Welding torch with wire electrode guide

Abstract

The welding torch includes a contact tip and a wire electrode guide extending distally from the contact tip, the wire electrode guide including a metallic outer sheath and a plurality of ring-shaped electrical insulators axially stacked within the metallic outer sheath to form a central wire electrode-receiving bore through which the plurality of ring-shaped electrical insulators extend.

Description

[Technical Field]

[0001] The present invention relates to arc welding, and more particularly to torches for submerged arc welding (SAW). [Background technology]

[0002] Various welding techniques utilize a welding wire that acts as a source of metal. For example, in metal arc welding, an electric arc is created when a voltage is applied between a consumable wire welding electrode, which acts as one electrode and is advanced toward the workpiece, and the workpiece, which acts as the other electrode. The arc melts the tip of the metal wire, thereby creating droplets of molten metal wire that are deposited on the workpiece to form a weldment or weld bead.

[0003] Submerged arc welding is a type of welding in which the arc between the wire electrode and the workpiece is completely immersed in a blanket of granular fusible flux. The flux protects the molten weld puddle from atmospheric contamination. Submerged arc welding systems, like other types of welding systems, may include a welding power source, a wire feed control and drive assembly, and a welding torch. Additionally, submerged arc welding systems also include a flux system, which holds and delivers the flux to the weld joint during welding. Submerged arc welding can provide a very economical solution for some applications. The high deposition rates achieved with SAW are a major factor in the economy achieved with this process. Summary of the Invention [Problem to be solved by the invention]

[0004] SAW deposition rates can be improved by utilizing a long stick-out (LSO) or extended stick-out (ESO) welding wire, due to current flow through the wire stick-out, which heats the distal portion of the welding wire. However, the heated LSO wire tends to wobble out of alignment in the weld groove, especially in deep, narrow grooves between thick workpieces. In deep welds and / or groove welds, it would be desirable to perform LSO-SAW while maintaining proper alignment of the heated wire electrode along the weld path within the groove. [Means for solving the problem]

[0005] The following summary presents a simplified summary in order to provide a basic understanding of some aspects of the devices, systems, and / or methods discussed herein. This summary is not an extensive overview of the devices, systems, and / or methods discussed herein. It is not intended to identify key elements or delineate the scope of such devices, systems, and / or methods. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0006] According to one aspect of the present invention, a welding torch is provided, the welding torch including a contact tip and a wire electrode guide extending distally from the contact tip, the wire electrode guide including a metallic outer sheath and a plurality of ring-shaped electrical insulators axially stacked within the metallic outer sheath to form a central wire electrode-receiving bore through the plurality of ring-shaped electrical insulators.

[0007] In accordance with another aspect of the present invention, a welding torch is provided. The welding torch includes a contact tip and a wire electrode guide extending distally of the contact tip. The wire electrode guide includes a metallic outer sheath and a plurality of ceramic electrical insulators axially stacked within the metallic outer sheath. Each ceramic electrical insulator has a central opening such that the plurality of ceramic electrical insulators axially stacked within the metallic outer sheath form a central wire electrode-receiving bore for a wire electrode energized by the contact tip.

[0008] According to another aspect of the present invention, a welding torch is provided. The welding torch includes a contact tip and a wire electrode guide mounted below the contact tip to receive a wire electrode energized by the contact tip. A gap exists between the contact tip and the wire electrode guide, exposing the energized wire electrode to ambient air. The wire electrode guide includes a metallic outer sheath and a plurality of ceramic ring-shaped electrical insulators stacked axially within the metallic outer sheath to form a central wire electrode-receiving bore through the plurality of ceramic ring-shaped electrical insulators. The plurality of ceramic ring-shaped electrical insulators electrically insulate the wire electrode from the metallic outer sheath.

[0009] These and other aspects of the present invention will become apparent to those skilled in the art to which the present invention pertains upon reading the following description and upon reference to the accompanying drawings. [Brief explanation of the drawings]

[0010] [Figure 1] 1 illustrates a schematic representation of a submerged arc welding system. [Figure 2] 1 shows a torch for long stick-out submerged arc welding. [Figure 3A] 1 shows a portion of a torch for long stick-out submerged arc welding. [Figure 3B] 1 shows a torch for long stick-out submerged arc welding. [Figure 4]1 shows a schematic diagram of a wire electrode guide for long stick-out submerged arc welding. [Figure 5] 1 shows a wire electrode guide for long stick-out submerged arc welding. [Figure 6] 1 shows a schematic diagram of a wire electrode guide for long stick-out submerged arc welding. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention relates to a torch for submerged arc welding (SAW). The present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It should be appreciated that the various figures are not necessarily drawn to scale from one figure to another, or within a given figure, and in particular, the sizes of components are arbitrarily drawn to facilitate understanding of the figures. In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the invention. However, it may be apparent that the invention can be practiced without these specific details. Furthermore, other embodiments of the invention are possible, and the invention can be practiced and carried out in ways other than as described. The terms and expressions used in describing the invention are used to facilitate understanding of the invention and should not be taken as limiting.

