CN113857249B - Manufacturing method of high-strength and high-toughness plate coil for high-precision spiral submerged-arc welding pipe - Google Patents
Manufacturing method of high-strength and high-toughness plate coil for high-precision spiral submerged-arc welding pipe Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
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- 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
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- 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
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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
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- C—CHEMISTRY; METALLURGY
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
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- 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
- B21B2015/0057—Coiling the rolled product
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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Abstract
The invention belongs to the field of low-carbon microalloy pipeline steel manufacturing, and particularly relates to a method for manufacturing a high-strength and high-toughness plate coil for a high-precision spiral submerged-arc welding pipe. The invention constructs a high-strength pipeline steel low-temperature toughness control system taking organization unit regulation as a core, develops a process technology of low-temperature accumulated large deformation and low-temperature phase change, solves the problems of refining and homogenization of a thick plate coil organization unit under a low compression ratio, and realizes the breakthrough of the low-temperature toughness control technology (DBTT 85 percent is less than or equal to minus 40 ℃). The method develops ultra-fast cooling 'water temperature-pressure coupling control + section temperature feedback control' and a plate coil camber compensation control technology, solves the problems of unstable temperature field of low temperature control cooling (500 ℃) of the plate coil and plate coil shape control deviation, realizes uniform coil passing performance (the strength fluctuation is less than or equal to 40 MPa) and the camber is less than or equal to 8mm/5m, and ensures the pipe forming precision.
Description
Technical Field
The invention belongs to the field of low-carbon microalloy pipeline steel manufacturing, and particularly relates to a method for manufacturing a high-strength and high-toughness plate coil for a high-precision spiral submerged-arc welding pipe.
Background
With the increase of the conveying amount and the conveying pressure, the steel requirements of energy pipe networks such as natural gas and the like develop towards the directions of large wall thickness, high steel grade and excellent low-temperature toughness. In addition to strict technical requirements on various mechanical properties in the welded pipe engineering requirements, strict technical requirements are provided for the forming dimensional accuracy of the steel pipe such as the shape ovality and the weld seam allowance height, if a certain engineering requirement is that the misalignment of two sides of the weld seam is less than or equal to 1.5mm, further requirements are provided for the dimensional accuracy and stress control of plate coils in the plate coil forming process of a steel plant in the previous process, and meanwhile, the high-strength, large-wall-thickness and high-steel-grade pipeline has the contradictions that the problems of poor dimensional accuracy, camber, tower shape and the like of the high-strength and high-toughness pipeline steel plate in the rolling and coiling process are prominent in the production process of the high-strength and high-wall-thickness high-steel-grade pipeline.
In order to realize the manufacturing of the high-strength and high-toughness coiled sheet for the high-precision spiral submerged arc welded pipe in a steel mill and solve the problem of difficult manufacturing of the high-strength coiled sheet for the high-precision spiral welded pipe, a material toughness improvement technology and a section temperature field homogenization control technology which take organization unit refinement control as a core are developed in the production process, and the low-temperature toughness control and the whole-plate surface process property homogenization control of the low-compression-ratio thick plate coil are realized.
Through literature search, a related patent 17 is searched. Among them, CN201310115896.3 discloses a pipeline steel with high toughness and high deformability and a manufacturing method thereof; the steel comprises the following components in percentage by mass: 0.01 to 0.06 percent of C, 0.05 to 0.55 percent of Si, 1.60 to 2.00 percent of Mn, less than or equal to 0.012 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.11 percent of Nb, less than or equal to 0.06 percent of V, less than or equal to 0.025 percent of Ti, less than or equal to 0.0080 percent of N, less than or equal to 0.50 percent of Cu, less than or equal to 0.50 percent of Cr, and the balance of Fe and inevitable impurities. CN201210152836.4 discloses a production method of pipeline steel, which adopts a process route comprising the following alloy elements in percentage by mass: c = 0.03-0.06, si = 0.20-0.35, mn = 1.60-1.70, P ≤ 0.015, S ≤ 0.005, nb = 0.04-0.06, ti = -0.008-0.02, ni = -0.15-0.25, cr = -0.20-0.35, mo = -0.10-0.15, H ≤ 0.0003, N ≤ 0.005, O ≤ 0.0015, and the balance of Fe. CN201310730844.7 introduces a method for producing high-toughness pipeline steel by adopting jet and laminar cooling linkage, according to the chemical composition of steel plate, the chemical composition of steel plate with continuous cooling transformation curve CCT curve of super-cooled austenite is: c: 0.045-0.075; si:0.1 to 0.3; mn:1.55 to 1.85; nb: 0.045-0.085; mo:0.1 to 0.2; ni:0.1 to 0.3; ti:0.01 to 0.02, and the balance of Fe and inevitable impurities.
