CN115094316B - Super-thick steel plate with excellent core low-temperature impact toughness and manufacturing method thereof - Google Patents
Super-thick steel plate with excellent core low-temperature impact toughness and manufacturing method thereof Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
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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
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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
- C21D8/0226—Hot rolling
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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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C22C33/04—Making ferrous alloys by melting
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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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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- 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
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Abstract
The invention discloses an extra-thick steel plate with excellent core low-temperature impact toughness and a manufacturing method thereof, belonging to the technical field of extra-thick plate production. According to the method, refined grain elements are added in the steelmaking process, a continuous casting blank with the extra thickness of 450-475 mm is adopted, the heating temperature and the austenite grain size of the continuous casting blank are controlled, forced cooling is carried out on the continuous casting blank in the rough rolling and finish rolling processes, the temperature difference is generated between the surface and the core of the continuous casting blank, rolling deformation is promoted to be deep into the core of a steel plate, weak water cooling is adopted to replace conventional air cooling after the steel plate is taken out of a furnace after normalizing, the phase transition temperature is reduced, grains are refined, and tempering heat treatment is carried out to release stress and homogenize tissues. The thickness of the extra thick plate with 170-200 mm produced by the method is 1/4 and the impact power at the temperature of-60 ℃ at the 1/2 central position, the central structure of the steel plate is uniformly thinned, the flaw detection result meets the standard requirements of NB/T47013.3-2015 and grade HI, and the comprehensive performance is excellent.
Description
Technical Field
The invention belongs to the technical field of super-thick plate production, and particularly relates to a super-thick steel plate with excellent core low-temperature impact toughness and a manufacturing method thereof.
Background
The ultra-thick plate is widely applied to the fields of ships, pressure vessels, wind power and the like, and is an important component for manufacturing ocean platforms, boiler pressure vessels, high-rise buildings, wind power generation foundation rings and other large-scale structural members. Generally, steel plates with the thickness of more than or equal to 60mm are called as extra thick plates, and for ultra thick plates with the thickness of more than 150mm, the traditional mode is to adopt a die casting steel ingot for production, and the production cost is high due to the large cutting loss, low yield. In order to reduce the production cost and improve the product competitiveness, the main steel factories in China begin to continuously advance to produce extra thick plates by adopting continuous casting billets in recent years, but because the thickness of the continuous casting billets is limited, the rolling compression ratio is small, the rolling deformation is difficult to go deep, the core of the extra thick plates is thick in structure and loose shrinkage cavity is difficult to heal, the impact performance of the core positions with the thickness of 1/4 and 1/2 is unstable, particularly the low-temperature impact toughness is poor, and the defect detection is not suitable in the high-grade defect detection according to the energy standard NB/T47013.3-2015 grade I or grade HI. The performance problem of the core part of the super-thick plate becomes an important constraint bottleneck for the development and production of the super-thick plate at the present stage.
In the method (CN 109013711A) for improving the quality and the flaw detection qualification rate of the core part of the super-thick plate, the method is characterized in that an instant cooling device is utilized in a rolling gap for carrying out one-pass or multi-pass online cooling on a 300-400 mm continuous casting blank, so that the aim of improving the quality of the core part of the super-thick plate is fulfilled. The patent does not effectively control the heating process, rolling pass, rolling reduction, rolling speed and the like, the thickness of the produced low-temperature impact extra-thick plate is only 100mm, and meanwhile, the low-temperature impact extra-thick plate can only meet the impact requirement of minus 20 ℃, and the flaw detection grade can only meet the national standard grade 2 requirement.
In comparative document 2, a Q460 grade high-strength and high-toughness extra-thick steel plate was developed by controlling rolling and cooling and performing normalizing treatment in a normalized high-strength and high-toughness extra-thick plate and a production method thereof (CN 104962814A). The patent has the advantages that the compression ratio is insufficient, the rolling processes such as rolling pass, rolling speed and the like and the heat treatment process are not accurately controlled, the thickness specification of the related steel plate can only reach 150mm, the core impact performance is unstable, and the flaw detection and the internal quality are difficult to ensure because special process control is not carried out.
