CN112522615A

CN112522615A - CrNiMo round steel for wind power gear and preparation method thereof

Info

Publication number: CN112522615A
Application number: CN202011316933.3A
Authority: CN
Inventors: 沙鹏飞; 徐乐钱; 庞卓纯; 沈艳; 林俊; 万文华; 叶玉奎
Original assignee: Zenith Steel Group Co Ltd; Changzhou Zenith Special Steel Co Ltd
Current assignee: Zenith Steel Group Co Ltd; Changzhou Zenith Special Steel Co Ltd
Priority date: 2020-11-20
Filing date: 2020-11-20
Publication date: 2021-03-19

Abstract

The invention discloses a CrNiMo round steel for a wind power gear and a preparation method thereof, wherein the CrNiMo round steel comprises the following components in percentage by weight of 0.15-0.21% of C, 0.17-0.37% of Si, 0.50-0.90% of Mn and Cr: 1.50-1.80 percent of Ni, 1.40-1.70 percent of Ni, less than or equal to 0.20 percent of Cu, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, 0.25-0.35 percent of Mo0.35 percent of O, less than or equal to 0.0020 percent of Al, 0.025-0.040 percent of N, 0.0080-0.0120 percent of N. The preparation method comprises electric furnace smelting, LF refining, VD vacuum degassing, five-machine five-flow arc-shaped continuous casting machine and rolling, the preparation method is simple to operate and high in production efficiency, and the prepared round steel has the characteristics of low oxygen content, narrow quenching band, high purity, accurate component control, light belt shape, excellent surface quality and the like, and completely meets various technical requirements of the steel for the wind power gear.

Description

CrNiMo round steel for wind power gear and preparation method thereof

Technical Field

The invention belongs to the field of metal material manufacturing, and particularly relates to CrNiMo round steel for a wind power gear and a production process thereof.

Technical Field

The gearbox in the wind generating set is an important mechanical component, and the main function of the gearbox is to transmit the power generated by the wind wheel under the action of wind power to the generator and enable the generator to obtain a corresponding rotating speed. Wind power generation is influenced by natural conditions, and the wind turbine generator set can be failed due to the occurrence of some special meteorological conditions, a narrow engine room cannot have a firm base foundation like the ground, the power matching and torsional vibration factors of the whole transmission system are always reflected on a weak link in a centralized manner, and a large number of practices prove that the link is often a gear box in the generator set. Therefore, it is important to enhance the research on the gear box.

In view of the complexity of the working environment of the wind power gear, the unit is arranged at wind gaps of mountains, wildlands, beaches, islands and the like, is influenced by the wind power of irregular direction change and load change and the impact of strong gusts, is subjected to the influence of severe heat and cold and extreme temperature difference all the year round, is inconvenient to traffic in the natural environment, and is difficult to repair once a fault occurs, so that the requirements on the reliability and the service life of the unit are much higher than those of common machinery, and the requirement on the raw material of the gear is very high.

In order to meet the reliability requirement and improve the contact fatigue and bending fatigue strength of the gear, the steel is required to have good consistency, high purity, good hardenability, low banded rating and low oxygen content. Relevant researches show that the oxygen content has great influence on the fatigue life of the gear, and the prior gear steel generally requires that the oxygen content is less than or equal to 20ppm, the chemical components of the steel are uniform, the component segregation is reduced, and the banded structure is lightened so as to improve the mechanical property and the fatigue life of the gear.

With the increasing requirements of raw materials, a single fixed mark cannot meet the requirements of product development, how to optimize chemical components, reasonably design process parameters and pursue the highest cost performance, and meanwhile, the production of products with the characteristics of high purity, narrow hardenability, low band rating and the like becomes a common problem for various manufacturers. In addition, in addition to the control of material properties such as purity, hardenability, strip shape and the like, the problem of phosphorus removal should be considered at the same time, because the Ni-containing steel is difficult to remove scale due to the viscosity of the scale, and the scale is pressed in during rolling, so that the pit and pit defects on the steel are more, and the surface quality of the product is seriously influenced. The Ni-containing steel oxide skin is difficult to remove completely because Ni element is difficult to oxidize, white metal Ni wires are enriched in iron oxide on the surface of the steel billet to form adhesive oxide skin and a matrix when the steel billet is heated, and the wedge-shaped Si-containing oxide skin is oxidized and embedded into the steel matrix along a grain boundary when the temperature is over 1200 ℃.

Therefore, the technical problem to be solved by the invention is how to provide the round steel for the wind power gear, ensure the excellent performances of high production purity, narrow hardenability, low strip rating and the like, and simultaneously ensure the complete phosphorus removal of steel and the quality of the inner and outer surfaces of the steel.

Disclosure of Invention

The invention aims to provide a preparation method of CrNiMo round steel for wind power gears by reasonably optimizing chemical component design and reasonably setting process parameters aiming at the technical problems, pursuing high cost performance and quality and quantity preservation, ensuring that indexes such as chemical component control, hardenability, purity, banded structure and the like of a produced product reach the leading level in the industry, solving the practical problem of difficult phosphorus removal in the production process and effectively ensuring the surface quality of rolled materials.

