A welding method for improving the cold bending performance of a welded joint of Q1400 steel

Abstract

The application provides a welding method for improving the cold bending performance of a Q1400 steel welded joint, the welding method comprising the following steps: S10: providing a steel plate with a thickness of δ mm; S20: using shielded metal arc welding to perform backing welding on a bevel of the steel plate to form a backing layer, wherein E 打底 ≥ δ + 3 kJ / cm; S30: using shielded metal arc welding to perform filling welding on the bevel of the steel plate on which the backing layer is formed to form a filling layer, wherein E 填充 satisfies: E 填充 ≤ δ + 2 kJ / cm; S40: using shielded metal arc welding to perform covering welding on the bevel of the steel plate on which the filling layer is formed to form a covering layer, so that a welded joint composed of the backing layer, the filling layer and the covering layer is obtained; wherein E 盖面 ≥ δ + 3 kJ / cm. By using the welding method to weld Q1400 steel with different thicknesses, the obtained welded joint has good cold bending performance and high strength.

Description

Technical Field

[0001] This application relates to the field of steel welding technology, specifically to a welding method for improving the cold bending performance of Q1400 steel welded joints. Background Technology

[0002] Q1400, a low-alloy high-strength steel developed to meet the requirements of ultra-high strength and lightweight for engineering machinery, has the following mechanical properties: yield strength ≥1400MPa, tensile strength ≥1650MPa; supplied in quenched and tempered condition; microstructure: tempered sorbite.

[0003] For gas metal arc welding (MAG) of Q1400 steel, the highest tensile strength grade of welding materials currently available on the market is 1000MPa, far lower than that of Q1400 steel. Therefore, low-strength matching is currently used in MAG welding of Q1400 steel, resulting in a weld tensile strength lower than that of the base metal. In the welding procedure qualification process for butt welds of the same material, the 180° cold bending test of the weld joint is a mandatory inspection item. However, during the cold bending test of Q1400 steel weld joints, the weld tensile strength is often much lower than that of the base metal, the weld is soft while the base metal is hard, and the deformation of the base metal and weld is not coordinated. The weld deforms before the base metal, and due to the large strength difference, there is significant stress concentration at the weld, leading to weld cracks or complete weld fracture before the base metal deforms. This results in a failed cold bending test. Figure 1 As shown.

[0004] Therefore, there is a need to provide a welding method for improving the cold bending performance of Q1400 steel welded joints. Summary of the Invention

[0005] This application provides a welding method for improving the cold bending performance of Q1400 steel welded joints. The welded joints obtained by this welding method for welding Q1400 steel have good cold bending performance.

[0006] In a first aspect, this application provides a welding method for improving the cold bending performance of Q1400 steel welded joints, comprising the following steps:

[0007] S10: Provides steel plates with a thickness of δ mm;

[0008] S20: Perform a root pass weld on the bevel of the steel plate using gas metal arc welding (GMAW) to form a root pass, wherein the welding heat input line energy E of the root pass weld is... 打底 ≥δ+3kJ / cm;

[0009] S30: Gas metal arc welding (GMAW) is used to perform filler welding on the bevel of the steel plate forming the root pass to form a filler layer, wherein the welding heat input line energy E of the filler welding is...填充 Satisfy: E 填充 ≤δ+2kJ / cm;

[0010] S40: Gas metal arc welding (GMAW) is used to perform a cover weld on the bevel of the steel plate forming the filler layer to form a cover layer, resulting in a welded joint consisting of a root pass, a filler layer, and a cover layer; wherein the welding heat input line energy E of the filler weld is... 盖面 ≥δ+3kJ / cm.

[0011] According to this application, by using this welding method to weld Q1400 steel of different thicknesses, the resulting welded joint has both good cold bending performance and high strength.

[0012] In some implementations, 8mm ≤ δmm ≤ 25mm.

[0013] In some embodiments, the steel plate has a yield strength ≥1400MPa and a tensile strength ≥1650MPa.

