CN115558850A - Hot rolled steel plate for 420 MPa-level engineering structure and manufacturing method thereof - Google Patents
Hot rolled steel plate for 420 MPa-level engineering structure and manufacturing method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 158
- 239000010959 steel Substances 0.000 title claims abstract description 158
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 37
- 238000005096 rolling process Methods 0.000 claims abstract description 131
- 238000009749 continuous casting Methods 0.000 claims abstract description 66
- 238000001816 cooling Methods 0.000 claims abstract description 34
- 238000000034 method Methods 0.000 claims abstract description 29
- 238000010438 heat treatment Methods 0.000 claims abstract description 27
- 230000008569 process Effects 0.000 claims abstract description 23
- 239000012535 impurity Substances 0.000 claims abstract description 13
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 11
- 239000000126 substance Substances 0.000 claims abstract description 9
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 8
- 230000009467 reduction Effects 0.000 claims description 32
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 26
- 238000003723 Smelting Methods 0.000 claims description 23
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 13
- 238000010583 slow cooling Methods 0.000 claims description 13
- 238000005507 spraying Methods 0.000 claims description 13
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- 238000007670 refining Methods 0.000 claims description 10
- 229910052799 carbon Inorganic materials 0.000 claims description 9
- 238000001953 recrystallisation Methods 0.000 claims description 9
- 238000002791 soaking Methods 0.000 claims description 9
- 238000005266 casting Methods 0.000 claims description 8
- 229910052698 phosphorus Inorganic materials 0.000 claims description 7
- 229910052717 sulfur Inorganic materials 0.000 claims description 7
- 229910052786 argon Inorganic materials 0.000 claims description 5
- 229910052742 iron Inorganic materials 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 5
- 238000010008 shearing Methods 0.000 claims description 5
- 239000010425 asbestos Substances 0.000 claims description 4
- 238000007664 blowing Methods 0.000 claims description 4
- 229910052748 manganese Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 4
- 239000002994 raw material Substances 0.000 claims description 4
- 229910052895 riebeckite Inorganic materials 0.000 claims description 4
- 238000010079 rubber tapping Methods 0.000 claims description 4
- 238000007711 solidification Methods 0.000 claims description 4
- 230000008023 solidification Effects 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 229910045601 alloy Inorganic materials 0.000 abstract description 11
- 239000000956 alloy Substances 0.000 abstract description 11
- 238000013461 design Methods 0.000 abstract description 6
- 238000009628 steelmaking Methods 0.000 abstract description 4
- 230000001105 regulatory effect Effects 0.000 abstract description 3
- 230000001276 controlling effect Effects 0.000 description 13
- 238000005728 strengthening Methods 0.000 description 11
- 239000011572 manganese Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 7
- 238000001556 precipitation Methods 0.000 description 7
- 229910001566 austenite Inorganic materials 0.000 description 6
- 230000006872 improvement Effects 0.000 description 5
- 238000009847 ladle furnace Methods 0.000 description 5
- 238000005204 segregation Methods 0.000 description 5
- 229910000746 Structural steel Inorganic materials 0.000 description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 239000013078 crystal Substances 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 238000012797 qualification Methods 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910000617 Mangalloy Inorganic materials 0.000 description 1
- 229910000742 Microalloyed steel Inorganic materials 0.000 description 1
- QFGIVKNKFPCKAW-UHFFFAOYSA-N [Mn].[C] Chemical compound [Mn].[C] QFGIVKNKFPCKAW-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000008642 heat stress Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 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 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
-
- 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
- C21D11/00—Process control or regulation for heat treatments
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- 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
-
- 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
- C21D2211/009—Pearlite
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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
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention relates to a hot rolled steel plate for a 420 MPa-level engineering structure and a manufacturing method thereof, wherein the steel plate comprises the following chemical components: 0.04-0.058% of C, 0.10-0.18% of Si, 0.95-1.25% of Mn, less than or equal to 0.020% of P, less than or equal to 0.015% of S, 0.025-0.034% of Nb0.03-0.05% of Mo0.03-0.05%, 0.015-0.020% of Ti0.015-0.045% of Al, 0.003-0.006% of N, and the balance of Fe and impurities; the steel plate has simple component design and low alloy cost, the steel plate structure obtained by regulating the steelmaking, continuous casting and controlled rolling and controlled cooling processes mainly comprises ferrite and pearlite, the technical requirements can be met without subsequent off-line heat treatment, the problems of large rolling resistance and straightening resistance, uniform steel plate performance and the like are solved, and the steel plate has high strength, excellent low-temperature toughness and good comprehensive performance.
Description
Technical Field
The invention relates to the technical field of low-carbon microalloyed steel production, in particular to a hot-rolled steel plate for a low-cost 420 MPa-level engineering structure with the thickness specification of 25-35 mm and excellent low-temperature toughness and ductility and a manufacturing method thereof.
