A method for annealing stress relief of a wind power tower cylinder door frame

Abstract

The present application belongs to the technical field of post-weld heat treatment, and specifically discloses a method for annealing and stress relieving of a wind power tower drum door frame, which comprises four steps: 1) determining a temperature measuring point; 2) determining a heating zone, a temperature equalizing zone and a heat insulation zone; 3) measuring the length of the tower drum bus, the ovality and flatness of the flange; and 4) local heat treatment; wherein the local heat treatment comprises four steps: 41) wrapping heat insulation cotton and placing a thermocouple; 42) interconnecting the thermocouple, a heat treatment temperature control box and a distribution box; 43) arranging a heating pad and heat insulation cotton; and 44) heating, heat insulation and slow cooling. The present application meets the standard requirements and drawing requirements of the tower drum size, the heating is more uniform, the problem that the heat transfer process is difficult to control due to uneven heating is avoided, the effect of reducing residual stress is improved, the production efficiency is improved, the generation of delayed cracks is prevented, the stability of the structure size is improved, the product performance of the wind power tower drum door frame is improved, and the stability and safety of the wind power basic product are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of post-weld heat treatment, and particularly relates to a method for annealing and stress relief of a wind power tower drum frame. BACKGROUND

[0002] Welding residual stress is caused by uneven temperature distribution of a welding part due to welding, thermal expansion and contraction of welding seam metal and the like, so residual stress will inevitably be generated during welding. The residual stress not only reduces the rigidity and stability of the tower drum frame structure, but also seriously affects the fatigue strength, brittle fracture resistance, stress corrosion cracking resistance and high temperature creep cracking resistance of the tower drum frame structure under the combined action of temperature and medium. In order to reduce residual stress, the current method is to use high-temperature tempering to reduce residual stress. Although this method can reduce the residual stress of the whole workpiece after welding, it cannot guarantee the range and temperature of the heating area for the residual stress of the local welding of the workpiece, and it is difficult to control the temperature gradient, so the stress relief effect is poor.

[0003] At present, the heat treatment method of heating plate plus heat preservation cotton is used to reduce the residual stress of the local welding of the workpiece. For example, Chinese Patent No. CN102839270A, published on December 26, 2021, discloses a post-weld stress relief heat treatment technology for pressure-bearing equipment. The document proposes "including steps: 1) installing a heating plate; 2) wrapping the workpiece surface on both sides of the heating plate with heat preservation cotton; 3) heating and heat treatment, and detecting the temperature of the weld and the weld on both sides. The steps include: a) for the post-weld heat treatment of the girth weld or longitudinal weld after the weld detection is qualified: the heating area width ; the heat insulation area width ; b) for the post-weld heat treatment of the repair weld, the post-weld heat treatment is performed on the local repair weld of the girth weld or the local repair weld of the longitudinal weld." The heating area and the heat insulation area of the prior art are calculated by a formula, which can accurately guarantee the range and temperature of the local heating area. However, the prior art uses a double-sided heating heat treatment method. Since the thickness of the tower drum frame is relatively thick, the double-sided heating heat treatment method easily leads to uneven heating of the tower drum frame, making it difficult to control the heat transfer process, thereby affecting the reduction effect of the residual stress of the tower drum frame. Therefore, a new technical solution is needed to solve the above technical problems. SUMMARY

[0004] The purpose of the present application is to provide a method for annealing and stress relief of a wind power tower drum frame, to solve the problem of the current post-weld stress relief heat treatment technology, which uses a double-sided heating method, easily leading to uneven heating of the tower drum frame, making it difficult to control the heat transfer process, thereby affecting the reduction effect of the residual stress of the tower drum frame.

[0005] In order to achieve the above object, the present application provides the following technical scheme: a wind power tower drum door frame annealing stress relief method, the wind power tower drum door frame is arranged as an elliptical structure, and the specific method steps are as follows:

[0006] S1, determine and mark the elliptical structure mutation point of the door frame, that is, the temperature measuring point of the door frame, and the temperature measuring point of the door frame is distributed at the end points of the elliptical length direction and the end points of the intersection of the circular arc segment and the straight line segment of the ellipse;

[0007] S2, the heating width formula , the uniform temperature width formula and the heat insulation width formula are used to calculate and mark the heating zone, the uniform temperature zone and the heat insulation zone of the door frame in turn, wherein, HB is the heating width, n is the conditional coefficient, the value range of n is between 1-3, hK is the maximum width of the weld, h is the door frame weld leg size, t is the thickness of the weld position cylinder steel plate, HB is the heating width, a is the heat insulation additional value, the value range of a is between 200-350mm;

[0008] S3, first measure the tower drum generatrix length and the flange ellipticity by using a laser range finder, and then measure the flatness size by using a laser flatness meter, wherein the ellipticity is the difference between the distances of the two 90-degree directions of the ellipse;

[0009] S4, the door frame is locally heat treated by using the single-side heating and double-side heat preservation mode;

[0010] According to the specific steps of the above local heat treatment by using the single-side heating and double-side heat preservation mode, the following steps are taken:

[0011] S41, the outer side of the door frame is wrapped with heat preservation cotton through a magnet clamp and a steel wire, and a thermocouple is placed in the inner side of the door frame, wherein the number of thermocouples is more than the number of temperature measuring points;

[0012] S42, the thermocouple is electrically connected with a heat treatment temperature control box through a secondary cable, and the heat treatment temperature control box is electrically connected with a distribution box through a primary cable;

[0013] S43, the inner side of the door frame where the thermocouple is placed is arranged around the full circumference of the door frame, and heat pads are covered with heat preservation cotton;

[0014] S44, start the heat treatment temperature control box to heat and preserve the door frame and slow cool.

