CN113025913A - 700MPa steel based on multi-mode sheet billet continuous casting and rolling production line and production method thereof - Google Patents
700MPa steel based on multi-mode sheet billet continuous casting and rolling production line and production 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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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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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- 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
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
Abstract
The invention provides 700MPa steel based on a multi-mode sheet billet continuous casting and rolling production line, which belongs to the technical field of steel, and comprises the following chemical components in percentage by mass: c: 0.03-0.15%, Si: less than or equal to 0.05 percent, Mn: 1.3-2.1%, Al: 0.02-0.35%, P: less than or equal to 0.010, S: not more than 0.005, Nb: 0.010-0.10%, Ti: 0.015-0.15%, V: 0.02-0.10%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities. By improving the chemical components, the production line and the preparation method of the steel, the obtained steel plate has good shape, high dimensional precision and small strength fluctuation. The invention also provides a production method of 700MPa steel based on the multi-mode thin slab continuous casting and rolling production line.
Description
Technical Field
The invention belongs to the technical field of steel, and relates to 700MPa steel based on a multi-mode sheet billet continuous casting and rolling production line and a production method thereof.
Background
Driven by the factors of 'replacing cold with heat', reducing cost, saving energy, reducing emission, shortening flow, improving efficiency and the like, the market has ever-increasing demand on high-performance thin/ultrathin hot-rolled strip steel, and the endless rolling technology has obvious effects on improving the product proportion, yield, size and shape precision and structural property uniformity of ultrathin strip steel, reducing energy consumption and roller consumption, saving energy and reducing emission. In recent years, several ESP production lines are put into production in domestic enterprises represented by Japanese steel, and common low-carbon ultrathin sheets and high-strength ultrathin hot rolled sheet products can be stably, reliably and accurately produced. The difference between the multi-mode thin slab continuous casting and rolling production line and the conventional ESP production line is that: the thickness of the plate blank is increased by 20-30mm compared with that of an ESP production line, a roller hearth type tunnel furnace is additionally arranged between the outlet of a continuous casting machine and rough rolling, the tunnel furnace comprises a fixed section and a movable section, the plate blank offline function is realized, single-blank, semi-endless and full-endless multi-mode rolling can be realized, and the product thickness range is expanded.
The high-strength steel can meet the safety and use requirements and achieve the purposes of weight reduction, energy conservation and emission reduction, becomes a new generation of environment-friendly material, is widely applied to the fields of engineering machinery, automobile manufacturing, container manufacturing and the like, and has increasingly expanded demand and good market prospect. 700 MPa-level high-strength steel is widely applied to the fields of automobile girders, automobile frames, carriages, crane booms and container carriage plates in the engineering machinery industry and the like, replaces low-strength-level products, and realizes reduction production. At present, 700 MPa-level high-strength steel is still produced by adopting a traditional hot continuous rolling production line, the traditional production line has the current situations of high production cost, long process flow, low efficiency, higher energy consumption and the like, and the traditional production line has the defects of poor plate shape, large strength fluctuation, poor dimensional precision control stability and the like in the aspect of product quality for producing 700 MPa-level high-strength steel with thin specification (1.5-4.0 mm). Therefore, the development of a new 700MPa high-strength steel production process is urgently needed.
Disclosure of Invention
In order to solve the technical problem that the precision and mechanical property of the high-strength steel with the thin specification of 700MPa produced by the traditional production line fluctuate greatly, the invention provides the 700MPa steel based on the multi-mode thin slab continuous casting and rolling production line, and the tensile strength of the obtained steel reaches above 700MPa by improving the chemical components, the production line and the preparation method of the steel, and the steel has high dimensional precision and small strength fluctuation.
The invention also provides a 700MPa steel production method based on the multi-mode sheet billet continuous casting and rolling production line, which can achieve the purposes of energy conservation, consumption reduction, environmental protection and cost reduction by using the multi-mode sheet billet continuous casting and rolling production line for production.
The invention is realized by the following technical scheme:
the 700MPa steel based on the multi-mode sheet billet continuous casting and rolling production line comprises the following chemical components in percentage by mass:
c: 0.03-0.15%, Si: less than or equal to 0.05 percent, Mn: 1.3-2.1%, Al: 0.02-0.35%, P: less than or equal to 0.010, S: not more than 0.005, Nb: 0.010-0.10%, Ti: 0.015-0.15%, V: 0.02-0.10%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities;
the metallographic structure of the steel is calculated by volume fraction as follows: 80-90% of ferrite, and the balance of pearlite;
the grain size of the ferrite is 4.0-5.2 μm;
the thickness of the steel is 1.0-12.7 mm.
