CN112760562B - Delayed fracture-resistant 2000 MPa-grade steel plate and preparation method thereof - Google Patents
Delayed fracture-resistant 2000 MPa-grade steel plate and preparation method thereof Download PDFInfo
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
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- B22D11/111—Treating the molten metal by using protecting powders
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- 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
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- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C21D1/26—Methods of annealing
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
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- C21D6/00—Heat treatment of ferrous alloys
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- C21D6/00—Heat treatment of ferrous alloys
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- C21D6/008—Heat treatment of ferrous alloys containing Si
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- 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
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
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- C22C33/04—Making ferrous alloys by melting
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- 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
- C21D2211/008—Martensite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Abstract
The invention discloses a delayed fracture-resistant 2000 MPa-grade steel plate, which comprises the following components in percentage by weight: 0.30% -0.40%; si: 0.20 to 0.40 percent; mn: 1.0% -1.5%; cr: 0.18 to 0.28 percent; mo: 0.10 to 0.30 percent; and Als: 0.020% -0.050%; nb: 0.02% -0.048%; mg: 0.0035 to 0.0065 percent; o is less than or equal to 0.0015 percent; n is less than or equal to 0.006 percent, and the balance of Fe and inevitable impurities by mass. The steel plate of the invention not only has tensile strength of more than 2000Mpa, but also has excellent delayed fracture resistance, the hydrogen embrittlement index is lower than 30 percent, and the steel plate can meet the requirements of steel plates for automobiles.
Description
Technical Field
The invention belongs to the technical field of steel plates for automobiles, and particularly relates to a delayed fracture-resistant 2000 MPa-grade steel plate, and a preparation method of the delayed fracture-resistant 2000 MPa-grade steel plate.
Background
At present, parts such as an A column, a B column, a reinforcing plate, an anti-collision beam and the like of an automobile are mostly manufactured by a cold stamping process of a high-strength steel plate, the steel plate is high in strength, easy to crack and severe in resilience due to stamping deformation at normal temperature, and parts with complex shapes are difficult to stamp and form. The hot forming process mainly utilizes the characteristics that the plasticity and the ductility of metal are rapidly increased and the yield strength is rapidly reduced at high temperature, the part is formed through a die, and simultaneously, a die provided with a water cooling system is utilized to form a steel plate and quench the steel plate in the die to obtain a martensite structure, so that the aim of preparing the high-strength automobile steel is fulfilled.
However, as the strength is improved, the delayed fracture problem of the steel also appears, and particularly for the ultrahigh-strength steel with the strength of more than 1000MPa, the delayed fracture sensitivity is more obvious, which becomes a significant problem restricting the application and development of the ultrahigh-strength steel. Delayed fracture of steel often occurs suddenly when the level of applied stress to which the material is subjected is significantly lower than its yield strength, is unpredictable, and often results in more serious damage and consequences, so delayed fracture of ultra-high strength steel has become a problem that must be solved for lightweight automobiles.
Disclosure of Invention
The present invention is based on the discovery and recognition by the inventors of the following facts and problems: the problem that the delayed fracture resistance of the steel plate is insufficient exists in the process of preparing the ultrahigh-strength steel plate by using the steel plate components in the prior art, the strengthening and toughening mechanism and delayed fracture behavior of the ultrahigh-strength hot forming steel need to be researched, and the composition elements of the steel plate are deeply researched to obtain the high-strength steel plate with excellent delayed fracture resistance, so that the popularization and application of the ultrahigh-strength hot forming steel are promoted.
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.
To this end, the embodiment of the first aspect of the present invention proposes a delayed fracture 2000MPa grade steel sheet, which not only has a tensile strength of 2000MPa or more, but also has excellent delayed fracture resistance, has a hydrogen embrittlement index of less than 30%, and can meet the requirements of steel sheets for automobiles.
