CN114807761A - EH36 grade ocean engineering steel with high ductility and manufacturing method thereof - Google Patents
EH36 grade ocean engineering steel with high ductility and manufacturing method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The invention relates to EH36 grade ocean engineering steel with high ductility, which is characterized in that the steel comprises the following chemical components by weight percent: c: 0.05-0.08%, Si: 0.10-0.30%, Mn: 1.00% -1.50%, Nb: 0.01% -0.04%, V: 0.02% -0.05%, Ti: 0.005% -0.02%, P: less than or equal to 0.01 percent, S: less than or equal to 0.01 percent, Als: 0.01 to 0.05 percent, and the balance of Fe and inevitable impurities. The chemical components of the steel are not added with noble alloy elements such as Ni and the like; the steel plate with high yield, stable strength and toughness and particularly high ductility is obtained by controlling the contents of sulfur and phosphorus, and regulating and controlling the microstructure and the grain size of the steel plate by adopting continuous casting billet induction heating, two-stage controlled rolling, relaxation and controlled cooling processes.
Description
Technical Field
The invention relates to the field of preparation of steel materials,
background
In recent years, although marine accidents involving marine engineering equipment are decreasing, severe marine troubles occur occasionally, and huge property and life losses are often caused. Therefore, it is important not only to provide measures for preventing collision and grounding of marine engineering equipment, but also to discuss how to minimize the loss in the event of a marine accident, and as offshore resources of various countries decrease and the united nations "ocean law convention" is implemented, the development of the offshore engineering industry toward the deep sea and the open sea becomes a necessary trend, and the offshore industry is gradually transformed into the ocean industry, and the offshore engineering industry is upgraded to the open sea. Once a marine accident involving marine engineering equipment occurs, huge property loss and life loss are caused. It is therefore important not only to provide measures against collision and grounding of marine engineering equipment, but also to minimize losses in the event of a shipwreck.
Therefore, the development of mobile deep-sea platforms, FPSOs and ocean engineering ships requires that ocean engineering steel have good obdurability matching, stability and low-temperature toughness, and particularly provides that steel plates have high ductility so as to deal with the possible collision and grounding accidents of ships and ocean engineering equipment. The high ductility is an important index in the concept of 'high safety service performance' of steel for ocean engineering, mainly aims to improve the collision safety, the ductility of a structural material is better, the more energy is absorbed during collision, the high ductility performance index is brought into the standard by American ABS classification society at present, and the purpose is to ensure that a steel plate absorbs the collision energy when the ship and ocean engineering equipment collide and are stranded, so that structural instability is not easy to occur, the collision resistance of the equipment is improved, a plurality of guarantees are provided, and the risk of serious ocean pollution caused by leakage of cargo oil and fuel oil is reduced. Such marine engineering steel plates ("NSafe-Hull" series) having high ductility and collision resistance have been developed from japanese new day iron and sumitomo metals, and are currently in the stage of trial application. However, the ocean engineering in China has not formed large-scale application on the steel plates, steel enterprises have not carried out systematic research, and the steel plates with high ductility and collision resistance for the ocean engineering belong to new requirements of the steel for the ocean engineering. The invention will contribute to safer and more reliable offshore operation and transportation.
Publications of related patents report:
the invention patent with the publication number of CN105803330B discloses a structural steel plate for a normalizing ship body and a preparation method thereof, the structural steel plate adopts Nb, V and Ti refined crystal grain elements, TMCP and normalizing heat treatment are adopted to prepare an EH 36-grade high-strength ship plate, the production and manufacturing period is longer, the energy consumption is high, the production cost is increased, and the elongation after the steel plate is broken is 24-32%.
The invention patent with the publication number of CN108517462A provides high-ductility EH40 grade ship plate steel and a preparation method thereof. The patent is designed by using low carbon and microalloy strengthening components, and adopts two-stage rolling and water cooling-air cooling-water cooling three-stage cooling, and the technology has the advantages of complex production process, higher requirement on equipment control capacity, long production period and narrow process window.
The invention patent with the publication number of CN110714171A discloses a high-ductility EH 420-grade ship plate steel and a production method thereof, the patent uses Nb and Ti micro-alloy for reinforcement, adopts a two-stage rolling and two-stage cooling mode, and utilizes an ultra-fast cooling technology with the cooling speed of 60 ℃/s to obtain a composite structure of soft-phase ferrite and hard bainite, but the technology has higher difficulty, the required cooling speed condition is difficult to achieve in the actual industrial production, and the limitation exists on the thickness condition of the steel plate.