In order to achieve the purpose, the gear steel comprises the following chemical components in percentage by weight:

[C]0.15～0.21％、[Si]0.17～0.37、[Mn]0.50～0.90％、[Cr]：1.50～1.80％、[Ni]1.40～1.70％、[Cu]≤0.20％、[P]≤0.025％、[S]≤0.025％、[Mo]0.25～0.35％、[O]≤0.0020％、[Al]0.025～0.040％、[N]0.0080～0.0120％。

preferably, the chemical components are as follows by weight percent: [C]0.16 to 0.18 percent, 0.17 to 0.27 percent of [ Si ], 0.62 to 0.68 percent of [ Mn ], 1.61 to 1.69 percent of [ Cr ], 1.46 to 1.54 percent of [ Ni ], less than or equal to 0.10 percent of [ Cu ], less than or equal to 0.020 percent of [ P ], lessthan or equal to 0.015 percent of [ S ], [ 0.26 to 0.29 percent of [ Mo ], lessthan or equal to 0.0020 percent of [ O ], [ Al ]0.025 to 0.040 percent, and less than or equal to 0.0080 to 0.0120 percent of [ N ].

The main component design reason of the invention is as follows:

c is the most effective element for improving the strength of the steel, particularly the heat treatment performance of the steel, but the steel hardness is obviously increased and the toughness is sharply reduced due to excessively high content, the influence on the hardness at a position close to the tail end is obvious, and the content of C is preferably 0.16-0.18%.

Mn has very strong capability of stabilizing an austenite structure, can remarkably increase the hardenability of steel, and can improve the surface quality, but too much Mn is unfavorable for ductility, and the brittleness of the steel is increased due to too high content, and the Mn content is preferably 0.62-0.68%.

Cr can improve hardenability, has obvious influence on the position after J9, improves wear resistance and corrosion resistance, and is beneficial to maintaining strength at high temperature, and the preferable range of the invention is 1.61-1.69%.

Ni can improve the strength of the steel without remarkably reducing the toughness, and the Ni is preferably 1.46-1.54 percent in the invention.

Mo can improve the heat strength of steel and the hardenability of the steel, the adverse effect of the Mo is the tendency of graphitizing the low-alloy molybdenum steel, and the Mo is preferably 0.26-0.29 percent in the invention.

O has great influence on the purity of steel, and oxygen mainly comprises FeO, MnO and SiO in steel₂、Al₂O₃And the like, which lower the strength and plasticity of the steel, and particularly have a severe influence on the fatigue strength, impact toughness, and the like, and preferably, the oxygen content must be strictly controlled to be within 20 ppm.

Al is used as an effective element for grain refinement, and a proper amount of Al is added to play a role in grain refinement, and the optimal proportion of the Al is 0.025-0.040%.

The combination of N and Al exists in the form of aluminum nitride, which is mainly distributed in the crystal boundary and organizes the growth of crystal grains by the binding effect, when the aluminum and the nitrogen of the steel reach a certain degree and accord with a certain proportion (Al/N is more than or equal to 2.5), the two elements are combined into fine and dispersed aluminum nitride particles, and the particles can generate the growth of the binding effect organization crystal grains on the crystal boundary; when any one of aluminum and nitrogen is insufficient, the nailing effect is weakened. The content of N is preferably 0.0080-0.0120%.

The invention provides a production process of the round steel for the wind power gear, which comprises the steps of 90t electric furnace smelting, LF refining, VD vacuum degassing, five-machine five-flow arc continuous casting machine (220mm multiplied by 260mm) and rolling, and specifically comprises the following operations:

(1) the total charging amount of the electric furnace is adjusted according to the actual smelting situation, the electric furnace utilizes a molten iron tipping device to adopt an online molten iron charging mode, and the aim of removing P and controlling temperature is fulfilled by combining a foamed slag operation process. The steel tapping process has the components including C not more than 0.10%, P not more than 0.012% and T not less than 1630 deg.c. And deoxidizing and alloying in the tapping process and adding ladle slag charge, wherein the electric furnace alloy preparation uses low-carbon ferromanganese, low-carbon ferrochrome and ferrosilicon, the alloy usage is adjusted according to actual conditions, a deoxidizer, alloy and slag charge are added in the tapping process, the sliding plate slag stopping operation is adopted in the tapping process, slag is strictly forbidden, and the tapping time is 3-5 minutes.

Preferably, the steelmaking raw materials adopted in the step (1) are scrap steel and molten iron, the scrap steel accounts for 5-15% of the total weight of the steelmaking raw materials, the molten iron accounts for 85-95% of the total weight of the steelmaking raw materials, the total loading amount of the steelmaking raw materials is 100-110 t/furnace, and the tapping temperature is 1630-1660 ℃.

