Welding torch with wire electrode guide

Abstract

A welding torch includes a contact tip and a wire electrode guide extending distally of the contact tip. The wire electrode guide includes a metal outer sheath and a plurality of annular electrical insulators axially stacked within the metal outer sheath so as to form a central wire electrode receiving aperture through the plurality of annular electrical insulators.

Description

Background of the Invention Field of the Invention

[0002] The present invention relates to arc welding, and more particularly to a torch for submerged arc welding (SAW).

[0003] Description of the Related Art

[0004] Various welding techniques utilize a welding wire that serves as a metal source. For example, in shielded metal arc welding, an arc is generated when a voltage is applied between a consumable welding wire electrode (serving as one electrode advancing towards the workpiece) and the workpiece (serving as the other electrode). The arc melts the tip of the metal welding wire, thereby producing droplets of molten metal welding wire that are deposited onto the workpiece to form a weld bead or a weld pass.

[0005] Submerged arc welding is a type of welding in which the arc between the welding wire electrode and the workpiece is completely submerged in a layer of granular fusible flux. The flux protects the molten weld pool from atmospheric contamination. Like other types of welding systems, a submerged arc welding system may include a welding power source, a wire feeding control and drive assembly, and a torch. In addition, a submerged arc welding system also includes a flux system. The flux system holds the flux during welding and delivers the flux to the weld joint. Submerged arc welding can provide a highly economical solution for some applications. The high deposition rate obtained by SAW is the main reason for the economic benefits of this process.

[0006] Since the current flowing through the wire dry extension heats the distal portion of the wire, the deposition rate of SAW can be increased by utilizing a long wire dry extension (LSO) or an extended wire dry extension (ESO) of the wire. However, the heated LSO wire is prone to misalignment and deviation in the weld groove, especially in deep and narrow grooves between thick workpieces. It is desirable to perform LSO SAW in deep and / or groove welds while maintaining proper alignment of the heated wire electrode along the welding path within the groove. Summary of the Invention

[0008] The following summary presents a simplified overview to provide a basic understanding of some aspects of the devices, systems, and / or methods discussed herein. This summary is not an extensive review of the devices, systems, and / or methods discussed herein. It is not intended to identify key elements or to delineate the scope of such devices, systems, and / or methods. The sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description presented later.

[0009] According to one aspect of the present invention, there is provided a torch. The torch includes a contact tip and a wire electrode guide extending distally from the contact tip. The wire electrode guide includes a metal outer sheath and a plurality of annular electrical insulators axially stacked within the metal outer sheath so as to form a central wire electrode receiving hole through the plurality of annular electrical insulators.

[0010] According to another aspect of the present invention, there is provided a welding torch. The welding torch includes a contact tip and a wire electrode guide extending distally from the contact tip. The wire electrode guide includes a metal outer sheath and a plurality of ceramic electrical insulators axially stacked within the metal outer sheath. Each ceramic electrical insulator has a central opening such that the plurality of ceramic electrical insulators axially stacked within the metal outer sheath form a central wire electrode receiving hole for a wire electrode energized by the contact tip.

[0011] According to another aspect of the present invention, there is provided a welding torch. 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. There is an air gap between the contact tip and the wire electrode guide that exposes the energized wire electrode to ambient air. The wire electrode guide includes a metal outer sheath and a plurality of ceramic annular electrical insulators axially stacked within the metal outer sheath so as to form a central wire electrode receiving hole through the plurality of ceramic annular electrical insulators. The plurality of ceramic annular electrical insulators electrically insulate the wire electrode from the metal outer sheath. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] After reading the following description with reference to the accompanying drawings, those skilled in the art in the field to which the present invention pertains will understand the above and other aspects of the present invention, in which:

[0013] Figure 1 A submerged arc welding system is schematically shown;

[0014] Figure 2 A welding torch for long stick-out submerged arc welding is shown;

[0015] Figure 3A A portion of a welding torch for long stick-out submerged arc welding is shown;

[0016] Figure 3B A welding torch for long stick-out submerged arc welding is shown;

[0017] Figure 4 A wire electrode guide for long stick-out submerged arc welding is schematically shown;

[0018] Figure 5 A wire electrode guide for long stick-out submerged arc welding is shown; and