[0014] In some embodiments, the chemical composition of the steel plate, in mass percentage, comprises: C: 0.15%–0.3%, Si: 0.15%–0.4%, Mn: 0.8%–1.1%, P: 0–0.01%, S: 0–0.002%, Cr: 0.25%–0.5%, Ni: 1.0%–1.4%, Mo: 0.4%–0.8%, Ti: 0.01%–0.06%, V: 0.03%–0.07%, Nb: 0.01%–0.05%, B: 0.001%–0.005%, Als: 0.02%–0.06%, with the balance being iron and other unavoidable impurities.

[0015] In some embodiments, the chemical element composition of the welding wire in steps S20, S30, and S40, in the root pass, fill pass, and cover pass, comprises, by mass percentage: C: 0.05%–0.12%, Si: 0.3%–0.55%, Mn: 1.2%–1.6%, Cr: 0.1%–0.8%, Ni: 1.8%–2.9%, Mo: 0.5%–1.2%, Ti: 0–0.3%, V: 0–0.1%, with the balance being iron and other unavoidable impurities.

[0016] In some embodiments, in steps S20, S30 and S40, the shielding gas in the root pass, the fill pass and the cover pass includes at least two of argon, oxygen and carbon dioxide, and the volume percentage of argon is 95% to 99% based on the total volume of the shielding gas.

[0017] In some embodiments, in step S20, the welding heat input line energy E of the root pass welding is...打底 Satisfy: δ + 3 kJ / cm ≤ E 打底 ≤δ+5kJ / cm.

[0018] In some embodiments, in step S30, the welding heat input line energy E of the filler weld is... 填充 Satisfying: δkJ / cm≤E 填充 ≤δ+2kJ / cm.

[0019] In some embodiments, in step S30, the welding heat input line energy E of the cover weld is... 盖面 Satisfy: δ + 3 kJ / cm ≤ E 盖面 ≤δ+5kJ / cm.

[0020] In some embodiments, the welded joint can be cold-bent 180° without cracking when the mandrel diameter is 9δmm. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0022] Figure 1 This is a sample image of a Q1400 steel welded joint that failed the cold bending performance test.

[0023] Figure 2 The curve showing the relationship between t8 / 5 and microhardness of Q1400 steel.

[0024] Figure 3 This is a schematic diagram of the stress state of the metal in each zone of the welded joint during cold bending.

[0025] Figure 4 This is a schematic diagram of a welded joint in one embodiment of this application.

[0026] Figure 5 These are sample images of welded joints used for cold bending performance testing in some embodiments of this application.

[0027] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0028] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0029] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. 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.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0031] As mentioned in the background section above, the highest tensile strength grade of commercially available welding materials is 1000MPa, far lower than that of Q1400 steel. Therefore, the weld strength is significantly lower than that of the unheated zone and heat-affected zone of the base metal. During cold bending, the deformation of different zones in the welded joint is uncoordinated. Furthermore, due to the low weld strength, the weld deforms preferentially, resulting in significant stress concentration during cold bending. This leads to weld fracture even at a very small bending angle, resulting in poor cold bending performance of the welded joint. By analyzing the stress state of the welded joint during cold bending, such as... Figure 2 As shown, during the cold bending process, one side of the centerline 1 of the steel plate is the tension zone 2 and the other side is the compression zone 3. The reason for the fracture is that the strength of the heat-affected zone adjacent to the weld is too different from the strength of the weld. When the weld deforms in the tension zone 2 and the compression zone 3, the base material cannot deform due to its high strength, resulting in stress concentration at the weld and causing the welded joint to fracture during cold bending.

[0032] Based on this, the inventors conceived of improving the cold bending performance of the weld joint by reducing the strength of the heat-affected zone to match the strength of the weld, so that both the weld and the heat-affected zone deform simultaneously during the cold bending process, thereby reducing stress concentration at the weld. The specific embodiments of this application are described below.

