A welding wire for plateau climate and a preparation method thereof

Abstract

The application discloses a welding wire for plateau climate and a preparation method thereof, relates to the technical field of welding materials, and aims to solve the problems of poor welding toughness, unstable arc, poor protection and easy generation of hydrogen-induced cracks in an extreme environment on a plateau. The welding wire comprises a metal outer skin and an internal core structure. The core structure has the following components: a plurality of twisted core wire bundles treated with nickel or potassium compounds on the surface; an internal magnetic field coil wound outside the core wire bundles, provided with a high-temperature insulation layer, and having a diameter changing in a specific manner from the rear end to the front end; and a plurality of layers of functionalized powder cores concentrically surrounding the core wire bundles and the coil, which are divided into an inner layer focusing on initial purification and alloying, a middle layer providing main gas slag protection and deoxidation, and an outer layer adjusting the characteristics of the final arc and the molten slag. The preparation method comprises the following steps of core wire treatment, preparation and winding of the variable-diameter coil, ultra-low moisture drying of the powder, synchronous and precise filling of the multiple layers, outer skin forming and closing, drawing and sizing, and ultra-low humidity vacuum packaging.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, specifically a welding wire for high-altitude climates and its preparation method. Background Technology

[0002] High-altitude regions are typically characterized by low air pressure, low temperatures with large diurnal temperature variations, strong winds, and intense ultraviolet radiation. These conditions pose severe challenges to welding operations conducted in the field or on-site, especially in critical projects such as bridges, pipelines, power facilities, and building steel structures. These conditions place extremely high demands on the quality and reliability of welded joints. Conventional welding materials and methods are often unsuitable or perform poorly in high-altitude environments. This is mainly manifested in the following ways: materials are prone to brittle fracture at low temperatures; low air pressure and strong winds cause unstable arc combustion, and shielding gas (whether externally supplied or self-generated) is easily dispersed, resulting in welding defects such as porosity and inclusions; rapid cooling at low temperatures increases the risk of hydrogen-induced cracking (cold cracking) in the weld. Therefore, developing specialized welding materials with superior performance that can adapt to the unique climate of high-altitude regions has significant practical and engineering value.

[0003] Currently, there are some studies on welding materials for special environments (including high altitudes), such as: Chinese invention patent CN112935625B discloses a high-toughness alkaline all-position flux-cored welding wire that can adapt to high-altitude climates. This welding wire uses a specific alkaline flux powder formula (containing various fluorides, oxides, alloy powders, etc.) and carbon dioxide gas shielding (FCAW-G) to achieve good all-position weldability, low spatter, non-porosity welding at an altitude of 5200 meters, and excellent low-temperature impact toughness (-40℃>180J, -50℃>150J) and cold crack resistance.

[0004] Chinese invention patent CN114310036B discloses a flux-cored welding wire for overlaying wear-resistant alloys on the surface of extrusion rollers. It adopts a specific wear-resistant powder formula (containing cesium carbonate, nickel hydroxyl, silicon carbide whiskers, etc.) and mentions that it can be welded under high-altitude climate conditions, achieving stable arc, high hardness of the overlay layer, and no defects.

[0005] The existing technologies mentioned above mainly improve the performance of welding wires in certain aspects (such as low-temperature toughness or wear resistance) by optimizing the powder formulation of specific chemical composition systems. Furthermore, some solutions (such as CN112935625B) still rely on external gas protection, which may be unstable or inconvenient to use at high-altitude sites. Although these designs have achieved certain results, they basically follow the traditional flux-cored welding wire structure (a single metal outer sheath wrapping mixed powders). They fail to address the comprehensive challenges of low pressure, strong winds, and low temperatures at high altitudes from a more fundamental physical structure and multi-functional synergy perspective. For example, they fail to solve: how to achieve ultra-high toughness and excellent arc stability simultaneously under self-protection conditions; how to optimize current transmission and heat distribution through structural design; how to precisely control the timing and position of different functional powder components during the welding process; and whether an internal physical field regulation mechanism can be introduced to further enhance arc characteristics and molten pool behavior. These limitations may restrict the upper limit of welding wire performance and reliability under more extreme high-altitude conditions (such as lower temperatures, stronger winds, and higher altitudes). Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a welding wire for high-altitude climates and its preparation method, so as to solve the above-mentioned problems.