The invention patent with publication number CN201910182915 proposes a process for producing a medium plate, which comprises the following steps: steel making; continuous casting; liquid core rolling; cutting a casting blank; carrying out online induction heating; rolling in the whole longitudinal direction; cooling; finishing and shearing; in the online induction heating step, the surface temperature of the continuous casting billet is 1050-1150 ℃ by induction heating, the average temperature of the continuous casting billet is 1150-1200 ℃, and the heating speed of compensation heating is not less than the maximum billet drawing speed of a continuous casting machine.
Disclosure of Invention
The invention aims to provide EH36 grade ocean engineering steel with high ductility and a manufacturing method thereof, wherein the yield is high, the strength and the toughness are stable, and the steel particularly has high ductility.
In order to achieve the purpose, the invention adopts the following technical scheme:
the high-ductility EH36 grade ocean engineering steel comprises the following chemical components in percentage by weight: c: 0.05-0.08%, Si: 0.10-0.30%, Mn: 1.00% -1.50%, Nb: 0.01% -0.04%, V: 0.02% -0.05%, Ti: 0.005% -0.02%, P: less than or equal to 0.01 percent, S: less than or equal to 0.01 percent, Als: 0.01 to 0.05 percent, and the balance of Fe and inevitable impurities.
Properties of EH36 grade ocean engineering steel with high ductility: the elongation after tensile fracture of the steel plate is more than or equal to 32 percent, the maximum force elongation is more than or equal to 28 percent, the yield strength is more than or equal to 360MPa, the tensile strength is 490-630 MPa, the Charpy impact power is more than or equal to 200J at minus 40 ℃, and the zero plastic transition temperature NDTT is less than minus 40 ℃; the microstructure is ferrite and pearlite, wherein the average grain size of the ferrite is 5.0-10.0 mu m, and the content of the ferrite is 85-95%.
The action mechanism of each alloy component in the steel is shown in percentage symbol percent by weight:
c: the high-ductility EH36 steel sheet of the present invention has a final structure of F/B dual-phase structure, and the C content is an important factor affecting the ratio of the two phases in the case of the F/B dual-phase steel. Under the same TCMP condition, the lower the content of C in the steel plate, the higher the ferrite proportion. The ductility of the dual-phase steel mainly depends on the proportion of the soft-phase ferrite, and the stress generated by bainite plastic deformation in the integral coordinated deformation process can be released by inducing the surrounding soft-phase ferrite to deform the metallographic phase, so that the phenomenon that the bainite is shrunk due to early stress concentration is avoided. Considering the high ductility characteristics as the object of the invention of the product, a lower C content is required to ensure a high ferrite proportion of the final structure. However, the content of C is not lower than 0.05%, too low C content not only causes high austenite grain boundary mobility and causes great problems to the uniform refined structure in the TMCP process, mixed crystal structure is easy to form, but also causes the yield ratio to be increased, and too low C content also causes the grain boundary binding force to be reduced, thereby causing low-temperature impact toughness of the steel plate and low-temperature impact toughness of a welding heat affected zone to be degraded. In combination with the above factors, the C content is preferably controlled to be 0.05-0.08%.
Si: it is a main deoxidizing component in the steel making process, and it is necessary to contain 0.10% or more in order to obtain a sufficient deoxidizing effect, but if it exceeds the upper limit, the toughness of the base material and the welded portion is lowered, and Si present in a solid solution form can increase the ductile-brittle transition temperature as well as the strength, so the Si content is preferably 0.10 to 0.30%.
Mn: is an essential element for ensuring the strength and toughness of the steel. In order to improve the toughness of the material, the content of Mn is 1.00-1.50%.
Nb: both Nb and C, N, O have strong affinity and form corresponding very stable compounds. Nb can refine the crystal grains of the steel, reduce the overheating sensitivity of the steel, improve the strength and the toughness of the steel under certain existing conditions, and particularly precipitate fine Nb carbonitride refined austenite grains under the induction heating condition with high heating rate. The Nb content of the invention is controlled to be 0.01-0.04%.
V: v is a ferrite refining element, improves the strength, yield ratio and low-temperature toughness of the steel, improves the welding performance of the steel, and can also increase the heat resistance and creep resistance of the steel. However, the V content should not be too high, and too high of V content lowers the toughness of the steel, which is not favorable for the creep property of the steel. The V content of the invention is controlled between 0.02 and 0.05 percent.