[0012] As used herein, "at least one," "one or more," and "and / or" are open-ended expressions that are both conjunctive and disjunctive in operation. For example, the expressions "at least one of A, B, and C," "at least one of A, B, or C," "one or more of A, B, and C," "one or more of A, B, or C," and "A, B, and / or C" mean A only, B only, C only, A and B together, A and C together, B and C together, or A, B, and C together. Any disjunctive word or phrase expressing two or more alternative terms, whether in the description of the embodiments, claims, or drawings, should be understood to mean that one of the terms, either of the terms, or both of the terms may be included. For example, the phrase "A or B" should be understood to include the possibilities of "A" or "B," or "A and B."

[0013] Although embodiments of the invention described herein are discussed in connection with submerged arc welding (SAW) systems, other embodiments of the invention are not so limited. For example, embodiments can be utilized in gas metal arc welding (GMAW), flux-cored arc welding (FCAW), metal-cored arc welding (MCAW), and other similar types of welding operations. Furthermore, embodiments of the invention can be used in manual, semi-automated, and robotic welding operations. Embodiments of the invention can also be used in metal deposition operations similar to welding, such as additive manufacturing, hardfacing, and cladding. As used herein, the term "welding" is intended to include all of these techniques, as all involve material deposition to join or strengthen workpieces. Therefore, for efficiency, the term "welding" is used hereinafter in the description of exemplary embodiments, but is intended to include all of these material deposition operations, whether or not they join multiple workpieces.

[0014] The submerged arc welding process (SAW) differs from other flux processes in that it uses two consumables, wire and flux, which may be supplied separately. FIG. 1 shows a schematic of the submerged arc welding process. Heat for the submerged arc welding process comes from an arc between a bare metal wire welding electrode 100 and a workpiece 102. The arc is protected by a blanket of granular fusible material, called flux 104, which is placed over the joint area in front of the arc. Filler metal is primarily obtained from the electrode wire 100, which is continuously fed through the blanket of flux 104 into the arc and into the pool of molten flux. Additional filler may be obtained by adding cold wire to the granular flux in the weld pool or from metal powder contained in the flux.

[0015] A distinguishing feature of SAW is the flux 104, which coats the weld area and prevents arc radiation, sparks, spatter, and fumes from escaping. The flux 104 enables high deposition rates and high-quality weld deposit characteristics. In addition to shielding the arc from view, the flux 104 protects the weld metal 108 as it cools, deoxidizes and refines the weld metal, and provides slag 106 that insulates the weld to reduce the cooling rate and aid in shaping the weld profile.

[0016] During welding, the heat of the arc melts a portion of the flux 104 along with the tip of the electrode 100, as shown in FIG. 1 . The tip of the electrode 100 and the weld zone are always surrounded and shielded by molten flux, which is covered by a layer of unmelted flux. The electrode 100 is held a short distance above the workpiece 102, with an arc between the electrode and the workpiece. As the electrode 100 advances along the joint, the lighter molten flux emerges above the molten metal 110 in the form of slag 106. The weld metal 108, which has a higher melting point (freezing point), solidifies while the slag 106 above it remains molten. The slag 106 then solidifies on the newly solidified weld metal 108, protecting the metal from contamination while it is very hot and will react with atmospheric oxygen and nitrogen. After cooling and removing any unmelted flux for reuse, the solidified slag 106 can be easily removed from the weld.

[0017] High currents can be used in submerged arc welding, and extremely high heat can be generated. Because current is applied to the electrode 100 a short distance above its tip, relatively high amperages can be used on small-diameter electrodes. This results in extremely high current densities on the electrode's relatively small cross-section (e.g., 6 to 10 times the current density carried on a stick electrode). Because of the high current density, the melting rate is much greater for a given electrode diameter than with stick electrode welding. The melting rate is affected by the electrode material, flux, current type, polarity, and the length of the wire beyond the point of electrical contact in the welding gun or torch head.

