CN116770198A - Steel plate for low-compression-ratio hydropower and preparation method thereof - Google Patents
Steel plate for low-compression-ratio hydropower and preparation method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 145
- 239000010959 steel Substances 0.000 title claims abstract description 145
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 238000001816 cooling Methods 0.000 claims abstract description 104
- 238000005096 rolling process Methods 0.000 claims abstract description 67
- 238000007906 compression Methods 0.000 claims abstract description 58
- 238000009749 continuous casting Methods 0.000 claims abstract description 37
- 230000006835 compression Effects 0.000 claims abstract description 29
- 238000005496 tempering Methods 0.000 claims abstract description 21
- 238000003723 Smelting Methods 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000007600 charging Methods 0.000 claims abstract description 9
- 238000000034 method Methods 0.000 claims description 25
- 230000009467 reduction Effects 0.000 claims description 23
- 229910001563 bainite Inorganic materials 0.000 claims description 18
- 239000000126 substance Substances 0.000 claims description 15
- 239000012535 impurity Substances 0.000 claims description 14
- 230000035945 sensitivity Effects 0.000 claims description 14
- 229910000859 α-Fe Inorganic materials 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 10
- 238000005204 segregation Methods 0.000 claims description 9
- 238000005266 casting Methods 0.000 claims description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims description 8
- 229910052698 phosphorus Inorganic materials 0.000 claims description 8
- 238000004321 preservation Methods 0.000 claims description 8
- 229910052720 vanadium Inorganic materials 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 229910052717 sulfur Inorganic materials 0.000 claims description 7
- 238000001514 detection method Methods 0.000 abstract description 10
- 230000007547 defect Effects 0.000 abstract description 7
- 238000005457 optimization Methods 0.000 abstract description 5
- 239000002994 raw material Substances 0.000 abstract description 4
- 229910045601 alloy Inorganic materials 0.000 abstract description 2
- 239000000956 alloy Substances 0.000 abstract description 2
- 238000010583 slow cooling Methods 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 30
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 10
- 230000008569 process Effects 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- 238000007670 refining Methods 0.000 description 7
- 238000006477 desulfuration reaction Methods 0.000 description 6
- 230000023556 desulfurization Effects 0.000 description 6
- 238000003466 welding Methods 0.000 description 6
- 238000013461 design Methods 0.000 description 5
- 230000005611 electricity Effects 0.000 description 5
- 238000009863 impact test Methods 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 230000002411 adverse Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 241001062472 Stokellia anisodon Species 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
-
- 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
-
- 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
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with 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
- C21D2211/002—Bainite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Abstract
The invention relates to the technical field of alloys, in particular to a low-compression-ratio steel plate for hydropower and a preparation method thereof. According to the preparation method of the low-compression-ratio hydroelectric steel plate, smelting and continuous casting are carried out on raw materials of the low-compression-ratio hydroelectric steel plate to obtain a continuous casting blank, then stacking and slow cooling, charging and heating, dephosphorization treatment are carried out to obtain a plate blank, first-stage rolling is carried out after primary quick cooling, second-stage quick cooling and second-stage rolling are carried out, and finally water cooling, tempering and air cooling are carried out to obtain the low-compression-ratio hydroelectric steel plate. The invention controls the quality of continuous casting billets, is matched with the optimization of a rolling process, and under the condition of the compression ratio of 2.3-3.2, the flaw detection of the steel plate meets the 1-grade standard in NB/T47013, and the steel plate for low-compression ratio hydropower has no defect in the center and good low-temperature toughness.
Description
Technical Field
The invention relates to the technical field of alloys, in particular to a low-compression-ratio steel plate for hydropower and a preparation method thereof.
Background
In order to meet the reduction requirement, the steel plate for the hydropower station pressure pipeline is required to have the requirements of large thickness, high strength, high toughness and easiness in welding, particularly, the bifurcated pipe and the crescent rib plate are required to bear three-way alternating stress in the service process, so that an extremely thick steel plate is required to be adopted, and higher requirements are simultaneously provided for the core toughness and Z-direction performance of the steel plate. Therefore, slabs of these extra-thick steel plates are usually produced by adopting a method of ingot casting or electroslag remelting, and thus cause problems of high price and long production period, which have great influence on the construction of hydropower stations. In order to solve the problems of high price and long production period, a common continuous casting blank can be adopted to produce the steel plate for large-thickness hydropower, but when the common continuous casting blank is adopted to produce the steel plate for large-thickness hydropower, the compression ratio is insufficient, deformation cannot penetrate into the core part, so that the problems of failure in welding of the center crack, coarse grains and failure in flaw detection and low center impact value are easily caused.
Chinese patent document CN114134407a discloses a steel plate for spiral case with excellent low-temperature toughness of easy-to-weld core and a manufacturing method thereof, which adopts ultra-low C and is assisted by Ni, mo, nb micro-alloyed component system and quenching and tempering process to produce a high-strength steel plate for ultra-thick hydropower station with finished thickness of 60-100 mm, however, the steel plate has higher compression ratio and lower strength. Therefore, how to produce a large-thickness steel sheet for hydropower with high strength and excellent internal quality using a conventional continuous casting slab under a low compression ratio condition is a difficult problem in the development of medium plate products.
