CN115537666A - 450 MPa-grade high-strength steel with different microstructures and preparation method thereof - Google Patents

450 MPa-grade high-strength steel with different microstructures and preparation method thereof Download PDF

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CN115537666A
CN115537666A CN202211291595.1A CN202211291595A CN115537666A CN 115537666 A CN115537666 A CN 115537666A CN 202211291595 A CN202211291595 A CN 202211291595A CN 115537666 A CN115537666 A CN 115537666A
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steel
temperature
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余灿生
郑之旺
李伟
刘庆春
郑昊青
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Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226Hot rolling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236Cold rolling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/001Ferrous alloys, e.g. steel alloys containing N
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/005Ferrite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/008Martensite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/009Pearlite

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  • Mechanical Engineering (AREA)
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  • Physics & Mathematics (AREA)
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  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

The invention discloses 450 MPa-grade high-strength steel with different microstructures and a preparation method thereof, and belongs to the technical field of cold-rolled sheet strip production. The high-strength steel comprises the following chemical components in percentage by weight: c:0.04 to 0.11%, si:0.15 to 0.45%, mn: 0.65-1.25%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, als: 0.010-0.070%, N is less than or equal to 0.0050%, and the balance of Fe and inevitable impurities. The invention prepares the high-strength steel with different microstructures by the same component, greatly optimizes the production rhythm, reduces the proportion of the joined blank, reduces the cost and is beneficial to meeting the requirements of different users.

Description

450 MPa-grade high-strength steel with different microstructures and preparation method thereof
Technical Field
The invention belongs to the technical field of cold-rolled plate strip production, and particularly relates to 450 MPa-grade high-strength steel with different microstructures and a preparation method thereof.
Background
With the continuous development of automobile lightweight technology and the continuous improvement of safety requirements of passengers, the development of high-strength steel for automobiles becomes a trend. Different parts need different microstructures to meet the requirements, the tissues are determined by chemical components and production processes, different chemical components are usually adopted for products with different microstructure types, more mixed casting blanks (unstable chemical components) can be produced in the smelting link due to different components, waste is caused, and meanwhile, the optimization of the production rhythm is not facilitated. The same or similar processes can be adopted to smoothly finish the production of the casting blank with the same components in the processes of pickling, welding and the like, and the reduction of transition materials is beneficial to reducing the cost and improving the quality. In addition, products with the same components and different microstructures can meet personalized use requirements of different users, and user satisfaction is improved. Through the inquiry of related patent applications, the patent applications which are similar to 450MPa grade high-strength steel with different microstructures prepared by the same components are as follows:
CN 104233068A discloses a hot-dip galvanized high-strength steel with tensile strength of 440MPa for an internal structural member of a car and a production method thereof, wherein the hot-dip galvanized high-strength steel comprises the following chemical components in percentage by mass: 0.0036-0.0049%, si is less than or equal to 0.020%, mn:1.55 to 1.75%, P: 0.078-0.095%, S is less than or equal to 0.003%, als:0.015 to 0.03%, nb:0.015 to 0.035%, ti: 0.025-0.035%, B:0.0010 to 0.0014 percent, less than or equal to 0.003 percent of N, and the balance of Fe and inevitable impurities; the hot-galvanized high-strength steel with the tensile strength of more than 440MPa is obtained by final rolling at 920-940 ℃, coiling at 580-600 ℃ and annealing at 810-830 ℃. The plasticity is improved by adopting extremely low C content, but the alloy cost is obviously increased by adding Mn, nb, ti, B and the like, and meanwhile, the P reinforcement is not beneficial to obtaining good plasticity and toughness.
