Manufacturing method for and use of corrosion-resistant and low-temperature-resistant continuous-cast steel billet for wind turbine

Abstract

The present invention relates to the technical field of metallurgy. Disclosed are a manufacturing method for and use of a corrosion-resistant and low-temperature-resistant continuous-cast steel billet for a wind turbine. The manufacturing method comprises the following steps: carrying out electric furnace steelmaking, carrying out LF refining, carrying out VD vacuum treatment, carrying out continuous casting by means of three-stage vibration crystallization, i.e., non-sinusoidal, sinusoidal and non-sinusoidal vibration crystallization, and carrying out gradual slow-cooling aging, i.e., strong, medium and weak slow-cooling aging, to obtain a continuous-cast steel billet for a wind turbine. According to the present invention, by means of composition and process control, a specific microstructure can be formed. On one hand, a continuous-cast billet is manufactured by means of three-stage vibration crystallization, i.e., non-sinusoidal, sinusoidal and non-sinusoidal vibration crystallization, in a crystallization process; and on the other hand, in the present invention, by means of gradual slow-cooling, i.e., strong, medium and weak slow-cooling, a characteristic composite microstructure having a 0.1-5.5 μm (Nb, V, Ti)CN phase and a 0.3-3.8 nm dispersed copper-rich nanophase is finally formed, and the composite microstructure has excellent low-temperature impact resistance and multiple biological corrosion resistance.

Description

A method for manufacturing a corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power and its application Technical Field

[0001] The invention relates to a method for manufacturing a corrosion-resistant and low-temperature-resistant continuous casting billet of wind power steel and application thereof, belonging to the technical field of metallurgy. Background Art

[0002] Wind energy, a new energy source with enormous potential, has experienced rapid global growth in recent years. While onshore wind turbines are undergoing vigorous development and large-scale construction, offshore wind energy has become an increasingly attractive development direction. Offshore wind energy offers enormous potential and is more cost-competitive, and offshore wind turbine technology is already mature in Europe.

[0003] my country boasts a vast territory and abundant wind energy resources, which have been well-developed. Wind energy technology has also advanced significantly, with wind turbines already reaching the megawatt level. Both the number and capacity of installed wind power equipment in my country are showing positive growth trends, effectively meeting the growing demand for energy. With the advancement of the wind power industry, and the increasing scale of wind power equipment, performance requirements for its components are also constantly increasing.

[0004] Currently, most wind turbines are built in remote areas such as coastal areas, grasslands, and deserts. These areas are home to a wide variety of microorganisms, which can significantly affect key wind turbine components such as towers and foundations, which are exposed to the elements and in contact with the ground or water. Furthermore, northern regions often face extreme cold, low operating temperatures, and the presence of a variety of microbial corrosion factors, which pose challenges to wind turbine operation and maintenance.

[0005] Therefore, those skilled in the art urgently need to develop a method for manufacturing corrosion-resistant and low-temperature-resistant wind power steel continuous casting billets and their applications to solve the problems of low-temperature fracture tendency and severe biological corrosion faced by the above-mentioned key wind power components.

[0006] Summary of the Invention

[0007] The problem to be solved by the present invention is to provide a method for manufacturing corrosion-resistant and low-temperature resistant wind power steel continuous casting billets, which can solve the problems of low-temperature fracture tendency and severe biological corrosion faced by existing wind power.

[0008] At the same time, the present invention provides a corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power.

[0009] At the same time, the present invention provides a corrosion-resistant and low-temperature-resistant wind power steel continuous casting billet for use in wind turbines under extremely cold conditions.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0011] A method for manufacturing a corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power generation, comprising the following steps:

[0012] S1, electric furnace steelmaking: the electric furnace is blown with oxygen for decarburization and dephosphorization, slag is formed and the slag is blocked before tapping to obtain molten steel;

[0013] S2, LF refining: The molten steel obtained in S1 is subjected to ladle argon blowing, stirring, refining, deoxidation, desulfurization, and inclusion removal in the LF refining furnace;

[0014] S3, VD vacuum treatment: using VD furnace to remove gas;

[0015] S4, continuous casting: The molten steel treated in S3 is continuously cast to form continuous casting billets. The process includes three steps:

[0016] S41, the ladle is transferred to the continuous casting machine for casting, and the molten steel enters the tundish through the ladle nozzle;

[0017] S42, after the molten steel level reaches the pouring position, the continuous casting machine is started and the molten steel flows into the crystallizer. The crystallization process adopts a three-stage crystallization method.

