Flux compositions and corresponding methods for welding metals

Abstract

This invention relates to fluxes comprising titanates and nanoparticle niobium compounds selected from niobium oxides, alkali metal niobates, and mixtures thereof.

Description

[0001] This invention relates to welding of metal substrates, particularly in cases where at least one of the metal substrates is steel. The invention also relates to compositions of fluxes for improving weld quality. The flux may be contained in a solution to be locally applied to the steel substrate to form a pre-coating, or it may be contained in a powder-cored wire to be used as a substitute for the pre-coating. The invention further relates to corresponding methods for manufacturing welded joints. These methods are particularly suitable for the construction, shipbuilding, transportation (railways and automobiles), energy-related structures, oil and gas, and offshore industries.

[0002] It is known that various welding techniques are used to weld metal substrates, including: Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW), also known as Tungsten Inert Gas Welding (TIGW), Submerged Arc Welding (SAW), Laser Beam Welding (LBW), Narrow Gap Welding (also known as Narrow Bevel Welding), and Laser Arc Hybrid Welding. This welding can be accomplished with the aid of flux to enhance penetration into the substrate. This flux differs from potential protective fluxes primarily used to protect the weld zone from oxidation during welding.

[0003] It is also known to weld metal substrates with filler wire, particularly when the gap has been filled. The filler wire can feed the weld from the side (e.g., in gas-shielded tungsten inert gas welding and laser welding) or it can be a consumable electrode (e.g., in submerged arc welding, gas-shielded metal arc welding, gas-shielded cored wire arc welding, narrow gap welding, and hybrid laser welding, where the arc head is a gas-shielded metal arc). In some cases, the filler wire is in the form of a cored wire, i.e., hollow and filled with flux containing components that improve performance.

[0004] Patent application WO00 / 16940 discloses deep penetration gas-shielded tungsten inert gas (TSG) welding achieved using titanates such as Na2Ti3O7 or K2TiO3. Titanates are added to the molten pool as part of the flux or as part of the filler wire to provide deep penetration welds in carbon steel, chromium-molybdenum steel, stainless steel, and nickel-based alloys. The titanate compounds in WO00 / 16940 are used in the form of high-purity powders of about 325 mesh or finer, where 325 mesh corresponds to 44 μm. To control arc blow, weld bead consistency, and slag and surface appearance of the weldment, various additional components, including transition metal oxides such as TiO, TiO2, Cr2O3, and Fe2O3, silicon dioxide, manganese silicide, fluorides, and chlorides, can optionally be added to the titanate-based filler wire. All compounds in the flux have a micron-sized structure.

[0005] Although the flux disclosed in WO00 / 16940 improved the penetration, the penetration was not optimal for steel substrates.

[0006] Therefore, it is necessary to improve weld penetration in the steel substrate and thus improve the mechanical properties of the welded steel substrate. It is also necessary to increase the deposition rate and productivity of the weld.

[0007] For this purpose, the present invention relates to a flux comprising titanate and nanoparticle niobium compounds selected from niobium oxides, alkali metal niobates, and mixtures thereof.

[0008] The welding according to the invention may also have the following optional features, considered individually or in combination:

[0009] - The niobium nanoparticles are selected from NbO, NbO2, and Nb2O5, and mixtures thereof.

[0010] - The percentage of niobium nanoparticles in the flux is less than or equal to 80% by weight.

[0011] - The percentage of niobium nanoparticles in the flux is 2% to 30% by weight.

[0012] - The size of niobium nanoparticles ranges from 5 nm to 150 nm.

[0013] - Titanates are selected from: Na₂Ti₃O₇, NaTiO₃, K₂TiO₃, K₂Ti₂O₅, MgTiO₃, SrTiO₃, BaTiO₃, CaTiO₃, FeTiO₃, and ZnTiO₄, and mixtures thereof.

[0014] - The percentage of titanate in the flux is greater than or equal to 45% by weight.

[0015] -Titanium ions have diameters ranging from 1 μm to 40 μm.

[0016] The flux also contains at least one additional nanoparticle oxide selected from TiO2, SiO2, ZrO2, Y2O3, Al2O3, MoO3, CrO3, CeO2, La2O3, and mixtures thereof.

[0017] - The flux also contains microparticle compounds selected from microparticle oxides and / or microparticle fluorides.

[0018] - The flux also contains microparticle compounds selected from the list of CeO2, Na2O, Na2O2, NaBiO3, NaF, CaF2, cryolite (Na3AlF6), and mixtures thereof.

[0019] - The flux also contains solvents.

[0020] - The flux contains 1 g / L to 200 g / L of nano-particle niobium compound.

[0021] - The flux contains 100 g / L to 500 g / L of titanate.

[0022] - The flux also contains binder precursors.

[0023] The present invention also relates to a method for manufacturing a pre-coated steel substrate, the method comprising the step of depositing, at least partially, a flux according to the invention onto the steel substrate.