[0019] Figure 6 A wire electrode guide for long stick-out submerged arc welding is schematically shown. DETAILED DESCRIPTION

[0020] The present invention relates to a torch for submerged arc welding (SAW). The present invention will now be described with reference to the accompanying drawings, in which like reference numerals are used throughout to refer to like elements. It will be understood that these different drawings need not be drawn to scale with respect to one another, nor within a given drawing, and in particular, the dimensions of the components are arbitrarily drawn for ease of understanding the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it may be apparent that the present invention may be practiced without these specific details. Further, other embodiments of the present invention are possible and the present invention can be practiced and implemented in ways other than as described. The terms and phrases used in describing the present invention are employed for the purpose of facilitating an understanding of the present invention and should not be considered limiting.

[0021] 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, each of 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" refers to A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together. Any disjunctive word or phrase giving two or more alternative terms, whether in the description of embodiments, claims, or drawings, shall be understood to cover the possibilities of including one of these terms, any one of these terms, or all of these terms. For example, the phrase "A or B" shall be understood to cover the possibilities of "A", or "B", or "A and B".

[0022] Although the embodiments of the present invention described herein are discussed in the context of a submerged arc welding (SAW) system, other embodiments of the present invention are not limited thereto. For example, the embodiments can be used in gas metal arc welding (GMAW), flux cored arc welding (FCAW), metal cored arc welding (MCAW), and other similar types of welding operations. Further, the embodiments of the present invention can be used in manual, semi-automatic, and robotic welding operations. The embodiments of the present invention can also be used in metal deposition operations similar to welding, such as additive manufacturing, wear-resistant surfacing, and plating. As used herein, the term "welding" is intended to cover all of these techniques, as all of these techniques involve material deposition for joining or building workpieces. Thus, for efficiency, the term "welding" is used hereinafter to describe exemplary embodiments, but is intended to include all of these material deposition operations, whether or not multiple workpieces are joined together.

[0023] The submerged arc welding process (SAW) uses two consumables (the welding wire and the flux, which can be supplied separately), which is different from other processes that use flux. Figure 1 Figure 1 schematically shows the submerged arc welding process. The heat for the submerged arc welding process is derived from the arc between the bare metal welding wire electrode 100 and the workpiece 102. The arc is shielded by a covering layer of granular fusible material called the flux 104 placed on the joint area in front of the arc. The filler metal is mainly obtained from the electrode wire 100, which is continuously fed through the covering layer of the flux 104 into the arc and the molten flux pool. Additional filler can be obtained by adding cold wire to the granular flux in the weld pool or from the metal powder contained in the flux.

[0024] A significant feature of SAW is the flux 104, which covers the welding area and prevents the escape of arc radiation, sparks, spatter, and fumes. The flux 104 allows for high deposition rates and high-quality welding deposition characteristics. In addition to shielding the arc from view, the flux 104 also provides a slag 106 that protects the weld metal 108 when it cools, deoxidizes and refines the weld metal, insulates the weld to reduce the cooling rate, and helps to shape the weld profile.

[0025] During welding, the heat of the arc melts some of the flux 104 along with the tip of the electrode 100, as Figure 1 shown. The tip of the electrode 100 and the welding area are always surrounded and shielded by molten flux, which is covered by a layer of unmelted flux. The electrode 100 is held at a short distance above the workpiece 102, where the arc is between the electrode and the workpiece. As the electrode 100 travels along the joint, the lighter molten flux rises above the molten metal 110 in the form of slag 106. The weld metal 108 with a higher melting point (freezing point) solidifies, while the slag 106 above it remains in a molten state. Then the slag 106 solidifies on the newly solidified weld metal 108, thus continuing to protect the metal from contamination while it is very hot and would 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.

[0026] High currents can be used in submerged arc welding and extremely high heat can be generated. Since the current is applied to the electrode 100 at a short distance above its tip, relatively high amperages can be used on small diameter electrodes. This results in extremely high current densities on relatively small cross-sections of the electrode (e.g., the current density is six to ten times that carried on a stick electrode). Due to the high current density, for a given electrode diameter, the melting rate is much higher than in stick electrode welding. The melting rate is affected by the electrode material, the flux, the type of current, the polarity, and the length of the wire extending beyond the electrical contact point in the welding gun or torch head.

