CN115354220B - Low-cost high-performance low-carbon bainitic steel and production method thereof - Google Patents

Low-cost high-performance low-carbon bainitic steel and production method thereof Download PDF

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CN115354220B
CN115354220B CN202210873048.8A CN202210873048A CN115354220B CN 115354220 B CN115354220 B CN 115354220B CN 202210873048 A CN202210873048 A CN 202210873048A CN 115354220 B CN115354220 B CN 115354220B
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steel
cost high
rolling
carbon
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CN115354220A (en
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韩承良
周德光
董占斌
问川
黄乐庆
王根矶
于文飞
王彦锋
杨永达
狄国标
冯伟
王庆敏
田鹏
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Shougang Group Co Ltd
Shougang Jingtang United Iron and Steel Co Ltd
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Shougang Group Co Ltd
Shougang Jingtang United Iron and Steel Co Ltd
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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
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • 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
    • C21D2211/002—Bainite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention particularly relates to low-cost high-performance low-carbon bainite steel and a production method thereof, which belong to the technical field of steel preparation, and the chemical components of the steel comprise the following components in percentage by mass: c:0.04 to 0.06 percent, 0.35 to 0.45 percent of Si, mn:1.52% -1.6%, alt:0.02% -0.05%, nb:0.04% -0.06%, ti:0.010% -0.02%, cr:0.4% -0.5%, P is less than 0.012%, S is less than 0.002%, and the balance is Fe and residual elements; the hardenability of the steel plate is improved by adding more Cr elements, the tensile strength of the steel plate is improved, the yield ratio is reduced, and the cost is greatly reduced compared with the cost of adding Ni and Mo elements. Meanwhile, more Si element is added, and the strength is improved by adopting low-cost elements.

Description

Low-cost high-performance low-carbon bainitic steel and production method thereof
Technical Field
The invention belongs to the technical field of steel preparation, and particularly relates to low-cost high-performance low-carbon bainite steel and a production method thereof.
Background
The high-strength steel is widely applied to the fields of engineering machinery, coal mine machinery, steel structures and the like. Along with the upgrading of the manufacturing industry in China, the requirement of high-strength steel is continuously increased, and higher requirements are put on the quality of the high-strength steel. In order to improve the strength, the traditional high-strength steel is produced by adopting a controlled rolling or tempering process, has poor impact toughness, plasticity and weldability and is high in energy consumption.
The TMCP low-carbon bainite can enable the steel plate to have high strength, high toughness and good weldability, shortens the process flow and reduces the energy consumption. The composition design and process control of the low-carbon bainite steel obviously influence the type of phase change products, the proportion of each phase and the tissue refinement degree, finally determine the mechanical properties of the steel plate, and research on TMCP+tempering process low-cost high-performance bainite steel has great significance in promoting the upgrading and green manufacturing of high-strength steel products.
Disclosure of Invention
The invention aims to provide low-cost high-performance low-carbon bainitic steel and a production method thereof, so as to solve the problem that the current strength and other performances are not compatible.
The embodiment of the invention provides low-cost high-performance low-carbon bainite steel, which comprises the following chemical components in percentage by mass:
c:0.04 to 0.06 percent, 0.35 to 0.45 percent of Si, mn:1.52% -1.6%, alt:0.02% -0.05%, nb:0.04% -0.06%, ti:0.010% -0.02%, cr:0.4% -0.5%, P < 0.012%, S < 0.002%, and the balance of Fe and residual elements.
Optionally, the chemical composition of the steel comprises, in mass fraction:
c:0.045% -0.055%, si 0.38% -0.42%, mn:1.54% -1.58%, alt:0.03% -0.04%, nb:0.045% -0.055%, ti:0.013% -0.017%, cr:0.43% -0.47%, P < 0.012%, S < 0.002%, and the balance of Fe and residual elements.
Optionally, the steel has a CEV of 0.42% or less.
Optionally, pcm of the steel is less than or equal to 0.18%.
Based on the same inventive concept, the embodiment of the invention also provides a production method of the low-cost high-performance low-carbon bainitic steel, which comprises the following steps:
pretreating molten iron, and then smelting in a converter to obtain converter molten steel;
refining the converter molten steel to obtain refined molten steel;
continuously casting the refined molten steel to obtain a casting blank;
heating the casting blank to obtain a heated blank;
rolling the heating blank, and then cooling to obtain a steel plate;
tempering the steel plate to obtain the low-cost high-performance low-carbon bainite steel.
