CN114395728B - Microalloy hot-rolled high-strength steel coil and preparation method thereof - Google Patents
Microalloy hot-rolled high-strength steel coil and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- 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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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
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- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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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
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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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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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- 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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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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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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- 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
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The invention discloses a microalloy hot-rolled high-strength steel coil and a preparation method thereof, belongs to the technical field of steel coil manufacturing, and solves the problems of insufficient microalloy precipitation and poor coil passing performance uniformity of the steel coil in the prior art. The method comprises the following steps: rolling and laminar cooling a continuous casting billet of microalloy hot rolled steel, controlling the finish rolling temperature to be 850-870 ℃, and performing induction heating on a rolled steel plate to maintain the temperature of the rolled steel plate at 610-630 ℃; and coiling the steel plate after induction heating, and putting the steel coil to be cooled into a slow cooling pit for cooling. The microalloy hot-rolled high-strength steel coil is prepared by the method. The microalloy hot-rolled high-strength steel coil and the preparation method thereof can improve the uniformity of the coil-through performance of the hot-rolled steel plate.
Description
Technical Field
The invention belongs to the technical field of steel coil manufacturing, and particularly relates to a microalloy hot-rolled high-strength steel coil and a preparation method thereof.
Background
With the technical progress of the steel industry, the production technology of microalloy hot-rolled high-strength steel based on MX phase (including MC and MN phase) nano precipitation strengthening is continuously optimized, the mechanical property is continuously improved, the tensile strength is gradually developed from 550MPa to 900MPa, and the microalloy hot-rolled high-strength steel is widely applied to the fields of containers, engineering machinery, commercial vehicles and the like. The performance fluctuation of the whole coil and the different coils of the hot rolled steel product is large, the problems of out-of-balance warping, cutting deformation, bending and rolling springback angle, reduction of the service life of a punching die, instability of structural strength and the like are caused, and the downstream manufacturing cost and the application risk are greatly increased. Therefore, the requirement of the microalloy hot-rolled high-strength steel coil on the performance uniformity is higher and higher.
The microstructure and mechanical property of Ti and Nb microalloyed steel are sensitive to the cooling speed and coiling temperature, and under a certain proper coiling temperature range, a fine-grained ferrite structure with fully precipitated nano particles is obtained, and the strength is highest, and the temperature range is narrow (generally within 20 ℃). The actual coiling temperature fluctuation of different hot rolled steel coils often reaches 40 ℃, so that the micro-alloy precipitation is insufficient, and the coil passing performance uniformity of the steel coils is poor (the strength fluctuation of the hot rolled steel coils reaches 150-200MPa at most).
Disclosure of Invention
In view of the analysis, the invention aims to provide a microalloy hot-rolled high-strength steel coil and a preparation method thereof, and solves the problems of insufficient microalloy precipitation and poor coil passing performance uniformity of the steel coil in the prior art.
The purpose of the invention is mainly realized by the following technical scheme:
the invention provides a preparation method of a microalloy hot-rolled high-strength steel coil, which comprises the following steps:
step 1: providing a continuous casting billet of microalloy hot rolled steel;
step 2: rolling and laminar cooling a continuous casting billet of the microalloy hot rolled steel, and controlling the finish rolling temperature to be 850-870 ℃ to obtain a rolled steel plate;
and step 3: induction heating is carried out on the rolled steel plate, so that the temperature of the rolled steel plate is maintained at 610-630 ℃;
and 4, step 4: coiling the steel plate after induction heating to obtain a steel coil to be cooled;
and 5: and (3) placing the steel coil to be cooled into the slow cooling pit for cooling to obtain the microalloy hot-rolled high-strength steel coil.
Further, the thickness of the rolled steel sheet is 12mm or less (for example, 1.5 to 12 mm).
Further, the temperature of the rolled steel sheet is less than 580 ℃ before entering induction heating.
Further, in the step 2, the rolling comprises heating, rough rolling and finish rolling, wherein the heating temperature is 1250-1270 ℃, the heating time is 3-5 h, the finish rolling temperature of the rough rolling is 1070-1120 ℃, and the start rolling temperature of the finish rolling is 1040-1070 ℃.
