MXPA00012301A

MXPA00012301A - Gas-metal-arc welding contact tip.

Info

Publication number: MXPA00012301A
Application number: MXPA00012301A
Authority: MX
Inventors: Julio Villafuerte
Original assignee: Tregaskiss Ltd
Priority date: 1998-06-18
Filing date: 1999-06-16
Publication date: 2002-04-24
Also published as: WO1999065635A1; CA2334118A1

Abstract

A contact tip for use in an electric welding torch includes an electrically conductive component or tube including a mounting end and a distal contact end extending along a longitudinal wire feed axis. The conductive component is made of copper, copper alloys or mixtures of copper powder and conductive ceramic materials synthesized by powder metallurgy methods. The size of the conductive component has been enlarged to minimize operating temperatures. The mounting end of the conductive component includes a high heat transfer mounting surface. The conductive component includes a through-bore having a large diameter portion extending from the mounting end and a small diameter portion, sized for guiding the welding wire, proximate to the distal end and extending along the wire feed axis. The outlet of the small diameter portion has no chamber but clean right-angle corners around the outlet. An elongated high temperature resistant, ceramic insert is coaxially mounted in the large diameter portion of the electrically conductive component and includes a corresponding through-bore also sized for guiding the welding wire. The insert through-bore and conductive component small diameter portion define a wire feed passageway for supporting the welding wire.

Description

CONTACT NOZZLE FOR METAL ARC WELDING IN GASEOUS ATMOSPHERE Cross Reference to Related Requests. This application claims the benefits of the U.S. Provisional Application. No. 60 / 089,752, filed on June 18, 1998.

Field of the Invention This invention relates to torches for electric welding torches, and more particularly, to a contact nozzle that is formed of copper mixtures and ceramic-conductive powders that uses powder metallurgy processes, which can have a non-conductive ceramic insert in the nozzle through which a continuous metal wire electrode with sufficient current is passed and charged to transform the filler metal onto the workpiece or piece to be welded .

BACKGROUND OF THE INVENTION In a conventional welding operation, a filler metal wire or a ref: 125563 welding wire is continuously fed, and is charged through a contact nozzle of a welding torch having a welding torch. wire feed opening with a receiving end, through which the supply wire enters the contact nozzle, and has a contact end through which a short length of the supply wire protrudes to be present in a convenient position next to the welding zone. An electric arc is formed between the charged end of the wire and the charged workpiece, oppositely, which provides heat to form a weld pool. In many methods and apparatus, a welding machine further includes a nozzle for blowing an inert gas or an active gas over the weld pool to keep it under a controlled atmosphere. This prevents unwanted reactions of the molten metal with the surrounding air resulting in poor weld quality. In welding methods of this general category, the welding wire is unwound from a spool and fed automatically to the welding assembly as the welding wire is consumed.

The welding wire has a behavior in the coil, which curves by nature, as the wire is formed and rolled on the reel. It is desirable to maintain good electrical continuity between the wire and the contact nozzle. Control rolls are often used to feed the wire off the spool and into the welding torch. The wire has to move smoothly through the wire feed opening, without shaking or vibration, so that a precise and high-quality welding is achieved satisfactorily. Welding methods of this type, measure the efficiency of process by means of the percentage of arc time in operation during production. Manual, mechanized, automatic systems or robotic systems that use these welding methods often provide efficiencies of less than 50%. The time during which a worker or machine is not welding is attributed, in general, to the operational difficulty of the welding apparatus, which often refers to the performance of the contact nozzle.

