MXPA06003042A

MXPA06003042A - Electrode tip

Info

Publication number: MXPA06003042A
Application number: MXPA/A/2006/003042A
Authority: MX
Inventors: M Burt Randall; Sterling Ogborn Jonathan
Original assignee: Lincoln Globalinc*
Priority date: 2005-06-13
Filing date: 2006-03-17
Publication date: 2007-04-20

Abstract

A welding electrode comprising a metal core and a coating material that includes flux compounds is at least partially coated on an outer surface of said metal core. The tip of the welding electrode is beveled and a portion of the beveled tip has an end coating material which includes an electrically-conductive material.

Description

ELECTRODE TIP Field of the Invention The present invention relates to the general field of welding, and more particularly, relates to a rod-type electrode having improved weld bead formation properties.

BACKGROUND OF THE INVENTION In the field of arc welding, the main types of welding processes are gas-metal arc welding with solid (GMAW) or metal core (GMAW-C) welding, arc welding with core gas protected flux (FCAW-G), arc welding with self-protected flux core (FCAW-S), protected metal arc welding (SMAW), and submerged arc welding (SAW). Of these processes, gas-metal arc welding with solid or "metallic" core electrodes is increasingly being used for the joining or overlapping of metallic components.These types of welding processes are becoming increasingly popular due to that these processes provide increased productivity and versatility.This increase in productivity and versatility results from the continuous nature of welding electrodes in gas-metal arc welding (GMAW and GMAW-C) that offers substantial productivity gains with respect to In addition, these electrodes produce very good looking welds with very little slag, thus saving time and expense associated with the cleaning of welds and the removal of slag, a problem that frequently encountered in other welding processes: in submerged arc welding, coalescence occurs by heating with an arc electrical between a bare metal electrode and the metal being worked. The weld is covered with a granular or meltable material, or flux. The welding operation is initiated by striking an arc below the flux to produce heat to melt the surrounding flux so that it forms a sub-surface conductive mixture that is kept fluid by the continuous flow of current. The end of the electrode and the workpiece directly below it come to melt, and the molten filler metal is deposited from electrodes on the job. The molten filler metal displaces the flux mixture and forms the weld. In protected metal arc welding, protection is obtained by a flux coating instead of a loose granular flux blanket. In the flux cored electrodes, the flux is contained within the metal sheath. In the welding technique, much effort has been put into developing flux compositions of the type having predetermined flux components proposed to perform in predetermined ways. A large number of compositions have been developed for use as fluxes in arc welding both for general use and as solder flux and for use as a coating on a metal core or within a sheath. Fluxes are used in arc welding to control the stability of the arc, to modify the composition of the weld metal, and to provide protection from atmospheric pollution. Commonly, the stability of the arc is controlled by modifying the composition of the flux. Therefore, it is desirable to have substances that function as carriers of the plasma charge in the flux mixture. The fluxes also modify the composition of the weld metal by reverting to more easily meltable impurities in the metal and by providing substances with which these impurities can preferably be combined with the metal to form slag. Other materials can be added to lower the melting point of the slag, to improve the flowability of the slag, and to serve as binders for the flux particles. A problem encountered with welding with rod-type electrodes is the resulting porosity of the weld metal, especially at the beginning of the welding process. At the beginning of the welding process using a rod-type electrode, the heat transferred to the tip of the electrode is initially relatively low and then increases rapidly. As a result, at the beginning of the welding process, some of the rod-type electrode is melted and transferred to the workpiece to begin the formation of a weld bead. Although the initial heating of the tip of the electrode is sufficient to melt the internal wire rod of the rod-type electrode, the initial heat is insufficient to sufficiently heat the coating on the electrode, which coating provides a protective gas during the welding operation . The protective gas generated by the coating produces an environment around the weld metal that inhibits or prevents oxygen and nitrogen from dissolving in the weld metal, dissolved gases that can be subsequently expelled from the weld metal during cooling of the weld metal. Weld. Expelling these gases from the weld metal can result in porosity in the weld metal which in turn can result in a lower weld bead. As a result, at the beginning of the welding process, the metal transferred to the workpiece can have an unacceptable amount of porosity that can result in a reduction in the quality of the weld bead. U.S. Patent Application Serial No. 10 / 840,701 filed May 6, 2004, which is incorporated herein by reference, discloses a type of rod type electrode for addressing the porosity problems associated with type electrodes. dipstick. Another problem encountered with rod-type electrode welding is the control of the molten metal weld pool at the beginning of the welding process. This is especially a matter when welding in the vertical down position. Typically, the welding wire does not melt easily at the beginning of the welding process, so the quality of the weld bead is less acceptable at the beginning of a welding process. In view of the problems of the porosity of the weld bead and of the control of the molten weld metal bath at the beginning of the weld when using rod-type electrodes of the prior art, the need remains for a rod-type electrode forming a bead High quality welding from beginning to end of the welding process.

Brief Description of the Invention The present invention relates to welding electrodes, and more particularly, to a welding electrode that at least partially provides protection to the welding metal during a welding process. The welding electrode of the present invention refers in particular to a rod-type electrode; however, the invention can be applied to other types of electrodes. The welding electrode includes a coating composition that is formulated to at least partially protect the weld metal from oxygen and nitrogen during a welding process. The welding electrode also includes a terminal coating material located in the terminal region of the welding electrode. The coating composition is typically used in self-protection rod type electrodes formed from a metal rod coated with a coating composition; However, the electrode coating can be used on and / or within other types of electrodes (e.g., electrodes with a flux core, etc.). The coating composition includes a flux composition. The flux composition of the coating composition and the terminal coating material include one or more components different from each other. The end coating material is formulated in part to inhibit or prevent porosity problems that may occur in the weld bead during the commencement of the welding operation. The flux composition is formulated in part to generate a protective gas to at least partially protect the weld metal from the atmosphere. In a different and / or alternative aspect of the present invention, the composition of the metal rod is selected to correspond at least closely to the desired composition of the weld metal. Typically, the metal rod includes a majority of iron when welding a work piece based on ferrous composition (e.g., carbon steel, stainless steel, etc.); however, the composition of the welding rod can include various types of metals to achieve a particular weld bead composition. The metal rod is typically a solid metal rod; however, the metal rod may be a metal rod with a core.

