A welding connection method of a UHPC beam-steel beam laminated structure

Abstract

The application discloses a welding connection method of a UHPC beam-steel beam laminated structure and relates to the technical field of bridge construction in fixed buildings, and specifically comprises the following steps: S1, embedding a temperature sensor under a UHPC beam embedded part to monitor the temperature in real time; S2, hoisting the UHPC beam and the steel beam to the pier, positioning, and adopting an angle joint horse plate to fix the T-shaped full penetration fillet weld on the outer side of the steel beam; S3, preheating the to-be-welded area of the T-shaped full penetration fillet weld between the steel beam web plate and the UHPC beam embedded part; S4, sequentially performing backing welding, filling welding and cap welding on the T-shaped full penetration fillet weld between the steel beam web plate and the UHPC beam embedded part, controlling the layer temperature during welding, and controlling the temperature of the weld area; and S5, after the welding is completed, covering the joint area with heat preservation cotton to perform heat preservation and slow cooling to normal temperature, reducing the cooling speed of the weld, and completing the welding connection. The application solves the technical problem of poor quality of the weld after the UHPC beam and the steel beam are welded in the prior art.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology in fixed structures, and more particularly to a welding connection method for a UHPC beam-steel beam laminated structure. Background Technology

[0002] UHPC is a high-performance material with excellent properties such as high strength, high durability, and low permeability, but it is highly sensitive to high temperatures. During T-welding of the steel beam web to the embedded flange of the UHPC beam, the sudden temperature imbalance between the inside and outside of the UHPC can lead to a series of physicochemical damage phenomena, including dehydration, decomposition, and embrittlement of hydration products, as well as uncoordinated thermal deformation. This can even result in serious consequences such as decreased UHPC strength, bursting, cracking, and deformation. The higher the temperature, the more severe these damage phenomena become, ultimately threatening the stability and service life of the structure.

[0003] In the existing technology, there is a lack of effective temperature control methods for welding UHPC to steel structures, which often leads to post-weld performance deterioration, low first-pass inspection pass rate, and increased manufacturing costs and structural risks. Summary of the Invention

[0004] The purpose of this invention is to provide a welding connection method for UHPC beam-steel beam laminated structures, which solves the technical problem of poor weld quality after welding UHPC beam-steel beams in the prior art.

[0005] This application discloses a welding connection method for a UHPC beam-steel beam laminated structure, including the following steps: S1: A temperature sensor is embedded under the UHPC beam pre-embedded part to monitor the temperature in real time; S2: Hoist the UHPC beams and steel beams to the piers, position them, and use corner joints to secure the T-shaped full penetration fillet welds on the outside of the steel beams; S3: Preheat the area to be welded for the T-shaped full penetration fillet weld between the web of the steel beam and the embedded parts of the UHPC beam; S4: For the T-shaped full penetration fillet weld at the flat corner between the web of the steel beam and the embedded part of the UHPC beam, perform root pass welding, fill pass welding and cover pass welding in sequence. During welding, perform layer temperature control and control the temperature of the weld area. S5: After welding, cover the joint area with insulation cotton to keep it warm and cool it slowly to room temperature, thereby reducing the cooling rate of the weld and completing the weld connection.

[0006] This application incorporates a temperature detection system to control the temperature and prevent excessively high temperatures from affecting the welding quality of the corresponding areas.

[0007] Based on the above technical solution, the present application can be further improved as follows: Furthermore, the specific content of step S1 is as follows: S101: Aluminum silicate insulation cotton is laid under the embedded parts of the UHPC beam and cast together with the embedded parts of the UHPC beam in the UHPC beam to reduce the maximum temperature of the UHPC in the weld area. S102: Arrange temperature sensors on the contact surface between the UHPC beam embedded part and the UHPC, and arrange temperature sensors inside the 0cm, 1cm and 2cm segments below the center of the UHPC beam embedded part to monitor the temperature of the concrete. The beneficial effect of this step is that temperature monitoring can be carried out through appropriate arrangement.

[0008] Furthermore, the T-type full penetration fillet weld in step S2 adopts a single-sided V-groove.