Disclosure of Invention
The invention aims to provide an extra-thick steel plate with excellent core low-temperature impact toughness and a manufacturing method thereof, which are used for solving the problems in the prior art.
The invention is realized by the following technical scheme: an extra-thick steel plate with excellent core low-temperature impact toughness is characterized in that: the super-thick plate comprises the following components in percentage by mass: c:0.12-0.16%; si:0.20-0.40%; mn:1.40-1.60%; nb:0.015-0.040%; ti:0.008-0.025%; alt:0.020-0.050%; cu:0.10-0.30%; ni:0.15-0.40%; p: less than or equal to 0.012%; s: less than or equal to 0.003%; n: less than or equal to 0.0050%; o: less than or equal to 0.0040 percent; h: less than or equal to 0.0002 percent; the balance of Fe and unavoidable impurities.
Further: the super-thick plate comprises the following components in percentage by mass: c:0.13-0.14%; si:0.25-0.27%; mn:1.52-1.55%; nb:0.021-0.025%; ti:0.011-0.013%; alt:0.025-0.033%; cu:0.15-0.17%; ni:0.18-0.19%; p: less than or equal to 0.010 percent; s: less than or equal to 0.002%; n: less than or equal to 0.0038 percent; o: less than or equal to 0.0032 percent; h: less than or equal to 0.00014 percent; the balance of Fe and unavoidable impurities.
The other technical scheme of the invention is as follows: the manufacturing method of the ultra-thick steel plate with excellent core low-temperature impact toughness comprises the steps of continuous casting billet smelting, continuous casting billet heating, steel plate rolling, steel plate stacking slow cooling, steel plate normalizing and steel plate tempering, and is characterized in that:
1) Smelting continuous casting billets: molten iron is subjected to pretreatment, desulfurization and slag skimming, refining treatment of an LF furnace and an RH furnace, electromagnetic stirring and end heavy pressing in the continuous casting process are carried out, constant-pulling-speed production is carried out, the pulling speed is 0.45 m/min-0.60 m/min, the superheat degree is 15-30 ℃, the ultra-thick continuous casting blank with the thickness of 450-475 mm is adopted, and the continuous casting blank is stacked and slowly cooled;
2) Heating a continuous casting blank: cooling the continuous casting blank into a furnace, heating the continuous casting blank in a step beam type heating furnace in sections, wherein the temperature of a first section is 900-1040 ℃, the temperature of a second section is 1020-1140 ℃, the temperature of a third section is 1130-1200 ℃, the temperature of a soaking section is 1150-1180 ℃, and the heating time of the continuous casting blank in the furnace is 500-650 min;
3) Rolling a steel plate: the rough rolling is carried out in two stages of transverse rolling and longitudinal rolling, the initial rolling temperature is 1040-1090 ℃, after transverse rolling is finished, a water cooling device is started to carry out forced cooling, the surface temperature of a continuous casting billet is rapidly cooled to 830-870 ℃, a temperature difference is generated between the surface and the core of the continuous casting billet, rolling deformation is promoted to be deep into the core of a steel plate, the core is fully recrystallized to refine grains, longitudinal rolling is carried out after water cooling, low-speed large-pressure rolling is adopted in the longitudinal rolling, the single-pass rolling reduction is 35-70 mm, the total longitudinal rolling reduction is 80-120 mm, and the rolling speed is controlled to be 0.80-1.50 m/s; the water spraying cooling device is started at intervals of rolling pass, the surface temperature of the steel plate is reduced, the temperature difference between the surface and the core is kept, and the thickness of the intermediate billet after rough rolling is +50mm-80 mm of the thickness of the finished steel plate; starting a water cooling device to forcedly cool the intermediate blank in the process