CA2109271C - Flux cored gas shielded electrode - Google Patents
Flux cored gas shielded electrodeInfo
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- CA2109271C CA2109271C CA 2109271 CA2109271A CA2109271C CA 2109271 C CA2109271 C CA 2109271C CA 2109271 CA2109271 CA 2109271 CA 2109271 A CA2109271 A CA 2109271A CA 2109271 C CA2109271 C CA 2109271C
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Abstract
A cored electrode for gas shielded arc welding to deposit a weld metal bead, where the electrode has a core of fill material surrounded by a ferrous tube with the fill material having alloying agents and oxide fluxing ingredients including, by weight of fill material, 40-60% titanium dioxide, 0.3-0.5% boron oxide, and 1.0-5.0% aluminum powder, with said aluminum powder having a higher affinity for oxygen than the oxide fluxing ingredients and with the amount of aluminum powder selected to produce .02-.08% titanium, less than .002% boron and less than 0.10% aluminum in said weld metal.
Description
-FLUX CORED GAS SHIELDED ELECTRODE
This invention relates to the art of arc welding using consumable steel electrodes and more particularly to an improved flux cored gas shielded electrode. Unless otherwise stated, all percentages referred to in this specification are percentages by weight.
As background information, U.S. Patent No. 5,233,160 should be referred to.
U.S. 5,233,160 is directed toward a flux cored electrode of the type used with shielding gas that employs a small amount of aluminum powder in the core of the electrode to reduce fume created during the arc welding process. The powdered alu.~ ll reacts with o other constituents in the core material and sheath of the electrode in the area or reaction zone defined as the arc surrounded by the shielding gas. The reaction zone is between the electrode and molten metal weld bead. During development of a novel flux cored electrode having reduced fume characteristics, a more general invention in gas shielded flux cored electrode technology was made. This novel advance in the art of flux cored electrodes is the subject of the present invention. The prior application contains background information and certain aspects of the present invention which need not be repeated.
Oku 3,558,851 is referred to as background information. Ferro-aluminum, in minor amounts is added to the fill material as a strong deoxidizing ingredient. The small 2 o amount of ferro-alll.llilllllll or aluminum powder is used to kill the steel of the weld bead and does not react in the arc zone above the molten metal of the weld bead. The amounts of ferro-all " " i . l l l,,, in this patent are substantially less than found necessary for practicing the present invention. This patent does not teach the advantage of using aluminum for the purposes of reducing lil~ l dioxide and/or boron oxide for alloying purposes, nor 2 5 is the aluminum in the electrode of the Oku patent of sufficient amount to perform the nitrogen removing function of the present invention.
Kobayashi 4,510,374 relates to the use of a low carbon sheath for an electrode to be used in a shielded arc welding process. Again, aluminum is mentioned as a deoxidizer which is common practice; however, the alllllli~lllln employed in this prior patent is in the 3 o form of ferro-aluminum or alumillulll powder for alloying purposes. In addition, there is no teaching of the amount of alllminllm necessary for performing the function of the present invention wherein the al~ ulll powder reacts above the molten metal in the weld metal to perform a reduction function in a location removed from the molten metal.
In this prior patent, the ferro-allllllillulll or alllllli~lulll powder enters the weld metal and is then used as a deoxidizer. This action creates alllminum oxide which must float to the surface of the weld bead for inclusion in the slag over the weld bead. The present invention employs alnminllm powder for a chemical reaction above the weld bead at a time prior to the aluminum entering the weld bead itself. Thus, a chemical reduction effect takes place by the action of the aluminum in the reaction zone outside the weld bead. Moreover, the aluminum in the present invention is available for nitrogen 0 scavenging of the weld metal.
Munz 4,723,061 is directed to a flux cored electrode using alnminum oxide for the purpose of controlling the physical properties of the molten slag over the weld bead.
The alllminnm oxide is for slag forming purposes only. A high amount of aluminumoxide was used as the slag viscosity controlling constituent contained in the fill material.
Aluminum powder could be provided for oxidation and used to control the slag. This patent does not teach the amount of alu~l,in~ll used to create allllllillulll oxide since provision of all ~ u ~ ~ ~ oxide was the only objective explained in this prior patent. There is no example ofthe use of allllllirllllll powder in any proportionto obtain any particular function in the gas shielded electrode other than formation of aluminum oxide.
2 o Bushey 5,095,191 discloses a gas shielded arc welding electrode using cesium.
A certain amount of alllll~illu,~ is suggested as one of many alloying elements; however, there is no te~hing of the manner by which alllminum can be employed for any particular use, except for alloying purposes.
BACKGROUND OF INVENTION
For many years, alll...illll.ll alloying systems have been successfully used in self shielded flux cored welding electrodes to produce weld deposits with exceptional impact 3 o and strength properties. Exceptional mechanical properties can be developed when using self shielding flux cored welding electrodes when the deposited weld metal has an aluminum content of approximately 0.5%. It is believed that the al-lminum forms a nitride which precipitates in the metal of the weld bead and enhances the mechanical properties of the weld metal. The alllminllm is employed for alloying with the weld metal to remove oxygen and free nitrogen from the solidified weld bead. In the well developed specialized technology used to create self shielded flux cored weldingelectrodes, the use of alumimlm to alloy with the weld bead metal has resulted in a weld bead alloy about 0.5 to 1% al~ With this alloy composition, the allllllilllllll nitride is formed and free nitrogen is not generally available. As the amount of alloyedalllminllm was decreased in the weld metal, it was found that the porosity of the weld 0 metal increased to decrease the strength and impact characteristics of the weld joint.
Consequently, it was believed that when alnminllm was used as an alloying agent for the weld metal in self shielded welding, it was necessary to create more than 0.5% allllllit~lllll in the weld metal. This use of an alllminllm for the controlling properties of the weld bead allowed the aluminum to interact within the weld bead as an alloying constituent.
Since the electrode was self shielding, the gases created by the arc expelled air and prevented oxygen and nitrogen from ingressing into the molten metal due to the rapid egress of gas created by the arc. Thus, there was no reaction zone in the arc in which the alulllit-lll-~ was primarily reacted with other con~titll~nt~ The al--minllm entered the weld bead and alloyed with the metals of the weld bead.
2 o When using gas shielded flux cored arc welding electrodes as contemplated by the present invention, deoxidation of the weld metal or control of nitrogen in the weld metal is not prim~rily dependent on alnmimlm These particular electrodes are prim~rily carbon-m~ng~nese-silicon type systems which rely on the gas shielding to preventnitrogen corl~ "i l~tion of the weld pool metal by excluding the surrounding atmosphere.
2 5 M~n~;~nese and silicon are used as alloying agents for deoxidizing or killing the metal in the weld metal bead. The use of alulllhlulll of any type in gas shielded electrodes, which is not a concept employed in practice, has merely been suggested as one of many possible means of alloying the weld metal. There has been no suggestion of usingaluminum for reaction in the reaction zone of the arc above the weld metal pool in an 3 o electric arc welding process of the type using shielding gas. Consequently, electrodes used in arc welding with shielding gas intentionally avoided alll~it~ in the weld metal V. ~
deposit believing that this lack of aluminllm in the deposit would assist in providing better mechanical properties. In the past, the use of alllminum alloying agent for a gas shielded electrode was not used in practice, and the weld metal generally had noalllminllm in the weld metal. This was believed to assure better strength and impact characteristics. There was no effort to use aluminum as an alloying agent in the weld bead when using shielded gas type of flux cored electrodes.
THE INVENTION
It has been recently discovered that small amounts of alulllillulll in powder form in the core of an electrode of the type having no internal shielding gas was instrumental in reducing the fume level and improving the arc action at high wire feed speeds. The use of up to about 1.0-2.0% aluminum powder in the core was found to modify the traditional carbon-m~ng~n~se-silicon systems to reduce fume. It has now been found that, contrary to conventional wisdom in the shielded flux cored electrode technology, aluminum powder in the core of the electrode can result in tensile strength and Charpy impact characteristics approaching those levels obtainable by solid wire welding. This is an ultimate objective of the flux cored electrode technology. Heretofore, flux cored 2 o electrodes had advantages of convenience, but sacrificed mechanical properties. The objective of approaching properties of solid wire welding is approached by the use of controlled amounts of aluminum powder in the core of a gas shielded flux cored arc welding electrode in accordance with the present invention. Consequently, the present invention relates to the use of alllminllm in a conventional carbon-m~ng~nese-silicon 2 5 system for a gas shielded flux cored electrode, in which it is highly reactive in the arc above the weld metal to p~lrolln the desired functions, before any residual amount enters the weld metal. It has been found that the alllminllm in the arc reduces lil~liulll dioxide and boron oxide to allow slight amounts of lil~ ll and boron metals to enter the molten pool of weld metal as alloying elements. It also seems to decrease the total nitrogen in 3 o the weld deposit when compared to the C-Mn-Si-Ti system. Sufficient amounts of all, . " i l l l l l l l, defined as a percentage in this application, creates a certain amount of residual y ~ !
aluminum in the weld metal. This alumi~ constituent of the weld metal in the amounts caused by use of the present invention is highly beneficial. This residual al lmim-m is used to reduce the free nitrogen in weld metal. This is an advantage since notch toughness and CTOD properties of the weld deposit metal deteriorate rapidly as the free nitrogen in the weld metal increases.
By use of the present invention, the alllminllm reduces the lil~iulll dioxide and/or the boron oxide for the purposes of creating a certain amount of elemental lil~liulll and/or boron in the weld metal. The advantages of titanium and boron are well known in the technology of gas shielded flux cored electrodes. The invention is also 0 useful in TiBor type electrodes. In addition, the invention allows the combination of boron oxide and a controlled amount of alll.l.illll.ll powder to control the actual boron in the weld metal. This concept is superior to the use of boron as an alloy in the steel sheath of the electrode and is easier to control than the use of elemental boron in the core of the electrode.
In the present invention, one of the most important features is the reduction oftotal nitrogen in the weld metal by the use of alllminllm when compared to the conven-tional C-Mn-Si-Ti system for a given nitrogen content in the cored wire. This isaccomplished either by reducing the nitrogen intake in the weld metal by reduction of nitrogen oxide formation in the arc or by helping nitrogen evolution from the weld metal 2 o by preventing iron oxide formation on the weld metal surface.
Moreover, in the present invention, the residual allllllillll... in the weld metal is less than 0.1% by weight of the weld metal. This controlled amount of alllminllm in the weld metal is sufficient to reduce the amount of free nitrogen in the weld bead. The reduction of total and free nitrogen in the weld metal enhances its mechanical properties.
2 5 As an explanation of this concept, details of the states of nitrogen in the weld metal can be helpful. Total nitrogen in the weld bead represents nitrogen in the following forms:
free, interstitial nitrogen that is dispersed or collected around grain boundaries, nitrogen in the form of simple or complex nitrides, and occluded nitrogen in the molecular gaseous state contributing to the porosity of the weld metal. In gas shielded systems, 3 o total nitrogen in the weld metal tends to be quite low due to shielding of the arc and the weld metal from the atmosphere. By the use of the present invention, alulllinulll in the 2109~7l core of electrode in the amount of 1 to 5 wt%, reduces total nitrogen in the weld deposit even further. This precludes the existence of occluded nitrogen in the weld metal.
Thelefole, total nitrogen in the weld metal in this system is the sum of free nitrogen and nitrogen in the form of nitrides, the relative amounts of which are determined by the amount of available nitride formers. Since titanium and boron are strong nitride formers, some of the nitrogen would be fixed as lil~~ l nitride and boron nitride. The rem~ining nitrogen is present as free nitrogen which is available to combine with aluminllm. By the use of the present invention, a slight amount of alll.llilllllll which is less than 0.1% of the weld metal and preferably less than .03% of the weld metal is in the deposited metal.
0 This aluminum reacts with the free nitrogen and forms aluminum nitride. Since the amounts of alu~ni~ and nitrogen in the weld metal are low, these alulllillulll nitride particles develop late, presumably in the solid weld metal. In any event, aluminum decreases free nitrogen in the weld metal. Moreover, the amount of these nitride inclu-sions in the weld metal are low. Both these factors improve the impact properties of the weld metal.
In accordance with the present invention, the residual alumimlm in the weld metal is less than 0.10% by weight of the weld metal. This controlled amount of aluminum in the weld metal is sufficient to reduce the amount of free nitrogen in the weld bead for the purposes of enhancing the physical properties of the weld bead. As an explanation of this 2 0 concept, details of nitrogen formation can be helpful. Nitrogen can be present in the weld bead as free, interstitial nitrogen that is dispersed or collected around grain boundaries.
Also nitrogen can be present as nitrides in either simple or complex precipitated phases.
In addition, occluded nitrogen can be present in the molecular gaseous state which contributes to the porosity ofthe weld metal. By the use ofthe present invention, a slight 2 5 amount of allllllilllllll which is less than 0.10% of the weld metal and preferably less than about .03% of the weld metal is in the deposited metal. This amount of aluminum has been found to produce superior mechanical pl~p~;llies in the weld deposit al)palelllly through the further reduction of free nitrogen by the formation of stable aluminum nitrides.
