Method for manufacturing a welded joint by laser-arc hybrid welding

Abstract

The present invention relates to a method for the production of a welded joint, comprising the following successive steps: I. providing at least two metal substrates, at least one of which is a steel substrate having a thickness of at least 8 mm and separated by at least one beveled edge, said beveled edge being at least partially coated with a pre-coating comprising a titanate and a nanoparticulate oxide selected from the group consisting of TiO2, SiO2, ZrO2, YO3, Al2O3, MoO3, CrO3, CeO2, La2O3 and mixtures thereof; and II. welding of the at least two metal substrates along the at least partially coated beveled edges by laser-arc hybrid welding in an arc-first configuration.

Description

Technical Field

[0001] The present invention relates in particular to the welding of metal substrates by laser-arc hybrid welding, in the case where at least one of the metal substrates is a steel substrate locally coated with a welding flux in order to improve the quality of the welding. The present invention also relates to a corresponding steel substrate and a method for the production of the steel substrate. The present invention is particularly well suited for construction, shipbuilding, transport industries (railway and automotive), energy-related structures, oil and gas and the offshore industry.

Background Art

[0002] It is known to weld steel substrates by laser-arc hybrid welding. This welding technique combines the principles of laser beam welding and arc welding. Depending on the settings used, there are four main types of laser-arc hybrid welding processes: tungsten inert gas (TIG), also known as gas tungsten arc (GTA), gas metal arc (GMA), which may also be called by its subtypes mig (MIG) or mag (MAG), plasma arc and submerged arc (SA).

[0003] The combination of the laser process and the arc process results in an improvement in both the welding penetration depth and the welding speed (compared to each process alone). However, despite these improvements, there remains room to limit the occurrence of cracks in the weld and to improve the process stability and, as a result, the welding penetration.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, it is necessary to improve the quality of the welding performed by laser-arc hybrid welding and thus the mechanical properties of the welded steel substrate. There is also a need to improve the deposition rate and productivity of laser-arc hybrid welding.

Means for Solving the Problems

[0005] For this purpose, the present invention is a method for manufacturing a welded joint, comprising the following successive steps: I. Providing at least two metal substrates, at least one of the metal substrates being a steel substrate having a thickness of at least 8 mm and at least one being delimited by a bead edge, said bead edge being pre-coated at least in part with a pre-coating containing nanoparticulate oxides selected from the group consisting of titanate and TiO 2 , SiO 2 , ZrO 2 , Y 2 O 3 , Al 2 O 3 , MoO 3 , CrO 3 , CeO 2 , La 2 O 3 and their mixtures, and providing at least two metal substrates; II. Welding the at least two metal substrates along the at least partially coated bead edge by laser-arc hybrid welding in an arc-leading configuration; relates to a method comprising.

[0006] The method according to the invention may also have any of the following features, considered individually or in combination.

[0007] · The titanate is selected from Na 2 Ti 3 O 7 , NaTiO 3 , K 2 TiO 3 , K 2 Ti 2 O 5 , MgTiO 3 , SrTiO 3 , BaTiO 3 , CaTiO 3 , FeTiO 3 and ZnTiO 4 and their mixtures; · The thickness of the pre - coating is 10 - 140 μm. · The percentage of nano - particulate oxide in the pre - coating is 80 wt% or less. · The percentage of nano - particulate oxide in the pre - coating is 10 wt% or more. · The nano - particles have a size included in 5 - 60 nm. · The percentage of titanate in the pre - coating is 45 wt% or more. · The diameter of the titanate is 1 - 40 μm. · The pre - coating further contains a binder. · The percentage of the binder in the pre - coating is 1 - 20 wt%. · The arc of the laser - arc hybrid welding is selected from submerged arc, gas metal arc, gas tungsten arc and plasma arc. · The pre - coating further contains a particulate compound selected from particulate oxides and / or particulate fluorides. · The pre - coating contains CeO 2 , Na 2 O, Na 2 O 2 , NaBiO 3 , NaF, CaF 2 , cryolite (Na 3 AlF 6 ) and further contains a particulate compound selected from the list consisting of their mixtures.

[0008] The present invention is a method for the manufacture of a pre - coated steel substrate, comprising the following successive steps: A. Providing a steel substrate delimited by at least one chamfer edge having a thickness of at least 8 mm and a chamfer angle included in 1 - 10°. B. A titanate and TiO 2 , SiO 2 , ZrO 2 , Y 2 O 3 , Al 2 O 3 , MoO 3 , CrO 3, CeO 2 , La 2 O 3 and at least partial deposition of the precoating solution containing nanoparticulate oxides selected from the group consisting of these and their mixtures onto the said edge, also relates to a method comprising.