of waiting for temperature, rapidly cooling the surface temperature to 800-830 ℃, then performing finish rolling, starting a water spray cooling device at intervals of finish rolling passes, controlling the finish rolling speed to be 1.00-2.00 m/s, and controlling the finish rolling finishing temperature to be 810-840 ℃; the rolled steel plate is cooled by water, the water quantity is 120m m/h-140 m m/h, the number of water groups is 15-22, the water cooling roller speed is 0.4-1.0 m/s, the steel plate returns to red for more than 90s after water cooling, and the temperature of returning to red is 650-690 ℃;
4) Stacking and slow cooling of steel plates: the temperature for the initial stacking and slow cooling of the steel plates is 500-600 ℃, and the stacking and slow cooling time is more than 72 hours;
5) Normalizing the steel plate: normalizing treatment is carried out by adopting a continuous heat treatment furnace, wherein the first-stage temperature is 840 ℃, the second-stage temperature is 850 ℃, the third-stage temperature is 860 ℃, the fourth-stage temperature is 870 ℃, the fifth-stage temperature is 880 ℃, the sixth-stage temperature to the ninth-stage temperature are 890 ℃, and the total furnace time of the steel plate is as follows: (1.6-2.0). Times.the thickness of the steel plate is min. The steel plate is cooled by weak water cooling after being discharged from the furnace, the temperature of the steel plate returns to 620 ℃ to 650 ℃ after the steel plate is cooled by weak water cooling, and then the steel plate is cooled to room temperature by air cooling;
6) Tempering a steel plate: the tempering temperature is 550-580 ℃, and the total in-furnace tempering time is as follows: (2.5-3.5) the thickness of the steel plate is multiplied by min, and the steel plate is cooled to room temperature after being tempered and taken out of the furnace.
Further: the thickness of the super-thick plate is 170-200 mm.
Further: the metallographic structure of the extra-thick plate is ferrite and pearlite, and the grain size at the 1/4 position and the 1/2 position of the thickness is more than or equal to 7.5 level.
The invention has the advantages that: the 170-200 mm extra thick plate produced by the method has the thickness of 1/4 and 1/2 of the core position, the impact value at minus 60 ℃ is more than or equal to 88J, the core grain size is thinned to 7.5 level by increasing the supercooling degree, reducing the phase transition temperature, thinning ferrite grains and reducing the lamellar spacing of pearlite, the defects of continuous casting blanks such as loose core, shrinkage cavity and the like are fully healed in the rolling process, and the flaw detection result meets the standard requirements of NB/T47013.3-2015 and grade HI.
Drawings
The example of FIG. 1 shows a microstructure at 1/4 of the thickness of the steel sheet.
FIG. 2 shows the microstructure at 1/2 of the thickness of the steel plate according to the example.
Detailed Description
The invention discloses an extra-thick steel plate with excellent core low-temperature impact toughness, which comprises the following components in percentage by mass: c:0.12-0.16%; si:0.20-0.40%; mn:1.40-1.60%; nb:0.015-0.040%; ti:0.008-0.025%; alt:0.020-0.050%; cu:0.10-0.30%; ni:0.15-0.40%; p: less than or equal to 0.012%; s: less than or equal to 0.003%; n: less than or equal to 0.0050%; o: less than or equal to 0.0040 percent; h: less than or equal to 0.0002 percent; the balance of Fe and unavoidable impurities.
Preferably: the super-thick plate comprises the following components in percentage by mass: c:0.13-0.14%; si:0.25-0.27%; mn:1.52-1.55%; nb:0.021-0.025%; ti:0.011-0.013%; alt:0.025-0.033%; cu:0.15-0.17%; ni:0.18-0.19%; p: less than or equal to 0.010 percent; s: less than or equal to 0.002%; n: less than or equal to 0.0038 percent; o: less than or equal to 0.0032 percent; h: less than or equal to 0.00014 percent; the balance of Fe and unavoidable impurities.
