A production method of a near-net-shape 15MW land wind power gear box sun gear forging

Abstract

The application discloses a production method of a near-net-shaped 15MW land wind power gear box sun gear forge piece, which comprises the following steps in sequence: pre-forging heating, forging, post-forging cooling, dehydrogenation treatment, normalizing and tempering, and the forge piece is made of high-strength carburizing steel of 18CrNiMo7-6, and the high-strength carburizing steel comprises the following components in percentage by mass: C: 0.17% to 0.21%, Si: 0.15% to 0.3%, Mn: 0.6% to 0.9%, Cr: 1.55% to 1.8%, Ni: 1.5% to 1.7%, Mo: 0.25% to 0.35%, P: less than or equal to 0.015%, S: less than or equal to 0.005%, Cu: less than or equal to 0.2%, H: less than or equal to 1.5ppm, O: less than or equal to 15ppm, N: 75ppm to 125ppm, Ti: less than or equal to 30ppm, Ca: less than or equal to 10ppm, Sn: less than or equal to 100ppm, Pb: less than or equal to 100ppm, Bi: less than or equal to 100ppm, Sb: less than or equal to 30ppm, As: less than or equal to 150ppm, Al: 0.025% to 0.038%, As+Sn+Pb+Sb+Bi: less than or equal to 0.03%, Nb: 0.02% to 0.03%, and the balance is Fe and inevitable impurities. The production method is simple, and is beneficial to improving raw material utilization rate and large-scale production. The preferred Nb element content is beneficial to improving the flaw detection detectability grade of the forge piece.

Description

Technical Field

[0001] This invention relates to the field of sun gear technology, and specifically to a method for producing a near-net-shape 15MW onshore wind turbine gearbox sun gear forging. Background Technology

[0002] Sun gear forgings are the core components of planetary gear systems, mainly used in the transmission systems of heavy machinery such as bulldozers, excavators, and wind power equipment.

[0003] With the advancement of grid parity policies for wind power, the price of wind turbines has continued to decline, and cost pressures have been passed on to core components such as gearboxes. Currently, wind power equipment manufacturers have an intensified demand for cost reduction in the sun gear, a component of gearbox forgings. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects in the existing technology and provide a near-net-shape production method for a 15MW onshore wind turbine gearbox sun gear forging. This method improves the detectability level of the forging while increasing the utilization rate of raw materials.

[0005] To address the aforementioned technical problems, this invention provides a near-net-shape production method for a 15MW onshore wind turbine gearbox sun gear forging, comprising sequential steps of pre-forging heating, forging, post-forging cooling, dehydrogenation treatment, normalizing, and tempering. The forging is made of 18CrNiMo7-6 high-strength carburizing steel, and by mass percentage, the high-strength carburizing steel comprises: C: 0.17%~0.21%, Si: 0.15%~0.3%, Mn: 0.6%~0.9%, Cr: 1.55%~1.8%, Ni: 1.5%~1.7%, Mo: 0.25%~0.35%, P≤0.015%, S≤0.005%, Cu≤0.2%, H≤1.5ppm, O≤15ppm, N: 75ppm~125ppm, Ti≤30ppm, Ca≤10ppm, Sn≤100ppm, Pb≤100ppm, Bi≤100ppm, Sb≤30ppm, As≤150ppm, Al: 0.025%~0.038%, As+Sn+Pb+Sb+Bi≤0.03%, Nb: 0.02%~0.03%, balance Fe and unavoidable impurities.

[0006] Furthermore, the content of the Nb element can be selected as a point value of 0.02%, 0.023%, 0.024%, 0.026%, or 0.03%, or a range of the above two point values ​​as the maximum and minimum values.

[0007] The preferred technical solution is that the mass ratio of Al to N elements in the high-strength carburized steel is 2 to 5.

[0008] Furthermore, the mass ratio of Al to N elements in the high-strength carburized steel composition can be selected as a point value of 2, 3, 3.13, 4, or 5, or as a range of two of the above point values ​​as the maximum and minimum values.

[0009] A preferred technical solution is that the pre-forging heating step includes: The forgings are fed into the furnace at an initial temperature below 700°C, heated to 780~820°C at a heating rate of no more than 100°C / h and held at that temperature, and then heated to 1200~1240°C at a heating rate of no more than 100°C / h and held at that temperature.

