Method for welding thick plate structure in cutterhead

Abstract

The invention discloses a method for welding a thick plate structure in a cutterhead, which belongs to the technical field of shield tunneling machines and comprises the steps of preparation before welding, preheating before welding, welding operation, heat preservation after welding and detection after welding. The pre-welding preparation comprises selection of an adaptive plate and pretreatment of a welding seam; the pre-welding preheating is used for preheating a steel plate according to a set temperature range and a preheating range; the welding operation adopts a set welding bead arrangement sequence, matched welding materials and grading process parameters, the post-welding heat preservation adopts a temperature return heat preservation mode, and the post-welding detection executes corresponding flaw detection standards according to weld penetration types. The problems that in the traditional technology, Z-direction cracks and transverse cracks frequently occur in the cutterhead welding process, and the welding qualification rate is low are solved.

Description

Technical Field

[0001] This invention belongs to the field of tunnel boring machine technology, specifically relating to a welding method for a medium-thick plate structure of a cutterhead. Background Technology

[0002] As the core equipment for tunnel construction, the tunnel boring machine (TBM) uses its cutterhead, a key load-bearing structural component that directly contacts the ground and enables excavation. It is typically constructed from thick steel plates and pipes, welded together after cutting, with diameters ranging from 6 to 18 meters and weights from 40 to 300 tons. Due to significant differences in the construction requirements, engineering geological conditions, and hydrogeological conditions of various tunnels, the TBM cutterhead requires customized design. Furthermore, as a large structural component welded from ultra-thick steel plates, the welding workload is substantial, and the quality requirements are stringent, directly impacting the safety and efficiency of tunnel construction.

[0003] As the core area for force transmission of the cutterhead, the torsion leg base needs to withstand complex ground reaction forces and impact loads during tunneling, making it a typical stress concentration area. Welding in this area involves Z-axis welding of thick plates, with welding stress mainly distributed along the plate thickness. However, existing welding methods for thick plates in the cutterhead have several shortcomings. Firstly, the steel plates used in traditional welding lack sufficient toughness in the thickness direction, making it difficult to withstand the localized tensile stress generated during welding. This leads to uneven performance in the thickness direction due to segregation, a high tendency for hardening in the heat-affected zone, and consequently, defects such as Z-axis cracks and interlayer tearing. Secondly, the existing preheating process has unreasonable temperature settings, resulting in excessively rapid interlayer temperature loss and a lack of effective post-weld insulation measures, leading to frequent transverse cracks and post-weld cooling cracks. Furthermore, the traditional weld arrangement sequence often involves welding from the bottommost weld joint with the base material upwards, which fails to effectively disperse welding stress, further exacerbating the risk of Z-axis cracking in thick plates.

[0004] For example, patent CN102773592A discloses a welding method for medium-thick carbon steel plates. Although it optimizes the welding process for medium-thick carbon steel plates, it does not consider the special stress conditions and Z-axis crack resistance requirements of the ultra-thick plates of the tunnel boring machine cutterhead. Therefore, its effect on welding stress control and crack resistance improvement is limited. Patent CN118543930A proposes a welding method for F550 high-strength steel thick plates, which is mainly adapted to the welding characteristics of high-strength steel. It does not specifically design the welding sequence, preheating, and insulation parameters for stress concentration areas such as the cutterhead torsion leg base, making it difficult to directly apply to welding scenarios of key structures in the medium-thick plates of the cutterhead. The aforementioned existing technologies cannot effectively solve the problems of frequent Z-axis and transverse cracks and low welding qualification rates during cutterhead welding. This leads to frequent weld cracking near the torsion leg base during cutterhead construction, requiring frequent shutdowns for maintenance and severely impacting tunnel excavation efficiency. Therefore, there is an urgent need for a welding method that adapts to the structural characteristics of medium-thick cutterhead plates, achieves high welding quality, and has excellent crack resistance. Summary of the Invention

