A low-hydrogen welding process for pipe piles

Abstract

The invention discloses a low-hydrogen type welding process for pipe piles, which comprises the following steps: tower segment assembly, bottom welding, preheating before SAW girth welding and SAW girth welding; in the invention, welding preheating is cancelled before bottom welding, so as to simplify the process, save heating energy and improve production efficiency: the preheating temperature of a single weld saves 80 to 160 hours; the preheating temperature of submerged arc welding is reduced from 100°C to 60°C. The heating energy is saved by about 100°C, and the production efficiency is improved: the preheating temperature of a single weld saves 6 to 9 hours; the post-weld dehydrogenation process is cancelled; the heating energy is saved by about 100°C, and the production efficiency is improved: the preheating temperature of a single weld saves 6 to 9 hours; the post-weld dehydrogenation process is cancelled; the heating energy is saved by about 100°C, and the production efficiency is improved: the single weld saves 25 to 31 hours; ultra-low hydrogen welding materials are used, the source of hydrogen is controlled during welding, and a relatively large welding heat input is used to more fundamentally control the generation of diffused hydrogen, and the actual effect is more obvious. The actual measured content of diffused hydrogen is less than 5 ml / 100g, and no hydrogen-induced cracks are generated in actual applications.

Description

Technical Field

[0001] The invention relates to the field of offshore wind turbine towers, and in particular to a low-hydrogen welding process for pipe piles. Background Art

[0002] Steel pipe piles are the foundation of offshore wind turbine towers, generally consisting of 20 to 40 tower sections. The welds include longitudinal welds (LW) and circumferential welds (CW). The yield strength of the steel pipe pile material is 355Mpa level, generally DH36, EH36 and other materials; the diameter of the steel pipe pile is generally 8 to 10m; the wall thickness of the pipe pile is 50mm to 100mm.

[0003] The circumferential welding of steel pipe piles includes five processes: assembly, base preheating, flux-cored wire gas shielded welding (FCAW) assembly, preheating before circumferential welding, submerged arc welding (SAW) of the circumferential seam, and hydrogen removal after welding.

[0004] Materials such as DH36 and EH36 have good welding properties, and the probability of hydrogen-induced cracks caused by welding is not high. However, for large-diameter, thick-walled steel pipe pile products, large welding tensile stress will be generated after welding. When there is a lot of diffused hydrogen in the weld, there is a risk of hydrogen-induced cold cracks. The greater the welding tensile stress, the lower the requirement for the amount of diffused hydrogen.

[0005] Traditional manufacturing technology has preheating and post-heating requirements. The preheating temperature and post-heating dehydrogenation plan given by the domestic design institute is: preheating to above 100°C before welding; the minimum preheating temperature for assembly and base welds is 120°C; after welding, post-heating to 200-300°C is required, and insulation is required for 1-2 hours. However, for steel pipe piles with such a large diameter and wall thickness, it takes huge energy to preheat and post-heat the entire circle to such a high temperature. Up to now, the industry has not found suitable equipment to heat the steel pipe piles in the entire circle; and using traditional flame heating, it is difficult to achieve the expected effect for large-diameter and thick-walled steel pipe piles.

[0006] In response to the above problems, this application document proposes a low-hydrogen welding process for pipe piles. Under the condition of a relatively low preheating temperature (60°C), the generation of hydrogen-induced cracks can be avoided by controlling the diffusible hydrogen content of the welding material, the welding heat input, and the control of diffusible hydrogen during the welding process, thereby effectively solving the above problems. Summary of the invention

[0007] The purpose of the present invention is to provide a low-hydrogen welding process for pipe piles. Compared with the prior art, instead of focusing on the generation of diffusible hydrogen and taking measures to eliminate the diffusible hydrogen, it is better to focus on how to generate as little diffusible hydrogen as possible. The generation of hydrogen-induced cracks is not only related to preheating and post-heating, but also to the carbon equivalent, thickness, diffusible hydrogen of the welding material, and heat input factors of welding. The purpose of the present invention is to provide a method to avoid the generation of hydrogen-induced cracks under the condition of a lower preheating temperature (60°C) by controlling the diffusible hydrogen content of the welding material, welding heat input, and control of diffusible hydrogen in the welding process, given the carbon equivalent and thickness of the tower section.

