CN111286669A - Martensite hot-rolled high-strength steel with yield strength not less than 900Mpa and preparation method thereof - Google Patents
Martensite hot-rolled high-strength steel with yield strength not less than 900Mpa 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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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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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
- 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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- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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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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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- 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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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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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
- 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
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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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
- C21D2211/008—Martensite
Abstract
The invention discloses martensite hot-rolled high-strength steel with yield strength of more than or equal to 900MPa and a preparation method thereof, the martensite hot-rolled high-strength steel with yield strength of more than or equal to 900MPa ensures that the comprehensive performance meets the requirements by adjusting the proportion of each component, and in the preparation method of the martensite hot-rolled high-strength steel with yield strength of more than or equal to 900MPa, an LF refining and RH refining dual-path form is adopted, and calcium treatment is carried out by matching with a calcium-silicon wire, so that the molten steel is pure, the comprehensive performance of steel is improved, in addition, the preparation method adopts low-temperature coiling, the hot-rolled high-strength steel with martensite structure is directly obtained, the subsequent tempering treatment is omitted, the cost is reduced, and the preparation period is also shortened. The martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa and the preparation method thereof have the advantages of excellent comprehensive performance, low production cost, short production period and the like.
Description
Technical Field
The invention relates to the technical field of steel smelting, in particular to martensite hot-rolled high-strength steel with yield strength of more than or equal to 900MPa and a preparation method thereof.
Background
With the progress of society and the development of science and technology, the requirements of people on engineering machinery are continuously improved, for example, the engineering machinery has higher working efficiency, longer service life, lower use cost and the like, and in order to improve the working efficiency of the engineering machinery, reduce the energy consumption of the engineering machinery and reduce the self weight, the engineering machinery is continuously developed towards high parametrization, large-scale and light-weight. In order to meet the above requirements for construction machines, high-strength steel must be used in large quantities in the manufacture of construction machines.
At present, the ultrahigh-strength structural steel with the yield strength of more than 900MPa cannot be completely made in China, and the difficulty mainly comprises the matching of comprehensive properties, the control of plate shapes, cost and the like. The high-strength steel of 900MPa grade produced by domestic steel mills is mainly quenched and tempered steel, namely, a large amount of microalloyed elements such as Nb, V, Ti and the like are added into the steel, and then the steel is quenched and tempered at high temperature to produce the steel for high-strength engineering machinery meeting performance requirements. When the preparation method is used, the comprehensive performance of the high-strength steel is influenced due to the influence of the addition of micro-alloying elements such as Nb, V, Ti and the like, and the high-strength steel needs to be quenched and tempered at high temperature again, so that the preparation cost is increased, and the preparation period is prolonged.
Therefore, it is an urgent need to solve the problem of reducing the manufacturing cost, shortening the manufacturing cycle, and satisfying the requirements of high-strength steel with comprehensive performance from the two aspects of components and manufacturing method.
Disclosure of Invention
In view of the above, the invention provides the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa and the preparation method thereof, which can improve the comprehensive performance of the existing high-strength steel and solve the problems of high preparation cost and long preparation period when the existing preparation method is adopted to prepare the high-strength steel.
On the one hand, the invention provides martensite hot-rolled high-strength steel with yield strength more than or equal to 900MPa, which comprises, by weight, 0.11-0.13% of C, 0.15-0.25% of Si, 1.15-1.25% of Mn, 0.020-0.045% of Al, 0.20-0.80% of Cr + Mo, 0.15-0.25% of Nb + V + Ti, 0.0015-0.0025% of B, 0.002-0.004% of Ca0.002%, less than or equal to 0.010% of P, less than or equal to 0.002% of S, less than or equal to 0.045% of N, less than or equal to 0.0020% of O, and the balance of Fe and unavoidable impurities.