[0027] Figure 1 An example welding power supply 112 for supplying electrical energy to a wire electrode 100 to generate a welding arc is schematically shown. The electrical energy is conducted to the wire electrode 100 via a torch 114 having a contact tip electrically connected to the electrode. Submerged arc welding can be accomplished using DC or AC power. DC electricity better controls bead shape, penetration, and welding speed, and is also easy to strike an arc with. The bead shape is generally best with DC electrode positive (reverse polarity), which also provides maximum penetration. The highest deposition rate and minimum penetration are obtained with DC electrode negative. AC electricity minimizes arc blow and can provide penetration between DCEP and DCEN.

[0028] The insulating cover layer of the flux 104 above the arc prevents rapid heat escape and concentrates it in the welding area. Not only are the electrode 100 and the base metal 102 rapidly melted, but the melting penetrates deeply into the base metal. Deep penetration allows the use of small welding grooves, thus minimizing the amount of filler metal per foot of joint and allowing a rapid welding speed. The rapid welding in turn minimizes the total heat input to the component and thus minimizes the problem of thermal distortion. Even relatively thick joints can be welded in one pass by submerged arc welding.

[0029] The weld 108 made under the protective layer of the flux 104 has good ductility, impact resistance, and uniformity of bead appearance. Mechanical properties at least equal to those of the base metal 102 are always obtained. In a single-pass weld, the amount of molten base material 102 is large compared to the amount of filler metal used. Therefore, in such welds, the base metal can greatly affect the chemistry and mechanical properties of the weld 108. For this reason, it is sometimes not necessary to use an electrode 100 of the same composition (or overmatched composition) as the base metal 102 to weld many low-alloy steels. However, the chemical composition and properties of multi-pass welds are less affected 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.

[0030] By adjusting the current, voltage, and torch travel speed, the operator can closely control the penetration to provide any depth in the range from a deep and narrow bead with a high crown reinforcement to a wide and nearly flat bead with shallow penetration. A bead with deep penetration may contain about 70% molten base metal, while a shallow bead may contain as little as 10% base metal. In some cases, the deep penetration properties of submerged arc can be used to eliminate or reduce the cost of edge preparation.

[0031] The flux 104 has multiple functions in submerged arc welding. These functions include covering the molten weld metal 110 to protect it from the atmosphere and acting as a slag 106 that refines the molten deposit by removing oxides and other non-metallic inclusions. Metallic additions to the flux can increase the alloy content of the weld metal deposit 108 and deoxidize it.

[0032] By proper selection of equipment, submerged arc welding is widely applicable to industrial welding requirements. It can be used for all types of joints and allows welding of the full range of carbon and low alloy steels from 16 gauge sheet to the thickest plates. It is also applicable to some high alloy heat-treated stainless steels and is a favorable process for rebuilding and hardfacing. Any degree of mechanization can be used, from a hand-held semi-automatic welding gun to multiple welding heads carried by booms or crawlers and held by fixtures.

[0033] The high quality, high deposition rate, deep penetration, adaptability of the process to full mechanization, and comfort characteristics (no glare, sparks, spatter, fumes, or excessive heat radiation) of submerged arc welding make it a preferred process in steel fabrication. It is widely used in ship and barge construction, railway vehicle construction, pipe fabrication, and the fabrication of structural beams, girders, and columns that require long welds. Automatic submerged arc facilities are also a key feature of the welding areas of equipment that produces batch-produced components joined by repetitive short welds.

[0034] Other factors besides the deposition rate also reduce the welding cost. Continuous electrode feed from coils weighing from 60 pounds to over 2,000 pounds contributes to a high operating factor. The cost is reduced when the deep penetration characteristics of the process allow elimination or reduction of joint preparation. After welding is completed, the cleaning cost is minimized because the protective flux eliminates spatter.

[0035] When submerged arc welding is properly performed, the weld beads are smooth and uniform, so little grinding or machining is required. Since the rapid heat input of the process minimizes distortion, the cost of straightening the finished components is reduced, especially when a carefully planned welding sequence is followed. In fact, submerged arc welding often allows pre-machining of parts, further saving on manufacturing costs.

