Continuous casting round billet for wind power yaw and variable pitch bearing and preparation method of continuous casting round billet

Abstract

The invention provides a continuous casting round billet for wind power yaw and variable pitch bearings and a preparation method thereof.The preparation method comprises the steps that (1) KR desulfurization, converter smelting, LF refining and VD vacuum refining are sequentially conducted on molten iron, and treated molten steel is obtained; (2) the treated molten steel obtained in the step (1) is sequentially subjected to continuous casting treatment, slow cooling treatment and finishing, and the continuous casting round billet is obtained; the continuous casting treatment comprises crystallizer electromagnetic stirring, secondary cooling area cooling, tail end electromagnetic stirring and solidification tail end heavy pressure which are sequentially carried out. By integrating crystallizer electromagnetic stirring, secondary cooling area cooling, tail end electromagnetic stirring, solidification tail end heavy pressing and other technologies, the carbon uniformity of the continuous casting round billet is improved, the cross section carbon range is smaller than or equal to 0.05%, the center porosity is smaller than or equal to 1.0 grade, the center shrinkage cavity is 0 grade, the use requirements of steel for high-end wind power yaw and variable pitch bearings are met, and the production cost is reduced. Therefore, the reliability and the service life of the bearing are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of steelmaking, and particularly relates to a continuous casting round billet for a wind power yaw and pitch bearing and a preparation method thereof. Background Art

[0002] Since the 21st century, there have been serious energy crises and environmental deteriorations worldwide. Countries around the world have actively sought solutions and finally focused on wind energy, a renewable green energy source. As one of the renewable energy sources, China ranks first in the world in terms of reserves and development of wind power generation, and it has now been included in the national energy development policy. Due to the fact that wind energy sources are located in mountains, plateaus, coasts and offshore areas, with large temperature and environmental differences, and wind turbines are installed on towers dozens or hundreds of meters high, the following requirements are put forward by wind power manufacturers for the pitch and yaw turntable bearings used in the units: they cannot be replaced or overhauled within 20 years; they are resistant to wind and sand and saline-alkali climate; they meet the environmental requirements of ±45°C, and their impact work Akw is not less than 27J at -45°C.

[0003] Bearings for wind power generation can be roughly divided into three categories, namely: pitch bearings, pitch bearings, and transmission system bearings (main shaft and gearbox bearings). The pitch bearing is installed at the connection part between the root of each blade and the hub. During operation, it needs to bear a large overturning moment. At the same time, the design life of a wind turbine is generally 20 years, which requires the fatigue life of the wind turbine bearing to also reach 20 years. Inclusions, as an important index for the inspection of wind power bearing forgings, directly affect the service life of the final product in terms of their level.

[0004] In the production field of steel for wind power bearings, the carbon element uniformity of continuous casting large round billets is a key index affecting the bearing fatigue life and reliability. In the prior art, the following problems exist in large-section continuous casting round billets with a diameter of more than Φ600mm: (1) Severe carbon segregation: The carbon extreme difference in the cross-section of continuous casting billets produced by traditional processes is usually 0.06%-0.08%, which is difficult to meet the requirement of ≤0.05% for high-end wind power bearings; (2) Insufficient cooling control: The secondary cooling zone uses a fixed specific water volume for cooling, which cannot adapt to the heat conduction requirements at different stages during the solidification process of the casting billet, resulting in an aggravation of center segregation; (3) Limited electromagnetic stirring effect: The parameter settings of the mold and final electromagnetic stirring are unreasonable, and it is impossible to effectively inhibit the growth of columnar crystals and promote the formation of equiaxed crystals; (4) Lack of slow cooling process: After the continuous casting billet is taken off the production line, it is directly air-cooled, with internal stress concentration, further deteriorating the carbon distribution uniformity.

[0005] In view of the above problems, there is an urgent need to develop a new preparation method to effectively control the carbon uniformity of continuous casting large round billets to meet the requirements of high-performance materials for wind power bearings. Summary of the Invention

[0006] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide a continuous casting round billet for wind power yaw and pitch bearings and its preparation method. By optimizing the cooling process, electromagnetic stirring technology, and slow cooling process during continuous casting, the carbon segregation degree of the continuous casting large round billet is significantly reduced, and the uniformity of carbon element distribution is improved.

[0007] To achieve the purpose of this invention, the following technical solutions are adopted by the present invention:

[0008] The present invention provides a continuous casting round billet for wind power yaw and pitch bearings. In terms of mass percentage, the chemical elements of the continuous casting round billet include: C 0.38 - 0.42%, Si 0.15 - 0.35%, Mn 0.65 - 0.75%, Cr 1.00 - 1.10%, Mo 0.20 - 0.25%, Ni 0.10 - 0.15%, and the balance is Fe and inevitable impurities.