[0007] The purpose of this invention is achieved through the following technical solution: a welding wire for high-altitude climate, comprising a metal outer sheath (1) and a core structure wrapped in the metal outer sheath (1), the core structure comprising: a multi-strand core wire bundle (2), a variable diameter endogenous magnetic field coil (3) and a multi-layer functionalized powder core; The multi-strand core bundle (2) is formed by twisting 7 or 19 low-carbon low-alloy steel or nickel-containing alloy steel filaments at a predetermined twist pitch; at least a portion of the filaments are treated on their surface before being twisted to form a functional coating containing at least one selected from nickel, potassium, nickel compounds, potassium compounds and combinations thereof. The variable diameter internal magnetic field coil (3) is made of high-purity nickel wire or alloy coil wire compatible with the core wire. The outer end of the coil wire is coated with a high-temperature electrical insulation layer. The coil wire is spirally wound in one or more layers around the outer end of the multi-strand core wire bundle. The diameter of the coil wire gradually decreases from the welding wire near the welding clamp clamp end to the welding clamp clamp end away from the welding clamp clamp end according to the law of d²∝remaining length. The total weight of the multi-layer functionalized powder core accounts for 18% of the total weight of the welding wire. It fills and surrounds the multi-strand core wire bundle (2) and the variable diameter endogenous magnetic field coil (3). The multi-layer functionalized powder core includes at least three concentric powder layers with different preset functions from the inside to the outside, including inner powder (4), middle powder (5) and outer powder (6). In terms of the total powder weight, the inner powder (4) accounts for 15%, the middle powder (5) accounts for 60%, and the outer powder (6) accounts for 25%.

[0008] The inner layer powder (4) consists of the following components by weight percentage: 10.0% aluminum powder, 8.0% titanium powder, 6.0% zirconium silicon iron containing 40% Zr, 30.0% nickel powder, 5.0% molybdenum iron containing 60% Mo, 8.0% potassium carbonate, 18.0% fluorite, 5.0% calcium carbonate, and 10.0% iron powder.

[0009] The middle layer powder (5) consists of the following components by weight percentage: calcium carbonate 30.0%, rutile (TiO2) 28.0%, silica (SiO2) 6.0%, manganese iron containing 75% Mn 15.0%, ferrosilicon containing 75% Si 5.0%, fluorite (CaF2) 10.0%, magnesium oxide (MgO) 3.0%, ferroboron containing 17% B 0.15%, and iron powder 2.85%.

[0010] The outer layer powder (6) consists of the following components by weight percentage: 20.0% potassium silicate solid powder, 4.0% lithium carbonate (Li2CO3), 15.0% fluorite (CaF2), 5.0% cryolite (Na3AlF6), 25.0% wollastonite (CaSiO3), 10.0% rutile (TiO2), 3.0% aluminum powder (Al), and 18.0% iron powder.

[0011] The multi-strand core wire bundle (2) contains a mixture of low-carbon low-alloy steel wire and steel wire with a nickel content of 5-8%, and the variable diameter innate magnetic field coil (3) forms a parallel path with the multi-strand core wire bundle (2).

[0012] The metal outer skin (1) is formed by butt welds of ultra-low carbon steel strips through laser welding or high frequency welding, with uniform wall thickness.

[0013] A method for preparing welding wire for high-altitude climates includes the following steps: S1, Preparation of multi-strand core wire bundle (2): drawing fine wires, performing surface treatment on at least part of the fine wires including coating with a Ni or K compound, and twisting the treated fine wires into multi-strand core wire bundle (2). S2, Preparation and winding of variable diameter internal magnetic field coil (3): Prepare a variable diameter conductive filament with a high temperature insulation layer, the diameter of which varies according to the law d²∝L, and spirally wind it around the outside of a multi-strand core wire bundle (2); S3. Preparation and filling of multi-layer functionalized drug powder core: Prepare inner layer drug powder (4), middle layer drug powder (5) and outer layer drug powder (6) according to the formula of inner layer drug powder (4), middle layer drug powder (5) and outer layer drug powder (6) respectively, and perform sufficient ultra-low moisture drying treatment; adopt multi-channel concentric synchronous filling technology, fill the inner layer drug powder (4), middle layer drug powder (5) and outer layer drug powder (6) around the variable diameter endogenous magnetic field coil (3) and multi-strand core wire bundle (2) in the inner-middle-outer order; S4. Metal outer skin (1) Forming and closing: The metal strip is rolled up to wrap the powder core and closed by high frequency or laser welding to form an outer skin, thus obtaining the welding wire prototype. S5. Drawing and sizing: The welding wire prototype is cold-drawn in multiple passes to the final nominal diameter and the flux core is compacted. S6. Final processing and packaging: The finished welding wire is inspected, and optional surface treatment is performed. It is then vacuum-sealed in a controlled low-humidity environment using a vacuum aluminum foil bag with a desiccant inside, or by filling it with a protective atmosphere.

[0014] The multi-channel concentric synchronous filling technology used in step S3 controls the filling rate and radial distribution of each layer of powder.

[0015] The content of diffusible hydrogen in every 100 grams of deposited metal in the drying process in step S3 and the finished welding wire in step S6 shall not exceed 4 ml.