[0010] Furthermore, the forging is fed into the furnace at an initial temperature of no more than 700°C, heated at a heating rate of no more than 100°C / h to a point value that can be selected as 780, 790, 800, 810, or 820°C, or a range of two of the above points as the maximum and minimum values, and then held at that temperature. Finally, it is heated at a heating rate of no more than 100°C / h to a point value that can be selected as 1200, 1230, or 1240°C, or a range of two of the above points as the maximum and minimum values, and then held at that temperature.

[0011] The preferred technical solution is that the forging step includes three alternating upsetting and two drawing operations, with the forging ratio of each upsetting or drawing operation being greater than 1.6, and the forging ratio of at least one upsetting or drawing operation being not less than 2.

[0012] Furthermore, the forging ratios for upsetting and drawing decrease with each pass.

[0013] A preferred technical solution is that the forging is near-net-shape forging, and the forging further includes drawing and then rolling the ring with a shaped mandrel having annular grooves, wherein the forging ratio of the shaped mandrel rolling ring is 1.7~2.1. The ring forging has an inner hole step corresponding to the toothed part of the sun gear forging; The ratio of the width of the annular groove to the height of the inner hole step is 1.05 to 1.15, and the ratio of the depth of the annular groove to the difference between the maximum and minimum radii of the inner hole step is 1.02 to 1.06.

[0014] Furthermore, the forging ratio of the irregularly shaped core roller forming the rolling ring can be selected as a value of 1.7, 1.9, 2, or 2.1, or a range of two of the above values ​​as the maximum and minimum values; the ratio of the width of the annular groove to the height of the inner hole step can be selected as a value of 1.05, 1.1, or 1.15, or a range of two of the above values ​​as the maximum and minimum values; the ratio of the depth of the annular groove to the difference between the maximum and minimum radii of the inner hole step can be selected as a value of 1.02, 1.03, 1.04, 1.05, or 1.06, or a range of two of the above values ​​as the maximum and minimum values.

[0015] The preferred technical solution is that the initial forging temperature of the forging is not higher than 1200℃ and the final forging temperature of the forging is not lower than 850℃.

[0016] A preferred technical solution is that the post-forging cooling step includes: The forgings are air-cooled to 450~550℃ and then air-cooled to 300~350℃.

[0017] Furthermore, the temperature at which the forging is air-cooled can be selected as a point value of 450, 470, 490, 510, 530, or 550°C, or a range of two of the above points as the maximum and minimum values; the temperature at which the forging is air-cooled can be selected as a point value of 300, 310, 320, 330, 340, or 350°C, or a range of two of the above points as the maximum and minimum values.

[0018] A preferred technical solution is that the dehydrogenation treatment step includes: The forging is first held at 300~350℃ for 2.5~3.5h, then heated to 630~670℃ at a heating rate of no more than 80℃ / h, and then held at the effective cross section of the forging for no less than 6min / mm before being cooled to below 450℃ at a cooling rate of no more than 40℃ / h.

[0019] Furthermore, the holding time of the forging at 300~350℃ can be selected as 2.5, 3, or 3.5 hours, or the above two values ​​can be used as a range of maximum and minimum values.

[0020] The advantages and beneficial effects of this invention are as follows: The present invention provides a simple production method for the near-net-shape 15MW onshore wind turbine gearbox sun gear forging, which is conducive to improving raw material utilization and large-scale production. The optimal Nb content is beneficial to improving the detectability level of forgings. Furthermore, the system employs a preferred ratio of the depth of the annular groove to the difference between the maximum and minimum radii of the inner hole step, thus preventing the collapse of the inner hole step. Attached Figure Description

[0021] Figure 1 This is a cross-sectional schematic diagram of the near-net-shape 15MW onshore wind turbine gearbox sun gear forging produced in Example 1; Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0023] Detectability of forgings After confirming the sensitivity of flaw detection for forgings, forging manufacturers consider a signal-to-noise ratio of not less than 6dB as sufficient for detecting flaws, using this sensitivity as a benchmark. Furthermore, manufacturers assess the detectability level based on the magnitude of the recorded defect equivalent.

