A method for rolling large flange rings for wind turbine towers

Abstract

This invention pertains to the manufacturing of large flange rings for wind turbine towers, specifically relating to a method for rolling large flange rings for wind turbine towers. In existing technologies, after the rolling process, forged large flange rings require transfer to a dedicated heat treatment area for heating and cooling, disrupting production continuity. Addressing this issue, this invention cools the rings simultaneously during rolling. For the specific large flange ring blanks used in wind turbine towers, by controlling the roll rate, cooling conditions, and the initial and final rolling temperatures during the rolling process, the internal structure of the rings remains stable upon leaving the rolling process, exhibiting excellent mechanical properties. This allows them to be directly used for subsequent machining processes without requiring separate heat treatment.

Description

Technical Field

[0001] This invention belongs to the field of manufacturing large flange rings for wind turbine towers, and in particular relates to a method for rolling large flange rings for wind turbine towers. Background Technology

[0002] Large flange rings are key connecting components in wind turbine towers. Since tower heights can exceed 100 meters, the flanges, as connecting elements, bear various loads at high altitudes, resulting in highly complex stress conditions. Therefore, large flange rings are often extremely thick. The most advanced manufacturing process for such large rings is rolling, which involves blanking, heating, forging, heating, ring rolling, heat treatment, rough machining, and finish machining.

[0003] However, current heat treatment processes require moving the ring to a dedicated heat treatment area, where it undergoes heating and cooling before roughing and finishing. This disconnects it from other processes, disrupting the continuity of production, reducing efficiency, wasting resources such as electricity and coal, increasing energy consumption per unit of output, and hindering the development of high-precision manufacturing industries. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for rolling large flange rings for wind turbine towers, which allows the flange rings to directly enter subsequent machining processes (rough machining and finish machining) without further heat treatment after the rolling process.

[0005] The present invention discloses a method for rolling large flange rings for wind turbine towers, comprising the following steps:

[0006] The forged ring blank enters the ring rolling process, which includes the biting stage, the ring rolling stage, and the rounding stage; after the ring is placed into the ring rolling mechanism and successfully bitten in, it enters the ring rolling stage, and the surface of the ring is cooled at the same time.

[0007] The core roll reduction rate during the ring rolling stage is 0.44–2.35 mm / s, the cone roll reduction rate is 0.8 times that of the core roll reduction rate, and the drive roll rotation speed is 8–20 r / min.

[0008] The cooling rate during the ring rolling stage is 15℃ / s to 100℃ / s, and the cooling range width is 200 to 900 mm. This cooling range width refers to the chord length between any two points on the inner or outer circumference of the ring. The cooling medium covers the axial height of the ring, and the inner and outer walls of the ring are cooled simultaneously by two cooling units, one inner and one outer. Cooling causes the deformation during rolling to penetrate into the core of the axial section of the ring.

[0009] At the beginning of the ring rolling stage, the ring temperature is 1100-1200℃, and at the end of the ring rolling stage, the ring temperature is 700-850℃.

[0010] At the start of ring rolling, the thickness of the ring (the difference between the inner and outer radii) is 120–750 mm, and the outer diameter is 800–5500 mm.

[0011] After the ring rolling stage, cooling is stopped, and after the rounding stage, the rolled part is obtained that can be directly used for machining.

[0012] This invention cools the ring surface during rolling, lowering the surface temperature and significantly increasing the temperature difference between the core and surface of the axial section. During rolling, the lower-temperature surface matrix exhibits greater deformation resistance, reducing deformation and making it less prone to deformation. Conversely, the higher temperature at the center of the axial section makes it more susceptible to deformation. Based on the principle of constant volume, the volume of the pressed metal will shift towards the ring core, allowing deformation to penetrate deep into the axial section core. This invention is specifically designed for large flange ring blanks used in wind turbine towers. By controlling the roll speed, cooling conditions, and the initial and final rolling temperatures during the ring rolling process, the internal structure of the ring is stabilized, resulting in excellent mechanical properties. This not only improves the overall performance of the ring but also eliminates the need for subsequent heat treatment processes, allowing it to directly enter the machining process after rolling, thus reducing the production cost of large flange rings.