Disclosure of Invention
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art of conventional continuous casting billets, and has as its object to overcome the disadvantages of the prior art of conventional continuous casting billets in that it is difficult to produce a large-thickness steel sheet for hydropower having high strength and excellent internal quality, thereby providing a steel sheet for hydropower having a low compression ratio and a method for manufacturing the same.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a preparation method of a low-compression-ratio steel plate for hydropower comprises the following steps:
1) Smelting and continuously casting the low-compression ratio steel plate for hydropower to obtain a continuous casting blank with the thickness of more than or equal to 300 mm; si in the continuous casting blank is less than or equal to 0.1%;
2) Stacking and slowly cooling the continuous casting billet obtained in the step 1), charging and heating to 1100-1150 ℃ and preserving heat for 370-420 min, and then carrying out dephosphorization treatment to obtain a slab; the center segregation of the slab is not higher than class C grade 0.5, and the center porosity is not higher than grade 0.5;
3) Performing primary quick cooling on the slab obtained in the step 2), forming a temperature gradient of 0.8-1.5 ℃/mm in the thickness direction through primary quick cooling, and performing first-stage rolling after primary quick cooling to obtain an intermediate billet, wherein the single-pass rolling reduction rate of the first-stage rolling is more than or equal to 12%, and the thickness of the intermediate billet is more than or equal to 245 mm; then performing secondary quick cooling on the intermediate blank, forming a temperature gradient of 0.5-0.8 ℃/mm in the thickness direction through the secondary quick cooling, and performing second-stage rolling after the secondary quick cooling to obtain a steel plate; the reduction rate of at least two passes in the second stage rolling is more than or equal to 18%, and the reduction rate of the last pass is 3-7%; the compression ratio of the steel plate is 2.3-3.2;
4) And (3) performing water cooling, tempering and air cooling on the steel plate obtained in the step (3) to obtain the low-compression-ratio steel plate for hydropower.
Preferably, the stack is slowly cooled to a strand temperature of 300 ℃ or less.
Preferably, the primary quick cooling is carried out until the surface temperature of the slab is 1000-1030 ℃, and the quick cooling speed is 10-15 ℃/s;
and/or the secondary rapid cooling is carried out until the surface temperature of the intermediate blank is 770-820 ℃, and the rapid cooling speed is 3-5 ℃/s.
Preferably, the smelting step includes: KR desulfurization, converter smelting, LF refining, RH treatment and pouring.
Preferably, the reddening temperature after rolling in the first stage is more than or equal to 1010 ℃;
and/or the final rolling temperature of the second stage rolling is 780-810 ℃.
Preferably, the cooling speed of the water cooling is 6-10 ℃/s, the final cooling temperature of the water cooling is less than or equal to 200 ℃, and the steel plate after water cooling is in a complex phase structure of acicular ferrite, lath bainite and Ma Ao.
Preferably, the tempering temperature is 600-670 ℃, and the tempering heat preservation coefficient is 2.5-3.0 min/mm.
Preferably, the thickness of the low-compression ratio hydroelectric steel plate is 100-140 mm.
The invention also provides a low-compression ratio steel plate for hydropower, which is prepared by the preparation method of the low-compression ratio steel plate for hydropower.
Specifically, the low-compression ratio steel plate for hydropower comprises the following chemical components in percentage by mass: c:0.04-0.06%, si: less than or equal to 0.1 percent, mn:1.15-1.35%, cr:0.1-0.25%, ni:0.10-0.25%, mo:0.15-0.3%, cu:0.15-0.35%, V:0.035-0.055%, nb:0.01-0.025%, al:0.02-0.04%, ti:0.01-0.03%, B:0.0006-0.0012%, the balance being Fe and unavoidable impurities; simultaneously satisfies: the carbon equivalent Ceq is less than or equal to 0.41 percent; the cold crack sensitivity index Pcm is less than or equal to 0.21 percent. The calculation formula of the carbon equivalent is Ceq=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14; the cold crack sensitivity index calculation formula is pcm=c+si/30+ (mn+cu+cr)/20+ni/60+mo/15+v/10+5b.
Preferably, the tensile strength of the steel plate for low-compression-ratio hydropower is more than or equal to 620 MPa;
and/or the thickness center impact value of the low-compression ratio steel plate for hydropower is more than or equal to 150J at the temperature of minus 40 ℃;
and/or, the content of acicular ferrite in the low-compression ratio steel plate for hydropower is 12-20%, the content of tempered bainite is 25-40% and the content of granular bainite is 40-55% by volume percent;
and/or, the impurities comprise H less than or equal to 0.00015%, P less than or equal to 0.010%, S less than or equal to 0.002%, O less than or equal to 0.0025%, and N less than or equal to 0.005%.
The invention adopts low segregation component design, the requirements of bonding strength, thickness of the steel plate and low crack sensitivity, adopts Cr, ni, mo and microalloy strengthening means, and obtains continuous casting blanks with good low-power tissues through KR desulfurization, LF refining and other means, thereby reducing the defects of center looseness, cracks and the like.
Based on the component optimization, the steel plate with the acicular ferrite content of 12-20%, the tempering bainite content of 25-40% and the granular bainite structure content of 40-55% is finally obtained through the optimization of the control rolling and heat treatment processes, the 610CF requirement is met, the impact value at the thickness center at-40 ℃ is more than or equal to 150J, the cold crack sensitivity index Pcm is less than or equal to 0.21%, the flaw detection meets the level 1 standard in NB/T47013, and the center is free from defects and has good low-temperature toughness. Under the condition that the compression ratio is 2.3-3.2, the requirements of the hydroelectric steel on field construction can be met, and the comprehensive performance is excellent.