[0009] Preferably, the diameter of the continuous casting round billet ≥ 600 mm, for example, it can be 600 mm, 610 mm, 620 mm, 640 mm, 650 mm, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0010] Exemplarily, in the continuous casting round billet, the C content is 0.38 - 0.42%, for example, it can be 0.38 wt%, 0.39 wt%, 0.40 wt%, 0.41 wt%, 0.42 wt%, etc., but not limited to the listed values, and the values within the numerical range are equally applicable;

[0011] The Si content is 0.15 - 0.35%, for example, it can be 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, etc., but not limited to the listed values, and the values within the numerical range are equally applicable;

[0012] The Mn content is 0.65 - 0.75%, for example, it can be 0.65 wt%, 0.67 wt%, 0.69 wt%, 0.71 wt%, 0.73 wt%, 0.75 wt%, etc., but not limited to the listed values, and the values within the numerical range are equally applicable;

[0013] The Cr content is 1.00 - 1.10%, for example, it can be 1.00 wt%, 1.02 wt%, 1.04 wt%, 1.06 wt%, 1.08 wt%, 1.10 wt%, etc., but not limited to the listed values, and the values within the numerical range are equally applicable;

[0014] The Mo content is 0.20 - 0.25%, for example, it can be 0.20wt%, 0.21wt%, 0.22wt%, 0.23wt%, 0.24wt% or 0.25wt%, etc., but is not limited to the listed values, and the values within the range are equally applicable;

[0015] The Ni content is 0.10 - 0.15%, for example, it can be 0.10wt%, 0.11wt%, 0.12wt%, 0.13wt%, 0.14wt% or 0.15wt%, etc., but is not limited to the listed values, and the values within the range are equally applicable.

[0016] In a second aspect, the present invention provides a method for preparing a continuous casting round billet for a wind power yaw and pitch bearing provided in the first aspect, and the preparation method includes the following steps:

[0017] (1) Perform KR desulfurization, converter smelting, LF refining, and VD vacuum refining on the molten iron in sequence to obtain the treated molten steel;

[0018] (2) Perform continuous casting treatment, slow cooling treatment, and finishing on the treated molten steel obtained in step (1) in sequence to obtain the continuous casting round billet;

[0019] The continuous casting treatment includes continuous casting electromagnetic stirring, secondary cooling zone cooling, final electromagnetic stirring, and heavy reduction at the solidification end in sequence.

[0020] In the present invention, by integrating technologies such as continuous casting electromagnetic stirring, secondary cooling zone cooling, final electromagnetic stirring, and heavy reduction at the solidification end, the improvement of the carbon uniformity of the continuous casting round billet is realized, so that the carbon difference in the cross-section ≤ 0.05%, the central porosity ≤ 1.0 grade, and the central shrinkage cavity is grade 0, meeting the use requirements of high-end wind power yaw and pitch bearing steel, thereby improving the reliability and service life of the bearing.

[0021] As a preferred technical solution of the present invention, the P content in the molten iron after KR desulfurization in step (1) ≤ 0.01%, for example, it can be 0.01%, 0.09%, 0.08%, 0.07% or 0.06%, etc., but is not limited to the listed values, and other unlisted values within the range are equally applicable;

[0022] The S content ≤ 0.005%, for example, it can be 0.005%, 0.004%, 0.003% or 0.002%, etc., but is not limited to the listed values, and other unlisted values within the range are equally applicable.

[0023] Preferably, by mass percentage, the refining slag used in the LF refining includes: CaO 48 - 52wt%, SiO2 3 - 6wt%, and Al2O3 37 - 42wt%.

[0024] Exemplarily, the content of CaO in the refining slag is 48 - 52 wt%, for example, it can be 48 wt%, 49 wt%, 50 wt%, 51 wt% or 52 wt% etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable;

[0025] The content of SiO2 is 3 - 6 wt%, for example, it can be 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt% or 6 wt% etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable;

[0026] The content of Al2O3 is 37 - 42 wt%, for example, it can be 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt% or 42 wt% etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] Preferably, the basicity of the refining slag used for LF refining is 10.5 - 11.5, for example, it can be 10.5, 10.7, 10.9, 11.1, 11.3 or 11.5 etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0028] Preferably, the aluminum loss rate of the molten steel after LF refining is 15 - 20%, for example, it can be 15%, 16%, 17%, 18%, 19% or 20% etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0029] Preferably, the aluminum loss rate of the molten steel after VD vacuum refining is 25 - 30%, for example, it can be 25%, 26%, 27%, 28%, 29% or 30% etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] As a preferred technical solution of the present invention, the superheat temperature of the molten steel in the continuous casting process is 15 - 22, for example, it can be 15 °C, 16 °C, 17 °C, 18 °C, 19 °C, 20 °C, 21 °C or 22 °C etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the casting speed of the continuous casting process is 0.15 - 0.2 m / min, for example, it can be 0.15 m / min, 0.16 m / min, 0.17 m / min, 0.18 m / min, 0.19 m / min or 0.2 m / min etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0032] As a preferred technical solution of the present invention, the current of the electromagnetic stirring of the mold is 240 - 340 A, for example, it can be 240 A, 260 A, 280 A, 300 A, 320 A or 340 A, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0033] Preferably, the frequency of the electromagnetic stirring of the mold is 1 - 1.5 Hz, for example, it can be 1 Hz, 1.1 Hz, 1.2 Hz, 1.3 Hz, 1.4 Hz or 1.5 Hz, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the steering time of the electromagnetic stirring of the mold is 15 - 20 s, for example, it can be 15 s, 16 s, 17 s, 18 s, 19 s or 20 s, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] Preferably, the taper of the mold used for the electromagnetic stirring of the mold is 1.0 - 1.2% / m, for example, it can be 1.0% / m, 1.05% / m, 1.1% / m, 1.15% / m or 1.2% / m, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0036] In the present invention, the rotating magnetic field generated by the electromagnetic stirring of the mold can effectively break the front end of columnar crystals, promote the formation of equiaxed crystals, and reduce carbon segregation in the initial solidification stage.