3 o Since this nitride develops late in the solidification process, the nitrides that form when using the present invention are dirr~lclll than the earlier formed nitrides of a ~r standard carbon-m~ng~nese-silicon system. Such nitrides in conventional systems for flux cored electrodes of the type to which the present invention is directed are formed early in the solidification process. This will produce coherent precipitate particles which cause a skain in the lattice of the solidified weld metal which creates forces that tend to fracture the crystalline skucture of the weld metal. Consequently, the amount of energy required to break a weld joint of a Charpy V notch impact specimen is substantially increased by use of the present invention because the amount of internal strain energy produced by the incoherent nitrogen precipitates is substantially less than the coherent precipitate particles of the nitride compound realized in conventional 0 carbon-m~ng:~nese-silicon electrode system.
In accordance with the preferred embodiment of the present invention, titanium dioxide and boron oxide is contained in the core of the electrode. Alllminllm powder within the electrode core chemically reacts in the zone created by the arc to reduce the boron oxide and a portion of the titanium dioxide. This allows a conkolled amount of titanium and boron to be introduced into the weld metal. The advantages of these two alloying agents for the weld metal is well documented. The present invention has the ability to accurately control the lil~liulll or boron in the weld metal bead by proper selection of the amount of alulllhlu~ll powder within the core of the electrode. This is a feature of the present invention that is not employed in other gas shielded flux cored arc 2 o welding electrodes.
The present invention employs a controlled amount of alllminllm powder which is added to the fill of somewhat standard flux cored electrodes. By using the present invention, it has been found that removal of foundry grade ferro-type titanium from an electrode does not decrease the impact properties of the resulting weld metal. These 2 5 mechanical properties are retained by the use of alumillulll powder in the core material.
It is believed that the superior mechanical properties are obtained by the present invention because the added alulllinulll, in a conkolled amount, creates the proper levels of li~lium and boron in the weld deposit for o~lhllulll mechanical properties through a direct reduction of titanium dioxide and boron oxide by the added al~ l l l l Consequently, 3 o metallic titanium, such as ferro-titanium, and metallic boron are not required in the fill material. The aluminum reacts in the zone of the electric arc above the weld metal to ~7 ~ jl ~1 Oq271 yield a controlled amount of titanium and boron for depositing into the weld bead to obtain the desired mechanical characteristics. Residual alllminllm content of the weld deposit remains low by using the present invention as long as the fill m~t~ri~l in the core has sufficient oxides with a negative free energy more positive than the negative free energy of aluminum oxide. Consequently, the present invention employs a controlled amount of alllmimlm powder in the core. This powder reacts in the zone above themolten metal pool to reduce lil~~ l oxide or boron oxide or both for alloying of the two elements in the weld bead. The alulllinlllll powder is selected so that the amount of residual alllmimlm in the weld bead is less than 0.1% by weight of the weld bead metal.
This amount of all ", lilllll " is sufficient to react with the nitrogen in the weld bead metal to form alllminum nitride. The amount of lil~ n and boron recovered in the weld bead deposit for a given fill composition of the electrode is proportional to the amount of metallic aluminllm powder in the core of the electrode. Increased amounts of alllminum will result in greater recovery of li~liulll and boron from the lil~liulll dioxide and boron oxide compounds present in the fill m~t~ri~l of the electrode. Consequently, the amount of aluminum powder is selected to produce a desired amount of titanium, boron, and residual alll,,,illll,,, in the weld metal. It has been found that the percentage of aluminum powder required in the fill material is approximately 1.0-5.0% by weight of the fill m~teri~l.
2 o A substantial percentage of aluminum powder is consumed in the reaction zone of the arc, with only a slight amount of aluminum actually entering the weld metal in accordance with the present invention. By using the present invention, the nitrogen content of the weld bead is lower than that realized in conventional electrode systems using carbon-m~ng~n~se-silicon and lil~liulll. It would appear initially that the addition 2 5 of aluminum would result in a higher level of deposited nitrogen due to the aluminum nitrides which would be created. However, as mentioned before, alulllilllllll lowers the oxidation potential in the arc. This presumably minimi7es the nitrogen oxide formation which reduces nitrogen pickup in the weld. Alllminum also reduces formation of iron oxides on the weld metal surface which helps nitrogen evolution from the weld metal.
3 o Residual all.ll li lllll l l combines with free nitrogen rem~inin~ in the weld metal to form alllminllm nitride. Consequently, the use of the present invention substantially enhances ~ 1 oq27 1 the mechanical properties of the weld bead metal by reducing the total and free nitrogen and having a controlled low amount of alumillulll. A substantially high percentage of al~ is used in the fill m~teri~l so that the allllllilllll,l is available to react above the weld metal pool to reduce lil~ l or boron or both for alloying purposes with a slight residual alllminllm that appears in small quantities in the weld bead metal.
Theuseofpowderedall""i,~-l",inthecoreofagasshieldedfluxcoredelectrode has been found, in low levels, to reduce the fume emission of the electrode. By increasing the amount of alulllilllllll powder to a controlled amount, dependent upon the desired reduction of titanium oxide or boron oxide or both, optimum mechanical 0 properties can be achieved. The amount of lil~liulll and boron within the weld metal is also controlled. Titanium in the weld metal should be in the range of .020-.080% by weight of the weld metal. Preferably the titanium in the weld metal is in the range of .025-.055% by weight of weld metal. The amount of boron should be at least .002% by weight of metal and preferably in the range of .0025-.0065% by weight of the metal in the deposit. The selection of alllll li~ to obtain these desired characteristics of the weld metal bead is an aspect of the present invention.
The use ofthe allllllilllllll system ofthe present invention will provide mechanical properties substantially greater than that obtained by conventional alloying systems employing carbon m~ng~n~se and silicon only. This result is confirmed when colllpafing 2 o the weld bead formed by electrode A as compared to the prior art weld bead identified as example II. The use of the alllminnm system of the present invention which results in substantially enhanced mechanical characteristics also has other advantages. As mentioned before, the weld deposit nitrogen using an aluminum system of the present invention is lower than that obtained using conventional systems for a given nitrogen 2 5 content in the cored wire. This is evidenced when comparing the results obtained by electrode A having sufficient aluminum in the core to deposit alumimlm in the weld metal, and prior art example II which did not use allll-~illul~. This data is consistent with the various other electrodes A-E formulated in accordance with the present invention.
An advantage of the present invention is the decrease of total nitrogen in the weld metal 3 o together with the availability of titanium and boron for alloying in the weld metal from the allll~ -- reducing titanium dioxide and boron in the reaction zone above the weld ;~ ~
21 0~27 1 metal. It is presumed that the total nitrogen in the weld metal is reduced by the aluminum in the arc zone combining with the available oxygen in this zone.
Consequently, the oxygen can not absorb nitrogen to form the nitrogen oxide which is a compound that will create nitrogen in the weld metal. In addition, the oxygen in the reaction zone above the weld metal creates FeO. This oxide forms a layer on the surface of the weld pool. This layer prohibits the evolution of nitrogen from the solidifying weld metal. Consequently, the barrier of iron oxide results in a higher nitrogen content in the weld metal. The use of alll"~ llll ofthe present invention tends to prevent the formation of iron oxide as a layer or barrier on the surface of the weld pool.
0 Since the present invention produces a lower nitrogen weld deposit than the conventional system for gas shielded flux cored electrodes, the present invention will result in a welding process which is less sensitive to the loss of shielding gas. In the past, electrodes for use with shielding gas have presented serious problems when the shielding gas has been discontinuecl Increased nitrogen is absorbed by the weld metal from the atmosphere. This causes a corresponding decrease of the notch toughness of the weld metal deposit. This deleterious phenomenon is reduced with the use of aluminulll powder in the core of the electrode to absorb the nitrogen and oxygen in the arc above the molten metal, thus preventing nitrogen from ent~ring the molten metal even with an inadvertent discontinll~tion of the shielding gas envelope around the electrode.
2 o The present invention results in a flux cored electrode to be used with shielding gas that obtains the required deposit chemistry as far as lila~ and/or boron areconcerned, and provides a more consistent weld deposit. In conventional systems, the use of titanium and boron alloying elements in small controlled amounts within the electrode core is accomplished only with extreme care, to prevent segregation and 2 5 variations in the chemistry of the weld deposit along its length. By using the present invention, the lila~lium and boron is made available to the weld metal more easily in controlled small amounts which prevent these deleterious effects on the weld metal.
The use of the present invention permits production of the steel sheath for the electrode from continuous cast steels. In the past, such inexpensive steels could not be 3 o employed for gas shielded flux cored electrodes because the steel included a certain amount of alu-lli-lll--l and nitrogen. The present invention permits the use of continuous X~J
cast steels which are naturally higher in nitrogen content, since the al~ lll that is incorporated in the electrode will reduce the total nitrogen intake in the weld metal and fix the residual free nitrogen into innocuous alllminllm nitride particles.
A major concern when using gas shielded flux cored electrodes is the resulting high strength levels achieved when the m:~ng~nese and silicon levels of the deposited metal have been optimized for impact properties. ~ng~nese and silicon in the weld metal result in relatively high strength when used in amounts to create the desired impact properties. This is especially a concern when the electrodes are designed for use with carbon dioxide shielding gas, but are actually used with argon blends of shielding gas.
0 Such blends result in higher strength levels due to higher pickup of m~ng~nese and silicon in the weld metal. Consequently, the strength level will be in excess of the desired strength levels for the desired impact properties in the m~ng~nese and silicon system. By using the present invention, the strength of the weld metal deposit is significantly lowered in comparison to that produced in the conventional m~ng~nese and silicon system. Consequently, if the electrode is designed for carbon dioxide, and argon blends are employed as the shielding gas, the strength will not exceed desired parameters.
This characteristic is evidenced when collIp~ g the weld metal deposits by electrode A
as compared to the prior art electrode example II. The alnminllm content of the core, as controlled in accordance with the present invention, provides a mechanism to limit the strength levels of the deposited weld metal to allow m~ng~nese and silicon levels necessary for high impact properties. It is believed that the reduction in the strength level when using the present invention results from a weld deposit with less micro-inclusions than that resulting from a standard conventional carbon-m~ng~nese-silicon system.
These inclusions serve to retard slip of the internal platelets and increase the strength of 2 5 the resulting weld metal.
Another advantage of the present invention is the inclusion of alllminllm withinthe core of the electrode, which alllminllm reacts early in the welding process to break apart and evolve any moisture bearing materials. Consequently, the electrode is less sensitive to moisture and lubricant cont~min~nt~ than other electrodes of the type used 3 o in gas shielded arc welding. This reduced moisture sensitivity also provides lower hydrogen content for a given moisture content in the electrode. Consequently, the present ~ .~
~ 1 0927 1 invention reduces the requirement for electrode baking to drive out moisture.
The aluminum powder in the novel electrode tends to reduce the iron oxide content in the welding fume and, thus, lower the fume level.
In accordance with the present invention, there is provided a cored electrode for gas shielded arc welding to deposit a weld metal bead. This novel electrode has a core of fill material surrounded by a ferrous tube. The fill material includes alloying agents and oxide fluxing ingredients together with 1.0-5.0% aluminum powder, wherein the alumimlm powder has a higher affinity for oxygen than the alloying agents or oxide flux ingredients of the fill m~tf~ri~l The amount of alu~ lul~l powder is selected to produce 0 less than 0.10% aluminum in the resulting weld metal. The proper selection of the amount of aluminum powder to produce only a low amount of residual alllminllm for alloying allows reduction of nitrogen in the weld metal and deoxidizes the alloying agents in the arc reaction zone above the weld metal.
In accordance with another aspect of the present invention, there is provided 40-60% lil~liulll dioxide in the fill material and the alulllhlulll powder is selected to produce .02-.08% titanium in the weld metal.
In accordance with another aspect of the present invention, the fill material includes boron oxide in the range of 0.3-0.5% by weight of the fill material and the aluminum is selected to produce a weld metal that contains at least .002% boron by 2 o weight. Preferably, the boron in the weld metal is in the range of .0025-.0065% by weight of the weld metal.
Yet another aspect of the present invention is the provision of a cored electrode wherein the fill material includes both ~ iun~ dioxide and boron oxide with the weld metal producing a ratio of titanium to boron in the general range of 9-11:1. This range is preferably approximately 10:1.
In accordance with yet another aspect of the present invention, there is provided a method of gas shielded arc welding with a cored electrode to deposit a weld metal bead.
The method comprises the steps of using an electrode having a core of fill material surrounded by a ferrous tube. The fill material includes, by weight of fill material, 3 o 40-60% titanium dioxide and 1.0-5.0% aluminum powder. The amount of aluminum powder is selected to produce .02-.08% by weight titanium and less than 0.10% by ~1 09271 weight alllminum in the weld metal.
