Patent Publication Number: US-2018029167-A1

Title: Filler metal with flux for brazing and soldering and method of using same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     N/A 
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     TECHNICAL FIELD 
     The invention relates to relates to wire used in brazing and soldering. More particularly, the present invention is directed to a channeled wire having a flux solution deposited therein for use in joining two similar or dissimilar metals in industrial applications. 
     BACKGROUND OF THE INVENTION 
     Brazing and soldering are two methods commonly used to join two similar or dissimilar metals together. These processes typically involve joining metal components together by disposing a brazing composition such as an aluminum or metal alloy adjacent to or between the faying surfaces, i.e., the surfaces to be joined. The brazing filler alloy and the faying surfaces are then heated to the brazing temperature, typically above the melting temperature of the braze alloy but below the melting temperature of the components to be joined. The brazing composition then melts, flows into the joint by capillary action and forms a fillet and seal that bonds the faying surfaces. 
     In most cases, these processes require a chemical flux in addition to the filler alloy. The flux prepares the base metals to accept the filler alloy which results in a strong bond. Fluxes are generally grouped under two categories: corrosive (must be removed) and non-corrosive (residues are left on the part). 
     Historically, the alloy and flux are applied as two separate steps. In recent years however, an increasing number of options have been developed that combine the filler alloys and fluxes in one complete form. These developments have taken place with brazing alloys that are aluminum based and silver based. 
     For instance, Omni Technologies Corporation (Epping, N.H.) developed a flux core wire, which is sold under the trademark SIL-CORE™. In order to accomplish this, Omni takes aluminum in the form of narrow sheet, deposits a quantity of powdered flux down the middle, and then form rolls the narrow sheet around the flux. This material is then put through draw dies to reduce the diameter and compact the flux inside. From this process, Omni offers several wire diameters as well as different flux compositions. In addition, the amount of flux can be changed as needed. This material is available on spools, large coils and custom fabricated shapes. The inventors of the present invention believe Omni uses a flux sold by Solvay Chemical Company under the name NOCOLOK®. NOCOLOK® brand is one of the most widely recognized non-corrosive aluminum fluxes. This product is described in U.S. Pat. No. 5,781,846, which is hereby incorporated by reference as if fully set forth herein. Omni claims the SIL-CORE™ product does not contain a binding agent. 
     The S.A. Day Corporation (Buffalo, N.Y.) produces an aluminum flux coated rod sold under name DAYROD. This rod includes an aluminum wire cut to 12 inch rods, and dipped in an aluminum flux bath. After dipping, the rods are hung to dry. Day does not use NOCOLOK® brand flux. Instead, Day uses a similar formulation which is mixed with a polymer-based binder system. This binder allows for the flux to remain ductile and not brittle. The flux coated rods can be bent or twisted and the flux will not fall off. 
     Day also produces a flux coated ring. Day purchases metallic rings from Bellman-Melcor, Inc. The rings are then loaded on a machine that “paints” a thin coating of flux on the outside edge of each ring. While the end product is acceptable, it is very slow to produce and consequently very expensive. Similar to the rods, the rings can be handled roughly and the flux remains intact. 
     Protechno-Richard (France) offers a product very similar to the Omni product. 
     Kin-Met (Korea) produces an extruded product. A powdered form of aluminum braze alloy is mixed with powdered flux. The combination is pressurized and extruded into final form. 
     Wolverine and Omni teamed up to create a flux coating for silver based materials. Made from a ductile binder system, this technology is sold under the name SILVACOTE™. SILVACOTE™ is a continuously coated, flux-coated brazing material. 
     U.S. Pat. No. 7,858,204, which is hereby incorporated by reference as if fully set forth herein, describes a wire for use in a brazing or soldering operation. The wire includes an elongated body of a metallic material, a channel having an opening formed along a length of the elongated body, the opening having a width of about 30% to 70% of a major axis of a cross-section of the elongated body, a cured flux solution formed by curing a flux solution comprising a polymer-based binder material and a flux material within the channel and along at least a portion of the length of the elongated body with a surface of the cured flux solution being exposed through the opening in the channel. The wire is formed into an annular ring, and the cured flux solution within the channel forms a portion of an inner wall of the annular ring. The &#39;204 patent also describes alternative embodiments, one of which includes a plurality of flux solution-containing channels formed in a wire. The channels are formed along a transverse length of the wire. The wire maybe formed into an annular ring such that the channels bearing the flux solution form a portion of an inner wall of the ring. The outer wall of the ring includes a section or portion of each channel and thus the flux solution within each channel also forms a portion of the outer wall of the ring. 