[0018] FIG. 1 schematically illustrates an exemplary welding power supply 112 for supplying electrical energy to a wire electrode 100 to generate a welding arc. Electrical energy is conducted to the wire electrode 100 via a welding torch 114 having a contact tip electrically connected to the electrode. Submerged arc welding may be performed with DC or AC power. DC current provides better control of bead shape, penetration, and welding speed, and arc initiation is thereby easier. Bead shape is typically best with a DC electrode positive (reverse polarity), which also provides maximum penetration. The highest deposition rate and minimum penetration are obtained with a DC electrode negative. AC can minimize arc blow and provide penetration between DCEP and DCEN.

[0019] The insulating blanket of flux 104 above the arc prevents heat from quickly escaping and concentrates it within the weld zone. Not only are the electrode 100 and base metal 102 melted quickly, but the melt is deep into the base metal. Deep penetration allows for the use of a small weld groove, thereby minimizing the amount of filler metal per leg of the joint and allowing for fast welding speeds. Fast welding, in turn, minimizes the total heat input to the assembly, thereby minimizing thermal distortion problems. Even relatively thick joints can be welded in a single pass with submerged arc welding.

[0020] Welds 108 made under a protective layer of flux 104 have good ductility and impact resistance, as well as uniformity in bead appearance. Mechanical properties at least equal to those of the base metal 102 are consistently obtained. In single-pass welds, the molten base material 102 is large compared to the amount of filler metal used. Thus, in such welds, the base metal can significantly affect the chemical and mechanical properties of the weld 108. For this reason, it is sometimes not necessary to use an electrode 100 of the same composition as (or superior to) the base metal 102 to weld many low-alloy steels. However, the chemical composition and properties of multi-pass welds are less influenced by the base metal and depend to a greater extent on the composition of the electrode 100, the activity of the flux 104, and the welding conditions.

[0021] Through adjustments of current, voltage, and torch travel speed, the operator has precise control over penetration to provide any depth ranging from deep and narrow with high crown reinforcement to wide, nearly flat beads with shallow penetration. A bead with deep penetration may contain as much as 70% molten base metal, while a shallow bead may contain as little as 10% base metal. In some cases, the deep penetration characteristics of the submerged arc can be used to eliminate or reduce the cost of bevel preparation.

[0022] The flux 104 serves several functions in submerged arc welding. These include covering the molten weld metal 110 to protect it from the atmosphere and acting as a slag 106 that purifies the molten deposit by removing oxides and other non-metallic inclusions. Metal additions to the flux can add to the alloy content of the weld metal deposit 108 and can deoxidize it.

[0023] With the proper selection of equipment, submerged arc welding is widely applicable to industrial welding requirements. It can be used with all types of joints and is capable of welding a full range of carbon and low-alloy steels, from 16-gauge sheet to the thickest plate. It is also applicable to some high-alloy, heat-treated, and stainless steels and is the preferred process for rebuilding and hardfacing. Any degree of mechanization can be used, from handheld, semi-automatic guns to boom- or truck-transported and stationary multiple weld heads.

[0024] Submerged arc welding's high quality, high deposition rate, deep penetration, process suitability for full mechanization, and pleasant characteristics (no glare, sparks, spatter, smoke, or excessive heat radiation) make it the preferred process in steel fabrication. It is used extensively in ship and barge construction, railcar manufacturing, pipe fabrication, and the fabrication of structural beams, girders, and columns where long welds are required. Automated submerged arc equipment is also a major feature in the welding areas of plants that produce mass-produced assemblies joined by repetitive short welds.

[0025] Other factors besides deposition rate contribute to lower welding costs. Continuous electrode feed from coils ranging in weight from 60 to over 2,000 pounds contributes to high utilization rates. Expenses are reduced when the deep penetration nature of the process allows for the elimination or reduction of joint preparation. Cleaning costs are minimized due to the removal of spatter with protective fluxes after the weld is performed.

[0026] When submerged arc welding is done properly, the weld bead is smooth and uniform, so polishing or machining is rarely required. The rapid heat input of the process minimizes distortion, reducing the cost of straightening the completed assembly, especially if a carefully planned welding sequence is followed. Submerged arc welding actually often allows for pre-machining of parts, further increasing the reduction in manufacturing costs.

[0027] Because of these and other advantages provided by SAW, there is a desire and demand to further improve various aspects of SAW, including even higher productivity and weld quality. For example, because one of the technical advantages of SAW is derived from preheating the consumable electrode, there is a desire and demand to further improve the preheating configuration through improved electrode assembly or torch designs.

