Arc starting process for long-rod extension submerged-arc welding

Abstract

The disclosed technology generally relates to welding technology, and more particularly to an electrode assembly for arc welding (e.g., submerged arc welding). In one aspect, a welding system includes a welding power source and an electrode assembly operably coupled to the welding power source and an electrode. The welding power source is configured to apply a direct current electrode negative (DCEN) to the electrode using the electrode assembly to establish an arc between the electrode and the workpiece, and to apply a direct current electrode positive (DCEP) or alternating current (AC) to the electrode after establishing the arc.

Description

[0001] By invoking inclusion in any priority application

[0002] Any and all applications that identify their foreign or domestic priority claims in the application data sheet filed with this application are incorporated herein by reference in accordance with 37 CFR 1.57.

[0003] This application was filed August 9, 2024, pursuant to 35 U.S. SC §119(e), with U.S. Provisional Patent Application No. 63 / 681731 entitled "ARC-STARTPROCESSES FOR LONG STICK OUT SUBMERGED ARC WELDING". The entire contents of the above application are incorporated herein by reference.

[0004] background

[0005] TECHNICAL FIELD

[0006] The disclosed technologies generally relate to welding technology, and more specifically to methods for operating arc welding equipment (such as submerged arc welding (SAW) equipment).

[0007] Description of the Related Art

[0008] Various welding techniques utilize welding wire as a metal source. For example, in metal arc welding, an arc is generated when a voltage is applied between a consumable welding electrode wire (which acts as one electrode moving toward the workpiece) and the workpiece (which acts as the other electrode). The arc melts the tip of the metal welding wire, thereby producing molten metal droplets that deposit onto the workpiece to form a weldment or weld bead.

[0009] The complexity of the technical and economic demands on welding technologies continues to grow. For example, there is a growing need for higher weld quality in terms of appearance and mechanical properties, including high yield strength, ductility, and fracture toughness. At the same time, higher weld quality is often required while maintaining economic viability. Some welding technologies aim to address these competing requirements by improving consumables, such as by refining the physical design and / or composition of the electrode wire.

[0010] Submerged arc welding (SAW) can provide a highly economical solution for some applications. The high deposition rate achieved through submerged arc welding is the main reason for the process's cost-effectiveness.

[0011] Overview

[0012] In one aspect, a welding system includes a welding power source and welding tools operatively connected to the welding power source and electrodes. The welding power source is configured to apply DC electrode negative (DCEN) to the electrodes using the welding tools to establish an arc between the electrodes and the workpiece, and to apply DC electrode positive (DCEP) or alternating current (AC) to the electrodes after the arc has been established.

[0013] On the other hand, a method for operating a welding system is provided. The method includes applying DC electrode negative (DCEN) to the electrodes to establish an electric arc between the electrodes and the workpiece, and then, after establishing the electric arc, applying DC electrode positive (DCEP) or alternating current (AC) to the electrodes. Attached Figure Description

[0014] Figure 1 A submerged arc welding (SAW) system according to an embodiment of the present technology is illustrated schematically.

[0015] Figure 2 A conventional electrode assembly for SAW systems is shown.

[0016] Figure 3A A conventional electrode assembly for a SAW system is shown above a workpiece with a bevel.

[0017] Figure 3B The image shows a long stem extension (LSO) electrode assembly for a SAW system mounted above a workpiece with a bevel.

[0018] Figure 4 It is a flowchart of a method for operating a welding system, in which DC electrode positive (DCEP) is applied to the electrode to initiate welding.

[0019] Figure 5 Shown in Figure 4 The graphs show the voltage, current, and wire feed speed of the welding system during the demonstration method.

[0020] Figures 6A-6G Shown in Figure 4 The LSO electrodes are shown at different times during the process.

[0021] Figure 7 It is a flowchart illustrating a method of operating a welding system according to some embodiments, wherein a DC electrode negative (DCEN) is applied to the electrodes to initiate welding.

[0022] Figure 8 Shown in Figure 7 The graphs show the voltage, current, and wire feed speed of the welding system during the demonstration method.

[0023] Figures 9A-9G Shown in Figure 7The LSO electrodes are shown at different times during the process.

[0024] Figure 10 It is a flowchart illustrating a method of operating a welding system according to some embodiments, wherein an asymmetrical alternating current (AC) biased by DCEN is applied to the electrodes to initiate welding.

[0025] Figure 11 Shown in Figure 10 The method shown is illustrated with graphs of voltage and current in the welding system. Detailed Implementation

[0026] In processes using consumable electrodes, the electrode or welding wire melts to provide additive metal to fill gaps, thereby forming a welded joint that joins two metal workpieces. 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).

[0027] Submerged arc welding

[0028] Figure 1 A submerged arc welding (SAW) system 100 for depositing filler metal or weld metal onto a workpiece 102 is schematically shown. System 100 includes an electrode 104 having a tip 106, a contact tip 110 coupled to the electrode 104, and a power supply 108 electrically coupled to the contact tip 110 and the workpiece 102. Although not shown, system 100 also includes one or more processors or controllers communicatively coupled to the power supply 108 and a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium stores instructions that, when executed by the one or more processors or controllers, cause the one or more processors to perform the various welding methods disclosed herein. System 100 also includes a flux delivery system 112 configured to dispense flux 114 onto the workpiece 102 during the SAW process. The electrode 104 typically comprises a metal or alloy, while the flux comprises a granular fusible material. During the SAW process, heat originates from an electric arc 116 between the electrode 104 and the workpiece 102. The electric arc is shielded by a coating of flux 114 placed on the joint area in front of the arc 116. Filler metal is primarily obtained from electrode 104, which is continuously fed into the arc 116 and the molten flux pool 122 through the coating of flux 114. Additional filler metal can be obtained by adding cold or hot welding wire to the weld pool 122 or from metal powder contained in the flux 114. Therefore, unlike other flux-treated processes, SAW uses two consumables (electrode 104 and flux 114), and these two consumables can be supplied separately.

[0029] A key feature of SAW is flux 114, which covers the welding area and prevents arc radiation, sparks, spatter, and fumes from escaping. Flux 114 allows for high deposition rates and high-quality weld deposition characteristics. In addition to shielding the arc 116 from view, flux 114 provides slag 118, which protects the weld metal 120 as it cools, deoxidizes and refines the weld metal 120, insulates the weld to reduce the cooling rate, and helps to shape the weld profile.

[0030] During the SAW process, the heat from the arc 116 melts some of the flux 114 along with the tip 106 of the electrode 104 to form a solder pool 122, such as Figure 1 As shown. The tip 106 of electrode 104 and the welding area are always surrounded and shielded by molten flux 114, which itself is covered by a layer of unmelted flux 114. Electrode 104 is held at a short distance above workpiece 102, where an arc 116 is formed between electrode 104 and workpiece 102. As electrode 104 travels along the joint, the lighter molten flux 114 rises as slag 118 above the molten metal in weld pool 122. The molten metal in weld pool 122, which has a higher melting point (freezing point), solidifies, while the slag 118 above it remains molten. The slag 118 then solidifies on the newly solidified weld metal 120, thus continuing to protect the metal 120 from contamination, while it is very hot and will react with atmospheric oxygen and nitrogen. After cooling and removing any unmelted flux 114 for reuse, the solidified slag 118 can be easily removed from the weld.