If the metal rod includes a core, the core may be empty, include one or more alloying agents, include one or more fluxing agents, and include one or more fluxing or alloying agents (e.g., coating composition). In yet a different and / or alternative aspect of the present invention, the coating composition includes a binder, one or more conductive materials, and one or more weld metal protection compounds. The components of the coating composition can include metal oxides (for example aluminum oxide, boron oxide, calcium oxide, chromium oxide, iron oxide, magnesium oxide, niobium oxide, potassium oxide, silicon dioxide, sodium oxide, tin oxide, titanium oxide, vanadium oxide, zirconium oxide, etc.), metal carbonates (eg, calcium carbonate, etc.), metal fluorides (eg, barium fluoride, fluoride bismuth, calcium fluoride, potassium fluoride, sodium fluoride, Teflon, etc.), and / or metallic alloying agents (eg, aluminum, boron, calcium, carbon, chromium, iron, manganese, nickel, silicon, titanium , zirconium, etc.) that are combined with the binder. In a non-limiting embodiment of the invention, the binder is formulated to secure the coating composition to the outer surface of the wire rod. In a different and / or alternative, non-limiting embodiment of the invention, the binder includes silicates (eg, sodium silicate, potassium silicate, etc.); however, other additional binders can be used. Examples of silicate binders are described in U.S. Patent Nos. 4,103,0677; 4,131,784; 4,208,563; 4,355,224; 4,741,974 and 5,300,754, and U.S. Patent Application Serial No. 11 / 457,502 filed June 9, 2003, all of which are incorporated herein by reference. As can be appreciated, other types of binders may be used, such as, but not limited to, the binders described in U.S. Patent Nos. 4,103,067 and 4,662,952, which are incorporated herein by reference. Silicate binders are popular due to 1) their resistance to decomposition under conditions of use, 2) their bond strength, 3) their ability to extrude at relatively high speeds, 4) their ability to form a hard film when they dry , 5) its ease of handling 6) its ability to knead and mix with other components, 7) its cheap cost of material, etc. The use of silicates can also improve the welding process such as, without limitation, improving arc stability during welding, facilitating the formation of the low melting point component, facilitating melting range adjustment. freezing of the slag. In still a different and / or non-limiting alternative embodiment of the invention, the coating composition is coated and / or extruded on the inner surface of the wire rod. The materials that are included in the coating composition are generally added to a liquid binder and then kneaded to a consistency that is suitable for subsequent extrusion. The mass of the kneaded mixture is commonly formed into "pieces" which facilitate handling during the storage time and the loading of the press with the mixture for the extrusion operation. The plasticity of the coating composition on the wire rod is controlled at least partially by the composition of the binder. In still a different and / or non-limiting alternative embodiment of the invention, the coated wire is typically cut and then the coating composition on the cut wire is dried. The drying of the coating composition is generally carried out at a low temperature starting at about 100-150 ° C with controlled humidity in order to obtain uniform drying without cracking. This drying step is generally followed by one or more drying steps at a higher temperature at a lower humidity depending on the nature of the coating composition. In a further and / or non-limiting alternative embodiment of the invention, the binder constitutes at least about one (1%) percent by weight of the coating composition after it is dried. In one aspect of this non-limiting embodiment, the binder constitutes about 1-80 weight percent of the coating composition after it is dried. In a non-limiting additional and / or alternative embodiment of the invention, the coating composition includes one or more conducting materials that conduct current to facilitate fusion of the electrode end. In general, the conductive material is supplied as small particles to facilitate the dispersion of the conductive material in the binder. These conductive materials include, but are not limited to, graphite, titanium, iron and / or iron alloys (e.g., Fe-Al, Fe-Mn, Fe-Si, Fe-Ti, etc.), aluminum, etc.; however, it can be appreciated that other additional conductive materials can be used. The average particle size of conductive materials is generally close to 40-300 mesh, and typically close to 100-250 mesh; however, other sizes may be used. In one aspect of this non-limiting embodiment, the conductive material constitutes approximately 0.1-80 weight percent of the coating composition after it is dried. In still a non-limiting additional and / or alternative embodiment of the invention, at least one of the weld metal protection compounds includes a gas generating compound that generates a shielding gas during the welding operation. The gas generating compounds are generally decomposed during the welding operation and release a gas that at least partially protects the weld metal (e.g., C02 generating compounds, fluoride generating compounds, etc.). In one aspect of this non-limiting embodiment, the gas generating compound, when used, constitutes approximately 0.1-75 weight percent of the coating composition after it is dried. In yet a further and / or non-limiting alternative embodiment of the invention, the coating composition includes one or more alloying agents used to facilitate the formation of a weld metal with the desired composition. In one aspect of this non-limiting embodiment, the alloying agent, when used, constitutes approximately 0.1-75 weight percent of the coating composition after it is dried. In still a further and / or non-limiting alternative embodiment of the invention, the coating composition includes one or more slag modifiers. In a different and / or non-limiting alternative embodiment of the invention, the coating composition includes one or more electric arc modifiers. In still a different and / or non-limiting alternative embodiment of the invention, the coating composition includes one or more smoke production modifiers. In still a different and / or alternative aspect of the present invention, the terminal coating material 1) has a composition that is different from the coating composition, and 2) is placed in the terminal region of the electrode. The end coating material can be coated at least partially 1) on the end of the metal rod, 2) on the outer lateral surface of the metal rod in the terminal region of the metal rod, and / or 3) on the surface of the metal rod. at least a portion of the coating composition in the terminal region of the metal rod. In a non-limiting embodiment of the invention, the terminal coating material is at least partially formulated to facilitate the formation and maintenance of an electric arc between the end of the welding electrode and the workpiece, especially at the beginning of the welding process. In a non-limiting embodiment of the invention, the terminal coating material includes one or more electrically conductive materials. The electrically conductive material is used to conduct at least partially current in and / or through the terminal coating material to facilitate fusion of the electrode end at the beginning of the arc between the welding electrode and the workpiece. The electrically conductive material can also be used to maintain the arc between the electrode and the workpiece once the arc is formed. In general, the electrically conductive material is supplied as small particles to facilitate the dispersion of the electrically conductive material in the terminal coating material. The average particle size of the electrically conductive material in general is not greater than about 100 mesh, and typically about 200-400 mesh.; however, other types may be used. The electrically conductive material may include one or more materials such as, but not limited to, graphite, magnesium, titanium, iron and / or iron alloys (e.g., Fe-Al, Fe-Mn, Fe-Si, Fe- Ti, etc.), aluminum, etc. In one aspect of this non-limiting embodiment, the electrically conductive material generally constitutes about 0.5-70 weight percent of the terminal coating material before it dries, typically about 1-60 weight percent of the terminal coating material before drying, more typically about 5-50 weight percent of the terminal coating material before it dries, most typically about 6-40 weight percent of the terminal coating material before it dry, and still more typically about 10-30 weight percent of the terminal coating material before it dries; however, it can be appreciated that other percentages by weight can be used. In yet another different and / or non-limiting alternative embodiment of the invention, the terminal coating material includes one or more binders for securing and / or bonding the components of the terminal coating material to the metal rod and / or the coating composition of the coating material. the metal rod. In one aspect of this non-limiting embodiment, the one or more binders in the terminal coating material constitutes approximately 0.5-70 weight percent of the terminal coating material before it dries, typically about 1-60 weight percent. of the terminal coating material before it dries, more typically about 5-50 weight percent of the terminal coating material before it dries, most typically about 10-55 weight percent of the final coating material. end coating material before it dries, and still about 20-40 weight percent of the terminal coating material before it dries; however, other percentages by weight may be used. The one or more binders may include a variety of compounds. The composition of one or more binders may be the same as, or different from, one or more binders used in the coating composition. In a non-limiting formulation of the binder, the one or more binders may include one or more silicates (eg, potassium silicate, sodium silicate, etc.). In a non-limiting formulation, the binder includes a combination of potassium silicate and sodium silicate in a weight ratio of about 0.1-10: 1, typically about 0.5-2: 1, and more typically about 1: 1. . In a different and / or non-limiting alternative formulation of the binder, one or more binders may include a microemulsion of silicon dioxide. The silicon dioxide can be used in the pure and / or impure form. Examples of impure forms of silicon dioxide include, but are not limited