CN111607748A - High-flatness large-thickness lamellar tearing resistant 780CF-Z35 hydroelectric steel and manufacturing method thereof - Google Patents
High-flatness large-thickness lamellar tearing resistant 780CF-Z35 hydroelectric steel and manufacturing method thereof Download PDFInfo
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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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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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- 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
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- 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
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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
- C22C38/18—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
Abstract
The invention relates to high-flatness large-thickness lamellar tearing resistant 780CF-Z35 hydroelectric steel, which adopts low-carbon design, carbon equivalent is less than or equal to 0.56%, welding crack sensitivity coefficient is less than or equal to 0.27%, and tensile property is as follows: the yield strength is 690MPa grade, the tensile strength is 770-930 MPa, the elongation is more than or equal to 15%, and the low-temperature toughness is as follows: the low-temperature impact absorption energy at minus 40 ℃ is more than or equal to 100J, and the low-temperature impact absorption energy at minus 20 ℃ of 5% aging deformation is more than or equal to 100J; the reduction of area in Z direction is more than or equal to 35 percent, and the flatness of the steel plate is less than or equal to 3 mm/m. The steel plate finished product with the thickness of 150mm at most is manufactured by adopting a continuous casting billet with the thickness of more than or equal to 370mm, the element components comprise C, Si, Mn, P, S, Cr, Ni, Mo, V, Cu, Al, H and B, and the balance of Fe and impurity elements.
Description
Technical Field
The invention belongs to the field of ferrous metallurgy, and particularly relates to 780CF-Z35 hydroelectric steel and a manufacturing method thereof.
Background
Hydroelectric power is a renewable and non-petrochemical clean energy source and is the most technically mature and economic energy source in the clean energy sources. The water and electricity has increasingly obvious effects and effects on reducing carbon dioxide emission, preventing pollution, protecting the environment and developing low-carbon economy. The water and electricity energy is used as clean energy, and is a necessary choice for ensuring the sustainable development of energy industry and meeting the requirement of building harmonious social energy. The development of hydroelectric engineering requires corresponding manufacturing materials for producing equipment, and the hydroelectric steel is produced accordingly. According to the result of the national hydraulic resource reexamination in 2003, the electricity quantity of Chinese water resources is 6.08 trillion kilowatts in the year of storage, and the installed capacity of the Chinese water resources can be developed economically and is 4.02 trillion kilowatts. With the progress of science and technology and the deepening of exploration planning, the exploitable amount of Chinese water resource technology is further increased. The power supply of the hydropower station in China is predicted to reach 3.3 hundred million kilowatts in 2020. The tongue plate and the volute required by the most core part of the hydropower station generator set both put forward more severe requirements on steel materials. It not only requires easy welding of steel plates, good low-temperature impact toughness, but also has high strength. The yield strength of high-strength hydroelectric steel is required to be more than or equal to 690MPa, the tensile strength is in the range of 770-920MPa, the elongation is more than or equal to 15%, the impact absorption energy at the thickness of 1/4 steel plate at the temperature of minus 40 ℃ is more than or equal to 100J, the 5% aging impact value at the temperature of minus 20 ℃ is required to be more than or equal to 100J, the tensile section shrinkage in the thickness direction (namely Z direction) is more than or equal to 35%, and the flatness is less than or equal to 3 mm/m.
The maximum thickness of a steel plate prepared by adopting an ultra-fast cooling technology UFC + ACC laminar cooling mode in the Chinese invention patent document with the patent publication number CN 103725973A in the high-strength steel plate for the hydraulic pipeline of the 800 MPa-level hydropower station and the production method thereof is 30mm, the maximum thickness of a steel plate prepared by adopting the UFC + ACC laminar cooling mode in the Chinese invention patent document with the patent publication number CN101418418A is 690 MPa-level low crack sensitivity steel plate and the preparation method thereof, and the maximum thickness of the manufactured steel plate is 60mm in the manufacturing method of the high-strength steel plate for the hydraulic pipeline of the 800 MPa-level hydropower station in the invention patent document with the patent publication number CN103292339A, so that the requirements of the steel for the hydropower station cannot be met.
