CN117778891A - Hot rolled high-strength steel with extremely thin specification below 2.0mm and preparation method thereof - Google Patents
Hot rolled high-strength steel with extremely thin specification below 2.0mm and preparation method thereof Download PDFInfo
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- 238000005461 lubrication Methods 0.000 claims description 11
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Abstract
The invention discloses hot rolled high-strength steel with an extremely thin specification below 2.0mm and a preparation method thereof, belonging to the field of hot continuous steel rolling. The hot rolled high-strength steel with the extremely thin specification below 2.0mm comprises the following chemical components in percentage by weight: 0.04 to 0.10 percent of C,0.05 to 0.20 percent of Si, 0.40 to 1.40 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.008 percent of S, 0.010 to 0.050 percent of Als, 0.040 to 0.130 percent of Ti+Zr, less than or equal to 0.005 percent of N and the balance of Fe and impurities.
Description
Technical Field
The invention belongs to the field of hot continuous rolling, relates to a production method of thin-specification high-strength hot continuous rolling steel, and in particular relates to ultra-thin-specification hot rolling high-strength steel below 2.0mm and a preparation method thereof.
Background
The industrial production difficulty of the hot rolled high-strength steel with the extremely thin specification below 2.0mm is high mainly because Nb element is generally added into the high-strength steel to promote grain refinement and improve the forming flanging performance of the material, but Nb element can form Nb (CN) in the rolling process of the steel plate (about 900-1000 ℃), and has a nailing and rolling effect on dislocation in the steel to improve the heat deformation resistance of the steel, so that the problems of heavier rolling load, difficult plate shape control, easy occurrence of waste heads, waste tails, poor plate shape and the like of the high-strength steel with the extremely thin specification below 2.0mm are caused. In order to solve the rolling difficulty of the hot-rolled high-strength steel with extremely thin specification, domestic steel enterprises adopt Ti microalloying to replace Nb microalloying, and because the ferrite supersaturation precipitation strengthening effect of Ti is strong, and the Ti is not easy to precipitate in a large amount in the finish rolling process so as to improve the thermal deformation resistance, the problem that the rolling with extremely thin specification accords with the weight bias can be better solved, but Ti and N are easy to form liquid precipitation TiN, and the forming performance of the steel is deteriorated. Therefore, the invention adopts Ti-Zr microalloying to solve the difficult problem of rolling in extremely thin specifications and the problem of material forming property at the same time.
Through searching, CN104131238B discloses a high-forming high-weather-resistance extremely-thin hot rolled steel plate and a CSP production process thereof, wherein the steel comprises the following components: 0.035-0.065% of C, 0.15-0.3% of Si, 1.3-1.6% of Mn, 0.12-0.2% of Cu, 0.2-0.6% of Cr, 0.1-0.2 Ni, 0.1-0.13% of Ti, 0.1-0.2% of Mo, 0.025-0.045% of Als, less than or equal to 0.018% of P, less than or equal to 0.005% of S, less than or equal to 0.006% of N, and the balance of Fe and unavoidable impurities. And provides the preparation process: the heat flow of the crystallizer is 2.45-2.55 mw/m < 2 >, the specific water content of the secondary cooling water for continuous casting is 1.77-1.83L/Kg, the thickness of the casting billet for casting is 65-75 mm, and the secondary cooling water is pressed down to 55-60 mm through multiple liquid cores; the tapping temperature of the casting blank is 1230-1250 ℃; the finishing temperature is 880-920 ℃; and (3) coiling after laminar cooling, and rapidly cooling after coiling and off-line cooling to 280-320 ℃ at a cooling rate of less than or equal to 10 ℃/s.
CN104550256a discloses a TMCP thin gauge high strength steel sheet shape control method: heating the steel billet to 1100-1200 ℃, and controlling the temperature difference of the upper layer, the middle layer and the lower layer of the steel billet to be 0-30 ℃; the rolling process parameters are set unchanged, and rolling is carried out by adopting a rolling schedule set by a secondary model; ACC cooling is carried out on the steel plate after finish rolling, the speed of an ACC roller way is set to be 1.0-1.25 m/s, and the final cooling temperature is controlled to be 400-500 ℃; and (3) carrying out online straightening after cooling the steel plate, adopting a secondary model to automatically straighten, and controlling the redness returning temperature of the steel plate to be 500-550 ℃ after straightening.
CN112496085B discloses a method for improving the edge wave defect of 1500MPa grade hot rolled ultra-high strength steel, according to the wave shape and wave height of the edge wave, the rough rolling and finish rolling parameters are respectively set as: when the wave height is 5-10 mm/m, the lower roller positions of the coarse correction and fine correction working rollers are set to be 4-8 mm; when the wave height is 10.1-15 mm/m, the lower roller positions of the rough correction and the fine correction working rollers are set to be 9-12 mm. When the wave type is operation side unilateral wave type, the inclination of the rough correction and fine correction working rolls is set to be 0.5-1.2 mm; when the waves are unilateral waves at the driving side, the inclination of the rough correction and fine correction working rolls is set to be minus 0.5 to minus 0.2mm; when the waves are double-sided waves, the inclination of the rough correction and fine correction working rolls is set to be 0.1-0.4 mm. The invention can control the unevenness of the steel plate below 5 mm/m.
CN113522967B discloses a control method for short-process rolling 550 MPa-level wide and thin-specification high-strength steel plate shape, which solves the technical problems of low finishing efficiency, low comprehensive yield and the like caused by poor plate shape of 550 MPa-level wide and thin-specification steel plate through slab thickness and wedge control, finish rolling strip steel load distribution control and finish rolling strip steel convexity and flatness control.
CN113522988B discloses a control method for the shape of a DQ process thin ultra-high strength steel plate, comprising: rolling, cooling, leveling and transverse cutting. The invention emphasizes a micro-medium wave compensation strategy during rolling, and adopts a sectional cooling mode after the steel coil is rolled, so that the problem of poor plate shape caused by overlarge cooling speed after the steel coil is rolled is mainly solved. The steel coil is immediately flattened within 48 hours after rolling, so that excessive work hardening of the steel plate is avoided, and the flattening effect is ensured. The unevenness of the steel plate produced by the method is between 5 and 8mm/m, and the most preferable can reach 2mm/m.
From the above, the prior patent of the thin high-strength steel mainly controls rolling load and steel plate shape through rolling, leveling, straightening and other processes, and the stable rolling of the thin high-strength steel is realized through comprehensive improvement of chemical components and rolling processes.
Disclosure of Invention
Aiming at the technical problems, the invention provides hot rolled high-strength steel with the extremely thin specification below 2.0mm and a preparation method thereof.