Background
The Q420 grade medium plate is a main variety of medium plates, typical steel types comprise bridge structure steel Q420qC/D/E, pipeline steel X56 and the like, the steel is mainly based on carbon manganese steel, and meanwhile, micro-alloying elements such as Nb, V, ti and other carbonitride forming elements are added into the steel, so that the strength and toughness of the steel plate are improved through solid solution strengthening, precipitation strengthening and fine grain strengthening. According to statistics, the medium plate with the strength grade accounts for 20-30% of the total yield of the medium plate every year. Therefore, it is of great significance to develop such low-cost steel sheets and research on manufacturing techniques thereof.
With the rigidness of design indexes in engineering application fields such as bridges, pipelines and the like, the requirements on indexes such as low-temperature toughness of steel plates are gradually improved while the economy and safety of steel products are ensured, for example, the toughness of the steel plates of some bridge, building or branch pipeline projects needs to meet the technical requirements that the horizontal Charpy impact energy at minus 20 ℃ is more than or equal to 210J and the horizontal DWTT shearing area at minus 15 ℃ is more than 85 percent.
At present, the higher the grade of steel for engineering and structural use, the lower the carbon content and the higher the addition of alloying elements, so that the production cost of the steel for engineering and structural use is correspondingly increased while the quality grade of the steel for engineering and structural use is continuously improved. The Q420 grade engineering structural steel for the pipelines in service in environments such as cold regions, geological active areas, pipeline crossing areas and the like must also have good strain resistance and low-temperature toughness so as to meet the requirements of severe service environments. Therefore, the development of steel for engineering structure having all-purpose technical properties such as high strength, high toughness, and good strain resistance is an urgent problem to be solved.
Firstly, the increase of the thickness of a steel plate increases the rolling deformation resistance, and the pass deformation rate is limited, so that the grain refinement and control difficulty is multiplied; meanwhile, the increase of the thickness of the steel plate leads to the increase of the temperature gradient of the thickness section and the deterioration of the cooling and the structural uniformity in the thickness direction; secondly, the thick specification characteristics of the steel plate also influence the toughness performance matching, and the performance control difficulty is further increased. In addition, as the thickness of the steel plate increases, the content of precious alloys is higher and higher in order to ensure the toughness of the steel plate, so that the production cost of the engineering structure with excellent performance is correspondingly increased while the quality grade is continuously improved. On the premise of ensuring the performance, the method reduces the alloy cost and is also the key for improving the product competitiveness. Therefore, how to solve the problems in the production of the Q420 grade steel grade structural steel with the thickness specification of 25-35 mm and reduce the production cost is a key problem to be solved urgently in realizing the mass production of the 420 grade steel grade engineering structural steel.
So far, few research reports on the production of engineering structural steel with good low-temperature toughness and grade of 420MPa at home and abroad are reported.
Chinese patent application No. CN201811450143.7 discloses a method for producing a thin steel plate for a bridge structure with low yield ratio, wherein the components of the steel plate comprise C0.10-0.15, si is less than or equal to 0.50, mn is 1.20-1.50, P is less than or equal to 0.015, S is less than or equal to 0.005, alt is 0.02-0.05, ti is 0.008-0.025, nb is less than or equal to 0.020, and Cr is 0.25-0.50.
Chinese patent application No. CN201010243234.0 discloses 'X56 pipeline steel and a production method thereof', wherein the chemical components of the steel are C0.060-0.090%, si 0.20-0.30%, mn 1.30-1.50%, S is less than or equal to 0.008%, P is less than or equal to 0.020%, nb0.035-0.055%, V0.020-0.040%, ti 0.010-0.022%, N is less than or equal to 0.008%, and Als0.010-0.040%.
Chinese patent application No. CN201780038335.4 discloses a hot-rolled steel plate for a thick-wall high-strength pipeline steel pipe, a welded steel pipe for the thick-wall high-strength pipeline steel pipe and a manufacturing method thereof, wherein the steel grade mainly aims at X60-X80, the DWTT temperature is-25 ℃, the alloy cost is high, and the production process aims at a rolled plate.
The steel X56 for oil and gas transmission pipelines described in journal paper "trial production of steel X56 for oil and gas transmission pipelines" (weming, xiaokou, wide and thick plate, 2000, 04) adopts a high-carbon composition design: 0.260 percent of C, less than or equal to 1.35 percent of Mn, less than or equal to 0.03 percent of Nb and lower alloy cost, but because the carbon content is higher, the requirements of strain resistance and low-temperature toughness can not be met when the alloy is used for pipelines serving in environments such as cold regions, geological active areas, pipeline cross-over areas and the like, and in addition, the thickness specification, yield ratio and DWTT performance indexes of the steel plate are not clear.
The steels disclosed in the above patent applications and literature documents have high toughness in some parts, but among them, the steels are thin or have no clear description on product specifications and technical indexes, and therefore, the steels are not suitable for producing hot rolled steel sheets for engineering structures having a thickness specification of 25 to 35mm and good low-temperature toughness and plasticity. The invention overcomes the defects of the prior art, realizes the production of 420MPa steel grade hot rolled steel plate with the thickness of 25-35 mm by using a continuous casting billet with the thickness of 250-300 mm, and the steel plate has the characteristics of high strength, excellent low-temperature toughness and the like.