The invention also provides a preparation method of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa, which comprises the following steps:
pretreating molten iron: pretreating molten iron, and controlling the S content in the molten iron to be less than or equal to 0.006 percent according to mass percentage;
converter: carrying out converter carbon drawing on the pretreated molten iron, alloying according to the designed element content, and purging a steel ladle by adopting argon before tapping;
refining: sequentially performing LF refining and RH refining on the molten steel after the converter, and performing calcium treatment by adopting a calcium-silicon wire;
continuous casting: continuously casting the refined molten steel into a plate blank by adopting a continuous casting machine;
rolling and coiling: the method is characterized in that a hot rolling mode is adopted, a plate blank is placed into a heating furnace to be heated, a 3+3 mode is selected for controlling the rough rolling pass, the finish rolling temperature is more than or equal to 820 ℃, the curling temperature is less than or equal to 300 ℃, and the cooling mode is a front-section continuous uniform cooling mode.
Preferably, in the converter step, the ALs in the steel ladle is controlled to be 0.010-0.030% by weight, and the N in the steel ladle is controlled to be less than or equal to 25ppm by weight.
Preferably, during LF refining, positive pressure is maintained, the N increase amount is controlled to be less than or equal to 10ppm, and active lime and fluorite are adopted to produce reducing slag with good fluidity in the LF refining.
Further preferably, in the rolling and coiling steps, the heating temperature is 1210-1260 ℃, and the heat preservation time is 30 minutes.
Further preferably, in the continuous casting step, the drawing speed is kept constant, and the continuous casting superheat degree is less than or equal to 25 ℃.
Further optimizing, wherein in the continuous casting step, the N increasing amount is controlled to be less than or equal to 5 ppm.
The martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa provided by the invention has the advantages that the mechanical property of the martensite hot-rolled high-strength steel is improved by controlling the C, Si and Mn contents in the martensite hot-rolled high-strength steel, and the martensite hot-rolled high-strength steel not only has higher yield strength, but also has higher tensile strength. Meanwhile, the content of P, S, N and O in the martensite hot-rolled high-strength steel is controlled, so that the adverse effects of the components on the martensite hot-rolled high-strength steel, such as increased cold brittleness, reduced impact toughness, reduced toughness and plasticity and the like, are avoided, and the mechanical property of the martensite hot-rolled high-strength steel is further ensured. In addition, by adding a proper amount of Ca, Cr, Mo, Nb, V and Ti, the yield strength and tensile strength of the martensite hot-rolled high-strength steel can be further improved, and simultaneously the toughness and wear resistance are also improved, so that the comprehensive performance of the martensite hot-rolled high-strength steel is improved.
According to the preparation method of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa, the inclusion in the molten steel is effectively removed while degassing, decarbonization, desulfurization and deoxidation are effectively carried out on the molten steel by adopting an LF refining and RH refining dual-path mode and adopting a calcium-silicon wire for calcium treatment, so that the purity of the molten steel is ensured, and the accuracy of the target component of the prepared martensite hot-rolled high-strength steel is further ensured. In addition, the hot-rolled high-strength steel with the martensite structure can be directly obtained by adopting the ultra-low curling temperature, the martensite hot-rolled high-strength steel with the comprehensive performance meeting the requirement and the yield strength of more than or equal to 900MPa can be obtained without subsequent quenching and tempering, the preparation cost is saved, and the preparation period is shortened.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is a microstructure diagram of a martensitic hot-rolled high-strength steel with a yield strength of not less than 900MPa, which is provided by the disclosed embodiment of the invention.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of methods consistent with certain aspects of the invention, as detailed in the appended claims.
In order to solve the problem that the composition ratio of the existing high-strength steel influences the comprehensive performance, the embodiment provides the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa, and specifically, the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa comprises, by weight, 0.11-0.13% of C, 0.15-0.25% of Si, 1.15-1.25% of Mn, 0.020-0.045% of Al, 0.20-0.80% of Cr + Mo, 0.15-0.25% of Nb + V + Ti, 0.0015-0.0025% of B, 0.002-0.004% of Ca0.002%, less than or equal to 0.010% of P, less than or equal to 0.002% of S, less than or equal to 0.045% of N, less than or equal to 0.0020% of O, and.
The martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa has the advantages that the mechanical property of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa is improved by controlling the component proportion in the high-strength steel, so that better comprehensive performance is achieved.
The specific component properties are as follows:
carbon (C): carbon is the main alloying element in steel, and carbon is used to form sufficient carbide strengthening phase, and as the carbon content in steel increases, the yield point and tensile strength increase, and the plasticity and impact properties decrease. Therefore, too high carbon content can lower the plasticity and impact toughness of the steel, and deteriorate cold formability and weldability, so that the carbon content in the steel should be minimized on the premise of ensuring the strength, and the C content is preferably in the range of 0.11 to 0.13 wt% because of the high strength.
Silicon (Si): silicon and oxygen have a strong affinity, belong to strong deoxidizing elements, and exist in solid solution in steel. Si can improve the strength, fatigue limit, corrosion resistance and wear resistance of steel, but Si content is too high, oxides are easily generated during hot rolling, and the surface quality of steel is reduced. Therefore, the silicon content is preferably 0.15 to 0.25 wt%.
Manganese (Mn): manganese exists in the steel in a solid solution state, belongs to a solid solution strengthening element, and can improve the strength of ferrite. However, since an excessive amount of manganese lowers toughness and weldability of the steel, the manganese content is preferably 1.15 to 1.25 wt%.
Phosphorus (P): phosphorus is a harmful element in steel, increases cold brittleness of steel, deteriorates weldability, and reduces plasticity. Therefore, the phosphorus content is preferably 0.010% by weight or less.
Sulfur (S): sulfur is a harmful element in steel, so that the steel generates hot brittleness, the toughness and the plasticity of the steel are reduced, cracks are easy to generate in the rolling process, and the sulfur content of high-quality steel is generally required to be less than 0.04 percent, so the sulfur content is preferably less than or equal to 0.002 percent by weight.
Nitrogen (N): too high a nitrogen content in the steel affects the impact toughness of the steel. Therefore, the nitrogen content is preferably 0.045 wt% or less.
Oxygen (O): the oxygen content in the steel is controlled by low oxygen, so that inclusions are reduced, and the toughness and plasticity are improved. Therefore, the oxygen content is preferably 0.0020 wt% or less.
Calcium (Ca): the calcium treatment is adopted to modify MnS in the steel to eliminate the harm of MnS, so the calcium content is preferably 0.002-0.004 wt%.
Niobium (Nb), vanadium (V), titanium (Ti): niobium (Nb), vanadium (V) and titanium (Ti) are added into steel to promote grain refinement, and the toughness is gradually increased while the strength is improved, so that the content of niobium (Nb) + vanadium (V) + titanium (Ti) is preferably 0.15-0.25 wt%
Chromium (Cr), molybdenum (Mo): the elements of chromium (Cr) and molybdenum (Mo) are added into the steel, and in the structural steel, the strength, the hardness and the wear resistance of the steel can be obviously improved, and the hardenability of the steel is improved. Therefore, the content of chromium (Cr) + molybdenum (Mo) is preferably 0.20 to 0.80 wt%.
In order to solve the problems of high cost and long preparation period of the existing high-strength steel preparation method, the embodiment provides a preparation method of martensite hot-rolled high-strength steel with yield strength of more than or equal to 900MPa, which comprises the following steps:
1) pretreating molten iron: pretreating molten iron, and controlling the S content in the molten iron to be less than or equal to 0.006 percent according to mass percentage;
2) converter: carrying out converter carbon drawing on the pretreated molten iron, alloying according to the designed element content, and purging a steel ladle by adopting argon before tapping;
3) refining: sequentially performing LF refining and RH refining on the molten steel after the converter, and performing calcium treatment by adopting a calcium-silicon wire;
4) continuous casting: continuously casting the refined molten steel into a plate blank by adopting a continuous casting machine;
5) rolling and coiling: the method is characterized in that a hot rolling mode is adopted, a plate blank is placed into a heating furnace to be heated, a 3+3 mode is selected for controlling the rough rolling pass, the finish rolling temperature is more than or equal to 820 ℃, the curling temperature is less than or equal to 300 ℃, and the cooling mode is a front-section continuous uniform cooling mode.