Preferably, the addition amount of the deoxidizer in the step (1) is 0.7-0.9kg/t of the aluminum block; the alloy in the step (1) is ferrosilicon, low-carbon ferromanganese and low-carbon ferrochrome, wherein the ferrosilicon accounts for 0.7-0.8 kg/t, the low-carbon ferromanganese accounts for 5.0-6.0 kg/t and the low-carbon ferrochrome accounts for 27-28 kg/t relative to the addition amount of the steelmaking raw materials; the slag charge and the adding amount in the step (1) are 350 kg/furnace of slagging agent and 650 kg/furnace of lime.

The slag is strictly forbidden in the tapping process, so that the oxidability of the refining slag can be effectively reduced, and the rapid component adjustment and deoxidation operations are facilitated.

(2) Aluminum particles and silicon carbide are used for deoxidation in the early stage of LF refining, and silicon carbide is uniformly added for deoxidation and slag retention in small batches in the later stage, so that the good reducing atmosphere of refining slag is maintained, and the good fluidity of the refining slag is ensured; rapidly adjusting alloy components to meet the target component control requirement in the early stage of refining, and adding ferromolybdenum and a nickel plate, wherein 4.0-5.0 kg/t of ferromolybdenum, 15-15.5 kg/t of the nickel plate, 2.5-3.0 kg/t of low-carbon ferrochromium and 0.8-1.2 kg/t of ferrosilicon are added relative to the amount of the steelmaking raw materials, the refining components are uniformly and accurately controlled, the deviation of C, Si, Mn, Cr, Mo and Ni between furnaces is guaranteed to be within +/-0.02%, the refining time is controlled to be 50-70 min/furnace, and the white slag time is guaranteed to be more than 30 min.

Further, the binary alkalinity in the step (2) is 4.0-4.5; in the step (2), the LF refining ladle is at the temperature of 1640-1660 ℃ in the casting furnace, and 1620-1630 ℃ in the continuous casting furnace;

reasonably controlling the alkalinity of the refining slag, the addition amount of the deoxidizer and the refining time, and properly adding slag charge into the refining furnace according to the condition of the slag, wherein the surface of the slag is required to be bright and have good fluidity, and the slag is strictly prohibited from being sticky; deep deoxidation is carried out on aluminum particles in the early stage of refining, and the reference dosage is about 0.18-0.22 kg/ton; aluminum wires are used for refining to adjust the aluminum content, and the aluminum in the refined steel is controlled to be 0.035-0.040%; silicon in the refining furnace is controlled according to the middle and lower limits, the tapping Si is controlled to be 0.018-0.020%, and the VD furnace is paid attention to silicon return.

(3) VD vacuum degassing

The VD vacuum treatment high vacuum (67Pa) is kept for more than or equal to 10 minutes, the argon bottom stirring flow is controlled to be 150-0.4 MPa at 200L/min during high vacuum pressure maintaining, and the vacuum aluminum loss is controlled to be 40-50 percent; and feeding pure calcium wires after the VD breaks the air, feeding a proper amount of nitrogen-manganese wires according to the content of N, ensuring that argon is in a soft blowing state before feeding the silk threads, ensuring that the flow of the argon is 50-80L/min, the pressure is 0.15-0.2MPa, strictly prohibiting the silk threads from being fed without fluctuation of slag surface, and ensuring the soft argon blowing time and effect after feeding the silk threads, wherein the soft blowing time is more than or equal to 20 min.

Further, sampling is carried out after the nitrogen-manganese line is broken in the adding time of the nitrogen-manganese line in the step (3), a proper amount of the nitrogen-manganese line is added according to the analyzed N content, preferably, the N target is controlled to be 80-120 ppm, the N content in the steel after the breaking is 50-60ppm, the average nitrogen increase of 30ppm per 100m of the nitrogen-manganese line is considered, and the feeding amount of the nitrogen-manganese line is controlled to be 120-150 m.

Preferably, the continuous casting temperature of the VD ladle is controlled to be 1585-1600 ℃, and the initial furnace temperature is controlled to be 1565-1580 ℃.

(4) In the continuous casting process, the nozzle of a tundish uses aluminum carbon, the tundish uses magnesium coating, the baking temperature of the tundish is above 1100 ℃, full-protection pouring is adopted from a ladle to the tundish, argon sealing protection is adopted from the ladle to the long nozzle of the tundish, the nozzle of the tundish is internally installed, the diameter of the nozzle is phi 40mm, a slag dam and a double-layer covering agent are used, reasonable superheat degree and pulling speed control are adopted, the superheat degree is controlled to be 20-35 ℃, and the pulling speed is controlled to be 0.85 +/-0.05 m/min; meanwhile, the homogenization of the casting blank solidification process is improved by adopting a combined regulation and control means of M-MES (crystallizer electromagnetic stirring) + PMO (pulse magnetic oscillation) + F-MES (tail end electromagnetic stirring).

