CN115491596A - 590MPa reinforced plasticity dual-phase steel and preparation method thereof - Google Patents
590MPa reinforced plasticity dual-phase steel and preparation method thereof Download PDFInfo
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Images
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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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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- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention particularly relates to 590MPa reinforced plasticity dual-phase steel and a preparation method thereof, belonging to the field of steel preparation. A590 MPa reinforced plastic dual-phase steel comprises the following chemical components in percentage by mass: c:0.09-0.12%, si:0.1-0.7%, mn:1.4-2.1%, P: less than or equal to 0.015 percent, S: less than or equal to 0.006 percent, al:0.2-0.6%, nb:0.01-0.04%, and the balance of Fe and inevitable impurities. The dual-phase steel can effectively solve the technical problems that the existing dual-phase steel is insufficient in plasticity and cannot be applied to complex stamping treatment.
Description
Technical Field
The invention belongs to the field of steel preparation, and particularly relates to 590MPa reinforced plasticity dual-phase steel and a preparation method thereof.
Background
Along with the development of energy conservation, emission reduction and light weight in the automobile industry, the high-strength steel has more and more use proportion, and the dual-phase steel has the most extensive application due to good comprehensive mechanical properties. However, in the using process, the traditional DP steel is still difficult to form on a plurality of high-ductility parts and is difficult to meet the requirement of complex stamping structural parts of automobile design, which directly causes severe cracking phenomenon in the stamping process, for example, the traditional 590MPa grade dual-phase steel has the elongation of only about 24-30%, and greatly limits the application of the traditional DP steel in complex stamping parts. The TRIP steel is adopted, so that the alloy content is high, the welding problem is high, the elongation is redundant, and waste is caused. Therefore, some concepts of plastic-reinforced dual-phase steel have been proposed in galloping and VDA, etc., that is, a small amount of retained austenite is introduced on the basis of dual-phase steel ferrite and martensite structure to obtain a certain TRIP effect to improve elongation. But at present, corresponding ingredient design and tissue performance regulation and control experience is lacked in China.
Disclosure of Invention
The application aims to provide 590MPa reinforced plasticity dual-phase steel and a preparation method thereof, and aims to solve the technical problems that the existing dual-phase steel is enough in strength, insufficient in plasticity and incapable of being applied to complex stamping treatment.
The embodiment of the invention provides 590MPa reinforced plastic dual-phase steel, which comprises the following chemical components in percentage by mass:
c:0.09-0.12%, si:0.1-0.7%, mn:1.4-2.1%, P: less than or equal to 0.015%, S: less than or equal to 0.006 percent, al:0.2-0.6%, nb:0.01-0.04%, and the balance of Fe and inevitable impurities.
Optionally, in the chemical components of the steel, the sum of the mass percentages of Al and Si is: 0.4 to 1.3 percent.
Optionally, the metallographic structure of the steel comprises, by volume percent:
ferrite: 42-82%, martensite: 8-37%, retained austenite: 2-13%, bainite: 2 to 9 percent.
Optionally, the martensite is dispersed in the ferrite, and the size of the martensite is 2-10 μm;
the residual austenite is in a film shape, and the interlayer spacing of the residual austenite is 2-5 mu m.
Optionally, the ferrite contains a plurality of NbC nanometer precipitated phases, the size of the NbC nanometer precipitated phases is 2-10nm,the number of the NbC nanometer precipitated phases is less than 5000 per mu m 3 。
Based on the same inventive concept, the embodiment of the invention also provides a preparation method of the 590MPa reinforced plastic dual-phase steel, which comprises the following steps:
smelting to obtain molten steel according with the chemical components;
continuously casting the molten steel, heating, roughly rolling, removing phosphorus and finely rolling to obtain a hot rolled plate;
carrying out laminar cooling, coiling, acid pickling and cold rolling on the hot rolled plate to obtain strip steel;
cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plastic dual-phase steel;
wherein:
the water pressure of the dephosphorization solution for dephosphorization is 25-40MPa;
the finish rolling temperature of the finish rolling is 870-950 ℃;
the coiling temperature is more than or equal to 600 ℃;
the total rolling reduction rate of the cold rolling is 40-65%;
the slow cooling end point temperature is 600-700 ℃;
the temperature of the aging treatment is 260-330 ℃, and the time of the aging treatment is 250-330s;
the final cooling temperature is 120-150 ℃;
the elongation of the finishing is 0.1-0.7%.
Optionally, the chemical components of the continuous casting mold flux comprise, by mass:
CaO：25-30％，SiO 2 ：21-38％，Al 2 O 3 ：1-3％，MgO：2-4％；
the section of the continuous casting is 1400-1600mm, the drawing speed of the continuous casting is 1.0-1.2m/min, and the viscosity of the continuous casting covering slag is 0.12-0.16.
Optionally, the cleaning comprises physical brushing and electrolytic cleaning.
Optionally, the rapid cooling is performed in a hydrogen atmosphere, the concentration of the hydrogen atmosphere is 40-60%, and the end point temperature of the rapid cooling is 260-330 ℃.