[0018] In the initial stage, i.e. the first 15 minutes of the entire casting time, the crystallizer adopts non-sinusoidal vibration, and the vibration process is: amplitude ±4.5-5mm, vibration frequency 120-130min -1 , the correction rate a is 19.6-20.3%;

[0019] In the middle stage, that is, 30 minutes after the completion of the initial stage to the end of casting, the crystallizer adopts sinusoidal vibration combined with electromagnetic stirring casting. The vibration process is: amplitude ±4-4.5mm, vibration frequency 130-140min -1 , electromagnetic stirring current 260-270A;

[0020] In the later stage, that is, after the completion of the intermediate stage and until the end of casting, the crystallizer adopts non-sinusoidal vibration. The vibration process is: amplitude ±3-3.5mm, vibration frequency 140-150min -1 , the correction rate a is 22.1-23.6%;

[0021] S43, the billet is pulled out of the crystallizer and enters the next process;

[0022] S5, slow cooling aging: the round billets cast out are quickly placed in a slow cooling pit at 900-950℃, and a strong slow cooling-medium slow cooling-weak slow cooling progressive method is adopted. Among them, the strong slow cooling time is 8-9h, the slow cooling cover is sealed, and the cooling rate is 5-8℃ / h; the medium slow cooling time is 5-7h, the slow cooling cover is semi-sealed, and the cooling rate is 20-30℃ / h; the weak slow cooling time is 10-20h, the slow cooling cover is fully opened, and the cooling rate is 50-80℃ / h, and then the continuous casting billets of steel for wind power are obtained.

[0023] In the S1 electric furnace steelmaking process, the smelting temperature is 1600-1680℃, and the smelting time is based on the C and P content meeting the standards, where C: 0.09-0.10wt%, P≤0.007wt%.

[0024] In the S2 LF refining process, the white slag holding time of ladle refining is 20-60min, the refining time is 100-150min, the argon flow rate is 80-250NL / min, and the O percentage content is controlled to be ≤35ppm.

[0025] In the S2 LF refining process,

[0026] In the early stage of refining, i.e. 0-30min, 25-50kg of lime is added for slag adjustment, and the argon flow rate is 230-250NL / min;

[0027] In the middle stage of refining, i.e. 30-80 minutes, the argon intensity is maintained at 130-180 NL / min;

[0028] In the later stage of refining, that is, from 80 minutes to the end of refining, the argon intensity is 80-100NL / min to prevent the molten steel from tumbling and oxidation.

[0029] In the S3 VD vacuum treatment process, the vacuum degree is 55-95 Pa, the vacuum holding time is 15-20 min, the vacuum treatment temperature is 1630-1665 ° C, and the soft argon blowing time is 15-20 min.

[0030] In the S4 continuous casting process, the casting speed is 0.10-0.15m / min; the continuous casting temperature is 1510-1535℃.

[0031] The manufacturing method of the present invention obtains a corrosion-resistant and low-temperature-resistant continuous casting billet of steel for wind power.

[0032] Corrosion-resistant and low-temperature-resistant continuous casting steel ingot for wind power generation, the components of the continuous casting ingot are calculated by mass percentage: C: 0.085-0.096%; Si: 0.18-0.20%; Mn: 0.8-1.0%; Cr: 0.28-0.32%; V: 0.49-0.52%; Nb: 0.036-0.052%; Mo: 0.38-0.42%; Al: 0.025-0.035%; Ti: 0.059-0.087%; Ni: 0.93-0.97%; Cu: 0.11-0.17%; N: 0.015-0.018%; P: ≤0.007%; S: ≤0.004%; O: ≤20ppm and the balance Fe.

[0033] The continuous casting ingot of steel for wind power forms an ACN phase of 0.1-5.5 microns at the grain boundaries. The A in the ACN phase is Nb, V and Ti, that is, the ACN phase is a (Nb, V, Ti)CN phase; a copper-rich nanophase of 0.3-3.8 nanometers is dispersed in the grain boundaries.

[0034] The corrosion-resistant and low-temperature-resistant wind power steel continuous casting billet of the present invention is used in wind turbine generator sets under extremely cold conditions, where the temperature is -80°C.

[0035] The low-temperature impact energy of continuous casting steel billets for wind power generation at -80°C is 236-241J; the pitting density is 52.6-54.4 / mm -2 The maximum pitting depth is 1.7-1.8 microns, and the average pitting depth is 1.1-1.2 microns.

