Casting method and apparatus

Abstract

This invention is concerned with the productions of unidirectionally solidified castings and remelting processed ingots such as ESR or VAR, which has paid special attention to the liquid flow phenomena within solid-liquid coexisting phase (mushy phase) during solidification, and made it clear for the first time that by applying high static magnetic field onto the whole mushy phase, the extremely slow interdendritic liquid flow responsible for the formation of macrosegregation can be suppressed, and thereby that the macrosegregation such as freckles can completely be eliminated. Thus, this invention provides with a novel casting technology for producing high quality castings and ingots without macrosegregation.

1 . A unidirectional solidification method for nickel-containing superalloys for producing a grain structure selected from the group consisting of a single crystal dendrite structure (SX material), a polycrystalline columnar dendrite structure (DS material) and a mixed structure of said SX and said DS materials, said method comprising:
 Step (1) forming a solid phase, solid-liquid coexisting phase (mushy phase) and liquid phase, and moving said mushy phase from one end toward the other to establish unidirectional solidification to obtain said grain structure; and   Step (2) during said step (1), exerting onto at least the whole region of said mushy phase and its vicinity of said liquid phase a static magnetic field in a direction substantially parallel to a withdrawal direction of a grain structure with a magnitude of at least 0.5 Tesla so as to reduce interdendritic liquid flow in transverse directions except for said withdrawal direction and thereby to suppress [formation of macrosegregation.   
     
     
         2 . A unidirectional solidification method for nickel-containing superalloys for producing a grain structure selected from the group consisting of a single crystal dendrite structure (SX material), a polycrystalline columnar dendrite structure (DS material), and a mixed structure of said SX and said DS materials, said method comprising:
 Step (1) forming a solid phase, solid-liquid coexisting phase (mushy phase) and liquid phase, and moving said mushy phase from one end toward the other to establish unidirectional solidification to obtain said grain structure; and   Step (2) during said step (1), exerting onto at least the whole region of said mushy phase and its vicinity of said liquid phase a static magnetic field in a direction substantially parallel to a withdrawal direction of a grain structure with a magnitude of at least — 0.5 Tesla so as to reduce liquid flow in transverse directions, and thereby to suppress formation of misoriented grain defects in said grain structure.   
     
     
         3 . The unidirectional solidification method as described in  claim 1 , wherein said structure is of an upward type alloy of buoyancy, and the static magnetic field is exerted onto said at least the whole region of said mushy phase and its vicinity of said liquid phase the static magnetic field in a direction substantially parallel to the withdrawal direction the grain structure with a magnitude necessary to suppress at least one of upward channel flow causing freckles and interdendritic liquid flow causing said macrosegregation within said mushy phase. 
     
     
         4 . The unidirectional solidification method as described in  claim 1 , wherein said grain structure is characterized by having a cellular structure. 
     
     
         5 . The unidirectional solidification method as described in  claim 1 , wherein said structure is of an alloy selected from the group consisting of a Ni-base alloy, Co-base alloy, Fe-base alloy and TiAl-base allay. 
     
     
         6 . The unidirectional solidification method as described in  claim 1 , wherein said macrosegregation comprises freckle defects. 
     
     
         7 . The unidirectional solidification method as described in  claim 2 , wherein said structure is of an upward type alloy of buoyancy, and the static magnetic field is exerted onto said at least the whole region of said mushy phase and its vicinity of said liquid phase the static magnetic field in a direction substantially parallel along the crystal grain growth direction of a magnitude necessary to suppress at least one of upward channel flow causing freckles and interdendritic liquid flow causing said macrosegregation within said mushy phase. 
     
     
         8 . The unidirectional solidification method as described in  claim 2 , wherein said grain structure is characterized by having a cellular structure. 
     
     
         9 . The unidirectional solidification method as described in  claim 2 , wherein said structure is of an alloy selected from the group consisting of a Ni-base alloy, Co-base alloy, Fe-base alloy and TiAl-base alloy. 
     
     
         10 . The unidirectional solidification method as described in  claim 2 , wherein said formation of misoriented grain defects in said grain structure comprises freckle defects.