CN 105369135A discloses a 450MPa class galvanized dual-phase steel for a car and a production method thereof, wherein the steel comprises the following chemical components in percentage by weight: c: 0.04-0.09%, si is less than or equal to 0.01%, mn: 1.0-2.0%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, als:0.01 to 0.08%, mo:0.01 to 0.30%, cr:0.01 to 1.0%, nb:0.001 to 0.03 percent, less than or equal to 0.005 percent of N, and the balance of Fe and inevitable impurities. The rolling process comprises the following steps: final rolling at 890-920 ℃, finish rolling at 580-620 ℃ and cold rolling reduction rate of 45-75 percent; the hot galvanizing process comprises the following steps: annealing temperature: 770-810 ℃, the dew point in the annealing furnace is controlled below minus 40 ℃, and the oxygen content is less than or equal to 3ppm; the temperature of the zinc liquid is controlled between 455 and 465 ℃, the aluminum content in the zinc liquid is controlled between 0.18 and 0.23 percent, the Fe content is less than or equal to 0.009 percent, and the finishing elongation is controlled between 0.7 and 1.1 percent. The patent application adds precious alloy elements of Mo (0.01-0.30%), cr (0.01-1.0%) and Nb (0.001-0.03%), increases production cost, introduces finishing temperature and coiling temperature, and is not beneficial to stable control of structure performance and surface quality. Furthermore, no attempt was made to prepare compositionally different microstructures.
CN 106011644B discloses a high-elongation cold-rolled high-strength steel plate and a preparation method thereof, wherein the high-elongation cold-rolled high-strength steel plate comprises the following chemical components in percentage by weight: c:0.03 to 0.05%, si:0.40 to 0.50%, mn:1.35 to 1.50%, al:0.030 to 0.050 percent, less than or equal to 0.015 percent of P, less than or equal to 0.010 percent of S, less than or equal to 0.005 percent of N, and the balance of Fe and inevitable impurities. The initial rolling temperature of hot rolling is 1000-1100 ℃, the final rolling temperature is 850-950 ℃, and the coiling temperature is 610-690 ℃. And (3) cold rolling by adopting a cold rolling reduction ratio of 50-70%, soaking at 780-820 ℃, then slowly cooling to 640-680 ℃ in sequence, wherein the slow cooling rate (CR 1) is 1-7 ℃/s, immediately rapidly cooling to the overaging temperature of 240-345 ℃, and the rapid cooling rate (CR 2) is 10-30 ℃/s, and finally cooling to room temperature, thereby obtaining the high-elongation cold-rolled high-strength steel plate. The patent application does not try to prepare microstructures with the same components and different components, and only introduces the opening rolling temperature, the finishing rolling temperature and the coiling temperature, which is not beneficial to the stable control of the structure performance and the surface quality.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides 450MPa grade high-strength steel with different microstructures and a preparation method thereof, and the 450MPa grade high-strength steel with different microstructures is obtained by adjusting component proportion and process parameters under the same components.
The invention provides 450 MPa-grade high-strength steel with different microstructures, which comprises the following chemical components in percentage by weight: c:0.04 to 0.11%, si:0.15 to 0.45%, mn: 0.65-1.25%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, als: 0.010-0.070%, N is less than or equal to 0.0050%, and the balance of elements are Fe and unavoidable impurities.
Further, the 450 MPa-grade high-strength steel comprises the following chemical components in percentage by weight: c:0.06 to 0.09%, si:0.15 to 0.30%, mn:0.07 to 1.10%, als:0.02 to 0.055 percent, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, less than or equal to 0.0045 percent of N, and the balance of Fe and inevitable impurities.
Further, the 450 MPa-grade high-strength steel comprises carbon structural steel and dual-phase structural steel; the microstructure of the carbon structural steel consists of 90-95% of ferrite matrix (the average grain size is 4.0 mu m) and 5-10% of pearlite which is distributed along grain boundaries and is in a lamellar shape; the yield strength of the carbon structural steel is 342-375 MPa, the tensile strength is 451-468 MPa, and the elongation rate A is 80 The value is 30.0-34.5%; the microstructure of the dual-phase structural steel is composed of 85-90% of ferrite matrix (the average grain size is 6 mu m) and 10-15% of island-shaped martensite distributed along grain boundaries; the yield strength of the dual-phase structural steel is 270-310 MPa, the tensile strength is 461-493 MPa, and the elongation rate A is 80 The value is 33.5-36.5%, and the hole expansion ratio is 45-57%.