A700 MPa steel production method based on a multi-mode sheet billet continuous casting and rolling production line comprises the following steps:
obtaining molten steel of 700MPa steel based on the multi-mode sheet billet continuous casting and rolling production line;
continuously casting the molten steel into a plate blank;
heating the plate blank, and then sequentially carrying out rough descaling, rough rolling, induction heating, fine descaling, finish rolling, laminar cooling, coiling and air cooling on the plate blank to obtain 700MPa steel based on the multi-mode sheet billet continuous casting and rolling production line;
the heating temperature of the slab is 1150-1200 ℃.
Further, the continuous casting speed of the molten steel is 3.5-6.5m/min, and the thickness of the plate blank is 110-123 mm.
Further, the dephosphorization pressure of the slab rough dephosphorization is more than or equal to 30 MPa.
Further, the inlet temperature of the rough rolling is more than or equal to 1150 ℃, 3-pass rolling is adopted, and the outlet temperature of the rough rolling is controlled to be 930-1000 ℃.
Further, the temperature of the induction heating outlet is controlled to be 1050-.
Further, the finish rolling is performed by any one of single billet rolling, semi-endless rolling and endless rolling;
when the single billet rolling is adopted in the finish rolling, double rows of phosphorus removal are adopted in the finish descaling, and the phosphorus removal pressure is more than or equal to 30 MPa;
when the semi-endless rolling or endless rolling is adopted for the finish rolling, the finish descaling adopts single-row dephosphorization, and the dephosphorization pressure is more than or equal to 30 MPa;
in the fine descaling, the distance from the dephosphorization nozzle to the intermediate billet is 60-110 mm.
Furthermore, the finish rolling adopts 5-pass rolling, the accumulated deformation of the finish rolling is 70-80%, and the finish rolling temperature is controlled to be 800-880 ℃.
Further, the cooling speed of the laminar cooling is more than or equal to 25 ℃/s, the coiling temperature is controlled to be 560 ℃ and 660 ℃, and the obtained steel coil is cooled to the room temperature by air.
Optionally, the molten steel is prepared by KR desulfurization, converter smelting, LF refining and VD refining in sequence.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
1. the invention relates to 700MPa steel based on a multi-mode sheet billet continuous casting and rolling production line, which is produced based on the multi-mode sheet billet continuous casting and rolling production line, the component design mainly adopts a C-Si-Mn-Nb-Ti-V component system, the strength of the material is ensured mainly by solid solution strengthening of C, Mn, fine grain strengthening of Nb and precipitation strengthening of Ti-V, the yield strength of the obtained steel is more than 640MPa, the tensile strength is more than 730MPa, the elongation is more than 20 percent, transverse cold bending D is 0a, 180 degrees is qualified, and the thickness of a steel plate can reach 1.0-12.7mm by combining the improvement of a rolling process.
2. The invention relates to a production method of 700MPa steel based on a multi-mode sheet billet continuous casting and rolling production line, which is based on the multi-mode sheet billet continuous casting and rolling production line, adopts two times of dephosphorization of rough rolling and finish rolling to ensure the surface quality of strip steel, induction heating is carried out on an intermediate billet before finish rolling to ensure that carbo-nitrides of Nb and Ti formed after rough rolling are redissolved, Nb is separated out again in the finish rolling stage to refine austenite grains and further refine ferrite grains, the precipitation amount of Ti and V microalloy elements is less in the finish rolling stage, and the C type (Ti, V and Nb) is separated out mainly in a laminar cooling process and a coiling stage to improve the strength of the material, laminar cooling is adopted after rolling, and the coiling temperature is adjusted according to different strip steel thicknesses to obtain 700MPa hot rolled strip steel with uniform performance, good steel plate type, high size precision and small strength fluctuation.
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 are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a metallographic structure diagram of a steel coil in example 3 of the present 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 embodiment of the invention provides the following general ideas:
the invention abandons the traditional hot continuous rolling production line, innovatively adopts a multi-mode thin slab continuous casting and rolling production line to produce 700MPa high-strength steel, improves the chemical components and the preparation process of the steel, obtains the steel with yield strength more than 640MPa, tensile strength more than 730MPa, elongation more than 20 percent, qualified transverse cold bending D of 0a and 180 degrees, and has good steel plate type, high dimensional precision, small strength fluctuation and controllable steel plate thickness of 1.0-12.7 mm.
