Welding electrode with functional coatings

Abstract

To provide a welding electrode with functional coatings.SOLUTION: The disclosed technology generally relates to welding electrodes, and particularly to consumable welding electrodes having functional coatings. In one aspect, a welding electrode comprises a core wire having a base metal composition, and two or more coatings covering at least a portion of the core wire. The two or more coatings comprise an electrically conductive coating including one or more electrically conducting elements or compounds in addition to or other than copper (Cu). The two or more coatings additionally comprise an additional functional coating including one or more additional elements or compounds adapted to modify a surface tension of a molten droplet formed from the welding electrode. In another aspect, a method of manufacturing a welding electrode comprises providing the core wire having the base metal composition, and forming the two or more coating layers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 261,462, entitled "WELDING ELECTRODE WITH FUNCTIONAL COATINGS," filed September 21, 2021, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THE INVENTION The presently disclosed technology relates generally to welding electrodes, and more particularly to consumable welding electrodes having a functional coating on a core wire. [Background technology]

[0003] Various welding techniques utilize a consumable welding electrode that serves as a source of weld metal. For example, in metal arc welding, an electric arc is created when a voltage is applied between a consumable welding electrode, which serves as one electrode and is advanced toward the base metal, and the base metal, which serves as the other electrode. The arc melts the tip of the metal wire, thereby creating a droplet of molten metal electrode that is deposited on the base metal to form the weld metal, or weld bead.

[0004] The technical and economic demands on welding technologies are becoming more complex, with a simultaneous need for greater manufacturing flexibility and greater mechanical performance. Additionally, optimizing one performance parameter of the weld metal can force compromises in other parameters. Some welding technologies attempt to address these competing demands by improving consumables, for example, by improving the physical design and / or composition of the consumable electrode. The technology disclosed herein addresses the need for an improved consumable welding electrode having a functional coating. Summary of the Invention [Means for solving the problem]

[0005] In a first aspect, a welding electrode includes a solid core wire having an iron (Fe)-based base metal composition and a conductive coating formed on the solid core wire. The conductive coating includes one or more conductive elements or compounds in addition to or other than copper (Cu). The welding electrode additionally includes an additional functional coating formed on the conductive coating, the coating including one or both of elemental antimony (Sb) and one or more Sb oxides.

[0006] In a second embodiment, a welding electrode includes a solid core wire having an iron (Fe)-based base metal composition and two or more coatings covering at least a portion of the core wire. The two or more coatings include a conductive coating formed on the solid core wire that includes one or more conductive elements or compounds in addition to or other than copper (Cu). The two or more coatings additionally include an additional functional coating formed on the conductive coating and having a porous structure that includes antimony (Sb). [Brief explanation of the drawings]

[0007] [Figure 1] 1 illustrates an arc welding system usable with a consumable electrode according to embodiments disclosed herein. [Figure 2] 1 illustrates a welding process using a consumable electrode according to embodiments disclosed herein. [Figure 3] 1 illustrates a coated welding consumable electrode according to an embodiment. [Figure 4A] 1 illustrates a coated welding consumable electrode including two or more coatings according to an embodiment. [Figure 4B] 1 illustrates a coated welding consumable electrode including three or more coatings according to an embodiment. [Figure 5] 1 illustrates a method for manufacturing a coated welding consumable electrode according to an embodiment. [Figure 6A] 1 shows the weld metal formed using a conventional consumable electrode. [Figure 6B] 1 illustrates a weld metal formed using a consumable electrode having a functional coating according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Some welding electrodes have two main components: a core wire or rod and a covering or coating. The core contains the base alloying elements of the weld metal. The coating can include various materials that contribute to various functionalities. For example, coatings can serve to shield the weld metal, stabilize the arc, alloy the weld metal for various physical properties, provide slag for fluxing, reduce gas pockets in the weld metal, increase electrical conductivity or insulation, protect from the environment, provide lubrication for feed, and an attractive appearance, to name a few.

[0009] Some conventional solid welding wires are coated with a copper-containing coating to improve the electrical conductivity and corrosion resistance of the wire and welding nozzle and to reduce friction with the delivery hose or welding nozzle. However, during the welding process, some of the copper can undesirably melt and migrate into the weld. Copper contamination of the weld can cause "copper cracking" or reduce the mechanical properties of the weld joint, particularly impact toughness and elongation at low temperatures. Copper can also oxidize and leak into the air as copper particles, which are harmful to human health if inhaled. The production of copper-coated welding wire can also generate waste acids and pollutants in the environment. Therefore, there is a need for coated wires that at least reduce or eliminate the copper in welding electrode coatings while retaining its functional benefits.

[0010] To address these and other needs, embodiments disclosed herein relate to a welding electrode that includes a core wire having a base metal composition and two or more coatings covering at least a portion of the core wire. The two or more coatings include a conductive coating that includes one or more conductive elements or compounds in addition to or other than copper (Cu). The two or more coatings additionally include an additional functional coating that includes one or more additional elements or compounds (molten weld metal surface tension modifiers) adapted to modify the surface tension of molten droplets formed from the welding electrode.

[0011] Arc welding process for welding with electrodes having functional coatings - Patent Application 20070122997 Arc welding is one of several fusion processes for joining metals. By applying high heat, the metal at the joint between two parts melts and mixes directly, or more commonly with an intermediate molten filler metal.

