transformation. If the rolling start temperature of the finishing rolling is too high, the deformation amount of the austenite non-recrystallized region during the finishing rolling process is insufficient, which is disadvantageous for the refinement of the structure. If the final rolling temperature is too low, the difference from the rolling start temperature is large, so the cooling rate of the finishing rolling process becomes too fast, and there is a risk that the frames of the last few passes of the finishing rolling will be rolled in the two-phase region, which will reduce the comprehensive performance of the product. If the final rolling temperature is too high, the deformation amount of the non-recrystallized region is insufficient, which is disadvantageous for the refinement of the final structure. Therefore, in the present invention, 7 passes of finishing rolling are performed in the finishing rolling stage, and the frame reduction ratios of the last 3 passes are set to ≥17%, ≥13%, and ≥10%, respectively. The rolling start temperature of the finishing rolling is set to ≤1030℃, and the final rolling temperature is set to 840 to 880℃.

In addition, in the laminar cooling stage, using the pre-cooling mode can achieve greater supercooling and refine the final structure, and using a large cooling rate can improve the band-like structure in the center to a certain extent, and at the same time, the finely diffused second phase can be precipitated to enhance the microcrystal strengthening and precipitation strengthening effects, but if the cooling rate is too high, medium and low temperature structures such as bainite and martensite are easily generated, which increases the yield ratio and reduces the yield point elongation. Therefore, the present invention adopts a pre-cooling mode with a cooling rate of 40 to 80°C/s.

In addition, in the coiling step, if the coiling temperature is too low, the cooling rate is too high during the cooling process, which causes low- and medium-temperature structures such as bainite and martensite to be generated, which increases the yield ratio and reduces the yield point elongation, and if the coiling temperature is too high, the crystal grains and second phase particles become thicker, which reduces the strength and toughness. Therefore, in the present invention, the coiling temperature is set to 650 to 690°C.

The present invention has the following advantages.

The present invention improves the atmospheric corrosion resistance of the product by adding a certain amount of elements such as Si, Cr, Ni, and Cu, so that the atmospheric corrosion resistance index is I ≥ 6.5, and the V-N microalloying method exerts the effects of microcrystal strengthening and precipitation strengthening, so that the product obtains excellent strength, plasticity and toughness, and at the same time, the rolling and cooling processes are controlled to adjust the organizational performance of the product, and the metal microstructure of the product is uniform polygonal ferrite + pearlite, and the yield ratio is low, the yield point elongation and the high strain low-cycle fatigue performance are high. The structural steel manufactured using the components of the present invention and the manufacturing method thereof has a yield strength ≥ 550 MPa, a tensile strength ≥ 600 MPa, an elongation at break ≥ 20%, a yield ratio ≤ 0.85, an elongation at yield point Ae ≥ 2.0%, a 180° bending test D = 2a, an impact energy KV2 ≥ 70 J at full size V-notch -40°C, a relative corrosion rate ≤ 45% with respect to Q355B, and a fatigue life of more than 200 cycles in a high-strain low-cycle fatigue test with a strain amplitude range of ±2%, thereby realizing excellent atmospheric corrosion resistance and earthquake resistance.

For the above reasons, the present invention can be widely used in the fields of earthquake-resistant and weather-resistant steel plates, etc.

In order to more clearly explain the embodiments of the present invention or the technical solutions of the prior art, drawings necessary for the description of the embodiments or the prior art are briefly introduced. The drawings described below are some embodiments of the present invention, and it is obvious to those skilled in the art that other drawings can be obtained based on these drawings without making creative efforts.
Figure 1 is a metal microstructure diagram of a V-type 550 MPa grade earthquake-resistant weather-resistant steel plate for building structures of Example 1 of the present invention.

As a part that requires explanation, the embodiments of the present invention and the features of the embodiments can be combined with each other as long as there is no conflict. Hereinafter, the present invention will be described in detail by combining the embodiments with reference to the drawings. In order to more clearly explain the purpose, technical solution and advantage of the embodiments of the present invention and to clearly and completely explain the technical solution of the embodiments of the present invention, it is obvious that the described embodiments are not the entire embodiments but a part of the present invention.