Disclosure of Invention
The invention provides a hot rolled steel plate for 420 MPa-level engineering structures and a manufacturing method thereof, wherein the hot rolled steel plate is simple in component design and low in alloy cost, the steel plate structure obtained by regulating and controlling steel making, continuous casting and controlled rolling and controlled cooling processes mainly comprises ferrite and pearlite, the technical requirements can be met without subsequent off-line heat treatment, the problems of high rolling resistance, high straightening resistance, steel plate performance uniformity and the like are solved, and the steel plate has high strength, excellent low-temperature toughness and good comprehensive performance and can ensure the safety when the steel plate is applied to engineering structures such as pipelines, bridges and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
a hot rolled steel plate for 420 MPa-level engineering structures comprises the following chemical components in percentage by weight: 0.04 to 0.058 percent of C, 0.10 to 0.18 percent of Si, 0.95 to 1.25 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, 0.025 to 0.034 percent of Nb0.03 to 0.05 percent of Mo0, 0.015 to 0.020 percent of Ti, 0.015 to 0.045 percent of Al, 0.003 to 0.006 percent of N, the balance of Fe and inevitable impurities, less than or equal to 0.0050 percent of O in the impurities, and the total amount of other impurity elements is less than 0.05 percent.
A manufacturing method of a hot rolled steel plate for a 420 MPa-level engineering structure comprises the production processes of molten steel smelting → external refining → continuous casting + slow cooling → continuous casting heating → controlled rolling → controlled cooling → air cooling to room temperature, wherein:
1) Smelting molten steel: pretreating the raw material by KR molten iron, controlling the content of S to be lower than 0.015%, and performing converter smelting after slagging-off; controlling the content of P in the converter smelting to be less than or equal to 0.020%, controlling the content of C in the converter smelting end point to be 0.04-0.058%, and blowing argon for 15-20 min during tapping;
2) Continuous casting and slow cooling: refining the molten steel in an LF (ladle furnace), and then carrying out plate blank continuous casting, wherein the continuous casting superheat degree is 15-20 ℃, and the continuous casting and billet drawing speed is 1.1-1.4 m/min; putting the horizontal fan-shaped section, namely the solidification tail end, into soft reduction, wherein the reduction is 6-12 mm, and the slow cooling time after the continuous casting billet is off line is more than or equal to 24h;
3) Heating a continuous casting blank: the temperature of the preheating section is 955-1120 ℃, the temperature of the heating section is 1200-1230 ℃, the temperature of the soaking section is 1190-1210 ℃, the total time in the furnace is 4-4.5 h, wherein the accumulated time of the heating section and the soaking section is not more than 2h;
4) Controlled rolling: rolling in two stages;
the first stage rolling is recrystallization rolling, namely rough rolling, the initial rolling temperature of the rough rolling is more than or equal to 1100 ℃, and the final rolling temperature of the rough rolling is 975-1010 ℃; the rough rolling is not more than 6 passes, wherein the reduction rate of the first 2 passes is more than 15%, and the reduction rate of 1 pass in the last 3 passes is not less than 10%;
the descaling water of the rolling mill is sprayed in the last 2 passes of rough rolling, the time for spraying the descaling water in each pass is 0.5-1 min, and the pressure is 20-25 MPa; spraying scale removing water for the rolling mill for 2 passes in the process of rolling the intermediate blank to be warmed, wherein the time for spraying the scale removing water for each pass is 1-1.5 min, and the pressure is 15-20 MPa;
the second stage rolling is non-recrystallization rolling, namely finish rolling, the start rolling temperature of the finish rolling is 850-930 ℃, and the finish rolling temperature of the finish rolling is 770-830 ℃; the finish rolling is not more than 8 passes, wherein the reduction rate of 2 passes in the first 4 passes is more than 18%, and the reduction rate of 1 pass in the last 2 passes is not less than 10%; the steel plate is rolled at an increased speed, the steel is cast at a reduced speed after rolling, the steel casting speed is 1-2.5 m/s, and pre-straightening is put into the steel plate;
5) And (3) controlling cooling: laminar cooling is adopted, the initial cooling temperature is 720-770 ℃, the final cooling temperature is 430-460 ℃, and the cooling speed is 20-30 ℃/s.
Further, in the step 2), the number of the stacks of the continuous casting billets is not less than 10, and the uppermost layer and the lowermost layer are respectively subjected to asbestos heat preservation treatment.
Further, in the step 3), the thickness of the continuous casting billet is 250-300 mm.
Further, in the step 4), before rolling, the continuous casting billet after leaving the heating furnace is descaled by using high-pressure water for 1-1.5 min, and the pressure of the descaler is 25-35 MPa.
Further, in the step 4), the thickness of the rolled intermediate billet is 3 to 4.5 times of that of the finished steel plate.
Further, in the step 4), the increasing speed rolling specifically comprises: after the head of the rolled intermediate billet is bitten into the roller at a low speed, the speed of the roller way is quickly increased to 40-60 r/min from 15-25 r/min.
Furthermore, the structure of the prepared steel plate is a complex phase structure mainly comprising ferrite and pearlite.