[0036] The present invention has the following technical effects or advantages:

[0037] The corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power of the present invention can form a specific microstructure through composition and process control during the preparation process. On the one hand, the continuous casting billet adopts non-sinusoidal-sinusoidal-non-sinusoidal three-stage vibration crystallization during the crystallization process. Non-sinusoidal vibration is adopted in the initial stage to produce a flushing contact effect between the molten steel and the wall of the crystallizer, and new crystal nuclei are continuously and repeatedly formed at the crystallization wall, thereby increasing the number of crystal nuclei in the melt and releasing a large amount of crystallization latent heat. Sinusoidal vibration is adopted in the intermediate stage. The periodic reciprocating vibration and the release of crystallization latent heat cause local temperature fluctuations between the crystallized grains and the melt, forming a local negative temperature gradient at the solid-liquid interface to accelerate the directional diffusion of alloy elements, causing the alloy elements Nb, V, and Ti to be redistributed at the solid-liquid interface, and forming element segregation at the grain boundaries after complete solidification. In the later stage, non-sinusoidal vibration is used to reduce the tensile stress of the shell under the curved moon surface during the positive sliding time, and to increase the pressure of the blank during the negative sliding time, forming a directional stress distribution, thereby accelerating the diffusion of alloying elements Nb, V, and Ti to defects, and finally concentrating them at the grain boundaries. Due to the affinity of alloying elements with C and N elements, (Nb, V, Ti)CN is formed at the grain boundaries;

[0038] On the other hand, the round billet continuously cast in the present invention adopts a strong slow-medium slow-weak slow progressive slow cooling method, which takes advantage of the diffusion of high-temperature elements under strong slow cooling to form a uniform solid solution of Cu. The solid solution of Cu is then supersaturated by combining the temperature change under medium slow cooling with the difference in the solubility of Cu in the structure at different temperatures. Finally, the temperature is lowered under weak slow cooling to precipitate the supersaturated Cu to form a copper-rich nanophase, ultimately forming a characteristic composite microstructure of (Nb, V, Ti)CN at the level of 0.1-5.5 microns + dispersed copper-rich nanophase at the level of 0.3-3.8 nanometers.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] 1. The composite microstructure has low-temperature impact resistance: The continuous casting steel ingot for wind power generation of the present invention has a characteristic microstructure of (Nb, V, Ti)CN at the level of 0.1-5.5 microns + dispersed copper-rich nanophase at the level of 0.3-3.8 nanometers. Therefore, the continuous casting steel ingot for wind power generation of the present invention has the effect of synergistically hindering crack propagation and improving low-temperature impact resistance, so that it has excellent low-temperature impact resistance. The principle is: 1) (Nb, V, Ti) CN is distributed on the grain boundaries, which can pin the grain boundaries and inhibit grain growth, thereby refining the grain size. In addition, the (Nb, V, Ti) CN with a size of 0.1-5.5 microns and the grain boundaries jointly block crack propagation, causing the cracks to frequently change paths during the propagation process, thereby consuming more energy and significantly improving the material's resistance to low-temperature impact. 2) Through the alloying of a trace amount of 0.11-0.17% Cu, a dispersed copper-rich nanophase is formed in the preparation process of the continuous casting billet of the wind power steel of the present invention. On the one hand, the copper-rich nanophase in the steel will reduce the rheological stress, shift the ductile-brittle transition temperature to the left, and improve the resistance to low-temperature impact. On the other hand, the copper-rich nanophase not only prevents the growth of newly recrystallized submicron grains, but also improves the thermodynamic stability of the organization while blocking crack propagation through the pinning mechanism, thereby significantly improving the material's resistance to low-temperature impact.

[0041] 2. Multiple bio-corrosion resistance properties of copper-rich nanophases: The copper-rich nanophases are dispersed in the structure of the continuous casting steel billet for wind power generation of the present invention, which makes the continuous casting steel billet for wind power generation of the present invention have excellent bio-corrosion resistance. The principle is: 1) The copper-rich nanophase improves the bio-corrosion resistance of the material. When the surface of the material is exposed to the service environment, microbial corrosion occurs, and the copper ions released by the exposed copper-rich nanophases change the oxidation state of the copper ions by gaining and losing single electrons. Among them, Cu can act as a catalyst to produce reactive oxygen species, which cause oxidative damage to bacterial proteins, nucleic acids or lipids by contacting them, causing them to lose their activity. At the same time, free copper ions can also kill bacteria by coagulating bacterial proteins. The final result of these two aspects is that the bacteria lose their activity, achieving the purpose of reducing microbial corrosion. 2) The corrosion potential of iron is -0.60V, and the corrosion potential of copper is -0.20V. A large amount of copper-rich nanophase increases the corrosion potential of the continuous casting billet, weakens its tendency to electrochemical corrosion, and inhibits the electrochemical corrosion process during the biocorrosion process. 3) Copper is easily oxidized during the corrosion process to form a passivation film, which in turn protects the continuous casting round billet and further improves its resistance to biocorrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG1 is a flow chart of the present invention;