The description of at least one embodiment below is actually merely illustrative and does not constitute any limitation to the present invention and its application or use. According to the embodiment of the present invention, all other embodiments obtained by a person skilled in the art without creative labor fall within the protection scope of the present invention.

In order to facilitate understanding of the present invention, the present invention is further explained by combining examples and comparative examples.

The V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures provided by the present invention contains, in chemical compositions according to mass percentage, C: 0.07 to 0.12%, Si: 0.35 to 0.45%, Mn: 1.30 to 1.40%, P≤0.020%, S≤0.008%, Cr: 0.60 to 0.70%, Ni: 0.25 to 0.35%, Cu: 0.30 to 0.40%, V: 0.08 to 0.12%, Als: 0.015 to 0.055%, N: 0.0200 to 0.0220%, and the remainder is Fe and unavoidable impurities.

In order to further understand the present invention, three examples and two comparative examples are provided in which the composition and manufacturing method of the earthquake-resistant weather-resistant steel plate for building structures described in the present invention are applied.

The atmospheric corrosion resistance index I of the above earthquake-resistant weathering steel plate for building structures 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 at break of the above earthquake-resistant weathering steel plate for building structures are tested in accordance with “Tensile Test for Metallic Materials, Part 1: Test Method at Room Temperature” (GB/T 228.1), the bending performance is tested in accordance with “Bending Test Method for Metallic Materials” (GB/T 232), and the impact performance is tested in accordance with “Charpy Pendulum Impact Test Method for Metallic Materials” (GB/T 229). Corrosion resistance is tested for 72 hours in accordance with the “Cyclic Corrosion Test Method for Railway Weathering Steel” (TB/T 2375), and high-strain low-cycle fatigue performance is tested in accordance with the “Axial Strain Control Method for Fatigue Test of Metallic Materials”, where the strain amplitude is ±2%, strain R=-1, strain rate is 2Х10 ^-3 , and load is 3 kN. If the sample is fractured or the stress value decreases to 30% of the stable stress value, the sample is judged to be invalid.

Example 1

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

The manufacturing method of V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures is as follows. According to the chemical composition, the slab is refined by the conventional method, and the slab obtained by the refinement is further processed by heating, rough rolling, finish rolling, laminar cooling and coiling in sequence. The specific processing process is that the heating temperature is 1190℃, the heating time is 220 minutes, 6 passes of rough rolling are performed, of which the deformation of each pass is 18% or more, and the thickness of the intermediate slab is 51mm. 7 passes of finish rolling are performed, of which the frame reduction ratios of the last 3 passes are ≥17%, ≥13% and ≥10%, respectively, and the rolling start temperature of the finish rolling is 1010~1020℃, and the final rolling temperature is 850~860℃. The pre-cooling mode is adopted to cool to the target coiling temperature, of which the cooling speed is about 70℃/s and the coiling temperature is 650~660℃. The metal microstructure is uniform polygonal ferrite + pearlite, and the volume fraction of ferrite is 75% and the volume fraction of pearlite is 25%, as shown in Fig. 1.

Example 2

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

The manufacturing method of V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures is as follows. According to the chemical composition, the slab is refined by the conventional method, and the slab obtained by the refinement is further processed by heating, rough rolling, finish rolling, laminar cooling and coiling in sequence. The specific processing process is that the heating temperature is 1210℃, the heating time is 250 minutes, and 6 passes of rough rolling are performed, of which the deformation of each pass is 18% or more, and the thickness of the intermediate slab is 54mm. 7 passes of finish rolling are performed, of which the frame reduction ratios of the last 3 passes are ≥17%, ≥13% and ≥10%, respectively, and the rolling start temperature of the finish rolling is 1010~1030℃, and the final rolling temperature is 860~870℃. The pre-cooling mode is adopted to cool to the target coiling temperature, of which the cooling speed is about 65℃/s and the coiling temperature is 660~690℃. The metal microstructure is uniform polygonal ferrite + pearlite, with a volume fraction of ferrite of 78% and a volume fraction of pearlite of 22%.