According to the invention, the delayed fracture 2000 MPa-grade steel plate comprises C: 0.30% -0.40%; si: 0.20 to 0.40 percent; mn: 1.0% -1.5%; cr: 0.18 to 0.28 percent; mo: 0.10 to 0.30 percent; and Als: 0.020% -0.050%; nb: 0.02% -0.048%; mg: 0.0035 to 0.0065 percent; o is less than or equal to 0.0015 percent; n is less than or equal to 0.006 percent, and the balance of Fe and inevitable impurities by mass.
According to the advantages and technical effects brought by the independent claims of the embodiment of the first aspect of the invention, 1, the steel plate of the embodiment of the invention is added with Mg element, and the addition of trace Mg element improves the composition, size and form of inclusions in the steel, enhances the deformability of the inclusions in the steel, and improves the delayed fracture resistance of the steel plate of the embodiment of the invention by the synergistic effect of Mo and Nb elements; 2. the steel plate disclosed by the embodiment of the invention not only has the tensile strength of more than 2000MPa, but also has excellent delayed fracture resistance, the hydrogen brittleness index is lower than 30%, meanwhile, the excellent toughness is maintained, the elongation A50 is more than 5%, and the requirement of the steel plate for the automobile can be met.
The delayed fracture 2000 MPa-grade steel plate according to the embodiment of the first aspect of the invention is characterized in that Mg is 0.004-0.006%.
According to the first aspect of the invention, the delayed fracture 2000MPa grade steel plate is provided, wherein Nb, Mo and Mg in the steel plate satisfy the relation: nb, Mo and Mg are more than or equal to 0.18 percent and less than or equal to 0.38 percent.
According to the first aspect of the invention, the delayed fracture 2000MPa grade steel plate is provided, wherein Nb, Mo and Mg in the steel plate satisfy the relation: nb, Mo and Mg are more than or equal to 0.31 percent and less than or equal to 0.35 percent.
According to the first aspect of the invention, the delayed fracture 2000MPa grade steel plate is provided, wherein Nb, Mo and Mg in the steel plate satisfy the relation: nb + Mo + Mg ═ 0.31%.
The embodiment of the second aspect of the invention also provides a preparation method of the delayed fracture-resistant 2000 MPa-grade steel plate, which comprises the following steps:
a. smelting the raw materials in the designed proportion to obtain a continuous casting billet;
b. reheating the continuous casting billet obtained in the step a;
c. carrying out hot rolling, coiling and acid washing on the continuous casting billet obtained in the step b to obtain a hot rolled steel plate;
d. and c, carrying out heat treatment on the steel plate obtained in the step c.
According to the advantages and technical effects brought by the independent claims of the embodiment of the second aspect of the invention, the preparation method of the embodiment of the invention is simple and easy to apply industrially, the prepared steel plate not only has the tensile strength of more than 2000Mpa, but also has excellent delayed fracture resistance, the hydrogen brittleness index is lower than 30%, meanwhile, the excellent toughness is maintained, the elongation A50 is more than 5%, and the requirement of the steel plate for the automobile can be met.
According to the second aspect of the invention, the preparation method of the 2000 MPa-grade steel plate with the delayed fracture resistance is implemented, wherein the step c comprises the following steps:
c1, carrying out hot rolling and acid pickling on the continuous casting billet obtained in the step b;
c2, cold rolling, coiling and annealing the steel plate obtained in the step c1 to obtain a cold-rolled steel plate.
According to the second aspect of the invention, the preparation method of the delayed fracture 2000MPa grade steel plate is implemented, wherein the step d comprises the following steps:
d1, heating the steel plate rolled in the step c in a heating furnace under the nitrogen protection atmosphere at 870-940 ℃, and preserving heat for 180-300 s;
d2, carrying out stamping forming on the steel plate obtained in the step d1 in a die with a cooling device, wherein the quenching cooling speed is not less than 40 ℃/s, and the pressure maintaining time is 3-6 s.
