Friction surface stir process

Abstract

A process is described that employs what can be termed a friction surface stirring (FSS) process on the surface of a metal object. The FSS process occurs on some or the entire surface of the metal object, at a location(s) separate from a friction stir welded joint. The FSS process on the surface produces a corrosion resistant mechanical conversion “coating” on the object. The “coating” is formed by the thickness of the material of the object that has been FSS processed. In one exemplary application, the process can be applied to a metal strip that is later formed into a tube whereby the “coated” surface resides on the inside of the tube making it highly resistant to corrosive flow such as seawater.

1 . A friction surface stir process, comprising:
 using a friction stir welding tool to friction surface stir at least a portion of a non-jointed surface of a metal object.   
     
     
         2 . A process, comprising:
 friction surface stirring a non jointed surface of a metal object using a friction stir welding tool.   
     
     
         3 . A method of increasing corrosion resistance of a surface of a metal object, comprising:
 friction surface stirring at least a portion of a non jointed surface of the metal object using a friction stir welding tool to produce a mechanical conversion coating.   
     
     
         4 . The method of  claim 3 , comprising surface stirring the entire surface area of the metal object that in its intended use is exposed to water, a marine environment or corrosive environment. 
     
     
         5 . The method of  claim 3 , further comprising after surface stirring, machining, fly-cutting, sanding, grinding or polishing the surface stirred portion of the surface. 
     
     
         6 . The method of  claim 3 , wherein the metal object is formed from a single metal material. 
     
     
         7 . The method of  claim 3 , wherein the non-jointed surface of the metal object is a substantially flat and planar surface. 
     
     
         8 . The method of  claim 3 , wherein the non-jointed surface of the metal object is a curved or non-flat surface. 
     
     
         9 . The method of  claim 3 , wherein the metal object has both curved and flat surfaces. 
     
     
         10 . The method of  claim 3 , wherein the metal object is a plate, bar, rod or tube. 
     
     
         11 . The method of  claim 3 , wherein the metal object is completely friction surface stirred and the friction surface stirring penetrates the entire thickness of the metal object. 
     
     
         12 . The method of  claim 6 , wherein the single metal material comprises an aluminum alloy, a titanium alloy, or stainless steel. 
     
     
         13 . The method of  claim 12 , wherein the aluminum alloy comprises a marine-grade aluminum alloy, 
     
     
         14 . The method of  claim 4 , wherein the metal object is an object used in an ocean thermal energy conversion plant, a desalination plant, or a component of a maritime vessel or aircraft. 
     
     
         15 . The method of  claim 4 , wherein the metal object is a heat exchanger used in an ocean thermal energy conversion plant. 
     
     
         16 . The method of  claim 11 , wherein the metal object is cut into strips. 
     
     
         17 . The method of  claim 16 , wherein after cutting, each of the strips is formed into a tubular object. 
     
     
         18 . The method of  claim 17 , wherein adjoining edges of the tubular object formed by the strip are friction stir welded down the seam to produce a completely friction surface stirred and friction stir welded tube. 
     
     
         19 . The method of  claim 11 , wherein the metal object is machined, stamped or processed to create surface enhancements on at least one surface thereof. 
     
     
         20 . The method of  claim 19 , wherein the metal object is cut into strips. 
     
     
         21 . The method of  claim 20 , wherein after cutting, each of the strips is formed into a tubular object. 
     
     
         22 . The method of  claim 21 , wherein adjoining edges of the tubular object formed by the strip are friction stir welded down the seam to produce a completely friction surface stirred and friction stir welded tube. 
     
     
         23 . The method of  claim 21 , wherein adjoining edges of the tubular object formed by the strip are joined along a seam. 
     
     
         24 . The method of  claim 23 , wherein the joined edges are friction stir welded along the seam to produce a completely friction surface stirred and friction stir welded tubular object.