[0024] The present invention also relates to a pre-coated steel substrate, which can be obtained by the method according to the invention, having at least partially coated with a pre-coating comprising titanate and a nanoparticle niobium compound selected from niobium oxide, alkali metal niobate, and mixtures thereof.

[0025] The present invention also relates to a method for manufacturing a welded joint, the method comprising the following sequential steps:

[0026] I. Provide at least two metal substrates, wherein at least one metal substrate is a pre-coated steel substrate according to the present invention, and

[0027] II. Weld at least two metal substrates.

[0028] The present invention also relates to a powder-cored welding wire comprising the flux of the present invention.

[0029] The present invention also relates to a method for manufacturing welded joints, the method comprising arc welding or laser welding of steel with a powder-cored welding wire according to the present invention.

[0030] The present invention also relates to a method for manufacturing a welded joint, the method comprising the following sequential steps:

[0031] I. Provide at least two metal substrates, wherein at least one metal substrate is a steel substrate, and

[0032] II. The flux according to the invention is applied simultaneously to at least two metal substrates in front of the welding head while the welding head is used to weld at least two metal substrates.

[0033] The following terms are defined:

[0034] - Nanoparticles are particles with a size of 1 nanometer (nm) to 200 nanometers (nm). The term "nanoparticle" refers to compounds in the form of nanoparticles within the above range.

[0035] Titanates are inorganic compounds containing titanium, oxygen, and at least one other element, such as an alkali metal, alkaline earth, transition metal, or metallic element. These inorganic compounds may be in the form of their salts.

[0036] - "Coating" means that a steel substrate is at least partially covered by a pre-coating. The coverage may be limited, for example, to the area of ​​the steel substrate that will be welded. "Coating" includes both "directly on" (without intermediate materials, elements, or spaces) and "indirectly on" (with intermediate materials, elements, or spaces). For example, coating a steel substrate can include applying a pre-coating directly to the substrate without intermediate materials / elements, and applying a pre-coating indirectly to the substrate with one or more intermediate materials / elements (e.g., an anti-corrosion coating).

[0037] Without being bound by any theory, it is believed that flux and the corresponding pre-coated and cored wire primarily alter the physical properties of the molten pool. It appears that in this invention, not only the properties of the compounds, but also the size of oxide particles equal to or less than 100 nm, change the physical properties of the molten pool.

[0038] In practice, the flux is melted and incorporated into the molten metal as a dissolved substance, and if the welding technique involves an electric arc, it is incorporated into the arc as an ionized substance. The arc contracts due to the presence of titanates and nanoparticle niobium compounds within it.

[0039] Furthermore, the flux dissolved in the molten metal alters the Marangoni flow, which is the mass transfer at the liquid-gas interface caused by the surface tension gradient. Specifically, the flux composition changes the surface tension gradient along the interface. This change in surface tension causes a reversal of fluid flow towards the center of the molten pool. This reversal leads to improved weld penetration and welding efficiency, resulting in an increased deposition rate and thus increased productivity. Without being bound by any theoretical framework, it is assumed that nanoparticles dissolve at lower temperatures than microparticles, and therefore dissolve more oxygen in the molten pool, which drives the reverse Marangoni flow.

[0040] When welding techniques involve an electric arc, the effect of reverse Marangoni flow, combined with the higher plasma temperature due to arc contraction, further improves weld penetration and material deposition rate. When welding techniques involve a laser beam, reverse Marangoni flow helps maintain a proper orifice shape, which in turn prevents gas entrainment and thus prevents porosity in the weld.

[0041] In addition, dissolved oxygen acts as a surfactant, thereby improving the wetting of the molten metal into the base metal and thus avoiding serious defects such as lack of edge fusion that are prone to occur in the weldment.

[0042] Furthermore, because the composition of the flux causes the surface tension to increase with temperature, the wettability of the welding material is enhanced along the edges, which are cooler than the center of the molten pool, thus preventing slag inclusions.

[0043] When welding involves a laser beam, the flux alters the interaction between the plasma plume and the laser beam. Specifically, the increase in oxygen due to flux dissolution reduces laser beam scattering. Consequently, the laser spot diameter decreases, while the keyhole effect is enhanced. This allows the energy beam to penetrate even deeper and be delivered very efficiently into the joint. This enhances weld penetration and minimizes the heat-affected zone, which in turn limits component deformation.

[0044] The invention will be better understood by reading the following description, which is provided for illustrative purposes only and is in no way intended to be limiting.

[0045] This invention relates to welding of steel substrates. Preferably, the steel substrate is carbon steel.

[0046] Carbon steel may optionally be coated with an anti-corrosion coating on at least a portion of one of its sides. Preferably, the anti-corrosion coating comprises a metal selected from zinc, aluminum, copper, silicon, iron, magnesium, titanium, nickel, chromium, manganese, and alloys thereof.

