Forming large titanium parts

Abstract

Apparatus for superplastically forming large parts from titanium comprising: a furnace ( 10 ) having an interior, the inside surface of the furnace ( 10 ) being contoured and finished so as to form a mold for the part to be superplastically formed; means ( 70 ) for heating the interior of the furnace ( 10 ); and a supply ( 60 ) of an inert gas. The surface of the mold is adapted to receive a substantially unformed titanium blank ( 80 ). The heating means ( 70 ) is adapted to heat the titanium blank ( 80 ) to the required temperature for superplastic forming. The supply ( 60 ) of the inert gas is operable to exert a pressure onto the surface of the titanium blank ( 80 ) furthermost from the surface of the mold such that the inert gas causes the titanium blank ( 80 ) to deform and take up the shape of the mold, thereby forming the required part. The heating means ( 70 ) includes one or more electrical induction coils positioned in the furnace ( 10 ) so as to be on the side of the titanium blank ( 80 ) furthermost from the mold when that titanium blank ( 80 ) is positioned in the furnace ( 10 ) for superplastic forming in the mold, such that the or each induction coil induces a current in the titanium blank ( 80 ) which is heated thereby.

1 . A method of superplastically forming large parts from titanium, comprising the steps of: 
 a) constructing a furnace ( 10 ) with an inside surface which is contoured and finished so as to form a mould for the part to be superplastically formed;    b) introducing a substantially unformed titanium blank ( 80 ) into the furnace ( 10 );    c) heating the titanium blank ( 80 ) to the required temperature for superplastic forming;    d) applying inert gas to the surface of the titanium blank ( 80 ) furthermost from the mould, wherein the gas pressure is such that it causes the titanium blank ( 80 ) to deform and take up the shape of the mould, thereby forming the required part, characterised in that the heating is by one or more electrical induction coils positioned on the side of the titanium blank ( 80 ) furthermost from the mould such that the or each induction coil induces a current in the titanium blank ( 80 ) which is heated thereby.    
     
     
         2 . A method according to  claim 1 , wherein the or each induction coil extends the full height of the mould.  
     
     
         3 . A method according to  claim 1  or  claim 2 , wherein the substantially unformed blank ( 80 ) is substantially cylindrical and the or each induction coil is positioned inside said substantially cylindrical blank ( 80 ).  
     
     
         4 . A method according to  claim 3 , wherein the or each induction coil is orientated such that its axis is substantially parallel to the axis of said substantially cylindrical blank ( 80 ).  
     
     
         5 . A method according to  claim 3  or  claim 4 , wherein there is a plurality of such induction coils, the induction coils being distributed so that collectively they define an annulus that is substantially coaxial with the substantially cylindrical blank ( 80 ).  
     
     
         6 . A method according to any one of the preceding claims, wherein the furnace ( 10 ) is constructed from a plurality of furnace walls or furnace wall sections ( 30 ) which collectively form the inside surface of the furnace ( 10 ).  
     
     
         7 . A method according to  claim 6 , wherein the or each furnace wall or furnace wall section ( 30 ) is formed of a ceramic material.  
     
     
         8 . A method according to any one of the preceding claims, wherein the inert gas is argon.  
     
     
         9 . Apparatus for superplastically forming large parts from titanium comprising: a furnace ( 10 ) having an interior, the inside surface of the furnace ( 10 ) being contoured and finished so as to form a mould for the part to be superplastically formed; means ( 70 ) for heating the interior of the furnace ( 10 ); and a supply ( 60 ) of an inert gas, wherein the surface of the mould is adapted to receive a substantially unformed titanium blank ( 80 ), the heating means ( 70 ) is adapted to heat the titanium blank ( 80 ) to the required temperature for superplastic forming when that titanium blank ( 80 ) is positioned in the furnace ( 10 ) for superplastic forming in the mould, and the supply ( 60 ) of the inert gas is operable to exert a pressure onto the surface of the titanium blank ( 80 ) furthermost from the surface of the mould when that titanium blank ( 80 ) is positioned in the furnace ( 10 ) for superplastic forming in the mould such that the inert gas causes the titanium blank ( 80 ) to deform and take up the shape of the mould, thereby forming the required part, characterised in that the heating means ( 70 ) include one or more electrical induction coils positioned in the furnace ( 10 ) so as to be on the side of the titanium blank ( 80 ) furthermost from the mould when that titanium blank ( 80 ) is positioned in the furnace ( 10 ) for superplastic forming in the mould, such that the or each induction coil induces a current in the titanium blank ( 80 ) which is heated thereby.  
     
     
         10 . Apparatus according to  claim 9 , wherein the or each induction coil extends the full height of the mould.  
     
     
         11 . Apparatus according to  claim 9  or  claim 10 , wherein the substantially unformed blank ( 80 ) is substantially cylindrical and the or each induction coil is positioned in the furnace ( 10 ) so as to be inside said substantially cylindrical blank ( 80 ) when that titanium blank ( 80 ) is positioned in the furnace ( 10 ) for superplastic forming in the mould.  
     
     
         12 . Apparatus according to  claim 11  wherein the or each induction coil is orientated such that its axis is substantially parallel to the axis of said substantially cylindrical blank ( 80 ) when that titanium blank ( 80 ) is positioned in the furnace ( 10 ) for superplastic forming in the mould.  
     
     
         13 . Apparatus according to  claim 11  or  claim 12 , wherein there is a plurality of such induction coils, the induction coils being distributed so that collectively they define an annulus that is substantially coaxial with the substantially cylindrical blank ( 80 ) when that titanium blank ( 80 ) is positioned in the furnace ( 10 ) for superplastic forming in the mould.  
     
     
         14 . Apparatus according to any one of  claims 9  to  13 , wherein the furnace ( 10 ) is constructed of a plurality of furnace walls or furnace wall sections ( 30 ), which collectively form the inside surface of the furnace ( 10 ).  
     
     
         15 . Apparatus according to  claim 14 , wherein the or each furnace wall or furnace wall section ( 30 ) is formed of a ceramic material.  
     
     
         16 . Apparatus according to any one of  claims 9  to  15 , wherein the inert gas is argon.