Q550D high-strength steel flat position robot automatic welding method

Abstract

The application discloses a kind of Q550D high-strength steel flat-position robot automatic welding methods, comprising the following steps: (1) carry out welding groove processing, do not leave blunt edge, and the gap of groove root is 1-3mm;(2) using solid argon-rich gas shielded welding to carry out backing layer welding;(3) using flux-cored wire CO2 gas shielded welding to carry out filling layer welding;(4) using flux-cored wire CO2 gas shielded robot automatic welding to carry out cover layer welding.The application solves the welding problem of single-sided welding double-sided forming butt joint weld under the condition of not sticking backing pad and not cleaning root, and can effectively guarantee the first-time flaw detection pass rate of butt joint weld;Using the robot automatic welding method filled with flux-cored wire shielded welding to fill or cover welding, the welding process has high degree of automation, and the appearance of weld after welding is uniformly and beautifully formed;The weld has good strength index and excellent low-temperature impact toughness index, and meets the anti-impact performance requirements of high-strength level crash barrier.

Description

Technical Field

[0001] This invention relates to a welding method for high-strength steel, and more particularly to an automated welding method for Q550D high-strength steel using a parallel robot. Background Technology

[0002] Crash barriers play a crucial role in highway traffic safety. Currently, for high-speed railway bridges and cable-stayed bridges such as large suspension bridges and cable-stayed bridges, the highest-grade HA level crash barrier is directly recommended. Because HA-level crash barriers have extremely high requirements for resisting lateral collision loads from vehicles, some design institutes, when considering balancing improving the impact resistance of crash barriers with cost control, have taken an alternative approach by using higher-grade steel plates for the crash barriers to resolve this contradiction. Currently, Q550-grade high-strength steel crash barriers have been designed and applied on the Lingdingyang Bridge of the Shenzhen-Zhongshan Bridge and the Gaolan Port Bridge of the Huangmaohai Cross-Sea Channel.

[0003] While Q550 steel does not meet the same strength requirements as Q690qE high-strength steel, the highest grade currently used in bridges, it surpasses the highest grade of Q500 high-strength steel commonly used in bridges. Its welding conditions are stringent, and the internal quality control of the welds is challenging. Furthermore, as the crash barriers are a key part of the bridge's overall image, the requirements for the weld appearance are even higher. In particular, the side crash barriers of the Lingdingyang Bridge in the Shenzhen-Zhongshan Bridge were designed with Q550C material (but Q550D was used as a substitute due to steel mill production constraints). The structure is a spatially irregular hexagonal prism, and the two vertical butt welds are enclosed spaces, making it impossible to use air gouging or backing welding. Ensuring the required penetration depth presents a significant challenge in bevel design and welding process selection.

[0004] Therefore, how to select a suitable welding process for Q550D high-strength steel to meet the design requirements for weld quality and ensure excellent weld appearance is an urgent problem to be solved. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide an automatic welding method for Q550D high-strength steel using a flat-position robot, which involves single-sided welding and double-sided forming without backing or root cleaning.

[0006] Technical solution: The automatic welding method for Q550D high-strength steel using a parallel-position robot according to the present invention includes the following steps:

[0007] (1) Perform welding beveling, leaving no blunt edge, and the gap at the root of the beveling is 1-3mm;

[0008] (2) Solid argon-rich gas shielded welding is used for the root pass welding, and no backing is provided on the back of the weld; the welding current is 126-154A, the welding voltage is 16-20V, and the welding speed is 180-220mm / min.

[0009] (3) The filler layer is welded using CO2 gas shielded welding with flux-cored wire; the welding current is 165-195A, the welding voltage is 18-22V, and the welding speed is 180-220mm / min.

[0010] (4) The cover layer is welded by a robot automatic welding with CO2 gas protection using flux-cored welding wire; the welding current is 190-230A, the welding voltage is 22-26V, and the welding speed is 200-240mm / min.

[0011] In this invention, welding of Q550D high-strength steel thin plates is preferred; a V-shaped bevel is preferably opened with a bevel angle of 57° to 63°.

[0012] In step (2), the solid welding wire used for the bottom layer is model G69A4M21ZN2M4T, and its chemical composition by mass percentage is as follows: C≤0.12%, Si=0.40%~0.90%, Mn=1.50%~2.00%, P≤0.020%, S≤0.015%, Cr≤0.15%, Ni=0.50%~1.50%, Mo=0.20%~0.60%, V≤0.05%, with the balance being Fe; the protective gas is an argon-rich mixture, 80%Ar+20%CO2.