[0009] Furthermore, the specific content of step S3 is as follows: a tracked electromagnetic heating pad is used to preheat the 60mm area to be welded around the T-shaped full penetration fillet weld between the steel beam web and the UHPC beam embedded parts to 60℃-80℃. The beneficial effect of this step is that the weld quality can be improved through preheating.

[0010] Furthermore, the following is included between steps S3 and S4: applying ceramic lining to the outside of the steel beam, setting up a welding platform inside the UHPC beam, and welding on one side with the bevel facing the inside of the steel beam. The advantage of this step is that it facilitates subsequent welding.

[0011] Furthermore, the specific content of the layer temperature control in step S4 is as follows: the interlayer temperature of the weld is controlled between 60-140℃. When the temperature is higher than 140℃ or lower than 60℃, the welding of the next layer is stopped. The beneficial effect of this step is to ensure the quality of the weld by controlling the layer temperature.

[0012] Furthermore, in step S4, during welding, the T-shaped full penetration fillet welds between the webs on both sides of the steel beam and the embedded parts of the UHPC beam are alternately welded. This increases the cooling time in the near-weld area and controls the post-weld angular deformation of the thick plate T-shaped full penetration fillet welds by alternating welding on both sides. The beneficial effect of this step is that alternating welding can avoid deformation.

[0013] Furthermore, the specific content of step S4 is as follows: S401: A drag-and-drop collaborative robot is used in conjunction with a gas metal arc welding (GMAW) equipment to perform a T-shaped full penetration fillet weld at the flat corner between the web of the steel beam and the embedded part of the UHPC beam. An electric straight grinder is used to grind and remove welding spatter and slag in the near-weld area, and the root weld bead is ground into a concave shape to avoid defects such as slag inclusion or incomplete fusion. S402: A dragged teaching collaborative robot is used in conjunction with a gas metal arc welding equipment to fill the T-shaped full penetration fillet weld between the web of the steel beam and the embedded part of the UHPC beam. Multi-layer and multi-pass welding is used during the filling welding. An electric straight grinder is used to grind and remove welding spatter and slag in the near-weld area to avoid defects such as slag inclusion or incomplete fusion. S403: A drag-and-drop collaborative robot is used in conjunction with a gas metal arc welding (GMAW) equipment to perform a T-shaped full penetration fillet weld at the flat corner between the web of the steel beam and the embedded part of the UHPC beam. An electric straight grinder is used to grind and remove welding spatter and slag in the near-weld area to avoid defects such as slag inclusion or incomplete fusion. The beneficial effect of this step is that by using multi-step welding, the quality of the weld can be guaranteed.

[0014] Furthermore, the step of controlling the temperature of the weld area in step S4 is as follows: during the welding process, the temperature value transmitted by the temperature sensor is monitored in real time; if the temperature value is greater than the UHPC damage temperature, welding is stopped; if the temperature value is not greater than the UHPC damage temperature, welding is carried out. The damage temperature range of the UHPC is 300-350℃.

[0015] Furthermore, in step S4, the collaborative robot is equipped with an arc tracking function. When the welding groove is irregular, the arc path of the welding torch can be changed by changing the parameters to achieve real-time correction and ensure the fusion quality of the weld.

[0016] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: 1. This application ensures the quality of the weld without damaging the UHPC by controlling the layer temperature and the temperature during weld welding.