[0013] The ring rolling method of the present invention is applicable to flange steel specified in JB / T 11218-2020 standard, preferably Q355NE flange steel.

[0014] Using the ring rolling method of this invention, without subsequent heat treatment, the average yield strength in all directions is ≥350MPa, the average tensile strength in all directions is ≥520MPa, the elongation is ≥25%, and the average room temperature impact energy KV2 in all directions is ≥170J, exhibiting excellent performance. The surface and core of the rolled part are both pearlite + ferrite structures with a grain size ≥7.5 and no mixed crystal phenomenon. Attached Figure Description

[0015] Figure 1 The image shows the metallographic structure of the rolled part in Example 1.

[0016] Figure 2 The image shows the metallographic structure of the rolled part in Example 2.

[0017] Figure 3 The image shows the metallographic structure of the rolled part in Example 3.

[0018] Figure 4 The image shows the metallographic structure of the rolled part in Example 4.

[0019] Figure 5The image shows the metallographic structure of the rolled part in Example 5.

[0020] Figure 6 The image shows the metallographic structure of the rolled part in Comparative Example 2.

[0021] Figure 7 The image shows the metallographic structure of the rolled part in Comparative Example 3.

[0022] Figure 8 This is a three-dimensional schematic diagram showing the positional relationship between the ring and each roll in the ring rolling process.

[0023] Figure 9 This is a top-view schematic diagram showing the positional relationship of the ring components, cooling unit, and rolls during the ring rolling stage.

[0024] Wherein: 1-Drive roller, 2-Left guide roller, 3-Right guide roller, 4-Core roller, 5-Conical roller, 6-Ring, 7-Inner cooling unit, 8-Outer cooling unit, 9-Cooling unit moving track. Detailed Implementation

[0025] The present invention will be further described below with reference to specific implementation examples and accompanying drawings. It should be noted that the specific embodiments described below are only for explaining the present invention, but the present invention is not limited to these embodiments. Those skilled in the art can make equivalent substitutions based on the present invention without departing from the spirit and scope of the present technical solution, and all such substitutions should be covered within the protection scope of the present invention.

[0026] The ring blanks used in the ring rolling process of this invention are obtained by melting and smelting according to the composition requirements of Q355NE steel for flange rings, and then punching holes in the round blanks to obtain the ring blanks. After rolling, the rolled parts do not undergo heat treatment such as normalizing. After cooling to room temperature, they can be directly used for roughing and finishing in subsequent machining processes.

[0027] The chemical composition and mass percentage of each chemical component in the Q355NE steel used in this invention are as follows: C: ≤0.18%, Si: ≤0.50%, Mn: 0.9~1.65%, P: ≤0.012%, S: ≤0.005%, Nb: 0.005~0.05%, V: 0.01~0.12%, Ti: 0.006~0.05%, Cr: ≤0.3%, Ni: ≤0.5%, Cu: ≤0.2%, Mo: ≤0.1%, N: ≤0.015%, Al: ≥0.015%, with the balance being iron and unavoidable impurities.

[0028] In the embodiments, parameters such as yield strength were tested in accordance with JB / T 11218-2020 for wind power generation tower flange forgings.

[0029] The positional relationship between the ring and each roll in the ring rolling process is as follows: Figure 8 As shown.

[0030] The positional relationships of the ring components, cooling unit, and rolls during the ring rolling stage are as follows: Figure 9 As shown, at the start of rolling, the drive roller 1 rotates the ring 6, and the core roller 4 and the cone roller 5 are fed simultaneously. After the biting stage, the ring rolling stage begins. At this time, the cooling device is activated so that the inner and outer cooling units are aligned with the inner and outer surfaces of the ring, respectively. After the cooling device is aligned with the ring 6, cooling (water spray cooling) is turned on, and the cooling water covers the axial height of the ring 6.

[0031] The outer cooling unit 8 is located on the outside of the ring 6, and the inner cooling unit 7 is located on the inside of the ring 6. There are gaps between the inner cooling unit 7 and the outer cooling unit 8 and the ring 6. Displacement sensors are provided on the inner and outer cooling units to monitor the movement of the ring 6 and to move the cooling units on the cooling unit moving track 9 as the ring 6 grows, so that the distance between the outer cooling unit 8 and the inner cooling unit 7 and the surface of the ring 6 is always consistent.