The above patents are essentially different from the steel coil produced by the hot continuous rolling production line of the present patent in terms of the production processes of organization unit refinement control, low-temperature accumulation large deformation + low-temperature phase change, water temperature and pressure coupling control, camber compensation control and section temperature feedback control; therefore, the production of high-quality steel coils in the field is tried to be realized by another concept, the processing technology can be enriched, and products with higher performance are researched.
Disclosure of Invention
Technical problem to be solved
The method mainly solves the technical problems of two aspects, namely the difficulty of refining the low-compression ratio structure of a thick plate, the difficulty of unstable low-temperature control cold (< 500 ℃) temperature field of the high-strength plate coil and the difficulty of shape control deviation of the plate coil. Aiming at the difficulty of producing X70 and X80 pipeline steel plate coils with the wall thickness of 17-25.4mm for high-precision spiral welded pipes by the conventional hot continuous rolling production line, the invention constructs a high-strength pipeline steel low-temperature toughness control system taking organization unit regulation as a core, develops the process technology of low-temperature accumulated large deformation and low-temperature phase change, solves the problems of refining and homogenization of thick plate coil organization units under a low compression ratio, and realizes the breakthrough of the low-temperature toughness control technology. The method develops ultra-fast cooling 'water temperature-pressure coupling control + section temperature feedback control' and a plate coil camber compensation control technology, solves the problems of unstable temperature field of low temperature control cooling (500 ℃) of the plate coil and plate coil shape control deviation, realizes the uniformity of coil passing performance (the strength fluctuation is less than or equal to 40 MPa) and the camber is less than or equal to 8mm/5m, and ensures the forming precision after pipe making.
(II) technical scheme
The invention aims to overcome the defects in the prior art and provides a method for manufacturing a high-strength and high-toughness coil for a high-precision spiral submerged arc welding pipe so as to explore a coil processing mode with better performance.
A high-strength and high-toughness plate coil manufacturing method for a high-precision spiral submerged arc welding pipe comprises the following steps:
(1) Casting the molten metal into a casting blank with the thickness of 230mm, and heating and preserving heat in a heating furnace; the heating temperature is 1160-1200 ℃;
(2) Increasing the deformation of the rough rolling pass by more than or equal to 10 percent, and reducing the pass reduction by 20-30mm, so as to realize the low-temperature accumulated deformation recrystallization of austenite grains and avoid the rapid growth of the grains; through the surface water mist cooling in the rough rolling process, the temperature gradient from the surface to the core of the plate blank is formed, the deformation of the core which is easy to coarsen the structure is improved, and the penetration of the deformation center and the homogenization of the deformation recrystallization are realized; the temperature of the rough rolling RT2 is controlled to be 980-1030 ℃, and the thickness of the intermediate blank after rough rolling is 55-65 mm;
(3) The No. 5 frame is subjected to nominal finish rolling, the deformation quantities of the No. 6 frame and the No. 7 frame are increased, the deformation accumulation effect of an unrecrystallized area is improved, and uniform ferrite nucleation is promoted; controlling the finish rolling temperature to be 790-830 ℃;
(4) Based on an ultra-fast cooling technology, in a phase transition region from fast cooling to low temperature in a critical cooling speed range, obtaining a fine tissue unit mainly comprising AF, and controlling the temperature of the whole plate thickness to be less than or equal to 500 ℃ after ultra-fast cooling;
(5) According to the condition of the ultra-fast cold water temperature, pressure control is matched, forced convection heat exchange is increased or reduced by changing the pressure, and the influence of temperature change on the heat exchange efficiency is compensated; feedback of cooling effect is carried out according to the temperature field of the section, and fine adjustment of pressure parameters is carried out; the homogenization of the surface temperature field of the steel coil is realized through water temperature and water pressure coupling control, and the fluctuation control of the coil passing strength of the steel coil is finally ensured to be 40MPa;
(6) The camber of each coil of plate coil in the rolling and coiling process is quickly identified and evaluated, the characteristic data of the camber of the rolled plate coils in a rolled batch is utilized, and the pre-intervention is carried out through micro-wedge rolling in the finish rolling process, so that the plate coil is pre-provided with the reverse camber characteristic before entering ultra-fast cooling, and the reverse camber characteristic is balanced with the camber caused in the cooling process to carry out compensation and correction, and further the shape of the plate coil is improved.