The crystallizer adopts electromagnetic stirring, and the water flow of the crystallizer is 110 +/-10 m³And h, the water temperature difference is 7.0-9.0 ℃, and the secondary cooling adopts a weak cooling water distribution mode. PMO (pulse magnetic oscillation solidification homogenization technology) forms a specific electromagnetic induction effect at the front edge of a solid-liquid interface of a casting blank through an induction coil so as to refine a solidification structure; the end electric stirring parameter is set to be 50A/6 Hz.

Preferably, the using time of the tundish in the step (4) is less than or equal to 12 hours, the electromagnetic stirring parameter of the crystallizer is 150 +/-10A/2 HZ, the non-sinusoidal vibration parameter is amplitude +/-2.5 mm, and the frequency is 130+40V opm; the PMO direct current voltage is set to be 50V; the end electric stirring adopts a positive and negative rotation mode, positive-stop-negative: 12s-3s-12 s;

the crystallizer selects special covering slag, the alkalinity is 0.85-0.90, the melting point is 1100-1120 ℃, and the viscosity is 0.55-0.65Pa.S/1300 ℃; and measuring the thickness of the liquid slag layer every 2 hours to ensure that the depth of the liquid slag layer is 5-10 mm.

Further, in the weak cold water distribution mode in the step (4), the specific water amount is 0.20L/kg;

the casting blank is discharged at high temperature by adopting a transition cooling bed, and is slowly cooled by covering in a straight line for more than or equal to 36 hours;

(5) the heating temperature is lower than 1100 ℃, so that the diffusion of steel billet elements is insufficient, the heating temperature is higher than 1200 ℃, so that the crystal grains of the steel billet are coarse, the product performance is influenced, phosphorus removal is not facilitated, the heating temperature is reduced, the adhesiveness of oxide skin of Ni-containing steel is reduced, the descaling effect is enhanced, the temperature of a soaking section is preferably selected from 1140-1160 ℃, the total heating time is 350-400min, and the air-fuel ratio is 0.7-0.8.

When the initial rolling temperature is lower than 1000 ℃, the rolling load is too large, so that the smooth production is difficult, and when the initial rolling temperature exceeds 1150 ℃, the crystal grains are difficult to refine, so that the crystal grains are coarse, and preferably, the initial rolling temperature interval is selected from 1030-1080 ℃.

The finishing temperature is higher than 930 ℃, the austenite stability is strong, the tissue transformation is slow, and non-equilibrium tissues are easy to generate; preferably, the finishing temperature range is selected from 850 to 930 ℃, and the diffusion of C, Mn elements is suppressed at a low finishing temperature, which contributes to the control of the strip shape.

The invention has the beneficial effects that:

according to the invention, through reasonably optimizing the component design, a proper amount of Mn, Cr, Ni and Mo is added, and through adding alloy control and adopting narrow component control in steel making, the stable control of a narrow hardenability zone is realized; the clean steel refining process technology is adopted, the continuous casting parameter setting is optimized, the casting process is perfected and protected, the continuous casting process control and unsteady state casting emergency treatment capacity are enhanced, the molten steel purity is improved, and the inclusion is effectively controlled; the superheat degree of molten steel is reduced and stabilized, constant-pulling-speed casting is realized, the uniformity is improved, and the internal quality of a casting blank is effectively improved; the homogenization of the casting blank solidification process is effectively improved by adopting a combined regulation and control means of M-MES (crystallizer electromagnetic stirring) + PMO (pulsed magnetic oscillation) + F-MES (tail end electromagnetic stirring), so that the component segregation is reduced, and the banding is improved; by optimizing the controlled rolling process, the problem of phosphorus removal in the rolling process is solved, and the effective guarantee of phosphorus removal in the rolling process is realized

The preparation method of the round steel for the wind power gear, provided by the invention, is simple to operate, high in production efficiency and has the following advantages:

compared with the traditional electric furnace, the electric converter can improve the molten iron ratio by 85-95 percent in the aspect of material preparation, improve the heat source, avoid the increase of the nitrogen content of the molten steel caused by power supply without power supply, reduce the loading amount of scrap steel by improving the molten iron ratio, effectively control the residual elements such as Cu, B and the like, and be beneficial to the control of the narrow hardenability band of the subsequent rolled material;

secondly, the white slag of the refining furnace is kept for more than 30min, the full floating time of the inclusions in the deep deoxidizer in the refining process is ensured, the discharged steel and aluminum are 0.030-0.035%, and the free oxygen of the molten steel in the over-vacuum furnace is controlled to be less than 3 ppm; the flow and pressure of argon are controlled in the vacuum process, the aluminum loss is 40-60% in the vacuum process, and the full mixing, flushing and degassing effects of the steel slag are ensured; effectively reduces the inclusions.

