Welding method for improving comprehensive mechanical property of Q1300 steel welded joint

Abstract

The invention discloses a welding method for improving the comprehensive mechanical property of a Q1300 steel welded joint and the welded joint, a Q1300 steel plate is subjected to groove cutting to obtain a to-be-welded joint containing a double-sided V-shaped groove, and after the to-be-welded joint containing the double-sided V-shaped groove is welded and assembled, the groove is sequentially subjected to bottom sealing welding, filling welding and cosmetic welding treatment, a gas metal arc welding process is adopted for bottom sealing welding and cosmetic welding, a laser welding process is adopted for filling welding, a Q1300 steel welding joint composed of a bottom sealing layer, a filling layer and a cosmetic layer is finally obtained, Q1300 steel plates of different thicknesses are welded through the welding method, and the obtained welding joint has high strength and good bending performance.

Description

Technical Field

[0001] This application belongs to the technical field of steel welding, and particularly relates to a welding method for improving the comprehensive mechanical properties of Q1300 steel welded joints. Background Art

[0002] For low-alloy high-strength steel Q1300 steel, its mechanical properties are as follows: yield strength ≥ 1300 MPa, tensile strength ≥ 1550 MPa, elongation ≥ 10%, and impact energy at -40°C ≥ 36 J. Due to its excellent strength and toughness, high specific strength, good formability and weldability, low-alloy ultra-high-strength steel Q1300 is widely used in equipment manufacturing industries such as construction machinery, mining machinery, metallurgical machinery and bridge construction, and is particularly suitable for the production of large welded structural parts.

[0003] When welding Q1300 steel using traditional metal active gas (MAG) welding, due to the limitation of the strength of the welding consumables by MAG, the tensile strength of the welded joint is generally lower than 1100 MPa, at least 450 MPa lower than the tensile strength of Q1300 steel; when welding Q1300 steel using traditional laser beam welding (LBW) or laser-arc hybrid welding (LAHW), the coordinated deformation ability of each zone of the welded joint is poor, and the welded joint is prone to fracture in the bending test, and the bending performance is poor. Summary of the Invention

[0004] The embodiments of this application provide a welding method and a welded joint for improving the comprehensive mechanical properties of Q1300 steel welded joints. The welded joint obtained by using this welding method to weld Q1300 steel has both high strength and good bending performance.

[0005] In a first aspect, the embodiments of this application provide a welding method for improving the comprehensive mechanical properties of Q1300 steel welded joints, including: performing groove cutting on a Q1300 steel plate to obtain a welded joint to be welded with a double-sided V-groove; performing welding assembly on the welded joint to be welded with a double-sided V-groove to obtain the welded joint to be welded after assembly; performing back welding, filling welding and capping welding treatments on the groove of the welded joint to be welded after assembly in sequence to obtain a Q1300 steel welded joint composed of a back weld layer, a filling layer and a capping layer, wherein the back welding includes using metal active gas welding to perform back welding on the groove of the welded joint to be welded to form a back weld layer; the filling welding includes using laser beam welding to perform filling welding on the groove of the welded joint to be welded to form a filling layer; the capping welding includes using metal active gas welding to perform capping welding on the groove of the welded joint to be welded to form a capping layer.

[0006] According to an embodiment of the first aspect of the present application, the double-sided V-groove is a double-sided V-groove with a root face, and the root face thickness of the double-sided V-groove is b; the laser power of the laser welding is γ; the ratio of the root face thickness b to the laser power γ is X, where 0.92 ≤ X ≤ 1.20; wherein, the unit of the root face thickness b is mm, and the unit of the laser power γ is kW.

[0007] According to an embodiment of the first aspect of the present application, the thickness of the Q1300 steel plate is δ; the height of the upper surface groove in the double-sided V-groove is a, and a = 0.4 * (δ - b); the height of the lower surface groove in the double-sided V-groove is c, and c = 0.6 * (δ - b); wherein, the unit of the thickness of the Q1300 steel plate is mm, the unit of the height of the upper surface groove is mm, and the unit of the height of the lower surface groove is mm.

[0008] According to an embodiment of the first aspect of the present application, the steps of welding and assembling a weld joint to be welded containing a double-sided V-groove to obtain the weld joint to be welded after assembly include: welding and assembling the weld joint to be welded containing a double-sided V-groove, wherein the assembly gap of the weld joint to be welded is p, and 0 mm ≤ p ≤ 0.5 mm.

[0009] According to an embodiment of the first aspect of the present application, the angle of the upper surface groove is α, and the angle of the lower surface groove is β, wherein 90° ≤ β < α ≤ 130°.

[0010] According to an embodiment of the first aspect of the present application, the welding current in the gas metal arc welding is I, where 180 ≤ I ≤ 210; the welding voltage in the gas metal arc welding is U, where 19 ≤ U ≤ 23; the welding speed in the gas metal arc welding is M1, and M1 = 0.34 * U * I / δ to 0.40 * U * I / δ; wherein, the unit of I is A, the unit of U is V, and the unit of M1 is mm / min.

[0011] According to an embodiment of the first aspect of the present application, the chemical element composition of the welding wire in the gas metal arc welding, in terms of mass percentage, includes: C 0.1%, Si 0.46%, Mn 1.49%, Cr 0.6%, Ni 2.4%, Mo 0.9%, Ti 0.1%, V 0.03%, Al 0.12%, P 0.009%, S 0.013%; the shielding gas in the gas metal arc welding includes argon and carbon dioxide. Based on the total volume of the shielding gas, the volume percentage of argon is 95%, and the volume percentage of carbon dioxide is 5%; the flow rate of the shielding gas in the gas metal arc welding is Q1, where 18 ≤ Q1 ≤ 22, and the unit of Q1 is L / min.