[0005] Therefore, this invention provides a welding method for a medium-thick plate structure of a cutter head, which solves the problem that traditional techniques cannot effectively address the frequent occurrence of Z-direction cracks and transverse cracks and the low welding qualification rate during the cutter head welding process.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a welding method for a medium-thick plate structure of a cutter head, including pre-welding preparation, pre-welding preheating, welding operation, post-welding heat preservation and post-welding inspection steps; The pre-welding preparation includes the selection of suitable plates and pretreatment of welds; the preheating is performed on the steel plates according to the set temperature range and preheating range; the welding operation adopts the set weld bead arrangement sequence, matching welding materials and graded process parameters; the post-weld heat preservation adopts the reheating heat preservation method; and the post-weld inspection is performed according to the weld penetration type and the corresponding flaw detection standard.

[0007] As a preferred method for welding the medium-thick plate structure of the cutter head, the plate selection process before welding requires that the toughness in the thickness direction of the selected steel plate meets the Z15 requirement in GB / T5313, and the thickness of the steel plate is not less than 40mm. The specific process for cleaning the weld seam involves grinding a 30mm radius around the weld seam until it exhibits a metallic luster and is free of rust, oil, water, and other foreign matter; at the same time, the basic shape and dimensions of the bevel are inspected.

[0008] As a preferred method for welding medium-thick plate structures of cutterheads, the preheating before welding is implemented for steel plates with a thickness of 40mm or more, the preheating range is at least 100mm on both sides of the bevel, and the preheating temperature is controlled at 200-250℃. Preheating inspection is carried out by measuring the temperature on both sides of the steel plate. The temperature difference between the two sides should not exceed 5°C. After reaching the set preheating temperature, the temperature is kept constant until the welding is completed.

[0009] As a preferred method for welding the medium-thick plate structure of the cutter head, the welding operation adopts carbon dioxide gas shielded welding, the welding material is GB / T8110-2020 / φ1.2 solid welding wire, and the welding polarity is set to DC reverse polarity; The interpass temperature of the welding operation is controlled at 100-250℃, which is connected with the preheating temperature before welding. When welding is stopped for more than the set time or after each weld is completed, the weld is insulated with insulating cotton.

[0010] As a preferred method for welding thick plate structures in cutterheads, the specific sequence of welding operations is as follows: The first step is to perform root welding on the top, middle and bottom three weld seams of the thick plate of the cutter head, with a welding layer of 3 layers; The second step is to stand the workpiece up and then perform filler welding using a flat welding method, leaving two layers unwelded for the time being. The welding sequence is from both sides to the middle, first welding the weld beads that are in contact with the base material, and then welding the middle weld beads, gradually dispersing the welding stress. The third step is to keep the workpiece upright and perform cover welding, with the welding sequence being the same as the fill welding sequence.

[0011] As a preferred method for welding medium-thick plate structures with a cutter head, the welding operation is configured with corresponding parameters according to the welding position to adapt to the quality requirements of different welding scenarios: For flat welding, the current is 180-320A, the voltage is 22-32V, and the carbon dioxide gas flow rate is 15-25L / min; During horizontal welding, the current is 180-320A, the voltage is 22-32V, and the carbon dioxide gas flow rate is 15-25L / min; For vertical welding, the current is 120-220A, the voltage is 16-26V, and the carbon dioxide gas flow rate is 15-25L / min. When welding overhead, the current is 120-150A, the voltage is 15-18V, and the carbon dioxide gas flow rate is 15-25L / min.

[0012] As a preferred method for welding the medium-thick plate structure of the cutter head, the welding operation adopts a multi-layer, multi-pass welding process, with each weld pass not exceeding 6mm in height.

[0013] As a preferred method for welding the medium-thick plate structure of the cutter head, the width of the filler weld and cover weld of the flat and horizontal welds shall not exceed 12mm, the width of the filler weld of the vertical weld shall be 18±2mm, and the width of the cover weld of the vertical weld shall be 15±2mm.