Thirdly, the continuous casting tundish adopts an integral immersion type integral water gap, and the material of a water gap wrist adopts magnesium carbon (SiO)₂The content is less than 1.5 percent), and the material of the nozzle slag line adopts magnesium-carbon-zirconium (the zirconium content is 45-50 percent, so that the corrosion is effectively prevented); the tundish uses magnesium coating material, MgO is more than or equal to 90 percent, and SiO₂Less than or equal to 6 percent, and the baking temperature of the tundish is more than 1100 ℃; meanwhile, argon sealing protection pouring is carried out in the whole continuous casting pouring process, and secondary oxidation is effectively avoided in the process, and the situations of inclusion and nozzle nodulation caused by a nozzle and a coating refractory material are reduced.

And fourthly, the continuous casting adopts a combined regulation and control means of M-MES (crystallizer electromagnetic stirring) + PMO (pulse magnetic oscillation) + F-MES (tail end electromagnetic stirring) to effectively improve the homogenization of the casting blank solidification process, improve the isometric crystal rate of the casting blank, improve the low-power quality and segregation condition of the casting blank, provide a good foundation for the properties of the subsequent rolled material such as the uniformity of the structure and the like, and play an important role in controlling the strip shape.

Fifthly, 1140-1160 ℃ is selected in a heating temperature target control interval, and the heating time is 350-400min, so that the uniform diffusion of C, Mn element can be ensured on the premise of ensuring the uniform and fine austenite, and the good phosphorus removal effect is ensured; the finishing temperature range is selected from 850-930 ℃, and the long-range diffusion of C, Mn element is inhibited at a lower finishing temperature, which is beneficial to controlling the strip shape.

Sixthly, the hardenability band is narrow

The added ferroalloy is strictly controlled in steel making, boron in the alloy is controlled to be brought into molten steel, fluctuation caused by influence of B on hardenability is effectively avoided, accurate control of components is guaranteed, component fluctuation between furnaces is reduced, the fluctuation range of C, Mn is controlled within +/-0.01%, the fluctuation range of Cr is controlled within +/-0.02%, fluctuation of end quenching hardness can be effectively reduced to the maximum degree, and the hardenability is controlled within 3 HRC ranges.

The round steel prepared by the method has the characteristics of low oxygen content, narrow quenching through bandwidth, high purity, low strip rating and the like, simultaneously solves the practical problem of difficult dephosphorization in the production process, effectively ensures the surface quality of the round steel, completely meets various technical requirements of the steel for the gear, has excellent performance and long service life, improves the market competitiveness of the product, and has remarkable economic benefit and social benefit.

Drawings

FIG. 1 is a graph showing the phosphorus removal effect of example 1;

FIG. 2 is a graph showing the phosphorus removal effect of example 7.

Detailed Description

The production process is briefly described as follows:

90t electric furnace smelting → LF refining → VD vacuum degassing → continuous casting of bloom (220X 260mm)²) → rolling in a rolling mill.

Example 1

(1) The steelmaking raw materials adopted by the electric furnace are scrap steel and molten iron, the scrap steel accounts for 10% of the total weight of the steelmaking raw materials, the molten iron accounts for 90% of the total weight of the steelmaking raw materials, and the total charging amount is 102 t/furnace.

The electric furnace utilizes a molten iron tipping device to adopt an online molten iron loading mode, and combines a foam slag operation process to achieve the purpose of removing P and controlling the temperature, wherein 0.08 percent of steel tapping [ C ], 0.009 percent of steel tapping [ P ], 0.040 percent of residual [ Cu ], 0.0002 percent of [ B ] and 1635 percent of steel tapping temperature are added, 0.80kg/t of aluminum block, 0.75kg/t of silicon iron, 5.5kg/t of low-carbon ferromanganese, 27.5kg/t of low-carbon ferrochromium, 500 kg/furnace of lime and 550 kg/furnace of slag melting agent are sequentially added along with steel flow during steel tapping, eccentric steel tapping is adopted during the steel tapping process, and slag tapping is strictly forbidden.

(2) LF adopts 1.5kg/t of silicon carbide and 0.17kg/t of aluminum particles to perform slag surface deoxidation, the slag surface deoxidation is timely adjusted according to the slag condition, the fluidity of slag is ensured, the binary alkalinity of refining slag is R4.2, the white slag holding time is 35min, the total refining time is 65min, after the components and the temperature are properly adjusted, the ladle temperature of a casting furnace is started at 1640 ℃, and the components are strictly regulated and controlled according to the designed target values

(3) The vacuumizing time of VD vacuum treatment is 15 minutes, the high vacuum (67Pa) holding time is more than or equal to 10 minutes, the nitrogen-manganese wires are fed into the furnace for 130m, after the temperature is properly adjusted, the operation is switched to soft argon blowing, the soft argon blowing time is 25 minutes, and the ladle temperature is 1590 ℃ after the casting furnace is started and the soft argon blowing is carried out.