The technical scheme adopted for solving the technical problems is as follows: the hot rolled high-strength steel with the extremely thin specification below 2.0mm comprises the following chemical components in percentage by weight: 0.04 to 0.10 percent of C,0.05 to 0.20 percent of Si, 0.40 to 1.40 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.008 percent of S, 0.010 to 0.050 percent of Als, 0.040 to 0.130 percent of Ti+Zr, less than or equal to 0.005 percent of N, and the balance of Fe and unavoidable impurity elements.
The microstructure of the extremely-thin hot rolled high-strength steel below 2.0mm is ferrite with the volume fraction of more than or equal to 95 percent and pearlite or cementite with the volume fraction of less than or equal to 5 percent; the tensile strength is 500-900 MPa, the elongation is more than or equal to 20%, the yield ratio is less than or equal to 0.88, the inclusion grade is less than or equal to 0.5, and the grade of the liquid-separated TiN is less than or equal to 0.5 according to the class-D inclusion grade.
Further, when the tensile strength of the extremely-thin gauge hot-rolled high-strength steel of 2.0mm or less is 500MPa, the chemical composition thereof is 0.40 to 0.80% Mn and 0.040 to 0.060% Ti+Zr.
Further, when the tensile strength of the extremely-thin gauge hot-rolled high-strength steel of 2.0mm or less is 600MPa, the chemical composition thereof is 0.50 to 1.00% Mn and 0.050 to 0.070% Ti+Zr.
Further, when the tensile strength of the extremely-thin gauge hot-rolled high-strength steel of 2.0mm or less is 700MPa, the chemical composition thereof is 0.90 to 1.10% Mn and 0.080 to 0.110% Ti+Zr.
Further, when the tensile strength of the extremely-thin gauge hot-rolled high-strength steel of 2.0mm or less is 800MPa, the chemical composition thereof is Mn of 1.20 to 1.40% and Ti+Zr of 0.090 to 0.130%.
The preparation method of the hot rolled high-strength steel with the extremely thin specification below 2.0mm comprises the following steps: the steel casting blank is obtained through converter smelting, LF refining, RH refining and continuous casting, and then a finished steel plate is obtained through plate blank heating, rough rolling, finish rolling, laminar cooling, coiling and cooling; wherein the thickness of the steel casting blank is 200-250 mm, the steel casting blank is hot-fed and hot-packed into a slab heating furnace for heating, and the discharging temperature of the slab is 1220-1280 ℃.
Further, the rough rolling inlet temperature of the slab is 1160-1200 ℃, the rough rolling outlet temperature is 1120-1160 ℃, and the rough rolling outlet speed is 2-5 m/s; rough rolling to obtain an intermediate blank with the thickness of 30-40 mm, wherein the convexity of the intermediate blank is 80-120 mu m, and the wedge shape is 80-120 mu m; the intermediate billet is transported on a roller way after rough rolling, and is sent to a finishing mill group after passing through a heat preservation cover and a hot rolling box.
Further, the temperature of the finish rolling inlet of the intermediate billet is 1060-1120 ℃, the temperature of the finish rolling outlet is 860-900 ℃, the speed of the finish rolling outlet is 8-12 m/s, the number of cooling water opening groups among the racks is not more than 1 group, and the number of lubrication rolling opening groups is not less than 3 groups; the working mileage of the working rolls is 10 Km-20 Km during finish rolling, the temperature difference of the working rolls in the width direction is not more than 30 ℃, and the temperature difference of the upper working rolls and the lower working rolls is not more than 15 ℃; the intermediate blank is finish rolled to obtain a steel plate with the thickness of 1.2-2.0 mm, the convexity of the steel plate is 20-40 mu m, and the wedge shape is not higher than 25 mu m.
Further, the laminar cooling rate of the steel plate is 20-50 ℃/s, the flow ratio of the lower header to the upper header is 1.2-1.4 when the lower header is cooled, the laminar cooling model adopts sparse cooling, namely 2 groups of headers are opened and 1 group of headers are closed, the coiling temperature is controlled according to U-shaped coiling, namely the coiling temperature of the head and the tail of a steel coil is controlled according to 650-700 ℃, and the coiling temperature of the middle part of the steel coil is controlled according to 600-650 ℃; and (3) after the steel plate is coiled, placing the steel plate into a slow cooling pit, or placing hot steel coils around the steel coils, controlling the steel coils to be cooled to 200-300 ℃ at a cooling rate of not higher than 20 ℃/h, and then performing air cooling to room temperature.
The beneficial effects of the invention are as follows: compared with Nb and Nb-Ti microalloying, the method adopts the Ti-Zr microalloying thought, has the advantages of low rolling load, low rolling waste rate and easier control of the plate shape when being used for producing the hot rolled steel plate with extremely thin specification (less than or equal to 2.0 mm); compared with Nb and Ti microalloying, the method has the advantages of low inclusion grade, low yield ratio and high elongation of the liquid-separated TiN inclusion, and is favorable for improving the forming performance of steel.
The invention provides a full-flow key process technology of the thin high-strength steel in terms of chemical components, hot rolling process, equipment control and the like, provides a new thought for preparing the thin high-strength steel, and has technical advancement, operability and popularization.
Drawings
FIG. 1 is a plate shape monitoring chart of the steel of example 1 of the present invention;
FIG. 2 is a graph showing the monitoring of the shape of the steel of comparative example 1 according to the present invention;
FIG. 3 is an actual coil of the steel of example 1 of the present invention;
FIG. 4 is an actual coil of comparative example 1 steel of the present invention;
FIG. 5 is an actual plate shape of the steel of example 2 of the present invention;
FIG. 6 is an actual plate shape of the steel of comparative example 2 of the present invention;
FIG. 7 is a drawing showing the inclusion of the steel of example 2 of the present invention;
FIG. 8 is inclusions in the steel of comparative example 2 of the present invention;
FIG. 9 is a microstructure of the steel of example 1 of the present invention;
FIG. 10 is a microstructure of the steel of example 2 of the present invention;
FIG. 11 is a microstructure of the steel of example 3 of the present invention;
FIG. 12 is a microstructure of the steel of example 4 of the present invention;
FIG. 13 is a microstructure of the steel of comparative example 1 of the present invention;
FIG. 14 shows the microstructure of the steel of comparative example 2 according to the present invention.
Detailed Description
The technical scheme of the invention can be implemented in the following way.
The invention provides hot rolled high-strength steel with an extremely thin specification below 2.0mm and a preparation method thereof.