[0014] As a preferred method for welding thick plate structures in cutterheads, the post-weld insulation specifically includes: After welding, reheat the weld to 200-250℃, wrap the weld with insulation cotton and keep it at room temperature. The cooling time of the weld should not be less than 2-3 times the natural cooling time to stabilize the weld microstructure and properties.

[0015] As a preferred method for welding thick plate structures in cutterheads, the post-weld inspection specifically includes: The welds shall be inspected according to the drawings. Butt welds whose thicknesses are equal to the minimum thickness of the base material shall be inspected according to the full penetration weld inspection standard. Butt welds whose thicknesses are less than the minimum thickness of the base material shall be inspected according to the non-full penetration weld inspection standard. A flaw detection report shall be issued after the inspection is qualified.

[0016] The beneficial effects of this invention are as follows: First, by selecting steel plates with thickness-direction toughness meeting the Z15 requirement in GB / T5313, and combining them with preheating at 200-250℃, post-weld reheating and heat preservation, and optimized weld bead arrangement sequence, this invention effectively solves the core defects such as Z-direction cracks, transverse cracks, and interlayer tearing in the thick plates of the cutter head through multi-dimensional synergy in material selection, temperature control, and stress dispersion. It also significantly reduces the adverse effects of hardening tendency and segregation in the heat-affected zone. The pass rate of non-destructive testing of key structural welds after welding can reach over 95%.

[0017] Secondly, the present invention adopts a welding process of root welding, upright filling, and upright covering, replacing the traditional top-down weld arrangement method. Combined with multi-layer and multi-pass welding process, the welding stress is evenly distributed to each weld and area, avoiding stress concentration in key stress-bearing parts such as the torsion leg base. This significantly improves the impact resistance of the cutterhead in complex strata tunneling and reduces the frequency of downtime maintenance caused by weld cracking during construction.

[0018] Third, the welding process parameters of this invention are precisely graded according to different positions such as flat welding, horizontal welding, vertical welding, and overhead welding. The preheating and interpass temperature control are clear, and the steps such as pre-weld cleaning and post-weld heat preservation are clearly defined. The skill requirements for operators are moderate, and it can be implemented without complex special equipment. At the same time, it meets the parameter adaptation requirements of robotic arm automated welding and can realize large-scale standardized production.

[0019] Fourth, this invention requires no additional equipment investment, reduces the number of times welding cracks need to be reworked and repaired by optimizing the process, avoids material waste and labor time loss, and reduces the overall production cost; the welding process uses carbon dioxide gas shielded welding with GB / T8110-2020 / φ1.2 solid welding wire, which produces no extra pollutants, and the insulation cotton after welding can be reused, which meets the requirements of green and environmentally friendly production.

[0020] Fifth, practical application has verified that the cutterhead using the welding method of this invention has a significantly reduced risk of weld cracking under tunneling impact loads, eliminating the need for frequent shutdowns for maintenance due to welding defects, effectively ensuring the continuity of tunnel construction and tunneling efficiency; the weld formation quality is uniform, the root weld has good fusion and a smooth transition with the base material, and the dimensions of the filler and cover welds are accurate, resulting in better structural stability and load-bearing capacity during long-term use. Attached Figure Description

[0021] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0022] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0023] Figure 1 This is a schematic diagram of the welding method for a medium-thick plate structure of a cutter head provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the overall welding sequence of the workpiece in the welding method for the medium-thick plate structure of the cutter head provided in this embodiment of the invention; Figure 3 This is a schematic diagram of the weld bead arrangement in the welding method for the medium-thick plate structure of the cutter head provided in an embodiment of the present invention. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] See Figure 1 This invention provides a welding method for a medium-thick plate structure of a cutterhead, including pre-weld preparation, pre-weld preheating, welding operation, post-weld heat preservation, and post-weld inspection steps. The pre-weld preparation includes the selection of suitable plate material and weld pretreatment. The pre-weld preheating involves preheating the steel plate according to a set temperature range and preheating range. The welding operation uses a set weld bead arrangement sequence, matching welding materials, and graded process parameters. The post-weld heat preservation adopts a reheating heat preservation method. The post-weld inspection performs corresponding flaw detection standards according to the weld penetration type.