[0009] The method for the production of a precoated steel substrate according to the invention may also have any of the following features considered individually or in combination.

[0010] · The deposition of the precoating solution is carried out by spin coating, spray coating, dip coating or brush coating, · In step B), the precoating solution further contains a solvent, · In step B), the precoating solution contains 1 to 200 g / L of nanoparticulate oxides, · In step B), the precoating solution contains 100 to 500 g / L of titanate, · In step B), the precoating solution further contains a binder precursor, · The method further comprises a drying step of the precoated steel substrate obtained in step B).

[0011] The present invention relates to a steel substrate having a thickness of at least 8 mm and delimited by at least one edge having a bevel angle comprised between 1 and 10°, said edge being at least partially coated with a precoating containing titanate and nanoparticulate oxides selected from the group consisting of TiO 2 , SiO 2 , ZrO 2 , Y 2 O 3 , Al 2 O 3 , MoO 3 , CrO 3 , CeO 2 , La 2 O 3 and their mixtures.

[0012] The following terms are defined.

[0013] · A nanoparticle is a particle with a size of 1 to 100 nanometers (nm).

[0014] · Titanate refers to an inorganic compound containing titanium, oxygen, and at least one additional element such as an alkali metal element, an alkaline earth metal element, a transition metal element, or a metal element. They can be in the form of their salts.

[0015] · "Coated" means that the steel substrate is at least locally covered with a pre - coating. The coating can be limited, for example, to the area where the steel substrate is welded. "Coated" inclusively includes "directly on top" (with no intermediate material, element, or space disposed therebetween) and "indirectly on top" (with an intermediate material, element, or space disposed therebetween). For example, coating a steel substrate can include directly applying a pre - coating on the substrate without an intermediate material / element therebetween, and indirectly applying a pre - coating on the substrate with one or more intermediate materials / elements (such as an anticorrosion coating) therebetween.

[0016] Without being bound by any theory, the pre - coating is thought to modify mainly the physics of the molten pool during welding. In the present invention, not only the nature of the compound but also the size of the oxide particles being 100 nm or less is thought to modify the physics of the arc and the molten pool.

[0017] In fact, the initially advancing arc melts and incorporates the pre - coating into the molten metal in the form of dissolved species and into the arc in the form of ionized species. The presence of titanate and nanoparticles in the arc causes the arc to converge and the temperature of the molten metal pool to rise. As a result, the keyhole, i.e., the literal hole in the steel substrate caused by its evaporation, is more easily formed by a laser impinging on the molten metal pool. This improves the efficiency of the process.

[0018] Furthermore, the precoating dissolved in the molten metal modifies the Marangoni flow, which is the mass transfer at the liquid-gas interface caused by the surface tension gradient. In particular, the components of the precoating modify the gradient of the surface tension along the interface. This change in surface tension results in a reversal of the fluid flow towards the center of the weld pool. Without being bound by any theory, it is believed that the nanoparticles dissolve at a lower temperature than the microparticles, and thus more oxygen dissolves in the molten pool, activating the reverse Marangoni flow. The latter contributes to the retention of an appropriate keyhole shape, which in turn prevents gas entrainment and thus the generation of pores in the weld.

[0019] Furthermore, titanate mixed with nanoparticle oxides modifies the plasma plume interaction with the laser beam. In particular, the increase in oxygen due to the dissolution of the precoating reduces the scattering of the laser beam. As a result, while the laser spot diameter is reduced, the keyhole effect is enhanced. This enables the energy beam to penetrate deeper and be delivered to the joint extremely efficiently. This increases the weld penetration, minimizes the heat affected zone, which in turn limits the distortion of the part.

[0020] Furthermore, as the components of the precoating increase the surface tension with temperature, the wettability of the welding material increases along the bevel that is colder than the center of the molten pool, which prevents slag entrainment.

[0021] Furthermore, it has been observed that the nanoparticles improve the uniformity of the applied precoating by filling the gaps between the microparticles and covering the surface of the microparticles. This helps to stabilize the welding arc and thus improve the weld penetration and quality.