[0012] According to an embodiment of the first aspect of the present application, in laser welding, the welding speed is M2, the ratio of the laser power γ to M2 is Y, and 4.0 ≤ Y ≤ 6.8; the defocus amount in laser welding is D, and -3 ≤ D ≤ 3; the shielding gas in laser welding is high-purity argon, and based on the total volume of the shielding gas, the volume percentage content of argon is 99.99%, and the flow rate of the shielding gas in laser welding is Q2, and 20 ≤ Q2 ≤ 30; wherein, the unit of M2 is m / min, the unit of D is mm, and the unit of Q2 is L / min.

[0013] According to an embodiment of the first aspect of the present application, the steps of welding and assembling a weld joint to be welded with a double-sided V-groove include: using gas metal arc welding to weld and assemble the weld joint to be welded with a double-sided V-groove. In the welding and assembly, the welding speed of the gas metal arc welding is M3, and M3 = 0.34*U*I / δ ~ 0.40*U*I / δ, wherein the unit of M3 is mm / min; the chemical element composition of the welding wire in the gas metal arc welding during welding and assembly, by mass percentage, includes: C 0.1%, Si 0.46%, Mn 1.49%, Cr 0.6%, Ni 2.4%, Mo 0.9%, Ti 0.1%, V 0.03%, Al 0.12%, P 0.009%, S 0.013%; the shielding gas in the gas metal arc welding during welding and assembly includes argon and carbon dioxide, and based on the total volume of the shielding gas, the volume percentage content of argon is 95%, and the volume percentage content of carbon dioxide is 5%.

[0014] In a second aspect, an embodiment of the present application provides a welded joint prepared according to the above welding method; the tensile strength of the welded joint is not less than 1280 MPa; the impact energy of the welded joint at -40 °C is not less than 36 J; the welded joint is subjected to three-point bending under the condition that the indenter diameter d = (11 - 12)*δ, and there is no crack after bending 90°, and the units of d and δ are both mm.

[0015] The welding method provided by the embodiment of the present application performs groove cutting on a Q1300 steel plate to obtain a weld joint to be welded with a double-sided V-groove. After welding and assembling the weld joint to be welded with a double-sided V-groove, the groove is sequentially subjected to back welding, filling welding, and surfacing welding treatments. Among them, the back welding and surfacing welding adopt the welding process of gas metal arc welding, and the filling welding adopts the welding process of laser welding. Finally, a Q1300 steel welded joint composed of a back weld layer, a filling layer, and a surfacing layer is obtained. By using this welding method to weld Q1300 steel plates with different thicknesses, the obtained welded joints have both high strength and good bending performance. Description of the Drawings

[0016] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the accompanying drawings required for the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 This is the performance of the gas shielded arc welding (MAG) joint and the laser beam welding (LBW) joint of the embodiments of the present application in the bending test (where, Figure a is the bending schematic diagram of the gas shielded arc welding joint; Figure b is the bending schematic diagram of the laser beam welding joint).

[0018] Figure 2 This is the sample diagram of the bending test of the gas shielded arc welding joint of the embodiments of the present application;

[0019] Figure 3 This is the sample diagram of the bending test of the laser beam welding joint of the embodiments of the present application;

[0020] Figure 4 This is the groove schematic diagram of the embodiments of the present application (where, a is the height of the upper surface groove (unit: mm), b is the root face size (unit: mm), c is the height of the lower surface groove (unit: mm), p is the groove gap (unit: mm), α is the angle of the upper surface groove, β is the angle of the lower surface groove, and δ is the steel plate thickness (unit: mm)).

[0021] Figure 5 This is the weld layer schematic diagram of the embodiments of the present application. Detailed implementation manners

[0022] In order to make the application purpose, technical solutions and beneficial technical effects of the present application clearer, the following further details the present application in combination with embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application and not for limiting the present application.

[0023] For simplicity, the present application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, although not explicitly recorded, each point or single value between the range endpoints is included in this range. Thus, each point or single value can be used as its own lower limit or upper limit and combined with any other point or single value or combined with other lower limits or upper limits to form a range not explicitly recorded.

[0024] It should be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or apparatus comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or apparatus. Without further limitation, an element defined by the statement "comprising..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising the said element.

[0025] Unless otherwise specified, the values of the various parameters mentioned in this application can be measured by various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application). Unless otherwise specified, the test temperature for each parameter mentioned in this application is 25°C and the test pressure is standard atmospheric pressure.

[0026] The above application content of this application does not intend to describe every disclosed embodiment or every implementation mode in this application. The following description more specifically exemplifies exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, and these embodiments can be used in various combinations. In each instance, the enumeration is only a representative group and should not be construed as exhaustive.

[0027] In the manufacturing process of a crane boom, welding is the most important process. The most commonly used welding methods for boom steel are metal active gas welding (MAG), laser beam welding (LBW), or laser-arc hybrid welding (LAHW); among them, MAG is limited by the strength of the welding material, and the tensile strength of the welded joint is generally lower than 1100 MPa, which is more than 450 MPa lower than the tensile strength of Q1300 steel; although the tensile strength of the welded joint of LBW or LAHW is relatively high, its bending performance is poor, and fracture will occur during face bend or root bend. The inventor has carried out a large number of welding process tests, and reasonably optimized parameters such as the size of the welding groove (such as root face size, groove angle, groove height, groove gap), welding parameters (such as MAG welding speed, LBW welding speed, welding current, welding voltage), and welding sequence. Using the welding method of the present invention to weld Q1300 steel plates with different thicknesses, the obtained welded joints have both high strength and good bending performance. Specifically, good bending performance is obtained on the premise of obtaining high strength of the welded joint. Among them, the bending performance is specifically manifested as that the welded joint undergoes a three-point bending test under the condition that the indenter diameter d = (11 - 12)*δ, and no crack occurs after bending 90°.