[0033] In a first aspect, this application provides a welding method for improving the cold bending performance of Q1400 steel welded joints, comprising the following steps:

[0034] S10: Provides steel plates with a thickness of δ mm;

[0035] S20: Gas metal arc welding (GMAW) is used to perform root pass welding on the bevel of the steel plate to form the root pass, wherein the welding heat input line energy E of the root pass welding is... 打底 ≥δ+3kJ / cm;

[0036] S30: Gas metal arc welding (GMAW) is used to perform filler welding on the bevel of the steel plate forming the root pass to form a filler layer, wherein the welding heat input line energy E of the filler welding is... 填充 Satisfy: E 填充 ≤δ+2kJ / cm;

[0037] S40: Gas metal arc welding (GMAW) is used to perform a cover weld at the bevel of the steel plate forming the filler layer to form a cover layer, resulting in a welded joint consisting of a root pass, a filler layer, and a cover layer; wherein the welding heat input line energy E of the filler weld is... 盖面 ≥δ+3kJ / cm.

[0038] According to this application, Q1400 steel refers to low-alloy high-strength steel with a yield point of 1400MPa. Based on the analysis above, the greatest influence on the cold bending performance of welded joints is the significant difference in strength between the heat-affected zone and the weld in the compression and tension regions. The strength of the weld is affected by the welding wire and cannot reach the same strength as the base material. Therefore, this application improves the cold bending performance of welded joints by controlling the heat input line energy of welding and adjusting the strength of the heat-affected zone of different weld layers to make it comparable to the weld strength.

[0039] Specifically, due to the high hardenability and hardenability of Q1400 steel, and its sensitivity to diffusible hydrogen content, the strength of Q1400 steel is significantly affected by the cooling rate. If the cooling rate of the welded joint is too fast, the heat-affected zone (HAZ) is prone to acquiring a high-hardness martensitic structure, and the diffusible hydrogen cannot fully escape, resulting in a large difference in strength between the weld and the HAZ. Furthermore, excessively high diffusible hydrogen content can exacerbate cold cracking. Therefore, the inventors conducted welding thermal simulation experiments, establishing the relationship between t8 / 5 and microhardness of Q1400 steel, as shown in the curve... Figure 3 As shown, t8 / 5 represents the time it takes for the temperature of the heat-affected zone to cool from 800℃ to 500℃ during the welding cooling process. Figure 3 As can be seen, with the increase of t8 / 5, the hardness of the weld heat-affected zone of Q1400 steel generally shows a downward trend; when t8 / 5 is within 30s, the hardness of the weld heat-affected zone of Q1400 steel is basically equivalent to or not much different from that of the Q1400 steel base material; when t8 / 5 is greater than 30s, the hardness of the weld heat-affected zone of Q1400 steel is much lower than that of the Q1400 steel base material.

[0040] It is understandable that the larger t8 / 5 is, the slower the cooling rate. The cooling rate of the welded joint is related to the welding heat input line energy and the steel plate thickness. Therefore, the strength of the heat-affected zone can be controlled by controlling the steel plate thickness and the welding heat input line energy, so that the strength of the heat-affected zone matches the strength of the weld, thereby improving the cold bending performance of the Q1400 steel welded joint.

[0041] In addition, multi-layer welding can be performed using gas metal arc welding (GMAW), with separate root pass, fill pass, and cap pass welds to form a root pass, fill pass, and cap pass. For example,... Figure 4 As shown, the weld consists of a root pass 10, a fill pass 20, and a cap pass 30. Using gas metal arc welding (GMAW) allows for more precise control of the welding heat input line energy, which is beneficial for stabilizing the strength of the heat-affected zone and making its strength comparable to that of the weld, thereby improving the cold bending performance of the welded joint.