[0036] Due to these and other advantages provided by SAW, further improvements in various aspects of SAW are desired and needed, including even higher productivity and welding quality. For example, since one of the technical advantages of SAW is derived from preheating the consumable electrode, further improvement of the preheating arrangement is desired and needed through improved electrode assemblies or torch designs.

[0037] Figure 2Disclosed is a torch or electrode assembly 200 that defines the elongation of the electrode stem. The electrode stem elongation or the live 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 stem elongation portion of the wire welding electrode 100 is preheated by Joule heating due to the welding current flowing through the wire and the resistance of the wire. If the electrode extension is insufficient, the electrode wire will not be preheated sufficiently. On the other hand, an increase in the length of the electrode stem elongation increases the resistance of the circuit, which in turn increases the heating and thus increases the temperature of the tip of the electrode, resulting in an increased melting and deposition rate. The stem elongation length thus controls the size of the weld bead because the length of the filler wire extension affects the melting rate. In addition, the electrode extension affects the penetration by its effect on the welding current. As the extension length increases, the preheating of the wire increases and the current decreases. The decrease in current in turn decreases the amount of penetration into the workpiece.

[0038] For traditional welding processes, the stem elongation distance can typically vary from 1 / 8 inch to 1 / 2 inch, and for submerged arc welding (SAW), the stem elongation distance can vary from 3 / 4 inch to 1.5 inches. To further improve SAW technology, long stem elongation (LSO) or extended stem elongation (ESO) can be employed. Long stem elongation SAW refers to a SAW process in which the length of the wire extending from the electrode contact tip ("stem elongation length") or the contact tip to workpiece distance (CTWD) is increased relative to a conventional SAW process (e.g., longer than about 25 mm). The longer stem elongation length allows for greater preheating of a greater length of the electrode before melting occurs at the electrode tip. Thus, preheating allows for an increased melting rate because for a given current density, the preheated electrode wire is more easily melted. Compared to traditional SAW processes, the LSO SAW process can significantly increase productivity and the submerged arc welding deposition rate can be increased by up to 100%. The LSO SAW process can reduce or eliminate arc starting problems by allowing for full customization of the arc starting characteristics. LSO SAW can also improve the control of the energy input to the weld, reduce the heat input (reduce distortion), and reduce the flux / wire ratio. Another benefit of LSO SAW is that higher deposition and productivity can be achieved at lower heat inputs.

[0039] As discussed above, increasing the dry extended length can provide certain advantages, such as a higher deposition rate without increasing energy consumption. However, for dry extended lengths exceeding, for example, 25 mm, various problems may occur. For example, as the dry extended distance increases, the heated wire electrode may misalign and deviate within the weld groove. This can cause problems, especially when welding deep and narrow grooves that can be used to minimize the time and cost of joining thick workpiece sections, because the LSO welding electrode assembly may be too large to reach the bottom of the groove. To address this and other challenges, in addition to the contact tip 202, the SAW torch 200 can employ an extension to serve as a wire electrode guide 204 (see Figure 2 ). The extension or wire electrode guide 204 provides electrical insulation, thermal insulation, and mechanical rigidity to the heated wire electrode 100 in particular. Figure 2 An example electrode assembly configured for submerged arc welding with a long dry extension is shown, which includes a wire electrode guide 204 or an extension. As shown, the wire electrode guide 204 extends distally from the contact tip 202. The wire electrode guide 204 is located between the contact tip and the workpiece (not shown). In certain embodiments, as can be seen in Figure 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 that 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 each other with no air gap therebetween, such that the wire electrode 100 is not exposed to ambient air.

[0040] Conventional electrode assemblies may not be suitable for some applications, for example, for filling narrow and deep grooves, such as triangular or U-shaped grooves with a depth exceeding 4 inches and a vertex angle of 16 degrees or less. Among other disadvantages, the inventors have found that existing designs of electrode assemblies may be deficient in one or more of the following: optimized vertical and lateral dimensions, thermal and electrical insulation, arc instability caused by magnetic materials, and compact flux delivery. The various embodiments of the electrode assembly for submerged arc welding described herein address these and other needs.

