CN110129673B - 800 MPa-grade high-strength-ductility Q & P steel plate and preparation method thereof - Google Patents
800 MPa-grade high-strength-ductility Q & P steel plate and preparation method thereof Download PDFInfo
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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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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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
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- 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
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C21D2211/005—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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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
The invention discloses an 800 MPa-grade high-strength-ductility product Q & P steel plate and a preparation method thereof, and belongs to the technical field of cold-rolled automobile steel production. The steel plate comprises the following chemical components in percentage by weight: c: 0.38-0.42%, Si: 0: 10-0.30%, Mn: 0.80-1.20%, Al: 2.80 to 3.20 percent of the total weight of the alloy, less than or equal to 0.020 percent of P, less than or equal to 0.0030 percent of S, less than or equal to 0.0060 percent of N, and the balance of Fe and inevitable residual impurity elements. The preparation method comprises smelting, continuous casting, hot rolling, acid washing, cold rolling and continuous annealing; heating the cold-rolled sheet to 830-860 ℃ during continuous annealing; then slowly cooling to 700-730 ℃; and finally, rapidly cooling to 350-400 ℃ at a cooling rate of 40-60 ℃/s for overaging distribution treatment. The Q & P steel plate has excellent mechanical properties, the yield strength is greater than or equal to 480MPa, the tensile strength is greater than or equal to 800MPa, the elongation is greater than or equal to 25%, n is greater than or equal to 0.20, the yield ratio is less than or equal to 0.75, and the cold forming performance is good. The invention has low requirements on process equipment and is suitable for the production of the existing continuous annealing production line.
Description
The technical field is as follows:
the invention belongs to the technical field of cold-rolled automobile steel production, and particularly relates to a cold-rolled Q & P steel plate with a tensile strength of 800MPa grade and high strength-ductility product and a preparation method thereof.
Background art:
in recent years, with the rapid development of the automobile industry in China and the increasing sharpness of energy and environmental problems, the fuel economy of automobiles is improved and CO is reduced2The emission is to cope with global climate change, the average fuel consumption of the passenger cars produced in China is reduced to 5 liters/hundred kilometers by 2020 specified in 'passenger car fuel consumption limit' of China. Increasingly stringent emission standards place higher demands on automobile manufacturers and also provide opportunities for the reduction of weight of automobile materials. When the weight of the automobile is reduced by 100 kilograms, the oil consumption is reduced by 0.64 liter/hundred kilometers, and the emission of carbon dioxide is reduced by 1 kilogram. Therefore, the improvement of the dynamic property of the automobile, the reduction of the fuel consumption and the reduction of the emission pollution by reducing the quality of the automobile has become a future development trend. The most obvious characteristic of the light weight of the vehicle body is the selection of materials. At present, the lightweight materials applied to automobiles mainly comprise high-strength steel, aluminum alloy, magnesium alloy, carbon fiber and the like. Steel remains the best choice for the automotive industry because of its low manufacturing cost and low full life cycle emissions compared to other competing materials (e.g., aluminum, magnesium, carbon fiber reinforced polymers). Moreover, steel has extensive experience in the automotive industry, which is familiar with its properties; these will greatly reduce the development costs of new design, manufacturing, tooling and forming techniques. The production of higher strength and better performance steels will be driven by the fuel economy and crash safety requirements of the automotive industry.
As a representative steel grade of the third-generation advanced high-strength steel, the Q & P steel has higher strength and plasticity, namely excellent comprehensive performance, under the condition of adding a small amount of alloy, thereby arousing wide interest in the metallurgical industry and the automobile industry. At present, the wide popularization and application of Q & P steel mainly meet two bottlenecks: (1) in the production process of the traditional Q & P steel, in order to obtain better comprehensive performance, quenching is often required to be carried out at a lower temperature, then the temperature is rapidly raised to a higher distribution temperature for alloy element distribution, the difference between the quenching temperature and the distribution temperature is often about 100 ℃, and the process is difficult to popularize and use in the traditional continuous annealing production line because the overaging section of the traditional continuous annealing production line has no rapid induction heating function. (2) At present, for cold forming, the bearing capacity of stamping equipment and a die in the automobile industry is generally 600-800MPa, and the existing stamping equipment for higher-grade steel is difficult to meet the force and energy requirements. Therefore, the development of the high-strength-product Q & P steel which can meet the requirements of the production equipment capacity of the metallurgy and the automobile industry at present has very important significance for the promotion and improvement of the light weight and the safety of the automobile at present.