[0022] The present invention will be better understood by reading the following description, which is provided purely for illustrative purposes and is in no way intended to be limiting, with reference to FIG. 1, which illustrates a substrate having a double-Y edge.

Brief Description of the Drawings

[0023]

Figure 1

Modes for Carrying Out the Invention

[0024] The precoating contains titanate and nanoparticle oxides selected from the group consisting of TiO 2 、SiO 2 、ZrO 2 、Y 2 O 3 、Al 2 O 3 、MoO 3 、CrO 3 、CeO 2 、La 2 O 3 and mixtures thereof. In other words, the precoating contains titanate and at least one nanoparticle oxide, and at least one nanoparticle oxide is selected from the group consisting of TiO 2 、SiO 2 、ZrO 2 、Y 2 O 3 、Al 2 O 3 、MoO 3 、CrO 3 、CeO 2 、La 2 O 3 and mixtures thereof. This means that the precoating does not contain other nanoparticle oxides other than those listed.

[0025] The titanate is selected from the group of titanates consisting of alkali metal titanates, alkaline earth metal titanates, transition metal titanates, metal titanates and mixtures thereof. The titanate is more preferably Na 2 Ti 3 O 7 、NaTiO 3 、K 2 TiO 3 、K 2 Ti 2O 5 , MgTiO 3 , SrTiO 3 , BaTiO 3 , CaTiO 3 , FeTiO 3 and ZnTiO 4 and are selected from among them and their mixtures. These titanates are considered to further increase the penetration depth based on the effect of the reverse Marangoni flow. It is the understanding of the inventors that all titanates behave somewhat similarly and increase the penetration depth. Therefore, all titanates are part of the present invention. Those skilled in the art will know which titanate to select depending on the specific case. To do so, those skilled in the art will consider how easily the titanate melts and dissolves, how much the titanate increases the dissolved oxygen content, and how the additional elements of the titanate affect the physics of the molten pool and the microstructure of the final weld. For example, NaTiO 7 is preferred due to the presence of Na which improves slag formation and desorption.

[0026] Preferably, the titanate has a diameter of 1 to 40 μm, more preferably 1 to 20 μm, and advantageously 1 to 10 μm. This diameter of the titanate is considered to further improve the arc convergence and the reverse Marangoni effect. Furthermore, having small micrometer-sized titanate particles increases the specific surface area available for mixing with nanoparticle oxides and further adheres the nanoparticle oxides to the titanate particles. Also, having small micrometer-sized titanate particles makes it easier to spray the particles.

[0027] Preferably, the weight percentage of the titanate in the dry weight of the precoating is 45% or more, more preferably 45% to 90%, and even more preferably 45% to 75%.

[0028] The nanoparticle oxide is TiO 2 , SiO 2 , ZrO 2 , Y 2 O 3 , Al2 O 3 、 MoO 3 、 CrO 3 、 CeO 2 、 La 2 O 3 and selected from their mixtures. These nanoparticles can be easily dissolved in the molten pool, supplying oxygen to the molten pool, as a result of which, the penetration depth is increased and the keyhole for preventing defects is stabilized. CaO, MgO, B 2 O 3 、 Co 3 O 4 or Cr 2 O 3 In contrast to other oxides such as these, they do not tend to form brittle phases, do not have a high refractory effect that hinders the accurate melting of steel by heat, and their metal ions do not tend to recombine with oxygen in the molten pool.

[0029] Preferably, the nanoparticles are SiO 2 and / or TiO 2 , more preferably a mixture of SiO 2 and TiO 2 . SiO 2 mainly increases the penetration depth and facilitates slag removal, while TiO 2 is considered to mainly increase the penetration depth and form Ti-based inclusions that improve mechanical properties.

[0030] Another example of a mixture of nanoparticle oxides is · Yttria-stabilized zirconia (YSZ), a ceramic in which the cubic crystal structure of zirconium dioxide (ZrO 2 O 3 ) is stabilized at room temperature by the addition of yttrium oxide (Y 2 ), · La 2 O 3 、 ZrO 2 and Y 2 O 3 in a 1:1:1 combination that helps to adjust the refractory effect and promotes the formation of inclusions.

[0031] Preferably, the nanoparticles have a size included in 5 to 60 nm. This nanoparticle diameter is considered to further improve the uniform distribution of the coating.