Ti: ti not only can improve the strength of steel, refine crystal grains and reduce aging sensitivity and cold brittleness, but also can improve welding performance by a small amount of Ti. Ti acts in the form of TiN, and when Ti is less than 0.005%, the effect is small, and when Ti is more than 0.04%, large-grain TiN is easily formed and the effect is lost. Therefore, the Ti content is preferably 0.005 to 0.02%.
P: the low-temperature toughness-reducing alloy is an element which brings adverse effects on low-temperature toughness and ductility, can be segregated in the central part of a slab, is aggregated in a grain boundary and the like to damage the low-temperature toughness, and is controlled to be not higher than 0.01 percent.
S: the material is an element which brings adverse effects on low-temperature toughness and ductility, can form sulfide inclusions to become a crack source, and is controlled to be not higher than 0.01%.
And Als: the content of the deoxidizing and grain refining element to be added in the present invention is 0.01% or more, but if it exceeds 0.08%, hot cracking of the cast slab is likely to occur, and the toughness of the steel is lowered. The content of Als is controlled between 0.01 and 0.05 percent.
The manufacturing method of the EH36 grade ocean engineering steel with high ductility comprises the following process flows: smelting, continuous casting, heating a casting blank, rolling, straightening, relaxing and cooling; wherein:
1) heating a casting blank: induction heating at a heating rate of 5.5 to 7 ℃ s -1 Rapidly heating the continuous casting blank to 1150-1180 ℃, and controlling the temperature uniformity of the casting blank within the range of +/-30 ℃;
2) the rolling process comprises the following steps: two-stage rolling is adopted for a continuous casting billet, the rolling temperature of the first stage is an austenite recrystallization temperature region of 950-1000 ℃, the average single-pass reduction rate is more than 10%, so that austenite is fully recrystallized, and the grain size of austenite is refined; in the austenite non-recrystallization temperature region with the rolling temperature of 750-800 ℃ in the second stage, the average single-pass reduction rate reaches 15-20%, so that austenite grains are fully deformed, energy storage and positions are provided for phase change nucleation, the phase change nucleation rate is improved, and ferrite grains are further reduced by deformation in a two-phase region;
3) post-rolling relaxation phase change control: the steel plate is cooled to 680-730 ℃ by air and then enters a cooling system, the relaxation time of the steel plate in an alpha/gamma two-phase region after final rolling is increased, eutectoid ferrite is fully nucleated firstly, and the ferrite structure proportion of the final structure is ensured to be more than 85%;
4) and (3) a cooling process: and a rapid laminar cooling system with the average cooling speed of 3-10 ℃/s is adopted, the temperature of red returning is controlled to be 550-600 ℃, the composition and the size of a phase change structure are controlled, the steel plate is slowly cooled after cooling, and the slow cooling time is more than or equal to 24 hours.
And a longitudinal magnetic flux induction heating mode is adopted in the casting blank heating process.
The thickness range of the steel plate finished product is 20-50 mm.
Compared with the prior art, the invention has the beneficial effects that:
the chemical components of the steel plate are not added with noble alloy elements such as Ni and the like; the steel plate with high yield, stable strength and toughness and particularly high ductility is obtained by controlling the contents of sulfur and phosphorus, and regulating and controlling the microstructure and the grain size of the steel plate by adopting continuous casting billet induction heating, two-stage controlled rolling, relaxation and controlled cooling processes. The elongation after tensile fracture of the steel plate is more than or equal to 32 percent, the maximum force elongation is more than or equal to 28 percent, the yield strength is more than or equal to 360MPa, the tensile strength is 490-630 MPa, the Charpy impact power is more than or equal to 200J at minus 40 ℃, and the zero plastic transition temperature NDTT is less than minus 40 ℃; the microstructure is ferrite and pearlite, wherein the average grain size of the ferrite is 5.0-10.0 mu m, and the content of the ferrite is 85-95%. The mechanical property and high service safety performance of the steel plate can reach the service condition of ocean engineering equipment.
Drawings
FIG. 1 is a microstructure diagram of the present invention.
Detailed Description
The following further illustrates embodiments of the invention:
the high-ductility EH36 grade ocean engineering steel comprises the following chemical components in percentage by weight: c: 0.05 to 0.11 percent, Si: 0.10-0.30%, Mn: 1.00% -1.50%, Nb: 0.01% -0.04%, V: 0.02% -0.05%, Ti: 0.005% -0.02%, P: less than or equal to 0.01 percent, S: less than or equal to 0.01 percent, Als: 0.01 to 0.05 percent, and the balance of Fe and inevitable impurities.