The invention also discloses a manufacturing method of the super-thick steel plate with excellent core low-temperature impact toughness, which comprises the steps of continuous casting billet smelting, continuous casting billet heating, steel plate rolling, steel plate stacking slow cooling, steel plate normalizing and steel plate tempering, wherein:
1) Smelting continuous casting billets: molten iron is subjected to pretreatment, desulfurization and slag skimming, refining treatment of an LF furnace and an RH furnace, electromagnetic stirring and end heavy pressing in the continuous casting process are carried out, constant-pulling-speed production is carried out, the pulling speed is 0.45 m/min-0.60 m/min, the superheat degree is 15-30 ℃, the ultra-thick continuous casting blank with the thickness of 450-475 mm is adopted, and the continuous casting blank is stacked and slowly cooled;
2) Heating a continuous casting blank: cooling the continuous casting blank into a furnace, heating the continuous casting blank in a step beam type heating furnace in sections, wherein the temperature of a first section is 900-1040 ℃, the temperature of a second section is 1020-1140 ℃, the temperature of a third section is 1130-1200 ℃, the temperature of a soaking section is 1150-1180 ℃, and the heating time of the continuous casting blank in the furnace is 500-650 min;
3) Rolling a steel plate: the rough rolling is carried out in two stages of transverse rolling and longitudinal rolling, the initial rolling temperature is 1040-1090 ℃, after transverse rolling is finished, a water cooling device is started to carry out forced cooling, the surface temperature of a continuous casting billet is rapidly cooled to 830-870 ℃, a temperature difference is generated between the surface and the core of the continuous casting billet, rolling deformation is promoted to be deep into the core of a steel plate, the core is fully recrystallized to refine grains, longitudinal rolling is carried out after water cooling, low-speed large-pressure rolling is adopted in the longitudinal rolling, the single-pass rolling reduction is 35-70 mm, the total longitudinal rolling reduction is 80-120 mm, and the rolling speed is controlled to be 0.80-1.50 m/s; the water spraying cooling device is started at intervals of rolling pass, the surface temperature of the steel plate is reduced, the temperature difference between the surface and the core is kept, and the thickness of the intermediate billet after rough rolling is +50mm-80 mm of the thickness of the finished steel plate; starting a water cooling device to forcedly cool the intermediate blank in the process of waiting for temperature, rapidly cooling the surface temperature to 800-830 ℃, then performing finish rolling, starting a water spray cooling device at intervals of finish rolling passes, controlling the finish rolling speed to be 1.00-2.00 m/s, and controlling the finish rolling finishing temperature to be 810-840 ℃; the rolled steel plate is subjected to water cooling to reduce the phase transition temperature of the core part of the steel plate, refine ferrite grains and reduce the lamellar spacing of pearlite, the water quantity is 120m to 140 to m W/h, the water quantity is 15 to 22, the water cooling roller speed is 0.4 to 1.0m/s, the steel plate returns to red for more than 90s after water cooling, and the return red temperature is 650 to 690 ℃;
4) Stacking and slow cooling of steel plates: the temperature for the initial stacking and slow cooling of the steel plates is 500-600 ℃, and the stacking and slow cooling time is more than 72 hours;
5) Normalizing the steel plate: normalizing treatment is carried out by adopting a continuous heat treatment furnace, wherein the first-stage temperature is 840 ℃, the second-stage temperature is 850 ℃, the third-stage temperature is 860 ℃, the fourth-stage temperature is 870 ℃, the fifth-stage temperature is 880 ℃, the sixth-stage temperature to the ninth-stage temperature are 890 ℃, and the total furnace time of the steel plate is as follows: (1.6-2.0). Times.the thickness of the steel plate is min. The steel plate is cooled by weak water cooling after being discharged from the furnace, the temperature of the steel plate returns to 620 ℃ to 650 ℃ after the steel plate is cooled by weak water cooling, and then the steel plate is cooled to room temperature by air cooling;
6) Tempering a steel plate: the tempering temperature is 550-580 ℃, and the total in-furnace tempering time is as follows: (2.5-3.5) the thickness of the steel plate is multiplied by min, and the steel plate is cooled to room temperature after being tempered and taken out of the furnace.