According to the second aspect of the invention, the preparation method of the 2000 MPa-grade steel plate with delayed fracture resistance is provided, wherein in the step a, smelting comprises converter refining, LF furnace refining and slab continuous casting; and/or in the step b, the heating temperature is 1190-1230 ℃, and the temperature is kept for 2-3 h; in the step c, the finishing temperature is 860-930 ℃, laminar cooling is adopted to the coiling temperature after rolling, the cooling speed is more than 10 ℃/s, and the coiling temperature is 580-650 ℃.
According to the second aspect of the invention, the preparation method of the 2000 MPa-grade steel plate with delayed fracture resistance is provided, wherein in the step a, lime, fluorite and bauxite are added in the LF refining process for slagging, and the refining slag comprises the following steps: SiO 22：7.8～11.2、Al2O3: 19.2 to 27.1, CaO: 52.6 to 65.2, MgO: 6.3-7.9 in percentage by mass; and/or, the tundish in the continuous casting process adopts a hollow particle covering agent, which comprises: SiO 22：27～35、Al2O3: 8-14, CaO: 14-24, MgO: 8-13, C: 20 to 25, the particle size is 0.1 to 1mm, and the bulk density is 0.5 to 0.9g/cm3。
Detailed Description
The following detailed description of embodiments of the invention is intended to be illustrative, and is not to be construed as limiting the invention.
According to the invention, the delayed fracture 2000 MPa-grade steel plate comprises C: 0.30% -0.40%; si: 0.20 to 0.40 percent; mn: 1.0% -1.5%; cr: 0.18 to 0.28 percent; mo: 0.10 to 0.30 percent; and Als: 0.020% -0.050%; nb: 0.02% -0.048%; mg: 0.0035 to 0.0065 percent; o is less than or equal to 0.0015 percent; n is less than or equal to 0.006 percent, and the balance of Fe and inevitable impurities by mass.
According to the 2000 MPa-grade steel plate with delayed fracture resistance, provided by the embodiment of the invention, the Mg element is added into the steel plate, the addition of trace Mg element improves the composition, size and form of inclusions in the steel, enhances the deformability of the inclusions in the steel, and improves the delayed fracture resistance of the steel plate provided by the embodiment of the invention under the synergistic effect of the Mo element and the Nb element; the steel plate disclosed by the embodiment of the invention not only has the tensile strength of more than 2000MPa, but also has excellent delayed fracture resistance, the hydrogen brittleness index is lower than 30%, meanwhile, the excellent toughness is maintained, the elongation A50 is more than 5%, and the requirement of the steel plate for the automobile can be met.
The action mechanism of each element in the 2000 MPa-grade delayed fracture resistant steel plate in the first aspect of the invention is as follows:
c: carbon mainly determines the hardenability of steel and is an element for forming martensite, so that the content of C is controlled to be 0.30-0.40% in the embodiment of the invention;
si: silicon is an element for improving the hardenability and the strength of the steel plate, so that the content of Si is controlled to be 0.20-0.40% in the embodiment of the invention;
mn: manganese is an element for enlarging an austenite region, the amount of manganese is increased, the hardenability is improved, and the element is very effective for stabilizing the strength after quenching, and the content of Mn is controlled to be 1.0-1.5% in the embodiment of the invention;
cr: chromium is an element for improving the hardenability of steel, and is beneficial to improving the strength of the steel plate after quenching, and the content of Cr is controlled to be 0.18-0.28 percent in the embodiment of the invention;
mo: mo can greatly improve hardenability and ensure the hardness and strength of the material after quenching, and in addition, the element has extremely strong delayed fracture resistance, and the content of Mo in the embodiment of the invention is controlled to be 0.10-0.30%;
nb: in the embodiment of the invention, a small amount of Nb is added, and solidification refinement, controlled rolling and controlled cooling refinement are realized by utilizing Nb microalloying, so that the content of Nb is controlled to be 0.010-0.030%;
mg: the addition of trace Mg can improve the composition, size and form of inclusions in steel, enhance the deformability of the inclusions in the steel, and improve the delayed fracture resistance of the steel plate in the embodiment of the invention under the synergistic effect of Mo and Nb elements, wherein the content of Mg in the steel plate is controlled to be 0.0035-0.0065%.