[0043] FIG2 is a microstructure diagram of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples. The following examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0045] Example 1

[0046] As shown in FIG1 , a method for manufacturing a corrosion-resistant and low-temperature-resistant continuous casting steel slab for wind power generation includes the following steps:

[0047] S1, electric furnace steelmaking: oxygen blowing decarburization and dephosphorization treatment in the electric furnace, slag blocking and tapping after slag formation to obtain molten steel; in the electric furnace steelmaking process, the smelting temperature is 1650°C, and the smelting time is based on the C and P content meeting the standards, where C: 0.095wt% and P: 0.007wt%;

[0048] S2, LF refining: The molten steel obtained in S1 is subjected to ladle argon blowing and stirring refining, deoxidation, desulfurization, and inclusion removal in an LF refining furnace. In the LF refining process, the white slag from the ladle refining is held for 40 minutes, the refining time is 125 minutes, and the oxygen content is controlled at 35 ppm.

[0049] In the early stage of refining, i.e. 0-30 min, 35 kg of lime is added for slag adjustment, and the argon flow rate is 240 NL / min;

[0050] During the middle stage of refining, i.e. 30-80 min, the argon intensity is maintained at 150 NL / min;

[0051] In the late refining period, i.e. 80-125 min, the argon intensity is 90 NL / min to prevent the molten steel from tumbling and oxidation;

[0052] S3, VD vacuum treatment: VD furnace is used to remove gas; in the VD vacuum treatment process, the vacuum degree is 75Pa, the vacuum holding time is 18min, the vacuum treatment temperature is 1650℃, and the soft blowing time of argon is 18min;

[0053] S4, continuous casting: The molten steel treated in S3 is continuously cast to form continuous casting billets. The process includes three steps:

[0054] S41, the ladle is transferred to the continuous casting machine for casting, and the molten steel enters the tundish through the ladle nozzle;

[0055] S42, after the molten steel level reaches the pouring position, the continuous casting machine is started and the molten steel flows into the crystallizer. The crystallization process adopts a three-stage crystallization method.

[0056] In the initial stage, i.e. the first 15 minutes of the entire casting time, the mold adopts non-sinusoidal vibration, and the vibration process is: amplitude ±4.8mm, vibration frequency 125min -1 , the correction rate a is 20.0%;

[0057] In the middle stage, that is, the first 30 minutes after the completion of the initial stage to the end of casting, the crystallizer adopts sinusoidal vibration combined with electromagnetic stirring casting. The vibration process is: amplitude ±4.2mm, vibration frequency 135min -1 , electromagnetic stirring current 265A;

[0058] In the later stage, that is, after the completion of the intermediate stage and until the end of casting, the crystallizer adopts non-sinusoidal vibration, and the vibration process is: amplitude ±3.2mm, vibration frequency 145min -1 , the correction rate a is 22.3%;

[0059] S43, the billet is pulled out of the crystallizer and enters the next process;

[0060] In the S4 continuous casting process, the casting speed is 0.12m / min and the continuous casting temperature is 1520℃;

[0061] S5, slow cooling aging: the round billets cast out are quickly placed in the slow cooling pit at 930℃, and a strong slow cooling-medium slow cooling-weak slow cooling progressive method is adopted. Among them, the strong slow cooling time is 8.5h, the slow cooling cover is sealed, and the cooling rate is 6℃ / h; the medium slow cooling time is 6h, the slow cooling cover is semi-sealed, and the cooling rate is 25℃ / h; the weak slow cooling time is 15h, the slow cooling cover is fully opened, and the cooling rate is 65℃ / h. Then the continuous casting billets of steel for wind power are obtained.

[0062] The manufacturing method of this embodiment obtains a corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power.