Wherein: the thickness of the super-thick plate is 170-200 mm.
And (3) carrying out metallographic detection on the steel plate, wherein as shown in fig. 1 and 2, the metallographic structure of the extra-thick steel plate is ferrite and pearlite, the pearlite is precipitated in a block shape along grain boundaries, the grain size at the 1/2 center position of the thickness reaches 7.5 level, the ferrite is tiny and uniform, the defects of loose center, shrinkage cavity and the like are fully healed in the rolling process, and the excellent low-temperature toughness of the center is obtained.
The following further illustrates the embodiments of the present invention by way of specific examples:
adopting an extra-thick continuous casting blank with the thickness of 450-475 mm to finish the steps of continuous casting blank smelting, steel plate rolling, steel plate normalizing, steel plate tempering and the like.
The present embodiment includes 3 specific examples, respectively denoted by the numbers 1, 2, and 3, and the specific examples are as follows:
the actual chemical composition of this example is shown in Table 1.
TABLE 1 chemical composition (wt.%)
| Sequence number | C | Si | Mn | P | S | Alt | Nb | Ti | Cu | Ni | H | O | N |
| 1 | 0.13 | 0.27 | 1.53 | 0.010 | 0.002 | 0.030 | 0.021 | 0.011 | 0.15 | 0.18 | 0.00013 | 0.0025 | 0.0035 |
| 2 | 0.14 | 0.26 | 1.52 | 0.010 | 0.001 | 0.025 | 0.025 | 0.013 | 0.17 | 0.19 | 0.00010 | 0.0032 | 0.0038 |
| 3 | 0.13 | 0.25 | 1.55 | 0.009 | 0.002 | 0.033 | 0.023 | 0.011 | 0.16 | 0.18 | 0.00014 | 0.0030 | 0.0032 |
The rolling and heat treatment process of the extra-thick plate comprises heating, rough rolling, finish rolling, controlled cooling, stacking slow cooling, normalizing, tempering and the like, wherein the technological parameters of the heating stage are as follows:
TABLE 2 heating process parameters
| Sequence number | One-stage temperature DEG C | The temperature of the secondary section is DEG C | Temperature of the three-stage heating | The temperature of the soaking section is DEG C | Heating time min |
| 1 | 927 | 1110 | 1180 | 1165 | 558 |
| 2 | 925 | 1105 | 1170 | 1160 | 565 |
| 3 | 930 | 1118 | 1175 | 1162 | 570 |
The process parameters of the rough rolling stage are as follows:
TABLE 3 roughing Rolling Process parameters
| Sequence number | The initial rolling temperature is DEG C | Water cooling device | Single pass reduction in longitudinal rolling | Longitudinal rolling pass | Start temperature of longitudinal rolling (slab surface) | Total rolling reduction of mm | Rolling speed m/s |
| 1 | 1055 | Opening the valve | 47-45 | 2 | 840 | 92 | 1.20 |
| 2 | 1057 | Opening the valve | 48-46 | 2 | 838 | 94 | 1.15 |
| 3 | 1060 | Opening the valve | 49-45 | 2 | 845 | 94 | 1.20 |
The process parameters of the finish rolling stage are as follows:
TABLE 4 finish rolling parameters
| Sequence number | Thickness of the heated material is mm | Water cooling device | Finish rolling start temperature ℃ (slab surface) | Finish rolling speed m/s | Finish rolling finishing temperature °c |
| 1 | 230 | Opening the valve | 805 | 1.65 | 831 |
| 2 | 240 | Opening the valve | 809 | 1.65 | 835 |
| 3 | 260 | Opening the valve | 812 | 1.60 | 830 |
The technological parameters of water cooling and stacking of the steel plates are as follows:
TABLE 5 Water cooling and stacking Process parameters
| Sequence number | Water yield m cm/h | Number of water groups | Roller speed m/s | Time to redback s | Temperature of reddening °c | Stacking initiation temperature °c | Stacking time h |
| 1 | 120 | 20 | 0.5 | 120 | 672 | 526 | 82 |
| 2 | 125 | 20 | 0.5 | 120 | 679 | 535 | 82 |
| 3 | 130 | 20 | 0.5 | 120 | 685 | 540 | 85 |