to, quartz, feldspar, mica, biotite, olivine, hornblende, muscovite, pyroxenes, and / or other sources of silicon dioxide. In still a different and / or non-limiting alternative embodiment of the invention, the terminal coating material includes a liquid component before the terminal coating material is dried. The liquid component is liquid that is not associated with one or more binders. The liquid component is generally used to disperse the components of the terminal coating material in solution so that the terminal coating material can be applied to the electrode. In general, the liquid component mainly includes water; however, additional and / or alternative liquids may be used. The liquid facilitates the suspension of the particles of the terminal coating material and / or facilitates the application of the terminal coating material on the electrode. In one aspect of this non-limiting modality, the liquid component constitutes approximately 0.1-80 weight percent of the terminal coating material before it dries, typically about 5-70 weight percent of the terminal coating material before it dries, most typically by 20-65 weight percent of the terminal coating material before it dries, most typically about 30-60 weight percent of the terminal coating material before it dries, and even more approximately about 40-55 weight percent of the terminal coating material before it dries; however, other percentages by weight may be used. In a further and / or alternative aspect of the present invention, the terminal coating material may include a thickening agent to facilitate the suspension of one or more components of the terminal coating composition. The thickening agent may include a variety of compounds such as, without limitation, starches (eg, arrowroot, corn starch, etc.), starch, gelatins (eg agar-agar, etc.), rosin, clays, silicas, cellulose thickeners, (for example, sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, microcrystalline cellulose, etc.), gums (cellulose gum, xanthan gum, guar gum, gum arabic, etc.), gelatin, hydrocolloids , alginates, carragahen, pectin, etc. In a non-limiting mode, the thickening agent, when used, includes CMC. The content of one or more thickening agents, when used, in the terminal coating material is generally about 0.05-20 by weight of the terminal coating material before it dries, typically about 0.5-10 weight percent. of the terminal coating material before it dries, and more typically about 1-5 weight percent of the terminal coating material before it dries; however, other percentages by weight may be used. In yet a further and / or alternative aspect of the present invention, the terminal coating material may include a moisture picking agent that reduces the rate of moisture collection by the terminal coating material. High levels of moisture in the end coating material can introduce hydrogen into the weld metal which can result in hydrogen cracking of the weld metal and / or porosity problems in the weld material. In a non-limiting embodiment, the terminal coating composition includes a lithium compound (e.g., lithium hydroxide, etc.). The content of one or more moisture collection resistance agents, when used, in the terminal coating material is generally about 0.01-10 by weight of the terminal coating material before it dries, typically about 0.05- 5 weight percent of the terminal coating material before it dries, most typically about 0.1-2 weight percent of the final coating material before it dries; however, other percentages by weight may be used. In still a further and / or alternative aspect of the present invention, the end coating material may include one or more compounds that at least partially protect the weld metal at the beginning of a welding process. The mechanism for this protection may include, without limitation, at least partially increasing the surface tension of the metal droplets that are formed and / or transferred to the workpiece, and / or at least partially forming a protective environment around it. of the metallic drops that are formed and / or transferred to the workpiece. The mechanism for increasing the surface tension includes, but is not limited to, the formation of larger droplet formation, molten metal at the end of the electrode that is transferred to the workpiece. These larger droplets reduce the amount of oxygen and / or nitrogen that can be mixed with the molten metal thereby reducing the porosity problems of the weld bead. The mechanism for forming a protective mechanism includes, without limitation, 1) the at least partial coating of the drop formed of molten metal with a material that inhibits or prevents oxygen and / or nitrogen from entering the drop and / or in the molten metal in the workpiece, and / or 2) the release of a protective gas around the formed drop and / or weld metal deposited. In a non-limiting mode, the terminal coating composition includes a fluoride compound. A non-limiting fluoride compound includes, without limitation, Na3AlF6. A source of Na3AlF6 includes cryolite. In yet a different and / or alternative aspect of this non-limiting embodiment, one or more compounds that at least partially protect the weld metal, when used, generally constitute about 0.05-60 by weight of the terminal coating material before dry, typically about 1-55 weight percent of the terminal coating material before it dries, most typically about 2-50 weight percent of the terminal coating material before it dries, even more typical way about 3-45 weight percent of the terminal coating material before it dries; however, other percentages by weight may be used. The average size of one or more protective compounds in general is not greater than about 100 mesh, and typically close to 150-400 mesh; however, other sizes may be used. In a different and / or alternative aspect of the present invention, the terminal coating material may include a coloring agent to modify the color of the terminal coating material. In some applications, it may be desirable to closely match the terminal coating material to the coating composition on the electrode. In other applications, it may be desirable to make the color of the terminal coating material different from the coating composition on the electrode. The different color of the end coating material can be used to visually indicate one or more properties of the electrode such as, without limitation, 1) the fact that the electrode includes a terminal coating material, 2) the integrity of the terminal coating, 3) the type of end coating material, 4) the type of electrode, 5) the type of coating composition on the electrode, 6) the type of wire rod on the electrode, etc. Many different types of coloring agents can be used (e.g., carbon black, titanium dioxide, iron oxides, etc.). A coloring agent that can be used is titanium dioxide. Titanium dioxide typically adds a white pigment to the terminal coating material when it is used, thereby whitening the color of the terminal coating material. As can be appreciated, a different and / or additional coloring agent can be used to obtain a wide variety of colors for the terminal coating material. In one aspect of this non-limiting embodiment, the coloring agent, when used, generally constitutes about 0.01-15 weight percent of the terminal coating material before it dries, typically about 0.5-10 percent by weight. weight of the terminal coating material before it dries, most typically about 0.1-8 weight percent of the terminal coating material before it dries, and still more typically about 0.2-5 percent by weight. weight of the terminal coating material before it dries; however, other percentages by weight may be used. The average size of one or more coloring agents in general is not greater than about 100 mesh, and typically about 150-400 mesh; however, other sizes may be used. In yet a different and / or alternative aspect of the present invention, the end coating material is applied to the electrode before and / or after the coating composition is applied to the wire rod. In a non-limiting embodiment of the invention, the terminal coating material is applied to the electrode at least partially after the coating composition is applied. When the end coating material is applied to the electrode after the coating composition is partially applied, the end coating material is generally applied after the coating composition is at least partially dried; however, this is not required. In a different and / or alternative, non-limiting embodiment of the invention, the end coating material can be applied to the electrode by a variety of mechanisms such as, without limitation, spray coating, dipping, laminating, brushing coating. , etc. One or more coating mechanisms may be used to apply one or more coatings of the terminal coating material on the electrode. The end coating material is generally applied to the tip of the welding rod to cover or substantially coat the tip of the welding rod. In still a different and / or non-limiting alternative embodiment of the invention, the coating thickness of the terminal coating material is at least about 0.0001 inches, and typically about 0.0005-0.5 inches.; however, other thicknesses may be used. In yet a different and / or non-limiting alternative embodiment of the invention, the average length of the coating of the terminal coating material starting from the end of the electrode is generally at least about 0.01 inches, typically about 0.05-1 inches, of most typical manner approximately 0.05-0.5 inches, and still more typically approximately 0.075-0.4; however, other lengths may be used. In still a different and / or alternative aspect of the present invention, the end of the wire rod is treated to remove and / or bias at least partially the tip of the welding rod. The biased or tapered tip of the welding rod facilitates a "hot start" of the welding arc at the beginning of a welding process. Due to the smaller cross section of the welding rod in the tapered region of the tip of the welding rod, the current density at the start of the arc is greater. The higher current density facilitates a "hot start" to the arc and also facilitates the establishment of control of the molten metal bath of the weld metal, especially when welding in the vertical down position. The treatment of the tip of the welding rod can be achieved by one or more mechanisms such as, without limitation, cleaning with sand, grinding, cutting, etc. The region of the tip of the welding rod is treated as measured from the tip of the welding rod which is typically less than about 1.5 inches, typically about 0.1-1 inch, and more typically about 0.2-0.5. inches; however, other lengths may be used.