[0008] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0009] The present invention is a low-hydrogen welding process for pipe piles, comprising the following steps:

[0010] S1. Tower segment assembly: adjust the height of the two cylinder segments on the roller frame so that the two cylinder segments are placed at the same height, and adjust the relative displacement of the roller frame so that the two cylinder segments can be assembled, and the two cylinder segments can be fixedly connected by locking the assembly bolts;

[0011] S2. Base welding: After assembly is completed, use solid wire gas shielded welding to perform base welding on the grooves between positioning welds;

[0012] S3. Preheating before SAW girth welding: Preheat to 60°C before girth welding. The preheating time for welding inner girth is 1 to 2 hours. When welding outer girth, the preheating time is 3 to 5 hours. Preheat the flux before welding.

[0013] S4, SAW circumferential welding: welding is performed using a welding carriage system with a flux heating and insulation device;

[0014] In step S2, the shielding gas is 73% Ar + 27% CO2, the welding current is 320A, the welding voltage is 34V, the welding speed is 270mm / min, and the welding heat input is: 2.4KJ / mm;

[0015] In step S4, the welding material selected is Korean Hyundai SAW welding wire H-14, and the flux is S-787TB.

[0016] The welding carriage system used in circumferential seam welding includes a travel unit, a flux heating and insulation unit, a control unit and a welding unit;

[0017] The flux heating and heat preservation unit is used to store, heat and keep the flux warm, and to deliver the flux to the welding unit;

[0018] The control unit is used to adjust the welding current and voltage of the welding unit, and to set the heating temperature of the welding machine in the flux heating and heat preservation unit.

[0019] Preferably: the flux heating and insulation unit comprises an insulation barrel, a insulation plug and a feeding hopper are arranged on the top of the insulation barrel, a thermocouple, a heating belt and an air compressor are arranged inside the insulation barrel, the thermocouple is used to measure the temperature of the flux in the insulation barrel, the heating belt is used to heat the flux, one end of the insulation barrel is connected to a feeding pipe, one end of the feeding pipe is connected to a flux sleeve, and one end of the flux sleeve is connected to the welding unit.

[0020] Preferably, in step S2, the welding material is Atlantic solid welding wire CHW-50C6SM, and the welding wire diameter is φ1.2 mm.

[0021] Preferably: in step S4, the welding wire diameter is φ5.0 mm.

[0022] Preferably, in step S4, the flux is preheated and dried at a temperature of 300-350°C before welding, and the drying time is 2 hours with insulation at a temperature of 150°C.

[0023] Preferably, in step S4, the welding current is 720-770A, the welding voltage is 32-34V, the welding speed is 360-420mm / min, and the welding heat input range is: 3.3KJ / mm~4.4 KJ / mm.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. In the present invention, welding preheating is eliminated before base welding, thereby simplifying the process, saving heating energy, and improving production efficiency: the preheating temperature of a single weld saves 80 to 160 hours.

[0026] 2. In the present invention, the preheating temperature of submerged arc welding is reduced from 100° C. to 60° C. This saves heating energy and improves production efficiency: the preheating time of a single weld is saved by 6 to 9 hours.

[0027] 3. In the present invention, the post-weld dehydrogenation process is eliminated, which saves heating energy and improves production efficiency: a single weld saves 25 to 31 hours.

[0028] 4. The present invention adopts ultra-low hydrogen welding materials, controls the source of hydrogen during welding, and adopts a relatively large welding heat input method to more fundamentally control the generation of diffused hydrogen. The actual effect is more obvious. The actual measured content of diffused hydrogen is <5ml / 100g. In actual applications, no hydrogen-induced cracks are generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of a low-hydrogen welding process flow of a pipe pile according to the present invention;

[0030] Figure 2This is a schematic diagram of the welding carriage system in the present invention;

[0031] Figure 3 It is a schematic diagram of the flux heating and heat preservation unit in the present invention;