The delayed fracture 2000 MPa-grade steel plate according to the embodiment of the first aspect of the invention is characterized in that Mg is 0.004-0.006%.
According to the first aspect of the invention, the delayed fracture 2000MPa grade steel plate is provided, wherein Nb, Mo and Mg in the steel plate satisfy the relation: 0.18% or more and 0.38% or less of Nb + Mo + Mg, preferably 0.31% or more and 0.35% or less of Nb + Mo + Mg, and more preferably 0.31% or less of Nb + Mo + Mg. In the steel plate provided by the embodiment of the invention, the three elements of Nb, Mo and Mg are controlled to satisfy the relation that Nb, Mo and Mg are more than or equal to 0.18% and less than or equal to 0.38%, so that the delayed fracture resistance of the steel plate is effectively improved.
The preparation method of the delayed fracture 2000MPa grade steel plate according to the second aspect of the invention comprises the following steps:
a. smelting raw materials with a designed ratio to obtain a continuous casting blank, preferably, the smelting comprises refining in a converter and an LF (ladle furnace) and continuous casting of a plate blank, further preferably, lime, fluorite and bauxite are added in the LF refining process for slagging, and the refining slag comprises: SiO 22：7.8～11.2、Al2O3: 19.2 to 27.1, CaO: 52.6 to 65.2, MgO: 6.3-7.9 in percentage by mass; the tundish in the continuous casting process adopts a hollow particle covering agent, which comprises: SiO 22：27～35、Al2O3: 8-14, CaO: 14-24, MgO: 8-13, C: 20 to 25, the particle size is 0.1 to 1mm, and the bulk density is 0.5 to 0.9g/cm3；
b. B, reheating the continuous casting billet obtained in the step a, preferably, heating at a temperature of 1190-1230 ℃, keeping the temperature for 2-3 hours, discharging the billet at a temperature of 1180-1210 ℃, and further preferably, carrying out dephosphorization treatment;
c. carrying out hot rolling, coiling and acid pickling on the continuous casting billet obtained in the step b to obtain a hot rolled steel plate, preferably, the final rolling temperature is 860-930 ℃, and after rolling, adopting laminar flow cooling to the coiling temperature, wherein the cooling speed is more than 10 ℃/s, and the coiling temperature is 580-650 ℃;
d. and c, carrying out heat treatment on the steel plate obtained in the step c.
According to the preparation method of the delayed fracture-resistant 2000 MPa-grade steel plate disclosed by the embodiment of the second aspect of the invention, the preparation method is simple and easy to industrially apply, the prepared steel plate not only has the tensile strength of more than 2000MPa, but also has excellent delayed fracture resistance, the hydrogen brittleness index is lower than 30%, meanwhile, the excellent toughness is kept, the elongation A50 is higher than 5%, and the requirement of the steel plate for an automobile can be met.
According to the second aspect of the invention, the preparation method of the 2000 MPa-grade steel plate with the delayed fracture resistance is implemented, wherein the step c comprises the following steps: c1, carrying out hot rolling and acid pickling on the continuous casting billet obtained in the step b; c2, cold rolling, coiling and annealing the steel plate obtained in the step c1 to obtain a cold-rolled steel plate. In the method of the embodiment of the invention, not only the delayed fracture 2000 MPa-grade steel plate of the invention can be obtained by heat treatment of the hot-rolled steel plate, but also the delayed fracture 2000 MPa-grade steel plate of the invention can be obtained by heat treatment of the cold-rolled steel plate.
According to the method for preparing the delayed fracture 2000 MPa-level steel plate of the second aspect of the invention, the hot-formed steel plate obtained by hot rolling or cold rolling has uniform ferrite and pearlite structures, and the mechanical properties of the steel plate obtained by rolling are as follows: (1) hot rolling of the plate: the thickness is 1.70-4.00 mm; ReL: 550 to 650 MPa; rm: 750-900 MPa; a50 is more than or equal to 18 percent; (2) cold rolling and annealing the plate: the thickness is 0.70-3.0 mm; ReL: 500-600 MPa, Rm: 700 to 850 MPa; a50 is more than or equal to 20 percent.