The relevant literature currently involved in high product of strength and elongation Q & P steels is disclosed as follows: chinese patent CN108193138A discloses 980MPa grade cold-rolled high-strength Q & P steel for automobiles and a production method thereof, wherein the Si content is properly reduced mainly on the basis of the traditional CSiMn component, 0.5-1.0% of Al is used for substitution, and 0.04-0.07% of microalloy element Nb is added. Wherein, the contents of Si and Mn are relatively high, and the external oxidation is easily generated during the production of the traditional continuous annealing production line, so that the surface color is yellow. Chinese patent CN105018843A discloses Q & P steel added with vanadium and titanium in a composite manner and a manufacturing method thereof, the strength of the Q & P steel reaches 1350-1450 MPa, the strength is high, cold forming is difficult, and the Q & P steel can only be used for producing simple parts. Chinese patent CN108660369A discloses a quenching distribution cold-rolled steel plate with tensile strength more than 1180MPa and a production method thereof, Chinese patent CN103555902A discloses a heat treatment process of 980MPa grade high-strength-ductility product automobile steel, Chinese patent CN103555894A discloses a heat treatment process of Q & P980 steel, the quenching and distribution temperatures are quite different in the annealing process, and the batch production of the traditional continuous annealing production line is more difficult. Chinese patent CN104988391A discloses 1200 MPa-grade cold-rolled Q & P steel and a manufacturing method thereof, wherein the quenching temperature and the distribution temperature are greatly different in the annealing process, and meanwhile, the roller cooling and the water cooling are required in the rapid cooling process, which cannot be realized by the traditional continuous annealing production line at present. Chinese patent CN101487096A discloses a low-alloy high-strength C-Mn-Al Q & P steel and a manufacturing method thereof, which adopts a low-Si and Al component system, wherein the Al content is 1.0-1.5%, the quenching temperature and the distribution temperature are higher in the heat treatment process, and the implementation on the traditional continuous annealing production line has certain difficulty. Chinese patent CN103215491A discloses a method for preparing carbon-silicon-manganese Q & P steel by utilizing alloy element distribution, the annealing temperature of the method is as high as 900-950 ℃, the pre-distribution is carried out for 250-600 s at 720-800 ℃ before annealing, and the difference between the quenching temperature and the final distribution temperature is more than 100 ℃, which can not be realized in the existing continuous annealing production line.
The technology mainly improves the strength and the plasticity of the Q & P steel by various strengthening means, stable austenite elements and processes. However, for Q & P steel production, the tensile strength is easy to design and produce within the range of 1000-1200 MPa, and the Q & P steel can be obtained by controlling the conventional CSiMn alloy elements and adding a small amount of other alloy elements and properly controlling the production process. However, for 800MPa grade Q & P steel, the production has certain difficulty, the production cannot be realized by adopting a conventional CSiMn component system, the addition of alloy elements is less, and the hardenability requirement cannot be met; the added alloy elements are slightly high, and the strength of the alloy elements reaches 1000MPa or above, so that the alloy elements need to be realized by adopting a new component system and a design concept. In addition, the technology has high soaking temperature requirement, high cooling speed requirement and great difference between quenching temperature and distribution temperature, and is difficult to realize on the existing continuous annealing production line.
The invention content is as follows:
aiming at the defects in the existing Q & P steel preparation technology, the invention provides an 800 MPa-grade high-strength-plastic-product Q & P steel plate which is suitable for existing process equipment and market requirements and a preparation method thereof. The yield strength of the high-strength-product Q & P steel plate prepared by the method is more than or equal to 480MPa, the tensile strength is more than or equal to 800MPa, the elongation is more than or equal to 25%, n is more than or equal to 0.20, and the yield ratio is less than or equal to 0.75.