[0012] An arc welding system 100 usable with embodiments disclosed herein is shown in FIG. 1. A power system 110, including an AC or DC power source and controls, is connected by a work cable 114 to a workpiece 102 to be welded and by a "hot" cable to an electrode holder 118 in electrical contact with a welding electrode 106. An arc is established in the gap between the workpiece 102 and the welding electrode 106 when the current-carrying circuit and the electrode tip contact the workpiece 102 and is terminated with the contact remaining closed. The electric arc can be established between the welding electrode 106, which may be a consumable electrode and acts as one electrode (e.g., a DC anode (+)), and the workpiece 102, which acts as the other electrode (e.g., a DC cathode (-)). After the arc is struck, a plasma 108 is sustained, which includes neutral and ionized gas molecules as well as neutral and charged clusters or droplets of metal wire material vaporized by the arc. The welding electrode 106 is paid out toward the base metal 102, and droplets of metal wire are deposited on the base metal, thereby forming a weld bead or weld metal. The arc can generate high temperatures of approximately 6500°F at its tip. This heat melts both the base metal 102 and the welding electrode 106, creating a pool of molten metal, sometimes called a "crater." The crater solidifies behind the electrode as it is moved along the joint. Upon cooling and solidification, a metallurgical bond is created. Because the joint is a blend of metals, the final weld can have mechanical properties, e.g., strength, comparable to or substantially the same as the metals in that portion of the base metal 102. This is a significant difference from non-fusion joining processes (e.g., soldering, brazing, etc.), in which the mechanical and physical properties of the base material may be unequal to those of the base metal 102 at the joint.

[0013] Hot metals have a tendency to chemically react with elements in the air—oxygen and nitrogen. When the metal in the weld pool comes into contact with air, oxides and nitrides can form, which can negatively affect the strength and toughness of the weld. Therefore, some arc welding processes offer some means to shield the arc and weld pool with protective shielding gases, steam, and / or slag. This is called arc shielding. This shielding reduces or minimizes contact between the molten metal and air. Shielding can also improve the weld. One example is flux, which can contain deoxidizers for the weld metal.

[0014] During welding, the arc not only provides the heat necessary to melt the electrode and base metal, but also, under certain conditions, must provide a means for transporting the molten metal from the electrode tip to the base metal. Several mechanisms exist for metal transport. Examples include surface tension transport, in which a droplet of molten metal contacts the molten metal pool and is drawn into it by surface tension, and spray arc, in which an electric pinch ejects a droplet from the molten metal at the electrode tip and propels it into the molten pool.

[0015] If the electrode 106 is a consumable electrode as disclosed herein, the tip melts due to the heat of the arc, and droplets break off and are transported through the arc column to the workpiece 102. Arc welding according to the embodiments described herein, in which the electrode melts through and becomes part of the fusion zone, is referred to as metal arc welding. This differs from carbon or tungsten (TIG) welding, in which no droplets are forced across the gap to the workpiece. The filler metal is fused to the joint from a separate rod or wire. A consumable electrode transfers a greater portion of the heat generated by the arc to the weld pool, resulting in higher thermal efficiency and a smaller heating area.

[0016] Arc welding can be performed with either direct current (DC), with the electrode being positive (DCEP) or negative (DCEN), or with alternating current (AC). The choice of current and polarity depends on the process, the type of electrode, the arc atmosphere, and the metals being welded.

[0017] In processes using consumable electrodes, the electrode or wire melts to provide additional metal that fills the gap and forms a weld joint joining two base metals. Welding processes using consumable electrodes include shielded metal arc welding (SMAW), gas metal arc welding (GMAW), or metal inert gas (MIG) welding, flux-cored arc welding (FCAW), metal-cored arc welding (MCAW), and submerged arc welding (SAW). Welding processes using consumable welding electrodes can be performed in direct current electrode positive (DCEP) mode, direct current electrode negative (DCEN) mode, or alternating current (AC) mode. In DCEP mode, direct current is used, and the wire is connected to the positive terminal of the power source and the base metal or plate to be welded is connected to the negative terminal, while in DCEN mode welding, the opposite is true. In AC mode, the wire and base metal or plate alternate from positive to negative in a frequency-dependent cycle. The terminal acting as the positive electrode may be called the anode, and the terminal acting as the negative electrode may be called the cathode. The following describes various consumable electrode-based welding processes that can be implemented using oxide-coated welding wire according to embodiments.

[0018] FIG. 2 illustrates a gas metal arc welding (GMAW) process 200, sometimes referred to as a metal inert gas (MIG) welding process, which can be used with embodiments disclosed herein. The GMAW process uses a continuous solid wire electrode 106 for the filler metal and an externally supplied gas (typically from a high-pressure cylinder) for shielding. The electrode 106 can be mild steel and can be coated with a thin layer of a coating according to various embodiments, which can include two or more coatings, including a conductive coating and an additional functional coating (molten weld metal surface tension modifier) ​​designed to alter the surface tension of the molten metal droplets formed from the welding electrode. When an arc 108 is applied between the electrode 106 and the base metal 102, both the electrode 106 and the surface of the base metal 102 vaporize, forming small globules of metal that are transported to the surface of the base metal 102, thereby forming a weld pool 204 containing the metal of the coated electrode 106 and the metal of the base metal 102. The welder can be configured for DC positive polarity. The shielding gas, typically carbon dioxide or a mixture of carbon dioxide and argon, protects the molten metal from the atmosphere. The shielding gas flows through the gun and cable assembly and exits the gun nozzle with the welding wire, shielding and protecting the molten weld pool. When exposed to the atmosphere, the molten metal can easily react with oxygen, nitrogen, and hydrogen from the atmosphere. According to various embodiments, a welding electrode configured for the various welding processes described above, such as GMAW, includes a core wire having a base metal composition and two or more coatings covering at least a portion of the core wire. As described herein, the two or more coatings include a conductive coating that includes one or more conductive elements or compositions in addition to or other than copper (Cu). The two or more coatings may additionally include an additional functional coating. The additional functional coating includes one or more additional elements or compounds configured to alter the surface tension of a molten metal droplet formed from the welding electrode.