The second aspect of the invention provides a preparation method of 450 MPa-grade high-strength steel with different microstructures, which comprises the following steps:
s1, smelting process: casting molten steel into a plate blank, wherein the plate blank comprises the following chemical components in percentage by weight: c:0.04 to 0.11%, si:0.15 to 0.45%, mn: 0.65-1.25%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, als: 0.010-0.070%, N is less than or equal to 0.0050%, and the rest elements are Fe and inevitable impurities;
s2, hot rolling process: heating, dephosphorizing, roughly rolling, finely rolling and cooling by laminar flow to obtain a hot rolled coil, wherein the laminar cooling temperature is divided into a front-section cooling mode and a sparse cooling mode, the temperature of the front-section cooling mode is 580-650 ℃, the hot rolled coil is cooled by the front-section cooling mode to obtain a carbon structure hot rolled coil, and the hot rolled thickness of the carbon structure hot rolled coil is 2.5-5.8 mm; the temperature of the sparse cooling mode is 640-730 ℃, and a hot rolled coil with a dual-phase structure is obtained through the sparse cooling mode, wherein the hot rolling thickness of the hot rolled coil with the dual-phase structure is 2.0-6.0 mm;
s3, acid rolling process: respectively carrying out acid pickling and cold rolling on the carbon structure hot-rolled coil and the double-phase structure hot-rolled coil to form a carbon structure cold-rolled thin strip steel and a double-phase structure cold-rolled thin strip steel;
s4, continuous annealing process: respectively carrying out different continuous annealing processes on the carbon structure cold-rolled thin strip steel and the double-phase structure cold-rolled thin strip steel to obtain carbon structural steel and double-phase structural steel; the continuous annealing process of the carbon structural steel comprises soaking temperature of 760-800 ℃, slow cooling end point temperature of 590-630 ℃, fast cooling end point temperature of 410-430 ℃, overaging temperature of 340-400 ℃, unit speed of 120-200 m/min and finishing elongation of 1.10-1.75%; the continuous annealing process of the dual-phase structural steel comprises soaking temperature of 770-800 ℃, slow cooling end point temperature of 660-690 ℃, fast cooling end point temperature of 270-320 ℃, overaging temperature of 260-300 ℃, unit speed of 80-150 m/min and finishing elongation of 0.40-0.8%.
Further, the heating temperature in the step S2 is 1200-1245 ℃.
Further, the finish rolling in the step S2 has a start rolling temperature of 1000 to 1100 ℃, and the finish rolling temperature of the finish rolling is 840 to 900 ℃.
Further, the dual-phase hot rolled coil in the step S2 is prepared by adjusting the head and the tail of the strip by using a hot coil box before the strip enters a finishing mill group and coiling the strip by a U shape, wherein the coiling temperature of 80m before the head of the strip is 680-740 ℃, and the coiling temperature of 100m after the tail of the strip is 640-730 ℃.
Further, the thicknesses of the carbon structure cold-rolled thin strip steel and the dual-phase structure cold-rolled thin strip steel in the step S3 are both 0.5-2.5 mm; the cold rolling reduction rate of the carbon structure cold rolling thin strip steel is 57.0-80.0%, and the cold rolling reduction rate of the dual-phase structure cold rolling thin strip steel is 65-85%.
Further, when the thickness of the carbon structural steel is increased by 0.5mm in the continuous annealing process of the carbon structural steel, the speed of a unit is reduced by 20m/min, and the finishing elongation is increased by 0.15%; in the continuous annealing process of the dual-phase structural steel, the speed of a machine set is reduced by 15m/min and the finishing elongation is reduced by 0.15% when the thickness of the dual-phase structural steel is increased by 0.5 mm.
Has the advantages that:
the invention prepares the high-strength steel with different microstructures by the same component, greatly optimizes the production rhythm, reduces the proportion of the joined blank, reduces the cost and is beneficial to meeting the requirements of different users. The continuous annealing process comprises the steps of firstly, slowly heating the carbon structural cold-rolled thin strip steel and the dual-phase structural cold-rolled thin strip steel to a soaking temperature respectively, keeping the temperature for a period of time to form a certain ferrite-austenite ratio, slowly cooling the carbon structural cold-rolled thin strip steel to a pearlite transformation region, and forming pearlite in a pearlite transformation region in a fast cooling and overaging stage; and slowly cooling the dual-phase structure cold-rolled thin strip steel to the slow cooling end point temperature to decompose partial super-cooled austenite to form a small amount of oriented ferrite and perform carbon enrichment on the residual austenite, then rapidly cooling the dual-phase structure cold-rolled thin strip steel to convert the austenite into martensite, performing low-temperature tempering in an overaging section to properly improve plasticity, finally cooling to room temperature, and adjusting the shape of the strip steel through a finishing mill to increase the yield strength.