[0028] FIG. 2 shows a torch or electrode assembly 200 that defines electric stick-out. Electric stick-out, or electric electrode extension, refers to the distance Y between the tip of the contact tip 202 and the end of the wire welding electrode 100. The stick-out portion of the wire welding electrode 100 is preheated by Joule heating due to the welding current flowing through the wire and its electrical resistance. If the electrode extension is not long enough, the electrode wire will not be sufficiently preheated. On the other hand, increasing the length of the electric stick-out increases the electrical resistance of the circuit, which in turn increases heating and therefore the temperature of the electrode tip, resulting in increased melting and deposition rates. The stick-out length controls the size of the weld bead because the length of the filler wire extension affects the burn-out rate. Furthermore, the electrode extension affects penetration through its effect on the welding current. As the extension length increases, wire preheating increases and the current decreases. The decrease in current reduces the amount of penetration into the workpiece.

[0029] The stick-out distance typically varies from 1 / 8 to 1 / 2 inch for conventional welding processes and from 3 / 4 to 1.5 inches for submerged arc welding (SAW). To further improve SAW technology, long stick-out (LSO) or extended stick-out (ESO) techniques may be employed. Long stick-out SAW refers to a SAW process in which the length of the wire protruding from the electrode contact tip ("stick-out length"), or contact-to-workpiece distance (CTWD), is increased compared to conventional SAW processes, e.g., by approximately 25 mm. A longer stick-out length allows a longer length of the electrode to be preheated before melting at the electrode tip. Preheating results in increased melting rates because it is easier to melt a preheated electrode wire for a given current density. The LSO-SAW process can significantly improve productivity and increase the deposition rate of submerged arc welding by up to 100% compared to conventional SAW processes. The LSO-SAW process can reduce or eliminate arc-striking problems by enabling perfect matching of arc starting characteristics. LSO-SAW can also provide improved control over the energy input into the weld, lower heat input (less distortion), and reduced flux / wire ratio. Another benefit of LSO-SAW is that higher deposition and productivity can be achieved with less heat input.

[0030] As mentioned above, increased stick-out length can provide several benefits, such as higher deposition rates without increased energy consumption. However, for stick-out lengths greater than, for example, 25 mm, various problems can arise. For example, the heated wire may become out of alignment and wander within the weld groove as the stick-out distance increases. This can be problematic, particularly when welding deep and narrow grooves, which can be used to minimize the time and cost of joining thick workpiece sections, because the LSO welding electrode assembly may be too bulky to reach the bottom of the groove. To address this and other challenges, in addition to the contact tip 202, the SAW welding torch 200 can employ an extension that acts as a wire electrode guide 204 (see FIG. 2). The extension or wire electrode guide 204 provides, among other things, electrical and thermal insulation and mechanical rigidity for the heated wire electrode 100. FIG. 2 shows an exemplary electrode assembly configured for long stick-out submerged arc welding, including the wire electrode guide 204 or extension. As shown, the wire electrode guide 204 extends distally of the contact tip 202. The wire electrode guide 204 is positioned between the contact tip and a workpiece (not shown). In some embodiments, as can be seen in FIG. 2 , there is an air gap between the contact tip 202 and the wire electrode guide 204. The air gap exposes the wire electrode 100, which extends through the contact tip 202 and the wire electrode guide 204, to ambient air. In other embodiments, the contact tip 202 and the wire electrode guide 204 can be directly adjacent to one another without an air gap existing between them, so that the wire electrode 100 is not exposed to ambient air.

[0031] Conventional electrode assemblies may not be suitable for some applications, for example, filling narrow, deep grooves, such as triangular or U-shaped grooves having depths greater than 4 inches and apex angles of 16 degrees or less. Among other shortcomings, the inventors have discovered that existing designs of electrode assemblies may be deficient with respect to one or more of optimized vertical and lateral dimensions, thermal and electrical insulation, arc instability caused by magnetic materials, and compact flux delivery. Various embodiments of electrode assemblies for submerged arc welding described herein address these and other needs.