Optionally, the center segregation of the casting blank is lower than class C1.0.
Optionally, the heating temperature is 1150-1190 ℃, and the heating time is 200-500 min.
Optionally, the rolling adopts a two-stage rolling control process, the initial rolling temperature of rough rolling of the two-stage rolling control process is 1050-1100 ℃, the maximum rolling reduction of the rough rolling of the two-stage rolling control process is more than or equal to 20%, the initial rolling temperature of finish rolling of the two-stage rolling control process is 860-900 ℃, and the final rolling temperature of finish rolling of the two-stage rolling control process is 820-860 ℃.
Optionally, the final cooling temperature of the cooling is 300 ℃ to 380 ℃, and the cooling speed is 25 ℃/s to 40 ℃/s.
Optionally, the tempering temperature is 450-550 ℃, and the tempering furnace time t and the thickness d of the low-cost high-performance low-carbon bainitic steel satisfy the following relation: t=3.5d, where t is in minutes and d is in millimeters.
One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:
according to the low-cost high-performance low-carbon bainite steel provided by the embodiment of the invention, the hardenability of the steel plate is improved by adding more Cr elements, the tensile strength of the steel plate is improved, the yield ratio is reduced, and the cost is greatly reduced compared with that of adding Ni and Mo elements. Meanwhile, more Si element is added, and the strength is improved by adopting low-cost elements.
The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present invention more readily apparent.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a rolling schedule diagram provided in example 1 of the present invention;
FIG. 2 is a metallographic structure diagram provided in example 1 of the present invention;
FIG. 3 is a rolling schedule diagram provided in example 2 of the present invention;
FIG. 4 is a metallographic structure diagram provided in example 2 of the present invention;
FIG. 5 is a rolling schedule diagram provided in example 3 of the present invention;
FIG. 6 is a metallographic structure diagram of the invention according to example 3;
fig. 7 is a flowchart of a method provided by an embodiment of the present invention.
Detailed Description
The advantages and various effects of the present invention will be more clearly apparent from the following detailed description and examples. It will be understood by those skilled in the art that these specific embodiments and examples are intended to illustrate the invention, not to limit the invention.
Throughout the specification, unless specifically indicated otherwise, the terms used herein should be understood as meaning 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. In case of conflict, the present specification will control.
Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or may be prepared by existing methods.
The technical scheme of the embodiment of the application aims to solve the technical problems, and the overall thought is as follows:
according to an exemplary embodiment of the present invention, there is provided a steel comprising, in mass fraction:
c:0.04 to 0.06 percent, 0.35 to 0.45 percent of Si, mn:1.52% -1.6%, alt:0.02% -0.05%, nb:0.04% -0.06%, ti:0.010% -0.02%, cr:0.4% -0.5%, P < 0.012%, S < 0.002%, and the balance of Fe and residual elements.
The C content is controlled to be 0.04-0.06%, so that the steel plate can be ensured to have good low-temperature toughness and weldability.
The Nb content is controlled to be 0.04-0.06%, and compared with the prior art, more Nb is added, so that the structure can be thinned, and the generation of proeutectoid ferrite is avoided.
The Cr content is controlled to be 0.4-0.5%, compared with the prior art, more Cr elements are added, the hardenability of the steel plate is improved, MA structure is refined, tensile strength of the steel plate is improved, noble metals such as Ni, mo and the like are avoided, and cost is reduced.
The Si content is controlled to be 0.35-0.45%, more Si elements are added compared with the prior art, the strength is improved, the cost is reduced, and the metal mobility of a weld pool is improved.
In some embodiments, the chemical composition of the steel comprises, in mass fractions:
c:0.045% -0.055%, si 0.38% -0.42%, mn:1.54% -1.58%, alt:0.03% -0.04%, nb:0.045% -0.055%, ti:0.013% -0.017%, cr:0.43% -0.47%, P < 0.012%, S < 0.002%, and the balance of Fe and residual elements.
In some embodiments, the steel has a CEV of 0.42%; the Pcm of the steel is less than or equal to 0.18 percent.
According to another exemplary embodiment of the present invention, there is provided a method for producing a low cost high performance low carbon bainitic steel as described above, the method comprising:
s1, preprocessing molten iron, and then smelting in a converter to obtain converter molten steel;
specifically, in the embodiment, KR S removal and converter smelting are adopted, and converter molten steel is obtained through top-bottom combined blowing.