[0028] To solve the problems of the prior art, the embodiments of this application provide a welding method and a welded joint for improving the comprehensive mechanical properties of Q1300 steel welded joints.

[0029] The embodiment of the present application provides a welding method for improving the comprehensive mechanical properties of the Q1300 steel welded joint, including: performing groove cutting on the Q1300 steel plate to obtain a welded joint to be welded with a double-sided V-groove; performing welding assembly on the welded joint to be welded with a double-sided V-groove to obtain the welded joint to be welded after assembly; performing back welding, filling welding, and capping welding on the groove of the welded joint to be welded after assembly in sequence to obtain a Q1300 steel welded joint composed of a back weld layer, a filling layer, and a capping layer, wherein the back welding includes using gas metal arc welding to perform back welding on the groove of the welded joint to be welded to form a back weld layer; the filling welding includes using laser welding to perform filling welding on the groove of the welded joint to be welded to form a filling layer; the capping welding includes using gas metal arc welding to perform capping welding on the groove of the welded joint to be welded to form a capping layer.

[0030] In some alternative embodiments, the way of welding assembly is butt welding.

[0031] In some alternative embodiments, the Q1300 steel plate is subjected to groove cutting by cold working to obtain a welded joint to be welded with a double-sided V-groove.

[0032] In some alternative embodiments, after the Q1300 steel plate is subjected to groove cutting and before the welded joint to be welded with a double-sided V-groove is subjected to welding assembly, the groove can also be mechanically polished to remove machining marks.

[0033] In some alternative embodiments, after using laser welding to perform filling welding on the groove of the welded joint to be welded to form a filling layer, tools such as wire brushes are used to clean the welding slag on the side wall of the groove and the surface of the weld bead to prevent defects such as slag inclusion and lack of fusion in the welded joint.

[0034] According to the embodiment of the present application, the Q1300 steel plate is subjected to groove cutting to obtain a welded joint to be welded with a double-sided V-groove; after the welded joint to be welded with a double-sided V-groove is subjected to welding assembly, back welding, filling welding, and capping welding are performed on the groove in sequence. Due to the tempering effect of the capping layer on the filling layer, the above specific welding sequence can improve the plasticity and toughness of the filling layer.

[0035] Among them, the welding process of gas metal arc welding is adopted for back welding and capping welding. Compared with laser welding, the heat input of MAG welding is larger and the cooling time is longer. Therefore, the width of the MAG weld and the width of the welding heat affected zone are larger (see Figure 1 (a)), and moreover, the plasticity and toughness of the weld and the welding heat affected zone are better. When performing the bending test of the welded joint, the wider weld + the wider welding heat affected zone can ensure that the metal in the weld and the heat affected zone within a larger width can deform coordinately, so as to ensure that no fracture occurs during the bending test, and the front bend and back bend of 180° are qualified, and the bending performance is good (see Figure 2);Laser welding has a small heat input during welding, the weld microstructure is relatively brittle, the weld elongation rate is low, and moreover, its heat affected zone is very narrow and the softened area is very narrow (see Figure 1 (b)). In the bending test of the welded joint, only a very narrow weld and a very narrow heat affected zone participate in the deformation, and the coordinated deformation ability of each zone of the welded joint is poor. The welded joint is very easy to break in the bending test (see Figure 3 ). Therefore, laser welding is not suitable for welding the backing layer and the capping layer.

[0036] The filling welding adopts the welding process of laser welding. It is mainly used to melt the root face of the groove. Moreover, relying on the characteristics of high energy density of the laser heat source and fast laser welding speed, the filling layer can obtain a higher tensile strength, so that the entire welded joint can obtain a higher tensile strength. In addition, in the deep penetration welding mode, laser welding can melt a larger root face of the groove, which can greatly reduce the consumption of welding materials and improve the welding efficiency. Finally, a Q1300 steel welded joint composed of a backing layer, a filling layer and a capping layer is obtained (as Figure 5 shown). By using this welding method to weld Q1300 steel plates with different thicknesses, the obtained welded joints have both high tensile strength and good bending performance.

[0037] In some alternative embodiments, the double-sided V-groove is a double-sided V-groove with a root face, and the root face thickness of the double-sided V-groove is b; the laser power of the laser welding is γ; the ratio of the root face thickness b to the laser power γ is X, and 0.92 ≤ X ≤ 1.20; wherein, the unit of the root face thickness b is mm, and the unit of the laser power γ is kW.

[0038] According to the embodiments of the present application, during the bending of the welded joint, the outermost layer of metal is most severely tensioned and will be stretched the longest. Therefore, the welding groove is designed as a double-sided V-shaped structure, especially a double-sided V-groove with a root face (as Figure 4 shown), which can make the surface of the welded joint have a relatively wide and tough metal at the tensioned part, avoid the welded joint from breaking during the bending force process (such as face bend and root bend), and thus improve the bending performance of the welded joint; the ratio X of the root face size b to the laser power is taken as 0.92 to 1.20, so that the advantages of laser welding can be fully utilized to melt the root face and obtain a higher welded joint strength, higher welding efficiency and lower consumption of welding materials.

[0039] In some alternative embodiments, the thickness of the Q1300 steel plate is δ; the height of the upper surface groove in the double-sided V-groove is a, and a = 0.4*(δ - b); the height of the lower surface groove in the double-sided V-groove is c, and c = 0.6*(δ - b); wherein, the unit of the thickness δ of the Q1300 steel plate is mm, the unit of the height of the upper surface groove is mm, and the unit of the height of the lower surface groove is mm.