The patent publication No. CN102260823A patent document discloses an economic high-strength steel plate with yield strength of 690MPa and a manufacturing method thereof, the strength is improved by adopting higher manganese content, but the manganese content exceeds the control upper limit of the manganese in GB/T1591-.
Patent publication No. CN 103215516A discloses "a high-strength hot-rolled steel with a yield strength of 700MPa grade", which contains Si element in an amount of 1.0-2.0%, and excessively high Si content results in poor surface quality of the steel sheet.
Disclosure of Invention
The invention provides 780CF-Z35 hydroelectric steel with high flatness, large thickness and lamellar tearing resistance and a manufacturing method thereof. 780CF-Z35 hydroelectric steel carbon equivalent is less than or equal to 0.56%, welding crack sensitivity coefficient is less than or equal to 0.27%, tensile property: the yield strength is 690MPa grade, the tensile strength is 770-930 MPa, the elongation is more than or equal to 15%, and the low-temperature toughness is as follows: the low-temperature impact absorption energy at minus 40 ℃ is more than or equal to 100J, and the low-temperature impact absorption energy at minus 20 ℃ of 5% aging deformation is more than or equal to 100J; the reduction of area in Z direction is more than or equal to 35 percent, and the flatness of the steel plate is less than or equal to 3 mm/m.
The technical scheme of the invention is described as follows:
the invention relates to 780CF-Z35 hydroelectric steel with high flatness, large thickness and lamellar tearing resistance, which adopts a low-carbon design and comprises the following elements in percentage by mass: 0.06-0.11%, Si: 0.15 to 0.35%, Mn: 0.8-1.5%, P: less than or equal to 0.010 percent, S: less than or equal to 0.005 percent, Cr: 0.2-0.7%, Mo: 0.3-0.6%, Ni: 0.5-1.8%, Cu: less than or equal to 0.35 percent, Alt: 0.015-0.06%, Nb: 0.02-0.08%, V: 0.02-0.05%, B: 0.001-0.004%, H0.00015%, carbon equivalent Ceq less than or equal to 0.56%, Pcm less than or equal to 0.27%, and the balance of Fe and impurity elements.
Furthermore, the carbon equivalent Ceq is C% + Mn/6+ Si/24+ Cr/5+ Mo/4+ Ni/40+ V/14), and Ceq is less than or equal to 0.56%; the welding crack sensitivity coefficient Pcm is C + Si/30+ Mn/20+ Cu/20+ Ni/60+ Cr/20+ Mo/15+ V/10+ 5+ B), and Pcm is less than or equal to 0.27%.
The function and amount of the components contained in the present invention are specifically described:
carbon: as a conventional strengthening element in low-carbon steel, the strength and hardness of the steel can be improved, but the influence on plasticity, toughness and weldability is large. The tensile strength of the material is almost in a linear relation with the weight percentage content of C, but the increase of the carbon content almost damages almost all the performances except the strong hardness, so the content of the material is reduced as far as possible on the premise of ensuring the strength, and therefore, the content of C in the invention is controlled to be 0.06-0.11%.
Manganese: manganese is present as a solid-solution strengthening element in steel, and is also a main element for improving strength in low-carbon steel. Meanwhile, manganese is also an important deoxidizer in the steelmaking process, but when the content of manganese is too high, serious center segregation can be caused to a casting blank, and adverse effects can be brought to later-stage welding and Z-direction performance of a steel plate, so that the content of manganese is controlled to be 0.8-1.5%.
Silicon: silicon has strong solid solution strengthening effect and is beneficial to improving the strength of the material, but also has the unfavorable tendency of increasing the coarsening and the tempering brittleness, and is not beneficial to controlling the surface quality, so the content of the silicon is controlled to be 0.15-0.35 percent.