[0042] Since the tension and compression zones are most prone to cracking, the strength of the heat-affected zone (HAZ) corresponding to the root pass and cover pass should match the weld strength. For the filler pass, which experiences less stress, the strength of its corresponding HAZ can be appropriately increased to improve the cold bending performance of the weld joint while maintaining a certain level of joint strength. The welding heat input line energy for the root pass and cover pass should be controlled above δ+3 kJ / cm to ensure that the strength of the corresponding HAZ matches the weld strength. This allows the HAZ and weld to undergo phase transformation as synchronously as possible during cold bending, reducing stress and improving the cold bending performance of the weld joint. The welding heat input line energy for the filler pass should be controlled below δ+2 kJ / cm to ensure that the corresponding HAZ of the filler pass maintains a certain strength, thus improving the cold bending performance of the weld joint while maintaining a certain level of joint strength.

[0043] In this application, the welding bevel and butt joint gap can be selected according to processes known in the art. As an example, the welding bevel is a V-shaped bevel with a bevel angle of 60°±5° and a butt joint gap of 2 to 4 mm.

[0044] In some implementations, the steel plate is not preheated before welding, which helps to save resources and improve welding efficiency.

[0045] In some implementations, 8mm ≤ δmm ≤ 25mm.

[0046] In some of the above embodiments, the thickness of the steel plate is specifically limited to 8-25 mm. This is because when using gas metal arc welding, the thickness of the weld layer is related to the welding heat input line energy. The higher the line energy, the thicker the weld layer. Therefore, in order to better adjust the welding heat input line energy so that the strength of the heat-affected zone matches the strength of the weld, this welding method has better cold bending performance when used to weld Q1400 steel plates with a thickness of 8-25 mm.

[0047] In some embodiments, the steel plate has a yield strength ≥1400MPa and a tensile strength ≥1650MPa. Q1400 steel has a yield strength above 1400MPa and a tensile strength above 1650MPa. Due to the significant difference in strength between the base material and the weld, the cold bending performance of the welded joint is poor. The welding method of this application is particularly suitable for improving the cold bending performance and strength of welded joints of such steel plates.

[0048] In some embodiments, the chemical composition of the steel plate, by mass percentage, includes: C: 0.15%–0.3%, Si: 0.15%–0.4%, Mn: 0.8%–1.1%, P: 0–0.01%, S: 0–0.002%, Cr: 0.25%–0.5%, Ni: 1.0%–1.4%, Mo: 0.4%–0.8%, Ti: 0.01%–0.06%, V: 0.03%–0.07%, Nb: 0.01%–0.05%, B: 0.001%–0.005%, Als: 0.02%–0.06%, with the balance being iron and other unavoidable impurities.

[0049] In some of the above embodiments, the chemical element composition of the steel plate is specifically defined. Since the relationship curve between t8 / 5 and microhardness of Q1400 steel in the above text was obtained by testing the steel plate with the above chemical element composition, the welding heat input line energy of different weld layers determined in this application is used to weld the steel plate with the above chemical element composition, which has a better effect on improving the cold bending performance and strength of the weld joint.

[0050] In some embodiments, in steps S20, S30, and S40, the chemical elemental composition of the welding wire in the root pass, fill pass, and cover pass includes, by mass percentage: C: 0.1%, Si: 0.46%, Mn: 1.49%, Cr: 0.6%, Ni: 2.4%, Mo: 0.9%, Ti: 0.1%, V: 0.03%, Als: 0.12%, P: 0-0.01%, S: 0-0.02%, with the balance being iron and other unavoidable impurities.

[0051] In some of the above embodiments, the chemical element composition of the welding wire in the root pass, fill pass, and cover pass is specifically defined. The weld formed by using this type of welding wire has high strength. Using this welding wire can further improve the strength of the welded joint while ensuring the cold bending performance of the welded joint.

[0052] In some embodiments, in steps S20, S30 and S40, the shielding gas in the root pass, fill pass and cover pass includes at least two of argon, oxygen and carbon dioxide, and the volume percentage of argon is 95% to 99% based on the total volume of the shielding gas.