[0032] In the ring rolling stage, the ring 6 rotates with the rolling mechanism and is cooled during rotation. The ring 6 is rolled when it passes through the radial rolling mechanism (the die pattern of the drive roll 1 and the core roll 4), and then rolled through the axial rolling mechanism (the die pattern of the tapered roll 5). It then rotates to the cooling unit area for rapid cooling. The left guide roll 2 and right guide roll 3 are driven rolls that rotate freely, acting as limiters to assist in ring forming. After the above process, the entire ring completes one rolling pass. During the ring rolling process, the pressing rate of the core roll 4 and the rotation speed of the drive roll 1 remain constant. After the ring 6 has undergone multiple rolling passes, the ring rolling stage ends, and the cooling device is shut off. The ring then enters the rounding stage. After the rounding stage is completed, the rolling mechanism is shut off, resulting in the finished rolled part.

[0033] Example 1

[0034] The forged ring blank is placed into the ring rolling mill. The mill is started to allow the ring to bite into the roll and rotate with the rolls, initiating the ring rolling stage. During this stage, the initial rolling temperature is 1163℃, the mandrel reduction rate is 0.8mm / s, the tapered roll reduction rate is 0.64mm / s, and the drive roll speed is 10r / min. Simultaneously, the ring surface is cooled at a rate of 90℃ / s over a cooling area of ​​200mm. This cooling process allows the deformation from the rolling process to penetrate towards the core of the ring's axial cross-section. Cooling is stopped at the end of the ring rolling stage, with a final rolling temperature of 792℃. The ring then enters the rounding stage. After rounding, the rolled part is obtained and cooled to room temperature before proceeding directly to subsequent machining processes.

[0035] The chemical composition of the steel for the ring components, by mass percentage, is as follows: C: 0.147%, Si: 0.24%, Mn: 1.34%, P: 0.010%, S: 0.003%, Nb: 0.04%, V: 0.032%, Ti: 0.029%, Cr: 0.12%, Ni: 0.04%, Cu: 0.03%, Mo: 0.02%, N: 0.0072%, Al: 0.04%, with the balance being iron and unavoidable impurities.

[0036] The ring has a thickness of 130mm and an outer diameter of 1000mm before rolling. After rolling, the ring has a thickness of 90mm and an outer diameter of 1640mm.

[0037] The rolled part has an average yield strength of 377 MPa in all directions, an average tensile strength of 528 MPa in all directions, an elongation of 28%, and an average room-temperature impact energy of 187 J in all directions. The surface and core microstructure of the rolled part is pearlite + ferrite. Metallographic features are as follows: Figure 1 As shown, the grain size is 8 to 8.5 and there is no mixed crystal phenomenon.

[0038] Example 2

[0039] The forged ring blank is placed into the ring rolling mill. The mill is started to allow the ring to bite into the roll and begin the rolling stage. During this stage, the initial rolling temperature is 1172℃, the mandrel reduction rate is 1.2 mm / s, the tapered roll reduction rate is 0.96 mm / s, and the drive roll speed is 16 r / min. Simultaneously, the ring surface is cooled at a rate of 75℃ / s over a cooling area of ​​300 mm. This cooling process allows the deformation from the rolling process to penetrate towards the core of the ring's axial cross-section. Cooling is stopped at the end of the rolling stage, with a final rolling temperature of 783℃. The ring then enters the rounding stage. After rounding, the rolled part is obtained and cooled to room temperature before proceeding directly to subsequent machining processes.

[0040] The chemical composition of the steel for the ring components, by mass percentage, is as follows: C: 0.125%, Si: 0.36%, Mn: 1.12%, P: 0.009%, S: 0.001%, Nb: 0.012%, V: 0.07%, Ti: 0.02%, Cr: 0.1%, Ni: 0.06%, Cu: 0.04%, Mo: 0.06%, N: 0.0094%, Al: 0.03%, with the balance being iron and unavoidable impurities.

[0041] The ring has a thickness of 230mm and an outer diameter of 1200mm before rolling. After rolling, the ring has a thickness of 172mm and an outer diameter of 2200mm.