Niobium, vanadium, titanium: carbon and nitride are easily formed in steel. The fine particles of these precipitates can pin the grain boundaries, and have a strong effect of inhibiting the growth of grains. The pinning effect of the precipitates of the above three elements to the grain boundary is reduced in order. When the Ti content is 0.02%, the entire Ti content is combined with N in the steel to form TiN in the solidification process and the austenite high-temperature region. Therefore, the Ti content of about 0.02% causes a very small change in strength, and when the Ti content exceeds this range, the change in strength tends to be similar to Nb. However, too much Ti coarsens TiN, and is not beneficial to toughness. When the Nb content reaches 0.04%, a remarkable strengthening effect occurs, and when the Nb content exceeds 0.08%, the increase in strength tends to be saturated. In the microalloyed steel, the effect of composite microalloying is greater than the sum of certain elements added independently, so that V is controlled to be 0.02-0.05%, the Nb content is controlled to be 0.02-0.08%, and Ti is only used as a residual element and is not added specially.
Molybdenum: molybdenum is a strong carbide forming element, the transformation capability of inhibiting austenite to pearlite is strongest, so that the hardenability of the material is improved, and meanwhile, the tempering brittleness caused by other elements can be reduced. Under a higher tempering temperature, dispersed carbides are formed, the secondary hardening effect is achieved, the heat strength and the creep strength of the steel can be improved, and the molybdenum content is controlled to be 0.3-0.6%.
Copper: the copper has the functions of solid solution strengthening and corrosion resistance and weather resistance improvement, and the copper can generate the effect of aging strengthening after solid solution strengthening and actual effect. However, when the copper content is more than 0.35%, the steel tends to be enriched in grain boundaries and surfaces due to selective oxidation, and the melting point of copper is low, so that high-copper steel is liable to be hot-brittle and causes difficulty in continuous casting. The Cu content of the invention is less than or equal to 0.35 percent.
Aluminum: al is also added to steel as a deoxidizer, and aluminum nitride improves the strength of steel like other precipitates. Because of the low solid solubility of Al, the precipitation strengthening effect is limited, but Al and nitrogen are combined to form AlN, so that the AlN has the functions of fixing nitrogen and protecting B to refine grains. Therefore, the invention controls the aluminum content to be 0.015-0.06%.
The chromium can improve the hardenability of the steel plate and can make up for part of the strength lost due to low carbon, but the excessive addition can reduce the toughness of the material, and the chromium is controlled to be 0.2-0.7%.
Boron: the compactness and hot rolling performance of the steel can be greatly improved by adding a small amount of boron into the steel, and the hardenability of the steel is obviously improved. However, when the B content exceeds 0.005%, the toughness of the steel sheet is easily deteriorated by boride, so that boron in the present invention is controlled to 0.001 to 0.004%.
Sulfur and phosphorus as impurity elements: the sulfur element is easy to cause hot brittleness, and the more the content of the sulfur is, the welding performance of the steel is seriously influenced; phosphorus element acts as a solid solution strengthening effect to increase hardness and strength, but at the same time causes cold brittleness. The shape of the inclusions must be changed by a calcium treatment technology, so that the damage to the toughness of the material is reduced.
H. O, N: as harmful gas elements, the steel plate has direct harm to the toughness and the lamellar tearing resistance, and particularly, the H content is too high, which can cause the generation of white spots and hydrogen embrittlement of the steel plate, so the H content of the invention is controlled to be less than 0.00015 percent.
Secondly, preparing the 780CF-Z35 hydroelectric steel with high flatness, large thickness and lamellar tearing resistance, which is disclosed by the invention:
and (3) adopting a continuous casting billet with the thickness of more than 370mm as a steel billet to produce a finished steel plate with the maximum thickness of 150mm through hot rolling. Wherein, the molding process of continuous casting billet: molten iron pretreatment, desulfurization and slagging-off → converter smelting → LF refining → RH refining → continuous casting, wherein the superheat degree of molten steel is controlled to be 5-25 ℃, the center segregation of a plate blank is less than or equal to C1.0 level, the center porosity is less than or equal to 0.5, and no corner crack defect exists.