Contact nozzles are traditionally manufactured as cylindrical tubes made of pure copper or high copper alloys, which have a high electrical and thermal conductivity. Under normal service conditions, contact nozzles can be exposed to operating temperatures above 400 ° C (752 ° F). The operating temperature is critical to determine the performance of the contact nozzles. Higher temperatures degrade material properties and accelerate contact nozzle failures. The heat is transferred, mainly by means of conduction from the contact nozzle to the welding torch. Under normal service conditions, the contact nozzles are subject to a systematic accumulation of waste carried by the wire surface into the wire feed opening of the contact nozzle. These residues burn during the welding operation, which leaves non-conductive refractory byproducts. The wire feed openings of the contact nozzle are manufactured with a dimensional tolerance that minimizes friction with the passage of the welding wire. At the contact nozzles, actual electrical contact is only possible at discrete points along the wire feed opening, and depends on the thickness of the wire feed opening and the emptying in the welding wire. The presence of non-conductive metal inside the wire feed opening causes an electrical contact that becomes unstable, which results in faults in the contact nozzle. Also, the presence of additional material inside the wire feeding opening increases the likelihood of acoramiento or obstruction due to repetitive expansion and contraction cycles, which can prevent regular feeding that causes bad welding initiations or return of flame, a condition in which the wire melts to the end of the contact nozzle. In welding methods of this type, there are sporadic bursts of liquid metal that originate from regular routings of the molten wire. / bath bridge of molten metal or by regular disturbances to the molten metal bath surface.

Bursts of this nature result in liquid metal being expelled, from a regular basis, from the weld zone as small droplets or as a splash of molten metal which clumps together and collects on top of the contact end of the nozzle. contact inside the wire feed opening around the outlet hole. The excessive accumulation of molten metal spatter on the front of the contact nozzle creates a metal bridge between the moving welding wire and the contact nozzle, which eventually causes power fluctuations and can lead to the process to an interruption. Also the accumulation of molten metal spatter in and around the outlet opening of the wire feed opening causes clogging of the supply wire leading to similar feeding problems. The feeding instability leads to failures in the contact nozzle due to flame return or due to bad welding starts. In addition, the contact wire feed opening is subject to wear damage. by abrasion or by electrical erosion that causes sliding friction between the loaded surface of the wire feed opening and the moving welding wire. Excessive unidirectional wear of the outlet opening of the wire feed opening or the "key hole" causes the wire to fail the reference target of the seam line resulting in poorly placed welds. This is critical for robotic welding, in which program forecasts are not designed to compensate for such variation origins. It is known in the art, which relates to continuous feeding welding torches, to use replaceable contact nozzles that have an insert, which is placed at the distal end of the contact nozzle next to the workpiece. Typically, these inserts are made of a stronger material than the copper in the nozzle. It is intended that these inserts extend the life of the contact nozzle by reducing wear as the welding wire is fed through the nozzle. However, these inserts, and other inserts that are placed in this manner, inhibit the transfer of current along with the arc where it is most efficient for arc stability and for the strength of the weld. Copper-carbon "alloys" have been suggested to improve lubricity and to reduce the coefficient of expansion of the wire feed opening of the contact nozzle. This prior art also refers to copper-carbon "alloys" that provide high electrical conductivity as they have low thermal conductivity and a high melting point. This technique refers to the manufacture of cylindrical contact nozzles by means of the injection molding process or by means of traditional machining. Carbon-carbon "alloys" are not possible because carbon is immiscible in copper (that is, carbon can not be mixed in copper). However, copper and carbon can be integrated into a single material by means of powder metallurgy methods, which involve the injection molding process under pressure, followed by the controlled sintering process. Carbon results in many different crystallographic groups that include diamond, graphite, amorphous carbons and crushing balls (ie, "soccer balls" type carbon configurations). Each of these groups has contrasting properties, both mechanical and physical. Furthermore, within each specific group the mechanical and physical properties depend on the level of impurities and the orientation of the crystalline structure with respect to the external forces applied. The diamond presents the highest thermal conductivity and hardness of all materials, as it has the lowest electrical conductivity of all materials. Graphites have a limited electrical and thermal conductivity, which depends on the orientation of the crystal. The good lubricity of the graphite results from the hexagonal arrangement of layer planes. Each of the layer planes is free to slide or slide by one another. Amorphous carbons have smaller monoplanes that are stacked in static turbo mounds, which. They have a variety of properties that include a lower coefficient of expansion with a variety of thermal and electrical conductivities. Trituration balls are special configurations of carbon "soccer balls" that have special electrical properties and other properties. The powder metallurgy (P / M) materials have a certain percentage of undesirable porosity, which is inherent in the P / M process. A challenge of any P / M process is to minimize the porosity, so that the density of the P / M material is as close as possible to its theoretical density.