[0047] In one preferred embodiment, the corrosion-resistant coating is an aluminum-based coating comprising: less than 15% Si, less than 5.0% Fe, optionally 0.1% to 8.0% Mg, and optionally 0.1% to 30.0% Zn, with the remainder being Al and unavoidable impurities arising from the processing. In another preferred embodiment, the corrosion-resistant coating is a zinc-based coating comprising: 0.01% to 8.0% Al, optionally 0.2% to 8.0% Mg, with the remainder being Zn and unavoidable impurities arising from the processing.

[0048] The anti-corrosion coating is preferably applied to both sides of the steel substrate.

[0049] Steel can be welded to steel substrates of the same or different compositions. Steel can also be welded to other metals, such as aluminum.

[0050] The flux comprises titanate and nanoparticle niobium compounds selected from niobium oxides, alkali metal niobates, and mixtures thereof. In other words, the pre-coating comprises titanate and at least one nanoparticle niobium compound, wherein the at least one nanoparticle niobium compound is selected from niobium oxides, alkali metal niobates, and mixtures thereof. This means that the pre-coating does not contain any other nanoparticle niobium compounds besides those listed.

[0051] Titanates are selected from the group consisting of alkali metal titanates, alkaline earth titanates, transition metal titanates, metal titanates, and mixtures thereof. More preferably, titanates are selected from: Na₂Ti₃O₇, NaTiO₃, K₂TiO₃, K₂Ti₂O₅, MgTiO₃, SrTiO₃, BaTiO₃, CaTiO₃, FeTiO₃, and ZnTiO₄, and mixtures thereof. These titanates are believed to further increase the penetration depth based on the effect of reverse Marangoni flow. The inventors understand that all titanates exhibit similar penetration depths to a certain extent and increase the penetration depth. Therefore, all titanates are part of this invention. Those skilled in the art will recognize that one must be selected according to the specific circumstances. For this purpose, those skilled in the art will consider the ease with which the titanate melts and dissolves, how much dissolved oxygen content the titanate increases, and how other elements of the titanate affect the physical properties of the molten pool and the microstructure of the final weld. For example, NaTiO₇ is advantageous due to the presence of Na, which improves slag formation and separation.

[0052] Preferably, the titanate has a diameter of 1 μm to 40 μm, more preferably 1 μm to 20 μm, and advantageously 1 μm to 10 μm. This titanate diameter is believed to further improve arc contraction and the reverse Marangoni effect. Furthermore, the small micrometer-sized titanate particles increase the specific surface area available for mixing with nanoparticle niobium compounds and allow the latter to further adhere to the titanate particles.

[0053] Preferably, the weight percentage of titanate in the dry weight of flux is greater than or equal to 45%, more preferably 45% to 90%, and even more preferably 55% to 87%.

[0054] The nanoparticle niobium compounds are selected from niobium oxides, alkali metal niobates, and mixtures thereof. Niobium oxides can be particularly selected from NbO, NbO2, and Nb2O5. Alkali metal niobates can be particularly selected from LiNbO3, NaNbO3, and KNbO3. These nanoparticles readily dissolve in the molten pool, providing oxygen to the pool and thus improving wettability and material deposition, allowing for deeper weld penetration. Unlike other oxides such as CaO, MgO, B2O3, Co3O4, or Cr2O3, nanoparticle niobium compounds do not tend to form brittle phases, do not possess the high refractoriness that prevents heat from accurately melting the steel, and their metal ions do not tend to recombine with oxygen in the molten pool. Furthermore, they cause fewer health and safety issues compared to other nanoparticle oxides and can therefore very effectively replace some other nanoparticle oxides, even improving the results.

[0055] The preferred niobium compound for nanoparticles is Nb2O5 because it has the highest oxygen content, is stable, and is readily available at a reasonable cost.

[0056] Preferably, the size of the nanoparticles of the niobium compound is 5 nm to 150 nm, more preferably 50 nm to 150 nm.

[0057] The flux may also contain at least one additional nanoparticle oxide selected from TiO2, SiO2, ZrO2, Y2O3, Al2O3, MoO3, CrO3, CeO2, La2O3, and mixtures thereof. These nanoparticle oxides readily dissolve in the molten pool and further improve wettability, material deposition, and weld penetration.

[0058] Preferably, the additional nanoparticle oxide is SiO2, which further increases the penetration depth and makes slag removal easier.

[0059] Other examples of mixtures of nanoparticle oxides are:

[0060] - Yttria-stabilized zirconia (YSZ) is a ceramic in which the cubic crystal structure of zirconia (ZrO2) is stabilized at room temperature by adding yttria (Y2O3).

[0061] The 1:1:1 combination of La2O3, ZrO2 and Y2O3 helps to regulate the refractory effect and promote the formation of inclusions.

[0062] Preferably, the size of the additional nanoparticle oxide nanoparticles is from 1 nm to 100 nm, more preferably from 5 nm to 60 nm. It is believed that this nanoparticle diameter further improves the uniform distribution of the flux.