[0024] 1. Examples and Comparative Examples Example 1

[0025] The near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Example 1 consists of the following components by weight percentage: C: 0.18%, Si: 0.27%, Mn: 0.69%, P: 0.014%, S: 0.0012%, Cr: 1.64%, Ni: 1.55%, Mo: 0.27%, Cu: 0.02%, Nb: 0.024%, Al: 0.031%, Ti: 14ppm, Pb: 10ppm, Sn: 49ppm, Sb: 10ppm, As: 53ppm, Ca: 5ppm, Bi: 30ppm, N: 98.9ppm, O: 9.1ppm, H: 0.5ppm, balance being Fe and unavoidable impurities. Al / N = 3.13, As + Sn + Pb + Sb + Bi = 0.0152%.

[0026] The manufacturing process of the near-net-shape 15MW onshore wind turbine gearbox sun gear forging in Example 1 includes the following steps: S1: A long billet with a diameter of 800 mm and a length of 1165 mm is fed into the furnace and heated to 800℃ at a heating rate of 90℃ / h, and held at that temperature for 2 hours. Then it is heated to 1220℃ at a heating rate of 90℃ / h and held at that temperature for 3 hours. S2: The billet is upset using a 5000T hydraulic press. Before upset drawing, the surface and core temperatures of the billet are measured to be 1200℃. The billet is first upset to a diameter of 1118mm and a length of 580mm, then drawn to a diameter of 830mm and a length of 1050mm, then upset to a diameter of 1098mm and a length of 600mm, then drawn to a diameter of 851mm and a length of 1000mm, then upset to a diameter of 1118mm and a length of 585mm, and finally punched to obtain a billet with an outer diameter of 1166mm, an inner diameter of 360mm, and a length of 585mm. At this time, the surface temperature of the billet is measured to be 870℃. S3: Reheat the billet in the furnace until the surface and core temperatures of the forging are both 1200℃; S4: A 6.3m CNC ring rolling machine is used to roll the billet into a ring. The rolling roller is a special-shaped core roller with annular grooves to obtain a forging with an outer diameter of 1632mm, an inner diameter of 1154mm, and a length of 523mm. The rolled ring forging has an inner hole step corresponding to the toothed part of the sun gear forging. The height of the inner hole step is 100mm, and the difference between the inner and outer diameters is 40mm. S5: Cool the forging to 500℃ with air cooling, then air cool to 330℃; S6: Place the forging in a heating furnace at 350℃ and hold for 3 hours. Then, heat it to 650℃ at a heating rate of 75℃ / h, hold for 24 hours, and then cool it down to 434℃ at a cooling rate of 35℃ / h before taking it out of the furnace. S7: The forging is heated to 650℃ at a heating rate of 90℃ / h and held for 2.5h, then heated to 950℃ at a heating rate of 90℃ / h and held for 6h, and then cooled. S8: After the forgings cooled to 400°C are loaded into the furnace, they are heated to 680°C at a heating rate of 90°C / h and held at that temperature for 9 hours. Then they are cooled to 430°C at a cooling rate of 35°C / h and removed from the furnace.

[0027] The irregular core roller used in Example 1 has an annular groove with a width of 110 mm and a depth of 21 mm.

[0028] Example 2

[0029] The near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Example 2 is based on Example 1, except that the width of the annular groove of the irregular core roller used in Example 2 is 110mm and the depth of the annular groove is 20.3mm.

[0030] Example 3

[0031] The near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Example 3 is based on Example 1, except that the width of the annular groove of the irregular core roller used in Example 3 is 110mm and the depth of the annular groove is 22mm.

[0032] Example 4

[0033] The near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Example 4 is based on Example 1, except that in S2: the billet is upset using a 5000T hydraulic press. Before upset drawing, the surface and core temperatures of the billet are measured to be 1200℃. The billet is first upset to a diameter of 996mm and a length of 730mm, then drawn to a diameter of 851mm and a length of 1000mm, then upset to a diameter of 1098mm and a length of 600mm, then drawn to a diameter of 851mm and a length of 1000mm, then upset to a diameter of 1118mm and a length of 585mm, and finally punched to obtain a billet with an outer diameter of 1166mm, an inner diameter of 360mm, and a length of 585mm. At this time, the surface temperature of the billet is measured to be 868℃.