     U.S. Pat. No. 8,274,014 was issued from a continuation-in-part application claiming priority from the application from which the &#39;204 patent issued. The &#39;014 patent is also incorporated by reference as if fully set forth herein. The &#39;014 patent is directed to wire for brazing or soldering comprising a first channel and a second channel, both extending lengthwise along the central axis of the wire. The first and second channels comprise a pair of sidewalls extending lengthwise along the central axis separated by a transverse base. Each sidewall extends radially outwardly from the base and forming an angle with the base greater than 90 degrees; 
     Despite the advancement provided by the &#39;204 and &#39;014 patents, there is a need for a brazing or soldering wire that can be used to create a better joint between connected parts. It would be an advancement in the art of brazing or soldering wire to provide such a wire capable of forming a larger joint area with improved distribution of flux over the area of the part or parts to be joined. 
     The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior brazing or soldering wires of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is directed to a wire for use in a brazing or soldering operation. The wire comprises an elongated body of a metallic material. A pair channels each have an opening formed along a length of the elongated body. A divider is formed by a portion of the elongated body and separates the pair of channels. The divider has opposing walls extending outwardly from corresponding base portions of the pair of channels. The opposing walls terminate at distal ends, and a first engagement surface is formed therebetween. A pair of outer walls are separated by the pair of channels and the divider. The outer walls each extend outwardly from corresponding base portions of each of the pair of channels. A second engagement surface is formed between an outer surface of the elongated wire and a terminal end of one of the outer walls and is substantially coplanar with the first engagement surface. A third engagement surface is formed between the outer surface of the elongated wire and a terminal end of the other of the outer walls and substantially is coplanar with the first engagement surface. A cured flux solution within the pair of channels. Corresponding surfaces of the cured flux solution are exposed through the opening in each channel. 
     This aspect of the invention may include one or more of the following features, alone or in any reasonable combination. Each channel may have an angled wall extending outwardly from a corresponding base portion. The angled walls may each have an angle orientation relative to a common axis, and each angle orientation may be identical. The angled walls may each have an angle orientation relative to a common axis, and a first angle orientation of a first angled wall may be opposite a second angle orientation of a second angled wall. The pair of channels may be substantially parallel and extend lengthwise along the elongated body. The divider may have opposing walls extending outwardly from corresponding base portions of the pair of channels and angled such that the opposing walls converge and terminate at distal ends wherein a first engagement surface is formed therebetween. The first engagement surface may have a substantially planar profile. The wire may further comprise a pair of diverging walls separated by the pair of channels and the divider. The diverging walls may each extend outwardly from corresponding base portions of each of the pair of channels and angle such that a first distance between the diverging walls adjacent the corresponding base portions is less than a second distance between the diverging walls at corresponding terminal ends of the diverging walls opposite the corresponding base portions. The wire may be substantially E-shaped when viewed in cross-section taken transverse to a length of the wire. The second and third engagement surfaces may be substantially coplanar. 
     Another aspect of the present invention is also directed to a wire for use in a brazing or soldering operation. The wire comprises an elongated body of a metallic material. A pair channels each have an opening formed along a length of the elongated body. A divider is formed by a portion of the elongated body separating the pair of channels. The divider has opposing walls extending outwardly from corresponding base portions of the pair of channels. The opposing walls terminate at distal ends wherein a first engagement surface is formed therebetween. A pair of outer walls is separated by the pair of channels and the divider. The outer walls each extend outwardly from corresponding base portions of each of the pair of channels. A second engagement surface is formed between an outer surface of the elongated wire and a terminal end of one of the outer walls. A third engagement surface is formed between the outer surface of the elongated wire and a terminal end of the other of the outer walls and is substantially coplanar with the second engagement surface. A cured flux solution is within the pair of channels. Corresponding surfaces of the cured flux solution are exposed through the opening in each channel. 