[0031] Power supply 108 generates voltage and current for system 100, and the voltage and current are applied to workpiece 102 and electrode 104. Current is applied to the electrode via contact tip 110. High currents can be used in submerged arc welding, and extremely high heat can be generated. Because the current is applied to the electrode at a short distance above the tip 106 of electrode 104, relatively high amperes can be used on small-diameter electrodes. This results in extremely high current densities on the relatively small cross-section of the electrode. Currents as high as or exceeding 600 amperes can be carried on electrodes as small as 64”, resulting in a density of approximately 100,000 amperes per square inch, which is six to ten times the current density carried on a rod-shaped electrode.

[0032] Due to the high current density, the melting rate is much higher than that of welding with rod electrodes for a given electrode diameter. The melting rate is affected by the electrode material, flux 114, current type, polarity, and the length of the welding wire beyond the electrical contact point in the welding torch or head.

[0033] Submerged arc welding can be performed using direct current (DC) or alternating current (AC). DC offers better control over weld bead shape, penetration, and welding speed, and is relatively easy to start. The best weld bead shape is generally achieved with a DC electrode connected to positive polarity (DCEP or reverse polarity), which also provides maximum penetration. Using a DC electrode connected to negative polarity (DCEN or positive polarity) yields the highest deposition rate and minimum penetration. Alternating current minimizes arc blow and provides penetration between DCEP and DCEN.

[0034] An insulating coating of flux 114 above arc 116 prevents heat from escaping rapidly and concentrates it in the welding area. Not only do the base metals of electrode 104 and workpiece 102 melt rapidly, but the melt penetrates deep into the base metal. This deep penetration allows for the use of small weld bevels, minimizing the amount of filler metal per foot of joint and allowing for rapid welding speeds. Rapid welding, in turn, minimizes the total heat input to the assembly and thus minimizes thermal deformation issues. Even relatively thick joints can be welded in a single pass using submerged arc welding.

[0035] Welds formed under the protective layer of flux 114 exhibit good ductility, impact resistance, and uniform weld bead appearance. Mechanical properties at least equal to those of the base metal are consistently achieved. In single-pass welds, the amount of molten base material is relatively large compared to the amount of filler metal used. Therefore, in such welds, the base metal can significantly influence the chemical and mechanical properties of the weld. For this reason, it is sometimes unnecessary to use electrodes with the same composition as the base metal when welding many low-alloy steels. However, the chemical composition and properties of multi-pass welds are less affected by the base metal and depend more heavily on the electrode composition, flux activity, and welding conditions.

[0036] By adjusting the current, voltage, and travel speed, the operator can precisely control the penetration to provide any depth, ranging from deep, narrow weld beads with high top reinforcement to wide, nearly flat weld beads with shallow penetration. Deep-penetration weld beads may contain approximately 70% molten base metal, while shallow weld beads may contain as little as 10% base metal. In some cases, the deep penetration properties of submerged arc welding can be used to eliminate or reduce edge preparation costs.

[0037] Flux serves multiple functions in submerged arc welding. These functions include covering the molten weld metal to protect it from atmospheric influences and acting as slag to refine the molten deposit by removing oxides and other non-metallic inclusions. Metallic additives to the flux can increase the alloy content of the deposit and deoxidize it.

[0038] Based on their manufacturing methods, there are four types of fluxes: molten fluxes, bonded fluxes, sintered fluxes, and mechanically hybrid fluxes.

[0039] Fluxes are also labeled as basic, acidic, and neutral. Basic fluxes contain readily free metal oxides, while acidic fluxes contain oxides that are free to a very small extent. Neutral fluxes do not increase or decrease the composition of the solder deposit. Fluxes with a CaO or MnO to SiO2 ratio greater than 1 are considered basic, those close to 1 are considered neutral, and those less than 1 are considered acidic.

[0040] With proper equipment selection, submerged arc welding (SAW) 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 sheets to the thickest plates. It is also suitable for some high-alloy heat-treated stainless steels and is a favorable process for rebuilding and hard surface surfacing. Any degree of mechanization can be used, from handheld semi-automatic welding torches to boom or track-borne and clamp-held multiple weld joints.

[0041] Submerged arc welding (SAW) is a preferred process in steel manufacturing due to its high quality, high deposition rate, deep penetration, adaptability to full mechanization, and comfort characteristics (no glare, sparks, spatter, smoke, or excessive heat radiation). It is widely used in shipbuilding and barge construction, railway car construction, pipe manufacturing, and the fabrication of structural beams, girders, and columns requiring long welds. Automated SAW facilities are also a key feature of the welding area in equipment used to produce batches of components joined by repeated short weld seams.

[0042] Other factors besides deposition rate also reduce welding costs. Continuous electrode feeding from wire rods weighing between 60 and 1,000 pounds contributes to a high operating factor. Costs are reduced where the deep penetration characteristics of the process allow for the elimination or reduction of joint preparation. Cleaning costs are minimized after welding is complete because the flux shielding eliminates spatter.

[0043] When submerged arc welding equipment is used appropriately, the weld bead is smooth and uniform, requiring little grinding or machining. Because the process's rapid heat input minimizes deformation, the cost of straightening finished components is reduced, especially when a carefully planned welding sequence is followed. In fact, submerged arc welding often allows for pre-machining of parts, further reducing manufacturing costs.

[0044] Given these and other advantages offered by SAW, further improvements to all aspects of SAW are expected and necessary, including even higher productivity and weld quality. For example, since one of the technological advantages of SAW stems from the preheating of consumable electrodes, further improvements to the preheating arrangement are expected and necessary through improved electrode assembly design.

[0045] Long dry-stretch electrode assembly for submerged arc welding

[0046] Figure 2 An electrode assembly 200 is shown, defining an electrical extension and positioning it above a workpiece 202. The electrode assembly 200 includes a head portion 224 configured to receive an electrode 204. The head portion 224 includes a conductive tip 210, an electrode conduit 226, and an insulating guide 228. The conductive tip 210 is radially disposed around the electrode 204 and configured to receive power from a power source (e.g., Figure 1 Current from the power supply device 108 (shown) is transmitted to the electrode 204. The electrode 204 includes a tip portion 206 configured to extend beyond the head portion 224. The portion of the electrode 204 extending between the end portion 206 and the end of the head portion 224 is referred to as the visible extension 232, while the portion of the electrode 204 extending between the tip portion 206 and the conductive tip 210 is referred to as the electrical extension or charged electrode extension 230. Unless otherwise stated, the extension length as used herein refers to the length of the electrical extension 230, which is a parameter that primarily affects the electrical response of the electrode assembly 200. During operation of the electrode assembly 200, the tip portion 206 is positioned adjacent to the workpiece 202, and the distance between the conductive tip 210 and the workpiece 202 is referred to as the conductive tip to workpiece distance (CTWD) 234.