Further, the properties of the prepared steel plate are as follows: the yield strength of transverse stretching is 420-470 MPa, the tensile strength is 500-570 MPa, the yield ratio is less than or equal to 0.85, the elongation is more than or equal to 35 percent, the transverse Charpy impact energy at minus 20 ℃ is more than or equal to 210J, and the transverse DWTT shearing area at minus 15 ℃ is more than 85 percent.
Furthermore, the thickness of the prepared steel plate is 25-35 mm.
Compared with the prior art, the invention has the beneficial effects that:
1) The KR molten iron is pretreated for deep desulfurization and then is completely drossed, the converter adopts a double-slag method for removing P, so that the P and S contents of the casting blank are lower, the argon blowing time is controlled, the defects of casting blank center segregation, inclusion, excessive O content and the like caused by higher Mn content are avoided, and the improvement of the ductility and toughness of pipeline steel is facilitated; the superheat degree and the withdrawal rate of the continuous casting billet are reasonably controlled, and the continuous casting billet is put into soft reduction, so that the segregation of the billet is reduced, austenite grains are refined, the internal structure defects are reduced, the casting billet after being off-line is stacked and slowly cooled, alloy elements enriched in the center of the billet are gradually diffused, the diffusion of hydrogen elements is accelerated, the center porosity grade and the segregation of the casting billet are reduced, and the flaw detection qualification rate of a finished steel plate is improved;
2) The steel has reasonable design of chemical components and low alloy addition, and the alloy cost is greatly reduced by increasing the C content, reducing the Mn content and adding a small amount of microalloy elements Nb, ti and Mo; high-temperature rolling is adopted, so that the high-temperature deformation resistance of a rough rolling stage and a finish rolling stage is reduced, and the reduction per pass is favorably improved, so that the comprehensive performance of the steel plate is ensured;
3) The two-stage rolling process is adopted, the pass rolling reduction of rough rolling and finish rolling is controlled, the thickness of the intermediate billet is optimized, and the high-pressure water descaling process is adopted, so that the temperature gradient exists between the surface and the core of the intermediate billet, the structure from the surface to the core of the steel plate is uniform, and the growth of crystal grains is inhibited; in addition, the initial rolling temperature of finish rolling is increased, and the steel is slowly thrown after rolling, so that the static recovery and the dispersion precipitation of nano-phase NbC and the like of the steel plate are promoted, the internal crystal grains of the steel plate are uniformly distributed, the stress concentration is inhibited, the DWTT performance is improved, and the precipitation strengthening effect is generated; the final cooling temperature of the steel plate is controlled to be 430-460 ℃ by measures such as pre-straightening investment, laminar cooling and the like, so that the mechanical property of the steel plate can meet the requirement;
4) The invention reduces the alloy cost through simple component design, combines the processes of regulating and controlling steel making, continuous casting and controlled rolling and controlled cooling, and obtains the steel plate with the thickness specification of 25-35 mm and the grade of 420MPa for the engineering structure, the structure mainly comprises ferrite and pearlite, and the steel plate has good low-temperature toughness; the concrete properties are as follows: the yield strength performance of transverse stretching is between 420 and 470MPa, the tensile strength is between 500 and 570MPa, the yield ratio is less than or equal to 0.85, the elongation is more than or equal to 35 percent, the transverse Charpy impact energy at the temperature of minus 20 ℃ is more than or equal to 210J, the transverse DWTT shearing area at the temperature of minus 15 ℃ is more than 85 percent, and the flaw detection qualification rate of the steel plate is more than 99.5 percent.
Detailed Description
The invention relates to a hot rolled steel plate for a 420 MPa-level engineering structure, which comprises the following chemical components in percentage by weight: 0.04 to 0.058 percent of C, 0.10 to 0.18 percent of Si, 0.95 to 1.25 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, 0.025 to 0.034 percent of Nb0.03 to 0.05 percent of Mo0, 0.015 to 0.020 percent of Ti0.015 to 0.045 percent of Al, 0.003 to 0.006 percent of N, the balance of Fe and inevitable impurities, less than or equal to 0.0050 percent of O in the impurities, and less than 0.05 percent of other impurity elements.
