CN114985461A - Preparation method for large-size bar material by controlled rolling and controlled cooling - Google Patents
Preparation method for large-size bar material by controlled rolling and controlled cooling Download PDFInfo
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- CN114985461A CN114985461A CN202210585022.3A CN202210585022A CN114985461A CN 114985461 A CN114985461 A CN 114985461A CN 202210585022 A CN202210585022 A CN 202210585022A CN 114985461 A CN114985461 A CN 114985461A
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- 238000005096 rolling process Methods 0.000 title claims abstract description 179
- 238000001816 cooling Methods 0.000 title claims abstract description 84
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 239000000463 material Substances 0.000 title claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 51
- 238000000034 method Methods 0.000 claims abstract description 37
- 238000010438 heat treatment Methods 0.000 claims abstract description 32
- 238000009749 continuous casting Methods 0.000 claims abstract description 31
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 30
- 239000010959 steel Substances 0.000 claims abstract description 30
- 238000005520 cutting process Methods 0.000 claims abstract description 29
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims abstract description 8
- 230000007547 defect Effects 0.000 claims abstract description 6
- 238000004513 sizing Methods 0.000 claims abstract description 6
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- 230000000149 penetrating effect Effects 0.000 claims description 5
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- 238000007599 discharging Methods 0.000 claims description 2
- 238000004806 packaging method and process Methods 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 5
- 238000007670 refining Methods 0.000 abstract description 3
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- 230000009466 transformation Effects 0.000 description 21
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- 238000011084 recovery Methods 0.000 description 5
- RMLPZKRPSQVRAB-UHFFFAOYSA-N tris(3-methylphenyl) phosphate Chemical compound CC1=CC=CC(OP(=O)(OC=2C=C(C)C=CC=2)OC=2C=C(C)C=CC=2)=C1 RMLPZKRPSQVRAB-UHFFFAOYSA-N 0.000 description 5
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/02—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
- B21B1/026—Rolling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/02—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
- B21B1/04—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing in a continuous process
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
- B21B1/18—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section in a continuous process
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B15/0007—Cutting or shearing the product
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B43/00—Cooling beds, whether stationary or moving; Means specially associated with cooling beds, e.g. for braking work or for transferring it to or from the bed
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/004—Heating the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
- B21B45/0209—Cooling devices, e.g. using gaseous coolants
- B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
- B21B45/0224—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for wire, rods, rounds, bars
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/04—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing
- B21B45/08—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing hydraulically
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/02—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
- B21B2001/022—Blooms or billets
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
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Abstract
The invention relates to a preparation method for rolling and cooling control of a large-size bar, belonging to the technical field of rolling of special steel bars. The method comprises the following steps: putting the continuous casting billet into a walking beam type heating furnace with a plurality of temperature control areas for heating; removing the iron oxide scales on the continuous casting billet by the high-pressure water striking force of a descaling box after the high-temperature continuous casting billet is discharged; the high-temperature continuous casting billet is subjected to primary temperature waiting before entering a roughing mill; carrying out high-temperature high-reduction rolling on the continuous casting billet subjected to primary temperature waiting; removing the head defect of the intermediate blank; the intermediate billet after the end cutting is subjected to secondary temperature waiting before entering a continuous rolling unit; rolling the rectangular intermediate billet into an intermediate round bar by a continuous rolling unit; cutting off the head and the tail of the middle round rod, and dividing the middle round rod into a plurality of sections according to multiple scales; carrying out three times of temperature waiting on the segmented bar; and (4) rolling the steel bar into a bar with the diameter of 60-150 mm in a reducing and sizing mill set. The invention has obvious structure and grain refining effect, and can solve the technical problems of uneven structure and performance and the like after rolling and cooling control of large-size bars.
Description
Technical Field
The invention relates to a preparation method for rolling and cooling control of a large-size bar, belonging to the technical field of rolling of special steel bars.
Background
The special steel material can be widely used in large quantity, and becomes an indispensable important basic material in national economy, and has special chemical components and special performance and meets special use requirements. In order to achieve these characteristics, it is necessary to reinforce steel materials by adding alloying elements to steel or heat treatment to achieve different strength and toughness property matching, but the mere addition of a large amount of alloying elements to steel has limited reinforcing effect and is not economical, and it is difficult to meet the requirements of a large number of applications of special steel. The method of heat treatment (normalizing or the like) also has a remarkable effect of finely dividing and strengthening the microstructure of the material, but requires a large amount of energy and causes environmental problems such as emission of pollutants. How to efficiently and economically improve the properties of the steel material, such as strength and toughness, becomes a problem to be considered in the development of special steel products.