[0015] Compared with the prior art, the present application has the following beneficial effects:

[0016] 1. The application can compare the data of the door frame of the wind power tower before and after heat treatment by measuring the length of the tower barrel bus, the ovality and the flatness of the flange before heat treatment, so that the door frame after heat treatment can meet the standard requirements and drawing requirements of the tower size, the local heat treatment mode of single-sided heating and double-sided insulation is adopted, the heating of the door frame is more uniform, the problem that the heat transfer process is difficult to control due to uneven heating is effectively avoided, the door frame is locally electrically heated by heating pads and insulation cotton, the residual stress of the door frame can be reduced under local electric heating, the residual stress reduction effect is effectively improved, the production efficiency is improved, the generation of delayed cracks is prevented, the stability of the door frame structure size is improved, the product performance of the wind power tower door frame is improved, and the stability and safety of the wind power basic product are further improved.

[0017] 2. The application utilizes the structural characteristics of the ellipse to quickly find and determine the temperature measurement points of the wind power tower door frame, thereby effectively improving the efficiency of heat treatment, and through the heating band width formula, the uniform temperature band width formula and the heat insulation band width formula, the heating zone, the uniform temperature zone and the heat insulation zone of the wind power tower door frame can be quickly and accurately found and determined, thereby effectively improving the accuracy and effect of residual stress reduction, and also effectively improving the production efficiency, preventing the generation of delayed cracks, improving the stability of the door frame structure size, improving the product performance of the wind power tower door frame, and further improving the stability and safety of the wind power basic product.

[0018] 3. The application adopts more thermocouples than temperature measurement points, so that the wind power tower door frame can better compare data, so that the wind power tower door frame after heat treatment can more easily meet the standard requirements and drawing requirements of the tower size, the insulation cotton is fixed on the outer side of the door frame by the magnet clamping block and the steel wire, which effectively avoids the problem of damaging the surface steel plate of the wind power tower door frame due to fixing the insulation cotton, and also effectively prevents the generation of delayed cracks, improves the stability of the door frame structure size, improves the product performance of the wind power tower door frame, and further improves the stability and safety of the wind power basic product. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the wind power tower door frame of the application (including the distribution state of the temperature measurement points, the heating zone, the uniform temperature zone and the heat insulation zone);

[0020] Figure 2 It is a post-weld heat treatment process curve diagram of the application.

[0021] Wherein: 1, door frame; 2, temperature measurement point; 3, heating zone; 4, uniform temperature zone; 5, heat insulation zone. DETAILED DESCRIPTION

[0022] The following examples are intended to further illustrate the application and are not intended to limit the application.

[0023] Referring to Figures 1-2 , a method for annealing and stress relieving a wind turbine tower door frame, first, the wind turbine tower door frame 1 is set as an elliptical structure, before local heat treatment, six structure mutation points are selected as temperature measuring points 2 of the wind turbine tower door frame 1 according to the structure characteristics of the ellipse, the six temperature measuring points 2 are distributed at the end points of the length direction of the ellipse and the end points of the intersection of the circular arc segment and the straight line segment of the ellipse, then the heating band width formula is used to calculate the heating zone 3 (as shown in , where HB is the heating band width, n is the conditional coefficient, the value range of n is between 1-3, hK is the maximum width of the weld, the heating zone 3 (as shown in Figure 1 ) is calculated, then the uniform temperature band width formula is used to calculate the uniform temperature zone 4 (as shown in , where h is the size of the door frame weld, t is the thickness of the weld position cylinder steel plate, the uniform temperature zone 4 (as shown in Figure 1 ) is calculated, then the heat insulation band width formula is used to calculate the heat insulation zone 5 (as shown in , where HB is the heating band width, a is the heat insulation additional value, the value range of a is between 200-350mm, the heat insulation zone 5 (as shown in Figure 1 ) is calculated, then the tower cylinder bus length, the flange ellipticity and the flatness size are measured by the laser range finder (the measurement and other basic structures possessed by the existing laser range finder are not specifically described here, but the function implementation should not be limited thereby) and the laser leveling instrument (the measurement and other basic structures possessed by the existing laser leveling instrument are not specifically described here, but the function implementation should not be limited thereby), where the ellipticity is the difference between the distances of the two 90-degree directions of the ellipse, the measurement of these data is to compare with the corresponding data after heat treatment, to ensure that the door frame after heat treatment can meet the standard requirements and drawing requirements of the tower size, that is, to complete the preparation work before local heat treatment, where the data of the six temperature measuring points before local heat treatment are as follows:

[0024] .