[0053] In some of the above embodiments, the main component of the shielding gas is argon, which helps to protect the metal from oxidation during the welding process and maintain the stability of the electric arc. At the same time, adding a small amount of oxygen or carbon dioxide can increase the heat input of the welding process and improve the welding efficiency.

[0054] In some implementations, in step S20, the welding heat input line energy E for the root pass is... 打底 Satisfy: δ + 3 kJ / cm ≤ E 打底 ≤δ+5kJ / cm.

[0055] In some of the above embodiments, the welding heat input line energy E of the root pass is further limited. 打底 With a strength of δ+3 to δ+5 kJ / cm, the cooling rate of the heat-affected zone of the root pass is kept from being too slow, which would result in low strength. This ensures that the strength of the root pass is more closely matched with that of the weld, allowing for synchronous deformation during cold bending and further improving its cold bending performance. At the same time, it can also further improve the strength of the weld joint while ensuring its cold bending performance.

[0056] In some embodiments, in step S30, the welding heat input line energy E of the filler weld is... 填充 Satisfying: δkJ / cm≤E 填充 ≤δ+2kJ / cm.

[0057] In some of the above embodiments, the welding heat input line energy E of the filler weld is further limited. 填充 The value is δ~δ+2kJ / cm. At this value, the cooling rate of the corresponding heat-affected zone of the filler layer is not too slow, which would result in excessively high strength. This can reduce the stress concentration near the filler layer during the cold bending process of the welded joint and further improve the cold bending performance of the welded joint.

[0058] In some embodiments, in step S30, the welding heat input line energy E of the cover weld is... 盖面 Satisfy: δ + 3 kJ / cm ≤ E 盖面 ≤δ+5kJ / cm.

[0059] In some of the above embodiments, the welding heat input line energy E of the cover weld is further limited. 打底 With a strength of δ+3 to δ+5 kJ / cm, the cooling rate of the heat-affected zone of the cover weld is not too slow, which would result in low strength. This makes the strength of the cover weld more compatible with that of the weld, allowing for synchronous deformation during cold bending and further improving its cold bending performance. At the same time, it can also further improve the strength of the weld joint while ensuring its cold bending performance.

[0060] In some implementations, the welded joint can be cold-bent 180° without cracking when the mandrel diameter is 9δmm.

[0061] In some of the above embodiments, after testing, the welded joint of Q1400 steel welded using the welding method of this application showed no cracks when cold-bent 180° under the condition of a bending mandrel diameter of 9δmm. This indicates that the welded joint of Q1400 steel welded using the welding method of this application has excellent cold bending performance and can be well applied to welding Q1400 steel. Figure 5 The following are some embodiments of the present application showing the 9δ cold bending test results of the welded joint. It can be seen that the heat-affected zone of the weld and the base material deforms synchronously and uniformly. No cracks appeared when the cold bending was 180°, indicating that it has good cold bending performance.

[0062] In some implementations, the thickness of the cover weld is reduced by mechanical means, the weld excess is removed, and the weld is ground flat and smooth, with planing or grinding performed along the welding direction.

[0063] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0064] Cold bending performance test: GB / T 2653-2008 Method for bending test of welded joints.

[0065] Tensile strength test: GB / T 2651-2008 Tensile test method for welded joints.

[0066] Example 1

[0067] Welding of 8mm thick Q1400 steel plate:

[0068] Open a V-shaped bevel with a bevel angle of 60±5° and no blunt edge; use a manual grinding wheel to grind and clean the bevel to remove iron oxide scale and iron filings, and clean the surface rust and oil within 25mm on both sides of the bevel; control the gap of the welded joint assembly to be 2-3mm, and fix it at both ends of the test plate with arc-starting plates and arc-extinguishing plates;

[0069] Gas metal arc welding (GMAW) was used to sequentially perform root pass, fill pass, and cover pass welding on the bevel of the steel plate. The welding heat input line energy for the root pass, fill pass, and cover pass welding is shown in Table 1. The shielding gas was a mixture of 95% argon and 5% carbon dioxide. The chemical composition of the welding wire, by mass percentage, included: C: 0.1%, Si: 0.46%, Mn: 1.49%, Cr: 0.6%, Ni: 2.4%, Mo: 0.9%, Ti: 0.1%, V: 0.03%, Als: 0.12%, P: 0-0.01%, S: 0-0.02%, with the balance being iron and other unavoidable impurities.

