Method for assembling a titanium shell with a titanium fire resistant alloy shell

Abstract

A method for assembling metal shells, including: (a) providing a first shell made of a titanium fire-resistant alloy with a shape similar to a final shape thereof and having first and second opposite surfaces, the second surface including raised portions acting as anchoring points between shells; (b) providing at least one second shell made of a titanium alloy and having first and second opposite surfaces; (c) placing the first surface of the second shell on the second surface of the first shell; (d) heating the second shell to a temperature higher than a second temperature; (e) deforming the second shell at the second temperature on the first shell, such that the first surface of the second shell matches the second surface of the first shell, the second shell thus being secured to the first shell; and (f) cooling an assembly of the first and second shells to ambient temperature.

1 - 9 . (canceled) 
     
     
         10 . A method of assembling metal shells, the method comprising:
 a) providing a first shell made of titanium fire resistant alloy in a shape close to its final shape, the first shell including a first face and a second face opposite from the first face, the second face including portions in relief that act as anchor points for anchoring a second shell on the first shell;   b) providing at least one second shell of titanium alloy, the second shell including a first face and a second face opposite from the first face;   c) placing the first face of the second shell on the second face of the first shell;   d) heating the second shell to a temperature higher than a second temperature T 2 ;   e) deforming the second shell on the first shell at the second temperature T 2 , such that the first face of the second shell fits closely to the second face of the first shell, the second shell thus being secured to the first shell; and   f) cooling an assembly formed by the first shell and the second shell to ambient temperature.   
     
     
         11 . A method according to  claim 10 , wherein in d) the first shell is maintained at a temperature lower than a first temperature T 1 , the second temperature T 2  being higher than the first temperature T 1 , and in e) the second shell is superplastically deformed at the second temperature T 2  against the first shell. 
     
     
         12 . A method according to  claim 11 , wherein the temperature T 1  is less than 200° C. 
     
     
         13 . A method according to  claim 11 , wherein prior to c), the first face of the first shell rests against a rigid core with which it is in contact. 
     
     
         14 . A method according to  claim 11 , wherein the superplastic deformation of the titanium second shell is performed by using at least one die that is placed against the second face of the second shell and that is moved to deform the second shell and press it against the first shell. 
     
     
         15 . A method according to  claim 10 , wherein in c) the shells are placed in a hermetically closed enclosure, in d) the first shell is heated to a temperature higher than the second temperature T 2 , and in e) a pressure is established in the enclosure that is high enough to deform the second shell at the second temperature T 2 . 
     
     
         16 . A method according to  claim 10 , wherein the second temperature T 2  is higher than 500° C. 
     
     
         17 . A method according to  claim 10 , wherein the second temperature T 2  is less than a temperature Tb, the temperature Tb being a temperature above which the titanium alloy has a β microstructure. 
     
     
         18 . A method according to  claim 10 , wherein a difference Δα between the coefficient of expansion of the titanium of the second shell and the coefficient of expansion of the alloy of the first shell is less than 3×10 −6 /° C.