[0013] The filler and capping layer flux-cored welding wire used is model T624T1-1C1A-GXU, with the following chemical composition by mass percentage: C≤0.10%, Si≤0.80%, Mn=1.00%~1.80%, P≤0.020%, S≤0.015%, Cr≤0.2%, Ni=0.80%~2.00%, Cu≤0.2%, with the balance being Fe; the shielding gas is CO2 with a purity ≥99.9%.

[0014] In step (2), for the root pass welding, the power supply polarity is DC reverse polarity, the dry extension is 12-18mm, the shielding gas flow rate is 15-25L / min, and the heat input is 5.5-10.3KJ / cm.

[0015] In step (3), for the welding of the filler layer, the power supply polarity is DC reverse polarity, the dry extension is 12-18mm, the shielding gas flow rate is 15-25L / min, and the heat input is 8.1-14.3KJ / cm.

[0016] In step (3), the filler layer is welded using a flux-cored wire CO2 gas shielded semi-automatic welding or a robot automatic welding; when the filler layer is welded using a flux-cored wire CO2 gas shielded robot automatic welding, the wire feeding speed is 120-130 m / min.

[0017] In step (4), for the welding of the cover layer, the power supply polarity is DC reverse polarity, the dry extension is 12-18mm, the protective gas flow rate is 15-25L / min, and the heat input is 10.5-17.9KJ / cm.

[0018] In step (4), the wire feeding speed is 120-130 m / min during robot automatic welding; the oscillation frequency is 4-6 Hz, the oscillation amplitude is 3-4 mm, the left dwell time is 0-0.1 s, and the right dwell time is 0-0.1 s; the oscillation frequency is 7-9 Hz, the oscillation amplitude is 6-7 mm, the left dwell time is 0-0.2 s, and the right dwell time is 0-0.2 s.

[0019] Invention Principle: Compared with existing technologies, this invention mainly innovates in single-sided welding with double-sided forming technology, solving the welding problem of single-sided welding with double-sided forming butt welds in confined spaces (such as the inner cavity of guardrail posts) where backing cannot be applied and root cleaning is not possible. Through experimental welding with predetermined welding parameters, it was found that under conventional flat welding process parameters, the flat root pass weld formation was poor and prone to burn-through. After multiple experiments, the welding current and voltage parameters were gradually reduced, and the welding operation method was specifically optimized. The post-weld formation was observed and compared to determine the required welding parameter configuration. Under these welding parameters, the root pass weld of the Q550D high-strength steel flat butt weld formed well, the appearance quality was effectively guaranteed, and the internal quality and mechanical properties of the weld were excellent.

[0020] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects: (1) The present invention solves the welding problem of single-sided double-sided forming butt welds without backing or root cleaning, and can effectively ensure the first-time flaw detection pass rate of butt welds. (2) The present invention adopts a robotic automatic welding method with flux-cored welding wire for cover welding, which has a high degree of automation in the welding process and the appearance of the weld after welding is uniform and beautiful. (3) Using the welding method of the present invention, the weld after welding has good strength indicators and excellent low-temperature impact toughness indicators, which meet the impact resistance requirements of high-strength anti-collision guardrails. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the robotic automatic welding equipment of the present invention;

[0022] Figure 2These are schematic diagrams of the joint bevels in embodiments 1 and 2 of the present invention;

[0023] Figure 3 This is a physical image of the joint bevel according to Embodiment 1 of the present invention;

[0024] Figure 4 These are schematic diagrams of weld deposition in embodiments 1 and 2 of the present invention;

[0025] Figure 5 This is a physical image of the root pass weld in Comparative Example 1 of the present invention. Detailed Implementation

[0026] The present invention will now be described in further detail.

[0027] Example 1

[0028] The chemical composition of the Q550D bridge structural steel used in this embodiment is shown in Table 1, and its mechanical properties are shown in Table 2.