[0042] The rolled part has an average yield strength of 371 MPa in all directions, an average tensile strength of 530 MPa in all directions, an elongation of 26%, and an average room-temperature impact energy of 191 J in all directions. The surface and core microstructure of the rolled part is pearlite + ferrite. The metallographic characteristics are as follows: Figure 2 As shown, the grain size is 8 to 8.5 and there is no mixed crystal phenomenon.

[0043] Example 3

[0044] The forged ring blank is placed into the ring rolling mill. The mill is started to allow the ring to bite into the roll and begin the rolling stage. During this stage, the initial rolling temperature is 1157℃, the mandrel reduction rate is 0.94mm / s, the tapered roll reduction rate is 0.75mm / s, and the drive roll speed is 14r / min. Simultaneously, the ring surface is cooled at a rate of 70℃ / s over a cooling area of ​​400mm. This cooling process allows the deformation from the rolling process to penetrate towards the core of the ring's axial cross-section. Cooling is stopped at the end of the rolling stage, with a final rolling temperature of 779℃. The ring then enters the rounding stage. After rounding, the rolled part is obtained and cooled to room temperature before proceeding directly to subsequent machining processes.

[0045] The chemical composition of the steel for the ring components, by mass percentage, is as follows: C: 0.134%, Si: 0.22%, Mn: 1.38%, P: 0.009%, S: 0.003%, Nb: 0.04%, V: 0.03%, Ti: 0.01%, Cr: 0.05%, Ni: 0.2%, Cu: 0.1%, Mo: 0.005%, N: 0.005%, Al: 0.04%, with the balance being iron and unavoidable impurities.

[0046] The ring has a thickness of 290mm and an outer diameter of 2000mm before rolling. After rolling, the ring has a thickness of 214mm and an outer diameter of 3800mm.

[0047] The rolled part has an average yield strength of 368 MPa in all directions, an average tensile strength of 534 MPa in all directions, an elongation of 27%, and an average room-temperature impact energy of 203 J in all directions. The surface and core microstructure of the rolled part is pearlite + ferrite. The metallographic characteristics are as follows: Figure 3 As shown, the grain size is 7.5-8 and there is no mixed crystal phenomenon.

[0048] Example 4

[0049] The forged ring blank is placed into the ring rolling mill. The mill is started to allow the ring to bite into the roll and rotate with the rolls, initiating the ring rolling stage. During this stage, the initial rolling temperature is 1147℃, the mandrel reduction rate is 0.98mm / s, the tapered roll reduction rate is 0.78mm / s, and the drive roll speed is 18r / min. Simultaneously, the ring surface is cooled at a rate of 55℃ / s over a cooling area of ​​600mm. This cooling process allows the deformation from the rolling process to penetrate towards the core of the ring's axial cross-section. Cooling is stopped at the end of the ring rolling stage, with a final rolling temperature of 764℃. The ring then enters the rounding stage. After rounding, the rolled part is obtained and cooled to room temperature before proceeding directly to subsequent machining processes.

[0050] The chemical composition of the steel for the ring components, by mass percentage, is as follows: C: 0.17%, Si: 0.27%, Mn: 1.43%, P: 0.007%, S: 0.003%, Nb: 0.01%, V: 0.08%, Ti: 0.04%, Cr: 0.14%, Ni: 0.35%, Cu: 0.01%, Mo: 0.02%, N: 0.01%, Al: 0.03%, with the balance being iron and unavoidable impurities.

[0051] The ring has a thickness of 412 mm and an outer diameter of 3889 mm before rolling. After rolling, the ring has a thickness of 325 mm and an outer diameter of 7362 mm.

[0052] The rolled part has an average yield strength of 359 MPa in all directions, an average tensile strength of 536 MPa in all directions, an elongation of 30%, and an average room-temperature impact energy of 194 J in all directions. The surface and core microstructure of the rolled part is pearlite + ferrite. The metallographic characteristics are as follows: Figure 4 As shown, the grain size is 8 to 8.5 and there is no mixed crystal phenomenon.