[0063] The components of the continuous casting billet are calculated by mass percentage: C: 0.092%; Si: 0.19%; Mn: 0.9%; Cr: 0.30%; V: 0.50%; Nb: 0.045%; Mo: 0.40%; Al: 0.030%; Ti: 0.070%; Ni: 0.95%; Cu: 0.15%; N: 0.016%; P: 0.007%; S: 0.004%; O: 20 ppm and the balance Fe.

[0064] As shown in FIG2 , the continuous casting steel slab for wind power generation obtained in this embodiment forms a (Nb, V, Ti)CN phase of 0.1-5.5 micrometers at the grain boundary, and a copper-rich nanophase of 0.3-3.8 nanometers is dispersed in the grain boundary.

[0065] The corrosion-resistant and low-temperature-resistant wind power steel continuous casting billet of this embodiment is used in wind turbines under extremely cold conditions, where the temperature is -80°C.

[0066] The low-temperature impact energy of continuous casting steel billets for wind power generation at -80°C is 239J; the pitting density is 54.4 / mm -2 , the maximum pitting depth is 1.8 microns and the average pitting depth is 1.2 microns.

[0067] Example 2

[0068] A method for manufacturing a corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power generation, comprising the following steps:

[0069] S1, electric furnace steelmaking: oxygen blowing decarburization and dephosphorization treatment in the electric furnace, slag blocking and tapping after slag formation to obtain molten steel; in the electric furnace steelmaking process, the smelting temperature is 1600°C, and the smelting time is based on the C and P content meeting the standards, where C: 0.09wt% and P: 0.005wt%;

[0070] S2, LF refining: The molten steel obtained in S1 is subjected to ladle argon blowing and stirring refining, deoxidation, desulfurization, and inclusion removal in an LF refining furnace; in the LF refining process, the white slag from the ladle refining is held for 20 minutes, the refining time is 100 minutes, and the oxygen content is controlled at 20 ppm;

[0071] In the early stage of refining, i.e. 0-30 min, 25 kg of lime is added for slag adjustment, and the argon flow rate is 230 NL / min;

[0072] During the middle stage of refining, i.e. 30-80 min, the argon intensity is maintained at 130 NL / min;

[0073] In the late refining period, i.e. 80-100 min, the argon intensity is 80 NL / min to prevent the molten steel from tumbling and oxidation;

[0074] S3, VD vacuum treatment: VD furnace is used to remove gas; in the VD vacuum treatment process, the vacuum degree is 55 Pa, the vacuum holding time is 15 minutes, the vacuum treatment temperature is 1630 ° C, and the soft blowing time of argon is 15 minutes;

[0075] S4, continuous casting: The molten steel treated in S3 is continuously cast to form continuous casting billets. The process includes three steps:

[0076] S41, the ladle is transferred to the continuous casting machine for casting, and the molten steel enters the tundish through the ladle nozzle;

[0077] S42, after the molten steel level reaches the pouring position, the continuous casting machine is started and the molten steel flows into the crystallizer. The crystallization process adopts a three-stage crystallization method.

[0078] In the initial stage, i.e. the first 15 minutes of the entire casting time, the mold adopts non-sinusoidal vibration, and the vibration process is: amplitude ±4.5mm, vibration frequency 120min -1 , the correction rate a is 19.6%;

[0079] In the middle stage, that is, 30 minutes after the completion of the initial stage to the end of casting, the crystallizer adopts sinusoidal vibration combined with electromagnetic stirring casting. The vibration process is: amplitude ±4mm, vibration frequency 130min-1 , electromagnetic stirring current 260A;

[0080] In the later stage, that is, after the completion of the intermediate stage and until the end of casting, the crystallizer adopts non-sinusoidal vibration, and the vibration process is: amplitude ±3mm, vibration frequency 140min -1 , the correction rate a is 22.1%;

[0081] S43, the billet is pulled out of the crystallizer and enters the next process;

[0082] In the S4 continuous casting process, the casting speed is 0.10 m / min and the continuous casting temperature is 1510°C;

[0083] S5, slow cooling aging: the round billets cast out are quickly placed in a slow cooling pit at 900℃, and a strong slow cooling-medium slow cooling-weak slow cooling progressive method is adopted. Among them, the strong slow cooling time is 8h, the slow cooling cover is sealed, and the cooling rate is 8℃ / h; the medium slow cooling time is 5h, the slow cooling cover is semi-sealed, and the cooling rate is 30℃ / h; the weak slow cooling time is 10h, the slow cooling cover is fully opened, and the cooling rate is 80℃ / h. Then the continuous casting billets of steel for wind power are obtained.