[0029] Table 1 Chemical Composition of Q550D Bridge Structural Steel (t8) Base Material

[0030]

[0031] Table 2 Mechanical Properties of Q550D Bridge Structural Steel (t8) Base Material

[0032]

[0033] In this embodiment, the test steel plate to be welded is 8mm thick and has dimensions of 8×200×800mm. The joint bevel type is shown below. Figure 2 , 3 The weld bevel is V-shaped. The root pass welding material is G69A4M21ZN2M4T, with a wire diameter of Φ1.2mm, and the shielding gas is an argon-rich mixture (80% Ar + 20% CO2). The fill and cap coat welding material is T624T1-1C1A-GXU, with a wire diameter of Φ1.2mm, and the shielding gas is 100% CO2. The robotic automatic welding equipment uses a Diman DMKJ welding machine. Figure 1 As shown, the robot body mainly includes a welding torch 1, a welding robotic arm 2, a wire feeding mechanism 3, a wire spool 4, a base 5, a support platform 6, a welding power source 7, a welding workpiece 8, and a workpiece placement bench 9. During welding, the welding workpiece can be placed on the bench to meet the operating range of the robot's rotating arm. The power supply polarity is reverse DC.

[0034] The chemical composition of the core of the solid welding wire G69A4M21ZN2M4T (Φ1.2) is shown in Table 3, and the mechanical properties of the cladding metal are shown in Table 4. The chemical composition of the core of the flux-cored welding wire T624T1-1C1A-GXU (Φ1.2) is shown in Table 5, and the mechanical properties of the cladding metal are shown in Table 6.

[0035] Table 3 Chemical composition of the core wire of G69A4M21ZN2M4T (Φ1.2) solid welding wire

[0036]

[0037] Table 4 Mechanical Properties of Clad Metal of G69A4M21ZN2M4T (Φ1.2) Solid Welding Wire

[0038]

[0039] Table 5 Chemical composition of the core wire of T624T1-1C1A-GXU (Φ1.2) flux-cored welding wire

[0040]

[0041] Table 6 Mechanical Properties of Coated Metal of T624T1-1C1A-GXU (Φ1.2) Flux-Cored Welding Wire

[0042]

[0043] Perform welding according to the following steps:

[0044] (1) Welding beveling:

[0045] like Figure 2 As shown, after machining or flame cutting, clean the rust, oil and other impurities within 20mm on both sides of the bevel of the two butt steel plates to expose the metallic luster; the bevel is a V-shaped bevel, and the bevel angle formed by the two steel plates is 60°, without leaving any blunt edges;

[0046] (2) Make a 2mm gap at the root of the bevel and perform tack welding assembly;

[0047] (3) Solid argon-rich gas shielded welding is used for the root pass:

[0048] The welding current for the root pass is 126–154 A, the welding voltage is 16–20 V, the welding speed is 180–220 mm / min, the power supply polarity is DC reverse polarity, the weld extension is 12–18 mm, the shielding gas flow rate is 15–25 L / min, and the heat input is 5.5–10.3 KJ / cm. Welding process parameters are shown in Table 8.

[0049] When welding the root pass, a certain gap is controlled and no backing is used on the back. When starting to weld, the welding torch is slightly off-center from the weld seam and the arc is struck at the bottom of the bevel. In areas with small gaps, continuous arc welding can be used with a slightly higher welding speed to prevent burn-through. In areas with large gaps, intermittent arc welding can be used with a slower welding speed to ensure good root fusion. In this way, full penetration of the root weld can be achieved without backing, root cleaning, single-sided welding, and double-sided forming.

[0050] (4) Filler layer welding was performed using CO2 gas shielded semi-automatic welding with flux-cored wire:

[0051] The welding current for the filler layer is 165–195 A, the welding voltage is 18–22 V, the welding speed is 180–220 mm / min, the power supply polarity is DC reverse polarity, the weld extension is 12–18 mm, the shielding gas flow rate is 15–25 L / min, and the heat input is 8.1–14.3 KJ / cm. Welding process parameters are shown in Table 8.

[0052] (5) Cover layer welding was performed using a robotic automated welding system with CO2 gas shielded flux-cored wire:

[0053] The welding current for the capping layer is 190–230 A, the welding voltage is 22–26 V, the welding speed is 200–240 mm / min, the power supply polarity is DC reverse polarity, the weld extension is 12–18 mm, the shielding gas flow rate is 15–25 L / min, and the heat input is 10.5–17.9 KJ / cm. The process parameters for the robotic automatic welding of the capping layer are shown in Table 7, and the welding process parameters are shown in Table 8.

[0054] Table 7. Process parameters for robot-automated welding of cap layer in Example 1

[0055]

[0056] Table 8 Welding process parameters for Example 1

[0057]

[0058] See the schematic diagram of weld bead deposition. Figure 4 The mechanical properties of the welded joints are shown in Table 11.