     This aspect of the invention may include one or more of the following features, alone or in any reasonable combination. Each channel may have an angled wall extending outwardly from a corresponding base portion. The angled walls may each have an angle orientation relative to a common axis, and each angle orientation may be identical. The angled walls may each have an angle orientation relative to a common axis, and a first angle orientation of a first angled wall may be opposite a second angle orientation of a second angled wall. The pair of channels may be substantially parallel and extend lengthwise along the elongated body. The divider may have opposing walls extending outwardly from corresponding base portions of the pair of channels and angled such that the opposing walls converge and terminate at distal ends wherein a first engagement surface is formed therebetween. The first engagement surface may have a substantially planar profile. The wire may further comprise a pair of diverging walls separated by the pair of channels and the divider. The diverging walls may each extend outwardly from corresponding base portions of each of the pair of channels and angle such that a first distance between the diverging walls adjacent the corresponding base portions is less than a second distance between the diverging walls at corresponding terminal ends of the diverging walls opposite the corresponding base portions. The wire may be substantially E-shaped when viewed in cross-section taken transverse to a length of the wire. The second and third engagement surfaces may be substantially coplanar. 
     Another aspect of the present invention is also directed to a wire for use in a brazing or soldering operation. The wire comprises an elongated body of a metallic material. A pair of substantially parallel channels each have an opening formed along a length of the elongated body. A divider is formed by a portion of the elongated body separating the pair of channels. The divider has opposing walls extending outwardly from corresponding base portions of the pair of channels and is angled such that the opposing walls converge and terminate at distal ends wherein a first engagement surface is formed therebetween having a substantially planar profile. A pair of diverging walls is separated by the pair of channels and the divider. The diverging walls each extend outwardly from corresponding base portions of each of the pair of channels and each is angled such that a first distance between the diverging walls adjacent the corresponding base portions is less than a second distance between the diverging walls at corresponding terminal ends of the diverging walls opposite the corresponding base portions. A second engagement surface is formed between an outer surface of the elongated wire and the terminal end of one of the diverging walls and has a substantially planar profile substantially coplanar with the first engagement surface. A third engagement surface is formed between the outer surface of the elongated wire and the terminal end of the other of the diverging walls and has a substantially planar profile substantially coplanar with the second engagement surface. A cured flux solution is formed by curing a flux solution comprising a polymer-based binder material and a flux material within the pair of channels. Corresponding surfaces of the cured flux solution are exposed through the opening in each channel. The elongated body is formed into an annular ring. The cured flux solution within the channels forms a portion of an inner wall of the annular ring. The cured flux solution within a first channel is located below a plane extending from the terminal end of one of the diverging walls to the distal end of one of the opposing walls of the divider, and the cured flux solution within a second channel is located below a plane extending from the terminal end of the other of the diverging walls to the distal end of the other of the opposing walls of the divider. 
     Another aspect of the present invention is directed to a preform produced from a wire and used in a brazing or soldering operation. The preform comprises a wire of an elongated body having a continuous external surface defining an exterior of the wire formed into an annular ring centered about a longitudinal axis and a flux solution. The wire comprises a first substantially circumferential channel recessed within the external surface of the wire. A second substantially circumferential channel is also recessed within the external surface of the wire. A substantially annular divider separates the first channel from the second channel and defines a first engagement surface therebetween The first engagement surface is positioned at a first radial distance from the longitudinal axis. A second engagement surface of the external surface of the wire is opposite the divider wherein the first substantially circumferential channel lies therebetween. The second engagement surface is positioned at a second radial distance from the longitudinal axis. A third engagement surface of the external surface of the wire is opposite the divider wherein the second substantially circumferential channel lies therebetween. The third engagement surface is positioned at a third radial distance from the longitudinal axis. A flux solution is cured within the first and second substantially circumferential channels and each have an exposed surface through respective openings in the first and second substantially circumferential channels. The exposed surface of the flux solution within the first substantially circumferential channel is positioned at a fourth radial distance from the longitudinal axis, and the exposed surface of the flux solution within the second substantially circumferential channel is positioned at a fifth radial distance from the longitudinal axis. 