The invention relates to a manufacturing method of a hot rolled steel plate for a 420 MPa-level engineering structure, which comprises the production processes of molten steel smelting → external refining → continuous casting + slow cooling → continuous casting heating → controlled rolling → controlled cooling → air cooling to room temperature, wherein:
1) Smelting molten steel: pretreating the raw materials by KR molten iron, controlling the content of S to be lower than 0.015 percent, and smelting in a converter after slagging off; controlling the content of P to be less than or equal to 0.020% in the converter smelting process, controlling the content of C to be 0.04-0.058% at the smelting end point of the converter, and blowing argon for 15-20 min during tapping;
2) Continuous casting and slow cooling: refining the molten steel in an LF (ladle furnace), and then carrying out plate blank continuous casting, wherein the continuous casting superheat degree is 15-20 ℃, and the continuous casting and billet drawing speed is 1.1-1.4 m/min; putting the horizontal fan-shaped section, namely the solidification tail end, into soft reduction, wherein the reduction is 6-12 mm, and the slow cooling time after the continuous casting billet is off line is more than or equal to 24h;
3) Heating a continuous casting blank: the temperature of the preheating section is 955-1120 ℃, the temperature of the heating section is 1200-1230 ℃, the temperature of the soaking section is 1190-1210 ℃, the total time in the furnace is 4-4.5 h, wherein the accumulated time of the heating section and the soaking section is not more than 2h;
4) Controlling rolling: rolling in two stages;
the first stage rolling is recrystallization rolling, namely rough rolling, the initial rolling temperature of the rough rolling is more than or equal to 1100 ℃, and the final rolling temperature of the rough rolling is 975-1010 ℃; the rough rolling is not more than 6 passes, wherein the reduction rate of the first 2 passes is more than 15%, and the reduction rate of 1 pass in the last 3 passes is not less than 10%;
the descaling water of the rolling mill is sprayed in the last 2 passes of rough rolling, the time for spraying the descaling water in each pass is 0.5-1 min, and the pressure is 20-25 MPa; spraying scale removing water for the rolling mill for 2 passes in the process of rolling the intermediate blank to be warmed, wherein the time for spraying the scale removing water for each pass is 1-1.5 min, and the pressure is 15-20 MPa;
the second stage rolling is non-recrystallization rolling, namely finish rolling, the start rolling temperature of the finish rolling is 850-930 ℃, and the finish rolling temperature of the finish rolling is 770-830 ℃; the finish rolling is not more than 8 passes, wherein the reduction rate of 2 passes in the first 4 passes is more than 18%, and the reduction rate of 1 pass in the last 2 passes is not less than 10%; the steel is rolled at an increasing speed, the steel plate is cast at a decreasing speed after rolling, the steel casting speed is 1-2.5 m/s, and pre-straightening is put into the steel plate;
5) And (3) controlling cooling: laminar cooling is adopted, the initial cooling temperature is 720-770 ℃, the final cooling temperature is 430-460 ℃, and the cooling speed is 20-30 ℃/s.
Further, in the step 2), the number of the stacks of the continuous casting billets is not less than 10, and the uppermost layer and the lowermost layer are respectively subjected to asbestos heat preservation treatment.
Further, in the step 3), the thickness of the continuous casting billet is 250-300 mm.
Further, in the step 4), the continuous casting billet after being discharged from the heating furnace is descaled for 1-1.5 min by using high-pressure water before rolling, and the pressure of a descaler is 25-35 MPa.
Further, in the step 4), the thickness of the rolled intermediate billet is 3-4.5 times of that of the finished steel plate.
Further, in the step 4), the speed-increasing rolling specifically comprises: after the head of the rolled intermediate billet is bitten into the roller at a low speed, the speed of the roller way is quickly increased to 40-60 r/min from 15-25 r/min.
Furthermore, the structure of the prepared steel plate is a complex phase structure which mainly comprises ferrite and pearlite.
Further, the properties of the prepared steel plate are as follows: the yield strength of transverse stretching is 420-470 MPa, the tensile strength is 500-570 MPa, the yield ratio is less than or equal to 0.85, the elongation is more than or equal to 35 percent, the transverse Charpy impact energy at minus 20 ℃ is more than or equal to 210J, and the transverse DWTT shearing area at minus 15 ℃ is more than 85 percent.
Furthermore, the thickness of the prepared steel plate is 25-35 mm.
The hot rolled steel plate for the 420 MPa-level engineering structure has the characteristics of good low-temperature toughness, low yield ratio and low cost, the target thickness is 25-35 mm, a continuous casting billet with the thickness of 250-300 mm is produced on a medium-thick plate reciprocating rolling mill, and the cooling medium is water.
The hot rolled steel plate for the 420 MPa-level engineering structure has the following main elements in chemical components:
c: the most economical and basic strengthening elements in steel obviously improve the strength of the steel through solid solution strengthening and precipitation strengthening, but the improvement of the content of C has negative effects on the plasticity, toughness and weldability of the steel. Therefore, the content range of C is set to be 0.04-0.058 percent.
Mn: the strength of the steel is improved by solid solution strengthening while compensating for the loss of strength due to the decrease in C content. In addition, mn can also reduce the gamma-alpha phase transformation temperature, further refine ferrite grains, contribute to obtaining fine low-temperature phase transformation products and improve the toughness of steel. However, when the content of Mn is increased, center segregation and structure deterioration of the continuous casting slab are aggravated, which is not favorable for improving the low-temperature toughness of the steel plate, and uniformity of the cross-sectional structure of the steel plate cannot be ensured. Therefore, the Mn content range of the present invention is set to 0.95% to 1.25%.
Si: has the functions of steelmaking deoxidization and matrix strength improvement. The ferrite can be purified by increasing the content of Si, the content of pearlite is reduced, and the Bauschinger effect of a base material is reduced. However, when Si is excessive, the toughness of the weld heat affected zone of the base material is lowered. Therefore, the Si content range in the present invention is set to 0.10% to 0.18%.
Nb: is one of common elements in modern microalloyed pipeline steel, has good fine grain strengthening and precipitation strengthening effects, and can delay austenite recrystallization; however, excessive Nb increases the production cost and the difficulty of controlling the continuous casting process. The invention selects Nb content range of 0.025 percent to 0.034 percent, and can obtain uniform composite phase mainly based on the formation structure of acicular ferrite or M-A island by matching with a reasonable TMCP process, so that the steel has good toughness.