[0059] Example 2

[0060] The steel plate dimensions, bevel type, and other conditions are basically the same as in Example 1. Welding is performed according to the following steps:

[0061] (1) Welding beveling:

[0062] like Figure 2After machining or flame cutting, clean the rust, oil and other impurities within 20mm on both sides of the bevel of the two butt steel plates to expose the metallic luster; the bevel is a V-shaped bevel with a bevel angle of 60° formed by the two steel plates, leaving no blunt edge.

[0063] (2) Make a 2mm gap at the root of the bevel and perform tack welding assembly;

[0064] (3) Solid argon-rich gas shielded welding is used for the root pass:

[0065] The welding current for the root pass is 126–154 A, the welding voltage is 16–20 V, the welding speed is 180–220 mm / min, the power supply polarity is DC reverse polarity, the dry extension is 12–18 mm, the shielding gas flow rate is 15–25 L / min, and the heat input is 5.5–10.3 KJ / cm; the welding process parameters are shown in Table 10.

[0066] When welding the root pass, a certain gap is controlled and no backing is used on the back. When starting to weld, the welding torch is slightly off-center from the weld seam and the arc is struck at the bottom of the bevel. In areas with small gaps, continuous arc welding can be used with a slightly higher welding speed to prevent burn-through. In areas with large gaps, intermittent arc welding can be used with a slower welding speed to ensure good root fusion. In this way, full penetration of the root weld can be achieved without backing, root cleaning, single-sided welding, and double-sided forming.

[0067] (4) Filler layer welding was performed using a robotic automated welding system with CO2 gas shielded flux-cored wire:

[0068] The welding current for the filler layer is 165–195 A, the welding voltage is 18–22 V, the welding speed is 180–220 mm / min, the power supply polarity is DC reverse polarity, the weld extension is 12–18 mm, the shielding gas flow rate is 15–25 L / min, and the heat input is 8.1–14.3 KJ / cm. The process parameters for robotic automatic welding of the filler layer are shown in Table 9, and the welding process parameters are shown in Table 10.

[0069] (5) Cover layer welding was performed using a robotic automated welding system with CO2 gas shielded flux-cored wire:

[0070] The welding current for the capping layer is 190–230 A, the welding voltage is 22–26 V, the welding speed is 200–240 mm / min, the power supply polarity is DC reverse polarity, the weld extension is 12–18 mm, the shielding gas flow rate is 15–25 L / min, and the heat input is 10.5–17.9 KJ / cm. The process parameters for the robotic automatic welding of the capping layer are shown in Table 9, and the welding process parameters are shown in Table 10.

[0071] Table 9. Process parameters for robot-automated welding of filler and capping layers in Example 2.

[0072]

[0073] See the schematic diagram of weld bead deposition. Figure 4 The mechanical properties of the welded joints are shown in Table 11.

[0074] Table 10 Welding process parameters for Example 2

[0075]

[0076] Table 11 Mechanical properties of welded test plates from Examples 1 and 2

[0077]

[0078] Example 3

[0079] Based on Example 1, the difference from Example 1 is that the robot automatically welds the cover layer process parameters are shown in Table 12, and the welding process parameters are shown in Table 13.

[0080] Table 12 Process parameters for robot-automated welding of the cap layer in Example 3

[0081]

[0082] Table 13 Welding process parameters for Example 3

[0083]

[0084] Example 4

[0085] Based on Example 1, the difference from Example 1 is that the robot automatically welds the cover layer process parameters are shown in Table 14, and the welding process parameters are shown in Table 15.

[0086] Table 14 Process parameters for robot-automated welding of cap layer in Example 4

[0087]

[0088] Table 15 Welding process parameters for Example 4

[0089]

[0090] Comparative Example 1

[0091] Based on Example 1, the difference is that the current parameters used are 200±20A, the voltage is 24±2V, and the welding speed is 240±20mm / min. These welding parameter values ​​are relatively large, resulting in poor weld formation. Figure 5 As shown, Figure 5The left frame shows the weld formation of the root pass under the larger welding parameters, with burn-through on the back side. After adjusting the welding parameters multiple times on other test plates, it was determined that welding under the welding parameters in Example 1 resulted in a good root pass weld formation and no appearance defects such as burn-through on the back side. Figure 5 Under the welding parameters of Example 1, the right-side continuous weld was formed.