Optionally, the annealing temperature is 770-860 ℃, and the annealing heat preservation time is 2-5min.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
according to the 590MPa reinforced plasticity dual-phase steel provided by the embodiment of the invention, the strength performance and the plasticity can be considered at the same time by designing the chemical components of the steel, and specifically, the upper limit of the C content is controlled on the premise of ensuring the strength performance, so that the plasticity and the welding performance are improved; by controlling the content of Si, the enrichment of C to the retained austenite is promoted, the hardenability of the retained austenite is improved, and simultaneously, a ferrite phase is purified, and the plasticity and the elongation are improved; by controlling the upper limit of the Mn content, the lower limit of plasticity is ensured while the strength of the steel is strengthened; by controlling the Al content, the enrichment of C to unconverted residual austenite is promoted, the precipitation of carbide is inhibited, and the plasticity and the elongation are improved; the upper limit of the Nb content is controlled, the refined crystal grains are utilized to improve the strength of the steel, and the lower limit of plasticity is controlled; through the combined action of the elements, the 590MPa reinforced plastic dual-phase steel has better strength and plasticity, and effectively solves the technical problems that the existing dual-phase steel has enough strength, but insufficient plasticity and cannot be applied to complex stamping treatment.
The above description is only an overview of the technical solutions of the present invention, and the present invention can be implemented in accordance with the content of the description so as to make the technical means of the present invention more clearly understood, and the above and other objects, features, and advantages of the present invention will be more clearly understood.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a flow chart of a method for producing a 590MPa reinforced plastic dual-phase steel according to an embodiment of the present invention;
FIG. 2 is a metallographic structure drawing of a 590MPa reinforced plastic dual phase steel provided in example 1 of the present invention;
FIG. 3 is a partially enlarged view showing a crack of a cast slab in the continuous casting of dual phase steel according to comparative example 2 of the present invention.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. For example, room temperature may refer to a temperature in the interval of 10 to 35 ℃.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
In order to solve the technical problems, the general idea of the embodiment of the application is as follows:
according to an exemplary embodiment of the present invention, there is provided a 590MPa reinforced plastic dual phase steel, the chemical composition of which comprises, in mass%:
c:0.09-0.12%, si:0.1-0.7%, mn:1.4-2.1%, P: less than or equal to 0.015 percent, S: less than or equal to 0.006 percent, al:0.2-0.6%, nb:0.01-0.04%, and the balance of Fe and inevitable impurities.
The actions and the limited ranges of the main alloy elements are explained in detail as follows:
c: the C element is the most important solid solution strengthening element and the element for improving the residual austenite hardenability in the reinforced plastic dual-phase steel, the C content is required to be more than or equal to 0.07 percent in order to obtain enough martensite in the cooling process to ensure the strength, and simultaneously, the C element and the microalloy Nb element form carbonitride in the heat treatment process, refine grains and strengthen ferrite, but the C content is required to be controlled to be 0.09-0.12 percent in order to avoid the welding performance deterioration caused by the overhigh C content.
Si: si is also an important solid solution strengthening element, and Si can effectively promote C to be enriched to retained austenite, improve the hardenability of the retained austenite, purify ferrite phase and improve elongation, but Si has the defect that the excessive content (more than 0.5 percent) of Si forms iron scales which are difficult to remove in the hot rolling heating process, so the Si content needs to be controlled to be 0.1-0.7 percent.
Mn: mn is also an important element for solid solution strengthening and residual austenite stabilization, and plays an important role in strengthening, but too high Mn content is easy to cause structure segregation, is easy to cause forming cracking and worsen the comprehensive performance of steel, and can be enriched to the surface in the annealing process, so that the Mn content is not suitable to be too high and needs to be controlled to be 1.4-2.1%.
P: the element P can inhibit the formation of carbide, so that the element P is considered to be favorable in a very small amount, but the segregation at the grain boundary can cause the reduction of the grain boundary strength to deteriorate the mechanical property of the material, and the element P is a significant influence element contributing to carbon equivalent, and the content of the element P is controlled below 0.015 percent.
S: the S element is used as a harmful element, mainly prevents MnS from being generated by combining with Mn so as to deteriorate the material performance, and contributes significant influence elements for carbon equivalent, and the content of the S element is controlled below 0.006 percent.
Al: similar to the action of Si, al can promote the enrichment of C to unconverted residual austenite, inhibit carbide precipitation and improve elongation, but the effect is lower than that of Si, the solid solution strengthening effect of Al is weaker than that of Si, and the content of Al is too high, so that transverse and longitudinal cracks of a continuous casting billet occur frequently, and the continuous casting billet is broken or generates holes during hot rolling, therefore, the content of Al is controlled to be 0.2-0.6%.
Nb: nb element as microalloy element can combine with C to generate nanometer precipitated phase, plays the role of grain refinement and precipitation strengthening, has obvious effects of improving the structure form and increasing the yield strength, but the elongation is adversely affected by too high content, so the content of Nb element needs to be controlled at 0.01-0.04%.
As an optional embodiment, in the chemical composition of the steel, the sum of the mass percentages of Al and Si is: 0.4 to 1.3 percent.
The reason why the sum of the mass percentages of aluminum and silicon is controlled is that: the two are similar in thermodynamic action, in order to ensure that ferrite is purified, residual austenite is stabilized, and finally the elongation of the reinforced plastic dual-phase steel is improved, the effect of improving the elongation of Al is weaker than that of Si, and the crack risk of a continuous casting billet is increased, so that Al is added as an auxiliary additive, and the sum of the contents of the Al and the Al is controlled to meet 0.5-1.3%.
As an alternative embodiment, the metallographic structure of the steel comprises, in volume percent: ferrite: 42-82%, martensite: 8-37%, retained austenite: 2-13%, bainite: 2 to 9 percent.