[0019] FIG. 3 illustrates a welding consumable electrode 300 according to various embodiments. The electrode 300 includes a core wire 304 and a coating 308. The core wire 304 can include a suitable carbon steel, such as a mild steel for GMAW, which is coated with the coating 308 to provide alloying elements for the resulting weld metal, as well as various additional functionalities beyond alloying, as described herein. The chemical elements and compounds of the core wire 304 and coating 308 disclosed herein can be distinguished based on whether or not the constituent elements are incorporated as part of the alloy of the weld metal. Hereinafter, elements that are substantially incorporated into the resulting weld metal may be referred to as alloying elements, while elements that are not substantially incorporated into the resulting weld metal and that contribute to other functions, such as slag or gas formation or arc stabilization, may be referred to as non-alloying elements.

[0020] 4A and 4B show coated welding consumable electrodes 400A and 400B, respectively, according to some other embodiments. Electrodes 400A and 400B are configured similarly to electrode 300A shown in FIG. 3, including a core wire 304 and a coating 308, except that electrodes 400A and 400B include multiple coatings. For example, electrode 400A includes two coatings 308, including a first coating 308A and a second coating 308B. Electrode 400B includes multiple coatings 308, including a first coating 308A, a second coating 308B, and a third coating 308C. Additionally, although not shown, multiple coatings according to other embodiments may include n coatings, including coatings 1 through n.

[0021] As previously mentioned, the weld metal can include solidified metal from the base metal and the metal from the consumable electrode. Because the amount of dilution or enrichment of elements in the weld metal due to the inclusion of molten base metal can vary significantly, unless expressly stated otherwise, the weight percentages of various elements and compounds in the weld metal disclosed herein refer to that of the undiluted weld metal that would result if no dilution or enrichment from the base metal had occurred.

[0022] Continuing with reference to FIGS. 3 and 4A-4B, core wire 304 comprises a carbon steel composition, e.g., a mild steel composition. Carbon steel compositions according to various embodiments include Fe and one or more of C, Cr, Ni, Mo, V, Cu, Mn, and Si at concentrations above impurity levels. In some embodiments, core wire 304 comprises a low-alloy steel composition having an alloying element content of about 1.5% to 5% by weight. Other elements may be present at impurity levels. As described herein, impurity levels refer to the weight percentage of elements that are not intentionally included but are still present, and may generally be less than 0.05%. Impurities that are not intentionally added but are still present in core wire 304 include S, P, Al, Cu, N, Cr, Ni, Mo, V, Nb, and Ti. The remaining weight of core wire 304 may be Fe.

[0023] 4A-4B, coating 308 includes a conductive coating including one or more conductive elements or compounds in addition to copper (Cu) or other than copper, and an additional functional coating including one or more additional elements or compounds adapted to alter the surface tension of droplets formed from the welding electrode. As described herein, any one of first and second coatings 308A, 308B of electrode 400A (FIG. 4A) or any one of first, second, and third coatings 308A, 308B, and 308C of electrode 400B (FIG. 4B) can be conductive layers or additional functional layers, in any order. Thus, although a conductive coating according to an embodiment may be referred to as the first coating 308A, which is the innermost coating of the plurality of coatings 308 on electrodes 400A, 400B, it should be understood that the conductive coating could also be the second coating 308B of electrodes 400A, 400B or the third coating 308C of electrode 400B. Similarly, an additional functional coating according to an embodiment may be referred to as the first coating 308A, which is the innermost coating of the plurality of coatings 308 on electrodes 400A, 400B, it should be understood that the additional functional coating could also be the second coating 308B of electrodes 400A, 400B or the third coating 308C of electrode 400B.

[0024] Conductive Coating According to various embodiments, the first, second, and third coatings 308A, 308B, 308C (FIG. 4A or 4B) are conductive coatings that include one or more conductive elements or compounds selected from the group consisting of magnesium (Mg), aluminum (Al), zinc (Zn), tin (Sn), chromium (Cr), platinum (Pt), silver (Ag), graphite, graphene, graphene oxide, and titanium (Ti).

[0025] According to various embodiments, the conductive coating serves to provide substantial electrical conductivity to the electrodes 400A, 400B such that during welding, a substantial amount (e.g., >10%, >30%, >50%, >70%, >90%, or a value within a range defined by any of these values) of the electrical current passing through the electrodes 400A, 400B flows through the first coating 308A. In some embodiments, the one or more conductive elements or compounds are present in an amount and form such that the welding electrodes 400A, 400B have a lower electrical resistance relative to a core wire 304 lacking the conductive element or compound.