The maximum amount of the welding rod that tapers is generally at least about 10% of the maximum width or diameter of the welding rod, typically about 15-80% of the maximum width or diameter of the welding rod, so more typical about 25-60% of the maximum width of the welding rod; however, other dimensions can be used. The taper on the welding rod may be uniform or may vary. Typically, the taper is a substantially uniform taper. When the tip of the welding rod becomes taut or slanted, the biased angle is about 15-80 °, and typically about 20-50 °; however, other angles can be used. In a non-limiting design, the welding rod has a diameter of approximately 3.2-4.5 mm (0.126-0.177 inches), and the tip of the welding rod tapers so that the tip has a diameter of approximately 0.0625-0.125 inches, and the taper begins at approximately 0.31-0.44 inches from the tip of the welding rod. In a different and / or alternative aspect of the present invention, the terminal coating material and / or coating composition in the terminal region of the wire rod can be applied and / or treated to at least partially form a skewed terminal region or tapered of the welding rod; however, this is not required. When the end coating material and / or the coating composition are treated to form a bevel or taper, this bevel or taper can be achieved by one or more mechanisms such as, without limitation, sand treatment, grinding, cutting. , dissolution, etc. A portion or all of the terminal coating material and / or coating composition can form the skewed terminal region. The taper angle may be uniform or non-uniform. When the end coating material and / or coating composition is taut or biased, the biased angle is about 15-85 °, and typically about 30-75 °; however, other angles can be used. When the end coating material and / or coating composition is coated in a biased or tapered region of the welding rod, the taper angle of the end coating material and / or the coating composition may be the same as, or different from, the coating material. of, the taper angle of the tip of the welding rod. Further, when the end coating material and / or coating composition is coated in a tapered or biased region of the welding rod, the entire tapered portion of the welding rod may be coated with the terminal coating material or only a portion thereof. of the tapered portion of the welding rod and can be coated with the terminal coating material. In a non-limiting configuration, the entire tapered portion of the welding rod is coated with the coating composition and at least a portion of the coating composition is coated with the terminal coating material. In another non-limiting configuration, only a portion of the tapered region of the wire rod is coated with the coating composition and the terminal portion of the tapered region of the rod is coated with the terminal coating material. In this configuration, some of the end coating material may be coated on a portion of the coating composition. In this particular configuration, the end coating material generally bears about 2-85% of the outer surface of the tapered portion of the welding rod, typically about 5-50% of the outer surface of the tapered portion. of the welding rod, and more typically about 5-30% of the outer surface of the tapered portion of the welding rod; however, other coverage percentages may be used. When the outer surface of the tapered portion of the welding rod is not completely covered with the terminal coating material, the remaining portion of the tapered portion of the welding rod is generally covered by the coating composition. In another non-limiting configuration, the coating composition does not taper or partially skew in the welding rod in the tapered region of the welding wire. The portion of the coating composition that does not taper in the taper region of the tip of the welding rod results in a greater ratio of the amount of coating composition to the amount of welding rod, thereby allowing A higher concentration of arc stabilization, gas protection and flux components to provide stability and protection to the weld metal during the beginning of a welding process. It is a main object of the invention to provide improved protection to a weld bead, especially at the beginning of a welding process. A different and / or alternative object of the present invention is the provision of a consumable electrode that reduces the porosity of a weld bead, especially at the beginning of a welding process. Even a different and alternative object of the present invention is the provision of a consumable electrode that is provided in a "hot start" of the welding arc. Even a different and / or alternative object of the present invention is the provision of a consumable electrode that includes a terminal coating material on at least the end of the electrode that facilitates the formation of an arc between the electrode and the workpiece. A further and / or alternative object of the present invention is the provision of a consumable electrode that includes a terminal coating material that is different from the electrode coating composition. Yet a further and / or alternative object of the present invention is the provision of a consumable electrode that includes a terminal coating material having a different color than the exterior of the metal rod and / or a coating composition on the metal rod. These and other objects and advantages will become apparent from the analysis of the distinction between the invention and the prior art and when the preferred embodiment is considered as shown in the appended Figures.