[0016] The beneficial effects of this invention are: 1. This invention ensures that the weld metal maintains high toughness at extreme low temperatures through multiple methods, significantly reducing the risk of brittle fracture. It employs nickel-containing steel wire mixed into a multi-strand core wire bundle, uses high-purity nickel wire to manufacture a variable-diameter in-situ magnetic field coil, and adds a high proportion of nickel powder to the inner layer flux powder. This ensures an optimized and uniformly distributed nickel content in the weld. Simultaneously, the molybdenum element in the inner layer flux powder helps improve strength and tempering resistance. The introduction of microalloying elements such as titanium and boron into the inner and middle layers of flux powder, combined with the theoretically generated magnetic stirring effect of the variable-diameter in-situ magnetic field coil, intervenes in the solidification process, jointly promoting the formation of a fine, uniform equiaxed grain structure in the weld. The layered functionalized powder core design (especially the powerful purification effect of the inner powder layer and the sufficient protection and deoxidation of the middle powder layer) can effectively remove impurities (such as O, N, S, P) and reduce the generation of brittle phases. High-altitude and low-temperature environments are more sensitive to hydrogen-induced cracking. This invention improves crack resistance by using strict raw material selection (such as low-hygroscopic potassium silicate binder) and ultra-low moisture drying treatment, combined with high-barrier vacuum sealing packaging (guaranteed by a specific preparation method), to ensure that the diffusible hydrogen content of the welding wire itself and the final weld reaches (≤4mL / 100g) or lower. Excellent low-temperature toughness can improve the material's ability to resist hydrogen-induced cracking.

[0017] 2. The potassium compound coating on the surface of the multi-strand core wire bundle provides initial stability at the arc root; the potassium and lithium (powerful arc stabilizers) compounds in the outer powder further stabilize the entire arc column; the optimized titanium-calcium slag system (derived from the middle powder) itself is also conducive to stable arc combustion; the longitudinal magnetic field generated by the variable-diameter endogenous magnetic field coil can theoretically exert centripetal force on the arc plasma, making it straighter and more concentrated, improving its ability to resist external airflow (wind) interference; the high carbonate content in the middle powder ensures that it can decompose to generate sufficient CO2 protective gas even under low pressure; the multi-layer powder core structure ensures that the protective slag (initiated by the inner powder, formed by the middle powder, and optimized by the outer powder) can quickly, completely, and stably cover the molten pool; the synergistic effect of the powerful deoxidizers (Al, Ti, Zr, Mn, Si) distributed in the inner and middle powders minimizes the oxidation and nitriding that may be caused by air intrusion under low pressure.

[0018] 3. The multi-layer flux core design enables more refined metallurgical process control, especially the powerful purification step, which helps to obtain welds with extremely low impurity content. The slag system (the comprehensive result of the chemical composition of the multi-layer flux, especially the role of various modifiers in the outer flux) ensures a smooth weld surface, good wetting with the base metal, and an aesthetically pleasing shape. Furthermore, the slag is easy to peel off in whole pieces or easily removed after cooling, reducing slag removal time. The stable arc and more concentrated energy input allow for higher welding currents or faster welding speeds while ensuring penetration and quality. The physical properties of the slag (such as viscosity and solidification temperature range) make the welding wire suitable for various welding positions, including flat, vertical, horizontal, and overhead. Attached Figure Description

[0019] Figure 1 This is an overall structural diagram of the present invention; Figure 2 This is an exploded view of the entire invention; Figure 3 This is a front view of the present invention; Figure 4 For the present invention Figure 3 Sectional view of AA; Figure 5 For the present invention Figure 4 BB section view; Figure 6 This is a structural diagram of the present invention; Figure 7 This is a diagram showing the raw material proportions for this invention.

[0020] Explanation of the labels in the diagram 1. Metal outer sheath; 2. Multi-strand core wire bundle; 3. Variable diameter internal magnetic field coil; 4. Inner layer powder; 5. Middle layer powder; 6. Outer layer powder. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that the directional concepts of "left", "right", "up", "down", "front", "back", "inner", and "outer" in the following scheme are all relative directions, and will not be listed one by one here.

[0023] Example 1: like Figures 1 to 7 As shown, this embodiment provides a core structure for a high-performance self-protected flux-cored welding wire suitable for high-altitude climates. The welding wire is mainly composed of a metal outer sheath 1 and a core structure wrapped within it.

[0024] The metal outer skin 1 is preferably made of ultra-low carbon steel strip, which is rolled and formed into a butt weld by advanced laser welding or high frequency welding technology to ensure that the weld is dense, has good closure and uniform wall thickness, thus ensuring the overall strength of the welding wire and the sealing of the internal flux.

[0025] The core structure is the core of this embodiment, and mainly consists of the following three parts: The multi-strand core wire bundle 2 is located in the central region of the core structure. As one of the main sources of conductor and filler metal, it is not a traditional single solid wire, but is made of 7 or 19 precision-drawn filaments twisted together with an optimized twist pitch. These filaments are made of a specific blend of low-carbon low-alloy steel filaments and high-toughness steel wires with a nickel content of 5-8%. Nickel elements, which help improve the low-temperature toughness of the weld, are introduced directly from the core. Before these filaments are twisted together to form the multi-strand core wire bundle 2, their individual filament surfaces are pretreated: first, they are deeply cleaned, and then coated with a functional coating containing nickel (or its compounds) or potassium (or its compounds). This coating is designed to provide additional nickel elements to the molten pool at close range during welding and to release potassium ions to stabilize the arc root.