[0026] In some embodiments, one or more conductive elements or compounds are present in the absence of Cu as part of the conductive coating or as part of any of the plurality of coatings 308. That is, in some embodiments, the one or more conductive elements or compounds may obviate the need for Cu as part of a coating, e.g., to provide the necessary conductivity, and Cu may be omitted from the plurality of coatings 308. In some other embodiments, the one or more conductive elements or compounds are present in addition to Cu as part of the conductive coating or as part of any of the plurality of coatings 308. That is, in some embodiments, the one or more conductive elements or compounds may supplement Cu, e.g., as part of the same or a different coating, to provide the necessary conductivity.

[0027] The one or more conductive elements or compounds can significantly reduce or eliminate the need for copper as part of the coating in conventional coated electrode wires. Thus, according to embodiments, the one or more conductive elements or compounds can be present without or in addition to Cu. When present in addition to Cu, the one or more conductive elements are present in an amount greater than 50 atomic %, 60 atomic %, 70 atomic %, 80 atomic %, 90 atomic % of the total of the one or more conductive elements or compounds and Cu, or a value within a range defined by any of these values. Therefore, reducing the Cu content can advantageously reduce the adverse effects of copper-induced cracking in the weld.

[0028] When present, Cu is present in an amount greater than 0.0005%, 0.0010%, 0.0020%, 0.0050%, 0.010%, 0.020%, 0.050%, 0.10%, 0.20%, 0.5% by weight of the welding wire, or a value within a range defined by any of these values.

[0029] Additional Functional Coatings According to various embodiments, any one of the first, second, and third coatings 308A, 308B, 308C (FIGS. 4A or 4B) is an additional functional coating that includes a molten weld metal surface tension modifier, as described below.

[0030] Various productivity parameters, such as the welding speed for forming the weld metal, can be determined in part by the surface tension of the weld metal droplets. To provide a desired molten weld metal surface tension, according to some embodiments, the additional functional coating includes a molten weld metal surface tension modifier. The molten weld metal surface tension modifier includes one or more additional elements or compounds adapted to change the surface tension of the weld metal droplets formed from the welding electrodes 400A, 400B. According to various embodiments, the one or more additional elements or compounds adapted to change the surface tension are selected from the group consisting of cadmium (Cd), mercury (Hg), gallium (Ga), indium (In), germanium (Ge), tin (Sn), lead (Pb), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po).

[0031] The one or more additional elements or compounds adapted to change the surface tension of the molten weld metal can change, e.g., lower, the surface tension of the molten weld metal droplet, causing the droplet to detach from the electrode at a faster rate than a metal droplet formed from a reference electrode without the one or more additional elements or compounds adapted to change the surface tension of the molten weld metal. The droplet size can be related to the equilibrium contact angle of the droplet formed on the solidified weld metal or base metal, which is defined by a relationship known as the Young-Dupré equation. The solid-gas interfacial energy between the molten weld metal and the base metal can be expressed as γ SG and the solid-liquid interfacial energy is expressed as γ SL and the liquid-gas interfacial energy (i.e., surface tension) is expressed as γ LG The equilibrium contact angle θ C is determined from these quantities by the Young-Dupré formula: gamma SG -γ SL -γ LG cosθ C =0

[0032] In other words, the contact angle is determined by the balance between adhesive forces (the liquid's desire to maintain contact with the solid) and cohesive forces within the liquid (both internal cohesive forces and surface tension). Increased adhesive forces between the liquid and the solid or decreased cohesive forces (surface tension) within the liquid result in greater wettability and a smaller contact angle. Lower surface tension can be advantageous for increasing welding speeds, due to reduced droplet size and improved wetting of the base metal or solidified weld metal by the molten weld metal. For example, the average droplet size formed by electrodes according to embodiments can be reduced by 30%, 40%, 50%, 60%, or a value within a range defined by any of these values, with the addition of these elements. The surface tension of molten droplets formed from a welding electrode can be reduced by 10%, 20%, 30%, 40%, 50%, or more than reference droplets formed from the same reference welding electrode under the same welding conditions, excluding the presence of the surface tension modifier. By reducing the average droplet size and surface tension, the welding speed at which weld metal is formed using welding electrodes according to embodiments can be 30%, 40%, 50%, 60% or more higher than the welding speed at which weld metal is formed without a welding electrode that does not employ one or more additional elements or compounds adapted to alter the surface tension of the molten weld.

[0033] The inventors have discovered that one or more additional elements or compounds adapted to alter the surface tension of the molten weld metal can simultaneously synergistically reduce the amount of residual oxide or silicate islands that form on the slag or weld metal. Oxide islands are difficult to remove and can degrade the visual appearance of the weld metal. The relative ease of removal of oxide or silicate islands can be related to the equilibrium contact angle of the oxide or silicate islands that form on the weld metal, which is defined by a relationship known as the Young-Dupré equation. The solid-gas interfacial energy is defined as γ SG and the solid-liquid interfacial energy is expressed as γ SL and the liquid-gas interfacial energy (i.e., surface tension) is expressed as γ LG The equilibrium contact angle θ Cis determined from these quantities by the Young-Dupré equation, also mentioned above, i.e., the interface of interest is that between the silicate island and the underlying weld metal, although the same equation may be applicable.

[0034] According to embodiments, the one or more additional elements or compounds adapted to alter the surface tension of the molten weld metal are present in an amount and form such that the volume of silicate islands formed on the weld metal formed from the welding wire is at least 30%, 40%, 50%, 60%, or more less than the volume of silicate islands formed on the weld metal formed from the core wire without the one or more additional elements or compounds adapted to alter the surface tension of the molten weld.