The 800 MPa-grade high-strength-ductility product Q & P steel plate provided by the invention comprises the following chemical components in percentage by mass: c: 0.38-0.42%, Si: 0: 10-0.30%, Mn: 0.80-1.20%, Al: 2.80 to 3.20 percent of the total weight of the alloy, less than or equal to 0.020 percent of P, less than or equal to 0.0030 percent of S, less than or equal to 0.0060 percent of N, and the balance of Fe and inevitable residual impurity elements.
The invention provides a preparation method of an 800 MPa-grade high-strength-ductility Q & P steel plate, which comprises the following steps of smelting, refining, continuous casting, hot rolling, pickling, cold rolling and annealing:
(1) smelting, wherein the smelting is carried out in an electric arc furnace or a converter, and P in the steel is controlled to be less than or equal to 0.02 wt%.
(2) And refining, wherein LF and RH are adopted for refining, and in order to improve the quality of the casting blank and the finished product and the comprehensive performance of the final product, the content of S, O, N impurity elements in the steel is removed as much as possible in the refining process.
(3) Continuous casting, wherein full-protection casting and electromagnetic stirring are adopted in the continuous casting, and a plate blank after the continuous casting is cut and directly hot-loaded into a heating furnace;
(4) hot rolling, wherein the hot rolling heating temperature is 1300-1350 ℃, the rough rolling is carried out in an austenite recrystallization region, the rough rolling stage adopts 8-10 passes, the total reduction rate of the austenite recrystallization region is more than 70%, the thickness of an intermediate blank is 30-50 mm, the finish rolling is carried out in an austenite non-recrystallization region, the finish rolling stage adopts 6-7 passes, the total reduction rate of the austenite non-recrystallization region is more than 80%, the final rolling temperature is controlled at 890-920 ℃, and the rolling is carried out in the range of 600-650 ℃ after the rolling is carried out to the target thickness;
(5) acid washing, wherein the acid washing adopts push-pull type acid washing, and the hot rolled strip steel is acid washed by a hydrochloric acid tank to remove surface iron oxide scales;
(6) cold rolling is carried out on a single-rack reversible rolling mill, multiple times of small reduction are adopted in the rolling process, and the total depression rate is 50-65%;
(7) annealing, wherein a continuous annealing furnace is adopted for annealing, firstly, strip steel is heated to 170 ℃ at a heating rate of 5-8 ℃/s for preheating, then, the strip steel is further heated to 830-860 ℃ at a heating rate of 1.5-2.5 ℃/s for temperature equalization, the heat preservation time is 100-150 s, and then, the cooling rate is 4-6 ℃/sCooling to 700-730 ℃, and then passing through 30% H2+N2Cooling the mixed gas to 350-400 ℃ at a cooling rate of 40-60 ℃/s for overaging treatment for 400-900 s, and finally cooling to room temperature at a rate of 2-3 ℃/s.
In order to ensure the strength of 800MPa level, excellent comprehensive performance and processability, the invention adopts the medium-carbon low-manganese and high-Al component design on the component design of steel and fully utilizes the composite structure strengthening and toughening technology of increasing the strength by martensite and increasing the plasticity by ferrite and austenite. The basic principle of the design of the content of each alloy element is as follows:
c: c is the most economical and effective strengthening element in steel and is an indispensable alloy element for improving hardenability, forming martensite and stabilizing austenite, and the addition of a proper amount of C in the steel can not only prevent the plasticity from being reduced, but also improve the stability of the austenite because the C diffuses into the austenite in the distribution process, so that the TRIP effect occurs in the deformation process, and the plasticity is greatly improved, so the content of the C cannot be too low. However, since too high a content causes deterioration in weldability and formability of steel, the present invention controls the C content within a range of 0.38 to 0.42%.
Si: the addition of silicon in the steel can improve the purity and deoxidation of the steel, play a role in solid solution strengthening in the steel and also can inhibit the precipitation of carbides. Because the invention adds high Al content, certain Si is added to deoxidize to prevent Al and O from combining to generate flocculation phenomenon, and when the Si content is less than 0.1%, the sufficient deoxidation effect is difficult to obtain. However, the viscosity of oxide skin is high when the plate blank is heated due to too high silicon content, and descaling is difficult after the plate blank is taken out of a furnace, so that red oxide scales on the surface of a rolled steel plate are serious, the surface quality is poor, and meanwhile, Si is easy to generate an external oxidation reaction in a weak reducing atmosphere in an annealing process, and a thin oxide scale is formed on the surface of strip steel, so that the surface quality of the steel plate is deteriorated, and therefore, the Si content is controlled within the range of 0.10-0.30%.