[0041] An electrode assembly for improved LSO SAW and a method of using the same are disclosed herein. The inventors have found that significant further improvements in LSO SAW can be achieved by optimizing various aspects of the extended dry extension portion of the electrode's electrical insulation. Figures 2 to 4 A portion of a SAW torch configured for submerged arc welding with a long dry extension according to various embodiments is shown. Figure 4Shows the wire electrode guide 204 of the welding torch 200. Electrode assemblies according to various embodiments include a contact tip portion 202 and an extension portion or wire electrode guide 204 that are arranged in series and configured to feed a consumable electrode therethrough. In the example shown, the contact tip 202 and the guide 204 that are arranged in series are physically separated and the consumable electrode 100 is exposed therebetween. In other arrangements, the contact tip 202 and the guide 204 may be in contact with each other. During welding, the contact tip 202 is disposed upstream of the starting tip of the consumable electrode 100, and the wire electrode guide 204 is disposed adjacent to the starting tip of the electrode. The contact tip 202 is in electrical contact with the consumable electrode 100 to supply power thereto. The consumable electrode 100 is fed through the contact tip 202 and exits the contact tip. Subsequently, the consumable electrode 100 is fed through the 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 (such as a ceramic material) that surrounds the consumable electrode. Reference is made below to Figure 4 Further discuss the insulating material. The consumable welding electrode 100 is preheated by Joule heating in the insulating extension portion or wire electrode guide 204 and then melting occurs at the starting tip of the consumable electrode. The degree of preheating is a function of the distance / resistance between the contact point of the welding circuit with the wire electrode 100 at the contact tip 202 and the starting point of the wire and the workpiece. The wire electrode guide 204 provides physical support and protection for the preheated wire to ensure the correct positioning of the deposited metal during SAW.

[0042] In various embodiments, the guide 204 is configured to electrically insulate the consumable electrode from the workpiece and has a shape, length, and lateral dimension such that the guide is configured to be insertable into a narrow groove between the workpieces. The insulating material that surrounds the consumable electrode 100 inside the guide 204 allows for a significant reduction in the lateral dimension. As a result, the guide 204 is configured to not contact the sidewalls of a narrow groove (such as a triangular or U-shaped groove) having a depth greater than 4 inches, 5 inches, 6 inches, 7 inches, or a value within the range defined by any one of these values and having a vertex angle less than 16 degrees, 12 degrees, 10 degrees, 8 degrees, 6 degrees, or a value within the range defined by any one of these values, while the tip of the consumable electrode 100 contacts the vertex. It should be understood that the shallower the groove, the narrower the vertex angle. For example, this relationship may follow an example dependency such as that shown in Table 1, but is not limited thereto. It should be understood that the groove or trench may not have a triangular cross-section. Instead, some grooves may have, for example, a rectangular or tapered rectangular shape. In these geometries, the "vertex" angle or acceptance angle may be defined by the arctangent of the width of the trench to the depth.

[0043] Table 1

[0044] Groove depth Vertex angle > 2 inches <8 degrees > 3 inches <10 degrees > 4 inches <12 degrees

[0045] 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 of a substantially non-magnetic material surrounding the consumable electrode. The outer envelope or sheath of the guide 204 can be metallic, such as formed of non-magnetic steel (e.g., stainless steel) or another non-magnetic metal. The inventors have found that the non-magnetic sheath advantageously improves the magnetic field around the electrode and reduces the resulting arc instability and welding defects. The non-magnetic sheath also reduces any instability in the welding parameters that may be caused by magnetization of the guide 204 over time.

[0046] 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 dimension such that the contact tip-to-workpiece distance (CTWD) during welding exceeds 25 mm, 100 mm, 125 mm, 150 mm, 175 mm, or a length within the range defined by any one of these values, e.g., 150 mm to 160 mm. Compared to conventional SAW welding processes, the longer CTWD significantly increases the deposition rate for a given current density because the extended portion provides a longer joule heating zone.

[0047] In various embodiments, as Figure 3A and Figure 3B shown, the flux delivery or dispensing nozzle 206 can be attached to the support for the wire electrode guide 204. The flux delivery nozzle 206 is positioned adjacent to the wire electrode guide 204 and dispenses flux during SAW to cover the welding zone. Advantageously, the flux delivery nozzle 206 can have a narrow cross-section similar to the diameter of the guide 204 to allow both to be inserted into a narrow groove during welding.