The forming method of the finished steel plate is as follows,
(1) heating the continuous casting slab to 1220-1280 ℃, soaking in a furnace for 2-3 hours to fully austenitize, removing scale by using high-pressure water after discharging, and then rolling in two stages: the first stage is rough rolling, the initial rolling temperature is 1000-1080 ℃, the total reduction rate of the rough rolling is more than or equal to 40%, and the single-pass reduction rate is more than 17% to ensure that the rolling force penetrates into the center of the steel plate, thereby achieving the effect of improving the center defects; and the second stage of rolling is finish rolling, the initial rolling temperature is 820-960 ℃, the total reduction rate is more than or equal to 20%, the final rolling temperature is more than or equal to 760 ℃, the structure after final rolling is austenite, a hot straightening machine is adopted to straighten the steel plate after rolling is finished, the steel plate is straightened and then is subjected to offline air cooling, the residual stress in the steel plate is released, and the flatness of the steel plate can reach the level of less than or equal to 3 mm/m. Air cooling is adopted to reduce the structural stress caused by water cooling after the rolling of the steel plate, and the air cooling after the rolling enables the austenite phase to be changed into uniform ferrite and pearlite structures; specifically, the straightened steel plate is off-line for slow cooling in a stacking or covering mode, and the time for slow cooling in the stacking or covering mode is more than or equal to 72 hours.
(3) Quenching and tempering the steel plate after the slow cooling, wherein the quenching is carried out in a continuous furnace, the heating temperature is 900-930 ℃, the furnace time is 1.5-2.0 h, and the steel plate is taken out of the furnace and then cooled by water to obtain a quenched martensite structure; the tempering process is carried out in a continuous furnace, the tempering temperature is 600-650 ℃, the time in the furnace is 2.5-3.5 h, the steel is air-cooled after being taken out of the furnace, and the quenched martensite is transformed into tempered sorbite.
Compared with the prior art, the invention has the advantages that:
(1) after rolling, air cooling is adopted, and the purpose is to obtain uniform ferrite and pearlite structures in the cooling phase transformation process and reduce the generation of bainite as much as possible.
(2) The steel sheet is mainly austenite structure after the finish rolling, steel sheet structure turns into ferrite + pearlite and a small amount of bainite structure gradually after the air cooling, the change of structure makes the inside of material produce internal stress in the tissue phase transition process, will make the material produce not equidimension deformation when stress is too big, and then bring very big difficulty for the control of board type, especially to and thin plate and wide plate, and heap slow cooling can make the inside stress of steel sheet obtain the release to a certain extent through the temperature and the action of gravity of self of steel sheet, the convenient certain benefit that has to the board type control of steel sheet.
(3) The steel plate is subjected to heat treatment, the structure is austenitized after quenching and heating, a martensite structure is obtained after quenching, and the quenched martensite structure has higher brittleness and hardness, so that the martensite in the steel plate is converted into tempered sorbite by high-temperature tempering of the steel plate, and the toughness of the material is well matched with the Z-direction performance.
(4) The invention adopts the design of low carbon and low carbon equivalent, the carbon content C is 0.06-0.11%, and the carbon equivalent Ceq is less than or equal to 0.56%, thus being beneficial to the welding of large-thickness hydroelectric steel plates. Meanwhile, the welding crack sensitivity index Pcm is less than or equal to 0.27 percent, and the welding performance is excellent.
Drawings
FIG. 1 is a structure of 780CF-Z35 steel plate with a thickness of 100mm according to example 1 of the present invention;
FIG. 2 shows a 780CF-Z35 steel plate structure with a thickness of 150mm according to example 2 of the present invention.
Detailed Description
The present invention will be described in further detail below with reference to the embodiments of the drawings, which are illustrative and intended to be illustrative of the present invention and are not to be construed as limiting the present invention.
Example 1
The thickness of the hydroelectric steel plate designed in the embodiment is 100mm, and the element components are shown in Table 1.