The reason why the metallographic structure of steel is controlled to the above-described structure combination is that: ferrite is a soft phase in a matrix, bears most strain during deformation, ensures the plasticity and the formability of the dual-phase steel, is difficult to ensure to obtain excellent plasticity when the content is less than 42 percent, and cannot ensure to reach the expected strength target when the content exceeds 82 percent. Martensite is transformed from austenite by rapid cooling in the continuous annealing process, belongs to a hard phase in a matrix, is an important composition phase for ensuring the strength of the dual-phase steel, has insufficient strength when the volume fraction is less than 8 percent, and has seriously reduced plasticity and formability when the volume fraction exceeds 37 percent. The retained austenite is an important composition phase of the steel grade, and is transformed into martensite in the deformation process, so that the stress concentration can be relieved, the necking is delayed, the plasticity and the formability of the material are improved, in order to ensure that the elongation is more than 30%, the content of the retained austenite is more than 2% except the contribution of ferrite in a matrix, and when the volume fraction is more than 13%, the stability is reduced due to insufficient internal carbon content, strain-induced phase transformation is easy to occur at the initial stage of deformation, and the continuous target of delayed necking is difficult to realize. The bainite phase is used as an intermediate phase in a structure, is formed by transforming partial austenite in a continuous cooling process, has the hardness between that of martensite and that of ferrite, is favorable for uniform expansion of strain in a deformation process, has important significance for improving the local formability of the material, and has the content of 2-9%.
As an alternative embodiment, the martensite is dispersed in the ferrite, and the size of the martensite is 2-10 μm; the residual austenite is in a film shape, and the interlayer spacing of the residual austenite is 2-5 mu m.
The reasons for controlling the above morphology and particle size are: martensite is used as a hard phase in a matrix structure, the size of the martensite is too small, the martensite plays an important role in distribution and expansion of strain in the structure, when the size of martensite crystal grains is too small, the process realization difficulty is increased, the crystal grain strengthening effect is obvious, the strength cannot reach the expected target, when the size of the martensite crystal grains is too large, the interface of ferrite and martensite phase is also larger, cracks are easy to crack and transfer at the interface of the ferrite and the martensite phase during deformation, and good formability is not facilitated to obtain. The retained austenite is an important composition phase for improving plasticity, the form and the interlayer spacing thereof are important indexes for evaluating the stability and playing a role in improving the plasticity, the form is a film shape and has better stability, and the interlayer spacing of 2-5 mu m can enable the strain-induced plasticity to be better played in the deformation process.
As an alternative embodiment, the ferrite contains several NbC nano precipitates, the size of the NbC nano precipitates is 2-10nm, and the number of the NbC nano precipitates is less than 5000/μm 3 。
The function of NbC nanometer precipitated phase is as follows: on one hand, the nano precipitation refines the grain size of original residual austenite to realize fine grain strengthening, on the other hand, a nano precipitation phase is precipitated in ferrite to achieve the purpose of strengthening the ferrite, and the nano precipitation phase is beneficial to improving the reaming performance.
The reason for controlling the number of NbC nanometer precipitated phases is as follows: the number of the nanometer precipitated phases is statistically significant, if the precipitated number is too large, good strong plasticity is not obtained, and if the precipitated number is too small, the precipitation strengthening purpose cannot be achieved, and the hole expansion rate cannot be increased by more than 50%.
According to another exemplary embodiment of the present invention, there is provided a manufacturing method of the 590 MPa-reinforced plastic dual-phase steel provided as above, including the steps of:
s1, smelting to obtain molten steel according with the chemical components.
S2, continuously casting the molten steel, heating, roughly rolling, removing phosphorus and finely rolling to obtain the hot rolled plate.
And S3, carrying out laminar cooling, coiling, acid pickling and cold rolling on the hot rolled plate to obtain the strip steel.
And S4, cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plasticity dual-phase steel.
As an optional embodiment, the water pressure of the dephosphorization liquid for dephosphorization is 25-40MPa.
The reason for controlling the dephosphorization liquid pressure is that: if the pressure is lower than the pressure, the removal of the iron scale in the hot rolling process is not facilitated, and if the pressure is higher than the pressure, the removal of the iron scale is facilitated, but the pressure is excessive, and the energy is wasted.
As an alternative embodiment, the finishing temperature of the finish rolling is 870 to 950 ℃.
The reason why the finish rolling temperature of the finish rolling is controlled is that: if the finish rolling temperature is too low, the resistance to deformation of the hot-rolled sheet increases, and the problem of edge cracking tends to occur, and if the finish rolling temperature is too high, it is not preferable to obtain good texture properties.
As an alternative embodiment, the coiling temperature is 600 ℃ or higher.
The reason why the coiling temperature is controlled is that: the reason why the coiling temperature is controlled is that: when the coiling temperature is more than or equal to 600 ℃, the intermediate structure of the target hot-rolled coil can be a few bainite and a large amount of ferrite structures, and in order to facilitate rolling in the cold rolling process, a large amount of bainite is generated when the coiling temperature is too low, so that the cold rolling difficulty is increased, and edge cracks are easily caused.
As an alternative embodiment, the total reduction of the cold rolling is 40-65%.
The reason why the total reduction ratio of the cold rolling is controlled is that: the reasons for controlling the total reduction are: if the total reduction rate is less than 40%, the deformation energy storage is unfair, and the grains are easy to be uneven; and is not beneficial to recrystallization and nucleation in the annealing process; if the total reduction is more than 65%, the steel plate has excessive deformation resistance, which increases the load of the rolling mill and is prone to cracking.
As an alternative embodiment, the number of cold rolling passes is 5, if the number of cold rolling passes is less than 5, the rolling load is large, which is not favorable for smooth rolling, and if the number of cold rolling passes is more than 5, the production rhythm is slow, which is not favorable for exerting the productivity.
As an alternative embodiment, the terminal temperature of the slow cooling is 600 to 700 ℃.