[0040] Preferably, 8 ≤ δ ≤ 16 (such as 8, 9, 10, 11, 12, 13, 14, 15, 16). According to the embodiments of the present application, for the height a of the upper surface groove and the height c of the lower surface groove, in order to avoid burning through the bottom layer weld during laser welding of the filling layer, therefore, the upper surface groove height a is set to 0.4*(δ - b), and the lower surface groove height c is set to 0.6*(δ - b).

[0041] In some alternative embodiments, the steps of welding and assembling a weld joint to be welded with a double-sided V-groove to obtain the weld joint to be welded after assembly include: welding and assembling the weld joint to be welded with a double-sided V-groove, wherein the assembly gap of the weld joint to be welded is p, and 0 mm ≤ p ≤ 0.5 mm.

[0042] According to the embodiments of the present application, the groove gap p is as small as possible, which can reduce the consumption of welding materials, improve the welding efficiency and the strength of the welded joint. Therefore, the groove gap p is taken as 0 - 0.5 mm.

[0043] In some alternative embodiments, the angle of the upper surface groove is α, and the angle of the lower surface groove is β, wherein 90° ≤ β < α ≤ 130°.

[0044] According to the embodiments of the present application, setting the groove angle α of the upper surface and the groove angle β of the lower surface to 90 ≤ β < α ≤ 130° can ensure that the bottom layer and the cover layer obtain a relatively large weld width, and the weld widths of the upper and lower surfaces are basically the same (since a < c, therefore, β < α is required to ensure that the weld widths of the bottom layer and the cover layer are basically the same, so as to ensure that the widths of the welds + the heat affected zones of the bottom layer and the cover layer are basically the same, and the bending properties are basically the same during positive bending and back bending).

[0045] In some alternative embodiments, the welding current in the gas metal arc welding is I, 180 ≤ I ≤ 210; the welding voltage in the gas metal arc welding is U, 19 ≤ U ≤ 23; the welding speed in the gas metal arc welding is M1, M1 = 0.34*U*I / δ - 0.40*U*I / δ; wherein, the unit of I is A, the unit of U is V, and the unit of M1 is mm / min.

[0046] Exemplarily, M1 can be 0.34*U*I / δ, 0.35*U*I / δ, 0.36*U*I / δ, 0.37*U*I / δ, 0.375*U*I / δ, 0.380*U*I / δ, 0.381*U*I / δ, 0.382*U*I / δ, 0.383*U*I / δ, 0.384*U*I / δ, 0.385*U*I / δ, 0.39*U*I / δ, 0.395*U*I / δ, 0.40*U*I / δ. Preferably, M1 is 0.38*U*I / δ to 0.40*U*I / δ.

[0047] According to an embodiment of the present application, the welding speed M1 in gas metal arc welding depends on the welding current I, the welding voltage U, and the steel plate thickness δ. When M1 satisfies: 0.34*U*I / δ to 0.40*U*I / δ, a high welding efficiency, a large weld surface width, and a large heat affected zone width of the weld can be ensured, obtaining more surface metals that can coordinate deformation, and thus the welded joint can obtain better bending deformation ability.

[0048] In some alternative embodiments, the chemical element composition of the welding wire in gas metal arc welding, by mass percentage, includes: C 0.1%, Si 0.46%, Mn 1.49%, Cr 0.6%, Ni 2.4%, Mo 0.9%, Ti 0.1%, V 0.03%, Al 0.12%, P 0.009%, S 0.013%; the shielding gas in gas metal arc welding includes argon and carbon dioxide. Based on the total volume of the shielding gas, the volume percentage of argon is 95%, and the volume percentage of carbon dioxide is 5%; the flow rate of the shielding gas in gas metal arc welding is Q1, 18 ≤ Q1 ≤ 22, and the unit of Q1 is L / min.

[0049] Exemplarily, Q1 can be 18, 19, 20, 21, 22.

[0050] According to an embodiment of the present application, the weld formed using the welding wire with the above specific chemical composition and content has a higher strength. Using this welding wire can further improve the strength of the welded joint while ensuring the bending performance of the welded joint;

[0051] The main component of the shielding gas is argon + a small amount of carbon dioxide, with good arc stability, less alloying element burn-off, and good weld toughness.

[0052] In some alternative embodiments, gas metal arc welding further includes the processing steps of preheating before welding and heat preservation and slow cooling after welding. Among them, the preheating temperature before welding is 120°C to 150°C, and heat preservation and slow cooling after welding include covering with heat preservation materials such as asbestos cloth for heat preservation and slow cooling.

[0053] In some alternative embodiments, the welding speed in laser welding is M2, the ratio of the laser power γ to M2 is Y, and 4.0 ≤ Y ≤ 6.8; the defocus amount in laser welding is D, and -3 ≤ D ≤ 3; the shielding gas in laser welding is high-purity argon, and the flow rate of the shielding gas in laser welding is Q2, and 20 ≤ Q2 ≤ 30; wherein, the unit of M2 is m / min, the unit of D is mm, and the unit of Q2 is L / min.

[0054] In some alternative embodiments, the volume percentage content of high-purity argon is 99.99%.

[0055] Exemplarily, Y can be 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8.

[0056] Exemplarily, D can be -3, -2.5, -2, -1.5, -1, -0.5, 0, 0.5, 1, 1.5, 2, 2.5, 3.