The production process of the 780CF-Z35 hydroelectric steel plate with high flatness and large thickness and lamellar tearing resistance comprises the following steps:
preparing smelting raw materials according to the chemical composition of the high-flatness large-thickness anti-laminar-tearing 780CF-Z35 hydroelectric steel plate, and sequentially performing KR molten iron pretreatment → converter smelting → LF refining → RH refining → continuous casting → blank cover slow cooling → heating → high-pressure water descaling → controlled rolling → thermal straightening → steel plate stack slow cooling or cover slow cooling → flaw detection → tempering. The superheat degree of the continuous casting billet during casting is controlled to be 5-25 ℃, the casting billet is detected after the continuous casting billet is formed, the center segregation of the slab is less than or equal to C1.0 level, the center porosity is less than or equal to 0.5, the defects of corner cracks and the like are avoided, and a foundation is laid for the good Z-direction performance of the steel plate. The specific process of reheating, rolling and controlled cooling of the continuous casting billet comprises the following steps: heating the continuous casting slab to 1220-1280 ℃, performing furnace for 2-3 hours, removing scale by high-pressure water after discharging, and performing two-stage controlled rolling (rough rolling and finish rolling). The first stage controlled rolling (namely rough rolling) is 1000-1080 ℃, the total reduction rate is more than or equal to 40%, the single-pass reduction is more than or equal to 17%, the rolling force is ensured to permeate into the center of the steel plate so as to bridge the defects of the center of the steel plate and ensure the Z-direction performance of the steel plate; and in the second stage (namely finish rolling), the initial rolling temperature is 900 ℃, the total rolling reduction rate is more than or equal to 20%, the defects of small waves and the like of the steel plate caused by water cooling are avoided by adopting air cooling after the rolling is finished, the steel plate is straightened by adopting a hot straightening machine so as to ensure that the straightness of the steel plate can reach the level of less than or equal to 3mm/m, and the time for slow cooling of the steel plate in a stacking or covering process is more than or equal to 72 hours after the steel plate is straightened by adopting.
After the slow cooling is finished and flaw detection is passed, quenching and tempering are carried out:
for example 1: quenching the steel plate by using a quenching machine: the heating temperature is 910 ℃, the furnace is taken out after the furnace time is 1.8h, and the furnace is cooled by water. And (3) tempering at 640 ℃ by adopting a continuous furnace, keeping the furnace for 2.5-3.5 h, and cooling by air after discharging.
Example 2
The thickness of the hydroelectric steel plate related to the embodiment is 150mm, and the element composition is shown in Table 1.
The raw materials for smelting were arranged in the elemental compositions shown in table 1, and KR hot metal pretreatment → converter smelting → LF refining → RH refining → continuous casting → billet cover annealing → heating → high pressure water descaling → controlled rolling → thermal straightening → steel plate stack annealing or cover annealing → flaw detection → tempering were performed in this order. The superheat degree of the continuous casting billet during casting is controlled to be 5-25 ℃, the casting billet is detected after the continuous casting billet is formed, the center segregation of the slab is less than or equal to C1.0 level, the center porosity is less than or equal to 0.5, the defects of corner cracks and the like are avoided, and a foundation is laid for the good Z-direction performance of the steel plate. Heating the continuous casting slab to 1220-1280 ℃, performing furnace for 2-3 hours, removing scale by high-pressure water after discharging, and performing two-stage controlled rolling (rough rolling and finish rolling). The first stage is controlled to roll at the beginning at 1000-1080 ℃, the total reduction rate is more than or equal to 40%, the single-pass reduction is more than or equal to 17%, and the rolling force is ensured to penetrate into the center of the steel plate so as to close the defects of the center of the steel plate and ensure the Z-direction performance of the steel plate; the second stage is at the beginning rolling temperature of 880 ℃, the total rolling reduction rate is more than or equal to 20 percent, the defects of small waves and the like caused by water cooling are avoided by adopting air cooling after the rolling is finished, the steel plate is straightened by adopting a hot straightening machine so as to ensure that the straightness of the steel plate is less than or equal to 3mm/m, and the time for slow cooling in stacking or covering the steel plate after the hot straightening is more than or equal to 72 hours.