[0026] Specifically, the challenges in welding thick plates in a cutter head are concentrated in Z-direction cracks, transverse cracks, and interlayer tearing, with welding stress concentrated in critical areas such as the torsion leg base. This invention establishes a collaborative prevention and control system through the design of preparation, preheating, welding, heat preservation, and testing. Pre-welding preparation addresses inherent defects by considering the basic conditions of the material and weld; preheating specifically addresses the issue of large temperature gradients in thick plates, reducing thermal stress; welding operations are optimized through process parameters and sequence to disperse welding stress; and post-weld heat preservation stabilizes the weld microstructure, preventing cooling cracking.

[0027] In one possible embodiment, the plate selection process for pre-welding preparation involves selecting steel plates whose thickness-direction toughness meets the Z15 requirement in GB / T5313, and whose thickness is not less than 40mm; the weld cleaning specifically involves grinding a 30mm radius around the weld until it exhibits a metallic luster and is free of rust, oil, water, and other foreign matter; and simultaneously inspecting the basic shape and dimensions of the bevel.

[0028] Specifically, the cutter head torsion leg base is welded in the Z-direction of a thick plate. The plate thickness direction bears the main welding stress. Using steel plates conforming to the Z15 requirement in GB / T5313 significantly improves the toughness in the thickness direction, resists local tensile stress, reduces the adverse effects of segregation on thickness direction properties, and lowers the risk of interlayer tearing and Z-direction cracking at the material level. When the steel plate thickness is not less than 40mm, the impact of Z-direction performance defects on weld quality is more pronounced. Rust, oil, water, and other foreign matter within a 30mm radius around the weld can cause defects such as porosity, inclusions, and lack of fusion. Grinding to a metallic luster ensures good fusion between the base metal and filler metal during welding. Inspecting the bevel shape and dimensions ensures the butt joint accuracy, allowing the weld to bear stress evenly and avoiding stress concentration due to bevel defects.

[0029] In one possible embodiment, the preheating is performed on steel plates with a thickness of 40mm or more, the preheating range is at least 100mm on both sides of the bevel, and the preheating temperature is controlled at 200-250℃; the preheating is checked by measuring the temperature on both sides of the steel plate, the temperature difference between the two sides is not greater than 5℃, and after the set preheating temperature is reached, the temperature is kept constant until the welding is completed.

[0030] Specifically, medium-thick plates with a thickness of 40mm or more have high thermal conductivity, and the intense alternation of heating and cooling during welding easily generates significant thermal stress. Furthermore, the heat-affected zone exhibits a pronounced hardening tendency, which can lead to cracking. Setting the preheating range to at least 100mm on both sides of the bevel ensures uniform heating of the weld joint and surrounding area, reducing temperature gradients and preventing localized overheating or undercooling. Controlling the preheating temperature between 200-250℃ reduces the hardness of the steel plate, improving weldability, and effectively reduces interpass temperature loss during welding, preventing weld cracks caused by excessively low interpass temperatures. Using double-sided temperature measurement with a temperature difference not exceeding 5℃ prevents overheating or incomplete heating on one side of the steel plate, ensuring uniform preheating. Maintaining a constant temperature until the end of welding stabilizes the temperature environment of the welding area, avoiding stress changes caused by temperature fluctuations and further reducing the probability of crack formation.

[0031] In one possible embodiment, the welding operation employs carbon dioxide gas shielded welding, the welding material is GB / T8110-2020 / φ1.2 solid welding wire, and the welding polarity is set to DC reverse polarity; the interpass temperature of the welding operation is controlled at 100-250℃, forming a connection with the preheating temperature before welding; when welding is stopped for more than the set time or after each weld is completed, the weld is insulated with heat insulation cotton.