Specifically, the 700MPa steel based on the multi-mode sheet billet continuous casting and rolling production line comprises the following chemical components in percentage by mass:
c: 0.03-0.15%, Si: less than or equal to 0.05 percent, Mn: 1.3-2.1%, Al: 0.02-0.35%, P: less than or equal to 0.010, S: not more than 0.005, Nb: 0.010-0.10%, Ti: 0.015-0.15%, V: 0.02-0.10%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities;
the metallographic structure of the steel is calculated by volume fraction as follows: 80-90% of ferrite, and the balance of pearlite;
the grain size of the ferrite is 4.0-5.2 μm;
the thickness of the steel is 1.0-12.7 mm.
A700 MPa steel production method based on a multi-mode sheet billet continuous casting and rolling production line comprises the following steps:
obtaining molten steel of 700MPa steel based on the multi-mode sheet billet continuous casting and rolling production line;
continuously casting the molten steel into a plate blank;
heating the plate blank, and then sequentially carrying out rough descaling, rough rolling, induction heating, fine descaling, finish rolling, laminar cooling, coiling and air cooling on the plate blank to obtain 700MPa steel based on the multi-mode sheet billet continuous casting and rolling production line;
the heating temperature of the slab is 1150-1200 ℃.
Further, the continuous casting speed of the molten steel is 3.5-6.5m/min, and the thickness of the plate blank is 110-123 mm.
Further, the dephosphorization pressure of the slab rough dephosphorization is more than or equal to 30 MPa.
Further, the inlet temperature of the rough rolling is more than or equal to 1150 ℃, 3-pass rolling is adopted, and the outlet temperature of the rough rolling is controlled to be 930-1000 ℃.
Further, the temperature of the induction heating outlet is controlled to be 1050-.
Further, the finish rolling is performed by any one of single billet rolling, semi-endless rolling and endless rolling;
when the finish rolling adopts single-billet rolling, the fine descaling adopts double-row dephosphorization, and the dephosphorization pressure is more than or equal to 30 MPa;
when the finish rolling adopts semi-endless rolling or endless rolling, the finish descaling adopts single-row dephosphorization, and the dephosphorization pressure is more than or equal to 30 MPa;
in the fine descaling, the distance from the dephosphorization nozzle to the intermediate billet is 60-110 mm.
Furthermore, the finish rolling adopts 5-pass rolling, the accumulated deformation of the finish rolling is 70-80%, and the finish rolling temperature is controlled to be 800-880 ℃.
Further, the cooling speed of the laminar cooling is more than or equal to 25 ℃/s, the coiling temperature is controlled to be 560 ℃ and 660 ℃, and the obtained steel coil is cooled to the room temperature by air.
Optionally, the molten steel is prepared by KR desulfurization, converter smelting, LF refining and VD refining in sequence.
The main alloy elements of the invention have the following functions and limited ranges:
c: carbon is the most important alloy element in steel and is one of the most economical elements for improving the strength, carbon atoms are limitedly and fixedly dissolved in gamma-Fe, a gamma phase region is enlarged, the influence on the structure and the performance is great, the strength and the hardness are mainly controlled, and the carbon and the micro alloy elements form carbonitrides to adjust the performance of the steel in a large range. The steel with too high carbon content is easy to form a banded structure in the slab smelting and rolling processes, the severe banded structure has adverse effects on the cold forming performance and the fatigue performance of the steel plate, and in addition, the C content is high, which is adverse to the welding performance of the material. If the carbon content is too low or even ultra-low, the smelting difficulty is increased. In order to meet the requirements of strength of S500MC with different thicknesses, C content is controlled as follows: 0.03 to 0.15 percent.
Si: in the invention, Si mainly influences the surface quality of hot-rolled strip steel, pickled steel plates and hot-dip galvanized strip steel, and according to the Sandlin effect, when the Si content is controlled to be below 0.05 percent, the coating structure is basically not influenced by silicon, and a bright coating with normal thickness can be obtained. In order to ensure the surface quality of the strip steel, Si is controlled to be less than or equal to 0.05 percent.