Further, in the step (1), the heating time in the furnace is 130 min-260 min.
Further, in the step (1), the heat preservation time is 60-100 min.
The main elements and the action and mechanism of the process in the invention are as follows:
the control of the low-temperature toughness of the high-strength plate coil of the pipeline steel is always a key and difficult point of attention in the industry, the conventional toughness improvement method is grain refinement, and a structure mainly comprising acicular ferrite is obtained through conventional two-stage rolling and laminar cooling; however, the method can not meet the low-temperature toughness requirement of the pipeline steel thick plate coil. High grade pipeline steel generally consists mainly of Acicular Ferrite (AF) + quasi-polygonal ferrite (QF) + Granular Bainite (GB) multiphase structure, but a large number of experiments show that microcracks near drop hammer fractures almost always selectively propagate in coarse QF or GB plates with transgranular cleavage characteristics and end at AF structure boundaries. Based on the crack propagation characteristics, the patent provides a core idea of the refinement control of organization units (AF crystal grains, QF crystal grains and GB blocks are all organization units), and the fundamental method realizes the refinement and homogenization of the organization units. Based on the thought, a process technology of low-temperature accumulation large deformation and low-temperature phase change is developed, and the specific process route is as follows: 1) The deformation of the rough rolling pass is increased progressively, so that the low-temperature accumulated deformation recrystallization of austenite grains is realized, the grains are prevented from growing up rapidly, and the problem of refining the austenite grains of the thick plate coil under the low-compression condition is solved; 2) The rough rolling plate blank has the advantages that a temperature gradient is formed from the surface to the center of the rough rolling plate blank, the surface deformation is greatly reduced due to larger surface resistance, and the center deformation is increased due to smaller center resistance, so that the penetration of a deformation center and the homogenization of deformation recrystallization are realized; 3) The No. 5 frame is subjected to nominal finish rolling, the deformation quantities of the No. 6 frame and the No. 7 frame are increased, the deformation accumulation effect of an unrecrystallized area is improved, and uniform ferrite nucleation is promoted; 4) Based on an ultra-fast cooling technology, in a phase transition region from fast cooling to low temperature in a critical cooling speed range, a fine organization unit mainly comprising AF is obtained, and the formation and further growth of coarse organization units such as QF and GB are reduced or avoided.
The controlled cooling is one of the cores of the production process of the pipeline steel, and the stability of the controlled cooling process is related to the stability of the performance. The traditional controlled cooling is realized by monitoring and feeding back the temperature in a mode of replacing surfaces by lines, namely: the full-length temperature measurement of the positioning points is adopted to represent the temperature of the whole board, and the feedback control cooling is carried out according to the temperature, so that the defect that the distribution condition of the temperature field of the board cannot be truly reflected is overcome. The production practice of the pipeline steel ultra-fast cooling process shows that in the process of low-temperature controlled cooling (< 500 ℃), the maximum temperature difference of the plate surface can reach more than 150 ℃ (figure 3 a), and the stability of the product performance is seriously influenced; and ultra-fast cold water temperature and water pressure have proven to be important influencing factors. Aiming at the problems, based on the idea of ultra-fast cooling technology, the patent provides a technology of water temperature-pressure coupling control and section temperature feedback control, namely: 1) According to the condition of the ultra-fast cold water temperature, pressure control is matched, forced convection heat exchange is increased or reduced by changing pressure (namely changing the flow of a collecting pipe and the impact force of water flow), and the influence of temperature change on heat exchange efficiency is compensated; 2) And feeding back the cooling effect according to the section temperature field, and finely adjusting the pressure parameter.