[0063] Preferably, the weight of the nanoparticles (as a niobium compound alone or in combination with other nanoparticle oxides) constitutes less than or equal to 80% of the dry weight of the flux, preferably 2% to 50%, more preferably 10% to 40%. More preferably, the weight of the nanoparticle niobium compound constitutes 2% to 30% of the dry weight of the flux. More preferably, if present, the weight of additional nanoparticle oxides constitutes 5% to 20% of the dry weight of the flux.

[0064] According to another variation of the invention, the flux further comprises microparticle compounds such as microparticle oxides and / or microparticle fluorides, such as Na₂O, Na₂O₂, CeO₂, NaBiO₃, NaF, CaF₂, and cryolite (Na₃AlF₆). For some of the nanoparticle oxides listed above, the shift from nanoparticles to microparticles mitigates the health and safety concerns associated with the use of some of these oxides. Na₂O, Na₂O₂, NaBiO₃, NaF, CaF₂, and cryolite can be added to improve slag formation, thereby further preventing slag inclusions. They also help form easily separable slag. The flux may contain 0.1% to 5% by weight of Na₂O, Na₂O₂, NaBiO₃, NaF, CaF₂, cryolite, or mixtures thereof, based on the dry weight of the flux.

[0065] According to one embodiment of the invention, the flux is contained in the sheath of the lead-cored wire. This configuration is particularly advantageous compared to the same composition having a pre-coating applied to the substrate to be welded. First, the additional step of coating the substrate before welding is eliminated. Furthermore, it is unnecessary to remove excess pre-coating along the weldment after welding. In this respect, the particles are also used more efficiently because all particles supplied by the lead-cored wire dissolve in the molten pool. Finally, solvents and sprays during the coating step are avoided, which is beneficial to the health and safety of the operator.

[0066] According to one variant of the invention, the flux in the powder-cored wire is composed of titanate and nanoparticle niobium compound.

[0067] According to another variation of the invention, the flux in the powder-cored wire may further contain iron powder as a remainder. This remainder may potentially comprise up to 55% by weight of the flux.

[0068] In the case of this invention, the material of the foreskin is not particularly limited. It can be steel, such as copper-plated C-Mn steel.

[0069] The diameter of the welding wire is typically between 0.8 mm and 4 mm. Regarding the sheath, its thickness varies depending on the selected filler ratio. The filler ratio is the ratio of the weight of the flux component, or "filler," to the total weight of the welding wire.

[0070] In terms of the process, in the first step, titanate and nanoparticle niobium compound are preferably mixed. Mixing can be done under humid conditions with a solvent (e.g., acetone) or under dry conditions (e.g., in a 3D powder oscillating mixer). This mixing facilitates the aggregation of the nanoparticles on the titanate particles, preventing unintended release of the nanoparticles into the air (which would be a health and safety concern). In the second step, the resulting flux is deposited onto a thin, narrow strip that has been passed through forming rollers in the previous step to form a U-shaped cross-section. The flux-filled U-shaped strip is then passed through a specialized closing roll, which shapes it into a tube and tightly compresses the core material. The tube is then pulled out through a stretching die to reduce its diameter and further compress the core material. Stretching tightly seals the sheath and further secures the core material within the tube under compression, thus avoiding discontinuities in the flux.

[0071] After the powder-cored welding wire according to the invention has been provided, welded joints can be manufactured by arc welding or laser welding of steel using the powder-cored welding wire. There are no limitations on the type of welding technique, as long as it is compatible with the powder-cored welding wire according to the invention and used as a filler wire for side feeding of the weld (e.g., in gas-shielded tungsten inert gas welding and laser welding) or as a consumable electrode (e.g., in submerged arc welding, gas-shielded metal arc welding, gas-shielded powder-cored wire arc welding, narrow-gap welding, and hybrid laser welding, wherein the arc head is a gas-shielded metal arc). Depending on the welding technique, the weld zone can be covered with a protective flux. The protective flux prevents oxidation of the weld zone during welding.

[0072] According to another embodiment of the invention, the flux is at least partially applied to the steel substrate to form a pre-coating.

[0073] In this case, the flux can advantageously further contain a solvent. This allows for a well-dispersed pre-coating. Preferably, the solvent is volatile at ambient temperature. For example, the solvent is selected from: water; volatile organic solvents such as acetone, methanol, isopropanol, ethanol, ethyl acetate, diethyl ether; and non-volatile organic solvents such as ethylene glycol.

[0074] Specifically, the solvent-based flux contains 100 g / L to 500 g / L of titanate, more preferably 175 g / L. -1 Up to 250g.L -1 Titanate. Specifically, the solvated flux contains 1 g / L. -1 Up to 200g.L -1 The nanoparticle niobium compound, more preferably containing 5 g.L -1 Up to 80g.L -1The nanoparticle niobium compound. Due to the concentration of these titanates and nanoparticle niobium compounds, the quality of the weld obtained by means of the corresponding pre-coating is further improved.