Mn: manganese and iron can be mutually replaced, and are replaced solute atoms in the iron-based solid solution, so that the Mn solid solution strengthening effect is good. Manganese, which is an austenite-forming element, also refines grains to improve strength, and expands a single austenite phase region. Manganese can lower the temperature of gamma → alpha transition obviously, so that the point A1 can be lowered, and ferrite grains can be refined. Manganese content design is primarily considered in terms of both performance requirements and production costs. In terms of production cost, manganese is the most economical alloying element for enlarging the austenite region, and meanwhile, manganese and sulfur form MnS, which is beneficial to improving the sulfide form in the test steel. However, too high manganese content as an alloying element increases the production cost of the test steel. Therefore, manganese is controlled to be 1.3 to 2.1%.
S, P and N: s, P and N elements are too high, which adversely affects the plasticity, toughness and fatigue properties of the material. The invention limits the S content to be controlled within 0.005%, the P content to be controlled within 0.015% and the N content to be controlled within 0.005%.
Nb: nb is one of key strengthening elements in HSLA steel, and has various strengthening mechanisms such as solid solution strengthening and precipitation in the thermomechanical process. The solid solution of Nb can obviously improve the dynamic recrystallization temperature of steel, thereby promoting the generation of deformation induced ferrite and precipitation through non-zone rolling; the dispersed precipitates of Nb can strengthen the matrix through the dragging effect on dislocation, and also can refine grains through the pinning effect on grain boundaries, thereby improving the strength of the steel. In addition, Nb can also ensure the refinement of weld joint structure and improve the strength after welding. Considering the cost factor, the production cost of the material is increased due to the excessively high Nb content, and Nb is controlled to be 0.010-0.10%.
Ti: titanium is a ferrite-forming element that expands the single austenite phase region, with a maximum solubility of 0.75% for Ti in pure gamma-Fe and a maximum solubility of about 6% for pure alpha-Fe. Ti is a strong carbonitride element that first forms TiN in the steel, the size of TiN particles being related to its precipitation process. Coarse TiN (> 0.5 μm) is a precipitated phase in the liquid state or molten steel solidification process, and cannot effectively prevent the crystal grains from growing due to coarse and sparse distribution, and does not play a role in strengthening. Fine TiN particles are precipitated after the molten steel is solidified, and the fine TiN particles are very stable and can effectively prevent austenite grains from growing large, so that the structure is refined. As the Ti content increases, TiN particles coarsen, the amount of fine TiC increases, and the precipitation strengthening effect causes the strength of the steel to be obviously improved along with the increase of the Ti content. The fine TiC precipitation in the steel is influenced by the transformation temperature, the higher the transformation temperature is, the greater the tendency of the precipitated particles to lose the coherent relationship is, and the precipitation strengthening is weakened through diffusion and growth. Therefore, at a higher Ti content, the number of non-coherent precipitates increases, and the precipitation strengthening effect is weakened. The Ti-containing second phase particles can prevent the growth of a coarse crystal area in the welding process and refine crystal grains, and the two kinds of particles jointly act to improve the welding performance of the steel.
Al: al is one of effective deoxidizing elements, and can form nitrides to refine grains. Too high Al content impairs the toughness of the steel and also deteriorates the toughness of the weld heat-affected zone.
V: v is a strong carbonitride forming element, and the strengthening effect is similar to that of Ti, but the effect is relatively small. In the welding process, V and C are combined in the cooling process of the heat affected zone to form a VC precipitated phase, the strength of the heat affected zone is improved, the heat affected zone is prevented from softening, the welding performance of the material is improved, but the low-temperature toughness of the steel is obviously deteriorated when the V content is higher, particularly the toughness of the welding heat affected zone, and the V content is controlled as follows: 0.02-0.10%.
The production process adopted by the invention has the following control key points:
based on the production of multi-mode sheet billet continuous casting and rolling production line, multi-mode sheet billet continuous casting and rolling production line compares traditional production line, has increased a roller hearth type tunnel furnace between conticaster export and the rough rolling, and the tunnel furnace includes fixed section and removal section, possesses the slab function of inserting the production line, can realize single billet, half endless and full endless multi-mode rolling, expands product thickness range.
The molten iron is subjected to KR desulfurization pretreatment and a conventional converter smelting process, and LF and VD double refining treatment is adopted to obtain molten steel with required components.
The continuous casting speed is controlled to be 3.5-6.5m/min, the thickness of the casting blank is 110-.