Brief Description of the Figures Figure 1 is an enlarged sectional view of a terminal or end portion of a prior art rod-type electrode having a flux coating on a metal rod; Figure 2 is an enlarged sectional view of the end or end portion of another prior art rod-type electrode having a flux coating on a metal rod and a graphite plug attached to the end of the metal rod; and Figure 3 is an enlarged sectional view of the terminal or end portion of a rod-type electrode according to the present invention.

BRIEF DESCRIPTION OF THE INVENTION Referring now in greater detail to the figures, wherein the figures are for the purpose of illustrating preferred embodiments of the invention only, and not for the purpose of limiting the invention, Figure 1 illustrates a lower sectional portion of a rod-type electrode 10 of the prior art. The rod-type electrode includes a solid metallic rod 12 and a coating 14 of flux coated on the outer surface of the metal rod. The flux coating generally includes a binder that secures a flux agent 16 and / or metal alloy agent 18 to the metal rod. The flux agent components typically include metal oxides (eg, aluminum oxide, boron oxide, calcium oxide, chromium oxide, iron oxide, magnesium oxide, niobium oxide, potassium oxide, silicon dioxide, oxide). sodium, tin oxide, titanium oxide, vanadium oxide, zirconium oxide, etc.), metal carbonates (eg, calcium carbonate, etc.), and / or metal fluorides (eg, barium fluoride, bismuth fluoride, calcium fluoride, potassium fluoride, sodium fluoride, Teflon, etc.). The metal alloying agents can include a variety of metals (eg, aluminum, boron, calcium, carbon, iron, manganese, nickel, silicon, titanium, zirconium, etc.). The particular components of the flux coating and / or metal alloying agents depend in general on the type of welding process used and / or the type of work piece being welded and the composition of the weld bead that is welded. form The end of the region of the rod-like electrode is shown as tapering or skewing 20; however, this is not required. Referring now to Figure 2, a lower sectional portion of another rod-type electrode 30 of the prior art is illustrated. The rod-type electrode includes a solid metal rod 32 and a coating 34 of flux coated on the outer surface of the metal rod. The flux coating generally includes a binder that secures a fluxing agent and / or metal alloying agent 38 to the metal rod. The end of the region of the rod-type electrode is shown as being tapered or biased type 40; however, this is not required. A graphite plug 42 is secured to the end of the rod-type electrode by a binder 44. The graphite plug is typically used to assist in starting the arc between the end of the rod-type electrode and the workpiece. Referring now to Figure 3, a rod-type electrode 50 according to the present invention is illustrated. The rod-type electrode 50 includes a metal rod 52 which may be a solid metal rod or a metal rod with a core. The metal rod is typically a rod with a diameter of 3.2 mm, 4 mm or 4.5 mm; however, rods of another size can be used. The outer surface of the metal rod is coated with a coating material 54. The coating material includes a binder to secure a fluxing agent 56 and one or more agents 58 of metal alloy to the metal rod. The average thickness of the coating material on the metal rod is typically about 0.05-0.2 inches; however, other thicknesses may be used. The terminal or end region of the metal rod is shown as tapering or skewing 60. The taper has an angle α of typically about 25-45 °; however, other angles can be used. The length L of the tip of the welding rod that includes the taper is typically about 0.1-1 inch, and more typically about 0.25-0.5 inches; however, other lengths may be used. The width W of the tip of the welding rod is typically about 0.01-0.25 inches, and more typically about 0.07-0.11 inches; however, other widths may be used. The ratio of the length L to the width W of the tapered terminal region is typically about 1.5-10: 1, and more typically about 2-6.5: 1; however, other relationships can be used. The tapered end of the metal rod is designed to facilitate a "hot start" to the electric arc at the beginning of a welding process. As shown in Figure 3, the coating material 54 covers all or a portion of the tapered end. Typically, when the metal rod is coated with the coating material 54 (eg, extrusion process, etc.), the entire tapered end 60 is coated with the coating material. After the coating material has been applied to the metal rod, the front and rear ends of the electrode are typically treated to remove some of the coating material from the electrode. As shown in Figure 3, the front of the electrode was treated (e.g., brushing, milling, dissolving, etc.), to remove some of the coating material and to expose a small region of the metal rod at the tip of the portion. tapered of the metal rod. Typically, only 1-50% of the tapered portion of the metal rod is exposed, and more nearly 5-40% of the tapered portion of the metal rod is exposed, and even more typically exposed near the metal rod. 10-30% of the tapered portion of the metal rod; however, other exposure percentages may be used. After the coating material at the front end of the electrode has been treated, a terminal coating material 70 is applied to the front end of the electrode. Typically, the end coating material is applied to the electrode by an immersion process, however, other or additional processes (eg, brushing, spraying, etc.) can be used. As illustrated in Figure 3, the end coating material completely covers the tapered portion of the metal rod that is not coated with the coating material 54; however, this is not required. The terminal coating material is also described as having a taper of an angle ß; however, this is not required. When the terminal liner is tapered, the angle ß is typically about 45-89 °, and more typically about 60-85 °; however, other angles can be used. The end coating material as illustrated can be coated at least partially on another surface of a portion of the coating material 54; however, this is not required. The end coating material may include a pigment for mixing the color of the end coating material with the color of the coating material or for causing the end coating material to protrude from the coating material. Typically, the end coating material or the end end coating only covers about 5-80% of the length L of the taper, and more typically about 10-60% of the length L of the taper; however, other amounts may be used. As shown in Figure 3, the coating material 54 is not tapered in the region of the taper 60; however, it can be appreciated that some tapering of the coating material may be used in this region. The end coating material 70 has a different composition from the coating material 54. The terminal coating material is formulated primarily to facilitate the