CN111519097A - 460 MPa-level structural steel and preparation method thereof - Google Patents
460 MPa-level structural steel and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Abstract
The invention discloses 460MPa structural steel and a preparation method thereof, wherein the structural steel comprises the following chemical components in percentage by mass, C is less than or equal to 0.20%, and Si: 0.20 to 0.50%, Mn: 1.00-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.020-0.05%, Nb is less than or equal to 0.050%, Ti is less than or equal to 0.030%, and Cr: 0.10 to 0.40%, Ni: 0.10-0.60%, Mo: 0.1-0.40%, and the balance of Fe and inevitable impurities. By adopting the method, the prepared structural steel has high strength, high plasticity, low yield ratio and stable mechanical property, and simultaneously improves the rolling efficiency and diversifies the production specifications.
Description
Technical Field
The invention belongs to the technical field of steel rolling, and particularly relates to 460MPa structural steel and a preparation method thereof.
Background
Structural steels are commonly used for load bearing applications, where strength of the structural steel is an important design criterion in the application. In recent years, the field of steel structures such as steel bridges, ships, wind power towers, high-rise buildings and the like in China is developed rapidly, the structural steel with high strength, high plasticity and low yield ratio is favorable for improving the overall safety reserve of the steel structure, and the steel structure bearing static load and dynamic load periodically is favorable for maintainers to find defects and repair the defects in time, so that the domestic market has urgent needs for the structural steel with high strength, high plasticity and low yield ratio.
At present, structural steel with high strength, high plasticity and low yield ratio is mostly produced in a temperature waiting mode after rolling, and the production mode enables a steel plate after finish rolling to stay on a line or swing on the line because of a unique temperature waiting process, and isothermal reduction is carried out to a design value and then cooling is carried out, so that the structural steel has large fluctuation of strength, plasticity and yield ratio and unstable performance.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides 460MPa structural steel and a preparation method thereof, and solves the problem of large performance fluctuation of structural steel with high strength, high plasticity and low yield ratio in the prior art on the basis of diversified production specifications.
The invention realizes the purpose through the following technical scheme:
on one hand, the invention provides 460MPa structural steel which comprises the following chemical components in percentage by mass, C is less than or equal to 0.20%, and Si: 0.20 to 0.50%, Mn: 1.00-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.02-0.05%, Nb is less than or equal to 0.050%, Ti is less than or equal to 0.030%, and Cr: 0.10 to 0.40%, Ni: 0.10-0.60%, Mo: 0.10-0.40%, and the balance of Fe and inevitable impurities.
Further, the microstructure of the structural steel comprises ferrite and pearlite, the volume fraction of the ferrite is 80-90%, the volume fraction of the pearlite is 10-20%, and the ferrite comprises acicular ferrite and polygonal ferrite.
Further, the cold crack sensitivity index of the structural steel is less than or equal to 0.30.
Further, the thickness of the structural steel is 20-100 mm.
On the other hand, the invention also provides a preparation method of the 460MPa structural steel, which comprises the following steps,
continuously casting the smelted molten steel to obtain a plate blank; the slab comprises the following chemical components in percentage by mass, wherein C is less than or equal to 0.20%, Si: 0.20 to 0.50%, Mn: 1.00-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.02-0.05%, Nb is less than or equal to 0.050%, Ti is less than or equal to 0.030%, and Cr: 0.10 to 0.40%, Ni: 0.10-0.60%, Mo: 0.10-0.40%, and the balance of Fe and inevitable impurities;
and sequentially heating, rough rolling, finish rolling and water cooling the plate blank to obtain the structural steel.
Further, the thickness of slab is 150 ~ 400mm, the width of slab is 1600 ~ 2400 mm.
Further, the heating temperature is 1200-1300 ℃, and the heating time is 200-400 min.
Further, the rough rolling starting temperature is 1100-1200 ℃, the thickness of the rough rolled plate blank is 2t, wherein t is the thickness of the structural steel.
Further, the finish rolling starting temperature is 1000-1100 ℃, and the finish rolling finishing temperature is 950-1050 ℃.