The defects of plate edge milling, large pipe diameter fluctuation, poor welding seam internal quality and the like easily caused by the plate coil camber are important factors influencing the pipe production yield and the production efficiency, and more than half of quality problems or waste cutting loss are related to the quality problems or the waste cutting loss. The essence of the method lies in that the deformation of two sides of the width is different, and the key point of the conventional control method lies in the wedge-shaped control of the plate coil and ensures the straightness of the plate coil after finish rolling as much as possible. In practice, however, even if the coil is finished with good straightness, after ultra-fast cooling, there is a high probability that the coil will be sickled. The essence of the problem lies in the phase change volume expansion difference and the cooling shrinkage difference at two sides in the ultra-fast cooling process of the plate coil, but the caused reasons are more complex, and possible reasons comprise that the temperature difference of the cross section of the plate blank is transmitted to the position before the cold is started and affects the cooling process, the single-side wave shape of the plate coil affects the cooling process, the flow difference at two sides of the ultra-fast cooling water, abnormal measurement and spraying and the like; but overall the camber described above is characteristic of lot-to-lot performance.
To complicated camber cause, developed camber compensation control technique, specifically include: 1) The camber detection and identification technology is characterized in that the camber of the plate roll is quickly identified and evaluated (including camber deviation direction and degree) based on-line transverse vibration curve (plate roll central line deviation curve) analysis; 2) The wedge rolling compensation control technology is characterized in that pre-intervention is carried out through micro-wedge rolling in the finish rolling process based on camber characteristic data of rolled plate coils in batches, so that the plate coils are pre-provided with reverse camber characteristics before entering ultra-fast cooling and balanced with camber caused in the cooling process, and the shape of the plate coils is further improved.
(III) advantageous effects
Compared with the prior art, the invention constructs a high-strength pipeline steel low-temperature toughness control system taking organization unit regulation as a core, develops the process technology of low-temperature accumulated large deformation and low-temperature phase change, solves the problems of refining and homogenization of the thick plate coil organization unit under low compression ratio, and realizes the breakthrough of the low-temperature toughness control technology (DBTT 85 percent is less than or equal to minus 40 ℃). The method develops ultra-fast cooling 'water temperature-pressure coupling control + section temperature feedback control' and a plate coil camber compensation control technology, solves the problems of unstable temperature field of low temperature control cooling (500 ℃) of the plate coil and plate coil shape control deviation, realizes uniform coil passing performance (the strength fluctuation is less than or equal to 40 MPa) and the camber is less than or equal to 8mm/5m, and ensures the pipe forming precision. The developed product and the process technology are applied in batches in thick-specification high-steel-grade pipeline steel, the organization units of the product are fine and uniform, the maximum size unit is reduced to about 5 mu m from more than 20 mu m, and the low-temperature toughness is greatly improved; taking 17.5mm L485M as an example for a new gas project, the ductile-brittle transition temperature (DBTT 85%) of the drop hammer is as low as-40 ℃, which is far superior to the traditional process and the industrial level (about-20 ℃).
