Welding method for S450J0 hot-rolled H-shaped steel

Abstract

The invention discloses a welding method for S450J0 hot-rolled H-shaped steel. The welding method comprises the steps that S1, a welding joint is machined to form a groove structure; s2, preheating treatment is conducted, specifically, the base metal is preheated, and the preheating temperature of the base metal is larger than or equal to 60 DEG C; s3, welding is conducted, specifically, CO2 gas shielded welding is adopted, multi-layer and multi-pass surfacing welding is adopted, and the interlayer temperature is smaller than or equal to 250 DEG C; and S4, heat preservation treatment is conducted, specifically, heat preservation treatment is conducted on a welded joint after welding, and the heat preservation temperature ranges from 170 DEG C to 210 DEG C. By means of the S450J0 hot-rolled H-shaped steel welding method, a welded joint can obtain the same mechanical property as a base material, and the engineering use requirement is met.

Description

Technical Field

[0001] This invention belongs to the field of metal material welding technology, specifically relating to a method for welding thick flange corner joints of heavy hot-rolled H-beams. Background Technology

[0002] Hot-rolled H-beams, with their uniform cross-sectional properties, stable quality, ease of processing, and short construction cycle, have become a readily standardized structural material. As an environmentally friendly steel structural material, hot-rolled H-beams are widely used in transportation, construction, bridges, and offshore oil platforms. Among them, S450J0 hot-rolled H-beams are particularly outstanding, with a yield strength exceeding 490MPa, a tensile strength exceeding 610MPa, and an elongation after fracture greater than 20%. These superior properties make them highly favored in construction projects and have led to their widespread application.

[0003] Welding is a crucial connection method for heavy hot-rolled H-beams, especially for S450J0 hot-rolled H-beams. However, due to the large flange thickness of S450J0 hot-rolled H-beams (up to 80mm), the processing dwell time during welding is relatively long, which can easily lead to problems such as grain coarsening, unbalanced microstructure transformation, and hardening in the heat-affected zone. These problems directly affect the mechanical properties of the welded joint, potentially causing substandard performance or even cracking, seriously hindering project progress and causing economic losses, posing significant engineering hazards. Although riveting can be used as an alternative connection method in bridge and building construction, it does not support lightweight structural design. Furthermore, the microstructure of S450J0 heavy hot-rolled H-beams differs from that of carbon steel of the same grade, and lower heat input is required in actual welding operations to avoid crack initiation. Therefore, in-depth research into the welding process of S450J0 hot-rolled H-beams and its successful application in practical engineering is particularly necessary and urgent.

[0004] In conclusion, it is necessary to conduct corner joint welding tests on S450J0 hot-rolled H-beams to determine reasonable welding methods and processes so that the welded joints can meet the engineering requirements.

[0005] Chinese patent application number 201610765126.7 discloses a welding method for Q390GJC structural steel, which presents an optimized welding method for Q390GJC structural steel. This method combines submerged arc welding and CO2 gas shielded welding technologies. By preheating to 60℃ before welding and controlling the interpass temperature to 150-200℃, it achieves mechanical properties in the welded joint comparable to the base material, successfully solving the welding challenges of Q390GJC steel and meeting engineering requirements.

[0006] Chinese Patent Application No. 202211025842.3 discloses a method for testing the weldability of hot-rolled H-beams and an apparatus for using this method. The method involves securing the upper and lower hot-rolled H-beams of an I-beam component using an upper sample fastening assembly and a lower sample fastening assembly, respectively. A simulated test environment and test mode are selected, and the weldability test is initiated by applying force to the upper and lower sample fastening assemblies. The two hot-rolled H-beams of the I-beam component are then fixed using the upper and lower sample fastening assemblies. By changing the ambient temperature and applying force to the upper and lower sample fastening assemblies, the method simulates the weldability of the I-beam component under earthquake conditions in different environments.

[0007] Chinese Patent Application No. 202222245142.7 discloses a welding performance testing system for hot-rolled H-beams, belonging to the field of welding performance testing for hot-rolled H-beams. The system includes a frame, an upper sample fastening assembly, a lower sample fastening assembly, a horizontal moving assembly, and an upper / lower moving assembly. The upper / lower moving assembly and / or the horizontal moving assembly are fixedly installed within the frame, and the upper sample fastening assembly and / or the lower sample fastening assembly are fixedly installed at the output end of the upper / lower moving assembly and / or the horizontal moving assembly. The upper and lower sample fastening assemblies are used to fix the upper and lower hot-rolled H-beams of the H-beam structure. The horizontal moving assembly applies a horizontal force to the upper and lower hot-rolled H-beams, while the upper / lower moving assembly applies a vertical compressive or tensile load. The coordination between the horizontal and upper / lower moving assemblies simulates the alternating diagonal load tension of the structural member during an earthquake.