After the slow cooling is finished and flaw detection is passed, quenching and tempering are carried out: quenching the steel plate by using a quenching machine: the heating temperature is 930 ℃, the furnace time is 2.0h, and water cooling is carried out after discharging. And tempering at 610 ℃ by adopting a continuous furnace, keeping the temperature in the furnace for 2.5-3.5 h, and cooling by air after discharging.
The finished steel plate produced by the manufacturing process has the advantages of low carbon equivalent, low crack sensitivity, high strength, good plasticity and toughness, lamellar tearing resistance, excellent comprehensive performance and properties shown in table 2.
Table 1 chemical compositions of the hydroelectric steel sheet according to examples 1 to 2 of the present invention, Ceq and Pcm (wt%):
TABLE 2 Steel sheet testing Properties and flatness of examples 1-2
1D is the bend diameter and a is the specimen thickness.
Claims (7)
1. The utility model provides a high straightness big thickness anti lamellar tear 780CF-Z35 hydroelectric steel which characterized in that: the element components comprise C: 0.06-0.11%, Si: 0.15 to 0.35%, Mn: 0.8-1.5%, P: less than or equal to 0.010 percent, S: less than or equal to 0.005 percent, Cr: 0.2-0.7%, Mo: 0.3-0.6%, Ni: 0.5-1.8%, Cu: less than or equal to 0.35 percent, Alt: 0.015-0.06%, Nb: 0.02-0.08%, V: 0.02-0.05%, B: 0.001-0.004%, H0.00015%, carbon equivalent Ceq less than or equal to 0.56%, Pcm less than or equal to 0.27%, and the balance of Fe and impurity elements.
2. The high flatness, high thickness, delamination tear resistance 780CF-Z35 hydroelectric steel of claim 1, wherein: the carbon equivalent Ceq is C% + Mn/6+ Si/24+ Cr/5+ Mo/4+ Ni/40+ V/14), and Ceq is less than or equal to 0.56%; the welding crack sensitivity coefficient Pcm is C + Si/30+ Mn/20+ Cu/20+ Ni/60+ Cr/20+ Mo/15+ V/10+ 5+ B), and Pcm is less than or equal to 0.27%.
3. The high flatness, high thickness, delamination tear resistance 780CF-Z35 hydroelectric steel of claim 1, wherein: and (3) adopting a continuous casting billet with the thickness of more than 370mm as a steel billet to produce a finished steel plate with the maximum thickness of 150mm through hot rolling.
4. The high flatness, high thickness, delamination tear resistance 780CF-Z35 hydroelectric steel of claim 3, wherein: the forming method of the finished steel plate is as follows,
(1) heating the continuous casting slab to 1220-1280 ℃, soaking in a furnace for 2-3 hours to fully austenitize, removing scale by using high-pressure water after discharging, and then rolling in two stages: the first stage is rough rolling, the initial rolling temperature is 1000-1080 ℃, the total reduction rate of the rough rolling is more than or equal to 40%, and the single-pass reduction rate is more than 17% to ensure that the rolling force penetrates into the core of the steel plate; the second stage of rolling is finish rolling, the initial rolling temperature is 820-960 ℃, the total reduction rate is more than or equal to 20%, the final rolling temperature is more than or equal to 760 ℃, the final rolling structure is still austenite, air cooling is adopted after rolling is completed, and the austenite is converted into uniform ferrite and pearlite structures after air cooling;
(3) quenching and tempering the steel plate after the slow cooling, wherein the quenching is carried out in a continuous furnace, the heating temperature is 900-930 ℃, the furnace time is 1.5-2.0 h, and the steel plate is taken out of the furnace and then cooled by water to obtain a quenched martensite structure; the tempering process is carried out in a continuous furnace, the tempering temperature is 600-650 ℃, the time in the furnace is 2.5-3.5 h, the steel is air-cooled after being taken out of the furnace, and the quenched martensite is transformed into tempered sorbite.
5. The high flatness, high thickness, delamination tear resistance 780CF-Z35 hydroelectric steel of claim 4, wherein: and (2) straightening the steel plate by using a hot straightening machine after rolling in the step (1), and performing offline air cooling after straightening the steel plate to release residual stress in the steel plate so that the flatness of the steel plate can reach the level of less than or equal to 3 mm/m.