[0070] After welding, the weld was ground smooth, and the cold bending performance and tensile strength of the welded joint were tested. The results are shown in Table 1.

[0071] Example 2

[0072] Welding of 12mm thick Q1400 steel plate:

[0073] Open a V-shaped bevel with a bevel angle of 60±5° and no blunt edge; use a manual grinding wheel to grind and clean the bevel, remove iron oxide scale and iron filings, and clean the surface rust and oil within 25mm on both sides of the bevel; control the gap of the welded joint assembly to be 2-3mm, and fix it at both ends of the test plate with arc-starting plates and arc-extinguishing plates;

[0074] Gas metal arc welding (GMAW) was used to sequentially perform root pass, fill pass, and cover pass welding on the bevel of the steel plate. The welding heat input line energy for the root pass, fill pass, and cover pass welding is shown in Table 1. The shielding gas was a mixture of 95% argon and 5% carbon dioxide. The chemical composition of the welding wire, by mass percentage, included: C: 0.1%, Si: 0.46%, Mn: 1.49%, Cr: 0.6%, Ni: 2.4%, Mo: 0.9%, Ti: 0.1%, V: 0.03%, Als: 0.12%, P: 0-0.01%, S: 0-0.02%, with the balance being iron and other unavoidable impurities.

[0075] After welding, the weld was ground smooth, and the cold bending performance and tensile strength of the welded joint were tested. The results are shown in Table 1.

[0076] Example 3

[0077] Welding of 20mm thick Q1400 steel plate:

[0078] Open a V-shaped bevel with a bevel angle of 60±5° and no blunt edge; use a manual grinding wheel to grind and clean the bevel, remove iron oxide scale and iron filings, and clean the surface rust and oil within 25mm on both sides of the bevel; control the gap of the welded joint assembly to be 2-3mm, and fix it at both ends of the test plate with arc-starting plates and arc-extinguishing plates;

[0079] Gas metal arc welding (GMAW) was used to sequentially perform root pass, fill pass, and cover pass welding on the bevel of the steel plate. The welding heat input line energy for the root pass, fill pass, and cover pass welding is shown in Table 1. The shielding gas was a mixture of 95% argon and 5% carbon dioxide. The chemical composition of the welding wire, by mass percentage, included: C: 0.1%, Si: 0.46%, Mn: 1.49%, Cr: 0.6%, Ni: 2.4%, Mo: 0.9%, Ti: 0.1%, V: 0.03%, Als: 0.12%, P: 0-0.01%, S: 0-0.02%, with the balance being iron and other unavoidable impurities.

[0080] After welding, the weld was ground smooth, and the cold bending performance and tensile strength of the welded joint were tested. The results are shown in Table 1.

[0081] Comparative Example 1

[0082] Welding of 8mm thick Q1400 steel plate:

[0083] Open a V-shaped bevel with a bevel angle of 60±5° and no blunt edge; use a manual grinding wheel to grind and clean the bevel, remove iron oxide scale and iron filings, and clean the surface rust and oil within 25mm on both sides of the bevel; control the gap of the welded joint assembly to be 2-3mm, and fix it at both ends of the test plate with arc-starting plates and arc-extinguishing plates;

[0084] Gas metal arc welding (GMAW) was used to sequentially perform root pass, fill pass, and cover pass welding on the bevel of the steel plate. The welding heat input line energy for the root pass, fill pass, and cover pass welding is shown in Table 1. The shielding gas was a mixture of 95% argon and 5% carbon dioxide. The chemical composition of the welding wire, by mass percentage, included: C: 0.1%, Si: 0.46%, Mn: 1.49%, Cr: 0.6%, Ni: 2.4%, Mo: 0.9%, Ti: 0.1%, V: 0.03%, Als: 0.12%, P: 0-0.01%, S: 0-0.02%, with the balance being iron and other unavoidable impurities.