[0026] The variable-diameter internal magnetic field coil 3 is tightly, in a single layer or multiple layers, spirally wound around the outside of the multi-strand core wire bundle 2. The variable-diameter internal magnetic field coil 3 is composed of high-purity nickel wire (which further contributes nickel element) or other alloy wires that are compatible with the chemical composition of the core wire. The outer surface (or between turns) of the coil wire is coated with an extremely thin but heat-resistant electrical insulation layer, which is designed to prevent short circuits between turns before the coil melts. The variable-diameter internal magnetic field coil 3 adopts a variable-diameter design. The diameter of the wires constituting the coil is not constant, but gradually decreases from the rear end of the welding wire near the welding clamp to the front end (melting end) away from the welding clamp according to the law d²∝remaining length (d is the diameter, and the remaining length is the remaining length from the front end).

[0027] A multi-layer functionalized powder core is filled inside the metal outer sheath 1, completely covering the internal multi-strand core wire bundle 2 and the variable-diameter endogenous magnetic field coil 3 wound around it. The total weight of the powder core accounts for 18% of the total weight of the welding wire, and its internal structure is not uniformly mixed, but presents at least three concentric ring layers with different functions. From the inside to the outside, they are: inner powder layer 4 (closest to the variable-diameter endogenous magnetic field coil 3 and multi-strand core wire bundle 2, accounting for 15% of the total powder weight), middle powder layer 5 (constituting the main body of the powder core, accounting for 60% of the total powder weight), and outer powder layer 6 (closest to the metal outer sheath 1, accounting for 25% of the total powder weight). Each powder layer has a specific chemical formula and plays different metallurgical and protective roles in the optimal spatiotemporal sequence during the welding process.

[0028] Work process The welding wire is fed into the welding gun's contact tip through the wire feeding mechanism. The welding current is applied to the welding wire through the contact tip. The current is mainly conducted to the welding end through the metal outer sheath 1 and the multi-strand core wire bundle 2. Since the variable diameter innate magnetic field coil 3 and the multi-strand core wire bundle 2 form a parallel path, a portion of the current will be diverted through the variable diameter innate magnetic field coil 3.

[0029] The end of the welding wire melts under the action of the electric arc. The multi-strand core wire bundle 2 and its surface functional coating, variable diameter endogenous magnetic field coil 3, multi-layer functionalized powder core and metal outer skin 1 all participate in the melting process. The electric arc is generated between the end of the melted multi-strand core wire bundle 2 and the base material.

[0030] The current flowing through the variable-diameter endogenous magnetic field coil 3 generates a longitudinal magnetic field along the welding wire axis around it. The variable-diameter design compensates for the resistance change caused by the shortening of the coil length, so as to maintain the current flowing through the variable-diameter endogenous magnetic field coil 3 relatively stable, thereby generating a dynamic magnetic field with more controllable intensity and shape. This magnetic field acts on the arc plasma and droplet through the Lorentz force, which can compress the arc, improve its stiffness and stability, and affect the droplet transfer behavior.

[0031] As the welding wire melts, the inner layer of flux powder 4 comes into contact with the molten multi-strand core wire bundle 2 and the variable-diameter endogenous magnetic field coil 3 first or at the closest distance, performing purification, alloying and root arc stabilization functions. The middle layer of flux powder 5 decomposes in large quantities to generate protective gas and forms the main molten slag covering the molten pool. The outer layer of flux powder 6 adjusts the final arc shape, slag surface characteristics and provides outer protection. The layered structure realizes the spatiotemporal optimization of functions.

[0032] The molten filler metal (mainly from the multi-strand core wire bundle 2, the variable diameter endogenous magnetic field coil 3, and the metal outer skin 1) is transferred to the base material in the form of molten droplets to form a molten pool. The molten pool undergoes a metallurgical reaction under the combined protection of gas and slag generated by the powder core, and finally solidifies to form a weld.

[0033] By directly mixing high-nickel steel wire into the multi-strand core wire bundle 2 and using nickel wire or compatible alloy to manufacture the variable-diameter endogenous magnetic field coil 3, and with the nickel functional coating on the surface of the multi-strand core wire bundle 2, it is possible to ensure that the weld metal obtains sufficient and uniformly distributed nickel elements, thereby improving its impact toughness in high-altitude and low-temperature environments and reducing the risk of brittle fracture.

[0034] The potassium functional coating on the surface of the multi-strand core wire bundle 2 can provide a stable potassium ion source at the root of the arc, effectively stabilizing the arc. At the same time, the longitudinal magnetic field generated by the variable diameter endogenous magnetic field coil 3 has a restraining effect on the arc, which can improve the arc stiffness and anti-interference ability, making welding operations easier to control under low air pressure and windy plateau conditions. The structure of the multi-strand core wire bundle 2 also helps to improve the stability of current transmission.

[0035] The multi-layer functionalized powder core structure (inner powder 4, middle powder 5, outer powder 6) allows powder components with different functions such as deoxidation, denitrification, gas generation, slag formation, arc stabilization, and alloying to play their roles in the most appropriate positions and at the most appropriate times. Compared with traditional uniformly mixed powders, it can achieve more efficient and thorough metallurgical reactions and molten pool protection, which helps to obtain purer weld metal with fewer defects.