Further, in the water cooling, the starting temperature of the water cooling is 870-930 ℃, the cooling rate is 10-60 ℃/S, and the final cooling temperature is 650-750 ℃.
The beneficial effects of the invention at least comprise:
the invention provides 460MPa structural steel and a preparation method thereof, wherein the structural steel comprises the following chemical components in percentage by mass, C is less than or equal to 0.20%, and Si: 0.20 to 0.50%, Mn: 1.00-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.02-0.05%, Nb is less than or equal to 0.050%, Ti is less than or equal to 0.030%, and Cr: 0.10 to 0.40%, Ni: 0.10-0.60%, Mo: 0.10-0.40%, and the balance of Fe and inevitable impurities. According to the method, the fine-grain strengthening and precipitation strengthening are realized through the low-carbon Nb and Ti added component design, so that the strength of the structural steel is improved, and the hardenability of the structural steel is improved by adding alloy elements such as Ni, Cr and Mo, so that the strength of the structural steel is improved; the method is matched with a direct rolling process to control the tissue types and contents of ferrite and pearlite, the ferrite is used as a soft phase and can control the yield strength and improve the elongation, the pearlite is used as a hard phase and can improve the tensile strength of the structural steel, and the stable control of high strength, high plasticity and low yield ratio is realized by controlling the proportion of a ferrite phase and a pearlite phase through the process.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a metallographic structure of a structural steel of 20mm thickness according to example 1 of the present invention at a thickness of 1/4;
FIG. 2 is a metallographic structure of a structural steel of 20mm thickness according to example 1 of the present invention at a thickness of 1/2;
FIG. 3 is a metallographic structure of a structural steel of 70mm thickness at a thickness of 1/4 according to example 2 of the present invention;
FIG. 4 is a metallographic structure of a structural steel of 70mm thickness at a thickness of 1/2 according to example 2 of the present invention;
FIG. 5 is a process step diagram of a preparation method of 460MPa structural steel according to an embodiment of the invention.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
In order to solve the technical problems, the technical scheme in the embodiment of the invention has the following general idea:
on one hand, the invention provides 460MPa structural steel which comprises the following chemical components in percentage by mass, C is less than or equal to 0.20%, and Si: 0.20 to 0.50%, Mn: 1.00-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.02-0.05%, Nb is less than or equal to 0.050%, Ti is less than or equal to 0.030%, and Cr: 0.10 to 0.40%, Ni: 0.10-0.60%, Mo: 0.10-0.40%, and the balance of Fe and inevitable impurities.
C: the content of C element has great influence on the mechanics and welding performance of steel. At the same temperature, the C content is increased, the C atoms to be migrated for the diffusion-controlled interface movement are increased, and the diffusion-type transformation such as ferrite and pearlite transformation is suppressed. If the C content is too high, the growth of the end faces of the bainite precipitation phase controlled by diffusion in a lamellar state is further suppressed, and a martensite phase is formed during cooling. The martensite phase is hard and brittle and its low temperature impact properties are poor. In the invention, proper C is added, polygonal ferrite and pearlite are obtained through proper diffusion type phase transformation, and martensite is not formed in the cooling process, so that the content of C in the invention is controlled to be less than or equal to 0.20%.
Si: si does not form carbide with C, exists in the steel in a solid solution mode, and impedes dislocation movement through interaction with a stress field of dislocation, so that the strength of the steel plate is improved. According to a calculation formula of welding crack sensitivity, when the content of Si is higher, the welding performance of steel is not good, so that the content of Si in the invention is controlled to be 0.20-0.50%.
Mn: mn is an austenite forming element, and expands an austenite phase region. During cooling, Mn dissipates free energy through solute drag, inhibiting diffusion-type phase transitions. By adding a proper amount of Mn, the microstructure of the steel plate can be controlled under proper process conditions, and a refined bainite lath structure with high strength and high toughness is formed. An excessively high Mn content may cause cracks in the steel slab during continuous casting and subsequent cooling. The Mn content in the invention is controlled to be 1.00-1.60%.