And phosphorus removal is carried out before rough rolling, and the phosphorus removal pressure is more than or equal to 30 MPa. The rough rolling adopts irreversible 3-pass rolling, and the temperature of the outlet of the rough rolling is controlled to be 930-1000 ℃. In order to ensure the final rolling temperature, the slab is heated by electromagnetic induction after rough rolling, and the heating outlet temperature is controlled at 1050-. The finish rolling adopts 5-pass rolling, the accumulated deformation of the finish rolling is 70-80%, and the finishing temperature is controlled to be 800-880 ℃. After rolling, laminar cooling is adopted, the coiling temperature is controlled to be 560-.
According to the rolling mode, different phosphorus removal modes are adopted before finish rolling, double-row phosphorus removal is adopted for single-billet rolling, single-row phosphorus removal is adopted for semi-endless or endless rolling, phosphorus removal pressure is larger than or equal to 30MPa, the distance between a phosphorus removal nozzle and a slab is adjusted according to the thickness of the slab, and the adjustment range is 60-110 mm.
The 700MPa hot rolled steel is produced on the basis of a multi-mode sheet billet continuous casting and rolling production line, a component design mainly adopts a C-Si-Mn-Nb-Ti-V component system, the strength of the material is guaranteed mainly by means of solid solution strengthening of C, Mn, fine grain strengthening of Nb and precipitation strengthening of Ti-V, and in the casting and rolling process, rough rolling and finish rolling are adopted for removing phosphorus twice, so that the surface quality of strip steel is guaranteed. And induction heating is carried out on the intermediate billet before finish rolling, so that carbo-nitrides of Nb and Ti formed in the rough rolling are redissolved, Nb is separated out again in the finish rolling stage, austenite grains are refined, and ferrite grains are further refined. The precipitation amount of Ti and V microalloy elements is small in the finish rolling stage, and the Ti, V and Nb microalloy elements are mainly precipitated in a (Ti, V and Nb) C form in the laminar cooling process and the coiling stage, so that the strength of the material is improved. After rolling, laminar cooling is adopted, and the coiling temperature is adjusted according to different strip steel thicknesses, so that 700MPa hot rolled strip steel with uniform performance is obtained.
The following will explain in detail a 700MPa steel based on multi-mode thin slab continuous casting and rolling production line and its production method in combination with examples, comparative examples and experimental data.
Examples
700MPa steel based on a multi-mode sheet billet continuous casting and rolling production line is prepared by the following method:
(1) performing KR desulfurization, conventional converter smelting and LF and VD furnace double refining treatment to obtain target molten steel, wherein the molten steel comprises the following chemical components in percentage by mass:
c: 0.03-0.15%, Si: less than or equal to 0.05 percent, Mn: 1.3-2.1%, Al: 0.02-0.35%, P: less than or equal to 0.010, S: not more than 0.005, Nb: 0.010-0.10%, Ti: 0.015-0.15%, V: 0.02-0.10%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities.
(2) Continuously casting the molten steel into a plate blank: the pulling speed of the plate blank is 3.5-6.5m/min, and the thickness of the plate blank is 110-123 mm.
(3) The soaking temperature of the slab in a tunnel furnace of the multi-mode sheet billet continuous casting and rolling production line is 1150-plus-1200 ℃, rough phosphorus removal is carried out before rough rolling, the phosphorus removal pressure is not less than 30MPa, the inlet temperature of the rough rolling is not less than 1150 ℃, the rough rolling adopts irreversible 3-pass rolling, and the outlet temperature of the rough rolling is controlled to 930-plus-1000 ℃.
(4) Induction heating and rough descaling are carried out before finish rolling, the temperature of an induction heating outlet is controlled to be 1050-;
when the finish rolling adopts single-billet rolling, the fine descaling adopts double-row dephosphorization, and the dephosphorization pressure is more than or equal to 30 MPa;
when the finish rolling adopts semi-endless rolling or endless rolling, the finish descaling adopts single-row dephosphorization, and the dephosphorization pressure is more than or equal to 30 MPa:
in the fine descaling, the distance between the dephosphorization nozzle and the slab is 60-110 mm.
(5) Finish rolling: the finish rolling adopts 5-pass rolling, the accumulated deformation of the finish rolling is 70-80%, the finish rolling temperature is controlled to be 880-.
The chemical compositions of the steels of the examples of the invention are shown in table 1, table 2 shows the manufacturing process of the steels of the examples of the invention, and table 3 shows the mechanical properties of the steels of the examples of the invention.