[0084] The manufacturing method of this embodiment obtains a corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power.

[0085] The components of the continuous casting billet are calculated by mass percentage: C: 0.085%; Si: 0.18%; Mn: 0.8%; Cr: 0.28%; V: 0.49%; Nb: 0.036%; Mo: 0.38%; Al: 0.025%; Ti: 0.059%; Ni: 0.93%; Cu: 0.11%; N: 0.015%; P: 0.005%; S: 0.002%; O: 10 ppm and the balance Fe.

[0086] The wind power steel continuous casting slab obtained in this embodiment forms a (Nb, V, Ti)CN phase of 0.1-5.5 micrometers at the grain boundary, and a copper-rich nanophase of 0.3-3.8 nanometers is dispersed in the grain boundary.

[0087] The corrosion-resistant and low-temperature-resistant wind power steel continuous casting billet of this embodiment is used in wind turbines under extremely cold conditions, where the temperature is -80°C.

[0088] The low-temperature impact energy of continuous casting steel billets for wind power generation at -80°C is 236J; the pitting density is 52.6 / mm -2 , the maximum pitting depth is 1.7 microns and the average pitting depth is 1.1 microns.

[0089] Example 3

[0090] A method for manufacturing a corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power generation, comprising the following steps:

[0091] S1, electric furnace steelmaking: oxygen blowing decarburization and dephosphorization in the electric furnace, slag blocking and tapping after slag formation to obtain molten steel; in the electric furnace steelmaking process, the smelting temperature is 1680°C, and the smelting time is based on the C and P content meeting the standards, where C: 0.10wt% and P: 0.002wt%;

[0092] S2, LF refining: The molten steel obtained in S1 is subjected to ladle argon blowing and stirring refining, deoxidation, desulfurization, and inclusion removal in an LF refining furnace. In the LF refining process, the white slag from the ladle refining is held for 60 minutes, the refining time is 150 minutes, and the oxygen content is controlled at 35 ppm.

[0093] In the early stage of refining, i.e. 0-30 min, 50 kg of lime is added for slag adjustment, and the argon flow rate is 250 NL / min;

[0094] During the middle stage of refining, i.e. 30-80 min, the argon intensity is maintained at 180 NL / min;

[0095] In the late refining period, i.e. 80-150 min, the argon intensity is 100 NL / min to prevent the molten steel from tumbling and oxidation;

[0096] S3, VD vacuum treatment: VD furnace is used to remove gas; in the VD vacuum treatment process, the vacuum degree is 95Pa, the vacuum holding time is 20min, the vacuum treatment temperature is 1665℃, and the soft blowing time of argon is 20min;

[0097] S4, continuous casting: The molten steel treated in S3 is continuously cast to form continuous casting billets. The process includes three steps:

[0098] S41, the ladle is transferred to the continuous casting machine for casting, and the molten steel enters the tundish through the ladle nozzle;

[0099] S42, after the molten steel level reaches the pouring position, the continuous casting machine is started and the molten steel flows into the crystallizer. The crystallization process adopts a three-stage crystallization method.

[0100] In the initial stage, i.e. the first 15 minutes of the entire casting time, the crystallizer adopts non-sinusoidal vibration, and the vibration process is: amplitude ±5mm, vibration frequency 130min -1 , the correction rate a is 20.3%;

[0101] In the middle stage, that is, 30 minutes after the completion of the initial stage to the end of casting, the crystallizer adopts sinusoidal vibration combined with electromagnetic stirring casting. The vibration process is: amplitude ±4.5mm, vibration frequency 140min -1 , electromagnetic stirring current 270A;

[0102] In the later stage, that is, after the completion of the intermediate stage and until the end of casting, the crystallizer adopts non-sinusoidal vibration, and the vibration process is: amplitude ±3.5mm, vibration frequency 150min -1 , the correction rate a is 23.6%;

[0103] S43, the billet is pulled out of the crystallizer and enters the next process;

[0104] In the S4 continuous casting process, the casting speed is 0.15m / min and the continuous casting temperature is 1535℃;

[0105] S5, slow cooling aging: the round billets cast out are quickly placed in a slow cooling pit at 950℃, and a strong slow cooling-medium slow cooling-weak slow cooling progressive method is adopted. Among them, the strong slow cooling time is 9h, the slow cooling cover is sealed, and the cooling rate is 5℃ / h; the medium slow cooling time is 7h, the slow cooling cover is semi-sealed, and the cooling rate is 20℃ / h; the weak slow cooling time is 20h, the slow cooling cover is fully opened, and the cooling rate is 50℃ / h. Then the continuous casting billets of steel for wind power are obtained.