[0037] As a preferred technical solution of the present invention, according to the direction away from the mold outlet, the secondary cooling zone cooling includes first zone cooling, second zone cooling, and third zone cooling.

[0038] Preferably, the first zone cooling includes: using a solid conical nozzle for steam-water atomization cooling.

[0039] Preferably, the spraying angle of the first zone cooling is 80 - 100°, for example, it can be 80°, 85°, 90°, 95° or 100°, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0040] Preferably, the specific water volume of the first zone cooling is 0.8 - 1.0 L / kg, for example, it can be 0.8 L / kg, 0.85 L / kg, 0.9 L / kg, 0.95 L / kg or 1.0 L / kg, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0041] Preferably, the cooling intensity of the first zone cooling is 0.2 - 0.3 MW / m 2, for example, it can be 0.2 MW / m 2 , 0.22 MW / m 2 , 0.24 MW / m 2 , 0.26 MW / m 2 , 0.28 MW / m 2 or 0.3 MW / m 2 etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0042] Preferably, the cooling in the second zone includes: using a fan-shaped nozzle for steam-water atomization cooling.

[0043] Preferably, the spraying angle of the cooling in the second zone is 110 - 130°, for example, it can be 110°, 115°, 120°, 125° or 130° etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0044] Preferably, the water ratio of the cooling in the second zone is 0.6 - 0.8 L / kg, for example, it can be 0.6 L / kg, 0.65 L / kg, 0.7 L / kg, 0.75 L / kg or 0.8 L / kg etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0045] Preferably, the cooling intensity of the cooling in the second zone is 0.15 - 0.2 MW / m 2 , for example, it can be 0.15 MW / m 2 , 0.16 MW / m 2 , 0.17 MW / m 2 , 0.18 MW / m 2 , 0.19 MW / m 2 or 0.2 MW / m 2 etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0046] Preferably, the cooling in the third zone includes: using a hollow cone nozzle for water spray cooling.

[0047] Preferably, the spraying angle of the cooling in the third zone is 120 - 140°, for example, it can be 120°, 125°, 130°, 135° or 140° etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0048] Preferably, the specific water ratio for cooling in the third zone is 0.4 to 0.6 L / kg. For example, it can be 0.4 L / kg, 0.45 L / kg, 0.5 L / kg, 0.55 L / kg, 0.6 L / kg, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0049] Preferably, the cooling intensity in the third zone is 0.1 to 0.15 MW / m 2 , for example, it can be 0.1 MW / m 2 , 0.11 MW / m 2 , 0.12 MW / m 2 , 0.13 MW / m 2 , 0.14 MW / m 2 or 0.15 MW / m 2 , etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0050] In the present invention, by dynamically controlling the specific water ratio, cooling intensity, and casting speed in the secondary cooling zone, the surface temperature of the continuous casting billet is ensured to be controlled within the range of 900 to 1000 °C, avoiding the phenomenon of surface temperature rise.

[0051] As a preferred technical solution of the present invention, the solid fraction at the solidification end of the continuous casting billet in the terminal electromagnetic stirring area is 0.3 to 0.7. For example, it can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, or 0.7, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0052] Preferably, the current of the terminal electromagnetic stirring is 1000 to 1100 A. For example, it can be 1000 A, 1020 A, 1040 A, 1060 A, 1080 A, or 1100 A, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0053] Preferably, the frequency of the terminal electromagnetic stirring is 9 to 10 Hz. For example, it can be 9 Hz, 9.2 Hz, 9.4 Hz, 9.6 Hz, 9.8 Hz, or 10 Hz, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0054] Preferably, the stirring direction of the terminal electromagnetic stirring is opposite to the direction of continuous casting.

[0055] The present invention promotes the flow of molten steel at the solidification front through terminal electromagnetic stirring, which can eliminate the accumulation of solute-rich molten steel in the central region, thereby reducing the central carbon segregation.

[0056] As a preferred technical solution of the present invention, the solid fraction at the solidification end of the continuous casting billet in the area of heavy reduction at the solidification end is 0.8 to 0.95. For example, it can be 0.8, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92 or 0.95, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0057] Preferably, the reduction rate of the heavy reduction at the solidification end is 0.5 to 1.0 mm / min. For example, it can be 0.5 mm / min, 0.6 mm / min, 0.7 mm / min, 0.8 mm / min, 0.9 mm / min or 1.0 mm / min, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0058] Preferably, the reduction amount of the heavy reduction at the solidification end is 10 to 15 mm. For example, it can be 10 mm, 11 mm, 12 mm, 13 mm, 14 mm or 15 mm, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0059] In the present invention, the compaction of the central porosity part of the casting billet is realized through the heavy reduction technology, thereby realizing the improvement of the central carbon segregation.