The technical scheme of the invention has the following advantages:
1. a preparation method of a low-compression-ratio steel plate for hydropower comprises the following steps: 1) Smelting and continuously casting the low-compression ratio steel plate for hydropower to obtain a continuous casting blank with the thickness of more than or equal to 300 mm; si in the continuous casting blank is less than or equal to 0.1%; 2) Stacking and slowly cooling the continuous casting billet obtained in the step 1), charging and heating to 1100-1150 ℃ and preserving heat for 370-420 min, and then carrying out dephosphorization treatment to obtain a slab; the center segregation of the slab is not higher than class C grade 0.5, and the center porosity is not higher than grade 0.5; 3) Performing primary quick cooling on the slab obtained in the step 2), forming a temperature gradient of 0.8-1.5 ℃/mm in the thickness direction through primary quick cooling, and performing first-stage rolling after primary quick cooling to obtain an intermediate billet, wherein the single-pass rolling reduction rate of the first-stage rolling is more than or equal to 12%, and the thickness of the intermediate billet is more than or equal to 245 mm; then performing secondary quick cooling on the intermediate blank, forming a temperature gradient of 0.5-0.8 ℃/mm in the thickness direction through the secondary quick cooling, and performing second-stage rolling after the secondary quick cooling to obtain a steel plate; the reduction rate of at least two passes in the second stage rolling is more than or equal to 18%, and the reduction rate of the last pass is 3-7%; the compression ratio of the steel plate is 2.3-3.2; 4) And (3) performing water cooling, tempering and air cooling on the steel plate obtained in the step (3) to obtain the low-compression-ratio steel plate for hydropower. The method adopts the raw materials of the low-compression ratio hydropower steel plate to smelt to obtain good low-power tissues, thereby reducing the defects of loose center, cracks and the like. Specific:
obtaining a continuous casting blank with the thickness of more than 300 mm according to the design scheme of the chemical components of the raw materials of the steel plate for the hydropower with the low compression ratio, stacking and slowly cooling the continuous casting blank, then charging into a furnace for heating, and heating to 1100-1150 ℃ for heat preservation for 370-420 min; the low-temperature long-time heating is utilized, the sufficient burning-through of the slab is ensured, meanwhile, the excessive growth of austenite is ensured, the phenomenon of tilting and buckling of the head due to the non-burning-through of the slab in the rolling process is avoided, and the shape and the performance of a final product are ensured;
the dephosphorization treatment is carried out after the continuous casting billet is discharged, the low Si design of the continuous casting billet ensures the dephosphorization effect, and guarantees are provided for the uniform cooling of the subsequent slab; carrying out primary quick cooling after dephosphorization, and carrying out first-stage rolling after quick cooling to obtain an intermediate blank; the single-pass reduction rate of the first-stage rolling is more than or equal to 12 percent, and the thickness of the intermediate billet is more than or equal to 245 mm; in order to eliminate the defects of small rolling reduction and impermeable deformation, the first stage rolling belongs to austenite recrystallization zone rolling, and the deformation is concentrated at the center of a plate blank by forming a temperature gradient of 0.8-1.5 ℃/mm in the thickness direction through rapid cooling, so that the step is important for improving the flaw detection performance of the steel plate produced with low compression ratio;
then performing secondary quick cooling on the intermediate blank, forming a temperature gradient of 0.5-0.8 ℃/mm in the thickness direction through the secondary quick cooling, and performing second-stage rolling after the secondary quick cooling to obtain a steel plate; the second stage of rolling belongs to rolling in a non-recrystallized zone, and austenite is flattened through accumulated deformation, so that a larger surface area is obtained. The reduction rate of at least two passes in the second stage rolling is more than or equal to 18%, and the reduction rate of the last pass is 3-7%; the compression ratio of the steel plate is 2.3-3.2; the thickness of the intermediate blank plays an important role in improving the impact toughness of the steel plate, a temperature gradient of 0.5-0.8 ℃/mm in the thickness direction is obtained by utilizing a smaller cooling rate at the stage, and the thickness direction is uniformly deformed by large-pressure rolling, so that the impact toughness of the thickness center is improved; the small reduction is carried out in the last pass, so that the shape of the plate can be ensured, and the generation of wave shape and uneven cooling caused by the wave shape can be prevented; finally, the steel plate is subjected to water cooling, tempering and air cooling to obtain the low-compression-ratio steel plate for hydropower. The tempering process mainly ensures elimination of the Ma Ao complex phase structure of large particles and reduces the influence of the complex phase structure on impact toughness;
the method of the invention controls the quality of the continuous casting billet, is matched with the optimization of the rolling process, and under the condition of the compression ratio of 2.3-3.2, the obtained steel plate flaw detection meets the 1-grade standard in NB/T47013, and has good low-temperature toughness and no defect in the center.