Example 3

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

The manufacturing method of V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures is as follows. According to the chemical composition, the slab is refined by the conventional method, and the slab obtained by the refinement is further processed by heating, rough rolling, finish rolling, laminar cooling and coiling in sequence. The specific processing process is that the heating temperature is 1185℃, the heating time is 235 minutes, and 6 passes of rough rolling are performed, of which the deformation of each pass is 18% or more, and the thickness of the intermediate slab is 56mm. 7 passes of finish rolling are performed, of which the frame reduction ratios of the last 3 passes are ≥17%, ≥13% and ≥10%, respectively, and the rolling start temperature of the finish rolling is 1010~1030℃, and the final rolling temperature is 850~870℃. The pre-cooling mode is adopted to cool to the target coiling temperature, of which the cooling speed is about 50℃/s and the coiling temperature is 670~680℃. The metal microstructure is uniform polygonal ferrite + pearlite, with a volume fraction of ferrite of 80% and a volume fraction of pearlite of 20%.

Comparative Example 1

(For specific details of Comparative Example 1, refer to Example 2 of “Large Thickness Q500GJCD High-Strength Building Structural Steel Plate and Manufacturing Method Thereof” (CN107385324A))

The chemical composition of structural steel for construction is as shown in Table 1, and the remainder is Fe and unavoidable impurities.

The manufacturing method of structural steel for building construction is as follows. According to the chemical composition, the slab is smelted by the conventional method, and the slab obtained by smelting is further processed by heating, rough rolling, finish rolling, laminar cooling and coiling in sequence in a wide plate rolling mill. The specific processing process is that the heating temperature is 1200~1220℃, the heating time is 375 minutes, and the rough rolling is performed and rolled. The thickness under the atmospheric temperature is 50mm, and after the atmospheric temperature, the finish rolling is performed at the rolling start temperature of 900℃ in the finish rolling mill, and the final rolling temperature of the finish rolling is ≥796℃. After the rolling is completed, the rolled material is sent to the Acc equipment and water is sprayed to accelerate the cooling speed. The cooling speed is 6~7℃/s, and the final cooling temperature is 690~710℃. Afterwards, after being straightened by a hot straightener, it is sent to a cold room and stacked offline (non-production line) at 320℃, and then slowly cooled naturally for 24 hours.

Comparative Example 2

(For specific details of Comparative Example 2, refer to Example 2 of “High-strength Q500GJD tempered-state structural steel plate for building structures and its manufacturing method” (CN107604248A))

The chemical composition of structural steel for construction is as shown in Table 1, and the remainder is Fe and unavoidable impurities.

The manufacturing method of structural steel for building is as follows. According to the chemical composition, the slab is smelted in a conventional way, and the slab obtained by smelting is further processed by heating, rough rolling, finish rolling, laminar cooling, and coiling in a wide plate rolling mill in sequence. The specific processing process is heating temperature 1180~1220℃, heating time 220 minutes, rough rolling is performed, and the thickness is rolled to 65mm, and then sent to the finish rolling mill for finish rolling, and the final rolling temperature of the finish rolling is 795℃. After rolling is completed, the rolled material is directly sent to a hot straightening machine for straightening. After that, it is sent to a cold bed for natural cooling. The qualified plate is transferred to the heat treatment process, where the quenching temperature is 905℃, the furnace residence time is 25 minutes, and it is cooled with water. The tempering temperature is 660℃, the furnace residence time is 27 minutes, and it is cooled to room temperature by air cooling.

[Table 1] Mass percentage/wt% of chemical components of examples and comparative examples

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

[Table 2] Performance test results for examples and comparative examples

Note 1: Diameter D of the bending head, thickness a of the sample.

Note 2: For the impact test, Example 1 uses a half-size sample, and Examples 2 and 3 and Comparative Examples 1 and 2 use a full-size sample. The impact test temperature of the Example is -40°C, and the impact test temperature of Comparative Examples 1 and 2 is -20°C.