Since TMCP technology was formally developed in the 80 th of the 20 th century, the technology became an indispensable technology in the field of medium plate rolling through decades of development and was widely applied. In brief, the rolling technology method of comprehensively applying controlled rolling and controlled cooling is called as TMCP technology, does not depend on alloy elements, controls the cooling of steel by controlling the rolling temperature and cheaper cooling water on line, is a process for saving alloy and energy, and has great application value and environmental protection significance. Controlled rolling and controlled cooling are developed as manufacturing technologies of medium plates, are popularized and applied as generalized TMCP technologies in the production of hot rolled strip steel, section steel and bar materials, and are indispensable technologies for producing high-grade special steel. The technology is characterized in that after controlled rolling, rapid cooling is carried out to a certain degree in a temperature region of austenite to ferrite phase transformation, so that a phase transformation structure is finer than that of simple controlled rolling, and higher strength is obtained at the same time. The generalized TMCP rolling technology is gradually applied to bar rolling, and particularly in the field of special steel rolling, the common rolling and cooling control technology in the special steel bar rolling is applied as follows: the separation of the steel-meshed carbide of the bearing is inhibited by the water-through process after rolling, the superfine grain gear steel is produced by controlling rolling and cooling, and the mechanical properties of the non-quenched and tempered steel are improved by the low-temperature rolling technology. Compared with the traditional TMCP application fields such as medium and thick plates, the research and the application of the controlled rolling and the controlled cooling of the bar wire, particularly the medium and large-sized bar are not mature.
The patent No. CN107185968A discloses a rolling and cooling control method for a special steel bar, which is a typical rolling and cooling control arrangement mode on a continuous rolling line, the arrangement of each frame is compact, the rolling speed is high, the deformation time is short, and the existing rolling control technology cannot realize the deformation with large reduction due to the limitation of the capability of a continuous rolling mill, so that the deformation cannot be uniformly permeated into a central rolled piece, and the surface and the center of the large-size bar are easily deformed unevenly. Because the static recovery and static recrystallization time of austenite can not be controlled in the continuous rolling rough rolling, the austenite recrystallization and non-recrystallization processes can not be accurately controlled due to the higher rolling speed and deformation speed, and the control of the combination of deformation and phase transformation processes is not sufficient. The method for controlling cooling adopts a 2-section water tank for cooling before the intermediate rolling and the finish rolling, adopts 3-section water tanks for water cooling before the finish rolling machine and a Reducing Sizing Mill (RSM), and adopts 5-section water tanks for water cooling after the RSM. On a rolling line before RSM, the outlet speed and the water passing speed of the bar are high, the surface of the large-size bar is completely cooled to be lower than a phase change point, and the core of the large-size bar is still kept near or above the phase change point in the prior art, so that the defect that strong water cooling easily causes large temperature difference on the core surface, and finally causes the difference of the section performance of the finished bar. The invention provides a remedial method for improving the nonuniformity of the section temperature caused by strong water penetration cooling before rolling by prolonging the recovery time after rolling for medium and small-sized bars with the specification of phi 12-70 mm, but an effective solution is not provided for the rolling and cooling control mode of large-sized bars (particularly more than or equal to phi 80 mm).
Disclosure of Invention
The technical problem to be solved by the invention is to provide a rolling and cooling control preparation method for large-size bars aiming at the prior art, break through the technical difficulty of rolling and cooling control of the large-size bars at present, solve the problem that the deformation of the core of the large bars is difficult to permeate through the rolling process of rough rolling and large reduction, control the deformation and temperature of the large-size bars (especially phi is more than or equal to 80mm) in the processes of recrystallization and non-recrystallization of austenite through multiple temperature control and slow cooling control before finish rolling, and simultaneously adopt the deformation induced phase transition technology to promote the gamma → alpha phase transition to occur in advance to refine the tissues and the crystal grains, thereby solving the problems of the uniformity of the tissues and the performances of different positions of the section of the large-size bars.