[0032] Preferably, the weight percentage of the nanoparticle oxide in the dry weight of the precoating is 80% or less, preferably 10% or more, more preferably 10 to 60%, and even more preferably 20 to 55%. In some cases, the percentage of nanoparticles may have to be limited to avoid an overly high refractory effect. Those skilled in the art who know the various refractory effects of nanoparticles will adapt the percentage for each case.

[0033] According to one modification of the present invention, when the precoating is applied on a steel substrate and dried, the precoating consists of titanate and nanoparticle oxide.

[0034] According to another modification of the present invention, the precoating further includes at least one binder that embeds titanate and nanoparticle oxide and improves the adhesion of the precoating on the steel substrate. This improved adhesion further prevents the particles of the precoating from being blown away by the flow of the shielding gas when the shielding gas is used. Preferably, the binder is purely inorganic in order to avoid toxic gases that may be generated by organic binders, especially during welding. Examples of inorganic binders are sol-gels of organofunctional silanes or siloxanes. Examples of organofunctional silanes are silanes functionalized with groups of the families of amines, diamines, alkyls, amino-alkyls, aryls, epoxies, methacrylates, fluoroalkyls, alkoxys, vinyls, mercaptans, and aryls. Aminoalkylsilanes are particularly preferred because they significantly promote adhesion and have a long shelf life. Preferably, the binder is added in an amount of 1 to 20% by weight of the dried precoating.

[0035] According to another modification of the present invention, the precoating is, for example, CeO 2 , Na 2 O, Na 2 O 2, NaBiO 3 , NaF, CaF 2 , cryolite (Na 3 AlF 6 ), etc., and further contains particulate oxides such as particulate fluorides. For some of the nanoparticle oxides listed above, the transition from nanoparticles to microparticles reduces health and safety concerns associated with some uses of these oxides. To further prevent slag entrainment, to improve slag formation, Na 2 O, Na 2 O 2 , NaBiO 3 , NaF, CaF 2 , cryolite can be added. They also help to form a slag that can be easily separated. The precoating can contain 0.1 - 5 wt% of Na 2 O, Na 2 O 2 , NaBiO 3 , NaF, CaF 2 , cryolite or a mixture thereof based on the dry weight of the precoating.

[0036] Preferably, the thickness of the precoating is between 10 - 140 μm, more preferably between 30 - 100 μm.

[0037] The precoating at least partially covers one edge of the steel substrate. The steel substrate can have any shape suitable for laser - arc hybrid welding. In the present invention, the steel substrate is simply defined by a thickness of at least 8 mm such that the steel substrate is suitable for laser - arc hybrid welding and by an edge that should be at least partially welded to another metal substrate. The bevel can have a single Y or double Y shape depending on the thickness of the sample. The bevel angle is preferably included in the range of 1 - 10°. Lower angles can promote poor fusion at the edge, and higher angles require more welding passes to fill the material. When the bevel has a double Y shape, the bevel angle refers to the angle of each Y.

[0038] Preferably, the lotus leaf edge is serrated such that the roughness Rz is higher than 4 μm, more preferably included in 4 to 16 μm. Such roughness improves the adhesion of the pre - coating on the lotus leaf edge.

[0039] Preferably, the steel substrate is carbon steel.

[0040] The steel substrate can optionally have at least a part of one of its surfaces coated with an anticorrosion coating. Preferably, the anticorrosion coating contains a metal selected from the group consisting of zinc, aluminum, copper, silicon, iron, magnesium, titanium, nickel, chromium, manganese, and alloys thereof.

[0041] In a preferred embodiment, the anticorrosion coating is an aluminum - based coating containing less than 15 wt% Si, less than 5.0 wt% Fe, optionally 0.1 - 8.0 wt% Mg, and optionally 0.1 - 30.0 wt% Zn, with the balance being Al and unavoidable impurities resulting from the manufacturing process. In another preferred embodiment, the anticorrosion coating is a zinc - based coating containing 0.01 - 8.0 wt% Al, optionally 0.2 - 8.0 wt% Mg, with the balance being Zn and unavoidable impurities resulting from the manufacturing process.

[0042] The anticorrosion coating is preferably applied to both sides of the steel substrate.

[0043] Regarding the process, when a steel substrate is provided, a pre - coating solution is at least partially applied onto the substrate lotus leaf edge to form a pre - coating.