[0017] 2. The welding method of this application solves the problem of poor quality of UHPC after welding. It is simple, convenient and safe to operate, effectively controls the maximum temperature of UHPC in the near weld area, ensures the post-weld performance of UHPC, and improves the first-pass inspection qualification rate of T-type penetration welding of high-strength steel thick plate, which greatly improves the service life and operational safety of UHPC beam-steel beam laminated structure. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1This is a schematic flowchart illustrating a welding connection method for a UHPC beam-steel beam laminated structure according to a specific embodiment of the present invention. Figure 2 This is a schematic diagram of the overall structure of the UHPC beam-steel beam laminated structure according to a specific embodiment of the present invention; Figure 3 This is a partial structural diagram of the welded connection of the UHPC beam-steel beam laminated structure according to a specific embodiment of the present invention; Figure 4 This is a photograph of the actual welded T-shaped full penetration fillet weld between the steel beam web and the UHPC beam embedded part as described in Specific Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the T-shaped full penetration fillet weld between the steel beam web and the UHPC beam embedded part as described in specific embodiment 1 of the present invention. The numbers ①-㊵ indicate the alternating welding sequence on both sides. Figure 6 This is a macroscopic metallographic image of the T-shaped full penetration fillet weld between the steel beam web and the UHPC beam embedded part as described in Specific Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of UHPC damage during the high-temperature test of UHPC as described in Specific Embodiment 1 of the present invention; Figure 8 This is a schematic diagram of the temperature sensor arrangement for the T-shaped full penetration fillet weld between the steel beam web and the UHPC beam embedded parts as described in Specific Embodiment 1 of the present invention; Figure 9 This is a temperature change curve of the near-weld region of the T-shaped full penetration fillet weld between the steel beam web and the UHPC beam embedded part as described in Specific Embodiment 1 of the present invention. Figure 10 This is a schematic diagram of specimen IV after processing according to Comparative Example 1; Figure 11 This is a schematic diagram of specimen V after processing in Comparative Example 2; Figure 12 This is a schematic diagram of specimen VI after processing in comparative example 3.

[0020] The attached figures are labeled as follows: 1-UHPC beam, 2-steel beam, 3-steel beam web, 4-UHPC beam embedded part, 5-alumina silicate insulation cotton, 6-T-type full penetration fillet weld; 7-ceramic gasket. Detailed Implementation

[0021] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention. It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0022] In the description of this application, it should be understood that the terms "upper", "lower", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0023] In this application, unless otherwise expressly specified and limited, the terms "installation," "setup," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0025] like Figure 2 , 3 As shown, the UHPC beam-steel beam laminated structure in this application includes a UHPC beam and a steel beam. The steel beam is stacked on top of the UHPC beam. A full-length UHPC beam embedded part is arranged on the top side of the UHPC beam (the UHPC beam and the UHPC beam embedded part are combined to form the UHPC). The web of the steel beam extends beyond the bottom plate. Both the UHPC beam embedded part and the steel beam web are made of 36mm thick Q500qE high-strength steel plate. The steel beam web and the UHPC beam embedded part are connected by a T-shaped full penetration fillet weld.

[0026] Based on the above structure, six specimens were made and numbered as Specimen I, Specimen II, Specimen III, Specimen IV, Specimen V and Specimen VI.

[0027] Example 1: like Figure 1-9 As shown, the welding connection method of this application was used to process specimen I; The specific steps are as follows: S1: Embed a temperature sensor under the UHPC beam pre-embedded parts to monitor the temperature in real time. The specific details of this step are as follows: S101: Aluminum silicate insulation cotton is laid under the embedded parts of the UHPC beam and cast together with the embedded parts of the UHPC beam in the UHPC beam to reduce the maximum temperature of the UHPC in the weld area. S102: Arrange temperature sensors on the contact surface between the UHPC beam embedded part and the UHPC, and arrange temperature sensors inside the 0cm, 1cm and 2cm segments below the center of the UHPC beam embedded part to monitor the temperature of the concrete. S2: Hoist the UHPC beam and steel beam onto the pier, position them, and use corner joints to secure the T-shaped full penetration fillet weld on the outside of the steel beam. The specific steps are as follows: Hoist the UHPC beam and steel beam onto the pier, precisely position the relative positions between segments, focusing on controlling the top surface elevation, assembly gap, and alignment. Use corner joints to secure the T-shaped full penetration fillet weld on the outside of the steel beam. Simultaneously, grind away dirt and coatings from the 25mm area around the T-shaped full penetration fillet weld to reveal a metallic luster. This T-shaped full penetration fillet weld uses a single-sided V-groove. S3: Preheat the area to be welded for the T-shaped full penetration fillet weld between the web of the steel beam and the embedded part of the UHPC beam. Specifically, use a crawler-type electromagnetic heating pad for heating. The area is the 60mm area to be welded around the T-shaped full penetration fillet weld between the web of the steel beam and the embedded part of the UHPC beam. The preheating temperature is 60℃. A ceramic liner is attached to the outside of the steel beam, and a welding platform is set up inside the UHPC beam. Welding is performed on one side with the bevel facing the inside of the steel beam. S4: For the T-shaped full penetration fillet welds at the flat corner between the web of the steel beam and the embedded parts of the UHPC beam, perform root pass welding, fill pass welding and cover pass welding in sequence. During welding, the layer temperature is controlled. During welding, the T-shaped full penetration fillet welds between the web of the steel beam on both sides and the embedded parts of the UHPC beam are welded alternately to increase the cooling time of the near weld area. At the same time, the post-weld angular deformation of the thick plate T-shaped full penetration fillet welds is controlled by alternating welding on both sides. S5: After welding, cover the joint area with insulation cotton to keep it warm and cool it slowly to room temperature, thereby reducing the cooling rate of the weld and completing the weld connection.

