MXPA06006125A - Modified flux system - Google Patents

Abstract

A titanium based welding flux that includes titanium dioxide and a moisture resistant agent. The titanium oxide includes purified titanium dioxide that includes little or no impurities that can act as nucleation sites for carbide formation in a weld metal. The moisture resistant compound includes a colloidal metal oxide.

Description

MODIFIED FOUNDRY SYSTEM DESCRIPTION BACKGROUND OF THE INVENTION The invention relates generally to the field of welding and is more particularly oriented to electrodes having better characteristics of weld bead formation, and even more particularly refers to flux systems that reduce the amount of impurities introduced into a bead. welding. In the field of arc welding, the main types of welding processes are metal arc welding in gaseous atmosphere (GMAW), metal arc welding in a gaseous atmosphere with core (GMAW-C), arc welding with low tubular wire gaseous protection (FCAW-G), arc welding with self-protected tubular wire (FCAW-S), arc welding with coated electrode (SMA) and submerged arc welding (SAW). From these processes, arc welding with solid or metal core electrodes is increasingly being used to join or superimpose metal components. These types of welding processes are becoming increasingly popular because such processes provide greater productivity and flexibility. Such an increase in productivity and flexibility is the result of the continuous nature of welding electrodes in metal-gas arc welding (GNAW and GNAW-C) which offer substantial productivity gain over SMAW coated electrode welding) . These electrodes produce very good looking welds with very little slag, thus saving time and cost associated with cleaning the weld and slag waste, a problem that is often encountered in other welding processes. In metal-gas arc welding with solid or core electrodes, a shielding gas is used to provide protection to the weld against atmospheric contamination during welding. The solid electrodes are appropriately alloyed with ingredients that, together with the protective gas, provide porosity free welds with the desired physical and mechanical characteristics. In core electrodes, these ingredients are inside, in the core (filler) of a metallic outer shell and provide a similar function as in the case of solid electrodes. The solid and core electrodes are designed to provide, under appropriate gas protection, a sound weld virtually free of porosities with elastic limit, tensile strength, ductility and impact resistance suitable to perform satisfactorily in end uses. These electrodes are also designed to minimize the amount of slag generated during welding. Core electrodes are increasingly used as an alternative to solid wires due to their higher productivity during the fabrication of welding of structural components. Core electrodes are composite electrodes that consist of a core material (filler) surrounded by a metallic outer shell. The core consists mainly of metallic powder and flux ingredients to help with the stability of the arc, the adhesion of the weld and the appearance of the weld, etc., in such a way that the desired physical and mechanical properties are obtained in the welding. The core electrodes are manufactured by mixing the ingredients of the core material and depositing them within a formed strip, and then enclosing and extruding the strip to the final diameter. The core electrodes provide higher deposition rates and produce a wider and more constant penetration profile of the weld compared to solid electrodes. On the other hand, they provide better arc action, generate less smoke and splash, and provide weld deposits with better solder adhesion compared to solid electrodes.

In submerged arc welding, heating occurs with a voltaic arc between an electrode of bare metal and the metal that is being worked. The weld is covered with a granular or meltable material. The welding operation is initiated by pressing an arc under the flux to produce heat to melt the surrounding flow so that it forms a conductive puddle below the surface which is kept liquid by the continuous flow of current. The end of the electrode and the workpiece directly below it are fused and the molten filler metal is deposited, from the electrode, on the work piece. The molten filler metal displaces the melting puddle and forms the weld. In metallic arc welding with protection, the protection is obtained by means of a flux coating instead of a loose granular flux blanket. In the field of welding, many resources have been invested to develop flux compositions of the type having predetermined flux components intended to perform in predetermined ways. A large number of compositions have been developed for use as fluxes in arc welding. The fluxes are used in arc welding to control the stability of the arc, modify the composition of the weld metal and provide protection against air pollution. The stability of the arch is commonly controlled by modifying the composition of the flux. It is therefore desirable to have substances that function well as carriers of the plasma charge in the flux mixture. The fluxes also modify the composition of the weld metal making the impurities in the metal more easily meltable and providing substances with which these impurities can be combined in preference to the metal to form the 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 an obstruction to the flux particles. Core electrodes are commonly used in electric arc welding of base metals steel. These electrodes generally produce welds with high strength in one step and multiple passes at high welding speeds. These electrodes are formulated to provide a substantially pore-free healthy weld bead with tensile strength, ductility and impact resistance to meet the desired end use of various applications. One of the many challenges during the formation of a weld metal is to reduce the amount of diffusible hydrogen in the weld bead. Diffusible hydrogen is a known cause of cracking in weld seams. Many studies have shown that an increasing amount of moisture content in the flux system results in an increasing amount of diffusible hydrogen in the weld metal. During welding, the heat evaporates and dissociates the water, releasing hydrogen gas, which can dissolve in the metal. The hydrogen in the weld metal can result in hydrogen-induced cracking and eventual detrimental welding failure. The fragility by hydrogen is a phenomenon that implies the loss of ductility and increasing susceptibility of cracks in the steel at room temperature due to the presence of hydrogen in the steel. Hydrogen-induced cracking can occur to a certain degree as long as sufficient hydrogen and tension are present in a hard steel at temperatures above -100 ° C and below 150 ° C. Sodium and potassium silicates are commonly used as arc stabilizers and are often used in binder systems for the flux components. Potassium silicate is known for its great tendency to collect moisture. Another challenge during the formation of a weld metal is to control the amount and effect of impurities in the weld metal. Many of the flux components are derived from natural sources, therefore they have impurities contained within such components. A common component of the flux is titanium dioxide (TiO). This component is commonly added to a flux system in the rutile form. There are many different sources of rutile around the world. Each of these rutile sources includes various amounts and types of impurities. In flux systems where rutile comprises a significant portion of the flux system, these impurities can adversely affect the resulting weld metal. For example, many forms of rutile include small amounts of niobium and / or vanadium. These two components in small amounts can cause the formation of carbides in the weld metal, resulting in increasing brittleness of the weld metal. The formation of carbides can also result in high stress for metal welding which can lead to cracking of the weld metal and to a reduction in the impact resistance of the weld metal. The formation of carbides in the weld metal is especially detrimental in multi-pass welding processes. Considering current state-of-the-art flux systems, there is a need for a flux system having a reduced moisture content and a reduced amount of impurities to form a high quality weld bead.