The reason for controlling the temperature of the slow cooling is: the slow cooling is carried out below 700 ℃, so that the generation of new ferrite is facilitated, C, mn elements are further distributed between ferrite and residual austenite, the formation of the residual austenite and the improvement of plasticity are facilitated, and if the temperature is lower than 600 ℃, the proportion of ferrite is too high, and the required tensile strength cannot be ensured.
As an alternative embodiment, the temperature of the aging treatment is 260-330 ℃, and the time of the aging treatment is 250-330s.
The reasons for controlling the temperature and time of the failure treatment are: the aging time is controlled by the length of the aging section and the running speed of the strip steel, the aging time of the invention is 250-330s, when the time is less than 250s, the homogenization of C in the unconverted residual austenite is insufficient, and when the time is more than 330s. Excessive tempering of martensite readily leads to decomposition of the retained austenite. Leveling is to obtain better surface quality and further adjust yield strength, so that fine defects on the surface cannot be completely covered, the surface quality is poor, the leveling is insufficient, a yield platform is easy to appear during tensile deformation, and if the yield strength is higher than 0.7%, the yield strength of the steel plate is too high, and the plasticity is poor.
As an alternative embodiment, the final cooling temperature is 120 to 150 ℃.
As an alternative embodiment, the finishing has an elongation of 0.1 to 0.7%.
As an alternative embodiment, the chemical composition of the continuously cast mold flux includes, in mass percent:
CaO：25-30％，SiO 2 ：21-38％，Al 2 O 3 ：1-3％，MgO：2-4％；
the section of the continuous casting is 1400-1600mm, the drawing speed of the continuous casting is 1.0-1.2m/min, and the viscosity of the continuous casting covering slag is 0.12-0.16.
The reason why the chemical composition of the mold flux for continuous casting and the above parameters are controlled is that: when high-aluminum steel is cast, peritectic reaction and mold powder denaturation in the solidification process can simultaneously aggravate the unevenness of a blank shell, so that the generation of depressions and transverse cracks is caused, and therefore specific mold powder needs to be developed.
As an alternative embodiment, the cleaning includes physical brushing and electrolytic cleaning.
As an alternative embodiment, the rapid cooling is performed by using a hydrogen atmosphere, the concentration of the hydrogen atmosphere is 40-60%, and the end temperature of the rapid cooling is 260-330 ℃.
The transformation from the retained austenite to the martensite of the strip steel can be realized by hydrogen under the condition of a higher cooling rate, and if the hydrogen concentration is too low, the transformation of the martensite is not facilitated, and the required tensile strength is obtained. And (3) rapidly cooling to the end point temperature to realize the transformation of the retained austenite to the martensite, entering an aging period, redistributing the aging C from the martensite to the non-transformed retained austenite, and eliminating the internal stress in the martensite. If the end point temperature and the aging temperature of the rapid cooling are too high, the proportion of martensite is low, the tempering is serious, the tensile strength is insufficient, and if the end point temperature and the aging temperature of the rapid cooling are too low, the C diffusion rate is slow, the stability of the unconverted retained austenite is insufficient, the austenite cannot be reserved to the room temperature, and the plasticity is deteriorated.
As an optional embodiment, the annealing temperature is 770-860 ℃, and the annealing holding time is 2-5min.
The reason for controlling the annealing temperature is that: the control of phase proportion of different phases of a two-phase region is realized, so that the control is not beneficial to obtaining enough retained austenite, the sufficient retained austenite can not be realized, the annealing is insufficient, and a cold-rolled strip-shaped structure is remained; the austenite content is increased to almost completely turn into austenite, and ferrite is further decreased, which is not favorable for improving plasticity.
The reason for controlling the annealing holding time is that: the method realizes a certain degree of retained austenite, realizes the sufficient diffusion of the element C, is beneficial to improving the hardenability of the retained austenite, ensures that the grain annealing is insufficient due to the short heat preservation time, and can keep the banded structure. If the holding time is too long, the crystal grains will be coarsened.
The present application will be described in detail below with reference to examples, comparative examples, and experimental data.
Example 1
A590 MPa reinforced plastic dual-phase steel has the chemical components expressed in mass percent as shown in the following table 1.
TABLE 1 chemical composition (wt%) of steel of example 1
| C | Si | Mn | P | S | Al | Nb | |
| Example 1 | 0.095 | 0.38 | 2.09 | 0.008 | 0.002 | 0.59 | 0.039 |
The metallographic structure of steel includes: ferrite: 48%, martensite: 36%, retained austenite: 8%, bainite: 8 percent;
martensite is dispersed in ferrite, and the size of the martensite is 4 mu m;
the retained austenite is in a thin film shape, and the interlayer spacing of the retained austenite is 4 mu m;
the ferrite contains a plurality of NbC nano precipitated phases, the size of the NbC nano precipitated phases is 8nm, the number of the NbC nano precipitated phases is 4000 per mu m 3 。
The preparation method of the 590MPa reinforced plastic dual-phase steel comprises the following steps:
s1, smelting to obtain molten steel with chemical components according with the table.
And S2, carrying out continuous casting, heating, rough rolling, dephosphorization and finish rolling on the molten steel to obtain the hot rolled plate.
Wherein:
the thickness of the hot-rolled plate is 3.0mm;
the chemical components of the continuous casting mold flux comprise the following components in percentage by mass: caO:27% of SiO 2 ：28％，Al 2 O 3 ：2％，MgO：3％；
The section of the continuous casting is 1500mm, the drawing speed of the continuous casting is 1.1m/min, and the viscosity of the continuous casting covering slag is 0.14;
the water pressure of the dephosphorization solution for dephosphorization is 30MPa;
the finish rolling temperature of the finish rolling was 894 ℃.