(4) The continuous casting process adopts full-process protection casting, argon sealing protection is carried out on a large ladle long water gap, the middle ladle is covered by an alkaline covering agent and carbonized rice hulls in a double-layer mode, the continuous casting middle ladle adopts an integral stopper rod middle ladle, the diameter of the water gap is 40mm, the service time of the water gap is 6h, the superheat degree is 30 ℃, and the drawing speed is 0.85 m/min; the crystallizer adopts electromagnetic stirring, the parameters are 150A/2HZ, the sine vibration mode is adopted, the amplitude is +/-2.5 mm, and the frequency is 130+40V opm; PMO, parameter 50V; the end electric stirring parameter is set to be 50A/6Hz, and a positive and negative rotation mode is adopted, wherein the positive-stop-negative rotation mode comprises the following steps: 12s-3s-12 s; the crystallizer casting powder is special casting powder, the alkalinity is 0.87, the melting point is 1110 ℃, and the viscosity is 0.60Pa.S/1300 ℃; measuring the thickness of the liquid slag layer every 2 hours to ensure that the depth of the liquid slag layer is 7 mm; the water flow of the crystallizer is 1850 +/-100L/min, the water temperature difference is 8 ℃, and the secondary cooling adopts a weak cooling water distribution mode, and the specific water amount is 0.20L/kg.

(5) The temperature of the soaking section is 1140-1160 ℃, the heating time is 350-370 min, the air-fuel ratio is controlled to be 0.70-0.80, the starting rolling temperature is 1050-1070 ℃, the finishing rolling temperature is 870-890 ℃, the tension in rolling is stable, an imported KOCKS rolling mill is adopted, the controlled size precision is high, the rolling specification is less than or equal to 70mm, and the size tolerance is controlled to be-0.2- +0.2 mm.

Example 2

Compared with example 1, the difference is that: the molten iron accounts for 93 percent of the total weight of the steelmaking raw materials, the total loading amount is 108 t/furnace, the tapping temperature is 1650 ℃, the white slag refining time is 31min, the total refining time is 60min, the binary alkalinity of the refined slag is 4.0, and the rest of the operation is the same as that of the embodiment 1.

Example 3

The operation of tapping [ C ] 0.09% from the electric furnace, tapping [ P ] 0.010%, residual [ Cu ] 0.037%, tapping [ B ] 0.0002%, and tapping temperature 1630 ℃ in step (1) was the same as in example 1.

Example 4

In the LF refining in the step (2), the binary alkalinity of the refining slag is 6.2, white slag is kept for 20min, VD in the step (3) is carried out for 8min of high vacuum pressure maintaining time and 15min of soft blowing time, and the rest of the operation is the same as that of the example 1.

Example 5

The continuous casting speed in the step (4) was 0.9m/min, the tundish superheat degree was 40 ℃, PMO (pulse magnetic oscillation) + F-MES (end electromagnetic stirring) was not used, and the rest of the operation was the same as in example 1.

Example 6

The steel-making scrap ratio was 40% (so that the participating elements were higher than those in example 1), and the rest of the operation was the same as in example 1.

Example 7

The heating temperature of 1190-1210 ℃ in the step (5), the heating time of 320-350 min, the finishing temperature of 930 ℃ and the rest of the operation are the same as those of the embodiment 1.

The chemical composition, end hardenability, non-metallic inclusion detection, band-shaped rating of the round steel obtained in examples 1 to 7 are shown in tables 1, 2, 3 and 4, respectively. The phosphorus removal effect of example 1 is shown in fig. 1, and the phosphorus removal effect of example 7 is shown in fig. 2. Wherein the chemical components, the nonmetallic inclusions and the strip are detected after rolling, and the end hardenability is detected after heat treatment.

TABLE 1 examples 1-7 chemical composition (wt/%) of round bars prepared

Examples	C	Si	Mn	P	S	Cr	Al	Ni	Mo	Cu	B	N	O
														1	0.168	0.238	0.667	0.009	0.002	1.655	0.028	1.500	0.277	0.040	0.0002	0.0090	0.0006
2	0.168	0.227	0.673	0.010	0.001	1.641	0.030	1.492	0.273	0.037	0.0003	0.0092	0.0009
														3	0.166	0.231	0.674	0.010	0.002	1.658	0.029	1.496	0.268	0.040	0.002	0.0095	0.0007
4	0.167	0.240	0.680	0.008	0.003	1.648	0.025	1.495	0.260	0.023	0.001	0.0098	0.0014
														5	0.167	0.226	0.682	0.011	0.003	1.655	0.027	1.508	0.265	0.015	0.0002	0.0100	0.0007
6	0.172	0.235	0.679	0.015	0.004	1.660	0.030	1.512	0.270	0.15	0.0010	0.0089	0.0008
														7	0.167	0.230	0.670	0.013	0.001	1.645	0.026	1.490	0.262	0.027	0.0003	0.0086	0.0006