S2, refining the converter molten steel to obtain refined molten steel;
specifically, in this example, the converter molten steel was vacuum-treated by using an LF furnace and a VD furnace, and the contents of harmful gases such as O and H and P, S were reduced.
S3, continuously casting the refined molten steel to obtain a casting blank;
in some embodiments, the center segregation of the cast slab is less than class C1.0.
Specifically, in the embodiment, a continuous casting blank is designed, the thickness specification is 200mm-400mm, and the compression ratio is increased; the width is 1800-2400 mm, the reduction of the longitudinal rolling pass is increased, and the core performance of the steel plate is improved; and controlling the center segregation of the casting blank to be lower than class C1.0.
S4, heating the casting blank to obtain a heated blank;
in some embodiments, the temperature of heating is 1150 ℃ to 1190 ℃ and the time of heating is 200min to 500min.
Specifically, in this embodiment, the steel billet is cold-charged into the furnace, and the steel billet is heated at 1150-1190 ℃ for 200-500 min, so as to control the growth of the prior austenite grains and make Nb fully solid-dissolved.
S5, rolling the heating blank, and cooling to obtain a steel plate;
in some embodiments, the rolling employs a two-stage controlled rolling process, wherein the initial rolling temperature of rough rolling of the two-stage controlled rolling process is 1050-1100 ℃, the maximum rolling reduction of rough rolling of the two-stage controlled rolling process is more than or equal to 20%, the initial rolling temperature of finish rolling of the two-stage controlled rolling process is 860-900 ℃, and the final rolling temperature of finish rolling of the two-stage controlled rolling process is 820-860 ℃.
In some embodiments, the cooling is at a final cooling temperature of 300 ℃ to 380 ℃ and at a rate of 25 ℃/s to 40 ℃/s.
Specifically, in the embodiment, a two-stage controlled rolling process is adopted for rolling, the initial rolling temperature of rough rolling is 1050-1100 ℃, the maximum rolling reduction rate of rough rolling is defined to be more than or equal to 20%, grains are fully refined through recrystallization, and the structure is homogenized. After rough rolling, the thickness of the billet to be heated is 3.0 times of the thickness (mm) of the finished product, the initial rolling temperature of finish rolling is 860 ℃ to 900 ℃, and the final rolling temperature is 820 ℃ to 860 ℃. The austenite grains are fully flattened by adopting a large waiting temperature thickness so as to refine the structure, the finishing temperature is increased, the load of the rolling mill is reduced, and the generation of proeutectoid ferrite before water entering is avoided. The cooling adopts water cooling, the final cooling temperature and the cooling speed of laminar flow cooling are strictly controlled by the water cooling, the final cooling temperature is 300-380 ℃, the cooling speed is 25 ℃/s-40 ℃/s, the low final cooling and the large cooling speed are adopted, the generation of a fine bainitic structure is ensured, and the high strength and the high toughness are realized.
S6, tempering the steel plate to obtain the low-cost high-performance low-carbon bainitic steel.
In some embodiments, the tempering temperature is 450-550 ℃, the tempering at furnace time t and the thickness d of the low cost high performance low carbon bainitic steel satisfy the following relationship: t=3.5d, where t is in minutes and d is in millimeters.
Specifically, in this embodiment, the tempering process is strictly controlled. Tempering at 500 deg.c for 3.5 times the thickness of the product, and the tempering process has tissue stabilizing treatment and eliminating stress.
The low cost high performance low carbon bainitic steels of the present application and the method of producing the same will be described in detail with reference to examples, comparative examples and experimental data.
Example 1
The TMCP+tempering process has the advantages that the thickness of the low-cost low-carbon bainite high-strength steel plate is 20mm, and the chemical components are as follows in percentage by mass: c:0.052, si:0.40, mn:1.56, alt:0.032, nb:0.055, ti:0.014, cr:0.45, P:0.0060, S:0.0017, the balance being Fe and residual elements, CEV:0.41, pcm:0.17.
the preparation method comprises the following steps:
s1, preprocessing molten iron, and then smelting in a converter to obtain converter molten steel;
s2, refining the converter molten steel to obtain refined molten steel;
s3, continuously casting the refined molten steel to obtain a casting blank;
s4, heating the casting blank to obtain a heated blank;
s5, rolling the heating blank, and cooling to obtain a steel plate;
s6, tempering the steel plate to obtain the low-cost high-performance low-carbon bainitic steel.