[0047] The electrical extension 230 of electrode 204 is preheated by Joule heating or resistance heating. If the charged electrode extension 230 is not long enough, electrode 204 may not be adequately preheated. Increasing the length of the electrical extension 230 increases the resistance of the circuit, which in turn increases heating and thus the temperature of the tip 206 of electrode 204, resulting in an increased melting and deposition rate. The length of the electrical extension 230 then controls the weld bead size, as the length of the filler wire extension affects the burn-in rate. Furthermore, the charged electrode extension 230 influences penetration through its effect on the welding current. As the length of the charged electrode extension 230 increases, the preheating of electrode 204 and the voltage drop across electrode 204 increase. A larger voltage drop may result in a more convex weld bead shape, which can be overcome by increasing the input voltage by 2 to 5 volts. For conventional steel welding processes, the length of the electrical extension 230 can be approximately 3 to 10 times the diameter of electrode 204 (for conventional SAW processes), depending on the type of steel being welded.

[0048] Figure 3AAn electrode assembly 300A is depicted positioned above a workpiece 302 having a bevel 303. In the illustrated configuration, the extended portion 330A of the electrode 304A extends beyond the conventional distance of the contact tip 310A (e.g., 3 to 12 times the diameter of the electrode). The electrode assembly 300A is positioned such that a head portion 324A is positioned above the bevel 303 and the tip 306A of the electrode 304A is located within the bevel 303. More specifically, the head portion 324A is positioned such that the tip 306A is adjacent to the bottom of the bevel 303, while the head portion 324A does not contact the workpiece 302. In the illustrated embodiment, the tip 306A is positioned within the bevel such that the CTWD 334A is approximately 25 mm. Positioning the tip 306A close to the bottom of the bevel 303 allows for a better and more consistent arc to be formed between the tip 306A and the workpiece 302, resulting in more consistent deposition of filler metal into the bevel 303 and improved welding quality and efficiency.

[0049] To further improve submerged arc welding (SAW) technology, long extension wire (LSO) or extended extension wire technology developed by Lincoln Electric Company can be employed. Long extension wire SAW refers to a SAW process in which the length of the electrode tip extending beyond the welding wire (“extension length”) is increased relative to conventional SAW processes, for example, by approximately 25 mm, resulting in an increased total current-to-weight ratio (CTWD). As used herein, LSO refers to an electrode configuration in which the extension wire exceeds approximately 10 times the diameter of the 304A electrode. The longer extension length allows for preheating of a larger length of electrode before melting at the electrode tip, which increases the electrode melting rate because it is easier to melt the preheated electrode wire for a given current density. Compared to conventional SAW processes, LSO SAW processes can significantly improve productivity and submerged arc welding deposition rates by up to 100%. LSO SAW processes can reduce or eliminate arc initiation problems by allowing for complete customization of arc initiation characteristics. LSO SAW can also improve the control of welding energy input, reduce heat input (reduce deformation), and reduce flux / wire ratio.

[0050] Figure 3B An electrode assembly 300B is depicted positioned above a bevel 303 in workpiece 302. The electrode assembly 300B employs LSO technology, such that the electrical extension 330B extends beyond the conductive tip 310B compared to the extension 330A extending beyond the conductive tip 310A. Figure 3ASignificantly more. For example, in some embodiments, the dry extension 330B can have a length between 10 and 40 times the diameter of the electrode 304B. In some embodiments, the dry extension 330B can have a length greater than 40 times the diameter of the electrode 304B. As explained above, the increased length of the dry extension portion 330B allows for preheating of a larger length of the electrode 304B before melting occurs at the electrode tip, thereby allowing for increased melting and deposition rates.

[0051] The increased extension length in LSO SAW systems also allows for the easy filling of bevels that conventional SAW systems cannot fill, or can only fill with extremely precise placement and high operator skill. Specifically, while conventional SAW systems can be used with wide and / or short bevels, they are generally not easily used with deeper and / or narrower bevels because the size and shape of the head portion prevents it from being positioned further within deep / narrow bevels without contact and interaction with the workpiece. This results in the electrode tip being too far from the bottom of the bevel, leading to a poor arc between the electrode and the workpiece, and causing poor filler metal deposition rates and poor weld quality. Therefore, SAW systems with conventional extension lengths may struggle to form high-quality welds within deep and / or narrow bevels. In contrast, the increased extension length of LSO SAW systems allows the electrode tip to be closer to the bottom of narrow / deep bevels, and the reduced distance between the electrode tip and the bottom of the bevel results in a better arc between the electrode and the workpiece. Therefore, in addition to improving weld quality and deposition rate by allowing additional preheating of the electrodes before arc formation, LSO SAW technology also allows filler metal to be deposited into deeper and narrower bevels compared to conventional SAW technology.

[0052] According to various embodiments, for the same current, LSO SAW electrode assemblies can achieve significantly higher deposition rates compared to conventional SAW electrode assemblies. During the welding process, current is delivered to the electrode through the contact tip at a specific ampere and voltage. As the current flows through the electrode to the tip, the voltage drops and the electrode heats up. At the tip of the electrode, the current forms an arc on the workpiece. For LSO SAW assemblies, the increased electrode length compared to conventional SAW assemblies results in a higher portion of the total voltage drop occurring within the electrode. In some embodiments, LSO SAW assemblies can be configured such that the voltage drop between the contact tip and the tip of the consumable electrode is at least 5%, at least 10%, at least 15%, or at least 20% of the total voltage drop over the total CTWD (or a value within a range defined by any of these values). In other embodiments, the electrode assembly is configured such that the voltage drop between the conductive tip and the tip of the consumable electrode represents at least 1 / 30, at least 1 / 15, at least 1 / 10, at least 1 / 7, at least 1 / 5, or a value within a range defined by any of these values. For example, in a conventional SAW electrode assembly with a total voltage drop of 30V along the CTWD, only about 1V of this total voltage drop may occur within the consumable electrode, while the remaining voltage drop (about 29V) may decrease along the arc length. In contrast, for an LSO SAW system with the same total voltage drop of 30V, about 4V of this voltage drop may occur on the CTWD, while the remaining voltage drop (about 26V) may decrease along the arc length. The increased voltage drop through the longer electrode results in the electrode being heated to a higher temperature than electrodes in a conventional SAW configuration, and thus an increased deposition rate.

[0053] Experiments have shown that during soldering, the deposition rate per unit current of LSO SAW modules 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 the range defined by any of these values. Furthermore, experiments have shown that LSO SAW modules can achieve a given deposition rate with a lower current than conventional SAW electrode modules. For example, LSO SAW modules can achieve deposition rates exceeding 35 lbs. / hr. at currents less than about 900 A, 850 A, 800 A, 750 A, 700 A, or within the range defined by any of these values ​​(e.g., at currents of about 700 A to 750 A), while conventional SAW electrode modules require currents exceeding about 900 A to achieve similar deposition rates. Advantageously, due to Joule heating (I 2R) varies with the square of the current, therefore the improvement in deposition rate relative to conventional SAW electrodes increases at higher currents. In other words, the relative improvement in deposition rate is expected to increase with increasing current.