[0032] Specifically, CO2 gas shielded welding features high welding efficiency, good weld formation, and low cost, making it suitable for the mass welding needs of medium and thick plates in cutterheads. The chemical composition and mechanical properties of the GB / T8110-2020 / φ1.2 solid welding wire are stable, exhibiting good compatibility with the materials of medium and thick plates in cutterheads, ensuring that the strength and toughness of the weld match the base material. Setting the welding polarity to DC reverse polarity increases arc stability, improves penetration, reduces spatter, and enhances weld formation quality. Interpass temperature control at 100-250℃ effectively connects with the preheating temperature, preventing stress concentration caused by sudden temperature drops during welding. This temperature range also prevents excessive grain size in the heat-affected zone, ensuring the weld microstructure and properties. When welding is stopped for more than the set time or after a single weld pass, the weld temperature will drop rapidly. Using insulation cotton can slow down the cooling rate, preventing the formation of hardened structures due to rapid cooling and reducing cold cracking.

[0033] See Figure 2 and Figure 3 In one possible embodiment, the specific sequence of the welding operation is as follows: First, perform root pass welding on the upper, middle and lower three weld seams of the thick plate of the cutter head, with a welding layer of 3 layers; Second, after the workpiece is erected, perform filler welding using a flat welding method, leaving two layers unwelded temporarily, and the welding sequence is from both sides to the middle, first welding the weld bead in contact with the base material, then welding the middle weld bead, gradually dispersing the welding stress; Third, while keeping the workpiece erected, perform cover pass welding, with the welding sequence being the same as the filler weld sequence. The welding operation is configured with corresponding parameters according to the welding position to adapt to the quality requirements of different welding scenarios: for flat welding, the current is 180-320A, the voltage is 22-32V, and the carbon dioxide gas flow rate is 15-25L / min; for horizontal welding, the current is 180-320A, the voltage is 22-32V, and the carbon dioxide gas flow rate is 15-25L / min; for vertical welding, the current is 120-220A, the voltage is 16-26V, and the carbon dioxide gas flow rate is 15-25L / min; for overhead welding, the current is 120-150A, the voltage is 15-18V, and the carbon dioxide gas flow rate is 15-25L / min.

[0034] Traditional welding sequences start from the bottom layer where it meets the base material and work upwards, which can easily lead to stress concentration in the middle area, increasing the risk of Z-axis cracking. The optimized welding sequence of this invention is as follows: First, a three-layer root pass is welded, which quickly fixes the workpiece shape, forming a stable welding foundation and preventing workpiece deformation during subsequent welding. Second, the workpiece is erected and filled using a flat welding method. Flat welding makes it easier to control weld formation and penetration depth compared to horizontal or overhead welding. Leaving two layers unwelded allows for stress release space. The welding sequence from both sides to the middle ensures that welding stress is evenly distributed towards the center, avoiding stress concentration at the junction of the base material and the weld, and reducing crack formation. Third, the cap weld follows the same filling welding sequence, ensuring uniform weld formation and further stabilizing stress distribution. The parameter differentiation settings for different welding positions are based on the welding characteristics of each position: flat welding and horizontal welding are easier to operate, and using a larger current and voltage can improve welding efficiency and ensure penetration depth; when welding vertically, the molten pool is prone to flow, so the current and voltage need to be reduced to control the shape of the molten pool; when welding overhead, the operating space is limited and the molten pool is difficult to control, so a smaller current and voltage are selected to ensure the quality of weld formation; the carbon dioxide gas flow rate is uniformly set to 15-25L / min, which can effectively isolate air, prevent weld oxidation, and ensure weld purity.

[0035] In one possible embodiment, the welding operation employs a multi-layer, multi-pass welding process, with each weld pass not exceeding 6 mm in height.