Drawings
FIG. 1 is a schematic view showing the microstructure of a carbon structural steel according to an embodiment of the present invention.
Fig. 2 is a schematic view of the microstructure of a dual phase structural steel according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The principle of setting the chemical components and the proportion in the invention is as follows:
c, one of the most important components in steel, determines the strength, plasticity and formability of the steel sheet. C is the most obvious element for the solid solution strengthening effect in the steel material, the solid solution C content in the steel is increased by 0.1 percent, and the strength can be improved by about 450MPa. When the content of C is too low, the solid solution strengthening effect of the carbon structural steel is reduced, the stability of austenite and the martensite hardenability in the dual-phase steel are reduced, and the strength is low, wherein the content of C in the dual-phase steel is generally not lower than 0.02%; when the content of C is too high, the plasticity and weldability of the high-strength steel decrease, and therefore, the content of C in the present invention is 0.04 to 0.11%, preferably 0.06 to 0.09%.
Si plays a remarkable role in solid solution strengthening in steel, effectively inhibits precipitation of carbide, delays pearlite transformation and the like in the phase transformation process, but the excessively high Si content can remarkably increase the deformation resistance during thin gauge rolling, is not favorable for the thin gauge rolling, and the Si can improve the activity of carbon element and promote the segregation of carbon in a manganese-rich area. When the two-phase region is subjected to heat preservation, the diffusion of carbon to austenite is accelerated, the ferrite is obviously purified, the purity of the ferrite in the dual-phase steel is improved, the formation of the ferrite is promoted, and a process window for forming the ferrite is enlarged, so that a lower yield ratio is obtained. On the other hand, too high a silicon content increases the brittleness of martensite to deteriorate the toughness, and a high-melting oxide is formed on the surface of the steel sheet to affect the surface quality of the steel sheet, and it is necessary to reduce the silicon content in the steel as much as possible. Therefore, the Si content in the present invention is 0.15 to 0.45%, preferably 0.15 to 0.30%.
Mn is a good deoxidizer and desulfurizer, and is also a common solid solution strengthening element in steel. Mn can be combined with C to form various carbides to play a role in precipitation strengthening, and can also be dissolved in a matrix to enhance the solid solution strengthening effect. Mn is easily combined with S to form a high melting point compound MnS, thereby eliminating or weakening hot embrittlement caused by FeS and improving hot workability of the steel. Mn can improve the stability of austenite and shift the C curve to the right, thereby obviously reducing the critical cooling rate of martensite. However, when the Mn content is too high, the surface is easily enriched in the annealing process to form a large amount of manganese compounds, thereby causing the reduction of the surface galvanizing quality. Accordingly, in the present invention, the Mn content is 0.65 to 1.25%, preferably 0.07 to 1.10%.
Al is a common deoxidizer in steel, and can form an AlN pinning grain boundary so as to play a role in refining grains; in addition, al acts similarly to Si, and suppresses carbide precipitation, thereby making austenite sufficiently rich in carbon. Therefore, the Al content in the present invention is 0.010 to 0.070%, preferably 0.02 to 0.055%.
The embodiment of the invention comprises the following steps:
s1, smelting process: the molten steel is cast into a plate blank, and the weight percentage of the chemical components of the plate blank is shown in the following table 1:
table 1 chemical composition (wt.%) of each example slab
Figure BDA0003898724550000071
S2, hot rolling: heating, dephosphorizing, roughly rolling, finely rolling and laminar cooling the plate blank to obtain a hot rolled coil, wherein the specific hot rolling process parameters of each embodiment are shown in table 2:
TABLE 2 parameters of the Hot Rolling Process of the examples
Figure BDA0003898724550000072
S3, acid rolling process: the hot rolled coil was acid washed and cold rolled into a thin strip steel, wherein the thickness of the strip steel of examples 1 and 2 was 1.5mm, and the cold rolling reduction was 66.7% and 70%, respectively.