Further, the heating rate of the induction heating is 48-52 ℃/s, and the fluctuation of the coiling temperature of the head, the middle and the tail of the steel plate after the induction heating is less than or equal to +/-10 ℃.
Further, the above-mentioned coiling includes the following steps:
coiling from the steel sheet head after induction heating to the afterbody, obtain waiting to cool off the coil of strip, wherein, from the center to inferior skin of coil of strip, closely laminate between each layer, inferior skin has the clearance with outmost, and the both ends of coil of strip are detained and are established the heat preservation lid for inferior skin is sealed cavity with outmost clearance.
Further, the coiling from the head to the tail of the steel plate after induction heating comprises the following steps:
calculating and marking the position of a connecting line between the secondary outer layer and the outermost layer, and processing a plurality of through holes penetrating through the steel plate after induction heating along the connecting line;
coiling the steel plate from the head of the steel plate after induction heating to a secondary outer layer, and passing a fixing band through the through hole to bind the secondary outer layer steel plate, so that the layers are tightly attached from the center of the steel coil to the secondary outer layer;
and coiling the tail part of the steel plate from the connecting wire to the induction heated tail part of the steel plate to form an outermost layer, wherein a gap is formed between the secondary outer layer and the outermost layer.
Further, the method for obtaining the steel coil further comprises the following steps:
and the outer wall of the steel coil is coated with a heat-insulating cover.
Further, in the step 5, the cooling may include the steps of:
placing the steel coil to be cooled into a slow cooling pit, and cooling the steel coil to be cooled;
or, box-stacking a plurality of steel coils to be cooled, and cooling the steel coils to be cooled;
the cooling time of the two methods is 48-72 h.
The invention also provides a microalloy hot-rolled high-strength steel coil which is prepared by the preparation method of the microalloy hot-rolled high-strength steel coil.
Further, the composition of the continuous casting billet of the microalloy hot-rolled high-strength steel coil comprises the following components in percentage by mass: 0.05 to 0.12 percent of C, 1.50 to 2.00 percent of Mn, 0.05 to 0.30 percent of Si, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.01 to 0.06 percent of Nb, 0.02 to 0.20 percent of Ti, less than or equal to 0.25 percent of Mo, less than or equal to 0.20 percent of Cr, less than or equal to 0.20 percent of V, less than or equal to 0.0050 percent of N, al S 0.015-0.050% and the balance of Fe and inevitable impurities.
Further, the microstructure of the microalloy hot-rolled high-strength steel coil comprises a quasi-polygonal ferrite structure and/or an acicular ferrite structure.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
a) On one hand, because the microalloy is not uniformly precipitated and the grain diameter is uncontrollable before induction heating, the microalloy is not uniformly precipitated and the final rolling temperature is controlled to be lower than the conventional final rolling temperature (generally above 880 ℃), so that microalloy elements such as Ti, nb and the like are not sufficiently precipitated in the rolling process, namely the precipitation amount of the microalloy elements such as Ti, nb and the like in the rolling process is reduced as much as possible; on the other hand, induction heating is additionally arranged between the rolling step and the coiling step, the temperature uniformity of the whole rolled steel plate is controlled through induction heating, the whole steel plate can be ensured to be in the optimal temperature range (610-630 ℃) for precipitating microalloy elements, at the moment, the steel plate after induction heating is heated, the temperature uniformity of the head part, the middle tail part and the inner side and the outer side of the steel coil can be effectively improved, meanwhile, the sufficient and uniform precipitation of nano-phases such as Nb and Ti is promoted, and the purpose of improving the uniformity of the coil passing performance of the hot rolled steel plate is finally achieved.