2. The invention relates to a low-compression ratio hydropower steel plate, which adopts a low segregation component design, and adopts the requirements of bonding strength, steel plate thickness and low crack sensitivity to obtain a raw material chemical component design scheme of the low-compression ratio hydropower steel plate; wherein the low-compression ratio steel plate for hydropower comprises the following chemical components in percentage by mass: c:0.04-0.06%, si: less than or equal to 0.1 percent, mn:1.15-1.35%, cr:0.1-0.25%, ni:0.10-0.25%, mo:0.15-0.3%, cu:0.15-0.35%, V:0.035-0.055%, nb:0.01-0.025%, al:0.02-0.04%, ti:0.01-0.03%, B:0.0006-0.0012%, and the balance of Fe and unavoidable impurities, wherein the impurities comprise H less than or equal to 0.00015%, P less than or equal to 0.010%, S less than or equal to 0.002%, O less than or equal to 0.0025%, and N less than or equal to 0.005%, and simultaneously the following conditions are satisfied: carbon equivalent Ceq=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14 is less than or equal to 0.41%; cold crack sensitivity index pcm=c+si/30+ (mn+cu+cr)/20+ni/60+mo/15+v/10+5b is less than or equal to 0.21%; the crack sensitivity coefficient of the low-compression-ratio hydroelectric steel plate prepared by the invention is lower, the tensile strength is more than or equal to 650 MPa, the flaw detection meets the 1-level standard in NB/T47013, the thickness center impact value of the steel plate at-40 ℃ is more than or equal to 150J, the center has no crack defect and good low-temperature toughness, and even under the condition of low compression ratio, the requirements of the hydroelectric steel in field construction are met;
the optimization mechanism of each chemical component of the low-compression-ratio hydroelectric steel plate is as follows:
C. mn: both elements are important components for improving the strength and hardenability of the steel plate; the steel plate for hydropower needs field operation, and has very high requirements on carbon equivalent and cold crack sensitivity coefficient; in order to achieve the strength and good welding performance of the steel plate, the C content is controlled to be between 0.04 and 0.06 percent, and the Mn content is controlled to be between 1.15 and 1.35 percent;
si: si is used as deoxidizing element, and the strength of the material is improved through solid solution strengthening, but Si has adverse effect on the surface dephosphorization of the slab, so that the Si content is controlled to be less than or equal to 0.1 percent;
cr, mo: cr and Mo can effectively improve the hardenability of the material, and simultaneously expand the tempering process window, thereby being beneficial to the expansion of the process window and having important influence on the center hardenability of the steel plate with large thickness; however, if the content is too high, crack sensitivity and carbon equivalent of the material are greatly improved, and toughness of a welding heat affected zone is reduced; therefore, the invention controls the Cr content to be 0.1-0.25% and the Mo content to be 0.15-0.3%;
cu: cu has strong precipitation strengthening effect in steel, and can obtain excellent low-temperature toughness while maintaining strength; the precipitation strengthening of Cu can effectively eliminate the strength loss caused by tissue softening in the high-temperature tempering process; however, when the Cu content is too high, surface cracks of the slab are easy to cause, and the welding performance is reduced, so that the Cu is controlled to be 0.15-0.35%;
ni: ni is a pure solid solution element in steel, and has obvious effect of reducing cold-brittle transition temperature; ni refines ferrite grains through adsorption in the grains, so that the impact toughness of the steel is improved; meanwhile, the reasonable collocation of Ni and Cu is favorable for alleviating surface cracks caused by Cu, but meanwhile, ni is used as noble metal, the cost is high, and the use amount of Ni is reduced as much as possible under the condition of meeting the use requirement; therefore, ni is controlled to be 0.10-0.25% in the invention;
b: mo-B combined action is beneficial to improving the hardenability of steel and improving the strength of the steel, but excessive B element segregates to austenite grain boundaries, and a large amount of carbide Fe is precipitated on the grain boundaries 23 (BC) 6 The grain boundary is strengthened, so that the grain boundary is difficult to deform, and the impact performance is not facilitated; therefore, in the invention, B is controlled to be 0.0006-0.0012%;
ti, nb, V: as a microalloy element, ti can obviously inhibit the growth of crystal grains in the heating process, weaken the generation of transverse microcracks on the surface, and simultaneously serve as nucleation points of Nb, thereby having positive effects on precipitation strengthening of Nb; nb plays an important role in refining grains after rolling and promoting acicular ferrite to generate in the welding process; in the high temperature tempering process, the precipitation of V (C, N) plays an important role in tempering stability. However, when the content is too high, the elongation and the yield ratio are adversely affected, so that the V is controlled to be 0.035-0.055%, the Nb is controlled to be 0.01-0.025%, the Al is controlled to be 0.02-0.04%, and the Ti is controlled to be 0.01-0.03%.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a method for producing a low compression ratio steel sheet for hydropower in examples 1 to 5 of the invention;
FIG. 2 is a photograph showing the microstructure of a continuous casting slab having a thickness of 320. 320 mm in example 1 of the present invention;
FIG. 3 is a photograph showing the center position of a steel sheet for low compression ratio hydropower prepared in example 1 of the present invention;
FIG. 4 is a photograph showing the center position of a steel sheet for low compression ratio hydropower use prepared in example 3 of the present invention.
Detailed Description
The following examples are provided for a better understanding of the present invention and are not limited to the preferred embodiments described herein, but are not intended to limit the scope of the invention, any product which is the same or similar to the present invention, whether in light of the present teachings or in combination with other prior art features, falls within the scope of the present invention.
The specific experimental procedures or conditions are not noted in the examples and may be followed by the operations or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
Example 1
The present embodiment provides a low-compression ratio steel sheet for hydropower having a thickness of 100 mm, comprising, in mass percent: c:0.043%, si:0.03%, mn:1.20%, cr:0.15%, ni:0.12%, mo:0.30%, cu:0.32%, V:0.040%, nb:0.015%, B:0.0007%, al:0.025%, ti:0.028%, the balance being iron and unavoidable impurities, said impurities comprising H.ltoreq.0.00015%, P.ltoreq.0.010%, S.ltoreq.0.002%, O.ltoreq.0.0025% and N.ltoreq.0.005%. The chemical composition in the steel sheet satisfies the carbon equivalent ceq=c+mn/6+si/24+ni/40+cr/5+mo/4+v/14=0.36%; cold crack sensitivity index pcm=c+si/30+ (mn+cu+cr)/20+ni/60+mo/15+v/10+5b=0.16%.