[0028] The specific content of the layer temperature control in step S4 is as follows: the interlayer temperature of the weld is controlled at 60°C. When the temperature is higher than 140°C or lower than 60°C, the welding of the next layer is stopped.

[0029] Among them, such as Figure 4 , 5 As shown, the specific content of step S4 is as follows: S401: A drag-and-drop collaborative robot is used in conjunction with a gas metal arc welding (GMAW) equipment to perform a T-shaped full penetration fillet weld at the flat corner between the web of the steel beam and the embedded part of the UHPC beam. An electric straight grinder is used to grind and remove welding spatter and slag in the near-weld area, and the root weld bead is ground into a concave shape to avoid defects such as slag inclusion or incomplete fusion. S402: A dragged teaching collaborative robot is used in conjunction with a gas metal arc welding equipment to fill the T-shaped full penetration fillet weld between the web of the steel beam and the embedded part of the UHPC beam. Multi-layer and multi-pass welding is used during the filling welding. An electric straight grinder is used to grind and remove welding spatter and slag in the near-weld area to avoid defects such as slag inclusion or incomplete fusion. S403: A drag-and-drop collaborative robot is used in conjunction with a gas metal arc welding (GMAW) equipment to perform a T-shaped full penetration fillet weld at the flat corner between the web of the steel beam and the embedded part of the UHPC beam. An electric straight grinder is used to grind and remove welding spatter and slag in the near-weld area to avoid defects such as slag inclusion or incomplete fusion.

[0030] The step of controlling the temperature of the weld area in step S4 is as follows: During the welding process, the temperature value transmitted by the temperature sensor is monitored in real time; if the temperature value is greater than the UHPC damage temperature, welding is stopped; if the temperature value is not greater than the UHPC damage temperature, welding is carried out. The damage temperature range of the UHPC is 300-350℃.

[0031] In step S4, the collaborative robot is equipped with an arc tracking function. When the welding groove is irregular, the arc path of the welding torch can be changed by changing the parameters to achieve real-time correction and ensure the fusion quality of the weld.

[0032] The robot's operating method in steps S401, S402, and S403 of this application is existing, and can also be implemented in the following manner: Specifically, for step S401: the robot control program calls the automatic pulse argon-rich gas shielded welding mode, the gas shielded welding material is solid welding wire G69A4M21ZN2M4T (φ1.2mm), the shielding gas is 80% Ar and 20% CO2 by volume, the welding current is 200A, the arc voltage is 23V, the welding speed is 190mm / min, the wire extension is 12mm, the gas flow rate is 25L / min, the arc swinging method is triangular, the swing width is 4mm, the swing frequency is 40 times / min, and the left and right stop times are both 0.5s. Regarding step S402: The robot control program calls the automatic pulse argon-rich gas shielded welding mode. The welding material used is solid welding wire G69A4M21ZN2M4T (φ1.2mm). The shielding gas is 80% Ar and 20% CO2 by volume. The welding current is 240A, the arc voltage is 26V, the welding speed is 300mm / min, the wire extension is 12mm, the gas flow rate is 25L / min, the arc swing is sinusoidal, the swing width is 4mm, the swing frequency is 50 times / min, and the left and right stop times are both 0.7s. For step S403: The robot control program calls the automatic pulse CO2 gas shielded welding mode. The welding material selected for gas shielded welding is flux-cored wire T624T1-1C1A-GXU (φ1.2mm). The welding current is 260A, the arc voltage is 27V, the welding speed is 330mm / min, the wire extension is 12mm, the gas flow rate is 25L / min, the arc swing is sinusoidal, the swing width is 4-6mm, the swing frequency is 55 times / min, and the left and right stop times are both 0.6s.