[0048] According to various embodiments, for the same current, compared to a conventional SAW electrode assembly, an LSO SAW electrode assembly having an insulating extension portion is configured to achieve a significantly higher deposition rate. Example experimental deposition rates achievable for one example configuration with a CTWD of 5" and an electrode diameter of 5 / 32" are as follows: During welding, the deposition rate per unit current can exceed 0.05 lbs. / hr. / A, 0.06 lbs. / hr. / A, 0.07 lbs. / hr. / A, 0.08 lbs. / hr. / A, or a value within the range defined by any one of these values; a deposition rate exceeding 35 lbs. / hr. can be achieved at a value less than about 900 A, 850 A, 800 A, 750 A, 700 A, or within the range defined by any one of these values (e.g., at about 700 A to 750 A). In the case of using a conventional SAW electrode assembly, it is expected that a similar deposition rate can only be achieved at a current exceeding about 900 A. Advantageously, since joule heating (I 2 2R) varies with the square of the current, the improvement in the deposition rate relative to a conventional SAW electrode increases at higher currents. That is, it is expected that the relative improvement in the deposition rate increases as the current increases.

[0049] Due to the longer CTWD, a higher fraction of the voltage between the contact tip and the workpiece drops across the LSO wire electrode. The LSO wire electrode according to an embodiment is configured to drop at least 5%, 10%, 15%, 20% of the total voltage drop across the contact tip to workpiece distance (CTWD), or a value within the range defined by any one of these values. The remaining voltage drop occurs across the arc. The electrode assembly according to an embodiment is configured to drop a fraction of the total voltage drop across the contact tip to workpiece distance (CTWD) that exceeds 1 / 30, 1 / 15, 1 / 10, 1 / 7, 1 / 5, or a value within the range defined by any one of these values. For example, in the case of an example total voltage drop of 30 V, about 4 V drops across the LSO wire electrode, while the remaining amount (about 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 about 1 V drops across the electrode, while the remaining amount (about 29 V) drops across the arc length. Therefore, compared to a conventional SAW electrode configuration, a longer length of the welding electrode is heated to a higher temperature, which increases the deposition rate.

[0050] An additional benefit provided by the electrode assembly according to an embodiment is a reduced flux to wire consumption ratio. The electrode assembly according to an embodiment is configured to heat the consumable wire electrode within the extension portion to a temperature up to 600 °C, 700 °C, 800 °C, 900 °C, or a temperature within the range defined by any one of these values.

[0051] Figure 4An example embodiment of a wire electrode guide 204 is shown. The wire electrode guide 204 has an outer sheath 208. In some embodiments, the outer sheath 208 is metallic, such as made of stainless steel or another metal. The outer sheath 208 may be made of a non-magnetic material (such as a non-magnetic metal). In other embodiments, the outer sheath 208 may be non-metallic, such as made of a high-temperature polymer.

[0052] Within the metallic outer sheath 208, a plurality of electrical insulators 210 are 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, in particular their axially aligned central openings 212, forms a central wire electrode receiving hole through the plurality of insulators for the wire electrode 100. The energized wire electrode 100 (energized by a contact tip in a torch) is fed through the central wire electrode receiving hole 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 adjacent workpiece(s) to prevent short circuits. If the wire electrode guide 204 contacts the workpiece, the insulator 210 will prevent the wire electrode 100 from accidentally forming a short circuit with the workpiece.

[0053] The inner perimeter or surface of the metallic outer sheath 208 and the outer perimeter surface of the electrical insulators 210 may closely match (e.g., both may have a cylindrical shape or another shape, such as a polygonal shape). In Figure 4 the example embodiment shown, the plurality of electrical insulators 210 are annular or have an annular shape. The upper or proximal portion of the sheath 208 may be generally cylindrical. The bottom or distal portion of the sheath 208 may be tapered to hold the insulators 210 within the sheath; however, various methods for holding the insulators within the sheath will be apparent to those of ordinary skill in the art.