[0054] In an LSO SAW system, the consumable electrode (e.g., electrode 304B) extends beyond the end of the head portion (e.g., head portion 324B), making the arc tip (e.g., tip 306B) visible. As previously discussed, the portion of the electrode extending beyond the conductive tip portion is referred to as the arc extension. In some embodiments, the arc extension can be based on the diameter of the electrode. In some embodiments, the length of the arc extension can depend on the type of steel being welded, for example, whether the steel being welded is a low-alloy steel containing less than about 8 wt.% of nonferrous elements or a high-alloy steel containing more than about 8 wt.% of nonferrous elements. For example, in a conventional SAW process, the arc extension length can be about 7-10 times the diameter of the electrode used for welding low-carbon steel and mild steel, but can be about 3-5 times the diameter of the electrode used for welding high-alloy steel. In contrast, in the LSO SAW process according to various embodiments, the electrical extension distance (measured between the conductive tip portion at the end of the head portion and the arc tip of the consumable electrode) can be at least 15 times the electrode diameter, such that the extension-to-diameter ratio of the LSO SAW process and system can be 15, about 20, about 25, about 30, about 35, about 40, about 45, about 50, about 55, about 60, greater than 60, or a value within the range defined by any of these values. In some embodiments, the electrode can have a diameter between 2.5 mm and 5.0 mm, and the electrical extension distance can be about 125 mm, about 130 mm, about 135 mm, about 140 mm, about 145 mm, about 150 mm, about 155 mm, about 160 mm, about 165 mm, or a value within the range defined by any of these values. For example, in at least one embodiment, the electrode extension length can be 155 mm, and the electrode diameter can be 3.2 mm, which means the ratio of extension length to diameter is approximately 48. In another embodiment, the electrode extension length can be 125 mm, and the electrode diameter can be 4.0 mm, which means the ratio of extension length to diameter is approximately 31.

[0055] While increased lead length can offer certain advantages, such as higher deposition rates, lead lengths exceeding, for example, 25 mm can cause various problems when using conventional electrode assemblies. For instance, with increasing lead length, the heated welding wire may shift and deviate within the weld groove. This can be problematic, especially when welding deep, narrow grooves where time and cost can be minimized for joining thick sections, as LSO welding electrode assemblies may be too large to reach the bottom of the groove. To address this and other challenges, some electrode assemblies include ceramic extensions that act as insulating guides for the electrodes. These extensions provide electrical and thermal insulation, as well as mechanical rigidity, specifically for the heated electrodes.

[0056] Arcing process

[0057] One problem with LSO in SAW is that the arc-starting performance of LSO SAW systems has never matched that of SAW systems with standard dry extension.

[0058] Figure 4 It is a flowchart illustrating method 400 for operating a welding system including conventional arc initiation processes. Figure 5 The graphs show the voltage, current, and wire feed rate (WFS) of the system before, during, and after method 400. Figures 6A-6G These are images of the electrode 604 of system 600 on workpiece 602 at various time points during method 400. In some embodiments, system 600 may be an LSO SAW system, which is generally similar to the above-described combination. Figure 3B Electrode assembly 300B is shown and described.

[0059] like Figure 6A As shown, at step 402 of method 400, the welding process is initiated by embedding the tip 606 of electrode 604 in flux 614 and positioning it above workpiece 602 without applying a load between electrode 604 and workpiece 602. Figure 5 During the time period 501, the voltage measured by the welding system is the open-circuit voltage. In some embodiments, the open-circuit voltage may be approximately 70 volts. However, because no load is applied between the electrode and the workpiece during time period 501, typically no current flows between electrode 604 and workpiece 602. Additionally, no arc has been established, therefore the WFS is 0 ipm.

[0060] In step 404, a DC electrode positive (DCEP) load is applied to electrode 604. Figure 6B As shown, DCEP is applied to electrode 604 to form an arc 616 between electrode 604 and workpiece 602, which allows current to flow from workpiece 602 into electrode 604.Figure 5 The time period 502 represents the time period during which the voltage decreases from the open-circuit voltage and the current jumps as current begins to flow. In some embodiments, the current fluctuates immediately after arc 616 is established (e.g., during the initial few 100ms of time period 502), but may stabilize shortly after arc 616 is established. For example, in some embodiments, the current may initially fluctuate between about 1200A and 400A, and then stabilize at about 750A after about 200ms.

[0061] System 600 is configured to continuously feed wire during the welding process, such that electrode tip 606 is maintained at a suitable distance from workpiece 602 during the welding process to ensure arc 616 is maintained and weld quality is appropriate. In some embodiments, system 600 is capable of detecting voltage changes between electrode 604 and workpiece 602 and adjusting the WFS of system 600 based on these voltage changes. The voltage between electrode 604 and workpiece 602 is related to the melting rate of electrode 604, therefore adjusting WFS based on voltage changes allows system 600 to account for changes in the melting rate. In some embodiments, system 600 is configured to automatically increase WFS when it detects an increase in voltage to account for a corresponding increase in the melting rate, thereby ensuring that electrode tip 606 maintains a suitable distance from workpiece 602 during the welding process, allowing arc 616 to be maintained.

[0062] Shortly after DCEP is applied and arc 616 is formed, system 600 detects the voltage change and automatically increases WFS to account for the increased distance between the unmelted portion of electrode 604 and workpiece 602 (due to melting and breakage of tip 606). For example, in some embodiments, system 600 may increase WFS to approximately 80 ipm. In some embodiments, the voltage between electrode 604 and workpiece 602 may increase steadily during time period 502, and system 600 may automatically increase WFS during time period 503 to account for the increased melting rate due to the increased voltage.

[0063] During time period 502, the current flowing through electrode 604 causes the portion of electrode 604 between the conductive tip 610 and the workpiece 602 to heat up (via resistance heating) and causes portion 636 of electrode 604 to begin emitting light. Figure 6B As shown, the light-emitting portion 636 is initially very small and extends only a short distance away from the tip 606. However, as the electrode continues to heat up during time period 502, the length of the light-emitting portion 636 increases. For example, as... Figure 6C As shown, the light-emitting portion 636 can extend to directly below the top of the flux pile 614 at approximately half of time period 502, and as... Figure 6DAs shown, it can extend far above the flux 614 and can be about halfway to the conductive tip 610 at almost the end of time period 502.

[0064] At the end of time period 502, electrode 604 can be significantly preheated, and system 600 increases the voltage between electrode 604 and workpiece 602 to maintain arc 616. However, this significant increase in voltage leads to even greater heating of electrode 604, resulting in an increased melting rate and increased WFS in an attempt to compensate for the increased melting rate. This feedback loop continues until... Figure 6E As shown, most of electrode 604 melts and falls onto workpiece 602. When this occurs, arc flash 638 occurs. Arc flash 638 causes current fluctuations and voltage spikes, which in turn causes the system to ramp up the WFS (Weld Spectrum Speed) in an attempt to reduce the apparent gap between electrode tip 606 and workpiece when the increased voltage is detected. High arc voltage, fluctuating current, and spikes in WFS result in poor weld bead shape. In some embodiments, arc flash 638 causes voltage spikes of approximately 70V and WFS spikes exceeding 200 ipm. In some embodiments, when the system detects an increased voltage due to arc flash, the system may automatically ramp up the WFS to the system's maximum WFS.

[0065] When the system increases the WFS to reduce the gap between electrode 604 and workpiece 602, the system may overcalibrate the sensed gap between electrode 604 and workpiece 602, potentially increasing the WFS too much. When this occurs, the unmelted tip 606 of electrode 604 may not have sufficient time to preheat and melt before it contacts workpiece 602, which could cause the still-solid electrode 604 to strike workpiece 602. Therefore, in some embodiments, when system 600 detects a voltage spike caused by arc flash 638 and subsequently increases the WFS, the system may overcalibrate, and this overcalibration could cause a hard short circuit between electrode 604 and workpiece 602.