[0034] Comparative Example 1 The near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Comparative Example 1 is based on Example 1, except that the near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Comparative Example 1 is composed of the following components by weight percentage: C: 0.185%, Si: 0.24%, Mn: 0.77%, P: 0.011%, S: 0.0018%, Cr: 1.59%, Ni: 1.61%, Mo: 0.31%, Cu: 0.01%, Nb: 0.018%, Al: 0.027%, Ti: 24ppm, Pb: 20ppm, Sn: 23ppm, Sb: 20ppm, As: 21ppm, Ca: 4ppm, Bi: 26ppm, N: 100ppm, O: 8.3ppm, H: 1.1ppm, balance being Fe and unavoidable impurities. Al / N = 2.7, As + Sn + Pb + Sb + Bi = 0.011%.

[0035] Comparative Example 2 The near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Comparative Example 2 is based on Example 1, except that the near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Comparative Example 2 is composed of the following components by weight percentage: C: 0.18%, Si: 0.28%, Mn: 0.73%, P: 0.009%, S: 0.0009%, Cr: 1.71%, Ni: 1.58%, Mo: 0.29%, Cu: 0.03%, Nb: 0.033%, Al: 0.027%, Ti: 20ppm, Pb: 30ppm, Sn: 41ppm, Sb: 11ppm, As: 33ppm, Ca: 7ppm, Bi: 34ppm, N: 111ppm, O: 7ppm, H: 0.3ppm, balance being Fe and unavoidable impurities. Al / N = 2.43, As + Sn + Pb + Sb + Bi = 0.0149%.

[0036] Comparative Example 3 The near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Comparative Example 3 is based on Example 1, except that: S1: A long billet with a diameter of 800 mm and a length of 1222 mm is fed into the furnace and heated to 800℃ at a heating rate of 90℃ / h, and held at that temperature for 2 hours. Then it is heated to 1220℃ at a heating rate of 90℃ / h and held at that temperature for 3 hours. S2: The billet is upset using a 5000T hydraulic press. Before upset drawing, the surface and core temperatures of the billet are measured to be 1200℃. The billet is first upset to a diameter of 1125mm and a length of 600mm, then drawn to a diameter of 839mm and a length of 1080mm, then upset to a diameter of 1125mm and a length of 600mm, then drawn to a diameter of 872mm and a length of 1000mm, then upset to a diameter of 1139mm and a length of 585mm, and finally punched to obtain a billet with an outer diameter of 1186mm, an inner diameter of 360mm, and a length of 585mm. At this time, the surface temperature of the billet is measured to be 875℃. S3: Reheat the billet in the furnace until the surface and core temperatures of the forging are both 1220℃; S4: A 6.3m CNC ring rolling machine is used to roll the billet to obtain a forging with an outer diameter of 1632mm, an inner diameter of 1114mm, and a length of 523mm.

[0037] Comparative Example 4 The near-net-shape 15MW onshore wind turbine gearbox sun gear forging of Comparative Example 4 is based on Example 1, except that S7 is performed directly after S5.

[0038] 2. Material utilization calculation method and flaw detection method of the examples and comparative examples 2.1. Divide the final machined product weight by the forging raw material weight and then multiply by 100% to obtain the material utilization rate; 2.2. The standards for the detectability level of forgings are as follows: For records with a defect equivalent of 0.4 mm or more, the detectability level is 001; for records with a defect equivalent of 0.5 mm or more, the detectability level is 01; and for records with a defect equivalent of 0.6 mm or more, the detectability level is 1. 001 is the highest detectability level, and 1 is the lowest.

[0039] 3. Material utilization and exploreability rating results of the examples and comparative examples

[0040] In Examples 2 and 3, some areas of the tooth region and inner hole steps collapsed, but were restored to normal after rough machining. Comparative Example 4 showed white spot defects and was rejected. Comparative Example 2 was more expensive than Example 1.

[0041] 4. Performance Results Analysis of Examples and Comparative Examples Example 1 and Comparative Examples 1, 2, and 3 show that using irregularly shaped rollers is beneficial for improving material utilization. The optimal Nb content is beneficial for improving the detectability level of forgings.