[0053] Example 5

[0054] The forged ring blank is placed into the ring rolling mill. The mill is started to allow the ring to bite into the roll and rotate with the rolls, initiating the ring rolling stage. During this stage, the initial rolling temperature is 1152℃, the mandrel reduction rate is 0.88 mm / s, the tapered roll reduction rate is 0.7 mm / s, and the drive roll speed is 12 r / min. Simultaneously, the ring surface is cooled at a rate of 40℃ / s over a cooling area of ​​800 mm. Cooling allows the deformation from the rolling process to penetrate towards the core of the ring's axial cross-section. Cooling is stopped at the end of the ring rolling stage, with a final rolling temperature of 725℃. The ring then enters the rounding stage. After rounding, the rolled part is obtained and cooled to room temperature before proceeding directly to subsequent machining processes.

[0055] The chemical composition of the steel for the ring components, by mass percentage, is as follows: C: 0.15%, Si: 0.43%, Mn: 1.26%, P: 0.009%, S: 0.002%, Nb: 0.042%, V: 0.10%, Ti: 0.04%, Cr: 0.25%, Ni: 0.37%, Cu: 0.15%, Mo: 0.08%, N: 0.009%, Al: 0.017%, with the balance being iron and unavoidable impurities.

[0056] The ring has a thickness of 732 mm and an outer diameter of 5000 mm before rolling. After rolling, the ring has a thickness of 468 mm and an outer diameter of 8500 mm.

[0057] The rolled part has an average yield strength of 374 MPa in all directions, an average tensile strength of 529 MPa in all directions, an elongation of 26%, and an average room-temperature impact energy of 179 J in all directions. The surface and core microstructure of the rolled part is pearlite + ferrite. Metallographically, it is as follows... Figure 5 As shown, the grain size is 7.5-8 and there is no mixed crystal phenomenon.

[0058] Comparative Example 1

[0059] The chemical composition of the steel for the ring components, by mass percentage, is as follows: C: 0.13%, Si: 0.26%, Mn: 1.11%, P: 0.007%, S: 0.001%, Nb: 0.003%, V: 0.0018%, Ti: 0.001%, Cr: 0.11%, Ni: 0.12%, Cu: 0.01%, Mo: 0.03%, N: 0.001%, Al: 0.002%, with the balance being iron and unavoidable impurities.

[0060] The initial rolling temperature of the ring was 1157°C, and the final rolling temperature was 784°C. Other preparation methods were the same as in Example 1.

[0061] The rolled part has an average yield strength of 314 MPa in all directions, an average tensile strength of 437 MPa in all directions, an elongation of 24%, and an average room temperature impact energy of 97 J in all directions. The surface and core microstructure of the rolled part are both pearlite + ferrite, with a grain size of 7.5-8 and no mixed crystals.

[0062] Even if the process remains the same, changes in the composition of the ring will lead to a decline in all aspects of the ring's performance, and it will no longer meet the requirements of the enterprise.

[0063] Comparative Example 2

[0064] The initial rolling temperature of the ring was 1050°C, and the final rolling temperature was 732°C. Other preparation methods were the same as in Example 1.

[0065] The rolled part has an average yield strength of 318 MPa in all directions, an average tensile strength of 504 MPa in all directions, an elongation of 22%, and an average room-temperature impact energy of 144 J in all directions. The surface and core microstructure of the rolled part is pearlite + ferrite. Metallographic features are as follows: Figure 6 As shown, the grain size is 7-9, and obvious mixed crystal phenomenon is observed.

[0066] The initial rolling temperature was too low, resulting in insufficient deformation of the ring. Although it could meet the company's requirements, all performance characteristics were significantly reduced.

[0067] Comparative Example 3

[0068] The initial rolling temperature of the ring was 1161℃, and the final rolling temperature was 980℃. No cooling was applied to the ring during the rolling stage, but air cooling still occurred during the rolling process, causing the ring to exchange heat with the air and its temperature to drop. Other preparation methods were the same as in Example 1.

[0069] The rolled part has an average yield strength of 301 MPa in all directions, an average tensile strength of 475 MPa in all directions, an elongation of 24%, and an average room-temperature impact energy of 149 J in all directions. The surface and core microstructure of the rolled part is pearlite + ferrite. Metallographic characteristics are as follows: Figure 7 As shown, the grain size is 7-9, and obvious mixed crystal phenomenon is observed.