The technical scheme adopted by the invention for solving the problems is as follows: a preparation method for controlling rolling and cooling of a large-size bar comprises the following steps:
the method comprises the following steps: heating a continuous casting blank: putting the continuous casting billet into a walking beam type heating furnace with a plurality of temperature control areas for heating;
step two: descaling: removing the iron oxide scales on the high-temperature continuous casting billet by the high-pressure water striking force of a descaling box after the high-temperature continuous casting billet is discharged;
step three: primary temperature waiting: the high-temperature continuous casting billet is subjected to primary temperature waiting before entering a roughing mill;
step four: rough rolling: carrying out high-temperature high-reduction rolling on the continuous casting billet subjected to primary temperature waiting;
step five: cutting heads: removing the head defect of the intermediate blank;
step six: secondary temperature waiting: the intermediate billet after end cutting is subjected to secondary temperature waiting before entering a continuous rolling unit;
step seven: and (3) continuous rolling: the continuous rolling unit rolls the rectangular intermediate billet into an intermediate round bar;
step eight: cutting head and tail, and segmenting by multiple lengths: cutting off the head and the tail of the middle round rod, and dividing the middle round rod into a plurality of sections according to multiple scales;
step nine: and (3) waiting for temperature for three times: carrying out three times of temperature waiting on the sectional bar through blowing or air convection;
step ten: finish rolling: after the temperature is kept for the third time, the steel plate enters a reducing sizing mill set to be rolled into a bar with the diameter of 60-150 mm;
step eleven: cooling through water: the rod after finish rolling enters a multi-section water penetrating water tank for water cooling;
step twelve: cutting to length: cutting the cooled bar into the required fixed length or single length;
step thirteen: cooling by a cooling bed: the bar material enters a cooling bed to be slowly cooled;
fourteen steps: and (3) component collection: and packaging, collecting, discharging and stacking the rods.
Eight temperature control areas are arranged in the walking beam type heating furnace in the first step: the temperature of the eight region is less than or equal to 800 ℃, the temperature of the seven region is 700-900 ℃, the temperature of the six region is 900-1000 ℃, the temperature of the five region is 1000-1100 ℃, the temperature of the four region is 1050-1260 ℃, the temperature of the three region is 1100-1260 ℃, the temperature of the two region is 1100-1280 ℃, the temperature of the one region is 1150-1280 ℃, and the total heating time is 3.5-8 h.
And the working pressure of the descaler in the second step is more than or equal to 20 MPa.
The temperature for one time in the third step is 950-1100 ℃; in the sixth step, the secondary temperature is 830-950 ℃; in the ninth step, the temperature of the third time is 10-50 ℃ above Ar 3.
The primary temperature is 980-1030 ℃; the secondary temperature is 830-880 ℃.
The rolling reduction of the rough rolling in the fourth step is more than or equal to 60mm, the rolling ratio of the rough rolling is 3-7, and the number of rolling completion passes is 5-13.
And the rolling intermittent time is controlled by controlling the stay time of the rolled piece on the roller way of the cogging mill, and the stay time is 1-5 s.
And eighthly, cutting the end of the intermediate blank by adopting a hydraulic end cutting device, wherein the length of the cut end is more than or equal to 50 mm.
In the step ten, the deformation of each pass is controlled to be more than or equal to 20 percent, and the accumulated deformation is controlled to be more than or equal to 60 percent.
The water pressure of all sections of water tanks in the step eleven is 0.5-1.0 MPa, and the final cooling temperature surface red-returning temperature of the bar is not less than 600 ℃.
Compared with the prior art, the invention has the advantages that: a preparation method of large-size bars by controlled rolling and controlled cooling,
1. the conventional heating furnace only controls four sections, namely a preheating section, a heating section, a second heating section and a soaking section, the temperature control area of the process adopted by the invention is finer, the heating temperature and the heating time of the steel type in a certain area can be accurately controlled according to the thermoplastic difference of the steel, the alloy elements or micro-alloy elements in the steel can be fully dissolved during heating, the austenite of the steel billet is more uniform, and the retention time of the steel billet at high temperature can be accurately controlled to avoid the coarsening of austenite grains at high temperature, so the heating uniformity of the steel billet is better than that of the traditional process method.