In the preparation process of the embodiment, specific parameter values are as follows: the slab size was 200×1850×3500 (mm), and the steel sheet size was 20×2700×21500 (mm). The center segregation of the casting blank is C class 0.5. The heating temperature is 1178 ℃, the furnace time is 267min, the two-stage controlled rolling is carried out on the two frames, the finish rolling start temperature is 892 ℃, the finish rolling temperature is 851 ℃, the thickness is 60mm, the finish cooling temperature is 367 ℃, the cooling speed is 38 ℃/S, the tempering temperature is 500 ℃, and the furnace time is 70min, and the rolling schedule is shown in figure 1.
Example 2
The TMCP+tempering process has the advantages that the thickness of the low-cost low-carbon bainite high-strength steel plate is 30mm, and the chemical components are as follows in percentage by mass: c:0.053, si:0.42, mn:1.55, alt:0.027, nb:0.052, ti:0.016, cr:0.46, P:0.0075, S:0.0016, the balance being Fe and residual elements, CEV:0.41, pcm:0.17.
the preparation method comprises the following steps:
s1, preprocessing molten iron, and then smelting in a converter to obtain converter molten steel;
s2, refining the converter molten steel to obtain refined molten steel;
s3, continuously casting the refined molten steel to obtain a casting blank;
s4, heating the casting blank to obtain a heated blank;
s5, rolling the heating blank, and cooling to obtain a steel plate;
s6, tempering the steel plate to obtain the low-cost high-performance low-carbon bainitic steel.
In the preparation process of the embodiment, specific parameter values are as follows: the slab size was 300×2000×2700 (mm), and the steel sheet size was 30×2530×19200 (mm). The center segregation of the casting blank is C class 0.5. The heating temperature is 1182 ℃, the furnace time is 316min, the two-stage controlled rolling is carried out on the double frames, the finish rolling start temperature is 881 ℃, the finish rolling temperature is 841 ℃, the thickness is 90mm, the finish cooling temperature is 350 ℃, the cooling speed is 33 ℃/S, the tempering temperature is 500 ℃, and the furnace time is 105min, and the rolling schedule is shown in figure 3.
Example 3
The TMCP+tempering process has the advantages that the thickness of the low-cost low-carbon bainite high-strength steel plate is 40mm, and the chemical components are as follows in percentage by mass: c:0.057, si:0.41, mn:1.58, alt:0.035, nb:0.056, ti:0.018, cr:0.48, P:0.0080, S:0.0013, the balance being Fe and residual elements, CEV:0.42, pcm:0.18.
the preparation method comprises the following steps:
s1, preprocessing molten iron, and then smelting in a converter to obtain converter molten steel;
s2, refining the converter molten steel to obtain refined molten steel;
s3, continuously casting the refined molten steel to obtain a casting blank;
s4, heating the casting blank to obtain a heated blank;
s5, rolling the heating blank, and cooling to obtain a steel plate;
s6, tempering the steel plate to obtain the low-cost high-performance low-carbon bainitic steel.
In the preparation process of the embodiment, specific parameter values are as follows: the slab size was 300×1620×3700 (mm), and the steel sheet size was 40×2400×16800 (mm). The center segregation of the casting blank is C class 0.5. The heating temperature is 1168 ℃, the furnace time is 307min, the two-stage controlled rolling is carried out on the double frames, the finish rolling start temperature is 865 ℃, the finish rolling temperature is 835 ℃, the thickness is 120mm when the temperature is up to 120mm, the finish cooling temperature is 316 ℃, the cooling speed is 29 ℃/S, the tempering temperature is 500 ℃, and the furnace time is 140min, and the rolling schedule is shown in figure 5.
Experimental example
The steels prepared in examples 1 to 3 were subjected to performance tests, and the test results are shown in the following table.
As can be obtained from the table above, the yield strength of the steel prepared by the method is more than or equal to 500MPa, the tensile strength is more than or equal to 630MPa, the yield ratio is less than or equal to 0.80, and the impact energy at minus 60 ℃ is more than or equal to 300J. The low-carbon bainite high-strength steel is low in cost, high in efficiency and stable in production, and has higher strength, low yield ratio, good low-temperature toughness and weldability.