The preparation method of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa adopts a dual-path mode of LF refining and RH refining, namely, the LF refining and the RH refining are sequentially carried out on molten steel. RH refining (vacuum circulation deoxidation method) is characterized in that a small part of molten steel enters a vacuum environment by blowing inert gas, and the contact area of the steel and the gas is increased, the degassing effect is improved and the decarburization effect is good through vacuum treatment. In LF refining (i.e. a submerged arc heating furnace method), submerged arc is used for heating molten steel, and inert gas is blown into the molten steel, so that refining in a non-oxidizing atmosphere is realized, and further, the effects of desulfurization, deoxidation and inclusion removal are achieved. According to the preparation method of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa, the molten steel is subjected to LF refining and RH refining in sequence, so that the molten steel is purer, the prepared high-strength steel has better mechanical properties, and the comprehensive performance requirements of the high-strength steel are met.
In addition, the preparation method of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa adopts the ultralow coiling temperature, can directly obtain the hot-rolled high-strength steel with a martensite structure, omits the quenching and tempering process in the existing high-strength steel preparation method, and ensures that the high-strength steel prepared by the preparation method of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa meets the comprehensive performance standard, reduces the preparation process, shortens the preparation period and reduces the preparation cost.
In the converter step, the ALs in the ladle is controlled to be 0.010-0.030% and the N in the ladle is controlled to be less than or equal to 25ppm according to weight percentage. By controlling the content of ALs, the total amount of impurities can be effectively controlled, so that the purity of steel is improved, the mechanical property of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa prepared by the preparation method is better, and the requirement on the comprehensive property of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa is met. By controlling the content of N in the steel ladle, N elements in the steel ladle are prevented from entering molten steel in the refining process, so that the content of N in molten steel components exceeds the standard, the condition that the mechanical property of high-strength steel does not reach the standard due to the fact that the content of N exceeds the standard is further avoided, and the comprehensive performance of the high-strength steel meets the requirements.
In the refining step, positive pressure is kept during LF refining, the N increase amount is controlled to be less than or equal to 10ppm, and active lime and fluorite are adopted to produce reducing slag with good fluidity in the LF refining. By controlling the N increasing amount, the N content in the steel can be ensured to meet the requirement, and the comprehensive performance of the prepared high-strength steel is further ensured to meet the requirement. By adding active lime and fluorite to make reducing slag with good fluidity, the fluidity of the slag can be improved, and the desulfurization and dephosphorization efficiency can be improved.
In the rolling and coiling steps, the heating temperature is 1210-1260 ℃, and the heat preservation time is 30 minutes. By controlling the heating temperature and the heat preservation time, the generation of the casting blank iron oxide scale can be effectively reduced, the uniform heating temperature of the casting blank is ensured, the generation of internal stress is reduced, and the plate shape is further ensured.
In the continuous casting step, the drawing speed is kept constant, and the continuous casting superheat degree is less than or equal to 25 ℃. By controlling the constant drawing speed and the continuous casting superheat degree, the internal and external quality of the plate blank can be ensured, the comprehensive performance of the prepared high-strength steel is further ensured, and the conditions that the shell of the crystallizer is thin, steel leakage is easy to occur, non-metal impurities are increased and the like caused by overhigh speed or overhigh continuous casting superheat degree are avoided.
In the continuous casting step, the N increasing amount is controlled to be less than or equal to 5 ppm. By controlling the N content, N can be prevented from entering the steel during continuous casting, so that the content of N in the steel is too high, and the condition that the comprehensive performance is reduced due to the fact that the content of N in the steel exceeds the standard is avoided. Therefore, the comprehensive performance of the high-strength steel can be further ensured by controlling the N increasing amount.