[0032] Disclosed herein are improved electrode assemblies for LSO-SAW welding and methods of using the same. The inventors have discovered that further significant improvements in LSO-SAW welding can be realized by optimizing various aspects of the electrically insulated extended stick-out portion of the electrode. Figures 2-4 illustrate a portion of a SAW torch configured for long stick-out submerged arc welding, according to various embodiments. Figure 4 illustrates a wire electrode guide 204 for the torch 200. The electrode assembly, according to various embodiments, includes a contact tip portion 202 and a serially arranged extended portion or wire electrode guide 204 configured to feed a consumable electrode therethrough. In the illustrated example, the serially arranged contact tip 202 and guide 204 are physically separated, exposing the consumable electrode 100 therebetween. In other configurations, the contact tip 202 and guide 204 may be in contact with each other. During welding, the contact tip 202 is positioned upstream of the arcing tip of the consumable electrode 100, and the wire electrode guide 204 is positioned adjacent to the arcing tip of the electrode. The contact tip 202 electrically contacts and provides power to the consumable electrode 100. The consumable electrode 100 is fed through and exits the contact tip 202. The consumable electrode 100 then feeds through a wire electrode guide 204. The guide 204 is configured to electrically insulate the consumable electrode 100 from the workpiece (e.g., from the sidewall of the workpiece) via an insulating material, e.g., a ceramic material, surrounding the consumable electrode. Insulating materials are discussed further below with reference to FIG. 4. The consumable welding electrode 100 is preheated within the insulated extension or wire electrode guide 204 by Joule heating before melting at the arcing tip of the consumable electrode. The extent of preheating is a function of the distance / resistance between the welding circuit contact point with the wire electrode 100 at the contact tip 202 and the wire's arcing point with the workpiece. The wire electrode guide 204 provides physical support and protection for the preheated wire and ensures proper placement of the deposited metal during SAW.

[0033] In various embodiments, the guide 204 is configured to electrically insulate the consumable electrode from the workpieces and has a shape, length, and lateral dimensions that allow the guide to be inserted into a narrow groove between workpieces. The insulating material surrounding the consumable electrode 100 within the guide 204 allows for a significant reduction in the lateral dimensions. As a result, the guide 204 is configured not to contact the sidewalls of a narrow groove, such as a triangular or U-shaped trench, having a depth greater than 4 inches, 5 inches, 6 inches, 7 inches, or a value within a range defined by any of these values, and having an apex angle less than 16 degrees, 12 degrees, 10 degrees, 8 degrees, 6 degrees, or a value within a range defined by any of these values, while the tip of the consumable electrode 100 contacts the apex. It will be appreciated that the shallower the groove, the narrower the apex angle. For example, the relationship may follow an exemplary dependency, such as, but not limited to, that shown in Table 1. It will be appreciated that the groove or trench need not have a triangular shape in cross section. Alternatively, some grooves may have, for example, a rectangular or tapered rectangular shape. In these geometries, the "apex" angle or acceptance angle can be defined by the arctangent of the width over the depth of the trench.

[0034] [Table 1]

[0035] In various embodiments, the wire electrode guide 204 is configured to electrically insulate the consumable electrode 100 from the workpiece during welding while having an outer surface formed from a substantially non-magnetic material that surrounds the consumable electrode. The outer envelope or outer sheath of the guide 204 can be metallic, for example, formed from non-magnetic steel, e.g., stainless steel, or another non-magnetic metal. The inventors have discovered that the non-magnetic envelope advantageously improves the magnetic field around the electrode, reducing the resulting arc instability and weld defects. The non-magnetic envelope also similarly reduces any instability in welding parameters that may be caused by magnetization of the guide 204 over time.

[0036] In various embodiments, the wire electrode guide 204 is configured to electrically insulate the consumable electrode 100 from the workpiece and has a shape, length, and lateral dimensions such that during welding, the contact-to-workpiece distance (CTWD) is greater than 25 mm, 100 mm, 125 mm, 150 mm, 175 mm, or a length within a range defined by any of these values, e.g., 150-160 mm. The longer CTWD, when compared to conventional SAW welding processes, significantly improves the deposition rate for a given current density due to the longer Joule heated region provided by the extension.

[0037] 3A and 3B, a flux delivery or dispensing nozzle 206 can be attached to a bracket for the wire electrode guide 204. The flux delivery nozzle 206 is positioned adjacent to the wire electrode guide 204 and dispenses flux that covers the weld during SAW. Advantageously, the flux delivery nozzle 206 can have a narrow cross-section similar to the diameter of the guide 204, allowing both to be inserted into a narrow groove during welding.