[0033] The solid welding wire G69A4M21ZN2M4T (φ1.2mm) comprises the following components by mass percentage: C: ≤0.12%, S: ≤0.015%, Mn: 1.5-2.0%, P: ≤0.020%, Si: 0.40-0.90%. Using argon-rich gas shielded welding with this solid welding wire for root pass and fill pass significantly improves the crack resistance of the weld joint and the first-pass inspection pass rate. The flux-cored welding wire T624T1-1C1A-GXU (φ1.2mm) comprises the following components by mass percentage: C: ≤0.10%, S: ≤0.015%, Mn: 1.0-1.8%, P: ≤0.020%, Si: ≤0.80%, Ni: 0.80-2.00%. Using flux-cored wire CO2 gas shielded welding for cover welding effectively improves the appearance quality of T-type full penetration fillet welds at the flat corner of thick plates.

[0034] When welding the T-shaped full penetration fillet weld between the steel beam web and the UHPC beam embedded part, the collaborative robot uses a drag-and-drop teaching function. The operator can directly drag the robot arm to program the welding path, eliminating the need for a traditional teaching pendant or coding. This is more suitable for long, straight welds, enabling fast and intuitive path planning. Furthermore, compared to manual welding, the parameters during collaborative robot welding are more controllable, preventing significant fluctuations. The operator can start and stop the welding equipment based on real-time data from the temperature sensor.

[0035] In this embodiment, 36 hours after the welding of specimen I was completed, the weld was inspected visually, magnetically, and ultrasonically, and all tests were qualified. At the same time, the UHPC near the weld area was inspected and no cracks were found.

[0036] Further explanation is provided regarding this application: like Figure 7 As shown, the UHPC damage temperature described in this application is determined by a high-temperature test. The specific operation method is as follows: Test blocks cured under the same conditions at the UHPC segmental beam prefabrication yard are used. The cubic specimens are 100mm × 100mm × 100mm in size. Before undergoing high-temperature testing, the specimens were steam-cured at 80℃ for 3 days. The steam-cured UHPC cubic specimens were then placed in a muffle furnace for heating tests. This test set 8 temperature gradients, with 3 cubes in each group, namely 150℃, 200℃, 225℃, 240℃, 250℃, 260℃, 280℃, 300℃, and 350℃. The specimens were kept at a constant temperature in the high-temperature furnace for 3 hours to investigate the damage characteristics of UHPC within this temperature range. During the UHPC high-temperature test, due to the different main components of UHPC, the damage characteristics of UHPC after 3 hours of constant temperature in the high-temperature furnace also differ. It is necessary to determine the UHPC damage temperature based on the test results to prevent serious consequences such as decreased UHPC strength, bursting, cracking, and deformation caused by excessively high temperatures. After the high-temperature test, the UHPC specimens were naturally cooled to room temperature. The surface of the specimens was observed to see if cracks were generated. The compressive strength of the cubic specimens was also tested to evaluate the effect of high temperature on the mechanical properties of UHPC. Finally, the damage temperature range of the UHPC was determined to be 300-350℃.

[0037] Example 2: In this embodiment, specimen II is welded together. The welding method used differs from that in Embodiment 1 as follows (all other steps are the same): The preheating temperature in step S3 is 80°C.

[0038] In step S4, the interlayer temperature of the weld is controlled at 140°C.