[0036] Specifically, multi-layer, multi-pass welding can decompose a thick weld into multiple thin weld passes, which can reduce the heat input during single-pass welding, reduce the width and hardening tendency of the heat-affected zone, and reduce welding deformation and stress concentration. Controlling the height of each weld pass to within 6mm ensures sufficient fusion and avoids defects such as incomplete fusion and porosity caused by excessively thick weld passes. Simultaneously, the multi-layer, multi-pass welding method allows each weld pass to preheat the next and the next to temper the previous, improving the weld microstructure and further enhancing its toughness and crack resistance.

[0037] In one possible embodiment, the width of the filler and capping weld beads for flat and horizontal welds shall not exceed 12 mm, the width of the filler weld bead for vertical welds shall be 18 ± 2 mm, and the width of the capping weld bead for vertical welds shall be 15 ± 2 mm. See Table 1 for weld size requirements.

[0038]

[0039] When welding flat or horizontally, the weld width should be controlled within 12mm to avoid problems such as incomplete fusion at the weld edge and irregular formation caused by excessively wide welds, ensuring good connection between the weld and the base material, and between welds themselves. When welding vertically, the molten pool tends to flow downwards due to gravity. Appropriately increasing the width of the filler weld to 18±2mm can ensure full weld filling. The width of the cap weld should be slightly smaller than that of the filler weld to make the weld surface smooth and flat, reduce stress concentration points, and meet the appearance and stress requirements of the welded structure, ensuring the overall mechanical properties of the weld are balanced.

[0040] In one possible embodiment, the post-weld heat preservation specifically involves: after welding, reheating the weld to 200-250°C, wrapping the weld with insulation cotton and keeping it at room temperature, and ensuring that the weld cooling time is not less than 2-3 times the natural cooling time to stabilize the weld microstructure and properties.

[0041] Specifically, after welding, the weld and heat-affected zone are at high temperatures. If allowed to cool naturally, the rapid temperature drop can lead to the formation of hardened martensite in the weld microstructure, increasing its brittleness and crack susceptibility. Reheating the weld to 200-250℃ promotes the tempering transformation of the weld microstructure, refines the grains, reduces hardness, and improves toughness. Wrapping the weld in insulating cotton and maintaining it at room temperature slows down the cooling rate, allowing for a complete transformation of the weld microstructure and reducing internal stress. A cooling time of at least 2-3 times the natural cooling time ensures complete transformation of the weld microstructure, further stabilizing weld performance and preventing cracks caused by stress release during post-weld cooling.

[0042] In one possible embodiment, the post-weld inspection specifically involves: performing flaw detection on the weld according to the drawing requirements; for butt welds where the sum of the thickness dimensions marked on the weld is equal to the minimum thickness of the base material, the inspection standard for full penetration welds shall be followed; for butt welds where the sum of the thickness dimensions marked on the weld is less than the minimum thickness of the base material, the inspection standard for non-full penetration welds shall be followed; and a flaw detection report shall be issued after the inspection is qualified.

[0043] Specifically, the stress conditions of welds in different parts of the cutterhead's thick plates vary. Full penetration welds need to withstand greater loads and have higher requirements for welding quality. Therefore, performing full penetration testing can ensure that there are no defects such as internal cracks or lack of fusion that affect structural strength. The stress requirements of non-full penetration welds are relatively lower, and testing according to the corresponding standards can improve testing efficiency while ensuring safe use. Targeted testing according to the drawings can cover critical load-bearing welds and general welds, comprehensively verifying whether the welding quality meets the design requirements and avoiding cutterhead failure during tunneling due to weld defects.

[0044] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method of welding a thick plate structure in a cutter head, characterized by, The method comprises the steps of welding preparation, pre-welding preheating, welding operation, post-welding holding and post-welding detection. The welding preparation comprises adaptive plate selection and weld pretreatment; the pre-welding preheating preheats the steel plate according to a set temperature range and a preheating range; the welding operation adopts a set welding pass arrangement sequence, matched welding materials and hierarchical process parameters, the post-welding holding adopts a temperature recovery holding mode, and the post-welding detection performs corresponding flaw detection standards according to the weld penetration type.

