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 producing alloy castings or
 ingots having a structure selected from the group essentially consisting of single crystal dendrite structure (SX material), polycrystalline columnar dendrite structure (DS material) and the mixed structure of said SX and said DS materials, said method comprising:   Step (1) forming 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 structure; and   Step (2) during said step (1), exerting onto the whole region of said mushy phase the static magnetic field of the magnitude necessary to suppress interdendritic liquid flow within said mushy phase which causes macrosegregation such as freckles, and thereby suppressing the formation of said macrosegregation such as freckles.   
   
   
       2 . A unidirectional solidification method for producing alloy castings or ingots essentially consisting of single crystal dendrite structure (SX material), said method comprising:
 Step (1) forming 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 single crystal dendrite structure (SX material); and   Step (2) during said step (1), exerting onto said mushy phase and the vicinity of said mushy phase-said liquid phase boundary the static magnetic field of the magnitude necessary to suppress the formation of misoriented grain defects in said castings or ingots.   
   
   
       3 . The unidirectional solidification method for producing alloy castings or ingots described in  claim 1 , wherein the magnitude of said static magnetic field is characterized by being higher than at least 0.5 Tesla. 
   
   
       4 . The unidirectional solidification method for producing alloy castings or ingots described in  claim 1 , wherein said alloy is characterized by being of upward type of buoyancy, and the static magnetic field is characterized by exerting onto the whole region of said mushy phase the static magnetic field of the magnitude necessary to suppress at least one of upward channel flow causing freckles and interdendritic liquid flow causing macrosegregation within said mushy phase. 
   
   
       5 . The unidirectional solidification method for producing alloy castings or ingots described in  claim 1 , wherein the grain structure of said castings or ingots is characterized by being cellular structure. 
   
   
       6 . The unidirectional solidification method for producing alloy castings or ingots described in  claim 1 , wherein said alloy is characterized by being an alloy selected from the group consisting of Ni-base alloy, Co-base alloy, Fe-base alloy and TiAl-base alloy. 
   
   
       7 . A unidirectional solidification apparatus for producing alloy castings or ingots having a structure selected from the group essentially consisting of single crystal dendrite structure (SX material), polycrystalline columnar dendrite structure (DS material) and the mixed structure of said SX and said DS materials, said apparatus comprising:
 unidirectional solidification means for forming 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 structure; and,   means for exerting static magnetic field to exert onto the whole region of said mushy phase the static magnetic field of the magnitude higher than at least 0.5 Tesla to suppress interdendritic liquid flow within said mushy phase which causes macrosegregation such as freckles, and thereby suppressing the formation of said macrosegregation such as freckles.   
   
   
       8 . An ingot making apparatus via remelting process such as ESR or VAR comprising:
 means for melting electrodes, casting into mold, thus forming solid phase, solid-liquid coexisting phase (termed mushy phase) and liquid phase, and moving said mushy phase from one end toward the other to solidify; and   means for exerting static magnetic field necessary to suppress interdendritic liquid flow within said mushy zone which causes macrosegregation such as freckles, and thereby suppressing the formation of said macrosegregation such as freckles.   
   
   
       9 . The ingot making apparatus described in the  claims 8 , wherein said means for exerting the static magnetic field is characterized by generating the magnetic field higher than at least 1 Tesla. 
   
   
       10 . An ingot making method via remelting process such as ESR or VAR comprising:
 Step (1) melting electrodes, casting into mold, thus forming solid phase, solid-liquid coexisting phase (termed mushy phase) and liquid phase, and moving said mushy phase from one end toward the other to solidify, and   Step (2) exerting onto the whole region of said mushy phase the static magnetic field of the magnitude necessary to suppress interdendritic liquid flow within said mushy zone which causes macrosegregation such as freckles, and thereby suppressing the formation of said macrosegregation such as freckles.   
   
   
       11 . The ingot making method described in  claim 10 , which is characterized by arranging molten slag pool on the top of said mold, by refining molten metal droplets falling down through said molten slag pool from said electrodes above the top of said molten slag pool, and casting into said mold. 
   
   
       12 . The ingot making method described in  claim 11 , which is characterized by heating and keeping hot said molten slag pool. 
   
   
       13 . The ingot making method described in  claim 10 , which is characterized by insulating said magnetic field against said electrodes. 
   
   
       14 . The ingot making method described in  claim 10 , wherein said static magnetic field is characterized by being higher than at least 1 Tesla.