[0035] According to various embodiments, each of the one or more conductive elements or compounds and additional elements or compounds is present in an amount greater than 0.0005%, 0.0010%, 0.0020%, 0.0050%, 0.010%, 0.020%, 0.050%, 0.10%, 0.20%, 0.5%, 1.0%, 2.0%, 5.0% by weight of the welding wire, or a value within a range defined by any of these values.

[0036] Thus, welding wire includes core wire having an Fe-based or steel composition, e.g., a mild steel composition, including Fe and one or more of C, Mn, Si, Ni, Mo, Cr, and V, conductive elements or compounds, and additional elements or compounds at concentrations above impurity levels. Core wire, as used herein, refers to solid wire having a substantially homogeneous composition.

[0037] 4B, in some embodiments, two of the first, second, and third coatings 308A, 308B, and 308C are configured as conductive coatings. For example, the first and third coatings 308A and 308C can be the same or different conductive coatings, with the second coating 308B disposed as an additional functional coating interposed therebetween.

[0038] 4B, in some other embodiments, two of the first, second, and third coatings 308A, 308B, and 308C are configured as additive functional coatings. For example, the first and third coatings 308A and 308C can be the same or different additive functional coatings, with the second coating 308B disposed as a conductive coating interposed therebetween.

[0039] 3 and 4A-4B, according to various embodiments, the diameter of the core wire 304 can be 1 / 16 inch (1.6 mm), 3 / 32 inch (2.5 mm), 1 / 8 inch (3.2 mm), 5 / 32 inch (4.0 mm), 3 / 16 inch (5.0 mm), or a diameter within a range defined by any of these values, e.g., 3.2 mm. The length of the core wire 304 can be 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, or a length within a range defined by any of these values. The thickness of the coating 308 can be 1-1.5 mm, 1.5-2.0 mm, 2.0-2.5 mm, 2.5-3.0 mm, or a thickness within a range defined by any of these values, e.g., 1.2 mm. By way of example only, an electrode with a 3.2 mm core wire diameter and a 1.2 mm coating thickness may have an overall diameter of 5.6 mm, while an electrode with a 4.0 mm core wire diameter and a 1.35 mm coating thickness may have an overall diameter of 6.7 mm. According to various embodiments, the weight percentage of the coating 308, based on the total weight of the electrode 300, may be 10-15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, or a value within a range bounded by any of these values.

[0040] In certain embodiments, additional functional coating 308B is formed on conductive coating 308A. When additional functional coating 308B includes a molten weld metal surface tension modifier, it includes elemental antimony (Sb) and / or one or more Sb oxides. The one or more Sb oxides may be diantimony tetroxide (Sb2O4), antimony trioxide (Sb2O3), antimony pentoxide (Sb2O5), antimony hexitatridecoxide (Sb6O 13 ), and Sb3O6(OH). Substoichiometric oxides of these oxides can also be used.

[0041] The inventors have discovered that forming the additional functional coating 308B comprising Sb by electrochemical deposition can be particularly advantageous for various reasons described herein. The electrode structures described herein comprising a solid core wire coated with two or more functional coatings are particularly advantageous for electrodeposition because the underlying solid core wire 304 or conductive coating 308A can serve as an effective electrode for the associated electrochemical reaction. This is in contrast to electrodes where the core may be discontinuous or have poor electrical conductivity, such as when the core is formed from a powder, such as a metal-core electrode.

[0042] The inventors have further discovered that forming the Sb-containing additional functional coating 308B by electrochemical deposition can be particularly advantageous because it provides a high degree of control over composition at both the macroscopic and microscopic levels. In particular, electrodeposition allows for the formation of elemental antimony (Sb) and / or one or more Sb oxides. In one particular example, for example, an additional functional coating containing particles of Sb and one or more Sb oxides can be deposited by the galvanostatic reduction of antimony tartrate. Using such an electrodeposition method, composite thin films containing elemental antimony (Sb) and / or one or more Sb oxides can be formed. The relative amounts of Sb and / or Sb oxides can be controlled so that the overall composition of the resulting Sb / Sb oxide mixture has an Sb:O ratio of 0.1, 0.2, 0.5, 1, 2, 5, 10, or a value within a range defined by any of these values.

[0043] In some embodiments, the resulting thin film can be a homogeneous mixture of elemental Sb and Sb oxide. In other embodiments, the resulting additional functional coating 308B can include islands, regions, grains, or particles that can include any one or more of elemental Sb and / or Sb oxide. As an example, the relative amounts of elemental Sb and Sb oxide, e.g., the relative amounts of elemental Sb particles and Sb oxide particles, can be controlled by controlling the local pH at the electrode / electrolyte interface. The intermediate product of a welding electrode having a solid-core wire coated with a conductive coating, e.g., a Cu coating, can serve as an electrode in these electrochemical reactions. Without being bound by any theory, Sb is thermodynamically stable at low pH, while higher pH values ​​favor the formation of SbO. Therefore, by controlling the pH at the electrode / electrolyte interface, the additional functional coating can have controlled amounts of Sb particles and one or more Sb oxide particles. Furthermore, depending on the initial pH at the electrode / electrolyte interface, the additional functional coating 308B can be controlled to have an initial nucleation layer that is predominantly or more abundant in one or the other of elemental Sb and Sb oxide. Using these and other approaches, the weight ratio of elemental Sb particles to Sb oxide particles can be controlled to be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or a value within a range bounded by any of these values.