[0008] The aim is to provide an improved method for welding thick flange corner joints of heavy-duty hot-rolled H-beams, particularly regarding how to achieve the same mechanical properties as the base material in the welded joint to meet engineering requirements. Summary of the Invention

[0009] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a welding method for S450J0 hot-rolled H-beams, with the purpose of enabling the welded joint to achieve mechanical properties equivalent to the base material, thus meeting engineering application requirements.

[0010] To achieve the above objectives, the technical solution adopted by this invention is: a welding method for S450J0 hot-rolled H-beams, comprising the following steps:

[0011] S1. A bevel structure is formed at the welded joint;

[0012] S2. Preheating treatment:

[0013] The base material is preheated to a temperature ≥60℃.

[0014] S3, Welding:

[0015] CO2 gas shielded welding is performed using multi-layer, multi-pass surfacing welding with an interpass temperature ≤250℃.

[0016] S4. Thermal insulation treatment:

[0017] After welding, the welded joint is insulated at a temperature of 170–210℃.

[0018] In step S3, the welding wire is subjected to heat preservation and drying treatment before welding, with the heat preservation temperature ≤200℃.

[0019] The time for heat preservation and drying of the welding wire is 2.5 to 3.5 hours.

[0020] The welding joints are of the form of T-type corner joints and L-type corner joints.

[0021] In step S3, the bevel structure adopts a double-sided V-shaped bevel with a bevel angle of 60°.

[0022] In step S3, the root pass welding is performed using CO2 gas shielded welding, with CHT711 flux-cored welding wire, a wire diameter of 1.2 mm, a welding current of 180–240 A, a voltage of 25–33 V, a welding speed of 13–25 cm / min, and a line energy of 10.8–36.5 kJ / cm.

[0023] In step S3, the filler welding adopts the submerged arc welding method, the shielding gas is 80% Ar + 20% CO2, the welding wire is ER50-6 flux-cored welding wire with a diameter of 5mm, the welding current is 600-800A, the welding voltage is 28-36V, the welding speed is 40-70cm / min, and the heat input is 14.4-43.2kJ / cm.

[0024] In step S3, the cover welding adopts submerged arc welding method, the shielding gas is 80% Ar + 20% CO2, the welding wire is ER50-6 flux-cored welding wire with a diameter of 5mm, the welding current is 650-800A, the welding voltage is 34-38V, the welding speed is 40-70cm / min, and the heat input is 18.9-45.6kJ / cm.

[0025] In step S3, the base material is the flange of S450J0 hot-rolled H-beam, with a flange thickness of 50-80mm. The base material is welded at room temperature of 10-30℃.

[0026] The S450J0 hot-rolled H-beam welding method of the present invention enables the welded joint to obtain the same mechanical properties as the base material, thus meeting the requirements of engineering use. Attached Figure Description

[0027] This manual includes the following figures, which illustrate the following:

[0028] Figure 1 This is a flowchart of the welding method for S450J0 hot-rolled H-beams of the present invention;

[0029] Figure 2 This is a schematic diagram of a T-type corner weld joint;

[0030] Figure 3 This is a schematic diagram of an L-shaped corner weld joint;

[0031] Figure 4 This is a schematic diagram of the weld bead layout for Implementation Case 1;

[0032] Figure 5 This is a schematic diagram of the weld bead layout for Implementation Case 2;

[0033] Figure 6 This is a schematic diagram of the weld bead layout for Implementation Case 3;

[0034] Figure 7 This is a schematic diagram of the weld layout in Implementation Case 4. Detailed Implementation

[0035] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation.

[0036] like Figure 1 As shown, the present invention provides a welding method for S450J0 hot-rolled H-beams, comprising the following steps:

[0037] S1. A bevel structure is formed at the welded joint;

[0038] S2. Preheating treatment:

[0039] The base material is preheated to a temperature ≥60℃.

[0040] S3, Welding:

[0041] CO2 gas shielded welding is performed using multi-layer, multi-pass surfacing welding with an interpass temperature ≤250℃.

[0042] S4. Thermal insulation treatment:

[0043] After welding, the welded joint is insulated at a temperature of 170–210℃.

[0044] Specifically, the base material is the flange of S450J0 hot-rolled H-beam, with a thickness of 50–80 mm. The welded joints are T-type and L-type corner joints.

[0045] T-shaped corner welded joints, such as Figure 2 As shown, a T-shaped corner weld joint refers to a structure in which two base materials form a T-shape at the joint, with the end of one base material forming a right angle or near right angle with the surface of the other base material, and are connected together by welding.

[0046] L-shaped corner weld joints, such as Figure 3 As shown, an L-shaped corner weld joint refers to a structure in which two base materials form an L-shape at the joint, with the end of one base material forming a right angle or near right angle with the end surface of the other base material, and are connected together by welding.