[0066] During time period 504, when solid electrode 604 is shorted to workpiece 602, the voltage decreases and the current increases. For example, in some embodiments, the voltage decreases to approximately 47V and the current increases to approximately 750A. On the other hand, WFS remains at an increasing rate for the duration of time period 505. In some embodiments, system 600 monitors the voltage and maintains WFS at an increasing rate when the voltage is above a threshold. After time period 505, system 600 decreases WFS.

[0067] During time period 505, the voltage and WFS initially decrease, while the current initially increases, and then all three stabilize. For example, in some embodiments, the voltage decreases to about 28V and then stabilizes at about 35V, the current increases to about 850A and then stabilizes at about 750A, and the WFS decreases to about 70ipm and then stabilizes at about 100ipm.

[0068] Voltage and current fluctuations after a short circuit can lead to poor weld quality. Additionally, electrode 604 may not be sufficiently heated for optimal welding during the extended period following the arc flash. Figure 6F As shown, at the end of time period 506, the light-emitting portion 636 of the electrode wire is less than... Figure 6D The duration is as long as shown in the image, indicating that electrode 604 is heated less after the arc flash than before and during the arc flash. However, once the system reaches equilibrium (by the end of time period 505), electrode 604 continues to preheat during time period 506 until as shown in the image. Figure 6G As shown, the light-emitting part is 636 times larger than... Figure 6F The luminescent portion of the electrode 604 is long and extends above the flux bed 614, indicating that the electrode 604 is sufficiently preheated for optimal welding during time period 508. Therefore, when welding begins using method 400, system 600 may require several seconds to reach a stable state for optimal welding. In some embodiments, the amount of time elapsed from the initial application of DCEP (at the start of time period 502) to the system 600 reaching a stable state (after time period 505) can be between approximately 4 and 8 seconds. For example, in some embodiments, when welding begins using a conventional DCEP process, the system may require approximately 6 seconds to reach a stable state for optimal welding. Furthermore, the force of the electrode 604, still solid after the arc flash, impacting the workpiece 602 can cause the electrode 604 to bend, and in embodiments where system 600 is an LSO SAW system, the bent electrode 604 may contact the ceramic extension, potentially damaging or destroying it.

[0069] Therefore, it is desirable and necessary to improve the arc initiation characteristics of welding systems.

[0070] To improve the arc initiation characteristics of a welding system, an arc can be established by first applying DC electrode negative (DCEN) to the electrode and then switching to DCEP. (As mentioned above...) Figures 4-6G As described, when the power supply operates in DCEP mode, the electrode is connected to the positive terminal, the workpiece is connected to the negative terminal, and the applied current flows from the workpiece into the electrode. In contrast, when the system operates in DCEN mode, the electrode is connected to the negative terminal, the workpiece is connected to the positive terminal, and the current flows from the electrode into the workpiece. Figure 7 This is a flowchart illustrating method 700 for operating a welding system including the DCEN arc initiation process.Figure 8 It shows the voltage, current, and WFS curves of the welding system before, during, and after Method 700, and... Figures 9A-9G This refers to images of electrode 904 of system 900 on workpiece 902 at various time points during method 700. In some embodiments, system 900 may include one or more processors or controllers communicatively coupled to a welding power supply and a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium stores instructions that, when executed by one or more processors or controllers, cause one or more processors to perform various welding methods, including method 700. In some embodiments, system 900 may be an LSO SAW system, generally similar to the above-described combination. Figure 3B Electrode assembly 300B is shown and described. In some embodiments, including the illustrated embodiment, system 900 is a single-arc system comprising a single electrode 904. However, in other embodiments, system 900 may be a multi-arc system comprising a plurality of electrodes 904 positioned adjacent to each other, and each electrode being configured to generate an arc 916 during the welding process.

[0071] like Figure 9A As shown, at step 702 of method 700, the welding process is initiated by embedding the tip of electrode 904 in flux 914 and positioning the tip 906 above workpiece 902 without applying a load between electrode 904 and workpiece 902. In this process... Figure 8 The time period 801 represents the time during which the voltage measured by the welding system is the open-circuit voltage. In some embodiments, the open-circuit voltage may be approximately 70 volts. However, because no load is applied between the electrode and the workpiece during time period 801, typically no current flows between electrode 904 and workpiece 902. Additionally, no arc has been established, therefore WFS is 0 ipm.

[0072] At step 704, a DC electrode negative (DCEN) is applied to electrode 904. Figure 9B As shown, applying DCEN to electrode 904 causes an arc 916 to form between electrode 904 and workpiece 902, which allows current to flow from electrode 904 into workpiece 902. Figure 8 The time period 802 indicates a period during which the voltage is negative, and in some embodiments, it can be between approximately -20V and approximately -60V. For example, in some embodiments, once DCEN is applied, the voltage between workpiece 902 and electrode 904 can be approximately -20V, approximately -30V, approximately -40V, approximately -50V, approximately -60V, between -30V and -50V, between -40V and -60V, or a value within a range defined by any of these values.

[0073] The current may also be negative during time period 802, and in some embodiments, it may be between approximately -100 A and approximately -1200 A. For example, in some embodiments, the current may be approximately -100 A, approximately -200 A, approximately -300 A, approximately -400 A, approximately -500 A, approximately -600 A, approximately -700 A, approximately -800 A, approximately -900 A, approximately -1000 A, approximately -1100 A, approximately -1200 A, or a value within a range defined by any of these values. In some embodiments, the current fluctuates immediately after arc 916 is established (e.g., during the initial few hundred ms of time period 802), but may stabilize shortly after arc 916 is established. For example, in some embodiments, the current may initially fluctuate between approximately -100 A and approximately -1200 A, but may stabilize at approximately -750 A after approximately 200 ms. In an embodiment where system 900 is a multi-arc system with multiple electrodes 904, the multiple electrodes 904 can be connected in parallel such that the total current flowing between the electrodes 904 and the workpiece 902 is the sum of the currents of each electrode 904.

[0074] The heat emitted by the electric arc 916 melts the surrounding metal (including the metal at the tip 906 and the workpiece metal near the arc 916). As the tip 906 melts, it falls onto the workpiece 902 and mixes with the molten metal from the workpiece 902 to form a weld pool 922. Shortly after the arc 916 is formed and the tip 906 melts, the system 900 increases the weld pool space (WFS) to account for the increased distance between the workpiece 902 and the electrode 904 (due to the melting of the tip 906). In some embodiments, the WFS of the system during time period 802 is between 75 ipm and 200 ipm. For example, in some embodiments, the WFS of the system during time period 802 may be approximately 110 ipm.

[0075] During time period 802, the current flowing through the electrode causes the portion of electrode 904 between the conductive tip 910 and the workpiece 902 to heat up (via resistance heating), and portion 936 of electrode 904 begins to emit light. Figure 9B As shown, the light-emitting portion 936 is initially very small and extends only a short distance away from the tip 906. However, as Figure 9C As shown, the luminescent portion 936 can extend to directly below the top of the flux pile 914 for a little more than half of the time period 802, as... Figure 9D As shown, it can extend above flux pile 914 at the end of time period 802.