SUMMARY OF THE INVENTION The present invention relates to solder fluxes and, more particularly, to a solder flux which resists water absorption and has a reduced amount of impurities. The flux system of the present invention can be used in all types of welding, such as submerged arc welding and armored metal arc welding. The flux system can be coated on a welding electrode, inserted into the core of a metal electrode and / or formed into a granular flux. The flux system of the present invention is particularly directed to a flux system based on titanium dioxide. The titanium dioxide content of the flux system is generally at least 4 weight percent of the flux system, typically about 5-90 weight percent of the flux system, more typically about 10-60 percent by weight. weight of the flux system, and more typically about 10-40 weight percent of the flux system; however, other percentages by weight may be used. The titanium dioxide in the flux system based on titanium dioxide is selected such that at least a portion of the titanium dioxide in the flux system includes purified titanium dioxide. The flux system of the present invention also includes a moisture resistant composite to reduce moisture collection from the flux system. It has been found that the use of a flux system that includes purified titanium dioxide in conjunction with a moisture resistant compound overcomes many of the latest problems associated with welding metals that have an undesired amount of hydrogen in the weld metal and metals. of solder that have an unwanted impurity content. In another and / or alternate non-limiting aspect of the present invention, the titanium dioxide in the flux system includes about 5 percent purified titanium dioxide. The use of purified titanium dioxide in the flux system based on titanium dioxide produces a reduction in the amount of impurities that are transported to the weld metal during a welding process. Small amounts of impurities in the natural sources of titanium dioxide can cause a high voltage in the welding metals, especially in operations of several welding passes. These small amounts of impurities can result in premature cracking of the weld metal and / or a reduction in the impact resistance of the weld metal. These harmful effects on the weld metal are partly caused by the formation of carbides in the weld metal. Various types of metals for example, but not limited to, Nb and V can form nucleation sites for such formation of carbides in the weld metal. Only very small amounts of these metals are needed to function as nucleation sites. In a titanium based flux system, the amount of titanium in the flux system can be significant. As such, although titanium dioxide includes very small amounts of impurities, a large amount of titanium dioxide in the flux system can result in a sufficient amount of these impurities that will be transferred to the weld metal during a welding process and in this way they function as the nucleation sites for the formation of carbides in the weld metal. To overcome this problem of impurities, a portion or all of the titanium oxide included in the flux system is purified titanium dioxide. The purified titanium dioxide generally includes less than about 5% by weight of impurities which can function as nucleation sites in the weld metal for the formation of carbides, typically less than about 1% by weight which can function as nucleation in the weld metal for the formation of carbides, more typically less than about 0.5% by weight of impurities that can function as nucleation sites in the weld metal for the formation of carbides, even more typically less than about 0.1% by weight of impurities that can function as nucleation in the weld metal for the formation of carbides, even more typically less than about 0.05% by weight of impurities that can function as nucleation sites in the weld metal for the formation of carbides, but still more typically less than about 0.01% by weight of impurities that can function as nucleation sites in the weld metal for the formation of carbides. In one embodiment of the invention, the titanium dioxide in the flux system includes at least about 25 percent purified titanium dioxide, the titanium dioxide in the flux system typically includes at least about 40 percent. of purified titanium dioxide, the titanium dioxide in the flux system includes, more typically, at least about 50 percent purified titanium dioxide, yet the titanium dioxide in the flux system more typically includes at least about 70 percent of purified titanium dioxide, and even more typically titanium dioxide in the flux system includes at least about 90 percent purified titanium dioxide. The flux system may include a combination of purified and natural titanium dioxide. A common source of natural titanium dioxide is rutile; however, it should be appreciated that another or additional natural sources of titanium dioxide can be used in the flux system. The purified titanium dioxide is defined in the present invention as titanium dioxide which is artificially manufactured and / or which comes from a natural source of titanium dioxide which has been purified. In a non-limiting embodiment of the invention, the sulfate process used to form the titanium dioxide may include the use of ilmenite ore, which contains iron and titanium and sulfuric acid; however, it can be appreciated that other additional minerals can be used. This process includes finally grinding and drying the ore. The mineral can also be classified. The ground ore is then digested into concentrated sulfuric acid where the titanium in the mineral changes to soluble titanyl sulfate. The drying and grinding of the ore helps to ensure the efficient sulfation of the mineral during the agitation with concentrated sulfuric acid. The solution formed is then purified and the iron is separated as crystallized green iron, or ferrous sulfate. The iron can be separated by dissolving metal sulphates in water or weak acid, and then treating the solution to ensure that iron is present only in the ferrous state. The solution temperature can be reduced to avoid premature hydrolysis and clarified by sedimentation and chemical flocculation. The clear solution is then further cooled to coarse and crystalline ferrous sulfate heptahydrate (known as "copperas", FeS04-7H20) which can then be separated from the process. During the precipitation step, the titanium oxide hydrate is precipitated and calcined in rotating high temperature ovens at about 800-1200 ° C to form the crystalline titanium dioxide. Precipitation is typically carefully controlled to achieve the necessary particle size, generally employing a seeding or nucleation technique; however, this is not regulated. The calcined titanium dioxide typically undergoes one or more washing steps to remove impurities from the raw materials used to form the titanium dioxide. The titanium dioxide formed can then be ground and finally classified to obtain a specific particle size. In another non-limiting embodiment of the invention, the chloride process used to form the titanium dioxide may include the use of natural and / or synthetic rutile; however, one or more additional sources of titanium dioxide may be used. Typically, the base material for the chloride process includes at least about 80-90% by weight of titanium dioxide. The base material is generally mixed with a carbon source and then reacted together in a fluidized bed