Nb: nb is added into the steel, and through the inhibition effect on single-phase (austenite) interface motion in the recrystallization process, on one hand, the recrystallization temperature is improved, the second-stage rolling efficiency of the steel plate is improved, and on the other hand, austenite recrystallization grains are refined, so that the final structure is refined. Nb and C, N form MX-type carbides, and fine carbides formed during rolling hinder the movement of grain boundaries by pinning to refine austenite grains. The Nb content in the invention is controlled to be less than or equal to 0.050%.
Al: al increases the phase change driving force, Al interacts with N in the steel to form fine and dispersed AlN precipitation, and can inhibit the growth of crystal grains, thereby achieving the purposes of refining the crystal grains and improving the toughness of the steel at low temperature. The Al content in the invention is controlled to be 0.020-0.05%.
Ti: ti element shrinks austenite phase area, Ti can form TiN with N in steel, and form fine TiC or Ti carbosulfide with C, S in steel, and fine Ti carbo-nitride precipitation can inhibit grain growth. Ti dissolved in austenite is fixed, and the hardenability of the steel is improved. The Ti content in the invention is controlled to be less than or equal to 0.030 percent.
Cr: cr can prevent the graphitization tendency of Mo-added steel, belongs to stable austenite elements, can greatly improve the hardenability of the steel and improve the strength of the steel, but excessively high Cr can reduce the welding performance of the steel, and the proper amount of Cr is controlled to be 0.10-0.40%.
Ni: ni plays a role of strengthening ferrite by forming simple replacement solid solution, can improve the strength of steel, is an austenite stabilizing element, can obviously improve the low-temperature impact toughness of the steel, and is controlled to be 0.10-0.60 percent.
Mo: the Mo element can improve the most effective element for improving the high-temperature strength of the steel plate, the higher the content of the Mo element is, the higher the influence on the tensile strength is than the influence on the yield strength, and the content of the Mo element is controlled to be 0.10-0.40 percent.
Further, the microstructure of the structural steel comprises ferrite and pearlite, the volume fraction of the ferrite is 80-90%, the volume fraction of the pearlite is 10-20%, and the ferrite comprises acicular ferrite and polygonal ferrite.
The ferrite of the soft phase can control the yield strength of the structural steel and improve the elongation, and the pearlite phase harder than the ferrite phase can improve the tensile strength of the structural steel, thereby reducing the yield ratio. The metallographic structure of the structural steel is shown in detail in fig. 1, 2, 3 and 4. Wherein, calculated according to fig. 1 and fig. 2, the ferrite of example 1 is 88.15% on average, and the pearlite is 11.85% on average; calculated from fig. 3 and 4, example 2 had an average ferrite of 85.15% and an average pearlite of 14.85%.
The metallographic structure of the structural steel produced by the conventional process of temperature treatment after rolling is ferrite and bainite, and the content of some martensite is small.
Further, the cold crack sensitivity index of the structural steel is less than or equal to 0.30. The cold crack sensitivity index of the structural steel is calculated by the formula of Pcm, namely C + Si/30+ Mn/20+ Ni/60+ Cr/20+ Cu/20+ Mo/15+ V/10+5B, wherein Pcm represents the cold crack sensitivity index. The cold crack sensitivity index is controlled below 0.30, so that cracks of the structural steel can be effectively prevented during welding.
Further, the thickness of the structural steel is 20-100 mm.
On the other hand, the invention also provides the preparation method of the 460MPa structural steel, fig. 5 is a process step diagram of the preparation method of the 460MPa structural steel according to the embodiment of the invention, and with reference to fig. 5, the method comprises,
and S1, continuously casting the smelted molten steel to obtain a plate blank. The slab comprises the following chemical components in percentage by mass, wherein C is less than or equal to 0.20%, Si: 0.20 to 0.50%, Mn: 1.00-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.02-0.05%, Nb is less than or equal to 0.050%, Ti is less than or equal to 0.030%, and Cr: 0.10 to 0.40%, Ni: 0.10-0.60%, Mo: 0.10-0.40%, and the balance of Fe and inevitable impurities.
Further, the thickness of slab is 150 ~ 400mm, the width of slab is 1600 ~ 2400 mm.