Mn: belongs to typical austenite stabilizing elements, can remarkably improve the hardenability of steel, can remarkably delay the transformation of pearlite and bainite, and reduces the critical cooling rate of martensite formation; in addition, Mn is combined with S in the steel to form MnS to prevent the steel from hot embrittlement. However, the high Mn content delays pearlite transformation and also delays ferrite precipitation, and causes segregation in the center of the steel, thereby deteriorating the performance. Therefore, the Mn content is controlled within the range of 0.8-1.2%.
Al: al is used as a light element, so that on one hand, the weight reduction and energy saving are facilitated; on the other hand, Al is a ferrite forming element, is easy to dissolve into ferrite, can effectively improve C, Mn chemical potential in ferrite, and during the two-phase zone annealing process, the addition of Al remarkably accelerates C, Mn to transfer into austenite, thereby indirectly increasing the stability of austenite. Al "cleans" the ferrite sufficiently to avoid the formation of coarse carbides when C is solutionized in a large amount of interstitial spaces in the ferrite and cooled. Al can also enlarge the alpha + gamma region of the Fe-C phase diagram, widen the temperature range of the two-phase region heat treatment and is beneficial to maintaining the stability and reproducibility of the mechanical property of the product. Meanwhile, Al can obviously improve the Ms point, martensite can be obtained at a higher quenching temperature, and the activity of C can be ensured to be diffused into austenite. In addition, Al can inhibit the formation of carbide, so that C is diffused into residual austenite in the distribution process, the stability of the austenite is improved, and the product of strength and elongation of the steel is improved. Al can also improve surface quality compared to Si. However, too high Al may block the nozzle during continuous casting, increasing the difficulty of continuous casting. By combining the effects, the Al content is controlled within the range of 3.8-3.2%.
N, S and P: n, S and P belong to impurity elements in steel, which deteriorate the plasticity and toughness of steel, and generally, the lower the content, the better.
Influence of the manufacturing process on the product of the invention:
converter blowing and refining treatment: the method aims to ensure the basic component requirements of molten steel, remove harmful gases such as oxygen, nitrogen and hydrogen and harmful impurities such as P, S in the steel, and add necessary alloy elements such as carbon, manganese, silicon and aluminum to adjust the alloy elements.
Continuous casting: the internal components of the casting blank are ensured to be uniform, the surface quality is good, and the continuous casting adopts full-protection pouring and electromagnetic stirring, so that the flocculation phenomenon caused by the oxidation of Al in the pouring process is avoided, the inclusion in steel is reduced, the casting blank quality is improved, and dendritic crystals are crushed; and directly hot charging the continuously cast plate blank to reduce the occurrence of hot cracking.
Hot rolling: in order to enable the cast ferrite to generate austenite transformation in the heating process, refine the structure and improve the performance, the heating temperature is controlled to be 1300-1350 ℃, and the temperature is kept for 2-3 hours. The rough rolling adopts multi-pass small-reduction rolling in an austenite recrystallization region, and the total reduction is more than 70 percent, so that the austenite structure is fully refined and crack defects are prevented in the rolling process. Finish rolling is carried out in an austenite non-recrystallization region, the finish rolling temperature is controlled to be 890-920 ℃, and rolling in a two-phase region is prevented; the total reduction rate of the austenite non-recrystallization region is more than 80 percent so as to improve the phase transformation nucleation point and refine the structure. And coiling at 600-650 ℃ after rolling to further refine the structure.
Acid washing: the acid washing adopts push-pull type acid washing, and hot rolled strip steel is subjected to hydrochloric acid turbulent flow acid washing to remove surface iron scale and prepare for cold rolling.