[0038] According to various embodiments, an LSO-SAW electrode assembly with an insulated extension is configured to achieve significantly higher deposition rates when compared to a conventional SAW electrode assembly for the same current. Exemplary experimental deposition rates that can be achieved for one exemplary configuration with a CTWD of 5 inches and an electrode diameter of 5 / 32 inches are as follows: The deposition rate per current can exceed 0.05 lbs / hr / A, 0.06 lbs / hr / A, 0.07 lbs / hr / A, 0.08 lbs / hr / A, or values ​​within a range defined by any of these values ​​during welding. Deposition rates of greater than 35 lbs / hr can be achieved at approximately 900 A, 850 A, 800 A, 750 A, less than 700 A, or within a range defined by any of these values, e.g., between about 700 A and 750 A. Similar deposition rates are expected to be achieved only at currents greater than about 900 A using a conventional SAW electrode assembly. Advantageously, the improvement in deposition rate over conventional SAW electrodes is due to the Joule heating (I 2 At higher currents, R increases because R varies as the square of the current, i.e., the relative improvement in deposition rate is expected to increase with increasing current.

[0039] As a result of the longer CTWD, a higher fraction of the voltage between the contact tip and the workpiece drops across the LSO wire electrode. LSO wire electrodes according to embodiments are configured to drop by at least 5%, 10%, 15%, 20%, or a value within a range defined by any of these values, of the total voltage drop across the contact-to-workpiece distance (CTWD). The remaining voltage drop occurs across the arc. Electrode assemblies according to embodiments are configured to drop by a fraction of the total voltage drop greater than 1 / 30, 1 / 15, 1 / 10, 1 / 7, 1 / 5, or a value within a range defined by any of these values, across the contact-to-workpiece distance (CTWD). For example, with an exemplary total voltage drop of 30 V, approximately 4 V drops across the LSO wire electrode, while the remainder (approximately 26 V) drops across the arc length. In contrast, for a conventional SAW electrode assembly, with the same total voltage drop of 30 V, only approximately 1 V drops across the electrode, while the remainder (approximately 29 V) drops across the arc length. As a result, the longer length of the welding electrode heats to a higher temperature, which increases the deposition rate, compared to conventional SAW electrode configurations.

[0040] An additional benefit provided by electrode assemblies according to embodiments is a reduced flux-to-wire consumption ratio. Electrode assemblies according to embodiments are configured to heat a consumable wire electrode within the extension to a temperature within a range defined by 600°C, 700°C, 800°C, 900°C, or any of these values.

[0041] 4 shows an exemplary embodiment of a wire electrode guide 204. The wire electrode guide 204 has an outer sheath 208. In some embodiments, the outer sheath 208 is metallic, for example, made from stainless steel or another metal. The outer sheath 208 can be made from a non-magnetic material, such as a non-magnetic metal. In other embodiments, the outer sheath 208 can be non-metallic, for example, made from a high-temperature polymer.

[0042] Within the metallic outer sheath 208 are a plurality of electrical insulators 210 axially stacked within the metallic outer sheath. Each of the electrical insulators 210 has a central opening 212 for receiving the wire electrode 100. The stack of electrical insulators 210, and in particular their axially aligned central openings 212, form a central wire electrode receiving bore through the insulating material for the wire electrode 100. The energized wire electrode 100 (energized by the contact tip of the torch) is fed through the central wire electrode receiving bore formed by the stack of electrical insulators 210. The electrical insulators 210 electrically insulate the energized wire electrode 100 from the outer sheath 208 and the adjacent workpiece to prevent short circuits. When the wire electrode guide 204 contacts the workpiece, the insulators 210 prevent the wire electrode 100 from unintentionally shorting out with the workpiece.

[0043] The inner periphery or inner surface of the metallic outer sheath 208 and the outer periphery of the electrical insulators 210 can closely match (e.g., both can have another shape, such as a cylindrical shape or a polygonal shape). In the exemplary embodiment shown in FIG. 4, the plurality of electrical insulators 210 are ring-shaped or have an annular shape. The top or proximal portion of the sheath 208 can be generally cylindrical. The bottom or distal portion of the sheath 208 can be tapered to retain the insulators 210 within the sheath. However, various methods of retaining the insulators within the sheath will be apparent to those skilled in the art.