And S3, carrying out laminar cooling, coiling, acid pickling and cold rolling on the hot rolled plate to obtain the strip steel.
Wherein:
the thickness of the strip steel is 1.5mm;
the coiling temperature is 635 ℃;
the total rolling reduction in cold rolling was 50%.
And S4, cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plasticity dual-phase steel.
Wherein:
cleaning comprises physical brushing and electrolytic cleaning;
the annealing temperature is 780 ℃, and the annealing heat preservation time is 3min;
the slow cooling end point temperature is 680 ℃;
cooling by adopting a hydrogen atmosphere in the rapid cooling process, wherein the concentration of the hydrogen atmosphere is 50%, and the end point temperature of the rapid cooling process is 290 ℃;
the temperature of the aging treatment is 290 ℃, and the time of the aging treatment is 290s;
the final cooling temperature is 140 ℃;
the elongation of the finish was 0.5%.
Example 2
A590 MPa reinforced plastic dual-phase steel, the chemical composition of which is shown in the following table 2 in mass percent.
Table 2 chemical composition (wt%) of steel of example 2
| C | Si | Mn | P | S | Al | Nb | |
| Example 2 | 0.09 | 0.1 | 1.4 | 0.006 | 0.003 | 0.3 | 0.032 |
The metallographic structure of steel includes: ferrite: 70%, martensite: 25%, retained austenite: 3%, bainite: 2 percent;
martensite is dispersed in ferrite, and the size of the martensite is 7 mu m;
the residual austenite is in a film shape, and the interlayer spacing of the residual austenite is 2 mu m;
ferrite contains several NbC nano precipitated phases, the size of NbC nano precipitated phase is 6nm, the number of NbC nano precipitated phases is 4500/micrometer 3 。
The preparation method of the 590MPa reinforced plastic dual-phase steel comprises the following steps:
s1, smelting to obtain molten steel with chemical components according with the table.
And S2, carrying out continuous casting, heating, rough rolling, dephosphorization and finish rolling on the molten steel to obtain the hot rolled plate.
Wherein:
the thickness of the hot-rolled plate is 3.2mm;
the chemical components of the continuous casting mold flux comprise the following components in percentage by mass: caO:28% of SiO 2 ：30％，Al 2 O 3 ：1.8％，MgO：2.8％；
The section of the continuous casting is 1400mm, the drawing speed of the continuous casting is 1.15m/min, and the viscosity of the continuous casting covering slag is 0.15;
the water pressure of the dephosphorization solution for dephosphorization is 40MPa;
the finish rolling temperature of the finish rolling was 950 ℃.
And S3, carrying out laminar cooling, coiling, acid pickling and cold rolling on the hot rolled plate to obtain the strip steel.
Wherein:
the thickness of the strip steel is 1.5mm;
the coiling temperature is 635 ℃;
the total reduction in cold rolling was 53%.
And S4, cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plasticity dual-phase steel.
Wherein:
cleaning comprises physical brushing and electrolytic cleaning;
the annealing temperature is 860 ℃, and the annealing heat preservation time is 5min;
the slow cooling end point temperature is 620 ℃;
cooling by adopting a hydrogen atmosphere in the rapid cooling process, wherein the concentration of the hydrogen atmosphere is 50%, and the end point temperature of the rapid cooling process is 260 ℃;
the temperature of the aging treatment is 260 ℃, and the time of the aging treatment is 250s;
the final cooling temperature is 120 ℃;
the elongation of the finish was 0.3%.
Example 3
A590 MPa reinforced plastic dual-phase steel, the chemical composition of which is shown in the following Table 3 in mass percent.
Table 3 chemical composition (wt%) of steel of example 3
| C | Si | Mn | P | S | Al | Nb | |
| Example 3 | 0.12 | 0.5 | 1.4 | 0.006 | 0.003 | 0.5 | 0.022 |
The metallographic structure of steel includes: ferrite: 64%, martensite: 30%, retained austenite: 4%, bainite: 2 percent;
martensite is dispersed in ferrite, and the size of the martensite is 9 μm;
the retained austenite is in a thin film shape, and the interlayer spacing of the retained austenite is 4 mu m;
the ferrite contains a plurality of NbC nano precipitated phases, the size of the NbC nano precipitated phases is 5nm, the number of the NbC nano precipitated phases is 4000 per mu m 3 。
The preparation method of the 590MPa reinforced plastic dual-phase steel comprises the following steps:
s1, smelting to obtain molten steel with chemical components according with the table.
And S2, carrying out continuous casting, heating, rough rolling, dephosphorization and finish rolling on the molten steel to obtain the hot rolled plate.
Wherein:
the thickness of the hot-rolled plate is 3.5mm;
the chemical components of the continuous casting mold flux comprise the following components in percentage by mass: caO:25% of SiO 2 ：22％，Al 2 O 3 ：1.4％，MgO：2.2％；
The section of the continuous casting is 1600mm, the drawing speed of the continuous casting is 1.1m/min, and the viscosity of the continuous casting mold powder is 0.12;
the water pressure of the dephosphorization solution for dephosphorization is 38MPa;
the finish rolling temperature of the finish rolling was 870 ℃.
And S3, carrying out laminar cooling, coiling, acid pickling and cold rolling on the hot rolled plate to obtain the strip steel.
Wherein:
the thickness of the strip steel is 1.3mm;
the coiling temperature is 605 ℃;
the total reduction in cold rolling was 62.8%.