[0039] Specifically, for step S401: the robot control program calls the automatic pulse argon-rich gas shielded welding mode, the gas shielded welding material is solid welding wire G69A4M21ZN2M4T (φ1.2mm), the shielding gas is 80% Ar and 20% CO2 by volume, the welding current is 210A, the arc voltage is 24V, the welding speed is 200mm / min, the wire extension is 18mm, the gas flow rate is 30L / min, the arc swinging method is triangular, the swing width is 6mm, the swing frequency is 45 times / min, and the left and right stop times are both 0.5s. Regarding step S402: The robot control program calls the automatic pulse argon-rich gas shielded welding mode. The welding material used is solid welding wire G69A4M21ZN2M4T (φ1.2mm). The shielding gas is 80% Ar and 20% CO2 by volume. The welding current is 250A, the arc voltage is 27V, the welding speed is 310mm / min, the wire extension is 18mm, the gas flow rate is 30L / min, the arc swing is sinusoidal, the swing width is 6mm, the swing frequency is 55 times / min, and the left and right stop times are both 0.7s. For step S403: The robot control program calls the automatic pulse CO2 gas shielded welding mode. The welding material used for gas shielded welding is T624T1-1C1A-GXU flux-cored wire (φ1.2mm). The welding current is 270A, the arc voltage is 28V, the welding speed is 340mm / min, the wire extension is 18mm, the gas flow rate is 30L / min, the arc swing is sinusoidal, the swing width is 6mm, the swing frequency is 60 times / min, and the left and right stop times are both 0.6s.

[0040] The solid welding wire G69A4M21ZN2M4T (φ1.2mm) comprises the following components by mass percentage: C: ≤0.12%, S: ≤0.015%, Mn: 1.5-2.0%, P: ≤0.020%, Si: 0.40-0.90%. Using argon-rich gas shielded welding with this solid welding wire for root pass and fill pass significantly improves the crack resistance of the weld joint and the first-pass inspection pass rate. The flux-cored welding wire T624T1-1C1A-GXU (φ1.2mm) comprises the following components by mass percentage: C: ≤0.10%, S: ≤0.015%, Mn: 1.0-1.8%, P: ≤0.020%, Si: ≤0.80%, Ni: 0.80-2.00%. Using flux-cored wire CO2 gas shielded welding for cover welding effectively improves the appearance quality of T-type full penetration fillet welds at the flat corner of thick plates.

[0041] In this embodiment, 36 hours after the welding of specimen II was completed, the weld was inspected visually, magnetically, and ultrasonically, and all tests were qualified. At the same time, the UHPC near the weld area was inspected and no cracks were found.

[0042] Example 3: In this embodiment, specimen III is welded together. The welding method used differs from that in Embodiment 1 as follows (all other steps are the same): The preheating temperature in step S3 is 70°C.

[0043] In step S4, the interlayer temperature of the weld is controlled at 100°C.

[0044] Specifically, for step S401: the robot control program calls the automatic pulse argon-rich gas shielded welding mode, the gas shielded welding material is solid welding wire G69A4M21ZN2M4T (φ1.2mm), the shielding gas is 80% Ar by volume and 20% CO2 by volume, the welding current is 205A, the arc voltage is 24V, the welding speed is 195mm / min, the wire extension is 16mm, the gas flow rate is 28L / min, the arc swinging method is triangular, the swing width is 5mm, the swing frequency is 42 times / min, and the left and right stop times are both 0.5s. Regarding step S402: The robot control program calls the automatic pulse argon-rich gas shielded welding mode. The welding material used is solid welding wire G69A4M21ZN2M4T (φ1.2mm). The shielding gas is 80% Ar and 20% CO2 by volume. The welding current is 240-250A, the arc voltage is 26V, the welding speed is 305mm / min, the wire extension is 16mm, the gas flow rate is 28L / min, the arc swing is sinusoidal, the swing width is 5mm, the swing frequency is 52 times / min, and the left and right stop times are both 0.7s. For step S403: The robot control program calls the automatic pulse CO2 gas shielded welding mode. The welding material selected for gas shielded welding is T624T1-1C1A-GXU flux-cored wire (φ1.2mm). The welding current is 265A, the arc voltage is 28V, the welding speed is 335mm / min, the wire extension is 16mm, the gas flow rate is 27L / min, the arc swing is sinusoidal, the swing width is 6mm, the swing frequency is 58 times / min, and the left and right stop times are both 0.6s.