2. Continuous rolling cannot realize deformation of large rolling reduction, and for large-size bars, rolling deformation is often only stopped on the surface and cannot permeate to the center of the bar due to limited deformation, so that the uniformity of the structure and the performance of the controlled rolling bar is difficult to ensure. The rough rolling adopts a semi-continuous rolling process with a large rolling reduction function, and has the technical advantages that the center of the deformed and permeated continuous casting billet can be better treated by larger rolling reduction, the welding of the defect structure of the center of the continuous casting billet is promoted, the coarse columnar crystals are crushed, and the good macrostructure and more uniform section performance of a finished product can be obtained. The invention utilizes the reciprocating rolling intermittent time control to fully carry out static recovery and static recrystallization on austenite, and has the beneficial effects that the rolling process of rough rolling austenite in a crystallization area can be accurately controlled, and more refined equiaxed austenite grains can be obtained.
3. The invention adopts secondary temperature waiting to control the rolling temperature and deformation of an austenite non-recrystallization area before continuous rolling, and adopts lower rolling temperature and continuous rolling deformation accumulation in the stage to control the non-recrystallization austenite grains to be continuously elongated and flattened and increase the area of a grain boundary in unit area.
4. The invention does not penetrate water or spray water for cooling in the whole cooling process before rolling, which is greatly different from the traditional cooling control mode.
5. The invention keeps the rolling temperature at a certain temperature slightly higher than the phase change point, so that the deformation temperature can be kept near Ar3, thereby leading the initial temperature of gamma → alpha phase change to be higher than the equilibrium phase change temperature, and the phase change is induced to occur in advance through the accumulation of larger deformation amount at low temperature, namely, the phase change is induced through deformation, thereby generating ultrafine ferrite grains. Different from the traditional method of controlling the structure transformation by rapid water penetration cooling, the method introduces the influence of deformation in the phase transformation process, and has the characteristics of obvious effect, more uniform nucleation transformation and the like by phase transformation refinement through deformation induction. According to the invention, the water penetration after rolling is only used as a means for further refining the structure, the supercooling degree of pearlite transformation is increased, and the pearlite lamellar spacing is further refined to improve the strength and hardness of the bar.
Drawings
FIG. 1 is a process layout diagram of a method for manufacturing large-sized bars by controlled rolling and controlled cooling according to an embodiment of the present invention;
in the figure, 1 a stepping heating furnace, 2 a high-pressure water descaling box, 3 a roller way to be heated before rough rolling, 4 two-roller reversible cogging mills, 5 a hydraulic head cutting device, 6 a roller way to be heated before continuous rolling, 7 a first continuous rolling unit, 8a second continuous rolling unit, 9 a flying shear, 10 a rack type transverse moving cooling bed, 11 a reducing and sizing unit, 12 a water penetrating water tank, 13 a grinding wheel saw and 14 a cooling bed are arranged.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
Example one
The production method of the invention is further described by taking the example of producing the steel rod with the diameter phi of 80mm in combination with the figure 1, the continuous casting slab is medium carbon steel containing 0.4C-1.4Mn-0.1V-0.06S (%), and the preparation method comprises the following steps:
the method comprises the following steps: heating a continuous casting blank: cold loading a continuous casting billet with the specification of 300 x 340mm into a stepping heating furnace 1 for heating, wherein the stepping heating furnace is internally provided with eight temperature control areas, and the temperature of each area is controlled: the temperature of the eight zone is 655 deg.C, the temperature of the seven zone is 810 deg.C, the temperature of the six zone is 954 deg.C, the temperature of the five zone is 1047 deg.C, the temperature of the four zone is 1105 deg.C, the temperature of the three zone is 1171 deg.C, the temperature of the two zone is 1203 deg.C, the temperature of the first zone is 1205 deg.C, and the total heating time is 6 h.
Step two: and (3) dephosphorization: and removing the iron oxide scales on the surface of the high-temperature continuous casting billet by the striking force of the high-pressure water descaling box 2 after the high-temperature continuous casting billet is discharged from the furnace, wherein the descaling working pressure is 28 MPa.
Step three: primary temperature waiting: before entering the rough rolling mill, the temperature is kept for one time on the roller bed 3 to be heated before rough rolling, and the temperature is kept to be 1000 ℃.