In accordance with the broadest aspect of the present invention in the area of anovel method, a method is provided for gas shielded arc welding with a cored electrode to deposit a weld metal bead. This method comprises the steps of using an electrode having a core of fill m~t~ri~l surrounded by a ferrous tube. The fill m~tçri~l includes, by weight of fill material, 1.0-5.0% alulllh~ powder and selecting the amount of aluminum powder to produce less than 0. l 0% aluminum in the weld metal.
The invention further involves a method of arc welding with a shielding gas to deposit a weld metal bead. This method comprises the steps of providing an electrode 0 having a ferrous tube with a core of fill material including metal oxides and l.0-5.0%
al~ l", powder by weight ofthe fill m~teri~l; creating an arc between the weld metal bead and an electrode for melting the ferrous tube in a reaction zone in the electric plasma or arc between the electrode and the metal bead; and, introducing the allll,,illll.ll powder into the arc reaction zone to reduce the metal oxides in the reaction zone with a portion or residual amount ofthe allll.. ilul.ll entering the metal bead to form an alllminllm alloy of less than 0.10% of the alul~illlllll by weight of the metal in the weld bead.In accordance with still a further aspect of the present invention, the aluminumin the weld bead when practicing the present invention is in the range of 0.01-0.05% by weight of the metal of the weld bead.
2 oThe primary object of the present invention is the provision of a flux cored electrode used in gas shielded arc welding, which electrode has strength and impact characteristics approaching those of solid wire used in arc welding.
Another object of the present invention is the provision of a flux cored arc welding electrode, which electrode uses powdered alllmimlm in the core in an amount to 2 5react within the electric arc or plasma zone to create alloying metal, while also depositing a small controlled, residual amount of alu-ni~ ll within the weld bead itself.
A further object of the present invention is the provision of a flux cored shielding gas electrode, as defined above, which electrode controls the amount of titanium or boron or both in the weld bead alloying system.
3 oYet another object of the present invention is the provision of a flux cored electrode, as defined above, which flux cored electrode can use a sheath made from 9 ~ ~ 1 continuous cast steel and need not require substantial baking for removal of moisture.
Still a further object of the present invention is the provision of a flux cored gas shielded electrode, as defined above, which electrode decreases the amount of nitrogen in the weld bead without increasing the amount of alll,ni.~lll" beyond small amounts, which small amounts do not deleteriously affect the grain characteristics of the weld metal.
Another object of the present invention is the provision of a novel method of gas shielded arc welding, which method results in a weld bead having a low amount ofnitrogen and a controlled minor amount of residual aluminum with controlled alloying 0 of the weld metal with titanium or boron, or both.
These and other objects and advantages will become a~alell~ from the following description l1tili~ing the drawings herein.
BRIEF DESCRIPTION OF DRAWINGS
FIGURE l is a schematic, cross-sectional view of an electrode constructed in accordance with the plerelled embodiment of the present invention and illustrating the reaction zone instrumental in the practice of the present invention; and, FIGURE 2 is a graph showing the relationship between decreasing the amount of nitrogen in the weld metal and the impact characteristics of the weld bead metal or 2 o joint.
PREFERRED EMBODIMENT
Referring to the drawings wherein the showings are for the purpose of illustrating the plefelled embodiment only and not for the purpose of limiting same, FIGURE lshows a consumable electrode l0 having an outer steel sheath 12 formed from low carbon steel preferably having a carbon content of less than .07% by weight of the steel in the sheath. Electrode l 0 is used with shielding gas 20, preferably carbon dioxide for lowest cost, however, blends of shielding gas with components such as oxygen, helium, argon, etc. can be employed. Within core 30 of electrode l0, there is provided 3 o particulated m~t~.ri~l in the form of alloying agents, fluxing agents, and other constituents necessary to form the proper slag over the weld bead or molten metal pool 40 when an ~1 arc 50 is created between the end of electrode lO and the weld metal pool 40. Inaccordance with the preferred embodiment of the invention, core 30 includes aluminum powder schematically illustrated as particles 60 dispersed throughout the core and having a weight of l .0-5.0% of the fill material constituting core 30. Metallic alumimlm from core 30 reacts in arc 50 in a zone indicated as reaction zone 70. In accordance with the invention, the amount of alulllhlulll is selected to reduce the ~ ium dioxide or boron oxide, or both, to release a certain amount of li~liulll and boron for alloying in the metal of weld bead 40. Sufficient amount of al-lmimlm powder is placed into core 30 so that there is a small amount of residual al-lmim-m that alloys with the weld metal in molten 0 pool 40. In practice, the amount of alllminllm is selected to produce less than 0.10%
alumillulll in the weld metal of pool 40. Consequently, al~ powder in the range of l .0-5.0% is used to directly react with the core m~t~ri~l in zone 70. This chemical and thermal action releases certain alloying agents, such as titanium and boron, as well as allowing a minor amount of residual allll,lillul~ to be available for alloying, nitrogen removal and reaction with dissolved oxygen in the weld metal.
It has been found that the all~ in the core material reduces the total and free nitrogen in the weld metal. As is known, nitrogen in the weld metal affects the impact characteristics of the weld metal. FIGURE 2 illustrates this concept wherein increased amounts of total nitrogen in the weld deposit decreases the Charpy V notch strength of 2 0 the weld metal bead. Alll",il~ in the core m~t~ l reduces the oxygen potential in zone 70, reducing nitrogen oxygen formation and, hence, nitrogen pickup in the weld metal.
Residual aluminum provided in accordance with the present invention from the reaction in arc zone 70 enters the weld metal when it is molten and combines with free nitrogen and aluminum nitride is formed. Thus, most of the nitrogen in the weld metal is in the fixed nitride form. Consequently, the alllmimlm and nitrogen have no substantivedeleterious effects upon the strength and impact characteristics of the weld metal when using the present invention.
The present invention employs a controlled amount of allll~ .l" powder in a carbon-m~ng~nese-silicon electrode system. This all.",il,ll", reduces titanium dioxide, 3 o which is the preferred fluxing constituent of the electrode. The amount of aluminum controls the amount of lil~liulll reduced and deposited in the weld metal. This amount ~i~
of titanium is relatively small to give about 0.02-.08% lil~~ by weight of the weld metal. Also, the aluminllm powder reduces boron oxide included in core 30 to provide a controlled amount of boron in the weld metal. Only a small amount of boron is required; thus, only a small amount of boron oxide is placed into the core 30. This amount is in the range of 0.30-0.50% by weight of the fill. There is enough aluminum to give the desired lilaniuill and/or boron in the weld metal. In addition, aluminum reduces the oxidizing potential of the arc atmosphere in zone 70. As a result, for reasons mentioned before, nitrogen can not be absorbed effectively from the atmosphere.
Zirconium metal could be employed for removing oxygen from the weld metal. However, a substantial amount of zirconium would be required, and control of titanium and boron in the weld metal would become difficult. In addition, the resulting oxide would not enhance the slag characteristics to the extent accomplished by alllminllm oxide.It has heretofore been believed that al~ illu.ll could not be used in a gas shielded welding electrode of the flux cored type without decreasing the mechanical properties of the resulting deposited weld metal. When an electrode especially formlll~ted for use with external shielding gas is employed, it has heretofore been realized that excess, residual alllminum in the elemental form in the weld metal produced undesirable microstructures.
However, by this invention, this problem is resolved in a unique manner. Residual alu. ., i llUI~ consists of uncombined, free all ." ,i rllll " and combined alllminllm in the oxide 2 o form. It is the intent of the present invention to leave a certain amount of residual all Ill lil lllll l in the weld metal by careful control of the alulllinulll amount in the core. In accordance with this invention, the weld metal has less than 0.1% alllminllm and, preferably, less than about 0.05% alll.-~illulll. The part of this residual alllmimlm that is free (not combined with oxygen), combines with the existing free nitrogen forming 2 5 aluminum nitride. Therefore, the amount of elemental aluminum in the weld metal is reduced, thereby elimin~ting undesirable microstructures. The amount of free nitrogen in the weld metal is also reduced. Consequently, the deleterious effects of both excess elemental aluminum and free nitrogen in the weld metal are avoided.
When using the present invention, selection of a controlled amount of aluminum 3 o powder within the core is novel. Alll.. l;llll.. l powder is less than 0.10% by weight of the weld metal and preferably less than 0.05% aluminum in the weld metal. The aluminum .,.~ ~ i 2 1 0q27 ~
in the core is in the form of powdered metallic alulllhlulll so that it reacts directly and immediately with the constituents of core 30 in the reaction zone 70. Ferro-aluminum and other alllminllm alloys react after entering the molten metal pool 40. These alloys generally do not react in zone 70, as anticipated by the present invention. The major use of the present invention is with a titanium dioxide flux cored consumable electrode;
however, the invention can also be employed in a flux cored electrode where the core is basic. The alulllinulll powder provides uniformity in the resulting weld metal, since it reduces the oxides, reduces the oxygen and, thus, reduces the nitrogen in the weld bead.
When using liL~liulll dioxide, the amount of alu",illul" is selected to produce the desired 0 amount of li~li~ll in the weld metal. In essence, at least l .O% alll"~illlllll is added to the electrode core and less than 0. l 0% is deposited in the weld metal. It has been found that the resulting electrode is somewhat insensitive to moisture and inadvertent loss of shielding gas.
In reaction zone 70, the aluminum powder removes a majority of the oxygen.
Consequently, nitrogen oxide can not be formed. Alllminl-m nitride is formed in the weld metal when using the present invention. Consequently, most of the aluminum in the weld metal is generally in the form of allllllillulll nitride and alllminllm oxide and not elemental alulllhlulll.
The aluminum powder is primarily useful in a TiB type flux cored electrode 2 o specially designed for use with a shielding gas. This is a specialized technology. The combination of titanium and boron in the weld metal reduces the amount of proeutectoid ferrite at the austenite grain boundaries. In addition, titanium produces fine acicular ferrite in the prior austenite grains. The ~ ium, boron and aluminum reduce the free nitrogen in the system. Thus, lil~ium, boron and allll~lilllllll, which results from the use 2 5 of the present invention, all contribute to an alloying system with improved strength and impact characteristics. The preferred embodiments ofthe present invention are illustrated as electrodes A-E shown with flux cored electrodes that employ nickel. Nickel improves ductility at colder temperatures; however, it is not essential in the practice of the present invention. The nickel content of the electrodes A-E of the preferred embodiments of the 3 o present invention are electrodes used in welding where nickel is desired; however, other alloying agents could be employed in the present invention.
~r l I
In the past, TiB electrodes of the flux cored gas shielded type have contained asmall amount of boron in the resulting weld metal. The boron can be provided in the weld metal by various mech~ni~m~ In accordance with an aspect of the invention, boron is included in core 30 as boron oxide. It is reduced by the metallic alllminum powder in the core to allow subsequent alloying of boron in the weld bead metal. The boron shifts the primary ferrite C curve to the right as is well known. The aluminum forms nitrides and oxides. Titanium protects boron from oxidation at the grain boundaries. Boron is a nitride former, but lil~liuln is more capable than either boron or alllmimlm of forming a nitrogen compound. But alul"ill~ is a stronger deoxidizer, and, herein lies the benefit of using it inthis system. Allll--il~lllll can reduce no formation in the arc which reduces nitrogen intake in the weld metal. Alul~ ll can also help the evolution of nitrogen from the surface of the weld metal. This feature is facilitated when the iron oxide cannot form on the surface of the weld bead due to the preferred reaction of oxygen with the alumimlm powder. Thus, the level of nitrogen in the weld metal decreases with the use of aluminum, in accordance with the present invention. The alllminllm nitride in the amount present in the metal also has less deleterious effects than free nitrogen or occluded nitrogen.
The present invention results in a major portion of the alllmimlm powder formingaluminum oxide in zone 70. This compound is beneficial for controlling the 2 o characteristics of the slag. The aluminum powder also controls the amount of titanium and boron that enters into the weld metal. The residual amount of alllminllm available from zone 70 is used in the weld metal to combine with the nitrogen to remove free nitrogen from the weld metal by forming stable alll...il~ - nitride particles. The lil~liu to boron ratio in the weld metal is preferably about l 0: l . The ratio, in practice, can be 2 5 approximately 9-l l: l ratio of lil~lium to boron. The use of the present invention is advantageous and made possible by the control of the amount of alu~ lulll in core 30 and the realization that aluminum forms nitrogen compounds which are beneficial in controlling the physical characteristics of the weld bead metal.
Prior art flux cored electrodes for arc welding with shielding gas are given below.