[0032] In the figure: 1. Travel unit; 2. Flux heating and insulation unit; 3. Control unit; 4. Welding unit; 21. Insulation barrel; 22. Insulation plug; 23. Feeding hopper; 24. Thermocouple; 25. Heating track; 26. Air compressor; 27. Feeding pipe; 28. Flux sleeve. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] First of all, it should be noted that in the traditional process, the circumferential welding of steel pipe piles includes: assembly, preheating of base, FCAW assembly, preheating before circumferential welding, submerged arc welding (SAW) of circumferential welding, and dehydrogenation after welding. High preheating temperature and dehydrogenation after welding are used to reduce the content of diffused hydrogen in the weld to control hydrogen-induced cracks. In actual operation, due to the large diameter of the tower section of the steel pipe pile of 8 to 10m and the large plate thickness of 50 to 100mm, large welding tensile stress will be generated after welding. When there is more diffused hydrogen in the weld, there is a risk of hydrogen-induced cold cracks. The greater the welding tensile stress, the lower the requirement for the content of diffused hydrogen.

[0035] Traditional manufacturing technology has preheating and post-heating requirements. The preheating temperature and post-heating dehydrogenation plan given by the domestic design institute is: preheating to above 100°C before welding; the minimum preheating temperature for assembly and base welds is 120°C; after welding, post-heating to 200-300°C is required, and insulation is required for 1-2 hours. However, for steel pipe piles with such a large diameter and wall thickness, it takes huge energy to preheat and post-heat the entire circle to such a high temperature. Up to now, the industry has not found suitable equipment to heat the entire circle of steel pipe piles; and using traditional flame heating, it is difficult to achieve the expected effect for large-diameter and thick-walled steel pipe piles, and in actual operation, it is inevitable that the preheating temperature is uneven and the post-heating is insufficient.

[0036] The design institute requires that the steel pipe piles be preheated to above 100℃ before welding, and then heated to 200℃~300℃ for 1~2 hours. The purpose is:

[0037] Higher preheating temperature is conducive to the escape of diffusible hydrogen produced during welding;

[0038] Diffusible hydrogen is more active in the temperature range of 200℃~300℃, and a holding time of 1 to 2 hours is conducive to the overflow of diffusible hydrogen in the weld.

[0039] It is feasible to remove the diffused hydrogen from the weld by preheating and post-heating, but for welds with a diameter of 8 to 10 m

[0040] For steel pipe piles with a diameter of 50 to 100 mm in thickness, not only a lot of energy is wasted, but there is no such large equipment to heat the weld of the steel pipe pile. In actual engineering, a flame spray gun is used to heat the weld of the steel pipe pile. In the following steps, the main disadvantages are:

[0041] The tower section is preheated before assembly and primer. The length of each assembly weld is at least 50mm; the length of each primer weld is at most 300mm. The preheating width of the weld width, including the weld width, is about 250mm; the preheating length of the assembly and primer weld is 300mm. The preheating method using a handheld spray gun has the following disadvantages:

[0042] Preheating is an intermittent operation, which is not conducive to continuous operation;

[0043] Due to different ambient temperatures, the preheating time for each weld is about 1 to 2 hours, while the base welding time is about 1 minute, and the assembly welding time is only a dozen seconds. The time used for different processes is seriously unbalanced, affecting the production progress;

[0044] During preheating, the heat of the steel plate is dissipated along the axial, circumferential and radial directions of the tower section, resulting in a large amount of energy waste;

[0045] The preheating method of the handheld spray gun is uneven in each section, resulting in residual stress within the preheating plane;

[0046] The thickness of the steel pipe pile is 50mm to 100mm. The temperature is uneven in the thickness direction, which produces residual stress in the thickness direction.

[0047] For pairing and base welding, the welding process adopts FCAW, CHT-71 flux-cored welding wire, the outside is a hollow thin steel tube with a seam, the outer diameter is φ1.2mm, and the inside of the thin steel tube is a flux core. The disadvantage of this welding wire is that after the welding wire is unpacked, the flux core contacts the air through the gap of the seam steel tube and absorbs water molecules in the air. The more humid the air and the longer the time, the more water is absorbed by the flux core. During welding, the water molecules in the flux core decompose into hydrogen atoms. During the cooling process of the weld, the hydrogen atoms do not overflow the weld to form diffused hydrogen. The diffused hydrogen content exceeds the critical value of the weld, resulting in hydrogen-induced cracks.

[0048] Preheating before SAW welding of the annular seam. The diameter of the steel pipe pile ranges from 25 to 31 m. During the preheating process, as the tower section rotates, the heat is dissipated in the axial, circumferential and radial directions of the tower section, resulting in serious heat energy loss.