[0044] The inventors have further discovered that it can be particularly advantageous to form the Sb-containing additional functional coating 308B by electrochemical deposition, thereby controlling the morphology of the additional functional coating. In particular, the inventors have discovered that it can be advantageous to form the coating with submicron particles, thereby providing a high degree of control over the morphology of the resulting coating at both the macroscopic and microscopic levels. By controlling the surface condition of the underlying conductive coating, e.g., a Cu coating, formed on the solid core wire, the nucleation density during electrochemical deposition of elemental Sb and Sb oxides can be controlled. For example, by providing a rougher underlying surface, a higher density of nuclei can be achieved, resulting in smaller average island, region, grain, or particle diameters. The average island, region, grain, or particle diameter can be less than 1000 nm, 800 nm, 600 nm, 400 nm, 200 nm, 100 nm, 50 nm, 20 nm, 10 nm, or a value within a range defined by any of these values.

[0045] The islands, regions, grains, or particles can have a controlled shape and average diameter and size distribution so that the resulting additional functional coating 308B has controlled porosity. Controlled porosity can be advantageous for a variety of reasons, including physical appearance, improved adhesion with overlying coatings, and controlled exposure of underlying materials, to name a few. For example, porosity, defined as the ratio of void volume to total volume of the coating, can be controlled to be 0.1, 0.2, 0.3, 0.4, 0.5, or a value within a range defined by any of these values.

[0046] Additionally, in some embodiments, the additional functional coating 308B can be discontinuous, patchy, or in other forms to partially cover the underlying solid core wire 304 or conductive coating 308A. Partial coverage can be advantageous in some situations, for example, to optimize the surface friction of the welding wire and welding speed. For example, if the friction of the underlying conductive coating 308A, such as a Cu coating, is substantially lower, it may be desirable to partially expose the conductive coating 308A. The surface coverage ratio, defined as the ratio of the surface area of ​​the underlying material (e.g., the conductive coating 308A) covered by the additional functional coating 308B to the total surface area of ​​the underlying material, can be controlled to be 0.1, 0.2, 0.3, 0.4, 0.5, or a value within a range defined by any of these values.

[0047] The inventors have discovered that it may be advantageous to configure a welding wire so that a controlled amount of Sb becomes part of the weld metal to enhance the surface tension-reducing effect of Sb while reducing the potential for Sb's adverse effects on the mechanical properties of the resulting weld metal. According to embodiments, the amount of Sb alloyed with the weld metal in a welding electrode can be less than 60%, 50%, 40%, 30%, or 20% of the total amount of Sb present in the welding wire, e.g., 25-60% of the total amount of Sb present in the welding wire. The relatively small amount of Sb included in the weld metal can contribute to various features of the aforementioned additional functional coating 308B, including the presence of both elemental Sb and Sb oxides, which may be possible through electrochemical deposition. Various amounts of Sb can be vaporized, for example, by controlling the ratio of elemental Sb to Sb oxides. Table 1 below shows the experimental atomic % of Sb in experimentally produced welding wires and the detected atomic % of Sb in the resulting weld metal. As shown, when the Sb content in the welding wire is 0.009-0.024%, the Sb content in the resulting weld metal is 0.004-0.010%.

[0048] [Table 1]

[0049] Method for manufacturing coated electrodes FIG. 5 illustrates a method 500 for forming two or more coatings on a core wire according to an embodiment. Method 500 includes step 510 of providing a core wire 304 (FIGS. 4A and 4B) having a base metal composition and step 520 of treating the surface of the core wire in preparation for forming two or more coatings. Method 500 includes step 530 of forming a first coating 308A (FIGS. 4A and 4B) including one of a conductive coating including one or more conductive elements or compounds in addition to copper (Cu) or other than copper (Cu) and an additional functional coating. After step 530 of forming first coating 308A, method 500 proceeds to step 540 of post-treating the surface of first coating 308A. Method 500 also includes step 550 of forming a second coating 308B (FIGS. 4A and 4B) including the other of a conductive coating and an additional functional coating. After forming 550 the second coating 308B, the method 500 proceeds to step 560 of post-treating the surface of the second coating 308B.

[0050] In some embodiments, the method 500 optionally proceeds to step 540 of forming a third coating 308C (FIG. 4B). In some embodiments, the third coating 308C can be a second conductive coating that includes one or more conductive elements or compounds in addition to copper (Cu), or other than copper (Cu). In other embodiments, the third coating 308C can be a second, additional functional coating that is different from the first functional coating.

[0051] As previously mentioned, any one of the first and second coatings 308A, 308B of electrode 400A (FIG. 4A), or any one of the first, second, and third coatings 308A, 308B, and 308C of electrode 400B (FIG. 4B), can be disposed in either order as either a conductive coating or an additional functional coating.

[0052] The method 500 may be performed in a production line including a loading station for step 510 of providing a core wire, a surface treatment station for step 520 of processing the core wire, a drawing station, a first coating station for step 530 of forming a first coating, a first post-treatment station for step 540 of post-treating the surface of the first coating, a second coating station for step 550 of forming a second coating, a second post-treatment station for step 560 of post-treating the surface of the second coating, a third coating station for step 570 of forming a third coating, and a third post-treatment station for step 580 of post-treating the surface of the third coating.