[0076] During time period 802, as system 900 continues to apply DCEN to electrode 904, electrode 904 continues to preheat at a steady rate. Voltage, current, and WFS remain essentially stable, which can significantly improve the weld bead shape formed during time period 802.

[0077] At step 706, DCEP is applied to electrode 904. In this process... Figure 8 The time period 803 represents the period during which voltage and current are positive, and current flows from workpiece 902 into electrode 904. In some embodiments, during time period 803, the current can be between 20V and 60V, and the current can be between 200A and 1000A. For example, in some embodiments, during time period 903, the voltage can be about 40V, and the current can be about 650A. WFS can also remain relatively constant during time period 903, and in some embodiments, it can be substantially the same as the WFS during time period 802. For example, in some embodiments, during time period 803, the WFS can be between 75ipm and 150ipm. Additionally, electrode 904 can be kept sufficiently preheated for optimal welding during time period 803. For example, as Figures 9E-9G As shown, the light-emitting portion 936 can extend above the flux pile 914 throughout the entire time period 803, and the length of the light-emitting portion 936 can remain relatively constant during this time. At this time, the welding system 900 operates in a completely steady state, and the voltage, current, WFS, and temperature of the electrode 904 remain constant.

[0078] In some embodiments, system 900 is configured to switch from applying DCEN to applying DCEP once electrode 904 has been sufficiently preheated. However, automatically determining whether electrode 904 has been sufficiently preheated can be challenging for system 900. Therefore, in some embodiments, system 900 may be configured to switch from applying DCEN to electrode 904 to applying DCEP after a predetermined amount of time. For example, in some embodiments, system 900 is configured to apply DCEN for a duration between 0.5 and 7 seconds, 0.5 and 1 second, 1 and 2 seconds, 2 and 3 seconds, 3 and 4 seconds, 4 and 5 seconds, 5 and 6 seconds, 6 and 7 seconds, 2 and 6 seconds, less than 5 seconds, less than 3 seconds, less than 2 seconds, or a value within a range determined by any of these values, and then switch to applying DCEP to electrode 904. In some embodiments, system 900 is configured to determine the stability of arc 916 and switch to applying DCEP once arc 916 is determined to be sufficiently stable. For example, in some embodiments, system 900 is configured to switch to applying DCEP once it is determined that the voltage of arc 916 remains within a given percentage of a predetermined voltage for a given amount of time, such as 20%, 15%, 10%, 5%, 2%, 1% of a value within a range defined by -50V, -45V, -40V, -35V, -30V, or any of these values, for a duration between 0.5 seconds and 4 seconds, between 0.5 seconds and 1 second, between 1 second and 2 seconds, between 2 seconds and 3 seconds, between 3 seconds and 4 seconds, or any of these values. In some embodiments, the amount of time for which system 900 applies DCEN before switching to applying DCEP can be determined experimentally and can be based on specific conditions and materials used during the welding process, such as the composition of workpiece 902, electrode 904 and / or flux 914, the capability of welding system 900, and / or desired welding parameters (e.g., voltage, current, travel speed, etc.). In some embodiments, the amount of time for applying DCEN before switching to applying DCEP can be pre-programmed into system 900 and / or can be set by the operator of welding system 900.

[0079] As mentioned above Figures 4-6GThe discussed scenario involves current flowing from the workpiece to the electrodes when the system operates in DCEP mode. When this occurs, most of the heat generated by the arc is produced at the workpiece. For example, in some embodiments, when DCEP is applied, at least two-thirds of the arc heat is generated in the workpiece, while the remaining arc heat is generated in the electrodes. In contrast, when DCEN is applied to both the electrodes and the workpiece, current flows from the electrodes to the workpiece, and most of the heat generated by the arc is produced in the electrodes rather than in the workpiece. For example, in some embodiments, when DCEN is applied, at least two-thirds of the arc heat is generated in the electrodes rather than in the workpiece.

[0080] By using DCEN to initiate the welding process and establish an arc between the electrode and the workpiece, the voltage, current, WFS, and electrode temperature remain more stable and less prone to fluctuations compared to using DCEP. This increased stability prevents arc flashes and hard short circuits between the welding electrode and the workpiece. Furthermore, the greater amount of heat generated in the electrode when DCEN is applied allows for faster and more stable electrode preheating than with DCEP, preventing premature melting of the electrode wire and thus avoiding system overcalibration that could lead to unmelted wire striking the workpiece. Therefore, the increased stability also reduces the likelihood of ceramic extension breakage due to electrode wire contact. Additionally, using DCEN to initiate the welding process allows the welding electrode to preheat sufficiently and reach a steady state faster than with DCEP. For example, as described above... Figures 4-6G The system discussed above, when starting soldering using DCEP, may take between 4 and 8 seconds to reach a stable soldering state. In contrast, when starting soldering using DCEN, the system may take approximately 2 seconds to reach a stable soldering state. This means that reaching a stable state is approximately 2-4 times faster than when starting soldering using DCEP.

[0081] In some embodiments, the welding system can operate in a constant current (CC) mode, in which the system adjusts the voltage and WFS to maintain the current at preset values. For example, in the illustrated embodiment, the welding system operates in CC mode, and the current is preset to -750A during the arc initiation process and preset to 750A during the steady-state mode, while the voltage and WFS fluctuate to maintain those currents. However, in other embodiments, the welding system can operate in a constant voltage (CV) mode, wherein the system adjusts the current to maintain the voltage (and WFS) at preset values. In some embodiments, the system may be able to switch between CC and CV modes. For example, in some embodiments, the system may be configured to operate in CC or CV mode during the arc initiation process and then switch to the other mode during the steady-state process.

[0082] existFigures 4-6G In the illustrated embodiment, system 600 applies DCEP to electrode 604 after applying DCEN to initiate welding. However, in other embodiments, system 600 may apply alternating current to the electrode after applying DCEN to initiate welding.

[0083] Asymmetric AC welding initiation

[0084] In the previously described embodiments, welding is initiated using a direct current welding technique (DCEN), and then a second direct current welding technique (DCEP) is used during steady-state welding conditions. However, in other embodiments, an alternating current (AC) welding process can be used during both welding initiation and steady-state welding. In AC welding, the welding power source periodically reverses the current flow, causing the welding system to oscillate rapidly between DCEP and DCEN. In conventional AC welding processes, symmetrical AC is used for both welding initiation and steady-state welding. In symmetrical AC, the positive and negative portions of the AC waveform are mirror images of each other and balanced, such that the root mean square (RMS) voltage and length of the positive and negative half-cycles are the same. However, using symmetrical AC to initiate welding can result in poor arc quality during the arc initiation process because the welding electrodes are not adequately preheated. Therefore, improved AC welding initiation processes are desired, which produce improved arc initiation characteristics.