Cold rolling: cold rolling is carried out on a single-stand reversible rolling mill, the rolling process adopts multi-pass low pressure, the total depression rate is 50-65%, and the phenomenon of crack and cracking in the high pressure process is mainly avoided;
annealing: annealing by using a continuous annealing furnace, wherein the annealing temperature is 830-860 ℃, and the ferrite and austenite contents are mainly controlled; the slow cooling temperature is 700-730 ℃, so that a certain amount of ferrite is precipitated on one hand, and the quick cooling pressure is reduced on the other hand, so that shaking and buckling in the quick cooling process are prevented; using 30% H2+N2And cooling the mixed gas to 350-400 ℃ at a cooling rate of 40-60 ℃/s for overaging treatment for 400-900 s, mainly obtaining martensite structure and C-distributed stable austenite, improving the content and stability of residual austenite and improving the comprehensive performance of the product.
The invention has the following technical characteristics:
the components and process design of the invention are easy to implement and control, the process control is simple and easy to implement, and the problems of high cooling speed, low quenching temperature, higher distribution temperature and the like of the existing Q & P process are solved. The invention provides a brand-new alloy design idea and concept, and solves the problem that the existing CSiMn component system can not produce 800MPa grade Q & P steel. Compared with the existing CSiMn component system, the method prevents Si and O from being combined with the surface of the strip steel to form oxides, and improves the surface quality of the strip steel. Compared with the existing Q & P process, the process has the advantages that roller cooling and water cooling are not needed, the quenching temperature is consistent with the distribution temperature, the problem that the existing continuous annealing production line has no rapid induction heating in the overaging section is solved, and the batch production can be stabilized without modification in the existing continuous annealing production line. Compared with the existing DP800, under the condition of consistent strength, the plasticity, the n value and the product of strength and elongation are greatly improved, which is beneficial to stamping parts with relatively complex structure and improving the safety of collision.
The specific implementation mode is as follows:
the present invention will be described in further detail with reference to specific examples.
Smelting in a vacuum induction smelting furnace according to the chemical composition proportion of table 1, casting into an ingot, forging the ingot into a slab with the thickness of 80mm, and performing hot rolling, acid pickling, cold rolling and continuous annealing simulation in a laboratory, wherein the process is shown in table 2, and hot rolling coiling is simulated by adopting a box-type resistance furnace (the set temperature of the box-type furnace is consistent with the coiling temperature, and the temperature is kept for 2 hours and then is slowly cooled along with the furnace); and the continuous annealing is carried out on a continuous annealing simulator by adopting a set process.
The mechanical properties of the steel plates of examples 1 to 5 of the present invention were measured according to GB/T228-2010 part 1 of the tensile test for metallic materials, room temperature test method, and the results are shown in Table 3.
The invention provides a high-strength-ductility product Q with the strength of 800MPa&The P steel plate comprises the following chemical components in percentage by mass: c: 0.38-0.42%, Si: 0: 10-0.30%, Mn: 0.80-1.20%, Al: 2.80 to 3.20 percent of the total weight of the alloy, less than or equal to 0.020 percent of P, less than or equal to 0.0030 percent of S, less than or equal to 0.0060 percent of N, and the balance of Fe and inevitable residual impurity elements. The finish rolling temperature is 890-920 ℃, rolling is carried out at 600-650 ℃ after rolling, then pickling and cold rolling are carried out, the strip steel is rolled to the target thickness and then continuous annealing treatment is carried out, and the specific annealing process is as follows: firstly, the strip steel is heated to 170 ℃ at a heating rate of 5-8 ℃/s for preheating, and then the strip steel is further heated at a heating rate of 1.5-2.5 ℃/sHeating to 830-860 ℃ for temperature equalization for 100-150 s, cooling to 700-730 ℃ at a cooling rate of 4-6 ℃/s, and passing through 30% H2+N2Cooling the mixed gas to 350-400 ℃ at a cooling rate of 40-60 ℃/s for overaging treatment for 400-900 s, and finally cooling to room temperature at a rate of 2-3 ℃/s.