[0045] The solid welding wire G69A4M21ZN2M4T (φ1.2mm) comprises the following components by mass percentage: C: ≤0.12%, S: ≤0.015%, Mn: 1.5-2.0%, P: ≤0.020%, Si: 0.40-0.90%. Using argon-rich gas shielded welding with this solid welding wire for root pass and fill pass significantly improves the crack resistance of the weld joint and the first-pass inspection pass rate. The flux-cored welding wire T624T1-1C1A-GXU (φ1.2mm) comprises the following components by mass percentage: C: ≤0.10%, S: ≤0.015%, Mn: 1.0-1.8%, P: ≤0.020%, Si: ≤0.80%, Ni: 0.80-2.00%. Using flux-cored wire CO2 gas shielded welding for cover welding effectively improves the appearance quality of T-type full penetration fillet welds at the flat corner of thick plates.

[0046] In this embodiment, 36 hours after the welding of specimen III was completed, the weld was inspected visually, magnetically, and ultrasonically, and all tests were qualified. At the same time, the UHPC near the weld area was inspected and no cracks were found.

[0047] Comparative Example 1: The welding method used in this comparative example, specimen IV, differs from that in Example 1 as follows (all other steps are the same): Temperature sensors were not embedded under the UHPC beam pre-embedded parts, making it impossible to monitor the temperature development and maximum temperature of the steel plate and UHPC beam at different locations in real time during the welding process. Although the interlayer temperature of the weld was controlled at 60-140℃, intermittent cracks still appeared in the UHPC near the weld area within a 3.5-meter weld range during the welding process, failing to meet the design and usage requirements.

[0048] Comparative Example 2: The welding method used in this comparative example, specimen V, differs from that in Example 2 as follows (all other steps are the same): The maximum interlayer temperature of the weld was controlled at 200℃. During the welding process, multiple cracks appeared in the UHPC near the weld within a 3.5-meter weld area, failing to meet the design and usage requirements.

[0049] Comparative Example 3: The welding method used in this comparative example, specimen VI, differs from that in Example 3 as follows (all other steps are the same): With other variables remaining constant, the following parameters were used for root pass, fill pass, and cover pass welding: welding current of 280-300A, arc voltage of 30-32V, welding speed of 280-300mm / min, and welding with high line energy. During the welding process, multiple cracks appeared in the UHPC near the weld within a 3.5-meter weld seam range, failing to meet the design and usage requirements.

[0050] In summary, this application discloses a welding connection method for a UHPC beam-steel beam laminated structure, which controls the maximum temperature of the UHPC near the weld area, ensures the post-weld performance of the UHPC, and improves the first-pass inspection qualification rate of T-type penetration welds.

[0051] Taking the welded connection of a UHPC beam-steel beam laminated structure of a Yellow River bridge as an example, the specific structure is as follows: Figure 1 As shown, both the UHPC beam embedded parts and the steel beam web are made of 36mm thick Q500qE high-strength steel plates. The steel beam web and the UHPC embedded parts are connected by T-shaped full penetration fillet welds, using the welding method described in Example 1. 36 hours after welding, the T-shaped full penetration fillet welds at the flat corners between the steel beam web and the UHPC beam embedded parts were visually inspected, magnetically tested, and ultrasonically tested. All tests were qualified, with the ultrasonic testing results meeting the requirements of Q / CR 9211-2015 Class I. Simultaneously, the UHPC near the weld area was inspected and found to be free of cracks.