And S2, sequentially heating, roughly rolling, finely rolling and water cooling the plate blank to obtain the structural steel.
The slab rolling adopts a double-stand direct rolling process, the temperature is not required before finish rolling, and the diversity of rolling specifications is realized.
Further, the heating temperature is 1200-1300 ℃, and the heating time is 200-400 min.
Heating to raise the temperature of the plate blank to the temperature of a recrystallization zone, wherein the heating temperature cannot be too high, and too high can cause too much iron scale on the surface of the plate blank, serious burning loss and energy waste; the heating temperature is too low to reach the temperature of a recrystallization zone, and rolling cannot be realized.
Further, the rough rolling starting temperature is 1100-1200 ℃, the thickness of the rough rolled plate blank is 2t, wherein t is the thickness of the structural steel.
The full thickness of waiting to warm is favorable to guaranteeing the deformation of finish rolling district, creates the condition for improving the dislocation density of deformation zone. And finishing temperature of the finish rolling is 950-1050 ℃. And the phenomenon that the finish rolling temperature is too low and enters a partial recrystallization area to generate an oversize structure is avoided. The starting temperature of water cooling is 870-930 ℃, the cooling rate is 10-60 ℃/S, and the final cooling temperature is 650-750 ℃.
Further, the finish rolling starting temperature is 1000-1100 ℃, and the finish rolling finishing temperature is 950-1050 ℃.
Further, in the water cooling, the starting temperature of the water cooling is 870-930 ℃, the cooling rate is 10-60 ℃/S, and the final cooling temperature is 650-750 ℃.
The method adopts higher water cooling starting temperature, can form a pearlite structure, can obtain polygonal ferrite and acicular ferrite structures at the same time, can improve the strength and plasticity of the structural steel and reduce the yield ratio under the condition of a certain proportion of the pearlite structure and the ferrite structure, and has stable performance because the structure proportion is controlled. In the post-rolling temperature-waiting process, the temperature drop of the middle part is small, and the temperature drop of the head and the tail is large, so that the difference of the structures of the head part, the middle part and the tail part of the steel plate is large, and the performance fluctuation of the head part, the tail part and the middle part of the steel plate is large.
The invention provides 460MPa structural steel and a preparation method thereof, wherein the carbon content must be properly increased in composition, microalloy elements Nb and Ti are added, and the strength of the structural steel is improved by utilizing the fine grain strengthening and precipitation strengthening means of Nb and Ti; and proper elements such as Ni, Cr, Mo and the like are added, so that the hardenability of the components is improved, and a foundation is laid for improving the hardenability by subsequent water cooling. The B element is strictly forbidden to be added in consideration of avoiding the adverse effect of the B element on the low-temperature toughness of the structural steel. The process adopts a direct rolling process, the reduction deformation is carried out under the high temperature condition, the dislocation accumulated density is favorably reduced, the crystal grains after rolling are properly cooled, the growth of the crystal grains after rolling is inhibited, the allowance of yield strength is favorably controlled, and the condition is created for low yield ratio. Meanwhile, the higher final cooling temperature is beneficial to precipitation strengthening of Nb and Ti, the strength is improved, and a polygonal ferrite soft phase structure is obtained to improve the plasticity. The direct rolling process is adopted, so that the temperature is not required in the rolling process, the production period is greatly shortened, and the production efficiency is greatly improved; the finish rolling temperature and the final cooling temperature are higher, so that the temperature difference of the head part, the middle part and the tail part of the structural steel is favorably reduced, the trimming amount of the structural steel caused by large performance fluctuation is reduced, and the yield is improved. Under the condition of component design and process conditions, the structural steel with the thickness of 20-100 mm has excellent mechanical properties, the yield strength is more than 460MPa, the tensile strength is more than 590MPa, the yield ratio is less than 0.80, the elongation after fracture is more than 22 percent, the longitudinal impact energy at minus 20 ℃ is more than 120J, the Z-direction section shrinkage rate is more than or equal to 35 percent, and the developed structural steel has good mechanical indexes. By adopting the production process without waiting for temperature in the rolling process, the rolling period is greatly shortened, and the production efficiency is greatly improved.