And S4, cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plasticity dual-phase steel.
Wherein:
cleaning comprises physical brushing and electrolytic cleaning;
the annealing temperature is 820 ℃, and the annealing heat preservation time is 2min;
the slow cooling end point temperature is 700 ℃;
cooling by adopting a hydrogen atmosphere in the rapid cooling process, wherein the concentration of the hydrogen atmosphere is 50%, and the final temperature of the rapid cooling process is 330 ℃;
the temperature of the aging treatment is 330 ℃, and the time of the aging treatment is 250s;
the final cooling temperature is 120 ℃;
the elongation of the finish was 0.4%.
Example 4
A590 MPa reinforced plastic dual phase steel, the chemical composition of which is shown in the following Table 4 in mass percent.
Table 4 chemical composition (wt%) of steel of example 4
| C | Si | Mn | P | S | Al | Nb | |
| Example 4 | 0.12 | 0.3 | 2.0 | 0.006 | 0.003 | 0.2 | 0.012 |
The metallographic structure of steel includes: ferrite: 60%, martensite: 29%, retained austenite: 8%, bainite: 3 percent;
martensite is dispersed in ferrite, and the size of the martensite is 7 mu m;
the retained austenite is in a film shape, and the interlayer spacing of the retained austenite is 2 mu m;
the ferrite contains a plurality of NbC nano precipitated phases, the size of the NbC nano precipitated phase is 6nm, the number of the NbC nano precipitated phases is 3000 per mu m 3 。
The preparation method of the 590MPa reinforced plastic dual-phase steel comprises the following steps:
s1, smelting to obtain molten steel with chemical components according with the table.
And S2, carrying out continuous casting, heating, rough rolling, dephosphorization and finish rolling on the molten steel to obtain the hot rolled plate.
Wherein:
the thickness of the hot-rolled plate is 3.5mm;
the chemical components of the continuous casting mold flux comprise the following components in percentage by mass: caO:28% of SiO 2 ：28％，Al 2 O 3 ：1.7％，MgO：2.2％；
The section of the continuous casting is 1600mm, the drawing speed of the continuous casting is 1.1m/min, and the viscosity of the continuous casting covering slag is 0.12;
the water pressure of the dephosphorization solution for dephosphorization is 36MPa;
the finish rolling temperature of the finish rolling was 870 ℃.
And S3, carrying out laminar cooling, coiling, acid pickling and cold rolling on the hot rolled plate to obtain the strip steel.
Wherein:
the thickness of the strip steel is 1.3mm;
the coiling temperature is 645 ℃;
the total reduction in cold rolling was 62.8%.
And S4, cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plasticity dual-phase steel.
Wherein:
cleaning comprises physical brushing and electrolytic cleaning;
the annealing temperature is 820 ℃, and the annealing heat preservation time is 2min;
the slow cooling end point temperature is 680 ℃;
cooling by adopting a hydrogen atmosphere in the rapid cooling process, wherein the concentration of the hydrogen atmosphere is 50%, and the end point temperature of the rapid cooling process is 290 ℃;
the temperature of the aging treatment is 290 ℃, and the time of the aging treatment is 330s;
the final cooling temperature is 120 ℃;
the elongation of the finish was 0.1%.
Comparative example 1
A dual phase steel having the chemical composition in mass percent as shown in Table 5 below.
TABLE 5 chemical composition (wt%) of steel of comparative example 1
| C | Si | Mn | P | S | Al | Nb | |
| Comparative example 1 | 0.06 | 0.2 | 2.2 | 0.006 | 0.003 | 0.2 | 0.012 |
The metallographic structure of steel includes: ferrite: 83%, martensite: 9%, retained austenite: 5%, bainite: 3 percent;
martensite is dispersed in ferrite, and the size of the martensite is 5 mu m;
the retained austenite is in a film shape, and the interlayer spacing of the retained austenite is 2 mu m;
the ferrite contains a plurality of NbC nanometer precipitated phases, the size of the NbC nanometer precipitated phases is 22nm, the number of the NbC nanometer precipitated phases is 1000/mum 3 。
The preparation method of the 590MPa reinforced plastic dual-phase steel comprises the following steps:
s1, smelting to obtain molten steel with chemical components according with the table.
And S2, carrying out continuous casting, heating, rough rolling, dephosphorization and finish rolling on the molten steel to obtain the hot rolled plate.
Wherein:
the thickness of the hot-rolled plate is 3.5mm;
the chemical components of the continuous casting mold flux comprise the following components in percentage by mass: caO:28% of SiO 2 ：28％，Al 2 O 3 ：1.7％，MgO：2.2％；
The section of the continuous casting is 1600mm, the drawing speed of the continuous casting is 1.1m/min, and the viscosity of the continuous casting covering slag is 0.12;
the water pressure of the dephosphorization solution for dephosphorization is 38MPa;
the finish rolling temperature of the finish rolling was 870 ℃.
And S3, carrying out laminar cooling, coiling, acid washing and cold rolling on the hot rolled plate to obtain the strip steel.
Wherein:
the thickness of the strip steel is 1.3mm;
the coiling temperature is 645 ℃;
the total reduction in cold rolling was 62.8%.
And S4, cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plasticity dual-phase steel.
Wherein:
cleaning comprises physical brushing and electrolytic cleaning;
the annealing temperature is 820 ℃, and the annealing heat preservation time is 2min;
the slow cooling end point temperature is 680 ℃;
cooling by adopting a hydrogen atmosphere in the rapid cooling process, wherein the concentration of the hydrogen atmosphere is 50%, and the final temperature of the rapid cooling process is 330 ℃;
the temperature of the aging treatment is 290 ℃, and the time of the aging treatment is 330s;
the final cooling temperature is 120 ℃;
the elongation of the finish was 0.2%.