S4, continuous annealing process: the cold-rolled thin strip steel is processed by a continuous annealing process to be made into a required product, the strip steel is slowly heated to a soaking temperature and is kept warm for a period of time to form a certain ferrite-austenite ratio, the carbon structural steel is slowly cooled to a pearlite transformation area, and the fast cooling and overaging stages are the pearlite transformation area to form pearlite; the dual-phase steel is slowly cooled to the slow cooling end point temperature to decompose part of super-cooled austenite to form a small amount of oriented periphytic ferrite and carry out carbon enrichment on the rest austenite, then the strip steel is quickly cooled to convert the austenite into martensite, low-temperature tempering is carried out in an overaging section to properly improve plasticity, finally the strip steel is cooled to room temperature, and the strip steel shape is adjusted through a finishing machine to increase the yield strength; specific parameters of the continuous annealing process are shown in table 3:
TABLE 3 parameters of the continuous annealing process
Figure BDA0003898724550000081
Wherein the product obtained in example 1 is a carbon structural steel, the microstructure of which is shown in fig. 1, the carbon structural steel is composed of 90-95% of ferrite matrix and 5-10% of pearlite distributed in lamellar form along grain boundaries, and the average grain size of the ferrite matrix is 4 μm.
The product obtained in example 2 was a dual-phase structural steel having a microstructure shown in FIG. 2, which consisted of 85 to 90% of a ferrite matrix and 10 to 15% of martensite distributed in island-like shapes along grain boundaries, and the average grain size of the ferrite matrix was 6 μm.
Comparative examples 1-4 were provided, wherein comparative example 1 was the carbon structural steel in patent application CN 104233068A, comparative example 2 was the dual phase steel in patent application CN 105369135A, comparative example 3 was the high strength steel in patent application CN 106011644B, and comparative example 4 was the high strength steel in patent application CN 104233068A.
The properties of the dual-phase steels of examples 1 to 3 and comparative examples 1 to 4 were tested according to GB/T228-2010 "method for testing metallic materials at room temperature for tensile test", and the mechanical properties thereof are shown in Table 4 below:
TABLE 4 mechanical Properties of examples and comparative examples
Figure BDA0003898724550000091
As can be seen from Table 4, 450MPa grade high strength steel with carbon structure and dual-phase structure is obtained by changing the process parameters.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.

Claims (9)

1. The 450 MPa-grade high-strength steel with different microstructures is characterized by comprising the following chemical components in percentage by weight: c:0.04 to 0.11%, si:0.15 to 0.45%, mn: 0.65-1.25%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, als: 0.010-0.070%, N is less than or equal to 0.0050%, and the balance of Fe and inevitable impurities.
2. The 450MPa grade high strength steel with different microstructures according to claim 1, wherein the 450MPa grade high strength steel comprises the following chemical components in percentage by weight: c:0.06 to 0.09%, si:0.15 to 0.30%, mn:0.07 to 1.10%, als:0.02 to 0.055 percent, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, less than or equal to 0.0045 percent of N, and the balance of Fe and inevitable impurities.
3. The 450MPa grade high strength steel with different microstructures according to claim 1, wherein the 450MPa grade high strength steel comprises a carbon structural steel and a dual phase structural steel; the microstructure of the carbon structural steel consists of 90-95% of ferrite matrix and 5-10% of pearlite distributed along grain boundary in lamellar form, the yield strength of the carbon structural steel is 342-375 MPa, the tensile strength is 451-468 MPa, and the elongation A is 80 The value is 30.0-34.5%; the microstructure of the dual-phase structural steel consists of 85 to 90 percent of ferrite matrix and 10 to 15 percent of martensite which is distributed along grain boundaries and is in an island shape, the yield strength of the dual-phase structural steel is 270 to 310MPa, the tensile strength is 461 to 493MPa, and the elongation A is 80 The value is 33.5-36.5%, and the hole expansion ratio is 45-57%.