The steel microstructure of the invention is ferrite with volume fraction more than or equal to 95% and pearlite or cementite with volume fraction less than or equal to 5%, the tensile strength is 500-900 MPa, the elongation is more than or equal to 20%, the yield ratio is less than or equal to 0.88, the inclusion grade is less than or equal to 0.5, and the liquid-out TiN is less than or equal to 0.5 grade according to the grade of D-type inclusion. Meanwhile, the steel has the advantages of low rolling load, high rolling yield, good plate shape and good forming flanging performance.
In order to achieve the above purpose, the invention provides that the chemical components of the hot rolled high strength steel with the extremely thin specification below 2.0mm comprise the following components in percentage by weight: c:0.04 to 0.10 percent, si:0.05 to 0.20 percent, mn: 0.40-1.40%, P is less than or equal to 0.015%, S is less than or equal to 0.008%, als:0.010 to 0.050%, ti+Zr: 0.040-0.130%, N is less than or equal to 0.005%, and the balance is Fe and unavoidable impurity elements.
Further, the chemical components of the 500 MPa-grade hot rolled high-strength steel with the extremely-thin specification below 2.0mm comprise the following components in percentage by weight: c:0.04 to 0.10 percent, si:0.05 to 0.20 percent, mn:0.40 to 0.80 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.008 percent, als:0.010 to 0.050%, ti+Zr: 0.040-0.060%, N is less than or equal to 0.005%, and the balance is Fe and unavoidable impurity elements.
Further, the chemical components of the 600 MPa-grade hot rolled high-strength steel with the extremely-thin specification below 2.0mm comprise the following components in percentage by weight: c:0.04 to 0.10 percent, si:0.05 to 0.20 percent, mn:0.50 to 1.00 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.008 percent, als:0.010 to 0.050%, ti+Zr:0.050 to 0.070 percent, N is less than or equal to 0.005 percent, and the balance is Fe and unavoidable impurity elements.
Further, the chemical components of the 700 MPa-grade hot rolled high-strength steel with the extremely-thin specification below 2.0mm comprise the following components in percentage by weight: c:0.04 to 0.10 percent, si:0.05 to 0.20 percent, mn:0.90 to 1.10 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.008 percent, als:0.010 to 0.050%, ti+Zr:0.080 to 0.110 percent, N is less than or equal to 0.005 percent, and the balance is Fe and unavoidable impurity elements.
Further, the chemical components of the 800 MPa-grade hot rolled high-strength steel with the extremely-thin specification below 2.0mm comprise the following components in percentage by weight: c:0.04 to 0.10 percent, si:0.05 to 0.20 percent, mn:1.20 to 1.40 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.008 percent, als:0.010 to 0.050%, ti+Zr: 0.090-0.130%, N less than or equal to 0.005%, and Fe and unavoidable impurity elements as the rest.
The reasons for the limitation of the main alloying elements in the steel according to the invention will be explained below.
C is an important strengthening element in steel, the strength of the steel can be improved through solid solution strengthening and precipitation strengthening, but the content of C is not too high, otherwise, alloy cementite containing Ti and Zr is easy to form with elements such as Fe, ti, zr and the like in the subsequent phase transition, and the cementite is large in size and easy to enrich in a grain boundary, so that the forming performance of the material is influenced. Thus, the present invention controls the C content to a lower level of 0.04 to 0.10%.
Si is an important interstitial solid solution strengthening element in steel, and Si can improve the activity of C in the phase transformation process, promote outward diffusion of C from austenite, promote the formation of cementite, and lower Si content is preferable for reducing the cementite content; meanwhile, si element is used as a solid solution strengthening element, the content of the Si element is increased, the thermal deformation resistance is easily improved, and the finish rolling load of the thin steel plate is increased, so that the Si content is controlled at a lower level of 0.05-0.20%.
Mn has the functions of solid solution strengthening and toughness improvement in steel, but when the Mn content is higher, not only is the composition segregation easily formed in the thickness center, and the structure uniformity is reduced, but also the heat deformation resistance is easily improved, and the rolling load is improved, so that the Mn content is controlled at a lower level of 0.40-1.40 percent, and is graded according to the strength grade.
P, S, N is an impurity element in steel, impurities are easy to form, the toughness and plasticity of the steel are reduced, sulfide and nitride impurities are formed with Ti and Zr in the steel when the S, N content is higher, the liquid separation TiN is in a cuboid shape, a cracking source is easy to form when a large amount of liquid separation TiN exists in the steel, and the influence on toughness and plasticity is large, so that the invention limits the P content to less than or equal to 0.015%, the S content to less than or equal to 0.008% and the N content to less than or equal to 0.005%.
Al mainly plays a role in deoxidizing steel, so that the content of Als is controlled to be 0.010-0.050%.
Ti can be combined with C element in steel to form nano TiC precipitated phase, which can play a strong role in precipitation strengthening, and meanwhile, ti can inhibit coarsening of original austenite structure in the slab reheating process, thereby being beneficial to grain refinement. However, the Ti content should not be too high to form large-size, high-density liquid-out TiN inclusions. In order to solve the problems of more liquid-out TiN, larger size and poor microstructure uniformity of Ti microalloyed steel, the invention provides a method for compounding and adding Ti and Zr, because the chemical property of Zr is more active than that of Ti, zrN is preferentially formed during smelting, the shape of the liquid-out TiN cube is changed, the edges and corners of the liquid-out TiN are passivated, the stress concentration of the liquid-out TiN and a steel matrix is reduced, meanwhile, the size and the number of the liquid-out TiN can be reduced by adding Zr, in addition, the austenite recrystallization activation energy of the Ti microalloyed steel can be improved by Zr, the prior austenite structure refinement is promoted, and the mixed crystal structure which is easy to occur in the Ti microalloyed steel is lightened. Therefore, the present invention is limited to a Ti+Zr content of 0.040 to 0.130%.
The steel is manufactured by adopting the production flow of obtaining a steel casting blank through converter smelting, LF refining, RH refining and continuous casting, and obtaining a finished steel plate through slab heating, rough rolling, finish rolling, laminar cooling, coiling and cooling.
Further, the thickness of the steel casting blank is 200-250 mm.
Further, the steel casting blank is hot-charged into a slab heating furnace, and the discharging temperature of the slab is 1220-1280 ℃.
Further, the rough rolling inlet temperature of the billet is 1160-1200 ℃, the rough rolling outlet temperature is 1120-1160 ℃, and the rough rolling outlet speed is 2-5 m/s.