[0036] The variable diameter design of the variable diameter endogenous magnetic field coil 3 compensates for the resistance changes during the welding wire consumption process, and obtains a relatively stable excitation current and magnetic field strength, so that the endogenous magnetic field can stabilize the arc and stir the molten pool, making it more continuous and predictable throughout the welding process.

[0037] The metal outer skin 1, formed by welding high-quality ultra-low carbon steel strip, ensures the overall strength of the welding wire and the sealing of the internal flux powder, which is conducive to achieving stable and smooth wire feeding. The structure of the multi-strand core wire bundle 2 may also bring better flexibility.

[0038] In summary, the welding wire defined in Example 1, which includes a metal outer sheath 1, a multi-strand core wire bundle 2 with surface treatment, a variable-diameter endogenous magnetic field coil 3, and a basic multi-layer functionalized powder core structure, provides a solid structural foundation for its excellent comprehensive welding performance under extreme conditions such as high-altitude climates.

[0039] Example 2: like Figures 1 to 7 As shown, the self-shielded flux-cored welding wire for high-altitude climates in this embodiment has the same overall structure as in Embodiment 1, including a metal outer sheath 1 and an inner core structure. The core structure consists of a multi-strand core wire bundle 2 made of 7 or 19 low-carbon low-alloy steel wires mixed and twisted together with 5-8% Ni steel wires after surface treatment (including Ni / K functional coating), a variable-diameter (d²∝ remaining length) high-purity nickel wire (or compatible alloy wire) variable-diameter internal magnetic field coil 3 with a high-temperature insulation layer wrapped around the multi-strand core wire bundle 2, and a multi-layer functionalized flux powder core filled and covering the former two. The metal outer sheath 1 is formed by laser or high-frequency welding of ultra-low carbon steel strip.

[0040] The core of this embodiment lies in the clear definition of the specific chemical composition of the multi-layer functionalized flux core. The total weight of the flux core accounts for 18% of the total weight of the welding wire and is divided into three layers. The weight percentage of each layer and the detailed chemical formula (based on the internal weight percentage of each layer) are as follows: Inner layer powder 4 (accounting for 15% of the total powder): Aluminum powder (Al): 10.0%, Titanium powder (Ti): 8.0%, Zirconium silicon iron (FeSiZr, containing Zr~40%): 6.0%, Nickel powder (Ni): 30.0%, Ferromolybdenum (FeMo, containing Mo~60%): 5.0%, Potassium carbonate (K2CO3): 8.0%, Fluorite (CaF2): 18.0%, Calcium carbonate (CaCO3): 5.0%, Iron powder (Fe): 10.0%; This layer is adjacent to the multi-strand core wire bundle 2 and the variable-diameter endogenous magnetic field coil 3, which are about to melt. Its high content of strong deoxidizers (Al, Ti, Zr) captures oxygen and nitrogen in the first time, achieving deep purification. The high content of nickel powder and ferromolybdenum is integrated into the initial droplets at close range, which is one of the key sources to ensure the high toughness (Ni) and strength (Mo) of the final weld. Potassium carbonate provides easily ionized K+ ions to stabilize the arc root. Fluorite lowers the melting point, increases fluidity and assists in dehydrogenation. A small amount of calcium carbonate provides initial alkalinity.

[0041] Middle layer powder 5 (accounting for 60% of the total powder): Calcium carbonate (CaCO3): 30.0%, Rutile (TiO2): 28.0%, Silica (SiO2): 6.0%, Ferromanganese (FeMn, high carbon, containing Mn~75%): 15.0%, Ferrosilicon (FeSi, containing Si~75%): 5.0%, Fluorite (CaF2): 10.0%, Magnesium oxide (MgO): 3.0%, Ferroboron (FeB, containing B~17%): 0.15%, Iron powder (Fe): 2.85%; As the main component of the flux powder, the high content of calcium carbonate decomposes to provide the main CO2 protective gas; rutile, silica, magnesium oxide, and manganese oxide provided by ferromanganese together constitute a well-balanced titanium-calcium (or nearly titanium-alkaline) slag system, ensuring good molten pool coverage, moderate viscosity, and solidification range, which is conducive to all-position welding; ferromanganese and ferrosilicon are responsible for macroscopic deoxidation of the molten pool; an appropriate amount of fluorite adjusts the slag fluidity and assists in arc stabilization; and trace amounts of ferroboron, as a potential grain refiner, work synergistically with the inner titanium layer to optimize the weld microstructure.

[0042] Outer layer powder 6 (accounting for 25% of the total powder): Potassium silicate (K2SiO3, solid powder, pre-dried): 20.0%, Lithium carbonate (Li2CO3): 4.0%, Fluorite (CaF2): 15.0%, Cryolite (Na3AlF6): 5.0%, Wollastonite (CaSiO3): 25.0%, Rutile (TiO2): 10.0%, Aluminum powder (Al): 3.0%, Iron powder (Fe): 18.0%; This layer, close to the metal outer skin 1, uses potassium silicate as the main low-hygroscopic binder and provides potassium ions to stabilize the arc; lithium carbonate acts as a powerful arc stabilizer, improving the arc's smoothness; a high content of fluorite, cryolite, and wollastonite works together to finely adjust the surface tension, solidification characteristics, and wetting angle of the slag, achieving excellent automatic slag removal or easy removal characteristics after welding; appropriate amounts of rutile and aluminum powder finely adjust the properties of the outer slag and provide a certain degree of protection.