[0047] In step S2 above, the base material is preheated before welding, and the preheating temperature is set reasonably to avoid cold cracking defects at the joint.

[0048] In step S3 above, the welding wire is subjected to heat preservation and drying treatment before welding, with the heat preservation temperature ≤200℃. The heat preservation and drying time for the welding wire is 2.5 to 3.5 hours, preferably 3.0 hours. This setting can reduce the probability of the welding wire surface rusting when exposed to air and avoid cold cracking caused by hydrogen increase in the weld during welding.

[0049] In step S3 above, multi-layer, multi-pass welding is used, with an interpass temperature ≤250℃. This setup improves the quality of the weld metal, as each subsequent weld layer acts as a heat treatment for the preceding layer, effectively performing a normalizing process and improving the secondary microstructure.

[0050] In step S3 above, during the full penetration welding process of the flange base material of S450J0 with a thickness of 50-80mm, a double-sided V-groove with a groove angle of 60° is adopted. Specifically: the root pass welding uses CO2 gas shielded welding with CHT711 flux-cored wire of 1.2mm diameter, a welding current of 180-240A, a voltage of 25-33V, a welding speed of 13-25cm / min, and a thermal energy of 10.8-36.5kJ / cm; the fill pass welding uses submerged arc welding with a shielding gas of 80% Ar + 20% CO2, and the welding wire is... The welding wire used is ER50-6 flux-cored wire with a diameter of 5mm. The welding current is 600-800A, the welding voltage is 28-36V, the welding speed is 40-70cm / min, and the heat input is 14.4-43.2kJ / cm. The cover pass welding uses submerged arc welding with a shielding gas of 80%Ar + 20%CO2. The welding wire is ER50-6 flux-cored wire with a diameter of 5mm. The welding current is 650-800A, the welding voltage is 34-38V, the welding speed is 40-70cm / min, and the heat input is 18.9-45.6kJ / cm.

[0051] In step S3 above, the base material is the flange of S450J0 hot-rolled H-beam, with a flange thickness of 50-80mm. The base material is welded at room temperature of 10-30℃.

[0052] In step S4 above, the welded joint is subjected to post-weld heat treatment at a temperature of 170–210℃ for at least 2 hours. This post-weld heat treatment, with its carefully set temperature and time, aims to prevent cold cracking defects at the joint. Too low a temperature or too short a time will hinder hydrogen release and increase the risk of cold cracking; too high a temperature or too long a time will lead to coarse grains in the joint structure, reducing its mechanical properties. Tests conducted using the specified temperature and time parameters showed good weld joint quality.

[0053] This invention addresses the compositional range and technical conditions of S450J0 hot-rolled H-beams, providing a solution for achieving full penetration welding of flange corner joints in hot-rolled H-beams with flange thicknesses of 50-80mm. Specifically, the method includes: 1) proposing reasonable bevel shapes and welding methods based on the joint type and base metal thickness; 2) specifying preheating and post-weld holding temperatures to prevent cold cracking defects at the joint; 3) selecting appropriate welding materials based on the joint type, bevel shape, and welding method; and 4) proposing suitable welding process parameters. Using this solution for full penetration welding of S450J0 hot-rolled H-beam flange corner joints ensures the quality of the welded joint and meets the engineering requirements.

[0054] The specific embodiments of the present invention will be further described in detail below through the description of implementation examples.

[0055] The chemical composition of S450J0 hot-rolled H-beams is shown in Table 1, and the mechanical properties are shown in Table 2.

[0056] Table 1 Chemical composition of S450J0 hot-rolled H-beam (unit: wt%)

[0057] C Si Mn P S V N ≤0.20 ≤0.55 ≤1.60 ≤0.030 ≤0.030 ≤0.130 ≤0.025

[0058] Table 2 Mechanical Properties of S450J0 Hot-Rolled H-Beams

[0059]

[0060] In step S2 above, the base material comprises the following components by mass percentage:

[0061] C≤0.20%, Si≤0.55%, Mn≤1.60%, P≤0.030%, S≤0.030%, N≤0.025%, V≤0.130%, with the remainder being Fe and trace residual elements.

[0062] Implementation Case 1

[0063] The S450J0 flange thickness is 50mm thick, and a T-type full penetration weld is performed using CO2 gas shielded welding for the root pass and submerged arc welding. The two base materials are 400*100*50mm in size. See [link to details] for bevel dimensions and joint specifications. Figure 2 As shown, a schematic diagram of the weld bead arrangement is available. Figure 4 As shown.

[0064] Implementation Case 2

[0065] The S450J0 flange has a 50mm flange thickness and L-shaped full penetration weld. The welding method involves CO2 gas shielded welding for the root pass and submerged arc welding. The two base materials are 400*100*50mm in size. See [link to details] for bevel dimensions and joint specifications. Figure 3 As shown, a schematic diagram of the weld bead arrangement is available. Figure 5 As shown.