[0044] The wire electrode guide 204 may include a removable cap 214 (e.g., a threaded cap) that provides access to the insulators 210. During use, one or more of the insulators 210 may be damaged (e.g., cracked or shattered). For example, the wire electrode guide 204 may be inserted into a weld groove between workpieces and may unintentionally strike a workpiece during weld setup or actual welding. Because the electrical insulators 210 may be fragile, a collision with a workpiece may damage one or more of the electrical insulators 210. The removable cap 214 allows the wire electrode guide 204 to be repaired and the insulators 210 to be replaced as needed. In some embodiments, the inner circumference of the sheath 208 and the outer circumference of the insulators 210 may closely match to allow for minimal radial movement of the insulators within the sheath. To allow for relative radial movement between adjacent insulators within the sheath, a gap may be provided between the outer circumference of each insulator 210 and the inner wall of the sheath 208. Such clearances may allow axially adjacent insulators 210 to slightly slide radially over one another within the sheath 208 while maintaining a central wire electrode-receiving bore (e.g., during impact of the wire electrode guide 204 with a workpiece). In certain embodiments, the top and / or bottom surfaces of the insulators 210 may have protrusions or projections that provide a small space or gap between adjacent insulators (e.g., adjacent insulators are slightly spaced apart from one another). The stack of electrical insulators 210 provides some flexibility to the wire electrode guide 204. When the guide 204 impacts a workpiece, the insulators 210 may move within the metallic sheath 208 and not crack. However, if one or more insulators 210 crack, they can be easily replaced. Compared to a single, integral ceramic sleeve, the stack of insulators 210 provides a more durable and less expensive insulated wire guide.

[0045] The insulator 210 can have the shape of a washer or O-ring with a short height and a relatively wide diameter, or can be donut-shaped with a greater height compared to a washer or O-ring. The insulator 210 can be made from a ceramic material or other suitable insulating material. For example, the insulator 210 can be formed from a material selected from the group consisting of silicon nitride, magnesia-stabilized zirconia, yttria-stabilized zirconia, silicon carbide, magnesium oxide, alumina, or zirconia-toughened alumina. Ceramic insulators can be manufactured using a variety of methods, such as powder pressing, cold isostatic pressing, hot pressing, injection molding, and slip casting.

[0046] FIG. 5 shows the wire electrode guide 204 attached to the SAW torch at the proximal end of the guide. Various attachment mechanisms can be used to attach the wire electrode guide 204 to the torch, such as a threaded connection of the guide. In some embodiments, the wire electrode guide 204 or torch can include a magnet 216 that attaches the wire electrode guide to the welding torch. The magnet 216 can act as a crush box that allows the guide 204 to easily separate from the torch if the guide impacts the workpiece without damaging the ceramic insulator. As will be appreciated by those skilled in the art, other forms of quick separation can be provided between the guide 204 and the torch to allow the guide to easily separate from the torch if the guide impacts the workpiece without damaging the ceramic insulator.

[0047] The wire electrode guide 204 may include a sensor 218 for detecting contact or impending contact between the guide and the workpiece. Examples of such sensors include a touch sensor, an accelerometer, a vibration sensor, etc. The touch sensor may provide a signal to the torch motion controller to inform the torch motion controller that the torch has contacted or is about to contact the workpiece. The touch sensor may be particularly useful during weld setup to define the limits of the weld path or groove. An accelerometer or vibration sensor may be used to detect torch vibration due to broken insulators 210 in the guide 204. The sensor 218 may provide a signal to a welding power supply or another device in the SAW system to sound an alarm or alert an operator to inspect and / or repair the guide 204. Alternatively or additionally, the insulators 210 may include isolated, electrically conductive circuits built into each separate insulator. Breaking the circuit indicates that the insulator is damaged, and the welding power supply or another device in the SAW system may notify the operator which specific insulator needs replacement. The torch or wire electrode guide 204 may further include stuck-wire detection to notify the torch motion controller and / or welding power supply that the wire electrode has stuck to the weld metal so that remedial action can be taken to free the stuck wire.

[0048] Figure 6 shows a quick disconnect that can be used to attach the wire electrode guide 204 to a torch. One exemplary quick disconnect is a captive ball quick disconnect, similar to those used on pneumatic systems. In Figure 6, a female quick disconnect 220 can be attached to the torch, allowing the guide 204 to be easily removed therefrom.

[0049] Submerged arc welding systems typically do not utilize shielding gas. However, the systems discussed above (see, for example, FIG. 1) may include shielding gas if desired. Shielding gas may be used to control the amount of oxygen in the weld metal and prevent oxidation of the heated LSO wire electrode. Shielding gas may be discharged from the torch upstream of the wire electrode guide and above or proximate the gap between the contact tip and the wire electrode guide.