[0057] According to the embodiments of the present application, the laser power and the welding speed jointly determine the welding quality and the weld formation; if the ratio of the laser power to the welding speed is too large, it will cause the heat-affected zone of the welding to overheat, generate coarse grains, and result in a significant decrease in toughness; if the ratio of the laser power to the welding speed is too small, the heat input is insufficient, the cooling rate of the weld is too fast, excessive hard and brittle tissues are generated, and the weld quality and the weld formation are poor. Therefore, the ratio of the laser power γ to M2 is taken as 4.0 to 6.8; the defocus amount is set to -3 to +3 mm, so that the laser can weld in the deep penetration welding mode, which can efficiently melt the root face of the groove and ensure complete penetration.

[0058] In some alternative embodiments, the steps of welding and assembling a weld joint to be welded with a double-sided V-groove include: performing welding and assembling on the weld joint to be welded with a double-sided V-groove by using gas metal arc welding. In the welding and assembling, the welding speed of the gas metal arc welding is M3, and M3 = 0.34 * U * I / δ to 0.40 * U * I / δ, where the unit of M3 is mm / min. The chemical element composition of the welding wire in the gas metal arc welding during the welding and assembling, in terms of mass percentage, includes: C 0.1%, Si 0.46%, Mn 1.49%, Cr 0.6%, Ni 2.4%, Mo 0.9%, Ti 0.1%, V 0.03%, Al 0.12%, P 0.009%, S 0.013%. The shielding gas in the gas metal arc welding during the welding and assembling includes argon and carbon dioxide. Based on the total volume of the shielding gas, the volume percentage of argon is 95%, and the volume percentage of carbon dioxide is 5%.

[0059] Exemplarily, M3 can be 0.34 * U * I / δ, 0.341 * U * I / δ, 0.342 * U * I / δ, 0.343 * U * I / δ, 0.344 * U * I / δ, 0.345 * U * I / δ, 0.35 * U * I / δ, 0.351 * U * I / δ, 0.352 * U * I / δ, 0.353 * U * I / δ, 0.354 * U * I / δ, 0.355 * U * I / δ, 0.356 * U * I / δ, 0.36 * U * I / δ, 0.365 * U * I / δ, 0.40 * U * I / δ.

[0060] Preferably, M3 is 0.35 * U * I / δ to 0.36 * U * I / δ.

[0061] In some alternative embodiments, the flow rate of the shielding gas in the gas metal arc welding during the welding and assembling is 15 L / min to 25 L / min (such as 15 L / min, 16 L / min, 17 L / min, 18 L / min, 19 L / min, 20 L / min, 21 L / min, 22 L / min, 23 L / min, 24 L / min, 25 L / min).

[0062] According to the embodiments of the present application, the weld formed by the welding wire composed of the above chemical elements has a relatively high strength. Using this welding wire can further improve the strength of the welded joint while ensuring the bending performance of the welded joint. In the welding assembly, the welding speed M1 of the gas metal arc welding depends on the welding current I, the welding voltage U, and the steel plate thickness δ. When the welding speed satisfies: 0.34*U*I / δ - 0.40*U*I / δ, the welding heat input is the most appropriate, and appropriate weld properties can be obtained, avoiding defects such as cracks. The shielding gas for the gas metal arc welding in the welding assembly has argon as the main component, which is beneficial to protecting the metal during the welding process from oxidation and maintaining the stability of the arc. At the same time, adding a small amount of carbon dioxide can increase the heat of the welding heat input and improve the welding efficiency.

[0063] In some of the above optional embodiments, during the welding process, the interpass temperature and the interlayer temperature should be strictly controlled within 200°C to avoid excessive interlayer temperature and slow cooling speed, which may cause the microstructure of the welded joint to be coarse and reduce the low-temperature toughness.

[0064] In some of the above optional embodiments, welding assembly refers to the process of machining the ends to be welded of the workpieces into grooves (i.e., bevels) with a certain shape before welding, and then combining these workpieces in a certain manner. It is necessary to ensure that the gap, angle, and position of the assembly meet the requirements for welding. Welding assembly is also called bevel assembly, and its main purpose is to achieve full penetration, adjust the weld composition and properties, improve the crystallization conditions, and enhance the performance of the joint.

[0065] The embodiments of the present application provide a welded joint prepared according to the above welding method; the tensile strength of the welded joint is not less than 1280 MPa; the impact energy of the welded joint at -40°C is not less than 36 J; the welded joint is subjected to three-point bending under the condition that the indenter diameter d = (11 - 12)*δ, and there is no crack after bending 90°, where the units of d and δ are mm.

[0066] The welding method provided by the embodiments of the present application includes bevel cutting of the Q1300 steel plate to obtain a welded joint to be welded with a double-sided V-shaped bevel. After welding assembly of the welded joint to be welded with a double-sided V-shaped bevel, the bevel is successively subjected to back welding, filling welding, and capping welding treatments. Among them, the back welding and capping welding adopt the welding process of gas metal arc welding, and the filling welding adopts the welding process of laser welding. Finally, a Q1300 steel welded joint composed of a back weld layer, a filling layer, and a capping layer is obtained. By using this welding method to weld Q1300 steel plates with different thicknesses, the obtained welded joints have both relatively high strength and good bending performance.

[0067] Embodiment

[0068] The following examples describe more specifically the content disclosed in the present application. These examples are for illustrative purposes only, as various modifications and variations within the scope of the present application disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0069] Example 1 Butt Welding of Q1300 Steel Plate with a Thickness of 12.5 mm

[0070] First step, a 10 kW solid laser is used to weld a Q1300 steel plate with a thickness δ of 12.5 mm. During welding, the laser power γ is taken as 8.1 kW.

[0071] Second step, a groove is machined by wire cutting and the groove is mechanically polished to remove machining marks to obtain a double V-groove; the blunt edge size b of the groove is taken as 7.5 mm, the groove height a on the upper surface is taken as 2 mm, and the groove height c on the lower surface is taken as 3 mm; the groove angle α on the upper surface is taken as 116°, and the groove angle β on the lower surface is taken as 94°.