[0054] The wire electrode guide 204 can include a removable cap 214 (e.g., a threaded cap) that provides access to the insulator 210. One or more insulators 210 may be damaged (e.g., cracked or broken) during use. For example, the wire electrode guide 204 can be inserted into the welding groove between workpieces and may inadvertently strike the workpiece during welding setup or during actual welding. The impact with the workpiece may damage one or more of the plurality of electrical insulators 210 as they may be brittle. The removable cap 214 allows the wire electrode guide 204 to be repaired and the insulator 210 to be replaced as needed. In some embodiments, the inner circumference of the sheath 208 and the outer circumference of the insulator 210 can closely match such that the insulator has little radial movement within the sheath. A gap can be provided between the outer circumference of each of the insulators 210 and the inner wall of the sheath 208 to allow relative radial movement between adjacent insulators within the sheath. This gap can allow axially adjacent insulators 210 to slightly radially slide on each other within the sheath 208 (e.g., during impact of the wire electrode guide 204 with the workpiece), while maintaining the central wire electrode receiving hole. In some embodiments, the upper surface and / or lower surface of the insulator 210 can have protrusions or bumps (e.g., adjacent insulators will be slightly spaced apart from each other) that create a small space or air gap between adjacent insulators. The stack of electrical insulators 210 provides some flexibility to the wire electrode guide 204. If the guide 204 strikes the workpiece, the insulators 210 can shift within the metal sheath 208 and may not break. However, if one or more of the insulators 210 break, they can be easily replaced. The stack of insulators 210 provides a more durable and less expensive insulated wire guide compared to a single monolithic ceramic sleeve.

[0055] The insulators 210 can have the shape of a washer or O-ring with a small height and a relatively wider diameter, or they can be in the shape of a circular ring with a greater height compared to a washer or O-ring. The insulators 210 can be made of a ceramic material or other suitable insulating material. For example, the insulators 210 can be formed from a material selected from the group consisting of silicon nitride, magnesia-stabilized zirconia, yttria-stabilized zirconia, silicon carbide, magnesia, alumina, or zirconia-toughened alumina. The ceramic insulators can be manufactured using various methods such as powder pressing, cold isostatic pressing, hot pressing, injection molding, and slip casting.

[0056] Figure 5The wire electrode guide 204 is shown, which is 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 on the guide. In some embodiments, the wire electrode guide 204 or the torch may include a magnet 216 that attaches the wire electrode guide to the torch. The magnet 216 can act as a collision box that allows the guide 204 to easily separate from the torch when the guide hits the workpiece without damaging the ceramic insulator. As will be understood by those of ordinary skill in the art, other forms of off-the-shelf separation can be provided between the guide 204 and the torch to allow the guide to easily separate from the torch when the guide hits the workpiece without damaging the ceramic insulator.

[0057] The wire electrode guide 204 may include a sensor 218 for sensing contact or impending contact between the guide and the workpiece. Examples of such sensors include touch sensors, accelerometers, vibration sensors, etc. The touch sensor can provide a signal to the torch motion controller to notify the controller that the torch has or is about to contact the workpiece. The touch sensor can be particularly useful during welding setup to define the boundaries of the welding path or the weld groove. The accelerometer or vibration sensor can be used to sense the vibration of the torch due to the rupture of the insulator 210 within the guide 204. The sensor 218 can provide a signal to the welding power source or another device within the SAW system to generate an alert or warning to the operator to inspect and / or repair the guide 204. Alternatively or additionally, the insulator 210 may include isolated electrically continuous circuits incorporated into each individual insulator. Disrupting the circuit will indicate that the insulator is damaged, and the welding power source or another device within the SAW system can notify the operator which specific insulator needs to be replaced. The torch or the wire electrode guide 204 may further include wire jamming detection to notify the torch motion controller and / or the welding power source that the wire electrode is jammed into the weld metal so that remedial action can be taken to unjam the wire.

[0058] Figure 6 A quick-disconnect device is shown that can be used to attach the wire electrode guide 204 to the torch. One example of a quick-disconnect device is a tethered ball quick-disconnect device, similar to those used on pneumatic systems. In Figure 6 this, a female quick-disconnect device 220 can be attached to the torch to allow the guide 204 to be easily removed from it.