The preparation method of the low-compression-ratio hydroelectric steel plate with the thickness of 100 mm comprises the following steps as shown in the flow chart of fig. 1:
1) Smelting and continuously casting the low-compression ratio hydroelectric steel plate according to the chemical composition ratio to obtain a continuous casting blank, wherein the thickness of the continuous casting blank is 320 mm; the smelting step comprises the following steps: KR desulfurization, converter smelting, LF refining, RH treatment and pouring;
2) Slowly cooling the continuous casting billet stack obtained in the step 1) to 100 ℃, wherein the low-power structure of the continuous casting billet after stacking and slow cooling is shown in figure 2; then charging into a furnace and heating to 1120 ℃, keeping the furnace at the temperature for 380 min, and removing phosphorus after discharging to obtain a plate blank; the center segregation of the slab is class C0.5, and the center porosity is class 0.5;
3) Placing the slab obtained in the step 2) into an accelerated cooling device (Acc) for primary quick cooling until the surface temperature of the slab is 1020 ℃, the quick cooling speed is 10 ℃/s, the temperature gradient formed in the thickness direction is 1.0 ℃/mm, then performing first-stage rolling to obtain an intermediate slab, wherein the first-stage rolling comprises two passes, the first pass is performed to 280 mm, the second pass is performed to 245 mm, and the reddening temperature after rolling is 1020 ℃;
4) Putting the intermediate blank obtained in the step 3) into an accelerated cooling device (Acc) for secondary rapid cooling, wherein the surface temperature of the intermediate blank is 770 ℃, the rapid cooling speed is 4.8 ℃/s, the temperature gradient formed in the thickness direction is 0.7 ℃/mm, and then immediately rolling in a second stage to obtain a steel plate, wherein the reduction of the first two passes is 20% and 18%, the reduction of the last pass is 3%, and the final rolling temperature is 780 ℃;
5) And 4) water-cooling the steel plate obtained in the step 4) at a cooling speed of 10 ℃/s and a final cooling temperature of 200 ℃, then sending the steel plate into a tempering furnace, heating to 660 ℃ and preserving heat for 300 min, and finally cooling to room temperature in air to obtain the steel plate with the thickness of 100 mm for low compression ratio for hydropower.
The structure property of the steel sheet for low compression ratio water and electricity having the thickness of 100 mm was measured, wherein the content of acicular ferrite was 15%, the content of tempered bainite was 30%, and the content of granular bainite was 55%; the tensile strength is 670 MPa, the steel plate thickness center impact value is 172J at minus 40 ℃, the flaw detection meets the level 1 standard in NB/T47013, and the center structure of the steel plate for low compression ratio hydropower use of 100 mm is shown in figure 3.
The tensile strength test sample is obtained from a 1/4-width and 1/4-thickness steel plate according to GB/T2975, a sample blank perpendicular to the rolling direction is processed into a standard round section test sample, and the impact value test sample is obtained from a 1/4-thickness and 1/2-width steel plate according to GB/T2975, and is milled and ground into a standard impact value test sample with the section of 55 mm multiplied by 10 mm multiplied by 10 mm. The tensile strength is tested according to the method A of GB/T228.1, the impact value is measured according to the standard impact value of GB/T229, a test sample is placed into a low-temperature alcohol tank with the temperature of minus 40 ℃ for heat preservation for not less than 5 minutes, then the test sample is rapidly taken out and placed into an impact testing machine for breaking, and the time from the taking out of the alcohol tank to breaking is ensured to be not more than 5 seconds.
Example 2
The present embodiment provides a low-compression ratio steel sheet for hydropower having a thickness of 120 mm, comprising, in mass percent: c:0.057%, si:0.07%, mn:1.33%, cr:0.25%, ni:0.22%, mo:0.22%, cu:0.20%, V:0.052%, nb:0.024%, B:0.0008%, al:0.035%, ti:0.015 percent of Fe and the balance of unavoidable impurities, wherein the impurities comprise less than or equal to 0.00015 percent of H, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of S, less than or equal to 0.0025 percent of O and less than or equal to 0.005 percent of N. The chemical composition in the steel sheet satisfies the carbon equivalent ceq=c+mn/6+si/24+ni/40+cr/5+mo/4+v/14=0.40%; cold crack sensitivity index pcm=c+si/30+ (mn+cu+cr)/20+ni/60+mo/15+v/10+5b=0.18%.
The preparation method of the steel plate for low-compression-ratio hydropower comprises the following steps:
1) Smelting and continuously casting the low-compression ratio hydroelectric steel plate according to the chemical composition ratio to obtain a continuous casting blank, wherein the thickness of the continuous casting blank is 320 mm; the smelting step comprises the following steps: KR desulfurization, converter smelting, LF refining, RH treatment and pouring;
2) Slowly cooling the continuous casting billet stack prepared in the step 1) to 200 ℃, then charging into a furnace, heating to 1150 ℃, keeping the furnace at the temperature for 400 min, discharging, and performing dephosphorization treatment to obtain a slab; the center segregation of the slab is class C0.5, and the center porosity is class 0.5;
3) Placing the slab obtained in the step 2) into an accelerated cooling device (Acc) for primary quick cooling until the surface temperature of the slab is 1030 ℃, the quick cooling speed is 13 ℃/s, the temperature gradient formed in the thickness direction is 1.2 ℃/mm, then performing first-stage rolling to obtain an intermediate slab, wherein the first-stage rolling comprises two passes, the first pass is performed to 280 mm, the second pass is performed to 245 mm, and the reddening temperature after rolling is 1020 ℃;
4) Putting the intermediate blank obtained in the step 3) into an accelerated cooling device (Acc) for secondary rapid cooling, wherein the surface temperature of the intermediate blank is 800 ℃, the rapid cooling speed is 3.5 ℃/s, the temperature gradient formed in the thickness direction is 0.6 ℃/mm, and then immediately rolling in the second stage to obtain a steel plate, wherein the reduction of the first two passes is 18% and 18%, the reduction of the last pass is 3%, and the final rolling temperature is 805 ℃;
5) And 4) water-cooling the steel plate obtained in the step 4) at a cooling speed of 10 ℃/s and a final cooling temperature of 200 ℃, then sending the steel plate into a tempering furnace, heating to 640 ℃ and preserving heat for 340 min, and finally cooling to room temperature in air to obtain the steel plate with the thickness of 120 mm for low compression ratio for hydropower.