Mo: mo can improve hardenability, promote medium and low temperature structure transformation, and has the function of refining grains, but the excessively high Mo content can inhibit ferrite transformation, is not beneficial to improving the plastic deformation performance of steel, and meanwhile, the strain aging performance can be deteriorated; on the other hand, the high price of molybdenum can increase the production cost, therefore, the content of the molybdenum is controlled to be 0.03-0.05 percent.
N: the N element in the steel has no other obvious effect except for forming fine TiN grain refined austenite grains, so that the content needs to be kept at a lower level, and the N content range is selected from 0.003 to 0.006 percent.
Ti: is a strong solid N element and exists in the form of TiN in the continuous casting billet. The fine TiN particles can effectively inhibit the growth of austenite grains when reheating a continuous casting slab, and contribute to the improvement of the solid solubility of Nb in austenite and the improvement of the impact toughness of a welding heat affected zone. When the addition amount of Ti exceeds a certain value, the TiN particles will be coarsened, and the stress concentration level between the particle interface and the matrix is increased. Therefore, the content range of Ti is selected to be 0.015-0.020%.
Al: in general, alN formation as a deoxidizer in steel also has a function of refining the structure. When the content of Al exceeds 0.045%, excessive alumina inclusions may degrade cleanliness of steel. On the other hand, if the Al content is too low, deoxidation is insufficient, and easily oxidizable elements such as Ti form oxides, so that the Al content is set to 0.015% to 0.045% in the present invention.
P, S: is an inevitable impurity element in steel, and the lower the content, the better. But cannot be lowered without limit due to smelting cost and process. Therefore, the upper limits of the contents of P and S are set to 0.020% and 0.015% in the present invention.
The production process of the hot rolled steel plate for the 420 MPa-level engineering structure comprises the steps of molten steel smelting → external refining → continuous casting + slow cooling → continuous casting heating → controlled rolling → controlled cooling → air cooling to room temperature, wherein the main control process comprises the following steps:
1) Smelting molten steel: smelting according to the designed components, pretreating the raw materials by KR molten iron, controlling the content of S to be lower than 0.015 percent, and entering a converter after slagging off; the double-slag method is adopted to remove P in the converter smelting, the content of P is controlled to be less than or equal to 0.020%, the content of C is controlled to be 0.04-0.058% at the smelting end point of the converter, and argon is blown for 15-20 min during tapping;
2) Continuous casting and slow cooling: carrying out slab continuous casting on the molten steel after LF refining, wherein the continuous casting superheat degree is 15-20 ℃, and the continuous casting and billet drawing speed is 1.1-1.4 m/min; putting the horizontal fan-shaped section, namely the solidification tail end, into soft reduction, wherein the reduction of the continuous casting billet is 6-12 mm, and the slow cooling time after the continuous casting billet is off line is more than or equal to 24h, so that the central porosity level and the segregation degree of the continuous casting billet are reduced, and the flaw detection qualification rate of a finished steel plate is improved; during slow cooling, the stacking number of the continuous casting billets is not less than 10, and asbestos heat preservation treatment is carried out on the uppermost layer and the lowermost layer, so that the phenomenon that H elements overflow unevenly due to too fast temperature drop of the continuous casting billets and the flaw detection qualified rate is influenced is prevented;
3) Heating a continuous casting blank: feeding a continuous casting billet (with the thickness of 250-300 mm) into a stepping heating furnace for heating, and discharging the continuous casting billet from the furnace after the continuous casting billet sequentially passes through a preheating section, a heating section and a soaking section; wherein the temperature interval of the preheating section is 955-1120 ℃, and the aim is to promote the carbide and the nitride of Nb generated in the cooling process of the continuous casting billet to be rapidly dissolved in the matrix again and to be fully and uniformly diffused, so that the structure of the continuous casting billet is homogenized; the temperature interval of the heating section is 1200-1230 ℃, the temperature interval of the soaking section is 1190-1210 ℃, the total in-furnace time is 4-4.5 hours, and the accumulation of the heating section time and the soaking section time is controlled not to exceed 2 hours, so that elements such as C, N and the like are further uniformly distributed, the in-furnace time and temperature are controlled, and the excessive growth of original austenite grains is inhibited;
4) Descaling and controlled rolling by high-pressure water:
descaling the continuous casting billet after the continuous casting billet is taken out of the heating furnace for 1-1.5 min by using high-pressure water before rolling, wherein the pressure of a descaling machine is 25-35 MPa; rolling in two stages:
the first stage is recrystallization rolling (rough rolling), the initial rolling temperature of the rough rolling is more than or equal to 1100 ℃, and the final rolling temperature range of the rough rolling is 975-1010 ℃; the rough rolling is not more than 6 times, and the pass reduction system is as follows: the first 2 passes ensure that the reduction rate is more than 15%, and the reduction rate of 1 pass of the last 3 passes is not less than 10%; the thickness of the obtained rolling intermediate billet is 3 to 4.5 times of that of the finished steel plate.