TABLE 1 thickness and chemical composition of steels of examples 1-10 and comparative examples 1-3
TABLE 2 production Process of steels of examples 1-10 and comparative examples 1-3
TABLE 3 mechanical Properties of the steels of examples 1-10 and comparative examples 1-3
As can be seen from tables 1-3: the invention adopts a multi-mode sheet billet continuous casting and rolling production line, adopts a C-Si-Mn-Nb-Ti-V component system by adjusting the chemical components of steel and improving the continuous casting and rolling process, and the obtained steel has yield strength of more than 640MPa, tensile strength of more than 730MPa, elongation of more than 20 percent, qualified transverse cold bending D of 0a and 180 degrees, good steel plate shape, high dimensional precision, small strength fluctuation and controllable steel plate thickness of 1.0-12.7 mm.
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 700MPa steel based on the multi-mode sheet billet continuous casting and rolling production line is characterized by comprising the following chemical components in percentage by mass:
c: 0.03-0.15%, Si: less than or equal to 0.05 percent, Mn: 1.3-2.1%, Al: 0.02-0.35%, P: less than or equal to 0.010, S: not more than 0.005, Nb: 0.010-0.10%, Ti: 0.015-0.15%, V: 0.02-0.10%, N: less than or equal to 0.005 percent, and the balance of Fe and inevitable impurities;
the metallographic structure of the steel is calculated by volume fraction as follows: 80-90% of ferrite, and the balance of pearlite;
the grain size of the ferrite is 4.0-5.2 m;
the thickness of the steel is 1.0-12.7 mm.
2. A production method of 700MPa steel based on multi-mode thin slab continuous casting and rolling production line according to claim 1, characterized in that the method comprises:
obtaining molten steel of 700MPa steel based on the multi-mode sheet billet continuous casting and rolling production line;
continuously casting the molten steel into a plate blank;
heating the plate blank, and then sequentially carrying out rough descaling, rough rolling, induction heating, fine descaling, finish rolling, laminar cooling, coiling and air cooling on the plate blank to obtain 700MPa steel based on the multi-mode sheet billet continuous casting and rolling production line;
the heating temperature of the slab is 1150-1200 ℃.
3. The method for producing the 700MPa steel based on the multi-mode thin slab continuous casting and rolling production line as claimed in claim 2, wherein the molten steel continuous casting speed is 3.5-6.5m/min, and the slab thickness is 110-123 mm.
4. The production method of 700MPa steel based on the multi-mode thin slab continuous casting and rolling production line according to claim 2, characterized in that the dephosphorization pressure of the crude dephosphorization is more than or equal to 30 MPa.
5. The method for producing the 700MPa steel based on the multi-mode thin slab continuous casting and rolling production line as claimed in claim 2, wherein the rough rolling inlet temperature is more than or equal to 1150 ℃, and the rough rolling outlet temperature is controlled to 930-1000 ℃ by adopting 3-pass rolling.
6. The method for producing 700MPa steel based on multi-mode thin slab continuous casting and rolling production line as claimed in claim 2, wherein the temperature of the induction heating outlet is controlled to 1050-.
7. The method for producing 700MPa steel based on the multi-mode thin slab continuous casting and rolling production line according to claim 2, wherein the finish rolling is any one of single slab rolling, semi-endless rolling and endless rolling;
when the single billet rolling is adopted in the finish rolling, double rows of phosphorus removal are adopted in the finish descaling, and the phosphorus removal pressure is more than or equal to 30 MPa;
when the semi-endless rolling or endless rolling is adopted for the finish rolling, the finish descaling adopts single-row dephosphorization, and the dephosphorization pressure is more than or equal to 30 MPa;
in the fine descaling, the distance from the dephosphorization nozzle to the intermediate billet is 60-110 mm.
8. The production method of 700MPa steel based on the multi-mode thin slab continuous casting and rolling production line as claimed in claim 2, characterized in that the finish rolling adopts 5-pass rolling, the accumulated deformation of the finish rolling is 70-80%, and the finish rolling temperature is controlled to be 800-880 ℃.
9. The method for producing 700MPa steel based on the multi-mode thin slab continuous casting and rolling production line as claimed in claim 2, wherein the cooling speed of laminar cooling is not less than 25 ℃/s, the coiling temperature is controlled to be 560 ℃ and 660 ℃, and the obtained steel coil is air-cooled to room temperature.
10. The production method of 700MPa steel based on the multi-mode thin slab continuous casting and rolling production line of claim 2, characterized in that the molten steel is prepared by KR desulfurization, converter smelting, LF refining and VD refining in sequence.
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Application publication date: 20210625 |