     This aspect of the invention may include one or more of the following features, alone or in any reasonable combination. The first, second, and third radial distances may be equal. The first and second radial distances may be equal. The second and third radial distances may be equal. The fourth and fifth radial distances may be greater than the first, second, and third radial distances. The fourth and fifth radial distances may be about equal to the first, second, and third radial distances. The fourth and fifth radial distances may be less than the first, second, and third radial distances. A cross-sectional shape of the preform may be E-shaped. The annular ring may have a radially inner surface and a radially outer surface opposite the radially inner surface, and the radially inner surface may comprise the first, second, and third engagement surfaces. The annular ring may have a radially inner surface and a radially outer surface opposite the radially inner surface. The radially outer surface may comprise the first, second, and third engagement surfaces. 
     Another aspect of the present invention is directed to a wire for use in a brazing or soldering operation. The wire comprises: an elongated body of a metallic material; a channel having an opening formed along a length of the elongated body, the channel defined by a width of an opening thereto, first and second opposing inner angled walls and an inner base, the first and second inner angled walls converging from the opening towards the inner base such that a width of the opening is greater than a width of the inner base; first and second outer angled walls are separated from the first and second inner angled walls, respectively, by first and second engagement surfaces, the first and second outer angled walls converging from the first and second engagement surfaces towards an outer base such that a width of the outer base is greater than a width of the wire defined by a width of the first engagement surface, a width of the second engagement surface, and the width of the opening; and a cured flux solution within the channel, wherein a surface of the cured flux solution is exposed through the opening in the channel. 
     This aspect of the invention may include one or more of the following features, alone or in any reasonable combination. The outer base may be positioned entirely on a first plane that is substantially parallel to a second plane on which the inner base is entire positioned. The first inner angled wall may be parallel to the first outer angled wall. The second inner angled wall may be parallel to the second outer angled wall. The first and second engagement surfaces may be entirely positioned on a third plane which is substantially parallel to the first and second planes. The wire may be formed into an annular preform. A radially innermost contacting area of an annular preform may comprise the first engagement surface, the second engagement surface, and the surface of the cure flux solution exposed through the opening in the channel. A radially outermost contacting area of an annular preform may comprise the first outer angled wall. A sum of the width of the first engagement surface and the width of the second engagement surface may be less than the width of the opening in the channel. An outer surface of the wire may comprise the first and second engagement surfaces, the first and second outer angled walls, the outer base, and the exposed surface of the cured flux solution, forming a trapezoidal shape in a cross-section taken transverse to a length of the elongated body. 
     Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a wire of the present invention; 
         FIG. 2  is a cross-sectional view of the wire of  FIG. 1 ; 
         FIG. 3  is a perspective view of a preform formed from the wire of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the preform of  FIG. 3 ; 
         FIG. 5  is a perspective view of an alternative preform formed from the wire of  FIG. 1 ; 
         FIG. 6  is a cross-sectional view of the preform of  FIG. 5 ; 
         FIG. 7  is a view of the preform of  FIG. 3  is use; 
         FIG. 8  is a view of the preform of  FIG. 5  in use; 
         FIG. 9  is a cross-sectional view of an alternative embodiment of a wire of the present invention; 
         FIG. 10  is a cross-sectional view of an alternative embodiment of a wire of the present invention; 
         FIG. 11  is a cross-sectional view of an alternative embodiment of a wire of the present invention; 
         FIG. 12  is a cross-sectional view of an alternative embodiment of a wire of the present invention; 
         FIG. 13  is a cross-sectional view of an alternative embodiment of a wire of the present invention; 
         FIG. 14  is a perspective view of another embodiment of a wire of the present invention; 
         FIG. 15  is a cross-sectional view of the wire of  FIG. 14 ; 
         FIG. 16  is a cross-sectional view of the wire of  FIG. 14  having a cured flux solution located within a channel; 
         FIG. 17  is a cross-sectional perspective view of the wire of  FIG. 16  formed into an annular preform for a subsequent brazing or soldering operation; 
         FIG. 18  is a cross-sectional view of a brazing operation employing the annular preform illustrated in  FIG. 17 ; and 
         FIG. 19  is a reproduction of a portion of an evaporator coil showing a brazed connection using a preform of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. 