formation of an electric arc between the end of the electrode and a workpiece during the start of a welding process. The cladding material is mainly designed to provide arc stabilityprotective gas, deoxidizing agents, slag-forming agents, slag modifiers and / or alloying metals to the welding metal during the welding process. The combined effect of the end coating material, the profile of the end coating material, the coating material, the profile of the coating material, the composition of the welding rod, and the profile of the welding rod is the formation of a welding metal that has low porosity, and in some cases low hydrogen content. It has been found that at the beginning of a welding process, the weld metal at the beginning of a welding process can not be provided with adequate protection against water, oxygen and nitrogen in the air, thereby resulting in the components they will dissolve in the weld metal during a welding process. As the weld metal cools, the oxygen and nitrogen are re-released into the atmosphere, thereby causing porosity problems in the weld bead that may compromise the quality and / or strength of the weld bead, moisture in the weld Air can increase the hydrogen content of the weld metal. The end coating material 70 is formulated to facilitate the initiation of an arc so that the welding rod will melt and will properly start the formation of a weld bead at the beginning of a welding process. The terminal coating material includes a binder and an electrically conductive material. The electrically conductive material facilitates the conduction of current to the tip of the electrode which results in the heating and melting of the electrode during a welding process. The electrically conductive material is typically graphite; however, different or additional electrically conductive materials may be used. The average particle size of the electrically conductive material is selected to be sufficiently small to be in suspension until the end coating material can be applied to the welding electrode. Typically, the average particle size of the electrically conductive material is approximately 100-250 mesh. The binder is used to secure the electrically conductive material to the end of the rod-type electrode. The binder is typically a combination of potassium and silicate; however, different or additional binders may be used. The binder may also include a compound that reduces the moisture collection of the terminal coating material. A compound like that is lithium hydroxide. The terminal coating material may include a thickening agent which is used to facilitate the maintenance of the electrically conductive material in suspension in the terminal coating material. A thickener that can be used is CMC; however, different or additional thickeners may be used; The end coating material may also include a gas generating compound to provide some protection to the weld metal at the beginning of the welding process. This compound is a fluoride compound; however, different or additional compounds can be used. The terminal coating material may also include a pigment to alter the color of the terminal coating material. A general formulation of the terminal coating material before drying is reported in percent by weight as follows: Electrically conductive material 5-50 Binder 10-60 Pigment 0-10 Gas generator material 0-50 Moisture Resistance Resistance Agent 0-10 Thickener 0-10 Water 20-75 The most specific examples of the terminal coating material before drying are exposed in percent by weight and are listed below: Example 1 Electrically conductive material 10-40 Binder 15-50 Pigment 0-8 Gas generator material 0-45 Moisture Collection Resistance Agent 0-5 Thickener 0-8 Water 30-60 Example 2 Electrically conductive material 10-30 Binder 20-40 Pigment 0-4 Gas generator material 0-45 Moisture Collection Resistance Agent 0-2 Thickener 0-5 Water 40-55 Example 3 Graphite 10-30 Potassium silicate 5-30 Sodium silicate 5-30 Pigment 0-4 fluoride compound 0-45 Compound of lithium 0-2 CMC 0-5 Water 40-55 Example 4 Graphite 10-30 Potassium silicate 10-25 Sodium silicate 10-25 Pigment 0-4 Fluoride compound 0-45 Lithium compound 0.1-1 CMC 0.2-5 Water 40-55 As illustrated in Figure 3, the thickness of the coating material 54 increases in the region of the bias or taper 60 in the welding rod. The increased thickness of the coating material 54 in this region of the welding rod results in an increased amount of protective gas production due to the increased amounts of coating material. This increased amount of protective gas facilitates the protection of the weld metal from adverse gases in the atmosphere to reduce the porosity, and potentially, the hydrogen content of the weld metal. The end coating material illustrated in Figure 3 may have a color similar to the coating material, or may have a different color from the coating material. When a different coloration is used for the end coating material, this coloration can be used to identify one or more properties of the electrode (e.g., type of electrode, electrode composition, etc.). The use of a pigment in the end coating material can be used to obtain the desired coloration of the terminal coating material. The end coating material or end coating is typically applied to the rod type electrode after the coating material has been applied, but before it is completely dried to the flux coating; however, the end coating material can be applied after the coating material has dried. In a specific manufacturing process, the wire rod is pre-cut and the tip of the wire rod is skewed or taper by a rectifier. The wire rod then directs to a coating composition and the coating composition is extruded around the outer surface of the wire rod. The coating composition at the trailing end of the rod is removed by a rectifier to form a clamping end and a portion of the cladding material at the front of the wire rod is also removed. The exposed front end of the wire rod is then immersed and / or brushed with the terminal coating material. The end coating material can then be brushed and / or milled to form a tapered or tapered end; however, this is not required. After the end coating material is applied, the coated wire rod is dried to remove substantially all of the water in the coating material and the terminal coating material. After the drying process, the rod-type electrode can be sealed in a container and / or rolled up to inhibit moisture absorption as long as the rod-type electrode is stored. These and other modifications of the modalities analyzed, as well as other embodiments of the invention, will be obvious and will be suggested by those skilled in the art of the description herein, so that it will be understood differently than the previous descriptive material. it should be interpreted only as illustrative of the present invention and not as a limitation thereof.