~' 2 1 0 ~ 2 7 1 EXAMPLE I
Impact at -40 ~ F (ft-lbs) Side A 73, 67, 65, 70, Root 47, 51, 56, 55, Side B 67, 67, 62, 66 Weld bead analysis for this example is:
Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.069 1.28 0.33 0.009 0.005 0.00 0.97 0.02 0.02 0.016 0.033 0.001 0.001 0.0033 0.007 Root 0.088 1.32 0.33 0.008 0.006 0.00 0.88 0.03 0.02 0.014 0.035 0.001 0.001 0.0033 0.006 Side B 0.079 1.32 0.34 0.009 0.006 0.00 0.90 0.03 0.02 0.015 0.035 0.001 0.002 0.0033 0.007 21 0~271 -EXAMPLE II
Impact at -40~ F (ft-lbs) Side A 73, 71, 64, 67 Root 55, 52, 46, 52 Side B 59, 49, 66, 58 Weld bead analysis for this example is:
~1 Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.06 1.45 0.35 0.011 0.007 0.00 1.23 0.04 0.01 0.019 0.03 0.002 0.003 0.0037 0.007 Root 0.067 1.47 0.35 0.011 0.007 0.00 1.23 0.04 0.01 0.018 0.035 0.002 0.003 0.0045 0.006 Side B 0.041 1.45 0.36 0.012 0.007 0.00 1.34 0.03 0.01 0.02 0.032 0.002 0.003 0.0045 EXAMPLE III
Impact at -40~ F (ft-lbs) Side A 71, 74, 76, 71 Root 61, 45, 52, 39 Side B 84, 81, 82, 90 Weld bead analysis for this example is:
~1 _~ - 24 -Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry V907T1 0.060 1.37 0.33 0.013 0.017 0.00 1.48 0.03 0.01 0.014 0.034 0.003 0.009 0.0028 0.003 Side A
V907R 0.069 1.43 0.35 0.013 0.017 0.00 1.52 0.03 0.01 0.015 0.034 0.003 0.010 0.0048 0.004 Root V907T2 0.038 1.40 0.35 0.015 0.017 0.00 1.64 0.02 0.01 0.017 0.033 0.003 0.011 0.0030 0.003 0.056 Side B
~ 1 0927 1 The flux ingredients (in weight percent) of the above electrodes of Examples I and II are as follows:
Ingredients I II III
Na2O 2.86 2.85 MgO 3.91 3.91 SiO2 4.21 4.20 TiO2 53.45 53.45 B2O3 0.26 0.28 CaF2 1.80 2.07 Al 0.15 0.17 Si 2.09 2.10 Ti 3.13 3.49 Mn 12.75 14.19 Ni 5.15 8.81 Ca 0.67 10.0 Fe Bal. Bal.
Example III is a commercial product having no alllmimlm metal in alloy form or in powder form in the core of the metal sheath forming the electrode.
2 o In a preferred embodiment, the weld bead is laid down between two 2" (50 mm) thick A537 steel plates with the edges of the plates bevelled to provide a 50~ included angle and the plates positioned so that the lower sharper edges are spaced 1/4" (6.4 mm).
The plates are preheated to 212~F (100~C), and between each weld pass the temperature ofthe previously deposited bead is allowed to decrease to about 325~F (163~C).
2 5 In nine passes using electrodes A, B, C, D and E described below, the following impact values were obtained:
~ i X~ ,1 ~ ~ 0927 1 Impact at -40~ F (ft-lbs) (x 1.3 for cm-Kg) Electrode A Side A 71,76, 70, 72 Root 50, 50, 52,48 Side B50, 61, 56, 67 Electrode B Side A61, 60, 56, 54 Root 44, 48, 45, 45 Side B56, 55, 54, 72 1 o Electrode C Side A52, 53, 59, 62 Root 50, 54, 49, 48 SideB 31,29,33,41 Electrode D Side A47, 55, 52, 55 Root 47, 45, 46, 43 Side B38, 37, 45, 52 Electrode E Side A66, 75, 72, 73 Root 41, 33, 42, 53 Side B32, 50, 68, 63 2 o An analysis of the weld bead produced by the plerel~cd embodiment, electrode A, is as follows:
~1 Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.07 1.41 0.14 0.01 0.006 0.02 0.97 0.05 0.01 0.02 0.041 0.002 0.006 0.004 0.003 Root 0.079 1.45 0.14 0.009 0.006 0.02 O.9B 0.05 0.01 0.02 0.04 0.002 0.006 0.0053 0.003 Side B 0.053 1.41 0.13 0.01 0.006 0.02 1.06 0.04 0.01 0.022 0.042 0.002 0.006 0.0062 0.002 ~ 1 0927 1 An analysis of the weld bead produced by the preferred embodiment, electrode B, is as follows:
~ I !
Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.058 1.28 0.14 0.011 0.005 0.03 1.51 0.05 0.01 0.023 0.057 0.003 0.006 0.0024 0.004 Root 0.075 1.15 0.14 0.010 0.006 0.03 1.35 0.05 0.0 0.021 0.057 0.003 0.005 0.0027 0.004 Side B 0.042 1.18 0.13 0.010 0.005 0.02 1.53 0.05 0.0 0.023 0.050 0.003 0.006 0.0028 An amalysis ofthe weld bead produced by the preferred embodiment, electrode C, is r~s follows:
~:7 /
Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.053 1.37 0.12 0.009 0.004 0.02 1.54 0.04 0.00 0.022 0.038 0.002 0.006 0.0022 0.004 Root 0.062 1.32 0.12 0.008 0.004 0.02 1.44 0.04 0.00 0.021 0.042 0.002 0.005 0.0036 0.005 SideB 0.036 1.3 0.11 0.011 0.004 0.02 1.59 0.03 0.00 0.023 0.043 0.002 0.006 0.0019 0.004 An analysis of the weld bead produced by the preferred embodiment, electrode D, is as follows:
~, - ~'' ( Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.072 1.25 0.13 0.011 0.004 0.01 1.44 0.04 0.01 0.021 0.042 0.003 0.006 0.0042 0.004 Root 0.084 1.27 0.12 0.009 0.005 0.01 1.35 0.04 0.01 0.019 0.038 0.003 0.005 0.0032 0.004 Side B 0.055 1.32 0.10 0.010 0.004 0.01 1.62 0.03 0.01 0.022 0.035 0.003 0.006 0.0027 0.004 0.066 r ~O
2 1 0~271 An analysis of the weld bead produced by the preferred embodiment, electrode E, is as follows:
~' Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.067 1.35 0.23 0.012 0.005 0.01 1.62 0.03 0.02 0.005 0.036 0.004 0.002 0.0036 0.004 Root 0.078 1.30 0.22 0.011 0.005 0.01 1.47 0.03 0.01 0.004 0.037 0.004 0.001 0.0034 0.005 Side B 0.055 1.29 0.21 0.012 0.004 0.00 1.64 0.02 0.01 0.005 0.034 0.004 0.001 0.0034 0.004 These test specimens of the present invention were obtained by using the following electrodes where the steel is in the form of a low carbon steel tube (<0.07) and the core of the tube was filled with flux ingredients as follows (in weight percent):
A B C D E
Na20 1.88 1.91 1.91 2.23 2.52 Cr2O3 0.12 0.12 0.12 0.12 0.03 V2o5 0.10 0.10 0.10 0.10 0.02 Cb205 0.08 0.08 0.08 0.08 0.02 SiO2 2.72 2.76 2.76 3.16 3.79 TiO2 53.44 53.44 53.44 54.00 52.85 Al2~3 0.0 0.0 0.0 0.0 0.01 FeOx 0.23 0.23 0.23 0.23 0.07 Zr~2 0.56 0.56 0.56 0.56 0.12 B203 0.26 0.15 0.15 0.24 0.18 CaF2 1.22 1.23 1.23 1.32 1.98 MgO 0.0 0.0 0.0 0.0 3.91 KF 0.0 0.27 0.27 0.27 0.0 Al 3.27 3.48 3.48 2.49 1.33 2 o Cr 0.04 0.03 0.03 0.03 0.03 Mn 14.53 13.74 13.74 13.74 12.64 Ni 8.91 8.91 8.91 8.91 8.91 Ca 0.0 0.0 0.0 0.0 0.67 Si 0.0 0.01 0.01 0.01 1.22 Zr 0.0 1.15 1.15 1.14 1.89 Fe Bal. Bal. Bal. Bal. Bal.
Typical welding parameters with the above electrodes were:
a. Electrode 0.045 of an inch in diameter;
3 o b. DC electrode positive polarity;
c. 3/4 inch electrical stickout;
~ ~ I
2 i O~27 1 d. Electrode fill 14-17 weight percent of total electrode; and e. Wire feed speed approximately 275 inches/min.
Electrodes A-E were constructed in accordance with the present invention and used al~ powder in the core to enhance the physical properties of the weld metalusing certain nickel consumable electrodes.
The electrodes used in accordance with the present invention contain various alloying agents such as alllminum, chromium, m~ng~nese, nickel, cadmium, silicon, zirconium and iron. Other alloying agents may also be used in the flux system. The various types of alloying agents are limited to only those that have a lower affinity for 0 oxygen or nitrogen than the alumimlm powder. The alllmimlm powder is designed to be the primary deoxidizer and denitrider in the flux system to obtain the desired alloy metal precipitation into the weld metal while simultaneously reducing the fume production during welding. Alloying agents, such as m~gn~ium or magnesium alloys, which have a greater affinity for oxygen or nitrogen than the aluminum powder, adversely affect and interfere with the aluminum powder reaction occurring within reaction zone 70. The deleterious effects of magnesium, m~gnP~ium alloys and/or other alloying agents having a higher affinity for oxygen and nitrogen than aluminum cause increased fume production and increased spattering during welding and/or lower weld bead quality.
The invention has been described with reference to a preferred embodiment and alternatives thereof. It is believed that many modifications and alterations to the embodiments discussed herein will readily suggest themselves to those skilled in the art upon reading and understanding the detailed description of the invention. It is intended to include all such modifications and alterations insofar as they come within the scope of the present invention.
This invention relates to the art of arc welding using consumable steel electrodes and more particularly to an improved flux cored gas shielded electrode. Unless otherwise stated, all percentages referred to in this specification are percentages by weight.
As background information, U.S. Patent No. 5,233,160 should be referred to.
U.S. 5,233,160 is directed toward a flux cored electrode of the type used with shielding gas that employs a small amount of aluminum powder in the core of the electrode to reduce fume created during the arc welding process. The powdered alu.~ ll reacts with o other constituents in the core material and sheath of the electrode in the area or reaction zone defined as the arc surrounded by the shielding gas. The reaction zone is between the electrode and molten metal weld bead. During development of a novel flux cored electrode having reduced fume characteristics, a more general invention in gas shielded flux cored electrode technology was made. This novel advance in the art of flux cored electrodes is the subject of the present invention. The prior application contains background information and certain aspects of the present invention which need not be repeated.
Oku 3,558,851 is referred to as background information. Ferro-aluminum, in minor amounts is added to the fill material as a strong deoxidizing ingredient. The small 2 o amount of ferro-alll.llilllllll or aluminum powder is used to kill the steel of the weld bead and does not react in the arc zone above the molten metal of the weld bead. The amounts of ferro-all " " i . l l l,,, in this patent are substantially less than found necessary for practicing the present invention. This patent does not teach the advantage of using aluminum for the purposes of reducing lil~ l dioxide and/or boron oxide for alloying purposes, nor 2 5 is the aluminum in the electrode of the Oku patent of sufficient amount to perform the nitrogen removing function of the present invention.
Kobayashi 4,510,374 relates to the use of a low carbon sheath for an electrode to be used in a shielded arc welding process. Again, aluminum is mentioned as a deoxidizer which is common practice; however, the alllllli~lllln employed in this prior patent is in the 3 o form of ferro-aluminum or alumillulll powder for alloying purposes. In addition, there is no teaching of the amount of alllminllm necessary for performing the function of the present invention wherein the al~ ulll powder reacts above the molten metal in the weld metal to perform a reduction function in a location removed from the molten metal.
In this prior patent, the ferro-allllllillulll or alllllli~lulll powder enters the weld metal and is then used as a deoxidizer. This action creates alllminum oxide which must float to the surface of the weld bead for inclusion in the slag over the weld bead. The present invention employs alnminllm powder for a chemical reaction above the weld bead at a time prior to the aluminum entering the weld bead itself. Thus, a chemical reduction effect takes place by the action of the aluminum in the reaction zone outside the weld bead. Moreover, the aluminum in the present invention is available for nitrogen 0 scavenging of the weld metal.
Munz 4,723,061 is directed to a flux cored electrode using alnminum oxide for the purpose of controlling the physical properties of the molten slag over the weld bead.
The alllminnm oxide is for slag forming purposes only. A high amount of aluminumoxide was used as the slag viscosity controlling constituent contained in the fill material.
Aluminum powder could be provided for oxidation and used to control the slag. This patent does not teach the amount of alu~l,in~ll used to create allllllillulll oxide since provision of all ~ u ~ ~ ~ oxide was the only objective explained in this prior patent. There is no example ofthe use of allllllirllllll powder in any proportionto obtain any particular function in the gas shielded electrode other than formation of aluminum oxide.
2 o Bushey 5,095,191 discloses a gas shielded arc welding electrode using cesium.
A certain amount of alllll~illu,~ is suggested as one of many alloying elements; however, there is no te~hing of the manner by which alllminum can be employed for any particular use, except for alloying purposes.