Comparative example 2
A dual phase steel whose chemical composition is shown in Table 6 below in mass%.
TABLE 6 chemical composition (wt%) of steel of comparative example 2
| C | Si | Mn | P | S | Al | Nb | |
| Comparative example 2 | 0.08 | 0.2 | 2.2 | 0.006 | 0.003 | 0.2 | 0.012 |
The metallographic structure of steel includes: ferrite: 63%, martensite: 31%, retained austenite: 3%, bainite: 3 percent;
martensite is dispersed in ferrite, and the size of the martensite is 5 mu m;
the retained austenite is in a film shape, and the interlayer spacing of the retained austenite is 2 mu m;
ferrite contains several NbC nano precipitated phases, the size of NbC nano precipitated phase is 6nm, and the number of NbC nano precipitated phases is 4000/micrometer 3 。
The preparation method of the 590MPa reinforced plastic dual-phase steel comprises the following steps:
s1, smelting to obtain molten steel with chemical components according with the table.
And S2, carrying out continuous casting, heating, rough rolling, dephosphorization and finish rolling on the molten steel to obtain the hot rolled plate.
Wherein:
the thickness of the hot-rolled plate is 3.5mm;
the chemical components of the continuous casting mold flux comprise the following components in percentage by mass: caO:13% of SiO 2 ：12％，Al 2 O 3 ：5.4％，MgO：7.8％；
The section of the continuous casting is 1600mm, the drawing speed of the continuous casting is 1.8m/min, and the viscosity of the continuous casting covering slag is 0.22;
the water pressure of the dephosphorization solution for dephosphorization is 32MPa;
the finish rolling temperature of the finish rolling was 870 ℃.
And S3, carrying out laminar cooling, coiling, acid pickling and cold rolling on the hot rolled plate to obtain the strip steel.
Wherein:
the thickness of the strip steel is 1.3mm;
the coiling temperature is 625 ℃;
the total reduction in cold rolling was 62.8%.
And S4, cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plasticity dual-phase steel.
Wherein:
cleaning comprises physical brushing and electrolytic cleaning;
the annealing temperature is 840 ℃, and the annealing heat preservation time is 2min;
the slow cooling end point temperature is 680 ℃;
cooling by adopting a hydrogen atmosphere in the quick cooling process, wherein the concentration of the hydrogen atmosphere is 50%, and the end point temperature of the quick cooling process is 330 ℃;
the temperature of the aging treatment is 290 ℃, and the time of the aging treatment is 330s;
the final cooling temperature is 120 ℃;
the elongation of the finish was 0.2%.
Comparative example 3
A dual phase steel having the chemical composition in mass percent as shown in Table 7 below.
TABLE 7 chemical composition (wt%) of steel of comparative example 3
The metallographic structure of steel includes: ferrite: 56%, martensite: 38%, retained austenite: 4%, bainite: 2 percent;
martensite is dispersed in ferrite, and the size of the martensite is 3 mu m;
the residual austenite is in a film shape, and the interlayer spacing of the residual austenite is 2 mu m;
the ferrite contains a plurality of NbC nanometer precipitated phases, the size of the NbC nanometer precipitated phases is 1nm, the number of the NbC nanometer precipitated phases is 4000/mum 3 。
The preparation method of the 590MPa reinforced plastic dual-phase steel comprises the following steps:
s1, smelting to obtain molten steel with chemical components according with the table.
And S2, carrying out continuous casting, heating, rough rolling, dephosphorization and finish rolling on the molten steel to obtain the hot rolled plate.
Wherein:
the thickness of the hot-rolled plate is 3.5mm;
the chemical components of the continuous casting mold flux comprise the following components in percentage by mass: caO:28% of SiO 2 ：28％，Al 2 O 3 ：1.7％，MgO：2.2％；
The section of the continuous casting is 1600mm, the drawing speed of the continuous casting is 1.1m/min, and the viscosity of the continuous casting covering slag is 0.12;
the water pressure of the dephosphorization solution for dephosphorization is 29MPa;
the finish rolling temperature of the finish rolling was 870 ℃.
And S3, carrying out laminar cooling, coiling, acid washing and cold rolling on the hot rolled plate to obtain the strip steel.
Wherein:
the thickness of the strip steel is 1.3mm;
the coiling temperature is 645 ℃;
the total reduction in cold rolling was 62.8%.
And S4, cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plasticity dual-phase steel.
Wherein:
cleaning comprises physical brushing and electrolytic cleaning;
the annealing temperature is 750 ℃, and the annealing heat preservation time is 6min;
the slow cooling end point temperature is 600 ℃;
cooling by adopting a hydrogen atmosphere in the rapid cooling process, wherein the concentration of the hydrogen atmosphere is 50%, and the end point temperature of the rapid cooling process is 250 ℃;
the temperature of the aging treatment is 250 ℃, and the time of the aging treatment is 350s;
the final cooling temperature is 120 ℃;
the elongation of the finish was 0.2%.