Step four: rough rolling and cogging rolling: and (3) carrying out high-temperature large-reduction rolling on the continuous casting billet subjected to primary temperature waiting by a two-roller reversible cogging mill 4 with the rolling reduction of 1 st, 3 rd, 5 th and 7 th passes of 60mm, the rough rolling ratio of 3.3, the rolling passes of 9 passes of completion, the dwell time of the rolled piece on a roller way of 2 seconds and the final rolling temperature of 940 ℃. And the austenite is fully subjected to the processes of static recovery and static recrystallization by utilizing the control of the rolling pause time, wherein the finish rolling temperature of rough rolling is slightly higher than the non-recrystallization temperature Tnr of the austenite, so that the rolling of the austenite in a crystallization area is ensured to be finished in the rough rolling, and more refined isometric grains of the austenite are obtained.
Step five: cutting heads: the head of the intermediate billet is cut off by the hydraulic head cutting device 5, the head cutting length is 120mm, and rolling accidents caused by head biting of rolled pieces are reduced.
Step six: secondary temperature waiting: and after the rough rolling is finished, the intermediate blank is subjected to secondary temperature waiting on a temperature waiting roller table 6 before continuous rolling before being sent to a continuous rolling unit, the temperature waiting is 860 ℃, and all austenite is not performed in a crystallization area during the continuous rolling.
Step seven: and (3) continuous rolling: the continuous rolling mill group adopts two vertical alternative phi 650 rolling mills and two phi 450 rolling mills, the two phi 650 rolling mills form a first continuous rolling mill group 7, the two phi 450 rolling mills form a second continuous rolling mill group 8, and the number of the stands can be increased or decreased according to different rolling specifications. And rolling the rectangular intermediate blank into an intermediate round bar with a certain size.
Step eight: cutting head and tail, and segmenting by multiple scales: the head and tail regions of the middle round rod are cut off by a flying shear 9, and the middle round rod is divided into a plurality of sections according to multiple scales.
Step nine: and (3) waiting for temperature for three times: the sectional bar materials are sent into a rack type transverse moving cooling bed 10 to be heated for three times, the middle round bar is rapidly cooled to 810 ℃ on the rack type transverse moving cooling bed through blowing or air convection and the like, and water penetration or water spray cooling is not needed in the whole cooling process.
Step ten: finish rolling: and after the temperature reaches the third time, keeping the temperature of the middle round rod at 810 ℃, then, rolling the middle round rod in the high-precision reducing and sizing mill set 11, wherein the deformation of each pass is 20%, the accumulated deformation is 60%, and the final rolling specification is phi 80 mm. The rolling temperature is kept at a certain temperature slightly higher than the phase transformation point, so that the deformation temperature can be kept near Ar3, the initial temperature of the gamma → alpha phase transformation is higher than the equilibrium phase transformation temperature, and the phase transformation can be induced in advance through the accumulation of larger deformation amount at low temperature, namely, the phase transformation is induced through deformation, so as to generate ultrafine ferrite grains.
Step eleven: cooling through water: the rolled bar enters three sections of water penetrating water tanks 12 for water cooling, the water pressure of each section of water tank is 0.5MPa, the final cooling surface re-reddening temperature of the bar is 610 ℃, the transformation structure is further refined, the lamellar spacing of pearlite is reduced, and the strength, hardness and plasticity of the bar are improved.
Step twelve: cutting to length: the bar is cut into a fixed length of 7m by a grinding wheel saw 13 after being penetrated with water, thereby meeting the requirement of the delivery size of the bar.
Step thirteen: cooling by a cooling bed: the rod enters the cooling bed 14 to be slowly cooled, and the temperature difference and the internal stress are further reduced.
Fourteen steps: and (3) component collection: and after the cooling bed is off-line, packing, collecting and off-line stacking are carried out by adopting automatic packing equipment.
The comparison results of the phi 80mm large-size bar directly rolled by the conventional processes such as controlled rolling and controlled cooling in the example 1 and the comparative example 1 are shown in the first table (the macroscopic structure rating comparison result) and the second table (the grain structure and the performance comparison result).