And in the normalizing process, each heating section is heated by adopting stepped temperature, the first-section temperature is 840 ℃, the second-section temperature is 850 ℃, the third-section temperature is 860 ℃, the fourth-section temperature is 870 ℃, the fifth-section temperature is 880 ℃, the six-section temperature to the nine-section temperature are 890 ℃, the steel plate is cooled by adopting weak water cooling after being discharged from the furnace, then the steel plate is cooled to room temperature by air, and then tempering heat treatment is carried out. The normalizing and tempering process parameters are as follows:
TABLE 6 normalizing and tempering process parameters
| Sequence number | Normalizing total in-furnace time min | Weak water cooling redback temp | Tempering temperature (DEG C) | Tempering in furnace time min |
| 1 | 306 | 635 | 570 | 510 |
| 2 | 324 | 638 | 570 | 540 |
| 3 | 360 | 640 | 570 | 600 |
Through inspection, the comprehensive performance of the steel plate at the 1/4 position and the 1/2 center position is good, wherein 305MPa is less than or equal to ReH (yield strength) is less than or equal to 325MPa, 490MPa is less than or equal to Rm (tensile strength) is less than or equal to 512MPa, A (elongation after break) is more than or equal to 23.0%, the impact value at the 1/2 center position is more than or equal to 88J at-60 ℃, the grain size at the 1/4 position is 8.0 level, the grain size at the 1/2 center position is 7.5 level, the metallographic structure is ferrite and pearlite, the center structure is uniformly refined, the flaw detection result meets the standard requirements of 'NB/T47013.3-2015 and TII level', and the specific inspection result is as follows:
TABLE 7 test results
The above examples are merely illustrative of the best modes of carrying out the invention and do not limit the scope of the invention in any way.
Claims (5)
1. An extra-thick steel plate with excellent core low-temperature impact toughness is characterized in that: the super-thick plate comprises the following components in percentage by mass: c:0.12-0.16%; si:0.20-0.40%; mn:1.40-1.60%; nb:0.015-0.040%; ti:0.008-0.025%; alt:0.020-0.050%; cu:0.10-0.30%; ni:0.15-0.40%; p: less than or equal to 0.012%; s: less than or equal to 0.003%; n: less than or equal to 0.0050%; o: less than or equal to 0.0040 percent; h: less than or equal to 0.0002 percent; the balance of Fe and unavoidable impurities;
the steel plate is prepared by the following steps:
the method comprises the steps of continuous casting billet smelting, continuous casting billet heating, steel plate rolling, steel plate stacking slow cooling, steel plate normalizing and steel plate tempering, wherein:
1) Smelting continuous casting billets: molten iron is subjected to pretreatment, desulfurization and slag skimming, refining treatment of an LF furnace and an RH furnace, electromagnetic stirring and end heavy pressing in the continuous casting process are carried out, constant-pulling-speed production is carried out, the pulling speed is 0.45 m/min-0.60 m/min, the superheat degree is 15-30 ℃, the ultra-thick continuous casting blank with the thickness of 450-475 mm is adopted, and the continuous casting blank is stacked and slowly cooled;
2) Heating a continuous casting blank: cooling the continuous casting blank into a furnace, heating the continuous casting blank in a step beam type heating furnace in sections, wherein the temperature of a first section is 900-1040 ℃, the temperature of a second section is 1020-1140 ℃, the temperature of a third section is 1130-1200 ℃, the temperature of a soaking section is 1150-1180 ℃, and the heating time of the continuous casting blank in the furnace is 500-650 min;