The manufacturing method of the EH36 grade ocean engineering steel with high ductility comprises the following process flows: smelting, continuous casting, heating a casting blank, rolling, straightening, relaxing and cooling; wherein:
(1) the smelting process comprises the following steps: smelting according to the component range, obtaining a continuous casting blank after smelting and continuous casting, wherein the LF refining furnace and the RH refining furnace are respectively required to be treated for 10-30 min, the superheat degree of the tundish molten steel is less than or equal to 25 ℃, and the whole process is protected for casting; the A, B, C, D type inclusions in the steel meet the following requirements: a is less than or equal to 0.5, B is less than or equal to 0.5, C is less than or equal to 1.0, and D is less than or equal to 1.0;
(2) heating a casting blank: an induction heating process: the structure change in the austenitizing process has an important influence on the structure performance of subsequent steel, a longitudinal magnetic flux induction heating mode is adopted, the temperature of a continuous casting billet is rapidly increased to 1150-1180 ℃ at a heating rate of 5.5-7 ℃ s-1, the temperature uniformity of the casting billet is controlled within a range of +/-30 ℃, and under the induction heating condition, a skin effect surface chilling fine grain region of the continuous casting billet is rapidly increased to an austenite phase region in a short time, and then heat is rapidly conducted inwards. The higher the heating rate, the higher the degree of superheat, and the austenite rapidly nucleates a large amount at cementite and ferrite grain boundaries. Meanwhile, when the heating speed is high, the crystal grains of the austenite do not grow for a sufficient time, and the growth trend of the austenite is weakened.
(3) The rolling process comprises the following steps: two-stage rolling is adopted for a continuous casting billet, the rolling temperature of the first stage is an austenite recrystallization temperature region of 950-1000 ℃, the average single-pass reduction rate is more than 10%, so that austenite is fully recrystallized, and the grain size of austenite is refined; the rolling temperature of the second stage is in an austenite non-recrystallization temperature region of 750-800 ℃, the average single pass reduction rate reaches 15-20%, austenite grains are fully deformed, energy storage and positions are provided for phase change nucleation, the phase change nucleation rate is improved, ferrite grains are further reduced through deformation of a two-phase region, and the purpose of grain refinement is finally achieved.
(4) Straightening process: after the finish rolling, the steel plate is straightened in a straightening machine, so that the flatness of the steel plate is improved, and the problems of warping and the like of the steel plate in the cooling process are prevented.
(5) Post-rolling relaxation phase change control: the relaxation time of an alpha/gamma two-phase region is controlled by adjusting the cooling temperature, so that the proportion and the morphology of an F/B two-phase structure of the steel plate are regulated and controlled. The steel plate is air-cooled to 680-730 ℃ and then enters a cooling system, so that the relaxation time of the steel plate in an alpha/gamma two-phase region after final rolling is prolonged, sufficient nucleation of proeutectoid ferrite is facilitated, and the ferrite structure proportion of a final structure is ensured to be more than 85%. During relaxation, carbon elements in the undercooled austenite develop from uniform distribution to aggregation, and a region where carbon migrates out forms proeutectoid ferrite, namely the proeutectoid ferrite diffuses to the austenite for a long distance of carbon removal. Therefore, the longer the steel sheet relaxes before cooling, the more the transformation and carbon diffusion process proceeds sufficiently, the higher the degree of C element aggregation in the austenite region around the proeutectoid ferrite, and the bainite is formed in the subsequent laminar rapid cooling process. Therefore, the C content is required to be less than 0.08 percent, the carbon enrichment phenomenon of surrounding austenite in the process can be effectively reduced when the proeutectoid ferrite is nucleated and grown, the dispersion distribution of bainite is facilitated, and the local stress concentration generated in the deformation process is avoided.
(6) And (3) a cooling process: and a rapid laminar cooling system with the average cooling speed of 3-10 ℃/s is adopted, the temperature of the red returning is controlled to be 550-600 ℃, the purpose is to control the composition and the size of a phase change structure, the steel plate is slowly cooled after being cooled, and the slow cooling time is more than or equal to 24 hours.
Examples
Table 1 shows the chemical composition of steel for marine engineering examples;
table 2 shows the process of smelting the steels of the examples;
table 3 shows the rolling process of the example steels;
table 4 shows the mechanical properties of the steels of the examples;
table 5 shows the low temperature properties and NDTT temperatures of the steels of the examples of the present invention.