[0106] The manufacturing method of this embodiment obtains a corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power.

[0107] The components of the continuous casting billet are calculated by mass percentage: C: 0.096%; Si: 0.20%; Mn: 1.0%; Cr: 0.32%; V: 0.52%; Nb: 0.052%; Mo: 0.42%; Al: 0.035%; Ti: 0.087%; Ni: 0.97%; Cu: 0.17%; N: 0.018%; P: 0.002%; S: 0.002%; O: 15 ppm and the balance Fe.

[0108] As shown in FIG2 , the continuous casting steel slab for wind power generation obtained in this embodiment forms a (Nb, V, Ti)CN phase of 0.1-5.5 micrometers at the grain boundary, and a copper-rich nanophase of 0.3-3.8 nanometers is dispersed in the grain boundary.

[0109] The corrosion-resistant and low-temperature-resistant wind power steel continuous casting billet of this embodiment is used in wind turbines under extremely cold conditions, where the temperature is -80°C.

[0110] The low-temperature impact energy of continuous casting steel billets for wind power generation at -80°C is 241J; the pitting density is 53.9 / mm -2 , the maximum pitting depth is 1.8 microns and the average pitting depth is 1.2 microns.

[0111] Comparative Example 1

[0112] It is commercial 42CrMo.

[0113] Comparative Example 2: Only the (Nb, V, Ti)CN phase was formed.

[0114] The only difference between this comparative example and Example 1 is that the slow cooling aging is that after the steel ingot is continuously cast and ejected from the mold, it is piled in a slow cooling pit at 930°C, immediately covered and slowly cooled at a cooling rate of 4°C / h. Slow cooling is used for aging, and when the ingot body cools to below 200°C, it is taken out of the pit and air-cooled to room temperature.

[0115] Comparative Example 3: Only the copper-rich nanophase was formed.

[0116] The only difference between this comparative example and Example 1 is that in S4, the molten steel is allowed to flow into the crystallizer for continuous casting, the casting temperature is 1520° C., and the continuous casting speed is 0.12 m / min.

[0117] Table 1 shows the comparison results of low temperature impact properties.

[0118] A series of impact tests from 0 to -80°C were conducted using a 10 mm × 10 mm × 55 mm transverse V8 impact specimen (test standard: ASTM E23-12c). The impact results are shown in Table 1 below.

[0119] Table 1 Comparison of low temperature impact properties

[0120] Table 2 shows the comparison results of biocorrosion resistance.

[0121] The microbial corrosion resistance test was carried out in a soil leachate environment containing sulfate-reducing bacteria, and the immersion time at room temperature was 20 days.

[0122] The maximum pitting depth and average pitting depth were measured by CLSM after the corroded samples were taken out.

[0123] Pitting density: The number of pits per unit area is used for statistics.

[0124] Table 2 Comparison of biocorrosion resistance

[0125] It should be understood that in order to streamline the present disclosure and aid understanding of one or more of the various inventive aspects, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in less than all of the features of the previously disclosed embodiments. Accordingly, the claims that follow the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of the invention.

[0126] Although the present invention has been described with respect to a limited number of embodiments, it will be apparent to those skilled in the art, having benefit of the foregoing description, that other embodiments are contemplated within the scope of the invention thus described. Furthermore, it should be noted that the language used in this specification has been selected primarily for readability and didactic purposes, rather than for the purpose of explaining or limiting the subject matter of the present invention. Consequently, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is intended to be illustrative rather than restrictive of the scope of the invention, which is defined by the appended claims.