TABLE 2 end Hardenability (HRC) of round bars prepared in examples 1 to 7

Examples	J1.5	J3	J5	J7	J9	J11	J13	J15	J20	J25
											1	45.5	44.5	44.5	44.0	44.5	44.0	43.5	42.5	39.5	37.5
2	45.5	45.0	44.5	44.5	44.5	44.0	43.5	41.5	38.5	37.0
											3	45.0	44.5	44.5	44.0	44.0	43.5	43.0	41.5	38.5	37.0
4	45.5	44.5	44.5	44.0	44.5	44.0	43.5	42.5	39.5	37.5
											5	45.0	44.5	44.5	44.0	44.0	43.5	43.0	41.5	38.5	37.0
6	46.5	46.0	45.5	45.0	44.5	44.5	44.0	43.0	40.5	39.0
											7	45.5	45.0	44.5	44.5	44.5	44.0	43.5	41.5	38.5	37.0

The end hardenability heat treatment process system comprises the following steps: normalizing at 920 +/-10 deg.C for 30min and quenching at 860 +/-5 deg.C. The rolled stock is tested for non-metallic inclusions according to method A of GB/T10561.

TABLE 3 non-metallic inclusions (HRC) of the prepared round bars of examples 1 to 7

Examples	A (thin)	A (Thick)	B (thin)	B (Thick)	C (thin)	C (Thick)	D (thin)	D (Thick)
									1	0.0	0.0	0.5	0.0	0.0	0.0	0.0	0.0
2	0.0	0.0	0.0	0.0	0.0	0.0	0.5	0.0
									3	0.0	0.0	0.0	0.0	0.0	0.0	0.5	0.0
4	0.0	0.0	2.0	1.0	0.0	0.0	2.0	1.5
									5	0.0	0.0	0.0	0.0	0.0	0.0	0.5	0.5
6	0.0	0.0	0.0	0.0	0.0	0.0	0.5	0.0
									7	0.0	0.0	0.0	0.0	0.0	0.0	0.5	0.5

Steel material detects banded structure according to GB/T13299 standard

TABLE 4 banded ratings of round bars prepared in examples 1-7

Through the first 3 groups of examples, the properties of the round steel, such as chemical components, hardenability, non-metallic inclusions and banding, are well controlled, the purity of the steel is obviously inferior to that of other examples through the adjustment of LF and VD processes in example 4, and the rating of the non-metallic inclusions is obviously superior to that of other examples; the continuous casting process adjustment in example 5 shows that the strip rating is obviously higher than that of other examples by comparison; in example 6, the steel-making raw material has a higher scrap ratio than other examples, and the high residual element is not favorable for stable control of end quenching. In example 7, the heating time and the heating temperature are adjusted, and under different combinations of heating temperature and heating time, the comparison shows that the dephosphorization effect is much worse than that of example 1, the scale is very thick, the scale is difficult to remove after descaling, and the quality of rolled steel is directly affected by more large scale covering on the surface of the billet. Other conditions outside the scope of the present invention will affect the internal or external steel weight. Therefore, the smelting in the embodiments 1 to 3 meets the indexes of chemical component control, hardenability, purity, banded structure and the like, reaches the leading level in the industry, and simultaneously solves the problem of difficult dephosphorization in the production process.

Claims

1. The utility model provides a wind-powered electricity generation is CrNiMo round steel for gear which characterized in that: the CrNiMo round steel comprises the following chemical components in percentage by weight: [C]0.15 to 0.21%, [ Si ]0.17 to 0.37%, [ Mn ]0.50 to 0.90%, and [ Cr ]: 1.50 to 1.80 percent, 1.40 to 1.70 percent of [ Ni ], less than or equal to 0.20 percent of [ Cu ], lessthan or equal to 0.025 percent of [ P ], lessthan or equal to 0.025 percent of [ S ], [ Mo ]0.25 to 0.35 percent, less than or equal to 0.0020 percent of [ O ], [ Al ]0.025 to 0.040 percent, and [ N ]0.0080 to 0.0120 percent.

2. The CrNiMo round steel for the wind power gear as claimed in claim 1, wherein: the CrNiMo round steel comprises the following chemical components in percentage by weight: [C]0.16 to 0.18 percent, 0.17 to 0.27 percent of [ Si ], 0.62 to 0.68 percent of [ Mn ], 1.61 to 1.69 percent of [ Cr ], 1.46 to 1.54 percent of [ Ni ], less than or equal to 0.10 percent of [ Cu ], less than or equal to 0.020 percent of [ P ], lessthan or equal to 0.015 percent of [ S ], [ 0.26 to 0.29 percent of [ Mo ], lessthan or equal to 0.0020 percent of [ O ], [ Al ]0.025 to 0.040 percent, and less than or equal to 0.0080 to 0.0120 percent of [ N ].