[0044] The pre - coating solution contains titanate and nano - particulate oxide as described above for the pre - coating. In particular, the pre - coating solution contains 100 - 500 g / L, more preferably 175 - 250 g / L -1 of titanate. In particular, the pre - coating solution contains 1 - 200 g / L -1 , more preferably 5 - 80 g / L -1It contains nano-particle oxides. Thanks to these concentrations in the titanate and nano-particle oxides, the quality of the welding obtained with the help of the corresponding precoating is further improved.

[0045] Advantageously, the precoating solution further contains a solvent. This enables a well-dispersed precoating. Preferably, the solvent is volatile at ambient temperature. For example, the solvent is selected from volatile organic solvents such as water, acetone, methanol, isopropanol, ethanol, ethyl acetate, diethyl ether and non-volatile organic solvents such as ethylene glycol.

[0046] According to a variant of the invention, the precoating solution further contains a binder precursor in order to embed the titanate and nano-particle oxides and to improve the adhesion of the precoating on the steel substrate. Preferably, the binder precursor is a sol of at least one organofunctional silane. Examples of organofunctional silanes are silanes functionalized in particular with groups of the amine, diamine, alkyl, amino-alkyl, aryl, epoxy, methacryl, fluoroalkyl, alkoxy, vinyl, mercapto and aryl families. Preferably, the binder precursor is added in an amount of 40 - 400 g.L of the precoating solution. -1 of the amount.

[0047] The precoating solution can be obtained by first mixing the titanate and the nano-particle oxides. This can be done either under wet conditions or dry conditions using a solvent such as acetone, for example in a 3D powder shaker mixer. Mixing promotes strong aggregation of the nanoparticles on the titanate particles, which prevents the unintentional release of nanoparticles into the air, which is a health and safety issue.

[0048] The deposition of the precoating solution can be carried out in particular by spin coating, spray coating, dip coating or brush coating.

[0049] Preferably, the precoating solution is deposited only locally. In particular, the precoating solution is applied to the edge region where the steel substrate is welded.

[0050] Once the precoating solution is applied onto the steel substrate, optionally the precoating solution can be dried. Drying can be carried out by blowing air or an inert gas at ambient temperature or elevated temperature. When the precoating contains a binder, the drying step is preferably also a curing step during which the binder is cured. Curing can be carried out by infrared (IR), near-infrared (NIR), or a conventional oven.

[0051] Preferably, when the organic solvent is volatile at ambient temperature, the drying step is not carried out. In that case, the organic solvent evaporates, resulting in a dried precoating on the metal substrate.

[0052] Once the precoating is formed on a part of the edge of the steel substrate, this part can be welded to another metal substrate by laser-arc hybrid welding.

[0053] The arc of the laser-arc hybrid welding can be selected from a submerged arc, a gas metal arc, a gas tungsten arc, and a plasma arc. All of these arcs can benefit from the present invention.

[0054] The average current is preferably 40 - 1000 A. The voltage is preferably 1 - 40 V.

[0055] The laser of the laser-arc hybrid welding can be selected from solid-state lasers such as Nd:YAG, Nd:glass, ruby, Nd:YLF, Yb:YAG, Yb:fiber, Ti:sapphire, etc. Preferably, the laser of the laser-arc hybrid welding is a Nd:YAG laser or a Yb:YAG laser (at 1030 nm) whose most common emission wavelength is 1064 nm.

[0056] Since the precoating has a similar effect on different arcs and different lasers, any combination of arc and laser can benefit from the present invention.

[0057] Welding is operated in an arc-first configuration. This means that the arc is in front of the laser beam. The arc first strikes the steel substrate, melting the steel substrate to form a molten pool. Then, the laser impinges on the molten pool.

[0058] The other metal substrate can be a steel substrate having the same composition or a different composition as the precoated steel substrate. The other metal substrate can also be made of another metal such as aluminum, for example. More preferably, the other metal substrate is a precoated steel substrate according to the present invention. The other metal substrate is disposed along the precoated flange of the steel substrate. Then, the two substrates are welded by laser-arc hybrid welding.

[0059] Depending on the welding technique, a consumable electrode in the form of a wire (SAW, GMAW) can be present, or if the electrode is not consumable, a material for filling the joint can be supplied laterally in the form of a wire (GTAW, plasma). In both cases, the wire is made of, for example, Fe, Si, C, Mn, Mo, and / or Ni.

[0060] Depending on the welding technique, the flange can be at least locally covered by a shielding flux. The shielding flux protects the welded zone from oxidation during welding.