[0085] To improve arc initiation characteristics during AC welding startup, an arc can be established by first applying an asymmetrical AC with DCEN bias, followed by a symmetrical AC. An asymmetrical AC refers to an AC waveform where the positive and negative portions are not mirror images of each other, and an imbalance exists between the positive and negative half-cycles due to differences in the RMS voltage and / or length of the positive and negative half-cycles. Therefore, an asymmetrical AC with DCEN bias is one where the RMS voltage and / or length of the negative half-cycle is greater than that of the positive half-cycle. Figure 10 It is a flowchart illustrating a method 1000 for operating a welding system including an asymmetric AC arc initiation process with DCEN bias, and Figure 11 This is a graph showing the voltage and current of the welding system before, during, and after method 1000. In some embodiments, the welding system may include one or more processors or controllers communicatively coupled to a welding power supply and a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium stores instructions that, when executed by one or more processors or controllers, cause one or more processors to perform various welding methods, including method 1000.

[0086] In step 1002 of this method, the welding process is initiated by burying the tip of the electrode above the workpiece without applying a load between the electrode and the workpiece. Figure 11The time period 1101 indicates that the voltage measured by the welding system is the open-circuit voltage, but since no load has been applied, no current flows between the electrode and the workpiece.

[0087] At step 1004, an asymmetric AC biased by DCEN is applied to the electrode, which causes an arc to form between the electrode and the workpiece and allows current to flow between the electrode and the workpiece. In this process... Figure 11 The time period 1102 represents the time period during which voltage and current oscillate between the negative half-cycle 1104A and the positive half-cycle 1104B. However, because the applied load is DC-EN biased, the duration of the negative half-cycle 1104A is longer than the duration of the positive half-cycle 1104B. In some embodiments, the negative half-cycle 1104A is 2 to 4 times longer than the positive half-cycle 1104B. However, in other embodiments, the negative half-cycle 1104A may be longer than the positive half-cycle by a different amount. For example, in some embodiments, the negative half-cycle is 1.5 to 10 times the length of the positive half-cycle 1104B, 1.5 to 10 times the length of the positive half-cycle 1104B, 5 to 10 times the length of the positive half-cycle 1104B, 2 to 4 times the length of the positive half-cycle 1104B, 4 to 6 times the length of the positive half-cycle 1104B, 6 to 10 times the length of the positive half-cycle 1104B, or a value within a range defined by any of these values. Because the negative half-cycle 1104A is longer than the positive half-cycle 1104B, most of each full AC waveform is negative, and the system applies DCEN for most of the time period 1102. For example, in some embodiments, the asymmetric AC is DCEN biased such that 70%–80% of it is DCEN and 20%–30% is DCEP. However, in other embodiments, the DCEN-biased asymmetric AC can be biased by different amounts. For example, in some embodiments, the asymmetric AC is DCEN biased such that it is 60%-90% DCEN and 10%-40% DCEP, 60%-70% DCEN and 30%-40% DCEP, 65%-85% DCEN and 15%-35% DCEP, or a value within a range defined by any of these ranges.

[0088] In some embodiments, such as Figure 11 In the illustrated embodiment, the lengths of the negative half-cycle 1104A and the positive half-cycle 1104B remain constant throughout the time period 1102. However, in other embodiments, the length of one or both of the negative half-cycle 1104A and the positive half-cycle 1104B may vary during the time period 1102.

[0089] In some embodiments, such as Figure 11In the embodiment shown, the asymmetric AC with DCEN bias is configured such that the length of the negative half-cycle 1104A is longer than the length of the positive half-cycle 1104B, but the RMS voltages of the negative half-cycle 1104A and the positive half-cycle 1104B are the same (or within 10% of each other). However, in other embodiments, the RMS voltages of the negative half-cycle 1104A and the positive half-cycle 1104B may be different. For example, in some embodiments, the RMS voltage of the negative half-cycle 1104A may be greater than the RMS voltage of the positive half-cycle 1104B. In some embodiments, such as Figure 11 In the illustrated embodiment, the RMS voltages of the negative half-cycle 1104A and the positive half-cycle 1104B can remain constant throughout the time period 1102. In other embodiments, the RMS voltages of one or both of the negative and positive half-cycles can vary during the time period 1102.

[0090] At step 1106, symmetrical AC is applied to the electrode. In this process... Figure 10 During the time period 1003, the RMS voltage and length of the negative half-cycle 1105A are approximately the same as those of the positive half-cycle 1105B. In some embodiments, the RMS voltages of the negative half-cycle 1105A and positive half-cycle 1105B of the symmetrical AC are the same as the RMS voltages of the negative half-cycle 1104A and positive half-cycle 1104B of the DCEN-biased asymmetrical AC. In some embodiments, the length of the negative half-cycle 1104A of the DCEN-biased asymmetrical AC is greater than the length of the negative half-cycle 1105A of the symmetrical AC. In some embodiments, the length of the positive half-cycle 1104B of the DCEN-biased asymmetrical AC is less than the length of the positive half-cycle 1105B of the symmetrical AC.

[0091] In some embodiments, the system is configured to switch from applying asymmetric AC with DCEN bias once the electrode has been sufficiently preheated. However, automatically determining whether the electrode has been sufficiently preheated can be challenging. Therefore, in some embodiments, the system may be configured to switch from applying asymmetric AC with DCEN bias after a predetermined amount of time. For example, in some embodiments, the system is configured to apply asymmetric AC with DCEN bias for a period between 0.5 and 7 seconds, 0.5 and 1 second, 1 and 2 seconds, 2 and 3 seconds, 3 and 4 seconds, 4 and 5 seconds, 5 and 6 seconds, 6 and 7 seconds, 2 and 6 seconds, less than 5 seconds, less than 3 seconds, less than 2 seconds, or a value within any of these ranges, and then switch to applying symmetric AC. In some embodiments, the system is configured to determine the stability of the arc between the electrode and the workpiece, and switch to applying symmetric AC once the arc is determined to be sufficiently stable. In some embodiments, the amount of time the system applies the asymmetric AC with DCEN bias before switching to applying the symmetric AC can be determined experimentally and can be based on specific conditions and materials used during the welding process, such as the composition of the workpiece, electrodes, and / or flux, the capabilities of the welding system, and / or desired welding parameters (e.g., voltage, current, travel speed, etc.). In some embodiments, the amount of time the system applies the asymmetric AC with DCEN bias before switching to applying the symmetric AC can be pre-programmed into the system and / or can be set by the operator of the welding system.

[0092] Unless the context explicitly requires it, throughout the specification and claims, the terms “comprise,” “comprising,” “include,” “including,” etc., shall be interpreted in an inclusive sense, rather than an exclusive or exhaustive one; that is, in the sense of “including but not limited to.” As commonly used herein, the term “connected” refers to two or more elements that can be directly connected or connected via one or more intermediate elements. Similarly, as commonly used herein, the term “connected” refers to two or more elements that can be directly connected or connected via one or more intermediate elements. Additionally, when used in this application, the terms “here,” “above,” “below,” and similar terms shall refer to the entire application and not any particular part of it. Where the context permits, the use of singular or plural terms in the above specific embodiments may also include either the plural or the singular, respectively. The term “or” refers to a list of two or more entries, and covers all of the following interpretations: any entry in the list, all entries in the list, and any combination of entries in the list.

[0093] Furthermore, unless otherwise specifically stated or otherwise understood within the context in which they are used, the conditional language used herein (among others, such as “can,” “could,” “might,” “may,” “eg,” “for example,” “such as,” etc.) is generally intended to convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not include certain features, elements, and / or steps. Therefore, this conditional language is not generally intended to imply that such features, elements, and / or statements are necessary in any one or more embodiments, or whether such features, elements, and / or statements are included in any particular embodiment or are to be performed in any particular embodiment.