Watch 1
| Item | Composition of steel grade | Rolled gauge/mm | Generally loose | Center porosity | Segregation of ingot form |
| Example 1 | 0.4C-1.4Mn-0.1V-0.06S(％) | Ф80 | 1 | 1 | 1 |
| Comparative example 1 | 0.4C-1.4Mn-0.1V-0.06S(％) | Ф80 | 1.5 | 1.5 | 1 |
Watch two
Example two
The production method of the invention is further described by taking the example of producing the steel rod with the diameter phi of 80mm in combination with the attached figure 1, wherein the continuous casting slab is a medium carbon steel grade containing 0.35C-1.3Mn-0.12V-0.05S (%), and the preparation method comprises the following steps:
the method comprises the following steps: heating a continuous casting blank: cold charging a continuous casting billet with the specification of 300 x 340mm into a stepping heating furnace 1 for heating, wherein the stepping heating furnace is internally provided with eight temperature control areas, and the temperature of each area is controlled as follows: the eight-zone temperature is 667 ℃, the seven-zone temperature is 809 ℃, the six-zone temperature is 961 ℃, the five-zone temperature is 1053 ℃, the four-zone temperature is 1102 ℃, the three-zone temperature is 1175 ℃, the two-zone temperature is 1197 ℃ and the first-zone temperature is 1210 ℃ and the total heating time range is 6 h.
Step two: and (3) dephosphorization: and after the high-temperature continuous casting billet is discharged out of the furnace, the scale on the surface of the high-temperature continuous casting billet is removed by the striking force of the high-pressure water descaling box 2, and the descaling working pressure is 27 MPa.
Step three: primary temperature waiting: before entering a rough rolling mill, carrying out primary temperature waiting on a temperature waiting roller way before rough rolling, wherein the temperature waiting is 1000 ℃.
Step four: rough rolling and cogging rolling: and (3) carrying out high-temperature high-reduction rolling on the continuously cast blank subjected to primary temperature waiting by a phi 850 two-roller reversible cogging mill, wherein the rolling reductions of 1, 3, 5 and 7 passes are 60mm, the rough rolling ratio is 3, the rolling passes are completed for 7 passes, the dwell time of a rolled piece on a roller way is 2 seconds, and the final rolling temperature is 953 ℃. And the austenite is fully subjected to the processes of static recovery and static recrystallization by utilizing the control of the rolling pause time, wherein the finish rolling temperature of rough rolling is slightly higher than the non-recrystallization temperature Tnr of the austenite, so that the rolling of the austenite in a crystallization area is ensured to be finished in the rough rolling, and more refined isometric grains of the austenite are obtained.
Step five: cutting heads: the head of the intermediate billet is cut off by the hydraulic head cutting device 5, the head cutting length is 110mm, and rolling accidents caused by head biting of rolled pieces are reduced.
Step six: secondary temperature waiting: and after the rough rolling is finished, performing secondary temperature waiting on the intermediate blank on a temperature waiting roller way before the continuous rolling before the intermediate blank is sent into a continuous rolling unit, wherein the temperature waiting is 860 ℃, and all austenite is not performed in a crystallization area during the continuous rolling.
Step seven: and (3) continuous rolling: the continuous rolling unit adopts two vertical alternative phi 650 rolling mills, and the number of the stands can be increased or decreased according to different rolling specifications. And rolling the rectangular intermediate billet into an intermediate round bar with a certain size.
Step eight: cutting head and tail, and segmenting by multiple scales: the head and tail regions of the middle round bar are cut off by a flying shear 9, and the middle round bar is divided into a plurality of sections according to multiple scales.
Step nine: and (3) waiting for temperature for three times: the sectional bar materials are sent into a rack type transverse moving cooling bed 10 to be heated for three times, the middle round bar is rapidly cooled to 810 ℃ on the rack type transverse moving cooling bed through blowing or air convection and the like, and water penetration or water spray cooling is not needed in the whole cooling process.
Step ten: finish rolling: and after the temperature reaches the third time, keeping the temperature of the middle round rod at 810 ℃, then, rolling the middle round rod in the high-precision reducing and sizing mill set 11, wherein the deformation of each pass is 20 percent, the accumulated deformation is 60 percent, and the final rolling specification is phi 1400 mm. The rolling temperature is kept at a certain temperature slightly higher than the phase transformation point, so that the deformation temperature can be kept near Ar3, the initial temperature of the gamma → alpha phase transformation is higher than the equilibrium phase transformation temperature, and the phase transformation can be induced in advance through the accumulation of larger deformation amount at low temperature, namely, the phase transformation is induced through deformation, so as to generate ultrafine ferrite grains.