[0050] It will be apparent that this disclosure is for illustrative purposes and that various changes may be made by adding, modifying, or removing details without departing from the fair scope of the teachings contained in this disclosure. Accordingly, the invention is not limited to the particular details of this disclosure except as the following claims necessarily so limiting.

Claims

1. A contact tip; a wire electrode guide extending distally of the contact tip; A welding torch comprising: a metal outer sheath; a plurality of ring-shaped electrical insulators axially stacked within the metallic outer sheath to define a central wire electrode receiving bore through the plurality of ring-shaped electrical insulators; Equipped with Welding torch.

2. The welding torch of claim 1 , wherein a gap exists between the contact tip and the wire electrode guide, exposing the wire electrode extending through the contact tip and the wire electrode guide to ambient air.

3. The welding torch of claim 1 , wherein the ring-shaped electrical insulator is formed from a ceramic material.

4. The welding torch of claim 1 , further comprising a flux delivery nozzle positioned adjacent the wire electrode guide.

5. The welding torch of claim 1 , wherein the ring-shaped electrical insulator electrically insulates the wire electrode extending through the contact tip and the wire electrode guide from the metallic outer sheath.

6. The welding torch of claim 1 , wherein the metallic outer sheath comprises stainless steel.

7. 2. The welding torch of claim 1, wherein a gap between an outer periphery of each of the ring-shaped electrical insulators and an inner wall of the metallic outer sheath allows relative radial movement between adjacent ring-shaped electrical insulators within the metallic outer sheath.

8. The welding torch of claim 1 , further comprising a captive ball quick disconnect that attaches the wire electrode guide to the welding torch.

9. The welding torch of claim 1 , further comprising a magnet attaching the wire electrode guide to the welding torch.

10. The welding torch of claim 1 , further comprising a touch sensor configured to determine contact between the metallic outer sheath and a workpiece.

11. A contact tip; a wire electrode guide extending distally of the contact tip; A welding torch comprising: a metal outer sheath; a plurality of ceramic electrical insulators axially stacked within said metallic outer sheath; each ceramic electrical insulator having a central opening such that the plurality of ceramic electrical insulators axially stacked within the metallic outer sheath form a central wire electrode receiving bore for a wire electrode energized by the contact tip; Welding torch.

12. The welding torch of claim 11 , wherein each ceramic electrical insulator has a torus shape.

13. 13. The welding torch of claim 12, wherein a gap between an outer periphery of each of the ceramic electrical insulators and an inner wall of the metallic outer sheath allows relative radial movement between adjacent ceramic electrical insulators within the metallic outer sheath.

14. 12. The welding torch of claim 11, wherein a gap exists between the contact tip and the wire electrode guide, exposing the wire electrode extending through the contact tip and the wire electrode guide to ambient air.

15. The welding torch of claim 11 , further comprising a flux delivery nozzle positioned adjacent the wire electrode guide.

16. 12. The welding torch of claim 11, wherein the ceramic electrical insulator electrically insulates the wire electrode from the metallic outer sheath and extending through the contact tip and the wire electrode guide.

17. The welding torch of claim 11 , wherein the metallic outer sheath comprises stainless steel.

18. 12. The welding torch of claim 11, further comprising a captive ball quick disconnect that attaches the wire electrode guide to the welding torch.

19. The welding torch of claim 11 further comprising a magnet attaching the wire electrode guide to the welding torch.

20. The welding torch of claim 11 , further comprising a touch sensor configured to determine contact between the metallic outer sheath and a workpiece.

21. A contact tip; a wire electrode guide mounted below the contact tip for receiving a wire electrode energized by the contact tip; A welding torch comprising: a gap between the contact tip and the wire electrode guide that exposes the energized wire electrode to ambient air; and the wire electrode guide comprising: a metal outer sheath; a plurality of ceramic ring-shaped electrical insulators axially stacked within the metallic outer sheath to define a central wire electrode receiving bore through the plurality of ceramic ring-shaped electrical insulators; wherein the plurality of ceramic ring-shaped electrical insulators electrically insulate the wire electrode from the metallic outer sheath. Welding torch.

22. 22. The welding torch of claim 21, further comprising a flux delivery nozzle positioned adjacent the wire electrode guide.

23. 22. The welding torch of claim 21, further comprising a captive ball quick disconnect that attaches the wire electrode guide to the welding torch.

24. 22. The welding torch of claim 21, further comprising a magnet attaching the wire electrode guide to the welding torch.

25. 22. The welding torch of claim 21, further comprising a touch sensor configured to determine contact between the metallic outer sheath and a workpiece.

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