3) Rolling a steel plate: the rough rolling is carried out in two stages of transverse rolling and longitudinal rolling, the initial rolling temperature is 1040-1090 ℃, after transverse rolling is finished, a water cooling device is started to carry out forced cooling, the surface temperature of a continuous casting billet is rapidly cooled to 830-870 ℃, a temperature difference is generated between the surface and the core of the continuous casting billet, rolling deformation is promoted to be deep into the core of a steel plate, the core is fully recrystallized to refine grains, longitudinal rolling is carried out after water cooling, low-speed large-pressure rolling is adopted in the longitudinal rolling, the single-pass rolling reduction is 35-70 mm, the total longitudinal rolling reduction is 80-120 mm, and the rolling speed is controlled to be 0.80-1.50 m/s; the water spraying cooling device is started at intervals of rolling pass, the surface temperature of the steel plate is reduced, the temperature difference between the surface and the core is kept, and the thickness of the intermediate billet after rough rolling is +50mm-80 mm of the thickness of the finished steel plate; starting a water cooling device to forcedly cool the intermediate blank in the process of waiting for temperature, rapidly cooling the surface temperature to 800-830 ℃, then performing finish rolling, starting a water spray cooling device at intervals of finish rolling passes, controlling the finish rolling speed to be 1.00-2.00 m/s, and controlling the finish rolling finishing temperature to be 810-840 ℃; the rolled steel plate is cooled by water, the water quantity is 120m m/h-140 m m/h, the number of water groups is 15-22, the water cooling roller speed is 0.4-1.0 m/s, the steel plate returns to red for more than 90s after water cooling, and the temperature of returning to red is 650-690 ℃;
4) Stacking and slow cooling of steel plates: the temperature for the initial stacking and slow cooling of the steel plates is 500-600 ℃, and the stacking and slow cooling time is more than 72 hours;
5) Normalizing the steel plate: normalizing treatment is carried out by adopting a continuous heat treatment furnace, wherein the first-stage temperature is 840 ℃, the second-stage temperature is 850 ℃, the third-stage temperature is 860 ℃, the fourth-stage temperature is 870 ℃, the fifth-stage temperature is 880 ℃, the sixth-stage temperature to the ninth-stage temperature are 890 ℃, and the total furnace time minutes of the steel plate are as follows: (1.6-2.0) x the thickness of the steel plate in millimeters; the steel plate is cooled by weak water cooling after being discharged from the furnace, the temperature of the steel plate returns to 620 ℃ to 650 ℃ after the steel plate is cooled by weak water cooling, and then the steel plate is cooled to room temperature by air cooling;
6) Tempering a steel plate: the tempering temperature is 550-580 ℃, and the total number of minutes in the furnace is: (2.5-3.5) multiplied by the thickness millimeter of the steel plate, and air cooling to room temperature after tempering and discharging.
2. The ultra-thick steel plate excellent in low-temperature impact toughness of a core according to claim 1, wherein: the super-thick plate comprises the following components in percentage by mass: c:0.13-0.14%; si:0.25-0.27%; mn:1.52-1.55%; nb:0.021-0.025%; ti:0.011-0.013%; alt:0.025-0.033%; cu:0.15-0.17%; ni:0.18-0.19%; p: less than or equal to 0.010 percent; s: less than or equal to 0.002%; n: less than or equal to 0.0038 percent; o: less than or equal to 0.0032 percent; h: less than or equal to 0.00014 percent; the balance of Fe and unavoidable impurities.