with chlorine at about 800-1100 ° C. The reaction produces titanium tetrachloride, TiCl4 and chlorides of other impurities in the base material. The chlorides formed are cooled and the impurities of low volatility chloride (e.g., iron chloride, manganese chloride, chromium chloride, etc.) are separated by condensation and removed from the gas stream with another unreacted solid base material. The gaseous intermediate TiCl4 is condensed to a liquid and typically distilled fractionally to produce a pure, colorless and mobile TiCl liquid. The intermediate product TiCl4 is then reacted with oxygen in an exothermic reaction to form titanium dioxide and release the chlorine. The reaction at high temperature ensures that the Ti02 crystal is formed essentially. The formed Ti02 is then cooled and typically treated with a gas stream to remove the chlorine from Ti02. The titanium dioxide formed can then be finally milled and graded to obtain a particular particle size. The purified titanium dioxide generally includes at least about 85% by weight of titanium dioxide, typically at least about 90% by weight of titanium dioxide, more typically at least about 93% by weight of titanium dioxide, more typically at least about 95% by weight of titanium dioxide, even more typically at least about 98.5% by weight of titanium dioxide, and still more typically at least about 99 wt.% titanium dioxide, still still more typically at least about 99.5 weight percent titanium dioxide, and more typically at least about 99.9 wt.% titanium dioxide. The average particle size of the purified titanium oxide is generally no greater than about 100 mesh, typically no greater than about 200 mesh, and more typically about 200-400 mesh.; however, other particle sizes can be used. In yet another and / or alternate non-limiting aspect of the present invention, the moisture resistant composite includes one or more colloidal metal oxides. In addition to the moisture resistance characteristics of one or more colloidal metal oxides, the one or more colloidal metal oxides may also have slag-forming properties, binding properties, etc .; however, this is not regulated. When the one or more colloidal metal oxides are also used as a binder, the one or more colloidal metal oxides can form the complete binder function or can be used in conjunction with one or more additional binders for example, but not limited to, one or more silicate compounds (eg, potassium silicate, sodium silicate, etc.). The moisture resistant compound content of the flux system is generally at least about 1% by weight of the flux system, typically about 2-60% by weight of the flux system, and more typically about 2-35% by weight of the flux system. % by weight of the flux system; however, other percentages by weight may be used. In one embodiment of the invention, the moisture resistant compound includes colloidal silicone. In another and / or alternate embodiment of the invention, the one or more colloidal metal oxides form all or a portion of the moisture resistant compound. In another and / or alternative embodiment of the invention, the metal oxide which at least partially forms the colloidal metal oxide includes silicon dioxide. The silicon dioxide may be in a pure and / or impure form. Examples of impure forms include, but are not limited to, quartz, feldspar, mica, biotite, olivine, hornblende, muscovite, pyroxenes, and / or additional sources of silicon dioxide. In one aspect of this embodiment, at least about 5% silicon dioxide in the colloidal metal oxide is a pure form of silicon dioxide. In another and / or alternate aspect of this embodiment, typically at least about 10% of the silicon dioxide in the colloidal metal oxide is pure silicon dioxide, more typically at least about 30% of the silicon dioxide in the colloidal metal oxide is pure silicon dioxide, more typically at least about 50% of the silicon dioxide in the colloidal metal oxide is pure silicon dioxide, even more typically at least about 70% of the silicon dioxide in the colloidal metal oxide is pure silicon dioxide, but more typically at least about 90% of the silicon dioxide in the colloidal metal oxide is pure silicon dioxide. In yet another and / or alternate non-limiting aspect of the present invention, the moisture resistant composite functions at least partially as a binder for the flux system. When the moisture resistant compound functions at least partially as a binder, the average particle size of the solid particles in the colloidal metal oxide is selected small enough to achieve a binding effect of the colloidal particles. It has been found that when sufficiently small particles are used, a chemical binding effect, which is believed to be due to a Brownian effect, on the surface of the colloidal particles results in agglutination in conjunction with one or more components of the flux system by the colloidal particles. In one aspect of this embodiment, the average particle size of the particles in the colloidal particles in the moisture resistant composite are less than about 800 nm, typically less than about 200 nm, more typically less than about 100 nm. nm, still more typically less than about 70 nm, still more typically less than about 40 nm, still still more typically less than about 20 nm, even more typically less than about 10 nm, and still more typically close to 0.5-10 nm. In a non-limiting design, the average particle size of the colloidal particles is about 1-30 nm, typically around 2-25 nm, more typically about 5-15 nm and more typically about 5-10 nm. In one embodiment of the invention, the moisture resistant compounds may comprise 100% of the binder of the flux system or constitute a fraction of the binder of the flux system. When the moisture resistant composite represents a fraction of the binder of the flux system, the moisture resistant compound can be included and / or mixed with other binders. Such other binders may include, but not limited to, soluble silicate (potassium silicate and / or sodium silicate), boric acid, borax, soluble carbonates, nitrates, oxylates or oxychlorides, various types of resins, sugar, starch, agar, and / or the like. In yet another and / or alternate embodiment of the invention, the moisture resistant composite, by constituting a fraction of the total binder of the flux system, is generally combined with one or more silicates. When the colloidal particles in the moisture resistant composite are combined with one or more silicates, these components may constitute a majority of the flux system binder; however, this is not required. In one aspect of this embodiment, the colloidal particles together with one or more silicates constitute at least about 60% of the binder of the flux system, more typically constituting at least about 70% of the binder of the flux system, and still more typically it constitutes at least about 90% of the binder of the flux system. In another and / or alternative embodiment, when the colloidal particles of the moisture resistant composite constitute a fraction of the total binder of the flux system, the colloidal particle generally constitutes at least about 5% of the total binder, typically at least about 10% of the total binder, more typically at least about 20% of the total binder, still more typically at least about 50% of the total binder, still more typically at least about 70% of the total binder, but more typically at least about 90% of the total binder.