[0070] Without added cooling, the performance of all components of the ring is significantly reduced, and it cannot meet the requirements of enterprise use.

[0071] Comparative Example 4

[0072] The initial rolling temperature of the ring was 1160℃, the final rolling temperature was 657℃, and the cooling rate during the ring rolling stage was 140℃ / s. Other preparation methods were the same as in Example 1.

[0073] The rolled part has an average yield strength of 322 MPa in all directions, an average tensile strength of 489 MPa in all directions, an elongation of 22%, and an average room temperature impact energy of 110 J in all directions. The core microstructure of the rolled part is pearlite + ferrite with a grain size of 7.5-8, while the surface microstructure contains a large amount of bainite and a small amount of Widmanstätten.

[0074] Excessive cooling rate leads to insufficient deformation of the ring component. Although it can meet the company's requirements, all performance aspects are significantly reduced.

[0075] Comparative Example 5

[0076] The ring was rolled at an initial temperature of 1147°C and a final temperature of 974°C. No cooling was added during the rolling process, and the rolled part was normalized before entering the machining process. The normalizing temperature was 850°C, and the normalizing time was 150 min. Other preparation methods were the same as in Example 1.

[0077] After normalizing, the average yield strength in all directions is 372 MPa, the average tensile strength in all directions is 524 MPa, the elongation is 24%, and the average room temperature impact energy in all directions is 176 J. After normalizing, both the surface and core microstructures are pearlite + ferrite, with a grain size of 8-8.5 and no mixed crystals.

[0078] The performance of ring parts that are normalized but not cooled is similar to that of ring parts that are cooled but not normalized, meeting the enterprise's usage requirements.

Claims

1. A method for rolling large flange rings for wind turbine towers, characterized in that: Includes the following steps: The forged rings enter the ring rolling process, which includes the biting stage, the ring rolling stage, and the rounding stage. After the rings are successfully bitten into the ring rolling mechanism, they enter the ring rolling stage. During the ring rolling process, the surface of the rings is cooled at a rate of 15–100 °C / s. The cooling range width is 200–900 mm, which refers to the chord length between any two points on the inner or outer circumference of the ring. During the ring rolling stage, the mandrel reduction rate is 0.44–2.35 mm / s, the tapered roll reduction rate is 0.8 times that of the mandrel reduction rate, and the drive roll rotation speed is 8–20 r / min. After the ring rolling stage, cooling is stopped, and after the rounding stage, the rolled parts are obtained for direct machining.

2. The method for rolling large flange rings for wind turbine towers according to claim 1, characterized in that: At the beginning of the ring rolling stage, the ring temperature is 1100-1200℃, and at the end of the ring rolling stage, the ring temperature is 700-850℃.

3. The method for rolling large flange rings for wind turbine towers according to claim 1, characterized in that: At the beginning of the ring rolling stage, the difference between the inner and outer radii of the ring is 120-750 mm, and the outer diameter is 800-5500 mm.

4. The method for rolling large flange rings for wind turbine towers according to claim 1, characterized in that: The inner and outer walls of the ring are cooled simultaneously by an internal cooling unit and an external cooling unit, respectively. The cooling process causes the deformation during rolling to penetrate into the core of the axial section of the ring.

5. A method for rolling large flange rings for wind turbine towers according to any one of claims 1 to 4, characterized in that: The ring rolling method described herein is applicable to flange steel as specified in JB / T 11218-2020 standard.

6. A method for rolling large flange rings for wind turbine towers according to any one of claims 1 to 4, characterized in that: The ring rolling method is applicable to steel for Q355NE flanges.

7. A method for rolling large flange rings for wind turbine towers according to claim 6, characterized in that: The elements and their mass percentages in the Q355NE flange steel are as follows: C: ≤0.18%, Si: ≤0.50%, Mn: 0.9~1.65%, P: ≤0.012%, S: ≤0.005%, Nb: 0.005~0.05%, V: 0.01~0.12%, Ti: 0.006~0.05%, Cr: ≤0.3%, Ni: ≤0.5%, Cu: ≤0.2%, Mo: ≤0.1%, N: ≤0.015%, Al: ≥0.015%, with the balance being iron and unavoidable impurities.

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