[0043] Work process: During welding, in addition to the physical processes described in Example 1 (wire feeding, conductivity, melting, and magnetic field generation), the specific chemical compositions of each layer of flux theoretically work synergistically in the following manner: After the electric arc is ignited, the K2CO3 in the inner powder 4 decomposes or ionizes first, releasing K+ to stabilize the root of the electric arc. At the same time, strong deoxidizers such as Al, Ti, and Zr quickly react with O and N in the initial molten metal to generate stable oxides / nitrides (such as Al2O3, TiO2, TiN, ZrO2), which enter the slag or fine dispersion to achieve deep purification. Ni and Mo powders melt in to form rich gold droplets.

[0044] As the temperature rises, a large amount of CaCO3 in the middle layer powder 5 decomposes to produce CO2 protective gas. TiO2, SiO2, MgO, MnO, CaF2 and other components form the main slag. Its basicity and viscosity are optimized to suit all-position welding and can absorb impurities such as sulfur and phosphorus. FeMn and FeSi undergo the main deoxidation reaction in the molten pool. Trace amounts of FeB decompose to release B, which may agglomerate at the solidification front and inhibit grain growth.

[0045] The Li2CO3 in the outer layer powder 6 further enhances the stability of the entire arc. K2SiO3, CaF2, Na3AlF6, CaSiO3, TiO2 and other substances work together to regulate the final physicochemical properties of the slag, ensuring that it can completely cover the weld and form an easy-to-peel morphology during the cooling process.

[0046] Throughout the process, the fluorides (CaF2, Na3AlF6) in each layer of powder help to lower the melting point of the slag, improve fluidity, and promote the escape of hydrogen from the molten pool. The strictly controlled low moisture content (ensuring through raw material drying and preparation process) is the basis for achieving a diffusible hydrogen content of no more than 4 ml per 100 grams of deposited metal.

[0047] By using 30% nickel powder in the inner layer powder 4, combined with the nickel source of the multi-strand core wire bundle 2 and the variable diameter endogenous magnetic field coil 3, the weld metal is ensured to have a nickel content of 1.8-2.5%. At the same time, the high purity brought by the strong deoxidation (Al, Ti, Zr) and the combined effect of microalloying (Ti, B) to refine the grains make the weld exhibit excellent impact toughness at temperatures of -50°C or even lower.

[0048] The K2CO3 in the inner layer of flux powder 4 provides root stability, while the K2SiO3 and high-efficiency Li2CO3 in the outer layer of flux powder 6 provide overall arc softness and stability. Combined with the constraint effect of the variable diameter internal magnetic field coil 3, it can achieve the purpose of stable welding and less spatter under high altitude and low air pressure.

[0049] The 30% CaCO3 in the middle layer powder provides ample gas protection; the titanium-calcium type slag system (composed of TiO2, SiO2, MgO, MnO, CaF2, etc.) has good coverage and impurity absorption capacity; the powerful deoxidation system with the inner and middle layers working together ensures extremely low oxygen and nitrogen content, resulting in high-purity weld metal.

[0050] The various slag modifiers in the outer layer powder 6 give the weld good wetting and spreading properties and a beautiful surface shape. At the same time, they make the slag moderately brittle after cooling and have a weak bond with the weld, making it very easy to remove and even potentially peel off automatically, thus improving production efficiency.

[0051] Example 3: like Figures 1 to 7As shown, this embodiment provides a precision manufacturing method for the self-shielded flux-cored welding wire used in high-altitude climates, which is theoretically used to prepare the wires of Embodiments 1 and 2. This method aims to precisely construct a structure comprising a multi-strand surface-treated multi-strand core wire bundle 2, a variable-diameter endogenous magnetic field coil 3, a multi-layer functionalized flux core (inner layer flux 4, middle layer flux 5, outer layer flux 6), and a metal sheath 1, ensuring that the final product meets key performance requirements such as ultra-low hydrogen content. The method mainly includes the following steps: S1, Preparation of multi-strand core fiber bundle 2: High-quality low-carbon low-alloy steel or alloy steel wire rod containing the required nickel content is selected and subjected to multiple cold drawing processes, possibly including intermediate annealing, to precisely draw it into a fine-diameter monofilament that meets the design requirements.

[0052] After drawing, the monofilament is thoroughly cleaned (e.g., ultrasonic degreasing, pickling, multi-stage washing, and drying). Then, using advanced physical vapor deposition (PVD), chemical vapor deposition (CVD), or precision electrochemical deposition techniques, a functional coating containing nickel and / or potassium compounds of a designed thickness (e.g., 1-2 μm) is uniformly coated onto the surface of the cleaned monofilament. If necessary, flash copper plating can be performed on this coating to ensure uniformity and strong adhesion.