[0053] Providing a core wire 510 includes providing a core wire 304 (FIGS. 3, 4A-4B) comprising a base metal composition as described above, e.g., a steel composition such as a mild steel composition. Treating a surface of the core wire 520 includes cleaning the surface at a cleaning station. In one exemplary embodiment, the cleaning station uses a cleaning and / or coating agent to clean the exterior surface of the material.

[0054] After cleaning, the material moves to a wire drawing station. The wire drawing station includes at least one die. In one exemplary embodiment, the wire drawing station includes a series of dies, each with a successively smaller opening than the preceding die. A lubricant (e.g., a powder lubricant) may be added to the dies to facilitate passage of the core wire through the dies and reduce die wear. As the core wire passes through the wire drawing station, the diameter of the material may gradually decrease by plastic deformation to the desired dimension. In some embodiments, the wire drawing process uses a wire drawing soap, which may be a stearate salt, such as calcium stearate, sodium stearate, etc. These soaps aid in the wire drawing process. After the drawing step, the core wire may further pass through an acid tank to further clean the incoming core wire and prepare it for forming one or more coatings thereon. After the cleaning step, the desired Ca range on the wire is such that the wire is usable for further coatings. The Ca content may range from 0.0005% to 1% by weight of the wire to create an optimized surface for further coatings.

[0055] After step 520 of treating the surface of the core wire, method 500 proceeds to step 530 of forming a first coating 308A (FIGS. 4A, 4B) that includes a conductive coating that includes one or more conductive elements or compounds in addition to copper (Cu) or other than copper, and an additional functional coating, such as one of the Sb-containing coatings described herein.

[0056] In various embodiments, forming a first coating 530 includes wet coating, for example, in a wire plating tank containing a desired coating recipe. The wet coating process can be performed by a chemical / electrochemical or mechanical / physical process. Chemical processes can be displacement reactions, sol-gel thin film processes, electroplating, or electroless plating, to name a few. In mechanical / physical processes, the coating is adhered to the wire surface using a binder.

[0057] After forming 530 the first coating 308A, the method 500 proceeds to post-treating 540 the surface of the first coating 308A. In some examples, post-treating 540 includes curing using, for example, in-line heating. In-line heating can be achieved by conduction, convection, radiation, or Joule heating, etc. Heating can be electrical / resistance heating, induction heating, heating by flame or hot air, laser heating, plasma heating, etc.

[0058] The method 500 additionally includes forming 550 a second coating 308B (FIGS. 4A, 4B) comprising the other of the conductive coating and the additional functional coating. In various embodiments, forming 550 a second coating includes wet coating, for example, in a wire plating tank containing the desired coating recipe. The wet coating process can be performed through a chemical / electrochemical or mechanical / physical process. The chemical process can be a displacement reaction, a sol-gel thin film process, electroplating, or electroless plating, to name a few. In the mechanical / physical process, the coating is adhered to the wire surface using a binder.

[0059] If present, the method 500 includes forming the additional coating 308C (FIG. 4B), which process may be similar to steps 530, 550 of forming the first and / or second coatings 308A, 308B.

[0060] In some embodiments, one or both of the conductive coating and the additional functional coating comprises a plurality of pores, and the pores are at least partially filled with a material different from the porous conductive coating and the additional functional coating. If present, having a pore structure can be advantageous for improving adhesion between the different layers.

[0061] After forming the second coating 308B in step 550, the method 500 proceeds to post-treating the surface of the second coating 308B in step 560. In some embodiments, post-treating step 560 includes passing the wire through a finishing / polishing die. If the final coating includes a metallic coating, such as a Cu coating, the polishing die specifically smooths the wire surface, removes excess copper, and ensures that the wire has a uniform, shiny appearance. The die can be a polycrystalline diamond die or a tungsten carbide die.

[0062] FIG. 6A shows a weld metal formed using a conventional consumable electrode. FIG. 6B shows a weld metal formed using a consumable electrode having a functional coating according to an embodiment. The two consumable electrodes used to form the weld metals of FIGS. 6A and 6B have the same composition, except for the functional coating. In particular, the weld metal shown in FIG. 6B was formed using an electrode having a conductive coating including one or more conductive elements including copper (Cu) and an additional functional coating formed on the conductive coating and including antimony (Sb) and one or more Sb oxides. As discussed above with respect to FIG. 4A, the amount of silicate islands is significantly reduced in the weld metal formed using a consumable electrode according to an embodiment due to an increased contact angle between the silicate islands and the weld metal. For example, as shown, the coated surface area of ​​the weld metal is

[0063] Unless the context clearly requires otherwise, throughout the specification and claims, words like "comprise," "comprising," "include," "including," and the like, are to be construed in an inclusive sense, i.e., "including, but not limited to," rather than an exclusive or exhaustive sense. The word "coupled," as generally used herein, refers to two or more elements that are directly connected or that may be connected by one or more intermediate elements. Similarly, the word "connected," as generally used herein, refers to two or more elements that are directly connected or that may be connected by one or more intermediate elements. Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context allows, words in the foregoing Detailed Description using the singular or plural number may also include the plural or singular number, respectively. The word "or" in reference to a list of two or more items covers all of the following interpretations of that word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0064] Additionally, conditional language used herein, such as "can," "could," "might," "may," "eg," "for example," "etc.", and the like, is intended to generally convey that certain embodiments include certain features, elements, and / or conditions, while other embodiments do not, unless specifically stated otherwise or understood otherwise within the context of use. Thus, such conditional language generally is not intended to imply that features, elements, and / or conditions are in any way required by one or more embodiments, or that these features, elements, and / or conditions will or will not be included in or practiced in any particular embodiment.