The steel sheet for low compression ratio water and electricity having the above thickness of 120 mm was examined for structural properties, wherein the content of acicular ferrite was 18%, the content of tempered bainite was 35%, and the content of granular bainite was 47%. The tensile strength is 665 MPa, the steel plate thickness center impact value is 166-J at-40 ℃, and the flaw detection meets the level 1 standard in NB/T47013.
The tensile strength test sample is obtained from a 1/4-width and 1/4-thickness steel plate according to GB/T2975, a sample blank perpendicular to the rolling direction is processed into a standard round section test sample, and the impact value test sample is obtained from a 1/4-thickness and 1/2-width steel plate according to GB/T2975, and is milled and ground into a standard impact value test sample with the section of 55 mm multiplied by 10 mm multiplied by 10 mm. The tensile strength is tested according to the method A of GB/T228.1, the impact value is measured according to the standard impact value of GB/T229, a test sample is placed into a low-temperature alcohol tank with the temperature of minus 40 ℃ for heat preservation for not less than 5 minutes, then the test sample is rapidly taken out and placed into an impact testing machine for breaking, and the time from the taking out of the alcohol tank to breaking is ensured to be not more than 5 seconds.
Example 3
This example provides a steel sheet for low compression ratio hydropower having a thickness of 140 a mm a, which is the same slab as in example 2 and has the same chemical composition as in example 2. The method for manufacturing the low compression ratio steel sheet for hydropower having a thickness of 140 a mm of this example is similar to the rolling method of example 2, except that the tempering temperature is 600 c and the heat is kept for 350 min.
The structure property of the steel sheet for low compression ratio water and electricity having the thickness of 140. 140 mm was measured, wherein the content of acicular ferrite was 16%, the content of tempered bainite was 38%, and the content of granular bainite was 46%; the tensile strength is 660 MPa, the thickness center impact value 155J of the steel plate at-40 ℃ meets the level 1 standard in NB/T47013, and the center structure of the low-compression ratio hydroelectric steel plate with the thickness of 140 mm is shown in FIG. 4.
The tensile strength test sample is obtained from a 1/4-width and 1/4-thickness steel plate according to GB/T2975, a sample blank perpendicular to the rolling direction is processed into a standard round section test sample, and the impact value test sample is obtained from a 1/4-thickness and 1/2-width steel plate according to GB/T2975, and is milled and ground into a standard impact value test sample with the section of 55 mm multiplied by 10 mm multiplied by 10 mm. The tensile strength is tested according to the method A of GB/T228.1, the impact value is measured according to the standard impact value of GB/T229, a test sample is placed into a low-temperature alcohol tank with the temperature of minus 40 ℃ for heat preservation for not less than 5 minutes, then the test sample is rapidly taken out and placed into an impact testing machine for breaking, and the time from the taking out of the alcohol tank to breaking is ensured to be not more than 5 seconds.
Example 4
The present embodiment provides a low-compression ratio steel sheet for hydropower having a thickness of 110 a mm, comprising, in mass percent: c:0.04%, si:0.1%, mn:1.15%, cr:0.15%, ni:0.1%, mo:0.15%, cu:0.15%, V:0.035%, nb:0.01%, B:0.0012%, al:0.02%, ti:0.01 percent of Fe and the balance of unavoidable impurities, wherein the impurities comprise less than or equal to 0.00015 percent of H, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of S, less than or equal to 0.0025 percent of O and less than or equal to 0.005 percent of N. The chemical composition in the steel sheet satisfies the carbon equivalent ceq=c+mn/6+si/24+ni/40+cr/5+mo/4+v/14=0.31%; cold crack sensitivity index pcm=c+si/30+ (mn+cu+cr)/20+ni/60+mo/15+v/10+5b=0.14%.
The preparation method of the steel plate for low-compression-ratio hydropower comprises the following steps:
1) Smelting and continuously casting the low-compression ratio hydroelectric steel plate according to the chemical composition ratio to obtain a continuous casting blank, wherein the thickness of the continuous casting blank is 320 mm; the smelting step comprises the following steps: KR desulfurization, converter smelting, LF refining, RH treatment and pouring;
2) Slowly cooling the continuous casting billet stack prepared in the step 1) to 100 ℃, then charging into a furnace, heating to 1150 ℃, keeping the furnace for 370 min, discharging, and performing dephosphorization treatment to obtain a slab; the center segregation of the slab is class C0.5, and the center porosity is class 0.5;
3) Placing the slab obtained in the step 2) into an accelerated cooling device (Acc) for primary quick cooling, wherein the surface temperature of the slab is 1000 ℃, the quick cooling speed is 10 ℃/s, the temperature gradient formed in the thickness direction is 0.9 ℃/mm, then rolling in the first stage to obtain an intermediate slab, rolling in the first stage, wherein the rolling in the first stage comprises two passes, rolling in the first pass to 280 mm, rolling in the second pass to 245 mm, and returning to the red temperature after rolling;
4) Putting the intermediate blank obtained in the step 3) into an accelerated cooling device (Acc) for secondary rapid cooling, wherein the surface temperature of the intermediate blank is 820 ℃, the rapid cooling speed is 5 ℃/s, the temperature gradient formed in the thickness direction is 0.5 ℃/mm, and then immediately performing second-stage rolling to obtain a steel plate, wherein the reduction of the first two passes is 18% and 18%, the reduction of the last pass is 7%, and the final rolling temperature is 810 ℃;
5) And 4) water-cooling the steel plate obtained in the step 4) at a cooling speed of 6 ℃/s and a final cooling temperature of 200 ℃, then sending the steel plate into a tempering furnace, heating to 670 ℃ and preserving heat for 280 minutes, and finally cooling to room temperature in air to obtain the steel plate with the thickness of 110 mm for low compression ratio for hydropower.