Further, the steel is rough rolled to obtain an intermediate billet with the thickness of 30-40 mm, the convexity of the intermediate billet is 80-120 mu m, and the wedge shape is 80-120 mu m.
Further, the steel intermediate billet is transported on a roller way after rough rolling, and is sent to a finishing mill group after passing through a heat preservation cover and a hot rolling box.
Further, the temperature of the finish rolling inlet of the steel intermediate billet is 1060-1120 ℃, the temperature of the finish rolling outlet is 860-900 ℃, the speed of the finish rolling outlet is 8-12 m/s, the number of cooling water opening groups among the frames is not more than 1 group, and the number of lubrication rolling opening groups is not less than 3 groups.
Further, the working mileage of the working rolls during finish rolling of the steel is 10 Km-20 Km, the temperature difference in the width direction of the working rolls is not more than 30 ℃, and the temperature difference between the upper working rolls and the lower working rolls is not more than 15 ℃.
Further, the steel is finish rolled to obtain a steel plate with a thickness of 1.2-2.0 mm, a convexity of 20-40 μm and a wedge shape of not more than 25 μm.
Further, the laminar cooling rate of the steel plate is 20-50 ℃/s, the flow ratio of the lower header to the upper header is 1.2-1.4 when the lower header is cooled, the laminar cooling model adopts sparse cooling, namely 2 groups of headers are opened and 1 group of headers are closed, the coiling temperature is controlled according to U-shaped coiling, namely the coiling temperature of the head and the tail of the steel coil is controlled according to 650-700 ℃, and the coiling temperature of the middle part of the steel coil is controlled according to 600-650 ℃.
Further, the steel plate is coiled and then placed in a slow cooling pit, or a hot steel coil is placed around the steel coil, so that the steel coil is cooled to 200-300 ℃ at a cooling rate of not higher than 20 ℃/h, and then air-cooled to room temperature.
The reasons for the limitation of the production process will be described below in connection with the requirements for controlling the shape of the steel sheet according to the present invention.
First, in terms of heating schedule. Because the slab heating furnace adopts the nozzle for heating, the main heat transfer mode is heat radiation, and the heat is transferred to the core by the slab surface, the core temperature is lower when the slab is cold-packed, the heating speed is slower, the condition of the core temperature being lower easily occurs when the heating system is improper, the deformation can not be fully transferred to the slab core in the follow-up rough rolling, the rolling load is improved, the rolling difficulty is increased, and the core structure is coarse easily caused. When the hot feeding and hot charging are adopted, the slab is naturally cooled in the air after being taken off from continuous casting, the temperature of the core is higher than that of the surface, and the core is higher after being heated by the slab, so that the subsequent rough rolling is easy. Thus, the present invention requires: the billet obtained after continuous casting is fed into a plate blank heating furnace by adopting hot feeding, and the tapping temperature of the heating furnace is controlled at a higher level of 1220-1280 ℃.
Second, in terms of rough rolling process. When the temperature and the deformation system are designed, the austenite recrystallization region is considered for rolling, the austenite structure is refined through recrystallization, and the strong plasticity of the material is improved, so that the rough rolling temperature is controlled at a higher level, the rolling deformation is controlled at a higher level, namely the thickness of the intermediate blank is controlled at a lower level; secondly, taking the plate shape control of rough rolling into consideration, adopting a higher rough rolling temperature and a faster rough rolling speed to reduce the rolling load. The invention requires that: the rough rolling inlet temperature is 1160-1200 ℃, the rough rolling outlet temperature is 1120-1160 ℃, the rough rolling outlet speed is 2-5 m/s, the thickness of the rough rolled intermediate blank is 30-40 mm, and the convexity and the wedge shape are 80-120 mu m.
Thirdly, a heat preservation cover and a hot rolling box are arranged on a roller way between the rough rolling unit and the finish rolling unit, so that the finish rolling temperature is improved, the rolling load is reduced, and on the other hand, the high-temperature intermediate billet is coiled to remove surface iron scales, so that the head and tail temperatures of the steel plate are uniform, and the stable rolling of the thin-specification steel plate is realized.
Fourth, in the finish rolling process. Firstly, the main function of finish rolling is to provide a large number of nucleation points for subsequent phase transformation through large compression ratio rolling, promote the subsequent phase transformation to form fine and uniform tissues, and improve the toughness of the material through fine grain strengthening. The invention adopts higher finish rolling temperature, namely the finish rolling inlet temperature is 1060-1120 ℃, the finish rolling outlet temperature is 860-900 ℃, and mainly aims to ensure that the finish rolling earlier stage (F1-F4) is still in an austenite recrystallization zone for rolling, uniform and fine equiaxed crystals are formed through recrystallization, the finish rolling later stage (F5-F7) is in an austenite non-recrystallization zone for rolling, and sufficient nucleation work and a large number of nucleation points are provided for subsequent phase transformation through flattening of an austenite structure. In addition, the invention adopts higher finish rolling outlet speed of 8-12 m/s, mainly aims to finish rolling the steel plate rapidly, reduces the head-tail temperature difference caused by natural temperature drop of the steel plate, and thus reduces the head-tail performance difference of the steel plate.
Secondly, the finish rolling process is set in consideration of the problem of controlling the shape of the thin gauge steel sheet. The thickness of the steel plate is thinner and is 1.2-2.0 mm, the finish rolling compression ratio is large, and the plate shape is difficult to control. Thus, the present invention: (1) The number of the cooling water opening groups among the frames is required to be not more than 1 group so as to reduce the temperature drop in the finish rolling process of the steel plate; (2) The number of the lubrication rolling starting groups is not less than 3, and the friction force on the surface of the steel plate is relieved through oil-water lubrication, so that the finish rolling load is relieved; (3) The working mileage of the finish rolling working roll is required to be 10 Km-20 Km, namely the number of rolling blocks is 30-60, namely the surface state of a roller at the front section of a roller changing period is unstable, and the thickening and the roughness of an oxide scale on the surface of a roller at the rear section of the roller changing period are not beneficial to the stable rolling and the plate shape control of a thin-specification steel plate; (4) The temperature difference in the width direction of the working rolls is required to be not more than 30 ℃, the temperature difference between the upper working rolls and the lower working rolls is not more than 15 ℃, mainly because the working rolls are in contact with the steel plate and are in a high temperature state for a long time, and the upper working rolls and the lower working rolls are in different positions in the width direction of the working rolls, and because of different heat dissipation rates, certain temperature difference exists, if the temperature difference is large, tiny fluctuation of roll shapes can occur, and the regulation and control capability of roll bending on the shapes and convexities can be influenced. (5) The convexity and wedge are controlled to be 20-40 μm or below by roll shape design and roll bending and shifting.