[0053] Using high-precision cable stranding equipment, 7 or 19 surface-treated filaments are tightly and regularly stranded into a multi-strand core bundle according to a pre-set, optimized twist pitch and stranding direction.

[0054] S2. Preparation and winding of variable diameter endogenous magnetic field coil 3: High-purity nickel wire (or other selected alloy wire) is drawn into a fine wire whose diameter changes precisely and continuously from one end to the other according to the law of d²∝remaining length by using a drawing process (e.g., using a special-shaped die that varies with the drawing length, or a theoretical technique such as laser-assisted drawing with precise control).

[0055] For the prepared variable diameter filament, use theoretically advanced thin film technologies such as atomic layer deposition (ALD), plasma enhanced chemical vapor deposition (PECVD) or magnetron sputtering to uniformly coat its surface with an extremely thin (e.g. <10μm), dense inorganic electrical insulating material (such as aluminum nitride AlN, boron nitride BN, etc.) that can withstand the high temperature of subsequent high-temperature processing and welding arc (e.g. >1500°C).

[0056] Using a precision CNC coil winding machine, variable diameter filaments with an insulating layer are spirally wound in one or more layers tightly and uniformly around the outside of the multi-strand core wire bundle 2 prepared in step S1, according to the set pitch and tension, to form a variable diameter endogenous magnetic field coil 3.

[0057] S3. Preparation and filling of multi-layer functionalized drug powder core: High-purity raw material powders that meet the formulation requirements of Example 2 are selected and weighed according to the formulation ratio of each layer (inner layer powder 4, middle layer powder 5, outer layer powder 6). The materials of each layer are placed in a mixing device (such as a three-dimensional mixer) under an inert atmosphere (such as argon) for a long time to ensure that the components are uniform.

[0058] The uniformly mixed powder layers are placed in a vacuum oven or an atmosphere-protected (such as nitrogen) oven and dried thoroughly and for a long time (e.g., 2-4 hours or longer, until the moisture content meets the standard) at a set high temperature (e.g., the optimized temperature in the theoretical range of 350°C-450°C). The goal is to make the residual moisture content of the powder reach an extremely low level (e.g., <100ppmH2O). After drying, it is cooled and stored in a low-humidity or inert environment.

[0059] A multi-channel concentric synchronous filling and molding equipment is used to continuously feed the coil core wire bundle assembly completed in step S2 into the central channel of the equipment. At the same time, through at least three powder feeding systems that surround the central channel and whose feeding rate can be independently controlled, the dried inner layer powder 4, middle layer powder 5, and outer layer powder 6 are synchronously, continuously, and uniformly filled into the corresponding concentric ring-shaped areas according to the preset radial distribution (inner layer powder 4 is adjacent to the variable diameter innate magnetic field coil 3, middle layer powder 5 wraps the inner layer powder 4, and outer layer powder 6 wraps the middle layer powder 5) weight ratio (inner 15% / middle 60% / outer 25%). This process must ensure that the interfaces between each layer are clear, the filling density is uniform, and the requirements are met.

[0060] S4. Metal outer skin 1 forming and closing: A strip of ultra-low carbon steel of predetermined width and thickness is rolled into a tube shape by a set of precision forming rollers, simultaneously with or immediately after the filling in step S3, so as to completely encapsulate the multi-layered drug powder core inside.

[0061] Next, high-frequency induction welding or laser welding technology is used to continuously weld and close the longitudinal seam of the steel strip at high speed and with high quality, forming a sealed and complete metal outer skin 1, and obtaining a continuous welding wire prototype.

[0062] S5. Drawing and sizing: The welding wire prototype formed in step S4 is then passed through a drawing production line consisting of multiple (e.g., 5-10) precision cemented carbide or diamond shaped and circular drawing dies.

[0063] Under precisely controlled tension and lubrication conditions, multiple cold drawing passes are performed to gradually reduce the diameter of the welding wire to the final nominal diameter (such as 1.2mm, 1.6mm, etc.). This process improves the filling density and uniformity of the internal flux core and gives the welding wire precise dimensions and good surface finish.

[0064] S6. Final Processing and Packaging: The finished welding wire is inspected online / offline for diameter, roundness, and surface defects (such as eddy current testing). The final surface cleaning treatment is performed to remove the drawing lubricant residue. Optionally, an extremely thin rust inhibitor or a surface coating to improve wire feeding performance is applied.

[0065] In summary, the preparation method described in Example 3 is intended to precisely manufacture the high-performance welding wire for high-altitude climates described in Examples 1 and 2.