[0072] Third step, MAG is used for test plate assembly, and the groove gap p is taken as 0.2 mm; the welding parameters are as follows: the welding current I is taken as 180 A, the welding voltage U is taken as 20 V, and the welding speed M3 is taken as 0.365*U*I / δ, that is, about 105 mm / min. The main chemical components of the welding wire are as follows (wt%): C 0.1, Si 0.46, Mn 1.49, Cr 0.6, Ni 2.4, Mo 0.9, Ti 0.1, V 0.03, Al 0.12, P 0.009, S 0.013. The welding shielding gas uses an argon-rich mixture, and its mixing ratio is 95% argon + 5% carbon dioxide; the shielding gas flow rate is taken as 20 L / min.

[0073] Fourth step, MAG is used for root pass welding, and preheating is carried out at 120 °C before welding; the welding parameters are as follows: the welding current I is taken as 180 A, the welding voltage U is taken as 20 V, and the welding speed M1 is taken as 0.382*U*I / δ, that is, about 110 mm / min. The main chemical components of the welding wire are as follows (wt%): C 0.1, Si 0.46, Mn 1.49, Cr 0.6, Ni 2.4, Mo 0.9, Ti 0.1, V 0.03, Al 0.12, P 0.009, S 0.013. The welding shielding gas uses an argon-rich mixture, and its mixing ratio is 95% argon + 5% carbon dioxide, and the shielding gas flow rate is taken as 20 L / min. After welding, it is covered with asbestos cloth and kept warm and slowly cooled.

[0074] In the fifth step, LBW is used for welding the filling layer; the welding parameters are as follows: the laser power γ is 8.1 kW, the welding speed M2 is 1.4 m / min; the defocus amount is set to +2 mm; high-purity argon is used as the shielding gas, with post-side blowing, and the gas flow rate is 25 L / min. After the filling layer is welded, a wire brush is used to clean the welding slag on the side walls of the groove and the surface of the weld bead.

[0075] In the sixth step, MAG is used for welding the cover layer, and preheating is carried out at 120 °C before welding; the welding parameters are as follows: the welding current I is 180 A, the welding voltage U is 20 V, the welding speed M1 is 0.382 * U * I / δ, which is approximately 110 mm / min; the main chemical components of the welding wire are as follows (wt%): C 0.1, Si 0.46, Mn 1.49, Cr 0.6, Ni 2.4, Mo 0.9, Ti 0.1, V 0.03, Al 0.12, P 0.009, S 0.013. The welding shielding gas is an argon-rich mixture, and its mixing ratio is 95% argon + 5% carbon dioxide, and the shielding gas flow rate is 20 L / min. After welding, it is covered with asbestos cloth for heat preservation and slow cooling.

[0076] The obtained welded joint has a beautiful weld formation, and there are no defects such as cracks, pores, and lack of fusion in the weld; the room-temperature tensile strength of the weld metal is 1285 MPa; the impact energy of the V-notch impact test of the weld metal and the heat-affected zone of the welded joint is greater than 36 J at the test temperature of -40 °C; according to GBT

[0077] 2653-2008 Welding Joint Bending Test Method, in the three-point bending test of the welded joint, the diameter d of the indenter is 12 * δ, and the welded joint bends 90° without cracking.

[0078] Butt welding of Q1300 steel plates with a thickness of 8 mm in Example 2

[0079] In the first step, a 4 kW solid-state laser is used to weld a Q1300 steel plate with a thickness δ of 8 mm. During welding, the laser power γ is 3.5 kW.

[0080] In the second step, a groove is machined by wire cutting, and the groove is mechanically polished to remove machining marks; the blunt edge size b of the groove is 4 mm, the groove height a on the upper surface is 1.8 mm, and the groove height c on the lower surface is 2.2 mm; the groove angle α on the upper surface is 117°, and the groove angle β on the lower surface is 106°.

[0081] Step 3: Use MAG for the trial plate assembly. The groove gap p is taken as 0.2 mm. The welding parameters are as follows: the welding current I is taken as 180 A, the welding voltage U is taken as 20 V, and the welding speed M3 is taken as 0.355 * U * I / δ, which is approximately 160 mm / min. The main chemical components of the welding wire are as follows (wt%): C 0.1, Si 0.46, Mn 1.49, Cr 0.6, Ni 2.4, Mo 0.9, Ti 0.1, V 0.03, Al 0.12, P 0.009, S 0.013. The welding shielding gas uses an argon-rich mixture, and its mixing ratio is 95% argon + 5% carbon dioxide; the shielding gas flow rate is taken as 20 L / min.

[0082] Step 4: Use MAG for the root pass welding. Preheat to 120 °C before welding. The welding parameters are as follows: the welding current I is taken as 180 A, the welding voltage U is taken as 20 V, and the welding speed M1 is taken as 0.38 * U * I / δ, which is approximately 170 mm / min. The main chemical components of the welding wire are as follows (wt%): C 0.1, Si 0.46, Mn 1.49, Cr 0.6, Ni 2.4, Mo 0.9, Ti 0.1, V 0.03, Al 0.12, P 0.009, S 0.013. The welding shielding gas uses an argon-rich mixture, and its mixing ratio is 95% argon + 5% carbon dioxide, and the shielding gas flow rate is taken as 20 L / min. After welding, cover with asbestos cloth and keep warm and slow-cool.

[0083] Step 5: Use LBW for the filler pass welding; the welding parameters are as follows: the laser power γ is taken as 3.5 kW, the welding speed M2 is taken as 0.8 m / min; the defocus amount is set to +3 mm; use high-purity argon as the shielding gas, with post-side blowing, and the gas flow rate is 25 L / min. After the filler pass welding is completed, use a wire brush to clean the welding slag on the side wall of the groove and the surface of the weld bead.