According to the second aspect of the invention, the preparation method of the delayed fracture 2000MPa grade steel plate is implemented, wherein the step d comprises the following steps: d1, heating the steel plate rolled in the step c in a heating furnace under the nitrogen protection atmosphere, wherein the heating temperature is 870-940 ℃, and the heat is preserved for 180-300 s to perform austenitization; d2, performing stamping forming on the steel plate obtained in the step d1 in a die with a cooling device, wherein the quenching cooling speed is not less than 40 ℃/s, the pressure maintaining time is 3-6 s, a lath martensite structure and a retained austenite structure are obtained, and the retained austenite content is measured to be about 4-6% by using an XRD diffractometer. In the method of the embodiment of the invention, after the heat treatment, the mechanical properties of the quenched steel plate are as follows: rp0.2 is 1000-1200 MPa, Rm is more than or equal to 2000MPa, and A50 is 5-9%.
The present invention will be described in detail with reference to examples.
Example 1
The elements with the designed proportion are taken to smelt the molten steel, and the chemical components are shown in the table 1. The smelting process comprises the refining of a converter and an LF furnace and the continuous casting of a plate blank, lime, fluorite and bauxite are added in the LF refining process for slagging, a covering agent is added in a tundish in the continuous casting process, and the components of refining slag and the covering agent are shown in a table 2. Heating the continuous casting plate blank obtained by refining to 1220 ℃, keeping the temperature for 2h, then discharging the blank at 1200 ℃, carrying out descaling treatment, rough rolling, then fine rolling at multiple passes under high pressure, wherein the final rolling temperature is 890 ℃, carrying out laminar cooling after rolling, and cooling to the coiling temperature at the cooling speed of 13 ℃/s, wherein the coiling temperature is 600 ℃. And carrying out acid pickling and oil coating after hot rolling, and then packaging.
And further performing cold rolling treatment on the hot-rolled steel plate, pickling and cold rolling the hot-rolled steel plate, annealing the steel plate in a bell-type furnace, and oiling and packaging the steel plate.
And (2) carrying out heat treatment on the cold-rolled steel plate, heating the steel plate in a heating furnace in a nitrogen protective atmosphere at the heating temperature of 910 ℃, keeping the temperature for 230s, carrying out austenitization, quickly feeding the austenitized steel plate into a die with a cooling device for stamping and forming, wherein the quenching cooling speed is 45 ℃/s, the pressure maintaining time is 5s, a lath martensite structure and a retained austenite structure are obtained, and the retained austenite content is about 5% measured by using an XRD diffractometer.
The process parameters in this example are shown in Table 3, the mechanical properties of the steel sheet after hot rolling, cold rolling annealing, heat treatment quenching are shown in Table 4, and the delayed fracture properties of the steel sheet after heat treatment quenching are shown in Table 5.
Examples 2 to 5 are the same as example 1 except that the steel sheet components and process parameters are different, as shown in tables 1 to 3, mechanical properties are shown in table 4, and delayed fracture properties are shown in table 5.
Comparative example 1 the same procedure as in example 1, except that no Mg element was added, and the specific ingredients, process parameters and properties are shown in tables 1 to 5.
The heat-treated and quenched steel plate obtained in the example of the invention is subjected to an SSRT slow tensile test in an HCl solution, and the delayed fracture performance is evaluated by calculating the hydrogen embrittlement index I, wherein I epsilon is (epsilon A-epsilon E)/epsilon A, wherein epsilon A is the elongation rate of the sample during stretching in air, epsilon E is the elongation rate of the sample during stretching in an acid medium, and the smaller the value of I epsilon represents the better delayed fracture performance.
TABLE 1
Note: the balance of Fe and inevitable impurities in the table in percent.