Spraying descaling water on the rolling mill in each pass of the last 2 passes of rough rolling, wherein the time for spraying the descaling water in each pass is 0.5-1 min, and the pressure is 20-25 MPa; spraying scale removing water for the rolling mill for 2 passes in the process of rolling the intermediate blank to be warmed, wherein the time for spraying the scale removing water for each pass is 1-1.5 min, and the pressure is 15-20 MPa;
the second stage is non-recrystallization rolling (finish rolling), the temperature range of the start rolling of the finish rolling is 850-930 ℃, and the temperature range of the finish rolling is 770-830 ℃; the finish rolling is not more than 8 times, and the pass reduction system is as follows: 2 passes of the first 4 passes ensure that the reduction rate is more than 18 percent, and the reduction rate of 1 pass of the last 2 passes ensure that the reduction rate is not less than 10 percent;
and (3) adopting accelerated rolling, namely quickly increasing the speed of a roller way from 15-25 r/min to 40-60 r/min after the head of the rolled intermediate billet is bitten into the roller way at a low speed, and preventing the finish rolling temperature of finish rolling from being lower than a required temperature interval. And (3) the steel plate is subjected to speed reduction and steel throwing at the steel throwing speed of 1-2.5 m/s after rolling, so that the static recovery in the thickness direction of the steel plate is promoted, the dispersion and precipitation of nano-phase NbC and the like are promoted, the crystal grains in the steel plate are uniformly distributed, and the precipitation strengthening effect is generated. The purpose of putting in pre-straightening is to prevent the influence on the uniformity of performance caused by water stored on the surface of the steel plate in the subsequent controlled cooling process due to the upwarp of the steel plate head in the rolling process; and simultaneously, the heat stress generated in the steel plate rolling process is released.
The invention adopts the components and the controlled rolling and controlled cooling process, overcomes the defects in the prior art, realizes the production of the steel plate with the thickness specification of 25-35 mm, the 420MPa grade and good low-temperature ductility and toughness for the engineering structure, and the steel plate has a complex phase structure with ferrite and pearlite as main components.
In order to make the purpose, technical solution and technical effect of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is now clearly and completely described. The embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art without any inventive step in connection with the embodiments of the present invention shall fall within the scope of protection of the present invention.
[ examples ] A
Table 1 shows the chemical components of the steel in this example, table 2 shows the process parameters of smelting and continuous casting of the steel in this example, and table 3 shows the heating schedule of the continuous casting slab and the process parameters of high-pressure water descaling before rolling in this example; table 4 shows the rolling process parameters of the steels in this example; table 5 shows the rolling reduction of each pass in different rolling stages in this example; table 6 shows the controlled cooling process parameters of the steels in this example; table 7 shows the transverse mechanical properties of the steel sheets of this example.
TABLE 1 chemical composition of steel (wt%)
| Examples | C | Si | Mn | Ti | Nb | Mo | N | Al |
| 1 | 0.043 | 0.18 | 1.15 | 0.017 | 0.026 | 0.031 | 0.0042 | 0.017 |
| 2 | 0.052 | 0.15 | 0.95 | 0.018 | 0.031 | 0.042 | 0.0033 | 0.035 |
| 3 | 0.058 | 0.16 | 1.02 | 0.015 | 0.033 | 0.048 | 0.0057 | 0.043 |
| 4 | 0.051 | 0.17 | 1.16 | 0.019 | 0.027 | 0.049 | 0.0048 | 0.037 |
| 5 | 0.046 | 0.13 | 0.98 | 0.020 | 0.028 | 0.035 | 0.0036 | 0.045 |
| 6 | 0.042 | 0.15 | 1.24 | 0.016 | 0.033 | 0.033 | 0.0041 | 0.040 |
Note: the impurity element P in the steel is less than or equal to 0.02 percent; s is less than or equal to 0.015 percent; 0 percent or less than 0.0050 percent and the total amount of other impurity elements is less than 0.05 percent.
TABLE 2 Process parameters for smelting and continuous casting of steels
TABLE 3 heating system of casting blank and high-pressure water descaling process parameters before rolling
TABLE 4 Rolling Process parameters of the steels
TABLE 5 reduction of each pass in different rolling stages
TABLE 6 controlled Cooling Process parameters of the steels
Table 7 transverse mechanical properties of the steel sheets.
As can be seen from the examples, compared with the prior art, the 420 MPa-grade steel plate manufactured by the invention has simple components, excellent mechanical properties and particularly excellent low-temperature toughness.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (10)
1. A hot rolled steel plate for a 420 MPa-level engineering structure is characterized by comprising the following chemical components in percentage by weight: 0.04 to 0.058 percent of C, 0.10 to 0.18 percent of Si, 0.95 to 1.25 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, 0.025 to 0.034 percent of Nb, 0.03 to 0.05 percent of Mo, 0.015 to 0.020 percent of Ti, 0.015 to 0.045 percent of Al, 0.003 to 0.006 percent of N, the balance of Fe and inevitable impurities, less than or equal to 0.0050 percent of O in the impurities, and the total amount of other impurity elements is less than 0.05 percent.