Table 1: chemical composition of steel
| Examples | C | Si | Mn | Nb | V | Ti | P | S | Als |
| 1 | 0.05 | 0.21 | 1.41 | 0.021 | 0.026 | 0.012 | 0.005 | 0.001 | 0.03 |
| 2 | 0.06 | 0.14 | 1.48 | 0.025 | 0.031 | 0.007 | 0.004 | 0.001 | 0.01 |
| 3 | 0.07 | 0.10 | 1.05 | 0.012 | 0.036 | 0.012 | 0.005 | 0.001 | 0.02 |
| 4 | 0.08 | 0.12 | 1.21 | 0.015 | 0.021 | 0.005 | 0.005 | 0.001 | 0.02 |
| 5 | 0.05 | 0.18 | 1.13 | 0.013 | 0.042 | 0.012 | 0.005 | 0.001 | 0.03 |
| 6 | 0.08 | 0.26 | 1.31 | 0.022 | 0.033 | 0.018 | 0.004 | 0.001 | 0.05 |
| 7 | 0.07 | 0.16 | 1.16 | 0.023 | 0.029 | 0.015 | 0.005 | 0.001 | 0.04 |
| 8 | 0.06 | 0.29 | 1.36 | 0.023 | 0.032 | 0.012 | 0.005 | 0.001 | 0.03 |
Table 2: smelting process
Table 3: rolling process
Table 4: conventional tensile mechanical properties, ferrite content and average grain size
Table 5: low temperature performance and NDTT temperature
| Examples | Thickness/mm of finished product | NDTT/℃ | Akv/J of impact work (-40 ℃ C.) |
| 1 | 22 | -50 | 236 |
| 2 | 25 | -50 | 242 |
| 3 | 29 | -45 | 221 |
| 4 | 32 | -45 | 251 |
| 5 | 35 | -45 | 232 |
| 6 | 45 | -50 | 230 |
| 7 | 48 | -50 | 242 |
| 8 | 50 | -50 | 228 |
The foregoing is considered as illustrative only of the principles of the invention and is not to be in any way limiting, since all equivalent changes and modifications are intended to be included within the scope of the appended claims.
Claims (3)
1. The high-ductility EH36 grade ocean engineering steel is characterized by comprising the following chemical components in percentage by weight: c: 0.05-0.08%, Si: 0.10-0.30%, Mn: 1.00% -1.50%, Nb: 0.01% -0.04%, V: 0.02% -0.05%, Ti: 0.005% -0.02%, P: less than or equal to 0.01 percent, S: less than or equal to 0.01 percent, Als: 0.01 to 0.05 percent, and the balance of Fe and inevitable impurities.
2. The manufacturing method of the high-ductility EH36 grade steel for ocean engineering according to claim 1, comprising the following steps: smelting, continuous casting, heating a casting blank, rolling, straightening, relaxing and cooling; the method is characterized in that:
1) heating a casting blank: induction heating at a heating rate of 5.5 to 7 ℃ s -1 Rapidly heating the continuous casting blank to 1150-1180 ℃, and controlling the temperature uniformity of the casting blank within the range of +/-30 ℃;
2) the rolling process comprises the following steps: two-stage rolling is adopted for the continuous casting billet, the rolling temperature of the first stage is an austenite recrystallization temperature region of 950-1000 ℃, and the average single-pass reduction rate is more than 10%; the rolling temperature of the second stage is in an austenite non-recrystallization temperature region of 750-800 ℃, and the average single-pass reduction rate reaches 15-20%;
3) post-rolling relaxation phase change control: the steel plate is air-cooled to 680-730 ℃, then enters a cooling system, the relaxation time of the steel plate in an alpha/gamma two-phase region after final rolling is increased, eutectoid ferrite is fully nucleated, and the proportion of the ferrite structure of the final structure is ensured to be more than 85%;
4) and (3) a cooling process: and a rapid laminar cooling system with the average cooling speed of 3-10 ℃/s is adopted, the temperature of red returning is controlled to be 550-600 ℃, the composition and the size of a phase change structure are controlled, the steel plate is slowly cooled after cooling, and the slow cooling time is more than or equal to 24 hours.
3. The high-ductility grade EH36 steel for ocean engineering according to claim 1, wherein longitudinal magnetic flux induction heating is used in the slab heating process.
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| CN115418460A (en) * | 2022-08-30 | 2022-12-02 | 南京钢铁股份有限公司 | FH32-HD50 high-ductility ship plate steel and preparation method thereof |
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