BACKGROUND OF INVENTION
For many years, alll...illll.ll alloying systems have been successfully used in self shielded flux cored welding electrodes to produce weld deposits with exceptional impact 3 o and strength properties. Exceptional mechanical properties can be developed when using self shielding flux cored welding electrodes when the deposited weld metal has an aluminum content of approximately 0.5%. It is believed that the al-lminum forms a nitride which precipitates in the metal of the weld bead and enhances the mechanical properties of the weld metal. The alllminllm is employed for alloying with the weld metal to remove oxygen and free nitrogen from the solidified weld bead. In the well developed specialized technology used to create self shielded flux cored weldingelectrodes, the use of alumimlm to alloy with the weld bead metal has resulted in a weld bead alloy about 0.5 to 1% al~ With this alloy composition, the allllllilllllll nitride is formed and free nitrogen is not generally available. As the amount of alloyedalllminllm was decreased in the weld metal, it was found that the porosity of the weld 0 metal increased to decrease the strength and impact characteristics of the weld joint.
Consequently, it was believed that when alnminllm was used as an alloying agent for the weld metal in self shielded welding, it was necessary to create more than 0.5% allllllit~lllll in the weld metal. This use of an alllminllm for the controlling properties of the weld bead allowed the aluminum to interact within the weld bead as an alloying constituent.
Since the electrode was self shielding, the gases created by the arc expelled air and prevented oxygen and nitrogen from ingressing into the molten metal due to the rapid egress of gas created by the arc. Thus, there was no reaction zone in the arc in which the alulllit-lll-~ was primarily reacted with other con~titll~nt~ The al--minllm entered the weld bead and alloyed with the metals of the weld bead.
2 o When using gas shielded flux cored arc welding electrodes as contemplated by the present invention, deoxidation of the weld metal or control of nitrogen in the weld metal is not prim~rily dependent on alnmimlm These particular electrodes are prim~rily carbon-m~ng~nese-silicon type systems which rely on the gas shielding to preventnitrogen corl~ "i l~tion of the weld pool metal by excluding the surrounding atmosphere.
2 5 M~n~;~nese and silicon are used as alloying agents for deoxidizing or killing the metal in the weld metal bead. The use of alulllhlulll of any type in gas shielded electrodes, which is not a concept employed in practice, has merely been suggested as one of many possible means of alloying the weld metal. There has been no suggestion of usingaluminum for reaction in the reaction zone of the arc above the weld metal pool in an 3 o electric arc welding process of the type using shielding gas. Consequently, electrodes used in arc welding with shielding gas intentionally avoided alll~it~ in the weld metal V. ~
deposit believing that this lack of aluminllm in the deposit would assist in providing better mechanical properties. In the past, the use of alllminum alloying agent for a gas shielded electrode was not used in practice, and the weld metal generally had noalllminllm in the weld metal. This was believed to assure better strength and impact characteristics. There was no effort to use aluminum as an alloying agent in the weld bead when using shielded gas type of flux cored electrodes.
THE INVENTION
It has been recently discovered that small amounts of alulllillulll in powder form in the core of an electrode of the type having no internal shielding gas was instrumental in reducing the fume level and improving the arc action at high wire feed speeds. The use of up to about 1.0-2.0% aluminum powder in the core was found to modify the traditional carbon-m~ng~n~se-silicon systems to reduce fume. It has now been found that, contrary to conventional wisdom in the shielded flux cored electrode technology, aluminum powder in the core of the electrode can result in tensile strength and Charpy impact characteristics approaching those levels obtainable by solid wire welding. This is an ultimate objective of the flux cored electrode technology. Heretofore, flux cored 2 o electrodes had advantages of convenience, but sacrificed mechanical properties. The objective of approaching properties of solid wire welding is approached by the use of controlled amounts of aluminum powder in the core of a gas shielded flux cored arc welding electrode in accordance with the present invention. Consequently, the present invention relates to the use of alllminllm in a conventional carbon-m~ng~nese-silicon 2 5 system for a gas shielded flux cored electrode, in which it is highly reactive in the arc above the weld metal to p~lrolln the desired functions, before any residual amount enters the weld metal. It has been found that the alllminllm in the arc reduces lil~liulll dioxide and boron oxide to allow slight amounts of lil~ ll and boron metals to enter the molten pool of weld metal as alloying elements. It also seems to decrease the total nitrogen in 3 o the weld deposit when compared to the C-Mn-Si-Ti system. Sufficient amounts of all, . " i l l l l l l l, defined as a percentage in this application, creates a certain amount of residual y ~ !
aluminum in the weld metal. This alumi~ constituent of the weld metal in the amounts caused by use of the present invention is highly beneficial. This residual al lmim-m is used to reduce the free nitrogen in weld metal. This is an advantage since notch toughness and CTOD properties of the weld deposit metal deteriorate rapidly as the free nitrogen in the weld metal increases.
By use of the present invention, the alllminllm reduces the lil~iulll dioxide and/or the boron oxide for the purposes of creating a certain amount of elemental lil~liulll and/or boron in the weld metal. The advantages of titanium and boron are well known in the technology of gas shielded flux cored electrodes. The invention is also 0 useful in TiBor type electrodes. In addition, the invention allows the combination of boron oxide and a controlled amount of alll.l.illll.ll powder to control the actual boron in the weld metal. This concept is superior to the use of boron as an alloy in the steel sheath of the electrode and is easier to control than the use of elemental boron in the core of the electrode.
In the present invention, one of the most important features is the reduction oftotal nitrogen in the weld metal by the use of alllminllm when compared to the conven-tional C-Mn-Si-Ti system for a given nitrogen content in the cored wire. This isaccomplished either by reducing the nitrogen intake in the weld metal by reduction of nitrogen oxide formation in the arc or by helping nitrogen evolution from the weld metal 2 o by preventing iron oxide formation on the weld metal surface.
Moreover, in the present invention, the residual allllllillll... in the weld metal is less than 0.1% by weight of the weld metal. This controlled amount of alllminllm in the weld metal is sufficient to reduce the amount of free nitrogen in the weld bead. The reduction of total and free nitrogen in the weld metal enhances its mechanical properties.
2 5 As an explanation of this concept, details of the states of nitrogen in the weld metal can be helpful. Total nitrogen in the weld bead represents nitrogen in the following forms:
free, interstitial nitrogen that is dispersed or collected around grain boundaries, nitrogen in the form of simple or complex nitrides, and occluded nitrogen in the molecular gaseous state contributing to the porosity of the weld metal. In gas shielded systems, 3 o total nitrogen in the weld metal tends to be quite low due to shielding of the arc and the weld metal from the atmosphere. By the use of the present invention, alulllinulll in the 2109~7l core of electrode in the amount of 1 to 5 wt%, reduces total nitrogen in the weld deposit even further. This precludes the existence of occluded nitrogen in the weld metal.
Thelefole, total nitrogen in the weld metal in this system is the sum of free nitrogen and nitrogen in the form of nitrides, the relative amounts of which are determined by the amount of available nitride formers. Since titanium and boron are strong nitride formers, some of the nitrogen would be fixed as lil~~ l nitride and boron nitride. The rem~ining nitrogen is present as free nitrogen which is available to combine with aluminllm. By the use of the present invention, a slight amount of alll.llilllllll which is less than 0.1% of the weld metal and preferably less than .03% of the weld metal is in the deposited metal.
0 This aluminum reacts with the free nitrogen and forms aluminum nitride. Since the amounts of alu~ni~ and nitrogen in the weld metal are low, these alulllillulll nitride particles develop late, presumably in the solid weld metal. In any event, aluminum decreases free nitrogen in the weld metal. Moreover, the amount of these nitride inclu-sions in the weld metal are low. Both these factors improve the impact properties of the weld metal.
In accordance with the present invention, the residual alumimlm in the weld metal is less than 0.10% by weight of the weld metal. This controlled amount of aluminum in the weld metal is sufficient to reduce the amount of free nitrogen in the weld bead for the purposes of enhancing the physical properties of the weld bead. As an explanation of this 2 0 concept, details of nitrogen formation can be helpful. Nitrogen can be present in the weld bead as free, interstitial nitrogen that is dispersed or collected around grain boundaries.
Also nitrogen can be present as nitrides in either simple or complex precipitated phases.
In addition, occluded nitrogen can be present in the molecular gaseous state which contributes to the porosity ofthe weld metal. By the use ofthe present invention, a slight 2 5 amount of allllllilllllll which is less than 0.10% of the weld metal and preferably less than about .03% of the weld metal is in the deposited metal. This amount of aluminum has been found to produce superior mechanical pl~p~;llies in the weld deposit al)palelllly through the further reduction of free nitrogen by the formation of stable aluminum nitrides.
3 o Since this nitride develops late in the solidification process, the nitrides that form when using the present invention are dirr~lclll than the earlier formed nitrides of a ~r standard carbon-m~ng~nese-silicon system. Such nitrides in conventional systems for flux cored electrodes of the type to which the present invention is directed are formed early in the solidification process. This will produce coherent precipitate particles which cause a skain in the lattice of the solidified weld metal which creates forces that tend to fracture the crystalline skucture of the weld metal. Consequently, the amount of energy required to break a weld joint of a Charpy V notch impact specimen is substantially increased by use of the present invention because the amount of internal strain energy produced by the incoherent nitrogen precipitates is substantially less than the coherent precipitate particles of the nitride compound realized in conventional 0 carbon-m~ng:~nese-silicon electrode system.
In accordance with the preferred embodiment of the present invention, titanium dioxide and boron oxide is contained in the core of the electrode. Alllminllm powder within the electrode core chemically reacts in the zone created by the arc to reduce the boron oxide and a portion of the titanium dioxide. This allows a conkolled amount of titanium and boron to be introduced into the weld metal. The advantages of these two alloying agents for the weld metal is well documented. The present invention has the ability to accurately control the lil~liulll or boron in the weld metal bead by proper selection of the amount of alulllhlu~ll powder within the core of the electrode. This is a feature of the present invention that is not employed in other gas shielded flux cored arc 2 o welding electrodes.
The present invention employs a controlled amount of alllminllm powder which is added to the fill of somewhat standard flux cored electrodes. By using the present invention, it has been found that removal of foundry grade ferro-type titanium from an electrode does not decrease the impact properties of the resulting weld metal. These 2 5 mechanical properties are retained by the use of alumillulll powder in the core material.
It is believed that the superior mechanical properties are obtained by the present invention because the added alulllinulll, in a conkolled amount, creates the proper levels of li~lium and boron in the weld deposit for o~lhllulll mechanical properties through a direct reduction of titanium dioxide and boron oxide by the added al~ l l l l Consequently, 3 o metallic titanium, such as ferro-titanium, and metallic boron are not required in the fill material. The aluminum reacts in the zone of the electric arc above the weld metal to ~7 ~ jl ~1 Oq271 yield a controlled amount of titanium and boron for depositing into the weld bead to obtain the desired mechanical characteristics. Residual alllminllm content of the weld deposit remains low by using the present invention as long as the fill m~t~ri~l in the core has sufficient oxides with a negative free energy more positive than the negative free energy of aluminum oxide. Consequently, the present invention employs a controlled amount of alllmimlm powder in the core. This powder reacts in the zone above themolten metal pool to reduce lil~~ l oxide or boron oxide or both for alloying of the two elements in the weld bead. The alulllinlllll powder is selected so that the amount of residual alllmimlm in the weld bead is less than 0.1% by weight of the weld bead metal.
This amount of all ", lilllll " is sufficient to react with the nitrogen in the weld bead metal to form alllminum nitride. The amount of lil~ n and boron recovered in the weld bead deposit for a given fill composition of the electrode is proportional to the amount of metallic aluminllm powder in the core of the electrode. Increased amounts of alllminum will result in greater recovery of li~liulll and boron from the lil~liulll dioxide and boron oxide compounds present in the fill m~t~ri~l of the electrode. Consequently, the amount of aluminum powder is selected to produce a desired amount of titanium, boron, and residual alll,,,illll,,, in the weld metal. It has been found that the percentage of aluminum powder required in the fill material is approximately 1.0-5.0% by weight of the fill m~teri~l.
2 o A substantial percentage of aluminum powder is consumed in the reaction zone of the arc, with only a slight amount of aluminum actually entering the weld metal in accordance with the present invention. By using the present invention, the nitrogen content of the weld bead is lower than that realized in conventional electrode systems using carbon-m~ng~n~se-silicon and lil~liulll. It would appear initially that the addition 2 5 of aluminum would result in a higher level of deposited nitrogen due to the aluminum nitrides which would be created. However, as mentioned before, alulllilllllll lowers the oxidation potential in the arc. This presumably minimi7es the nitrogen oxide formation which reduces nitrogen pickup in the weld. Alllminum also reduces formation of iron oxides on the weld metal surface which helps nitrogen evolution from the weld metal.
3 o Residual all.ll li lllll l l combines with free nitrogen rem~inin~ in the weld metal to form alllminllm nitride. Consequently, the use of the present invention substantially enhances ~ 1 oq27 1 the mechanical properties of the weld bead metal by reducing the total and free nitrogen and having a controlled low amount of alumillulll. A substantially high percentage of al~ is used in the fill m~teri~l so that the allllllilllll,l is available to react above the weld metal pool to reduce lil~ l or boron or both for alloying purposes with a slight residual alllminllm that appears in small quantities in the weld bead metal.