2. The manufacturing method of the hot rolled steel sheet for the 420MPa grade engineering structure according to claim 1, wherein the production process comprises molten steel smelting → external refining → continuous casting + slow cooling → continuous casting heating → controlled rolling → controlled cooling → air cooling to room temperature, wherein:
1) Smelting molten steel: pretreating the raw materials by KR molten iron, controlling the content of S to be lower than 0.015 percent, and smelting in a converter after slagging off; controlling the content of P to be less than or equal to 0.020% in the converter smelting process, controlling the content of C to be 0.04-0.058% at the smelting end point of the converter, and blowing argon for 15-20 min during tapping;
2) Continuous casting and slow cooling: refining the molten steel in an LF, and then carrying out slab continuous casting, wherein the continuous casting superheat degree is 15-20 ℃, and the continuous casting and billet drawing speed is 1.1-1.4 m/min; putting the horizontal sector section, namely the solidification tail end, under light pressure, wherein the reduction amount is 6-12 mm, and the slow cooling time is more than or equal to 24 hours after the continuous casting billet is off line;
3) Heating a continuous casting blank: the temperature of the preheating section is 955-1120 ℃, the temperature of the heating section is 1200-1230 ℃, the temperature of the soaking section is 1190-1210 ℃, the total time in the furnace is 4-4.5 h, wherein the accumulated time of the heating section and the soaking section is not more than 2h;
4) Controlled rolling: rolling in two stages;
the first stage rolling is recrystallization rolling, namely rough rolling, the initial rolling temperature of the rough rolling is more than or equal to 1100 ℃, and the final rolling temperature of the rough rolling is 975-1010 ℃; the rough rolling is not more than 6 passes, wherein the reduction rate of the first 2 passes is more than 15%, and the reduction rate of 1 pass in the last 3 passes is not less than 10%;
the descaling water of the rolling mill is sprayed in the last 2 passes of rough rolling, the time for spraying the descaling water in each pass is 0.5-1 min, and the pressure is 20-25 MPa; spraying scale removing water for the rolling mill for 2 passes in the process of rolling the intermediate blank to be warmed, wherein the time for spraying the scale removing water for each pass is 1-1.5 min, and the pressure is 15-20 MPa;
the second stage rolling is non-recrystallization rolling, namely finish rolling, wherein the start rolling temperature of the finish rolling is 850-930 ℃, and the finish rolling temperature of the finish rolling is 770-830 ℃; the finish rolling is not more than 8 passes, wherein the reduction rate of 2 passes in the first 4 passes is more than 18%, and the reduction rate of 1 pass in the last 2 passes is not less than 10%; the steel is rolled at an increasing speed, the steel plate is cast at a decreasing speed after rolling, the steel casting speed is 1-2.5 m/s, and pre-straightening is put into the steel plate;
5) And (3) controlling cooling: laminar cooling is adopted, the initial cooling temperature is 720-770 ℃, the final cooling temperature is 430-460 ℃, and the cooling speed is 20-30 ℃/s.
3. The manufacturing method of the hot rolled steel sheet for the 420MPa grade engineering structure according to claim 2, wherein in the step 2), the number of the continuous casting slabs stacked is not less than 10, and the uppermost layer and the lowermost layer are respectively subjected to asbestos heat preservation treatment.
4. The manufacturing method of the hot rolled steel sheet for the 420MPa grade engineering structure according to claim 2, wherein in the step 3), the thickness of the continuous casting billet is 250-300 mm.
5. The manufacturing method of the hot rolled steel plate for the 420 MPa-level engineering structure according to claim 2, wherein in the step 4), the continuous casting blank after being discharged out of the heating furnace is descaled for 1-1.5 min by using high-pressure water before rolling, and the pressure of a descaler is 25-35 MPa.
6. The method for manufacturing the hot rolled steel sheet for the 420MPa grade engineering structure according to claim 2, wherein in the step 4), the thickness of the rolled intermediate blank is 3 to 4.5 times of the thickness of the finished steel sheet.
7. The method for manufacturing the hot-rolled steel plate for the 420 MPa-level engineering structure according to claim 2, wherein in the step 4), the accelerated rolling is specifically as follows: after the head of the rolled intermediate billet is bitten into the roller at a low speed, the speed of the roller way is quickly increased to 40-60 r/min from 15-25 r/min.
8. The method of manufacturing a hot rolled steel sheet for a 420MPa grade engineering structure according to claim 2, wherein the structure of the manufactured steel sheet is a complex phase structure mainly including ferrite and pearlite.
9. The manufacturing method of the hot rolled steel plate for the 420 MPa-level engineering structure according to claim 2, is characterized in that the properties of the manufactured steel plate are as follows: the yield strength of transverse stretching is 420-470 MPa, the tensile strength is 500-570 MPa, the yield ratio is less than or equal to 0.85, the elongation is more than or equal to 35 percent, the transverse Charpy impact energy at the temperature of minus 20 ℃ is more than or equal to 210J, and the transverse DWTT shearing area at the temperature of minus 15 ℃ is more than 85 percent.
10. The manufacturing method of the hot rolled steel plate for the 420 MPa-level engineering structure according to claim 2, wherein the thickness of the manufactured steel plate is 25-35 mm.
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Application publication date: 20230103 |