[0061] Using the method according to the present invention, it is possible to obtain at least a welded joint of a first metal substrate and a second metal substrate in the form of a steel substrate, the first and second metal substrates being at least partially welded together by laser-arc hybrid welding, and the welded zone including a dissolved and / or precipitated precoating containing titanate and nanoparticle oxides.

[0062] The titanate is selected from the group of titanates consisting of alkali metal titanates, alkaline earth metal titanates, transition metal titanates, metal titanates, and mixtures thereof. The titanate is more preferably Na 2 Ti 3 O 7 , NaTiO 3 , K 2 TiO 3 , K 2 Ti 2 O 5 , MgTiO 3 , SrTiO 3 , BaTiO 3 , CaTiO 3 , FeTiO 3 and ZnTiO 4 and is selected from among mixtures thereof.

[0063] The nano-particle oxide is selected from TiO 2 , SiO 2 , ZrO 2 , Y 2 O 3 , Al 2 O 3 , MoO 3 , CrO 3 , CeO 2 , La 2 O 3 and mixtures thereof.

[0064] "Dissolved and / or precipitated precoating" means that due to reverse Marangoni flow, the components of the precoating can be drawn towards the center of the liquid-gas interface of the molten pool and even into the molten metal. Some components dissolve in the molten pool, resulting in an enrichment of the corresponding elements in the weld. Other components precipitate and are part of the complex oxides that form precipitates in the weld.

[0065] In particular, when the Al content of the steel substrate exceeds 50 ppm, the welded zone contains inclusions, particularly those containing Al-Ti oxides or Si-Al-Ti oxides or other oxides, depending on the nature of the added nanoparticles. These precipitates of mixed elements are smaller than 5 μm. As a result, these precipitates of mixed elements do not impair the toughness of the welded zone. The inclusions can be observed by electron probe microanalysis (EPMA). Without being bound by any theory, it is considered that the nanoparticle oxides promote the formation of inclusions of limited size so that the toughness of the welded zone is not impaired.

[0066] Finally, the present invention relates to the use of the welded joint according to the present invention for the manufacture of parts for the oil and gas and offshore industries, shipbuilding, construction and transport (railway and automotive).

Examples

[0067] Steel substrates having a chemical composition in weight percentages disclosed in Table 1 were selected:

[0068]

Table 1

[0069] The steel substrate had a thickness of 25 mm. The steel substrate had a tensile strength of 485 - 620 MPa and a yield strength of 260 MPa.

[0070] [Example 1] As shown in FIG. 1, a sample 1 of 100×150 mm was prepared with a double-V edge, each bevel being inclined at an angle α of 4°, and the upper and lower bevels being separated by a gap 2 of 5 mm. The edge was serrated so that the bevel had a roughness Rz of 5 - 8 μm and the 5 mm gap had a roughness Rz of 6 - 15 μm. The edge to be welded was degreased and cleaned with acetone.

[0071] Sample 1 was not coated with a precoating.

[0072] For Sample 2, by mixing acetone with the following elements, MgTiO 3 (diameter: 2 μm), SiO 2 (diameter: 10 nm), and TiO 2 (diameter: 50 nm), an acetone solution was prepared. In the acetone solution, the concentration of MgTiO 3 was 175 g / L -1 . The concentration of SiO 2 was 25 g / L -1 . The concentration of TiO 2 was 50 g / L -1 . Next, the cleaned sidewalls of Sample 2 were coated with the acetone solution by spraying. The acetone was evaporated. The percentage of MgTiO 3 in the dried pre - coating was 70 wt%, the percentage of SiO 2 was 10 wt%, and the percentage of TiO 2 was 20 wt%. The pre - coating had a thickness of 50 μm.

[0073] Samples 1 and 2 were each placed side by side with a sample of the bare selected steel substrate separated by a 0.3 - mm gap, and welded by laser - arc hybrid welding in an arc - leading configuration without preheating by performing welding passes until the bevel was filled and the joint was completed. The laser was a 16 - kW Yb:YAG laser with a 0.3 - mm spot. The arc device was a gas - metal arc welding torch using an argon / CO 2 80 / 20 shielding gas. The supplied wire contained up to 0.06 wt% C, 0.8 wt% Si, and 1.5 wt% Mn. The welding parameters are listed in Table 2 below.

[0074]

Table 2

[0075] As is clear from Table 2, Sample 1 required two welding passes to be completely welded, while Sample 2 required only one welding pass with the same welding parameters. This first result already shows that the precoating according to the present invention increases the penetration depth and productivity of laser-arc hybrid welding in an arc-leading configuration.