Summary of the Invention. The present invention provides an improved contact nozzle for metal arc welding in gas atmosphere, where a continuous wire of a filler metal or a welding wire is passed through a contact nozzle that is electrically charged, which -passes its charge to the welding wire as the work piece is loaded, in opposite manner. As will be described below, in a more complete manner, the contact nozzle that minimizes friction in its wire feed opening, shows a high thermal diffusivity, has a high electrical conductivity, provides a permanent anti-splash protection molten metal, stabilizes ^ the position of the current transfer point (insert), minimizes operating temperatures and eliminates excessive wear of the opening wire feed. More specifically, the present invention provides a contact nozzle for use in a welding torch which guides a welding wire to a workpiece and transfers the current welding from a torch to the welding wire. The contact nozzle comprises a conductive component, electrically, which includes a mounting end and a distal contact end extending along an axis longitudinal wire feed. The conductive component ff includes a bore-through or wire feed opening which may have a larger diameter portion, which extends from a mounting, receiving end; of wire, and that can have a The smaller diameter portion is dimensioned to guide the welding wire and to transfer the welding current, close to the distal end and extending along the wire feed axis. In one embodiment of the invention, an elongate ceramic insert resistant to high temperatures, including a corresponding bore-hole that is dimensioned to guide the welding wire, is mounted coaxially in the larger diameter portion of the electrical conductive component. In that place, the drill-through of the insert and the smaller diameter part of the conductive component define a gangway or runner to support the welding wire. Preferably, the smaller diameter portion of the conductive component proximate to its distal end extends less than 100% of the length of the drill-through that extends through the nozzle. The smaller diameter portion of the conductive component has a smaller tolerance between the size of the wire and the size of the bore, so that the actual electrical contact is improved. One end of the drill-through of the insert can be tilted. This inclined end is the end that is mounted adjacent the mounting end of the conductive component to facilitate insertion. of the welding wire through the insert part of the contact nozzle. Preferably, the inclined end includes a side wall which is generally positioned at an angle of about 30 degrees with respect to the longitudinal axis of the wire feed. The outer geometry of the nozzle front-end comprises an elongated outer diameter at the front end, which increases the capacity of the nozzle to propagate heat, and thus lowers the operating temperatures. Another characteristic of the front-end geometry is the lack of a bevel in the outlet part of the wire feed opening. An edge at the right angle corner provides an increase in current transfer, low operating temperatures and prevents micro splashes from entering the wire feed opening. Another characteristic of the end-face geometry comprises an elongated radius of curvature and a bulb shape, which maximizes the mass of metal at the front end by lowering the operating temperatures in the wire feed opening. Another characteristic of the front-end may be a coating of a diamond-like carbon-resistant protective film similar to diamond, which increases the ability to reject the splash of accumulated molten metal. The mounting end of the contact nozzle includes a connector that provides high heat transfer. In one embodiment, the mounting end comprises a frusto-conical surface and a taper-tapered thread arrangement that increases the ability to conduct heat transfer out of the contact nozzle. In one embodiment of the invention, the conductive component comprises copper or an alloy with a high copper content. The invention also comprises a conductive component made of a composite material, consisting of high purity sintered copper powders and conductive ceramic particles. Conductive ceramic particles include special crystalline forms of carbon, which in turn include, but are not limited to, graphite. The graphite particles oriented, in particular, in sufficient density increase the anti-spatter properties of the material and increase the lubricity in the wire feed opening. The copper-graphite P / M compounds have a lower electrical and thermal conductivity than pure copper. Therefore, excessive amounts of graphite (above the %) could impede the main function of the contact nozzle and lead to catastrophic failures. The copper-graphite P / M compounds have to have a density higher than 80% of the ideal densities of their solid counterparts. In another embodiment of the invention, the conductive component could comprise a cylindrical insert made of ceramic material including, but not limited to, aluminum oxide, boron carbide, silicon carbide, silicon oxide, aluminum nitrate, oxide of zirconium, boron nitrate or any mixture of these substances. The ceramic insert limits the transfer to the front end of the contact nozzle, which minimizes the presence of flame return.