3. The preparation method of the CrNiMo round steel for the wind power gear according to claim 1 or 2, which is characterized in that: the method comprises the following steps of electric furnace smelting, LF refining, VD vacuum degassing, continuous casting and rolling process, and comprises the following preparation steps:

(1) when the electric furnace is smelted and tapped, the components of C is less than or equal to 0.10 percent, P is less than or equal to 0.012 percent, the tapping temperature is more than or equal to 1630 ℃, a deoxidizer, alloy and slag charge are added in the tapping process, the sliding plate slag stopping operation is adopted in the tapping process, slag is strictly forbidden to be discharged, and the tapping time is 3-5 minutes;

(2) LF refining: aluminum particles and silicon carbide are used for deoxidation in the early stage of LF refining, silicon carbide is added for deoxidation and slag retention in the later stage, the alloy components are quickly adjusted in the early stage of refining to meet the control requirement of target components, the binary alkalinity of refining slag is 4.0-4.5, the refining time is controlled at 50-70 min/furnace, the white slag time is ensured to be more than 30min, and the aluminum and silicon contents are controlled during refining tapping;

(3) VD vacuum degassing: the high vacuum maintaining time of VD vacuum treatment is more than or equal to 10 minutes, the argon bottom stirring flow is controlled to be 150-200L/min and the pressure is controlled to be 0.3-0.4MPa during high vacuum pressure maintaining, and the vacuum aluminum loss is controlled to be 40-50 percent; after the VD breaks the air, a pure calcium line is fed, a nitrogen-manganese line is fed according to the content of N, and before the silk thread is fed, the argon is ensured to be in a soft blowing state, the flow of the argon is 50-80L/min, the pressure is 0.15-0.2MPa, and the soft blowing time is more than or equal to 20 min;

(4) the continuous casting process adopts full-process protective casting and argon sealing protection of a ladle long nozzle, the tundish is covered by an alkaline covering agent and carbonized rice hulls in a double-layer manner, the continuous casting tundish adopts an integral stopper tundish, the superheat degree is controlled at 20-35 ℃, and the drawing speed is controlled at 0.85 +/-0.05 m/min; meanwhile, the homogenization of the casting blank solidification process is improved by adopting a combined regulation and control means of M-MES (crystallizer electromagnetic stirring) + PMO (pulsed magnetic oscillation) + F-MES (tail end electromagnetic stirring), and the crystallizer casting powder uses special casting powder;

(5) and (5) rolling.

4. The preparation method of the CrNiMo round steel for the wind power gear as claimed in claim 3, wherein the preparation method comprises the following steps: the steelmaking raw materials adopted in the step (1) are scrap steel and molten iron, the scrap steel accounts for 5% -15% of the total weight of the steelmaking raw materials, the molten iron accounts for 85% -95% of the total weight of the steelmaking raw materials, the total loading amount of the steelmaking raw materials is 100-.

5. The preparation method of the CrNiMo round steel for the wind power gear as claimed in claim 3, wherein the preparation method comprises the following steps: in the step (1), the addition amount of the deoxidizer is 0.7-0.9kg/t of the aluminum block; the alloy in the step (1) is ferrosilicon, low-carbon ferromanganese and low-carbon ferrochrome; the slag charge and the adding amount in the step (1) are 350 kg/furnace of slagging agent and 650 kg/furnace of lime.

6. The preparation method of the CrNiMo round steel for the wind power gear as claimed in claim 3, wherein the preparation method comprises the following steps: step (2) in LF refining, the ladle temperature is 1640-1660 ℃ for the first casting time and 1620-1630 ℃ for the continuous casting time; controlling the aluminum content to be 0.035-0.040% during refining tapping in the step (2); the Si content of the steel is controlled between 0.018 and 0.020 percent.

7. The preparation method of the CrNiMo round steel for the wind power gear as claimed in claim 3, wherein the preparation method comprises the following steps: after the step (3) is carried out, the N content in the steel is 50-60ppm, the continuous casting temperature on the VD ladle is controlled at 1585-.

8. The preparation method of the CrNiMo round steel for the wind power gear as claimed in claim 3, wherein the preparation method comprises the following steps: the crystallizer in the step (4) adopts electromagnetic stirring, and the water flow of the crystallizer is 110 +/-10 m³H, the water temperature difference is 7.0-9.0 ℃, and the secondary cooling adopts a weak cooling water distribution mode, and the specific water amount is 0.20L/kg; the electromagnetic stirring parameter of the crystallizer is 150 +/-10A/2 HZ, the non-sinusoidal vibration parameter is amplitude +/-2.5 mm, and the frequency is 130+40V opm; the PMO direct current voltage is set to be 50V; the end electric stirring parameter is set to be 50A/6 Hz.

9. The preparation method of the CrNiMo round steel for the wind power gear as claimed in claim 3, wherein the preparation method comprises the following steps: in the step (4), the basicity of the special covering slag selected by the crystallizer is 0.85-0.90, the melting point is 1100-; the thickness of the liquid slag layer is measured every 2 hours, and the depth of the liquid slag layer is ensured to be 5-10 mm.

10. The preparation method of the CrNiMo round steel for the wind power gear as claimed in claim 3, wherein the preparation method comprises the following steps: the rolling process in the step (5) comprises the following steps: the temperature range of the soaking section is 1140-1160 ℃, the heating time is 350-400min, the air-fuel ratio is 0.7-0.8, the rolling start temperature range is 1030-1080 ℃, and the final rolling temperature range is 850-930 ℃.