Exothermic Wire for Bonding Substrates

Abstract

An exothermic cord, foil, or ribbon is produced by first cold drawing individual round wires of the constituent materials under a cover gas. The cold drawing operation yields a clean surface that is free of oxidation and other contaminants. Next, the constituent wires are brought together and twisted, cold drawn, swaged, and/or friction welded to create a unitary cord exhibiting intimate contact between the constituent materials. The unitary cord may then be used directly or further shaped to a desired form and/or thickness. By controlling the size ratio between the cross-sections of the constituents, a degree of control can be exercised over the exothermic reaction characteristics. The unitary cord, once formed, can be coated with braze and/or flux materials to aid in a subsequent joining operation. Multiple cords can be woven together to form a cloth structure. The exothermic assembly can be applied in the field of gaskets to permanently affix opposing surfaces together, such as affixing a cylinder head in an operative position over a cylinder block.

1 . A method for producing a multi-stranded exothermic assembly of the type for propagating an exothermic reaction between the strands in response to an initiating thermal impulse, said method comprising the steps of: 
 providing an elongated first wire of a constituent metallic material having a generally round cross-section;    providing an elongated second wire of a constituent metallic material dissimilar from that of the first wire and having a generally round cross-section;    cold drawing the first wire through a reduction die in a non-oxidating atmosphere;    cold drawing the second wire through a reduction die in a non-oxidating atmosphere;    bringing the first and second wires into contact with one another in a non-oxidizing atmosphere; and    simultaneously plastically deforming the first and second wires together into a unitary cord so that the surfaces of the first and second wires are pressed into contact to facilitate a sustained propagating exothermic reaction in response to an initiating thermal impulse.    
     
     
         2 . The method of  claim 1 , wherein said step of plastically deforming the first and second wires includes cold drawing the first and second wires through a reducing die.  
     
     
         3 . The method of  claim 1 , wherein said step of simultaneously plastically deforming the first and second wires includes twisting the first and second wires together in a generally helical pattern.  
     
     
         4 . The method of  claim 1 , wherein said step of simultaneously plastically deforming the first and second wires includes simultaneously cold drawing and twisting the first and second wires together.  
     
     
         5 . The method of  claim 1 , wherein said step of simultaneously plastically deforming the first and second wires includes swaging.  
     
     
         6 . The method of  claim 5 , wherein said step of simultaneously plastically deforming the first and second wires further includes twisting the wires into a generally helical configuration.  
     
     
         7 . The method of  claim 1 , wherein said step of simultaneously plastically deforming the first and second wires includes ultrasonically welding the first and second wires to one another.  
     
     
         8 . The method of  claim 7 , wherein said step of simultaneously plastically deforming the first and second wires further includes twisting the wires in a helical configuration.  
     
     
         9 . The method of  claim 1 , further including the step of applying a material coating to the unitary cord following said step of simultaneously plastically deforming the first and second wires.  
     
     
         10 . The method of  claim 9 , wherein said step of applying a material coating includes coating the unitary cord.  
     
     
         11 . The method of  claim 1 , further including the step of weaving a plurality of the cords into a cloth.  
     
     
         12 . The method of  claim 1 , further including the step of flattening the unitary cord following said step of simultaneously plastically deforming the first and second wires.  
     
     
         13 . The method of  claim 12 , wherein said flattening step further includes passing the unitary cord through a rolling mill.  
     
     
         14 . A one-time use gasket of the type for sealing a cylinder head to a cylinder block in an internal combustion engine, said gasket comprising: 
 a sheet-like body;    at least one cylinder bore opening formed in said body;    at least one fluid flow passage formed in said body, said fluid flow passage isolated from said cylinder bore opening; and    said body being fabricated from a reactive multi-stranded exothermic assembly of the type for propagating an exothermic reaction in response to an initiating thermal impulse, whereby the heat produced during the exothermic reaction is sufficient to metallurgically fuse the cylinder head to the cylinder block while maintaining fluidic isolation between said cylinder bore opening and said fluid flow passage.    
     
     
         15 . The assembly of  claim 14 , wherein said body includes a protruding wick.  
     
     
         16 . The assembly of  claim 14 , wherein said multi-stranded exothermic assembly consists essentially of alternating wires of a first constituent metallic material and a second constituent metallic material, said second constituent metallic material being dissimilar to said first constituent metallic material.  
     
     
         17 . The assembly of  claim 16 , wherein said first constituent metallic material consists essentially of an aluminum-based alloy.  
     
     
         18 . The assembly of  claim 16 , wherein said second constituent metallic material consists essentially of a nickel-based alloy.  
     
     
         19 . A method for establishing a fluid-tight seal between opposing surfaces having formed therebetween at least two discrete flow passages, said method comprising the steps of: 
 forming a gasket from a reactive multi-stranded exothermic assembly of the type for propagating an exothermic reaction in response to an initiating thermal impulse;    forming at least two spaced and isolated flow passages in the gasket for conducting a fluid material between the two opposing surfaces;    aligning the openings in the gasket with the flow passages in the opposing surfaces;    compressing the gasket between the opposing surfaces;    initiating a propagating exothermic reaction in the gasket body;    melting the opposing surfaces in response to the heat generated during the exothermic reaction; and    metallurgically fusing the opposing surfaces together in regions around the flow passages to permanently seal the opposing surfaces together while permitting fluid exchange between the isolated flow passages.    
     
     
         20 . The method of  claim 19 , wherein said step of forming a gasket includes providing an elongated first wire of a constituent metallic material having a generally round cross-section, providing an elongated second wire of a constituent metallic material dissimilar from that of the first wire and also having a generally round cross-section, cold drawing the first wire through a reduction die in a non-oxidizing atmosphere, cold drawing the second wire through a reduction die in a non-oxidizing atmosphere, bringing the first and second wires into contact with one another in a non-oxidizing atmosphere, and simultaneously plastically deforming the first and second wires together into a unitary cord.