[0092] This invention employs a composite welding method combining solid argon-rich gas shielded welding and flux-cored wire robotic automatic welding. The resulting welds exhibit excellent formation, and their appearance quality meets the requirements of Table 4.9.12 in the "Railway Steel Bridge Manufacturing Specification" (Q / CR9211-2015). After UT ultrasonic testing, the internal quality of the welds meets the Class I requirements in the "Railway Steel Bridge Manufacturing Specification" (Q / CR9211-2015). The weld yield strength, tensile strength, elongation after fracture, and tensile strength of the butt joint are all greater than the standard values ​​of the base metal (referring to GB / T1591-2018 standard); the weld is intact in the bending test of the joint (referring to Q / CR 9211-2015 standard); the Charpy impact energy of the weld and heat-affected zone at -20℃ of the joint is ≥47J (referring to GB / T 1591-2018 standard), and the average value exceeds the standard value by about 3 times, indicating a high degree of low-temperature impact reserve; the highest hardness HV10 of the three zones of the welded joint is ≤380 (referring to Q / CR9211-2015 standard).

[0093] In summary, the embodiments of this application employ a robotic automatic welding method for Q550D high-strength steel. By designing reasonable welding grooves and welding process parameters and measures, and adapting to the use of G69A4M21ZN2M4T (Φ1.2) solid welding wire for the root pass and T624T1-1C1A-GXU (Φ1.2) flux-cored welding wire for the filler and cover passes, the resulting welded joint exhibits excellent appearance and internal quality. All mechanical properties of the welded joint meet the requirements of relevant standards (Q / CR9211-2015 and GB / T 1591-2018), thus verifying the operability and applicability of the proposed robotic automatic composite welding method.

[0094] This invention will be widely applied to the construction of the Lingdingyang Bridge of the Shenzhen-Zhongshan Bridge and the Gaolan Port Bridge of the Huangmaohai Cross-Sea Channel, and has important demonstrative and reference significance for solving the welding problem of Q550 grade high-strength steel anti-collision guardrails.

Claims

1. An automated welding method for Q550D high-strength steel using a parallel welding robot, characterized in that, Includes the following steps: (1) Perform welding beveling without leaving blunt edges, and the gap at the root of the beveling is 1-3mm; open a V-shaped beveling with a beveling angle of 57°-63°, and do not place a backing on the back of the weld. (2) Solid argon-rich gas shielded welding is used for the root pass welding; the welding current is 126~154A, the welding voltage is 16~20V, the welding speed is 180~220mm / min, the dry extension is 12~18mm, the shielding gas flow rate is 15~25L / min, and the heat input is 5.5~10.3KJ / cm; (3) The filler layer is welded using CO2 gas shielded welding with flux-cored wire; the welding current is 165~195A, the welding voltage is 18~22V, the welding speed is 180~220mm / min, the dry extension is 12~18mm, the shielding gas flow rate is 15~25L / min, and the heat input is 8.1~14.3KJ / cm; when the filler layer is automatically welded by robot, the wire feeding speed is 120~130m / min, the oscillation frequency is 4~6Hz, the oscillation amplitude is 3~4mm, the left dwell time is 0~0.1s, and the right dwell time is 0~0.1s. (4) The cover layer welding is performed by a robot automatic welding with CO2 gas shielded by flux-cored wire; the welding current is 190~230A, the welding voltage is 22~26V, the welding speed is 200~240mm / min, the dry extension is 12~18mm, the shielding gas flow rate is 15~25L / min, and the heat input is 10.5~17.9KJ / cm; when the cover layer is automatically welded by the robot, the wire feeding speed is 120~130m / min, the oscillation frequency is 7~9Hz, the oscillation amplitude is 6~7mm, the left dwell time is 0~0.2s, and the right dwell time is 0~0.2s.

2. The automatic welding method for Q550D high-strength steel using a parallel-position robot according to claim 1, characterized in that, In step (2), solid welding wire is used for the bottom layer. The solid welding wire is of type G69A4M21ZN2M4T and its chemical composition by mass percentage is as follows: C≤0.12%, Si=0.40%~0.90%, Mn=1.50%~2.00%, P≤0.020%, S≤0.015%, Cr≤0.15%, Ni=0.50%~1.50%, Mo=0.20%~0.60%, V≤0.05%, and the balance is Fe.

3. The automatic welding method for Q550D high-strength steel using a parallel-position robot according to claim 1, characterized in that, In steps (3) and (4), the flux-cored wire for the filler layer and the cover layer is model T624T1-1C1A-GXU, and its chemical composition by mass percentage is as follows: C≤0.10%, Si≤0.80%, Mn=1.00%~1.80%, P≤0.020%, S≤0.015%, Cr≤0.2%, Ni=0.80%~2.00%, Cu≤0.2%, and the balance is Fe.

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