[0060] As a preferred technical solution of the present invention, the temperature of the slow cooling treatment is 600 to 700 °C. For example, it can be 600 °C, 620 °C, 640 °C, 660 °C, 680 °C or 700 °C, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0061] Preferably, the holding time of the slow cooling treatment is ≥ 24 h. For example, it can be 24 h, 25 h, 26 h, 27 h, 28 h, 29 h or 30 h, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0062] Preferably, cooling treatment is carried out after holding in the slow cooling treatment; the cooling rate of the cooling treatment is 45 to 55 °C / h. For example, it can be 45 °C / h, 47 °C / h, 49 °C / h, 51 °C / h, 53 °C / h or 55 °C / h, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable;

[0063] Preferably, the end temperature of the cooling treatment is ≤ 200 °C. For example, it can be 200 °C, 190 °C, 180 °C, 170 °C, 160 °C or 150 °C, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0064] As a preferred technical solution of the present invention, the second aspect of the present invention provides a preparation method for continuous casting round billets for wind power yaw and pitch bearings, and the preparation method includes the following steps:

[0065] (1) Successively carry out KR desulfurization, converter smelting, LF refining and VD vacuum refining on the molten iron to obtain the treated molten steel;

[0066] After KR desulfurization, the P content in the molten iron is ≤0.01%, and the S content is ≤0.005%;

[0067] By mass percentage, the refining slag used in LF refining includes: 48 - 52 wt% of CaO, 3 - 6 wt% of SiO2 and 37 - 42 wt% of Al2O3; the basicity of the refining slag is 10.5 - 11.5;

[0068] The aluminum loss rate of the molten steel after LF refining is 15 - 20%, and the aluminum loss rate of the molten steel after VD vacuum refining is 25 - 30%;

[0069] (2) Successively carry out continuous casting treatment, slow cooling treatment and finishing on the treated molten steel obtained in step (1) to obtain the continuous casting round billet;

[0070] The continuous casting treatment includes successively carried out mold electromagnetic stirring, secondary cooling zone cooling, final electromagnetic stirring and solidification end heavy reduction;

[0071] The superheat temperature of the molten steel in the continuous casting treatment is 15 - 22°C; the casting speed of the continuous casting treatment is 0.15 - 0.2 m / min;

[0072] The current of the mold electromagnetic stirring is 240 - 340 A, the frequency is 1 - 1.5 Hz, and the steering time is 15 - 20 s; the taper of the mold used for the mold electromagnetic stirring is 1.0 - 1.2% / m;

[0073] In the direction away from the mold outlet, the secondary cooling zone cooling includes the first zone cooling, the second zone cooling and the third zone cooling; the first zone cooling includes: using a solid conical nozzle for steam - water atomization cooling, the spraying angle of the first zone cooling is 80 - 100°, the specific water volume is 0.8 - 1.0 L / kg, and the cooling intensity is 0.2 - 0.3 MW / m 2 ; the second zone cooling includes: using a sector nozzle for steam - water atomization cooling, the spraying angle of the second zone cooling is 110 - 130°, the specific water volume is 0.6 - 0.8 L / kg, and the cooling intensity is 0.15 - 0.2 MW / m 2; The third - zone cooling includes: water spray cooling using a hollow - conical nozzle; the spraying angle of the third - zone cooling is 120 - 140°, the specific water quantity is 0.4 - 0.6 L / kg, and the cooling intensity is 0.1 - 0.15 MW / m 2 ;

[0074] The solid - phase fraction at the solidification end of the continuous - casting billet in the terminal electromagnetic stirring area is 0.3 - 0.7; the current of the terminal electromagnetic stirring is 1000 - 1100 A, the frequency is 9 - 10 Hz; the stirring direction of the terminal electromagnetic stirring is opposite to the continuous - casting drawing direction;

[0075] The solid - phase fraction at the solidification end of the continuous - casting billet in the solidification - end heavy reduction area is 0.8 - 0.95; the reduction rate of the solidification - end heavy reduction is 0.5 - 1.0 mm / min, and the reduction amount is 10 - 15 mm;

[0076] The temperature of the slow - cooling treatment is 600 - 700 °C, and the holding time is ≥24 h.

[0077] The numerical ranges described in the present invention not only include the point values listed above, but also include any point values between the above - mentioned numerical ranges not listed. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the ranges.

[0078] Compared with the prior art, the present invention has the following beneficial effects:

[0079] By integrating technologies such as mold electromagnetic stirring, secondary - cooling zone cooling, terminal electromagnetic stirring, and solidification - end heavy reduction, the present invention realizes the improvement of the carbon uniformity of the continuous - casting round billet, making the carbon difference in the cross - section ≤0.05%, the central porosity ≤1.0 grade, and the central shrinkage cavity grade 0, meeting the usage requirements of high - end wind - power yaw and pitch bearing steels, thereby improving the reliability and service life of the bearings. Specific Embodiments

[0080] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0081] Example 1

[0082] This example provides a continuous - casting round billet for wind - power yaw and pitch bearings with a diameter of 600 mm. In terms of mass percentage, the chemical elements of the continuous - casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and unavoidable impurities.