[0025] After the preparation work before local heat treatment is completed, the wind turbine tower door frame 1 is subjected to local heat treatment by using the single-sided heating and double-sided insulation method. Specifically: first, the insulation cotton is wrapped on the outer side of the wind turbine tower door frame 1 through the magnet clamp and the steel wire (the insulation cotton is placed as shown in Figure 1The internal insulation zone 5 is shown on the outer side of the wind turbine tower door frame 1, and the thermocouples are placed on the inner side of the door frame. The number of thermocouples is greater than the number of temperature measuring points 2. That is, the number of thermocouples is greater than six, and the six thermocouples are placed on the six temperature measuring points. The extra thermocouples are evenly distributed on the inner side of the door frame to better compare the data. Then, the thermocouples are electrically connected to a heat treatment temperature control box through a secondary cable. The functions and structures of the heat treatment temperature control box and other conventional devices are well known in the art, and the connection settings are also well known. Therefore, they will not be described here, and they are not shown in the attached drawings. Then, the heat treatment temperature control box is electrically connected to a distribution box through a primary cable. The functions and structures of the distribution box and other conventional devices are well known in the art, and the connection settings are also well known. Therefore, they will not be described here, and they are not shown in the attached drawings. Then, the inner side of the door frame where the thermocouples are placed is surrounded by a heating pad arranged on the full circumference of the door frame. The heating pad is placed on the heating zone 3 and the uniform temperature zone 4, and the temperature change of the uniform temperature zone 4 is more uniform. Figure 1 The external insulation zone 5 is shown on the inner side of the wind turbine tower door frame 1, which is set on the wind turbine tower. Finally, the heat treatment temperature control box is started, and the door frame is heated, insulated, and slowly cooled according to the post-weld heat treatment process curve shown in the figure. The data of the six temperature measuring points 2 after local heat treatment are as follows: Figure 2

[0026] ;

[0027] According to the comparison of the data of the six temperature measuring points 2 before and after local heat treatment, the residual stress of the wind turbine tower door frame 1 after single-sided heating and double-sided insulation local heat treatment is effectively reduced, and the effect is good. The single-sided heating and double-sided insulation local heat treatment method can make the heating of the wind turbine tower door frame 1 more uniform, effectively avoid the problem of difficult control of heat transfer process caused by uneven heating, effectively improve the residual stress reduction effect, improve the production efficiency, prevent the generation of delayed cracks, improve the stability of the door frame structure size, improve the product performance of the wind turbine tower door frame, and further improve the stability and safety of the wind power basic product.​

Claims

1. A method for annealing stress relief of a wind turbine tower door frame, the wind turbine tower door frame being provided as an elliptical structure, characterized in that, The specific method steps are as follows: S1, determine and mark the elliptical structure mutation point of the door frame, that is, the temperature measuring point of the door frame, and the temperature measuring point of the door frame is distributed at the two end points in the length direction of the ellipse and the end points where the circular arc segment and the straight line segment of the ellipse meet; S2, the heating zone, the uniform temperature zone and the heat insulation zone of the door frame are calculated and marked in sequence by the heating band width formula, the uniform temperature band width formula and the heat insulation band width formula, wherein the heating band width formula is , HB is the heating band width, n is a conditional coefficient and its value range is between 1-3, hK is the maximum width of the weld; the uniform temperature band width formula is , wherein h is the size of the door frame weld toe, t is the thickness of the steel plate at the weld position; the heat insulation band width formula is , GCB is the heat insulation band width, HB is the heating band width, a is the heat insulation additional value and its value range is between 200-350mm; S3, measure the size of the tower cylinder bus length, flange ellipticity and flatness; S4, the door frame is locally heat treated by using the mode of single-sided heating and double-sided heat preservation; The specific steps of the local heat treatment are as follows: S41, wrap the outer side of the door frame with the magnet clamp and the steel wire, and then place the thermocouples on the inner side of the door frame, the number of the thermocouples is more than the number of the temperature measuring points; S42, the thermocouples are electrically connected with the heat treatment temperature control box through the secondary cable, and the heat treatment temperature control box is electrically connected with the distribution box through the primary cable; S43, the inner side of the door frame where the thermocouples are placed is surrounded by the heating pad around the full circumference of the door frame, and then the heating pad is covered with heat preservation cotton; S44, start the heat treatment temperature control box to heat and heat preservation slow cooling of the door frame.

2. The method of annealing and stress relieving a wind turbine tower door frame of claim 1, wherein, In S3, the tower cylinder bus length and the flange ellipticity are measured by a laser range finder, and the flatness is measured by a laser flatness meter.

3. A method of annealing stress relief of a wind turbine tower section door frame according to claim 2, characterized in that, The ellipticity is the difference between the distances of two 90-degree directions of the ellipse.

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