Fifth, in laminar cooling. (1) In order to avoid the formation of coarse ferrite or cementite structures, a higher laminar cooling rate of 20-50 ℃/s is required to refine the final structure and improve the strong plasticity of the material. (2) The coiling temperature is controlled at 600-650 ℃, mainly because the nose temperature of Ti and Zr precipitated phases is near 600 ℃, and the proper improvement of the coiling temperature is beneficial to the improvement of the elongation of the thin steel plate. (3) Because the lower header cooling water is influenced by gravity, the upward spraying speed to the surface of the steel plate is low, and therefore, in order to ensure that the upper and lower surface cooling speeds are close, the flow rate of the lower header cooling water is appropriately higher than that of the upper header, and the flow ratio of the lower header to the upper header is controlled to be 1.2-1.4 by combining industrial production experience. (4) Because the steel plate is subjected to phase transition during laminar cooling, internal stress is easy to generate during phase transition, and the internal stress is increased when the cooling rate is higher, the cooling rate of the steel plate is properly reduced on the premise of meeting the performance requirement of the steel plate, namely a sparser cooling boiled water mode is adopted, and 2 groups of headers are opened and 1 group of headers are closed. (5) The head and tail parts of the coiled steel plate are directly contacted with air, and the temperature drop of the head and tail parts of the coiled steel plate is higher than that of the interior of the steel coil, so that the control of the coiling temperature is required to be controlled according to a U shape, namely, the head and tail coiling temperature is higher, the middle coiling temperature is lower and the temperature is controlled according to 650-700 ℃, so that the temperature of the whole coiled steel coil is uniform before the steel coil enters a pit, and the internal stress of the steel coil caused by the temperature difference is reduced.
Sixth, in the slow cooling process. The aim of the slow cooling treatment on the steel coil is to remove stress annealing, and the internal stress of the steel coil is relieved by keeping the temperature of the steel coil at a certain temperature through the heat of the steel coil and the slow cooling pit, eliminating dislocation, defects and the like in the steel coil. The cooling rate of the steel coil is required to be controlled below 20 ℃/h.
The technical scheme and effect of the present invention will be further described by practical examples.
Examples
Example 1
Adopting a converter-LF electric heating-RH vacuum refining-continuous casting process flow to prepare a steel billet with the thickness of 200mm and the mass percentage as follows: 0.06% C,0.09% Si,0.88% Mn,0.010% P,0.005% S,0.033% Als,0.038% Ti,0.023% Zr,0.0033% N, and the balance Fe and unavoidable impurities. The steel billet is prepared into a steel plate with the thickness of 1.5mm through the technological processes of heating, rough rolling, hot rolling box, finish rolling, laminar cooling and slow cooling. The specific process is as follows: the billet is fed into a slab heating furnace by adopting hot feeding, and the tapping temperature is 1247 ℃. The rough rolling inlet temperature is 1177 ℃, the rough rolling outlet temperature is 1131 ℃, the rough rolling outlet speed is 3.3m/s, the thickness of a middle blank obtained after rough rolling is 34mm, the convexity of the middle blank is 89 mu m, and the wedge shape is 82 mu m. The middle part is transported by a roller way after rough rolling, is sequentially subjected to heat preservation by a heat preservation cover, and is sent to a finishing mill group after being coiled by a hot coil box. The temperature of the finish rolling inlet is 1083 ℃, the temperature of the finish rolling outlet is 866 ℃, the speed of the finish rolling outlet is 11.0m/s, cooling water between 1 group of racks is started, 3 groups of lubrication rolling are started, the working mileage of a finish rolling working roll is 18.2Km, the maximum temperature difference in the width direction of the working roll is 26 ℃, the temperature difference between the upper working roll and the lower working roll is 14 ℃, the convexity of a steel plate is 36 mu m, and the wedge shape is 21 mu m after finish rolling. The finish rolled steel plate is subjected to laminar cooling, the laminar cooling rate is 28 ℃/s, the laminar cooling model is formed by opening 2 groups of pipes 1 group, the water flow ratio of the lower header to the upper header is 1.38, the coiling temperature is controlled according to the U shape, and the coiling temperatures of the head part, the middle part and the tail part are respectively 688 ℃, 622 ℃ and 691 ℃. The steel plate after laminar cooling is coiled by a coiling machine and then is transferred to a warehouse, and hot steel coils are placed around the steel coils, wherein the temperature of the steel coils is 566 ℃, the temperature of the steel coils is 238 ℃ after 30 hours, and the average temperature drop rate is 10.9 ℃/h.
The steel described in example 1 had a thickness of 1.5mm, a tensile strength of 663MPa, an elongation of 31%, a yield ratio of 0.86, inclusion grades A and B, C, D of 0, 0.5, 0, and a liquid-out TiN grade of 0 as class D inclusion. The microstructure is ferrite plus trace pearlite, and the grain size is 11 grade. FIG. 1, FIG. 3 and FIG. 9 are the plate shape monitoring, actual coil, and microstructure morphology of the steel of example 1. As can be seen from FIG. 1, the steel sheet of example 1 is good in shape (the darker the color from green to red, the worse the shape of the plate is), and as can be seen from FIG. 3, the steel of example 1 is good in coil shape, and no tower type defect caused by poor plate shape is seen.
Example 2
Adopting a converter-LF electric heating-RH vacuum refining-continuous casting process flow to prepare a billet with the thickness of 230mm and the mass percentage as follows: 0.07% C,0.12% Si,1.36% Mn,0.008% P,0.002% S,0.025% Als,0.090% Ti,0.031% Zr,0.0022% N, the balance being Fe and unavoidable impurities. The steel billet is prepared into a steel plate with the thickness of 1.8mm through the technological processes of heating, rough rolling, hot rolling box, finish rolling, laminar cooling and slow cooling. The specific process is as follows: the billet is fed into a plate blank heating furnace by adopting hot feeding, and the tapping temperature is 1270 ℃. The rough rolling inlet temperature is 1192 ℃, the rough rolling outlet temperature is 1156 ℃, the rough rolling outlet speed is 4.3m/s, the thickness of a rough rolling intermediate billet is 36mm, the convexity of the intermediate billet is 96 mu m, and the wedge-shaped intermediate billet is 85 mu m. The middle part is transported by a roller way after rough rolling, is sequentially subjected to heat preservation by a heat preservation cover, and is sent to a finishing mill group after being coiled by a hot coil box. The temperature of a finish rolling inlet is 1107 ℃, the temperature of a finish rolling outlet is 896 ℃, the speed of the finish rolling outlet is 11.6m/s, cooling water between frames is not started, lubrication rolling is started for 5 groups, the working mileage of a finish rolling working roll is 12.7Km, the maximum temperature difference in the width direction of the working roll is 18 ℃, the temperature difference between an upper working roll and a lower working roll is 10 ℃, and the convexity of a steel plate is 23 mu m and the wedge-shaped diameter is 18 mu m after finish rolling. The finish rolled steel plate is subjected to laminar cooling at a laminar cooling rate of 30 ℃/s, a laminar cooling model is formed by opening 2 groups of pipes 1, the water flow ratio of a lower header to an upper header is 1.27, the coiling temperature is controlled according to a U shape, and the coiling temperatures of the head part, the middle part and the tail part are 679 ℃, 608 ℃ and 693 ℃ respectively. And (3) coiling the steel plate subjected to laminar cooling, then feeding the coiled steel plate into a slow cooling pit for slow cooling for 48 hours, wherein the temperature of steel coils before and after slow cooling is 564 ℃, 221 ℃, and the average temperature drop rate is 7.1 ℃/h.