[0059] Submerged arc welding systems typically do not utilize a shielding gas. However, if needed, the systems discussed above (see, for example, Figure 1) may include a shielding gas. The shielding gas can be used to control the amount of oxygen in the welded metal and prevent oxidation of the heated LSO wire electrode. The shielding gas can be discharged from the torch upstream of the wire electrode guide and above or proximal to the air gap between the contact tip and the wire electrode guide.

[0060] It should be clear that this disclosure is by way of example, and various changes can be made by adding, modifying, or removing details without departing from the reasonable scope of the teachings contained in this disclosure. Accordingly, the present invention is not limited to the specific details of this disclosure unless the appended claims are necessarily so limited.

Claims

1. A welding torch, comprising: A contact tip; And A wire electrode guide extending distally of the contact tip, wherein the wire electrode guide comprises: A metal outer sheath; and A plurality of annular electrical insulators axially stacked within the metal outer sheath to form a central wire electrode receiving hole through the plurality of annular electrical insulators.

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

3. The welding torch according to claim 1, wherein, The annular electrical insulators are formed of a ceramic material.

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

5. The welding torch according to claim 1, wherein, The annular electrical insulators electrically insulate the wire electrode extending through the contact tip and the wire electrode guide from the metal outer sheath.

6. The welding torch according to claim 1, wherein, The metal outer sheath comprises stainless steel.

7. The welding torch according to claim 1, wherein, A gap between the outer circumference of each of the annular electrical insulators and the inner wall of the metal outer sheath allows relative radial movement between adjacent annular electrical insulators within the metal outer sheath.

8. The welding torch according to claim 1, further comprising a tethered ball quick disconnect device for attaching the wire electrode guide to the welding torch.

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

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

11. A welding torch, comprising: A contact tip; And A wire electrode guide extending distally of the contact tip, wherein the wire electrode guide comprises: A metal outer sheath; and A plurality of ceramic electrical insulators axially stacked within the metal outer sheath, wherein each ceramic electrical insulator has a central opening such that the plurality of ceramic electrical insulators axially stacked within the metal outer sheath form a central wire electrode receiving hole for a wire electrode energized by the contact tip.

12. The welding torch according to claim 11, wherein, Each ceramic electrical insulator has an annular shape.

13. The welding torch according to claim 12, wherein, A gap between the outer circumference of each of the ceramic electrical insulators and the inner wall of the metal outer sheath allows relative radial movement between adjacent ceramic electrical insulators within the metal outer sheath.

14. The blowtorch according to claim 11, wherein, An air gap exists between the contact tip and the wire electrode guide, the air gap exposing the wire electrode extending through the contact tip and the wire electrode guide to ambient air.

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

16. The welding torch according to claim 11, wherein, The ceramic electrical insulators electrically insulate the wire electrode extending through the contact tip and the wire electrode guide from the metal outer sheath.

17. The blowtorch according to claim 11, wherein, The metal outer sheath comprises stainless steel.

18. The welding torch according to claim 11, further comprising a tethered ball quick disconnect device for attaching the wire electrode guide to the welding torch.

19. The torch as claimed in claim 11, further comprising a magnet for attaching the wire electrode guide to the torch.

20. The torch as claimed in claim 11, further comprising a touch sensor configured to determine contact between the metal outer sheath and the workpiece.

21. A torch comprising: A contact tip; And A wire electrode guide mounted below the contact tip for receiving a wire electrode energized by the contact tip, wherein an air gap exists between the contact tip and the wire electrode guide, the air gap exposing the energized wire electrode to ambient air, wherein the wire electrode guide comprises: A metal outer sheath; and A plurality of ceramic annular electrical insulators axially stacked within the metal outer sheath so as to form a central wire electrode receiving hole through the plurality of ceramic annular electrical insulators, wherein the plurality of ceramic annular electrical insulators electrically insulate the wire electrode from the metal outer sheath.

22. The torch as claimed in claim 21, further comprising a flux delivery nozzle positioned adjacent the wire electrode guide.

23. The torch as claimed in claim 21, further comprising a tethered ball quick disconnect device for attaching the wire electrode guide to the torch.

24. The torch as claimed in claim 21, further comprising a magnet for attaching the wire electrode guide to the torch.

25. The torch as claimed in claim 21, further comprising a touch sensor configured to determine contact between the metal outer sheath and the workpiece.

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