The structure property of the steel sheet for low compression ratio water and electricity having the thickness of 110. 110 mm was measured, wherein the content of acicular ferrite was 18%, the content of tempered bainite was 30%, and the content of granular bainite was 52%; the tensile strength is 620 MPa, the steel plate thickness center impact value at-40 ℃ is 160 and J, and the flaw detection meets the 1-level standard in NB/T47013.
The tensile strength test sample is obtained from a 1/4-width and 1/4-thickness steel plate according to GB/T2975, a sample blank perpendicular to the rolling direction is processed into a standard round section test sample, and the impact value test sample is obtained from a 1/4-thickness and 1/2-width steel plate according to GB/T2975, and is milled and ground into a standard impact value test sample with the section of 55 mm multiplied by 10 mm multiplied by 10 mm. The tensile strength is tested according to the method A of GB/T228.1, the impact value is measured according to the standard impact value of GB/T229, a test sample is placed into a low-temperature alcohol tank with the temperature of minus 40 ℃ for heat preservation for not less than 5 minutes, then the test sample is rapidly taken out and placed into an impact testing machine for breaking, and the time from the taking out of the alcohol tank to breaking is ensured to be not more than 5 seconds.
Example 5
The present embodiment provides a low-compression ratio steel sheet for hydropower having a thickness of 130, 130 mm, comprising, in mass percent: c:0.06%, si:0.05%, mn:1.35%, cr:0.1%, ni:0.25%, mo:0.15%, cu:0.35%, V:0.055%, nb:0.025%, B:0.0006%, al:0.04%, ti:0.03 percent of Fe and the balance of unavoidable impurities, wherein the impurities comprise less than or equal to 0.00015 percent of H, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of S, less than or equal to 0.0025 percent of O and less than or equal to 0.005 percent of N. The chemical composition in the steel sheet satisfies the carbon equivalent ceq=c+mn/6+si/24+ni/40+cr/5+mo/4+v/14=0.36%; cold crack sensitivity index pcm=c+si/30+ (mn+cu+cr)/20+ni/60+mo/15+v/10+5b=0.17%.
The preparation method of the steel plate for low-compression-ratio hydropower comprises the following steps:
1) Smelting and continuously casting the low-compression ratio hydroelectric steel plate according to the chemical composition ratio to obtain a continuous casting blank, wherein the thickness of the continuous casting blank is 320 mm; the smelting step comprises the following steps: KR desulfurization, converter smelting, LF refining, RH treatment and pouring;
2) Slowly cooling the continuous casting billet stack prepared in the step 1) to 100 ℃, then charging into a furnace, heating to 1100 ℃, keeping the furnace at the temperature for 420 min, discharging, and performing dephosphorization treatment to obtain a slab; the center segregation of the slab is class C0.5, and the center porosity is class 0.5;
3) Placing the slab obtained in the step 2) into an accelerated cooling device (Acc) for primary quick cooling until the surface temperature of the slab is 1020 ℃, the quick cooling speed is 15 ℃/s, the temperature gradient formed in the thickness direction is 1.4 ℃/mm, then performing first-stage rolling to obtain an intermediate slab, wherein the first-stage rolling comprises two passes, the first pass is performed to 280 mm, the second pass is performed to 245 mm, and the reddening temperature after rolling is 1020 ℃;
4) Putting the intermediate blank obtained in the step 3) into an accelerated cooling device (Acc) for secondary rapid cooling, wherein the surface temperature of the intermediate blank is 770 ℃, the rapid cooling speed is 3 ℃/s, the temperature gradient formed in the thickness direction is 0.5 ℃/mm, and then immediately rolling in the second stage to obtain a steel plate, wherein the reduction of the first two passes is 18% and 18%, the reduction of the last pass is 3%, and the final rolling temperature is 780 ℃;
5) And 4) water-cooling the steel plate obtained in the step 4) at a cooling speed of 10 ℃/s and a final cooling temperature of 200 ℃, then sending the steel plate into a tempering furnace, heating to 660 ℃, preserving heat for 360 minutes, and finally cooling to room temperature in air to obtain the steel plate with the thickness of 130 mm for low compression ratio for hydropower.
The structure property of the steel sheet for low compression ratio water and electricity having the thickness of 130 mm was measured, wherein the content of acicular ferrite was 20%, the content of tempered bainite was 35%, and the content of granular bainite was 45%; the tensile strength is 630 MPa, the impact value at the center of the thickness of the steel plate at minus 40 ℃ is 165 and J, and the flaw detection meets the 1-level standard in NB/T47013.