     The present invention is directed to a brazing/soldering wire for use in multiple metal combinations including aluminum applications. The end use for these materials is typically industrial applications, such as automobiles and automobile component manufacturing as well as other heat transfer applications including air conditioning and refrigeration manufacture. Of course, other applications can be had as well. The brazing/soldering wire of the present invention may be used on many different materials including aluminum alloys, zinc alloys, copper alloys and silver alloys, etc. The wire itself can be produced from an aluminum alloy, a silver alloy, a copper alloy, and/or a zinc alloy. 
     The Wire 
     The present invention includes a solid wire  10  rather than a narrow sheet or strip that is preferably very robust and will not move when assembled onto component parts. This is important because in air conditioning applications, braze wire is commonly supplied in ring-form. The rings are friction fit or snuggly placed around tubes. Because current ring shaped braze wires often lose their grip on component parts, causing the rings to shift or fall off altogether, rings formed from the wire  10  of the present invention are specifically constructed so as to be less likely to plastically deform by the friction fit about the component parts. As a result, they are less likely to shift or fall off prior to the brazing or soldering process. This important aspect of the present invention is described in more detail below. 
     Referring to  FIGS. 1 and 2 , a wire  10  having an elongated body  12  with a plurality of channels  14   a,b  reformed along an entire length of an external surface  18  is illustrated. The channels  14   a,b  are preferably a pair of lengthwise at least substantially parallel recesses formed in the external surface  18 . The wire  10  is formed from a metallic material supplied at a diameter of about 0.031 inches to 0.125 inches (0.787 mm to 3.18 mm), preferably 0.079 inches to 0.090 inches (2.00 mm to 2.29 mm), or any range or combination of ranges therein. The wire  10  has been rolled or reformed to a new geometric shape, such as an E-shape configuration when viewed in a cross-section taken transverse to the length of the wire  10 , generally perpendicular to the direction of the channels  14   a,b . The channels  14   a,b  are formed in the external surface  18  of the wire  10 . A deformation of the external surface  18  defines the shape of the wire  10 . 
     A lengthwise divider  22  separates the channels  14   a,b . According to the invention, the divider  22  is formed by a portion of the elongated body. The divider  22  has opposing walls  26   a,b  extending outwardly from corresponding base portions  30   a,b  of the pair of channels  14   a,b . The walls  26   a,b  are angled such that they converge towards one another. Thus, walls  26   a,b  each have an angle orientation relative to a common axis wherein a first angle orientation of a first of the walls  26   a  is opposite a second angle orientation of a second of the walls  26   b . The walls  26   a,b  terminate at distal ends. An engagement surface  34  of the external surface  18  is formed therebetween. 
     The engagement surface  34  preferably has a substantially planar profile. 
     A pair of channel outer walls  38   a,b  are separated by the pair of channels  14   a,b  and the divider  22 . The outer walls  38   a,b  each extend outwardly from corresponding base portions  30   a,b  of each of the pair of channels  14   a,b . The outer walls  38   a,b  are preferably diverging walls relative to each other and angled such that a first distance between the diverging outer walls  38   a,b  adjacent the corresponding base portions  30   a,b  is less than a second distance between the diverging outer walls  38   a,b  at corresponding terminal ends of the diverging outer walls  38   a,b  opposite the corresponding base portions  30   a .B. The outer walls  38   a,b  each have an angle orientation relative to a common axis wherein each angle orientation is identical. 
     A second engagement surface  42  is formed outwardly of one of the outer walls  38   a  and is formed between an outer surface  46  of the elongated wire  10  and the terminal end of one of the outer walls  38   a . The second engagement surface preferably has a substantially planar profile and is preferably, though not necessarily substantially coplanar with the first engagement surface  34 . 
     A third engagement surface  50  is formed outwardly of the other of the outer walls  30   b  and is also formed between the outer surface  46  of the elongated wire  10  and the terminal end of the other of the outer walls  38   b . The third engagement surface preferably has a substantially planar profile and is preferably substantially coplanar with the second engagement surface  42  and/or the first engagement surface  34 . 