Step eleven: cooling through water: the rolled bar enters three sections of water penetrating water tanks 12 for water cooling, the water pressure of each section of water tank is 0.5MPa, the final cooling surface re-reddening temperature of the bar is 630 ℃, the transformation structure is further refined, the lamellar spacing of pearlite is reduced, and the strength, hardness and plasticity of the bar are improved.
Step twelve: cutting to length: the bar is cut into a fixed length of 6m by a grinding wheel saw after being penetrated with water, thereby meeting the requirement of the delivery size of the bar.
Step thirteen: cooling by a cooling bed: the rod enters the cooling bed 14 to be slowly cooled, and the temperature difference and the internal stress are further reduced.
Fourteen steps: and (3) piece collection: and after the cooling bed is off-line, packing, collecting and off-line stacking are carried out by adopting automatic packing equipment.
In comparative example 2, the comparison results of the phi 80mm large-sized bar directly rolled by the conventional processes such as controlled rolling and controlled cooling and the like with those of example 2 are shown in table three (macrostructure rating comparison result) and table four (grain structure and performance comparison result).
Watch III
| Item | Composition of steel grade | Rolled gauge/mm | Generally loose | Center porosity | Segregation of ingot form |
| Example 2 | 0.35C-1.3Mn-0.12V-0.05S(％) | Ф140 | 1 | 1 | 1 |
| Comparative example 2 | 0.35C-1.3Mn-0.12V-0.05S(％) | Ф140 | 1.5 | 1.5 | 1 |
Watch four
As can be seen from the comparison results of the macrostructure grades of the table I and the table III, the process has an obvious effect on welding continuous casting billet macrostructure defects, and can obtain better finished macrostructure and more uniform section performance compared with the conventional process.
As can be seen from the results of comparing the grain structure and the performance in the second table and the fourth table, the mechanical properties such as yield strength, tensile strength and impact toughness of the embodiment of the invention are obviously improved, and the impact toughness of the embodiment of the invention has small fluctuation and relatively uniform and stable performance. Compared with the traditional process, the method has the advantages that the performance is obviously improved, the structure and the grain refining effect are also obvious, and the technical problems of uneven structure and performance and the like after the large-size bar is rolled and cooled are solved.
In addition to the above embodiments, the present invention also includes other embodiments, and any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of the claims of the present invention.
Claims (10)
1. A preparation method of large-size bars by controlled rolling and controlled cooling is characterized by comprising the following steps: the preparation method comprises the following steps:
the method comprises the following steps: heating a continuous casting blank: putting the continuous casting billet into a walking beam type heating furnace with a plurality of temperature control areas for heating;
step two: descaling: removing the iron oxide scales on the high-temperature continuous casting billet through high-pressure water after the high-temperature continuous casting billet is discharged from the furnace;
step three: primary temperature waiting: the high-temperature continuous casting billet is subjected to primary temperature waiting before entering a roughing mill;
step four: rough rolling: carrying out high-temperature high-reduction rolling on the continuous casting billet subjected to primary temperature waiting;
step five: cutting heads: removing the head defect of the intermediate blank;
step six: secondary temperature waiting: the intermediate billet after the end cutting is subjected to secondary temperature waiting before entering a continuous rolling unit;
step seven: and (3) continuous rolling: the continuous rolling unit rolls the rectangular intermediate billet into an intermediate round bar;
step eight: cutting head and tail, and segmenting by multiple scales: cutting off the head and the tail of the middle round rod, and dividing the middle round rod into a plurality of sections according to multiple scales;
step nine: and (3) waiting for temperature for three times: carrying out tertiary temperature waiting on the sectional bar by blowing or air convection;
step ten: finish rolling: after the temperature is kept for the third time, the steel plate enters a reducing sizing mill set to be rolled into a bar with the diameter of 60-150 mm;
step eleven: water cooling: the rod after finish rolling enters a multi-section water penetrating water tank for water cooling;
step twelve: cutting to length: cutting the cooled bar into the required fixed length or single length;
step thirteen: cooling by a cooling bed: the bar material enters a cooling bed to be slowly cooled;
fourteen steps: and (3) component collection: and packaging, collecting, discharging and stacking the rods.