In yet another and / or alternate aspect of the present invention, the moisture resistant composite is formed at least partially from a solution of colloidal metal oxides. The solution generally includes 10-70% by weight of colloidal metal oxides and a liquid content of at least about 10 weight percent, and typically about 30-80 weight%; however, other percentages by weight may be used for metal oxides and / or liquid content. The pH of the solution is typically basic; however, this is not required. Generally, the liquid component includes mostly water, however, additional and / or alternative liquids may be used. The liquid is used to suspend the colloidal particles to allow the colloidal particles to bind the components in the flux system. In one embodiment of the invention, the liquid component substantially does not contain any hydrocarbon compound. The introduction of the hydrocarbon compounds into the liquid system can introduce hydrogen to weld metal during a welding process. In one aspect of this embodiment, the liquid contains less than about 10% hydrocarbon compounds, typically less than about 5% hydrocarbon compounds, more typically less than about 2% hydrocarbon compounds, and more typically less of about 0.05% hydrocarbon compounds.

In another and / or alternative non-limiting aspect of the present invention, the flux system is particularly oriented for use in core electrodes having a metal shell surrounding the flux system in the core of the shell; however, the flux system can be applied to other types of electrodes (e.g., coating on bar electrodes, etc.), or used as or part of a flux system in a submerged arc welding process. The flux system is formulated particularly for use with electrodes used to weld low alloy and low carbon steel; however, the flux system can be used with electrodes for the formation of weld beads in other types of metals. The metal electrode is typically formed especially of iron (e.g., carbon steel, low carbon steel, stainless steel, low alloy steel, etc.); however, the base metal can be formed from other materials. In one embodiment of the invention, the metal electrode includes a metal shell that includes the flux system in the core of the metal electrode. The metal wrap generally includes a majority of iron when welding a ferrous workpiece (e.g., carbon steel, stainless steel, etc.).; however, the composition of the wrap can include various types of metals to achieve a particular composition of the weld bead. In one aspect of this embodiment, the metal envelope includes mostly iron and may include one or more other elements, for example, but not limited to, aluminum, antimony, bismuth, boron, carbon, cobalt, copper, lead, manganese, molybdenum, nickel, niobium, silicon, sulfur, tin, titanium, tungsten, vanadium, zinc and / or zirconium. In yet another and / or alternate aspect of this embodiment, the iron content of the metal shell is at least about 80% by weight. In yet another and / or alternate embodiment of the invention, the flux system typically constitutes at least about 1% by weight of the total weight of the electrode, and no more than about 80% by weight of the total weight of the electrode, and typically about 8-60% by weight of the total weight of the electrode, and more typically about 10-40% by weight of the total weight of the electrode, and still more typically about 11-30% by weight of the total weight of the electrode; still more typically about 12-20% of the total weight of the electrode; however, other percentages by weight may be used. In yet another and / or alternative non-limiting aspect of the present invention, the flux system includes one or more slag-forming agents, other than titanium dioxide. Slag-forming agents are generally used to facilitate the formation of the weld bead and / or to at least partly protect the weld bead from the atmosphere; however, slag-forming agents may have other or additional functions. Non-limiting examples of such slag-forming agents include metal oxides (eg, aluminum oxide, boron oxide, calcium oxide, chromium oxide, iron oxide, magnesium oxide, manganese oxide, niobium oxide, potassium, sodium oxide, tin oxide, vanadium oxide, zirconium oxide, etc.), metal carbonates (eg, calcium carbonate, etc.), and / or metal fluorides (eg, barium fluoride, fluoride of bismuth, calcium fluoride, potassium fluoride, sodium fluoride, Teflon, etc.). The content of the slag forming agent of the flux system is typically at least about 2% by weight, of the flux system, typically about 5-60% by weight of the flux system and more typically about 5-45% by weight of the flux system; however, other percentages by weight may be used. In yet another and / or alternative aspect of the present invention, the flux system includes one or more metal agents. The flux system may include metal alloying agents (eg, aluminum, boron, calcium, carbon, cobalt, copper, chromium, iron, magnesium, manganese, molybdenum, nickel, selenium, silicon, tantalum, tin, titanium, zirconium, zinc, etc.) which are used at least partially to provide protection to the weld metal during and / or after a welding process, to facilitate a particular welding process, and / or to modify the composition of the weld bead. In one embodiment of the invention, the flux system includes at least one of the welding metal protection agents. In another and / or alternate embodiment of the invention, the flux composition includes one or more metal alloying agents that are used to facilitate the formation of a weld metal with the desired composition. In yet another and / or alternate embodiment of the invention, the flux composition includes one or more metal slag modification agents. Slag modification agents are typically used to increase and / or decrease the slag viscosity, to improve the ease of removal of slag from metal welding, reduce smoke production, reduce splash, etc. The metal agents, when included in the flux system, generally constitute at least 1% by weight of the flux system, typically about 5-85% by weight of the flux system, more typically about 10-60% by weight. weight of the flux system; however, other percentages by weight may be used.