[0066] Implementation Case 3

[0067] The S450J0 flange thickness is 70mm thick, and a T-type full penetration weld is performed using CO2 gas shielded welding for the root pass and submerged arc welding. The two base materials are 200*100*70mm in size. See details for bevel dimensions and joint specifications. Figure 2 As shown, a schematic diagram of the weld bead arrangement is available. Figure 6 As shown.

[0068] Implementation Case 4

[0069] The S450J0 flange has a 70mm flange thickness and L-shaped full penetration weld. The welding method involves CO2 gas shielded welding for the root pass and submerged arc welding. The two base materials are 200*100*70mm in size. See [link to details] for bevel dimensions and joint specifications. Figure 3 As shown, a schematic diagram of the weld bead arrangement is available. Figure 7 As shown.

[0070] Welding was carried out for the above-mentioned joint types and welding methods, and the relevant processes are shown in Table 3.

[0071] Table 3 Implementation Cases

[0072]

[0073] The root pass welding material involved in this invention is CHT711 flux-cored welding wire with a diameter of 1.2 mm, and CO2 gas shielded welding is used with DC reverse polarity; the fill pass welding is performed using submerged arc welding with a shielding gas of 80% Ar + 20% CO2, and the welding wire is ER50-6 flux-cored welding wire with a diameter of 5 mm.

[0074] The effects of implementing this invention are as follows:

[0075] Visual inspection: The weld surface is well formed and there are no welding defects.

[0076] Non-destructive testing of welds: Ultrasonic testing is used, and the evaluation level is Level II, indicating that the internal quality of the welds is qualified.

[0077] Sample processing and inspection:

[0078] Hardness testing was performed in accordance with the "Test Method for Hardness of Welded Joints" GB / T2654.

[0079] The impact test specimens were processed in accordance with the "Impact Test Method for Welded Joints" GB / T2650.

[0080] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A welding method for S450J0 hot-rolled H-beams, characterized in that, Including the following steps: S1. A bevel structure is formed at the welded joint; S2. Preheating treatment: The base material is preheated to a temperature ≥60℃. S3, Welding: CO2 gas shielded welding is performed using multi-layer, multi-pass surfacing welding with an interpass temperature ≤250℃. S4. Thermal insulation treatment: After welding, the welded joint is insulated at a temperature of 170–210℃.

2. The welding method for S450J0 hot-rolled H-beams according to claim 1, characterized in that, In step S3, the welding wire is subjected to heat preservation and drying treatment before welding, with the heat preservation temperature ≤200℃.

3. The welding method for S450J0 hot-rolled H-beams according to claim 2, characterized in that, The time for heat preservation and drying of the welding wire is 2.5 to 3.5 hours.

4. The welding method for S450J0 hot-rolled H-beams according to any one of claims 1 to 3, characterized in that, The welding joints are of the form of T-type corner joints and L-type corner joints.

5. The welding method for S450J0 hot-rolled H-beams according to any one of claims 1 to 3, characterized in that, In step S3, the bevel structure adopts a double-sided V-shaped bevel with a bevel angle of 60°.

6. The welding method for S450J0 hot-rolled H-beams according to claim 5, characterized in that, In step S3, the root pass welding is performed using CO2 gas shielded welding, with CHT711 flux-cored welding wire, a wire diameter of 1.2 mm, a welding current of 180–240 A, a voltage of 25–33 V, a welding speed of 13–25 cm / min, and a line energy of 10.8–36.5 kJ / cm.

7. The welding method for S450J0 hot-rolled H-beams according to claim 5, characterized in that, In step S3, the filler welding adopts the submerged arc welding method, the shielding gas is 80% Ar + 20% CO2, the welding wire is ER50-6 flux-cored welding wire with a diameter of 5mm, the welding current is 600-800A, the welding voltage is 28-36V, the welding speed is 40-70cm / min, and the heat input is 14.4-43.2kJ / cm.

8. The welding method for S450J0 hot-rolled H-beams according to claim 5, characterized in that, In step S3, the cover welding adopts submerged arc welding method, the shielding gas is 80% Ar + 20% CO2, the welding wire is ER50-6 flux-cored welding wire with a diameter of 5mm, the welding current is 650-800A, the welding voltage is 34-38V, the welding speed is 40-70cm / min, and the heat input is 18.9-45.6kJ / cm.

9. The welding method for S450J0 hot-rolled H-beams according to any one of claims 1 to 8, characterized in that, In step S3, the base material is the flange of S450J0 hot-rolled H-beam, with a flange thickness of 50-80mm. The base material is welded at room temperature of 10-30℃.

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