Theuseofpowderedall""i,~-l",inthecoreofagasshieldedfluxcoredelectrode has been found, in low levels, to reduce the fume emission of the electrode. By increasing the amount of alulllilllllll powder to a controlled amount, dependent upon the desired reduction of titanium oxide or boron oxide or both, optimum mechanical 0 properties can be achieved. The amount of lil~liulll and boron within the weld metal is also controlled. Titanium in the weld metal should be in the range of .020-.080% by weight of the weld metal. Preferably the titanium in the weld metal is in the range of .025-.055% by weight of weld metal. The amount of boron should be at least .002% by weight of metal and preferably in the range of .0025-.0065% by weight of the metal in the deposit. The selection of alllll li~ to obtain these desired characteristics of the weld metal bead is an aspect of the present invention.
The use ofthe allllllilllllll system ofthe present invention will provide mechanical properties substantially greater than that obtained by conventional alloying systems employing carbon m~ng~n~se and silicon only. This result is confirmed when colllpafing 2 o the weld bead formed by electrode A as compared to the prior art weld bead identified as example II. The use of the alllminnm system of the present invention which results in substantially enhanced mechanical characteristics also has other advantages. As mentioned before, the weld deposit nitrogen using an aluminum system of the present invention is lower than that obtained using conventional systems for a given nitrogen 2 5 content in the cored wire. This is evidenced when comparing the results obtained by electrode A having sufficient aluminum in the core to deposit alumimlm in the weld metal, and prior art example II which did not use allll-~illul~. This data is consistent with the various other electrodes A-E formulated in accordance with the present invention.
An advantage of the present invention is the decrease of total nitrogen in the weld metal 3 o together with the availability of titanium and boron for alloying in the weld metal from the allll~ -- reducing titanium dioxide and boron in the reaction zone above the weld ;~ ~
21 0~27 1 metal. It is presumed that the total nitrogen in the weld metal is reduced by the aluminum in the arc zone combining with the available oxygen in this zone.
Consequently, the oxygen can not absorb nitrogen to form the nitrogen oxide which is a compound that will create nitrogen in the weld metal. In addition, the oxygen in the reaction zone above the weld metal creates FeO. This oxide forms a layer on the surface of the weld pool. This layer prohibits the evolution of nitrogen from the solidifying weld metal. Consequently, the barrier of iron oxide results in a higher nitrogen content in the weld metal. The use of alll"~ llll ofthe present invention tends to prevent the formation of iron oxide as a layer or barrier on the surface of the weld pool.
0 Since the present invention produces a lower nitrogen weld deposit than the conventional system for gas shielded flux cored electrodes, the present invention will result in a welding process which is less sensitive to the loss of shielding gas. In the past, electrodes for use with shielding gas have presented serious problems when the shielding gas has been discontinuecl Increased nitrogen is absorbed by the weld metal from the atmosphere. This causes a corresponding decrease of the notch toughness of the weld metal deposit. This deleterious phenomenon is reduced with the use of aluminulll powder in the core of the electrode to absorb the nitrogen and oxygen in the arc above the molten metal, thus preventing nitrogen from ent~ring the molten metal even with an inadvertent discontinll~tion of the shielding gas envelope around the electrode.
2 o The present invention results in a flux cored electrode to be used with shielding gas that obtains the required deposit chemistry as far as lila~ and/or boron areconcerned, and provides a more consistent weld deposit. In conventional systems, the use of titanium and boron alloying elements in small controlled amounts within the electrode core is accomplished only with extreme care, to prevent segregation and 2 5 variations in the chemistry of the weld deposit along its length. By using the present invention, the lila~lium and boron is made available to the weld metal more easily in controlled small amounts which prevent these deleterious effects on the weld metal.
The use of the present invention permits production of the steel sheath for the electrode from continuous cast steels. In the past, such inexpensive steels could not be 3 o employed for gas shielded flux cored electrodes because the steel included a certain amount of alu-lli-lll--l and nitrogen. The present invention permits the use of continuous X~J
cast steels which are naturally higher in nitrogen content, since the al~ lll that is incorporated in the electrode will reduce the total nitrogen intake in the weld metal and fix the residual free nitrogen into innocuous alllminllm nitride particles.
A major concern when using gas shielded flux cored electrodes is the resulting high strength levels achieved when the m:~ng~nese and silicon levels of the deposited metal have been optimized for impact properties. ~ng~nese and silicon in the weld metal result in relatively high strength when used in amounts to create the desired impact properties. This is especially a concern when the electrodes are designed for use with carbon dioxide shielding gas, but are actually used with argon blends of shielding gas.
0 Such blends result in higher strength levels due to higher pickup of m~ng~nese and silicon in the weld metal. Consequently, the strength level will be in excess of the desired strength levels for the desired impact properties in the m~ng~nese and silicon system. By using the present invention, the strength of the weld metal deposit is significantly lowered in comparison to that produced in the conventional m~ng~nese and silicon system. Consequently, if the electrode is designed for carbon dioxide, and argon blends are employed as the shielding gas, the strength will not exceed desired parameters.
This characteristic is evidenced when collIp~ g the weld metal deposits by electrode A
as compared to the prior art electrode example II. The alnminllm content of the core, as controlled in accordance with the present invention, provides a mechanism to limit the strength levels of the deposited weld metal to allow m~ng~nese and silicon levels necessary for high impact properties. It is believed that the reduction in the strength level when using the present invention results from a weld deposit with less micro-inclusions than that resulting from a standard conventional carbon-m~ng~nese-silicon system.
These inclusions serve to retard slip of the internal platelets and increase the strength of 2 5 the resulting weld metal.
Another advantage of the present invention is the inclusion of alllminllm withinthe core of the electrode, which alllminllm reacts early in the welding process to break apart and evolve any moisture bearing materials. Consequently, the electrode is less sensitive to moisture and lubricant cont~min~nt~ than other electrodes of the type used 3 o in gas shielded arc welding. This reduced moisture sensitivity also provides lower hydrogen content for a given moisture content in the electrode. Consequently, the present ~ .~
~ 1 0927 1 invention reduces the requirement for electrode baking to drive out moisture.
The aluminum powder in the novel electrode tends to reduce the iron oxide content in the welding fume and, thus, lower the fume level.
In accordance with the present invention, there is provided a cored electrode for gas shielded arc welding to deposit a weld metal bead. This novel electrode has a core of fill material surrounded by a ferrous tube. The fill material includes alloying agents and oxide fluxing ingredients together with 1.0-5.0% aluminum powder, wherein the alumimlm powder has a higher affinity for oxygen than the alloying agents or oxide flux ingredients of the fill m~tf~ri~l The amount of alu~ lul~l powder is selected to produce 0 less than 0.10% aluminum in the resulting weld metal. The proper selection of the amount of aluminum powder to produce only a low amount of residual alllminllm for alloying allows reduction of nitrogen in the weld metal and deoxidizes the alloying agents in the arc reaction zone above the weld metal.
In accordance with another aspect of the present invention, there is provided 40-60% lil~liulll dioxide in the fill material and the alulllhlulll powder is selected to produce .02-.08% titanium in the weld metal.
In accordance with another aspect of the present invention, the fill material includes boron oxide in the range of 0.3-0.5% by weight of the fill material and the aluminum is selected to produce a weld metal that contains at least .002% boron by 2 o weight. Preferably, the boron in the weld metal is in the range of .0025-.0065% by weight of the weld metal.
Yet another aspect of the present invention is the provision of a cored electrode wherein the fill material includes both ~ iun~ dioxide and boron oxide with the weld metal producing a ratio of titanium to boron in the general range of 9-11:1. This range is preferably approximately 10:1.
In accordance with yet another aspect of the present invention, there is provided a method of gas shielded arc welding with a cored electrode to deposit a weld metal bead.
The method comprises the steps of using an electrode having a core of fill material surrounded by a ferrous tube. The fill material includes, by weight of fill material, 3 o 40-60% titanium dioxide and 1.0-5.0% aluminum powder. The amount of aluminum powder is selected to produce .02-.08% by weight titanium and less than 0.10% by ~1 09271 weight alllminum in the weld metal.
In accordance with the broadest aspect of the present invention in the area of anovel method, a method is provided for gas shielded arc welding with a cored electrode to deposit a weld metal bead. This method comprises the steps of using an electrode having a core of fill m~t~ri~l surrounded by a ferrous tube. The fill m~tçri~l includes, by weight of fill material, 1.0-5.0% alulllh~ powder and selecting the amount of aluminum powder to produce less than 0. l 0% aluminum in the weld metal.
The invention further involves a method of arc welding with a shielding gas to deposit a weld metal bead. This method comprises the steps of providing an electrode 0 having a ferrous tube with a core of fill material including metal oxides and l.0-5.0%
al~ l", powder by weight ofthe fill m~teri~l; creating an arc between the weld metal bead and an electrode for melting the ferrous tube in a reaction zone in the electric plasma or arc between the electrode and the metal bead; and, introducing the allll,,illll.ll powder into the arc reaction zone to reduce the metal oxides in the reaction zone with a portion or residual amount ofthe allll.. ilul.ll entering the metal bead to form an alllminllm alloy of less than 0.10% of the alul~illlllll by weight of the metal in the weld bead.In accordance with still a further aspect of the present invention, the aluminumin the weld bead when practicing the present invention is in the range of 0.01-0.05% by weight of the metal of the weld bead.
2 oThe primary object of the present invention is the provision of a flux cored electrode used in gas shielded arc welding, which electrode has strength and impact characteristics approaching those of solid wire used in arc welding.
Another object of the present invention is the provision of a flux cored arc welding electrode, which electrode uses powdered alllmimlm in the core in an amount to 2 5react within the electric arc or plasma zone to create alloying metal, while also depositing a small controlled, residual amount of alu-ni~ ll within the weld bead itself.
A further object of the present invention is the provision of a flux cored shielding gas electrode, as defined above, which electrode controls the amount of titanium or boron or both in the weld bead alloying system.
3 oYet another object of the present invention is the provision of a flux cored electrode, as defined above, which flux cored electrode can use a sheath made from 9 ~ ~ 1 continuous cast steel and need not require substantial baking for removal of moisture.
Still a further object of the present invention is the provision of a flux cored gas shielded electrode, as defined above, which electrode decreases the amount of nitrogen in the weld bead without increasing the amount of alll,ni.~lll" beyond small amounts, which small amounts do not deleteriously affect the grain characteristics of the weld metal.
Another object of the present invention is the provision of a novel method of gas shielded arc welding, which method results in a weld bead having a low amount ofnitrogen and a controlled minor amount of residual aluminum with controlled alloying 0 of the weld metal with titanium or boron, or both.
These and other objects and advantages will become a~alell~ from the following description l1tili~ing the drawings herein.
BRIEF DESCRIPTION OF DRAWINGS
FIGURE l is a schematic, cross-sectional view of an electrode constructed in accordance with the plerelled embodiment of the present invention and illustrating the reaction zone instrumental in the practice of the present invention; and, FIGURE 2 is a graph showing the relationship between decreasing the amount of nitrogen in the weld metal and the impact characteristics of the weld bead metal or 2 o joint.
PREFERRED EMBODIMENT
Referring to the drawings wherein the showings are for the purpose of illustrating the plefelled embodiment only and not for the purpose of limiting same, FIGURE lshows a consumable electrode l0 having an outer steel sheath 12 formed from low carbon steel preferably having a carbon content of less than .07% by weight of the steel in the sheath. Electrode l 0 is used with shielding gas 20, preferably carbon dioxide for lowest cost, however, blends of shielding gas with components such as oxygen, helium, argon, etc. can be employed. Within core 30 of electrode l0, there is provided 3 o particulated m~t~.ri~l in the form of alloying agents, fluxing agents, and other constituents necessary to form the proper slag over the weld bead or molten metal pool 40 when an ~1 arc 50 is created between the end of electrode lO and the weld metal pool 40. Inaccordance with the preferred embodiment of the invention, core 30 includes aluminum powder schematically illustrated as particles 60 dispersed throughout the core and having a weight of l .0-5.0% of the fill material constituting core 30. Metallic alumimlm from core 30 reacts in arc 50 in a zone indicated as reaction zone 70. In accordance with the invention, the amount of alulllhlulll is selected to reduce the ~ ium dioxide or boron oxide, or both, to release a certain amount of li~liulll and boron for alloying in the metal of weld bead 40. Sufficient amount of al-lmimlm powder is placed into core 30 so that there is a small amount of residual al-lmim-m that alloys with the weld metal in molten 0 pool 40. In practice, the amount of alllminllm is selected to produce less than 0.10%
alumillulll in the weld metal of pool 40. Consequently, al~ powder in the range of l .0-5.0% is used to directly react with the core m~t~ri~l in zone 70. This chemical and thermal action releases certain alloying agents, such as titanium and boron, as well as allowing a minor amount of residual allll,lillul~ to be available for alloying, nitrogen removal and reaction with dissolved oxygen in the weld metal.