The tensile strength test sample is obtained from a 1/4-width and 1/4-thickness steel plate according to GB/T2975, a sample blank perpendicular to the rolling direction is processed into a standard round section test sample, and the impact value test sample is obtained from a 1/4-thickness and 1/2-width steel plate according to GB/T2975, and is milled and ground into a standard impact value test sample with the section of 55 mm multiplied by 10 mm multiplied by 10 mm. The tensile strength is tested according to the method A of GB/T228.1, the impact value is measured according to the standard impact value of GB/T229, a test sample is placed into a low-temperature alcohol tank with the temperature of minus 40 ℃ for heat preservation for not less than 5 minutes, then the test sample is rapidly taken out and placed into an impact testing machine for breaking, and the time from the taking out of the alcohol tank to breaking is ensured to be not more than 5 seconds.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (10)
1. The preparation method of the steel plate for the low-compression ratio hydropower is characterized by comprising the following steps of:
1) Smelting and continuously casting the low-compression ratio steel plate for hydropower to obtain a continuous casting blank with the thickness of more than or equal to 300 mm; si in the continuous casting blank is less than or equal to 0.1%;
2) Stacking and slowly cooling the continuous casting billet obtained in the step 1), charging and heating to 1100-1150 ℃ and preserving heat for 370-420 min, and then carrying out dephosphorization treatment to obtain a slab; the center segregation of the slab is not higher than class C grade 0.5, and the center porosity is not higher than grade 0.5;
3) Performing primary quick cooling on the slab obtained in the step 2), forming a temperature gradient of 0.8-1.5 ℃/mm in the thickness direction through primary quick cooling, and performing first-stage rolling after primary quick cooling to obtain an intermediate billet, wherein the single-pass rolling reduction rate of the first-stage rolling is more than or equal to 12%, and the thickness of the intermediate billet is more than or equal to 245 mm; then performing secondary quick cooling on the intermediate blank, forming a temperature gradient of 0.5-0.8 ℃/mm in the thickness direction through the secondary quick cooling, and performing second-stage rolling after the secondary quick cooling to obtain a steel plate; the reduction rate of at least two passes in the second stage rolling is more than or equal to 18%, and the reduction rate of the last pass is 3-7%; the compression ratio of the steel plate is 2.3-3.2;
4) And (3) performing water cooling, tempering and air cooling on the steel plate obtained in the step (3) to obtain the low-compression-ratio steel plate for hydropower.
2. The method of claim 1, wherein the stack is slowly cooled to a strand temperature of 300 ℃ or less.
3. The method according to claim 1 or 2, wherein the primary rapid cooling is performed until the surface temperature of the slab is 1000 ℃ to 1030 ℃ and the rapid cooling speed is 10 ℃ to 15 ℃/s;
and/or the secondary rapid cooling is carried out until the surface temperature of the intermediate blank is 770-820 ℃, and the rapid cooling speed is 3-5 ℃/s.
4. The method according to claim 1 or 2, wherein the first stage rolling is followed by a reddening temperature of not less than 1010 ℃;
and/or the final rolling temperature of the second stage rolling is 780-810 ℃.
5. The preparation method according to claim 1 or 2, wherein the water cooling speed is 6-10 ℃/s, the final cooling temperature of the water cooling is less than or equal to 200 ℃, and the steel plate after water cooling has acicular ferrite, lath bainite and Ma Ao complex phase structure.
6. The method according to claim 1 or 2, wherein the tempering temperature is 600-670 ℃, and the tempering heat preservation coefficient is 2.5-3.0 min/mm.
7. The method according to claim 1 or 2, wherein the low-compression ratio steel sheet for hydropower has a thickness of 100 to 140 a mm a.
8. A low-compression ratio steel sheet for hydropower use, characterized in that it is produced by the production method of the low-compression ratio steel sheet for hydropower use as claimed in any one of claims 1 to 7.
9. The low-compression-ratio steel sheet for hydropower use as recited in claim 8, wherein the chemical composition of the low-compression-ratio steel sheet for hydropower use comprises, in mass percent: c:0.04-0.06%, si: less than or equal to 0.1 percent, mn:1.15-1.35%, cr:0.1-0.25%, ni:0.10-0.25%, mo:0.15-0.3%, cu:0.15-0.35%, V:0.035-0.055%, nb:0.01-0.025%, al:0.02-0.04%, ti:0.01-0.03%, B:0.0006-0.0012%, the balance being Fe and unavoidable impurities; simultaneously satisfies: the carbon equivalent Ceq is less than or equal to 0.41 percent; the cold crack sensitivity index Pcm is less than or equal to 0.21 percent.
10. The low-compression-ratio steel sheet for hydropower according to claim 9, wherein the tensile strength of the steel sheet for hydropower is equal to or more than 620 MPa;
and/or the thickness center impact value of the low-compression ratio steel plate for hydropower is more than or equal to 150J at the temperature of minus 40 ℃;
and/or, the content of acicular ferrite in the low-compression ratio steel plate for hydropower is 12-20%, the content of tempered bainite is 25-40% and the content of granular bainite is 40-55% by volume percent;
and/or, the impurities comprise H less than or equal to 0.00015%, P less than or equal to 0.010%, S less than or equal to 0.002%, O less than or equal to 0.0025%, and N less than or equal to 0.005%.
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Address after: 215625 Zhangjiagang, Suzhou, Jiangsu, Jinjiang Fengzhen Patentee after: Jiangsu Shagang Steel Co.,Ltd. Country or region after: China Patentee after: INSTITUTE OF RESEARCH OF IRON & STEEL, JIANGSU PROVINCE/SHA-STEEL, Co.,Ltd. Patentee after: JIANGSU SHAGANG GROUP Co.,Ltd. Address before: 215625 Zhangjiagang, Suzhou, Jiangsu, Jinjiang Fengzhen Patentee before: ZHANGJIAGANG HONGCHANG STEEL PLATE Co.,Ltd. Country or region before: China Patentee before: INSTITUTE OF RESEARCH OF IRON & STEEL, JIANGSU PROVINCE/SHA-STEEL, Co.,Ltd. Patentee before: JIANGSU SHAGANG GROUP Co.,Ltd. |