     A cured flux solution  54  formed by curing a flux solution comprising a polymer-based binder material and a flux material is located within one or both of the channels  14   a,b , preferably both. Corresponding surfaces  58  of the cured flux solution  54  are exposed through openings in each channel  14   a,b . The cured flux solution  54  within a first channel  14   a  is preferably located below a plane extending from the terminal end of one of the outer walls  38   a  to the distal end of one of the opposing walls  26   a  of the divider  22 . The cured flux solution  54  within a second channel  14   b  is preferably located below a plane extending from the terminal end of the other of the outer walls  38   b  to the distal end of the other of the opposing walls  26   b  of the divider  22 . 
       FIGS. 9-13  are examples of alternative embodiments of wires  10  of the present invention. In particular,  FIG. 9  shows a channel-less wire  10  wherein the flux solution  54  is cured on an external surface of the wire which does not exhibit a channel, recess, or other striation.  FIG. 10  shows a wire  10  having a channel  14   a  wherein outer walls  38   a,b  are flared outwardly at an angle greater than 90 degrees as measured from a base  30   a  of the channel.  FIG. 11  shows another embodiment of wire  10 .  FIG. 12  shows a wire  10  having a faceted outer surface  46 , substantially trapezoidal in cross-section. 
     An alternative embodiment is illustrated in  FIG. 14 . The reference numerals used relative to the previous embodiments are consistently with this embodiment. The preferred nominal dimensions of this wire  10  are 0.052 inches×0.125 inches. 
     The wire  10  of  FIG. 14  has a single channel  14 . The channel  14  is formed by a pair of opposing inner angled walls  38   a,b  which terminate at an inner base  30 . Opposing outer angled walls  46  terminate at an outer base  32 . One of the inner angled walls  38   a  is generally parallel to a corresponding outer angled wall  46 , and the other of the inner angled walls  38   b  is generally parallel to the other outer angled wall  46 . Engagement surfaces  42 , 50  separate each angled inner wall  38   a,b  from its corresponding angled outer wall  46 . 
     The channel  14  has a depth D. The depth is preferably about 0.03 inches. An opening to the channel  14  has a cross-sectional width W of preferably 0.080 inches. The channel  14  is defined by the inner angled walls  38   a,b , the inner base  30 , and the width W of the opening. The angled walls  38   a,b  form a converging structure wherein the width W of the opening is wider than a width of the inner base  30 . Because the outer angled walls  46  are parallel to the inner angled walls  38   a,b , the outer base  32  has a greater width that the inner base  30 . A sum of a width of a first engagement surface  42  and a width of the second engagement surface  50  is less than the width W of the opening in the channel  14 . 
     A flux solution  54  is cured within the channel  14 . The outer surface  18  of the wire  10  and an exposed surface  58  of the cured flux solution  54  form a trapezoidal shape in cross-section as illustrated in  FIG. 16 . 
     The engagement surfaces  42 , 50  are generally positioned on a common plane that is parallel to a plane on which the outer base  32  is positioned and a separate plane on which the inner base  30  is positioned. A sum of a width of a first engagement surface  42  and a width of the second engagement surface  50  is less than the width W of the opening in the channel  14 . 
     The widths of the engagement surfaces  42 , 50  are preferably equal. Lengths of the outer angled walls  46  are preferably equal. Lengths of the inner angled walls  38   a,b  are preferably equal. When the parallel relationship of corresponding inner angled walls and outer angled walls exists, the wire  10  has consistent material thickness whereby a thickness of the wire does not vary when viewed in cross-section taken transverse to the elongated body of the wire. In other words, a width of the wire between the inner and outer bases is equal the widths of the engagement surfaces  42 , 50 . 
     The wire  10  preferably has a constant thickness as measured along a line drawn at a right angle from both the inner angled walls  38   a,b  and the outer angled walls  46 . Thus, the material between the inner angled walls  38   a,b  and the outer angled walls  46  has the same thickness as the material between the inner and outer bases  30 , 32 , except for a segment of the wire  10  adjacent the engagement surfaces  42 , 50  where no such can be drawn. In this region, as shown in  FIGS. 14-18 , a length of the engagement surface  42 , 50 , and by consequence and area of the engagement surface  42 , 50 , can be expanded by reducing an angle α between the inner angled wall  38   a,b  and the engagement surfaces  42 , 50 . This will create a region of the wire  10  wherein: 
     
       
         
           
             
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                 wire 
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     wherein: 
       θ=360°−(α+90°)
 
     In one embodiment, the angle α is greater than 180 degrees and less than 260 degrees. 