b) According to the preparation method of the microalloy hot-rolled high-strength steel coil, provided by the invention, the microalloy hot-rolled high-strength steel coil mainly takes ferrite as a matrix, and the grain is refined and second phase particles are precipitated by adding microalloy elements such as Ti, nb and the like, so that the strengthening effect is realized. Compared with the traditional microalloy design, the key for obviously improving the precipitation strengthening increment is to improve the volume fraction (mass fraction) of the nanometer MX particles and refine the size of the nanometer MX particles. In the rolling process, the head, the middle, the tail and the inner side and the outer side of the steel plate have unavoidable temperature differences, low-temperature rolling is adopted, the temperature uniformity of different positions of the head, the middle, the tail and the inner side and the outer side of the steel plate is improved by controlling the insufficient precipitation of micro-alloy elements such as Ti, nb and the like in the steel and most of the micro-alloy elements still exist in a solid solution state, the optimal precipitation temperature range of a nano precipitation phase of the micro-alloy elements such as Ti, nb and the like in ferrite is selected as the coiling temperature, and a slow cooling measure is adopted after coil stripping, so that an MX phase is uniformly and sufficiently precipitated after coiling.
c) On one hand, each layer is tightly attached from the center of the steel coil to the secondary outer layer, and because each layer is subjected to induction heating, the temperature is high, heat radiation can be carried out between the layers, and the whole body is maintained in the optimal temperature range of microalloy precipitation; on the other hand, outmost and inferior skin have the clearance, and make the clearance form airtight cavity through setting up of heat preservation lid, and thus, the clearance will be outmost and the skin is separated once, because the clearance is airtight cavity, avoid the convection current of air in the clearance, the coefficient of heat conductivity of air is less than the coefficient of heat conductivity of metal, be equivalent to increased one deck insulation construction at the skin outer wall once, effectively slow down coil of strip center to the outer cooling rate of inferior, for the microalloy is appeared and is reserved sufficient separation time, thereby can further improve microalloy and precipitate the volume.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
Fig. 1 is a MX nanophase grain size distribution at a coil end position in a microalloy hot-rolled high-strength steel coil provided in example 1 of the present invention;
fig. 2 is a MX nanophase grain size distribution at the position of +100m of the coil head in the microalloy hot rolled high strength steel coil provided in example 1 of the present invention;
fig. 3 is a grain size distribution of MX +200m nanophase at the coil end position in the microalloy hot rolled high strength steel coil provided in example 1 of the present invention;
fig. 4 is a diagram illustrating a MX nanophase grain size distribution at a coil tail position in the microalloy hot-rolled high-strength steel coil provided in example 1 of the present invention.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention.
The coiling temperature of the head, the middle and the tail of the same hot rolled steel coil is different when the same hot rolled steel coil is coiled, the air cooling speed of the head, the middle and the tail of the coil is uneven after the coil is coiled and uncoiled, the cooling of the inner ring, the outer ring and the two sides of the steel coil is faster, the internal cooling is slower, the cooling speed is different, the microscopic structure and the nano particles are separated out to have difference, and therefore the hot rolled steel coil is enabled to be uneven in performance. At present, most methods for improving the performance uniformity of a microalloy hot rolled steel plate adopt measures such as head and tail shielding, roller speed change or sectional cooling in the hot rolling control cooling process to improve the cooling uniformity of the steel plate, and the measures cannot fundamentally solve the problem of large temperature fluctuation of the head, the middle and the tail of a steel coil and the inner side and the outer side of the steel coil in coiling.
The invention provides a preparation method of a microalloy hot-rolled high-strength steel coil, which comprises the following steps:
step 1: providing a continuous casting billet of microalloy hot rolled steel;
step 2: rolling and laminar cooling a continuous casting billet of the microalloy hot rolled steel, and controlling the finish rolling temperature to be 850-870 ℃ to obtain a rolled steel plate, wherein the thickness of the rolled steel plate is less than 12mm (for example, 1.5-12 mm);
and step 3: induction heating is carried out on the rolled steel plate, so that the temperature of the rolled steel plate is maintained at 610-630 ℃;
and 4, step 4: coiling the steel plate after induction heating to obtain a steel coil to be cooled;
and 5: and (4) placing the steel coil to be cooled into a slow cooling pit for cooling to obtain the microalloy hot-rolled high-strength steel coil.
