A welding method for Q355ME hot-rolled H-beams with flange thickness of 30-50mm

Abstract

This invention discloses a welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm, comprising the following steps: 1) forming a bevel structure at the weld joint; 2) preheating treatment: preheating both the welding wire and the hot-rolled H-beam base material, with the preheating temperature of the hot-rolled H-beam base material ≥60℃; 3) welding: CO2 gas shielded welding, using multi-layer, multi-pass surfacing welding; 4) heat preservation treatment: heat preservation treatment of the weld joint after welding, with a heat preservation temperature of 160-180℃. This invention uses a single-sided bevel, and by reasonably controlling the preheating temperature before welding and the heat preservation temperature after welding, crack defects at the weld joint can be effectively avoided, and the mechanical properties of the weld joint are basically the same as those of the base material.

Description

Technical Field

[0001] This invention relates to the field of hot-rolled H-beam welding technology, and in particular to a welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm. Background Technology

[0002] Hot-rolled H-beams have good cross-sectional uniformity, stable quality, simple processing, short construction cycle, and are easy to standardize components. Q355ME hot-rolled H-beams have a yield strength of over 355MPa, a tensile strength of 470-630MPa, and an elongation after fracture of over 22%. As an environmentally friendly steel structure material, they are widely used in transportation, construction, bridges, and offshore oil platforms.

[0003] Welding is one of the important connection methods for heavy hot-rolled H-beams. However, Q355ME hot-rolled H-beams have large flange thickness (30-50mm), and the processing dwell time during welding is long. This leads to key issues such as grain coarsening, unbalanced microstructure transformation, and hardening in the heat-affected zone, which directly affect the mechanical properties of the welded joint. Inconsistent performance or even cracking can seriously affect the progress of the project and cause economic losses, posing significant hidden dangers. Although riveting can be used in bridges and buildings, it cannot achieve lightweighting. Therefore, it is essential to study the welding process of Q355ME hot-rolled H-beams and apply it to practical engineering projects.

[0004] In summary, welding tests are needed on Q355ME hot-rolled H-beams to determine reasonable welding methods and processes so that the welded joints can meet the engineering requirements. Currently, welding methods for other steels are not suitable for welding H-beams with relatively large flange thicknesses. For example, Chinese patent CN106270951A discloses a welding method for Q420GJC steel used in building structures, which involves welding slabs with a thickness of 3-50mm at room temperature of -10 to 0℃ using CO2+Ar gas shielded welding or submerged arc welding. The method includes: 1) preheating temperature before welding to avoid cold cracking at the joint; 2) proposing reasonable bevel shapes and welding methods according to the joint type and plate thickness; 3) selecting appropriate welding materials based on the joint type, bevel shape, and welding method; and 4) proposing appropriate welding process parameters. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm. The welded joint has essentially the same mechanical properties as the base material, is stable and reliable, and is not prone to cracking.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] The welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm includes the following steps:

[0008] 1) The welded joint is machined to form a bevel structure;

[0009] 2) Preheating treatment:

[0010] Both the welding wire and the hot-rolled H-beam base material are preheated, and the preheating temperature of the hot-rolled H-beam base material is ≥60℃.

[0011] 3) Welding:

[0012] CO2 gas shielded welding is performed using multi-layer, multi-pass surfacing welding.

[0013] 4) Thermal insulation treatment:

[0014] After welding, the welded joint is insulated at a temperature of 160–180℃.

[0015] in,

[0016] In the aforementioned welding method, the welding operation is performed at a room temperature of 10–30°C.

[0017] The bevel structure is a single-sided inclined bevel.

[0018] After step 2), the welding wire is CHT711 flux-cored welding wire with a diameter of 1-1.4 mm. The welding wire is dried in a drying oven for 2.5-3.5 hours before welding, with a holding temperature ≤200℃.

[0019] In step 3), the welding joint is either a butt flat weld or a butt horizontal weld.

[0020] In step 3), the interlayer temperature is ≤200℃.

[0021] In step 4), the heat preservation time is ≥2h.

[0022] When the butt welding is performed using CO2 gas shielded welding, a single-sided V-groove is used with a groove angle of 45°, a blunt edge ≤10mm, a root gap ≤10mm, a welding current of 175~220A, a voltage of 27~32V, a welding speed of 15~24cm / min, and a heat input of 11.8~28.2kJ / cm. The interpass temperature for the root pass is 145~160℃, the interpass temperature for the fill pass is 170~198℃, and the interpass temperature for the cover pass is 170~190℃.

[0023] When the butt joint horizontal welding is performed using CO2 gas shielded welding, a single-sided V-groove is adopted with a groove angle of 45°, a blunt edge ≤10mm, a root gap ≤10mm, a welding current of 165~210A, a voltage of 26~29V, a welding speed of 15~23cm / min, and a linear energy of 11.3~24.4kJ / cm. The interpass temperature for the root pass is 160~190℃, the interpass temperature for the fill pass is 180~200℃, and the interpass temperature for the cover pass is 185~196℃.