In still another and / or alternative aspect of the present invention, a protective gas is used in conjunction with the electrode to provide protection to the weld bead of elements and / or compounds in the atmosphere. The protective gas generally includes one or more gases. These one or more gases are generally inert or substantially inert with respect to the composition of the weld bead. In one embodiment, argon, carbon dioxide or mixtures thereof are used at least partially as a protective gas. In one aspect of this mode, the protective gas includes about 2-40 percent by volume of carbon dioxide and the argon balance. In another and / or alternate aspect of this mode, the protective gas includes about 5-25 percent by volume of carbon dioxide and the argon balance. As can be appreciated, other and / or additional inert or substantially inert gases can be used. In another and / or alternate aspect of the present invention, the flux system of the present invention is dried and then milled to a certain particle size. The ground particles can be screened or otherwise sorted to obtain a desired particle size profile. Generally, the flux system is milled and then sieved to obtain an average particle size of the flux system of less than about 48 mesh, typically close to 80-400 mesh, and more typically close to 100-200 mesh; however, other particle sizes can be selected. When the flux system is used in a submerged arc welding process, the ground flux system typically empties into a groove in a work piece and then is subjected to an electric arc as a metal rod is melted to form the welding metal. When a flux core electrode is being formed, a certain amount of ground flux is deposited on the electrode before the electrode is formed on a core electrode, where the flux system fills the base region of the electrode. It is an object of the invention to provide a flux system that reduces the amount of impurities that reside in the weld metal. Another and / or alternative object of the present invention is to provide a flux system that reduces the incidences of cracking in the weld metal. Still another and / or alternate object of the present invention is to provide a flux system that reduces the amount of carbide formation in the weld metal. Another and / or alternative subject of the present invention is to provide a flux system that reduces the diffusible hydrogen content in the weld metal.