The invention will now be further illustrated with reference to specific examples, which are not intended to limit the scope of the invention.
The following examples were prepared as follows: 1) pretreating molten iron: the molten iron is pretreated, the S content in the molten iron is controlled to be less than or equal to 0.006 percent according to the mass percentage, and the material is selected from fine material scrap steel. 2) Converter: carrying out converter carbon drawing on the pretreated molten iron, alloying according to the designed element content, purging a steel ladle by adopting argon before tapping, controlling ALs in the steel ladle to be 0.010-0.030%, and controlling N in the steel ladle to be less than or equal to 25 ppm. By controlling the content of ALs. 3) Refining: after LF refining and RH refining are carried out on molten steel after a converter in sequence, positive pressure is kept during LF refining, the quantity of increased N is required to be less than or equal to 10ppm, reducing slag with good fluidity is made of active lime and fluorite in the LF refining, argon blowing strength is controlled, and calcium treatment is carried out by adopting a calcium-silicon line. 4) Continuous casting: the refined molten steel is continuously cast into a slab by a continuous casting machine, argon is adopted to purge a tundish before casting, no molten steel is exposed in the casting process, the N increase is controlled to be less than or equal to 5ppm, the constant drawing speed is kept, and the continuous casting superheat degree is less than or equal to 25 ℃. 5) Rolling and coiling: and (3) heating the plate blank in a heating furnace by adopting a hot rolling mode, wherein the heating temperature is 1210-1260 ℃, and the heat preservation time is 30 minutes. The rough rolling pass is controlled by selecting a 3+3 mode, the finish rolling temperature is more than or equal to 820 ℃, the curling temperature is less than or equal to 300 ℃, and the cooling mode is continuous and uniform cooling of the front section. And 3, the hot head and the hot tail are put in, so that the coiling is convenient, and a finished product is obtained.
And (3) carrying out component detection on the finished product, wherein the specific components are in the range of table 1.
Table 1:
| C(％) | Si(％) | Mn(％) | Al(％) | Cr+Mo(％) | Nb+V+Ti(％) | B％ |
| 0.11-0.13 | 0.15-0.25 | 1.15-1.25 | 0.020-0.045 | 0.020-0.045 | 0.15-0.25 | 0.0015-0.0025 |
| Ca％ | P％ | S％ | N％ | O％ | Fe | |
| 0.002-0.004 | ≤0.010 | ≤0.002 | ≤0.045 | ≤0.0020 | balance of |
Comparative example 1
Heating the steel belt to 720 ℃ within 10-15 seconds by adopting a quenching and tempering process, heating the steel belt to 900 ℃ within 2 minutes by adopting resistance heating at the rear part, keeping the temperature for 5 minutes, quenching by adopting an air mist and air cooling mode, and subsequently tempering for 15 minutes at 600 ℃.
The specific components are shown in Table 2.
Table 2:
comparative example 2
And (3) adopting an annealing process, keeping the temperature at 500 ℃ for 6 hours, heating for about 3-4 hours, cooling the furnace to 120 ℃, discharging, and taking 8-9 hours.
The specific components are shown in Table 3.