According to the manufacturing methods of the three groups of examples and the three groups of comparative examples and the chemical components in Table 1 and the performance test results of the examples and comparative examples in Table 2, in the examples, excellent atmospheric corrosion prevention performance is achieved by adding a certain amount of elements such as Si, Cr, Ni and Cu, and the V-N microalloying method exerts the effects of microcrystal strengthening and precipitation strengthening so that the product obtains excellent strength, plasticity and toughness matching, and at the same time, the tissue performance of the product is adjusted through control of the rolling and cooling processes, and the product has a low yield ratio and high yield point elongation and high high-strain low-cycle fatigue performance. Therefore, the V series 550MPa grade earthquake-resistant weather-resistant steel plate for building structures of the present invention and its manufacturing method have realized excellent atmospheric corrosion resistance and earthquake resistance and other comprehensive performance matching, and have good application prospects.

Finally, it should be noted that the above embodiments are only intended to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood that those skilled in the art may modify the technical solutions described in each of the above-mentioned embodiments or replace some or all of the technical features thereof equally, and such modifications or replacements should be understood that the essence of the technical solutions does not go beyond the scope of the technical solutions of each embodiment of the present invention.

Claims (10)

A V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures, characterized in that the chemical composition contains, by mass percentage, C: 0.07 to 0.12%, Si: 0.35 to 0.45%, Mn: 1.30 to 1.40%, P≤0.020%, S≤0.008%, Cr: 0.60 to 0.70%, Ni: 0.25 to 0.35%, Cu: 0.30 to 0.40%, V: 0.08 to 0.12%, Als: 0.015 to 0.055%, N: 0.0200 to 0.0220%, and the remainder is iron and unavoidable impurities. In the first paragraph,
The above earthquake-resistant weather-resistant steel plate for building structures is characterized by a V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures, wherein the metal microstructure is polygonal ferrite + pearlite, and the volume fraction is 75 to 80% ferrite and 20 to 25% pearlite. In the first paragraph,
The atmospheric corrosion resistance index of the earthquake-resistant weather-resistant steel plate for the above building structure is I≥6.5,
A V-series 550MPa earthquake-resistant weather-resistant steel plate for building structures, characterized in that the above earthquake-resistant weather-resistant steel plate for building structures has a yield strength of ≥550MPa, a tensile strength of ≥600MPa, an elongation at break of ≥20%, a yield ratio of ≤0.85, an elongation at yield point of Ae of ≥2.0%, a 180° bending test of D=2a, and an impact energy of full-size V-notch of -40°C of KV2 of ≥70J. In the first paragraph,
A V-series 550MPa grade earthquake-resistant weather-resistant steel plate for building structures, characterized in that the corrosion rate of the above earthquake-resistant weather-resistant steel plate for building structures with respect to Q355B is ≤ 45%, and the fatigue life in a high-strain low-cycle fatigue test with a strain amplitude range of ±2% is 200 cycles or more. In the first paragraph,
A V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures, characterized in that the thickness of the earthquake-resistant weather-resistant steel plate for building structures is 6.0 to 16.0 mm. A method for manufacturing a V-type 550 MPa grade earthquake-resistant steel plate for building structures, characterized by comprising the steps of 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 an earthquake-resistant steel plate for building structures. In Article 6,
A method for manufacturing a V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures, characterized in that in the above heating step, the heating temperature is 1180 to 1220°C and the heating time is 180 to 400 minutes. In Article 6,
In the above rough rolling step, 6 passes of rough rolling are performed, among which the deformation amount of each pass is ≥18%, and when the thickness of the finished product is 6.0 to 10.0 mm, the thickness of the intermediate billet is 48 to 52 mm, and when the thickness of the finished product is 10.0 to 16.0 mm, the thickness of the intermediate billet is 53 to 57 mm.
A method for manufacturing a V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures, characterized in that in the above-mentioned finishing rolling step, seven passes of finishing rolling are performed, among which the frame reduction ratios of the last three passes are ≥17%, ≥13%, and ≥10%, respectively, the rolling start temperature of the finishing rolling is ≤1030℃, and the final rolling temperature is 840 to 880℃. In Article 6,
A method for manufacturing a V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures, characterized in that in the laminar cooling step, a pre-stage cooling mode is adopted and the cooling speed is 40 to 80°C/s. In Article 6,
A method for manufacturing a V-type 550MPa grade earthquake-resistant weather-resistant steel plate for building structures, characterized in that in the above-mentioned coiling step, the coiling temperature is 650 to 690°C.