[0085] After welding, the weld was ground smooth, and the cold bending performance and tensile strength of the welded joint were tested. The results are shown in Table 1.

[0086] Table 1

[0087]

[0088]

[0089] As shown in Table 1, the welding method provided in this application yields welded joints with good cold bending performance and high tensile strength when used to weld Q1400 steel of different thicknesses. In contrast, in Comparative Example 1, the use of the same heat input line energy in multi-layer welding led to stress concentration in the welded joint, resulting in cracks during cold bending. Furthermore, the higher heat input line energy in the filler layer also caused a certain degree of reduction in tensile strength. Therefore, the welding method provided in this application can be used to improve the cold bending performance of welded joints of Q1400 steel of different thicknesses.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should 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 this application.

Claims

1. A welding method for improving the cold bending performance of Q1400 steel welded joints, characterized in that, Includes the following steps: S10: Provides steel plates with a thickness of δ mm; S20: Perform a root pass weld on the bevel of the steel plate using gas metal arc welding (GMAW) to form a root pass, wherein the welding heat input line energy E of the root pass weld is... 打底 Satisfy: δ+3 kJ / cm≤E 打底 ≤δ+5 kJ / cm; S30: Gas metal arc welding (GMAW) is used to perform filler welding on the bevel of the steel plate forming the root pass to form a filler layer, wherein the welding heat input line energy E of the filler welding is... 填充 Satisfying: δ kJ / cm ≤ E 填充 ≤δ+2 kJ / cm; S40: Gas metal arc welding (GMAW) is used to perform a cover weld on the bevel of the steel plate forming the filler layer to form a cover layer, resulting in a welded joint consisting of a root pass, a filler layer, and a cover layer; wherein the welding heat input line energy E of the cover weld is... 盖面 Satisfy: δ+3 kJ / cm≤E 盖面 ≤δ+5 kJ / cm; The chemical element composition of the steel plate, in mass percentage, includes: C: 0.15%~0.3%, Si: 0.15%~0.4%, Mn: 0.8%~1.1%, P: 0~0.01%, S: 0~0.002%, Cr: 0.25%~0.5%, Ni: 1.0%~1.4%, Mo: 0.4%~0.8%, Ti: 0.01%~0.06%, V: 0.03%~0.07%, Nb: 0.01%~0.05%, B: 0.001%~0.005%, Als: 0.02%~0.06%, with the balance being iron and other unavoidable impurities.

2. The welding method according to claim 1, characterized in that, 8 mm ≤ δ mm ≤ 25 mm.

3. The welding method according to claim 1, characterized in that, The steel plate has a yield strength ≥1400MPa and a tensile strength ≥1650MPa.

4. The welding method according to claim 1, characterized in that, In steps S20, S30, and S40, the chemical element composition of the welding wire in the root pass, the fill pass, and the cover pass, by mass percentage, includes: C: 0.05%~0.12%, Si: 0.3%~0.55%, Mn: 1.2%~1.6%, Cr: 0.1%~0.8%, Ni: 1.8%~2.9%, Mo: 0.5%~1.2%, Ti: 0~0.3%, V: 0~0.1%, with the balance being iron and other unavoidable impurities.

5. The welding method according to claim 1, characterized in that, In steps S20, S30 and S40, the shielding gas in the root pass, the fill pass and the cover pass includes argon and carbon dioxide, and the volume percentage of argon is 95% to 99% based on the total volume of the shielding gas.

6. The welding method according to claim 1, characterized in that, The welded joint showed no cracks when cold-bent 180° under a bending mandrel diameter of 9δ mm.

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