[0075] According to a variant of the invention, the flux further comprises a binder precursor for embedding titanate and nanoparticle niobium compounds and improving the adhesion of the pre-coating to 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 from the families of amines, diamines, alkyl, amino-alkyl, aryl, epoxy, methacryl, fluoroalkyl, alkoxy, vinyl, mercapto, and aryl. Preferably, the binder precursor is in 40 g / L of the pre-coating solution. -1 Up to 400g.L -1 Add the amount.

[0076] In terms of the process, in the first step, titanate and nanoparticle niobium compound are preferably mixed. Mixing can be performed under humid conditions with a solvent (e.g., acetone) or under dry conditions (e.g., in a 3D powder oscillating mixer). This mixing facilitates the aggregation of the nanoparticles on the titanate particles, which prevents the unintended release of the nanoparticles into the air (which would be a health and safety issue). In the second step, flux is at least partially applied to the steel substrate to form a pre-coating.

[0077] Flux deposition can be accomplished specifically by spin coating, spraying, dip coating, or brushing.

[0078] Preferably, flux is deposited only locally. In particular, flux is applied to the area of ​​the steel substrate to be welded. This can be on the edge of the steel substrate to be welded, on a sidewall of the substrate to be welded, or on a portion of one side of a bevel (if any).

[0079] After the flux has been applied to the steel substrate, it can optionally be dried. Drying can be carried out by blowing air or an inert gas at ambient temperature or a high temperature. When the flux contains a binder, the drying step is also preferably a curing step, during which the binder is cured. Curing can be carried out by infrared (IR), near-infrared (NIR), or a conventional oven.

[0080] Preferably, when the solvent is volatile at ambient temperature, the drying step is not performed. In that case, the solvent evaporates, thereby creating a pre-coating on the steel substrate.

[0081] According to a variant of the invention, after the pre-coating is formed on a steel substrate and dried, the pre-coating consists of titanate and nanoparticle niobium compound.

[0082] According to another variation of the invention, the pre-coating further comprises at least one binder embedded with titanate and nanoparticle niobium compounds and improving the adhesion of the pre-coating to the steel substrate. This improved adhesion further prevents the particles of the pre-coating from being blown away by the flow of such gas when using a protective gas. Preferably, the binder is entirely inorganic, particularly to avoid the fumes that may be generated during welding with organic binders. Examples of inorganic binders are sol-gels of organofunctional silanes or siloxanes. Examples of organofunctional silanes are silanes functionalized, in particular, with groups from the families of amines, diamines, alkyl, amino-alkyl, aryl, epoxy, methacryloxy, fluoroalkyl, alkoxy, vinyl, mercapto, and aryl. Amino-alkyl silanes are particularly preferred because they significantly improve adhesion and have a long shelf life. Preferably, the binder is added in an amount of 1% to 20% by weight of the pre-coating.

[0083] Preferably, the thickness of the pre-coating is 10 μm to 140 μm, more preferably 30 μm to 100 μm.

[0084] After a pre-coating has been formed on a portion of a steel substrate, that portion can be welded to another metal substrate. There are no restrictions on the type of welding technique. It can be, for example, gas-shielded metal arc welding (GMAW), gas-shielded tungsten inert gas welding (GTAW), also known as tungsten inert gas welding (TIGW), submerged arc welding (SAW), laser beam welding (LBW), narrow gap welding, also known as narrow groove welding, or laser-arc hybrid welding.

[0085] According to another embodiment of the invention, the flux is applied directly to the metal substrate during welding, particularly to the welding area.

[0086] Specifically, when welding two metal substrates, flux is simultaneously and at least partially applied to both substrates. The flux is applied in front of the welding equipment, particularly in front of the welding head. Depending on the welding technique, the welding head here refers to a consumable or non-consumable electrode that generates an electric arc, or a laser head. Thus, when the energy applied through the welding head strikes the flux-covered portion of the substrate, the flux components melt and dissolve in the molten pool. The dissolved titanate and nanoparticle niobium compound exhibit the aforementioned effects.

[0087] Preferably, the flux is applied to a portion of the metal substrate just before it is struck by the energy applied through the welding head.

[0088] Preferably, the flux is applied along the edge of the metal substrate to be welded at a width at least equal to the weld width, so that the flux effectively dissolves in the molten pool.

[0089] Preferably, the flux is stored in a flux hopper. This hopper is positioned in front of the welding apparatus, particularly in front of the welding head, and moves with it. During welding, the hopper deposits flux onto a small portion of the metal substrate in front of the welding head. The flux hopper controls the rate of flux deposition.