[0066] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be modified within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A welding wire for high-altitude climates, characterized in that, It includes a metal outer skin (1) and a core structure wrapped inside the metal outer skin (1). The core structure includes: a multi-strand core wire bundle (2), a variable diameter endogenous magnetic field coil (3), and a multi-layer functionalized drug powder core. The multi-strand core bundle (2) is formed by twisting 7 or 19 low-carbon low-alloy steel or nickel-containing alloy steel filaments at a predetermined twist pitch; wherein at least a portion of the filaments are treated on their surface before being twisted to form a functional coating comprising at least one selected from nickel, potassium, nickel compounds, potassium compounds and combinations thereof. The variable-diameter internal magnetic field coil (3) is composed of high-purity nickel wire or alloy coil wire compatible with the core wire. The outer end of the coil wire is coated with a high-temperature electrical insulation layer. The coil wire is spirally wound in one or more layers around the outer end of a multi-strand core wire bundle. The diameter of the coil wire gradually decreases from the welding wire near the welding clamp clamping end to the welding clamp clamping end away from the welding clamp clamping end according to the law of d²∝remaining length. d is the diameter of the coil wire constituting the variable-diameter internal magnetic field coil (3). The multi-layer functionalized powder core accounts for 18% of the total weight of the welding wire, filling and surrounding the multi-strand core wire bundle (2) and the variable-diameter endogenous magnetic field coil (3). The multi-layer functionalized powder core includes at least three concentric powder layers with different preset functions from the inside to the outside, including an inner powder layer (4), a middle powder layer (5) and an outer powder layer (6). In terms of the total powder weight, the inner powder layer (4) accounts for 15%, the middle powder layer (5) accounts for 60%, and the outer powder layer (6) accounts for 25%. The inner layer powder (4) comprises the following components by weight percentage: 10.0% aluminum powder, 8.0% titanium powder, 6.0% zirconium silicon iron containing 40% Zr, 30.0% nickel powder, 5.0% molybdenum iron containing 60% Mo, 8.0% potassium carbonate, 18.0% fluorite, 5.0% calcium carbonate, and 10.0% iron powder; The middle layer powder (5) comprises the following components by weight percentage: calcium carbonate 30.0%, rutile (TiO2) 28.0%, silica (SiO2) 6.0%, ferromanganese containing 75% Mn 15.0%, ferrosilicon containing 75% Si 5.0%, fluorite (CaF2) 10.0%, magnesium oxide (MgO) 3.0%, ferroboron containing 17% B 0.15%, and iron powder 2.85%. The outer layer powder (6) comprises, by weight percentage: 20.0% potassium silicate solid powder, 4.0% lithium carbonate (Li2CO3), 15.0% fluorite (CaF2), 5.0% cryolite (Na3AlF6), 25.0% wollastonite (CaSiO3), 10.0% rutile (TiO2), 3.0% aluminum powder (Al), and 18.0% iron powder; The multi-strand core wire bundle (2) contains a mixture of low-carbon low-alloy steel wire and steel wire with a nickel content of 5-8%, and the variable diameter endogenous magnetic field coil (3) forms a parallel path with the multi-strand core wire bundle (2).

2. The welding wire for high-altitude climates according to claim 1, characterized in that: The metal outer skin (1) is formed by butt welds of ultra-low carbon steel strips through laser welding or high frequency welding, and has a uniform wall thickness.

3. A method for preparing the welding wire for high-altitude climates as described in claim 1, characterized in that: Includes the following steps: S1, Preparation of multi-strand core wire bundle (2): drawing fine wires, performing surface treatment on at least part of the fine wires including coating with a Ni or K compound, and twisting the treated fine wires into multi-strand core wire bundle (2). S2, Preparation and winding of variable diameter internal magnetic field coil (3): Prepare a variable diameter conductive filament with a high temperature insulation layer, the diameter of which varies according to the law of d²∝remaining length, and spirally wind it around the outside of the multi-strand core wire bundle (2); S3. Preparation and filling of multi-layer functionalized drug powder core: Prepare inner layer drug powder (4), middle layer drug powder (5) and outer layer drug powder (6) according to the formula of inner layer drug powder (4), middle layer drug powder (5) and outer layer drug powder (6) respectively, and perform sufficient ultra-low moisture drying treatment; adopt multi-channel concentric synchronous filling technology, fill the inner layer drug powder (4), middle layer drug powder (5) and outer layer drug powder (6) around the variable diameter endogenous magnetic field coil (3) and multi-strand core wire bundle (2) in the inner-middle-outer order; S4. Metal outer skin (1) Forming and closing: The metal strip is rolled up to wrap the powder core and closed by high frequency or laser welding to form an outer skin, thus obtaining the welding wire prototype. S5. Drawing and sizing: The welding wire prototype is cold-drawn in multiple passes to the final nominal diameter and the flux core is compacted. S6. Final processing and packaging: The finished welding wire is inspected, and optional surface treatment is performed. It is then vacuum-sealed in a controlled low-humidity environment using a vacuum aluminum foil bag with a desiccant inside, or by filling it with a protective atmosphere.

4. The method according to claim 3, characterized in that: The multi-channel concentric synchronous filling technology used in step S3 controls the filling rate and radial distribution of each layer of powder.

5. The method according to claim 3, characterized in that: The drying process in step S3 and the diffusible hydrogen content in the deposited metal of the finished welding wire in step S6 shall not exceed 4 ml per 100 grams.

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