TABLE 2
TABLE 3
TABLE 4
TABLE 5
| Thickness (mm) | Slow elongation in air (%) | Slow elongation in HCL solution (%) | Hydrogen embrittlement index Iε(％) | |
| Example 1 | 1.4 | 18.3 | 13.7 | 25 |
| Example 2 | 1.4 | 17.4 | 12.5 | 28 |
| Example 3 | 1.4 | 16.6 | 12.8 | 22 |
| Example 4 | 1.4 | 15.5 | 11.3 | 27 |
| Example 5 | 1.4 | 16.3 | 11.41 | 30 |
| Comparative example 1 | 1.4 | 9.4 | 3.5 | 62 |
In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" and the like mean that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (8)
1. A2000 MPa-grade delayed fracture-resistant steel sheet, characterized by comprising, C: 0.30% -0.40%; si: 0.20 to 0.40 percent; mn: 1.0% -1.5%; cr: 0.18 to 0.28 percent; mo: 0.10 to 0.30 percent; and Als: 0.020% -0.050%; nb: 0.02% -0.048%; mg: 0.0035 to 0.0065 percent; o is less than or equal to 0.0015 percent; n is less than or equal to 0.006 percent, and the balance of Fe and inevitable impurities, wherein the mass of Nb, Mo and Mg in the steel sheet satisfies the following relational expression: nb, Mo and Mg are more than or equal to 0.18 percent and less than or equal to 0.35 percent.
2. The delayed fracture 2000 MPa-grade steel sheet according to claim 1, wherein Mg is 0.004% to 0.006%.
3. The delayed fracture 2000MPa grade steel sheet of claim 1, wherein Nb, Mo and Mg in the steel sheet satisfy the relationship: nb + Mo + Mg = 0.31%.
4. The method for producing a delayed fracture 2000MPa grade steel sheet according to any one of claims 1 to 3, comprising the steps of:
a. smelting the raw materials in the designed proportion to obtain a continuous casting billet;
b. reheating the continuous casting billet obtained in the step a;
c. carrying out hot rolling, coiling and acid washing on the continuous casting billet obtained in the step b to obtain a hot rolled steel plate;
d. and c, carrying out heat treatment on the steel plate obtained in the step c.
5. The method for preparing a delayed fracture 2000MPa grade steel plate according to claim 4, wherein the step c comprises:
c1, carrying out hot rolling and acid pickling on the continuous casting billet obtained in the step b;
c2, cold rolling, coiling and annealing the steel plate obtained in the step c1 to obtain a cold-rolled steel plate.
6. The method for preparing a delayed fracture 2000MPa grade steel plate according to claim 4, wherein the step d comprises:
d1, heating the steel plate rolled in the step c in a heating furnace under the nitrogen protection atmosphere at 870-940 ℃, and preserving heat for 180-300 s;
d2, carrying out stamping forming on the steel plate obtained in the step d1 in a die with a cooling device, wherein the quenching cooling speed is not less than 40 ℃/s, and the pressure maintaining time is 3-6 s.
7. The method for preparing the delayed fracture 2000MPa grade steel plate according to claim 4, wherein in the step a, the smelting comprises converter, LF furnace refining and slab continuous casting; and/or in the step b, the heating temperature is 1190-1230 ℃, and the temperature is kept for 2-3 h; in the step c, the finishing temperature is 860-930 ℃, laminar cooling is adopted to the coiling temperature after rolling, the cooling speed is more than 10 ℃/s, and the coiling temperature is 580-650 ℃.
8. The method for preparing a delayed fracture 2000MPa grade steel plate according to claim 7, wherein in the step a, lime, fluorite and bauxite are added in the LF refining process for slagging, and the refining slag comprises: SiO 22：7.8～11.2、Al2O3: 19.2 to 27.1, CaO: 52.6 to 65.2, MgO: 6.3-7.9 in percentage by mass; and/or, the continuous casting process tundishUsing a hollow particle capping agent comprising: SiO 22：27～35、Al2O3: 8-14, CaO: 14-24, MgO: 8-13, C: 20 to 25, the particle size is 0.1 to 1mm, and the bulk density is 0.5 to 0.9g/cm3。
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