Still another and / or alternative object of the present invention is to provide a flux system having reduced moisture collection properties. Another and / or alternative object of the present invention is the provision of a flux system that includes titanium dioxide and colloidal metal oxide. Still another and / or alternate object of the present invention is to provide a flux system that can be used in a submerged arc welding process, which can be coated on an electrode, and / or can be used in the core of an electrode of flux core. Still another and / or alternative object of the present invention is to provide a flux system that includes a binder that chemically agglutinates together one or more components of the flux system. Still another and / or alternative object of the present invention is to provide a flux system that is used in conjunction with a protective gas. Still another and / or alternative object of the present invention is to provide a flux system that is used with a self-protecting electrode. These and other objects and advantages will become apparent from the discussion of the distinction between the invention and the state of the art and when the preferred embodiment is considered as shown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an illustration of two different titanium oxide purification processes that can be used to form purified titanium dioxide for use in the flux system of the present invention. Figure 2 is an illustration of a non-limiting process that can be used to form the flux system of the present invention.

DESCRIPTION OF THE INVENTION Referring now in more detail to the figures, wherein the illustrations are for the purpose of illustrating the preferred embodiments of the invention only, and not for the purpose of limiting the invention, Figure 1 illustrates two processes (eg, the process of sulfate and the chloride process) which can be used to produce purified titanium oxide for use in the flux system of the present invention. The sulfate process typically includes the use of il enite as the base material. The ilmenite is mixed with hydrogen sulfate, and the ferrous sulfate heptahydrate is then removed. The remaining mixture is washed and then calcined. The titanium dioxide can then be ground and classified. The formation of titanium dioxide by a sulphate process is known in the medium and will not be described in more detail. The chloride process typically includes rutile as the base material. The rutile is mixed with a carbon source and reacted in a fluidized bed with chlorine to form titanium tetrachloride. The titanium tetrachloride is then oxidized to form titanium dioxide. The titanium dioxide can then be milled and classified. The formation of titanium dioxide by a chloride process is known in the medium and will not be described further. The purified titanium dioxide is used in a flux system based on titanium dioxide to overcome the above limitations of the flux systems of the state of the art with respect to the introduction of impurities in the weld metal during a welding process. The purified titanium dioxide has very little or no metal impurities that can act as nucleation sites in the weld metal for the formation of carbides. Impurities such as niobium and vanadium are eliminated from or reduced significantly in purified titanium dioxide. The purified titanium dioxide typically includes impurities of less than about 0.1% by weight which can function as nucleation sites in the weld metal for the formation of carbides. The purified titanium dioxide is generally a fluffy compound having a relatively low bulk density. As such, the purified titanium dioxide may not produce sufficient volume in the flux system, especially when used in the core of an electrode. As such, the purified titanium dioxide is typically agglomerated with one or more other components of the flux system; however, this is not regulated. When the purified titanium dioxide is agglomerated at least partially, the purified titanium dioxide is typically mixed with one or more binders (e.g., cidal metal oxide, soluble silicate, etc.). The titanium based flux system typically includes cidal silicone as a moisture resistant composite to reduce the moisture cction characteristics of the titanium based flux system; however, this is not required. The moisture in the flux system can provide a source of hydrogen on the weld metal that can lead to increasing levels of diffusible hydrogen in the weld metal. The moisture resistant compound in the titanium based flux system reduces the amount of water in the flux system in a way that facilitates the reduction of diffusible hydrogen in the weld metal. The cidal silicone can also function as a binder for one or more components of the flux system for example, but not limited to, purified titanium dioxide. In addition to titanium dioxide and cidal silicone, the flux system may include one or more metal oxides (eg, aluminum oxide, boron oxide, calcium oxide, chromium oxide, iron oxide, magnesium oxide, niobium oxide, potassium oxide, sodium, tin oxide, vanadium oxide, zirconium oxide, etc.), metal carbonates (eg, calcium carbonate, etc.), metal fluorides (eg, barium fluoride, bismuth fluoride, calcium fluoride, potassium fluoride, sodium fluoride, Teflon, etc.), and / or metal alloying agents (eg, aluminum, boron, calcium, carbon, iron, manganese, nickel, silicon, titanium, zirconium, etc.). The particular components of the flux system typically depend on the type of welding process (SAW, SMAW, FCAW) to be used and / or on the type of workpiece to be welded. Referring now to Figure 2, a process for forming part of or a complete flux system for use in submerged arc welding or for filling the core of a flux core electrode is illustrated. The purified titanium oxide is combined with a colloidal silicone solution in a mixer. As can be appreciated, other components of the flux system can also be added. The average particle size of the purified titanium oxide is typically close to 200-400 mesh and the average particle size of the colloidal silicone is typically close to 2-50 mesh; however, other particle