[0083] The preparation method of the continuous casting round billet for the above-mentioned wind power yaw and pitch bearings comprises the following steps:

[0084] (1) The hot metal is successively subjected to KR desulfurization, converter smelting, LF refining and VD vacuum refining to obtain the treated molten steel;

[0085] The P content in the hot metal after KR desulfurization is 0.008%, and the S content is 0.002%;

[0086] By mass percentage, the refining slag used in the LF refining comprises: 52 wt% of CaO, 6 wt% of SiO2 and 42 wt% of Al2O3; the basicity of the refining slag is 11.5;

[0087] The aluminum loss rate of the molten steel after LF refining is 18%, and the aluminum loss rate of the molten steel after VD vacuum refining is 28%;

[0088] (2) The treated molten steel obtained in step (1) is successively subjected to continuous casting treatment, slow cooling treatment and finishing to obtain the continuous casting round billet;

[0089] The continuous casting treatment includes successively carried out mold electromagnetic stirring, secondary cooling zone cooling, final electromagnetic stirring and solidification end heavy reduction;

[0090] The superheat temperature of the molten steel in the continuous casting treatment is 20 °C; the casting speed of the continuous casting treatment is 0.18 m / min;

[0091] The current of the mold electromagnetic stirring is 300 A, the frequency is 1.25 Hz, and the steering time is 18 s; the taper of the mold used for the mold electromagnetic stirring is 1.1% / m;

[0092] According to the direction away from the mold outlet, the secondary cooling zone cooling includes first zone cooling, second zone cooling and third zone cooling; the first zone cooling includes: using a solid conical nozzle for steam-water atomization cooling, the spraying angle of the first zone cooling is 90°, the specific water volume is 0.9 L / kg, and the cooling intensity is 0.25 MW / m 2 ; the second zone cooling includes: using a sector nozzle for steam-water atomization cooling, the spraying angle of the second zone cooling is 120°, the specific water volume is 0.7 L / kg, and the cooling intensity is 0.18 MW / m 2 ; the third zone cooling includes: using a hollow conical nozzle for water spray cooling; the spraying angle of the third zone cooling is 130°, the specific water volume is 0.5 L / kg, and the cooling intensity is 0.13 MW / m 2 ;

[0093] The solid fraction at the solidification end of the continuous casting slab in the described final electromagnetic stirring zone is 0.5; the current of the final electromagnetic stirring is 1050 A and the frequency is 9.5 Hz; the stirring direction of the final electromagnetic stirring is opposite to the continuous casting withdrawal direction.

[0094] The solid fraction at the solidification end of the continuous casting slab in the described heavy reduction in the solidification end zone is 0.9; the reduction rate of the heavy reduction in the solidification end is 0.75 mm / min and the reduction amount is 12.5 mm.

[0095] The temperature of the slow cooling treatment is 650 °C and the holding time is 28 h.

[0096] Example 2

[0097] This example provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. In terms of mass percentage, the chemical elements of the continuous casting round billet include: C 0.38%, Si 0.15%, Mn 0.65%, Cr 1.00%, Mo 0.20%, Ni 0.10%, and the balance is Fe and inevitable impurities.

[0098] The preparation method of the above continuous casting round billet for wind power yaw and pitch bearings includes the following steps:

[0099] (1) The hot metal is successively subjected to KR desulfurization, converter smelting, LF refining, and VD vacuum refining to obtain the treated molten steel.

[0100] The P content in the hot metal after KR desulfurization is 0.01% and the S content is 0.005%.

[0101] In terms of mass percentage, the refining slag used in the LF refining includes: CaO 48 wt%, SiO2 6 wt%, and Al2O3 42 wt%; the basicity of the refining slag is 10.5.

[0102] The aluminum loss rate of the molten steel after LF refining is 20%, and the aluminum loss rate of the molten steel after VD vacuum refining is 30%.

[0103] (2) The treated molten steel obtained in step (1) is successively subjected to continuous casting treatment, slow cooling treatment, and finishing to obtain the continuous casting round billet.

[0104] The continuous casting treatment includes successively carried out mold electromagnetic stirring, secondary cooling zone cooling, final electromagnetic stirring, and heavy reduction in the solidification end.

[0105] The superheat temperature of the molten steel in the continuous casting treatment is 15 °C; the casting speed of the continuous casting treatment is 0.15 m / min.

[0106] The current of the mold electromagnetic stirring is 240 A, the frequency is 1.5 Hz, and the steering time is 20 s; the taper of the mold used for the mold electromagnetic stirring is 1.2% / m;

[0107] In the direction away from the mold outlet, the secondary cooling zone cooling includes the first zone cooling, the second zone cooling, and the third zone cooling; the first zone cooling includes: using a solid cone nozzle for steam-water atomization cooling, the spraying angle of the first zone cooling is 80°, the specific water volume is 0.8 L / kg, and the cooling intensity is 0.2 MW / m 2 ; the second zone cooling includes: using a sector nozzle for steam-water atomization cooling, the spraying angle of the second zone cooling is 110°, the specific water volume is 0.6 L / kg, and the cooling intensity is 0.15 MW / m 2 ; the third zone cooling includes: using a hollow cone nozzle for water spray cooling; the spraying angle of the third zone cooling is 120°, the specific water volume is 0.4 L / kg, and the cooling intensity is 0.1 MW / m 2 ;

[0108] The solid fraction at the solidification end of the continuous casting slab in the final electromagnetic stirring area is 0.3; the current of the final electromagnetic stirring is 1000 A, and the frequency is 9 Hz; the stirring direction of the final electromagnetic stirring is opposite to the continuous casting drawing direction;

[0109] The solid fraction at the solidification end of the continuous casting slab in the solidification end heavy reduction area is 0.8; the reduction rate of the solidification end heavy reduction is 0.5 mm / min, and the reduction amount is 10 mm;

[0110] The temperature of the slow cooling treatment is 600 °C, and the holding time is 48 h.