Table 3:
| code | E364201 | E364201 | E364201 | E364201 | Melting analysis |
| Composition (I) | Standard of merit | Release | Internal control | Target | 1955301 |
| C | ≤0.20 | 0.11-0.13 | 0.11-0.13 | 0.12 | 0.11 |
| Si | ≤0.60 | 0.15-0.30 | 0.15-0.25 | 0.20 | 0.24 |
| Mn | ≤2.20 | 1.10-1.30 | 1.15-1.25 | 1.20 | 1.17 |
| P | ≤0.025 | ≤0.010 | ≤0.010 | ≤0.008 | 0.012 |
| S | ≤0.010 | ≤0.002 | ≤0.002 | ≤0.001 | 0.001 |
| Alt | ≥0.015 | 0.015-0.055 | 0.020-0.045 | 0.030 | 0.043 |
| Nb | ≤0.090 | 0.015-0.030 | 0.015-0.025 | 0.020 | 0.019 |
| V | ≤0.200 | 0.070-0.090 | 0.075-0.085 | 0.080 | 0.079 |
| Ti | ≤0.250 | 0.090-0.115 | 0.090-0.110 | 0.100 | 0.100 |
| Cr | -- | 0.15-0.25 | 0.15-0.25 | 0.20 | 0.20 |
| Mo | ≤1.00 | 0.35-0.45 | 0.35-0.45 | 0.40 | 0.41 |
| B | ≤0.0050 | 0.0015-0.0030 | 0.0015-0.0025 | 0.0020 | 0.0028 |
| Ca | -- | 0.0015-0.0045 | 0.0020-0.0040 | 0.0025 | 0.0022 |
| N | -- | ≤0.0050 | ≤0.0045 | ≤0.0040 | 0.0037 |
| O | -- | ≤0.0020 | ≤0.0020 | ≤0.0018 | 0.0014 |
| Ni | -- | ≤0.80 | -- | -- | 0.01 |
| Cu | -- | ≤0.80 | -- | -- | 0.01 |
Example 3
The high-strength steels of example 1, example 2, comparative example 1 and comparative example 2 were subjected to performance tests, which are specifically shown in table 4.
Table 4:
among them, the microstructure of the high strength steel prepared in example 1 is shown in fig. 1.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
It is to be understood that the present invention is not limited to what has been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (7)
1. The martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa is characterized by comprising, by weight, 0.11-0.13% of C, 0.15-0.25% of Si, 1.15-1.25% of Mn, 0.020-0.045% of Al, 0.20-0.80% of Cr + Mo0.20%, 0.15-0.25% of Nb + V + Ti, 0.0015-0.0025% of B, 0.002-0.004% of Ca, less than or equal to 0.010% of P, less than or equal to 0.002% of S, less than or equal to 0.045% of N, less than or equal to 0.0020% of O, and the balance of Fe and unavoidable impurities.
2. The preparation method of the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa according to claim 1 is characterized by comprising the following steps:
pretreating molten iron: pretreating molten iron, and controlling the S content in the molten iron to be less than or equal to 0.006 percent according to mass percentage;
converter: carrying out converter carbon drawing on the pretreated molten iron, alloying according to the designed element content, and purging a steel ladle by adopting argon before tapping;
refining: sequentially performing LF refining and RH refining on the molten steel after the converter, and performing calcium treatment by adopting a calcium-silicon wire;
continuous casting: continuously casting the refined molten steel into a plate blank by adopting a continuous casting machine;
rolling and coiling: the method is characterized in that a hot rolling mode is adopted, a plate blank is placed into a heating furnace to be heated, a 3+3 mode is selected for controlling the rough rolling pass, the finish rolling temperature is more than or equal to 820 ℃, the curling temperature is less than or equal to 300 ℃, and the cooling mode is a front-section continuous uniform cooling mode.
3. The method for preparing the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa according to claim 2, wherein in the converter step, the ALs in the steel ladle is controlled to be 0.010-0.030% by weight, and the N in the steel ladle is controlled to be less than or equal to 25 ppm.
4. The method for preparing the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa according to claim 2, wherein positive pressure is kept during LF refining, N increase is controlled to be less than or equal to 10ppm, and active lime and fluorite are adopted to produce reducing slag with good fluidity during LF refining.
5. The method for preparing the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa according to claim 2, wherein in the rolling and coiling steps, the heating temperature is 1210-1260 ℃, and the heat preservation time is 30 minutes.
6. The method for preparing the martensite hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa according to claim 2, wherein in the continuous casting step, the constant drawing speed is kept, and the continuous casting superheat degree is less than or equal to 25 ℃.
7. The method for preparing the martensitic hot-rolled high-strength steel with the yield strength of more than or equal to 900MPa according to claim 2, wherein in the continuous casting step, the N increase amount is controlled to be less than or equal to 5 ppm.
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