[0065] While specific embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the present disclosure. Indeed, the novel apparatus, methods, and systems described herein may be embodied in a variety of other forms, and various omissions, substitutions, and modifications to the methods and systems described herein may be made without departing from the spirit of the present disclosure. For example, while blocks are described in certain arrangements, alternative embodiments may realize similar functions using different component and / or circuit arrangements, and some blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of such blocks may be implemented in a variety of ways. Any suitable combination of elements and acts of the various embodiments described above may be combined to provide yet further embodiments. The various features and processes described above may be performed independently of each other or combined in various ways. All conceivable combinations and subcombinations of features of the present disclosure are intended to be within the scope of the present disclosure. [Explanation of symbols]

[0066] 100 Arc Welding System 102 Base material 106 Electrode 108 Arc 110 Power System 114 Work Cable 118 Electrode holder 204 Molten pool 300 Welding Consumable Electrodes 304 Core Wire 308 coating 308A First Coating 308B Second Coating 308C Third Coating 400A, 400B consumable electrode

Claims

1. a solid core wire having an iron (Fe) based base metal composition; a conductive coating formed on the solid core wire, the conductive coating including one or more conductive elements or compounds in addition to copper (Cu) or other; an additional functional coating formed on the conductive coating, the functional coating comprising elemental antimony (Sb) and / or one or more Sb oxides; Including welding electrodes.

2. 2. The welding electrode of claim 1, wherein the total amount of Sb in the welding electrode is effective to reduce the surface tension of a droplet formed from the welding electrode by 10% or more compared to a reference droplet formed under the same welding conditions from a reference welding electrode that is identical to the welding electrode except for the presence of Sb.

3. 3. The welding electrode of claim 2, wherein the total amount of Sb is 0.0005 to 2% by weight of the welding electrode.

4. The welding electrode of claim 1 , wherein the additional functional coating comprises submicron particles comprising elemental Sb and the one or more Sb oxides.

5. The submicron particles are Sb element particles and Sb ２ O ３ The welding electrode of claim 4 including particles.

6. The welding electrode of claim 4 , wherein the additional functional coating is a porous layer including a plurality of pores formed between adjacent submicron particles.

7. The welding electrode of claim 6 , wherein the pores expose the underlying conductive coating.

8. 3. The welding electrode of claim 2, configured to form a weld metal at a welding speed that is at least 30% higher than a welding speed for forming a reference weld metal under the same welding conditions using the reference welding electrode that is identical to the welding electrode except for the presence of Sb or one or more Sb oxides.

9. 10. The welding electrode of claim 1, wherein the one or more conductive elements or compounds are selected from the group consisting of magnesium (Mg), aluminum (Al), zinc (Zn), tin (Sn), chromium (Cr), platinum (Pt), silver (Ag), graphite, graphene, graphene oxide, and titanium (Ti).

10. The welding electrode of claim 9 , wherein the one or more conductive elements or compounds are present in the conductive coating without Cu.

11. 10. The welding electrode of claim 9, wherein the one or more conductive elements or compounds are present in an amount in addition to Cu that is greater than 90 atomic % of the sum of the one or more conductive elements or compounds and Cu.

12. 4. The welding electrode of claim 3, wherein the welding electrode is configured such that a weld metal formed using the welding electrode contains 25 to 60% of the total amount of Sb present in the welding electrode.

13. In welding electrodes, a solid core wire having an iron (Fe) based base metal composition; two or more coatings covering at least a portion of the solid core wire; Includes The two or more coatings are a conductive coating formed on the solid core wire, the conductive coating including one or more conductive elements or compounds in addition to copper (Cu) or other; an additional functional coating comprising antimony (Sb), having a porous structure, and formed on the conductive coating; Including welding electrodes.

14. 14. The welding electrode of claim 13, wherein the total amount of Sb present in the welding electrode is an amount effective to increase the contact angle of oxide islands formed on a weld metal formed from the welding electrode by 10% over the contact angle of reference oxide islands formed on a reference weld metal formed from a reference welding wire identical to the welding electrode under the same welding conditions except for the presence of Sb.

15. The welding electrode according to claim 14, wherein the total amount of Sb in the welding electrode is 0.0005 to 2 wt %.

16. 14. The welding electrode of claim 13, wherein the Sb is in the form of elemental Sb and one or more Sb oxides.

17. 17. The welding electrode of claim 16, wherein the additional functional coating comprises submicron particles comprising the element Sb and the one or more Sb oxides.

18. The submicron particles are Sb element particles and Sb ２ O ３ 20. The welding electrode of claim 17, comprising particles.

19. 18. The welding electrode of claim 17, wherein the submicron particles partially cover the conductive coating such that a portion of the conductive coating is exposed between adjacent ones of the submicron particles.

20. 14. The welding electrode of claim 13, wherein the total amount of Sb is present in the welding electrode in an amount and form such that the volume of silicate islands formed on a weld metal formed from the welding electrode is at least 50% smaller than the volume of reference silicate islands formed on a reference weld metal formed under the same welding conditions using a reference welding electrode that is the same as the welding electrode except for the presence of Sb.

21. 14. The welding electrode of claim 13, further comprising calcium (Ca) in an interface region between the solid core wire and the two or more coating layers in an amount of 0.0005 to 1 weight percent of the weight of the welding electrode.

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