[0111] Example 3

[0112] This example provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. In terms of mass percentage, the chemical elements of the continuous casting round billet include: C 0.42%, Si 0.35%, Mn 0.75%, Cr 1.10%, Mo 0.25%, Ni 0.15%, and the balance is Fe and unavoidable impurities.

[0113] The preparation method of the above-mentioned continuous casting round billet for wind power yaw and pitch bearings includes the following steps:

[0114] (1) Successively perform KR desulfurization, converter smelting, LF refining, and VD vacuum refining on the molten iron to obtain the treated molten steel;

[0115] The P content in the molten iron after KR desulfurization is 0.01%, and the S content is 0.005%;

[0116] By mass percentage, the refining slag used in LF refining comprises: 52 wt% of CaO, 3 wt% of SiO2 and 42 wt% of Al2O3; the basicity of the refining slag is 11;

[0117] The aluminum loss rate of the molten steel after LF refining is 15%, and the aluminum loss rate of the molten steel after VD vacuum refining is 25%;

[0118] (2) The treated molten steel obtained in step (1) is successively subjected to continuous casting, slow cooling and finishing to obtain the continuous casting round billet;

[0119] The continuous casting process includes successively carried out mold electromagnetic stirring, secondary cooling zone cooling, final electromagnetic stirring and solidification end heavy reduction;

[0120] The superheat temperature of the molten steel in the continuous casting process is 22 °C; the casting speed of the continuous casting process is 0.2 m / min;

[0121] The current of the mold electromagnetic stirring is 340 A, the frequency is 1 Hz, and the steering time is 15 s; the taper of the mold used for the mold electromagnetic stirring is 1.0% / m;

[0122] In the direction away from the mold outlet, the secondary cooling zone cooling includes first zone cooling, second zone cooling and third zone cooling; the first zone cooling includes: using a solid conical nozzle for steam-water atomization cooling, the spraying angle of the first zone cooling is 100°, the specific water volume is 1.0 L / kg, and the cooling intensity is 0.3 MW / m 2 ; the second zone cooling includes: using a sector nozzle for steam-water atomization cooling, the spraying angle of the second zone cooling is 130°, the specific water volume is 0.8 L / kg, and the cooling intensity is 0.2 MW / m 2 ; the third zone cooling includes: using a hollow conical nozzle for water spray cooling; the spraying angle of the third zone cooling is 140°, the specific water volume is 0.6 L / kg, and the cooling intensity is 0.15 MW / m 2 ;

[0123] The solid fraction at the solidification end of the continuous casting billet in the final electromagnetic stirring area is 0.7; the current of the final electromagnetic stirring is 1100 A, and the frequency is 10 Hz; the stirring direction of the final electromagnetic stirring is opposite to the continuous casting direction;

[0124] The solid fraction at the solidification end of the continuous casting billet in the solidification end heavy reduction area is 0.95; the reduction rate of the solidification end heavy reduction is 1.0 mm / min, and the reduction amount is 15 mm;

[0125] The temperature of the slow cooling treatment is 700 °C, and the holding time is 24 h.

[0126] Example 4

[0127] This example provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. By mass percentage, the chemical elements of the continuous casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and unavoidable impurities.

[0128] The difference between the preparation method of the above continuous casting round billet for wind power yaw and pitch bearings and that of Example 1 is only that:

[0129] In this example, the superheat temperature of the molten steel in the continuous casting process described in step (2) is adjusted to 30 °C.

[0130] Example 5

[0131] This example provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. By mass percentage, the chemical elements of the continuous casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and unavoidable impurities.

[0132] The difference between the preparation method of the above continuous casting round billet for wind power yaw and pitch bearings and that of Example 1 is only that:

[0133] In this example, the superheat temperature of the molten steel in the continuous casting process described in step (2) is adjusted to 10 °C.

[0134] Example 6

[0135] This example provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. By mass percentage, the chemical elements of the continuous casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and unavoidable impurities.

[0136] The difference between the preparation method of the above continuous casting round billet for wind power yaw and pitch bearings and that of Example 1 is only that:

[0137] In this example, the casting speed in the continuous casting process described in step (2) is adjusted to 0.1 m / min.

[0138] Example 7

[0139] This embodiment provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. By mass percentage, the chemical elements of the continuous casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and inevitable impurities.

[0140] The difference between the preparation method of the above-mentioned continuous casting round billet for wind power yaw and pitch bearings and that of Example 1 is only that:

[0141] In this embodiment, the casting speed in the continuous casting process described in step (2) is adjusted to 0.3 m / min.