Examples of the experiments
The mechanical properties of the dual-phase steels provided in examples 1 to 4 and comparative examples 1 to 3 were measured, and the specific results are shown in the following table.
| Continuous casting heat | Rm/MPa | Rp0.2/MPa | A80/％ | Hole expansion ratio/% | |
| Example 1 | 5 | 642 | 375 | 32.5 | 52 |
| Example 2 | 6 | 628 | 384 | 21.5 | 51 |
| Example 3 | 6 | 635 | 365 | 31.5 | 54 |
| Example 4 | 6 | 625 | 385 | 32.5 | 54 |
| Comparative example 1 | 6 | 582 | 328 | 34 | 32 |
| Comparative example 2 | 3 | 672 | 402 | 31 | 52 |
| Comparative example 3 | 5 | 723 | 502 | 22 | 44 |
As can be seen from the above table, examples 1 to 4 of the present application have higher tensile strength than comparative example 1, have higher continuous casting heat times than comparative example 2, and have more excellent plasticity and hole expansibility than comparative example 3; the yield strength can reach 330-440MPa, the tensile strength can reach 590-700MPa, the elongation can be more than or equal to 30%, the hole expansion performance and the surface quality are excellent, the hole expansion rate is more than or equal to 50%, continuous casting with steel grades of more than 5 furnaces can be realized, and the production cost is greatly reduced.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A590 MPa reinforced plastic dual phase steel, characterized in that the chemical composition of the steel comprises, in mass%:
c:0.09-0.12%, si:0.1-0.7%, mn:1.4-2.1%, P: less than or equal to 0.015%, S: less than or equal to 0.006 percent, al:0.2-0.6%, nb:0.01-0.04%, and the balance of Fe and inevitable impurities.
2. The 590MPa reinforced plastic dual phase steel of claim 1, wherein the chemical composition of the steel, the sum of Al and Si in mass percent is: 0.4 to 1.3 percent.
3. The 590MPa reinforced plastic dual phase steel of claim 1, wherein the metallographic structure of the steel comprises, in volume percent:
ferrite: 42-82%, martensite: 8-37%, retained austenite: 2-13%, bainite: 2 to 9 percent.
4. 590MPa reinforced plastic dual phase steel according to claim 3, characterized in that:
the martensite is dispersed in the ferrite, and the size of the martensite is 2-10 μm;
the residual austenite is in a film shape, and the interlayer spacing of the residual austenite is 2-5 mu m.
5. 590MPa reinforced plastic dual phase steel according to claim 3, characterized in that: the ferrite contains a plurality of NbC nanometer precipitated phases, the size of the NbC nanometer precipitated phases is 2-10nm, and the number of the NbC nanometer precipitated phases is less than 5000/mum 3 。
6. A method of producing a 590MPa reinforced plastic dual phase steel according to any one of claims 1-5, comprising the steps of:
smelting to obtain molten steel according with the chemical components;
continuously casting the molten steel, heating, roughly rolling, removing phosphorus and finely rolling to obtain a hot rolled plate;
carrying out laminar cooling, coiling, acid pickling and cold rolling on the hot rolled plate to obtain strip steel;
cleaning, heating, annealing, slow cooling, fast cooling, aging treatment, final cooling and finishing the strip steel to obtain the 590MPa reinforced plastic dual-phase steel;
wherein:
the water pressure of the dephosphorization solution for dephosphorization is 25-40MPa;
the finish rolling temperature of the finish rolling is 870-950 ℃;
the coiling temperature is more than or equal to 600 ℃;
the total rolling reduction rate of the cold rolling is 40-65%;
the slow cooling end point temperature is 600-700 ℃;
the temperature of the aging treatment is 260-330 ℃, and the time of the aging treatment is 250-330s;
the final cooling temperature is 120-150 ℃;
the elongation of the finishing is 0.1-0.7%.
7. The method for preparing 590MPa reinforced plastic dual-phase steel according to claim 6, wherein the chemical composition of the continuously cast mold flux comprises, in mass percent:
CaO：25-30％，SiO 2 ：21-38％，Al 2 O 3 ：1-3％，MgO：2-4％；
the section of the continuous casting is 1400-1600mm, the drawing speed of the continuous casting is 1.0-1.2m/min, and the viscosity of the continuous casting covering slag is 0.12-0.16.
8. The method of making 590MPa reinforced plastic dual phase steel of claim 6, wherein said cleaning includes physical scrubbing and electrolytic cleaning.
9. The method of manufacturing 590MPa reinforcement plastic dual phase steel according to claim 6, wherein the rapid cooling is performed using a hydrogen atmosphere, the concentration of the hydrogen atmosphere is 40-60%, and the final temperature of the rapid cooling is 260-330 ℃.
10. The method for preparing 590MPa reinforced plastic dual phase steel according to claim 6, wherein the annealing temperature is 770-860 ℃ and the annealing holding time is 2-5min.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20220010394A1 (en) * | 2018-11-23 | 2022-01-13 | Baoshan Iron & Steel Co., Ltd. | High-yield-ratio cold-rolled dual-phase steel and manufacturing method therfor |
| CN114540707A (en) * | 2022-02-11 | 2022-05-27 | 武汉钢铁有限公司 | 590 MPa-grade cold-rolled high-strength steel and production method thereof |
| CN114799103A (en) * | 2022-03-27 | 2022-07-29 | 华北理工大学 | non-Newtonian fluid continuous casting covering slag for low-carbon steel and preparation method thereof |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20220010394A1 (en) * | 2018-11-23 | 2022-01-13 | Baoshan Iron & Steel Co., Ltd. | High-yield-ratio cold-rolled dual-phase steel and manufacturing method therfor |
| CN114540707A (en) * | 2022-02-11 | 2022-05-27 | 武汉钢铁有限公司 | 590 MPa-grade cold-rolled high-strength steel and production method thereof |
| CN114799103A (en) * | 2022-03-27 | 2022-07-29 | 华北理工大学 | non-Newtonian fluid continuous casting covering slag for low-carbon steel and preparation method thereof |
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