These and other features and advantages of the invention will be understood in their entirety from the following detailed description of the invention taken together with the accompanying drawings.

Brief Description of the Drawings. In the drawings: Figure 1 is a sectional view of the welding torch contact nozzle constructed in accordance with the present invention; and Figure 2 is a sectional view of the welding torch contact nozzle constructed in accordance with the present invention and includes a ceramic insert at the receiving end of the welding wire.

Detailed Description of the Invention Referring now to Figures 1-2 in detail, the number 10 indicates, generally, a contact nozzle that is used in a continuous feeding welding torch, which is not shown. The contact nozzle 10 guides the feeding of a welding wire, as shown, to a workpiece and transfers the welding current from the torch to the wire. With reference to Figures 1-2, the contact nozzle 10 includes an electrical conductive component 12, which in turn includes a mounting end 14 and a distal contact end 16 extending along the longitudinal axis of the feed of wire 18. The conductive component 12 includes a bore-through 20, which has a larger diameter portion 22 extending from the mounting end 14, and has a smaller diameter portion 24 that is sized to guide the welding wire , close to the distant end 16 and extending along the wire feed axis. The mounting end 14 includes a connector that provides high heat transfer. In the embodiments shown, the mounting extrusion 14 is a frusto-conical surface and a tapered-closure thread arrangement for joining the nozzle 10 to a cooperating surface in the welding torch. The outlet orifice 30 of the smaller diameter part 24 does not contain a bevel or edge around the hole, and generally forms a right angle with no metal debris and no edges inconsistently. As illustrated, the radius of curvature of the front end 32 or the contact end of the nozzle is increased and has a bulb shape that lowers the operating temperatures around the outlet orifice 30 of the smaller diameter part 24. Where is it? Applicable, an elongate ceramic insert resistant to high temperature 26 is mounted, coaxially, on the large diameter 22 of the conductive component 12. The insert 26 includes a bore-through 28 corresponding to the part of smaller diameter 24 and which it is sized to guide the welding wire through that place. The drill-through 28 of the insert and the smaller diameter part 24 of the conductive component define the runway or runner to support the welding wire. In the illustrated embodiments, the conductive component 12 comprises copper, a high copper alloy or sintered copper blends and conductive ceramic particles including composite materials made of copper and certain forms of graphite with a final density higher than 80% . The ceramic insert 26 comprises ceramic material that includes, but, which is not limited to, a substance of aluminum oxide, boron carbide, silicon carbide, silicon oxide, aluminum nitrate, zirconium oxide, boron nitrate or any mixture of these substances. With continuous reference to Figure 1, the smaller diameter portion of the conductive component 12 proximate the distal end 16 of the conductive component has a length in the range of 100% of the length of wire feed opening of the contact nozzle. It is in this part 24 that the welding current is transferred from the welding torch to the welding wire. In Figure 2, the smaller diameter portion 24 of the conductive component 12 proximate the distal end 16 of the conductive component has a length of 50% of the length of the bore-through of the contact nozzle. The limited length of the smaller diameter part 24, provides better arc stability during the transfer of the welding current from the torch to the wire and thereby keeps the nozzle 10 cleaner and reduces the occurrence of flame return. The ceramic insert 26 confines the arc to the smaller diameter portion 24 of the conductive component 12. Preferably, the insert bore 28 of the insert is inclined at one end 31 adjacent to the conductive component or tilts toward the mounting end of the insert. the contact nozzle for facilitating the feeding of the welding wire towards the insert part of the nozzle 10. Preferably, the inclined end 31 is defined by means of a side wall which is generally placed at an angle of about 30 degrees with respect to the longitudinal axis of wire feed. In the illustrated embodiments, an optional thin carbon coating 34 similar to diamond has been applied for a further increase in anti-splash properties of molten metal. Although the invention has been described by reference to specific embodiments, it is to be understood that numerous changes can be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described modalities, but have the full scope defined by the language of the following claims.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Reference Numbers 10 contact nozzle 12 conductive component 14 mounting end 16 remote contact end 18 wire feed shaft drill-through 22 large diameter 24 small diameter part 26 ceramic insert 28 drill-through 30 outlet hole 32 external front corner