2. The method of claim 1, wherein, In the plate selection process of the welding preparation, the selected steel plate has a thickness direction toughness meeting the Z15 requirement in GB / T5313, and the thickness of the steel plate is not less than 40 mm. The weld cleaning specifically comprises polishing a 30 mm range around the weld to present a metallic luster without rust, oil stain and water foreign matter residue, and simultaneously inspecting the basic form and size of the groove.

3. The method of claim 1, wherein, The pre-welding preheating is implemented for the steel plate with a thickness of more than 40 mm, the preheating range is at least 100 mm on both sides of the groove, and the preheating temperature is controlled in a range of 200-250 DEG C. The preheating inspection is performed by adopting a steel plate two-side temperature measurement mode, the temperature difference between the two sides is not greater than 5 DEG C, and after reaching the set preheating temperature, the constant temperature is maintained until the welding is completed.

4. The method of claim 1, wherein, The welding operation adopts carbon dioxide gas shielded welding, the welding material selects GB / T8110-2020 / φ1.2 solid core welding wire, and the welding polarity is set as direct current reverse connection. The interlayer temperature of the welding operation is controlled in a range of 100-250 DEG C, and is connected with the pre-welding preheating temperature; after stopping welding for more than a set time length or after completing each weld, the weld is treated by using holding cotton.

5. The method of claim 1, wherein, The specific sequence of the welding operation is as follows: Firstly, the three welds on the upper, middle and lower thick plates of the cutter head are welded, and the welding layer number is three; Secondly, the workpiece is erected and then filled and welded by using the flat welding mode, two layers are temporarily not welded, and the welding sequence is from both sides to the middle, the weld contacting with the base material is welded first, then the middle weld is welded, and the welding stress is dispersed gradually; Thirdly, the workpiece is kept in the erected state and then covered and welded, and the welding sequence is consistent with that of the filling welding.

6. The method of claim 1, wherein, The welding operation sets corresponding parameters according to the welding position, and adapts to the quality requirements of different welding scenes: When flat welding, the current is 180-320 A, the voltage is 22-32 V, and the carbon dioxide gas flow is 15-25 L / min; When horizontal welding, the current is 180-320 A, the voltage is 22-32 V, and the carbon dioxide gas flow is 15-25 L / min; When vertical welding, the current is 120-220 A, the voltage is 16-26 V, and the carbon dioxide gas flow is 15-25 L / min; When overhead welding, the current is 120-150 A, the voltage is 15-18 V, and the carbon dioxide gas flow is 15-25 L / min.

7. The method of claim 6, wherein, The welding operation adopts a multi-layer and multi-pass welding process, and the height of each weld is not greater than 6 mm.

8. The method of claim 6, wherein, The width of the filling weld and the width of the covering weld in flat welding and horizontal welding are not greater than 12 mm, the width of the filling weld in vertical welding is 18±2 mm, and the width of the covering weld in vertical welding is 15±2 mm.

9. The method of claim 1, wherein, The post-welding holding specifically comprises After the welding is completed, the weld is reheated to 200-250℃, the weld is wrapped with heat preservation cotton and heat preservation is carried out to room temperature, and the weld cooling time is not less than 2-3 times of the natural cooling time, so as to stabilize the weld structure performance.

10. The method of claim 1, wherein, The post-weld detection specifically is: According to the drawing requirements, the weld is detected by flaw detection, the sum of the marked thickness size of the weld is equal to the minimum plate thickness of the butt weld of the base material, and the full penetration weld detection standard is executed, the sum of the marked thickness size of the weld is less than the minimum plate thickness of the butt weld of the base material, and the non-full penetration weld detection standard is executed, and a flaw detection report is issued after the detection is qualified.

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