[0142] Example 8

[0143] This embodiment provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. By mass percentage, the chemical elements of the continuous casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and inevitable impurities.

[0144] The difference between the preparation method of the above-mentioned continuous casting round billet for wind power yaw and pitch bearings and that of Example 1 is only that:

[0145] In this embodiment, the mold electromagnetic stirring process is omitted.

[0146] Example 9

[0147] This embodiment provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. By mass percentage, the chemical elements of the continuous casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and inevitable impurities.

[0148] The difference between the preparation method of the above-mentioned continuous casting round billet for wind power yaw and pitch bearings and that of Example 1 is only that:

[0149] In this embodiment, the third zone cooling in the secondary cooling zone cooling is omitted.

[0150] Example 10

[0151] This embodiment provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. By mass percentage, the chemical elements of the continuous casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and inevitable impurities.

[0152] The preparation method of the above-mentioned continuous casting round billet for wind power yaw and pitch bearings is only different from that of Example 1 in that:

[0153] In this example, the first-zone cooling and the second-zone cooling in the secondary cooling zone are omitted.

[0154] Example 11

[0155] This example provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. In terms of mass percentage, the chemical elements of the continuous casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and unavoidable impurities.

[0156] The preparation method of the above-mentioned continuous casting round billet for wind power yaw and pitch bearings is only different from that of Example 1 in that:

[0157] In this example, the final electromagnetic stirring is omitted.

[0158] Example 12

[0159] This example provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. In terms of mass percentage, the chemical elements of the continuous casting round billet include: C 0.40%, Si 0.21%, Mn 0.70%, Cr 1.05%, Mo 0.23%, Ni 0.13%, and the balance is Fe and unavoidable impurities.

[0160] The preparation method of the above-mentioned continuous casting round billet for wind power yaw and pitch bearings is only different from that of Example 1 in that:

[0161] In this example, the heavy reduction process at the solidification end is omitted.

[0162] Comparative Example 1

[0163] This comparative example provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. The difference between the continuous casting round billet and Example 1 is only that:

[0164] In this comparative example, the content of Mn in the continuous casting round billet is adjusted to 0.78%.

[0165] The preparation method of the above-mentioned continuous casting round billet for wind power yaw and pitch bearings is the same as that of Example 1.

[0166] Comparative Example 2

[0167] This comparative example provides a continuous casting round billet with a diameter of 600 mm for wind power yaw and pitch bearings. The difference between the continuous casting round billet and Example 1 is only that:

[0168] In this comparative example, the C content in the continuous casting round billet was adjusted to 0.44%.

[0169] Performance detection:

[0170] The continuous casting round billets for wind power yaw and pitch bearings provided in the above examples and comparative examples were detected for cross-sectional carbon grade difference, central porosity, and central shrinkage cavity, and the results are shown in Table 1.

[0171] Among them, the cross-sectional carbon grade difference was carried out according to the method provided in GB / T 122913.1; the central porosity was carried out according to the method provided in GB / T 226-2015; the central shrinkage cavity was carried out according to the method provided in GB / T 226-2015.

[0172] Table 1

[0173] Cross-sectional carbon difference / % Center porosity / level Center shrinkage cavity / level Example 1 0.032 ≤1.0 0 Example 2 0.042 ≤1.0 0 Example 3 0.034 ≤1.0 0 Example 4 0.037 ≤1.5 0.5 Example 5 0.036 ≤1.5 0 Example 6 0.036 ≤1.5 0 Example 7 0.037 ≤1.0 0.5 Example 8 0.062 ≤1.0 0.5 Example 9 0.059 ≤1.5 0.5 Example 10 0.063 ≤1.5 0.5 Example 11 0.058 ≤1.5 0 Example 12 0.063 ≤1.5 0 Comparative Example 1 0.053 ≤1.0 0 Comparative Example 2 0.057 ≤1.0 0

[0174] It can be seen from Table 1 that:

[0175] (1) Through comprehensive analysis of Examples 1-3, it can be seen that the method provided by the present invention can significantly reduce the carbon segregation degree of the continuous casting round billet and improve the uniformity of carbon element distribution;

[0176] (2) Through comprehensive analysis of Example 1 and Examples 4-7, it can be seen that too high superheat temperature of the molten steel during continuous casting will lead to an increase in the range of central porosity, and too low superheat temperature will lead to a decrease in the range of central porosity; too fast drawing speed during continuous casting will lead to an increase in the range of central porosity; on the contrary, if the drawing speed is too slow, it will lead to a decrease in the range of central porosity;

[0177] (3) Through comprehensive analysis of Example 1 and Examples 8-12, it can be seen that the stirring crystallization process during continuous casting will affect the carbon segregation degree of the continuous casting round billet, and will cause an increase in the cross-sectional carbon grade difference;

[0178] (4) Through comprehensive analysis of Example 1 and Comparative Examples 1-2, it can be seen that the present invention can effectively improve the cross-sectional carbon segregation grade difference of the cast billet and improve the service life of the steel by optimizing the contents of elements such as C and Mn in the steel.