[0049] The preheating temperature is 100℃. It takes a long time for large diameter and thick steel pipe piles to reach the requirements. The preheating time will be different depending on the ambient temperature. The preheating time for welding the inner ring seam is 2 to 4 hours. When welding the outer ring seam, due to the rotation from the lower preheating point to the top, a large amount of heat loss occurs, so the preheating time is 8 to 12 hours. The production efficiency is low.

[0050] The diameter range of steel pipe piles is 25 to 31 meters. During the post-heating process, as the tower section rotates, the heat is dissipated in the axial, circumferential and radial directions of the tower section, resulting in serious heat energy loss.

[0051] The post-heating temperature is 200~300℃, and the insulation time is 1 hour. Depending on the ambient temperature, the time for the post-heating temperature to reach 200℃ will also be different. The whole weld reaches 200℃, and the post-heating time is 24~30 hours; the production efficiency is very low.

[0052] Circumferential SAW welding material is Atlantic SAW welding wire CHW-S3, wire diameter φ5.0mm, flux is CHF-101; the diffusible hydrogen content of the welding material is 7-10ml / 100g, and the diffusible hydrogen content of the welding material is relatively high;

[0053] Even if the flux is placed in an insulation bucket, as the lid of the insulation bucket is repeatedly opened and closed during the use of the flux, the temperature of the flux in the insulation bucket will continue to decrease. The actual temperature of the flux in the insulation bucket is lower than 100°C. When the flux below 100°C comes into contact with the air, the moisture in the air condenses and diffused hydrogen is formed during the welding process. This is another major factor that causes the diffused hydrogen content in the weld to be too high.

[0054] Hydrogen removal after welding, steel pipe pile diameter range: 25 ~ 31m, during the post-heating process, as the tower section rotates, the heat is dissipated along the axial, circumferential and radial directions of the tower section, resulting in serious heat energy loss;

[0055] Post-heating temperature is 200~300℃, and the temperature is kept for 1 hour. Depending on the ambient temperature, the time for the post-heating temperature to reach 200℃ will also be different. The entire weld reaches 200℃, and the post-heating time is 24~30 hours; the production efficiency is very low

[0056] See also Figure 1-3 , for a low-hydrogen welding process for pipe piles provided by the present invention;

[0057] A specific application of the embodiment is:

[0058] The thickness of steel pipe pile material is 50-100mm; commonly used materials are DH36 and EH36. According to GB712-2011 structural steel for hull, the carbon equivalent of the material is ≤0.40 within the plate thickness range of 50-100mm; no preheating is required for assembly and base welding, and preheating is 60℃ for circumferential submerged arc welding.

[0059] Under the above prerequisites, the technical solution of the present invention:

[0060] Assembly and base welding process:

[0061] Welding equipment: Panasonic YD-500KR GMAW welding machine;

[0062] Protective gas: 73%Ar+27%CO2;

[0063] The welding material is Atlantic solid welding wire CHW-50C6SM, with a wire diameter of φ1.2mm;

[0064] Reverse connection of DC current;

[0065] The welding current is 320A, the welding voltage is 34V, the welding speed is 270mm / min, and the calculated welding heat input is: 2.4KJ / mm.

[0066] Preheating before SAW girth welding, SAW welding parameters are as follows:

[0067] Preheat to 60℃ before welding the girth seam: the preheating time for welding the inner girth seam is 1 to 2 hours; when welding the outer girth seam, the preheating time is 3 to 5 hours;

[0068] SAW welding equipment: Panasonic ZD5-1250E;

[0069] The welding material is Hyundai SAW welding wire H-14 from South Korea, the wire diameter is φ5.0mm, and the flux is S-787TB;

[0070] The drying temperature of the flux is 300~350℃, the drying time is 2 hours and the insulation temperature is 150℃;

[0071] The welding current is 720-770A, the welding voltage is 32-34V, and the welding speed is 360-420mm / min. The calculated welding heat input range is: 3.3KJ / mm~4.4 KJ / mm;

[0072] The current is reverse direct current;