[0052] Numerous specific details are set forth in this specification. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification. In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A welding connection method for a UHPC beam-steel beam laminated structure, characterized in that, Includes the following steps: S1: A temperature sensor is embedded under the UHPC beam pre-embedded part to monitor the temperature in real time; S101: Aluminum silicate insulation cotton is laid under the embedded parts of the UHPC beam and cast together with the embedded parts of the UHPC beam in the UHPC beam to reduce the maximum temperature of the UHPC in the weld area. S102: Arrange temperature sensors on the contact surface between the UHPC beam embedded part and the UHPC, and arrange temperature sensors inside the 0cm, 1cm and 2cm segments below the center of the UHPC beam embedded part to monitor the temperature of the concrete. S2: Hoist the UHPC beam and steel beam to the pier, position them, and use corner joints to secure the T-type full penetration fillet weld on the outside of the steel beam. The T-type full penetration fillet weld uses a single-sided V-groove. S3: Preheat the area to be welded for the T-shaped full penetration fillet weld between the steel beam web and the UHPC beam embedded parts; use a crawler-type electromagnetic heating pad to preheat the 60mm area to be welded around the T-shaped full penetration fillet weld between the steel beam web and the UHPC beam embedded parts to 60℃-80℃; attach a ceramic liner to the outside of the steel beam, set up a welding platform inside the UHPC beam, and weld on one side with the bevel facing the inside of the steel beam; S4: For the T-shaped full penetration fillet weld at the flat corner between the web of the steel beam and the embedded part of the UHPC beam, perform root pass welding, fill pass welding and cover pass welding in sequence. During welding, perform layer temperature control and control the temperature of UHPC in the weld area. S5: After welding, cover the joint area with insulation cotton to keep it warm and cool it slowly to room temperature, thereby reducing the cooling rate of the weld and completing the weld connection.

2. The welding connection method according to claim 1, characterized in that, The specific content of the layer temperature control in step S4 is as follows: the interlayer temperature of the weld is controlled between 60-140℃. When the temperature is higher than 140℃ or lower than 60℃, the welding of the next layer is stopped.

3. The welding connection method according to claim 2, characterized in that, In step S4, during welding, the T-shaped full penetration fillet welds between the web plates on both sides of the steel beam and the embedded parts of the UHPC beam are alternately welded. This increases the cooling time in the near-weld area and controls the post-weld angular deformation of the thick plate T-shaped full penetration fillet welds by alternating welding on both sides.

4. The welding connection method according to claim 3, characterized in that, The specific content of step S4 is as follows: S401: A drag-and-drop collaborative robot is used in conjunction with a gas metal arc welding (GMAW) equipment to perform a T-shaped full penetration fillet weld at the flat corner between the web of the steel beam and the embedded part of the UHPC beam. An electric straight grinder is used to grind and remove welding spatter and slag in the near-weld area, and the root weld bead is ground into a concave shape to avoid defects such as slag inclusion or incomplete fusion. S402: A dragged teaching collaborative robot is used in conjunction with a gas metal arc welding equipment to fill the T-shaped full penetration fillet weld between the web of the steel beam and the embedded part of the UHPC beam. Multi-layer and multi-pass welding is used during the filling welding. An electric straight grinder is used to grind and remove welding spatter and slag in the near-weld area to avoid defects such as slag inclusion or incomplete fusion. S403: A drag-and-drop collaborative robot is used in conjunction with a gas metal arc welding (GMAW) equipment to perform a T-shaped full penetration fillet weld at the flat corner between the web of the steel beam and the embedded part of the UHPC beam. An electric straight grinder is used to grind and remove welding spatter and slag in the near-weld area to avoid defects such as slag inclusion or incomplete fusion.

5. The welding connection method according to claim 4, characterized in that, The steps for controlling the temperature of the weld area in step S4 are as follows: During the welding process, the temperature value transmitted by the temperature sensor is monitored in real time; if the temperature value is greater than the UHPC damage temperature, welding is stopped; if the temperature value is not greater than the UHPC damage temperature, welding is carried out. The damage temperature range of the UHPC is 300-350℃.

6. The welding connection method according to claim 5, characterized in that, In step S4, the collaborative robot is equipped with an arc tracking function. When the welding groove is irregular, the arc path of the welding torch can be changed by changing the parameters to achieve real-time correction and ensure the fusion quality of the weld.

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