[0090] In one variant of the invention, flux is applied to both metal substrates before the application of protective flux. A flux hopper for storing protective flux is first present in front of the welding joint, followed by a flux hopper for storing the flux itself. In other words, the flux hopper is further ahead of the welding joint than the protective flux hopper. Therefore, flux is applied to the metal substrates first, followed by the application of protective flux to cover them. Thus, the welding zone is protected from oxidation during welding. From a process perspective, both the application of flux and the application of protective flux occur simultaneously with welding.

[0091] In another variation of the invention, the flux is also a protective flux. It preferably comprises lime, silica, manganese oxide, and calcium fluoride in the form of micron and / or millimeter-sized particles. These compounds provide the flux with protective effects in addition to those provided by titanates and nanoparticle niobium compounds. Therefore, the weld zone is protected from oxidation during welding.

[0092] In that case, titanate and nanoparticle niobium compound are mixed early with other components such as lime, silica, manganese oxide and calcium fluoride in the form of micron and / or millimeter-sized particles, and then the mixture is applied to two metal substrates, preferably using a flux hopper.

[0093] There are no limitations on the types of welding techniques that can be used with this embodiment of the invention. These can be, for example, gas-shielded metal arc welding (GMAW), gas-shielded tungsten arc welding (GTAW), also known as tungsten inert gas welding (TIGW), submerged arc welding (SAW), laser beam welding (LBW), narrow gap welding, also known as narrow groove welding, or laser-arc hybrid welding.

[0094] In other words, fluxes are also variants of protective fluxes that are particularly advantageous for welding techniques that use protective fluxes, such as submerged arc welding (SAW), narrow gap welding based on submerged arc welding, and laser arc hybrid welding based on submerged arc welding.

[0095] Finally, the present invention relates to the use of fluxes, corresponding pre-coated or corresponding cored wires according to the invention in the manufacture of, for example, pressure vessels, offshore oil and gas components, shipbuilding, automobiles, nuclear components, and heavy industry and general manufacturing. Example

[0096] Example 1 – Narrow Gap Welding:

[0097] Select a steel substrate having the chemical composition by weight percentage disclosed in Table 1:

[0098] 0.12 1.65 0.15-0.55 0.015-0.050 0.002 0.0008 0.30 0.70 0.20

[0099] 0.030 0.08 0.060 0.0025 0.0005 0.010 The remaining part

[0100] The steel substrate is 50 mm thick. It has a tensile strength of 470 MPa to 630 MPa and a yield strength of 335 MPa.

[0101] Prepare a 100mm × 150mm sample with a 0° beveled sidewall. Clean the oil and dirt from the sidewall to be welded with acetone.

[0102] Sample 1 was not coated with a pre-coating.

[0103] For Sample 2, an acetone solution containing the aforementioned elements was prepared by mixing acetone with MgTiO3 (diameter: 2 μm), Nb2O5 (diameter: 100 nm), and SiO2 (diameter: 10 nm). The concentration of MgTiO3 in the acetone solution was 175 g / L. -1 The concentration of Nb₂O₅ is 50 g·L⁻¹. -1 And the concentration of SiO2 is 25 g / L. -1 Then, the cleaned sidewalls of sample 2 were coated with the acetone solution by spraying. The acetone evaporated. The pre-coating contained 70% by weight of MgTiO3, 20% by weight of Nb2O5, and 10% by weight of SiO2, and the pre-coating was 50 μm thick.

[0104] For sample 3, an acetone solution containing the aforementioned elements was prepared by mixing acetone with a 1:1:1 combination of MgTiO3 (diameter: 2 μm), Nb2O5 (diameter: 100 nm), SiO2 (diameter: 10 nm), premixed La2O3, ZrO2, and Y2O3 (diameters: 50 nm, 40 nm, and 40 nm, respectively), and NaBiO3 (diameter: 1.5 μm). The concentration of MgTiO3 in the acetone solution was 187.5 g / L. -1 The concentration of Nb₂O₅ was 25 g·L⁻¹. -1 The concentration of SiO2 is 25 g / L. -1 The concentration of the additional nanoparticle oxide was 0.125 g / L. -1 And the concentration of NaBiO3 was 12.38 g / L. -1Then, the cleaned sidewalls of sample 3 were coated with the acetone solution by spraying. The acetone evaporated. The pre-coating contained 75% by weight of MgTiO3, 10% by weight of Nb2O5, 10% by weight of SiO2, 0.05% by weight of additional nanoparticle oxides, and 4.95% by weight of NaBiO3. The pre-coating was 50 μm thick.

[0105] Samples 1 to 3 were each placed side-by-side with a bare sample of the selected steel substrate separated by a 13mm gap, and welded by narrow-gap gas shielded metal electrode welding through several welding passes until the bevel was filled and the joint was completed. The welding parameters are shown in Table 2 below.