The steel described in example 2 had a thickness of 1.8mm, a tensile strength of 841MPa, an elongation of 25%, a yield ratio of 0.87, inclusion grades of 0, and 0.5 for A and B, C, D, and a grade of 0.5 for liquid-out TiN for class D inclusions. The microstructure is ferrite plus trace cementite, and the grain size is 13 grade. Fig. 5, fig. 7 and fig. 10 are respectively the actual plate shape, the morphology of the inclusions and the morphology of the microstructure of the steel of example 2. As shown in FIG. 5, the steel plate of example 2 has good shape, no plate shape defects such as side waves and middle waves, and the like, and as shown in FIG. 7, the steel of example 2 has no TiN precipitation.
Example 3
Adopting a converter-LF electric heating-RH vacuum refining-continuous casting process flow to prepare a steel billet with the thickness of 200mm and the mass percentage as follows: 0.07% C,0.08% Si,0.65% Mn,0.011% P,0.006% S,0.028% Als,0.035% Ti,0.020% Zr,0.0038% N, and the balance of Fe and unavoidable impurities. The steel billet is prepared into a steel plate with the thickness of 1.2mm through the technological processes of heating, rough rolling, hot rolling box, finish rolling, laminar cooling and slow cooling. The specific process is as follows: the billet is hot-fed into a slab heating furnace, and the tapping temperature is 1253 ℃. The rough rolling inlet temperature 1181 ℃, the rough rolling outlet temperature 1140 ℃, the rough rolling outlet speed 2.8m/s, the thickness of the intermediate billet obtained after rough rolling is 32mm, the convexity of the intermediate billet is 103 mu m, and the wedge shape is 97 mu m. The middle part is transported by a roller way after rough rolling, is sequentially subjected to heat preservation by a heat preservation cover, and is sent to a finishing mill group after being coiled by a hot coil box. The temperature of a finish rolling inlet is 1104 ℃, the temperature of a finish rolling outlet is 889 ℃, the speed of the finish rolling outlet is 11.8m/s, cooling water between racks is not started, lubrication rolling is started for 5 groups, the working mileage of a finish rolling working roll is 11.8Km, the maximum temperature difference in the width direction of the working roll is 22 ℃, the temperature difference between an upper working roll and a lower working roll is 8 ℃, and the convexity of a steel plate is 38 mu m and the wedge-shaped thickness is 22 mu m after finish rolling. The finish rolled steel plate is subjected to laminar cooling at a laminar cooling rate of 23 ℃/s, a laminar cooling model is formed by opening 2 groups of pipes 1, the water flow ratio of a lower header to an upper header is 1.33, the coiling temperature is controlled according to a U shape, and the coiling temperatures of the head part, the middle part and the tail part are 677 ℃, 636 ℃ and 683 ℃ respectively. The steel plate after laminar cooling is coiled by a coiling machine and then is sent into a slow cooling pit for slow cooling for 48 hours, the temperature of the steel plate entering and exiting the slow cooling pit is 573 ℃, 225 ℃, and the average temperature drop rate is 7.25 ℃/h.
The steel described in example 3 had a thickness of 1.2mm, a tensile strength of 577MPa, an elongation of 35%, a yield ratio of 0.85, inclusion grades A and B, C, D of 0.5, 0 and 0, and a liquid-out TiN grade of 0.5 as class D inclusion grade. The microstructure is ferrite plus trace pearlite, and the grain size is grade 10.5 (see figure 11).
Example 4
Adopting a converter-LF electric heating-RH vacuum refining-continuous casting process flow to prepare a billet with the thickness of 230mm and the mass percentage as follows: 0.04% C,0.05% Si,1.02% Mn,0.011% P,0.003% S,0.035% Als,0.081% Ti,0.025% Zr,0.0024% N, and the balance Fe and unavoidable impurities. The steel billet is prepared into a steel plate with the thickness of 1.6mm through the technological processes of heating, rough rolling, hot rolling box, finish rolling, laminar cooling and slow cooling. The specific process is as follows: the billet is fed into a slab heating furnace by adopting hot feeding, and the tapping temperature is 1263 ℃. The rough rolling inlet temperature is 1189 ℃, the rough rolling outlet temperature is 1145 ℃, the rough rolling outlet speed is 4.0m/s, the thickness of a middle blank obtained after rough rolling is 35mm, the convexity of the middle blank is 116 mu m, and the wedge shape is 109 mu m. The middle part is transported by a roller way after rough rolling, is sequentially subjected to heat preservation by a heat preservation cover, and is sent to a finishing mill group after being coiled by a hot coil box. The temperature of the finish rolling inlet is 1110 ℃, the temperature of the finish rolling outlet is 890 ℃, the speed of the finish rolling outlet is 11.5m/s, cooling water between frames is not started, 4 groups of lubrication rolling are started, the working mileage of a finish rolling working roll is 15.6Km, the maximum temperature difference in the width direction of the working roll is 20 ℃, the temperature difference between the upper working roll and the lower working roll is 11 ℃, and the convexity of a steel plate is 26 mu m and the wedge shape is 20 mu m after finish rolling. The finish rolled steel plate is subjected to laminar cooling, the laminar cooling rate is 32 ℃/s, the laminar cooling model is formed by opening 2 groups of pipes 1 group, the water flow ratio of the lower header to the upper header is 1.28, the coiling temperature is controlled according to the U shape, and the coiling temperatures of the head part, the middle part and the tail part are respectively 690 ℃, 616 ℃ and 698 ℃. And (3) coiling the steel plate subjected to laminar cooling, then feeding the coiled steel plate into a slow cooling pit for slow cooling for 48 hours, wherein the temperature of the steel coil before and after slow cooling is 570 ℃, 230 ℃, and the average temperature drop rate is 7.1 ℃/h.