It should be noted that, after the step 2 rolling and between the step 3 induction heating, the rolled steel sheet undergoes a laminar cooling process, which lowers the temperature of the rolled steel sheet, which is lower than 580 ℃ before entering the induction heating.
Compared with the prior art, the preparation method of the microalloy hot-rolled high-strength steel coil provided by the invention has the advantages that on one hand, because the microalloy is not uniformly precipitated and the grain size is uncontrollable before induction heating, the microalloy elements such as Ti, nb and the like are not sufficiently precipitated in the rolling process by controlling the finishing rolling temperature to be lower than the conventional finishing rolling temperature (usually above 880 ℃), namely, the precipitation amount of the microalloy elements such as Ti, nb and the like in the rolling process is reduced as much as possible; on the other hand, induction heating is additionally arranged between the rolling step and the coiling step, the temperature uniformity of the whole rolled steel plate is controlled through induction heating, the whole steel plate can be ensured to be in the optimal temperature range (610-630 ℃) for precipitating microalloy elements, at the moment, the steel plate after induction heating is heated, the temperature uniformity of the head part, the middle tail part and the inner side and the outer side of the steel coil can be effectively improved, meanwhile, the sufficient and uniform precipitation of nano-phases such as Nb and Ti is promoted, and the purpose of improving the uniformity of the coil passing performance of the hot rolled steel plate is finally achieved.
Specifically, the preparation method is based on the following steps: the microalloy hot-rolled high-strength steel coil mainly takes ferrite as a matrix, and microalloy elements such as Ti, nb and the like are added to refine grains and precipitate second-phase particles, so that the strengthening effect is realized. Compared with the traditional microalloy design, the key for obviously improving the precipitation strengthening increment is to improve the volume fraction (mass fraction) of the nanometer MX particles and refine the size of the nanometer MX particles. In the rolling process, the head, the middle, the tail and the inner side and the outer side of the steel plate have unavoidable temperature differences, low-temperature rolling is adopted, the temperature uniformity of different positions of the head, the middle, the tail and the inner side and the outer side of the steel plate is improved by controlling the insufficient precipitation of micro-alloy elements such as Ti, nb and the like in the steel and most of the micro-alloy elements still exist in a solid solution state, the optimal precipitation temperature range of a nano precipitation phase of the micro-alloy elements such as Ti, nb and the like in ferrite is selected as the coiling temperature, and a slow cooling measure is adopted after coil stripping, so that an MX phase is uniformly and sufficiently precipitated after coiling.
In order to further improve the comprehensive performance of the microalloy hot-rolled high-strength steel coil, the rolling in the step 2 comprises heating, rough rolling and finish rolling.
Wherein the heating temperature is 1250-1270 ℃, the heating time is 3-5 h, the final rolling temperature of rough rolling is 1070-1120 ℃, and the initial rolling temperature of finish rolling is 1040-1070 ℃.
In order to reduce the fluctuation of the coiling temperature of the head, middle and tail portions of the steel sheet after induction heating, the heating rate of the above induction heating is, for example, 48 to 52 ℃/s. Through the heating rate of the induction heating, the fluctuation of the coiling temperature of the head, the middle and the tail of the steel plate after the induction heating is less than or equal to +/-10 ℃.
Considering that the microalloy is mainly precipitated slowly in the cooling process after coiling, in order to slow down the cooling speed and provide enough time and temperature for the microalloy to be precipitated, the coiling exemplarily comprises the following steps:
coiling from the steel sheet head after induction heating to the afterbody, obtain waiting to cool off the coil of strip, wherein, from the center to inferior skin of coil of strip, closely laminate between each layer, inferior skin has the clearance with outmost, and the both ends of coil of strip are detained and are established the heat preservation lid for inferior skin is sealed cavity with outmost clearance.