3. The method for producing an extra thick steel plate excellent in core low temperature impact toughness according to claim 1 or 2, comprising the steps of continuous casting billet smelting, continuous casting billet heating, steel plate rolling, steel plate stacking slow cooling, steel plate normalizing, steel plate tempering, characterized in that:
1) Smelting continuous casting billets: molten iron is subjected to pretreatment, desulfurization and slag skimming, refining treatment of an LF furnace and an RH furnace, electromagnetic stirring and end heavy pressing in the continuous casting process are carried out, constant-pulling-speed production is carried out, the pulling speed is 0.45 m/min-0.60 m/min, the superheat degree is 15-30 ℃, the ultra-thick continuous casting blank with the thickness of 450-475 mm is adopted, and the continuous casting blank is stacked and slowly cooled;
2) Heating a continuous casting blank: cooling the continuous casting blank into a furnace, heating the continuous casting blank in a step beam type heating furnace in sections, wherein the temperature of a first section is 900-1040 ℃, the temperature of a second section is 1020-1140 ℃, the temperature of a third section is 1130-1200 ℃, the temperature of a soaking section is 1150-1180 ℃, and the heating time of the continuous casting blank in the furnace is 500-650 min;
3) Rolling a steel plate: the rough rolling is carried out in two stages of transverse rolling and longitudinal rolling, the initial rolling temperature is 1040-1090 ℃, after transverse rolling is finished, a water cooling device is started to carry out forced cooling, the surface temperature of a continuous casting billet is rapidly cooled to 830-870 ℃, a temperature difference is generated between the surface and the core of the continuous casting billet, rolling deformation is promoted to be deep into the core of a steel plate, the core is fully recrystallized to refine grains, longitudinal rolling is carried out after water cooling, low-speed large-pressure rolling is adopted in the longitudinal rolling, the single-pass rolling reduction is 35-70 mm, the total longitudinal rolling reduction is 80-120 mm, and the rolling speed is controlled to be 0.80-1.50 m/s; the water spraying cooling device is started at intervals of rolling pass, the surface temperature of the steel plate is reduced, the temperature difference between the surface and the core is kept, and the thickness of the intermediate billet after rough rolling is +50mm-80 mm of the thickness of the finished steel plate; starting a water cooling device to forcedly cool the intermediate blank in the process of waiting for temperature, rapidly cooling the surface temperature to 800-830 ℃, then performing finish rolling, starting a water spray cooling device at intervals of finish rolling passes, controlling the finish rolling speed to be 1.00-2.00 m/s, and controlling the finish rolling finishing temperature to be 810-840 ℃; the rolled steel plate is cooled by water, the water quantity is 120m m/h-140 m m/h, the number of water groups is 15-22, the water cooling roller speed is 0.4-1.0 m/s, the steel plate returns to red for more than 90s after water cooling, and the temperature of returning to red is 650-690 ℃;
4) Stacking and slow cooling of steel plates: the temperature for the initial stacking and slow cooling of the steel plates is 500-600 ℃, and the stacking and slow cooling time is more than 72 hours;
5) Normalizing the steel plate: normalizing treatment is carried out by adopting a continuous heat treatment furnace, wherein the first-stage temperature is 840 ℃, the second-stage temperature is 850 ℃, the third-stage temperature is 860 ℃, the fourth-stage temperature is 870 ℃, the fifth-stage temperature is 880 ℃, the sixth-stage temperature to the ninth-stage temperature are 890 ℃, and the total furnace time minutes of the steel plate are as follows: (1.6-2.0) x the thickness of the steel plate in millimeters; the steel plate is cooled by weak water cooling after being discharged from the furnace, the temperature of the steel plate returns to 620 ℃ to 650 ℃ after the steel plate is cooled by weak water cooling, and then the steel plate is cooled to room temperature by air cooling;
6) Tempering a steel plate: the tempering temperature is 550-580 ℃, and the total number of minutes in the furnace is: (2.5-3.5) multiplied by the thickness millimeter of the steel plate, and air cooling to room temperature after tempering and discharging.
4. The method for producing a super-thick steel plate excellent in low-temperature impact toughness at a core as set forth in claim 3, wherein: the thickness of the super-thick plate is 170-200 mm.
5. The method for producing a super-thick steel plate excellent in low-temperature impact toughness at a core as set forth in claim 3, wherein: the metallographic structure of the extra-thick plate is ferrite and pearlite, and the grain size at the 1/4 position and the 1/2 position of the thickness is more than or equal to 7.5 level.
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