Multilayer metal composite products obtained by compound strand casting

Abstract

A metallurgical product, such as brazing sheet, comprises a core, on at least one side of the core an interlayer bonded to the core and a cladding bonded to the interlayer. The core and the interlayer are a compositely cast material having at their mutual interface a bond formed in a casting process by their simultaneous solidification from contacting melts of their respective materials. This provides a simple process, with good adhesion. The cladding is applied subsequently and the composite material is rolled into a sheet or plate product.

1 . A metallurgical product comprising a core, on at least one side of the core an interlayer bonded to the core and a cladding bonded to the interlayer, characterized in that said core and interlayer are a compositely cast material having at their mutual interface a bond formed by their simultaneous solidification from contacting melts of their respective materials in a casting process.  
     
     
         2 . A metallurgical product comprising a core, on at least one side of the core an interlayer bonded to the core and a cladding bonded to the interlayer, characterized in that said core and interlayer are a compositely cast material having at their mutual interface a bonding zone formed by mutual mixing of their respective compositions in the molten state prior to their solidification in a casting process.  
     
     
         3 . A metallurgical product according to  claim 1  or  2 , which is plate or sheet and in which, on at least one side of said core, said interlayer has, in the thickness direction of said plate or sheet, a thickness in the range 1 to 30% of the thickness of said compositely cast material.  
     
     
         4 . A metallurgical product according to  claim 1  or  2 , which in section transverse to the length direction of said bar, rod or wire, said interlayer has a thickness which is in the range 1 to 30% of the radius of said compositely cast material.  
     
     
         5 . A metallurgical product according to any one of  claims 1  to  4 , wherein the core and the interlayer are essentially free from oxides at their interface.  
     
     
         6 . A metallurgical product according to any one of  claims 1  to  5 , wherein the cladding has a solidus temperature different from that of the core.  
     
     
         7 . A metallurgical product according to  claim 6 , wherein the cladding has a solidus temperature lower than that of the core.  
     
     
         8 . A metallurgical product according to  claim 6  or  7 , wherein the cladding is a brazing alloy.  
     
     
         9 . A metallurgical product according to  claim 8 , wherein the cladding is an aluminium brazing alloy.  
     
     
         10 . A metallurgical product according to any one of  claims 1  to  9 , wherein the core is an aluminium alloy.  
     
     
         11 . A metallurgical product according to  claim 10 , wherein the core comprises a heat treatable aluminium alloy.  
     
     
         12 . A metallurgical product according to  claim 11 , wherein the core comprises a non-heat treatable aluminium alloy.  
     
     
         13 . A metallurgical product according to any one of  claims 1  to  12 , wherein the interlayer has a corrosion potential different from that of the core.  
     
     
         14 . A metallurgical product according to any one of  claims 1  to  13 , wherein the interlayer has a corrosion potential lower than that of the core.  
     
     
         15 . A metallurgical product according to any one of  claims 1  to  14 , wherein the interlayer acts as a diffusion barrier between the cladding and the core.  
     
     
         16 . A metallurgical product according to any one of  claims 13  to  15 , wherein the interlayer comprises a heat treatable aluminium alloy.  
     
     
         17 . A metallurgical product according to any one of  claims 13  to  15 , wherein the interlayer comprises a non-heat treatable aluminium alloy.  
     
     
         18 . A metallurgical product in the form of sheet or plate, comprising a compositely cast material comprising a core and an interlayer bonded together by their simultaneous solidification, and a cladding layer bonded to said interlayer after solidification of the compositely cast material.  
     
     
         19 . A method of producing a metallurgical product according to any one of  claims 1  to  18 , comprising the steps of 
 (i) preparing said compositely cast material comprising said core and said interlayer bonded to said core by a process including casting said core and said interlayer in such a manner that their respective melts solidify simultaneously and in contact with each other, and  
 (ii) bonding said cladding to said interlayer after solidification of said interlayer.  
 
     
     
         20 . A method according to  claim 19 , wherein, after casting, said compositely cast material has a thickness of at least 100 mm.  
     
     
         21 . A method according to  claim 19  or  20 , wherein said compositely cast material is subjected to a homogenization heat treatment prior to step (ii).  
     
     
         22 . A method according to any one of  claims 19  to  21 , wherein said compositely cast material is hot rolled prior to step (ii).  
     
     
         23 . A method according to any one of  claims 19  to  22 , wherein said compositely cast material is subjected to a surface treatment prior to step (ii).  
     
     
         24 . A method according to any one of  claims 19  to  23 , wherein after step (ii), the product is rolled into a sheet or plate product.  
     
     
         25 . A metallurgical product according to  claim 1  in the form of a sheet product for thickness less than 3 mm.  
     
     
         26 . A metallurgical product according to  claim 1  or  25 , in the form of brazing sheet.  
     
     
         27 . A metallurgical product according to  claim 26 , wherein said cladding in an aluminium alloy having a Si content in the range 3 to 18 weight %.  
     
     
         28 . A metallurgical product according to  claim 1  in the form of a plate product having a thickness in the range 3 to 8 mm.  
     
     
         29 . A brazed assembly comprising at least one component which is a metallurgical product according to any one of  claims 1  to  18 .