By adopting the coiling method, on one hand, the layers are tightly attached from the center to the secondary outer layer of the steel coil, and because the layers are heated by induction, the temperature is high, heat radiation can be carried out between the layers, and the whole body is maintained in the optimal temperature range of micro-alloy precipitation; on the other hand, outmost and time skin have the clearance, and make the clearance form airtight cavity through setting up of heat preservation lid, and like this, the clearance separates outmost and time skin, because the clearance is airtight cavity, avoid the convection current of air in the clearance, the coefficient of heat conductivity of air is less than the coefficient of heat conductivity of metal, has increased one deck insulation construction in the skin outer wall of time in other words, effectively slows down coil of strip center to the outer cooling rate of time, for the microalloy is appeared and is reserved sufficient separation time, thereby can further improve the microalloy and precipitate the volume.
It should be noted that, because the outermost layer is directly contacted with the cold air, the precipitation amount and uniformity of the microalloy are not ideal, so that in practical application, the outermost layer can be removed as waste material, and only the center of the steel coil to the next outer layer is reserved.
It should be noted that the steel coil is tightly attached from the center to the secondary outer layer, and the secondary outer layer and the outermost layer have a gap, and in order to form the structure in practical application, the coiling from the head to the tail of the steel plate after induction heating comprises the following steps:
calculating and marking the position of a connecting line between the secondary outer layer and the outermost layer, and processing a plurality of through holes penetrating through the steel plate after induction heating along the connecting line;
coiling the steel plate from the head of the steel plate after induction heating to a secondary outer layer, and passing a fixing band through the through hole to bind the secondary outer layer steel plate, so that the layers are tightly attached from the center of the steel coil to the secondary outer layer;
and coiling the connecting wire to the tail part of the steel plate after induction heating to form an outermost layer, wherein a gap is formed between the secondary outer layer and the outermost layer.
In addition, in order to further slow down the cooling speed and provide sufficient time and temperature for the precipitation of the micro-alloy, the steel coil obtained by the method further comprises the following steps:
and the outer wall of the steel coil is coated with a heat-insulating cover.
For slowing down the cooling rate, in the step 5, the cooling may include the following steps:
placing the steel coil to be cooled into a slow cooling pit, and cooling the steel coil to be cooled;
or, box-stacking a plurality of steel coils to be cooled, and cooling the steel coils to be cooled;
the cooling time of the two methods is 48-72 h.
It should be noted that, through the outermost layer and the secondary outer layer, gaps, protective covers, slow cooling pits, box type stacking and other modes are arranged, the slow and uniform cooling from the center of the steel coil to the secondary outer layer and the two sides of the steel coil can be effectively controlled, so that a quasi-polygonal ferrite and/or acicular ferrite structure with the grain size not very sensitive to the coiling temperature can be obtained, micro-alloy elements such as Ti, nb and the like are uniformly and sufficiently separated out, and the stable control of the coil feeding performance and the batch different coil performance is realized.
The invention also provides a microalloy hot-rolled high-strength steel coil which is prepared by the preparation method of the microalloy hot-rolled high-strength steel coil.
Compared with the prior art, the beneficial effects of the microalloy hot-rolled high-strength steel coil provided by the invention are basically the same as those of the preparation method of the microalloy hot-rolled high-strength steel coil, and are not repeated herein.
Specifically, the composition of the continuous casting slab of the microalloy hot-rolled high-strength steel coil comprises the following components in percentage by mass: 0.05 to 0.12 percent of C, 1.50 to 2.00 percent of Mn, 0.05 to 0.30 percent of Si, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.01 to 0.06 percent of Nb, 0.02 to 0.20 percent of Ti, less than or equal to 0.25 percent of Mo, less than or equal to 0.20 percent of Cr, less than or equal to 0.20 percent of V, less than or equal to 0.0050 percent of N, al S 0.015-0.050%, and the rest is Fe and inevitable impurities, and the microstructure thereof comprises quasi-polygonal ferrite and/or acicular ferrite。
Example 1
The microalloy hot-rolled high-strength steel coil continuous casting slab comprises the following components in percentage by mass: c:0.08%, mn:1.70%, si:0.16%, P:0.011%, S:0.002%, nb:0.03%, ti:0.08%, N:0.0046% of Al S :0.033% and the balance Fe and unavoidable impurities. The soaking temperature of the heating furnace is 1250 ℃, the total in-furnace time is 183min, and the rough rolling and final rolling temperature is 1071 ℃; the initial rolling temperature of the finish rolling is 1045 ℃, the finishing temperature of the finish rolling is 860 ℃, and the finish rolling is carried out until the thickness is 5.0mm; after finishing the finish rolling, the temperature of the steel plate before entering an induction heating furnace is 578 ℃, the steel plate is rapidly and inductively heated to 627 ℃, the heating rate is 50 ℃/s, the coiling temperature is 624 ℃, and the steel plate is rolled and then slowly cooled in a slow cooling pit for 72 hours and then the performance is tested.