[0094] While certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of this disclosure. In fact, the novel apparatuses, methods, and systems described herein can be implemented in a variety of other forms; furthermore, various omissions, substitutions, and changes can be made to the form of the methods and systems described herein without departing from the spirit of this disclosure. For example, although blocks are presented in a given arrangement, alternative embodiments may perform similar functions with different components and / or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these blocks can be implemented in a variety of different ways. Any suitable combination of elements and functions of the different embodiments described above can be combined to provide further embodiments. The various features and processes described above can be implemented independently of each other or combined in various ways. All possible combinations and sub-combinations of the features of this disclosure are intended to fall within the scope of this disclosure.

Claims

1. A welding system, the welding system comprising: Welding power source; as well as An electrode assembly, operatively connected to the welding power source and the electrode, The welding power source is configured to apply DC electrode negative (DCEN) to the electrode using the electrode assembly to establish an arc between the electrode and the workpiece, and to apply DC electrode positive (DCEP) or alternating current (AC) to the electrode after the arc is established.

2. The welding system as claimed in claim 1, wherein, The electrode assembly includes a conductive tip, and wherein the electrode assembly is configured to provide the DCEN to the electrode using the conductive tip.

3. The welding system as claimed in claim 1, wherein, The welding system includes a submerged arc welding (SAW) system.

4. The welding system as claimed in claim 3, wherein, The welding system is configured such that during welding, the ratio between the electrical extension distance and the diameter of the electrode exceeds 15.

5. The welding system as claimed in claim 1, wherein, The welding power source is configured to apply the DCEP to the electrode within 5 seconds after the DCEN is applied to the electrode.

6. The welding system as claimed in claim 1, wherein, The welding power source is configured to apply the AC to the electrode within 5 seconds after the DCEN is applied to the electrode.

7. The welding system as claimed in claim 1, wherein, The DCEN has a voltage between approximately -20V and -60V and a current between approximately -100A and approximately -1200A.

8. A method of operating a welding system, the method comprising: Apply DC electrode negative (DCEN) to the electrode to establish an electric arc between the electrode and the workpiece; as well as After applying DCEN to the electrode, apply DC electrode positive (DCEP) or AC current to the electrode.

9. The method of claim 8, wherein, Applying the DCEP or AC to the electrode includes automatically applying the DCEP or AC to the electrode without receiving any additional input from the operator of the welding system.

10. The method of claim 8, wherein, Applying the DCEP or AC to the electrode includes applying the DCEP to the electrode within 5 seconds after applying the DCEN to the electrode.

11. The method of claim 10, wherein, Applying the DCEP or AC to the electrode includes applying the AC to the electrode within 5 seconds after applying the DCEN to the electrode.

12. The method of claim 8, wherein, When the DCEN is applied to the electrode, the ratio between the electrical extension distance and the diameter of the electrode exceeds 15.

13. The method of claim 8, wherein, The voltage of DCEN is between approximately -20V and -60V.

14. The method of claim 8, wherein, The current of the DCEN is between approximately -100A and approximately -1200A.

15. A method of operating a welding system, the method comprising: An asymmetrical alternating current (AC) with a DC electrode negative (DCEN) bias is applied to the electrode to establish an electric arc between the electrode and the workpiece. as well as After applying the DCEN bias with asymmetric AC to the electrode, a symmetric AC is applied to the electrode.

16. The method of claim 15, wherein, The asymmetric AC of the DCEN bias includes at least one negative half-cycle and at least one positive half-cycle, wherein the at least one negative half-cycle is longer than the at least one positive half-cycle.

17. The method of claim 16, wherein, The first root mean square (RMS) voltage of the at least one negative half-cycle is within 10% of the second RMS voltage of the at least one positive half-cycle.

18. The method of claim 16, wherein, The at least one negative half-cycle includes a first negative half-cycle, wherein the symmetrical AC includes a second negative half-cycle, and wherein the first negative half-cycle is longer than the second negative half-cycle.

19. The method of claim 15, wherein, Applying the symmetrical AC to the electrode includes applying the symmetrical AC to the electrode within 5 seconds after applying the asymmetrical AC with the DCEN bias to the electrode.

20. The method of claim 19, wherein, Applying the symmetrical AC to the electrode includes applying the symmetrical AC to the electrode within 3 seconds after applying the asymmetrical AC with the DCEN bias to the electrode.

21. The method of claim 15, wherein, When the asymmetric AC of the DCEN bias is applied to the electrode, the ratio between the electrical extension distance and the diameter of the electrode exceeds 15.

22. A non-transitory computer-readable storage medium storing instructions, said instructions causing the one or more processors, when executed by a system of one or more processors, to: Applying a direct current electrode electrode polarity (DCEN) to the electrodes of the welding system to establish an arc between the electrodes and the workpiece; and After applying DCEN to the electrode, apply DC electrode positive (DCEP) or AC current to the electrode.

23. The non-transitory computer-readable storage medium of claim 22, wherein, When executed by the system, which is powered by one or more processors, the instructions cause the one or more processors to automatically apply the DCEP or AC to the electrode without receiving any additional input from the operator of the welding system.

24. The non-transitory computer-readable storage medium of claim 22, wherein, When the instruction is executed by the system, which is composed of one or more processors, the one or more processors cause the one or more processors to apply the DCEP to the electrode within 5 seconds after the DCEN is applied to the electrode.

25. The non-transitory computer-readable storage medium of claim 22, wherein, When the instruction is executed by the system of one or more processors, the one or more processors cause the one or more processors to apply the AC to the electrode within 5 seconds after applying the DCEN to the electrode.

26. A non-transitory computer-readable storage medium storing instructions, said instructions causing the one or more processors, when executed by a system of one or more processors, to: An asymmetrical alternating current (AC) with a DC electrode negative (DCEN) bias is applied to the electrodes of the welding system to establish an arc between the electrodes and the workpiece; and After applying the DCEN bias with asymmetric AC to the electrode, a symmetric AC is applied to the electrode.

27. The non-transitory computer-readable storage medium of claim 26, wherein, When executed by the system of one or more processors, the instructions cause the one or more processors to automatically apply the symmetrical AC to the electrode without receiving any additional input from the operator of the welding system.

28. The non-transitory computer-readable storage medium of claim 26, wherein, When the instruction is executed by the system of one or more processors, the one or more processors cause the one or more processors to apply the symmetrical AC to the electrode within 5 seconds after applying the asymmetric AC of the DCEN bias to the electrode.

29. The non-transitory computer-readable storage medium of claim 26, wherein, The asymmetric AC of the DCEN bias includes at least one negative half-cycle and at least one positive half-cycle, wherein the at least one negative half-cycle is longer than the at least one positive half-cycle.

30. The non-transitory computer-readable storage medium of claim 29, wherein, The first root mean square (RMS) voltage of the at least one negative half-cycle is within 10% of the second RMS voltage of the at least one positive half-cycle.

31. The non-transitory computer-readable storage medium as claimed in claim 29, wherein, The at least one negative half-cycle includes a first negative half-cycle, wherein the symmetrical AC includes a second negative half-cycle, and wherein the first negative half-cycle is longer than the second negative half-cycle.

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