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

[0025] The welding method for Q355ME hot-rolled H-beams with flange thickness of 30-50mm is reasonably designed. It adopts a single-sided bevel and effectively avoids crack defects at the weld joint by reasonably controlling the preheating temperature before welding and the heat preservation temperature after welding. The mechanical properties of the weld joint are basically the same as those of the base material. Attached Figure Description

[0026] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0027] Figure 1 This is a schematic diagram of the butt weld groove dimensions and joint of the present invention.

[0028] Figure 2 This invention relates to the arrangement of weld beads for butt flat welding.

[0029] Figure 3 This is a schematic diagram of the butt weld groove dimensions and joint of the present invention.

[0030] Figure 4 This invention relates to the arrangement of horizontal weld beads for butt welding. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and through the description of the examples.

[0032] like Figures 1 to 4 As shown, the welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm involves welding the flange base material of Q355ME with a flange thickness of 30-50mm at room temperature of 10-30℃, and the welding joint type adopts butt flat welding or butt horizontal welding.

[0033] The welding method for hot-rolled H-beams includes the following steps:

[0034] 1) The welded joint is machined to form a bevel structure:

[0035] The bevel structure is a single-sided bevel; the single-sided bevel is simple to process, and can improve efficiency and save welding materials while meeting welding requirements, and facilitate welding operations.

[0036] 2) Preheating treatment:

[0037] Both the welding wire and the hot-rolled H-beam base material are preheated. The preheating temperature of the hot-rolled H-beam base material is ≥60℃. Preheating can be stopped after the required temperature is reached.

[0038] The welding wire is CHT711 flux-cored welding wire with a diameter of 1-1.4mm. Before welding, the welding wire is dried in a drying oven for 2.5-3.5 hours at a temperature ≤200℃.

[0039] 3) Welding:

[0040] CO2 gas shielded welding employs multi-layer, multi-pass surfacing welding with an interpass temperature ≤200℃. Excessive interpass temperature can lead to coarse grains in the heat-affected zone of the weld, reducing weld strength and low-temperature toughness. Therefore, the interpass temperature must be controlled within a reasonable range during welding.

[0041] The welding joints are either butt flat welding or butt horizontal welding.

[0042] 4) Thermal insulation treatment:

[0043] After welding, the welded joint should be kept warm at a temperature of 160-180℃ for ≥2 hours. Post-weld heat preservation can reduce the cooling rate of the weld, effectively release residual stress, facilitate the escape of diffusible hydrogen in the weld metal, and avoid crack defects.

[0044] Further:

[0045] When using CO2 gas shielded welding for butt welding, a single-sided V-groove is used with a groove angle of 45°, a blunt edge ≤10mm, a root gap ≤10mm, a welding current of 175~220A, a voltage of 27~32V, a welding speed of 15~24cm / min, and a heat input of 11.8~28.2kJ / cm. The interpass temperature for the root pass is 145~160℃, the interpass temperature for the fill pass is 170~198℃, and the interpass temperature for the cover pass is 170~190℃.

[0046] When using CO2 gas shielded welding for butt welding, a single-sided V-groove is used with a groove angle of 45°, a blunt edge ≤10mm, a root gap ≤10mm, a welding current of 165~210A, a voltage of 26~29V, a welding speed of 15~23cm / min, and a heat input of 11.3~24.4kJ / cm. The interpass temperature for the root pass is 160~190℃, the interpass temperature for the fill pass is 180~200℃, and the interpass temperature for the cover pass is 185~196℃.

[0047] The welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm is reasonably designed. It adopts a single-sided bevel and effectively avoids crack defects at the weld joint by reasonably controlling the preheating temperature before welding and the heat preservation temperature after welding. The mechanical properties of the weld joint are basically the same as those of the base material.

[0048] In this invention, the chemical composition of Q355ME hot-rolled H-beams is shown in Table 1, and the mechanical properties are shown in Table 2.

[0049] Table 1: Chemical Composition of Q355ME Hot-Rolled H-Beam Steel (Unit: wt%)

[0050]

[0051] Table 2: Mechanical Properties of Hot-Rolled H-Beams

[0052]

[0053] Implementation Case 1:

[0054] The butt weld of Q355ME steel with a flange thickness of 30mm is performed using CO2 gas shielded welding. The dimensions of the two base materials are 400*100*30mm. For bevel dimensions and joint details, please refer to [link / reference]. Figure 1 As shown, a schematic diagram of the weld bead arrangement is available. Figure 2 As shown.

[0055] Implementation Case 2

[0056] The Q355ME has a flange thickness of 40mm and is butt-welded using CO2 gas shielded welding. The dimensions of the two base materials are 400*100*40mm.

