CN114395728A - 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 PDF

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CN114395728A
CN114395728A CN202111516533.1A CN202111516533A CN114395728A CN 114395728 A CN114395728 A CN 114395728A CN 202111516533 A CN202111516533 A CN 202111516533A CN 114395728 A CN114395728 A CN 114395728A
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coil
steel coil
microalloy
steel
steel plate
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CN114395728B (en
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曹燕光
李昭东
雍岐龙
杨忠民
陈颖
王慧敏
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Zhonglian Advanced Steel Technology Co ltd
Central Iron and Steel Research Institute
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Zhonglian Advanced Steel Technology Co ltd
Central Iron and Steel Research Institute
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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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
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    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • 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
    • 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
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • 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
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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  • Metal Rolling (AREA)

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 carrying out induction heating on a rolled steel plate to ensure that the temperature of the rolled steel plate is maintained 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

Microalloy hot-rolled high-strength steel coil and preparation method thereof
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 roll and the different roll of the hot rolled steel product is large, the problems of flat-opening warping, cutting deformation, poor resilience angle of bending and rolling, reduction of the service life of a punching die, unstable 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-.
Disclosure of Invention
In view of the above 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 (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.
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 modes is 48-72 hours.
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, AlS0.015-0.050%, 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, the microalloy hot-rolled high-strength steel coil is not uniformly precipitated and the grain diameter is uncontrollable before induction heating, so that microalloy elements such as Ti, Nb and the like are insufficiently 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 ℃) in which micro alloy elements are precipitated, 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 rolling 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 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.
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 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 of methods for improving the performance uniformity of a microalloy hot rolled steel plate improve the cooling uniformity of the steel plate by measures such as head and tail shielding, roller table speed change or sectional cooling in the hot rolling control cooling process, and the measures cannot fundamentally solve the problem of large temperature fluctuation of the head, the middle and the tail and the inner and outer sides of a steel coil during 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 ℃) in which micro alloy elements are precipitated, 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 rolling 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 part, the middle part and the tail part of the steel plate after induction heating, the heating rate of the induction heating is 48-52 ℃/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 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.
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 modes is 48-72 hours.
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, AlS0.015-0.050%, the balance of Fe and inevitable impurities, and the microstructure of the steel comprises a quasi-polygonal ferrite structure and/or an acicular ferrite structure.
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 AlS: 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 start rolling temperature of finish rolling is 1045 ℃, the finish rolling temperature of finish rolling is 860 ℃, and the finish rolling is carried out until the thickness is 5.0 mm; 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 thickness grade 700MPa
Sampling site Rm/MPa Rp0.2/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 whole hot rolled steel coil with the thickness of 5.0mm and the thickness of 700MPa produced in the example is within 20MPa at different positions.
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 precipitated sufficiently and uniformly at different positions in the whole roll, and the ratio of the size of less than 60nm was 93% or more.
Example 2
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: 0.15%, P: 0.010%, S: 0.003%, Mo: 0.21%, Ti + Nb + V: 0.215%, N: 0.0043% of AlS: 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 3.0 mm; 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 EXAMPLE 2 Performance stability of 3.0mm thick 850MPa microalloyed hot rolled steel
Sampling site Rm/MPa Rp0.2/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 whole 3.0mm thick 850MPa hot rolled steel produced by the present example is within 20MPa at different positions.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims (10)

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;
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 (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.
2. The method for preparing the microalloy hot-rolled high-strength steel coil as claimed in claim 1, wherein 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 ℃.
3. The method for preparing the microalloy hot rolled high-strength steel coil as claimed in claim 1, wherein the coiling 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.
4. The method for preparing the microalloy hot rolled high-strength steel coil as claimed in claim 3, wherein the step of 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.
5. The method for preparing a microalloy hot rolled high strength steel coil as claimed in claims 1 to 4, wherein the method further comprises the following steps after obtaining the steel coil:
and the outer wall of the steel coil is coated with a heat-insulating cover.
6. The method for preparing the microalloy hot rolled high-strength steel coil as claimed in claims 1 to 4, 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.
7. The method of producing a microalloyed hot rolled high strength steel coil as claimed in any one of claims 1 to 4, wherein the thickness of the rolled steel sheet is 12mm or less.
8. 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 1250-1270 ℃, 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 ℃.
9. A microalloy hot-rolled high-strength steel coil, characterized by being manufactured by the method for manufacturing the microalloy hot-rolled high-strength steel coil as claimed in any one of claims 1 to 8.
10. The microalloy hot-rolled high-strength steel coil as claimed in claim 9, wherein the composition of the continuous casting slab of the microalloy hot-rolled high-strength steel coil comprises, 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, AlS0.015-0.050%, and the balance of Fe and inevitable impurities.
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WO2001023625A1 (en) * 1999-09-29 2001-04-05 Nkk Corporation Sheet steel and method for producing sheet steel
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CN102226249A (en) * 2011-06-13 2011-10-26 马鞍山钢铁股份有限公司 High-strength hot rolled steel plate with excellent cold forming property and preparation method thereof
CN103526111A (en) * 2013-10-17 2014-01-22 马鞍山市安工大工业技术研究院有限公司 Hot-rolled plate band steel with yield strength being 900MPa and preparation method thereof
CN110616301A (en) * 2018-06-19 2019-12-27 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
CN112941408A (en) * 2021-01-28 2021-06-11 日照钢铁控股集团有限公司 Method for manufacturing 500 MPa-grade seat sliding rail steel based on continuous casting and rolling line

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001023625A1 (en) * 1999-09-29 2001-04-05 Nkk Corporation Sheet steel and method for producing sheet steel
JP2005248286A (en) * 2004-03-05 2005-09-15 Nippon Steel Corp Method for manufacturing high-tensile steel sheet having excellent hole-expansibility
CN102226249A (en) * 2011-06-13 2011-10-26 马鞍山钢铁股份有限公司 High-strength hot rolled steel plate with excellent cold forming property and preparation method thereof
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CN112941408A (en) * 2021-01-28 2021-06-11 日照钢铁控股集团有限公司 Method for manufacturing 500 MPa-grade seat sliding rail steel based on continuous casting and rolling line

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