[0042] Example 1 and Comparative Example 4 show that dehydrogenation heat treatment helps to avoid white spot defects in forgings.

[0043] Examples 1, 2, and 3 show that the preferred ratio of the depth of the annular groove to the difference between the maximum and minimum radii of the inner hole step can prevent the collapse of the inner hole step.

[0044] Examples 1 and 4 show that the preferred forging ratio can improve the overall detectability level of the forging.

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a near-net-shape onshore wind turbine gearbox sun gear forging, characterized in that, The process includes sequential steps of pre-forging heating, forging, post-forging cooling, dehydrogenation treatment, normalizing, and tempering. The forging is made of 18CrNiMo7-6 high-strength carburizing steel, and the composition of the high-strength carburizing steel by mass percentage is as follows: C: 0.17%~0.21%, Si: 0.15%~0.3%, Mn: 0.6%~0.9%, Cr: 1.55%~1.8%, Ni: 1.5%~1.7%, Mo: 0.25%~0.35%, P≤0.015%, S≤0.005%, Cu≤0.2%, H≤1.5ppm, O≤15ppm, N: 75ppm~125ppm, Ti≤30ppm, Ca≤10ppm, Sn≤100ppm, Pb≤100ppm, Bi≤100ppm, Sb≤30ppm, As≤150ppm, Al: 0.025%~0.038%, As+Sn+Pb+Sb+Bi≤0.03%, Nb: 0.02%~0.03%, balance Fe and unavoidable impurities; The mass ratio of Al to N elements in the high-strength carburized steel is 2 to 5. The pre-forging heating step includes: The forging is fed into the furnace at an initial temperature of no more than 700°C, heated to 780~820°C at a heating rate of no more than 100°C / h and held at that temperature, and then heated to 1200~1240°C at a heating rate of no more than 100°C / h and held at that temperature. The dehydrogenation treatment step includes: The forging is first held at 300~350℃ for 2.5~3.5h, then heated to 630~670℃ at a heating rate of no more than 80℃ / h, and then held at the effective cross section of the forging for no less than 6min / mm before being cooled to below 450℃ at a cooling rate of no more than 40℃ / h. The normalizing step includes: The forging is first heated to 640~660℃ at a heating rate of no more than 100℃ / h and held for 2~3h, then heated to 940~960℃ at a heating rate of no more than 100℃ / h, and then held for no less than 2.5h / 100mm of the effective cross section of the forging before being cooled to 300~500℃. The tempering step includes: The forging is first heated to 670~700℃ at a heating rate of no more than 100℃ / h, then held at a temperature of no less than 3.75h / 100mm for the effective cross section of the forging, and then cooled to below 450℃ at a cooling rate of no more than 40℃ / h.

2. The method for producing a near-net-shape onshore wind turbine gearbox sun gear forging according to claim 1, characterized in that, The forging steps include three alternating upsetting and two drawing operations, with the forging ratio of each upsetting or drawing operation being greater than 1.6, and the forging ratio of at least one upsetting or drawing operation being not less than 2.

3. The method for producing a near-net-shape onshore wind turbine gearbox sun gear forging according to claim 2, characterized in that, The forging is near-net-shape forging, and the forging also includes drawing and rolling a ring with a shaped mandrel having annular grooves after drawing. The forging ratio of the shaped mandrel to the ring is 1.7 to 2.

1. The ring forging has an inner hole step corresponding to the toothed part of the sun gear forging; The ratio of the width of the annular groove to the height of the inner hole step is 1.05 to 1.15, and the ratio of the depth of the annular groove to the difference between the maximum and minimum radii of the inner hole step is 1.02 to 1.

06.

4. The method for producing a near-net-shape onshore wind turbine gearbox sun gear forging according to claim 1, characterized in that, The initial forging temperature of the forging is not higher than 1200℃, and the final forging temperature of the forging is not lower than 850℃.

5. The method for producing a near-net-shape onshore wind turbine gearbox sun gear forging according to claim 1, characterized in that, The post-forging cooling step includes: The forgings are air-cooled to 450~550℃ and then air-cooled to 300~350℃.

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