The 460MPa grade structural steel and the preparation method thereof will be further described with reference to specific examples.
Examples
Examples 1 to 5 provide a 460MPa structural steel and a method for preparing the same, the method comprising,
and continuously casting the smelted molten steel to obtain a plate blank. The chemical components and mass fractions of the chemical components of the slab are shown in table 1 (the balance being Fe and unavoidable impurities). And (3) cold-charging the plate blank into a heating furnace for heating, adopting a double-frame continuous rolling, obtaining an intermediate blank after the rough rolling is finished, carrying out finish rolling on the intermediate blank, and carrying out water cooling after the rolling to obtain the structural steel.
Process control in the preparation of structural steels according to examples 1 to 5 is shown in tables 2 and 3 (balance Fe and inevitable impurities).
TABLE 1
| Numbering | C，％ | Si，％ | Mn，％ | P，％ | S，％ | Al，％ | Nb，％ | Ti，％ | Ni，％ | Cr，％ | Mo，％ | Ca，％ |
| Example 1 | 0.13 | 0.26 | 1.30 | 0.012 | 0.0020 | 0.035 | 0.035 | 0.015 | 0.15 | 0.20 | 0.15 | - |
| Example 2 | 0.15 | 0.30 | 1.25 | 0.012 | 0.0015 | 0.035 | 0.040 | 0.018 | 0.35 | 0.30 | 0.15 | - |
| Example 3 | 0.14 | 0.35 | 1.17 | 0.010 | 0.0035 | 0.038 | 0.035 | 0.019 | 0.45 | 0.25 | 0.21 | - |
| Example 4 | 0.15 | 0.48 | 1.55 | 0.013 | 0.0025 | 0.042 | 0.038 | 0.020 | 0.38 | 0.38 | 0.33 | - |
| Example 5 | 0.13 | 0.42 | 1.43 | 0.012 | 0.0022 | 0.028 | 0.042 | 0.022 | 0.52 | 0.16 | 0.29 | - |
| Comparative example 1 | 0.06 | 0.35 | 1.55 | 0.008 | 0.0015 | 0.025 | 0.038 | 0.012 | 0.20 | 0.40 | 0.15 | - |
| Comparative example 2 | 0.06 | 0.45 | 1.55 | 0.015 | 0.002 | 0.017 | 0.04 | 0.01 | - | 0.3 | - | 0.003 |
TABLE 2
TABLE 3
| Numbering | Water cooling onset temperature,. degree.C | Cooling rate, ° C/S | Final cooling temperature,. degree.C | Thickness of structural steel, mm |
| Example 1 | 875 | 52 | 720 | 20 |
| Example 2 | 912 | 25 | 670 | 70 |
| Example 3 | 890 | 30 | 680 | 50 |
| Example 4 | 905 | 20 | 670 | 80 |
| Example 5 | 920 | 18 | 655 | 100 |
TABLE 4
| Numbering | Ferrite content% | Pearlite,% | Cold crack sensitivity index |
| Example 1 | 88.15 | 11.85 | 0.23 |
| Example 2 | 85.15 | 14.85 | 0.25 |
| Example 3 | 86.23 | 13.77 | 0.24 |
| Example 4 | 83.57 | 16.43 | 0.29 |
| Example 5 | 83.62 | 16.38 | 0.25 |
Comparative example 1
Comparative example 1 provides a method for manufacturing a structural steel, wherein the structural steel is X70, the finished product thickness is 16.5mm, the structural steel is manufactured by a process of waiting for warm after rolling, the chemical components of the process are shown in table 1, and the structural steel is obtained by sequentially heating, rough rolling, finish rolling, and waiting for mild water cooling of a plate blank obtained by continuous casting. Wherein the starting temperature of finish rolling is 900 ℃, the finishing temperature is 820 ℃, the temperature is kept after rolling, the starting temperature of water cooling is 700 ℃, the finishing temperature is 300 ℃, and the water cooling rate is 25 ℃/s.