[0076] After welding, the welds of both welded assemblies were inspected by visual inspection and X-ray imaging, and the cross-sections were analyzed by micrographs.

[0077] Table 3 below details the micrograph analysis of each weld.

[0078]

Table 3

[0079] The precoating improved the arc penetration by 10% and the laser penetration by 50%.

[0080] X-ray imaging analysis revealed cracks along the welds of Sample 1, and cross-section analysis revealed cracks in Sample 1. These results show that the precoating improves the wettability.

[0081] Tensile tests, Charpy V tests, and hardness property evaluations also confirmed that the precoating on the edges of the steel substrate improves laser-arc hybrid welding in an arc-leading configuration without degrading the mechanical properties of the joint.

[0082] [Example 2] Sample 3 was prepared like Sample 2 (with precoating).

[0083] Then, the samples were welded at an increased travel speed (25 mm / s, i.e., a 56% increase) and a reduced gap (0.2 mm) with and without preheating at 320 °C before welding, while all other conditions were the same as in Example 1.

[0084] The obtained results confirmed that thanks to the precoating, it is possible to improve the travel speed of laser-arc hybrid welding and thus the productivity. Furthermore, as shown in Table 4 comparing the results obtained using the preheated sample 3 with those obtained using the preheated sample 1 (detailed in Example 1), this productivity improvement is not accompanied by a decrease in the mechanical properties of the joint, but even by an improvement in some mechanical properties of the joint.

[0085] [Table 4]

[0086] The Charpy V test was carried out in accordance with ISO 9016:2012 at T = -20 °C.

[0087] "Good" in the column of "Fracture in base metal" means that the fracture of the sample at the end of the tensile test was on the base metal, and the fracture of the sample is searched for on the welded sample.

[0088] "Good" in the "Hardness" column means that the hardness of the tested sample complies with the ISO 15614-1:2017 standard.

[0089] [Example 3] The effects of different precoatings on the welding of steel substrates were evaluated by finite element method (FEM) simulations. In the simulations, the precoating included nano-sized oxide particles with diameters of 10 - 50 nm and optionally MgTiO 3 (diameter: 2 μm). The coating thickness was 40 μm. Arc welding was simulated using each precoating, and the results are shown in Table 5 below.

[0090] [Table 5]

[0091] The results show that the pre - coating according to the present invention improves the penetration and quality of the welded part compared with the comparative example.

[0092] [Example 4] For sample 17, an aqueous solution containing the following components was prepared: 363 g.L -1 of MgTiO 3 (diameter: 2 μm), 77.8 g.L -1 of SiO 2 (diameter range: 12 - 23 nm), 77.8 g.L -1 of TiO 2 (diameter range: 36 - 55 nm) and 238 g.L -1 of 3 - aminopropyltriethoxysilane (Dynasylan(R) AMEO manufactured by Evonik(R)). The solution was applied onto the edges of a steel substrate and dried by 1) IR and 2) NIR. The dried pre - coating was 40 μm thick and contained 62 wt% of MgTiO 3 , 13 wt% of SiO 2 , 13 wt% of TiO 2 and 12 wt% of a binder obtained from 3 - aminopropyltriethoxysilane.

[0093] For sample 18, an aqueous solution containing the following components was prepared: 330 g.L -1 of MgTiO 3 (diameter: 2 μm), 70.8 g.L -1 of SiO 2 (diameter range: 12 - 23 nm), 70.8 g.L -1 of TiO 2 (diameter range: 36 - 55 nm), 216 g.L -1 of 3 - aminopropyltriethoxysilane (Dynasylan(R) AMEO manufactured by Evonik(R)) and 104.5 g.L -1 of nanoscale SiO functionalized with an organofunctional silane 2Composition with particles (Dynasylan(R) Sivo 110 manufactured by Evonik). The solution was applied on the edge of a steel substrate and dried by 1) IR and 2) NIR. The dried precoating had a thickness of 40 μm and contained 59.5 wt% of MgTiO 3 , 13.46 wt% of SiO 2 , 12.8 wt% of TiO 2 and 14.24 wt% of a binder obtained from 3-aminopropyltriethoxysilane and organofunctional silane.

[0094] In all cases, the adhesion of the precoating on the edge was significantly improved.