Claims

CLAIMS 1. Welding electrode, characterized in that it comprises a metal core having a front tip, a coating material at least partially coated on an outer surface of the metal core, and a terminal coating material or end coating coated in at least one portion of the front tip region of the metal core, the coating material including gas generating compounds that provide protection during the welding process, the terminal coating material including a binder and small particles of electrically conductive material, the small particles they have an average particle size of about 100-400 mesh, the terminal coating material having a different composition of a coating material.
2. Welding electrode according to claim 1, characterized in that the metal core is a solid metal rod.
Welding electrode according to claim 1 or 2, characterized in that the metallic core includes a majority of iron.
Welding electrode according to claims 1-3, characterized in that electrically conductive material includes graphite, metal or combinations thereof.
5. Welding electrode according to claims 1-4, characterized in that the electrically conductive material constitutes approximately 0.5-70 weight percent of the terminal coating material.
6. Welding electrode according to claims 1-5, characterized in that the terminal coating material includes gas generating material adapted to provide protection during a welding process.
7. Welding electrode according to claim 6, characterized in that the gas generating material includes a fluorine-containing compound.
8. Welding electrode according to claim 6 or 7, characterized in that - the gas generating material includes Na3AlFs.
9. Welding electrode according to claims 1-8, characterized in that the terminal coating material includes a moisture picking resistance agent.
10. Welding electrode according to claim 9, characterized in that the moisture pick-up resistance agent includes a lithium compound.
11. Welding electrode in accordance with the. claims 1-10, characterized in that the binder includes at least one silicate compound.
12. Welding electrode according to claims 1-11, characterized in that the binder includes sodium silicate and potassium silicate in a weight ratio of 0.1-10: 1.
13. Welding electrode according to claims 1-12, characterized in that the terminal coating material includes a thickener.
14. Welding electrode according to claim 13, characterized in that the thickener includes a cellulose compound.
15. Welding electrode according to claims 1-14, characterized in that the end coating material is a different color from the coating composition.
16. Welding electrode according to claims 1-15, characterized in that the front tip of the welding rod is biased.
Welding electrode according to claim 16, characterized in that the front portion of the biased front end is coated with the end coating material and the remainder of the skewed or tapered end tip is at least partially coated with a material selected from the group consisting of coating material, the terminal coating material, or combinations thereof.
18. Welding electrode according to claims 1-17, characterized in that the end coating material is coated only with the welding electrode.
19. Welding electrode according to claim 18, characterized in that the end coating material has a coating length of up to about 2.54 cm (1 inch).
20. Welding electrode accng to claims 1-19, characterized in that the end coating material has a composition in weight percent before it dries of: Electrically conductive material 5-50 Binder 10-60 Pigment 0-10 Gas Generating Material 0-50 Moisture Collection Resistance Agent 0-10 Thickener 0-10 Water 20-75
21. Welding electrode accng to claims 1-19, characterized in that the terminal coating material has a composition of percent by weight before it dries of: Graphite 10-30 Potassium silicate 5-30 Sodium silicate 5-30 Pigment 0-4 Fluoride compound 0-45 Lithium compound 0-2 CMC 0-5 Water 40-55
22. Welding electrode in accordance with the claims 1-19, characterized in that the end coating material has a composition in percent by weight before it dries of: Electrically conductive material 10-40 Binder 15-50 Pigment 0-8 Gas generating material 0-45 Resistance Agent a Moisture Collection 0-5 Thickener 0-8 Water 30-60
23. Welding electrode according to claims 1-19, characterized in that the end coating material has a composition in weight percent before it is dried from : Electrically conductive material 10-30 Binder 20-40 Pigment 0-4 Gas generator material 0-45 Moisture Collection Resistance Agent 0-2 Thickener 0-5 Water 40-55
24. Welding electrode according to the claims 1- 19, characterized in that the terminal coating material has a composition of percent by weight before it dries of: Graphite 10-30 Potassium silicate 10-25 Sodium silicate 10-25 Pigment 0-4 Fluoride compound 0-45 Lithium compound 0.1-1 CMC 0.2-5 Water 40-55
25. Method for forming a weld bead having a reduced porosity, characterized in that it comprises: a. providing a welding electrode formed of a metal core having a front tip, a coating material at least partially coated on an outer surface of the metal core, and a terminal facing material coated with at least a portion of the front tip region of the metal core, the coating material including gas generating compounds that provide protection during the welding process, the end coating material including a binder and small particles of electrically conductive material, the small particles have an average particle size of approximately 100-400 mesh, the terminal coating material having a composition different from the coating material; and b. applying an electric current to the welding electrode to at least partially melt one end of the welding electrode thereby causing the molten portions of the metallic core to at least partially form the weld bead, at least one component of the terminal coating material which improves the formation of an electric arc between the welding electrode and a work piece.
26. Method according to claim 25, characterized in that the metal core is a solid metal rod.
27. Method according to claim 25 or 26, characterized in that the metal core includes a majority of iron.
28. Method according to claims 25-27, characterized in that electrically conductive material t includes graphite, metal or combinations thereof.
29. Method of compliance with the claims 25-28, characterized in that the electrically conductive material constitutes approximately 0.5-70 weight percent of the terminal coating material.