sizes can be used. When other flux components are added, these other flux components typically have an average particle size of about 40-400 mesh. The flux components can be mixed in a variety of mixers for example, but not limited to, an Eirich mixer. The components of the flux and / or the metal alloying agents are then mixed by the mixer to form a wet mixture. As seen, the flux components can first be mixed with colloidal silicone and then with the metal alloying agents, or the metal alloying agents can first be mixed with colloidal silicone and then with the flux components, or in any another mixing order. Typically, more than 80% by weight of the small particles in the colloidal particles in the flux system are silicon dioxide particles. The liquid component of the colloidal solution typically constitutes about 60-85% by weight of the colloidal solution, and more typically about 70% by weight of the colloidal solution. The liquid is typically water; however, other and / or additional liquids may be used. The colloidal particles in the colloidal solution may function as the binder for the flux system, or one or more binders may be included in the flux system. When the colloidal particles are used with one or more other binders, the other binders typically include soluble silicate; however, this is not required. When the binder of the flux system is formed primarily of soluble silicate and the colloidal particles, the colloidal particles typically form about 5-75% by weight of the binder and more typically about 20-50% by weight of the binder. After the flux components have been properly mixed together, the flux components are dried to reduce the moisture content of the flux system. The flux may be dried in a variety of dryers for example, but not limited to, a continuous rotary or batch high temperature furnace. The drying temperature is typically about 93.3-982.2 ° C (200-1800 ° F); however, other temperatures can be used. The flux system is dried until the moisture content of the flux system is less than about 6% by weight, more typically less than about 3% by weight, even more typically less than about 1% by weight, yet more typically less than about 0.5% by weight, and even more typically less than about 0.2% by weight. The moisture content of the flux system after the drying process typically depends on the type of arc welding process used. Flux systems used in high strength steel welding processes where the hydrogen content is desired to be at extremely low levels, typically have less than about 1% of the moisture content of the flux system, more typically less of about 0.4%, more typically less than about 0.2%, and even more typically less than about 0.15%. After the flux system has dried, the flux system is milled and sieved or otherwise sorted to obtain the desired particle size of the flux system. The flux system typically has an average particle size of about 40-200 mesh. The flux system formed by this process can be the complete flux system used during a welding process, or form a portion of the complete flux system. When it only forms a portion of the complete flux system, the flux system formed by the above process is combined with one or more other flux agents and / or metal agents to form the complete flux system. Typically, the flux system formed by the above process constitutes at least about 15% by weight of the complete flux system, and more typically at least about 30% by weight of the complete flux system, and even more typically by at least a majority of the complete flux system. A general formulation of the flux system (percent by weight) according to the present invention is established as follows: Ti02 (at least 5% purified) 2-70% Colloidal metal oxide 1-40% Slag former 1-60% 0-80% metal alloy agent In another general formulation of the flux system (percent by weight): Ti0 (at least 20% purified) 3-60% Colloidal metal oxide 1-30% Slag forming agent 0-50% Metal alloying agent 0-70% In yet another general formulation of the flux system (for cent in weight): Ti02 (at least 50% purified) 5-40% Colloidal metal oxide 1-25% Slag forming agent 5-45% Metal alloy agent 0-50% In yet another general formulation of the flux system (percent by weight): Ti02 (at least 90% purified) 10-40% Colloidal silicone 1-20% Slag forming agent 10-40% Metal alloy agent 0-40% In the previous examples, the flux system can be used in a core electrode. The weight percent of the flux system in the core electrode is typically about 8-60% by weight of the core electrode, and more typically about 10-25% by weight of the core electrode; however, other percentages by weight may be used. The metal sheath that can be used to form the weld bead may include about 0-0.2 wt.% B, about 0-0.2 wt.% C, about 0-12 wt.% Cr, near 0-5% by weight of manganese, about 0-2% by weight of Mo, less than about 0.01% of N, about 0-5 of Ni, less than about 0.014% of P, about 0 -4% by weight of Si, less than about 0.02% of S, about 0-0.4% by weight of Ti, about 0-0.4% by weight of V and about 75-99.9% by weight of Fe. During an arc welding process, a shielding gas can be used with the core electrode; however, this is not required. When a protective gas is used, the shield is typically a mixture of carbon dioxide and argon. The slag forming agent typically includes, but is not limited to, metal oxides such as aluminum oxide, boron oxide, calcium oxide, chromium oxide, iron oxide, magnesium oxide, niobium oxide, potassium; sodium oxide, tin oxide, vanadium oxide and / or zirconium oxide. The metal alloying agent, when used, typically includes, but is not limited to, aluminum, boron, calcium, carbon, iron, manganese, nickel, silicon, titanium and / or zirconium. The flux system may include other compounds for example, but not limited to, metal carbonates (eg, calcium carbonate, etc.) and / or metal fluorides (eg, barium fluoride, bismuth fluoride, calcium fluoride, potassium fluoride, sodium fluoride, Teflon, etc.). The particular components of the flux system typically depend on the type of welding process (SAW, SMAW, FCAW) to be used and / or on the type of workpiece to be welded.