[0084] Step 6: Use MAG for the cover pass welding. Preheat to 120 °C before welding. The welding parameters are as follows: the welding current I is taken as 180 A, the welding voltage U is taken as 20 V, and the welding speed M1 is taken as 0.38 * U * I / δ, which is approximately 170 mm / min; the main chemical components of the welding wire are as follows (wt%): C 0.1, Si 0.46, Mn 1.49, Cr 0.6, Ni 2.4, Mo 0.9, Ti 0.1, V 0.03, Al 0.12, P 0.009, S 0.013. The welding shielding gas uses an argon-rich mixture, and its mixing ratio is 95% argon + 5% carbon dioxide, and the shielding gas flow rate is taken as 20 L / min. After welding, cover with asbestos cloth and keep warm and slow-cool.

[0085] The obtained welded joint has a beautiful weld formation, and there are no defects such as cracks, pores, and lack of fusion in the weld; the room temperature tensile strength of the weld metal is 1290 MPa; the impact energy of the V-notch impact test of the weld metal and the heat-affected zone of the welded joint at a test temperature of -40 °C is greater than 38 J; according to the bending test method of welded joints GBT2653-2008, in the three-point bending test of the welded joint, the indenter diameter d = 11 * δ, and the welded joint bends 90° without cracking.

[0086] Butt welding of Q1300 steel plate with a thickness of 16 mm in Example 3

[0087] First step, use a 16 kW solid-state laser to weld a Q1300 steel plate with a thickness δ of 16 mm. During welding, the laser power γ is taken as 13.2 kW.

[0088] Second step, use wire cutting to process the groove, and mechanically grind the groove to remove the processing marks; the root face size b of the groove is taken as 12.5 mm, the groove height a of the upper surface is taken as 1.5 mm, and the groove height c of the lower surface is taken as 2 mm; the groove angle α of the upper surface is taken as 125°, and the groove angle β of the lower surface is taken as 111°.

[0089] Third step, use MAG for test plate assembly, and the groove gap p is taken as 0.2 mm; the welding parameters are as follows: the welding current I is taken as 180 A, the welding voltage U is taken as 20 V, and the welding speed M3 is taken as 0.356 * U * I / δ, that is, about 80 mm / min. The main chemical components of the welding wire are as follows (wt%): C 0.1, Si 0.46, Mn 1.49, Cr 0.6, Ni 2.4, Mo 0.9, Ti 0.1, V 0.03, Al 0.12, P 0.009, S 0.013. The welding shielding gas uses an argon-rich mixture, and its mixing ratio is 95% argon + 5% carbon dioxide; the shielding gas flow rate is taken as 20 L / min.

[0090] Fourth step, use MAG for root pass welding, and preheat to 120 °C before welding; the welding parameters are as follows: the welding current I is taken as 180 A, the welding voltage U is taken as 20 V, and the welding speed M1 is taken as 0.4 * U * I / δ, that is, about 90 mm / min. The main chemical components of the welding wire are as follows (wt%): C 0.1, Si 0.46, Mn 1.49, Cr 0.6, Ni 2.4, Mo 0.9, Ti 0.1, V 0.03, Al 0.12, P 0.009, S 0.013. The welding shielding gas uses an argon-rich mixture, and its mixing ratio is 95% argon + 5% carbon dioxide, and the shielding gas flow rate is taken as 20 L / min. After welding, cover with asbestos cloth and keep warm and slow cool.

[0091] In the fifth step, LBW is used for welding the filling layer; the welding parameters are as follows: the laser power γ is 13.2 kW, the welding speed M2 is 1.95 m / min; the defocus amount is set to +1 mm; high-purity argon is used as the shielding gas, with post-side blowing, and the gas flow rate is 20 - 30 L / min. After the filling layer is welded, a wire brush is used to clean the welding slag on the side wall of the groove and the surface of the weld bead.

[0092] In the sixth step, MAG is used for welding the cover layer, and preheating is carried out at 120 °C before welding; the welding parameters are as follows: the welding current I is 180 A, the welding voltage U is 20 V, the welding speed M1 is 0.4 * U * I / δ, that is, approximately 90 mm / min; the main chemical components of the welding wire are as follows (wt%): C 0.1, Si 0.46, Mn 1.49, Cr 0.6, Ni 2.4, Mo 0.9, Ti 0.1, V 0.03, Al 0.12, P 0.009, S 0.013. The welding shielding gas uses an argon-rich mixture, and its mixing ratio is 95% argon + 5% carbon dioxide, and the shielding gas flow rate is 18 - 22 L / min. After welding, it is covered with asbestos cloth for heat preservation and slow cooling.

[0093] The obtained welded joint has a beautiful weld formation, and there are no defects such as cracks, pores, and lack of fusion in the weld; the room-temperature tensile strength of the weld metal is 1280 MPa; at the test temperature of -40 °C, the impact energy of the V-notch impact test of the weld metal and the heat-affected zone of the welded joint is greater than 36 J; according to GBT

[0094] 2653 - 2008 Test Method for Bending Test of Welded Joints, in the three-point bending test of the welded joint, the diameter d of the indenter is 12 * δ, and the welded joint bends 90° without cracking.

[0095] Comparative Example 1

[0096] The difference between it and Example 1 is only the different height of the upper surface groove. Specifically, the height of the upper surface groove in Comparative Example 1 is a = 0.3 * (δ - b) = 1.5 mm.

[0097] The finally obtained welded joint is subjected to a three-point bending test under the condition that the diameter d of the indenter is 12 * δ, and cracking occurs when it bends 60°.