[0057] Implementation Case 3

[0058] The butt joint of Q355ME steel with a flange thickness of 40mm is welded using CO2 gas shielded welding. The dimensions of the two base materials are 300*100*40mm. For bevel dimensions and joint details, please refer to [link / reference]. Figure 3 As shown, a schematic diagram of the weld bead arrangement is available. Figure 4 As shown.

[0059] Implementation Case 4

[0060] The butt weld of the Q355ME with a flange thickness of 30mm is performed using CO2 gas shielded welding, and the dimensions of the two base materials are 300*100*30mm.

[0061] Welding was carried out for the above-mentioned joint types and welding methods, and the relevant processes are shown in Table 3.

[0062] Table 3: Comparison of Implementation Cases

[0063]

[0064] The welding material involved in this invention is CHT711 flux-cored welding wire with a diameter of 1.2 mm. CO2 gas shielded welding is used, with DC reverse polarity.

[0065] The effects of this invention are as follows: Visual inspection: The weld surface is well-formed and free of welding defects. Non-destructive testing of the weld: Ultrasonic testing is used, and the evaluation level is Grade II, indicating that the internal quality of the weld is qualified. The performance is stable and reliable, and cracks are unlikely to occur during later use.

[0066] Specimen preparation and inspection: Tensile specimens shall be prepared in accordance with GB / T2651 "Tension Test Method for Welded Joints". Bending specimens shall be prepared in accordance with GB / T2653 "Bending Test Method for Welded Joints". Impact specimens shall be prepared in accordance with GB / T2650 "Impact Test Method for Welded Joints".

[0067] This invention addresses the compositional range and technical conditions of Q355ME hot-rolled H-beams, solving the welding method and process problems for flanges of hot-rolled H-beams with a flange thickness of 30-50mm. Specifically, it includes: 1) proposing reasonable bevel shapes and welding methods based on the weld joint type and base metal thickness; 2) specifying preheating temperature and post-weld holding temperature to avoid cold cracking defects at the weld joint; 3) selecting suitable welding materials based on the joint type, bevel shape, and welding method; and 4) proposing appropriate welding process parameters. Using this method for welding the flanges of Q355ME hot-rolled H-beams, the weld joint achieves mechanical properties equivalent to the base metal, meeting engineering requirements. Other existing welding methods for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm are prone to cracking during later use and are not suitable for this invention.

[0068] 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 concept and technical solution of the present invention, or the direct application of the concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm, characterized in that: The hot-rolled H-beam welding method includes the following steps: 1) The welded joint is machined to form a bevel structure; 2) Preheating treatment: Both the welding wire and the hot-rolled H-beam base material are preheated, and the preheating temperature of the hot-rolled H-beam base material is ≥60℃. 3) Welding: CO2 gas shielded welding is performed using multi-layer, multi-pass surfacing welding. 4) Thermal insulation treatment: After welding, the welded joint is insulated at a temperature of 160-180℃. in, In step 3), the welding joint is either butt flat welding or butt horizontal welding. When the butt joint is welded using CO2 gas shielded welding, a single-sided V-groove is used with a groove angle of 45°, a blunt edge ≤10mm, a root gap ≤10mm, a welding current of 175~220A, a voltage of 27~32V, a welding speed of 15~24cm / min, and a heat input of 11.8~28.2kJ / cm. The interpass temperature for the root pass is 145~160℃, the interpass temperature for the fill pass is 170~198℃, and the interpass temperature for the cover pass is 170~190℃. When the butt joint horizontal welding is performed using CO2 gas shielded welding, a single-sided V-groove is adopted with a groove angle of 45°, a blunt edge ≤10mm, a root gap ≤10mm, a welding current of 165~210A, a voltage of 26~29V, a welding speed of 15~23cm / min, and a linear energy of 11.3~24.4kJ / cm. The interpass temperature for the root pass is 160~190℃, the interpass temperature for the fill pass is 180~200℃, and the interpass temperature for the cover pass is 185~196℃.

2. The welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm as described in claim 1, characterized in that: In the aforementioned welding method, the welding operation is performed at a room temperature of 10–30°C.

3. The welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm as described in claim 1, characterized in that: The bevel structure is a single-sided inclined bevel.

4. The welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm as described in claim 1, characterized in that: After step 2), the welding wire is CHT711 flux-cored welding wire with a diameter of 1-1.4 mm. The welding wire is dried in a drying oven for 2.5-3.5 hours before welding, with a holding temperature ≤200℃.

5. The welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm as described in claim 1, characterized in that: In step 3), the interlayer temperature is ≤200℃.

6. The welding method for Q355ME hot-rolled H-beams with a flange thickness of 30-50mm as described in claim 1, characterized in that: In step 4), the heat preservation time is ≥2h.

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