Drawings
FIG. 1 is a process diagram of low temperature cumulative large deformation + low temperature phase change;
FIG. 2 is a temperature-pressure matching control diagram for typical specification pipeline steel;
FIG. 3 is a diagram of three types of ultra-fast cooling processes;
FIG. 4 is a graph of ductile-brittle transition temperature of drop hammer.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The parameters of the examples of the invention are as follows:
| serial number | Finish temperature of roughing (. Degree. C.) | Finish Rolling Start temperature (. Degree. C.) | Finish Rolling temperature (. Degree.C.) | Ultra-fast Cooling temperature (. Degree. C.) | Coiling temperature (. Degree. C.) |
| Example 1 | 1030 | 930 | 830 | 500 | 470 |
| Example 2 | 1020 | 920 | 820 | 470 | 460 |
| Example 3 | 1015 | 915 | 815 | 465 | 455 |
| Example 4 | 1000 | 905 | 810 | 460 | 450 |
| Example 5 | 990 | 910 | 832 | 450 | 430 |
| Example 6 | 990 | 895 | 820 | 440 | 420 |
| Example 7 | 995 | 900 | 800 | 430 | 415 |
| Example 8 | 980 | 890 | 790 | 420 | 400 |
| Comparative example 9 | 1000 | 900 | 810 | 420 | 540 |
| Comparative example 10 | 1000 | 905 | 810 | 490 | 480 |
The performance detection conditions of the embodiments of the invention are as follows:
the physical and chemical comprehensive performance data of 8 embodiments show that the comprehensive performance of 8 groups of embodiments can completely meet the technical index requirements of X70-grade pipeline steel, the toughness is better, no obvious temperature difference exists between the ultra-fast cooling and the coiling of the whole plate width, no obvious camber (less than or equal to 8mm/5 m) exists, and the tower shape of the steel coil is controlled to be less than or equal to 50mm. Comparative example 9 and comparative example 10 compared with examples 1-8, the tensile properties were 31-69MPa lower and were mainly affected by the cooling process fluctuations, where the full sheet width temperature difference reached 130 ℃ and 70 ℃ respectively. The ductile-brittle transition temperature (DBTT 85%) of the drop hammer is as low as-40 ℃, which is far superior to the traditional process and industry level (about-20 ℃) (see the right picture of the attached figure 1).
To further validate the process of the invention, the following procedure was followed and the examples added:
a21.4 mm X80-grade pipeline is rolled by a 230mm steel-making casting blank, and the specific implementation steps are as follows:
(1) And after casting into a casting blank with the thickness of 230mm, putting the casting blank into a heating furnace for heating and heat preservation. The heating temperature is 1160-1200 ℃; according to different charging temperatures, the furnace time is 130-260 min, and the holding time is 60-100 min at the high temperature of 1160-1200 ℃;
(2) The deformation of the rough rolling pass is increased gradually, the pass reduction rate is more than or equal to 10 percent, and the average pass reduction is 20-30mm, so that the low-temperature accumulated deformation recrystallization of austenite grains is realized and the grains are prevented from growing rapidly; through the surface water mist cooling in the rough rolling process, the temperature gradient from the surface to the core of the plate blank is formed, the deformation of the core which is easy to coarsen the structure is improved, and the penetration of the deformation center and the homogenization of the deformation recrystallization are realized; the temperature of the rough rolling RT2 is controlled to be 970-1020 ℃, and the thickness of the intermediate blank after rough rolling is 55-65mm.
(3) The No. 5 rack is nominal, the deformation quantity of the No. 6 and No. 7 racks is increased, the deformation accumulation effect of an unrecrystallized area is improved, and the uniform nucleation of ferrite is promoted; the finish rolling temperature is controlled to be 790-830 ℃.
(4) Based on an ultra-fast cooling technology, in a phase transition region from fast cooling to low temperature in a critical cooling speed range, a fine organization unit mainly comprising AF is obtained, and the formation and further growth of coarse organization units such as QF and GB are reduced or avoided. The temperature of the whole plate thickness after the ultra-fast cooling is controlled to be less than or equal to 430 ℃.
(5) According to the condition of the ultra-fast cold water temperature, pressure control is matched (figure 2), and the forced convection heat exchange is increased or reduced by changing the pressure (namely changing the flow of a collecting pipe and the impact force of water flow), so that the influence of temperature change on the heat exchange efficiency is compensated; and (5) feeding back the cooling effect according to the section temperature field, and finely adjusting the pressure parameters. The homogenization of the surface temperature field of the steel coil is realized through water temperature and water pressure coupling control (figure 3), and the fluctuation control of the coil passing strength of the steel coil is finally ensured to be 40MPa.
(6) The camber of each coil of plate coil in the rolling and coiling process is quickly identified and evaluated (including camber deviation direction and degree), and the camber characteristic data of the rolled plate coils in a batch is utilized, and pre-intervention is carried out through micro-wedge rolling in the finish rolling process, so that the plate coil is pre-provided with reverse camber characteristics before entering ultra-fast cooling, and the reverse camber characteristics are balanced with the camber caused in the cooling process for compensation and correction, and further the shape of the plate coil is improved.