[0095] The beneficial effect of the present invention was demonstrated in the case of laser-arc hybrid welding in an arc-leading configuration using a MAG arc and a Yb:YAG laser. All of these techniques use a precoating and a coatable edge such that the physics of the arc and the molten pool are modified, yet the beneficial effect of the present invention is extensible to other arcs and lasers.

Claims

1. A method for manufacturing a welded joint, comprising the following successive steps: I. Providing at least two metal substrates, wherein at least one metal substrate has a thickness of at least 8 mm and at least one is a steel substrate delimited by a bead edge, and the bead edge contains titanate and TiO ２ , SiO ２ , ZrO ２ , Y ２ O ３ , Al ２ O ３ , MoO ３ , CrO ３ , CeO ２ , La ２ O ３ and is at least partially coated with a pre - coating containing oxide nanoparticles selected from the group consisting of these and their mixtures, and wherein the percentage of the oxide nanoparticles in the pre - coating is 10 wt% or more and 55 wt% or less based on the dry weight of the pre - coating, The weight percentage of titanate in the precoating is 45% to 90% based on the dry weight of the precoating, II. Welding of at least two metal substrates along at least partially coated edges by laser-arc hybrid welding in an arc-leading configuration, and A method comprising the above.

2. wherein the titanate is Na ２ Ti ３ O ７ , NaTiO ３ , K ２ TiO ３ , K ２ Ti ２ O ５ , MgTiO ３ , SrTiO ３ , BaTiO ３ , CaTiO ３ , FeTiO ３ and ZnTiO ４ and the method according to claim 1, selected from among mixtures thereof.

3. The method according to any one of claims 1 or 2, wherein the thickness of the precoating is 10 to 140 μm.

4. The method according to any one of claims 1 to 3, wherein the oxide nanoparticles have a size included in 5 to 60 nm.

5. The method according to any one of claims 1 to 4, wherein the diameter of the titanate is 1 to 40 μm.

6. The method according to any one of claims 1 to 5, wherein the precoating further comprises a binder.

7. The method according to claim 6, wherein the percentage of the binder in the precoating is 1 to 20% by weight.

8. The method according to any one of claims 1 to 7, wherein the arc of the laser-arc hybrid welding is selected from a submerged arc, a gas metal arc, a gas tungsten arc, and a plasma arc.

9. A method for manufacturing a precoated steel substrate, comprising the following successive steps: A. Providing a steel substrate having a thickness of at least 8 mm and delimited by at least one flange edge having a bevel angle included in 1 to 10°, B. titanate and TiO ２ , SiO ２ , ZrO ２ , Y ２ O ３ , Al ２ O ３ , MoO ３ , CrO ３ , CeO ２ , La ２ O ３ and at least partial deposition of the precoating solution containing oxide nanoparticles selected from the group consisting of these and their mixtures onto the said edge of the substrate, comprising, The percentage of the oxide nanoparticles in the precoating is 10% by weight or more and 55% by weight or less based on the dry weight of the precoating, The weight percentage of titanate in the precoating is 45% to 90% based on the dry weight of the precoating, A method.

10. The method according to claim 9, wherein in step B), the deposition of the precoating solution is performed by spin coating, spray coating, dip coating, or brush coating.

11. The method according to any one of claims 9 or 10, wherein in step B), the precoating solution further comprises a solvent.

12. The method according to any one of claims 9 to 11, wherein in step B), the precoating solution comprises 1 to 200 g / L of oxide nanoparticles.

13. The method according to any one of claims 9 to 12, wherein in step B), the precoating solution contains 100 to 500 g / L of titanate.

14. The method according to any one of claims 9 to 13, wherein in step B), the precoating solution further contains a binder precursor.

15. The method according to any one of claims 9 to 14, further comprising a drying step of the precoated steel substrate obtained in step B).

16. A steel substrate having a thickness of at least 8 mm and delimited by at least one chamfer edge having a chamfer angle included in the range of 1 to 10°, said chamfer edge being coated at least in part with a pre - coating containing titanate and oxide nanoparticles selected from the group consisting of TiO ２ , SiO ２ , ZrO ２ , Y ２ O ３ , Al ２ O ３ , MoO ３ , CrO ３ , CeO ２ , La ２ O ３ and mixtures thereof. The percentage of the oxide nanoparticles in the precoating is 10% by weight or more and 55% by weight or less based on the dry weight of the precoating, and the weight percentage of titanate in the precoating is 45% to 90% based on the dry weight of the precoating. Steel substrate.

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