[0127] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for manufacturing a corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power, characterized in that: The following steps are involved: S1, electric furnace steelmaking: electric furnace oxygen blowing decarburization and dephosphorization treatment, slag blocking and steel tapping after slag making to obtain molten steel; S2, LF refining: The molten steel obtained in S1 is subjected to ladle argon blowing, stirring, refining, deoxidation, desulfurization, and inclusion removal in the LF refining furnace; S3, VD vacuum treatment: use VD furnace to remove gas; S4, continuous casting: The molten steel treated in S3 is continuously cast to form a continuous casting billet. The process includes three steps: S41, the ladle is transferred to the continuous casting machine for casting, and the molten steel enters the tundish through the ladle nozzle; S42, after the molten steel level reaches the pouring position, the continuous casting machine is started and the molten steel flows into the crystallizer. The crystallization process adopts a three-stage crystallization method. In the initial stage, i.e. the first 15 minutes of the entire casting time, the crystallizer adopts non-sinusoidal vibration, and the vibration process is: amplitude ±4.5-5mm, vibration frequency 120-130min -1 , the correction rate a is 19.6-20.3%; In the middle stage, that is, the first 30 minutes after the completion of the initial stage to the end of casting, the crystallizer adopts sinusoidal vibration combined with electromagnetic stirring casting. The vibration process is: amplitude ±4-4.5mm, vibration frequency 130-140min -1 , electromagnetic stirring current 260-270A; In the later stage, that is, after the intermediate stage is completed and until the casting is finished, the crystallizer adopts non-sinusoidal vibration, and the vibration process is: amplitude ±3-3.5mm, vibration frequency 140-150min -1 , the correction rate a is 22.1-23.6%; S43, the billet is pulled out of the crystallizer and enters the next process; S5, slow cooling aging: the round billet cast out is quickly placed in the slow cooling pit at 900-950℃, and a strong slow cooling-medium slow cooling-weak slow progressive slow cooling method is adopted, wherein the strong slow cooling time is 8-9h, the slow cooling cover is sealed, and the cooling rate is 5-8℃ / h; the medium slow cooling time is 5-7h, the slow cooling cover is semi-sealed, and the cooling rate is 20-30℃ / h; the weak slow cooling time is 10-20h, the slow cooling cover is fully opened, and the cooling rate is 50-80℃ / h, and then the continuous casting billet for wind power steel is obtained; The continuous casting ingot of wind power steel forms an ACN phase of 0.1-5.5 microns at the grain boundary, in which A is Nb, V and Ti; a copper-rich nanophase of 0.3-3.8 nanometers is dispersed in the grain boundary; The components of the continuous casting billet are calculated by mass percentage: C: 0.085-0.096%; Si: 0.18-0.20%; Mn: 0.8-1.0%; Cr: 0.28-0.32%; V: 0.49-0.52%; Nb: 0.036-0.052%; Mo: 0.38-0.42%; Al: 0.025-0.035%; Ti: 0.059-0.087%; Ni: 0.93-0.97%; Cu: 0.11-0.17%; N: 0.015-0.018%; P: ≤0.007%; S: ≤0.004%; O: ≤20ppm and the balance Fe.

2. The manufacturing method according to claim 1, characterized in that: In the S1 electric furnace steelmaking process, the smelting temperature is 1600-1680°C, and the smelting time is based on the C and P contents reaching the standards, where C: 0.09-0.10wt%, P≤0.007wt%.

3. The manufacturing method according to claim 1, characterized in that: In the S2 LF refining process, the white slag retention time of ladle refining is 20-60min, the refining time is 100-150min, the argon flow rate is 80-250NL / min, and the O percentage content is controlled to be ≤35ppm.

4. The manufacturing method according to claim 1, characterized in that: In the S2 LF refining process, In the early stage of refining, i.e. 0-30min, 25-50kg of lime is added for slag adjustment, and the argon flow rate is 230-250NL / min; In the middle stage of refining, i.e. 30-80min, the argon intensity is maintained at 130-180NL / min; In the later stage of refining, that is, from 80 minutes to the end of refining, the argon intensity is 80-100NL / min to prevent the molten steel from tumbling and oxidation.

5. The manufacturing method according to claim 1, characterized in that: In the S3 VD vacuum treatment process, the vacuum degree is 55-95pa, the vacuum holding time is 15-20min, the vacuum treatment temperature is 1630-1665℃, and the soft blowing argon time is 15-20min.

6. The manufacturing method according to claim 1, characterized in that: In the S4 continuous casting process, the pulling speed is 0.10-0.15m / min; the continuous casting temperature is 1510-1535℃.

7. A corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power obtained by the manufacturing method according to any one of claims 1 to 6.

8. The application of the corrosion-resistant and low-temperature-resistant wind power steel continuous casting billet in wind power under extremely cold conditions according to claim 7 is characterized in that: The temperature in extreme cold conditions is -80℃.

9. The corrosion-resistant and low-temperature-resistant continuous casting steel billet for wind power according to claim 7, characterized in that: The low-temperature impact energy of continuous casting steel billets for wind power generation at -80°C is 236-241J; the pitting density is 52.6-54.4 / mm -2 The maximum pitting depth is 1.7-1.8 microns, and the average pitting depth is 1.1-1.2 microns.

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