Comparative example 2
Comparative example 2 provides a 460 MPa-grade steel plate for a building structure, molten steel meeting the components in Table 1 is cast into a plate blank with the thickness of 250mm, a rolling process after rolling and waiting for warm rolling is adopted, the initial rolling temperature of the second stage is 1020 ℃, and the final rolling temperature of the second stage is 880 ℃. After the second stage rolling is finished, cooling is carried out, and the final cooling temperature is 630 ℃. The thickness of the steel plate is 10mm, the yield strength of the detected strip steel is 486MPa, the tensile strength is 595MPa, the elongation is 27 percent, and the longitudinal impact energy at 0 ℃ is 156J.
The structural steels prepared in examples 1 to 5 and comparative example 1 were sampled at the head, tail and middle portions of the steel sheets, respectively, as sample No. 1, sample No. 2 and sample No. 3, and mechanical properties were measured on the samples, and the results are shown in table 5, and the difference in properties between sample No. 1 and sample No. 2, and between sample No. 1 and sample No. 3 was calculated according to table 5, as shown in table 6.
TABLE 5
TABLE 6
According to the data in Table 6, the differences between the head and tail yield strength and the tensile strength of the samples of examples 1 to 5 are controlled within 12 MPa; the yield strength difference between the head part and the middle part is controlled within 23MPa, and the tensile strength difference is not more than 23 MPa; the elongation difference is not more than 2 percent, and the head and tail performance of the steel plate is stable.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. The 460MPa structural steel is characterized by comprising the following chemical components in percentage by mass, wherein C is less than or equal to 0.20%, and Si: 0.20 to 0.50%, Mn: 1.00-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.02-0.05%, Nb is less than or equal to 0.050%, Ti is less than or equal to 0.030%, and Cr: 0.10 to 0.40%, Ni: 0.10-0.60%, Mo: 0.10-0.40%, and the balance of Fe and inevitable impurities.
2. The 460MPa grade structural steel according to claim 1, wherein the microstructure of the structural steel includes ferrite and pearlite, the volume fraction of ferrite is 80-90%, the volume fraction of pearlite is 10-20%, and the ferrite includes acicular ferrite and polygonal ferrite.
3. The 460MPa grade structural steel according to claim 1, wherein the structural steel has a cold crack sensitivity index of 0.30 or less.
4. The 460MPa grade structural steel according to claim 1, wherein the thickness of the structural steel is 20-100 mm.
5. The preparation method of 460MPa structural steel according to any one of claims 1 to 4, wherein the method comprises,
continuously casting the smelted molten steel to obtain a plate blank; the slab comprises the following chemical components in percentage by mass, wherein C is less than or equal to 0.20%, Si: 0.20 to 0.50%, Mn: 1.00-1.60%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.020-0.05%, Nb is less than or equal to 0.050%, Ti is less than or equal to 0.030%, and Cr: 0.10 to 0.40%, Ni: 0.10-0.60%, Mo: 0.1-0.40%, and the balance of Fe and inevitable impurities;
and sequentially heating, rough rolling, finish rolling and water cooling the plate blank to obtain the structural steel.
6. The preparation method of 460MPa structural steel according to claim 5, wherein the thickness of the slab is 150-400 mm, and the width of the slab is 1600-2400 mm.
7. The preparation method of 460MPa structural steel according to claim 5, wherein the heating temperature is 1200-1300 ℃, and the heating time is 200-400 min.
8. The preparation method of 460MPa structural steel according to claim 5, wherein the rough rolling start temperature is 1100-1200 ℃, the thickness of the rough rolled slab is 2t, wherein t is the thickness of the structural steel.
9. The method for preparing 460MPa structural steel according to claim 5, wherein the finish rolling start temperature is 1000-1100 ℃, and the finish rolling end temperature is 950-1050 ℃.
10. The preparation method of 460MPa structural steel according to claim 5, wherein in the water cooling, the water cooling starting temperature is 870-930 ℃, the cooling rate is 10-60 ℃/S, and the final cooling temperature is 650-750 ℃.
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| CN116254468A (en) * | 2022-12-29 | 2023-06-13 | 莱芜钢铁集团银山型钢有限公司 | 420 MPa-grade high-toughness steel plate for wind power and preparation method thereof |
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Application publication date: 20200811 |