[0073] Use a welding carriage system with a flux heating and insulation device (such as Figure 2 ) for welding; after the flux is taken from the welding material warehouse, it is placed in the flux heating cylinder (such as Figure 3 ), heating and keeping warm at 150℃;

[0074] The system consists of four parts: a walking unit 1, a flux heating and heat preservation unit 2, a control unit 3 and a welding unit 4; wherein the control unit 3 can adjust the welding current, voltage and other parameters of the welding unit 4, and can set the flux heating temperature of the flux heating and heat preservation unit 2;

[0075] The flux heating and heat preservation unit 2 (such as Figure 3 ) The working principle is: the flux taken out from the welding material warehouse is added into the insulation barrel 21 through the feeding hopper 23, and the insulation plug 22 is covered. The thermocouple 24 measures the temperature of the flux in the insulation barrel 21. If the temperature cannot meet the set temperature (150°C), the heating track 25 heats the flux. When the temperature reaches the set temperature, the heating stops.

[0076] Before welding, the control unit 3 starts the air compressor 26, which delivers the flux into the flux sleeve 28 through the feed pipe 27, adjusts the welding parameters, and starts welding.

[0077] The above content is a further detailed description of the present invention in combination with specific implementation methods. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the scope of protection determined by the claims submitted for the present invention.

Claims

1. A low-hydrogen welding process for pipe piles, characterized in that: The method comprises the following steps: S1. Tower segment assembly: adjust the height of the two cylinder segments on the roller frame so that the two cylinder segments are placed at the same height, and adjust the relative displacement of the roller frame so that the two cylinder segments can be assembled, and the two cylinder segments can be fixedly connected by locking the assembly bolts; S2. Base welding: After assembly, use solid wire gas shielded welding to perform base welding on the groove between positioning welds. Cancel welding preheating before this step. In this step, the shielding gas is 73% Ar + 27% CO2, the welding current is 320A, the welding voltage is 34V, the welding speed is 270mm / min, and the welding heat input is: 2.4KJ / mm; S3. Preheating before SAW girth welding: Preheat to 60°C before girth welding. The preheating time for welding inner girth is 1 to 2 hours. When welding outer girth, the preheating time is 3 to 5 hours. Preheat the flux before welding. S4, SAW circumferential seam welding: Use a welding trolley system with a flux heating and insulation device for welding, and cancel the post-weld dehydrogenation process. The welding material selected in this step is South Korea's Hyundai SAW welding wire H-14, and the flux is S-787TB; the flux is preheated and dried at a temperature of 300~350℃ before welding, and the drying time is 2 hours of insulation at a temperature of 150℃; the welding current is 720~770A, the welding voltage is 32~34V, the welding speed is 360~420mm / min, and the welding heat input range is: 3.3KJ / mm~4.4 KJ / mm.

2. A low-hydrogen pipe pile welding process according to claim 1, characterized in that: A welding carriage system, comprising a travel unit (1), a flux heating and heat preservation unit (2), a control unit (3) and a welding unit (4); The flux heating and heat preservation unit (2) is used for storing, heating and heat preservation of the flux, and for conveying the flux to the welding unit (4); The control unit (3) is used to adjust the welding current and voltage of the welding unit (4), and to set the flux heating temperature in the flux heating and heat preservation unit (2).

3. A low-hydrogen pipe pile welding process according to claim 2, characterized in that: The flux heating and heat-insulating unit (2) comprises a heat-insulating barrel (21), the top of which is provided with a heat-insulating plug (22) and a feeding hopper (23), the interior of the heat-insulating barrel (21) is provided with a thermocouple (24), a heating track (25) and an air compressor (26), the thermocouple (24) is used to measure the temperature of the flux in the heat-insulating barrel (21), the heating track (25) is used to heat the flux, one end of the interior of the heat-insulating barrel (21) is connected to a feeding pipe (27), one end of the feeding pipe (27) is connected to a flux sleeve (28), and one end of the flux sleeve (28) is connected to the welding unit (4).

4. A low-hydrogen pipe pile welding process according to claim 1, characterized in that: In step S2, the welding material is Atlantic solid welding wire CHW-50C6SM, and the welding wire diameter is φ1.2 mm.

5. A low-hydrogen pipe pile welding process according to claim 1, characterized in that: In the step S4, the diameter of the welding wire is φ5.0 mm.

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