4. A method of producing a high strength steel according to any one of claims 1 to 3, characterized by comprising the steps of:
s1, smelting process: casting molten steel into a plate blank, wherein the plate blank comprises the following chemical components in percentage by weight: c:0.04 to 0.11%, si:0.15 to 0.45%, mn: 0.65-1.25%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, als: 0.010-0.070%, N is less than or equal to 0.0050%, and the rest elements are Fe and unavoidable impurities;
s2, hot rolling process: heating, dephosphorizing, roughly rolling, finely rolling and cooling by laminar flow to obtain a hot rolled coil, wherein the laminar cooling temperature is divided into a front-section cooling mode and a sparse cooling mode, the temperature of the front-section cooling mode is 580-650 ℃, the hot rolled coil is cooled by the front-section cooling mode to obtain a carbon structure hot rolled coil, and the hot rolled thickness of the carbon structure hot rolled coil is 2.5-5.8 mm; the temperature of the sparse cooling mode is 640-730 ℃, and a hot rolled coil with a dual-phase structure is obtained through the sparse cooling mode, wherein the hot rolling thickness of the hot rolled coil with the dual-phase structure is 2.0-6.0 mm;
s3, acid rolling procedure: respectively carrying out acid pickling and cold rolling on the carbon structure hot-rolled coil and the double-phase structure hot-rolled coil to form a carbon structure cold-rolled thin strip steel and a double-phase structure cold-rolled thin strip steel;
s4, continuous annealing process: respectively carrying out different continuous annealing processes on the carbon structure cold-rolled thin strip steel and the double-phase structure cold-rolled thin strip steel to obtain carbon structural steel and double-phase structural steel; the continuous annealing process of the carbon structural steel comprises soaking temperature of 760-800 ℃, slow cooling end point temperature of 590-630 ℃, fast cooling end point temperature of 410-430 ℃, overaging temperature of 340-400 ℃, unit speed of 120-200 m/min and finishing elongation of 1.10-1.75%; the continuous annealing process of the dual-phase structural steel comprises soaking temperature of 770-800 ℃, slow cooling end point temperature of 660-690 ℃, fast cooling end point temperature of 270-320 ℃, overaging temperature of 260-300 ℃, unit speed of 80-150 m/min and finishing elongation of 0.40-0.8%.
5. The method for preparing 450MPa grade high-strength steel with different microstructures according to claim 4, wherein the heating temperature in step S2 is 1200-1245 ℃.
6. The method of manufacturing 450MPa grade high strength steel having different microstructures according to claim 4, wherein the finish rolling temperature of the finish rolling in step S2 is 1000-1100 ℃ and the finish rolling temperature of the finish rolling is 840-900 ℃.
7. The method for preparing 450MPa grade high-strength steel with different microstructures according to claim 4, wherein the dual-phase structure hot rolled coil in the step S2 is prepared by adjusting a head and a tail of a strip by using a hot coil box before the strip enters a finishing mill group and adopting U-shaped coiling, wherein the coiling temperature of 80m before the head of the strip is 680-740 ℃, and the coiling temperature of 100m after the tail of the strip is 640-730 ℃.
8. The method of manufacturing 450MPa grade high strength steel having different microstructures according to claim 4, wherein the thicknesses of said carbon structure cold-rolled thin strip steel and said dual phase structure cold-rolled thin strip steel in said step S3 are both 0.5-2.5 mm; the cold rolling reduction rate of the carbon structure cold rolling thin strip steel is 57.0-80.0%, and the cold rolling reduction rate of the dual-phase structure cold rolling thin strip steel is 65-85%.
9. The method for preparing 450MPa grade high strength steel with different microstructures according to claim 4, wherein the machine speed is reduced by 20m/min and the finishing elongation is increased by 0.15% when the thickness of the carbon structural steel is increased by 0.5mm in the continuous annealing process of the carbon structural steel; in the continuous annealing process of the dual-phase structural steel, the speed of a machine set is reduced by 15m/min and the finishing elongation is reduced by 0.15% when the thickness of the dual-phase structural steel is increased by 0.5 mm.
CN202211291595.1A 2022-10-19 2022-10-19 450 MPa-grade high-strength steel with different microstructures and preparation method thereof Pending CN115537666A (en)

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