Claims

Claims Having described the invention as an antecedent, the content of the following claims is claimed as property: 1. A contact nozzle for use in a welding torch that guides the feeding of a welding wire to a workpiece and transfers the welding current from the torch to the wire, characterized in that it includes: a conductive tube, electrically, having a tube of an outside diameter and includes a mounting end and a remote contact end separated from the mounting end along an axis wire feed that extends longitudinally; the conductive tube includes a bore-hole that extends along an axis, through which the welding wire is fed; the conductive tube comprises copper, a high copper alloy or a conductive composite material consisting of high purity sintered copper powders and conductive ceramic particles; the distal contact end of the conductive tube has a bulbous shape to provide • a permanent splash guard and an outside diameter that exceeds the outer diameter of the conductive tube between the end of the assembly and the distal end, which provides a radius of elongated curvature which maximizes the metal mass at the front end and thereby lowers the operating temperatures at the wire feed opening.
2. The nozzle according to claim 1, characterized in that the bulb-shaped distal end includes an anti-splash coating.
The nozzle according to claim 2, characterized in that the coating comprises a carbon material similar to diamond.
The nozzle according to claim 1, characterized in that the bore-hole has a larger diameter part extending from the mounting end and a lower diameter part stepped down which is sized to guide the welding wire near the far end; and a non-conductive elongate insert resistant to the extreme end.
It includes a drill-through that is smaller than diameter and smaller in diameter. it is dimensioned to guide the wire with which it is mounted, coaxially, in the largest diameter of the tube; In the extreme, the non-conductive insert does not extend until ductive. : iao with the one of the insert and the small end part of the conductive tube define a gangway that is fed by wire to support the • welding surface. at the end of 5.
The nozzle in accordance with section 4, characterized in that the insert with the; ceramic material. extreme 6. 9a nozzle according to step 5, characterized in that the material comprises one of the following substances, with aluminum, boron carbide, silicon carbide, silicon slurry, aluminum nitrate, diamond zirconium oxide. : o- boron.
7. The nozzle in accordance with section 6, characterized in that the part of CONTACT NOZZLE FOR METAL ARC WELDING MACHINE IN GASEOUS ATMOSPHERE. SUMMARY OF THE INVENTION A contact nozzle that is used in an electric welding torch includes an electrical conductive component or a tube that includes a mounting end and a distal contact end that extends along the longitudinal axis of the wire feed. . The conductive component is made of copper, copper alloys or mixtures of copper powder and conductive ceramic materials synthesized by powder metallurgy methods. The size of the conductive component has been lengthened to minimize operating temperatures. The mounting end of the conductive component includes a mounting surface of a high heat transfer. The conductive component includes a bore-hole having a larger diameter portion extending from the mounting end and having a smaller diameter portion that is sized to guide the welding wire, near the far end and extending to. along the wire feed shaft. The exit hole of the smaller diameter part does not have a bevel but has clean corners at right angles around the hole. An elongated high temperature resistant ceramic insert is mounted, coaxially, in the larger diameter portion of the electrical conductive component and includes a corresponding bore-through, which is also sized to guide the welding wire. The drill-through of the insert and the smaller diameter part of the conductive component define a wire feeder or slide to support the welding wire.