The steel sheets produced according to the procedure of this example had the performance indexes shown in table 1, and the nanophase precipitation amount and the particle size distribution thereof are shown in table 2 and fig. 1 to 4.
TABLE 1 EXAMPLE 1 Performance stability of microalloyed hot rolled steel of 5.0mm 700MPa in thickness
| Sampling site | R m /MPa | R p0.2 /MPa | A/％ |
| Rolling head | 742 | 687 | 21.5 |
| Roll up end +100m | 755 | 706 | 21.0 |
| Roll up head +200m | 758 | 697 | 22.0 |
| Roll tail | 745 | 691 | 23.0 |
As can be seen from Table 1, the strength fluctuation of the hot rolled steel with the thickness of 5.0mm and the thickness of 700MPa in different positions of the whole coil is within 20 MPa.
Table 2 example 1 MX nanophase precipitates in steel (mass fraction, wt%)
| Sampling site | Nb | Ti | C* | Σ |
| Rolling head | 0.024 | 0.068 | 0.015 | 0.107 |
| Roll up end +100m | 0.028 | 0.073 | 0.016 | 0.117 |
| Roll up head +200m | 0.026 | 0.076 | 0.016 | 0.118 |
| Roll tail | 0.025 | 0.070 | 0.015 | 0.110 |
As can be seen from Table 2 and FIGS. 1 to 4, the MX nanophase in the steel of this example was sufficiently and uniformly precipitated at different positions in the whole coil, and the ratio of the size of less than 60nm was 93% or more.
Example 2
The microalloy hot rolling high-strength steel coil comprises the following continuous casting components in percentage by mass: c:0.08%, mn:1.70%, si:0.15%, P:0.010%, S:0.003%, mo:0.21%, ti + Nb + V:0.215%, N:0.0043% of Al S :0.040%, the balance being Fe and unavoidable impurities. The soaking temperature of the heating furnace is 1263 ℃, the total in-furnace time is 261min, and the rough rolling finishing temperature is 1113 ℃; the start rolling temperature of finish rolling is 1067 ℃, the finish rolling temperature is 867 ℃, and the finish rolling is carried out until the thickness is 3.0mm; after finishing the finish rolling, the temperature of the steel plate before entering an induction heating furnace is 583 ℃, the steel plate is quickly and inductively heated to 623 ℃, the heating rate is 50 ℃/s, the coiling temperature is 618 ℃, and the steel plate is rolled and then slowly cooled in a slow cooling pit for 72 hours, and then the performance is tested.
The steel sheets produced according to the procedure of this example had the performance indexes shown in Table 3.
TABLE 3 stability of properties of 3.0mm 850MPa-thick microalloy hot rolled steel of example 2
| Sampling site | R m /MPa | R p0.2 /MPa | A/％ |
| Rolling head | 884 | 806 | 21.5 |
| Roll up end +100m | 876 | 794 | 22.5 |
| Roll up head +200m | 880 | 810 | 21.0 |
| Roll tail | 868 | 804 | 20.0 |
As can be seen from Table 2, the strength fluctuation of the hot rolled steel with the thickness of 3.0mm and the thickness of 850MPa in different positions of the whole coil is within 20 MPa.