30. Method of compliance with the claims 25-29, characterized in that the terminal coating material includes gas generating material adapted to provide protection during a welding process.
31. Method according to claim 31, characterized in that the gas generating material includes a fluorine-containing compound.
32. Method according to claim 30 or 31, characterized in that the gas generating material includes Na3AlFs.
33. Method according to claims 25-32, characterized in that the terminal coating material includes an agent for resistance to moisture collection.
34. Method according to claim 33, characterized in that the moisture collection resistance agent includes a lithium compound.
35. Method according to claim 25-34, characterized in that the binder includes at least one silicate compound.
36. Method according to claim 35, characterized in that the binder includes sodium silicate and potassium silicate in a weight ratio of 0.1-10: 1.
37. Method according to claims 25-36, characterized in that the terminal coating material includes a thickener.
38. Method according to claim 37, characterized in that the thickener includes a cellulose compound.
39. Method according to claims 25-38, characterized in that the end coating material is a different color from the coating composition.
40. Method according to claims 25-39, characterized in that the front tip of the welding rod is biased.
41. Method according to claims 25-40, characterized in that the front portion of the biased front end is coated with the end coating material and the rest of the biased or tapered front end is at least partially coated with a material selected from the group consisting of coating material, the terminal coating material, or combinations thereof.
42. Method according to claims 25-41, characterized in that the end coating material is coated only the welding electrode.
43. Method of compliance with the claim 42, characterized in that the end coating material has a coating length of up to about 2.54 cm (1 inch).
44. Method according to claims 25-43, characterized in that the end coating material has a composition in weight percent before it dries of: Electrically conductive material 5-50 Binder 10-60 Pigment 0-10 Generating material 0-50 Moisture Collection Resistance Agent 0-10 Thickener 0-10 Water 20-75 45. Method according to the claims 25-43, characterized in that the terminal coating material has a composition of percent by weight before it dries of: Graphite 10-30 Potassium silicate 5-30 Sodium silicate 5-30 Pigment 0-4 Fluoride compound 0 -
45 Lithium Compound 0-2 'CMC 0-5 Water 40-55
46. Method of compliance according to claims 25-43, characterized in that the terminal coating material has a composition in weight percent before it is dry: Electrically conductive material 10-40 Binder 15-50 Pigment 0-8 Gas generator material 0-45 Moisture Collection Resistance Agent 0-5 Thickener 0-8 Water 30-60
47. Method according to the claims 25-43, characterized in that the terminal coating material has a composition in weight percent before it dries of: Electrically conductive material 10-30 Binder 20-40 Pigment 0-4 Gas generator material 0-45 Resistance agent aa Moisture Collection 0-2 Thickener 0-5 Water 40-55
48. Method according to claims 25-43, characterized in that the end coating material has a composition of weight percent before it dries of: Graphite 10-30 Potassium silicate 10-25 Sodium silicate 10-25 Pigment 0-4 Fluoride compound 0-45 Lithium compound 0.1-1 CMC 0.2-5 Water 40-55
49. Method for forming a welding electrode, characterized because it comprises: a. provide a metallic wire having a front tip; b. applying a coating material at least partially on an outer surface of the metallic wire, the coating material including gas generating compounds that provide protection during the welding process; c. applying an end coating material at least partially in the front end region of the metal wire, the end coating material including a binder and glue particles of electrically conductive material, the small particles have an average particle size of approximately 100- mesh 400, the terminal coating material having a composition different from the coating material; and d. Dry the coating material and the terminal coating material.
50. Method of compliance with the claim 49, characterized in that the step of applying the coating material is at least partially by an extrusion process.
51. Method according to claim 49 or 50, characterized in that the step of applying the end coating material is at least partially by a dipping process, a brushing process, a spraying process, a rolling process or combinations of the same .
52. Method of compliance with the claims 49-51, characterized in that it includes the step of tapering or biasing the front tip of the metal rod.
53. Method of compliance with the claim 52, characterized in that the step of tapering or skewing the front tip of the metal rod is before the step of applying the coating material.
54. Method according to claims 49-53, characterized in that it includes the step of removing the coating material from at least a portion of the biased front tip of the welding rod before the step of applying the end coating material.
55. Method of compliance with claims 49-54, characterized in that the end coating material has a composition in percent by weight before it dries of: Electrically conductive material 5-50 Binder 10-60 Pigment 0-10 Gas generating material 0-50 Resistance Agent Moisture 0-10 Thickener 0-10 Water 20-75
56. Method according to claims 49-54, characterized in that the end coating material has a composition of weight percent before it dries of: Graphite 10-30 Potassium silicate 5-30 Sodium silicate 5-30 Pigment 0-4 Fluoride compound 0-45 Lithium compound 0-2 CMC 0-5 Water 40-55
57. Method of conformity according to claims 49-54, characterized in that the end coating material has a composition in weight percent before it dries of: Electrically conductive material 10-40 Binder 15-50 Pigment 0-8 Gas generating material 0-45 Resistance Agent a Humidity Collection 0-5 Thickener 0-8 Water 30-60
58. Method according to claims 49-54, characterized in that the end coating material has a composition in weight percent before it dries of: Material electrically conductive 10-30 Binder 20-40 Pigment 0-4 Gas generator material 0-45 Moisture Collection Resistance Agent 0-2 Thickener 0-5 Water 40-55
59. Method according to the claims 49-54, characterized in that the end coating material has a composition by weight percent before it dries of: Graphite 10-30 Potassium silicate 10-25 Sodium silicate 10-25 Pigment 0-4 Fluoride compound 0 -45 Lithium compound 0.1-1 CMC 0.2-5 Water. 40-55