These and other modifications of the modalities discussed, as well as other modalities of the invention, will be obvious and suggested to the experts in the matter described herein, so it should be clearly understood that the preceding descriptive matter should simply be interpreted as illustrative of the current invention and not as a limitation of it.

Claims (26)

1. A solder flux comprising titanium dioxide and a moisture resistant agent, titanium oxide including purified titanium dioxide, moisture resistant compound including a colloidal metal oxide, colloidal metal oxide having a particle size average of less than about 800 nm, the purified titanium dioxide including less than about 5% by weight of impurities which can act as nucleation sites for the formation of metal carbides in a weld metal.

2. The solder flux as defined in claim 1, wherein the titanium dioxide constitutes about 5-90% by weight of the solder flux.

3. The solder flux as defined in claim 1, wherein at least about 5% by weight of titanium dioxide is purified titanium dioxide.

4. The solder flux as defined in claim 2, wherein at least about 5% by weight of titanium dioxide is purified titanium dioxide.

5. The solder flux as defined in claim 1, wherein the colloidal metal oxide includes silicone.

6. The solder flux as defined in claim 4, wherein the colloidal metal oxide includes silicone.

7. The solder flux as defined in claim 1, wherein the moisture resistant composite constitutes about 1-60% by weight of the solder flux.

8. The solder flux as defined in claim 6, wherein the moisture resistant composite constitutes about 1-60% by weight of the solder flux.

9. The solder flux as defined in claim 1, including metal agent, the metal agent constituting about 1-85% by weight of the solder flux.

10. The solder flux as defined in claim 8, including metal agent, the metal agent constituting about 1-85% by weight of the solder flux.

11. The solder flux as defined in claim 1, wherein the average particle size of the flux is close to 40-300 mesh.

12. The solder flux as defined in claim 10, wherein the average particle size of the flux is close to 40-300 mesh.

13. The solder flux as defined in claim 1, wherein the moisture content of the solder flux is less than about 1%.

14. The solder flux as defined in claim 12, wherein the moisture content of the solder flux is less than about 1%.

15. The solder flux as defined in claim 1, including a binder, the binder including a mixture of colloidal metal oxide and metal silicate, the mixture constituting a majority weight percentage of the binder, the metal silicate including potassium silicate, sodium silicate and their mixtures.

16. The solder flux as defined in claim 14, which includes a binder, the binder including a mixture of colloidal metal oxide and metal silicate, the mixture constituting a majority weight percentage of the binder, the metal silicate including potassium silicate, sodium silicate and their mixtures.

17. A method for forming a flux system based on titanium oxide, which has a low moisture content, resists moisture absorption and reduces the amount of impurities transferred to a weld metal comprising: providing titanium dioxide , titanium dioxide including purified titanium dioxide; provide a solution of colloidal metal oxide, colloidal metal oxide having an average particle size of less than about 800 nm; mix titanium dioxide and colloidal metal oxide solution together; and, drying the mixture at a temperature of at least about 400 ° C for at least about 30 minutes until a moisture content of the mixture is less than about 1%.

18. The method as defined in claim 17, including the step of grinding the dry mix to an average particle size of about 40-200 mesh.

19. The method as defined in claim 17, wherein the colloidal metal oxide includes silicone.

The method as defined in claim 18, wherein the colloidal metal oxide includes silicone.

The method as defined in claim 17, which includes the step of providing metal agent and mixing the metal agent with titanium dioxide and colloidal metal oxide solution.

22. The method as defined in claim 20, which includes the step of providing metal agent and mixing the metal agent with titanium dioxide and colloidal metal oxide solution.

The method as defined in claim 17, which includes the step of providing binder and mixing the binder with the titanium dioxide and colloidal metal oxide solution, including the metal silicate binder.

The method as defined in claim 22, which includes the step of providing binder and mixing the binder with the titanium dioxide and colloidal metal oxide solution, including the metal silicate binder.

25. The method as defined in claim 17, wherein the ground mixture is a submerged arc flux or a flux for a core electrode.

26. The method as defined in claim 20, wherein the ground mixture is a submerged arc flux or a flux for a core electrode.