[0106]

[0107] The composition of the consumable electrode for all applications is shown in Table 3 below:

[0108] 0.078 0.85 1.46 The remaining part

[0109] Sample 1 was welded in 12 passes, while samples 2 and 3 were welded in 10 passes. This first result demonstrates that the pre-coating according to the invention improves the deposition rate and productivity of narrow-gap welding.

[0110] It was also observed that the wetting of the inclined surface by the weld metal was improved in samples 2 and 3 compared with sample 1.

[0111] Following narrow-gap welding, all welded assemblies are first visually inspected, and then inspected using both linear and volumetric ultrasonic testing. Liquid penetrant inspection (LPI) is also used specifically for macroscopic and microscopic analysis of the welds.

[0112] The results are summarized in Table 4 below:

[0113] Visual inspection of the joint OK OK OK Ultrasonic testing of joints Not OK OK OK Permeable fluid from the joint OK OK OK Macro Analysis Defects (lack of sidewall fusion and undercut) OK OK

[0114] *: According to the present invention

[0115] The results show that the pre-coating on the sidewall of the steel substrate improves narrow-gap welding.

[0116] Example 2 – Powder-cored welding wire:

[0117] Three fluxes were prepared and incorporated into a 0.5mm C-Mn steel sheath to form a 1.6mm diameter welding wire. The compositions of the three fluxes are as follows:

[0118] - Flux 1: 85 wt% MgTiO3 (diameter: 2 μm), 10 wt% SiO2 (diameter range: 12 nm to 23 nm) and 5 wt% Nb2O5 (diameter range: 100 nm),

[0119] - Flux 2: 70 wt% MgTiO3 (diameter: 2 μm), 10 wt% SiO2 (diameter range: 12 nm to 23 nm) and 20 wt% Nb2O5 (diameter range: 100 nm),

[0120] - Flux 3: 68.5 wt% MgTiO3 (diameter: 2 μm), 10 wt% SiO2 (diameter range: 12 nm to 23 nm), 20 wt% Nb2O5 (diameter range: 100 nm), 1 wt% Na3AlF6 and 0.5 wt% CeO2 (diameter: ≤5 μm).

[0121] During the on-plate bead welding of structural steel (C-MnS355) with a strength of 110A and a voltage ranging from 10.8V to 12.8V, the corresponding leaded wires for samples 4, 5, and 6 were tested and identified. The composition of the structural steel (C-MnS355) is detailed in Table 5 below:

[0122] 0.102 0.903 0.012 0.04 0.0088 0.012

[0123] During these tests, samples 4, 5, and 6 were compared with the following commercial welding wires:

[0124] - MC710-H, which is manufactured by Lincoln The supplied mild steel metal-core welding wire has an sheath filled with iron powder (sample 7).

[0125] -OK Tubrodur 15CrMn O / G, which is composed of Powder-cored welding wire (sample 8) is supplied and ready for use with mild steel, low alloy steel, and C-Mn steel. The exact composition of its flux is unknown.

[0126] The results obtained using 500mm welding wire are detailed in Table 6:

[0127]

[0128] *: According to the present invention

[0129] The results show that there is a significant increase in welding speed and a significant increase in material deposition at the same time.

[0130] In addition, the widths of the deposited materials were measured and compared. It appears that the welds obtained with samples 4, 5, and 6 were on average 18% larger than the weld obtained with sample 7, and 24% larger than the weld obtained with sample 8.

[0131] This indicates that the composition of the flux according to the invention causes the surface tension to decrease with temperature, thereby increasing the wettability of the welding material along the edge of the molten pool.

[0132] Example 3 – Gas Shielded Tungsten Arc Welding (GTAW):

[0133] For this embodiment, a steel substrate having the chemical composition by weight percentage disclosed in Table 7 is used:

[0134] 0.102 0.903 0.012 0.04 0.0088 0.012 0.027 0.0222 0.027

[0135] 0.0012 0.002 0.0011 0.0008 0.0001 0.0035 The remaining part

[0136] The steel substrate is 5.5mm thick.

[0137] For sample 9, an ethyl acetate solution containing the aforementioned elements was prepared by mixing ethyl acetate with MgTiO3 (diameter: 2 μm), SiO2 (diameter range: 10 nm), and Nb2O5 (diameter range: 100 nm). The concentration of MgTiO3 in the ethyl acetate solution was 175 g / L. -1 The concentration of SiO2 is 25 g / L. -1 The concentration of Nb₂O₅ is 50 g·L⁻¹. -1 The ethyl acetate solution was sprayed onto a steel substrate over an area wider than the weld to be completed. The ethyl acetate evaporated. The pre-coating contained 70% by weight of MgTiO3, 10% by weight of SiO2, and 20% by weight of Nb2O5.

[0138] For sample 10, an aqueous solution containing the following components was prepared: 363 g / L -1 MgTiO3 (diameter: 2μm), 77.8gL -1 SiO2 (diameter range: 12nm to 23nm), 77.8gL -1 Nb₂O₅ (diameter range: 100 nm) and 238 g.L -1 3-Aminopropyltriethoxysilane (from Production The solution was applied to a steel substrate and dried by 1) IR and 2) NIR.