It has been found that the all~ in the core material reduces the total and free nitrogen in the weld metal. As is known, nitrogen in the weld metal affects the impact characteristics of the weld metal. FIGURE 2 illustrates this concept wherein increased amounts of total nitrogen in the weld deposit decreases the Charpy V notch strength of 2 0 the weld metal bead. Alll",il~ in the core m~t~ l reduces the oxygen potential in zone 70, reducing nitrogen oxygen formation and, hence, nitrogen pickup in the weld metal.
Residual aluminum provided in accordance with the present invention from the reaction in arc zone 70 enters the weld metal when it is molten and combines with free nitrogen and aluminum nitride is formed. Thus, most of the nitrogen in the weld metal is in the fixed nitride form. Consequently, the alllmimlm and nitrogen have no substantivedeleterious effects upon the strength and impact characteristics of the weld metal when using the present invention.
The present invention employs a controlled amount of allll~ .l" powder in a carbon-m~ng~nese-silicon electrode system. This all.",il,ll", reduces titanium dioxide, 3 o which is the preferred fluxing constituent of the electrode. The amount of aluminum controls the amount of lil~liulll reduced and deposited in the weld metal. This amount ~i~
of titanium is relatively small to give about 0.02-.08% lil~~ by weight of the weld metal. Also, the aluminllm powder reduces boron oxide included in core 30 to provide a controlled amount of boron in the weld metal. Only a small amount of boron is required; thus, only a small amount of boron oxide is placed into the core 30. This amount is in the range of 0.30-0.50% by weight of the fill. There is enough aluminum to give the desired lilaniuill and/or boron in the weld metal. In addition, aluminum reduces the oxidizing potential of the arc atmosphere in zone 70. As a result, for reasons mentioned before, nitrogen can not be absorbed effectively from the atmosphere.
Zirconium metal could be employed for removing oxygen from the weld metal. However, a substantial amount of zirconium would be required, and control of titanium and boron in the weld metal would become difficult. In addition, the resulting oxide would not enhance the slag characteristics to the extent accomplished by alllminllm oxide.It has heretofore been believed that al~ illu.ll could not be used in a gas shielded welding electrode of the flux cored type without decreasing the mechanical properties of the resulting deposited weld metal. When an electrode especially formlll~ted for use with external shielding gas is employed, it has heretofore been realized that excess, residual alllminum in the elemental form in the weld metal produced undesirable microstructures.
However, by this invention, this problem is resolved in a unique manner. Residual alu. ., i llUI~ consists of uncombined, free all ." ,i rllll " and combined alllminllm in the oxide 2 o form. It is the intent of the present invention to leave a certain amount of residual all Ill lil lllll l in the weld metal by careful control of the alulllinulll amount in the core. In accordance with this invention, the weld metal has less than 0.1% alllminllm and, preferably, less than about 0.05% alll.-~illulll. The part of this residual alllmimlm that is free (not combined with oxygen), combines with the existing free nitrogen forming 2 5 aluminum nitride. Therefore, the amount of elemental aluminum in the weld metal is reduced, thereby elimin~ting undesirable microstructures. The amount of free nitrogen in the weld metal is also reduced. Consequently, the deleterious effects of both excess elemental aluminum and free nitrogen in the weld metal are avoided.
When using the present invention, selection of a controlled amount of aluminum 3 o powder within the core is novel. Alll.. l;llll.. l powder is less than 0.10% by weight of the weld metal and preferably less than 0.05% aluminum in the weld metal. The aluminum .,.~ ~ i 2 1 0q27 ~
in the core is in the form of powdered metallic alulllhlulll so that it reacts directly and immediately with the constituents of core 30 in the reaction zone 70. Ferro-aluminum and other alllminllm alloys react after entering the molten metal pool 40. These alloys generally do not react in zone 70, as anticipated by the present invention. The major use of the present invention is with a titanium dioxide flux cored consumable electrode;
however, the invention can also be employed in a flux cored electrode where the core is basic. The alulllinulll powder provides uniformity in the resulting weld metal, since it reduces the oxides, reduces the oxygen and, thus, reduces the nitrogen in the weld bead.
When using liL~liulll dioxide, the amount of alu",illul" is selected to produce the desired 0 amount of li~li~ll in the weld metal. In essence, at least l .O% alll"~illlllll is added to the electrode core and less than 0. l 0% is deposited in the weld metal. It has been found that the resulting electrode is somewhat insensitive to moisture and inadvertent loss of shielding gas.
In reaction zone 70, the aluminum powder removes a majority of the oxygen.
Consequently, nitrogen oxide can not be formed. Alllminl-m nitride is formed in the weld metal when using the present invention. Consequently, most of the aluminum in the weld metal is generally in the form of allllllillulll nitride and alllminllm oxide and not elemental alulllhlulll.
The aluminum powder is primarily useful in a TiB type flux cored electrode 2 o specially designed for use with a shielding gas. This is a specialized technology. The combination of titanium and boron in the weld metal reduces the amount of proeutectoid ferrite at the austenite grain boundaries. In addition, titanium produces fine acicular ferrite in the prior austenite grains. The ~ ium, boron and aluminum reduce the free nitrogen in the system. Thus, lil~ium, boron and allll~lilllllll, which results from the use 2 5 of the present invention, all contribute to an alloying system with improved strength and impact characteristics. The preferred embodiments ofthe present invention are illustrated as electrodes A-E shown with flux cored electrodes that employ nickel. Nickel improves ductility at colder temperatures; however, it is not essential in the practice of the present invention. The nickel content of the electrodes A-E of the preferred embodiments of the 3 o present invention are electrodes used in welding where nickel is desired; however, other alloying agents could be employed in the present invention.
~r l I
In the past, TiB electrodes of the flux cored gas shielded type have contained asmall amount of boron in the resulting weld metal. The boron can be provided in the weld metal by various mech~ni~m~ In accordance with an aspect of the invention, boron is included in core 30 as boron oxide. It is reduced by the metallic alllminum powder in the core to allow subsequent alloying of boron in the weld bead metal. The boron shifts the primary ferrite C curve to the right as is well known. The aluminum forms nitrides and oxides. Titanium protects boron from oxidation at the grain boundaries. Boron is a nitride former, but lil~liuln is more capable than either boron or alllmimlm of forming a nitrogen compound. But alul"ill~ is a stronger deoxidizer, and, herein lies the benefit of using it inthis system. Allll--il~lllll can reduce no formation in the arc which reduces nitrogen intake in the weld metal. Alul~ ll can also help the evolution of nitrogen from the surface of the weld metal. This feature is facilitated when the iron oxide cannot form on the surface of the weld bead due to the preferred reaction of oxygen with the alumimlm powder. Thus, the level of nitrogen in the weld metal decreases with the use of aluminum, in accordance with the present invention. The alllminllm nitride in the amount present in the metal also has less deleterious effects than free nitrogen or occluded nitrogen.
The present invention results in a major portion of the alllmimlm powder formingaluminum oxide in zone 70. This compound is beneficial for controlling the 2 o characteristics of the slag. The aluminum powder also controls the amount of titanium and boron that enters into the weld metal. The residual amount of alllminllm available from zone 70 is used in the weld metal to combine with the nitrogen to remove free nitrogen from the weld metal by forming stable alll...il~ - nitride particles. The lil~liu to boron ratio in the weld metal is preferably about l 0: l . The ratio, in practice, can be 2 5 approximately 9-l l: l ratio of lil~lium to boron. The use of the present invention is advantageous and made possible by the control of the amount of alu~ lulll in core 30 and the realization that aluminum forms nitrogen compounds which are beneficial in controlling the physical characteristics of the weld bead metal.
Prior art flux cored electrodes for arc welding with shielding gas are given below.
~' 2 1 0 ~ 2 7 1 EXAMPLE I
Impact at -40 ~ F (ft-lbs) Side A 73, 67, 65, 70, Root 47, 51, 56, 55, Side B 67, 67, 62, 66 Weld bead analysis for this example is:
Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.069 1.28 0.33 0.009 0.005 0.00 0.97 0.02 0.02 0.016 0.033 0.001 0.001 0.0033 0.007 Root 0.088 1.32 0.33 0.008 0.006 0.00 0.88 0.03 0.02 0.014 0.035 0.001 0.001 0.0033 0.006 Side B 0.079 1.32 0.34 0.009 0.006 0.00 0.90 0.03 0.02 0.015 0.035 0.001 0.002 0.0033 0.007 21 0~271 -EXAMPLE II
Impact at -40~ F (ft-lbs) Side A 73, 71, 64, 67 Root 55, 52, 46, 52 Side B 59, 49, 66, 58 Weld bead analysis for this example is:
~1 Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.06 1.45 0.35 0.011 0.007 0.00 1.23 0.04 0.01 0.019 0.03 0.002 0.003 0.0037 0.007 Root 0.067 1.47 0.35 0.011 0.007 0.00 1.23 0.04 0.01 0.018 0.035 0.002 0.003 0.0045 0.006 Side B 0.041 1.45 0.36 0.012 0.007 0.00 1.34 0.03 0.01 0.02 0.032 0.002 0.003 0.0045 EXAMPLE III
Impact at -40~ F (ft-lbs) Side A 71, 74, 76, 71 Root 61, 45, 52, 39 Side B 84, 81, 82, 90 Weld bead analysis for this example is:
~1 _~ - 24 -Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry V907T1 0.060 1.37 0.33 0.013 0.017 0.00 1.48 0.03 0.01 0.014 0.034 0.003 0.009 0.0028 0.003 Side A
V907R 0.069 1.43 0.35 0.013 0.017 0.00 1.52 0.03 0.01 0.015 0.034 0.003 0.010 0.0048 0.004 Root V907T2 0.038 1.40 0.35 0.015 0.017 0.00 1.64 0.02 0.01 0.017 0.033 0.003 0.011 0.0030 0.003 0.056 Side B
~ 1 0927 1 The flux ingredients (in weight percent) of the above electrodes of Examples I and II are as follows:
Ingredients I II III
Na2O 2.86 2.85 MgO 3.91 3.91 SiO2 4.21 4.20 TiO2 53.45 53.45 B2O3 0.26 0.28 CaF2 1.80 2.07 Al 0.15 0.17 Si 2.09 2.10 Ti 3.13 3.49 Mn 12.75 14.19 Ni 5.15 8.81 Ca 0.67 10.0 Fe Bal. Bal.
Example III is a commercial product having no alllmimlm metal in alloy form or in powder form in the core of the metal sheath forming the electrode.
2 o In a preferred embodiment, the weld bead is laid down between two 2" (50 mm) thick A537 steel plates with the edges of the plates bevelled to provide a 50~ included angle and the plates positioned so that the lower sharper edges are spaced 1/4" (6.4 mm).
The plates are preheated to 212~F (100~C), and between each weld pass the temperature ofthe previously deposited bead is allowed to decrease to about 325~F (163~C).
2 5 In nine passes using electrodes A, B, C, D and E described below, the following impact values were obtained:
~ i X~ ,1 ~ ~ 0927 1 Impact at -40~ F (ft-lbs) (x 1.3 for cm-Kg) Electrode A Side A 71,76, 70, 72 Root 50, 50, 52,48 Side B50, 61, 56, 67 Electrode B Side A61, 60, 56, 54 Root 44, 48, 45, 45 Side B56, 55, 54, 72 1 o Electrode C Side A52, 53, 59, 62 Root 50, 54, 49, 48 SideB 31,29,33,41 Electrode D Side A47, 55, 52, 55 Root 47, 45, 46, 43 Side B38, 37, 45, 52 Electrode E Side A66, 75, 72, 73 Root 41, 33, 42, 53 Side B32, 50, 68, 63 2 o An analysis of the weld bead produced by the plerel~cd embodiment, electrode A, is as follows:
~1 Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.07 1.41 0.14 0.01 0.006 0.02 0.97 0.05 0.01 0.02 0.041 0.002 0.006 0.004 0.003 Root 0.079 1.45 0.14 0.009 0.006 0.02 O.9B 0.05 0.01 0.02 0.04 0.002 0.006 0.0053 0.003 Side B 0.053 1.41 0.13 0.01 0.006 0.02 1.06 0.04 0.01 0.022 0.042 0.002 0.006 0.0062 0.002 ~ 1 0927 1 An analysis of the weld bead produced by the preferred embodiment, electrode B, is as follows:
~ I !
Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.058 1.28 0.14 0.011 0.005 0.03 1.51 0.05 0.01 0.023 0.057 0.003 0.006 0.0024 0.004 Root 0.075 1.15 0.14 0.010 0.006 0.03 1.35 0.05 0.0 0.021 0.057 0.003 0.005 0.0027 0.004 Side B 0.042 1.18 0.13 0.010 0.005 0.02 1.53 0.05 0.0 0.023 0.050 0.003 0.006 0.0028 An amalysis ofthe weld bead produced by the preferred embodiment, electrode C, is r~s follows:
~:7 /
Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.053 1.37 0.12 0.009 0.004 0.02 1.54 0.04 0.00 0.022 0.038 0.002 0.006 0.0022 0.004 Root 0.062 1.32 0.12 0.008 0.004 0.02 1.44 0.04 0.00 0.021 0.042 0.002 0.005 0.0036 0.005 SideB 0.036 1.3 0.11 0.011 0.004 0.02 1.59 0.03 0.00 0.023 0.043 0.002 0.006 0.0019 0.004 An analysis of the weld bead produced by the preferred embodiment, electrode D, is as follows:
~, - ~'' ( Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.072 1.25 0.13 0.011 0.004 0.01 1.44 0.04 0.01 0.021 0.042 0.003 0.006 0.0042 0.004 Root 0.084 1.27 0.12 0.009 0.005 0.01 1.35 0.04 0.01 0.019 0.038 0.003 0.005 0.0032 0.004 Side B 0.055 1.32 0.10 0.010 0.004 0.01 1.62 0.03 0.01 0.022 0.035 0.003 0.006 0.0027 0.004 0.066 r ~O
2 1 0~271 An analysis of the weld bead produced by the preferred embodiment, electrode E, is as follows:
~' Weld C Mn Si S P Al Ni Cr Mo V Ti Zr Nb B N O
Chemistry Side A 0.067 1.35 0.23 0.012 0.005 0.01 1.62 0.03 0.02 0.005 0.036 0.004 0.002 0.0036 0.004 Root 0.078 1.30 0.22 0.011 0.005 0.01 1.47 0.03 0.01 0.004 0.037 0.004 0.001 0.0034 0.005 Side B 0.055 1.29 0.21 0.012 0.004 0.00 1.64 0.02 0.01 0.005 0.034 0.004 0.001 0.0034 0.004 These test specimens of the present invention were obtained by using the following electrodes where the steel is in the form of a low carbon steel tube (<0.07) and the core of the tube was filled with flux ingredients as follows (in weight percent):
A B C D E
Na20 1.88 1.91 1.91 2.23 2.52 Cr2O3 0.12 0.12 0.12 0.12 0.03 V2o5 0.10 0.10 0.10 0.10 0.02 Cb205 0.08 0.08 0.08 0.08 0.02 SiO2 2.72 2.76 2.76 3.16 3.79 TiO2 53.44 53.44 53.44 54.00 52.85 Al2~3 0.0 0.0 0.0 0.0 0.01 FeOx 0.23 0.23 0.23 0.23 0.07 Zr~2 0.56 0.56 0.56 0.56 0.12 B203 0.26 0.15 0.15 0.24 0.18 CaF2 1.22 1.23 1.23 1.32 1.98 MgO 0.0 0.0 0.0 0.0 3.91 KF 0.0 0.27 0.27 0.27 0.0 Al 3.27 3.48 3.48 2.49 1.33 2 o Cr 0.04 0.03 0.03 0.03 0.03 Mn 14.53 13.74 13.74 13.74 12.64 Ni 8.91 8.91 8.91 8.91 8.91 Ca 0.0 0.0 0.0 0.0 0.67 Si 0.0 0.01 0.01 0.01 1.22 Zr 0.0 1.15 1.15 1.14 1.89 Fe Bal. Bal. Bal. Bal. Bal.
Typical welding parameters with the above electrodes were:
a. Electrode 0.045 of an inch in diameter;
3 o b. DC electrode positive polarity;
c. 3/4 inch electrical stickout;
~ ~ I
2 i O~27 1 d. Electrode fill 14-17 weight percent of total electrode; and e. Wire feed speed approximately 275 inches/min.
Electrodes A-E were constructed in accordance with the present invention and used al~ powder in the core to enhance the physical properties of the weld metalusing certain nickel consumable electrodes.
The electrodes used in accordance with the present invention contain various alloying agents such as alllminum, chromium, m~ng~nese, nickel, cadmium, silicon, zirconium and iron. Other alloying agents may also be used in the flux system. The various types of alloying agents are limited to only those that have a lower affinity for 0 oxygen or nitrogen than the alumimlm powder. The alllmimlm powder is designed to be the primary deoxidizer and denitrider in the flux system to obtain the desired alloy metal precipitation into the weld metal while simultaneously reducing the fume production during welding. Alloying agents, such as m~gn~ium or magnesium alloys, which have a greater affinity for oxygen or nitrogen than the aluminum powder, adversely affect and interfere with the aluminum powder reaction occurring within reaction zone 70. The deleterious effects of magnesium, m~gnP~ium alloys and/or other alloying agents having a higher affinity for oxygen and nitrogen than aluminum cause increased fume production and increased spattering during welding and/or lower weld bead quality.
The invention has been described with reference to a preferred embodiment and alternatives thereof. It is believed that many modifications and alterations to the embodiments discussed herein will readily suggest themselves to those skilled in the art upon reading and understanding the detailed description of the invention. It is intended to include all such modifications and alterations insofar as they come within the scope of the present invention.
Claims (43)
1. A cored electrode for arc welding comprising a metal tube filled with a powder charge including titanium dioxide, alloying agents and deoxidizers characterized in that the charge includes about 40-60% weight percent titanium dioxide and about 1.0-5.0% weight percent aluminum powder, a group of elements used as deoxidizers and alloying agents, and aluminum among these elements having the highest affinity for oxygen to produce at least about 0.02% weight percent titanium and not more than about 0.10% weight percent aluminum in a weld metal.
2. A cored electrode as defined in claim 1, characterized in that said charge is about 14.0-17.0 weight percent of the total weight of said electrode.
3. A cored electrode as defined in claims 1 or 2, characterized in that said charge includes boron and/or a boron compound and the ratio of said titanium to said boron in said weld metal is at least about 6.77:1.
4. A cored electrode as defined in claim 3, characterized in that the ratio of said titanium to said boron in said weld metal is about 9-11:1.
5. A cored electrode as defined in claim 4, characterized in that said ratio of titanium to boron in said weld metal is about 10:1.
6. A cored electrode as defined in any one of the preceding claims 1-5, characterized in that said aluluminum in said weld metal is about 0.01-0.05% weight percent.
7. A cored electrode as defined in any one of the preceding claims 1-6, characterized in that titanium in said weld metal is about 0.02-0.08%
weight percent.
weight percent.
8. A cored electrode as defined in claim 7, characterized in that said aluminum in said weld metal is about 0.01-0.03% weight percent.
9. A cored electrode as defined in any one of the preceding claims 1-8, characterized in that said charge contains boron oxide in the range of about 0.3-0.5% by weight of said fill charge.
10. A cored electrode as defined in any one of the preceding claims 1-9, characterized in that said boron in said weld metal is at least about 0.002% weight percent.
11. A cored electrode as defined in any one of the preceding claims 1-10, characterized in that said titanium dioxide is about 50-60% by weight of said charge.
12. A cored electrode as defined in any one of the preceding claims 1-11, characterized in that said charge includes silicon dioxide of about 2.0-4.5% by weight of said charge.
13. A cored electrode as defined in any one of the preceding claims 1-12, characterized in that the charge includes at least about 10% weight percent manganese alloying agent by weight of said charge.
14. A cored electrode as defined in claim 13, characterized in that said manganese alloying agent is about 10-15% by weight of said charge.
15. A cored electrode as defined in any one of the preceding claims 1-14, characterized in that the charge includes nickel as an alloying agent.
16. A cored electrode as defined in claim 15, characterized in that said charge includes nickel of about 8-10% by weight of said charge.
17. A cored electrode as defined in any one of the preceding claims 1-16, characterized in that said charge includes chromium oxide.
18. A cored electrode suitable for use in gas shielded arc welding to deposit a TiB type weld bead, said electrode having a core of fill material including alloying agents, oxide fluxing ingredients, about 40-60% weight percent titanium dioxide, boron or a boron compound, about 1.0-5.0% weight percent aluminum powder, said aluminum having the highest affinity for oxygen in said filler material and said amount of aluminum powder selected selected to produce a weld metal containing less than about 0.10% weight percent aluminum, about 0.02-0.08% weight percent titanium and at least about 0.002% weight percent boron wherein the titanium-boron ratio is at least about 6.77:1.
19. A cored electrode as defined in claim 18, wherein said filler material is about 14-17 weight percent- of the total electrode.
20. A cored electrode as defined in either of claims 18-19, wherein said filler material contains boron oxide in the range of about 0.3-0.5% by weight of said filler material.
21. A cored electrode as defined in any one of claims 18-20, wherein the ratio of said titanium to said boron in said weld metal is about 9-11:1.
22. A cored electrode as defined in claim 21, wherein said ratio of said titanium to said boron is about 10:1.
23. A cored electrode as defined in any one of the preceding claims 18-22, wherein said titanium dioxide is in the range of about 50-60% by weight of said filler material.
24. A cored electrode as defined in any one of the preceding claims 18-23, wherein said filler material includes silicon dioxide in the range of about 2.0-4.5% by weight of said filler material.
25. A cored electrode as defined in any one of the preceding claims 18-24, wherein said filler material incudes at least about 10% manganese alloying agent by weight of said filler material.
26. A cored electrode as defined in claim 25, wherein said manganese alloying agent is in the range of about 10-15% by weight of said filler material.
27. A cored electrode as defined in any one of the preceding claims 18-26, wherein said filler material includes nickel as an alloying agent.
28. A cored electrode as defined in claim 27, wherein said nickel is in the range of about 8-10% by weight of said filler material.
29. A cored electrode as defined in any one of the preceding claims 18-28, wherein said filler material includes chromium oxide.
30. A method of arc welding with a shielding gas to deposit a weld metal bead, said method comprising the steps of providing an electrode having a metal tube with a core of fill material including alloying agents, oxide fluxing ingredients, about 40-60% weight percent titanium dioxide, boron or a boron compound, about 1.0-5.0% weight percent aluminum powder wherein said aluminum powder has the highest affinity for oxygen in said filler material; creating an arc between said weld metal bead and said electrode for melting said ferrous tube in a reaction zone between said electrode and said metal bead; introducing said aluminum powder into said reaction zone to reduce metal oxides in said reaction zone with a portion of said aluminum powder entering said metal weld bead to form an aluminum alloy of less than about 0.10% weight percent aluminum in said metal weld bead; and introducing metallic boron and metallic titanium into said metal weld bead to form a titanium-boron alloy in said weld bead, said metallic boron being deposited in said metal weld bead in an amount of at least about 0.002% weight percent and said metallic titanium being deposited in said metal weld bead in an amount of about 0.02-0.08% weight percent and said titanium-boron ratio in said metal weld bead being at least about 6.77:1.
31. A method as defined in claim 30, wherein said fill material is about 14-17 weight percent of the total weight of said electrode.
32. A method as defined in either of claims 30-31, wherein said aluminum alloy in said metal weld bead is about 0.01-0.05 weight percent.
33. A method as defined in claim 32, wherein said aluminum alloy in said metal weld bead is less than about 0.03 weight percent.
34. A method as defined in any one of the preceding claims 30-33, wherein said filler material contains boron oxide in the range of about 0.3-0.5% by weight of said filler material.
35. A method as defined in any one of the preceding claims 30-34, wherein the ratio of said titanium to said boron in said weld metal is about 9-11:1.
36. A method as defined in claim 35, wherein said ratio of said titanium to said boron is about 10:1.
37. A method as defined in any one of the preceding claims 30-36, wherein said titanium dioxide is in the range of about 50-60% by weight of said filler material.
38. A method as defined in any one of the preceding claims 30-37, wherein said filler material includes silicon dioxide in the range of about 2.0-4.5% by weight of said filler material.
39. A method as defined in any one of preceding claims 30-38, wherein said filler material includes at least about 10% manganese alloying agent by weight of said filler material.
40. A method as defined in claim 39, wherein said manganese alloying agent is in the range of about 10-15% by weight of said filler material.
41. A method as defined in any one of the preceding claims 30-40, wherein said filler material includes nickel as an alloying agent.
42. A method as defined in claim 41, wherein said nickel is in the range of about 8-10% by weight of said filler material.
43. A method as defined in any one of the preceding claims 30-42, wherein said filler material includes chromium oxide.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/902,020 US5233160A (en) | 1992-06-22 | 1992-06-22 | Cored electrode with fume reduction |
| US07/902,020 | 1992-06-22 | ||
| US07/977,086 | 1992-11-16 | ||
| US07/977,086 US5365036A (en) | 1992-06-22 | 1992-11-16 | Flux cored gas shielded electrode |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2109271A1 CA2109271A1 (en) | 1994-05-17 |
| CA2109271C true CA2109271C (en) | 1998-01-06 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2109271 Expired - Fee Related CA2109271C (en) | 1992-06-22 | 1993-10-26 | Flux cored gas shielded electrode |
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| CA (1) | CA2109271C (en) |
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| CN117086511B (en) * | 2023-10-19 | 2024-01-09 | 东北大学 | Smelting flux easy to deslagge and preparation method and application thereof |
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