The steel described in example 4 had a thickness of 1.6mm, a tensile strength of 787MPa, an elongation of 26%, a yield ratio of 0.87, inclusion grades A and B, C, D of 0, 0.5, and a liquid-out TiN grade of 0.5 as class D inclusion. The microstructure is ferrite plus trace cementite, and the grain size is grade 12.5 (see figure 12).
Comparative example 1
Adopting a converter-LF electric heating-RH vacuum refining-continuous casting process flow to prepare a steel billet with the thickness of 200mm and the mass percentage as follows: 0.08% C,0.13% Si,1.05% Mn,0.013% P,0.006% S,0.030% Als,0.019% Ti,0.038% Nb,0.0040% N, the balance being Fe and unavoidable impurities. The steel billet is prepared into a steel plate with the thickness of 1.5mm through the technological processes of heating, rough rolling, hot rolling box, finish rolling, laminar cooling and slow cooling. The specific process is as follows: the billet is hot-fed into a slab heating furnace, and the tapping temperature is 1229 ℃. The rough rolling inlet temperature is 1163 ℃, the rough rolling outlet temperature is 1124 ℃, the rough rolling outlet speed is 3.4m/s, the thickness of a rough rolling intermediate billet is 34mm, the convexity of the intermediate billet is 105 mu m, and the wedge shape is 94 mu m. The middle part is transported by a roller way after rough rolling, is sequentially subjected to heat preservation by a heat preservation cover, and is sent to a finishing mill group after being coiled by a hot coil box. The finish rolling inlet temperature is 1063 ℃, the finish rolling outlet temperature is 861 ℃, the finish rolling outlet speed is 10.9m/s, 1 group of cooling water among the frames is started, 3 groups of lubrication rolling are started, the working mileage of the finish rolling working rolls is 17.5Km, the maximum temperature difference in the width direction of the working rolls is 41 ℃, the temperature difference between the upper working rolls and the lower working rolls is 22 ℃, and the convexity of the steel plate is 56 mu m and the wedge shape is 44 mu m after finish rolling. The finish rolled steel plate is subjected to laminar cooling at a laminar cooling rate of 22 ℃/s, a laminar cooling model is formed by opening 2 groups of pipes 1 group, the water flow ratio of a lower header to an upper header is 1.34, the coiling temperature is controlled according to a U shape, and the coiling temperatures of the head part, the middle part and the tail part are respectively 681 ℃, 693 ℃ and 630 ℃. The steel plate after laminar cooling is coiled by a coiling machine and then is transferred to a warehouse, and hot steel coils are placed around the steel coils, wherein the temperature of the steel coils is 577 ℃, the temperature of the steel coils is 241 ℃ after 30 hours, and the average temperature drop rate is 11.2 ℃/h.
The steel of comparative example 1 had a thickness of 1.5mm, a tensile strength of 655MPa, an elongation of 29%, a yield ratio of 0.86, inclusion grades A, B, C, D of 0, 0.5, and a liquid-out TiN grade of 0 as class D inclusion grade. The microstructure is ferrite plus trace pearlite, and the grain size is 11 grade. FIG. 2, FIG. 4 and FIG. 13 are respectively a plate shape monitoring graph, an actual coil shape and a microstructure morphology of the steel of comparative example 1. As can be seen from fig. 2, the head of the steel coil has serious wave-shaped defects (red areas in the figure have poor plate shapes), the rolling state is unstable, and as can be seen from fig. 4, the steel coil has serious tower-shaped defects due to the poor plate shapes. Analysis of the production process of the steel of comparative example 1 revealed that the poor plate shape due to the large temperature difference between the work rolls in the width direction and the large temperature difference between the upper and lower rolls resulted in the large convexity and wedge of the finish rolled steel sheet.
Comparative example 2
Adopting a converter-LF electric heating-RH vacuum refining-continuous casting process flow to prepare a billet with the thickness of 230mm and the mass percentage as follows: 0.04% C,0.10% Si,1.31% Mn,0.006% P,0.003% S,0.029% Als,0.089% Ti,0.045% Nb,0.0044% N, and the balance Fe and unavoidable impurities. The steel billet is prepared into a steel plate with the thickness of 1.8mm through the technological processes of heating, rough rolling, hot rolling box, finish rolling, laminar cooling and slow cooling. The specific process is as follows: the billet is fed into a slab heating furnace by adopting hot feeding, and the tapping temperature is 1235 ℃. The rough rolling inlet temperature is 1157 ℃, the rough rolling outlet temperature is 1104 ℃, the rough rolling outlet speed is 4.2m/s, the thickness of a middle blank obtained after rough rolling is 36mm, the convexity of the middle blank is 113 mu m, and the wedge shape is 101 mu m. The middle part is transported by a roller way after rough rolling, is sequentially subjected to heat preservation by a heat preservation cover, and is sent to a finishing mill group after being coiled by a hot coil box. The temperature of a finish rolling inlet is 1038 ℃, the temperature of a finish rolling outlet is 856 ℃, the speed of the finish rolling outlet is 11.4m/s, cooling water between frames is not started, lubrication rolling is started for 5 groups, the working mileage of a finish rolling working roll is 13.4Km, the maximum temperature difference in the width direction of the working roll is 34 ℃, the temperature difference between an upper working roll and a lower working roll is 16 ℃, and the convexity of a steel plate is 43 mu m and a wedge-shaped 38 mu m after finish rolling is obtained. The finish rolled steel plate is subjected to laminar cooling, the laminar cooling rate is 31 ℃/s, the laminar cooling model is formed by opening 2 groups of pipes 1 group, the water flow ratio of the lower header to the upper header is 1.31, the coiling temperature is controlled according to the U shape, and the coiling temperatures of the head part, the middle part and the tail part are 670 ℃, 681 ℃ and 618 ℃ respectively. And (3) coiling the steel plate subjected to laminar cooling, then feeding the coiled steel plate into a slow cooling pit for slow cooling for 48 hours, wherein the temperature of the steel coil before and after slow cooling is 570 ℃, 225 ℃, and the average temperature drop rate is 7.2 ℃/h.