[0139] The dried pre-coating is 40 μm thick and contains 62 wt% MgTiO3, 13 wt% SiO2, 13 wt% Nb2O5 and 12 wt% binder obtained from 3-aminopropyltriethoxysilane.

[0140] For sample 11, an aqueous solution containing the following components was prepared: 330 g / L -1 MgTiO3 (diameter: 2μm), 70.8gL -1 SiO2 (diameter range: 12nm to 23nm), 70.8gL -1 Nb₂O₅ (diameter range: 100 nm), 216 g.L -1 3-Aminopropyltriethoxysilane (from Production AMEO) and 104.5gL -1 A composition of organofunctional silanes and functionalized nano-sized SiO2 particles (produced by Evonik) Sivo110). The solution was applied to a steel substrate and dried by 1) IR and 2) NIR. The dried pre-coating was 40 μm thick and contained 59.5 wt% MgTiO3, 13.46 wt% SiO2, 12.8 wt% Nb2O5 and 14.24 wt% binder obtained from 3-aminopropyltriethoxysilane and organofunctional silanes.

[0141] For sample 9, spraying was easy and the pre-coating was uniform, which confirms that ethyl acetate can easily replace acetone in the formulation of solvent-based flux.

[0142] For samples 10 and 11, the adhesion of the pre-coated layer to the steel substrate was greatly improved compared to sample 9.

[0143] Then, gas-shielded tungsten inert gas (GSIG) welding was performed on samples 9 to 11 and on the uncoated sample (sample 12) using the welding parameters detailed in Table 8:

[0144]

[0145] Measurements performed during welding indicate that:

[0146] - During welding of sample 9, the arc was more stable and the average instantaneous energy increased by 12% compared to the reference (sample 12). Complete penetration was achieved with sample 9, unlike sample 12. - During welding of samples 10 and 11, the arc was more stable and the average instantaneous energy increased by 14% compared to the reference (sample 12). Complete penetration was achieved with samples 10 and 11, unlike sample 12.

Claims

1. A flux comprising titanate and nanoparticle niobium compound; The titanate is selected from the group consisting of alkali metal titanates, alkaline earth titanates, transition metal titanates, metal titanates, and mixtures thereof, the diameter of the titanate is from 1 μm to 40 μm, and the percentage of titanate in the flux is greater than or equal to 45% by weight; The nanoparticle niobium compound is selected from NbO, NbO2 and Nb2O5, and mixtures thereof; the size of the nanoparticles of the nanoparticle niobium compound is from 5 nm to 150 nm, and the percentage of the nanoparticle niobium compound is from 2% to 30% by weight.

2. The flux according to claim 1, wherein the titanate is selected from: Na2Ti3O7, NaTiO3, K2TiO3, K2Ti2O5, MgTiO3, SrTiO3, BaTiO3, CaTiO3, FeTiO3 and ZnTiO4, and mixtures thereof.

3. The flux according to claim 1 or 2 further comprises at least one additional nanoparticle oxide selected from TiO2, SiO2, ZrO2, Y2O3, Al2O3, MoO3, CrO3, CeO2, La2O3, and mixtures thereof.

4. The flux according to claim 3 further comprises a solvent.

5. The flux according to claim 4, comprising 1 g / L to 200 g / L of nanoparticle niobium compound.

6. The flux according to claim 4, comprising 100 g / L to 500 g / L of titanate.

7. The flux according to claim 5, comprising 100 g / L to 500 g / L of titanate.

8. The flux according to claim 4 further comprises a binder precursor.

9. The flux according to claim 5 further comprises a binder precursor.

10. The flux according to claim 6, further comprising a binder precursor.

11. The flux according to claim 7, further comprising a binder precursor.

12. A method for manufacturing a pre-coated steel substrate, comprising the step of depositing flux, according to any one of claims 1 to 11, at least partially onto the steel substrate.

13. A pre-coated steel substrate, said pre-coated steel substrate being obtainable by the method according to claim 12, being at least partially coated with a pre-coating comprising titanate and nanoparticle niobium compound.

14. A method for manufacturing a welded joint, comprising the following sequential steps: I. Providing at least two metal substrates, wherein at least one metal substrate is a pre-coated steel substrate as described in claim 13, and II. Weld the at least two metal substrates.

15. A powder-cored welding wire comprising a flux according to any one of claims 1 to 3.

16. A method for manufacturing a welded joint, comprising arc welding or laser welding of steel with the powder-cored wire according to claim 15.

17. A method for manufacturing a welded joint, comprising the following sequential steps: I. Provide at least two metal substrates, wherein at least one metal substrate is a steel substrate, and II. Welding the at least two metal substrates simultaneously with the welding head while applying flux according to any one of claims 1 to 3 to the front of the welding head.

Images