[0098] Comparative Example 2

[0099] The difference between it and Example 1 is only the different welding speed M1 in the gas metal arc welding in the sixth step. Specifically, the welding speed M1 in the gas metal arc welding in the sixth step in Comparative Example 2 is 0.31 * U * I / δ, that is, approximately 90 mm / min.

[0100] For the finally obtained welded joint, the impact energy of the V-notch -40 °C impact test in its heat-affected zone is < 36 J.

[0101] Comparative Example 3

[0102] The difference between it and Example 1 is only that the welding speed M1 in gas metal arc welding in the sixth step is different. Specifically, the welding speed M1 in gas metal arc welding in the sixth step in Comparative Example 2 is 0.45*U*I / δ, that is, about 130 mm / min.

[0103] The finally obtained welded joint was subjected to a three-point bending test under the condition that the indenter diameter d = 12*δ, and cracking occurred when bent by 60°.

[0104] As described above, only the specific embodiments of the present application are provided. Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working process described above can refer to the corresponding process in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application.

Claims

1. A welding method for improving the comprehensive mechanical properties of Q1300 steel welded joints, characterized in that: include: Bevel cutting is performed on the Q1300 steel plate to obtain a welded joint with a double-sided V-shaped groove; Welding the to-be-welded joints with double-sided V-shaped grooves to obtain assembled to-be-welded joints; The groove of the assembled joint to be welded is subjected to backing welding, filling welding and capping welding in sequence to obtain a Q1300 steel welded joint consisting of a backing layer, a filling layer and a capping layer, wherein the backing welding includes performing backing welding on the groove of the joint to be welded using gas metal arc welding to form a backing layer; the filling welding includes performing filling welding on the groove of the joint to be welded using laser welding to form a filling layer; the capping welding includes performing capping welding on the groove of the joint to be welded using gas metal arc welding to form a capping layer.

2. The welding method according to claim 1, characterized in that: The double-sided V-shaped groove is a double-sided V-shaped groove with a blunt edge, and the blunt edge thickness of the double-sided V-shaped groove is b; The laser power of the laser welding is γ; The ratio of the blunt edge thickness b to the laser power γ is X, 0.92≤X≤1.20; The unit of the blunt edge thickness b is mm, and the unit of the laser power γ is kW.

3. The welding method according to claim 2, characterized in that: The thickness of the Q1300 steel plate is δ; The height of the upper surface groove in the double-sided V-shaped groove is a, a=0.4*(δ-b); The height of the lower surface groove in the double-sided V-shaped groove is c, c = 0.6*(δ-b); The thickness of the Q1300 steel plate is in mm, the height of the upper surface groove is in mm, and the height of the lower surface groove is in mm.

4. The welding method according to claim 1, characterized in that: The step of welding the heads to be welded having double-sided V-shaped grooves to obtain the paired heads to be welded includes: welding the heads to be welded having double-sided V-shaped grooves, wherein the pairing gap of the heads to be welded is p, 0mm≤p≤0.5mm.

5. The welding method according to claim 3, characterized in that: The angle of the upper surface groove is α, and the angle of the lower surface groove is β, wherein 90°≤β<α≤130°.

6. The welding method according to claim 3, characterized in that: The welding current in the metal-metal gas shielded welding is I, 180≤I≤210; The welding voltage in the metal-metal gas shielded welding is U, 19≤U≤23; The welding speed in the metal-metal gas shielded welding is M1, M1=0.34*U*I / δ~0.40*U*I / δ; Wherein, the unit of I is A, the unit of U is V, and the unit of M1 is mm / min.

7. The welding method according to claim 1, characterized in that: The chemical element composition of the welding wire in the metal-metal gas shielded welding 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%, Al 0.12%, P 0.009%, S 0.013%; The shielding gas in the metal arc welding comprises argon and carbon dioxide, and based on the total volume of the shielding gas, the volume percentage of argon is 95%, and the volume percentage of carbon dioxide is 5%; The flow rate of the shielding gas in the metal-metal gas shielded welding is Q1, 18≤Q1≤22, and the unit of Q1 is L / min.

8. The welding method according to claim 2, characterized in that: The welding speed in the laser welding is M2, the ratio of the laser power γ to the M2 is Y, 4.0≤Y≤6.8; The defocus amount in the laser welding is D, -3≤D≤3; The shielding gas in the laser welding is high-purity argon gas, and the flow rate of the shielding gas in the laser welding is Q2, 20≤Q2≤30; Wherein, the unit of M2 is m / min, the unit of D is mm, and the unit of Q2 is L / min.

9. The welding method according to claim 6, characterized in that: The step of welding the to-be-welded joints with double-sided V-shaped grooves to obtain the assembled to-be-welded joints comprises: The welded joint with double-sided V-shaped groove is welded by gas metal arc welding, and the welding speed of the gas metal arc welding in the welding is M3, M3=0.34*U*I / δ~0.40*U*I / δ, wherein the unit of M3 is mm / min; The chemical element composition of the welding wire for metal arc welding in the welding pair 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%, Al 0.12%, P 0.009%, S 0.013%; The shielding gas for the metal-metal-shielded gas welding of the welding group comprises argon and carbon dioxide. Based on the total volume of the shielding gas, the volume percentage of argon is 95%, and the volume percentage of carbon dioxide is 5%.

10. A welding joint, characterized in that: Prepared according to the welding method according to any one of claims 1 to 9; The tensile strength of the welded joint is not less than 1280 MPa; The impact energy of the welded joint at -40°C is not less than 36J; The welded joint is subjected to three-point bending under the condition of the pressure head diameter d=(11-12)*δ, and there is no crack when bent 90°, and the units of d and δ are both mm.

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