     In another embodiment, the angle α is greater than 200 degrees and less than 250 degrees. 
     In another embodiment, the angle α is greater than or equal to 215 degrees and less than or equal to 240 degrees. 
     The Preforms 
     Preforms produced from the wire  10  of the present invention are illustrated in  FIGS. 3-6 . Each preform  100  comprises a wire  10  of an elongated body having a continuous external surface  18  defining an exterior of the wire  10  formed into an annular ring centered about a longitudinal axis and a flux solution  54 . The wire  10  comprises a first substantially circumferential channel  14   a  recessed within the external surface  18  of the wire  10 . A second substantially circumferential channel  14   b  is also recessed within the external surface  18  of the wire  10 . A substantially annular divider  22  separates the first channel  14   a  from the second channel  14   b . A first engagement surface  34  of the external surface  18  lies therebetween. 
     The first engagement surface  34  is positioned at a first radial distance from the longitudinal axis. 
     A second engagement surface  42  of the external surface  18  of the wire  10  is opposite the divider  22  and separated therefrom by a channel  14   a  such that the first substantially circumferential channel  14   a  lies therebetween. The second engagement surface  42  is positioned at a second radial distance from the longitudinal axis  104 . 
     A third engagement surface  50  of the external surface  18  of the wire  10  is opposite the divider  22  and separated therefrom by the second substantially circumferential channel lies  14   b . The third engagement surface  50  is positioned at a third radial distance from the longitudinal axis. 
     The flux solution  54  is cured within the first and second substantially circumferential channels  14   a,b  and each have an exposed surface through respective openings in the first and second substantially circumferential channels  14   a,b . The exposed surface of the cured flux solution  54  within the first substantially circumferential channel  14   a  is positioned at a fourth radial distance from the longitudinal axis, and the exposed surface of the cured flux solution  14   b  within the second substantially circumferential channel  14   b  is positioned at a fifth radial distance from the longitudinal axis. 
     In at least one embodiment, the first and second radial distances are equal. 
     In at least embodiment, the first, second, and third radial distances are equal. 
     In at least one embodiment, the second and third radial distances are equal. 
     In at least one embodiment, the fourth and fifth radial distances are about equal to the first, second, and third radial distances. 
     In one embodiment illustrated in  FIGS. 3 and 4 , the fourth and fifth radial distances are greater than the first, second, and third radial distances. 
     In the embodiment illustrated in  FIGS. 3 and 4 , the preform  100  has a radially inner surface and a radially outer surface opposite the radially inner surface. The radially inner surface comprises the first, second, and third engagement surfaces  34 , 42 , 50 . 
     In one embodiment illustrate in  FIGS. 5 and 6 , the fourth and fifth radial distances are less than the first, second, and third radial distances. 
     In the embodiment illustrated in  FIGS. 5 and 6 , the annular ring has a radially inner surface and a radially outer surface opposite the radially inner surface. The radially outer surface comprises the first, second, and third engagement surfaces  34 , 42 , 50 . 
     In at least one embodiment, a cross-sectional shape of the preform  100  is E-shaped. 
     The preform of  FIG. 13  is an alternative embodiment of the present in invention, A plurality of channels  14 , 16  are spaced about a circumference of the wire  10 . A substantially round outer surface is formed by a combination of exposed surfaces  58  of the flux solution  54  within radially outer channels  14  and engagement surfaces  34  between each of the radially outer channels  14 . In addition or optionally, a substantially round inner surface may also be formed by a combination of cured flux solution exposed surfaces  58  with a plurality of radially inner channels  16  and radially inner engagement surfaces  35 . Channel walls converge at an apex wherein the channel walls diverge outwardly therefrom to promote flux solution flow upon a heating of the wire and/or flux solution  54  during use. The channels  14 , 16  have a substantially triangular shape when viewed in a cross-section taken transverse to the length of the elongated body  12 . 