The steel of comparative example 4 had a thickness of 1.8mm, a tensile strength of 887MPa, an elongation of 24%, a yield ratio of 0.89, inclusion grades A, B, C, D of 0, and a liquid-out TiN rating of 1.0 as class D inclusion. The microstructure is ferrite plus trace cementite, and the grain size is 12.5 grade. FIGS. 6, 8 and 14 show the actual plate shape, inclusion morphology and microstructure morphology of the comparative example 2 steel, respectively. As can be seen from FIG. 6, the steel of comparative example 2 had serious wave-shaped defects, and as can be seen from FIG. 8, the steel of comparative example 2 had a large amount of liquid-out TiN, which was rated as 1.0. Analysis of the composition process of the steel of comparative example 2 shows that the poor plate shape is mainly caused by lower tapping temperature and lower rolling temperature and larger temperature difference of working rolls, so that the convexity and wedge control of the finishing mill group on the steel plate is poor, and the wave defect of the steel plate is caused. The reason why the number of the liquid-out TiN inclusions is large is that the content of Ti and N is high, and the solubility product of Ti and N is large. As is clear from comparison with the steel of example 2, the steel of example 2 also has a high Ti content, but the Zr element added in example 2 is more reactive than Ti in chemical nature, and can react with S, N in molten steel to reduce the effect of combining Ti and N into liquated TiN, so that the level of liquated TiN inclusion in the steel of example 2 is lower.
Claims (10)
- The hot rolled high-strength steel with the extremely thin specification below 1.2.0mm is characterized by comprising the following chemical components in percentage by weight: 0.04 to 0.10 percent of C,0.05 to 0.20 percent of Si, 0.40 to 1.40 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.008 percent of S, 0.010 to 0.050 percent of Als, 0.040 to 0.130 percent of Ti+Zr0.005 percent of N, and the balance of Fe and unavoidable impurity elements.
- 2. The ultra-thin gauge hot rolled high strength steel of 2.0mm or less as claimed in claim 1, wherein: the microstructure is ferrite with volume fraction more than or equal to 95% and pearlite or cementite with volume fraction less than or equal to 5%; the tensile strength is 500-900 MPa, the elongation is more than or equal to 20%, the yield ratio is less than or equal to 0.88, the inclusion grade is less than or equal to 0.5, and the grade of the liquid-separated TiN is less than or equal to 0.5 according to the class-D inclusion grade.
- 3. The ultra-thin gauge hot rolled high strength steel of 2.0mm or less as claimed in claim 1 or 2, wherein: when the tensile strength is 500MPa, the Mn in the chemical components is 0.40-0.80%, and the Ti+Zr is 0.040-0.060%.
- 4. The ultra-thin gauge hot rolled high strength steel of 2.0mm or less as claimed in claim 1 or 2, wherein: when the tensile strength is 600MPa, the Mn in the chemical components is 0.50-1.00%, and the Ti+Zr is 0.050-0.070%.
- 5. The ultra-thin gauge hot rolled high strength steel of 2.0mm or less as claimed in claim 1 or 2, wherein: when the tensile strength is 700MPa, the Mn in the chemical components is 0.90-1.10%, and the Ti+Zr is 0.080-0.110%.
- 6. The ultra-thin gauge hot rolled high strength steel of 2.0mm or less as claimed in claim 1 or 2, wherein: when the tensile strength is 800MPa, the Mn in the chemical components is 1.20-1.40%, and the Ti+Zr is 0.090-0.130%.
- 7. The method for producing an extremely thin gauge hot rolled high strength steel of 2.0mm or less according to any one of claims 1 to 6, characterized by: the steel casting blank is obtained through converter smelting, LF refining, RH refining and continuous casting, and then a finished steel plate is obtained through plate blank heating, rough rolling, finish rolling, laminar cooling, coiling and cooling; wherein the thickness of the steel casting blank is 200-250 mm, the steel casting blank is hot-fed and hot-packed into a slab heating furnace for heating, and the discharging temperature of the slab is 1220-1280 ℃.
- 8. The method for producing an extremely thin gauge hot rolled high strength steel of 2.0mm or less according to claim 7, wherein: the rough rolling inlet temperature of the slab is 1160-1200 ℃, the rough rolling outlet temperature is 1120-1160 ℃, and the rough rolling outlet speed is 2-5 m/s; rough rolling to obtain an intermediate blank with the thickness of 30-40 mm, wherein the convexity of the intermediate blank is 80-120 mu m, and the wedge shape is 80-120 mu m; the intermediate billet is transported on a roller way after rough rolling, and is sent to a finishing mill group after passing through a heat preservation cover and a hot rolling box.
- 9. The method for producing an extremely thin gauge hot rolled high strength steel of 2.0mm or less according to claim 8, wherein: the finish rolling inlet temperature of the intermediate billet is 1060-1120 ℃, the finish rolling outlet temperature is 860-900 ℃, the finish rolling outlet speed is 8-12 m/s, the number of cooling water opening groups among the frames is not more than 1 group, and the number of lubrication rolling opening groups is not less than 3 groups; the working mileage of the working rolls is 10 Km-20 Km during finish rolling, the temperature difference of the working rolls in the width direction is not more than 30 ℃, and the temperature difference of the upper working rolls and the lower working rolls is not more than 15 ℃; the intermediate blank is finish rolled to obtain a steel plate with the thickness of 1.2-2.0 mm, the convexity of the steel plate is 20-40 mu m, and the wedge shape is not higher than 25 mu m.
- 10. The method for producing an extremely thin gauge hot rolled high strength steel of 2.0mm or less according to claim 9, characterized by: the laminar cooling rate of the steel plate is 20-50 ℃/s, the flow ratio of the lower header to the upper header is 1.2-1.4 when the lower header is cooled, the laminar cooling model adopts sparse cooling, namely 2 groups of headers are opened and 1 group of headers are closed, the coiling temperature is controlled according to U-shaped coiling, namely the coiling temperature of the head and the tail of a steel coil is controlled according to 650-700 ℃, and the coiling temperature of the middle part of the steel coil is controlled according to 600-650 ℃; and (3) after the steel plate is coiled, placing the steel plate into a slow cooling pit, or placing hot steel coils around the steel coils, controlling the steel coils to be cooled to 200-300 ℃ at a cooling rate of not higher than 20 ℃/h, and then performing air cooling to room temperature.
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| CN202311833767.8A CN117778891A (en) | 2023-12-28 | 2023-12-28 | Hot rolled high-strength steel with extremely thin specification below 2.0mm and preparation method thereof |
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| CN202311833767.8A CN117778891A (en) | 2023-12-28 | 2023-12-28 | Hot rolled high-strength steel with extremely thin specification below 2.0mm and preparation method thereof |
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