TABLE 1 chemical composition of inventive examples 1-5 (% by weight)
| Examples | C | Si | Mn | P | S | Al | N |
| 1 | 0.39 | 0.12 | 0.92 | 0.010 | 0.0021 | 2.93 | 0.0052 |
| 2 | 0.38 | 0.25 | 1.03 | 0.015 | 0.0028 | 3.12 | 0.0043 |
| 3 | 0.40 | 0.20 | 1.16 | 0.013 | 0.0024 | 2.86 | 0.0055 |
| 4 | 0.41 | 0.15 | 1.05 | 0.017 | 0.0027 | 3.17 | 0.0046 |
| 5 | 0.39 | 0.23 | 0.86 | 0.014 | 0.0026 | 3.09 | 0.0048 |
TABLE 2 Process parameters for inventive examples 1-5
TABLE 3 mechanical Properties of the Q & P Steel plates of the invention
| Examples | Yield strength/MPa | Tensile strength/MPa | Elongation A50/％ | n | Product of strength and elongation/GPa% |
| 1 | 486.7 | 801.5 | 27.8 | 0.26 | 22.28 |
| 2 | 497.4 | 814.6 | 26.6 | 0.26 | 21.67 |
| 3 | 571.6 | 809.5 | 29.7 | 0.22 | 24.04 |
| 4 | 580.3 | 816.5 | 30.4 | 0.21 | 24.82 |
| 5 | 544.8 | 833.7 | 27.8 | 0.25 | 23.18 |
Claims (1)
1. An 800 MPa-grade high-strength-ductility Q & P steel plate is characterized by comprising the following chemical components in percentage by mass: c: 0.38-0.42%, Si: 0: 10-0.30%, Mn: 0.80-1.20%, Al: 2.80-3.20 percent of the total weight of the alloy, less than or equal to 0.020 percent of P, less than or equal to 0.0030 percent of S, less than or equal to 0.0060 percent of N, and the balance of Fe and inevitable residual impurity elements; the preparation method of the high-strength-product Q & P steel plate comprises the following steps of smelting, refining, continuous casting, hot rolling, acid washing, cold rolling and annealing, and the preparation method comprises the following specific steps:
(1) smelting, wherein the smelting is carried out in an electric arc furnace or a converter, and P in the steel is controlled to be less than or equal to 0.02 wt%;
(2) refining, wherein LF and RH are adopted for refining;
(3) continuous casting, wherein full-protection casting and electromagnetic stirring are adopted in the continuous casting, and a plate blank after the continuous casting is cut and directly hot-loaded into a heating furnace;
(4) hot rolling, wherein the hot rolling heating temperature is 1300-1350 ℃, the rough rolling is carried out in an austenite recrystallization region, the rough rolling stage adopts 8-10 passes, the total reduction rate of the austenite recrystallization region is more than 70%, the thickness of an intermediate blank is 30-50 mm, the finish rolling is carried out in an austenite non-recrystallization region, the finish rolling stage adopts 6-7 passes, the total reduction rate of the austenite non-recrystallization region is more than 80%, the final rolling temperature is controlled at 890-920 ℃, and the rolling is carried out in the range of 600-650 ℃ after the rolling is carried out to the target thickness;
(5) acid washing, wherein the acid washing adopts push-pull type acid washing, and the hot rolled strip steel is acid washed by a hydrochloric acid tank to remove surface iron oxide scales;
(6) cold rolling is carried out on a single-rack reversible rolling mill, multiple times of small reduction are adopted in the rolling process, and the total depression rate is 50-65%;
(7) annealing, wherein a continuous annealing furnace is adopted for annealing, firstly, strip steel is heated to 170 ℃ at the heating rate of 5-8 ℃/s for preheating, then, the strip steel is further heated to 830-860 ℃ at the heating rate of 1.5-2.5 ℃/s for temperature equalization, the heat preservation time is 100-150 s, then, the strip steel is cooled to 700-730 ℃ at the cooling rate of 4-6 ℃/s, and then, 30% H passes through2+N2Cooling the mixed gas to 350-400 ℃ at a cooling rate of 40-60 ℃/s for overaging treatment for 400-900 s, and finally cooling to room temperature at a rate of 2-3 ℃/s.
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| CN113502382B (en) * | 2021-06-28 | 2023-06-30 | 东北大学 | Preparation method of 980 MPa-grade ultrahigh-ductility cold-rolled high-strength steel |
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