6. The high flatness, high thickness, delamination tear resistance 780CF-Z35 hydroelectric steel of claim 4, wherein: and (3) unloading the straightened steel plate for slow stacking cooling or slow cover cooling, wherein the slow stacking cooling or slow cover cooling time is more than or equal to 72 hours.
7. The high flatness, high thickness, delamination tear resistance 780CF-Z35 hydroelectric steel of claim 3, wherein: the molding process of the continuous casting billet comprises the following steps: molten iron pretreatment, desulfurization and slagging-off → converter smelting → LF refining → RH refining → continuous casting, wherein the superheat degree of molten steel is controlled at 5-25 ℃, the center segregation of a plate blank is less than or equal to C1.0 level, the center porosity is less than or equal to 0.5, and the corner crack defect is avoided.
Priority Applications (1)
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| CN112251670A (en) * | 2020-09-30 | 2021-01-22 | 鞍钢股份有限公司 | 690 MPa-grade steel plate with good extensibility and manufacturing method thereof |
| CN112575255A (en) * | 2020-11-24 | 2021-03-30 | 南阳汉冶特钢有限公司 | Preparation method of 15MnNiNbDR steel plate for ultralow-temperature storage tank |
| CN112981238A (en) * | 2021-01-28 | 2021-06-18 | 江阴兴澄特种钢铁有限公司 | Standard Q460D steel plate for forge piece production by continuous casting billet and manufacturing method thereof |
| CN113388775A (en) * | 2021-06-03 | 2021-09-14 | 南京钢铁股份有限公司 | Production method of 1000 MPa-grade high-strength steel plate for hydroelectric engineering |
| CN114134407A (en) * | 2021-06-04 | 2022-03-04 | 江阴兴澄特种钢铁有限公司 | Easy-to-weld steel plate with excellent low-temperature toughness at core for volute and manufacturing method thereof |
| CN115141969A (en) * | 2022-07-28 | 2022-10-04 | 湖南华菱湘潭钢铁有限公司 | Production method of 800MPa grade hydropower steel |
| CN115141968A (en) * | 2022-07-28 | 2022-10-04 | 湖南华菱湘潭钢铁有限公司 | Production method of quenched and tempered steel plate for Q620-level high-corrosion-resistance high-strength offshore structure |
| CN115961202A (en) * | 2022-12-05 | 2023-04-14 | 南京钢铁股份有限公司 | Production method of 1000 MPa-grade hydroelectric steel plate with thickness larger than 100mm |
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| CN112575255A (en) * | 2020-11-24 | 2021-03-30 | 南阳汉冶特钢有限公司 | Preparation method of 15MnNiNbDR steel plate for ultralow-temperature storage tank |
| CN112981238A (en) * | 2021-01-28 | 2021-06-18 | 江阴兴澄特种钢铁有限公司 | Standard Q460D steel plate for forge piece production by continuous casting billet and manufacturing method thereof |
| CN112981238B (en) * | 2021-01-28 | 2022-07-29 | 江阴兴澄特种钢铁有限公司 | Standard Q460D steel plate for forge piece production by continuous casting billet and manufacturing method thereof |
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| CN114134407A (en) * | 2021-06-04 | 2022-03-04 | 江阴兴澄特种钢铁有限公司 | Easy-to-weld steel plate with excellent low-temperature toughness at core for volute and manufacturing method thereof |
| CN115141969A (en) * | 2022-07-28 | 2022-10-04 | 湖南华菱湘潭钢铁有限公司 | Production method of 800MPa grade hydropower steel |
| CN115141968A (en) * | 2022-07-28 | 2022-10-04 | 湖南华菱湘潭钢铁有限公司 | Production method of quenched and tempered steel plate for Q620-level high-corrosion-resistance high-strength offshore structure |
| CN115961202A (en) * | 2022-12-05 | 2023-04-14 | 南京钢铁股份有限公司 | Production method of 1000 MPa-grade hydroelectric steel plate with thickness larger than 100mm |
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