[0179] In summary, the present invention integrates technologies such as mold electromagnetic stirring, secondary cooling zone cooling, final electromagnetic stirring, and heavy reduction at the solidification end, realizes the improvement of the carbon uniformity of the continuous casting round billet, makes the cross-sectional carbon grade difference ≤ 0.05%, the central porosity ≤ 1.0 grade, and the central shrinkage cavity is 0 grade, meeting the use requirements of high-end wind power yaw and pitch bearing steels, thereby improving the reliability and service life of the bearings.

[0180] The applicant declares that the specific embodiments described above further elaborate on the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A continuous casting round billet for a wind power yaw and pitch bearing, characterized in that, In terms of mass percentage, the chemical elements of the continuous casting round billet include: C 0.38 - 0.42%, Si 0.15 - 0.35%, Mn 0.65 - 0.75%, Cr 1.00 - 1.10%, Mo 0.20 - 0.25%, Ni 0.10 - 0.15%, and the balance is Fe and inevitable impurities.

2. The continuous casting round billet for the wind power yaw and pitch bearings according to claim 1, wherein, The diameter of the continuous casting round billet is ≥600 mm.

3. A method for preparing a continuous casting round billet for a wind power yaw and pitch bearing as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Successively perform KR desulfurization, converter smelting, LF refining, and VD vacuum refining on the hot metal to obtain the treated molten steel; (2) Successively perform continuous casting treatment, slow cooling treatment, and finishing on the treated molten steel obtained in step (1) to obtain the continuous casting round billet; The continuous casting treatment includes successively performing mold electromagnetic stirring, secondary cooling zone cooling, final electromagnetic stirring, and heavy reduction at the solidification end.

4. The preparation method according to claim 3, characterized in that, After KR desulfurization in step (1), the P content in the hot metal is ≤0.01%, and the S content is ≤0.005%; Preferably, in terms of mass percentage, the refining slag used in the LF refining includes: CaO 48 - 52 wt%, SiO2 3 - 6 wt%, and Al2O3 37 - 42 wt%; Preferably, the basicity of the refining slag used in the LF refining is 10.5 - 11.5; Preferably, the aluminum loss rate of the molten steel after LF refining is 15 - 20%; Preferably, the aluminum loss rate of the molten steel after VD vacuum refining is 25 - 30%.

5. The preparation method according to claim 3 or 4, characterized in that, The superheat temperature of the molten steel in the continuous casting treatment is 15 - 22 °C; Preferably, the casting speed in the continuous casting treatment is 0.15 - 0.2 m / min.

6. The preparation method according to any one of claims 3-5, characterized in that, The current of the mold electromagnetic stirring is 240 - 340 A; Preferably, the frequency of the mold electromagnetic stirring is 1 - 1.5 Hz; Preferably, the steering time of the mold electromagnetic stirring is 15 - 20 s; Preferably, the taper of the mold used for the mold electromagnetic stirring is 1.0 - 1.2% / m.

7. The preparation method according to any one of claims 3-6, characterized in that, According to the direction away from the mold outlet, the secondary cooling zone cooling includes first zone cooling, second zone cooling, and third zone cooling; Preferably, the first zone cooling includes: using a solid conical nozzle for steam-water atomization cooling; Preferably, the spraying angle of the first zone cooling is 80 - 100°; Preferably, the specific water volume of the first zone cooling is 0.8 - 1.0 L / kg; Preferably, the cooling intensity of the first zone cooling is 0.2 to 0.3 MW / m 2 ; Preferably, the second zone cooling includes: using a sector nozzle for steam-water atomization cooling; Preferably, the spraying angle of the second zone cooling is 110 - 130°; Preferably, the specific water volume of the second zone cooling is 0.6 - 0.8 L / kg; Preferably, the cooling intensity of the second-zone cooling is 0.15 to 0.2 MW / m 2 ; Preferably, the third zone cooling includes: using a hollow conical nozzle for water spray cooling; Preferably, the spraying angle of the third zone cooling is 120 - 140°; Preferably, the specific water volume of the third zone cooling is 0.4 - 0.6 L / kg; Preferably, the cooling intensity of the third-zone cooling is 0.1 to 0.15 MW / m 2 .

8. The preparation method according to any one of claims 3-7, characterized in that, The solid fraction at the solidification end of the continuous casting billet in the final electromagnetic stirring area is 0.3 - 0.7; Preferably, the current of the final electromagnetic stirring is 1000 - 1100 A; Preferably, the frequency of the final electromagnetic stirring is 9 - 10 Hz; Preferably, the stirring direction of the end electromagnetic stirring is opposite to the direction of continuous casting withdrawal.

9. The preparation method according to any one of claims 3-8, characterized in that, The solid fraction at the solidification end of the continuous casting slab in the solidification end heavy reduction area is 0.8 - 0.95; Preferably, the reduction rate of the solidification end heavy reduction is 0.5 - 1.0 mm / min; Preferably, the reduction amount of the solidification end heavy reduction is 10 - 15 mm.

10. The preparation method according to any one of claims 3-9, characterized in that, The temperature of the slow cooling treatment is 600 - 700 °C; Preferably, the holding time of the slow cooling treatment is ≥ 24 h.