     An alternative preform is illustrated in  FIG. 17 . This preform  300  follows the structural guidelines set forth above and is produced from the wire of  FIG. 14 , which is described above. Here, again, the wire  10  is formed into an annular preform  300 . A radially inner most surface is made up of the engagement surfaces  42 , 50  and the exposed surface  58  of the cured flux solution  54 . A radially outer surface is made up of the outer angled surfaces  46  converging to the outer base  32 . 
     A Method of Use 
     Methods of using a preform  100  of the present invention are illustrated in  FIGS. 7 and 8 . A first tubular metallic part  200  is to be joined to a second tubular metallic part  204 . As illustrated in  FIG. 7 , using a preform  100  according to  FIGS. 3 and 4 , the first tubular part  200  is passed through the preform  100 . The flux-laden channels  14   a,b  of the preforms  100  are located adjacent an outer surface  202  of the first tubular part  200 . The second tubular part  204  has a radially outwardly flared flange  208  to aid in guiding an end portion of the first tubular part  200  into the second tubular part  204 . The method illustrated in  FIG. 8  utilizes a preform  100  according to  FIGS. 5 and 6 . 
     A method of using a preform  300  of  FIG. 17  is illustrated in  FIG. 18 . A first tubular metallic part  200  is to be joined to a second tubular metallic part  204 . As illustrated in  FIG. 18 , using a preform  300  according to  FIG. 17 , the first tubular part  200  is passed through the preform  300 . The flux-laden channel  14  of the preform  300  is located adjacent an outer surface  202  of the first tubular part  200 . The second tubular part  204  has a radially outwardly flared flange  208  to aid in guiding an end portion of the first tubular part  200  into the second tubular part  204 . The outer angled walls  46  of the preform  300  have an angle that is substantially equal to the angle of the flared flange  208  of the second tubular part  204 , such that the preform  300  has engagement surfaces  42 , 50  in contact with the first tubular part  200 , and one of the two outer angled walls  46  in contact with the flared flange  208  of the second tubular part  204 . Preferably, a radially outer contacting surface is formed between the flared flange  208  and the outer angled wall  46  in engagement therewith is equal to an area of that outer angled wall  46 . A radially inner contacting surface is made up of the two engagement surfaces  42 , 50  and the exposed surface  58  of the cured flux solution  54  with the outer surface  202  of the first tubular part  200 . 
     The method of  FIG. 18  using the preform  300  of  FIG. 17  has several advantages, especially when used in a preferred method of joining tubed components in a refrigeration evaporator as illustrated in  FIG. 18 . First, the wire  10  has a consistent material thickness, so thermal transfer of heat is more even during use. Thus, the entirety of an annular preform  300  made according to the teachings of the wire of  FIG. 16  will liquefy simultaneously or substantially simultaneously. Secondly, due to the shape of the wire  10  of  FIG. 14 , when formed into the annular preform  300 , the preform fits well and mates with parts to be joined by brazing, providing perfect alignment. Thirdly, a gap, to the extent one exists, between the outer surface  202  of the first tubular part  200  and the engagement surfaces  42 , 50  of the preform  300  is exactly the same all around the joint interface and a return bend in the evaporator is always straight, i.e. this eliminates crooked return bends (see  FIG. 19 ). Finally, the structure is very resistant to distortion or “pull-back” during a heat cycle making this preform  300  product more forgiving and less dependent on a perfect heat pattern. 
     One of ordinary skill in the art would appreciate that the terms “first,” “second,” “upper,” “lower,” etc. are used for illustrative purposes only and are not intended to limit the embodiments in any way. The term “plurality” as used herein is intended to indicate any number greater than one, either disjunctively or conjunctively as necessary, up to an infinite number. The terms “joined,” “attached,” and/or “connected” as used herein are intended to put or bring two elements together so as to form a unit, and any number of elements, devices, fasteners, etc. may be provided between the joined, attached or connected elements unless otherwise specified by the use of the term “directly” and/or supported by the drawings. The term “annular” is used throughout the Specification to indicate a ring-like construction, and like many rings, the elements modified by the term “annular” are generally circumferential, but may have gaps, overlapping ends, unjoined ends, etc. that would improve the performance of the element in any way, especially in dimensional fit, strength, etc. 
     While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying Claims.