While the invention has been described with reference to specific preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
Claims (6)
1. A preparation method of a microalloy hot-rolled high-strength steel coil is characterized by comprising the following steps:
step 1: providing a continuous casting billet of microalloy hot rolled steel, wherein the composition of the continuous casting billet of the microalloy hot rolled high-strength steel coil comprises the following components in percentage by mass: 0.05 to 0.12 percent of C, 1.50 to 2.00 percent of Mn, 0.05 to 0.30 percent of Si, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.01 to 0.06 percent of Nb, 0.02 to 0.20 percent of Ti, less than or equal to 0.25 percent of Mo, less than or equal to 0.20 percent of Cr, less than or equal to 0.20 percent of V, less than or equal to 0.0050 percent of N, and Al S 0.015 to 0.050 percent, and the balance of Fe and inevitable impurities;
step 2: rolling and laminar cooling a continuous casting billet of the microalloy hot rolled steel, and controlling the finish rolling temperature to be 850-870 ℃ to obtain a rolled steel plate;
and step 3: carrying out induction heating on the rolled steel plate to ensure that the temperature of the rolled steel plate is maintained at 610-630 ℃, the heating rate of the induction heating is 48-52 ℃/s, and the fluctuation of the coiling temperature of the head, the middle and the tail of the steel plate after the induction heating is less than or equal to +/-10 ℃;
and 4, step 4: coiling the steel plate after induction heating to obtain a steel coil to be cooled;
and 5: placing the steel coil to be cooled into a slow cooling pit for cooling to obtain a microalloy hot-rolled high-strength steel coil;
the coiling comprises the following steps:
coiling the steel plate from the head to the tail of the steel plate after induction heating to obtain a steel coil to be cooled, wherein the steel coil to be cooled is tightly attached to the secondary outer layer from the center of the steel coil, a gap is formed between the secondary outer layer and the outermost layer, and heat insulation covers are buckled at two ends of the steel coil, so that the gap between the secondary outer layer and the outermost layer is a sealed chamber;
the coiling from the head to the tail of the steel plate after induction heating comprises the following steps:
calculating and marking the position of a connecting line between the secondary outer layer and the outermost layer, and processing a plurality of through holes penetrating through the steel plate after induction heating along the connecting line;
coiling the steel plate from the head of the steel plate after induction heating to a secondary outer layer, and passing a fixing band through the through hole to bind the secondary outer layer steel plate, so that the layers are tightly attached from the center of the steel coil to the secondary outer layer;
coiling the tail part of the steel plate after induction heating from the connecting wire to form an outermost layer, wherein a gap is formed between the secondary outer layer and the outermost layer;
the microstructure of the microalloy hot-rolled high-strength steel coil comprises a quasi-polygonal ferrite structure and/or an acicular ferrite structure.
2. The method for preparing the microalloy hot rolled high-strength steel coil as claimed in claim 1, wherein the step 4 is further performed after the steel coil is obtained, and comprises the following steps:
and the outer wall of the steel coil is coated with a heat-insulating cover.
3. The method for preparing the microalloy hot rolled high-strength steel coil as claimed in claim 1, wherein the cooling in the step 5 comprises the following steps:
placing the steel coil to be cooled into a slow cooling pit, and cooling the steel coil to be cooled;
or, box-type stacking is carried out on a plurality of steel coils to be cooled, and the steel coils to be cooled are cooled.
4. The method for preparing the microalloy hot rolled high-strength steel coil as claimed in claim 1, wherein the rolled steel coil has a thickness of 12mm or less.
5. The method for preparing the microalloy hot-rolled high-strength steel coil as claimed in claim 1, wherein in the step 2, the rolling comprises heating, rough rolling and finish rolling;
the heating temperature is 1250 to 1270 ℃, the heating time is 3 to 5h, the final rolling temperature of rough rolling is 1070 to 1120 ℃, and the initial rolling temperature of finish rolling is 1040 to 1070 ℃.
6. A microalloy hot rolled high-strength steel coil is characterized by being prepared by the preparation method of the microalloy hot rolled high-strength steel coil as set forth in any one of claims 1 to 5.
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| CN110616301B (en) * | 2018-06-19 | 2021-08-31 | 宝钢湛江钢铁有限公司 | Production method for improving precipitation strengthening effect of Ti microalloyed hot-rolled high-strength steel on line |
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