One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:
(1) Compared with the controlled rolling and tempering process, the method provided by the embodiment of the invention adopts the TMCP+tempering process to produce the low-carbon bainite high-strength steel, and the steel plate simultaneously meets the requirements of high strength, low yield ratio, excellent low-temperature toughness and weldability, and saves more energy sources;
(2) The method provided by the embodiment of the invention adopts a large temperature-waiting thickness and high finish rolling process, reduces the load of a rolling mill, and refines the structure of the steel plate at the same time;
(3) The method provided by the embodiment of the invention adopts a strong water cooling process to completely convert the steel plate into a fine bainitic structure, thereby improving the strength and low-temperature toughness of the steel plate;
(4) According to the method provided by the embodiment of the invention, the steel plate structure is stabilized and stress is eliminated by tempering;
(5) The method provided by the embodiment of the invention realizes low-cost, high-efficiency and stable production of the low-carbon bainite high-strength steel under the designed process conditions, and has higher strength, low yield ratio, good low-temperature toughness and weldability. The yield strength is more than or equal to 500MPa, the tensile strength is more than or equal to 630MPa, the yield ratio is less than or equal to 0.80, and the impact energy at minus 60 ℃ is more than or equal to 300J;
(6) The steel provided by the embodiment of the invention has the advantages that more Cr elements are added, so that the hardenability of the steel plate is improved, the tensile strength of the steel plate is improved, the yield ratio is reduced, and the cost is greatly reduced compared with the cost of adding Ni and Mo elements. Meanwhile, more Si element is added, and the strength is improved by adopting low-cost elements.
Finally, it is also 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. It is therefore intended that the following claims be interpreted as including the 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 modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims (7)

1. A low cost high performance low carbon bainitic steel characterized in that the steel comprises the chemical components in mass fraction:
c:0.045% -0.055%, si 0.38% -0.42%, mn:1.54% -1.58%, alt:0.03% -0.04%, nb:0.045% -0.055%, ti:0.013% -0.017%, cr:0.43% -0.47%, P < 0.012%, S < 0.002%, and the balance Fe and residual elements, wherein CEV of the steel is less than or equal to 0.42%, pcm of the steel is less than or equal to 0.18%, yield strength of the low-carbon bainite steel is more than or equal to 500MPa, tensile strength is more than or equal to 630MPa, yield ratio is less than or equal to 0.80, impact energy at minus 60 ℃ is more than or equal to 300J, the low-carbon bainite steel is prepared by adopting TMCP+ tempering process, tempering temperature is 450 ℃ -550 ℃, and tempering furnace time t and thickness d of the low-cost high-performance low-carbon bainite steel satisfy the following relation: t=3.5d, where t is in minutes and d is in millimeters.
2. A method of producing a low cost high performance low carbon bainitic steel according to claim 1, comprising:
pretreating molten iron, and then smelting in a converter to obtain converter molten steel;
refining the converter molten steel to obtain refined molten steel;
continuously casting the refined molten steel to obtain a casting blank;
heating the casting blank to obtain a heated blank;
rolling the heating blank, and then cooling to obtain a steel plate;
tempering the steel plate to obtain the low-cost high-performance low-carbon bainite steel.
3. The method for producing a low-cost high-performance low-carbon bainitic steel according to claim 2, wherein the center segregation of the cast slab is lower than 1.0 of C-type.
4. The method for producing a low cost high performance low carbon bainitic steel according to claim 2, wherein the heating temperature is 1150-1190 ℃ and the heating time is 200-500 min.
5. The method for producing low-cost high-performance low-carbon bainitic steel according to claim 2, wherein the rolling adopts a two-stage controlled rolling process, the rough rolling start temperature of the two-stage controlled rolling process is 1050-1100 ℃, the finish rolling start temperature of the two-stage controlled rolling process is 860-900 ℃, and the finish rolling finish temperature of the two-stage controlled rolling process is 820-860 ℃.
6. The method of producing a low cost high performance low carbon bainitic steel according to claim 2, wherein the cooling is carried out at a final cooling temperature of 300 ℃ to 380 ℃ and at a rate of 25 ℃/s to 40 ℃/s.
7. The method of producing a low cost high performance low carbon bainitic steel according to claim 2, wherein the tempering temperature is 450-550 ℃, and the tempering in-furnace time t and the thickness d of the low cost high performance low carbon bainitic steel satisfy the following relationship: t=3.5d, where t is in minutes and d is in millimeters.
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