2. The large-size bar rolling and cooling control preparation method of claim 1, wherein the large-size bar rolling and cooling control preparation method comprises the following steps: eight temperature control areas are arranged in the walking beam type heating furnace in the first step: the temperature of the eight region is less than or equal to 800 ℃, the temperature of the seven region is 700-900 ℃, the temperature of the six region is 900-1000 ℃, the temperature of the five region is 1000-1100 ℃, the temperature of the four region is 1050-1260 ℃, the temperature of the three region is 1100-1260 ℃, the temperature of the two region is 1100-1280 ℃, the temperature of the one region is 1150-1280 ℃, and the total heating time is 3.5-8 h.
3. The large-size bar rolling and cooling control preparation method of claim 1, wherein the large-size bar rolling and cooling control preparation method comprises the following steps: and the working pressure of high-pressure water adopted for descaling in the second step is more than or equal to 20 MPa.
4. The large-size bar rolling and cooling control preparation method of claim 1, wherein the large-size bar rolling and cooling control preparation method comprises the following steps: the temperature for one time in the third step is 950-1100 ℃; in the sixth step, the secondary temperature is 830-950 ℃; in the ninth step, the temperature of the third time is 10-50 ℃ above Ar 3.
5. The method for preparing large-size bars through controlled rolling and controlled cooling according to claim 4, characterized by comprising the following steps: the primary temperature is 980-1030 ℃; the secondary temperature-waiting temperature is 830-880 ℃.
6. The large-size bar rolling and cooling control preparation method of claim 1, wherein the large-size bar rolling and cooling control preparation method comprises the following steps: the rolling reduction of the rough rolling in the fourth step is more than or equal to 60mm, the rolling ratio of the rough rolling is 3-7, and the number of rolling completion passes is 5-13.
7. The method for preparing large-size bars through controlled rolling and controlled cooling according to claim 6, characterized by comprising the following steps: and the rolling intermittent time is controlled by controlling the stay of the rolled piece on the roller way of the cogging mill, and the stay time is 1-5 s.
8. The method for preparing large-size bars through controlled rolling and controlled cooling according to claim 1, characterized by comprising the following steps: and eighthly, cutting the end of the intermediate blank by adopting a hydraulic end cutting device, wherein the length of the cut end is more than or equal to 50 mm.
9. The large-size bar rolling and cooling control preparation method of claim 1, wherein the large-size bar rolling and cooling control preparation method comprises the following steps: in the step ten, the deformation of each pass is controlled to be more than or equal to 20 percent, and the accumulated deformation is controlled to be more than or equal to 60 percent.
10. The large-size bar rolling and cooling control preparation method of claim 1, wherein the large-size bar rolling and cooling control preparation method comprises the following steps: the water pressure of all sections of water tanks in the step eleven is 0.5-1.0 MPa, and the final cooling temperature surface red-returning temperature of the bar is not less than 600 ℃.
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| WO2007079625A1 (en) * | 2006-01-06 | 2007-07-19 | Angang Steel Company Limited | An ultrafine grain steel sheet produced by continuous casting and rolling a medium-thin slab and its manufacture process |
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| CN108994078A (en) * | 2018-06-11 | 2018-12-14 | 山东钢铁股份有限公司 | A kind of middle bar controlled rolling and controlled cooling method |
| CN111549282A (en) * | 2020-05-30 | 2020-08-18 | 靖江特殊钢有限公司 | Hot-rolled round steel and preparation method thereof |
| CN113245377A (en) * | 2021-06-23 | 2021-08-13 | 宝钢湛江钢铁有限公司 | Layout structure of sectional type thick plate intermediate cooling process and use method |
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| WO2007079625A1 (en) * | 2006-01-06 | 2007-07-19 | Angang Steel Company Limited | An ultrafine grain steel sheet produced by continuous casting and rolling a medium-thin slab and its manufacture process |
| CN102409245A (en) * | 2011-11-16 | 2012-04-11 | 济南钢铁股份有限公司 | Hot-rolled dual-phase steel sheet with high-elongation flange performance and manufacturing method thereof |
| CN108994078A (en) * | 2018-06-11 | 2018-12-14 | 山东钢铁股份有限公司 | A kind of middle bar controlled rolling and controlled cooling method |
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