| Serial number | Finish temperature of roughing (. Degree. C.) | Finish Rolling Start temperature (. Degree. C.) | Finish Rolling temperature (. Degree.C.) | Ultra-fast Cooling temperature (. Degree. C.) | Coiling temperature (. Degree. C.) |
| Example 11 | 1020 | 925 | 830 | 430 | 420 |
| Example 12 | 1015 | 920 | 820 | 415 | 410 |
| Example 13 | 1010 | 915 | 820 | 412 | 400 |
| Example 14 | 1000 | 905 | 810 | 400 | 390 |
| Example 15 | 995 | 900 | 815 | 405 | 360 |
| Example 16 | 990 | 895 | 810 | 390 | 350 |
| Example 17 | 980 | 900 | 800 | 380 | 340 |
| Example 18 | 970 | 895 | 790 | 370 | 330 |
The performance measurements are as follows:
the physical and chemical comprehensive performance data of the embodiments show that the comprehensive performance of 8 groups of embodiments can completely meet the index requirements of X80 grade pipeline steel, the ductile-brittle transition temperature of the drop hammer is as low as minus 40 ℃, the ductile-brittle transition temperature is far superior to that of the traditional process and the industry level (about minus 20 ℃) (see figure 4), and the ductile-brittle steel has better toughness. After the ultra-fast cooling and the coiling, the whole plate width has no obvious temperature difference and no obvious camber (less than or equal to 8mm/5 m), and the tower shape of the steel coil is controlled to be less than or equal to 50mm.
It should be noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (3)
1. A manufacturing method of a high-strength and high-toughness coiled sheet for a high-precision spiral submerged arc welding pipe is characterized by comprising the following steps:
(1) Casting the molten metal into a casting blank with the thickness of 230mm, and heating and preserving heat in a heating furnace; the heating temperature is 1160-1200 ℃;
(2) Increasing the deformation of the rough rolling pass by more than or equal to 10 percent, and reducing the pass reduction by 20-30mm, so as to realize the low-temperature accumulated deformation recrystallization of austenite grains and avoid the rapid growth of the grains; through the surface water mist cooling in the rough rolling process, the temperature gradient from the surface to the core of the plate blank is formed, the deformation of the core which is easy to coarsen the structure is improved, and the penetration of the deformation center and the homogenization of the deformation recrystallization are realized; controlling the temperature of rough rolling RT2 to be 980-1030 ℃, and controlling the thickness of the intermediate blank after rough rolling to be 55-65 mm;
(3) The No. 5 frame is subjected to nominal finish rolling, the deformation quantities of the No. 6 frame and the No. 7 frame are increased, the deformation accumulation effect of an unrecrystallized area is improved, and uniform ferrite nucleation is promoted; controlling the finish rolling temperature to be 790-830 ℃;
(4) Based on an ultra-fast cooling technology, fast cooling is carried out in a phase change region from a critical cooling speed range to a low temperature, fine tissue units mainly comprising AF are obtained, and the temperature of the whole plate thickness after ultra-fast cooling is controlled to be less than or equal to 500 ℃;
(5) According to the condition of the ultra-fast cold water temperature, pressure control is matched, forced convection heat exchange is increased or reduced by changing the pressure, and the influence of temperature change on the heat exchange efficiency is compensated; feeding back a cooling effect according to a section temperature field, and finely adjusting pressure parameters; the homogenization of the surface temperature field of the steel coil is realized through water temperature and water pressure coupling control, and the fluctuation control of the coil passing strength of the steel coil is finally ensured to be 40MPa;
(6) The camber of each rolled plate coil in the rolling and coiling process is quickly identified and evaluated, pre-intervention is carried out through micro-wedge rolling in the finish rolling process by utilizing the camber characteristic data of rolled plate coils in rolled batches, so that the plate coil is pre-provided with reverse camber characteristics before entering ultra-fast cooling, and the reverse camber characteristics are balanced with the camber caused in the cooling process for compensation and correction, thereby improving the shape of the plate coil.
2. The method for manufacturing a high-toughness coiled sheet for a high-precision spiral submerged arc welding pipe according to claim 1, wherein in the step (1), the in-furnace time for heating is 130min to 260min.
3. The method for manufacturing a high-toughness coiled sheet for a high-precision spiral submerged arc welding pipe according to claim 1, wherein in the step (1), the holding time is 60 to 100min.
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